JP5482338B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that starts an operation of forming an image to be transferred onto a sheet after a predetermined time has elapsed after the detection unit detects the leading edge of the sheet conveyed by the conveyance unit.

  2. Description of the Related Art Conventionally, in an image forming apparatus that forms an image using an electrophotographic image forming process, a timer is started when a registration sheet is turned on for a sheet (sheet) being transported, and when the timer finishes counting. A process using a registration technique for starting a process of forming a toner image to be transferred onto a sheet and aligning the sheet with a toner image formed on an image carrier (photosensitive member) has been put into practical use.

  In such an alignment technique, it is assumed that the rotation speed of the paper transport roller that transports the paper is stable (the paper transport speed is constant) when the paper being transported turns on the registration sensor. Therefore, the time value (timer value) set in the timer is set to a fixed value.

  However, when the paper being transported turns on the registration sensor, the motor that drives the paper transport roller is accelerating to a predetermined rotational speed, and the paper transport speed is not constant. Thus, if the fixed timer value is set assuming that the rotation speed of the paper transport roller is stable, the time from when the paper being transported turns on the registration sensor until the rotation speed of the paper transport roller stabilizes. Therefore, there is a problem that the position of the toner image on the photoconductor and the paper is shifted.

  In order to solve such a problem, for example, a conveying means is constructed so that the sheet being conveyed turns on the registration sensor while the rotation speed of the sheet conveying roller is stable, or the motor speed is increased in a short time. Although it is conceivable to use a motor having stable output characteristics, there are problems such as an increase in the size of the image forming apparatus and an increase in the cost of the motor.

  Japanese Patent Laid-Open No. 2004-260688 aims at performing printing processing at high speed by accurately matching the transfer start position of the sheet with the exposure start position of the image carrier, and detecting the sheet disposed between the transport unit and the transfer position. When the sensor detects the leading edge of the paper, there is disclosed one in which the transport speed of the paper transport unit is changed so that the image and the paper are aligned at the transfer position.

  Further, Patent Document 2 discloses a registration roller (based on the timing at which the passage states of a plurality of paper detection sensors are detected for the purpose of performing correction when the leading edge of the paper detection sensor is detected and aligning the position of the image and the paper. A device that controls the speed of the paper transport unit) is disclosed.

  Further, in Patent Document 3, the distance from the reference position where the leading edge of the sheet is positioned to the time when the sheet detection sensor detects the leading edge of the sheet is calculated. Even when the image is not detected, there is disclosed a device that can perform accurate conveyance control and jam detection.

  However, in the technologies disclosed in Patent Documents 1 and 2, it is necessary to use a motor having a capability of transporting paper at a speed higher than the transport speed necessary for the image forming process as a motor used in the paper transport unit. There is a problem that the cost increases.

  In the technique disclosed in Patent Document 3, when calculating the distance from the reference position where the leading edge of the paper is positioned until the paper detection sensor detects the leading edge of the paper, the speed of the paper conveying roller needs to be constant. As described above, there is a problem that the image forming apparatus becomes large.

  The present invention has been made in view of the above circumstances, and even when the rotation speed of the conveyance roller for conveying the sheet is not stable at the time when the detection unit detects the leading edge of the sheet being conveyed, the sheet and the toner It is an object of the present invention to appropriately perform image alignment.

The image forming apparatus according to the present invention is the image forming apparatus in which a predetermined time after the detecting unit detects the leading edge of the sheet conveyed by the conveying unit, and starts the image forming operation to be transferred onto the sheet. If the speed of the motor that is the drive source of the transport means has not reached a predetermined speed at the time when the detection means detects the leading edge of the sheet, the predetermined speed is determined according to the acceleration state of the motor at that time. Correction means for correcting the time in a direction to make the time larger than a specified value, and the correction means includes a time until the motor reaches a predetermined speed after the paper detection means detects the leading edge of the sheet and the time. The correction amount for the predetermined time is calculated using the movement distance of the sheet .

