JP2002040743A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always stably secure the detection accuracy of a color deviation correcting image position sensor, as for an image forming device provided with the color deviation correcting image position sensor. SOLUTION: The image forming device is provided with transfer material carrying devices (Rt, Rw, Rf and T2a) for successively carrying a transfer material (B) in plural transfer areas (Q3y to Q3k) where toner images separately formed on the surfaces of plural image carriers (PRy, PRm, PRc and PRk) are transferred to the transfer material (B), the image position sensor (SN) arranged on the downstream side of the image carrier (PRk) arranged on the most downstream side in the carrying direction of the transfer material (B) carrying path and for reading an image position detecting toner image transferred from respective image carriers to the transfer material (B), and an interchangeable transparent member (6) which is arranged on or adjacent to the counter surface of the image position sensor (SN) with respect to the transfer material (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly, to transferring a transfer material to which a toner image formed on each of a plurality of image carriers is transferred from each image carrier. The present invention relates to an image forming apparatus including a transfer material transporting device that sequentially transports a toner image to a material transfer area and an image position sensor that reads a toner image for detecting an image position transferred from each of the image carriers.

[0002]

2. Description of the Related Art FIG. 9 is an explanatory view of a main part of an example of a color image forming apparatus to which the present invention is applied. In FIG. 9, the image forming apparatus U converts image data of R, G, and B read by an image scanner (not shown) into Y (yellow), M (magenta), C (cyan), K
(Black) image data is converted into laser drive circuit DL
Is input to The laser drive circuit DL controlled by the controller C outputs R in accordance with the input image data.
The laser diodes (not shown) for writing the Y, M, C, and K images of the OS are driven, and the laser diodes (not shown) for Y, M, C, and K are used to write the laser beams L for writing the image.
Output y, Lm, Lc, Lk. The power supply circuit E for transfer and fixing is also controlled by the controller C.

The toner image forming devices Uy, Um, Uc and Uk arranged above the ROS are respectively Y (yellow), M (magenta), C (cyan) and K (black).
This is an apparatus for forming a toner image of each color. The Y toner image forming apparatus Uy has a rotating image carrier PRy, a charging roll CRy, a developing device Gy, a transfer roll T1y, and a cleaner CLy. The surface of the rotating image carrier PRy is a charging roll CRy. The laser beam Ly forms an electrostatic latent image of Y (yellow) at the latent image forming position Q1y by the laser beam Ly, and is developed into a Y toner image in the developing area Q2y. The developed Y toner image is in the primary transfer area. In Q3y, primary transfer is performed on the intermediate transfer belt B of the belt module BM. Each of the toner image forming apparatuses Um, Uc, and Uk has the Y
Of the toner image forming apparatus Uy. Then, the toner images of each color formed by the toner image forming devices Uy, Um, Uc, Uk are transferred to the primary transfer areas Q3y, Q3.
m, Q3c, and Q3k, the images are sequentially transferred onto the intermediate transfer belt B in a superimposed manner, and a full-color toner image is formed on the intermediate transfer belt B.

The toner image forming devices Uy, Um, Uc,
The belt module BM disposed above Uk has the intermediate transfer belt B and a plurality of belt support rolls that rotatably support the intermediate transfer belt B, and the plurality of belt support rolls receive a rotational driving force. Backup roll T2
a, walking roll Rw, tension roll Rt,
It is composed of a free roll Rf, primary transfer rolls T1y to T1k, and the like. A secondary transfer roll T2b is arranged to face the backup roll T2a, and a secondary transfer area Q4 is formed by a pressure contact area between the two rolls T2a and T2b. The sheet conveyed upward from below by the sheet conveying roll Ra arranged along the sheet conveying path SH is temporarily stopped by the registration roll Rr, and is conveyed to the secondary transfer area Q4 at a predetermined timing, where the secondary transfer is performed. When passing through the area Q4, the intermediate transfer belt B
The upper full-color toner image is secondarily transferred. The sheet on which the secondary transfer toner image is formed is conveyed upward, and is discharged to a discharge tray (not shown) after the toner image is fixed by a fixing device (not shown).

The intermediate transfer belt B on which the Y toner image has been transferred in the primary transfer area Q3y is sequentially placed on the image carrier PR.
m, PRc, PRk and their respective transfer rolls T1m, T
Transfer regions Q3m, Q3c, Q3k between 1c and T1k
The image writing timing of the image carriers PRm, PRc, and PRk is such that the leading ends of the M, C, and K toner images coincide with the leading ends of the Y toner images transferred to the intermediate transfer belt B. Stipulated.

