JP2006201340A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce toner consumption and shorten processing time for resist adjustment.
To this end, the present invention provides an image forming apparatus in which an intermediate transfer belt is brought into and out of contact with a photosensitive member by a black transfer member and a three-color integrated color transfer member to switch between black printing and color printing. A registration mark forming means (2) for forming a registration mark (3) on the transfer belt; a registration sensor (25) for reading the registration mark; and a registration mark forming means based on the registration mark read by the registration sensor; And a control means (1) for performing resist adjustment. The control means performs resist fine adjustment between black and one of the three colors, and then performs resist fine adjustment for all colors.
[Selection] Figure 4

Description

  The present invention relates to an image forming apparatus capable of switching between black printing and color printing by bringing an intermediate transfer belt into and out of contact with a photoreceptor by a black transfer member and a color transfer member.

Conventionally, in a tandem type full-color image forming apparatus, a scanning optical device is used to eliminate positional deviations such as a positional deviation in the conveyance direction of the intermediate transfer belt, a positional deviation in the scanning direction, a deviation in an oblique direction, and a deviation in magnification error. A reflector is placed in the light beam path from the photosensitive drum to the photosensitive drum to enable adjustment of the reflector position, detect the position of the mark on the intermediate transfer belt, and correct misalignment elements between images according to the detection result The thing to do is proposed (patent document 1).
Patent No. 2603254

  In Patent Document 1, when correcting misregistration elements between images, four color marks are formed each time, so that the amount of color toner consumed increases and the processing time for misregistration correction also increases. There was a problem that it took.

SUMMARY An advantage of some aspects of the invention is that an image forming apparatus capable of switching between black printing and color printing suppresses toner consumption and shortens processing time so that registration can be adjusted. And
Therefore, the present invention provides an image forming apparatus in which an intermediate transfer belt is brought into and out of contact with a photosensitive member by a black transfer member and a three-color integrated color transfer member to switch between black printing and color printing on the intermediate transfer belt. Said control means comprising: a resist mark forming means for forming a resist mark; a resist sensor for reading the resist mark; and a control means for controlling the resist mark forming means based on the resist mark read by the resist sensor and adjusting the resist. Is characterized in that after the resist coarse adjustment between black and one of the three colors, the resist fine adjustment of all colors is performed.
The present invention is characterized in that a reference color in the resist fine adjustment is either black or one of three colors.
Further, the present invention is characterized in that one of the three colors is a color closest to black.

According to the present invention, in an image forming apparatus provided with a black transfer member and a three-color integrated color transfer member, after performing the resist adjustment between black and color, where resist misregistration easily occurs, all color registration adjustment is performed. As a result, the consumption of color toner can be suppressed, and the processing time for resist adjustment can be shortened.
In addition, since the reference color for fine resist adjustment is either black or one of the three colors used in coarse adjustment, resist adjustment can be performed more effectively and the processing time for resist adjustment is shortened. can do.
Further, since one of the three colors is the color closest to black, it is possible to easily adjust the registration between black and color.

Hereinafter, the best mode for carrying out the present invention will be described.
FIG. 1 is a diagram for explaining an embodiment of a tandem color image forming apparatus to which the present invention is applied, FIG. 2 is a plan view for explaining the structure of a contact / separation unit, and FIG. 3 is for explaining a cam for driving a lever. FIG.

  In FIG. 1, the image forming apparatus of the present embodiment is stretched between a driving roller 21 and a driven roller 22, and extends in the length direction of an endless intermediate transfer belt 20 to which a predetermined tension is applied by a tension roller 23. In addition, four color photoconductor units 10 (a black photoconductor unit 10K, a cyan photoconductor unit 10C, a magenta photoconductor unit 10M, and a yellow photoconductor unit 10Y) are arranged. An intermediate transfer belt cleaner 24 is provided at a position facing the driven roller 22, and a registration sensor 25 for detecting the printing position is provided. Each color photoconductor unit 10 has a developing unit 12 having a toner supply roller 13 and a developing roller 14, an exposure unit 15, a charger 16, and a photoconductor cleaner 17 around the roller-shaped photoconductor 11. .

  Each color primary transfer roller 30 (a black primary transfer roller 30K, a cyan primary transfer roller 30C, a magenta primary transfer roller 30M, and a yellow primary transfer roller 30Y) is positioned at a position opposite to each color photoconductor with the intermediate transfer belt 20 interposed therebetween. A secondary transfer roller 47 is provided at a secondary transfer position that is disposed and faces the drive roller 34 with the intermediate transfer belt 20 interposed therebetween.

