JP2017189091A - Motor control device, sheet transportation device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that switching between a constant current control and a vector control may occur repeatedly when switching control of a motor.SOLUTION: Two threshold values for switching between a constant current control and a vector control are provided. To be specific, when a rotational speed ω of a rotor 402 becomes larger than a threshold value ω1 by acceleration during constant current control, control of a motor is switched from the constant current control to the vector control. During the vector control, even if the rotational speed ω of the rotor 402 comes to be less than the threshold value ω1 by deceleration, switching to the constant current control is not performed, and when the rotational speed of the rotor further decreases to be less than a threshold value ω2, the control of the motor is switched from the vector control to the constant current control. As a result, repeated switching between the constant current control and the vector control is suppressed.SELECTED DRAWING: Figure 6

Description

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

  2. Description of the Related Art Conventionally, as a method for controlling the driving of a motor, a control method called vector control for controlling a motor by controlling a current value in a rotating coordinate system based on the rotational phase of the rotor of the motor is known. . Specifically, a control method for controlling a motor by performing phase feedback control for controlling a current value of a rotating coordinate system so that a deviation between a rotor command phase and an actual rotation phase is small is known. . There is also known a control method for controlling the motor by performing speed feedback control for controlling the current value of the rotating coordinate system so that the deviation between the command speed of the rotor and the actual rotation speed becomes small.

  When vector control is used, the drive current supplied to the motor winding is divided into a current component (torque current component) that generates torque for rotating the rotor and a current component that affects the strength of the magnetic flux passing through the winding ( The excitation current component can be controlled separately. As a result, even if the load torque applied to the rotor changes, the torque necessary for the rotation can be efficiently generated by controlling the value of the torque current component in accordance with the change of the load torque. As a result, it is possible to suppress an increase in motor noise and an increase in power consumption due to the surplus torque. Also, because the load torque applied to the rotor exceeds the output torque corresponding to the drive current supplied to the motor windings, the rotor will not be synchronized with the input signal, and the motor will be uncontrollable (step-out state) ) Can be suppressed.

  The vector control requires a configuration for determining the rotational 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 decreases as the rotational speed of the rotor decreases. If the magnitude of the induced voltage generated in the winding is not large enough to determine the rotational phase of the rotor, the rotational phase may not be determined with high accuracy. That is, the smaller the rotational speed of the rotor, the worse the accuracy of determining the rotational phase of the rotor.
Patent Document 2 describes a configuration in which constant current control for controlling a motor by supplying a constant current to a winding of the motor is used when the rotation speed of the rotor is smaller than a predetermined rotation speed. In constant current control, neither phase feedback control nor speed feedback control is performed. Furthermore, a configuration is described in which vector control is used when the rotational speed of the rotor is equal to or higher than a predetermined rotational speed.

Japanese Patent No. 5537565 Japanese Patent Laid-Open No. 2005-39955

  However, when the motor control is switched from the constant current control to the vector control, there is a possibility that the rotational speed of the rotor is instantaneously reduced. That is, even if the rotational speed of the rotor exceeds the predetermined rotational speed and the motor control is switched from constant current control to vector control, the rotational speed of the rotor decreases and becomes lower than the predetermined rotational speed again. The motor control is switched from the vector control to the constant current control again. In this way, switching between constant current control and vector control occurs repeatedly. As a result, the increase and decrease in the magnitude of the motor sound repeatedly occur, or the motor becomes uncontrollable.

  In view of the above problems, an object of the present invention is to suppress repetitive switching between a first control mode and a second control mode as a control mode for controlling a motor.

In order to solve the above problems, the present invention provides:
In a motor control device that controls the motor based on a command phase representing a target phase of a rotor of the motor,
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
A current component of a current value represented in a rotating coordinate system based on the rotational phase determined by the phase determining means so that a deviation between the command phase and the rotational phase determined by the phase determining means is small. A first control mode for controlling the motor by controlling a value of a torque current component that generates torque in the rotor and a value of an excitation current component that affects the strength of a magnetic flux passing through the winding of the motor. And a second control mode for controlling the motor by supplying a constant current to the winding of the motor, and a control means comprising:
Have
In a state where the control unit is controlling the motor in the second control mode, the rotation speed of the rotor of the motor determined by the speed determination unit is determined from a value smaller than a first threshold value. When the value changes to a value larger than the threshold value of 1, the control mode for controlling the motor is switched from the second control mode to the first control mode, and the motor is controlled in the first control mode. In this state, the rotational speed of the rotor of the motor determined by the speed determining means is larger than the second threshold smaller than the first threshold from a value larger than the first threshold and the The first control mode is maintained even if the value is changed to a value smaller than the first threshold value.

  According to the present invention, it is possible to suppress repeated switching between the first control mode and the second control mode as the control mode for controlling the motor.

