JP2018109697A - Fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device and image formation apparatus which can suppress the lubricant from entering to the outer peripheral surface side of a fixation belt without applying the load to the fixation belt.SOLUTION: A fixation device includes: a roller member; a fixation belt; a pressing member which is arranged on the inner side of the fixation belt, forms a fixation nip by pressing the fixation belt between the roller member and itself, and is not rotatable; and a sliding member which reduces the sliding resistance between the pressing member and the fixation belt by being sandwiched between the pressing member and the fixation belt in the fixation nip. In the sliding member, the lubricant is applied to the surface facing the fixation belt. The pressing member is arranged so as not to press the fixation belt on the downstream side with respect to the fixation nip in the movement direction of the fixation belt and includes a coagulation part which coagulates the lubricant adhering to the fixation belt from the sliding member to the center part side from both end part sides in the width direction of the fixation belt as heading toward the downstream side in the movement direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device and an image forming apparatus.

  In general, an image forming apparatus (printer, copying machine, facsimile, etc.) using an electrophotographic process technology irradiates (exposes) a charged photosensitive drum (image carrier) with laser light based on image data. To form an electrostatic latent image. Then, by supplying toner from the developing device to the photosensitive drum on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, after the toner image is directly or indirectly transferred to the sheet, the toner image is formed on the sheet by fixing it by heating and pressing at the fixing nip.

  In particular, in a fixing nip in a color image forming apparatus, it is necessary to fix a plurality of colors of toner on a sheet without unevenness. Therefore, a fixing roller having an elastic layer having a large layer thickness is provided on the surface of the sheet on the toner image side. By using it, the fixability in the fixing nip is improved. However, in recent years, in view of the increasing demand for a configuration that achieves good and stable image quality and further achieves energy saving, there are known ones in which the fixing roller is changed to a pressing member (for example, Patent Document 1).

  The pressing member forms a fixing nip by sandwiching the fixing belt with the pressure roller without rotating. However, since the pressing member does not rotate, the sliding resistance between the pressing member and the fixing belt increases in the fixing nip. Therefore, a sheet-like sliding member is disposed in order to reduce the sliding resistance between the pressing member and the fixing belt. Further, the increase in sliding resistance is further reduced by applying a lubricant to the contact surface of the sliding member with the fixing belt.

  By making the surface of the sliding member uneven, it is possible to hold the lubricant in the fixing nip, but the lubricant cannot be completely held in the fixing nip. The fixing belt rotates with the lubricant attached.

  Here, when the lubricant adhering to the inner peripheral surface of the fixing belt goes around the outer peripheral surface of the fixing belt, the lubricant adheres to the outer peripheral surface of the fixing belt and the pressure roller facing the outer peripheral surface. As a result, image defects such as gloss unevenness occur due to the lubricant adhering to the outer peripheral surface of the fixing belt, or the conveyance force of the paper and the fixing belt is adversely affected due to the lubricant adhering to the pressure roller. It will occur.

  As the fixing belt circulates, it is considered that the lubricant spreads to both ends of the fixing belt and easily moves to the outer peripheral surface is the fixing nip portion where the pressure is strong. On the side, the spread lubricant needs to be returned to the center side.

  For example, in the configuration described in Patent Document 1, the stepped portion is provided in the downstream portion of the fixing nip of the sliding member, thereby suppressing the lubricant from moving to both end portions of the fixing belt.

JP-A-2005-77872

  However, in the configuration described in Patent Document 1, since it is necessary to strongly press the step portion against the fixing belt, the sliding resistance between the fixing belt and the pressing member (sliding member) becomes large, and the fixing belt is prevented from moving to the fixing belt. There was a risk that the load would increase.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device and an image forming apparatus capable of suppressing the lubricant from flowing around the outer peripheral surface side of the fixing belt without applying a load to the fixing belt.

