JPH06337612A - Fixing device - Google Patents

Abstract

PURPOSE:To obtain appropriate pressure in accordance with the kind of a recording material by simple constitution by providing a lever which can be operated by a user and by which a position for making a fixing rotating body generate normal fixing pressure and a position for making it generate the fixing pressure for special paper are switched. CONSTITUTION:The lever 15 is rotated to a position 17 in the case of performing jamming processing. At such a time, a pressure releasing plate 6 is pressed down to a position 19, and a space is formed between a fixing roller 2 and a pressure roller 3 in such a state, so that the jamming processing is easily performed. In the case the special paper passes, the lever 15 is rotated to get over a post 16 and reach a position 18 in order to prevent the paper from being wrinkled. At such a time, the plate 6 is pressed down to a position 20. Since the pressure of a pressuring spring 5 is received by the lever 15 through the plate 6 in such a state, only the pressure by as much as the elastic deformation of the roller 3 equivalent to a certain nip width acts between the rollers 2 and 3. By making the lever 15 in a specified shape, two functions are satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as a copying machine or a printer for fixing an unfixed image on a recording material.

[0002]

2. Description of the Related Art Conventionally, as a fixing method for fixing a toner image on a recording material, a recording material is sandwiched and conveyed by a pair of rotating members and fixed by pressure or pressure and heat.

Further, in recent years, in addition to plain paper, image formation has also been carried out on resin sheets such as OPH films and special paper such as envelopes.

[0004]

However, the proper pressure at the time of fixing is different between the plain paper and the special paper, and wrinkles occur when fixing the envelope.

Therefore, it is possible to automatically change the pressure of the pair of fixing rotators when fixing the special paper, but it is not easy to change the pressure of the pair of fixing rotators, and the size of the apparatus becomes large.

[0006]

SUMMARY OF THE INVENTION The present invention, which solves the above-mentioned problems, is a user-operable fixing device that fixes a recording material supporting an unfixed image between a pair of fixing rotating members by pinching and conveying the recording material. It is characterized by having a lever capable of switching between a first position for generating a normal fixing pressure on the rotating body and a second position for generating a fixing pressure for special paper.

[0007]

FIG. 8 is a sectional view of a fixing device according to an embodiment of the present invention.

In FIG. 8, 1: fixing unit side plate, 2: fixing roller having heater H inside, 3: pressure roller, 4:
Pressure roller bearing, 5: pressure spring, 6: pressure release plate, 7: pressure release lever, 8: envelope lever made of special paper, 9: shaft,
10: Shows the cover of the main body of the image forming apparatus.

9A, 9B, and 9C show the relationship between the axial distance between the fixing roller and the pressure roller during normal sheet passing, jam processing, and envelope sheet feeding, respectively.

When the jam is cleared, the user
First, the cover 10 of the main body of the image forming apparatus is opened to the position shown by the two-dot chain line in the figure, and the rear pressure release lever 7 is rotated about the shaft 9 to the state of 11 of the one-dot chain line. To the position of. Therefore, a slight gap is formed between the fixing roller 2 and the pressure roller 3 as shown in FIG. 9B, and the jam processing is facilitated.

Further, when forming an image on an envelope, the lever 8 in the figure is rotated from the solid line position where normal fixing pressure is generated to the position 12 indicated by the chain double-dashed line about the shaft 9.
The rotation of the lever 8 lowers the pressure release plate 6 to the position 14.

Therefore, the pressure between the fixing roller 2 and the pressure roller 3 becomes smaller than the normal fixing pressure, and has a predetermined small nip width as shown in FIG. 9C.

When the envelope is fed, only a pressure corresponding to the elastic deformation of the pressure roller acts on the envelope.

As described above, wrinkles can be prevented by reducing the fixing pressure when the envelope is passed.

Further, since the fixing pressure can be switched by the user simply by operating the lever, the mechanism is very simple.

S is a thermistor for detecting the surface temperature of the fixing roller 2, and the energization of the heater H is controlled so that the detected temperature of the thermistor becomes a predetermined fixing temperature.

In this embodiment, the same fixing temperature is set for both normal fixing and envelope fixing.

