JP2018064397A - Motor control device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: when a configuration is used that performs field weakening when the rotation speed of a rotor is equal to or faster than a predetermined rotation speed, field weakening is performed even when the field weakening does not need to be performed and an unnecessary current is supplied to winding, and to reduce an increase in power consumption as a result of the unnecessary current supply.SOLUTION: A motor control device performs field weakening only when a rotation speed ω is larger than a speed threshold ω0 and a drive voltage is larger than a voltage threshold. As a result of this, the motor control device can perform field weakening only when the field weakening is necessary, and as a result of this, can reduce an increase in power consumption.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a motor control device that controls driving of a motor and an image forming apparatus using the motor control device.

  2. Description of the Related Art Conventionally, as a method for controlling a motor, a control method called vector control is known in which a motor is controlled by controlling a current value in a rotating coordinate system based on the rotational phase of the rotor of the motor. Specifically, for example, the motor is controlled by performing phase feedback control for controlling the current value so that the deviation between the rotor command phase and the actual rotation phase is small. There is also a method of controlling the motor by performing speed feedback control for controlling the current value 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 winding of the motor is divided into a current component (q-axis current) that generates torque for rotating the rotor, and a current component (d-axis) that affects the magnetic flux strength of the rotor. Current) and control. 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 q-axis current according to the change of the load torque. In other words, the load torque applied to the rotor, which has been regarded as a problem in the past, exceeds the output torque corresponding to the drive current supplied to the motor windings, and the rotor does not synchronize with the input signal. ) Can be prevented. Further, an increase in power consumption and an increase in motor sound due to excess torque can be suppressed.

  An induced voltage is generated in the winding of each phase of the motor as the rotor rotates. When an induced voltage is generated in the motor winding, the voltage that can be applied to the motor winding is reduced. Specifically, for example, when the voltage of the power supply that applies a voltage to the motor winding is 24V, a voltage that can be applied to the winding by subtracting the induced voltage generated in the winding from the power supply voltage (24V) It becomes. Therefore, when an induced voltage is generated in the winding, the voltage that can be applied to the winding becomes smaller than 24V. The magnitude of the induced voltage increases as the rotational speed of the rotor increases. Therefore, the higher the rotational speed of the rotor, the smaller the voltage that can be applied to the motor windings. When the voltage that can be applied to the windings of the motor decreases, the torque that can be applied to the rotor (outputtable torque) also decreases. As a result, when the rotor rotates at high speed, it becomes impossible to give an optimum torque to the rotor.

  Patent Document 1 describes a configuration (weak field) that weakens the magnetic flux intensity of the rotor by controlling the d-axis current to a value smaller than 0 when the rotational speed of the rotor is equal to or higher than a predetermined rotational speed. It has been. When the field weakening is performed, it is possible to suppress an increase in the magnitude of the induced voltage generated in the winding. As a result, it is possible to suppress a decrease in the voltage that can be applied to the windings, and it is possible to suppress a decrease in the outputtable torque. As a result, when the rotor rotates at a high speed, it is possible to prevent the optimum torque from being applied to the rotor.

JP 2007-153273 A

  However, even when the rotational speed of the rotor is high, it may not be necessary to perform field weakening. For example, even if the rotation speed of the rotor is increased and the outputtable torque is reduced, it is not necessary to perform field weakening if the load torque applied to the rotor is smaller than the outputable torque. In such a case, when the configuration described in Patent Document 1 is applied, field weakening is performed even when field weakening is not necessary. That is, an unnecessary current is supplied to the winding. As a result, power consumption increases. For this reason, there has been a demand for a configuration in which field weakening is performed in a case where the output possible torque becomes smaller than the load torque applied to the rotor due to the magnitude of the induced voltage generated in the winding.

  It is an object of the present invention to perform field weakening in a case where the output possible torque becomes smaller than the load torque applied to the rotor due to the magnitude of the induced voltage generated in the winding.

In order to solve the above problems, the present invention provides:
In a motor control device that operates by power supplied from a power source and controls the motor based on a command phase that represents a target phase of a rotor of the motor,
Current supply means for supplying a drive current to the winding of the motor;
Voltage generating means for generating a driving voltage for driving the current supply means;
Current detection means for detecting a current value of a drive current flowing in the winding;
Based on the value of the drive voltage generated by the voltage generation means and the current value detected by the current detection means, the value of the induced voltage induced in the winding by the rotation of the rotor of the motor is determined. Induced voltage determining means for
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
Motor control means for controlling the motor based on a current value of a rotational coordinate system based on the rotational phase so that a deviation between the command phase and the rotational phase determined by the phase determining means is small;
Have
The motor control means includes setting means for setting a value of an excitation current component which is a current value of the rotating coordinate system and is a current value affecting the magnetic flux intensity of the rotor,
The setting means satisfies a first condition in which the rotation speed determined by the speed determination means is greater than a predetermined rotation speed, and the value of the drive voltage is determined from a voltage value output from the power source to the current supply means. When satisfying a second condition that is greater than a predetermined value that is equal to or less than a value obtained by subtracting the value of the induced voltage, the value of the excitation current component is set to a first value that is a negative value, and the first When at least one of the condition and the second condition is not satisfied, the value of the exciting current component is set to a second value larger than the first value.