  The time to reach the predetermined speed and the moving distance may be stored in a correction table means that holds corresponding values according to the stage of acceleration of the motor.

  The apparatus further comprises speed table means for storing a stage of acceleration state of the motor and speed information set in the transport means according to the stage of the acceleration state, the data stored in the correction table means, and the speed table The data stored in the means may be configured to be able to compare one-to-one in correspondence with the stage of acceleration of the motor.

  When the user sets sheets on the tray, it is preferable to further include a single sheet feeding unit that feeds the sheets set on the tray one by one to the conveying unit.

  The correction table means may store a plurality of data sets composed of combinations of values of the time and the moving distance according to the type of sheet.

  According to the image forming apparatus of the present invention as described above, even when the rotation speed of the conveying roller that conveys the sheet is not stable at the time when the detection unit detects the leading edge of the sheet being conveyed, the sheet and the toner image The effect that it can align appropriately is acquired.

1 is a schematic configuration diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a hardware configuration in the image forming apparatus illustrated in FIG. 1. 1 is a functional block diagram of an image forming apparatus according to an embodiment of the present invention. 6 is a diagram illustrating an example of a correction value table for plain paper that is referred to when the CPU 31 drives a stepping motor 34. FIG. 6 is a timing chart for explaining the relationship between the speed of the conveyance roller 3 and the time Tm from when the registration sensor 18 is turned on to when the sub-scanning image gate signal is turned on according to the timing when the registration sensor 18 is turned on. . 6 is a flowchart illustrating an example of a printing process performed by the image forming apparatus according to the present exemplary embodiment. FIG. 7 is a flowchart of processing for adjusting image formation timing in accordance with the output of the registration sensor 18 in step S100 of FIG. It is a flowchart of the drive control process of the stepping motor 34 which CPU31 performs. An example of a thick paper correction value table that is referred to when the CPU 31 drives the stepping motor 34 is shown. FIG. 13 is a flowchart showing processing corresponding to FIG. 7 when the paper type of the paper 4 can be selected (continuing from FIG. 11). FIG. 11 is a flowchart showing processing corresponding to FIG. 7 when the paper type of the paper 4 can be selected (continuation of FIG. 10).

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
〔Example〕
FIG. 1 is a schematic configuration diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention. This image forming apparatus has a configuration in which image forming portions of respective colors are arranged along a conveying belt (endless moving means), and is called a so-called tandem type.

  In FIG. 1, there is a conveyance roller 3 that conveys a sheet (sheet) 4 that is fed from a sheet feed tray 1 by a sheet feed roller 2. A belt 5 is provided.

  In addition, a plurality of image forming units (electrophotographic process units) 6Bk, 6M, 6C, and 6Y are arranged in this order from the upstream side in the transport direction of the transport belt 5. The plurality of image forming units 6Bk, 6M, 6C, and 6Y have the same internal configuration except that the colors of the toner images to be formed are different. The image forming unit 6Bk forms a black image, the image forming unit 6M forms a magenta image, the image forming unit 6C forms a cyan image, and the image forming unit 6Y forms a yellow image.

  Therefore, in the following description, the image forming unit 6Bk will be specifically described. However, since the other image forming units 6M, 6C, and 6Y have the same configuration as the image forming unit 6Bk, the image forming units 6M, 6C, For each component of 6Y, only the symbols distinguished by M, C, and Y are displayed in the drawing in place of Bk attached to each component of the image forming apparatus 6Bk, and the description thereof is omitted.

  The conveyor belt 5 is an endless belt wound around a driving roller 7 and a driven roller 8 that are rotationally driven. The drive roller 7 is rotationally driven by a drive motor (not shown), and the drive motor, the drive roller 7 and the driven roller 8 are driven to move the conveying belt 5 which is an endless moving means. Functions as a means.

  At the time of image formation, the sheets 4 stored in the sheet feeding tray 1 are sent out in order from the uppermost one, conveyed to the conveying belt 5 by the conveying roller 3, and adsorbed to the conveying belt 5 by the electrostatic adsorption action and driven to rotate. Is conveyed to the first image forming unit 6Bk by the conveying belt 5 where the black toner image is transferred.

