JP2018010039A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain photoreceptor drums in a predetermined phase relationship while reducing downtime due to phase adjustment before image formation.SOLUTION: A CPU 202 calculates the amount of delay or advance of the phase of a photoreceptor drum 109C with respect to the phase of a photoreceptor 109K (S603) on the basis of a result of detection performed by phase sensors 205C and 205K (S602), and performs phase adjustment stop processing of controlling a motor 118C to reduce the calculated amount of delay or advance (S605 to S607) from after the completion of an image forming operation (S604 Y) until the CPU stops the photoreceptor drums 109C and 109K (S610).SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus that performs color misregistration correction control, such as an electrophotographic copying machine and an electrophotographic printer.

  In recent years, with an increase in image forming speed, an inline type color image forming apparatus uses a configuration in which photosensitive drums of respective colors are driven by a plurality of motors. Therefore, in order to solve the color shift in the sub-scanning direction (AC component color shift) that fluctuates periodically due to the eccentricity of the gear driving each photosensitive drum or the uneven rotation of the motor, the following configuration is proposed. Has been. For example, a configuration has been proposed in which the relative color misregistration is reduced by adjusting the rotational phase of each photosensitive drum to a predetermined phase relationship (see, for example, Patent Document 1).

JP 2006-259176 A

  However, in order to shorten the FPOT (First Print Out Time), which is the time to output the first recording sheet on which image formation is completed after printing is started, the following is desired. . That is, it is desired to maintain a predetermined phase relationship so as not to be affected by motor shaft loads, inertia forces, and component variations that drive each photosensitive drum while suppressing downtime due to phase adjustment before image formation.

  The present invention has been made under such circumstances, and an object thereof is to maintain each photosensitive drum in a predetermined phase relationship while suppressing downtime due to phase adjustment before image formation.

  In order to solve the above-described problems, the present invention has the following configuration.

  (1) a first photosensitive member, a second photosensitive member, a first driving unit that drives the first photosensitive member, a second driving unit that drives the second photosensitive member, and First detection means for detecting the phase of the first photoconductor, second detection means for detecting the phase of the second photoconductor, detection by the first detection means and the second detection means And a control means for controlling the first drive means or the second drive means based on the result, the control means being based on the detection results of the first detection means and the second detection means. Based on the phase of the first photoconductor, the amount of delay or advance of the phase of the second photoconductor is calculated, and after the image forming operation is completed, the first photoconductor and the second photoconductor. The second drive so as to reduce the calculated delay amount or advance amount until the body is stopped. Image forming apparatus characterized by performing the adjustment processing for controlling the means.

  (2) a first photosensitive member, a second photosensitive member, a first driving unit that drives the first photosensitive member, a second driving unit that drives the second photosensitive member, and First detection means for detecting the phase of the first photoconductor, second detection means for detecting the phase of the second photoconductor, detection by the first detection means and the second detection means And a control means for controlling the first drive means or the second drive means based on the result, the control means being based on the detection results of the first detection means and the second detection means. Based on this, the phase difference between the first photoconductor and the second photoconductor is calculated, and after the image forming operation is finished, the first photoconductor is stopped so as to reduce the calculated phase difference. An image forming apparatus, wherein the second photoconductor is stopped after being stopped.

  According to the present invention, it is possible to maintain each photosensitive drum in a predetermined phase relationship while suppressing downtime due to phase adjustment before image formation.

1 is a diagram illustrating a color image forming apparatus according to first and second embodiments. The figure which shows the rotation phase detection mechanism of the photosensitive drum of Example 1,2. FIG. 3 is a diagram illustrating a driving configuration of the photosensitive drum according to the first exemplary embodiment, and a timing chart illustrating a rotational phase detection method of the photosensitive drum. Time chart showing phase adjustment stop control of embodiment 1 Flowchart illustrating phase adjustment stop control according to the first embodiment. The figure which shows the phase difference and image frequency before image formation of Example 1. FIG. Time chart showing phase adjustment stop control of embodiment 2 Flowchart illustrating phase adjustment stop control according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail by way of examples with reference to the drawings.

[Image forming apparatus]
FIG. 1 shows an outline of the configuration of the image forming apparatus 100 according to the first embodiment. The recording paper P loaded in the paper feed cassette 101 is conveyed to the process cartridges 105Y, 105M, 105C, and 105K at a predetermined timing via the pickup roller 102, the paper feed roller 103, and the registration roller 104. Here, Y represents yellow, M represents magenta, C represents cyan, and K represents black. Since the structure and image forming operation of the process cartridges 105Y, 105M, 105C, and 105K are the same, a description of the image forming operation of the process cartridges 105M, 105C, and 105K is omitted. Also in FIG. 1, detailed drawing of the process cartridges 105M, 105C, and 105K is omitted.

