JPH07287460A - Fixing device - Google Patents

Abstract

PURPOSE:To make a device compact and inexpensive by turning an endless sheet at almost the same speed as the carrying speed of a recording paper and forming the pressurized position with a pressure roller of a hollow pipe to a nearly plane shape. CONSTITUTION:A fixing device 1 is provided with the hollow pipe 4 having a heating element 3 inside, the pressure roller 5 pressurizing the hollow pipe 4 and a heat-resistant endless sheet 6 spread to wind around the outer periphery of the hollow pipe 4 and the recording paper 19 carrying unfixed toner T passes between the endless sheet 6 and the pressure roller 5, to be heated and pressurized for fixing. The surface carrying the unfixed toner T of the recording paper 19 comes into contact with the endless sheet 6 and it is turned at the same speed as the carrying speed of the recording paper 19, while following it. Then, the pressurized position A by the pressure roller 5 of the hollow pipe 4 is in the nearly plane shape. The surface coming into contact with the endless sheet 6 of the pressurized position A is made of, for instance, fluororesin, as a sliding layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a copying machine or a printer. More specifically, the present invention relates to a fixing device that fixes a recording material carrying unfixed toner by a heated endless belt.

[0002]

2. Description of the Related Art As a fixing device of an image forming apparatus, as described in JP-A-63-31382, a surface having a toner image is in contact with a transfer material and moves at the same speed as the transfer material. A fixing device has been proposed in which the unfixed toner is fixed by a heating element that heats up in a pulsed manner through a heat-resistant sheet.

[0003]

However, the fixing device described in the above-mentioned Japanese Patent Laid-Open No. 63-31382 has the following problems.
A pressure roller is provided at a position opposed to the heating element, and fixing is performed by the pressure applied from the pressure roller and the heat generated from the heating element, so the heating element itself receives a pressing force, There was a risk that the heat generation function would be adversely affected and that it would be damaged. Therefore, the pressing force that can be applied by the pressure roller is naturally limited, and good fixing cannot be performed. Furthermore, a rotating means for rotating the heat resistant sheet at the same speed as the transfer material is provided. Since it is provided separately, it becomes a great obstacle to downsizing and cost reduction of the device.

[0004]

In order to solve the above problems, the present invention provides a hollow pipe having a heat source therein, a pressure roller for pressurizing the hollow pipe, and heat resistance applied to the hollow pipe. In the fixing device which has an endless sheet of (1), and which carries out heating and pressure fixing by passing the recording paper carrying the unfixed toner between the endless sheet and the pressure roller, the unfixed toner of the recording paper is The surface carrying is in contact with the endless sheet, and the endless sheet is rotating at the same speed as the conveying speed of the recording paper,
Further, the pressing position of the hollow pipe by the pressure roller has a substantially planar shape.

[0005]

According to the fixing device constructed as described above, the heat generated from the heat source can be transmitted to the endless sheet through the hollow pipe, and the heat of the heated endless sheet and the pressure applied from the pressure roller are applied. By this, it becomes possible to fix the unfixed toner on the recording paper. Further, since a sufficient pressure is applied to the endless sheet by this pressure roller, both the endless sheet and the recording paper are conveyed at the same speed by rotating the pressure roller.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall schematic view of the internal mechanism of a laser printer according to the present invention. The device body is the upper structure 10a.
And the lower structure 10b, and the upper structure 10a is attached to the lower structure 10b by a shaft 11 so as to be openable and closable. A photoconductor 12 is provided substantially in the center of the apparatus main body. Around the photoconductor 12, a charging unit 13, a developing unit 14, a transfer unit 15, and a cleaning unit 16 are arranged. Then, the paper feed cassette 17 and the optical writing means 18 are arranged as shown in the drawing. Then, the recording paper 19 fed from the paper feed cassette 17 is
2 is conveyed to the upper side. The photoconductor 12 is driven to rotate in the counterclockwise direction. At that time, the surface of the photoconductor 12 is uniformly charged by the charging unit 13, and the laser beam from the optical writing unit 18 is irradiated to the photoconductor 12 to form an electrostatic latent image. Is formed. When the latent image passes through the developing unit 14, toner is carried on the latent image and is visualized. Then, this visible image is transferred to the lower surface of the recording paper 19 conveyed to the upper side of the photoconductor 12 by the transfer means. The transferred recording paper 19 is conveyed to the fixing device 1, and the fixing device 1 fixes the unfixed toner. Then, the recording paper 19 exiting the fixing device 1
Is discharged from the paper discharge port 20.

FIG. 2 is a diagram showing the structure of the fixing device.
The fixing device 1 is covered with a cover 2a and a cover 2b because of its heat retention and safety. A hollow pipe 4 having a heating element 3 therein, a pressure roller 5 for pressurizing the hollow pipe 4, and a heat-resistant endless sheet 6 that is wound around the outer periphery of the hollow pipe 4 are provided. Between the sheet 6 and the pressure roller 5, the unfixed toner T
The recording paper 19 carrying is passed through, and heat and pressure fixing is performed. The surface of the recording paper 19 carrying the unfixed toner T is in contact with the endless sheet 6, and the pressing position A of the hollow pipe 4 by the pressure roller 5 is substantially flat. A sliding layer is formed on the surface of the pressing position A that is in contact with the endless sheet 6, for example, with a fluororesin. By configuring the pressing position A in this way, the transportability of the recording paper 19 is excellent, and the pressing position A
Wrinkles and curls of the recording paper 19 (especially double paper such as an envelope and thin paper with a weak stiffness) passing through the sheet are prevented. It is preferable to use the endless sheet 6 having excellent heat resistance and slidability. Drive torque is transmitted from a motor (not shown) to a reduction gear (not shown),
The pressure roller 5 is rotated. Since the pressure roller 5 rotates while applying sufficient pressure to the hollow pipe 4 made of a material having a rigidity sufficient to withstand the pressure from the pressure roller 5, the recording paper 19 is driven. While being conveyed, the endless sheet 6 also rotates while being driven at the same speed as the conveying speed of the recording paper 19.

Further, as shown in FIG. 3, by providing a heat insulating member 7 on the inner wall surface of the hollow pipe at a position other than the pressing position A, it is possible to prevent wasteful heat dissipation to the area other than the fixing nip portion and to save energy. It is possible to save power due to high efficiency and suppress temperature rise inside the device.

[0009]

As described above, according to the present invention, in a fixing device using an endless sheet, a pressure is not directly applied to a heating element, and a sufficient pressure is applied to a recording paper. Since it can be added, it is possible to stabilize the fixing property, speed up the conveyance of the recording paper, and further reduce the size and cost of the fixing device.

[0010]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a laser printer showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of another embodiment of the present invention.

[Explanation of symbols]

 1 Fixing Device 3 Heating Element 4 Hollow Pipe 5 Pressure Roller 6 Heat Resistant Endless Sheet

Claims (2)

[Claims] 1. A recording sheet having a pressure roller and a heat-resistant endless sheet which surrounds a heat source, and a recording paper carrying unfixed toner is passed between the pressure roller and the endless sheet to heat and pressure fix the sheet. In the fixing device for performing the endless sheet, the endless sheet is wrapped around a hollow pipe having a heat source inside, and is rotated at the same speed as the conveyance speed of the recording paper, and the pressing position of the hollow pipe by the pressure roller. Is a substantially planar shape. 2. The fixing device according to claim 1, wherein a heat insulating member is provided on a part of an inner peripheral surface of the hollow pipe.