JP2007057728A - Motor control method in stop operation, and image forming apparatus performing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a transfer medium formed like an endless track belt and a photoreceptor drum being in rotational contact with the transfer medium from being damaged by mutual rubbing in their rotational contact parts when performing stop operation of them. <P>SOLUTION: In the image forming apparatus, the photoreceptor drum driven by a drum motor of a developing means is disposed so as to be in rotational contact with the transfer medium formed like an endless track belt which is driven to run by a belt motor, and a toner image formed on the photoreceptor drum by electrophotography is transferred onto the transfer medium, and the belt motor and at least one drum motor are constituted of different servo motors respectively. When stop operation of each servo motor is performed, a driving clock frequency of the servo motor is stepwise reduced, and the transfer medium formed like an endless track belt and the photoreceptor drum are synchronously decelerated to suppress rubbing due to the occurrence of a relative speed difference in the rotational contact parts, whereby they are prevented from being damaged. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In the present invention, a toner image formed on a photosensitive drum driven by a drum motor is transferred to an intermediate transfer belt as a transfer medium driven by a belt motor or a sheet-like recording medium on a conveying belt by an electrophotographic method. The present invention relates to a motor control method during a stop operation, which is executed when stopping the operation to be performed, and an image forming apparatus which performs a motor stop operation using this motor control method.

  In general, in an image forming apparatus employing an electrophotographic system, yellow (Y) for full-color development on a traveling path of an endless track-shaped intermediate transfer belt or a transport belt as a transfer medium driven and driven by a belt motor. Four developing devices (developing means) each having a photosensitive drum driven by each drum motor for forming a toner image of each color of magenta (M), cyan (C) or black (K) are arranged. Color tandem image forming apparatus.

  In recent years, some of such color tandem image forming apparatuses use a DC servo motor as a drum motor and a belt motor for cost reduction.

  This DC servo motor has a characteristic that the speed when the motor is stopped varies due to the load. For this reason, in a color tandem image forming apparatus employing a DC servo motor, if the drum motor and the belt motor are stopped simultaneously at the end of the image forming operation, a large load due to a flywheel or the like applied to the drum motor, Due to the difference from the applied load, a speed difference is generated at the nip portion where the intermediate transfer belt or the conveyance belt and the photosensitive drum that is in contact with the intermediate transfer belt contact with each other. There is a risk of scratching.

  Therefore, in the conventional image forming apparatus, the drive signal of the belt motor (intermediate transfer motor) is switched to stop, and at the same time, the drum motor (photoconductor motor) is braked by the brake means for a predetermined time. After that, the drum motor control means switches the drum motor drive signal to a stop for a short time and then reversely drives the drum motor, so that the rotation transition of the photosensitive drum and the transition transition of the intermediate transfer belt are Are substantially the same, and a means has been proposed in which both stop completely at the same time (see, for example, Patent Document 1).

However, even if a means for stopping the photosensitive drum and the intermediate transfer belt at the same time as described above is used, the motor stops due to differences in the characteristics of the drum motor and the belt motor and their motor drivers. It is possible to prevent a relative speed difference between the outer peripheral surface of the photosensitive drum and the surface of the intermediate transfer belt or the conveyance belt in the nip portion from the start of the operation to the complete stop. Because of the difficulty, the intermediate transfer belt or the conveyance belt and the photosensitive drum are rubbed against each other due to a relative speed difference, and the photosensitive drum and the intermediate transfer belt or the conveyance belt may be damaged. is there.
JP2001-13842

  In the present invention, in view of the above-described problems, the speed of the outer peripheral surface of the photosensitive drum and the surface of the intermediate transfer belt or the conveyance belt is equal between the start of the motor stop operation and the complete stop. The motor control during the stop operation is performed to prevent a speed difference from occurring at the nip portion between the intermediate transfer belt or the conveyance belt and the photosensitive drum, and the photosensitive drum and the intermediate transfer belt or the conveyance belt rub against each other. It is an object of the present invention to newly provide a motor control method during a stop operation and an image forming apparatus for performing the same, which can prevent damage from being caused.

  In the image forming apparatus according to the first aspect of the present invention, the photosensitive drum driven by the drum motor of the developing unit is brought into rolling contact with the transfer medium formed in an endless belt shape driven by the belt motor. In the image forming apparatus in which the toner image formed on the photosensitive drum by the electrophotographic method is transferred onto the transfer medium, the belt motor and at least one drum motor are respectively operated by individual servo motors. In the stop operation of each servo motor, the drive clock frequency of each servo motor is lowered stepwise and then stopped.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the frequency reduction speed when the drive clock frequency of each servo motor is lowered stepwise is set to the frequency of the control operation of each servo motor. It is characterized in that it is configured in a range that does not deviate from the stable operation holding state that is being followed.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, when the reference clock frequency of each servo motor is lowered stepwise, the reference clock of each servo motor is set to a print mode. It is characterized in that it is configured to be low while maintaining the ratio at the time of steady operation.

