JP2012189648A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent paper jams and exhibit appropriate separation performance, regardless of conditions such as thickness of a recording medium.SOLUTION: The fixing device includes: a heating roller 110 that allows a recording medium with an unfixed toner image formed thereon to pass under heating and pressure to form a fixing nip part N to fix the unfixed toner image on the recording medium; a pressure roller 120; and a separation pawl 130 inserted between the recording medium having passed the fixing nip part N and the heating roller 110 to separate the recording medium from the heating roller 110. The separation pawl 130 is driven to change the distance between a tip part 130a thereof and the heating roller 110 using a cam 140.

Description

  The present invention relates to a fixing device and an image forming apparatus, and more particularly, to pass a recording medium on which an unfixed toner image is formed under heat and pressure to form a pair of nip portions that fix the unfixed toner image on the recording medium. The present invention relates to a fixing device including a fixing member, a separation claw that is disposed between the recording medium and the recording member after passing through a nip portion, and separates the recording medium from the fixing member, and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copying machines and printers that employ an electrophotographic system are provided with a fixing device for fixing an unfixed toner image formed on a recording medium. This fixing device includes two rollers that rotate in contact with each other, and also uses an endless fixing belt as a heating side rotating body.

  For example, a fixing device using two rollers includes a fixing roller having a heat source therein, and a pressure roller pressed against the fixing roller by a pressure spring, and between the heating roller and the pressure roller. The unfixed toner image carried on the recording medium supplied to the fixing nip is heated and pressurized to fix it on the recording medium.

  By the way, in such a fixing device, after the recording medium passes through the fixing nip between the fixing roller and the pressure roller, it may be wound around the fixing roller by the fused toner. In order to cope with this, the fixing device may be provided with a separation claw for separating the recording medium from the fixing roller.

  In such a fixing apparatus, there is a fixing device in which the separation claw is switched between a position where it comes into contact with the fixing roller and a position where it is separated from the fixing roller. In Patent Document 1, the separation claw is displaced between a contact position where the separation claw is in contact with the surface of the fixing roller and a non-contact position which is separated from the surface of the fixing roller by rotation of the separation claw holding member. The separation claw holding member is driven by a solenoid so as to be displaced between a contact position and a non-contact position. The non-contact position is determined by the separation claw holding member coming into contact with the rotating member. It is described that the positioning member and the rotation member are rotationally driven to vibrate the separation claw holding member and the separation claw to remove unfixed toner from the separation claw.

  Patent Document 2 discloses a fixing roller and a pressure roller that are pressed against each other and a separation claw that contacts the surface of the fixing roller downstream of the fixing nip between the fixing roller and the pressure roller in the sheet conveying direction. A fixing device for fixing a toner image on a sheet by passing the sheet carrying the toner image through a fixing nip between a fixing roller and a pressure roller, and detecting a separation state of the sheet passing through the fixing nip. A sensor and a contact / separation means for contacting / separating the separation claw with respect to the surface of the fixing roller according to the separation state of the sheet detected by the sensor are described.

  Further, in Patent Document 3, a recording sheet carrying an unfixed image is sandwiched between a fixing roller and a pressure roller that are arranged to face each other, and a fixing process is performed so that the recording paper contacts the surface of the fixing roller. In the fixing device of the electrophotographic recording apparatus that peels and discharges the recording paper after fixing by a separation claw disposed on the paper, a paper discharge sensor that detects paper discharge of the recording paper and a plurality of the separation claws are rotated. Separable claw support member that is movably supported, an operating member having at least one of the separating claws in contact with the fixing roller, and a protrusion that rotates the other separating claw and separates it from the fixing roller, and the operating member And a drive member that transmits power to the cam member to move the actuating member.

  However, in the conventional fixing device, when the recording medium is separated, the separation claw is arranged at a constant interval with respect to the fixing member. For this reason, there is a problem that jamming occurs when thin paper is used as a recording medium. When the tip of the separation claw is in contact with the fixing member, the surface of the fixing member is damaged by the separation claw, resulting in poor durability and image quality.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus that can avoid the occurrence of a jam regardless of the thickness condition of a recording medium and exhibit normal separation performance.

  According to a first aspect of the present invention for solving the above problem, a recording medium on which an unfixed toner image is formed is passed under heating and pressure to form a nip portion for fixing the unfixed toner to the recording medium. A pair of fixing members; and a separation claw that is inserted between the recording medium and one of the fixing members after passing through the nip portion, and separates the recording medium from the fixing member. The fixing device includes a separation claw driving unit that moves the separation claw so that a distance between the tip portion of the separation claw and the fixing member can be changed.