  The process cartridge 105Y is integrally composed of a charging roller 106Y as a charging unit, a developing roller 107Y as a developing unit, a cleaner 108Y as a cleaning unit, and a photosensitive drum 109Y as an image carrier. A series of processes of a known electrophotographic process is performed by laser light emitted from the scanning device 111 as exposure means, and an unfixed toner image is formed on the photosensitive drum 109Y. When the unfixed toner image on the photosensitive drum 109Y is transferred to the recording paper P by the transfer roller 110Y, which is a transfer means, the recording paper P is heated and pressurized in the fixing device 115, and the unfixed toner image is recorded. It is fixed on the paper P. Thereafter, the recording paper P is discharged out of the main body of the image forming apparatus 100 via the intermediate paper discharge roller 116 and the paper discharge roller 117, and a series of printing operations is completed. A motor 118 that is a driving means applies a driving force to each unit. The controller 119 is a control board on which an electric circuit is mounted. The electric circuit includes a CPU 202 and the like which will be described later, which are control means including main body control, speed control means for the motor 118, and phase adjustment means for the photosensitive drum 109. The power supply device 120 supplies power to the fixing device 115, the motor 118, the controller 119, and the like. Hereinafter, the subscripts Y, M, C, and K representing colors are omitted unless necessary.

[Photosensitive drum rotation phase detection]
FIG. 2 shows the motor 118, the photosensitive drum 109, and the rotational phase detection mechanism of the photosensitive drum 109. FIG. 2A is a block diagram schematically showing the photosensitive drum 109 and the rotational phase detection mechanism. FIG. 2B is a diagram showing the photosensitive drum 109 and the motor 118 as viewed from a direction orthogonal to the rotation axis direction of the photosensitive drum 109. The motor 118 is a three-phase brushless motor, and includes a Y-connected coil and rotor, a hall element as rotor position detection means, and a motor drive circuit unit 201 that controls rotation of the rotor. The controller 119 includes a CPU 202 that is a control unit, a ROM 202 a that stores various programs executed by the CPU 202 and constants, and a RAM 202 b that is used as a temporary work area of the CPU 202. The CPU 202 mounted on the controller 119 outputs a rotation speed control signal to the motor 118 and drives the motor 118. The CPU 202 monitors the cycle of the rotational speed detection signal (FG signal) from the motor 118 and controls the rotational speed of the motor 118. The gear 203 rotates integrally with the photosensitive drum 109, and a flag 204 is provided on the gear 203 so that the optical path of the photosensor 205, which is a detecting unit that detects the phase of the photosensitive drum 109, is blocked as the photosensitive drum 109 rotates. To do. As a result, every time the photosensitive drum 109 makes one rotation, a signal is output from the photo sensor 205 (hereinafter, phase sensor 205). Further, a gear 206 is provided on the output shaft of the motor 118, and the drive of the motor 118 is transmitted to the photosensitive drum 109 when the gear 206 and the gear 203 are engaged with each other.

  FIG. 3A shows a driving configuration of the photosensitive drum 109. In this embodiment, description will be made on the assumption that the photosensitive drums 109Y, 109M, 109C, and 109K are driven by two motors (for example, for color and for black) as an example. A configuration is shown in which the color photosensitive drums 109Y, 109M, and 109C and the black photosensitive drum 109K are driven by gears 206C and 206K provided in the motors 118C and 118K, respectively. Here, the number of teeth of the gears 300YM, 300MC provided between the gears 203Y, 203M, 203C for driving the photosensitive drums 109Y, 109M, 109C is an integer ratio with respect to the number of teeth of the gears 203Y, 203M, 203C. ing. Note that the rotation phases of the photosensitive drums 109Y, 109M, and 109C are always the same. Accordingly, the rotational phase of the photosensitive drum 109 is detected by the phase sensor 205C and the phase sensor 205K, and the flag 204C and the flag 204K. In this embodiment, the state where the signals of the phase sensors 205 of the respective photosensitive drums 109 substantially match each other has a predetermined phase relationship that can suppress AC component color shift (periodically varying color shift). It shall be.