  Each color photoconductor unit 10 uniformly charges the photoconductor 11 to a predetermined potential with a charger 16, and then exposes the image with an exposure device 15 to form an image-like electrostatic latent image on the photoconductor. The toner image is developed to form a toner image, which is primarily transferred to the intermediate transfer belt 20, and the transfer residual toner is cleaned by the photoconductor cleaner 17. On the other hand, a paper feed cassette 40 is provided at the lower part of the apparatus, and the paper fed by the feed roller 41 is transported through a transport path 43, and the toner image on the intermediate transfer belt is collectively transferred onto the paper at the secondary transfer position. The After the secondary transfer, the toner image is fixed by the fixing device 49 and then discharged to a tray at the top of the apparatus. In the case of duplex printing, the paper after the front surface printing is conveyed to the secondary transfer position through the conveyance path 45, and after the toner image is transferred to the back surface, the toner image is fixed by the fixing device 49 and discharged to the tray at the top of the apparatus. To do.

  In the present embodiment, the black primary transfer roller 30K is supported at one end by a fulcrum shaft 32, rotates around the fulcrum shaft, and is biased in a direction away from the intermediate transfer belt by a spring member (not shown). It is driven at the other end of the moving lever (black contact lever) 31. On the other hand, one end of each of the color transfer rollers (the cyan primary transfer roller 30C, the magenta primary transfer roller 30M, and the yellow primary transfer roller 30Y) is supported by a fulcrum shaft 34, and rotates around the fulcrum shaft. These are integrally driven by a moving lever (color contact lever) 33 that is biased in a direction away from the photosensitive member and the intermediate transfer belt by a spring member (not shown).

  As shown in FIG. 2, the black contact / separation lever 31 and the color contact / separation lever 33 are provided for the color primary transfer rollers 30 (black primary transfer roller 30K, cyan primary transfer roller 30C, magenta primary transfer roller 30M, The primary transfer roller 30Y for each color is provided at both ends of the primary transfer roller 30Y for yellow, and supports the primary transfer roller 30K for black and the color transfer roller (in this example) that is disposed closest to this. A cam shaft 37 is provided at an intermediate position with respect to the cyan primary transfer roller 30C), and is driven by a drive source 38 such as a motor. A black contact cam 35 that engages with the black contact / separation lever 31 and a collar contact cam 36 that engages with the color contact / separation lever 33 are provided at both ends of the cam shaft 37. As a result, the black contact / separation lever 31 and the color contact / separation lever 33 are driven against the spring members, and the primary transfer rollers 30 of the respective colors are contacted / contacted with the intermediate transfer belt 20.

  In this embodiment, the fulcrum shaft 32 and the fulcrum shaft 34 are provided opposite to the cam shaft 37, and the black contact / separation lever 31 and the collar contact / separation lever 33 intersect with each other from the fulcrum shafts. It extends to overlap. By adopting such a configuration, the total length of the contact / detachment unit having the black and color transfer rollers, the two moving levers, and the drive source of the cam shaft can be shortened. As shown in FIG. It is possible to make it shorter than the length between the driving roller and the driven roller, and further shorter than the entire length of each color photoconductor unit arranged along the length direction of the intermediate transfer belt. It is possible to fit in the space in the intermediate transfer belt.

  Further, the intermediate transfer belt is inclined with respect to the horizontal, and the cam shaft 37 is disposed on or near a straight bisector of a straight line connecting the black primary transfer roller 30K and the cyan primary transfer roller 30C. Yes. Since the Y, M, and C transfer rollers are supported by one color contact / separation lever 33 and driven integrally, it is possible to maintain the printing position accuracy between Y, M, and C. Since the contact lever is separate for color and black, the printing position is liable to shift between them. Therefore, the cam shaft 37 is disposed at an equal distance from the primary transfer roller 30K for black and the primary transfer roller 30C for cyan, and the surface shape of the contact portion with each moving lever of the cam is made substantially the same. The movement path of the primary transfer roller for cyan is almost plane-symmetric with respect to the cam shaft, and the amount of displacement is equal, thereby preventing printing position deviation between black and cyan, and hence black and Y, M, and C. .

  Further, the color contact / separation lever 33 is parallel to the tangent to the cyan photoconductor 11C, the magenta photoconductor 11M, and the yellow photoconductor 11Y when the intermediate transfer belt contacts each color photoconductor 11 by each color transfer roller. It is comprised so that it may become. As a result, each color photoconductor contacts the intermediate transfer belt at the same timing. If the contact timing of each color photoconductor deviates, the photoconductor contacted first impacts and vibrates the intermediate transfer belt, causing a deviation in printing position accuracy. In this embodiment, each color photoconductor is deviated. Since this is in contact with the intermediate transfer belt at the same timing, this does not occur.