The fixing device according to the present invention includes:
A rotatable roller member;
An endless fixing belt movable while contacting the roller member;
A non-rotatable pressing member which is disposed inside the fixing belt and forms a fixing nip by pressing the fixing belt with the roller member;
A sliding member that reduces sliding resistance between the pressing member and the fixing belt by being sandwiched between the pressing member and the fixing belt in the fixing nip;
With
The sliding member is coated with a lubricant on the surface facing the fixing belt,
The pressing member is disposed so as not to press the fixing belt on the downstream side of the fixing nip in the moving direction of the fixing belt, and the lubricant attached to the fixing belt from the sliding member is moved in the moving direction. As it goes to the downstream side, it has an agglomerating part that aggregates from both ends in the width direction of the fixing belt to the central part.

An image forming apparatus according to the present invention includes:
A rotatable roller member;
An endless fixing belt movable while contacting the roller member;
A non-rotatable pressing member which is disposed inside the fixing belt and forms a fixing nip by pressing the fixing belt with the roller member;
A sliding member that reduces sliding resistance between the pressing member and the fixing belt by being sandwiched between the pressing member and the fixing belt in the fixing nip;
With
The sliding member is coated with a lubricant on the surface facing the fixing belt,
The pressing member is disposed so as not to press the fixing belt on the downstream side of the fixing nip in the moving direction of the fixing belt, and the lubricant attached to the fixing belt from the sliding member is moved in the moving direction. As it goes to the downstream side, it has an agglomerating part that aggregates from both ends in the width direction of the fixing belt to the central part.

  According to the present invention, it is possible to suppress the lubricant from entering the outer peripheral surface side of the fixing belt without applying a load to the fixing belt.

1 is a diagram schematically illustrating an overall configuration of an image forming apparatus according to an exemplary embodiment. FIG. 3 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. It is a figure which shows a fixing part. It is a figure which shows the cross-sectional shape of a nip downstream part. It is a figure for demonstrating a mode that a lubricant aggregates. It is a figure for demonstrating a mode that a lubricant aggregates. It is a figure which shows the fixing | fixed part which concerns on a 1st modification. FIG. 6 is a view of a downstream portion of a nip according to a first modification viewed from the downstream side of the fixing nip. It is a figure which shows the cross-sectional shape of the nip downstream part which concerns on a 2nd modification.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the present embodiment.

  As shown in FIG. 1, the image forming apparatus 1 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421. After the four color toner images are superposed on the intermediate transfer belt 421, an image is formed by secondary transfer onto the paper S sent from the paper feed tray units 51a to 51c.

  Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one step. Tandem system is adopted.

  As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, and a control unit 101. The fixing unit 60 corresponds to the “fixing device” of the invention.

  The control unit 101 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, and the like. The CPU 102 reads out a program corresponding to the processing content from the ROM 103 and develops it in the RAM 104, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 101 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Do. For example, the control unit 101 receives image data (input image data) transmitted from an external device, and forms an image on the paper S based on the image data. The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  As shown in FIG. 1, the image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

  The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on the document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  As shown in FIG. 2, the operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image states, operation states of functions, and the like according to a display control signal input from the control unit 101. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 101.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 101. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  As shown in FIG. 1, the image forming unit 40 is based on input image data, and image forming units 41Y, 41M, and 41C for forming an image using colored toners of Y component, M component, C component, and K component. , 41K, intermediate transfer unit 42 and the like.

  The Y component, M component, C component, and K component image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, or K are added to the reference numerals when distinguished from each other. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

  The photoreceptor drum 413 is made of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate, for example.

  The control unit 101 rotates the photosensitive drum 413 at a constant peripheral speed by controlling a driving current supplied to a driving motor (not shown) that rotates the photosensitive drum 413.

  The charging device 414 is, for example, a charging charger, and uniformly charges the surface of the photosensitive drum 413 having photoconductivity by generating corona discharge.

  The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. As a result, an electrostatic latent image of each color component is formed in the image area irradiated with laser light on the surface of the photosensitive drum 413 due to a potential difference from the background area.

  The developing device 412 is a two-component reversal developing device, and attaches a developer of each color component to the surface of the photosensitive drum 413 to visualize the electrostatic latent image and form a toner image.

