JP2018141835A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of restraining a belt from being biased to one side.SOLUTION: A fixing device comprises: a first guide face 211 for guiding an inner peripheral face of a fixing belt 110 at a right end part; a second guide face 221 for guiding an inner peripheral face of the fixing belt 110 at a left end part; and a center guide face 251 for guiding an inner peripheral face of the fixing belt 110 at a center part in a left-and-right direction. When setting a plane passing a center of a nip formation face 131N in a back and forth direction, and orthogonal to a plane P5 connecting a front end edge N1 and a rear end edge N2 of the nip formation face 131N as a first plane P1, and when setting a plane passing a center between the nip formation face 131N and the center guide face 251 on the first plane P1, and orthogonal to the first plane P1 as a second plane P2, the center guide face 251 is more remote from an intersection C rather than the first guide face 211 and the second guide face 221 on a third plane P3 which passes the intersection C and in which an inclination angle with respect to the first plane P1 is equal to an inclination angle with respect to the second plane P2, in a region more on a front side from the first plane P1 and more on an upper side from the second plane P2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device including an endless belt.

  2. Description of the Related Art Conventionally, a fixing device provided in an image forming apparatus includes an endless belt and a guide that guides the rotation of the belt. For example, in the fixing device described in Patent Document 1, in order to guide the rotation of the belt, a pair of end guides that guide the inner peripheral surface of the belt are provided at both ends of the belt.

JP-A-4-221983

  However, in the above-described technique, one end guide may hit the inner peripheral surface of the belt strongly due to variations in the dimensions of the pair of end guides. This sometimes caused the belt to move to one side.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of suppressing the belt from moving to one side.

In order to achieve the above-described object, a fixing device of the present invention has an endless belt, a nip forming surface that contacts an inner peripheral surface of the belt, a nip member that is long in a first direction, and a nip formation. A rotating body sandwiching the belt between the first surface, a first end guide having a first guide surface for guiding an inner peripheral surface of one end portion in the first direction of the belt, and the other end in the first direction of the belt A second end guide having a second guide surface for guiding the inner peripheral surface of the belt portion, and a central guide having a central guide surface for guiding the inner peripheral surface of the central portion in the first direction of the belt. .
A plane perpendicular to the plane connecting the upstream edge and the downstream edge in the second direction of the nip forming surface through the center of the nip forming surface in the second direction, which is the moving direction of the belt on the nip forming surface, is the first. A plane, a plane passing through the center of the nip forming surface on the first plane and the center guide surface and perpendicular to the first plane is the second plane, upstream from the first plane in the second direction, and nip formed from the second plane In a region far from the surface, a plane that passes through the intersection line and has the same inclination angle with respect to the first plane and the inclination angle with respect to the second plane is defined as a third plane, and the central guide surface on the third plane in the region. Is farther from the intersection line than the first guide surface and the second guide surface.

  In the fixing device configured as described above, the belt is directed between the nip forming surface and the rotating body in a region upstream of the first plane in the second direction and closer to the nip forming surface than the second plane. The belt hits each guide surface strongly. Then, in the region upstream of the first plane in the second direction and farther from the nip forming surface than the second plane, the contact of the belt with each guide is weakened. In the region upstream of the first plane in the second direction and farther from the nip forming surface than the second plane, particularly in the cross section of the third plane, the central guide plane is more than the first guide plane or the second guide plane. By being located outside, the central guide surface can be preferentially applied to the belt. As a result, it is possible to prevent the belt from striking strongly against one of the first guide surface and the second guide surface and moving toward one of the first directions.

  According to the present invention, the belt can be prevented from approaching either one.

1 is a diagram illustrating a schematic configuration of a laser printer including a fixing device according to an embodiment of the present invention. It is sectional drawing cut by the surface which passes along the 2nd edge part guide which shows a fixing device. It is a perspective view which shows a nip member. It is a perspective view which shows a heating member. It is sectional drawing in the 3rd plane of a heating member. FIG. 9 is a cross-sectional view taken along a plane passing between a second end portion guide and a central guide, showing a fixing device in a first modification. It is sectional drawing of the cover member and center guide which were cut by the plane which passes along the 1st guide rib and the 2nd guide rib in the 1st modification. It is sectional drawing in the 3rd plane of the heating member in a 2nd modification.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, the direction will be described with reference to the user who uses the laser printer 1. Specifically, the right side of FIG. 1 that is the front side when viewed from the user is “front”, the left side of FIG. 1 that is the back side when viewed from the user is “rear”, and the front side of FIG. "The back side of the paper is" right ". Further, the vertical direction in FIG.

