JP4062268B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a configuration of an entry path in which a recording sheet reaches a nip portion between a heat roller and a press roller in a fixing device including a heat roller and a press roller pressed against the heat roller.

  Image forming apparatuses such as copiers, facsimile machines, and printers are provided with a fixing device upstream of the discharge port, and an entry path through which recording paper reaches the nip portion between the heat roller and the press roller of the fixing device is as follows. There exists what was comprised (for example, refer patent document 1).

  As shown in FIG. 2 of the same document, the fixing device is connected to the fixing roller of the heat roller 21 through the upstream end A in the recording sheet conveying direction of the nip region 23 formed between the heat roller 21 and the press roller 22. The recording paper P is configured to enter the nip region 23 from a position closer to the heat roller 21 than the reference line L extending in the tangential direction.

  As shown in FIG. 3 of the document, in this configuration, most of the water vapor S generated when the toner image is fixed in the fixing device flows along the back surface of the recording paper P. The toner particles constituting the formed toner image T are prevented from being blown off, and the occurrence of the trailing phenomenon due to the toner particles adhering to the recording paper P can be reduced.

JP 2002-251087 A

  However, when the recording paper P is made to enter the nip area 23 from a position closer to the heat roller 21 than the reference line L, the recording paper P is reached before the leading edge of the recording paper P reaches the nip area 23. When the toner image is formed up to the front end of the recording paper P, the following problems occur.

  When the leading end surface of the recording paper P comes into contact with the rotating surface of the heat roller 21 before the leading end of the recording paper P reaches the nip region 23, the peripheral speed on the outer peripheral surface (rotating surface) of the heat roller 21 and the nip region 23, the toner image at the leading edge of the recording paper P is rubbed by the rotating surface of the heat roller 21 due to the difference in the conveyance speed of the recording paper P entering the recording medium 23. Had occurred.

  In view of the above, an object of the present invention is to provide a fixing device that prevents image distortion from occurring at the leading edge of a recording sheet.

The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.
First, as described in claim 1, in an image forming apparatus including a photoconductor, a heat roller, and a press roller that presses against the heat roller, the image forming apparatus includes the photoconductor to the heat roller. A spur is provided on the heat roller side of the transport path on both sides of the recording paper transport path leading to the nip portion with the press roller, and a guide section is provided on the press roller side of the transport path. The recording sheet is arranged upstream of the guide path with respect to the transport path, and the recording paper is bent and guided toward the guide section by the spur and hits the guide section to bend the transport direction. The recording paper guided by the guide portion is moved along an entry path through which the recording paper enters the nip portion until the leading edge of the recording paper reaches the nip portion. The entry path is based on a straight line connecting the upstream end and the downstream end in the recording paper conveyance direction of the nip portion between the heat roller and the press roller so that the surface does not contact the rotating surface of the heat roller. The tangent line of the press roller, the tangent line passing through the rotation center of the heat roller, the tangent line on the upstream side in the recording paper transport direction as an auxiliary line, and the angle of the auxiliary line with respect to the reference line Of these, when the acute angle is α, the approach angle θ of the recording paper conveyed toward the region surrounded by the rotating surface of the heat roller, the rotating surface of the press roller, and the auxiliary line is the reference angle θ. The angle with respect to the line was set to satisfy 0 <θ ≦ α.

According to a second aspect of the present invention, there is provided an image forming apparatus including a photoconductor, a heat roller, and a press roller that is in pressure contact with the heat roller. A spur is provided on the heat roller side of the transport path on both sides of the recording paper transport path leading to the nip portion with the press roller, and a guide section is provided on the press roller side of the transport path. The recording sheet is arranged upstream of the guide path with respect to the transport path, and the recording paper is bent and guided toward the guide section by the spur and hits the guide section to bend the transport direction. The recording paper guided by the guide portion is moved along an entry path through which the recording paper enters the nip portion until the leading edge of the recording paper reaches the nip portion. The entry path is based on a straight line connecting the upstream end and the downstream end in the recording paper conveyance direction of the nip portion between the heat roller and the press roller so that the surface does not contact the rotating surface of the heat roller. A tangent line of the press roller, the tangent line passing through the center of rotation of the heat roller, and the tangential line on the upstream side in the recording sheet conveyance direction being an auxiliary line, the recording sheet conveyance direction with respect to the auxiliary line The recording paper entered in a direction parallel to the reference line toward the rotating surface of the press roller located on the downstream side.

