JP2007017856A - Image forming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the time required to change print modes from monochromatic printing to color printing. <P>SOLUTION: An image forming apparatus with a tandem system is constituted so that an image is formed by superposing color toner images formed on a black-system photoreceptor and color-system photoreceptors onto an endless intermediate transfer body and transferring the images. The apparatus includes: a black-system driving motor to drive the black-system photoreceptor; a color-system driving motor to drive the color-system photoreceptor; and a driving system control unit which starts phase matching of the black-system photoreceptor and the color-system photoreceptor prior to finishing monochromatic printing by accelerating or decelerating only the color-system driving motor while the speed of the black-system driving motor is fixed, upon changing print modes from monochromatic printing by the black-system photoreceptor only to color printing with addition of the color-system photoreceptors. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method having an endless intermediate transfer member.

  Conventionally, in an image forming apparatus adopting an electrophotographic method, a photoconductor as an image carrier is charged by a charger, and a light is applied to the charged photoconductor according to image information to form a latent image, The latent image is developed by a developing device, and the developed toner image is transferred to a recording medium to form an image. Further, in recent years, a plurality of image forming stations for performing each of the image forming processes described above are provided, and toner images of cyan, magenta, yellow, and black images are formed on the respective photoconductors. There has also been proposed a tandem type color image forming apparatus capable of forming a full color image at high speed by superimposing and transferring these toner images onto an endless intermediate transfer member at a transfer position.

FIG. 5 is a relational diagram showing the relationship among a driving roller, a photoconductor, and a photoconductor pitch in a conventional image forming apparatus. Since the drive roller that rotates the intermediate transfer member rotates eccentrically, the intermediate transfer member necessarily has uneven speed. Therefore, in FIG. 5, the relationship between the outer diameter D ₁ of the driving roller and the pitch L of the photosensitive member is L = πD _1, and the relationship between the outer diameter D ₂ of the photosensitive member and the pitch L of the photosensitive member is L = πD ₂ . Thus, phase matching is performed so that the transfer timing of the toner image from each color photosensitive member to the intermediate transfer member in the speed variation pattern of the intermediate transfer member is matched, and the toner images are transferred from each color photosensitive member to the intermediate transfer member in an overlapping manner. Color misregistration between each color toner image was suppressed to a minimum.

According to this, a narrowing the pitch of the photosensitive member in order to reduce the size of the apparatus becomes smaller outer diameter D ₂ also depending on the photosensitive member, usually broken relationship L = [pi] D _2, and L <[pi] D ₂ turn into. As a result, the phases of the color photoconductors described above are not matched, and color misregistration occurs. Therefore, in order to prevent color misregistration by adjusting the phase while narrowing the pitch of the photoconductors, the amount of color misregistration is measured using a sensor, and the drive motor that rotates each color photoconductor is controlled to individually adjust the phase. Correction was performed.

  However, in such a technique, it takes time for phase alignment, so that the standby time until the start of printing becomes long, and comfortable operability is hindered. In view of this, the present applicant has proposed a phase alignment method and an image forming apparatus capable of performing phase alignment of each color photoconductor in a short time in (Patent Document 1).

In this phase matching method, the phase difference of the pulses obtained by the rotation of the respective photoconductors is obtained, and the rotational speed of the photoconductor having advanced phase is lowered until the phases of the photoconductors are matched based on the phase difference. This is a method in which the rotational speed of the photoconductors that are delayed in phase is increased, and after the phase alignment of both photoconductors is completed, these photoconductors are rotated at a constant speed. Since the rotation of both photoconductors in the photoconductor is accelerated and decelerated in the phase-matching direction, it is possible to perform the phase alignment of each color photoconductor in a short time.
JP 2003-66676 A

  The phase alignment needs to be performed when the printing mode is switched from monochrome printing with a single black photosensitive member to color printing with a plurality of photosensitive members of a black photosensitive member and a color photosensitive member. In this method, phase correction is performed by simultaneously accelerating and decelerating two drive motors, a black photoconductor drive motor and a color photoconductor drive motor, and the black drive motor also serves as a paper transport motor. The speed of the drive motor for the black photosensitive member cannot be changed until monochrome printing is completed. Therefore, it is necessary to start the phase alignment of the photoconductor after waiting for monochrome printing to end, and it takes time when switching the printing mode from monochrome printing to color printing.

  Accordingly, an object of the present invention is to provide an image forming apparatus and an image forming method capable of reducing the time required for switching the print mode from monochrome printing to color printing.

