JPH1010912A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation of a roller even when the stand-by time is long, and to provide an image of high quality free from the unevenness caused by the fixing, by making a fixing roller and a pressure roller kept into pressure contact with each other only in the printing operation, and installing a means for releasing the pressure at the time except for the printing. SOLUTION: A side plate holder 20 holds a bearing of a pressure roller 2, and is engaged with a pin 23. The side plate holder 20 is turnable on the pin 2 of fulcrum, and is pressed to a fixing roller 1 by a pressure spring 22 at the printing operation. A nip releasing can 21 moves the side plate holder 20 to the side of the pressure spring at the ordinary time, to release the pressure between the fixing roller 1 and the pressure roller 2. The nip releasing cam 21 is controlled by a pulse motor by 1/4 rotation. Thereby the fixing roller 1 and the pressure roller 2 are opened at the time when a power source is built up, and they are brought into pressure contact with each other as a print signal is triggered. The rollers are opened again, when the print signal is not reached for a certain time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fixing device for fusing toner with heat and pressure in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In a fixing device of an electrophotographic apparatus, a transfer paper carrying an unfixed toner image is passed through a nip portion of a pair of a fixing roller provided with a heater therein and a pressing roller pressed against the fixing roller. 2. Description of the Related Art A heat roller fixing device that forms paper, melts toner by heat, and fuses the toner to the transfer paper surface by pressing force is widely used.

Conventionally, the fixing roller has toner attached thereto,
The so-called offset phenomenon occurs, disturbing the image,
The paper may be soiled, or the paper may wind around the rollers. This phenomenon also occurs on the pressure roller side. That is, the minute toner adhering to the fixing roller moves to the pressure roller side between the sheets and accumulates to cause the phenomenon described above. Further, when a paper jam occurs in the fixing unit, the fused toner adheres to the fixing roller. By removing the paper and restarting, the toner on the roller surface is removed by the cleaning pad. Further, since the dirt on the fixing roller also moves to the pressure roller, a cleaning unit is required on the pressure roller side. Further, the fixing roller and the pressure roller wait for a print signal in a state in which they are pressed against each other, and the heater is repeatedly turned on and off to maintain a constant temperature. Therefore, if this state continues for a long time, there is a problem that the roller portion (nip portion) in pressure contact is permanently deformed and horizontal streaks are generated in the image. Therefore, when the product is shipped, it is shipped with the nip released by providing a nip release piece and release lever, etc., so that the roller does not permanently deform even if it is left for a long time, but at the time of installation, the release piece The fixing roller and the pressure roller are pressed against each other in order to remove the toner and return the lever, so that the roller is easily deformed.

[0004]

In the prior art, since toner adheres and accumulates on the pressure roller side as well, a cleaning means is required, and the configuration is complicated and expensive. Further, the deformation of the roller adversely affects the image.

[0005]

In order to solve the above-mentioned problems, there is provided means for pressing the fixing roller and the pressure roller only when printing, and releasing the pressure in other states.

That is, when the power supply is turned on, the fixing roller and the pressure roller are open and are brought into pressure contact with a print signal as a trigger. If the print signal does not arrive for a certain period of time, the rollers are opened again. Therefore, the pressure is applied only during printing, and the roller is not deformed. The certain time varies depending on the roller diameter, rubber thickness, rubber hardness and the like, but if it is between 1 and 5 minutes, there is no effect on the image. Further, when a paper jam occurs in the fixing unit, the operation is stopped together with the error message and the pressure roller is opened, so that the jammed paper can be easily removed. Further, since the fixing roller and the pressure roller are not in contact with each other, the toner adhered to the fixing roller is collected on the cleaning pad after several rotations, so that the pressure roller is not stained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of the fixing device of the present invention. Reference numeral 1 denotes a fixing roller formed by molding silicone rubber 3 on the surface of an aluminum tube 4 and a heat lamp 5 serving as a heat source in the center.
Is arranged. 2 is a pressure roller and is composed of a fixing roller 1
Is almost the same as Reference numeral 6 denotes an offset prevention liquid application device which applies the felt 8 impregnated with silicone oil 7 to the surface of the fixing roller 1. Reference numeral 9 denotes an oil blade for regulating the amount of oil applied to the surface of the fixing roller 1, which serves to apply the oil thinly and uniformly in the longitudinal direction of the fixing roller 1. Reference numeral 10 denotes a plastic oil pan which serves as an oil pan. Therefore, the oil blade 9 and the felt 8 are all incorporated therein, and do not leak out of the oil pan 10. In addition, an oil reservoir 11 is provided in a part of the oil pan 10 and a part of the felt 8 is immersed therein.
The silicone oil 7 is sucked up by the capillary phenomenon and is applied to the fixing roller 1. Numeral 12 denotes an oil bottle, which is automatically supplied when the water level falls below the draft level of the oil reservoir 11.
Reference numeral 13 denotes a cleaning pad that collects and cleans minute toner adhered to the fixing roller 1. Reference numeral 14 denotes a thermistor for controlling the temperature of the fixing roller 1 to be constant.

