JP2010091598A - Fixing device and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device that stably obtains a high-quality image while maintaining an optimum fixing pressure. <P>SOLUTION: The fixing device includes: a heat roller (heating member) and a pressure roller (pressure member) rotated in contact with each other; a rotatable pressure lever that presses the pressure roller against the heat roller; a pressure plate that engages with the pressure lever; an opening/closing lever rotated in synchronization with opening/closing of an opening/closing cover; a pressure spring interposed between the opening/closing lever and the pressure plate; and a conveying guide 28 that guides paper to a fixing nip between the heat roller and the pressure roller. The fixing device sets the pressure roller in a pressing state or a pressure-release state by rotating the opening/closing lever in synchronization with opening/closing of the opening/closing cover, thereby changing the pressing force of the pressure spring. In the fixing device, the conveying guide 28 is provided with a pressing rib 28a and regulating ribs 28b and 28c, as position regulating means, which regulate the positions of the opening/closing lever and the pressure plate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fixing device capable of changing the pressure (fixing pressure) applied to a heating member by a pressure member, and an image forming apparatus including the same.

  In an image forming apparatus such as a copying machine or a printer that forms an image on a sheet by electrophotography, the electrostatic latent image formed on the image carrier is developed by a developing device and visualized as a toner image. Transfer the image onto the paper. The sheet onto which the toner image has been transferred is conveyed to a fixing device, and after the toner image is fixed by heat and pressure by the fixing device, it is discharged out of the apparatus, thereby completing a series of image forming operations. .

  By the way, the fixing device is provided with a heating member and a pressure member that rotate in contact with each other, and a predetermined fixing pressure (nip pressure) is secured between them by pressing the pressure member against the heating member. Like to do.

When a paper jam (jam) occurs in such a fixing device, normally, after opening the opening / closing cover, the pressure member is separated from the heating member to release the pressure, and jammed paper sandwiched between the two members In order to improve the workability of this jam processing, a fixing device adopting a method in which the pressure member is brought into a pressure state or a pressure release state in conjunction with the opening / closing operation of the opening / closing cover is proposed. (For example, see Patent Documents 1 to 3).
JP-A-9-034299 JP-A-9-101696 JP 2008-122744 A

  By the way, in a fixing device that employs a system in which the pressure member is in a pressure state or a pressure release state in conjunction with the opening / closing operation of the opening / closing cover, a rotatable pressure lever that presses the pressure member against the heating member. A pressure plate that engages with the pressure lever, an opening / closing lever that rotates in conjunction with the opening / closing operation of the opening / closing cover, and a pressure spring interposed between the opening / closing lever and the pressure plate. The pressure member is brought into a pressurized state or a pressure released state by rotating the opening / closing lever in conjunction with the opening / closing operation of the opening / closing cover to change the pressing force of the pressure spring. There is something.

  However, in the fixing device adopting the above configuration, the biasing force (preset load) of the pressure spring changes due to deformation of the opening / closing lever, escape of the pressure plate, etc., and it is impossible to obtain an optimum fixing pressure. There were problems such as being possible, and a failure to return the open / close lever.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device capable of stably obtaining a high-quality image while maintaining a fixing pressure at an optimum value, and an image forming apparatus including the fixing device. It is to provide.

  In order to achieve the above object, a first aspect of the present invention includes a heating member and a pressure member that rotate in contact with each other, a rotatable pressure lever that presses the pressure member against the heating member, A pressure plate that engages with the pressure lever; an opening / closing lever that rotates in conjunction with an opening / closing operation of the opening / closing cover; a pressure spring interposed between the opening / closing lever and the pressure plate; A conveyance guide for guiding a sheet to a fixing nip between the member and the pressure member, and rotating the opening / closing lever in conjunction with the opening / closing operation of the opening / closing cover to change the pressing force of the pressure spring. In the fixing device in which the pressure member is in a pressure state or a pressure release state, the conveyance guide is provided with a position regulation unit that regulates a position of the opening / closing lever and the pressure plate. .

