JPH08123129A - Image forming device provided with image position sensor for correcting color slurring - Google Patents

Abstract

PURPOSE: To always stably secure the detecting accuracy of an image position sensor in an image forming device provided with an image position sensor for correcting color slurring. CONSTITUTION: This device is provided with a transfer material carrying device H successively carrying a transfer material P on which toner images respectively formed on plural image carriers Dy, Dm, Dc and Dk are transferred to a position where the toner image is transferred on the transfer material P from the respective image carriers Dy, Dm, Dc and Dk, and the image position sensor 37 reading a pattern image for detecting the position of the image transferred from the image carriers Dy, Dm, Dc and Dk; and it is provided with a staining preventing member 41 arranged more proximately to a transfer material carrying path than the sensor 37 between the image carrier Dk on the most downstream side of the transfer material carrying path and a reading position and attracting the toner unstably adhering to the transfer material P.

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 a transfer material to which a toner image formed on each of a plurality of image carriers is transferred. The present invention relates to an image forming apparatus including a transfer material conveying device that sequentially conveys a toner image onto a material and an image position sensor that reads an image position detecting pattern image transferred from each image carrier.

[0002]

2. Description of the Related Art FIG. 18 is a perspective view of a main part of a digital color copying machine as an image forming apparatus to which the present invention is applied. In FIG. 18, the image forming apparatus U has an image processing unit S1 to which R, G, and B image data read by an image scanner unit (not shown) is input. The image processing unit S1 is composed of a microcomputer, a memory, etc., and inputs the image data of R, G, B into Y (yellow), M
(Magenta), C (cyan), and K (black) digital image signals are converted and temporarily stored in the memory of the image processing unit S1, and at a predetermined timing, the four toner image forming apparatuses Uy, Um. , Uc, Uk.
The toner image forming devices Uy, Um, Uc and Uk are respectively
This is a device that forms toner images of Y (yellow), M (magenta), C (cyan), and K (black). The Y toner image forming device Uy has an image carrier Dy, a laser scanning system 01y arranged around the image carrier Dy, a developing device 02y, a cleaner 03y, a charger 04y, and the like. The toner image forming devices Um, Uc, and Uk are all configured similarly to the Y toner image forming device Uy.

The toner image forming devices Uy, Um, Uc, Uk
Is the Y input from the image processing unit S1,
The laser scanning systems 01y, 01m, 01c and 01k are driven according to the digital image signals of M, C and K, and the charger 04
An electrostatic latent image is written on the image carriers Dy, Dm, Dc and Dk uniformly charged by y, 04m, 04c and 04k. The electrostatic latent images on the image carriers Dy, Dm, Dc and Dk are transferred to the developing device 02y,
A toner image is developed by 02m, 02c, and 02k.

A transfer material conveying device H is arranged below the image carriers Dy, Dm, Dc and Dk. The transfer material transport device H has a drive roll 06, a peeling roll 07, an idler roll 08, a tension roll 09, and a transfer material transport belt 011 supported by these rolls. Transfer devices (not shown) are arranged at transfer positions where the image carriers Dy, Dm, Dc and Dk come into contact with the belt 011. Although not shown in FIG.
The transfer material (paper) P is supplied to the predetermined transfer material suction position on the upper surface of the belt 011 from the right side of the transfer material conveying device H at a predetermined timing. The transfer material P (not shown) attracted to the belt 011 at the transfer material adsorption position is conveyed by the belt 011. At that time, the writing start position of the transfer material P conveyed by the belt 011 and the tip of the Y (yellow) image on the Y (yellow) image carrier Dy arranged on the most upstream side in the transfer material conveyance direction are The transfer timing and the image writing timing of the transfer material P are determined so that the transfer points (the positions between the image carrier Dy and a transfer device (not shown)) coincide with each other. The toner image on the image carrier Dy is transferred to the transfer material P that has reached the transfer point by the transfer device (not shown). The transfer material P on which the Y toner image is transferred is sequentially transferred to the image carrier D.
It is conveyed to a transfer point between m, Dc, Dk and the respective transfer devices, but the image writing timing of the image carriers Dm, Dc, Dk is such that the front ends of the toner images of M, C, K are transfer materials. It is set so as to coincide with the tip of the Y toner image transferred to P.

Transfer material P on which the toner images of the respective colors have been transferred
Is peeled by a peeling corotron (not shown) or a stripper at the position of the peeling roller 07 and is conveyed to a fixing device (not shown) arranged on the left side in FIG.

As described above, in the multiple transfer type image forming apparatus for sequentially transferring a plurality of toner images to the transfer material, writing of the toner image of each color on each transfer material P in the main scanning direction and the sub scanning direction is started. If the position shifts, color shift occurs and the image quality deteriorates. Therefore, in order to align the writing start positions (writing start positions in the sub-scanning direction) of the toner images of Y, M, C, and K on the transfer material P in the main scanning direction and the sub-scanning direction, the transfer is performed. The laser scanning system 01y, 01m to the image carriers Dy, Dm, Dc, Dk is adjusted in accordance with the timing of the material P being conveyed to the transfer position and the position of the transfer material P in the main scanning direction when being conveyed to the transfer position. , 01c, 01k, the latent image writing timing needs to be adjusted. The timing at which the transfer material P is conveyed to the transfer position and the position of the transfer material P in the main scanning direction when the transfer material P is conveyed to the transfer position are such that a minute drum position shift and a transfer speed due to external force, temperature change, abrasion, etc. And it changes according to the fluctuation of the conveyance direction.

As described above, the pattern image for image position detection formed by the image forming apparatus is detected by using the image position detection sensor, the shift amount of each color is calculated, and the shift amount is formed for each image formation. The following techniques are conventionally known as a method for obtaining a stable image by performing correction by an apparatus. (J01) JP-A-63-271275, JP-A-1-
No. 281,468, JP-A-63-300260, etc.) In the techniques described in these publications, the position of the pattern image for image position detection necessary for adjusting the latent image writing timing is detected. , (That is, in order to detect the timing when the transfer material P is transported to the transfer position and the position of the transfer material P in the main scanning direction when transported to the transfer position), the toner image forming device Uk of the belt 011. The light sources 012 and 012 and the image position sensors 013 and 01 are provided on both sides in the width direction of the belt 011 at positions downstream thereof.
3 are arranged. This image position sensor 013,01
Reference numeral 3 denotes a sensor for reading the position detection pattern transferred from the toner image forming devices Uy, Um, Uc, and Uk to the transfer material P when a jam occurs or a temperature change in the device exceeds a specified value. Then, the detection signal is input to the signal processing unit S2. The signal processing unit S2 is a unit that calculates the deviation of the image of each color from the input signal.