  As shown in FIG. 1, the laser printer 1 mainly includes a housing 2, a paper feeding unit 3 that supplies paper P, a process unit 4 for forming a toner image on the paper P, and a fixing device 100. In preparation.

  The paper feed unit 3 is provided in the lower part of the housing 2, and includes a paper feed tray 31 that stores the paper P, a paper feed mechanism 32 that transports the paper P in the paper feed tray 31 toward the process unit 4, It has.

  The process unit 4 is accommodated in the housing 2 and includes an exposure device 5, a process cartridge 6, and a transfer roller 63.

  The exposure device 5 is arranged at the upper part in the housing 2 and irradiates the surface of the photosensitive drum 61 with laser light by high-speed scanning.

  The process cartridge 6 is disposed below the exposure device 5 and is detachable from the housing 2. The process cartridge 6 supplies a photosensitive drum 61 on which an electrostatic latent image is formed, a charger 62, a toner storage unit 65 for storing toner, and supply of toner in the toner storage unit 65 to the photosensitive drum 61. A roller 66 and a developing roller 64 are provided.

  In the process cartridge 6, the charger 62 uniformly charges the surface of the rotating photosensitive drum 61. The exposure device 5 emits laser light to the surface of the photosensitive drum 61 to expose the surface of the photosensitive drum 61, thereby forming an electrostatic latent image based on image data on the surface of the photosensitive drum 61.

  Next, the rotationally driven developing roller 64 supplies toner to the electrostatic latent image on the photosensitive drum 61 to form a toner image on the surface of the photosensitive drum 61. Thereafter, the toner image carried on the surface of the photosensitive drum 61 is attracted to the transfer roller 63 and transferred onto the paper P when the paper P is conveyed between the photosensitive drum 61 and the transfer roller 63. The

  The fixing device 100 is provided behind the process cartridge 6. The toner image transferred onto the paper P passes through the fixing device 100 and is thermally fixed onto the paper P. The paper P on which the toner image is thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

  As illustrated in FIG. 2, the fixing device 100 is an example of a rotating member that is disposed below the heating member H and the heating member H and conveys the paper P from the front to the back with the heating member H. And a pressure roller 140.

  The heating member H mainly includes a fixing belt 110 as an example of a belt, a halogen lamp 120, a nip member 130, a reflecting member 150, a stay 160, a cover member 170, and a guide member 200.

  The fixing belt 110 is an endless belt having heat resistance and flexibility. The fixing belt 110 is made of, for example, stainless steel and extends long in the left-right direction. A coating layer such as a fluororesin is formed on the outer peripheral surface of the fixing belt 110 to facilitate the peeling of the paper P.

  The halogen lamp 120 is a heater that emits light when energized and heats the nip member 130 by radiant heat, and is disposed inside the fixing belt 110.

  The nip member 130 is a plate-like member that receives radiant heat from the halogen lamp 120. As shown in FIG. 3, the nip member 130 is a member that is long in the left-right direction, which is an example of the first direction. The nip member 130 is a flat plate-like portion 131 that is long in the left-right direction, a front-side extension portion 132 that extends upward from the front end portion of the plate-like portion 131, and an upward extension from the rear end portion of the plate-like portion 131. And a rear extension 133. The nip member 130 is made of a metal having a high thermal conductivity, such as an aluminum plate.

  Returning to FIG. 2, the nip member 130 is disposed inside the fixing belt 110, and the lower surface of the plate-like portion 131 is in contact with the inner peripheral surface of the fixing belt 110.

  The pressure roller 140 is disposed below the nip member 130 and sandwiches the fixing belt 110 with the plate-like portion 131 of the nip member 130. Thus, a portion of the lower surface of the plate-like portion 131 that sandwiches the fixing belt 110 with the pressure roller 140 is a nip forming surface 131N.

