JP2003029498A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus of which the power consumption and the operation time are reduced. SOLUTION: An attaching/detaching operation of each transfer roller 32 is performed by an attaching/detaching mechanism 61 by displacing only one end side of a rotary shaft while supporting the other end side. In this case, sine the other end side is displaced closer as the one end is displaced further away in the case the oscillating center of the transfer roller is positioned in an image forming area, the oscillating center is positioned outside the image forming area. Then, the load of the member to be displaced is reduced, the rapid displacement is attained, and then, the operation time can be shortened, and also, the power consumption can be more reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus which is embodied as a copying machine, a printer and / or a facsimile, and which transfers a toner image onto a sheet. The present invention relates to an image forming apparatus preferably implemented as a tandem type color image forming apparatus.

[0002]

2. Description of the Related Art In the tandem type image forming apparatus, a plurality of image carriers for carrying toner images are arranged in order from one side of the apparatus main body to the other side, and recording paper is supported by the transfer / transport carrier. While sequentially passing through each image carrier,
A plurality of types of toner images such as the color image are transferred onto recording paper. In such an image forming apparatus, not only a color image but also a single color image can be formed.
Generally, the formation amount of a monochrome image using black toner is larger than that of a color image.

Therefore, conventionally, in an image forming station that is not used for image formation, the paper carrying belt and the transfer roller are lowered from the image carrier to separate them from each other, and the rotation of the image carrier is stopped, whereby the image carrier is carried. It extends the life of the body and reduces running costs. Further, the disturbance of the formed image due to the image carrier unnecessarily contacting the recording paper is eliminated.

[0004] And, a typical prior art Japanese Unexamined Patent Publication No. 9-2
In Japanese Patent No. 74354, the CMY toner color image forming station is arranged on the upstream side in the conveying direction of the recording sheet and the K toner monochrome image forming station is arranged on the downstream side in the conveying direction. The transfer rollers of all the image forming stations are lowered, the transfer rollers of only the monochrome image forming station are raised during monochrome image formation, and the transfer rollers of all image forming stations are raised during color image formation. Has been done. As a result, the power consumption of the separation / contact operation is reduced by dividing the image forming station and driving the transfer roller while extending the life of the image carrier and reducing the running cost.

[0005]

In the prior art as described above, the size and weight of the member to be displaced are both large, the power consumption is not sufficiently reduced, and image formation of color image formation and monochrome image formation is performed. There is a problem that the operation time for mode switching becomes long. In particular, in Japanese Patent Laid-Open No. 9-274354, the three transfer rollers of the color image forming station are integrally mounted on a mounting frame, and the mounting frame as a whole is moved up and down, thereby moving toward and away from the image carrier. Displace. Therefore, for example, an operation time of 5 to 8 seconds is required, and particularly when the image formation is alternately performed with the monochrome image and the color image, the image formation time becomes long.

An object of the present invention is to provide an image forming apparatus capable of further reducing power consumption and operating time.

[0007]

SUMMARY OF THE INVENTION In an image forming apparatus of the present invention, a plurality of image bearing members carrying a toner image on the surface thereof are arrayed along a conveying direction of a recording material, and the recording material is in the conveying direction. In an electrophotographic tandem image forming apparatus in which a plurality of types of toner images are transferred by being sequentially conveyed to one side, one end of the rotation shaft of the transfer roller is placed outside the image forming area. A separating / contacting mechanism that swingably supports as a fulcrum, holds the other end side at a predetermined position close to the image carrier, or displaces away from the image carrier,
It is characterized in that it is provided for at least a part of the transfer rollers.

