JP6539226B2 - Motor drive - Google Patents

Description

  The present invention relates to a motor drive device for driving a motor.

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

  Subsequently, 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 for driving the motor. When the phase current I is in the positive period T1 and the PWM + is high, the phase current I flows as shown by the solid line in FIG. After that, when PWM + becomes low, an induced voltage is generated in the coil L1 in the direction to block the change of the current. This induced electromotive force is superior to the 24 V power source for driving the motor, and the phase current I flows (regeneration current) as shown by the dotted line in FIG. On the other hand, when the phase current I is negative during the period T2, when the PWM + is low, the phase current I flows as shown by the solid line in FIG. 9, and when the PWM + becomes high thereafter, the induced electromotive force generated in the coil L1 The phase current I flows as indicated by a dotted line.

  A control unit that controls the motor needs to detect the phase current I in order to drive the motor drive circuit 100 properly. As a detection place of the phase current I, there are a point A, a point B and a point 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, current detection can be performed with inexpensive parts. However, in a period T1 in which the direction of the phase current I is positive, when PWM + is high, a current flows from the power supply terminal toward GND via Q1 and then through the coils L1 and Q4. On the other hand, in a period T1 in which the direction of the phase current I is positive, when PWM + is low, a current flows from GND to the power supply terminal via Q3 and then the coil L1 and Q2 in this order. That is, in a period T1 in which the direction of the phase current I is positive, current flows in both directions toward and away from GND at point C. The same applies to a period in which the direction of the phase current I is negative. That is, when the detection resistance is provided at the point C and the voltage Vsns at both ends thereof is obtained, only the waveform shown in FIG. 9 is obtained, and the direction of the phase current can not be determined.

  Therefore, Patent Document 1 discloses a configuration for switching the polarity of the voltage of the detection resistor to be input to the differential amplifier in synchronization with the PWM signal when amplifying the voltage of the detection resistor at point C with the differential amplifier. There is.

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 a period T1 in which the phase current in FIG. 10 is positive, PWM + is low for a very short period Toff1. In this very short period Toff1, PWM + is low, 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 fall below 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 can not be detected correctly. In addition, switching noise of Q1 to Q4 is generated when the PWM signal is switched between high and low, and there is a possibility that the noise may be superimposed on the detected current value. Also in this case, the phase current I can not be detected correctly.

  The present invention provides a motor drive device that drives a motor by detecting a drive current with high accuracy.

According to one aspect of the present invention, a motor drive device includes a plurality of bridge-connected switching elements and detects drive current for supplying drive current to the motor and current flowing between the drive and ground. And a PWM for turning on / off the plurality of switching elements based on the difference between the drive current obtained from the drive current and the target value of the drive current to be supplied to the motor. and a control unit which generates a signal for controlling the motor, wherein the control unit, the PWM signal is at a high level, and if the high-level period of the PWM signal becomes longer than the predetermined period, the The current detection is performed by the detection means during the high level period of the PWM signal, and the high level of the PWM signal is obtained even if the PWM signal is high level. If the period is equal to or less than the predetermined period is characterized by a period of high level of the PWM signal is not performed the sampling of the current by the detection means.

  According to the present invention, it is possible to drive the motor by accurately detecting the drive current.

BRIEF DESCRIPTION OF THE DRAWINGS 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. BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the motor drive circuit by one Embodiment. Explanatory drawing of phase current. Explanatory drawing of operation | movement of a motor drive circuit in case the high or low period of a PWM signal is short. BRIEF DESCRIPTION OF THE DRAWINGS The block diagram of the image forming apparatus in which the mode drive device by each embodiment is used.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The following embodiment is an exemplification, and the present invention is not limited to the contents of the embodiment. Further, in each of the following drawings, components that are not necessary for the description of the embodiment will be omitted from the drawings.

First Embodiment
FIG. 1 is a block 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. 8 and 9, and thus the description thereof will not be repeated. The detection resistor 110 is provided between the junction point of Q3 and Q4 of the motor drive circuit 100 and GND in order to detect the current flowing between the motor drive circuit 100 and the GND. Note that, in the detection resistor 110, a voltage Vsns occurs according to the amplitude of the phase current I which is a drive current for driving the motor. When receiving a sampling request from the motor control unit 210, the analog-to-digital (A / D) conversion unit 120 converts the voltage Vsns, which is an analog value, into a digital value and outputs the digital value. The motor control unit 210 is realized by the CPU 200 executing a program in the present embodiment. However, it can also be realized in hardware. Furthermore, the CPU 200 can execute part of the processing of the motor control unit 210 described below, and the remaining processing can be realized as hardware. The target current generation unit 211 outputs a target value of the phase current I to be supplied to the coil L1 as a target current signal. For example, when the phase current I is 1 amperes, the target current signal is a signal in which information indicating an amplitude of +1 amperes and information indicating an amplitude of −1 amperes alternately change according to the frequency. The detection current generation unit 212 generates a detection current signal corresponding to the phase current I based on the sampling value from the A / D conversion unit 120 and the PWM + output from the PWM generation unit 213. Although PWM + is input to the detected current generation unit 212 in this embodiment, PWM + may be input since PWM + and PWM− are in opposite phase to each other.

