JP2009122632A - Fixing device, image forming apparatus, and separating member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device with a stable and small gap between a fixing member and a separating member, having relatively shorter fixing member and separating member in a width direction and having an overall small size without influencing image quality, and to provide an image forming apparatus and a separating member. <P>SOLUTION: The fixing device includes the separating member 38 placed opposite to a fixing member 21 with a certain gap in between, and positioning members 39 installed on the separating member 38 to be in contact with width-direction ends of the fixing member 21 for determining the gap. The positioning members 39 are arranged such that edges of contact portions 39a on the width-direction center side in contact with the fixing member 21 are positioned outside an image area L2 and inside a paper-passing area L1 for a recording medium of a maximum passing-capable size. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, a fixing device installed therein, and a separating member installed in the fixing device.

  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 (for example, see Patent Document 1 and Patent Document 2).

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.

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 formed between a separation plate and a fixing member by bringing a portion into contact with the fixing member.
Further, Patent Document 2 and the like are provided with a position adjusting member that adjusts the gap between the two members for the purpose of stabilizing the gap between the separation member (peeling pad) and the fixing member even if the fixing member is thermally expanded. Technology is disclosed.

JP 2006-171551 A JP 2007-114415 A

  In the conventional fixing device described above, since the positioning member of the separation member is in contact with the both ends of the fixing member in the width direction and considerably away from the sheet passing region, the length of the fixing member and the separation member in the width direction is reduced. The size of the device has grown.

  The present invention has been made in order to solve the above-described problems. The fine gap between the fixing member and the separating member is stabilized without affecting the image quality, and the width direction of the fixing member or the separating member is improved. It is an object of the present invention to provide a fixing device, an image forming apparatus, and a separating member that are relatively small in length.

  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 traveling direction of the fixing member, and that faces the fixing member with a predetermined gap therebetween, and for defining the gap A positioning member that is urged directly or indirectly by the urging means and is placed on the separation member so as to abut against both ends in the width direction of the fixing member, and the positioning member includes the fixing member The position of the end of the abutting portion that abuts on the center in the width direction is located inside the sheet passing area of the largest recording medium that can pass the sheet and outside the image area. is there.

  According to a second aspect of the present invention, there is provided the fixing device according to the first aspect, wherein the separating member is capable of passing the position of the end in the width direction of the front end where the gap is formed. It is formed so as to be outside the maximum sheet passing area of the recording medium.

  The fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect, wherein the positioning member has a mounting portion for being detachably installed on the separation member. And the mounting portion is disposed outside the sheet passing area.

  According to a fourth aspect of the present invention, in the fixing device according to the third aspect of the present invention, the attachment portion is a snap fit.

  According to a fifth aspect of the present invention, in the fixing device according to the third aspect, the attachment portion is installed on the separation member by screw fastening.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the third to fifth aspects, wherein the positioning member rotates the contact portion around the mounting portion. It is provided with a restricting stopper portion.

  A fixing device according to a seventh aspect of the present invention is the fixing device according to the first or second aspect, wherein the positioning member is integrally formed with the separation member.

  The fixing device according to an eighth aspect of the present invention is the fixing device according to any one of the first to seventh aspects, wherein the contact portion of the positioning member is an end portion on the width direction end portion side. Is disposed so as to be inside the position of the end portion in the width direction of the fixing member.

  According to a ninth aspect of the present invention, there is provided the fixing device according to any one of the first to eighth aspects, wherein the gap is between 0.1 and 0.00 when the fixing member is heated. It is set to 8 mm.

  According to a tenth aspect of the present invention, in the fixing device according to any one of the first to ninth aspects, the positioning member is formed of a resin material or a metal material.

  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.

  A separating member according to a twelfth aspect of the present invention is a separating member that faces a fixing member that heats and melts a toner image and fixes the toner image on a recording medium with a predetermined gap therebetween. The nip portion formed by the fixing member and the pressure member is disposed downstream of the fixing member in the running direction, and is urged directly or indirectly by the urging means to define the gap. Positioning members that contact the both ends of the fixing member in the width direction are installed, and the positioning member has a position at the end of the contact portion that contacts the fixing member on the side in the center in the width direction that can pass the sheet. The recording medium is disposed inside the paper passing area and outside the image area.

  The separation member according to a thirteenth aspect of the present invention is the separation member according to the twelfth aspect of the present invention, wherein the positioning member includes an attachment portion for being detachably installed. It is arranged outside the paper area.

