JP2006133572A - Full color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a higher precision image formation by making color registration on an intermediate transfer body and registration of paper by reference of one sensor. <P>SOLUTION: The full color image forming apparatus of intermediate transfer method transfers and carries all visual color developed images formed by a plurality of monochrome image stations to the intermediate transfer body according to corresponding image signals for each color and carries out batch transferring on recording paper. The full color image forming apparatus is provided with a sensor which can read a full color image on the most downstream position in the image forming direction of the intermediate transfer body, a means detecting writing position misalignment in each color image station from a sensor output, a means transferring the image information to each image station and correcting image transferring timing by a deviation detecting means output, a switching means which switches the reading object of the sensor to main/sub scanning registration detection in recording paper and a means to detect the main/sub scanning registration from the result of reading the recording paper by the sensor and a correction control means correctes the image transfer timing by the result of the main/sub scanning registration detecting means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a full-color image forming apparatus that has an interface with an image reading apparatus or another external device and forms an image on a transfer material based on image information input from the external device.

  A conventional color image forming apparatus forms a plurality of electrostatic latent images corresponding to different colors on a photosensitive drum based on an image signal obtained by reading a document by a reading unit having a scanning optical system, for example, and uses a plurality of color toners. The image is developed by a developing device and transferred to an intermediate transfer member, the toner image on the intermediate transfer member is transferred to a recording paper, and the image is fixed on the recording paper by a fixing device (for example, see Patent Document 1). ).

  The intermediate transfer member used in recent color image forming apparatuses is generally in the form of a belt or drum. In order to obtain a high-quality color image, it is important to prevent the positions of the respective colors from shifting when transferring a plurality of color toner images onto the intermediate transfer member. For this purpose, conventionally, a specific pattern is formed on each image forming medium with toner of each color, read by a color registration detection sensor, and the amount of deviation is detected and fed back to image formation to correct the color deviation. (For example, refer to Patent Document 2).

It is also important to keep the image writing position on the recording paper constant. There are two write-out positions: a leading end position (sub-scanning registration) in the conveyance direction of the recording paper and a leading end position (main scanning registration) in the horizontal direction. In order to make these constant, the conveyance state of the recording paper is read by the paper registration detection sensor and corrected so that the writing position is constant (for example, see Patent Document 3). Particularly in double-sided printing, this is an important function because the main scanning registration is likely to be shifted when re-feeding the printed paper on the front surface. These registration corrections are important for obtaining a high-quality image.
Japanese Patent Laid-Open No. 62-182766 JP-A-4-240871 Japanese Patent Laid-Open No. 6-178034

  Such an image forming apparatus has a structure in which a recording paper transport unit and a unit including an image forming medium can be separated and pulled out in order to ensure jam handling and maintainability. For this reason, there is a possibility that the positional relationship between the transport path and the image forming medium is slightly deviated due to aging or unit replacement.

  The present invention has been made paying attention to the above points. By performing the color registration detection of the intermediate transfer body and the registration detection of the recording paper with one sensor reference, the intermediate transfer body and the recording paper conveyance path are separated from each other. It is an object of the present invention to provide a full-color image forming apparatus capable of correcting positional deviation with higher accuracy and forming a higher quality image.

  In order to solve the above problems, a first invention according to the present invention transfers and carries a visible color developed image formed at a plurality of single-color image stations on an intermediate transfer body in accordance with corresponding image signals of respective colors. In the intermediate transfer type full-color image forming apparatus in which a plurality of all color developed images are superimposed and transferred onto the intermediate transfer body and then transferred onto a recording sheet, the most downstream in the image forming direction of the intermediate transfer body A full-color image reading unit that is capable of reading a full-color image on the intermediate transfer member, a writing shift detection unit that detects a writing position shift of each color image station from an output of the full-color image reading unit, and Correction control means for transferring image information and correcting the image transfer timing by the output of the detection means; and the full color A switching means for switching the reading target of the image reading means to the main scanning / sub-scanning registration detection of the recording paper, and a paper registration detecting means for detecting the main scanning / sub-scanning registration of the recording paper from the result of the full-color image reading means. The correction control unit corrects the image transfer timing based on the detection result of the main scanning / sub-scanning registration detection unit.

  In the present invention, by using the above-mentioned means, the color registration detection of the intermediate transfer body and the registration detection of the recording paper are performed based on one sensor reference, so that the positional relationship between the intermediate transfer body and the recording paper conveyance path can be further shifted. It is possible to correct the image with high accuracy and form a higher quality image.