In such a multi-transfer type image forming apparatus for sequentially transferring a plurality of toner images onto a transfer material (eg, a sheet conveyed by an intermediate transfer belt or a sheet conveyance belt), a transfer material (eg, an intermediate transfer belt) is used. If the writing start position of the toner image of each color on B in the main scanning direction and the sub-scanning direction is shifted, a color shift occurs and the image quality is deteriorated. Then, Y, Y on the transfer material (for example, an intermediate transfer belt) B
To align the write start positions of the toner images of each color of M, C, and K in the main scanning direction (the width direction perpendicular to the transfer material transport direction) and the sub-scanning direction (the transfer material transport direction), (Intermediate Transfer Belt) The image carriers PRy, PR are adjusted in accordance with the timing at which B is conveyed to the transfer areas Q3y to Q3k and the position of the transfer material in the main scanning direction when conveyed to the transfer area.
It is necessary to adjust the timing of writing a latent image of a laser diode (not shown) of ROS to m, PRc, and PRk.
The timing at which the transfer material is conveyed to the transfer area and the position of the transfer material in the main scanning direction (width direction) when the transfer material is conveyed to the transfer area may have a slight drum position shift due to external force, temperature change, abrasion, etc. It changes according to the change of the transport speed and the transport direction.

As described above, the image position detecting toner image formed by the image forming apparatus is detected by using the image position detecting sensor SN, the shift amount of each color is calculated, and the shift amount is calculated for each image. In order to always obtain a stable image by correcting with a forming apparatus, the following techniques are conventionally known. That is, in order to detect the position of the toner image for image position detection, which is necessary for adjusting the latent image writing timing, (that is, the transfer material (intermediate transfer belt B) is in the transfer areas Q3y to Q3k).
(In order to detect the timing in which the transfer material is conveyed to the transfer region and the position of the transfer material in the main scanning direction (width direction) when the transfer material is conveyed to the transfer area), and the transfer material (intermediate transfer belt B) downstream of the toner image forming apparatus Uk The image position sensors SN are arranged on both sides and the center in the width direction of the intermediate transfer belt B at the side positions.

FIG. 10 is an explanatory diagram of the image position sensor SN. In FIG. 10, an image position sensor SN detects light L1 emitted from a light emitting element 01, diffused and reflected from the surface of the intermediate transfer belt B, and incident on a light receiving element 02. In addition,
The light receiving element 02 is constituted by a plurality of light receiving element cells (not shown) arranged along the main scanning direction (the width direction of the transfer material) X. In FIG. 10, a dustproof glass (transparent member) 03 is provided on the surface of the image position sensor SN. The outgoing light L1 from the light emitting element 01 is diffusely reflected by the toner image Tn on the intermediate transfer belt B, and the incident light L2 incident on the light receiving element 02 is detected. Can be detected on the intermediate transfer belt B. Accordingly, the image position sensors SN are arranged at both ends and the center in the width direction of the intermediate transfer belt B, and when a jam occurs or a temperature change exceeding a specified value inside the apparatus occurs, the toner image forming apparatuses Uy, A position detection toner image transferred from Um, Uc, Uk to a transfer material (intermediate transfer belt B) is read, and the detection signal is processed by a signal processing unit (computer) to calculate a shift between images of each color. be able to.

FIG. 11 is a view showing an example of the position detecting pattern. The position detecting toner image is recorded at a constant interval in the moving direction (sub-scanning direction) Y of the transfer material (intermediate transfer belt) B. It is a figure showing the V-shaped pattern as an example of a pattern. In the V-shaped pattern of the toner image for position detection in FIG. 11, the toner images Tn of the V-shaped pattern of each color of Y, M, C, and K are recorded at, for example, 1 mm intervals. By detecting and calculating with the image position sensor SN, the color shift of the formed image can be detected. Thereby, the toner image forming apparatuses Uy, Um, Uc,
It is possible to adjust the recording start timing in Uk in the sub-scanning direction Y and the main scanning direction X.

[0010]

In the image forming apparatus using the above-mentioned conventional image position sensor, it is required to detect the image position with high accuracy. That is, the allowable amount of color shift of a high-quality color image is about 0.15 mm at the maximum. Even in the conventional automatic color misregistration correction device, there is an error in arithmetic processing on each component or circuit. Therefore, if the permissible amount is allocated to each part, for example, several μm
Accuracy of up to several tens of micrometers is required. However, the output of the conventional image position sensor SN deteriorates due to the contamination of the dustproof glass 03 with time,
It has been difficult to maintain such strict accuracy.

The following techniques are known as stain prevention means, which are different from the techniques to which the present invention is directed. (J01) Technique described in Japanese Utility Model Publication No. 1-334173 This publication discloses a means in which an insulating member is provided around a lens portion of a write head. However, a transfer material carrying a toner image before fixing is always conveyed to a reading target portion of the reading portion of the color misregistration correction apparatus according to the present invention during a copy cycle. Under such conditions, little effect can be obtained by providing an insulating member around the lens portion.

The present invention has been made in view of the above circumstances, and has the following content as an object. (O01) In an image forming apparatus having an image position sensor for correcting color misregistration, the detection accuracy of the image position sensor is always ensured stably.

[0013]

Next, the present invention devised to solve the above-mentioned problems will be described. Elements of the present invention are used to facilitate correspondence with elements of the embodiments described later. , The reference numerals of the elements of the embodiment are enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention and not to limit the scope of the present invention to the embodiments.

