JP2020068594A - Motor control device, sheet conveying device, and image forming apparatus - Google Patents

Abstract

To solve the problem in which: when a torque constant as a fixed value is used regardless of the temperature of a motor, an error is included in a current value to be calculated, a current to be supplied immediately after a method for controlling the motor is changed may not be appropriately set.SOLUTION: A value obtained by multiplying a current value iq' as a result of detection of a current by a proportionality coefficient Kq is set as an initial value of integration in a phase controller 502. This can result in prevention of the occurrence of the difference between torque that corresponds to a current supplied immediately before the control of a motor is changed and is generated in a rotor, and torque that corresponds to a current supplied immediately after the control of the motor is changed and is generated in the rotor. This can result in prevention of a variation in rotation speed of the motor when the control of the motor is changed from constant current control to vector control.SELECTED DRAWING: Figure 12

Description

  The present invention relates to control of a motor in a motor control device, a sheet conveying device, and an image forming apparatus.

  2. Description of the Related Art Conventionally, as a method for controlling a motor, there is known a control method called vector control for controlling a motor by controlling a current value in a rotating coordinate system with a rotation phase of a rotor of the motor as a reference. Specifically, there is known a control method for controlling a motor by performing phase feedback control for controlling a current value in a rotating coordinate system so that a deviation between a command phase of a rotor and a rotating phase becomes small. A control method is also known in which the motor is controlled by performing speed feedback control that controls the current value in the rotating coordinate system so that the deviation between the command speed of the rotor and the rotation speed becomes small.

  In vector control, the drive current flowing through the motor winding affects the q-axis component (torque current component) that is the current component that generates the torque for the rotor to rotate and the strength of the magnetic flux that penetrates the motor winding. And a d-axis component (exciting current component) which is a current component to be generated. By controlling the value of the torque current component according to the change in the load torque applied to the rotor, the torque required for rotation is efficiently generated. As a result, an increase in motor noise and an increase in power consumption due to the excess torque are suppressed. In addition, because the load torque applied to the rotor exceeds the output torque corresponding to the drive current supplied to the winding of the motor, the rotor is no longer synchronized with the input signal and the motor is out of control (step-out). State) can be suppressed.

  Vector control requires a configuration that determines the rotation phase of the rotor. Patent Document 1 describes a configuration in which the rotation phase of the rotor is determined based on the induced voltage generated in the winding of each phase of the motor as the rotor rotates.

  The magnitude of the induced voltage generated in the winding becomes smaller as the rotation speed of the rotor becomes smaller. If the magnitude of the induced voltage generated in the winding is not large enough to determine the rotation phase of the rotor, the rotation phase may not be accurately determined. That is, the lower the rotational speed of the rotor, the worse the accuracy of determining the rotational phase of the rotor may be.

  Therefore, in Patent Document 2, when the command speed of the rotor is smaller than a predetermined rotation speed, a configuration is used in which constant current control is used to control the motor by supplying a predetermined current to the winding of the motor. Stated. Note that neither the phase feedback control nor the speed feedback control is performed in the constant current control. Further, it is described that the vector control is used when the command speed of the rotor is equal to or higher than a predetermined rotation speed.

  When the control of the motor is switched from the constant current control to the vector control, the rotation speed of the motor may momentarily decrease. This was given to the rotor by the drive current supplied first after the control of the motor was switched to, rather than the torque given to the rotor by the drive current last supplied before the control of the motor was switched. This is because the torque may be smaller. That is, there is a difference between the torque applied to the rotor immediately before the control of the motor is switched and the torque applied to the rotor immediately after the control of the motor is switched.

  In Patent Document 3, the load torque applied to the rotor during microstep driving is estimated (calculated) based on the signal output from the position detector. Then, a configuration is described in which the current to be supplied is determined (calculated) immediately after the control method of the motor is switched from the micro step drive control to the speed servo control based on the estimated load torque. Specifically, in Patent Document 3, the load estimator calculates the load torque in order to determine the current to be supplied immediately after the control method of the motor is switched. Then, the current value corresponding to the load torque is calculated by dividing the torque constant from the load torque, and the calculated current value is multiplied by the control gain to determine the current to be supplied.

Special table 2012-509056 gazette JP, 2005-39955, A JP, 2010-28949, A

  In Patent Document 3, a process of dividing a load torque by a preset torque constant is performed in order to determine a current to be supplied immediately after the motor control method is switched. The torque constant has different values depending on the temperature of the motor. Therefore, if the torque constant as a fixed value is used regardless of the motor temperature, the calculated current value includes an error. That is, the determined current may include an error, and the current to be supplied may not be set appropriately immediately after the control method of the motor is switched. As a result, control of the motor may become unstable.

  In view of the above problems, it is an object of the present invention to prevent the control of the motor from becoming unstable when the control mode for controlling the motor is switched.

In order to solve the above problems, the motor control device according to the present invention is
In a motor control device that controls the motor based on a command phase that represents a target phase of the rotor of the motor,
Detecting means for detecting a drive current flowing through the winding of the motor;
Phase determining means for determining the rotational phase of the rotor based on the drive current detected by the detecting means,
Converting means for converting the current value of the stationary coordinate system detected by the detecting means into a current value of the rotating coordinate system based on the rotating phase determined by the phase determining means,
The magnitude of the drive current detected by the detection means is adjusted so that the drive current becomes a target value set so that the deviation between the command phase and the rotation phase determined by the phase determination means becomes small. Control means having a first control mode for controlling, and a second control mode for controlling the drive current based on a current of a predetermined magnitude,
Have
The target value in the first control mode when the control mode for controlling the drive current is switched from the second control mode to the first control mode is converted by the conversion means during execution of the second control mode. Is set based on a value obtained by multiplying the value of the torque current component of the drive current by a predetermined value,
The torque current component is a current component represented in the rotational coordinate system of the drive current converted by the conversion means.

  According to the present invention, it is possible to prevent the control of the motor from becoming unstable when the control mode for controlling the motor is switched.

FIG. 3 is a cross-sectional view illustrating the image forming apparatus according to the first embodiment. FIG. 3 is a block diagram showing a control configuration of the image forming apparatus. It is a figure which shows the relationship between the two-phase motor which consists of A phase and B phase, and the rotating coordinate system represented by the d-axis and the q-axis. It is a block diagram which shows the structure of the motor control apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the phase controller which concerns on 1st Embodiment. It is a block diagram which shows the structure of the current controller which concerns on 1st Embodiment. It is a block diagram which shows the example of the control structure of the conventional constant current control. It is a figure explaining the constant current control which concerns on 1st Embodiment. It is a block diagram which shows the example of a structure of the constant current controller which concerns on 1st Embodiment. It is a figure which shows the relationship between rotation speed (omega) _ref 'and threshold value (omega) th, and a switching signal. It is a figure which shows an example of the relationship between the load torque Tm applied to the rotor of the motor and the q-axis current iq when the motor is driven at a predetermined rotation speed. It is a flow chart which shows the control method of the motor concerning a 1st embodiment. It is a block diagram showing the composition of the motor control device which performs speed feedback control.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the shapes of the components described in this embodiment and their relative arrangements should be appropriately changed depending on the configuration of the device to which the present invention is applied and various conditions, and the scope of the present invention is It is not intended to be limited to the following embodiments. In the following description, the case where the motor control device is provided in the image forming apparatus will be described, but the provision of the motor control device is not limited to the image forming apparatus. For example, it is also used in a sheet conveying device that conveys a sheet such as a recording medium or a document.

[First Embodiment]
[Image forming apparatus]
FIG. 1 is a cross-sectional view showing a configuration of a monochrome electrophotographic copying machine (hereinafter, referred to as an image forming apparatus) 100 having a sheet conveying device used in this embodiment. The image forming apparatus is not limited to the copying machine, and may be, for example, a facsimile machine, a printing machine, a printer, or the like. Further, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet or the like. Furthermore, the format of the image forming apparatus may be either monochrome or color.

