JP2009134080A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which corrects distortion in paper in the paper width direction and ensures a uniformly transporting state of paper. <P>SOLUTION: The fixing device 22 includes a heat roller 24 with a heat source and a pressing roller 26 for pressing while the paper 36 is inserted with the heat roller. In addition, the fixing device 22 includes a distortion detection means 28 for detecting the distortion in the paper in the paper width direction, a feeding speed varying means for varying the feeding speed for the paper which is held and transported in different positions in the paper width direction at a nip section and a control means for controlling an action of the feeding speed varying means. The control means controls the action of the feeding speed varying means so that the feeding speed of the paper which is held and transported is varied in different positions in the paper width direction at the nip part according to the distortion of the paper detected by the distortion detection means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions combined, and more particularly to a fixing device that fixes an unfixed toner image on a sheet.

  2. Description of the Related Art Conventionally, as a fixing device used in an electrophotographic image forming apparatus, a heating roller and a pressure roller are used while a sheet as a recording medium is sandwiched and conveyed by a pair of heating rollers and a pressure roller that are rotated in pressure contact with each other. There is known a fixing device that fixes an unfixed toner image on a sheet by heating and pressurizing the sheet at a nip portion formed therebetween.

  The fixing device is provided with a loop amount detection means for detecting a paper loop amount upstream of the nip portion in the paper conveyance direction, and the paper feed speed is determined based on the paper loop amount detected by the loop amount detection means. Even when the sheet feeding speed is controlled and changes due to long-term use, a stable sheet feeding speed is ensured and a stable fixing property is obtained.

  Various fixing devices intended to obtain such a stable fixing property have been proposed. For example, in Patent Document 1, an elastic pressing member is disposed inside an endless belt disposed in pressure contact with a heating roller. The elastic pressing member is supported by a movable support member, and the position of the movable support member is variably set so as to change the pressure state of the contact nip area formed between the heating roller and the endless belt. A fixing device is disclosed.

JP-A-10-228200

  By the way, the unfixed toner image on the sheet is fixed by heating and pressing the sheet nipped and conveyed by a nip formed between a heating member such as a heating roller and a pressure member such as a pressure roller. In the fixing device, the paper may be distorted in the paper width direction on the upstream side of the nip portion in the paper conveyance direction. In such a case, the fixing device may cause image noise such as paper wrinkles or blurring. .

  In the fixing device as disclosed in Patent Document 1, although the pressure load at the nip portion formed between the heating roller and the endless belt can be changed to change the feeding speed of the entire paper, When distortion of the paper in the width direction occurs, the distortion of the paper cannot be corrected, and image noise such as paper wrinkles and blurring may be caused.

  Therefore, the present invention has been made in view of the above technical problem, and can correct the distortion of the paper in the paper width direction, ensure a uniform paper conveyance state, and can produce images such as paper wrinkles and blurring. It is an object of the present invention to provide a fixing device capable of maintaining a stable paper conveyance state without generating noise, and an image forming apparatus including the fixing device.

For this reason, the fixing device according to the present invention is:
A nip portion formed between the heating member and the pressing member, the heating member having a heat source, and a pressing member that is provided facing the heating member and presses the sheet together with the heating member. In the fixing device for fixing the unfixed toner image on the paper by heating and pressurizing the paper held and conveyed by
A distortion detecting means for detecting the distortion of the sheet in the sheet width direction on the upstream side of the nip portion in the sheet conveying direction;
A feed speed varying means for varying the feed speed of the paper held and conveyed in the nip portion at different positions in the paper width direction;
Control means for controlling the operation of the feed speed variable means;
With
The control means may change the feed speed so that the feed speed of the paper nipped and conveyed by the nip portion can be varied at different positions in the paper width direction in accordance with the distortion of the paper detected by the distortion detection means. Control the operation of the means,
It is characterized by that.

  An image forming apparatus according to the present invention includes the above-described fixing device.

  According to the present invention, by changing the feeding speed of the paper nipped and conveyed at the nip portion at different positions in the paper width direction according to the paper distortion detected by the distortion detection means, the paper in the paper width direction is changed. It is possible to correct distortion and ensure a uniform paper conveyance state. Thereby, it is possible to maintain a stable paper conveyance state without generating image noise such as paper wrinkles or blurring.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, terms indicating a specific direction and position (for example, “up”, “down”, “right”, “left” and other terms including those terms) are used as necessary. These terms are used for easy understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms.

  FIG. 1 is a schematic configuration diagram schematically showing an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 2 is an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine having a combination of these functions. Currently, various types of electrophotographic image forming apparatuses have been proposed. The illustrated image forming apparatus is a so-called tandem color image forming apparatus.

