JP2002214940A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of preventing irregulari ties from occurring in an image formed on an image carrier by the vibration of the image carrier in its moving direction when a contacting member such as a transfer member and a cleaning member comes into contact with the surface of the image carrier. SOLUTION: A speed reducing means consisting of a cam device reducing the displacement amount of the follower piece 620b of a supporting body 620 per the rotational angle of an eccentric cam 630 just before a secondary transfer bias roller 605 comes into contact with the surface of an intermediate transfer belt 501 is provided for the contacting/separating mechanism of the roller 605. Thus, the roller 605 comes into contact with the surface of the belt 501 while gently moving. Then, the vibration of the belt 501 in its moving direction at such contacting time is hardly caused and the irregularities in the image on the belt 501 caused by the vibration of an intermediate transfer unit 500 are eliminated.

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 facsimile, and a printer.
An image forming apparatus includes a transfer unit that comes into contact with and separates from the surface of the image carrier, and a contact / separation member such as a cleaning member.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this type, an image carrier such as a photosensitive drum, a photosensitive belt, or an intermediate transfer belt is used, and a toner image formed on the image carrier is transferred. There is known an image forming apparatus which transfers an image to a transfer material such as a sheet or an OHP sheet by means to form an image. Further, after the toner image formed on the image carrier is transferred to the transfer material, the image forming apparatus removes the residual toner remaining on the image carrier without being transferred to the transfer material by a cleaning unit. Configured to remove.

For example, in an "image forming apparatus" disclosed in JP-A-11-231667, a toner image formed on the photosensitive drum is transferred by a primary transfer bias roller which is a primary transfer member of the transfer means. The primary transfer is performed on the intermediate transfer belt. Then, the toner image primarily transferred onto the intermediate transfer belt is secondarily transferred onto the transfer material by a secondary transfer bias roller which is a secondary transfer member. Further, the residual toner on the photosensitive drum and the intermediate transfer belt is removed by using a photosensitive member cleaning blade and a belt cleaning blade which are cleaning members of the cleaning unit.

Incidentally, the transfer member and the cleaning member are usually configured so as to be able to freely contact and separate from the surface of the image carrier by a contact and separation means. This prevents the transfer member and the cleaning member from being deformed over time due to constant contact with the surface of the image carrier, and prevents contact with the toner image on the image carrier when continuous image formation is performed. That's why.

In particular, in an image forming apparatus of an intermediate transfer system in which toner images of a plurality of colors, which are primary-transferred and superposed sequentially on the intermediate transfer belt, are collectively transferred by the secondary transfer bias roller, two or more color images are formed. At the time of image formation, the intermediate transfer belt must be in contact with and separated from the belt cleaning blade and the secondary transfer bias roller.

A plurality of photosensitive drums are arranged along the transfer material conveying path, and toner images of respective colors formed on the respective photosensitive drums are transferred by respective transfer members corresponding to the respective photosensitive drums. In a tandem-type image forming apparatus that sequentially superimposes and transfers images onto a transfer material, it is necessary to contact and separate each photosensitive drum and each transfer member when forming a monochrome image or a monochromatic image.

[0007]

However, as described above, in an image forming apparatus in which a contacting / separating member such as a transfer member or a cleaning member comes in contact with or separates from the surface of the image carrier, the image forming apparatus is moving. When the contact member comes into contact with the surface of the image carrier, the image carrier may momentarily vibrate in the moving direction. This is thought to be due to the fact that the contact between the surface of the image carrier and the contact / separation member applies a force (inertial force, frictional force, etc.) in a direction that prevents the image carrier from moving. Can be

Further, according to an experiment conducted by the present inventors,
It has been clarified that the greater the angular velocity at which the contact / separation member approaches / separates from the surface of the image carrier, the greater the vibration in the moving direction of the image carrier. This is because, when the angular velocity at which the contact / separation member approaches / separates increases, the impact at the time of contact between the contact member and the image carrier increases, and the force in the direction for preventing the movement of the image carrier also increases. It is thought to be due to this.

In particular, like the above-mentioned intermediate transfer belt,
When the image carrier is formed of a belt-shaped member, a moving direction of the image carrier formed of the belt-shaped member (hereinafter, referred to as an “image carrier belt”) when the image carrier is in contact with the contact member. Vibration becomes remarkable. That is, this kind of belt-like member has some slack even in a stretched state. For this reason, when the contact member comes into contact with the image carrier belt, a belt portion on the downstream side in the movement direction from the contact portion of the image carrier belt with the contact member is suddenly tensioned. As a result, the advance of the belt portion on the upstream side in the movement direction of the contact portion of the image carrier belt is temporarily stopped. The tension and the stop of the movement of the image carrier belt are repeated until the moving speed of the image carrier belt at the contact portion is stabilized. As a result,
Vibration in the moving direction of the image carrier belt in contact with the contact member is larger than that of a drum-shaped image carrier having relatively high rigidity.

For this reason, in the conventional image forming apparatus of this type, the image forming member is formed on the image carrier by the vibration in the moving direction of the image carrier generated when the contact member comes into contact with the image carrier. In some cases, the image was distorted.
For example, an A4 size image is placed on the surface of the image carrier 2
In an image forming apparatus configured to form a surface,
Usually, in order to reduce the size of the image carrier, the space of the non-image area between the previous image forming area and the next image forming area on the surface of the image carrier is set as small as possible. .
Therefore, in such an image forming apparatus, the contact member such as the transfer member or the cleaning member comes into contact with the surface of the image carrier, and the toner image of the previous image on the image carrier is transferred to the transfer material. In the state where the transfer and the removal of the residual toner have been started, an image of a part (generally, a rear end) of the next image is formed on the surface of the image carrier. Therefore, when the transfer member or the cleaning member comes into contact with the surface of the image carrier and the image carrier vibrates in the moving direction as described above, the vibration causes the next image on the image carrier to move. Is disturbed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an image carrier having a contact member such as a transfer member and a cleaning member which comes into contact with the surface of the image carrier. It is an object of the present invention to provide an image forming apparatus capable of preventing an image formed on the image carrier from being disturbed by vibration in a moving direction of the image forming apparatus.

