JP2007099483A - Fixing device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming device capable of improving conveyance property of a recording medium after fixation. <P>SOLUTION: A guide member 89 is provided with a main body 89A and a plurality of ribs (a movable rib 89B and a fixed rib 89C) protruding from the main body 89A and arranged in parallel in the direction of right angle for the direction of conveyance of the recording medium P. The plurality of ribs include the movable rib 89B supported on the main body 89A so as to displace. The movable rib 89B can change distance between an initial abutting section 89B3 where the recording medium P in the movable rib 89B is first abutted and the main body 89A. Distance between the initial abutting section 89B3 and the main body 89A when a tip part of the recording medium P is abutted on the initial abutting section 89B3 is smaller than distance between the initial abutting section 89B3 and the main body 89A when a part other than the tip part of the recording medium P is abutted on the initial abutting section 89B3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Image forming apparatuses such as printers, copiers, and facsimiles that employ an electrophotographic method form an image made of toner on a recording medium such as paper by a process of exposure, development, transfer, and fixing (for example, Patent Documents). 1). Such an image forming apparatus includes a fixing device that fixes the toner image to the recording medium by heating and pressurizing the toner image formed of toner onto a recording medium such as paper that is carried in an unfixed state. (For example, see Patent Document 1).

  Such a fixing device generally has a columnar or cylindrical fixing roller and a pressure roller that are pressed against each other and a halogen heater that heats the fixing roller. By passing a recording medium through a nip formed by the pressure contact between the fixing roller and the pressure roller, the recording medium is heated and pressurized to record a toner image formed on the recording medium. Fix to media.

  In Patent Document 1, a guide member for guiding the recording medium to a regular position is provided on the outlet side of the recording medium of the fixing device as described above. In the guide member, a plurality of ribs extending in the recording medium conveyance direction protrude from the guide member main body on the surface on the side of guiding the recording medium. Thereby, the recording medium is guided by the tip of the rib, and the friction between the recording medium and the guide member is reduced to improve the transportability.

However, in the guide member according to Patent Document 1, since the height of the rib from the guide member main body as described above is fixed, it is difficult to appropriately set the height of the rib from the guide member main body.
More specifically, if the height of the rib is set high, when the recording medium enters the guide member, the recording medium is greatly bent so as to wave in a direction perpendicular to the conveyance direction, and the leading edge of the recording medium after fixing is fixed. There is a risk of causing a conveyance failure such as bending or skew (an oblique feeding of the recording medium).

  On the other hand, when the height of the rib is lowered, the recording medium contacts not only the tip of the rib but also the guide member body between the ribs over the entire period guided by the guide member, and the friction between the recording medium and the guide member. Increases, leading to a decrease in transportability of the recording medium. In addition, when water vapor generated from the fixing device adheres to the guide member, water droplets may adhere to the image forming area of the recording medium, which may cause a problem. For example, when forming an image on both sides of a recording medium, the image is formed on a recording medium to which water droplets adhere, and a transfer defect occurs in a portion of the recording medium to which water droplets adhere, resulting in image blood defects.

JP 2004-205751 A

  An object of the present invention is to provide a fixing device and an image forming apparatus capable of improving the transportability of a recording medium after fixing.

Such an object is achieved by the present invention described below.
The fixing device of the present invention includes a pair of rotating bodies that rotate while being pressed against each other,
A heater for heating at least one of the pair of rotating bodies,
A fixing device for fixing the unfixed image to the recording medium by heating and pressurizing a recording medium carrying an unfixed image while passing the pressure contact portion of the pair of rotating bodies,
A guide member for guiding the recording medium discharged from the press contact portion to a normal position;
The guide member includes a main body and a plurality of ribs that protrude from the main body and are arranged in a direction perpendicular to the conveyance direction of the recording medium,
The plurality of ribs include a movable rib supported to be displaceable with respect to the main body, and the movable rib is between the main body and an initial contact portion of the movable rib where the recording medium first contacts. The distance of is variable,
The distance between the initial contact portion and the main body when the front end portion of the recording medium is in contact with the initial contact portion is such that the portion other than the front end portion of the recording medium is the initial contact portion. It is characterized by being smaller than the distance between the initial contact portion and the main body at the time of contact.

Thereby, when only the front end of the recording medium is in contact with the guide member, the distance between the recording medium and the main body of the guide member is reduced, the bending of the recording medium is suppressed, and the recording medium after fixing is fixed. It is possible to prevent conveyance failure such as bending of the tip and skew (oblique feeding of the recording medium). At this time, even if the recording medium comes into contact with the main body of the guide member, only the leading end portion of the recording medium comes into contact with the guide member, so that adverse effects on the image forming area of the recording medium can be prevented.
Further, when a portion other than the leading end of the recording medium reaches the guide member, the distance between the recording medium and the main body of the guide member is increased to prevent the contact between them and improve the transportability of the recording medium. It can be. In addition, contact between the image forming area of the recording medium and the main body of the guide member can be prevented, and adhesion of moisture or the like to the image forming area of the recording medium can be prevented.