  According to the present invention, field weakening can be performed in the case where the outputable torque becomes smaller than the load torque applied to the rotor by increasing the magnitude of the induced voltage generated in the winding. As a result, an increase in power consumption can be suppressed.

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 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 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 figure which shows the structure of the full bridge circuit provided in the PWM inverter. It is a block diagram which shows the structure of the motor control apparatus which performs speed feedback control. It is a figure which shows the relationship between the rotational speed (omega) of a rotor, the power supply voltage Vcc, and the amplitude e of an induced voltage. It is a figure which shows the relationship between the output possible torque T and the rotational speed (omega) of a rotor. It is a flowchart explaining the method in which the said motor control apparatus performs a field weakening.

  Hereinafter, 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 not limited. The present invention is not intended to be limited to the following embodiments. Note that the motor control device is not limited to the image forming apparatus.

[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 which is an image forming apparatus 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. Furthermore, the image forming apparatus may be in either monochrome or color format.

  The configuration and function of the image forming apparatus 100 will be described below with reference to FIG. The image forming apparatus 100 includes an automatic document feeder 201, a document reading device 202, and an image forming apparatus main body 301.

  Documents placed on the document placement unit 203 of the automatic document feeder 201 are fed one by one by a feed roller 204 and conveyed along a conveyance guide 206 onto a document glass table 214 of the document reading device 202. The 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 document reading device 202 is guided to the image reading unit 101 by the optical system including the reflection mirrors 210, 211, and 212, and is converted into an image signal by the image reading unit 101. Converted. The image reading unit 101 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 101 is subjected to various correction processes by an 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.

  Further, there are a flow reading mode and a fixed reading mode as a document reading mode in the reading device 202. The flow reading mode is a mode in which an image of a document is read while the document is conveyed at a constant speed while the illumination system 209 and the optical system are fixed at predetermined positions. The fixed reading mode is a mode in which an original is placed on the original glass 214 of the reading apparatus 202 and an image of the original placed on the original glass 214 is read while moving the illumination system 209 and the optical system at a constant speed. is there. Normally, a sheet-like document is read in a flow reading mode, and a bound document such as a book or booklet is read in a fixed 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, and includes, for example, paper, a resin sheet, cloth, an OHP sheet, a label, and the like.

  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 separator 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 to the conveyance roller 320. Carry in the direction of heading. Thereafter, the rotation of the conveyance roller 320 is reversed immediately before the trailing edge of the recording medium passes through the nip portion of the conveyance roller 320. As a result, the recording medium is discharged to the outside of the image forming apparatus 100 via the discharge roller 324 with the first surface of the recording medium facing downward.

  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 can be 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 image forming apparatus 100 includes a power source 1. The power source 1 is connected to an AC power source (AC), and various devices inside the image forming apparatus 100 are operated by power output from the power source 1. Further, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c as shown in FIG. 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 set 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 the like), 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 (the charger 310, the developer 314, the transfer separator 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 that drives the load described above in accordance with a command output from the CPU 151a. The power supply 1 supplies the voltage Vcc to the full bridge circuit 50 provided in the motor control device 157. The full bridge circuit 50 will be described later.

  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 images formed, whether or not an image is being formed, occurrence of a jam, and a location where the jam occurs. 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 controls the motor using vector control. In the following description, a stepping motor is used as a motor for driving a load, but the present invention is not limited to this. Further, the motor is not necessarily a two-phase motor. Further, 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, but may be configured with a sensor such as a rotary encoder. .

  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 is a block diagram showing an example of the configuration of a motor control device 157 that controls a stepping motor (hereinafter referred to as a motor) 509.

  FIG. 4 is a diagram showing the relationship between the motor 509 having two phases of A phase (first phase) and B phase (second phase) and the d-axis and q-axis of the rotating coordinate system. In FIG. 4, in the stationary coordinate system, the axis corresponding to the A-phase winding is defined as the α axis, and the axis corresponding to the B-phase winding is defined as the β-axis. In addition, an angle formed by the α axis in the stationary coordinate system and the direction of the magnetic flux (d-axis direction) created by the magnetic poles of the permanent magnet used in the rotor 402 is defined as θ. The rotational phase of the rotor 402 is represented by an angle θ. In the vector control, the motor 509 is expressed by a d-axis along the magnetic flux direction of the rotor 402 and a q-axis along a direction advanced 90 degrees counterclockwise from the d-axis (perpendicular to the d-axis). A rotational coordinate system based on the rotational phase θ of the rotor 402 is used.

