JP2009128575A - Image fixing unit and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing unit and an image forming device having a small gap between a fixing member and a separating member which is stable even after a long time use without affecting the image quality. <P>SOLUTION: This fixing unit has a separating member 38 disposed downstream the nip section in the traveling direction of the fixing member 21 and facing it with a predetermined gap, and positioning members 39 disposed between the fixing member 21 and the separating member 38 to define a gap between them. The positioning members 39 are in contact with the fixing member 21 and free to move in its width direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed therein, and in particular, a separating member that faces the fixing member with a gap. The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, in a fixing device installed in an image forming apparatus such as a copying machine or a printer, a separation member such as a separation plate is used as a fixing member in order to suppress a problem that a recording medium after the fixing process is wound around the fixing member. A technique for making them face each other is known (see, for example, Patent Document 1, Patent Document 2, etc.).

  The fixing device includes a fixing member such as a fixing roller and a fixing belt, and a pressure member such as a pressure roller, a pressure belt, and a pressure pad that are in pressure contact with each other by a pressing unit. A nip portion (fixing nip portion) is formed on the surface. Then, the fixing member is heated by heating means such as a heater and an excitation coil, and the toner image on the recording medium conveyed toward the nip portion is fixed on the recording medium by receiving heat and pressure.

In such a fixing device, a separation member is installed at a position downstream of the nip portion in the running direction of the fixing member so as to face the fixing member with a minute gap. By providing the separation member, even if the recording medium immediately after the fixing process is adsorbed to the fixing member, the recording medium is forcibly separated from the fixing member without being wound around the fixing member by the separation member, and is moved to the conveyance path. Will be guided.
The separation member (separation plate) that faces the fixing member with a minute gap is separated on the output image as compared with the separation claw that directly contacts the fixing member (for example, see Patent Document 3). It is known that there is no problem of occurrence of gloss streaks corresponding to the positions of and no problem of damaging the surface of the fixing member.

On the other hand, in Patent Document 1 or the like, abutting portions (positioning members) formed by rolling or bending are provided at both ends in the width direction of the separation plate, and the separation plate is urged toward the fixing member to abut. A technique is disclosed in which a minute gap is accurately formed between the separation plate and the fixing member by bringing the portion into contact with the fixing member.
Further, in Patent Document 2 and the like, a separation claw configured to be able to contact and separate from the fixing member is provided separately from the separation plate, and the separation claw is applied to the fixing member only when the separation function is insufficient. A technique for contact is disclosed.

JP 2006-171551 A JP 2007-33557 A JP 2007-33474 A

In the fixing device disclosed in Patent Document 1 and the like described above, the position in the width direction of the positioning member (abutting portion) is fixed, and the positioning member is in sliding contact with the same position in the width direction of the fixing member. The fixing member was easily worn. If a large amount of wear occurs at the position where the positioning member abuts on the fixing member, the gap between the fixing member and the separating member fluctuates, and the separating member hits the fixing member, and the fixing member extends over the entire width direction. There may be secondary problems such as scratches.
Further, the positioning member is in contact with both end portions in the width direction of the fixing member. For this reason, the gap between the fixing member and the separation member is likely to change due to the influence of drooping and jumping on processing and deterioration with time of rubber hardness at both ends of the elastic layer (rubber layer) of the fixing member.

  The present invention has been made in order to solve the above-described problems. A fixing device and an image forming apparatus in which a minute gap between a fixing member and a separation member is stabilized over time without affecting image quality. To provide an apparatus.

  According to a first aspect of the present invention, a fixing device forms a fixing member that heats and melts a toner image and fixes the toner image on a recording medium, and a nip portion that is pressed against the fixing member and the recording medium is conveyed. A pressure member, a separation member that is disposed downstream of the nip portion in the running direction of the fixing member, and that faces the fixing member with a predetermined gap therebetween, and for defining the gap A positioning member interposed between the fixing member and the separating member, and the positioning member is disposed so as to contact the fixing member so as to be movable in the width direction. is there.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the positioning member is movably held on a shaft member fixed to the separating member. .

  According to a third aspect of the present invention, in the fixing device according to the first aspect, the positioning member is movably held on a shaft member fixed to a frame that supports the fixing member. It is a thing.