[0012]

In order to achieve the above object, the present invention is directed to an image carrier that carries a toner image formed on a surface thereof and moves, and a method for moving the image carrier relative to the surface of the image carrier. Transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material by a transfer member which is a contact member that comes into contact with and separates from the image carrier; An image forming apparatus having a contacting / separating unit for displacing a member, wherein the contacting / separating unit sets a displacement speed of the transfer member when displacing in a direction in which the transfer member comes into contact with the surface of the image carrier; Has deceleration means for decelerating just before contacting the surface of the image carrier.

In this image forming apparatus, the transfer member is displaced by the contact / separation means in a direction in which the transfer member contacts / separates from the surface of the image carrier. The displacement speed of the transfer member when the transfer member is displaced in the direction in which the transfer member comes into contact with the surface of the image carrier is reduced by the deceleration means at least immediately before the transfer member comes into contact with the surface of the image carrier. You. As a result, the transfer member comes into contact with the surface of the image carrier while being gently displaced, and vibrations in the moving direction of the image carrier during this contact are less likely to occur. Therefore, in this image forming apparatus, the disturbance of the image on the image carrier due to the vibration in the moving direction of the image carrier is eliminated.

According to a second aspect of the present invention, there is provided an image carrier which carries a toner image formed on a surface thereof and moves, and a transfer means for transferring the toner image formed on the surface of the image carrier to a transfer material. Contacting a cleaning member, which is a contact / separation member that comes into contact with / separates from the surface of the image carrier, with the surface of the image carrier after the toner image has been transferred onto the transfer material by the transfer means; An image forming apparatus comprising: a cleaning unit that removes residual toner remaining on a surface of the image forming unit; and a contacting / separating unit that displaces the cleaning member in a direction toward and away from the surface of the image carrier. Has deceleration means for reducing the displacement speed of the cleaning member when displacing in the direction in which it contacts the surface of the image carrier, at least immediately before the transfer member contacts the surface of the image carrier. You are The one in which the features.

In this image forming apparatus, the cleaning member is displaced by the contacting / separating means in a direction to contact / separate from the surface of the image carrier. The displacement speed of the cleaning member when the cleaning member is displaced in a direction in which the cleaning member contacts the surface of the image carrier is reduced by the deceleration means at least immediately before the cleaning member contacts the surface of the image carrier. You. As a result, the cleaning member comes into contact with the surface of the image carrier while being gently displaced, and vibration in the moving direction of the image carrier at the time of this contact is less likely to occur. Therefore, in this image forming apparatus, the disturbance of the image on the image carrier due to the vibration in the moving direction of the image carrier is eliminated.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image carrier is constituted by an endless belt which is stretched and moved by a plurality of stretch rollers. It is assumed that.

When the image carrier is constituted by an endless belt, when the contact member such as the transfer member or the cleaning member contacts the surface of the image carrier, as described above, The tension and stop of the movement of the endless belt are repeated until the moving speed of the endless belt at the contact portion is stabilized. Therefore, in this case, the vibration of the endless belt in the moving direction at the time of contact with the contact member becomes larger than that of the drum-shaped image carrier having relatively high rigidity. In the image forming apparatus of the present invention, the speed is reduced by the speed reduction unit at least immediately before the contact member comes into contact with the surface of the endless belt. Accordingly, the contact member comes into contact with the surface of the endless belt while being gently displaced, and the degree of tension of the endless belt at the time of this contact is reduced. Accordingly, the moving speed of the endless belt at the contact portion with the contact member becomes relatively fast and stable, and the vibration in the moving direction of the endless belt at the time of contact with the contact member is reduced.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second or third aspect, the image carrier is formed by a primary transfer means from the latent image carrier on which the toner image is formed. After the image is primarily transferred, the toner image is an intermediate transfer member that is secondarily transferred to the transfer material by a secondary transfer unit.

In this image forming apparatus, a plurality of color toner images are superimposed on the intermediate transfer member and primary-transferred, and then the superposed plural color toner images are transferred to the transfer material by the secondary transfer means. By performing the secondary transfer, a color image can be formed on the transfer material. In forming such a color image, if the intermediate transfer body vibrates when the secondary transfer means contacts the intermediate transfer body, the vibration causes the next transfer to be performed on the intermediate transfer body. The image is distorted. Such image disturbance during the formation of a color image causes a color shift of the image that is secondarily transferred onto the transfer material. In the image forming apparatus of the present invention, since the vibration of the intermediate transfer member can be reduced, a color image without color shift can be formed.

Further, the invention of claim 5 is based on claims 1, 2,
In the image forming apparatus of (3) or (4), the contacting / separating means includes: a support for supporting the contacting / separating member so as to be movable toward and away from the surface of the image carrier; A cam for displacing in the separating and moving direction, wherein the deceleration means reduces the displacement of the support per rotation angle of the cam at least immediately before the contacting / separating member contacts the surface of the image carrier. And a cam device that performs the operation.

In this image forming apparatus, the transfer member and the cleaning member, which are the contacting / separating members, are moved by the cam to displace the supporting member in the contact / separating direction of the contacting / separating member. Is displaced in a direction approaching / separating from the surface. At this time, the displacement speed of the contact / separation member when displacing in the direction of contact with the surface of the image carrier is such that at least the contact / separation member is brought into contact with the surface of the image carrier by the cam device of the reduction means. Slow down just before contact.
As a result, the contacting / separating member comes into contact with the surface of the image carrier while being gently displaced, and vibration in the moving direction of the image carrier during this contact is less likely to occur. Therefore, in this image forming apparatus, the disturbance of the image on the image carrier due to the vibration in the moving direction of the image carrier is eliminated.