With the above arrangement, when the transfer roller of the image forming station not used for image formation is separated from the image carrier, the separating / contacting mechanism supports one end of the rotary shaft for each transfer roller. As it is, it is performed by displacing only the other end side. At this time, when the swing center of the transfer roller is within the image forming area, the one end side is displaced closer to the image carrier side as the other end side is displaced away from the image carrier, so that the swing center Is outside the image forming area, so that the one end side is displaced away from the image carrier as the other end side is displaced away from the image carrier. When used for image formation, the other end side is held at a position close to a predetermined image carrier, whereby the transfer roller is held parallel to the image carrier and at a predetermined constant interval. The recording paper or the intermediate transfer belt passes through the nip portion between them, and the toner image formed on the image carrier is transferred to them.

Therefore, for each transfer roller, one end side of the transfer roller is supported while only the other end side is displaced, so that the load of the member to be displaced is reduced, and quick displacement is enabled, and the operating time is shortened. Can be shortened and power consumption can be further reduced.

Further, in the image forming apparatus of the present invention, the separating / contacting mechanism includes a pair of support pieces that pivotally support the rotation shaft of the transfer roller while elastically urging the rotation shaft toward the image carrier. A frame connecting the support pieces, extending substantially parallel to the transfer roller, having one end swingably supported outside the image forming area and the other end capable of being displaced toward and away from the image carrier. Displacement means for holding the other end of the frame at a predetermined position close to the image carrier or for displacing the frame away from the image carrier.

According to the above construction, it is possible to specifically realize the construction in which only the other end side is displaced while the one end side of the transfer roller is supported as described above.

Furthermore, in the image forming apparatus of the present invention,
The rotation shaft of the transfer roller is extended from the support piece and extends to the one end side, and the separation / contact mechanism is extended in a state where the frame is in a position close to the predetermined image carrier. Proximity to one end of the transfer roller, the frame is in contact with the one end in a state of being separated from the image carrier,
It is characterized by further comprising a restriction member for preventing the displacement toward the image carrier side.

According to the above arrangement, as described above, when the transfer roller changes from the image forming state parallel to the image carrier to the non-image forming state in which the transfer roller is separated from the other end side, that is, lowered. Outside the swing center of the frame, the rotary shaft of the transfer roller moves toward the image carrier, that is, rises. Therefore, one end of the rotary shaft is extended and the rising is restricted by the restricting member.

Therefore, one end side of the rotary shaft of the transfer roller is displaced downward against the elastic force of the support piece, that is, in the direction away from the image carrier. Accordingly, when the one end side of the transfer roller is sufficiently separated from the image carrier, the swing center can be provided at a position relatively close to the image forming area, and the depth of the image forming apparatus can be shortened. it can.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Regarding one embodiment of the present invention,
The following is a description with reference to FIGS. 1 to 5.

FIG. 1 is a vertical sectional view schematically showing the overall structure of an image forming apparatus 1 according to an embodiment of the present invention. The image forming apparatus 1 is realized as a so-called color copying machine, and the image forming unit 3 performs electrophotography on a predetermined sheet such as a recording paper or an OPC film according to document image data read by the scanner 2. A color image is formed by the method. Therefore, in general, the image forming unit 3
And the scanner 2 mounted on the scanner 2 and the automatic document feeder 4 mounted on the scanner 2.

The image forming section 3 includes an optical unit 11,
Developer 12, photoconductor drum 13, cleaner unit 1
4, a charger 15, a transfer / conveying belt unit 16, a paper feeding tray 17, a paper feeding / conveying unit 18, a fixing unit 19 and a paper discharging unit 20.

The image data handled by the image forming apparatus 1 corresponds to a color image using each color of black (BK), cyan (C), magenta (M) and yellow (Y). Therefore, the optical unit 11
(11bk, 11c, 11m, 11y), developing device 12
(12bk, 12c, 12m, 12y), photoconductor drum 13 (13bk, 13c, 13m, 13y), cleaner unit 14 (14bk, 14c, 14m, 14y) and charger 15 (15bk, 15c, 15m, 15y).
Are provided so as to form four types of latent images corresponding to the respective colors, bk is set to black, c is set to cyan, m is set to magenta, and y is set to yellow.
Four image stations are arranged in tandem from one side of the device body to the other. In the following description, the subscripts bk, c, m and y are omitted when the colors are collectively referred to.

