JP5075066B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly, can prevent scratches, positional deviation, color deviation, and the like that occur between a photosensitive drum and a transfer belt during acceleration / deceleration, and can output a high-quality printed matter. The present invention relates to an image forming apparatus.

  In recent years, image forming apparatuses are provided with a plurality of functions that can be provided, and are becoming multifunctional. The functions include a facsimile transmission / reception function, a scan function, a print function, a post-processing function represented by a staple function and a punch function, a power saving function, and the like in addition to a copy function, and various types. Further, along with the diversification of the above functions, an automatic document feeder (ADF) capable of automatically and sequentially feeding documents to be provided with functions has been installed.

  Such an image forming apparatus is commercially available as, for example, a copying machine, a printer, a facsimile machine, or a multifunction machine. Among the image forming methods, for example, a toner image on an image carrier (photosensitive drum) is intermediately transferred. A system (intermediate transfer image forming apparatus) that transfers to a recording medium (sheet) through a body is employed.

  In the intermediate transfer type image forming apparatus, the image carrier is rotated by a carrier motor, and the intermediate transfer member and the record carrier are rotated by a drive motor. Since the image carrier and the intermediate transfer member rotate while being in contact with each other, if the surface linear velocity (surface linear velocity) of the image carrier and the intermediate transfer member is different, the surface of the image carrier and the surface of the intermediate transfer member Rub against each other and wear, and the wear is promoted. Therefore, conventionally, a stepping motor is used as a carrier motor for rotating the image carrier and a drive motor for rotating the intermediate transfer member, respectively, and the number of input pulses is controlled to control the surface of the image carrier and the intermediate transfer member. The linear velocity of the surface of the was matched.

  However, the stepping motor consumes a large amount of power and generates a large operating noise. Therefore, a carrier motor that rotates the image carrier and a drive motor that rotates the intermediate transfer member or the recording medium carrier are controlled by a drive pulse (command clock signal) that is a pulse that rotates the motor and a feedback signal. If a clock control motor (hereinafter referred to as an image carrier motor), for example, a DC brushless motor, is used, occurrence of the above-described problems can be suppressed. Therefore, DC brushless motors have begun to be adopted.

  However, with a DC brushless motor, it is difficult to correctly control the rotation speed of the motor at the time of startup and shutdown. Therefore, when a DC brushless motor is used as the carrier motor and the drive motor, the DC brushless motor is started and started up. At the time of lowering, there is a large difference in the linear velocity of the surface between the image carrier and the intermediate transfer member, or between the image carrier and the recording medium carrier, and this causes significant friction and wear between them, shortening the service life. It is done.

  Furthermore, if there is a large difference between the surface linear velocities of the image carrier and the intermediate transfer member, the image carrier and the intermediate transfer member are rubbed, causing blurring and horizontal streaks in the image, and the image quality is deteriorated. . The same applies to the case where a DC brushless motor is used for the drive motor that drives the recording medium carrier and the carrier motor that drives the image carrier. For these reasons, conventionally, a stepping motor is usually used as the carrier motor and the drive motor. However, this has unavoidably suffered from the disadvantage that the power consumption and the operating noise increase.

  In order to solve the above problem, Japanese Patent Application Laid-Open No. 2005-189794 (Patent Document 1) transfers at least one image carrier on which a toner image is formed and a toner image formed on the image carrier. An intermediate transfer member, a carrier motor for rotating the image carrier, and a drive motor for rotating the intermediate transfer member. The toner image transferred to the intermediate transfer member is transferred to a recording medium for recording. In the image forming apparatus for obtaining an image, at least one of the carrier motor and the drive motor is composed of a clock control motor controlled by a command clock signal and a feedback signal. Disclosed is an image forming apparatus characterized by controlling the rotation speed of the clock control motor in accordance with a predetermined speed curve at least at one time of lowering It has been.

With the above configuration, since the clock control motor controlled by the command clock signal and the feedback signal is used as at least one of the carrier motor and the drive motor, the power consumption can be reduced, and the operation noise can be generated. It can be suppressed.
JP 2005-189794 A

  However, in the technique described in Patent Document 1, the startup time, which is the time from the start of acceleration (deceleration) to the stabilization of the rotation speed, is extended to stabilize the operation, and the startup time may be increased. There is sex. In addition, there is a possibility that sufficient constant speed characteristics cannot be obtained for providing a stepped speed clock (a driving pulse having a stepped frequency) for reducing the amount of memory used. In addition, depending on the use conditions, it is considered that the drum speed overshoot (undershoot) is greatly generated at the steady speed, and there is a problem that the rotation control of the motor is not stable at the time of startup and at the time of startup.

  In recent years, in response to a user request or a command / instruction signal of a connected other machine, a printing mode for image formation (for example, a color printing mode, a monochrome printing mode, a high-speed printing mode, a normal printing mode, a half-speed printing). Image forming apparatuses that appropriately switch between modes and the like have appeared. In an image forming apparatus having such various modes, it is necessary to appropriately switch the rotation speed of the motor in accordance with the diversification of modes. If the rotation speed of the motor is not properly switched, problems such as scratches, slip marks, and misalignment between the image carrier and the intermediate transfer member that occur during startup and shutdown will be switched. It can happen every time.

  In particular, in an image forming apparatus capable of color printing, since it is necessary to ensure a sufficient fixing time, the rotation speed of the motor in the color printing mode is normally set to be lower than that in the monochrome printing mode. Therefore, for example, when shifting from the monochrome printing mode to the color printing mode, it is necessary to switch the rotation speed from high speed to low speed. The switching of the rotation speed is highly likely to cause the occurrence of color misalignment that occurs during color printing as well as the above-described scratches and position misalignment. Scratches, misalignment, color misalignment, blurring of images, horizontal stripes, and the like are problems related to the image quality of printed matter and are one of the problems that need to be solved.

  Therefore, the present invention has been made to solve the above problem, and has improved the above problem by changing the fundamental configuration, and scratches generated between the photosensitive drum and the transfer belt during acceleration / deceleration. An object of the present invention is to provide an image forming apparatus capable of preventing a positional shift, a color shift, and the like and outputting a high-quality printed matter.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes an intermediate transfer member that controls rotation of an intermediate transfer member motor based on a control signal that is a pulse signal that controls rotation of the motor. An image for controlling the acceleration / deceleration of the rotation of the image carrier motor in accordance with the acceleration / deceleration of the rotation of the intermediate transfer motor based on the motor control means and the control signal of the image carrier motor synchronized with the control signal of the intermediate transfer motor. An image forming apparatus provided with a carrier motor control unit is assumed.

  In the image forming apparatus, when a signal for accelerating / decelerating the rotation speed of the image carrier motor together with the rotation speed of the intermediate transfer body motor is received, with respect to the rotation speed of the image carrier motor at the time of receiving the signal, The change rate determination means for determining whether or not the change rate of the designated speed, which is the rotation speed of the image carrier motor designated by the signal, is equal to or greater than a predetermined threshold, and the change rate determination means includes the change rate of the designated speed. Is determined to be equal to or greater than a predetermined threshold value, the image carrier motor control means includes synchronization changing means for synchronizing the rotation of the image carrier motor with the rotation of the intermediate transfer body motor.

  The control signal that is a pulse signal is a signal for controlling the rotation of the motor, and the shape of the pulse does not have to be strictly a square wave (rectangular wave), and if the object of the present invention is achieved, It may be a sawtooth wave, a triangular wave, or a pulse having a shape related thereto. The control signal is completely different from the drive pulse described later.

  Any image carrier can be used as long as it can form a toner image. For example, a photosensitive drum having a cylindrical shape or a drum having a related shape is applicable.

  The image carrier motor may be a motor that transmits (rotates) rotation based on, for example, a control signal for controlling rotation of the motor based on feedback control and a pulse fed back from rotation of the image carrier motor. Any motor may be used. The motor corresponds to, for example, a motor that employs a pulse width modulation (hereinafter referred to as PWM) control method. For example, a DC brushless motor corresponds to the motor that rotates by PWM control, but other motors that employ a control method related to the PWM control method may be used.

  The pulse fed back from the rotation of the image carrier motor is a feedback signal (encoder pulse signal, feedback pulse) generated by the rotation of the motor, and is a periodic signal corresponding to the rotational speed of the motor. This feedback pulse is output by, for example, a speed detection sensor including a rotary encoder (encoder). The rotary encoder has a function to convert the number of rotations of the motor (analog signal) into the number of pulses (digital signal). There are photoelectric conversion methods such as photoelectric, brush, and magnetic types. But it can be adopted. The feedback pulse may be, for example, a function generator signal (Frequency Generator signal, FG signal, Frequency) that is a signal oscillated by a function generator connected to a DC brushless motor.

  The intermediate transfer member may be any member as long as the formed toner image is transferred to the image carrier, and may be, for example, an endless transfer belt or a belt having a related shape.

  The intermediate transfer member motor may be any motor as long as it is a motor that transmits (rotates) rotation based on a control signal. The motor corresponds to, for example, a stepping motor that is a motor that can rotate at a predetermined angle when a control signal having a predetermined frequency is input.

  Accelerating the rotation speed of the motor corresponds to starting up (starting up) the motor, and reducing the rotation speed of the motor corresponds to lowering (stopping) the motor.

  A method for controlling the acceleration / deceleration of the rotation of the image carrier motor according to the acceleration / deceleration of the rotation of the intermediate transfer body motor based on the control signal of the image carrier motor synchronized with the control signal of the intermediate transfer body motor is, for example, This method can be adopted.

  For example, the number of pulses, frequency, speed, acceleration, phase, etc. of the control signal for controlling the rotation of the intermediate transfer body motor are calculated, and the calculation result is converted into a control signal for the image carrier motor, and the conversion is performed. There is a method of rotating the image carrier motor based on the control signal. For example, the control signal for controlling the rotation of the intermediate transfer body motor is compared with the internal timer pulse to calculate the count number of the control signal, the count number is multiplied by a predetermined speed coefficient, and the result of further multiplication is imaged. There is a method of converting the control signal for the carrier motor and controlling the rotation of the image carrier motor based on the control signal.

  As the internal timer pulse (internal timer clock, internal timer clock signal), for example, a time capture circuit (time capture means) that generates an internal timer pulse with a stable pulse period can be used. The image carrier motor control means can calculate the count number of the control signal based on the internal timer pulse and the control signal for controlling the rotation of the intermediate transfer body motor.

  Since the speed coefficient only needs to indicate the ratio of the rotational speed of the image carrier motor to the rotational speed of the intermediate transfer body motor at the time of steady rotation, for example, the reference rotational speed when calculating the speed coefficient, You may change into parameters, such as a frequency of a drive pulse, and surface linear velocity.

  The rate of change of the specified speed is the rate of change when accelerating / decelerating from the previous rotation speed to the next rotation speed based on the rotation speed of the image carrier motor, but the specified speed based on other parameters You may comprise so that change rate of may be calculated. For example, the frequency of the control signal corresponding to the rotation speed of the image carrier motor may be used.

  The predetermined threshold is a value stored in a predetermined memory in advance, and is appropriately changed according to, for example, the type, performance, and specifications of the image forming apparatus.

  The method for synchronizing the rotation of the image carrier motor with the rotation of the intermediate transfer member motor is the same as the method for controlling the acceleration / deceleration of the rotation of the image carrier motor according to the acceleration / deceleration of the rotation of the intermediate transfer member motor. can do.

