JP2008102309A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus in which a distance for conveying a sheet material S when forming an image of a specific color can be shortened in the apparatus capable of multi-color image formation and a reduction in the size of the apparatus is achieved. <P>SOLUTION: The image forming apparatus having a plurality of image forming sections 1 has: a multi-color image mode in which images formed by the two or more image forming sections 1C, 1Y, and 1M are superposed on an intermediate transfer belt 11 and primarily transferred and then the primarily transferred image is secondarily transferred to a sheet material S conveyed; and a monochrome image mode in which an image formed by the single image forming section 1B is directly transferred to a sheet material S being conveyed. The apparatus has a secondary transfer section for use in the transfer of images to the sheet material S in a conveyance path in the multi-color image mode, and a transfer section for use in the transfer of an image in the monochrome image mode. All the image forming sections 1B, 1C, 1Y, and 1M are disposed in a straight line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that transfers an image formed by a plurality of image forming units provided for each color, superimposes, and forms an image on a recording material.

  Conventionally, there is a color image forming apparatus in which two different transfer points are juxtaposed on a transfer material. This is because in order to shorten the initial printout time during monochrome image formation, one portion is directly transferred to the black image forming portion, and the other portion is the second portion of the multicolor image forming portion using the intermediate transfer method. This is the next transfer (Patent Document 1).

  This color image forming apparatus has a secondary transfer portion of an intermediate transfer body on which a multicolor image has been formed in a transfer portion on the upstream side in the conveyance direction of the recording sheet, and a black image forming portion directly on the downstream transfer portion. Has a transcription section. In the arrangement of the four color image forming units, three color image forming units are arranged horizontally on the intermediate transfer member, and a black image forming unit is arranged on the color image forming unit.

  According to this, at the time of monochrome printing, the image can be directly transferred to the sheet material without being transferred to the intermediate transfer member by the black image forming unit. Therefore, the initial printout time can be shortened as compared with the case where a black image is transferred to a sheet material by a direct transfer method having a four-color inline configuration.

  Further, the image transfer positions from the black image forming unit and the multicolor image forming unit are arranged side by side in the sheet material conveyance path. For this reason, the sheet material fed to the sheet conveyance path from one feeding cassette can be conveyed to both the image transfer position by the black image forming unit and the image transfer position where a multicolor image is formed.

JP 2004-205943 A

  However, since the image forming apparatus shown in Patent Document 1 has a black image forming unit having a different capacity disposed above the color image forming unit, when the image forming unit is taken out for replacement or replenishment, the photoconductor The drum is pulled out in the direction of the rotation axis. When the photosensitive drum is replaced, the photosensitive drum and the intermediate transfer belt are normally in contact with each other. Therefore, when pulling out the photosensitive drum in the rotation axis direction, first, the separation work between the photosensitive drum and the intermediate transfer belt is performed. Need to do. This necessitates a main body structure that enables the photosensitive drum and the intermediate transfer belt to be separated and pulled out, and the mechanism is complicated.

  Further, in the image forming apparatus of Patent Document 1, since the black image forming apparatus is attached to the upper part of the color image forming apparatus, in the monochrome image mode, the height of the color image forming unit is equal to the conveyance distance. Long printout time can occur. Since the black image forming unit and the multicolor image forming unit are in a vertical relationship, the height of the main body is increased.

  The present invention has been made in view of the above points, and an object of the present invention is an apparatus capable of multicolor image formation, which can shorten the recording material conveyance distance when forming an image of a specific color, and can downsize the apparatus. An image forming apparatus that can be configured is provided.

  A typical means in the present invention for solving the above problems includes a plurality of image forming units and an intermediate transfer member to which an image is transferred, and the first image forming unit among the plurality of image forming units. In the first mode in which the image is directly transferred onto the recording material, and in the image forming unit different from the first image forming unit among the plurality of image forming units, the image is transferred to the intermediate transfer member, and then the intermediate transfer is performed. In the image forming apparatus capable of a second mode in which an image on a body is transferred onto a recording material, the plurality of image forming units are arranged in a straight line.