  According to a fourth aspect of the present invention, there is provided the fixing device according to any one of the first to third aspects, wherein the positioning member is a roller-shaped member that is driven to rotate following the travel of the fixing member. It is what.

  A fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, further comprising a regulating member that regulates a movement range in the width direction of the positioning member. is there.

  A fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the positioning member is biased toward the fixing member together with the separation member. A member is provided.

  A fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, wherein the fixing device contacts the fixing member in conjunction with the movement in the width direction with respect to the fixing member. It is equipped with a separation claw that separates.

  The fixing device according to an eighth aspect of the present invention is the fixing device according to the seventh aspect, wherein the separation claw is installed on the separation member.

  According to a ninth aspect of the present invention, there is provided a fixing device according to the seventh or eighth aspect, wherein the arm moves in the width direction together with the separation claw and is manually operated from outside the device. It has a part.

  A fixing device according to a tenth aspect of the present invention is the fixing device according to the seventh or eighth aspect, further comprising driving means for automatically moving the separation claw in the width direction.

  An image forming apparatus according to an eleventh aspect of the present invention includes the fixing device according to any one of the first to tenth aspects.

  In the present invention, since the positioning member that defines the gap between the fixing member and the separation member is in contact with the fixing member so as to be movable in the width direction, the fixing member is separated from the fixing member without affecting the image quality. It is possible to provide a fixing device and an image forming apparatus in which a minute gap with a member is stabilized over time.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
The first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
As shown in FIG. 1, the image forming apparatus 1 according to the first embodiment is a tandem type color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.
An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 1 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).
Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (development process). .)
Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photosensitive drums 5Y, 5M, and so on. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).
Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by the three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is rotationally driven in the counterclockwise direction in FIG. 1, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image has been transferred at the position of the secondary transfer nip is conveyed to the nip portion of the fixing portion 20 (where the fixing roller 21 and the pressure roller 31 are in pressure contact). The color image transferred onto the surface is fixed on the recording medium P by the heat and pressure generated by the fixing roller 21 and the pressure roller 31 at the nip portion (fixing nip portion).
Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram showing the fixing device 20, and FIG. 3 is a perspective view showing the fixing device 20. FIG. 4 is a schematic view showing the fixing roller 21 and the separation plate 38 in the width direction.

As shown in FIGS. 2 and 3, the fixing device 20 includes a fixing roller 21 as a fixing member, a pressure roller 31 as a pressure member, a separation plate 38 as a separation member, a guide plate 35, a temperature sensor 70, and the like. Consists of.
Here, the fixing roller 21 as a fixing member is a thin cylindrical body that rotates in the direction of the arrow in FIG. 2, and a heater 25 (heat source) as a heating means is fixed inside the cylindrical body. Yes. The fixing roller 21 is a multi-layered structure in which an elastic layer 23 and a release layer 24 are sequentially laminated on a cored bar 22 and press-contacts with a pressure roller 31 as a pressure member to form a nip portion.

The cored bar 22 of the fixing roller 21 is formed of an iron-based material such as SUS304.
The elastic layer 23 of the fixing roller 21 is made of an elastic material such as fluorine rubber, silicone rubber, or foamable silicone rubber.
Further, as the release layer 24 of the fixing roller 21, PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like can be used. By providing the release layer 24 on the surface layer of the fixing roller 21, the releasability (peelability) for the toner T (toner image) is secured.

  The heater 25 (heating means) of the fixing roller 21 is a halogen heater, and both ends thereof are fixed to the frame of the fixing device 20. Then, the fixing roller 21 is heated by the heater 25 whose output is controlled by the power supply unit (AC power supply) of the apparatus main body 1, and heat is applied to the toner image T on the recording medium P from the surface thereof. The output control of the heater 25 is performed based on the detection result of the roller surface temperature by the temperature sensor 70 (thermistor) that contacts the surface of the fixing roller 21. Specifically, the AC voltage is applied to the heater 25 for the energization time determined based on the detection result of the temperature sensor 70. By such output control of the heater 25, the temperature (fixing temperature) of the fixing roller 21 can be adjusted and controlled to a desired temperature (target control temperature). The temperature sensor 70 may be a non-contact type thermopile or the like in addition to the contact type thermistor.

