JP7208351B2 - MOTOR CONTROL DEVICE, SHEET CONVEYING DEVICE, AND IMAGE FORMING APPARATUS - Google Patents

Description

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

2. Description of the Related Art Conventionally, as a method of controlling a motor, a control method called vector control is known, in which the motor is controlled by controlling the 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 commanded phase of the rotor and the 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 difference between the commanded speed of the rotor and the rotational speed is reduced.

When vector control is used, the driving current supplied to the windings of the motor is divided into a current component (q-axis current) that generates torque for the rotor to rotate, and a current component (d-axis current) that affects the magnetic flux strength of the rotor. current) can be controlled separately. 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 q-axis current according to the change in the load torque. In other words, the load torque applied to the rotor exceeds the output torque corresponding to the drive current supplied to the windings of the motor, and the motor is out of control (out of synchronism) in which the motor does not synchronize with the input signal. can be prevented from becoming Also, it is possible to suppress an increase in power consumption and an increase in motor noise caused by surplus torque.

Vector control requires a configuration for estimating the phase of the rotor. Patent Document 1 describes an estimation method for estimating the rotor phase by calculating the arctangent of the ratio of the induced voltages generated in the windings of the motor.

However, the magnitude of the induced voltage generated in the windings decreases as the rotation speed of the rotor decreases. If the magnitude of the induced voltage generated in the windings is not large enough to estimate the phase of the rotor, it may not be possible to accurately estimate the phase. In other words, if the rotational speed of the rotor is low, it may become impossible to accurately estimate the phase of the rotor.

In Patent Document 2, when the commanded speed of the rotor is smaller than a predetermined rotation speed, the motor is controlled by controlling the drive current so that the magnitude of the drive current supplied to the windings is constant. constant current control (open control) is used. In constant current control, neither the phase feedback control nor the speed feedback control is performed. Furthermore, it is described that when the command speed is equal to or higher than the predetermined rotational speed, the above-described vector control is used.

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

In motor control, if the load torque applied to the rotor exceeds the output torque corresponding to the drive current supplied to the windings, the motor may go out of step. Therefore, there is a demand for a configuration that can accurately determine an abnormality in rotation of a motor in controlling the motor.

In view of the above problems, the present invention provides a motor control apparatus for determining the rotational speed of a rotor of a motor in a first control mode in which a constant current is supplied to the windings of the motor to control the drive current flowing through the windings. intended to provide

In order to solve the above problems, a motor control device according to the present invention includes:
In a motor control device that accelerates a rotor of a motor to a predetermined speed,
detection means for detecting a drive current flowing through the windings of the motor ;
speed determining means for determining the rotation speed of the rotor of the motor based on the drive current detected by the detecting means;
phase determining means for determining a rotational phase of the rotor;
a first control mode for controlling the drive current flowing through the winding by supplying a constant current to the winding; a second control mode that performs vector control for controlling the drive current flowing through the windings based on the current component of the value , wherein the rotational speed of the rotor in a state in which the first control mode is executed; changes from a value smaller than the first threshold value to a value larger than the first threshold value, the control mode for controlling the drive current flowing through the winding is changed from the first control mode to the first control mode. a control means for switching to control mode 2 ;
has
The speed determining means controls the speed of the rotor when the control means is in the first control mode and the value corresponding to the rotational speed of the rotor is greater than a second threshold smaller than the first threshold. determining the rotational speed of the rotor in a state in which the control means performs the first control mode and the value corresponding to the rotational speed of the rotor is smaller than the second threshold value; figure,
The first threshold value and the second threshold value are values smaller than the value corresponding to the predetermined speed .

According to the present invention, there is provided a motor control apparatus for determining the rotational speed of a rotor of a motor in a first control mode in which a constant current is supplied to the windings of the motor to control the drive current flowing through the windings of the motor. be able to.

1 is a cross-sectional view for explaining an image forming apparatus according to a first embodiment; FIG. 3 is a block diagram showing a control configuration of the image forming apparatus; FIG. 1 is a block diagram showing the configuration of a motor control device according to a first embodiment; FIG. 2 is a diagram showing the relationship between a two-phase motor consisting of A phase and B phase and the d-axis and q-axis of a rotating coordinate system; FIG. FIG. 4 is a diagram showing the relationship between a command speed ω_ref, an estimated rotation speed ω, a switching threshold ωth, and a step-out determination threshold ωsnl in the first embodiment; FIG. 4 is a diagram for explaining a method for determining out-of-step in the first embodiment; 4 is a flowchart showing a motor drive control method using the motor control device; 5 is a flow chart showing a motor out-of-step determination method using the abnormality determiner according to the first embodiment.

Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shape and relative arrangement of the components described in this embodiment should be changed as appropriate according to the configuration of the device to which this invention is applied and various conditions, and the scope of this invention is not limited. It is not intended to be limited to the following embodiments. In the following description, a case where the motor control device is provided in the image forming apparatus will be described, but it is not limited to the image forming apparatus where the motor control device is provided. For example, the motor control device is also used in a sheet conveying device that conveys sheets such as recording media and originals.

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

The configuration and functions of the image forming apparatus 100 will be described below with reference to FIG. The image forming apparatus 100 has a document feeding device 201 , a reading device 202 and an image printing device 301 .

