JP4292689B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called tandem type color image forming apparatus.
[0002]
[Prior art]
Conventionally, for example, Japanese Patent Application Laid-Open No. 7-28294 discloses a so-called tandem type color image forming apparatus in which a plurality of image forming units containing different color toners are arranged side by side along an intermediate transfer belt. .
[0003]
In this type of image forming apparatus, in order to form a fine color image without color misregistration, each image forming unit forms a resist mark on the intermediate transfer belt, and the resist mark is read by a resist sensor to prevent color misregistration. I try to detect it.
[0004]
[Problems to be solved by the invention]
However, when the registration mark formed on the intermediate transfer belt passes through the transfer roller, the registration mark is disturbed. Therefore, it is necessary to retract the transfer roller during detection. Further, since the registration sensor is in a narrow and difficult position around the intermediate transfer belt, cleaning and maintenance are difficult. Furthermore, reading a registration mark formed on the intermediate transfer belt with a registration sensor has a poor accuracy due to the bending of the belt.
[0005]
The present invention has been made in view of such problems, and it is not necessary to retract the transfer roller to read the registration mark, and it is easy to clean and maintain, and the image formation can read the registration mark with high accuracy. It is an object to provide an apparatus.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides:
A plurality of image forming means for forming images of different colors including the photoconductor;
An intermediate recording medium on which images of different colors are transferred from the plurality of image forming means to form a multiple image;
Transfer means for transferring the multiple images on the intermediate recording medium to paper;
Image forming position detecting means for detecting an image forming position on the intermediate recording medium;
An image forming apparatus comprising: a sheet conveyance guide member provided on both sides of a sheet conveyance path extending in a substantially vertical direction for conveying a sheet between the intermediate recording medium and the transfer unit;
While the paper transport guide member is detachably provided from the apparatus main body,
The image forming position detection means is disposed between the transfer means and the image forming means closest to the transfer means, and is supported on the back surface of the paper transport guide member.
[0007]
According to the above configuration, since the image formation position detection means (registration sensor) is disposed between the transfer means and the image formation means closest to the transfer means, the image formation position (registration mark) formed on the intermediate recording medium The resist mark can be detected before passing through the transfer means. For this reason, the registration mark on the intermediate recording medium is not broken or disturbed (noise) and can be detected with high accuracy, and the transfer means need not be retracted, and the structure is simplified. In addition, since the image forming position detecting means is provided on the back surface of the sheet conveyance guide member that can be removed from the apparatus main body, cleaning and maintenance are facilitated.
[0008]
It is preferable that the paper transport guide member is provided so as to be removable by opening the door of the apparatus. Thus, the image forming position detecting means can be cleaned and maintained more easily by simply opening the apparatus door and removing the paper transport guide member.
[0009]
Preferably, the intermediate recording medium comprises a belt supported by a driving roller and a driven roller, and the image forming position detecting means is provided on the tension side of the belt around the driving roller. Thereby, the registration mark on the belt can be detected with high accuracy on the tight side where the belt is not slack.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a tandem digital color printer (hereinafter simply referred to as “printer”) 10 according to an embodiment of the present invention.
[0011]
First, the schematic configuration and operation of the printer 10 will be described. The printer 10 includes an intermediate transfer belt 12 at substantially the center of the inside thereof. The intermediate transfer belt 12 is supported on the outer peripheral portions of the three rollers 14, 16 and 18. Of the three rollers 14, 16, and 18, the roller 18 is a driving roller that rotates the intermediate transfer belt 12 in the direction of arrow A.
[0012]
Below the lower horizontal portion of the intermediate transfer belt 12, four image forming units 20Y, 20M, 20C, and 20K corresponding to yellow (Y), magenta (M), cyan (C), and black (K) colors, respectively. Are arranged side by side along the intermediate transfer belt 12.