1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment. 2 is a block diagram illustrating a control configuration of the image forming apparatus. FIG. It is a figure which shows the relationship between the two-phase motor which consists of A phase and B phase, and d-axis and q-axis of a rotation coordinate system. It is a block diagram which shows the structure of the motor control apparatus which concerns on 1st Embodiment. It is a figure which shows the relationship between the threshold value which switches constant current control which concerns on 1st Embodiment, and vector control, and the rotational speed and instruction | command speed of the rotor of a motor. It is a flowchart which shows the control method of the motor which concerns on 1st Embodiment. It is a block diagram which shows the structure of the motor control apparatus which performs speed feedback control.

  In the following, preferred embodiments of the present invention will be described with reference to the drawings. However, the shape of the component parts described in this embodiment and the relative arrangement thereof should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention is limited. It is not intended to be limited to the following embodiments. In the following description, a case where the motor control device is provided in the image forming apparatus will be described, but the motor control device is not limited to the image forming apparatus. For example, the motor control device 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 illustrating a configuration of a monochrome electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 100 having a sheet conveying device used in the present embodiment. The image forming apparatus is not limited to a copying machine, and may be, for example, a facsimile machine, a printing machine, a printer, or the like. The recording method is not limited to the electrophotographic method, and may be, for example, an ink jet. Further, 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. The image forming apparatus 100 includes a document feeding device 201, a reading device 202, and an image forming device main body 301.

  The originals stacked on the original stacking unit 203 of the original feeder 201 are fed one by one by the paper feed roller 204 and conveyed along the conveyance guide 206 onto the original glass plate 214 of the reading apparatus 202. Further, the document is conveyed at a constant speed by the conveyance belt 208 and discharged to a discharge tray (not shown) by a discharge roller 205. Reflected light from the document 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, and 212, and converted into an image signal by the image reading unit 111. Is done. The image reading unit 111 includes a lens, a CCD that is a photoelectric conversion element, a CCD drive circuit, 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 configured by a hardware device such as an ASIC, and then output to the image forming apparatus main body 301. As described above, the document is read. That is, the document feeder 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 an illumination system 209 and an optical system fixed at a predetermined position. The second reading mode is a mode in which an image of an original placed on the original glass 214 of the reading apparatus 202 is read by the illumination system 209 and the optical system that move at a constant speed. Normally, an image of a sheet-like document is read in the first reading mode, and an image of a bound document such as a book or booklet is read in the second reading mode.

  Inside the image forming apparatus main body 301, sheet storage trays 302 and 304 are provided. Each of 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 an image on which an image is formed by an image forming apparatus. For example, paper, a resin sheet, a cloth, an OHP sheet, a label, and the like are included in the recording medium.

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

  The image signal output from the reading device 202 is input to an optical scanning device 311 including a semiconductor laser and a polygon mirror. Further, 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 photosensitive The drum 309 is irradiated on the outer peripheral surface. 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.

  Subsequently, the electrostatic latent image is developed with 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 to a recording medium by a transfer charger 315 provided at a position (transfer position) facing the photosensitive drum 309. At this time, the registration roller 308 sends the recording medium to the transfer position in synchronization with the toner image.

  As described above, the recording medium to which the toner image has been transferred is sent to the fixing device 318 by the conveyance belt 317, and is heated and pressurized by the fixing device 318 to fix the toner image to the recording medium. In this manner, the image forming apparatus 100 forms an image on the recording medium.

  When image formation is performed in the single-sided printing mode, the recording medium that has passed through the fixing device 318 is discharged to a discharge tray (not shown) by discharge rollers 319 and 324. When image formation is performed in the double-sided printing mode, after the fixing process is performed on the first surface of the recording medium by the fixing device 318, the recording medium is a discharge roller 319, a conveyance roller 320, and a reverse roller 321. Is conveyed to the reverse path 325. Thereafter, 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. Thereafter, the recording medium is discharged to a discharge tray (not shown) by discharge rollers 319 and 324.

  When the recording medium on which the image is formed on the first surface is discharged face-down to the outside of the image forming apparatus 100, the recording medium that has passed through the fixing device 318 passes through the discharge roller 319 and the conveyance roller 320. It is transported in the direction toward. Thereafter, the rotation of the conveyance roller 320 is reversed immediately before the rear end of the recording medium passes through the nip portion of the conveyance roller 320, so that the recording medium is discharged to the discharge roller with the first surface of the recording medium facing downward. The sheet 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. In addition, the load in this invention is the target object driven by a motor. For example, various rollers (conveyance rollers) such as paper feed rollers 204, 303, 305, registration rollers 308 and paper discharge rollers 319, photosensitive drums 309, conveyance belts 208, 317, illumination system 209, optical system, etc. Corresponds to the load. The motor control device of this embodiment is applied to a motor that drives these loads.

  FIG. 2 is a block diagram illustrating an example of a 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. The system controller 151 is connected to the image processing unit 112, the operation unit 152, an analog / digital (A / D) converter 153, a high voltage control unit 155, a motor control device 157, sensors 159, and an AC driver 160. . The system controller 151 can send and receive data and commands to and from each connected unit.