  Similarly, the invention according to claim 2 is the fixing device according to claim 1, wherein the separation claw driving means includes a cam mechanism.

  Similarly, according to a third aspect of the present invention, in the fixing device according to the first or second aspect, the separation claw driving means passes the distance between the front end of the separation claw and the fixing member. It is characterized by changing according to the paper type.

  Similarly, the invention of claim 4 is the fixing device according to any one of claims 1 to 3, wherein the separation claw is a plate-like member.

  Similarly, according to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the tip of the separation claw is formed of a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) resin. It is characterized by being.

  Similarly, the invention of claim 6 includes an image forming apparatus comprising: the fixing device according to any one of claims 1 to 5; and a toner image forming unit that forms an unfixed toner image on the recording medium. Device.

  According to the present invention, the separation dimension between the front end of the separation claw and the front end of the fixing member can be changed according to the state of the paper by the separation claw driving means, so that a good separation performance can always be obtained.

1 is a cross-sectional view conceptually showing an image forming apparatus according to Embodiment 1. FIG. FIG. 2 is a schematic diagram illustrating a schematic configuration of the fixing device. FIG. 2 is a plan view showing the structure of the fixing device. FIG. 6 is a schematic diagram illustrating a case where a sheet having a normal thickness is fixed by the fixing device. FIG. 6 is a schematic diagram illustrating a case where thin paper is fixed by the fixing device. FIG. 6 is a schematic diagram illustrating a configuration of a fixing device according to a second embodiment. FIG. 10 is a plan view illustrating a configuration of a fixing device according to a fourth embodiment. FIG. 10 is a schematic diagram illustrating a configuration of a fixing device according to a fourth embodiment. FIG. 10 is a schematic diagram illustrating a configuration of a fixing device according to a fourth embodiment.

  The fixing device according to the embodiment includes a pair of fixing members that pass a recording medium on which an unfixed toner image is formed under heat and pressure, and form a nip portion that fixes the unfixed toner to the recording medium; In the fixing device, having a separation claw inserted between the recording medium and one of the fixing members after passing through the nip portion, and separating the recording medium from the fixing member, The separation claw is provided with a separation claw driving means for moving the separation claw so that the distance between the front end portion and the fixing member can be changed.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present invention (hereinafter simply referred to as an embodiment) will be described. Several examples are described below, but the present invention is not limited to these examples, and numerous improvements, modifications, variations, substitutions and application examples are possible without departing from the true spirit and scope of the present invention. It will be possible for those skilled in the art to conceive.

<Example 1>
An image forming apparatus according to Embodiment 1 will be described. FIG. 1 is a sectional view conceptually showing the image forming apparatus according to the first embodiment. The image forming apparatus 10 according to this example includes a reading unit 11 that reads a document, an image forming unit 12 that forms an image, an automatic document feeder (ADF) 13, a document discharge tray 14 that stacks documents sent from the ADF 13, A paper feed unit 19 including paper cassettes 15 to 18 and a paper discharge unit (discharge tray 20) for stacking recording paper are provided.

  In this image forming apparatus 10, when the document D is set on the document table 21 of the ADF 13 and an operation on an operation unit (not shown) is performed, for example, a print key is pressed, the uppermost document D is rotated by the pickup roller 22. The paper is fed in the direction of the arrow B1, and is conveyed onto the contact glass 24 fixed to the image reading unit 11 by the rotation of the original conveying belt 23, and stops there.

  The image of the document D placed on the contact glass 24 is read by a reading device 25 located between the image forming unit 12 and the contact glass 24. The reading device 25 includes a light source 26 that illuminates the document D on the contact glass 24, an optical system 27 that forms an image of the document, a photoelectric conversion element 28 that includes a CCD that forms an image of the document, and the like. After the image reading is completed, the document D is transported in the direction of the arrow B2 by the rotation of the document transport belt 23 and discharged onto the document discharge tray 14. In this way, the document D is fed one by one onto the contact glass 24 and the document image is read by the image reading unit 11.

  On the other hand, inside the image forming unit 12, a photoconductor 30 as an image carrier is disposed. The photosensitive member 30 is driven to rotate clockwise in the drawing, and the surface is charged to a predetermined potential by the charging device 31. Further, the writing unit 32 emits a laser beam L that is light-modulated in accordance with image information read by the reading device 25, and the surface of the charged photoreceptor 30 is exposed with the laser beam L, whereby the photoreceptor is exposed. An electrostatic latent image is formed on the surface 30. When the electrostatic latent image passes through the developing device 33, the electrostatic latent image is transferred to the recording medium P fed between the photosensitive member 30 and the transfer device 34 by the opposing transfer device 34. The surface of the photoconductor 30 after the toner image is transferred is cleaned by a cleaning device 35.

