JP2001166600A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device that an image of high quality without any deviation in position of an image is formed by preventing differential in reading of a detecting sensor by preventing soiling of a mark for position detection provided for a belt state member. SOLUTION: In the device, a groove 507a that is deeper than thickness of the mark for position detection 550 and wider than width of the mark for position detection 550 is formed on an outer periphery surface of a retaining roll 507 in a position facing the mark for position detection 550, so that the mark for position detection 550 and the retaining roll 507 do not come in contact with each other. The soiling that is attached to the retaining roll 507 is not transmitted to the mark for position detection 550, the soiling the mark for position detection 550 is decreased and the differential in reading of the detection sensor 514 due to the soiling above is prevented.

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, a printer, a facsimile and the like, and more particularly, to a belt-shaped member provided with at least one mark for position detection, and a rotation of the belt-shaped member. The present invention relates to an image forming apparatus having a plurality of holding members movably held, and a detection sensor for detecting a position detection mark of the belt-shaped member, and using a detection result of the detection sensor for sequence control.

[0002]

2. Description of the Related Art Hitherto, an image forming apparatus using a belt-shaped member as a component thereof has been known. For example, there is an image forming apparatus provided with an intermediate transfer belt that is disposed to face a photoconductor made of a rotating body that is driven to rotate, and that is rotated at the same peripheral speed as the photoconductor in a contact state. This type of image forming apparatus has a detection sensor that detects the position detection mark in a passage area of the position detection mark provided on the intermediate transfer belt. Further, the primary transfer section which is in contact with the photoreceptor has a primary transfer means, and a charging means at a charging position on the upstream side in the rotation direction of the photoreceptor from the position where the primary transfer means is provided. When forming an image, during rotation of the photoconductor and the intermediate transfer belt,
An image forming process is started at a certain timing from the detection of the position detection mark by the detection sensor. Specifically, optical writing on the photoconductor is started. Particularly, in an image forming apparatus for forming a color image, a toner image of a predetermined color is formed by light writing and development on a charged area of a photoconductor charged by passing through the charging position, and the toner image of the predetermined color is formed. The image is transferred to the intermediate transfer belt by the primary transfer unit in the primary transfer unit. Such an operation is repeated for each different color to form a color superimposed toner image on the intermediate transfer belt, and the color image is obtained by collectively transferring the superimposed toner image onto transfer paper. The overlapping toner image is formed for each of the different colors on the intermediate transfer belt without a positional shift by starting an image forming process at a fixed timing from the detection of the position detection mark by the detection sensor. It has become so.

[0003]

However, a reading error may occur in the detection of the position detection mark by the detection sensor. When an error occurs in reading by the detection sensor, the timing of starting the image forming process is shifted, and the position of the superimposed toner image on the intermediate transfer belt may be shifted. The main cause of the reading error is erroneous detection of the detection sensor due to contamination of the position detection mark provided on the intermediate transfer belt. Usually, since the position detection mark is provided on the inner peripheral surface of the intermediate transfer belt, it comes into contact with the roller holding the intermediate transfer belt. When the holding roller becomes dirty due to toner scattering or the like, the stain adheres to the position detection mark. Then, when a reflection type optical sensor is used as the detection sensor, the amount of light reflected by the position detection mark out of the light emitted from the optical sensor decreases, and the detection by the optical sensor is delayed or detected. May disappear.

FIG. 9A is a perspective view showing an example of a case where the above-mentioned optical sensor detects a position detecting mark provided on the inner peripheral surface of the intermediate transfer belt. When the intermediate transfer belt 501 rotates and moves in the direction of the arrow in the figure and the position detection mark 550 passes through the detection area of the optical sensor 514, a detection signal is output from the optical sensor 514 as shown in FIG. . FIG. 9B shows a case where the position detection mark 550 is not dirty and no reading error of the optical sensor 514 occurs. On the other hand, if the position detection mark 550 is dirty, as shown in FIG.
4, the detection of the position detection mark 550 may be delayed. The detection delay is a distance in the moving direction of the intermediate transfer belt 501, for example, from 40 μm to 10 mm (less than the mark width). This detection delay is caused by the intermediate transfer belt 501.
This is a cause of misregistration when forming the superposed toner image thereon.

