Motor control device and image forming apparatus

Abstract

To provide a technique to stably rotate a rotor.SOLUTION: A motor controller comprises: current supply means that supplies coil current to a plurality of coils of a motor by controlling voltage applied to the plurality of coils based on a first command value of current for excitation and a second command value of current for torque; and control means that controls the first command value based on the rotation speed of a rotor of the motor.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to motor control technology.

Background Art

[0002] As a drive source of an image forming apparatus, a sensorless type motor without a sensor for detecting the rotor position is used. When starting the motor, a motor control device that controls the sensorless type motor first detects the stop position of the rotor by a predetermined method. Patent Document 1 discloses a configuration for detecting the stop position of the rotor by utilizing the characteristic that the inductance value of the motor coil changes according to the stop position of the rotor (the rotation phase of the stopped rotor). The motor control device starts driving the motor by forced commutation control based on the detected stop position of the rotor. When the rotation speed of the rotor becomes a predetermined speed or higher, as described in Patent Document 2, the motor control device can detect the rotation position (rotation phase) and rotation speed of the rotor by the induced voltage generated in the coil. Therefore, after the rotation speed of the rotor becomes a predetermined speed or higher, the motor control device switches to sensorless control for detecting the rotation position (rotation phase) and rotation speed of the rotor by the induced voltage generated in the coil and controlling the rotation of the rotor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the rotational speed of the rotor is low, the induced voltage generated in the coil becomes small. When the induced voltage generated in the coil is small, the detection accuracy of the rotational position and rotational speed of the rotor may deteriorate. Also, when the load on the motor is small, the coil current flowing through the coil becomes small. Even when the coil current is small, the detection accuracy of the rotational position and rotational speed of the rotor may deteriorate. When the detection accuracy of the rotational position and rotational speed of the rotor deteriorates, the rotational unevenness of the rotor may increase and the rotation of the rotor may become unstable.

[0005] The present invention provides a technique for stably rotating a rotor.

Means for Solving the Problem

[0006] According to one aspect of the present invention, a motor control device controls a voltage applied to a plurality of coils of a motor based on a first command value of an exciting component current and a second command value of a torque component current, thereby supplying a coil current to the plurality of coils. Current supply means, and control means for controlling the first command value based on the rotational speed of the rotor while performing sensorless control for controlling the rotation of the rotor of the motor based on the induced voltage generated in the plurality of coils. When the rotation speed of the rotor is lower than a first threshold value, the control means sets the first command value to a value that makes the excitation current greater than 0. It is characterized by this.

Effect of the Invention

[0007] According to the present invention, the rotor can be stably rotated.

Brief Description of the Drawings

[0008] [Figure 1] Configuration diagram of an image forming apparatus according to one embodiment. [Figure 2] Control configuration diagram of an image forming apparatus according to one embodiment. [Figure 3] Configuration diagram of a motor control unit according to one embodiment. [Figure 4] Configuration diagram of a motor according to one embodiment. [Figure 5] Functional block diagram of a microcomputer during forced commutation control according to one embodiment. [Figure 6] Functional block diagram of a microcontroller during sensorless control according to an embodiment. [Figure 7] Diagram showing the relationship between rotational speed and induced voltage, and the relationship between load and coil current. [Figure 8] Explanatory diagram of motor control according to an embodiment. [Figure 9] Flowchart of motor control according to an embodiment. [Figure 10] Explanatory diagram of motor control according to an embodiment. [Figure 11] Flowchart of motor control according to an embodiment.

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant explanations are omitted.

