JP4946390B2 - Image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine or a printer, and more particularly to a structure of a pre-transfer guide unit that guides a recording medium to a transfer unit that transfers a toner image carried on an image carrier to the recording medium.

Conventionally, in Patent Document 1, by adhering a conductive PET sheet to a conductive conveyance guide that conveys a recording medium to a transfer unit, electrostatic adsorption between the recording medium and the sheet is prevented, and there is no transfer failure. There has been proposed an image forming apparatus that enables reliable transfer paper conveyance.
In Patent Document 2, by depositing aluminum on the surface of Mylar as a guide member and grounding it through a metal Mylar support member, it is possible to release electric charges generated by frictional charging of the Mylar surface. An image forming apparatus capable of preventing charging has been proposed.
Patent Document 3 discloses that image formation can be prevented by friction, by providing a thin-walled flexible member made of PET or the like and containing an antistatic agent at a portion where the paper guide member contacts the paper. A device has been proposed.
Patent Document 4 proposes an image forming apparatus in which the friction portion between the guide and the recording medium is covered with a semiconductive material to eliminate static electricity and prevent the occurrence of image noise.

  However, in any of the image forming apparatuses described in the patent documents, since the conductive material is formed up to the tip of the pre-transfer guide, there is a problem that the toner on the intermediate transfer belt is pulled at the tip and the recording medium is soiled. In addition, there is a problem in that a hand touches the pre-rolling guide during jam processing and the tip of the pre-rolling guide comes into contact with the image carrier, that is, the intermediate transfer belt, and the belt surface is damaged.

JP 11-288188 A JP 2000-172083 A JP 2006-64748 A Japanese Patent Laid-Open No. 2004-12551

  The present invention has been made in view of conventional problems, and prevents leakage of the toner image from the image carrier to the pre-transfer guide, protects the image carrier, prevents charging, and prevents transfer failure. It is an object of the present invention to provide an image forming apparatus including a pre-rolling guide that can be used.

As means for solving the above problems, an image forming apparatus according to the present invention includes:
An image carrier that carries the toner image while being carried, a transfer unit that contacts the image carrier and transfers the toner image on the image carrier to a recording medium, and a toner image side of the recording medium In the image forming apparatus comprising: a pre-rolling guide portion that guides the recording medium along a paper path to a nip portion formed by contact between the image carrier and the transfer portion. A first member disposed along the sheet passing path, and attached to the sheet passing path side of the first member, and protrudes toward the nip portion from the tip of the first member to the downstream side of the sheet passing section. A second member made of a flexible material having an insulating property and attached to the sheet passing path side of the second member, and positioned upstream of the sheet passing portion from the tip of the second member. ground is made of a flexible material having a tip, a conductive A third member, characterized in that it comprises a. Here, the recording medium is not limited to plain paper but includes cardboard, OHP sheets, and the like.

  It is preferable that a step portion is provided so that a portion of the first member to which the second member is attached approaches the image carrier.

  The first member is preferably in contact with a frame of the image carrier.

  The first member is preferably urged toward the image carrier by an elastic member.

  According to the present invention, since a member such as insulating flexible PET is used as the second member of the pre-rolling guide portion, it is possible to prevent leakage of the toner image from the image carrier to the pre-rolling guide portion. . In addition, since the third member made of a conductive material is attached to the sheet passing path side of the second member made of an insulating material and grounded, transfer defects due to charging of the second member can be prevented. Furthermore, since the second member made of a flexible material extending toward the nip portion is provided on the first member, the second member made of the flexible material can carry the image even when the pre-rolling guide is touched during the jam processing. Since it contacts the body, the image carrier is protected without being damaged.

Since the first member is provided with the stepped portion, the fixed portion of the second member can be prevented from jumping out onto the recording medium paper surface.

  In addition, since the tip of the third member is located upstream of the tip of the second member and the paper passing path, the second member, which is an insulating member, is interposed between the image carrier and the third member. It is possible to prevent the toner image on the body from being pulled and soiling the recording medium.

  Further, since the first member is brought into contact with the frame of the image carrier, the insulation distance between the pre-rolling guide portion and the image carrier can be accurately determined.