The optical unit 11 is the optical unit 1.
As shown for 1 bk, it is realized by a so-called laser scanning unit (LSU) including a laser irradiation unit 21, a polygon mirror 22, various reflection mirrors 23 to 25, a lens 26, and the like, and is uniformly charged by a charger 15. By irradiating the surface of the photosensitive drum 13 thus formed with laser light, an electrostatic latent image corresponding to image data is formed. Instead of the LSU that scans the laser beam from the single light source in the axial direction of the photosensitive drum 13, an LED head or the like in which LED elements are arranged in the axial direction of the photosensitive drum 13 may be used.

The developing unit 12 visualizes the electrostatic latent images formed on the respective photosensitive drums 13 as described above with the toners of BK, C, M and Y. The cleaner unit 14 removes and collects the toner remaining on the surface of the photosensitive drum 13 after the image transfer from the development. The charger 15 is for uniformly charging the surface of the photoconductor drum 13 to the predetermined potential as described above, and a charger-type charger or a contact-type charger is used.

The transfer / transport belt unit 16 disposed below the photosensitive drum 13 includes a transfer belt 31, a transfer roller 32 (32bk, 32c, 32m, 32y), a transfer belt driving roller 33, a transfer belt driven roller 34, and
The transfer belt tension rollers 35 and 36, the transfer belt cleaner unit 37, and the attraction charger 38 are provided. The transfer belt 31 is in contact with each photoconductor drum 13 by a transfer roller 32, and the transfer belt 31 is placed on the photoconductor drum 13 with respect to a sheet that is attracted and conveyed on the transfer belt 31 by being charged by the attraction charger 38. The toner images of the respective colors formed on are sequentially transferred in an overlapping manner to form a color toner image (multicolor toner image). The transfer belt 11 is formed in an endless shape using, for example, a film having a thickness of about 100 μm.

To the transfer roller 32, a high voltage (a positive polarity (+) opposite to the toner charging polarity (for example, −)) is applied in order to transfer the toner image. The transfer roller 32 is
For example, the surface of a metal roller made of stainless steel or the like having a diameter of 8 to 10 mm is formed by being coated with a conductive elastic material such as EPDM or urethane foam. The conductive elastic material makes it possible to adhere to the sheet and apply a high voltage uniformly.

The transfer belt cleaner unit 37 includes
Since the toner adhering to the transfer belt 31 from the photosensitive drum 13 causes the back surface of the sheet to be soiled, it is removed.
It is provided for collection.

In the present invention, as will be described later, the transfer rollers 32bk, 32c, 32m and 32y are individually supported, and the transfer roller 32bk is always in contact with the photoconductor drum 13bk, but the remaining color image is formed. Only the transfer rollers 32c, 32m, 32y for forming, which are necessary for forming a full-color or single-color image, contact the corresponding photoconductor drums 13c, 13m, 13y,
At other times, it is separated from the photoconductor drums 13c, 13m, 13y.

The paper feed tray 17 is a tray for accumulating sheets used for image formation, and is provided below the image forming section of the image forming apparatus 1. Further, the paper discharge tray 39 provided on the left side of the image forming apparatus 1 is
It is a tray for placing a sheet on which an image has been formed.

The sheet of the paper feed tray 17 is taken out by the pickup roller 41, and the paper feed / convey unit 1 is provided.
From the recording paper conveyance path 42 of 8 through the registration roller 43,
Transfer / conveying belt unit 1 at a predetermined image forming timing
6 is sent. A static eliminator 4 is attached to the transferred sheet.
An alternating current is applied from 4 to transfer belt 3
The sheet peeled from 1 is taken into the fixing unit 19,
After the toner is heated and fixed, the toner is discharged from the recording paper conveyance path 45 of the paper discharge unit 20 through the paper discharge roller 46 and onto the paper discharge tray 39.

