JP2008225173A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing the decrease in guide performance, and the like, for a recording medium by a recording medium guide member, by suppressing variations in the gap between a fixing belt member and the recording medium guide member. <P>SOLUTION: The fixing device 60 has its main part comprises a fixing belt module 61 having a fixing belt 610, a pressure roll 62 disposed in press contact with the fixing belt module 61, and a paper discharge guide 70, which is disposed downstream from a nip part N in the paper-conveying direction and guides a form P having passed through the nip part N downstream in the paper-conveying direction. The fixing belt module 61 has a belt guide member 69, which guides the fixing belt 610 having passed through the nip part N downstream in the moving direction, directed downstream from the nip part N at a location in proximity to a peeling pad 64. While the belt guide member 69 is pressed and disposed inside the fixing belt 610, it will not be pressed and disposed against a pressure roll 62 with the fixing belt 610. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, or a facsimile.

In order to prevent the unfixed image held on the recording medium from being rubbed, a fixing device is known in which a fixing belt is stretched around at least one of two fixing rolls. (For example, refer to Patent Document 1).
In addition, in order to enable self-separation of the recording medium from the fixing belt (self-stripping), the exit separating surface is a shape portion having a large curvature at a position corresponding to the outlet separating portion of the nip and inside the fixing belt. A fixing device having a fixing member is known (for example, see Patent Document 2).

JP-A-3-133871 Japanese Patent Laid-Open No. 2003-5565

Here, in the fixing device, for example, a fixing member disposed inside the fixing belt member, and a pressure contact member that is pressed against the fixing member via the fixing belt member and forms a nip portion between the fixing belt member and the fixing member. May be provided. In some cases, a recording medium guide member that guides the recording medium that has passed through the nip portion to the downstream side in the transport direction is provided at a position that is downstream of the nip portion and has a predetermined gap with the fixing belt member.
By the way, in the fixing device having such a configuration, the passing position of the fixing belt member may fluctuate due to deformation of the fixing member and the gap between the fixing belt member and the recording medium guide member may fluctuate. As a result, the recording medium guiding performance by the recording medium guiding member may be reduced.

  The present invention has been made to solve the technical problems as described above, and can suppress a change in the gap between the fixing belt member and the recording medium guide member, thereby suppressing a decrease in the guiding performance of the recording medium. It is to provide a fixing device.

  For this purpose, a fixing device to which the present invention is applied is a fixing device that fixes a toner image transferred onto a recording medium onto the recording medium, and a fixing belt member that rotates around and performs a fixing action. A non-rotating fixing member disposed inside the fixing belt member, a pressure member that presses the fixing belt member against the fixing member to form a pressure region with the fixing belt member, and A contact member provided downstream of the pressurizing region in the moving direction of the fixing belt member and disposed in contact with an inner peripheral surface of the fixing belt member; and provided downstream of the pressurizing region in the moving direction of the fixing belt member. A recording medium guide member that guides the moving direction of the recording medium; and a position defining portion that defines a position of the recording medium guide member with respect to the contact member outside the lateral side of the moving area of the fixing belt member. .

  Here, the contact member may be disposed in contact with the inner peripheral surface of the fixing belt member in a pressed state. In addition, the fixing belt member between the contact member and the recording medium guide member may be arranged in a stretched state. Further, the contact member may be arranged in non-pressure contact with the pressure member via the fixing belt member. Further, the contact member bends the fixing belt member by pressing the inner peripheral surface of the fixing belt member, and the bent portion of the fixing belt member formed by the contact member is downstream of the pressurizing region. The distance from the end may be 10 mm or less.

  From another point of view, a fixing device to which the present invention is applied is a fixing device that fixes a toner image transferred onto a recording medium onto the recording medium, and is a fixing belt member that performs a fixing action around the fixing medium. A fixing roll member that stretches and rotates the fixing belt member, and a pressure member that presses the fixing belt member against the fixing roll member to form a first pressure region between the fixing belt member and the fixing belt member The fixing belt member is provided so as not to rotate downstream in the moving direction of the fixing belt member from the first pressure region, and is continuous with the first pressure region by pressing the fixing belt member against the pressure member. A pressing member that forms a second pressurizing zone; a contact member that is provided downstream of the second pressurizing zone in the moving direction of the fixing belt member and is disposed in contact with an inner peripheral surface of the fixing belt member; The fixing belt from the second pressure area A recording medium guide member that is provided on the downstream side of the movement direction of the material and guides the movement direction of the recording medium; A position defining unit for defining.

  Here, the contact member may be disposed in non-pressure contact with the pressure member via the fixing belt member. The contact member may be disposed in pressure contact with the pressure member via the fixing belt member at a unit pressure smaller than a unit pressure acting between the pressing member and the pressure member. be able to. The pressing member may press the fixing belt member against the pressure member on one end side, and the contact member may be attached to the other end side of the pressing member. Further, the contact member is formed integrally with the pressing member in a state in which a slit having an opening on the side where the pressing member is disposed is disposed between the pressing member and the pressing member. can do.