Since the present invention is configured as described above, the following effects can be obtained.
According to the first aspect of the present invention, a recording paper conveyance path that is bent at the spur portion and heads toward the guide portion is formed, and the recording paper is conveyed to the guide portion along the conveyance path. Even if the leading edge of the recording paper guided by the guide portion comes into contact with the rotating surface of either the heat roller or the press roller, the leading edge of the recording paper is guided by the rotating surface of the roller. without surface is in contact with the rotating surface of the heat roller, because it is adapted to enter the nip portion between the heat roller and the press roller, even when the toner image is formed to the front end of the recording paper, the toner The image is not rubbed by the rotating surface of the heat roller, image distortion at the leading edge of the recording paper is prevented, and reliability is improved.

According to the second aspect of the present invention, since a recording paper conveyance path that is bent at the spur portion and heads toward the guide portion is formed, the recording paper is conveyed to the guide portion along the conveyance path. The leading edge of the recording paper guided by the guide portion comes first in contact with the rotating surface of the press roller, and the leading edge of the recording paper is guided by the rotating surface of the press roller. contact without, because is adapted to enter the nip portion between the heat roller and the press roller, when the toner image is formed to the front end of the recording sheet is also rotating surface the toner image is the heat roller Therefore, the occurrence of image distortion at the leading edge of the recording paper is prevented and the reliability is improved.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a front sectional view of an image forming apparatus 1 provided with a fixing unit 4. First, an outline of the image forming apparatus 1 provided in a copying machine, a facsimile machine, or the like will be described.

  As shown in FIG. 1, the image forming apparatus 1 is disposed above the paper feed cassette 5, and a paper discharge tray 6 is formed on the upper part of the image forming apparatus 1. Inside the image forming apparatus 1, there are formed a first recording paper transport path 11 and a second recording paper transport path 12 for transporting the recording paper fed from the paper feed cassette 5, and the first recording paper A developing unit 2, a photosensitive unit 3, and a fixing unit 4 are arranged along the transport path 11 toward the downstream side (upward). These units 2, 3, 4 constitute an image forming unit, and the recording paper fed from the paper feed cassette 5 is image-transferred and fixed by the image forming unit. 6 to be discharged.

Next, the fixing unit 4 disposed above the photosensitive unit 3 in the apparatus main body 1a will be described.
As shown in FIG. 1, a fixing device unit 4 as a fixing device is detachably attached to an upper portion in the apparatus main body 1a, and a jam access cover 7 is provided on the outer side of the fixing device unit 4 with respect to the apparatus main body 1a. It can be opened and closed. The jam access cover 7 is configured to cover the longitudinal portion of the fixing unit 4 and is disposed on one side of the apparatus main body 1a. The jam access cover 7 can be turned up and down around the lower position of one end of the apparatus main body 1a. It is configured.

  If a second recording paper transport path 12 is formed between the inner side of the jam access cover 7 and the outer side of the fixing unit 4, and this jam occurs in the recording paper transport paths 11 and 12, etc. The jam access cover 7 is opened to open one side of the apparatus main body 1a.

  As shown in FIG. 2, the fixing unit 4 has a frame divided into a first frame 43 that pivotally supports the heat roller 41 and a second frame 44 that pivotally supports the press roller 42. A lower end portion of the first frame 43 and a lower end portion of the second frame 44 are rotatably engaged, and the second frame 44 is attached to the first frame 43 so as to be tiltable. The frame of the fixing unit 4 is assembled by fastening the upper end of 43 and the upper end of the second frame 44, and the first frame 43 is detachably attached to the apparatus main body 1a. Yes.