[0010] <First Embodiment> Hereinafter, as an example of a motor control device, the present embodiment will be described using an image forming apparatus. Note that the present invention is not limited to an image forming apparatus, and can be applied to any motor control device that performs vector control. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus can be, for example, a printer, a copier, a multifunction peripheral, a facsimile machine, or the like. The image forming unit 101 forms a toner image on the photoreceptor 102. The image forming unit 101 includes a charging unit, an exposure unit, a developing unit, and the like for forming a toner image on the photoreceptor 102. The image forming unit 101 transfers the toner image of the photoreceptor 102 to a sheet that has been conveyed along the conveyance path from the cassette 104. The sheet is then heated and pressurized in the fixing unit 105, and the toner image is fixed. After the fixing of the toner image, the sheet is discharged outside the image forming apparatus. The sensorless motor (hereinafter simply referred to as a motor) 103 is a drive source that generates a driving force for driving the photoreceptor 102. However, there is no limitation on the load driven by the motor 103, and the present invention can be applied to the control of the motor 103 that drives any load (member) within the image forming apparatus.

[0011] FIG. 2 shows the control configuration of the image forming apparatus. The printer control unit 107 controls the entire image forming apparatus including the above-described image forming unit 101 and fixing unit 105. The printer control unit 107 includes a processor (not shown) and a memory that stores programs and various control data. The processor of the printer control unit 107 performs various processes for controlling the image forming apparatus by executing the programs stored in the memory of the printer control unit 107. At that time, the printer control unit 107 uses the control data stored in the memory. The communication controller 115 communicates with the host computer 116 and receives image data of the image formed by the image forming apparatus from the host computer 116. The motor control unit 110 controls the motor 103 under the control of the printer control unit 107.

[0012] Figure 3 shows the control configuration of the motor 103. The motor control unit 110 communicates with the printer control unit 107 and controls the motor 103 under the control of the printer control unit 107. In the non-volatile memory 205 of the microcomputer (MCU) 201, programs executed by the MCU 201 and various data used for controlling the motor 103 are stored. The memory 207 is used by the MCU 201 for temporarily storing data. The PWM port 208 has a total of six terminals for outputting two PWM signals (high side, low side) for each of the three phases (U, V, W) of the motor 103. That is, the PWM port 208 has three high-side terminals (U-H, V-H, W-H) and three low-side terminals (U-L, V-L, W-L).

[0013] The inverter 211 has high-side switching elements M1, M3, and M5 and low-side switching elements M2, M4, and M6 for each of the three phases of the motor 103. In FIG. 3, M1 and M2 are the switching elements of the U phase, M3 and M4 are the switching elements of the V phase, and M5 and M6 are the switching elements of the W phase. As the switching elements, for example, transistors or FETs can be used. The gate driver 210 controls the ON / OFF of the corresponding switching element based on the PWM signal from the PWM port 208. For example, the gate driver 210 controls the ON / OFF of the switching element M1 by controlling the voltage applied to the gate G1 of the switching element M1 based on the PWM signal output from the U-H terminal.

[0014] The U, V, and W phase outputs 217 of the inverter 211 are connected to the coils 213 (U phase), 214 (V phase), and 215 (W phase) of the motor 103. By controlling the ON / OFF of each switching element, the coil current flowing through each of the coils 213, 214, and 215 can be controlled. In this way, the inverter 211 functions as a current supply unit that supplies coil current to each of the coils 213, 214, and 215. The coil current flowing through each of the coils 213, 214, and 215 is converted into a voltage by the current detection resistors 219, 220, and 221. The amplifier 218 amplifies the voltages of the current detection resistors 219, 220, and 221 corresponding to the coil current and outputs them to the AD converter 203 of the microcomputer 201. The AD converter 203 converts the voltage output by the amplifier 218 into a digital value. The current value calculation unit 209 measures and detects the current value of the coil current of each phase based on the digital value output by the AD converter 203.

[0015] Figure 4 is a configuration diagram of the motor 103. The motor 103 has a 6-slot stator 501 and a 4-pole rotor 502. The stator 501 has a U-phase coil 213, a V-phase coil 214, and a W-phase coil 215. The rotor 502 is composed of permanent magnets. The rotational phase of the rotor 502 is defined based on the state when the rotor 502 is in a predetermined state. As an example, as shown in FIG. 4, the state where the S pole of the rotor 502 faces the U-phase coil 213 is used as a reference, that is, the electrical angle 0, and it can be defined that the electrical angle increases in the counterclockwise direction. In this embodiment, since the number of poles of the rotor 502 is 4, when the rotor rotates by a mechanical angle of π / 2 in the counterclockwise direction from the state of FIG. 3, the electrical angle becomes π.

