Motor control device and image forming apparatus

Abstract

To provide a motor control technique to prevent a failure in starting a motor.SOLUTION: A motor control unit comprises: a motor; a transmission mechanism that transmits a driving force of the motor to a load of the motor; and control means that, when stopping the motor rotated at a first speed, reduces the speed of the motor at least at a first deceleration in a first period during which the rotation speed of the motor is decreased from the first speed to a second speed lower than the first speed, and reduces the speed of the motor at least at a second deceleration in a second period from the second speed to stoppage of the motor. The second deceleration is smaller than the first deceleration.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a motor control technique. [Background technology]

[0002] Image forming apparatuses use sensorless motors (hereinafter referred to as sensorless motors) as their drive sources. When starting a sensorless motor, a motor control device first detects the rotor's stop position (rotational phase of the stopped rotor) using a predetermined method. Patent Document 1 discloses a configuration for detecting the rotor's stop position by utilizing the characteristic that the inductance value of the motor's coil changes depending on the rotor's stop position. The motor control device starts driving the motor using forced commutation control based on the detected rotor stop position. When the rotor's rotational speed reaches a predetermined speed or higher, the motor control device can detect the rotor's rotational position and rotational speed based on the induced voltage generated in the coil, as described in Patent Document 2. Therefore, after the rotor's rotational speed reaches a predetermined speed or higher, the motor control device switches from forced commutation control to sensorless control, which controls rotor rotation based on the induced voltage generated in the coil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-104263 [Patent Document 2] Japanese Patent Application Publication No. 8-223970 Summary of the Invention [Problem to be solved by the invention]

[0004] The driving force of a motor is transmitted to a load via a drive transmission mechanism that includes a gear train. Gear trains generally have a certain amount of play, so when the motor is stopped, it may rotate in the opposite direction to the direction of rotation of the motor when it is operating, within the range of the play provided in the gear train. If the motor starts rotating in this state, a time lag occurs between the start of motor rotation and the transmission of the motor's driving force to the load, resulting in a large load fluctuation when the motor's driving force is transmitted to the load. This load fluctuation can cause the motor to malfunction, such as losing synchronization.

[0005] The present invention provides a motor control technique that suppresses motor start-up failures. [Means for solving the problem]

[0006] According to one aspect of the present invention, a motor control device includes a motor, a transmission mechanism that transmits a driving force of the motor to a load of the motor, and a control circuit that, when stopping the motor rotating at a first speed, decelerates the motor at at least a first deceleration during a first period until the rotational speed of the motor is decelerated from the first speed to a second speed lower than the first speed, and decelerates the motor at at least a first deceleration during a second period until the rotational speed of the motor is decelerated from the second speed to a second speed lower than the first speed. smaller than the first deceleration and control means for decelerating the motor at a second deceleration rate; the control means performs a first control on the motor based on an induced voltage generated in the motor when the rotation speed of the motor is higher than a threshold value, and performs a second control, which is a forced commutation control, on the motor when the rotation speed of the motor is lower than the threshold value, the first speed being higher than the threshold value and the second speed being lower than the threshold value; It is characterized by: [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress starting failure of the motor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment. [Figure 2] FIG. 2 is a configuration diagram of a motor control unit according to an embodiment. [Figure 3] FIG. 1 is a diagram illustrating the configuration of a motor according to an embodiment. [Figure 4] FIG. 2 is a functional block diagram of a microcomputer during forced commutation control according to an embodiment. [Figure 5] FIG. 2 is a functional block diagram of a microcomputer during sensorless control according to an embodiment. [Figure 6] FIG. 2 is an explanatory diagram of a drive transmission mechanism of a motor according to an embodiment. [Figure 7] 10 is an explanatory diagram of why a startup failure occurs. [Figure 8] FIG. 4 is an explanatory diagram of a motor stop process according to an embodiment. [Figure 9] 10 is a flowchart of a motor stopping process according to an embodiment. [Figure 10] FIG. 2 is a diagram illustrating the configuration of a fixing unit according to an embodiment. [Figure 11] FIG. 2 is a diagram illustrating a drive configuration of a motor according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] First Embodiment FIG. 1 is a diagram illustrating the configuration of a tandem-type color image forming apparatus using an electrophotographic process according to this embodiment. In FIG. 1, the letters Y, M, C, and K at the end of a reference number indicate the color of the toner image formed by the component designated by the reference number: yellow, magenta, cyan, and black, respectively. Note that when it is not necessary to distinguish the color of the toner image formed by the component, the reference number is used without the letter at the end. The image forming apparatus includes cartridges 12. The cartridges 12 are replaceable parts for the image forming apparatus and are configured to be detachable from the main body of the image forming apparatus. Each cartridge 12 has the same configuration, including a photoconductor 13, a charging roller 15, a developing roller 16, and a cleaning blade 14, and contains toner of the corresponding color.