In the fixing device according to the aspect of the invention, it is preferable that the movable rib is rotatably provided, and the distance between the initial contact portion and the main body is changed by the rotation.
Thereby, the distance between the initial contact part of the movable rib and the main body of the guide member can be changed with a relatively simple configuration.
In the fixing device according to the aspect of the invention, the recording medium is in contact with a rear portion of the movable rib that is downstream of the initial contact portion in the conveyance direction of the recording medium. It is preferable to change the distance between the two.
Thereby, the distance between the initial contact portion of the movable rib and the main body of the guide member can be changed without using a driving means such as a motor or a solenoid. As a result, the cost of the apparatus can be reduced.

In the fixing device of the present invention, the distance between the rear part and the main body is larger than the distance between the initial contact part and the main body before the recording medium comes into contact with the rear part. Is preferred.
Accordingly, the distance between the recording medium and the main body of the guide member is reduced at the initial contact portion of the movable rib, thereby suppressing the bending of the recording medium, and the initial contact portion of the movable rib and the main body of the guide member. The distance between can be changed.

In the fixing device of the present invention, it is preferable that a plurality of the movable ribs are arranged in parallel in a direction perpendicular to the conveyance direction of the recording medium.
Thereby, it is possible to change the distance between the recording medium and the main body of the guide member while reducing the displacement amount of the movable rib.
In the fixing device according to the aspect of the invention, it is preferable that the plurality of ribs include a plurality of fixed ribs arranged in a direction perpendicular to the conveyance direction of the recording medium.
Thereby, contact with a recording medium and the main body of a guide member can be prevented more reliably.

In the fixing device of the present invention, it is preferable that the fixed ribs and the movable ribs are alternately arranged in parallel in a direction perpendicular to the conveyance direction of the recording medium.
Thereby, contact with the main body of a recording medium and a guide member between movable ribs can be prevented more reliably.
In the fixing device of the present invention, it is preferable that a rotatable disk-like member that reduces a contact resistance between the recording medium and the guide member is attached to the movable rib and / or the fixed rib.
Thereby, the conveyance property of the recording medium on a guide member can be made more favorable.

In the fixing device according to the aspect of the invention, the distance between the initial contact portion and the main body when the front end portion of the recording medium is in contact with the initial contact portion is determined by the front end of the fixing rib and the main body. It is preferable that the distance is approximately the same.
As a result, it is possible to further reduce the bending of the leading end of the recording medium while improving the transportability of the recording medium.

In the fixing device of the present invention, it is preferable that the distance between the initial contact portion and the main body of each movable rib is variable.
Thereby, only the necessary movable ribs can be displaced according to the size of the recording medium, and the force necessary for the displacement of the movable ribs can be reduced. In addition, even if the posture of the recording medium varies, the distance between the recording medium and the main body of the guide member can be reliably changed.

In the fixing device according to the aspect of the invention, it is preferable that the guide member is disposed so as to be in contact with a surface of the recording medium opposite to the unfixed image.
Thereby, the contact between the image forming area of the recording medium and the guide member can be prevented, and the image quality after fixing can be improved.
In the fixing device of the present invention, a separation member that separates the recording medium from the rotating body is in contact with or close to the rotating body of the pair of rotating bodies that contacts the unfixed image of the recording medium. Preferably it is.
Thereby, sticking with a rotary body and a recording medium can be prevented.
In the fixing device of the present invention, it is preferable that the unfixed image is not formed at the leading end of the recording medium.
Thereby, the contact between the image forming area of the recording medium and the guide member can be prevented, and the image quality after fixing can be improved.

An image forming apparatus of the present invention is an image forming apparatus that forms an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing,
The fixing device according to the present invention is provided.
Thereby, it is possible to prevent the recording medium from staying (jamming) in the image forming apparatus and to form an image with excellent image quality.

