JPH04338787A - Fixing device - Google Patents

Abstract

PURPOSE:To provide the fixing device which prevents the generation of wrinkles in a fixing film right after passage through a fixing nip part and can avert the failure of the film. CONSTITUTION:The fixing device of a film heating system is provided with a guide member 13 having a crown shape in the position between a driving roller 8 for driving the fixing film 7 and a heating element 1 where this member comes into contact with the inside surface of the fixing film 7 and regulates the traveling orbit of this fixing film in the direction parting from the heating element. Then, the generation of the wrinkles in the fixing film right after the passage through the nip part is prevented and the failure of this film is averted.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention applies thermal energy to a recording material carrying a visible image (hereinafter referred to as a toner image) to be heat-fixed to a heating body through a fixing film to form a toner image. The present invention relates to a film heating type fixing device that heats and fixes an image.

[0002] This device is used in image forming devices such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recorders, to perform appropriate processing such as electrophotography, electrostatic recording, magnetic recording, etc. By using an image forming process means, toner made of heat-melting resin or the like is applied directly or indirectly ( The present invention can be utilized as an image fixing device that heats and fixes an unfixed toner image corresponding to target image information formed by a transfer method on the surface of a recording material carrying the image as a permanently fixed image.

0003

2. Description of the Related Art Conventionally, in a heating type fixing device, an unfixed toner image is formed by a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and in pressure contact with the heating roller. A heat roller fixing type fixing device that heats the recorded recording material while nipping and conveying it is often used.

[0004] However, this heat roller fixing type fixing device requires, firstly, a so-called wait time, which is the time required to raise the temperature to a predetermined temperature (a time during which image forming operation is inhibited), and secondly, it requires a high heat capacity. , so a relatively large amount of electric power is required. Thirdly, the rotating rollers have a high temperature, so special heat-resistant bearings are required. Fourthly, the rollers are in direct contact with the hands. It is dangerous and requires a protective member.Fifth, there are drawbacks such as the recording material being wrapped around the roller due to the fixing temperature and curvature, causing a jam.

[0005]Therefore, as a heating type fixing device that does not have the above-mentioned drawbacks, the above-mentioned film heating type fixing device has recently attracted attention, and research and development for its practical use is progressing. .

For example, the method and apparatus described in Japanese Patent Application Laid-Open No. 63-313182 belong to this category, and include a thin heat-resistant fixing film (sheet), a moving drive means for the film, and a device for moving the film. A heating body is fixedly supported on one side of the heating body, and a recording material on which an image is to be fixed to the heating body is placed opposite to the heating body on the other side of the recording material through the film. It has a pressure member that brings the image bearing surface into close contact with the film, and at least when image fixing is performed, the film is transported between the film and the pressure member and is moved at the same speed in the forward direction as the recording material to which the image is to be fixed. By moving the recording material and passing it through a fixing nip formed by pressure contact between a heating member and a pressure member with the traveling film in between, the image-bearing surface of the recording material is applied to the heating member through the film. Either by applying heat energy to the visible image (unfixed toner image) to soften and melt it, and then separating the fixing film from the recording material, or by separating the fixing film from the recording material after the toner has cooled and solidified. These are the basic heating means and equipment.

[0007] The heating body is formed in the form of a line or strip along the length of the film contacting surface of a horizontally elongated heat-resistant, insulating, and low heat capacity heater substrate whose longitudinal direction is the width direction of the fixing film. The heater is equipped with a current-carrying heating resistor (heating element) with a low heat capacity, and when electric power is supplied between both ends of the heating element, the heating element generates heat, and the heater board is also heated. The temperature of the entire body rapidly rises, and the heat from the heating body is applied to the recording material via the fixing film.

The temperature control of the heating element is carried out by a temperature sensor provided on the heating element, a microcomputer in the main body of the image forming apparatus, and a heating element driving (heating by energization) circuit, and the temperature is controlled to a predetermined fixing temperature. Ru. Furthermore, although the heating element is at a high temperature, at least when the heating element is generating heat, the fixing film is moved over the heating element at a predetermined speed. Fixation is performed.

Such a film heating type fixing device has advantages such as a short wait time, and is a fixing device that meets the needs of the times.

0010

[Problems to be Solved by the Invention] However, in the above-mentioned conventional film heating type fixing device, the heating element that is pressed against the pressure member is bent to some extent, and when the fixing film rotates, the pressure Immediately after passing through the fixing nip formed by the member and the heating element, the fixing film slips and wrinkles from a high position to a low position, that is, from both ends of the heating element, where the deflection is small, to the central part, where the deflection is large. However, there was a problem in that the fixing film was damaged.

The present invention aims to solve the above problems. That is, an object of the present invention is to provide a fixing device that can prevent wrinkles from occurring in the fixing film immediately after passing through the fixing nip, thereby avoiding damage to the film.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention has a fixing film that is driven to run, a heating member and a pressure member that sandwich and press the fixing film. A recording material carrying an unfixed visible image is introduced between the fixing film and the pressure member in the fixing nip formed by pressure between the heating body and the pressure member, and the fixing nip is closed together with the moving fixing film. In a fixing device that heats and fixes a visible image by applying thermal energy to a recording material from a heating body through a fixing film by moving the fixing film through the recording material, the fixing film is heated between a drive roller that drives the fixing film and the heating body. A guide member having a crown shape is provided at a position that contacts the inner surface of the fixing film and restricts the running trajectory of the fixing film in a direction away from the heating element.

[0013]

[Function] According to the present invention, in a film heating type fixing device, a driving roller that drives the fixing film and a heating body are brought into contact with the inner surface of the fixing film and the running trajectory of the fixing film is changed by the heating body. Since a guide member having a crown shape is provided at a position regulating the direction away from the fixing film, the effect of the shape of the guide member prevents the occurrence of wrinkles in the fixing film.