The pressure roller 31 as a pressure member mainly includes a cored bar 32 and an elastic layer 33 formed on the outer peripheral surface of the cored bar 32 via an adhesive layer. The elastic layer 33 of the pressure roller 31 is formed of a material such as fluorine rubber, silicone rubber, or foamable silicone rubber. A thin release layer made of PFA or the like can be provided on the surface layer of the elastic layer 33.
The pressure roller 31 is in pressure contact with the fixing roller 21 by an urging force of a pressure unit (not shown). Thus, a desired nip portion (fixing nip portion) is formed between the pressure roller 31 and the fixing roller 21.

  Guide plates 35 for guiding the conveyance of the recording medium P are disposed on the entrance side and the exit side of the contact portion (a nip portion) between the fixing roller 21 and the pressure roller 31, respectively. The guide plate 35 is fixed to the housing of the fixing device 20.

  Further, on the downstream side in the running direction (rotation direction) of the fixing roller 21 with respect to the nip portion (near the exit side of the nip portion), a separation member that faces the fixing roller 21 with a predetermined gap G therebetween. A separating plate 38 is provided. The separation plate 38 (separation member) is for suppressing a problem that the recording medium P after the fixing process is wound around the fixing roller 21 along with the rotation of the fixing roller 21. In the first embodiment, the separation plate 38 is made of a metal material.

  Here, referring to FIGS. 2 and 4, in order to define a gap G between the separation plate 38 and the fixing roller 21 at both ends of the separation plate 38 in the width direction (the direction perpendicular to the paper surface of FIG. 2). The positioning member 39 (abutting member) is interposed between the members 21 and 38. The positioning member 39 is indirectly urged by an urging means (not shown) such as a torsion coil spring connected to both ends of the separation plate 38 (with the separation plate 38 toward the fixing roller 38). And abuts against both ends of the fixing roller 21 in the width direction. As a result, a desired gap G is stably formed between the separation plate 38 and the fixing roller 21. The configuration and operation of the separation plate 38 and the positioning member 39 will be described in detail later.

The gap G between the fixing roller 21 and the separation plate 38 is set to be 0.1 to 0.8 mm when the fixing roller 21 is heated (when hot). That is, the gap G between the fixing roller 21 and the separating plate 38 is 0.1 to 0. 0 in a state where the fixing device 20 is operated and the components such as the fixing roller 21, the separating plate 38, and the positioning member 39 are thermally expanded. It is set to be 8 mm. If the gap G is smaller than 0.1 mm, the fouling of the fixing roller 21 moves to the separation plate 38 and fouls the recording medium P after the fixing process, or the separation plate 38 contacts the fixing roller 21 and the surface thereof is covered. It will hurt you. On the other hand, if the gap G is larger than 0.8 mm, the original function of preventing jamming of the recording medium P around the fixing roller 21 is deteriorated.
In the first embodiment, the positioning member 39 is indirectly biased by the biasing means. However, the positioning member 39 may be biased directly by the biasing means.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 1 is turned on, AC voltage is applied (powered) from the AC power source to the heater 25, and rotation driving of the fixing roller 21 and the pressure roller 31 in the direction of the arrow in FIG. The
Thereafter, the recording medium P is fed from the paper feeding unit 12 and an unfixed image is carried on the recording medium P at the position of the secondary transfer nip. The recording medium P carrying the unfixed image T (toner image) is conveyed in the direction of the arrow Y10 in FIG. 2 and sent to the nip portion (fixing nip portion) of the fixing roller 21 and the pressure roller 31 in the pressure contact state. Entered. Then, the toner image T is fixed on the surface of the recording medium P by the heating by the fixing roller 21 and the pressing force of the fixing roller 21 and the pressure roller 31. Thereafter, the recording medium P sent out from the nip portion by the rotating fixing roller 21 and the pressure roller 31 is conveyed in the direction of the arrow Y11.

