JP6497339B2 - Motor control device, image forming apparatus, and motor control method - Google Patents

Description

  The present invention relates to a motor control device, an image forming apparatus, and a motor control method for controlling a motor.

  An image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine is provided with a plurality of conveyance rollers for conveying a sheet, and these conveyance rollers are driven by a motor. As such a motor, a DC motor (including a brushless DC motor) may be used.

  When the DC motor is driven at a constant speed, it is known that the value of the current flowing through the motor changes according to the load amount. In view of this, there is an image forming apparatus capable of detecting a fixing load abnormality by detecting a current value flowing through a motor and determining whether or not the detected current value is within a reference range (for example, Patent Documents). 1).

JP 2007-206204 A

  However, in the above image forming apparatus, since it is necessary to detect the value of the current flowing through the motor, for example, an existing unit in which a motor driver and a motor are integrated cannot be used.

  An object of the present invention is to provide a motor control device, an image forming apparatus, and a motor control method capable of determining whether or not a motor is in an overload state without significantly changing an existing configuration. is there.

  A motor control device according to one aspect of the present invention includes a speed command unit, a speed detection unit, a motor control unit, a duty ratio detection unit, and an overload determination unit. The speed command unit outputs a speed command signal indicating a command rotation speed. The speed detector detects an actual rotation speed of the motor. The motor control unit supplies a PWM signal whose duty ratio is feedback controlled in accordance with the actual rotation speed to a motor driver that controls the motor based on the speed command signal. The duty ratio detection unit detects a duty ratio of the PWM signal supplied to the motor driver. The overload determination unit determines whether the motor is in an overload state based on the duty ratio detected by the duty ratio detection unit.

  An image forming apparatus according to another aspect of the present invention includes the motor control device and an image forming unit that forms an image on a sheet.

  A motor control method according to another aspect of the present invention includes a speed command step, a speed detection step, a motor control step, a duty ratio detection step, and an overload determination step. In the speed command step, a speed command signal indicating the command rotation speed is output. In the speed detection step, the actual rotational speed of the motor is detected. In the motor control step, based on the speed command signal, a PWM signal whose duty ratio is feedback-controlled according to the actual rotational speed is supplied to a motor driver that controls the motor. In the duty ratio detection step, a duty ratio of the PWM signal supplied to the motor driver is detected. In the overload determination step, it is determined whether or not the motor is in an overload state based on the duty ratio detected in the duty ratio detection step.

  According to the present invention, there are provided a motor control device, an image forming apparatus, and a motor control method capable of determining whether or not a motor is in an overload state without greatly changing an existing configuration.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of the motor control device in the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of an input signal and an output signal of the overload determination unit in the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a flowchart showing an example of the procedure of the motor speed control process executed in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a block diagram showing a configuration of a modified example of the motor control device in the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, embodiment described below is only an example which actualized this invention, and does not limit the technical scope of this invention.

[Configuration of Image Forming Apparatus]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 10 according to an embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 is a printer that prints an image on a sheet using toner. The present invention is not limited to a printer, and can be applied to, for example, an image forming apparatus such as a facsimile, a copier, or a multifunction machine having these functions. Furthermore, the present invention is not limited to an image forming apparatus, and can be applied to an arbitrary apparatus including a motor such as a scanner.

  The image forming apparatus 10 prints an image on a sheet based on image data input from the outside via a network communication unit (not shown). The image forming apparatus 10 includes a paper feed unit 15, an image forming unit 18, a fixing unit 19, a paper discharge unit 21, a control unit 90, and a motor control device 60 (see FIG. 2).

  The paper feed unit 15 includes a paper feed tray 50, a pickup roller 51, and a paper feed roller pair 52. When an instruction to start the sheet feeding operation is input to the image forming apparatus 10, the sheet is fed from the paper feed tray 50 by the pickup roller 51 and the paper feed roller pair 52. The sheet fed by the pickup roller 51 is conveyed to the first conveyance path 26 formed on the downstream side in the sheet feeding direction by the sheet feeding roller pair 52.

  A plurality of conveyance rollers 44 and a plurality of rotating rollers 45 are arranged in the first conveyance path 26. The sheet fed to the first transport path 26 by the pair of paper feed rollers 52 is transported to the image forming unit 18 while being sandwiched between the transport roller 44 and the rotating roller 45.

  The image forming unit 18 includes a photosensitive drum 31, a charging unit 32, a developing unit 33, an exposure unit 34, a transfer unit 35, and a cleaning unit 36. The image forming unit 18 forms an image on the sheet by transferring the toner image formed based on the image data onto the sheet.

