JP6036062B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing device including a belt, a nip member, and a stay.

  2. Description of the Related Art Conventionally, a fixing device used in an electrophotographic image forming apparatus includes a belt, a slidable belt, and a nip member that extends long in a direction orthogonal to the sliding direction of the belt. There is a known one provided with a stay that is disposed on the opposite side of the nip member from the rotating body and has a support portion that supports the nip member (see, for example, Patent Document 1).

  As for the support portion of the stay provided in the fixing device, both end portions in the longitudinal direction of the nip member are located closer to the rotating body than the center portion. By having such a support portion, the pressure applied between the nip member and the rotator at the time of fixing becomes larger at both ends than at the center, so the center of the recording sheet is pulled to both ends. It is possible to suppress wrinkles on the recording sheet.

US Pat. No. 6,266,510

  However, since the support portion of the stay has a shape in which both end portions in the longitudinal direction are located closer to the rotating body than the center portion, the shape of the nip member also follows the shape of the support portion so that both end portions are closer to the center portion. The shape is located on the rotating body side. In this state, when the belt passes through the sliding surface with the nip member, there arises a problem that the central portion of the belt is easily recessed to correspond to the shape of the nip member.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device capable of suppressing a dent in a central portion of a belt.

  In order to achieve the above-described object, the fixing device of the present invention includes a belt, a nip member having a sliding surface on which the belt slides, and extending long in a direction perpendicular to the sliding direction of the belt, and the sliding device. Facing the belt in the direction perpendicular to the direction of the nip member and the longitudinal direction of the nip member, sandwiching the belt between the nip member and rotating the rotator provided on the side opposite to the rotator side of the nip member And a stay having a support portion that supports the nip member. In at least a part of the sliding direction, the support portion is such that both end portions of the nip member in the longitudinal direction are located closer to the rotating body than the center portion. Further, the fixing device includes a downstream guide having a guide surface that guides the belt on the downstream side in the sliding direction with respect to the sliding surface and on the central portion side in the longitudinal direction. It is located on the rotating body side with respect to the extended surface extending from the downstream end in the sliding direction to the downstream side in the sliding direction.

  In a fixing device having a stay having a support portion in which both end portions are positioned closer to the rotating body than the central portion side, a dent is likely to be formed in the central portion of the belt after the belt passes through the sliding surface of the nip member. For example, after the belt passes through the sliding surface, there is a guide surface located on the rotating body side of the extended surface from the downstream end in the sliding direction of the sliding surface at the position of the central portion of the belt. Can be restored.

  In the above-described configuration, the distance in the facing direction between the end on the rotating body side in the facing direction of the guide surface and the extension surface in the facing direction is smaller than the distance in the facing direction between the center portion and both ends of the support portion. Can do.

  According to such a configuration, since the guide surface does not protrude greatly with respect to the belt, it is possible to restore the dent in the central portion of the belt while reducing the dent in the reverse direction.

  In the above-described configuration, the guide surface extends longer than half of the belt width in the longitudinal direction, and the central portion of the guide surface in the longitudinal direction is positioned on the rotating body side than the both end sides. it can.

  According to such a configuration, the guide surface has a convex shape that extends longer than half the width of the belt when viewed from the sliding direction, and thus the guide surface has a convex shape that is shorter than half the width of the belt. In comparison, local load on the belt from the guide surface can be suppressed.

  In the above-described configuration, the support portion may be configured such that both end portions are positioned closer to the rotating body than the center portion at least at the end portion on the downstream side in the sliding direction.

  In the structure in which the support portion is located at the end on the downstream side in the sliding direction and the both end portions are located closer to the rotating body side than the central portion side, a recess is particularly likely to occur in the central portion of the belt after the belt has passed the sliding surface. Even with such a configuration, it is possible to suppress the dent in the central portion of the belt by the guide surface.

  According to the present invention, after the belt passes through the sliding surface, there is a guide surface located on the rotating body side of the extended surface from the downstream end in the sliding direction of the sliding surface at the position of the central portion of the belt. The center dent can be restored.

