JP7188214B2 - Twin drive and motor control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a twin drive device and a motor control method, and more particularly to a twin drive device that rotates the same load using a stepping motor and a brushless motor, and a motor control method in the twin drive device.

2. Description of the Related Art In recent years, with the speeding up of image forming apparatuses such as MFPs (Multi-Functional Peripherals), there has been a demand for shortening the acceleration time of a conveying roller that conveys a recording medium and increasing the target speed. However, since general-purpose stepping motors used in image forming apparatuses have insufficient output torque, stepping out is likely to occur, and the conveying rollers cannot be accelerated in a short period of time. Moreover, when using an expensive stepping motor with a large output torque, it is necessary to constantly supply an excessive current to ensure a torque margin, resulting in an increase in power consumption.

In response to this problem, Patent Document 1 below discloses a stepping motor, a brushless motor, and a first power transmission section for transmitting the power of the stepping motor to a drive shaft, which is a connection for transmitting the power to the drive shaft. a first power transmission section that can be switched to a release state that releases transmission; a second power transmission section that transmits power of the brushless motor to the drive shaft; the stepping motor, the brushless motor, and the second power transmission section; 1 a power transmission unit and a control unit for controlling transmission of power to the drive shaft, wherein the control unit accelerates the rotation of the drive shaft to a predetermined speed in a first operation phase in which the stepping In a second operation phase in which power of both the motor and the brushless motor is transmitted to drive the drive shaft, and after the first operation phase, the drive shaft is rotated at a constant speed at the predetermined speed, the first power A driving device is disclosed in which power transmission of the stepping motor by a transmission section is canceled and the drive shaft is driven only by the brushless motor.

JP 2018-161003

In Patent Document 1, both a stepping motor and a brushless motor provided with an encoder are used to drive one roller shaft (referred to as twin drive). It is designed to switch between connection and disconnection to the drive shaft. However, in the above technology, the rotation of the stepping motor is controlled by the drive pulse signal, and the rotation of the brushless motor is controlled by the pulse signal output from the encoder. There is a problem that the stepping motor cannot be properly assisted and the stepping motor cannot be prevented from stepping out.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its main object is to appropriately adjust the assist amount of the brushless motor in twin driving of a stepping motor and a brushless motor to prevent stepping out of the stepping motor. It is an object of the present invention to provide a twin drive device and a motor control method that can prevent this.

One aspect of the present invention is a stepping motor, a brushless motor, a drive mechanism that rotates the same load using the stepping motor and the brushless motor, and a control that controls the operation of the stepping motor and the brushless motor. and an encoder on the rotating shaft of the brushless motor or the rotating shaft of the drive mechanism, and the control unit compares a pulse signal for driving the stepping motor and a pulse signal output from the encoder. and calculating the amount of angular deviation of the stepping motor, and increasing or decreasing the output of the brushless motor according to the amount of angular deviation.

One aspect of the present invention includes a stepping motor, a brushless motor, and a drive mechanism that rotates the same load using the stepping motor and the brushless motor, wherein the rotating shaft of the brushless motor or the drive mechanism A motor control method for a twin drive device having an encoder on a rotating shaft of the stepping motor, wherein a pulse signal for driving the stepping motor and a pulse signal output from the encoder are compared to calculate an angular deviation amount of the stepping motor. A calculating step and a controlling step of increasing or decreasing the output of the brushless motor according to the angular deviation amount are executed.

According to the twin drive device and the motor control method of the present invention, in the twin drive of the stepping motor and the brushless motor, it is possible to appropriately adjust the assist amount of the brushless motor and prevent stepping out of the stepping motor.

The reason for this is that the twin drive device includes a stepping motor, a brushless motor, a driving mechanism that rotates the same load using the stepping motor and the brushless motor, and a control unit that controls the operation of the stepping motor and the brushless motor. , and an encoder is provided on the rotary shaft of the brushless motor or the rotary shaft of the drive mechanism, and the control unit compares a pulse signal for driving the stepping motor and a pulse signal output from the encoder to determine the angle deviation of the stepping motor. This is because the amount is calculated and the output of the brushless motor is increased or decreased according to the angular deviation amount.