  For example, a DC developing bias having the same polarity as the charging polarity of the charging device 414 or a developing bias in which a DC voltage having the same polarity as the charging polarity of the charging device 414 is superimposed on an AC voltage is applied to the developing device 412. As a result, reverse development is performed in which toner is attached to the electrostatic latent image formed by the exposure device 411.

  The drum cleaning device 415 is in contact with the surface of the photoconductive drum 413 and has a flat drum cleaning blade made of an elastic material, etc., and remains on the surface of the photoconductive drum 413 without being transferred to the intermediate transfer belt 421. Remove toner.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

  The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The intermediate transfer belt 421 is a belt having conductivity and elasticity, and has a high resistance layer on the surface. The intermediate transfer belt 421 is rotationally driven by a control signal from the control unit 101.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B disposed on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the intermediate transfer belt 421, that is, the side in contact with the primary transfer roller 422. It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a secondary transfer bias is applied to the secondary transfer roller 424, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the sheet S, that is, the side in contact with the secondary transfer roller 424. Is electrostatically transferred to the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

  The fixing unit 60 is disposed on the fixing surface of the sheet S, that is, the upper fixing unit 60A having a fixing surface side member disposed on the surface on which the toner image is formed, and on the back surface of the sheet S, that is, on the surface opposite to the fixing surface. A lower fixing unit 60B having a back-side support member, a heating source, and the like. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for nipping and transporting the sheet S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image is secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit.

  The upper fixing unit 60A includes an endless fixing belt 61, a heating roller 62, and a pressing unit 200, which are fixing surface side members. The fixing belt 61 is stretched between the heating roller 62 and the pressing unit 200. The pressing unit 200 will be described later.

  The lower fixing unit 60B includes a pressure roller 64 that is a back side support member. The pressure roller 64 forms a fixing nip that sandwiches and conveys the sheet S with the fixing belt 61.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, etc. is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs including a registration roller pair 53a. The registration roller portion in which the registration roller pair 53a is disposed corrects the inclination and deviation of the paper S.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one side of the sheet S at a time, and the fixing unit 60 performs a fixing process. The sheet S on which the image has been formed is discharged out of the apparatus by a discharge unit 52 having a discharge roller 52a.

  Next, the detailed structure of the pressing part 200 will be described. FIG. 3 is a diagram illustrating the fixing unit 60. As shown in FIG. 3, the pressing unit 200 includes a pressing member 210, a sliding member 220, and a support member 230.

  The pressing member 210 has a nip forming part 211 and a nip downstream part 212. The nip forming portion 211 is a portion that forms a fixing nip by sandwiching the fixing belt 61 with the pressure roller 64. The nip forming unit 211 presses the fixing belt 61 by being pressed by the pressure roller 64. The pressure roller 64 corresponds to the “roller member” of the present invention.

  The nip downstream portion 212 is a portion located on the downstream side of the fixing nip in the pressing member 210 in the moving direction of the fixing belt 61 (arrow direction, hereinafter, simply referred to as “moving direction”). Further, since the nip downstream portion 212 is a portion that is not pressed by the pressure roller 64, it is a portion that does not press the fixing belt 61 by the pressing member 210. The nip downstream portion 212 is inclined so as to go to the side opposite to the fixing belt 61 side as it goes to the downstream side in the moving direction.

  The surface of the nip downstream portion 212 facing the fixing belt 61 is opposed to the central portion of the fixing belt 61 in the width direction (the left-right direction in the drawing) in the entire moving direction, and the area decreases as it goes downstream in the moving direction. It is formed to become.

  Specifically, as shown in FIGS. 4A, 4B, and 4C, the facing surface of the nip downstream portion 212 is opposed to substantially the entire width direction of the fixing belt 61 at the most upstream position of the nip downstream portion 212. (See FIG. 4A), but the facing area becomes smaller toward the downstream side (see FIG. 4B). The nip downstream portion 212 is opposed to only the central portion in the width direction of the fixing belt 61 at the most downstream position (see FIG. 4C). 4A, 4B, and 4C exemplify the case where the fixing belt 61 and the nip downstream portion 212 are brought into contact with each other in consideration of ease of understanding.