An image forming apparatus of the present invention is an image forming apparatus that forms an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing,
A fixing device for fixing the unfixed image to the recording medium by heating and pressurizing the recording medium carrying the unfixed image through the pressure contact portions of a pair of rotating members that are in pressure-contact rotation with each other;
A guide member for guiding the recording medium discharged from the press contact portion to a normal position;
The guide member includes a main body and a plurality of ribs that protrude from the main body and are arranged in a direction perpendicular to the conveyance direction of the recording medium,
The plurality of ribs include a movable rib supported to be displaceable with respect to the main body, and the movable rib is between the main body and an initial contact portion of the movable rib where the recording medium first contacts. The distance of is variable,
The distance between the initial contact portion and the main body when the front end portion of the recording medium is in contact with the initial contact portion is such that the portion other than the front end portion of the recording medium is the initial contact portion. It is characterized by being smaller than the distance between the initial contact portion and the main body at the time of contact.
Thereby, it is possible to prevent the recording medium from staying (jamming) in the image forming apparatus and to form an image with excellent image quality.

Preferred embodiments of a fixing device and an image forming apparatus having the same according to the present invention will be described below with reference to the accompanying drawings.
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic cross-sectional view of the overall configuration showing an image forming apparatus according to the present embodiment, FIG. 2 is a schematic view showing a fixing device provided in the image forming apparatus shown in FIG. 1 and its vicinity, and FIG. 2 is a view of the guide member provided in the fixing device shown in FIG. 2 as viewed from the guide surface side. FIG. 4 is a view of the guide member provided in the fixing device shown in FIG. 2 as viewed from the upstream side in the recording medium conveyance direction. FIG.

≪Image forming device≫
Prior to the fixing device of the present invention, an image forming apparatus including the fixing device of the present invention will be briefly described.
An image forming apparatus 10 according to this embodiment shown in FIG. 1 forms an image on a recording medium such as paper or an OHP sheet by a series of image forming processes including exposure, development, transfer, and fixing. As shown in FIG. 1, the image forming apparatus 10 has a photosensitive member 20 that carries an electrostatic latent image and rotates in the direction of the arrow in the figure. An exposure unit 40, a developing unit 50, a primary transfer roller 60, and a cleaning unit 75 are provided. In addition, the image forming apparatus 10 is provided with a paper feed tray 82 for storing a recording medium P such as paper at the bottom in FIG. The next transfer roller 80 and the fixing device 90 are sequentially arranged along the conveyance direction of the recording medium P. Further, in the image forming apparatus 10, when an image is formed on both sides of a recording medium, the recording medium P fixed on one side by the fixing device 90 is reversed and returned to the secondary transfer roller 80. The conveyance part 88 is provided.

The photoconductor 20 has a cylindrical conductive substrate (not shown) and a photosensitive layer (not shown) formed on the outer peripheral surface thereof, and can rotate around the axis in the direction of the arrow in FIG. It has become.
The charging unit 30 is a device for uniformly charging the surface of the photoconductor 20 by corona charging or the like.
The exposure unit 40 receives image information from a host computer such as a personal computer (not shown) and irradiates a laser on the uniformly charged photoreceptor 20 to form an electrostatic latent image. It is a device to do.

  The developing unit 50 includes four developing devices, a black developing device 51, a magenta developing device 52, a cyan developing device 53, and a yellow developing device 54. These developing devices are converted into latent images on the photosensitive member 20. It is an apparatus that visualizes the latent image as a toner image, selectively used correspondingly. The black developing device 51 uses black (K) toner, the magenta developing device 52 uses magenta (M) toner, the cyan developing device 53 uses cyan (C) toner, and the yellow developing device 54 uses yellow (Y) toner.

  The YMCK developing unit 50 in the present embodiment is rotatable so that the above-described four developing devices 51, 52, 53, 54 are selectively opposed to the photoconductor 20. Specifically, in this YMCK developing unit 50, four developing devices 51, 52, 53, and 54 are respectively held by four holding portions 55a, 55b, 55c, and 55d of a holding body 55 that can rotate around a shaft 50a. The four developing devices 51, 52, 53, and 54 are selectively opposed to the photoconductor 20 while maintaining the relative positional relationship by the rotation of the holding body 55.

The intermediate transfer member 61 has an endless belt-like intermediate transfer belt 70, and this intermediate transfer belt 70 is stretched by a primary transfer roller 60, a driven roller 72, and a drive roller 71, and is rotated by the rotation of the drive roller 71. 1 is driven to rotate in the direction of the arrow shown in FIG.
The primary transfer roller 60 is a device for transferring a single color toner image formed on the photoconductor 20 to the intermediate transfer belt 70.

  On the intermediate transfer belt 70, a toner image of at least one of black, magenta, cyan, and yellow is carried. For example, when a full-color image is formed, four color toner images of black, magenta, cyan, and yellow are sequentially formed. The toner images are transferred to form a full-color toner image. In the present embodiment, the drive roller 71 also functions as a backup roller for the secondary transfer roller 80 described later. Further, the primary transfer roller 60, the driving roller 71, and the driven roller 72 are supported by the base body 73.

