JP2012048110A - Sheet separation apparatus, fixing apparatus and image formation apparatus - Google Patents

Abstract

In a configuration in which a separation member is disposed in a very narrow space in a sheet passage portion immediately after a nip, the separation member is prevented from contacting a pressure roller.
An abutting member has a tip concealing portion at the tip of the member. The separation plate 75 is provided so that the tip of the separation plate 75 is positioned within the projection range of the tip concealment portion 79. When the separation plate 75 and the abutting member 74 are integrally rotated, even if the pressing member facing portion 74e of the abutting member 74 contacts the pressure roller 56, the tip of the separating plate 75 contacts the pressure roller. Without damage, the pressure roller is prevented from being damaged. Further, since the pressing member facing portion 74e of the abutting member 74 is provided in a curved cross section, the abutting member 74 does not damage the pressure roller.
[Selection] Figure 9

Description

  The present invention relates to a sheet separating apparatus that separates a sheet (recording medium) from a fixing member, a fixing apparatus including the sheet separating apparatus, and an image forming apparatus.

  In an image forming apparatus using toner for image formation, a fixing device is provided to fix the toner image on a recording medium such as transfer paper as a permanent image. The fixing device is formed by a fixing member (a fixing roller, a fixing belt, etc.) that is heated and rotated by a heating means, and a pressure member (a pressure roller, a pressure belt, etc.) that is pressed against and rotated by the fixing member. When the recording medium passes through the pressure contact portion (fixing nip), the toner carried on the recording medium is melted and the toner image is fixed on the recording medium.

  Toner composed mainly of resin melts at the above-mentioned pressure contact part and adheres to the fixing roller and fixing belt, so that the wax component is added to the toner, and the surface of the fixing roller and fixing belt is a releasable material. The fixing roller or the fixing belt and the toner are prevented from sticking by using various methods such as coating with a coating agent or applying a release agent such as silicone oil to the surface of the fixing roller or fixing belt.

  Further, a sheet separating device including a separation claw and a separation plate is attached to the fixing roller and the fixing belt, and the sheet to be wound around the fixing roller and the fixing belt is forcibly separated by the melted toner. For example, Japanese Patent Application Laid-Open No. 2003-241557 (Patent Document 1) discloses a separation claw capable of suppressing toner adhesion and causing less damage to a roll. Japanese Patent Publication No. 07-086726 (Patent Document 2) discloses a separation claw that is excellent in heat resistance and in which toner does not easily accumulate at the tip of the claw.

  However, in the separation means using the separation claw as described above, since the separation claw is in sliding contact with a fixing member such as a fixing belt or a fixing roller, toner easily collects at the contact portion. Problems such as dirtying the recording medium have occurred. Further, since the separation claw and the rotating member as the fixing member slide, a sliding mark is generated on the rotating member, the service life is reduced, and the sliding mark is generated as an abnormal image on the recording medium. The problem has arisen.

  In recent years, the release agent of the fixing device tends to eliminate the addition of a wax component to the toner due to poor handleability and the application of a release agent such as silicone oil to the surface of the rotating body as a fixing member. The above issues are becoming more prominent.

  On the other hand, there is an example in which a configuration in which a gap (gap) is provided between the tip of the separation plate and the rotating body is performed by an abutting member, which is disclosed in, for example, Japanese Patent Application Laid-Open No. 2006-11193 (Patent Document 3). Yes.

The separating member generally has a so-called separating plate shape having a sharp tip and a wedge-shaped cross section.
Certainly, if the separation means secures a gap (gap) between the leading edge of the separation plate and the fixing member, the separation means and the fixing member are in contact with each other even if the fixing member is scratched or toner is fixed to the separation means. Therefore, it is possible to prevent such a problem that the fixed toner is retransferred to the fixing member again to stain the image.

  For example, Japanese Patent No. 2823168 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2009-31759 (Patent Document 4) and Japanese Patent Application Laid-Open No. 2009-31759 (Patent Document 4) (for example) There is a disclosure in Patent Document 5).

  However, in the case where the fixing roller and the pressure roller have a large diameter (about Φ50 mm or more) like a fixing device compatible with a color high-speed engine as in recent years, a separating member is used in order not to give an excessive amount of heat to the image after fixing. The tip must be placed as close as possible to the nip. This is because if the leading edge of the separation plate is arranged away from the nip, problems with image quality due to excessive heat quantity such as distorted skin, blistering, glossing, and hot faceting are likely to occur in the image after fixing.

  Therefore, a layout is adopted in which the wedge shape of the separator plate is made thin and the tip of the separator plate is close to the nip, but the fixing device for color high-speed engines has a rubber layer on the surface of the fixing member and pressure member. Generally, the structure is soft and easily damaged, so when a paper jam occurs, the separation plate tip faces the fixing member when the separation plate opens in the direction opposite to the urging direction of the abutting member. It is easy to damage the pressure member surface.

