JP2017011987A - Motor drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive for driving a motor by detecting a drive current accurately.SOLUTION: A motor drive includes a motor drive circuit (100) including a plurality of switching elements in bridge connection, and supplying a dive current to a motor, a detection resistor (110) for detecting a current flowing between the motor drive circuit (100) and the ground, and a motor control section (210) for controlling the motor by determining a drive current from the detection result of current, and generating a PWM signal for turning the plurality of switching elements on/off based on the difference of the drive current thus determined and the target value of a drive current to be supplied to the motor. When the PWM signal is high level and the width of high level of the PWM signal goes above a predetermined value, the motor control section (210) performs current sampling by the detection resistor (110) in the high level period of the PWM signal. When the width of high level of the PWM signal goes below a predetermined value, even if the PWM signal is high level, the motor control section (210) does not performs current sampling by the detection resistor (110) in the high level period of the PWM signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor driving device that drives a motor.

  FIG. 8 is a configuration diagram of a general motor drive circuit 100. Four FETs Q1 to Q4 (hereinafter simply referred to as Q1 to Q4) are bridge-connected, and the motor coil L1 is connected to bridge the connection point between Q1 and Q3 and the connection point between Q2 and Q4. . In FIG. 8, Q1 to Q4 are n-channel FETs, and the drain terminals of Q1 and Q2 are connected to a 24V power supply terminal. The source terminals of Q3 and Q4 are connected to the ground (GND). Q1 and Q4 are driven by PWM + which is the same PWM signal, and Q2 and Q3 are driven by PWM− which is the same PWM signal. Note that PWM + and PWM− are in an opposite phase relationship.

  Next, the operation of the motor drive circuit 100 will be described with reference to FIG. In FIG. 9, a period T1 is a period in which the phase current I flowing through the coil L1 in FIG. 8 is positive (in the direction of the arrow), and a period T2 is a period in which the phase current I is negative (in the direction opposite to the arrow). is there. The phase current is a drive current that drives the motor. When PWM + is high during the period T1 in which the phase current I is positive, the phase current I flows as shown by the solid line in FIG. Thereafter, when PWM + becomes low, an induced electromotive voltage is generated in the coil L1 in a direction to prevent a change in current. The induced electromotive voltage is superior to the 24V power source for driving the motor, and the phase current I flows (regenerative current) as shown by the dotted line in FIG. On the other hand, when PWM + is low during the period T2 when the phase current I is negative, the phase current I flows as shown by the solid line in FIG. 9, and then when PWM + becomes high, the induced electromotive voltage generated in the coil L1 The phase current I flows like a dotted line.

  The controller that controls the motor needs to detect the phase current I in order to drive the motor drive circuit 100 appropriately. The detection locations of the phase current I include points A, B, and C in FIG. Here, in order to detect the current at the points A and B, a current detection unit capable of inputting a high voltage of 24 V is required, which increases the cost. On the other hand, when detecting at the point C, it is possible to detect the current with inexpensive components. However, if PWM + is high during the period T1 in which the direction of the phase current I is positive, a current flows from the power supply terminal to GND via the Q1, coils L1, and Q4 in this order. On the other hand, when PWM + is low during the period T1 in which the direction of the phase current I is positive, a current flows from GND toward the power supply terminal via Q3, coils L1, and Q2. That is, in the period T1 in which the direction of the phase current I is positive, currents flowing in both directions in the direction toward GND and in the direction from GND flow at the point C. The same applies to a period in which the direction of the phase current I is negative. That is, when a detection resistor is provided at point C and the voltage Vsns at both ends is obtained, only the waveform shown in FIG. 9 is obtained, and the direction of the phase current cannot be determined.

  For this reason, Patent Document 1 discloses a configuration that switches the polarity of the voltage of the detection resistor that is input to the differential amplifier in synchronization with the PWM signal when the voltage of the detection resistor at point C is amplified by the differential amplifier. Yes.

JP-A-8-99645

  FIG. 10 is a timing chart of each signal when the high or low period of the PWM signal is very short. For example, in the period T1 in which the phase current of FIG. 10 is positive, PWM + is low for a very short period Toff1. In this very short period Toff1, PWM + is low and ideally Q1 and Q4 are off, but in reality Q1 and Q4 remain on. This is because the gate charges of Q1 and Q4 are not sufficiently discharged during the period Toff1, and thus the voltage between the gate and the source does not become lower than the threshold voltage. Therefore, as shown in FIG. 10, the voltage Vsns remains positive in the period Toff1, and as a result, the input to the differential amplifier in the configuration of Patent Document 1 becomes negative as shown in FIG. Therefore, even in the configuration of Patent Document 1, the phase current I cannot be detected correctly. Further, switching noise of Q1 to Q4 is generated by switching the PWM signal between high and low, and may be superimposed on the detected current value. Also in this case, the phase current I cannot be detected correctly.