  The image forming unit 6Bk includes a photoconductor drum 9Bk as a photoconductor, a charger 10Bk arranged around the photoconductor drum 9Bk, an exposure device 11, a developing device 12Bk, a photoconductor cleaner (not shown), and the like. Yes. The exposure device 11 is configured to irradiate laser beams 14Bk, 14M, 14C, and 14Y that are exposure lights corresponding to image colors formed by the image forming units 6Bk, 6M, 6C, and 6Y.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 9Bk is uniformly charged by the charger 10Bk in the dark, and then exposed by the laser beam 14Bk corresponding to the black image from the exposure device 11, thereby forming an electrostatic latent image. It is formed. The developing device 12Bk visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photosensitive drum 9Bk.

  This toner image is transferred onto the sheet 4 by the action of the transfer unit 15Bk at a position (transfer position) where the photosensitive drum 9Bk and the sheet 4 on the conveying belt 5 are in contact with each other. By this transfer, an image of black toner is formed on the paper 4. After the transfer of the toner image is completed, the photosensitive drum 9Bk waits for the next image formation after unnecessary toner remaining on the outer peripheral surface is removed by the photosensitive cleaner.

  As described above, the sheet 4 on which the black toner image is transferred by the image forming unit 6Bk is conveyed to the next image forming unit 6M by the conveying belt 5. In the image forming unit 6M, a magenta toner image is formed on the photosensitive drum 9M by a process similar to the image forming process in the image forming unit 6Bk, and the toner image is superimposed on the black image formed on the paper 4. And is transcribed.

  The sheet 4 is further transported to the next image forming units 6C and 6Y, and a cyan toner image formed on the photosensitive drum 9C and a yellow toner image formed on the photosensitive drum 9Y by the same operation. Are superimposed on the paper 4 and transferred. Thus, a full-color image is formed on the paper 4. The sheet 4 on which the full-color superimposed image is formed is peeled off from the conveying belt 5 and fixed on the image by the fixing device 16, and then discharged to the outside of the image forming apparatus.

  In the image forming apparatus, a sheet sensor 17 for detecting the sheet 4 placed on a manual feed tray (not shown) and a registration sensor 18 for detecting that the sheet 4 is located in the vicinity of the registration position. Although the applications of these sensors will be described later.

FIG. 2 is a block diagram illustrating a hardware configuration of the image forming apparatus illustrated in FIG.
In FIG. 2, a CPU (Central Processing Unit) 31 reads and writes data stored in a RAM (Random Access Memory) 33 in accordance with a program stored in a ROM (Read Only Memory) 32 and an image forming apparatus. It controls each part which comprises.

  The stepping motor 34 drives the conveyance roller 3 and is rotated / stopped at a predetermined rotational speed by a stepping motor clock signal 35 output from the CPU 31. The stepping motor clock signal 35 is composed of four general A phase, B phase, A ′ phase (reverse phase of A phase), and B ′ phase (reverse phase of B phase). Drive control of -2 phase excitation is performed. Further, the conveying roller 3 is rotated / stopped by transmitting the driving force of the stepping motor 34 through a transmission mechanism such as a gear (not shown).

  The registration sensor 18 is composed of an appropriate paper sensor such as a photo interrupter, and outputs a Hi level signal to the CPU 31 while the paper 4 passes through the registration sensor 18.

  The controller 37 is configured to receive the sub-scanning image gate signal 36 from the CPU 31 and irradiate laser beams 14Bk, 14M, 14C, and 14Y that are exposure light via the exposure device 11 shown in FIG. Here, the sub-scanning image gate signal 36 is composed of four lines, and is assigned to each of Bk, M, C, and Y.