  As described with reference to FIG. 10, the polarity of the voltage Vsns does not match the direction of the phase current I. Therefore, when PWM + is low, the detection current generation unit 212 inverts the polarity of the voltage Vsns to generate a detection current signal. Therefore, the polarity of the detected current signal corresponds to the direction of the phase current I.

  The amplification unit 214 amplifies an error that is the difference between the target current signal and the detected current signal, and outputs the result as an error current 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 the triangular wave carrier wave having a predetermined cycle. 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, the relationship between the generation of the PWM signal in the motor control unit 210 and the sampling in the A / D conversion unit 120 will be described. FIG. 2 shows the relationship between a triangular wave carrier wave of a predetermined frequency (hereinafter simply referred to as a triangular wave), an error current signal, PWM +, and the sampling timing of the output of A / D converter 120 by motor control unit 210. ing. The PWM generator 213 compares the error current signal with the 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 + becomes high level, and otherwise PWM + becomes low level. Therefore, the duty ratio is 100% when the error current signal remains at or above the maximum value of the triangular wave, and the duty ratio is 0% when the error current signal is smaller than the minimum value of the triangular wave. The duty ratio is a ratio of a high period to one cycle of PWM +.

  In the present embodiment, two thresholds (Threshold 1 and Threshold 2) which are larger than the minimum value of the triangular wave and smaller than the maximum value are provided. Here, threshold 1 is assumed to be larger than threshold 2. For example, threshold 1 may be 95% of the maximum value of the triangular wave, and threshold 2 may 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 the triangular wave becomes minimum. Then, the detection current generation unit 212 generates a detection current signal according to the sampling value and the high / low of PWM +. FIG. 2 shows PWM + and sampling timing when the error current signal is between threshold 1 and threshold 2. FIG. However, as described above, when the high and low periods of PWM + and PWM− are very short, the sign of the detected current signal generated in this short period does not correctly represent the direction of the phase current I. Therefore, in the present embodiment, sampling is not performed when the error current signal meets either of the following two conditions. First, condition 1 is the case where the error current signal is equal to or greater than threshold 1 and PWM + is low. Condition 2 is the case where the error current signal is less than or equal to threshold 2 and PWM + is high. The state satisfying this condition is a state in which the high level period of PWM + is equal to or less than a predetermined period, or a period in which the low level of PWM + is equal to or shorter than the predetermined period. Therefore, when the high level period of PWM + is equal to or less than the predetermined period, sampling is not performed in the high level period, and when the low level period of PWM + is equal to or less than the predetermined period, the low level period is There is no sampling. Similarly, if the high level period of PWM- is less than or equal to the predetermined period, sampling is not performed within the high level period, and if the low level period of PWM- is less than or equal to the predetermined period, the low level There is no sampling within the period.

  FIG. 3A shows the case where the error current signal conforms to condition 1. As shown in FIG. 3A, when the error current signal is higher than the threshold 1, the low period of PWM + due to the triangular wave becoming equal to or higher than the error current signal becomes very short. Therefore, the detection 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, sampling is not performed when the error current signal conforms to condition 1. FIG. 3B shows the case where the error current signal conforms to condition 2. As shown in FIG. 3B, when the error current signal is lower than the threshold 2, the high period of PWM + due to the triangular wave being less than the error current signal becomes very short. Therefore, the detection 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, if the error current signal conforms to condition 2, sampling is not performed. Even if the error current signal conforms to Condition 1 or Condition 2 at the sampling timing, if the error current signal changes rapidly thereafter, the high or low period may be extended as a result. However, since the change in the error current signal is in fact slow, it is unlikely that the high or low period will be extended as a result, while the error current signal conforms to condition 1 or condition 2.

  In this embodiment, since the sampling is not performed when the error current signal conforms to the condition 1 or the condition 2, the value of the detection current signal obtained at the previous sampling timing is used instead as the detection current signal at the current sampling timing. . The detection current generation unit 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 motor current can be detected more accurately than before by reducing the difference between the current detection result based on Vsns and the actual phase current I. Can. As a result, stable motor current control is possible.