  By configuring as described above, the transfer medium formed in the belt shape of the endless track and the photosensitive drum are decelerated synchronously, so that a relative speed difference is generated at these rolling contact portions and the sliding contact occurs. It is possible to prevent these from being damaged.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, when at least one reference clock of each servo motor reaches the minimum operating frequency during the stop operation of each servo motor, The frequency of the reference clock of the servo motor is fixed and the ON signal of all servo motors is stopped.

  By configuring as described above, in addition to the operations and effects described in claims 1 to 3, the minimum operating frequency in the servo motor to be controlled can be reduced from the start of the servo motor stop control operation. Within the period up to the time when the highest frequency is reached, the transfer medium formed in the belt shape of the endless track that is decelerating synchronously and the photosensitive drum are decelerated synchronously, To prevent slidable contact due to the occurrence of a specific speed difference, and to turn off the ON signal of each servo motor when the lowest operating frequency reaches a predetermined frequency. Therefore, even if a speed difference occurs between the transfer medium formed in the belt shape of an endless track and the photosensitive drum, these speeds are sufficiently reduced, so the speed difference becomes small and they stop. Run So also of time short, it can be as scratch in these does not occur.

  According to a fifth aspect of the present invention, there is provided a motor control method for a stop operation in an image forming apparatus in which a transfer medium formed in a belt shape of an endless track is driven and driven by a belt servo motor that is driven and controlled by a control means. The photosensitive drum, which is driven by a drum servo motor and has a toner image formed by an electrophotographic method, is arranged on the transfer medium so as to be in contact with the transfer medium, and the toner image formed on the photosensitive drum is transferred to the transfer medium. When the belt servomotor and the drum servomotor are stopped after the transfer, the transfer medium is stored stepwise after a plurality of predetermined times from the start of the stop, which is stored in advance in the memory of the control means. Stop motion that reduces the frequency of the servo motor for the belt and the servo motor for the drum that is set to synchronize the speed at the rolling contact portion between the drum and the photosensitive drum While maintaining the stable operation holding state in which the rotation speed of the servo motor for the belt and the servo motor for the drum follows the frequency of the control operation of each servo motor according to the time frequency data, Decrease in steps until at least one reference clock reaches the minimum operating frequency, and control all servo motors to stop when at least one reference clock of each servo motor reaches the minimum operating frequency. It is characterized by.

  According to the motor control method during the stop operation in the image forming apparatus described above, the period from the start of the stop control operation of the servo motor to the time when the lowest operating frequency reaches the predetermined frequency that is the highest among the servo motors to be controlled In this, the transfer medium formed in the belt shape of an endless track that is decelerating synchronously and the photosensitive drum are decelerated synchronously, and a relative speed difference is generated at these rolling contact portions to make sliding contact. Suppressing and preventing these from being scratched, and further, when the lowest operating frequency reaches the highest predetermined frequency, the ON signal of each servo motor is turned OFF, so it is formed in an endless belt shape. Even if a speed difference occurs between the transfer medium and the photosensitive drum, these speeds are sufficiently reduced, so the speed difference is small and the time until they stop is short. Possible so that the wound does not occur to.

  According to a sixth aspect of the present invention, in the motor control method during the stop operation in the image forming apparatus according to the fifth aspect, a plurality of profiles having different frequencies with different speeds when the frequency is lowered are stored in the memory of the control means. Normally, the servo motor is stopped using the profile with the fastest speed when the frequency is lowered, and the control operation frequency of at least one servo motor is followed during the stop operation control. If the stable operation holding state is lost, the frequency profile is switched to a frequency profile whose speed when lowering the frequency is reduced by one step, and the servo motor and drum for the belt according to the data of the one step slower frequency profile. To control the rotational speed with the servo motor for the motor to be lowered step by step And features.

  According to the motor control method during the stop operation in the above-described image forming apparatus, in addition to the operation and effect of the above-described claim 5, even one of the servo motors can follow the frequency of the control operation. Stable operation that follows the frequency of the control operation during the next motor stop control operation by switching the profile to a profile that slows down the frequency (it takes time to stop) every time the operation holding state is released It is possible to prevent the holding state from being released. Therefore, in this control, the stable operation holding state that follows the frequency of the control operation is frequently released, so that the transfer medium formed in the belt shape of the endless track and the photosensitive drum are damaged. Can prevent sticking.