  In the state in which the frames 43 and 44 are assembled, the press roller 42 is in pressure contact with the heat roller 41, and the entry path through which the recording paper reaches the nip portion 48 between the heat roller 41 and the press roller 42 is the nip. The leading end surface of the recording paper is configured not to contact the rotating surface of the heat roller 42 until the leading end of the recording paper reaches the section 48.

Next, two embodiments will be described with respect to an entry path through which the recording paper reaches the nip portion 48 between the heat roller 41 and the press roller 42.
First, a description will be given of a first embodiment of the approach path 16 where the recording paper reaches the nip portion 48.
As shown in FIG. 3, the approach path 16 according to the first embodiment is a straight line connecting the upstream end and the downstream end of the nip portion 48 between the heat roller 41 and the press roller 42 in the recording paper conveyance direction. The reference line X is a tangent line of the press roller 42, and the tangent line passing through the rotation center of the heat roller 41 is the auxiliary line Y, and the auxiliary line Y is the reference line. The recording paper conveyed toward the area D surrounded by the rotation surface of the heat roller 41, the rotation surface of the press roller 42, and the auxiliary line Y, where α is the acute angle of the angles formed with respect to X Is an angle with respect to the reference line X, and 0 <θ ≦ α.

The guide sheet 44b (see FIG. 2) below the second frame 44 of the fixing unit 4 and the first recording sheet conveyance path 11 are exposed so that the recording sheet enters the nip portion 48 through the entry path 16. The recording paper is guided by a spur 13 provided between the body unit 3 and the fixing unit 4.
A large number of guide portions 44b protrude from the second frame 44 toward the first recording paper transport path 11 side, and are provided at predetermined intervals in the longitudinal direction of the second frame 44. The frictional resistance is reduced by reducing the area.

  As shown in FIG. 2, image information is transferred to the surface of the recording paper by the photosensitive unit 3 (the surface on the heat roller 41 side when passing through the fixing unit 4), and the spur 13 guides the fixing unit 4. Guided toward the portion 44b. Then, the recording paper abuts against the guide portion 44b and the conveyance direction is lightly bent, and after being guided along the guide portion 44b, the recording paper enters the region D and the leading edge of the recording paper reaches the heat roller 41 (or The leading end of the recording paper is guided to the rotating surface of the heat roller 41 (or the press roller 44) without contacting the rotating surface of the heat roller 44 with the rotating surface of the pressing roller 44). Thus, the heat roller 41 and the press roller 42 are configured to enter the nip portion 48.

  With the configuration as described above, the leading edge of the recording paper is guided to the rotating surface of the roller 41 (or 42) even if the leading edge of the recording paper hits the rotating surface of either the heat roller 41 or the press roller 42 first. However, the front end surface of the recording paper is configured to enter the nip portion 48 between the heat roller 41 and the press roller 42 without contacting the rotating surface of the heat roller 44, Even when the toner image is formed up to the front end of the surface, the toner image is not rubbed by the rotating surface of the heat roller 41, and image distortion at the front end of the recording paper is prevented. Reliability is improved.

Next, a second embodiment of the entry path 17 where the recording paper reaches the nip portion 48 will be described.
As shown in FIG. 4, the approach path 17 according to the second embodiment is a straight line connecting the upstream end and the downstream end of the nip portion 48 between the heat roller 41 and the press roller 42 in the recording paper conveyance direction. When the reference line X is a tangent line of the press roller 42, and the tangent line passing through the rotation center of the heat roller 41 on the upstream side in the recording paper transport direction is the auxiliary line Y, the auxiliary line Y On the other hand, the recording paper enters in a direction parallel to the reference line X toward the rotation surface of the press roller 42 located downstream in the recording paper conveyance direction.

  Similarly to the entry path 16 according to the first embodiment, the recording sheet entry path 17 also extends along the guide portion 44 b below the second frame 44 of the fixing unit 4 and the first recording sheet conveyance path 11. It is formed by being guided by a spur 13 provided between the photoreceptor unit 3 and the fixing unit 4.