The scanner 2 scans the original image placed on the original table 51 through the two scanning units 52 and 53 and the lens 54 at a set magnification for each line by a CCD (charge coupled device). An image is formed on the line image sensor 55, and data corresponding to the original image is output. The data is given to the laser irradiation unit 21 of the optical unit 11 after being subjected to image processing and the like. The automatic document feeder 4 is openably and closably supported on the rear side of the document table 51, presses a sheet-shaped or book-shaped document placed on the document table 51 from the rear side, and also supports a document tray. The sheet-like originals stacked on the sheet 56 are taken out one by one and conveyed to the original table 51.

FIG. 2 is a front view showing a schematic structure of the present invention. As described above, in the present invention, the black transfer roller 32bk is fixed to the apparatus main body by a support member (not shown) so as to be in constant contact with the photosensitive drum 13bk at a constant interval. On the other hand, the remaining transfer rollers 32c, 32m, and 32y are separated by the separating / contacting mechanisms 61c, 61m, and 61y, which are individually provided, to cause the photosensitive drum 1
Contact / non-contact with 3c, 13m and 13y is switched.

Each of the photosensitive drums 13bk, 13c, 1
3m and 13y are motors 62bk, 62c, 62m and 6
Each of them is driven to rotate individually by 2y. The rotation speed of the photosensitive drum 13 is, for example, 100 mm at the peripheral speed.
/ Sec, which can reach the constant speed for image formation from the start of rotation within 1 sec, and stop from the constant speed within 1 sec. Therefore, the transfer belt drive roller 33 is also driven by the motor 63.
It is driven at 0 mm / sec. Each motor 62, 63
The rotation speed and the rotation position are controlled by the control unit 64, and by using stepping motors for these motors 62 and 63, the control can be performed with high accuracy in an open loop.

Further, the separating / connecting mechanisms 61c, 61m, 61
y is also controlled by the control unit 64, and the mode is switched to the full color mode, the single color mode or the monochrome mode according to the image forming condition input from the input operation unit (not shown), and the transfer is selectively performed corresponding to the mode. The rollers 32c, 32m and 32y are driven to separate from and contact each other. At that time, when the rotation of the photoconductor drums 13c, 13m, 13y is stopped, the separation of the transfer rollers 32c, 32m, 32y is completed, and the transfer belt 31 moves the photoconductor drums 13c, 13m, 13y.
It is performed at a time point when it is surely separated from 13y. Furthermore, when the process speed of the image formation is changed due to enlargement / reduction, the motors 62 and 63 are controlled in conjunction with each other.

FIGS. 3 and 4 are side views for explaining the structure and the separating / connecting operation of the separating / connecting mechanism 61, and FIG. 5 is a rear view of FIG. The contact / separation mechanism 61 generally includes a pair of support pieces 71 and 72 that pivotally support the pair of rotation shafts 32a and 32b of the transfer roller 32 while elastically urging the pair of rotation shafts 32a and 32b toward the photosensitive drum 13. Connect the support pieces 71, 72,
One end of the photosensitive drum extends substantially parallel to the transfer roller 32 and is swingably supported in a vertical plane by a horizontal pin 73 having one end thereof as a swing center outside the image forming area W and the other end side of the photosensitive drum. A frame 74 that can be displaced toward and away from 13,
Photosensitive drum 1 in which the other end of the frame 74 is predetermined
3 and a displacement mechanism 75 for holding it at a position close to the photosensitive drum 3 or moving it away from the photosensitive drum 13.