  According to the motor control method at the time of the stop operation of the present invention and the image forming apparatus that performs the same, the motor control at the time of the stop operation executed by the image forming apparatus is completely stopped after the motor stop operation is started. Until the speed of the outer peripheral surface of the photosensitive drum is equal to the speed of the intermediate transfer belt or the surface of the conveyance belt, a speed difference is generated at the nip portion between the intermediate transfer belt or the conveyance belt and the photosensitive drum. There is an effect that the photosensitive drum and the intermediate transfer belt or the conveyance belt can be prevented from being rubbed against each other and damaged.

  An embodiment relating to an image forming apparatus of the present invention will be described with reference to FIGS.

  A color tandem image forming apparatus 10 that employs a DC servo motor in the electrophotographic system according to the present embodiment is configured as a printer or a multifunction peripheral as shown in the schematic configuration diagram of FIG. In addition, the paper feeding unit 12 as an image output device (IOT), the intermediate transfer belt device 14, and yellow (Y), magenta (M), cyan (C), and black (K) colors for full-color development are supported. The four developing devices (developing means) 16Y, 16M, 16C, and 16K are provided. Although not shown, the image forming apparatus 10 includes an image capturing device (IIT), an image processing device (IPS), and the like.

  In this image forming apparatus 10, RGB image data captured from the image capturing apparatus and a signal of print information (image mode information, etc.) are transmitted to the image processing apparatus, and the RGB image data and image creation generated by the image processing apparatus are transmitted. The condition signal is transmitted to the image output apparatus, and the sheet-like recording medium on which the image is formed is output.

  The intermediate transfer belt device 14 in the image forming apparatus 10 is configured by winding an endless track-shaped intermediate transfer belt 20 around a plurality of rolls 18. Among these rolls 18, a predetermined roll 18 configured as a drive roll is connected to a belt motor that is a DC servo motor that is driven and controlled to drive the intermediate transfer belt 20.

  Of these rolls 18, one that also serves as a predetermined roll configured as a backup roll 18 </ b> A is a secondary transfer roll 22 for transferring an image on the intermediate transfer belt 20 onto a sheet-like recording medium such as paper. The sheet-like recording medium is disposed at a position facing the sheet recording medium.

  On the running path of the intermediate transfer belt 20, there are four developments containing a developer containing toner of each color of yellow (Y), magenta (M), cyan (C) or black (K) for full color development. The devices 16Y, 16M, 16C, and 16K are arranged at predetermined positions at regular intervals. Although not shown, a belt cleaner or the like that scrapes off residual toner on the intermediate transfer belt 20 with a cleaner blade is disposed on the traveling path of the intermediate transfer belt 20.

  The four developing devices 16Y, 16M, 16C, and 16K are provided with photosensitive drums 24 that are photosensitive members (image carriers) that are in rolling contact with the intermediate transfer belt 20, respectively.

  The photosensitive drum 24 is connected to and rotated by a drum motor which is a DC servo motor that is driven and controlled.

  Since the photosensitive drum 24 of the black (K) developing device 16K is frequently used, the photosensitive drum 24 is formed to have a larger diameter than the photosensitive drums 24 of the other developing devices 16Y, 16M, and 16C. Are formed in the same diameter.

  Further, around each photosensitive drum 24, an exposure device (imager) 26 for forming a latent image by exposure, a developing device 28 for forming a toner image, a charger (not shown), and the like are arranged.

  In each of the developing devices 16Y, 16M, 16C, and 16K, an image portion or a background portion is selectively selected by the exposure device 26 on the surface of each of the Y, M, C, and K photosensitive drums 24 that is charged by a charger (not shown). Then, an electrostatic latent image is generated, and thereafter, the electrostatic latent images are visualized as toner images by the developing devices 16Y, 16M, 16C, and 16K using toner.

  The toner images of the respective colors developed on the photosensitive drums 24 are sequentially primary-transferred to the intermediate transfer belt 20 and finally the four color toner images are overlaid.

  In the image output apparatus of the image forming apparatus 10, the recording sheets 11 are carried out one by one onto the conveying path by the feed roll 30 from the sheet feeding unit 12 that stores the recording sheets 11 that are sheet-like recording media on which images are to be formed. Then, the sheet is fed by the sheet conveying roll 32 and aligned by the registration roll 34, and then the toner image is transferred by the secondary transfer roll 22 by being pressed against the intermediate transfer belt 20 on which the toner image is formed.

  The recording paper 11 to which the toner image has been transferred in this manner is not shown, but is further transported on the transport path, carried into the fixing device, and heated by a heater built in the fixing device, so that the toner is melted and fixed on the paper. Is done. The recording paper 11 on which the image is formed in this way is conveyed on the conveyance path and discharged onto the tray of the discharge unit.

