JP7475157B2 - Image forming apparatus, motor control device for controlling a motor, and motor control method - Google Patents

Description

The present invention relates to motor control technology.

A sensorless type motor (hereinafter, sensorless motor) that does not have a sensor for detecting the rotor position such as a Hall element is used as a drive source for the rotating member of an image forming device. Patent Document 1 discloses a configuration in which the rotor position of a sensorless motor is detected by the induced voltage generated in a coil.

Japanese Patent Application Laid-Open No. 8-223970

In order to detect the rotor position (rotor rotation phase) of a sensorless motor in a stopped state where no induced voltage is generated, the characteristic that the coil's inductance value changes depending on the rotor position is used. Specifically, the rotor position can be determined by detecting the coil's inductance value based on the coil current that flows through the coil when a specified voltage is applied to the coil. The motor is then driven using forced commutation control until the rotor position can be detected from the induced voltage, at which point it switches to sensorless drive. Note that if the rotor rotation speed estimated from the coil current is not within a specified speed range after the motor starts to drive, start-up will fail.

In this way, it is possible to determine whether the motor has failed to start from the rotor rotation speed, but it is not possible to determine from the rotor rotation speed whether the cause of the failure to start is a motor failure or an abnormality in the motor load.

The present invention provides a technology that determines whether the cause of a motor's failure to start is due to a motor malfunction.

According to one aspect of the present invention, an image forming apparatus includes: an image forming means having a rotating member and forming an image on a sheet by using the rotating member; a motor having a plurality of coils and a rotor that rotates by a combination of excited coils among the plurality of coils ; a transmission mechanism that transmits a driving force of the motor to the rotating member included in the image forming means , the transmission mechanism having backlash ; and a control means that controls the motor to rotate the rotor in a first direction to rotate the rotating member , and the control means controls the rotation of the rotor by rotating the rotor in the first direction when starting the motor. The motor is determined to have failed if the detected rotational speed of the rotor is lower than a predetermined speed, and if the startup process fails, a first stop position of the rotor is detected from the detection results of the current flowing through the coil when a predetermined voltage is applied, the rotor is rotated a predetermined amount in a second direction opposite to the first direction, and after rotating the rotor a predetermined amount in the second direction, a predetermined voltage is again applied to detect a second stop position of the rotor, and if the first stop position and the second stop position match, it is determined that the motor has failed, and if they do not match, it is determined that the rotating member driven by the motor has failed .

The present invention makes it possible to determine whether the cause of a motor's failure to start is due to a motor malfunction.

FIG. 1 is a diagram illustrating the configuration of an image forming apparatus according to an embodiment. FIG. 2 is a diagram showing a driving configuration of a photoconductor according to an embodiment. FIG. 2 is a control configuration diagram of a motor according to an embodiment. FIG. 1 is a configuration diagram of a motor according to an embodiment. 4A and 4B are diagrams showing the relationship between the excitation phase and the total inductance, and a method for detecting the total inductance. FIG. 4 is an explanatory diagram of a motor start-up process according to an embodiment. 11 is a flowchart of a cause identification process according to an embodiment. FIG. 2 is a diagram illustrating a driving configuration of a fixing unit according to an embodiment. 11 is a flowchart of a cause identification process according to an embodiment.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

First Embodiment
FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus of FIG. 1 forms a full-color image by superimposing four toner images of yellow, magenta, cyan, and black. In FIG. 1, the suffixes Y, M, C, and K of the reference symbols indicate that the colors of the toner images formed by the members indicated by the reference symbols are yellow, magenta, cyan, and black, respectively. In the following description, when it is not necessary to distinguish the colors, the reference symbols are used without the suffixes Y, M, C, and K. During image formation, the photoconductor 13 is rotated clockwise in the drawing. The charging roller 15 charges the surface of the corresponding photoconductor 13 to a uniform potential. The exposure unit 11 exposes the surface of the corresponding photoconductor 13 to light to form an electrostatic latent image on the photoconductor 13. The development roller 16 of the development unit 12 develops the electrostatic latent image of the corresponding photoconductor 13 with toner to visualize it as a toner image. The primary transfer rollers 18 use a primary transfer bias to transfer the toner images formed on the corresponding photoconductors 13 onto the intermediate transfer belt 19. The cleaners 14 remove toner that has not been transferred to the intermediate transfer belt 19 and remains on the corresponding photoconductors 13. Note that a full-color image is formed on the intermediate transfer belt 19 by transferring the toner images formed on the respective photoconductors 13 onto the intermediate transfer belt 19 in an overlapping manner.

