JP2006098903A - Separating device and fixing unit with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separating device that restrains wear of a roller surface without degrading separability and prolongs a roller life. <P>SOLUTION: The separating device 10 separates paper from a roller after the paper conveyed while held in a nip part 6 formed by a pair rollers 4 and 8 rotated in firm contact with each other is passed through the nip part. At least the one roller 4 has a surface layer having a toner releasability. The separating device 10 abuts on the surface layer of the roller 4 downstream of the nip part 6 in the direction of paper conveyance. The separating device 10 includes a separating claw 12 by which the paper passed through the nip is separated from the roller 4, and a holder 14 holding the separating claw. The width of the leading end of the separating claw 12, which abuts on the surface layer of the roller 4 is set to 2.6 mm or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a separating apparatus that separates a sheet, which is nipped and conveyed at a nip formed by a pair of rotating bodies that rotate in pressure contact with each other, from the rotating body after passing through the nip. The present invention also relates to a fixing device incorporating a separation device.

  Conventionally, as a fixing device of an image forming apparatus such as a copying machine or a printer, an unfixed image is formed by heating and pressurizing a sheet while nipping and conveying the sheet at a nip portion formed by a pair of rollers that rotate in pressure contact with each other. A configuration for fixing to paper is widely used. At least one surface of the roller is in contact with a separation claw for separating the paper after passing through the nip portion from the roller.

  Further, a roller having a toner release layer is known. When the separation claw is brought into contact with such a roller, the surface is easily worn and scratched, so that image noise due to scratches on the surface of the roller may occur on the paper that has passed through the roller.

  Since the film thickness of the roller that wears when the separation claw comes into contact with the surface increases as the linear pressure at which the tip of the separation claw contacts the roller increases, Patent Document 1 discloses that the tip linear pressure is 0.02 N / mm. In the following, a method is disclosed in which the separation claw is brought into contact with the roller with as little force as possible.

On the other hand, in consideration of thermal expansion of the roller, a countermeasure against scratches by a non-contact type separation claw having a tip as close as possible to the roller is generally performed.
JP 2002-14565 A

  However, if the linear pressure is set to the value described in Patent Document 1 simply by weakening the force of a mechanism (for example, a spring) that causes the separation claw to contact the roller, the claw tip load cannot be secured and the separability is impaired. In the case of a non-contact type separation claw, it is possible to prevent the occurrence of image noise due to wear on the roller surface. However, it is necessary to strictly define the gap between the claw tip and the roller. Must be configured to be adjustable. In addition, the separation is inferior compared to the contact type, so it is highly possible that the paper cannot be separated and the paper is wound around the roller. Therefore, it is necessary to provide means for removing the wound paper in the fixing device. And expensive.

  Therefore, the present invention provides a separation apparatus having a contact-type separation claw that is advantageous for realizing low cost, and suppresses wear of the roller surface without impairing the separation performance, thereby extending the life of the roller. Objective.

  It is another object of the present invention to provide a fixing device that extends the life by suppressing the wear of the roller surface with which the separation claw contacts without impairing the separation performance of the separation device.

In order to achieve the above object, a separation apparatus according to the present invention comprises:
In a separation device that separates a sheet conveyed and held in a nip formed by a pair of rotating bodies that are in pressure contact with each other after passing through the nip,
At least one of the rotating bodies has a surface layer having toner releasability,
Separation device
A separation claw that comes into contact with at least one surface layer of the rotator on the downstream side of the nip portion in the sheet conveying direction and separates the sheet that has passed through the nip from at least one of the rotators;
A holder for holding the separation claw;
With
The width of the tip of the separation claw that contacts the surface layer is set to 2.6 mm or more and a predetermined value or less.

A fixing device according to the present invention is a fixing device that fixes a toner image on a sheet by heating and pressurizing the sheet while nipping and conveying the sheet at a nip formed by a pair of rotating bodies that are pressed against each other. A separation device that separates from the rotating body after passing through the nip part,
At least one of the rotating bodies has a surface layer having toner releasability,
Separation device
A separation claw that comes into contact with at least one surface layer of the rotator on the downstream side of the nip portion in the sheet conveying direction and separates the sheet that has passed through the nip from at least one of the rotators;
A holder for holding the separation claw;
With
The width of the tip of the separation claw that contacts the surface layer is set to 2.6 mm or more and a predetermined value or less.