  In the present invention, since only the two transfer portions are arranged in the recording material conveyance path, the recording material conveyance path can be shortened, and the printing time in the first mode can be shortened. be able to. The apparatus can be miniaturized by arranging a plurality of image forming units in a straight line. Further, when the image forming unit is configured to be replaceable, it can be configured to be replaceable without providing an intermediate transfer member separation mechanism.

  Next, an image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings.

[First Embodiment]
FIG. 1 is an explanatory cross-sectional view of the image forming apparatus according to the first embodiment. The overall configuration of the image forming apparatus will be described with reference to FIG.

(overall structure)
The image forming apparatus according to the present embodiment is an electrophotographic color image forming apparatus, and includes four image forming units 1 (1C, 1Y, 1M, and 1B) that form cyan, yellow, magenta, and black color images. is set up.

  Each color image forming unit includes a photosensitive drum 2 (2C, 2Y, 2M, 2B), and sequentially surrounds the vicinity of the peripheral surface thereof to charge the charger 3 (3C, 3Y, 3M, 3B) and the developing device 4. (4C, 4Y, 4M, 4B) are arranged. Further, a blade 8 (8C, 8Y, 8M, 8B) for cleaning residual toner on each photosensitive drum is provided.

  Each image forming unit 1 is configured as an integrated unit as an integrated process cartridge including a charger 3, a developing device 4, a photosensitive drum 2, and a blade 8, and is detachable from the apparatus main body. A predetermined interval is provided between the charger 3 and the developing unit 4, and exposure irradiation is performed on the peripheral surface of each photosensitive drum 2 from the scanner device 10 as an exposure unit through this gap. In the image forming apparatus, an endless belt-like intermediate transfer belt 11 as an intermediate transfer member, and a driving roller 12 and a driven roller 13 that stretch the intermediate transfer belt 11 are arranged below the image forming unit 1. .

  Further, a feeding cassette 14 is attached to the lower part of the apparatus main body, and conveying means is provided so that the sheet material S as a recording material loaded in the feeding cassette 14 is conveyed upward from below the apparatus main body. Yes. This conveying means includes a feeding roller 15, a registration roller pair 16, a fixing roller 17, a discharge roller pair 18, 19 and the like, and a conveying path for the sheet material S is formed from the lower side to the upper side of the apparatus main body.

  The four image forming units 1C, 1Y, 1M, and 1B are linearly arranged in a horizontal row, and an intermediate transfer belt 11 is disposed below the image forming units 1C, 1Y, 1M, and 1B. The intermediate transfer belt 11 is pressed against the photosensitive drums 2C, 2Y, and 2M other than the black photosensitive drum 2B by the primary transfer rollers 5C, 5Y, and 5M, and is rotated clockwise by the driving roller 12 that is rotationally driven by the driving motor. Move.

  The driving roller 12 is disposed in the sheet conveyance path, and the secondary transfer roller 6 is provided at a position facing the driving roller 12. A secondary transfer portion which is a nip portion between the driving roller 12 and the secondary transfer roller 6 via the intermediate transfer belt 11 is located in the sheet material conveyance path. Then, a black image formed by a nip portion between the photosensitive drum 2B of the black image forming unit 1B serving as the first image forming unit and the transfer roller 7 on the sheet material conveying path on the downstream side in the sheet material conveying direction of the secondary transfer unit. The transfer part is located.

  The image forming apparatus is configured to be able to form an image by selecting a single color image mode which is a first mode and a multicolor image mode which is a second mode. Here, the monochromatic image mode is a mode in which an image formed by the black image forming unit 1B is directly transferred onto a recording material. In the multicolor image mode, images formed by the yellow, magenta, and cyan image forming units 1Y, 1M, and 1C are transferred to the intermediate transfer belt 11, and the image on the intermediate transfer belt 11 is transferred onto the recording material. It is a mode to do. Next, an image forming operation in the multicolor image mode and the single color image mode will be described.