Hereinafter, configurations and operations of the separation plate 38 and the positioning member 39 which are characteristic in the fixing device 20 according to the first embodiment will be described.
With reference to FIG. 4, a separation plate 38 as a separation member is rotatably held on a frame 40 of the apparatus 20 via a collar 50. Specifically, bent portions 38a extending in the direction perpendicular to the paper surface of FIG. 4 are formed at both ends of the separation plate 38 by bending. A holding portion for holding the collar 50 is formed in the bent portion 38 a of the separation plate 38. A collar 50 is interposed between the pin portion 40 a of the frame 40 and the bent portion 38 a of the separation plate 38.
Although not shown, a torsion coil spring as an urging means is wound (held) on the pin portion 40a of the frame 40. One arm portion of the torsion coil spring is in contact with the stay of the fixing device 20. Further, the other arm portion of the torsion coil spring is in contact with the collar 50. With such a configuration, the biasing force of the torsion coil spring is transmitted to the separation plate 38 via the collar 50, and the separation plate 38 is biased toward the fixing roller 21 together with the positioning member 39. The gap G between the separation plate 38 and the fixing roller 21 is stably determined.

Here, the positioning member 39 is in contact with the fixing roller 21 so as to be movable in the width direction (the left-right direction in FIG. 4). Specifically, a shaft member 38 b (shaft) is fixed to the bent portion 38 a of the separation plate 38. The shaft member 38b stands up in the width direction (the rotation axis direction of the fixing roller 21). The positioning member 39 is held so as to be movable on the shaft member 38b. The positioning member 39 is a roller-like member that rotates following the rotation (running) of the fixing roller 21 and can be formed of a resin material having heat resistance and a low friction coefficient.
With such a configuration, since the position in the width direction of the positioning member 39 is not fixed, the problem that the fixing roller 21 is locally worn due to the positioning member 39 slidingly contacting at the same position in the width direction of the fixing roller 21 is suppressed. . Therefore, the gap G between the fixing roller 21 and the separation plate 38 is stably maintained over time.
In particular, in the first embodiment, since the shaft member 40b that holds the positioning member 39 is fixed to the separation plate 38, the stacking tolerance of the gap G by the positioning member 39 can be made relatively small.

Further, in the first embodiment, a retaining ring 42 is installed as a restricting member that restricts the range of movement of the positioning member 39 in the width direction (the range indicated by the double-headed arrow in FIG. 4). Specifically, retaining rings 42 are installed at both ends of the shaft member 38b so as to sandwich the positioning member 39. Here, the position of the retaining ring 42 is set so that the positioning member 39 does not move to the end of the fixing roller 21 (the end that is as close as possible to the end surface of the roller).
With such a configuration, the positioning member 39 is prevented from falling off from the shaft member 38b, and processing at both ends of the elastic layer 23 of the fixing roller 21 (both ends close to both ends of the fixing roller). The problem that the gap G between the fixing roller 21 and the separation plate 38 fluctuates due to the influence of drooping or jumping of the sheet is suppressed.

  As described above, in the first embodiment, the positioning member 39 that defines the gap G between the fixing roller 21 (fixing member) and the separation plate 38 (separation member) is moved in the width direction with respect to the fixing roller 21. Since the contact is possible, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality.

Embodiment 2. FIG.
The second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a schematic view showing a part of the fixing device in the second embodiment in the width direction, and corresponds to FIG. 4 in the first embodiment. The fixing device according to the second embodiment is different from the first embodiment in the method of holding the positioning member 39.

As in the first embodiment, the fixing device according to the second embodiment is also the fixing roller 21 (fixing member), the pressure roller 31 (pressure member), the separation plate 38 (separation member), and the positioning member 39. , Etc.
Also in the second embodiment, the positioning member 39 is in contact with the fixing roller 21 so as to be movable in the width direction (the left-right direction in FIG. 5).

  Here, in the second embodiment, the shaft member 40 b is fixed to the frame 40 that supports the fixing roller 21. The shaft member 40b is installed between the frames 40 at both ends. The positioning member 39 is held so that it can move on the shaft member 40b. The positioning member 39 is a roller-like member that rotates following the rotation (running) of the fixing roller 21. Further, a retaining ring 42 as a restricting member is installed on the shaft member 40 b so as to sandwich the positioning member 39.

With such a configuration, since the position in the width direction of the positioning member 39 is not fixed, the problem that the fixing roller 21 is locally worn due to the positioning member 39 slidingly contacting at the same position in the width direction of the fixing roller 21 is suppressed. . Therefore, the gap G between the fixing roller 21 and the separation plate 38 is stably maintained over time. Further, by installing the retaining ring 42, the positioning member 39 is prevented from falling off from the shaft member 38b, and the fixing roller 21 is affected by the influence of dripping or jumping on both ends of the elastic layer 23 of the fixing roller 21. The problem that the gap G between 21 and the separation plate 38 fluctuates is suppressed.
In particular, in the second embodiment, since the shaft member 40b that holds the positioning member 39 is fixed to the frame 40 that supports the fixing roller 21, the accuracy of the parallelism between the fixing roller 21 and the shaft member 40b is improved. Can be increased. Therefore, the deviation in the width direction of the gap G by the positioning member 39 can also be reduced.