In this embodiment, since the jam clearance lever and the pressure switching lever are provided, the user may make a mistake in the operation.

Next, a more preferred embodiment of the present invention will be described.

FIG. 1 is a sectional view of this embodiment, and FIGS. 3 and 4 are a partial top view and a partial sectional view of this embodiment, respectively.

Reference numeral 15 is a lever, 16 is a stopper, and other reference numerals are the same as those in the embodiment shown in FIG.

The pressing force of the spring 5 acts on the pressure roller 3 via the pressure release plate 6.

In the case of carrying out the jam clearance in this embodiment, the lever 15 is rotated to the position 17 in the figure shown by the chain double-dashed line. At this time, the pressure release plate 6 is pushed down by the portion 15a in FIG. 2 to the position 19 in FIG. In this state, a gap is formed between the fixing roller 2 and the pressure roller 3 as shown in FIG. 9B, so that the jam processing can be easily performed. Further, when the lever 15 is at the position 17, the knob portion (15c in FIG. 2) of the lever 15 hits the cover 10 as shown in FIG. 1, and the cover does not close. Therefore, it is possible to prevent the user from forgetting to return the lever after the jam processing and passing the sheet as it is.

Next, when the special paper is passed, the lever 15 is rotated over the boss 16 to the position 18 in the drawing in order to prevent the occurrence of wrinkles. At this time, the pressure release plate 6 is 1 in FIG.
It is lowered to the position of 20 by the part of 5b. In this state (see FIG. 9C), the pressure of the pressure spring 5 is received by the lever 15 via the pressure release plate, so that there is a certain nip width between the fixing roller 2 and the pressure roller 3. That is, only the pressure corresponding to the elastic deformation of the pressure roller corresponding to the above is acting.

As described above, according to this embodiment, it is possible to satisfy the two functions only by forming one lever 15 into the shape shown in FIG. Therefore, it is possible to prevent a user's erroneous operation. Furthermore, since the number of parts is reduced, it is possible to reduce costs and save space.

In the present embodiment, the fixing temperature is changed according to the position of the lever 15 by detecting the position of the lever 15 by a detection mechanism (not shown).

That is, the fixing temperature is set to be lower when the envelope is passed than when it is normally passed.

For this reason, it is possible to prevent the temperature rise of the non-sheet passing portion when a narrow envelope is continuously fed in the longitudinal direction.

FIG. 5 is a partial sectional view of still another embodiment of the present invention, and FIG. 6 is a schematic view of the apparatus shown in FIG.

In the figure, 22 is a pressure release plate, 23 is a pressure release cam,
24 is a boss, 25 is a pressure release cam lever portion, and 33 is a 2
3 shows three moving rails. The other numbers represent the same numbers as the above numbers.

The pressure release plate 22 and the bearing 4 are press-fitted, and when the pressure release plate 22 is lowered, the bearing 4 is also lowered together with the pressure roller 3.

Further, as shown in FIG. 6, the boss 24 is not in contact with any part of the pressure releasing cam 23 in a normal state. Therefore, the pressure of the pressure spring 5 is applied to the bearing 4 via the pressure release plate 22.
The pressure roller is structured so that the pressure acts on the pressure roller.

In the case of carrying out the jam processing, the lever 25 in FIG. 6 is moved to the left in the drawing along the rail 33, so that the boss 24 is pushed downward by the surface 26 of the cam 23. Therefore, the pressure roller bearing 4 and the pressure roller 3 are also pushed down via the pressure release plate 22. At this time,
Similar to the first embodiment, since a gap is formed between the fixing roller and the pressure roller as shown in FIG. 9B, the jam processing can be easily performed. Furthermore, lever 2 is used for jam clearance
Since the tip of 5 has a structure that abuts against the cover 10, the cover 10 does not close. Therefore, it is possible to prevent the user from forgetting to return the lever.

When the envelope is passed, the lever 25 is pushed rightward in the figure contrary to the time of jam processing. By this operation, the boss 24 is slightly lowered by the surface 27 in the cam 23. At this time, the nip width required for passing the special paper is maintained between the fixing roller and the pressure roller (see FIG. 9C), and the envelope has an elastic deformation amount of the pressure roller. It has a structure in which only the pressure of acts.

