JP2015069007A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus that can suppress the outflow of lubricant from a rubbing surface of a nip member.SOLUTION: A fixing device 100 includes a nip plate 130 that has, on a surface opposite to an inner surface 110A of a fixing belt 110, a central area 131A corresponding to a range rubbed with the fixing belt 110 in the sheet conveyance direction, and an upstream side area 132A and downstream side area 133A each extending from the edge on the upstream side and downstream side in the sheet conveyance direction across the central area 131A; at least in one of the upstream side and downstream side areas 132A and 133A, a holding part LR is formed having a holding power for holding lubricant larger than that of the central area 131A.

Description

  The present invention relates to a fixing device used in an electrophotographic image forming apparatus and an image forming apparatus including the fixing device.

  In general, an electrophotographic image forming apparatus includes an image carrier configured to carry a developer image such as toner, a transfer member that transfers the developer image carried on the image carrier to a recording sheet, and a recording And a fixing device that thermally fixes the developer image transferred to the sheet. As a fixing device, a belt is sandwiched between a nip member disposed on an inner surface side of an endless belt (fixing film) and a rotating body (pressure roller) disposed on an outer surface side, and a developer is interposed between the belt and the rotating body. There is known a method in which a developer is heated and melted and fixed to a recording sheet in the process of conveying the recording sheet carrying an image.

  In this type of fixing device, in order to uniformly disperse the lubricant used to improve the slidability between the nip member and the belt, a configuration in which a flow guide groove is provided on the surface of the nip member that is in sliding contact with the belt is known. (Patent Document 1).

JP 2008-146964 A

  In the configuration of Patent Document 1, it is possible to uniformly disperse the lubricant on the sliding contact surface of the nip member, but no consideration is given to the lubricant that flows out of the sliding contact surface. When the lubricant flows out from the sliding contact surface, the lubricant travels along the surface of the smooth nip member and goes around to the back side of the nip member, which may contaminate the inside of the apparatus. Further, the reduction of the lubricant due to such outflow lowers the slidability of the belt, increases the driving torque of the belt and increases the risk of slipping, and may accelerate the deterioration of the apparatus.

  The inventor of the present application has come up with the present invention while paying attention to the problem of suppressing the outflow of the lubricant from the sliding surface of the nip member to the outside in the recording sheet conveyance direction, and through intensive research.

  In one embodiment of the present invention, an endless belt having an inner surface and an outer surface, a nip member extending inside the endless belt, the endless belt sandwiched between the nip member and a recording sheet between the endless belt And a rotator configured to convey the toner in the conveying direction. The surface of the nip member that faces the inner surface of the endless belt has a central region corresponding to a range in which the endless belt contacts with the lubricant in the transport direction, and an upstream end of the central region in the transport direction. An upstream region extending from the endless belt, and a downstream region extending from the downstream end of the central region in the transport direction and away from the endless belt. In at least one of the upstream region and the downstream region, a holding portion having a holding force for holding the lubricant larger than that in the central region is formed.

  According to such a configuration, the outflow of the overflowing lubricant can be suppressed in a region where the upstream and / or downstream endless belts on the surface of the nip member facing the inner surface of the endless belt do not contact.

  The holding part can be configured as a rough surface part having a surface roughness in the transport direction larger than that of the central region.

  According to this, the holding portion is formed only by increasing the surface roughness of the recording sheet in the region where the upstream and / or downstream endless belts on the surface of the nip member facing the inner surface of the endless belt do not contact. Therefore, the holding portion can be easily formed.

  For example, on the surface of the nip member that faces the inner surface of the endless belt, a film is provided in the central region, and no film is provided in at least one of the upstream and downstream regions. It can be created by configuring.

  According to this, a process such as selectively performing the film forming process normally performed in the creation of the nip member, or removing the film after forming the film on the entire surface on the side facing the inner surface of the endless belt. Thus, the formation of the holding portion can be easily realized.

  The holding portion may be formed over the entire range corresponding to the width of the endless belt in a direction orthogonal to the transport direction. This is because it is possible to effectively suppress the outflow of the lubricant that is pushed to the downstream side in the conveying direction of the region (center region) where the endless belt contacts the surface of the nip member that faces the inner surface of the endless belt, and is scraped upstream. .

  The holding portion may have an end edge in a direction orthogonal to the transport direction positioned outside a range corresponding to the width of the endless belt. With this configuration, it is possible to reliably suppress the outflow of the lubricant even when the endless belt is displaced in the width direction, and to suppress the outflow of the lubricant overflowing from both end edges in the width direction of the endless belt. Can do.

  In this case, the holding portion may be formed leaving a predetermined margin from both ends of the nip member in a direction orthogonal to the transport direction. For example, in a form in which the holding portion is formed by engraving a line in a direction orthogonal to the conveyance direction of the recording sheet, the lubricant overflowing outward from both end edges in the width direction of the endless belt is applied to the marking line. It can act to pull back inward along.