  FIG. 3B shows a method for detecting the rotational phase of the photosensitive drum 109. FIG. 3B shows the waveforms of the output signals from the phase sensors 205C and 205K that detect the rotational phases of the photosensitive drums 109C and 109K and the internal clock generated inside the CPU 202 from above. The CPU 202 starts phase detection at an arbitrary timing after the peripheral speeds of the photosensitive drums 109C and 109K reach the steady speed. The CPU 202 starts the count operation (Ccnt, Kcnt) synchronized with the internal clock until the rising edge of the output signal of the phase sensors 205C, 205K is detected from the timing (phase broken line) at which the phase detection is started. Hereinafter, the values of the count operation (Ccnt, Kcnt) of the phase sensor 205 are described as Ccnt and Kcnt. The CPU 202 measures at least once the count value (hereinafter referred to as Tcnt) (photosensitive drum cycle) when the photosensitive drums 109C and 109K make one revolution and the above-described values of Ccnt and Kcnt. A rotational phase shift amount (hereinafter referred to as phase difference) of the photosensitive drums 109C and 109K calculated from the measured values of Tcnt, Ccnt, and Kcnt is stored in advance in, for example, the RAM 202b in preparation for phase adjustment control described later. Note that Tcnt may be measured in advance prior to the measurement of Ccnt and Kcnt, and stored in, for example, the RAM 202b. Various forms of the above-described phase difference calculation and storage update method are conceivable. For example, each stored value may be updated based on the values of Tcnt, Ccnt, and Kcnt measured every round. In addition, for each of a plurality of values of Tcnt, Ccnt, and Kcnt measured every round, an arithmetic processing such as an average may be stored. Accordingly, the method of calculating the phase difference α and updating the storage between the photosensitive drum 109C and the photosensitive drum 109K is not limited to the embodiments shown in FIGS.

The CPU 202 calculates a relative phase shift (advance and delay) amount based on the photosensitive drum cycle Tcnt and the count values Ccnt and Kcnt when the rising edges of the output signals of the phase sensors 205C and 205K are detected from the start of phase detection. Can be detected. Here, the phase delay amount of the photosensitive drum 109C with respect to the phase of the photosensitive drum 109K is positive. The phase delay amount α of the photosensitive drum 109C, which is the second photosensitive member, with reference to the photosensitive drum 109K, which is the first photosensitive member in this embodiment, is
α = (Ccnt−Kcnt) / (Tcnt) × 360 [deg] (1)
Can be detected by computing as follows. In this embodiment, since the phase delay amount of the photosensitive drum 109C with respect to the phase of the photosensitive drum 109K is positive, if α is negative as a result of Expression (1), the phase of the photosensitive drum 109K is The phase of the photosensitive drum 109C is advanced. Note that the advance amount of the phase of the photosensitive drum 109C with respect to the phase of the photosensitive drum 109K may be positive. Hereinafter, α calculated by Expression (1) is referred to as a phase difference, and represents a delay amount when α is positive, and an advance amount when α is negative.

  For example, when Ccnt = 260, Kcnt = 520, and Tcnt = 720, the phase difference α is −130 [deg]. This means that the phase of the photosensitive drum 109C is advanced by 130 [deg] from the phase of the photosensitive drum 109K (the photosensitive drum serving as a reference among the photosensitive drums 109). In the final phase adjustment for the above-described example, the phase of the photosensitive drum 109C is controlled to a phase relationship that is delayed by 130 [deg] from the phase when the phase is detected (the phase is opposite to the phase difference α calculated by the calculation). Then, the image forming apparatus 100 is controlled to stop. By stopping the photosensitive drum 109 by performing such phase control, the phase of the photosensitive drum 109C is set to the photosensitive drum 109K without performing phase adjustment control when restarting for the next printing operation. It is a feature of the present invention to make them substantially coincide.

[Phase adjustment stop]
FIG. 4 shows a time chart of the phase adjustment stop of this embodiment in which the CPU 202 performs phase adjustment of the photosensitive drum 109C after the printing operation is completed and stops the photosensitive drum 109C and the photosensitive drum 109K substantially simultaneously. 4 (i) shows the state of the photosensitive drum 109K (stop, rotation operation, etc.), FIG. 4 (ii) shows the state of the photosensitive drum 109C (stop, rotation operation, etc.), and FIG. 4 (iii) shows the state of the image forming apparatus 100. (Standby, print, phase detection, etc.) are shown respectively. The horizontal axis is time.

  When the image forming apparatus 100 is in the standby state, the photosensitive drum 109C and the photosensitive drum 109K both stop rotating. When the image forming apparatus 100 starts printing, the photosensitive drum 109C and the photosensitive drum 109K start to rotate. As described above, the CPU 202 starts phase detection at an arbitrary timing after the peripheral speeds of the photosensitive drums 109C and 109K reach the steady speed. In a period A during the printing operation (image forming operation) after the phase detection is performed, the CPU 202 calculates the phase difference α of the photosensitive drum 109C using the photosensitive drum 109K as a reference, and the calculated phase difference α is, for example, the RAM 202b. Save to. The phase difference α is obtained from Expression (1) based on the phases detected by the phase sensor 205K as the first detection means and the phase sensor 205C as the second detection means. As shown in FIG. 4 (iii), the CPU 202 performs phase detection from the start to the end of printing, calculates the phase difference α, and stores the calculated phase difference α in the RAM 202b.