  The pressure roller 140 is configured to be driven to rotate counterclockwise in FIG. Thus, the fixing belt 110 is driven to rotate clockwise in FIG. 2 by the frictional force with the fixing belt 110 or the paper P. Therefore, the moving direction of the fixing belt 110 on the nip forming surface 131N is a direction from front to back. In the following description, the moving direction of the fixing belt 110 on the nip forming surface 131N, that is, the direction from the front to the rear is referred to as a “second direction”.

  The reflecting member 150 is a member that reflects the radiant heat from the halogen lamp 120 toward the nip member 130, and is disposed so as to surround the halogen lamp 120 inside the fixing belt 110.

  The stay 160 is a member that suppresses deformation of the nip member 130 to which a load is applied from the pressure roller 140 by supporting the nip member 130 via the reflecting member 150, and is formed so as to cover the reflecting member 150. The stay 160 is formed by bending a metal having relatively high rigidity, such as a steel plate.

  The cover member 170 is a member that holds the halogen lamp 120, the nip member 130, the reflection member 150, and the stay 160. The cover member 170 is formed of a resin having a lower thermal conductivity than the nip member 130 and the stay 160.

  The cover member 170 is formed so as to cover the stay 160 on the side opposite to the halogen lamp 120 with the stay 160 interposed therebetween. The cover member 170 includes an upper wall portion 171 provided on the stay 160, a front wall portion 172 extending downward from the front end of the upper wall portion 171, and a rear wall portion 173 extending downward from the rear end of the upper wall portion 171. And a downstream guide portion 174.

  The downstream guide part 174 protrudes rearward from the rear wall part 173. The surface of the downstream guide portion 174 that faces the inner peripheral surface of the fixing belt 110 is a downstream guide surface 174 </ b> A that contacts the inner peripheral surface of the fixing belt 110 and guides the rotation of the fixing belt 110. The downstream guide surface 174 </ b> A is formed so as to receive the inner peripheral surface of the fixing belt 110 exiting from the nip between the nip member 130 and the pressure roller 140 as the fixing belt 110 rotates.

  As shown in FIG. 4, the downstream guide surface 174 </ b> A is provided in a range from the left end to the right end of the cover member 170.

  The guide member 200 includes a first end guide 210 provided at the right end of the cover member 170, a second end guide 220 provided at the left end of the cover member 170, and the left-right direction of the first end guide 210. The first end surface restricting portion 230 provided on the outer side, the second end surface restricting portion 240 provided on the outer side in the left-right direction of the second end guide 220, and the center guide 250 provided in the center portion in the left-right direction of the cover member 170. And.

  The first end portion guide 210 and the second end portion guide 220 are provided from the downstream guide portion 174 to the front side of the front wall portion 172 through the upper wall portion 171. The first end guide 210 and the second end guide 220 are fixed to the cover member 170.

  The surface of the first end guide 210 facing the inner peripheral surface of the fixing belt 110 is in contact with the inner peripheral surface of the right end portion which is one end portion in the left-right direction of the fixing belt 110 to guide the rotation of the fixing belt 110. One guide surface 211 is formed.

  Further, the surface of the second end guide 220 facing the inner peripheral surface of the fixing belt 110 is in contact with the inner peripheral surface of the left end portion of the fixing belt 110 and the second guide surface 221 that guides the rotation of the fixing belt 110. It has become.

  The first end surface regulating portion 230 is formed in a wall shape that protrudes above and in the front-rear direction from the first guide surface 211. The first end surface regulating unit 230 has a regulating surface 231 that faces the right end surface of the fixing belt 110.

  The second end surface regulating portion 240 is formed in a wall shape that protrudes above and in the front-rear direction from the second guide surface 221. The second end surface regulating unit 240 has a regulating surface 241 that faces the left end surface of the fixing belt 110.

  The central guide 250 is provided from the downstream guide portion 174 to the front side of the front wall portion 172 through the upper wall portion 171. The central guide 250 is fixed to the cover member 170.

  The surface of the central guide 250 facing the inner peripheral surface of the fixing belt 110 is a central guide surface 251 that contacts the inner peripheral surface of the central portion in the left-right direction of the fixing belt 110 and guides the rotation of the fixing belt 110. .

  Next, the first end guide 210, the second end guide 220, and the center guide 250 will be described in detail.

