JP6789851B2 - Motor control device, sheet transfer device, document reader and image forming device - Google Patents

Description

The present invention, motors control, the sheet conveying device, to the control of the motor in the document reading apparatus and an image forming apparatus.

Conventionally, as a method of controlling a motor, a control method called vector control is known in which the motor is controlled by controlling a current value in a rotating coordinate system based on the rotation phase of the rotor of the motor. Specifically, for example, the motor is controlled by performing phase feedback control that controls the current value so that the deviation between the command phase of the rotor and the actual rotation phase becomes small. There is also a method of controlling the motor by performing speed feedback control that controls 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 (torque current component) that generates torque for the rotor to rotate and a current component that affects the strength of the magnetic flux that penetrates the winding (torque current component). It can be controlled separately from the exciting current component). As a result, even if the load torque applied to the rotor changes, the torque required for rotation can be efficiently generated by controlling the value of the torque current component according to the change in the load torque. As a result, it is possible to suppress an increase in motor noise and an increase in power consumption due to excess torque. In addition, the load torque applied to the rotor exceeds the output torque corresponding to the drive current supplied to the winding of the motor, which has been a problem in the past, and the rotor is not synchronized with the input signal, which is an uncontrollable state (step-out state). ) Can be suppressed.

Vector control requires a configuration that determines the rotation phase of the rotor. In Patent Document 1, the induced voltage generated in the windings of each phase of the motor due to the rotation of the rotor is determined (calculated) by calculation, and the rotor is calculated by calculating the inverse positive connection of the determined induced voltage ratio. The configuration that determines the rotation phase of is described. When the induced voltage is calculated, a preset resistance value or inductance value of the winding is used.

The magnitude of the induced voltage determined becomes smaller as the rotation speed of the rotor is smaller. If the magnitude of the induced voltage to be determined is not large enough to determine the rotation phase of the rotor, it may not be possible to determine the rotation phase accurately. In this case, if the motor is controlled based on the determined rotation phase of the rotor, the control of the motor becomes unstable.

In Patent Document 2, when the command speed of the rotor is smaller than the threshold value, constant current control is used in which the motor is controlled by supplying a constant current to the winding. In the constant current control, neither the phase feedback control nor the velocity feedback control is performed. Further, a configuration is described in which vector control is used when the command speed is equal to or higher than the threshold value. The threshold value is a preset value.

Special Table 2012-509056 Japanese Unexamined Patent Publication No. 2005-39955

The magnitude of the induced voltage to be determined also differs depending on the resistance value and the inductance value of the winding. Specifically, as the resistance value of the winding increases, the magnitude of the induced voltage determined increases. Further, as the inductance value of the winding increases, the magnitude of the induced voltage determined increases. The resistance value and inductance value of the winding differ depending on the environment such as the temperature around the motor. That is, the magnitude of the induced voltage determined depends on the environment such as the temperature around the motor.

Therefore, even if the command speed of the rotor is equal to or higher than the threshold value, the determined magnitude of the induced voltage may not be large enough to accurately determine the rotation phase of the rotor. That is, even if the command speed of the rotor is equal to or higher than the threshold value, the control of the motor may become unstable if the vector control is performed based on the determined rotation phase. Further, even when the command speed of the rotor is smaller than the threshold value, the determined magnitude of the induced voltage may be large enough for the rotational phase of the rotor to be accurately determined. .. That is, even when the command speed of the rotor is smaller than the threshold value, there is a possibility that vector control can be performed based on the determined rotation phase of the rotor. In such a case, although the vector control can be performed, the constant current control is performed, so that the power consumption increases and the motor noise increases.

In this way, when switching between constant current control and vector control based on a preset threshold value and the command speed of the rotor, motor control becomes unstable, power consumption increases, and motor noise increases. It can happen.

In view of the above problems, an object of the present invention is to prevent the control of the motor from becoming unstable .

In order to solve the above problems, the motor control device in the present invention
In a motor control device that controls the motor based on a command phase representing the target phase of the rotor of the motor.
A detection means for detecting the drive current flowing through the winding and
A phase determining means for determining the rotational phase of the rotor based on the drive current detected by the detecting means, and
A first control mode for controlling the driving current flowing through the winding so that the deviation becomes small rotational phase and determined by the phase determining means and the command phase, supplying a constant current prior Kimaki line A control means including a second control mode for controlling the motor by means of
Have,
Wherein, even in a state that controls the motor in either of the control modes of the first control mode and the second control mode, to determine the pre Kihen difference,
When the control means is executing the second control mode and the state in which the deviation is within a predetermined range continues for a predetermined time, the control mode for controlling the motor is changed from the second control mode to the control mode. In the state of switching to the first control mode and executing the second control mode , if the state in which the deviation is within the predetermined range does not continue for the predetermined time, the second control mode is maintained. It is a feature.