  In the B period after the printing is finished, the CPU 202 changes the rotational speed of the photosensitive drum 109C and controls so as to cancel the phase difference α calculated in the A period as described above (FIG. 4 (iii) phase adjustment). Note that the control to cancel the phase difference α is hereinafter also referred to as the control so that the opposite phase is −α. After the phase difference α is canceled by the phase adjustment control of the CPU 202, both the photosensitive drum 109C and the photosensitive drum 109K are stopped (FIG. 4 (iii) is stopped). In FIG. 4 (ii), the state in which the rotational speed of the photosensitive drum 109C is changed and the rotational phase is controlled to be opposite to the phase difference α is referred to as rotational correction of the photosensitive drum 109C. While the phase adjustment control is performed in the period B, the rotational speed of the photosensitive drum 109K is driven by the motor 118K as the first driving unit so that the rotational speed during image formation is maintained. As shown in FIG. 4 (ii), in the period B, the photosensitive drum 109C is corrected by changing the rotation speed in order to eliminate the phase difference α with respect to the photosensitive drum 109K. As described above, in the photosensitive drum 109C, the phase difference α is −130 [deg], and the phase is advanced from that of the photosensitive drum 109K. For this reason, by changing the rotational speed of the photosensitive drum 109C, the phase advance amount 130 [deg] is corrected to be canceled, that is, 130 [deg] delayed. Since the phase adjustment involves changing the rotational speed of the photosensitive drum 109C, the period B is provided after the printing is completed. When the phase adjustment of the photosensitive drum 109C is completed, the image forming apparatus 100 shifts to a standby state. At this time, the rotation of both the photosensitive drum 109C and the photosensitive drum 109K is stopped. Thereafter, when the next printing is started, the same processing is repeated. At the start of the next printing, the printing operation can be started without performing the phase adjustment processing of the photosensitive drums 109C and 109K.

[Phase adjustment stop processing]
FIG. 5 shows a flowchart of the phase adjustment stop processing of the present embodiment by the CPU 202. In this processing example, the description will be made on the assumption that the configuration for measuring and storing Ccnt and Kcnt is measured and updated a predetermined number of times during the printing operation of the image forming apparatus 100. Regarding Tcnt, the CPU 202 measures the period based on the detection result of the phase sensor 205 in advance and stores it in the RAM 202b before the phase detection start processing performed in step (hereinafter referred to as S) 602. Will be described. In step S601, the CPU 202 determines whether printing has started. If it is determined that printing has not started, the process returns to step S601. If it is determined that printing has started, the process proceeds to step S602. In step S602, the CPU 202 starts phase detection of the photosensitive drums 109C and 109K by the phase sensors 205C and 205K. In step S602, as described with reference to FIG. 3B, the CPU 202 receives a phase detection start instruction and starts a count operation after resetting the count values Ccnt and Kcnt (Ccnt = Kcnt = 0).

  In step S <b> 603, the CPU 202 calculates the phase difference α between the photosensitive drum 109 </ b> C and the photosensitive drum 109 </ b> K using the count values Tcnt, Ccnt, and Kcnt according to the above equation (1). The CPU 202 stores the calculated phase difference α as a stored value in the RAM 202b. In step S604, the CPU 202 determines whether printing has ended. If it is determined that printing has not ended, the process returns to step S602. If it is determined that printing has ended, the process proceeds to step S605. As described above, when printing continues, the CPU 202 repeatedly executes the processing of S602 and S603, thereby updating the value of the phase difference α obtained by the calculation to the RAM 202b.

  In step S605, the CPU 202 executes a phase adjustment stop process. Here, the phase adjustment stop will be described. The CPU 202 starts a phase adjustment stop process after stopping the printing operation and before stopping the photosensitive drums 109C and 109K. The CPU 202 reads out information on the phase difference α between the photosensitive drum 109C and the photosensitive drum 109K stored in the RAM 202b in S603 from the RAM 202b. The CPU 202 sets an opposite phase −α (+130 [deg] in the above example) of the phase difference α, which is a target value for phase control, from the phase difference α (−130 [deg] in the above example) read from the RAM 202b. .

  In S606, the CPU 202 determines whether or not the phase difference α of the photosensitive drum 109C with respect to the photosensitive drum 109K is within a predetermined range, that is, whether or not −α−β <−α <−α + β [deg] is satisfied. To do. Here, β represents an adjustment error when adjusting the phase difference. The adjustment error β is set in consideration of variations among products. If the CPU 202 determines in S606 that the phase difference α is not within the predetermined range (−α ≦ −α−β [deg], −α + β ≦ −α [deg]), the process proceeds to S607. If the CPU 202 determines that the phase difference α is within a predetermined range (−α−β <−α <−α + β [deg]), the process proceeds to S610. In step S607, the CPU 202 executes phase control so that the phase difference of the photosensitive drum 109C with respect to the photosensitive drum 109K is −α. The CPU 202 controls the motor 118C, which is the second driving means, by changing the rotation speed control signal for the motor drive circuit unit 201, changes the rotation speed of the photosensitive drum 109C, and changes the photosensitive drum 109K to the photosensitive drum 109K. 109C phase adjustment is executed. The phase control described above is continued until the CPU 202 determines in step S606 that the phase difference α satisfies −α−β <−α <−α + β [deg].