  According to a second aspect of the present invention, in the first aspect of the invention, the position restricting means includes a hook-shaped pressing rib that presses a central portion in the longitudinal direction of a shaft connecting the pair of left and right opening / closing levers, and the pressure plate. It is characterized by comprising a regulating rib arranged in proximity to the.

  An image forming apparatus according to a third aspect includes the fixing device according to the first or second aspect.

  According to the present invention, the positions of the opening / closing lever and the pressure plate are restricted by the position restriction members such as the holding ribs and the restriction ribs provided on the conveyance guide, so that the deformation of the opening / closing lever and the escape of the pressure plate are prevented. Can be removed. For this reason, the distance between the open / close lever and the pressure plate does not change, the urging force (preset load) of the pressure spring interposed between the two is maintained at the optimum value (design value), and the proper fixing pressure is maintained. A high-quality image can be stably obtained by being held, and problems such as a return failure of the open / close lever can be solved.

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

[Image forming apparatus]
FIG. 1 is a cross-sectional view of a color laser printer as an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a perspective view of the color laser printer with an open / close cover opened.

  The color laser printer according to the present embodiment is a tandem type, and as shown in FIG. 1, a magenta image forming unit 1M, a cyan image forming unit 1C, and a yellow image forming unit 1Y are arranged at the center of the main body 100. The black image forming units 1K are arranged in tandem at regular intervals.

  Each of the image forming units 1M, 1C, 1Y, and 1K is provided with photosensitive drums 2a, 2b, 2c, and 2d, which are image carriers, and a charger 3a is disposed around each of the photosensitive drums 2a to 2d. 3b, 3c, 3d, developing devices 4a, 4b, 4c, 4d, transfer rollers 5a, 5b, 5c, 5d and drum cleaning devices 6a, 6b, 6c, 6d, respectively.

  Here, the photosensitive drums 2a to 2d are drum-shaped photosensitive members, and are driven to rotate at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving motor (not shown). The chargers 3a to 3d uniformly charge the surfaces of the photosensitive drums 2a to 2d to a predetermined potential by a charging bias applied from a charging bias power source (not shown).

  Further, the developing devices 4a to 4d contain magenta (M) toner, cyan (C) toner, yellow (Y) toner, and black (K) toner, respectively, and are formed on the photosensitive drums 2a to 2d. In addition, the toner of each color is attached to each electrostatic latent image to visualize each electrostatic latent image as a toner image of each color.

  The transfer rollers 5a to 5d are arranged so as to be able to contact the photosensitive drums 2a to 2d via the intermediate transfer belt 7 in the respective primary transfer portions. Here, the intermediate transfer belt 7 is stretched between the secondary transfer counter roller 8 and the tension roller 9 and is disposed on the upper surface side of each of the photosensitive drums 2a to 2d. The roller 8 is disposed so as to be in contact with the secondary transfer roller 10 via the intermediate transfer belt 7 in the secondary transfer portion. A belt cleaning device 11 is provided in the vicinity of the tension roller 9.

  Incidentally, toner containers 12a, 12b, 12c, and 12d for supplying toner to the developing devices 4a to 4d are arranged in a line above the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100. It is installed.

  In addition, a laser scanner unit (LSU) 13 is disposed below the image forming units 1M, 1C, 1Y, and 1K in the apparatus main body 100, and a paper feed cassette 14 is detachably attached to the bottom of the main body 100 below the image forming units. is set up. A plurality of sheets of paper (not shown) are stacked and accommodated in the paper feed cassette 14, and a pickup roller 15 for picking up paper from the paper feed cassette 14 and a picked up paper are placed near the paper feed cassette 14. A feed roller 16 and a retard roller 17 that are separated and fed one by one to the transport path L are provided.