The secondary transfer roller 80 is a device for transferring a single-color or full-color toner image formed on the intermediate transfer belt 70 to a recording medium P such as paper, film, or cloth.
The fixing device 90 is a device for fusing the toner image to the recording medium P and fixing it as a permanent image by heating and pressing the recording medium P that has received the transfer of the toner image. The fixing device 90 will be described in detail later.

The cleaning unit 75 has a rubber cleaning blade 76 that contacts the surface of the photoconductor 20 between the primary transfer roller 60 and the charging unit 30, and the toner image is transferred onto the intermediate transfer belt 70 by the primary transfer roller 60. Then, the toner remaining on the photoreceptor 20 is scraped off and removed by the cleaning blade 76.
The conveyance unit 88 reverses the front and back of the conveyance roller pair 88A and 88B for nipping and conveying the recording medium P fixed on one surface by the fixing device 90 and the conveyance medium pair 88A and 88B. And a conveyance path 88C for guiding the registration roller 86. As a result, when an image is formed on both sides of the recording medium, the recording medium P fixed on one side by the fixing device 90 is reversed and returned to the secondary transfer roller 80.

Next, the operation of the image forming apparatus 10 configured as described above will be described.
First, in response to a command from a host computer (not shown), the photosensitive member 20, the developing roller (not shown) provided in the developing unit 50, and the intermediate transfer belt 70 start to rotate. The photoreceptor 20 is sequentially charged by the charging unit 30 while rotating.
The charged area of the photoconductor 20 reaches the exposure position as the photoconductor 20 rotates, and the exposure unit 40 forms a latent image corresponding to the image information of the first color, for example, yellow Y, in the area. .

The latent image formed on the photoconductor 20 reaches the development position as the photoconductor 20 rotates, and is developed with yellow toner by the yellow developing device 54. As a result, a yellow toner image is formed on the photoreceptor 20. At this time, in the YMCK developing unit 50, the yellow developing device 54 faces the photoconductor 20 at the developing position.
The yellow toner image formed on the photoconductor 20 reaches the primary transfer position (that is, the portion where the photoconductor 20 and the primary transfer roller 60 face each other) as the photoconductor 20 rotates. Transfer (primary transfer) is performed on the transfer belt 70. At this time, a primary transfer voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 60. During this time, the secondary transfer roller 80 is separated from the intermediate transfer belt 70.

The same processing as described above is repeatedly executed for the second color, the third color, and the fourth color, so that the toner images of the respective colors corresponding to the respective image signals are transferred onto the intermediate transfer belt 70 in an overlapping manner. The As a result, a full-color toner image is formed on the intermediate transfer belt 70.
On the other hand, the recording medium P is conveyed from the paper feed tray 82 to the secondary transfer roller 80 by the paper feed roller 84 and the registration roller 86.

  The full-color toner image formed on the intermediate transfer belt 70 reaches the secondary transfer position (that is, the portion where the secondary transfer roller 80 and the driving roller 71 face each other) as the intermediate transfer belt 70 rotates, and the secondary transfer. The image is transferred (secondary transfer) to the recording medium P by the roller 80. At this time, the secondary transfer roller 80 is pressed against the intermediate transfer belt 70 and a secondary transfer voltage (secondary transfer bias) is applied.

The full-color toner image transferred to the recording medium P is heated and pressurized by the fixing device 90 and fused to the recording medium P. Thereafter, the recording medium P is discharged to the outside of the image forming apparatus 10 by the discharge roller pair 87.
On the other hand, after the primary transfer position has elapsed, the toner adhering to the surface of the photoconductor 20 is scraped off by the cleaning blade 76 of the cleaning unit 75 to prepare for charging for forming the next latent image. The toner that has been scraped off is collected by a residual toner collecting section in the cleaning unit 75.

  In the case of forming an image on both sides of the recording medium, the recording medium P fixed on one side by the fixing device 90 is once sandwiched between the discharge roller pair 87, and then the discharge roller pair 87 is driven in reverse. By driving the conveyance roller pair 88A, 88B, the recording medium P is turned upside down through the conveyance path 88C and returned to the secondary transfer roller 80, and an image is printed on the other surface of the recording medium P by the same operation as described above. Form.

≪Fixing device≫
Here, the fixing device 90 will be described in detail with reference to FIGS.
As shown in FIG. 2, the fixing device 90 includes a pair of a fixing roller (first roller) 91 and a pressure roller (second roller) 92 that are pressed against each other, and a heater for heating the fixing roller 91. 93, a temperature detecting body 94 for detecting the temperature of the fixing roller 91, a separating member 95 for separating (peeling) the recording medium from the fixing roller 91, and a nip of the discharge recording roller pair 87 for the recording medium P after fixing. And a guide member 89 that guides it toward the (regular position).