  An image forming apparatus of the present invention is a tandem type image forming apparatus that forms an image by superimposing and transferring each color toner image formed on a black photosensitive member and a color photosensitive member on an endless intermediate transfer member. From black and white printing using only a black photoconductor to color printing with the addition of a color photoconductor, a black drive motor that drives a black photoconductor, a color drive motor that drives a color photoconductor When switching the print mode, with the speed of the black drive motor fixed, only the color drive motor is accelerated or decelerated, so that the black photoconductor and color photoconductor can be And a drive system controller for starting phase matching.

  According to the present invention, when the printing mode is switched from monochrome printing to color printing, the speed of the black driving motor is increased without simultaneously accelerating or decelerating both the black driving motor and the color driving motor. Only the color drive motor is accelerated or decelerated in the fixed state, and the photoconductor phase alignment is started before monochrome printing ends, so the print mode is switched when the print mode is switched from monochrome printing to color printing. Time can be shortened.

  According to the first aspect of the present invention, a tandem type image forming an image by superimposing and transferring each color toner image formed on a black photosensitive member and a color photosensitive member on an endless intermediate transfer member. A black color drive motor for driving a black photoconductor, a color drive motor for driving a color photoconductor, and color printing in which a color photoconductor is added from monochrome printing using only a black photoconductor When the printing mode is switched to, the black and color photoconductors are printed before the end of monochrome printing by accelerating or decelerating only the color drive motor while keeping the speed of the black drive motor fixed. An image forming apparatus having a drive system control unit that starts phase alignment with the printer, and the print mode is switched from monochrome printing to color printing. In this case, only the color drive motor is accelerated or decelerated while the black drive motor and the color drive motor are not accelerated or decelerated at the same time, and the speed of the black drive motor is fixed. Since the phase alignment of the photosensitive member is started before the monochrome printing is completed, the printing mode switching time when the printing mode is switched from the monochrome printing to the color printing can be shortened.

  The invention of claim 2 of the present invention is an image of a tandem system that forms an image by superimposing and transferring each color toner image formed on a black photosensitive member and a color photosensitive member on an endless intermediate transfer member. A black driving motor that drives a black photosensitive member, a color driving motor that drives a color photosensitive member, and a black photosensitive member and a black photosensitive member at the start of color printing by the color photosensitive member. The black and color photoconductors are phase-matched by simultaneously accelerating or decelerating the black drive motor that drives the body and the color drive motor that drives the color photoconductor and only the black photoconductor When switching the printing mode from monochrome printing to color printing with a color photoconductor, the speed of the black drive motor A drive system controller that starts phase matching between the black photoconductor and the color photoconductor before the end of monochrome printing by accelerating or decelerating only the color drive motor in a fixed state. A first mode in which both the black drive motor and the color drive motor are simultaneously accelerated or decelerated for phase alignment of the photoconductor; and a second mode in which only the color drive motor is accelerated or decelerated. The first printing is performed by adjusting the phase of the photoconductor in the first mode at the start of printing and in the second mode when the printing mode is changed from monochrome printing to color printing. It is possible to improve the printing mode switching time when the printing mode is changed without reducing the printing time.

  The invention of claim 3 of the present invention is an image of a tandem system in which an image is formed by superimposing and transferring each color toner image formed on a black photoreceptor and a color photoreceptor on an endless intermediate transfer member. In the formation method, when switching the printing mode from monochrome printing using only the black photoconductor to color printing including the color photoconductor, the speed of the black drive motor for driving the black photoconductor is fixed. In this state, only the color drive motor that drives the color photoconductor is accelerated or decelerated to start phase matching between the black photoconductor and the color photoconductor before the end of monochrome printing. When the printing mode is switched from monochrome printing to color printing, both the black drive motor and the color drive motor are Sometimes the color system drive motor is accelerated or decelerated while the speed of the black system drive motor is fixed, without accelerating or decelerating, and the photoconductor phase alignment is started before monochrome printing is completed. The print mode switching time when the print mode is switched from color printing to color printing can be shortened.