Further, the invention of claim 6 is the invention of claims 1, 2,
In the image forming apparatus of (3) or (4), the contacting / separating means includes: a support for supporting the contacting / separating member so as to be movable toward and away from the surface of the image carrier; And a support moving member that moves in the separating and moving direction, wherein the deceleration means is configured to move the support against the moving force of the support when the contact and separation member comes into contact with the surface of the image carrier. It is characterized by comprising a buffer member for reducing the speed of displacement.

In this image forming apparatus, the transfer member and the cleaning member, which are the contact and separation members, are displaced by the support moving member in the contact and separation direction of the contact and separation member. It is displaced in the direction of coming and going with respect to the surface of the image carrier. At this time, the displacement speed of the contact / separation member when displacing in the direction in which it contacts the surface of the image carrier is such that at least the contact / separation member is at a surface of the image carrier by the buffer member of the speed reduction means. Slow down just before contact. As a result, the contacting / separating member comes into contact with the surface of the image carrier while being gently displaced, and vibration in the moving direction of the image carrier during this contact is less likely to occur. Therefore, in this image forming apparatus, the disturbance of the image on the image carrier due to the vibration in the moving direction of the image carrier is eliminated.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an electrophotographic color copying machine (hereinafter, referred to as a color copying machine) as an image forming apparatus will be described. First, the schematic configuration and operation of the color copying machine according to the present embodiment will be described with reference to FIG. This color copier includes a color image reading device (hereinafter, referred to as a color scanner) 1,
Color image recording device (hereinafter referred to as color printer)
2, a paper feed bank 3 and the like.

The color scanner 1 converts the image of the original 4 on the contact glass 121 into an illumination lamp 122, mirror groups 123a, 123b, 123c, and a lens 124.
And form an image on the color sensor 125 via. Then, the color image information of the document 4 is stored in, for example, Red, Green.
The image data is read for each of n, Blue (hereinafter, R, G, B) color separation lights and converted into an electric image signal. The color sensor 125 of this example is composed of R, G, and B color separation means and a photoelectric conversion element such as a CCD, and photoelectrically converts a three-color image of the document 4 separated by the color separation means. Reading by the element at the same time. Then, based on the intensity levels of the R, G, B color separation image signals obtained by the color scanner 1, a color conversion process is performed by an image processing unit (not shown), and Black (hereinafter, referred to as Bk), Cyan
(Hereinafter, referred to as C), Magenta (hereinafter, referred to as M), and Yellow (hereinafter, referred to as Y) color image data are obtained.

The operation of the color scanner 1 for obtaining the color image data of Bk, C, M and Y is as follows. Upon receiving a scanner start signal that is timed with the operation of the color printer 2 described later, an optical system including an illumination lamp 122 and mirror groups 123a, 123b, 123c scans the document 4 in the left direction of the arrow, and performs once. To obtain four color image data. This is stored in a memory (not shown) and pulled out, thereby sequentially obtaining four color image data. Then, each time the color printer 2 sequentially visualizes and superimposes the images to form a final four-color full-color image.

The color printer 2 includes a photosensitive drum 200 as an image carrier, a writing optical unit 220,
Revolver developing unit 230, intermediate transfer unit 50
0, a secondary transfer unit 600, a fixing device 270, and the like. The photosensitive drum 200 rotates in the counterclockwise direction indicated by an arrow, and the photosensitive drum cleaning device 2 surrounds the photosensitive drum 200.
01, static elimination lamp 202, charger 203, potential sensor 2
04, a selected developing unit of the revolver developing unit 230, a developing density pattern detector 205, an intermediate transfer unit 500, a secondary transfer unit 600, and the like.

The writing optical unit 220
Converts the color image data from the color scanner 1 into an optical signal, performs optical writing corresponding to the image of the document 4, and forms an electrostatic latent image on the photosensitive drum 200. The writing optical unit 220 includes a semiconductor laser 221 as a light source, a laser emission drive control unit (not shown), a polygon mirror 222 and a rotation motor 223, an f / θ lens 224, a reflection mirror 225, and the like.

The revolver developing unit 230
Is composed of a Bk developing unit 231K, a C developing unit 231C, an M developing unit 231M, a Y developing unit 231Y, and a revolver rotation drive unit which rotates each developing unit in a counterclockwise direction indicated by an arrow. A developing bias in which an AC voltage Vac is superimposed on a negative DC voltage Vdc is applied to each developing sleeve by a developing bias power supply (not shown), and the developing sleeve is set at a predetermined potential with respect to the metal base layer of the photosensitive drum 200. Biased.

When the copying machine main body is in a standby state, the revolver developing unit 230 moves the Bk developing unit 231K to the developing position 30K.
When the copy operation is started, reading of the Bk color image data is started from the color scanner 1 at a predetermined timing. Image formation starts (hereinafter, an electrostatic latent image based on Bk image data is converted to Bk image data).
It is called a latent image. The same applies to C, M, and Y). Before the front end of the electrostatic latent image reaches the Bk developing position, the Bk developing unit 231K is moved to the developing position and the rotation of the Bk developing sleeve is started before the front end of the electrostatic latent image reaches the Bk developing position so that development can be performed from the front end of the Bk electrostatic latent image. And B
The k electrostatic latent image is developed with Bk toner. And after that Bk
The developing operation of the electrostatic latent image area is continued, but when the trailing end of the electrostatic latent image passes the Bk developing position, the revolver developing unit 230 is immediately moved until the developing device for the next color comes to the developing position.
Rotates. This is completed at least before the leading end of the electrostatic latent image based on the next image data arrives.