Documents stacked on the document stacking unit 203 of the document feeding device 201 are fed one by one by the feeding roller 204 and conveyed to the document glass table 214 of the reading device 202 via the conveying guide 206 . Further, the document is conveyed at a constant speed by the conveying belt 208 and discharged to the outside of the apparatus by the discharge rollers 205 . Reflected light from the document image illuminated by the illumination 209 at the reading position of the reading device 202 is guided to the image reading unit 101 by an optical system consisting of reflecting mirrors 210, 211, and 212, and converted into an image signal by the image reading unit 101. be done. 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. An 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 printing apparatus 301 . The document is read as described above. That is, the document feeding device 201 and the reading device 202 function as a document reading device.

Further, document reading modes in the reading device 202 include a flow reading mode and a fixed reading mode. 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 with the illumination system 209 and the optical system fixed at predetermined phases. In the fixed reading mode, a document is placed on the document glass 214 of the reading device 202, and the image of the document placed on the document glass 214 is read while the illumination system 209 and the optical system are moved at a constant speed. be. Normally, a sheet-shaped original is read in the skimming mode, and a bound original such as a book or a booklet is read in the fixed reading mode.

Sheet storage trays 302 and 304 are provided inside the image printing apparatus 301 . The sheet storage trays 302 and 304 can store different types of recording media. For example, the sheet storage tray 302 stores A4 size plain paper, and the sheet storage tray 304 stores A4 size thick paper. A recording medium is a medium on which an image is formed by an image forming apparatus, and includes, for example, paper, resin sheets, cloth, OHP sheets, labels, and the like.

A print medium stored in a sheet storage tray 302 is fed by a paper feed roller 303 and sent to a registration roller 308 by a transport roller 306 . Also, the print medium accommodated in the sheet accommodation tray 304 is fed by a paper feed roller 305 and sent to a registration roller 308 by conveying rollers 307 and 306 .

An 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 photosensitive drum 309 is charged on its outer peripheral surface 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 is emitted from the optical scanning device 311 via polygon mirrors and mirrors 312 and 313 to be exposed to light. 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 . As a method 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 to form a toner image on the outer peripheral surface of the photosensitive drum 309 . A toner image formed on the photosensitive drum 309 is transferred onto a recording medium by a transfer charger 315 provided at a position facing the photosensitive drum 309 (transfer position). The registration roller 308 feeds the recording medium to the transfer position in synchronization with this transfer timing.

As described above, the recording medium to which the toner image has been transferred is sent to the fixing device 318 by the conveying belt 317, and is heated and pressed by the fixing device 318 to fix the toner image on 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 paper discharge tray (not shown) by paper discharge rollers 319 and 324 . Further, when image formation is performed in the double-sided printing mode, after the first side of the recording medium is subjected to fixing processing by the fixing device 318 , the recording medium is transferred to the discharge rollers 319 , the conveying rollers 320 and the reversing rollers 321 . to the reversing path 325 . After that, the recording medium is transported again to the registration rollers 308 by transport rollers 322 and 323, and an image is formed on the second side of the recording medium in the manner described above. After that, the recording medium is discharged to a paper discharge tray (not shown) by paper discharge rollers 319 and 324 .

When the recording medium on which an image is formed on the first side is turned over so that the first side faces downward and is ejected outside the image forming apparatus 100, the recording medium that has passed through the fixing device 318 is ejected. The paper is conveyed in the direction toward the conveying roller 320 through the paper roller 319 . Then, just before the trailing edge of the recording medium passes through the nip portion of the transport roller 320, the rotation of the transport roller 320 is reversed. As a result, the recording medium can be conveyed toward the discharge roller 324 and discharged to the outside of the image forming apparatus 100 with the first surface of the recording medium facing downward.

The configuration and functions of the image forming apparatus 100 have been described above. A load in the present invention is an object driven by a motor. For example, various rollers (conveyance rollers) such as the paper feed rollers 204, 303, 305, the registration roller 308, and the paper discharge roller 319, the photosensitive drum 309, the conveyance belts 208, 317, the illumination system 209, the optical system, etc. accommodate the load. The motor control device of this embodiment can be applied to motors that drive these loads.

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

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

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

The system controller 151 transmits setting value data of various devices provided inside the image forming apparatus 100 , which is necessary for image processing in the image processing unit 112 , to the image processing unit 112 . Furthermore, the system controller 151 receives signals from the sensors 159 and sets the setting values of the high voltage control section 155 based on the received signals. The high-voltage controller 155 supplies necessary voltages to the high-voltage unit 156 (charger 310 , developer 314 , transfer charger 315 , etc.) according to set values set by the system controller 151 .

The A/D converter 153 receives a detection signal detected by a 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 digital signal to the system controller 151 . The system controller 151 controls the AC driver 160 based on the digital signal received from the A/D converter 153 . The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 reaches a temperature necessary for performing the fixing process. Note that the fixing heater 161 is a heater used for fixing processing and is included in the fixing device 318 .

The system controller 151 causes the operation unit 152 to display an operation screen for the user to set the type of recording medium to be used (hereinafter referred to as paper type) on the display unit provided in the operation unit 152. to control. The system controller 151 receives information set by the user, such as the type of paper to be used, from the operation unit 152, and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. Also, 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, the number of images to be formed, whether or not image formation is in progress, the occurrence of a jam and the location of the occurrence, and the like. The operation unit 152 displays information received from the system controller 151 on the display unit.