  The configuration and function of the image forming apparatus 100 will be described below with reference to FIG. As shown in FIG. 1, the image forming apparatus 100 includes a document feeding device 201, a reading device 202, and an image printing device 301.

  The originals stacked on the original stacking unit 203 of the original feeding device 201 are fed one by one by the paper feed roller 204, and are conveyed along the conveyance guide 206 onto the original glass table 214 of the reading device 202. Further, the original is conveyed at a constant speed by the conveyor belt 208, and is ejected by a paper ejection roller 205 to a paper ejection tray (not shown). Reflected light from the original image illuminated by the illumination 209 at the reading position of the reading device 202 is guided to the image reading unit 111 by the optical system including the reflection mirrors 210, 211, 212, and converted into an image signal by the image reading unit 111. To be done. The image reading unit 111 includes a lens, a CCD that is a photoelectric conversion element, a drive circuit for the CCD, and the like. The image signal output from the image reading unit 111 is subjected to various correction processes by the image processing unit 112 including a hardware device such as an ASIC, and then output to the image printing apparatus 301. The document is read as described above. That is, the document feeding device 201 and the reading device 202 function as a document reading device.

  Further, there are a first reading mode and a second reading mode as document reading modes. The first reading mode is a mode in which an image of a document conveyed at a constant speed is read by the illumination system 209 and the optical system fixed at a predetermined position. The second reading mode is a mode in which the image of the original placed on the original glass 214 of the reading device 202 is read by the illumination system 209 and the optical system which move at a constant speed. Normally, the image of a sheet-shaped document is read in the first reading mode, and the image of a bound document such as a book or booklet is read in the second reading mode.

  Sheet storage trays 302 and 304 are provided inside the image printing apparatus 301. The sheet storage trays 302 and 304 can store different types of recording media. For example, A4 size plain paper is stored in the sheet storage tray 302, and A4 size thick paper is stored in the sheet storage tray 304. The recording medium is one on which an image is formed by the image forming apparatus, and examples of the recording medium include paper, resin sheet, cloth, OHP sheet, label and the like.

  The recording medium stored in the sheet storage tray 302 is fed by the paper feed roller 303, and is delivered to the registration roller 308 by the transport roller 306. Further, the recording medium stored in the sheet storage tray 304 is fed by the paper feed roller 305, and is delivered to the registration roller 308 by the transport rollers 307 and 306.

  The image signal output from the reading device 202 is input to the optical scanning device 311 including a semiconductor laser and a polygon mirror. The outer peripheral surface of the photosensitive drum 309 is charged by the charger 310. After the outer peripheral surface of the photosensitive drum 309 is charged, a laser beam corresponding to an image signal input from the reading device 202 to the optical scanning device 311 passes through the polygon mirror and the mirrors 312 and 313 from the optical scanning device 311 and is exposed. The outer peripheral surface of the drum 309 is irradiated. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309. For charging the photosensitive drum, for example, a charging method using a corona charger or a charging roller is used.

  Then, the electrostatic latent image is developed by the toner in the developing device 314, and a toner image is formed on the outer peripheral surface of the photosensitive drum 309. The toner image formed on the photosensitive drum 309 is transferred onto a recording medium by a transfer charger 315 provided at a position (transfer position) facing the photosensitive drum 309. The registration roller 308 feeds the recording medium to the transfer position at the transfer timing.

  As described above, the recording medium on which the toner image has been transferred is sent to the fixing device 318 by the conveyor belt 317, heated and pressed by the fixing device 318, and the toner image is fixed on the recording medium. In this way, the image is formed on the recording medium by the image forming apparatus 100.

  When image formation is performed in the single-sided printing mode, the recording medium that has passed through the fixing device 318 is discharged by a discharge roller 319 or 324 to a discharge tray (not shown). When image formation is performed in the double-sided printing mode, after the fixing device 318 performs the fixing process on the first surface of the recording medium, the recording medium is the discharge roller 319, the conveyance roller 320, and the reverse roller 321. Is conveyed to the reverse path 325. After that, the recording medium is conveyed again to the registration roller 308 by the conveying rollers 322 and 323, and an image is formed on the second surface of the recording medium by the method described above. After that, the recording medium is discharged to a discharge tray (not shown) by discharge rollers 319 and 324.

  When the recording medium having the image formed on the first surface is discharged face-down to the outside of the image forming apparatus 100, the recording medium passing through the fixing device 318 passes through the discharging roller 319 and the conveying roller 320. It is transported in the direction toward. Then, immediately before the trailing edge of the recording medium passes through the nip portion of the conveying roller 320, the rotation of the conveying roller 320 is reversed, so that the first surface of the recording medium faces downward and the recording medium is ejected. It is discharged to the outside of the image forming apparatus 100 via 324.

  The above is the description of the configuration and functions of the image forming apparatus 100. The load in the present invention is an object driven by a motor. For example, various rollers (conveying rollers) such as the sheet feeding rollers 204, 303 and 305, the registration roller 308, and the discharging roller 319, the photosensitive drum 309, the conveying belts 208 and 317, the illumination system 209, and the optical system are included in the invention. Handle the load. The motor control device of this embodiment can be applied to a motor that drives these loads.

  FIG. 2 is a block diagram showing an example of the control configuration of the image forming apparatus 100. As shown in FIG. 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. Further, the system controller 151 is connected to the image processing unit 112, the operation unit 152, the analog / digital (A / D) converter 153, the high voltage control unit 155, the motor control device 157, the sensors 159, and the AC driver 160. . The system controller 151 can send and receive data and commands to and from each connected unit.

  The CPU 151a reads various programs stored in the ROM 151b and executes them to execute various sequences related to a predetermined image forming sequence.

  The RAM 151c is a storage device. The RAM 151c stores various data such as set values for the high voltage controller 155, command values for the motor controller 157, and information received from the operation unit 152.

  The system controller 151 transmits to the image processing unit 112 the set value data of various devices provided inside the image forming apparatus 100, which are necessary for the image processing in the image processing unit 112. Further, the system controller 151 receives signals from the sensors 159 and sets the set value of the high voltage controller 155 based on the received signals. The high voltage controller 155 supplies a necessary voltage to the high voltage unit 156 (the charger 310, the developing device 314, the transfer charger 315, etc.) according to the set value set by the system controller 151. It should be noted that the sensors 159 include a sensor for detecting the recording medium conveyed by the conveying rollers.

  The motor control device 157 controls the motor 509 that drives the load in accordance with the command output from the CPU 151a. Although only the motor 509 is shown as the motor of the image forming apparatus in FIG. 2, it is assumed that the image forming apparatus is actually provided with a plurality of motors. Alternatively, one motor control device may control a plurality of motors. Further, although only one motor control device is provided in FIG. 2, it is assumed that a plurality of motor control devices are actually provided in the image forming apparatus.

  The A / D converter 153 receives the detection signal detected by the thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal into a digital signal, and transmits the digital signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature necessary for performing the fixing process. The fixing heater 161 is a heater used for fixing processing and is included in the fixing device 318.

  The system controller 151 causes the operation unit 152 to display an operation screen for the user to set the type of recording medium to be used (hereinafter referred to as paper type) and the like on the display unit provided in the operation unit 152. To control. The system controller 151 receives the information set by the user from the operation unit 152, and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. The system controller 151 also transmits information indicating the state of the image forming apparatus to the operation unit 152. Note that the information indicating the state of the image forming apparatus is, for example, information regarding the number of image formations, the progress of the image forming operation, the jam of the sheet material in the document reading apparatus 201 and the image printing apparatus 301, and the double feeding. The operation unit 152 displays the information received from the system controller 151 on the display unit.

  As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100.

[Motor controller]
Next, the motor control device according to the present embodiment will be described. The motor control device in the present embodiment can control the motor by any of the vector control as the first control mode and the constant current control as the second control mode.