(Multicolor image mode)
First, the image forming operation in the multicolor image mode will be described in the case of forming a full color image. The surface of each photosensitive drum 2 that is driven to rotate is uniformly charged by each charger 3. Then, an image forming signal is transmitted to the image forming apparatus via various networks and the like, and the scanner device 10 irradiates each photosensitive drum with laser light corresponding to each place based on the image forming signal. In this manner, each developing device develops the electrostatic latent image formed by the potential difference formed on the photosensitive drum 2 with each color toner, and visualizes it.

  The toner images of the respective colors formed on the surfaces of the cyan, yellow, and magenta photosensitive drums 2C, 2Y, and 2M are electrostatically generated by the action of an electric field at positions facing the respective primary transfer rollers 5C, 5Y, and 5M. Is primarily transferred onto the intermediate transfer belt 11 which is driven to rotate. At this time, a cyan toner image is primarily transferred onto the intermediate transfer belt 11 rotating in the clockwise direction in FIG. 1 at a primary transfer position where the primary transfer roller 5C faces. Subsequently, a yellow toner image is primary-transferred over the cyan toner image at a primary transfer position facing the primary transfer roller 5Y. Similarly, magenta toner images are superimposed, and a three-color toner image is formed on the intermediate transfer belt 11. As the intermediate transfer belt 11 rotates, the color toner image is conveyed to a secondary transfer portion where the drive roller 12 and the secondary transfer roller 6 face each other.

  On the other hand, one sheet material S in the feeding cassette 14 is also conveyed to the secondary transfer section via the feeding roller 15 and the registration roller 16, and the intermediate transfer is performed at the timing when the registration roller 16 passes. The belt 11 and the sheet material S reach the secondary transfer portion at the same time. The toner image is electrostatically transferred onto the sheet material by the action of the transfer electric field generated by the intermediate transfer belt 11 and the secondary transfer roller 6.

  The sheet material onto which the color toner image has been transferred as described above is conveyed to the black image forming unit 1B by the conveying force obtained by the driving roller 12 and the secondary transfer roller 6. Then, the toner image formed on the surface of the black photosensitive drum 2B is transferred by being superimposed on the sheet material onto which the color toner image that has been transferred is transferred at the black transfer portion opposed to the black transfer roller 7. An image is formed.

  Then, the sheet material that holds the full-color toner image on the surface passes through the nip portion of the fixing roller 17. At that time, the full-color toner image is melted by the action of heat and pressure, and is fixed on the sheet material as a permanent image, thereby completing the image formation.

  In color image formation, required performance with respect to a positional deviation amount (color deviation amount) between a plurality of toner images of different colors is high. In the present embodiment, when the required performance of the color misregistration amount is high, a process black that is formed by mixing three colors of cyan, yellow, and magenta on the intermediate transfer belt 11 to create a mixed color of the three colors is formed, thereby producing a full-color image. Form. In this case, only the three image forming portions 1C, 1Y, and 1M that intermediately transfer the toner image to the intermediate transfer belt 11 are used, and the black image forming portion 1B that directly transfers the toner image to the sheet material is not used. Thereby, even if the required performance of the color misregistration amount is high, the performance can be satisfied.

(Single color image mode)
Next, a monochrome image forming operation in the monochrome image mode will be described. In this case, toner image formation by the color image forming portions 1C, 1Y, 1M, primary transfer to the intermediate transfer belt 11, and secondary to the sheet material S at the nip portion between the intermediate transfer belt 11 and the secondary transfer roller 6 are performed. No transcription is performed. The sheet material S on which the toner image is not transferred is conveyed from the feeding cassette 14 to the black image forming unit. The secondary transfer roller 6 has a mechanism that is separated from the intermediate transfer belt 11, and is separated from the intermediate transfer belt 11 when a monochrome image is formed.