  In addition, the conveyance path L extending in the vertical direction on the side of the apparatus main body 100 includes a conveyance roller pair 18 that conveys the sheet, and the secondary transfer counter roller 8 and the second transfer opposing roller 8 at a predetermined timing after the sheet is temporarily held. A registration roller pair 19 is provided to be supplied to a secondary transfer portion which is a contact portion with the next transfer roller 10. Next to the transport path L, another transport path L ′ used for forming an image on both sides of the sheet is formed, and a plurality of transport roller pairs 20 are appropriately used in the transport path L ′. Are provided at regular intervals.

  By the way, the conveyance path L arranged in the vertical direction on one side of the apparatus main body 100 extends to the paper discharge tray 21 provided on the upper surface of the apparatus main body 100, and in the middle thereof, the fixing according to the present invention. A device 22 and a pair of paper discharge rollers 23 and 24 are provided. As shown in FIG. 2, an opening / closing cover (front cover) 101 that can be opened and closed is provided on the front surface of the main body 100. When a sheet jams in the fixing device 22 or the like, the opening / closing cover 101 is provided. Is opened as shown in the figure and processing such as removing jammed paper is performed.

  Next, an image forming operation by the color laser printer having the above configuration will be described with reference to FIG.

  When an image formation start signal is issued, the photosensitive drums 2a to 2d are driven to rotate at a predetermined process speed in the direction of the arrow in FIG. 1 (clockwise) in each of the image forming units 1M, 1C, 1Y, and 1K. The drums 2a to 2d are uniformly charged by the chargers 3a to 3d. The laser scanner unit 13 emits a laser beam modulated by a color image signal for each color, irradiates the surface of each photosensitive drum 2a to 2d with the laser beam, and each color is applied to each photosensitive drum 2a to 2d. An electrostatic latent image corresponding to the color image signal is formed.

  First, magenta toner is attached to the electrostatic latent image formed on the photosensitive drum 2a of the magenta image forming unit 1M by the developing device 4a to which a developing bias having the same polarity as the charged polarity of the photosensitive drum 2a is applied. The electrostatic latent image is visualized as a magenta toner image. This magenta toner image is transferred to the arrow shown in FIG. 1 by the action of the transfer roller 5a to which a primary transfer bias having a polarity opposite to that of the toner is applied at the primary transfer portion (transfer nip portion) between the photosensitive drum 2a and the transfer roller 5a. Primary transfer is performed on the intermediate transfer belt 7 which is rotationally driven in the direction.

  The intermediate transfer belt 7 on which the magenta toner image has been primarily transferred as described above moves to the next cyan image forming unit 1C. In the cyan image forming unit 1C as well, the cyan toner image formed on the photosensitive drum 2b is transferred to the magenta toner image on the intermediate transfer belt 7 in the primary transfer portion in the same manner as described above.

  Similarly, yellow and black toners respectively formed on the photosensitive drums 2c and 2d of the yellow and black image forming units 1Y and 1K on the magenta and cyan toner images superimposed and transferred on the intermediate transfer belt 7, respectively. The images are sequentially superimposed at each primary transfer portion, and a full-color toner image is formed on the intermediate transfer belt 7. The transfer residual toner which is not transferred onto the intermediate transfer belt 7 and remains on the photosensitive drums 2a to 2d is removed by the drum cleaning devices 6a to 6d, and the photosensitive drums 2a to 2d are prepared for the next image formation. It is done.

  Then, the pickup from the paper feed cassette 14 is performed in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 7 reaches the secondary transfer portion (transfer nip portion) between the secondary transfer counter roller 8 and the secondary transfer roller 10. The sheet fed to the conveyance path L by the roller 15, the feed roller 16 and the retard roller 17 is conveyed to the secondary transfer unit by the registration roller pair 19. Then, a full-color toner image is collectively transferred from the intermediate transfer belt 7 to the sheet conveyed to the secondary transfer unit by the secondary transfer roller 10 to which a secondary transfer bias having a polarity opposite to that of the toner is applied. .

