JP7534931B2 - MOTOR CONTROL DEVICE, SHEET CONVEYING DEVICE, AND IMAGE FORMING APPARATUS - Google Patents

Description

The present invention relates to motor drive control.

In recent years, there has been a demand for faster image formation speeds in image forming devices and for image formation on various types of recording materials (e.g., cardboard). To achieve this, there is a demand for higher output motors used to drive loads such as conveyor rollers and fixing devices in image forming devices.

As a configuration for achieving high motor output, a configuration in which the same load is driven by multiple motors is known (for example, Patent Documents 1 and 2). In such a configuration, for example, one motor is driven by feedback control, and the other motors are rotated at a constant rotational speed to assist the driving of the load by the one motor.

JP 2014-240869 A JP 2008-222334 A

In an image forming apparatus, in order to prevent uneven gloss in the formed image and waviness in the recording material, it is required that the load to be driven be rotated at a constant speed. However, when feedback control of the rotation speed of only one motor is performed as described above, it is difficult to suppress fluctuations in the rotation speed of the load due to load fluctuations. Even if such fluctuations are suppressed by feedback control of the rotation speed of multiple motors, if deviations in rotation speed occur between the motors for some reason, it becomes difficult to appropriately control the ratio of torque that each motor outputs to the load. As a result, it becomes impossible to rotate the load to be driven at a constant speed. In other words, the rotation of the load becomes unstable.

Therefore, the present invention aims to make it possible to prevent the rotation of the load from becoming unstable.

A motor control device according to one aspect of the present invention comprises a first control means for controlling a first motor that drives a load, a second control means for controlling a second motor that outputs a driving force to assist the first motor in driving the load, and an acquisition means for acquiring a fluctuation component of the rotational speed of the load based on a first signal corresponding to the rotational speed of the first motor or a second signal corresponding to the rotational speed of the second motor, wherein the first control means controls the first motor based on a first command value representing a target rotational speed of the first motor and the first signal, and the second control means controls the second motor based on a second command value representing the target rotational speed of the second motor and the fluctuation component acquired by the acquisition means so that the rotational speed of the second motor fluctuates in the opposite phase to the fluctuation component with respect to the target rotational speed indicated by the second command value.

An image forming apparatus according to one aspect of the present invention is characterized in that it comprises a first motor for driving a load, a second motor for outputting a driving force to assist the first motor in driving the load, a first output means for outputting a first signal corresponding to a rotational speed of the first motor, a second output means for outputting a second signal corresponding to the rotational speed of the second motor, a first control means for controlling the first motor based on a first command value representing a target rotational speed of the first motor and the first signal, an acquisition means for acquiring a fluctuation component of the rotational speed of the load based on the first signal or the second signal , and a second control means for controlling the second motor based on a second command value representing the target rotational speed of the second motor and the fluctuation component acquired by the acquisition means so that the rotational speed of the second motor fluctuates in the opposite phase to the fluctuation component with respect to the target rotational speed indicated by the second command value.

The present invention makes it possible to prevent the rotation of the load from becoming unstable.

FIG. 1 is a diagram showing an example of the overall configuration of an image forming apparatus; FIG. 1 is a block diagram showing an example of a control configuration of an image forming apparatus. FIG. 2 is a diagram showing an example of a driving configuration of the pressure roller 16; FIG. 13 is a diagram showing an example of a control configuration for motors M1 and M2 in a first comparative example; FIG. 13 is a diagram showing an example of an FG signal obtained in a control configuration of Comparative Example 1. FIG. 11 is a diagram showing an example of a control configuration for motors M1 and M2 in a comparative example 2. FIG. 13 is a diagram showing an example of an FG signal obtained in a control configuration of Comparative Example 2. FIG. 2 is a diagram showing an example of a control configuration for motors M1 and M2 in the embodiment; FIG. 13 is a diagram showing an example of the frequency characteristics of a BPF to which an FG signal is input; FIG. 13 is a diagram showing an example of an FG signal obtained in the control configuration of the embodiment; A flowchart showing a procedure for controlling the drive of the motors M1 and M2.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any combination. In addition, the same reference numbers are used for the same or similar configurations, and duplicate descriptions are omitted.

<Image forming apparatus>
FIG. 1 shows an example of the configuration of an image forming apparatus in which a motor control device according to an embodiment of the present invention is implemented. The image forming apparatus 100 shown in FIG. 1 is an electrophotographic image forming apparatus that forms a multi-color image using yellow (Y), magenta (M), cyan (C) and black (K) developers (toners). However, the image forming apparatus 100 may be an image forming apparatus that forms a monochromatic image using a monochromatic developer. The image forming apparatus 100 may be, for example, a printing device, a printer, a copier, a multifunction peripheral (MFP) or a facsimile machine, or may be an image forming apparatus that employs a recording method other than the electrophotographic method (such as an inkjet method). The suffixes Y, M, C and K of the reference symbols indicate that the colors of the developer (toner) targeted by the corresponding member are yellow, magenta, cyan and black, respectively. In the following description, when it is not necessary to distinguish between colors, reference symbols without the suffixes Y, M, C and K are used.