FIG. 19 is a diagram showing an example of the position detecting pattern. FIG. 19A shows the moving direction of the transfer material P (sub-scanning direction).
FIG. 19B is a position detection pattern formed by lines of each color which are recorded in Y at regular intervals and which extend in the main scanning direction (width direction of the transfer material P) X. FIG. 19B is formed of lines of each color extending in the sub-scanning direction. Is a pattern for position detection. FIG.
In the 9A position detection pattern, lines of each color of Y, M, C, and K are recorded at intervals of, for example, 1 mm, and variations in the actual intervals are detected and calculated by the image position sensor 013. The amount of color misregistration of the formed image can be detected. Toner image forming devices Uy, Um, U
The timing of recording start in the sub-scanning direction Y at c and Uk can be adjusted. Further, in the position detecting pattern of FIG. 19B, the lines of each color of Y, M, C, and K are recorded so as to form a straight line extending in the sub-scanning direction Y, and the actual scanning line of each color line ( It is possible to adjust the recording start timing in the main scanning direction X in the toner image forming devices Uy, Um, Uc, Uk by detecting the variation in the position of the transfer material P in the width direction) X by the image position sensor 013. it can.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
1) has the following problems. Problem of (J01) In the image forming apparatus using the above-mentioned image position sensor, highly accurate detection of the image position is required. That is, the maximum allowable color misregistration for high-quality color images is 0.15 mm.
It is a degree. The conventional automatic color misregistration correction device also has an error due to arithmetic processing on each component and circuit. Therefore, if the permissible amount is distributed to each part, for example, with respect to the detection unit, several μm to several tens μm or less The accuracy of is required. However, if the image position sensor is on the upper surface of the belt as in the prior art, the output deteriorates due to dirt, and it is difficult to maintain such strict accuracy.

Although different from the technique targeted by the present invention, the following technique is known as a stain prevention means. (J02) Jpn. Pat. Appln. KOKAI Publication No. 1-34173 This publication discloses a means in which an insulating member is provided around the lens portion of the write head. However, the reading target portion of the reading portion of the color misregistration correction device that is the subject of the present invention always conveys the transfer material on which the toner image before fixing is placed during the copy cycle. Under such conditions, almost no effect can be obtained by providing an insulating member around the lens portion.

In view of the above-mentioned circumstances, the present invention has the following contents. (O01) In an image forming apparatus having an image position sensor for color misregistration correction, always ensure stable detection accuracy of the image position sensor.

[0012]

The present invention devised to solve the above problems will now be described. The elements of the present invention are to facilitate correspondence with the elements of the embodiments described later. Note that the reference numerals of the elements of the embodiments are enclosed in parentheses. Further, the reason why the present invention is described in association with the reference numerals of the embodiments described later is to facilitate understanding of the present invention and not to limit the scope of the present invention to the embodiments.

(First Invention) In order to solve the above problems,
An image forming apparatus having an image position sensor for color misregistration correction of the first invention of the present application has the following requirements (Y01) a plurality of image carriers (Dy, Dm, Dc, Dk). )
The transfer material (P) to which the toner image formed on each of the image transfer members (P) is attracted to the belt (25),
(Y, Dm, Dc, Dk), a transfer material conveying device (H) for sequentially conveying the transfer material (P) to the transfer position of the toner image onto the transfer material (P), (Y02) in the conveying path of the transfer material (P), the most downstream in the conveying direction. The image position detecting pattern image transferred from each of the image carriers (Dy, Dm, Dc, Dk) to the belt (25) is arranged at a position downstream of the image carrier (Dk). Image position sensor (37) to be read, (Y03) Light source (36) for illuminating the reading position of the image position sensor (37) on the transfer material transport path, (Y04) Image carrying on the most downstream side of the transfer material transport path The image position sensor (3) extends over a region from the downstream part of the body (Dk) to the upstream part of the reading position.
A stain prevention member (41) disposed closer to the transfer material conveyance path than 7) and adsorbing the toner that is unstablely attached on the transfer material (P).

(Second Invention) An image forming apparatus having an image position sensor (37) for color misregistration correction of the second invention of the present application has the following requirements (Y0
5) The transfer material (P) onto which the toner images formed on the plurality of image carriers (Dy, Dm, Dc, Dk) are transferred is attracted to the belt (25), and the image carriers (Dy, Dm) are attracted. , Dc, D
transfer material transporting devices (H) and (Y06) for sequentially transporting the toner image from k) to the transfer material (P) to the transfer position of the toner image.
Of the image carrier (Dy, Dm, Dc, Dk) arranged on the downstream side of the image carrier (Dk) arranged at the most downstream side in the carrying direction, and transferred from the image carrier (Dy, Dm, Dc, Dk) to the belt (25). An image position sensor (37) that reads the formed image position detection pattern image, (Y07) a light source (3) that illuminates the reading position of the image position sensor (37) on the transfer material transport path.
6), (Y08) The image position sensor (37) is arranged on the toner adhering surface side of the transfer material (P), and the light source (3)
6) is arranged at a position facing the image position sensor (37) with the transfer material (P) interposed therebetween, and (Y09) the light source (3) is operated while the operation of the image position sensor (37) is stopped.
A means for moving 6) to a position away from the reading position,
That is, the light source moving means.

(Third Invention) An image forming apparatus having an image position sensor (43) for color misregistration correction of the third invention of the present application has the following requirements (Y01).
0) The transfer material (P) onto which the toner images formed on the plurality of image carriers (Dy, Dm, Dc, Dk) are transferred is attracted to the belt (25), and the image carriers (Dy, Dm) are attracted. , Dc, D
k) a transfer material transporting device (H) for sequentially transporting the toner image from the transfer material (P) to the transfer position, and (Y011) an image carrier arranged at the most downstream side in the transport direction in the transport path of the transfer material (P). The image bearing members (Dy, Dm, Dc, Dk) are arranged on the downstream side of the body (Dk) and the belt (2
Image position sensor (43) for reading the image position detection pattern image transferred to (5), (Y012) Light source (36) for illuminating the reading position of the image position sensor (43) on the transfer material conveyance path, (Y013) ) The image position sensor (43)
Is arranged on the opposite side of the transfer material (P) from the toner adhering surface, and the light source (36) is arranged at a position facing the image position sensor (43) with the transfer material (P) interposed therebetween.