By the mechanism described above, one lever 2
Only by operating 5, it is possible to satisfy the two fixing conditions of normal paper feeding and special paper feeding.

Furthermore, since there is only one lever, the number of parts is reduced, and space saving and cost reduction are possible.

FIG. 7 shows still another embodiment of the present invention. In FIG. 7, 28 is a pressure release lever, 29 is a fixing roller bearing, and 30 is a knob of the pressure release lever. Other numbers mean the same as those described above.

In the present embodiment, FIG. 7 shows a state of normal sheet passing (see FIG. 9A). When a jam occurs in this state, the knob 30 of the pressure release lever 28 is rotated in the direction of the arrow along the outer circumference of the fixing roller bearing 29, so that the protrusion 3 present on the circumference of the pressure release lever 28.
1 pushes down the pressure roller bearing 4, and a slight gap is generated between the fixing roller and the pressure roller as shown in FIG. 9B. Therefore, the jam processing can be easily performed.

Next, when the special paper is passed, various problems may occur in a normal state. In view of this, in this embodiment, the knob 30 of the pressure release lever is rotated further in the direction of the arrow around the outer periphery of the fixing roller bearing from the position during jam processing, so that the protrusion 32, which is lower than the protrusion 31, causes the pressure roller bearing 4 to move. Push down. The relationship between the fixing roller and the pressure roller at this time is as shown in FIG. In this state, the pressure of the pressure spring 5 is the pressure release lever 28.
Are all received by the pressure roller, and only the pressure corresponding to the elastic deformation of the pressure roller acts in the nip of the pressure roller.

By using the mechanism as described above,
Only the pressure release lever 28 can handle jam processing and special paper passing. That is, since the number of levers is one, it is possible to prevent erroneous operation by the user. Further, by disposing the rotation center of the lever on the fixing roller bearing, the pressure release plate described in the first and second embodiments becomes unnecessary, so the number of parts is reduced as compared with the first and second embodiments,
Enables space saving and cost reduction.

In the present proposal, the description has been limited to the case where the second pressing force becomes weak. However, in the present proposal, the second pressing force can be made stronger than the first pressing force depending on the type of special paper.

[0042]

As described above, according to the present invention, an appropriate fixing pressure according to the type of recording material can be obtained by a simple operation by the user, and the mechanism is simple.

Further, by also using the jam clearance lever, there is an effect of preventing a user's erroneous operation.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a fixing device according to an exemplary embodiment of the present invention.

FIG. 2 is an external view of the lever of the embodiment shown in FIG.

FIG. 3 is a partial top view of the embodiment shown in FIG.

FIG. 4 is a partial sectional view of the embodiment shown in FIG.

FIG. 5 is a partial cross-sectional view of another embodiment of the present invention.

FIG. 6 is a schematic view of the embodiment shown in FIG.

FIG. 7 is a schematic view of still another embodiment of the present invention.

FIG. 8 is a cross-sectional view of yet another embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a fixing roller and a pressure roller.

[Explanation of symbols]

 1 side plate of fixing device 2 fixing roller 3 pressure roller 4 pressure roller bearing 5 pressure spring

Front page continued (72) Inventor Katsuhiko Nishimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Toru Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A fixing device which holds and conveys a recording material supporting an unfixed image between a pair of fixing rotators for fixing, wherein a normal fixing pressure is generated by the user so as to generate a normal fixing pressure on the pair of fixing rotators. And a second position for generating a fixing pressure for special paper, the fixing device having a lever. 2. The fixing device according to claim 1, wherein the lever further assumes a third position for releasing the pressure between the pair of fixing rotary members for jam clearance. 3. At least one of the pair of fixing rotators is heated and regulated to a predetermined fixing temperature, and the fixing temperature is changed in response to switching between the first position and the second position of the lever. The fixing device according to claim 1 or 2. 4. The fixing device according to claim 1, wherein the special paper is an envelope, and the fixing pressure is reduced by moving the lever from the first position to the second position.