  The CPU 151a executes various sequences related to a predetermined image forming sequence by reading and executing various programs stored in the ROM 151b.

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

  The system controller 151 transmits setting value data of various apparatuses provided in the image forming apparatus 100 necessary for image processing in the image processing unit 112 to the image processing unit 112. Furthermore, the system controller 151 receives signals from various devices (signals from the sensors 159), and sets a setting value for the high-voltage control unit 155 based on the received signals. The high voltage controller 155 supplies a necessary voltage to the high voltage unit 156 (charging device 310, developing device 314, transfer charging device 315, etc.) according to the set value set by the system controller 151. The sensors 159 include a sensor that detects a recording medium conveyed by the conveyance roller.

  The motor control device 157 controls the motor 509 in accordance with a command output from the CPU 151a. In FIG. 2, only the motor 509 is described as the motor for driving the load. However, in reality, the image forming apparatus is provided with a plurality of motors. Further, a configuration in which one motor control device controls a plurality of motors may be employed. Further, in FIG. 2, only one motor control device is provided in the image forming apparatus, but in actuality, a plurality of motor control devices are 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 to a digital signal, and transmits it 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 displays the operation screen for the user to set the type of recording medium to be used (hereinafter referred to as paper type) on the display unit provided in the operation unit 152. To control. The system controller 151 receives information set by the user from the operation unit 152 and controls an operation sequence of the image forming apparatus 100 based on the information set by the user. In addition, the system controller 151 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 such as the number of image formations, whether or not an image is being formed, occurrence of a jam, and the occurrence location thereof. The operation unit 152 displays 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.

[Vector control]
Next, the motor control device in the present embodiment will be described. The motor control device in the present embodiment can control the motor by any control method of vector control and constant current control. Note that the motor in this embodiment is not provided with a sensor such as a rotary encoder for detecting the rotational phase of the rotor of the motor.

  First, a method in which the motor control device 157 according to the present embodiment performs vector control will be described with reference to FIGS. 3 and 4.

  FIG. 3 shows a stepping motor (hereinafter referred to as a motor) 509 having two phases of A phase (first phase) and B phase (second phase), and a rotating coordinate system represented by d-axis and q-axis. It is a figure which shows the relationship. In FIG. 3, 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 in the static coordinate system. In FIG. 3, the d-axis is defined along the direction of the magnetic flux created by the magnetic poles of the permanent magnet used in the rotor 402, and the direction is 90 degrees counterclockwise from the d-axis (perpendicular to the d-axis). The q-axis is defined along the direction of The angle formed by the α axis and the d axis is defined as θ, and the rotational phase of the rotor 402 is represented by the angle θ. In the vector control, a rotational coordinate system based on the rotational phase θ of the rotor 402 is used. Specifically, in the vector control, the current component in the rotating coordinate system of the current vector corresponding to the drive current flowing through the winding, and the q-axis component (torque current component) value for generating torque in the rotor, The d-axis component (excitation current component) value that affects the strength of the magnetic flux passing through the winding is used.

  Vector control is a motor that performs phase feedback control that controls the value of the torque current component and the value of the excitation current component so that the deviation between the command phase representing the target phase of the rotor and the actual rotation phase is small. It is the control method which controls. In addition, the motor is controlled by performing speed feedback control that controls the value of the torque current component and the value of the excitation 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 technique.

  FIG. 4 is a block diagram illustrating an example of the configuration of the motor control device 157 that controls the motor 509.

  As shown in FIG. 4, the motor control device 157 includes a constant current controller 517 that performs constant current control and a vector controller 518 that performs vector control. Further, the motor control device 157 determines whether to control the drive of the motor 509 using the constant current controller 517 or to control the drive of the motor 509 using the vector controller 518 based on the rotation speed of the rotor 402. To be switched. Specifically, the motor control device 157 includes a speed determiner 514, a control switch 515, and control switch 516a, 516b, 516c (hereinafter referred to as each switch).

  The motor control device 157 includes a phase controller 502, a current controller 503, a coordinate inverse converter 505, a coordinate converter 511, a PWM inverter 506 that supplies a drive current to the motor windings, and the like as a circuit that performs vector control. . The coordinate converter 511 represents the current vector corresponding to the drive current flowing through the A-phase and B-phase windings of the motor 509 from the stationary coordinate system represented by the α-axis and β-axis by the q-axis and the d-axis. Convert coordinates to a rotating coordinate system. As a result, the drive current flowing in the winding is represented by the current value of the q-axis component (q-axis current) and the current value of the d-axis component (d-axis current) that are current values in the rotating coordinate system. Note that the q-axis current corresponds to a torque current that causes the rotor 402 of the motor 509 to generate torque. Further, the d-axis current corresponds to an excitation current that affects the strength of magnetic flux passing through the winding of the motor 509 and does not contribute to the generation of torque of the rotor 402. The motor control device 157 can control the q-axis current and the d-axis current independently. As a result, the motor control device 157 can efficiently generate the torque necessary for the rotor 402 to rotate.