  The present invention provides a motor drive device that drives a motor by accurately detecting a drive current.

  According to one aspect of the present invention, a motor driving device includes a plurality of switching elements connected in a bridge, and includes a driving unit that supplies a driving current to the motor, and a detection that detects a current flowing between the driving unit and the ground. And a PWM for turning on / off the plurality of switching elements based on a difference between the obtained drive current and a target value of the drive current to be supplied to the motor. Control means for generating a signal to control the motor, wherein the control means is configured to control the PWM signal when the PWM signal is at a high level and the width of the high level of the PWM signal is greater than a predetermined value. The current is sampled by the detecting means during a high level period of the signal, and the PWM signal has a high level width even if the PWM signal is at the high level. If equal to or less than the predetermined value, characterized in that it does not perform the sampling of the current by the detection means in the period of the high level of the PWM signal.

  According to the present invention, the motor can be driven by accurately detecting the drive current.

The schematic block diagram of the motor drive device by one Embodiment. The time chart of each signal by one Embodiment. The time chart of each signal by one Embodiment. The time chart of each signal by one Embodiment. The flowchart of the process in the motor control part by one Embodiment. The flowchart of the process in the motor control part by one Embodiment. The flowchart of the process in the motor control part by one Embodiment. The block diagram of the motor drive circuit by one Embodiment. Explanatory drawing of a phase current. Explanatory drawing of operation | movement of a motor drive circuit when the high or low period of a PWM signal is short. 1 is a configuration diagram of an image forming apparatus in which a mode driving device according to each embodiment is used.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In addition, the following embodiment is an illustration and does not limit this invention to the content of embodiment. In the following drawings, components that are not necessary for the description of the embodiments are omitted from the drawings.

<First embodiment>
FIG. 1 is a configuration diagram of a motor drive device 1 according to the present embodiment. The configuration and operation of the motor drive circuit 100 of the motor drive device 1 are the same as those described with reference to FIGS. The detection resistor 110 is provided between the connection point of Q3 and Q4 of the motor drive circuit 100 and GND in order to detect a current flowing between the motor drive circuit 100 and GND. Note that a voltage Vsns corresponding to the amplitude of the phase current I that is a drive current for driving the motor is generated in the detection resistor 110. When there is a sampling request from the motor control unit 210, the analog / digital (A / D) conversion unit 120 converts the voltage Vsns, which is an analog value, into a digital value and outputs the digital value. In this embodiment, the motor control unit 210 is realized by the CPU 200 executing a program. However, it can also be realized in hardware. Furthermore, the CPU 200 can execute some processes of the motor control unit 210 described below, and the remaining processes can be realized by hardware. The target current generator 211 outputs the target value of the phase current I that should flow through the coil L1 as a target current signal. For example, when the phase current I is 1 ampere, the target current signal is a signal in which information indicating an amplitude of +1 ampere and information indicating an amplitude of −1 ampere are alternately changed according to the frequency. The detection current generator 212 generates a detection current signal corresponding to the phase current I based on the sampling value from the A / D converter 120 and the PWM + output from the PWM generator 213. In the present embodiment, PWM + is input to the detection current generation unit 212. However, since PWM + and PWM− have opposite phases, a configuration in which PWM− is input may be employed.

  As described with reference to FIG. 10, the polarity of the voltage Vsns does not coincide with the direction of the phase current I. Therefore, when PWM + is low, the detection current generation unit 212 generates a detection current signal by inverting the polarity of the voltage Vsns. Therefore, the polarity of the detection current signal depends on the direction of the phase current I.

  The amplification unit 214 amplifies an error that is a difference between the target current signal and the detection current signal, and outputs the amplified error signal to the PWM generation unit 213. The gain of the amplification unit 214 is the sum of the proportional gain and the integral gain. The PWM generation unit 213 generates PWM + and PWM− to be output to the motor drive circuit 100 by comparing the error current signal with a triangular wave carrier wave having a predetermined period. As described above, the motor control unit 210 detects the phase current based on the voltage Vsns of the detection resistor 110, corrects the polarity based on PWM +, and performs feedback control.