<Vector control>
First, a method in which the motor control device 157 in this embodiment performs vector control will be described with reference to FIGS. 3 and 4. The motor in the following description is not provided with a sensor such as a rotary encoder for detecting the rotation phase of the rotor of the motor.

  FIG. 3 shows a stepping motor (hereinafter, referred to as a motor) 509 including two phases of an A phase (first phase) and a B phase (second phase), and a rotary coordinate system represented by the d axis and the q axis. It is a figure which shows the relationship of. In FIG. 3, in the stationary coordinate system, an α axis that is an axis corresponding to the A-phase winding and a β axis that is an axis corresponding to the B-phase winding are defined. Further, in FIG. 3, the d-axis is defined along the direction of the magnetic flux created by the magnetic poles of the permanent magnets used in the rotor 402, and the direction advances 90 degrees counterclockwise from the d-axis (perpendicular to the d-axis. The q-axis is defined along the direction (). The angle formed by the α axis and the d axis is defined as θ, and the rotation phase of the rotor 402 is represented by the angle θ. In vector control, a rotating coordinate system based on the rotating phase θ of the rotor 402 is used. Specifically, in the vector control, a q-axis component (torque current component) that is a current component in a rotating coordinate system of a current vector corresponding to a drive current flowing through the winding, and generates a torque in the rotor, and the winding. The d-axis component (exciting current component) that affects the strength of the magnetic flux penetrating

  Vector control is a motor that performs phase feedback control that controls the value of the torque current component and the value of the exciting current component so that the deviation between the command phase that represents the target phase of the rotor and the actual rotation phase becomes small. Is a control method for controlling. Further, the motor is controlled by performing speed feedback control for controlling the value of the torque current component and the value of the exciting current component so that the deviation between the command speed representing the target speed of the rotor and the actual rotation speed becomes small. There is also a method.

  FIG. 4 is a block diagram showing an example of the configuration of the motor control device 157 that controls the motor 509. The motor control device 157 is composed of at least one ASIC and executes each function described below.

  As shown in FIG. 4, the motor control device 157 includes a constant current controller 700 that performs constant current control and a vector controller 701 that performs vector control.

  The motor controller 157 is a circuit for performing vector control, and includes a phase controller 502, current controllers 503 and 504, a coordinate inverse converter 505, a coordinate converter 511, a PWM inverter 506 that supplies a drive current to a winding of a motor, and the like. Have. The coordinate converter 511 expresses a current vector corresponding to the drive currents flowing in the A-phase and B-phase windings of the motor 509 from the static coordinate system represented by the α axis and the β axis by the q axis and the d axis. Convert coordinates to the rotating coordinate system. As a result, the drive current flowing through the winding is represented by a q-axis component current value (q-axis current) and a d-axis component current value (d-axis current) that are current values in the rotating coordinate system. The q-axis current corresponds to the torque current that causes the rotor 402 of the motor 509 to generate torque. The d-axis current corresponds to an exciting current that affects the strength of the magnetic flux that penetrates the winding of the motor 509. The motor control device 157 can independently control the q-axis current and the d-axis current. As a result, the motor control device 157 can efficiently generate the torque required for the rotor 402 to rotate by controlling the q-axis current according to the load torque applied to the rotor 402. That is, in vector control, the magnitude of the current vector shown in FIG. 3 changes according to the load torque applied to the rotor 402.

  The motor control device 157 determines the rotation phase θ of the rotor 402 of the motor 509 by a method described later, and performs vector control based on the determination result. The CPU 151a generates a command phase θ_ref representing the target phase of the rotor 402 of the motor 509, and outputs the command phase θ_ref to the motor control device 157. Actually, the CPU 151a outputs a pulse signal to the motor control device 157, the number of pulses corresponds to the command phase, and the frequency of the pulses corresponds to the target speed. The command phase θ_ref is generated, for example, based on the target speed of the motor 509.

  The subtractor 101 calculates the deviation between the rotation phase θ of the rotor 402 of the motor 509 and the command phase θ_ref, and outputs the deviation to the phase controller 502.

  FIG. 5 is a block diagram showing the configuration of the phase controller 502. The configuration of the phase controller 502 shown in FIG. 5 is an example in this embodiment, and the configuration of the phase controller 502 is not limited to this.

  As shown in FIG. 5, the phase controller 502 includes a proportional control unit 502a that performs proportional control (P), an integral control unit 502b that performs integral control (I), and a differential control unit 502c that performs differential control (D). . The phase controller 502 also has an adder 502d that adds the signals output from the proportional controller 502a, the integral controller 502b, and the derivative controller 502c. The phase controller 502 further includes a q-axis current generation unit 502e that generates a q-axis current command value (target value) iq_ref based on the signal output from the adder 502d, and a d-axis current command value (target value) id_ref. Has a d-axis current generation unit 502f that generates

  The phase controller 502 generates the q-axis current command value iq_ref based on the proportional control (P), the integral control (I), and the derivative control (D) so that the deviation output from the subtractor 101 becomes small. Output. Specifically, the phase controller 502 generates and outputs the q-axis current command value iq_ref so that the deviation output from the subtractor 101 becomes 0 based on the P control, the I control, and the D control.

  More specifically, the proportional control unit 502a outputs a value proportional to the deviation so that the deviation output from the subtractor 101 becomes zero. Further, the integration control unit 502b outputs a value proportional to the time integration of the deviation so that the deviation output from the subtractor 101 becomes zero. Further, the differential control unit 502c outputs a value proportional to the time change of the deviation so that the deviation output from the subtractor 101 becomes zero. The current value iq ′ input to the integration controller 502b will be described later.

  Then, the adder 502d adds the values output from the proportional controller 502a, the integral controller 502b, and the derivative controller 502c, and the added value is output to the q-axis current generator 502e. The q-axis current generation unit 502e generates and outputs the q-axis current command value iq_ref based on the value output from the adder 502d. Specifically, for example, the q-axis current command value iq_ref is generated and output by multiplying the value output from the adder 502d by a preset proportional coefficient.

  Further, the d-axis current generation unit 502f sets the d-axis current command value id_ref to 0 and outputs it. In the present embodiment, the d-axis current generation unit 502f sets the d-axis current command value id_ref, which affects the strength of the magnetic flux passing through the winding, to 0, but the present invention is not limited to this. For example, the d-axis current generation unit 502f may set the d-axis current command value id_ref to a value other than 0 and output it, based on a command from the CPU 151a.

  Although the phase controller 502 in the present embodiment generates the q-axis current command value iq_ref based on PID control, the present invention is not limited to this. For example, the phase controller 502 may generate the q-axis current command value iq_ref based on PI control.

  The drive currents flowing through the A-phase and B-phase windings of the motor 509 are detected by the current detectors 507 and 508, and then converted from an analog value to a digital value by the A / D converter 510. The cycle in which the current detectors 507 and 508 detect the current may be the same cycle as the cycle T in which the CPU 151a outputs the command phase θ_ref to the motor control device 157, or may be shorter than the cycle T, for example.

The current value of the drive current converted from the analog value to the digital value by the A / D converter 510 is expressed by the following equation using the phase θe of the current vector shown in FIG. 3 as the current values iα and iβ in the stationary coordinate system. expressed. The phase θe of the current vector is defined as the angle formed by the α axis and the current vector. I indicates the magnitude of the current vector.
iα = I * cos θe (1)
iβ = I * sin θe (2)

  These current values iα and iβ are input to the coordinate converters 511 and 517 and the induced voltage determiner 512.

The coordinate converter 511 converts the current values iα and iβ in the stationary coordinate system into the current value iq of the q-axis current and the current value id of the d-axis current in the rotating coordinate system by the following equation.
id = cos θ * iα + sin θ * iβ (3)
iq = -sin θ * iα + cos θ * iβ (4)

  In vector control, the q-axis current command value iq_ref output from the phase controller 502 is input to the subtractor 102 via the changeover switch 516a. The current value iq output from the coordinate converter 511 is input to the subtractor 102. The subtractor 102 calculates the deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 503.