[0016] 5 is a functional block diagram of the microcomputer 201 during forced commutation control. In this embodiment, the microcomputer 201 vector-controls the motor 103. The current control unit 302 acquires an excitation current command value Id_ref and a torque current command value Iq_ref, which are pre-stored in the nonvolatile memory 205. The current control unit 302 also receives a measured excitation current value Id and a measured torque current value Iq from the coordinate conversion unit 306. The excitation current is a component of the coil current that contributes to the generation of magnetic flux, and the torque current is a component of the coil current that contributes to output torque. Based on these values, the current control unit 302 outputs voltage command values Vd_ref and Vq_ref in a rotating coordinate system. The coordinate conversion unit 305 performs coordinate conversion from the rotating coordinate system to a stationary coordinate system, and further performs two-phase-to-three-phase conversion to generate and output voltage command values Vu, Vv, and Vw for the U-phase, V-phase, and W-phase from the voltage command values Vd_ref and Vq_ref. Note that the coordinate conversion from the rotating coordinate system to the stationary coordinate system is performed based on the electrical angle θ_ref output from the angle calculation unit 303. The microcomputer 201 generates PWM signals to be output to the gate driver 210 based on the voltage command values Vu, Vv, and Vw.

[0017] Furthermore, the current values Iu, Iv, and Iw of the coil currents of the U phase, V phase, and W phase detected by the current value calculation unit 209 based on the output of the amplifier 218 are input to a coordinate conversion unit 306. The coordinate conversion unit 306 converts the current values Iu, Iv, and Iw into current values in a stationary coordinate system by three-phase-two-phase conversion, and further performs coordinate conversion from the stationary coordinate system to a rotating coordinate system to obtain a measured value Id of the excitation component current and a measured value Iq of the torque component current. The coordinate conversion from the stationary coordinate system to the rotating coordinate system is performed based on the electrical angle θ_ref output from the angle calculation unit 303. The coordinate conversion unit 306 outputs the measured value Id of the excitation component current and the measured value Iq of the torque component current to the current control unit 302.

[0018] When the motor 103 is started, the detection unit 301 determines the initial phase of the rotor 502, that is, the electrical angle (hereinafter referred to as the stop angle) θ_std at the time of stop. For detecting the electrical angle of the rotor 502 at the time of stop, for example, the configuration described in Patent Document 1 can be applied. In this case, the detection unit 301 detects the inductance of each coil 213, 214, and 215 based on the current values Iu, Iv, and Iw, and thereby detects the stop angle θ_std. The detection unit 301 outputs the detected stop angle θ_std to the subtractor 307. The offset setting unit 304 outputs the offset amount Δ held by the non-volatile memory 205 to the subtractor 307. The subtractor 307 outputs the electrical angle obtained by subtracting the offset amount Δ from the stop angle θ_std as the initial angle θ_ini to the angle calculation unit 303. Note that setting the electrical angle obtained by subtracting the offset amount Δ from the stop angle θ_std as the initial angle θ_ini is to prevent detuning at startup.

[0019] Based on the initial angle θ_ini and the speed command value ω_ref input from the printer control unit 107, the angle calculation unit 303 obtains the electrical angle θ_ref (rotation phase) of the rotor 502 and notifies the coordinate conversion units 305 and 306. Specifically, the angle calculation unit 303 obtains the electrical angle θ_ref of the rotor 502 by using the initial angle θ_ini as the initial value and increasing the electrical angle based on the speed command value ω_ref.