  The fixing device 90 applies an unfixed toner image T (unfixed image) to the nip portion N (pressure contact portion) formed by the pressure contact between the fixing roller 91 and the pressure roller 92 from below in FIG. The recording medium P to be carried is conveyed to the nip portion N, and the toner image T is fixed to the recording medium by heating and pressurizing the recording medium P. In the present embodiment, the recording medium P conveyed to the nip portion N carries a toner image T on the fixing roller 91 side.

The fixing roller 91 has a cylindrical shape and is rotatable around its axis.
As shown in FIG. 2, the fixing roller 91 includes a cylindrical metal base (core metal) 91A, an elastic layer 91B covering the outer peripheral surface of the base 91A, and a separation covering the outer peripheral surface of the elastic layer 91B. And a mold layer 91C.
The base 91A has a cylindrical shape and is made of a metal such as iron or an aluminum alloy. An elastic layer 91B is formed so as to cover the outer peripheral surface of the base portion 91A over the entire circumference.

  The constituent material of the elastic layer 91B is not particularly limited. For example, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, butyl rubber, acrylic rubber, ethylene-propylene rubber, hydrin rubber, urethane rubber , Various rubber materials such as silicon rubber and fluoro rubber (especially those vulcanized), styrene, polyolefin, polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene, trans polyisoprene, Various thermoplastic elastomers, such as a fluororubber type and a chlorinated polyethylene type, can be mentioned, and one or more of these can be mixed and used. Among these, as a constituent material of the elastic layer 91B, for example, silicon rubber, EPDM, fluorine rubber, or the like can be suitably used.

  The thickness of the elastic layer 91B is preferably smaller than the thickness of the elastic layer 92B of the pressure roller 92 described later. More specifically, the thickness of the elastic layer 91B is not particularly limited, but is preferably 0.1 to 3 mm, and more preferably 0.5 to 1.5 mm. As a result, as shown in FIG. 2, a nip portion N in which the pressure roller 92 side forms a concave curved surface can be reliably formed.

A release layer 91C is formed so as to cover the outer circumferential surface of such an elastic layer 91B over the entire circumference. Further, in the axial direction of the fixing roller 91, the length of the release layer 91C is substantially the same as the length of the elastic layer 91B, and the positions of both end faces thereof are substantially the same.
In addition, the thickness of the release layer 91C is preferably 10 to 80 μm, and more preferably 20 to 50 μm. Thereby, the elasticity of the elastic layer 91B can be sufficiently exhibited while maintaining the strength required for the release layer 91C.
Moreover, as a constituent material of the release layer 91C, for example, PTFE, PFA, or the like can be suitably used.

In such an internal space of the fixing roller 91, a heater 93 such as a halogen heater is disposed.
Further, a temperature detector 94 such as a thermistor is provided in contact with or close to the outer peripheral surface of the fixing roller 91. Based on the temperature detected by the temperature detector 94, the driving of the heater 93 described above is controlled by a control unit (not shown) so that the outer surface of the fixing roller 91 becomes the target temperature.

The pressure roller 92 has a cylindrical shape or a columnar shape, is rotatable about its axis, and is in pressure contact with the fixing roller 91.
2 and 3, the pressure roller 92 includes a columnar metal base (core metal) 92A, an elastic layer 92B covering the outer peripheral surface of the base 92A, and an outer periphery of the elastic layer 92B. And a release layer 92C covering the surface.

Further, the separation member 95 is in contact with or close to the fixing roller 91. The separating member 95 separates (peels) the recording medium P from the fixing roller 91 when the recording medium P is stuck to the fixing roller 91. That is, a separation member 95 that separates the recording medium P from the fixing roller 91 is in contact with or close to the fixing roller 91 that is a rotating body on the side of the recording medium P that contacts the toner image T. Thereby, sticking between the fixing roller 91 and the recording medium P can be prevented.
A guide member 89 that guides the recording medium P toward the paper discharge roller pair 87 is disposed above the nip portion N so as to face the separating member 95.

The guide member 89 includes a main body 89A, and a plurality of movable ribs 89B and a plurality of fixed ribs 89C protruding from the main body 89A on the recording medium P guide side of the main body 89A.
The main body 89A extends in parallel with the direction in which the nip portion N extends. A plurality of movable ribs 89B and a plurality of fixed ribs 89C protrude from the main body 89A to the separating member 95 side.
As shown in FIG. 3, the plurality of movable ribs 89B are arranged in parallel in the longitudinal direction of the main body 89A. As shown in FIG. 2, each movable rib 89B is supported so as to be rotatable around a shaft portion 89B1 with respect to the main body 89A. The first position shown by a solid line in FIG. 2 and the broken line in FIG. It can be displaced to the second position shown.