  It is preferable that at least a part of the holding portion is formed within a range of 3 mm or less from an upstream edge or a downstream edge of the central region in the recording sheet conveyance direction. By providing the lubricant suppressing portion within the range of 3 mm or less in the immediate vicinity of the central region, it is expected that the lubricant overflowing from the sliding surface due to flapping during driving of the endless belt can be recovered by the endless belt.

  The holding unit is configured to process a part of the surface of the nip member facing the inner surface of the endless belt by one or more methods selected from scribing, filing, cutting, film formation, and film removal. Can be formed. By adopting these methods, the holding part can be easily realized at a low cost.

  Embodiments of the present invention are a fixing device including an endless belt and a nip member facing the inner surface of the endless belt, the nip member being a surface facing the inner surface of the endless belt, A first region in contact with the endless belt via the lubricant, and a second region extending from the first region and away from the endless belt, the second region attempting to hold the lubricant A holding portion having a holding force larger than that of the central region may be provided. Since the second region has the holding portion, it is possible to suppress the overflow of the overflowing lubricant in the region where the endless belt does not contact the surface of the nip member that faces the inner surface of the endless belt.

  The present invention provides an image forming apparatus comprising: an image carrier configured to carry a developer image; a transfer member that transfers the developer image carried on the image carrier to a recording sheet; and the fixing device. Can be implemented. Due to the excellent characteristics of the fixing device, it is possible to prevent deterioration of the fixing performance of the image forming apparatus, to reduce contamination in the apparatus by the lubricant, and to extend the life of the apparatus.

  In the image forming apparatus, the remarkable effect of the present invention may be obtained when the nip member is arranged such that the central region is in an upward or obliquely upward posture. This is because the lubricant is more likely to flow out due to the action of gravity compared to a configuration in which the central region faces downward, and there is a concern that the lubricant will fall into the fixing device when the lubricant overflows.

  According to the present invention, it is possible to suppress the outflow of the lubricant from the sliding contact surface of the nip member.

1 is a diagram illustrating an overall configuration of a laser printer as an example of an image forming apparatus according to an embodiment. 1 is a diagram illustrating a configuration of a fixing device according to an embodiment. It is (a) perspective view, (b) sectional view, (c) enlarged sectional view of the upstream end, and (d) enlarged sectional view of the downstream end, showing an example of the configuration of the nip plate. FIG. 6 is a plan view of the fixing belt and the nip plate with the ends thereof enlarged and viewed from above. (A) perspective view, (b) cross-sectional view, (c) enlarged cross-sectional view of upstream end, and (d) enlarged cross-sectional view of downstream end showing a modification of the configuration of the nip plate. It is figure (a), (b) which shows the other modification of a structure of a nip board. It is (a) sectional drawing and (b) the perspective view of a nip board which show the modification of a heating member.

  Next, embodiments of the present invention will be described with reference to the drawings as appropriate. In the following description, the direction is based on the user who uses the image forming apparatus. Specifically, the left side of FIG. 1 as viewed from the user is “front”, the right side of FIG. 1 as viewed from the user is “rear”, and the front side of FIG. 1 is “right”. ”, The left side of the page is“ left ”. Further, the vertical direction in FIG.

First, the overall configuration of the image forming apparatus according to the present embodiment will be described.
As shown in FIG. 1, a laser printer 1 as an example of an image forming apparatus transfers a toner image (developer image) formed on a photosensitive drum 41 (described later) onto a sheet (recording sheet) S to transfer a recording sheet. As an example, the apparatus forms an image on paper S, and mainly includes a housing 2, a paper feed unit 3, an image forming unit 4, and a paper discharge unit 5.

The housing 2 mainly includes a main body frame 21 that supports the photosensitive drum 41 and the like, and a front cover 22.
The main body frame 21 has an opening 21 </ b> A for attaching / detaching a developing cartridge 44 described later on the front side surface.

  The front cover 22 is a cover (refer to a chain line) that covers the front opening 21A. The front cover 22 is supported with respect to the main body frame 21 so that the upper end is pivotable about the lower end, and is described later in an open state indicated by a solid line. A part of the tray 31 is configured. Note that the housing 2 includes a second front cover 24 that is disposed inside the front cover 22 in a closed state indicated by a chain line and that opens and closes the opening 21A by rotating around the lower end. Thereby, even when the front cover 22 is opened and used as a part of the paper feed tray 31, it is possible to suppress the intrusion of dust into the housing 2 by the second front cover 24.

  The paper feed unit 3 is configured to supply the paper S to the image forming unit 4 and mainly includes a paper feed tray 31 and a paper feed mechanism 33. The paper feed tray 31 is a tray on which paper S to be supplied to the image forming unit 4 is placed.