The supporting pieces 71, 72 have a concave groove 81 on the outer circumference.
And a bearing 83 that pivotally supports the rotating shafts 32a and 32b by a hole 82 of the cylinder, and a U-shaped bearing 83, and a concave groove 8 of the bearing 83 in a central long hole 84.
1, the guide piece 87 that slidably supports the inside of the elongated hole 84 while preventing the bearing 83 from falling off by the claws 85 and 86 formed at the free ends, and the guide piece 8
7, the bearing 83 is attached to the claws 85 and 86.
A spring 88 for elastically urging the spring 88 in the direction and a pin 89 for preventing the spring 88 from falling out of the elongated hole 84 are configured. Therefore, the transfer roller 32 is rotatably supported while being elastically biased toward the photoconductor drum 13 indicated by the arrow 90.

The displacement mechanism 75 includes a pin 91 parallel to the pin 73, a lever 92 swingably supported by the pin 91 in a vertical plane, and a solenoid for applying a driving force to one end of the lever 92. 93 and a spring 94,
The frame 74 is attached to the other end of the lever 92.
And a roller 95 that rotates on the back surface on the other end side of the.

Therefore, when the operating piece 93a of the solenoid 93 is retracted, the other end of the lever 92 is moved to the roller 95.
3, the frame 74, and thus the transfer roller 32, rises in the direction of the photoconductor drum 13 as indicated by the arrow 90, and the other end of the frame 74 abuts the positioning member 96 to move the transfer roller 32. Adheres to the photosensitive drum 13 at a predetermined positioning position.

On the other hand, when the operating piece 93a of the solenoid 93 is extended, the other end of the lever 92 is moved to the roller 9
5, the frame 74, and thus the transfer roller 32, separates from the photosensitive drum 13 in the direction opposite to the arrow 90, as shown in FIG.

With this configuration, the transfer roller 32 of the image forming station not used for image formation is used.
c, 32m, 32y are the photoconductor drums 13c, 13m, 1
When separating from 3y, the separating / connecting mechanism 62c,
62m and 62y are transfer rollers 32c, 32m and 32, respectively.
For each y, the rotary shaft 32b is supported while the rotary shaft 32a side is supported.
This is done by displacing only the side. At this time, if the center of swing of the transfer rollers 32c, 32m, 32y is within the image forming area W, the rotary shaft 32b side is placed on the photosensitive drums 13c, 1.
The more it is displaced away from 3m and 13y, the rotary shaft 32a
Since the side is displaced closer to the transfer rollers 32c, 32m, 32y, by setting the swing center to the outside of the image forming area W, the rotation shaft 32b side is set to the transfer roller 32b.
The farther away from the transfer rollers 32c, 32m and 32y, the farther away from the transfer rollers 32c, 32m and 32y, the further away from the transfer rollers 32c, 32m and 32y. When used for image formation, the rotary shaft 32b side is held at a predetermined positioning position by the positioning member 96, whereby the transfer rollers 32c, 32m, 32y are moved to the photosensitive drum 13.
c, 13m, 13y are held in parallel with each other at a predetermined constant interval, and the recording paper or the intermediate transfer belt passes through the nip portion between them, and the photosensitive drum 13
The toner images formed on c, 13m, and 13y are transferred to them.

Therefore, the transfer rollers 32c, 32
The transfer rollers 32c, 32m, 32y for every m, 32y
Since only the rotating shaft 32b side is displaced while supporting the rotating shaft 32a side, the load of the member to be displaced is reduced, prompt displacement is possible, operating time can be shortened, and power consumption is reduced. Can be further reduced.

Further, the transfer rollers 32c, 32m, 3
The rotation shaft 32a of 2y is extended so as to project from the support piece 71, and the separation / contact mechanism 61 has the frame 74 shown in FIG. 4 is brought into contact with the leading end of the frame 74 shown in FIG. 4 in the lowered state of non-image forming, and the regulating member 97 for preventing the displacement thereof toward the photoconductor drums 13c, 13m, 13y is provided. Further provided.