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. Around the intermediate transfer belt 501, the second transfer unit 600
Secondary transfer bias roller 60 as 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 member of a lubricant applying unit, and the like are disposed so as to face each other.

A position detecting mark is provided on the outer peripheral surface or the inner peripheral surface of the intermediate transfer belt 501. However, on the outer peripheral surface side of the intermediate transfer belt 501, it is necessary to devise a method of providing a position detection mark so as to avoid the pass area of the belt cleaning blade 504, and it may be difficult to arrange the mark. A position detection mark is provided on the inner peripheral surface side of the intermediate transfer belt 501. An optical sensor 514 as a mark detecting sensor is provided with an intermediate transfer belt 501.
Are provided between the primary transfer bias roller 507 and the drive roller 508, which are bridged.

The intermediate transfer belt 501 includes a primary transfer bias applying roller 507, a belt driving roller 508, a belt tension roller 509, and a primary transfer charge applying means.
Secondary transfer opposed roller 510, cleaning opposed roller 5
11 and a feedback current detection roller 512. Each roller is formed of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. A transfer bias controlled to a predetermined magnitude of current or voltage in accordance with the number of superimposed toner images is applied to the primary transfer bias roller 507 by a primary transfer power supply 801 controlled by a constant current or a constant voltage. ing.

The intermediate transfer belt 501 is driven in the direction of the arrow by a belt drive roller 508 that is driven to rotate in the direction of the arrow by a drive motor (not shown). The intermediate transfer belt 501 is made of a semiconductor or an insulator and has a single-layer or multilayer structure. Further, the intermediate transfer belt is set to be larger than the maximum paper-passable size in order to overlap the toner images formed on the photosensitive drum 200.

A secondary transfer bias roller 605, which is a secondary transfer unit, has a contact / separation mechanism as a contact / separation unit, which will be described later, with respect to the surface of the intermediate transfer belt 501 at a portion stretched by the secondary transfer opposed roller 510. , So as to be able to come and go. The secondary transfer bias roller 605 is a part of the intermediate transfer belt 50 that is stretched around the secondary transfer facing roller 510.
1 is provided so as to sandwich the recording paper P therebetween.
A transfer bias of a predetermined current is applied by a secondary transfer power supply 802 controlled by a constant current.

The registration roller 610 feeds the transfer paper P as a transfer material at a predetermined timing between the secondary transfer bias roller 605 and the intermediate transfer belt 501 stretched over the secondary transfer opposing roller 510. A cleaning blade 608, which is a cleaning unit, is in contact with the secondary transfer bias roller 605. The cleaning blade 608 is for removing the adhered matter attached to the surface of the secondary transfer bias roller 605 for cleaning.

In the color copying machine having such a configuration,
When the image forming cycle is started, the photosensitive drum 200
Is rotated in a counterclockwise direction indicated by an arrow by a drive motor (not shown), and Bk toner image formation, C toner image formation, M toner image formation, and Y toner image formation are performed on the photosensitive drum 200. The intermediate transfer belt 501 is rotated clockwise by an arrow by a belt driving roller 508.
The Bk toner image, the C toner image, the M toner image, and the Y toner are transferred by a transfer bias caused by a voltage applied to the primary transfer bias roller 507 with the rotation of the intermediate transfer belt 501.
The primary transfer of the toner image is performed, and finally Bk, C, M,
The toner images are formed on the intermediate transfer belt 501 in the order of Y so as to overlap each other.

For example, the formation of the Bk toner image is performed as follows. In FIG. 2, the charging charger 203 includes:
The surface of the photosensitive drum 200 is uniformly charged to a predetermined potential with a negative charge by corona discharge. The timing is determined based on the belt mark detection signal, and a writing optical unit (not shown) performs raster exposure using laser light based on the Bk color image signal. When this raster image is exposed, in the exposed portion of the surface of the photosensitive drum 200 that is initially uniformly charged, the charge proportional to the amount of exposure light disappears, and a Bk electrostatic latent image is formed. In this Bk electrostatic latent image,
The negatively charged Bk on the developing roller of the Bk developing device 231K
Due to the contact of the toner, the toner does not adhere to the portion of the photosensitive drum 200 where the charge remains, and the toner is attracted to the portion having no charge, that is, the exposed portion, and Bk similar to the electrostatic latent image is obtained. A toner image is formed.

The Bk toner image formed on the photosensitive drum 200 in this manner is primarily transferred onto the surface of the intermediate transfer belt 501 which is rotating at a constant speed while being in contact with the photosensitive drum 200. The photosensitive drum 20 after this primary transfer
A small amount of untransferred residual toner remaining on the surface of
The photoconductor drum 200 is cleaned by the photoconductor cleaning device 201 in preparation for reuse. This photosensitive drum 200
On the side, the process proceeds to the Y image forming process after the Bk image forming process, and the reading of the Y image data by the color scanner starts at a predetermined timing.
An electrostatic latent image is formed.

After the trailing end of the previous Bk electrostatic latent image has passed and before the leading end of the T electrostatic latent image has arrived, the rotating operation of the revolver developing unit 230 is performed, and the Y developing device 231Y is set at the development position, and the Y electrostatic latent image is developed with the Y toner. Thereafter, the development of the Y electrostatic latent image area is continued, but when the rear end of the Y electrostatic latent image passes, the revolver developing unit rotates as in the case of the Bk developing machine 231K, and the next operation is performed. Is moved to the developing position. This is also completed before the leading end of the next C electrostatic latent image reaches the developing position. In the image forming processes of C and M, the operations of reading the color image data, forming the electrostatic latent image, and developing are the same as those in the processes of Bk and Y described above, and thus the description is omitted.