That is, each movable rib 89B is supported displaceably with respect to the main body 89A, and the distance between the main body 89A and the initial contact portion 89B3 (see FIG. 3) where the recording medium P of the movable rib 89B first contacts. Is variable.
The distance h1 between the initial contact portion 89B3 and the main body 89A when the front end portion of the recording medium P is in contact with the initial contact portion 89B3 is such that the portion other than the front end portion of the recording medium P is in initial contact. It is smaller than the distance h2 between the initial contact portion 89B3 and the main body 89A when it is in contact with the portion 89B3 (see FIG. 4).

  Thereby, when only the front end portion of the recording medium P is in contact with the guide member 89, the distance between the recording medium P and the main body 89A of the guide member 89 is reduced, and the bending of the recording medium P is suppressed. It is possible to prevent a conveyance failure such as bending of the leading end of the recording medium P after fixing and skew (an oblique feeding of the recording medium P). At this time, even if the recording medium P comes into contact with the main body 89A of the guide member 89, only the leading end portion of the recording medium P comes into contact with the guide member 89, so that adverse effects on the image forming area of the recording medium P are prevented. can do.

  Further, when a portion other than the front end portion of the recording medium P reaches the guide member 89, the distance between the recording medium P and the main body 89A of the guide member 89 is increased to prevent the contact of the recording medium P. The transportability can be improved. Further, it is possible to prevent contact between the image forming area of the recording medium P and the main body 89A of the guide member 89, thereby preventing adhesion of moisture or the like to the image forming area of the recording medium P.

Further, each movable rib 89B is rotatably provided, and the distance between the initial contact portion 89B3 and the main body 89A is changed by the rotation, so that the initial contact of the movable rib 89B can be made with a relatively simple configuration. The distance between the contact part 89B3 and the main body 89A of the guide member 89 can be changed.
Further, when the recording medium P comes into contact with the rear portion 89B4 on the downstream side in the transport direction of the recording medium P from the initial contact portion 89B3 in each movable rib 89B, the space between the initial contact portion 89B3 and the main body 89A is reached. The distance is changed. Thereby, the distance between the initial contact portion 89B3 of the movable rib 89B and the main body 89A of the guide member 89 can be changed without using a driving means such as a motor or a solenoid. As a result, the cost of the apparatus can be reduced.

  Further, before the recording medium P contacts the rear part 89B4, the distance between the rear part 89B4 and the main body 89A is larger than the distance between the initial contact part 89B3 and the main body 89A. As a result, the distance between the recording medium P and the main body 89A of the guide member 89 is reduced at the initial contact portion 89B3 of the movable rib 89B, so that the bending of the recording medium P is suppressed and the initial contact of the movable rib 89B is reduced. The distance between the contact part 89B3 and the main body 89A of the guide member 89 can be changed.

Further, since the plurality of movable ribs 89B are arranged in a direction perpendicular to the conveyance direction of the recording medium P, the amount of displacement of each movable rib 89B is reduced and the recording medium P and the main body 89A of the guide member 89 are reduced. The distance between can be changed.
Each movable rib 89B has a variable distance between the initial contact portion 89B3 and the main body 89A independently. Thereby, only the necessary movable rib 89B is displaced according to the size of the recording medium P, and the force necessary for the displacement of the movable rib 89B can be reduced. Even if the posture of the recording medium P changes, the distance between the recording medium P and the main body 89A of the guide member 89 can be changed reliably. Note that the distance between the initial contact portion 89B3 and the main body 89A may be variable by interlocking the plurality of movable ribs 89B.

Further, as shown in FIG. 2, such a guide member 89 is disposed so as to be in contact with the surface opposite to the toner image T of the recording medium P. Therefore, the image forming area of the recording medium P and the guide member are arranged. By preventing contact with 89, the image quality after fixing can be improved.
Further, it is preferable that the toner image T is not formed at the leading end of the recording medium P. Thereby, the contact between the image forming area of the recording medium P and the guide member 89 can be prevented, and the image quality after fixing can be improved.

Each movable rib 89B is rotatably attached with a thin wheel gear 89B2. The star wheel 89B2 is a rotatable disk-shaped member that reduces the contact resistance between the recording medium P and the guide member 89. Thereby, conveyance of the recording medium P on the movable rib 89B can be made smoother.
Fixed ribs 89C are provided between the movable ribs 89B, and the movable ribs 89B and the fixed ribs 89C are alternately arranged in parallel in the longitudinal direction of the main body 89A. The fixing rib 89C is fixed to the main body 89A. That is, the height of the fixing rib 89C (the height of the portion protruding from the main body 89A) is fixed.