Therefore, the transfer rollers 32c, 32m,
The tip side of the rotating shaft 32a of 32y is directed downward against the elastic force of the spring 88, that is, the photosensitive drums 13c, 13c.
It is displaced in the direction away from m and 13y.
Accordingly, when the one end sides of the transfer rollers 32c, 32m, 32y are sufficiently separated from the photosensitive drums 13c, 13m, 13y, the swing center can be provided at a position relatively close to the image forming area W, The depth of the image forming apparatus 1 can be shortened.

Another embodiment of the present invention will be described below with reference to FIG.

FIG. 6 is a vertical sectional view schematically showing the overall structure of an image forming apparatus 101 according to another embodiment of the present invention. This image forming apparatus 101 is the same as the image forming apparatus 1 described above.
, And corresponding parts are given the same reference numerals,
The description is omitted. The image forming apparatus 101 is a so-called intermediate transfer type copying machine. In the image forming unit 103, the toner images formed at the image forming stations are sequentially transferred to the intermediate transfer belt 102, and then the secondary transfer roller is used. 111 is collectively transferred onto the recording paper. The recording paper is supplied from the paper feed / conveyance unit 18 to the fixing unit 19 via the conveyance belt unit 112. The conveyor belt unit 112 is configured by winding a belt 114 between a pair of the secondary transfer roller 111 and the roller 113.

The present invention is used not only in the structure for directly transferring to the recording paper as in the image forming apparatus 1 but also in the structure for transferring to the recording paper via the intermediate transfer belt 102 as in the image forming apparatus 101. be able to.

As described above, the black transfer roller 32
bk is a photoconductor drum 1 by a support member (not shown).
Although it is fixed to the apparatus main body so as to be in constant contact with 3 bk at a constant interval, the structure composed of the above-mentioned supporting pieces 71, 72 and the frame 74 may be used.

[0044]

As described above, according to the image forming apparatus of the present invention, in the electrophotographic tandem type image forming apparatus, when the transfer roller of the image forming station not used for image formation is separated from the image carrier, The separating / contacting mechanism is performed by displacing only the other end side of each transfer roller while supporting one end side of the rotating shaft. At that time, the swing center is located outside the image forming area, and the one end side is displaced away from the image carrier as the other end side is displaced away from the image carrier.

Therefore, for each transfer roller, only one end side of the transfer roller is supported while only the other end side is displaced, so that the load of the member to be displaced is reduced, and the quick displacement is possible. The time can be shortened and the power consumption can be further reduced.

Further, in the image forming apparatus of the present invention, as described above, the pair of contact / separation mechanisms pivotally support the rotation shaft of the transfer roller while elastically urging the rotation shaft of the transfer roller toward the image carrier. The support piece and the support piece are connected to each other, extend substantially parallel to the transfer roller, one end is swingably supported outside the image forming area, and the other end side is displaced toward or away from the image carrier. It is provided with a movable frame and a displacement means for holding the other end of the frame at a predetermined position close to the image carrier or for displacing the frame away from the image carrier.

Therefore, it is possible to specifically realize the above-described structure in which only one end side of the transfer roller is supported while the other end side is displaced.

Furthermore, in the image forming apparatus of the present invention, as described above, the image forming state in which the transfer roller is parallel to the image carrier is changed to the non-image forming state in which the transfer roller is separated from the other end side, that is, lowered. When changing, outside the swing center of the frame, the rotation axis of the transfer roller rises to the image carrier side, that is, rises, so one end side of the rotation axis is extended and the rise is regulated by the regulation member. To do.

Therefore, one end side of the rotary shaft of the transfer roller is displaced downward against the elastic force of the support piece, that is, in the direction away from the image carrier, so that the transfer roller is rotated. When the one end side is sufficiently separated from the image carrier, the swing center can be provided at a position relatively close to the image forming area, and the depth of the image forming apparatus can be shortened.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing the overall configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a front view showing a schematic configuration of the present invention.