  The invention according to claim 4 of the present invention is a tandem type image forming an image by transferring each color toner image formed on the black photoreceptor and the color photoreceptor on the endless intermediate transfer member. In the formation method, at the start of color printing by the black photoconductor and the color photoconductor, the black drive motor for driving the black photoconductor and the color drive motor for driving the color photoconductor are simultaneously accelerated or decelerated. Therefore, the black photoconductor and the color photoconductor are phase-matched, and the black drive is used when switching the print mode from monochrome printing using only the black photoconductor to color printing with the addition of the color photoconductor. Finish monochrome printing by accelerating or decelerating only the color drive motor while keeping the motor speed fixed. The image forming method starts phase matching between the black photoconductor and the color photoconductor from the first stage, and the black drive motor and the color drive motor are simultaneously accelerated or decelerated for phase matching of the photoconductor. The first mode and the second mode for accelerating or decelerating only the color system drive motor are provided. The first mode is used when printing starts, and the first mode when the printing mode changes from monochrome printing to color printing. By performing phase alignment of the photoconductor in the mode 2, it is possible to improve the printing mode switching time when the printing mode is changed without reducing the printing time at the time of the first printing.

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

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing a change in speed of the drive motor when the two drive motors of the black photosensitive drum and the color photosensitive drum are simultaneously accelerated or decelerated. FIG. 3 is a diagram showing changes in the speed of the drive motor when only the color photosensitive drum is accelerated or decelerated. FIG. 4 is a diagram comparing the print mode switching time when the print mode from monochrome printing to color printing is switched between the conventional example and the present embodiment.

  In FIG. 1, the image forming apparatus according to the present embodiment includes four image forming stations Pa, Pb, Pc, and Pd, and the image forming stations Pa, Pb, Pc, and Pd rotate in the circumferential direction. Photosensitive drums 1a, 1b, 1c, and 1d as photosensitive members are provided as image carriers. The photosensitive drum 1a is for forming a black (K) color toner image as a black system, and the photosensitive drums 1b, 1c, and 1d are cyan (C) and magenta (M) as color systems, respectively. This is for forming a color, yellow (Y) toner image. These photosensitive drums 1a, 1b, 1c, and 1d are arranged in a row so that their rotation center axes are parallel to each other.

  Around the photosensitive drums 1a, 1b, 1c, and 1d, charging means 3a, 3b, 3c, and 3d for charging the surfaces of the photosensitive drums 1a, 1b, 1c, and 1d uniformly to a predetermined potential are charged. Exposure means 4 for forming an electrostatic latent image by irradiating exposure light beams 4K, 4C, 4M, and 4Y corresponding to image data of a specific color onto the photosensitive drums 1a, 1b, 1c, and 1d; The photosensitive drum is tuned and supported by developing means 5a, 5b, 5c, 5d, a driving roller 9a, and a driven roller 9b that visualize the electrostatic latent images formed on 1b, 1c, 1d to form toner images. An endless intermediate transfer belt (intermediate transfer member) 8 on which toner images visualized on 1a, 1b, 1c, and 1d are superimposed and transferred to each other to form a color toner image, and this intermediate transfer belt 8 Transfer hand to transfer toner image to Cleaning for removing residual toner remaining on the photosensitive drums 1a, 1b, 1c, and 1d after the toner images are transferred from the photosensitive drums 1a, 1b, 1c, and 1d to the intermediate transfer belt 8 Means 7a, 7b, 7c, 7d are respectively arranged.

  Here, the intermediate transfer belt 8 provided so as to be in contact with the photosensitive drums 1a, 1b, 1c, and 1d is rotated in the direction of arrow A by a driving roller 9a in the illustrated case. Note that a black image, a cyan image, a magenta image, and a yellow image are formed at the image forming stations Pa, Pb, Pc, and Pd, respectively. The single-color images of the respective colors formed on the photosensitive drums 1a, 1b, 1c, and 1d are sequentially transferred onto the intermediate transfer belt 8 to form a full-color image. Here, the image is formed in the order of a yellow image, a magenta image, a cyan image, and a black image. Therefore, the yellow image is first transferred onto the intermediate transfer belt 8, and the magenta image, the cyan image, A black image is sequentially transferred.

  A paper feed cassette 12 in which a sheet material 11 such as printing paper is stored is provided at the lower part of the apparatus. Then, the sheet material 11 is sent out one by one from the paper feed cassette 12 to the paper transport path 15 by the paper feed roller 10.

  A sheet material transfer roller 13 that contacts the outer peripheral surface of the intermediate transfer belt 8 over a predetermined amount on the sheet conveyance path 15 and transfers a color image formed on the intermediate transfer belt 8 to the sheet material 11, the sheet material 11. A fixing device 14 is provided for fixing the color image transferred on the sheet material 11 by pressure and heat accompanying the nipping rotation of the roller.