  In other words, in a configuration in which a separation plate or the like is arranged in a very narrow space immediately after the nip, the surface of the pressure member is damaged by the leading edge of the separation member when a jam occurs. This is particularly noticeable in engine-compatible fixing devices.

  The present invention solves the above-mentioned problems in the conventional sheet separating apparatus in which the separating member is disposed in a very narrow space in the sheet passing portion immediately after the nip, prevents the separating member from contacting the pressure member, and increases the height. It is an object of the present invention to provide a sheet separating apparatus, a fixing apparatus, and an image forming apparatus capable of obtaining a quality fixed image.

  According to the present invention, there is provided a sheet separation apparatus for separating a sheet-like recording medium conveyed from a fixing nip formed by a fixing member and a pressure member from the fixing member or the pressure member. At least one separation member held rotatably about a support shaft parallel to the rotation axis of the member; and provided so as to be able to rotate substantially integrally with the separation member. An abutting member that abuts against the fixing member so as to provide a minute gap therebetween, and the abutting member positions the distal end of the separating member within a projection range in the rotation axis direction. This is solved by providing a pressure member facing portion facing the pressure member of the tip concealing portion on the curved cross section.

Further, it is preferable that the tip concealing portion is provided with a contact portion with the fixing member, which is the tip portion of the abutting member, in a curved cross section.
Further, it is preferable that the radius of curvature of the pressure member facing portion and the fixing member abutting portion of the tip concealing portion is such that the pressure member facing portion> the fixing member abutting portion.

Further, it is preferable that the cross-sectional shape of the fixing member abutting portion is formed in an arc shape, and the tip of the separation member is positioned at the center of the arc.
Further, when the separation member and the abutting member rotate substantially integrally and the pressing member facing portion of the abutting member contacts the pressing member, the tip of the separating member is It is preferable to be configured not to contact the pressure member.

Further, it is preferable that the abutting member is abutted against the fixing member outside the sheet passing area.
The abutting member is preferably made of a fluorine resin material or coated with a fluorine resin.

Moreover, it is preferable to provide gap adjusting means for adjusting the minute gap.
Moreover, the said subject is solved by the sheet separation apparatus of any one of Claims 1-8 by this invention.

Further, it is preferable that a gap between the pressing member facing portion of the abutting member and the pressing member is 1 mm or less when the maximum temperature rises when the fixing device is used.
According to the present invention, the above problem is solved by an image forming apparatus including the sheet separating apparatus according to any one of claims 1 to 8 or the fixing apparatus according to claim 9 or 10.

  According to the sheet separating apparatus of the present invention, even when the paper is wound around the fixing member and a paper jam occurs, the abutting member having the tip concealing portion prevents the leading end of the separating member from contacting the pressure member, In addition, since the abutting member does not damage the pressing member even if it contacts the pressing member due to the shape of the pressing member facing portion, it is possible to prevent the pressing member from being damaged when a jam occurs. .

  Since the pressure member can be prevented from being damaged, the separation member can be disposed in a very narrow space in the paper passage portion immediately after the nip, so that high separation performance and stable paper conveyance can be realized. .

  According to the configuration of the second aspect, the tip concealing portion is provided with a curved section in contact with the fixing member that is the tip portion of the abutting member, so that the fixing member is not damaged and an abnormal image is generated. In addition to preventing this, the life of the fixing member is not shortened.

  According to the configuration of claim 3, the pressure member facing portion and the fixing member abutting portion of the tip concealing portion have a radius of curvature of the pressure member facing portion> the fixing member abutting portion. Since the curved portion of the pressing member facing portion contacts when the member contacts the pressing member, the pressing member can be prevented from being damaged.

  According to the configuration of claim 4, the fixing member contact portion is formed in an arc shape in cross section, and the tip of the separation member is positioned at the center of the arc. When the abutting member and separation member rotate, the positional relationship between the separation member tip and the fixing member surface does not change, and does not affect the paper separation performance, and always exhibits good paper separation performance. can do.

According to the fifth aspect of the present invention, since the tip of the separating member does not contact the pressure member when the abutting member comes into contact with the pressure member, it is possible to prevent the pressure member from being damaged.
According to the configuration of the sixth aspect, the abutting member is abutted against the fixing member outside the paper passing region, so that the fixing member is not worn.

  According to the configuration of the seventh aspect, since the abutting member is formed of a fluorine resin material or is coated with a fluorine resin, toner adhesion to the abutting member can be suppressed as much as possible, and the paper is soiled. And other problems can be prevented.