  In the vector control, the d-axis current command value id_ref output from the phase controller 502 is input to the subtractor 103 via the changeover switch 516a. Further, the current value id output from the coordinate converter 511 is input to the subtractor 103. The subtractor 103 calculates a deviation between the d-axis current command value id_ref and the current value id, and outputs the deviation to the current controller 504. The changeover switch 516a will be described later.

  FIG. 6 is a block diagram showing the configuration of the current controller 503. The configuration of the current controller 503 shown in FIG. 6 is an example in this embodiment, and the configuration of the current controller 503 is not limited to this.

  As shown in FIG. 6, the current controller 503 includes a proportional control unit 503a that performs P control, an integral control unit 503b that performs I control, and a differential control unit 503c that performs D control. Further, the current controller 503 has an adder 503d that adds the signals output from the proportional controller 502a, the integral controller 502b, and the derivative controller 502c. Further, the current controller 503 generates the drive voltage Vq as the value of the q-axis component of the voltage vector corresponding to the drive voltage to be applied to the winding of the motor 509 based on the signal output from the adder 503d. It has a generation unit 503e.

  The current controller 503 generates the drive voltage Vq based on the PID control so that the deviation output from the subtractor 102 becomes small. Specifically, the current controller 503 generates the drive voltage Vq so that the deviation output from the subtractor 102 becomes 0, and outputs the drive voltage Vq to the coordinate inverse converter 505.

  More specifically, the proportional control unit 503a outputs a value proportional to the deviation so that the deviation output from the subtractor 102 becomes zero. Further, the integration controller 503b outputs a value proportional to the time integral of the deviation so that the deviation output from the subtractor 102 becomes zero. Further, the differential control unit 503c outputs a value proportional to the time change of the deviation so that the deviation output from the subtractor 102 becomes zero.

  Then, the adder 503d adds the values output from the proportional control unit 503a, the integral control unit 503b, and the differential control unit 503c, and the added value is output to the drive voltage generation unit 503e. The drive voltage generation unit 503e generates and outputs the drive voltage Vq based on the value output from the adder 503d. Specifically, for example, the drive voltage Vq is generated and output by multiplying the value output from the adder 503d by a preset proportional coefficient.

  In this way, the current controller 503 functions as a generation unit that generates the drive voltage. The current controller 504 has the same configuration as the current controller 503, and in the same manner as the current controller 503, the d-axis component of the voltage vector corresponding to the drive voltage to be applied to the winding of the motor 509. The drive voltage Vd is generated as the value of.

  The current controllers 503 and 504 in the present embodiment generate the drive voltages Vq and Vd based on PID control, but the present invention is not limited to this. For example, the current controller 503 may generate the drive voltages Vq and Vd based on PI control.

The coordinate inverse converter 505 inversely converts the drive voltages Vq and Vd in the rotating coordinate system output from the current controllers 503 and 504 into the drive voltages Vα and Vβ in the stationary coordinate system by the following equation.
Vα = cos θ * Vd−sin θ * Vq (5)
Vβ = sin θ * Vd + cos θ * Vq (6)

  The coordinate inverse converter 505 outputs the inversely converted drive voltages Vα and Vβ to the induced voltage determiner 512 and the PWM inverter 506.

  The PWM inverter 506 has a full bridge circuit. The full bridge circuit is driven by the PWM signal based on the drive voltages Vα and Vβ input from the coordinate inverse converter 505. As a result, the PWM inverter 506 generates the drive currents iα and iβ according to the drive voltages Vα and Vβ, and supplies the drive currents iα and iβ to the windings of the respective phases of the motor 509 to drive the motor 509. . That is, the PWM inverter 506 functions as a supply unit that supplies current to the winding of each phase of the motor 509. Although the PWM inverter has a full bridge circuit in the present embodiment, the PWM inverter may be a half bridge circuit or the like.

Next, a configuration for determining the rotation phase θ will be described. The values of the induced voltages Eα and Eβ induced in the A-phase and B-phase windings of the motor 509 by the rotation of the rotor 402 are used to determine the rotation phase θ of the rotor 402. The value of the induced voltage is determined (calculated) by the induced voltage determiner 512. Specifically, the induced voltages Eα and Eβ are input from the A / D converter 510 to the induced voltage determiner 512 and the current values iα and iβ, and from the coordinate inverse converter 505 to the induced voltage determiner 512. It is determined from the drive voltages Vα and Vβ by the following equation.
Eα = Vα-R * iα-L * diα / dt (7)
Eβ = Vβ-R * iβ-L * diβ / dt (8)

  Here, R is winding resistance, and L is winding inductance. The values of the winding resistance R and the winding inductance L are values specific to the motor 509 used, and are stored in advance in the ROM 151b or a memory (not shown) provided in the motor control device 600 or the like.

  The induced voltages Eα and Eβ determined by the induced voltage determiner 512 are output to the phase determiner 513.

The phase determiner 513 determines the rotation phase θ of the rotor 402 of the motor 509 based on the ratio between the induced voltage Eα and the induced voltage Eβ output from the induced voltage determiner 512 by the following equation.
θ = tan ^ -1 (-Eβ / Eα) (9)

  In addition, in the present embodiment, the phase determiner 513 determines the rotational phase θ by performing the calculation based on the equation (9), but the present invention is not limited to this. For example, the phase determiner 513 rotates by referring to a table stored in the ROM 151b or the like and showing the relationship between the induced voltage Eα and the induced voltage Eβ and the rotational phase θ corresponding to the induced voltage Eα and the induced voltage Eβ. The phase θ may be determined.

  The rotation phase θ of the rotor 402 obtained as described above is input to the subtractor 101, the changeover switch 516b, and the coordinate converter 517. When vector control is performed, the rotation phase θ is input to the coordinate inverse converter 505 and the coordinate converter 511 via the changeover switch 516b. The changeover switch 516b and the coordinate converter 517 will be described later.

  When performing vector control, the motor control device 157 repeats the above control.

  As described above, the motor control device 157 in the present embodiment performs vector control using phase feedback control that controls the current value in the rotating coordinate system so that the deviation between the command phase θ_ref and the rotating phase θ becomes small. By performing the vector control, it is possible to prevent the motor from being out of step, the motor noise from increasing due to the excess torque, and the power consumption from increasing. Further, by performing the phase feedback control, the rotation phase of the rotor can be controlled so that the rotation phase of the rotor becomes a desired phase. Therefore, in the image forming apparatus, the vector control by the phase feedback control is applied to the motor that drives the load (registration roller or the like) that needs to control the rotation phase of the rotor with high accuracy, and the image on the recording medium is The formation can be carried out appropriately.

<Constant current control>
Next, the constant current control in the present embodiment will be described in comparison with the conventional constant current control.

  In the constant current control, a drive current flowing through the winding is controlled by supplying a predetermined current to the winding of the motor based on the operation sequence of the motor. In the constant current control, the torque corresponds to the torque that is required to rotate the rotor plus a predetermined margin so that the motor does not get out of step even if the load torque applied to the rotor fluctuates. A drive current having an amplitude is supplied. This is because the constant current control does not use a configuration in which the amplitude of the drive current is controlled based on the determined (estimated) rotation phase or rotation speed of the rotor (feedback control is not performed), so This is because the drive current cannot be adjusted according to the load torque applied to the child. The torque applied to the rotor increases as the amplitude of the current increases. Also, the amplitude corresponds to the magnitude of the current vector.

  In the following description, during constant current control, the motor is controlled by supplying a current having a constant amplitude to the winding of the motor, but the present invention is not limited to this. For example, during constant current control, the motor may be controlled by supplying a current having a predetermined amplitude to the winding of the motor in accordance with each of acceleration and deceleration of the motor.

  FIG. 7 is a block diagram showing an example of a control configuration of conventional constant current control. First, the conventional constant current control will be described.