  In the image forming apparatus having such a configuration, first, a yellow component color latent image of image information is formed on the photosensitive drum 1d by the charging unit 3d and the exposure unit 4 of the image forming station Pd. This latent image is visualized as a yellow toner image by the developing means 5d having yellow toner, and transferred to the intermediate transfer belt 8 as a yellow toner image by the transfer means 6d.

  On the other hand, while the yellow toner image is being transferred to the intermediate transfer belt 8, a magenta component color latent image is formed at the image forming station Pc, and then the magenta toner image made of magenta toner is visualized by the developing means 5c. The Then, the magenta toner image is transferred by the transfer means 6c of the image forming station Pc to the intermediate transfer belt 8 where the transfer of the yellow toner image has been completed at the previous image forming station Pd, and is superposed on the yellow toner image.

  Thereafter, the cyan toner image and the black toner image are formed in the same manner, and when the four color toner images are superimposed on the intermediate transfer belt 8, the paper is fed from the paper feed cassette 12 by the paper feed roller 10. The four color toner images are collectively transferred onto the sheet material 11 by the sheet material transfer roller 13. The transferred toner image is heat-fixed on the sheet material 11 by the fixing device 14, and a full-color image is formed on the sheet material 11.

  The photosensitive drums 1a, 1b, 1c, and 1d that have completed the transfer have the residual toner removed by the cleaning means 7a, 7b, 7c, and 7d, and are prepared for the next subsequent image formation.

  In such an image forming apparatus, the color photosensitive drums 1b, 1c, and 1d on which cyan, magenta, and yellow toner images are formed are already phase-matched at the assembly stage and are gear-coupled to each other. It is rotated by a common first drive motor (not shown; hereinafter referred to as a “color drive motor”). The black photosensitive drum 1a on which a black toner image is formed is rotationally driven by a second drive motor (not shown; hereinafter referred to as “black drive motor”). .

  The photosensitive drums 1b, 1c, and 1d receive the rotational force of the color driving motor and the photosensitive drums 1b, 1c, and 1d rotate the photosensitive drums 1b, 1c, and 1d. It is mounted on a 1d rotating shaft. Further, a photosensitive member driving gear for rotating the photosensitive drum 1a by transmitting the rotational force of the black driving motor is mounted on the rotating shaft of the photosensitive drum 1a.

  Accordingly, there is no phase shift between the photosensitive drums 1b, 1c, and 1d on which cyan, magenta, and yellow toner images are formed, but these photosensitive drums 1b, 1c, and 1d and a black toner image are formed. The phase difference between the photosensitive drum 1a and the photosensitive drum 1a is formed because the photosensitive drum 1a is driven by mutually different drive motors, or only the photosensitive drum 1a is rotationally driven to print only black. Will occur.

  Conventionally, in order to perform this phase alignment in a short time, as shown in FIG. 2, the drive motor for driving the black photosensitive drum A whose phase is advanced is decelerated to reduce the rotational speed of the black photosensitive drum A. The rotational speed of the color photoconductor drum B is increased by accelerating the drive motor that drives the color photoconductor drum B that is delayed in phase until the phases of the photoconductor drums A and B match each other. Had gone for hours.

  However, when the printing mode is switched from monochrome printing to color printing, it is necessary to perform phase alignment of the photoconductor before color printing. However, since the black drive motor also serves as a paper transport motor, monochrome printing is not possible. The speed of the drive motor for the black photosensitive drum cannot be changed until the process is completed. Therefore, it is necessary to start the phase alignment of the photosensitive member after the monochrome printing is completed, and it takes time to switch the printing mode from the monochrome printing to the color printing.

  Therefore, the image forming apparatus according to the present embodiment does not simultaneously accelerate or decelerate the black photosensitive drum A and the color photosensitive drum B as shown in FIG. 2, and the black photosensitive drum as shown in FIG. A drive system control unit (not shown) that starts the phase alignment of the photoconductor before the end of monochrome printing by accelerating or decelerating only the color photoconductor drum B with the speed A fixed. Prepare. As a result, as shown in FIG. 4, it is possible to shorten the printing mode switching time when the printing mode is switched from monochrome printing to color printing.

  In addition to the second control mode for accelerating or decelerating only the color photosensitive drum B while the speed of the black photosensitive drum A is fixed, the drive system control unit performs the black photosensitive drum. At the start of color printing by both the photoconductor drum A and the color photoconductor drum B, the phase of the photoconductor is increased by simultaneously accelerating or decelerating the two drive motors of the black photoconductor drum A and the color photoconductor drum B. A first control mode for performing alignment is provided.

