JP2005181381A - Fixing device and image forming apparatus with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device in which the printed side of paper is prevented from being damaged when the paper is separated from a heat roller and the surface of the heat roller is also prevented from being damaged. <P>SOLUTION: The fixing device has a heat roller and a pressure roller which rotate in firm contact with each other, and fixes an unfixed toner image under heat by allowing paper with the unfixed toner image held on it to pass through a nip between both the rollers. The fixing device is characterized by including: a separating body 22 which comes into elastic contact with the heat roller 7 downstream of the nip 21 between the rollers 7a and 7b and separates the paper P on the heat roller 7a; and a peeling claw 24 which peels the paper P sticking to the separation body 22 from it. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device in an image forming apparatus such as a laser printer and an image forming apparatus including the fixing device.

2. Description of the Related Art Conventionally, as a fixing device in an image forming apparatus such as a laser printer, for example, a device described in Japanese Patent Application Laid-Open No. 2002-323827 (hereinafter referred to as patent document) is known. In the fixing device described in this patent document, a nip portion is formed between a heating roller and a pressure roller that rotates in pressure contact with the heating roller, and a sheet on which an unfixed toner image is carried on the nip portion. Heat fixing is performed by passing it through. Further, when the paper is heat-fixed, the paper may be wound around the heat roller by the heat and pressure of the heat roller. For this reason, since it is necessary to separate and discharge the paper wound around the heating roller, in the above-mentioned patent document, the separation roller having a large number of radial resin claws formed on the surface is used as the nip portion of the heating roller. The sheet is wound on the surface of the heating roller so that a large number of claw portions of the separating roller are pressed against the surface of the heating roller to separate the paper wound around the heating roller. At this time, the rotation direction of the heating roller and the separation roller are rotated in the same direction, for example, when the heating roller is rotated clockwise, the separation roller is also rotated in the same clockwise direction, and the claw portions sequentially contact in the counter direction. Thus, the sheet separating action from the heating roller is increased.
JP 2002-323827 A

  In the above prior art, when the nail part is pressed against the heating roller and separated from the heating roller, the nail part rotates in the same direction as the heating roller, so that the nail part knocks down the paper edge. That is, it enters and separates on the printing surface side of the paper. Therefore, extreme care must be taken so that the print surface of the paper is not damaged by the nail portion, and the arrangement of the separation roller on which the nail portion is formed and the setting of the pressure contact state of the nail portion to the heating roller are very important. There is a problem of being troublesome.

  In addition, the claw part is made of resin, but in order to improve the paper separation action, its hardness must be increased, and when the claw part is strongly pressed against the heating roller, the surface of the heating roller There is a problem that it is easily scratched.

  The present invention solves the above-mentioned problems of the prior art, and there is no risk of scratching the printing surface of the paper when separating the paper from the heating roller, and the fixing device does not damage the surface of the heating roller. An object of the present invention is to provide an image forming apparatus provided with the fixing device.

  In order to achieve the above object, the invention described in claim 1 includes a heating roller and a pressure roller that rotate in pressure contact with each other, and a sheet on which an unfixed toner image is carried at a nip portion between both rollers. In a fixing device that performs heat fixing by passing, a separator that elastically contacts the heating roller and separates the paper on the heating roller on the downstream side from the nip portion between the two rollers, and a paper that adheres to the separator It has the peeling nail | claw which peels from a isolation | separation body, It is characterized by the above-mentioned.

  Thus, the paper wound around the heating roller is separated from the heating roller by the separator, and the back surface of the separated paper is attached to the separator. Further, the paper attached to the separator is peeled off from the back side of the paper by a peeling claw and discharged from the inside of the apparatus to the outside. Therefore, the separator and the peeling claw do not come into contact with the printing surface on the surface of the paper, and the printing surface is not damaged.

  Further, since the separator is elastically contacted with the heating roller to separate the paper from the heating roller, it is not necessary to increase the contact pressure between the separator and the heating roller, and the surface of the heating roller is damaged. It is prevented from sticking.

The invention according to claim 2 is the invention according to claim 1,
The separation body is constituted by a separation rotating body having a diameter smaller than that of the heating roller.

  As a result, the paper wound around the heating roller is separated from the heating roller by the separation rotator and the back surface of the paper is attached to the separation rotator, so that the printing surface of the paper is not damaged. Further, since the separation rotating body has a small diameter, the sheet can be reliably separated from the heating roller.