  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 151 a generates a command phase θ_ref that represents the target phase of the rotor 402 of the motor 509 and outputs the command phase θ_ref to the motor control device 157 at a predetermined time period.

  The subtractor 101 calculates a deviation between the rotational 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.

  The phase controller 502 uses the q-axis current command value iq_ref and the d-axis so that the deviation output from the subtractor 101 becomes small based on proportional control (P), integral control (I), and differential control (D). A current command value id_ref is generated and output. Specifically, the phase controller 502 controls the q-axis current command value iq_ref and the d-axis current command value id_ref so that the deviation output from the subtractor 101 is 0 based on P control, I control, and D control. Is generated and output. The P control is a control method for controlling the value to be controlled based on a value proportional to the deviation between the command value and the estimated value. The I control is a control method for controlling the value to be controlled based on a value proportional to the time integral of the deviation between the command value and the estimated value. The D control is a control method for controlling the value to be controlled based on a value proportional to the time change of the deviation between the command value and the estimated value. The phase controller 502 in the present embodiment generates the q-axis current command value iq_ref and the d-axis current command value id_ref based on PID control, but is not limited to this. For example, the phase controller 502 may generate the q-axis current command value iq_ref and the d-axis current command value id_ref based on the PI control. When a permanent magnet is used for the rotor 402, the d-axis current command value id_ref that normally affects the strength of the magnetic flux passing through the winding is set to 0, but the present invention is not limited to this.

  Drive currents flowing in the A-phase and B-phase windings of the motor 509 are detected by current detectors 507 and 508, and then converted from analog values to digital values by an A / D converter 510.

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 by the current vector phase θe shown in FIG. 3 as current values iα and iβ in the stationary coordinate system. expressed. The phase θe of the current vector is defined as an angle formed by the α axis and the current vector. I represents 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 converter 511 and the induced voltage determiner 512.

The coordinate converter 511 converts the current values iα and iβ 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)
The subtractor 102 receives the q-axis current command value iq_ref output from the phase controller 502 and the current value iq output from the coordinate converter 511. The subtractor 102 calculates a deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 503.

  Further, the subtracter 103 receives the d-axis current command value id_ref output from the phase controller 502 and the current value id output from the coordinate converter 511. 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 503.

  The current controller 503 generates drive voltages Vq and Vd based on PID control so that the deviations are reduced. Specifically, the current controller 503 generates drive voltages Vq and Vd so that the deviations become 0, and outputs them to the coordinate inverse converter 505. That is, the current controller 503 functions as a generation unit. Note that the current controller 503 in the present embodiment is not limited to this, which generates the drive voltages Vq and Vd based on PID control. For example, the current controller 503 may generate the drive voltages Vq and Vd based on PI control.

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

  The coordinate inverse converter 505 converts the drive voltages Vq and Vd in the rotating coordinate system into the drive voltages Vα and Vβ in the stationary coordinate system, and then outputs 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 a 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 drive currents iα and iβ corresponding to the drive voltages Vα and Vβ, and drives the motor 509 by supplying the drive currents iα and iβ to the windings of each phase of the motor 509. . That is, the PWM inverter 506 functions as a supply unit that supplies current to the windings of each phase of the motor 509. In this embodiment, the PWM inverter has a full bridge circuit, but the PWM inverter may have a half bridge circuit or the like.

Next, a method for determining the rotational phase θ will be described. For the determination of the rotational phase θ of the rotor 402, values of 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. 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 input from the coordinate inverse converter 505 to the induced voltage determiner 512. From the drive voltages Vα and Vβ, it is determined 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 being used, and are stored in advance in a memory (not shown) or the like provided in the ROM 151b or the motor control device 157.

  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 rotational phase θ of the rotor 402 of the motor 509 based on the ratio of the induced voltage Eα and the induced voltage Eβ output from the induced voltage determiner 512 according to the following equation.
θ = tan ^ −1 (−Eβ / Eα) (9)

In the present embodiment, the phase determiner 513 determines the rotational phase θ by performing a calculation based on Expression (9), but this is not restrictive. For example, the phase determiner 513 rotates by referring to a table stored in the ROM 151b or the like and showing a 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 rotational phase θ of the rotor 402 obtained as described above is input to the subtractor 101, the speed determiner 514, the coordinate inverse converter 505, and the coordinate converter 511.

  The motor control device 157 repeatedly performs this control when performing vector control.