1 is a cross-sectional view illustrating a laser printer including a fixing device according to an embodiment of the present invention. 2 is a cross-sectional view illustrating a fixing device. FIG. 3 is a cross-sectional view taken along line AA in FIG. 2 of a cover member to which a stay is assembled. It is an enlarged view of a guide surface concerning the 1st modification.

  Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, a schematic configuration of the laser printer 1 including the fixing device 100 according to the present embodiment will be briefly described, and then a detailed configuration of the fixing device 100 will be described.

  In the following description, the direction will be described with reference to the user who uses the laser printer 1. That is, the left side in FIG. 1 is “front”, the right side is “rear”, the back side is “left”, and the front side is “right”. Also, the vertical direction in FIG.

<Schematic configuration of laser printer and fixing device>
As shown in FIG. 1, the laser printer 1 is a process of transferring a toner image (developer image) onto a paper feed unit 3 that supplies a paper S, an exposure device 4, and the paper S in a main body housing 2. It mainly includes a cartridge 5 and a fixing device 100 that thermally fixes the toner image transferred onto the paper S.

  The paper feed unit 3 is provided at a lower portion in the main body housing 2 and mainly includes a paper feed tray 31, a paper pressing plate 32, and a paper feed mechanism 33. The paper S stored in the paper feed tray 31 is moved upward by the paper pressing plate 32 and supplied toward the process cartridge 5 (between the photosensitive drum 61 and the transfer roller 63) by the paper feed mechanism 33.

  The exposure apparatus 4 is disposed in the upper part of the main body housing 2 and includes a laser light emitting unit (not shown), a polygon mirror, a lens, a reflecting mirror, and the like that are not shown. In this exposure device 4, the surface of the photosensitive drum 61 is exposed by scanning the surface of the photosensitive drum 61 at high speed with laser light (see the chain line) based on the image data emitted from the laser light emitting unit.

  The process cartridge 5 is disposed below the exposure apparatus 4 and is detachably mounted on the main body housing 2 through an opening formed when the front cover 21 provided on the main body housing 2 is opened. Yes. The process cartridge 5 includes a drum unit 6 and a developing unit 7.

  The drum unit 6 mainly includes a photosensitive drum 61, a charger 62, and a transfer roller 63. The developing unit 7 is configured to be detachably attached to the drum unit 6, and includes a developing roller 71, a supply roller 72, a layer thickness regulating blade 73, and a toner that contains toner (developer). The housing part 74 is mainly provided.

  In the process cartridge 5, the surface of the photosensitive drum 61 is uniformly charged by the charger 62 and then exposed by high-speed scanning of the laser light from the exposure device 4, whereby an image is formed on the photosensitive drum 61. An electrostatic latent image based on the data is formed. Further, the toner in the toner container 74 is supplied to the developing roller 71 via the supply roller 72 and enters between the developing roller 71 and the layer thickness regulating blade 73 to form a thin layer of a certain thickness on the developing roller 71. It is carried on.

  The toner carried on the developing roller 71 is supplied from the developing roller 71 to the electrostatic latent image formed on the photosensitive drum 61. As a result, the electrostatic latent image is visualized and a toner image is formed on the photosensitive drum 61. Thereafter, the sheet S is conveyed between the photosensitive drum 61 and the transfer roller 63 so that the toner image on the photosensitive drum 61 is transferred onto the sheet S.

  The fixing device 100 is provided behind the process cartridge 5. The toner image (toner) transferred onto the paper S is thermally fixed onto the paper S by passing through the fixing device 100. The paper S on which the toner image has been thermally fixed is discharged onto the paper discharge tray 22 by the transport rollers 23 and 24.

<Detailed configuration of fixing device>
As shown in FIG. 2, the fixing device 100 includes a fixing belt 110 as an example of a belt, a halogen lamp 120, a nip plate 130 as an example of a nip member, a pressure roller 140 as an example of a rotating body, The reflector 150, the stay 160, and the cover member 210 are mainly provided.

  The fixing belt 110 is an endless stainless steel belt having heat resistance and flexibility, and its rotation (traveling direction) is guided by the upstream guide 310 and the downstream guide 320 formed on the cover member 210, and the nip plate 130, the upstream guide 310 and the downstream guide 320 are configured to slide.