1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a block diagram showing the configuration of an image forming apparatus according to one embodiment of the present invention; FIG. 1 is a schematic diagram showing the configuration of a twin drive device according to an embodiment of the present invention; FIG. FIG. 4 is a block diagram illustrating twin drive according to one embodiment of the present invention; FIG. 4 is a waveform diagram showing a stepping motor pulse signal and an encoder pulse signal in a twin drive device according to an embodiment of the present invention (when the frequency of the stepping motor pulse signal is an integral multiple of the frequency of the encoder pulse signal); . FIG. 4 is a waveform diagram showing a pulse signal of a stepping motor and a pulse signal of an encoder in a twin drive device according to an embodiment of the present invention (when the frequency of the pulse signal of the stepping motor is not an integral multiple of the frequency of the pulse signal of the encoder); . FIG. 4 is a diagram showing phase calibration of a pulse signal of a stepping motor and a pulse signal of an encoder in a twin drive device according to an embodiment of the present invention; FIG. 5 is a diagram showing the relationship between the deviation between the pulse signal of the stepping motor and the pulse signal of the encoder and the speed of the motor in the twin drive device according to the embodiment of the present invention; FIG. 4 is a flow chart showing the operation of the twin drive system according to one embodiment of the present invention; FIG. 4 is a flow chart showing the operation of the twin drive system according to one embodiment of the present invention;

As described in the background art, general-purpose stepping motors used in image forming apparatuses have insufficient output torque, so stepping out is likely to occur, and the conveying roller cannot be accelerated in a short period of time. Moreover, when using an expensive stepping motor with a large output torque, an excessive current must always flow to ensure a torque margin, which increases power consumption.

In response to this problem, Patent Document 1 proposes a twin drive in which a single roller shaft is driven using both a stepping motor and a brushless motor equipped with an encoder. and the rotation of the brushless motor is controlled by the pulse signal output from the encoder. There is a problem that the stepping motor cannot be prevented from stepping out.

Therefore, in one embodiment of the present invention, in a twin drive configuration, a pulse signal output from an encoder provided on the rotary shaft of the brushless motor (or the rotary shaft of the drive mechanism) is used to determine the angular deviation amount of the stepping motor. (the amount of deviation between the angle estimated from the pulse signal that drives the stepping motor and the angle specified based on the pulse signal output from the encoder) is monitored. When this occurs, the output of the brushless motor is increased to increase the amount of assist, thereby preventing stepping out of the stepping motor.

Specifically, the twin drive device includes a stepping motor, a brushless motor, a driving mechanism that rotates the same load using the stepping motor and the brushless motor, and a control unit that controls the operation of the stepping motor and the brushless motor. and an encoder is provided on the rotating shaft of the brushless motor or the rotating shaft of the driving mechanism, and the control unit compares the pulse signal for driving the stepping motor with the pulse signal output from the encoder to determine the angle of the stepping motor. The amount of deviation is calculated, and control is performed to increase or decrease the output of the brushless motor according to the amount of angular deviation.

As a result, it is possible to prevent the stepping motor from stepping out without providing a separate encoder for the stepping motor. Also, by controlling a brushless motor driven by current control instead of a stepping motor, the operation of the twin drive device can be controlled more accurately and simply.

In order to describe the above embodiment of the present invention in further detail, a twin drive system and a motor control method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 10. FIG. FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus of this embodiment, and FIG. 2 is a block diagram showing the configuration of the image forming apparatus of this embodiment. FIG. 3 is a schematic diagram showing the configuration of the twin drive device of this embodiment, and FIG. 4 is a block diagram for explaining the twin drive of this embodiment. 5 to 8 are diagrams for explaining the angular deviation of the stepping motor in the twin drive device of this embodiment, and FIGS. 9 and 10 are flow charts showing the operation of the twin drive device of this embodiment. be.

The twin drive device of this embodiment can be used in various devices having a drive mechanism, but in this embodiment, an image forming apparatus in which the twin drive device is used to drive the conveying rollers will be described.

As shown in FIG. 1, the image forming apparatus 10 of this embodiment performs image processing based on image data acquired by reading a document or image data input from an external information device (for example, a client device) via a communication network. It is a device that forms an image by superimposing colors on a sheet of paper. This is a tandem type image forming apparatus in which body drums 83Y, 83M, 83C, and 83K are arranged in series in the running direction of a transfer medium (intermediate transfer belt).