(Fourth Invention) An image forming apparatus having an image position sensor (43) for color misregistration correction according to the fourth invention of the present application has the following requirements (Y01).
4) The transfer material (P) onto which the toner images formed on the plurality of image bearing members (Dy, Dm, Dc, Dk) are transferred is attracted to the belt (25), and the image bearing members (Dy, Dm) are attracted. , Dc, D
k) a transfer material transporting device (H) for sequentially transporting the toner image from the transfer material (P) to the transfer position, and (Y015) an image carrier arranged at the most downstream side in the transport direction in the transport path of the transfer material (P). A transfer material peeling means arranged at a position on the downstream side of the body (Dk) for peeling the transfer material (P) from the belt (25), and (Y016) a transfer material peeling means in a moving path of the belt (25). Is also arranged on the downstream side, and the belt (2) is connected to each of the image carriers (Dy, Dm, Dc, Dk).
Image position sensor (43) for reading the image position detection pattern image transferred to 5), (Y017) A light source (36) for illuminating the reading position of the image position sensor (43).

[0017]

Next, the operation of the present invention having the above features will be described.

(Operation of the First Invention) An image position sensor (3) for color misregistration correction of the first invention of the present application having the above-mentioned characteristics.
In the image forming apparatus having 7), the transfer material conveying device (H)
The toner from each image carrier (Dy, Dm, Dc, Dk) is a transfer material (P) to which the toner image formed on each of the plurality of image carriers (Dy, Dm, Dc, Dk) is transferred. The image is sequentially conveyed to the image transfer position. The image position sensor (37) is arranged at a position on the downstream side of the image carrier (Dk) arranged at the most downstream side in the conveying direction in the conveying path of the transfer material (P). The light source (36) illuminates the reading position of the image position sensor (37) on the transfer material conveyance path. Then, the image position sensor (37) is configured to detect the image carriers (Dy, Dm, D).
The image position detecting pattern image transferred to the belt (25) is read from c, Dk). Stain prevention member (41)
Is the most downstream image carrier (D
It is arranged closer to the transfer material conveying path than the image position sensor (37) over the area from the downstream part of k) to the upstream part of the reading position, and unstablely adheres to the transfer material (P). Adsorbs the toner that is holding. Since the stain prevention member (41) arranged in the area on the upstream side of the reading position adsorbs the toner, the image position sensor (37) is prevented from being stained by the toner and the detection accuracy of the image position sensor (37) is improved. It can always be secured in a stable manner.

(Operation of the Second Invention) An image position sensor (3) for color misregistration correction of the second invention of the present application having the above-mentioned characteristics.
In the image forming apparatus having 7), the transfer material conveying device (H)
Is a transfer material (P) to which the toner images respectively formed on the plurality of image carriers (Dy, Dm, Dc, Dk) are transferred from each image carrier (Dy, Dm, Dc, Dk). The toner image is sequentially conveyed to the toner image transfer position to (P). Image position sensor (3
7) is arranged on the downstream side of the image carrier (Dk) arranged on the most downstream side in the conveyance direction in the conveyance path of the transfer material (P) and on the toner adhesion surface side of the transfer material (P). It The image position sensor (3
The light source (36) arranged at a position facing 7) illuminates the reading position of the image position sensor (37) on the transfer material conveyance path. And the image position sensor (37)
Reads the pattern image for image position detection transferred from the image carriers (Dy, Dm, Dc, Dk) to the belt (25). When the light source (36) is charged to the same polarity as the charge of the toner, the toner on the transfer material (P) receives a force in the direction away from the transfer material (P) by the light source (36). However, while the operation of the image position sensor (37) is stopped, the light source moving means moves the light source (36) to a position away from the reading position, so that the light source (3
It is possible to prevent the toner on the transfer material (P) from moving to the image position sensor (37) due to 6).

(Operation of Third Invention) An image position sensor (4) for correcting color misregistration according to the third invention of the present application having the above-mentioned characteristics.
In the image forming apparatus having 3), the transfer material conveying device (H)
Is a transfer material (P) to which the toner images respectively formed on the plurality of image carriers (Dy, Dm, Dc, Dk) are transferred from each image carrier (Dy, Dm, Dc, Dk). The toner image is sequentially conveyed to the toner image transfer position to (P). Image position sensor (4
3) is located on the downstream side of the image carrier (Dk) arranged on the most downstream side in the transport direction in the transport path of the transfer material (P) and on the opposite side of the toner adhesion surface of the transfer material (P). Will be placed. The light source (36) arranged at a position facing the image position sensor (43) with the transfer material (P) interposed therebetween is
The reading position of the image position sensor (43) on the transfer material conveyance path is illuminated. Then, the image position sensor (4
3) reads the image position detection pattern image transferred from the image carriers (Dy, Dm, Dc, Dk) to the belt (25). Since the image position sensor (43) is arranged at a position opposite to the toner adhering surface of the transfer material (P), the toner on the transfer material (P) can be detected by the image position sensor (4).
Adhesion to 3) is prevented.

(Operation of Fourth Invention) An image position sensor (4) for color misregistration correction of the fourth invention of the present application having the above-mentioned characteristics.
In the image forming apparatus having 3), the transfer material conveying device (H)
The belt (25) adsorbs the transfer material (P) onto which the toner images formed on the plurality of image carriers (Dy, Dm, Dc, Dk) are transferred to the image carriers (Dy, Dm). , Dc, D
The toner image is sequentially conveyed from k) to the transfer material (P). The image position detection pattern image transferred from each of the image carriers (Dy, Dm, Dc, Dk) to the belt (25) is located downstream of the transfer material peeling unit in the moving path of the belt (25). Is illuminated by the light source (36). The image position sensor (43) reads the image position detection pattern image of the belt (25) illuminated by the light source (36). Since the image position sensor (43) is arranged on the downstream side of the transfer material peeling means in the moving path of the belt (25),
When an image is formed using a normal transfer material (P), the transfer material (P) to which toner adheres does not come close to the image position sensor (43). Therefore, the image position sensor (43) is not contaminated by the toner attached to the transfer material (P).

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus having an image position sensor for color shift correction according to an embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiment. . In order to facilitate understanding of the explanation below,
In the drawings, orthogonal coordinate axes X, Y, and Z are defined in directions of arrows X, Y, and Z that are orthogonal to each other, and the arrow X direction is forward, the arrow Y direction is left, and the arrow Z direction is upward. In this case, the X direction (front) and the opposite direction (-X direction) are backward,
The opposite direction (-Y direction) to the Y direction (left side) is the right side, and the opposite direction (-Z direction) to the Z direction (upper direction) is the lower side. The front (X direction) and the rear (-X direction) are referred to as the front-back direction or the X-axis direction, and the left (Y direction) and the right (-Y direction) are included in the left-right direction or the Y-axis direction. That is, the upper direction (Z direction) and the lower direction (−Z direction) are referred to as the vertical direction or the Z axis direction. Furthermore, in the figure, "○" is put in "○".
The one with "" means an arrow from the back of the paper to the front, and the one with "x" in "○" means an arrow from the front to the back of the paper.

