JP2018106045A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing an outflow of a lubricant from the inner side of a fixing belt.SOLUTION: A fixing device includes a fixing belt 110, a holding member 133, groove forming parts 134 and 135 and a pressure roller 120. The holding member 133 is slidably arranged on an inner peripheral surface 110c of the fixing belt 110 via a lubricant. The groove forming parts 134 and 135 are slidably arranged on the inner peripheral surface 110c of the fixing belt 110 via the lubricant. The pressure roller 120 forms a nip part N between itself and an outer peripheral surface 110d of the fixing belt 110. A sliding surface with the fixing belt 110 in the groove forming parts 134 and 135 is provided with groove parts 134b and 135b inwardly inclined to an inner side of the width direction toward the rotation direction of the fixing belt 110. The groove parts 134b and 135b are formed across a pressure region K1 and a non-pressure region K2 in the width direction of the holding member 133.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device.

  Patent Document 1 discloses a fixing device used in a laser printer. This fixing device sandwiches a fixing belt between a cylindrical fixing belt, a heating element disposed inside the fixing belt, a nip member disposed so as to be in sliding contact with the inner surface of the fixing belt, and the nip member. And a pressure roller that forms a nip portion.

JP 2012-53105 A

  In general, when the pressure contact portion for forming the nip portion is disposed inside the endless fixing belt, in order to reduce friction between the inner peripheral surface of the fixing belt and the pressure contact portion, the inner peripheral surface of the fixing belt A lubricant is applied to the surface. In this case, it is desirable to hold the lubricant for a long time in a region where the nip portion is formed on the inner peripheral surface of the fixing belt.

  However, in the region where the nip portion is formed, pressure from the fixing belt and the pressure contact portion is applied to the lubricant. In this case, the lubricant easily moves from a position where the pressure is high to a position where the pressure is low. In particular, at the end portion of the fixing belt, a large pressure difference occurs between the pressure region where the nip portion is formed and the non-pressure region outside the nip portion region. Therefore, the lubricant is likely to move from the pressure area to the non-pressure area, and the lubricant may flow out from the end of the fixing belt. In this case, the outflow of the lubricant may cause adverse effects such as breakage of component parts due to increased frictional force, generation of abnormal noise, and occurrence of paper stains.

  An object of the present invention is to provide a fixing device capable of suppressing the outflow of lubricant from the inside of the fixing belt to the outside.

  The fixing device on one side conveys the recording material on which the toner image is formed in the conveying direction, and fixes the toner image on the recording material. The fixing device includes an endless fixing belt, a heating element, a pressure contact portion, a groove forming portion, a pressure roller, and a belt guide. The fixing belt has an end portion in the width direction that intersects the conveyance direction as an open end portion. The heating element is disposed inside the fixing belt. The pressure roller forms a nip portion with the outer peripheral surface of the fixing belt. The pressure contact portion is slidably disposed on the inner peripheral surface of the fixing belt via a lubricant, and is pressed against the pressure roller via the fixing belt. The groove forming portion is slidably disposed on the inner peripheral surface of the fixing belt via a lubricant. The pair of belt guides support the opening end of the fixing belt. The contact surface is slidably in contact with the end surface of the opening end of the fixing belt. The support surface protrudes from the contact surface and slidably contacts the inner peripheral surface of the opening end portion of the fixing belt. A groove portion that is inclined inward in the width direction toward the rotation direction of the fixing belt corresponding to the conveying direction is provided on the sliding surface of the groove forming portion with the fixing belt. The groove portion is formed across the pressurization region where the nip portion is formed in the width direction of the press contact portion and the non-pressurization region outside the nip portion in the width direction.

  In such a fixing device, the recording material can be conveyed so as to pass through the nip portion while being sandwiched between the fixing belt and the pressure roller. The toner image formed on the recording material is fixed by the fixing belt heated by the heating element. Here, the lubricant applied between the fixing belt and the pressure contact portion moves in the rotation direction as the fixing belt rotates. In this case, the lubricant can move inward in the width direction along the groove portion on the sliding surface with the fixing belt in the pressure contact portion. And the groove part straddles a pressurization field and a non-pressurization field. Thereby, even if the lubricant moves from the pressurization region to the non-pressurization region, the lubricant can be moved again to the pressurization region by the groove. Therefore, the lubricant can be prevented from flowing out from the inside of the fixing belt to the outside.

  In one aspect, the groove portion may be inclined at an angle of 45 ° or less with respect to the rotation direction of the fixing belt. According to this configuration, the frictional resistance between the groove portion and the fixing belt can be kept low, and an increase in torque of the fixing belt can be suppressed.

