JP2009288692A - Heat fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat fixing device wherein a gap between a non-contact type separation plate and a fixing member can be adjusted and separability of a front end part and a middle part of a transfer paper is enhanced, and to provide an image forming apparatus including the heat fixing device. <P>SOLUTION: The heat fixing device includes a rotating fixing member 4, a pressure member 3 which is brought into contact with the fixing member to form a nip part for fixing unfixed toner onto a sheet, a heating means for heating the fixing member, and a separation plate 30 disposed on the sheet discharge side of the nip part without coming into contact with the fixing member. The separation plate has a projecting member 30a which is displaced to project toward a sheet discharge path A. The image forming apparatus includes this heat fixing device. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a heat fixing device used in an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and an image forming apparatus including the heat fixing device.

  An apparatus using an electrophotographic system repeatedly forms a toner image on an image carrier by repeating charging, writing, developing, transferring, cleaning, static elimination, etc., and sequentially transferring the toner image to record a sheet, an OHP film, or the like. An image is recorded on the medium. For example, a laser printer has a rotating photosensitive drum, and the photosensitive layer of the photosensitive drum is uniformly charged and then exposed to a laser beam from a laser scanning unit to form an electrostatic latent image. Further, this laser printer develops the electrostatic latent image with toner to form a toner image, transfers the toner image onto a transfer paper, and further passes the transfer paper through a heat fixing device to thermally fix the toner image. It is configured.

  In such a conventional heat fixing apparatus, for example, there is a fixing roller provided with an adhesion preventing layer made of a fluororesin layer for preventing toner adhesion on the outer peripheral surface of a cored bar made of a hollow cylindrical body such as aluminum. in use. In such a fixing roller, a heater such as a halogen lamp is disposed along the rotation center line in the hollow portion of the core metal, and the fixing roller is heated from the inside by its radiant heat.

  In addition, a pressure roller that is in pressure contact with the fixing roller is provided, and the transfer paper is passed between the pressure roller and the fixing roller, so that the toner adhering to the transfer paper is melted by the heat of the fixing roller. And fixing on the transfer paper by pressurization.

  At this time, since the toner melts and is discharged in close contact with the fixing roller, the transfer paper is provided with a heat-resistant resin separation claw made of polyimide, polyamideimide, or PPS (polyphenylene sulfide) in order to peel off the transfer paper from the fixing roller. It is in contact with the fixing roller.

  In recent years, with colorization, as a method of fixing transfer paper on which several color toners are laminated, an elastic layer made of silicone rubber is formed on a polyimide or metal belt, and fluorine is used to prevent toner adhesion. A fixing belt provided with an anti-adhesion layer made of a resin layer or the like is used.

  Also, in full-color photographic printing, the toner is a low softening type (so-called sharp melt), so it tends to cause an offset, which is disadvantageous to the winding jam of the fixing separation part. Therefore, the fixing member (fixing roller, fixing belt) A material with good releasability is required. Specific examples include high release type silicone rubber such as LTV and RTV.

  For such a fixing member (roller or belt), a release material such as silicone oil is applied, and means for separating the transfer paper immediately after the fixing nip by a separation claw in contact with the fixing roller or the fixing belt is taken. However, when the separation claw comes into contact with the fixing member, the separation claw bites into the elastic layer, causing the surface of the fixing member to be worn or damaged, resulting in image stains, oil streaks, and the like.

  Therefore, in order to enhance the durability of the fixing member, an apparatus in which a non-contact type separation plate is installed has been proposed (Patent Documents 1 and 2).

  In Patent Document 1, a configuration in which a gap between the separation plate and the fixing member, that is, a gap on the sheet passing surface is maintained by providing a bent portion for abutting against the fixing member at the end of the separation plate in the non-sheet passing portion. Proposed. Japanese Patent Application Laid-Open No. 2004-228561 proposes a configuration that maintains a gap on the sheet passing surface by increasing the diameter of the end portion (non-sheet passing portion) of the fixing member. Each of these is a structure for ensuring a gap on the sheet passing surface, and the position of the tip is fixed.