  Further, when the change rate determining means determines that the change rate of the designated speed is less than a predetermined threshold value, the synchronization changing means sends the image carrier motor control means to the image carrier based on the designated speed. It can comprise so that rotation of a body motor may be accelerated / decelerated.

  The method of accelerating / decelerating the rotation of the image carrier motor based on the designated speed is different from the method of synchronizing the rotation of the image carrier motor with the rotation of the intermediate transfer member motor described above. A method is employed in which the rotation of the intermediate transfer member motor and the rotation of the image carrier motor are independently accelerated and decelerated.

  Furthermore, the predetermined threshold value can be configured to be a value of 10% or more with respect to the rotation speed at which the image carrier motor can form an image.

  According to the image forming apparatus of the present invention, when the signal indicating that the rotational speed of the image carrier motor is accelerated and decelerated together with the rotational speed of the intermediate transfer body motor is received, whether or not the change rate of the designated speed is equal to or greater than a predetermined threshold value. When the change rate determination means and the change rate determination means determine that the change rate of the designated speed is equal to or greater than a predetermined threshold, the image carrier motor control means is instructed to rotate the intermediate transfer body motor. And a synchronization changing means for synchronizing the rotation of the image carrier motor.

  As a result, a print mode (high-speed mode, half-speed mode, etc.) for accelerating or decelerating the rotation speed of the image carrier motor together with the rotation speed of the intermediate transfer body motor is activated in cases other than the time of startup and shutdown. Even so, it is possible to control the rotation speed of the image carrier motor so as to be synchronized with the rotation speed of the intermediate transfer body motor. Therefore, the rotation of the image carrier motor is performed by synchronizing (or following) the surface linear velocity of the image carrier rotated by the image carrier motor with the surface linear velocity of the intermediate transfer member rotated by the intermediate transfer member motor. The speed and the rotational speed of the intermediate transfer body motor can be accelerated or decelerated. As a result, the difference in speed generated between the surface linear velocity of the image carrier and the surface linear velocity of the intermediate transfer member is minimized, and the scratch between the image carrier and the intermediate transfer member caused by the speed difference, It is possible to prevent slip marks, misregistration, and the like, and to prevent troubles such as color misregistration occurring during color printing. Further, by suppressing troubles such as color misregistration, the image forming apparatus can provide a printed material to the user without degrading the image quality.

  Further, when the change rate determining means determines that the change rate of the designated speed is less than a predetermined threshold value, the synchronization changing means sends the image carrier motor control means to the image carrier based on the designated speed. It can comprise so that rotation of a body motor may be accelerated / decelerated.

  Accordingly, when it is necessary to accelerate / decelerate the rotation of the image carrier motor based on the designated speed without synchronizing the rotation speed of the image carrier motor with the rotation speed of the intermediate transfer body motor, for example, When correcting, adjusting, and correcting the rotation speed of the body motor and the rotation speed of the intermediate transfer body motor separately, the image bearing body is not synchronized with the rotation speed of the intermediate transfer body motor. It becomes possible to appropriately realize correction, adjustment, and correction of the rotation speed of the motor. For this reason, the image forming apparatus can be flexibly adapted according to the condition / situation, and the convenience of the user to the image forming apparatus can be improved. Further, by adjusting a predetermined threshold by a user / administrator or the like, it is possible to easily adjust whether or not the rotation speed of the image carrier motor is synchronized with the rotation speed of the intermediate transfer body motor.

  Furthermore, the predetermined threshold value can be configured to be a value of 10% or more with respect to the rotation speed at which the image carrier motor can form an image.

  As a result, when the printing mode is switched at a rate of change of the designated speed of 10% or more, the synchronization changing means sends the rotation speed of the image carrier motor to the image carrier motor control means. In synchronization with the speed, when correcting the rotational speed of the motor whose rate of change of the designated speed is less than 10%, the image carrier motor control means accelerates or decelerates the rotation of the image carrier motor based on the designated speed. Is possible. Therefore, it is possible to appropriately control the rotation of the image carrier motor in accordance with conditions / situations for accelerating / decelerating the rotation speed of the motor, and it is possible to improve the convenience of the user to the image forming apparatus.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.

<Image forming apparatus>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the position and size of the members are drawn with emphasis as appropriate in the drawings. In the following embodiments, a printer will be described as an example of the image forming apparatus of the present invention, but the present invention is not limited to this. That is, the image forming apparatus of the present invention only needs to include an image forming unit, such as a copying machine or a multifunction machine having a function as a facsimile machine (MFP: Multi Function Peripheral) or a copying machine having only a copying function. There may be.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment.

  FIG. 1 shows an example of an image forming apparatus to which the present invention is applied, using a printer 100 as an example, and includes tandem image forming units FY, FM, FC, and FK for forming a color image. Yes. The image forming units FY, FM, FC, and FK are in contact with the transfer belt B1, the cleaning unit B2 for cleaning the surface of the transfer belt B1, and the transfer belt B1 along the moving direction of the transfer belt B1. The yellow, cyan, magenta, and black photosensitive drums 10Y, 10M, 10C, and 10K are provided.

  The yellow photosensitive drum 10Y includes a developing device HY for developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum 10Y with toner, and a peripheral surface for charging the peripheral surface of the photosensitive drum 10Y. A charger 11Y is provided next to the charger 11Y. Similarly, chargers 11M and 11C for charging the peripheral surfaces of the developing devices HM, HC, and HK and the photosensitive drums 10M to 10K with respect to the photosensitive drums 10M, 10C, and 10K for magenta, cyan, and black. , 11K are provided. Further, in order to transfer the toner images carried on the peripheral surfaces of the photosensitive drums 10Y to 10K to the transfer belt B1, the transfer rollers B1 are provided on the peripheral surfaces of the photosensitive drums 10Y to 10K with the transfer belt B1 therebetween. 20Y, 20M, 20C, and 20K are arranged.

  The rotation of the motor that transmits the rotation to each photosensitive drum is controlled by feedback control based on a control signal (clock signal) for controlling the rotation of the motor and a feedback pulse generated by the rotation of the motor. For example, a DC brushless motor (DC brushless motor) is employed as the image carrier motor.

  The transfer belt B <b> 1 is stretched between the driving roller 21 and the driven roller 22, and is given a predetermined tension by the tension roller 23. The transfer belt B1 moves in the direction of the arrow. Therefore, the four photosensitive drums 10Y to 10K rotate counterclockwise in FIG.

  The motor that transmits the rotation to the transfer belt B1 includes an intermediate transfer body motor whose rotation is controlled based on a control signal for controlling the rotation of the motor, and the intermediate transfer body motor has a predetermined frequency, for example. When the control signal is input, a stepping motor that is a motor that can rotate at a predetermined angle is employed. Note that the stepping motor changes the rotation angle by adjusting the frequency of the control signal, and as a result, the rotation speed (rotation speed) is changed.

  As shown in FIG. 2, the peripheral surfaces of the photosensitive drums 10Y to 10K are charged to predetermined potentials by chargers 11Y, 11M, 11C, and 11K, respectively, and originals are exposed by exposure devices 12Y, 12M, 12C, and 12K. An image corresponding to the image is written, thereby forming an electrostatic latent image. The electrostatic latent images are developed into different color toner images by the developing devices HY, HM, HC, and HK, respectively. The toner images of the respective colors are transferred onto the transfer belt B1 by the transfer rollers 20Y to 20K, and the toner images are superimposed on the transfer belt B1.

  The toner remaining on the surface of the photosensitive drums 10Y to 10K after the transfer is performed as described above is wiped off by the blade 35, and is output to a predetermined container by the discharge roller 31, and then the photosensitive drums 10Y to 10K. The surface is neutralized by the static eliminator 13.

  On the other hand, the paper P is separated from the cassette 2 capable of storing a plurality of paper P by the transport unit 6 with a predetermined interval between the paper P toward the image forming units FY, FM, FC, and FK. Be transported. The toner image transferred to the transfer belt B1 is transferred by the secondary transfer unit 3 to the paper P conveyed to the image forming units FY, FM, FC, and FK.

  The control unit 30 includes image forming units FY and FM including the photosensitive drums 10Y to 10K, the developing devices HY, HM, HC, and HK, the chargers 11Y, 11M, 11C, and 11K, and the transfer rollers 20Y to 20K. , Controls the operation control of each image forming member in FC and FK. Also, the operation control of the transport mechanism including the transport roller B1 is performed.

  Next, the configuration of the developing device HY will be described. The configurations of the developing devices HY, HM, HC, and HB for the respective colors are the same.

  The developing device HY includes a developing container 40 and a developing roller 40a, and the developing container 40 stores therein a powdery developer composed of yellow toner particles and a carrier.

  The developing roller 40a is in contact with the photosensitive drum 10, and a toner corresponding to an image instructed to be formed from the upper apparatus by the potential difference between the electrostatic latent image on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 40a. An image is formed on the surface of the photosensitive drum 10 (development operation).

  Under such a configuration, the image forming apparatus 1 that has received an instruction for image formation from a host device such as a personal computer (PC) or the like forms toner images of each color corresponding to the received image data in the image forming units FY, FM. , FC, and FB. The toner image formed in each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is fed to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray section 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2 of the intermediate transfer belt.

  FIG. 3 is a schematic configuration diagram relating to control of the printer 100 according to the present embodiment.

  The printer 100 includes a CPU (CENTRAL Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each driving unit in the above printing. 306 is connected. The CPU 301 uses, for example, the RAM 202 as a work area, executes a program stored in the ROM 303, the HDD 304, or the like, and exchanges data and commands with the driver 305 based on the execution result, as shown in FIG. The operation of each driving unit is controlled.

  The above is a description of the printer 100 in general.

  Here, the printer 100 according to the embodiment of the present invention does not employ a conventionally known mechanical configuration of a DC brushless motor, a control circuit, a configuration equivalent to a CPU, and the like.

  Conventionally known DC brushless motor control circuits include, for example, a phase comparator, a filter control processing circuit, a PWM circuit, and a DC brushless motor driver. The phase comparator compares a command clock signal (control signal) input from the printer engine with a feedback signal input from the encoder of the DC brushless motor to calculate a phase difference or the like. The filter control processing circuit performs a filtering process, a predetermined calculation process, and the like on the phase difference input from the phase comparator, and inputs a predetermined control value to the PWM circuit. The PWM circuit generates a PWM signal that is a speed command signal based on the input control value, and inputs the PWM signal to the DC brushless motor driver. Then, the DC brushless motor driver inputs a drive pulse (drive signal) corresponding to the PWM signal to the DC brushless motor, and controls the rotation of the DC brushless motor. Conventionally, the rotation of the DC brushless motor is feedback-controlled with the above-described configuration and procedure.

  The machine configuration, control configuration, control procedure, and the like in the printer 100 according to the embodiment of the present invention will be described in detail below.

<Embodiment of the present invention>
<< Machine configuration of printer >>
FIG. 4 shows a mechanical configuration of the printer 100 according to the embodiment of the present invention.

  The printer 100 includes an engine 401, a stepping motor driver 402, a stepping motor 402a, a DC brushless motor CPU 403 that controls the rotation of each DC brushless motor, and the color of each photosensitive drum (yellow, cyan, magenta, black). DC brushless motor drivers 4041, 4042, 4043, and 4044 (also referred to as power drivers) and DC brushless motors 4041a, 4042a, 4043a, and 4044a corresponding to the respective colors.