According to the present invention, it is possible to prevent the control of the motor from becoming unstable .

It is sectional drawing explaining the image forming apparatus which concerns on 1st Embodiment. It is a block diagram which shows the control structure of the image forming apparatus. It is a figure which shows the relationship between the two-phase motor which consists of A phase and B phase, and the rotating coordinate system represented by d-axis and q-axis. It is a block diagram which shows the structure of the motor control device which concerns on 1st Embodiment. It is a timing chart which shows the state of the rotation speed ω_ref', the deviation σ, and the degree of change α. 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 device which performs speed feedback control.

Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the component parts and their relative arrangements described in this embodiment should be appropriately changed depending on 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, the case where the motor control device is provided in the image forming device will be described, but the case where the motor control device is provided is not limited to the image forming device. For example, it is also used in a sheet transfer device for transporting a sheet such as a recording medium or a document.

[First Embodiment]
[Image forming device]
FIG. 1 is a cross-sectional view showing the configuration of a monochrome electrophotographic copying machine (hereinafter, referred to as an image forming apparatus) 100 having a sheet transporting apparatus used in the present embodiment. The image forming apparatus is not limited to the copying machine, and may be, for example, a facsimile apparatus, a printing machine, a printer, or the like. Further, the recording method is not limited to the electrophotographic method, and may be, for example, an inkjet or the like. 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. As shown in FIG. 1, the image forming apparatus 100 includes a document feeding apparatus 201, a reading apparatus 202, and an image printing apparatus 301.

The documents loaded on the document loading section 203 of the document feeding device 201 are fed one by one by the paper feed roller 204, and are conveyed on the document glass base 214 of the reading device 202 along the transfer guide 206. Further, the original document is conveyed at a constant speed by the conveying belt 208, and is ejected by the paper ejection roller 205 to an output tray (not shown). The reflected light from the original image illuminated by the illumination 209 at the reading position of the reading device 202 is guided to the image reading unit 101 by the optical system including the reflecting mirrors 210, 211, and 212, and converted into an image signal by the image reading unit 101. Will be done. The image reading unit 101 is composed of a lens, a CCD which is a photoelectric conversion element, a driving circuit of the CCD, and the like. The image signal output from the image reading unit 101 is output to the image printing device 301 after various correction processes are performed by the image processing unit 112 configured by a hardware device such as an ASIC. As described above, the original is read. That is, the document feeding device 201 and the reading device 202 function as the document reading device.

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

Sheet storage trays 302 and 304 are provided inside the image printing device 301. Different types of recording media can be stored in the sheet storage trays 302 and 304. For example, the sheet storage tray 302 stores A4 size plain paper, and the sheet storage tray 304 stores A4 size thick paper. The recording medium is one in which an image is formed by an image forming apparatus, and for example, a 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. Further, 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 the optical scanning device 311 including the semiconductor laser and the 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, the laser beam corresponding to the image signal input from the reading device 202 to the optical scanning device 311 is photosensitiveed from the optical scanning device 311 via the polygon mirror and the mirrors 312 and 313. The outer peripheral surface of the drum 309 is irradiated. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 309.

Subsequently, the electrostatic latent image is developed by the toner in the developer 314, and the 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 the 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 feeds the recording medium to the transfer position in time with the toner image.

As described above, the recording medium on which the toner image is transferred is sent to the fixing device 318 by the transport belt 317, heated and pressurized by the fixing device 318, and the toner image is fixed on the recording medium. In this way, 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 ejected to an output tray (not shown) by the output rollers 319 and 324. When image formation is performed in the double-sided printing mode, the recording medium is a paper ejection roller 319, a transport roller 320, and an inversion roller 321 after the fixing process is performed on the first surface of the recording medium by the fixing device 318. Is transported to the reverse path 325. After that, the recording medium is conveyed to the registration roller 308 again by the conveying rollers 322 and 323, and an image is formed on the second surface of the recording medium by the method described above. After that, the recording medium is ejected to an output tray (not shown) by the output rollers 319 and 324.

