JP4291063B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus applied as, for example, an electrophotographic copying machine that forms a color image.
[0002]
[Prior art]
In this type of image forming apparatus, each time a toner image of each color is formed on a photosensitive drum, the toner image is transferred onto an intermediate transfer belt, and after the transfer is completed, the image is transferred onto the intermediate transfer belt. Some transfer images onto a sheet by a transfer roller.
[0003]
By the way, in this image forming apparatus, if the transfer roller is brought into contact with the intermediate transfer belt before the toner images of the respective colors are overlaid, the toner image is rubbed. For this reason, the transfer roller is in a state of being separated from the intermediate transfer belt, and is brought into contact with the intermediate transfer belt after the toner image overlap transfer is completed.
[0004]
The transfer roller described above is attached to the rotating end side of the rotating frame, and is brought into contact with the intermediate transfer belt when the rotating frame is biased by a spring. Further, the rotation frame is pressed in the reverse direction by the rotation of the cam and is rotated against the urging force of the spring, whereby the transfer roller is separated from the intermediate transfer belt (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP-A-8-190288 [0006]
[Problems to be solved by the invention]
However, in the prior art, the transfer roller is brought into contact with the intermediate transfer belt by the biasing force of the spring. Therefore, when the transfer roller moves from the state of being separated from the intermediate transfer belt to the state of contact by the rotation of the cam, The rotational speed of the cam is accelerated by the biasing force.
[0007]
For this reason, there is a problem in that the transfer roller strongly contacts the intermediate transfer belt, vibrates the intermediate transfer belt, and adversely affects the image forming operation.
[0008]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus that can abut a transfer roller against an intermediate transfer member without applying vibration.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, an invention according to claim 1 is directed to an image forming unit for forming an electrostatic latent image on an image carrier, and a developer by developing the electrostatic latent image formed by the image forming unit. A developing unit that forms an image, an intermediate transfer member that transfers the developer image developed by the developing unit, a transfer roller that transfers the developer image transferred to the intermediate transfer member to a transfer material, and a fulcrum The transfer roller is mounted on the rotation end side, and has a mounting unit having a pressed body and an elastic material mounted on one surface side of the pressed body, and a fulcrum of the mounting unit. A support frame that is movably supported, and a pressing member that rotates the mounting unit in a direction in which the transfer roller is separated from the intermediate transfer body by elastically pressing the other surface side of the pressed body of the mounting unit. And said It is provided on the holding frame and rotates to press one surface of the pressed body of the mounting unit via the elastic material, and the pressing rotates the mounting unit against the pressing force of the pressing member. And a cam for bringing the transfer roller into contact with the intermediate transfer member.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
[0011]
FIG. 1 is an external perspective view showing an electrophotographic copying machine as an image forming apparatus according to an embodiment of the present invention.
[0012]
In FIG. 1, reference numeral 1 denotes a copying machine main body. On the upper surface of the copying machine main body 1, a document conveying unit 22 for conveying a document to a document table is provided. An operation panel 23 is provided on the upper front side of the copying machine main body 1, and a plurality of paper cassettes 24 are arranged on the lower side. On one side surface of the copying machine main body 1, a double-sided printing unit 25 used for printing an image on both sides of a sheet is provided so as to be openable and closable.
[0013]
FIG. 2 shows a state where the duplex printing unit 25 is opened.
[0014]
When the double-sided printing unit 25 is opened, an opening / closing cover 26 as a support frame for mounting a secondary transfer unit described later appears.
[0015]
FIG. 3 shows the internal structure of the electrophotographic copying machine.
[0016]
In the copying machine main body 1, a photosensitive drum 2 as an image carrier is rotatably provided. A charger 5 for charging the surface of the photosensitive drum 2 to a predetermined potential along the rotation direction around the photosensitive drum 2, a monochrome developing device 8B for developing an electrostatic latent image, and a color developer. A rotary developing device 8A, an intermediate transfer belt 3 as an intermediate transfer member for temporarily transferring a developer image, and a cleaner 6 for removing residual toner on the photosensitive drum 2 are provided.
[0017]
The color rotary developing device 8A includes a first developing unit 8a that supplies yellow toner, a second developing unit 8b that supplies cyan toner, and a third developing unit 8c that supplies magenta toner.
[0018]
The intermediate transfer belt 3 is stretched between the first to fourth rollers 3 a to 3 d with a predetermined tension to constitute a transfer belt unit 35, and is pressed against the photosensitive drum 2 by the primary transfer roller 12. A cleaner 15 a that cleans the intermediate transfer belt 3 is in contact with a portion of the intermediate transfer belt 3 that is wound around the first roller 3 a.