[0011] During image formation, the photoconductors 13 are rotated clockwise in the figure. The charging rollers 15 charge the surfaces of the corresponding photoconductors 13. The scanning unit 11 scans and exposes the surfaces of the photoconductors 13 of the corresponding cartridges 12 with light based on image data, forming electrostatic latent images on the photoconductors 13. The developing rollers 16 output a development voltage to develop the electrostatic latent images on the corresponding photoconductors 13 with toner, thereby forming toner images on the corresponding photoconductors 13. The primary transfer rollers 18 output a primary transfer voltage to transfer the toner images on the corresponding photoconductors 13 to the intermediate transfer belt 19. The cleaning blade 14 removes toner remaining on the photoconductors 13 that was not transferred to the intermediate transfer belt 19. By transferring the toner images on the photoconductors 13 of the respective cartridges 12 onto the intermediate transfer belt 19 in layers, it is possible to reproduce colors different from yellow, magenta, cyan, and black. The intermediate transfer belt 19 is rotated counterclockwise in the figure during image formation. As a result, the toner image on the intermediate transfer belt 19 is conveyed to a position facing the secondary transfer roller 29 .

[0012] Meanwhile, the sheet 21 stored in the cassette 22 is fed to the conveying path by a feed roller 25. Separation rollers 26a and 26b are provided to prevent double feeding of sheets. The sheet 21 fed to the conveying path is transported by a registration roller 27 to a position facing a secondary transfer roller 29. The secondary transfer roller 29 outputs a secondary transfer voltage to transfer the toner image on the intermediate transfer belt 19 to the sheet 21. The sheet 21 is then transported to a fixing unit 30. The fixing unit 30 has a pressure roller and a heating roller (heating film), and fixes the toner image to the sheet 21 by applying pressure and heat to the sheet 21. After the toner image is fixed, the sheet 21 is discharged outside the image forming apparatus.

[0013] The printer control unit 107 has a CPU (Central Processing Unit) 32 and controls the entire image forming apparatus. The printer control unit 107 has a non-volatile memory 32a that stores control programs executed by the CPU 32 and control data used by the CPU 32 to control the image forming apparatus. The printer control unit 107 also has a volatile memory 32b that the CPU 32 uses as a work area when controlling the image forming apparatus. The image forming apparatus also has one or more sensorless motors (not shown in FIG. 1) for driving rollers for conveying the sheet 21, such as the photoconductor 13, the intermediate transfer belt 19, the developing roller 16, the pressure roller of the fixing unit 30, and the registration roller 27. In the following description, the sensorless motor will be simply referred to as a "motor."

[0014] 2 shows the control configuration of the motor 103 provided in the image forming apparatus. The motor control unit 110 communicates with the printer control unit 107 and controls the motor 103 under the control of the printer control unit 107. The nonvolatile memory 205 of the microcomputer (MCU) 201 stores programs executed by the MCU 201 and various data used to control the motor 103. The memory 207 is used by the MCU 201 for temporary data storage. The PWM port 208 has a total of six terminals for outputting two PWM signals (high side, low side) for each of the three phases (U, V, W) of the motor 103. That is, the PWM port 208 has three high-side terminals (UH, VH, WH) and three low-side terminals (UL, VL, WL).