(1st invention) In order to solve the aforementioned problem,
An image forming apparatus according to a first aspect of the present invention includes the following constituent features (A01) to (A03).
1) A plurality of image carriers (PRy, PRm, PRc, PR
k) The plurality of transfer areas (Q3y to Q3) where the toner images respectively formed on the surface of (k) are transferred to the transfer material (B).
k) a transfer material transport device (Rt, Rw, Rf, T2a) for sequentially transporting the transfer material (B); (A02) an image disposed at the most downstream in the transport direction on the transport path of the transfer material (B); An image position which is arranged at a position downstream of the carrier (PRk) and reads a toner image for image position detection transferred from each of the image carriers (PRy, PRm, PRc, PRk) to the transfer material (B). Sensors (SN), (A03) Replaceable transparent members (6, 9, 12) arranged on the surface of the image position sensor (SN) facing the transfer material (B) or close to the surface.

In the first invention, the "transfer material" is an intermediate transfer material such as an intermediate transfer belt (B) or an intermediate transfer drum, or a toner image on a plurality of image carriers which is electrostatically attracted to a sheet conveying belt. Means a transfer material (paper or sheet for image recording) which is sequentially conveyed to a plurality of transfer areas where the image is transferred.

(Operation of the First Invention) In the image forming apparatus of the first invention of the present application having the above configuration, the transfer material transport device (R
t, Rw, Rf, T2a) are a plurality of transcription regions (Q3
The transfer material (B) is sequentially conveyed to y to Q3k). The toner images formed on the surfaces of the plurality of image carriers (PRy, PRm, PRc, PRk) are transferred to the transfer material (B) in the plurality of transfer areas (Q3y to Q3k). An image position sensor (SN) arranged at a position downstream of the image carrier (PRk) arranged at the most downstream in the conveyance direction on the conveyance path of the transfer material (B) is provided with the image carrier (PRy, PRy, PRy). PRm, PRc, PRk) and the toner image (Tn) for image position detection transferred to the transfer material (B).
Read. The transparent members (6, 9, 12) arranged close to the image position sensor (SN) are replaceable.
Therefore, when the transparent member (6, 9, 12) becomes dirty, the toner is replaced by replacing it with the toner image (Tn) for image position detection transferred to the transfer material (B).
The image can be read through the transparent member (6, 9, 12) with less contamination and high transparency. Therefore, stable detection accuracy can be maintained for a long period of time without lowering the detection accuracy of the image position sensor (SN).

(Second Invention) The image forming apparatus according to the second invention of the present application has the following constituent features (A01), (A02),
(A03 ') and (A05).
01) A plurality of image carriers (PRy, PRm, PRc, PR
k) The plurality of transfer areas (Q3y to Q3) where the toner images respectively formed on the surface of (k) are transferred to the transfer material (B).
k) a transfer material transport device (Rt, Rw, Rf, T2a) for sequentially transporting the transfer material (B); (A02) an image disposed at the most downstream in the transport direction on the transport path of the transfer material (B); The toner image (Tn) for image position detection, which is arranged at a position downstream of the carrier (PRk) and is transferred from each of the image carriers (PRy, PRm, PRc, PRk) to the transfer material (B). Image position sensor (SN) to be read, (A0
3 ') A transparent member (6) provided on the surface of the image position sensor (SN), (A05) an air flow which is disposed near the transparent member (6) and flows in contact with the surface of the transparent member (6). An air flow ejection member (13).

(Operation of the Second Invention) In the image forming apparatus according to the second invention of the present application having the above configuration, the transfer material transporting device (R
t, Rw, Rf, T2a) are a plurality of transcription regions (Q3
The transfer material (B) is sequentially conveyed to y to Q3k). The toner images formed on the surfaces of the plurality of image carriers (PRy, PRm, PRc, PRk) are transferred to the transfer material (B) in the plurality of transfer areas (Q3y to Q3k). An image position sensor (SN) arranged at a position downstream of the image carrier (PRk) arranged at the most downstream in the conveyance direction on the conveyance path of the transfer material (B) is provided with the image carrier (PRy, PRy, PRy). PRm, PRc, PRk) and the toner image (Tn) for image position detection transferred to the transfer material (B).
Read. The air flow ejection member (13) is disposed near the transparent member (6) provided on the surface of the image position sensor (SN) and ejects an air flow flowing in contact with the surface of the transparent member (6). Therefore, the image position sensor (S
N) The transparent member (6) provided on the surface is cleaned by the air flow. Therefore, the image position sensor (SN) always
The toner image (Tn) for detecting the image position can be read through the transparent member (6) with little contamination and high transparency. Therefore, stable detection accuracy can be maintained for a long period of time without lowering the detection accuracy of the image position sensor (SN).

