JP2006039091A - Multicolor image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multicolor image forming apparatus capable of shortening a waiting time by phase adjustment and shortening a first print time with an inexpensive configuration.
SOLUTION: A plurality of rotating bodies for image holding, a plurality of motors for driving these rotating bodies, a means for detecting a detected member provided on the rotating body, speed control for the motor, and Motor control means for performing position control and phase detection means for detecting the phase of each rotating body from the result of detecting the detected member provided on each rotating body, and adjusting the phase of the rotating body to prevent color misregistration. In the multicolor image forming apparatus to be suppressed, the phase adjustment reference is made variable.
[Selection] Figure 1

Description

  The present invention relates to a multicolor image forming apparatus and method, for example, an electrophotographic multicolor image forming apparatus, and a control apparatus therefor.

  FIG. 1 shows images of four colors, that is, yellow (hereinafter referred to as “Y”), magenta (hereinafter referred to as “M”), cyan (hereinafter referred to as “C”), and black (hereinafter referred to as “K”). 1 shows a multicolor image forming apparatus provided with forming means. In the figure, 10a to 10d are photosensitive drums for forming an electrostatic latent image (a, b, c and d are for Y, M, C and K, respectively). And 15a to 15d are motors for driving the photosensitive drums.

  11a to 11d are laser scanners that perform exposure according to image signals and form an electrostatic latent image on the photosensitive drum 10, 12 is an endless conveyance belt that sequentially conveys paper to each color image forming unit, and 13 is , A driving roller connected to driving means including a motor and a gear, and the like, and a driving roller for driving the conveying belt 12, a motor for driving the driving roller 13, and a fixing device for melting and fixing the toner transferred to the paper, Reference numerals 16 a to 16 d denote phase detection sensors that detect the rotational phase of the photosensitive drum 10.

  When data to be printed is sent from the PC to the printer and image formation according to the printer engine system is completed and printing is possible, paper 17 is supplied from a paper cassette (not shown) in the direction of the arrow and reaches the conveyor belt 12. Then, the sheet 17 is sequentially conveyed to the image forming units of the respective colors by the conveying belt 12. The image signal of each color is sent to each laser scanner 11 in synchronism with the paper conveyance by the conveyance belt 12, and an electrostatic latent image is formed on the photosensitive drum 12, and electrostatically is applied to the photosensitive drum 10 by a developing device (not shown). The latent image is developed with toner and transferred onto the paper 17 at a transfer portion where the photosensitive drum and the transport belt are in contact with each other. In the figure, images are sequentially formed in the order of Y, M, C, and K. Thereafter, the paper 17 is separated from the conveyance belt, and the toner image is fixed on the paper 17 by heat by the fixing device 14 and discharged to the outside.

  By the way, in the multi-color image forming apparatus configured as described above, the mismatch of the image forming positions of the respective colors appears in the image as a color shift, leading to deterioration of the image quality. Color misregistration includes regular color misregistration (hereinafter referred to as DC color misregistration) that occurs due to positional misalignment when assembling the developing devices for each color, and periodic color that occurs due to shaft flutter of the rotating body. It can be roughly divided into shifts (hereinafter referred to as AC color shifts).

  Among these, as a measure against AC color misregistration, a method of individually controlling the rotation phase of each color rotator is known. Specifically, when the motors 15a to 15d are started, rotation control of the motors 15a to 15c is performed so that the rotation phases of the photosensitive drums 10a to 10c are matched with reference to the rotation phase of the photosensitive drum 10d.

  FIG. 15 schematically shows the phases of the conventional photosensitive drums 10a to 10d. Reference numerals 61a to 61d denote the phases of the photosensitive drums 10a to 10d, respectively. The photosensitive drum 10a is 50 °, the photosensitive drum 10b is 180 °, and the photosensitive drum 10c is 110 ° out of phase with respect to the photosensitive drum 10d. It represents that.

In the conventional example, when it takes 0.1 seconds to adjust the phase of the photosensitive drum by 10 °, the photosensitive drum control including phase adjustment will be described. (In actuality, the deviation amount and the adjustment time do not have a simple proportional relationship as described above. However, although the time varies depending on the control method, the adjustment time increases as the deviation amount increases. In this example, the case where 10 ° adjustment = 0.1 second is described as an example.)
FIG. 16 is a diagram for explaining a timing chart relating to driving of each photosensitive drum when the multicolor image forming apparatus is started up and when an image is formed in the conventional example. The description of FIG.