  The halogen lamp 120 is a member that emits radiant heat to heat the toner on the paper S by heating the nip plate 130 and the fixing belt 110. Fixing is performed on the side of the nip plate 130 opposite to the side on which the fixing belt 110 slides. The belt 110 and the nip plate 130 are disposed at a predetermined distance from the inner surfaces.

  The nip plate 130 is a plate-like member that extends in the left-right direction (a direction perpendicular to the sliding direction of the fixing belt 110) and receives radiant heat from the halogen lamp 120. In the present embodiment, the nip plate 130 is made of metal, for example, is formed on a plane with an aluminum plate or the like having a higher thermal conductivity than the steel stay 160, and has a thickness that can be flexibly deformed. Yes. In addition, the nip plate 130 may include a metal including a non-metallic protective layer (for example, a fluorine coating) provided on a sliding surface with the fixing belt 110.

The nip plate 130 has a plate-like portion 131 and a bent portion 132.
The plate portion 131 is formed in a plate shape extending in the left-right direction, and has a sliding surface 135 on which the fixing belt 110 slides. The plate-like portion 131 forms a nip portion N with the fixing belt 110 by sandwiching the fixing belt 110 vertically with the pressure roller 140 on the sliding surface 135. The plate-like portion 131 is arranged below the halogen lamp 120 and transmits heat from the halogen lamp 120 to the toner on the paper S via the fixing belt 110.
The bent portion 132 is formed to be bent in a substantially arc shape upward from the front end side of the plate-like portion 131.

  The pressure roller 140 is a member that forms a nip portion N with the fixing belt 110 by sandwiching the fixing belt 110 with the nip plate 130. The pressure roller 140 faces the fixing belt 110 in the vertical direction (the sliding direction and the direction perpendicular to the longitudinal direction of the nip plate 130), and is provided to be rotatable at a position below the nip plate 130. . In the present embodiment, in order to form the nip portion N, one of the nip plate 130 and the pressure roller 140 is urged toward the other. The pressure roller 140 rotates with the fixing belt 110 sandwiched between the nip plate 130 and rotates together with the fixing belt 110 to convey the paper S backward.

  The pressure roller 140 is configured to be rotated by a driving force transmitted from a motor (not shown) provided in the main body housing 2, and the frictional force with the fixing belt 110 or the sheet S by being driven to rotate. As a result, the fixing belt 110 is driven to rotate. The sheet S on which the toner image is transferred is transported between the pressure roller 140 and the heated fixing belt 110 (nip portion N), whereby the toner image (toner) is thermally fixed.

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

The reflecting plate 150 is formed by curving an aluminum plate or the like in a U shape in a sectional view, for example, having high infrared and far-infrared reflectance. More specifically, the reflecting plate 150 includes a reflecting portion 151 having a U-shape, and a flange 152 extending from both end edges (each end edge on the nip plate 130 side) in the front-rear direction of the reflecting portion 151 toward the outer side in the front-rear direction. Have.
Each flange 152 is sandwiched between the stay 160 and the nip plate 130, and can be deformed so that the entire reflecting plate 150 is bent by being deformed by bending.

  The stay 160 is a member that receives a load from the pressure roller 140 by supporting the nip plate 130 via the reflection plate 150, and the halogen lamp 120 and the reflection on the opposite side of the nip plate 130 from the pressure roller 140 side. It arrange | positions so that the board 150 may be enclosed. The load referred to here is a reaction force when the nip plate 130 urges the pressure roller 140 in the configuration in which the nip plate 130 urges the pressure roller 140.

Specifically, the stay 160 extends downward from the upper wall 161, the front wall 162 extending downward from the front end that is upstream of the upper wall 161 in the sliding direction, and the rear end that is downstream of the upper wall 161 in the sliding direction. The rear wall 163 is formed in a U shape in a sectional view. A flange 164 extending to the front side is formed at the lower end of the front wall 162.
Such a stay 160 has relatively high rigidity, for example, is formed by bending a steel plate or the like.