  In the present invention, since the position of the end of the contact portion of the positioning member on the center side in the width direction is set to be inside the paper passing area and outside the image area, the image quality is affected. And a fixing device, an image forming apparatus, and a separation member, in which a minute gap between the fixing member and the separation member is stabilized, and the length in the width direction of the fixing member and the separation member is relatively small. be able to.

  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.
A 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. FIG. 5 is an enlarged perspective view showing the vicinity of the positioning member 39 installed on the separation plate 38.

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 40, 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 40 (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 40. 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 40 may be a non-contact type thermopile other than a 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). In this way, a desired 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. The separation plate 38 can be formed of a metal material or a heat resistant resin material.

  Here, referring to FIGS. 3 to 5, the gap G between the separation plate 38 and the fixing roller 21 is defined 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 installed. The positioning member 39 is indirectly biased by a biasing means (not shown) such as a spring connected to both ends of the separation plate 38 (along 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 gap G corresponding to the thickness of the positioning member 39 (a portion interposed between the separation plate 38 and the fixing roller 21) is formed.

  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.

The positioning member 39 is preferably formed of a heat-resistant resin material or metal material. When the positioning member 39 is formed of a resin material, the surface of the fixing roller 21 is hardly damaged. In addition, when the positioning member 39 is formed of a metal material, a large gap does not occur even when the positioning member 39 reaches a high temperature, so that a stable gap G can be maintained.
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, the configuration and operation of the fixing device 20 that are characteristic of the first embodiment will be described with reference to FIGS.
As described above, the positioning members 39 (abutting members) for determining the gap G between the separation plate 38 and the fixing roller 21 are installed at both ends in the width direction of the separation plate 38.
Here, the positioning member 39 is provided with an abutting portion 39 a that abuts on the fixing roller 21 and an attaching portion 39 b for detachably installing on the separation plate 38. Referring to FIG. 4, the contact portion 39a of the positioning member 39 is located at the end of the central portion in the width direction inside the sheet passing region L1 of the maximum recording medium that can be passed. Further, it is disposed outside the image area L2.

  The “sheet passing area L1” is determined by the specification in the range in the width direction of the maximum recording medium P (for example, A3 size) that can be passed, which is determined by the specification of the image forming apparatus 1. Further, the variation in the transport position of the recording medium P and the skew amount are added together. The “image area L2” is the image quality defined by the specifications for the maximum recording medium P (for example, A3 size) that can be passed by the sheets defined by the specifications of the image forming apparatus 1. This is a range in which the transport position of the recording medium P and the skew amount determined by the specifications are added to the guaranteed range in the width direction (image quality guarantee width).

With such a configuration, the abutting portion 39a of the positioning member 39 can be arranged on the central side in the width direction within a marginal range that does not affect the image quality.
Since the contact portion 39a is in sliding contact with the fixing roller 21 and may damage the surface of the fixing roller 21, the contact portion 39a is not desired to be contacted in the image region L2, but at a position far away outside the image region L2. If the contact portion 39a is disposed (if a margin in the width direction is increased), the fixing roller 21 and the separation plate 38 are increased in the width direction. On the other hand, in the first embodiment, even if a part (or all) of the contact part 39a enters the sheet passing area L1, the contact part 39a is disposed outside the image area L2. Since the margin in the width direction is minimized as described above, the size of the fixing roller 21 and the separation plate 38 in the width direction can be set to the minimum. Therefore, the fixing device 20 can be reduced in size, weight, and cost.

  Here, a part (or all) of the abutting portion 39a is disposed in the sheet passing area L1, and the sheet passing area L1 is obtained by adding the variation in the transport position of the recording medium P and the skew amount. Since the margin in the width direction is taken in advance, the recording medium P hardly comes into contact with the contact portion 39a, and jamming hardly occurs (the transportability of the recording medium P is not deteriorated). ). Even if the recording medium P being conveyed comes into contact with the contact portion 39a, the contact range is very small, so that the contact portion of the recording medium P is transported so as to escape from the contact portion 39a. Thus, the recording medium P is hardly jammed by the contact between the contact portion 39a and the recording medium P.

  In the first embodiment, the attachment portion 39b of the positioning member 39 is disposed outside the paper passing area L1. The attachment portion 39b is configured to have a large size in order to securely fix the positioning member 39 to the separation plate 38. For this reason, there is a possibility that the attachment portion 39b protrudes toward the fixing roller 21 and obstructs the conveyance of the recording medium P. Therefore, by disposing the attachment portion 39b outside the paper region L1, it is possible to prevent a problem that the transportability of the recording medium P is lowered.