  Vector control is a control method 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. Specifically, for example, the motor is controlled by performing phase feedback control for controlling the current value so that the deviation between the command phase representing the target phase of the rotor and the actual rotational phase becomes small. There is also a method of controlling the motor by performing speed feedback control for controlling the current value so that the deviation between the command speed representing the target speed of the rotor and the actual rotational speed becomes small. The current value in the rotating coordinate system includes a current value of a q-axis component (torque current component) that generates torque in the motor rotor and a d-axis component (excitation current component) that affects the magnetic flux strength of the motor rotor. Corresponds to the current value.

  As shown in FIG. 3, the motor controller 157 includes a phase controller 502, a current controller 503, a coordinate inverse converter 505, a coordinate converter 511, and a driving current for the motor windings as a vector control circuit. A PWM inverter 506 to be supplied is provided. The coordinate converter 511 represents a current vector corresponding to the drive current flowing in the A-phase and B-phase windings of the motor 509 from the stationary 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 to be supplied to the A-phase and B-phase windings of the motor 509 is expressed by the q-axis component current value (q-axis current) and the d-axis component current value (d-axis current) in the rotating coordinate system. Can be used. Note that the q-axis current corresponds to a torque current that causes the rotor 402 of the motor 509 to generate torque. The d-axis current corresponds to an excitation current that affects the magnetic flux intensity of the rotor 402 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. That is, the torque necessary for the rotor 402 to rotate can be efficiently generated.

  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 adder 101 calculates a 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.

  The phase controller 502 is composed of a proportional (P) and integral (I) compensator. The phase controller 502 uses a proportional (P) and integral (I) compensator to generate and output a q-axis current command value iq_ref so that the deviation output from the adder 101 is reduced. Specifically, the phase controller 502 uses the proportional (P) and integral (I) compensator to generate the q-axis current command value iq_ref so that the deviation output from the adder 101 becomes zero. Output. The phase controller 502 in this embodiment is composed of a proportional (P) and integral (I) compensator, but is composed of a proportional (P), integral (I), and differential (D) compensator. May be.

  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 using the current vector phase θe shown in FIG. 4 as the 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.
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.

In the coordinate converter 511, the current values iα and iβ are coordinate-converted into the q-axis current value iq and the d-axis current value id in the rotating coordinate system by the following equations.
id = cos θ * iα + sin θ * iβ (3)
iq = −sin θ * iα + cos θ * iβ (4)

  As described above, the coordinate converter 511 converts the current vector corresponding to the drive current 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 to the q axis and Coordinates are converted into a rotating coordinate system represented by the d axis.

  The adder 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 adder 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.

  The adder 103 receives the d-axis current command value id_ref output from the phase controller 502 and the current value id output from the field controller 540. The adder 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 field controller 540 will be described later.

  The current controller 503 includes a proportional (P) and integral (I) compensator. The current controller 503 generates current values iq * and id * so that the deviations are reduced. Specifically, the current controller 503 generates the current values iq * and id * so that the deviations are zero. Thereafter, the current controller 503 generates drive voltages Vq and Vd corresponding to the current values iq * and id *, and outputs them to the coordinate inverse converter 505. That is, the current controller 503 functions as voltage generation means. The current controller 503 in this embodiment is composed of a proportional (P) and integral (I) compensator, but is composed of a proportional (P), integral (I), and differential (D) compensator. May be.

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 converts Vα and Vβ into the induced voltage determiner 512, the field controller 540, and the PWM inverter 506. Output to. In the present embodiment, the drive voltages Vq and Vd corresponding to the current values iq * and id * are generated, and the drive voltages Vα and Vβ in the stationary coordinate system are converted by inversely transforming the drive voltages Vq and Vd. I got, but this is not the case. For example, the current values iq * and id * are inversely transformed into the current values iα * and iβ * in the stationary coordinate system to generate the drive voltages Vα and Vβ corresponding to the current values iα * and iβ *. Also good.

  The PWM inverter 506 has a full bridge circuit. FIG. 5 is a diagram illustrating an example of the configuration of the full bridge circuit 50 provided in the PWM inverter 506. As described above, the voltage Vcc is supplied from the power supply 1 to the full bridge circuit 50. Further, the full bridge circuit 50 is provided with FETs Q1 to Q4 as switching elements, a winding L1 of a motor 509, and the like.

  The FETs Q1 to Q4 are driven by signals based on the drive voltages Vα and Vβ input from the coordinate inverse transformer 505. As a result, a voltage is applied from the power source 1 to the winding L1. As a result, drive currents iα and iβ corresponding to the drive voltages Vα and Vβ are supplied to the winding L1. That is, the PWM inverter 506 functions as a current supply unit. In this embodiment, the PWM inverter has a full bridge circuit, but may be a half bridge circuit or the like. The full bridge circuit is provided corresponding to each of the A phase and the B phase of the motor 509.