[0015] The inverter 211 has high-side switching elements M1, M3, and M5 and low-side switching elements M2, M4, and M6 for each of the three phases of the motor 103. In FIG. 2, M1 and M2 are U-phase switching elements, M3 and M4 are V-phase switching elements, and M5 and M6 are W-phase switching elements. The switching elements may be, for example, transistors or FETs. The gate driver 210 controls the ON / OFF of the corresponding switching element based on a PWM signal from the PWM port 208. For example, the gate driver 210 controls the ON / OFF of the switching element M1 by controlling the voltage applied to the gate G1 of the switching element M1 based on the PWM signal output from the UH terminal.

[0016] The U-, V-, and W-phase outputs 217 of the inverter 211 are connected to coils 213 (U-phase), 214 (V-phase), and 215 (W-phase) of the motor 103. By controlling the ON / OFF of each switching element, the coil current flowing through each of the coils 213, 214, and 215 can be controlled. In this manner, the inverter 211 functions as a current supply unit that supplies the coil current to each of the coils 213, 214, and 215. The coil current flowing through each of the coils 213, 214, and 215 is converted into a voltage by current detection resistors 219, 220, and 221. An amplifier 218 amplifies the voltage of the current detection resistors 219, 220, and 221, which corresponds to the coil current, and outputs the amplified voltage to an AD converter 203 of the microcomputer 201. The AD converter 203 converts the voltage output by the amplifier 218 into a digital value. The current value calculation unit 209 determines the current value of the coil current of each phase based on the digital value output by the AD converter 203 .

[0017] FIG. 3 is a configuration diagram of the motor 103. The motor 103 has a six-slot stator 501 and a four-pole rotor 502. The stator 501 has a U-phase coil 213, a V-phase coil 214, and a W-phase coil 215. The rotor 502 is formed of a permanent magnet. The rotational phase of the rotor 502 is defined based on a state in which the rotor 502 is in a predetermined state. As an example, as shown in FIG. 3, the state in which the south pole of the rotor 502 faces the U-phase coil 213 is defined as a reference, that is, an electrical angle of 0, and the electrical angle can be defined as increasing in the counterclockwise direction. In this embodiment, the number of poles of the rotor 502 is four, so when the rotor rotates counterclockwise by a mechanical angle of π / 2 from the state in FIG. 3, the electrical angle becomes π.

[0018] 4 is a functional block diagram of the microcomputer 201 during forced commutation control. In this embodiment, the microcomputer 201 performs vector control of the motor 103. The current control unit 302 acquires an excitation current command value Id_ref and a torque current command value Iq_ref, which are pre-stored in the nonvolatile memory 205. The current control unit 302 also receives a measured excitation current value Id and a measured torque current value Iq from the coordinate conversion unit 306. The excitation current is a component of the coil current that contributes to the generation of magnetic flux, and the torque current is a component of the coil current that contributes to output torque. Based on these values, the current control unit 302 outputs voltage command values ​​Vd_ref and Vq_ref in a rotating coordinate system. The coordinate conversion unit 305 performs coordinate conversion from the rotating coordinate system to a stationary coordinate system, and further performs two-phase-to-three-phase conversion to generate and output voltage command values ​​Vu, Vv, and Vw for the U-phase, V-phase, and W-phase from the voltage command values ​​Vd_ref and Vq_ref. Note that the coordinate conversion from the rotating coordinate system to the stationary coordinate system is performed based on the electrical angle θ_ref output from the angle calculation unit 303. The microcomputer 201 generates PWM signals to be output to the gate driver 210 based on the voltage command values ​​Vu, Vv, and Vw.

[0019] Furthermore, the current values ​​Iu, Iv, and Iw of the coil currents of the U phase, V phase, and W phase detected by the current value calculation unit 209 based on the output of the amplifier 218 are input to a coordinate conversion unit 306. The coordinate conversion unit 306 converts the current values ​​Iu, Iv, and Iw into current values ​​in a stationary coordinate system by three-phase-two-phase conversion, and further performs coordinate conversion from the stationary coordinate system to a rotating coordinate system to obtain a measured value Id of the excitation component current and a measured value Iq of the torque component current. The coordinate conversion from the stationary coordinate system to the rotating coordinate system is performed based on the electrical angle θ_ref output from the angle calculation unit 303. The coordinate conversion unit 306 outputs the measured value Id of the excitation component current and the measured value Iq of the torque component current to the current control unit 302.