  As described above, also in the second embodiment, as in the first embodiment, the positioning member 39 that determines the gap G between the fixing roller 21 (fixing member) and the separation plate 38 (separating member) is fixed. Since the roller 21 is in contact with the roller 21 so as to be movable in the width direction, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality. .

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a schematic view showing a part of the fixing device in the third embodiment in the width direction, and corresponds to FIG. 4 in the first embodiment. The fixing device according to the third embodiment is different from that according to the first embodiment in the method of holding the positioning member 39.

As in the first embodiment, the fixing device according to the third embodiment also has a fixing roller 21 (fixing member), a pressure roller 31 (pressure member), a separation plate 38 (separation member), and a positioning member 39. , Etc.
Also in the third embodiment, the positioning member 39 is in contact with the fixing roller 21 so as to be movable in the width direction (the left-right direction in FIG. 6).

  Here, in the third embodiment, the shaft member 38b is fixedly provided by providing the cut and bent portions 38c at the three portions of the both ends and the center of the separation plate 38, respectively. The three shaft members 38b are respectively installed between the two cut and bent portions 38c. The positioning member 39 is held so that it can move on the shaft member 38b. The positioning member 39 is a roller-shaped member that rotates following the rotation of the fixing roller 21. Further, the moving range of the positioning member 39 in the width direction is restricted by the cut and bent portions 38c at both ends. That is, the cut and bent portion 38c functions as a restricting member.

With such a configuration, since the position in the width direction of the positioning member 39 is not fixed, the problem that the fixing roller 21 is locally worn due to the positioning member 39 slidingly contacting at the same position in the width direction of the fixing roller 21 is suppressed. . Therefore, the gap G between the fixing roller 21 and the separation plate 38 is stably maintained over time. In addition, each positioning member 39 is prevented from falling off from the shaft member 38b by the cut and bent portion 38c, and is also affected by dripping or jumping in processing at both ends of the elastic layer 23 of the fixing roller 21. Deterred.
In particular, in the third embodiment, since the three positioning members 39 are held by the independent shaft members 38b, the accuracy of the gap G is reduced even when the accuracy of the straightness of the separating plate 38 is low. Can be enhanced over direction. In the third embodiment, since the positioning member 39 is also provided in the center portion in the width direction, the accuracy of the gap G in the center portion in the width direction is improved, and small-size paper (recording with a small size in the width direction) is performed. Even when a large amount of the medium P is passed, the separation performance by the separation plate 38 can be improved.

  As described above, also in the third embodiment, the positioning member 39 that defines the gap G between the fixing roller 21 (fixing member) and the separating plate 38 (separating member) is fixed as in the above embodiments. Since the roller 21 is in contact with the roller 21 so as to be movable in the width direction, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality. .

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a schematic diagram showing a part of the fixing device according to the fourth embodiment in the width direction, and corresponds to FIG. 4 according to the first embodiment. The fixing device according to the fourth embodiment is different from that according to the first embodiment in the method of holding the positioning member 39.

As in the first embodiment, the fixing device according to the fourth embodiment also has a fixing roller 21 (fixing member), a pressure roller 31 (pressure member), a separation plate 38 (separation member), and a positioning member 39. , Etc.
Also in the fourth embodiment, the positioning member 39 is in contact with the fixing roller 21 so as to be movable in the width direction (the left-right direction in FIG. 7).

  Here, in the fourth embodiment, the shaft member 38 b is fixed between the bent portions 38 a at both ends of the separation plate 38. The positioning member 39 is held so that it can move on the shaft member 38b. The positioning member 39 is a roller-shaped member that rotates following the rotation of the fixing roller 21. Also, retaining rings 42 as restricting members are installed at both ends of the shaft member 38b so as to sandwich the positioning member 39.