  According to the present invention, by setting the tip end width of the separation claw to 2.6 mm or more, the total contact pressure of the separation claw tip with respect to the roller is ensured to such an extent that the separability is not impaired, and at the same time, the contact line pressure is worn on the roller surface Can be made small enough to suppress

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a fixing device provided with an embodiment of a separation device according to the present invention. The fixing device 2 forms a latent image on an electrophotographic image forming apparatus (for example, a copying machine, a printer, etc.), that is, an image carrier (for example, a photosensitive drum), and then visualizes the latent image with toner. To form a toner image, and then detachably incorporated in a device for transferring the toner image onto a sheet.

  Specifically, the fixing device 2 includes a heating roller 4 having a heating halogen heater (not shown) therein, a pressure roller 8 that presses against the heating roller 4 to form a nip portion 6 through which the sheet passes, and a sheet Are arranged on the upstream side and the downstream side of the nip portion 6 with respect to the conveying direction of the paper, and are provided with guides (not shown) for guiding the paper.

  The heating roller 4 has a hollow metal (for example, aluminum) (having a halogen heater therein) as a base (core metal), and a layer having toner releasability (for example, PTFE (polytetrafluoroethylene) resin) on its surface. Laura. The pressure roller 6 is a roller having a metal (for example, aluminum) as a base, an elastic layer (for example, silicone rubber) on its surface, and a layer having toner releasability (for example, PFA (perfluoroalkoxy) resin) on its surface. is there.

  The fixing device 2 also includes a separation device 10 on the downstream side of the nip portion 6, and separates the paper that has passed through the nip portion 6 from the heating roller 4. When the toner image formed on the sheet is heat-fixed, the heating roller 4 is disposed on the print surface side. However, since the sheet is easily wound around the heating roller, the separation device 10 is provided on the heating roller side. The separated paper is guided along a guide to a paper discharge unit disposed on the downstream side of the fixing device 2.

The separation device 10 includes one or more separation claws 12 arranged along the axial direction of the heating roller 4 (the front and back direction in FIG. 1), and a holder 14 that holds the separation claws 12. The separation claw 12 has an elongated shape extending in a direction substantially perpendicular to the axial direction of the heating roller 4 (the horizontal direction in FIG. 1) in a state where the holder 14 is incorporated in the fixing device 2. The holder 14 includes a pin 16 extending substantially parallel to the axial direction (rotation center axis) of the heating roller 4. As shown in FIG. 2A, the separation claw 12 is provided with projections 15 protruding toward the holder 14 at both ends of the separation claw in the width direction, as shown in FIG. The protrusion 15 is formed with a pin hole 18 [FIG. 2 (b)] in which the inner diameter D _i is slightly larger than the outer diameter D _{o of the} pin 16 and the pin 16 is fitted into the clearance. Is rotatably supported by the pin 16.

  A protrusion (not shown) is provided on one end side (rear end side) of the separation claw 12 so as to face the holder 14. On the other hand, a protrusion (not shown) is also provided in the portion of the holder 14 facing the protrusion of the separation claw 12. One end and the other end of the spring 20 (FIG. 1) are fixed to these protrusions, so that the separation claw 12 is attached to the direction opposite to the rotation direction of the heating roller 4 (the clockwise direction in FIG. 1) around the pin 16. I'm trying to help. Therefore, the other end, that is, the tip of the separation claw 12 comes into contact with the heating roller 4. The tip width W [FIG. 2 (c)] of the separation claw 12 is defined as a predetermined value as shown below.

  In the fixing device 2 having such a configuration, at the time of image formation, the sheet onto which the toner image has been transferred is pressed and heated while being nipped and conveyed through the nip portion 6 formed by the heating roller 4 and the pressure roller 8. Unfixed toner is fixed. The paper that has passed through the nip portion 6 is separated from the heating roller 4 by the separation claw 12 of the separation device 10 and then conveyed to the paper discharge portion.