  FIG. 4 is a timing chart showing the relationship of each signal. The motor control unit 210 samples the output of the A / D conversion unit 120, that is, the value obtained by converting the voltage Vsns into a digital value at each sampling timing. The result is shown as (f) sampling result. The motor control unit 210 generates a detection current signal which is a detection value of the phase current I, using the high / low of PWM + 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, at the sampling timing in the period of Toff1 and Ton1 of FIG. 4, the error current signal is not sampled because it conforms to the conditions described above. Then, the detection current generation unit 212 directly outputs the value of the detection current signal output at the sampling timing immediately before the timing at which the sampling was not performed. This makes it possible to reduce the difference between the detection result of the phase current I based on Vsns and the actual phase current I compared to the prior art, even when the high period and low period of the PWM signal are very short.

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

  As described above, in the present embodiment, when the value of the error current signal does not fall within the predetermined range at the sampling timing, the value of the detected current signal obtained at the previous sampling timing is used 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 detected current value using the detection resistor 110. The predetermined range is determined such that the time during which the logic (high / low) of the pulse signals PWM + and PWM- does not change is larger than the predetermined time. The predetermined time is a time longer than the time required to switch Q1 to Q4 which are switching elements of the motor drive circuit 100. According to the above configuration, it is possible to control the motor stably by determining the value and direction of the phase current I correctly.

Second Embodiment
Subsequently, a second embodiment will be described focusing on differences from the first embodiment. In the first embodiment, as shown in FIG. 5, when the error current signal conforms to the condition 1 or 2, the sampling is not performed. In this embodiment, the output of the A / D converter 120 is always sampled at a predetermined timing, that is, the timing at which the amplitude of the triangular wave is maximum and the timing at which the amplitude of the triangular wave is maximum in this embodiment. However, when the error current signal conforms to condition 1 or condition 2, the detection current is not updated by the sampling value, and the value of the detection current at the previous sampling timing stored in the detection current generation unit 212 Maintain.

  FIG. 6 is a flowchart of a process of generating a detection current signal 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, and in S21, the detection current generation unit 212 determines whether the error current signal conforms to Condition 1 or Condition 2. If the error current signal does not meet any of the conditions, the detected current generation unit 212 determines in S22 whether or not PWM + at the time of sampling in S20 is low. If PWM + is low, the detected current generation unit 212 inverts the polarity of the sampling value acquired in S20, and updates the value of the detected current signal to the inverted sampling value in S24. On the other hand, if PWM + is high in S22, the detected current generation unit 212 updates the value of the detected current signal to the sampling value acquired in S20 in S24. Furthermore, in S21, when the error current signal conforms to 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 conforms to Condition 1 or Condition 2, the value of the detected current signal at the previous sampling timing is used as the value of the detected current signal at the current sampling timing. In this embodiment, when the error current signal conforms to Condition 1 or Condition 2, the value of the detected current signal at the sampling timing is predicted and output from the detected current signal at the previous sampling timing.

  In the present embodiment, the motor control unit 210 stores in advance the inductance value of the coil L1. For example, it is assumed that time t1 is a sampling timing, and time t2 is a sampling timing next to time t1. Further, a sampling interval, that is, t2−t1 is Δt, an inductance value of the coil L1 is L, and a power supply voltage of the motor (24 V 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. Therefore, when the error current signal conforms to condition 1 or condition 2 at time t2, the value I2 of the detected current signal at time t2 is obtained from the value I1 of the detected current signal at time t1 It can be predicted as L. The phase current I1 is stored in the detection current generator 212 each time it is detected.

  FIG. 7 is a flowchart of a process of generating a detection current signal performed by the detection current generation unit 212 in the present embodiment. In FIG. 7, when the error current signal conforms to condition 1 or condition 2 in S30, the predicted value of the detection current signal is determined as described above in S35, and the detection current signal is updated in S34. This is different from the first embodiment shown in FIG. The process in the case where the error current signal does not conform to the conditions 1 and 2 in S30 is the same as that in the first embodiment. If the error current signal conforms to the condition 1 or 2 in S21 of the second embodiment shown in FIG. 6, the predicted value of the detected current signal may be determined and updated.

  As described above, in the present embodiment, when the value of the error current signal does not fall 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 more accurately, and hence the motor can be more accurately controlled.