Next, a cam structure for independently driving two moving levers will be described with reference to FIG.
As shown in the figure, the black abutting cam 35 has a shape in which the axial cross section is cut out in a substantially circular shape, and the remaining cam portion other than the cutout portion (non-cam portion) is the contact for black. The cam surface, which is a contact surface with the lever, is driven at an angle larger than 180 ° around the cam shaft. Therefore, when the cam shaft is rotated and the non-cam portion having an angle range smaller than 180 ° faces the black contact / separation lever 31, the intermediate transfer belt does not contact the black photoconductor. When the cam portion having an angle range larger than ° is opposed to the black contact lever 31, it comes into contact and pushes down the lever so that the intermediate transfer belt contacts the black photoconductor near the position where the push-down amount is maximum. It is configured.

  On the other hand, the collar abutment cam 36 has a cam surface (a surface that contacts the collar contact lever 33) that is substantially the same as a part of the cam surface of the black abutment cam 35 as viewed from the axial section. The cam 35 is formed so as to be within the angular range of the cam surface. A line C2 passing through the center of the cam shaft and passing through the center of the cam surface of the collar contact cam 36 (color contact cam center line) C2 passes through the center of the cam shaft and passes through the center of the cam surface of the black contact cam 35. It corresponds to a position of approximately 60 ° from the line (black contact cam center line) C1.

  As described above, the cam shaft is on a bisector that is substantially perpendicular to the straight line connecting the black primary transfer roller and the cyan primary transfer roller. In FIG. 3A, the black contact cam surface is symmetrical with respect to the perpendicular bisector (corresponding to C1 in the figure), and the non-cam portion faces the black contact / separation lever. Therefore, the lever is not driven, and the collar contact cam center line C2 is at a position of 60 ° to the right from the black contact cam center line, and the collar contact cam 36 located within the cam surface of the black contact cam 35 is provided. The cam surface does not face the color contact / separation lever, so the lever is not driven, and the intermediate transfer belt is not in contact with each color photoconductor and is in a standby mode.

  In FIG. 3A, when the camshaft is rotated 120 ° to the left, a part of the cam surface of the black contact cam 35 pushes down the black contact / separation lever 31 while the collar contact cam 36 The cam surface does not come into contact with the color contact / separation contact lever 33 only by rotating the contact cam center line by 120 °, and the intermediate transfer belt comes into contact with only the black photoconductor to enter the monochrome mode (FIG. 3B). ).

  In FIG. 3A, when the camshaft is rotated 120 ° clockwise, a part of the cam surface of the black contact cam 35 pushes down the black contact / separation lever 31 and the collar contact cam center line is vertical 2. The color contact cam 36 at a position rotated 60 ° to the right of the equipartition line also pushes down the color contact / separation lever 33, so that the intermediate transfer belt contacts the photoconductors of all colors and enters the full color mode. (FIG. 3C).

  Thus, the black contact cam 35 and the color contact cam 36 rotate coaxially and are controlled by the drive source 38 to stop at three positions corresponding to the color mode, monochrome mode, and standby mode. As the drive source 38, for example, a stepping motor or a stepping clutch capable of stopping at three positions is used. In this way, the full color mode, the monochrome mode, and the standby mode can be switched at an equal rotation angle of 120 °, the switching speed can be increased, and switching can be performed with the same time lag.

Next, registration control in the image forming apparatus in which the primary transfer rollers of Y, M, and C are integrally driven by the color contact / separation lever as described above will be described with reference to FIGS.
FIG. 4 is a block diagram for performing resist control, FIG. 5 is a diagram for explaining fine resist adjustment and coarse adjustment, and FIG. 6 is an explanatory diagram for resist control in the case where a color shift between black and color is large.
The control device 1 is a control unit that performs registration adjustment of the image forming apparatus, and is configured as an independent single controller or a part of a controller that controls the entire process. The registration adjustment is a process for preventing the positional deviation between the color images formed on the intermediate transfer belt. For example, the exposure timing and driving speed of each color photoconductor, the driving speed of the intermediate transfer belt, etc. are set so that each color image (registration mark) of Y, M, C, Bk is formed on the intermediate transfer belt at equal intervals. At this time, the registration mark 3 actually formed on the intermediate transfer belt is read by the registration sensor 25 having a light projecting / receiving unit, and the controller 1 checks whether or not they are at equal intervals. As a result, if the color registration marks are not formed at equal intervals, the control device 1 controls the registration mark forming means (photosensitive unit, intermediate transfer belt, intermediate transfer belt driving means, etc.) so as to be equally spaced. To do. By this control, for example, the exposure timing in the exposure apparatus, the driving speed of the photosensitive member, the driving speed of the intermediate transfer belt, and the like are adjusted. Here, the resist adjustment in which the resist marks are formed at equal intervals is illustrated, but the resist marks are formed not only at equal intervals but also in an arbitrary pattern so that the set pattern is formed. You may make it adjust. In this way, if it can be adjusted to form registration marks as set, image formation without color misregistration between colors can be performed.