  A plurality of paper feed cassettes 15 to 18 arranged below the image forming unit 12 contain recording media P such as paper, and the recording media P is fed from any of the paper feed cassettes 15 to 18 in the direction of arrow B3. The toner image formed on the surface of the photoreceptor 30 as described above is transferred onto the surface of the recording medium P. Next, the recording medium P is passed through the fixing device 100 in the image forming unit 12 as indicated by an arrow B4, and the toner image transferred to the surface of the recording medium P by the action of heat and pressure is fixed. The recording medium P that has passed through the fixing device 100 is conveyed by the discharge roller pair 37, discharged to the discharge tray 20 as indicated by an arrow B5, and stacked.

  Next, the fixing device 100 according to the first embodiment will be described. FIG. 2 is a schematic diagram illustrating a schematic configuration of the fixing device according to the first exemplary embodiment, and FIG. 3 is a plan view illustrating the structure of the fixing device. As shown in FIG. 2, the fixing device 100 includes a heating roller 110 and a pressure roller 120 as a pair of fixing members that form the fixing nip portion N. The heating roller 110 includes a heating unit 111 such as a halogen heater. In the fixing device 100 according to the first exemplary embodiment, the separation claw 130 is disposed on the downstream side of the fixing nip portion N of the heating roller 110 so that the tip end portion 130a thereof is adjacent. Note that the separation claw 130 can be disposed not on the heating roller 110 but on the pressure roller 120 side, or in two adjacent to the heating roller 110 and the pressure roller 120. The fixing member can be configured as an endless belt in addition to a roller.

  Further, the fixing device 100 is provided with an inlet guide plate 160 and an outlet guide plate 170, and the recording material 180 on which an unfixed toner image is formed passes through the fixing nip portion N, and the image is fixed and conveyed. Is done.

  In the fixing device 100 according to the first embodiment, the separation claw 130 is disposed so as to be rotatable around the rotation fulcrum 131, and the tip portion 130 a is pressed toward the heating roller 110 by the spring 150. A cam 140 is arranged on the heating roller 110 side of the separation claw 130 so as to contact the separation claw 130 and change the distance between the tip 130a and the heating roller 110. The cam 140 is an elliptical plate cam having a shaft 141 at an eccentric position. When the cam 140 is driven to rotate about the shaft 141, the separation claw 130 that comes into contact with the cam 140 swings about the rotation fulcrum 131 so that the tip 130 a of the separation claw 130 and the surface of the heating roller 110 are separated. The distance can be changed.

  In the fixing device 100, a plurality of, for example, five separation claws 130 are provided in the longitudinal direction of the heating roller 110, as shown in FIG. At this time, one cam 140 is arranged for each separation claw 130, and each cam 140 is fixed to one cam shaft 141 and is driven to rotate simultaneously. The cam shaft 141 is driven by the driving means 161. The drive unit 161 can be configured using, for example, a stepping motor and a gear train, and the drive is controlled by the control unit 162. In the fixing device 100 according to the first exemplary embodiment, the cam 140, the driving unit 161, and the control unit 162 constitute a separation claw driving unit. As the driving means 161, other devices such as an electromagnetic solenoid can be used in addition to the combination of the stepping motor and the gear train.

  The control unit 162 controls driving of the driving unit 161 based on the thickness of the paper. The sheet thickness is acquired based on the type of the recording medium input from the input unit of the image forming apparatus 10 and the output of the thickness sensor. The control unit 162 is composed of, for example, a microcomputer including a CPU, a ROM, a RAM, and the like, and executes control by executing a program stored in the ROM by the CPU. For example, the ROM is provided with a table storing the driving amount of the driving unit 161 with respect to the sheet thickness, and the driving unit 161 is driven by reading out the driving amount that matches the sheet thickness input from the table. Note that the driving amount of income can be calculated based on a calculation formula.

  Next, the operation of the fixing device 100 will be described. The fixing device 100 performs the following operations that are different when fixing a sheet having a normal thickness and when fixing a thin sheet having a thickness smaller than usual. First, a description will be given of fixing a sheet having a normal thickness. FIG. 4 is a schematic diagram illustrating a case where a sheet having a normal thickness is fixed by the fixing device. At the time of fixing the recording material 180, the fixing device 100 has an outline with a large distance from the shaft 141 of the cam 140 arranged on the separation claw 130 side as shown in FIG. As a result, the cam 140 comes into contact with the separation claw 130 (A portion in FIG. 3), and a gap of a predetermined dimension G is formed between the tip 130a of the separation claw 130 and the heating roller 110 (in FIG. 3). B part).