  The first end guide 210 is disposed adjacent to the inner side in the left-right direction of the first end surface restricting portion 230. Therefore, the first guide surface 211 is a surface located on the outermost side in the left-right direction among the surfaces that guide the inner peripheral surface of the fixing belt 110 on the right side of the center in the left-right direction.

  The second end guide 220 is disposed adjacent to the inner side in the left-right direction of the second end surface restricting portion 240. Accordingly, the second guide surface 221 is a surface located on the outermost side in the left-right direction among the surfaces that guide the inner peripheral surface of the fixing belt 110 on the left side from the center in the left-right direction.

  The first guide surface 211, the second guide surface 221 and the central guide surface 251 are each a smooth curved surface. Since the first guide surface 211 and the second guide surface 221 have substantially symmetrical shapes, only the second guide surface 221 is shown in FIG.

  Here, as shown in FIG. 2, the front end edge N1 which is the upstream end edge in the second direction of the nip forming surface 131N and the rear end which is the downstream end edge pass through the center of the nip forming surface 131N in the second direction. A plane orthogonal to the plane P5 connecting the edge N2 is defined as a first plane P1. A plane that passes through the center of the nip forming surface 131N and the central guide surface 251 on the first plane P1 and is orthogonal to the first plane P1 is defined as a second plane P2. Then, the upstream side in the second direction from the first plane P1, that is, the front side, and the far side from the nip forming surface 131N from the second plane P2, that is, the upper side area is defined as a first area A1. In the first region A1, a plane passing through the intersection line C between the first plane P1 and the second plane P2 and having the same inclination angle with respect to the first plane P1 and the inclination angle with respect to the second plane P2, that is, with respect to the first plane P1 A plane inclined by 45 degrees is defined as a third plane P3. Further, a region on the downstream side in the second direction from the first plane P1, that is, the rear side, and on the side farther from the nip forming surface 131N than the second plane P2, that is, on the upper side is defined as a second region A2. In the second region A2, a plane that passes through the intersection line C between the first plane P1 and the second plane P2 and is inclined 45 degrees with respect to the first plane P1 is defined as a fourth plane P4. Further, the upstream side in the second direction from the first plane P1, that is, the front side, and the side closer to the nip forming surface 131N than the second plane P2, that is, the lower side is defined as a third area A3.

  The center guide 250 protrudes above the first end guide 210 and the second end guide 220 within a predetermined range across the first plane P1 when viewed from the left-right direction.

  As a result, in the first region A1, the central guide surface 251 passes through the intersection line C between the first plane P1 and the second plane P2 and is inclined with respect to the first plane P1. And it is farther from the intersection line C than the second guide surface 221. In the present embodiment, the central guide surface 251 is farther from the intersection line C than the first guide surface 211 and the second guide surface 221 on the third plane P3 in the first region A1. In the first region A1, the central guide surface 251 is more than the first guide surface 211 and the second guide surface 221 on any plane that passes through the intersection line C and is inclined by 0 to 45 degrees with respect to the first plane P1. Is far from intersection C.

  Also in the second region A2, the central guide surface 251 passes through the intersection line C between the first plane P1 and the second plane P2 and is inclined at 0 to 45 degrees with respect to the first plane P1. It is farther from the intersection line C than the first guide surface 211 and the second guide surface 221.

  That is, in a region farther from the nip forming surface 131N than the second plane P2, within a range between the third plane P3 and the fourth plane P4 (a plane inclined by ± 45 degrees with respect to the first plane P1 through the intersection line C). In the range between the central guide surface 251 and the first guide surface 211 and the second guide surface 221, the central guide surface 251 is farther from the intersection line C.

  The amount of projection of the central guide surface 251 with respect to the guide surfaces 211 and 221, that is, the distance between the central guide surface 251 and the intersection line C on the plane passing through the intersection line C, and the distance between the guide surfaces 211 and 221 and the intersection line C The difference in distance is the largest in the first area A1.