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 R and 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 and the field controller 540.

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)

  The rotational phase θ of the rotor 402 obtained as described above is input to the speed determiner 515, the adder 101, the coordinate inverse converter 505, and the coordinate converter 511.

The speed determiner 515 determines the rotational speed ω based on the temporal change of the rotational phase θ output from the phase determiner 513. Note that the following equation (11) is used to determine the speed.
ω = dθ / dt (10)

  Thereafter, the speed determiner 515 outputs the determined rotational speed ω to the field controller 540.

  The field controller 540 is based on the drive voltages Vα and Vβ output from the coordinate inverse converter 505, the induced voltages Eα and Eβ output from the induced voltage determiner 512, and the rotational speed ω output from the speed determiner 515. The d-axis current command value id_ref is determined by a method described later. Thereafter, the field controller 540 outputs the determined d-axis current command value id_ref to the adder 103.

  Thereafter, the motor control device 157 repeats the above control.

  As described above, in the vector control in the present embodiment, the motor is controlled by performing the phase feedback control for controlling 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. . When the vector control is performed, it is possible to suppress the motor from being stepped out, an increase in motor noise due to excessive torque, and an increase in power consumption. Further, since the phase feedback control is performed, the rotation phase of the rotor can be controlled to be a desired phase. Therefore, in the image forming apparatus, a vector using phase feedback control for a motor that drives a load (for example, a registration roller) that needs to accurately control the rotational phase in order to appropriately form an image on a recording medium. Apply control. As a result, it is possible to appropriately form an image on the recording medium.

  In the vector control in this embodiment, the motor 509 is controlled by performing the above-described phase feedback control, but the present invention is not limited to this. For example, the motor 509 may be controlled by feeding back the rotational speed ω of the rotor 402. Specifically, as shown in FIG. 6, the CPU 151 a outputs a command speed ω_ref indicating 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 a q-axis current command value iq_ref so that a deviation between the rotational speed ω and the command speed ω_ref is small. . 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 can be controlled to be a predetermined speed. Therefore, in the image forming apparatus, speed feedback control is performed on a motor that drives a load (for example, a photosensitive drum, a conveyor belt, etc.) that needs to control the rotation speed to a constant speed in order to appropriately form an image on a recording medium. Apply the vector control used. As a result, it is possible to appropriately form an image on the recording medium.

[Weak field]
Next, the field weakening will be described. As described above, an induced voltage is generated in the winding of each phase of the motor as the rotor rotates. When an induced voltage is generated in the motor winding, the voltage that can be applied to the motor winding (hereinafter referred to as usable voltage) is reduced. Specifically, for example, when the voltage value output from the power supply 1 is Vcc, the usable voltages Vα ′ and Vβ ′ are as follows due to the generation of induced voltages in the windings of each phase. It will be limited to the values shown in equations (11) and (12).
Vα ′ = Vcc−eα (11)
Vβ ′ = Vcc−eβ (12)
Here, eα represents the amplitude of the induced voltage Eα that changes sinusoidally. Further, eβ represents the amplitude of the induced voltage Eβ that changes in a sinusoidal shape.

In addition, the amplitude e of the induced voltage generated in the winding of each phase due to the rotation of the rotor increases as the rotation speed ω of the rotor increases, as shown in the following equation (13).
e = Ke * ω (13)
Here, Ke is an induced voltage coefficient and is a value unique to the motor.

  FIG. 7 is a diagram showing the relationship between the rotational speed ω of the rotor, the power supply voltage Vcc, and the amplitude e of the induced voltage.

  As shown in FIG. 7 and Expressions (11) to (13), the usable voltage (motor drive voltage) decreases as the rotational speed of the rotor increases. When the usable voltage decreases, the torque that can be applied to the rotor (hereinafter referred to as “outputtable torque”) also decreases. As a result, when the rotor rotates at high speed, it becomes impossible to give an optimum torque to the rotor.

  The induced voltage is generated as the magnetic flux passing through the winding changes. Therefore, the magnitude of the induced voltage generated in the winding can be suppressed by weakening the magnetic flux penetrating the winding. Specifically, by controlling the d-axis current that affects the magnetic flux intensity of the rotor to a negative value, the magnetic flux passing through the winding is weakened, and as a result, the magnitude of the induced voltage generated in the winding increases. This can be suppressed. Such a method is called field weakening.

  By performing field weakening when the rotational speed ω of the rotor is high, it is possible to suppress a decrease in the usable voltages Vα ′ and Vβ ′, and it is possible to suppress a decrease in the outputable torque. . As a result, when the rotor rotates at a high speed, it is possible to prevent the optimum torque from being applied to the rotor.

