JP2007119214A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct a curl caused on a paper delivered on a paper delivery tray and swelling a central region in the direction of conveyance downward. <P>SOLUTION: A printer 2 is provided with the paper delivery tray 64, a fixing device 50, a delivery conveyance passage 60, a pair of delivery rollers 66, and a pair of conveyance rollers 68 arranged at upstream side positions of the pair of delivery rollers 66. Peripheral speed of the pair of delivery rollers 66 is set to be lower than peripheral speed of the pair of conveyance rollers 68. The centers of axes of a driving roller 66a and a driven roller 66b of the pair of delivery rollers 66 when viewing the pair of delivery rollers 66 and the pair of conveyance rollers 68 in the axial direction are arranged at positions on the opposite side to the direction of delivery by using a virtual vertical line L passing through the center of axis of the driving roller 68a in the pair of conveyance rollers 68 positioned on the opposite side to the direction of delivery of paper by the pair of delivery rollers 66. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

Electrophotographic image forming apparatuses such as copiers, laser printers, and facsimile machines. More specifically, a discharge tray, a fixing device disposed below the discharge tray, and an upper side from the downstream side of the fixing device. A discharge conveyance path that curves in the upper end area and is directed toward the paper discharge tray, reverses the sheet on which the toner image is fixed by the fixing device, and guides the paper to the paper discharge tray, and a downstream end of the discharge conveyance path The present invention relates to an image forming apparatus provided with a pair of discharge rollers disposed on the upstream side and a pair of conveyance rollers disposed at an upstream position of the discharge conveyance path closest to the pair of discharge rollers.

One typical example of the image forming apparatus is a paper discharge tray that extends substantially in the horizontal direction, a fixing device that is disposed below the paper discharge tray, and extends upward from the downstream side of the fixing device. In addition, the paper is curved at the upper end region and directed toward the paper discharge tray, and is disposed at the downstream end of the paper discharge conveyance path that reverses the paper on which the toner image is fixed by the fixing device and guides it to the paper discharge tray. And a pair of transport rollers disposed in the upstream position of the discharge transport path closest to the pair of discharge rollers (see Patent Document 1). The paper discharge tray is formed by a partial area on the upper surface of the image forming apparatus main body, and the paper on which the toner image is formed is reversed and discharged to the paper discharge tray. The discharge conveyance path extends substantially vertically upward on one side of the image forming apparatus main body along the one side, curves in a substantially perpendicular direction in the upper end region, and then substantially toward the discharge tray. Extends horizontally. Two pairs of conveyance rollers are provided in the discharge conveyance path. Another discharge conveyance path for discharging the sheet without being reversed by the fixing apparatus is formed at a position immediately downstream of the fixing apparatus, and a conveyance path switching guide member is provided at a branch portion with the discharge conveyance path. . The conveyance path switching guide member is switched so as to selectively guide the sheet on which the toner image is fixed by the fixing device to the discharge conveyance path or another discharge conveyance path. The sheet guided to the other discharge conveyance path is discharged from the discharge port formed on the one side of the image forming apparatus main body to the other discharge tray without being reversed.

In the image forming apparatus, it is desirable that the paper discharged to any of the paper discharge trays has as little curling as possible. The causes of curling are generally the difference in expansion due to the difference in the amount of heat applied to the front and back of the paper in the fixing device, the shape of the nip formed between the heat fixing roller and the pressure roller of the fixing device, and heat fixing. The difference in thickness or hardness in the rubber layer of the roller and the pressure roller can be mentioned, but it may also occur due to the layout of the conveying roller pair arranged immediately downstream of the heat fixing roller of the fixing device. Was confirmed by the present inventors.

That is, in order to provide the image forming apparatus with a double-sided image forming function, a sheet reversing device for double-sided image formation may be attached to the image forming apparatus body. In this case, when performing double-sided image formation, the sheet on which the toner image is fixed on one side by the fixing device is guided to another discharge conveyance path by the conveyance path switching guide member, and the one side of the image forming apparatus main body From the discharge port formed in the sheet, it is carried into the sheet reversing device. Then, in order to smoothly carry in the paper from the image forming apparatus to the paper reversing device, the position of the conveying roller pair disposed immediately downstream of the fixing device must be disposed below a predetermined position. There was a case where it was not possible to obtain. In such a layout, the sheet on which the toner image is fixed on one side by the fixing device is guided to the discharge conveyance path by the conveyance path switching guide member, and the pair of conveyance rollers disposed in the discharge conveyance path and the fixing device When the paper is transported upward along the discharge transport path by cooperation with the transport roller pair disposed on the immediately downstream side, the transport roller pair disposed on the immediately downstream side of the fixing device. Is pulled downward at the nip portion of As a result, when the paper was reversed and discharged to the paper discharge tray, curling occurred such that the central area in the paper conveyance direction swelled downward.
JP 2004-331387 A

SUMMARY OF THE INVENTION An object of the present invention is to make it possible to correct a curl that occurs in a sheet that is reversed and discharged to a discharge tray after passing through a fixing device, such that the central region in the transport direction swells downward. An image forming apparatus is provided.