The problem of image displacement due to a reading error of the detection sensor is not limited to the above-mentioned intermediate transfer belt, but a problem that can occur in a belt-shaped member provided with a mark for position detection. In addition, when optical writing is performed on the photoconductor using the detection result of the detection sensor for sequence control, a reading error of the detection sensor causes a problem of image displacement.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to prevent a position detection mark provided on a belt-shaped member from being stained, thereby preventing a reading error of a detection sensor. Another object of the present invention is to provide an image forming apparatus capable of forming a high-quality image without image displacement or the like.

[0007]

To achieve the above object, according to the present invention, there is provided a belt-like member provided with at least one mark for position detection, and the belt-like member is rotatably held. A plurality of holding members, and a detection sensor that detects a mark for detecting the position of the belt-shaped member, and in an image forming apparatus that uses a detection result of the detection sensor for sequence control, at least one of the plurality of holding members A non-contact portion that does not contact the position detection mark is provided on one holding member.

In the image forming apparatus according to the first aspect of the present invention, the non-contact portion provided on at least one of the plurality of holding members does not contact the position detection mark. Dirt is not transferred to the position detection mark, and the contamination of the position detection mark can be reduced. Therefore, it is possible to prevent a reading error of the detection sensor due to contamination of the position detection mark, and to use a detection result without the reading error for sequence control.

According to a second aspect of the present invention, there is provided the image forming apparatus according to the first aspect, wherein a latent image carrier for forming a latent image of a decomposed image on a surface thereof and a plurality of latent image developing devices for developing the latent image using an internal developer. A developing device provided with a developing device, and an intermediate transfer member on which the developed separated images are sequentially superimposed and transferred and combined to form a combined image. It is characterized by using a member.

According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the plurality of holding members are holding rollers, and the position of the plurality of holding members is set at a position opposed to the position detection mark. A groove is formed so as not to contact the detection mark.

In the image forming apparatus according to the third aspect, since the groove is formed in the holding roller, the position detection mark does not contact the holding roller.
Dirt adhering to the holding roller does not transfer to the position detection mark, so that dirt on the position detection mark can be reduced.

According to a fourth aspect of the present invention, there is provided a belt-shaped member provided with at least one mark for position detection, a plurality of holding members for rotatably holding the belt-shaped member, and position detection of the belt-shaped member. A detection sensor for detecting a mark for use,
In the image forming apparatus that uses the detection result of the detection sensor for sequence control, at least one of the plurality of holding members is provided with a cleaning unit that cleans a portion that comes into contact with the position detection mark. It is assumed that.

In the image forming apparatus according to the fourth aspect, the cleaning means cleans a portion of the holding member that comes into contact with the position detection mark and removes dirt attached to the contact portion. It is possible to reduce contamination of the position detection mark without transferring to the position detection mark. Therefore, it is possible to prevent a reading error of the detection sensor due to contamination of the position detection mark, and to use a detection result without the reading error for sequence control.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, a latent image carrier for forming a latent image of a decomposed image on a surface thereof, and a plurality of developing units for developing the latent image by using an internal developer. A developing device provided with a developing device, and an intermediate transfer member on which the developed separated images are sequentially superimposed and transferred and combined to form a combined image. It is characterized by using a member.

In the image forming apparatus according to the second and fifth aspects, it is possible to prevent a reading error of the detection sensor, so that when the detection result is used for sequence control and the separated images are superimposed on the intermediate transfer member, It is possible to prevent a displacement due to a reading error of the detection sensor.

The invention of claim 6 is the invention of claims 1, 2, 3, 4
Alternatively, in the image forming apparatus according to the fifth aspect, at least one of the plurality of holding members is a holding member to which dirt easily adheres due to the influence of airflow inside the apparatus main body.

In the image forming apparatus according to the sixth aspect, a non-contact portion that does not contact the position detection mark is provided on a holding member to which dirt is likely to adhere due to an air current inside the apparatus main body, or the position detection mark is provided. Clean the parts that come in contact with As described above, by applying the present invention to a holding member to which dirt easily adheres, dirt on the position detection mark can be efficiently reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] An example of an embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter, referred to as "color copying machine") as an image forming apparatus will be described with reference to the drawings. It will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of the entire color copying machine according to this embodiment. FIG. 2 is a schematic configuration diagram of an image forming unit which is a main part of the color copying machine.