  With such a configuration, the leading edge of the recording paper conveyed toward the fixing unit 4 comes into contact with the rotation surface of the press roller 42 and the leading edge of the recording paper is guided to the rotation surface of the press roller 42. The front end surface of the recording paper enters the nip portion 48 between the heat roller 41 and the press roller 42 without coming into contact with the rotating surface of the heat roller 41, and the surface of the recording paper on the heat roller 41 side. Even when the toner image is formed up to the leading edge, the toner image is not rubbed by the rotating surface of the heat roller 41, and image distortion at the leading edge of the recording paper is prevented, and reliability is improved. Improvements are being made.

1 is a front sectional view showing a schematic configuration of an image forming apparatus 1. FIG. FIG. 3 is a front cross-sectional view showing the configuration of the fixing unit 4. FIG. 4 is a diagram for explaining an entry path 16 where a recording sheet reaches a nip portion 48 between a heat roller 41 and a press roller. FIG. 4 is a diagram for explaining an entry path 16 where a recording sheet reaches a nip portion 48 between a heat roller 41 and a press roller.

Explanation of symbols

1 image forming apparatus 4 fixing unit 7 jam access cover 13 spur 16 approach path 17 approach path 41 heat roller 42 press roller 43 first frame 44 second frame 44b guide portion D area X reference line Y auxiliary line α angle θ approach angle

Claims (2)

A photoreceptor,
In an image forming apparatus comprising: a heat roller; and a fixing device that includes a press roller that is in pressure contact with the heat roller.
A spur is provided on the heat roller side of the conveyance path on both sides of the conveyance path of the recording paper from the photoconductor to the nip portion between the heat roller and the press roller, and a guide is provided on the press roller side of the conveyance path. Set up a section,
The spur is arranged on the upstream side of the conveyance path from the guide part,
The recording paper is bent and guided toward the guide portion by the spur so that the recording paper abuts on the guide portion and bends in the conveying direction, and the recording paper guided by the guide portion is conveyed to the nip. In order to prevent the leading end surface of the recording paper from coming into contact with the rotating surface of the heat roller until the leading end of the recording paper reaches the nip,
The approach route is
A straight line connecting the upstream end and the downstream end in the recording paper conveyance direction of the nip portion between the heat roller and the press roller is a reference line,
The tangent line of the press roller, and the tangent line passing through the rotation center of the heat roller as the auxiliary line is the tangent line on the upstream side in the recording paper conveyance direction
When an acute angle among the angles formed by the auxiliary line with respect to the reference line is α,
The approach angle θ of the recording paper conveyed toward the region surrounded by the rotating surface of the heat roller, the rotating surface of the press roller, and the auxiliary line is an angle with respect to the reference line, and 0 <θ ≦ α. To be,
An image forming apparatus. A photoreceptor,
A fixing device comprising: a heat roller; and a press roller in pressure contact with the heat roller;
In an image forming apparatus comprising:
A spur is provided on the heat roller side of the conveyance path on both sides of the conveyance path of the recording paper from the photoconductor to the nip portion between the heat roller and the press roller, and a guide is provided on the press roller side of the conveyance path. Set up a section,
The spur is arranged on the upstream side of the conveyance path from the guide part,
The recording paper is bent and guided toward the guide portion by the spur so that the recording paper abuts on the guide portion and bends the conveyance direction, and is conveyed.
The recording paper guided by the guide portion enters the nip portion so that the leading edge of the recording paper does not contact the rotating surface of the heat roller until the leading edge of the recording paper reaches the nip portion. ,
The approach route is
A straight line connecting the upstream end and the downstream end in the recording paper conveyance direction of the nip portion between the heat roller and the press roller is a reference line,
When the tangent line of the press roller and the tangent line passing through the rotation center of the heat roller is the auxiliary line, the tangent line on the upstream side in the recording paper conveyance direction,
The recording paper enters in a direction parallel to the reference line toward the rotation surface of the press roller located on the downstream side in the recording paper conveyance direction with respect to the auxiliary line.
An image forming apparatus.

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