<Summary>
As described above, in each of the above-described 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 the current flowing between the motor drive circuit 100 and the ground, a detection resistor 110 is provided as a detection unit of the current. Then, the motor control unit 210 obtains the drive current from the detection result of the detection unit at the sampling timing, and 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 based on the determined error evaluation value, generates a pulse signal for turning on / off the FET 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 a proportional gain and an integral gain in PI control. Is required.

  Here, when the pulse signal is at a high level and the width of the high level of the pulse signal becomes 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. Do the sampling of On the other hand, when the width of the high level of the pulse signal is equal to or less than the predetermined value even if the pulse signal is high, the motor control unit 210 samples the current detected by the detection resistor 110 during the high level period of the pulse signal. 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 driving current at the sampling timing from the driving 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 the predicted value of the drive current at the sampling timing from the drive current obtained at the previous sampling timing. This prediction can be configured to use a motor inductance value. On the other hand, when the error evaluation value is within the 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.

  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 if the pulse signal is the first logic at the sampling timing. On the other hand, in the motor control unit 210, when the pulse signal is the second logic different from the first logic, the drive current flows in the direction corresponding to the direction opposite to the direction of the current detected by the detection unit. It is determined that 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 with the triangular wave, but the predetermined range is determined such that the time during which the logic of the pulse signal does not change is larger than the predetermined time. Furthermore, the predetermined time can be obtained from the time required to switch the FET on and off. This is because, as described with reference to FIG. 10, when the time interval at which the logic of the pulse signal switches is shorter than a predetermined time, the FET does not switch from the on state to the off state, and remains in the on state. Further, in this case, the detection result of the detection unit does not accurately indicate the drive current. Therefore, in the present embodiment, when the error evaluation value is not within the predetermined range, the detection result of the detection unit at that time is It does not use it. As a result, the drive current is accurately detected, and stable motor control becomes possible.

  Therefore, each of the above embodiments discloses a configuration in which the motor control unit 210 determines whether the time interval of switching of the pulse signal before and after the sampling timing is smaller than a predetermined value. Then, when determining that the time interval of switching of the pulse signal 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 the threshold. That is, at the sampling timing, when the error current signal is equal to or greater than threshold 1 or equal to or smaller than threshold 2, it is determined that the time interval of switching of the pulse signal is smaller than a predetermined value. Even if the error current signal is greater than or equal to the threshold 1 or less than 2 as a result, the time interval of switching of the pulse signal may be greater than or equal to the predetermined value.

  In addition, the detection result of the electric current of the motor mentioned above is utilized for the vector control of a motor, etc. For example, the motor control unit 200 determines the position of the rotor of the motor based on the value of the current flowing through the winding of the motor acquired by the above-described method, and the value of the drive current to be supplied in the rotational coordinate system according to the determined position. Decide.

  Further, the motor drive device according to each of the above-described embodiments is used to drive a motor in an image forming apparatus that forms an image on a sheet. As an example, an image forming apparatus in which the motor drive device 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 toners (developers) of a plurality of colors is assumed. The image forming apparatus may be, for example, any of a printing apparatus, a printer, a copier, a multifunction peripheral (MFP), and a facsimile apparatus. The image forming apparatus includes four image forming stations that form toner images using four color toners of yellow (Y), magenta (M), cyan (C), and black (K). There is. In FIG. 11, reference numerals are given only to the components of the station of Y color, but all the four stations can adopt the same configuration. 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 and the intermediate transfer belt 116.

  The primary charging unit 112 uniformly charges the rotating photosensitive drum 111. The exposure unit 113 outputs a laser beam (light beam) modulated based on an image signal, and scans the surface of the photosensitive drum 111 with the laser beam. Thus, 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, a multi-color toner image is formed on the intermediate transfer belt 116 by sequentially overlapping and primarily transferring the toner images of the respective colors formed on the photosensitive drums 111 of each station on the intermediate transfer belt 116. .

  A sheet P in a sheet feeding cassette (sheet feeding unit) 124 is fed to a sheet conveyance path by a sheet feeding roller (pickup roller) 121. The sheet P may be referred to as recording paper, recording material, recording medium, paper, transfer material, transfer paper, and the like. The sheet P fed to the sheet conveyance path is conveyed by the conveyance roller 122 to the secondary transfer unit. At 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 applies heat and pressure to the toner image to fix it on the sheet P. Thereafter, the sheet P on which the toner image is fixed is discharged by the sheet discharge roller 126 to the sheet discharge tray (sheet discharge unit). 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 the paper feed roller 121, the conveyance roller 122, and the paper discharge roller 126, as conveyance rollers for a sheet on which an image is formed. A motor corresponding to a drive source for driving these rollers is driven by the motor drive device of each of the above embodiments in accordance with an instruction from a higher 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 drive device according to the above embodiments.