  The sheet on which the toner image has been transferred is conveyed to the fixing unit 19 through the second conveyance path 27. The fixing unit 19 fixes the toner image transferred on the sheet to the sheet by the heating roller 41 and the pressure roller 42.

  The sheet on which the image has been fixed by the fixing unit 19 is conveyed by a pair of paper discharge rollers 23 provided in the third conveyance path 28 and is discharged from the paper discharge port 22 to the paper discharge unit 21.

  The control unit 90 is a microcomputer configured with, for example, a CPU, a ROM, a RAM, and the like. The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage unit used as a primary storage memory (working area) for various processes executed by the CPU. The control unit 90 performs overall control of the operation of the image forming apparatus 10 by the CPU executing a program stored in the ROM.

[Configuration of motor controller]
As shown in FIG. 2, the image forming apparatus 10 includes driven bodies such as a pickup roller 51, a paper feed roller pair 52, a transport roller 44, a heating roller 41, a pressure roller 42, and a paper discharge roller pair 23. A motor 70 for driving 80, a motor driver 71, and a motor control device 60 for controlling the motor 70 are provided. The driven body 80 also includes a driving force transmission mechanism such as a gear (not shown) for transmitting the driving force generated by the motor 70.

  For example, the motor 70 is integrated with a motor driver 71 for driving the motor 70. The motor 70 is a DC motor, for example.

  The motor control device 60 performs control for rotating the motor 70 at a desired rotation speed. The motor control device 60 includes a control unit 61, a motor control unit 62, a speed detection unit 63, a duty ratio detection unit 64, and an overload determination unit 65.

  The control unit 61 is, for example, an engine control unit that executes processing related to print processing in response to an instruction from the control unit 90. The control unit 61 is, for example, a microcomputer configured with a CPU, a ROM, a RAM, or the like, or an integrated circuit (ASIC). The control unit 61 functions as a speed command unit 611 when the CPU executes a program stored in the ROM.

  The speed command unit 611 outputs a speed command signal Sa indicating the command rotation speed in response to an instruction from the control unit 90 (speed command step). The speed command signal Sa may be, for example, a clock signal (pulse signal) having a frequency corresponding to the command rotational speed.

  The speed detector 63 detects the actual rotational speed of the motor 70 (speed detection step). The speed detector 63 is a rotary encoder provided on the motor shaft of the motor 70, for example. A signal Sc corresponding to the actual rotational speed of the motor 70 is output from the speed detector 63. The signal Sc is a pulse signal having a frequency corresponding to the actual rotational speed of the motor 70, for example.

  The motor control unit 62 is, for example, a microcomputer configured with a CPU, a ROM, a RAM, or the like, or an integrated circuit (ASIC). The motor control unit 62 supplies the PWM signal Sb to the motor driver 71 based on the speed command signal Sa output from the speed command unit 611. At this time, the duty ratio of the PWM signal Sb is feedback-controlled based on the signal Sc so that the actual rotation speed detected by the speed detection unit 63 matches the command rotation speed indicated by the speed command signal Sa. . That is, based on the speed command signal Sa, the motor control unit 62 supplies the motor driver 71 with a PWM signal Sb whose duty ratio is feedback-controlled according to the actual rotational speed (motor control step).

  The motor driver 71 supplies a current corresponding to the PWM signal Sb to the motor coil, and the motor shaft rotates. As the duty ratio of the PWM signal Sb increases, a larger current flows through the motor 70 (motor coil), and the rotation speed of the motor 70 (motor shaft) increases.

  By the way, when driving a DC motor at a constant speed, it is known that the value of the current flowing through the motor changes according to the load amount. In view of this, there is an image forming apparatus capable of detecting a fixing load abnormality by detecting a current value flowing through a motor and determining whether or not the detected current value is within a reference range. However, in such an image forming apparatus, since it is necessary to detect the current value flowing through the motor, for example, an existing unit in which a motor driver and a motor are integrated cannot be used.

  On the other hand, in the image forming apparatus 10 according to the present embodiment, the PWM signal Sb supplied from the motor control unit 62 to the motor driver 71 is not directly detected as described below. Is detected, it is determined whether or not the motor 70 is in an overload state (that is, whether or not an abnormal current is flowing in the motor 70).