  The engine 401 controls the printer 100 such as driving, stopping, and image formation, and inputs a control signal A (command signal, instruction clock signal) related to the rotation of the stepping motor 402 a to the stepping motor driver 402. The control signal A corresponds to, for example, an instruction clock signal that is a pulse signal for controlling the rotation of the stepping motor 402a. Further, the engine 401 is configured to input the control signal A to the stepping motor driver 402 and simultaneously to the DC brushless motor CPU 403 (described later).

  The engine 401 is a control signal different from the control signal A, and inputs a control signal B relating to the rotation start and rotation stop of each DC brushless motor 4041a, 4042a, 4043a, 4044a to the DC brushless motor CPU 403.

  The stepping motor driver 402 inputs a drive pulse to the stepping motor 402a based on the control signal A input from the engine 401. The stepping motor 402a transmits rotation to the driving roller 21 (not shown).

  In addition to the control signal B from the engine 401, the DC brushless motor CPU 403 receives a control signal A input from the engine 402 to the stepping motor driver 402. Based on the control signal B and the control signal A, the DC brushless motor CPU 403 inputs a predetermined speed command signal to the DC brushless motor drivers 4041, 4042, 4043, and 4044 (described later).

  The DC brushless motor drivers 4041, 4042, 4043, and 4044 input drive pulses to the DC brushless motors 4041a, 4042a, 4043a, and 4044a based on a speed command signal input from the CPU 403 for DC brushless motor. Each DC brushless motor 4041a, 4042a, 4043a, 4044a transmits rotation to the respective photosensitive drums 10Y, 10C, 10Y, 10K (not shown) (described later).

<< Printer control configuration >>
Next, the DC brushless motor CPU 403 which is a control configuration (control circuit) of the DC brushless motor 4041a will be described in detail.

  FIG. 5 shows the configuration of the CPU 403 for DC brushless motor according to the embodiment of the present invention. As shown in FIG. 5, in the printer 100 according to the embodiment of the present invention, a mechanism that automatically operates based on a CPU or the like so as to follow a target value using a feedback pulse or the like generated from an encoder (described later) as a control amount. The servo control mechanism is adopted.

  The DC brushless motor CPU 403, which will be described later, is described as controlling the photosensitive drum 10Y corresponding to yellow and the DC brushless motor 4041a that transmits the rotation to the photosensitive drum 10Y, but magenta, cyan, black The same applies to the photosensitive drums 10C, 10Y, and 10K and the DC brushless motors 4042a, 4043a, and 4044a corresponding to the above.

  The DC brushless motor CPU 403 mainly includes a first time capture circuit 501, a speed coefficient circuit 502, a target speed setting circuit 503, a second time capture circuit 504, a control arithmetic circuit 505, and a PWM circuit 506. It consists of.

  The first time capture circuit 501 is configured such that a signal equivalent to the control signal A input from the engine 401 to the stepping motor driver 402 is input simultaneously. The first time capture circuit 501 compares the control signal A input from the engine 401 with the internal timer pulse signal, and counts the number of internal timer pulse signals included in one pulse width of the control signal A ( Will be described later). The counted number is input to the speed coefficient circuit 502.

  The speed coefficient circuit 502 multiplies the input count number by a speed coefficient stored in advance in the memory unit of the speed coefficient circuit 502 to calculate a target speed that is a target value. By the multiplication, the count number is converted from a value corresponding to the stepping motor 402a to a value corresponding to the DC brushless motor 4041a. The target speed is calculated and updated every time the count number is input to the speed coefficient circuit 502 (every time the count number is counted). The speed coefficient circuit 502 inputs the calculated target speed to the target speed setting circuit 503.

  The target speed setting circuit 503 inputs the target speed input from the speed coefficient circuit 502 to the control arithmetic circuit 505, or sets the target speed to a steady speed input from the engine 401 in advance when the printer 100 is started or stopped. Switching to a stop speed (described later).

  The second time capture circuit 504 is configured to receive an encoder pulse signal (motor rotation speed signal, feedback signal) generated from an encoder 507 provided in the DC brushless motor 4041a. The second time capture circuit 504 compares the encoder pulse signal input from the encoder 507 with the internal timer pulse signal, and counts the number of internal timer pulse signals included in one pulse width of the encoder pulse signal (described later). To do). The counted number is calculated as a value (current rotation speed) corresponding to the current rotation speed of the DC brushless motor 4041a.

  As the target speed and the current rotational speed, a speed difference obtained by dividing the current rotational speed from the target speed is calculated, and the speed difference is input to the control arithmetic circuit 505.

  The control arithmetic circuit 505 employs PID control, which is one of feedback control methods, and calculates a control value from the input speed difference based on a control parameter used for PID control. The control arithmetic circuit 505 inputs the calculated control value to the PWM circuit 506.

  The PWM circuit 506 generates a PWM signal based on the input control value, and inputs the PWM signal to the DC brushless motor driver 4041 as a speed command signal.

  The rotation of the DC brushless motor 4041a is controlled by executing a program or the like stored in a predetermined memory. The above circuits, drivers and the like operate as respective means described later.

<< Printer control procedure >>
Next, referring to FIG. 6 to FIG. 7, the image forming apparatus of the present invention prevents scratches, misregistration, color misregistration, etc. that occur between the photosensitive drum and the transfer belt during acceleration / deceleration. The procedure for outputting a high printed matter will be described. FIG. 6 is a functional block diagram of the printer according to the present invention. FIG. 7 is a flowchart for illustrating the execution procedure of the present invention. Details of each part not directly related to the present invention are omitted.

  First, rotation control of the stepping motor 402a and rotation control of the DC brushless motor 4041a when the printer 100 is in a state where image formation is possible will be described.

  The state in which image formation is possible means a state in which color printing is possible, and the photosensitive drums corresponding to yellow, magenta, cyan, and black are all rotated, the surface linear velocity of the transfer belt B1, and each photosensitive drum. This corresponds to a condition in which the surface linear velocities of 10Y, 10C, 10Y, and 10K coincide.

  Hereinafter, the rotation of the photosensitive drum 10Y corresponding to yellow and the DC brushless motor 4041a that transmits the rotation to the photosensitive drum 10Y will be described. However, the photosensitive drum corresponding to magenta, cyan, and black, and the DC brushless are described. The same applies to the rotation of the motor 4041a.

  A stepping motor control unit 603 that controls the rotation of the stepping motor 402a is supplied with a control signal (referred to as color printing steady speed A) by the image forming unit 602 corresponding to the rotation speed at which the stepping motor 402a can perform color printing (color printing steady speed A) 4, a maintenance instruction control signal A (hereinafter referred to as a color printing maintenance signal A) is input, so that the stepping motor control means 603 maintains the rotation speed of the stepping motor 402 a at the color printing steady speed A. It will be. The frequency of the color printing maintenance signal A is constant, and the color printing maintenance signal A is input to the target speed calculation means 605 constituting the DC brushless motor control means 604 for the reason of the configuration of the printer 100. It becomes.

  On the other hand, the DC brushless motor control unit 604 rotates the DC brushless motor 4041a based on the rotation speed (color printing steady speed B) of the DC brushless motor 4041a transmitted by the image forming unit 602. Is maintained.

  Specifically, the target speed calculation means 605 constituting the DC brushless motor control means 604 is based on the target speed calculated based on the color printing maintenance signal A (the target speed previously set, which will be described later). The color printing steady speed B is reset (switched) as a target value and transmitted to the feedback control means 606.

  The feedback control unit 606 that has received the color printing steady speed B executes feedback control based on PID control. The feedback control unit 606 determines a predetermined control value based on the current rotation speed corresponding to the current rotation speed of the DC brushless motor 4041a calculated by a feedback pulse (described later) and the color printing steady speed B. And the control value is transmitted to the PWM means 609.

  The calculation of the control value will be briefly described below.

  The DC brushless motor 4041a has a predetermined number corresponding to the rotation of the connecting shaft that connects the rotating shaft of the DC brushless motor 4041a and the rotating shaft of the photosensitive drum 10Y by a predetermined rotation angle. Encoder 507 that outputs encoder pulses (encoder pulses, hereinafter referred to as feedback pulses) is provided, and the encoder 507 outputs the feedback pulses to the current rotational speed calculation means 607 constituting the DC brushless motor control means 604. It is input from time to time.

  In addition to the first time capture circuit (described later), the current rotation speed calculation means 607 includes a second time capture circuit that generates an internal timer pulse with a stable pulse period. The speed calculation means 607 compares the internal timer pulse with the feedback pulse input from the encoder 507, and counts the number of internal timer pulses existing per one feedback pulse. This counted number is defined as a DC brushless motor count number Nb.

  When the current rotation speed calculation unit 607 calculates the DC brushless motor count number Nb in one pulse, the count number Nb is transmitted to the feedback control unit 606 as the current rotation speed of the DC brushless motor 4041a.

  The feedback control unit 606 calculates a speed difference between the received color printing steady speed B and the current rotation speed, and the control parameter (“Kp”, “K”) corresponding to the speed difference and the steady speed of the DC brushless motor 4041a. Kd "," Ki "), a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated.

  The control parameter is based on PID control that controls the current rotational speed to converge to a target value (for example, corresponding to the color printing steady speed B) by combining proportional control, integral control, and differential control. It is a defined parameter.

  For example, the control parameter includes a proportional control parameter “Kp” (also referred to as a proportional constant) that calculates (outputs) a proportional control value corresponding to the speed difference between the target value and the current rotational speed, and integrates the speed difference. An integral control parameter “Ki” (also referred to as an integral constant) for calculating an integral control value corresponding to the integrated value, and a differential control parameter “Kd” for calculating a differential control value corresponding to a differential value obtained by differentiating the speed difference ( This is also referred to as a differential constant).

  At the time of steady rotation of the DC brushless motor 4041a, the proportional control parameters “Kp”, “Kd”, and “Ki” are employed.

  With the above configuration, the DC brushless motor control means 604 can stably control the rotation of the DC brushless motor 4041a.

  Note that both the current rotation speed and the steady speed (for example, the color printing steady speed B) correspond to numerical values (data), and the feedback control unit 606 calculates a control value based on the numerical values. Therefore, it should be noted that a phase comparator or the like used for rotation control of the DC brushless motor 4041a has not been conventionally used.

  When the control value is calculated, the Fordback control unit 606 transmits the control value to the PWM unit 609. The PWM means 609 generates a PWM signal based on the control value and inputs it to the drive pulse input means 610. The drive pulse input unit 610 inputs a drive pulse corresponding to the control value to the DC brushless motor 4041a based on the PWM signal. The rotation of the DC brushless motor 4041a is maintained by the drive pulse.

  In the area 8A of FIG. 8, the frequency of the control signal (color printing maintenance signal A) input to the stepping motor control unit 603 when the image forming unit 602 maintains the color printable state, and DC The time-dependent change with the frequency of the encoder pulse of the brushless motor 4041a is shown.

  As can be seen from the region 8A in FIG. 8, in a state where color printing is possible, the frequency of the encoder pulse of the DC brushless motor 4041a is a speed factor (a = B /) with respect to the frequency of the color printing maintenance signal A of the stepping motor 402a. A, that is, the ratio of the frequency of the encoder pulse of the DC brushless motor 4041a to the frequency of the color printing maintenance signal A of the stepping motor 402a during the steady rotation of color printing, which will be described later).