Other Embodiments
The present invention supplies a program that implements one or more functions of the above-described embodiments to a system or apparatus via a network or storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. Can also be realized. It can also be implemented by a circuit (eg, an ASIC) that implements one or more functions.

  100: Motor drive circuit 110: Detection resistor 210: Motor controller

Claims (14)

Drive means for supplying a drive current to the motor, the drive means including a plurality of bridge-connected switching elements;
Detection means for detecting a current flowing between the drive means and the ground;
A drive current is determined 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 determined drive current and a target value of the drive current to be supplied to the motor. and control means for controlling the motor and,
Equipped with
Wherein, the PWM signal is at a high level, and if the high-level period of the PWM signal becomes longer than the predetermined time period, performs a sampling of the current by the detection means in the period of the high level of the PWM signal , said PWM signal if the high-level period of the PWM signal is also a high level is equal to or less than the predetermined period of time, not to perform sampling of current by said detecting means during a period of a high level of the PWM signal A motor drive device characterized by   The motor drive device according to claim 1, wherein the control means generates the PWM signal by comparing the difference with a triangular wave. Drive means for supplying a drive current to the motor, the drive means including a plurality of bridge-connected switching elements;
Detection means for detecting a current flowing between the drive means and the ground;
A drive current is obtained from the detection result of the detection means at sampling timing, and a pulse for turning on / off the plurality of switching elements based on a difference between the drive current obtained and the target value of the drive current to be supplied to the motor. and control means for controlling the motor to generate a signal,
Equipped with
The motor drive device, wherein the control means determines a drive current at the sampling timing from the drive current obtained at the previous sampling timing if the difference is not within a predetermined range at the sampling timing.   4. The apparatus according to claim 3, wherein, when the difference is within the predetermined range at the sampling timing, the control means determines a drive current at the sampling timing from a detection result of the detection means at the sampling timing. Motor drive.   The control means may set the drive current at the sampling timing to the same value as the drive current obtained at the previous sampling timing if the difference is not within the predetermined range at the sampling timing. Or the motor drive as described in 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 according to claim 1.   If the difference is not within the predetermined range at the sampling timing, the control means predicts the driving current at the sampling timing based on the driving current obtained at the previous sampling timing and the inductance value of the motor. The motor drive device according to claim 6. Wherein, when the pulse signal at the sampling timing is at the first logic, the determination and the drive current flows in a direction corresponding to the direction of current the detection means detects the pulse signal is the When the first logic is different from the second logic claims, characterized in that said detecting means determines that said drive current in a direction corresponding to the opposite direction flow in the direction of the current detected Item 8. A motor drive device according to any one of Items 3 to 7. The control means generates the pulse signal by comparing the difference with a triangular wave;
The motor drive device according to any one of claims 3 to 8, wherein the predetermined range is determined such that a time in which the logic of the pulse signal does not change is longer than a predetermined time.   10. The motor drive device according to claim 9, wherein the predetermined time is obtained from the time required to switch the plurality of switching elements. Drive means for supplying a drive current to the motor, the drive means including a plurality of bridge-connected switching elements;
Detection means for detecting a current flowing between the drive means and the ground;
At sampling timing, a drive current is determined from the detection result of the detection means, and a pulse signal for turning on / off the plurality of switching elements is generated based on the determined drive current and a target value of the drive current to be supplied to the motor. and control means for controlling the motor and,
Equipped with
If the control means determines that the time interval of switching of the pulse signal before and after the sampling timing is smaller than a predetermined value, the control means determines the driving current at the sampling timing from the driving current obtained at the previous sampling timing. Motor drive.   If 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, then the control means determines 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, characterized in that: Drive means for supplying a drive current to the motor, the drive means including a plurality of bridge-connected switching elements;
Detection means for detecting a current flowing between the drive means and the ground;
A drive current is determined 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 determined drive current and a target value of the drive current to be supplied to the motor. Control means for controlling the motor;
Equipped with
The control means performs sampling of the current by the detection means in the low level period of the PWM signal when the PWM signal is at the low level and the low level period of the PWM signal is longer than a predetermined period. Even if the PWM signal is low level, if the low level period of the PWM signal is equal to or less than the predetermined period, sampling of the current by the detection means is not performed in the low level period of the PWM signal. A motor drive device characterized by The motor drive device according to claim 13, wherein the control means generates the PWM signal by comparing the difference with a triangular wave.

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