  By having such a shape, a lubricant G, which will be described later, attached to the fixing belt 61 is aggregated so as to be closer to the center side toward the downstream side in the movement direction (see FIGS. 5 and 6). That is, the nip downstream portion 212 causes the lubricant G to aggregate from the both end portions of the fixing belt 61 to the central portion as it goes downstream in the moving direction. The nip downstream portion 212 corresponds to the “aggregation portion” of the present invention.

  In addition, the nip downstream portion 212 includes an oil-repellent material (for example, a fluororesin such as PTFE). This makes it difficult for the lubricant G to adhere to the nip downstream portion 212. Note that the nip downstream portion 212 may be coated on the surface with an oil-repellent material.

  The sliding member 220 is a sheet-like member, for example, processed with Teflon (registered trademark), which is sandwiched between the pressing member 210 and the fixing belt 61. Thereby, the sliding member 220 has a function of reducing sliding resistance between the pressing member 210 and the fixing belt 61.

  A lubricant G is applied between the sliding member 220 and the fixing belt 61. Thereby, the sliding resistance of the fixing belt 61 in the fixing nip portion is further reduced.

  The support member 230 is a part that supports the pressing member 210 pressed by the pressure roller 64. The pressure at the fixing nip is secured by being supported by the support member 230.

The effect of this Embodiment comprised as mentioned above is demonstrated.
When the fixing belt 61 rotates, the sliding resistance of the fixing belt 61 in the fixing nip is reduced by the lubricant G applied between the fixing nip portion and the sliding member 220. Since the pressure is high in the fixing nip, the lubricant G easily spreads from the central portion of the fixing belt 61 to both end portions, and the sliding resistance in the entire width direction of the fixing belt 61 is reduced.

  Incidentally, since the lubricant G adheres to the fixing belt 61, the lubricant G attached to the fixing belt 61 moves in the moving direction of the fixing belt 61. For this reason, the lubricant G spreading to both end portions at the fixing nip portion may further move to both end portions and wrap around the outer peripheral surface side of the fixing belt 61.

  When the lubricant G wraps around the outer peripheral surface of the fixing belt 61, the lubricant G adheres to the outer peripheral surface of the fixing belt 61 and the pressure roller 64 facing the outer peripheral surface. As a result, an image defect such as uneven gloss occurs due to the lubricant G adhering to the outer peripheral surface of the fixing belt 61, or the paper and the fixing belt 61 are caused due to the lubricant G adhering to the pressure roller 64. The conveyance force may be adversely affected.

  However, in the present embodiment, the facing surface of the nip downstream portion 212 is formed so as to face the center portion in the width direction of the fixing belt 61 and the area becomes smaller toward the downstream side in the moving direction. .

  As a result, when the lubricant G adhering to the fixing belt 61 passes through the portion of the nip downstream portion 212, the lubricant G is applied to the nip downstream portion 212 due to the cohesive force that tries to keep the lump in the lubricant G. Gravitate. Specifically, since the nip downstream portion 212 is gradually narrowed from the upstream position in the moving direction (see FIG. 5), the downstream position (see FIG. 6) Also, the lubricant G aggregates on the center side.

  Thus, since the lubricant G can be aggregated from both ends to the center, the lubricant G does not spread to both ends of the fixing belt 61, and the lubricant G wraps around the outer peripheral surface of the fixing belt 61. This can be suppressed.

  In addition, since the fixing belt 61 is not pressed in the portion of the nip downstream portion 212, the lubricant G can be prevented from entering the outer peripheral surface side of the fixing belt 61 without applying a load to the fixing belt 61.

  Further, the facing surface of the nip downstream portion 212 is inclined to the opposite side to the fixing belt 61 as it goes downstream in the moving direction. Therefore, since the space between the nip downstream portion 212 and the fixing belt 61 can be expanded toward the downstream side in the moving direction, more lubricant G can be aggregated toward the central portion side.