  Subsequently, a relationship between generation of a PWM signal in the motor control unit 210 and sampling in the A / D conversion unit 120 will be described. FIG. 2 shows a relationship among a triangular wave carrier wave (hereinafter simply referred to as a triangular wave) having a predetermined frequency, an error current signal, PWM +, and a sampling timing of the output of the A / D converter 120 by the motor controller 210. ing. The PWM generation unit 213 compares the error current signal with a triangular wave to generate PWM + and PWM−. More specifically, when the value (amplitude) of the error current signal is equal to or greater than the value (amplitude) of the triangular wave, PWM + is at a high level, and otherwise, PWM + is at a low level. Accordingly, the duty ratio is 100% if the error current signal remains above the maximum value of the triangular wave, and the duty ratio becomes 0% if the error current signal remains below the minimum value of the triangular wave. The duty ratio is the ratio of the high period to one PWM + cycle.

  In the present embodiment, two threshold values (threshold value 1 and threshold value 2) that are larger than the minimum value of the triangular wave and smaller than the maximum value are provided. Here, the threshold 1 is assumed to be larger than the threshold 2. For example, the threshold value 1 can be 95% of the maximum value of the triangular wave, and the threshold value 2 can be 5% of the maximum value of the triangular wave. The motor control unit 210 normally samples the output of the A / D conversion unit 120 at the timing when the triangular wave becomes maximum and the timing when it becomes the minimum. Then, the detection current generation unit 212 generates a detection current signal according to the sampling value and PWM + high / low. FIG. 2 shows PWM + and sampling timing when the error current signal is between the threshold value 1 and the threshold value 2. However, as described above, when the PWM + and PWM− high and low periods are very short, the sign of the detection current signal generated in this short period does not correctly represent the direction of the phase current I. Therefore, in this embodiment, sampling is not performed when the error current signal meets one of the following two conditions. First, Condition 1 is a case where the error current signal is equal to or greater than the threshold value 1 and PWM + is low. Condition 2 is when the error current signal is equal to or less than the threshold 2 and PWM + is high. The state satisfying this condition is a state in which the PWM + high level period is equal to or less than the predetermined period, or the PWM + low level period is equal to or less than the predetermined period. Therefore, when the high level period of PWM + is equal to or shorter than the predetermined period, sampling is not performed within the high level period, and when the low level period of PWM + is equal to or shorter than the predetermined period, the sampling is not performed within the low level period. Sampling is not performed. Similarly, when the high level period of PWM− is equal to or shorter than the predetermined period, sampling is not performed within the high level period, and when the low level period of PWM− is equal to or lower than the predetermined period, Sampling is not performed within the period.

  FIG. 3A shows a case where the error current signal meets the condition 1. As shown in FIG. 3A, when the error current signal is higher than the threshold value 1, the PWM + low period due to the triangular wave being equal to or higher than the error current signal becomes very short. Therefore, the detected current signal based on the sampling value at this time does not correctly represent the actual phase current I. Therefore, as shown in FIG. 3A, when the error current signal meets the condition 1, sampling is not performed. FIG. 3B shows a case where the error current signal meets the condition 2. As shown in FIG. 3B, when the error current signal is lower than the threshold value 2, the high period of PWM + due to the triangular wave being less than the error current signal becomes very short. Therefore, the detected current signal based on the sampling value at this time does not correctly represent the actual phase current I. Therefore, as shown in FIG. 3B, when the error current signal meets the condition 2, sampling is not performed. Note that even if the error current signal conforms to the condition 1 or the condition 2 at the sampling timing, if the error current signal changes rapidly thereafter, the high or low period may become longer as a result. However, since the change of the error current signal is actually gentle, the error current signal conforms to Condition 1 or Condition 2, and as a result, the high or low period hardly occurs.

  In the present embodiment, since sampling is not performed when the error current signal meets Condition 1 or Condition 2, the value of the detected current signal obtained at the previous sampling timing is used instead as the detected current signal at the current sampling timing. . The detection current generator 212 stores the value of the detection current signal obtained at the sampling timing until the next sampling timing. As a result, even when the high period and low period of the PWM signal are very short, the difference between the current detection result based on Vsns and the actual phase current I is reduced to detect the motor current with higher accuracy than in the past. Can do. As a result, stable motor current control is possible.