  The image forming apparatus 2 includes an endless intermediate transfer belt 30, and the intermediate transfer belt 30 is wound around a pair of rollers 32 and 34 disposed on the right side and the left side of the drawing, respectively. The roller 32 on the right side of the drawing is drivingly connected to a motor (not shown) and is rotated based on the driving of the motor. As the roller 32 rotates, the intermediate transfer belt 30 and the roller 34 on the left side of the drawing that supports the intermediate transfer belt 30 are rotated counterclockwise in the drawing.

  On the outer side of the intermediate transfer belt 30 supported by the roller 32 arranged on the right side in the drawing, a secondary transfer roller 40 is arranged to face the roller 32 with the intermediate transfer belt 30 interposed therebetween. The secondary transfer roller 40 is in contact with the outer peripheral surface of the intermediate transfer belt 30, and the contact portion (nip portion) forms a secondary transfer region 41.

  An intermediate transfer belt cleaning member 42 is provided outside the intermediate transfer belt 30 supported by the roller 34 disposed on the left side in the drawing. The intermediate transfer belt cleaning member 42 is pressed against the roller 34 via the intermediate transfer belt 30, and the contact portion forms a collection region 62 for collecting untransferred toner.

  Further, on the lower side of the intermediate transfer belt 30 moving from the roller 34 on the left side in the drawing to the roller 32 on the right side in the drawing, yellow (Y), magenta (M), cyan (in order from the left side to the right side in the drawing). Four image forming units 3 (3Y, 3M, 3C, and 3K) that generate toner images of colors corresponding to the four colors C) and black (K) are arranged along the intermediate transfer belt 30.

  Each image forming unit 3 has a cylindrical photoreceptor 4 as an electrostatic latent image carrier. The primary transfer is arranged around the photosensitive member 4 so as to face the photosensitive member 4 via the charger 8, the developing device 18, and the intermediate transfer belt 30 in order along the rotation direction (clockwise direction in the drawing). A roller 14 and a photosensitive member cleaning member 16 are disposed. An exposure device 10 is disposed below the four photoconductors 4. The exposure device 10 performs exposure by irradiating each photoconductor 4 with light between the charger 8 and the developing device 18. It has become.

  Above the image forming apparatus 2, specifically, above the intermediate transfer belt 30, a hopper 20 (20 </ b> Y, 20 </ b> M, 20 </ b> C, 20 </ b> K) containing toner to be supplied to each color developing device 18 is disposed. ing.

  A paper feed cassette 44 as a paper feed device is detachably disposed below the image forming apparatus 2. Sheets 36 serving as recording media stacked and housed in the sheet feed cassette 44 are sent one by one from the top to the sheet transport path 50 by rotation of the sheet feed roller 52 disposed in the vicinity of the sheet feed cassette 44. It is like that. A pair of registration rollers 54 for sending the paper 36 to the secondary transfer area 41 at a predetermined timing is provided near the paper feed roller 52.

  A sheet conveyance path 50 is formed from a sheet feeding cassette 44 to a nip portion of the registration roller pair 54, a secondary transfer region 41 that is a nip portion between the transfer belt 30 and the secondary transfer roller 40, and a secondary transfer region 41, which will be described later. It extends to the paper discharge unit 58 through the fixing device 22 disposed above and the nip portion of the paper discharge roller pair 56 provided above the fixing device 22.

  Next, the operation of the image forming apparatus 2 configured as described above will be described. The image forming apparatus 2 can be switched between a monochrome mode in which a monochrome image is formed using one color toner such as black and a color mode in which a color image is formed using four color toners. Hereinafter, an example of the image forming operation in the color mode will be described.

  First, in each image forming unit 3, the outer peripheral surface of the photoreceptor 4 that is rotationally driven at a predetermined peripheral speed is charged by the charger 8. Next, light corresponding to the image information is projected from the exposure device 10 on the outer peripheral surface of the charged photoconductor 4 to form an electrostatic latent image. Subsequently, the electrostatic latent image is made visible by the developer toner supplied from the developing device 18. The toner images of the respective colors formed on the photoconductor 4 are sequentially transferred (primary transfer) from the photoconductor 4 onto the intermediate transfer belt 30 in the order of yellow, magenta, cyan, and black by the primary transfer roller 14. Each color toner image is superimposed on the transfer belt 30.

  On the other hand, untransferred toner remaining on the photoconductor 4 without being transferred to the intermediate transfer belt 30 reaches the contact portion between the photoconductor 4 and the photoconductor cleaning member 16 as the photoconductor 4 rotates. Then, it is scraped off by the photoconductor cleaning member 16 and removed from the outer peripheral surface of the photoconductor 4.

