JP2008170597A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device consisting of a fixing belt, pressing member and pressure roller, and has high releasability of a recording member from the fixing belt or pressure roller, and is free from slip between the fixing belt and pressure roller, and to provide an image forming apparatus having the fixing device. <P>SOLUTION: The fixing device consisting of the fixing belt, pressing member and pressure roller, is constituted so that the fixing belt is heated by a heating member to a temperature required to melt toner, the pressing member is disposed inside the fixing belt, the pressing member and pressure roller are pressed against each other via the fixing belt, and an insulative fluororesin layer is formed on the surfaces of the pressure roller and fixing belt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a belt-type fixing device and an image forming apparatus using the same.

A fixing device including a fixing belt, a pressing member, and a pressure roller. The pressing member is disposed inside the fixing belt, and the pressing member and the pressure roller are pressed through the fixing belt to form a nip portion. A fixing device in which a sheet heating element is brought into contact with the inside of the fixing belt and the fixing belt is heated has been studied (for example, see Patent Document 1). The fixing belt of the fixing device was charged by an eddy current from the sheet heating element, and the recording member that passed through the nip portion was difficult to peel from the fixing belt.
On the other hand, it is a fixing device comprising a roller pair consisting of a fixing roller and a pressure roller, and a recording member on which an unfixed toner image is placed is nipped and conveyed by the roller pair, and the toner image is heated and melted to be fixed to the recording member. In order to improve the releasability of the recording member from the fixing roller, a fixing device that applies a bias to a pressure roller provided with a PFA (perfluoroalkoxyalkane) layer containing carbon black on the surface has been studied (for example, Patent Document 2). When the pressure roller of the fixing device is a driving roller, a sufficient frictional force cannot be obtained, so the fixing roller slides stably without being driven and rotated, and the recording member is wound around the pressure roller. The problem occurs.
JP 2003-287969 A JP 2003-84615 A

  The problem to be solved by the present invention is composed of a fixing belt, a pressing member, and a pressure roller. The recording member is highly peelable from the fixing belt and the pressure roller, and the fixing belt and the pressure roller do not slip. A fixing device and an image forming apparatus including the fixing device are provided.

The present invention is a fixing device including a fixing belt, a pressing member, and a pressure roller. The fixing belt is heated to a temperature necessary for melting the toner by a heating member, and the pressing member is disposed inside the fixing belt. This is a fixing device in which a pressing member and a pressure roller are pressed via a fixing belt, and an insulating fluororesin layer is formed on the surface of the pressure roller and the surface of the fixing belt.
In a preferred embodiment of the present invention, in the fixing device, the fluororesin is a perfluoroalkoxyalkane.
The present invention is an image forming apparatus including the fixing device.
A sufficiently high frictional force is generated between the pressure roller and the fixing belt of the fixing device of the present invention, and the fixing belt is stably driven and rotated. The fixing belt of the fixing device of the present invention is not charged by eddy current, and the recording member is peelable from the fixing belt. Furthermore, the pressure roller of the fixing device of the present invention has an insulating fluororesin layer on the surface, and the recording member is highly peelable from the pressure roller.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating the overall configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming unit irradiates the photosensitive member 1 that is an image carrier, the charging roller 2 that uniformly charges the photosensitive member, and the uniformly charged photosensitive member 1 with a laser beam modulated by an image signal. It comprises an exposure device 3 for forming an electrostatic latent image. The developing unit is composed of yellow, magenta, cyan, and black color developing machines 5 arranged in the developing rotary 4, and each color developing machine sequentially contacts the photoconductor 1 by the rotation of the rotary, and electrostatic on the photoconductor 1 is developed. Develop the latent image.

