JP2006194963A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of sustaining a high image quality while keeping productivity high by solving the problem that the productivity of image formation is lowered due to the switching of a transfer roller bias when a test patch pattern for image quality adjustment is performed between paper sheets. <P>SOLUTION: In the image forming apparatus, a test patch is formed at the end in a main scanner and a configuration for avoiding soiling with the test patch is provided, thereby performing a print image formation and an image adjustment by the test patch simultaneously in parallel. Thus, the frequency of test patch formations is increased without lowering the productivity and more stable image quality can be provided to a user without raising cost. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention generally relates to an image forming apparatus such as an electrophotographic system or an electrostatic recording system, and more particularly to an image forming apparatus capable of forming a full-color image.

In recent years, following the rapid shift of inkjet printers to color printers, electrophotographic image forming apparatuses (copiers and printers) have also shifted from monochrome machines to color machines. In a color image forming apparatus, a configuration has been proposed in which a test patch pattern is formed and detected, and image density and position are adjusted based on the detection result. In this case, since this adjustment operation is performed, the productivity of image formation may be reduced. In order to solve this problem, a configuration in which a test patch pattern is formed between sheets, which is an image formation interval (Patent Document) In order to prevent the transfer roller from being soiled, a configuration has been proposed in which a high voltage is switched and a reverse bias is applied, or a charger is provided.
JP 2001-109219 A

  However, in the above-described prior art, it is necessary to allow a startup margin of about 100 msec at least for switching the high voltage. Further, when switching to the reverse bias, it takes much longer time. For this reason, it is necessary to sacrifice productivity to some extent in order to form a test patch between sheets and to prevent the transfer roller from being soiled. In addition, if a high-performance configuration using hardware-accurate components is used, it is possible to achieve a certain degree of high-speed switching, but there is also a problem of cost increase.

  According to the present invention, the latent image forming means for forming the latent image on the photosensitive drum, the developing means for developing the latent image, the transfer means for transferring to the recording medium, and the end in the longitudinal direction are individually provided. An image forming apparatus comprising: a transfer roller divided into a detachable shape; and a test patch reading unit for image adjustment at a position corresponding to a division position of the transfer roller.

  According to the present invention, an image forming apparatus that maintains high image quality while maintaining high productivity by adopting a configuration in which a test patch pattern for image adjustment is performed simultaneously with print image formation without using expensive parts. The purpose is to provide.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic cross-sectional configuration of an electrophotographic full-color image forming apparatus which is an embodiment of the image forming apparatus of the present invention. The full-color image forming apparatus of this embodiment has a digital color image reader unit 1R in the upper part and a digital color image printer part 1P in the lower part.

  In the reader unit 1R, the original 30 is placed on the original platen glass 31 and exposed and scanned by the exposure lamp 32, and the reflected light image from the original 30 is condensed on the full-color CCD sensor 34 by the lens 33, and the color separation image. Get a signal. The color-separated image signal is subjected to image processing by a video processing unit (not shown) through an amplification circuit (not shown) and sent to the printer unit 1P via an image memory (not shown).

  In addition to a signal from the reader unit 1R, an image signal from a computer, an image signal from a FAX, and the like are similarly sent to the printer unit 1P.

  In the present embodiment, as an example, it is assumed that the printer unit 1P operates based on a signal from the reader unit 1R.

  In the printer unit 1P, two photosensitive drums 1a and 1b, which are image carriers, are each supported rotatably in the direction of the arrow in the figure, and pre-exposure lamps 11a and 11b and coronas are disposed around the respective photosensitive drums 1a and 1b. Primary chargers 2a and 2b, laser exposure optical systems 3a and 3b, potential sensors 12a and 12b, rotary developing device holder, that is, rotary 4a and 4b, and each rotary 4a and 4b are loaded with different color toners The three developing devices 41, 42, 43 and 44, 45, 46, the transfer devices 5a, 5b, and the cleaning devices 6a, 6b are arranged.