The image forming apparatus 100 forms an image on a recording material S based on image data received from an external device via a network. The image forming apparatus 100 has four image forming units that respectively form toner images of yellow (Y), magenta (M), cyan (C) and black (K). The image forming unit that forms the yellow (Y) toner image has a photosensitive drum 1Y, a charger 2Y, a laser scanner 3Y, a developer 4Y, a primary transfer roller 5Y and a cleaning device 7Y. The image forming units that form the magenta (M), cyan (C) and black (K) toner images have the same configuration as the image forming unit that forms the yellow (Y) toner image.

The formation of a yellow (Y) toner image will be described below, but the formation of magenta (M), cyan (C), and black (K) toner images is similar. An image signal generated based on image data received from an external device is input to the laser scanner 3Y. The laser scanner 3Y is equipped with a semiconductor laser and a polygon mirror, and outputs laser light modulated by the input image signal from the semiconductor laser. The laser light output from the semiconductor laser is reflected by the polygon mirror and irradiated onto the surface of the photosensitive drum 1Y, thereby exposing the photosensitive drum 1Y. An electrostatic latent image is formed on the photosensitive drum 1Y by exposing the photosensitive drum 1Y, the surface of which has been uniformly charged by the charger 2Y.

The electrostatic latent image formed on the photosensitive drum 1Y is developed with toner supplied from the developing device 4Y, forming a yellow (Y) toner image on the photosensitive drum 1Y. As the photosensitive drum 1Y rotates, the toner image on the photosensitive drum 1Y moves to position T1 facing the primary transfer roller 5Y. The primary transfer roller 5Y transfers the toner image on the photosensitive drum 1Y to the intermediate transfer belt 6 by applying a primary transfer bias of the opposite polarity to the charging polarity of the toner (from the high voltage control unit 155 shown in FIG. 2). The cleaning device 7Y cleans the surface of the photosensitive drum 1Y by collecting the toner remaining on the surface of the photosensitive drum 1Y after the toner image is transferred to the intermediate transfer belt 6.

Similar to the yellow (Y) toner image, magenta (M), cyan (C) and black (K) toner images are formed on the photosensitive drums 1M, 1C and 1C, respectively. The toner images formed on the photosensitive drums 1Y, 1M, 1C and 1C, respectively, are transferred in order onto the intermediate transfer belt 6 in a superimposed state. As a result, a multi-color toner image is formed on the intermediate transfer belt 6. The toner image is transported toward a position (secondary transfer portion) T2 between the secondary transfer roller 8 and the opposing roller 9 as the peripheral surface of the intermediate transfer belt 6 moves.

The recording material S set by the user is stored in the paper feed cassette 10. The recording material S is fed from the paper feed cassette 10 to the transport path by the paper feed roller 11 and sent towards the registration roller pair 12. The recording material S is transported to the registration roller pair 12, which is in a stopped state, and temporarily stops with its leading edge abutting against the registration roller pair 12. The registration roller pair 12 is driven in synchronization with the timing at which the toner image on the intermediate transfer belt 6 reaches the secondary transfer section T2, so that the recording material S is sent towards the secondary transfer section T2.

The secondary transfer roller 8 transfers the toner image from the intermediate transfer belt 6 to the recording material S at the secondary transfer section T2 by applying a bias voltage (from the high voltage control section 155 shown in FIG. 2). The recording material S to which the toner image has been transferred is transported to the fixing device 14. The cleaning device 13 cleans the surface of the intermediate transfer belt 6 by collecting toner remaining on the surface of the intermediate transfer belt 6 after the toner image has been transferred to the recording material S.

The fixing device 14 includes a fixing roller 15 and a pressure roller 16. The fixing roller 15 includes a heater (fixing heater 161 in FIG. 2) inside, and is heated by the heater. The fixing roller 15 is configured to heat the recording medium S, and the pressure roller 16 is configured to pressurize the recording material S. The fixing device 14 uses the fixing roller 15 and the pressure roller 16 to perform a fixing process in which the toner image (image) formed by the image forming unit is fixed to the recording material S. Specifically, while the recording material S is being conveyed while being sandwiched between the fixing roller 15 and the pressure roller 16, the fixing roller 15 and the pressure roller 16 apply heat and pressure to the recording material S. As a result, the toner image on the recording material S is fixed to the recording material. The recording material S that has been fixed by the fixing device 14 is discharged to the outside of the image forming apparatus 100 by the paper discharge roller 17.

In order to realize image formation on various types of recording materials (e.g., thin paper, thick paper, glossy paper, film, etc.) in such an image forming apparatus, it is necessary to increase the amount of heat and pressure that can be applied to the recording material in the fixing process. Increasing the pressure in the fixing process increases the torque for driving the pressure roller 16. Therefore, in the image forming apparatus 100 of this embodiment, two motors (motors M1 and M2) are used as the driving source for the pressure roller 16 of the fixing device 14. The pressure roller 16 is rotated by being driven by the motors M1 and M2 via the corresponding gears. The fixing roller 15 rotates following the rotation of the pressure roller 16.

In this embodiment, motors M1 and M2 are examples of multiple motors that drive the same load, and motor M2 is configured to assist motor M1 in driving the load. Motor M1 is an example of a first motor that drives a load, and motor M2 is an example of a second motor that outputs a driving force to assist motor M1 in driving the load.