(Embodiment 1) FIG. 1 is an overall explanatory view of an image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 1 of the present invention. FIG. 2 is an explanatory diagram of the belt module B in the first embodiment shown in FIG. FIG. 3 is an explanatory diagram of an image position sensor for color misregistration correction according to the first embodiment. A digital color copying machine U as an image forming apparatus has a transparent platen glass 2 on which an original 1 is placed. Below the platen glass 2, a document illumination unit 3 that scans while illuminating the document 1 is arranged. The document illumination unit 3 includes a document illumination light source 4 and a first mirror 5.
have. Further, below the platen glass 2, a mirror unit 6 that moves at a speed half that of the original illumination unit 3 is arranged. The mirror unit 6 is emitted from the illumination light source and reflected by the original 1,
A second mirror that reflects the original image light reflected by the first mirror 5
It has a mirror 7 and a third mirror 8. The original image light reflected by the third mirror passes through the imaging lens 9 and is read by the color image reading sensor 10 as R, G, B analog signals. The signals read by the color image reading sensor 10 are Y (yellow), M (magenta), C (cyan), and K by the image processing unit S1.
The image processing section S is converted into a (black) digital image signal.
It is temporarily stored in memory 1.

The digital color copying machine U comprises four toner image forming devices Uy, Um, Uc and Uk. The toner image forming devices Uy, Um, Uc and Uk are respectively Y (yellow), M (magenta), C (cyan) and K.
This is a device that forms a toner image of each color (black). Said Y
The toner image forming apparatus Uy includes an image carrier Dy, a laser scanning system 16y arranged around the image carrier Dy, a developing device 17y, a cleaner 18y, and a charger 19y. The toner image forming devices Um, Uc, and Uk are all configured similarly to the Y toner image forming device Uy. The suction roller 20 arranged below the Y toner image forming device Uy is a transfer material P.
Is a member for pressing and adsorbing on the belt module B.

The image processing unit S1 outputs the Y, M, C and K digital image signals temporarily stored in the memory to the toner image forming devices Uy, Um, Uc and Uk.
The toner image forming devices Uy, Um, Uc, Uk drive the laser scanning systems 16y, 16m, 16c, 16k according to the digital image signals of the respective colors input from the image signal processing unit S1, and the chargers 19y, 19m. , 19c, 10k uniformly write an electrostatic latent image on the image carriers Dy, Dm, Dc, Dk. The electrostatic latent images on the image carriers Dy, Dm, Dc and Dk are developed into toner images by developing devices 17y, 17m, 17c and 17k.

A transfer material conveying device H is arranged below the image bearing members Dy, Dm, Dc and Dk. The transfer material transport device H has a belt module B shown in FIG. The belt module B has a belt supporting drive roll 21, a peeling roll 22, a tension roll 23, and an idler roll 24, which are rotatably supported by a front plate Pf and a rear plate Pr. A belt 25 for transferring the transfer material is supported by the rolls 21 to 24. A driven gear 21a is mounted on the rear end of the drive roll 21. When the belt module B is mounted on the image forming apparatus U, the drive gear Ma mounted on the output shaft of the drive motor M and the driven gear 21a mesh with each other.

Transfer devices 26y, 26m, and 26b are provided at transfer positions where the image carriers Dy, Dm, Dc, Dk and the belt 25 come into contact with each other.
26c and 26k are arranged. A peeling corotron 27 is arranged on the upstream side of the peeling roll 22 and a stripper (peeling claw) 28 is arranged on the downstream side. A fixing device 29 is disposed on the left side of the belt 25, and the belt 25 is provided between the transfer roll 23 and the drive roll 21.
A belt cleaner 30 for collecting the toner adhering to the surface of is disposed. In FIG. 1, a transfer material (paper) P is stored in a paper feed cassette 31 arranged below the transfer material transport device H. The transfer material P is taken out by the transfer material take-out roll 32 and conveyed to the registration roll 33. The registration roller 33 conveys the conveyed transfer material P to a transfer material suction position between the belt 25 and the suction roller 20 at a predetermined timing.

The transfer material P adsorbed to the belt 25 at the transfer material adsorbing position is conveyed by the belt 25. At that time, the image forming start position on the transfer material P conveyed by the belt 25 and the leading edge of the Y (yellow) image on the Y (yellow) image carrier Dy arranged on the most upstream side in the transfer material conveying direction. The transfer timing and the image writing timing of the transfer material P are determined so that the transfer points of the transfer device 26y and the image carrier Dy coincide with each other. On the transfer material P that has reached the transfer point, the toner image on the image carrier Dy is transferred by the transfer device 26y. The transfer material P on which the Y toner image has been transferred is sequentially transferred to the image bearing members Dm, Dc, Dk.
It is conveyed to the transfer point between the transfer device 26m, 26c, and 26k, but the image writing timing of the image carriers Dm, Dc, and Dk is such that the front ends of the toner images of M, C, and K are transferred to the transfer material P. It is determined so as to coincide with the front end of the transferred Y toner image.

Transfer material P on which the toner images of the respective colors have been transferred
Is peeled by the peeling corotron 27, the stripper 28 and the like at a peeling point on the outer periphery of the peeling roller 22 and conveyed to the fixing device 29. The transfer material P on which the color toner image is fixed by the fixing device 29 is discharged from the discharge roll 34 to the discharge tray 35. The surface of the image carrier Dy, Dm, Dc, Dk after the toner image is transferred is the cleaner 1.
Cleaned by 8y, 18m, 18c, 18k,
The belt 25 is cleaned by the belt cleaner 30.

In the multiple transfer type image forming apparatus U for sequentially transferring a plurality of toner images to the transfer material, the writing of the toner image of each color on each transfer material P in the main scanning direction and the sub scanning direction is started. If the position shifts, color shift occurs and the image quality deteriorates. Therefore, in order to make the writing start positions (writing start positions in the sub-scanning direction) of the toner images of Y, M, C, and K on the transfer material P in the main scanning direction and the sub-scanning direction uniform,
Laser scanning system 16y for image carriers Dy, Dm, Dc, Dk
It is necessary to adjust the latent image writing timing of 16m, 16c, 16k.

To detect the writing position of each color image necessary for adjusting the latent image writing timing (when the transfer material P is conveyed to the transfer position and when the transfer material P is conveyed to the transfer position). To detect the position of the transfer material P in the main scanning direction), the toner image forming device U of the belt 25
Light sources 36, 36 (only one is shown in FIG. 1) and image position sensors 37, 37 are arranged on both sides in the width direction of the belt 25 (direction perpendicular to the paper surface of FIG. 1) at a position downstream of k. There is.