  In this embodiment, light magenta (light M) and light cyan in addition to the four colors used in a conventional color copying machine of magenta (M), cyan (C), yellow (Y), and black (Bk). Image formation is performed with six colors including two colors (light C).

  By using light color toner, one pixel (dot) at the time of image formation is less noticeable than a normal density toner, resulting in a very smooth halftone image without graininess. High image quality can be reproduced.

  Note that light cyan and light magenta are toners using the same pigment as cyan and magenta, respectively, and differing only in the amount of pigment contained.

  In this embodiment, as will be described in detail later, the developing devices 41 to 46 can be loaded with magenta toner, cyan toner, yellow toner, black toner, and light magenta toner and light cyan toner.

  In this embodiment, the developing devices 41 to 46 are loaded with a two-component developer used by mixing toner and carrier, but there is no problem with a one-component developer containing only toner. Further, the number of developing devices is six in this embodiment, but any number may be used as long as it is four or more.

  In the laser exposure optical system 3 (3a, 3b), an image signal from the reader unit 1R is converted into an optical signal by a laser output unit (not shown), and the laser beam converted into the optical signal is reflected by a polygon mirror, and the lens. Then, the light is projected onto the surfaces of the photosensitive drums 1a and 1b through the reflecting mirrors.

  At the time of image formation on the printer unit, the photosensitive drums 1a and 1b are rotated in the direction of the arrows, and the photosensitive drums 1a and 1b after being neutralized by the pre-exposure lamps 11a and 11b are uniformly charged by the primary chargers 2a and 2b. Each separation color is exposed to form an electrostatic image on the photosensitive drums 1a and 1b.

  Next, the rotary 4a, 4b is rotated to move a predetermined developing device to the developing position on the photosensitive drums 1a, 1b, and then the developing device is operated to develop the latent image on the photosensitive drums 1a, 1b. Then, a visible image (toner image) using a resin and a pigment as a base is formed on the photosensitive drums 1a and 1b.

  With this configuration, the image forming apparatus according to the present exemplary embodiment can always make the distance from the exposure unit to the development unit constant regardless of the color, and hardly causes a difference in output image characteristics depending on the color. It is configured.

  Further, as shown in FIG. 1, the toner in the developing device is a toner container (hopper) 61-66 for each color disposed between the laser exposure optical systems 3a and 3b and beside the laser exposure optical system 3b. From time to time, the toner ratio (or toner amount) in the developing device is replenished as needed at a desired timing so as to keep constant.

  The toner images formed on the photosensitive drums 1a and 1b are primarily transferred to the intermediate transfer belt 5 as an intermediate transfer member in the respective transfer devices 5a and 5b, and the respective toner images are sequentially transferred on the intermediate transfer belt 5. Overlaid.

  The intermediate transfer belt 5 is stretched between the driving roller 51, the driven roller 52, and the rollers 53 and 54, and is driven by the driving roller 51. Further, a transfer cleaning device 50 is arranged at a position facing the intermediate transfer belt 5 so as to be able to contact and separate from the driving roller 51.

  In addition, a detection sensor 55 for detecting the positional deviation and density of the images transferred from the respective photosensitive drums 1a and 1b is disposed at a position facing the driven roller 52, and the image density, Corrections are made to the toner replenishment amount, image writing timing, image writing start position, and the like.

  The transfer cleaning device 50 cleans the residual toner on the intermediate transfer belt 5 after being applied to the driving roller 51 and transferred to the transfer material after the necessary color has been superimposed on the intermediate transfer belt 5.

  On the other hand, the transfer material is conveyed one by one from each storage unit 71, 72, 73 or manual sheet feeding unit 74 by each sheet feeding unit 81, 82, 83, or 84, and is skewed by registration rollers 85. Then, the toner image on the intermediate transfer belt 5 is transferred to a secondary transfer unit 56 that transfers the toner image onto the transfer material at a desired timing.