The toner images of Bk, Y, C, and M sequentially formed on the photosensitive drum 200 in this manner are sequentially aligned on the same surface of the intermediate transfer belt 501 and primary-transferred. As a result, a toner image in which a maximum of four colors are superimposed on the intermediate transfer belt 501 is formed. on the other hand,
At the time when the image forming operation is started, the transfer paper P is fed from a paper feed unit such as a transfer paper cassette or a manual feed tray, and stands by at the nip of the registration roller 610.

The leading end of the toner image on the intermediate transfer belt 501 is applied to a secondary transfer portion where a nip is formed by the intermediate transfer belt 501 stretched around the secondary transfer opposing roller 510 and the secondary transfer bias roller 605. When the transfer paper P is moved, the registration roller 610 is driven so that the leading end of the transfer paper P coincides with the leading end of the toner image.
And the toner image are registered.

As described above, when the transfer paper P passes through the secondary transfer section, four colors on the intermediate transfer belt 501 are generated by the transfer bias by the voltage applied to the secondary transfer bias roller 605 by the secondary transfer power supply 802. The superimposed toner image is collectively transferred (secondarily transferred) onto the transfer paper P. The transfer paper P is neutralized by passing through a portion facing a transfer paper neutralization charger 606 disposed on the downstream side of the secondary transfer unit.
0 (see FIG. 1). Then, the transfer paper P is melted and fixed at the nip portion between the fixing rollers 271 and 272 of the fixing device 270,
The paper is sent out of the apparatus main body 2 and is stacked face up on a copy tray (not shown).

On the other hand, the photosensitive drum 2 after the belt transfer
The surface of the cleaning member 201 is cleaned by the photoconductor cleaning device 201, and is uniformly discharged by the discharging lamp 202. Further, the residual toner remaining on the surface of the intermediate transfer belt 501 after the secondary transfer of the toner image onto the transfer paper P is cleaned by the belt cleaning blade 504. The belt cleaning blade 504 is configured to be brought into and out of contact with the surface of the intermediate transfer belt 501 at a predetermined timing by a cleaning member separation / contact mechanism (not shown). On the upstream side of the belt cleaning blade 504 in the moving direction of the intermediate transfer belt 501, a toner seal member 503 that comes into contact with and separates from the surface of the intermediate transfer belt 501 is provided. The toner seal member 503 receives the dropped toner dropped from the belt cleaning blade 504 during the cleaning of the residual toner, and prevents the dropped toner from scattering on the transfer path of the transfer paper P. The toner seal member 503 is brought into and out of contact with the surface of the intermediate transfer belt 501 together with the belt cleaning blade 504 by the cleaning member separation / contact mechanism.

The lubricant 506 shaved off by the lubricant application brush 505 is applied to the surface of the intermediate transfer belt 501 from which the residual toner has been removed.
The lubricant 506 is made of, for example, a solid such as zinc stearate, and is provided so as to be in contact with the lubricant applying brush 505. Also, the intermediate transfer belt 501
Remaining on the surface of the intermediate transfer belt 501
The toner is removed by the charge removing bias applied by the belt charge removing brush 502 in contact with the surface of the sheet. Here, the lubricant applying brush 505 and the belt neutralizing brush 502
Are brought into contact with and separated from the surface of the intermediate transfer belt 501 at a predetermined timing by respective contact / separation mechanisms (not shown).

Here, at the time of a repeat copy, the operation of the color scanner and the image formation on the photosensitive drum 200 are performed as follows.
After the fourth sheet (M) image forming step of the first sheet, the process proceeds to the second sheet first color (Bk) image forming step at a predetermined timing. Further, after the batch transfer process of the first four-color superimposed toner image onto the transfer paper, the second Bk toner image is formed on the surface of the intermediate transfer belt 501 by the belt cleaning blade 504. The primary transfer is performed. 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. However, 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. In the case of the single color copy mode,
Until the predetermined number of sheets is completed, the revolver developing unit 2
The copying operation is performed with only the 30 color developing machines in the developing operation state and the belt cleaning blade 504 kept in contact with the intermediate transfer belt 501.

The above is the copy mode for obtaining a four-color full-color copy. However, 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 device of the predetermined color of the revolver developing unit 230 is in the developing operation state until the predetermined number of copies are completed, and the belt cleaning blade 504 is brought into contact with the intermediate transfer belt 501. The copy operation is performed in the state in which the copy operation is performed.

Incidentally, the belt cleaning blade 504 and the secondary transfer bias roller 605 are configured to be able to freely contact and separate from the intermediate transfer belt 501 by a contact and separation mechanism as the contact and separation means. Conventionally, in this type of copying machine, the secondary transfer bias roller 605 (or the belt cleaning blade 504) suddenly contacts the intermediate transfer belt 501, and the intermediate transfer belt 501 vibrates in the moving direction. There was something to do.

That is, the intermediate transfer belt 501 is
It has some looseness even when stretched. Therefore, the secondary transfer bias roller 605 (or the belt cleaning blade 50) is attached to the intermediate transfer belt 501.
4), the belt portion on the downstream side in the moving direction from the contact portion of the intermediate transfer belt 501 with the secondary transfer bias roller 605 (or the belt cleaning blade 504) is sharply tensioned. As a result, the progress of the belt portion of the intermediate transfer belt 501 that contacts the secondary transfer bias roller 605 (or the belt cleaning blade 504) on the upstream side in the movement direction from the contact portion is temporarily stopped. Then, the tension and the stop of the movement of the image carrier belt are repeated until the moving speed of the intermediate transfer belt 501 at the contact portion is stabilized, and the intermediate transfer belt 501 vibrates in the moving direction. Such vibrations of the intermediate transfer belt 501 are greater than when the image carrier is formed of a drum-shaped image carrier having relatively high rigidity.