[0020] FIG. 6 is a functional block diagram of the microcomputer 201 during sensorless control. In the following, the description will focus on the differences from the functional block diagram during forced commutation control shown in FIG. 5. The estimation unit 801 determines the induced voltage generated in the coil based on the current values Iu, Iv, and Iw, the voltage command values Vd_ref and Vq_ref, and the estimated rotational speed ω_est, and estimates the electrical angle θ_est and the rotational speed ω_est of the rotor 502. The estimated electrical angle θ_est is used for coordinate transformation in the coordinate transformation units 305 and 306. Also, the speed control unit 802 calculates a command value Iq_ref for generating the torque necessary to make the rotational speed ω_est follow the speed command value ω_ref (target speed) based on the speed command value ω_ref from the printer control unit 107 and the rotational speed ω_est estimated by the estimation unit 801. The field current control unit 803 determines the value of the command value Id_ref based on the rotational speed ω_est as will be described later, and outputs the determined command value Id_ref to the current control unit 302.

[0021] FIG. 7(A) shows the relationship between the rotational speed of the rotor 502 and the induced voltage generated in the coil. As shown in FIG. 7(A), the induced voltage is proportional to the rotational speed of the rotor 502, and the proportionality constant is called the induced voltage constant Ke. FIG. 7(B) shows the relationship between the load of the rotor 502 and the coil current. As shown in FIG. 7(B), the coil current is proportional to the load of the rotor 502, and the reciprocal of the proportionality constant is called the torque constant Kt.

[0022] Subsequently, the method for controlling the coil current according to the present embodiment will be described with reference to FIGS. 8(A) to 8(C). FIG. 8(A) shows the case where the rotational speed of the rotor 502 is constant and equal to or higher than the first threshold value, and FIGS. 8(B) and 8(C) show the case where the rotational speed of the rotor 502 is constant and lower than the first threshold value. In any of the figures, the case where the load of the rotor 502 changes from a high load to a low load is shown.

[0023] First, FIG. 8(A) will be described. As described in FIG. 7(A), since the induced voltage generated in the coil is proportional to the rotational speed of the rotor 502, when the rotational speed is constant, the induced voltage also becomes constant. Also, as described in FIG. 7(B), the coil current is proportional to the load. Therefore, as the load of the motor 103 changes from a high load to a low load, the coil current also decreases accordingly. In FIG. 8(A), the command value Id_ref of the field current component is always set to Id_ref = 0, that is, a value that sets the field current component to 0. This is to achieve highly efficient motor control by setting the field current component that does not contribute to torque to 0 and controlling only the torque current component that contributes to torque, which is a common practice in vector control.

[0024] In vector control, coil current and induced voltage are used to calculate the electrical angle θ_est (corresponding to the rotational phase) and the rotational speed ω_est of the rotor 502. Therefore, if either the coil current or the induced voltage becomes too small, the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est may deteriorate. In particular, when both the coil current and the induced voltage become small, the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est is likely to deteriorate. In FIG. 8(A), although the coil current decreases as the load becomes lower, the rotational speed is high, and thus the induced voltage is large. Therefore, the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est is good.

[0025] On the other hand, in FIG. 8(B), since the rotational speed of the rotor 502 is lower than the first threshold value in the case of FIG. 8(A), the induced voltage also decreases compared to the case of FIG. 8(A). In FIG. 8(B) as well, the command value Id_ref of the field current component is set to 0 as in FIG. 8(A). In the case of FIG. 8(B), since the induced voltage is always small, when the load of the motor 103 becomes low, both the coil current and the induced voltage become small, and the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est may deteriorate. When the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est deteriorates, uneven rotation of the rotor 502 may occur, and the rotational control of the rotor 502 may become unstable.

[0026] Therefore, in this embodiment, when the rotational speed is less than the first threshold, as shown in FIG. 8(C), the field current control unit 803 sets the command value Id_ref of the field current to a value α greater than 0, and controls the field current that does not contribute to torque to a value greater than 0. By flowing the field current, a force in a direction that does not contribute to the rotation of the rotor 502 is generated on the rotor 502. To compensate for the force generated by this field current, the torque current is increased compared to when the field current is 0. That is, by setting the field current to a value greater than 0, the torque current increases compared to when the field current is 0. Since the coil current is the vector sum of the field current and the torque current, by increasing the field current greater than 0, the coil current increases by the vector sum of the increase amount of the torque current and the increase amount from 0 of the field current. The shaded portion in FIG. 8(C) shows the increase amount of the coil current due to increasing the field current greater than 0.