  In one aspect, the material forming the groove forming portion is a resin having heat resistance and chemical resistance. This material may be any one of a liquid crystal polymer, a polyether ether ketone resin, and a polyphenylene sulfide resin. According to this structure, it is suppressed that a groove part is damaged by the heating by a heat generating body, or a lubricant.

  Further, on one side surface, the nip portion and the sliding surface may be separated from each other when viewed from the width direction. According to this configuration, the fixing belt and the sliding surface do not interfere with each other at the position where the nip portion is formed, and the load on the fixing belt can be reduced.

  Further, in one aspect, the groove forming portion is provided downstream of the pressure contact portion in the recording material conveyance direction, and the sliding surface of the groove forming portion is more than the support surface of the belt guide when viewed in the width direction. The outer side may be in contact with the inner peripheral surface of the fixing belt. In this configuration, the sliding surface of the groove forming portion protrudes downstream in the transport direction, and the groove forming portion and the inner peripheral surface of the fixing belt slide against each other in the vicinity of the exit of the nip portion. As a result, the lubricant can be moved more reliably.

  In one aspect, the fixing belt has a wall portion that protrudes inward from the inner circumferential surface over the entire circumference in the circumferential direction, and the wall portion is disposed between the belt guide and the groove forming portion. Good. According to this configuration, even if the lubricant moves outside the groove forming portion, the lubricant is prevented from flowing out of the fixing belt.

  Moreover, in one side surface, the radiation prevention member is arrange | positioned between a press-contact part and a groove | channel formation part, and a heat generating body. The radiation preventing member may be a reflector that reflects light radiated from the heating element. According to this configuration, the fixing belt can be efficiently heated by the heating element.

  In one aspect, the arithmetic average roughness Ra of the contact surface may be 2.6 μm or less, and the ten-point average roughness Rz of the contact surface may be 38.3 μm or less. According to this configuration, friction between the end portion of the fixing belt and the contact surface is reduced, and generation of abnormal noise or the like can be suppressed.

  In one aspect, the radius of curvature of the corner between the contact surface and the support surface may be not less than 0.8 mm and not more than 2 mm. According to this configuration, the end portion of the fixing belt can be brought into contact with the contact surface in a state of being curved outward in the radial direction. Therefore, the force applied from the fixing belt to the contact surface is reduced.

  According to the fixing device on one side, it is possible to prevent the lubricant from flowing out from the inside of the fixing belt to the outside.

1 is a diagram illustrating an image forming apparatus including a fixing device according to an embodiment. FIG. 4 is a side view of the fixing device as viewed from the conveyance direction side. FIG. 2 is a cross-sectional view schematically showing the structure of a fixing device. FIG. 3 is a longitudinal sectional view schematically showing a belt guide and a fixing belt. FIG. 4 is a perspective view illustrating a cross section of a belt guide and a fixing belt. FIG. 4 is an enlarged side view of the fixing device as viewed from the upstream side in the conveyance direction. FIG. 5 is an enlarged side view of the fixing device as viewed from the downstream side in the conveyance direction. FIG. 4 is a schematic diagram for explaining a positional relationship among a belt guide, a pressure roller, and a pressure contact member in the fixing device.

  Embodiments according to the present invention will be specifically described below with reference to the drawings. For convenience, the same reference numerals are given to substantially the same elements, and the description thereof may be omitted. In the following description, the sheet conveyance direction when the normal fixing operation is performed is simply referred to as the conveyance direction, and the upstream side and the downstream side are defined with reference to the conveyance direction. Similarly, the upstream side and the downstream side of the rotation direction of the fixing belt and the pressure roller are defined. Further, the width direction of the fixing belt may be simply referred to as the width direction. The width direction of the fixing belt is along the direction of the rotation axis of the belt guide and the pressure roller.

  FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus including a fixing device according to an embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a recording medium conveyance device 10, a transfer device 20, four photosensitive drums 30, four developing devices 40, and a fixing device 100. .

  The recording medium conveyance device 10 accommodates a sheet (recording material) P as a recording medium on which an image is formed, and conveys the sheet P onto a recording medium conveyance path. The paper P is stacked and accommodated in a cassette. The recording medium conveyance device 10 causes the paper P to reach the secondary transfer region R at a timing when the toner image transferred to the paper P reaches the secondary transfer region R.