As shown in FIG. 2A, the image forming apparatus 10 includes a control section 20, a high-voltage power supply section 30, a display operation section 40, an image reading section 50, an image processing section 60, a conveying section 70, an image forming section 80, and the like. consists of

The control unit 20 includes a CPU (Central Processing Unit) 21, memories such as ROM (Read Only Memory) 22 and RAM (Random Access Memory) 23, and storage such as HDD (Hard Disk Drive) and SSD (Solid State Drive). 24, and a network I/F unit 25 such as a NIC (Network Interface Card) or modem. The CPU 21 centrally controls the operation of each part of the image forming apparatus 10 by reading out a program corresponding to the processing contents from the ROM 22 or the storage part 24, developing it in the RAM 23, and executing it. The storage unit 24 stores a program for the CPU 21 to control each unit, information on processing functions of the device itself, image data read by the image reading unit 50, image data input from a client device (not shown), and the like. The network I/F unit 25 connects the image forming apparatus 10 to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network), and exchanges various data with an external information device (for example, a client device). Send and receive.

The high-voltage power supply unit 30 is a circuit that generates a high voltage used for charging, development, and transfer, and applies an alternating waveform high voltage to a charging device 84, a developing device 82, a primary transfer roller 86, and an intermediate transfer unit 87, which will be described later. Output. For example, secondary transfer is performed by converting a DC voltage of 24 V into a transfer voltage and outputting the converted transfer voltage to the secondary transfer roller.

The display operation unit 40 is a pressure-sensitive or capacitive operation unit (touch sensor) in which transparent electrodes are arranged in a grid pattern on a display unit such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) display. ), and functions as a display unit and an operation unit. The display unit displays various operation screens, image status display, operation status of each function, etc. according to a display control signal input from the control unit 20 . The operation unit receives various input operations by the user and outputs operation signals to the control unit 20 .

The image reading unit 50 includes an automatic document feeder 51 called an ADF (Auto Document Feeder), a document image scanning device (scanner) 52, and the like. The automatic document feeder 51 transports the document placed on the document tray by the transport mechanism and sends it to the document image scanning device 52 . The document image scanning device 52 optically scans the document conveyed onto the contact glass from the automatic document feeder 51 or the document placed on the contact glass, and converts the light reflected from the document into a CCD (Charge Coupled Device). ) The document image is read by forming an image on the light receiving surface of the sensor. An image (analog image signal) read by the image reading section 50 is subjected to predetermined image processing in the image processing section 60 .

The image processing unit 60 includes a circuit that performs analog-to-digital (A/D) conversion processing, a circuit that performs digital image processing, and the like. The image processing section 60 generates digital image data by performing A/D conversion processing on the analog image signal from the image reading section 50 . The image processing unit 60 also analyzes a print job acquired from an external information device (for example, a client device), rasterizes each page of the document, and generates digital image data. Then, the image processing unit 60 performs image processing such as color conversion processing, correction processing (shading correction, etc.), and compression processing on the image data as necessary, and forms the image data after the image processing. Output to unit 80 .

As shown in FIGS. 1 and 2B, the conveying unit 70 includes a conveying roller 71 and a twin driving device for driving the conveying roller 71. The twin driving device includes a stepping motor 72 and a brushless motor. 73 , a drive mechanism 74 , and a control unit such as a CPU 75 that controls the operations of the stepping motor 72 and the brushless motor 73 . The transport roller 71 is arranged at a predetermined position in the paper transport path, transports the paper accommodated in the paper feed tray to the image forming section 80, and transports the paper on which the image has been formed to the paper discharge tray. The stepping motor 72 is a motor that operates in synchronization with the drive pulse signal. The brushless motor 73 is a motor that does not have brushes and a commutator (a DC brushless motor in which the function of the brushes of a DC motor is replaced with an electronic circuit). The brushless motor 73 of this embodiment includes an encoder 73a for detecting phase and angle, and feedback control is performed by a pulse signal output from the encoder 73a. The drive mechanism 74 includes a gear, a drive shaft, and the like for rotating the conveying roller 71 , and is rotated by the stepping motor 72 and the brushless motor 73 . Instead of the encoder 73a of the brushless motor 73, the drive mechanism 74 may be provided with an encoder 74b for detecting the phase and angle of the drive shaft. A CPU 75 is a CPU used for twin drive control, and includes a stepping motor control section 76 that controls the stepping motor 72, a brushless motor control section 77 that controls the brushless motor 73, and the like. A detailed configuration of the twin drive device will be described later.