  The CPU 151a outputs the command phase θ_ref to the constant current controller 801. The constant current controller 801 generates and outputs command values iα_ref and iβ_ref of the current in the stationary coordinate system corresponding to the command phase θ_ref output from the CPU 151a. In the present embodiment, the magnitude of the current vector corresponding to the current command values iα_ref and iβ_ref in the stationary coordinate system is always constant.

  The drive currents flowing in the A-phase and B-phase windings of the motor 509 are detected by the current detectors 806 and 807. The detected drive current is converted from an analog value to a digital value by the A / D converter 809, and is represented as current values iα and iβ as in equations (1) and (2).

  The current value iα output from the A / D converter 809 and the current command value iα_ref output from the constant current controller 801 are input to the subtractor 802. The subtractor 102 calculates the deviation between the current command value iα_ref and the current value iα, and outputs the deviation to the current controller 804.

  Further, the current value iβ output from the A / D converter 809 and the current command value iβ_ref output from the constant current controller 801 are input to the subtractor 803. The subtractor 803 calculates the deviation between the current command value iβ_ref and the current value iβ, and outputs the deviation to the current controller 804.

  The current controller 804 outputs the drive voltages Vα and Vβ based on the PID control so that the input deviation becomes small. Specifically, the current controller 804 outputs the drive voltages Vα and Vβ so that the input deviation approaches 0.

  The PWM inverter 506 supplies the drive current to the winding of each phase of the motor 509 to drive the motor 509 based on the input drive voltages Vα and Vβ by the method described above.

  Thus, in the conventional constant current control, the current values iα and iβ in the stationary coordinate system are used.

  Next, the constant current control in this embodiment will be described.

  FIG. 8 is a diagram for explaining constant current control in this embodiment. The dc axis shown in FIG. 8 indicates the direction in which the command phase θ_ref advances from the α axis in the counterclockwise direction, and the qc axis indicates the direction in which the instruction phase θ_ref advances by 90 degrees in the counterclockwise direction (the direction orthogonal to the dc axis). In the constant current control in the present embodiment, a rotating coordinate system represented by the dc axis and the qc axis with reference to the command phase θ_ref is used. Specifically, in the constant current control in the present embodiment, as shown in FIG. 8, the phase θe of the current vector corresponding to the drive current supplied to the winding is set to θ_ref. That is, the drive current supplied to the winding is generated so that the direction of the current vector corresponding to the drive current supplied to the winding matches the dc axis. Note that in FIG. 8, the configuration of the windings of the motor as shown in FIG. 3 is omitted.

  FIG. 9 is a block diagram showing an example of the configuration of the constant current controller 700 shown in FIG. As shown in FIG. 9, the constant current controller 700 has a current generator 700a and a coordinate converter 700b.

  Hereinafter, a method of performing constant current control by the motor control device 157 according to the present embodiment will be described with reference to FIGS. 4, 8 and 9.

  The CPU 151a outputs the command phase θ_ref to the current generator 700a and the coordinate converter 700b provided in the constant current controller 700. The current generator 700a generates current command values iα_ref and iβ_ref in the stationary coordinate system corresponding to the command phase θ_ref output from the CPU 151a and outputs the current command values iα_ref and iβ_ref to the coordinate converter 700b.

  The coordinate converter 700b uses the command values iα_ref and iβ_ref of the current in the stationary coordinate system to calculate the command values iq_ref and the d-axis of the q-axis current in the rotating coordinate system with the command phase θ_ref as a reference according to equations (3) and (4). The current is converted into a command value id_ref and output. In the present embodiment, the magnitude of the current vector corresponding to the current command values iα_ref and iβ_ref (the magnitude of the current vector corresponding to the q-axis current command value iq_ref and the d-axis current command value id_ref) is always It is constant.

  The drive currents flowing in the A-phase and B-phase windings of the motor 509 are detected by the current detectors 507 and 508. The detected drive current is converted from an analog value to a digital value by the A / D converter 510, and is represented as current values iα and iβ as in equations (1) and (2).

  In the constant current control, the command phase θ_ref is input to the coordinate converter 511 via the switch 516b. The coordinate converter 511 calculates the current values iα and iβ in the stationary coordinate system output from the A / D converter 510 using the equations (3) and (4) as the q-axis in the rotating coordinate system based on the command phase θ_ref. The current value iq of the current and the current value id of the d-axis current are converted.

  In the constant current control, the q-axis current command value iq_ref output from the constant current controller 700 is input to the subtractor 102 via the changeover switch 516a. The current value iq output from the coordinate converter 511 is input to the subtractor 102. The subtractor 102 calculates the deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 503.

  In the constant current control, the d-axis current command value id_ref output from the constant current controller 700 is input to the subtractor 103 via the changeover switch 516a. Further, the current value id output from the coordinate converter 511 is input to the subtractor 103. The subtractor 103 calculates a deviation between the d-axis current command value id_ref and the current value id, and outputs the deviation to the current controller 504. The changeover switch 516a will be described later.

  The current controllers 503 and 504 output the driving voltages Vq and Vd in the rotating coordinate system with the command phase θ_ref as a reference so that the input deviation becomes small. Specifically, the current controller 503 outputs the drive voltages Vq and Vd so that the input deviation approaches 0.

  In the constant current control, the command phase θ_ref is input to the coordinate inverse converter 505 via the switch 516b. The coordinate inverse converter 505 calculates the drive voltages Vq and Vd in the rotating coordinate system based on the command phase θ_ref, which are output from the current controllers 503 and 504, in the stationary coordinate system by the equations (5) and (6). The drive voltages Vα and Vβ are inversely converted.

  The coordinate inverse converter 505 outputs the inversely converted drive voltages Vα and Vβ to the PWM inverter 506. The PWM inverter 506 supplies a drive current to the winding of each phase of the motor 509 to drive the motor 509 by the method described above.

  As described above, in the constant current control according to the present embodiment, the rotating coordinate system represented by the dc axis and the qc axis with reference to the command phase θ_ref is used.

  Further, in the constant current control in this embodiment, neither phase feedback control nor speed feedback control is performed. That is, in the constant current control in the present embodiment, the drive current supplied to the winding is not adjusted according to the rotation status of the rotor. Therefore, in the constant current control, a current obtained by adding a predetermined margin to the current required to rotate the rotor is supplied to the winding so that the motor is not out of step. Specifically, the current command values iα_ref and iβ_ref in the stationary coordinate system include a current value necessary to rotate the rotor and a current value corresponding to a predetermined margin.

<Switching between vector control and constant current control>
Next, a method of switching between vector control and constant current control will be described. As shown in FIG. 4, the motor control device 157 in this embodiment has a configuration for switching between constant current control and vector control. Specifically, the motor control device 157 includes a control switch 515, changeover switches 516a and 516b, and a delay circuit 518. It should be noted that during the period in which the constant current control is performed, the circuit that performs the vector control is also operating. That is, the circuit that determines the rotation phase θ of the rotor is operating while the constant current control is being performed. On the other hand, during the period in which the vector control is performed, the circuit that performs the constant current control may be operating or may be stopped.

  As shown in FIG. 4, the control switch 515 receives the rotation speed ω_ref ′ corresponding to the target speed determined by the CPU 151a based on the command phase θ_ref. The control switching device 515 switches between constant current control and vector control by comparing the rotational speed ω_ref ′ with a threshold value ωth as a predetermined value, and further outputs a switching signal indicating switching of control.

  FIG. 10 is a diagram showing a relationship between the rotation speed ω_ref ′ and the threshold value ωth and a switching signal. The threshold value ωth in the present embodiment is set to the lowest rotation speed among the rotation speeds in which the rotation phase θ is accurately determined, but is not limited to this. For example, the threshold ωth may be set to a value equal to or higher than the lowest rotation speed among the rotation speeds in which the rotation phase θ is accurately determined.