  The transfer device 20 conveys the toner images formed by the four developing devices 40 to the secondary transfer region R where the secondary transfer is performed on the paper P. The transfer device 20 includes a transfer belt 21, suspension rollers 21a, 21b, 21c, and 21d that suspend the transfer belt 21, four primary transfer rollers 22 that sandwich the transfer belt 21 together with the photosensitive drum 30, and a suspension roller 21d. And a secondary transfer roller 24 that sandwiches the transfer belt 21.

  The transfer belt 21 is an endless belt that circulates and moves along the suspension rollers 21a, 21b, 21c, and 21d. The primary transfer roller 22 presses the photosensitive drum 30 from the inner peripheral side of the transfer belt 21. The secondary transfer roller 24 presses the suspension roller 21 d from the outer peripheral side of the transfer belt 21. Further, the transfer device 20 may include a belt cleaning device that removes the toner adhering to the transfer belt 21.

  The photosensitive drum 30 is an electrostatic latent image carrier on which an image is formed on the outer peripheral surface thereof, and includes, for example, an OPC (Organic Photo Conductor). The image forming apparatus 1 is an apparatus capable of forming a color image. For example, four photosensitive drums 30 are provided along the moving direction of the transfer belt 21 corresponding to each color of magenta, yellow, cyan, and black. Yes. On the circumference of each photosensitive drum 30, a charging roller 32, an exposure device 34, a developing device 40, and a cleaning device 38 are provided.

  The charging roller 32 uniformly charges the outer peripheral surface of the photosensitive drum 30 to a predetermined potential. The exposure device 34 exposes the outer peripheral surface of the photosensitive drum 30 charged by the charging roller 32 according to the image formed on the paper P. As a result, the potential of the portion exposed by the exposure device 34 on the outer peripheral surface of the photosensitive drum 30 changes, and an electrostatic latent image is formed.

  The four developing devices 40 develop the electrostatic latent image formed on the photosensitive drum 30 with the toner supplied from the toner tank 36 provided corresponding to each developing device 40 to generate a toner image. The four toner tanks 36 are filled with magenta, yellow, cyan, and black toners, respectively.

  The cleaning device 38 collects the toner remaining on the photosensitive drum 30 after the toner image formed on the photosensitive drum 30 is primarily transferred to the transfer belt 21. The cleaning device 38 includes, for example, a cleaning blade, and scrapes off residual toner on the photosensitive drum 30 by bringing the cleaning blade into contact with the outer peripheral surface of the photosensitive drum 30. Note that a discharge lamp that resets the potential of the photosensitive drum 30 may be disposed between the cleaning device 38 and the charging roller 32 on the outer peripheral surface of the photosensitive drum 30.

  The fixing device 100 fixes the toner image secondarily transferred from the transfer belt 21 to the paper P on the paper P. The fixing device 100 includes a fixing belt 110 that heats the paper P and a pressure roller 120 that presses the fixing belt 110. In the present embodiment, a nip portion N is formed between the fixing belt 110 and the pressure roller 120, and the toner image is melted and fixed on the paper P by passing the paper P through the nip portion N in the transport direction D. Details of the fixing device 100 will be described later.

  Further, the image forming apparatus 1 is provided with discharge rollers 52 and 54 for discharging the paper P on which the toner image is fixed by the fixing device 100 to the outside of the apparatus.

  Next, the operation of the image forming apparatus 1 will be described. When an image signal of an image to be recorded is input to the image forming apparatus 1, the control unit of the image forming apparatus 1 uniformly charges the surface of the photosensitive drum 30 to a predetermined potential by the charging roller 32 based on the received image signal. Then, the exposure device 34 irradiates the surface of the photosensitive drum 30 with laser light to form an electrostatic latent image.

  In the developing device 40, the developer generated by mixing and stirring the toner and the carrier to be charged is carried on the developing roller 45. When the developer is transported to a region facing the photosensitive drum 30 by the rotation of the developing roller 45, toner in the developer carried on the developing roller 45 is formed on the outer peripheral surface of the photosensitive drum 30. The electrostatic latent image is developed and the electrostatic latent image is developed.

  The toner image formed in this way is primarily transferred from the photosensitive drum 30 to the transfer belt 21 in a region where the photosensitive drum 30 and the transfer belt 21 face each other. On the transfer belt 21, toner images formed on the four photosensitive drums 30 are sequentially stacked to form one stacked toner image. The laminated toner image is secondarily transferred to the paper P conveyed from the recording medium conveying device 10 in the secondary transfer region R where the suspension roller 21d and the secondary transfer roller 24 face each other.