(Third Invention) The image forming apparatus according to the third invention of the present application includes (A01 '), (A02'), (A03 '),
(A06) wherein the toner images (Tn) formed on the surfaces of the plurality of image carriers (PRy, PRm, PRc, PRk) are provided on the intermediate transfer material (B). A plurality of primary transfer regions to be transferred (Q3y to Q3
k) a transfer material transport device (Rt, Rw, Rf, T2a) for sequentially transporting the intermediate transfer material (B); (A02 ') disposed at the most downstream in the transport direction in the transport path of the intermediate transfer material (B); The image carrier (PRy, PRm, PRc, PR) is disposed at a position downstream of the image carrier (PRk).
k) reads an image position detecting toner image (Tn) transferred from the intermediate transfer material (B) to the intermediate transfer material (B).
N), (A03 ') a transparent member (6) provided on the surface of the image position sensor (SN), (A06) a recording sheet on which the toner image primarily transferred to the intermediate transfer material (B) is secondarily transferred A sheet conveying device (SH + Ra + Rr) for conveying (S) while making contact with the surface of the transparent member (6).

(Operation of the Third Invention)
In the image forming apparatus of the present invention, the transfer material transport device (Rt, Rt
w, Rf, T2a) include a plurality of primary transfer regions (Q3y to
Q3k), the intermediate transfer material (B) is sequentially conveyed. The toner images (Tn) formed on the surfaces of the respective image carriers (PRy, PRm, PRc, PRk) correspond to the plurality of the respective ones.
In the next transfer area (Q3y to Q3k), the image is transferred to the intermediate transfer material (B). The image carrier (PR) disposed at the most downstream in the transport direction in the transport path of the intermediate transfer material (B)
k) The image position sensor (S
N) are the respective image carriers (PRy, PRm, PRc, P
Rk), the toner image (Tn) for image position detection transferred to the intermediate transfer material (B) is read. The sheet conveying device (SH + Ra + Rr) is a recording sheet (S) on which the toner image primarily transferred to the intermediate transfer material (B) is secondarily transferred.
Is transported while making contact with the surface of the transparent member (6) provided on the surface of the image position sensor (SN). Therefore, the transparent member (6) provided on the surface of the image position sensor (SN)
Is cleaned by being rubbed against the recording sheet (S). For this reason, the toner image (Tn) for detecting the image position can always be read via the transparent member (6) with little contamination and high transparency. Therefore, stable detection accuracy can be maintained for a long period of time without lowering the detection accuracy of the image position sensor (SN).

[0021]

(Embodiment 1) Embodiment 1 of the image forming apparatus of the present invention is characterized in that the first invention has the following requirement (A04). (A04) The transparent member (12) supported by another component (CLk) of the image forming apparatus and simultaneously replaced when the other component (CLk) is replaced.

(Operation of the First Embodiment) In the first embodiment of the image forming apparatus of the first invention having the above configuration, the transparent member (12) supported by another component (CLk) of the image forming apparatus is provided. Are automatically replaced at the same time when the other component (CLk) is replaced. For this reason, the transparent member (12)
Only the number of replacement operations can be reduced.

(Embodiment) Next, an image forming apparatus having an image position sensor for correcting color misregistration according to an embodiment of the present invention will be described with reference to the drawings. However, the present invention is limited to the following embodiment. Not something. In order to facilitate the understanding of the following description, in the drawings, the front-rear direction is the X-axis direction, the right-left direction is the Y-axis direction, and the up-down direction is the Z-axis direction.
The directions or sides indicated by Y, -Y, Z, and -Z are front, rear, right, left, upper, lower, or front, rear, right, left, upper, and lower, respectively. Also, in the figure, those with “•” in “○” mean arrows pointing from the back of the paper to the front, and those with “x” in “○” indicate the arrow on the paper. From the back to the back.

(Embodiment 1) FIG. 1 is a front sectional view of Embodiment 1 of the image forming apparatus of the present invention. In FIG. 1, the image forming apparatus U includes an automatic document feeder U1 and an image forming apparatus main body (copier) U2 supporting the same and having a platen glass PG at an upper end. The automatic document feeder U1
Is a document feed tray TG1 on which a plurality of documents Gi to be copied are stacked, and a document conveyed from the document feed tray TG1 through a copy position (document reading position) on the platen glass PG. And a document discharge tray TG2 from which Gi is discharged. The image forming apparatus main body U2 has a UI (user interface) through which a user inputs an operation command signal such as a copy start signal, and an exposure optical system A.

Light reflected from a document conveyed on the platen glass PG by the automatic document feeder U2 or a document (not shown) manually placed on the platen glass PG passes through the exposure optical system A. , CCD (solid-state imaging device)
(Red), G (green), and B (blue).
IPS (Image Processing System) is CCD
The RGB electrical signals input from
The image data is converted into (yellow), M (magenta), and C (cyan) image data and temporarily stored, and the image data is output to the laser drive circuit DL as latent image formation image data at a predetermined timing. When the original image is monochrome, the image data of only K (black) is stored in the laser drive circuit DL.
Is input to The laser drive circuit DL is provided for each color Y,
M, C, and K laser drive circuits (not shown) for writing a latent image of each color of the latent image forming optical system ROS at a predetermined timing with a laser drive signal corresponding to the input image data. Output to a laser diode (not shown).