  Next, in the image forming apparatus 10 configured as described above, FIG. 1 shows the configuration of the control means that controls the motor including the motor control during the stop operation for at least the belt motor and each drum motor. This will be described with reference to a block diagram.

  The control means provided on the control board of the image forming apparatus 10 includes a CPU (central processing unit) 36 that controls the entire image forming apparatus 10. A ROM 38 (memory), a RAM 40 (memory), and a peripheral IC 42 are connected to the CPU 36 via a CPU bus 44. Although not shown, the CPU 36 performs control of other motors, solenoids, chargers, developing devices 16Y, 16M, 16C, 16K, etc., reads input of various sensors and switches, and performs image forming apparatus. Configure to control the whole.

  The CPU 36 operates according to a program on the ROM 38, and the belt motor 46 is directly controlled by the CPU 36. The drum motors Y, M, C, K, 48, 50, 52, 54 are controlled via the peripheral IC 42. Are configured to control each of them.

  Each of these drum motors Y, M, C, K, 48, 50, 52, 54 is a DC servo motor and operates at a rotational speed proportional to the drum drive clocks Y, M, C, K supplied from the peripheral IC 42. To do.

  These drum motors Y, M, C, K, 48, 50, 52, and 54 are DC servo motors that do not require frequency step-up and step-down, and are turned on when receiving a drum motor ON signal. The operation is started, the rotation speed is automatically reached in proportion to the drive clock, and thereafter, stable operation is performed.

  That is, when each drum motor Y, M, C, K, 48, 50, 52, 54 receives the drum motor ON signal transmitted from the peripheral IC 42 and is turned ON, the drum motor Y starts rotating. In general, the rotation speed is reached in proportion to the drive clock, and thereafter, stable operation is performed.

  Furthermore, each of the drum motors Y, M, C, K, 48, 50, 52, and 54 reaches a stable operation holding state (referred to as a PLL lock state in this specification) that follows the frequency of the control operation. In this case, a stabilization lock signal indicating that the device is locked in the stable operation holding state is transmitted to the peripheral IC 42.

  The belt motor 46 for rotating the intermediate transfer belt 20 is constituted by a DC servo motor, and is controlled by a belt driving clock (reference clock) supplied from the CPU 36 and a belt ON signal.

  This belt motor 46 is a DC servo motor that does not require frequency step-up and step-down, receives a belt motor ON signal, and is turned ON to start rotating, and automatically rotates in proportion to the drive clock. After reaching the number, it is configured to operate stably.

  Further, when the belt motor 46 reaches a stable operation holding state (referred to as a PLL lock state in this specification) that follows the frequency of the control operation, the belt motor 46 is locked in the stable operation holding state. A stabilization lock signal is transmitted to the CPU 36.

  That is, the CPU 36 is connected to the belt motor 46 so as to be able to transmit and receive signals such as transmission of a belt motor ON signal, transmission of a belt motor clock, and reception of a signal indicating that the belt PLL is locked.

  Further, the CPU 36 transmits the drum motor ON signals Y, M, C, K to the drum motors Y, M, C, K, 48, 50, 52, 54 via the peripheral IC 42, and the drum motor clock Y. , M, C, and K, and drum PLL lock Y, M, C, and K are connected so as to be able to transmit and receive signals such as signals indicating that they are in the state.

  As a result, the CPU 36 directly or indirectly through the peripheral IC 42 sends the required drive clocks for control to the belt motor 46 and the drum motors Y, M, C, K, 48, 50, 52, 54, respectively. By transmitting and controlling the belt motor 46 and the drum motors Y, M, C, K, 48, 50, 52, 54, the surface speed of the intermediate transfer belt 20 and the drum motors that are in rolling contact with the surface speed. The surface speeds of Y, M, C, K, 48, 50, 52, and 54 are controlled to be substantially equal. By controlling in this way, the photosensitive drums 24 and the intermediate transfer belt 20 are rubbed while the belt motors 46 and the drum motors Y, M, C, K, 48, 50, 52, and 54 are in stable operation. This prevents the toner image from being deteriorated and the surface of each photosensitive drum 24 and the surface of the intermediate transfer belt 20 from being damaged.

  In the image forming apparatus 10 according to the present embodiment, the drum motors Y, M, C, 48, 50, and 52 having the same diameter have a common clock frequency, and the drum motor having a large diameter is used. The drum drive clock K of K54 and the drive clock of the intermediate transfer belt 20 are set to different frequencies. Further, depending on the configuration of the image forming apparatus 10, the frequencies of the drive clocks Y, M, C, K and the belt drive clock may all be the same.