As shown in FIG. 1, the color copying machine according to the present embodiment has a color image reading unit 1 (hereinafter, referred to as a "color scanner"), an image forming unit 2, a paper feeding unit 3, and a control for driving and controlling these units. It is composed of parts. The color scanner 1 converts color image information of a document into, for example, red, green, and blue (hereinafter, “R”,
(“G” and “B”) for each color separation light, and is converted into an electric image signal. Then, based on the intensity levels of the R, G, and B color separation image signals obtained by the color scanner, a color conversion process is performed by an image processing unit (not shown).
Image data of black, cyan, magenta, and yellow (hereinafter, referred to as “Bk”, “C”, “M”, and “Y”, respectively) are obtained.

The image forming section 2 includes a photosensitive drum 100 as an image carrier, and a charger 20 as a charging unit.
0, a writing optical unit 220 as an exposure unit, a photosensitive member cleaning device 300 including a cleaning blade and a fur brush, a revolver developing unit 400 as a developing unit, an intermediate transfer unit 500, a secondary transfer unit 600, and a fixing roller pair 701. The fixing unit 700 is used. Photoconductor drum 10
Reference numeral 0 denotes a counterclockwise rotation as indicated by an arrow in the figure. Around the charging roller 200, the photoconductor cleaning device 300, the selected developing machine of the revolver developing unit 400, and the intermediate transfer of the intermediate transfer unit 500. An intermediate transfer belt 501 as a body is disposed. The writing optical unit 220 converts the color image data from the color scanner 1 into an optical signal, and applies a laser beam corresponding to the image of the document on the surface of the photosensitive drum 100 uniformly charged by the charger 200. Light is written by irradiating L to form an electrostatic latent image on the surface of the photosensitive drum 100. The writing optical unit 220 can be composed of, for example, a semiconductor laser as a light source, a laser emission drive control unit, a polygon mirror and its rotation motor, an f / θ lens, a reflection mirror, and the like.

The revolver developing unit 400 has a Bk
Bk developing machine 401 using toner, C using toner C
The image forming apparatus includes a developing device 402, an M developing device 403 using M toner, a Y developing device 404 using Y toner, and a developing revolver driving unit (not shown) for rotating the entire unit counterclockwise. Each of the developing machines 401 to 404 installed in the revolver developing unit 400 is a developing device as a developing material carrier which rotates by bringing a spike of the developing material into contact with the surface of the photosensitive drum 100 in order to develop an electrostatic latent image. It comprises a sleeve, a developer paddle that rotates to pump up and agitate the developer, and a developing sleeve drive unit that rotates the developing sleeve clockwise as indicated by the arrow. In this embodiment, the toner in each of the developing devices 401 to 404 is negatively charged by stirring with the ferrite carrier, and a negative DC voltage is applied to each developing sleeve by a developing bias power source (not shown) as a developing bias applying unit. Vdc (DC component) and AC voltage Vac (AC component)
Are applied, and each developing sleeve is biased to a predetermined voltage with respect to the metal base layer of the photosensitive drum 100.

In the standby state of the main body of the color copying machine, the revolver developing unit 400 is stopped at the home position where the Bk developing machine 401 is located at the developing position, and when the copy start key is pressed, the original starts reading image data. Then, based on the color image data, the optical writing by the laser beam L, that is, the formation of the electrostatic latent image starts (hereinafter, referred to as an electrostatic latent image)
The electrostatic latent image based on the Bk image data is called “Bk electrostatic latent image”. The same applies to C, M, and Y). In order to enable development from the front end of the Bk electrostatic latent image, before the front end of the electrostatic latent image reaches the Bk development position, rotation of the Bk developing sleeve is started to convert the Bk electrostatic latent image into Bk toner. Develop with. And
Thereafter, the developing operation of the Bk electrostatic latent image is continued. When the trailing end of the Bk electrostatic latent image passes the Bk developing position, the revolver developing unit is immediately moved until the developing machine of the next color comes to the developing position. 400 rotates. This is completed at least before the leading end of the electrostatic latent image based on the next image data reaches the developing position.