  The sheet P on which the laminated toner image is secondarily transferred is conveyed to the fixing device 100. In the fixing device 100, the paper P passes through a nip portion N formed between the fixing belt 110 and the pressure roller 120. In the nip portion N, heat and pressure are applied to the paper P, whereby the laminated toner image is melted and fixed on the paper P. Thereafter, the paper P is discharged to the outside of the image forming apparatus 1 by the discharge rollers 52 and 54. On the other hand, after the laminated toner image is secondarily transferred to the paper P, the transfer belt 21 may remove the toner remaining on the transfer belt 21 with a belt cleaning device.

  Hereinafter, the fixing device will be described in detail. FIG. 2 is a side view of the fixing device as viewed from the conveyance direction. FIG. 3 is a cross-sectional view schematically showing the structure of the fixing device. The fixing device 100 includes a pair of belt guides 115, a heating element 113, and a pressure contact member 130 in addition to the above-described fixing belt 110 and pressure roller 120.

  The fixing belt 110 is endless and has a width wider than the width of the paper P. The fixing belt 110 has an end portion in the width direction orthogonal (crossing) the conveyance direction D as an opening end portion 110a. FIG. 4 is a cross-sectional view along the width direction schematically showing the fixing belt and the belt guide. FIG. 5 is a perspective view showing cross sections of the fixing belt and the belt guide. A wall 110b is formed at the opening end 110a of the fixing belt 110 so as to protrude inward from the inner peripheral surface over the entire circumference in the circumferential direction. In this embodiment, the wall part 110b is formed in the position of the inner side of the width direction only predetermined distance from the end surface of the opening edge part 110a. The wall portion 110b is disposed between the belt guide 115 and the pressure contact member 130. For example, the wall portion 110b has a thickness of about 1 mm to 3 mm in the width direction and a height of about 1 mm to 3 mm in the radial direction orthogonal to the width direction. The fixing belt 110 includes, for example, a base layer that forms the inner peripheral surface 110c, a surface release layer that forms the outer peripheral surface 110d, and an elastic layer that is intermediate between the base layer and the surface release layer. The base layer of the fixing belt 110 can be composed of, for example, a Ni—Cu composite layer having a thickness of 10 to 100 μm, a Ni single layer, a SUS single layer, a PI resin single layer, or the like. The intermediate layer of the fixing belt 110 may be formed of, for example, a heat-resistant rubber layer (Si) having a thickness of 150 to 350 μm. The surface release layer of the fixing belt 110 is made of, for example, PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) having a thickness of 10 to 100 μm, PTFE (tetrafluoroethylene resin), or the like.

  A lubricant is applied to the inner peripheral surface 110 c of the fixing belt 110. The lubricant may be, for example, a fluorine-based lubricant having heat resistance and fluidity.

  As shown in FIG. 3, the heating element 113 heats the fixing belt 110 from the inner peripheral surface 110c side. The heating element 113 is disposed in the inner space of the fixing belt 110 along the width direction of the fixing belt 110. In the present embodiment, the heating element 113 is configured by two long halogen lamps 113 a, and the longitudinal direction of the halogen lamp 113 a coincides with the width direction of the fixing belt 110.

  The pair of belt guides 115 supports the open end portions 110 a at both ends of the fixing belt 110. As shown in FIGS. 4 and 5, the belt guide 115 has a contact surface 115c and a support surface 115d. The contact surface 115 c can slidably contact the end surface of the opening end portion 110 a of the fixing belt 110. The support surface 115 d protrudes from the contact surface 115 c and can slidably contact the inner peripheral surface 110 c of the opening end portion 110 a of the fixing belt 110. In the present embodiment, the belt guide 115 includes an annular plate-like portion 115a and a cylindrical portion 115b protruding from the plate-like portion 115a. The outer diameter of the cylindrical portion 115b is smaller than the outer diameter of the plate-like portion 115a. A contact surface 115c is constituted by the surface of the plate-like portion 115a, and a support surface 115d is constituted by the outer peripheral surface of the cylindrical portion 115b. Further, the axial length of the cylindrical portion 115b is, for example, the same as or smaller than the distance from the end surface of the opening end portion 110a of the fixing belt 110 to the wall portion 110b. The arithmetic average roughness (Ra) of the contact surface 115c is, for example, 2.6 μm or less. Further, the ten-point average roughness (Rz) of the contact surface 115c is, for example, 38.3 μm or less. An entering corner 115e between the contact surface 115c and the support surface 115d is formed by a curved surface continuous to the contact surface 115c and the support surface 115d. The curvature radius (r) of the corner 115e is, for example, not less than 0.8 mm and not more than 2 mm. The pair of belt guides 115 are rotatably supported by a pair of frames 117 and 117, for example.