In FIG. 3, the light source 36 is arranged inside the belt 25 for transporting the transfer material (on the side opposite to the transfer material suction side of the belt 25), and the image position sensor 37 is outside the belt 25 (transfer of the belt 25). It is located on the material suction side). The image position sensor 37 is a member for reading a position detection pattern image formed on the belt upper surface position where a straight line connecting the light source 36 and the image position sensor 37 intersects with the belt, that is, the belt 25 conveyed to the image reading position. Is. The image position sensor 37 has a housing 38. An opening 38a is arranged on the lower surface of the housing 38. The image position sensor 37 includes a CCD sensor 39 and a short focus lens array 4 supported by the housing 38.
Has 0. The short focus lens array 40 is supported by the housing 38 so that its position in the optical axis direction can be adjusted, and the position detection pattern image transferred to the upper surface of the belt 25 is formed on the CCD sensor 39. It is arranged. The detection signal of the CCD sensor 39 is input to the signal processing unit S2. The signal processing unit S2 is a unit that calculates the positional deviation of the image of each color according to the input signal. The image position sensor 3 in the conveying direction of the transfer material P
On the upstream side of 7, there is a stain prevention member 41 composed of a plate-shaped insulating member supported by the housing 38 from the downstream portion of the black toner image carrier Dk to the upstream portion of the image position sensor 37. It is arranged. This stain prevention member 41
The lower surface of the housing is disposed below the lower surface of the housing 38.

(Operation of First Embodiment) Next, the operation of the first embodiment having the above-described structure will be described. In the case of the image position sensor 37 using the short focus lens array 40, the short focus lens array 40 cannot be moved far away from the belt 25, and therefore is arranged close to each other. In that case, if the stain prevention member 41 is not provided, a large potential difference is generated between the transfer material P and the image position sensor 37 that are arranged close to each other, and the unstable toner that is not sufficiently attracted to the transfer material P. Adheres to the lower surface of the short focus lens array 40 of the image position sensor 37 and becomes dirty, and the dirt causes the performance of the short focus lens array 40 to deteriorate with several thousand to tens of thousands of copies. However, in the first embodiment, the unstable toner adhering to the transfer material P reaches the downstream side of the image carrier Dk arranged on the most downstream side of the upstream side before reaching the image position sensor 37. To the dirt prevention member 41 arranged over the upstream portion of the image position sensor 37, the dirt on the short focus lens array 40 of the image position sensor 37 can be greatly improved. The closer the position of the stain prevention member 41 is to the transfer material P and the larger the area thereof, the greater the stain prevention effect. Further, in order to prevent the short focus lens array from being contaminated, it is possible to provide a seal glass in the opening 38a on the lower surface of the housing 38, and in that case, it is possible to prevent the seal glass from being contaminated.

(Embodiment 2) FIG. 4 is an explanatory diagram of an image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 2 of the present invention. In the description of the second embodiment, constituent elements corresponding to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. Example 2
Is different from Example 1 in the following points, but is configured similarly to Example 1 in other points. (S01) The stain prevention member 41 is supported by the K (black) toner image forming device Uk on the upstream side of the image position sensor 37. The second embodiment has the same operation as the first embodiment. In addition, the second embodiment has a stain prevention member 41.
Since the cleaner 18k of the toner image forming apparatus Uk is arranged above the above, the stain preventing member 41 can be arranged without increasing the size of the image forming apparatus.

(Embodiment 3) FIG. 5 is an explanatory view of a main portion of an image forming apparatus having an image position sensor for correcting color shift according to Embodiment 3 of the present invention. In the description of the third embodiment, constituent elements corresponding to those of the second embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The third embodiment differs from the second embodiment in the following points,
In other respects, the configuration is the same as that of the first embodiment. (S02) K (black) on the upstream side of the image position sensor 37
The stain preventing member 41 supported by the toner image forming apparatus Uk is formed in a corrugated cross section in order to increase the surface area. The third embodiment has the same operation as the second embodiment. In addition, since the surface area of the stain preventing member 41 can be increased in the third embodiment as compared with the second embodiment, a larger amount of toner can be attached to the stain preventing member 41.

(Embodiment 4) FIG. 6 is an explanatory diagram of a main portion of an image forming apparatus having an image position sensor for correcting color shift according to Embodiment 4 of the present invention. In the description of the fourth embodiment, constituent elements corresponding to those of the second embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. Example 4 is different from Example 2 in the following points,
In other respects, the configuration is the same as that of the first embodiment. (S03) The stain prevention member 4 supported by the K (black) toner image forming device Uk upstream of the image position sensor 37.
1 and a point at which an insulating member 42 is disposed at a position facing the belt 25 with the belt 25 interposed therebetween.

(Operation of Embodiment 4) Since the transfer material P on which the toner has been transferred is attracted to the belt 25, the lower surface of the belt 25 is charged with the opposite polarity to the toner. This belt 25
A charge having the same polarity as that of the toner is induced on the upper surface of the insulating member 42 arranged adjacent to the lower surface. In other words, electric charges that cancel the electric charges on the lower surface of the belt 25 are induced in the insulating member 42. By this action, the unstable suction force of the toner on the transfer material P is weakened, and the adhesion of the toner to the stain prevention member 41 is promoted. Therefore, it is possible to further reduce the contamination of the short focus lens array 40. Therefore, in Example 4, even if the length of the stain prevention member 41 is shortened, a sufficient stain prevention effect can be obtained.

(Embodiment 5) FIG. 7 is an explanatory diagram of a main portion of an image forming apparatus having an image position sensor for correcting color shift according to Embodiment 5 of the present invention. In the description of the fifth embodiment, constituent elements corresponding to those of the fourth embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The fifth embodiment differs from the fourth embodiment in the following points,
The other points are the same as those in the fourth embodiment. (S04) The dirt prevention member 4 with the belt 25 interposed therebetween.
The point where the insulating member 42 arranged at a position facing 1 is charged to the same polarity as the toner. In this Example 5, the transfer material P
The above unstable toner suction force is surely weakened, and the adhesion of the toner to the toner stain prevention member 41 is promoted. Therefore, it is possible to further reduce the contamination of the short focus lens array 40.

(Embodiment 6) FIG. 8 is an explanatory view of a main portion of an image forming apparatus having an image position sensor for correcting color shift according to Embodiment 6 of the present invention. In the description of the sixth embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. Example 6 is different from Example 1 in the following points,
In other respects, the configuration is the same as that of the first embodiment. (S05) The stain prevention member 41 of the first embodiment is omitted,
A point in which the light source 36 is movably arranged between a use position (see a solid line) facing the image position sensor 37 with the belt 25 interposed therebetween and a non-use position (two-dot chain line position) apart from the use position. . It should be noted that the non-use position of the image position sensor 37 should be a position separated from the lower surface of the belt 25 downward, a position moved along the lower surface of the belt 25, or the like, as shown by the chain double-dashed line in FIG. Is possible. Although a means for moving the light source 36, that is, a light source moving means is not shown, it can be easily configured by various conventionally known moving means such as a pinion driven by a motor and a rack or a solenoid.