  Further, in the area 8A of FIG. 8, the feedback control means 606 determines the control parameters (“Kp”, “Kd”, “Ki”) based on the speed difference between the color printing steady speed B as the target value and the current rotational speed. It is understood that a control value corresponding to) is calculated.

  Next, the control procedure of the present invention will be described.

  For example, when the user inputs a command A (monochrome printed matter output instruction) related to image formation for monochrome printing to the printer 100 using a terminal connected to the printer 100 in a state where color printing is possible, the communication means of the printer 100 601 receives the command A via the network connected to the terminal.

  The communication unit 601 transmits the command A to the image forming unit 602, and the image forming unit 602 shifts from a color printable state (color print mode) to a monochrome printable state (monochrome print mode) of the printer 100. .

  Normally, in a state where monochrome printing is possible, the speed is set higher than the rotational speed of the motor where color printing is possible. In color printing, it is necessary to apply sufficient fixing heat to each color toner image, whereas in monochrome printing, since the color toner image is lacking, the fixing heat can be reduced. This setting is made in order to sufficiently fix the toner image and to satisfy the user's desire to output the printed matter quickly. Therefore, when the image forming unit 602 shifts to a state capable of monochrome printing, it is necessary to accelerate the rotational speed of the DC brushless motor 4041a to the rotational speed capable of monochrome printing together with the rotational speed of the stepping motor 402a.

  The image forming unit 602 that has received the command A refers to a predetermined memory, acquires the rotation speed of the motor during monochrome printing (monochrome printing steady speed B of the DC brushless motor 4041a), and rotates the DC brushless motor 4041a. A signal for accelerating the speed to the monochrome printing steady speed together with the rotation speed of the stepping motor 402a (corresponding to a signal for shifting from the color printing mode to the monochrome printing mode, and a monochrome shifting instruction signal), and at the time of the monochrome printing The motor rotation speed (monochrome printing steady speed B of the DC brushless motor 4041a) is transmitted to the change rate determination means 617 (FIG. 7: S101).

  The predetermined memory stores in advance the rotation speed of the motor for monochrome printing, the rotation speed of the motor for color printing, and the like, and the image forming unit 602 refers to the memory to determine the stepping motor control unit 603. And DC brushless motor control means 604 is configured to output a control signal related to acceleration / deceleration of the rotational speed.

  Further, the signal transmitted from the image forming unit 602 to the change rate determining unit 617 is accompanied by the rotational speed of the motor designated by the signal. For example, the monochrome transition instruction signal is accompanied by a monochrome printing steady speed. The same applies to a correction instruction signal and a color shift instruction signal described later.

  The change rate determination means 617 that has received the monochrome transition instruction signal confirms that the rotational speed of the DC brushless motor 4041a is accelerated together with the rotational speed of the stepping motor 402a. Further, after the confirmation, the change rate determination unit 617 receives the monochrome transition instruction signal from the image forming unit 602 (may be from a predetermined memory provided in the image forming unit 602). A rotation speed (color printing steady speed B of the DC brushless motor 4041a) is acquired, and a designated speed that is a rotation speed of the DC brushless motor 4041a designated by the monochrome transition instruction signal with respect to the color printing steady speed B of the DC brushless motor 4041a. The change rate of (monochrome printing steady speed B of the DC brushless motor 4041a) is calculated (FIG. 7: S102).

  The change rate is a percentage obtained by dividing the color printing steady speed B by the speed difference between the monochrome printing steady speed B and the color printing steady speed B. The rate of change takes an absolute value.

  For example, if the frequency (Hz) of the encoder pulse during monochrome printing is B + B1, and the frequency of the encoder pulse during color printing is B, the change rate b of the designated speed is B1 / B (%).

  Here, it is assumed that B1 / B> 10% is satisfied.

  The change rate determination means 617 that has calculated the change rate b compares the change rate b with a predetermined threshold value a (10%) stored in advance in a predetermined memory, and determines whether or not the change rate b is greater than or equal to the predetermined threshold value. Is determined (FIG. 7: S103).

  Although the predetermined threshold value a is 10%, a mode (for example, a color printing mode, a monochrome printing mode, a high-speed printing mode, a normal printing mode, a half-speed mode, etc.) indicating the performance of the printer or a preset printing mode is set. The design is changed accordingly. Corresponding to the mode, the rotational speed of the motor is stored in advance in a predetermined memory of the image forming unit 602. Further, the predetermined threshold value a may be set to 20% according to the performance and mode of the printer.

  As described above, in order to satisfy b = B1 / B> a, the change rate determination unit 617 determines that the change rate b of the rotational speed of the DC brushless motor 4041a is equal to or greater than the predetermined threshold value a, and sets the determination result as a synchronous change unit. It transmits to 618 (FIG. 7: S104 YES).

  The synchronization changing unit 618 that has received the determination result causes the DC brushless motor control unit 604 to synchronize the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a (FIG. 7: S105).

  Specifically, the synchronization changing unit 618 transmits a signal (acceleration instruction signal) for accelerating the rotation speed of the stepping motor 402a to the monochrome printing steady speed A to the image forming unit 602 and then the stepping motor 402a. A signal (synchronization instruction signal) for synchronizing the rotation of the DC brushless motor 4041a with the rotation is transmitted.

  First, the image forming unit 602 that has received the acceleration instruction signal causes the stepping motor control unit 603 to accelerate the rotational speed of the stepping motor 402a from the control signal corresponding to the color printing steady speed A (acceleration signal A). In FIG. 4, the acceleration signal A is transmitted to the stepping motor control means 603.

  The stepping motor control unit 603 inputs a driving pulse for accelerating the rotation speed of the stepping motor 402a to the stepping motor 402a based on the acceleration signal A input from the image forming unit 602. When the rotation of the stepping motor 402a is started, the rotation of the driving roller 21 connected to the rotation shaft of the motor is started, and the rotation is transmitted to the transfer belt B1 wound around the driving roller 21, and the rotation of the transfer belt B1 is started. Is started.

  Since the frequency of the drive pulse input to the stepping motor 402a corresponds to the number of rotations (rotational speed) of the stepping motor 402a, the image forming unit 602 increases the frequency of the acceleration signal A with the acceleration of the stepping motor 402a. To the stepping motor control means 603. The frequency of the acceleration signal A corresponds to the frequency of the drive pulse, and the rotation speed of the stepping motor 402a increases as the frequency of the drive pulse increases.

  The image forming unit 602 continuously increases the frequency of the acceleration signal A to the frequency of the monochrome printing maintenance signal A until the current rotation speed of the stepping motor 402a reaches the monochrome printing steady speed A of the stepping motor 402a (step). Will increase).

  Further, the image forming unit 602 inputs the acceleration signal A to the target speed calculation unit 605 constituting the DC brushless motor control unit 604 due to the configuration of the printer.

  On the other hand, the image forming unit 602 that has received the synchronization instruction signal sends a signal (calculation signal B) for calculating the target speed to the target speed calculation unit 605 (calculation instruction B in FIG. 4) separately from the acceleration signal A. Control signal B) and the monochrome printing steady speed B of the DC brushless motor 4041a are transmitted. The target speed is the rotational speed of the DC brushless motor 4041a synchronized with the rotational speed of the stepping motor 402a.

  When the target speed calculation means 605 receives the calculation signal B, the target speed calculation means 605 calculates the target speed based on the acceleration signal A, and resets the target speed from the color printing steady speed B set as the target value (switching). The rotation of the DC brushless motor 4041a is controlled.

  The procedure from calculating the target speed to controlling the rotation of the DC brushless motor 4041a is as follows.

  The target speed calculation means 605 is provided with a first time capture circuit that generates an internal timer pulse (also referred to as an internal timer clock signal) with a stable pulse period. The timer pulse is compared with the acceleration signal A input from the image forming unit 602, and the number of internal timer pulses existing per one pulse of the acceleration signal A is counted. This counted number is defined as a stepping motor count number Na.

  When the target speed calculation unit 605 calculates the stepping motor count number Na in one pulse, the target number calculation unit 605 multiplies the count number Na by a predetermined correction coefficient (hereinafter referred to as a speed coefficient). That is, the target speed is calculated.

  The speed coefficient indicates the ratio of the rotational speed of the DC brushless motor 4041a to the rotational speed of the stepping motor 402a during color printing steady rotation (during color printing). This ratio corresponds to a ratio of conditions in which the surface linear velocity of the transfer belt B1 rotated by the stepping motor 402a and the surface linear velocity of the photosensitive drum 10Y rotated by the DC brushless motor 4041a coincide. Therefore, the value obtained by multiplying the count number Na by the speed coefficient is a value obtained by converting the rotation speed capable of color printing of the stepping motor 402a into the rotation speed capable of color printing of the DC brushless motor 4041a, and is calculated based on the acceleration signal A. It is understood that the set target speed corresponds to the rotational speed at the time of acceleration of the DC brushless motor 4041a synchronized with the rotational speed at the time of acceleration of the stepping motor 402a.

  The speed coefficient depends on, for example, the number of rotations (rpm) of the motor corresponding to the rotation speed of the motor and the frequency (Hz) of the control signal (corresponding to the above-mentioned maintenance signal and instruction clock signal) input to the motor control means. It is determined. Using the frequency as a reference, the frequency of a control signal used for rotation control of the stepping motor 402a during steady rotation is A (Hz), and the frequency of the encoder pulse generated from the encoder 507 of the DC brushless motor 4041a during steady rotation is B (Hz). ), The speed coefficient a (−) is B / A.

  When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the feedback control unit 606. The feedback control means 606 that has received the target speed calculates a speed difference between the target speed and the current rotational speed input from the current rotational speed calculation means 607, and based on the speed difference, the target speed (acceleration) The control value corresponding to the control parameter ("Kp") corresponding to (hour) is calculated.

  When the DC brushless motor 4041a is accelerated or decelerated, the proportional control parameter “Kp” is employed.

  With the above configuration, when accelerating the rotational speed of the DC brushless motor 4041a, the feedback control means 606 calculates the control value so that the current rotational speed follows the target speed of the DC brushless motor 4041a as needed, and the PWM means 609, The DC brushless motor control means 604 inputs the drive pulse to the DC brushless motor 4041a via the drive pulse input means 610. Therefore, the rotational speed of the DC brushless motor 4041a is sequentially accelerated, and it is possible to prevent an overshoot phenomenon that is a phenomenon in which the rotational speed of the DC brushless motor 4041a greatly exceeds the rotational speed of the target value.

  Even when the DC brushless motor control means 604 sequentially reduces the rotational speed of the DC brushless motor 4041a, the DC brushless motor control unit 604 adopts the control parameter “Kp” corresponding to the target speed (during deceleration) of the DC brushless motor 4041a. It is possible to prevent an undershoot phenomenon, which is a phenomenon in which the rotation speed of the motor 4041a is larger than the rotation speed of the target value.

  When the PWM means 609 receives the control value calculated by the feedback control means 606, it generates a PWM signal based on the control value and inputs it to the drive pulse input means 610. Based on the PWM signal, the drive pulse input means 610 inputs a drive pulse for accelerating the rotation speed of the DC brushless motor 4041a to the DC brushless motor 4041a. The DC brushless motor 4041a starts rotating based on the input drive pulse.