Further, 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 paper ejection roller 319 and is conveyed to the roller 320. It is transported in the direction toward. After that, just before the rear end of the recording medium passes through the nip portion of the transfer roller 320, the rotation of the transfer roller 320 is reversed, so that the recording medium is a paper ejection roller with the first surface of the recording medium facing downward. It is discharged to the outside of the image forming apparatus 100 via 324.

The above is a description of the configuration and function of the image forming apparatus 100. The load in the present invention is an object driven by a motor. For example, various rollers (conveying rollers) such as paper feed rollers 204, 303, 305, registration rollers 308 and paper ejection rollers 319, photosensitive drums 309, transport belts 208, 317, lighting systems 209, optical systems and the like are in the present invention. Corresponds to the load. The motor control device of the present embodiment can be applied to a motor that drives these loads.

FIG. 2 is a block diagram showing 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 as higher-level devices. Further, the system controller 151 is connected to an image processing unit 112, an operation unit 152, an analog-to-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 formation sequence by reading and executing various programs stored in the ROM 151b.

The RAM 151c is a storage device. The RAM 151c stores, for example, 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.

The system controller 151 transmits to the image processing unit 112 the setting value data of various devices provided inside the image forming device 100, which is necessary for the image processing in the image processing unit 112. Further, the system controller 151 receives signals from various devices (signals from sensors 159) and sets a set value of the high voltage control unit 155 based on the received signals. The high-voltage control unit 155 supplies the voltage required for the high-voltage unit 156 (charger 310, developer 314, transfer charger 315, etc.) according to the set value set by the system controller 151. The sensors 159 include sensors and the like that detect the recording medium conveyed by the transfer roller.

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

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 the detection signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature required for performing the fixing process. The fixing heater 161 is a heater used for the fixing process, 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 the information set by the user from the operation unit 152, and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. Further, the system controller 151 transmits information indicating the state of the image forming apparatus to the operation unit 152. The information indicating the state of the image forming apparatus is, for example, information regarding the number of images formed, the progress of the image forming operation, jams and double feeds of sheet materials in the document reading apparatus 201 and the image printing apparatus 301. The operation unit 152 displays the information received from the system controller 151 on the display unit.

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

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

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

FIG. 3 shows a stepping motor (hereinafter referred to as a motor) 509 composed of two phases, A phase (first phase) and B phase (second phase), and a rotating coordinate system represented by the d-axis and the q-axis. It is a figure which shows the relationship of. In FIG. 3, in the rest coordinate system, the α-axis, which is the axis corresponding to the A-phase winding, and the β-axis, which is the axis corresponding to the B-phase winding, are defined. Further, in FIG. 3, the d-axis is defined along the direction of the magnetic flux generated 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 magnet. The angle formed by the α-axis and the d-axis is defined as θ, and the rotation phase of the rotor 402 is represented by the angle θ. In vector control, a rotating coordinate system based on the rotation phase θ of the rotor 402 is used. Specifically, in vector control, the q-axis component (torque current component) and winding, which are the current components in the rotational coordinate system of the current vector corresponding to the drive current flowing in the winding, and generate torque in the rotor. A d-axis component (exciting current component) that affects the strength of the magnetic flux penetrating the is used.

Vector control is a motor by performing phase feedback control that controls the value of the torque current component and the value of the exciting current component so that the deviation between the command phase representing the target phase of the rotor and the actual rotation phase becomes small. It is a control method to control. 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 exciting current component so that the deviation between the command speed representing the target speed of the rotor and the actual rotation speed becomes small. There is also a method.

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

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.

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 winding of the motor, and the like as circuits that perform vector control. .. The coordinate converter 511 represents the current vector corresponding to the drive current flowing through the windings of the A phase and the B phase 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 a rotating coordinate system. As a result, the drive current flowing through 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), which are current values in the rotating coordinate system. The q-axis current corresponds to the torque current that generates torque in the rotor 402 of the motor 509. Further, the d-axis current corresponds to an exciting current that affects the strength of the magnetic flux penetrating 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 independently control the q-axis current and the d-axis current. As a result, the motor control device 157 can efficiently generate the torque required for the rotor 402 to rotate by controlling the q-axis current according to the load torque applied to the rotor 402.