The toner image forming devices Uy, Um, Uc, Uk disposed above the ROS are respectively Y (yellow), M (magenta), C (cyan), and K (black).
This is an apparatus for forming a toner image of each color. The Y, M, C, and K laser beams Ly, Lm, Lc, and Lc emitted from the laser diodes (not shown) of the latent image forming optical system ROS.
Lk represents the rotating image carriers PRy, PRm,
It is incident on PRc and PRk. The Y toner image forming apparatus Uy includes a rotating image carrier PRy, a charging roll CRy,
It has a developing device Gy, a transfer roll T1y, and a cleaner CLy, and each of the toner image forming devices Um, Uc, Uk is configured similarly to the Y toner image forming device Uy.

Each of the image carriers PRy, PRm, PRc,
PRk is the respective charging rolls CRy, CRm, CR
c and CRk, the image writing position Q
At 1y, Q1m, Q1c, and Q1k, an electrostatic latent image is formed on the surface by the laser beams Ly, Lm, Lc, and Lk. The image carrier PRy, PRm, PR
The electrostatic latent images on the surfaces c and PRk are developed areas Q2y and Q2.
m, Q2c, Q2k, the developing units Gy, Gm, Gc,
The toner image is developed by Gk. The developed toner image is transferred to a primary transfer area Q3 that comes into contact with the intermediate transfer belt B.
It is conveyed to y, Q3m, Q3c, and Q3k. In the primary transfer areas Q3y, Q3m, Q3c, Q3k, the primary transfer roll T1 disposed on the back side of the intermediate transfer belt B
To y, T1m, T1c, and T1k, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied at a predetermined timing from a power supply circuit E controlled by the controller C. The toner images on the image carriers PRy to PRk are primarily transferred to the intermediate transfer belt B by the primary transfer rolls T1y, T1m, T1c, and T1k. Image carrier PRy, P after primary transfer
Residual toner on the surfaces of Rm, PRc and PRk is cleaned by image carrier cleaners CLy, CLm, CLc and CLk.

Above the image carriers PRy to PRk,
A belt module BM that can move up and down and can be pulled out forward is arranged. The belt module BM
Is the intermediate transfer belt B, a tension roll Rt,
Walking roll Rw, idler roll (free roll) Rf, and backup roll T also serving as drive roll
2a containing belt support rolls (Rt, Rw, Rf, T2
a) and the primary transfer rolls T1y, T1m, T1c, T1
k. The intermediate transfer belt B is rotatably supported by the belt support rolls (Rt, Rw, Rf, T2a). Therefore, the driving device for rotating and driving the backup roll T2a also serving as the driving roll and the belt supporting rolls (Rt, Rw,
Rf, T2a) and the like constitute an intermediate transfer belt driving device, that is, a transfer material transport device (Rt, Rw, Rf, T2a) for transporting the intermediate transfer material (intermediate transfer belt).

The secondary transfer roll T2b faces the surface of the intermediate transfer belt B in contact with the backup roll T2a.
Are arranged, and each of the rolls T2a and T2b
The next transfer device T2 is configured. Further, a secondary transfer area Q4 is formed in an area where the secondary transfer roll T2b and the intermediate transfer belt B face each other. The primary transfer area Q3y,
Transfer devices T1y, T1m, and T1 at Q3m, Q3c, and Q3k
The color toner images sequentially transferred on the intermediate transfer belt B by c and T1k are conveyed to the secondary transfer area Q4.

Below the ROS, a paper feed tray TR1 is provided.
A pair of left and right guide rails GR, GR that support TR3 to TR3 so that they can move in and out in the front-rear direction (X-axis direction) are provided. The recording sheets S in the paper feed trays TR1 to TR3 are taken out by the pickup rolls Rp, separated one by one by the separating rolls Rs, and then sent to the registration rolls Rr by the plurality of transport rolls Ra. The sheet transport roll Ra
Are provided along a sheet conveying path SH formed by a sheet guide, and a registration roll Rr is disposed upstream of the secondary transfer area Q4 in the sheet conveying direction. The sheet conveyance path (SH + Ra + Rr) is constituted by the sheet conveyance path SH, the sheet conveyance roll Ra, the registration roll Rr, and the like.

The registration roll Rr is connected to the intermediate transfer belt B.
The recording sheet S is conveyed to the secondary transfer area Q4 at the same time as the color toner image formed on the second transfer area Q4 is conveyed. When the recording sheet S passes through the secondary transfer area Q4, the backup roll T
2a is grounded, and a secondary transfer voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roll T2b at a predetermined timing from a power supply circuit E controlled by the controller C. At this time, the color toner image on the intermediate transfer belt B is transferred to the recording sheet S by the secondary transfer unit T2.
Is transferred to The intermediate transfer belt B after the secondary transfer is
The belt is cleaned by the belt cleaner CLb.