With such a configuration, since the position in the width direction of the positioning member 39 is not fixed, the problem that the fixing roller 21 is locally worn due to the positioning member 39 slidingly contacting at the same position in the width direction of the fixing roller 21 is suppressed. . Therefore, the gap G between the fixing roller 21 and the separation plate 38 is stably maintained over time. Further, by installing the retaining ring 42, the positioning member 39 is prevented from falling off from the shaft member 38b, and the fixing roller 21 is affected by the influence of dripping or jumping on both ends of the elastic layer 23 of the fixing roller 21. The problem that the gap G between 21 and the separation plate 38 fluctuates is suppressed.
In particular, in Embodiment 4, since the shaft member 38b that holds the positioning member 39 is not cantilevered but supported at both ends, the strength against falling of the shaft member 38b can be improved.

  As described above, also in the fourth embodiment, the positioning member 39 that determines the gap G between the fixing roller 21 (fixing member) and the separation plate 38 (separation member) is fixed as in the above embodiments. Since the roller 21 is in contact with the roller 21 so as to be movable in the width direction, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality. .

Embodiment 5 FIG.
8 and 9, the fifth embodiment of the present invention will be described in detail.
FIG. 8 is a configuration diagram illustrating the fixing device according to the fifth embodiment, and corresponds to FIG. 2 according to the first embodiment. FIG. 9 is a perspective view showing the vicinity of the separation claw 55. The fixing device according to the fifth embodiment is different from that according to the first embodiment in that a separation claw 55 is provided separately from the separation plate 38.

As in the first embodiment, the fixing device according to the fifth embodiment also has a fixing roller 21 (fixing member), a pressure roller 31 (pressure member), a separation plate 38 (separation member), and a positioning member 39. , Etc.
Also in the fifth embodiment, the positioning member 39 is in contact with the fixing roller 21 so as to be movable in the width direction (the vertical direction in FIG. 8).

Here, in the fifth embodiment, with reference to FIG. 8A, the separation claw 55 is held on the back surface side of the separation plate 38 (the side opposite to the sheet passing surface). In FIG. 8A, the separation claw 55 is not in contact with the fixing roller 21 and is housed on the back side of the separation plate 38. 8B and 9, the separation claw 55 is moved in the width direction (the vertical direction in FIG. 8 and the arrow direction in FIG. 9), so that the separation claw 55 is moved. Is biased by a torsion coil spring (not shown), and the separation claw 55 protrudes from the notch 38 d of the separation plate 38 and comes into contact with the fixing roller 21. On the other hand, the separation claw 55 in the state of FIG. 8B and FIG. 9 is moved in the direction opposite to the movement direction described above so that the separation claw 55 resists the biasing force of the torsion coil spring. Then, it is housed on the back side of the separation plate 38 and is separated from the fixing roller 21 (the state shown in FIG. 8A). That is, the separation claw 55 is configured to contact and separate from the fixing roller 21 in conjunction with the movement in the width direction with respect to the fixing roller 21. The separation claws 55 are respectively installed at both ends of the separation plate 38.
The separation claw 55 configured in this way is normally separated from the fixing roller 21 (in a state shown in FIG. 8A). On the other hand, when the separability only by the separation plate 38 is not sufficient (for example, when the output rate of the output image is high and easily attracted to the fixing roller 21), the separation claw 55 is fixed to the fixing roller 21. (The state shown in FIGS. 8B and 9), the recording medium P with poor separation is surely separated from the fixing roller 21.

  Such a contact / separation operation (movement operation) of the separation claw 55 is performed manually by a user or serviceman from outside the fixing device. Specifically, referring to FIG. 9, separation claw 55 is sandwiched on the lower end side of arm portion 51 so as to be movable in the front-rear direction. The arm unit 51 is configured to slide on the two shafts 52 and 53. Then, a user or a serviceman grasps the upper end side of the arm unit 51 (not shown, but is exposed to the outside of the fixing device 20 with the cover of the apparatus main body opened), and the arm unit. As the slide 51 is moved, the separation claw 55 is moved toward and away (moving operation).

