JP2006308978A - Separating apparatus for heat fixing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separating apparatus for a heat fixing apparatus in which clearance between a separating plate and a heating roller is at high precision and which can be manufactured at low cost and an image forming apparatus provided with it. <P>SOLUTION: The separating apparatus for the heat fixing apparatus is provided with the heating roller 2 heating paper, a pressurizing roller 3 facing the heating roller 2 and forming a nip part in between and a plate like separating member 6 provided in the vicinity of the nip part. A non paper passing part H of the heating roller is formed to be greater than an exterior diameter of a paper passing part K and the plate like separating member 6 is aligned by being abutted to the non paper passing part H. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat fixing apparatus separating apparatus including a heating roller that heats a sheet and a pressure roller that forms a nip portion between the heating roller and an image forming apparatus including the same.

2. Description of the Related Art Image forming apparatuses (copiers, printers, facsimiles) using electrophotographic technology use a heat fixing device that melts and presses a toner image transferred onto a sheet to fix it on the sheet (for example, a patent) Reference 1).
The heat fixing device fixes a toner image on a sheet by passing the sheet on which an unfixed toner image is formed through a nip formed by a heating roller heated by a heater and a pressure roller.
When the toner is melted, adhesiveness is generated, so that the paper on which the toner image is formed is wound around the fixing roller. For this reason, a release layer made of a material such as fluororesin or silicon rubber is provided on the surface of the fixing roller to prevent winding around the fixing roller due to adhesion of toner.
FIG. 6 is a schematic view showing a first example of a separation device of a conventional heat fixing device. FIG. 7 is a schematic view showing a second example of a separation device of a conventional heat fixing device. 6 and 7, the heat fixing device 1 includes a heat roller 2 and a pressure roller 3 disposed to face the heat roller 2.
In the vicinity of the exit of the nip formed by the heating roller 2 heated by a heater (not shown) and the pressure roller 3 facing each other, a separation member 5 as a separation device is disposed.
Referring to FIG. 6, the separation member 5 that is a separation device is made of heat-resistant resin and is supported so as to be rotatable around a fulcrum. The separation member 5 includes a separation claw 5a extending in the vicinity of the nip portion outlet. In this case, a pressure is applied to the separation member 5 by the spring 4 so that the separation claw 5 a contacts the heating roller 2.
The separation claw 5a is coated with a fluororesin in order to prevent wear with the heating roller 2. The separation claw 5a has a claw width of about 2 to 10 mm, and a plurality of claw widths are installed within the sheet passing range.
Since the separation claw 5a is in contact with the heating roller 2, the portion where the separation claw 5a is in contact with the heating roller 2 is worn out, and there is a problem that the abrasion scratches appear in the toner image.
Further, the tip angle of the separation claw 5a is limited to about 20 ° in the manufacturing method, and it is difficult to bring the tip of the claw close to the nip portion outlet. Since the image at the front end of the paper is wound around the heating roller 2 from the nip exit to the front end of the separation claw 5a, the longer the distance is, the more the image at the front end of the paper becomes so much heat that an abnormal image is generated.

Therefore, in recent years, as shown in FIG. 7, the separation plate 6 has begun to be used as a separation member that is a separation device. The separation plate 6 includes a sheet metal frame 6a provided with a rotation fulcrum, an abutting member 6b made of heat-resistant resin, and a thin plate 6c of about 0.3 mm connecting the sheet metal frame 6a and the abutting member 6b. A pressure is applied to the thin plate 6c by a spring 4 so as to contact the heating roller 2.
The thin plate 6c extends over the entire sheet passing range, and is provided by the abutting member 6b so that the clearance between the heating roller 2 and the thin plate 6c is 0.5 mm. According to the disclosure of Patent Document 1, the clearance is determined by providing convex members at both ends of the separation plate and adjusting and fixing the separation plate with a jig or the like.
Since the leading edge of the thin plate 6c is provided close to the exit of the nip portion, if a margin of several millimeters is provided at the leading edge of the sheet, the sheet is separated from the heating roller 2 by the separating plate 6 before being wound around the heating roller 2. Securely separated.
Since the thin plate 6c rubs against the paper, it is coated with a fluororesin to prevent toner adhesion. Since the thin plate 6c of the separation plate 6 is disposed in non-contact with the heating roller 2 and is close to the exit of the nip portion, the problem of the separation claw described with reference to FIG. 6 can be prevented.
JP 2002-311741 A