The recording sheet S on which the toner image has been secondarily transferred is heated by a heating roll Fh and a pressure roll Fp of a fixing device F.
After being conveyed to the fixing area Q5, which is a pressure contact area, and heat-fixed when passing through the fixed area, the sheet is discharged from the discharge roller Rh to the discharge tray TRh. The heating roll Fh
On the surface, a release agent for improving the releasability of the recording sheet S from the heating roll is applied by a release agent application device Fa.

Above the belt module BM, Y
(Yellow), M (magenta), C (cyan), K
Developer cassettes Ky and K containing each of the (black) developers
m, Kc and Kk are arranged. Each developer cassette K
The developers contained in the developing units Gy, Gm, Gc, and Kk are supplied to the developing units Gy, Gm, and G from a developer supply path (not shown) in accordance with the consumption of the developing units Gy, Gm, Gc, and Gk.
c and Gk are supplied.

In FIG. 1, the image forming apparatus U has an upper frame UF and a lower frame LF, and the upper frame UF has the ROS and a member (image carrier) disposed above the ROS. PRy, PRm, PRc,
PRk, developing units Gy, Gm, Gc, Gk, belt module BM, etc.) are supported. Also, the lower frame L
On F, a guide rail GR supporting the paper feed trays TR1 to TR3 and the paper feed members (pickup roll Rp, separating roll Rs, sheet transport roll Ra, etc.) for feeding paper from the respective trays TR1 to TR3 are supported. Have been.

In FIG. 1, downstream of the K (black) image carrier PRk in the transport direction of the intermediate transfer belt B, the both ends and the center of the intermediate transfer belt B in the width direction (X-axis direction) are respectively provided. , Three image position sensors SN are arranged respectively. The image position sensor SN is supported by a member (not shown) fixed to the upper frame UF. FIG. 2 shows the image position sensor S shown in FIG.
It is an enlarged view of N and its adjacent part. FIG.
3 is a perspective view of the image position sensor SN shown in FIG. In FIGS. 1 and 2, the image position sensor SN is drawn larger than the image carrier cleaner CLk. However, the image position sensor SN is actually much smaller than the image carrier cleaner CLk. It is a member. In FIG. 2, an image position sensor SN detects light L1 for diffuse reflection light detection on the toner image Tn in order to detect reflected light from the toner image Tn for image position detection formed on the surface of the intermediate transfer belt B. A light-emitting element (LED) 1 that emits light, a light-receiving element 2 that receives light L2 emitted from the light-emitting element 1 and diffusely reflected in the toner image Tn, and a detection element supporting member 3 that supports them. I have.

The detecting element supporting member 3 includes a supporting member main body 4, an optical path forming member 5 joined to one end surface thereof, and a dustproof transparent member (glass) 6 disposed on the upper surface of the optical path forming member 5. have. The detection element supporting member 3 includes an emission optical path 7 for emitting the light L1 emitted from the light emitting element 1 toward an external toner image Tn, and a toner image reflected light L2 reflected on the toner image Tn. 2 is formed. 2 and 3, the transparent member 6 arranged on the upper surface of the optical path forming member 5 has both ends in the Y-axis direction supported so as to be slidable forward (X direction). ,
It is configured to be removable from the optical path forming member 5.

(Operation of the First Embodiment) In the image forming apparatus having the image position sensor SN of the present invention having the above-described configuration, the intermediate transfer belt B is disposed below both ends and the center in the width direction of the intermediate transfer belt B. 3 image position sensors S
Using N and SN, Y, M, C and K toner images Tn for image position detection as shown in FIG. 11 (see FIG. 2)
Is detected. Based on this toner image detection position signal,
Y, M, C, K toner image forming apparatuses Uy, Um, Uc,
The writing start timing of the ROS to the image carriers PRy to PRk of Uk by the laser beams Ly to Lk of ROS is adjusted.
With this adjustment, it is possible to prevent the occurrence of color misregistration in the color image. During the use of the image forming apparatus U, the transparent member 6 of the image position sensor SN gradually becomes dirty and the transparency decreases, and the transparency of the transparent member 6 decreases.
n (see FIG. 2) detection accuracy is reduced. In the first embodiment, when the transparent member 6 becomes dirty, the transparent member 6
By taking out and cleaning or replacing it with a new one, a decrease in the transparency of the transparent member 6 can be prevented, and a decrease in the detection accuracy of the toner image Tn (see FIG. 2) can be prevented.

(Embodiment 2) FIG. 4 is an explanatory view of Embodiment 2 of the image forming apparatus of the present invention and corresponds to FIG. 2 of Embodiment 1. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The image forming apparatus according to the second embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points.
4, the image position sensor SN includes a transparent sheet (sheet-like sheet) in which the transparent member 6 shown in FIG. 2 of the first embodiment is fixed to the upper surface of the optical path forming member 5, and is disposed close to the upper surface. A transparent member 9, a sheet supply roll 10 around which the transparent sheet 9 is wound, and a sheet winding roll 11. As the transparent sheet 9, for example, a transparent acrylic resin can be used.