In the first embodiment, the attachment portion 39b is snap fit. Thereby, the assembling property of the positioning member 39 to the separation plate 38 is simplified, and the number of parts related to the assembling can be reduced.
Specifically, as shown in FIGS. 6 and 7, the positioning member 39 is moved from below the separation plate 38 in the direction of the arrow, and the positioning member 39 is attached to the hole 38 c provided in the separation plate 38. The positioning member 39 is assembled to the separation plate 38 by engaging the portion 39b (snap fit).
6 and 7, the positioning member 39 is formed with a protrusion 39d that protrudes from the contact portion 39a toward the center in the width direction. Thereby, when the positioning member 39 is assembled to the separation plate 38, a mistake of erroneously assembling the positioning member (formed symmetrically) installed at the other end is prevented.

  In the first embodiment, the contact portion 39a of the positioning member 39 is disposed so as to overlap the back side of the separation plate 38 (the side opposite to the conveyance surface of the recording medium P). As a result, as shown in FIG. 8, the position of the end portion in the width direction of the front end portion 38 b where the gap G with the fixing roller 21 is formed on the separation plate 38 is passed through the largest recording medium P that can be passed. It becomes possible to arrange | position outside the area | region L1. Therefore, the problem that the recording medium P jams at the position of the separation plate 38 can be reliably suppressed.

  Further, in the first embodiment, referring to FIG. 4, the contact portion 39 a of the positioning member 39 is positioned at the end of the fixing roller 21 in the width direction end. It is arranged so as to be inside (within the area D). Specifically, the position of the end portion on the width direction end portion side of the abutting portion 39 a is disposed 3 mm or more inside (width direction center portion side) from the width direction end portion of the fixing roller 21. This is the case where a burr-like crumb in manufacturing (like a burr that slightly protrudes in the direction in which the outer diameter increases) is formed at the end in the width direction of the fixing roller 21. However, it is possible to prevent the problem of interference between the contact and the contact portion 39a.

In the first embodiment, as shown in FIG. 5, the positioning member 39 is provided with a stopper portion 39 c that restricts the rotation of the contact portion 39 a around the attachment portion 39 b (snap fit). As described above, the contact portion 39a is disposed so as to be in the sheet passing region L1, and the attachment portion 39b is disposed outside the sheet passing region L1, so that the contact portion 39a and the fixing roller are arranged. By the sliding contact with 21, a rotational moment about the mounting portion 39 b acts on the positioning member 39. When the positioning member 39 rotates, the posture of the contact portion 39a changes, and the gap G between the fixing roller 21 and the separation plate 38 may change. As described above, if the gap G is small, the separation plate 38 is soiled or the fixing roller 21 is damaged, and if the gap G is large, the original function of the separation plate 38 is degraded.
On the other hand, in the first embodiment, the stoppers 39c that come into contact with the lower end of the separation plate 38 when a rotational moment is generated in the positioning member 39 are provided at both ends of the mounting portion 39b. , And fluctuations in the gap G can be suppressed.

Hereinafter, it will be described in more detail with reference to FIGS.
FIG. 9 is a view of the positioning member 39 as seen from the back side (the side opposite to the conveying surface of the separation plate 38). FIG. 10 is a diagram showing the force acting on the positioning member 39 installed on the separation plate 38 and is a view seen from the back side of the separation plate 38. FIG. 11 is a diagram showing the force acting on the positioning member 39 installed on the separation plate 38 and is a view seen from the conveying surface side of the separation plate 38. FIG. 12 is a top view showing the positioning member 39.
As shown in FIGS. 9 to 11, a force is applied to the contact portion 39 a of the positioning member 39 that contacts the fixing roller 21 in the direction of arrow N along the rotation direction of the fixing roller 21. As a result, a rotational moment M about the center (fulcrum) of a part Q (see FIG. 10) of the mounting portion 39b acts on the positioning member 39. However, a stopper portion 39 c is formed at the lower end of the positioning member 39, and the rotation of the positioning member 39 due to the rotational moment M is suppressed when the stopper portion 39 c abuts against the separation plate 38.