  The toner image is transferred onto the transfer material by the secondary transfer unit 56, the transfer material passes through the conveyance unit 86, the toner image is fixed by the heat roller fixing device 9, and is discharged to a paper discharge tray or a post-processing device. .

  On the other hand, the intermediate transfer belt 5 after the secondary transfer is cleaned with the transfer residual toner by the transfer cleaning device 50 as described above, and again used for the primary transfer process of each image forming unit.

  When images are formed on both sides of the transfer material, the conveyance path guide 91 is driven immediately after the transfer material passes through the fixing device 9, and the transfer material is once guided to the reverse path 76 via the conveyance path 75. Due to the reverse rotation of the reversing roller 87, the rear end of the feeding roller 87 is used as the head, and the sheet is withdrawn in the direction opposite to the feeding direction and sent to the duplex conveyance path 77. After that, the paper passes through the double-sided conveyance path 77, the skew feeding correction and timing are performed by the double-sided conveyance roller 88, and conveyed to the registration roller 85 at a desired timing, and the image is again formed on the other surface by the image forming process described above. Transcript.

  Here, the image forming mode including the rotary developing device holding portion, that is, the arrangement of the rotary devices 4a and 4b, the developing devices 41 to 46, the color distribution, and the switching control of the rotary devices 4a and 4b, which is a feature of the present invention. explain.

  First, a four-color image forming mode using magenta M, cyan C, yellow Y, and black Bk will be described.

  In this embodiment, the image formation order is assumed to be magenta M, cyan C, yellow Y, and black Bk as described above.

  For this reason, a magenta developing device 41 containing magenta toner and a yellow developing device 42 containing yellow toner are arranged on the photosensitive drum 1a side, and a cyan developing device 44 containing cyan toner and black toner are arranged on the photosensitive drum 1b side. By disposing the accommodated black developing device 45, four color images can be formed in the above-described color order while the intermediate transfer belt 5 rotates twice.

  As will be described later, the developing device 43 can be loaded with light cyan toner, and the developing device 46 can be loaded with light magenta toner, but this is not used in this embodiment.

  By disposing the black developing device 45 on the downstream photosensitive drum 1b side as in this embodiment, the first copy time (Fcot) in the monochrome mode of black Bk moves the distance between the drums by the intermediate transfer belt 5. And a black toner image that has been primarily transferred onto the intermediate transfer belt 5 passes through the nip portion between the other photosensitive drum and the intermediate transfer belt 5 and there is no image deterioration due to secondary transfer. There is also.

  The driving operation at the time of switching the developing device of the photosensitive drum 4a at this time is always controlled at a rotation angle of 120 ° by the reciprocating rotation of the photosensitive drum 4a between the magenta developing device 41 and the yellow developing device 42.

  In other words, the forward / reverse rotation eliminates the need for the required 240 ° rotation during one-way rotation. Further, the rotary 4a and 4b are driven by dedicated stepping motors, respectively, so that forward and reverse rotation is possible.

  Next, an image forming mode with six colors obtained by adding two colors of light cyan C and light magenta M to four colors of magenta M, cyan C, yellow Y, and black Bk will be described.

  The light cyan toner and the light magenta toner are distributed to the rotary 4a and 4b, respectively, the magenta M, yellow Y, and light cyan C on the rotary 4a, and cyan C and black on the rotary 4b. When three colors Bk and light magenta M are arranged and the intermediate transfer member 5 makes three turns, image formation for all six colors is completed.

  That is, a magenta developing device 41 containing magenta toner, a yellow developing device 42 containing yellow toner, and a light cyan developing device 43 containing light cyan toner are arranged on the photosensitive drum 1a side, and are arranged on the photosensitive drum 1b side. A cyan developing device 44 containing cyan toner, a black developing device 45 containing black toner, and a light cyan developing device 46 containing light magenta toner are arranged.