During image formation, the intermediate transfer belt 19 is driven to rotate in a counterclockwise direction in the figure. As a result, the toner image transferred to the intermediate transfer belt 19 is transported to a position opposite the secondary transfer roller 29. Meanwhile, the sheet 21 stored in the cassette 22 is fed from the cassette 22 to the transport path by the rotation of each roller provided along the transport path, and is transported to a position opposite the secondary transfer roller 29. The secondary transfer roller 29 transfers the toner image of the intermediate transfer belt 19 to the sheet 21 by the secondary transfer bias. The sheet 21 is then transported to the fixing unit 30. The fixing unit 30 heats and presses the sheet 21 to fix the toner image to the sheet 21. After the toner image is fixed, the sheet 21 is discharged outside the image forming apparatus. A control unit 31 that controls the entire image forming apparatus includes a CPU 32.

Figure 2 shows the drive configuration of the photoreceptors 13Y, 13M, and 13C. The drive transmission gear of the motor 101 and the drive transmission gears of the photoreceptors 13Y, 13M, and 13C are connected at the couplings 17Y, 17M, and 17C, respectively. Thus, the drive force of the motor 101 is transmitted to the photoreceptors 13Y, 13M, and 13C via the couplings 17Y, 17M, and 17C. The photoreceptors 13Y, 13M, and 13C can be removed from the image forming apparatus by disconnecting the drive transmission gears at the couplings 17Y, 17M, and 17C. The couplings 17Y, 17M, and 17C are provided with backlash so that the gears can be smoothly connected when the photoreceptors 13Y, 13M, and 13C are attached.

Figure 3 is a control configuration diagram of the motor 101. The motor control unit 120 has a microcomputer (hereinafter referred to as MCU) 121. A communication port 122 of the MCU 121 performs serial communication with the control unit 31. The control unit 31 controls the rotation of the motor 101 by controlling the motor control unit 120 via serial communication. The reference clock generation unit 125 generates a reference clock based on the output of the crystal oscillator 126. The counter 123 measures the pulse period based on this reference clock. The non-volatile memory 124 stores programs and various data used to control the motor. The MCU 121 outputs a pulse width modulation signal (PWM signal) from a PWM port 127. In this embodiment, the microcomputer 121 outputs a total of six PWM signals, including high-side PWM signals (U-H, V-H, W-H) and low-side PWM signals (U-L, V-L, W-L), for each of the three phases (U, V, W) of the motor 101. For this reason, the PWM port 127 has six terminals: U-H, V-H, W-H, U-L, V-L, and W-L.

Each terminal of the PWM port 127 is connected to a gate driver 132, which controls the on/off of each switching element of the three-phase inverter 131 based on the PWM signal. The inverter 131 has a total of six switching elements, three on the high side and three on the low side for each phase, and the gate driver 132 controls each switching element based on the corresponding PWM signal. For example, a transistor or an FET can be used as the switching element. In this embodiment, when the PWM signal is high, the corresponding switching element is turned on, and when the PWM signal is low, the corresponding switching element is turned off. The output 133 of the inverter 131 is connected to coils 135 (U phase), 136 (V phase), and 137 (W phase) of the motor 101. By controlling the on/off of each switching element of the inverter 131, the excitation current (coil current) of each coil 135, 136, and 137 can be controlled. In this way, the microcontroller 121, the gate driver 132, and the inverter 131 function as a voltage control unit that controls the voltages applied to the multiple coils 135, 136, and 137.