  Also, under the control of the control unit 101, the moving speed of the fixing belt 61 is set to be slower than the timing at which the paper passes through the fixing nip at the timing when the paper does not pass through the fixing nip (for example, between jobs and between papers). May be. By doing so, the time during which the lubricant G stays between the fixing belt 61 and the nip downstream portion 212 becomes longer, so that more lubricant G can be easily aggregated toward the central portion side. The control unit 101 corresponds to the “speed control unit” of the present invention.

  Next, the fixing unit 60 according to the first modification will be described. FIG. 7 is a diagram illustrating the fixing unit 60 according to the first modification. FIG. 8 is a view of the nip downstream portion 240 according to the first modification viewed from the downstream side of the fixing nip.

  As shown in FIG. 7, unlike the above embodiment, the pressing member 210 is composed only of the nip forming portion 211, and the nip downstream portion 240 is provided at the downstream end of the nip forming portion 211. .

  The nip downstream portion 240 is rotatably provided on a rotation shaft 213 provided at the downstream end portion of the nip forming portion 211. The nip downstream portion 240 is configured to be able to advance and retreat with respect to the fixing belt 61 by rotating about the rotation shaft 213.

  The lubricant G is drawn from both ends of the fixing belt 61 to the central portion in an attempt to maintain a lump shape by the cohesive force. 240 may remain.

  If the lubricant G remains in the nip downstream portion 240, the lubricant G cannot play the role of reducing the sliding resistance between the fixing belt 61 and the pressing member 210. Since the nip downstream portion 240 contains an oil-repellent material, the lubricant G hardly remains in the nip downstream portion 240, but the lubricant G may still remain in the nip downstream portion 240.

  Therefore, under the control of the control unit 101, the nip downstream portion 240 is rotated to the fixing belt 61 side. Thus, the lubricant G remaining in the nip downstream portion 240 can be returned to the fixing belt 61 side by rubbing the fixing belt 61.

  In addition, the control unit 101 controls the nip downstream portion 240 to rotate toward the fixing belt 61 at a timing when the sheet does not pass through the fixing nip (for example, between jobs and between sheets). By doing so, it is possible to avoid the timing of fixing the image on the sheet at the fixing nip.

  Further, a recess 250 is formed in the nip downstream portion 240. The recess 250 is formed on the surface of the nip downstream portion 240 facing the fixing belt 61. By forming the concave portion 250, the lubricant G attached to the fixing belt 61 enters the concave portion 250.

  When the amount of the lubricant G is small, the lubricant G hardly aggregates, so that the lubricant G tends to pass through the portion of the nip downstream portion 240 without approaching the center portion. Therefore, the lubricant G can be easily aggregated by storing the lubricant G in the recess 250.

  Further, the fixing belt 61, the pressing member 210, the concave portion 250, and the sliding member 220 are formed so that the width becomes smaller in this order. Specifically, the width D2 of the concave portion 250 is larger than the width D1 of the sliding member 220, and the width D3 of the pressing member 210 is larger than the width D2 of the concave portion 250. The width D4 of the fixing belt 61 is larger than the width D3 of the pressing member 210.

  By forming in this way, it is possible to realize an optimum configuration in which the lubricant G is unlikely to go around to the outer peripheral surface side of the fixing belt 61 from the viewpoint of the surface tension acting to reduce the surface area.

  In the above-described embodiment, the facing surface of the nip downstream portion 212 facing the fixing belt 61 is formed so that the facing area becomes smaller toward the downstream side in the moving direction. However, the present invention is not limited to this. . For example, as shown in FIGS. 9A, 9B, and 9C, the surface facing the fixing belt 61 in the nip downstream portion 212 is formed in a convex shape such that the portion facing the center portion of the fixing belt 61 is the apex. And a plane area including the vertex. Then, the area of the planar region on the facing surface of the nip downstream portion 212 becomes smaller as it goes downstream in the moving direction.