  The pressure contact member 130 is disposed on the inner peripheral surface 110c side of the fixing belt 110, and is slidable with respect to the inner peripheral surface 110c of the fixing belt 110 via a lubricant. The pressure contact member 130 sandwiches the fixing belt 110 in cooperation with the pressure roller 120. The pressure contact member 130 in this embodiment includes a support 131 and a holding member 133. The support 131 is, for example, a long member having a substantially U-shaped cross section (substantially U-shaped cross section), and has a length that is larger in the longitudinal direction than the width of the fixing belt 110. The support 131 is supported by the pair of frames 117 and 117 and supports the holding member 133. The support 131 includes, for example, steel materials such as SECC (electrogalvanized steel plate), SGHC (hot dip galvanized steel plate), and SUS (stainless steel), LCP (liquid crystal polymer), PEEK (polyether ether ketone resin), PTFE (polyethylene). It is formed by integral molding of a heat-resistant resin material such as tetrafluoroethylene resin) or PET (polyethylene terephthalate resin), or a heat-resistant resin material and a steel material.

  The holding member 133 is a long member having an accommodating portion 133a into which the support 131 is fitted, and has a substantially U-shaped cross section (a substantially U-shaped cross section) in a region where the nip portion N is formed. The holding member 133 is formed of a resin having heat resistance and chemical resistance such as LCP, PEEK, and PPS (polyphenylene sulfide resin). The length of the holding member 133 in the longitudinal direction is shorter than the width of the fixing belt 110 and longer than the width of the pressure roller 120. The holding member 133 is formed with concave holder portions 133b and 133c on the upstream side and the downstream side in the transport direction D. The holding member 133 includes a plate 137 supported by the holder portions 133b and 133c. The plate 137 covers the surface of the holding member 133 facing the pressure roller 120 and is slidable with respect to the inner peripheral surface 110 c of the fixing belt 110. For example, the surface of the plate 137 facing the pressure roller 210 is formed flat.

  In the present embodiment, the fixing belt 110 is sandwiched between the surface of the holding member 133 on which the plate 137 is supported and the pressure roller 120. That is, when the pressure roller 120 is pressed against the holding member 133 including the plate 137 via the fixing belt 110, a nip portion N is formed between the outer peripheral surface 110 d of the fixing belt 110 and the pressure roller 120. . In this case, as shown in FIG. 2, the fixing belt 110 has a pressure area K1 and a non-pressure area K2 in the width direction. The pressure region K1 is a region where the nip portion N can be formed, and is a region facing the pressure roller 120. The non-pressure area K2 is an area that is not pressed by the pressure roller 120, and is an area outside the nip portion N in the width direction.

  The pressure roller 120 has a cylindrical outer peripheral surface 120a, and is formed of an elastic body such as silicon rubber. The rotation of the pressure roller 120 is controlled by a drive source (not shown) connected to the rotation shaft 121. When the pressure roller 120 is driven to rotate, the fixing belt 110 is driven to rotate. For example, in FIG. 3, the pressure roller 120 rotates clockwise in the drawing so that the paper P passes through the nip portion N along the transport direction D. When the paper P passes through the nip portion N, it is pressed toward the fixing belt 110 by the pressure roller 120.

  Returning to the description of the holding member 133 again. Groove forming portions 134 and 135 are integrally formed at both ends of the holding member 133 in the width direction. That is, the groove forming portions 134 and 135 are formed of a resin having heat resistance and chemical resistance such as LCP, PEEK, and PPS. The groove forming portion 134 is formed in the holding member 133 on the upstream side of the plate 137 in the rotation direction of the fixing belt 110. The groove forming portion 135 is formed on the holding member 133 on the downstream side of the plate 137 in the rotation direction of the fixing belt 110. The groove forming portions 134 and 135 have a sliding surface with the fixing belt 110, and are slidable with respect to the inner peripheral surface 110 c of the fixing belt 110.

