JPH08335002A - Fixing apparatus - Google Patents

Abstract

PURPOSE: To provide a fixing apparatus with which damage of heat pipe is prevented, temperature difference of heat roller is eliminated, and fixation failure is prevented. CONSTITUTION: In the fixing apparatus which includes a heat roller 11 having a heater 15 inside and a heat pipe 16 to diffuse heat from the heater 15 and a pressing roller 12 pushed to the heat roller 11 by pressure and by which toner image is fixed on a transfer paper P by leading the transfer paper P on which the toner image is formed in the contact part of the heat roller 11 and the pressing roller 12, the heat pipe 16 is composed of a plurality of units extended in the axial direction of the heat roller 11 and arranged separately at a prescribed distance in the circumferential direction and of the heat pipe 16, the units neighboring mutually in the axial direction are arranged while being shifted in the circumferential direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a copying machine, a facsimile,
The present invention relates to a fixing device applied to an image forming apparatus such as a printer.

[0002]

2. Description of the Related Art As a fixing device for fixing a toner image on a transfer sheet, a heat roller having a heater therein and a heat pipe for uniformly diffusing heat from the heater, and a pressure roller pressed against the heat roller. Those with and are well known. Further, in a fixing device capable of forming an image on a large-sized sheet of A0 or A1, a plurality of heat pipes are provided in the axial direction of the heat roller for the purpose of making the temperature uniform in the axial direction of the heat roller and reducing the cost. Those arranged in a continuous manner are considered.

[0003]

The above-mentioned device has a problem in that the heat pipes come into contact with each other and the heat pipes are damaged. Further, there is a difference in temperature between the end portion and the central portion of the heat pipe, and due to this temperature difference, a temperature difference also occurs on the surface of the heat roller, causing wrinkles and the like on the transfer paper and causing fixing failure. There was also a problem.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of preventing damage to a heat pipe and eliminating a temperature difference between heat rollers to prevent defective fixing. To do.

[0005]

According to the first aspect of the present invention,
A heat roller having an internal heater and a heat pipe for diffusing heat from the heater, and a pressure roller in pressure contact with the heat roller are provided, and toner is provided at a contact portion between the heat roller and the pressure roller. Pass the transfer paper on which the image is formed,
In the fixing device for fixing the toner image to the transfer paper, the heat pipe extends in the axial direction of the heat roller and is divided into a plurality of groups arranged at a predetermined interval in the circumferential direction. The heat pipes of the groups adjacent to each other in the axial direction are arranged so as to be displaced in the circumferential direction.

According to a second aspect of the invention, a heater is provided inside,
A heat roller having a heat pipe for diffusing heat from the heater and a pressure roller in pressure contact with the heat roller were provided, and a toner image was formed at a contact portion between the heat roller and the pressure roller. In a fixing device that allows a toner image to be fixed onto the transfer paper by passing the transfer paper, the heat pipe extends from one end of the heat roller in the axial direction thereof and is spaced apart at a predetermined interval in the circumferential direction. The first group arranged and the other end of the heat roller extend in the axial direction thereof and are arranged apart from each other in the circumferential direction at the above-mentioned interval, in the circumferential direction with respect to the arrangement of the heat pipes of the first group. It is characterized in that it is divided into a second group that is offset.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the heat pipes of the adjacent groups are partially overlapped with each other in the axial direction.

[0008]

According to the first and second aspects of the present invention, since the heat pipes of the adjacent groups are arranged so as to be displaced in the circumferential direction, the heat pipes do not come into contact with each other.

According to the third aspect of the present invention, since the heat pipes of the adjacent groups partially overlap each other in the axial direction, the temperature of the surface of the heat roller becomes uniform.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 10 represents a fixing device applied to the image forming apparatus. First, the image forming apparatus will be described.

As shown in FIG. 2, the image forming apparatus includes a reading section 2 for reading an image of a document, an image processing section 3 for converting the read image information into an electric image signal, and a photoconductor 1.
A charging charger 4 for uniformly charging the photoconductor 1, a writing unit 5 for forming an electrostatic latent image corresponding to a document on the charged photoconductor 1, and a developing device for visualizing the electrostatic latent image. 6 and
A transfer separation charger 7 that transfers the visible image formed by the developing device 6 to the transfer paper that is conveyed from the paper feed cassette 8 and is conveyed by the registration rollers 27, and separates the transferred transfer paper from the photoconductor 1. It has a fixing device 10 for fixing the transferred toner image, a cleaning unit 9 for removing the toner remaining on the photoconductor 11 after the transfer and cleaning the photoconductor 1, and a charge eliminating lamp 22.

The fixing device 10 has therein a heat roller 11 having a heater 15 for thermally melting the toner T on the transfer paper P, a heat pipe for diffusing heat from the heater 15, and a pressing means for pressing the heat roller 11. Pressure roller 12 pressed by 23
And a cleaning roller 13 in contact with the heat roller 11,
A blade 1 that abuts on the cleaning roller 13 and scrapes off adhered substances such as toner adhered to the cleaning roller 13.
4, a felt 17 that applies the release agent 21 to the outer peripheral surface of the heat roller 11, and a release agent blade 18 that scrapes off the excess release agent of the release agent 21 applied by the felt 17.
Separation claw 19 for separating the transfer paper P, on which the toner image is fixed by the heat roller 11 and the pressure roller 12, from the heat roller 11.
And a pair of paper discharge rollers 20a and 20b for discharging the transfer paper P separated by the separation claw 19.