  Specifically, the opposing surface of the nip downstream portion 212 is flat on the entire surface in the width direction at the position on the most upstream side of the nip downstream portion 212 (see FIG. 9A). It is convex with respect to the belt 61 and is on a plane including the apex portion (see FIG. 9B). And the nip downstream part 212 becomes a shape where a convex part does not have a plane in the position of the most downstream side (refer FIG. 9C).

  Even with such a configuration, the lubricant G can be aggregated from both ends of the fixing belt 61 to the center.

  In the above embodiment, the facing surface of the nip downstream portion 212 is inclined to the opposite side of the fixing belt 61 as it goes downstream in the moving direction. However, the present invention is not limited to this, and the inclined surface You don't have to.

  In addition, each of the above-described embodiments is merely an example of actualization in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 60 Fixing part 61 Fixing belt 64 Pressure roller 200 Pressing part 210 Pressing member 211 Nip forming part 212 Nip downstream part 220 Sliding member

Claims (12)

A rotatable roller member;
An endless fixing belt movable while contacting the roller member;
A non-rotatable pressing member which is disposed inside the fixing belt and forms a fixing nip by pressing the fixing belt with the roller member;
A sliding member that reduces sliding resistance between the pressing member and the fixing belt by being sandwiched between the pressing member and the fixing belt in the fixing nip;
With
The sliding member is coated with a lubricant on the surface facing the fixing belt,
The pressing member is disposed so as not to press the fixing belt on the downstream side of the fixing nip in the moving direction of the fixing belt, and the lubricant attached to the fixing belt from the sliding member is moved in the moving direction. As it goes to the downstream side, it has an agglomeration part that aggregates from both ends in the width direction of the fixing belt to the center side.
Fixing device. The surface facing the fixing belt in the aggregation portion is opposed to the central portion in the width direction of the fixing belt in the entire moving direction.
The fixing device according to claim 1. The facing surface of the aggregation portion is inclined to the opposite side of the fixing belt as it goes downstream in the moving direction.
The fixing device according to claim 2. The facing surface of the aggregation portion has a facing area that decreases as it goes downstream in the moving direction.
The fixing device according to claim 2 or 3. The opposing surface of the aggregation part is
The fixing belt is formed in a convex shape such that a portion facing the central portion is a vertex, and has a planar region including the vertex,
The area of the planar region becomes smaller as it goes downstream in the moving direction,
The fixing device according to claim 2 or 3. The agglomerated part is formed with a recess into which the lubricant attached to the fixing belt can enter.
The fixing device according to claim 1. The fixing belt, the pressing member, the concave portion, and the sliding member are formed so that the length in the width direction becomes smaller in this order.
The fixing device according to claim 6. The surface of the aggregation part contains an oil-repellent material,
The fixing device according to claim 1. The aggregation portion is configured to be able to advance and retreat with respect to the fixing belt.
The fixing device according to claim 1. A control unit that controls the aggregating unit to advance toward the fixing belt at a timing when the sheet does not pass through the fixing nip;
The fixing device according to claim 9. A speed control unit configured to make the moving speed of the fixing belt slower than the timing at which the paper passes through the fixing nip at a timing at which the paper does not pass through the fixing nip;
The fixing device according to claim 1. A rotatable roller member;
An endless fixing belt movable while contacting the roller member;
A non-rotatable pressing member which is disposed inside the fixing belt and forms a fixing nip by pressing the fixing belt with the roller member;
A sliding member that reduces sliding resistance between the pressing member and the fixing belt by being sandwiched between the pressing member and the fixing belt in the fixing nip;
With
The sliding member is coated with a lubricant on the surface facing the fixing belt,
The pressing member is disposed so as not to press the fixing belt on the downstream side of the fixing nip in the moving direction of the fixing belt, and the lubricant attached to the fixing belt from the sliding member is moved in the moving direction. As it goes to the downstream side, it has an agglomeration part that aggregates from both ends in the width direction of the fixing belt to the center side.
Image forming apparatus.

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