  With such a configuration, a normal four-color image forming mode with four colors is achieved by the intermediate transfer belt 5 making two revolutions, and a high-quality image forming mode without graininess with six colors is achieved with the intermediate transfer belt. 5 is achieved by making 3 laps.

  FIG. 2 is a block diagram of a control system in the color image forming apparatus according to the embodiment of the present invention. The color image forming apparatus is roughly divided into two blocks for control. One is a reader controller 700 that mainly controls the reader unit 201 and the image processing unit 203, and the other is a printer controller 701 that controls the printer unit 202.

  An optical motor driver 702 drives an optical motor (not shown) that moves the scanning mirrors 32a, 32b, and 32c and the exposure lamp 32, and 703 controls an automatic document feeder RDF400 that automatically replaces the document. RDF controller, 704 is a CCD driver for controlling the CCD for image reading, 705 is a ROM storing a control program of the reader controller 700, 706 is a RAM storing data such as control values, and 707 is an exposure. This is an I / O for driving a load such as the lamp 32. The RAM 706 is backed up by a battery so that data can be retained even when the power is turned off.

  Next, the peripheral control unit of the printer controller 701 will be described. A ROM 750 stores a control program for the printer controller 701, a RAM 751 stores data such as control values, and 752 converts analog signals from the potential sensor 12 and the on-drum light amount detection sensor 13 into digital data. An A / D converter, 753 is a D / A converter that outputs an analog set value to the high voltage control unit 770, and 754 is an I / O that drives a load such as a motor and a clutch.

  Reference numeral 708 denotes a sorter controller that communicates with the printer controller 701 and performs stacking control according to the non-sort mode, sort mode, and group mode stacking mode instructions set by the operation unit 704, and also performs stapling control according to the stapling instructions. .

  A known ACS function (automatic color mode selection function) in the image processing unit 203 in the present embodiment will be briefly described. A CCD reading unit (not shown) in the reader unit 1R includes an amplifier for amplifying the analog RGB signals input from the full color sensor, and an A / D converter for converting the analog RGB signals into, for example, an 8-bit digital signal. It comprises a shading correction circuit for performing known shading correction, and outputs a digital RGB image signal of a document image.

  A shift memory (not shown) in the image processing unit 203 corrects, for example, a color shift or a pixel shift of the RGB image signal input from the CCD reading unit in accordance with a shift amount control signal from the image processing control unit. . The signal is input to a complementary color conversion circuit, and the RGB image signal input from the shift memory is converted into an MCY image signal. In the black extraction circuit, in accordance with the black extraction signal input from the image processing control unit, the black region of the image is extracted from the MCY (magenta, cyan, yellow) image signal input from the complementary color conversion circuit, and the extracted black region A Bk (black) image signal is output.

  By determining the black region extracted from the above steps, it is determined whether the image is a full color image or a Bk image.

  FIG. 3 shows an operation unit of the color image forming apparatus of the present invention. In FIG. 6, reference numeral 351 denotes a numeric keypad which is used for setting the number of images to be formed and inputting numerical values for mode setting. Reference numeral 352 denotes a clear / stop key, which is used for stopping the set number of image forming sheets and the image forming operation. Reference numeral 353 denotes a reset key for returning the set number of image forming sheets, operation mode, selected paper feed stage, etc. to a specified value. Reference numeral 354 denotes a start key. When the start key 354 is pressed, an image forming operation is started.

  Reference numeral 369 denotes a display panel composed of a liquid crystal or the like, and the display content changes according to the setting mode in order to facilitate detailed mode setting. In this embodiment, the cursor keys 366 to 368 are used to move the cursor on the display panel 369 and the OK key 364 is used to determine the setting. Such a setting method can also be configured by a touch panel.

  A paper type setting key 371 is set when an image is formed on a recording material thicker than the standard. When the thick paper mode is set by the paper type setting key 371, the LED 370 is controlled to be lit. In this embodiment, only the thick paper mode can be set, but the function can be expanded so that the mode for OHP and other special paper can be set as necessary.