[0020] When the motor 103 is started, the detection unit 301 determines the initial phase of the rotor 502, i.e., the electrical angle at the time of stopping (hereinafter referred to as the stop angle) θ_std. The detection of the electrical angle at the time of stopping the rotor 502 can be performed using, for example, the configuration described in Patent Document 1. In this case, the detection unit 301 detects the stop angle θ_std by detecting the inductance of each of the coils 213, 214, and 215 based on the current values ​​Iu, Iv, and Iw. The detection unit 301 outputs the detected stop angle θ_std to the subtractor 307. The offset setting unit 304 outputs the offset amount Δ stored in the nonvolatile memory 205 to the subtractor 307. The subtractor 307 outputs the electrical angle obtained by subtracting the offset amount Δ from the stop angle θ_std as the initial angle θ_ini to the angle calculation unit 303. Note that the electrical angle obtained by subtracting the offset amount Δ from the stop angle θ_std is set as the initial angle θ_ini in order to prevent loss of synchronism during start-up.

[0021] The angle calculation unit 303 calculates the electrical angle θ_ref of the rotor 502 based on the initial angle θ_ini and the speed command value ω_ref input from the printer control unit 107, and notifies the coordinate conversion units 305 and 306. Specifically, the angle calculation unit 303 calculates the electrical angle θ_ref of the rotor 502 by setting the initial angle θ_ini as an initial value and increasing the electrical angle based on the speed command value ω_ref.

[0022] FIG. 5 is a functional block diagram of the microcomputer 201 during sensorless control. The following description will focus on differences from the functional block diagram during forced commutation control shown in FIG. 4. An estimator 801 estimates the electrical angle θ_est and rotational speed ω_est of the rotor 502 based on the current values ​​Iu, Iv, and Iw, voltage command values ​​Vd_ref and Vq_ref, and the estimated rotational speed ω_est. The estimated electrical angle θ_est is used for coordinate conversion in the coordinate converters 305 and 306, as in the case of forced commutation control. Furthermore, a speed controller 802 calculates a command value Iq_ref for causing the rotational speed ω_est to follow the speed command value ω_ref, based on the speed command value ω_ref from the printer controller 107 and the rotational speed ω_est estimated by the estimator 801. Unlike the forced commutation control, the speed control unit 802 calculates the command value Iq_ref and outputs it to the current control unit 302, so the current control unit 302 obtains only the command value Id_ref from the nonvolatile memory 205 and uses it.

[0023] FIG. 6 shows a drive transmission mechanism that transmits the driving force of the motor 103 to the photosensitive member 13, which is a load. FIGS. 6A and 6B show a state in which the motor 103 is driving the photosensitive member 13 to rotate. Note that FIG. 6A is an enlarged view of a portion of FIG. 6B. The motor 103 is connected to a gear 131. The gear 131 transmits the driving force of the motor 103 to a coupling 132. The coupling 132 is attached to the rotation shaft of the photosensitive member 13, and the driving force transmitted to the coupling 132 is also transmitted to the photosensitive member 13. The driving force transmitted to the coupling 132 is also transmitted to a torque limiter 133. The torque limiter 133 contains a spring, which is an elastic member, and when the spring compresses, a predetermined load is applied to the motor 103. Torque limiter 133 is provided to increase the load (photoconductor 13 in this example) of motor 103 when the load is light, thereby stably rotating the load. As shown in Fig. 6(B), gear 131, coupling 132, and torque limiter 133 are arranged coaxially, and the driving force of motor 103 is transmitted in the clockwise direction in the figure through gear 131, coupling 132, and torque limiter 133 in that order.

