JP2013007765A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus equipped with a fixing device that prevents drawbacks such as printing failure and adhesion of water droplet to a recording medium, is reduced in the number of parts, has a simple configuration, and is low in cost.SOLUTION: Heat and pressure are applied to a recording medium by a pressure-welding part between a fixing roller 30 and a pressure roller 40, and an unfixed toner image is consequently fused and fixed on the recording medium. A separation member 50 in the form of wire is disposed parallel to the fixing roller 30, with a gap left from the outer peripheral surface of the fixing roller 30. Accordingly, the leading end of the recording medium passed through the pressure welding part is separated by the separation member 50 so as not to enter the gap between the outer peripheral surface of the fixing roller 30 and the separation member 50. As the leading end of the separated recording medium is peeled, the recording medium part adhering to the fixing roller 30 is also separated by the separation member 50, and the whole recording medium is separated and ejected from the fixing roller 30.

Description

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

  2. Description of the Related Art Conventionally, a fixing device provided in an image forming apparatus such as an electrophotographic recording apparatus is configured to rotate while pressing a fixing member against a pressure member. A recording medium such as a sheet on which a toner image as a developer image is transferred is conveyed while being sandwiched between a pressure member and a fixing member. At this time, the recording medium is conveyed so that the surface on which the toner image is transferred is opposed to the fixing member, and the toner of the toner image is dissolved and recorded by the heat applied from the fixing member and the pressure from the pressure member. It is fixed on the medium. The melted toner is sticky to the fixing member because it has adhesiveness.

  For example, in the fixing device described in Patent Document 1 below, in order to reliably separate the recording medium from the fixing member, a separation plate is provided to peel the recording medium from the fixing member.

JP 2008-262228 A

  However, the fixing device provided in the conventional image forming apparatus has the following problems (a) to (c).

  (A) The separation plate and the fixing member may be brought into contact with each other by an instantaneous impact, and the fixing member may be damaged, which causes a printing defect.

  (B) Since most of the fixing member is surrounded by the separation plate, the water vapor generated from the recording medium during the fixing operation stays in the atmosphere between the separation plate and the fixing member, causing condensation and recording. The adhesion of water droplets to the medium cannot be completely suppressed.

  (C) In the conventional separation plate, the size of the gap between the tip of the plate to be separated and the surface of the fixing member is determined by a combination of a plurality of members. For this reason, it is necessary to consider the accumulation of manufacturing dimensional errors, and high-precision manufacturing is required, which increases the number of manufacturing steps and costs.

  The fixing device according to a first aspect of the present invention includes a pressure member that presses against the recording medium when the recording medium to which the developer image is attached is sent from the upstream side in the recording medium conveyance direction; A fixing member that is rotatably pressed against the pressure member via a recording medium, fixes the developer image attached to the recording medium, and sends the fixing image downstream in the recording medium conveyance direction; and And a wire-like separation member disposed at a predetermined interval with respect to the fixing member on the downstream side.

  A fixing device according to a second invention has a frame for supporting the fixing member and the separating member in the fixing device according to the first invention, and both end portions of the rotation shaft of the fixing member are rotatable with respect to the frame. The separation member is disposed substantially parallel to the rotation axis of the fixing member, and both end portions are attached to the frame.

  A fixing device according to a third aspect of the invention is the fixing device according to the second aspect, further comprising an elastic member attached to an end portion of the separation member and applying a tension in a longitudinal direction of the separation member. To do.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus including the fixing device according to any one of the first to third aspects, wherein the developer image is formed and attached to the recording medium, and the developer image is attached. And a developer image forming unit for supplying the recording medium to the fixing device.

  According to the fixing device of the first aspect of the present invention, the wire-shaped separating member is disposed at a predetermined interval with respect to the fixing member, and the recording medium is separated from the fixing member by the separating member. I have to. Therefore, it is possible to prevent printing defects accurately without damaging the fixing member. Furthermore, since a wire-shaped separating member is used to separate the recording medium, the surface area is small and water vapor generated from the recording medium is easily removed. Thereby, since water vapor does not stay around the separating member, no condensation occurs, and no water droplets adhere when the recording medium is discharged.