The motor control device 157 determines the rotation phase θ of the rotor 402 of the motor 509 by a method described later, and performs vector control based on the determination result. The CPU 151a generates a command phase θ_ref representing the target phase of the rotor 402 of the motor 509, and outputs the command phase θ_ref to the motor control device 157 at a predetermined time cycle.

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

The phase controller 502 is based on the proportional control (P), the integral control (I), and the differential control (D), and the q-axis current command value (target value) is set so that the deviation output from the subtractor 101 becomes small. iq_ref and d-axis current command value id_ref (target value) are generated and output. Specifically, the phase controller 502 has a q-axis current command value iq_ref and a d-axis current command value id_ref so that the deviation output from the subtractor 101 based on P control, I control, and D control becomes 0. Is generated and output. The P control is a control method in which the value of the object to be controlled is controlled based on a value proportional to the deviation between the command value and the estimated value. Further, the I control is a control method in which the value of the object to be controlled is controlled based on a value proportional to the time integration of the deviation between the command value and the estimated value. Further, the D control is a control method in which the value of the object to be controlled is 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 the PID control, but is not limited thereto. 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 PI control. When a permanent magnet is used for the rotor 402, the d-axis current command value id_ref, which normally affects the strength of the magnetic flux penetrating the winding, is set to 0, but the present invention is not limited to this.

The drive currents flowing through the A-phase and B-phase windings of the motor 509 are detected by the current detectors 507 and 508, and then converted from analog values to digital values by the 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 determined by the following equation using the phase θe of the current vector shown in FIG. 3 as the current values iα and iβ in the stationary coordinate system. expressed. The phase θe of the current vector is defined as the angle formed by the α axis and the current vector. Further, I indicates the magnitude of the current vector.
iα = I * cosθe (1)
iβ = I * sinθe (2)
These current values iα and iβ are input to the coordinate converter 511 and the induced voltage determinant 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 = cosθ * iα + sinθ * iβ (3)
iq = −sinθ * iα + cosθ * iβ (4)

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 are input to the subtractor 102. The subtractor 102 calculates the deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 503.

Further, 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 are input to the subtractor 103. The subtractor 103 calculates the 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 so that the deviations become smaller, respectively, based on the PID control. Specifically, the current controller 503 generates drive voltages Vq and Vd so that the deviations become 0, respectively, and outputs them to the coordinate inverse converter 505. That is, the current controller 503 functions as a generation means. The current controller 503 in the present embodiment generates drive voltages Vq and Vd based on PID control, but the present invention is not limited to this. For example, the current controller 503 may generate drive voltages Vq and Vd based on PI control.

The coordinate inverse converter 505 reversely converts the drive voltages Vq and Vd in the rotating coordinate system output from the current controller 503 into the drive voltages Vα and Vβ in the static coordinate system by the following equation.
Vα = cosθ * Vd-sinθ * Vq (5)
Vβ = sinθ * Vd + cosθ * Vq (6)
The coordinate inverse converter 505 outputs the inversely converted Vα and Vβ to the induced voltage determinant 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 supplies the drive currents iα and iβ to the windings of each phase of the motor 509 to drive the motor 509. .. That is, the PWM inverter 506 functions as a supply means for supplying a current to the windings of each phase of the motor 509. In the present embodiment, the PWM inverter has a full bridge circuit, but the PWM inverter may be a half bridge circuit or the like.

Next, a method of determining the rotation phase θ will be described. The values of the induced voltages Eα and Eβ induced in the A-phase and B-phase windings of the motor 509 by the rotation of the rotor 402 are used to determine the rotation phase θ of the rotor 402. The value of the induced voltage is determined (calculated) by the induced voltage determinant 512. Specifically, the induced voltages Eα and Eβ were input to the induced voltage determinant 512 from the coordinate inverse converter 505 and the current values iα and iβ input from the A / D converter 510 to the induced voltage determinant 512. It is determined by the following equation from the drive voltages Vα and Vβ.
Eα = Vα-R * iα-L * diα / dt (7)
Eβ = Vβ-R * iβ-L * diβ / dt (8)
Here, R is the winding resistance and L is the winding inductance. The values of the winding resistance R and the winding inductance L are values specific to the motor 509 used, and are stored in advance in a memory (not shown) provided in the ROM 151b or the motor control device 157.

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

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

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

The rotation phase θ of the rotor 402 obtained as described above is input to the subtractor 101, the coordinate inverse converter 505, and the coordinate converter 511.