[0008] With the above construction, the unfixed image is fixed by heat and pressure. Therefore, if the standby state continues for a long time, the nip portion between the fixing roller 1 and the pressure roller 2
The heat lamp 5 is left in the pressed state, and is repeatedly turned on and off. Therefore, unevenness occurs when the rubber in the nip portion is deformed and the image is fixed. The deformation of the nip portion differs depending on the leaving time, and there is no problem if it is several minutes. However, if it is left for several hours, it takes time for the deformation of the nip portion to return to the original state. A typical example is that the time from shipment from a factory to installation is often six months to one year or two years, and if the fixing roller 1 and the pressure roller 2 are left pressed against each other during that time, In the image, uneven fixation occurs. To prevent this, as described in the prior art section, a nip release piece (installed at the time of shipment and removed at the time of installation) or a nip release lever (a structure that can release or hang the nip structurally) is used. Although it is provided and handled, in any case, the response after installation is not made.

FIG. 2 is a cross-sectional view of the fixing device of the present invention which can be used even after installation. Reference numeral 20 denotes a side plate holder for holding a bearing of the pressure roller 2, which is engaged with a pin 23. The side plate holder 20 is rotatable around a pin 23, and presses the fixing roller 1 by a pressing spring 22 during printing. Reference numeral 21 denotes a nip release cam, which normally moves the side plate holder 20 to the pressure spring 22 side to release the pressure between the fixing roller 1 and the pressure roller 2 as shown in FIG. The nip release cam 21 is controlled by a 1/4 turn by a pulse motor (not shown).

FIG. 4 is an application example. Reference numeral 24 denotes a pressurizing spring which presses and fixes the anti-offset liquid applying device 6 and 25 transmits the moving distance of the nip release cam 21 to the anti-offset liquid applying device 6. And a state where the felt 8 and the oil blade 9 are separated from the fixing roller 1.
Accordingly, the deformation of the fixing roller 1 due to the felt 8 and the oil blade 9 is eliminated.

[0011]

According to the present invention, the roller is not deformed, no matter how long the leaving time from shipment from the factory to the installation and the waiting time after the installation are performed. Can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a fixing device according to the present invention.

FIG. 2 is an explanatory diagram of a fixing device according to the present invention.

FIG. 3 is an explanatory diagram of a fixing device according to the present invention.

FIG. 4 is an explanatory diagram of a fixing device according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing roller, 2 ... Pressure roller, 3 ... Silicone rubber, 6 ... Offset prevention liquid coating device, 8 ... Felt, 9
... oil blade, 11 ... oil reservoir, 12 ... oil bottle, 13 ... cleaning pad, 14 ... thermistor, 20 ... side plate holder, 21 ... nip release cam, 22,
24 ... Pressure spring, 23 ... Pin, 25 ... Stay.

Claims (3)

[Claims] 1. A fixing device for fixing an unfixed toner image by passing a supporting material for supporting the unfixed toner image between a pair of rollers. A fixing device, comprising: means for releasing a force. 2. The fixing device according to claim 1, further comprising means for canceling the pressing force between the rollers by using a print signal as a trigger, and canceling the pressing force if the print signal does not come for 1 to 5 minutes. 3. A fixing device comprising means for avoiding an oil unit having an oil applying device and an oil blade from a fixing roller, wherein the pressing operation between the rollers is released simultaneously with one rotation operation. 3. The fixing device according to 1 or 2.