  Thus, the sheet on which the full-color toner image has been transferred is conveyed to the fixing device 22, and the sheet on which the full-color toner image has been fixed by being heated and pressurized and thermally fixed on the surface of the sheet. Then, the paper is discharged onto the paper discharge tray 21 by the paper discharge roller pair 23 and 24, and a series of image forming operations is completed. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 7 is removed by the belt cleaning device 11, and the intermediate transfer belt 7 is prepared for the next image formation.

[Fixing device]
Next, details of the fixing device 22 according to the present invention will be described with reference to FIGS.

  3 is a perspective view of the fixing device according to the present invention, FIGS. 4 and 5 are cross-sectional views of the identification fixing device, FIG. 6 is a perspective view showing the configuration of the fixing pressure reducing mechanism of the identification fixing device, and FIG. It is a perspective view.

  As shown in FIGS. 4 and 5, the fixing device 22 is configured by housing a heating roller 25 and a pressure roller 26 that rotate in contact with each other in a housing 27. The roller 26 is arranged to be parallel and rotatable along the direction perpendicular to the plane of FIG. 4 and FIG. The pressure roller 26 is pressed against the heating roller 25 by a pressure mechanism described later, whereby a fixing nip N having a predetermined pressure (fixing pressure) is formed between the rollers 25 and 26. Note that a heater (not shown) as a heating source is accommodated in the hollow heating roller 25.

In the housing 27 of the fixing device 22, a conveyance guide 28 for guiding the sheet to the fixing nip N between the heating roller 25 and the pressure roller 26 is provided.
Thus, as described above, the sheet on which the full-color toner image is secondarily transferred collectively from the intermediate transfer belt 7 by the secondary transfer roller 10 is conveyed to the fixing device 22, and the fixing device 22 is heated. A full color toner image is fixed by being heated and pressed in the process of being nipped and conveyed in the fixing nip N between the roller 25 and the pressure roller 26. Then, the sheet on which the toner image is fixed is discharged to the discharge tray 21 by the discharge roller pair 23 and 24.

  Next, a pressure mechanism for pressing the pressure roller 26 against the heating roller 25 will be described.

  A pair of left and right pressure levers 30 are rotatably supported at both ends in the axial direction of the rotation shaft 29 (see FIG. 6) of the pressure roller 26, as shown in FIGS. As shown in FIG. 5, a claw 30a is formed at one end of each pressure lever 30, and the claw 30a engages with an engagement hole 40a formed in the left and right side plates 40 shown in FIG. Therefore, if each pressure lever 30 is rotated about the claw 30a, the pressure roller 26 is also rotated about the claw 30a together with the rotary shaft 29, and each pressure lever 30 is moved to the timepiece of FIGS. By rotating in the direction, the pressure roller 26 is pressed against the heating roller 25, and a fixing nip N having a predetermined pressure is formed between the rollers 25 and 26.

  Also, as shown in FIG. 4, an engagement groove 30b is formed at the other end (tip) of each pressure lever 30, and a pair of left and right bent in an L shape in side view is formed in this engagement groove 30b. Each pressure plate 31 is engaged. That is, as shown in FIG. 6, each pressurizing plate 31 is formed with a rectangular engagement hole 31a that is long in the vertical direction, and the tip end portion of each pressurization lever 30 is passed through the engagement hole 31a. The engagement groove 30 b formed at the tip is engaged with the engagement hole 31 a of the pressure plate 31.

  Further, as shown in FIGS. 3 to 6, in the vicinity of the pair of left and right pressure levers 30, the shaft 32 rotates around the shaft 32 in conjunction with the opening / closing operation of the opening / closing cover 101 (see FIGS. 1 and 2). A pair of left and right open / close levers 33 are provided on the main body frame side, and the upper end of the rod 34 is connected to one end of each open / close lever 33. The pair of left and right rods 34 penetrates the pressure plate 31 and the brackets 40b of the left and right side plates 40 and extends below them. A pressure spring 35 is interposed between the opening / closing lever 33 on the outer periphery of each rod 34 and the pressure plate 31.