According to the first aspect of the present invention, there is provided a fixing device capable of suppressing a change in the gap between the fixing belt member and the recording medium guiding member and suppressing a decrease in the guiding performance of the recording medium as compared with the case where this configuration is not adopted. Can be provided.
According to the second aspect of the invention, sagging of the fixing belt member can be suppressed, and fluctuations in the gap between the fixing belt member and the recording medium guide member can be further suppressed as compared with the case where the present configuration is not provided. be able to.
According to the third aspect of the present invention, the sag of the fixing belt member can be suppressed, and the variation in the gap between the fixing belt member and the recording medium guide member is further suppressed as compared with the case where the present configuration is not provided. be able to.
According to the fourth aspect of the present invention, fluctuations in the gap between the fixing belt member and the recording medium guiding member can be further suppressed as compared with the case where this configuration is not provided.
According to the fifth aspect of the present invention, it is possible to suppress a decrease in image quality as compared with a case where this configuration is not provided.

According to the sixth aspect of the present invention, there is provided a fixing device capable of suppressing a variation in the gap between the fixing belt member and the recording medium guide member and suppressing a decrease in the guiding performance of the recording medium as compared with the case where this configuration is not adopted. Can be provided.
According to the seventh aspect of the present invention, fluctuations in the gap between the fixing belt member and the recording medium guide member can be further suppressed as compared with the case where this configuration is not provided.
According to the eighth aspect of the present invention, fluctuations in the gap between the fixing belt member and the recording medium guiding member can be further suppressed as compared with the case where this configuration is not provided.
According to the ninth aspect of the present invention, fluctuations in the gap between the fixing belt member and the recording medium guide member can be suppressed with a simple configuration as compared with the case where the present configuration is not provided.
According to the tenth aspect of the present invention, the variation in the gap between the fixing belt member and the recording medium guide member can be suppressed with a simple configuration as compared with the case where the present configuration is not provided.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of an image forming apparatus 1 to which the present exemplary embodiment is applied.
The image forming apparatus 1 is an intermediate transfer type image forming apparatus called a so-called tandem type, and includes a plurality of image forming units 1Y, 1M, 1C, and 1K that form toner images of respective color components by electrophotography, and each image. And a primary transfer unit 10 that sequentially superimposes and transfers (primary transfer) the color component toner images formed by the forming units 1Y, 1M, 1C, and 1K onto the intermediate transfer belt 15. The image forming apparatus 1 also includes a secondary transfer unit 20 that batch-transfers (secondary transfer) toner images transferred onto the intermediate transfer belt 15 to a sheet P as a recording medium, and the second-transferred image on a sheet. And a fixing device 60 for fixing on P. Further, the image forming apparatus 1 includes a recording paper transport mechanism 50 and a control unit (not shown) that controls the operation of each device (each unit). The present embodiment is not limited to such a tandem type color image forming apparatus, but may be applied to a color image forming apparatus using a rotary developing device, a monochrome copying machine, or the like. is there.

  Each of the image forming units 1Y, 1M, 1C, and 1K includes a photosensitive drum 11 that rotates in the direction of arrow A, as representatively shown by the image forming unit 1Y in the drawing. Around the photosensitive drum 11, there are a charger 12 for charging the photosensitive drum 11, and a laser exposure unit 13 for writing an electrostatic latent image on the photosensitive drum 11 (the exposure beam is indicated by Bm in the figure). And a developing device 14 that accommodates each color component toner and visualizes the electrostatic latent image on the photosensitive drum 11 with the toner. Further, a primary transfer roll 16 that transfers each color component toner image formed on the photosensitive drum 11 to the intermediate transfer belt 15 by the primary transfer unit 10, and a drum cleaner 17 that removes residual toner on the photosensitive drum 11; Is arranged. These image forming units 1Y, 1M, 1C, and 1K are arranged in a substantially straight line from the upstream side of the intermediate transfer belt 15 in the order of yellow (Y), magenta (M), cyan (C), and black (K). Has been.

The intermediate transfer belt 15 is stretched by various rolls so as to have a path extending linearly along the arrangement direction of the photosensitive drums 11, and circulates (circulates) at a predetermined speed in the direction of arrow B shown in FIG. It is designed to be driven.
The primary transfer unit 10 includes a primary transfer roll 16 that is disposed to face the photosensitive drum 11 with the intermediate transfer belt 15 interposed therebetween. The primary transfer roll 16 presses the intermediate transfer belt 15 against the photosensitive drum 11. Further, a voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roll 16. As a result, the toner images on the respective photosensitive drums 11 are electrostatically attracted sequentially to the intermediate transfer belt 15, and the toner images are superimposed on the intermediate transfer belt 15.

The secondary transfer unit 20 includes a secondary transfer roll 22 disposed on the toner image forming surface side of the intermediate transfer belt 15 and a backup roll 25 disposed opposite to the secondary transfer roll 22 with the intermediate transfer belt 15 interposed therebetween. It is constituted by. In the secondary transfer unit 20, a secondary transfer bias is applied between the secondary transfer roll 22 and the backup roll 25, and a secondary transfer electric field is formed between both members. The secondary transfer unit 20 secondarily transfers the toner image supported by the intermediate transfer belt 15 onto the paper P that is conveyed and supplied. An intermediate transfer belt that removes residual toner and paper dust on the intermediate transfer belt 15 after the secondary transfer and cleans the surface of the intermediate transfer belt 15 on the downstream side of the secondary transfer portion 20 of the intermediate transfer belt 15. A cleaner 35 is provided.
The recording paper transport mechanism 50 transports the paper P from the storage unit 51 to the secondary transfer unit 20 and transports the paper P on which the toner image is transferred (secondary transfer) by the secondary transfer unit 20 to the fixing device 60. To do.