Therefore, in this type of conventional copying machine, as described above, the secondary transfer bias roller 60
5 (or the belt cleaning blade 504) and the vibration in the moving direction of the intermediate transfer belt 501 generated when the intermediate transfer belt 501 comes into contact with the primary transfer image formed on the intermediate transfer transfer belt 501. May occur.

For example, in a copying machine configured so that two A4 size images can be formed on the surface of the intermediate transfer belt 501, the intermediate transfer belt 501 is usually reduced in size. On the surface of the belt 501,
The space in the non-image area between the previous image formation area and the next image formation area is set as small as possible. Therefore,
In such a copying machine, the secondary transfer bias roller 605 (or the belt cleaning blade 50) is used.
4) is in contact with the surface of the intermediate transfer belt 501, and the transfer of the toner image of the previous image on the intermediate transfer belt 501 to the transfer paper P and the removal of the residual toner are started.
An image of a part (generally, a rear end) of the next image is formed on the intermediate transfer belt 501. Therefore, the secondary transfer bias roller 6 is placed on the surface of the intermediate transfer belt 501.
If the intermediate transfer belt 501 vibrates in the moving direction when the belt 05 (or the belt cleaning blade 504) comes into contact, the next image during the image formation on the intermediate transfer belt 501 may be disturbed by the vibration.

Therefore, in the copying machine according to the present embodiment, the secondary transfer bias roller 605 and the belt cleaning blade 504 are connected to the intermediate transfer belt 501.
The intermediate transfer belt 5
When the secondary transfer bias roller 605 and the belt cleaning blade 504 are displaced in a direction in which they contact the surface of the secondary transfer bias roller 605 and the belt cleaning blade 504, at least the secondary transfer bias roller 605 and the belt cleaning blade 504 A belt having a decelerating means for decelerating just before contacting the surface of the transfer belt 501 is used.

In the copying machine constructed as described above, the secondary transfer bias roller 605 (or the belt cleaning blade 50) is driven by the speed reducing means of the contact / separation mechanism.
4) when the secondary transfer bias roller 6 is displaced in a direction in which it contacts the surface of the intermediate transfer belt 501.
The displacement speed of the belt 05 (or the belt cleaning blade 504) is reduced at least immediately before it comes into contact with the surface of the intermediate transfer belt 501. Accordingly, the secondary transfer bias roller 605 (or the belt cleaning blade 504) comes into contact with the surface of the intermediate transfer belt 501 while being gently displaced. This makes it difficult for the intermediate transfer belt 501 to vibrate in the moving direction during the contact. Therefore, in this copying machine, the disturbance of the image on the intermediate transfer belt 501 caused by the vibration of the intermediate transfer belt 501 in the moving direction can be eliminated.

FIGS. 3 and 4 show the secondary transfer unit 6.
10 shows an example of a contact / separation mechanism of the secondary transfer bias roller 605 at 00. FIG. 3 shows the secondary transfer bias roller 60.
Reference numeral 5 denotes a state in which the belt 5 is separated from the intermediate transfer belt 501 (hereinafter, this state is referred to as “during separation”). Also,
FIG. 4 shows a state in which the secondary transfer bias roller 605 is in contact with the intermediate transfer belt 501 (hereinafter, this state is referred to as “at the time of contact”).

The contact / separation mechanism includes a support 620 for supporting the secondary transfer bias roller 605 so as to be capable of moving toward and away from the surface of the intermediate transfer belt 501, and a support 62.
And an eccentric cam 630 for displacing the secondary transfer roller 0 in the direction of movement of the secondary transfer bias roller 605. The support 620 is swingably supported by a support shaft 621 provided at a position near the belt transport device 210. The secondary transfer bias roller 605 is rotatably supported by a portion of the support 620 that faces the secondary transfer opposing roller 510 with the intermediate transfer belt 501 interposed therebetween.

A pressing piece 620a provided at a free end of the support 620 near the registration roller includes:
The pressing member 640 is pressed against the elastic force of the pressing spring 641. When the pressing member 640 is pressed into contact with the support 620, the support shaft 621 is pivoted around the support shaft 621 as shown in FIG.
In this case, a swinging habit of swinging in a counterclockwise direction is provided. The swing of the support 620 due to this swing behavior is
At the time of separation shown in FIG. 3, the driven piece 620b of the support 620 is prevented by abutting against the cam edge 630a of the eccentric cam 630.

In the contact / separation mechanism having such a structure, the toner image on the intermediate transfer belt 501 is
At the time of the next transfer, in FIG.
The 0 camshaft 630b is rotated clockwise (in the direction of the arrow) by 180 degrees by a cam drive source (not shown). This allows
The eccentric cam 630 rotates by 180 degrees.
By the rotation of 30, the support 620 swings counterclockwise by the elastic force of the pressing spring 641 via the pressing member 640. Then, by the swing of the support 620, the driven piece 620b in contact with the cam edge 630a of the eccentric cam 630 rises so as to follow the cam edge 630a, and as shown in FIG. The secondary transfer bias roller 605 contacts the intermediate transfer belt 501. At the time of this contact, a gap G is formed between the cam edge 630a of the eccentric cam 630 and the driven piece 620b.
05 and the intermediate transfer belt 501 are surely in contact with each other.