The pressing means 23 comprises a pressing arm 24 which is in contact with the bearing 12c of the pressing roller 12 and a spring 25 which urges the pressing arm 24. A thermistor 26 that detects the temperature of the heat roller 11 is arranged on the surface of the heat roller 11 at the center in the axial direction. The temperature information of the thermistor 26 is input to the control means (not shown), and the control means controls the energization of the heater 15 based on the temperature information of the thermistor 26 to keep the temperature of the heat roller 11 at a predetermined temperature.

The pressure roller 12 is composed of a cored bar 12a made of aluminum or the like and a rubber layer 12b made of silicon rubber and provided outside the cored bar 12a. A resin layer 11b of ethylene tetrafluoride or the like is formed on the outer peripheral surface of the heat roller 1 in order to improve the releasability of the toner T.

The heat pipe 16 is, as shown in FIG.
A first group A extending in the axial direction from one end 11A of the heat roller 11 and arranged at a predetermined interval in the circumferential direction.
And a second roller extending from the other end 11B of the heat roller 11 in the axial direction thereof and arranged at intervals in the circumferential direction with a space therebetween and displaced in the circumferential direction with respect to the array of the heat pipes 16 of the first group A. It is divided into group B and. The heat pipes 16 of the first group A and the second group B are arranged so that their respective inner end portions axially overlap each other. The heat pipe 16 is
For example, it is formed by enclosing a liquid such as water in a glass or copper tube and conducts heat uniformly. In this example, the heat pipes 16 of the first group A and the second group B are arranged 60 degrees apart from each other in the circumferential direction of the heat roller 11, as shown in FIG.

The operation of the above configuration will be briefly described below. The image information of the document is read by the reading unit 2 and converted into an electrical image signal by the image processing unit 3. The image of the document is projected by the writing unit 5 onto the surface of the photoconductor 1 whose surface is uniformly charged by the charging charger 4, and an electrostatic latent image is formed. Toner is attached to the electrostatic latent image on the photoconductor 1 by the developing device 6 to form a toner image.

On the other hand, one transfer sheet P is fed from one of the sheet feeding cassettes 8 of the sheet feeding device and sent to the registration rollers 27. The registration roller 27 sends the transfer paper P to the transfer / separation charger 7 at the timing when the toner image on the photoconductor 1 and the transfer paper are matched by the transfer / separation charger 7. The image is transferred by the transfer separation charger 7, and the photoconductor 1
The transfer paper P separated from is sent to the fixing device 10.

As shown in FIG. 1, the transfer paper P is inserted between the heat roller 11 heated to a predetermined temperature by the control means and the pressure roller 12, and the toner image is heat-fixed. At this time, the temperature of the surface of the heat roller 11 is made uniform by the heat of the heater 15 being diffused by the heat pipe 16. After that, the transfer paper P is separated from the surface of the heat roller 11 by the separation claw 19, and is conveyed and discharged by the paper discharge roller pair 20a, 20b.

The toner remaining on the photosensitive member 1 is removed and cleaned by the cleaning unit 9 so as to be prepared for the next image formation. In this example, the heat pipe 16
Were divided into two groups, a first group A and a second group B. As shown in FIG. 4, A1, B1 and C1 are arranged in the axial direction of the heat roller 11.
Alternatively, the heat pipes 16 of the adjacent groups may be partly overlapped with each other in the axial direction. Further, it goes without saying that the heat pipes 16 may be divided into three or more groups.

[0020]

According to the invention described in claims 1 and 2, since the heat pipes of the adjacent groups are arranged so as to be displaced in the circumferential direction,
The heat pipes will not contact each other and damage due to contact can be prevented.

According to the third aspect of the present invention, the heat pipes of the adjacent groups are partially overlapped with each other in the axial direction, so that the temperature of the surface of the heat roller becomes uniform and defective fixing can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic side view of a fixing device according to an embodiment of the present invention.

FIG. 2 is a side view of an image forming apparatus to which the fixing device shown in FIG. 1 is applied.

3 is a sectional view of a heat roller of the fixing device shown in FIG.

FIG. 4 is a cross-sectional view showing another heat roller.

[Explanation of symbols]

 10 Fixing Device 11 Heat Roller 12 Pressure Roller 13 Cleaning Roller 14 Blade 15 Heater 16 Heat Pipe 17 Felt 18 Release Agent Blade 19 Separation Claws 20a, 20b Paper Ejection Roller Pair 23 Pressurizing Means 26 Thermistor

Claims (3)

[Claims] 1. A heat roller having therein a heater, a heat pipe for diffusing heat from the heater, and a pressure roller in pressure contact with the heat roller, and the heat roller and the pressure roller. In a fixing device for fixing the toner image on the transfer paper by passing the transfer paper on which the toner image is formed on the contact portion of the heat pipe, the heat pipe extends in the axial direction of the heat roller,
A fixing device characterized in that the heat pipes are grouped into a plurality of groups arranged at a predetermined interval in the circumferential direction and spaced apart from each other, and heat pipes of groups adjacent to each other in the axial direction are displaced in the circumferential direction. 2. A heat roller having a heater therein, a heat pipe for diffusing heat from the heater, and a pressure roller in pressure contact with the heat roller, and the heat roller and the pressure roller. In the fixing device for fixing the toner image on the transfer paper by passing the transfer paper having the toner image formed on its contact portion, the heat pipe extends in the axial direction from one end of the heat roller, and A first group, which is arranged at a predetermined interval in the direction away from the other end of the heat roller, extends in the axial direction from the other end of the heat roller, and is arranged at a distance in the circumferential direction at the first group.
A fixing device characterized in that the fixing device is divided into a second group which is displaced in the circumferential direction with respect to the arrangement of the heat pipes of the group. 3. The fixing device according to claim 1 or 2, wherein the heat pipes of adjacent groups partially overlap each other in the axial direction.