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

As described above, the motor control device 157 in the present embodiment performs vector control using phase feedback control that controls the current value in the rotating coordinate system so that the deviation between the command phase θ_ref and the rotation phase θ becomes small. By performing vector control, it is possible to suppress the motor from being out of step, the increase in motor noise due to excess torque, and the increase in power consumption. Further, by performing the phase feedback control, the rotation phase of the rotor can be controlled so that the rotation phase of the rotor becomes a desired phase. Therefore, in the image forming apparatus, the vector control by the phase feedback control is applied to the motor that drives the load (for example, the registration roller) that needs to accurately control the rotation phase, so that the image is formed on the recording medium. Can be done properly.

<Constant current control>
Next, constant current control will be described with reference to FIG. Constant current control is a control method for controlling a motor by supplying a constant current to the windings of the motor.

The CPU 151a outputs the command phase θ_ref to the constant current controller 517. The constant current controller 517 generates and outputs the command values iα_ref and iβ_ref of the current in the rest coordinate system corresponding to the command phase θ_ref output from the CPU 151a.

Next, the current detectors 507 and 508 detect the drive current flowing through the A-phase and B-phase windings of the motor 509. After that, 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). The deviation between the current value iα and the command value iα_ref and the deviation between the current value iβ and the command value iβ_ref are input to the current controller 503. The current controller 503 outputs the 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 deviations approach 0, respectively. The drive voltages Vα and Vβ output from the current controller 503 are input to the PWM inverter 506, and the PWM inverter 506 supplies a drive current to the windings of each phase of the motor 509 to drive the motor 509 by the method described above. ..

As described above, in the constant current control, neither the phase feedback control nor the velocity feedback control is performed. That is, in the constant current control, the drive current supplied to the winding is not adjusted according to the rotation state of the rotor. Therefore, in the constant current control, a current obtained by adding a predetermined margin to the current required to rotate the rotor is supplied to the winding so that the motor does not step out. Specifically, the command values iα_ref and iβ_ref of the current in the rest coordinate system include a current value required for rotating the rotor and a current value corresponding to a predetermined margin.

The above is the description of the constant current control.

<Switching between vector control and constant current control>
Next, a method of switching between vector control and constant current control in the present embodiment will be described. In the present embodiment, by applying the following configuration to the motor control device 157, it is possible to suppress instability of motor control, increase in power consumption, and increase in motor noise. In the following description, it is assumed that the circuit that performs vector control is operating even during the period when constant current control is being performed. That is, it is assumed that the circuit for determining the rotation phase θ of the rotor is operating even during the period during which the constant current control is performed. Further, it is assumed that the circuit that performs constant current control is operating even during the period when vector control is being performed.

As shown in FIG. 4, the motor control device 157 has a configuration for switching between controlling the motor 509 using the constant current controller 517 and controlling the motor 509 using the vector controller 518. Specifically, the motor control device 157 includes a control changeover device 515 and control changeover switches 516a, 516b, and 516c (hereinafter, referred to as each switch).

The control switch 515 has a command phase θ_ref output from the CPU 151a, a rotation phase θ output from the phase determiner 513, and a rotation speed ω_ref instead of the command speed of the rotor determined by the CPU 151a based on the command phase θ_ref. ´ is input.

The control switch 515 has a difference value determinant 515a. The difference value determinant 515a determines the deviation σ between the command phase θ_ref and the rotation phase θ by the following equation.
σ ＝ θ_ref−θ (10)

Further, the difference value determinant 515a determines the time change Δσ / Δt (hereinafter, referred to as the degree of change α) of the determined deviation σ by the following equation.
α = Δσ / Δt = (σ (t2) −σ (t1)) / (t2-t1) (11)

The time t1 and the time t2 indicate the time when the deviation σ is determined, and t1 <t2. Further, the difference value determinant 515a acquires the command phase θ_ref and the rotation phase θ in a predetermined cycle, and repeatedly determines the deviation σ and the degree of change α in the cycle corresponding to the predetermined cycle.

FIG. 5 is a timing chart showing the state of the rotation speed ω_ref', the deviation σ, and the degree of change α. The rotation speed ω_ref', the deviation σ, and the degree of change α shown in FIG. 5 are examples in the present embodiment, and are not limited thereto.

As shown in FIG. 5, when the driving of the motor is started, the motor control device 157 controls the motor 509 by constant current control.