  The duty ratio detection unit 64 detects the duty ratio of the PWM signal Sb supplied from the motor control unit 62 to the motor driver 71 (duty ratio detection step). The duty ratio detection unit 64 is, for example, an RC low-pass filter composed of a resistor and a capacitor as shown in FIG. By such an RC low pass filter, the PWM signal Sb is converted into a duty ratio signal Sd having a voltage corresponding to the duty ratio of the PWM signal Sb.

  The overload determination unit 65 determines whether or not the motor 70 is in an overload state based on the duty ratio detected by the duty ratio detection unit 64 (overload determination step). For example, as shown in FIG. 2, the overload determination unit 65 is a comparator that compares the voltage of the duty ratio signal Sd with a predetermined threshold voltage Vsh. The overload determination unit 65 outputs a signal Se that indicates whether or not the motor 70 is in an overload state. For example, as shown in FIG. 3, the signal Se is at a low level while the voltage of the duty ratio signal Sd does not exceed the threshold voltage Vsh, and while the voltage of the duty ratio signal Sd exceeds the threshold voltage Vsh. Become high level.

  Incidentally, as described above, the duty ratio of the PWM signal Sb is feedback-controlled so that the rotation speed of the motor 70 (the actual rotation speed) matches the command rotation speed. Therefore, even if the command rotational speed is constant, when the load on the motor 70 increases, the current supplied to the motor 70 increases accordingly.

  There are various causes for the load of the motor 70 increasing. For example, the load on the motor 70 increases due to aging degradation of the image forming apparatus 10, scraping of gears included in the driven body 80, jamming of sheets, and the like. If the state in which the current supplied to the motor 70 is abnormally large (overload state) continues, abnormal heat generation or failure of the motor 70 may occur.

  Therefore, in the present embodiment, the speed command unit 611 stops the motor 70 when it is determined that the motor 70 is in an overload state for a certain time or more based on the determination result of the overload determination unit 65. For example, the speed command unit 611 monitors the signal Se output from the overload determination unit 65, and stops the motor 70 when the state where the voltage level of the signal Se is at a high level continues for 5 seconds or more, for example. As a result, the current flowing through the motor 70 becomes 0, and the motor 70 can be prevented from being broken or abnormally heated. If the duration of the overload state is less than 5 seconds, for example, it is determined that there is a low possibility of abnormal heat generation or failure of the motor 70, so the speed command unit 611 continues to drive the motor 70. May be.

[Speed command section]
Hereinafter, an example of the procedure of the motor speed control process executed by the speed command unit 611 will be described with reference to FIG. Here, steps S1, S2,... Represent processing procedure (step) numbers executed by the speed command unit 611. The motor speed control process is started, for example, in response to a print instruction from the control unit 90, and then ended in response to the completion of the print process.

<Step S1>
In step S <b> 1, the speed command unit 611 starts outputting the speed command signal Sa in response to a print instruction from the control unit 90.

<Step S2>
In step S2, the speed command unit 611 determines whether the motor 70 is in an overload state based on the signal Se output from the overload determination unit 65. When it is determined that the motor 70 is in an overload state (S2: Yes), the process proceeds to step S3. On the other hand, when it is determined that the motor 70 is not overloaded (S2: No), the process returns to step S2.

<Step S3>
In step S3, the speed command unit 611 determines whether or not the overload state has continued for a certain time or more. If it is determined that the overload state has continued for a certain period of time (S3: Yes), the process proceeds to step S4. On the other hand, if it is determined that the overload state has not continued for a certain time (S3: No), the process returns to step S2.

<Step S4>
In step S <b> 4, the speed command unit 611 stops the motor 70.

  As described above, according to the present embodiment, it is determined whether the motor 70 is in an overload state based on the duty ratio of the PWM signal Sb supplied from the motor control unit 62 to the motor driver 71. Therefore, for example, an existing unit in which the motor driver 71 and the motor are integrated can be used. It is possible to determine whether the motor is in an overload state without significantly changing the existing configuration.

  In the present embodiment, the duty ratio detection unit 64 and the overload determination unit 65 are configured by a circuit as shown in FIG. 2, but the present invention is not limited to this. In another embodiment, one or both of the duty ratio detection unit 64 and the overload determination unit 65 may be configured with a circuit different from that in FIG. 2 or may be configured with software.

[Modification of motor controller]
A configuration in which an abnormality of the driven body 80 is detected based on the duty ratio of the PWM signal Sb will be described below as a modification of the motor control device 60 of the present embodiment.

  FIG. 5 is a diagram illustrating a configuration of a modified example of the motor control device 60. The modification shown in FIG. 5 is different from the configuration shown in FIG. 2 only in that the control unit 61 further includes an abnormality detection unit 612. Therefore, the description of the configuration other than the abnormality detection unit 612 is omitted.