  As described above, in the first embodiment, the position of the end of the abutting portion 39a of the positioning member 39 on the center side in the width direction is inside the sheet passing area L1 and outside the image area L2. Therefore, the fine gap G between the fixing roller 21 (fixing member) and the separating member 38 is stabilized without affecting the image quality, and the length of the fixing roller 21 and the separating member 38 in the width direction is stabilized. Thus, the fixing device 20 (or the image forming apparatus 1) having a relatively small size can be provided.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 13 is an enlarged perspective view showing the vicinity of the positioning member of the fixing device in the second embodiment, and corresponds to FIG. 5 in the first embodiment. The fixing device according to the second embodiment is different from that according to the first embodiment in the method of installing the positioning member 39 on the separating member 38.

  Similarly to the first embodiment, the fixing device according to the second embodiment also includes a fixing roller 21 (fixing member), a pressure roller 31 (pressure member), a separation plate 38 (separation member), and the like. Is done. A positioning member 39 is detachably installed on the separation plate 38. Further, the position of the abutting portion 39a of the positioning member 39 at the center in the width direction is on the inner side of the paper passing area L1 of the largest recording medium that can pass the paper and on the outer side of the image area L2. It is arranged to become. Further, the attachment portion 39b of the positioning member 39 is disposed outside the sheet passing region L1.

Here, in the second embodiment, as shown in FIG. 13, the attachment portion 39b of the positioning member 39 is installed on the separation plate 38 by screw fastening. Specifically, the attachment portion 39b is provided with a hole, and the screw 50 is screwed into the female screw portion of the separation plate 38 through the hole of the attachment portion 39b, so that the positioning member 39 is placed on the separation plate 38. It is concluded.
With such a configuration, the positioning member 39 can be firmly fixed to the separation plate 38 as compared with the case where the mounting portion 39b is snap-fit. Therefore, the mounting portion 39b is centered on the positioning member 39. The problem that the gap G fluctuates due to the rotation moment is less likely to occur.

  As described above, also in the second embodiment, as in the first embodiment, the position of the end portion on the center side in the width direction of the contact portion 39a of the positioning member 39 is inside the sheet passing region L1. Therefore, the fine gap G between the fixing roller 21 (fixing member) and the separating member 38 is stabilized without affecting the image quality, so that the fixing roller 21 does not affect the image quality. In addition, it is possible to provide the fixing device 20 in which the length in the width direction of the separation member 38 is relatively small and downsized.

Embodiment 3 FIG.
The third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 14 is an enlarged perspective view showing the vicinity of the positioning member of the fixing device in the third embodiment, and corresponds to FIG. 5 in the first embodiment. The fixing device according to the third embodiment is that the positioning member 39 is provided integrally with the separating member 38 in that the positioning member 39 is provided separately from the separating member 38. Is different.

  The fixing device according to the third embodiment also includes a fixing roller 21 (fixing member), a pressure roller 31 (pressure member), a separation plate 38 (separation member), and the like, as in the above-described embodiments. Is done.

Here, in the third embodiment, a positioning portion 38 a as a positioning member is formed integrally with the separation plate 38. Specifically, as shown in FIG. 14, positioning portions 38a (abutting portions) are formed by bending at both ends of the separation plate 38 formed of a metal material. Then, the positioning portion 38a is brought into contact with the fixing roller 21, and the separating plate 38 is urged toward the fixing roller 21 by the urging means, so that a desired gap is provided between the separating plate 38 and the fixing roller 21. G is formed.
In addition, the positioning portion 38a of the separating plate 38 (abutting portion of the positioning member) has an end portion on the side in the center in the width direction inside the sheet passing region L1 of the maximum recording medium that can be passed. Further, it is disposed outside the image area L2.

  As described above, also in the third embodiment, the position of the end portion on the center side in the width direction of the positioning portion 38a (the contact portion of the positioning member) is the same as in each of the above embodiments. Is set to be outside the image region L2, and the fine gap G between the fixing roller 21 (fixing member) and the separation member 38 is stabilized without affecting the image quality. It is possible to provide the fixing device 20 in which the length in the width direction of the fixing roller 21 and the separating member 38 is relatively small and downsized.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 15 is a perspective view showing the fixing device according to the fourth embodiment, and corresponds to FIG. 3 according to the first embodiment. The fixing device according to the fourth 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. 15, the fixing device 20 according to the fourth 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). And a separation plate 38 as a separation member.

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.
In the fixing belt 41 described above, the layer thickness of the base layer can be set to 70 μm, and the layer thickness of the release layer can be set to 30 μm.