  The four color toner images superimposed on the intermediate transfer belt 30 are conveyed to the secondary transfer region 41 as the intermediate transfer belt 30 moves. On the other hand, the paper 36 accommodated in the paper feed cassette 44 is conveyed to the secondary transfer area 41 at the timing, and the four color toner images are transferred from the intermediate transfer belt 30 to the paper 36 in the secondary transfer area 41. Are collectively transferred (secondary transfer). The paper 36 on which the four color toner images have been transferred is conveyed further downstream of the paper conveyance path 50 along the conveyance guide 31. After the unfixed toner image is fixed on the paper 36 by the fixing device 22, the paper 36 is discharged. It is sent out to the paper discharge unit 58 via the roller pair 56.

  On the other hand, when the intermediate transfer belt 30 that has passed through the secondary transfer region 41 reaches the contact portion between the intermediate transfer belt 30 and the intermediate transfer belt cleaning member 42 as the intermediate transfer belt 30 moves, the intermediate transfer belt cleaning is performed. The member 42 is cleaned. Thereafter, the rotation of each photoconductor 4 and the intermediate transfer belt 30 is stopped.

Next, the configuration of the fixing device according to the embodiment of the present invention will be described.
FIG. 2 is a schematic configuration diagram illustrating the fixing device according to the first embodiment, and FIG. 3 is a top view of the fixing device according to the first embodiment. As shown in FIG. 2, the fixing device 22 includes a heating roller 24 as a heating member that heats and melts an unfixed toner image transferred from the intermediate transfer belt 30 in the secondary transfer region 41 and fixes it to the paper 36. A pressure roller 26 is provided as a pressure member provided to face the heat roller 24 and presses the paper 36 with the heat roller 24 therebetween.

  The heating roller 24 is formed in a substantially cylindrical shape using an elastic material such as silicone rubber or foamed silicone rubber, and the outer peripheral surface thereof is coated with, for example, a fluororesin. The heating roller 24 extends in the paper width direction orthogonal to the paper transport direction, and both end portions 25a and 25b thereof are rotatably supported by the frame 70 and are drivingly connected to a motor (not shown) based on the driving of the motor. Thus, it is driven to rotate counterclockwise in the figure.

  A heat source (not shown) is provided inside the heating roller 24, and the heating roller 24 is heated by this heat source. As the heat source, for example, a halogen heater, an IH heater, a resistance heating element, or the like is used. Moreover, you may make it use the heat source using an ultrasonic wave.

  The pressure roller 26 is formed in a substantially cylindrical shape using an elastic material such as silicone rubber or foamed silicone rubber, and the outer peripheral surface thereof is coated with, for example, a fluororesin. The pressure roller 26 extends in the sheet width direction orthogonal to the sheet conveyance direction, and is provided substantially along the longitudinal direction of the heating roller 24. Both end portions 27a and 27b are spaced apart from each other in the sheet width direction. The two supported members 73a and 73b are rotatably supported.

  A motor 75a as a support member driving means for moving the position of the support member 73a is connected to the support member 73a via a gear (not shown) attached to the motor rotation shaft 74a, and the motor 75a is operated. The support member 73a can be moved to the heating roller side or in a direction away from the heating roller (in the direction of arrow Z1).

  Further, a motor 75b as a support member driving means for moving the position of the support member 73b is connected to the support member 73b via a gear (not shown) attached to the motor rotation shaft 74b to operate the motor 75b. Thus, the support member 73b can be moved toward the heating roller or in a direction away from the heating roller (in the direction of arrow Z2).

  In the fixing device 22, the pressure roller 26 is configured such that the positions of the two support members 73 a and 73 b that support both ends 27 a and 27 b of the pressure roller 26 are moved independently, and pressure is applied to the heating roller 24 at different positions in the paper width direction. The position of the roller 26 is variable. As a result, the pressure load at the nip portion 92 is varied at different positions in the paper width direction, the length of the nip portion 92 in the paper conveyance direction is varied at different positions in the paper width direction, and the feed speed of the paper 36 is changed to the paper width. It can be varied at different positions. Further, as shown in FIG. 2, the pressure roller 26 is pressed against the heating roller 24 and is driven to rotate in the clockwise direction in the drawing as the heating roller 26 rotates.

  The fixing device 22 is provided with position detection sensors 71a and 71b that detect the positions of the support members 73a and 73b, respectively, and the positions of the support members 73a and 73b are accurately determined based on the detection values of the position detection sensors 71a and 71b. Be controlled. As the position detection sensors 71a and 71b, for example, a photoswitch via a pulse plate can be used.

  The fixing device 22 includes a loop amount detection unit (not shown) that detects the loop amount of the paper 36 on the upstream side of the nip portion 92 in the paper conveyance direction, and a paper width on the upstream side of the nip portion 92 in the paper conveyance direction. Distortion detecting means 28 for detecting the distortion of the paper 36 in the direction is provided.