  However, even when the rotational speed ω is high, it may not be necessary to perform field weakening. For example, even if the outputtable torque decreases as the rotational speed ω increases, if the load torque applied to the rotor is smaller than the outputtable torque, it is not necessary to perform field weakening. In such a case, if the above-described configuration is applied, field weakening is performed even when field weakening is not necessary. That is, an unnecessary current is supplied to the winding. As a result, power consumption increases. For this reason, there is a demand for a configuration in which field weakening is performed in the case where the outputable torque is smaller than the load torque applied to the rotor due to the magnitude of the induced voltage generated in the winding.

  Next, a method in which the motor control device 157 according to this embodiment performs field weakening will be described.

  As shown in FIG. 3, a field controller 540 is provided in the motor control device 157 in the present embodiment. The field controller 540 receives the rotational speed ω, induced voltages Eα and Eβ, and drive voltages Vα and Vβ. The field controller 540 generates and outputs a d-axis current command value id_ref based on the rotational speed ω, the induced voltages Eα and Eβ, and the drive voltages Vα and Vβ. Hereinafter, a method in which the field controller 540 generates the d-axis current command value id_ref based on the rotation speed ω, the induced voltages Eα and Eβ, and the drive voltages Vα and Vβ will be described.

  In the present embodiment, the field controller 540 generates the d-axis current command value id_ref based on whether or not the input rotation speed, induced voltage, and drive voltage satisfy the following two conditions.

The first condition is that the rotational speed ω output from the speed determiner 515 is larger than a predetermined rotational speed (speed threshold) ωth, as shown in the following formula (14).
ω> ωth (14)

  The field controller 540 compares the speed threshold value ωth stored in the memory 540a provided inside the field controller 540 with the rotational speed ω output from the speed determiner 515, so that the rotational speed ω is expressed by the formula ( 14) It is determined whether or not the above is satisfied.

  FIG. 8 is a diagram showing the relationship between the outputtable torque T and the rotational speed ω of the rotor. FIG. 8 shows a torque T-rotational speed ω characteristic (broken line) when the d-axis current is controlled to 0 and a torque T-rotational speed ω characteristic (solid line) when the d-axis current is controlled to a negative value. Has been. Further, the rotational speed at the intersection of the broken line and the solid line is defined as ω0. The torque T-rotational speed ω characteristic shown in FIG. 8 is an example in the present embodiment, and the present invention is not limited to this.

  As shown in FIG. 8, when the rotational speed ω is smaller than ω0 (ω <ω0), the d-axis current is controlled to 0 rather than the outputtable torque T when the d-axis current is controlled to a negative value. The output possible torque T is larger. That is, when the rotational speed ω is smaller than ω0 (ω <ω0), a larger torque can be applied to the rotor when the field weakening is not performed than when the field weakening is performed.

  Further, as shown in FIG. 8, when the rotational speed ω is higher than ω0 (ω> ω0), the d-axis current is controlled to a negative value rather than the outputtable torque T when the d-axis current is controlled to 0. In this case, the output possible torque T is larger. That is, when the rotational speed ω is larger than ω0 (ω> ω0), a larger torque can be applied to the rotor when the field weakening is performed than when the field weakening is not performed.

  Therefore, in the present embodiment, the speed threshold value ωth in equation (14) is ω0 (ωth = ω0), and the rotational speed ω is greater than ω0 is the first condition for performing field weakening. .

  In equation (14), the speed threshold value ωth is set to ω0, but is not limited to this. However, when the speed threshold is set to a value smaller than ω0, there is a period during which field weakening is performed in a state where the rotational speed ω is smaller than ω0. As described above, when field weakening is performed in a state where the rotational speed ω is smaller than ω0, the outputtable torque is rather reduced. When the speed threshold is set to a value larger than ω0, there is a period during which field weakening is not performed in a state where the rotational speed ω is larger than ω0. As described above, when the field weakening is not performed in a state where the rotational speed ω is greater than ω0, the outputtable torque is smaller than when the field weakening is performed. Therefore, the torque can be efficiently generated in the rotor by setting the speed threshold value ωth to ω0.

  However, if only the expression (14) is used as a condition for performing field weakening, as described above, field weakening is performed even when it is not necessary to perform field weakening, and an unnecessary current is supplied to the winding. There is a possibility that.

Therefore, in this embodiment, as shown in the following formula (15), the fact that the drive voltage is larger than a predetermined value (voltage threshold value) that is equal to or lower than the usable voltage is a second for performing field weakening. The conditions are as follows.
Vα> Vα ′ * γ = (Vcc−eα) * γ (15)

Here, γ (0 <γ ≦ 1) is a variation correction coefficient, which is a value determined in consideration of component variations and calculation errors, and is a preset value. Further, it is assumed that the power supply voltage Vcc and the variation correction coefficient γ are stored in the memory 540a.