  FIG. 6 is an enlarged side view of the fixing device as viewed from the upstream side in the conveyance direction. FIG. 7 is an enlarged side view of the fixing device as viewed from the downstream side in the conveyance direction. Groove portions are provided on the sliding surfaces of the groove forming portions 134 and 135, respectively. In the present embodiment, a plurality of ribs 134a are erected on the upstream groove forming portion 134, and a plurality of groove portions 134b are formed by gaps between adjacent ribs 134a. A sliding surface with the fixing belt 110 is configured by the tip surface 134c of the rib 134a. In addition, a plurality of ribs 135a are erected in the groove forming portion 135 on the downstream side, and a plurality of groove portions 135b are formed by gaps between adjacent ribs 135a. Further, a sliding surface with the fixing belt 110 is constituted by the front end surface 135c of the rib 135a. In the illustrated example, the range in the rotational direction of the upstream groove 134b is smaller than that of the downstream groove 135b in the rotational direction. Therefore, the light generated from the heating element 113 can efficiently irradiate the upstream side of the nip portion N.

  The grooves 134b and 135b are inclined at a constant angle θ inward in the width direction toward the rotation direction of the fixing belt 110 corresponding to the transport direction D. For example, the grooves 134 b and 135 b may be inclined at an angle of 45 ° or less with respect to the rotation direction of the fixing belt 110.

  The groove forming portions 134 and 135 are both formed across the pressure region K1 and the non-pressure region K2 in the width direction of the holding member 133. Therefore, at least a part of the plurality of groove portions 134b and 135b straddles the pressurizing region K1 and the non-pressurizing region K2. That is, in some of the grooves 134b and 135b, the upstream side of the grooves 134b and 135b is located in the non-pressurized area K2, and the downstream side of the grooves 134b and 135b is located in the pressurized area K1.

  Further, the holding member 133 further has a groove 136 between the groove forming part 134 and the groove forming part 135 in the transport direction D. The groove 136 is formed on the surface of the holding member 133 facing the pressure roller 120 side. Similarly to the grooves 134 b and 135 b, the groove 136 may be inclined at a predetermined angle θ inward in the width direction toward the rotation direction of the fixing belt 110. In the present embodiment, the groove 136 is formed only in the non-pressurized region K2.

  A radiation preventing member is disposed between the pressure contact member 130 and the heating element 113. In the present embodiment, a radiation preventing member is formed by the reflector 119. The reflector 119 reflects the light radiated from the heating element 113. The reflector 119 is made of, for example, an aluminum steel sheet metal. As shown in FIG. 3, the reflector 119 entirely covers the pressure contact member 130, and includes a first portion 119 a that covers the groove forming portion 134, a second portion 119 b that covers the support 131, and a groove forming portion. 135 and a third portion 119c covering 135. The first portion 119a and the third portion 119c are inclined so as to reflect light upstream in the transport direction.

  Next, the positional relationship between the nip portion N and the groove forming portions 134 and 135 with respect to the support surface 115d in the belt guide 115 will be described. As shown in FIG. 3, when viewed from the width direction, in the groove forming portion 134 provided on the upstream side of the plate 137, the sliding surface (that is, the tip surface 134c of the rib 134a) extends along the support surface 115d. Is formed. Therefore, in this region, the inner peripheral surface 110c of the fixing belt 110 can contact both the groove forming portion 134 and the support surface 115d.

  FIG. 8 is a schematic diagram for explaining the positional relationship among the belt guide, the pressure roller, and the pressure contact member in the fixing device. As shown in FIG. 8, when viewed from the width direction, the surface of the plate 137 on the pressure roller 120 side is separated from the support surface 115d, and is shifted from the support surface 115d to the pressure roller 120 side. doing. That is, when viewed from the width direction, the nip portion N and the support surface 115d are separated from each other. For example, the minimum gap L between the surface on the pressure roller 120 side of the plate 137 and the support surface 115d may be about 5 mm or less. In the present embodiment, since the surface of the plate 137 on the side of the pressure roller 120 is formed flat, the minimum gap L is the nip surface normal H1 passing through the rotation center C1 of the belt guide 115 when viewed from the width direction. Formed on top.

  Further, when viewed from the width direction, the rotation center C1 of the belt guide 115 is arranged to be shifted to the upstream side in the transport direction D with respect to the nip surface normal H2 passing through the rotation center C2 of the pressure roller 120. That is, as illustrated, the nip surface normal line H1 is shifted to the upstream side in the transport direction D with respect to the nip surface normal line H2. As an example, these deviations may be about 1 mm to 10 mm.