JP 2007-047381 A JP 2006-308978 A

  In the case of the configuration described above, the leading end of the separation plate must naturally be disposed above the straight line (so-called conveyance path) connecting the fixing nip outlet and the next paper discharge roller. However, a solid image or the like in which toner adheres to the entire surface of a thin transfer paper is weak in the transfer paper itself. Therefore, even if the front end of the transfer paper is separated, the middle portion of the transfer paper that continues to the front end of the transfer paper remains wrapped around the fixing member. Is caught in the gap (boundary) between the separation plate and the fixing member, and there is a possibility that jamming occurs.

  To solve this problem, a method of reducing the gap between the separation plate and the fixing member is conceivable. However, if the non-contact separation plate has an integrated structure, it is difficult to keep the small gap constant in the longitudinal direction. is there.

  The present invention has been made in view of the above problems in the prior art, and the gap between the non-contact type separation plate and the fixing member can be adjusted, and the separation property of not only the front end portion of the transfer paper but also the middle portion thereof is achieved. It is another object of the present invention to provide a heat fixing device having an improved temperature and an image forming apparatus including the heat fixing device.

The present invention provided to solve the above problems is as follows.
[1] A rotating fixing member, a pressure member that contacts the fixing member and forms a nip portion that fixes unfixed toner on the sheet, a heating unit that heats the fixing member, and a sheet in the nip portion A separation plate disposed on the discharge side in a non-contact manner with respect to the fixing member, the separation plate having a protruding member that is displaced and protrudes toward the sheet discharge path.
[2] The thermal fixing device according to [1], wherein the plurality of separation plates are arranged in a sheet width direction so that gaps between the separation members and the fixing member can be respectively adjusted.
[3] The protruding member protrudes from the separation plate toward the sheet discharge path when the leading end of the sheet passes through the nip portion, and is stored in the separating plate when the leading end of the sheet is separated from the fixing member. [2] The heat fixing device according to [2].
[4] When the leading end of the sheet passes through the nip portion, the protruding member protrudes from the separation plate toward the sheet discharge path, and reaches the next conveyance roller or discharge roller after the leading end of the sheet is separated from the fixing member. The thermal fixing device according to any one of [1] to [3], which is stored in the separator plate until the time until.
[5] The protruding member protrudes beyond the virtual sheet discharge path connecting the nip portion and the position where the sheet is held by the next conveying roller or the discharge roller with a straight line. ] The heat fixing apparatus in any one of.
[6] The thermal fixing device according to any one of [1] to [5], wherein at least a surface of the protruding member is made of a fluorine-based resin.
[7] An image forming apparatus comprising the thermal fixing device according to any one of [1] to [6].

  According to the present invention, the gap between the non-contact type separation plate and the fixing member can be adjusted, and the heat fixing device in which not only the front end portion of the transfer paper but also the middle portion is improved in separation, and the heat fixing device Can be provided.

As an effect of the present invention, according to the invention of claim 1, a rotating fixing member, a pressure member that contacts the fixing member and forms a nip portion that fixes unfixed toner on a sheet, and the fixing member And a separation plate disposed in a non-contact manner with respect to the fixing member on the sheet discharge side of the nip portion, and the separation plate is displaced and protrudes toward the sheet discharge path Since the heat fixing device has a member, it is possible to further improve the separation of the leading end of the paper by the protruding member.
According to a second aspect of the present invention, in the thermal fixing device of the first aspect, the plurality of separation plates are arranged in the sheet width direction so that the gaps with the fixing member can be respectively adjusted. The gap between the separation plate and the fixing member (fixing belt or fixing roller) can be managed small individually.
According to a third aspect of the present invention, in the thermal fixing device according to any one of the first to second aspects, the protruding member protrudes from the separation plate to the sheet discharge path side when the leading end of the sheet passes through the nip portion, Since the configuration is such that when the leading edge of the sheet is separated from the fixing member, it is stored in the separation plate, so that the winding of the leading edge portion and the middle portion of the transfer paper to the fixing roller can be suppressed.
According to a fourth aspect of the present invention, in the thermal fixing device according to any one of the first to third aspects, the protruding member protrudes from the separation plate toward the sheet discharge path when the leading end of the sheet passes through the nip portion, Since the sheet is stored in the separation plate between the time when the sheet leading edge is separated from the fixing member and the time when it reaches the next conveying roller or sheet discharging roller, the fixing roller at the leading edge portion and the middle portion of the transfer sheet And the occurrence of abnormal images can be suppressed without interfering with the transport path.
According to a fifth aspect of the present invention, in the thermal fixing device according to any one of the first to fourth aspects, the protruding member has a nip portion and a position where the sheet is carried by the next conveyance roller or the discharge roller. Since it is configured to protrude beyond the virtual sheet discharge path connected by a straight line, the middle part of the transfer sheet can be reliably separated from the fixing roller.
According to a sixth aspect of the present invention, in the thermal fixing device according to any one of the first to fifth aspects, since the protruding member has a configuration in which at least the surface is made of a fluorine-based resin, the toner is fixed. It is possible to prevent the fixing jam and to facilitate the maintenance of the protruding member.
According to the seventh aspect of the present invention, since the image forming apparatus is provided with the thermal fixing device according to any one of the first to sixth aspects, an apparatus capable of stable paper discharge without a fixing jam is provided. Can be supplied.