However, in the conventional contact / separation mechanism having such a configuration, as described above, the intermediate transfer belt 501 vibrates in the moving direction at the time of the contact. The vibration between the secondary transfer unit 600 and the intermediate transfer unit 500 at the time of this contact was measured by a vibration recorder. As a result, as shown in FIG. 5, the secondary transfer unit 600 and the intermediate transfer unit 500 as shown in FIG.
It was clear that the contact vibrated greatly during the contact. Further, when the relationship of the angular displacement of the eccentric cam 630 of this conventional contact / separation mechanism was examined, a cam diagram as shown by A in FIG. 7 was obtained.

Therefore, in the color copying machine according to the present embodiment, the swing speed of the secondary transfer bias roller 605 immediately before contact with the intermediate transfer belt 501 at the time of the contact, that is, the secondary transfer bias roller 605 The contact / separation mechanism is provided with a decelerating means including a cam device for reducing a displacement amount of the driven piece 620b of the supporter 620 per rotation angle of the eccentric cam 630 just before contacting the surface of the intermediate transfer belt 501. The configuration was adopted.

In this color copying machine, the displacement speed of the secondary transfer bias roller 605 during the contact is
By the cam device of the speed reduction means, the speed is reduced at least immediately before the secondary transfer bias roller 605 comes into contact with the surface of the intermediate transfer belt 501. As a result, the secondary transfer bias roller 605 comes into contact with the surface of the intermediate transfer belt 501 while being gently displaced, and vibration in the moving direction of the intermediate transfer belt 501 during this contact is less likely to occur. Therefore, in this color copying machine, the disturbance of the image on the intermediate transfer belt 501 caused by the vibration of the intermediate transfer unit 500 is eliminated.

More specifically, as the cam device of the speed reduction means, the displacement speed of the secondary transfer bias roller 605 is reduced immediately before the contact as shown in the cam diagram of FIG. An eccentric cam 630 having a cam profile as shown in FIG. 8 having a cam edge 630a formed thereon is used to swing the support 620. Here, at the time of the above-mentioned contact of the secondary transfer bias roller 605 having a diameter of 300 mm and an altitude of JIS 50 °, the angular velocity at the contact portion between the eccentric cam 630 and the driven piece 620 b is 77 mm / in the conventional cam device. In the cam device of the present embodiment, the speed was 38.5 mm / sec. Further, the angular velocity at a contact portion between the secondary transfer bias roller 605 and the intermediate transfer belt 501 is about 1/1 / of the above value.
It was 2 Here, the secondary transfer bias roller 605
Energy at the time of contact at the contact portion between the intermediate transfer belt 501 and is proportional to the velocity V ^2, by a cam device of the present embodiment includes a conventional 1/4.

As described above, in the color copying machine according to the present embodiment, the vibration between the secondary transfer unit 600 and the intermediate transfer unit 500 at the time of contact is measured by a vibration recorder, and as a result, Unit 60
0 indicates that the intermediate transfer unit 500 does not vibrate much at the time of the contact as shown in FIG. Then, the disturbance of the image caused by the vibration of the intermediate transfer belt 501 of the intermediate transfer unit 500 in the moving direction is eliminated.

Here, an example in which the cam device is used as the deceleration means has been described. As the deceleration means, for example, the secondary transfer bias roller 605 is in contact with the surface of the intermediate transfer belt 501. It may be configured by a buffer member such as an air damper or an oil damper that reduces the speed at which the support 620 is displaced against the moving force of the support 620 at the time.

Further, in the above-described embodiment, the deceleration means of the contact / separation mechanism for bringing the secondary transfer bias roller 605 into and out of contact with the intermediate transfer belt 501 has been described, but the belt cleaning blade 504 is connected to the intermediate transfer belt 501. The deceleration means of the contact / separation mechanism for contacting / separating from / to can be similarly configured.

Further, in this embodiment, the case where the image carrier is the intermediate transfer belt 501 has been described.
The present invention can also be applied to an image forming apparatus in which the image carrier is a drum-shaped intermediate transfer body. Further, the present embodiment is an example in which the present invention is applied to an image forming apparatus including the intermediate transfer unit 500. For example, a transfer material that does not include the intermediate transfer unit and is transported from the image carrier by a transfer material transport belt. The present invention can be similarly applied to an image forming apparatus having a configuration in which image data is directly transferred to an image forming apparatus. In this case, the transfer material transport belt serves as an image carrier. The deceleration means is also effective in a tandem type image forming apparatus.

[0066]

According to the first aspect of the present invention, the image on the image carrier caused by the vibration in the moving direction of the image carrier when the transfer member comes into contact with or separates from the surface of the image carrier. There is an excellent effect that it is possible to eliminate the disturbance.

According to the second aspect of the present invention, when the cleaning member comes into contact with or separates from the surface of the image carrier, the image on the image carrier is disturbed due to vibration in the moving direction of the image carrier. There is an excellent effect that can be solved.

In particular, according to the third aspect of the present invention, when a contact member such as a transfer member or a cleaning member comes into contact with the surface of an endless belt as an image carrier, the contact member is gradually displaced and the endless belt is displaced. It comes into contact with the surface of the belt. Thereby, the degree of tension of the endless belt at the time of the contact is reduced, so that the moving speed of the endless belt at the contact portion with the contact member becomes relatively fast and stable, and There is an excellent effect that vibration in the moving direction at the time of contact with the contact member is reduced.

Further, according to the invention of claim 4, since the vibration of the intermediate transfer member can be reduced, there is an excellent effect that a color image without color shift can be formed.

According to the fifth aspect of the present invention, the displacement speed of the contact / separation member when displacing in the direction of contact with the surface of the image carrier is at least controlled by the cam device as the speed reduction means. The speed is reduced just before the member contacts the surface of the image carrier. As a result, the contacting / separating member comes into contact with the surface of the image carrier while being gently displaced, and vibration in the moving direction of the image carrier during this contact is less likely to occur. There is an excellent effect that the disturbance of the image on the image carrier due to the vibration in the direction is eliminated.