  In this embodiment, the image forming apparatus uses only a black toner developing station to form an image in BW mode, and forms an image in 4C mode (normal image quality mode) using four colors Y, M, C, and K. 6C mode (high quality mode) image formation. Therefore, a color mode selection button is prepared for 6-1 on the operation unit interface. There are three key selections: (1) BW mode, (2) normal image quality mode, and (3) high image quality mode. The user can set a desired print mode by selecting the above button.

  Reference numeral 375 denotes an ACS mode setting key. The LEDs 372 to 374 are turned on according to the set ACS mode, the LED 372 is turned on in the ACS, only the LED 372 is turned on in the BW mode, and only the LED 373 is turned on in the full color mode. Is done.

  Similarly, a photo / character mode setting key for setting a photograph image and a character image is provided on the operation unit interface in order to perform processing according to the type of image. When printing a character image, the user can select a character mode to obtain a high-quality print image in which character contrast is enhanced by black character determination. Further, by selecting the photographic mode, it is possible to select a photographic image with good gradation.

  In this embodiment, the developing device does not have a sensor for measuring the toner density. Based on the video count number of the printed image data, the amount of toner consumption is calculated, and this is used as the amount of toner replenished from the toner cartridge to the developing device. The toner cartridge is equipped with a screw (not shown). The replenishment amount G when the screw is rotated for a predetermined time is known in advance, and the relationship between the replenishment amount X and the screw rotation time t is calculated by a linear expression X = Gt.

  At the time of toner replenishment, the replenishment operation must be performed within the time during which the developer is operating in order to uniformly replenish the toner to the developer. When the rotation time of the screw accompanying replenishment exceeds the development time of one time, the replenishment operation is performed over two development operations.

  The toner replenishment operation based on the video count can maintain a substantially correct replenishment amount in a short period of time, but there is an error, and it cannot be controlled whether or not the actually developed toner image has the correct density. Therefore, in this embodiment, after a predetermined number of prints, a test patch is imaged and its density is measured to provide feedback to the toner replenishment amount. As a result, an error in the replenishment amount generated by the replenishment with the video count is compensated. The formed test patch is detected by a sensor that measures the amount of reflected light of the test patch, and the detection result is fed back to the supply control.

  In the image forming apparatus of this embodiment, the length of the photosensitive drum and the intermediate transfer belt in the longitudinal direction is set to about 330 mm. This is because the user can pass large-size paper such as 13 × 19 inches used by cutting off the end. However, such large-size paper is contrasted with special users, and is not frequently used for general office use. In this embodiment, a size of A4 size (210 mm × 297 mm) or less is a normal size paper, and a paper whose length in the direction perpendicular to the feeding direction exceeds 297 mm is a large size paper.

  However, in the case other than the image forming apparatus based on the office use as in the present embodiment, for example, in the A4 printer based on the home use or the large format printer that handles the A1 and A2 versions for the printing business, the normal size is used. The size of the paper corresponds to that, and the definition of large size paper refers to a size that is larger than normal size paper and that can be used for cutting off the edge.

  FIG. 4 is an explanatory diagram of the image forming position of the test patch pattern in this embodiment. As shown in the figure, the test patch pattern is formed at the end in the drum longitudinal direction. In this embodiment, this position is further on the end side than the length of the normal size paper in the longitudinal direction. Similarly, a density sensor for reading the test patch pattern is also provided at a position corresponding to the density sensor, and is opposed to the intermediate transfer belt so that the test patch pattern on the intermediate transfer belt can be read. It is provided with the composition to do.

  During the printing operation with normal size paper, a test patch pattern is formed at the position of the longitudinal end of the drum at the same time as the image formation, and is read by the density sensor to perform image correction. Therefore, even when the test patch pattern is formed, the print image forming operation is not interrupted. The operation can be continued without reducing productivity.

