JP2557780Y2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fixing device of an image forming apparatus that heats and fixes a toner image on a recording material.

[Related Art] Conventionally, a fixing device used in an image forming apparatus of this type includes a heating roller maintained at a predetermined temperature and a pressing roller having an elastic layer and pressing against the heating roller. ,
A heating roller fixing method in which a recording material on which an unfixed toner image is formed is heated while being nipped and conveyed is often used. However, in this heating roller fixing method, it is necessary to maintain the heating roller at an optimum temperature in order to prevent so-called offset development in which toner is transferred to the heating roller, and the heat capacity of the heating roller and the heating element must be increased. Because of this, the time required to elevate the temperature of the heating roller to a predetermined temperature becomes longer, and the use of the apparatus has a drawback that the standby time becomes longer and the power consumption becomes larger.

In order to solve such a disadvantage, a belt fixing system is known as described in US Pat. No. 3,578,797.

[Problems to be Solved by the Invention] However, in the belt fixing system described in the above-mentioned US Pat. No. 3,578,797, a driving force and a tension by a roller or the like are used as a means for forming a conveyance path of a thin endless film. , And there is a problem that a film shift occurs.

As a means for solving this problem, it is thought that it is possible to reduce the pitch between rollers by increasing the number of rollers, or to increase the accuracy of each component to a certain level, but it is possible to reduce the cost. There is a problem that mass production is not possible due to the increase. In the case of a film having a large elastic modulus, such as rubber, self-centering with a crown-shaped roller can be considered.However, in an endless film used in the above-mentioned belt fixing method, the elastic modulus is small and a very thin film is used. Therefore, the effect cannot be expected. Furthermore, the method of providing abutting ribs at the ends of the rollers, the method of providing perforations, and the like cannot be actually implemented due to the strength of the film itself and an increase in processing costs. There is.

The present invention is intended to solve the above problems. That is, the present invention has a simple structure and
It is an object of the present invention to provide a fixing device which can be obtained at a low price and can surely control the shift of the fixing film.

[Means for Solving the Problems] A heating element, an endless film in contact with the heating element, a driving member for driving the film, a driven member for following the movement of the film, and the heating via the film A pressurizing member that presses against the body, wherein the film is hung around the heating body, the driving member and the driven member, and carries an unfixed image at a fixing unit where the film and the pressurizing member contact. In a fixing device for nipping and conveying the recording material to perform fixing, the driving member is fixed in position, the driven member is displaceable to control the shift of the film, and the driven member is movable with respect to a moving direction of the film. It is provided on the upstream side of the fixing unit and on the downstream side of the driving member.

According to the present invention, among the members forming the conveyance path of the fixing film, members other than the pressing member for bringing the recording material into close contact with the heating element via the fixing film are displaced to dispose the fixing film. Since the shift control is performed, the structure is simplified, the structure can be obtained at low cost, and the control can be reliably performed.

FIG. 1 shows a first embodiment of the present invention, and FIG. 2 shows a second embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a low-heat-capacity heating element fixed to a fixing device, and 2 denotes a fixing film which comes into contact with the heating element 1 and moves in the direction of an arrow. The fixing film 2 is moved by applying a driving force and a tension by a driving roller 3 and a driven roller 4 as a film transport path forming means. Reference numeral 5 denotes a pressure roller having a rubber elastic layer of silicon rubber or the like with good releasability, and rotates by pressing while heating the heating element 1 via the fixing film 2.

A recording material (not shown) having an unfixed image is guided to a fixing unit (nip portion) 6 to obtain a fixed image.

At the end of the fixing film 2, there is provided a detecting unit 7 such as a photo sensor for detecting the film position. The eccentric cam 8 is designated by reference numeral 8 'by a control means synchronized with the detection signal.
And the position of the fixing film 2 is controlled by displacing the driven roller 4 as shown by reference numeral 4 '. In other words, when the fixing film 2 starts to move in a certain direction and the detecting unit 7 detects the fixing film 2, the driven roller 4 is displaced to apply a deviating force of the fixing film 2 in the opposite direction. The driving force of the fixing film 2 can be realized in a state where the position of the fixing film 2 is pressed within a certain range (in this embodiment, within the detection area on both sides). With this control method, the deviation of the fixing film 2 can be controlled without changing the condition of the heating unit of the fixing unit 6.