In such a separating plate 6, since it is important to manage the clearance with the heating roller 2, it is desirable to provide an abutting member 6b at the tip of the thin plate 6c. However, since the abutting member 6b made of heat resistant resin has a thickness of several millimeters, it abuts at a position away from the vicinity of the nip portion.
Moreover, since it is comprised by three components, the abutting member 6b, the sheet metal frame 6a, and the thin plate 6c, the difference | error of a component and the attachment error between components also generate | occur | produce. Therefore, an error is likely to occur in the clearance at the tip of the thin plate 6c, and there is a problem that the target value of the clearance has to be increased. The wider the clearance, the easier it is for the paper to slip into it, and the frequency of paper jams increases.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a separation apparatus for a heat fixing device and an image forming apparatus provided with the separation device, which can be manufactured at a low cost with a high clearance between the separation plate and the heating roller in consideration of the above situation. It is in.

In order to solve the above problems, the invention described in claim 1 is directed to a heating roller, a pressure roller that presses against the heating roller to form a nip portion, and a plate-like separation provided in the vicinity of the nip portion. A heating fixing device including a member, and the heating roller includes a small-diameter paper passing portion and a large-diameter non-paper passing portion positioned at both ends of the paper passing portion. The leading end is positioned by being abutted against the non-sheet passing portion.
According to a second aspect of the present invention, in the first aspect, the plate-like separation member is a thin plate, and a minute clearance between the thin plate and the paper passing portion of the heating roller is reduced with a non-paper passing portion at both ends of the heating roller. It is characterized by determining by the step between.
According to a third aspect of the present invention, there is provided an image forming apparatus including the heat fixing device separation device according to the first or second aspect.

  According to the present invention, since the large-diameter non-sheet passing portion is disposed at both ends of the small-diameter sheet passing portion located in the center of the heating roller, and the thin plate itself of the separating plate is abutted against the portions, The cost of parts can be reduced by eliminating the need for the abutting member provided at the same time, and the accuracy of the tip position of the thin plate as the separation plate can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a heat fixing apparatus to which the present invention is applied. In FIG. 1, the heating roller 2 includes a cored bar 2a made of a metal pipe and a release layer 2b applied on the surface thereof.
As the release layer 2b, various configurations such as a fluororesin coating (thickness of 10 to 50 μm), silicon rubber (thickness of 0.3 to 3 mm) and a fluororesin coating (thickness of 10 to 50 μm) can be adopted.
A halogen heater 7 is provided inside the pipe-shaped cored bar 2a, and on / off control is performed so that the measured temperature of a temperature detecting element (not shown) for detecting the surface temperature of the heating roller 2 becomes constant.
A pressure roller 3 having a configuration similar to that of the heating roller 2 is pressed against the heating roller 2 and is driven to rotate. The paper 8 on which the toner image is formed is conveyed from the right to the left in the figure, and is guided by the entrance guide plate 9 to the nip portion formed by the pressure roller 3 facing the heating roller 2.
The toner heated and pressurized in the nip portion is fixed on the paper 8 and guided to the separation plate 6 and the outlet guide plate 10 to be discharged. Since the sheet 8 is wrapped around the heating roller 2 side in contact with the toner surface due to the adhesive force of the toner, the front end of the separation plate 6 is disposed immediately after the nip portion, and the front end of the separation plate and the peripheral surface of the heating roller 2 The clearance is about 0.5 mm.
On the other hand, on the pressure roller 3 side, no toner adhesive force is generated. Therefore, the clearance between the outlet guide plate 10 made of heat-resistant resin and the heating roller 2 is set to about 2 to 3 mm.