The current sensor 130 outputs a detection voltage according to the value of the coil current flowing through each of the coils 135, 136, and 137. The amplifier 134 amplifies the detection voltage of each phase and applies an offset voltage to output the voltage to the analog-digital converter (AD converter) 129. The AD converter 129 converts the amplified detection voltage into a digital value. The current value calculation unit 128 determines the coil current of each phase based on the output value (digital value) of the AD converter 129. For example, the current sensor 130 outputs a voltage of 0.01 V per 1 A, the amplification factor (gain) of the amplifier 134 is set to 10 times, and the offset voltage applied by the amplifier 134 is set to 1.6 V. If the range of the coil current flowing through the motor 101 is -10 A to +10 A, the voltage range output by the amplifier 134 is 0.6 V to 2.6 V. For example, if the AD converter 129 converts a voltage of 0 to 3 V into a digital value of 0 to 4095 and outputs it, then an excitation current of -10 A to +10 A is converted into a digital value of approximately 819 to 3549. Note that when the excitation current flows from the inverter 131 to the motor 101, the current value is positive, and when it flows in the opposite direction, the current value is negative.

The current value calculation unit 128 calculates the excitation current by subtracting an offset value corresponding to the offset voltage from the digital value and multiplying it by a predetermined conversion coefficient. In this example, the offset value corresponding to the offset voltage (1.6 V) is approximately 2184 (1.6 x 4095/3). The conversion coefficient is approximately 0.000733 (3/4095). In this way, the current sensor 130, the amplifier unit 134, the AD converter 129, and the current value calculation unit 128 constitute a current detection unit.

Figure 4 is a configuration diagram of the motor 101. The motor 101 is a sensorless motor. The motor 101 is composed of a 6-slot stator 71 and a 4-pole rotor 72, and the stator 71 is provided with U-phase, V-phase, and W-phase coils 135, 136, and 137. The rotor 72 is made of a permanent magnet and has two sets of N poles and S poles. The position at which the rotor 72 stops is determined according to the combination of excited coils 135, 136, and 137, i.e., the excitation phase. Since the rotor 72 rotates, the position of the rotor 72 is also the rotation phase of the rotor 72. For example, when the rotor 72 is excited so that a coil current flows from the U-phase coil 135 to the V-phase coil 136, the rotor 72 stops at the position shown in Figure 4 (A). When a coil current flows from the U-phase coil 135 to the V-phase coil 136, the U-phase becomes an N pole and the V-phase becomes an S pole. Then, when excitation is applied so that coil current flows from the U-phase coil 135 to the W-phase coil 137, the U-phase becomes a north pole and the W-phase becomes a south pole, and the rotor 72 stops in the position shown in FIG. 4(B).

In the following description, the two phases to be excited are referred to as excitation phases. When the excitation phase is X-Y phase, a coil current is passed from the X-phase coil to the Y-phase coil to excite it. In this case, the X-phase becomes the north pole and the Y-phase becomes the south pole. When the motor 101 is stopped and the coil current is no longer flowing, the force holding the rotor 72 is no longer applied. In this state, when an external force is applied to the rotor 72, the rotor 72 rotates. When the image forming apparatus is powered on, the image forming apparatus does not know the stopping position of the rotor 72. Therefore, when starting the rotation of the motor 101 by forced commutation control, the image forming apparatus must first detect the stopping position of the rotor 72.

In general, a coil is constructed by winding copper wire around a core made of laminated electromagnetic steel sheets. Here, the magnetic permeability of the electromagnetic steel sheets is small when there is an external magnetic field. Therefore, the inductance of the coil, which is proportional to the magnetic permeability of the core, is small when there is an external magnetic field. For example, as in the U-phase coil 135 in FIG. 4(A), in a state in which only the S pole of the rotor 72 faces, the influence of the external magnetic field caused by the rotor 72 is large, so the rate of decrease in inductance of the U-phase coil 135 is large. Note that when there is an external magnetic field, if the direction of the magnetic field generated by the coil current is the same as the direction of the external magnetic field, the amount of decrease in inductance is larger than when it is in the opposite direction. In the state of FIG. 4(A), since the S pole of the rotor 72 faces the U-phase, the amount of decrease in inductance when the coil current flows in a direction that makes the U-phase the N pole is larger than when the coil current flows in a direction that makes the U-phase the S pole.

In the state shown in FIG. 4(A), the W-phase coil 137 faces the midpoint between the south and north poles of the rotor 72, so the effect of the external magnetic field from the rotor 72 is small, and the rate of inductance decrease is small. In this way, the inductance of the U-phase coil 135, the V-phase coil 136, and the W-phase coil 137 changes depending on the stopping position of the rotor 72. An example of the combined inductance when each excitation phase is excited when the rotor 72 is stopped in the state shown in FIG. 4(A) is shown in FIG. 5(A). In the following explanation, the position where the rotor 72 stops when the X-Y phases are excited is referred to as the "X-Y phase position."