  When the sheet material S is conveyed to a transfer portion which is a nip between the black image photosensitive drum 2B and the black transfer roller 7, the black toner image is transferred to the sheet material S at the nip portion. Then, the sheet material after transfer of the black toner image is conveyed to the nip portion of the fixing roller 17 to fix the toner image. As a result, a monochrome image including only a black image is formed on the sheet material. The sheet material that has passed through the fixing device is discharged to the sheet discharge portion. During the series of monochrome image formation, the intermediate transfer belt 11 and the color image forming units 1C, 1Y, 1M are not driven and are in a stopped state.

  According to the image forming apparatus, there are only two toner image transfer points in the sheet material conveyance path, and the length of the sheet material conveyance path from the feeding cassette 14 to the discharge portion downstream of the fixing device is set to the conventional direct transfer distance. It can be shortened compared to the transfer method. As a result, the sheet material can be conveyed from the feeding cassette 14 to the black image forming unit without passing through the color image forming unit unnecessary for the image formation at the time of black image formation, and the printout time at the time of monochrome printing Can be shortened.

  In addition, in the conventional indirect transfer method, it is necessary to perform primary transfer of a toner image formed by black image formation to an intermediate transfer member and then secondary transfer to a sheet material even when performing monochrome printing. Therefore, according to the image forming apparatus, it is possible to reduce the time compared to the indirect transfer method in which the printout time is increased by the time for performing the transfer twice. Further, during monochrome printing, the color image forming units 1C, 1Y, 1M and the intermediate transfer belt 11 do not rotate, so that it is possible to extend the life of the intermediate transfer belt 11 and the color image forming units 1C, 1Y, 1M.

(Removal of image forming unit)
Next, attachment / detachment of the image forming unit formed into a cartridge in the image forming apparatus of the present embodiment will be described.

  As shown in FIG. 2, the image forming apparatus of the present embodiment is configured such that a scanner device 10 attached to the upper part of the apparatus main body can be rotated by a rotation mechanism 20. For this reason, the upper part of the apparatus main body is opened by rotating the scanner apparatus 10. As described above, since all the image forming units 1 (1C, 1Y, 1M, 1B) are linearly arranged in the image forming apparatus according to the present embodiment, all the image forming units 1 (1C, 1Y, 1M, 1B) are opened. Four image forming units can be looked down side by side.

  Therefore, each image forming unit 1 can be pulled out upward, which is a direction intersecting with the rotation axis of the photosensitive drum, and the photosensitive drum 2 in contact with the intermediate transfer belt 11 can be pulled out without rubbing. it can. Since the drawing direction is perpendicular to the surface of the intermediate transfer belt 11, the separation operation between each image forming unit 1 and the intermediate transfer belt 11 is not necessary.

  Here, when the image forming units 1 are not arranged in a straight line, the replacement / replenishment operation of the image forming unit 1 uses a slide type in the direction of the rotation axis of the photosensitive drum 2. In this case, since the photosensitive drum 2 is in contact with the intermediate transfer belt 11, it is necessary to provide a mechanism for separating the photosensitive drum 2 from the belt before replacement / replenishment work.

  Therefore, the mechanism can be simplified by arranging each image forming unit 1 in a straight line as in the present embodiment so that the image forming unit 1 can be detached from the intermediate transfer belt 11 in the vertical direction.

{Simplification of scanner device}
In the image forming apparatus according to the present embodiment, since all the image forming units 1 are arranged in a straight line as described above, in the case of an optical system using the scanner device 10, exposure is possible with a unit integrated type and one polygon mirror. .