  The field controller 540 stores the induced voltage Eα acquired from the induced voltage determiner 512 and the time when the induced voltage Eα is determined in the memory 540a for one period. Furthermore, when the induced voltage Eα is stored in the memory 540a for one period, the field controller 540 determines the maximum value or the minimum value of the induced voltage Eα as the amplitude value eα. Thereafter, the field controller 540 determines whether or not the drive voltage Vα satisfies Expression (15) based on the determined amplitude value eα, power supply voltage Vcc, and drive voltage Vα acquired from the coordinate inverse converter 505.

  In the present embodiment, the memory 540a is configured to delete the stored induced voltage when the field controller 540 determines the amplitude value, but this is not restrictive. In the present embodiment, the field controller 540 is configured to determine and update the amplitude value every time the induced voltage Eα is stored in the memory 540a for one period. The field controller 540 may be configured to store the induced voltage Eα acquired from the induced voltage determiner 512 in the memory 540a for n cycles in association with the time when the induced voltage Eα is determined. (N is a positive integer.) Furthermore, in the present embodiment, the A-phase driving voltage and the induced voltage are used in Equation (15), but the B-phase driving voltage and the induced voltage may be used. Note that one power source is provided for each of the A phase and the B phase, but this is not a limitation.

  The field controller 540 sets id_ref to a negative value (for example, −0.3 A) and outputs it when the rotational speed and the drive voltage satisfy the above two conditions. That is, the motor control device 157 performs field weakening. If the set id_ref value is a negative value and the absolute value is too large, the magnetic field generated from the permanent magnet as the rotor is excessively weakened, resulting in a small torque generated in the rotor. turn into. Also, if the set id_ref value is a negative value and the absolute value is close to 0, the magnetic field generated from the permanent magnet as the rotor cannot be weakened. It becomes impossible to reduce the induced voltage. The negative value is determined in advance in consideration of the above and is stored in the memory 540a or the like. The field controller 540 sets the negative value stored in the memory 540a or the like as id_ref.

  Further, the field controller 540 sets id_ref to 0 when the rotation speed and the drive voltage do not satisfy the above two conditions. That is, the motor control device 157 does not perform field weakening.

  In the present embodiment, the value of the d-axis current command value id_ref set by the field controller 540 when the rotational speed and the drive voltage satisfy the above-described two conditions is a value obtained by experiments. However, this is not the case. For example, the field controller 540 may be configured to change the value of the d-axis current command value id_ref based on the rotation speed ω input to the field controller 540. Specifically, the field controller 540 may be configured to set the d-axis current command value id_ref smaller as the rotational speed ω increases. As a result, it is possible to suppress an induced voltage generated in the winding from increasing with an increase in the rotation speed. In the present embodiment, the rotational speed ω determined based on the rotational phase θ determined by the phase determiner 513 is used when determining whether or not Expression (14) is satisfied. is not. For example, the speed determiner 515 calculates a rotational speed ω_ref ′ instead of the command speed ω_ref based on the command phase θ_ref using the formula (10), and the field controller 540 uses the rotational speed ω_ref ′ to formula It may be determined whether or not (14) is satisfied.

  FIG. 9 is a flowchart for explaining a method in which the motor control device 157 according to this embodiment performs field weakening. Hereinafter, a method in which the motor control device 157 according to this embodiment performs field weakening will be described with reference to FIG. The processing of this flowchart is executed by the motor control device 157 that has received an instruction from the CPU 151a.

  First, in S1001, when the enable signal 'H' is output from the CPU 151a to the motor control device 157, the motor control device 157 starts driving control of 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 drive of the motor 509 based on a command output from the CPU 151a. Do.

  Next, in S1002, the motor control device 157 performs vector control. After that, in S1003, when the CPU 151a outputs the enable signal 'L' to the motor control device 157, the motor control device 157 finishes driving the motor 509. In S1003, if the CPU 151a outputs the enable signal 'H' to the motor control device 157, the motor control device 157 advances the process to S1004.

  In S1004, the field controller 540 acquires the rotational speed ω, the induced voltages Eα and Eβ, and the drive voltages Vα and Vβ. Further, the field controller 540 determines the amplitude value eα of the induced voltage Eα in S1005, and the motor control device advances the process to S1006.

  In S1006, when any one of the expressions (14) and (15) is not satisfied, the field controller 540 sets the d-axis current command value id_ref to 0 and outputs it in S1007. As a result, the motor control device 157 does not perform field weakening.

  In S1006, when the rotational speed ω satisfies Expression (14) and the drive voltage Vα satisfies Expression (15), in S1008, the field controller 540 sets the negative value stored in the memory 540a or the like to id_ref. Set as output. As a result, the motor control device 157 performs field weakening.