As shown in FIGS. 1 and 2C, the image forming unit 80 includes exposure devices 81 (81Y, 81M, 81C, 81K) provided corresponding to different color components Y, M, C, and K, Developing devices 82 (82Y, 82M, 82C, 82K), photosensitive drums 83 (83Y, 83M, 83C, 83K), charging devices 84 (84Y, 84M, 84C, 84K), cleaning devices 85 (85Y, 85M, 85C, 85K), primary transfer rollers 86 (86Y, 86M, 86C, 86K), an intermediate transfer unit 87, a fixing device 88, and the like. In the following description, symbols other than Y, M, C, and K are used as necessary.

The photoreceptor drums 83 for the respective color components Y, M, C, and K are provided with an organic photoreceptor layer (OPC) provided with an overcoat layer as a protective layer on the outer peripheral surface of a cylindrical metal substrate made of an aluminum material. image carrier. The photosensitive drum 83 is rotated counterclockwise in FIG. 1 by being driven by an intermediate transfer belt, which will be described later, while being grounded.

The charging device 84 for each of the color components Y, M, C, and K is, for example, a charging roller type. It is arranged close to the corresponding photoreceptor drum 83, and applies a uniform potential to the surface of the photoreceptor drum 83 by applying a high voltage to the charging member. During this charging, a high voltage having an alternating waveform is output from the output terminal of the high voltage power supply section 30 as required.

The exposure device 81 for each of the color components Y, M, C, and K performs scanning parallel to the rotation axis of the photosensitive drum 83 by using, for example, a polygon mirror, and exposes the uniformly charged surface of the corresponding photosensitive drum 83. An electrostatic latent image is formed by performing imagewise exposure based on image data.

The developing device 82 for each of the color components Y, M, C, and K accommodates a two-component developer composed of a small particle size toner of the corresponding color component and a magnetic substance, and the toner is applied to the surface of the photosensitive drum 83 . Then, the electrostatic latent image carried on the photosensitive drum 83 is visualized with toner. During this development, a high voltage having an alternating waveform is output from the output terminal of the high voltage power supply unit 30 as required.

The primary transfer rollers 86 for the respective color components Y, M, C, and K press the intermediate transfer belt against the photoreceptor drum 83 to sequentially superimpose the respective color toner images formed on the corresponding photoreceptor drums 83 to primary transfer onto the intermediate transfer belt. to transcribe. During this primary transfer, a high voltage having an alternating waveform is output from the output terminal of the high voltage power supply section 30 as required.

The cleaning device 85 for each color component Y, M, C, and K collects residual toner remaining on the corresponding photosensitive drum 83 after the primary transfer. A lubricant application mechanism (not shown) is provided adjacent to the cleaning device 85 on the downstream side of the photosensitive drum 83 in the rotation direction, and applies the lubricant to the photosensitive surface of the corresponding photosensitive drum 83 . there is

The intermediate transfer unit 87 includes an endless intermediate transfer belt 87a serving as a transfer target, a support roller 87b, a secondary transfer roller 87c, and an intermediate transfer cleaning section 87d. It is constructed by hanging. When the intermediate transfer belt 87a on which the toner images of each color are primarily transferred by the primary transfer rollers 86Y, 86M, 86C, and 86K is pressed against the paper by the secondary transfer roller 87c, the toner images are secondarily transferred to the paper, and the fixing device Sent to 88. The intermediate transfer cleaning section 87d has a belt cleaning blade (BCL blade) that slides on the surface of the intermediate transfer belt 87a. Transfer residual toner remaining on the surface of the intermediate transfer belt 87a after the secondary transfer is scraped off and removed by the BCL blade. During this secondary transfer, a high voltage having an alternating waveform is output from the output terminal of the high voltage power supply section 30 as required.

The fixing device 88 includes a heating roller 88a and a fixing roller 88b serving as heat sources, and a fixing belt 88c and a pressure roller 88d that are stretched over these rollers. The pressure contact portion constitutes a nip portion. Then, the fixing belt 88c heated by the heating roller 88a and the rollers heat and press the paper passing through the nip portion to fix the unfixed toner image formed on the paper.