  The inventor has found the desired tip width W of the separation claw by the following experiment.

Experiment 1
Using the fixing device of FIG. 1, the probability of occurrence of separation failure was determined when 50 sheets of paper were passed for each of the plurality of claw tip loads under the following conditions.

Experimental conditions Room temperature 30 ° C, humidity 85%
Paper type: 54 g / mm ² paper Image: Formed from the leading edge in the transport direction

  The experimental results are shown in FIG. As shown in the figure, the ability (separability) of separating the paper to be wound around the heating roller 4 depends on the total pressure with which the tip of the separation claw 12 contacts the heating roller, and is about 0.08 N by experiment. If it was above, it turned out that the separability is ensured.

Experiment 2
The amount of wear on the surface of the heating roller 4 after traveling distance equivalent to 120,000 sheets (accelerated durability test) is measured for each of the plurality of separation pawl 12 tip linear pressures under the following conditions using the fixing device of FIG. Measured with a meter. Thereafter, the sample image was visually judged.

Experimental conditions The peripheral speed of the heating roller 4: 390 mm / sec The surface temperature of the heating roller 4: 190 ° C.

  The result of the experiment is shown in FIG. When the linear pressure at the tip of the separation claw 12 is large, the amount of wear also increases.

  From the results of Experiments 1 and 2, if the width of the tip of the separation claw 12 is about 2.6 mm (≈0.08 N ÷ 0.03 N / mm) or more, the heating roller 4 and thus the fixing device 2 is high while ensuring separation. It was found that the lifetime could be realized.

  By the way, it is desirable that the tip of the separation claw 12 is completely parallel to the surface of the heating roller 4. However, when the tip of the separation claw is widened, for example, as shown in FIG. Thus, when the pin 16 of the holder is slightly inclined with respect to the surface of the heating roller, the tip of the claw may come into contact with the one end 12S in the width direction of the tip without contacting the entire surface of the heating roller. As a result, the amount of wear increases and the life of the heating roller 4 decreases.

Therefore, in order to make the tip of the separation claw 12 parallel to the surface of the heating roller 4, the inner diameter of the pin hole 18 of the separation claw is slightly increased with respect to the outer diameter of the pin 16 that supports the separation claw. By providing a play of a predetermined size between them, the tip of the separation claw can be brought into contact with the surface of the heating roller without contact even if the pin 16 is inclined as shown in FIG. Referring to FIG. 2B, in the present embodiment, the maximum fitting clearance L between pin 16 and pin hole 18 (the difference between pin hole inner diameter _Di and pin hole outer diameter _Do ) is a predetermined value. Stipulated in the value. 2B and 5, the difference between the outer diameter of the pin 16 and the inner diameter of the pin hole 18 is shown larger than the actual.

  The inventor changes the claw width for each of the plurality of maximum fitting gaps, and even if the pin 16 (holder 14) is tilted, the angle of the limit at which the tip of the separation claw 12 can be kept parallel to the surface of the heating roller 4 ( The angle formed between the axial direction of the pin and the axial direction of the heating roller was determined by numerical simulation. FIG. 6 shows the simulation result.

  When the holder 14 is incorporated in the fixing device 2, the inclination of the axial direction of the pin 16 with respect to the axial direction of the heating roller 4 is within about 1 degree (actual value including assembly and component tolerance). Has been confirmed. Therefore, when the separation claw width is about 2.6 mm or more, the maximum fitting gap in which the inclination of the axial direction of the pin 16 with respect to the axial direction of the heating roller 4 is within about 1 degree is 0.05 mm from FIG. (For example, if the maximum fitting clearance is 0.03 mm, the allowable angle is less than 1 degree when the claw width is 2.6 mm. Therefore, when the holder 14 is incorporated in the fixing device 2, the angle is about 1 degree. If there is, a win will occur.)