  FIG. 5 is a configuration diagram of the secondary transfer unit 56 in the present embodiment. The secondary transfer roller provided facing the intermediate transfer member is divided into three in the longitudinal direction. Two at both ends are end transfer rollers A and B used when transferring a large size paper. The central portion is used for transferring normal size paper, and is a central transfer roller.

  The central transfer roller has an eccentric structure inside the bearing. By rotating the central roller attaching / detaching eccentric shaft, the central transfer roller can be kept in contact with the intermediate transfer belt. Further, the central transfer roller can be separated from the intermediate transfer belt by reversely rotating the detachable eccentric shaft. This control is performed by a stepping motor (not shown).

  The end transfer rollers A and B have the same structure as that of the central transfer roller, and rotate around a detachable eccentric shaft. However, it is in contact with the central roller attaching / detaching eccentricity through a bearing and does not rotate by driving the shaft. Normally, a spring structure (not shown) applies pressure in a direction away from the intermediate transfer belt, and does not contact the intermediate transfer belt. An end transfer roller pressure cam is provided in contact with a projection provided in contact with the bearing of the end transfer roller. The detachable cam is rotationally driven by a stepping motor (not shown) around an eccentrically provided shaft. With this rotation of the cam, the end transfer roller moves to a position in contact with the intermediate transfer belt. When the cam rotates in the reverse direction, the cam moves to a position away from the intermediate transfer belt by the pressure of a spring (not shown). In this embodiment, the high transfer pressure is provided in such a manner that it is applied to a roller provided at a position facing the secondary transfer roller inside the intermediate transfer belt. The center and end transfer rollers provided outside the intermediate transfer belt are connected to GRAND via bearings.

  FIG. 6 is a schematic diagram illustrating the positions of the center and end transfer rollers corresponding to the operation state of the image forming apparatus. FIG. 6A is an explanatory diagram when transferring normal size paper. In normal size paper transfer, only the central transfer roller is in contact with the intermediate transfer belt, and the end transfer roller is separated. To adjust the image density, the toner image of the patch pattern developed on the drum surface and the intermediate transfer member is developed at a position corresponding to the end roller, so that the secondary transfer roller is not stained. Pass through the department. Thereafter, the toner image is cleaned in the transfer cleaning unit 50.

  FIG. 6B is an explanatory diagram when transferring a large size paper. In the case of large-size paper, it is necessary to transfer to the edge. For this reason, when the central transfer roller moves to a position in contact with the intermediate transfer belt, the end transfer roller similarly moves to a position in contact with the intermediate transfer member. In this case, it is impossible to adjust the density by forming a patch pattern for adjusting the image density simultaneously with the image formation. Therefore, once image formation is completed, the patch pattern is developed again on the photosensitive drum and the intermediate transfer belt. Therefore, the productivity of the printing operation is sacrificed slightly.

  FIG. 6C is a diagram illustrating the position of the secondary transfer roller in the middle of superimposing a plurality of color toner images on the intermediate transfer belt before the secondary transfer. While the image forming apparatus of the present embodiment is performing color development, the secondary transfer roller is removed from both the center and the end, and toners of a plurality of colors are superimposed.

  FIG. 7 is a diagram for explaining the configuration in the second embodiment of the present invention. The vicinity of the secondary transfer portion 56 in FIG. 1 will be described in detail. An end cleaning blade is provided on the upstream side of the secondary transfer roller so as to face the intermediate transfer belt. This blade is a spring, and pressure is applied in a direction away from the intermediate transfer belt. For this reason, it is usually stopped away from the transfer belt. An end eccentric cam provided in contact with the end blade rotates about an eccentric shaft by driving a stepping motor (not shown). At this time, the cam pressurizes the end blade, and the end blade contacts the intermediate transfer belt. The positions and widths of the end blades are provided so that the outside is cleaned in the longitudinal direction of the drum rather than the portion corresponding to the normal size paper. A transfer cleaner for cleaning the entire region in the longitudinal direction is provided downstream of the secondary transfer roller. This cleaner cleans transfer residual toner in the secondary transfer. The cleaning area overlaps with the end blade.