Next, the twin driving of the conveying rollers 71 in the twin driving device will be described. FIG. 3 is a schematic diagram showing the configuration of the twin drive device. A stepping motor 72 (abbreviated as STPM) controlled by a stepping motor control section 76 and a brushless motor 73 (abbreviated as DCBLM) controlled by a brushless motor control section 77 are connected to the same drive shaft via gears or the like. 74a (rotating shaft), and rotating the driving shaft 74a rotates a conveying roller (not shown) connected to the driving shaft 74a. Note that FIG. 3 is an example of a twin drive device, and as long as the stepping motor 72 and the brushless motor 73 can be used to rotate the same drive shaft 74a, the arrangement of each component, the configuration and shape of the gears can be changed. , gear ratio, etc. can be changed as appropriate.

FIG. 4 is a block diagram for explaining the twin drive of this embodiment. A stepping motor controller 76 of the CPU 75 drives the stepping motor 72 under open loop control. Specifically, the stepping motor control unit 76 controls the rotational speed and torque of the stepping motor 72 by transmitting pulse signals such as a clock signal (CLK) and an enable signal (ENABLE) to the stepping motor 72 .

A brushless motor control unit 77 of the CPU 75 drives the brushless motor 73 by PWM control (in particular, PWM current control that is less susceptible to fluctuations in the resistance component of the motor due to changes in load torque). Specifically, the brushless motor control unit 77 controls the rotation speed and torque of the brushless motor 73 by transmitting a PWM signal to the brushless motor 73 . Further, the brushless motor control section 77 performs feedback control based on the current (shunt current) detected by the current detection section (not shown) and the pulse signal output from the encoder 73a.

Then, the CPU 75 controls the pulse signal for driving the stepping motor 72 obtained from the stepping motor control unit 76 (hereinafter abbreviated as the pulse of the stepping motor 72) and the pulse output from the encoder 73a obtained from the brushless motor control unit 77. signal (hereinafter abbreviated as the pulse of the encoder 73a) and the angle deviation amount of the stepping motor 72 (the angle estimated from the pulse signal for driving the stepping motor 72 and the pulse signal output from the encoder 73a). and the amount of deviation from the angle specified based on the calculation. Specific examples will be described below.

FIG. 5 shows an example in which the pulse frequency of the stepping motor 72 is an integral multiple (two times in this case) of the pulse frequency of the encoder 73a. In this case, the angle deviation amount of the stepping motor 72 is calculated by comparing the pulse of the stepping motor 72 with the rising edge and falling edge of the pulse of the encoder 73a.

For example, the stepping motor 72 makes one rotation with 200 pulses (when the rotation angle per step is 1.8°, the rotation angle per pulse is 1.8 in the full step mode, and the number of pulses per rotation is 1.8°). is 360°/1.8°=200.) and the encoder 73a is one that outputs 100 pulses per rotation. Since the frequency is doubled, the rising edge or falling edge of every second pulse of the stepping motor 72 is compared with the rising edge or falling edge of each pulse of the encoder 73a to determine the frequency of the stepping motor 72. Calculate the amount of angular deviation.

FIG. 6 shows an example in which the pulse frequency of the stepping motor 72 is not an integral multiple of the pulse frequency of the encoder 73a. In this case, the greatest common divisor of the two pulses is obtained, and the rising edge or falling edge of the pulse is compared for each multiple of the greatest common divisor to calculate the angular deviation amount of the stepping motor 72 .

For example, the stepping motor 72 rotates once with 200 pulses in the same manner as described above (when the rotation angle per step is 1.8°, the rotation angle per pulse is 1.8° in the full step mode, and 1 The number of pulses per rotation is 360°/1.8°=200.) and the encoder 73a that outputs 80 pulses per rotation is selected. Since it is not an integral multiple (2.5 times) of the pulse frequency of the encoder 73a, the greatest common divisor (40) of 200 and 80 is obtained. Since 200 is 5 times 40 and 80 is 2 times 40, the rising edge or falling edge of every fifth pulse of the stepping motor 72 and the rising edge of every second pulse of the encoder 73a The edge or the falling edge is compared to calculate the angular deviation amount of the stepping motor 72 .

FIG. 7 shows the relative phases of the pulses of the stepping motor 72 and the pulses of the encoder 73a when the stepping motor 72 and the brushless motor 73 are driven and the assist torque of the brushless motor 73 is changed. When the phase of the pulse of the encoder 73a and the phase of the pulse of the encoder 73a change by a predetermined angle or more (when the angle shift amount becomes a predetermined value or more), the angle shift amount is calculated based on the phase immediately before the change. do.