  Next, at the time of a stop operation to be performed on the belt motor 46 and each of the drum motors Y, M, C, K, 48, 50, 52, and 54 by the control unit of the image forming apparatus 10 configured as described above. The contents of the control method will be described with reference to the timing chart shown in FIG.

  In the control unit of the image forming apparatus 10, in the standby mode, the CPU 36 and the peripheral IC 42 on the control board output the Drum drive clocks Y, M, C, K and the belt drive clock in a fixed frequency state.

  Next, when the image forming apparatus 10 enters the print mode, the CPU 36 and the peripheral IC 42 simultaneously transmit a belt (Belt) On signal and the Drum motor ON signals Y, M, C, and K to switch to the ON state.

  As a result, the belt motor 46 and the drum motors Y, M, C, K, 48, 50, 52, and 54 start rotating, reach a rotational speed proportional to each driving clock frequency, and enter a stable operating state. Each PLL lock signal generated by the belt motor 46 and the drum motors Y, M, C, K, 48, 50, 52, 54 is output to the control board.

  Next, when the printing operation of the image forming apparatus 10 is completed and the standby mode is entered, the CPU 36 and the peripheral IC 42 shift to a motor stop control operation, and each motor drive clock frequency is not stopped without stopping the ON signal of each motor. (Reference clock frequency) is reduced.

  At this time, if the reference clock frequency is suddenly lowered, the reduction in the rotation speed cannot be followed by each motor, and the stable operation stops, so that the so-called PLL lock is released (out of the stable operation holding state following the control operation frequency). ), The speed difference between each drum and belt occurs.

  Therefore, the CPU 36 and the peripheral IC 42 execute control for, for example, gradually reducing the speed of decreasing the frequency of each motor within a range in which the PLL lock cannot be released.

  At the same time, when the CPU 36 and the peripheral IC 42 reduce the frequency of each motor, each motor drive frequency is set to each motor drive frequency during the printing operation so that no speed difference occurs between each drum and the belt. Control to decrease while maintaining the same ratio.

  For example, the CPU 36 and the peripheral IC 42 perform the above-described motor stop control, and at the time of the stop operation shown in at least one of the table 1, the table 2 or the table 3 in FIG. In accordance with the frequency data, control is executed to gradually decrease the frequency of each motor after a plurality of predetermined times have elapsed since the start of the stop.

  Further, it is desirable that the timing when the CPU 36 and the peripheral IC 42 switch the drive frequency of each motor is switched as much as possible at the same time. However, if the CPU 36 and the peripheral IC 42 switch the drive frequency of each motor within 50 ms between the motors, there is virtually no problem.

  In the image forming apparatus 10, when there is a minimum operating frequency at which the servomotor used can be stably operated, when the control for decreasing the frequency of each motor is executed step by step. When one of the motors reaches the minimum operating frequency, it can no longer be reduced in speed while maintaining synchronization.

  Therefore, the CPU 36 and the peripheral IC 42 of the image forming apparatus 10 in this case stably operate the servo motors in the belt motor 46 and the drum motors Y, M, C, K, 48, 50, 52, and 54 when the motor stop control is performed. When the lowest operating frequency that can be generated reaches a predetermined frequency, control is performed to turn off the ON signal of each motor while the frequency is fixed at that time.

  That is, the CPU 36 and the peripheral IC 42 step each motor drive clock frequency (reference clock frequency) from the start of the motor stop control operation to the time when the lowest operation frequency reaches the predetermined frequency in the motor to be controlled. When the minimum operating frequency reaches the highest predetermined frequency, control for turning off the ON signal of each motor is executed.

  In the image forming apparatus 10, when the control is performed as described above, in the image forming apparatus 10, from the start of the motor stop control operation to the time when the lowest operating frequency reaches the predetermined frequency in the motor to be controlled. Within the period, as shown in FIG. 3, the intermediate transfer belt 20 that is decelerating synchronously and each belt motor 46, drum motors Y, M, C, K, 48, 50, 52, 54 are relatively Thus, it is possible to prevent these from being damaged by preventing the occurrence of a specific speed difference (making the acceleration of deceleration constant).

  Further, in this image forming apparatus 10, when the minimum operating frequency reaches the highest predetermined frequency, the ON signal of each motor is turned OFF, and then the intermediate transfer belt 20, each belt motor 46, and the drum motors Y, M. , C, K, 48, 50, 52, and 54, there is a speed difference between them, but since the speed of both of them is sufficiently reduced, the speed difference becomes small and until they stop. Because of the short time, these are not scratched.

  In this image forming apparatus 10, for example, when the control shown in Table 1 of FIG. 6 is performed, the belt motor drive frequency reaches the minimum operation frequency of the drum motor K54 after 700 ms from the start of the stop operation. The control to turn off the ON signal is performed with each frequency fixed.