  4 is a cross-sectional view taken along line Y4-Y4 in FIG. As shown in this figure, in the fixing device 22, the distortion detection means 28 is arranged on the upstream side of the nip portion 92 in the paper conveyance direction, and is sequentially spaced from the left side of the drawing to the right side of the drawing in the paper width direction. Three position detection sensors 28a, 28b, and 28c for detecting the position of the paper 36 at different positions are provided.

  Each of the position detection sensors 28 a, 28 b, and 28 c includes an actuator 82 that is rotatably attached to the main body 81, and can detect the position of the sheet 36 according to the angle of the actuator 82 that contacts the sheet 36. It is like that. In the fixing device 22, the distortion of the sheet 36 in the sheet width direction is detected based on the position of the sheet 36 detected by the position detection sensors 28a, 28b, and 28c. In this embodiment, the distortion detection means 28 is constituted by three position detection sensors 28a, 28b, and 28c. However, a plurality of position detection means for detecting the position of the paper 36 at different positions in the paper width direction are provided. By providing, it is possible to detect distortion of the paper 36 in the paper width direction.

  In addition, the fixing device 22 includes a control unit (not shown) that comprehensively controls the operation of the fixing device 22, and the control unit operates the heat source, rotationally drives the heating roller 24, and operates the motors 75a and 75b. Control etc. Further, the control unit controls the operation of the motors 75a and 75b so as to vary the feeding speed of the entire sheet in the sheet conveying direction based on the loop amount of the sheet 36 detected by the loop amount detecting means, and also warps. The operation of the motors 75a and 75b is controlled so that the feeding speed of the paper nipped and conveyed by the nip portion is varied at different positions in the paper width direction according to the paper distortion detected by the detecting means. The control unit is configured with a microcomputer as a main part, for example.

  In the fixing device 22 configured as described above, when the sheet 36 is distorted in the sheet width direction, for example, as shown in FIG. When separated from the conveyance guide 31, the motor 75a is moved so that the end 27a of the pressure roller 26 is moved from the end 27b of the pressure roller 26 to the heating roller 24 side so as to eliminate the distortion of the paper 36. When activated, the pressure load of the nip portion 92 where the left end portion of the sheet 36 is nipped and conveyed is made larger than the pressure load of the nip portion 92 where the right end portion of the sheet 36 is nipped and conveyed. The length of the nip portion 92 in which the left end portion of the drawing 36 is nipped and conveyed is made longer than the length of the nip portion 92 in which the right end portion of the drawing 36 is nipped and conveyed, and the feeding speed of the left end portion of the sheet 36 in the drawing is set. Paper 3 Larger than the feeding speed of the drawing right end of, corrects the distortion of the sheet 36 in the sheet width direction.

  As shown in FIG. 4, when the left end of the sheet 36 is separated from the conveyance guide 31 from the right end of the sheet 36, the end 27 b of the pressure roller 26 is replaced with the end of the pressure roller 26. The motor 75b is actuated so as to move away from the heating roller 26 from 27a, and the pressure load of the nip portion 92 where the right end of the sheet 36 is nipped and conveyed is nipped and conveyed at the left end of the sheet 36. Therefore, the length of the nip portion 92 in which the right end portion of the sheet 36 is nipped and conveyed is set to the length of the nip portion 92 in which the left end portion of the sheet 36 is nipped and conveyed. It is possible to correct the distortion of the paper 36 in the width direction of the paper 36 by making it shorter than the length and making the feed speed of the right edge of the paper 36 smaller than the feed speed of the left edge of the paper 36 in the drawing.

  In the fixing device 22, the operation of the motors 75 a and / or 75 a is controlled by the control unit in accordance with the distortion of the paper 36 detected by the distortion detection means 28, and the nip portion 92 is configured to eliminate the distortion of the paper 36. The feeding speed of the paper 36 that is nipped and conveyed is varied at different positions in the paper width direction.

  Further, in the fixing device 22, when the distortion of the sheet 36 in the sheet width direction is eliminated, the nip portion 92 is set so that the feeding speed of the sheet 36 is constant at different positions in the sheet width direction, that is, at different positions in the sheet width direction. The operation of the motors 75a and / or 75b is controlled so that the length of the motor is constant. When the feeding speed of the paper 36 becomes constant at different positions in the paper width direction, the whole paper 36 is fed in the paper transport direction based on the loop amount of the paper 36 detected by the loop amount detecting means (not shown). Speed is optimized.

  In the present embodiment, two support members 73a and 73b that support the pressure roller 26 at both ends in the paper width direction and motors 75a and 75b that move the positions of the two support members 73a and 73b independently of each other. In addition, there is configured a feed speed varying means for varying the feed speed of the sheet 36 nipped and conveyed by the nip portion 92 at different positions in the sheet width direction.