  At the time of 0 second, the start-up of the motors 15a to 15d of the respective colors is started, and the start-up is completed to a steady speed by 0.5 seconds. Thereafter, between 0.5 and 1 second, the phase detection sensor 16d detects the rotational phase of the K photosensitive drum 10d serving as a reference, and the phase detection sensors 16a to 16c detect the phase difference between the other photosensitive drums 10a to 10c. Is detected. As a result, the phase shift as described above is detected, and the control shown by the arrow in FIG. 15 is executed. The photosensitive drum 10a is 0.5 seconds, the photosensitive drum 10b is 1.8 seconds, and the photosensitive drum 10c is 1.. Adjustment is made so that the phase with the photosensitive drum 10d is matched over one second.

As a result, the image forming apparatus is ready to start image formation 2.8 seconds after start-up.
JP 2003-211943 A

  However, the conventional method has the following drawbacks.

  Since the phase adjustment sequence is executed as necessary when the motor is started, image formation must be waited until the phase adjustment is completed at the time of executing the phase adjustment sequence, which causes a long first print time. At this time, since the reference for phase adjustment is set to a predetermined specific photoconductor, the phase adjustment time may become very long depending on the phase relationship with other photoconductors. .

  The present invention has been made in view of the above points, and an object of the present invention is a multicolor image forming apparatus capable of reducing the waiting time by phase adjustment and shortening the first print time with an inexpensive configuration. Is to provide.

  In order to achieve the above object, a first invention according to the present application includes a plurality of rotating bodies for carrying images, a plurality of motors for driving these rotating bodies, and a detected member provided on the rotating body. Detecting means; motor control means for performing speed control and position control on the motor; and phase detection means for detecting the phase of each rotating body from the result of detecting the detected member provided on each rotating body. In the multicolor image forming apparatus that suppresses color misregistration by adjusting the phase of the rotating body by controlling the motor, the phase adjustment reference for adjusting the phase of the rotating body is made variable. Features.

  According to a second aspect of the present application, in the multicolor image forming apparatus according to the first aspect, the reference is a specific rotating body in which the time required for phase adjustment is the shortest among the plurality of rotating body phases. It is characterized by being a phase.

  According to a third aspect of the present application, in the multicolor image forming apparatus according to the first aspect, the reference is a specific phase that minimizes the time required for phase adjustment.

  According to a fourth aspect of the present application, in the multicolor image forming apparatus according to any one of the first to third aspects, a change in phase adjustment time due to a load change of the motor is taken into account when the reference is set.

  In the above configuration, since the control is performed to reduce the time required for the phase adjustment with an inexpensive configuration, it is possible to provide an image forming apparatus capable of reducing the first print time.

  As described above, according to the present invention, it is possible to provide a multicolor image forming apparatus capable of reducing the waiting time by phase adjustment and shortening the first print time with an inexpensive configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

  The configuration of the multicolor image forming apparatus according to the first embodiment of the present invention is the same as that of FIG. In the figure, phase control is performed on the photosensitive drums 10a to 10d according to the present invention to suppress color misregistration. Since other configurations and operations are the same as those of the conventional example, description thereof is omitted.

  FIG. 2 shows a schematic configuration of the control system of this apparatus. Reference numeral 20 denotes a printer as a multicolor image forming apparatus. A printer control unit 21 controls each device in the printer. A power supply 22 supplies power to each device in the printer. Reference numerals 23 denote sensors for detecting the status of each unit in the printer. A motor control unit 24 controls the motors according to instructions from the printer control unit. Reference numeral 25 denotes motors which are power sources of the respective devices in the printer. A display unit 26 notifies the user of the operation status of the printer. A communication controller 27 performs communication between the printer and the host computer. A host computer 28 transfers data to be printed to the printer.

  FIG. 3 shows the configuration of the main part according to the present invention.

  Reference numeral 30 denotes a DSP (digital signal processor), 31 a motor, 32 a driver for controlling electric power to the motor, and 33 a rotating body such as a photosensitive drum driven by the motor. A flag 35 is provided on the shaft 34 of the rotating body 33, and the optical path of the photosensor 36 is blocked as the shaft 34 rotates. As a result, a signal is output once for each rotation of the shaft. Alternatively, a configuration may be adopted in which a flag is provided in the rotating body or a gear that drives the rotating body, and the flag shields the photosensor.

  The DSP 30 controls the rotational position of the motor, starts and stops the motor by a control signal from the printer control unit, compares the speed signal from the printer control unit with the output of the speed detection means, and performs speed control via the driver. .

  Next, a method in which the reference rotating body is the photosensitive drum 10a and the drive control of the photosensitive drum 10b is performed will be described with reference to FIGS.