As shown in FIG. 2, the intermediate transfer unit 500 includes an intermediate transfer belt 501 which is an intermediate transfer member stretched over a plurality of rollers described later. Around the intermediate transfer belt 501, the secondary transfer unit 6
The secondary transfer belt 601, which is a transfer material carrier, and the secondary transfer bias roller 60, which is a secondary transfer charge applying means.
5. A belt cleaning blade 504 serving as an intermediate transfer body cleaning unit, a lubricant applying brush 505 serving as a lubricant applying unit, and the like are provided so as to face each other. The intermediate transfer belt 501 includes a primary transfer bias roller 507 as a primary transfer charge applying unit, a belt driving roller 5
08, a belt tension roller 509, a secondary transfer opposing roller 510, a cleaning opposing roller 511, and an earth roller 512. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. Also, the intermediate transfer belt 501
A mark 550 for position detection is provided on the inner peripheral surface of, and a detection sensor 514 is provided in an area where the mark 550 for position detection passes. As the detection sensor 514, for example, a reflection type optical sensor is used. Then, the image forming process is started at a certain timing from the detection of the position detection mark 550 by the detection sensor 514. Specifically, optical writing on the photoconductor is started.

The primary transfer bias roller 507 is supplied with a primary transfer power supply 801 controlled by a constant current or a constant voltage.
A transfer bias controlled at a predetermined current or voltage according to the number of superimposed toner images is applied. The intermediate transfer belt 501 is driven by a drive motor (not shown) in a direction indicated by an arrow.
8 is driven in the direction of the arrow. The intermediate transfer belt 501 is made of a semiconductor or an insulator and has a single-layer or multilayer structure. A transfer unit (hereinafter referred to as “1”) that transfers the toner image on the photosensitive drum 100 to the intermediate transfer belt 501
Primary transfer bias roller 50).
The nip portion having a predetermined width is formed between the photosensitive drum 100 and the intermediate transfer belt 501 by stretching the intermediate transfer belt 501 so that the intermediate transfer belt 501 is pressed against the photosensitive drum 100 by the ground roller 7 and the ground roller 512. . The lubricant application brush 505 is for polishing zinc stearate 506 as a lubricant formed in a plate shape, and applying the polished fine particles to the intermediate transfer belt 501. The lubricant application brush 505 is configured to be detachable from the intermediate transfer belt 501, and is provided at a predetermined timing.
01 is controlled.

The secondary transfer unit 600 includes a secondary transfer belt 601 stretched around three support rollers 602, 603, and 604, and a stretched portion between the support rollers 602 and 603 of the secondary transfer belt 601. Can be pressed against the secondary transfer facing roller 510. One of the three support rollers 602, 603, and 604 is a driving roller that is rotationally driven by a driving unit (not shown), and the driving roller drives the secondary transfer belt 601 in a direction indicated by an arrow in the drawing. The secondary transfer bias roller 605 is
A secondary transfer means, which is disposed so as to sandwich the intermediate transfer belt 501 and the secondary transfer belt 601 between the secondary transfer opposing roller 510 and a secondary transfer power source 8 controlled at a constant current.
02, a transfer bias of a predetermined current is applied. Further, the supporting roller 602 and the secondary transfer bias roller 605 are arranged such that the secondary transfer belt 601 and the secondary transfer bias roller 605 can take a position where the secondary transfer belt 601 is pressed against the secondary transfer opposing roller 510 and a position where the secondary transfer bias roller 605 is separated therefrom. Is provided in the direction of the arrow. The secondary transfer belt 601 and the support roller 602 at the separated position are shown by two-dot chain lines in FIG.

The registration roller pair 650 is a transfer material at a predetermined timing between the intermediate transfer belt 501 and the secondary transfer belt 601 sandwiched between the secondary transfer bias roller 605 and the secondary transfer opposing roller 510. The transfer paper P is sent.

The fixing roller pair 70 of the secondary transfer belt 601
A transfer sheet discharging charger 606 serving as a transfer material discharging unit and a belt discharging charger 607 serving as a transfer material carrier discharging unit are provided on a portion stretched around the first support roller 603.
Are opposed to each other. A cleaning blade 608, which is a transfer material carrier cleaning unit, is in contact with a portion of the secondary transfer belt 601 that is stretched around the lower support roller 604 in the drawing. Transfer paper static elimination charger 606
Is to remove the electric charge held in the transfer paper, thereby enabling the transfer paper to be satisfactorily separated from the secondary transfer belt 601 by the strength of the transfer paper itself. The belt static elimination charger 607 eliminates electric charges remaining on the secondary transfer belt 601. Further, the cleaning blade 608 is for removing the adhered matter adhered to the surface of the secondary transfer belt 601 for cleaning.