[0024] 6(C) and 6(D) show a state in which the motor 103 is stopped. Note that FIG. 6(C) is an enlarged view of a portion of FIG. 6(D). When the motor 103 stops, the spring of the torque limiter 133, which had contracted during rotation, is released. With the torque limiter spring released, the coupling 132 and the gear 131 are pushed by the torque limiter 133 in the direction opposite to the rotation direction of the photosensitive member 13 (to the left in FIG. 6(C) and counterclockwise in FIG. 6(D)). This causes the motor 103 to rotate (reversely rotate) in the direction opposite to the direction in which the photosensitive member 13 is rotated. Note that the amount by which the gear 131 can reversely rotate is equal to or less than the amount of "play" that exists between the gear 131 and the coupling 132. The stronger the spring pressure of the torque limiter 133, the greater the amount by which the gear 131 reversely rotates. Since the photosensitive member 13, which is a load, is connected to the coupling 132, the coupling 132 hardly rotates in the reverse direction, as shown in FIG. 6(D).

[0025] FIG. 7A shows the speed change of the motor 103 when the motor 103 is started. When the motor 103 is started, it is subjected to forced commutation control. Then, when the speed command value ω_ref (FIG. 4) reaches a predetermined threshold, it is rotated and driven under sensorless control. As shown in FIGS. 6A and 6B, when the motor 103 is started in a state where there is no play between the motor 103 and the photosensitive drum 13, the rotation speed of the photosensitive drum 13 changes in the same manner as the motor 103, although at a certain rate depending on the reduction ratio.

[0026] On the other hand, as shown in Figures 6(C) and 6(D), when the motor 103 is started while there is play between the motor 103 and the photosensitive drum 13, the driving force of the motor 103 is not transmitted to the photosensitive drum 13 until there is no play. Then, when there is no play, the rotation speed of the photosensitive drum 13 rises sharply according to the speed of the motor 103 at that time. Figure 7(B) shows the state in which the rotation speed of the photosensitive drum 13 rises sharply at timing T1. At this time, the load on the motor 103 fluctuates greatly, and the motor 103 may lose synchronization.

[0027] As explained with reference to FIG. 6, the spring of the torque limiter 133 rotates while contracting during rotation of the motor 103. When the motor 103 stops, the energy stored in the spring of the torque limiter 133 during rotation acts in a direction that releases the spring, causing the motor 103 to rotate in the reverse direction. Therefore, by reducing the energy stored in the spring while the photoconductor 13 is rotating, the amount of reverse rotation of the motor 103 when the motor 103 is stopped can be reduced. For this reason, in this embodiment, when stopping the rotation of the motor 103, the motor 103 is rotated for a predetermined time at a rotation speed (hereinafter referred to as the stop preparation speed) that is lower than the rotation speed of the motor 103 when rotating the photoconductor 13 for image formation (hereinafter referred to as the steady speed). This will be explained in detail below with reference to FIG. 8.

[0028] FIG. 8 shows the speed change of the motor 103 when the motor is stopped according to this embodiment. First, the motor 103 rotates at a steady speed A. The steady speed A is, for example, approximately 500 rpm to 2500 rpm. While the motor 103 is rotating at the steady speed A, a large amount of energy is stored in the spring of the torque limiter 133. When stopping the motor 103, the printer control unit 107 first decelerates the speed of the motor 103 to a stop preparation speed B. Note that in this embodiment, the stop preparation speed B is lower than the threshold for switching between sensorless control and forced commutation control, so the motor control unit 110 switches from sensorless control to forced commutation control during the deceleration. The stop preparation speed B can be, for example, greater than 0 and equal to or less than 100 rpm. As an example, the stop preparation speed B can be set to 5 rpm or a value close to that. By rotating the motor 103 at the stop preparation speed B for a predetermined time, part of the energy stored in the spring of the torque limiter 133 is released, reducing the spring energy. Printer control unit 107 rotates motor 103 at stop preparation speed B for a predetermined time, and then stops motor 103. At this time, the spring of torque limiter 133 stores only energy equivalent to stop preparation speed B, so the amount by which motor 103 rotates in the reverse direction after motor 103 has stopped can be reduced.

