JP2865438B2 - Fixing device - Google Patents

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 which heats and fixes a toner image on a recording material.

[0002]

2. Description of the Related Art A fixing device for heating and fixing a toner image on a recording material via a fixing film by means of a fixedly supported heating element is described in, for example, JP-A-63-313182.

[0003]

However, in the above-mentioned prior art, since the deviation of the fixing film is controlled by detecting the fixing film and moving the driven roller up and down, the driven roller is moved up and down. Therefore, there is a problem that a complicated mechanism is required, the device becomes large, and the cost increases.

[0004] The present invention is to solve the above problems. That is, an object of the present invention is to provide a fixing device capable of reducing the size and cost of the device.

[0005]

In order to achieve the above-mentioned object, the present invention relates to a method in which a fixing film is brought into contact with a heating element, and a recording material is brought into close contact with a surface of the film opposite to the heating element side. In a fixing device that moves and passes through a heating element position to apply heat energy to the recording material from the heating element via the film, the heating element has a detection unit that detects a film end position, and the heating element has A plurality of energized heat generating layers that are energized from both ends with a direction intersecting the moving passage direction of the recording material as a longitudinal direction, and selectively detect each of the energized heat generating layers according to a detection signal from the detection unit. And a control means for controlling the bias of the film by thermally deforming the diameter of the drive roller for conveying and driving the film by controlling the current supply.

[0006]

According to the present invention, in a fixing device for heating and fixing a recording material via a fixing film, each of the heating elements provided on the heating element is detected by a detection signal from a detecting means for detecting an end position of the fixing film. Since the electrification of the energization heating layer is selected to have a predetermined temperature distribution and the diameter of the drive roller for driving the fixing film is thermally deformed so as to control the deviation of the fixing film, the stable running of the fixing film becomes possible.

[0007]

FIG. 1 is a perspective view showing a first embodiment of the present invention. FIG. 2 is an enlarged view of the heater of FIG. 1 and an explanatory view of a change in temperature distribution and a diameter of a driving roller. FIG. 2 is an explanatory diagram of a heating control circuit of the heater in FIG. 1.

In FIG. 1, reference numeral 1 denotes a driving roller for transporting a fixing film, 2 denotes a tension roller (driven roller) for applying a constant force to the film, 3 denotes a heat-resistant polyimide fixing film, and 4 denotes a heating element. Heater, as
5 is a pressure roller, 6 is a photo sensor 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 places, and the electrodes are arranged at four places such as electrodes 8a, 8b, 8c and 8d.

In this embodiment, when the heating temperature distribution is changed by switching the energization of the heating resistor 7 of the heater 4 in the fixing device using the driving roller 1 to rotate the thin fixing film 3, The known principle that the diameter of the drive roller 1 on the higher side of the drive roller 1 increases, thereby moving the fixing film 3 to the thicker side of the drive roller 1 having a taper (the fixing film 3 Climbs the slope of the roller 1).

Here, by rotating the driving roller 1, the fixing film 3 is conveyed, the heater 4 is energized, and the recording material on which the unfixed image is placed is pressed by the pressing roller 5 to obtain a fixed image. However, the fixing film 3 is shifted to the left or right in the longitudinal direction of the film 3 due to a shift in parallelism during assembly or a shift in cylindricity of the film 3.

In FIG. 2, when the film 3 is shifted in the direction X, the position of the end of the film 3 is detected by the photo sensor 6, and the detection signal is sent to the microcomputer (FIG. 3). MPU) 10 and the heating drive circuit I is driven by the computer 10, and the electrodes 8a,
8b and 8c are energized to be in a temperature distribution A state.

Here, the drive roller 1 uses a SVS having a small linear expansion coefficient of φ14 as a core metal, a thickness of 2 mm, and a linear expansion coefficient of 7.7 × 10 ^-5 (1 / ° C.) on the surface thereof. When the temperature distribution is 140 ° and 240 °, the difference in diameter of the driving roller 1 is about 0.
03 to 0.04, and the fixing film 3 moves in the direction of larger diameter, that is, in the Y direction according to the above-described known principle. Conversely, when the fixing film 3 moves to a certain extent in the Y direction, a signal is sent to the microcomputer 10 by the photo sensor to drive the heating drive circuit II and control the temperature distribution B to move the fixing film 3 in the X direction. Approach.

By repeating the above operation, it is possible to control the shift of the fixing film 3. At this time, the heater 4
Temperature setting is about 250 ℃ to prevent high temperature offset
The following is preferred.

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

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

Thus, similar to the first embodiment,
When the fixing film 3 is shifted in the X direction, the photo sensor 6
As a result, the position of the film is detected, the energizing position of the heater 4 is switched, and the heating resistor 7a is energized to be in the state of the temperature gradient A.

At this time, the driving roller 1 has a φ14 SVS.
2 mm thick linear expansion coefficient 7.7 × 10 ^-5 (1 /
° C), the difference in diameter between both ends of the drive roller 1 is about 0.
03, the fixing film 3 has a well-known principle,
Move in the direction of larger diameter. Conversely, when the fixing film 3 is shifted in the Y direction, the energizing position of the heater 4 is switched, and the heating resistor 7b is energized so as to be in a temperature gradient B state. The end on the side becomes thicker, and the fixing film 3 is moved to the side with the larger diameter. By repeating the above operation, the deviation control of the fixing film 3 can be performed.

[0018]

As described above, according to the present invention,
In a fixing device that heats and fixes a recording material via a fixing film, the energization of each energizing heating layer provided on the heating element is selected by a detection signal from a detection unit that detects an end position of the fixing film. Since a predetermined temperature distribution is set and the diameter of the driving roller for driving the fixing film is thermally deformed so as to control the deviation of the fixing film, the stable running of the fixing film becomes possible.

Therefore, a mechanism for raising and lowering the roller, which is conventionally required, is not required, so that the space can be reduced and the cost can be reduced.

[Brief description of the drawings]

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Drive roller 2 ... Tension roller 3 ... Fixing film 4 ... Heater 6 ... Photosensor 7 ... Heating resistor 8a, 8b, 8c, 8d ... Electrode 9 ... Thermistor 10 ... Microcomputer 11 ... Decoder

Claims (1)

(57) [Claims] 1. A fixing film is brought into contact with a heating body, a recording material is brought into close contact with a surface of the film opposite to the heating body side, and the film is moved and passed through the heating body together with the film to remove the film from the heating body. In a fixing device that applies thermal energy to the recording material through the fixing device, a detecting unit that detects a film edge position is provided, and the heating element has a longitudinal direction that intersects a moving passage direction of the recording material. It has a plurality of energized heat generating layers that are energized from both ends, and furthermore, selectively controls energization of each of the energized heat generating layers according to a detection signal from the detection means to reduce the diameter of a drive roller that conveys and drives the film. A fixing device comprising a control unit for controlling a shift of a film by thermal deformation.