  Specifically, the difference between the distance between the central guide surface 251 and the intersection line C and the distance between each guide surface 211 and 221 and the intersection line C in the second region A2 is closer to the first plane P1 from the fourth plane P4. Gradually grows. Further, the difference between the distance between the central guide surface 251 and the intersection line C in the first region A1 and the distance between each guide surface 211, 221 and the intersection line C gradually increases from the first plane P1 toward the third plane P3. growing. That is, the maximum value of the difference between the distance between the central guide surface 251 and the intersection line C in the second region A2 and the distance between each guide surface 211, 221 and the intersection line C is the central guide surface 251 in the first region A1. And the distance between the intersection line C and the maximum difference between the distances between the guide surfaces 211 and 221 and the intersection line C. The difference between the distance between the central guide surface 251 and the intersection line C and the distance between each guide surface 211, 221 and the intersection line C in the first region A1 gradually increases from the third plane P3 toward the second plane P2. Get smaller. Further, the difference between the distance between the central guide surface 251 and the intersection line C in the second region A2 and the distance between each guide surface 211, 221 and the intersection line C gradually increases from the fourth plane P4 toward the second plane P2. Get smaller.

  The center guide surface 251 has an end portion provided on the rear side downstream in the second direction from the first plane P1 and overlaps with the first guide surface 211 and the second guide surface 221 when viewed from the left-right direction. ing. Each guide surface 211, 221, 251 is smoothly connected to the downstream guide surface 174A.

  The center guide surface 251 is overlapped with the first guide surface 211 and the second guide surface 221 when viewed from the left-right direction at an end provided on the front side, which is the upstream side in the second direction from the first plane P1. Specifically, in the third region A3, the central guide surface 251 as a whole overlaps with the first guide surface 211 and the second guide surface 221 when viewed from the left-right direction. The two guide surfaces 221 and the central guide surface 251 have the same shape.

  The central guide surface 251 does not have a portion located on the intersection line C side from the first guide surface 211 and the second guide surface 221. That is, the first guide surface 211 and the second guide surface 221 overlap with the central guide surface 251 or closer to the intersection line C than the central guide surface 251 when viewed from the left-right direction.

  FIG. 5 is a cross-sectional view of the heating member H on the third plane P3 in the first region A1. As shown in FIG. 5, all the members in the fixing belt 110 located between the first guide surface 211 and the central guide surface 251 have a distance from the intersection line C in the third region A1. On the plane P3, a space that is shorter than the distance L2 from the intersection line C of the first guide surface 211 is formed between the first end guide 210 and the center guide 250 so that the fixing belt 110 is in a free state. For example, the upper wall portion 171 of the cover member 170 is located on the third plane P3 in the first region A1 from the intersection line C among the members positioned between the first guide surface 211 and the central guide surface 251. It is provided at a distant position. The distance L1 from the intersection line C of the upper wall portion 171 is shorter than the distance L2 from the intersection line C of the first guide surface 211 on the third plane P3 in the first region A1. As a result, the inner peripheral surface of the fixing belt 110 does not hit any member at a position between the first guide surface 211 and the central guide surface 251.

  Further, all the members in the fixing belt 110 located between the second guide surface 221 and the central guide surface 251 have distances from the intersection line C on the third plane P3 in the first region A1. A space that makes the fixing belt 110 a free state is formed between the second end guide 220 and the center guide 250, which is shorter than the distance L4 from the intersection line C of the second guide surface 221. For example, the upper wall portion 171 of the cover member 170 is located on the third plane P3 in the first region A1 from the intersection line C among the members positioned between the second guide surface 221 and the central guide surface 251. It is provided at a distant position. The distance L3 from the intersection line C of the upper wall portion 171 is shorter than the distance L4 from the intersection line C of the second guide surface 221 on the third plane P3 in the first region A1. As a result, the inner peripheral surface of the fixing belt 110 does not hit any member at a position between the second guide surface 221 and the central guide surface 251.

  In the present embodiment, the central guide surface 251 is a curved surface whose distance from the intersection line C decreases from the center of the first end surface restricting portion 230 and the second end surface restricting portion 240 in the left and right direction toward the outer side in the left and right direction. Yes.

  The central guide 250 has a lower thermal conductivity than the first end guide 210 and the second end guide 220. For example, the first end guide 210 and the second end guide 220 are made of LCP (Liquid Crystal Polymer) resin, and the central guide 250 is made of PPS (Poly Phenylene Sulfide) resin. As an example, the thermal conductivity of the LCP resin is 0.3-0.4 W / mK, and the thermal conductivity of the PPS resin is 0.22 W / mK. In addition, the PPS resin is more slidable than the LCP resin. The surface roughness of the central guide 250 is smaller than the surface roughness of the first end guide 210 and the second end guide 220. The center guide 250 is coated with a fluororesin such as PFA (polytetrafluoroethylene) on the surface, particularly the center guide surface 251.