The system controller 151 controls the operation sequence of the image forming apparatus 100 as described above.

Next, the motor control device according to this embodiment will be described. The motor control device according to the present embodiment can control the motor by either vector control (second control mode) or constant current control (first control mode). Although a stepping motor is used as the motor for driving the load in the following description, the motor is not limited to this. Also, the motor is not necessarily a two-phase motor. Furthermore, it is assumed that the motor in this embodiment is not provided with a sensor such as a rotary encoder for detecting the rotational phase of the rotor of the motor.

FIG. 3 is a block diagram showing an example of the configuration of a motor control device 157 that controls driving of a stepping motor (hereinafter referred to as a motor) 509. As shown in FIG. The motor control device 157 in this embodiment is provided with a constant current controller 517 that performs constant current control and a vector controller 518 that performs vector control. Furthermore, the motor control device 157 is configured to control the drive of the motor 509 using the constant current controller 517 or the vector controller 518, depending on the command speed of the rotor 402. An arrangement is provided for switching based on. Specifically, a control changeover (control changeover means) 515, control changeover switches (control changeover means) 516a, 516b, 516c (hereinafter referred to as each switch) and the like are provided. The motor control means in this embodiment corresponds to the constant current controller 517, the vector controller 518, the control switcher 515, and the switches 516a, 516b, and 516c. Also, the first control circuit in this embodiment corresponds to a circuit that controls driving of the motor 509 using the constant current controller 517 . Furthermore, the second control circuit in this embodiment corresponds to a circuit that controls driving of the motor 509 using the vector controller 518 . In the motor control device according to the present embodiment, the circuit for performing vector control and the circuit for performing constant current control share some parts (current controller 503, PWM inverter 506, etc.). is not. For example, a configuration in which a circuit for performing vector control and a circuit for performing constant current control are provided independently of each other may be used.

First, a method of performing vector control by the motor control device 157 in this embodiment will be described with reference to FIGS. 3 and 4. FIG.

FIG. 4 is a diagram showing the relationship between the motor 509 consisting of two phases, 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. Also, the angle between 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 magnets used in the rotor 402 is defined as θ. The rotational phase of rotor 402 is represented by angle θ. In vector control, the d-axis along the direction of the magnetic flux of the rotor 402 and the q-axis (perpendicular to the d-axis) along the direction 90 degrees counterclockwise from 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 commanded phase of the rotor and the 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 difference between the commanded speed of the rotor and the rotational speed is reduced. The current value in the rotating coordinate system is the current value of the q-axis component (torque current component) that generates torque in the rotor of the motor, and the d-axis component (excitation current component) that affects the magnetic flux strength of the rotor of the motor. corresponds to the current value.

The motor control device 157 is provided with a phase controller 502, a current controller (voltage generating means) 503, a coordinate inverter 505, a coordinate converter 511, a PWM inverter 506, and the like as circuits for vector control. A coordinate converter (coordinate conversion means) 511 converts the current vectors corresponding to the drive currents flowing through the A-phase and B-phase windings of the motor 509 from the static coordinate system represented by the α-axis and β-axis to the q-axis and The coordinates are transformed into a rotating coordinate system represented by the d-axis. As a result, the driving currents supplied to the A-phase and B-phase windings of the motor 509 are expressed as follows: can be expressed using Note that the q-axis current corresponds to a torque current that causes the rotor 402 of the motor 509 to generate torque. Also, the d-axis current corresponds to an exciting current that affects the magnetic flux intensity of the rotor 402 of the motor 509 and does not contribute to torque generation of the rotor 402 . The motor controller 157 can independently control the q-axis current and the d-axis current. That is, the torque required for rotating the rotor 402 can be efficiently generated.

The motor control device 157 estimates the rotation phase θ of the rotor 402 of the motor 509 by a method described later, and performs vector control based on the estimation result. The CPU 151a (higher-level device) generates a command value (command phase) θ_ref for the rotation 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.

A phase controller (phase control means) 502 generates a q-axis current command value iq_ref and a d-axis current command value id_ref so that the deviation between the rotation phase θ of the rotor 402 of the motor 509 and the command phase θ_ref becomes small. output. Specifically, the phase controller 502 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 phase θ of the rotor 402 of the motor 509 and the command phase θ_ref becomes zero. and 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. can be Also, when a permanent magnet is used for the rotor 402, the d-axis current command value id_ref that affects the magnetic flux intensity of the rotor 402 is normally set to 0, but is not limited to this.

Next, the drive currents flowing through the A-phase and B-phase windings of the motor 509 are detected by current detectors (current detection means) 507 and 508, and then converted from analog values to digital values by an A/D converter 510. is converted to

The driving currents flowing through the A-phase and B-phase windings of the motor 509 are converted from analog values to digital values by an A/D converter 510, and are used as current values iα and iβ in the stationary coordinate system of the rotor 402. It is represented by the following equation using the rotation phase θ.
iα=I*cosθ (1)
iβ=I*sinθ (2)

These current values iα and iβ are input to a coordinate converter 511 and an induced voltage calculator (induced voltage determination means) 512 .

In the coordinate converter 511, the current values iα and iβ are coordinate-transformed 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 equations.
id = cos θ * i α + sin θ * i β (3)
iq=-sin θ*iα+cos θ*iβ (4)

As described above, the coordinate converter 511 converts the current vectors corresponding to the drive currents flowing through the A-phase and B-phase windings of the motor 509 from the static coordinate system represented by the α and β axes to the q and Q axes. The coordinates are transformed into a rotating coordinate system represented by the d-axis.