  Here, the image forming apparatus 1 is controlled by a control unit (not shown) and forms an image as follows. First, based on image data output from an image reading device (not shown), a personal computer (not shown) or the like, toner images of respective colors are respectively formed on the respective photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K. Form. The toner images in the image forming units 1Y, 1M, 1C, and 1K are formed by forming a latent electrostatic image by scanning and exposing the photosensitive drum 11 charged by the charger 12 with the laser exposure device 13, The electrostatic latent image is developed by the developing device 14 to form a toner image.

  Next, the toner images formed on the photosensitive drums 11 of the image forming units 1Y, 1M, 1C, and 1K are transferred onto the intermediate transfer belt 15 in each primary transfer unit 10 and transferred to the secondary transfer unit 20. The electrostatic transfer is collectively performed on the paper P conveyed by the recording paper conveyance mechanism 50. Thereafter, the sheet P on which the toner image has been transferred is conveyed to the fixing device 60 by the recording sheet conveying mechanism 50, and the toner image is fixed on the sheet P by the heat and pressure by the fixing device 60, and is then placed in a paper discharge storage unit (not shown). Discharge.

Next, the fixing device 60 according to the embodiment of the present invention will be described in detail.
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the fixing device 60.
As shown in the figure, the fixing device 60 includes a fixing belt module 61 including a fixing belt 610, a pressure roll 62 disposed in pressure contact with the fixing belt module 61, and a nip portion N, which will be described later, on the downstream side in the sheet conveyance direction. A main part is configured by a paper discharge guide 70 that guides the paper P that has been disposed and passed through the nip portion N toward the downstream side in the paper transport direction.

  In this embodiment, as a result of the pressure roll 62 being disposed in pressure contact with the fixing belt module 61, the toner image is formed by pressing and heating the paper P between the fixing belt module 61 and the pressure roll 62. A nip portion N to be fixed is formed. Further, in the present embodiment, it is formed by passage plates 65U and 65L that are arranged to face each other with a predetermined gap on the downstream side in the paper conveyance direction of the paper discharge guide 70 (downstream in the movement direction of the paper P). A paper discharge passage 65 and a paper discharge roll 66 are disposed downstream of the paper discharge passage 65 in the paper conveyance direction. The nip portion N includes a roll nip portion N1 as a first pressurizing region and a peeling pad nip portion N2 as a second pressurizing region disposed downstream of the roll nip portion N1.

  The fixing belt module 61 includes a fixing belt 610 that is rotatably arranged, a fixing roll 611 that is rotationally driven while stretching the fixing belt 610, and a first stretching roll that stretches the fixing belt 610 from the inside. 612. In addition, it is arranged between the second tension roll 613 that is disposed outside the fixing belt 610 and defines its circulation path, and between the fixing roll 611 and the first tension roll 612 and inside the fixing belt 610. And a third tension roll 614 that defines the path of the fixing belt 610. In addition, a fourth stretching roll 615 is provided to stretch the fixing belt 610 from the inside on the downstream side of the nip portion N in the moving direction of the fixing belt 610.

  Further, the fixing belt module 61 includes a peeling pad 64 at a position near the fixing roll 611 in a downstream area of the nip portion N where the fixing belt module 61 and the pressure roll 62 are in pressure contact with each other. Further, a belt guide member 69 that guides the fixing belt 610 that has passed through the nip portion N toward the downstream side in the movement direction is provided at a position downstream of the nip portion N and close to the peeling pad 64.

  The fixing belt 610 is a flexible endless belt having a predetermined width and a predetermined circumferential length. The fixing belt 610 includes, for example, a base layer formed of a polyimide resin having a thickness of 80 μm, an elastic layer made of silicone rubber having a thickness of 200 μm laminated on the surface side (outer peripheral surface side) of the base layer, and further elastic. And a release layer made of a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA) tube having a thickness of 30 μm and coated on the body layer. The configuration of the fixing belt 610 can be appropriately selected in terms of material, thickness, hardness, and the like according to the apparatus design conditions such as the purpose of use and conditions of use.

  Further, the width of the fixing belt 610 (the length in a direction intersecting (orthogonal) with the moving direction of the fixing belt 610) is larger than the width of the sheet P to be fixed (that is, the width of the fixing area). Is formed. Further, the fixing belt 610 is formed so that the width thereof is shorter by a predetermined amount than the lengths of the fixing roll 611 and the stretching rolls 612 to 615 in the axial direction. Further, the fixing belt 610 is formed so that the width thereof is shorter by a predetermined amount than the length of the peeling pad 64 in the longitudinal direction and the length of the belt guide member 69 in the longitudinal direction.

  The fixing roll 611 includes, for example, a core roll (core metal) having a predetermined length and a protective layer that protects the surface of the core roll. The core roll is formed of aluminum or the like, and is formed in a cylindrical shape with an outer diameter of 65 mm and a thickness of 10 mm, for example. The protective layer has a function of preventing wear on the surface of the core roll, and is made of, for example, a fluororesin having a thickness of 200 μm. The fixing roll 611 is not limited to this configuration. When the nip portion N is formed between the fixing roll 611 and the fixing roll 611, the fixing roll 611 is sufficiently deformed so as not to cause a deformation with respect to the pressing force from the pressing roll 62. Any structure that functions as a hard roll may be used. The fixing roll 611 receives a driving force from a driving motor (not shown) and rotates in the direction of arrow C at a surface speed of, for example, 250 mm / s.