(Operation of Embodiment 6) In order to secure the required light quantity for the image position sensor 37, the light source 36 may be arranged as close as possible to the belt 25. Then, in the embodiment 4 shown in FIG. By the same action as the insulating member 42, the short focus lens array 40 of the image position sensor 37 above the light source 36 is soiled. Therefore, during normal image formation without using the image position sensor 37, by moving the light source from the use position to the non-use position, the short-focus lens array 40 of the image position sensor 37 can be prevented from becoming dirty. it can.

(Embodiment 7) Next, an image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 7 of the present invention will be described with reference to FIGS. FIG. 9 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a seventh embodiment of the present invention. FIG. 10 is an exploded perspective view of a structure for attaching the image position sensor 43 to the belt module according to the seventh embodiment. In the description of the seventh embodiment, constituent elements corresponding to those of the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. Example 7 is different from Example 1 in the following points,
In other respects, the configuration is the same as that of the first embodiment. The stain prevention member 41 of the first embodiment is omitted, and the image position sensor 43 is used instead of the image position sensor 37 of the first embodiment. In addition, the light source 36 is arranged outside the belt 25,
A position facing the light source 36 with the belt 25 interposed therebetween (the belt 2
The image position sensor 43 is arranged at a position (inside of 5). Therefore, in the seventh embodiment, the image position sensor 43 is attached to the inside of the belt 25 of the belt module B (see FIG. 2), and thus the configuration is slightly different from that of the image position sensor 37 of the first embodiment.

9 and 10, the image position sensor 43
Are arranged one by one on the mounting plate 44 extending in the front-rear direction and separated from each other in the front-rear direction. Mounting plate 44
Has a horizontal portion 45, a rear end vertical portion 46, and a front end vertical portion 47 that extend in the front-rear direction. The rear end vertical portion 46 is provided with two fitted studs 46a protruding rearward, and the front end vertical portion 47 is provided with two fitted studs 4 protruding rearward.
7a is provided. Further, the front vertical portion 47 is formed with two screw through holes 47b.

Further, on the left side edge of the horizontal portion 45, lens supporting portions 48, 48 are provided at two positions apart from each other in the front and rear direction. A short focus lens array 40 is held on the lens support 48 by a lens array holding member 49 so that the vertical position can be adjusted. A sensor support substrate 50 is positioned and fixed by screws 51 on the horizontal portion 45 below the short focus lens array 40. The screw 51 has a screw through hole whose inner diameter is larger than its outer diameter (sensor support substrate 50
Through the screw through hole) formed in the horizontal portion and screwed into the screw hole formed in the horizontal portion. As a result, the sensor support substrate 50 is fixed to the horizontal portion 45 so that its position can be adjusted in the front, rear, left and right directions. The sensor support substrate 50 has a CCD
The sensor 39 is fixed. The image position sensor 43 of the seventh embodiment includes the CCD sensor 39, the short focus lens array 40, and members 45, 48 to 51 for supporting them.
And the like. A sensor unit U1 is composed of the two image position sensors 43 and a mounting plate 44 supporting them.

A sensor insertion opening 56 is formed in the front plate Pf of the belt module B.
Further, the front plate Pf is provided with fitting holes 57, 57 on both sides of a lower portion of the sensor insertion opening 56, and screw holes 58, 58 are formed above the fitting holes 57, 57. Further, the rear plate Pr of the belt module B has two fitting holes 5 which are fitted to the stats 46a, 46a to be fitted.
9, 59 are formed.

(Operation of Embodiment 7) From the sensor insertion opening 56 of the front plate Pf to the sensor unit U1
And the rear end vertical portion 46 of the sensor unit U1 is inserted.
The fitted studs 46a, 46a of the rear plate Pr
Of the belt module B of the sensor unit U1 by fitting the fitted studs 47a, 47a of the front end vertical portion 47 into the fitting holes 57, 57 of the front plate Pf. To position. Then, the sensor unit U1 is positioned and fixed to the belt module B by screwing a screw penetrating the screw through hole 47b of the front end vertical portion 47 of the sensor unit U1 into the screw hole 58. As described above, the sensor unit U1 positioned and fixed to the belt module B is positioned at a predetermined position with respect to the belt 25.

By the way, at the positions of the short-focus lens array 40 and the CCD sensor 39 of the sensor unit U1, the image of the transfer material P adsorbed and conveyed on the upper surface of the belt 25 is CC.
It is necessary to arrange so as to form an image on the D sensor 39. Therefore, when assembling the sensor unit U1, a jig (not shown) is used. That is, the sensor unit U1
The position of the short focus lens array 40 and the CCD sensor 39 is adjusted in advance by using a jig in which the belt is arranged at the position where the belt 25 is present when the is attached to the belt module B. By mounting the sensor unit U1 thus assembled with the preadjusted position on the belt module B as described above, the image of the transfer material P sucked and conveyed on the upper surface of the belt 25 is transferred to the CCD sensor 39.
Short focus lens array 40 and CC
The D sensor 39 can be arranged.

According to the seventh embodiment, the image position sensor 4
Since 3 is disposed inside the belt 25, it is possible to prevent the image position sensor 43 from being soiled by the toner adhering to the transfer material P. Moreover, the sensor unit U1 can be easily positioned and attached to the belt module B.

(Embodiment 8) Next, an image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 8 of the present invention will be described with reference to FIGS. FIG. 11 is an exploded perspective view of the mounting structure of the image position sensor 43 to the belt module in the image forming apparatus having the image position sensor for color shift correction according to the eighth embodiment of the present invention. FIG. 12 is an explanatory view of the support structure of the rear end portion of the sensor unit U1 in the eighth embodiment. In the description of the eighth embodiment, constituent elements corresponding to those of the seventh embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. This Example 8
Is different from Example 7 in the following points, but is configured similarly to Example 7 in other points. In the eighth embodiment, the shape of the mounting plate 44 of the sensor unit U1,
Further, the mounting structure of the sensor unit U1 on the front plate Pf and the rear plate Pr of the belt module B is different from that of the seventh embodiment. Also, belt module B
Is provided with an idler roll 61 on the upstream side of the peeling roll 22.