  When the motor control is instructed from the printer control unit (step 1 in FIG. 4), the motor control unit performs speed control and position control for each motor, and minimizes the relative speed of each motor. The position command is updated according to a predetermined acceleration curve to accelerate the vehicle (step 2 in FIG. 4). When all the motors reach the steady rotational speed, the acceleration is finished (step 3 in FIG. 4).

  Next, when the printer control unit instructs execution of phase adjustment execution determination for each drum (step 4 in FIG. 4), detection of the rotational phase difference between the reference photosensitive drum 10a and the photosensitive drum 10b is started. That is, when the signal from the phase detection sensor 16a of the photosensitive drum 10a serving as a reference is output, the time measurement counter value cnt is cleared (steps 5 and 6 in FIG. 4), and thereafter the count value cnt is increased at a constant cycle. (Step 7 in FIG. 4). When the signal from the phase detection sensor 16b of the photosensitive drum 10b is output, the increase of the count value cnt at the time is stopped (step 8 in FIG. 4), the measured time is converted into the phase difference of each drum, and the position of the motor Conversion into error information (step 9 in FIG. 4). Then, the phase difference of each drum is compared with a predetermined value to determine whether or not phase adjustment of each drum is necessary (step 10 in FIG. 4), and the result is notified to the printer controller (step 11 in FIG. 4). .

  In this example, the count is started based on the signal output from the sensor 16a. However, this is not necessarily the case. Even if the sensor 16b is used as a reference, the sensor 16a and the sensor 16b output first. It may be based on.

  The printer control unit receives the notified phase adjustment execution determination result of each drum, and executes the print sequence when the phase adjustment execution is unnecessary, and instructs the motor control unit to execute the phase adjustment when the phase adjustment execution is necessary. The print sequence is executed after the completion of the phase adjustment.

  When the motor control unit is instructed to execute the phase adjustment by the printer control unit (step 1 in FIG. 5), the motor position error information obtained by the phase adjustment execution determination operation is fed back to the motor position control loop, and the position error is calculated. Control is performed so as to eliminate (step 2 in FIG. 5). Then, after phase adjustment is completed (step 3 in FIG. 5), image formation is started (step 4 in FIG. 5).

  At this time, the value of each parameter used for the operation amount calculation of the position control loop may be changed depending on the absolute value of the position error information. For example, when the absolute value of the position error information is large, the gain of the position control loop is lowered to ensure control stability.

  FIG. 6 schematically shows the phases of the photosensitive drums 10a to 10d in this embodiment, and the meaning of the symbols and the relationship of the phases are the same as in the conventional example. In the illustrated phase relationship, in order to minimize the time required for phase adjustment, the image forming apparatus determines a reference photosensitive drum using the following method.

  After detecting the phase of each of the photosensitive drums 10a to 10d, when the phase of each photosensitive drum is used as a reference, the phase difference from the other photosensitive drums is calculated, and based on that, 10 ° = 0.1 s. The phase adjustment time is calculated, and the largest phase adjustment time is selected for each color. The result is shown in FIG. The image forming apparatus compares the aforementioned maximum phase adjustment time between the photosensitive drums, and sets the photosensitive drum having the smallest maximum phase adjustment time as a reference photosensitive drum. In this example, when the photosensitive drum 10c is used as a reference, the maximum phase adjustment time is minimum at 1.1 seconds. Accordingly, the phases of the other photosensitive drums are adjusted based on the phase of the photosensitive drum 10c.

  FIG. 8 is a diagram for explaining a timing chart regarding driving of each photosensitive drum when the multicolor image forming apparatus is started up and when an image is formed in this embodiment. The description of FIG.

  At the time of 0 second, the start-up of the motors 15a to 15d of the respective colors is started, and the start-up is completed to a steady speed by 0.5 seconds. Thereafter, between 0.5 and 1 second, the phase detection sensors 16a to 16d detect the rotational phases of the photosensitive drums 10a to 10d. Based on the detection result, the reference determination as described above is performed, and the control as indicated by the arrow in FIG. 6 is executed. The photosensitive drum 10a is 0.6 seconds, the photosensitive drum 10b is 0.7 seconds, and the photosensitive drum 10d. Is adjusted to be in phase with the photosensitive drum 10c over 1.1 seconds. As a result, the image forming apparatus is ready to start image formation 2.1 seconds after start-up.

  In this embodiment, the image forming apparatus using the paper conveyance belt 12 has been described as an example. However, the image forming apparatus is not necessarily limited to this, and the same applies to an image forming apparatus using an intermediate transfer unit such as an intermediate transfer belt. The effect can be expected.

  As described above, in the present invention, the phase adjustment of the photosensitive drums of other colors is performed on the basis of the rotational phase of the C photosensitive drum 10c so that the time required for the phase adjustment is minimized. The waiting time due to phase adjustment can be shortened, and the first print time can be shortened.