  A full-color image forming apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1A is a schematic diagram illustrating a configuration of a laser printer as a full-color image forming apparatus according to an embodiment of the present invention.

  As shown in FIG. 1a, the laser printer forms an electrostatic latent image in an image forming unit by image light formed based on an image signal sent from a computer (both not shown) connected to a document. The electrostatic latent image is developed and a visible image is superimposed and transferred to form a color visible image, the color visible image is transferred to the transfer material 2, and the color visible image on the transfer material 2 is fixed. The image forming unit includes a photoconductor (5Y, 5M, 5C, 5K) for each station arranged in parallel for the number of development colors, an injection charging unit (7Y, 7M, 7C, 7K) as a primary charging unit, a developing unit (8Y, 8M, 8C, 8K), a toner cartridge (11Y, 11M, 11C, 11K), an intermediate transfer body 12, a paper feeding unit, a transfer unit, and a fixing unit 13.

  The photosensitive drums (photoconductors) 5Y, 5M, 5C, and 5K are configured by applying an organic optical conductive layer to the outer periphery of an aluminum cylinder, and are rotated by the driving force of a driving motor (not shown) being transmitted. Rotates the photosensitive drums 5Y, 5M, 5C, and 5K in the counterclockwise direction according to the image forming operation. Exposure light to the photosensitive drums 5Y, 5M, 5C, and 5K is sent from the scanner units 10Y, 10M, 10C, and 10K, and is selectively exposed on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K, so An image is formed.

  As primary charging means, four injection chargers 7Y, 7M, 7C, and 7K for charging yellow (Y), magenta (M), cyan (C), and black (K) photoconductors are provided for each station. In configuration, each injection charger is provided with a sleeve 7YS, 7MS, 7CS, 7KS.

  As developing means, in order to visualize the electrostatic latent image, four developing devices 8Y, 8M for developing yellow (Y), magenta (M), cyan (C), and black (K) for each station, Each developing device is provided with sleeves 8YS, 8MS, 8CS, and 8CK. Each developing device is detachably attached.

  The intermediate transfer body 12 is in contact with the photosensitive drums 5Y, 5M, 5C, and 5K, rotates clockwise when forming a color image, rotates with the rotation of the photosensitive drums 5Y, 5M, 5C, and 5K, and is visible. Receive image transfer. Further, the intermediate transfer body 12 simultaneously transfers a color visible image onto the intermediate transfer body 12 by transferring the transfer material 2 by nipping and conveying the transfer material 2 after contact with a transfer roller 9a, which will be described later.

  The registration sensor unit 6 detects color misregistration on the intermediate transfer member, and the detection surface of the sensor is directed toward the intermediate transfer member 12 when color misregistration detection is performed. Color misregistration detection on the intermediate transfer member will be described later.

  The transfer roller 9a is brought into contact with the intermediate transfer member while the color visible image is superimposed and transferred onto the intermediate transfer member 12, but is separated to a position 9b at the end of the printing process.

  The fixing unit 13 fixes the transferred color visible image while conveying the transfer material 2. The fixing roller 14 heats the transfer material 2 and the transfer material 2 to the fixing roller 14 as shown in FIG. And a pressure roller 15 for pressure contact. The fixing roller 14 and the pressure roller 15 are formed in a hollow shape, and heaters 16 and 17 are incorporated therein. That is, the transfer material 2 holding the color visible image is conveyed by the fixing roller 14 and the pressure roller 15, and the toner is fixed on the surface by applying heat and pressure.

  The transfer material 2 after fixing the visible image is then discharged by a discharge roller (not shown) to a paper discharge unit (not shown) to complete the image forming operation.

  In the case of performing double-sided printing, after the surface image forming operation is completed, the transfer material conveyance path switch mechanism (not shown) enters the reverse path 22 and switches back to the double-sided cassette (or double-sided path). .

  The transfer material 2 ′ stored in the double-sided cassette (or double-sided path) 23 is fed again to form an image on the back side. At that time, as shown in FIG. 1B, the registration sensor unit 6 moves the detection surface to the transfer material conveyance path side, detects the leading edge registration / lateral registration of the transfer material, forms an image on the back surface of the transfer material, The image is fixed and discharged from a paper discharge unit (not shown), and image formation is completed.

  The cleaning unit 21 cleans the toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K and the intermediate transfer body 12, and displays a visible image by the toner formed on the photosensitive drums 5Y, 5M, 5C, and 5K. Waste toner after being transferred to the intermediate transfer body 12 or waste toner after the transfer of the four color visible images formed on the transfer roller 9 to the transfer material 2 is stored in a cleaner container (not shown).