  According to the configuration of the eighth aspect, since the gap adjusting means for adjusting the minute gap between the separating member and the fixing member is provided, the leading end gap of the separating member can be finely and appropriately adjusted, and excellent separability can be obtained. it can.

According to the fixing device of the ninth aspect of the present invention, it is possible to achieve a long life of the fixing member while ensuring a good separation performance by a non-contacting separation plate with respect to the fixing member, and the pressing member is used when a paper jam occurs. A high-quality fixed image can be obtained without being damaged.
According to the configuration of the tenth aspect, the abutting member does not come into contact with the pressure member when the fixing device is used at the highest set temperature.

  According to the image forming apparatus of the eleventh aspect, since the fixing device including the separation device according to the present invention is mounted, it is possible to prevent the fixing member from being damaged, and it is possible that the fixing unit generates fixed toner. In addition, it is possible to prevent a problem that the fixing member is soiled again even if the fixed toner is generated, and it is possible to prevent a problem that the separation member is deformed even if a paper jam occurs. Therefore, an image forming apparatus excellent in image quality and transportability can be realized.

FIG. 3 is a cross-sectional view illustrating a main configuration of an example of a fixing device including a sheet separating device according to the present invention. 1 is an external perspective view of a sheet separating apparatus. It is a perspective view which shows the separation plate of a sheet separation apparatus alone. It is sectional drawing for demonstrating the front-end | tip gap adjustment mechanism of a separation plate. It is a perspective view which shows the abutting member of a sheet separation apparatus alone. It is the perspective view which looked at the abutting member from the opposite side to FIG. It is a side view of an abutting member. FIG. 6 is a cross-sectional view illustrating a state where a separation plate and a bump member are disposed in the vicinity of the exit of the fixing nip. It is an enlarged view which shows the front-end | tip part vicinity of a separating plate and an abutting member. It is a figure which shows a mode when a paper jam occurs. FIG. 5 is an enlarged view showing the vicinity of the separation plate rotated at the time of occurrence of paper jam and the front end portion of the abutting member. 1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus to which the present invention is applied.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a main configuration of an example of a fixing device including a sheet separating apparatus according to the present invention. The fixing device shown in this figure is a belt fixing method using a fixing belt, but the present invention is not limited to the belt fixing device, and can be applied without any problem to a roller fixing method using a fixing roller.

  In the fixing device 50 shown in FIG. 1, a fixing belt 51 as a fixing member is supported and stretched by a fixing roller 52 as a driving roller and a heating roller 53 as a driven roller, and rotates in the clockwise direction in the drawing. The fixing roller 52 has an elastic layer on the mandrel and is rotationally driven by a driving mechanism (not shown). A fixing heater 54 (for example, a halogen lamp) as a heat source is disposed inside the heating roller 53, the heating roller 53 is heated by the fixing heater 54, and the fixing belt 51 is heated by the heating roller 53.

  The fixing belt 51 has a structure in which a silicon rubber having a thickness of 200 μm is laminated on a surface layer of a substrate made of a polyimide resin having an inner diameter of 75 mm and a thickness of 90 μm, and a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether) having a thickness of 20 μm is formed on the outermost layer. (Polymer) Coated. A fixing roller 52 having an outer diameter of 90 mm and a heating roller 53 made of an aluminum hollow cylinder having an outer diameter of 80 mm are arranged in the loop of the fixing belt 51, and the fixing belt 51 is wound around both rollers. The configuration of the fixing roller 52 of this example is a configuration having a heat resistance / elastic layer made of silicone rubber having an outer diameter of 90 mm and a thickness of 20 mm.

  The structure of the pressure roller 56 is made of steel, a 1 mm thick hollow core metal is covered with 2.0 mm thick silicone rubber, and the outermost layer is provided with a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube. It is a roller having an outer diameter of 80 mm. A halogen heater is built in the cored bar. The pressure roller 56 is pressed against the fixing roller 52 with the fixing belt 51 sandwiched by a pressure mechanism (not shown), bites into the fixing roller 52, and has a nip width of about 20 to 26 mm.

  The fixing belt 51 rotates when the fixing roller 52 is driven to rotate, and the pressure roller 56 rotates with the fixing belt 51. The heating roller 53 may be a driving roller. Further, the pressure roller 56 may be driven.

  The surface temperature of the fixing belt 51 is detected by a temperature detection unit (not shown), and a temperature control unit (not shown) sets the fixing heater 54 and the surface temperature of the fixing belt 51 becomes a predetermined set temperature based on the output value of the temperature detection unit. To control.

  The sheet carrying the unfixed toner image on the surface is conveyed from the right to the left in the figure and is carried into the fixing nip portion, where the toner is melted and fixed. The pressure member is a pressure roller in this example, but a pressure belt or the like may be used.