[0014]

[Embodiment] FIG. 1 is a sectional view showing a first embodiment of the present invention, FIG. 2 is a front view showing an enlarged part of FIG. 1, and FIG.
2 is an enlarged cross-sectional view of a part of FIG. 1. FIG.

In FIGS. 1 and 2, 7 is an endless belt-shaped fixing film, and as shown in FIG.
, 9, and a guide member (film protection roller) 13 disposed on the left side of the heating element 1.

The driven roller 9 also serves as a tension roller for the fixing film 7, and the fixing film 7 is rotated clockwise at a predetermined peripheral speed as the drive roller 8 is rotated clockwise, that is, from the image forming section side. It is rotationally driven at the same circumferential speed as the transport speed of the recording material P carrying the unfixed toner image Ta on its upper surface, without wrinkling, meandering, or speed delay.

Reference numeral 10 denotes a pressure roller having a rubber elastic layer 12 made of silicone rubber or the like having good mold releasability as a pressure member. The recording material P is pressed against the recording material P by a biasing means (not shown) with a total contact pressure of, for example, 4 to 7 kg, and rotates about the shaft 11 in a forward counterclockwise direction in the conveying direction of the recording material P. .

The heating element 1 is a low heat capacity linear heating element whose length is in the direction (width direction of the film) that intersects the plane movement direction of the fixing film 7, and includes a heater substrate 3, a current-carrying heating resistor (
It consists of a heating element) 4, a temperature measuring element 5, etc., and is fixedly supported by being attached to a heater support 2.

The guide member 13 is a driven roller,
Both ends are supported by fixing device side plates 14 (see FIG. 2). In order to maintain the nip between the heating body 1 and the pressure roller 10 and to reduce the sliding surface between the fixing film 7 and the heater support 2, the angle θ between the sliding surface and the fixing film (see Fig. 3)) is set so that the angle is 0.5 to 5°.

Further, as shown in FIG. 2, the guide member 13 has an arcuate crown, and the difference between the diameter a at the center and the diameter b at both ends is 0.2 to 1 mm. When the fixing film 7 rotates, it is squeezed from the center to both ends on a crown-shaped driven roller guide member 13 to prevent wrinkles from forming.

FIG. 4 is a sectional view showing a second embodiment of the present invention, and FIG. 5 is a front view showing a part of FIG. 4 on an enlarged scale.

In this second embodiment, a film guide plate 16 is provided in place of the guide member 13 of the first embodiment.

The guide plate 16 is made of a sheet metal coated with Teflon to have good surface properties, and has a crown in the shape of an arc of 0.1 to 0.5 in the longitudinal direction. Due to the effect of this crown, when the fixing film 7 passes over the surface of the guide plate 16, it is possible to prevent the fixing film 7 from slipping from the center to both ends and from generating wrinkles in the fixing film 7.

It should be noted that this second embodiment has fewer parts compared to the first embodiment described above, making it possible to reduce costs.

FIG. 6 is a sectional view showing a third embodiment of the present invention, and FIG. 7 is an enlarged sectional view of a part of FIG.

In this third embodiment, a film guide plate 17 which also functions as a film cleaner is provided in place of the film guide plate 16 of the second embodiment.

That is, as shown in FIG. 7, a felt member 18 is fitted in the center of the guide plate 17, and in addition to producing the same functions and effects as the second embodiment described above, the fixing film 7 It can also be cleaned.

That is, when the fixing film 7 rotates and passes through the nip formed by the heating member 1 and the pressure roller 10, abrasion powder is generated from the inner surface of the fixing film 7 due to a large sliding force. When this abrasion powder adheres to the drive roller 8, the frictional force between the drive roller 8 and the fixing film 7 decreases, eventually causing the film to slip. Therefore, by fitting the felt member 18 into the guide plate 17 located between the heating element 1 and the driving roller 8 to collect the abrasion powder, the fixing film 7 can be cleaned accurately at low cost and has a long service life. will be promoted.

[0029]

[Effects of the Invention] As explained above, according to the present invention,
In a film heating type fixing device, a position is provided between the drive roller that drives the fixing film and the heating body, at a position where the fixing film comes into contact with the inner surface of the fixing film and restricts the traveling trajectory of the fixing film in a direction away from the heating body. Since the guide member having a crown shape is provided, the effect of the shape of the guide member prevents the formation of wrinkles in the fixing film, and this occurs at the position where the tension of the fixing film is greatest. Therefore, the wrinkles can be prevented more efficiently and the fixing film can be prevented from being damaged due to the wrinkles.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged front view of a part of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of a part of FIG. 1;

FIG. 4 is a sectional view showing a second embodiment of the present invention.

FIG. 5 is an enlarged front view of a part of FIG. 4;

FIG. 6 is a sectional view showing a third embodiment of the present invention.

FIG. 7 is an enlarged front view of a part of FIG. 6;

[Explanation of symbols]

Claims (1)

[Claims] 1. A fixing nip comprising a fixing film that is driven to run, a heating body and a pressure member that sandwich and press the fixing film, and is formed by pressure between the heating body and the pressure member with the fixing film sandwiched therebetween. A recording material carrying an unfixed visible image is introduced between the fixing film and the pressure member, and the recording material is transferred to the recording material from the heating body through the fixing film by moving and passing through the fixing nip with the traveling fixing film. In a fixing device that heats and fixes a visible image by applying thermal energy, a driving roller that drives the fixing film and a heating body contact the inner surface of the fixing film to change the travel trajectory of the fixing film away from the heating body. A fixing device characterized in that a guide member having a crown shape is provided at a position regulating the separation direction.