JPH1083124A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a device, which brings a transfer roller into contact with a latent-image carrier and separates it therefrom, by connecting an eccentric-camlike gap roller to both ends of the transfer roller in its axial direction so that it is relatively rotatable, and making the eccentric-cam face of the gap roller abut on the latent-image carrier and outside the image area of it. SOLUTION: Recording paper is carried from a carrying path 7 by a resist roller 6 so as to match the front end of a toner image formed on the surface 1a of the latent-image carrier 1, and also a transfer bias is applied to the transfer roller 3, thereby transferring the toner image to the recording paper from the surface 1a of the latent-image carrier 1. In the transfer roller 3, a common shaft 3A jutting out from both its ends is rotatably held in the proper part of the eccentric-camlike gap roller 4, and the eccentric-cam face 4 (the periphery of gap roller) abuts on the surface 1a of the latent-image carrier 1 and outside the image area of it. Therefore, the gap roller 4 is relatively rotatably connected to the transfer roller 3 which rotates for a transfer operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile machine, or a multifunction machine using an electrophotographic system, and more particularly, to an improvement in a latent image carrier. The present invention relates to an image forming apparatus that forms an image by transferring a toner image by pressing a recording sheet against the toner image.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, for example, an electrophotographic copying machine using an electrophotographic system, an arm is used to transfer a toner image formed on a latent image carrier onto a recording sheet. A technique in which the transfer roller is moved toward and away from the body is known (see Japanese Patent Application Laid-Open Nos. 6-308841, 6-317994, and 7-234595). A technique of moving a transfer roller to and from a latent image carrier using a cam and a bracket is also known (Japanese Patent Application Laid-Open No. Sho 62-62).
153874, JP-A-3-171702, etc.). However, according to these conventional examples, a space for providing an arm, a cam, and a bracket near the transfer roller is required, which not only increases the size of the apparatus, but also increases or decreases the pressure due to pressing the solenoid or spring through the arm. There was a problem that it was difficult. Further, a technique in which a transfer roller is brought into contact with and separated from a latent image carrier by a cylindrical body is also known (see JP-A-7-230222). However, in this conventional example, the types of recording paper that can be brought into contact with and separated from each other by using a cylindrical body are limited. In particular, in the case of thin recording paper, not only is it difficult to move the cylindrical body, but also There is also a problem that the distance between the carrier and the transfer member is large, and the efficiency of the transfer bias is low, so that the power supply cost is increased. Therefore, the conventional image forming apparatus has problems that not only the size of the device for moving the transfer roller to and away from the latent image carrier becomes large, but also it is difficult to control the pressure and the power supply cost increases.

[0003]

In the above-mentioned conventional image forming apparatus, not only the device for moving the transfer roller to and away from the latent image carrier becomes large, but also it is difficult to control the pressure.
There was a problem that the cost was high. Therefore, an object of the present invention is to solve such a problem. That is, it is an object of the present invention to provide an image forming apparatus in which the size of an apparatus for moving a transfer roller to and from a latent image carrier is small, and the pressure for moving the transfer roller is easily reduced.

[0004]

According to one aspect of the present invention, there is provided an image forming apparatus for forming an image by transferring a toner image formed on a latent image carrier onto recording paper. A latent image carrier that is rotatably supported to form an electrostatic latent image, a developing unit that visualizes the electrostatic latent image formed on the surface of the latent image carrier, and a developing unit that A transfer roller that presses a recording sheet to transfer the electrostatic latent image formed on the surface of the latent image carrier to a visualized toner image and transfers the toner image to the toner image; and a relative rotation about a common axis at both axial ends of the transfer roller. An eccentric cam-shaped gap roller connected in a possible state,
And the eccentric cam surface provided on the outer peripheral surface of the gap roller and abutting outside the image area of the latent image carrier. According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the eccentric cam surface is an image forming apparatus having a concave portion. According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the eccentric cam surface is an image forming apparatus having idle rollers. According to a fourth aspect of the present invention, in the image forming apparatus according to the second aspect, the concave portion is an image forming apparatus having the idle roller. According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, third or fourth aspect, the gap roller is arranged such that the transfer roller is separated from the latent image carrier when recording paper is not passed. The main feature is that it is a rotating image forming apparatus. The invention of claim 6 is
6. The image forming apparatus according to claim 1, wherein the gap roller rotates in accordance with a thickness of the recording paper to reduce a gap between the latent image carrier and the transfer roller. The main feature is that the image forming apparatus is to be adjusted.