<Control configuration>
Fig. 2 is a block diagram showing an example of a control configuration of the image forming apparatus 100. The system controller 150 shown in Fig. 2 includes a CPU 150a, a ROM 150b, and a RAM 150c, and controls the entire image forming apparatus 100. The system controller 150 is connected to an image processing unit 151, an operation unit 152, an analog-to-digital (A/D) converter 153, a high voltage control unit 155, a motor control unit 157, sensors 159, and an AC driver 160. The system controller 150 is capable of transmitting and receiving data to and from each unit connected thereto.

The CPU 150a reads and executes various programs stored in the ROM 150b to execute various sequences related to a predetermined image formation sequence. The RAM 150c is a volatile storage device. The RAM 150c is used as a work area for the CPU 150a to execute various programs, and is also used as a temporary storage area in which various data is temporarily stored. The RAM 150c stores data such as setting values for the high voltage control unit 155, command values for the motor control unit 157, and information received from the operation unit 152.

The system controller 150 accepts settings made by the user via the operation unit 152 by controlling the operation unit 152 to display an operation screen on a display unit provided on the operation unit 152, which allows the user to make various settings. The system controller 150 receives information indicating the contents of the settings made by the user via the operation unit 152 from the operation unit 152. The system controller 150 also transmits data to the operation unit 152 for informing the user of the status of the image forming device. The operation unit 152 displays information indicating the status of the image forming device on the display unit based on the data received from the system controller 150.

The system controller 150 (CPU 150a) transmits setting data of each device in the image forming apparatus 100 required for image processing in the image processing unit 151 to the image processing unit 151. The system controller 150 also receives signals from each device (such as signals from sensors 159) and controls the high voltage control unit 155 based on the received signals. The high voltage control unit 155 supplies the voltage required for each operation to each device constituting the high voltage unit 156 based on the setting values set by the system controller 150. The high voltage unit 156 is composed of chargers 2 (2Y, 2M, 2C, 2K), developers 4 (4Y, 4M, 4C, 4K), primary transfer rollers 5 (5Y, 5M, 5C, 5K), and secondary transfer roller 8. The sensors 159 also include sensors that detect the recording material (recording medium) transported by the transport roller.

The A/D converter 153 receives a detection signal from a thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and transmits it to the system controller 150. The system controller 150 controls the AC driver 160 based on the digital signal received from the A/D converter 153, thereby controlling the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature required for performing the fixing process. As described above, the fixing heater 161 is a heater included in the fixing device 14 and used for the fixing process.

The system controller 150 (CPU 150a) controls the operation of the motor control unit 157. The system controller 150 generates command signals for the rotational position (rotational phase) or rotational speed of the motor to be controlled by the motor control unit 157, and outputs them to the motor control unit 157. The motor control unit 157 performs drive control of the motors to be controlled (motor M1 and motor M2) according to the command signals provided by the CPU 150a.

The image forming apparatus 100 of this embodiment has a configuration in which multiple motors drive the same load for at least some of the loads equipped in the image forming apparatus. Motors M1 and M2 shown in Figures 1 and 2 are an example of such multiple motors driving the same load, and drive the pressure roller 16 of the fixing device 14. Motor M1 drives the load (pressure roller 16). Motor M2 outputs a driving force to assist the driving of the load (pressure roller 16) by motor M1. In this way, motor M2 is used as a motor for assisting the driving of the load.

<Drive Configuration of Pressure Roller 16>
3 shows an example of a drive configuration for rotating the pressure roller 16 of the fixing device 14. Fig. 3(A) is a plan view of the pressure roller 16 as seen from above. Fig. 3(B) is a cross-sectional view of the portion indicated by the dashed line X in Fig. 3(A). A gear 16g is provided on the shaft 16a of the pressure roller. A rotating shaft 31 of the motor M1 and a rotating shaft 32 of the motor M2 are each subjected to tooth cutting processing and are connected to the gear 16g of the pressure roller.

In this way, the drive system of the pressure roller 16 is configured so that the torque output from the motor M1 is transmitted from the rotating shaft 31 to the gear 16g, and the torque output from the motor M2 is transmitted from the rotating shaft 32 to the gear 16g. That is, the resultant force of the torques output from the motors M1 and M2 is transmitted to the gear 16g, and further transmitted to the pressure roller 16 via the gear 16g and the shaft 16a, thereby driving the pressure roller 16 to rotate.

Comparative Example
Here, two comparative examples of the control configurations of the motors M1 and M2 when the same load is driven by the motors M1 and M2 will be described with reference to Fig. 4 to Fig. 7. Fig. 4 shows the control configuration of Comparative Example 1, and Fig. 6 shows the control configuration of Comparative Example 2.

Comparative Example 1
The control configuration of the comparative example 1 shown in FIG. 4 is composed of a speed control unit 411, a speed detection unit 412, and a subtractor 413 used for controlling the motor M1, and a speed control unit 421 used for controlling the motor M2. The speed control unit 411 controls the rotation speed of the motor M1. The speed detection unit 412 detects the rotation speed of the motor M1. The speed control unit 421 controls the rotation speed of the motor M2. The motors M1 and M2 are composed of brushless motors or the like. Speed output units 451 and 452 are provided in circuit boards (not shown) attached to the motors M1 and M2, respectively. The speed output units 451 and 452 output FG (Frequency Generator) signals (synchronized with the rotation periods of the motors M1 and M2) as detection signals indicating the rotation speeds of the motors M1 and M2, respectively.