  In the present embodiment, the plate 137 that determines the position of the nip portion N is shifted to the downstream side in the transport direction D with respect to the rotation center C <b> 1 of the belt guide 115. As a result, as shown in FIGS. 3 and 6, the sliding surface of the groove forming portion 135 (that is, the front end surface 135c of the rib 135a) provided on the downstream side in the transport direction D from the plate 137 is viewed from the width direction. The belt guide 115 is in contact with the inner peripheral surface 110c of the fixing belt 110 outside the support surface 115d of the belt guide 115. In addition, when the fixing belt 110 is arranged in a shape along the pressure contact member 130 with the fixing belt 110 mounted on the belt guide 115, the inner peripheral surface 110 c of the fixing belt 110 and the sliding surface of the groove forming portion 135 are arranged. The error G in the radial direction may be about ± 1 mm.

  In such a fixing device 100, the paper P can be conveyed so as to pass through the nip portion N while being sandwiched between the fixing belt 110 and the pressure roller 120. The toner image formed on the paper P is fixed by the fixing belt 110 heated by the heating element 113. Here, the lubricant applied between the fixing belt 110 and the pressure contact member 130 moves in the rotation direction as the fixing belt 110 rotates. In this case, on the sliding surface of the pressure contact member 130 with the fixing belt 110, the lubricant can move inward in the width direction along the grooves 134b and 135b. And the groove parts 134b and 135b straddle the pressurization area | region K1 and the non-pressurization area | region K2. Thereby, even if the lubricant moves from the pressurization region K1 to the non-pressurization region K2, the lubricant can be moved again to the pressurization region K1 by the grooves 134b and 135b. Therefore, the lubricant can be prevented from flowing out from the inner space of the fixing belt 110 to the outside.

  In one aspect, the grooves 134 b and 135 b are inclined at an angle of 45 ° or less with respect to the rotation direction of the fixing belt 110. According to this configuration, the frictional resistance between the grooves 134b and 135b and the inner peripheral surface 110c of the fixing belt 110 can be suppressed low, and the torque increase of the fixing belt 110 can be suppressed.

  In one aspect, the material forming the ribs 134a and 135a is a resin having heat resistance and chemical resistance. According to this structure, it is suppressed that the groove parts 134b and 135b are damaged by the heating by the heat generating body 113 and the lubricant.

  On one side, the support surface 115d of the belt guide 115 and the nip portion N are separated from each other when viewed from the width direction. According to this configuration, the fixing belt 110 and the support surface 115d do not interfere with each other at the position where the nip portion N is formed, and the load on the fixing belt 110 can be reduced. Thereby, deterioration of the fixing belt 110 can be suppressed.

  Further, on one side surface, the groove forming portion 135 is provided on the downstream side in the transport direction D of the paper P from the plate 137. The front end surface 135c of the groove forming portion 135 is in contact with the inner peripheral surface 110c of the fixing belt 110 on the outer side of the support surface 115d of the belt guide 115 when viewed from the width direction. In this configuration, the leading end surface 135c of the groove forming portion 135 projects to the downstream side in the transport direction D, and the groove forming portion 135 and the inner peripheral surface 110c of the fixing belt 110 are close to each other in the vicinity of the exit of the nip portion N. Slide together. As a result, the lubricant can be moved more reliably.

  In one aspect, a wall portion 110b that protrudes inward from the inner peripheral surface 110c is formed on the opening end portion 110a of the fixing belt 110 over the entire circumference in the circumferential direction. The wall portion 110b is disposed between the belt guide 115 and the groove forming portions 134 and 135. According to this configuration, even if the lubricant moves to the outside in the width direction with respect to the groove forming portions 134 and 135, the lubricant is prevented from flowing out of the fixing belt 110.

  On one side, a reflector 119 is disposed between the pressure contact member 130 and the heating element 113. According to this configuration, the fixing belt 110 can be efficiently heated by the heating element 113.

  In one aspect, the arithmetic average roughness Ra of the contact surface 115c may be 2.6 μm or less, and the ten-point average roughness Rz of the contact surface 115c may be 38.3 μm or less. According to this configuration, the frictional resistance between the end portion of the fixing belt 110 and the contact surface 115c is reduced, and generation of abnormal noise or the like can be suppressed.

  In one aspect, the radius of curvature of the corner 115e between the contact surface 115c and the support surface 115d may be not less than 0.8 mm and not more than 2 mm. According to this configuration, the end portion of the fixing belt 110 can be brought into contact with the contact surface 115c in a state of being curved outward in the radial direction. Therefore, the force applied from the fixing belt 110 to the contact surface 115c is reduced. For example, consider the case where the end of the fixing belt 110 abuts against the abutment surface 115c without being bent. In this case, there is a possibility that the rotation of the fixing belt 110 is hindered by excessively applying a force from the fixing belt 110 to the contact surface 115c. When the rotation of the fixing belt 110 is hindered, the fixing belt may continue to rotate while repeating accumulation and elimination of distortion. In this case, abnormal noise may occur when the distortion of the fixing belt is eliminated. As in the present embodiment, when the force applied from the fixing belt 110 to the contact surface 115c is reduced, the rotation of the fixing belt is hardly hindered and the fixing belt is hardly distorted.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, a specific structure is not restricted to this embodiment.