  The paper feed tray 31 includes a pressing plate 31 </ b> A provided at the lower part in the housing 2 and an open front cover 22 that forms a base for placing the paper S. 31 A of press plates are comprised so that a rear-end part can be rotated up and down centering on a front-end part with respect to the main body frame 21, and a rear-end part is pushed up by the raising member 31B.

  The paper feed mechanism 33 includes a pickup roller 33A, a separation roller 33B, a separation pad 33C, and the like, and is disposed at the rear of the lower part in the housing 2. The paper feed mechanism 33 feeds the paper S placed on the paper feed tray 31 by the pickup roller 33A, separates the paper S one by one between the separation roller 33B and the separation pad 33C, and supplies it to the image forming unit 4. It is configured.

  The image forming unit 4 is configured to form an image on the fed paper S, and includes a photosensitive drum 41 as an example of an image carrier, a charging unit 42, an exposure unit 43, a developing cartridge 44, and a transfer A transfer roller 45 as an example of a member and a fixing device 100 are mainly provided.

  The photoconductive drum 41 is a member in which a photosensitive layer is formed on the outer peripheral surface of a cylindrical drum body having conductivity, and is disposed behind the center in the vertical direction in the housing 2. The photosensitive drum 41 is rotatably provided in a direction indicated by an arrow in FIG. 1, and toner (developer) is supplied to an electrostatic latent image formed by exposure, whereby toner as an example of a developer image. An image is formed, and the toner image can be carried.

  The charging unit 42 includes a corona wire, a grid electrode, and the like, and is disposed to face the photosensitive drum 41. The charging unit 42 is configured to uniformly charge the surface of the photosensitive drum 41 by applying a charging bias.

  The exposure unit 43 has a plurality of unillustrated blinking portions (light emitting diode elements) arranged in the left-right direction, which is the rotation axis direction of the photosensitive drum 41, and is disposed facing the front diagonally upper side of the photosensitive drum 41. ing. The exposure unit 43 is configured such that the surface of the photosensitive drum 41 after charging can be exposed by the blinking portion blinking based on the image data.

  The developing cartridge 44 includes a developing roller 44 </ b> A, a supply roller 44 </ b> B, a layer thickness regulating blade 44 </ b> C, a toner accommodating portion 44 </ b> D that accommodates toner, and the like, and is disposed opposite to the front lower side of the photosensitive drum 41. The developing cartridge 44 is configured to supply toner to the electrostatic latent image on the photosensitive drum 41 formed by exposure to form a toner image on the photosensitive drum 41. The developing cartridge 44 is configured to be detachable from the housing 2 through the opening 21 </ b> A by opening the front cover 22 and the second front cover 24, thereby being replaceable.

  The transfer roller 45 includes a metal shaft, a roller body having elasticity provided around the shaft, and the like, and is disposed facing the back of the photosensitive drum 41. The transfer roller 45 is configured to transfer the toner image onto the paper S passing between the photosensitive drum 41 by attracting the toner by applying a transfer bias.

  The fixing device 100 includes a heating member 101, a pressure roller 150, and the like, and is disposed in the housing 2 above the photosensitive drum 41. The fixing device 100 is configured to thermally fix the toner image transferred onto the paper S passing between the heating member 101 and the pressure roller 150. The detailed configuration of the fixing device 100 will be described later.

  The paper discharge unit 5 is configured to discharge the paper S on which an image is formed, and mainly includes a paper discharge roller 51 and a paper discharge tray 52. The paper discharge roller 51 is a roller for discharging the paper S carried out from the fixing device 100 to the outside of the housing 2, and is disposed at the upper part in the housing 2. The paper discharge tray 52 is a tray for placing the paper S discharged outside the housing 2, and is formed on the upper surface of the main body frame 21.

  The laser printer 1 configured as described above executes an image forming operation when an image forming instruction including image data is input. Specifically, the image forming unit 4 charges the surface of the photosensitive drum 41 that is rotationally driven by the charging unit 42, and exposes the charged surface of the photosensitive drum 41 by the exposure unit 43 to be placed on the photosensitive drum 41. An electrostatic latent image based on the image data is formed. Thereafter, the image forming unit 4 supplies toner to the exposed photosensitive drum 41 by the developing cartridge 44 to visualize the electrostatic latent image, and forms a toner image on the photosensitive drum 41.

  Further, at an appropriate timing so far, the paper feed unit 3 supplies the paper S placed on the paper feed tray 31 by the paper feed mechanism 33 to the image forming unit 4. Then, the image forming unit 4 transfers the toner image carried by the photosensitive drum 41 onto the paper S by conveying the paper S supplied from the paper feeding unit 3 between the photosensitive drum 41 and the transfer roller 45. To do. Thereafter, the image forming unit 4 heat-fixes the toner image transferred onto the paper S by the fixing device 100. The paper discharge unit 5 discharges the paper S on which the toner image is thermally fixed by the paper discharge roller 51 to the outside of the housing 2 and places it on the paper discharge tray 52.