The invention according to claim 3 is the invention according to claim 2,
The separation rotating body is a separation rotating roller whose surface is coated with silicon rubber.

  The elasticity of the silicon rubber prevents the separation rotator from damaging the heating roller, and the heat resistance of the silicon rubber prevents the separation rotator from being deteriorated due to heat from the heating roller.

  According to a fourth aspect of the present invention, in the invention according to the second or third aspect, the contact portion between the heating roller and the separation rotating body moves from the nip portion around the rotation center of the heating roller. It arrange | positions in the 90 degree area | region in the nip part downstream.

  As a result, the paper wound around the heating roller is separated from the heating roller by the separation rotator without bending, and the back surface of the paper is attached to the separation rotator.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the potential difference between the separator and the paper is made larger than the potential difference between the heating roller and the paper. The paper is separated from the heating roller.

  As a result, the paper wound around the heating roller is easily separated from the heating roller by the separator using the potential difference, and the back surface of the paper is attached to the separator.

  According to a sixth aspect of the invention, there is provided the paper according to the fifth aspect, wherein the separator is charged with the same polarity as the toner carried on the paper and is charged with the opposite polarity to the toner. Charging means for charging the pressure roller with the same polarity as the back surface is provided, and the sheet on the heating roller is attached to the separator by charging of the charging means.

  As a result, the paper wound around the heating roller is easily separated from the heating roller by the separator using the charging polarity, and the back surface of the paper is attached to the separator.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to fourth aspects, the sheet on the heating roller is separated by providing an adhesive portion on at least a surface of the separated body. It is characterized by being attached to the body.

  As a result, the paper wound around the heating roller is easily separated from the heating roller by the viscosity of the adhesive portion of the separator, and the back surface of the paper is attached to the separator.

  The invention described in claim 8 is characterized in that, in the invention described in claim 7, the separator is constituted by an adhesive roller.

  As a result, the paper wound around the heating roller is easily separated from the heating roller due to the viscosity of the separator made of an adhesive roller, and the back surface of the paper is attached to the separator.

  The invention according to a ninth aspect is the invention according to any one of the second to eighth aspects, wherein the peeling claw includes the heating roller, the separation rotator and the rotation center of the separation rotator. It arrange | positions in the 90 degree | times area | region in the contact part downstream from the contact part.

  As a result, the paper attached to the separation rotating body is peeled off from the back surface of the paper by the peeling claw before being attached too much to be peeled off and discharged.

  The invention described in claim 10 is characterized in that, in the invention described in any one of claims 1 to 9, the peeling claw is disposed apart from the separator.

  Thus, the paper attached to the separator is peeled off from the back surface of the paper by the peeling claw and discharged. At this time, since the peeling claw is arranged apart from the separated body, preferably with a gap of 0.4 mm, the peeling claw does not cause a damage to the separated body.

  The invention according to claim 11 is the invention according to any one of claims 1 to 10, wherein the peeling claw is configured by covering a rigid plate-like member with Teflon (registered trademark). It is characterized by that.

  Due to the abrasion resistance of Teflon (registered trademark), the peeling claw does not wear due to friction with the paper, and can maintain an appropriate peeling action of the paper for a long time.

According to a twelfth aspect of the present invention, there is provided a photosensitive member on which an electrostatic latent image is formed, a developing unit that develops the electrostatic latent image on the photosensitive member with toner, and a toner image developed by the developing unit. And a fixing device according to claim 1 for fixing the unfixed toner image transferred onto the paper by the transfer means. And
Thus, an image forming apparatus having the same operational effects as the invention according to any one of claims 1 to 11 can be provided.

  According to the present invention, the separation body attaches the back surface of the paper to the separation body without touching the printing surface of the paper on the heating roller, and further, the paper attached to the separation body does not touch the printing surface with the peeling claw. Since the back side of the paper is peeled off and discharged from the inside of the apparatus to the outside, it is possible to prevent the printing surface of the paper from being damaged.

  Further, since the separator can separate the paper by adhesion without increasing the contact pressure to the heating roller, it is possible to prevent the surface of the heating roller from being damaged.

  In a fixing device that includes a heating roller and a pressure roller that rotate in pressure contact with each other, and that heat-fixes when a sheet carrying an unfixed toner image passes through a nip portion between the two rollers. A separation member that elastically contacts the heating roller and separates the paper on the heating roller on the downstream side of the nip portion, and a separation claw that separates the paper adhering to the separation member from the separation member. To achieve.