  A tension roller 55 is disposed inside the belt between the fixing roller 52 and the heating roller 53, and a predetermined tension is applied to the fixing belt 51. In this example, the tension roller is disposed inside the belt. However, the tension roller may be disposed inside or outside the belt.

  A sheet separating device 70 is disposed near the exit of the fixing nip. Although the sheet separating device 70 will be described later, the sheet that has passed through the fixing nip is separated from the fixing belt 51 by a separating plate 75 provided in the sheet separating device, and the separated sheet is provided on the separating plate 75 (and the downstream side thereof). Is guided by a guide plate (not shown) and fed out of the fixing device. The distance from the nip outlet to the tip of the separation plate is set to about 2 to 5 mm in the fixing device of this example.

FIG. 2 is an external perspective view of the sheet separating apparatus.
The sheet separating apparatus 70 of this example includes a frame 71 fixed to the fixing device casing, and a stay 72 that is rotatably supported by the frame 71 by a support shaft 73. In this example, the stay 72 is fixed to the support shaft 73, and the support shaft 73 is rotatable with respect to the frame 71 via a bearing. The abutting members 74 and 74 are attached and fixed at positions outside the paper passing area at both ends of the stay 72. An urging means (for example, a spring) (not shown) is provided between the frame 71 and the stay 72, and urges the abutting members 74, 74 so as to be pressed against the fixing belt 51 (fixing roller 52). Positioning of the separating plate 75 attached to the support shaft 73 (management of the leading end gap with respect to the fixing belt 51) is performed with accuracy by the tip portions of the abutting members 74 and 74 being in contact with the fixing belt 51 and sliding.

  A plurality of separation plates 75 are attached to the support shaft 73 and are arranged in parallel in the fixing belt width direction (fixing roller axis direction). In the illustrated example, a total of eight separation plates 75 are provided, but the size, number and arrangement of the separation plates 75 are not limited to this. Moreover, the structure using one separation plate long in the sheet | seat width direction may be sufficient. In general, finer adjustments can be made with a structure divided into a plurality of parts (a structure including a plurality of separation plates). A single separator can reduce scratches and streaks in the image.

  FIG. 3 is a perspective view showing the separation plate 75 alone. Each part of the separation plate 75 is a base material (separation guide part) 75a, a tip separation part 75b, a shaft mounting part 75c, and an adjustment plate part 75d. A resin softer than the base material 75a is integrally formed by insert molding at the front end of the base material 75a having the shaft mounting part 75c as the front end separation part 75b. Further, since the base material 75a and the tip separation portion 75b are integrally formed by insert molding, the positional accuracy of the shaft mounting portion 75c and the tip separation portion 75b of the base material 75a can be molded with high accuracy. it can. Therefore, the separation performance is excellent as well as the separation member formed of the same material. In addition, although the example of the base material and the resin molded by insert molding is shown here, it may be completely molded by the same material.

  FIG. 4 is a cross-sectional view showing a front end gap adjusting mechanism for adjusting a minute gap (front end gap) between the separation plate 75 and the fixing member (fixing belt 51). The separation plate 75 is held by a stay 72 so as to be rotatable about a support shaft 73. A tension spring 76 is stretched between the stay 72 and the frame 71 to urge the stay 72 (separating plate 75) in the counterclockwise direction in the drawing. An abutting member 74 (not shown in the drawing) is fixed to the end portion of the stay 72, and the abutting member 74 is pressed against the fixing belt 51, whereby the leading end of the separation plate 75 and the fixing belt 51. A minute gap G is formed between them.

  A gap adjusting screw 77 is loosely fitted in a hole provided in the adjusting plate portion 75 d of the separation plate 75, and the tip of the adjusting screw 77 is screwed into the stay 72. A compression spring 78 is fitted to the adjustment screw 77, and an urging force in the counterclockwise direction in the figure about the support shaft 73 is applied to the adjustment plate portion 75d. When the gap adjusting screw 77 is tightened, the separation plate 75 rotates around the support shaft 73 in the clockwise direction in the figure. When the gap adjusting screw 77 is loosened, the separation plate 75 rotates in the reverse direction (counterclockwise in the figure). Accordingly, the gap G between the leading edge of the separation plate and the fixing belt 51 can be finely adjusted by the gap adjusting screw 77. In this example, the gap G between the leading end separation portion 75b of the separation plate and the fixing belt 51 can ensure a clearance of 0.1 to 0.6 mm, and the contact-type separation claw is separated by a non-contact-type separation member 75. Performance can be secured.

  Since the fixing belt 51 and the separation plate 75 can be kept in a non-contact state, it is possible to reliably prevent the fixing belt 51 from being damaged, and the fixing toner does not collect on the separation plate 75. Problems such as retransfer to the belt 51 can also be prevented. Further, even if a paper jam or the like occurs, the separation plate 75 is not deformed.