[0019]
Below the developing devices 8A and 8B, an exposure device 4 is provided as an image forming means for forming an electrostatic latent image on the photosensitive drum 2.
[0020]
The above-described paper feed cassette 24 is provided below the exposure apparatus 4. The paper feed cassette 24 is provided with a pickup roller 7 for taking out paper. The paper taken out by the pickup roller 7 is separated and sent out one by one by the paper feed roller 15 and the separation roller 16, and is conveyed along the conveyance system 19.
[0021]
In the conveyance system 19, a conveyance roller pair 9, a registration roller pair 17, and a secondary transfer roller 11 as a transfer roller are sequentially arranged along the sheet conveyance direction. The registration roller pair 17 temporarily stops the conveyed sheet, corrects the inclination of the sheet with respect to the conveying direction, and makes the leading end of the sheet coincide with the leading end of the toner image on the intermediate transfer belt 3.
[0022]
A fixing device 13 for fixing the toner image transferred to the paper to the paper is disposed downstream of the secondary transfer roller 11 in the paper conveyance direction. The fixing device 13 includes a heating roller 13a and a pressure roller 13b.
[0023]
A discharge roller pair 30 for discharging the paper is provided on the downstream side of the fixing device 13 in the paper conveyance direction. On the carry-out side of the discharge roller pair 30, a discharge tray 31 that receives discharged paper is provided.
[0024]
Next, the printing operation of the above-described electrophotographic copying machine will be described.
[0025]
First, a document is set on the document transport unit 22 and the copy button on the operation panel 23 is turned on. As a result, the document is conveyed and set on the document table, and is optically read by a reading device (not shown). At this time, the surface of the photosensitive drum 2 is uniformly charged by the charger 5. The charged photosensitive drum 2 is irradiated with information light corresponding to the read information by the exposure device 4 to form an electrostatic latent image.
[0026]
The electrostatic latent image is sent to the developing device 8B or the developing device 8A by the rotation of the photosensitive drum 2, and black toner is supplied from the developing device 8B, or cyan, magenta, and yellow toners are supplied from the developing device 8A. Supplied and developed. The developed toner image is sent onto the intermediate transfer belt 3 by the rotation of the photosensitive drum 2 and is primarily transferred by the primary transfer roller 12. After this transfer, the photosensitive drum 2 is subjected to light neutralization by a static eliminator (not shown), and the toner remaining on the photosensitive drum 2 is cleaned by a cleaner 6.
[0027]
On the other hand, at this time, a sheet is supplied and sent between the intermediate transfer belt 3 and the secondary transfer roller 11. The toner image on the intermediate transfer belt 3 is secondarily transferred to this sheet. After the transfer, the sheet is peeled off from the intermediate transfer belt 3 and sent to the fixing device 13 where the toner image is heated and pressurized and fixed. After this fixing, the paper is discharged to the outside via the discharge roller pair 30 and placed on the discharge tray 31.
[0028]
FIG. 4 is a perspective view showing the transfer belt unit 35, the secondary transfer unit 36 as an attachment unit, and the opening / closing cover 26.
[0029]
The opening / closing cover 26 is rotatably supported by the copying machine body 1 at both lower ends thereof via a support shaft (not shown), and a secondary transfer unit 36 is attached to the inner surface thereof. When paper is jammed between the secondary transfer unit 36 and the transfer belt unit 35, the secondary transfer unit 36 can be separated from the transfer belt unit 35 by removing the opening / closing cover 26 so that the paper can be removed. It has become.
[0030]
5 and 6 are perspective views showing the secondary transfer unit 36 attached to the opening / closing cover 26 from different angles, and FIG. 7 is a front view thereof.
[0031]
Support brackets 38 are integrally provided at both ends on the inner surface side of the opening / closing cover 26, and both ends of the secondary transfer unit 36 are rotatably attached to these support brackets 38 via a support shaft 39. .
[0032]
8 and 9 are perspective views showing the secondary transfer unit 36 from different angles.
[0033]
The secondary transfer roller 11 is rotatably attached to the secondary transfer unit 36. Bearing ports 41 are provided at both ends of the secondary transfer unit 36, and the support shaft 39 described above is inserted into the bearing ports 41 and is rotatably supported by the support bracket 38.
[0034]
An L-shaped sheet metal 42 as a pressed body is provided on the upper surface portion of the secondary transfer unit 36 along the longitudinal direction thereof. L-shaped plate springs 45 as elastic materials are provided at both ends of the L-shaped sheet metal 42, and the plate springs 45 are fixed to the sheet metal 42 by fixing screws 46. Further, compression springs 47 as pressing members are provided at both ends of the L-shaped metal plate 42 so as to be located on the opposite side of the plate spring 45.