  The CPU 36 and the peripheral IC 42 of the image forming apparatus 10 perform the printing operation in the next print mode with the driving frequency of each motor lowered to the lowest operating frequency after the motor stop control operation by the CPU 36 and the peripheral IC 42 is completed in the standby mode. At any time until the motor is started to start the control, the control is performed to return to the drive frequency of each predetermined motor used in the print mode.

  The CPU 36 and the peripheral IC 42 of the image forming apparatus 10 perform the motor stop control described above, so that the speed difference between the intermediate transfer belt 20 and each photosensitive drum 24 at the time of stopping is not changed without largely changing the configuration of the image forming apparatus 10. It is possible to prevent the occurrence of scratches.

  Next, this image forming apparatus 10 was performed to clarify the effect of preventing scratches on the intermediate transfer belt 20 and each photosensitive drum 24 by the motor stop control by the CPU 36 and the peripheral IC 42 of the image forming apparatus 10. A comparative example when the motor stop control is not performed will be described with reference to a timing chart shown in FIG.

  In the comparative example shown in FIG. 9, the control is performed in the same manner as the control by the timing chart shown in FIG. 3 described above until the image forming apparatus 10 finishes the printing operation.

  In the comparative example shown in FIG. 9, at the time when the print mode is finished and the mode is changed to the standby mode, each motor ON signal is turned off while the belt drive clock frequency and each drum drive clock frequency are output as they are. To do.

  When each motor ON signal is turned off in this way, each belt motor 46 and drum motors Y, M, C, K, 48, 50, 52, and 54 generate a variation in speed reduction due to the load of each motor. The motor speed decreases and the motor stops.

  For this reason, a speed difference occurs at the contact portion between the intermediate transfer belt 20 and each photosensitive drum 24 due to variations in speed reduction due to the load of each motor, and the intermediate transfer belt 20 and each photosensitive drum 24 have a difference in speed. Each could be scratched.

  Therefore, it was confirmed that the image forming apparatus 10 can prevent the intermediate transfer belt 20 and the photosensitive drums 24 from being damaged by performing motor stop control even when the same components are used.

  Next, the basic operation performed by the motor stop control of the image forming apparatus 10 will be described with reference to the flowchart of FIG.

  In the basic operation performed by the motor stop control, first, for example, the table 1 of FIG. 6 is read from the ROM 38 or the RAM 40, and the basic operation of the motor stop control shown in the flowchart of FIG.

  In the basic operation of the motor stop control shown in the flowchart of FIG. 7, after the control operation is started, in step 100, the image forming apparatus 10 is set to a standby mode for waiting for the start of the print mode and waits until the start of the print job.

  Next, when the print job is started, the process proceeds to step 102, the belt motor 46 is turned on, the drum motors Y, M, C, K, 48, 50, 52, 54 are turned on. Proceed to 104.

  In step 104, the intermediate transfer belt device 14 and the developing devices 16Y, 16M, 16C, and 16K are on standby until the processing for forming an image on the recording paper 11 is completed. Step 106 is started, and step-down processing for lowering each motor drive clock frequency related to motor stop control is started, and the process proceeds to the next Step 108.

  In this step 108, a step-down process for reducing the motor drive clock frequency is performed to wait until the operation of stopping the motor is completed. When the operation of stopping the motor is completed, the process proceeds to step 110, and the belt motor 46 performs 0FF operation, and each drum motor Y, M, C, K, 48, 50, 52, 54 performs 0FF operation, and the print mode ends.

  Next, a description will be given of the control when the PLL lock is released while the frequency is being stepped down for the DC servo motor for the motor stop control of the image forming apparatus 10 described above.

  In the motor stop control of the image forming apparatus 10, for example, as shown in FIG. 4, when each motor drive clock frequency is suddenly lowered when the motor drive clock frequency is controlled stepwise, In this case, the decrease in the rotation speed cannot catch up, the stable operation is not performed, and the PLL lock may be released.

  As shown in FIG. 4, if the PLL lock of the belt motor 46 is released during each motor stop control, the rotational drive control of the belt motor 46 becomes impossible after the PLL lock release occurs, and the intermediate transfer The speed of the belt 20 and the speed of each photosensitive drum 24 are out of synchronization to generate a speed difference, and the intermediate transfer belt 20 that operates at a relatively different speed and the photosensitive drum 24 are in sliding contact with each other. . If this is repeated many times, the intermediate transfer belt 20 and each photosensitive drum 24 may be damaged.

  Therefore, in the motor stop control of the image forming apparatus 10, as shown in the timing chart of FIG. 5, the frequency reduction speed when the motor drive clock frequency is decreased is set within a range in which the PLL lock of each motor is not released. Perform the same control.