  The above-described procedure is repeated by the target speed calculation means 605 and the feedback control means 606 until the stepping motor control means 603 reaches the monochrome printing steady speed A at the rotational speed of the stepping motor 402a. That is, when the image forming unit 602 continuously increases the frequency of the acceleration signal A to the frequency of the monochrome printing maintenance signal A corresponding to the monochrome printing steady speed A, the target speed calculating unit 605 corresponds to the increase. Calculates the target speed of the DC brushless motor 4041a synchronized with the rotation of the stepping motor 402a, and the feedback control means 606 is based on the speed difference between the target speed and the current rotational speed and a predetermined control parameter. Calculate the control value. The calculated control value is converted into a PWM signal via the PWM means 609. The PWM signal is a clock signal (speed command signal) whose duty is continuously increased while maintaining a predetermined frequency. Become. As a result, the drive pulse input means 610 inputs a drive pulse for increasing the rotational speed of the DC brushless motor to the DC brushless motor 4041a. The duty (duty ratio) is the ratio of the width of one pulse of the HI signal to the period of one pulse.

  When the rotation speed of the stepping motor 402a reaches the monochrome printing steady speed A, the rotation speed of the DC brushless motor 4041a reaches the monochrome printing steady speed B corresponding to the arrival. As a result, the printer 100 shifts to a state capable of monochrome printing (FIG. 7: S106).

  In the region 8B of FIG. 8, the frequency of the control signal (acceleration signal A) input to the stepping motor control unit 603 when the image forming unit 602 shifts from the color printable state to the monochrome printable state. The time-dependent change with the frequency of the encoder pulse of DC brushless motor 4041a was shown.

  As can be seen from region 8B in FIG. 8, the frequency of the encoder pulse of the DC brushless motor 4041a is increased while maintaining the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. In other words, it is understood that the rotation of the DC brushless motor 4041a is increased in synchronization with the rotation of the stepping motor 402a. Accordingly, the rotational speeds of the stepping motor 402a and the DC brushless motor 4041a are accelerated while the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y are matched.

  Further, in region 8B of FIG. 8, the feedback control means 606 calculates a control value with a control parameter (“Kp”) corresponding to the acceleration based on the speed difference between the target speed as the target value and the current rotational speed. It is understood.

  When the printer 100 shifts to a state in which monochrome printing is possible, the image forming unit 602 inputs a control signal corresponding to the monochrome printing steady speed A to the stepping motor control unit 603, so that the stepping motor control unit 603 includes the stepping motor 402a. The rotation speed is maintained at the monochrome printing steady speed A. The control signal corresponding to the monochrome printing steady speed A is input to the target speed calculation means 605. Since the frequency of the control signal is constant, the target speed calculated by the target speed calculation means 605 is It becomes constant.

  When the target speed calculation means 605 detects that the target speed calculated by the target speed calculation means 605 itself is constant, the monochrome print steady speed B received from the image forming means 602 is transmitted to the feedback control means 606. Switch to.

  For example, the target speed calculation unit 605 detects that the target speed calculated by the target speed calculation unit 605 is constant, or the target speed converges to a predetermined value. It is judged by detecting what happened.

  When the target speed calculation means 605 transmits the monochrome printing steady speed B to the feedback control means 606, the feedback control means 606 calculates the speed difference between the monochrome printing steady speed B and the current rotation speed, Based on the control parameters (“Kp”, “Kd”, “Ki”) corresponding to the steady speed, a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated.

  The feedback control means 606 having calculated the control values inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is executed stably.

  If the rotation speed of the stepping motor 402a and the rotation speed of the DC brushless motor 4041a are stabilized, the image forming unit 602 forms a toner image on the photosensitive drum based on a command for image formation for monochrome printing, and the toner image Is transferred to the transfer belt B1, and output of the printed matter is executed. Thereby, one job is completed.

  In the region 8C of FIG. 8, the frequency of the control signal (monochrome print maintenance signal A) input to the stepping motor control unit 603 when the image forming unit 602 maintains a monochrome printable state, and DC The time-dependent change with the frequency of the encoder pulse of the brushless motor 4041a is shown.

  As can be seen from the region 8C in FIG. 8, in a state where monochrome printing is possible, the frequency of the encoder pulse of the DC brushless motor 4041a is a speed coefficient (a = B /) with respect to the frequency of the monochrome printing maintenance signal A of the stepping motor 402a. It is understood that A) is maintained. Note that the frequency of the encoder pulse during monochrome printing of the DC brushless motor 4041a is B + B1.

  Further, in the area 8C of FIG. 8, the feedback control means 606 determines the control parameters (“Kp”, “Kd”, “Ki”) based on the speed difference between the monochrome printing steady speed B as the target value and the current rotational speed. It is understood that a control value corresponding to) is calculated.

  Next, a procedure when the change rate b of the designated speed is less than the predetermined threshold value a will be described.

  For example, in a state where color printing is possible, the user separately corrects / adjusts / corrects the rotational speed of the DC brushless motor 4041a and the rotational speed of the stepping motor 402a of the printer 100 using a terminal connected to the printer 100. In the case of performing the above, the user rotates the rotational speed of the motor (the designated speed A1 of the stepping motor 402a, the designated speed B1 of the DC brushless motor 4041a) at the time of rotational speed correction, and the correction command B (rotational speed correction instruction 1). Is input, the communication unit 601 receives the rotational speed of the motor and the command B when the rotational speed is corrected.

  The designated speed A1 of the stepping motor 402a is larger than the steady color printing speed A of the stepping motor 402a, and the designated speed B1 of the DC brushless motor 4041a is larger than the steady color printing speed B of the DC brushless motor 4041a. To do. Further, the rotational speed correction instruction 1 is assumed to accelerate the rotational speed of the DC brushless motor 4041a together with the rotational speed of the stepping motor 402a. In general, when correcting the rotation speed, the rotation speed is about 3% to 5%, or about 10% depending on the rotation speed in a state where image formation is possible (color printing or monochrome printing is possible). Correct as follows.

  The communication unit 601 transmits the rotational speed of the motor at the time of the rotational speed correction and the command B to the image forming unit 602, and the image forming unit 602 shifts from the color printable state of the printer 100 to the rotational speed corrected state. .

  The image forming unit 602 includes a signal (a correction instruction signal) for accelerating the rotation speed of the DC brushless motor 4041a to a specified speed together with the rotation speed of the stepping motor 402a, and a motor rotation speed (DC brushless at the time of rotation speed correction). The designated speed B1) of the motor 4041a is transmitted to the change rate determination means 617 (FIG. 7: S101).

  The rate-of-change determination means 617 that has received the correction instruction signal confirms that the rotational speed of the DC brushless motor 4041a is accelerated together with the rotational speed of the stepping motor 402a. Further, after the confirmation, the rate-of-change determination unit 617 receives the correction instruction signal from the predetermined memory of the image forming unit 602, and the rotation speed of the DC brushless motor 4041a (the color printing steady speed B of the DC brushless motor 4041a). ) And the change rate of the designated speed (designated speed B1 of the DC brushless motor 4041a), which is the rotational speed of the DC brushless motor 4041a designated by the correction instruction signal, with respect to the color printing steady speed B of the DC brushless motor 4041a. Calculate (FIG. 7: S102).

  For example, when the frequency of the encoder pulse at the designated speed B of the DC brushless motor 4041a is B + B2, and the frequency of the encoder pulse at the time of color printing is B, the change rate b of the designated speed is B2 / B (%).

  Here, it is assumed that B2 / B <10% is satisfied.

  The change rate determination means 617 that has calculated the change rate b compares the change rate b with a predetermined threshold value a (10%) stored in advance in a predetermined memory, and determines whether or not the change rate b is greater than or equal to the predetermined threshold value. Is determined (FIG. 7: S103).

  From the above, in order to satisfy b = B2 / B <a, the change rate determination unit 617 determines that the change rate b of the rotational speed of the DC brushless motor 4041a is less than the predetermined threshold value a, and the determination result is a synchronous change unit. It transmits to 618 (FIG. 7: S104 NO).

  The synchronization changing unit 618 that has received the determination result causes the DC brushless motor control unit 604 to accelerate the rotation of the DC brushless motor 4041a based on the designated speed B1 of the DC brushless motor 4041a (FIG. 7: S107). Further, the synchronization changing unit 618 causes the stepping motor control unit 603 to accelerate the rotation of the stepping motor 402a to the designated speed A1 of the stepping motor 402a.

  Specifically, the synchronization changing unit 618 signals to the image forming unit 602 that the rotational speed of the stepping motor 402a is accelerated to the designated speed A1 and the rotational speed of the DC brushless motor 4041a is accelerated to the designated speed B1 ( This corresponds to a signal for separately rotating the stepping motor 402a and the DC brushless motor 4041a, and is used as an independent rotation instruction signal).

  The image forming unit 602 that has received the independent rotation instruction signal causes the stepping motor control unit 603 to accelerate the rotational speed of the stepping motor 402a from the control signal corresponding to the color printing steady speed A (acceleration signal A) ( In FIG. 4, the acceleration signal A is transmitted to the stepping motor control means 603.

  The stepping motor control unit 603 inputs a driving pulse for accelerating the rotation speed of the stepping motor 402a to the stepping motor 402a based on the acceleration signal A input from the image forming unit 602. As the frequency of the drive pulse increases, the rotation speed of the stepping motor 402a increases.

  The image forming unit 602 continuously changes the frequency of the acceleration signal A to the frequency of the control signal corresponding to the designated speed A1 until the current rotational speed of the stepping motor 402a reaches the designated speed A1 of the stepping motor 402a ( Increase step by step).

  Further, the image forming unit 602 inputs the acceleration signal A to the target speed calculating unit 605 due to the configuration of the printer. The target speed calculating unit 605 uses the color printing steady speed B as a target value. Since it is set, at this time, it is not affected by the acceleration signal A.

  Also, the image forming unit 602 that has received the independent rotation instruction signal sends a signal (acceleration signal B) for accelerating the rotation speed of the DC brushless motor 4041a to the target speed calculation unit 605 (in FIG. 4, the control signal for the acceleration instruction). B) and the designated speed B1 of the DC brushless motor 4041a are transmitted.

  Upon receiving the acceleration signal B and the designated speed B1, the target speed calculation means 605 resets (switches) the color printing steady speed B set as the target value to the designated speed B1. Further, the target speed calculation means 605 transmits the designated speed B1 to the feedback control means 606. The feedback control means 606 that has received the designated speed B1 calculates a speed difference between the designated speed B1 and the current rotational speed, and the control parameter (“Kp”, “Kd”, Based on “Ki”), a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated.

  The feedback control means 606 having calculated the control values inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is accelerated and later stabilized (FIG. 7: S106).

  In the region 9A of FIG. 9, the frequency of the control signal input to the stepping motor control unit 603 when the image forming unit 602 shifts from the color printable state to the rotation speed correction state, and the DC brushless motor 4041a The change with time of the frequency of the encoder pulse is shown.

  As can be seen from the region 9A in FIG. 9, the frequency of the encoder pulse of the DC brushless motor 4041a does not maintain the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. It is understood that the frequency of the encoder pulse of the brushless motor 4041a and the frequency of the control signal of the stepping motor 402a are increased separately. Note also that the frequency of the encoder pulse of the DC brushless motor 4041a is B + B2.

  In addition, since the rotation of the DC brushless motor 4041a can be accelerated without being synchronized with the rotation of the stepping motor 402a, for example, it is possible to easily finely adjust the rotation speed, etc. Correction can be performed. If the rotation of the DC brushless motor 4041a is accelerated in synchronization with the rotation of the stepping motor 402a, the rotation speed and the stepping of the DC brushless motor 4041a are set to the rotation speeds (designated speed A1, designated speed B1) intended by the user. The rotation speed of the motor 402a cannot be adjusted, and appropriate correction cannot be executed.