  Since the first member is urged toward the image carrier by the elastic member, the insulation distance can be maintained.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an image forming apparatus 1 according to the present invention.
First, a schematic configuration of the image forming apparatus 1 will be described. The image forming apparatus 1 includes an intermediate transfer belt 2 as an image carrier at a substantially central portion inside. The intermediate transfer belt 2 includes rollers 3a,
It is supported by the outer peripheral part of 3b and is rotationally driven in the arrow A direction. Drive roller 3
a is connected to a drive motor (not shown), and the roller 3b is driven to rotate as the drive roller 3a rotates. Below the lower horizontal part of the intermediate transfer belt 2 is yellow (Y)
, Magenta (M), cyan (C), and black (K), corresponding to the respective colors, four image forming units 4Y, 4M, 4C, and 4K are arranged along the intermediate transfer belt 2. Each of the image forming units 4Y, 4M, 4C, and 4K includes photosensitive drums 5Y, 5M, 5C, and 5K, respectively. Around the photosensitive drums 5Y, 5M, 5C, and 5K, primary transfer rollers 6Y, 6M, 6C that face the photosensitive drums 5Y, 5M, 5C, and 5K with the intermediate transfer belt 2 interposed therebetween.
6K are arranged respectively. The portion of the intermediate transfer belt 2 supported by the driving roller 3 a is in pressure contact with the secondary transfer roller 7, and the nip portion between the secondary transfer roller 7 and the intermediate transfer belt 2 becomes the secondary transfer region 8. ing. A pre-rolling guide portion 10 is disposed in the paper passing path 9 on the upstream side of the secondary transfer region 8. A fixing roller 12 and a pressure roller 13 are arranged in the paper passing path 11 on the downstream side of the secondary transfer region 8. A pressure-contact portion between the fixing roller 12 and the pressure roller 13 is a fixing nip region 14.

At the bottom of the image forming apparatus 1, four types of first, second, third, and fourth types of paper feeding units 15a and 15b are provided.
, 15c, 15d, the first paper feeding unit 15a and the second paper feeding unit 15b are arranged vertically,
The third paper feed unit 15c and the fourth paper feed unit 15d are arranged on the left and right below the second paper feed unit 15b. The sheets stacked and accommodated in each of the paper feeding units 15a, 15b, 15c, and 15d are 1 from the top.
Each sheet is sent out to the sheet passing path 9. A circulation path 16 is provided on the side of the image forming apparatus 1. The single-sided printed paper switched back by the paper discharge roller 17 is the circulation path 1
6, the sheet passing path 9, 1 with the unprinted surface facing the intermediate transfer belt 2 side.
1 is again conveyed upward. A manual paper feeder 18 is provided below the circulation path 16. 19Y, 19M, 19C, and 19K are image forming units 4Y, 4M,
A toner cartridge that supplies toner of each color to 4C and 4K. Reference numeral 20 denotes a control unit that controls the image forming units 4Y, 4M, 4C, and 4K.

Next, a schematic operation of the image forming apparatus 1 having the above configuration will be described. Image reading unit 2
The color print data obtained by reading the image in 1 or the image data output from a personal computer or the like is subjected to predetermined signal processing by the control unit 20 and then yellow (Y),
As image signals of magenta (M), cyan (C), and black (K), each image forming unit 4Y, 4M
4C, 4K. In each of the image forming units 4Y, 4M, 4C, and 4K, a laser beam modulated by an image signal is projected onto the respective photosensitive drums 5Y, 5M, 5C, and 5K, thereby forming an image latent image. On each photosensitive drum 5Y, 5M, 5C, 5K, yellow, magenta,
Cyan and black toner images are formed. The formed yellow, magenta, cyan, and black toner images are primarily transferred onto the moving intermediate transfer belt 2 in sequence by the action of the primary transfer rollers 6Y, 6M, 6C, and 6K. The superimposed toner image formed on the intermediate transfer belt 2 in this way reaches the secondary transfer region 8 as the intermediate transfer belt 2 moves. In the secondary transfer region 8, the superimposed color toner images are collectively applied to the paper supplied from the paper supply units 15 a, 15 b, 15 c, 15 d or the manual paper supply device 18 by the action of the secondary transfer roller 7. Secondary transferred. Next, the sheet on which the toner image is secondarily transferred reaches the fixing nip region 14. In the fixing nip region 14, the toner image is fixed on the sheet by the action of the fixing roller 12 and the pressure roller 13. The sheet on which the toner image is fixed is discharged to the discharge tray 22 via the discharge roller 17.

  Next, the pre-rolling guide portion 10 that guides the sheet to the fixing area of the present invention will be described.

As shown in FIG. 2, the pre-rolling guide unit 10 is attached to the frame 33 of the image forming apparatus 1 so as to be rotatable about the shaft 31 along the sheet passing path 9, and the leaf spring 30 contacts the lower end. As a result, the upper end is biased toward the intermediate transfer belt 2. The upper end of the pre-rolling guide portion 10 is in contact with a protrusion 32 provided on the frame of the intermediate transfer belt 2 in order to determine the positional relationship with the intermediate transfer belt 2.