<Detailed configuration of fixing device>
Next, a detailed configuration of the fixing device 100 will be described.
As shown in FIG. 2, the fixing device 100 includes a heating member 101 and a pressure roller 150 as an example of a rotating body.

  The heating member 101 includes a fixing belt 110 as an example of an endless belt, a halogen lamp 120 as an example of a heater, a nip plate 130 as an example of a nip member, a reflection plate 140, a stay 160, and a guide frame 200. It has.

  The fixing belt 110 is an endless belt having heat resistance and flexibility. The fixing belt 110 contacts and follows the pressure roller 150 that rotates in the clockwise direction in the figure, so that the sheet S can be transferred to and from the pressure roller 150. On the clamping side (nip part), it is configured to move upward and obliquely forward from below. The fixing belt 110 is configured to rotate around an axis extending in the left-right direction (width direction), and has an inner surface 110A that slides on the nip plate 130 and an outer surface 110B that faces the pressure roller 150. . The fixing belt 110 has a metal pipe formed from a metal such as stainless steel. Further, the fixing belt 110 may have a rubber layer covering the surface of the metal base tube, and may further have a non-metal easily peelable material layer by fluorine coating or the like covering the surface of the rubber layer. .

  The halogen lamp 120 is a separate body from the nip plate 130 and is a heating element that heats the toner on the paper S by heating the nip plate 130 and the fixing belt 110. The halogen lamp 120 is disposed inside the fixing belt 110 at a predetermined interval from the inner surfaces of the fixing belt 110 and the nip plate 130.

  The nip plate 130 is a long metal plate extending in the left-right direction, and is formed by bending, for example, an aluminum plate having a higher thermal conductivity than a steel stay 160 described later. The nip plate 130 is disposed so as to be in sliding contact with the inner surface 110 </ b> A of the fixing belt 110, and transmits radiant heat received from the halogen lamp 120 to the toner on the paper S via the fixing belt 110. The structure of the nip plate 130 will be described later.

  The reflection plate 140 is a member that reflects the radiant heat from the halogen lamp 120 (radiant heat radiated mainly in the front-rear direction and the upward direction) toward the nip plate 130 (the inner surface of the base portion 131). Is arranged at a predetermined interval from the halogen lamp 120 so as to surround the halogen lamp 120.

  By collecting the radiant heat from the halogen lamp 120 on the nip plate 130 by such a reflector 140, the radiant heat from the halogen lamp 120 can be used efficiently, and the nip plate 130 and the fixing belt 110 can be heated quickly. Can do.

  The reflection plate 140 is formed by curving an aluminum plate or the like in a substantially U shape in cross section, for example, having a high infrared and far infrared reflectance. More specifically, the reflecting plate 140 mainly includes a reflecting portion 141 having a curved shape (substantially U-shaped in cross section) and a flange portion 142 that is bent substantially vertically outward at both ends of the reflecting portion 141 and extends in the vertical direction. doing. In order to increase the thermal reflectance, the reflection plate 140 may be formed using a mirror-finished aluminum plate or the like.

  The stay 160 is a member that secures the rigidity of the nip plate 130 by supporting both ends of the base portion 131 of the nip plate 130 in the conveyance direction of the sheet S via the flange portion 142 of the reflection plate 140. It is formed in a letter shape and is arranged so as to cover the reflection plate 140.

  The guide frame 200 is a member that supports components such as a temperature sensor 170 that detects the temperature of the nip plate 130 for temperature control of the fixing device 100, and is fixed to the stay 160. The temperature sensor 170 is disposed to face a temperature detection tab 135 (to be described later) of the nip plate 130, and is configured to send a detected temperature signal at each position of the nip plate 130 to a control device (not shown). The guide frame 200 includes a guide 230 that is in sliding contact with the inner surface 110 </ b> A of the fixing belt 110 on the upstream side and the downstream side of the nip plate 130.

  The pressure roller 150 sandwiches the fixing belt 110 with the nip plate 130 of the heating member 101, thereby driving the fixing belt 110 along with the rotation thereof, and sandwiching the paper S with the fixing belt 110 in the transport direction. It is configured to carry.

<Nip plate structure>
Next, the structure of the nip plate 130 will be described in detail.
As shown in FIGS. 2 and 3, the nip plate 130 includes a base portion 131 that is in sliding contact with the inner surface 110A of the fixing belt 110 during driving, and an upstream end that extends from an upstream edge and a downstream edge in the conveyance direction. Main part 132 and downstream end 133 and rectangular protrusion-shaped temperature detection tabs 135 formed at two locations along downstream end 133. A temperature sensor 170 is disposed opposite to each temperature detection tab 135, and the detected temperature at each position is used for controlling the fixing device 100. A surface 131A of the base portion 131 that faces the inner surface 110A of the fixing belt 110 is a “central region” that contacts the inner surface 110A of the fixing belt 110 during driving via a lubricant such as fluorine-based grease.