  As described above, in the image forming apparatus according to the present embodiment, the first control mode in which the two drive motors of the black photosensitive drum A and the color photosensitive drum B are simultaneously accelerated or decelerated for the phase alignment of the photosensitive member. Two modes of the second control mode for accelerating and decelerating only the color photosensitive drum B are provided, and the first control mode is used when printing is started, and the second mode is used when the printing mode is changed. By performing phase alignment of the photoconductor, it is possible to improve the printing mode switching time when the printing mode is changed without reducing the printing time at the first printing.

  The present invention is useful as an electrophotographic image forming apparatus and an image forming method having an endless intermediate transfer member. In particular, the present invention is suitable as an image forming apparatus and an image forming method capable of reducing the time required for switching the printing mode from monochrome printing to color printing.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The figure which shows the speed change of a drive motor when accelerating or decelerating two drive motors of a black photosensitive drum and a color photosensitive drum simultaneously. The figure which shows the speed change of the drive motor when accelerating or decelerating only the color photosensitive drum A diagram comparing the print mode switching time when the print mode from monochrome printing to color printing is switched between the conventional example and this embodiment Relationship diagram showing the relationship between the driving roller, the photosensitive member and the photosensitive member pitch in the conventional image forming apparatus

Explanation of symbols

1a, 1b, 1c, 1d Photosensitive drums 3a, 3b, 3c, 3d Charging means 4 Exposure means 5a, 5b, 5c, 5d Developing means 6a, 6b, 6c, 6d Transfer means 7a, 7b, 7c, 7d Cleaning means 8 Intermediate transfer belt 9a Drive roller 9b Driven roller 10 Paper feed roller 11 Sheet material 12 Paper feed cassette 13 Sheet material transfer roller 14 Fixing device 15 Paper transport path Pa, Pb, Pc, Pd Image forming station

Claims (4)

A tandem type image forming apparatus that forms an image by superimposing and transferring each color toner image formed on a black photosensitive body and a color photosensitive body on an endless intermediate transfer body,
A black drive motor for driving the black photoreceptor;
A color drive motor for driving the color photoreceptor;
When switching the printing mode from monochrome printing using only the black photoconductor to color printing including the color photoconductor, only the color driving motor is used with the speed of the black driving motor fixed. An image forming apparatus, comprising: a drive system control unit that starts phase matching between the black photoconductor and the color photoconductor before the end of the monochrome printing by accelerating or decelerating. A tandem type image forming apparatus that forms an image by superimposing and transferring each color toner image formed on a black photosensitive body and a color photosensitive body on an endless intermediate transfer body,
A black drive motor for driving the black photoreceptor;
A color drive motor for driving the color photoreceptor;
At the start of color printing by the black photoconductor and the color photoconductor, the black drive motor for driving the black photoconductor and the color drive motor for driving the color photoconductor are simultaneously accelerated or decelerated. Phase matching between the black photoconductor and the color photoconductor, and when switching the printing mode from monochrome printing using only the black photoconductor to color printing including the color photoconductor, While the speed of the black drive motor is fixed, only the color drive motor is accelerated or decelerated, so that the black photoconductor and the color photoconductor are phase-matched before the monochrome printing is completed. An image forming apparatus comprising: a drive system control unit for starting the operation. A tandem image forming method for forming an image by superimposing and transferring each color toner image formed on a black photoreceptor and a color photoreceptor on an endless intermediate transfer body,
When switching the printing mode from monochrome printing with only the black photosensitive member to color printing with the addition of the color photosensitive member, with the speed of the black driving motor driving the black photosensitive member being fixed, The phase alignment between the black photoconductor and the color photoconductor is started before the end of the monochrome printing by accelerating or decelerating only the color drive motor for driving the color photoconductor. Image forming method. A tandem image forming method for forming an image by superimposing and transferring each color toner image formed on a black photoreceptor and a color photoreceptor on an endless intermediate transfer body,
At the start of color printing by the black photoconductor and the color photoconductor, the black drive motor for driving the black photoconductor and the color drive motor for driving the color photoconductor are simultaneously accelerated or decelerated. Phase matching between the black photoconductor and the color photoconductor, and when switching the printing mode from monochrome printing using only the black photoconductor to color printing including the color photoconductor, While the speed of the black drive motor is fixed, only the color drive motor is accelerated or decelerated, so that the black photoconductor and the color photoconductor are phase-matched before the monochrome printing is completed. And starting an image forming method.

Images