(Operation of the Second Embodiment) When the transparent sheet 9 is soiled, the sheet winding roll 11 is rotated to wind up the soiled portion of the transparent sheet 9, and a new unsoiled transparent sheet 9 is removed. The sheet is supplied from the sheet supply roll 10. Therefore, in the second embodiment, the surface of the transparent member 6 can be covered with the transparent sheet 9 which is not always stained. Then, it is possible to prevent the transparency of the transparent sheet 9 and the transparent member 6 from lowering, and to prevent the detection accuracy of the toner image Tn (see FIG. 4) from lowering. In the second embodiment, the transparent glass 6 on the upper surface of the optical path forming member 5 can be omitted. In this case, the transparent sheet 9 covers the outer ends of the output light path 7 and the input light path 8 to prevent the light emitting element 1 and the light receiving element 2 from being stained.

(Embodiment 3) FIG. 5 is an explanatory view of Embodiment 3 of the image forming apparatus of the present invention and corresponds to FIG. 2 of Embodiment 1 described above. In the description of the third embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The image forming apparatus according to the third embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points.
In FIG. 5, the image position sensor SN is such that the transparent member 6 shown in FIG.
The transparent resin 12 is fixed to the image carrier cleaner CLk. As the transparent resin 12, for example, a transparent acrylic resin can be used.

(Operation of the Third Embodiment) Since the transparent member 6 is covered with the transparent resin 12, dirt hardly occurs. When the image carrier cleaner CLk is replaced, the transparent resin 12 is simultaneously replaced with a new one that is not contaminated. Therefore, in the third embodiment, the surface of the transparent member 6 can be covered with the transparent resin 12 which is not contaminated.
In addition, it is possible to prevent the transparency of the transparent member 6 and the transparent resin 12 from lowering, and to prevent the detection accuracy of the toner image Tn (see FIG. 4) from lowering.

(Embodiment 4) FIG. 6 is a front sectional view of Embodiment 4 of the image forming apparatus of the present invention. FIG. 7 is an enlarged view of the main part of FIG. In the description of the fourth embodiment, the same reference numerals are given to the components corresponding to the components of the first embodiment, and the detailed description thereof will be omitted. The image forming apparatus according to the fourth embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points. 6 and 7, in the image position sensor SN, the transparent member 6 shown in FIG. 2 of the first embodiment is fixed to the upper surface of the optical path forming member 5. Image position sensor SN of the fourth embodiment
Are arranged in the passage of the recording sheet S such that the recording sheet S comes into contact with the surface of the transparent member 6. Therefore, the surface of the transparent member 6 is rubbed by the recording sheet every time the recording sheet S passes, and the surface is cleaned. For this reason,
The transparent member 6 is always kept in a state with no dirt and high transparency.

(Embodiment 5) FIG. 8 is an enlarged view of a main part of an image forming apparatus according to a fifth embodiment of the present invention, corresponding to FIG. 7 of the fourth embodiment. In the description of the fifth embodiment, components corresponding to the components of the fourth embodiment are denoted by the same reference numerals, and a detailed description thereof will be omitted. Example 5
The image forming apparatus of the fifth embodiment is different from that of the fourth embodiment in the following points, but has the same configuration as that of the fourth embodiment in other points. In FIG. 8, an air ejection member 13 for forming an air flow on the surface of the transparent member 6 of the image position sensor SN is disposed adjacent to the image position sensor SN. As shown in FIG. 8, the air flow is formed by blowing air 13 a from a direction perpendicular to the surface of the transparent member 6 or by blowing air so that the air flow is formed along the surface of the transparent member 6. A jetting method (not shown) or the like can be adopted. In the fifth embodiment, the sheet S passing through in the same manner as the fourth embodiment is used.
Thus, the surface of the transparent member 6 can be cleaned, and dirt can be removed by the air flow formed on the surface of the transparent member 6.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. (H01) In the fifth embodiment, the image position sensor SN can be disposed so that the surface of the transparent member 6 is not rubbed by the recording sheet S. In this case, the surface of the transparent member 6 is prevented from being stained by the air flow. (H02) In each of Embodiments 1 to 5, it is possible to use a sheet conveying belt instead of the intermediate transfer belt B. In this case, the toner images formed on the image carriers PRy to PRk are directly superimposed and transferred onto the recording sheet adsorbed on the sheet conveying belt. Therefore, the secondary transfer roll is omitted. (H03) In each of the above embodiments, an intermediate transfer drum can be used instead of the intermediate transfer belt B. (H04) As the image position sensor SN of the fourth embodiment,
It is possible to use the image position sensor SN shown in FIG. 3 of the first embodiment.

[0045]

The above-described image forming apparatus of the present invention has the following effects. (E01) In an image forming apparatus having an image position sensor for correcting color misregistration, the detection accuracy of the image position sensor can always be stably ensured.