  The toner image on the photoconductor is transferred to the intermediate transfer belt 6 that contacts the photoconductor 1 at the primary transfer position. The intermediate transfer belt 6 is stretched between the driving roller 7 and the driven roller 8. The toner image on the intermediate transfer belt 6 transferred at the primary transfer position is secondarily transferred onto the recording member in the secondary transfer portion 10 where the secondary transfer roller 9 is disposed opposite to the driving roller 7. . The recording member is supplied from the paper feed cassette 11, is transported to the secondary transfer unit 10 through the transport path 12, is transported to the fixing unit 13 after the secondary transfer, and the toner image is fixed. In the case of double-sided printing, the recording member is reversed after fixing and conveyed again to the secondary transfer unit 10 via the conveyance path 14 during double-sided printing, and recording on the back surface is performed.

Next, details of the fixing unit in FIG. 1 will be described with reference to FIG.
FIG. 2 is a front sectional view of the fixing unit.
The fixing belt 20 is stretched in a state where a tension force is applied between the heating element 30 as a heating member and the pressing member 40, and is heated to a temperature necessary for melting the toner by the heating element. The amount of heat generated by the heating element 30 is controlled by an external control device (not shown) so that the surface temperature of the fixing belt 20 is kept constant in the range of 150 to 180 ° C. The diameter Φ of the fixing belt 20 is 30 to 50 mm (circumferential length 95 to 160 mm). The fixing belt 20 has (1) a heat-resistant resin film such as PI (polyimide) having a thickness of 30 to 50 μm, or (2) a surface layer of a metal base material such as SUS, Ni, or Fe having a thickness of 20 to 40 μm. It consists of a laminate provided with a layer of fluororesin such as (perfluoroalkoxyalkane) or PTFE (polytetrafluoroethylene). The fluororesin layer is an insulating layer that does not contain carbon black. A silicone rubber elastic layer having a thickness of about 150 to 300 μm can be provided between the heat resistant resin film or metal substrate and the insulating fluororesin layer.

  The pressing member 40 is disposed inside the fixing belt 20 and is a fixed member or a pressing roller shown in FIG. The pressing roller has a structure in which an elastic layer is provided on the surface layer of a metal pipe. The fixed pressing member 40 shown in FIG. 2 includes curved wing portions 40a and 40b that project the fixing belt 20 in the lateral direction, an intermediate portion 40c, and a plate-like member 40d provided at predetermined intervals in the longitudinal direction. It has become. The pressing member 40 is made of a heat resistant resin such as PPS (polyphenylsulfide), PAI (polyamideimide), and PI. A fluororesin layer such as PTFE or PFA can be provided on the surface of the pressing member 40 in order to reduce the frictional force with the inner surface of the fixing belt 6.

  The pressing member 40 is fixed to a metal deflection preventing shaft 60 having a diameter of about 10 to 20 mm, which is a deflection preventing member extending in the longitudinal direction, and presses the pressure roller 50 with a load of about 15 to 40 kgf via the fixing belt 20. A fixing nip is formed. The shape of the pressing member 40 sets the nip width. The nip width is about 8 to 12 mm. The plate-like member 40d provided at every predetermined interval in the longitudinal direction is formed with a depression at the center, and the protrusion 61 of the deflection preventing shaft 60 is fitted into this depression, and the pressing member 40 is caused to bend by this fitting. 60 is fixed. This structure prevents the pressing member 40 from rotating around the shaft due to friction with the inner surface of the fixing belt 20.

  The heating element 30 includes (1) a heating roller including a halogen heater or (2) a heating member in which a resistance heating element is formed on a ceramic or metal base material. The heating element 30 is provided inside the fixing belt 6 so as to face the pressing member 40 and on the side opposite to the pressure roller 50. A load of 1 to 3 kgf is applied as a tension force between the heating element 30 and the pressing member 40. Due to this tension force, the heating element 30 is sufficiently pressed against the fixing belt 20, the heat of the heating element 30 is efficiently transmitted to the fixing belt 20, and further, the deflection of the fixing belt 20 at the nip portion is prevented.