  FIG. 4 is a timing chart showing the relationship between the signals. The motor control unit 210 samples the output of the A / D conversion unit 120 at each sampling timing, that is, the value obtained by converting the voltage Vsns into a digital value. The result is shown as (f) sampling result. The motor control unit 210 generates a detection current signal that is a detection value of the phase current I by using the PWM + high / low and the sampling result. Specifically, when PWM + is high, the sampling value is output as it is, and when PWM + is low, the polarity of the sampling value is inverted and output to generate a detection current signal.

  However, sampling is not performed at the sampling timing within the period of Toff1 and Ton1 in FIG. 4 because the error current signal meets the above-described conditions. Then, the detection current generation unit 212 outputs the value of the detection current signal output at the sampling timing immediately before the timing when sampling is not performed. Thereby, even when the high period and the low period of the PWM signal are very short, the difference between the detection result of the phase current I based on Vsns and the actual phase current I can be reduced as compared with the conventional case.

  FIG. 5 is a flowchart of detection current signal generation processing performed by the detection current generation unit 212 in the present embodiment. The processing in FIG. 5 is performed at a predetermined sampling timing, which is the timing at which the amplitude of the triangular wave is maximum and minimum in this embodiment. In S10, the detection current generation unit 212 determines whether the error current signal satisfies the condition 1 or the condition 2. If the error current signal does not match any of the conditions, the detection current generator 212 samples the output of the A / D converter 120 in S11. Subsequently, in S12, the detection current generator 212 determines whether or not PWM + at the time of sampling in S11 is low. If PWM + is low, the detection current generator 212 inverts the polarity of the sampling value acquired in S11, and updates the value of the detection current signal to the inverted sampling value in S14. On the other hand, if PWM + is high in S12, the detection current generator 212 updates the value of the detection current signal to the sampling value acquired in S11 in S14. Furthermore, in S10, if the error current signal meets any of the conditions, the detection current generator 212 ends the process without updating the value of the detection current signal.

  As described above, in this embodiment, when the value of the error current signal is not within the predetermined range at the sampling timing, the value of the detected current signal obtained at the previous sampling timing is set as the value of the current sampling timing. On the other hand, when the value of the error current signal is within a predetermined range at the sampling timing, the value of the detected current signal is obtained based on the current value detected using the detection resistor 110. The predetermined range is determined so that the time during which the logic (high / low) of PWM + and PWM− that are pulse signals does not change is longer than the predetermined time. The predetermined time is a time longer than the time necessary for switching the switching elements Q1 to Q4 of the motor drive circuit 100. With the above configuration, it is possible to determine the value and direction of the phase current I correctly and to control the motor stably.

<Second embodiment>
Next, the second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment, as shown in FIG. 5, sampling is not performed when the error current signal meets condition 1 or condition 2. In the present embodiment, the output of the A / D converter 120 is always sampled at a predetermined timing, in the present embodiment, at a timing at which the amplitude of the triangular wave is maximized and at a timing at which it is minimized. However, when the error current signal conforms to Condition 1 or Condition 2, the detection current is not updated with the sampling value, and the value of the detection current at the previous sampling timing stored in the detection current generation unit 212 is not performed. To maintain.

  FIG. 6 is a flowchart of detection current signal generation processing performed by the detection current generation unit 212 in the present embodiment. In S20, the detection current generation unit 212 samples the output of the A / D conversion unit 120. In S21, the detection current generation unit 212 determines whether the error current signal meets the condition 1 or the condition 2. If the error current signal does not meet any of the conditions, the detection current generator 212 determines in S22 whether PWM + at the time of sampling in S20 is low. If PWM + is low, the detection current generator 212 inverts the polarity of the sampling value acquired in S20, and updates the value of the detection current signal to the inverted sampling value in S24. On the other hand, if PWM + is high in S22, the detected current generator 212 updates the value of the detected current signal to the sampling value acquired in S20 in S24. Furthermore, in S21, if the error current signal meets any of the conditions, the detection current generation unit 212 ends the process without updating the value of the detection current signal.

<Third embodiment>
Hereinafter, the third embodiment will be described focusing on differences from the first embodiment and the second embodiment. In the first embodiment and the second embodiment, when the error current signal satisfies the condition 1 or the condition 2, the value of the detection current signal at the previous sampling timing is set as the value of the detection current signal at the current sampling timing. In the present embodiment, when the error current signal meets the condition 1 or 2, the value of the detection current signal at the sampling timing is predicted and output from the detection current signal at the previous sampling timing.