Subsequently, the deviation between the current value iq obtained by coordinate transformation by the coordinate converter 511 and iq_ref output from the phase controller 502 and the deviation between the current value id and id_ref output from the phase controller 502 are They are output to the current controller 503 respectively. The current controller 503 generates current values iq* and id* such that the deviations are reduced. Specifically, the current controller 503 generates the current values iq* and id* so that the deviation becomes zero. After that, the current controller 503 generates drive voltages Vq and Vd corresponding to the respective current values iq* and id* and outputs them to the coordinate inverse converter (coordinate inverse conversion means) 505 . The current controller 503 in this embodiment is composed of proportional (P) and integral (I) compensators like the phase controller 502, but proportional (P), integral (I) and differential (D ) compensator.

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

The coordinate inverse converter 505 coordinates inversely transforms the driving voltages Vq and Vd in the rotating coordinate system to the driving voltages Vα and Vβ in the static coordinate system, and converts Vα and Vβ to the induced voltage calculator 512 and the PWM inverter (supply means) 506 . output to In the present embodiment, drive voltages Vq and Vd corresponding to current values iq* and id* are generated, and the drive voltages Vq and Vd are subjected to coordinate inverse transformation to obtain drive voltages Vα and Vβ in the stationary coordinate system. Got it, but not limited to this. For example, the current values iq* and id* are coordinate-inversely transformed into the current values iα* and iβ* in the static coordinate system, and the drive voltages Vα and Vβ corresponding to the current values iα* and iβ* are generated. Also good.

PWM inverter 506 has a full bridge circuit. The full-bridge circuit is driven by drive voltages Vα and Vβ input from coordinate inverter 505 . As a result, PWM inverter 506 generates drive currents iα and iβ corresponding to drive voltages Vα and Vβ, and supplies drive currents iα and iβ to windings of respective phases of motor 509 to drive motor 509. . Although the PWM inverter has a full-bridge circuit in this embodiment, it may be a half-bridge circuit or the like.

Next, a method for estimating the rotational phase θ of rotor 402 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 due to the rotation of the rotor 402 are used to estimate the rotational phase θ of the rotor 402 . The induced voltage value is calculated by the induced voltage calculator 512 . Specifically, from the current values iα and iβ input from the A/D converter 510 to the induced voltage calculator 512 and the driving voltages Vα and Vβ input from the coordinate inverter 505 to the induced voltage calculator 512, , the induced voltages Eα and Eβ are calculated by the following equations.
Eα=Vα−R*iα−L*diα/dt (7)
Eβ=Vβ−R*iβ−L*diβ/dt (8)

where R is the winding resistance and L is the winding inductance. The values of R and L are values specific to the motor 509 being used, and are stored in advance in the ROM 151b or a memory (not shown) provided in the motor control device 157 or the like.

The induced voltages Eα and Eβ calculated by the induced voltage calculator 512 are input to a phase estimator (phase determination means) 513 . The phase estimator 513 estimates the rotation phase θ of the rotor 402 of the motor 509 from the ratio of the A-phase induced voltage Eα and the B-phase induced voltage Eβ by the following equation.
θ=tan^-1(-Eβ/Eα) (9)

of the rotor 402 obtained as described above is input to the phase controller 502 , coordinate inverse converter 505 , coordinate converter 511 and speed estimator (speed determining means) 514 . After that, the above control is repeated.

As previously described, motor controller 157 controls motor 509 using vector control. By controlling the driving of the motor using vector control, it is possible to prevent the motor from going out of step, increase in motor noise due to excess torque, and increase in power consumption. In the vector control of this embodiment, the motor 509 is controlled by performing the phase feedback control described above, but the present invention is not limited to this. For example, the configuration may be such that the rotation speed ω of the rotor 402 is fed back to control the drive of the motor 509 . Specifically, the speed estimator estimates the rotation speed ω based on the time change of the rotation phase θ output from the phase estimator 513 . The following formula is used to estimate the velocity.
ω=dθ/dt (10)

The CPU 151a also outputs a command speed ω_ref of the rotor. Further, a speed controller (speed control means) is provided inside the motor control device, and the speed controller controls the q-axis current command value iq_ref and the d-axis current command value iq_ref so that the deviation between the rotation speed ω and the command speed ω_ref becomes small. It is configured to generate and output the value id_ref. The configuration may be such that the driving of the motor 509 is controlled by performing the speed feedback control as described above.

However, the magnitude of the induced voltage generated in the windings decreases as the rotation speed of the rotor decreases. If the magnitude of the induced voltage generated in the windings is not large enough to estimate the phase of the rotor, it may not be possible to accurately estimate the phase. In other words, if the rotational speed of the rotor is low, it may become impossible to accurately estimate the phase of the rotor. As a result, the drive control of the motor may become unstable.

As shown in FIG. 3, the motor control device 157 in this embodiment is provided with a configuration for switching between constant current control and vector control. Specifically, a control switch 515, switches 516a, 516b, 516c, and the like are provided.