  By the way, in the image forming apparatus that integrally drives the primary transfer rollers of Y, M, and C by the color contact lever as described in FIGS. Misalignment is unlikely to occur, but because the primary transfer roller for black is driven by a separate black contact / separation lever, registration misalignment is likely to occur between black and color. Therefore, in the present embodiment, a resist coarse adjustment mode performed between black and one of the three colors and a resist fine adjustment mode performed between all colors are provided, and after the resist coarse adjustment is performed, all colors are processed. The resist is finely adjusted.

  FIG. 5A shows an example of all-color resist fine adjustment mode. Bk, C, M, and Y resist marks are formed on the intermediate transfer belt at equal intervals, and the resist fine adjustment between all colors is performed. It is carried out. In this case, since the C, M, and Y are integrally driven by the color contact / separation lever, registration displacement hardly occurs. Therefore, if this adjustment is frequently performed, registration marks are frequently formed for C, M, and Y even though the resist accuracy is maintained, and toner is unnecessarily consumed. Time is required for the processing.

  Therefore, as shown in FIG. 5 (b), since the contact / separation lever of the primary transfer roller is a separate member, between black and any one of Y, M, and C, where registration misalignment easily occurs, First, rough adjustment of the resist is performed. In the coarse resist adjustment, the distance between black and one color is increased to perform rough resist adjustment compared to fine adjustment. Thus, by performing the resist rough adjustment, the resist fine adjustment between all the colors shown in FIG. 5A can be easily performed, the consumption of the color toner can be suppressed, and the processing time of the resist adjustment can be shortened. Note that the reference color in the resist coarse adjustment may be either black or one of the three colors.

  As shown in FIG. 6A, if the color misregistration between black and color is too large, the resist adjustment in the fine adjustment mode cannot cope. Even in such a case, after performing the resist adjustment in the coarse adjustment mode as shown in FIG. 5B, the adjustment in the fine adjustment mode for all colors as shown in FIG. 6B is performed. Thus, it is possible to easily adjust the resist.

  In the case of the image forming apparatus shown in FIGS. 1 to 3, one color to be adjusted with black is cyan when the image forming unit including the photosensitive unit and the primary transfer roller is located closest to black. However, it is preferable to adjust the resist between black and cyan.

  According to the present invention, the consumption of color toner can be suppressed and the processing time for resist adjustment can be shortened, so the industrial utility value is extremely high.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. It is a top view explaining the structure of the contact / separation unit. It is a figure explaining the cam which drives a movement lever. It is a block block diagram which performs resist control. It is a figure explaining resist fine adjustment and rough adjustment. It is explanatory drawing of the resist control in case the color shift between black and a color is large.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Control apparatus, 2 ... Registration mark formation means, 3 ... Registration mark, 25 ... Registration sensor, 10K ... Photoconductor unit for black, 10C ... Photosensitive unit for cyan, 10M ... Photosensitive unit for magenta, 10Y ... For yellow Photosensitive unit 20 ... Intermediate transfer belt 30K ... Black primary transfer roller 30C ... Cyan primary transfer roller 30M ... Magenta primary transfer roller 30Y ... Yellow primary transfer roller 31 ... Black contact / release lever 32, 34 ... fulcrum shafts, 33 ... color contact levers.

Claims (3)

In an image forming apparatus for switching between black printing and color printing by bringing the intermediate transfer belt into and out of contact with the photosensitive member by a black transfer member and a three-color color transfer member,
A resist mark forming means for forming a resist mark on the intermediate transfer belt;
A registration sensor that reads registration marks;
A control means for controlling the registration mark forming means based on the registration mark read by the registration sensor, and for adjusting the registration;
The image forming apparatus according to claim 1, wherein the control unit performs resist fine adjustment between black and one of the three colors, and then performs resist fine adjustment for all colors. 2. The image forming apparatus according to claim 1, wherein a reference color in the resist fine adjustment is one of black or three colors. The image forming apparatus according to claim 1, wherein one of the three colors is a color closest to black.

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