  A halogen heater 616 a is disposed inside the fixing roll 611. The halogen heater 616a is controlled by a control unit (not shown). The control unit controls the halogen heater 616a so that the surface temperature of the fixing roll 611 becomes 150 ° C. based on the measured value of the temperature sensor 617a disposed so as to contact the surface of the fixing roll 611.

  The first tension roll 612 is, for example, a cylindrical roll having an outer diameter of 30 mm, a thickness of 2 mm, and a predetermined length formed of aluminum or the like, and includes a halogen heater 616b as a heating source therein. . The halogen heater 616b is configured to be controlled by the control unit. Based on the measured value of the temperature sensor 617b arranged so as to come into contact with the surface of the first tension roll 612, the controller controls the halogen heater so that the surface temperature of the first tension roll 612 becomes 190 ° C. 616b is controlled. As a result, the first stretching roll 612 has a function of stretching the fixing belt 610 and a function of heating the fixing belt 610 from the inner peripheral surface side. Note that spring members (not shown) that press the fixing belt 610 outward via the first tensioning roll 612 are disposed at both ends of the first tensioning roll 612. The tension is applied.

  Although the detailed description is omitted, the first tension roll 612 is provided so as to be swingable in a direction in which the other end portion is separated from and contacting the fixing belt 610 with the fulcrum on one end side as a center. Yes. The fixing device 60 according to the present exemplary embodiment includes a drive source (not shown) that is controlled by the control unit and that swings the other end, and a sensor that detects the position of the fixing belt 610 in the width direction. It is installed. And a control part rocks | fluctuates the 1st tension roll 612 in the said contact / separation direction via a drive source according to the detection result from the said sensor. As a result, the fixing belt 610 moves within a predetermined range in the width direction.

  The second tension roll 613 is, for example, a cylindrical roll made of aluminum or the like and having an outer diameter of 30 mm, a thickness of 2 mm, and a predetermined length. Moreover, the 2nd tension roll 613 is provided with the peeling layer which consists of a 20-micrometer-thick fluororesin on the surface. This release layer has a function of preventing paper dust and offset toner attached to the outer peripheral surface of the fixing belt 610 from accumulating on the second stretching roll 613.

  The second tension roll 613 includes a halogen heater 616c as a heating source. The halogen heater 616c is configured to be controlled by the control unit. Based on the measured value of the temperature sensor 617c arranged so as to come into contact with the surface of the second tension roll 613, the control unit determines that the surface temperature of the second tension roll 613 is 190 ° C. 616c is controlled. As a result, the second stretching roll 613 has a function of stretching the fixing belt 610 and a function of heating the fixing belt 610 from the outer peripheral surface side. For this reason, the fixing device 60 in the present embodiment is configured such that the fixing belt 610 is heated by the fixing roll 611, the first tension roll 612, and the second tension roll 613.

The third tension roll 614 is a cylindrical roll formed of aluminum or the like and having a predetermined diameter and a predetermined length. The third tension roll 614 is rotatably supported and defines a path of the fixing belt 610 from the first tension roll 612 to the fixing roll 611.
The fourth tension roll 615 is a cylindrical roll formed of, for example, aluminum or the like, and has an outer diameter of 12 mm and a predetermined length, for example. The fourth tension roll 615 is disposed downstream of the belt guide member 69 in the moving direction of the fixing belt 610 and inside the fixing belt 610, and the fixing belt 610 is disposed downstream of the belt guide member 69. Stretch from the inside.

  The peeling pad 64 is a fixing member that is formed as a rigid body and is provided along the axial direction of the fixing roll 611 and over the entire axial direction of the fixing roll 611. The peeling pad 64 is a member whose cross section is formed in a substantially arc shape. Further, the peeling pad 64 is a member formed of, for example, a metal such as stainless steel or a resin. Further, the peeling pad 64 is disposed at a position near the downstream side of a region where the pressure roll 62 is pressed against the fixing roll 611 via the fixing belt 610 (“roll nip portion N1”). Further, the peeling pad 64 is disposed inside the fixing belt 610 and is installed so as to press the pressure roll 62 uniformly over the predetermined width region with a predetermined load via the fixing belt 610. As a result, the “peeling pad nip portion N2” is formed. Note that the peeling pad nip portion N <b> 2 in this embodiment is 5 mm along the traveling direction of the fixing belt 610.

Further, in the present embodiment, the fixing roll 611 is disposed on the outer side in the axial direction, one end thereof is attached to the end in the longitudinal direction of the peeling pad 64, and the other end is supported by the fixing roll 611. A support member 618 is provided that is rotatably mounted on the shaft. FIG. 2 shows a cross section, but the support member 618 is also shown for convenience of explanation. Two support members 618 are disposed on both sides of the fixing roll 611 in the axial direction, and support both ends of the peeling pad 64. As a result, the peeling pad 64 can move (swing) along the outer peripheral surface of the fixing roll 611.
In the present embodiment, an urging member (not shown) such as a spring that urges the peeling pad 64 toward the pressure roll 62 is provided. For example, the urging member urges the peeling pad 64 toward the pressure roll 62 so that the fixing belt 610 presses the pressure roll 62 with a predetermined load (for example, 10 kgf).