[0027] In FIG. 8(C), compared with FIG. 8(B), the coil current increases by the height of the shaded portion. Therefore, by appropriately setting the value α of the command value Id_ref of the field current, it is possible to suppress both the coil current and the induced voltage from decreasing. Therefore, it is possible to suppress the deterioration of the estimation accuracy of the electrical angle θ_est and the rotational speed ω_est, and realize stable rotational control of the rotor 502.

[0028] FIG. 9 is a flowchart of the motor control process according to this embodiment. In S10, the motor control unit 110 starts forced commutation control. During the forced commutation control, the command values Iq_ref and Id_ref are set to predetermined values. Note that this predetermined value for the command value Iq_ref is a value greater than 0. On the other hand, this predetermined value for the command value Id_ref is a value of 0 or more, for example, 0. The motor control unit 110 continues the forced commutation control in S11 until the speed command value ω_ref from the printer control unit 107 becomes equal to or greater than a second threshold which is a predetermined speed. After the speed command value ω_ref becomes equal to or greater than the second threshold, the motor control unit 110 switches from the forced commutation control to the sensorless control in S12. Note that the second threshold is lower than the first threshold.

[0029] After the start of sensorless control, when the rotation speed becomes substantially constant, the motor control unit 110 determines in S13 whether the rotation speed ω_est is equal to or greater than a first threshold. If the rotation speed ω_est is equal to or greater than the first threshold, the motor control unit 110 sets the command value Id_ref to 0, i.e., a value that sets the excitation current to 0, in S15. On the other hand, if the rotation speed ω_est is smaller than the first threshold, the motor control unit 110 sets the command value Id_ref to a predetermined value α>0, i.e., a value that causes the excitation current to flow, in S14. In S16, the motor control unit 110 determines whether a stop instruction has been received from the printer control unit 107. If a stop instruction has not been received, the motor control unit 110 repeats the process from S13. On the other hand, if a stop instruction has been received, the motor control unit 110 stops the rotation of the rotor 502 and ends the process of FIG. 9.

[0030] As described above, when the rotational speed of the rotor 502 is lower than the first threshold value during vector control, the excitation current command value Id_ref is set to a value greater than 0. This configuration allows stable rotation control of the rotor 502 even when the load is lighter when the rotational speed of the rotor 502 is low. In the above description, after vector control is started, the process in S13 is performed after waiting for the rotational speed of the rotor 502 to become approximately constant. This means that the process waits until the rotational speed of the rotor 502 reaches the target predetermined speed. If the speed command value ω_ref from the printer control unit 107 remains unchanged for a predetermined period of time, the motor control unit 110 determines that the target predetermined speed has been reached. However, after vector control is started in S12, the process in S13 can also be performed without waiting for the rotational speed of the rotor 502 to reach the target predetermined speed. In other words, when switching to sensorless control, the setting value of the excitation current command value Id_ref can be dynamically controlled based on the rotational speed ω_est.

[0031] Second Embodiment Next, the differences between the second embodiment and the first embodiment will be mainly described. In the first embodiment, when the rotational speed of the motor is less than the first threshold value, the exciting current control unit 803 sets the command value Id_ref of the exciting current to a value greater than 0. As a result, the coil current increases compared to the case where Id_ref = 0. However, when the load on the motor 103 is high, the coil current may become too large, and conversely, the rotation of the rotor 502 may become unstable. FIG. 10(A) shows the same figure as FIG. 8(C). However, in FIG. 10(A), the maximum allowable value of the coil current is indicated by a dashed-dotted line. In FIG. 10(A), at high loads, the coil current exceeds the maximum allowable value.