That is, the rear end vertical portion 46 of the mounting plate 44 of the sensor unit U1 is the belt module B.
It has a positioning recess 46c that fits into the bearing 22a of the peeling roll 22 and a horizontal support portion 46d that supports the lower end of the bearing 61a of the idler roll 61. Similarly, the front end vertical portion 47 also includes the peeling roll 2 of the belt module B.
The horizontal support portion 4 that supports the recess 47c that fits into the second bearing 22a and the lower end of the bearing 61a of the idler roll 61.
It has 7d. Further, the front end vertical portion 47 is provided with a screw through hole 47e for fixing to the front plate Pf with a screw. In FIG. 12, a unit support bracket 62 is provided on the rear plate Pr. A plate spring 63 having high rigidity is fixed to the upper surface of the unit support bracket 62. This leaf spring 63
Is a member for supporting the lower surface of the rear end of the sensor unit U1.

(Operation of Embodiment 8) From the sensor insertion opening 56 of the front plate Pf to the sensor unit U1
Is inserted, the lower surface of the rear end of the sensor unit U1 is supported by the unit support bracket 62 via the leaf spring 63. Then, the positioning recess 46c of the rear end vertical portion 46 of the sensor unit U1 fits with the outer periphery of the bearing 22a of the peeling roll 22, and the horizontal support portion 46d abuts on the lower end of the outer periphery of the bearing 61a of the idler roll 61. That is, the rear end of the sensor unit U1 is positioned in such a state. Then, the front end of the sensor unit U1 is similarly positioned. The screw through hole 47 provided in the front end vertical portion 47 in the thus positioned state.
The sensor unit U1 is attached to the belt module B by a screw (not shown) which penetrates e and is screwed into the screw hole of the front plate Pf. The eighth embodiment also has the same operation as the seventh embodiment. In addition, in this eighth embodiment, the belt 2
Peeling roll 22 and idler roll 61 supporting 5
Since the sensor unit U1 is positioned with reference to the outer circumferences of the bearings 22a and 61a, the image position sensor 43 can be positioned with respect to the belt 25 with higher accuracy.

(Ninth Embodiment) Next, an image forming apparatus having an image position sensor for color misregistration correction according to a ninth embodiment of the present invention will be described with reference to FIG. FIG. 13 shows the eighth embodiment of the present invention.
FIG. 6 is an exploded perspective view of the mounting structure of the image position sensor 43 on the belt module in the image forming apparatus having the image position sensor for color misregistration correction. In the description of the ninth embodiment, constituent elements corresponding to those of the eighth embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.
The ninth embodiment differs from the eighth embodiment in the following points, but is configured similarly to the eighth embodiment in other points. The ninth embodiment differs from the eighth embodiment in the structure of the sensor unit U1 and the mounting structure of the sensor unit U1 on the front plate Pf and the rear plate Pr of the belt module B. Further, the shapes of the front plate Pf and the rear plate Pr of the belt module B are also different from those in the eighth embodiment.

That is, the peeling roll 22 and the idler roll 23 are provided on the rear end vertical portion 46 and the front end vertical portion 47 of the mounting plate 44 extending in the front and rear of the sensor unit U1.
Are rotatably supported. The horizontal portion 45 of the mounting plate 44 is provided with mounting screw holes 45b, 45b. At the left end of the front plate Pf and the rear plate Pr of the belt module B to which the sensor unit U1 is attached, a horizontal unit mounting portion 6 that supports the horizontal portion 45 of the mounting plate 44 of the sensor unit U1.
6, 67 are provided. This unit mounting part 66,
The 67 has screw holes 66a and 67a, respectively.

(Operation of Embodiment 9) The sensor unit U is attached to the unit mounting portions 66 and 67 of the belt module B.
The sensor unit U1 is mounted on the belt module B1 by mounting 1 and screwing a screw (not shown) passing through the mounting screw hole 45b into the screw holes 66a and 67a.
Attached to. The ninth embodiment also has the same operation as the eighth embodiment. Further, in the ninth embodiment, since the peeling roll 22 and the idler roll 61 supporting the belt 25 are arranged in the sensor unit U1, the mounting plate 4
The position of the image position sensor 43 when the image position sensor 43 is attached to the roller 4 can be performed with a belt-shaped member stretched between the rolls 22 and 61. Therefore, the image position sensor 43 can be easily and accurately positioned and fixed to the mounting plate 44 without using a jig having a special structure.

When the sensor unit U1 thus positioned is attached to the belt module B,
Since the belt 25 is stretched between the peeling roll 22 and the idler roll 61 supported by the sensor unit U1, the position of the belt 25 with respect to the image position sensor 43 is set to the mounting plate 44 at the time of the positioning of the image position sensor 43. The position is exactly the same as that of the belt-shaped member. Therefore, in the ninth embodiment, the image position sensor 43 can be positioned with respect to the belt 25 very accurately.

(Embodiment 10) Next, an image forming apparatus having an image position sensor for correcting color shift according to Embodiment 10 of the present invention will be described with reference to FIG. FIG. 14 is an explanatory view of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a tenth embodiment of the present invention. In the description of the tenth embodiment, constituent elements corresponding to those of the seventh embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. The tenth embodiment differs from the seventh embodiment in the following points, but is substantially the same as the seventh embodiment in other points. In the tenth embodiment, the sensor unit U1 having the image position sensor 43 is provided with the belt 25 on the downstream side of the peeling point of the transfer material P (the outer peripheral portion of the peeling roller 22).
Is located outside of. The light source 36 is arranged at a position facing the image position sensor 43 with the belt 25 interposed therebetween. Thus, by disposing the image position sensor 43 on the downstream side of the peeling point, it is possible to prevent the image position sensor 43 from being contaminated by the toner attached to the transfer material P during copying. In the case of this embodiment, the image position detection pattern image is formed on the belt 25, not on the transfer material P. Then, the image position detecting pattern image is cleaned by the belt cleaner 30.

(Embodiment 11) An image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 11 of the present invention will be described with reference to FIG. FIG. 15 is an explanatory view of a main part of an image forming apparatus having an image position sensor for correcting color misregistration according to the eleventh embodiment of the present invention. The eleventh embodiment differs from the tenth embodiment shown in FIG. 14 in the following points, but is configured similarly to the tenth embodiment in other points. (S06) Sensor unit U1 and light source 3 of the tenth embodiment
The point where the sensor unit U1 is arranged inside the belt 25 by exchanging the position with 6. In this eleventh embodiment, the belt 2
Since the space inside 5 can be effectively used, it is useful for downsizing the entire image forming apparatus.

(Embodiment 12) Next, an image forming apparatus having an image position sensor for color misregistration correction according to Embodiment 12 of the present invention will be described with reference to FIG. FIG. 16 is an explanatory view of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a twelfth embodiment of the present invention. The twelfth embodiment differs from the tenth embodiment shown in FIG. 14 in the following points, but is configured similarly to the tenth embodiment in other points. (S07) While the sensor unit U1 having the image position sensor 43 and the light source 36 are arranged on the upstream side of the idler roll 24 in the tenth embodiment, the sensor unit U1 and the light source 36 are arranged on the downstream side of the idler roller 24 in the twelfth embodiment. Points located on the side. The twelfth embodiment also has the same operation as the tenth embodiment.