  The belt guide member 69 is a member that is formed as a rigid body and is provided along the axial direction of the fixing roll 611 and over the entire axial direction of the fixing roll 611. The belt guide member 69 functions as one of the contact members. The belt guide member 69 is formed such that the length in the width direction of the fixing belt 610 (direction intersecting (orthogonal) with the moving direction of the fixing belt 610) is longer than the width of the fixing belt 610. It is arranged so as to protrude a predetermined amount from both end portions (left and right side edges) in the width direction. Further, the belt guide member 69 is formed in a shape following the outer surface 64c and the contact surface 64d (see FIG. 3) of the peeling pad 64.

  Further, the belt guide member 69 is a rigid member formed of a metal such as stainless alloy steel (SUS) or a resin. Further, the belt guide member 69 is disposed inside the fixing belt 610, and is disposed downstream of the peeling pad 64 in the moving direction of the fixing belt 610. Further, the belt guide member 69 presses the fixing belt 610 that has passed through the nip portion N from the inside, and the fixing belt 610 is bent by this pressing. Although the belt guide member 69 is pressed and arranged inside the fixing belt 610, it is not pressed and arranged on the pressure roll 62 via the fixing belt 610. In other words, although the belt guide member 69 and the inner peripheral surface of the fixing belt 610 are in contact, the fixing belt is located at a position where the contact surface 69b (see FIG. 3) of the belt guide member 69 and the pressure roll 62 face each other. 610 and the pressure roll 62 are not in contact with each other.

  The pressure roll 62 as the pressure member is, for example, a cylindrical roll 621 as a base, an elastic layer 622 disposed on the outer peripheral surface of the cylindrical roll 621, and an outer peripheral surface of the elastic layer 622. A soft roll composed of a release material layer 623. The cylindrical roll 621 is formed with an outer diameter of 45 mm and a predetermined length, for example, with aluminum or the like. The elastic layer 622 is made of, for example, silicone rubber having a rubber hardness of 30 ° (JIS-A). The release material layer 623 is formed from, for example, a PFA tube having a thickness of 150 μm. The pressure roll 62 is installed so as to be pressed against the fixing belt module 61, and rotates in the direction of arrow E in the drawing as the fixing roll 611 rotates.

  Here, in this embodiment, as will be described later, the fixing belt 610 moves along the side surface of the belt guide member 69 after passing through the peeling pad nip portion N2. It changes rapidly so as to bend in the direction of the roll 615. For this reason, the sheet P cannot follow the fixing belt 610 and is peeled off from the fixing belt 610 by its so-called “koshi”. By the way, the ease of peeling of the paper P depends on the rigidity of the paper P, the smoothness, the size of the margin (non-image area) at the leading end in the traveling direction, the density of the image formed on the paper P, and the like. . For example, in the case of a sheet P having high rigidity such as a thickness, it is easy to peel off from the fixing belt 610, but in the case of a sheet P having low rigidity such as thin paper, it is difficult to peel off from the fixing belt 610. Also, the narrower the margin, the harder it is to separate the paper P, and the paper P holding an image with a high toner density such as a photographic image is more difficult to peel off.

When the paper P is difficult to peel from the fixing belt 610, the peeling position of the paper P is on the downstream side in the movement direction of the fixing belt 610 as compared with the case where the paper P is easily peeled. In the worst case, even if the blank portion where the image is not formed is peeled off, the portion where the image is formed may not be peeled off.
For this reason, in the present embodiment, a sheet discharge guide 70 is provided that guides paper P having different peeling positions to a predetermined conveyance path according to the difference in ease of peeling and promotes peeling. The paper discharge guide 70 is disposed at a position facing the belt guide member 69 with the fixing belt 610 interposed therebetween, and further on the downstream side of the nip portion N in the moving direction of the fixing belt 610. The paper discharge guide 70 is disposed in a wedge-shaped region formed by the fixing belt 610 that has passed through the belt guide member 69 and the pressure roll 62. Further, the paper discharge guide 70 is disposed on the fixing roll 611 side with respect to the paper transport path R (see FIG. 3) through which the paper P passes. Details of the paper discharge guide 70 will be described later.

  Here, the operation of the fixing device 60 will be described. When fixing is performed by the fixing device 60, first, the pressure roll 62 that is separated from the fixing belt module 61 is pressed against the fixing belt module 61 by a driving source (not shown). Next, the paper P on which the toner image is held is introduced into the nip portion N. At this time, the fixing roll 611 rotates in the direction of arrow C in response to a driving force from a driving source (not shown). Further, the fixing belt 610 rotates in the direction of arrow D following the fixing roll 611 as the fixing roll 611 rotates. Further, the pressure roll 62 also rotates in the direction of arrow E following the rotation of the fixing belt 610. The paper P introduced into the nip portion N is conveyed downstream by the rotating fixing belt 610 and the pressure roll 62, and sequentially passes through the roll nip portion N1 and the peeling pad nip portion N2.

  The paper P is subjected to pressure and heating action from the fixing belt 610 and the pressure roll 62 in the process of passing through the roll nip portion N1 and the peeling pad nip portion N2. As a result, the toner image is fixed on the paper P. The fixing belt 610 that has passed through the peeling pad nip portion N2 then moves following the side surface of the belt guide member 69. As a result, the advancing direction of the fixing belt 610 changes abruptly so as to bend in the direction of the fourth tension roll 615.