[0029] FIG. 9 is a flowchart of the process for stopping the motor 103 according to this embodiment. At the start of FIG. 9 , the printer control unit 107 rotates the motor 103 at a steady speed A. In S10, the printer control unit 107 waits until the motor 103 is stopped, for example, due to the end of image formation. When an event occurs that stops the motor 103, the printer control unit 107 starts decelerating the motor 103 by reducing the speed command value ω_ref output to the motor control unit 110 in S11. When the speed command value ω_ref reaches a threshold value for switching between sensorless control and forced commutation control, the motor control unit 110 switches to forced commutation control in S12. Next, in S13, the printer control unit 107 waits until the speed command value ω_ref reaches the stop preparation speed B. When the speed command value ω_ref reaches the stop preparation speed B, the printer control unit 107 maintains the speed command value ω_ref indicating the stop preparation speed B in S14, thereby stopping the deceleration of the motor 103. When a predetermined time has elapsed since the printer control unit 107 decelerated to the stop preparation speed B in S15, the printer control unit 107 decreases the speed command value ω_ref in S16, thereby stopping the motor 103 in S16.

[0030] In this embodiment, when stopping the motor 103 rotating at the steady speed A, once the rotation speed of the motor 103 has decelerated to the stop preparation speed B, the rotation speed of the motor 103 is kept constant at the stop preparation speed B for a predetermined time. However, once the stop preparation speed B is reached, the deceleration rate may be reduced to be lower than that before the stop preparation speed B is reached, and the motor 103 may be stopped. For example, the deceleration rate after the stop preparation speed B is reached may be set so that the motor 103 stops after at least a predetermined time has elapsed. With this configuration, the energy stored in the spring of the torque limiter 133 can be reduced over a predetermined time period.

[0031] As described above, when stopping the motor 103, after the motor 103 is decelerated to a predetermined stop preparation speed B, the deceleration of the motor 103 is set to be smaller than the deceleration before the rotational speed of the motor 103 reaches the stop preparation speed B. The deceleration before reaching the stop preparation speed B may be the maximum, average, or minimum value of the deceleration during the period from the steady speed A to the stop preparation speed B. Furthermore, the deceleration before reaching the stop preparation speed B may be the deceleration immediately before the stop preparation speed B is reached. Furthermore, the deceleration after the rotational speed of the motor 103 reaches the stop preparation speed B may be the maximum, average, or minimum value of the deceleration during the period from the stop preparation speed B to when the motor 103 stops. Furthermore, the deceleration after the rotational speed of the motor 103 reaches the stop preparation speed B may be the deceleration immediately after the rotational speed of the motor 103 reaches the stop preparation speed B. In one example, the deceleration can be set to 0 when the rotational speed of the motor 103 reaches the stop preparation speed B. In this case, the motor 103 is stopped after rotating at the stop preparation speed B for a predetermined time. This configuration reduces the energy stored in the spring of torque limiter 133 when motor 103 is stopped, thereby reducing the amount of reverse rotation of motor 103 after it has stopped. Reducing the amount of reverse rotation of motor 103 when it is stopped prevents large load fluctuations on motor 103 the next time it is started, and prevents startup problems such as loss of synchronism.

[0032] In this embodiment, the stop preparation speed B is a speed at which only forced commutation control is possible. However, the stop preparation speed B may be a speed at which sensorless control is possible as long as it is lower than the steady-state speed A. Furthermore, although the motor 103 in this embodiment is a brushless motor controlled by sensorless vector control, it may be another type of motor, such as a stepping motor, that operates by forced commutation control. Furthermore, FIG. 6 shows an example of a drive transmission mechanism for the motor 103, and the present invention may also be applied to drive transmission mechanisms other than that shown in FIG. 6. Specifically, the present invention may be applied to a configuration in which an elastic body, such as a spring or roller, is present in the drive transmission mechanism or load of the motor 103, and the drive transmission mechanism has "play."