  The nip plate 130 is bent at the upstream edge and the downstream edge of the base portion 131 in the sheet conveyance direction. As shown in FIG. 3B, the upstream end 132 extends from the upstream edge of the base 131 to the upstream side in a direction away from the inner surface 110A of the fixing belt 110, and similarly downstream. The side end portion 133 is a portion that extends from the downstream end edge of the base portion 131 toward the downstream side in a direction away from the inner surface 110 </ b> A of the fixing belt 110. In other words, the surface 132A on the side facing the inner surface 110A of the fixing belt 110 at the upstream end 132 is separated from the inner surface 110A of the fixing belt 110 being driven, and the fixing belt 110 at the downstream end 133 is separated. The surface 133A on the side facing the inner surface 110A is separated from the inner surface 110A of the fixing belt 110 being driven.

  At least one of the surfaces 132A and 133A on the side facing the inner surface 110A of the fixing belt 110 of the upstream end 132 and the downstream end 133 has a holding force (adhesive force) for holding the lubricant at the center. This is an “upstream area” and a “downstream area” where a “holding portion LR” larger than the area 131A is formed.

  As shown in FIGS. 3A to 3D, in this embodiment, two lines LS due to scribing are engraved in the upstream region 132A and the downstream region 133A, respectively, to retain the lubricant ( It acts to suppress the outflow to the upstream side and the downstream side). That is, the portion of the upstream region 132A and the downstream region 133A where the marking line LS is formed constitutes the holding portion LR. Accordingly, it is possible to suppress the lubricant that is about to overflow from the upstream region 132A and the downstream end portion 133 from entering the inside of the fixing device 100. Further, the lubricant retained and retained in the regions 132A and 133A. A part of the agent may be collected by the fixing belt 110 when the fixing belt 110 flutters.

As shown in FIG. 3C, in the downstream region 133A, the marking line LS as the holding portion LR is spaced L1 from the central region 131A (the sliding contact portion that contacts the inner surface 110A of the fixing belt 110). In the position. Further, as shown in FIG. 3D, in the upstream region 132A, the scribing line LS is provided at a position having a distance L2 from the central region 131A. The intervals L1 and L2 are appropriately set based on the estimated amount of lubricant that overflows. In the present embodiment, the amount of lubricant that overflows tends to increase on the upstream side, so L2> L1.
For example, the interval L1 may be 0.0 to 0.5 mm, 0.5 to 1.0 mm, or 1.0 to 2.0 mm. Further, the interval L2 may be, for example, 0.0 mm to 1.0 mm, 1.0 to 2.0 mm, or 2.0 to 3.0 mm.

  In the present embodiment, the fixing device 100 is arranged so that the central region 131A has an obliquely upward posture. Therefore, the downstream end portion 133 (downstream region 133A) is inclined obliquely downward, and the lubricant is more likely to flow out due to the action of gravity as compared with the configuration in which the central region 131A faces downward. Although there is a concern about falling into the inside of the apparatus 100, the inflow of the lubricant into the inside of the fixing apparatus 100 can be suppressed by the line LS caused by the scribing formed in the downstream region 133A.

  In this embodiment, the marking line LS constituting the holding portion LR is not interrupted over the entire range corresponding to the width of the fixing belt 110, and both end edges thereof exceed the range corresponding to the width of the fixing belt 110. It is provided so that it may be located outside.

  Since the marking line LS is formed over the entire range corresponding to the width of the fixing belt 110 in the direction orthogonal to the paper conveyance direction, the lubricant outflow suppression effect is uniformly distributed over the entire width direction of the fixing belt 110. It can be demonstrated.

  As shown in FIG. 4, in the present embodiment, the holding portion LR is formed leaving a predetermined margin M from both end edges of the nip member in the direction orthogonal to the paper transport direction. In other words, the marking line LS is formed up to the front of the edge of the nip plate 130 (with a predetermined margin M left) and does not reach the edge of the nip plate 130.

  This is because the marking line LS extending in the direction perpendicular to the paper conveyance direction acts to suppress and retain the flow of the lubricant in the paper conveyance direction, and the lubricant overflows at both edges in the width direction of the fixing belt 110. This is because it acts to guide the toner to the inside where the fixing belt 110 slides. In addition, the fixing belt 110 slightly fluctuates (displaces) in the width direction during the rotation of the fixing belt 110, but the width direction extension range of the marking line LS is the range of the displacement in the width direction of the fixing belt 110. The edge (margin M) is set so as to cover completely. That is, the holding portion LR is formed in a range in which the edge in the direction orthogonal to the sheet conveying direction is located outside the range corresponding to the width of the belt, and therefore the holding unit LR is affected by the fluctuation of the fixing belt 110 in the width direction. Therefore, the lubricant outflow suppressing effect can be effectively exhibited.