  For this reason, the paper P that has been pressurized and heated at the nip N cannot follow the change in the direction of travel of the fixing belt 610. As a result, first, the leading edge of the paper P is peeled off from the fixing belt 610 by its so-called “koshi”, and the peeled leading edge is captured (contacted) by the paper discharge guide 70. Then, the paper P whose leading edge is captured by the paper discharge guide 70 is forcibly guided downstream in the transport direction by the paper discharge guide 70 as the fixing belt 610 advances. As a result, the separation between the paper P and the fixing belt 610 is promoted, and the paper P is stably peeled from the fixing belt 610. The paper P peeled off from the fixing belt 610 passes through the paper discharge passage 65 and is then discharged out of the apparatus by the paper discharge roll 66, whereby the fixing process is completed.

  When the fixing process is completed, the pressure roll 62 is retracted from the fixing belt module 61 by a driving source (not shown) and is disposed at a predetermined position separated from the fixing belt module 61. When the paper P to be fixed is a thick paper having rigidity, the paper discharge guide 70 does not assist the peeling, and the paper P peels from the fixing belt 610 by its so-called “koshi” (self Strip). For this reason, the paper discharge guide 70 is particularly useful when the paper P to be fixed is thin paper or the like that has low rigidity and is difficult to peel off from the fixing belt 610.

  Note that heat acting on the nip portion N is mainly supplied by the fixing belt 610. The fixing belt 610 includes heat supplied from the halogen heater 616 a disposed inside the fixing roll 611 through the fixing roll 611, and a first stretch from the halogen heater 616 b disposed inside the first stretching roll 612. Heating is performed by heat supplied through the roll 612 and heat supplied through the second stretching roll 613 from the halogen heater 616c disposed inside the second stretching roll 613. For this reason, even if heat is deprived in the nip portion N, heat energy can be replenished to the fixing belt 610 appropriately and quickly mainly by the first tension roll 612 and the second tension roll 613. As a result, a sufficient amount of heat can be secured in the nip portion N even if the process speed is as high as 250 mm / s, for example.

  Here, the peeling pad 64, the belt guide member 69, the paper discharge guide 70, and the like will be described in more detail with reference to FIGS. 3 is an enlarged configuration diagram illustrating the downstream side of the nip portion N, and FIG. 4 is an explanatory diagram illustrating the paper discharge guide 70 in detail.

  As shown in FIG. 3, the peeling pad 64 has an inner surface 64a facing the fixing roll 611, a pressing surface 64b that presses the fixing belt 610 against the pressing roll 62, and a predetermined angle with respect to the pressing surface 64b. An outer surface 64c, a contact surface 64d having a predetermined angle with respect to the outer surface 64c and contacting the belt guide member 69, and an upper surface 64e pressed by the urging member are provided. The pressing surface 64b of the peeling pad 64 is affixed or coated with a resin sheet made of ethylene tetrafluoride or the like having a small friction coefficient and heat resistance, and the inner surface of the peeling pad 64 and the fixing belt 610. Smooth sliding is possible.

  As described above, the belt guide member 69 is formed in a shape following the outer surface 64c and the contact surface 64d of the peeling pad 64. More specifically, from a portion formed linearly along the outer surface 64c of the peeling pad 64 and a portion formed linearly along the contact surface 64d at a predetermined angle with respect to this portion. Is formed. More specifically, the belt guide member 69 includes an inner surface 69 a disposed to face the outer surface 64 c of the peeling pad 64, and a contact surface 69 b disposed to be pressed against the inner circumferential surface of the fixing belt 610. Further, an outer surface 69c is provided that has a predetermined angle with respect to the contact surface 69b and is disposed so as to be separated from the fixing belt 610 that has passed through the contact surface 69b. Furthermore, a contact surface 69d disposed in contact with the contact surface 64d of the peeling pad 64 and an upper surface 69e connecting the contact surface 69d and the outer surface 64c are provided.

  The belt guide member 69 has a contact surface 69d disposed in contact with the contact surface 64d of the separation pad 64, and is fastened and fixed to the separation pad 64 with a screw or the like in the contact disposed state. Further, the belt guide member 69 is attached to the other end side of the peeling pad 64, not the side (one end side) that presses the pressure roll 62 via the fixing belt 610. From another point of view, the belt guide member 69 is attached to the peeling pad 64 on the opposite side of the nip portion N across the joint portion between the support member 618 and the peeling pad 64.

  The belt guide member 69 is attached to the peeling pad 64 with a slit (gap) formed between the outer side surface 64c of the peeling pad 64 and the inner side surface 69a. This slit is in a state where an opening is formed on the pressure roll 62 side. Further, the slit has a width D1 of 1 mm in the traveling direction of the fixing belt 610. Further, in this embodiment, as a result of the belt guide member 69 being pressed and disposed on the inner peripheral surface of the fixing belt 610, the fixing belt 610 bends at the junction (intersection) between the contact surface 69b and the outer surface 69c. Yes. In the present embodiment, the distance D2 from the downstream end of the nip portion N to the bent portion is 5 mm.

Next, the paper discharge guide 70 will be described with reference to FIG.
The paper discharge guide 70 in this embodiment includes a baffle plate 71, a support shaft 72, a spiral spring 73, and a fixing member 74.