  When performing this motor stop control together with the control for setting the range in which the PLL lock of each motor is not released, the ROM 38 or RAM 40 provided on the control board as a control means is used to reduce the motor drive clock frequency. A plurality of profiles having different frequency reduction speeds are stored in advance, and each belt motor 46, drum motor Y, M, C, K, 48, 50, 52, 54 during motor stop control at the end of a certain print mode. If even one of the PLL locks is released, the motor stop control that is performed at the end of the next print mode is slower by the control that sets the PLL lock within the range that does not release the PLL lock. Switch to the profile and perform motor stop control according to this profile.

  When the motor stop control and the control for setting the range in which the PLL lock of each motor is not released are performed together, for example, Table 1, Table 2 and Table 3 in FIG. Is stored in advance.

  When the motor stop control and the control to set the range in which the PLL lock of each motor is not released are performed together, the table 1 of FIG. 6 which is the profile with the fastest decrease speed is first read from the ROM 38 or the RAM 40. According to this table 1, the motor stop control operation in the case where there is a profile change shown in the flowchart of FIG. 8 is executed.

  In the motor stop control operation when there is a profile change shown in the flowchart of FIG. 8, after the control operation is started, in step 120, the image forming apparatus 10 sets the standby mode to wait for the start of the print mode and starts the print job. Wait until.

  Next, when the print job is started, the process proceeds to step 122, a flag related to PLL lock failure (PLL lock release) is read, and the process proceeds to the next step 124.

  In step 124, it is determined whether or not the PLL lock fail flag that is set when a PLL lock failure occurs in the previous print mode is 1. If the flag is 1, the process proceeds to step 126.

  If it is determined in step 124 that the PLL lock fail flag is 0 instead of 1, the process proceeds to step 134.

  In step 126, it is determined whether or not table 1 has been used in the previous print mode. If it is determined that table 1 has been used last time, the process proceeds to step 128 to change the profile for switching table 1 to table 2. The change process is executed, and the process proceeds to step 134.

  If it is determined in step 126 that table 1 has not been used in the previous print mode, the process proceeds to step 130.

  In step 130, it is determined whether or not the table 2 is used in the previous print mode. If it is determined that the previous table 2 is not used, the process proceeds to step 134.

  If it is determined in step 130 that the table 2 has been used in the previous print mode, the process proceeds to step 132, a profile change process for switching the table 2 to the table 3 is executed, and the process proceeds to step 134.

  In step 134, the belt motor 46 is turned on, and each drum motor Y, M, C, K, 48, 50, 52, 54 is turned on, and the process proceeds to step 136.

  In step 136, the intermediate transfer belt device 14 and the developing devices 16Y, 16M, 16C, and 16K are on standby until the processing for forming an image on the recording paper 11 is completed. Step 138 is started, and step-down processing for lowering each motor drive clock frequency related to the motor stop control is started.

  In step 140, a step-down process for decreasing the motor drive clock frequency is performed to wait until the operation for stopping the motor is completed. When the operation for stopping the motor is completed, the process proceeds to step 142, and the PLL lock is performed. The flag relating to the failure (PLL unlocked) is read, and the process proceeds to the next step 144.

  In step 144, when the PLL lock failure occurs from the belt motor 46 and each of the drum motors Y, M, C, K, 48, 50, 52, 54, the CPU 36 or the peripheral IC 42 is transmitted and stored in the RAM 40. The PLL lock of the belt motor 46 and the PLL locks of all the drum motors Y, M, C, K, 48, 50, 52, 54 are read out, and the process proceeds to the next step 146.

  In step 146, it is determined whether or not all the PLL locks stored in the RAM 40 are 1. When it is determined that all the PLL locks are 1, the process proceeds to the next step 148, and all the PLL locks are performed. If it is determined that is not 1, the process proceeds to step 150.

  In step 148, 0 is written in the PLL lock fail flag, and further, the belt motor 46 is operated 0FF, each drum motor Y, M, C, K, 48, 50, 52, 54 is operated 0FF, and the print mode is set. To complete the control operation.

  In step 150, 1 is written in the PLL lock fail flag, and further, the belt motor 46 is operated 0FF, each drum motor Y, M, C, K, 48, 50, 52, 54 is operated 0FF, The print mode is completed and the control operation is terminated.

  By controlling in this way, in the motor stop control operation when there is a profile change of the image forming apparatus 10, the profile is switched from the table 1 to the table 2 every time one of the motors is released from the PLL lock. Furthermore, by switching to a profile in which the frequency reduction speed is slow (it takes time to stop), such as switching from Table 2 to Table 3, a PLL lock failure occurs in the next motor stop control operation. Can be prevented.