  Note that the marking line LS acts to suppress the lubricant from flowing out in the sheet conveyance direction and to uniformly disperse the fixing belt 110 in the width direction. In the present embodiment, the marking line LS (holding portion LR) does not reach the end edge of the nip plate 130 (is formed leaving a predetermined margin M), so the sheet from the end edge of the nip plate 130 is formed. It is also configured to suppress outflow in the transport direction.

  As described above, in the fixing device 100 according to the present embodiment, the nip plate 130 as an example of the nip member has a surface facing the inner surface 110A of the fixing belt 110 in the sheet conveyance direction. A central area 131A corresponding to the contact area, and an upstream area 132A and a downstream area 133A extending from the upstream and downstream edges of the central area 131A in the sheet conveying direction with the central area 131A interposed therebetween. And a holding portion LR having a holding force for holding the lubricant larger than that of the central region 131A is formed in at least one of the upstream region and the downstream region 132A, 133A. It is possible to suppress the contamination of the device and the reduction of the lubricant.

  Further, the holding portion LR is configured as a rough surface portion whose surface roughness (for example, maximum height) in the paper conveyance direction is larger than that of the central region 131A due to scribing, and thus can be realized by simple surface processing. . The surface roughness of the holding portion LR (maximum height Rz of JIS B0601-2001) is, for example, larger when the central region 131A is Rz = 0.10 to 2.00 μm, Rz = 2.00 to 5.5. What is necessary is just to set in the range of 00 micrometer. Further, the surface roughness of the central region 131A may be Rz = 2.00 to 5.00 μm, and the surface roughness of the holding portion LR may be set to a larger range of Rz = 5.00 to 10.0 μm. Alternatively, when the surface roughness of the central region 131A is Rz = 5.00 to 10.0 μm, the surface roughness of the holding portion LR may be larger than that in the range of Rz = 10.0 to 100 μm.

In the present embodiment, the holding portion LR is configured by the two marking lines LS, but the present invention is not limited to this specific form. For example, the number of marking lines may be one or three or more. Note that it is also possible to form the holding portion LR having a maximum height Rz larger than that of the central region 131 by forming a bowl-shaped protruding portion instead of the concave groove formed by scribing.
Further, as shown in FIGS. 5A to 5D, the same effect can be obtained by a rough surface portion formed by rasp or cutting. That is, a part or the whole of the upstream region 132A and the downstream region 133A is surface-treated so as to increase the surface roughness in the paper conveyance direction (for example, sanding or the like is performed in a direction perpendicular to the paper conveyance direction). Thus, the lubricant can be prevented from flowing out.

  Specifically, a part of the upstream region 132A and the downstream region 133A adjacent to the downstream edge of the central region 131A in sliding contact with the fixing belt 110 is subjected to surface roughness in the sheet conveyance direction (for example, arithmetic average roughness). By forming the rough surface portion substantially larger than the central region 131A, the holding portion LR that can obtain a desired effect can be obtained. The surface roughness of the holding portion LR (arithmetic average roughness Ra of JIS B0601-2001) is, for example, larger when the central region 131A is Ra = 0.02 to 0.20 μm, Ra = 0.20-0. It may be set in the range of 50 μm. Further, the surface roughness of the central region 131A may be Ra = 0.20 to 0.50 μm, and the surface roughness of the holding portion LR may be a range of Ra = 0.50 to 1.00 μm larger than that. Alternatively, when the surface roughness of the central region 131A is Ra = 0.50 to 1.00 μm, the surface roughness of the holding portion LR may be a range of Ra = 1.00 to 5.00 μm larger than that.

  As shown in FIG. 5C, in the upstream region 132A, the holding portion LR is provided at a position spaced from the central region 131A (sliding contact portion that contacts the inner surface 110A of the fixing belt 110) by a distance L1. . Further, as shown in FIG. 5D, in the downstream region 133A, the holding portion LR is provided at a position having a distance L2 from the central region 131A. Similar to the embodiment shown in FIG. 3, the intervals L1 and L2 are appropriately determined.

  The holding portion LR forms at least a part within a range within 3 mm from the upstream or downstream edge of the central region 131A in the sheet conveyance direction, thereby not only suppressing the outflow of the lubricant but also the fixing belt 110. Lubricant overflowing from the sliding surface due to flapping during driving is collected by the fixing belt 110 (that is, the inner surface 110A of the fixing belt 110 touches the lubricant held by the holding portion, and contacts the inner surface 110A of the fixing belt 110. Since the lubricant can be adhered and returned to the sliding contact surface, the outflow of the lubricant can be suppressed more effectively.