  As shown in FIG. 10, the control switch 515 sets the switching signal to “H” when the constant current control is performed, and sets the switching signal to “L” when the vector control is performed. The switching signal output from the control switch 515 is input to the phase controller 502 and the delay circuit 518, as shown in FIG. The control switch 515 outputs the switching signal in the same cycle as the cycle T in which the CPU 151a outputs the rotation speed ω_ref ′, for example.

  The delay circuit 518 outputs the input switching signal after a predetermined delay time after the switching signal is output from the control switch 515. The predetermined delay time is longer than the time from when the switching signal is output from the control switch 515 to when the phase controller 502 outputs iq_ref and id_ref according to the switching signal. The configuration in which the phase controller 502 outputs iq_ref and id_ref according to the switching signal will be described later.

  When the rotation speed ω_ref ′ becomes equal to or higher than the threshold value ωth (ω_ref ′ ≧ ωth) during the control by the constant current controller 700, the control switch 515 switches the controller that controls the motor 509. That is, the control switch 515 switches the switching signal from “H” to “L” and outputs the switching signal so that the controller controlling the motor 509 is switched from the constant current controller 700 to the vector controller 701. The delay circuit 518 outputs the input switching signal to the changeover switches 516a and 516b after a predetermined delay time from the output of the switching signal from the control switch 515. As a result, the states of the changeover switches 516a and 516b are switched according to the switching signal, and the vector control by the vector controller 701 is performed. The threshold value ωth is stored in advance in the ROM 151b, for example.

  Further, during the control by the constant current controller 700, when the rotation speed ω_ref ′ is smaller than the threshold value ωth (ω_ref ′ <ωth), the control switch 515 does not switch the controller that controls the motor 509. That is, the control switch 515 outputs the switch signal'H 'so that the motor 509 maintains the state controlled by the constant current controller 700. The delay circuit 518 outputs the input switching signal to the changeover switches 516a and 516b after a predetermined delay time from the output of the switching signal from the control switch 515. As a result, the states of the changeover switches 516a and 516b are maintained, and the constant current control by the constant current controller 700 is continued.

  During the control by the vector controller 701, when the rotation speed ω_ref ′ becomes smaller than the threshold value ωth (ω_ref ′ <ωth), the control switch 515 switches the controller that controls the motor 509. That is, the control switch 515 switches the switching signal from “L” to “H” so as to switch the controller for controlling the motor 509 from the vector controller 701 to the constant current controller 700, and outputs the switching signal. The delay circuit 518 outputs the input switching signal to the changeover switches 516a and 516b after a predetermined delay time from the output of the switching signal from the control switch 515. As a result, the states of the changeover switches 516a and 516b are switched, and the constant current controller 700 performs constant current control.

  Further, during the control by the vector controller 701, when the rotation speed ω_ref ′ is equal to or higher than the threshold value ωth (ω_ref ′ ≧ ωth), the control switch 515 does not switch the controller that controls the motor 509. That is, the control switch 515 outputs the switching signal'L 'so that the motor 509 maintains the state controlled by the vector controller 701. The delay circuit 518 outputs the input switching signal to the changeover switches 516a and 516b after a predetermined delay time from the output of the switching signal from the control switch 515. As a result, the states of the changeover switches 516a and 516b are maintained, and the vector control by the vector controller 701 is continued.

<Process when switching control>
Next, a process performed by the motor control device 157 when the motor control method is switched from the constant current control to the vector control will be described.

  As described above, when the control of the motor is switched from the constant current control to the vector control, the rotation speed of the motor may momentarily decrease (or increase). This is because there is a difference between the torque generated in the rotor immediately before the control of the motor is switched and the torque generated in the rotor immediately after the control of the motor is switched.

  Therefore, in the present embodiment, the following configuration is applied to the motor control device 157 to prevent the control of the motor from becoming unstable.

  As shown in FIG. 4, the motor control device 157 in this embodiment is provided with a coordinate converter 517. In the following description, the coordinate converter 517 is operating during the constant current control. Further, the coordinate converter 517 may be operating or may be stopped during the period in which the vector control is performed. Further, in the following description, the phase controller 502 is operating during the period when the constant current control is being performed.

  As shown in FIG. 4, the current values iα and iβ output from the A / D converter 510 and the rotation phase θ output from the phase determiner 513 are input to the coordinate converter 517. The coordinate converter 517 uses the equations (3) and (4) to calculate the current values iα and iβ based on the rotation phase θ output from the phase determiner 513, and then to the rotation coordinate system based on the rotation phase θ. Convert to current values iq 'and id'. The current value iq ′ converted by the coordinate converter 517 is input to the phase controller 502. Specifically, as shown in FIG. 5, the current value iq ′ is input to the integral control unit 502b provided inside the phase controller 502. The coordinate converter 517 outputs iq ′ in the same cycle as the cycle in which the current detectors 507 and 508 detect the current.

  When the switching signal switches from “H” to “L”, the integration control unit 502b outputs the control result of the integration control unit 502b based on the current value iq ′ acquired immediately before the switching signal switches. Specifically, when the switching signal is switched from “H” to “L”, the integral control unit 502b multiplies the current value iq ′ acquired immediately before the switching signal by the proportional coefficient Kq. It is set as an initial value of integration of 502b. That is, when the switching signal switches from “H” to “L”, the integration control unit 502b deletes the integration result until immediately before the switching signal is switched to the current value iq ′ acquired immediately before the switching signal is switched. A value obtained by multiplying the proportionality coefficient Kq is set as an initial value of integration.

<Proportional coefficient Kq>
The proportionality coefficient Kq will be described below. FIG. 11 is a diagram showing an example of the relationship between the load torque Tm applied to the rotor 402 of the motor 509 and the q-axis current iq when the motor is driven at a predetermined rotation speed. The solid line shows the relationship between the load torque Tm and the q-axis current iq when the d-axis current command value id_ref is set to 0 during the period when the vector control is being performed, and the broken line is performing the constant current control. The relationship between the load torque Tm and the q-axis current iq when the magnitude of the current vector is set to 0.8 A during the period is shown. Further, the alternate long and short dash line shows the relationship between the load torque Tm and the q-axis current iq when the magnitude of the current vector is set to 1.0 A during the period when the constant current control is executed, and the alternate long and two short dashes line shows the constant The relationship between the load torque Tm and the q-axis current iq in the case where the magnitude of the current vector is set to 1.2 A during the period in which the current control is executed is shown.

The torque T generated in the rotor due to the current flowing through the winding of the motor is represented by the sum of the magnet torque Tmg and the reluctance torque Trl as in the following expression (10). The magnet torque Tmg and the reluctance torque Trl are expressed by the following equations (11) and (12), respectively.
T = Tmg + Trl (10)
Tmg = Kt * iq (11)
Trl = (Ld-Lq) * id * iq (12)
Kt is a proportional coefficient indicating the relationship between the magnet torque Tmg and the q-axis current iq. Ld represents the d-axis component of the winding inductance, and Lq represents the q-axis component of the winding inductance.

When the d-axis current command value id_ref is set to 0 in vector control, the reluctance torque Trl becomes 0. When the d-axis current command value id_ref is set to 0 and the q-axis current iq required to drive the rotor under the load torque Tm0 by vector control is iq0, The torque T_vec generated in the rotor due to iq0 is
T_vec = Kt * iq0 (13)
Becomes

On the other hand, in the constant current control, control such that the d-axis current becomes 0 is not performed. For example, when the q-axis current iq is iq0 in constant current control, the torque T_opn generated in the rotor due to the iq0 is:
T_opn = Kt * iq0 + (Ld-Lq) * id0 * iq0 (14)
Becomes (Ld-Lq) is a negative value due to the saliency of the motor. That is, when the q-axis current iq is iq0, the torque T_opn generated in the rotor in the constant current control is smaller than the torque T_vec generated in the rotor in the vector control. Therefore, in order to drive the rotor under the load torque Tm0 by the constant current control, the q-axis current larger than iq0 is required. Specifically, for example, as shown in FIG. 11, when the load torque Tm is 50 [mNm] when the motor is driven at a predetermined rotation speed, the q-axis current in the constant current control is in the vector control. The value is larger than the q-axis current.