  As described above, the motor control device 157 according to 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 is small. By performing the vector control, it is possible to suppress the motor from being stepped out, an increase in motor noise due to excess torque, and an increase in power consumption. Further, by performing phase feedback control, the rotational phase of the rotor can be controlled so that the rotational phase of the rotor becomes a desired phase. Accordingly, in the image forming apparatus, the vector control using the phase feedback control is applied to a motor that drives a load (for example, a registration roller) that needs to control the rotational phase of the rotor with high accuracy. It is possible to appropriately perform image formation.

<Constant current control>
Next, constant current control will be described with reference to FIG. The constant current control is a control method for controlling the motor by supplying a constant current to the motor windings. In constant current control, neither phase feedback control nor speed feedback control is performed.

  The CPU 151a outputs a command phase θ_ref to the constant current controller 517. The constant current controller 517 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.

  Next, current detectors 507 and 508 detect drive currents flowing through the A-phase and B-phase windings of the motor 509. Thereafter, the detected drive current is converted from an analog value to a digital value by the A / D converter 510, and is expressed as current values iα and iβ as in equations (1) and (2). A deviation between the current value iα and the command value iα_ref and a deviation between the current value iβ and the command value iβ_ref are input to the current controller 503. The current controller 503 outputs drive voltages Vα and Vβ so that the deviation becomes small. Specifically, the current controller 503 outputs the drive voltages Vα and Vβ so that the deviation approaches 0 respectively. The drive voltages Vα and Vβ output from the current controller 503 are input to the PWM inverter 506. The PWM inverter 506 drives the motor 509 by supplying drive current to the windings of each phase of the motor 509 by the method described above.

  The above is an explanation of the constant current control.

<Switching between vector control and constant current control>
In the vector control in the present embodiment, the rotational phase of the rotor is determined based on the magnitude of the induced voltage generated in the winding of each phase of the motor. The magnitude of the induced voltage generated in the winding decreases as the rotational speed of the rotor decreases. If the magnitude of the induced voltage generated in the winding is not large enough to determine the rotational phase of the rotor, the rotational phase may not be determined accurately. In other words, the smaller the rotational speed of the rotor, the larger the error between the actual rotational phase of the rotor and the determined rotational phase of the rotor. If there is a large error between the actual rotor rotation phase and the determined rotor rotation phase, the motor control becomes unstable when the motor is controlled based on the determined rotor rotation phase. End up.

  In such a case, the configuration is such that constant current control is performed when the rotational speed of the rotor is smaller than the predetermined rotational speed, and vector control is performed when the rotational speed of the rotor is equal to or higher than the predetermined rotational speed. Conceivable.

  However, when the motor control is switched from constant current control to vector control, the rotational speed of the motor may decrease instantaneously. This is because the drive current supplied to the winding first after the control of the motor is switched is larger than the magnitude of torque generated in the rotor by the drive current supplied to the winding at the end before the control of the motor is switched. This is because the magnitude of the torque generated in the rotor may be smaller.

  As a result, even if the rotational speed of the rotor exceeds the predetermined rotational speed and the motor control is switched from the constant current control to the vector control, the rotational speed of the motor immediately after the motor control is switched to the predetermined rotational speed again. Slower than speed. As a result, the motor control is switched from vector control to constant current control again. In this way, switching between constant current control and vector control occurs repeatedly. As a result, the increase and decrease in the magnitude of the motor sound repeatedly occur, or the motor becomes uncontrollable. Note that when the motor control is switched from vector control to constant current control, the rotational speed of the motor may increase or decrease instantaneously.

  Therefore, in the present embodiment, the following configuration is applied to the motor control device.

<Control switching method in this embodiment>
FIG. 5 is a diagram illustrating a relationship between a threshold value for switching between constant current control and vector control, and the rotational speed and command speed of the rotor 402. In the present embodiment, as shown in FIG. 5, two threshold values of the rotor rotational speed for switching between constant current control and vector control are provided. Specifically, the threshold ω1 as a first threshold that is a threshold for switching the motor control from the constant current control to the vector control, and the threshold for the motor control to switch from the vector control to the constant current control. A threshold value ω2 is set as the second threshold value. Note that the threshold value ω1 is set to be larger than the threshold value ω2 (ω1> ω2). Hereinafter, the threshold values ω1 and ω2 will be described. In addition, the command speed shown in FIG. 5 is an example in this embodiment, and is not limited to this.

  The threshold ω2 is set to the rotational speed of the rotor that ensures the accuracy with which the phase determiner 513 determines the rotational phase θ. In the present embodiment, the threshold ω2 is set to the lowest rotational speed among the rotational speeds of the rotor that ensures the accuracy with which the phase determiner 513 determines the rotational phase θ. That is, the threshold value ω2 is set to a rotation speed at which a minimum induced voltage is generated in order for the phase determiner 513 to accurately determine the rotation phase θ of the rotor 402. As a result, even if the rotation speed decreases while the vector control is being performed, the motor control device 157 can continue the vector control as much as possible. That is, it is possible to suppress the motor 509 from being stepped out, an increase in motor noise due to excess torque, and an increase in power consumption as much as possible.