  Further, the central guide 250 has a lubricant layer made of a fluororesin or the like on the surface by being coated with the fluororesin or the like.

The operation and effect of the fixing device 100 configured as described above will be described.
As shown in FIG. 2, when the pressure roller 140 rotates, the fixing belt 110 rotates. At this time, the portion of the fixing belt 110 fed from between the nip forming surface 131N and the pressure roller 140 moves toward the rear side, which is the downstream side in the second direction, so that the fixing belt 110 is located behind the first plane P1. The side part becomes loose. The fixing belt 110 is pulled toward the gap between the nip forming surface 131N and the pressure roller 140 on the front side that is upstream in the second direction from the first plane P1. The fixing belt 110 pulled in this way is received by the guide surfaces 211, 221, 251. Then, the inner peripheral surface of the fixing belt 110 is guided by the guide surfaces 211, 221, and 251.

  In the third region A3, the fixing belt 110 is pulled toward the nip forming surface 131N and the pressure roller 140, and thus particularly strongly hits the guide surfaces 211, 221, and 251. In the present embodiment, in the third region A3, the first guide surface 211, the second guide surface 221 and the central guide surface 251 have the same shape, and the central guide surface 251 is the first guide when viewed from the left-right direction. Since the surface 211 and the second guide surface 221 overlap with each other, the fixing belt 110 contacts the first guide surface 211, the second guide surface 221, and the central guide surface 251, and the fixing contacts the respective guide surfaces 211, 221, and 251. The surface pressure of the belt 110 can be reduced. Further, since the fixing belt 110 can be prevented from being distorted in the third region A3, the fixing belt 110 and the paper P can be prevented from being distorted between the nip forming surface 131N and the pressure roller 140.

  At the position of the first region A1, particularly the third plane P3, the contact of the fixing belt 110 with the guide surfaces 211, 221, 251 starts to weaken, and the fixing belt 110 is always on the guide surfaces 211, 221, 251. It is not a hit. In the first region A1, the central guide surface 251 is farther from the intersection line C than the first guide surface 211 and the second guide surface 221 on the third plane P3. Since the central guide surface 251 is positioned outside the first guide surface 211 and the second guide surface 221 in the cross section of the first area A1, particularly the third plane P3, the central guide surface 251 is preferentially used. It can be applied to the fixing belt 110. Accordingly, it is possible to prevent the fixing belt 110 from strikingly hitting one of the first guide surface 211 and the second guide surface 221 and moving the fixing belt 110 to either one of the left and right directions.

  Further, the inner peripheral surface of the fixing belt 110 does not hit any member at a position between the first guide surface 211 and the central guide surface 251 and a position between the second guide surface 221 and the central guide surface 251. Therefore, the portion between the first guide surface 211 and the central guide surface 251 and the portion between the second guide surface 221 and the central guide surface 251 contact the fixing belt 110, and the fixing belt 110 is in the left-right direction. We can suppress approaching to either one.

  The first guide surface 211 and the second guide surface 221 overlap with the center guide surface 251 or are closer to the intersection line C than the center guide surface 251 when viewed from the left and right direction. Thus, the shape of the surface with which the inner peripheral surface of the fixing belt 110 abuts (the line connecting the surfaces farthest from the intersection line C among the guide surfaces 211, 221, 251) has a smooth shape with no dents on the outside. ing. Therefore, the fixing belt 110 can rotate smoothly.

  Further, since the center guide 250 has a lubricant layer on the surface, the slidability between the center guide surface 251 and the inner peripheral surface of the fixing belt 110 is improved. Thereby, the fixing belt 110 can rotate smoothly.

  Since the central guide 250 has a lower thermal conductivity than the first end guide 210 and the second end guide 220, the central guide 250 is less likely to take heat away from the fixing belt 110. Thereby, even if the center guide 250 is provided, it is possible to prevent the temperature of the central portion in the left-right direction of the fixing belt 110 from being significantly lower than the other portions.