The speed control unit 411 controls the rotation speed of the motor M1 based on the input speed command value ω_ref1. The speed detection unit 412 detects the rotation speed of the motor M1 based on the FG signal output from the speed output unit 451, and outputs the speed detection value ω_det1. The speed detection value ω_det1 output from the speed detection unit 412 is input to the subtractor 413. The subtractor 413 outputs the difference between the speed command value ω_ref1 and the speed detection value ω_det1 to the speed control unit 411. The speed control unit 411 controls the rotation speed of the motor M1 based on the output of the subtractor 413. In this way, the drive control of the motor M1 is performed by feedback control using the speed command value ω_ref1 and the speed detection value ω_det1 output from the speed detection unit 412.

The speed control unit 421 controls the rotation speed of the motor M2 based on the input speed command value ω_ref2 so that the motor M2 rotates at a constant rotation speed. The rotation speed of the motor M2 is set to a rotation speed higher than that of the motor M1. This is because the motor M2 assists the driving of the load by the motor M1. When the motor M2 rotates at a lower rotation speed than the motor M1, the motor M2 becomes a load for the motor M1, but when the motor M2 rotates at a higher rotation speed than the motor M1, the motor M2 does not become a load for the motor M1. Note that in the control configuration of the comparative example 1, feedback control such as that performed for the motor M1 is not performed for the motor M2.

In this way, in the control configuration of Comparative Example 1 shown in FIG. 4, motor M2 generates a constant torque according to the speed command value ω_ref2, and the generated torque assists motor M1 in driving the load. With this control configuration, it is possible to control the ratio of the torque that motors M1 and M2 each output to the load by the set value of the rotation speed of motor M2.

However, in the control configuration of Comparative Example 1, feedback control of the rotational speed is not performed for motor M2, and feedback control of the rotational speed is performed only for motor M1, so the responsiveness of the rotational speed control is relatively low. For this reason, it is difficult to sufficiently suppress fluctuations in the rotational speed of the load shaft caused by load fluctuations.

Figure 5 shows an example of an FG signal obtained in the control configuration of Comparative Example 1. Note that Figure 5 shows signals obtained by F-V (frequency-voltage) conversion of the FG signals output from speed output units 451 and 452 when fluctuations occur in the rotational speed of the load shaft. As shown in Figure 5, the FG signal corresponding to motor M1 and the FG signal corresponding to motor M2 each contain sinusoidal speed fluctuation components due to load fluctuations.

When the control configuration of Comparative Example 1 is applied to motors M1 and M2 in the image forming apparatus 100, fluctuations in the rotation speed of the pressure roller 16, which is the load driven by motors M1 and M2, can cause unevenness in the fixing state of the image. As a result, uneven gloss (gloss unevenness) in the formed image and waviness in the recording material can occur. For this reason, it is desirable to realize a control configuration that can control the rotation speed of the load (pressure roller 16) to a constant rotation speed regardless of load fluctuations.

Comparative Example 2
Comparative Example 2 is an example of a control configuration in which the responsiveness of the rotational speed control of motors M1 and M2 is improved compared to the control configuration of Comparative Example 1. The control configuration of Comparative Example 2 shown in Fig. 6 is composed of a speed control unit 611, a speed detection unit 612, and a subtractor 613 used for controlling motor M1, and a speed control unit 621, a speed detection unit 622, and a subtractor 623 used for controlling motor M2.

The speed control unit 611 controls the rotation speed of the motor M1. The speed detection unit 612 detects the rotation speed of the motor M1. The speed control unit 621 controls the rotation speed of the motor M2. The speed detection unit 622 detects the rotation speed of the motor M2. The motors M1 and M2 are composed of brushless motors or the like. The speed output units 651 and 652 are provided in circuit boards (not shown) attached to the motors M1 and M2, respectively. The speed output units 651 and 652 output FG signals (synchronized with the rotation periods of the motors M1 and M2) as detection signals indicating the rotation speeds of the motors M1 and M2, respectively.

The operations of the speed control unit 611, the speed detection unit 612, and the subtractor 613 are similar to those of the speed control unit 411, the speed detection unit 412, and the subtractor 413 in Comparative Example 1. As in Comparative Example 1, the drive control of the motor M1 is performed by feedback control using the speed command value ω_ref1 and the speed detection value ω_det1 output from the speed detection unit 612.

The operations of the speed control unit 621, the speed detection unit 622, and the subtractor 623 are similar to those of the speed control unit 611, the speed detection unit 612, and the subtractor 613, respectively. However, in the control configuration of the comparative example 2, the motors M1 and M2 are controlled based on a common speed command value ω_ref1. Specifically, the speed control unit 621 controls the rotation speed of the motor M2 based on the input speed command value ω_ref1. The speed detection unit 622 detects the rotation speed of the motor M2 based on the FG signal output from the speed output unit 652, and outputs the speed detection value ω_det2. The speed detection value ω_det2 output from the speed detection unit 622 is input to the subtractor 623. The subtractor 623 outputs the difference between the speed command value ω_ref1 and the speed detection value ω_det2 to the speed control unit 621. The speed control unit 621 controls the rotation speed of the motor M2 based on the output of the subtractor 623. In this way, the drive control of the motor M2 is performed by feedback control using the speed command value ω_ref1 and the speed detection value ω_det2 output from the speed detection unit 622.

