JP2962571B2 - Fixing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a film-type fixing device provided in an electrophotographic apparatus.

[Conventional technology]

As a fixing device of an electrophotographic apparatus, a heat roller system is most common. This method is basically a heating roller,
And a pressure roller that is in pressure contact with this roller.
Then, the unfixed image is passed between the two rollers and fixed.

The above-mentioned heat roller type has various features, but has a drawback that it takes a long time to rise to a predetermined temperature because the heat capacity of the heat roller is large.

Therefore, a film-type fixing device using a heating body having a low heat capacity and a thin wound heat-resistant film having a thickness of about 40 μ has been proposed. According to this device, there are advantages that the initial rise time can be shortened and the power consumption can be reduced.

[Problems to be solved by the invention]

However, in the above-described film-type fixing device, the thin film is driven while rubbing the fixedly supported heating element. There is a disadvantage that heat-resistant fluorine-based grease must be applied to the inner surface to form a lubricant. In this case, the grease viscosity at a low temperature is large due to grease temperature characteristics, so that the instantaneous torque at the time of starting the fixing device increases. Then, it is necessary to increase the strength of the drive transmission means, for example, the gears, and to increase the starting torque of the motor and the like of the drive means, which causes disadvantages such as an increase in cost and an increase in the size of the apparatus.

In addition, since the fixing film is driven when the temperature rises, the heat from the heating element escapes to the film, which causes a delay in the rise. As a countermeasure against this, it is conceivable to stop the film during the start-up. However, if the film is stopped and started, thermal damage to the film is so large that it cannot be performed.

Therefore, according to the present invention, the startup time is short, there is no shock at the time of starting, the load of the driving source is small,
It is another object of the present invention to provide a fixing device that does not receive heat damage.

[Means for solving the problem]

A configuration for achieving the object of the present invention includes a fixed heating element, a film in which one surface slides with the heating element and the other surface moves in contact with a recording material carrying an unfixed image, And a driving unit for driving, wherein a lubricant is interposed between the heating body and the film in a fixing device for fixing an unfixed image on a recording material by heat from the heating body via the film. The driving means drives the film at a first speed at the time of start-up, and then drives the film at a second speed higher than the first speed.

[Action]

With the above-described configuration, even when the viscosity of the lubricant is large at low temperatures, the shock due to the peak torque generated at the time of starting can be suppressed, and the load on the driving means can be reduced.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the speed is switched between two stages by switching the gear train. That is, a thin heat-resistant film 2 of less than about 40 μm, which is driven in the direction of arrow A while being opposed to and pressed against a low-heat-capacity heating element 1 fixedly supported by a fixing device.
1 shows a fixing device that has a pressure member 3 for bringing a recording material into close contact with the heating body via the fixing member and heat-fixes a toner image.

The fixing film 2 is conveyed without slack from the driving roller 4 and the tension roller 5. A drive gear 6 is provided on the rotational axis of the drive roller. A drive is supplied from a drive source through a gear train, and the fixing film is driven at a peripheral speed V. The output gear 7 of the drive source is constituted by a two-stage gear having a diameter R, r (R> r).
8 'is connected to a swing arm 9 which is rotatable with respect to the center of the output gear. One end of the swing arm has a spring 10 for heating in the direction of arrow B, and a driving means 11 made of, for example, an electromagnet, which pulls in a direction opposite to the biasing direction of the spring.

Therefore, in FIG. 1, since the swing arm is pulled in the direction opposite to the arrow B by the driving means 11, the output gear 7
Drive is transmitted from the idler 8 connected to the smaller diameter gear through the other idlers 11 and 12. The peripheral speed of the film at this time is V. When the driving means is released and the swing arm rotates in the direction of arrow B by the spring 10, the drive is transmitted from the idler 8 'connected to the large-diameter gear of the output gear 7 this time.

Assuming that the film peripheral speed at this time is V ', the relationship of V' = R / r V holds, and the relationship of V '> V holds from R> r. Further, if V 'is a regular recording material conveying speed, the fixing device can be driven at a speed V lower than the regular speed by operating the driving means 11 at the time of starting the main body or the like. After a predetermined time, for example, when the heating unit reaches a predetermined temperature, or when the driving unit is released before the leading end of the recording material enters the fixing device, the fixing device returns to the normal speed, and normal conveyance can be performed. .

FIG. 2 and FIG. 3 show another embodiment of the present invention. That is, FIG. 2 shows a pulley 20 having a drive diameter of, for example, two steps, a belt 21 wound around the pulley and the drive roller 4, and a pressing roller 22.
Thus, the driving means is constituted. Therefore, the drive speed can be changed by changing the belt 21. It should be noted that it can be obviously configured as a known continuously variable transmission.

FIG. 3 shows an example implemented by a pair of friction wheels. According to the present embodiment, the speed can be changed by changing the diameter of the point of contact between the tapered wheel 30 and the driven wheel 31k.

In each of the above-described embodiments, the driving source is also used for other than the fixing device. A means for detecting the temperature of the heating element, or until the recording material is conveyed from the main body paper feeding section and the leading end of the recording material enters the fixing device, or a certain time when the main body start signal is output. Until it reaches a certain temperature.
By controlling the rotation speed of the DC motor to be lower than the normal speed, it is possible to prevent shock at the time of starting and improve thermal efficiency.
Then, when the speed is returned to the normal speed, the image can be fixed without affecting the recording material conveyance. Further, the speed can be freely set according to the transport path of the apparatus, the recording material size, and the toner fixing condition. That is, the setting conditions of the speed switching and the timing detection method described above are not limited, and can be implemented in various forms. Is clear.

〔The invention's effect〕

According to the present invention, even at a low temperature, even when the viscosity of the lubricant is large, a shock due to a peak torque generated at the time of starting can be suppressed, and the load on the driving means can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing one embodiment of the present invention, and FIG.
FIG. 3 and FIG. 3 are similar schematic side views showing other different embodiments. DESCRIPTION OF SYMBOLS 1 ... Heating body 2 ... Fixing film 3 ... Pressure member 4 ... Driving roller 5 ... Tension roller, 6 ... Driving gear 7 ... Output gear 8, 8 ', 11, 12 ... Idler 9 ... Swing arm

Claims (1)

(57) [Claims] 1. A fixed heating element, a film having one surface sliding with the heating element and the other surface moving in contact with a recording material bearing an unfixed image, and a driving means for driving the film A fixing device for fixing an unfixed image on a recording material by heat from the heating element via the film, wherein a lubricant is interposed between the heating element and the film, A fixing device, wherein the driving means drives the film at a first speed at the time of startup, and then drives the film at a second speed higher than the first speed.