  The configuration of the multicolor image forming apparatus according to the second embodiment of the present invention is the same as that of the first embodiment. In the figure, phase control is performed on the photosensitive drums 10a to 10d according to the present invention to suppress color misregistration. Other configurations, operations, and control systems are the same as those in the first embodiment, and thus description thereof is omitted.

  FIG. 9 schematically shows the phases of the photosensitive drums 10a to 10d in this example, and the meaning of the symbols and the relationship of the phases are the same as in the first embodiment. In the illustrated phase relationship, in order to minimize the time required for phase adjustment, the image forming apparatus determines a reference phase using the following method.

  When each phase (angle) up to 360 ° corresponding to one round of the drum is used as a phase reference with the phase indicated as 0 ° in FIG. 9 as a phase reference, the phase difference from the photosensitive drums 10a to 10d is calculated and used as the basis. The phase adjustment time is calculated.

  FIG. 10 illustrates this, and the phase adjustment times of the photosensitive drums 10a to 10d are 101a to 101d when the angles of 0 ° to 360 ° are used as a reference. Here, the image forming apparatus calculates the maximum phase adjustment time 102 at each angle of 0 ° to 360 °. The image forming apparatus sets the angle at which the maximum phase adjustment time 102 is minimized as a reference. In this example, when the phase 91 (90 °) indicated by a circle in FIG. 10 is used as a reference, the maximum phase adjustment time is minimum at 0.9 s. Therefore, the phase of the photosensitive drums 10a to 10d is adjusted with the phase 91 as a reference.

  FIG. 11 is a diagram illustrating a timing chart relating to driving of each photosensitive drum when the multicolor image forming apparatus is started up and when an image is formed in this embodiment. The description of FIG.

  At the time of 0 second, the start-up of the motors 15a to 15d of the respective colors is started, and the start-up is completed to a steady speed by 0.5 seconds. Thereafter, between 0.5 and 1 second, the phase detection sensors 16a to 16d detect the rotational phases of the photosensitive drums 10a to 10d. Based on the detection result, the reference determination as described above is performed, and the control as indicated by the arrow in FIG. 9 is executed based on the phase 91. The photosensitive drum 10a is 0.4 seconds, and the photosensitive drum 10b is 0.9. Seconds, the photosensitive drum 10c is adjusted to be in phase with the phase 91 over 0.2 seconds, and the photosensitive drum 10d is adjusted over 0.9 seconds. As a result, the image forming apparatus is ready to start image formation after 1.9 seconds from the start-up.

  As described above, in the present invention, the phase adjustment of the photosensitive drums 10a to 10d is performed on the basis of the phase 91 so that the time required for the phase adjustment is minimized. It is possible to further shorten the first print time.

  The configuration of the multicolor image forming apparatus according to the third embodiment of the present invention is the same as that of the first embodiment. In the figure, phase control is performed on the photosensitive drums 10a to 10d according to the present invention to suppress color misregistration. Other configurations, operations, and control systems are the same as those in the first embodiment, and thus description thereof is omitted.

  In a general image forming apparatus, when the number of printed sheets exceeds a predetermined value, a change in the load torque of the photosensitive drum driving unit due to the deterioration of the sliding parts of the mechanical parts and the toner occurs. When this load torque change occurs, the controllability of the photosensitive drum is lowered and the time required for phase adjustment becomes longer. Therefore, it is necessary to set a reference for phase adjustment in consideration of the influence thereof. This example differs from Example 1 in that the phase reference is set in consideration of the influence of the load torque change described above.

  The presence or absence of the load torque change described above may be determined by whether or not the driving time (number of printed sheets) of the motor driven part exceeds a predetermined value, or monitoring whether or not the motor driving current exceeds a predetermined value. It can be determined by various methods such as

  In this embodiment, the load torque change of the photosensitive drum 10d occurs due to the deterioration, and the time required for the phase adjustment is 1.5 times the normal time, that is, 0.15 seconds are required to adjust the phase of the photosensitive drum by 10 °. A method for setting the phase adjustment reference in this case will be described below.

  FIG. 12 schematically shows the phases of the photosensitive drums 10a to 10d in this example, and the meaning of the symbols and the relationship of the phases are the same as in the first embodiment. In the illustrated phase relationship, in order to minimize the time required for phase adjustment, the image forming apparatus determines a reference photosensitive drum using the following method.