FIG. 5 is a diagram showing the relationship between the command speed ω_ref, the estimated rotational speed ω, the switching threshold ωth (second threshold), and the step-out determination threshold ωsnl (first threshold) in this embodiment. . The switching threshold ωth and the step-out determination threshold ωsnl will be described later. Also, the relationship between the command speed ω_ref, the estimated rotation speed ω, the switching threshold ωth, and the step-out determination threshold ωsnl shown in FIG. 5 is merely an example, and the present invention is not limited to this.

A control switching method between constant current control and vector control in this embodiment will be described below with reference to FIGS. 3 and 5. FIG.

In this embodiment, a switching threshold ωth of the rotational speed of the rotor 402 is set for switching between constant current control and vector control. When the motor drive control is switched from constant current control to vector control, the rotational speed of the motor may momentarily decrease. This is because the magnitude of the torque generated in the rotor by the first supplied drive current after switching the motor drive control is greater than the magnitude of the torque generated in the rotor by the last supplied drive current before switching the motor drive control. This is because the magnitude of the torque may be smaller. Therefore, if the switching threshold ωth is set to the smallest rotational speed among the rotational speeds at which the rotational phase can be accurately estimated (hereinafter referred to as the estimable speed), when the rotational speed momentarily decreases at the time of control switching, , the motor control by vector control becomes unstable. Therefore, it is effective to set the switching threshold ωth to a rotational speed higher than the estimable speed in consideration of the decrease in rotational speed.

As shown in FIG. 3 , the CPU 151 a outputs the command speed ω_ref of the rotor of the motor 509 to the control switcher 515 and the abnormality determination device (abnormality determination means) 519 .

A control switch 515 compares the switching threshold ωth with the command speed ω_ref. Note that the switching threshold ωth is stored in advance in a ROM or the like provided in the control switching device 520 . Further, in the present embodiment, the value of the switching threshold ωth is set to 3 rps, but it is not limited to this, and any rotation speed that allows accurate estimation of the rotation phase of the rotor may be used.

During control by the constant current controller 517 , when the command speed ω_ref becomes equal to or greater than the switching threshold ωth (ω_ref≧ωth), the control switcher 515 switches the controller that controls the drive of the motor 509 . That is, the control switcher 515 controls the states of the switches 516 a , 516 b , 516 c so as to switch the controller for controlling the drive of the motor 509 from the constant current controller 517 to the vector controller 518 . As a result, vector control is performed by the vector controller 518 .

Also, during control by the constant current controller 517 , when the command speed ω_ref is smaller than the switching threshold ωth (ω_ref<ωth), the control switcher 515 does not switch the controller that controls the drive of the motor 509 . In other words, the control switcher 515 controls the states of the switches 516a, 516b, and 516c so that the driving of the motor 509 is maintained under the control of the constant current controller 517. FIG. As a result, constant current control by the constant current controller 517 is continued.

During control by the vector controller 518 , when the command speed ω_ref becomes smaller than the switching threshold ωth (ω_ref<ωth), the control switcher 515 switches the controller that controls driving of the motor 509 . That is, the control switcher 515 controls the states of the switches 516 a , 516 b , 516 c so as to switch the controller for controlling 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 .

Also, during control by the vector controller 518 , when the command speed ω_ref is equal to or greater than the switching threshold ωth (ω_ref≧ωth), the control switcher 515 does not switch the controller that controls the drive of the motor 509 . That is, the control switcher 515 controls the states of the switches 516a, 516b, and 516c so that the driving of the motor 509 is maintained under the control of the vector controller 518. FIG. As a result, vector control by vector controller 518 continues. In this embodiment, the control is switched based on the command speed ω_ref output from the CPU 151a, but this is not the only option. For example, the speed estimator calculates the command speed ω_ref of the rotor of the motor 509 based on the time change of the command value θ_ref output from the CPU 151a. The control may be switched based on the command speed ω_ref calculated by the speed estimator. Note that equation (10) is used for the calculation.

Further, in the present embodiment, when determining whether to switch the motor drive control from constant current control to vector control, the rotation command speed ω_ref and the switching threshold ωth are compared. It may be the rotation speed ω. For example, the rotation speed ω of the rotor may be estimated using equation (10) based on the time change of the rotation phase θ output from the phase estimator, and the rotation speed ω may be compared with the switching threshold ωth. good.

Next, constant current control will be described with reference to FIG. Constant current control is a control method for controlling the motor by controlling the drive current so that the magnitude of the drive current supplied to the windings of the motor is constant. In constant current control, neither the phase feedback control nor the speed feedback control is performed.

The CPU 151 a outputs the command phase θ_ref to the constant current controller 517 provided in the motor control device 157 . The constant current controller 517 generates and outputs current command values iα_ref and iβ_ref in the stationary coordinate system corresponding to the command phase θ_ref output from the CPU 151a. In this embodiment, the command phase θ_ref is used when performing constant current control, but this is not the only option. For example, the command speed ω_ref is output to a constant current controller, and the constant current controller generates and outputs current command values iα_ref and iβ_ref in the stationary coordinate system corresponding to the command speed ω_ref. Also good.

Next, current detectors 507 and 508 detect drive currents flowing through the A-phase and B-phase windings of the motor 509 . The detected drive currents are then converted from analog to digital values by A/D converter 510 and represented as current values iα and iβ as in equations (1) and (2). The current controller 503 receives 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. The current controller 503 generates iα' and iβ' so as to reduce the deviation, and outputs drive voltages Vα and Vβ corresponding to the respective current values iα' and iβ'. Specifically, iα' and iβ' are generated so that the deviation approaches 0, respectively, and drive voltages Vα and Vβ corresponding to the respective current values iα' and iβ' are output. 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 the drive current to each phase winding of the motor 509 in the manner described above to drive the motor 509. .