  Hereinafter, a configuration of an embodiment of a thermal fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, and the like can be modified within a range that can be conceived by those skilled in the art. The embodiment is also included in the scope of the present invention as long as the operations and effects of the present invention are exhibited.

  FIG. 1 shows an example of a thermal fixing apparatus according to the present invention. A fixing belt 4, which is an embodiment of a fixing member, is stretched between a heating roller 1 incorporating a heater 5, which is an embodiment of a heating unit, and a fixing roller 2 whose surface layer is covered with silicone rubber.

  The heating roller 1 has a core metal made of aluminum and has a built-in heat pipe for keeping the temperature uniform in the longitudinal direction of the core metal. On the other hand, the fixing belt 4 is coated with a high release type silicone rubber such as LTV on the surface of a heat resistant resin as a base material and is tensioned by a tension roller 6.

  A cleaning web 9 is disposed upstream of the tension roller 6 and downstream of the nip. The cleaning web 9 cleans the belt surface via a cleaning roller 7 that is in direct contact with the fixing belt 4.

  The transfer paper carrying the toner is conveyed in the direction of the arrow, and is thermally fixed by passing through a nip portion formed by the fixing roller 2 and the pressure roller 3 incorporating the heater 18. At the nip outlet, a pressure separation claw 10 in contact with the pressure roller 3 and a separation plate 30 that maintains a gap of 0.5 mm or less from the surface of the fixing belt are arranged. A projection member 30a is attached to the separation plate 30 so as to be displaceable with respect to the image surface side direction.

  Since the protrusion member 30a has an inclined surface on the conveyance path side, an angle suitable for separation is formed in the paper discharge traveling direction, and the middle portion of the transfer paper following the transfer paper tip is a gap (boundary) between the separation plate and the fixing member. ) Easily peeled off.

FIG. 2 shows the arrangement of the separation plate with respect to the conveyance system path from the nip exit to the paper discharge roller.
A one-dot broken line A indicates a conveyance system path connecting the nip portion and the discharge rollers 41 and 42. The separation plate 30 has a protruding member (auxiliary separation plate) 30a. When the transfer paper tip passes through the nip outlet, the separation plate 30 projects toward the conveyance path as indicated by the oblique line, and after the transfer paper tip is separated, Is stored on the other side. “Stored” of the protruding member 30a represents a state in which the protruding member 30a does not protrude toward the conveyance path (broken line A).

  The protruding member 30a indicated by hatching in FIG. 2 protrudes into the area indicated by hatching on the transport path side while the leading edge of the transfer paper passes through the nip outlet, and is in the state shown in FIG. This state continues until the leading edge of the transfer paper reaches the paper discharge rollers 41 and 42, after which it is stored on the side opposite to the conveyance path side, resulting in the state shown in FIG.

  FIG. 3 shows the position of the protruding member 30a immediately after the leading edge of the transfer paper has passed through the nip exit, and FIG. 4 shows that the protruding member 30a is stored in the separating plate 30 after the leading edge of the transfer paper has passed the separating plate 30 and the protruding member 30a. Indicates the state that has been performed.

  Further, when the protruding member 30a protrudes, the protruding member 30a protrudes toward the straight line (conveyance path) connecting the nip outlet and the discharge roller shown in FIGS. When the protruding member 30a protrudes, at least the end portion protrudes beyond the virtual sheet discharge path connecting the nip portion and the position where the sheet is held by the next conveying roller or the discharge roller with a straight line. Is preferred.