FIG. 2 is a schematic view showing a heat fixing apparatus provided with a separation apparatus according to the present invention. FIG. 3 is a schematic view showing the configuration of the heating roller of the heat fixing device provided with the separation device according to the present invention.
2 and 3, the heating roller 2 is set so that the outer diameter of the non-sheet passing portion H is larger than the outer diameter of the sheet passing range K. That is, the heating roller 2 includes a sheet passing range K having a small diameter and a non-sheet passing portion H having a large diameter located on both sides of the sheet passing range K. The outer diameter difference between the non-sheet passing portion H and the sheet passing range K is 1 mm. Since there is a surface cutting process when the heating roller 2 is manufactured, the shape is manufactured during the cutting process.
After the cutting process, the surface of the non-sheet passing portion H and the sheet passing range K is coated with a fluororesin. The journal portion 11 protruding from the center of both ends of the heating roller 2 is rotatably supported by a housing 12 (not shown) of the heat fixing device 1 by a bearing 12.
Both end journal portions 13 of the pressure roller 3 are rotatably supported by bearings 14. The bearing 14 is pressed in the direction of the heating roller 2 by a spring 15.
As a result, the body of the pressure roller 3 comes into contact with the sheet passing surface (sheet passing range K) of the heating roller 2 to form a nip. The body length of the pressure roller 3 is shorter than the length of the sheet passing surface K of the heating roller 2.
As described above, the heat fixing apparatus of the present invention includes the heat roller 2, the pressure roller 3 that presses against the heat roller 2 to form a nip portion, and the plate-like separation member 6 (6c) provided near the nip portion. , The heating roller is composed of a small-diameter sheet passing portion K and large-diameter non-sheet passing portions H positioned at both ends of the sheet passing portion K, and the tip of the plate-shaped separation member Is positioned against the non-sheet passing portion.
Further, the plate-like separation member is a thin plate 6c, and a minute clearance between the thin plate and the sheet passing portion of the heating roller is determined by a step between the non-sheet passing portions at both ends of the heating roller.
FIG. 2 shows a separation plate 6 of a separation member which is a separation device partially corresponding to the conventional example of FIG. The separation plate 6 includes a sheet metal frame 6a provided with a rotation fulcrum 6d and a thin plate 6c appropriately fixed to the sheet metal frame 6a. A pressure is applied to the thin plate 6c by a spring 4 so as to contact the heating roller 2.

FIG. 4 is a detailed view illustrating the configuration of the separation plate of the separation member which is the separation device according to the present invention. In FIG. 4, the separating plate 6 comprises a sheet metal frame 6a and a flat plate 6c welded thereto. The thin plate 6c has a base portion fixed to the sheet metal frame 6a, and a tip portion protruding in a free end shape is extended toward the nip portion. A fluororesin coating is applied to the lower surface of the thin plate 6 c that contacts the paper (not shown) and the contact surface (upper surface) to the heating roller 2.
The length to the tip of the separation plate 6 is defined as 1 if the distance from the thin plate 6c portion intersecting the rotation fulcrum 6d of the separation plate 6 to the contact portion between the heating roller 2 and the thin plate 6c is l.
The length of the surface la in contact with the non-sheet-passing surface H is la> l
The length of the surface lb in contact with the sheet passing surface K is lb≈l
It is trying to become.
That is, as shown in the plan view of the main part of the thin plate shown in the lower side of FIG. 4, the portion of the thin plate that contacts the non-sheet passing surface (non-sheet passing portion) H is more than the portion adjacent to the sheet passing surface (sheet passing portion) K It is long.
With such a configuration, the thin plate 6 c of the separation plate 6 is in surface contact with the non-sheet passing portion H (both ends) of the heating roller 2. In the paper passing portion K, the clearance L with the heating roller 2 is
Heat roller outer diameter difference / 2
It is positioned with high accuracy so that

FIG. 5 is a schematic view showing an image forming apparatus to which the heat fixing apparatus separating apparatus according to the present invention is applied. In FIG. 5, a reading unit 12 is provided for scanning a document placed on a pressure plate. The reading unit 12 includes a contact glass 20 on which an original is placed and an optical scanning system.
The optical scanning system includes an exposure lamp 13, a first mirror 14, a second mirror 17, a third mirror 18, a lens 15, a CCD image sensor 16, and the like. The original image is read by the CCD image sensor 16 and converted into an electrical signal for processing.
In a sheet document automatic reading apparatus A for automatically reading a sheet document, a document (not shown) placed on a document table B is sent to the position of a document reading sensor G by a feed roller C. The original passes through the original reading sensor G at a constant speed, and at this time, the image on the front side of the original is read by the original reading sensor G.
The read image data is sequentially stored in an image memory (not shown) after image processing (various corrections, compression, etc.). The writing unit 49 includes a laser output unit 19, an imaging lens 21, and a mirror 22, and a laser beam output from the writing unit 49 is applied to the image forming type photoconductor 30.
The procedure for printing an image formed on the photoreceptor 30 is roughly as follows. The sheets stacked on the first tray 23, the second tray 24, and the third tray 25 are fed by the first paper feeding device 26, the second paper feeding device 27, and the third paper feeding device 28, respectively, and are vertically transported. 29 is conveyed to a position where it abuts against the photoreceptor 30.