  In the present embodiment, the motor control unit 210 stores the inductance value of the coil L1 in advance. For example, it is assumed that time t1 is the sampling timing and time t2 is the next sampling timing after time t1. Further, the sampling interval, that is, t2−t1 is Δt, the inductance value of the coil L1 is L, and the motor power supply voltage (24V in FIG. 1) is V. In this case, the difference ΔI between the phase current I1 at time t1 and the phase current I2 at time t2 can be predicted as ΔI = (V × Δt) / L. Accordingly, when the error current signal meets the condition 1 or 2 at the time t2, the value I2 of the detected current signal at the time t2 is changed from the detected current signal value I1 at the time t1 to I2 = I1 + (V × Δt) / L can be predicted. The phase current I1 is stored in the detected current generator 212 every time it is detected.

  FIG. 7 is a flowchart of detection current signal generation processing performed by the detection current generation unit 212 in the present embodiment. In FIG. 7, when the error current signal meets the condition 1 or 2 in S30, the predicted value of the detected current signal is determined as described above in S35, and the detected current signal is updated in S34. This is different from the first embodiment shown in FIG. In S30, the process when the error current signal does not meet the conditions 1 and 2 is the same as that in the first embodiment. In addition, when the error current signal meets the condition 1 or the condition 2 in S21 of the second embodiment shown in FIG. 6, the configuration may be such that the predicted value of the detected current signal is determined and updated.

  As described above, in this embodiment, if the value of the error current signal is not within the predetermined range at the sampling timing, the predicted value of the detected current signal at the current sampling timing is calculated based on the value of the detected current signal obtained at the previous sampling timing. decide. With this configuration, the phase current I can be determined with higher accuracy, and thus the motor can be controlled with higher accuracy.

<Summary>
As described above, in each of the above embodiments, a configuration is disclosed in which the drive current supplied to the motor is accurately detected by the motor drive circuit 100 including the FETs that are a plurality of bridge-connected switching elements. Specifically, in order to detect a current flowing between the motor drive circuit 100 and the ground, a detection resistor 110 is provided as a detection unit for the current. The motor control unit 210 obtains a drive current from the detection result of the detection unit at the sampling timing, and calculates an error evaluation value (error current signal) from the difference between the obtained drive current and the target value of the drive current to be supplied to the motor. ) And a pulse signal for turning on / off the FET is generated based on the obtained error evaluation value to control the motor. Here, the error evaluation value is a value obtained by amplifying the difference between the obtained drive current and the target value of the drive current to be supplied to the motor, and the amplification gain is, for example, the sum of the proportional gain and integral gain in PI control. As required.

  Here, when the pulse signal is at a high level and the width of the high level of the pulse signal is larger than a predetermined value, the motor control unit 210 detects the current detected by the detection resistor 110 during the high level period of the pulse signal. Sampling. On the other hand, the motor control unit 210 samples the current detected by the detection resistor 110 during the high level period of the pulse signal when the high level width of the pulse signal is equal to or less than a predetermined value even if the pulse signal is high level. Do not do. In other words, if the error evaluation value is not within the predetermined range at the sampling timing, the motor control unit 210 obtains the drive current at the sampling timing from the drive current obtained at the previous sampling timing. For example, the motor control unit 210 can set the drive current at the sampling timing to the same value as the drive current obtained at the previous sampling timing. The motor control unit 210 can also determine a predicted value of the drive current at the sampling timing from the drive current obtained at the previous sampling timing. For this prediction, the motor inductance value can be used. On the other hand, when the error evaluation value is within a predetermined range, the motor control unit 210 obtains the drive current at the sampling timing from the detection result of the detection unit at the sampling timing.

  If the pulse signal is the first logic at the sampling timing, the motor control unit 210 determines that the drive current is flowing in the direction corresponding to the direction of the current detected by the detection unit. On the other hand, if the pulse signal has a second logic different from the first logic, the motor control unit 210 has a drive current flowing in a direction corresponding to a direction opposite to the direction of the current detected by the detection unit. Is determined. This is because, as described with reference to FIG. 9, the relationship between the direction of the current flowing through the detection unit and the direction of the drive current differs between when the pulse signal is in the on state and when it is in the off state. is there.