[0005]

In the image forming apparatus constructed as described above, according to the first aspect, the recording paper is pressed against a toner image obtained by visualizing the electrostatic latent image formed on the surface of the latent image carrier. An eccentric cam-shaped gap roller is rotatably connected to both ends in the axial direction of the transfer roller to be transferred, and the eccentric cam surface provided on the gap roller is brought into contact with the outside of the image area of the latent image carrier. As a result, it is possible to provide an image forming apparatus in which the device for moving the transfer roller to and away from the latent image carrier is small and the pressure for moving the transfer roller to and away from the latent image carrier can be easily adjusted and the cost is low. According to a second aspect of the present invention, an eccentric cam is formed on both ends in the axial direction of a transfer roller which presses and transfers a recording paper to a toner image obtained by visualizing the electrostatic latent image formed on the surface of the latent image carrier. The gap rollers are connected so as to be relatively rotatable, and the eccentric cam surface having the recessed portion provided in the gap rollers is made to abut on the outside of the image area of the latent image carrier. It is possible to provide an image forming apparatus in which the size of the device for contacting and separating is reduced, the positioning of the gap roller is facilitated, and the pressing force for contacting and separating can be easily controlled and the cost is low.

According to the third aspect of the present invention, the eccentric cam surface having the idling rollers provided on the gap rollers comes into contact with the outside of the image area of the latent image carrier. In order to provide an image forming apparatus in which the size of the apparatus for performing the operation is small, the sliding between the latent image carrier and the gap roller is performed smoothly, and the pressing force for coming and going can be easily adjusted, and the cost is low. I do. According to the fourth aspect, the eccentric cam surface having the idling roller in the recess provided in the gap roller comes into contact with the outside of the image area of the latent image carrier. The size of the image forming apparatus is reduced, the positioning of the gap roller is facilitated, the sliding between the latent image carrier and the gap roller is performed smoothly, and the pressing force for coming and going can be easily adjusted to reduce the cost. Equipment can be provided.

According to a fifth aspect of the present invention, the eccentric cam surface provided on the gap roller comes into contact with the outside of the image area of the latent image carrier, and the transfer roller moves from the latent image carrier to the gap roller when the recording paper is not passing. Since the rotation is performed so as to be separated, the device for moving the transfer roller to and away from the latent image carrier becomes smaller, and the pressing force for moving to and away from the transfer roller can be easily adjusted, and the back of the transfer roller and the recording paper can be adjusted. It is possible to provide an image forming apparatus which prevents contamination and has low cost. According to the sixth aspect, the eccentric cam surface provided on the gap roller comes into contact with the outside of the image area of the latent image carrier, and the gap roller rotates corresponding to the thickness of the recording sheet to transfer the latent image carrier. Since the gap between the transfer roller and the roller is adjusted, the size of the device for moving the transfer roller toward and away from the latent image carrier can be reduced, and the pressing force for moving the transfer roller can be easily adjusted. The present invention can provide an image forming apparatus which maintains a predetermined contact force between a latent image carrier and a transfer roller and has a low cost.

[0008]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of an image forming unit of an image forming apparatus according to an embodiment of the present invention. A latent image carrier (photosensitive drum) 1 of the image forming apparatus is driven around a shaft 1A by a driving unit (not shown). A latent image is formed on the surface 1a, which is rotatably supported in the direction of arrow A and charged uniformly by the charger 5, by an exposure means (not shown). The developing unit 2 develops the electrostatic latent image formed on the surface 1 a of the latent image carrier 1 to form a visualized toner image. When the toner image formed on the surface 1a of the latent image carrier 1 reaches a transfer position at which the latent image carrier 1 and the transfer roller 3 contact each other, the toner image formed on the surface 1a of the latent image carrier 1 is The recording paper is transported from the transport path 7 by the registration roller 6 so as to be aligned with the leading end, and a transfer bias is applied to the transfer roller 3, so that the toner image is transferred from the surface 1 a of the latent image carrier 1 to the recording paper. The transfer roller 3 rotatably holds a common shaft 3A protruding from both ends at an appropriate position of the eccentric cam-shaped gap roller 4, and the eccentric cam surface 4a (outside the image area of the surface 1a of the latent image carrier 1). The outer peripheral surface of the gap roller) abuts. Therefore, the gap roller 4 is connected to the transfer roller 3 rotating for the transfer operation so as to be relatively rotatable.