FIG. 3 is a block diagram for explaining functional blocks of the image forming apparatus according to the embodiment of the present invention.
In FIG. 3, a control unit 40 controls a series of operations of the image forming apparatus, and a computer interface unit 41 communicates various data with a terminal that issues a print request to the image forming apparatus. The image forming process unit 42 outputs image data of each color component to the controller based on the image data stored in the image memory unit 43, and also uses the image forming units 6Bk, 6M, 6C, 6Y is controlled to create a toner image, the conveyance roller 3 is driven based on the output signal of the registration sensor 18, and process control for transferring the toner image to the paper 4 is performed. In addition, the image forming process unit 42 corrects a misalignment when it is detected during printing.

  The image memory unit 43 is for storing image data transmitted from a terminal that issues a print request to the image forming apparatus, and the operation unit 44 displays the status of the image forming apparatus and displays information on the image forming apparatus. It is for accepting operation input.

  The print job management unit 45 is for managing the printing order of print jobs requested by the image forming apparatus, and the fixing unit 46 is provided on the paper 4 on which the toner image is transferred by the image forming process unit 42. The fixing device 16 applies heat and pressure to fix the toner image on the paper.

  The reading unit 47 is for converting image information (printing information) on the read document into an electrical signal, and the storage unit 48 is for storing the state of the image forming apparatus at a certain point in time.

  In the present embodiment, the stepping motor 34 that drives the conveying roller 3 is driven through from the stop state until a predetermined rotational speed is reached, and the driving of the stepping motor 34 will be described below.

  FIG. 4 shows an example of a correction value table for plain paper that is referred to when the CPU 31 drives the stepping motor 34. This correction value table for plain paper is referred to when a paper type called plain paper is used as the paper 4, and in order from the left column, a step No (step number) indicating the driving state of the stepping motor 34, A set value representing the time during which the step number continues, and a distance and time used for a correction calculation described later are stored.

  When starting to drive the stepping motor 34, the CPU 31 sets a value (800) described in the set value of step No. “1” for a timer function (not shown). When the timer is set, a signal for driving the stepping motor 34 for one step is output as the stepping motor clock signal 35 for a time corresponding to the set value (800) (for example, 4.75 [milliseconds]). .

  When the time set in the timer elapses, the CPU 31 sets the value (850) described in the set value of the next step No (ie, “2”) to the timer function again, and when the timer is set, the stepping motor 34 is turned on. Further, a signal for driving by one step is output as a stepping motor clock signal 35 for a time corresponding to the set value (850) (for example, 4.65 [milliseconds]).

  Thereafter, the CPU 31 similarly increments the step number by 1 in ascending order up to “20” while referring to the value in the correction value table for plain paper, sets the time in the timer, and sets the time in the timer. A signal for driving one step is output as a stepping motor clock signal 35, and the stepping motor 34 is driven through one step to drive the stepping motor 34 to a predetermined speed.

  Here, when the time set in the timer in Step No. “20” elapses, the process proceeds to Step No. “21”. At this time, the set value stored in the step No. “21” is “0”, but this value is used as a value for indicating completion of the through-up drive in the design agreement.

  If the set value is “0”, the CPU 31 thereafter sets the value (1750) of the set value at “20” of the previous step No. until the stepping motor 34 is stopped to the timer function. Then, the stepping motor 34 is driven at a constant speed.

  Note that the distance column and the time column in the correction value table for plain paper in FIG. 4 indicate that the registration sensor 18 is ON when the step number is n (n = 1 to 20), that is, while the stepping motor 34 is through-up. The distance (correction distance) traveled by the sheet 4 and the time (correction time) required for the rotation of the stepping motor 34 until the rotation speed reaches a constant speed is shown. For example, when the registration sensor 18 is turned on when the step number is “12”, the correction distance is 4.95 [mm] and the correction time is 29.25 [milliseconds].

Next, an operation when the paper 4 is transported by the transport roller 3 and the registration sensor 18 detects the paper 4 will be described.
FIG. 5 shows the time (sub-scanning time) from when the registration sensor 18 is turned on to when the sub-scanning image gate signal is turned on according to the speed of the conveying roller 3 (speed of the stepping motor 34) and the timing when the registration sensor 18 is turned on. The timing chart for demonstrating the relationship with the scanning image gate timer value) Tm is shown.