  FIG. 8 is a schematic diagram for explaining the position of the end cleaner corresponding to the operation state in the present embodiment. FIG. 8A shows a case where an image corresponding to normal size paper is formed. The end cleaner is pressurized at a position in contact with the intermediate transfer belt. For this reason, only the test patch pattern formed at the end is cleaned. As a result, the toner image of the test patch pattern is removed before the secondary transfer portion. This prevents the secondary transfer roller from being stained by the test patch pattern, and as a result, the back surface of the output paper is not stained by the toner image of the patch pattern.

  FIG. 8B illustrates the position of the end cleaner corresponding to the large size paper. Since an image corresponding to a large size paper is formed on the photosensitive drum and the intermediate transfer belt, it is not possible to form a test patch on a single portion in the longitudinal direction. Therefore, once image formation is completed, the patch pattern is developed again on the photosensitive drum and the intermediate transfer belt. Therefore, the productivity of the printing operation is sacrificed slightly. At this time, the image corresponding to the large-size paper is formed to the full length in the longitudinal direction of the intermediate transfer belt. Separate the end cleaner to allow the print image to pass through.

  In the present embodiment, the end cleaner is realized by a configuration using a blade. In addition, as a mechanism capable of cleaning the toner image at the end, a configuration using a cleaning end transfer roller or a configuration in which a fur brush is provided at the end can be realized.

1 is a cross-sectional view of an image forming apparatus in an embodiment of the present invention. 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. It is a figure of the operation part in the Example of this invention. It is explanatory drawing of the test patch pattern in the Example of this invention. It is explanatory drawing of the secondary transfer roller in the Example of this invention. It is explanatory drawing of the secondary transfer roller in the Example of this invention. It is explanatory drawing of the transfer cleaner in the Example of this invention. It is explanatory drawing of the transfer cleaner in the Example of this invention.

Explanation of symbols

1R Reader 1P Printer 1 Photosensitive drum 2 Primary charger 3 Laser exposure unit 4 Rotating developer 4Bk Black developer 4M Magenta developer 4C Cyan developer 4Y Yellow developer 5 Intermediate transfer belt 71 1st cassette 72 2nd cassette 73 Three-stage cassette 9 Fixing device 30 Document 31 Document table 32 Exposure lamp 33 Lens 34 Full color sensor 700 Reader controller 701 Printer controller

Claims (7)

In an image forming apparatus that forms an image on an image carrier by electrophotography,
Pattern image forming means for forming a test patch pattern on the image carrier, and removable cleaning means;
An image processing apparatus that determines whether or not to simultaneously form the pattern image according to an image size to be formed on the image carrier, and that controls the attachment and detachment of the cleaning unit.   The image forming apparatus according to claim 1, wherein the cleaning unit is provided outside 105 mm from a longitudinal center position of the image carrier.   The image forming apparatus according to claim 1, wherein the cleaning unit is a cleaning blade.   The image forming apparatus according to claim 1, wherein the cleaning unit is a bias roller.   The image forming apparatus according to claim 1, wherein the cleaning unit is a bias fur brush. In an image forming apparatus that forms an image on an image carrier by electrophotography,
Pattern image forming means for forming a test patch pattern on the image carrier;
Transfer means for transferring an image on the image carrier to a recording medium,
The transfer means is configured to be detachable at the end in the longitudinal direction independently of the central portion,
An image processing apparatus according to claim 1, wherein when the pattern image is simultaneously formed according to an image size formed on the image carrier, an end of the transfer unit is controlled to be attached and detached.   The image forming apparatus according to claim 6, wherein the detachable position of the transfer unit is provided outside 105 mm from the longitudinal center position of the image carrier.

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