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.
In the fixing auxiliary roller 42 described above, the thickness of the elastic layer can be set to 8.5 mm, and the outer diameter can be set to 29 mm.

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. In the heating roller 43 described above, the outer diameter can be set to 20 mm.
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. In the pressure roller 31 described above, the thickness of the hollow cored bar can be set to 4.5 mm, and the thickness of the elastic layer can be set to 3.5 mm.
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.
Also in the fourth embodiment, a positioning member 39 is detachably installed on the separation plate 38. Further, the position of the abutting portion 39a of the positioning member 39 at the center in the width direction is on the inner side of the paper passing area L1 of the largest recording medium that can pass the paper and on the outer side of the image area L2. It is arranged to become. Further, the attachment portion 39b of the positioning member 39 is disposed outside the sheet passing region L1.

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 fourth embodiment, the position of the end of the contact portion 39a of the positioning member 39 on the center side in the width direction is the inside of the sheet passing region L1 as in the above embodiments. Therefore, the fine gap G between the fixing belt 41 (fixing member) and the separating member 38 is stabilized without affecting the image quality, so that the fixing belt 41 does not affect the image quality. In addition, it is possible to provide the fixing device 20 in which the length in the width direction of the separation member 38 is relatively small and downsized.

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 an expansion perspective view which shows the vicinity of a positioning member. It is a perspective view which shows the state by which a positioning member is installed in a separating plate. It is the perspective view which looked at the state by which a positioning member is installed in a separating plate from another angle. It is a figure which shows the relationship between the front-end | tip part of a separating plate, and a paper passing area | region. It is a figure which shows a positioning member. It is a figure which shows the force which acts on the positioning member installed in the separation plate. It is a figure which shows the force which acts on the positioning member installed in the separating plate from the conveyance surface side of a separating plate. It is a top view which shows a positioning member. It is an expansion perspective view which shows the vicinity of the positioning member of the fixing device in Embodiment 2 of this invention. It is an expansion perspective view which shows the vicinity of the positioning member of the fixing device in Embodiment 3 of this invention. It is a perspective view which shows the fixing device in Embodiment 4 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 positioning part (positioning member),
39 Positioning member,
39a contact part, 39b mounting part, 39c stopper part,
41 fixing belt (fixing member),
L1 paper passing area, L2 image area, P recording medium.

Claims (13)

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 installed on the separation member so as to be urged directly or indirectly by the urging means to determine the gap and to contact both ends of the fixing member in the width direction;
With
In the positioning member, the position of the end of the abutting portion in contact with the fixing member on the side in the center in the width direction is inside the sheet passing area of the largest recording medium that can pass the sheet and outside the image area. The fixing device is arranged as described above.   The separation member is formed so that a position of an end in a width direction of a leading end where the gap is formed is outside a sheet passing area of a maximum recording medium capable of passing a sheet. The fixing device according to 1. The positioning member comprises an attachment portion for being detachably installed with respect to the separation member,
The fixing device according to claim 1, wherein the attachment portion is disposed outside the sheet passing area.   The fixing device according to claim 3, wherein the attachment portion is a snap fit.   The fixing device according to claim 3, wherein the attachment portion is installed on the separation member by screw fastening.   The fixing device according to claim 3, wherein the positioning member includes a stopper portion that restricts rotation of the abutting portion around the attachment portion.   The fixing device according to claim 1, wherein the positioning member is formed integrally with the separation member.   The contact portion of the positioning member is disposed so that the position of the end portion on the width direction end portion side is inside the position of the width direction end portion of the fixing member. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the gap is set to 0.1 to 0.8 mm in a state where the fixing member is heated.   The fixing device according to claim 1, wherein the positioning member is formed of a resin material or a metal material.   An image forming apparatus comprising the fixing device according to claim 1. A separation member that is opposed to a fixing member that heats and melts the toner image and fixes the toner image on a recording medium with a predetermined gap;
Disposed on the downstream side of the fixing member in the running direction with respect to the nip formed by the fixing member and the pressure member;
Positioning members that are urged directly or indirectly by the urging means to determine the gap and abut against both ends of the fixing member in the width direction are installed,
In the positioning member, the position of the end of the abutting portion in contact with the fixing member on the side in the center in the width direction is inside the sheet passing area of the largest recording medium that can pass the sheet and outside the image area. Separation member characterized by being arranged as described above. The positioning member comprises a mounting portion for being detachably installed,
The separation member according to claim 12, wherein the attachment portion is disposed outside the sheet passing region.

Images