  In the above description, the separation device 70 is applied to the fixing device (as the fixing separation device). However, there are various situations in which the sheet-like medium is peeled off from the belt and rollers, not limited to the fixing device. To do. The sheet separating apparatus of the present invention can be used not only for a fixing apparatus but also for a transfer apparatus, for example.

  FIG. 5 is a perspective view showing a single abutting member 74 for forming a leading end gap G between the leading end of the separation plate and the fixing belt 51. FIG. 6 is a perspective view of the abutting member 74 viewed from the side opposite to FIG. 5 (pressure roller side). FIG. 7 is a side view of the abutting member 74. When the abutting member 74 is formed of a fluorine-based resin material or is coated with a fluorine-based resin, toner fixation can be suppressed as much as possible, and problems such as soiling of paper can be prevented. The abutting member is sometimes called a positioning member (a member that determines the position of the separation plate).

  As described with reference to FIG. 2, the abutting member 74 is mounted and fixed at a position outside the paper passing area at both end portions of the stay 72. In this example, it is fixed by screwing. As shown in FIG. 5, a base 74 a of the abutting member 74 is provided with a hole 74 b for screwing. Further, as shown in FIG. 6, on the lower surface side of the abutting member 74, a convex portion 74 c that is fitted into a hole (not shown) provided in the stay 72 and positions the abutting member 74 with respect to the stay 72. 74c are projected.

  As shown in FIG. 7, the portion returning from the tip 74 d of the abutting member 74 to the base 74 a through the lower pressure member facing portion 74 e has a shape swelled downward in the figure, and this portion is the tip. A concealing unit 79 is configured. The leading end 74d is a portion that comes into contact with the fixing member (the fixing belt 51 in the fixing device of FIG. 1), and is formed in a smooth curved shape. The pressure member facing portion 74e is a portion facing the pressure member (the pressure roller 56 in the fixing device of FIG. 1), and is also formed in a smooth curved shape. The portion connecting the distal end portion 74d and the pressing member facing portion 74e and the portion connecting the pressing member facing portion 74e and the base portion 74a may be connected by a straight line or may be connected by a smooth curve. When the tip 74d is slidably contacted with the fixing member, the pressure member facing portion 74e is opposed to the pressure member. That is, as shown in FIG. 8, in the normal state, the tip end portion 74 d of the abutting member 74 is in contact with and slides on the surface of the fixing belt 51, and the pressure member facing portion 74 e faces the pressure roller 56.

  As shown in an enlarged view in FIG. 9, a leading end 74 d of the abutting member 74 is brought into contact with the surface of the fixing belt 51, whereby a gap (tip gap) is formed between the leading end of the separation plate 75 and the fixing belt 51. Is done. At this time, the pressing member facing portion 74e of the abutting member 74 is not in contact with the surface of the pressing roller 56, and a gap (gap) S is formed between them. Further, in the direction perpendicular to the drawing, that is, in the longitudinal direction of the fixing member (the axial direction of the fixing roller 52), the leading end separating portion 75b of the separating plate 75 is within the projection range of the leading end concealing portion 79 formed at the leading end of the abutting member 74. Is located, and the tip of the separation plate 75 is hidden in the tip concealing portion 79.

Here, the movement of the separating device 70 when a paper jam occurs will be described with reference to FIG.
As described above, the separating plate 75 is held by the stay 72 via the support shaft 73, and the stay 72 is supported by the frame 71 (FIG. 2) so as to be rotatable about the support shaft 73. The abutting member 74 fixed to the stay 72 is rotatable substantially integrally with the separation plate 75.

  As shown in FIG. 10, when the paper is wound around the fixing belt 51 and paper jam occurs (the paper cannot be separated), the paper is sandwiched between the fixing belt 51 and the leading end of the separation plate 75, The separation plate is pushed by the jammed paper (rotates in the direction of arrow T about the support shaft 73). When the separation plate 75 rotates in the direction of arrow T, the stay 72 and the abutting member 74 (omitted in FIG. 10) also rotate in the same direction.

  Then, as shown in an enlarged view in FIG. 11, the pressing member facing portion 74 e of the abutting member 74 abuts against the pressure roller 56, thereby restricting further rotation of the abutting member 74 and the separation plate 75. To do. Since the pressing member facing portion 74e of the abutting member 74 is configured as a smooth curved second R-shaped portion, even if the abutting member 74 contacts the pressure roller 56, the surface of the pressure roller is damaged. There is no.