As described above, in the control of the motor 509 by the motor control device 157 in this embodiment, there are a period during which the constant current control is performed and a period during which the vector control is performed. In constant current control, the drive current supplied to the windings of the motor cannot be controlled according to the actual rotation of the rotor. The output torque may be exceeded and the motor may go out of step. If the motor continues to be driven while the motor is out of step, problems such as abnormal noise may occur from the motor. Therefore, there is a demand for a configuration that can accurately determine out-of-step in constant current control. In this embodiment, it is assumed that the circuit that performs vector control is in operation even when constant current control is being performed. In other words, it is assumed that the circuit for estimating the rotor phase θ and the rotation speed ω is in operation even when the constant current control is being performed. It is also assumed that the circuit that performs constant current control is in operation even when vector control is being performed.

As shown in FIG. 3, the motor control device 157 in this embodiment is provided with an abnormality determiner 519 as a configuration for determining whether or not the rotation of the motor is abnormal. In this embodiment, the abnormality determiner 519 determines whether the motor is out of step. In this embodiment, the abnormality determiner is provided inside the motor control device, but it is not limited to this. For example, it may be provided outside the motor control device. Rotational anomaly is not limited to step-out, but also includes locking of the rotor due to an external force or a decrease in rotational speed.

The command speed ω_ref output from the CPU 151 a and the rotation speed ω output from the speed estimator 514 are input to the abnormality determiner 519 . The abnormality determiner 519 determines whether or not the motor is out of step based on the command speed ω_ref and the rotation speed ω, and outputs a stop signal to the CPU 151a based on the determination result. The stop signal is a signal that determines the operation/stop of the motor control device. When the stop signal is 'H (high level)', the CPU 151a stops the motor control device. That is, the motor is stopped. Further, when the stop signal is 'L (low level)', the operation of the motor control device is continued. That is, the motor continues to be driven.

In order to accurately determine out-of-step, it is necessary to accurately estimate the rotational speed ω. That is, it is necessary to accurately estimate the rotational phase. In the present embodiment, a step-out determination threshold ωsnl, which is a rotational speed threshold for performing step-out determination, is set to the estimable speed. That is, the step-out determination threshold ωsnl is set to a value equal to or lower than the switching threshold ωth. As a result, even in a state in which constant current control is being performed, step-out determination can be performed if the rotation speed ω is equal to or greater than the threshold value ωsnl.

An abnormality determiner 519 compares the command speed ω_ref with a step-out determination threshold ωsnl. Note that the step-out determination threshold value ωsnl is stored in advance in a ROM or the like provided in the abnormality determination device 519 . The abnormality determiner 519 does not perform step-out determination when the command speed ω_ref is smaller than the step-out determination threshold value ωsnl (ω_ref<ωsnl), and when the command speed ω_ref is equal to or greater than the step-out determination threshold value ωsnl (ω_ref≧ωsnl). Step-out judgment is performed.

Next, the method by which the abnormality determiner 519 detects motor out-of-step will be described with reference to FIG.

FIG. 6 is a diagram for explaining a method for determining out-of-step in this embodiment. As described above, the command speed ω_ref and the actual rotation speed ω of the rotor 402 are used in the step-out determination of the present embodiment. Specifically, when the value obtained by dividing the deviation between the command speed ω_ref and the rotational speed ω by the command speed ω_ref (hereinafter referred to as Δ) is within a predetermined range, the abnormality determiner 519 outputs the stop signal ' L' is output to the CPU 151a. When the value of .DELTA. is not within the predetermined range, the abnormality determiner 519 determines that the motor is out of step, and outputs a stop signal 'H' to the CPU 151a. In the present embodiment, when Δ is not within the predetermined range, the abnormality determiner 519 determines that the motor is out of step, but this is not the case. For example, the abnormality determiner 519 may determine that the motor is out of step when the Δ is not within a predetermined range for a predetermined period of time. That is, even if the value of .DELTA. is out of the predetermined range, if the value of .DELTA. The configuration may be such that it does not. In addition, in the present embodiment, Δ is set to a value within the predetermined range from -0.2 to +0.2, but this is not the only option. Further, in the present embodiment, step-out determination is performed based on a value obtained by dividing the deviation between the command speed ω_ref and the rotational speed ω by the command speed ω_ref, but this is not the only option. For example, step-out determination may be performed based on the deviation between the command speed ω_ref and the rotational speed ω. Furthermore, in the present embodiment, the step-out determination is performed based on the command speed ω_ref and the rotation speed ω, but the present invention is not limited to this, and for example, the step-out determination is performed based only on the rotation speed ω. It may be a configuration.

FIG. 7 is a flow chart showing a motor drive control method using the motor control device 157 . Drive control of the motor 509 in this embodiment will be described below with reference to FIG. The processing of this flow chart is executed by the motor control device 157 that receives an instruction from the CPU 151a.

First, the CPU 151a outputs an enable signal 'H' to the motor control device 157, and the motor control device 157 starts drive control of the motor 509 based on the command output from the CPU 151a. The enable signal is a signal that permits or prohibits operation of the motor control device 157 . When the enable signal is 'L (low level)', the CPU 151a prohibits the motor control device 157 from operating. That is, the control of the motor 509 by the motor control device 157 ends. 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 the command output from the CPU 151a. conduct.