  In the fifth embodiment, the contact / separation operation (movement operation) of the separation claw 55 is performed manually, but the contact / separation operation (movement operation) of the separation claw 55 may be performed automatically. Specifically, the shaft 52 is connected to a drive means (drive motor) as a ball screw, and a female screw portion is formed in the hole portion of the arm portion 51 into which the shaft 52 is inserted. As a result, the separation claw 55 moves together with the arm portion 51 in conjunction with the rotational drive in the forward and reverse directions of the drive means (drive motor), and the separation claw 55 is brought into and out of contact with it. Note that the timing at which the separation claw 55 is automatically brought into and out of contact can be determined based on print rate data of the output image (for example, exposure duty data during the exposure process).

  As described above, also in the fifth embodiment, the positioning member 39 that determines the gap G between the fixing roller 21 (fixing member) and the separation plate 38 (separation member) is fixed as in the above embodiments. Since the roller 21 is in contact with the roller 21 so as to be movable in the width direction, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality. .

Embodiment 6 FIG.
A sixth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 10 is a perspective view illustrating the fixing device according to the sixth embodiment, which corresponds to FIG. 3 according to the first embodiment. The fixing device according to the sixth embodiment is different from the above-described embodiments in that the fixing belt 41 is used as a fixing member, and the fixing roller 21 is used as a fixing member.

  As shown in FIG. 10, the fixing device 20 according to the sixth embodiment includes a fixing belt 41 as a fixing member, a fixing auxiliary roller 42, a heating roller 43, a pressure roller 31 as a pressure member, and a tension roller (not shown). ), A separation plate 38 as a separation member, a positioning member (not shown), and the like.

  Here, the fixing belt 41 as a fixing member is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of polyimide resin and having a layer thickness of 90 μm. The elastic layer of the fixing belt 41 has a layer thickness of about 200 μm and is formed of an elastic material such as silicone rubber, fluorine rubber, and foamable silicone rubber. The release layer of the fixing belt 41 has a layer thickness of about 20 μm, and is formed of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. Has been. By providing the release layer on the surface layer of the fixing belt 41, the releasability (peelability) for the toner T (toner image) is ensured. The fixing belt 41 is stretched and supported by a plurality of roller members (a fixing auxiliary roller 42, a heating roller 43, and a tension roller) and travels in a predetermined direction.

  The fixing auxiliary roller 42 is a cylindrical member having an outer diameter of 52 mm in which an elastic layer (layer thickness is 14 mm) such as fluoro rubber, silicone rubber, and foamable silicone rubber is formed on a core metal such as SUS304. Then, a nip portion (fixing nip portion) is formed by contacting the pressure roller 31 as a pressure member via the fixing belt 41.

The heating roller 43 is a cylindrical body (thickness is 0.6 mm, outer diameter is 35 mm) made of a metal material such as aluminum, and a heater (heat source) is fixed inside the cylindrical body. Yes.
The heater of the heating roller 43 is a halogen heater, and both ends thereof are fixed to the frame of the fixing device 20. The heating roller 43 is heated by radiant heat from the heater whose output is controlled by the power supply unit (AC power supply) of the apparatus main body 1, and the toner on the recording medium P is further heated from the surface of the fixing belt 41 heated by the heating roller 43. Heat is applied to the image T. The output control of the heater is performed based on the detection result of the belt surface temperature by a thermopile (not shown) that faces the surface of the fixing belt 41 in a non-contact manner. Specifically, the AC voltage is applied to the heater for the energization time determined based on the thermopile detection result. By such heater output control, the temperature of the fixing belt 41 (fixing temperature) can be adjusted and controlled to a desired temperature (target control temperature).

The pressure roller 31 as a pressure member is formed by forming an elastic layer having a layer thickness of 1.5 mm made of silicone rubber, fluorine rubber, foamable silicone rubber, etc. on a hollow core metal having a thickness of 1 mm. Is.
The pressure roller 31 is pressed against the fixing auxiliary roller 42 via the fixing belt 41 by a pressure mechanism. Thus, a desired nip portion (fixing nip portion) is formed between the pressure roller 31 and the fixing belt 41.

Here, on the downstream side in the running direction of the fixing belt 41 (fixing member) with respect to the nip portion (near the exit side of the nip portion), a separation plate facing the fixing belt 41 with a predetermined gap. 38 is disposed. A positioning member (not shown) is interposed between the fixing belt 41 and the separation plate 38.
Also in the sixth embodiment, the positioning member is in contact with the fixing roller 21 so as to be movable in the width direction.