  FIG. 2 is a schematic view of the intermediate transfer body 12. The intermediate transfer body 12 is formed of a rubber belt or a resin belt, and a color registration correction pattern image formed on the intermediate transfer body 12 from the photosensitive drums 5Y, 5M, 5C, and 5K is provided around the intermediate transfer body 12. A registration sensor unit 6 for reading, and a drive unit 308 for moving the reading position of the registration sensor unit 6 to the color misregistration detection position of the intermediate transfer member and the registration detection position of the transfer material are provided. The registration sensor unit 6 and the driving means 308 are attached to the transfer material transport unit T.

  The photosensitive drums 5Y, 5M, 5C, and 5K are irradiated with lasers 10Y, 10M, 10C, and 10K, and the electrostatic latent images of the photosensitive members 5Y, 5M, 5C, and 5K are developed by an electrophotographic process to be on the intermediate transfer body 12. In the case of an image forming apparatus that has a plurality of image forming portions to be transferred to each other and obtains a color image by superimposing and transferring an image of each color on the intermediate transfer body 12, a mechanical attachment error of each photosensitive drum and an optical path length error of each laser beam When the electrostatic latent image is formed on each of the photosensitive drums 5Y, 5M, 5C, and 5K due to a change in the optical path length and transferred onto the intermediate transfer body 12, there is a problem that the registration of each color is not matched.

  Therefore, a color registration correction pattern image formed on the intermediate transfer body 12 from each of the photosensitive drums 5Y, 5M, 5C, and 5K is read by the registration sensor unit 6 including a pin photo sensor or a CCD sensor, and corresponds to each color. The color registration deviation on the photosensitive drum is detected, and mechanical correction and electrical correction are applied to the image signal to be recorded.

  A block diagram of the registration sensor unit 6 is shown in FIG.

  In this embodiment, the sensor used in the registration sensor unit is a CCD. The registration sensor unit 6 includes a light emitting unit 301, a light receiving unit 302, and a composite plastic lens 303. Light (hereinafter abbreviated as light source light) Io emitted from the light emitting unit 301 is reflected by the surface of the intermediate transfer body 12, and the reflected light Ir is measured by the light receiving unit 302. The reflected light measured by the light receiving unit 302 is monitored by the LED light amount control unit 304 at the CCD output 308 and sent to the CPU 305.

  The CPU 305 calculates the mechanical attachment error of each photosensitive drum, the optical path length error of each laser beam, the optical path length change, and the like based on the measured values of the light source light Io and the reflected light Ir, and mechanically corrects and electrically corrects the image signal. multiply.

  Reference numeral 308 denotes driving means for switching the reading position of the registration sensor unit 6 between a position for correcting the color registration of the intermediate transfer body 12 and a position for detecting the leading edge registration / lateral registration of the transfer material.

  4A shows the intermediate transfer body 12 and the registration sensor unit 6 as seen from the direction 205 (FIG. 2). Close up of the registration sensor area.

  The registration sensor unit 6 is used to detect the lateral registration of the transfer material at the position 6a when the color registration correction of the intermediate transfer body 12 is performed by the driving unit 308 attached to a transfer material conveyance unit (not shown). It is moved to the position 6b.

  5 to 7 show flowcharts of the operation of the registration sensor unit 6.

  First, as shown in the chart of FIG. 5, it is determined whether the CPU 305 is in the color registration correction mode. If the mode is the color registration correction mode (Yes in 500 determination), the sensor is directed to the intermediate transfer body using the driving unit 308 (to 400 in FIG. 6). If the transfer material lateral registration is detected (500 determination No), the sensor is directed to the transfer material conveyance path by using the driving unit 308 (to 600 in FIG. 7).

  FIG. 6 shows a flowchart of color registration correction control. First, a color registration correction pattern image is formed with the developer 1 on the surface of the intermediate transfer member (401). Subsequently, the correction pattern image (402) is formed with the developer 2, the correction pattern image (403) is formed with the developer 3, and the correction pattern image (404) of the developer 4 is formed (here, the developer 1, the developer). 2, developer 3 and developer 4 are any one of yellow, magenta, cyan and black).

  After the color developer image is formed on the surface of the intermediate transfer member, the reflection density of each color developed image is measured by the registration sensor 6 (405). If it is determined from the measurement results that there is a main scanning width error (406), the image frequency is finely adjusted (407). If it is determined that there is a main scanning direction writing position error (408), the horizontal synchronization timing is set. Fine adjustment (409). Further, when it is determined that there is a sub-scanning direction writing position error (410), the phase of the polygon motor is finely adjusted (411).