  The motor control unit 210 generates a pulse signal by comparing the error evaluation value and the triangular wave, and the predetermined range is obtained so that the time during which the logic of the pulse signal does not change is longer than the predetermined time. Further, the predetermined time is obtained from the time required for switching the FET on and off. This is because, as described with reference to FIG. 10, if the time interval at which the logic of the pulse signal is switched is shorter than a predetermined time, the FET does not switch from the on state to the off state but remains in the on state. In this case, the detection result of the detection unit does not accurately indicate the drive current. Therefore, in this embodiment, if the error evaluation value is not within the predetermined range, the detection result of the detection unit at that time is displayed. The configuration is not used. As a result, it is possible to detect the drive current with high accuracy and to perform stable motor control.

  Accordingly, each of the above embodiments discloses a configuration in which the motor control unit 210 determines whether or not the time interval of switching of the pulse signal before and after the sampling timing is smaller than a predetermined value. When the motor control unit 210 determines that the pulse signal switching time interval is smaller than the predetermined value, the motor control unit 210 obtains the drive current at the sampling timing from the drive current obtained at the previous sampling timing. In each of the above embodiments, this determination is made by comparing the value of the error current signal at the sampling timing with a threshold value. That is, at the sampling timing, if the error current signal is greater than or equal to the threshold value 1 or less than or equal to the threshold value 2, it is determined that the time interval for switching the pulse signal is smaller than the predetermined value. Even if the error current signal is greater than or equal to the threshold value 1 or less than or equal to the threshold value 2, the switching time interval of the pulse signal may result in a predetermined value or more, but the occurrence probability is low and does not cause a problem.

  The motor current detection result described above is used for motor vector control and the like. For example, the motor control unit 200 determines the rotor position of the motor based on the value of the current flowing through the motor winding acquired by the method described above, and the value of the drive current to be supplied in the rotating coordinate system according to the determined position To decide.

  In addition, the motor driving device according to each of the above embodiments is used to drive a motor in an image forming apparatus that forms an image on a sheet. As an example, the image forming apparatus on which the motor driving apparatus according to the present embodiment is mounted will be described with reference to FIG. The image forming apparatus may be an image forming apparatus that forms a single-color image, but here, an image forming apparatus that forms a multicolor image using a plurality of colors of toner (developer) is assumed. The image forming apparatus may be, for example, a printing apparatus, a printer, a copier, a multifunction peripheral (MFP), or a facsimile apparatus. The image forming apparatus includes four image forming stations that form toner images using toners of four colors of yellow (Y), magenta (M), cyan (C), and black (K). Yes. In FIG. 11, reference numerals are assigned only to the components of the Y-colored station, but the same configuration can be adopted for all four stations. Each station is an example of an image forming unit that forms an image using toner on an image carrier such as the photosensitive drum 111 or the intermediate transfer belt 116.

  The primary charging unit 112 uniformly charges the rotating photosensitive drum 111. The exposure unit 113 outputs laser light (light beam) modulated based on the image signal, and scans the surface of the photosensitive drum 111 with the laser light. Thereby, an electrostatic latent image is formed on the photosensitive drum 111. The developing unit 114 develops the electrostatic latent image using toner and forms a toner image on the photosensitive drum 111. The primary transfer roller 117 primarily transfers the toner image on the photosensitive drum 111 to the intermediate transfer belt 116. The intermediate transfer belt 116 rotates in the direction of arrow B. The toner image on the intermediate transfer belt 116 is conveyed to a secondary transfer portion formed by the intermediate transfer belt 116 and the secondary transfer roller 123. In the meantime, the toner images of the respective colors formed on the photosensitive drum 111 of each station are sequentially superimposed on the intermediate transfer belt 116 and primarily transferred, so that a multicolor toner image is formed on the intermediate transfer belt 116. .

  The sheet P in the paper feed cassette (paper feed unit) 124 is fed to the sheet conveyance path by a paper feed roller (pickup roller) 121. The sheet P may be referred to as recording paper, recording material, recording medium, paper, transfer material, transfer paper, or the like. The sheet P fed to the sheet conveyance path is conveyed by the conveyance roller 122 to the secondary transfer unit. In the secondary transfer portion, the toner image conveyed by the intermediate transfer belt 116 is secondarily transferred to the sheet P. The fixing unit 125 fixes the toner image on the sheet P by applying heat and pressure. Thereafter, the sheet P on which the toner image is fixed is discharged to a discharge tray (discharge section) by a discharge roller 126. The toner remaining on the surfaces of the photosensitive drum 111 and the intermediate transfer belt 116 is removed (collected) by the drum cleaner 115 and the belt cleaner 118, respectively.