  As described above, the rough surface portion constituting the holding portion LR is formed in a region (closest) close to the edge of the central region 131A, so that more effective recovery of the lubricant overflowing from the sliding surface can be achieved. However, for example, a rough surface portion can be formed continuously (or discontinuously) on the outside thereof. Since such a rough surface portion also has a holding force for holding the lubricant larger than that of the sliding contact surface, the outflow of the lubricant is suppressed and adhesion (contamination) to the inside of the fixing device 100 and other members of the laser printer 1. ) Can be suppressed.

  The formation method of the holding part LR is not limited to rough surface processing by scribing, filing or cutting. Conventionally, the nip plate 130 can be improved in slidability (smoothness) by coating the surface on the side facing the inner surface of the fixing belt 110 with an electroless nickel plating layer, a metal oxide film, or a fluororesin layer. Although being performed, the holding part having an effect of suppressing the lubricant outflow by not performing such a film forming process only in a desired range (for example, a part of the upstream region 132A and the downstream region 133A as described above). It can also be.

  FIG. 6A shows an example of forming the holding portion LR by selectively applying the film forming process. A coating C is provided on the surface of the nip plate 130 on the side facing the inner surface 110A of the fixing belt 110, which corresponds to the central region 131A, but the area where the inner surface 110A of the fixing belt 110 does not contact (downstream side). A coating C is not provided in a part of the region 133A).

  Alternatively, after a film forming process similar to the conventional film is performed on the entire surface of the nip plate 130 on the side facing the inner surface 110A of the fixing belt 110, the coating C in a desired range is removed, whereby the state shown in FIG. Such a holding part LR may be formed.

In addition to the method of increasing the surface roughness of the surface of the nip plate 130 facing the inner surface 110A of the fixing belt 110 by surface processing only in a desired range, the surface characteristics (roughness) can be changed by changing the type of the coating C. The holding portion LR can be formed by increasing the holding force for holding the lubricant only in a desired range by changing the surface shape and wettability with respect to the lubricant that can be measured by, for example. In the example shown in FIG. 6B, the coating C1 covers the entire portion corresponding to the central region 131A on the surface facing the inner surface 110A of the fixing belt 110, and the entire downstream region 133A where the inner surface 110A of the fixing belt 110 does not contact. Is provided with a coating C2 having a lubricant holding power larger than that of the coating C1.
For example, when a plating process including polytetrafluoroethylene (PTFE) is performed, the holding power can be increased by reducing the PTFE compounding ratio of C2 rather than C1.

  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 invention as follows.

  In the embodiment described with reference to FIGS. 3 to 5, the holding portion LR has been described with reference to FIG. 6, although an example in which the holding portion LR is formed in both the upstream region 132 </ b> A and the downstream region 133 </ b> A has been described. Like embodiment, the holding | maintenance part LR of this invention should just be formed only in either one of the upstream area | region 132A or the downstream area | region 133A. In addition, the holding portion LR may be provided in the entire region of the upstream region 132A and / or the downstream region 133A, or may be provided in a part.

  In the above-described embodiment, the nip plate 130 is exemplified as the nip member. However, the present invention is not limited to this, and may be a nip member having a block shape or a pad shape instead of a plate shape.

  In the above-described embodiment, the surface having the central region (sliding contact surface), upstream region, and downstream region of the nip member (on the side facing the inner surface 110A of the fixing belt 110) is a plate-shaped member (nip plate). 130) are defined as surfaces of a base portion 131, an upstream end portion 132, and a downstream end portion 133 that are formed by bending at the upstream and downstream edges in the sheet conveyance direction. It is not limited to.

  When the nip member is a block-like member, for example, a surface 132A spaced from the inner surface 110A of the driving fixing belt 110 and a surface 133A spaced from the inner surface 110A of the driving fixing belt 110 are respectively sliding surfaces ( If the configuration extends from the central region 131 </ b> A), the surfaces 132 </ b> A and 133 </ b> A can be used as an upstream region and a downstream region that form the holding portion LR.

  In the embodiment, the halogen lamp 120 employed as the heat source (heater) of the fixing device 100 is configured to heat the toner on the paper S by heating the fixing belt 110 via the nip plate 130 by the radiant heat. The heat source of the fixing device is not limited to such a configuration. For example, if the belt can be heated directly / indirectly, a heating element such as a carbon heater or a ceramic heater, or a metal belt or nip plate such as an IH heater does not generate heat. It may be one that generates heat by an induction heating method, and the type and arrangement thereof can be selected as appropriate.

  Various modifications can be made to the structure of the heating member 101 of the fixing device 100. For example, like the heating member 301 shown in FIG. 7A, a heat insulating resin member 370 is interposed between the halogen lamp 320 and the nip plate 330 so that the radiant heat from the halogen lamp 320 is directly or directly reflected by the reflector 340. It is possible to adopt a configuration in which the fixing belt 310 is provided via the belt (without the nip plate 330). In FIG. 7, reference numeral 360 denotes a stay that supports the nip plate 330 and the reflection plate 340.