According to the present invention,
A paper discharge tray that extends substantially in the horizontal direction, a fixing device disposed below the paper discharge tray, and extends upward from the downstream side of the fixing device and is curved and discharged in the upper end region. A discharge conveyance path that is directed to the paper tray and reverses the sheet on which the toner image has been fixed by the fixing device and guides it to the discharge tray, a pair of discharge rollers disposed at the downstream end of the discharge conveyance path, and a discharge conveyance path In the image forming apparatus provided with a pair of conveying rollers disposed at the upstream position closest to the pair of discharge rollers
The peripheral speed of the discharge roller pair is set slower than the peripheral speed of the pair of transport rollers,
When the discharge roller pair and the conveyance roller pair are viewed in the axial direction, the axial center of each of the pair of rollers constituting the discharge roller pair is the same as that of the pair of rollers constituting the conveyance roller pair. With reference to a virtual vertical line passing through the axial center of one of the rollers located on the opposite side with respect to the discharge direction, it is disposed at a position on the opposite side with respect to the discharge direction.
An image forming apparatus is provided.

Embodiments of an image forming apparatus configured according to the present invention will be described below in detail with reference to the accompanying drawings.

A tandem color printer 2 (hereinafter simply referred to as “printer 2”), which is an image forming apparatus according to the present invention, will be described with reference to FIG.

The printer 2 includes a printer main body 4 (hereinafter simply referred to as “main body 4”) which is a substantially rectangular parallelepiped image forming apparatus main body. In the main body 4, a yellow process unit 6, a magenta process unit 8, a cyan process unit 10, and a black process unit 12 are arranged in this order from left to right in FIG. Each of these process units 6, 8, 10, and 12 includes image forming elements such as the photosensitive drum 14, the charger 16, the LED head 18, the developing device 20, the primary transfer roller 22, and the cleaning device 24. In FIG. 1, for simplification of illustration, the symbol of the image forming element is attached only to the black process unit 12. These process units 6, 8, 10 and 12 are juxtaposed in the above order in a substantially horizontal direction, in the embodiment, in a substantially straight line from left to diagonally upward in FIG.

To the developing devices 20 of the process units 6, 8, 10 and 12, toner replenishing containers 20Y, 20M, 20C and 20B for replenishing the corresponding color toners are mounted, respectively. An intermediate transfer belt mechanism 26 is disposed below the process units 6, 8, 10, and 12. The intermediate transfer belt mechanism 26 includes a driving roller 28, driven rollers 30 and 32, and an intermediate transfer belt 34 wound around these rollers. A cleaning device 35 for cleaning the intermediate transfer belt 34 is disposed adjacent to the left end of the intermediate transfer belt mechanism 26 in FIG.

In each of the process units 6, 8, 10, and 12, the primary transfer roller 22 is pressed against the photosensitive drum 14 from below through the upper end travel region of the intermediate transfer belt 34. A secondary transfer roller 36 is disposed below the driven roller 32, and the secondary transfer roller 36 is pressed against the driven roller 32 from below via an intermediate transfer belt 34. Since the drive roller 28 is driven to rotate clockwise in FIG. 1, the intermediate transfer belt 34, the primary transfer roller 22, and the driven rollers 30 and 32 are also rotated clockwise.

Below the intermediate transfer belt mechanism 26, a main conveyance path 38 for conveying a sheet as a recording medium extends substantially horizontally in the left-right direction in FIG. A nip portion between the secondary transfer roller 36 and the driven roller 32 is disposed in the middle of the main conveyance path 38. A paper feed cassette 40 is disposed below the main conveyance path 38. A pickup roller 42 is disposed immediately above the right end of the sheet feeding cassette 40 in FIG. 1, and a separation roller pair 44 is disposed downstream of the pickup roller 42. The downstream side of the separation roller pair 44 is connected to the main conveyance path 38 via the reverse path 46. A registration roller pair 48 is disposed on the upstream side of the main transfer path 38 from the secondary transfer roller 36.