  From the above, the q-axis current iq during constant current control has a larger value than the q-axis current iq during vector control. Therefore, if the current value iq ′ acquired immediately before the switching signal is switched is directly set as the initial value of the integration of the integral control unit 502b, the torque applied to the rotor immediately after the motor control is switched from the constant current control to the vector control. However, the torque becomes larger than the torque applied to the rotor immediately before the control of the motor is switched from the constant current control to the vector control. As a result, when the control of the motor is switched from the constant current control to the vector control, the rotation speed of the motor fluctuates instantaneously.

  The proportional coefficient Kq in the present embodiment is a ratio of the q-axis current iq_opn when the motor is driven at a predetermined rotation speed by constant current control and the q-axis current iq_vec when the motor is driven at a predetermined rotation speed by vector control. Indicates (iq_vec / iq_opn). The q-axis current iq_opn and the q-axis current iq_vec are measured in advance by experiments, and the proportional coefficient Kq is calculated based on the result of the measurement. The proportional coefficient Kq is stored in, for example, a memory (not shown) provided in the phase controller 502.

  It should be noted that the predetermined delay time for the delay circuit 518 to delay the switching signal after the switching signal is output from the control switching unit 515 is longer than the time when the phase controller 502 performs the above-described processing, and the switching signal is the control switching. The time is shorter than the cycle output from the device 515.

  FIG. 12 is a flowchart showing a motor control method by the motor control device 157. The control of the motor 509 in this embodiment will be described below with reference to FIG. The process of this flowchart is executed by the motor control device 157 that receives an instruction from the CPU 151a.

  First, when the enable signal'H 'is output from the CPU 151a to the motor control device 157, the motor control device 157 starts driving the motor 509 based on the command output from the CPU 151a. The enable signal is a signal that permits or prohibits the operation of the motor control device 157. When the enable signal is'L (low level) ', the CPU 151a prohibits the operation of the motor control device 157. That is, the control of the motor 509 by the motor control device 157 is ended. When the enable signal is “H (high level)”, the CPU 151a permits the motor control device 157 to operate, and the motor control device 157 controls the motor 509 based on the command output from the CPU 151a. .

  Next, in S1001, the control switch 515 outputs the switch signal'H 'so that the drive of the motor 509 is controlled by the constant current controller 517. As a result, constant current control by the constant current controller 700 is performed.

  After that, in S1002, when the CPU 151a outputs the enable signal ‘L’ to the motor control device 157, the motor control device 157 ends the driving of the motor 509.

  If the CPU 151a outputs the enable signal ‘H’ to the motor controller 157 in S1002, the motor controller 157 advances the process to S1003.

  Next, in S1003, if the rotation speed ω_ref ′ is less than the threshold value ωth, the process returns to S1001 again. That is, the constant current control by the constant current controller 700 is maintained.

  If the rotation speed ω_ref ′ is equal to or higher than the threshold value ωth in S1003, the control switch 515 switches the switching signal from “H” to “L” and outputs the switching signal in S1004.

  After that, in S1005, the integration control unit 502b deletes the integration result up to immediately before the switching signal switches to “L”, and integrates the value obtained by multiplying the current value iq ′ acquired immediately before switching the switching signal by the proportional coefficient Kq. Set as the initial value of and output.

  Then, when a predetermined delay time elapses in S1006, the switching signal ‘L’ is output from the delay circuit 518 to the changeover switches 516a and 516b in S1007. As a result, vector control is performed by the vector controller 701.

  If the rotation speed ω_ref ′ is equal to or higher than the threshold value ωth in S1008, the process returns to S1007 again, and the vector control by the vector controller 701 is continued.

  If the rotation speed ω_ref ′ is smaller than the threshold value ωth in S1008, the process returns to S1001 again, and the control switch 515 switches the controller that controls the driving of the motor 509. That is, the control switch 515 switches the switching signal from “L” to “H” so as to switch the controller for controlling the motor 509 from the vector controller 701 to the constant current controller 700, and outputs the switching signal. The delay circuit 518 outputs the input switching signal to the changeover switches 516a and 516b after a predetermined delay time from the output of the switching signal from the control switch 515. As a result, the states of the changeover switches 516a and 516b are switched, and the constant current controller 700 performs constant current control.

  After that, the motor control device 157 repeats the above-described control until the CPU 151a outputs the enable signal ‘L’ to the motor control device 157. Even during vector control, when the CPU 151a outputs the enable signal ‘L’ to the motor control device 157, the motor control device 157 stops the control of the motor.

  As described above, in the present embodiment, the current value iq ′ corresponding to the load torque applied to the rotor is determined based on the current value detected during execution of the constant current control. Then, the q-axis current command value iq_ref immediately after the switching signal switches from “H” to “L” is generated based on the current value iq ′ immediately before the switching signal switches from “H” to “L”. Specifically, a value obtained by multiplying the current value iq 'as the current detection result by the proportionality coefficient Kq is set as the initial value of integration in the phase controller 502. The proportional coefficient Kq represents a ratio of the q-axis current iq_opn when the motor is driven at a predetermined rotation speed by constant current control and the q-axis current iq_vec when the motor is driven at a predetermined rotation speed by vector control. . As a result, the torque generated in the rotor corresponding to the current supplied immediately before the control of the motor is switched and the torque generated in the rotor corresponding to the current supplied immediately after the control of the motor is switched. It is possible to suppress the occurrence of a difference. As a result, when the control of the motor is switched from the constant current control to the vector control, it is possible to prevent the rotation speed of the motor from varying.

  In the motor control device according to the present embodiment, there are some shared portions (current controllers 503 and 504, PWM inverter 506, etc.) in the circuit that performs vector control and the circuit that performs constant current control. Not limited to this. For example, a circuit that performs vector control and a circuit that performs constant current control may be independently provided.

  In addition, in the present embodiment, the phase controller 502 sets the value obtained by multiplying the current value iq ′ by the proportional coefficient Kq as the initial value of the integration in the integration control unit 502b, but the present invention is not limited to this. For example, the phase controller 502 may set a value obtained by subtracting a predetermined value from the current value iq ′ as an initial value of integration in the integration control unit 502b.

  Further, in the present embodiment, the initial value of integration in the integration control unit 502b is set based on the current value iq 'acquired immediately before the switching signal is switched, but the present invention is not limited to this. For example, the initial value of integration in the integration control unit 502b may be set based on the current value iq ′ two times before, not immediately before.

  In addition, in the present embodiment, the phase controller 502 is in operation during the constant current control, but the phase controller 502 may be stopped. Specifically, for example, among the configurations provided in the phase controller 502, any configuration may be used as long as the integral control unit is operating.

  Further, in the present embodiment, the circuit that controls the drive of the motor 509 using the vector controller 518 corresponds to the first control circuit in the present invention. Further, in the first and second embodiments, the circuit that controls the drive of the motor 509 using the constant current controller 517 corresponds to the second control circuit in the present invention.

In the vector control according to the present embodiment, the motor 509 is controlled by performing the phase feedback control, but the present invention is not limited to this. For example, the configuration may be such that the rotation speed ω of the rotor 402 is fed back to control the motor 509. Specifically, as shown in FIG. 13, a speed determiner 514 is provided inside the motor control device, and the speed determiner 514 determines the rotation speed ω based on the time change of the rotation phase θ output from the phase determiner 513. decide. The following equation (10) is used to determine the speed.
ω = dθ / dt (10)

  Then, the CPU 151a outputs a command speed ω_ref representing the target speed of the rotor. Further, a speed controller 500 is provided inside the motor control device, and the speed controller 500 generates and outputs the q-axis current command value iq_ref so that the deviation between the rotation speed ω and the command speed ω_ref becomes small. . The motor 509 may be controlled by performing such speed feedback control. Since the rotation speed is fed back in such a configuration, it is possible to control the rotation speed of the rotor to be a predetermined speed. Therefore, in the image forming apparatus, speed feedback control is performed on the motor that drives the load (for example, the photosensitive drum, the conveyor belt, etc.) that needs to control the rotation speed to a constant speed in order to appropriately perform image formation on the recording medium. Apply the vector control used. As a result, it is possible to properly form an image on the recording medium. In this case, the command speed ω_ref is also used when performing the constant current control. Further, the control switching may be performed based on the command speed ω_ref, or may be performed based on the rotation speed ω determined by the speed determiner 514.