For example, at startup, the backlash of the gear of the drive shaft 74a is reduced and the load increases, so the assist torque of the brushless motor 73 is increased to rotate the drive shaft 74a. At that time, when the torque of the brushless motor 73 becomes equal to the load torque, the phase difference between the pulse of the encoder 73a and the pulse of the stepping motor 72 is used as a reference of 0° to detect the pulse of the encoder 73a. The amount of angular deviation of the stepping motor 72 is calculated by comparing with the pulse.

When assembling the twin drive mechanism, a jig is used to excite the stepping motor 72 to reduce the backlash of the gear of the drive shaft 74a, thereby reducing the phase difference between the pulses of the encoder 73a and the pulses of the stepping motor 72. is preferably adjusted to a predetermined specific angle.

FIG. 8 shows the relationship between the speed of the stepping motor 72 and the brushless motor 73 and the amount of angular deviation of the stepping motor 72 . When the angular deviation amount of the stepping motor 72 exceeds a predetermined constant value, the output of the brushless motor 73 is changed. For example, as shown in the upper part of FIG. 8, when the pulse of the encoder 73a is delayed (the speed of the brushless motor 73 is smaller than the speed of the stepping motor 72), the output of the brushless motor 73 is increased and the lower part of FIG. As shown in , when the pulse of the encoder 73a advances (the speed of the brushless motor 73 is higher than the speed of the stepping motor 72), the output of the brushless motor 73 is reduced, etc., depending on the amount of angular deviation of the stepping motor 72. , changes the output of the brushless motor 73 .

Specifically, when a load is suddenly applied, the phase of the pulse of the encoder 73a lags behind the phase of the stepping motor 72 (plus phase). On the other hand, when the actual load decreases, the phase of the pulse from the encoder 73a leads the phase of the pulse from the stepping motor 72 (minus phase). The PWM duty of the current that drives the brushless motor 73 is changed, for example, as shown in Table 1 below, according to the angle deviation amount (±).

Also, when the amount of angular deviation of the stepping motor 72 exceeds a predetermined limit value, the current for driving the brushless motor 73 is not increased (the output is not changed). For example, when the angular deviation of the stepping motor 72 exceeds 90° in the full step mode, stepping out occurs. Therefore, when the angular deviation becomes ±45°, the current of the brushless motor 73 is not increased.

The operation of the twin drive system of this embodiment will be described below with reference to the flow charts of FIGS. 9 and 10. FIG.

As shown in FIG. 9, when the power of the image forming apparatus 10 is turned on (S101) and an axis rotation command is issued from the control section 20 (Yes in S102), the CPU 75 (stepping motor control section 76) outputs a clock signal and an enable signal to start the stepping motor 72, and the CPU 75 (brushless motor control unit 77) sends a PWM signal to start the brushless motor 73 (S103).

Next, as shown in FIG. 7, the CPU 75 increases the assist torque of the brushless motor 73 to perform phase matching (S104). Then, when the CPU 75 detects the pulse of the encoder 73a (S105), it compares the pulse of the stepping motor 72 and the pulse of the encoder 73a to calculate the angular deviation amount of the stepping motor 72 (S106).

Next, the CPU 75 determines whether the amount of angular deviation of the stepping motor 72 exceeds a predetermined constant value (S107), and if the amount of angular deviation of the stepping motor 72 does not exceed the constant value (No in S107) , S113, and if the angular deviation of the stepping motor 72 exceeds a predetermined value (Yes in S107), it is determined whether the angular deviation of the stepping motor 72 exceeds a predetermined limit value (S108).

When the angular deviation amount of the stepping motor 72 exceeds the limit value (Yes in S108), the CPU 75 determines that the stepping motor 72 has stepped out (S109), and the CPU 75 (brushless motor control section 77) controls the brushless motor 73 is stopped (S110). On the other hand, if the angular deviation amount of the stepping motor 72 does not exceed the limit value (No in S108), the CPU 75 (brushless motor control section 77) controls the brushless motor 73 as shown in FIG. (S111).