When a stepping motor or an electromagnetic clutch as the driving source 4d is operated at a predetermined timing by a control means (not shown), the gap roller 4 rotates in the direction of arrow B, and the eccentric cam surface 4a rotates. The transfer roller 3 separates or abuts on the surface 1a of the latent image carrier 1 in the direction of arrow C, and the transfer roller 3 and the surface 1a of the latent image carrier 1
a can be freely adjusted and set to a predetermined gap and held. Further, by actuating the driving source 4d at a predetermined timing, when the recording paper is not passing, the transfer roller 3 is rotated in a direction in which the transfer roller 3 is separated from the latent image carrier 1, so that the latent image carrier and the transfer roller are rotated. This prevents occurrence of direct contact with the recording medium, thereby preventing the transfer roller 3 from being stained and the recording paper from being stained on the back side. When an electromagnetic clutch is used as the driving source 4d, the gap roller 4 is operated by using the rotational driving force of the transfer roller 3. That is, when the clutch is engaged, the gap roller 4 may be rotated by a desired angle using the rotation driving force from the transfer roller 3, and then the clutch may be turned off. The recording paper after the transfer of the toner image is separated from the latent image carrier 1, conveyed to the fixing device 8, and is fixed after being nipped and fixed by the heating roller 8 a and the pressure roller 8 b of the fixing device 8. The paper is discharged from the paper discharge roller 9 and stored. On the other hand,
Surface 1 of latent image carrier 1 after transfer of toner image to recording paper
In the case of a, foreign matters such as toner remaining after being adhered without being transferred to the recording paper are scraped off by the cleaning unit 10 to prepare for the next image formation.

FIG. 2 is a perspective view showing a configuration of a main part of another embodiment of the present invention. In this embodiment, a concave portion 4b is provided at an apex of an eccentric cam surface 4a provided on a gap roller 4. (Claim 2). Therefore, the recess 4 b is fitted on the surface 1 a of the latent image carrier 1, so that the transfer roller 3 can easily maintain the state separated from the surface 1 a of the latent image carrier 1. . Polyacetal (POM) is used as the eccentric cam surface 4a provided on the gap roller 4 in contact with the surface 1a of the latent image carrier 1 made of a metal material.
If a resin material that is easy to slide (has a small coefficient of friction) is used, the surface 1a of the latent image carrier 1 and the eccentric cam surface 4a of the gap roller 4 can easily slide. Therefore, the depression 4b does not provide resistance to rotation of the latent image carrier.

FIG. 3 shows another embodiment of the present invention, in which two idling rollers 4c are provided on both sides of a concave portion 4b of an eccentric cam surface 4a provided on a gap roller 4. The idle roller 4c is configured to roll while simultaneously contacting the surface 1a of the latent image carrier 1 (claim 4). Accordingly, since the two idle rollers 4c are in rolling contact with the surface 1a of the latent image carrier 1, there is no need to use a resin material such as polyacetal (POM) which is easy to slide as the eccentric cam surface 4a. The position where the idle roller 4c is arranged may be any position other than the recessed portion as long as it is located along the eccentric cam surface 4a.

FIG. 4 shows another embodiment of the present invention, in which the rotational driving force of a stepping motor as a driving source 4d is transmitted to a gap roller 4 via a gear (row) 4e to be rotated, and the eccentric cam surface is rotated. By rotating the roller 4a, the gap between the transfer roller 3 and the surface 1a of the latent image carrier 1 is freely controlled and adjusted. In this embodiment, one of the gears 4e is integrated with the gap roller 4, and the rotation angle of the integrated gear 4e is directly reflected on the rotation angle of the gap roller 4. The gap roller 4 and the transfer roller 3 are relatively rotatable in the same manner as in the above embodiment.

FIG. 5 is a schematic structural view of another embodiment of the present invention. The thickness of the recording paper is detected in a conveyance path 7 upstream of the position of the registration roller 6 in the conveyance direction of the recording paper. The recording paper thickness sensor 11 is provided.
Is input to the control means 12, the control means 12 activates the drive source 4d, and rotates the gap roller 4 in accordance with the thickness of the recording paper, so that the latent image carrier A predetermined gap and contact force between the transfer roller 1 and the transfer roller 3 are adjusted. In other words, according to this embodiment, by adjusting the gap and the contact force according to the thickness of the recording paper, optimal transfer conditions can be created, and the image quality can be improved. 6).

[0014]

As described above, according to the first aspect of the present invention, the electrostatic latent image formed on the surface of the latent image carrier is transferred by pressing the recording paper against a visualized toner image. A common shaft at both ends in the axial direction of the transfer roller is connected to an eccentric cam-shaped gap roller in a rotatable state, and the eccentric cam surface is brought into contact with the outside of the image area of the latent image carrier. It is possible to provide an image forming apparatus in which the size of the device for moving the transfer roller to and from the image carrier is small and the cost for moving the transfer roller to and away from the image carrier can be easily adjusted is low. According to the second aspect of the present invention, the common shafts at both ends in the axial direction of the transfer roller are connected to the eccentric cam-shaped gap roller in a relatively rotatable state, and at the top of the circumferential surface (eccentric cam surface) of the gap roller. Since the concave portion is provided so that the eccentric cam surface comes in contact with the image area of the latent image carrier, the device for moving the transfer roller to and away from the latent image carrier is reduced, and the positioning of the gap roller is facilitated. It has become possible to provide an image forming apparatus that can easily adjust the separating pressing force and has a low cost.