  For example, although the example which has arrange | positioned the groove formation part in both the upstream of the rotation direction of the plate 137 and the downstream was shown, it is not limited to this. For example, the groove forming part may be formed only on the downstream side of the plate.

  Moreover, although the groove part 134b, 135b showed the example inclined with the fixed angle (theta) with respect to the conveyance direction, it is not limited to this. That is, the groove part does not need to be formed linearly. For example, the groove part may be curved. In this case, for example, the groove may be curved so that the angle with respect to the transport direction gradually increases.

  Further, although the example in which the groove forming portions 134 and 135 are integrally formed with the holding member 133 is shown, the present invention is not limited to this. For example, a groove forming member formed as a separate body may be attached to the holding member.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 100 ... Fixing apparatus, 110 ... Fixing belt, 110c ... Inner peripheral surface, 113 ... Heat generating body, 115 ... Belt guide, 115c ... Contact surface, 115d ... Support surface, 120 ... Pressure roller, 130 ... pressure contact member, 133 ... holding member (pressure contact part), 134, 135 ... groove forming part, 134b, 135b ... groove part, 134c, 135c ... tip surface (sliding surface), 137 ... plate (pressure contact part), D ... transport Direction, K1 ... pressure area, K2 ... non-pressure area, N ... nip, P ... paper (recording material).

Claims (12)

A fixing device that conveys a recording material on which a toner image is formed in a conveying direction and fixes the toner image on the recording material;
An endless fixing belt having an end in the width direction intersecting the transport direction as an open end; and
A heating element disposed inside the fixing belt;
A pressure roller that forms a nip portion with the outer peripheral surface of the fixing belt;
A pressure contact portion that is slidably disposed on the inner peripheral surface of the fixing belt via a lubricant and is pressed against the pressure roller via the fixing belt;
A groove forming portion that is slidably disposed on the inner peripheral surface of the fixing belt via a lubricant;
A contact surface slidably contacting the end surface of the opening end of the fixing belt; a support surface protruding from the contact surface and slidably contacting the inner peripheral surface of the opening end of the fixing belt; And a pair of belt guides that support the opening end of the fixing belt,
On the sliding surface of the groove forming portion with the fixing belt, a groove portion that is inclined inward in the width direction toward the rotation direction of the fixing belt corresponding to the transport direction is provided.
The groove portion is formed across a pressure region where the nip portion is formed in a width direction of the pressure contact portion and a non-pressure region outside the nip portion in the width direction. Fixing device.   The fixing device according to claim 1, wherein the groove portion is inclined at an angle of 45 ° or less with respect to the rotation direction of the fixing belt.   The fixing device according to claim 1, wherein a material forming the groove forming portion is a resin having heat resistance and chemical resistance.   The fixing device according to claim 3, wherein the material is any one of a liquid crystal polymer, a polyether ether ketone resin, and a polyphenylene sulfide resin.   The fixing device according to claim 1, wherein the nip portion and the support surface are separated from each other when viewed from the width direction. The groove forming portion is provided on the downstream side in the conveyance direction of the recording material from the press contact portion,
The sliding surface of the groove forming portion is in contact with the inner peripheral surface of the fixing belt outside the support surface of the belt guide as viewed from the width direction. The fixing device according to claim 5. The fixing belt is formed with a wall portion protruding inward from the inner peripheral surface over the entire circumference in the circumferential direction.
The fixing device according to claim 1, wherein the wall portion is disposed between the belt guide and the groove forming portion.   The fixing device according to claim 1, wherein a radiation preventing member is disposed between the pressure contact portion and the groove forming portion and the heating element.   The fixing device according to claim 8, wherein the radiation preventing member is a reflecting plate that reflects light radiated from the heating element.   The fixing device according to claim 1, wherein an arithmetic average roughness Ra of the contact surface is 2.6 μm or less.   The fixing device according to claim 1, wherein a ten-point average roughness Rz of the contact surface is 38.3 μm or less.   The fixing device according to claim 1, wherein a radius of curvature of a corner of the contact surface and the support surface is 0.8 mm or more and 2 mm or less.

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