  According to the fixing device of the second invention, since the separation member for separating the recording medium is supported by the frame in the same manner as the fixing member, the number of parts is reduced and the cost is low. Can be obtained with high accuracy.

  According to the fixing device of the third aspect of the invention, since the tension is given to the separation member by the elastic member, the interval between the separation member and the fixing member is stabilized at a constant value even when the separation member is thermally expanded. It is possible to maintain a constant separation performance.

  According to the image forming apparatus of the fourth invention, since the fixing device according to any one of the first to third inventions is provided, there is no problem such as a printing failure or a recording medium clogging. Accurate image formation becomes possible.

FIG. 1 is a perspective view showing an appearance of the fixing device 10 in FIG. 2 according to the first embodiment of the present invention. FIG. 2 is a block diagram showing an outline of the image forming apparatus in Embodiment 1 of the present invention. FIG. 3 is an enlarged perspective view of portion A in FIG. FIG. 4 is an enlarged view showing the right side surface of FIG. FIG. 5 is a perspective view in which a part near the end of the fixing roller 30 in FIG. 3 is cut away. FIG. 6 is a perspective view in which a part near the end of the pressure roller 40 in FIG. 3 is cut away. FIG. 7 is a perspective view in which a part of the separation member 50 in FIG. 3 is cut away. FIG. 8 is a side view showing the fixing roller 30, the pressure roller 40, and the separating member 50 in FIG. FIG. 9 is a side view showing the fixing roller 30, the pressure roller 40, and the separating member 50 in FIG. FIG. 10 is a plan view in which a toner image is formed on the recording medium 1 in FIG. FIG. 11 is a view showing a modification of the separating member 50 of FIG. FIG. 12 is a perspective view showing the appearance of the fixing device according to the second embodiment of the present invention. FIG. 13 is an enlarged perspective view of a portion B in FIG. FIG. 14 is an enlarged view showing the end shape of the separating member 50 in FIG. FIG. 15 is a perspective view showing the vicinity of the leaf spring 60 in FIG. FIG. 16 is a plan view of the vicinity of the leaf spring 60 shown in FIG. FIG. 17 is an enlarged cross-sectional view of the leaf spring 60 before the separation member 50 is attached as viewed from the arrows Y1 and Y2 in FIG. FIG. 18 is an enlarged cross-sectional view of the leaf spring 60 in a state having an elastic force after the separation member 50 is attached as viewed from the arrows Y1 and Y2 in FIG. FIG. 19 is a schematic sectional view showing a modification of the leaf spring 60 in the second embodiment of the present invention. FIG. 20 is a cross-sectional view showing the configuration of the fixing device in Embodiment 3 of the present invention.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Example 1)
FIG. 2 is a configuration diagram showing an outline of the image forming apparatus in Embodiment 1 of the present invention.

  This image forming apparatus is, for example, an electrophotographic printer, and a recording medium cassette 2 containing a recording medium 1 such as paper is detachably attached to the lower part thereof. A plurality of recording medium transport units 3 including a pair of transport rollers for transporting the recording medium 1 are disposed from the recording medium discharge side of the recording medium cassette 2 to the upper downstream side. A toner image forming unit 4 as a developing device for forming a developer (for example, toner) image and a fixing device 10 located on the downstream side are provided between the plurality of recording medium conveying units 3 in the order of conveying the recording medium. It has been. Adjacent to the toner image forming unit 4, a light emitting diode (hereinafter referred to as “LED”) head 5 as a recording light exposure device is provided.

  The toner image forming unit 4 is a device that transfers and forms a toner image corresponding to the recording light emitted from the LED head 5 onto the recording medium 1. The fixing device 10 disposed on the downstream side is a device that fixes the toner image attached on the recording medium 1 by heating and pressing. In the image forming apparatus, a print control unit 6 and the like for controlling the internal mechanism are provided.

  FIG. 1 is a perspective view showing an appearance of the fixing device 10 in FIG. 2 according to the first embodiment of the present invention. Further, FIG. 3 is an enlarged perspective view of a portion A in FIG.