During a period when the rotation speed ω_ref'of the rotor is relatively small, such as immediately after the start of driving the motor, the error between the actual rotation phase of the rotor and the determined rotation phase of the rotor becomes large. Therefore, even if the actual rotation phase of the rotor follows the command phase, the deviation σ between the command phase θ_ref and the determined rotation phase θ fluctuates. As the rotation speed ω_ref'increases, the rotation speed of the rotor also increases, so that the accuracy with which the phase determiner 513 determines the rotation phase θ also improves, and the actual rotation phase of the rotor and the determined rotation phase of the rotor Error is reduced. As a result, when the actual rotation phase of the rotor follows the command phase, the deviation σ between the command phase θ_ref and the determined rotation phase θ converges to a predetermined value. Specifically, when the motor 509 drives the load, the deviation σ converges to a value caused by the load angle according to the load torque applied to the rotor by the load. When the deviation converges to a predetermined value, the degree of change α approaches 0. That is, when the accuracy with which the phase determinant 513 determines the rotation phase θ is improved, the degree of change α approaches zero.

Therefore, in the present embodiment, when the state in which the degree of change α is within the predetermined range continues for a predetermined time T, the motor control device 157 switches the control of the motor from the constant current control to the vector control. That is, when the state in which the fluctuation range (amplitude) of the degree of change α is within the predetermined range continues for a predetermined time T, the motor control device 157 switches the control of the motor from the constant current control to the vector control. Specifically, the control switch 515 controls the state of each switch 516a, 516b, 516c so as to switch the controller that controls the drive of the motor 509 from the constant current controller 517 to the vector controller 518. As a result, vector control by the vector controller 518 is performed. Further, the control switch 515 stores the rotation speed ω_ref'at the timing when the control of the motor 509 is switched from the constant current control to the vector control as the threshold value ωth in the memory 515b.

During control by the vector controller 518, when the rotation speed ω_ref'is smaller than the threshold value ωth, the control switch 515 switches the controller that controls the drive of the motor 509. That is, the control switch 515 controls the state of each switch 516a, 516b, 516c so as to switch the controller that controls the drive of the motor 509 from the vector controller 518 to the constant current controller 517. As a result, constant current control is performed by the constant current controller 517.

FIG. 6 is a flowchart showing a method of controlling the motor by the motor control device 157. The control of the motor 509 according to the present embodiment will be described below with reference to FIG. The processing of this flowchart is executed by the motor control device 157 that receives the instruction from the CPU 151a.

First, when the enable signal ‘H’ is output from the CPU 151a to the motor control device 157, the motor control device 157 starts driving the motor 509 based on the command output from the CPU 151a. The enable signal is a signal for permitting or prohibiting the operation of the motor control device 157. When the enable signal is'L (low level)', the CPU 151a prohibits the operation of the motor control device 157. That is, the control of the motor 509 by the motor control device 157 is terminated. 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 the command output from the CPU 151a. ..

Next, in S1001, the control switch 515 controls the states of the switches 516a, 516b, and 516c so that the drive of the motor 509 is controlled by the constant current controller 517. As a result, constant current control is performed by the constant current controller 517.

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

Further, in S1002, when the CPU 151a outputs the enable signal ‘H’ to the motor control device 157, the motor control device 157 advances the process to S1003.

Next, in S1003, if the state in which the degree of change α is within the predetermined range does not continue for a predetermined time T, the process returns to S1001 again. That is, the constant current control by the constant current controller 517 is maintained.

Further, in S1003, the difference value determining machine 515a determines the degree of change α by the method described above.

After that, in S1004, if the degree of change α determined in S1003 is not within the predetermined range, the process returns to S1001 again.

Further, in S1004, when the degree of change α determined in S1003 is within a predetermined range, the CPU 151a advances the process to S1005.

In S1005, when the state in which the degree of change α is within the predetermined range continues for a predetermined time T, in S1006, the control switch 515 switches the controller that controls the drive of the motor 509. That is, the control switch 515 controls the state of each switch 516a, 516b, 516c so as to switch the controller that controls the drive of the motor 509 from the constant current controller 517 to the vector controller 518. As a result, vector control by the vector controller 518 is performed.

After that, in S1007, the control switch 515 determines the rotation speed ω_ref'at the timing when the control of the motor 509 is switched from the constant current control to the vector control in S1006 as the threshold value ωth, and stores it in the memory 515b. After that, the process proceeds to S1008.