  Further, in the area 9A of FIG. 9, the feedback control means 606 switches the control parameter (“Kp”, “K”) corresponding to the steady speed even though the color printing steady speed B as the target value is switched to the designated speed B1. It is understood that the control values corresponding to “Kd”, “Ki”) are calculated.

  When the image forming unit 602 receives a correction-related command, the designated speed associated with the command is stored / updated in a predetermined memory.

  Thus, when a signal indicating that the rotational speed of the DC brushless motor is accelerated and decelerated together with the rotational speed of the stepping motor is received, the change rate determination means for determining whether the change rate of the designated speed is equal to or greater than a predetermined threshold value; If the change rate determination means determines that the change rate of the rotational speed of the DC brushless motor is equal to or greater than a predetermined threshold, the DC brushless motor control means causes the DC brushless motor control means to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor. Means.

  As a result, the print mode (color print mode, monochrome print mode, high-speed mode, half-speed mode, etc.) for accelerating or decelerating the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor is the case other than the time of startup and the time of shutdown. ) Is activated, the rotational speed of the DC brushless motor can be controlled to synchronize with the rotational speed of the stepping motor. For this reason, the rotational speed of the DC brushless motor and the stepping motor are set such that the surface linear speed of the photosensitive drum rotated by the DC brushless motor is synchronized with (or follows) the surface linear speed of the transfer belt rotated by the stepping motor. It becomes possible to accelerate or decelerate the rotational speed. As a result, the speed difference generated between the surface linear velocity of the photosensitive drum and the surface linear velocity of the transfer belt is minimized, and scratches and slip marks between the photosensitive drum and the transfer belt due to the speed difference are generated. In addition, it is possible to prevent misregistration and the like, and to prevent troubles such as color misregistration occurring during color printing. Further, by suppressing troubles such as color misregistration, the printer can provide a printed material to the user without deteriorating the image quality.

  Further, when the change rate determining means determines that the change rate of the designated speed is less than a predetermined threshold value, the synchronization changing means causes the DC brushless motor control means to determine the DC brushless motor based on the designated speed. It can be configured to accelerate and decelerate the rotation.

  Thereby, when it is necessary to accelerate and decelerate the rotation of the DC brushless motor based on the designated speed without synchronizing the rotation speed of the DC brushless motor with the rotation speed of the stepping motor, for example, the rotation speed of the DC brushless motor. When correcting, adjusting, and correcting the rotation speed of the stepping motor separately, the correction speed, adjustment, and correction of the rotation speed of the DC brushless motor can be performed without synchronizing the rotation speed of the DC brushless motor with the rotation speed of the stepping motor. It can be realized appropriately. Therefore, the printer can be flexibly adapted according to the condition / situation, and the convenience of the user to the printer can be improved. Further, it is possible to easily adjust whether or not the rotational speed of the DC brushless motor is synchronized with the rotational speed of the stepping motor by adjusting a predetermined threshold by a user / administrator or the like.

  Furthermore, the predetermined threshold value can be configured to be a value of 10% or more with respect to the rotational speed at which an image can be formed by the DC brushless motor.

  As a result, normally, at the time of printing mode switching where the change rate of the designated speed is 10% or more, the synchronization changing means causes the DC brushless motor control means to synchronize the rotational speed of the DC brushless motor with the rotational speed of the stepping motor. When correcting the rotational speed of the motor whose rate of change of the designated speed is less than 10%, the DC brushless motor control means can accelerate and decelerate the rotation of the DC brushless motor based on the designated speed. Therefore, it is possible to appropriately control the rotation of the DC brushless motor in accordance with conditions / situations for accelerating / decelerating the rotation speed of the motor, and it is possible to improve user convenience for the printer.

  In the following, for reference, a procedure for shifting from a monochrome printable state to a color printable state and a procedure for shifting from a monochrome printable state to a rotation speed correction state will be described.

<Procedure for transitioning from monochrome printing to color printing>
For example, in a state where monochrome printing is possible, when the user inputs a command C (color print output instruction) relating to image formation for color printing to the printer 100, the communication unit 601 receives the command C.

  The communication unit 601 transmits the instruction C to the image forming unit 602, and the image forming unit 602 shifts from the monochrome print ready state of the printer 100 to the color print ready state.

  As described above, in the state where color printing is possible, the speed is set to be lower than the rotational speed of the motor where monochrome printing is possible. Therefore, when the image forming unit 602 shifts to a state capable of color printing, it is necessary to reduce the rotational speed of the DC brushless motor 4041a to the rotational speed capable of color printing together with the rotational speed of the stepping motor 402a.

  The image forming unit 602 that has received the command C refers to a predetermined memory, acquires the rotation speed of the motor during color printing (color printing steady speed B of the DC brushless motor 4041a), and rotates the DC brushless motor 4041a. A signal for decelerating the speed to the color printing steady speed together with the rotation speed of the stepping motor 402a (a signal for shifting from the monochrome printing mode to the color printing mode, a color transition instruction signal), and a motor for the color printing The rotation speed is transmitted to the change rate determination means 617 (FIG. 7: S101).

  The change rate determination unit 617 that has received the color transition instruction signal confirms that the rotational speed of the DC brushless motor 4041a is decelerated together with the rotational speed of the stepping motor 402a. Further, after the confirmation, the change rate determination unit 617 acquires the rotation speed of the DC brushless motor 4041a (monochrome printing steady speed B of the DC brushless motor 4041a) at the time when the color transition instruction signal is received from the image forming unit 602. The change rate of the designated speed (the steady color printing speed B of the DC brushless motor 4041a), which is the rotational speed of the DC brushless motor 4041a designated by the color transition instruction signal, is calculated with respect to the monochrome printing steady speed B of the DC brushless motor 4041a. (FIG. 7: S102).

  For example, if the frequency (Hz) of the encoder pulse during monochrome printing is B + B1, and the frequency of the encoder pulse during color printing is B, the change rate b of the designated speed is B1 / (B + B1) (%). Here, it is assumed that B1 / (B + B1)> 10% is satisfied.

  The change rate determination means 617 that has calculated the change rate b compares the change rate b with a predetermined threshold value a (10%) stored in advance in a predetermined memory, and determines whether or not the change rate b is greater than or equal to the predetermined threshold value. Is determined (FIG. 7: S103).

  As described above, in order to satisfy b = B1 / (B + B1)> a, the change rate determination unit 617 determines that the change rate b of the rotational speed of the DC brushless motor 4041a is equal to or greater than the predetermined threshold value a, and synchronizes the determination results. It transmits to the change means 618 (FIG. 7: S104 YES).

  The synchronization changing unit 618 that has received the determination result causes the DC brushless motor control unit 604 to synchronize the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a (FIG. 7: S105).

  In the case described above, the synchronization changing unit 618 transmits a signal (deceleration instruction signal) indicating that the rotation speed of the stepping motor 402a is reduced to the color printing steady speed A to the image forming unit 602. A signal (synchronization instruction signal) indicating that the rotation of the DC brushless motor 4041a is synchronized with the rotation of the stepping motor 402a is transmitted.

  Here, when the rotational speed of the DC brushless motor 4041a is decelerated together with the rotational speed of the stepping motor 402a, it is better to decelerate the rotational speed of the DC brushless motor 4041a simultaneously with the deceleration of the rotational speed of the stepping motor 402a. The occurrence of deviation will be prevented appropriately. When the image forming unit 602 synchronizes the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a, it is necessary to exchange control signals corresponding to the synchronization. However, communication delay, control delay, and the like occur due to the exchange. there is a possibility. If the above-described deceleration instruction signal and synchronization instruction signal are transmitted at the same time, the synchronization timing may be delayed.

  Therefore, for example, when the rotational speed of the DC brushless motor 4041a is decelerated together with the rotational speed of the stepping motor 402a, the synchronization changing unit 618 causes the image forming unit 602 to synchronize the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a. It is preferable to transmit a signal (synchronization instruction signal) indicating that the rotation speed of the stepping motor 402a is reduced to the color printing steady speed A (deceleration instruction signal).

  With the above configuration, when the stepping motor control means 603 decelerates the rotation of the stepping motor 402a, the DC brushless motor 4041a already synchronized with the rotation of the stepping motor 402a also simultaneously decelerates the rotation. Therefore, when switching the rotation of the DC brushless motor 4041a to deceleration, generation of communication time (communication delay) required for exchange of control signals, generation of processing time required for predetermined calculation processing, control delay of rotation of the DC brushless motor 4041a Thus, it is possible to prevent the occurrence of deviation between the synchronization start time of the DC brushless motor 4041a, that is, the deceleration start time of the DC brushless motor 4041a and the deceleration start time of the stepping motor 402a.

  Hereinafter, for example, a procedure in which the synchronization changing unit 618 transmits a synchronization instruction signal to the image forming unit 602 and then transmits a deceleration instruction signal will be described.

  First, the image forming unit 602 that has received the synchronization instruction signal sends a signal (calculation signal B) (calculation instruction control signal B in FIG. 4) and a DC brushless motor to the target speed calculation unit 605 to calculate the target speed. The color printing steady speed B 4041a is transmitted.

  When the image forming unit 602 transmits the calculation signal B to the target speed calculation unit 605, the stepping motor control unit 603 controls the rotation while maintaining the rotation speed of the stepping motor 402a at the monochrome printing steady speed A. It will be in the state. In other words, since the image forming unit 602 has input a control signal (monochrome print maintenance signal A) corresponding to the monochrome printing steady speed A to the stepping motor control unit 603, the maintenance is performed due to the configuration of the printer 100. The signal A is being input to the target speed calculation means 605 simultaneously with the stepping motor control means 603.

  Upon receiving the calculation signal B, the target speed calculation means 605 calculates a target speed based on the monochrome printing maintenance signal A, and resets the target speed from the monochrome printing steady speed B set as the target value. The rotation of the DC brushless motor 4041a is controlled (by switching).

  When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the feedback control unit 606. The feedback control means 606 that has received the target speed calculates a speed difference between the target speed and the current rotation speed, and the control parameter (“Kp”) corresponding to the speed difference and the target speed (during deceleration). The control value is calculated based on

  The control value calculated by the feedback control means 606 is transmitted to the PWM means 609, and the PWM means 609 generates a PWM signal based on the control value and inputs it to the drive pulse input means 610. Based on the PWM signal, the drive pulse input means 610 inputs a drive pulse for maintaining the rotational speed of the DC brushless motor 4041a to the DC brushless motor 4041a. The DC brushless motor 4041a maintains rotation based on the input drive pulse.

  In the above-described procedure, the target speed calculation unit 605 continues until the synchronization changing unit 618 transmits a signal (deceleration instruction signal) indicating that the rotation speed of the stepping motor 402a is reduced to the color printing steady speed A to the image forming unit 602. And the feedback control means 606 are repeated. That is, when the image forming unit 602 continues to input the monochrome printing maintenance signal A to the target speed calculation unit 605 together with the stepping motor control unit 603, the target speed calculation unit 605 synchronizes with the monochrome printing steady speed A of the stepping motor 402a. The target speed of the DC brushless motor 4041a is calculated, and the feedback control unit 606 calculates a control value based on the speed difference between the target speed and the current rotation speed and a predetermined control parameter. The calculated control value is converted into a PWM signal via the PWM means 609. The PWM signal is a clock signal (speed command signal) corresponding to the monochrome printing steady speed B of the DC brushless motor 4041a. As a result, the drive pulse input means 610 maintains the rotation speed of the DC brushless motor 4041a at the monochrome printing steady speed B.