Here, in the present embodiment, in the fixing device 22, the pressure load of the nip portion 92 is varied in the paper width direction, and the feed speed ratio of the paper 36 with reference to the central portion of the paper 36 in the paper width direction is examined. The pressure load was changed, and the relationship between the pressure load ratio and the feed speed ratio of the paper 36 was examined. Specifically, in the fixing device 22, paper having a paper basis weight of 60 g / m ² and 100 g / m ² is used as the paper 36, and a reference value such as 300 N, for example, is used as the pressure load in the nip portion 92. A pressure load in which the pressure load ratio is changed by ± 5% is applied to the value, and the feed speed of the paper 36 in the nip 92 in the paper width direction is used as a reference for the paper 36. The feed rate ratio was investigated. Here, the reference value is a set value of a pressure load such as 300 N, for example, and the pressure load is applied to one end of the pressure roller 26 by operating the motor 75a or 75b.

FIG. 5 is a graph showing experimental results obtained by using a paper having a paper basis weight of 60 g / m ² and changing the pressure load at the nip portion in the paper width direction and examining the paper feed speed ratio. FIG. used paper amount 100 g / m ^2, is a graph showing the experimental result of examining the feed rate ratio of the sheet by changing the pressure load of the nip portion in the sheet width direction. 5 and 6, the horizontal axis is the position of the nip portion 92 in the paper width direction, and one end of the nip portion 92 where the motor 75a or 75b is operated is represented as driving, and the central portion of the nip portion 92 is the center. The other end portion of the nip portion 92 is represented as non-driven, and the feed speed ratio of the sheet 36 in the nip portion 92 based on the feed speed of the sheet 36 at the center of the nip portion 92 is represented on the vertical axis. .

As shown in FIGS. 5 and 6, the feeding speed of the paper 36 in the nip portion 92 can be varied in the paper width direction by changing the pressure load of the nip portion 92 at different positions in the paper width direction. It can be seen that the pressure increases when the pressure load is increased and decreases when the pressure load is decreased. Further, when a paper having a paper basis weight of 100 g / m ² is used, the feeding speed of the paper 36 is larger with respect to the same pressure load than when a paper having a paper basis weight of 60 g / m ² is used. I understand that In addition, in FIGS. 5 and 6, since the sheet feed speed ratio is expressed with the center as a reference, it was found that the feed speed ratio of the driven and non-driven sheets is equal.

  FIG. 7 is a graph showing the relationship between the pressure load ratio and the paper feed speed ratio. In FIG. 7, the pressure load ratio is shown on the horizontal axis, and the feed speed ratio of the paper 36 is shown on the vertical axis. As shown in FIG. 7, in the fixing device 22, when the pressure load of the nip portion 92 formed between the heating roller 24 and the pressure roller 26 is changed, the sheet 36 is fed according to the pressure load ratio. It can be seen that the speed ratio of the paper 36 in the nip portion 92 can be varied by + 0.15% by increasing the speed ratio and varying the pressure load by + 5%.

  Thereby, in the fixing device 22, the feeding speed of the sheet 36 nipped and conveyed by the nip portion 92 is changed by varying the pressure load of the nip portion 92 formed between the heating roller 24 and the pressure roller 26. It has been found that the feeding speed of the sheet 36 can be varied in the sheet width direction by varying the pressure load of the nip portion 92 in the sheet width direction.

  As described above, the fixing device 22 according to the present embodiment and the image forming apparatus 2 including the fixing device 22 are nipped and conveyed by the nip portion 92 according to the distortion of the paper 36 detected by the distortion detection unit 28. By varying the feeding speed of the paper 36 at different positions in the paper width direction, it is possible to correct the distortion of the paper 36 in the paper width direction and ensure a uniform paper conveyance state. Thereby, it is possible to maintain a stable paper conveyance state without generating image noise such as paper wrinkles or blurring.

  The distortion detection means 28 includes three position detection sensors 28a, 28b, and 28c that are provided on the upstream side of the nip portion 92 in the sheet conveyance direction and detect the position of the sheet 36 at different positions in the sheet width direction. By detecting the distortion of the sheet 36 in the sheet width direction based on the position of the sheet 36 detected by the sensors 28a, 28b, and 28c, it is possible to reliably detect the distortion of the sheet 36 with a relatively simple configuration. it can.

  Further, the feed speed varying means moves the positions of the support members 73a and 73b by the motors 75a and 75b, and varies the position of the pressure roller 26 at different positions in the paper width direction, thereby applying pressure at the nip portion 92. By changing the load at different positions in the paper width direction and changing the feeding speed of the paper 36 at different positions in the paper width direction, the above-described effect can be obtained with certainty.