  Further, when the pressing member facing portion 74e of the abutting member 74 abuts against the pressing roller 56 and further opening (rotation) of the separating plate 75 is restricted, the tip concealing portion 79 of the abutting member 74 is prevented. Since the front end separation portion 75b of the separation plate 75 is located (hidden) within the projection range, the front end of the separation plate 75 does not contact the pressure roller 56, and the surface of the pressure roller is covered by the separation plate 75. It is prevented from being damaged.

  As described above, in the separation device 70 according to the present embodiment, even when the paper is wound around the fixing member and the paper jam occurs, the front end of the separation plate 75 is pressed by the pressure roller 56 by the abutting member 74 having the front end concealing portion 79. When the jam occurs, the contact member 74 does not damage the surface of the pressure roller even if it contacts the pressure roller 56 due to the shape of the pressure member facing portion 74e. It is possible to prevent the pressure member surface from being damaged.

  In the conventional separating apparatus, when a jam occurs, the separating plate is opened by the jam paper, the leading end of the separating plate comes into contact with the pressing member, and the pressing member is damaged by the sharp separating plate tip. Some conventional separation devices have an abutment member (positioning member), but the abutment member cannot prevent the tip of the separation plate from contacting the pressure member, and the abutment member itself pressurizes. There was a risk of damaging the member. However, in the separation device according to the present invention, as described above, the tip of the separation member (separation plate 75) does not come into contact with the pressure member (pressure roller 56), and the pressure member is moved by the abutting member itself. There is no damage. Therefore, it is possible to effectively prevent the pressure member surface from being damaged when a jam occurs.

  By the way, as described above, the separation device 70 of the present embodiment includes the tip gap adjustment mechanism of the separation plate 75, and the position of the tip separation portion 75b of the separation plate 75 is changed by fine adjustment of the tip gap. Therefore, it is desirable to set so that the tip concealing portion 79 of the abutting member 74 covers the entire fine adjustment range of the tip separation portion 75b (the whole range in which the tip separation portion 75b moves by fine adjustment of the tip gap). .

  The gap S (FIG. 9), which is the gap between the pressure member facing portion 74e of the abutting member 74 and the pressure roller 56, is preferably small, but it is hot (when the fixing device is in a heated state) and cold. During this time (cooled state), the size of the gap S changes due to the thermal expansion of the roller pair (the fixing roller 51 and the pressure roller 56). Even during the maximum influence of thermal expansion, during normal operation (when no jam occurs), the pressure member facing portion 74e of the abutting member 74 and the surface of the pressure roller 56 are in contact with each other. I have to avoid it.

  When the pressure member facing portion 74e of the abutting member 74 and the pressure roller 56 come into contact with each other, the pressure member facing portion 74e is pressed by the pressure roller 56, and the tip end portion 74d of the abutting member 74 further bites into the fixing belt. This is because the gap (tip gap) between the leading edge separation portion 75b of the separation plate 75 and the fixing belt 51 varies.

  The gap S (FIG. 9), which is the gap between the pressure member facing portion 74e of the abutting member 74 and the pressure roller 56, is the smallest when the fixing device is used at the highest set temperature. In this case, the gap S may be set to be minimum. In the fixing device of this embodiment, the minimum value of the gap S is set to be 1 mm or less.

  In addition, as described above, the tip end portion 74d of the abutting member 74 and the pressing member facing portion 74e are both formed in a smooth curved shape, and the radius of curvature of both is such that the tip end portion 74d <the pressing member facing portion. 74e. In the embodiment, the curved portions of the tip portion 74d and the pressure member facing portion 74e are formed in an arc shape, and assuming that the radii are R1 (tip portion 74d) and R2 (pressure member facing portion 74e), R1 <R2.

  The reason why the radius of curvature (or the radius of the arc) of the tip 74d and the pressure member facing portion 74e is the tip 74d <the pressure member facing portion 74e is that the tip 74d is in contact with the fixing member from the beginning. Whereas the curved portion is always arranged so as to contact the fixing member, the pressing member facing portion 74e comes into contact with the pressing member only after the abutting member 74 is rotated during a paper jam, and therefore has a certain radius of curvature ( Otherwise, the curved portion may not come into contact with the pressing member unless the radius of the arc is increased, and the radius of curvature (or the radius of the arc) of the pressing member facing portion 74e is larger than that of the tip 74d. By doing so, the pressure member facing portion 74e (curved portion) comes into contact with the pressure member at the time of rotation, and damage to the pressure member can be reliably prevented.

  Further, in this embodiment, the tip of the separation plate 75 (tip separation portion 75b) is positioned at the center of R1 of the tip portion 74d configured in an arc shape (see FIG. 9). Thus, when the abutting member 74 and the separation plate 75 are rotated by the thermal expansion of the fixing roller 52, the positional relationship between the tip of the separation plate 75 and the surface of the fixing member (fixing belt 51) does not change, and the paper It is possible to always exhibit good paper separation without affecting the separation.