1 and 2, a fixing device 50 is disposed on the downstream side of the secondary transfer roller 36 in the main conveyance path 38, and a conveyance roller pair 52 is provided on the downstream side of the fixing device 50. Is arranged. The fixing device 50 includes a heat fixing roller 54 and a pressure belt unit 56. The pressure belt unit 56 includes a pair of support rollers 56A and an endless belt 56B wound around each of the support rollers 56A. Each of the support rollers 56A is pressed against the heat fixing roller 54 via an endless belt 56B by pressing means (not shown). The conveying roller pair 52 includes a driving roller 52 a and a driven roller 52 b that are a pair of rollers constituting the conveying roller pair 52. The main conveyance path 38 is connected to a discharge conveyance path 60 and another discharge conveyance path 72 (shown only in FIG. 1) at a downstream end thereof (a downstream end that is directly downstream of the conveyance roller pair 52). .

A paper discharge tray 64 is disposed in a partial area on the upper surface of the main body 4 so as to extend in a substantially horizontal direction. The discharge conveyance path 60 that reverses the sheet on which the toner image has been fixed by the fixing device 50 and guides the sheet to the paper discharge tray 64 is provided on the main body 4 from the downstream side of the fixing device 50, in the embodiment, from the downstream side of the conveyance roller pair 52. The inside of the one side 4a extends upward substantially along the one side 4a, and is arranged so as to curve in a substantially right angle direction toward the discharge tray 64 in the upper end region. A discharge roller pair 66 is disposed at the downstream end of the discharge conveyance path 60, and a conveyance roller pair 68 is disposed at an upstream position closest to the discharge roller pair 66 in the discharge conveyance path 60. The discharge roller pair 66 includes a drive roller 66 a and a driven roller 66 b that are a pair of rollers constituting the discharge roller pair 66. The conveying roller pair 68 includes a driving roller 68 a and a driven roller 68 b that are a pair of rollers constituting the conveying roller pair 68. In the illustrated embodiment, the driving roller 66a and the driven roller 66b of the discharge roller pair 66 are arranged in the vertical direction, and the driving roller 68a and the driven roller 68b of the conveying roller pair 68 are arranged in a substantially horizontal direction. . The heat fixing roller 54, the driving roller 52a of the conveying roller pair 52, the driving roller 68a of the conveying roller pair 68, and the driving roller 66a of the discharge roller pair 66 are connected to an electric motor (not shown).

Referring to FIG. 1, the position immediately downstream of fixing device 50, in the embodiment, the position immediately downstream of conveyance roller pair 52, is substantially obliquely downward toward discharge port 70 formed on one side 4 a of main body 4. Another discharge conveyance path 72 is formed to extend to. On one side 4a of the main body 4, another paper discharge tray (not shown) that receives the paper discharged through the discharge port 70 is disposed so as to be foldable along the one side 4a. A conveyance path switching guide member 74 is provided at a branch portion between the discharge conveyance path 60 and another discharge conveyance path 72. The conveyance path switching guide member 74 is switched by an actuator (not shown) so as to selectively guide the sheet on which the toner image is fixed by the fixing device 50 to the discharge conveyance path 60 or another discharge conveyance path 72.

Since the printing operation itself is performed in the printer 2 as is well known, a brief description will be given below with reference to FIG. When printing is performed, in the process units 6, 8, 10, and 12, the surface of the photosensitive drum 14 that is uniformly charged by the charger 16 is exposed by the LED head 18, thereby forming an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 20 to become a toner image. The toner images are sequentially superimposed and transferred from the toner images formed by the upstream process unit 6 onto the intermediate transfer belt 34 of the intermediate transfer belt mechanism 26 by the primary transfer roller 22. The color toner image transferred to the intermediate transfer belt 34 is transferred to the sheet while the sheet fed from the sheet feeding cassette 40 passes through the nip portion between the driven roller 32 and the secondary transfer roller 36. The toner image transferred onto the paper is thermally fixed onto the paper while passing through the fixing device 50.

The sheet on which the toner image is fixed is conveyed by the conveyance roller pair 52, and the sheet conveyed by the conveyance roller pair 52 is guided to the discharge conveyance path 60 or another discharge conveyance path 62 by the conveyance path switching guide member 74. The The sheet guided to the discharge conveyance path 60 is discharged to the discharge tray 64 by the conveyance roller pair 68 and the discharge roller pair 66 (in a face-down state). On the other hand, the sheet guided to the other discharge conveyance path 72 is discharged through the discharge port 70 in a state where it is not reversed (in a face-up state) to a discharge tray (not shown).