FIG. 10 shows the details of this step, and the CPU 75 (brushless motor control unit 77) refers to Table 1 or the like to calculate the current increase amount of the brushless motor 73 from the angle deviation amount of the stepping motor 72 ( S201), and corrects the target current of the brushless motor 73 (S202). Specifically, the post-FB current value due to the shunt current+STPM angle deviation amount correction value is corrected. Then, the CPU 75 (brushless motor control unit 77) corrects the PWM duty of the current of the brushless motor 73 and increases the assist torque (S203).

Returning to FIG. 9, by controlling the brushless motor 73 in S111, the output of the brushless motor 73 is changed, the stepping motor 72 can be normally rotated, and the drive shaft 74a can be normally rotated (S112). . After that, or if the amount of angular deviation of the stepping motor 72 does not exceed a certain value (No in S107), it is determined whether an axis stop command has been issued from the control unit 20 (S113), and an axis stop command is issued. If not (No in S113), the process returns to S105 to repeat the same processing. The brushless motor controller 77) stops the brushless motor 73 (S114).

As described above, in the mechanism for rotating the same load using the stepping motor 72 and the brushless motor 73, the pulse signal of the stepping motor 72 and the encoder 73a provided in the brushless motor 73 (or the driving mechanism 74) The amount of angular deviation of the stepping motor 72 is calculated by comparing the pulse signal of the provided encoder 74b), and the output of the brushless motor 73 is increased or decreased according to the amount of angular deviation of the stepping motor 72 (for example, a sudden If the amount of angular deviation of the stepping motor 72 increases due to torque fluctuation, the stepping motor 72 can be prevented from stepping out by increasing the output of the brushless motor 73 to increase the assist amount.

It should be noted that the present invention is not limited to the above embodiments, and its configuration and control can be modified as appropriate without departing from the gist of the present invention.

For example, in the above embodiment, the case where the motor control method of the present invention is applied to the image forming apparatus 10 has been described, but the motor control method of the present invention can be similarly applied to any device having a drive mechanism. can be applied.

INDUSTRIAL APPLICABILITY The present invention can be used for a twin drive device that rotates the same load using a stepping motor and a brushless motor, and a motor control method for the twin drive device.

10 image forming apparatus 20 control unit 21 CPU
22 ROMs
23 RAM
24 storage unit 25 network I/F unit 30 high-voltage power supply unit 40 display operation unit 50 image reading unit 51 automatic document feeder 52 document image scanning device 60 image processing unit 70 transport unit 71 transport roller 72 stepping motor 73 brushless motor 73a encoder 74 drive mechanism 74a drive shaft 74b encoder 75 CPU
76 stepping motor control section 77 brushless motor control section 80 image forming section 81, 81Y, 81M, 81C, 81K exposure device 82, 82Y, 82M, 82C, 82K developing device 83, 83Y, 83M, 83C, 83K photosensitive drum 84, 84Y, 84M, 84C, 84K Charging device 85, 85Y, 85M, 85C, 85K Cleaning device 86, 86Y, 86M, 86C, 86K Primary transfer roller 87 Intermediate transfer unit 87a Intermediate transfer belt 87b Support roller 87c Secondary transfer roller 87d Intermediate Transfer cleaning section 88 Fixing device 88a Heating roller 88b Fixing roller 88c Fixing belt 88d Pressure roller

Claims (17)

