JPH04285986A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device which can be miniaturized at a lower cost. CONSTITUTION:The, device is provided with a detection means 6 detecting edge position of a fixing film 3. Furthermore, a multiple number of energizing exothermic layers which are energized from both edge parts when the direction crossing with the movement passage direction of a recording material is the longitudinal direction are provided in the heating body 4. A control means controlling siding of the film by deforming the diameter of a driving roll 1 with heat is also provided. The driving roll carries and drives the concerned film by selectively energizing and controlling each of the energized exothermic layers concerned by a detection signal from the before mentioned detection means. The space is reduced and the cost is brought down by making a mechanism to raise and lower the roll for the siding control of the fixing film unnecessary.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a fixing device for an image forming apparatus that heats and fixes a toner image onto a recording material.

0002

2. Description of the Related Art A fixing device that heats and fixes a toner image on a recording material via a fixing film using a fixedly supported heating body is described, for example, in Japanese Patent Laid-Open No. 313182/1982.

0003

[Problem to be Solved by the Invention] However, in the above-mentioned conventional technology, the deviation of the fixing film is controlled by detecting the fixing film and moving the driven roller up and down. This necessitates a complicated mechanism, which increases the size and cost of the device.

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 be miniaturized and cost reduced.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention brings a fixing film into contact with a heating body, brings a recording material into close contact with the surface of the film on the side opposite to the heating body, and fixes the film by bringing the fixing film into contact with the heating body. In the fixing device, the fixing device moves and passes a heating body position to apply thermal energy from the heating body to the recording material via the film, the fixing device having a detection means for detecting a film end position; , a plurality of energized heat generating layers are energized from both ends with the longitudinal direction extending in a direction intersecting the moving direction of the recording material, and each of the energized heat generating layers is selectively energized by a detection signal from the detection means. The present invention has a control means for thermally deforming the diameter of a drive roller for transporting the film by controlling energization to control the deviation of the film.

[0006]

[Operation] According to the present invention, in a fixing device that heats and fixes a recording material via a fixing film, each of the heating elements provided on the heating body is The energization of the energizing heat generating layer is selected to achieve a predetermined temperature distribution, and the diameter of the drive roller that drives the fixing film is thermally deformed so as to control the shift of the fixing film, thereby enabling stable running of the fixing film.

[0007]

Embodiment FIG. 1 is a perspective view showing a first embodiment of the present invention, FIG. 2 is an enlarged view of the heater in FIG. 2 is an explanatory diagram of a heating control circuit for the heater in FIG. 1. FIG.

In the figure, 1 is a drive roller that conveys the fixing film, 2 is a tension roller (driven roller) that applies a constant force to the film, 3 is a fixing film made of heat-resistant polyimide, and 4 is a heating element. heater as,
5 is a pressure roller; 6 is a photosensor as means for detecting the position of the film 3; and the heater 4
As shown in FIG. 2, the heating resistor 7 is branched at two locations, and the electrodes are arranged at four locations, such as electrodes 8a, 8b, 8c, and 8d.

In this embodiment, in a fixing device that uses a drive roller 1 to rotate a thin fixing film 3, when the heating temperature distribution is changed by switching the energization to the heating resistor 7 of the heater 4, the temperature The diameter of the drive roller 1 on the higher side becomes larger, thereby causing the fixing film 3 to move toward the thicker side of the tapered drive roller 1. climbs the slope of the roller 1).

Here, by rotating the drive roller 1, the fixing film 3 is conveyed, the heater 4 is energized, and the recording material carrying the unfixed image is pressed by the pressure roller 5, thereby obtaining a fixed image. However, the fixing film 3 tends to shift to either the left or the right in the longitudinal direction due to deviations in parallelism or cylindricity of the film 3 during assembly.

Therefore, when the film 3 moves toward the X direction in FIG. 2, the position of the end of the film 3 is detected by the photosensor 6, and the detection signal is sent to the microcomputer ( MPU) 10, the computer 10 drives the heating drive circuit I, and the electrodes 8a,
8b and 8c are energized to achieve temperature distribution A.