  Hereinafter, a laser printer which is an electrophotographic image forming apparatus to which an embodiment of a fixing device according to the present invention is applied will be described.

  FIG. 1 is a side sectional view of the laser printer 1. The laser printer 1 includes a main body 2, an opening / closing door 3 provided on the front panel 2 a of the main body 2, a paper transport mechanism 4 provided in the main body 2, a scanner unit 5, a process unit 6, a fixing device 7 and the like. The rear upper surface 2b of the main body 2 functions as a tray that receives printed sheets.

  Here, the scanner unit 5, the process unit 6, the fixing unit 7, and the like correspond to the print mechanism unit. The process unit 6 can be attached to and detached from a predetermined part in the main body, and has a cartridge structure. The process unit 6 includes a photosensitive drum 8 as a photosensitive member, a scorotron charger 9, a developing roller 10 as a developing means, a toner box 11, a toner supply roller 13, and the like in a casing (not shown). And is detachably attached to the main body 2 by appropriate means.

  Further, the transfer roller 12 as a transfer means is arranged in contact with the photosensitive drum 8, and a transfer bias voltage, for example, a voltage of -3 kilovolts is applied to the transfer roller 12 from a negative power source. As a result, the paper P passing between the transfer roller 12 and the photosensitive drum 8 is charged to the negative electrode, and the toner image formed on the photosensitive drum 8 is transferred to the paper P.

  A cassette 14 for automatic paper feeding is mounted on the lower part of the main body 2, and the paper P in the cassette 14 is separated by a pickup roller 17 and conveyed toward a pair of registration rollers 15 and 16. After the leading ends of the paper P are aligned by the registration rollers 15 and 16, the paper P is conveyed to the process unit 6. Of the pair of registration rollers 15 and 16, one registration roller 15 is a driving roller, and the other registration roller 16 is a driven roller.

  The scanner unit 5 is disposed on the upper side of the process unit 6 and includes a laser light emitting unit (not shown), a polygon mirror 5a, lenses 5b and 5c, a reflecting mirror 5d, and the like. The laser beam from the scanner unit 5 irradiates and exposes the outer peripheral portion of the rotating photosensitive drum 8 charged by the scorotron charger 9 by high-speed scanning, as indicated by the solid arrow. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 8.

  As the toner, non-magnetic one-component toner is used, and has a structure that is positively charged by friction between a developing roller 10 and a toner supply roller 13 described later. The toner in the toner box 11 is supplied to the developing roller 10 via the toner supply roller 13, and is formed into a toner layer having a constant thickness by the blade 10a. Thereafter, the toner is carried on the developing roller 10 and supplied to the photosensitive drum 8.

  In addition, the electrostatic latent image formed on the surface of the photosensitive drum 8 is visualized as a toner image by being attached with toner from the developing roller 10. While the sheet P passes between the photosensitive drum 8 and the transfer roller 12, the toner image is transferred to the sheet P by the transfer roller 12, and the sheet P carrying the unfixed toner image is sent into the fixing device 7. It is fixed. The toner remaining on the surface of the photosensitive drum 8 is collected by the developing roller 10. As will be described in detail later, the fixing device 7 heats and fixes toner on a sheet, and includes a heating roller 7a and a pressure roller 7b pressed against the heating roller 7a. Conveying rollers 18a and 19a are arranged on the downstream side of these rollers 7a and 7b. In order to discharge the paper P conveyed by these rollers to the outside of the main body 2, paper discharge rollers 18 and 19 are provided.

  Next, the fixing device 7 will be described with reference to FIG. The heating roller 7a is formed in a cylindrical shape by drawing a metal such as aluminum which is a conductive material, and includes a halogen heater inside. The heating rotor 7a is rotatably supported by a bearing made of a conductive resin, and is grounded via the bearing. Normally, the surface of the heating roller 7a is almost zero volts. The pressure roller 7b is configured by covering a metal rotation shaft with an insulating material such as silicon rubber. In order to attract the positively charged toner on the paper P to the paper, the pressure roller 7b is applied with a bias voltage, for example, a voltage of −2 to −4 kilovolts via the rotating shaft by the negative power source 7c. . As described above, the paper P carrying the unfixed toner image transferred by the transfer roller 12 passes through the conveyance path 20 and is sent into the fixing device 7 in the arrow direction. The heating roller 7a and the pressure roller 7b rotate in directions opposite to each other as indicated by arrows, and the sheet P passes between the nip portions 21 of both rollers, whereby unfixed toner on the sheet P is obtained. The image is fixed by heating.