FIG. 3 is a side view for explaining the structure and the separating / connecting operation of the separating / connecting mechanism according to the present invention.

FIG. 4 is a side view for explaining the structure and the separating / connecting operation of the separating / connecting mechanism according to the present invention.

FIG. 5 is a rear view for explaining the structure and the separating / connecting operation of the separating / connecting mechanism according to the present invention.

FIG. 6 is a vertical sectional view schematically showing the overall configuration of an image forming apparatus according to another embodiment of the present invention.

[Explanation of symbols]

1, 101 Image forming apparatus 2 Scanner 3, 103 Image forming unit 4 Automatic document feeder 11bk, 11c, 11m, 11y Optical units 12bk, 12c, 12m, 12y Developing devices 13bk, 13c, 13m, 13y Photoconductor drum (image Carrier) 14bk, 14c, 14m, 14y Cleaner units 15bk, 15c, 15m, 15y Charger 16 Transfer / convey belt unit 17 Paper feed tray 18 Paper feed / conveyor unit 19 Fixing unit 20 Paper discharge unit 31 Transfer belts 32bk, 32c, 32m , 32y Transfer roller 33 Transfer belt drive roller 34 Transfer belt driven roller 35, 36 Transfer belt tension roller 37 Transfer belt cleaner unit 38 Adsorption charger 39 Paper discharge tray 44 Static eliminator 61c, 61m, 61y Separation mechanism 62bk, 62c, 62 m , 62y, 63 Motor 64 Control part 73 Pin (swing center) 71, 72 Support piece 74 Frame 75 Displacement mechanism 83 Bearing 87 Guide piece 88 Spring 93 Solenoid 96 Positioning member 97 Restricting member 102 Intermediate transfer belt 111 Secondary transfer roller

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takao Horiuchi             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F-term (reference) 2H030 AB02 AD07 AD08 AD17 BB02                       BB42 BB44 BB46 BB53 BB56                       BB63 BB71                 2H200 FA09 GA23 GA34 GA44 GA47                       GB12 GB22 GB25 HA02 HA12                       HB12 HB22 HB45 HB46 HB47                       JA02 JA23 JA25 JA26 JA27                       JA29 JB07 JB26 JB32 JB42                       JC04 JC07 JC12 LA24 LB02                       LB09 LB13 MA03 MA20 MB01                       MC01 PA12 PA26

Claims (3)

[Claims] 1. A plurality of image bearing members carrying a toner image on the surface thereof are arranged along a transport direction of a recording material, and the recording material is sequentially transported in the transport direction, so that a plurality of types of image carriers can be obtained. In an electrophotographic tandem type image forming apparatus in which a toner image is transferred, one end of the rotation shaft of the transfer roller is swingably supported with the outer side of the image forming area as a fulcrum, and the other end side. An image forming apparatus, wherein at least a part of the transfer rollers is provided with a detaching / contacting mechanism for holding the sheet at a predetermined position close to the image bearing body or displacing it away from the image bearing body. 2. The separating / connecting mechanism connects between a pair of support pieces that pivotally support the rotation shaft of the transfer roller while elastically biasing the rotation axis of the transfer roller toward the image carrier, and connects the support pieces to each other. A frame that extends substantially parallel to the transfer roller, one end of which is swingably supported outside the image forming area and the other end of which can be displaced toward and away from the image carrier, is provided with the other end of the frame in advance. The image forming apparatus according to claim 1, further comprising a displacement unit that holds the image carrier at a predetermined position close to the image carrier or displaces the image carrier away from the image carrier. 3. A rotation shaft of the transfer roller is extended from the support piece and extends to the one end side, and the separation / contact mechanism is provided in a state where the frame is in a position close to the predetermined image carrier. A regulating member which is close to one end of the extended transfer roller, contacts the one end of the frame in a state of being separated from the image carrier, and prevents the displacement to the image carrier side. The image forming apparatus according to claim 2, which is characterized in that.