  The phase adjustment in S607 will be described in more detail. When the CPU 202 determines that the phase of the photosensitive drum 109 </ b> C is delayed by −α−β [deg] or more with respect to the photosensitive drum 109 </ b> K (−α ≦ −α−β [deg]), the CPU 202 performs the following control. . That is, the CPU 202 performs phase control so that the motor 118C is accelerated with respect to the motor 118K, and adjusts the phase difference to satisfy −α−β <−α [deg]. On the other hand, when the phase of the photosensitive drum 109C is advanced by −α + β [deg] or more with respect to the photosensitive drum 109K (−α + β ≦ −α [deg]), the CPU 202 performs the following control. That is, the CPU 202 performs phase control so as to decelerate the motor 118C relative to the motor 118K, and adjusts the phase difference to satisfy −α <−α + β [deg]. After performing the phase adjustment in S607, the CPU 202 returns the process to S606.

  In step S610, the CPU 202 stops driving the photosensitive drums 109C and 109K in a state where the phase difference α between the photosensitive drums 109C and 109K is adjusted. In step S611, the CPU 202 ends the phase adjustment stop process. Thereafter, the CPU 202 returns the process to S601 to prepare for the start of the next print. As described above, in this embodiment, it is assumed that the photosensitive drums 109Y, 109M, 109C, and 109K are driven by two motors. Therefore, the phase control of the photosensitive drums 109Y and 109M is also performed by performing the phase control of the photosensitive drum 109C.

  As described above, the CPU 202 calculates the phase delay amount or advance amount of the photosensitive drum 109C with respect to the phase of the photosensitive drum 109K based on the detection results of the phase sensors 205C and 205K. Then, the CPU 202 performs phase adjustment stop processing (adjustment processing) for controlling the motor 118C so as to reduce the calculated delay amount or advance amount after the image forming operation is completed and before the photosensitive drums 109C and 109K are stopped. )I do. In the period B in FIG. 4, the CPU 202 performs phase adjustment stop processing by accelerating or decelerating the motor 118C based on the detection result of the phase sensor 205C. Further, the CPU 202 calculates a phase delay amount or an advance amount when performing an image forming operation in which the rotation of the photosensitive drums 109C and 109K is stable. When starting the next image forming operation, the CPU 202 starts the image forming operation without performing control for adjusting the phases of the photosensitive drums 109C and 109K.

[Phase difference and frequency]
FIG. 6 shows the result of an experiment in which the printing operation is repeatedly executed by one image forming apparatus. FIG. 6 shows the phase difference before the image formation of the photosensitive drum 109 </ b> C with respect to the photosensitive drum 109 </ b> K when the phase adjustment stop process is performed, and the frequency of the phase difference. In FIG. 6, the experimental result when the processing of the present embodiment is performed is indicated by a solid line, and the experimental result when the processing of the present embodiment is not performed is indicated by a broken line. In FIG. 6, the horizontal axis indicates the phase difference [deg] of the photosensitive drum 109C with the photosensitive drum 109K as a reference, and the vertical axis indicates the frequency of the phase difference. Note that the value and frequency of the phase difference shown in FIG. 6 vary depending on each image forming apparatus. Looking at the experimental results, the phase difference of the photosensitive drum 109C with respect to the photosensitive drum 109K when this embodiment is implemented converges within a range of ± 10 [deg]. In the image forming apparatus in which the experiment was performed, the relative color misregistration can be reduced by setting the phase difference between the photosensitive drums 109C and 109K within the range of ± 10 [deg]. On the other hand, when the phase adjustment stop process shown in FIG. 5 is not performed, the phase difference between the photosensitive drums 109 </ b> C and 109 </ b> K is 25 [deg] to 50 [deg] as shown by the broken line in FIG. 6. For this reason, the phase relationship between the photosensitive drums 109C and 109K is shifted from the predetermined phase relationship before the image formation of the next print job. In the image forming apparatus in which the experiment was performed, when the phase difference between the photosensitive drums 109C and 109K has a phase relationship of 25 [deg] to 50 [deg], the relative color shift cannot be reduced. This is because the motor 118C and 118K have axial load differences, inertial forces, and component variations when the motor 118C and the motor 118K are stopped, started, and when the load fluctuates. The motor shaft loads of the motors 118C and 118K vary depending on the gear configuration, component variations, deterioration due to use, and usage environment (temperature, humidity). The inertial force varies depending on the rotor diameter and weight of the motors 118C and 118K. The parts are affected by variations in the mechanical accuracy of the stators and rotors of the motors 118C and 118K, the resistance of the stator windings and variations in circuit constants, and the like.