  Thereafter, the process returns to S1002 again, and the vector control by the motor control device 157 is continued. 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 to control the motor 509.

  As described above, in the present embodiment, field weakening is performed only when the rotational speed ω satisfies Expression (14) and the drive voltage Vα satisfies Expression (15). Specifically, field weakening is performed only when the rotational speed ω is greater than the speed threshold value ω0 and the drive voltage Vα is greater than the voltage threshold value. As a result, field weakening can be performed only when the outputtable torque is smaller than the load torque applied to the rotor (when field weakening is required). As a result, an increase in power consumption can be suppressed.

  In the configuration in which field weakening is performed when the rotational speed ω does not satisfy Expression (14) and the drive voltage Vα satisfies Expression (15), the above-described effect cannot be obtained. Even if the drive voltage Vα satisfies the equation (15), as shown in FIG. 8, if the field weakening is performed when the rotational speed ω is smaller than ω0, the outputtable torque becomes smaller. Because. In such a case, it is necessary to perform processing such as interrupting control of the motor.

  In the present embodiment, the field controller 540 sets id_ref to a negative value when the rotational speed and the drive voltage satisfy the above-described two conditions. Further, when the rotation speed and the drive voltage do not satisfy any one of the two conditions described above, id_ref is set to 0, but this is not restrictive. For example, id_ref may be set to a value other than 0 when the rotation speed and the drive voltage do not satisfy either one of the two conditions described above, but it is better to set the value as close to 0 as possible. An increase in power consumption can be effectively suppressed.

  In the vector control in the present embodiment, a rotational coordinate system based on the rotational phase θ of the rotor 402 is used, but the present invention is not limited to this. For example, a rotational coordinate system based on the command phase θ_ref may be used.

  Further, the determination of the rotational speed ω_ref ′ instead of the command speed ω_ref is not limited to being performed using Expression (10). 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. A periodic signal that correlates with the rotational speed of is detected. The rotational speed ω_ref ′ instead of the command speed ω_ref may be determined by detecting a period (zero cross period) in which the value of the signal becomes 0.

157 Motor controller 402 Rotor 502 Phase controller 503 Current controller 506 PWM inverter 507, 508 Current detector 509 Stepping motor 512 Induced voltage determiner 513 Phase determiner 515 Speed determiner 540 Field controller

Claims (13)