In S1008, when the rotation speed ω_ref'is equal to or higher than the threshold value ωth, the process returns to S1006 again, and the vector control by the vector controller 518 is continued.

Further, in S1008, when the rotation speed ω_ref'is smaller than the threshold value ωth, the process returns to S1001 again, and the control switch 515 switches the controller that controls the drive of the motor 509. That is, the control switch 515 controls the state of each switch 516a, 516b, 516c so as to switch the controller that controls the drive of the motor 509 from the vector controller 518 to the constant current controller 517. As a result, constant current control is performed by the constant current controller 517.

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

As described above, in the present embodiment, the control of the motor is switched from the constant current control to the vector control based on the degree of change α. Specifically, when the state in which the degree of change α is within the predetermined range continues for a predetermined time T, the motor control device 157 switches the control of the motor from the constant current control to the vector control. That is, when the accuracy of the phase determining device 513 determining the rotation phase becomes relatively good, the control of the motor is switched from the constant current control to the vector control. As a result, it is possible to prevent the control of the motor from becoming unstable.

Further, in the present embodiment, the rotation speed ω_ref'at the timing when the motor control is switched from the constant current control to the vector control is set to the threshold value ωth. Then, when the rotation speed ω_ref'is smaller than the threshold value ωth in the state where the vector control is performed, the control of the motor is switched from the vector control to the constant current control. By using such a configuration, it is possible to suppress an increase in power consumption and an increase in motor noise. It is assumed that the threshold value ωth is determined every time the driving of the motor is started. That is, it is assumed that the threshold value ωth is updated every time the driving of the motor is started.

In the present embodiment, the constant current control and the vector control are switched based on the time change (degree of change α) of the deviation between the command phase θ_ref and the rotation phase θ, but this is not the case. For example, the constant current control and the vector control may be switched based on whether or not the state in which the deviation σ between the command phase θ_ref and the rotation phase θ is within a predetermined range continues for a predetermined time.

Further, in the present embodiment, the control of the motor is switched from the vector control to the constant current control based on the threshold value ωth, but this is not the case. For example, the motor control may be switched from the vector control to the constant current control based on the degree of change α in the same manner as when the motor control is switched from the constant current control to the vector control.

Further, in the present embodiment, the stepping motor is used as the motor for driving the load, but other motors such as a DC motor may be used. Further, the motor is not limited to a two-phase motor, and the present embodiment can be applied to other motors such as a three-phase motor.

Further, in the vector control in the present embodiment, the motor 509 is controlled by performing phase feedback control, but the present invention is not limited to this. For example, the motor 509 may be controlled by feeding back the rotation speed ω of the rotor 402. Specifically, as shown in FIG. 7, a speed determinant 514 is provided inside the motor control device, and the speed determinant 514 determines the rotation speed ω based on the time change of the rotation phase θ output from the phase determinant 513. decide. The following equation (12) shall be used to determine the speed.

ω = dθ / dt (12)
Then, the CPU 151a 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 the q-axis current command value iq_ref and the d-axis current command value id_ref so that the deviation between the rotation speed ω and the command speed ω_ref becomes small. And output. The motor 509 may be controlled by performing such speed feedback control. 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 applied to a motor that drives a load (for example, a photosensitive drum, a transport belt, etc.) in which the rotation speed needs to be controlled to a constant speed in order to properly form an image on a recording medium. Apply the vector control used. As a result, the image can be appropriately formed on the recording medium. In this case, the command speed ω_ref is also used when performing constant current control. Further, in this case, the constant current control and the vector control are switched based on whether or not the state in which the deviation between the command speed ω_ref and the rotation speed ω is within the predetermined range continues for a predetermined time.

Further, in the present embodiment, the circuit that controls the drive of the motor 509 by using the vector controller 518 corresponds to the first control circuit in the present invention. Further, in the present embodiment, the circuit that controls the drive of the motor 509 by using the constant current controller 517 corresponds to the second control circuit in the present invention. The motor control device in the present embodiment has a part (current controller 503, PWM inverter 506, etc.) that is partially shared between the circuit that performs vector control and the circuit that performs constant current control, but this is limited. is not. For example, a circuit that performs vector control and a circuit that performs constant current control may be provided independently.