[0035]
FIG. 10 is a perspective view showing the opening / closing cover 26.
[0036]
Bearing portions 26a for fitting support shafts (not shown) are provided at both lower ends of the opening / closing cover 26. Upper and lower guide ribs 49a and 49b for guiding the conveyance of the sheet are formed on the upper and lower portions on the inner surface side of the opening / closing cover 26. The above-described support brackets 38 are provided at both ends on the inner surface side of the opening / closing cover 26, and the secondary transfer unit 36 is rotatably supported by the support brackets 38 via a support shaft 39. Further, a cam 53 is attached to the upper side of the opening / closing cover 26 via a cam shaft 52.
[0037]
A power transmission gear train 57 is provided at one end on the inner surface side of the opening / closing cover 26, and the secondary transfer roller 11 is connected to a driving mechanism on the copier body 1 side via the power transmission gear train 57. A camshaft 52 is connected to the power transmission gear train 57 via a shaft 61, a drive belt 62, and an electromagnetic clutch 58. The cam shaft 52 is intermittently rotated by the operation of the clutch 58 every time it rotates 180 degrees.
[0038]
FIG. 11 shows an arrangement configuration of the L-shaped sheet metal 42, the compression spring 47, and the cam 53 described above.
[0039]
The cam 53 is opposed to the one surface side of the upright portion 42 a of the L-shaped sheet metal 42 via a leaf spring 45. The compression spring 47 is interposed between the other surface of the upright portion 42 a of the L-shaped sheet metal 42 and a receiving member 55 provided integrally in the opening / closing cover 26, and elastically supports the upright portion 42 a of the L-shaped sheet metal 42. It is designed to be pressed against.
[0040]
FIG. 12 shows an arrangement configuration of a roller 3c that spans the intermediate transfer belt 3, the secondary transfer roller 11, and a rotation fulcrum 36a of the secondary transfer unit 36 in a state where the secondary transfer roller 11 is pressed against the intermediate transfer belt 3. Is shown.
[0041]
The secondary transfer unit 36 is positioned so as to be perpendicular to a straight line L1 connecting the center S1 of the roller 3c and the center S2 of the secondary transfer roller 11 and on a straight line L2 passing through the center S2 of the secondary transfer roller 11. A rotation fulcrum 36a is provided.
[0042]
By the way, during the color image formation described above, a cyan toner image, a magenta toner image, and a yellow toner image that are formed on the photosensitive drum 2 with a time difference are sequentially transferred onto the intermediate transfer belt 3. The secondary transfer roller 11 needs to be separated from the intermediate transfer belt 3 as shown in FIG. 13 until the overlap transfer is completed, and after the overlap transfer is completed, it is necessary to contact the intermediate transfer belt 3 as shown in FIG.
[0043]
When the secondary transfer roller 11 is brought into contact with the intermediate transfer belt 3, clockwise rotational force is applied to the cam 53 via the power transmission gear train 57 and the cam shaft 52 from the state shown in FIG. 13. As a result, the cam 53 is rotated 180 degrees as shown in FIG. 14 and presses the standing portion 42 a of the L-shaped metal plate 42 against the urging force of the compression spring 47 via the plate spring 45. By this pressing, the secondary transfer unit 36 is rotated in the direction of arrow B to bring the secondary transfer roller 11 into contact with the intermediate transfer belt 3. The sheet is transported between the secondary transfer roller 11 and the intermediate transfer belt 3 that are pressed in this way, and the color toner image on the intermediate transfer belt 3 is transferred to the sheet.
[0044]
After this transfer, the secondary transfer roller 11 is separated from the intermediate transfer belt 3 again. In this case, a counterclockwise rotational force is applied to the cam 53 through the power transmission gear train 57 and the camshaft 52 from the state shown in FIG. As a result, the cam 53 is rotated 180 degrees again and rotated in a direction to release the pressing of the L-shaped sheet metal 42. By this rotation, as shown in FIG. 13, the secondary transfer unit 36 is rotated in the direction of arrow A about the rotation fulcrum 36a by the urging force of the compression spring 47, and the intermediate transfer belt 3 and the secondary transfer roller 11 A gap a is formed between the two.
[0045]
As described above, by rotating the cam 53, the standing portion 42 a of the L-shaped sheet metal 42 is pressed against the urging force of the compression spring 47 via the plate spring 45, thereby causing the secondary transfer roller 11 to move. Since the leaf spring 45 and the compression spring 47 act as a cushion because they are brought into contact with the intermediate transfer belt 3, the secondary transfer roller 11 can be brought into contact with the intermediate transfer belt 3 without giving an impact, which adversely affects the image forming operation. Never give.