  Further, the rotation speed ω_ref ′ has a magnitude of a periodic signal that is correlated with the rotation cycle of the rotor 402, such as the drive current iα or iβ, the drive voltage Vα or Vβ, the induced voltage Eα or Eβ, and the like. It may be determined based on the cycle.

  Further, in the present embodiment, the stepping motor is used as the motor for driving the load, but it may be another motor such as a DC motor. Further, the present embodiment is applicable not only to the case where the motor is a two-phase motor, but also to another motor such as a three-phase motor.

  Further, in this embodiment, a permanent magnet is used as the rotor, but the rotor is not limited to this.

157 Motor controller 402 Rotor 502 Phase controller 503, 504 Current controller 507, 508 Current detector 509 Motor 513 Phase determiner 511, 517 Coordinate converter 700 Constant current controller 701 Vector controller

Claims (20)

In a motor control device that controls the motor based on a command phase that represents a target phase of the rotor of the motor,
Detecting means for detecting a drive current flowing through the winding of the motor;
Phase determining means for determining the rotational phase of the rotor based on the drive current detected by the detecting means,
Converting means for converting the current value of the stationary coordinate system detected by the detecting means into a current value of the rotating coordinate system based on the rotating phase determined by the phase determining means,
The magnitude of the drive current detected by the detection means is adjusted so that the drive current becomes a target value set so that the deviation between the command phase and the rotation phase determined by the phase determination means becomes small. Control means having a first control mode for controlling, and a second control mode for controlling the drive current based on a current of a predetermined magnitude,
Have
The target value in the first control mode when the control mode for controlling the drive current is switched from the second control mode to the first control mode is converted by the conversion means during execution of the second control mode. Is set based on a value obtained by multiplying the value of the torque current component of the drive current by a predetermined value,
The motor control device, wherein the torque current component is a current component represented in the rotational coordinate system of the drive current converted by the conversion means. In a motor control device for controlling the motor based on a command speed representing a target speed of a rotor of the motor,
Detecting means for detecting a drive current flowing through the winding of the motor;
Phase determining means for determining the rotational phase of the rotor based on the drive current detected by the detecting means,
Speed determining means for determining the rotational speed of the rotor,
Converting means for converting the current value of the stationary coordinate system detected by the detecting means into a current value of the rotating coordinate system based on the rotating phase determined by the phase determining means,
The drive current is adjusted so that the magnitude of the drive current detected by the detection means becomes a target value set so that the deviation between the command speed and the rotation phase determined by the speed determination means becomes small. Control means having a first control mode for controlling, and a second control mode for controlling the drive current based on a current of a predetermined magnitude,
Have
The target value in the first control mode when the control mode for controlling the drive current is switched from the second control mode to the first control mode is converted by the conversion means during execution of the second control mode. Is set based on a value obtained by multiplying the value of the torque current component of the drive current by a predetermined value,
The motor control device, wherein the torque current component is a current component represented in the rotational coordinate system of the drive current converted by the conversion means. In the first control mode, integration control is performed based on the deviation so that the deviation becomes smaller, and the magnitude of the drive current detected by the detection means is set to the target set based on the integration control. It is a control mode for controlling the drive current so as to have a value,
The initial value of the integral control in the first control mode when the control mode for controlling the drive current is switched from the second control mode to the first control mode is the conversion during the execution of the second control mode. 3. The motor control device according to claim 1, wherein the value is set based on a value obtained by multiplying the value of the torque current component of the drive current converted by the means by a predetermined value.   The predetermined value is a value of the torque current component of the drive current in a state where the motor is driven at a predetermined rotation speed in the second control mode, and a predetermined rotation speed of the motor in the first control mode. 4. A value indicating a ratio between the value of the torque current component of the drive current and the value of the torque current component in the state of being driven by, which is a preset value. The described motor control device. In the first control mode, the drive current is adjusted so that the value of the torque current component of the drive current converted by the conversion unit becomes a target value of the torque current component set so as to reduce the deviation. Is a control mode for controlling
The motor control device according to claim 3 or 4, wherein the target value of the torque current component is set based on the integral control in which the initial value is set. The conversion means converts the drive current in a predetermined cycle,
The target value of the torque current component is based on the value of the torque current component of the drive current converted by the conversion unit at the end before the control mode is switched from the second control mode to the first control mode. The motor control device according to any one of claims 1 to 5, wherein the motor control device is set as follows.   The control means sets the control mode for controlling the drive current to the second control when the rotation speed corresponding to the target speed of the rotor becomes a value larger than a predetermined value during execution of the second control mode. The motor control device according to any one of claims 1 to 6, wherein the mode is switched to the first control mode. The control means controls the magnitude of the induced voltage induced in the first phase winding and the second phase winding by the rotation of the rotor of the motor based on the drive current detected by the detection means. Having an induced voltage determining means for determining,
The phase determining means determines the rotational phase of the rotor of the motor based on the magnitude of the induced voltage of the first phase and the magnitude of the induced voltage of the second phase determined by the induced voltage determining means. The motor control device according to claim 1, wherein the motor control device is a motor control device.   The predetermined value is based on the magnitude of the induced voltage of the first phase and the magnitude of the induced voltage of the second phase determined by the induced voltage determining means by the phase determining means, and the rotation phase of the rotor of the motor. The motor control device according to claim 8, wherein the motor control device is set to a rotation speed capable of determining   The motor control device according to claim 8 or 9, wherein the rotation speed corresponding to the target speed changes in a second predetermined cycle.   The motor control device according to claim 10, wherein the second predetermined cycle is the same cycle as the cycle in which the control unit controls the motor.   The motor control device according to claim 10, wherein the second predetermined cycle is the same cycle as the cycle in which the detection unit detects the drive current.   In the first control mode, the value of the exciting current component of the drive current detected by the detection unit is controlled to be 0, and the value of the torque current component of the drive current detected by the detection unit is controlled. 13. The motor control device according to claim 1, wherein the motor control device is in a control mode for controlling the motor. The motor control device,
A first control circuit that supplies a driving current to each of the first phase winding and the second phase winding of the motor when the first control mode is executed;
A second control circuit that supplies a driving current to each of the first phase winding and the second phase winding of the motor when the second control mode is executed;
Switching means for switching between controlling the motor using the first control circuit and controlling the motor using the second control circuit;
The motor control device according to any one of claims 1 to 13, further comprising: A transport roller for transporting the sheet,
A motor for driving the transport roller,
A motor control device according to any one of claims 1 to 14,
Have
The sheet conveyance device, wherein the motor control device controls driving of a motor that drives the conveyance roller. A sheet conveying device according to claim 15;
A document stacking unit for stacking documents,
Have
A document feeding device, wherein the sheet conveying device feeds the document stacked on the document stacking portion. A document feeder according to claim 16;
A reading unit that reads the document fed by the document feeding device;
An original reading device having: A sheet conveying device according to claim 15;
An image forming means for forming an image on a recording medium,
Have
The image forming apparatus, wherein the image forming unit forms an image on the recording medium conveyed by the sheet conveying apparatus. An image forming apparatus for forming an image on a recording medium,
A motor that drives the load,
A motor control device according to any one of claims 1 to 14,
Have
The image forming apparatus, wherein the motor control device controls driving of a motor that drives the load.   The image forming apparatus according to claim 19, wherein the load is a conveyance roller that conveys the recording medium.

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