  That is, in the fixing device 100, the separation claw 130 and the cam 140 come into contact with each other at the time of fixing, and the cam 140 serves as a stopper to restrict the movement of the separation claw 130. A gap of a certain distance (dimension G) can be held between them. As a result, the tip 130 a of the separation claw 130 is not in contact with the heating roller 110, and the recording material 180 can be separated from the heating roller 110 without damaging the surface of the heating roller 110.

  Next, a description will be given of fixing the thin paper. FIG. 5 is a schematic diagram showing a case where thin paper is fixed by the fixing device. In this state, the cam 140 is driven to rotate, and the cam 140 is not in contact with the separation claw 130 (FIG. 5C). Then, the separation claw 130 is pushed and rotated by the spring 150, and the tip portion 130a of the separation claw 130 comes into contact with the surface of the heating roller 110 (FIG. 5D portion). As a result, there is no gap between the tip 130a of the separation claw 130 and the heating roller 110, and even separation paper such as thin paper with poor separation properties is forcibly separated from the heating roller 110 by the separation claw 130. Can prevent jamming.

<Example 2>
Next, a fixing device according to the second embodiment will be described. In the fixing device according to the first embodiment, the distal end portion 130 a of the separation claw 130 is in contact with the heating roller 110. Here, if the distance between the front end portion 130a of the separation claw 130 and the heating roller 110 is smaller than when the front end portion 130a of the separation claw 130 fixes a sheet having a normal thickness (FIG. 4), the separation performance is improved. Jam when fixing bad paper can be reduced.

  Therefore, in the fixing device 200 according to the second embodiment, the distance between the leading end portion 130a of the separation claw 130 and the heating roller 110 is set to a dimension g smaller than the dimension G for normal paper (G> g) when fixing thin paper. . FIG. 6 is a schematic diagram illustrating a configuration of a fixing device according to the second embodiment. In the fixing device 200 according to the second embodiment, the contour shape of the cam 140 is changed from that of the first embodiment. It can be realized by controlling the rotational driving amount of the driving means 161 so that the tip end portion 130a of the separation claw 130 does not come into contact with the heating roller 110 and the distance between them is set to the dimension g.

  In the fixing device 100 according to the first embodiment, the tip portion 130a of the separation claw 130 and the heating roller 110 are in contact with each other, so that the best separation performance can be obtained, but the surface layer of the heating roller 110 is separated. There is a risk of injury at the tip 130a of the nail 130. On the other hand, in the fixing device 200 according to the second embodiment, there is a concern that the image quality is deteriorated. However, since the tip portion 130a of the separation claw 130 does not come into contact with the heating roller 110, a situation that damages the heating roller 110 does not occur. However, the separation performance is inferior to that of Example 1.

<Example 3>
Next, a fixing device according to Example 3 will be described. In the embodiment, the contour shape of the cam 140 is an ellipse. In the fixing device according to the third embodiment, the contour shape of the cam 140 is a complicated shape such as a stepped shape. In the third embodiment, by using such a cam, the interval between the cam 140 and the heating roller 110 can be switched to a plurality of values according to the rotation angle of the cam. According to the fixing device according to the third exemplary embodiment, it is possible to set an optimal interval value corresponding to a plurality of types of thickness paper.

<Example 4>
Next, a fixing device according to Embodiment 4 will be described. In the fixing device according to each of the embodiments, a plurality of separation claw width dimensions are provided. In the fixing device according to the fourth embodiment, the separation claw 130 is a single plate-like member. FIG. 7 is a plan view illustrating the configuration of the fixing device according to the fourth embodiment. In the fixing device 210 according to the fourth embodiment, the claw member 190 is a plate-like member, and the cams 140 are disposed at two positions on both ends thereof. The cams 140 can be provided at three or more locations. And the cam 140 is arrange | positioned in the outer side edge part rather than the inside of the paper passing range of the longitudinal direction center part of the heating roller 110. FIG.

  Therefore, according to the fixing device 210 according to the fourth exemplary embodiment, the paper, the cam 140, and the paper passing portion of the heating roller 110 are not in contact with each other so that no trace is left. Obtainable. Further, according to the fixing device 210 according to the fourth embodiment, the separation claw can be a single member, and the component configuration can be simplified and the cost can be reduced.