[0046]
Further, a straight line passing through the center S2 of the secondary transfer roller 11 is perpendicular to the straight line L1 connecting the rotation fulcrum 36a of the secondary transfer unit 36 to the center S1 of the roller 3c and the center S2 of the secondary transfer roller 11. Since it is provided so as to be positioned on L2, the secondary transfer roller 11 can be brought into contact with the intermediate transfer belt 3 without affecting the traveling speed of the traveling intermediate transfer belt 3, and good image formation can be achieved. I can expect.
[0047]
Of course, the present invention is not limited to the above-described embodiment, but can be variously implemented within the scope of the gist thereof.
[0048]
【The invention's effect】
As described above, the present invention rotates the secondary transfer unit by rotating the cam by pressing the pressed body against the urging force of the pressing member via the elastic member by rotating the cam. Since the roller is brought into contact with the intermediate transfer member, the elastic member and the pressing member act as a cushion, and the transfer roller is brought into contact without giving an impact to the intermediate transfer member, so that the image forming operation is not adversely affected. There is an effect.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing an electrophotographic copying machine according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing a state where a duplex printing unit of the electrophotographic copying machine is opened.
FIG. 3 is a diagram showing an internal configuration of the electrophotographic copying machine.
FIG. 4 is a perspective view showing a transfer belt unit, a secondary transfer unit, and an opening / closing cover of the electrophotographic copying machine.
FIG. 5 is a perspective view showing the secondary transfer unit and an opening / closing cover.
FIG. 6 is a perspective view showing the secondary transfer unit and the opening / closing cover from different angles.
FIG. 7 is a front view showing the secondary transfer unit and an opening / closing cover.
FIG. 8 is a perspective view showing the secondary transfer unit.
FIG. 9 is a perspective view showing the secondary transfer unit from different angles.
FIG. 10 is a perspective view showing the opening / closing cover.
FIG. 11 is a diagram illustrating a driving mechanism for moving the transfer roller of the secondary transfer unit to and from the intermediate transfer belt.
FIG. 12 is a diagram illustrating an arrangement configuration of the transfer belt unit and the secondary transfer unit.
FIG. 13 is a diagram illustrating a state where the transfer roller of the secondary transfer unit is separated from the intermediate transfer belt.
FIG. 14 is a diagram illustrating a state in which a transfer roller of the secondary transfer unit is in contact with an intermediate transfer belt.
[Explanation of symbols]
2 ... photosensitive drum (image carrier), 3 ... intermediate transfer belt (intermediate transfer member), 3c ... roller, 4 ... exposure unit (image forming means), 8A ... developing device (developing means), 11 ... secondary transfer Roller (transfer roller), 26: Opening / closing cover (support frame), 36a: Rotating fulcrum (fulcrum), 36 ... Secondary transfer unit (mounting unit), 42 ... L-shaped sheet metal (pressed body), 44 ... Compression Spring (pressing member), 45 ... leaf spring (elastic member), 52 ... camshaft, 53 ... cam, L1 ... straight line, L2 ... straight line, 57 ... power transmission gear train, 58 ... electromagnetic clutch.

Claims (3)

Image forming means for forming an electrostatic latent image on the image carrier;
Developing means for developing the electrostatic latent image formed by the image forming means into a developer image;
An intermediate transfer member for transferring the developer image developed by the developing means;
A transfer roller for transferring the developer image transferred to the intermediate transfer member to a transfer material;
A mounting unit that is supported rotatably about a fulcrum, has the transfer roller on the rotating end side, and has a pressed body and an elastic material that is mounted on one side of the pressed body;
A support frame that rotatably supports the fulcrum of the mounting unit;
A pressing member that rotates the mounting unit in a direction in which the transfer roller is separated from the intermediate transfer body by elastically pressing the other surface side of the pressed body of the mounting unit;
Provided on the support frame and rotated to press one side of the pressed body of the mounting unit through the elastic material, and the pressing unit rotates the mounting unit against the pressing force of the pressing member. An image forming apparatus comprising: a cam that is moved to bring the transfer roller into contact with the intermediate transfer member. The intermediate transfer member is stretched between a plurality of rollers, and one of the rollers is brought into contact with the transfer roller via the intermediate transfer member,
2. The fulcrum of the mounting unit is located on a straight line connecting the center of the transfer roller and the center of the one roller, and a straight line perpendicular to the straight line and passing through the center of the transfer roller. Image forming apparatus. The cam is attached to a camshaft;
The camshaft is connected to a drive source via a power transmission gear train to receive power, and the power transmission is interrupted by the operation of a clutch every time the camshaft is rotated 180 degrees, so that the transfer roller contacts the intermediate transfer body. The image forming apparatus according to claim 1, wherein the image forming apparatus is separated.

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