  By the way, as shown in FIG. 7, a pair of left and right hook-shaped pressing ribs 28a are formed at the upper end of the conveyance guide 28 in the center in the paper width direction, and these pressing ribs 28a are shown in FIGS. As shown, a position restricting means for restricting the position of the opening / closing lever 33 by engaging with the shaft 32 connecting the pair of left and right opening / closing levers 33 is configured.

  As shown in FIG. 7, two restricting ribs 28 a and 28 b positioned on the back side of the pair of left and right pressurizing plates 31 are integrally provided on the left and right ends of the inner surface of the conveyance guide 28. . These restricting ribs 28a, 28b constitute a position restricting means for restricting the position of each pressure plate 31 by being disposed close to the back side of each of the left and right pressure plates 31.

  Further, as shown in FIG. 3, a fixing pressure switching lever 36 slidable in the paper width direction (left and right direction in FIG. 3) is provided on the outer surface side of the conveyance guide 28. When the thick paper such as an envelope is passed, the fixing pressure switching lever 36 is inserted between the pressure plate 31 and the bracket 40b of the side plate 40 so that the pressure plate 31 moves downward. In this way, by restricting the downward movement of the pressure plate 31, the pressure roller 26 moves in a direction away from the heating roller 25. As a result, the pressure with the heating roller 25 is increased. The amount of nip between the rollers 26 is reduced.

  When plain paper is passed through the fixing device 22 configured as described above, when the open / close cover 101 is closed as shown in FIG. 1, the open / close lever 33 is moved by the open / close cover 101 as shown in FIG. 4. In order to rotate about the shaft 32 in the direction of arrow a and push down the rod 34 as shown in the figure, the pressure spring 35 interposed between the open / close lever 33 and the pressure plate 31 is compressed and its reaction force (Spring force) is transmitted to the pressure lever 30 via the pressure plate 31, and the tip of the pressure lever 30 is pushed down by the reaction force of the pressure spring 35. For this reason, the pressure lever 30 rotates around the claw 30a in the clockwise direction in FIG. 4 to pressurize the pressure roller 26 against the heating roller 25, whereby a predetermined gap is provided between the pressure roller 26 and the heating roller 25. A pressure fixing nip N is formed, and when the plain paper passes through the fixing nip N, the toner image is heated and pressurized to be fixed on the plain paper (normal pressure mode).

  For example, when the opening / closing cover 101 is opened as shown in FIG. 2 because a jam has occurred in the fixing device 22, the restriction of the opening / closing lever 33 by the opening / closing cover 101 is released, and the pressure spring 35 extends to a free length. The opening / closing lever 33 rotates about the shaft 32 in the direction of arrow b in FIG. For this reason, the reaction force that has been pushing down the pressure plate 31 by the pressure spring 35 until now becomes zero, so the pressure applied by the pressure roller 26 is also zero and the fixing pressure is released (fixing pressure released state). The jammed paper nipped in the fixing nip N between the pressure roller 26 and the fixing roller 25 can be easily removed.

  By the way, when passing thick paper such as an envelope with the opening / closing cover 101 closed and performing an image forming operation, the fixing pressure switching lever 36 is slid as described above, and both ends thereof are pressed against the pressure plate 31. And the bracket 40b of the side plate 40, the downward movement of the pressure plate 31 is restricted, so that the pressure roller 26 moves away from the heating roller 25. As a result, the heating roller 25 The nip amount between the pressure roller 26 and the pressure roller 26 is reduced.