[0033] Second Embodiment Next, the second embodiment will be described, focusing on differences from the first embodiment. FIG. 10 is a cross-sectional view of a fixing unit 30. The fixing unit 30 illustrated in FIG. 10 includes a fixing film 602 (fixing roller), which is a cylindrical film, and a pressure roller 603. Inside the fixing film 602, there are provided a heater 600, a heater holder 601 that securely holds the heater 600 so as to contact the heating element of the heater 600, and a thermistor 604 that measures temperature. The pressure roller 603 is driven to rotate counterclockwise in the figure by a motor 104 similar to the motor 103 of the first embodiment. Due to the frictional pressure between the outer surface of the pressure roller 603 and the fixing film 602 in the fixing nip region N, the rotational force of the pressure roller 603 acts on the fixing film 602, causing the fixing film 602 to rotate following the rotation.

[0034] The heater 600 is adjusted to a predetermined temperature based on the temperature measurement results of the thermistor 604. In this state, the sheet 21 carrying an unfixed toner image T is transported to the fixing nip area N. In the fixing nip area N, the toner image carrying surface of the sheet 21 comes into close contact with the outer surface of the fixing film 602, and the sheet 21 is sandwiched and transported together with the fixing film 602 through the fixing nip area N. During this sandwiching and transport process, heat from the heater 600 is applied to the sheet 21 via the fixing film 602, and the unfixed toner image T on the sheet 21 is heated and pressurized to be melted and fixed.

[0035] 11 shows the drive configuration of the motor 104 according to this embodiment. The configuration of the motor 104 and the control configuration of the motor 104 are the same as those explained using FIGS. 2 to 5. When the motor 104 is rotated forward, the drive switching unit 607 transmits the drive force to the pressure roller 603. On the other hand, when the motor 104 is rotated reversely, the drive switching unit 607 transmits the drive force of the motor 104 to the contact / separation mechanism 608.

[0036] The contact / separation mechanism 608 switches between a contact state in which the fixing film 602 and the pressure roller 603 are in contact with each other and a separated state in which the fixing film 602 and the pressure roller 603 are separated from each other. Specifically, when the motor 104 is rotated in the reverse direction by a predetermined amount in the separated state, the contact / separation mechanism 608 brings the pressure roller 603 and the fixing film 602 into a contact state using a cam (not shown). When the motor 104 is further rotated in the reverse direction by a predetermined amount, the contact / separation mechanism 608 brings the pressure roller 603 and the fixing film 602 into a separated state. Note that a sensor for detecting whether the state is contact or separated may be further provided. For example, when the image forming apparatus is turned off or transitions to sleep mode, the image forming apparatus brings the pressure roller 603 and the fixing film 602 into a separated state. This prevents setting marks or the like from remaining on the fixing film 602, which could cause image defects.

[0037] Because the pressure roller 603 is an elastic body, when the motor 104 is stopped, a force in a direction that eliminates the twist of the rotating pressure roller 603 is transmitted to the drive switching unit 607 via the drive transmission mechanism. Due to the play provided in the drive switching unit 607, the motor 104 can receive the force from the pressure roller 603 and rotate in the reverse direction. Therefore, as explained in the first embodiment, when the motor 104 is started, the pressure roller 603 can suddenly connect to the motor 104, causing loss of synchronization.

[0038] Therefore, when the rotation of the motor 104 is stopped, the motor 104 is stopped after rotating at the stop preparation speed B for a predetermined time, as explained with reference to Fig. 8. This configuration reduces the energy stored in the elastic body of the pressure roller 603, and reduces the amount of reverse rotation of the motor 104 when it is stopped.