  As described above, the image forming apparatus includes rollers such as a paper feed roller 121, a transport roller 122, and a paper discharge roller 126 as rollers for transporting a sheet on which an image is formed. A motor corresponding to a driving source for driving these rollers is driven by the motor driving device of each of the above embodiments in accordance with an instruction from a higher-level control circuit in the image forming apparatus. Further, the motor for driving the photosensitive drum 111 and the intermediate transfer belt 116 can be driven by the motor driving device according to each of the above embodiments.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

  100: motor drive circuit, 110: detection resistor, 210: motor control unit

Claims (12)

Drive means including a plurality of bridge-connected switching elements and supplying a drive current to the motor;
Detecting means for detecting a current flowing between the driving means and the ground;
A drive current is obtained from the detection result of the detection means, and a PWM signal for turning on / off the plurality of switching elements is generated based on a difference between the obtained drive current and a target value of the drive current to be supplied to the motor. Control means for controlling the motor,
With
When the PWM signal is at a high level and the width of the high level of the PWM signal is larger than a predetermined value, the control unit performs current sampling by the detection unit during a period of the high level of the PWM signal. Even if the PWM signal is at a high level, if the width of the high level of the PWM signal is equal to or less than the predetermined value, current sampling by the detection means is not performed during the high level period of the PWM signal. A motor drive device.   2. The motor driving apparatus according to claim 1, wherein the control unit generates the PWM signal by comparing the difference with a triangular wave. Drive means including a plurality of bridge-connected switching elements and supplying a drive current to the motor;
Detecting means for detecting a current flowing between the driving means and the ground;
A pulse for obtaining a drive current from a detection result of the detection means at a sampling timing and turning on / off the plurality of switching elements based on a difference between the obtained drive current and a target value of the drive current to be supplied to the motor Control means for generating a signal to control the motor;
With
If the difference is not within a predetermined range at the sampling timing, the control means obtains the drive current at the sampling timing from the drive current obtained at the previous sampling timing.   The said control means calculates | requires the drive current in the said sampling timing from the detection result of the said detection means in the said sampling timing, if the said difference exists in the said predetermined range in sampling timing. Motor drive device.   4. The control unit according to claim 3, wherein if the difference at the sampling timing is not within the predetermined range, the driving current at the sampling timing is set to the same value as the driving current obtained at the previous sampling timing. Or the motor drive unit of 4.   The control means predicts the drive current at the sampling timing from the drive current obtained at the previous sampling timing if the difference is not within the predetermined range at the sampling timing. The motor drive device described in 1.   The control means predicts the drive current at the sampling timing based on the drive current obtained at the previous sampling timing and the inductance value of the motor when the difference is not within the predetermined range at the sampling timing. The motor driving device according to claim 6.   The control means determines that the drive current is flowing in a direction corresponding to the direction of the current detected by the detection means when the pulse signal has the first polarity at the sampling timing, and the pulse signal is The second polarity different from the first polarity is determined to determine that the drive current is flowing in a direction corresponding to a direction opposite to the direction of the current detected by the detection means. The motor driving device according to any one of 3 to 7. The control means generates the pulse signal by comparing the difference with a triangular wave,
9. The motor driving apparatus according to claim 3, wherein the predetermined range is determined such that a time during which the polarity of the pulse signal does not change is longer than a predetermined time.   The motor driving apparatus according to claim 9, wherein the predetermined time is obtained from a time required for switching the plurality of switching elements. Drive means including a plurality of bridge-connected switching elements and supplying a drive current to the motor;
Detecting means for detecting a current flowing between the driving means and the ground;
A driving current is obtained from the detection result of the detecting means at a sampling timing, and a pulse signal for turning on / off the plurality of switching elements is generated based on the obtained driving current and a target value of the driving current to be supplied to the motor. Control means for controlling the motor,
With
When the control means determines that the time interval for switching the pulse signal before and after the sampling timing is smaller than a predetermined value, the control means obtains the drive current at the sampling timing from the drive current obtained at the previous sampling timing. A motor drive device.   When the control means determines that the time interval of switching of the pulse signal before and after the sampling timing is greater than the predetermined value, the control means obtains the drive current at the sampling timing from the detection result of the detection means at the sampling timing. The motor drive device according to claim 11, wherein

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