  Also in the nip plate 330, as shown in FIG. 7B, the holding portion LR (Lubricant is to be held in at least one of the upstream region 332A and the downstream region 333A not in contact with the inner surface of the fixing belt 310 being driven. Is formed by processing by one or more methods selected from scribing, filing, cutting, film formation, film removal, and the like as described above. (FIG. 7B shows an example in which the holding portion is formed only in the downstream region 333A).

  In the above-described embodiment, the photosensitive drum 41 is exemplified as the image carrier, but is not limited thereto. For example, the image carrier may be an intermediate transfer drum or an intermediate transfer belt configured to be able to carry a toner image transferred from a photosensitive drum.

  In the embodiment, the fixing device 100 as the image forming apparatus is arranged so that the surface (center region 131A) that is in sliding contact with the inner surface 110A of the fixing belt 110 of the nip plate 130 is in an upward or obliquely upward posture. The invention is not limited to this. The surface of the nip member on the side facing the inner surface of the belt has a central area corresponding to a range in which the belt contacts with the lubricant in the paper conveyance direction, and an upstream of the paper conveyance direction across the central area. As long as it has an upstream region and a downstream region that respectively extend from the side edge and the downstream edge, by adopting the configuration of the present invention, the lubricant outflow from the upstream region or the downstream region The action which suppresses can be provided. Therefore, the present invention can be suitably applied even to an image forming apparatus in which the nip member is arranged so that the central region thereof is in a downward or obliquely downward posture.

  In this embodiment, the paper S including thick paper, postcard, thin paper, etc. is exemplified as the recording sheet. However, the present invention is not limited to this, and may be, for example, an OHP sheet.

  In the above embodiment, the laser printer 1 is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be a copier or a multi-function machine including a document reading device such as a flat bed scanner.

DESCRIPTION OF SYMBOLS 1 Laser printer 41 Photosensitive drum 45 Transfer roller 100 Fixing device 110 Fixing belt 110A Inner surface 110B Outer surface 130 Nip plate 131 Base part 131A Central area 132 Upstream end part 132A Upstream area 133 Downstream end part 133A Downstream area LR Holding part 101 Heating member 150 Pressure roller S Paper

Claims (11)

An endless belt having an inner surface and an outer surface;
A nip member extending inside the endless belt;
A rotating body configured to sandwich the endless belt with the nip member and to convey the recording sheet to and from the endless belt,
The surface of the nip member that faces the inner surface of the endless belt has a central region corresponding to a range in which the endless belt contacts with the lubricant in the transport direction, and an upstream end of the central region in the transport direction. An upstream region extending away from the endless belt, and a downstream region extending from the downstream end of the central region in the transport direction and away from the endless belt,
At least one of the upstream region and the downstream region is formed with a holding portion having a holding force for holding the lubricant larger than that of the central region.   The fixing device according to claim 1, wherein the holding portion is a rough surface portion having a surface roughness in the transport direction larger than that of the central region.   In the surface of the nip member facing the inner surface of the endless belt, a film is provided in the central region, and a film is not provided in at least one of the upstream region and the downstream region. The fixing device according to claim 1.   The fixing device according to claim 1, wherein the holding unit is formed over the entire range corresponding to the width of the endless belt in a direction orthogonal to the conveyance direction. .   The fixing device according to claim 4, wherein an edge of the holding unit in a direction orthogonal to the conveyance direction is located outside a range corresponding to a width of the endless belt.   The fixing device according to claim 5, wherein the holding portion is formed leaving a predetermined margin from both end edges of the nip member in a direction orthogonal to the transport direction.   The said holding | maintenance part is at least one part formed in the range within 3 mm from the upstream edge of the said conveyance direction of the said center area | region in the said conveyance direction, or any one of Claims 1-6 characterized by the above-mentioned. The fixing device according to one item.   The holding unit is configured to process a part of the surface of the nip member facing the inner surface of the endless belt by one or more methods selected from scribing, filing, cutting, film formation, and film removal. The fixing device according to claim 1, wherein the fixing device is formed. An image carrier configured to carry a developer image;
A transfer member for transferring the developer image carried on the image carrier to a recording sheet;
An image forming apparatus comprising the fixing device according to claim 1.   The image forming apparatus according to claim 9, wherein the nip member is disposed such that the central region is in an upward or obliquely upward posture. Endless belt,
A nip member facing the inner surface of the endless belt,
The nip member is a surface facing an inner surface of the endless belt, a first region that contacts the endless belt via a lubricant, and a second region that extends from the first region and is separated from the endless belt. And
The fixing device according to claim 1, wherein the second region has a holding portion that has a holding force that is greater than the central region for holding the lubricant.

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