  In the present embodiment, by performing the above-described phase adjustment stop process, it is possible to minimize color misregistration (AC component color misregistration) in the sub-scanning direction in which the recording paper P is conveyed. In the present embodiment, the motor is stopped by adjusting the phase relationship so as to correct the phase difference between the motors caused by the motor shaft load difference, inertial force, and component variations. For this reason, it is possible to operate in a state where a predetermined phase relationship is maintained when each photosensitive drum is activated while shortening the FPOT. In the present exemplary embodiment, the phase adjustment stop process is described for each print job. However, the phase difference between the motors 118C and 118K that drive the photosensitive drum 109 also occurs when the image forming apparatus 100 is replaced. there's a possibility that. Therefore, the CPU 202 may be configured to perform the phase adjustment stop process described in the present embodiment even when it is determined that printing has been started before the power is turned on or when the part has been replaced. The timing for executing the phase adjustment stop process is the same in the second embodiment described below. In this embodiment, the phase difference α of the photosensitive drum 109C is obtained with the photosensitive drum 109K as a reference, and the rotational phase of the photosensitive drum 109C is corrected. However, the rotational phase of the photosensitive drum 109K may be corrected by obtaining the phase difference α2 of the photosensitive drum 109K with reference to the photosensitive drum 109C. In this case, the difference “Ccnt−Kcnt” in Expression (1) may be set to “Kcnt−Ccnt”. As in the present embodiment, the delay amount may be positive, and the advance amount may be positive.

  As described above, according to the present exemplary embodiment, it is possible to maintain each photosensitive drum in a predetermined phase relationship while suppressing downtime due to phase adjustment before image formation.

  The configuration of the second embodiment is the same as that of the first embodiment, and the phase adjustment processing after printing is different. Only different parts will be described with respect to FIG. 4 and FIG. 5, and overlapping parts will be denoted by the same reference numerals and description thereof will be omitted. Also in this embodiment, the phase difference is obtained based on the detection result of the phase detection described with reference to FIG. 3B, and phase correction is controlled based on the obtained phase difference.

[Period A and Period B]
FIG. 7 is a time chart of the phase adjustment stop of this embodiment in which the phase adjustment is performed by controlling the stop timing from the relative phase relationship between the photosensitive drum 109C and the photosensitive drum 109K by the CPU 202 after the printing operation is completed. Indicates. (I) to (iii) of FIGS. 7A and 7B are the same as FIGS. 4I to 4I. In FIG. 7A, in the period B after the end of printing, the photosensitive drum 109C whose phase is relatively advanced with respect to the photosensitive drum 109K is stopped until the phase difference α calculated in the period A coincides with the opposite phase. In this case, the photosensitive drum 109K is rotated and then stopped. On the other hand, FIG. 7B shows that the photosensitive drum 109K whose phase is relatively advanced with respect to the photosensitive drum 109C is stopped in the C period after the printing is finished, and coincides with the phase difference α calculated in the A period and the opposite phase. In this case, the photosensitive drum 109C is rotated until it is stopped.

  In FIG. 7A, when printing is completed and the period B is adjusted, the rotation of the photosensitive drum 109C whose phase is relatively advanced is stopped. On the other hand, the rotational speed of the photosensitive drum 109K having a relatively delayed phase is controlled by the motor 118K so that the phase difference is opposite to the phase difference α (−α). When the rotational phase of the photosensitive drum 109K becomes the opposite phase (−α) of the phase difference α (when the phase difference α is canceled), the rotation of the photosensitive drum 109K is stopped, and the standby state is entered.

  In FIG. 7B, when the printing is completed and the period shifts to the C period during which the phase adjustment is performed, the rotation of the photosensitive drum 109K whose phase is relatively advanced is stopped. On the other hand, the rotational speed of the photosensitive drum 109C whose phase is relatively delayed is controlled by the motor 118C so that the phase difference is opposite to the phase difference α (−α). When the rotation phase of the photosensitive drum 109C becomes the opposite phase (−α) of the phase difference α (when the phase difference α is canceled), the rotation of the photosensitive drum 109C is stopped and the standby state is entered. Other operations are the same as those in the first embodiment, and a description thereof will be omitted.