  When each of the photosensitive drums 10a to 10d is used as a reference, the phase difference from the other photosensitive drums is calculated, and the phase adjustment time is calculated based on the calculated phase difference. At this time, since the phase adjustment time of the photosensitive drum 10d is 10 ° adjustment = 0.15 seconds as described above, the phase adjustment time of each photosensitive drum becomes the value shown in FIG. 13, and the maximum phase adjustment time for each color. The results are different from those of the first embodiment.

  The image forming apparatus compares the aforementioned maximum phase adjustment time between the photosensitive drums, and sets the photosensitive drum having the smallest maximum phase adjustment time as a reference photosensitive drum. In this example, when the photosensitive drum 10a is used as a reference, the maximum phase adjustment time is minimum at 1.3 s. Accordingly, the phases of the other photosensitive drums are adjusted based on the phase of the photosensitive drum 10a.

  FIG. 14 is a diagram illustrating a timing chart regarding driving of each photosensitive drum at the time of starting up the multicolor image forming apparatus and at the time of image formation in this example. The description of FIG.

  At the time of 0 second, the start-up of the motors 15a to 15d of the respective colors is started, and the start-up is completed to a steady speed by 0.5 seconds. Thereafter, between 0.5 and 1 second, the phase detection sensors 16a to 16d detect the rotational phases of the photosensitive drums 10a to 10d. Based on the detection result, the reference judgment as described above is performed, and the control shown by the arrow in FIG. 6 is executed. The photosensitive drum 10b is 1.3 seconds, the photosensitive drum 10c is 0.6 seconds, and the photosensitive drum 10d. Is adjusted to be in phase with the photosensitive drum 10a over 0.75 seconds. As a result, the image forming apparatus is ready to start image formation 2.3 seconds after the start-up.

  In this embodiment, the case where a specific photosensitive drum is used as a reference, as in the first embodiment, is described as an example. However, this is not necessarily the case, and a specific phase is used as a reference as in the second embodiment. Even when the phase adjustment is performed, it can be set by taking into account the change in the phase adjustment time.

  As described above, in the present invention, it is possible to set a reference for phase adjustment more optimally by taking into account a change in phase adjustment time due to a change in load torque. It is possible to reduce the waiting time and the first print time.

The figure explaining the whole multicolor image forming apparatus concerning a prior art example and the Example of this invention. The figure explaining schematic structure of the control system concerning the Example of this invention The figure explaining the structure of the principal part concerning the Example of this invention. The figure explaining the control sequence concerning Example 1 of this invention. The figure explaining the control sequence concerning Example 1 of this invention. The figure which showed typically the phase of the photosensitive drum in Example 1 of this invention. FIG. 5 is a comparative diagram for determining a reference photosensitive drum in Embodiment 1 of the present invention. The figure explaining the timing chart in Example 1 of this invention The figure which showed typically the phase of the photosensitive drum in Example 2 of this invention. Comparison diagram for determining a reference angle in Embodiment 2 of the present invention The figure explaining the timing chart in Example 2 of this invention The figure which showed typically the phase of the photosensitive drum in Example 3 of this invention. Comparison diagram for determining a photosensitive drum as a reference in Embodiment 3 of the present invention The figure explaining the timing chart in Example 3 of this invention The figure which showed the phase of the photosensitive drum in a conventional example typically The figure explaining the timing chart in a prior art example

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photosensitive drum 11 Laser scanner 12 Conveyor belt 13 Drive roller 14 Fixing device 15 Motor 16 Phase detection sensor 17 Paper 18 Drive gear train 20 Printer 21 Printer control part 22 Power supply 23 Sensors 24 Motor control part 25 Motors 26 Display part 27 Communication Controller 28 Host computer 30 DSP
31 Motor 32 Driver 33 Rotating body 34 Shaft 35 Flag 36 Photo sensor

Claims (4)

A plurality of rotating bodies for image holding, a plurality of motors for driving these rotating bodies, a means for detecting a detected member provided on the rotating body, and speed control and position control for the motor Motor control means and phase detection means for detecting the phase of each rotating body from the result of detecting the detected member provided on each rotating body, and adjusting the phase of the rotating body by controlling the motor In a multicolor image forming apparatus that suppresses color misregistration by
A multicolor image forming apparatus characterized in that a phase adjustment reference for adjusting the phase of the rotating body is variable.   2. The multicolor image forming apparatus according to claim 1, wherein the reference is a phase of a specific rotating body in which a time required for phase adjustment is the shortest among the plurality of rotating body phases.   The multicolor image forming apparatus according to claim 1, wherein the reference is a specific phase in which time required for phase adjustment is shortest.   4. The multicolor image forming apparatus according to claim 1, wherein a change in phase adjustment time due to a load change of the motor is taken into account when the reference is set. 5.

Images