FIG. 5 shows the detailed configuration of the separation plate 30 provided with the protruding member 30a.
The separation plate 30 is made of a metal or a heat resistant resin as a base and coated with a Teflon (registered trademark) -based resin, or integrally formed with a Teflon (registered trademark) resin (for example, PFA resin). The separation plate 30 has a plurality of divided chips with a width of 20 mm to 50 mm arranged in a line in the longitudinal direction as shown in the figure, and each independently adjusts the gap with the surface of the fixing belt 4 as a fixing member. And can be maintained.

  A depression is provided in the central portion of the separation plate 30, and the protruding member 30 a is arranged corresponding to this portion. Similar to the separation plate 30, the protruding member 30 a is made of a metal or heat-resistant resin as a base and coated with a Teflon (registered trademark) resin or integrally with a Teflon (registered trademark) resin (for example, PFA resin). Yes.

FIG. 6 shows a state in which the protruding member 30a protrudes. FIG. 7 shows a state in which the protruding member 30a is stored.
As shown in FIG. 6, a compression spring 31 is mounted between the protruding member 30a and the separation plate 30, and the frame portion of the protruding member 30a is pressed in the direction of the arrow by a cam or pressing means (not shown). Thus, the protruding member 30a protrudes toward the conveyance path.
On the other hand, as shown in FIG. 7, when the protruding member 30 a is stored, the pressing means is released in the direction of the arrow, and is returned by the compression spring 31 by the distance L.

FIG. 8 shows the behavior when the leading edge of the conventional transfer paper is separated without the protruding member 30a.
The transfer paper is jammed when the leading end is separated while drawing the locus of the solid arrow, and the middle part collides with the leading end of the separation plate 30 and buckles.

  On the other hand, in the heat fixing device of the present invention shown in FIG. 9, the separation effect is maintained immediately after the leading edge of the transfer paper is separated by the protruding member 30a, so that the middle portion of the transfer paper is conveyed without buckling. . Further, since the protruding member 30a is stored before the leading edge of the transfer paper enters the paper discharge roller, the transfer paper is pulled by the paper discharge roller without interfering with the transfer paper path. However, since the protruding member 30a is stored at this time, image smear such as image blurring does not occur.

  The present invention can be applied not only to an aspect in which the fixing member is a fixing belt but also to an aspect including a fixing roller.

Next, the image forming apparatus according to the present invention will be described.
FIG. 10 shows a configuration of a tandem type color copying machine which is an image forming apparatus according to the present invention.
The color copying machine 200 includes an image forming unit 200A positioned at the center of the apparatus main body, a paper feeding unit 200B positioned below the image forming unit 200A, and an image reading unit (not shown) positioned above the image forming unit 200A. The fixing device 100 of the present invention is incorporated in the image forming unit 200A.

  The image forming unit 200A is provided with a fixing belt 202 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the fixing belt 202. Is provided. That is, photoconductors 203Y, 203M, 203C, and 203K as image carriers that can carry images of toners of complementary colors (yellow, magenta, cyan, and black) are juxtaposed along the transfer surface of the fixing belt 202. ing.

  Each of the photoconductors 203Y, 203M, 203C, and 203K is configured by a drum that can rotate in the same direction (counterclockwise direction). Around the drum, a charging device that performs image formation processing in the rotation process, and optical writing An apparatus, a primary transfer device, a developing device, and a cleaning device are arranged. In addition, each color toner is accommodated in each developing device.

  The transfer belt 202 is configured to be able to move in the same direction at the position facing the photoconductors 203Y, 203M, 203C, and 203K by being wound around a driving roller and a driven roller. A transfer roller 211 is provided at a position facing a roller 210 that is one of the driven rollers. Further, the conveyance path of the sheet P from the transfer roller 211 to the transfer device 100 is a horizontal path.

  The paper feed unit 200B separates the paper feed tray 215 for stacking and storing sheets P as recording media and the sheets P in the paper feed tray 215 one by one from the top to the position of the transfer roller 211. It has a transport mechanism for transporting.

  In image formation in the image forming apparatus 200 of the present invention, the surface of the photoreceptor 203Y is uniformly charged by the charging device, and an electrostatic latent image is formed on the photoreceptor 203Y based on image information from the image reading unit. The The electrostatic latent image is visualized as a toner image by a developing device containing yellow toner, and the toner image is primarily transferred onto the transfer belt 202 by a primary transfer device to which a predetermined bias is applied. . The other photoconductors 203M, 203C, and 203B also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred and superposed on the fixing belt 202 by electrostatic force.