<Example 5>
Next, a fixing device according to Embodiment 5 will be described. 8 and 9 are schematic diagrams illustrating the configuration of the fixing device according to the fourth embodiment. In the fixing device, a positioning member that slides in contact with the fixing member is provided on a support member that supports the separation claw 130 in order to reduce a variation in the distance between the thermally expanded fixing member and the tip of the separation claw. is there. In the fixing device 220 according to the fifth embodiment, the cam 140 also serves as the position determining member.

  The cam 140 is in contact with the heating roller 110 at a portion on the heating roller 110 side (I portion in FIG. 8), and the cam 140 and the separation claw 130 are connected to a common support member (located in the fixing device 220). (Not shown), when the heating roller 110 is thermally expanded, both the cam 140 and the separation claw 130 can move, and the gap between the tip 130a of the separation claw 130 and the heating roller 110 is kept constant. be able to.

  As shown in FIG. 9, when the cam 140 is rotated by the shaft 141, the cam 140 is in contact with the heating roller 110 with the contour on the heating roller 110 side (section I in FIG. 9). The distance d between the contact portion 140a of the cam 140 with the heating roller 110 and the rotation center O of the cam 140 is the distance d1 between the contact portion 140a and the rotation center O axis of the cam 140 before the cam 140 rotates (see FIG. 8). If the contours of the cams 140 are formed so as to be equal, the distance between the rotation center O of the cam 140 and the heating roller 110 remains the same before and after the rotation of the cam 140, and the state shown in FIG. By rotating the cam 140 to the state shown, the distance between the tip 130a of the separation claw 130 and the heating roller 110 can be changed to the dimension G and the dimension g. For this reason, regardless of the degree of thermal expansion of the heating roller 110, it is possible to increase the ability of the separation function for paper with poor separation.

<Example 5>
Next, a fixing device according to Embodiment 5 will be described. In the fixing device according to the fifth embodiment, the tip portion 130a of the separation claw 130 of the fixing device according to each of the above embodiments is made of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) resin. This PTF resin is softer than materials such as PEEK (polyether ether ketone resin), PPS (polyphenylene sulfide resin), PEK (polyether ketone), etc., which are generally used as materials for conventional separation nails, and the heating roller 110. It is hard to be damaged even if it touches. For this reason, the space | interval of the front-end | tip part 130a of the separation nail | claw 130 and the heating roller 110 can be narrowed, and more favorable separation performance can be obtained.

  In each embodiment, the image forming apparatus is described as performing a monochrome image using a single color toner. However, each fixing apparatus is configured to perform color image formation using a plurality of colors of toner. It can be applied to the device.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Reading unit 12 Image forming part 13 Automatic document feeder (ADF)
14 Document discharge trays 15 to 18 Paper feed cassette 19 Paper feed unit 20 Paper discharge tray 21 Document tray 22 Pickup roller 23 Document transport belt 24 Contact glass 25 Reading device 26 Light source 27 Optical system 28 Photoelectric conversion element 30 Photoconductor 31 Charging device 32 Writing unit 33 Developing device 34 Transfer device 35 Cleaning device 37 Discharge roller pair 100 Fixing device 110 Heating roller 111 Heating means 120 Pressure roller 130 Separation claw 130a Tip portion 130a Tip portion 131 Rotation fulcrum 140 Cam 140a Contact portion 140a Contact portion 141 Shaft 141 Cam shaft 150 Spring 160 Entrance guide plate 161 Driving means 162 Control unit 170 Exit guide plate 180 Recording material 190 Claw member

Japanese Patent Laying-Open No. 2005-099426 JP 2009-258327 A Japanese Patent Laid-Open No. 7-261589

Claims (6)

A pair of fixing members that pass through a recording medium on which an unfixed toner image is formed under heat and pressure and form a nip portion for fixing the unfixed toner to the recording medium;
A separation claw that is inserted between the recording medium and one of the fixing members after passing through the nip portion, and separates the recording medium from the fixing member;
In a fixing device having
A fixing device comprising: a separation claw driving means for moving the separation claw so that a distance between the front end portion and the fixing member can be changed.   The fixing device according to claim 1, wherein the separation claw driving unit includes a cam mechanism.   The said separation nail drive means changes the space | interval dimension between the front-end | tip of the said separation nail and the said fixing member according to the paper type through which paper passes. Fixing device.   The fixing device according to claim 1, wherein the separation claw is a plate-like member.   The fixing device according to any one of claims 1 to 4, wherein a tip end portion of the separation claw is formed of a PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) resin.   An image forming apparatus comprising: the fixing device according to claim 1; and a toner image forming unit that forms an unfixed toner image on the recording medium.