Since the rotor 72 is stopped at the U-V phase position, as shown in FIG. 5(A), the combined inductance of the U-V phase is smallest when the U-V phase is excited. Therefore, by exciting each excitation phase and finding and comparing the combined inductance of each excitation phase, the stopping position of the rotor 72 can be determined. In the following explanation, the process of exciting an excitation phase, finding the combined inductance of that excitation phase, and determining the relative magnitude relationship is referred to as relative value detection processing.

In this embodiment, the composite inductance is determined by exciting each of the six excitation phases in sequence and measuring the coil current after a predetermined time. The smaller the composite inductance, the faster the coil current rises. Therefore, when the rotor 72 is stopped at the U-V phase position, the coil current after a predetermined time when the U-V phase is excited is larger than when the other excitation phases are excited. It is assumed that the rotor 72 is stopped midway between two excitation phases adjacent in terms of electrical angle, that is, for example, midway between the U-V phase position and the U-W phase position. In this case, the coil current after a predetermined time when the U-V phase is excited and when the U-W phase is excited are approximately the same value, and are larger than when the other excitation phases are excited. In this embodiment, if the coil current when any one excitation phase is excited is larger than the coil current when the other excitation phases are excited, it is determined that the rotor 72 is stopped at the position of that one excitation phase. In addition, if the coil current when two excitation phases that are adjacent in electrical angle are excited is approximately the same value and is greater than when the other excitation phase is excited, it is determined that the rotor 72 is stopped at the midpoint between the two excitation phases.

The relative value detection process of this embodiment will be described in detail below. For example, when exciting the U-V phase, a PWM signal with a changing duty is output from the U-H terminal and the V-H terminal of the PWM port 127 as shown in FIG. 5B. Specifically, in the A section (0.5 ms), the duty of the PWM signal output from the U-H terminal is changed to a half-wave sine wave. The maximum value of the duty is, for example, 80%. During this period, the V-L terminal is set to a high level (duty 100%), and the other terminals are set to a low level (duty 0%). In the B section (0.5 ms) following the A section, the duty of the PWM signal output from the V-H terminal is changed to a half-wave sine wave. During this period, the U-L terminal is set to a high level (duty 100%), and the other terminals are set to a low level (duty 0%). The durations of section A and section B are determined so as to ensure detection accuracy while not rotating the rotor 72, and in this embodiment, are each set to 0.5 ms. The maximum value of the duty in section A is determined so that a coil current flows that provides sufficient detection accuracy. The maximum value of the duty in section B is set so that the sum of the voltage-time products generated in the coil inductance components in sections A and B is approximately zero. By setting it in this manner, as shown in FIG. 5(B), the coil current decreases smoothly during section B, and the coil current becomes approximately zero at the end of section B.

FIG. 6 is an explanatory diagram of the start-up process of the motor 101. In the following description, the rotation direction of the rotor 72 for rotating the photoconductors 13Y, 13M, and 13C in the rotation direction during image formation is called the forward direction, and the direction opposite to the forward direction is called the reverse direction. First, the control unit 31 performs a relative value detection process to detect the stop position of the rotor 72. When the stop position of the rotor 72, that is, the initial position at the start of rotation, is detected, the control unit 31 performs forced commutation control based on the initial position to rotate the rotor 72 in the forward direction. In the forced commutation control, the control unit 31 gradually speeds up the switching of the excitation phase, thereby increasing the rotation speed of the rotor 72. When the rotation speed of the rotor 72 reaches a predetermined threshold, the motor control unit 120 switches from the forced commutation control to sensorless driving. In the sensorless driving, the position and rotation speed of the rotor 72 are estimated based on the induced voltage. In the forced commutation control period, the control unit 31 determines the rotation speed of the rotor 72 based on the switching speed of the excitation phase. The control unit 31 detects the rotation speed of the rotor 72 at the timing of abnormality determination, and if the detected rotation speed of the rotor 72 is lower than a predetermined speed, the control unit 31 determines that the start of the motor 101, that is, the control to rotate the rotor 72 in the forward direction, has failed. Note that, at the timing of abnormality determination, the control unit 31 is performing control so that the rotor 72 rotates at a rotation speed higher than the predetermined speed.