[0032] Therefore, in this embodiment, the value of the command value Id_ref of the exciting current is controlled according to the magnitude of the load. In FIG. 10(B), at low loads, the value of the command value Id_ref of the exciting current is set to α, and at high loads, the value of the command value Id_ref of the exciting current is set to β. Here, α > β ≧ 0. As shown in FIG. 10(B), when the load increases, by reducing the value of the command value Id_ref of the exciting current, it is possible to prevent the coil current from exceeding the maximum value and perform stable rotation control of the motor 103. The relationship between the magnitude of the load and the value of the command value Id_ref of the exciting current is determined in advance and stored in the non-volatile memory 205 of the motor control unit 110 as control information. Then, information indicating the magnitude of the load is input to the exciting current control unit 803 from a load detection unit (not shown), and when the rotational speed of the rotor 502 is less than the first threshold value, the exciting current control unit 803 determines the value of the command value Id_ref of the exciting current based on the magnitude of the load and the control information.

[0033] Incidentally, the magnitude of the load can be determined from the measured value Iq of the torque component current. Therefore, instead of the relationship between the magnitude of the load and the value of the command value Id_ref of the field component current, the relationship between the measured value Iq of the torque component current and the value of the command value Id_ref of the field component current may be determined in advance and stored in the non-volatile memory 205. In this case, the measured value Iq of the torque component current is input to the field component current control unit 803. Note that the determination of the magnitude of the load is not limited to being determined by the measured value Iq of the torque component current. For example, it is also possible to measure in advance at what timing and with what magnitude of load in a predetermined sequence for image formation, and to store control information indicating the relationship between the timing and the magnitude of the load within the predetermined sequence in the non-volatile memory 205. In this case, information indicating the timing within the predetermined sequence is input to the field component current control unit 803 from, for example, the printer control unit 107.

[0034] FIG. 11 is a flowchart of the motor control process according to the present embodiment. Note that the same step numbers are assigned to the processing steps similar to those in the flowchart of FIG. 8, and the description thereof is omitted. The flowchart of FIG. 11 is obtained by replacing S14 in the flowchart of FIG. 8 with S20 and S21. When the rotational speed ω_est is less than the first threshold value, the motor control unit 110 determines the magnitude of the load on the motor in S20. In this example, the measured value Iq of the torque component current is used as an evaluation value indicating the magnitude of the load. The motor control unit 110 sets the value of the command value Id_ref of the field component current based on the magnitude of the load in S21.

[0035] By setting the value of the command value Id_ref of the field component current in consideration of both the rotational speed of the rotor 502 and the load as described above, stable rotational control of the rotor 502 can be performed regardless of the rotational speed and load of the rotor 502.

[0036] In this embodiment, when the rotational speed of the rotor 502 is equal to or higher than the first threshold value, the command value Id_ref of the exciting branch current is set to 0 regardless of the magnitude of the load. However, instead of providing the first threshold value, a configuration may be adopted in which the value set for the command value Id_ref is controlled based on both the rotational speed of the rotor 502 and the magnitude of the load. In this case, the volatile memory 205 stores control information indicating the relationship between the combination of the rotational speed and the load (or the evaluation value of the load) and the command value Id_ref of the exciting branch current. Also in this case, as the rotational speed of the rotor 502 increases, the command value Id_ref of the exciting branch current is decreased, and as the load increases, the command value Id_ref of the exciting branch current is decreased.

[0037] [Other Embodiments] In each of the above embodiments, it is described as the motor control unit 110 because it is a component of the image forming apparatus, but the motor control unit 110 may be a motor control device as one device. Further, a device including the printer control unit 107 and the motor control unit 110 may be a motor control device. Also, in the above embodiment, the motor 103 rotates the photoreceptor 102, but the present invention can also be applied to a motor that drives an arbitrary rotating member in the image forming apparatus. Further, the configuration of the motor 103 is not limited to the configuration shown in FIG. 4, and motors having other numbers of poles or phases may be used. Further, the motor 103 only needs to be vector-controlled and is not limited to a sensorless motor.