The fixing device 20 configured as described above operates as follows.
When the power switch of the apparatus main body 1 is turned on, an AC voltage is applied (powered) from the AC power source to the heater, and rotation driving of the pressure roller 31 is started by a drive motor (not shown). 41 (fixing auxiliary roller 42, heating roller 43) is driven to rotate.
Thereafter, the recording medium P is fed from the paper feeding unit 12 and an unfixed image is carried on the recording medium P at the position of the secondary transfer nip. The recording medium P carrying the unfixed image T (toner image) is fed into the nip portion between the fixing belt 41 and the pressure roller 31 that are in a pressure contact state. Then, the toner image T is fixed on the surface of the recording medium P by the heating by the fixing belt 41 and the pressing force of the fixing belt 41 (fixing auxiliary roller 42) and the pressure roller 31. Thereafter, the recording medium P is sent out from the nip portion by the rotating fixing belt 41 and the pressure roller 31.

  As described above, also in the sixth embodiment, the positioning member 39 that defines the gap G between the fixing roller 21 (fixing member) and the separating plate 38 (separating member) is fixed as in the above embodiments. Since the roller 21 is in contact with the roller 21 so as to be movable in the width direction, the minute gap G between the fixing roller 21 and the separation plate 38 can be stabilized over time without affecting the image quality. .

In each of the above embodiments, the present invention is applied to the fixing device 20 using the heater 25 as a heating unit. However, the electromagnetic induction heating type fixing device using an exciting coil as the heating unit is also used. Of course, the present invention can be applied.
In each of the embodiments, the present invention is applied to the fixing device using the pressure roller 31 as the pressure member. However, the present invention is applied to the fixing device using a pressure belt or a pressure pad as the pressure member. However, the present invention can be applied.
In these cases, the same effects as those in the above embodiments can be obtained.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. 2 is a configuration diagram illustrating a fixing device. FIG. FIG. 2 is a perspective view showing a fixing device. It is the schematic which shows a fixing roller and a separating plate in the width direction. It is the schematic which shows a part of fixing device in Embodiment 2 of this invention in the width direction. It is the schematic which shows a part of fixing device in Embodiment 3 of this invention in the width direction. It is the schematic which shows a part of fixing device in Embodiment 4 of this invention in the width direction. It is a block diagram which shows the fixing device in Embodiment 5 of this invention. It is a perspective view showing the neighborhood of a separation claw. It is a perspective view which shows the fixing device in Embodiment 6 of this invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
20 fixing device,
21 fixing roller (fixing member),
25 heater (heating means),
31 Pressure roller (pressure member),
38 Separation plate (separation member),
38a bending part,
38b, 40b shaft member,
38c cut and bent part,
38d Notch,
39 Positioning member (roller-shaped member),
40 frames,
41 fixing belt (fixing member),
42 Retaining ring (regulating member),
51 arm part,
52, 53 shaft,
55 Separating nails.

Claims (11)

A fixing member that heats and melts the toner image and fixes the toner image on the recording medium;
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the fixing member;
A separation member disposed downstream of the nip portion in the running direction of the fixing member and facing the fixing member with a predetermined gap;
A positioning member interposed between the fixing member and the separating member to define the gap;
With
The fixing device, wherein the positioning member is disposed so as to contact the fixing member so as to be movable in the width direction.   The fixing device according to claim 1, wherein the positioning member is movably held on a shaft member fixed to the separation member.   The fixing device according to claim 1, wherein the positioning member is movably held on a shaft member fixed to a frame that supports the fixing member.   The fixing device according to claim 1, wherein the positioning member is a roller-shaped member that rotates following the traveling of the fixing member.   The fixing device according to claim 1, further comprising a regulating member that regulates a range of movement of the positioning member in the width direction.   The fixing device according to claim 1, further comprising a biasing member that biases the positioning member together with the separation member toward the fixing member.   The fixing device according to claim 1, further comprising a separation claw that contacts and separates the fixing member in conjunction with a movement in the width direction with respect to the fixing member.   The fixing device according to claim 7, wherein the separation claw is installed on the separation member.   9. The fixing device according to claim 7, further comprising an arm portion that moves in the width direction together with the separation claw and performs a manual operation from outside the device.   9. The fixing device according to claim 7, further comprising driving means for automatically moving the separation claw in the width direction.   An image forming apparatus comprising the fixing device according to claim 1.

Images