[Phase adjustment stop processing]
FIG. 8 shows the phase adjustment stop processing of the present embodiment by the CPU 202. Note that the processing of S901 to S905 is the same as the processing of S601 to S605, and a description thereof will be omitted. In S906, the CPU 202 determines whether the phase of the photosensitive drum 109C is delayed with respect to the photosensitive drum 109K from the phase difference α calculated in S903. If the CPU 202 determines in S906 that the phase of the photosensitive drum 109C is delayed by [deg] with respect to the phase of the photosensitive drum 109K, the process proceeds to S907. In step S907, the CPU 202 stops the photosensitive drum 109K whose phase is relatively advanced with respect to the photosensitive drum 109C. In S908, the CPU 202 initializes the count value Ccnt (Ccnt = 0), starts phase detection of the photosensitive drum 109C by the phase sensor 205C, and starts measuring Ccnt. In step S909, the CPU 202 calculates the phase advance amount β of the photosensitive drum 109C with respect to the stopped photosensitive drum 109K based on Ccnt measured in step S908 and Tcnt measured in advance and stored in the RAM 202b using equation (2). Use to calculate.
β = (Ccnt) / (Tcnt) × 360 [deg] (2)
Then, the CPU 202 determines whether or not the calculated phase advance amount β of the photosensitive drum 109C is α. That is, the CPU 202 determines whether or not the phase of the photosensitive drum 109C has advanced by α [deg] so as to cancel the phase delay amount α with respect to the photosensitive drum 109K. If the CPU 202 determines in step S909 that the phase of the photosensitive drum 109C has not advanced by α [deg], the process returns to step S909. If the CPU 202 determines that the phase has advanced, the process proceeds to step S910. In S910, the CPU 202 stops the photosensitive drum 109C. The CPU 202 advances and stops the phase of the photosensitive drum 109C by the phase difference α [deg] (which is also a delay amount) of the photosensitive drum 109C with respect to the photosensitive drum 109K, ends the phase adjustment stop in S911, and advances the processing to S901. return.

If the CPU 202 determines in S906 that the phase of the photosensitive drum 109C is advanced by α [deg] with respect to the phase of the photosensitive drum 109K from the phase difference α calculated in S903, the process proceeds to S912. In S912, the CPU 202 stops the photosensitive drum 109C whose phase is relatively advanced with respect to the photosensitive drum 109K. In S913, the CPU 202 initializes the count value Kcnt (Kcnt = 0), starts phase detection of the photosensitive drum 109K by the phase sensor 205K, and starts measuring Kcnt. In step S914, the CPU 202 calculates the phase advance amount γ of the photosensitive drum 109K with respect to the stopped photosensitive drum 109C based on the Kcnt measured in step S913 and the Tcnt measured in advance and stored in the RAM 202b. Use to calculate.
γ = (Kcnt) / (Tcnt) × 360 [deg] (3)
Then, the CPU 202 determines whether or not the calculated phase advance amount γ of the photosensitive drum 109K is α. That is, the CPU 202 determines whether or not the phase of the photosensitive drum 109K has advanced by α [deg] so as to cancel the phase delay amount α with respect to the photosensitive drum 109C. If the CPU 202 determines in step S914 that the phase of the photosensitive drum 109K has not advanced by α [deg], the process returns to step S914. If the CPU 202 determines that the phase has advanced, the process proceeds to step S915. In S915, the CPU 202 stops the photosensitive drum 109K. The CPU 202 advances and stops the phase of the photosensitive drum 109K by the phase difference α [deg] (which is also a delay amount) of the photosensitive drum 109K with respect to the photosensitive drum 109C, ends the phase adjustment stop in S911, and advances the processing to S901. return.

  Thus, in this embodiment, the CPU 202 calculates the phase difference between the photosensitive drums 109C and 109K based on the detection results of the phase sensors 205C and 205K. After the image forming operation is completed, the CPU 202 stops the photosensitive drum 109 whose phase is delayed after stopping the photosensitive drum 109 whose phase is advanced so as to reduce the calculated phase difference. An adjustment stop process (adjustment process) is performed. The CPU 202 stops the photosensitive drum 109 whose phase is advanced before performing the phase adjustment stop process. Further, in the phase adjustment stop process shown in the period B or C in FIG. 7, the CPU 202 delays the phase based on the detection result of the phase sensor 205 that detects the phase of the photosensitive drum 109 that is delayed in phase. The phase of the photosensitive drum 109 that is present is advanced. The CPU 202 calculates the phase difference α when performing the image forming operation in which the rotation of the photosensitive drums 109C and 109K is stable. When starting the next image forming operation, the CPU 202 starts the image forming operation without performing control for adjusting the phases of the photosensitive drums 109C and 109K.