After the CPU 31 starts driving the stepping motor 34 and the conveying roller 3 rotates, the registration sensor 18 is detected at time t2 after the rotation speed of the conveying roller reaches a stable driving state at V [mm / sec]. When turned on, the distance from the CPU 31 to the position where the sub-scanning image gate signal 36 should be turned on (that is, from the distance from the registration sensor 18 to the transfer unit 15Bk to the transfer unit 15Bk from the exposure of the laser beam 14Bk to the photosensitive drum 9Bk When the value obtained by subtracting the distance (L) is L, the time (sub-scanning image gate timer value) Tm from when the registration sensor 18 is turned on to when the sub-scanning image gate signal 36 is turned on is expressed by the following equation (I). Can be represented.
Tm [seconds] = L / V (I)

  In this case, by turning on the sub-scanning image gate signal 36 after the time of the sub-scanning image gate timer value Tm calculated using the above equation (I) has elapsed after the registration sensor 18 is turned on, And the position of the paper 4 match.

  However, if the registration sensor 18 is turned on at time t1 during the through-up until the rotation speed of the transport roller 3 reaches V [mm / sec], the sub-scanning image gate timer is calculated using the above equation (I). When the value Tm is calculated, since the speed of the transport roller 3 does not reach a constant speed, the sheet does not advance by the distance L in Tm seconds, and the position of the image and the sheet is shifted.

  Therefore, in this embodiment, when the registration sensor 18 is turned on at the time t1 during the through-up until the rotation speed of the conveying roller 3 reaches V [mm / sec], the correction value table for plain paper in FIG. Using the correction distance and the correction time, the sub-scanning image gate timer value Tm is corrected and calculated as follows.

That is, when the registration sensor 18 is turned on at time t1 during the through-up until the rotation speed of the conveying roller 3 reaches V [mm / sec], the distance (correction distance) in the correction value table for plain paper is set. Assuming that L1 [mm] and time (correction time) are T1 [seconds], an image obtained when the registration sensor 18 is turned on during the through-up until the rotation speed of the transport roller 3 reaches V [mm / second] The sub-scanning image gate timer value Tm for aligning the paper position can be expressed by the following equation (II).
Tm [seconds] = (L−L1) ÷ V + T1 (II)

In this case, the part of “(L−L1) ÷ V” on the right side of the formula (II) indicates that the distance traveled by the sheet 4 at the speed V is shortened by the correction distance L1. Then, a correction time T1, which is a time required for the paper 4 to travel by the correction distance L1, is added. Thereby, Tm represented by the formula (II) corresponds to a time required to move to the target position at the speed V after the registration sensor 18 is turned on, through the through-up of the conveying roller 3.
Therefore, in this case, after the time of the sub-scanning image gate timer value Tm calculated using the above formula (II) has elapsed, the sub-scanning image gate signal 36 is turned on so that the image and the paper are aligned. become.

Next, a print processing operation performed by the image forming apparatus according to the present exemplary embodiment will be described.
FIG. 6 is a flowchart illustrating an example of a printing process performed by the image forming apparatus according to the present exemplary embodiment. In this flowchart, the processes of steps S100, S101, and S102 are repeatedly executed in order of 1 millisecond using the timer function and task switching function of the CPU 31 (not shown).

  In FIG. 6, step S <b> 100 is processing for detecting the state of the registration sensor 18. Step S101 is a process for carrying out a paper transport process during printing. Step S102 is processing for performing processing related to image formation during printing.

  Next, FIG. 7 shows a flowchart of processing for adjusting the image forming timing in accordance with the output of the registration sensor 18 in step S100 of FIG. In this process, the driving of the stepping motor 34 which is a driving unit is started, and the process from when the registration sensor 18 is turned on by detection of the paper 4 to when the sub-scanning image gate signal 36 is turned on is performed. The CPU 31 starts the process of FIG. 7 when feeding the paper 4.