As described above, when a plurality of fixing ribs 89C arranged in a direction perpendicular to the conveyance direction of the recording medium P are provided, the contact between the recording medium P and the main body 89A of the guide member 89 is more reliably prevented. be able to.
Further, since the fixed rib 89C and the movable rib 89B are alternately arranged in a direction perpendicular to the conveying direction of the recording medium P, the contact between the recording medium and the main body of the guide member between the movable ribs 89B is prevented. It can prevent more reliably.

The distance between the tip of the fixed rib 89C and the main body 89A is such that the tip of the recording medium P is in contact with the initial contact part 89B3 of the movable rib 89B and the main body 89A. Is almost the same as the distance between. As a result, it is possible to further reduce the bending of the leading end of the recording medium P while improving the transportability of the recording medium P.
In addition, a thin, gear-shaped star wheel 89C1 is also rotatably attached to each fixed rib 89C. Thereby, conveyance of the recording medium P on the fixed rib 89C can be made smoother.

Here, the operation of the guide member 89 as described above will be described in detail.
First, before the recording medium P enters the guide member 89, the movable rib 89B is in the first position indicated by the solid line in FIG. 2 due to gravity. That is, the distance between the initial contact portion 89B3 of the movable rib 89B and the main body 89A is h1.
Then, the leading end portion of the fixed recording medium P enters the guide member 89, and an initial contact portion 89B3 (lower end portion in FIG. 2) of the recording medium P and the movable rib 89B and the fixed rib 89C of the guide member 89. Touch. At this time, as shown in FIG. 4A, the distance between the initial contact portion 89B3 of the movable rib 89B and the main body 89A is h1, and the distance between the tip of the fixed rib 89C and the main body 89A is It is almost equal. Therefore, the space between the initial contact portion 89B3 of the movable rib 89B and the main body 89A is suppressed to be small, and the bending of the leading end portion of the recording medium P is suppressed to be small.

When the recording medium P is further conveyed, the leading end of the recording medium P pushes the rear portion 89B4 (upper end portion in FIG. 2) of the movable rib 89B, and the movable rib 89B is in the second position indicated by the broken line in FIG. It becomes. At this time, as shown in FIG. 4B, the distance between the initial contact portion 89B3 of the movable rib 89B and the main body 89A is h2, which is larger than h1. Therefore, contact between the recording medium P and the main body 89A of the guide member 89 can be prevented. At this time, the portion that is in contact with the initial contact portion 89B3 of the movable rib 89B is a portion other than the leading end portion of the recording medium P, and this portion is less likely to bend than the leading end portion. It is possible to prevent a conveyance failure due to the above.
Therefore, the recording medium P is guided to the paper discharge roller pair 87 by the guide member 89 while improving the transportability while suppressing the bending at the guide member 89.
The image forming apparatus 10 including the fixing device as described above can improve the transportability of the recording medium after fixing.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to this.
For example, each unit constituting the fixing device and the image forming apparatus of the present invention can be replaced with an arbitrary one that exhibits the same function, or another configuration can be added.
In the above-described embodiment, the guide member is installed in the fixing device. However, the guide member may be installed in the image forming apparatus outside the fixing device.

In the above-described embodiment, the switching between the first position and the second position of the movable rib of the guide member is performed by gravity and the conveyance force of the recording medium. However, the movable rib is a solenoid or a motor. Such other driving means may be used to switch between the first position and the second position of the movable rib.
In the above-described embodiment, the rotating body has a roller shape. However, the present invention is not limited to this, and the rotating body may have an endless film shape or a belt shape.
In the above-described embodiment, an example in which a halogen heater is used as the heater has been described. However, the present invention is not limited to this, and a ceramic heater or an induction heating type heater may be used as the heater. Further, when an induction heating type heater is used, the rotating body itself may be configured to generate heat.

1 is a schematic cross-sectional view of an overall configuration showing an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a fixing device provided in the image forming apparatus shown in FIG. 1 and its vicinity. FIG. 3 is a view of a guide member provided in the fixing device shown in FIG. 2 as viewed from the guide surface side. FIG. 3 is a view of a guide member provided in the fixing device shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Image forming device 20 ... Photoconductor 30 ... Charge unit 40 ... Exposure unit 50 ... Development unit 50a ... Shaft 51 ... Black development device 52 ... Magenta development device 53 ... Cyan developing device 54 ... Yellow developing device 55 ... Holding body 55a to 55d ... Holding section 60 ... Primary transfer roller 61 ... Intermediate transfer body 70 ... Intermediate transfer belt 71 Drive roller 72 Drive roller 73 Substrate 75 Cleaning unit 76 Cleaning blade 80 Secondary transfer roller 82 82 Feed tray 84 Feed roller 86 ... Registration roller 87 ... Discharge roller pair 88C ... Transport path 89 ... Guidance member 89A ... Main body 89B ... Movable rib 8 9B1 ... Shaft part 89B2 ... Star wheel 89B3 ... Initial contact part 89B4 ... Back part 89C ... Fixing rib 89C1 ... Star wheel 90 ... Fixing device 91 ... Fixing roller (First roller) 91A ... Base 92 ... Pressure roller (second roller) 92A ... Base 91B, 92B ... Elastic layer 91C, 92C ... Release layer 93 ... Heater 94 ... Temperature detector 95 ... Separation member N ... Nip part P ... Recording medium