[0013]
Each of the image forming units 20Y, 20M, 20C, and 20K has a photosensitive drum 22Y, 22M, 22C, and 22K, respectively. Around each of the photosensitive drums 22Y, 22M, 22C, and 22K, the chargers 24Y, 24M, 24C, and 24K, the print head units 26Y, 26M, 26C, and 26K, and the developing unit 28Y are sequentially arranged along the rotation direction. , 28M, 28C, 28K, primary transfer rollers 30Y, 30M, 30C, 30K facing the respective photosensitive drums 22Y, 22M, 22C, 22K across the intermediate transfer belt 12, cleaners 32Y, 32M, 32C, 32K Are arranged respectively. The print head portions 26Y, 26M, 26C, and 26K are composed of a large number of LEDs arranged in the main scanning direction parallel to the axial direction of the photosensitive drum.
[0014]
A secondary transfer roller 34 is pressed against the portion of the intermediate transfer belt 12 supported by the roller 18. A nip portion between the secondary transfer roller 34 and the intermediate transfer belt is a secondary transfer region 36.
[0015]
A belt cleaner 38 is pressed against the portion of the intermediate transfer belt 12 supported by the roller 16. The belt cleaner 38 is for scraping and collecting the toner remaining on the intermediate transfer belt 12 after the secondary transfer into the waste toner box 40.
[0016]
A paper feed cassette 42 is detachably disposed at the bottom of the printer 10. The sheets S stacked and accommodated in the sheet feeding cassette 42 are sent out one by one from the uppermost one to the conveying path 46 by the rotation of the sheet feeding roller 44.
[0017]
The conveyance path 46 extends in a substantially vertical direction from the paper feed cassette 42 to the discharge tray 11 through the nip portion of the timing roller pair 48, the secondary transfer region 36, and the fixing unit 50. On one side of the conveyance path 46, sheet conveyance guide members 47a, 47b, 47c are provided along the conveyance path 46, and on the other side, sheet conveyance guide members 47d, 47e, 47f are provided. The sheet conveyance guide members 47a, 47b, 47c, the secondary transfer roller 34, and one timing roller 48a are integrally provided on a door 66 on the right side of the apparatus main body that can be opened and closed by a hinge 65 in FIG. As shown, when the door 66 is opened, the conveyance path 46 is opened. The sheet conveyance guide member 47e between the timing roller pair 48 and the transfer area 36 is detachably attached to the apparatus main body as shown in FIG. It may be movable.
[0018]
Between the image forming unit 20K on the most downstream side of the intermediate transfer belt 12 and the secondary transfer region 36, a registration sensor 52 that reads a registration mark formed on the intermediate transfer belt 12 is installed. That is, the registration sensor 12 is provided on the tension side of the intermediate transfer belt 12 when viewed from the driving roller 18. The registration sensor is supported on the rear surface of the removable paper transport guide member 47e. Further, in the vicinity of the timing roller pair 48, a timing sensor 54 for detecting whether or not the sheet S has arrived at the timing roller pair 48 is installed.
[0019]
The fixing unit 50 is supported by a pair of rollers 56 and 58 and is driven to rotate in the direction of arrow B, and a fixing roller 62 that is pressed against the roller 56 via the fixing belt 60 and is driven to rotate in the direction of the arrow. The fixing region 64 is a nip portion between the fixing belt 60 and the fixing roller 62 through which the sheet on which the toner image is secondarily transferred passes.
[0020]
Next, a schematic operation of the printer 10 having the above configuration will be described.
When an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the printer 10, the image signal processing unit digitally converts the image signal into yellow, cyan, magenta, and black. A signal is generated and transmitted to the LED drive circuit for the print head. This drive circuit performs exposure by causing the print head portions 26Y, 26M, 26C, and 26K of the image forming units 20Y, 20M, 20C, and 20K to emit light based on the input digital signals. This exposure is performed with a time difference in the order of the print head units 26Y, 26M, 26C, and 26K. Thereby, electrostatic latent images for the respective colors are formed on the surfaces of the respective photosensitive drums 22Y, 22M, 22C, and 22K.
[0021]
The electrostatic latent images formed on the photosensitive drums 22Y, 22M, 22C, and 22K are developed by the developing devices 28Y, 28M, 28C, and 28K, respectively, and become toner images of the respective colors. Then, the toner images of the respective colors are primarily transferred in a superimposed manner on the intermediate transfer belt 12 that moves in the direction of arrow A by the action of the primary transfer rollers 30Y, 30M, 30C, and 30K.