In this way, in the control configuration of Comparative Example 2 shown in FIG. 6, feedback control of the rotational speed is performed for both motors M1 and M2. Therefore, with the control configuration of Comparative Example 2, it is possible to improve the responsiveness of the rotational speed control compared to the control configuration of Comparative Example 1, and to reduce fluctuations in the rotational speed of the load shaft caused by load fluctuations.

Figure 7 shows an example of an FG signal obtained in the control configuration of Comparative Example 2. Figure 7 also shows the signals obtained by F-V conversion of the FG signals output from speed output units 651 and 652 when fluctuations occur in the rotational speed of the load shaft. As shown in Figure 7, in both the FG signal corresponding to motor M1 and the FG signal corresponding to motor M2, the speed fluctuation components due to load fluctuations are reduced compared to Comparative Example 1 (Figure 5).

However, when feedback control of the rotational speed is performed independently for multiple motors, as in the control configuration of Comparative Example 2, a phase difference in the rotational phase (of the rotor) between the motors may occur even if control is performed based on the same speed command value ω_ref1. For example, such a phase difference may occur due to mounting errors of each motor or eccentricity of a gear attached to the load shaft. As a result, the deviation in the rotational speed between the motors may not converge to zero, making it difficult to appropriately control the ratio of the torque that each of the multiple motors outputs to the load.

<Control configuration of motors M1 and M2>
Therefore, in this embodiment, when the same load is driven by multiple motors, a control configuration is realized that can control the rotation speed of the load (load shaft) with higher precision (keep constant) while appropriately controlling the ratio of the torque output from each motor to the load. Below, an example configuration in which the same load is driven by two motors M1 and M2 is described, but this embodiment can also be applied to a configuration in which the same load is driven by three or more motors.

FIG. 8 is a block diagram showing an example of the configuration of the motor control unit 157 that controls the motors M1 and M2, as an example of the control configuration of the motors M1 and M2 in this embodiment. The motors M1 and M2 drive the pressure roller 16, which is the same load. In this embodiment, the motors M1 and M2 are configured as brushless motors, but may be configured as other types of motors, such as stepping motors or brushed motors. The motor control unit 157 may be realized by hardware (such as an FPGA or ASIC) that executes the functions described below, or may be realized in part by hardware and the other parts by one or more processors that execute programs. The entire motor control unit 157 may be realized by one or more processors that execute programs.

The motor control unit 157 has a speed control unit 811, a speed detection unit 812, and a subtractor 813 as components corresponding to the motor M1, and has a speed control unit 821, a fluctuation compensation unit 822, and an adder 823 as components corresponding to the motor M2. Speed output units 851 and 852 are provided in circuit boards (not shown) attached to the motors M1 and M2, respectively. The speed output units 851 and 852 output FG signals (synchronized with the rotational periods of the motors M1 and M2) as detection signals indicating the rotational speeds of the motors M1 and M2, respectively. In this way, the speed output unit 851 is an example of a first detection means corresponding to the first motor (motor M1), and the speed output unit 852 is an example of a second detection means corresponding to the second motor (motor M2). The speed output units 851 and 852 output detection signals (FG signals) indicating the rotational speeds of the corresponding motors, respectively.

The speed control unit 811 controls the rotation speed of the motor M1 based on the speed command value ω_ref1 output from the CPU 150a. The speed command value (command speed) ω_ref1 is an example of a first command value (first command speed) that represents the target rotation speed of the motor M1. The speed detection unit 812 detects the rotation speed of the motor M1 based on the FG signal output from the speed output unit 851, and outputs a speed detection value ω_det1 that indicates the detected rotation speed. The speed detection value ω_det1 output from the speed detection unit 812 is input to the subtractor 813. The subtractor 813 outputs the difference between the speed command value ω_ref1 and the speed detection value ω_det1 to the speed control unit 811. The speed control unit 811 controls the rotation speed of the motor M1 based on the output of the subtractor 813.

In this way, the drive control of motor M1 is performed by feedback control using the speed command value ω_ref1 and the speed detection value ω_det1 output from the speed detection unit 812. That is, the speed control unit 811 controls motor M1 based on the speed command value ω_ref1 representing the target rotation speed of motor M1 and the FG signal output from the speed output unit 851. More specifically, the speed control unit 811 controls motor M1 so that the deviation between the speed detection value ω_det1 and the detection value based on the FG signal output from the speed output unit 851 is reduced.

The speed control unit 821 controls the rotation speed of the motor M2 based on the speed command value ω_ref2 output from the CPU 150a so that the motor M2 rotates at a constant rotation speed. The speed command value (command speed) ω_ref2 is an example of a second command value (second command speed) that indicates the target rotation speed of the motor M2. The CPU 150a sets the rotation speed of the motor M2 to a rotation speed higher than the rotation speed of the motor M1. That is, the speed command value ω_ref2 is set to a value that indicates a target rotation speed higher than the speed command value ω_ref1 (ω_ref2>ω_ref1). This is because the motor M2 assists the driving of the load by the motor M1. When the motor M2 rotates at a lower rotation speed than the motor M1, the motor M2 becomes a load for the motor M1. On the other hand, when the motor M2 rotates at a higher rotation speed than the motor M1, the motor M2 does not become a load for the motor M1. In this case, the combined force of the output torque of motor M1 and the output torque of motor M2 is transmitted to the load (pressure roller 16) to be driven. This makes it possible for the drive of the load (pressure roller 16) by motor M1 to be assisted by motor M2. The CPU 150a outputs a speed command value ω_ref2 according to such a rotation speed setting to the motor control unit 157 (speed control unit 821).