In the color copier thus constructed, when the image forming cycle is started, the photosensitive drum 1
Reference numeral 00 denotes a counterclockwise rotation indicated by an arrow by a drive motor (not shown), and the intermediate transfer belt 501 is rotated clockwise by an arrow by a belt driving roller 508. As the intermediate transfer belt 501 rotates, primary transfer is performed by a transfer bias by a voltage applied to the primary transfer bias roller 507 to form a Bk toner image, a C toner image, an M toner image, and a Y toner image. Then, a toner image is finally formed on the intermediate transfer belt 501 in the order of Bk, C, M, and Y.

For example, a Bk toner image is formed as follows. The charging charger 200 uniformly charges the surface of the photosensitive drum 100 to a predetermined potential with negative charges by corona discharge. Then, raster exposure using laser light is performed by a writing optical unit (not shown) based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the surface of the photosensitive drum 100 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a Bk electrostatic latent image is formed. The Bk developing device 401
Contact with the negatively charged Bk toner on the Bk developing roller, no toner adheres to the portion of the photosensitive drum 100 where the charge remains, and the toner does not Bk that attracts and is similar to an electrostatic latent image
A toner image is formed. The Bk toner image formed on the photosensitive drum 100 is transferred onto the surface of the intermediate transfer belt 501 that is driven at a constant speed in a state of contact with the photosensitive drum 100. Hereinafter, the transfer of the toner image from the photosensitive drum 100 to the intermediate transfer belt 501 is referred to as “belt transfer”.

A small amount of untransferred toner remaining on the surface of the photosensitive drum 100 after the belt transfer is cleaned by the photosensitive member cleaning device 300 in preparation for reuse of the photosensitive drum 100. Bk on the photosensitive drum 100 side
After the image forming process, the process proceeds to the C image forming process. At a predetermined timing, reading of the C image data by the color scanner starts, and by writing the laser light based on the C image data, the C electrostatic latent image is formed on the surface of the photosensitive drum 100. To form Then, after the rear end of the previous Bk electrostatic latent image has passed and before the front end of the C electrostatic latent image has reached, the rotating operation of the revolver developing unit 400 is performed, and the C developing device 402
Is set to the developing position, and the C electrostatic latent image is developed with the C toner.

Thereafter, the development of the C electrostatic latent image area is continued.
When the rear end of the C electrostatic latent image has passed, the revolver developing unit is rotated in the same manner as in the case of the Bk developing device 401, and the next M developing device 403 is moved to the developing position.
This is also completed before the leading end of the next M electrostatic latent image reaches the developing position. Regarding the M and Y image forming processes, the operations of reading the color image data, forming the electrostatic latent image, and developing are the same as those of the above-described Bk and C processes, and thus the description is omitted.

On the intermediate transfer belt 501, Bk, C, M, and Y toner images sequentially formed on the photosensitive drum 100 are sequentially transferred to the same surface while being aligned. As a result, a toner image in which a maximum of four colors are superimposed on the intermediate transfer belt 501 is formed. At the time when the image forming operation is started, the transfer paper P is fed from a paper supply unit such as a transfer paper cassette (not shown) or a manual feed tray, and stands by at the nip of the registration roller pair 650. When the leading end of the toner image on the intermediate transfer belt 501 approaches the secondary transfer portion where the nip is formed by the secondary transfer facing roller 510 and the secondary transfer bias roller, the transfer paper P
The registration roller pair 650 is driven such that the tip of the toner image coincides with the tip of the toner image, and registration of the transfer sheet P with the toner image is performed.