In this embodiment, the driven roller 4 is displaced substantially vertically by the eccentric cam 8, but the displacement direction is not limited to this. However, fixing film 2
In order to drive the driven roller 4 without wrinkles, tension is applied to the driven roller 4 side by the tension spring 9 and the fixing unit 6 is heated as shown in FIG. In order to displace the fixing film 2 in the horizontal direction, that is, in the direction substantially the same as the tension direction, a larger displacement force is required, and elongation and wrinkles of the fixing film 2 due to heat are expected.

In addition, the displacement is not limited to the driven roller 4 as a matter of course. Even if the drive roller 3 is displaced, the deviation control can be performed.
For example, since a swinging part or the like is required, there is a case where it becomes complicated and causes a cost increase.

Further, it is preferable that the position of the displacement roller with respect to the fixing unit 6 is set at an upstream side of the fixing unit 6 rather than at a downstream side. That is, on the downstream side of the fixing unit 6, the recording material discharged from the fixing unit 6 needs to be separated from the fixing film 2. Therefore, if the roller is displaced on the downstream side, particularly in the vicinity thereof, the separation unit 10 is affected. Is expected. Separation unit
This is because, if an excessively deviating force is generated in 10, the separation conditions may fluctuate due to film wrinkles or the like, resulting in poor separation jam or offset to the fixing film 2.

Further, when the film in the state where the tension is strongly applied is displaced (twisted), the film is seriously damaged. However, in this embodiment, the film is not located between the driving roller 3 and the fixing unit 6 where the tension is applied strongly, but rather is compared. Fixing unit 6 with low mechanical tension
Since the film portion on the upstream side and on the downstream side of the drive roller 3 is displaced, damage to the film 2 due to displacement of the driven roller can be prevented.

Next, in FIG. 2, another displaceable member 11 for deviation control is provided.

The displacement means of the driven roller 4 includes a solenoid 12
It is also possible to perform the operation via the lever 13 by providing the same. Also as the detection unit 7, near the end of the fixing film 2,
Means for detecting a film position by providing a lever or the like is also conceivable.

The amount and timing of the displacement may be set according to the conditions of each member, and the detection position, the number, and the driving conditions for the displacement are not limited. What is necessary is just to set conditions.

[Effects of the Invention] As described above, in the present invention, the displaceable driven member is provided on the upstream side of the fixing unit and on the downstream side of the driving member. In this case, it is possible to suppress the fluctuation of the film at the time of recording, and to prevent the jam of the recording material from being poorly separated and the offset of the toner to the film. In addition, the present invention displaces the film portion on the upstream side of the fixing unit and the downstream side of the driving member on which the tension is relatively low, not on the film portion between the driving member and the fixing unit on which the tension is strong. Damage can be prevented. In addition, by this deviation control device, since the fixing film can be driven without depending on the adjustment of the crown-shaped roller and the pitch between the rollers, and the improvement of the accuracy of a single product,
It is possible to provide a more stable and low-cost apparatus even in mass production and processing.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a first embodiment of the present invention, and FIG.
The figure is a side sectional view showing the second embodiment. DESCRIPTION OF SYMBOLS 1 ... Heating body with low heat capacity, 2 ... Fixing film 3 ... Driving roller, 4 ... Follower roller 5 ... Pressure roller, 6 ... Fixing part 7, ... Detection part, 8 ... Eccentric cam.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-55-98016 (JP, A) JP-A-62-27210 (JP, A) JP-A-59-68766 (JP, A) JP-A-2- 157880 (JP, A) JP-A-57-136661 (JP, A) JP-A-57-160651 (JP, A) JP-A-57-8174 (JP, A)

Claims (1)

(57) [Scope of request for utility model registration] 1. A heating member, an endless film in contact with the heating member, a driving member for driving the film, a driven member for following the movement of the film, and being in pressure contact with the heating member via the film. A pressurizing member, wherein the film is hung around the heating element, the driving member and the driven member, and sandwiches a recording material carrying an unfixed image at a fixing unit where the film and the pressurizing member are in contact with each other. In a fixing device that conveys and fixes, the driving member has a fixed position, the driven member is displaceable to control the shift of the film, and the driven member is upstream of the fixing unit with respect to a moving direction of the film. A fixing device provided on the side of the fixing member and downstream of the driving member.