  As described above, according to the fixing device 22 of the present invention, the position of the open / close river 33 is regulated by the pressing ribs 28a provided on the conveyance guide 28, and the left and right pressure plates 31 are regulated by the left and right regulating ribs 28a and 28b. Therefore, the deformation of the opening / closing lever 33 and the escape of the pressure plate 31 are prevented. For this reason, the distance between the opening / closing lever 33 and the pressure plate 31 does not change, and the urging force (preset load) of the pressure spring 35 interposed between the two is held at the optimum value (design value), and the The fixing pressure is maintained and a high-quality image can be stably obtained, and problems such as poor return of the open / close lever 33 are solved.

  In the above, the embodiment in which the present invention is applied to the color laser printer and the roller type fixing device provided in the color laser printer has been described. However, the present invention relates to a monochrome monochrome image forming apparatus and the fixing provided therein. Of course, the present invention can be similarly applied to the apparatus. The fixing device may be a belt type other than the roller type.

1 is a cross-sectional view of a color laser printer according to the present invention. FIG. 3 is a perspective view of the color laser printer according to the present invention with an open / close cover opened. 1 is a perspective view of a fixing device according to the present invention. 1 is a cross-sectional view of a fixing device according to the present invention. 1 is a cross-sectional view of a fixing device according to the present invention. FIG. 3 is a perspective view showing a configuration of a fixing pressure reducing mechanism of the fixing device according to the present invention. FIG. 4 is a perspective view of a conveyance guide of the fixing device according to the present invention.

Explanation of symbols

1M Magenta image forming unit 1C Cyan image forming unit 1Y Yellow image forming unit 1K Black image forming unit 2a to 2d Photosensitive drum 3a to 3d Charger 4a to 4d Developing device 5a to 5d Transfer roller 6a to 6d Drum cleaning device 7 Intermediate transfer belt 8 Secondary transfer counter roller 9 Tension roller 10 Secondary transfer roller 11 Belt cleaning device 12a to 12d Toner container 13 Laser scanner unit (LSU)
DESCRIPTION OF SYMBOLS 14 Paper feed cassette 15 Pickup roller 16 Feed roller 17 Retard roller 18 Transport roller pair 19 Registration roller pair 20 Transport roller pair 21 Paper discharge tray 22 Fixing device 23, 24 Paper discharge roller pair 25 Heating roller (heating member)
26 Pressure roller (Pressure member)
27 Fixing Device Housing 28 Conveying Guide 28a Conveying Guide Holding Rib (Opening / closing Lever Position Restricting Means)
28b, 28c Conveying guide regulating rib (pressure plate position regulating means)
29 Rotating shaft of pressure roller 30 Pressure lever 30a Claw of pressure lever 30b Engagement groove of pressure lever 31 Pressure plate 31a Engagement hole of pressure plate 32 Opening / closing lever shaft 33 Opening / closing lever 34 Rod 35 Pressurizing Spring 36 Fixing pressure switching lever 40 Side plate 40a Side plate engagement hole 40b Side plate bracket 100 Image forming apparatus main body 101 Opening / closing cover (front cover)
L, L 'Transport path N Fixing nip

Claims (3)

A heating member and a pressure member that rotate in contact with each other; a rotatable pressure lever that presses the pressure member against the heating member; a pressure plate that engages with the pressure lever; An open / close lever that rotates in conjunction with the open / close operation, a pressure spring interposed between the open / close lever and the pressure plate, and guides a sheet to a fixing nip between the heating member and the pressure member. A conveyance guide is provided, and the pressing member is brought into a pressurized state or a released pressure state by rotating the opening / closing lever in conjunction with the opening / closing operation of the opening / closing cover to change the pressing force of the pressing spring. In such a fixing device,
A fixing device characterized in that a position restricting means for restricting positions of the opening / closing lever and the pressure plate is provided in the transport guide.   The position restricting means includes a hook-shaped pressing rib that presses a central portion in the longitudinal direction of a shaft that connects the pair of left and right opening / closing levers, and a limiting rib that is disposed in proximity to the pressure plate. The fixing device according to claim 1. An image forming apparatus comprising the fixing device according to claim 1.

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