  Therefore, in this motor stop control operation, it is possible to prevent the intermediate transfer belt 20 and each photosensitive drum 24 from being damaged due to frequent occurrence of PLL lock failure.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can take other various structures in the range which does not deviate from the summary of this invention.

FIG. 3 is a block diagram illustrating a control unit that controls a motor during a stop operation in the image forming apparatus according to the embodiment of the present invention. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus according to an embodiment of the present invention. 4 is a timing chart for illustrating the contents of a control method during a stop operation by the control means of the image forming apparatus according to the embodiment of the present invention. 6 is a timing chart illustrating a case where the belt motor is unlocked in the control during the stop operation by the control unit of the image forming apparatus according to the embodiment of the present invention. In the control at the time of stop operation by the control means of the image forming apparatus according to the embodiment of the present invention, the frequency reduction speed when the motor drive clock frequency is decreased is set within a range in which the PLL lock of each motor is not released. It is a timing chart which illustrates control. 4 is a table showing numerical values used for control when the motor driving clock frequency is lowered by setting the range in which the PLL lock of each motor is not released by the control means of the image forming apparatus according to the embodiment of the present invention. 3 is a flowchart showing a basic operation by a control unit of the image forming apparatus according to the embodiment of the present invention. 6 is a flowchart illustrating an operation when a profile is changed by the control unit of the image forming apparatus according to the embodiment of the present invention. 6 is a timing chart showing a comparative example for clearly showing the effect of the control during the stop operation by the control means of the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Recording paper 14 Intermediate transfer belt apparatus 16 Development apparatus 20 Intermediate transfer belt 24 Photosensitive drum 26 Exposure device 28 Development device 36 CPU
28 Developer 38 ROM
40 RAM
42 Peripheral IC
48 Drum motor Y
50 Drum motor M
52 Drum Motor C
54 Drum Motor K

Claims (6)

A photosensitive drum driven by a drum motor of the developing means is arranged to be in contact with a transfer medium formed in an endless track belt driven by a belt motor, and is electrophoretically arranged on the photosensitive drum. In the image forming apparatus configured to transfer the formed toner image onto the transfer medium,
The belt motor and at least one of the drum motors are respectively constituted by individual servo motors, and when the servo motors are stopped, the drive clock frequency of the servo motors is gradually lowered and then stopped. An image forming apparatus characterized by being configured as described above. The frequency reduction speed when the drive clock frequency of each servo motor is lowered stepwise is configured so as not to deviate from the stable operation holding state following the frequency of the control operation of each servo motor. The image forming apparatus according to claim 1. The reference clock frequency of each servo motor is configured to be lowered while maintaining the ratio during steady operation in the print mode when the reference clock frequency of each servo motor is lowered stepwise. The image forming apparatus according to claim 1. During the stop operation of each servo motor, when at least one reference clock of each servo motor reaches a minimum operating frequency, the frequency of the reference clock of all the servo motors is fixed, and all the servo motors are fixed. The image forming apparatus according to claim 3, wherein the ON signal is stopped. The transfer medium formed in the belt shape of an endless track is driven by a belt servo motor that is driven and controlled by a control means.
On the transfer medium, a photosensitive drum that is driven by a servo motor for the drum and on which a toner image is formed by an electrophotographic method is disposed so as to be in contact with the transfer medium,
After the toner image formed on the photosensitive drum is transferred onto the transfer medium, when the belt servomotor and the drum servomotor are stopped, they are stored in advance in the memory of the control means. The belt servomotor and the drum set to synchronize the speed at the rolling contact portion between the transfer medium and the photosensitive drum in a stepwise manner after a plurality of predetermined times from the start of the stop. According to the frequency data at the time of the stop operation for reducing the frequency with the servo motor of the servo motor, the rotation speed of the servo motor for the belt and the servo motor for the drum follows the frequency of the control operation of each servo motor. While maintaining the stable operation holding state, stepwise until at least one reference clock of each servo motor reaches the minimum operating frequency. Low,
A motor control method during stop operation in an image forming apparatus, wherein control is performed to stop all the servo motors when at least one reference clock among the servo motors reaches a minimum operating frequency. In the memory of the control means, a plurality of profiles having different frequencies when the frequency is lowered are stored, and usually the servo motor is stopped using a profile having the fastest speed when the frequency is lowered. If the stable operation holding state that follows the frequency of the control operation of at least one of the servo motors is removed during the stop operation control, the speed at which the frequency profile is reduced is reduced. Is switched to a one-step slow frequency profile, and the number of rotations of the belt servomotor and the drum servomotor is controlled to be lowered stepwise in accordance with the one-step slow frequency profile data. The image forming apparatus according to claim 5, wherein the mode during stop operation is Over control method.

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