[0022]
The superimposed toner image formed on the intermediate transfer belt 12 reaches the secondary transfer region 36 as the intermediate transfer belt 12 moves. In the secondary transfer region 36, the superimposed toner images are collectively sent to the sheet S fed from the paper feed cassette 42 to the conveyance path 46 by the action of the secondary transfer roller 34 and supplied by the timing roller pair 48. Secondarily transferred. The toner remaining on the intermediate transfer belt 12 after the secondary transfer is collected by the belt cleaner 38.
[0023]
The sheet S on which the toner image has been secondarily transferred is sent to the fixing unit 50 through the conveyance path 46, where the toner image is fixed on the sheet S by passing through the fixing region 64. Then, the paper S is discharged to the paper discharge tray 11.
[0024]
In the printer 10 of this embodiment, in order to perform color misregistration adjustment, the image forming units 20Y, 20M,. Registration marks are formed by 20C and 20K and transferred onto the intermediate transfer belt 12. The registration mark is detected by the registration sensor 52, and color misregistration is detected.
[0025]
Since the registration sensor 52 is disposed between the secondary transfer roller 34 and the image forming unit 20K closest to the secondary transfer roller 34, the registration mark formed on the intermediate transfer belt 12 is the secondary transfer roller. The registration mark is detected before passing through. Therefore, the registration mark on the intermediate transfer roller 12 is not broken or disturbed (noise) and can be detected with high accuracy, and the secondary transfer roller 34 does not need to be retracted, and the structure is simplified. Further, since the registration sensor 52 is provided on the tension side where the intermediate transfer belt 12 is not slack with respect to the driving roller 18, the registration mark on the intermediate transfer belt 12 can be detected with high accuracy. Further, since the registration sensor 52 is attached to the sheet conveyance guide member 47e, the registration sensor 52 is cleaned, the gain is adjusted, and the position (relative to the intermediate transfer belt 12) is removed by opening the door 66 and removing the sheet conveyance guide member 47e. Maintenance such as (distance) adjustment can be easily performed, and adjustment after replacement due to failure is easy.
[0026]
【The invention's effect】
As is apparent from the above description, according to the present invention, the image forming position detection means (registration sensor) is disposed between the transfer means and the image forming means closest to the transfer means. The registration mark can be detected before the image forming position (registration mark) to be formed passes through the transfer means. Therefore, the registration mark on the intermediate recording medium is not broken or disturbed (noise) and can be detected with high accuracy, and the transfer means does not need to be retracted, and the structure is simplified. In addition, since the image forming position detecting means is provided on the back surface of the sheet conveyance guide member that can be removed from the apparatus main body, there is an effect that cleaning and maintenance are facilitated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to the present invention.
FIG. 2 is a diagram illustrating a state in which the printer door of FIG. 1 is opened.
[Explanation of symbols]
10 Printer (image forming device)
12 Intermediate transfer belt 18 Drive roller 20Y, M, C, K Image forming unit (image forming means)
22Y, M, C, K Photosensitive drum 34 Secondary transfer roller 46 Transport path 47a-e Paper transport guide member 52 Registration sensor 66 Door

Claims (3)

A plurality of image forming means for forming images of different colors including the photoconductor;
An intermediate recording medium on which images of different colors are transferred from the plurality of image forming means to form a multiple image;
Transfer means for transferring the multiple images on the intermediate recording medium to paper;
Image forming position detecting means for detecting an image forming position on the intermediate recording medium;
An image forming apparatus comprising: a sheet conveyance guide member provided on both sides of a sheet conveyance path extending in a substantially vertical direction for conveying a sheet between the intermediate recording medium and the transfer unit;
While the paper transport guide member is detachably provided from the apparatus main body,
An image forming apparatus, wherein the image forming position detecting means is disposed between the transfer means and an image forming means closest to the transfer means, and is supported on the back surface of the paper transport guide member. The image forming apparatus according to claim 1, wherein the sheet conveyance guide member is detachable by opening the door of the apparatus. 3. The intermediate recording medium comprises a belt supported by a driving roller and a driven roller, and the image forming position detecting means is provided on the tension side of the belt around the driving roller. Image forming apparatus.

Images