  Further, in this embodiment, when the jam occurs, the separating plate 75 and the abutting member 74 are opened (rotated) so that the pressing member facing portion 74e of the abutting member 74 abuts against the pressing member (pressure roller) 56. When contacted, the tip 74d of the abutting member 74 is not in contact with the pressure member. Therefore, the tip 74d having a smaller radius of curvature (or arc radius) than the pressure member facing portion 74e does not come into contact with the pressure member and be damaged.

  As described above, according to the separation device of the present invention, when applied to a fixing device, it is possible to extend the life of the fixing member while ensuring good separation performance by a non-contact separation plate with respect to the fixing member. In addition, it is possible to provide an image forming apparatus excellent in fixed image quality without damaging the pressure member when a paper jam occurs.

Finally, an example of an image forming apparatus to which the present invention is applied will be described.
The image forming apparatus shown in FIG. 12 can form a full-color image by adopting a tandem method, and an endless belt-shaped intermediate transfer body 10 is provided in the substantially central part of the apparatus main body. The intermediate transfer belt 10 is wound around a plurality of support rollers and can be rotated and conveyed clockwise in the figure.

  Four photosensitive drums 1Y, 1M, 1C, and 1K of yellow, magenta, cyan, and black are arranged side by side in the belt conveyance direction along the upper running side of the intermediate transfer belt 10, and the tandem image forming unit is arranged. It is composed. A charging unit, a developing device, a cleaning unit, a static eliminator and the like are arranged around each photosensitive drum to constitute an image forming unit. Further, four transfer rollers 11 as primary transfer means are arranged in the belt loop of the intermediate transfer belt 10 so as to face each photoconductor drum 1.

  One of the support rollers of the intermediate transfer belt 10 is provided as a transfer counter roller 16, and a transfer roller 31 as a secondary transfer unit is pressed against the opposite side of the intermediate transfer belt 10 to form a secondary transfer portion. . A conveyance belt 24 is disposed on the downstream side (left side in the figure) of the secondary transfer roller 31 in the sheet conveyance direction, and the sheet carrying the body fixing toner image transferred by the secondary transfer unit is transferred to the downstream fixing device 50. Transport to. The fixing device 50 is as described above, and includes the separation device 70.

  An exposure device 20 is provided above the tandem image forming unit. Further, a scanner 50 for reading a document image is provided at the uppermost part of the apparatus. Further, the lowermost part of the apparatus main body is provided as a paper feed unit, and a paper feed cassette 40 for storing paper P is provided. Further, a duplex conveying unit 33 is provided above the sheet feeding cassette 40 and below the fixing device 60.

An image forming operation in the color copying machine of this example will be briefly described.
Each photosensitive drum 1 of the tandem image forming unit is rotated in the clockwise direction in the drawing by a driving unit (not shown), and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by a charging unit. The charged photoconductor surface is irradiated with laser light from the exposure device 20, whereby an electrostatic latent image is formed on the photoconductor drum 1 surface. At this time, the image information exposed on each photosensitive drum 1 is single-color image information obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. Each color toner is applied from the developing device to the electrostatic latent image formed in this way, and visualized as a toner image.

  Further, the intermediate transfer belt 10 is driven to run counterclockwise in the drawing, and in each image forming unit, the respective color toner images are sequentially transferred from the photosensitive drum 1 to the intermediate transfer belt 10 by the action of the primary transfer roller 11. . In this way, the intermediate transfer belt 10 carries a full-color toner image on its surface.

  Note that any one of the image forming units can be used to form a single-color image or a two-color or three-color image. In the case of monochrome printing, image formation is performed using the rightmost black (K) unit in the drawing among the four image forming units.

  The residual toner adhering to the surface of the photosensitive drum after the toner image is transferred is removed from the surface of the photosensitive drum by the cleaning means, and then the surface is subjected to the action of the static eliminator to initialize the surface potential. Ready for image formation.

  On the other hand, the paper is fed from the paper feed cassette 40 or the manual feed tray 34, and sent to the secondary transfer position at the timing of the toner image carried on the intermediate transfer belt 10 by the registration roller pair 36. . The toner images on the surface of the intermediate transfer belt are collectively transferred onto the paper by the secondary transfer roller 31. When the sheet on which the toner image is transferred passes through the fixing device 50, the toner image is fused and fixed to the sheet by heat and pressure. The fixed sheet is discharged to a discharge tray 35 provided on the side surface of the apparatus main body.