The fluctuation compensation unit 822 acquires the fluctuation component of the rotation speed of the load shaft from the FG signal output from the speed output unit 852, and generates and outputs an adjustment value ω_adj2 for compensating for the fluctuation of the rotation speed of the load shaft based on the acquired fluctuation component. The adjustment value ω_adj2 output from the fluctuation compensation unit 822 is added to the speed command value ω_ref2 by the adder 823, and is applied to the speed command value ω_ref2. The fluctuation compensation unit 822 may be configured to acquire the fluctuation component of the rotation speed of the load shaft from the FG signal output from the speed output unit 851.

The fluctuation compensation unit 822 includes a bandpass filter (BPF) 831, a calculation unit 832, and a signal generation unit 833. The FG signal output from the speed output unit 852 is input to the BPF 831 in the fluctuation compensation unit 822. The BPF 831 is a bandpass filter for extracting a predetermined frequency component from the input FG signal. Specifically, the BPF 831 is configured to extract a frequency component corresponding to the fluctuation in the rotation speed of the load shaft (shaft 16a of the pressure roller 16) due to load fluctuations such as rotation unevenness of the pressure roller 16. Thus, in this embodiment, the BPF 831 is an example of an acquisition means for acquiring the fluctuation component of the rotation speed of the load from the FG signal (detection signal) output from the (speed output unit 851 or) speed output unit 852.

Figure 9 shows an example of the frequency characteristics of the BPF 831. For example, if the rotation speed of the motor M1 is 50 Hz and the gear ratio between the rotation shaft 31 of the motor M1 and the gear 26 is 10, the rotation speed of the load shaft (shaft 16 of the pressure roller 16) is 5 Hz. In this case, as shown in Figure 9, the BPF 831 has a frequency characteristic that passes frequency components within a predetermined frequency range including a frequency corresponding to the rotation speed of the load (load shaft). That is, the BPF 831 has a frequency characteristic in which the cutoff frequencies on the low and high frequency sides are determined so as to pass frequency components within such a frequency range (within the pass band). The BPF 831 operates to attenuate (block) frequency components outside the pass band, such as DC components.

In this way, BPF 831 outputs a signal indicating the fluctuation component of the rotation speed of the load shaft. The signal output from BPF 831 is input to calculation unit 832. Calculation unit 832 inverts the polarity of the input signal and outputs it. That is, calculation unit 832 inverts the phase of the input signal, thereby outputting a signal of opposite phase to the input signal. That is, calculation unit 832 outputs a signal indicating fluctuation of opposite phase to the fluctuation component of the rotation speed of the load shaft.

The signal output from the calculation unit 832 is input to the signal generation unit 833. The signal generation unit 833 generates and outputs a control signal (adjustment value ω_adj2) for compensating for fluctuations in the rotation speed of the load shaft based on the input signal (a signal that indicates fluctuations in the opposite phase to the fluctuation components of the rotation speed of the load shaft). The adjustment value ω_adj2 is generated as a signal value that includes a fluctuation component in the opposite phase to the fluctuation components of the rotation speed of the load shaft.

The adjustment value ω_adj2 output from the fluctuation compensation unit 822 is added to the speed command value ω_ref2 by the adder 823. As a result, the speed command value input to the speed control unit 821 is adjusted from ω_ref2 to (ω_ref2 + ω_adj2). That is, the rotation speed command value (ω_ref2 + ω_adj2) including a fluctuation component in the opposite phase to the fluctuation component of the rotation speed of the load shaft is input to the speed control unit 821. The speed control unit 821 controls the motor M2 according to the command value (ω_ref2 + ω_adj2) obtained by adding the adjustment value ω_adj2 to the speed command value ω_ref2. In this way, the drive control of the motor M2 is performed by feedback control using the speed command value ω_ref1 and the adjustment value ω_adj2 output from the fluctuation compensation unit 822.

In this way, the speed control unit 821 controls the motor M2 based on the speed command value ω_ref2 and the fluctuation component of the rotation speed of the load so that the rotation speed of the motor M2 fluctuates in the opposite phase to the fluctuation component with respect to the target rotation speed indicated by the speed command value ω_ref2. More specifically, the speed control unit 821 controls the motor M2 based on the speed command value ω_ref2 and an inverted signal obtained by inverting the polarity of the signal output from the BPF 831 (i.e., the signal indicating the fluctuation component of the rotation speed of the load (load shaft)).

Figure 10 shows an example of an FG signal obtained in the control configuration shown in Figure 8. Figure 10 also shows the signals obtained by F-V conversion of the FG signals output from speed output units 851 and 852 when fluctuations occur in the rotational speed of the load shaft. As shown in Figure 10, similar to Comparative Example 2 (Figure 7), the speed fluctuation components due to load fluctuations are reduced more than in Comparative Example 1 in both the FG signal corresponding to motor M1 and the FG signal corresponding to motor M2.