  FIG. 8 is a schematic configuration diagram illustrating a fixing device according to the second embodiment. The fixing device 82 according to the second embodiment has the same configuration as the fixing device 22 except that the fixing device 22 shown in FIG. The description is omitted.

  In the fixing device 82, as shown in FIG. 8, a support member 83 that rotatably supports the end portion 27a of the pressure roller 26 is rotatably attached to the rotation shaft 84, and the support member 83 is attached to the heating roller. It is attached to a pressure spring 85 that applies pressure to the 24 side. The support member 83 is pressurized by the pressure spring 85, and the pressure of the pressure spring 85 against the support member 83 is varied to move the position of the support member 83 toward the heating roller 24 or away from the heating roller 24. Then, the end 27 a of the pressure roller 26 is moved toward the heating roller 24 or away from the heating roller 24. Note that the pressing force of the pressurizing spring 85 that pressurizes the support member 83 is controlled by the control unit.

  Similarly, the support member 83 that rotatably supports the end portion 27b of the pressure roller 26 is rotatably attached to the rotation shaft 84 and is also supported at the opposite end portion 27b of the pressure roller 26. It is attached to a pressure spring 85 that presses 83 toward the heating roller 24. The support member 83 is pressurized by the pressure spring 85, and the pressure of the pressure spring 85 against the support member 83 is varied to move the position of the support member 83 toward the heating roller 24 or away from the heating roller 24. Then, the end portion 27 b of the heating roller 26 is moved toward the heating roller 24 or away from the heating roller 24.

  In this manner, in the fixing device 82, the pressure spring 85 as a support member driving unit that independently moves the position of the support member 83 that supports the pressure roller 25 pressurizes the support member 83. The positions of the support members 83 are configured to move independently of each other.

  In the fixing device 82, the pressure roller 26 is configured such that the two support members 83 that support both ends 27 a and 27 b are pressed by the pressure springs 85, so that the positions of the two support members 83 are independent of each other. The position of the pressure roller 26 with respect to the heating roller 24 is varied at different positions in the paper width direction. As a result, the pressure load at the nip portion 92 is varied at different positions in the paper width direction, the length of the nip portion 92 in the conveyance direction of the paper 36 is varied at different positions in the paper width direction, and the feeding speed of the paper 36 is changed. It is variable at different positions in the paper width direction.

  Also in the fixing device 82 configured as described above, when the distortion of the sheet 36 occurs in the sheet width direction, the operation of the pressure spring 85 is controlled according to the distortion of the sheet 36 detected by the distortion detecting unit 28. Controlled by the unit, the feed speed of the paper 36 nipped and conveyed by the nip portion 92 is varied at different positions in the width direction of the paper 36 so as to eliminate the distortion of the paper 36.

  The fixing device 82 is also provided with a position detection sensor 86 that detects the positions of the two support members 83 that support the ends 27 a and 27 b of the pressure roller 26, and based on the detection value of the position detection sensor 86. The position of the support member 83 is accurately controlled.

  As described above, also in the fixing device 82, the feeding speed of the sheet 36 that is nipped and conveyed by the nip portion 92 so as to eliminate the distortion of the sheet 36 according to the distortion of the sheet 36 detected by the distortion detection unit 28. By varying the position at different positions in the width direction, it is possible to correct the distortion of the sheet 36 in the sheet width direction and ensure a uniform sheet conveyance state.

  In the fixing devices 22 and 82, the heating roller 24 is used as a heating member. However, as the heating member, a heating roller provided with a heat source, a fixing roller disposed at a position away from the heating roller, and the heating roller and fixing. A heating member provided with an endless fixing belt wound around a roller may be used.

  FIG. 9 is a schematic configuration diagram illustrating a fixing device using a fixing belt as a heating member. The fixing device 102 shown in FIG. 9 has the same configuration as the fixing device 82 except that the configuration of the heating member is different from that of the fixing device 82 shown in FIG. The description is omitted.

  The fixing device 102 includes, as a heating member, a heating roller 94 provided with a heat source (not shown) and rotatably provided, and rotatably provided at a position separated from the heating roller 94 and facing the pressure roller 26. A fixing roller 95, and a heating roller 94 and an endless fixing belt 96 wound around the fixing roller 95.

  In the fixing device 102, the pressure roller 26 is drivingly connected to a motor (not shown) and is driven to rotate in the clockwise direction in the drawing based on the driving of the motor. The fixing belt 96 is rotated in the clockwise direction in the drawing as the pressure roller 26 is driven to rotate, and the fixing belt 96 is heated by the heating roller 94 when the fixing belt 96 is rotated. After the fixing belt 96 is heated, an unfixed toner image on the sheet 36 is heated and melted and fixed at a nip portion 92 formed between the fixing belt 96 and the pressure roller 26. Thus, in the fixing devices 22 and 82, a fixing belt may be used as the heating member.