  Next, the toner image T primarily transferred from the photoreceptors 203Y, 203M, 203C, and 203K onto the fixing belt 202 is transferred to the sheet P conveyed by the roller 210 and the transfer roller 211. The sheet P to which the toner image T has been transferred is further conveyed to the fixing device 100 and is fixed at the nip portion N between the fixing belt 2 and the pressure roller 3.

  Next, the sheet P discharged from the nip portion N is sent out along the discharge path. At this time, the sheet P that has been wound around the fixing belt 2 is separated from the fixing belt 2 at the tip 10r of the fixing separation claw 10 and returned to the discharge path.

  As described above, by the image forming apparatus having the fixing device 100 according to the present invention, a more advanced fixing separation function can be obtained, and various paper types (from thin paper to thick paper) and images (reducing the image leading edge margin). Is possible).

1 is a schematic diagram illustrating a configuration of an embodiment of a thermal fixing device according to the present invention. FIG. 4 is an explanatory diagram showing an arrangement of a separation plate with respect to a transfer paper path in an embodiment of a thermal fixing device according to the present invention. FIG. 3 is a diagram showing a state immediately after the transfer paper has passed through the nip in an embodiment of the thermal fixing device according to the present invention. FIG. 6 is a diagram illustrating a state after the transfer paper has passed through the nip in the embodiment of the thermal fixing device according to the invention. It is a figure which shows the detail of a separating plate structure in one Embodiment of the thermal fixing apparatus which concerns on this invention. It is a figure which shows a mode that the protrusion member protruded to the image surface side in one Embodiment of the thermal fixing apparatus which concerns on this invention. It is a figure which shows the state in which the protrusion member in one Embodiment of the heat fixing apparatus which concerns on this invention was stored. It is a figure explaining the behavior of a transfer paper in the conventional heat fixing apparatus which is not provided with a protrusion member. It is a figure explaining the behavior of the transfer paper in one embodiment of the thermal fixing device according to the present invention. 1 is a cross-sectional view illustrating an outline of an embodiment of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating roller 2 Fixing roller 3 Pressure roller 4 Fixing member (fixing belt)
5, 18 Heating means (heater)
6 Tension roller 7 Cleaning roller 8 Web pressure roller 9 Cleaning web 10 Pressure separation claw 11 Thermopile 12 Fixing thermistor 14 Oil application roller 15 Oil supply roller 16 Felt 17 Entrance guide plate 19 Pressure arm 20 Pressure O / C cam 21 Addition Pressure sensor 30 Separator 30a Protruding member 31 Compression spring 35, 36 Paper discharge path cover 41, 42 Paper discharge roller 200 Image forming apparatus 200A Image forming part 200B Paper feed part 202 Transfer belt 203Y, 203M, 203C, 203B Photosensitive Body 210 Roller 211 Transfer roller 215 Paper feed tray

Claims (7)

A rotating fixing member;
A pressure member that contacts the fixing member and forms a nip portion for fixing the unfixed toner on the sheet;
Heating means for heating the fixing member;
A separation plate disposed on the sheet discharge side of the nip portion in a non-contact manner with respect to the fixing member,
The separation plate has a protruding member that is displaced and protrudes toward the sheet discharge path.   The thermal fixing device according to claim 1, wherein the plurality of separation plates are arranged in a sheet width direction so that a gap between the separation plates can be adjusted.   3. The projection member according to claim 1, wherein when the leading end of the sheet passes through the nip portion, the protruding member projects from the separation plate toward the sheet discharge path, and is stored in the separating plate when the leading end of the sheet is separated from the fixing member. Thermal fixing device.   When the leading edge of the sheet passes through the nip portion, the protruding member protrudes from the separation plate toward the sheet discharge path, and from when the leading edge of the sheet is separated from the fixing member until it reaches the next conveyance roller or discharge roller. The thermal fixing device according to claim 1, wherein the thermal fixing device is stored in the separation plate.   5. The protruding member according to claim 1, wherein the protruding member protrudes beyond a virtual sheet discharge path in which a nip portion and a position where the sheet is held by the next conveying roller or the discharge roller is connected by a straight line. Heat fixing device.   The thermal fixing device according to claim 1, wherein at least a surface of the protruding member is made of a fluorine-based resin.   An image forming apparatus comprising the thermal fixing device according to claim 1.

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