In this way, the control unit 31 can detect the failure of the motor 101 to start from the rotation speed of the rotor 72, but cannot determine whether the cause of the failure to start is a malfunction of the motor 101 or an abnormal load of the motor 101. Here, as described in FIG. 2, the couplings 17Y, 17M, and 17C are provided with backlash. Therefore, within the backlash amount, the rotor 72 can be rotated in the reverse direction without the power of the motor 101 being transmitted to the load. In other words, if the motor 101 is normal, the rotor 72 can be rotated in the reverse direction with an amount of rotation within the backlash amount. Note that if the motor 101 is malfunctioning, the rotor 72 cannot be rotated in the reverse direction. In this embodiment, if the motor 101 fails to start at the abnormality determination timing, the above characteristics are utilized to execute the cause identification process described below.

Figure 7 is a flowchart of the cause identification process according to this embodiment. In S10, the control unit 31 performs a relative value detection process to detect the stop position A of the rotor 72. In S11, the control unit 31 rotates the rotor 72 in the reverse direction by a predetermined amount by forced commutation control. The amount of rotation in the reverse direction is equal to or less than the backlash amount in the couplings 17Y, 17M, and 17C. In other words, the amount of rotation in the reverse direction is an amount at which the power of the motor 101 is not transmitted to the photoconductors 13Y, 13M, and 13C, which are the loads, and therefore the load on the motor 101 is approximately zero. In addition, the amount of rotation in the reverse direction is set so that the stop position of the rotor 72 after rotating in the reverse direction is not the stop position A. In S12, the control unit 31 performs a relative value detection process to detect the stop position B of the rotor 72. In S13, the control unit 31 determines whether the stop position A and the stop position B are the same. If stop position A and stop position B are the same, this means that the rotor 72 is not rotating, so the control unit 31 determines in S14 that the motor 101 is broken. On the other hand, if stop position A and stop position B are not the same, the motor control unit 120 determines in S15 that there is a load abnormality, that is, that the photoconductors 13Y, 13M, and 13C are broken.

By performing the process shown in FIG. 7, the control unit 31 can determine whether the cause of the failure to start the motor 101 is a malfunction of the motor 101 or an abnormal load on the motor 101. Depending on the result of the determination, the control unit 31 can notify the user whether the load, that is, the photoconductors 13Y, 13M, and 13C, should be replaced, or the motor 101 should be replaced.

As described above, a backlash is provided in the transmission mechanism that transmits the power of the motor 101 to the load, so that the power is not transmitted to the load even if the rotor 72 is rotated in reverse by this backlash amount. In other words, the motor 101 is configured to be able to rotate in reverse by the backlash amount with almost no load. Then, if the start of the motor 101 fails, the rotor 72 is rotated in reverse by a predetermined amount within the backlash amount, and it is determined whether the rotor 72 is rotating in reverse. With this configuration, it is possible to determine whether the start failure of the motor 101 is due to a load abnormality or a malfunction of the motor 101 itself. In this example, the couplings 17Y, 17M, and 17C are provided with backlash, but the present invention is not limited to such a configuration. Specifically, it is sufficient that the backlash is provided in the transmission mechanism that transmits the power of the motor 101 to the load (photoconductor).

In S13 of FIG. 7, if stop position A and stop position B are the same, it is determined that there is a failure of the motor 101, and otherwise it is determined that there is a load abnormality. However, it may be configured such that if the difference (phase difference) between stop position A and stop position B is smaller than a predetermined value, it is determined that there is a failure of the motor 101, and otherwise it is determined that there is a load abnormality. In this case, the predetermined amount of rotation in the reverse direction in S11 is set to an amount that makes the phase difference between stop position A and stop position B equal to or greater than the predetermined value.