Next, in S1001, the control switcher 515 controls the states of the switches 516a, 516b, and 516c so that the driving of the motor 509 is controlled by the constant current controller 517. FIG. 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 finishes driving the motor 509. FIG.

If the CPU 151a outputs the enable signal 'H' to the motor control device 157 in S1002, the motor control device 157 advances the process to S1003.

In S1003, if the command speed ω_ref is smaller than the step-out determination threshold value ωsnl, the process returns to S1001 and the constant current control by the constant current controller 517 is continued.

In S1003, if the command speed ω_ref is equal to or greater than the out-of-step determination threshold value ωsnl, in S1004, the abnormality determiner 519 performs out-of-step determination by the method described above, and the motor control device 157 advances the process to S1005. .

In S<b>1005 , when the abnormality determiner 519 outputs the stop signal “H” to the CPU 151 a, the CPU 151 a outputs the enable signal “L” to the motor control device 157 . As a result, the motor controller 157 stops driving the motor 509 .

Also, in S1005, when the abnormality determiner 519 outputs the stop signal 'L' to the CPU 151a, the motor control device 157 advances the process to S1006.

If the command speed ω_ref is equal to or greater than the switching threshold ωth in S1006, the control switcher 515 switches the controller that controls driving of the motor 509 in S1007. That is, the control switcher 515 controls the states of the switches 516 a , 516 b , 516 c so as to switch the controller for controlling the drive of the motor 509 from the constant current controller 517 to the vector controller 518 . As a result, vector control is performed by the vector controller 518 . After that, the process returns to S1002 again.

Also, in S1006, if the command speed ω_ref is smaller than the switching threshold ωth, the process returns to S1001 and the constant current control by the constant current controller 517 is continued.

After that, until the CPU 151 a outputs the enable signal 'L' to the motor control device 157 , the motor control device 157 repeats the control described above to control the driving of the motor 509 .

FIG. 8 is a flowchart showing a step-out determination method for motor 509 using abnormality determiner 519 . A method for determining out-of-step in this embodiment will be described below with reference to FIG. The processing of this flowchart is executed by the abnormality determiner 519 .

First, in S2001, the abnormality determiner 519 calculates the Δ and advances the process to S2002.

is within the predetermined range in S2002, the abnormality determiner 519 outputs a stop signal 'L' to the CPU 151a in S2003. In S2002, if .DELTA. is out of the predetermined range, in S2004, the abnormality determiner 519 outputs a stop signal 'H' to the CPU 151a.

After that, the abnormality determiner 519 repeats the above-described method every time the out-of-step determination is performed. It is assumed that the stop signal 'L' is output to the CPU 151a during the period from the start of motor drive control to the determination of out-of-step.

As described above, in the present embodiment, the step-out determination threshold value ωsnl is set to the estimable speed. That is, the step-out determination threshold ωsnl is set to be equal to or less than the switching threshold ωth. As a result, step-out determination can be started as early as possible. Specifically, step-out determination can be performed with high accuracy even in a state where constant current control is being performed. In addition, by configuring the motor to stop when the motor is out of synchronism, it is possible to prevent abnormal noise from being generated from the motor due to an attempt to drive the motor in the state of the motor being out of synchronism. can be suppressed. Furthermore, since step-out determination is performed even during vector control, the motor can be stopped even if the motor steps out during vector control due to a sudden load change or the like. That is, it is possible to suppress the generation of abnormal noise from the motor caused by trying to drive the motor when the motor is out of step.

Note that the vector control in this embodiment uses a rotational coordinate system based on the estimated value of the rotational phase θ of the rotor 402, but is not limited to this. For example, a rotating coordinate system based on the command phase θ_ref may be used. Moreover, the estimation of the rotation speed ω and the rotation command speed ω_ref is not limited to using the equation (10). For example, the drive current flowing in the A-phase (or B-phase) winding of the motor 509, the A-phase (or B-phase) drive voltage, the induced voltage generated in the A-phase (or B-phase) winding, etc. Detects a periodic signal that correlates with the rotation period of the The rotation speed ω and the rotation command speed ω_ref may be estimated by detecting the period in which the magnitude of the signal becomes zero. Furthermore, in the present embodiment, step-out determination is performed based on the rotation speed of the rotor, but this is not the only option. For example, out-of-step determination may be performed based on the rotational phase of the rotor.

151a CPU
157 Motor control device 402 Rotor 506 PWM inverter 507, 508 Current detector 509 Stepping motor 513 Phase estimator 514 Speed estimator 517 Constant current controller 519 Abnormality determiner

Claims (19)