  Thereby, before the rotational speed of the stepping motor 402a is decelerated, the surface linear speed of the photosensitive drum 10Y rotated by the DC brushless motor 4041a is synchronized with the surface linear speed of the transfer belt rotated by the stepping motor 402a. It is possible to maintain the rotation speed of the DC brushless motor 4041a at a rotation speed capable of forming an image.

  Subsequently, the synchronization changing unit 618 transmits a signal (deceleration instruction signal) to the image forming unit 602 to decelerate the rotation speed of the stepping motor 402a to the color printing steady speed A.

  Receiving the deceleration instruction signal, the image forming means 602 decelerates the rotation speed of the stepping motor 402a (deceleration signal A) (deceleration instruction in FIG. 4) from the monochrome print maintenance signal A transmitted so far. Corresponding to the control signal A) and the deceleration signal A is transmitted to the stepping motor control means 603. When the stepping motor control means 603 receives the deceleration signal A, it starts decelerating the rotation of the stepping motor 402a.

  The stepping motor control means 603 inputs a drive pulse for reducing the rotation speed of the stepping motor 402a to the stepping motor 402a based on the deceleration signal A input from the image forming means 602. The image forming means 602 continuously reduces the frequency of the deceleration signal A to the frequency of the control signal corresponding to the color printing steady speed A until the current rotation speed of the stepping motor 402a reaches the color printing steady speed A (stepwise). ) Will be reduced.

  As described above, since the control signal A output from the image forming unit 602 is input to the target speed calculating unit 605 simultaneously with the stepping motor control unit 603, the image forming unit 602 decelerates the monochrome print maintaining signal A. At the same time as switching to the signal A, the deceleration signal A is input to the stepping motor control means 603 and the target speed calculation means 605.

  Since the target speed calculation means 605 has already calculated the control value based on the monochrome printing maintenance signal A, the target speed calculation means 605 switches from the monochrome printing maintenance signal A to the deceleration signal A and at the same time the deceleration signal A control value is calculated based on A. Therefore, for example, the deceleration signal is input to the stepping motor control unit 603 at the same time as the communication speed of the calculation signal received by the target speed calculation unit 605 or the control delay caused by communication exchange does not occur. The calculating means 605 calculates the target speed corresponding to the deceleration signal A.

  Further, the feedback control means 606 calculates a control value based on the speed difference between the target speed and the current rotation speed and the control parameter corresponding to the deceleration, and as a result, the PWM means 609, the drive pulse input means Via 610, a driving pulse for reducing the rotational speed of the DC brushless motor 4041a is input to the DC brushless motor 4041a. The DC brushless motor 4041a reduces rotation based on the input drive pulse.

  The above-described procedure is repeated by the target speed calculation means 605 and the feedback control means 606 until the stepping motor control means 603 reaches the rotation speed of the stepping motor 402a to the color printing steady speed A. That is, when the image forming unit 602 continuously decreases the frequency of the deceleration signal A to the frequency of the color printing maintenance signal A corresponding to the color printing steady speed A, the target speed calculating unit 605 corresponds to the decrease. Calculates the target speed of the DC brushless motor 4041a synchronized with the rotation of the stepping motor 402a, and the feedback control means 606 is based on the speed difference between the target speed and the current rotational speed and a predetermined control parameter. Calculate the control value. The PWM signal converted based on the calculated control value becomes a clock signal whose duty continuously decreases while maintaining a predetermined frequency. As a result, the drive pulse input means 610 inputs a drive pulse for reducing the rotational speed of the DC brushless motor to the DC brushless motor 4041a.

  When the rotation speed of the stepping motor 402a reaches the color printing steady speed A, the rotation speed of the DC brushless motor 4041a reaches the color printing steady speed B corresponding to the arrival. As a result, the printer 100 shifts to a state capable of color printing (FIG. 7: S106).

  In the region 8D of FIG. 8, the frequency of the control signal (deceleration signal A) input to the stepping motor control unit 603 when the image forming unit 602 shifts from the monochrome printable state to the color printable state. The time-dependent change with the frequency of the encoder pulse of DC brushless motor 4041a was shown.

  As can be seen from the region 8D of FIG. 8, the frequency of the encoder pulse of the DC brushless motor 4041a is decreased while maintaining the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. In other words, it is understood that the rotation of the DC brushless motor 4041a is reduced in synchronization with the rotation of the stepping motor 402a. Accordingly, the rotational speeds of the stepping motor 402a and the DC brushless motor 4041a are decelerated while the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y are matched.

  Further, in region 8D of FIG. 8, the feedback control means 606 calculates a control value with a control parameter (“Kp”) corresponding to the time of deceleration based on the speed difference between the target speed as the target value and the current rotational speed. It is understood.

  When the printer 100 shifts to a state in which color printing is possible, the image forming unit 602 inputs a control signal corresponding to the color printing steady speed A to the stepping motor control unit 603, so that the stepping motor control unit 603 includes the stepping motor 402a. The rotational speed is maintained at the printing steady speed A. The control signal corresponding to the color printing steady speed A is input to the target speed calculation means 605. Since the frequency of the control signal is constant, the target speed calculated by the target speed calculation means 605 is It becomes constant.

  When the target speed calculation unit 605 detects that the target speed calculated by the target speed calculation unit 605 itself is constant, the target speed to be transmitted to the feedback control unit 606 is the steady color printing speed B received from the image forming unit 602. Switch to.

  When the target speed calculation means 605 transmits the switched color printing steady speed B to the feedback control means 606, the feedback control means 606 calculates the speed difference between the color printing steady speed B and the current rotational speed, and the speed. Based on the difference and the control parameters (“Kp”, “Kd”, “Ki”) corresponding to the steady speed, a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated. (FIG. 7: S106).

  The feedback control means 606 having calculated the control values inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is executed stably.

  When the rotation speed of the stepping motor 402a and the rotation speed of the DC brushless motor 4041a are stabilized, the image forming unit 602 forms a toner image of each color on each photosensitive drum based on a command related to color printing image formation, The toner image is transferred to the transfer belt B1, and the printed matter is output. Thereby, one job is completed.

  In the area 8E of FIG. 8, the frequency of the control signal (color printing maintenance signal A) input to the stepping motor control unit 603 when the image forming unit 602 maintains the color printable state, and DC The time-dependent change with the frequency of the encoder pulse of the brushless motor 4041a is shown.

  As can be seen from region 8E in FIG. 8, in a state where color printing is possible, the frequency of the encoder pulse of the DC brushless motor 4041a is a speed factor (a = B /) with respect to the frequency of the color printing maintenance signal A of the stepping motor 402a. It is understood that A) is maintained. Note that the frequency of the encoder pulse during color printing of the DC brushless motor 4041a is B.

  Further, in the area 8E of FIG. 8, the feedback control means 606 determines the control parameters (“Kp”, “Kd”, “Ki”) based on the speed difference between the color printing steady speed B as the target value and the current rotational speed. It is understood that a control value corresponding to) is calculated.

<Procedure for transition from monochrome printable state to rotational speed correction state>
Next, a procedure for shifting from a state capable of monochrome printing to a rotational speed correction state will be described.

  For example, when the user corrects, adjusts, and corrects the rotational speed of the DC brushless motor 4041a of the printer 100 and the rotational speed of the stepping motor 402a separately in a state where monochrome printing is possible, the user rotates the printer 100. When the rotational speed of the motor at the time of speed correction (designated speed A2 of the stepping motor 402a, designated speed B2 of the DC brushless motor 4041a) and the instruction D related to correction (rotational speed correction instruction 2) are input, the communication means 601 performs the rotation. The rotational speed of the motor at the time of speed correction and the command D are received.

  The designated speed A2 of the stepping motor 402a is smaller than the monochrome printing steady speed A of the stepping motor 402a and larger than the color printing steady speed A, and the designated speed B2 of the DC brushless motor 4041a is DC brushless. It is assumed that it is smaller than the monochrome printing steady speed B of the motor 4041a and larger than the color printing steady speed B. In the rotation speed correction instruction 2, the rotation speed of the DC brushless motor 4041a is decelerated together with the rotation speed of the stepping motor 402a.

  The communication unit 601 transmits the rotational speed of the motor at the time of the rotational speed correction and the command D to the image forming unit 602, and the image forming unit 602 shifts from the printer 100 capable of monochrome printing to the rotational speed corrected state. .

  The image forming unit 602 includes a signal (correction instruction signal) for decelerating the rotational speed of the DC brushless motor 4041a to the designated speed together with the rotational speed of the stepping motor 402a, and the rotational speed of the motor (DC brushless motor 4041a at the time of rotational speed correction). The designated speed B2) is transmitted to the change rate determination means 617 (FIG. 7: S101).

  The change rate determination means 617 that has received the correction instruction signal confirms that the rotational speed of the DC brushless motor 4041a is decelerated together with the rotational speed of the stepping motor 402a. Further, after the confirmation, the change rate determination unit 617 acquires the rotational speed of the DC brushless motor 4041a (monochrome printing steady speed B of the DC brushless motor 4041a) at the time when the correction instruction signal is received from the image forming unit 602. The change rate of the designated speed (designated speed B2 of the DC brushless motor 4041a), which is the rotational speed of the DC brushless motor 4041a designated by the correction instruction signal, with respect to the monochrome printing steady speed B of the DC brushless motor 4041a is calculated (FIG. 7). : S102).

  For example, when the frequency of the encoder pulse at the designated speed B2 of the DC brushless motor 4041a is B + B1-B3 and the frequency of the encoder pulse at the time of monochrome printing is B + B1, the change rate b of the designated speed is B3 / (B + B1) (% )

  Here, it is assumed that B3 / (B + B1) <10% is satisfied.

  The change rate determination means 617 that has calculated the change rate b compares the change rate b with a predetermined threshold value a (10%) stored in advance in a predetermined memory, and determines whether or not the change rate b is greater than or equal to the predetermined threshold value. Is determined (FIG. 7: S103).

  As described above, in order to satisfy b = B3 / (B + B1) <a, the change rate determination unit 617 determines that the change rate b of the rotational speed of the DC brushless motor 4041a is less than the predetermined threshold value a, and synchronizes the determination results. It transmits to the change means 618 (FIG. 7: S104NO).

  The synchronization changing unit 618 that has received the determination result causes the DC brushless motor control unit 604 to decelerate the rotation of the DC brushless motor 4041a based on the designated speed B2 of the DC brushless motor 4041a (FIG. 7: S107). Further, the synchronization changing unit 618 causes the stepping motor control unit 603 to decelerate the rotation of the stepping motor 402a to the designated speed A2 of the stepping motor 402a.

  As described above, the synchronization changing unit 618 causes the image forming unit 602 to reduce the rotation speed of the stepping motor 402a to the specified speed A2 and to reduce the rotation speed of the DC brushless motor 4041a to the specified speed B2 ( Independent rotation instruction signal) is transmitted.

  The image forming unit 602 that has received the independent rotation instruction signal causes the stepping motor control unit 603 to reduce the rotation speed of the stepping motor 402a from the control signal corresponding to the monochrome printing steady speed A (deceleration signal A) ( In FIG. 4, the deceleration signal A is transmitted to the stepping motor control means 603.