  Further, as described above, when the motor control method is switched from constant current control to vector control, the rotational speed of the motor may decrease instantaneously. Therefore, the threshold value ω1 is set in consideration of the magnitude of the rotational speed that instantaneously decreases when the motor control is switched from constant current control to vector control. That is, even if the rotation speed of the rotor 402 increases momentarily and exceeds the threshold value ω1, and the rotation speed of the rotor 402 decreases momentarily when the motor control is switched from the constant current control to the vector control, the rotation speed remains the threshold value. The threshold value ω1 is set so as not to be smaller than ω2. In the present embodiment, the threshold value ω1 is a rotation that does not fall below the threshold value ω2 even if the rotational speed of the rotor 402 decreases instantaneously when the motor control is switched from constant current control to vector control. The speed is set to the smallest value. As a result, the constant current control period can be shortened as much as possible, and the motor control can be switched from the constant current control to the vector control as soon as possible. That is, it is possible to suppress the motor 509 from being stepped out, an increase in motor noise due to excess torque, and an increase in power consumption as much as possible.

  By setting the threshold values ω1 and ω2 as described above, the motor control device 157 continues vector control even if the rotational speed decreases momentarily when the motor control is switched from constant current control to vector control. Can be made. That is, repeated switching between constant current control and vector control can be suppressed. In addition, it is possible to suppress the motor 509 from being stepped out, an increase in motor noise due to excess torque, and an increase in power consumption as much as possible.

  Next, a method in which the motor control device 157 switches between constant current control and vector control will be described with reference to FIG. As shown in FIG. 4, the motor control device 157 in this embodiment has a speed determiner 514, a control switch 515, and control switches 516 a, 516 b, 516 c (as a configuration for switching between constant current control and vector control. Hereinafter referred to as each switch).

The speed determiner 514 determines the rotational speed ω of the rotor 402 based on the temporal change of the rotational phase θ output from the phase determiner 513. It should be noted that the following equation (10) is used for determining the speed.
ω = dθ / dt (10)

  The speed determiner 514 outputs the determined rotation speed ω to the control switch 515.

  The control switch 515 switches between constant current control and vector control based on the rotational speed ω input from the speed determiner 514. The details will be described below. In the present embodiment, a circuit for determining the rotational speed ω of the rotor of the motor (the induced voltage determiner 512, the phase determiner 513, and the speed determiner 514 even during the period in which the constant current control is performed. Etc.) shall be in operation.

  During the control by the constant current controller 517, when the rotational speed ω becomes equal to or higher than the threshold ω1 (ω ≧ ω1), the control switch 515 switches the controller that controls the motor 509. In other words, the control switch 515 controls the states of the switches 516a, 516b, and 516c so that the controller that controls the driving of the motor 509 is switched from the constant current controller 517 to the vector controller 518. As a result, vector control by the vector controller 518 is performed.

  Further, during the control by the constant current controller 517, when the rotational speed ω is smaller than the threshold value ω1 (ω <ω1), the control switch 515 does not switch the controller that controls the driving of the motor 509. That is, the control switch 515 controls the states of the switches 516a, 516b, and 516c so that the motor 509 is maintained by the constant current controller 517. As a result, the constant current control by the constant current controller 517 is continued.

  Further, during the control by the vector controller 518, when the rotational speed ω becomes smaller than the threshold ω2 (ω <ω2), the control switch 515 switches the controller that controls the driving of the motor 509. That is, the control switching unit 515 controls the states of the switches 516a, 516b, and 516c so that the controller that controls the driving of the motor 509 is switched from the vector controller 518 to the constant current controller 517. As a result, constant current control by the constant current controller 517 is performed.

  Further, during the control by the vector controller 518, when the rotational speed ω is equal to or higher than the threshold ω2 (ω ≧ ω2), the control switch 515 does not switch the controller that controls the driving of the motor 509. That is, the control switch 515 controls the states of the switches 516a, 516b, and 516c so that the driving of the motor 509 is maintained by the vector controller 518. As a result, vector control by the vector controller 518 is continued.

  FIG. 6 is a flowchart showing a motor control method by the motor control device 157. Below, control of the motor 509 in this embodiment is demonstrated using FIG. The processing of this flowchart is executed by the motor control device 157 that has received 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 a 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 151 a 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 operation of the motor control device 157, and the motor control device 157 controls the motor 509 based on a command output from the CPU 151a. .

  In step S <b> 1001, the control switch 515 controls the states of the switches 516 a, 516 b, and 516 c so that the driving of the motor 509 is controlled by the constant current controller 517. As a result, constant current control by the constant current controller 517 is performed.

  In step S <b> 1002, when the CPU 151 a outputs an enable signal “L” to the motor control device 157, the motor control device 157 finishes driving the motor 509. If the CPU 151a outputs the enable signal 'H' to the motor control device 157, the motor control device 157 advances the process to S1003.