Then, the transfer paper P is transferred to the intermediate transfer belt 501.
The sheet passes through the secondary transfer portion while being superposed on the upper toner image. At this time, the four-color superimposed toner image on the intermediate transfer belt 501 is collectively transferred onto the transfer paper by the transfer bias by the voltage applied to the secondary transfer bias roller 605 by the secondary transfer power supply 802. Then, the secondary transfer belt 601
The transfer paper P is discharged when passing through a portion facing the transfer paper discharging charger 606 disposed on the downstream side of the secondary transfer portion in the moving direction of the transfer paper, and is separated from the secondary transfer belt 601 toward the fixing roller pair 701. Sent. The toner image is fused and fixed at the nip portion of the pair of fixing rollers 701, sent out of the apparatus body by a pair of discharge rollers (not shown), and stacked face-up on a copy tray (not shown) to obtain a full-color copy.

On the other hand, the photosensitive drum 1 after the belt transfer
The surface of No. 00 is cleaned by the photoconductor cleaning device 300 and is uniformly discharged by a discharge lamp (not shown). Further, the toner remaining on the surface of the intermediate transfer belt 501 after the transfer of the toner image onto the transfer paper P is cleaned by a belt cleaning blade 504 pressed against the intermediate transfer belt 501 by a separation / contact mechanism (not shown). Here, at the time of repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 100 are performed at a predetermined timing following the image formation process of the fourth sheet (Y) of the first sheet. Proceed to the image forming step (Bk). Further, the intermediate transfer belt 501 transfers the second sheet of Bk toner to the area of the surface cleaned by the belt cleaning blade 504 following the batch transfer step of the first sheet of four-color superimposed toner image onto transfer paper. The image is transferred to the belt. Thereafter, the operation is the same as that of the first sheet.

The above is the copy mode for obtaining a four-color full-color copy. In the three-color copy mode and the two-color copy mode, the same operation as described above is performed for the designated color and the number of times. Become. In the case of the single-color copy mode, only the developing machine of the predetermined color of the revolver developing unit 400 is in the developing operation state until the predetermined number of sheets is completed, and the belt cleaning blade 504 is pressed against the intermediate transfer belt 501. The copy operation is performed with the position as it is.

Next, the features of this embodiment will be described. FIG. 3 is a side view of the vicinity of the intermediate transfer belt 501, showing a flow of an air flow inside the apparatus. An airflow as shown by an arrow A in the figure is generated inside the color copier. When toner or lubricant scatters from the cleaning blade 504 or the lubricant application brush 505,
Under the influence of this air flow, the surface of the holding roller 507 was particularly soiled. Stain was the worst on the end of the surface of the holding roller 507 in the axial direction, in other words, the mark contact portion was the worst. If the holding roller 507 is soiled, as described above, the stain is transferred to the position detection mark 550, and a reading error by the detection sensor 514 may occur. Since the image forming process, specifically, the optical writing starts at a certain timing based on the detection result of the detection sensor 514, there is a possibility that a position shift of the superimposed toner image occurs on the intermediate transfer belt 501. Therefore, in the color copying machine according to the present embodiment, the holding roller 507 which is the most contaminated in the arrangement due to the influence of the air flow is marked with the position detection mark 550.
It was configured so as not to contact with.

FIG. 4A is a perspective view of the holding roller 507 and the intermediate transfer belt 501 provided with the mark 550 for position detection. FIG. 4B is a diagram viewed from the direction of arrow B in FIG. 4A. The holding roller 507 is configured such that the length in the axial direction in contact with the intermediate transfer belt 501 is shorter than the normal length, so that the outer peripheral surface does not contact the position detection mark 550. With such a configuration, since the position detection mark 550 does not contact the holding roller 507, dirt such as toner adhered to the surface of the holding roller 507 does not transfer to the position detection mark 550, and the position detection mark 550 does not. Contamination can be reduced.
By reducing the dirt on the position detection mark 550, it is possible to prevent a reading error of the detection sensor 514 due to the dirt. Thereby, the intermediate transfer belt 501
When the respective colors are superimposed on each other, it is possible to prevent a displacement caused by a reading error of the detection sensor 514, and it is possible to form a high-quality image.

Here, if the holding roller 507 is configured so as not to come into contact with the position detection mark 550, FIG.
Since the left end of the holding roller 507 does not come into contact with the non-stop guide 501a as shown in FIG.
There is a possibility that deviation of 1 may occur. In this case, another means for preventing the deviation of the intermediate transfer belt 501 may be provided. For example, it is conceivable to provide a deviation preventing member 520 to guide the right end of the intermediate transfer belt 501 in the drawing to prevent deviation.