The image data on the image memory is written onto the photoconductor 30 by the laser light from the writing unit 49 and passes through the developing unit 35 to form a toner image.
The toner image on the photoreceptor 30 is transferred while the sheet (not shown) is conveyed by the conveyor belt 31 at the same speed as the rotation of the photoreceptor 30. Thereafter, the image is fixed by the fixing device 1 and is discharged to the paper discharge tray 33 by the paper discharge unit 32.
When images are to be formed on both sides, the reversing path switching claw (not shown) is switched for the paper fed from each of the paper feed trays 23 to 25 and imaged. As a result, the sheet is conveyed to the duplex entrance conveyance path 38 without being guided to the discharge tray 33 side, is guided to the reversing unit 37 provided in the duplex conveyance unit 36, and is temporarily stored in the switchback conveyance 41.
The paper is fed back in the reverse direction (re-feeding direction) by the reverse conveying means, guided downward by a reverse paper discharge switching claw (not shown), reversed, and sent to a double-sided intermediate conveyance path 43 provided below the reverse paper feeding switching claw.
Then, the intermediate conveying means 40 and the double-sided outlet conveying means 42 connected to a driving source (motor) (not shown) are again sent to the vertical conveying unit 29 to print an image on the back surface and then discharged.
When the paper is reversed and discharged, the paper that has been switched back by the reversing unit 37 is sent out to the reverse paper discharge conveyance path 39 by the paper discharge reverse switching claw without passing through the double-sided intermediate conveyance 43 and discharged again. Returned to unit 32 and discharged out of main body.
The sheet discharged from the main body is discharged to either the discharge tray 33 or the finisher 44 of the main body by a discharge destination switching claw (not shown). The paper discharged to the finisher 44 passes through the punch unit 48 for punch hole processing, and is once stacked on the stack tray 45 for stapling. After all the sheets are collected in the stack tray, the sheet bundle is bound by the stapler unit 46 and discharged to the discharge tray 47.

1 is a schematic view showing a heat fixing apparatus to which the present invention is applied. 1 is a schematic view showing a heat fixing device provided with a separation device according to the present invention. Schematic which shows the structure of the heating roller of the heat fixing apparatus provided with the separation apparatus by this invention. FIG. 5 is a detailed view illustrating the configuration of a separation plate of a separation member that is a separation device according to the present invention. 1 is a schematic view showing an image forming apparatus to which a heat fixing device separation device according to the present invention is applied. Schematic which shows the 1st example of the separation apparatus of the conventional heat fixing apparatus. Schematic which shows the 2nd example of the separation apparatus of the conventional heat fixing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat-fixing apparatus, 2 Heating roller, 3 Pressure roller, 6 Separation member (separation plate), 6a Sheet metal frame, 6c Thin plate, H Non-sheet passing part, K Sheet passing part (sheet passing surface, sheet passing range)

Claims (3)

  In a heat fixing apparatus comprising a heating roller, a pressure roller that presses against the heating roller to form a nip portion, and a plate-like separation member provided in the vicinity of the nip portion, the heating roller has a small-diameter passage. It is composed of a paper part and a large-diameter non-paper passing part positioned at both ends of the paper passing part, and the tip of the plate-shaped separation member is abutted against the non-paper passing part and positioned. Separating device for heat fixing device.   The plate-like separation member is a thin plate, and a minute clearance between the thin plate and a sheet passing portion of the heating roller is determined by a step between the non-sheet passing portions at both ends of the heating roller. The separation apparatus for a heat fixing apparatus according to claim 1. An image forming apparatus comprising the heat fixing device separation device according to claim 1.

Images