Further, the lower end portions of the front wall 162 and the rear wall 163 serve as a support portion 165 that supports the nip plate 130 via the reflection plate 150.
As shown in FIG. 3, each support portion 165 (only the rear side is shown) is configured such that both end portions in the left-right direction of the nip plate 130 are positioned closer to the pressure roller 140 than the center portion. In other words, the support part 165 has a gentle arcuate concave shape when viewed from the sliding direction.

  Returning to FIG. 2, the cover member 210 has a U-shape in cross section and is formed to extend in the left-right direction, and is disposed so as to cover the stay 160 on the opposite side of the halogen lamp 120 with the stay 160 interposed therebetween. Has been. The cover member 210 includes a rear side wall 211, a front side wall 212, an upper wall 213 extending so as to connect the upper ends of the rear side wall 211 and the front side wall 212, and an extending wall extending rearward from the lower end of the rear side wall 211. 214.

  An upstream guide 310 that guides the front lower portion of the fixing belt 110 is formed at the lower end of the front side wall 212. A downstream guide 320 is formed at the rear end of the extending wall 214 to guide the lower rear portion of the fixing belt 110.

  The upstream guide 310 is provided on the upstream side in the sliding direction with respect to the sliding surface 135 and is formed to extend in the left-right direction. The upstream guide 310 guides the fixing belt 110 toward the nip portion N.

  As shown in FIGS. 2 and 3, the downstream guide 320 is provided on the downstream side in the sliding direction with respect to the sliding surface 135, and is formed to extend long along the left-right direction. The downstream guide 320 has a guide surface 321 that guides the inner peripheral surface of the fixing belt 110 on the center side in the left-right direction. In FIG. 3, the size of the guide surface 321 is exaggerated for convenience.

  The guide surface 321 is located closer to the pressure roller 140 than the extended surface 136 extending from the downstream end of the sliding surface 135 in the sliding direction to the downstream side in the sliding direction. More specifically, the guide surface 321 extends longer than half of the width of the fixing belt 110 in the left-right direction, and the center portion thereof is located closer to the pressure roller 140 than the both end portions, and the sliding direction The configuration is such that it has a convex shape with a gentle arc as viewed from the top.

  As shown in FIG. 2, the distance X in the vertical direction between the lower end 322 (the end on the pressure roller 140 side in the vertical direction) of the guide surface 321 and the extended surface 136 is set to the central portion 165A of the support portion 165 and both end portions. By making the distance Y smaller than the distance Y in the vertical direction with respect to 165B, the guide surface 321 does not protrude significantly from the fixing belt 110.

  The fixing device 100 configured as described above is configured such that the support portions 165 are positioned on the pressure roller 140 side at both end portions in the left-right direction rather than the central portion side. The flange 152 of the reflecting plate 150 is deformed following the support portion 165 so that both end portions in the left-right direction are positioned closer to the pressure roller 140 than the center portion. As a result, the pressure applied between the nip plate 130 and the pressure roller 140 is larger at both end portions than at the central portion in the left-right direction, so that wrinkles of the paper S are suppressed.

  Further, the fixing belt 110 passing through the sliding surface 135 is also in a state where the central portion in the left-right direction is recessed following the shape of the nip plate 130. If the fixing belt 110 remains indented after passing through the sliding surface 135, the fixing belt 110 continues to rotate while being indented, and a load is easily applied.

  However, since the fixing device 100 of the present embodiment has the guide surface 321 protruding from the extension surface 136 at the center of the fixing belt 110 after the fixing belt 110 passes through the sliding surface 135, the center of the fixing belt 110. The dent of the part can be restored.

  Further, the distance X in the vertical direction (opposite direction) between the lower end 322 of the guide surface 321 (the end on the pressure roller 140 side in the vertical direction) and the extension surface 136 is set to the distance between the center portion 165A and the both end portions 165B of the support portion 165. By making the distance Y smaller than the distance Y in the vertical direction, the guide surface 321 does not protrude greatly from the fixing belt 110. Therefore, it is possible to restore the dent at the center of the fixing belt 110 while reducing the dent in the fixing belt 110 in the reverse direction.