  When printing on both sides of the paper, the paper on which the toner image is fixed on one side of the paper is sent to the double-sided conveyance unit 33 by the switching claw, the paper is turned upside down, and the paper is fed again to the registration roller pair 36. The toner image is transferred from the intermediate transfer belt 10 to the back side of the re-feeded paper, and the back side image is fixed by the fixing device 50, whereby the paper carrying the images on both the front and back sides is discharged to the paper discharge tray 35. This completes double-sided printing.

  Since the color copying machine of this example is equipped with the fixing device equipped with the separation device according to the present invention, it is possible to prevent the fixing member from being damaged, and further, no fixing toner is generated on the separation means. Even if the fixed toner is generated, it is possible to prevent a problem that the fixing member is stained again, and it is possible to prevent a problem that the separation member is deformed even when a paper jam or the like occurs. Therefore, an image forming apparatus excellent in image quality and transportability can be realized.

  As mentioned above, although this invention was demonstrated by the example of illustration, this invention is not limited to this. For example, the separation device is not limited to fixing separation, and can be applied to sheet separation at a transfer unit. Further, the shape, size, number, etc. of the separating plate as the separating member are arbitrary and can be set as appropriate in relation to the abutting member. Arbitrary structures can be adopted for the tip gap adjustment mechanism of the separation member provided in the separation device.

  The configuration of the fixing device is also arbitrary, and is not limited to the belt fixing method, and may be a heat roll method. The heating means for the fixing member and the pressure member is not limited to a heater such as a halogen lamp, and an induction heating method can also be employed.

  The configuration of the image forming unit of the image forming apparatus is also arbitrary, and the arrangement order of the color process cartridges in the tandem type is arbitrary. In addition to the tandem type, a configuration in which a plurality of developing devices are arranged around a single photosensitive member, or a configuration using a revolver type developing device is also possible. The present invention can also be applied to a full color machine using three color toners, a multicolor machine using two color toners, or a monochrome apparatus. Of course, the image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile machine, or a multifunction machine having a plurality of functions.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 10 Intermediate transfer belt 20 Exposure apparatus 50 Fixing apparatus 51 Fixing belt (fixing member)
52 Fixing roller 53 Heating roller 55 Pressure roller (Pressure member)
70 Sheet separating device 71 Frame 72 Stay (separating member holding means)
73 Support shaft 74 Abutting member 75 Separating plate (separating member)
75b Tip separation portion 77 Tip gap adjusting screw 74 Abutting member 74a Base 74b Screw retaining hole 74c Positioning convex portion 74d Tip portion 74e Pressure member facing portion 79 Tip concealing portion

JP 2003-241557 A Japanese Patent Publication No. 07-086726 JP 2006-11193 A Japanese Patent No. 2823168 JP 2009-31759 A

Claims (11)

In a sheet separating apparatus for separating a sheet-like recording medium conveyed from a fixing nip formed by a fixing member and a pressure member from the fixing member or the pressure member,
At least one separation member held rotatably about a support shaft parallel to the rotation shaft of the fixing member; and the separation member and the fixing member provided so as to be rotatable substantially integrally with the separation member. An abutting member that is abutted against the fixing member so as to provide a minute gap therebetween,
The abutting member has a front end concealing portion that positions the front end portion of the separation member within the projection range in the rotation axis direction, and faces the pressure member of the front end concealing portion. A sheet separating apparatus, wherein the pressing member facing portion is provided in a curved cross section.   2. The sheet separating apparatus according to claim 1, wherein the leading edge concealing portion is provided with a curved section in contact with the fixing member which is the leading edge portion of the abutting member.   3. The pressure member facing portion and the fixing member abutting portion of the tip concealing portion have a radius of curvature that satisfies the pressure member facing portion> the fixing member abutting portion. The sheet separating apparatus according to 1.   The cross-sectional shape of the fixing member contact portion is formed in an arc shape, and the tip of the separation member is configured to be positioned at the center of the arc. Sheet separation device.   When the separating member and the abutting member rotate substantially integrally and the pressing member facing portion of the abutting member comes into contact with the pressing member, the tip of the separating member is the pressurizing member. The sheet separating apparatus according to any one of claims 1 to 4, wherein the sheet separating apparatus is configured not to contact a member.   The sheet separating apparatus according to claim 1, wherein the abutting member is abutted against the fixing member outside a sheet passing region.   The recording medium separating apparatus according to claim 1, wherein the abutting member is formed of a fluorine resin material or is coated with a fluorine resin.   The sheet separating apparatus according to claim 1, further comprising a gap adjusting unit that adjusts the minute gap.   A fixing device comprising the sheet separating device according to claim 1.   The fixing device according to claim 9, wherein when the maximum temperature rises when the fixing device is used, a gap between the pressing member facing portion of the abutting member and the pressing member is 1 mm or less. An image forming apparatus comprising the sheet separating apparatus according to claim 1 or the fixing apparatus according to claim 9 or 10.

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