A stepping motor, a brushless motor, a drive mechanism that rotates the same load using the stepping motor and the brushless motor, and a control unit that controls the operation of the stepping motor and the brushless motor,
having an encoder on the rotary shaft of the brushless motor or the rotary shaft of the drive mechanism;
The control unit compares a pulse signal for driving the stepping motor and a pulse signal output from the encoder to calculate an angle deviation amount of the stepping motor, and outputs the brushless motor according to the angle deviation amount. increase or decrease
A twin drive device characterized by: When the frequency of the pulse signal for driving the stepping motor is an integral multiple of the frequency of the pulse signal output from the encoder, the control unit controls, at rising edges and falling edges of the pulse signal output from the encoder, the calculating an angular deviation amount of the stepping motor by comparing a pulse signal for driving the stepping motor and a pulse signal output from the encoder;
The twin drive system according to claim 1, characterized in that: When the first frequency of the pulse signal for driving the stepping motor is not an integral multiple of the second frequency of the pulse signal output from the encoder, the control unit adjusts the first frequency and the second frequency. A greatest common divisor is calculated, and the rising edge or falling edge of each number obtained by dividing the first frequency by the greatest common divisor of the pulse signal for driving the stepping motor and the pulse signal output from the encoder. , calculating the angular deviation amount of the stepping motor by comparing the rising edge or the falling edge for each number obtained by dividing the second frequency by the greatest common divisor;
The twin drive system according to claim 1, characterized in that: The control unit drives the stepping motor and the brushless motor, and changes the phase of a pulse signal for driving the stepping motor and the phase of a pulse signal output from the encoder when the assist torque of the brushless motor is changed. is changed by a predetermined angle or more, the angle deviation amount of the stepping motor is calculated based on the phase immediately before the change.
4. The twin drive system according to any one of claims 1 to 3, characterized in that: The stepping motor and the brushless motor are assembled by adjusting the phase difference between the pulse signal for driving the stepping motor and the pulse signal output from the encoder to a predetermined specific angle.
5. A twin drive system according to claim 4, characterized in that: The control unit changes the output of the brushless motor when the amount of angular deviation of the stepping motor exceeds a predetermined constant value.
A twin drive system according to any one of claims 1 to 5, characterized in that: The controller increases the output of the brushless motor when the pulse signal output from the encoder lags behind the pulse signal for driving the stepping motor, and the pulse signal output from the encoder drives the stepping motor. reducing the output of the brushless motor when it is ahead of the pulse signal that
7. A twin drive system according to claim 6, characterized in that: The control unit does not change the output of the brushless motor when the amount of angular deviation of the stepping motor exceeds a predetermined limit value.
A twin drive system according to any one of claims 1 to 7, characterized in that: Driving a conveying roller using the twin driving device according to any one of claims 1 to 8,
An image forming apparatus characterized by: A stepping motor, a brushless motor, and a drive mechanism that rotates the same load using the stepping motor and the brushless motor, and an encoder is provided on the rotary shaft of the brushless motor or the rotary shaft of the drive mechanism A motor control method in a twin drive, comprising:
a calculating step of comparing a pulse signal for driving the stepping motor and a pulse signal output from the encoder to calculate an angular deviation amount of the stepping motor;
a control step of increasing or decreasing the output of the brushless motor according to the angular deviation amount;
A motor control method characterized by: In the calculating step, when the frequency of the pulse signal that drives the stepping motor is an integral multiple of the frequency of the pulse signal output from the encoder, the above calculating an angular deviation amount of the stepping motor by comparing a pulse signal for driving the stepping motor and a pulse signal output from the encoder;
11. The motor control method according to claim 10, wherein: In the calculating step, when the first frequency of the pulse signal for driving the stepping motor is not an integer multiple of the second frequency of the pulse signal output from the encoder, the first frequency and the second frequency A greatest common divisor is calculated, and the rising edge or falling edge of each number obtained by dividing the first frequency by the greatest common divisor of the pulse signal for driving the stepping motor and the pulse signal output from the encoder. , calculating the angular deviation amount of the stepping motor by comparing the rising edge or the falling edge for each number obtained by dividing the second frequency by the greatest common divisor;
11. The motor control method according to claim 10, wherein: In the calculating step, when the stepping motor and the brushless motor are driven and the assist torque of the brushless motor is changed, the phase of the pulse signal for driving the stepping motor and the phase of the pulse signal output from the encoder are calculated. is changed by a predetermined angle or more, the angle deviation amount of the stepping motor is calculated based on the phase immediately before the change.
13. The motor control method according to any one of claims 10 to 12, characterized in that: The stepping motor and the brushless motor are assembled by adjusting the phase difference between the pulse signal for driving the stepping motor and the pulse signal output from the encoder to a predetermined specific angle.
14. The motor control method according to claim 13, wherein: In the control step, when the amount of angular deviation of the stepping motor exceeds a predetermined constant value, the output of the brushless motor is changed.
15. The motor control method according to any one of claims 10 to 14, characterized in that: In the control step, when the pulse signal output from the encoder lags behind the pulse signal for driving the stepping motor, the output of the brushless motor is increased, and the pulse signal output from the encoder drives the stepping motor. reducing the output of the brushless motor when it is ahead of the pulse signal that
16. The motor control method according to claim 15, wherein: In the control step, when the amount of angular deviation of the stepping motor exceeds a predetermined limit value, the output of the brushless motor is not changed.
17. The motor control method according to any one of claims 10 to 16, characterized in that:

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