  The abnormality detection unit 612 is supplied with a signal Sf output from the speed command unit 611 and a duty ratio signal Sd output from the duty ratio detection unit 64. The signal Sf is a signal indicating the command rotational speed.

  As described above, when the command rotational speed is constant, the duty ratio detected by the duty ratio detection unit 64 increases as the load on the motor 70 increases. On the other hand, when the load of the motor 70 is constant, the duty ratio detected by the duty ratio detection unit 64 decreases as the command rotational speed decreases. Here, if the duty ratio detected by the duty ratio detection unit 64 is large even though the command rotational speed is low, the load of the motor 70 is increased for some reason. That is, it can be determined that some abnormality has occurred in the driven body 80.

  The abnormality detection unit 612 detects an abnormality of the driven body 80 driven by the motor 70 based on the command rotational speed and the duty ratio detected by the duty ratio detection unit 64. For example, the abnormality detection unit 612 can determine that there is an abnormality in the driven body 80 when the ratio of the duty ratio to the command rotational speed is greater than a predetermined ratio. Thereby, even if the command rotational speed is low, it can be determined that the driven body 80 is abnormal.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 18 Image forming part 19 Fixing part 21 Paper discharge part 22 Paper discharge port 23 Paper discharge roller pair 26 1st conveyance path 27 2nd conveyance path 28 3rd conveyance path 31 Photosensitive drum 32 Charging part 33 Developing part 34 Exposure unit 35 Transfer unit 36 Cleaning unit 41 Heating roller 42 Pressure roller 44 Transport roller 45 Rotating roller 50 Paper feed tray 51 Pickup roller 52 Paper feed roller pair 64 Duty ratio detection unit 65 Overload determination unit 71 Motor driver

Claims (8)

A speed command unit that outputs a speed command signal indicating the command rotation speed;
A speed detector that detects the actual rotational speed of the motor;
Based on the speed command signal, a motor control unit that supplies a PWM signal whose duty ratio is feedback controlled according to the actual rotational speed to a motor driver that controls the motor;
A duty ratio detector for detecting a duty ratio of the PWM signal supplied to the motor driver;
An overload determination unit that determines whether or not the motor is in an overload state based on the duty ratio detected by the duty ratio detection unit;
Based on the command rotational speed and the duty ratio detected by the duty ratio detection unit, an abnormality detection unit that detects an abnormality of the driven body driven by the motor;
With
The abnormality detection unit determines that the driven body is abnormal when a ratio of the duty ratio to the command rotational speed is larger than a predetermined ratio.
Motor control device.   2. The motor control device according to claim 1, wherein the duty ratio detection unit is an RC low-pass filter that converts the PWM signal into a duty ratio signal having a voltage corresponding to the duty ratio of the PWM signal.   The motor control device according to claim 2, wherein the overload determination unit is a comparator that compares the voltage of the duty ratio signal with a predetermined threshold voltage.   The speed command unit stops the motor when the motor is determined to be in an overload state for a predetermined time or more based on a determination result of the overload determination unit. Motor control device. In the state where the command rotational speed is constant, the abnormality detection unit detects an abnormality in the driven body when a ratio of the duty ratio to the command rotational speed is larger than the predetermined ratio. The motor control device according to claim 1, wherein the motor control device can be determined to be present . The motor control device according to any one of claims 1 to 5 ,
An image forming unit that forms an image on a sheet;
An image forming apparatus comprising: A speed command step for outputting a speed command signal indicating the command rotation speed;
A speed detection step for detecting the actual rotation speed of the motor;
A motor control step of supplying a PWM signal whose duty ratio is feedback controlled in accordance with the actual rotational speed based on the speed command signal to a motor driver that controls the motor;
A duty ratio detection step of detecting a duty ratio of the PWM signal supplied to the motor driver;
An overload determination step of determining whether or not the motor is in an overload state based on the duty ratio detected in the duty ratio detection step;
An abnormality detection step of detecting an abnormality of the driven body driven by the motor based on the command rotational speed and the duty ratio detected by the duty ratio detection unit;
With
In the abnormality detection step, when the ratio of the duty ratio to the command rotational speed is larger than a predetermined ratio, it is determined that the driven body is abnormal.
Motor control method. In the abnormality detection step, when the ratio of the duty ratio to the command rotation speed is larger than the predetermined ratio in a state where the command rotation speed is constant, an abnormality occurs in the driven body. The motor control method according to claim 6, wherein it can be determined that the motor is present.