According to the sixth aspect of the present invention, the displacement speed of the contact / separation member when displacing in the direction of contact with the surface of the image carrier is reduced by the buffer member of the speed reduction means. The speed is reduced just before contacting the surface of the image carrier. As a result, the contacting / separating member comes into contact with the surface of the image carrier while being gently displaced, and vibration in the moving direction of the image carrier during this contact is less likely to occur. There is an excellent effect that the disturbance of the image on the image carrier due to the vibration in the direction is eliminated.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a color copying machine according to an embodiment of the present invention.

FIG. 2 is a front view showing a schematic configuration of a main part of the color copying machine.

FIG. 3 is a schematic diagram of a main part of a mechanism for contacting and separating a secondary transfer bias roller in a secondary transfer unit of the color copying machine, showing a state in which the secondary transfer bias roller is separated from an intermediate transfer belt.

FIG. 4 is a schematic configuration diagram of a main part of a mechanism for contacting and separating a secondary transfer bias roller in a secondary transfer unit of the color copying machine, showing a state where the secondary transfer bias roller is in contact with an intermediate transfer belt.

FIG. 5 is a graph showing a vibration state of a secondary transfer unit when a secondary transfer bias roller in a conventional color copying machine comes into contact with an intermediate transfer belt.

FIG. 6 is a graph showing a vibration state of an intermediate transfer unit when a secondary transfer bias roller in a conventional color copying machine contacts an intermediate transfer belt.

FIG. 7 is a cam diagram showing a comparison between an angular displacement of an eccentric cam of a cam device and an angular displacement of an eccentric cam of a conventional contact / separation mechanism in a color copying machine according to an embodiment of the present invention.

FIG. 8 is a diagram showing a profile of an eccentric cam of a cam device in the color copying machine according to the embodiment of the present invention.

FIG. 9 is a graph showing a vibration state of the secondary transfer unit when the secondary transfer bias roller contacts the intermediate transfer belt in the color copying machine according to the embodiment of the present invention.

FIG. 10 is a graph illustrating a vibration state of the intermediate transfer unit when the secondary transfer bias roller contacts the intermediate transfer belt in the color copying machine according to the embodiment of the present invention.

[Explanation of symbols]

 200 Photoconductor drum 203 Charger 220 Writing optical unit 230 Revolver developing unit 500 Intermediate transfer unit 501 Intermediate transfer belt 502 Belt discharging brush 503 Toner seal member 504 Belt cleaning blade 505 Lubricant application brush 506 Lubricant 507 Primary transfer bias roller 508 Belt drive roller 510 Secondary transfer opposing roller 600 Secondary transfer unit 605 Secondary transfer bias roller 606 Transfer paper discharging charger 610 Registration roller 620 Support 620a Pressing piece 620b Follower piece 621 Support shaft 630 Eccentric cam 630a Cam edge 630b Cam shaft 640 Pressing member 641 Pressing spring P Transfer paper

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsuyoshi Fukao 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (Reference) 2H032 AA05 BA09 BA23 BA30 2H071 BA03 BA15 CA01 CA05 DA09 DA13 DA26

Claims (6)

[Claims] An image bearing member that moves while carrying a toner image formed on the surface thereof, and a transfer member that is a contacting / separating member that comes into contact with and separates from the surface of the image bearing member. An image forming apparatus comprising: a transfer unit that transfers a formed toner image to a transfer material; and a contact / separation unit that displaces the transfer member in a direction to contact / separate from a surface of the image carrier. Has a speed-reducing means for decelerating the displacement speed of the transfer member when displacing in the direction of contact with the surface of the image carrier, at least immediately before the transfer member contacts the surface of the image carrier. An image forming apparatus comprising: 2. An image carrier which carries a toner image formed on a surface thereof and moves, a transfer means for transferring a toner image formed on the surface of the image carrier to a transfer material, and a surface of the image carrier. A cleaning member, which is a contacting / separating member that comes in contact with / separates from the image carrier, is brought into contact with the surface of the image carrier after the toner image has been transferred onto the transfer material by the above-described transfer unit, so that the residual An image forming apparatus comprising: a cleaning unit that removes toner; and a contacting / separating unit that displaces the cleaning member in a direction to contact / separate from the surface of the image carrier. The image forming apparatus further includes a decelerating means for decelerating a displacement speed of the cleaning member when displacing in a direction of contact with the surface, at least immediately before the transfer member contacts the surface of the image carrier. Image forming equipment Place. 3. An image forming apparatus according to claim 1, wherein said image carrier is constituted by an endless belt which is stretched and moved by a plurality of stretching rollers. . 4. An image forming apparatus according to claim 1, wherein said toner image is primarily transferred from said latent image bearing member on which said toner image is formed by primary transfer means. An image forming apparatus, wherein the toner image is an intermediate transfer body that is secondarily transferred to the transfer material by a secondary transfer unit. 5. The image forming apparatus according to claim 1, wherein said contacting / separating means includes a support for supporting said contacting / separating member so as to be capable of moving toward and away from a surface of said image carrier. A cam for displacing the support in the contact / separation direction of the contact / separation member, wherein the deceleration means rotates the cam at least immediately before the contact member comes into contact with the surface of the image carrier. An image forming apparatus comprising a cam device for reducing the amount of displacement of the support per angle. 6. An image forming apparatus according to claim 1, wherein said contacting / separating means is configured to support said contacting / separating member so as to be movable toward and away from a surface of said image carrier. A support moving member that moves the support in the direction of movement of the contact / separation member, wherein the deceleration means is configured to move the support when the contact member comes into contact with the surface of the image carrier. An image forming apparatus comprising a buffer member for reducing the speed at which the support is displaced against the moving force of the image forming apparatus.