Also, it is possible to assume that the rotor 72 at stop position A has rotated in the reverse direction by a predetermined amount, calculate the calculated stop position Z of the rotor 72 after the reverse rotation, and compare the actual stop position B detected in S12 with the stop position Z to determine whether or not the motor 101 has failed. In this case, if the phase difference between stop position Z and stop position B is equal to or greater than a predetermined value, it is determined that the motor has failed, and if it is less than the predetermined value, it is determined that there is a load abnormality. In this case, the predetermined amount of rotation in the reverse direction in S11 is set to be equal to or greater than the predetermined value.

Second Embodiment
Next, the second embodiment will be described with a focus on differences from the first embodiment. FIG. 8 shows the drive configuration of the fixing unit 30. The fixing unit 30 has a heating roller and a pressure roller 203, and the heating roller rotates in accordance with the rotation of the pressure roller 203. The motor 102 transmits its power to the pressure roller 203 and the contact/separation mechanism 207 through a driving force transmission mechanism. The transmission mechanism is configured to transmit its power to the pressure roller 203 when the motor 102 rotates in the forward direction, and to transmit its power to the contact/separation mechanism 207 when the motor 102 rotates in the reverse direction. The contact/separation mechanism 207 is configured to operate a cam (not shown) in response to the rotation of the motor 102, and to set the fixing unit 30 to a contact state in which the pressure roller 203 contacts the heating roller, and a separation state in which the pressure roller 203 is separated from the heating roller. A sensor (not shown) detects whether the fixing unit 30 is in a contact state or a separation state. When the image forming apparatus is turned off or when the image forming apparatus transitions to a sleep mode, the fixing unit 30 is kept in a separated state to suppress deterioration of the heating roller and suppress the occurrence of image defects due to defects in the heating roller. Note that the configuration and control configuration of the motor 102 are similar to the configuration and control configuration of the motor 101, and therefore a description thereof will be omitted.

Figure 9 is a flowchart of the cause identification process according to this embodiment. In S20, the control unit 31 performs a relative value detection process to detect the stop position C of the rotor 72. In S21, the control unit 31 rotates the rotor 72 in the reverse direction by forced commutation control, and when the rotation speed of the rotor 72 reaches or exceeds a threshold value, in S22, the control unit 31 rotates the rotor 72 in the reverse direction by sensorless drive. In S23, the control unit 31 determines whether the rotation speed of the rotor 72 is equal to or greater than a predetermined speed. In other words, the processes in S20 to S23 are the same as those for determining start failure when the rotor 72 is rotated in the forward direction, but are also performed in the reverse direction. Note that the predetermined speeds for determining start failure in the forward and reverse directions do not need to be the same.

If the rotation speed of the rotor 72 is not equal to or greater than the predetermined speed in S23, the control unit 31 determines in S27 that the motor 102 is faulty. On the other hand, if the rotation speed of the rotor 72 is equal to or greater than the predetermined speed in S23, the control unit 31 determines in S24 that the fixing unit 30 is faulty. Furthermore, the control unit 31 determines in S25 whether the fixing unit 30 is in a separated state using a sensor (not shown). If it is in a separated state, the fixing unit 30 determines that the fixing unit 30 is faulty but that the contact/separation mechanism 207 is normal. On the other hand, if it is not in a separated state, the fixing unit 30 determines in S26 that not only the fixing unit 30 but also the contact/separation mechanism 207 is faulty.

As described above, a transmission mechanism is configured so that power is transmitted to different loads depending on the rotation direction of the motor 102. If start-up fails in both directions, it is determined that the motor 102 has failed. In contrast, if start-up fails in one rotation direction but succeeds in the other rotation direction, it is determined that there is an abnormality in the load that would rotate if the motor 102 were rotated in that one rotation direction. With this configuration, it is possible to determine whether the failure to start the motor 102 is due to a load abnormality or a failure of the motor 102 itself.

＜Other＞
In the first embodiment, the load is a photoconductor, and in the second embodiment, the load is the fixing unit 30 and the contact/separation mechanism 207, but these are examples and the load is not limited to these. Specifically, if a transmission mechanism configured to rotate a predetermined amount in the reverse direction with almost no load is used, the configuration of the first embodiment can be applied to any load. Also, if a transmission mechanism configured to transmit power to different loads depending on the rotation direction is used, the configuration of the second embodiment can be applied to any load. Also, in each of the above embodiments, if a predetermined rotation speed is not reached at the abnormality determination timing, it is determined that the start-up has failed, but it may be determined that the start-up has failed based on other criteria.