In a motor control device that accelerates a rotor of a motor to a predetermined speed,
detection means for detecting a drive current flowing through the windings of the motor ;
speed determining means for determining the rotation speed of the rotor of the motor based on the drive current detected by the detecting means;
phase determining means for determining a rotational phase of the rotor;
a first control mode for controlling the drive current flowing through the winding by supplying a constant current to the winding; a second control mode that performs vector control for controlling the drive current flowing through the windings based on the current component of the value , wherein the rotational speed of the rotor in a state in which the first control mode is executed; changes from a value smaller than the first threshold value to a value larger than the first threshold value, the control mode for controlling the drive current flowing through the winding is changed from the first control mode to the first control mode. a control means for switching to control mode 2 ;
has
The speed determining means controls the speed of the rotor when the control means is in the first control mode and the value corresponding to the rotational speed of the rotor is greater than a second threshold smaller than the first threshold. determining the rotational speed of the rotor in a state in which the control means performs the first control mode and the value corresponding to the rotational speed of the rotor is smaller than the second threshold value; figure,
The motor control device , wherein the first threshold value and the second threshold value are values smaller than a value corresponding to the predetermined speed . The motor controller controls the rotational speed determined by the speed determining means when the control means performs the first control mode and the value corresponding to the rotational speed of the rotor is greater than the second threshold value. 2. The motor control device according to claim 1, further comprising a determination means for determining whether or not the rotation of said motor is abnormal based on the above. 3. The motor control device according to claim 2, wherein the abnormality corresponds to a reduction in rotational speed of the rotor. The judging means judges whether or not the rotation of the motor is abnormal based on the speed representing the target speed of the rotor and the rotational speed determined by the speed determining means. 4. A motor control device according to item 2 or 3 . The second control mode is a control mode for controlling the drive current flowing through the windings so as to reduce the deviation between the command speed representing the target speed of the rotor and the rotation speed determined by the speed determining means. 5. The motor control device according to any one of claims 1 to 4 , characterized in that: The second control mode is a control mode for controlling the drive current flowing through the windings so as to reduce the deviation between the command phase representing the target phase of the rotor and the rotational phase determined by the phase determining means. 5. The motor control device according to any one of claims 1 to 4 , characterized in that: 7. The motor control device according to claim 1 , wherein the value corresponding to the rotation speed of the rotor is a speed representing a target speed of the rotor. 7. The motor control device according to claim 1 , wherein the value corresponding to the rotation speed of the rotor is the rotation speed determined by the speed determining means. The motor control device has induced voltage determination means for determining an induced voltage induced in the winding by the rotation of the rotor based on the drive current detected by the detection means,
9. The rotational speed of the rotor according to claim 1 , wherein the speed determining means determines the rotational speed of the rotor based on the value of the induced voltage determined by the induced voltage determining means. motor controller. In a motor control device that accelerates a rotor of a motor to a predetermined speed,
detection means for detecting a drive current flowing through the windings of the motor ;
phase determination means for determining a rotation phase of a rotor of the motor based on the drive current detected by the detection means;
a first control mode for controlling the drive current flowing through the winding by supplying a constant current to the winding; a second control mode that performs vector control for controlling the drive current flowing through the windings based on the current component of the value , wherein the rotational speed of the rotor in a state in which the first control mode is executed; changes from a value smaller than the first threshold value to a value larger than the first threshold value, the control mode for controlling the drive current flowing through the winding is changed from the first control mode to the first control mode. a control means for switching to control mode 2 ;
has
The phase determining means controls the phase of the rotor when the control means is in the first control mode and the value corresponding to the rotational speed of the rotor is greater than a second threshold smaller than the first threshold. A rotational phase is determined, and the rotational phase of the rotor is not determined in a state in which the control means performs the first control mode and a value corresponding to the rotational speed of the rotor is smaller than the second threshold value. ,
The motor control device , wherein the first threshold and the second threshold are values smaller than a value corresponding to the predetermined speed . The motor controller controls the rotational phase determined by the phase determination means when the control means performs the first control mode and the value corresponding to the rotational speed of the rotor is greater than the second threshold value. 11. The motor control device according to claim 10, further comprising a determination means for determining whether or not the rotation of said motor is abnormal based on the above. 12. The motor control device according to claim 11, wherein the abnormality corresponds to a decrease in rotation speed of the rotor. The motor control device has speed determination means for determining the rotational speed of the rotor,
The second control mode is a control mode for controlling the drive current flowing through the windings so as to reduce the deviation between the command speed representing the target speed of the rotor and the rotation speed determined by the speed determining means. 13. The motor control device according to any one of claims 10 to 12 , characterized in that: The second control mode is a control mode for controlling the drive current flowing through the windings so as to reduce the deviation between the command phase representing the target phase of the rotor and the rotational phase determined by the phase determining means. 13. The motor control device according to any one of claims 10 to 12 , characterized in that: 15. The motor control device according to any one of claims 10 to 14 , wherein the value corresponding to the rotation speed of the rotor is a speed representing a target speed of the rotor. The motor control device has speed determination means for determining the rotational speed of the rotor,
14. The motor control device according to any one of claims 10 to 13 , wherein the value corresponding to the rotation speed of the rotor is the rotation speed determined by the speed determining means. The motor control device has induced voltage determination means for determining an induced voltage induced in the winding by the rotation of the rotor based on the drive current detected by the detection means,
17. The phase determining means according to any one of claims 10 to 16, wherein the phase determining means determines the rotational phase of the rotor based on the value of the induced voltage determined by the induced voltage determining means. A motor controller as described. a conveying unit that conveys the sheet;
a motor that drives the conveying unit;
a motor control device according to any one of claims 1 to 17 ;
has
The sheet conveying apparatus, wherein the motor control device controls driving of a motor that drives the conveying section. an image forming means for forming an image on a recording medium;
a motor for driving a load;
18. The motor control device according to any one of claims 1 to 17 , wherein the motor control device controls a motor that drives the load;
An image forming apparatus comprising:

Images