In a motor control device that operates by power supplied from a power source and controls the motor based on a command phase that represents a target phase of a rotor of the motor,
Current supply means for supplying a drive current to the winding of the motor;
Voltage generating means for generating a driving voltage for driving the current supply means;
Current detection means for detecting a current value of a drive current flowing in the winding;
Based on the value of the drive voltage generated by the voltage generation means and the current value detected by the current detection means, the value of the induced voltage induced in the winding by the rotation of the rotor of the motor is determined. Induced voltage determining means for
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
Motor control means for controlling the motor based on a current value of a rotational coordinate system based on the rotational phase so that a deviation between the command phase and the rotational phase determined by the phase determining means is small;
Have
The motor control means includes setting means for setting a value of an excitation current component which is a current value of the rotating coordinate system and is a current value affecting the magnetic flux intensity of the rotor,
The setting means satisfies a first condition in which the rotation speed determined by the speed determination means is greater than a predetermined rotation speed, and the value of the drive voltage is determined from a voltage value output from the power source to the current supply means. When satisfying a second condition that is greater than a predetermined value that is equal to or less than a value obtained by subtracting the value of the induced voltage, the value of the excitation current component is set to a first value that is a negative value, When at least one of the condition and the second condition is not satisfied, the value of the exciting current component is set to a second value larger than the first value. In a motor control device that operates by power supplied from a power source and controls the motor based on a command speed that represents a target speed of a rotor of the motor,
Current supply means for supplying a drive current to the winding of the motor;
Voltage generating means for generating a driving voltage for driving the current supply means;
Current detection means for detecting a current value of a drive current flowing in the winding;
Based on the value of the drive voltage generated by the voltage generation means and the current value detected by the current detection means, the value of the induced voltage induced in the winding by the rotation of the rotor of the motor is determined. Induced voltage determining means for
Phase determining means for determining the rotational phase of the rotor;
Speed determining means for determining the rotational speed of the rotor;
Motor control means for controlling the motor based on a current value of a rotational coordinate system based on the rotational phase so that a deviation between the command speed and the rotational speed determined by the speed determining means is small;
Have
The motor control means includes setting means for setting a value of an excitation current component which is a current value of the rotating coordinate system and is a current value affecting the magnetic flux intensity of the rotor,
The setting means satisfies a first condition in which the rotation speed determined by the speed determination means is greater than a predetermined rotation speed, and the value of the drive voltage is determined from a voltage value output from the power source to the current supply means. When satisfying a second condition that is greater than a predetermined value that is equal to or less than a value obtained by subtracting the value of the induced voltage, the value of the excitation current component is set to a first value that is a negative value, and the first When at least one of the condition and the second condition is not satisfied, the value of the exciting current component is set to a second value larger than the first value.   The setting means sets the value of the exciting current component to 0 when at least one of the first condition and the second condition is not satisfied. The motor control apparatus described. When the first condition is not satisfied, the magnitude of torque that can be generated by the rotor in the state where the value of the excitation current component is set to the first value is the value of the excitation current component. A value equal to or less than the magnitude of torque that can be generated in the rotor in a state where the value is set to 0,
When the first condition is satisfied, the magnitude of torque that can be generated in the rotor in a state where the value of the excitation current component is set to the first value is the value of the excitation current component. 4. The motor control device according to claim 3, wherein the motor control device is larger than a magnitude of torque that can be generated in the rotor in a state in which is set to 0. 5.   The phase determining means is configured to rotate the rotation based on an induced voltage value induced in the first phase winding and an induced voltage value induced in the second phase winding determined by the induced voltage determining means. The motor control device according to any one of claims 1 to 4, wherein a rotation phase of the child is determined. The speed determining means determines a rotational speed corresponding to a command speed representing a target speed of the rotor based on a time change of a command phase representing the target phase of the rotor;
6. The motor control device according to claim 1, wherein the setting unit sets the value of the exciting current component based on a rotation speed corresponding to the command speed. 7. The drive current is represented using the excitation current component and a torque current component that generates torque in the rotor of the motor in the rotating coordinate system,
The said motor control means controls the drive of the said motor by controlling the value of the said excitation current component, and the value of the said torque current component, It is any one of Claim 1 thru | or 6 characterized by the above-mentioned. Motor control device. The motor control means includes
Phase control means for generating and outputting the value of the torque current component so that the deviation between the command phase and the rotational phase determined by the phase determination means is small;
Coordinate conversion means for coordinate-converting the current value of the stationary coordinate system detected by the current detection means to the current value of the rotation coordinate system based on the rotational phase determined by the phase determination means;
Have
Further, the motor control means includes a deviation between the value of the torque current component output from the phase control means and the value of the torque current component coordinate-converted by the coordinate conversion means, and the excitation output from the setting means. The current of the drive current that flows in each of the first phase winding and the second phase winding of the motor so that the deviation between the value of the current component and the value of the excitation current component coordinate-converted by the coordinate conversion means becomes small The motor control device according to claim 1, wherein the motor is controlled by controlling a value. The voltage generation means includes a deviation between a value of the torque current component output from the phase control means and a value of the torque current component coordinate-converted by the coordinate conversion means, and the excitation current component output from the setting means. A driving voltage of the rotating coordinate system is generated so that a deviation between the value of the excitation current component and the value of the excitation current component coordinate-converted by the coordinate conversion means is small,
The motor control means performs coordinate reverse conversion for converting the driving voltage of the rotating coordinate system generated by the voltage generating means into the driving voltage of the stationary coordinate system based on the rotational phase determined by the phase determining means. Having conversion means,
9. The motor control device according to claim 8, wherein the current supply unit is driven by a driving voltage that has been subjected to coordinate reverse conversion by the coordinate reverse conversion unit. The motor control means includes
Speed control means for generating and outputting a value of the torque current component so that a deviation between the command speed and the rotational speed determined by the speed determination means is small;
Coordinate conversion means for coordinate-converting the current value of the stationary coordinate system detected by the current detection means to the current value of the rotation coordinate system based on the rotational phase determined by the phase determination means;
Have
Further, the motor control means includes a deviation between the value of the torque current component output from the speed control means and the value of the torque current component coordinate-converted by the coordinate conversion means, and the excitation output from the setting means. The current of the drive current that flows in each of the first phase winding and the second phase winding of the motor so that the deviation between the value of the current component and the value of the excitation current component coordinate-converted by the coordinate conversion means becomes small 8. The motor control device according to claim 2, wherein the motor is controlled by controlling a value. The voltage generation means includes a deviation between the value of the torque current component output from the speed control means and the value of the torque current component coordinate-converted by the coordinate conversion means, and the excitation current component output from the setting means. A driving voltage of the rotating coordinate system is generated so that a deviation between the value of the excitation current component and the value of the excitation current component coordinate-converted by the coordinate conversion means is small,
The motor control means performs coordinate reverse conversion for converting the driving voltage of the rotating coordinate system generated by the voltage generating means into the driving voltage of the stationary coordinate system based on the rotational phase determined by the phase determining means. Having conversion means,
The motor control device according to claim 10, wherein the current supply unit is driven by a drive voltage that has undergone coordinate reverse conversion by the coordinate reverse conversion unit. 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 11,
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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