  Further, since the guide surface 321 has a convex shape extending longer than half the width of the fixing belt 110 when viewed from the sliding direction, the guide surface 321 is compared with a configuration having a convex shape shorter than half the width of the fixing belt. Thus, it is possible to suppress a local load from the guide surface 321 on the fixing belt 110.

  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 following description, the same components as those in the above embodiment are given the same reference numerals, and detailed description thereof is omitted.

  In the embodiment, the downstream guide 320 having the guide surface 321 is provided on the cover member 210. However, the present invention is not limited to this, and for example, a part of the nip plate 130 may be used as the downstream guide.

  In the above-described embodiment, the guide surface 321 has a convex shape that extends long in the left-right direction. However, only the central portion in the left-right direction may have a convex shape.

  In the above-described embodiment, the support portion 165 is configured such that both the front side and the rear side are positioned closer to the pressure roller 140 side than the center side on both end sides in the left-right direction, but only the rear support portion 165 is A configuration in which both end portions in the left-right direction are located closer to the pressure roller 140 than the center portion may be employed.

  In the said embodiment, although the extended surface 136 was extended in parallel with the front-back direction, the extending direction is not specifically limited. For example, as shown in FIG. 4, an extension surface 136 </ b> A that extends obliquely upward in the rear direction may be used.

  In this configuration, the nip plate 130A is formed to bend obliquely upward and rearward from the rear end of the plate-like portion 131A, and the downstream end in the sliding direction of the sliding surface 135A on which the fixing belt 110 slides is , Facing backwards diagonally upward. The downstream guide 320A is provided on the downstream side in the sliding direction with respect to the sliding surface 135A, and has a guide surface 321A that guides the inner peripheral surface of the fixing belt 110 on the central portion side in the left-right direction.

The guide surface 321A is positioned closer to the pressure roller 140 than the extended surface 136A extending from the sliding direction downstream end of the sliding surface 135A to the sliding direction downstream side.
In this case as well, the dent in the central portion of the fixing belt 110 can be returned to the original state as in the above embodiment.

DESCRIPTION OF SYMBOLS 100 Fixing device 110 Fixing belt 130 Nip plate 130A Nip plate 135 Sliding surface 135A Sliding surface 136 Extended surface 136A Extended surface 140 Pressure roller 150 Reflector plate 160 Stay 165 Support portion 165A Central portion 165B Both ends 320 Downstream guide 320A Downstream guide 321 Guide surface 321A Guide surface 322 Lower end X distance Y distance

Claims (5)

Belt,
A nip member having a sliding surface on which the belt slides and extending long in a direction perpendicular to the sliding direction of the belt;
A rotating body that is opposed to the belt in a direction perpendicular to the sliding direction and the longitudinal direction of the nip member, is sandwiched between the belt and the nip member, and is rotatable.
A stay that is disposed on the opposite side of the nip member from the rotating body and has a support portion that supports the nip member;
The support portion is located at least part of the sliding direction such that both end sides in the longitudinal direction of the nip member are located closer to the rotating body than the center portion side,
A downstream guide having a guide surface that guides the belt on the center side in the longitudinal direction on the downstream side in the sliding direction from the sliding surface;
The guide surface is positioned closer to the rotating body than an extended surface extending from the downstream end of the sliding surface in the sliding direction toward the downstream side of the sliding direction, and is half the width of the belt in the longitudinal direction. Longer than
The fixing device according to claim 1, wherein a central portion of the guide surface in the longitudinal direction is located closer to the rotating body than both ends .   The distance in the facing direction between the end on the rotating body side in the facing direction of the guide surface and the extended surface in the facing direction is smaller than the distance in the facing direction between the central portion and both ends of the support portion. The fixing device according to claim 1. The said support part is located in the said rotary body side rather than the said center part side at the said both ends part at least in the edge part of the said sliding direction downstream, The Claim 1 or Claim 2 characterized by the above-mentioned. Fixing device. The fixing device according to claim 1, wherein the guide surface has an arcuate convex shape when viewed from the sliding direction. The fixing device according to claim 1, wherein the downstream guide is a member different from the nip member.

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