  In the process of FIG. 7, the CPU 31 first initializes Step No. 1 for storing the driving state of the stepping motor 34 to 1 (S200), and starts driving the stepping motor 34 (S201). In step S201, the CPU 31 is set to start driving the stepping motor 34 and the initial setting value of the stepping motor clock signal 35 is set to drive the stepping motor 34. At the same time, the value of the set value corresponding to “1” of step No. is set in the timer function of the CPU 31 and the timer of the timer function is started at the same time.

  The subsequent drive control of the stepping motor 34 that has started driving here is realized by using a timer function and a timer interrupt function of the CPU 31 (not shown). Details of the drive control of the stepping motor 34 will be described with reference to FIG. Here, the CPU 31 has a plurality of independent timer functions and timer interrupt functions. For example, the timer function independent of the timer function used for the printing process shown in FIG. Used for and other processing.

  After step S201, the CPU 31 waits for the registration sensor 18 to turn on (NO loop of S202). When it is detected that the registration sensor 18 is turned on (the result of S202 is YES), it is confirmed whether or not the value of Step No is “21” (S203). If the value of Step No. is less than “21”, it can be seen that the stepping motor 34 (that is, the conveyance roller 3) is rotating through, and if Step No. is “21” or more, it is rotating at a constant speed.

  If the result of step S203 is NO, the stepping motor 34 is through-up. Therefore, the distance and time corresponding to step No at the time when the registration sensor 18 is turned on are acquired with reference to the above-mentioned plain paper correction value table, and the acquired distance and time values are substituted into L1 and T1, respectively. Then, the value of the sub-scanning image gate timer value Tm is calculated using the above equation (II) (S205).

  On the other hand, when the result of step S203 is YES, the stepping motor 34 is rotating at a constant speed. Therefore, the sub-scanning image gate timer value Tm is calculated based on the above-described equation (I) (S206).

  Next, timing of the sub-scanning gate timer value Tm calculated in step S205 or step S206 is started (S207), and waiting until the timing of the sub-scanning gate timer value Tm is completed (NO loop of S208).

  Then, when counting of the sub-scanning image gate timer value Tm is finished and the result of step S208 is YES, the CPU 31 starts outputting the sub-scanning image gate signal 36 (S209).

  As described above, by properly calculating the sub-scanning image gate timer Tm according to the operation state of the stepping motor 34 when the registration sensor 18 detects the paper 4, the paper 4 and the image can be aligned. Become. In particular, as in the case of a single-sheet manual feed tray (not shown), when the length of the sheet 4 being caught by the transport roller 3 is indefinite, the possibility that the registration sensor 18 is turned on during the through-up of the stepping motor 34 is increased. Therefore, this embodiment makes it possible to align with an image with little error.

Next, a specific example of driving the stepping motor 34 will be described.
FIG. 8 is a flowchart illustrating an example of drive control of the stepping motor 34. This process is initially started in step S201 of FIG. 7, and thereafter, the set value stored in the plain paper correction value table is set in the timer function of the CPU 31 every time the stepping motor 34 is driven by one step. When the timer of the timer function ends, the timer interrupt function of the CPU 31 executes the timer function.

  In the process of FIG. 8, the CPU 31 first checks whether or not the value of Step No is “21” of the final step (S300). If the result of step S300 is No, the value of step No is incremented by one (S301), and it is confirmed as a result of step S301 whether the value of step No is “21” of the final step (S302).

  Here, when the value of step N0 is less than “21” and the result of step S302 is NO, the value of the set value corresponding to the value of step No at that time is referred to the plain paper correction value table. Is acquired, and the acquired value is set in the timer function of the CPU 31, and at the same time, the timer function timer is started (S303).

  Further, when the result of step S302 is YES and when the result of step S300 is YES, the stepping motor 34 has already reached the constant speed since the through-up has been completed, and thus the rotation speed is continued. That is, a set value corresponding to the step No. value “20” in the correction value table for plain paper is acquired, and the acquired value is set in the timer function of the CPU 31 and at the same time, the timer of the timer function is started (S304). ).