  The pressure roller 50 has a structure in which an elastic layer of about 1 to 5 mm is provided on the surface layer of a metal pipe, and a fluororesin layer such as PFA or PTFE is provided on the surface layer of the elastic layer. The fluororesin layer is an insulating layer that does not contain carbon black. A driving force is applied to the pressure roller 50, the fixing belt 20 is rotated by a frictional force with the pressure roller 50, and the surface of the pressure roller 50 and the surface of the fixing belt 20 rotate at a constant speed. The outer diameter Φ of the pressure roller 50 is about 30 to 40 mm.

  Next, printing with the fixing device will be described. The recording member on which the image is formed with the toner is conveyed to the fixing device through the pre-fixing guide 15 with the fixing belt side as the printing surface, and between the pressure roller 50 and the fixing belt 20 driven by an external driving device. Passes through the nip part. At this time, the surface of the pressure roller 50, the recording member, and the surface of the fixing belt 20 all move at the same speed, and their moving speeds depend on the printing speed of the image forming apparatus.

(Example 1)
A printing test was performed using an image forming apparatus in which an insulating PFA layer was provided on the surfaces of the fixing belt and the pressure roller of the fixing device. As a result, the releasability of the recording member from the fixing belt and the pressure roller was good, and the fixing belt and the pressure roller did not slip.

(Comparative Example 1)
A printing test was conducted with an image forming apparatus in which a conductive PFA layer containing carbon black was provided on the surfaces of the fixing belt and the pressure roller of the fixing device. As a result, an eddy current is generated in the fixing belt, the recording member is wound around the fixing belt, and the recording member is also wound around the pressure roller. Since the fixing belt and the pressure roller are charged, the behavior of the recording member is unstable. Further, the fixing belt and the pressure roller slipped, and the recording member conveyance speed was low.

(Comparative Example 2)
A printing test was conducted with an image forming apparatus in which a conductive PFA layer containing carbon black was provided on the surface of the fixing belt of the fixing device, and an insulating PFA layer was provided on the surface of the pressure roller. As a result, an eddy current was generated in the fixing belt, and the recording member was wound around the fixing belt. Further, the fixing belt and the pressure roller slipped, and the recording member conveyance speed was low.

(Comparative Example 3)
A printing test was conducted with an image forming apparatus in which an insulating PFA layer was provided on the surface of the fixing belt of the fixing device, and a conductive PFA layer containing carbon black was provided on the surface of the pressure roller. As a result, the surface of the pressure roller was charged by the friction between the surface of the fixing belt and the surface of the pressure roller, and the recording member was wound around the pressure roller. Further, the fixing belt and the pressure roller slipped, and the recording member conveyance speed was low.

The figure explaining the whole structure of an image forming apparatus Front sectional view of fixing section

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Photoconductor, 2 ... Charging roller, 3 ... Exposure machine, 4 ... Development rotary, 5 ... Developer, 6 ... Intermediate transfer belt, 7 ... Drive roller, 8 ... Driving roller, 9 ... Secondary transfer roller, 10 ... Secondary transfer section, 11 ... feed cassette, 12 ... conveyance path, 13 ... fixing section, 14 ... conveyance path for double-sided printing, 15 ... pre-fixing guide, 20 ... fixing belt, 30 ... heating element, 40 ... pressing member, 50 ... Pressure roller, 60 ... Deflection prevention shaft, 61 ... Projection

Claims (3)

A fixing device including a fixing belt, a pressing member, and a pressure roller,
The fixing belt is heated to a temperature necessary for melting the toner by a heating member,
The pressing member is disposed inside the fixing belt,
The pressing member and the pressure roller are pressed through the fixing belt,
A fixing device in which an insulating fluororesin layer is formed on a pressure roller surface and a fixing belt surface. The fixing device according to claim 1, wherein the fluororesin is a perfluoroalkoxyalkane. An image forming apparatus comprising the fixing device according to claim 1.

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