According to the third aspect of the present invention, the common shaft at both ends in the axial direction of the transfer roller is connected to the eccentric cam-shaped gap roller in a relatively rotatable state, and the peripheral surface of the gap roller (eccentric cam surface). Since the idle rollers are provided so that the idle rollers come into contact with the outside of the image area of the latent image carrier, the device for moving the transfer roller to and away from the latent image carrier is reduced, and It is possible to provide an image forming apparatus in which the sliding with the gap roller is smoothly performed, and the pressing force for coming and going can be easily adjusted and the cost is low. According to the fourth aspect of the present invention, the common shafts at both ends in the axial direction of the transfer roller are connected to the eccentric cam-shaped gap roller in a relatively rotatable state, and at the top of the circumferential surface (eccentric cam surface) of the gap roller. A concave portion is provided, and an idle roller is provided in this concave portion, and the idle roller is brought into contact with the outside of the image area of the latent image carrier. Provided is an image forming apparatus which is small in size, facilitates the positioning of the gap rollers, smoothly slides the latent image carrier and the gap rollers, and can easily adjust the pressing force for contacting and separating, and has a low cost. I can do it.

According to the fifth aspect of the present invention, the common shaft at both ends in the axial direction of the transfer roller is connected to the eccentric cam-shaped gap roller in a rotatable state, and the eccentric cam surface provided on the gap roller is connected to the eccentric cam surface. Since the gap roller is brought into contact with the outside of the image area of the latent image carrier and the transfer roller is rotated so that the transfer roller is separated from the latent image carrier when the recording paper is not passed,
The device for moving the transfer roller to and from the latent image carrier becomes smaller,
It has become possible to provide an image forming apparatus which can easily adjust the pressure applied to and separates from the transfer roller, prevent the transfer roller and the recording paper from being stained on the back, and reduce the cost. According to the invention of claim 6, the common shafts at both ends in the axial direction of the transfer roller are connected to the eccentric cam-shaped gap roller in a rotatable state, and the eccentric cam surface provided on the gap roller carries the latent image. When the gap roller rotates in accordance with the thickness of the recording paper to adjust the gap between the latent image carrier and the transfer roller, it is transferred to the latent image carrier. The roller contacting / separating device becomes smaller, the pressure for contacting / separating can be easily adjusted, and the predetermined contact force between the latent image carrier and the transfer roller is maintained regardless of the thickness of the recording paper, An image forming apparatus with low cost can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a perspective view illustrating a main part of an image forming apparatus according to another embodiment of the present invention.

FIG. 4 is a perspective view illustrating a main part of an image forming apparatus according to another embodiment of the present invention.

FIG. 5 is an explanatory diagram illustrating another main part of the image forming apparatus according to the embodiment of the present invention.

[Explanation of symbols]

1 latent image carrier, 1a surface, 2 developing unit, 3
Transfer roller, 4 gap roller, 4a eccentric cam surface, 4
b Depression, 4c Roller around 4d, Drive source, 4e
Gear train, 5 charger, 6 registration roller, 7 transport path, 8 fixing device, 8a heating roller, 8b pressure roller, 9 paper discharge roller, 10 cleaning unit, 1
1 recording paper thickness sensor, 12 control means

Claims (6)

[Claims] 1. An image forming apparatus for forming an image by transferring a toner image formed on a latent image carrier to a recording sheet, wherein the latent image carrier is rotatably supported and forms an electrostatic latent image. A developing unit for visualizing the electrostatic latent image formed on the surface of the latent image carrier, and visualizing the electrostatic latent image formed on the surface of the latent image carrier by the developing unit. A transfer roller that presses the recording paper against the formed toner image to transfer it, an eccentric cam-shaped gap roller that is connected to both ends in the axial direction of the transfer roller in a rotatable manner, and provided on the outer peripheral surface of the gap roller. An eccentric cam surface abutting outside the image area of the latent image carrier. 2. The image forming apparatus according to claim 1, wherein
The eccentric cam surface has a concave portion. 3. The image forming apparatus according to claim 1, wherein the eccentric cam surface has an idle roller. 4. The image forming apparatus according to claim 2, wherein
The image forming apparatus according to claim 1, wherein the depression has the idle roller. 5. The image forming apparatus according to claim 1, wherein the gap roller rotates so that the transfer roller is separated from the latent image carrier when recording paper is not passed. An image forming apparatus comprising: 6. The image forming apparatus according to claim 1, wherein the gap roller is rotated in accordance with the thickness of the recording paper to transfer the latent image carrier and the transfer. An image forming apparatus for adjusting a gap with a roller.