As shown in FIG. 3, the pre-rolling guide portion 10 includes a first member 41, a second member 42, and a third member 43. The first member 41 is made of sheet metal having a thickness of about 1 mm having conductivity, and ears 34 for inserting the shaft 31 are formed on both side ends. A step portion 44 is provided at a predetermined position from the upper end of the first member 41 so that the step portion 45 approaches the intermediate transfer belt 2. The step 44 has a step difference between a step upper portion 45 and a step lower portion 46 of 1 mm to 2 mm. The second member 42 is made of an insulating flexible PET film and has a rectangular shape with a thickness of about 0.188 mm. The second member 42 is attached to the side of the sheet passing path 9 of the stepped upper portion 45 of the first member 41 with an adhesive S so as not to reach the stepped portion 44. The tip of the second member 42 protrudes from the tip of the first member 41 toward the downstream side of the sheet passing path 9. The third member 43 is made of a conductive film and has a rectangular shape with a thickness of about 0.12 mm. The third member 43 is attached to the sheet passing path 9 side of the second member 42 at the stepped upper portion 45 by an adhesive, but a plurality of third members 43 are attached to eliminate the stepped portion 44 of the first member 41. Another third member 43 is attached from the third member 43 to the stepped portion 46 of the first member 41 with an adhesive. The tip of the third member 43 is positioned upstream of the paper passage 9 between 0.5 mm and 1.5 mm from the tip of the second member 42. The third member 43 is grounded together with the first member 41.

In the pre-transfer guide portion 10 having the above-described configuration, the paper P conveyed through the paper passage path 9 is guided by the tip of the second member 42 and guided to the secondary transfer region 8. At this time, since the conductive third member 43 is grounded, the charge generated by the friction between the tip of the second member 42 made of PET film and the paper P is eliminated, and noise generation and transfer failure are prevented. The The tip of the third member 43 is located upstream of the tip of the second member 42 in the sheet passing path 9, and the distance S <b> 1 from the tip of the third member 43 to the tip of the second member 42 is from the tip of the second member 42. Since the insulation distance S1 + S2 including the distance S2 to the intermediate transfer belt 2 is ensured, no leakage occurs between the third member 43 and the intermediate transfer belt 2. As a result, the third member 43 is prevented from pulling the toner image on the intermediate transfer belt 2 and soiling the paper P. The insulation distance S1 is accurately determined when the third member is attached to the second member, and the insulation distance S2 is accurately determined because the first member 41 is in contact with the protrusion 32. The second member 42 fixed to the upper step 45 by the step portion 44 of the first member 41 does not protrude toward the sheet passing path 9 side of the paper P, so that the paper P does not get caught during conveyance and is smooth. Be transported. Furthermore, since the upper end portion of the first member 41 is in contact with the protrusion 32 of the intermediate transfer belt 2, an insulation distance between the first member 41 and the intermediate transfer belt 2 is ensured.

1 is a schematic diagram showing an image forming apparatus according to the present invention. The side view of an image carrier and a guide part. Sectional drawing of a guide part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Intermediate transfer belt (image carrier)
7 Secondary transfer roller (transfer section)
8 Secondary transfer area (nip)
9 Upstream side paper passage 10 Pre-rolling guide part 30 Leaf spring (elastic member)
32 Projection 33 Frame 41 First member 42 Second member 43 Third member 44 Step P Paper (recording medium)

Claims (4)

An image carrier that carries the toner image while being carried, a transfer unit that contacts the image carrier and transfers the toner image on the image carrier to a recording medium, and a toner image side of the recording medium is, in an image forming apparatus having a rolling front guide portion for guiding said image to said recording medium to a nip portion formed by contact with the carrier and transfer unit along a sheet passing path,
The pre-rolling guide portion includes a first member disposed along the paper passing path,
The first member is attached to the sheet passing path side, and has a tip protruding from the tip of the first member to the downstream side of the sheet passing portion toward the nip portion, and is made of an insulating flexible material. A second member;
The third member, which is attached to the sheet passing path side of the second member, has a tip positioned on the upstream side of the sheet passing portion from the tip of the second member, and is made of a conductive flexible material. When,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein a stepped portion is provided so that a portion of the first member to which the second member is attached approaches the image carrier. It said first member, the image forming apparatus according to claim 1 or 2, characterized in that it is brought into contact with the frame of the image bearing member. The image forming apparatus according to claim 3 , wherein the first member is biased toward the image carrier by an elastic member.

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