In this embodiment, the holding roller 507, which is the most contaminated in the arrangement due to the influence of the air flow, is configured not to contact the position detection mark 550, but other holding members for holding the intermediate transfer belt 501 are used. The roller may not be in contact with the position detection mark 550. Thus, the contamination of the position detection mark 550 can be further reduced.

Although the present embodiment has been described with reference to an example in which the position detection mark provided on the intermediate transfer belt is reduced in dirt to prevent a reading error of the detection sensor, the present invention is not limited to the intermediate transfer belt. The present invention can be applied to any belt-shaped member having a position detection mark.

[Modification 1] In the first embodiment,
The outer peripheral surface of the holding roller 507 is positioned at the position detecting mark 5.
The length in the axial direction was configured to be short so as not to contact with 50. However, a groove may be formed on the surface of the holding roller 507 so as not to contact the position detection mark.

FIG. 5A is a perspective view of a holding roller 507 and an intermediate transfer belt 501 having a position detection mark 550 according to the present modification. Further, FIG.
It is the figure seen from the arrow C direction in (a). Holding roller 5
Numeral 07 has a groove 507a formed on the outer peripheral surface at a position opposed to the position detection mark 550, which is deeper than the thickness of the position detection mark 550 and wider than the width of the position detection mark 550. When the intermediate transfer belt 501 rotates and the position detection mark 550 passes through the holding roller 507, the position detection mark 550 and the groove 5
07a, the position detection mark 5
There is no contact between the roller 50 and the holding roller 507. Therefore, the dirt attached to the holding roller 507 does not transfer to the position detection mark 550, and the dirt on the position detection mark 550 can be reduced.

FIG. 6 shows a holding roller 507 according to this modification.
It is an example figure which shows the more specific structure of FIG. Approximately 10mm in length and 0.1mm in depth from the roller end about 1mm
A groove of 3 mm or more is formed. Groove processing may be performed on the outer peripheral surface of a conventionally used holding roller, so that an increase in manufacturing cost can be suppressed. The roller end on the side where the groove is formed is an intermediate transfer belt 501.
Of the intermediate transfer belt 5
01 can be prevented.

[Second Embodiment] In the first embodiment and the first modification, the position detecting mark 550 is not stained by preventing the position of the holding roller 507 from coming into contact with the position detecting mark 550. It is also possible to provide a cleaning means for cleaning the position detection mark 550 so as not to stain the position detection mark 550. FIG. 7A shows the holding roller 5.
FIG. 7 is a perspective view of a cleaning brush 560 and an intermediate transfer belt 501. FIG. 8 shows an intermediate transfer belt 501.
It is a side view of the vicinity.

As shown in FIG. 7A, the holding roller 50
7 is a brush 5
Clean by 60. Thus, the dirt attached to the contact portion can be removed, and the dirt on the position detection mark 550 can be reduced. In the example shown in FIGS. 7A and 8, only the holding roller 507 is cleaned with the brush 560. However, all other holding rollers holding the intermediate transfer belt 501 are provided with the brush 560 for position detection. By cleaning the portion that comes into contact with the mark 550, the position detection mark 550 can be almost completely prevented from being stained. Further, the same effect can be obtained by a configuration in which cleaning is performed by a sponge member 570 as shown in FIG. 7B instead of the brush 560.

[0046]

According to the first to sixth aspects of the present invention, it is possible to prevent a reading error of the detection sensor due to contamination of the position detection mark from being used for sequence control. Becomes This allows
There is an excellent effect that accurate sequence control can be performed, and a high-quality image can be formed by preventing positional deviation of a formed image.

In particular, according to the third aspect of the present invention, the groove is formed in the holding roller, so that the holding roller does not contact the position detection mark, thereby reducing the contamination of the position detection mark. There is an excellent effect that you can.
Further, since the holding roller which has been conventionally used can be manufactured by performing groove processing, there is also an excellent effect that an increase in manufacturing cost can be suppressed.

In particular, according to the present invention, even if dirt adheres to the holding member, the dirt can be removed by the cleaning means, so that dirt on the position detecting mark can be reduced. Has an effect.

In particular, according to the second and fifth aspects of the present invention, the detection result of the detection sensor is used for sequence control, and the decomposed image can be accurately superimposed on the intermediate transfer member without positional deviation. There is an excellent effect that a high quality image can be formed.