(Thirteenth Embodiment) Next, an image forming apparatus having an image position sensor for color misregistration correction according to a thirteenth embodiment of the present invention will be described with reference to FIG. FIG. 17 is an explanatory view of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a thirteenth embodiment of the present invention. The thirteenth embodiment differs from the twelfth embodiment shown in FIG. 16 in the following points, but is configured similarly to the twelfth embodiment in other points. (S08) Sensor unit U1 and light source 3 of the twelfth embodiment
The point where the sensor unit U1 is arranged inside the belt 25 by exchanging the position with 6. In this example 13, the belt 2
Since the space inside 5 can be effectively used, it is useful for downsizing the entire image forming apparatus.

(Modifications) Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, but is within the scope of the gist of the present invention described in the claims. Thus, various changes can be made.

[0060]

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

[Brief description of drawings]

FIG. 1 is an overall explanatory diagram of an image forming apparatus having an image position sensor for color shift correction according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a belt module B in the first embodiment shown in FIG.

FIG. 3 is an explanatory diagram of a main part of the first embodiment.

FIG. 4 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for color shift correction according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for color misregistration correction according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for color misregistration correction according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for color shift correction according to a fifth embodiment of the present invention.

FIG. 8 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a sixth embodiment of the present invention.

FIG. 9 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a seventh embodiment of the present invention.

FIG. 10 is an exploded perspective view of a mounting structure of an image position sensor 43 on a belt module according to the seventh embodiment.

FIG. 11 is an exploded perspective view of a mounting structure of an image position sensor 43 on a belt module in an image forming apparatus having an image position sensor for color shift correction according to an eighth embodiment of the present invention.

FIG. 12 is an explanatory diagram of a support structure of a rear end portion of the sensor unit U1 according to the eighth embodiment.

FIG. 13 is an exploded perspective view of a mounting structure of an image position sensor 43 on a belt module in an image forming apparatus having an image position sensor for color shift correction according to an eighth embodiment of the present invention.

FIG. 14 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color shift according to a tenth embodiment of the present invention.

FIG. 15 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color misregistration according to an eleventh embodiment of the present invention.

FIG. 16 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color misregistration according to a twelfth embodiment of the present invention.

FIG. 17 is an explanatory diagram of a main part of an image forming apparatus having an image position sensor for correcting color misregistration according to a thirteenth embodiment of the present invention.

FIG. 18 is a perspective view of a main part of a digital color copying machine as an image forming apparatus to which the present invention is applied.

FIG. 19 is a diagram showing an example of the position detection pattern, and FIG. 19A is a moving direction of the transfer material P (sub-scanning direction).
FIG. 19B is a position detection pattern that is formed by lines of each color that are recorded at a constant interval and that extend in the main scanning direction (width direction of the transfer material P). FIG. 19B includes lines of each color that extend in the sub-scanning direction. It is a pattern for position detection.

[Explanation of Codes] Dy, Dm, Dc, Dk ... Image carrier, H ... Transfer material conveying device,
P ... Transfer material, 25 ... Belt, 36 ... Light source, 37 ... Image position sensor, 41 ... Stain prevention member, 43 ... Image position sensor,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03G 21/10 H04N 1/60 1/46 H04N 1/46 Z

Claims (4)

[Claims] 1. An image forming apparatus having an image position sensor for color misregistration correction, characterized by having the following requirements:
(Y01) A transfer material conveying device for adsorbing a transfer material, on which a toner image formed on each of a plurality of image carriers is transferred, onto a belt, and sequentially conveying the transfer material to a toner image transfer position from each image carrier to the transfer material, (Y02) An image position detection pattern image transferred from each of the image carriers to the belt is disposed at a position on the downstream side of the image carrier disposed at the most downstream side in the transport direction of the transfer material. Image position sensor to read, (Y
03) A light source that illuminates the reading position of the image position sensor on the transfer material conveyance path, (Y04) a region from the downstream part of the most downstream image carrier of the transfer material conveyance path to the upstream part of the reading position. A stain prevention member that is disposed closer to the transfer material conveying path than the image position sensor and that adsorbs toner that is unstablely attached on the transfer material. 2. An image forming apparatus having an image position sensor for color misregistration correction, characterized by having the following requirements:
(Y05) A transfer material conveying device for adsorbing a transfer material, on which a toner image formed on each of a plurality of image carriers is transferred, to a belt, and sequentially conveying the transfer material to a transfer position of the toner image from each image carrier. (Y06) The image position detection pattern image transferred from each of the image carriers to the belt is arranged at a position on the downstream side of the image carrier arranged at the most downstream side in the transport direction of the transfer material. Image position sensor to read, (Y
07) A light source for illuminating the reading position of the image position sensor on the transfer material conveyance path, (Y08) the image position sensor is arranged on the toner adhering surface side of the transfer material, and the light source sandwiches the transfer material to sandwich the transfer material. It is arranged at a position facing the image position sensor, and (Y09) means for moving the light source to a position away from the reading position while the operation of the image position sensor is stopped. 3. An image forming apparatus having an image position sensor for color misregistration correction, characterized by having the following requirements:
(Y010) A transfer material conveying device that adsorbs a transfer material, to which the toner images respectively formed on the plurality of image carriers are transferred, onto a belt, and sequentially conveys the transfer material from each image carrier to the transfer material to a toner image transfer position. (Y011) The image position detection pattern image transferred from each of the image carriers to the belt is arranged at a position on the downstream side of the image carrier arranged at the most downstream side in the conveying direction of the transfer material. Image position sensor to read,
(Y012) a light source that illuminates the reading position of the image position sensor on the transfer material transport path, (Y013) the image position sensor is disposed on the side opposite to the toner adhering surface of the transfer material, and the light source outputs the transfer material. It is arranged at a position facing the image position sensor with the pinch in between. 4. An image forming apparatus having an image position sensor for color misregistration correction, characterized by having the following requirements:
(Y014) A transfer material conveying device that adsorbs a transfer material, to which the toner images respectively formed on the plurality of image carriers are transferred, onto a belt and sequentially conveys the transfer material from each image carrier to the transfer position of the toner image to the transfer material. (Y015) A transfer material peeling unit that is arranged at a position on the downstream side of the image carrier arranged at the most downstream side in the conveyance direction of the transfer material, and peels the transfer material from the belt, (Y016) of the belt. An image position sensor which is arranged on the downstream side of the transfer material peeling means in the moving path and reads the image position detection pattern image transferred from each of the image carriers to the belt, (Y017) the reading position of the image position sensor Light source to illuminate.