  In S1003, when the rotation speed ω of the rotor 402 is smaller than the threshold ω1, the process returns to S1001 and the constant current control by the constant current controller 517 is continued.

  If the rotational speed ω of the rotor 402 is equal to or higher than the threshold ω1, the control switch 515 switches the controller that controls the drive of the motor 509 in S1004. In other words, the control switch 515 controls the states of the switches 516a, 516b, and 516c so that the controller that controls the driving of the motor 509 is switched from the constant current controller 517 to the vector controller 518. As a result, vector control by the vector controller 518 is performed.

  Next, in S1005, when the rotational speed ω is equal to or higher than the threshold ω2, the process returns to S1004 again, and the vector control by the vector controller 518 is continued.

  In S1005, when the rotational speed ω is smaller than the threshold ω2, 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 switching unit 515 controls the states of the switches 516a, 516b, and 516c so that the controller that controls the driving of the motor 509 is switched from the vector controller 518 to the constant current controller 517. As a result, constant current control by the constant current controller 517 is performed.

  Thereafter, until the CPU 151a outputs an enable signal 'L' to the motor control device 157, the motor control device 157 repeats the above-described control and continues to drive the motor 509.

  As described above, in this embodiment, the threshold value of the rotational speed of the rotor for switching between constant current control and vector control is set so that ω1> ω2. The threshold value ω2 is set to the rotational speed of the rotor that ensures the accuracy with which the phase determiner 513 determines the rotational phase θ. The threshold ω1 is set in consideration of the magnitude of the rotational speed of the rotor 402 that instantaneously decreases when switching from constant current control to vector control.

  Furthermore, in this embodiment, switching between constant current control and vector control is performed by comparing the rotational speed ω of the rotor with the threshold values ω1 and ω2. Specifically, when the rotational speed ω changes from a value smaller than the threshold value ω1 to a value equal to or larger than ω1 while the open control is performed, the motor control device 157 changes the motor control from the constant current control to the vector. Switch to control. Further, in the state where the vector control is being performed, the motor control device 157 does not switch the control even when the rotational speed ω becomes a value smaller than the threshold ω1 and larger than the threshold ω2 from a value equal to or larger than the threshold ω1. Further, when the rotational speed ω decreases and the rotational speed ω changes from a value equal to or higher than the threshold ω2 to a value smaller than the threshold ω2, the motor control device 157 switches the motor control from vector control to constant current control. As a result, repeated switching between constant current control and vector control can be suppressed. That is, it is possible to prevent the motor sound from repeatedly increasing and decreasing and the motor from being uncontrollable.

  Further, as described above, the threshold value ω2 is set to the rotational speed of the rotor that ensures the accuracy with which the phase determiner 513 determines the rotational phase θ. Therefore, if the rotational speed ω is equal to or greater than the threshold ω2, the speed determiner 514 can accurately determine the rotational speed ω of the rotor. Therefore, the motor control device 157 can perform switching from constant current control to vector control and switching from vector control to constant current control based on the rotational speed ω. By using the rotational speed ω, the control is switched more appropriately than when the command speed ω_ref is used.

  In the present embodiment, the rotational speed ω of the rotor 402 is calculated by the calculation using Expression (10), but this is not restrictive. For example, the rotor 402 includes a drive current flowing in the A-phase (or B-phase) winding of the motor 509, an A-phase (or B-phase) drive voltage, an induced voltage generated in the A-phase (or B-phase) winding, and the like. The rotational speed ω may be estimated based on a period in which the magnitude of a periodic signal having a correlation with the rotation period is zero.

  In the motor control device according to the present embodiment, there are portions (current controller 503, PWM inverter 506, etc.) that are partially shared by the circuit that performs vector control and the circuit that performs constant current control. is not. That is, a configuration in which a circuit that performs vector control and a circuit that performs constant current control are provided independently may be employed.

  In this embodiment, a stepping motor is used as a motor for driving a load, but another motor such as a DC motor may be used. The motor is not limited to a two-phase motor, and may be another motor such as a three-phase motor.

  Moreover, although the motor control apparatus in this embodiment controls the motor 509 by performing phase feedback control, it is not limited to this. For example, the configuration of the motor control device may be a configuration in which the motor 509 is controlled by feeding back the rotational speed ω of the rotor 402. Specifically, as shown in FIG. 7, the speed controller 500 provided in the motor control device has a small deviation between the command speed ω_ref representing the target speed of the rotor output from the CPU 151a and the rotational speed ω. The q-axis current command value iq_ref and the d-axis current command value id_ref are generated and output as described above. A configuration in which the motor 509 is controlled by performing such speed feedback control may be employed. In such a configuration, since the rotation speed is fed back, the rotation speed of the rotor is controlled to be a predetermined speed. Therefore, in the image forming apparatus, vector control using speed feedback control is applied to a motor that drives a load (for example, a photosensitive drum, a conveyance belt, etc.) that needs to control the rotation speed of the rotor to a constant speed. Therefore, it is possible to appropriately form an image on a recording medium.