[Brief description of the drawings]

FIG. 1 is a front sectional view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 shows the image position sensor S shown in FIG. 1;
It is an enlarged view of N and its adjacent part.

FIG. 3 is a perspective view of the image position sensor SN shown in FIG. 2;

FIG. 4 is an explanatory diagram of Embodiment 2 of the image forming apparatus of the present invention, and corresponds to FIG. 2 of Embodiment 1;

FIG. 5 is an explanatory view of Embodiment 3 of the image forming apparatus of the present invention, and corresponds to FIG. 2 of Embodiment 1;

FIG. 6 is a front sectional view of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of FIG. 6;

FIG. 8 is an enlarged view of a main part of a fifth embodiment of the image forming apparatus of the present invention, and corresponds to FIG. 7 of the fourth embodiment.

FIG. 9 is an explanatory diagram of a main part of an example of a color image forming apparatus to which the present invention is applied.

FIG. 10 is an explanatory diagram of a conventional image position sensor SN.

FIG. 11 is a view showing an example of the position detection pattern, and a toner image for position detection recorded at regular intervals in the moving direction (sub-scanning direction) Y of the transfer material (intermediate transfer belt) B; FIG. 5 is a diagram showing a V-shaped pattern as an example of the pattern of FIG.

[Explanation of symbols]

 B: transfer material (intermediate transfer belt); PRk: image carrier disposed at the most downstream in the transport direction; PRy, PRm, PRc, PRk: image carrier; Q3y to Q3k: transfer area (primary transfer area); SN: image position sensor, Tn: toner image, 6, 9, 12: transparent member, 13: ejection member, (Rt, Rw, Rf, T2a): transfer material transport device, (SH + Ra + Rr): sheet transport device,

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/00 510 G03G 21/00 510 (72) Inventor Kazuo Takano 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Inside (72) Inventor Susumu Yamashina 2274 Hongo, Ebina, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Teruyo Tatsuzaki 2274, Hongo, Ebina City, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. 2274 Hongo, Ebina-shi, Kanagawa Prefecture, Fuji Xerox Co., Ltd. Co., Ltd. (72) Inventor Takashi Hoshino Shrimp in Kanagawa Prefecture 2274, Hongo-shi, Fuji Xerox Co., Ltd. (72) Inventor Satoshi Fukada 2274, Hongo, Ebina-shi, Kanagawa Prefecture, Fuji Xerox Co., Ltd. (72) Inventor Norio Hokari 2274 Hongo, Ebina-shi, Kanagawa Prefecture F-term in Fuji Xerox Co., Ltd. EE05 HB16 HB20 JA03 JB16 2H030 AA01 AB02 AD05 AD16 BB02 BB42 BB44 BB46 BB56 2H032 AA05 AA15 BA09 BA15 BA23

Claims (4)

[Claims] An image forming apparatus comprising the following constitutional requirements (A01) to (A03): (A01) Toner images respectively formed on the surfaces of a plurality of image carriers are transferred to a transfer material (A02) a transfer material transport device for sequentially transporting the transfer material to a plurality of transfer areas to be transferred, which is disposed at a downstream position of an image carrier disposed at a most downstream position in a transport direction in the transfer material transport path. An image position sensor for reading a toner image for detecting an image position transferred from each of the image carriers onto the transfer material; (A03) a surface of the image position sensor facing the transfer material or a surface approaching the opposed surface; Replaceable transparent member arranged. 2. The image forming apparatus according to claim 1, further comprising the following constituent requirements (A04): (A04) The image forming apparatus is supported by another structural member of the image forming apparatus and is supported by the other structural member. The transparent member that is replaced at the same time as replacement. 3. The following components (A01), (A02),
(A03 '), an image forming apparatus provided with (A05), (A01) a plurality of transfer areas where toner images respectively formed on the surfaces of a plurality of image carriers are transferred to a transfer material. A transfer material transfer device for sequentially transferring the transfer material, (A02)
A toner image for image position detection, which is arranged on the downstream side of the image carrier arranged at the most downstream in the transport direction in the transport path of the transfer material and is transferred from each image carrier to the transfer material, is read. An image position sensor, (A03 ') a transparent member provided on the surface of the image position sensor, and (A05) an air flow ejecting member arranged near the transparent member and ejecting an air flow flowing in contact with the surface of the transparent member. 4. The following components (A01 '), (A0
2 '), (A03'), and (A06), (A01 ') toner images formed on the surfaces of a plurality of image carriers are transferred to an intermediate transfer material. (A02 ') a transfer material transport device for sequentially transporting the intermediate transfer material to a plurality of primary transfer areas, at a position downstream of an image carrier disposed at the most downstream in the transport direction in the transport path of the intermediate transfer material; An image position sensor that is disposed and reads a toner image for image position detection transferred from each of the image carriers to the intermediate transfer material; (A03 ′) a transparent member provided on the surface of the image position sensor; A sheet conveying device that conveys a recording sheet on which a toner image primarily transferred to a transfer material is secondarily transferred while contacting the surface of the transparent member.