In particular, according to the invention of claim 6, a non-contact portion which does not come into contact with the position detecting mark is provided on a holding member to which dirt is likely to adhere due to an air current inside the apparatus main body, or By cleaning the portion that comes into contact with the mark, it is possible to reduce the contamination of the position detection mark. Thereby, it is possible to effectively prevent the reading error of the detection sensor at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine showing an example of an image forming apparatus according to an embodiment.

FIG. 2 is an enlarged view of a primary transfer unit of the color copying machine.

FIG. 3 is a diagram showing the flow of airflow in a color copying machine.

FIG. 4A illustrates a holding roller 507 and an intermediate transfer belt 5;
FIG. (B) is the figure seen from arrow B direction in figure (a).

FIG. 5A is a perspective view of a holding roller 507 and an intermediate transfer belt 501 according to a modification. (B) is the figure seen from arrow C direction in figure (a).

FIG. 6 is a more specific view of a groove of a holding roller 507 according to a modification.

FIG. 7A illustrates a holding roller 507 according to another embodiment.
The perspective view which shows the state which is cleaning the brush 560 with.
(B) is a perspective view of a sponge as a cleaning member.

FIG. 8 is a side view near the intermediate transfer belt.

FIG. 9A is a perspective view showing a state in which a detection sensor detects a position detection mark provided on the inner peripheral surface of the intermediate transfer belt. (B) The figure which shows the detection sensor output when the position detection mark is not dirty. FIG. 3C is a diagram illustrating a detection sensor output when the position detection mark is dirty.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 photoconductor drum 200 charging charger 300 photoconductor cleaning device 400 revolver developing unit 500 intermediate transfer unit 501 intermediate transfer belt 501a detent guide 507 holding roller (primary transfer bias roller) 508 holding roller (belt drive roller) 514 detection sensor 550 Position detection mark 560 Cleaning brush 570 Cleaning sponge 600 Secondary transfer unit 601 Secondary transfer belt 602 to 604 Support roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akinori Kobayashi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Emi Kitagawa 1-3-6 Nakamagome, Ota-ku, Tokyo Share Company Ricoh F-term (reference) 2H032 AA05 AA15 BA05 BA09 BA23 BA30 CA13 CA14

Claims (6)

[Claims] 1. A belt-shaped member provided with at least one mark for position detection, a plurality of holding members for rotatably holding the belt-shaped member, and detecting a mark for position detection of the belt-shaped member. An image forming apparatus having a detection sensor and using a detection result of the detection sensor for sequence control;
At least one holding member of the plurality of holding members,
An image forming apparatus comprising a non-contact portion that does not contact the position detection mark. 2. The image forming apparatus according to claim 1, further comprising: a latent image carrier for forming a latent image of a decomposed image on a surface thereof; and a plurality of developing devices for developing the latent image using an internal developer. The developing device and the developed decomposed image are sequentially superimposed and transferred.
An image forming apparatus, comprising: an intermediate transfer member on which a composite image is formed by being combined, wherein the belt-shaped member is used as the intermediate transfer member. 3. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the plurality of holding members are holding rollers, and a groove is formed in a portion of the holding roller facing the position detection mark so as not to contact the position detection mark. 4. A belt-like member provided with at least one mark for position detection, a plurality of holding members for rotatably holding the belt-like member, and detecting a mark for position detection of the belt-like member. An image forming apparatus having a detection sensor and using a detection result of the detection sensor for sequence control;
At least one holding member of the plurality of holding members,
An image forming apparatus comprising: a cleaning unit that cleans a portion that comes into contact with the position detection mark. 5. The image forming apparatus according to claim 4, further comprising a latent image carrier for forming a latent image of a decomposed image on the surface, and a plurality of developing devices for developing the latent image using an internal developer. The developing device and the developed decomposed image are sequentially superimposed and transferred.
An image forming apparatus, comprising: an intermediate transfer member on which a composite image is formed by being combined, wherein the belt-shaped member is used as the intermediate transfer member. 6. The image forming apparatus according to claim 1, wherein at least one of the plurality of holding members is apt to adhere to dirt due to an air flow inside the apparatus main body. An image forming apparatus, which is a member.