  In this embodiment, after the photosensitive drum 109 whose phase is relatively advanced is stopped, the photosensitive drum 109 whose phase is relatively delayed is stopped to reduce the calculated phase difference. ing. However, the photosensitive drum 109 whose phase is advanced may be stopped after the photosensitive drum 109 whose phase is delayed is stopped. For example, when the phase difference between the photosensitive drum 109C and the photosensitive drum 109K is α ° and the phase of the photosensitive drum 109C is advanced, in the above-described control, after the photosensitive drum 109C is stopped so as to reduce the phase difference α °. Then, the photosensitive drum 109K is stopped. In this control, the photosensitive drum 109C may be stopped after the photosensitive drum 109K is stopped so as to reduce the phase difference (360 ° −α °).

  As described above, compared with the first embodiment, the stop timing in the phase adjustment stop processing of the photosensitive drum 109K and the photosensitive drum 109C is different. However, the target value of control and the technical idea of control are the same. Therefore, also in this embodiment, the same effect as that of Embodiment 1 can be obtained. In addition, as an embodiment of the image forming apparatus 100, it is sufficient to have at least one of the form described in the first embodiment or the form described in the present embodiment. Further, in the embodiment described in the first embodiment and the present embodiment, in order to shorten the FPOT, the plurality of photosensitive drums 109 are simultaneously rotated. In the embodiment described in the first embodiment and the present embodiment, it has been described that the photosensitive drums 109Y, 109M, 109C, and 109K are driven by two motors. However, in the configuration in which two or more photosensitive drums are driven by two or more motors, the same effect can be obtained by applying the embodiment shown in the first embodiment and this embodiment.

  As described above, according to the present exemplary embodiment, it is possible to maintain each photosensitive drum in a predetermined phase relationship while suppressing downtime due to phase adjustment before image formation.

109 Photosensitive drum 118 Motor 202 CPU
205 Phase sensor

Claims (12)

A first photoreceptor;
A second photoreceptor,
First driving means for driving the first photosensitive member;
Second driving means for driving the second photosensitive member;
First detection means for detecting the phase of the first photoconductor;
Second detection means for detecting the phase of the second photoconductor;
Control means for controlling the first drive means or the second drive means based on the detection results of the first detection means and the second detection means;
With
The control means calculates a delay amount or advance amount of the phase of the second photoconductor relative to the phase of the first photoconductor based on detection results of the first detection means and the second detection means. The second drive is performed so that the calculated delay amount or advance amount is reduced between the end of the image forming operation and the stop of the first photosensitive member and the second photosensitive member. An image forming apparatus that performs adjustment processing for controlling the means.   The control means controls the first driving means so that the rotation speed of the first photosensitive member during the image forming operation is maintained during the adjustment process. Item 2. The image forming apparatus according to Item 1.   3. The control unit according to claim 1, wherein the control unit performs the adjustment process by accelerating or decelerating the second driving unit based on a detection result of the second detecting unit. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the control unit calculates the delay amount or the advance amount when performing an image forming operation. A first photoreceptor;
A second photoreceptor,
First driving means for driving the first photosensitive member;
Second driving means for driving the second photosensitive member;
First detection means for detecting the phase of the first photoconductor;
Second detection means for detecting the phase of the second photoconductor;
Control means for controlling the first drive means or the second drive means based on the detection results of the first detection means and the second detection means;
With
The control unit calculates a phase difference between the first photoconductor and the second photoconductor based on detection results of the first detection unit and the second detection unit, and the image forming operation is completed. Then, an adjustment process is performed to stop the second photosensitive member after stopping the first photosensitive member so as to reduce the calculated phase difference.   The control means stops the photoconductor whose phase is relatively advanced determined based on the calculated phase difference, and then the photoconductor whose phase is relatively delayed determined based on the phase difference. The image forming apparatus according to claim 5, wherein the image forming apparatus is stopped.   The control means advances the phase of the photoconductor whose phase is delayed based on a detection result of a detection device for detecting the phase of the photoconductor whose phase is delayed. The image forming apparatus according to claim 5 or 6.   The control means stops the photoconductor whose phase is relatively delayed based on the calculated phase difference, and then stops the photoconductor whose phase is advanced based on the phase difference. The image forming apparatus according to claim 5, wherein the image forming apparatus is stopped.   The control means advances the phase of the photoconductor whose phase is advanced based on a detection result of a detection means for detecting the phase of the photoconductor whose phase is advanced. The image forming apparatus according to claim 5 or 8.   The image forming apparatus according to claim 5, wherein the control unit calculates the phase difference when an image forming operation is performed.   The control means performs the adjustment process every time the image forming operation is completed, before starting the image forming operation after the power is turned on, or when it is determined that the part has been replaced. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The control means starts the image forming operation without performing control for adjusting the phase of the first photoconductor and the phase of the second photoconductor when starting the next image forming operation. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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