Claims (15)

A pair of rotating bodies rotating while being pressed against each other;
A heater for heating at least one of the pair of rotating bodies,
A fixing device for fixing the unfixed image to the recording medium by heating and pressurizing a recording medium carrying an unfixed image while passing the pressure contact portion of the pair of rotating bodies,
A guide member for guiding the recording medium discharged from the press contact portion to a normal position;
The guide member includes a main body and a plurality of ribs that protrude from the main body and are arranged in a direction perpendicular to the conveyance direction of the recording medium,
The plurality of ribs include a movable rib supported to be displaceable with respect to the main body, and the movable rib is between the main body and an initial contact portion of the movable rib where the recording medium first contacts. The distance of is variable,
The distance between the initial contact portion and the main body when the front end portion of the recording medium is in contact with the initial contact portion is such that the portion other than the front end portion of the recording medium is the initial contact portion. A fixing device, wherein the fixing device is smaller than a distance between the initial contact portion and the main body at the time of contact.   The fixing device according to claim 1, wherein the movable rib is rotatably provided, and the distance between the initial contact portion and the main body is changed by the rotation.   The distance between the initial contact portion and the main body is changed by contacting the recording medium with a rear portion of the movable rib that is downstream of the initial contact portion in the conveyance direction of the recording medium. The fixing device according to claim 2.   The fixing device according to claim 3, wherein a distance between the rear portion and the main body is larger than a distance between the initial contact portion and the main body before the recording medium is in contact with the rear portion. .   The fixing device according to claim 1, wherein a plurality of the movable ribs are arranged side by side in a direction perpendicular to the conveyance direction of the recording medium.   The fixing device according to claim 5, wherein the plurality of ribs include a plurality of fixed ribs arranged in a direction perpendicular to the conveyance direction of the recording medium.   The fixing device according to claim 6, wherein the fixed rib and the movable rib are alternately arranged in parallel in a direction perpendicular to the conveyance direction of the recording medium.   The fixing device according to claim 6, wherein a rotatable disk-like member that reduces a contact resistance between the recording medium and the guide member is attached to the movable rib and / or the fixed rib.   The distance between the initial contact portion and the main body when the front end of the recording medium is in contact with the initial contact portion is substantially the same as the distance between the front end of the fixing rib and the main body. The fixing device according to claim 6, which is:   The fixing device according to claim 5, wherein each movable rib has a variable distance between the initial contact portion and the main body independently.   The fixing device according to claim 1, wherein the guide member is disposed in contact with a surface of the recording medium opposite to the unfixed image.   The separation member that separates the recording medium from the rotating body is in contact with or close to the rotating body of the pair of rotating bodies that contacts the unfixed image of the recording medium. Fixing device.   The fixing device according to claim 1, wherein the unfixed image is not formed at the leading end portion of the recording medium. An image forming apparatus for forming an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing,
An image forming apparatus comprising the fixing device according to claim 1. An image forming apparatus for forming an image on a recording medium by a series of image forming processes including exposure, charging, transfer, and fixing,
A fixing device for fixing the unfixed image to the recording medium by heating and pressurizing the recording medium carrying the unfixed image through the pressure contact portions of a pair of rotating members that are in pressure-contact rotation with each other;
A guide member for guiding the recording medium discharged from the press contact portion to a normal position;
The guide member includes a main body and a plurality of ribs that protrude from the main body and are arranged in a direction perpendicular to the conveyance direction of the recording medium,
The plurality of ribs include a movable rib supported to be displaceable with respect to the main body, and the movable rib is between the main body and an initial contact portion of the movable rib where the recording medium first contacts. The distance of is variable,
The distance between the initial contact portion and the main body when the front end portion of the recording medium is in contact with the initial contact portion is such that the portion other than the front end portion of the recording medium is the initial contact portion. An image forming apparatus, wherein the distance is smaller than a distance between the initial contact portion and the main body when the contact is made.

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