  In addition, the first control circuit in the present embodiment corresponds to a circuit that controls driving of the motor 509 using the vector controller 518. Further, the second control circuit in the present embodiment corresponds to a circuit that controls driving of the motor 509 using the constant current controller 517.

151a CPU
402 Rotor 502 Phase controller 509 Stepping motor 513 Position determiner 514 Speed determiner 515 Control switch 517 Constant current controller 518 Vector controller 600 Motor controller 516a, 516b, 516c Control switch

Claims (13)

In a motor control device that controls the motor based on a command phase representing a target phase of a rotor of the motor,
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
A current component of a current value represented in a rotating coordinate system based on the rotational phase determined by the phase determining means so that a deviation between the command phase and the rotational phase determined by the phase determining means is small. A first control mode for controlling the motor by controlling a value of a torque current component that generates torque in the rotor and a value of an excitation current component that affects the strength of a magnetic flux passing through the winding of the motor. And a second control mode for controlling the motor by supplying a constant current to the winding of the motor, and a control means comprising:
Have
In a state where the control unit is controlling the motor in the second control mode, the rotation speed of the rotor of the motor determined by the speed determination unit is determined from a value smaller than a first threshold value. When the value changes to a value larger than the threshold value of 1, the control mode for controlling the motor is switched from the second control mode to the first control mode, and the motor is controlled in the first control mode. In this state, the rotational speed of the rotor of the motor determined by the speed determining means is larger than the second threshold smaller than the first threshold from a value larger than the first threshold and the A motor control device that maintains the first control mode even when the value changes to a value smaller than the first threshold. In a motor control device that controls the motor based on a command speed that represents a target speed of the rotor of the motor,
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
A current component of a current value represented in a rotating coordinate system based on the rotational phase determined by the phase determining means so that a deviation between the command speed and the rotational speed determined by the speed determining means is small. A first control mode for controlling the motor by controlling a value of a torque current component that generates torque in the rotor and a value of an excitation current component that affects the strength of a magnetic flux passing through the winding of the motor. And a second control mode for controlling the motor by supplying a constant current to the winding of the motor, and a control means comprising:
Have
In a state where the control unit is controlling the motor in the second control mode, the rotation speed of the rotor of the motor determined by the speed determination unit is determined from a value smaller than a first threshold value. When the value changes to a value larger than the threshold value of 1, the control mode for controlling the motor is switched from the second control mode to the first control mode, and the motor is controlled in the first control mode. In this state, the rotational speed of the rotor of the motor determined by the speed determining means is larger than the second threshold smaller than the first threshold from a value larger than the first threshold and the A motor control device that maintains the first control mode even when the value changes to a value smaller than the first threshold.   In a state where the control unit is controlling the motor in the first control mode, the rotation speed of the rotor of the motor determined by the speed determination unit is larger than the second threshold value. The control mode for controlling the motor is switched from the first control mode to the second control mode when changing to a value smaller than a second threshold value. The motor control apparatus described. The control means includes
A first control circuit for supplying a drive 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 for supplying a drive current to each of the first-phase winding and the second-phase winding when the second control mode is executed;
Switching means for switching between controlling the motor using the first control circuit or controlling the motor using the second control circuit based on the rotational speed determined by the speed determining means; ,
The motor control device according to claim 1, wherein the motor control device includes:   5. The speed determination unit determines a rotation speed of a rotor of the motor based on a temporal change of the rotation phase determined by the phase determination unit. 6. Motor control device. The control means includes
Supply means for supplying the drive current to each of the first phase winding and the second phase winding of the motor;
Generating means for generating a drive voltage for driving the supply means;
Detecting means for detecting a current value of a driving current supplied to each of the first phase winding and the second phase winding of the motor by the supply means;
Based on the driving voltage generated by the generating unit and the current value detected by the detecting unit, the first phase winding and the second phase winding are induced by the rotation of the rotor of the motor. Induced voltage determining means for determining the magnitude of the induced voltage;
Have
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 control means controls the motor by controlling the value of the excitation current component to be 0 and controlling the value of the torque current component. The motor control device according to one item. A transport roller for transporting the sheet;
A motor for driving the transport roller;
The motor control device according to any one of claims 1 to 7,
Have
The sheet conveying apparatus, wherein the motor control apparatus controls driving of a motor that drives the conveying roller. A sheet conveying device according to claim 8;
A document stacking unit for loading documents,
Have
An original feeding apparatus, wherein the original loaded on the original stacking unit feeds the original. A document feeder according to claim 9;
Reading means for reading the document fed by the document feeding device;
A document reading apparatus comprising: A sheet conveying device according to claim 8;
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 driving the load;
The motor control device according to any one of claims 1 to 7,
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 12, wherein the load is a conveyance roller that conveys the recording medium.

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