  The baffle plate 71 is formed in a thin plate shape, and is arranged in a state where the tip thereof is close to the outer peripheral surface of the fixing belt 610. Further, the baffle plate 71 is disposed in a state having a predetermined angle with respect to the paper transport path R. The baffle plate 71 regulates the movement of the paper P by capturing the paper P whose tip is peeled off from the fixing belt 610 whose movement path has changed suddenly, and promotes the peeling of the paper P from the fixing belt 610. Further, the baffle plate 71 guides the captured paper P to a paper discharge passage 65 (see FIG. 2) arranged on the downstream side.

The baffle plate 71 is mainly composed of a substrate 71B and a guide plate 71A formed of a thin plate having a predetermined rigidity. The guide plate 71A is integrally fixed to the surface of the substrate 71B by adhesion or the like. The guide plate 71A functions as one of recording medium guide members.
The guide plate 71A is made of, for example, stainless steel alloy (SUS) having a thickness of 0.2 mm, and the width thereof is set to be a predetermined amount wider than the width of the fixing belt 610 (that is, the width of the fixing area). Further, a resin sheet made of ethylene tetrafluoride or the like having a small friction coefficient and heat resistance is attached to the surface (lower surface) so as to have low friction with the paper P. Further, the guide plate 71 </ b> A is disposed in a state of being separated from the fixing belt 610, and is disposed so that a predetermined gap is formed between the front end portion thereof and the outer peripheral surface of the fixing belt 610.

  The substrate 71B is formed of steel plate or the like so as to have a predetermined rigidity. Further, the substrate 71B is on the rear end side (downstream side in the moving direction of the paper P: right side in FIG. 4), and on the left and right sides (both sides in the width direction of the substrate 71B), the fourth tension roll 615 (FIG. 2). The mounting portion 71Ba is provided upright on the side where the reference is disposed. Further, the substrate 71B is provided with positioning protrusions 71Bb on the left and right sides at the front end portion. The positioning protrusion 71Bb functions as one of the position defining portions. Each positioning projection 71Bb is formed with a predetermined width and is erected in a state having a predetermined height on the side where the fourth tension roll 615 is disposed. Further, the substrate 71B is formed to have a width larger than the width of the fixing belt 610, like the guide plate 71A. Further, the positioning protrusion 71Bb is located outside the side edge of the fixing belt 610 and is disposed at a position where it can come into contact with the belt guide member 69 protruding sideward (outside) from the side edge of the fixing belt 610. .

  The support shaft 72 is configured as a cylindrical member, and is disposed in the width direction of the fixing belt 610, and its end (not shown) is attached to a casing (not shown) constituting the fixing device 60. It is in the state. The support shaft 72 is disposed in a through state in a through hole formed in the mounting portion 71Ba. As a result, the substrate 71B can swing (rotate) about the support shaft 72.

  The spiral spring 73 is disposed in a state where the support shaft 72 passes through the spiral spring 73, and one end and the other end are disposed between the fixing member 74 disposed in the casing and the substrate 71B. It has become a state. As a result, the elastic restoring force of the spiral spring 73 causes the substrate 71B to be urged in the direction of the fixing belt 610, and both the protrusions 71Bb disposed at the leading end are pressed against the belt guide member 69. As a result, the distal end portion of the guide plate 71A is disposed at a position with the predetermined gap from the fixing belt 610.

Incidentally, the positioning protrusion 71Bb can be pressed against the peeling pad 64 without providing the belt guide member 69. However, the peeling pad 64 may be greatly deformed by the pressing force from the pressure roll 62. As a result, for example, the gap between the front end portion of the guide plate 71A and the fixing belt 610 may vary.
Therefore, in the present embodiment, a belt guide member 69 is provided on the downstream side of the peeling pad 64, and the positioning protrusion 71Bb is pressed against the belt guide member 69. As described above, the belt guide member 69 is pressed on the inner side of the fixing belt 610 but is not pressed on the pressure roll 62 via the fixing belt 610. As a result, the pressing force from the pressure roll 62 does not act directly on the belt guide member 69, and the deformation of the belt guide member 69 can be suppressed.

  In this embodiment, the substrate 71B is pressed against the belt guide member 69. The paper discharge guide 70 may be configured not to press the substrate 71B against the belt guide member 69 but to be fixed only to a support housing (not shown) of the fixing device 60. However, in this case, it may be difficult to install the paper discharge guide 70 with high accuracy due to manufacturing tolerances such as the baffle plate 71, the support shaft 72, the spiral spring 73, and the fixing member 74. In addition, even if it can be mounted with high accuracy, there is a problem in that it requires strict position adjustment and the cost increases. Therefore, in the present embodiment, as described above, the substrate 71B is pressed against the belt guide member 69.

In the present embodiment, as described above, the contact surface 69 b of the belt guide member 69 is pressed against the inner peripheral surface of the fixing belt 610. As a result, the fixing belt 610 that has passed through the contact surface 69b is in a stretched state between the fourth stretch roll 615 (see FIG. 2). For this reason, flapping and sagging of the fixing belt 610 are prevented between the contact surface 69b and the fourth tension roll 615, and the fixing belt 610 moves stably.
Furthermore, in this embodiment, as described above, the belt guide member 69 is not on the side (one end side) of the peeling pad 64 that presses the pressure roll 62 via the fixing belt 610 but on the other end side. It is attached. That is, the belt guide member 69 is attached to a portion of the peeling pad 64 where deformation is difficult to occur. As a result, it is possible to suppress the positional variation and deformation of the belt guide member 69 due to the deformation of the peeling pad 64.