  In the fixing devices 22 and 82, the pressure roller 26 is used as a pressure member. However, the pressure member is an endless shape that is provided to face the heating roller 24 and sandwiches the paper 36 together with the heating roller 24 to pressurize it. The fixing belt may be used.

  FIG. 10 is a schematic configuration diagram showing a fixing device using a fixing belt as a pressure member. The fixing device 112 shown in FIG. 10 has the same configuration as the fixing device 82 except that the configuration of the pressure member is different from that of the fixing device 82 shown in FIG. Therefore, the description is omitted.

  The fixing device 112 includes, as a pressure member, an endless fixing belt 106 and a pressing member 107 that is provided inside the fixing belt 106 and presses the fixing belt 106 from the inner surface of the fixing belt 106. Further, as shown in FIG. 10, a guide member 108 that guides the movement of the fixing belt 106 may be provided inside the fixing belt 106.

  The pressing member 107 extends in the longitudinal direction (paper width direction) of the fixing belt 106 inside the fixing belt 106, and both ends thereof are supported by the support members 103. Each of the support members 103 is rotatably attached to the rotation shaft 84 and is attached to a pressure spring 85 that pressurizes the support member 103 toward the heating roller 24.

  Also in the fixing device 112, the support member 103 is pressed by the pressure spring 85, and the pressure of the pressure spring 85 with respect to the support member 103 is varied, so that the position of the support member 103 is on the heating roller 24 side or the heating roller. Accordingly, the pressing member 107 is moved toward the heating roller 24 or away from the heating roller 24, and both end portions of the fixing belt 106 are independently moved toward the heating roller 24 or It is moved away from the heating roller 24.

  In this manner, in the fixing device 112, the positions of the supporting members 103 that support both ends of the pressing member 107 are independently moved, and the position of the fixing belt 106 can be varied at different positions in the paper width direction. The pressure load in the nip portion 92 can be varied at different positions in the paper width direction, and the feed speed of the paper 36 can be varied at different positions in the paper width direction.

  The fixing device 112 is configured such that the heating roller 24 is drivingly connected to a motor (not shown) and is driven to rotate counterclockwise in the drawing based on the driving of the motor. When the fixing belt 106 is pressed by the pressing member 107, the fixing belt 106 is pressed against the heating roller 24, and is driven to rotate in the clockwise direction in the drawing as the heating roller 24 rotates.

  Also in the fixing device 112 configured as described above, when the sheet 36 is distorted in the sheet width direction, the operation of the pressure spring 85 is controlled according to the distortion of the sheet 36 detected by the distortion detecting unit 28. Controlled by the unit, the feeding speed of the paper 36 nipped and conveyed by the nip portion 92 is varied at different positions in the paper width direction so as to eliminate the distortion of the paper 36. Thereby, the distortion of the sheet 36 in the sheet width direction can be corrected, and a uniform sheet conveyance state can be ensured.

  In the fixing devices 22, 82, 102, and 112 described above, the position of the pressure member is varied at different positions in the paper width direction by moving the position of the support member that supports the pressure member, and the feeding speed of the paper 36. However, it is also possible to change the feed speed of the paper 36 at different positions in the paper width direction by changing the size of the pressure member itself.

  FIG. 11 is a schematic configuration diagram showing a fixing device according to a third embodiment, and the fixing device is shown in a top view. As shown in FIG. 11, the fixing device 122 includes a heating roller 114 and a pressure roller 26, and the heating roller 114 and the heating roller 26 are rotatably supported by a frame (not shown). The heating roller 114 is drivingly connected to a motor (not shown), and is driven to rotate based on the driving of the motor. The pressure roller 26 pressed against the heating roller 114 is driven to rotate as the heating roller 114 rotates. It has become.

  The heating roller 114 is formed in a substantially cylindrical shape using a material having a predetermined thermal expansion coefficient such as an elastic material such as silicone rubber, and the heating roller 114 is disposed inside the heating roller 114 in the longitudinal direction of the heating roller 114. 114, the first heater 115a for heating the left end of the heating roller 114, the second heater 115b for heating the central portion of the heating roller 114 in the drawing, and the first heating heater 114 for heating the right end of the heating roller 114 in the drawing. A heat source constituted by three heaters 115c is provided.

  In the fixing device 122, the operations of the first, second, and third heaters 115a, 115b, and 115c are independently controlled by the control unit, and the heaters 115a, 115b, and 115c are operated, thereby heating rollers. 114 in the longitudinal direction of the heating roller 114 in the longitudinal direction of the heating roller 114, the central portion of the heating roller 114, and the end of the heating roller 114 on the right side in the drawing are independently heated and expanded. The outer diameter of the heating roller 114 can be varied. As a result, at the different positions in the paper width direction, specifically, at the end of the heating roller 114 on the left side in the drawing, at the center of the heating roller 114, and at the right end of the heating roller 114 in the drawing, The pressure load is varied, the length of the nip portion 92 in the sheet conveyance direction is varied, and the feeding speed of the sheet 36 is varied.