  At the time of this heat fixing, the toner on the paper P is melted by the heat of the heating roller 7a and adheres to the heating roller 7a, so that the paper P may wrap around the heating roller 7a. In order to prevent this wrapping, the fixing device 7 has a separating body 22 and a peeling claw 24. The separator 22 is in elastic contact with the heating roller 7a on the downstream side from the nip portion 21 of the rollers 7a and 7b, and separates the paper on the heating roller 7a. The peeling claw 24 is disposed on the downstream side of the contact portion 25 between the heating roller 7 a and the separating body 22, and peels the paper P attached to the separating body 22 from the separating body 22. The peeling claw 24 is configured by coating a rigid plate-like member, for example, stainless steel with Teflon (registered trademark), and has improved wear resistance. The heating roller 7a and the separator 22 rotate in opposite directions. That is, in FIG. 2, when the heating roller 7a rotates in the clockwise arrow direction, the separator 22 rotates in the counterclockwise arrow direction.

  The separating body 22 is a separating rotating body having a smaller diameter than the heating roller 7 a, that is, a separating rotating roller 23. The separation rotation roller 23 is configured by covering a metal rotation shaft with elastic silicon rubber. Thereby, the separation rotation roller 23 is in contact with the heating roller 7a in an elastically pressed state. Since the separation rotating roller 23 has a smaller diameter than the heating roller 7a, the sheet P can be greatly curved to the side opposite to the heating roller 7a and can be reliably separated from the heating roller 7a.

  The separator 22 may be formed from a belt-like moving member such as a belt stretched between a pair of rotating rollers, instead of a roller-like moving member such as the separation rotating roller 23.

  Further, a bias voltage, for example, a voltage of +1 kilovolt is applied to the separation rotating roller 23 by a plus power source 22a. The voltage of the positive power source 22a is set sufficiently higher than the potential of the heating roller 7a so that the potential difference between the separation rotating roller 23 and the paper P is larger than the potential difference between the heating roller 7a and the paper P. Due to the charging of the power source 22 a, a suction force acts on the paper P on the heating roller 7 a from the separation rotating roller 23. The positive power source 22a constitutes a charging means together with the negative power source 7c for biasing the pressure roller 7b.

  As a result, when the paper P is wound around the heating roller 7a, the paper P is separated from the heating roller 7a by the separation rotating roller 23 that rotates in the direction opposite to the rotation direction of the heating roller 7a, and the back surface P2 of the paper P is It is sucked and adhered to the separation rotating roller 23. Thereafter, the leading end portion of the paper P attached to the separation rotating roller 23 is peeled off from the paper back surface P2 side by the peeling claw 24 as shown by a two-dot chain line in FIG. The peeled paper P is guided to the downstream transport rollers 18a and 19a by the paper guide member 7d disposed on the downstream side of the separation rotating roller 23 so as to face the peeling claw 24. Thereafter, the paper P is transported by both transport rollers 18a and 19a, and discharged from the inside of the device to the outside of the device by the paper discharge rollers 18 and 19. Therefore, the separation rotating roller 23 and the peeling claw 24 do not contact the printing surface of the surface P1 of the paper P, and the printing surface is not damaged. Further, since the suction force by charging is used for the attachment of the paper P to the separation rotating roller 23, the physical contact pressure between the separation rotating roller 23 and the heating roller 7a is increased to forcibly remove the paper. The paper P can be separated without being pulled away, and the surface of the heating roller 7a is prevented from being damaged.

  The contact portion 25 between the heating roller 7a and the separation rotating roller 23 is disposed at an angle θ1 within a 90-degree region downstream of the nip portion 21 from the nip portion 21 around the rotation center C1 of the heating roller 7a. ing. By disposing the contact portion 25 in the 90-degree region, it is possible to separate the paper before the paper P wound around the heating roller 7a gets bent.

  Further, the peeling claw 24 is disposed at an angle θ2 in a 90 ° region on the downstream side of the contact portion 25 from the contact portion 25 between the heating roller 7a and the separation rotation roller 23 around the rotation center C2 of the separation rotation roller 23. ing. As a result, the paper P attached to the separation rotating roller 23 is peeled off from the back surface P2 of the paper P by the peeling claw 24 before being too attached and difficult to peel off. Further, the paper P can be separated before the paper P adheres too much to the separation rotating roller 23 and becomes bent. On the other hand, if the angle θ2 is too small, the peeling claw 24 may cause jamming of the paper P. For this reason, it is preferable that angle (theta) 2 is 20 degree | times or more.