In this embodiment, the belt guide member 69 and the peeling pad 64 are separate members, and the belt guide member 69 is attached to the peeling pad 64. However, the belt guide member 69 and the peeling pad 64 may be configured as an integral member. In this case, it is desirable to form a slit (gap) having an opening on the nip portion N side as shown in FIG.
Furthermore, in this embodiment, the belt guide member 69 is attached to the peeling pad 64. However, the belt guide member 69 may be attached to a support housing (not shown) of the fixing device 60 or the like. It is. However, it is desirable to attach to the peeling pad 64 from the viewpoint of preventing the apparatus from becoming large and complicated and simplifying the configuration.

  When the belt guide member 69 is not pressed against the pressure roll 62 via the fixing belt 610 as in the present embodiment, the belt guide member 69 applies the pressing force from the pressure roll 62 as described above. It becomes the composition which does not receive directly. In such a configuration, in the region from the downstream end of the nip portion N to the bent portion of the fixing belt 610, a non-pressurized region where no pressure acts on the paper P from the pressure roll 62 is formed. When this non-pressurized area is formed, there is a possibility that a so-called blister phenomenon occurs in which the toner image is disturbed by the water vapor due to the vaporization of the water in the paper P or the thermal expansion of the air present in the toner gap. . In order to suppress the disturbance of the toner image by the blister, it is desirable that the distance D2 from the downstream end of the nip portion N to the bent portion of the fixing belt 610 is 10 mm or less.

  In this embodiment, as described above, the belt guide member 69 is not pressed against the pressure roll 62 via the fixing belt 610, but is configured to be pressed against the pressure roll 62 via the fixing belt 610. You can also. However, in this case, since the belt guide member 69 may be greatly deformed, the belt guide member has a unit pressure smaller than the unit pressure when the peeling pad 64 presses the pressure roll 62 via the fixing belt 610. It is desirable that 69 be pressed against the pressure roll 62 via the fixing belt 610.

1 is a schematic configuration diagram of an image forming apparatus to which an exemplary embodiment is applied. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing device. It is the block diagram which expanded and showed the downstream of the nip part. FIG. 6 is an explanatory view showing a paper discharge guide in detail.

Explanation of symbols

60 ... fixing device, 62 ... pressure roll, 64 ... peeling pad, 69 ... belt guide member,
71 ... baffle plate, 71Bb ... positioning protrusion, 610 ... fixing belt, 611 ... fixing roll

Claims (10)

A fixing device for fixing a toner image transferred onto a recording medium onto the recording medium,
A fixing belt member that circulates and performs a fixing action;
A non-rotating fixing member disposed inside the fixing belt member;
A pressure member that presses the fixing belt member against the fixing member to form a pressure region with the fixing belt member;
A contact member provided downstream of the pressurizing zone in the moving direction of the fixing belt member and disposed in contact with an inner peripheral surface of the fixing belt member;
A recording medium guide member provided on the downstream side in the moving direction of the fixing belt member from the pressurizing area and guiding the moving direction of the recording medium;
A position defining portion for defining the position of the recording medium guide member with respect to the contact member outside the lateral side of the moving range of the fixing belt member;
A fixing device comprising:   The fixing device according to claim 1, wherein the contact member is disposed in contact with the inner peripheral surface of the fixing belt member in a pressed state.   The fixing device according to claim 1, wherein the fixing belt member between the contact member and the recording medium guide member is disposed in a stretched state.   The fixing device according to claim 1, wherein the contact member is disposed in non-pressure contact with the pressure member via the fixing belt member. The contact member bends the fixing belt member by pressing the inner peripheral surface of the fixing belt member,
The fixing device according to claim 4, wherein the bent portion of the fixing belt member formed by the contact member is disposed at a position where the distance from the downstream end of the pressurizing region is 10 mm or less. A fixing device for fixing a toner image transferred onto a recording medium onto the recording medium,
A fixing belt member that circulates and performs a fixing action;
A fixing roll member that stretches and rotates the fixing belt member;
A pressure member that presses the fixing belt member against the fixing roll member to form a first pressure region with the fixing belt member;
A second belt that is provided so as not to rotate downstream in the moving direction of the fixing belt member from the first pressure region and that is continuous with the first pressure region by pressing the fixing belt member against the pressure member. A pressing member that forms a pressure zone of
A contact member provided on the downstream side in the moving direction of the fixing belt member from the second pressurizing zone and disposed in contact with an inner peripheral surface of the fixing belt member;
A recording medium guide member that is provided downstream of the second pressure area in the moving direction of the fixing belt member and guides the moving direction of the recording medium;
A position defining portion for defining the position of the recording medium guide member with respect to the contact member outside the lateral side of the moving range of the fixing belt member;
A fixing device comprising:   The fixing device according to claim 6, wherein the contact member is disposed in non-pressure contact with the pressure member via the fixing belt member.   The contact member is disposed in pressure contact with the pressure member via the fixing belt member at a unit pressure smaller than a unit pressure acting between the pressing member and the pressure member. 6. The fixing device according to 6. The pressing member presses the fixing belt member against the pressure member on one end side,
The fixing device according to claim 6, wherein the contact member is attached to the other end side of the pressing member.   The contact member is formed integrally with the pressing member in a state in which a slit having an opening on a side where the pressing member is disposed is disposed between the pressing member and the pressing member. Item 7. The fixing device according to Item 6.

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