[0038] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. Further, it can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

[0039] The invention is not limited to the above embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the claims are attached to disclose the scope of the invention.

Description of Signs

[0040] 211: Inverter, 802: Speed control unit, 201: Microcomputer

Claims

1. Current supply means for supplying coil current to a plurality of coils of a motor by controlling the voltage applied to the plurality of coils based on a first command value of the exciting branch current and a second command value of the torque branch current; Control means for controlling the first command value based on the rotational speed of the rotor while performing sensorless control for controlling the rotation of the rotor of the motor based on the induced voltage generated in the plurality of coils; Comprising: The control means sets, as the first command value, a value that makes the exciting branch current greater than 0 when the rotational speed of the rotor is less than a first threshold value. A motor control device characterized by this.

2. The control means controls the second command value based on the torque required to rotate the rotor at a target speed. The motor control device according to claim 1, characterized by this.

3. The control means sets, as the first command value, a value that makes the exciting branch current 0 when the rotational speed of the rotor is not less than the first threshold value. The motor control device according to claim 1 or 2, characterized by this.

4. Current supply means for supplying coil current to a plurality of coils of a motor by controlling the voltage applied to the plurality of coils based on a first command value of the exciting branch current and a second command value of the torque branch current; Control means for controlling the first command value based on the rotational speed of the rotor and the magnitude of the load of the rotor while performing sensorless control for controlling the rotation of the rotor of the motor based on the induced voltage generated in the plurality of coils; Comprising: The control means decreases the first command value as the load of the rotor increases. A motor control device characterized by this.

5. The control means decreases the first command value as the rotational speed of the rotor increases. The motor control device according to claim 4, characterized by this.

6. The control means sets, as the first command value, a value that makes the exciting branch current 0 when the rotational speed of the rotor is not less than the first threshold value, and sets the first command value based on the magnitude of the load when the rotational speed of the rotor is less than the first threshold value. The motor control device according to claim 4, characterized by this.

7. The control means decreases the first command value as the load increases when the rotational speed of the rotor is less than the first threshold value. The motor control device according to claim 6, characterized by this.

8. The motor control device according to any one of claims 4 to 7, wherein the control means determines the magnitude of the load based on the measured value of the torque component current.

9. The motor control device according to any one of claims 4 to 7, wherein the control means determines the magnitude of the load based on the timing in a predetermined sequence.

10. The control means performs sensorless control when the rotational speed of the rotor becomes greater than a second threshold value, The motor control device according to any one of claims 1 to 3, 6, and 7, wherein the second threshold value is smaller than the first threshold value.

11. A rotating member for conveying a sheet along a conveyance path, Image forming means for forming an image on the sheet conveyed along the conveyance path, A motor for driving the rotating member or the image forming means, Motor control means for controlling the motor, An image forming apparatus comprising: The motor control means, Current supply means for supplying coil current to the plurality of coils of the motor by controlling the voltage applied to the plurality of coils based on a first command value of the exciting current component and a second command value of the torque current component; Control means for controlling the first command value based on the rotational speed of the rotor while performing sensorless control for controlling the rotation of the rotor of the motor based on the induced voltage generated in the plurality of coils; Comprising: The image forming apparatus, wherein the control means sets, as the first command value, a value that makes the exciting current component greater than 0 when the rotational speed of the rotor is smaller than a first threshold value.

12. A rotating member for conveying a sheet along a conveyance path, Image forming means for forming an image on the sheet conveyed along the conveyance path, A motor for driving the rotating member or the image forming means, Motor control means for controlling the motor, An image forming apparatus comprising: The motor control means, Current supply means for supplying coil current to the plurality of coils of the motor by controlling the voltage applied to the plurality of coils based on a first command value of the exciting current component and a second command value of the torque current component; Control means for controlling the first command value based on the rotational speed of the rotor and the load of the rotor while performing sensorless control for controlling the rotation of the rotor of the motor based on the induced voltage generated in the plurality of coils; Comprising: An image forming apparatus, wherein the control means reduces the first command value as the load on the rotor increases.

Images