  Further, since the separation claw 24 is separated from the separation rotating roller 23, preferably with a gap of 0.4 mm, the surface of the separator 22 is not damaged.

  Next, since the basic configuration of the second embodiment in FIG. 3 is the same as that of the first embodiment, the same components are denoted by the same reference numerals, and the same description as that described in the first embodiment is omitted to avoid duplication. To do.

  In FIG. 3, the separation rotating roller is formed by an adhesive roller 27 formed by coating a metal rotating shaft with an adhesive material. Examples of the adhesive material include ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, polyolefin resin, polybutadiene resin, polyisoprene resin, polyester resin, polyurethane resin, acrylic resin, butyl rubber and the like. Due to this adhesiveness, the paper P is reliably and reliably attached to the adhesive roller 27 from the heating roller 7 a, and further peeled off from the adhesive roller 27 by the peeling claw 24.

  Although the adhesive roller 27 is used for the separation rotating roller, a configuration in which an adhesive tape is fixed to the surface of the normal separation rotating roller 23 may be used, and at least the adhesive portion is formed on the surface of the separation rotating roller 23. It is good.

1 is a side sectional view of a laser printer in which a fixing device according to a first embodiment of the present invention is used. FIG. 3 is an enlarged side sectional view of the fixing device according to the first embodiment. FIG. 6 is an enlarged side sectional view of a fixing device according to a second embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser printer 2 Apparatus main body 3 Opening / closing door 4 Paper conveyance mechanism 5 Scanner unit 6 Process unit 7 Fixing device 7a Heating roller 7b Pressure roller 7c Negative power supply 7d Paper guide member 8 Photosensitive drum 9 Charger 10 Developing roller 11 Toner box 12 Transfer Roller 13 Toner supply roller 14 Cassette 15, 16 Registration roller 17 Pickup roller 18, 19 Paper discharge roller 20 Transport path 21 Nip part 22 Separator 22a Plus power source 23, 26, 27 Separation rotor 24 Separation claw

Claims (12)

  In a fixing device that includes a heating roller and a pressure roller that rotate in pressure contact with each other, and that heat-fixes when a sheet carrying an unfixed toner image passes through a nip portion between the two rollers. And a separation member that elastically contacts the heating roller and separates the paper on the heating roller and a separation claw that separates the paper adhering to the separation member from the separation member. Fixing device.   The fixing device according to claim 1, wherein the separating body is constituted by a separating rotating body having a diameter smaller than that of the heating roller.   The fixing device according to claim 2, wherein the separation rotating body is a separation rotation roller whose surface is coated with silicon rubber.   3. The contact portion between the heating roller and the separation rotating body is disposed within a 90-degree region on the downstream side of the nip portion from the nip portion with the rotation center of the heating roller as a center. Or the fixing device according to 3;   The paper sheet is separated from the heating roller by making the potential difference between the separator and the paper larger than the potential difference between the heating roller and the paper. Fixing device.   A charging means for charging the separator with the same polarity as the toner carried on the paper and for charging the pressure roller with the same polarity as the back surface of the paper charged with the opposite polarity to the toner; The fixing device according to claim 5, wherein the sheet on the heating roller is attached to the separator by charging of the toner.   The fixing device according to claim 1, wherein a sheet on the heating roller is attached to the separator by providing an adhesive portion on at least a surface of the separator.   The fixing device according to claim 7, wherein the separator is configured by an adhesive roller.   3. The peeling claw is disposed in a 90-degree region on the downstream side of the contact portion from the contact portion between the heating roller and the separation rotator with the rotation center of the separation rotator as a center. The fixing device according to any one of 1 to 8.   The fixing device according to claim 1, wherein the peeling claw is disposed apart from the separator.   The fixing device according to claim 1, wherein the peeling claw is configured by covering a rigid plate-like member with Teflon (registered trademark). A photoreceptor on which an electrostatic latent image is formed;
Developing means for developing the electrostatic latent image on the photoreceptor with toner;
Transfer means for transferring the toner image developed by the developing means to paper;
An image forming apparatus comprising: the fixing device according to claim 1 for fixing an unfixed toner image transferred onto a sheet by the transfer unit.

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