  When the fixing device 100 is assembled, first, the guides 210, 220, and 250 are assembled to the cover member 170 in addition to the halogen lamp 120, the nip member 130, and the like, and these members are then attached to the fixing belt 110 in the horizontal direction. One side is inserted into the fixing belt 110. At this time, the central guide surface 251 is a curved surface that approaches the intersection line C from the center in the left-right direction toward the outer side in the left-right direction, so that the end edge of the fixing belt 110 is not easily caught by the center guide 250.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. About a concrete structure, it can change suitably in the range which does not deviate from the meaning of this invention.

  In the embodiment, the central guide 250 is fixed to the cover member 170, but the configuration of the central guide is not limited thereto. For example, as shown in FIG. 6, the central guide 250 is provided so as to be movable up and down with respect to the cover member 170, and the central guide surface 251 is biased toward the inner peripheral surface of the fixing belt 110 by the biasing member S <b> 1. May be.

  The center guide 250 has a first guide rib 252 that protrudes rearward and extends up and down on the surface of the cover member 170 that faces the front wall portion 172. Further, the central guide 250 has a second guide rib 253 that protrudes forward and extends up and down on the surface facing the rear wall portion 173 of the cover member 170.

  As shown in FIG. 7, the front wall portion 172 of the cover member 170 has a first guide groove 175 extending in the up-and-down direction with which the first guide rib 252 is engaged. Further, the rear wall portion 173 of the cover member 170 has a second guide groove 176 that extends in the up-down direction with which the second guide rib 253 is engaged. Accordingly, the central guide 250 can move up and down with respect to the cover member 170 by the first guide rib 252 and the second guide rib 253 being guided by the first guide groove 175 and the second guide groove 176. .

  As shown in FIG. 6, an urging member S <b> 1 such as a compression spring is provided between the center guide 250 and the upper wall portion 171 of the cover member 170. Accordingly, the central guide 250 is urged upward by the urging member S1. That is, the central guide surface 251 is biased toward the inner peripheral surface of the fixing belt 110.

  As described above, the central guide surface 251 is biased toward the inner peripheral surface of the fixing belt 110, so that the central guide surface 251 can be firmly applied to the inner peripheral surface of the fixing belt 110.

  In the above-described embodiment, the central guide 250 has a lower thermal conductivity than the first end guide 210 and the second end guide 220 because the surface is coated with fluororesin or the like. The configuration is not limited to this. For example, the central guide 250 may have a lower thermal conductivity than the first end guide 210 and the second end guide 220 by providing a layer of a heat insulating material such as rubber or urethane sponge on the surface.

  In the embodiment, the lubricant layer is provided on the surface of the central guide 250 by being coated with a fluororesin or the like, but the configuration of the central guide is not limited to this. For example, the central guide 250 may have a lubricant layer on the surface by applying a lubricant such as grease.

  In the embodiment, the surface that guides the inner peripheral surface of the right end portion in the left-right direction of the fixing belt 110 is only the first guide surface 211, and the surface that guides the inner peripheral surface of the left end portion in the left-right direction of the fixing belt 110. However, although only the second guide surface 221 is provided, the guide surface provided in the fixing device is not limited to this. For example, as shown in FIG. 8, the fixing device has a third guide surface 261 that guides the inner peripheral surface of the right end portion in the left-right direction of the fixing belt 110 inside the first end guide 210 in the left-right direction. An end guide 260 may be provided. Further, the fixing device has a fourth end guide 270 having a fourth guide surface 271 that guides the inner peripheral surface of the left end in the left-right direction of the fixing belt 110 inside the second end guide 220 in the left-right direction. It may be.

  In this case, the third guide surface 261 has the same distance from the intersection line C as the distance from the intersection line C of the first guide surface 211 on the third plane P3, or the intersection line of the first guide surface 211. It is shorter than the distance from C. Accordingly, it is possible to prevent the third guide surface 261 from strongly contacting the inner peripheral surface of the fixing belt 110 and the fixing belt 110 from moving to one side in the left-right direction.

  Further, the fourth guide surface 271 has the same distance from the intersection line C as the distance from the intersection line C of the second guide surface 221 on the third plane P3, or the intersection line C of the second guide surface 221. It is shorter than the distance from. Accordingly, it is possible to prevent the fourth guide surface 271 from strongly contacting the inner peripheral surface of the fixing belt 110 and the fixing belt 110 from moving to one side in the left-right direction.