Furthermore, although the above embodiments have been described using an image forming apparatus as an example, the present invention can be applied to any apparatus that transmits the power of a motor to a load using the above-mentioned transmission mechanism. Furthermore, the present invention can also be realized as a motor control device that controls a motor that transmits power to a load using the above-mentioned transmission mechanism. The motor control device has the motor control unit 120 of FIG. 3 and a functional block related to motor control of the control unit 31. Furthermore, the present invention can also be realized as a method of controlling a motor in the motor control device.

[Other embodiments]
The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a 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 implements one or more of the functions.

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

101: Motor, 17Y, 17M, 17C: Coupling, 31: Control unit

Claims (7)

an image forming means having a rotating member and forming an image on a sheet by using the rotating member;
a motor having a plurality of coils and a rotor that rotates by a combination of excited coils among the plurality of coils ;
a transmission mechanism for transmitting a driving force of the motor to the rotating member included in the image forming unit , the transmission mechanism having a backlash ;
a control means for controlling the motor to rotate the rotor in a first direction to rotate the rotating member ;
Equipped with
The control means
when starting the motor, rotating the rotor in the first direction to detect a rotation speed of the rotor, and determining that the start-up process of the motor has failed if the detected rotation speed of the rotor is lower than a predetermined speed;
If the startup process fails,
detecting a first stop position of the rotor from a detection result of a current flowing through the coil when a predetermined voltage is applied;
Rotating the rotor a predetermined amount in a second direction opposite to the first direction;
After rotating the rotor by the predetermined amount in the second direction, a predetermined voltage is applied again to detect a second stop position of the rotor;
When the first stop position and the second stop position match, it is determined that a failure has occurred in the motor, and when they do not match, it is determined that a failure has occurred in the rotating member driven by the motor. 2. The image forming apparatus according to claim 1 , wherein the predetermined amount is equal to or smaller than the amount of backlash. 3. The image forming apparatus according to claim 1, wherein the control means detects the rotational speed of the rotor by controlling the rotor to rotate in the first direction at a rotational speed faster than the predetermined speed, and if the detected rotational speed of the rotor is lower than the predetermined speed, determines that the startup process has failed . The image forming apparatus according to claim 1 , wherein the rotating member is a photoconductor. The transmission mechanism includes a coupling,
The image forming apparatus according to claim 1 , wherein the backlash is provided in the coupling. A motor control device that controls a motor configured to transmit a driving force to a rotating member by a transmission mechanism including a backlash,
a control means for controlling the motor to rotate a rotor of the motor in a first direction to rotate the rotating member ;
The control means
when starting the motor, rotating the rotor in the first direction to detect a rotation speed of the rotor, and determining that the start-up process of the motor has failed if the detected rotation speed of the rotor is lower than a predetermined speed;
If the startup process fails,
detecting a first stop position of the rotor from a detection result of a current flowing through a coil of the motor when a predetermined voltage is applied;
Rotating the rotor a predetermined amount in a second direction opposite to the first direction;
After rotating the rotor by the predetermined amount in the second direction, a predetermined voltage is applied again to detect a second stop position of the rotor;
A motor control device that determines that a failure has occurred in the motor when the first stop position and the second stop position match, and determines that a failure has occurred in the rotating member driven by the motor when they do not match. A method for controlling a motor by a motor control device, comprising:
the motor is configured to transmit a driving force to a rotating member by a transmission mechanism including a backlash;
The control method includes:
when starting the motor, rotating a rotor of the motor in a first direction to detect a rotation speed of the rotor, and determining that a start-up process of the motor has failed if the detected rotation speed of the rotor is lower than a predetermined speed;
If the startup process fails,
detecting a first stop position of the rotor from a detection result of a current flowing through a coil of the motor when a predetermined voltage is applied;
Rotating the rotor a predetermined amount in a second direction opposite to the first direction;
After rotating the rotor by the predetermined amount in the second direction, a predetermined voltage is applied again to detect a second stop position of the rotor;
determining that a failure has occurred in the motor when the first stop position and the second stop position coincide, and determining that a failure has occurred in the rotating member driven by the motor when the first stop position and the second stop position do not coincide .

Images