[0039] <Other> In the above embodiments, the motor control unit 110 is referred to as a motor control unit because it is a component of the image forming apparatus. However, the motor control unit 110 can also be a single device and referred to as a motor control device. Furthermore, a device including the printer control unit 107 and the motor control unit 110 can also be referred to as a motor control device. As described above, the present invention can be applied to a configuration in which at least one of the drive transmission mechanism and the load has an elastic body and the drive transmission mechanism has play, and the type of motor load is arbitrary. Therefore, the present invention can be applied to the control of a motor that drives any component, such as a motor that drives an image forming unit involved in image formation, such as the cartridge 12 or the intermediate transfer belt 19, or a motor that drives a roller (rotating member) for transporting the sheet 21. For example, the motor load can be one or more of the photoreceptor 13, the developing roller 16, the intermediate transfer belt 19, the pressure roller 603 of the fixing unit 30, and a roller for transporting the sheet 21. Furthermore, the configuration of the motor 103 is not limited to the configuration shown in FIG. 3 , and a motor with a different number of poles and phases may be used.

[0040] [Other embodiments] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0041] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0042] 103, 104: motor, 131: gear, 132: coupling, 133: torque limiter, 107: printer control unit, 110: motor control unit

Claims

1. A motor; a transmission mechanism that transmits the driving force of the motor to a load of the motor; a control means for, when stopping the motor rotating at a first speed, decelerating the motor at at least a first deceleration during a first period during which the rotational speed of the motor is decelerated from the first speed to a second speed lower than the first speed, and decelerating the motor at at least a second deceleration lower than the first deceleration during a second period during which the rotational speed of the motor is decelerated from the second speed to the stop; the control means performs a first control on the motor based on an induced voltage generated in the motor when the rotation speed of the motor is higher than a threshold value, and performs a second control, which is a forced commutation control, on the motor when the rotation speed of the motor is lower than the threshold value; the first speed is greater than the threshold; The second speed is a speed less than the threshold value.

2. A motor control device that controls a motor that transmits a driving force to a load by a transmission mechanism, a control means for, when stopping the motor rotating at a first speed, decelerating the motor at at least a first deceleration during a first period during which the rotational speed of the motor is decelerated from the first speed to a second speed lower than the first speed, and decelerating the motor at at least a second deceleration lower than the first deceleration during a second period during which the rotational speed of the motor is decelerated from the second speed to the stop; the control means performs a first control on the motor based on an induced voltage generated in the motor when the rotation speed of the motor is higher than a threshold value, and performs a second control, which is a forced commutation control, on the motor when the rotation speed of the motor is lower than the threshold value; the first speed is greater than the threshold; The second speed is a speed less than the threshold value.

3. 3. The motor control device according to claim 1, wherein the control means stops the motor after rotating the motor for at least a predetermined time when the rotation speed of the motor reaches the second speed.

4. The motor control device according to claim 1 , wherein the second speed is greater than 0 and equal to or less than 100 rpm.

5. The motor control device according to claim 1 , wherein at least one of the load and the transmission mechanism has an elastic body.

6. The motor control device according to claim 1 , wherein the transmission mechanism has play.

7. The motor control device according to claim 1 , wherein the motor is a sensorless motor.

8. The motor control device according to claim 1 , wherein the motor is a stepping motor.

9. 9. The motor control device according to claim 1, wherein the load includes at least one of a photosensitive member of an image forming device, a developing roller that forms a toner image on the photosensitive member by developing an electrostatic latent image formed on the photosensitive member, an intermediate transfer belt to which the toner image formed on the photosensitive member is transferred, a roller that fixes the toner image transferred from the intermediate transfer belt to a sheet, and a roller for transporting the sheet.

10. a rotating member for transporting the sheet along the transport path; an image forming means for forming an image on the sheet conveyed through the conveying path; a motor that drives the rotating member or the image forming means; a transmission mechanism that transmits the driving force of the motor to a load of the motor; a control means for, when stopping the motor rotating at a first speed, decelerating the motor at at least a first deceleration during a first period during which the rotational speed of the motor is decelerated from the first speed to a second speed lower than the first speed, and decelerating the motor at at least a second deceleration lower than the first deceleration during a second period during which the rotational speed of the motor is decelerated from the second speed to the stop; Equipped with the control means performs a first control on the motor based on an induced voltage generated in the motor when the rotation speed of the motor is higher than a threshold value, and performs a second control, which is a forced commutation control, on the motor when the rotation speed of the motor is lower than the threshold value; the first speed is greater than the threshold; The second speed is lower than the threshold value.

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