  Next, a pulse of the next step is output to the A phase, B phase, A 'phase, and B' phase of the stepping motor clock signal 35 (S305). Here, the pulses (Hi level or Lo level) necessary for moving the stepping motor 34 in a predetermined direction step by step are set for the pulses output to the A phase, B phase, A ′ phase, and B ′ phase. To do. As a state to be set, a state corresponding to a pulse output method set by general two-phase excitation or 1-2 phase excitation can be applied.

  After the CPU 31 drives the stepping motor 34 step by step with reference to the plain paper correction value table by the above processing, the stepping motor 34 is slewed up from the stopped state and accelerated to the steady speed. It is driven at a constant speed.

  By the way, although the case where plain paper is used as the paper 4 has been described so far, thick paper having a thickness greater than that of the plain paper may be used as the paper 4. When thick paper is used as the paper 4, since the stiffness and slipperiness of the paper are different from the plain paper, a thick paper correction table as shown in FIG. 9 should be used instead of the plain paper correction table shown in FIG. Can be considered. In the thick paper correction table, the distance (correction distance) and time (correction time) are set longer than the normal paper correction table shown in FIG.

  FIG. 10 and FIG. 11 are flowcharts showing processing corresponding to FIG. 7 when the paper type (plain paper and thick paper) of the paper 4 can be selected. In this process, the process from the start of driving of the stepping motor 34, which is a drive means, to turning on the registration sensor 18, until turning on the sub-scanning image gate signal 36 is performed.

  In this case, when determining whether to use plain paper or thick paper, it can be determined by referring to information on the paper type designated in advance by the user. It is also possible to determine whether the paper is plain paper or thick paper by using a sensor for detecting the paper type of the paper 4 such as a sensor to be measured.

  In the process of FIG. 10, the CPU 31 first initializes step No. 1 for storing the driving state of the stepping motor 34 to 1 (S400), and starts driving the stepping motor 34 (S401). In step S401, the CPU 31 is set to start driving the stepping motor 34, and the initial setting value of the stepping motor clock signal 35 for driving the stepping motor 34 is set. At the same time, the value of the setting value corresponding to “1” of step No. is simultaneously set in the timer function of the CPU 31, and at the same time, the timer function timer is started.

  Then, it waits for the registration sensor 18 to turn on (NO loop of S402). When it is detected that the registration sensor 18 is turned on (YES in S402), it is confirmed whether or not the value of Step No. is “21” (S403). If the value of Step No. is less than “21”, it can be seen that the stepping motor 34 (that is, the conveyance roller 3) is rotating through, and if Step No. is “21” or more, it is rotating at a constant speed.

  If the result of step S403 is NO, the stepping motor 34 is through-up. Therefore, first, it is determined whether the paper type of the paper 4 is thick paper or plain paper (S404). When it is determined in S404 that the paper type of the paper 4 is plain paper (NO in S404), the plain paper correction value table described above with the distance and time corresponding to step No when the registration sensor 18 is turned on is displayed. The distance and time values acquired by referring to the values are substituted into L1 and T1, respectively (S405).

On the other hand, if it is determined in step S404 that the paper type of the paper 4 is thick paper (YES in S404), the above-described thick paper correction value table shows the distance and time corresponding to step No when the registration sensor 18 is turned on. And the obtained distance and time values are substituted into L1 and T1, respectively (S406).
Next, the value of the sub-scanning image gate timer value Tm is calculated using the above equation (II) using L1 and L1 into which the values are substituted in steps S405 and S406 (step S407).

  On the other hand, when the result of step S403 is YES, the stepping motor 34 is rotating at a constant speed. Therefore, the sub-scanning image gate timer value Tm is calculated based on the above equation (I) (S408).

  Next, timing of the sub-scanning gate timer value Tm calculated in step S407 or step S408 is started (S409), and waiting until the timing of the sub-scanning gate timer value Tm is completed (NO loop of S410).

  Then, when counting of the sub-scanning image gate timer value Tm is finished and the result of step S410 is YES, the CPU 31 starts outputting the sub-scanning image gate signal 36 (S411).