[0012] Here, the drive roller 1 uses SVS with a small linear expansion coefficient of φ14 for the core metal, and the surface thereof has a thickness of 2 mm and a linear expansion coefficient of 7.7 × 10-5 (1/°C). When the drive roller 1 is coated with silicone rubber, the difference in diameter of the drive roller 1 is approximately 0 between the temperature distribution position of 140° and the position of 240°.
．． 03 to 0.04, and the fixing film 3 moves in the direction of the larger diameter, that is, in the Y direction, according to the above-mentioned known principle. On the other hand, when the fixing film 3 has moved to a certain extent in the Y direction, the photosensor sends a signal to the microcomputer 10, drives the heating drive circuit II, and controls the temperature distribution B to move the fixing film 3 in the X direction. send

By repeating the above operations, it becomes possible to control the shift of the fixing film 3. Also at this time, heater 4
The temperature setting is approximately 250℃ to prevent high temperature offset.
The following are preferred.

FIG. 4 is an explanatory diagram showing a part of a second embodiment of the present invention.

The heater 4 of this second embodiment has a structure in which heating resistors 7a and 7b having different widths are arranged in parallel in the longitudinal direction.

[0016] As a result, similar to the first embodiment described above,
When the fixing film 3 moves toward the X direction, the photo sensor 6
The film position is detected, the energizing position of the heater 4 is switched, and the temperature gradient A is created by energizing the heating resistor 7a.

At this time, the drive roller 1 is an SVS of φ14.
The core metal of the material has a thickness of 2 mm and a coefficient of linear expansion of 7.7 x 10-5 (1
Heater 4
Due to the temperature difference, the diameter difference between both ends of the drive roller 1 is approximately 0.
．． 03, the fixing film 3 moves in the direction of the larger diameter according to a known principle. Conversely, when the fixing film 3 is shifted in the Y direction, the current supply position of the heater 4 is switched, and the heating resistor 7b is supplied with current to bring the temperature gradient B into a state, so that the driving roller 1 is moved in the opposite direction. The end of the side becomes thicker, and the fixing film 3 is moved to the side with a larger diameter. By repeating the above operations, it becomes possible to control the deviation of the fixing film 3.

[0018]

[Effects of the Invention] As explained above, according to the present invention,
In a fixing device that heats and fixes a recording material via a fixing film, energization of each energizing heat generating layer provided on a heating body is selected based on a detection signal from a detection means that detects the edge position of the fixing film. Since a predetermined temperature distribution is achieved and the diameter of the drive roller that drives the fixing film is thermally deformed to control the shift of the fixing film, stable running of the fixing film is possible.

[0019] Therefore, a mechanism for moving the rollers up and down, which was necessary in the past, is no longer necessary, and space can be reduced, leading to cost reductions.

[Brief explanation of the drawing]

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

FIG. 2 is an enlarged view of the heater in FIG. 1 and an explanatory diagram of temperature distribution and changes in the diameter of a drive roller.

FIG. 3 is an explanatory diagram of a heating control circuit for the heater in FIG. 1;

FIG. 4 is an explanatory diagram showing a part of a second embodiment of the present invention.

[Explanation of symbols]

Claims (1)

[Claims] 1. A fixing film is brought into contact with a heating body, a recording material is brought into close contact with the surface of the film opposite to the heating body, and the film is moved and passed through the heating body position together with the film to remove the film from the heating body. The fixing device applies thermal energy to the recording material through the heating body, and the heating body has a detection means for detecting the position of the film end, and the heating body has a longitudinal direction that intersects with the moving direction of the recording material. The diameter of a drive roller that has a plurality of energized heat generating layers that are energized from both ends and that selectively controls the energization of each of the energized heat generating layers based on a detection signal from the detection means to drive the film to be conveyed is determined. A fixing device comprising a control means for controlling film deviation by thermally deforming the fixing device.