In this way, the motor control unit 157 of this embodiment acquires the speed fluctuation component appearing in the detection result of the rotation speed of motor M2 as the fluctuation component of the rotation speed of the load shaft. Furthermore, the motor control unit 157 controls (feedback control) motor M2 so that the rotation speed fluctuates in the opposite phase to the acquired fluctuation component. In other words, the motor control unit 157 controls the rotation speed of motor M2 so that the fluctuation in the rotation speed of the load shaft due to load fluctuation is cancelled out by the fluctuation in the rotation speed of motor M2. This makes it possible to reduce the fluctuation in the rotation speed of the load shaft due to load fluctuation, which is difficult to reduce with feedback control of motor M1 alone.

In addition, unlike Comparative Example 2, the motor control unit 157 of this embodiment is configured to generate a constant torque by the motor M2 according to the speed command value ω_ref2, and to assist the driving of the load by the motor M1 with the generated torque. This makes it possible to appropriately control the ratio of the torque output by the motors M1 and M2 to the load using the set value (speed command value ω_ref2) of the rotation speed of the motor M2. In this way, it becomes possible to control the rotation speed of the load (load shaft) to a constant rotation speed with higher accuracy while appropriately controlling the ratio of the torque output by the motors M1 and M2 driving the same load to the load. Therefore, according to this embodiment, it becomes possible to suppress the rotation of the load from becoming unstable.

<Flowchart>
11 is a flowchart showing a procedure for controlling the drive of the motors M1 and M2 when a print job is executed. When the CPU 150a starts the execution of a print job in accordance with a user's instruction via the operation unit 152 or an instruction from an external device, the CPU 150a starts the drive control of the motors M1 and M2 in the procedure shown in FIG.

In S101, the CPU 150a sets speed command values ω_ref1 and ω_ref2 for the motors M1 and M2 in accordance with the paper settings of the print job. Furthermore, in S102, the CPU 150a outputs the set speed command values ω_ref1 and ω_ref2 to the motor control unit 157, and outputs a drive start command for the motors M1 and M2 to the motor control unit 157. As a result, the motor control unit 157 starts driving the motors M1 and M2 in accordance with the set speed command values ω_ref1 and ω_ref2.

Then, in S103, the CPU 150a determines whether or not to end the execution of the print job, and when the execution of the print job is ended, in S104, it outputs a command to stop driving the motors M1 and M2 to the motor control unit 157. As a result, the motor control unit 157 stops driving the motors M1 and M2.

<Summary>
As described above, the motor control device (motor control unit 157) of this embodiment includes a speed control unit 811 that controls the motor M1 and a speed control unit 821 that controls the motor M2. The motor M1 is configured to drive a load (e.g., the pressure roller 16), and the motor M2 is configured to output a driving force for assisting the motor M1 in driving the load. The fluctuation compensation unit 822 (BPF 831) acquires a fluctuation component of the rotation speed of the load from an FG signal (detection signal) that indicates the rotation speed of the corresponding motor and is output from a speed output unit 851 corresponding to the motor M1 or a speed output unit 852 corresponding to the motor M2. The speed control unit 811 controls the motor M1 based on a speed command value ω_ref1 that indicates the target rotation speed of the motor M1 and the FG signal output from the speed output unit 851. The speed control unit 821 controls the motor M2 based on a speed command value ω_ref2 that indicates the target rotation speed of the motor M2 and the fluctuation component acquired by the fluctuation compensation unit 822 (BPF 831). Specifically, the speed control unit 821 controls the M2 motor so that the rotation speed of the motor M2 fluctuates in the opposite phase to the fluctuation component with respect to the target rotation speed indicated by the speed command value ω_ref2.

In this way, according to this embodiment, the speed control unit 821 acquires the fluctuation component of the rotation speed of the load (load shaft), and causes a fluctuation in the rotation speed of the motor M2 that is in the opposite phase to the acquired fluctuation component. In this way, the speed control unit 821 controls the drive of the motor M2 so that the fluctuation in the rotation speed of the load caused by the load fluctuation, which cannot be suppressed by the drive control of the motor M1, is canceled by the fluctuation caused in the rotation speed of the motor M2. This makes it possible to control the rotation speed of the load (load shaft) with higher accuracy while appropriately controlling the ratio of the torque output to the load by each of multiple motors driving the same load. Therefore, according to this embodiment, it is possible to suppress instability in the rotation of the load.

<Modification>
This embodiment can be modified in various ways as described below. For example, the motors M1 and M2 may be configured with other types of motors, such as stepping motors or brushed motors, instead of brushless motors. The configuration in this embodiment in which a plurality of motors drive the same load may be applied to driving a load other than the pressure roller 16, for example, to driving an image carrier such as the intermediate transfer belt 6 or the photosensitive drum 1. In this case, the motor control device (motor control unit 157) is configured to control the first motor and the second motor (motors M1 and M2) that rotate and drive the image carrier.

In this embodiment, a configuration is used in which the rotation speed of motors M1 and M2 is detected using the FG function of each motor, but the rotation speed may be detected using a different configuration. For example, a configuration may be used in which an encoder is attached to the load shaft and the rotation speed of motors M1 and M2 (their rotating shafts) is detected using the encoder.