  In the fixing device 122, a first temperature sensor 116 a that detects the temperature of the left end of the heating roller 114 in the drawing and a second temperature that detects the temperature of the central portion of the heating roller 114 outside the heating roller 114. A temperature sensor 116b and a third temperature sensor 116c for detecting the temperature of the right end of the heating roller 114 in the figure are provided, and based on the detection values of the first, second and third temperature sensors 116a, 116b and 116c. Thus, the outer diameter of the heating roller 114 is accurately controlled.

  Also in the fixing device 112 configured as described above, when the sheet 36 is distorted in the sheet width direction, the heaters 115 a, 115 b, and 115 c are changed according to the distortion of the sheet 36 detected by the distortion detection unit 28. The operation is controlled by the control unit, and the feeding speed of the paper 36 nipped and conveyed by the nip portion 92 is varied at different positions in the paper width direction so as to eliminate the distortion of the paper 36. Thereby, the distortion of the sheet 36 in the sheet width direction can be corrected, and a uniform sheet conveyance state can be ensured.

  The present invention is not limited to the illustrated embodiments, and it goes without saying that various improvements and design changes can be made without departing from the scope of the present invention. For example, the embodiment has been described with respect to a tandem type color printer, but the present invention can also be applied to other image forming apparatuses such as a four-cycle type color printer.

1 is a schematic configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a schematic configuration diagram illustrating a fixing device according to a first embodiment. FIG. 3 is a top view of the fixing device according to the first embodiment. FIG. 3 is a cross-sectional view taken along line Y4-Y4 in FIG. Using the paper of the paper basis weight 60 g / m ^2, is a graph showing the results of experiments with a pressure load of the nip is changed in the sheet width direction was examined feed rate ratio of the sheet. With paper sheet basis weight 100 g / m ^2, is a graph showing the experimental result of examining the feed rate ratio of the sheet by changing the pressure load of the nip portion in the sheet width direction. It is a graph which shows the relationship between a pressurization load ratio and a paper feed speed ratio. FIG. 6 is a schematic configuration diagram illustrating a fixing device according to a second embodiment. FIG. 2 is a schematic configuration diagram illustrating a fixing device using a fixing belt as a heating member. FIG. 2 is a schematic configuration diagram illustrating a fixing device using a fixing belt as a pressure member. It is a schematic block diagram which shows the fixing device which concerns on 3rd Embodiment.

Explanation of symbols

2 Image forming apparatus 22, 82, 102, 112, 122 Fixing device 24, 94 Heating roller 26 Pressure roller 28 Distortion detection means 36 Paper 71a, 71b, 28a, 28b, 28c, 86 Position detection sensors 73a, 73b, 83, 103 Support member 75a, 75b Motor 85 Pressurizing spring 92 Nip part 115a, 115b, 115c Heater

Claims (5)

A nip portion formed between the heating member and the pressing member, the heating member having a heat source, and a pressing member that is provided facing the heating member and presses the sheet together with the heating member. In the fixing device for fixing the unfixed toner image on the paper by heating and pressurizing the paper held and conveyed by
A distortion detecting means for detecting the distortion of the sheet in the sheet width direction on the upstream side of the nip portion in the sheet conveying direction;
A feed speed varying means for varying the feed speed of the paper held and conveyed in the nip portion at different positions in the paper width direction;
Control means for controlling the operation of the feed speed variable means;
With
The control means may change the feed speed so that the feed speed of the paper nipped and conveyed by the nip portion can be varied at different positions in the paper width direction in accordance with the distortion of the paper detected by the distortion detection means. A fixing device for controlling the operation of the means.   The distortion detection means includes a plurality of position detection means provided on the upstream side of the nip portion in the paper conveyance direction and detecting the position of the paper at different positions in the paper width direction, and is detected by the plurality of position detection means. The fixing device according to claim 1, wherein a distortion of the sheet in a sheet width direction is detected based on a position of the sheet.   The feed speed variable means includes a plurality of support members that support the pressure member, and a support member drive means that moves the positions of the plurality of support members independently, and the support member drive means supports the support member. By moving the position of the member and changing the position of the pressure member at a different position in the paper width direction, the pressure load in the nip portion is changed at a different position in the paper width direction, and the paper feed speed is changed. The fixing device according to claim 1, wherein the fixing device is variable at different positions in the paper width direction.   The fixing device according to claim 3, wherein the support member driving unit moves the positions of the plurality of support members independently by pressurizing the support member.   An image forming apparatus including the fixing device according to claim 1.

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