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

151a CPU
157 Motor control device 509 Stepping motor 513 Phase determinant 515 Control changer 515a Difference value determinant 516a, 516b, 516c Control changeover switch

Claims (11)

In a motor control device that controls the motor based on a command phase representing the target phase of the rotor of the motor.
A detection means for detecting the drive current flowing through the winding and
A phase determining means for determining the rotational phase of the rotor based on the drive current detected by the detecting means, and
A first control mode for controlling the driving current flowing through the winding so that the deviation becomes small rotational phase and determined by the phase determining means and the command phase, supplying a constant current prior Kimaki line A control means including a second control mode for controlling the motor by means of
Have,
Wherein, even in a state that controls the motor in either of the control modes of the first control mode and the second control mode, to determine the pre Kihen difference,
When the control means is executing the second control mode and the state in which the deviation is within a predetermined range continues for a predetermined time, the control mode for controlling the motor is changed from the second control mode to the control mode. In the state of switching to the first control mode and executing the second control mode , if the state in which the deviation is within the predetermined range does not continue for the predetermined time, the second control mode is maintained. A featured motor control device. The first control mode is based on a torque current component which is a current component represented in a rotating coordinate system based on a rotation phase determined by the phase determining means and which is a current component for generating torque in the rotor. The motor control device according to claim 1, further comprising a control mode for controlling the motor. The motor control device has an induced voltage determining means for determining the magnitude of the induced voltage induced in the winding by the rotation of the rotor based on the drive current detected by the detecting means.
The motor control device according to claim 1 or 2, wherein the phase determining means determines the rotation phase based on the magnitude of the induced voltage determined by the induced voltage determining means. In a motor control device that controls the motor based on a command speed that represents the target speed of the rotor of the motor.
A detection means for detecting the drive current flowing through the winding and
A speed determining means for determining the rotational speed of the rotor based on the drive current detected by the detecting means, and
A first control mode for controlling the driving current flowing through the winding so that the deviation is reduced rotational speed and which is determined by the command speed and the speed determining means, supplying a constant current prior Kimaki line A control means including a second control mode for controlling the motor by means of
Have,
Wherein, even in a state that controls the motor in either of the control modes of the first control mode and the second control mode, to determine the pre Kihen difference,
When the control means is executing the second control mode and the state in which the deviation is within a predetermined range continues for a predetermined time, the control mode for controlling the motor is changed from the second control mode to the control mode. In the state of switching to the first control mode and executing the second control mode , if the state in which the deviation is within the predetermined range does not continue for the predetermined time, the second control mode is maintained. A motor control device characterized by the fact that. The motor control device has a phase determining means for determining the rotational phase of the rotor.
The first control mode is based on a torque current component which is a current component represented in a rotating coordinate system based on a rotation phase determined by the phase determining means and which is a current component for generating torque in the rotor. The motor control device according to claim 4, further comprising a control mode for controlling the motor. The motor control device, before SL on the basis of the driving current detected by the detecting means, the induced voltage determining means to determine the magnitude of the voltage induced before Kimaki line by rotation of the front Machinery trochanter have,
It said speed determining means, the motor control device according to claim 4 or 5, characterized in that to determine the rotational speed based on the magnitude of the EMF determined by the induced voltage determining means. Said control means, said deviation to determine a short has periodic than the predetermined time,
Wherein, in a state that is running the second control mode, the difference value between the second deviation is determined in the following first deviation and the first deviation as the deviation of the second When the state within the predetermined range continues for the predetermined time, the control mode for controlling the motor is switched from the second control mode to the first control mode, and the second control mode is being executed . The method according to any one of claims 1 to 6 , wherein the second control mode is maintained when the state in which the difference value is within the second predetermined range does not continue for the predetermined time. Motor control device. A transport roller that transports the sheet and
The motor that drives the transfer roller and
The motor control device according to any one of claims 1 to 7 .
Have,
The motor control device is a seat transfer device characterized in that it controls the drive of a motor that drives the transfer roller. A transport unit that transports documents and
Reading means for reading the feeding has been originals by the conveyor unit,
The motor that drives the load and
The motor control device according to any one of claims 1 to 7.
Have a,
The motor control device is a document reading device characterized in that it controls the driving of a motor that drives the load . An image forming apparatus that forms an image on a recording medium.
The motor that drives the load and
The motor control device according to any one of claims 1 to 7 .
Have,
The motor control device is an image forming device that controls the drive of a motor that drives the load. The load image forming apparatus according to claim 1 0, characterized in that the conveying roller for conveying the recording medium.

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