  The stepping motor control unit 603 inputs a driving pulse for reducing the rotation speed of the stepping motor 402a to the stepping motor 402a based on the deceleration signal A input from the image forming unit 602. As the frequency of the drive pulse is reduced, the rotational speed of the stepping motor 402a is reduced.

  The image forming unit 602 continuously reduces the frequency of the deceleration signal A to the frequency of the control signal corresponding to the designated speed A2 until the current rotational speed of the stepping motor 402a reaches the designated speed A2 of the stepping motor 402a ( Decrease in steps).

  Further, the image forming unit 602 inputs the deceleration signal A to the target speed calculation unit 605 due to the configuration of the printer. The target speed calculation unit 605 uses the monochrome printing steady speed B as a target value. Since it is set, at this time, it is not affected by the deceleration signal A.

  In addition, the image forming unit 602 that has received the independent rotation instruction signal sends a signal (deceleration signal B) indicating that the rotational speed of the DC brushless motor 4041a is reduced to the target speed calculation unit 605 (in FIG. 4, a control signal for the deceleration instruction). B) and the designated speed B2 of the DC brushless motor 4041a are transmitted.

  Upon receiving the deceleration signal B and the designated speed B2, the target speed calculation means 605 resets (switches) the monochrome printing steady speed B set as the target value to the designated speed B2. Further, the target speed calculation means 605 transmits the designated speed B2 to the feedback control means 606. Upon receiving the designated speed B2, the feedback control means 606 calculates a speed difference between the designated speed B2 and the current rotation speed, and the control parameter (“Kp”, “Kd”, Based on “Ki”), a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated.

  The feedback control means 606 having calculated the control values inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is decelerated and later becomes stable.

  In the region 9B of FIG. 9, the frequency of the control signal input to the stepping motor control unit 603 when the image forming unit 602 shifts from the monochrome printable state to the rotation speed correction state, and the DC brushless motor 4041a. The change with time of the frequency of the encoder pulse is shown.

  As can be seen from the region 9B of FIG. 9, the frequency of the encoder pulse of the DC brushless motor 4041a does not maintain the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. It will be understood that the frequency of the encoder pulse of the brushless motor 4041a and the frequency of the control signal of the stepping motor 402a are reduced separately. The frequency of the encoder pulse of the DC brushless motor 4041a is B + B1-B3.

  Further, in the region 9B of FIG. 9, the feedback control means 606 switches the monochrome printing steady speed B, which is the target value, to the designated speed B2, but the control parameters (“Kp”, “ It is understood that the control values corresponding to “Kd”, “Ki”) are calculated.

  In the embodiment of the present invention, the rotational speed correction instruction 1 is an instruction to accelerate the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor, and the rotational speed correction instruction 2 is the rotational speed of the DC brushless motor. It is an instruction to decelerate with the rotation speed. For example, among the rotational speed correction instructions, for the instruction to accelerate or decelerate the rotational speed of the DC brushless motor alone, it is not necessary to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor. It is not necessary for the means to operate, and the image forming means transmits a control signal to the DC brushless motor control means based on an instruction to independently accelerate or decelerate the rotational speed of the DC brushless motor.

  Of the rotation speed correction instructions, the instruction to accelerate or decelerate the rotation speed of the stepping motor alone is not required to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor. However, a control signal is transmitted to the stepping motor control means based on an instruction to accelerate or decelerate the rotation speed of the stepping motor independently.

  In addition, among the rotational speed correction instructions, the rotational speed of the DC brushless motor is accelerated and the rotational speed of the stepping motor is decelerated, or the rotational speed of the DC brushless motor is decelerated and the rotational speed of the stepping motor is accelerated. In the same manner as described above, since it is not necessary to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor, the image forming unit transmits control signals separately to the DC brushless motor control unit and the stepping motor control unit. Will be.

  In the embodiment of the present invention, the change rate determination unit confirms whether or not to accelerate / decelerate the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor based on a signal transmitted from the image forming unit. ), But other configurations may be used. For example, when the image forming unit receives a predetermined command (command A, command B, command C, command D), it confirms whether or not the rotational speed of the DC brushless motor is accelerated and decelerated together with the rotational speed of the stepping motor. When the image forming means confirms that the rotational speed of the DC brushless motor is accelerated and decelerated together with the rotational speed of the stepping motor, the designated speed of the DC brushless motor designated by the control signal corresponding to the predetermined command is changed. You may comprise so that it may transmit to a determination means. With the above configuration, the confirmation procedure of the change rate determination unit can be omitted.

  In the embodiment of the present invention, the DC brushless motor and the photosensitive drum are directly connected (coupled). For example, a predetermined reduction ratio is set between the DC brushless motor and the photosensitive drum. It is also possible to provide a speed reducer that adjusts the rotational speed of the DC brushless motor and the rotational speed of the photosensitive drum as appropriate.

  In the embodiment of the present invention, the proportional control parameter “Kp” is adopted as the control parameter at the time of acceleration (deceleration) of the rotation of the DC brushless motor. The differential control value corresponding to the differential value obtained by differentiating the speed difference between the target speed of the DC brushless motor and the current rotation speed is calculated (output) according to the geared member, radius, circumference, specifications, etc. A differential control parameter “Kd” (also referred to as a differential constant) may be further added and employed.

  In the embodiment of the present invention, the DC brushless motor control means uses a predetermined control parameter corresponding to acceleration (deceleration) of the rotational speed of the DC brushless motor, and uses the difference between the current rotational speed and the target speed. The driving pulse for accelerating (decelerating) the rotational speed of the DC brushless motor corresponding to the speed is generated. For example, before the driving pulse is generated, the proportional control value calculated with a predetermined control parameter ( Hereinafter, a process for determining whether or not the control value belongs to a predetermined range may be provided. The range is determined by whether or not the duty of the drive pulse generated based on the control value belongs to a predetermined range (range from 0 to 100%). With the above configuration, it is possible to stably control the rotational drive.

  In the embodiment of the present invention, the case of shifting from a color printable state to a monochrome printable state has been described. For example, after a predetermined time (sleep time) has elapsed, the state in which image formation is possible shifts to the sleep state. When the printer is turned off, the image forming means receives a command signal corresponding to the stop of driving by the user, and the printer has a high-speed printing mode (high-speed mode) and a normal printing mode. The same applies when shifting from the high-speed printing mode to the normal printing mode, even when shifting from the normal printing mode to the high-speed printing mode.

  Furthermore, when the printer is equipped with a half-speed mode that is half the transport speed (motor rotation speed) in the normal print mode, and is shifted from the half-speed mode to the normal print mode, the normal print mode is changed to the half-speed mode. The same applies to the case of shifting to the above. Note that the synchronization changing means changes the synchronization according to the designated speed corresponding to the mode described above.

  In addition, all or a part of each means constituting the embodiment of the present invention may include predetermined circuit elements (for example, diodes, operational amplifiers, resistors, transistors, switching elements, etc.) and hardware resources (for example, CPU that is an arithmetic element) Etc.) may be realized as a circuit.

  For example, a stepping motor control circuit that controls the rotation of the stepping motor based on a control signal that is a pulse signal that controls the rotation of the motor, and a DC brushless according to the acceleration / deceleration of the rotation of the stepping motor based on the control signal of the stepping motor. In a printer having a DC brushless motor control circuit that controls acceleration / deceleration of motor rotation, when a signal indicating that the rotation speed of the DC brushless motor is accelerated and decelerated together with the rotation speed of the stepping motor is received, the signal is received. A change rate determination circuit that determines whether a change rate of a specified speed, which is a rotation speed of the DC brushless motor specified by the signal, with respect to a rotation speed of the DC brushless motor at a point in time is equal to or greater than a predetermined threshold; The circuit determines that the rate of change of the specified speed is greater than or equal to a predetermined threshold That when, in the image carrier motor control circuit may be configured and a synchronous change circuit for synchronizing the rotation of the DC brushless motor to rotation of the stepping motor.

  Further, when the change rate determination circuit determines that the change rate of the designated speed is less than a predetermined threshold value, the synchronization change circuit sends a DC brushless motor to the DC brushless motor control circuit based on the designated speed. The rotation can be configured to accelerate or decelerate.

  In the embodiment of the present invention, the printer is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. In the above configuration, the program is read by the printer, and the printer implements the above-described units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is also possible to provide a storage method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus according to the present invention is useful not only for a printer, but also for a copying machine, a multi-function machine, and the like, and scratches, misalignments, and the like that occur between a photosensitive drum and a transfer belt during acceleration / deceleration. This is effective as an image forming apparatus capable of preventing color misalignment and the like and outputting high-quality printed matter.

1 is a conceptual diagram illustrating an overall configuration inside a printer according to an embodiment of the present invention. FIG. 2 is a diagram illustrating details of an image forming unit according to an embodiment of the present invention. It is a figure which shows the structure of the control system hardware of the invention which concerns on embodiment of this invention. 1 is a diagram illustrating a mechanical configuration of a printer according to an embodiment of the present invention. It is a figure which shows the control structure of the DC brushless motor which concerns on embodiment of this invention. FIG. 2 is a functional block diagram of a printer in an embodiment of the present invention. It is a flowchart for showing the execution procedure of the embodiment of the present invention. It is a 1st figure which shows an example of a time-dependent change of the frequency of the control signal of the stepping motor which concerns on embodiment of this invention, and the frequency of the encoder pulse of DC brushless motor. It is a 2nd figure which shows an example of the time-dependent change of the frequency of the control signal of the stepping motor which concerns on embodiment of this invention, and the frequency of the encoder pulse of DC brushless motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Printer 601 Communication means 602 Image formation means 603 Stepping motor control means 604 DC brushless motor control means 605 Target speed calculation means 606 Feedback control means 607 Current rotation speed calculation means 609 PWM means 610 Drive pulse input means 617 Change rate determination means 618 Synchronization Change means

Claims (3)

An intermediate transfer body motor control means for controlling the rotation of the intermediate transfer body motor based on a control signal which is a pulse signal for controlling the rotation of the motor, and an image carrier motor control signal synchronized with the control signal of the intermediate transfer body motor. And an image carrier motor control means for controlling the acceleration / deceleration of the rotation of the image carrier motor according to the acceleration / deceleration of the rotation of the intermediate transfer motor.
When a signal for accelerating / decelerating the rotation speed of the image carrier motor together with the rotation speed of the intermediate transfer body motor is received, it is designated by the signal relative to the rotation speed of the image carrier motor at the time of receiving the signal. A rate-of-change determination means for determining whether the rate of change of the designated speed, which is the rotational speed of the image carrier motor, is greater than or equal to a predetermined threshold;
When the change rate determination means determines that the change rate of the specified speed is equal to or greater than a predetermined threshold, the image carrier motor control means is synchronized with the rotation of the image carrier motor in synchronism with the rotation of the intermediate transfer body motor. Change means,
An image forming apparatus comprising:   Further, when the change rate determining means determines that the change rate of the designated speed is less than a predetermined threshold value, the synchronization changing means sends the image carrier motor control means to the image carrier based on the designated speed. The image forming apparatus according to claim 1, wherein the rotation of the body motor is accelerated or decelerated. 3. The image forming apparatus according to claim 1, wherein the predetermined threshold value is a value of 10% or more with respect to a rotation speed at which an image can be formed by the image carrier motor.

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