  In the embodiment, the first end guide 210, the second end guide 220, and the center guide 250 are provided as separate parts from the cover member 170, but the first end guide, the second end guide, and the center are provided. The configuration of the guide is not limited to this. For example, the first end guide 210, the second end guide 220, and the center guide 250 may be formed integrally with the cover member 170.

  In the embodiment, the central guide 250 has a lower thermal conductivity than the first end guide 210 and the second end guide 220, but the configuration of the central guide 250 is not limited thereto. For example, the central guide 250 may have a thermal conductivity equivalent to that of the first end guide 210 and the second end guide 220. Specifically, the thermal conductivity of the central guide 250 may be set in a range of ± 5% with respect to the thermal conductivity of the first end guide 210 and the second end guide 220. For example, the first end guide 210, the second end guide 220, and the center guide 250 may be made of the same material, for example, PPS resin.

  In the above embodiment, the fixing device 100 includes the pressure roller 140 as a rotating body, but the configuration of the fixing device is not limited to this. For example, the rotating body may be an endless pressure belt.

  Moreover, each element of each above-mentioned embodiment and each modification can be implemented in arbitrary combinations.

DESCRIPTION OF SYMBOLS 100 Fixing device 110 Fixing belt 130 Nip member 131N Nip forming surface 140 Pressure roller 210 First end guide 211 First guide surface 220 Second end guide 221 Second guide surface 250 Central guide 251 Central guide surface P1 First plane P2 2nd plane P3 3rd plane

Claims (7)

An endless belt,
A nip member having a nip forming surface in contact with the inner peripheral surface of the belt and elongated in a first direction;
A rotating body that sandwiches the belt with the nip forming surface;
A first end guide having a first guide surface for guiding an inner peripheral surface of one end portion in the first direction of the belt;
A second end guide having a second guide surface for guiding an inner peripheral surface of the other end in the first direction of the belt;
A central guide having a central guide surface that guides an inner peripheral surface of a central portion in the first direction of the belt,
It passes through the center of the nip forming surface in the second direction which is the moving direction of the belt on the nip forming surface, and is orthogonal to the plane connecting the upstream end edge and the downstream end edge in the second direction of the nip forming surface. The plane to be the first plane,
A plane that passes through the center of the nip forming surface and the center guide surface on the first plane and is orthogonal to the first plane is a second plane,
In the region upstream of the first plane in the second direction and farther from the nip forming surface than the second plane, the angle of inclination with respect to the first plane and the second plane pass through the intersection line. A plane having the same inclination angle with respect to is defined as a third plane.
The fixing device, wherein the central guide surface is farther from the intersection line than the first guide surface and the second guide surface on the third plane in the region. The first guide surface and the second guide surface are surfaces located on the outermost side in the first direction among the surfaces that guide the inner peripheral surface of the belt,
All the members in the belt located between the first guide surface and the central guide surface have a distance from the intersecting line on the third plane in the region, the first guide surface. The same as the distance from the intersection line or shorter than the distance from the intersection line of the first guide surface,
All the members in the belt located between the second guide surface and the central guide surface have a distance from the intersecting line on the third plane in the region. The fixing device according to claim 1, wherein the fixing device is equal to a distance from the intersection line or shorter than a distance from the intersection line of the second guide surface. The first guide surface overlaps with the central guide surface as viewed from the first direction, or is closer to the intersection line than the central guide surface,
The said 2nd guide surface overlaps with the said center guide surface seeing from the said 1st direction, or it is closer to the said intersection line than the said center guide surface, The Claim 1 or Claim 2 characterized by the above-mentioned. Fixing device.   The fixing device according to claim 1, wherein the center guide has a lubricant layer on a surface thereof.   5. The fixing device according to claim 1, wherein the central guide has a smaller thermal conductivity than the first end guide and the second end guide. 6.   5. The fixing device according to claim 1, wherein the central guide has a thermal conductivity equivalent to that of the first end guide and the second end guide. 6.   The fixing device according to claim 1, wherein the central guide surface is biased toward an inner peripheral surface of the belt.

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