  By increasing the maximum fitting gap, it is possible to bring the separation claw into contact with the heating roller even if the claw tip is wide, but the experiment by the present inventors has shown that the maximum fitting gap is about 0.4 mm or more. Thus, it was found that when the heating roller 4 is driven, a slip stick is generated between the separation claw 12 and the heating roller, and a stable contact state cannot be maintained. Therefore, the upper limit of the maximum fitting clearance is set to about 0.3 mm. In order for the angle at this time to be within 1 degree, the usable nail width is about 18 mm at maximum from FIG.

  The above description relates to an embodiment of the present invention, and the present invention is not limited to this and can be variously modified. For example, in the above-described embodiment, the separation claw is provided on the heating roller side, but it may be provided on the pressure roller side instead of or in addition to this. The above discussion holds for the separation claw that also contacts the pressure roller. Further, the rotating body that contacts the separation claw and the rotating body that contacts the rotating body are not limited to a roller shape, and may be, for example, a belt shape.

  Furthermore, in the said embodiment, although the pin hole 18 was provided in the separation nail | claw 12, and the pin 16 was provided in the holder 14 which hold | maintains a separation claw, a pin is provided in a separation nail | claw and a pin is fitted in a clearance gap in a holder instead. A pin hole may be provided.

1 is a side view showing an embodiment of a fixing device according to the present invention. (A) Sectional drawing of the separation apparatus along the IIa-IIa line | wire of FIG. (B) The partial expanded side view of the separation apparatus of FIG. (C) The fragmentary figure which shows the front-end | tip part of the separation nail | claw of FIG. The graph which shows the relationship between the front-end | tip load of a separation nail | claw calculated | required in Experiment 1, and a separation defect incidence. The graph which shows the relationship between the tip linear pressure of the separation nail | claw calculated | required in Experiment 2, and the abrasion loss of the heating roller surface. (A) The figure which shows the state which a separation nail | claw contacts a heating roller, when the direction of the pin of a holder inclines. (B) The figure which shows the state which the front-end | tip of a separation nail contacts the heating roller over the width direction even if the direction of the pin of a holder inclines. The graph which shows the relationship between the width | variety of the separation nail | claw calculated | required from the numerical simulation, and the limit value in which the direction of the angle between the axial direction of a holder pin and the axial direction of a heating roller does not generate | occur | produce.

Explanation of symbols

2 Fixing device 4 Heating roller 6 Nip part 8 Pressure roller 10 Separating device 12 Separating claw 14 Holder 16 Pin 18 Pin hole L Maximum fitting gap

Claims (5)

In a separation device that separates a sheet conveyed and held in a nip formed by a pair of rotating bodies that are in pressure contact with each other after passing through the nip,
At least one of the rotating bodies has a surface layer having toner releasability,
Separation device
A separation claw that comes into contact with at least one surface layer of the rotator on the downstream side of the nip portion in the sheet conveying direction and separates the sheet that has passed through the nip from at least one of the rotators;
A holder for holding the separation claw;
With
A separation device characterized in that the width of the tip of the separation claw in contact with the surface layer is set to 2.6 mm or more and a predetermined value or less. The holder includes a pin that extends substantially parallel to at least one rotation center axis of the rotating body and supports the separation claw,
The separation claw has a pin hole that fits into the gap with the pin.
The separation device according to claim 1, wherein a maximum fitting gap between the pin and the pin hole is set to 0.05 mm or more and 0.3 mm or less. The separation claw includes a pin extending substantially parallel to at least one rotation center axis of the rotating body,
The holder has a pin hole that fits into the pin with a gap.
The separation device according to claim 1, wherein a maximum fitting gap between the pin and the pin hole is set to 0.05 mm or more and 0.3 mm or less.   The separation apparatus according to claim 2 or 3, wherein the predetermined value is 18 mm. 5. A fixing device that fixes a toner image onto a sheet by heating and pressurizing the sheet while nipping and conveying the sheet at a nip formed by a pair of rotating bodies that rotate in pressure contact with each other. 6. A fixing device comprising the separation device according to 1.

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