1 and 2, in the printer 2, the peripheral speed of the discharge roller pair 66 is higher than the peripheral speed of the transport roller pair 68 disposed at the upstream position closest to the discharge roller pair 66. Is set too late. When the discharge roller pair 66 and the transport roller pair 68 are viewed in the axial direction (as viewed in the direction perpendicular to the paper surface in FIGS. 1 and 2), the drive roller 66a and the driven roller 66b constituting the discharge roller pair 66 are The shaft center in each of the driving roller 68a and the driven roller 68b constituting the conveying roller pair 68 is opposite to the sheet discharge direction (rightward in FIGS. 1 and 2) by the discharge roller pair 66 (FIGS. 1 and 2). With reference to a virtual vertical line L (virtual vertical line L indicated by a two-dot chain line in FIG. 2) passing through the axial center of one roller located on the left side in FIG. 2, in the embodiment, the driving roller 68a, The sheet is disposed at a position opposite to the sheet discharge direction by the discharge roller pair 66. In the embodiment in which the shaft centers of the driving roller 66a and the driven roller 66b constituting the discharge roller pair 66 are arranged on the virtual vertical line L, the “by the discharge roller pair 66 on the basis of the virtual vertical line L” may be used. It is included in “disposed at a position opposite to the paper discharge direction”.

In relation to such a configuration, the discharge conveyance path 60 extends substantially vertically on the upstream side and the immediately downstream side of the conveyance roller pair 68, but on the downstream side, the discharge roller pair 66. (In FIG. 1 and FIG. 2, after extending substantially straight in the direction approaching the one side 4a), the straight line of the discharge roller pair 66 is extended. In the downstream position, it is formed to curve toward the discharge roller pair 66. In FIG. 2, reference numeral 60 </ b> C indicates the curve area formed in the discharge conveyance path 60. In the discharge conveyance path 60, the conveyance direction of the sheet is changed at an angle smaller than 90 degrees between the upstream end and the downstream end of the curved region 60C.

When the sheet on which the toner image is fixed by the fixing device 50 is conveyed to a position straddling the conveyance roller pair 68 and the discharge roller pair 66 in the discharge conveyance path 60, the sheet is conveyed to the conveyance roller pair 68 and the discharge roller pair. 66 is conveyed by cooperation. At this time, the peripheral speed of the discharge roller pair 66 is set slower than the peripheral speed of the transport roller pair 68 disposed at the closest upstream position with respect to the discharge roller pair 66. 68 and the discharge roller pair 66 are bent. This bending is absorbed by the curve region 60 </ b> C of the discharge conveyance path 60. As a result, it is possible to correct a curl that causes the central region in the transport direction to swell downward, which is to be generated on the paper discharged to the paper discharge tray 64 in a reversed state after passing through the fixing device 50. .

1 is a schematic cross-sectional view showing an embodiment of an image forming apparatus configured according to the present invention. FIG. 2 is an enlarged schematic cross-sectional view illustrating a part of the image forming apparatus illustrated in FIG. 1.

Explanation of symbols

2: Tandem color printer (image forming device)
4: Printer body (image forming apparatus body)
50: fixing device 60: discharge conveyance path 60C: curve area 64 of discharge conveyance path: discharge tray 66: discharge roller 66a: driving roller 66b: driven roller 68: conveying roller 68a: driving roller 68b: driven roller L: virtual vertical line

Claims (1)

A paper discharge tray that extends substantially in the horizontal direction, a fixing device disposed below the paper discharge tray, and extends upward from the downstream side of the fixing device and is curved and discharged in the upper end region. A discharge conveyance path that is directed to the paper tray and reverses the sheet on which the toner image has been fixed by the fixing device and guides it to the discharge tray, a pair of discharge rollers disposed at the downstream end of the discharge conveyance path, and a discharge conveyance path In the image forming apparatus provided with the pair of conveying rollers disposed at the upstream position closest to the pair of discharge rollers,
The peripheral speed of the discharge roller pair is set slower than the peripheral speed of the pair of transport rollers,
When the discharge roller pair and the conveyance roller pair are viewed in the axial direction, the axial center of each of the pair of rollers constituting the discharge roller pair is the same as that of the pair of rollers constituting the conveyance roller pair. With reference to a virtual vertical line passing through the axial center of one of the rollers located on the opposite side with respect to the discharge direction, it is disposed at a position on the opposite side with respect to the discharge direction.
An image forming apparatus.

Images