  Next, the lateral registration detection of the transfer material using the registration sensor 6 will be described with reference to the flowchart of FIG. First, it is determined whether or not the sheet has reached the position of the sensor 6 (601). If the sheet has not arrived (No in 601), the process continues to wait. When the sheet arrives (601 determination Yes), the sheet lateral registration position is detected (602). Next, using the result in 602, the main-scan writing position for all colors is adjusted. Next, it is determined whether or not image formation is complete (604). If not finished yet, the process returns to 601 again.

  The above is only an example of the embodiment, and the reading position switching configuration of the registration sensor 6 described with reference to FIG. 4A is fixed as shown in FIG. 4B, the mirror 25 and the light sources 24a and 24b are installed, and the light source is switched. You may carry out by structure.

  Further, the same effect can be obtained even if the registration sensor unit 6 and the driving means 308 are attached to a unit including the intermediate transfer body 12 as shown in FIG. 1c.

  In addition, the registration sensor unit 6 and the driving unit 308 may be configured to be attached to a frame of an image forming apparatus other than those when both the unit including the intermediate transfer body 12 and the transfer material transport unit are of a drawer type.

Overall configuration diagram of a laser printer as a full-color image forming apparatus Overall configuration diagram of a laser printer as a full-color image forming apparatus Overall configuration diagram of a laser printer as a full-color image forming apparatus Schematic diagram of intermediate transfer member Registration sensor block diagram Details of the area around the registration sensor, intermediate transfer member, and lateral registration detection Initial operation flowchart of registration sensor Flow chart of color registration correction control of intermediate transfer member Flow chart for lateral registration correction control of recording paper

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Paper cassette 2 Transfer material 6, 6a, 6b Registration sensor unit 12 Intermediate transfer body 22 Reverse path 23 Double-sided cassette 24a, 24b Light source 25 Mirror 301 Light-emitting part 302 Light-receiving part 303 Compound plastic lens 304 LED light quantity control part 305 CPU
308 Registration sensor unit driving means

Claims (9)

Visible color development images formed at a plurality of single color image stations are transferred and carried on an intermediate transfer body in accordance with the corresponding color image signals, and a plurality of all color development images are superimposed on the intermediate transfer body. In the full-color image forming apparatus of the intermediate transfer method that batch-transfers to the recording paper after transferring together,
A full-color image reading means located at the most downstream in the image forming direction of the intermediate transfer member and capable of reading a full-color image on the intermediate transfer member;
A writing deviation detecting means for detecting a writing position deviation of each color image station from an output of the full color image reading means;
Correction control means for transferring image information to each image station and correcting the image transfer timing by the output of the detection means;
Switching means for switching the reading target of the full-color image reading means to main scanning / sub-scanning registration detection of recording paper;
A paper registration detection means for detecting a main scanning / sub-scanning registration of the recording paper from the result of the full-color image reading means;
The full-color image forming apparatus according to claim 1, wherein the correction control unit corrects an image transfer timing based on a detection result of the main scanning / sub-scanning registration detection unit.   2. The full-color image forming apparatus according to claim 1, wherein the switching unit moves the position of the full-color image reading unit to a writing position deviation detection position or a paper lateral registration reading detection position of each color image station. A full-color image forming apparatus.   2. The full-color image forming apparatus according to claim 1, wherein each of the color image stations has a light source for detecting a writing position deviation and a main scanning / sub-scanning registration detection of a recording sheet, and the reflected light of the light source is used as the full-color image. A full-color image forming apparatus having at least one mirror guided to a reading unit, wherein the switching unit switches lighting of the light source.   The full-color image forming apparatus according to claim 1, wherein the full-color image information reading unit is attached to either a unit including the intermediate transfer member or a transport unit that transports the transfer paper. Forming equipment.   The full-color image forming apparatus according to claim 1, wherein the full-color image reading unit is attached to a part other than a unit including the intermediate transfer member or a transport unit that transports the transfer paper in the image forming apparatus. A full-color image forming apparatus.   2. The full-color image forming apparatus according to claim 1, wherein the detection of a writing position of each color image station is performed during an adjustment operation of the image forming apparatus.   The full-color image forming apparatus according to claim 1, wherein the main scanning / sub-scanning detection is performed during an image forming operation of the image forming apparatus.   2. The full color image forming apparatus according to claim 1, wherein the full color image reading means is a linear sensor such as a CCD.   2. The full-color image forming apparatus according to claim 1, wherein a length of the full-color image reading unit is longer than a main scanning length of a maximum paper size capable of forming an image.

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