In the control configuration of FIG. 8, a BPF capable of extracting frequency components corresponding to the fluctuation components of the rotation speed of the load shaft is used, but in order to enable acquisition of fluctuation components in higher frequency bands, a high pass filter (HPF) may be used instead of the BPF. In addition, in the control configuration of FIG. 8, the fluctuation components of the rotation speed of the load shaft are acquired from the FG signal corresponding to the motor M2, but they may be acquired from the FG signal corresponding to the motor M1. In addition, the fluctuation compensation unit 822 of this embodiment acquires frequency components corresponding to the fluctuation components of the rotation speed of the load shaft as speed fluctuation components, but different frequency components may be acquired depending on the speed fluctuation components to be reduced. For example, frequency components corresponding to the fluctuation components of the rotation speed of the motors M1 or M2 may be acquired.

In addition, in this embodiment, an example of a configuration in which the same load is driven by two motors M1 and M2 has been described, but a configuration in which the same load is driven by three or more motors can also be realized. In that case, the same effect can also be obtained.

The motor control device of the present invention is not limited to being provided in an image forming device as described in this embodiment, but may also be provided in, for example, a sheet transport device that transports sheets such as recording media and original documents. In this case, the motor control device is configured to control multiple motors (first and second motors) that drive transport rollers that transport the sheets.

The present invention can also be realized by supplying a program that realizes one or more of the functions of the above-mentioned embodiments to a system or device via a network or storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that realizes one or more of the functions.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

100: Image forming device, 150a: CPU, 157: Motor control unit, M1, M2: Motor, 16: Pressure roller, 811, 821: Speed control unit, 812: Speed detection unit, 822: Fluctuation compensation unit, 851, 852: Speed output unit

Claims (14)

a first control means for controlling a first motor that drives a load;
a second control means for controlling a second motor that outputs a driving force for assisting the first motor in driving the load;
an acquisition means for acquiring a fluctuation component of the rotation speed of the load based on a first signal corresponding to the rotation speed of the first motor or a second signal corresponding to the rotation speed of the second motor,
the first control means controls the first motor based on a first command value representing a target rotation speed of the first motor and the first signal;
the second control means controls the second motor based on a second command value representing a target rotational speed of the second motor and the fluctuation component acquired by the acquisition means, so that the rotational speed of the second motor fluctuates in an antiphase with respect to the target rotational speed indicated by the second command value and the fluctuation component. 2. The motor control device according to claim 1 , wherein the second control means controls the second motor based on the second command value and an inverted signal obtained by inverting the polarity of a signal indicating the fluctuation component . 3. The motor control device according to claim 2, wherein the second control means controls the second motor in accordance with a command value obtained by adding an adjustment value based on the inverted signal to the second command value. the acquiring means includes a filter to which the first signal or the second signal is input,
4. The motor control device according to claim 1, wherein the filter is configured to output a frequency component corresponding to a fluctuation component of a rotation speed of the load based on the first signal or the second signal . 5. The motor control device according to claim 4, wherein the filter has a frequency characteristic that passes frequency components within a predetermined frequency range including a frequency corresponding to a rotation speed of the load. further comprising an inverting means for inverting the polarity of the signal output from the filter and outputting the inverted signal;
6. The motor control device according to claim 5, wherein the second control means controls the second motor based on the second command value and an inversion signal output from the inversion means. the first control means controls the first motor so as to reduce a deviation between the first command value and a detection value based on the first signal;
7. The motor control device according to claim 6, wherein the second control means controls the second motor according to a command value obtained by adding an adjustment value based on the inverted signal to the second command value. The motor control device according to claim 1 , wherein the second command value is set to a value indicating a target rotation speed higher than that of the first command value. A conveying roller for conveying a sheet;
The motor control device according to claim 1 , which controls a first motor and a second motor that drive the conveying rollers;
A sheet conveying device comprising: an image forming means for forming an image on a recording medium;
a fixing unit having a pressure roller for applying pressure to the recording medium and fixing the image formed by the image forming unit onto the recording medium;
The motor control device according to claim 1 , which controls a first motor and a second motor that drive the pressure roller;
An image forming apparatus comprising: An image carrier;
an image forming means for forming an image on the image carrier to be transferred onto a recording medium;
The motor control device according to claim 1 , which controls a first motor and a second motor that rotate the image carrier;
An image forming apparatus comprising: A first motor that drives a load;
a second motor that outputs a driving force for assisting the first motor in driving the load;
a first output means for outputting a first signal corresponding to a rotation speed of the first motor;
a second output means for outputting a second signal corresponding to a rotation speed of the second motor;
a first control means for controlling the first motor based on a first command value representing a target rotation speed of the first motor and the first signal;
an acquisition means for acquiring a fluctuation component of a rotation speed of the load based on the first signal or the second signal ;
a second control means for controlling the second motor based on a second command value representing a target rotation speed of the second motor and the fluctuation component acquired by the acquisition means such that the rotation speed of the second motor fluctuates in an opposite phase to the fluctuation component with respect to the target rotation speed indicated by the second command value;
An image forming apparatus comprising: an image forming means for forming an image on a recording medium;
a fixing unit having a pressure roller for applying pressure to the recording medium and fixing the image formed by the image forming unit onto the recording medium,
The image forming apparatus according to claim 12 , wherein the load is the pressure roller. An image carrier;
and an image forming unit for forming an image to be transferred onto a recording medium on the image carrier.
The first motor drives the image carrier as the load.
13. The image forming apparatus according to claim 12.

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