  As described above, by appropriately calculating the sub-scanning image gate timer Tm according to the paper type and the operation state of the stepping motor 34 when the registration sensor 18 detects the paper 4, the paper 4, the image, and the position Matching is possible.

  In the above-described embodiments, plain paper or cardboard is used as the paper type, but other sheets such as an OHP sheet can also be used, and in that case, depending on each paper type A correction table may be created and a correction table matched to the paper type to be used may be used.

  In the above-described embodiment, the case where the tandem type full-color image forming apparatus shown in FIG. 1 is applied has been described. However, the present invention is similarly applied to a monochrome image forming apparatus capable of monochrome printing. Can do.

  A program for realizing the above-described various control processing procedures executed by the CPU 31 may be stored in a storage means such as a ROM, HDD, or SSD provided in the computer from the beginning, but may be a recording medium such as a CD. -Non-volatile recording media such as ROM or flexible disk, MO, CD-R, CD-RW, DVD + R, DVD + RW, DVD-R, DVD-RW, or DVD-RAM, SRAM, NOV-RAM, EEPROM, memory card, etc. (Memory) can also be recorded and provided. Each procedure described above can be executed by installing a program recorded in the memory in a computer and causing the CPU to execute the program, or causing the CPU to read and execute the program from the memory.

  Furthermore, it is also possible to download and execute an external device that is connected to a network and includes a recording medium that records the program, or an external device that stores the program in the storage unit.

  In addition, the configurations and modifications of the embodiments described above can be applied in appropriate combinations within a consistent range.

  The present invention can be applied to an image forming apparatus that uses an image forming process other than an electrophotographic process as long as the image forming apparatus forms an image on a sheet. Further, the present invention can be similarly applied to a copying machine, a printer device, a facsimile device, and a so-called multifunction device having a combination of functions of these devices.

  3: transport roller, 18: registration sensor, 31: CPU (central processing unit), 32: ROM (read only memory), 33: RAM (random access memory), 34: stepping motor, 35: stepping motor Clock signal 36: Sub-scanning image gate signal 37: Controller 40: Control unit 41: Computer interface unit 42: Image forming process unit 43: Image memory unit 44: Operation unit 45: Print job management unit 46: fixing unit, 47: reading unit, 48: storage unit.

JP-A-2005-352448 JP 2005-320093 A JP2008-174358

Claims (5)

In an image forming apparatus that starts a forming operation of an image to be transferred onto the sheet after a predetermined time from the detection unit detecting the leading edge of the sheet conveyed by the conveying unit,
When the speed of the motor that is the drive source of the transport means has not reached a predetermined speed at the time when the paper detection means detects the leading edge of the sheet, according to the acceleration state of the motor at that time, A correction unit that corrects the predetermined time in a direction larger than a specified value ;
The correction means uses the time from when the paper detection means detects the leading edge of the sheet until the motor reaches a predetermined speed and the moving distance that the sheet moves at that time, and the correction amount for the predetermined time An image forming apparatus that calculates The image forming apparatus according to claim 1 ,
The time required to reach the predetermined speed and the moving distance are stored in a correction table means that holds corresponding values according to the stage of acceleration of the motor. The image forming apparatus according to claim 2 ,
A speed table means for storing a stage of the acceleration state of the motor and speed information set in the transport means according to the stage of the acceleration state;
The data stored in the correction table means and the data stored in the speed table means are configured so that they can be compared on a one-to-one basis corresponding to the stage of acceleration of the motor. Image forming apparatus. The image forming apparatus according to any one of claims 1 to 3 ,
An image forming apparatus, further comprising a single sheet feeding unit that feeds sheets set on the tray one by one to the conveying unit when a user sets a sheet on the tray. The image forming apparatus according to claim 2 , wherein
The image forming apparatus according to claim 1, wherein the correction table unit stores a plurality of data sets composed of combinations of values of the time and the moving distance in accordance with the type of sheet.

Images