  As shown in FIG. 3, in the scanner device 10 of the present embodiment, a polygon mirror 10a is arranged at the center of the scanner device, and four lasers corresponding to the respective image forming units 1 are irradiated toward the polygon mirror 10a. Yes. The laser light is reflected by the polygon mirror 10a and applied to the four photosensitive drums 2 through the lens mirror 10b. Since the four image forming units 1 are arranged in a straight line as described above, the four photosensitive drums are formed by irradiating light reflected by one polygon mirror 10a in substantially the same direction. It becomes possible to expose.

  For this reason, the number of polygon mirrors can be minimized, the scanner device is simplified, and this is an effective means for cost reduction.

[Second Embodiment]
Next, an apparatus according to a second embodiment will be described with reference to FIGS. Note that the basic configuration of the apparatus of this embodiment is the same as that of the above-described embodiment, and thus a duplicate description is omitted. Here, a configuration that is a feature of this embodiment will be described. Moreover, the same code | symbol is attached | subjected to the member which has the same function as embodiment mentioned above.

  The image forming apparatus shown in FIG. 4 has four image forming units 1 (1C, 1Y, 1M, 1B) formed as cartridges arranged in a straight line in a vertical row. The replacement / replenishment operation of each image forming unit 1 is performed by the rotation mechanism 20 of the intermediate transfer belt 11. As shown in FIG. 5, the side of the apparatus main body can be opened by rotating the unit of the intermediate transfer belt 11 around the rotation mechanism 20.

  Even in this embodiment, since all the image forming units 1 are arranged in a straight line, when the apparatus main body is opened as described above, all the image forming units are exposed and pulled out in the lateral direction. Can do. Further, the rotation of the intermediate transfer belt 11 allows the image forming unit 1 and the intermediate transfer belt 11 to be separated without being rubbed.

  Therefore, the image forming unit 1 and the intermediate transfer belt 11 do not need to be separated before the intermediate transfer belt 11 is opened, so that it is not necessary to provide a separation mechanism, and the mechanism can be simplified.

1 is a schematic explanatory diagram of an image forming apparatus according to a first embodiment. FIG. 3 is an explanatory diagram illustrating replacement of an image forming unit of the image forming apparatus according to the first embodiment. It is exposure explanatory drawing by a scanner apparatus. It is a model explanatory drawing of the image forming apparatus which concerns on 2nd Embodiment. FIG. 10 is a diagram illustrating replacement of an image forming unit of an image forming apparatus according to a second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS S ... Sheet material 1 ... Image forming part 2 ... Photoconductor drum 3 ... Charger 4 ... Developing device 5 ... Primary transfer roller 6 ... Secondary transfer roller 7 ... Transfer roller 8 ... Blade
10 ... Scanner device
10a Polygon mirror
10b ... mirror
11… Intermediate transfer belt
12… Drive roller
13… driven roller
14 ... Feed cassette
15 ... Feed roller
16… Registration roller pair
17… Fixing roller
18, 19… discharge roller pair
20… Rotating mechanism

Claims (4)

A first mode in which a plurality of image forming units and an intermediate transfer body to which an image is transferred are transferred, and a first image forming unit directly transfers an image onto a recording material among the plurality of image forming units; A second mode in which an image is transferred to the intermediate transfer member at an image forming portion different from the first image forming portion among the plurality of image forming portions, and then the image on the intermediate transfer member is transferred onto a recording material; In a possible image forming apparatus,
The image forming apparatus, wherein the plurality of image forming units are arranged in a straight line. 2. The image forming apparatus according to claim 1, wherein in the second mode, the recording material onto which the image on the intermediate transfer member has been transferred is transferred by the first image forming unit. 2. The cartridge according to claim 1, wherein each of the plurality of image forming units includes a photosensitive member and at least one image forming unit that acts on the photosensitive member, and is a cartridge that is detachable from the apparatus main body. Image forming apparatus. The first image forming unit forms an image with black toner, and an image forming unit different from the first image forming unit among the plurality of image forming units forms an image with yellow toner, magenta toner, and cyan toner. The image forming apparatus according to claim 1.

Images