  The fixing device 10 has a metal frame 20 for accommodating the fixing device. The frame 20 includes two opposing side plates 21 and 22, an upper plate 23 fixed above the both side plates 21 and 22, and a lower plate 24 fixed below the both side plates 21 and 22. It is comprised by. The frame 20 is preferably grounded in order to gradually charge charges such as static electricity. Holes 21a and 22a for attaching separation members are respectively formed at substantially central positions of the side plates 21 and 22 facing each other.

  A fixing roller 30 as a fixing member is rotatably attached to the upper part between the side plates 21 and 22 via bearings 35 and 36. A pressure roller 40 as a pressure member is rotatably attached to a lower portion between the side plates 21 and 22 via a bearing (not shown). The pressure roller 40 is pressed against the fixing roller 30 by using an elastic body such as a spring (not shown). A gear (not shown) is attached to the rotation shaft of the fixing roller 30 or the pressure roller 40, and rotation from a drive motor (not shown) is transmitted to the gear so that the fixing roller 30 and the pressure roller 40 are connected to each other. It has a rotating structure.

  On the downstream side of the fixing roller 30 in the recording medium conveyance direction, a wire-shaped separating member 50 is disposed substantially parallel to the fixing roller 30 with a predetermined interval (that is, a gap). The length of the separating member 50 is larger than the length of the fixing roller 30 in the rotation axis direction. Further, both end portions 50a and 50b of the separating member 50 are inserted into the holes 21a and 22a of the side plates 21 and 22, respectively, and fixed by welding or the like.

FIG. 4 is an enlarged view showing the right side surface of FIG.
Both end portions 50a and 50b of the wire-like separation member 50 are fixed by welding or the like along the shapes of the holes 21a and 22a of the side plates 21 and 22 to which the fixing roller 30 is attached. The direction in which both end portions 50 a and 50 b of the separation member 50 are fixed is fixed so as to be directed to the rotation center 30 a of the fixing roller 30. This is because the separating member 50 is stretched so as to be parallel to the rotation axis of the fixing roller 30. The separating member 50 is not in contact with the outer peripheral surface of the fixing roller 30 and is maintained in a state where there is an appropriate gap (for example, about 1 mm). A transport plate (not shown) is provided at a position away from the separation member 50 on the outer peripheral surface of the fixing roller 30.

FIG. 5 is a perspective view in which a part near the end of the fixing roller 30 in FIG. 3 is cut away.
The fixing roller 30 has a metal core 31 such as aluminum or iron. An elastic body layer 32 such as fluoro rubber or silicone rubber is formed on the outer periphery of the core metal 31. A surface release layer 33 made of a fluorine-based resin or the like is formed on the outer periphery of the elastic layer 32 to facilitate separation of the recording medium 1. A heat source 34 for heating such as a halogen heater is provided inside the fixing roller 30.

6 is a perspective view in which a part near the end of the pressure roller 40 in FIG. 3 is cut away.
The pressure roller 40 includes a metal core 41 such as aluminum or iron. On the outer periphery of the cored bar 41, an elastic body layer 42 such as fluorine rubber or silicone rubber is formed. A surface release layer 43 made of a fluorine-based resin or the like is formed on the outer periphery of the elastic layer 42 in order to facilitate separation of the recording medium 1.

FIG. 7 is a perspective view in which a part of the separating member 50 in FIG. 3 is cut away.
The separating member 50 has a metal core 51 such as stainless steel (SUS) having a circular cross section. On the outer periphery of the cored bar 51, a surface peeling layer 52 made of a fluorine resin or the like typified by PTFE (polytetrafluoroethylene) is formed to prevent toner adhesion. The separation member 50 is better as the coefficient of linear thermal expansion is lower in order to prevent loosening due to heat. For example, the separation member 50 is desirably formed of a material of 18.0 × E-6 in an environment where the linear expansion coefficient is 300 ° C. or less. Further, the separating member 50 is preferably formed of a conductive material and grounded via the frame 20 in order to gradually discharge charges such as static electricity.

  8-10 is a figure for demonstrating the arrangement | positioning state of the separation member 50. FIG. 8 and 9 are side views showing the fixing roller 30, the pressure roller 40, and the separating member 50 in FIG. 1, and FIG. 10 shows a toner image formed on the recording medium 1 in FIG. It is a top view.

  As shown in FIGS. 8 and 9, the recording medium 1 such as a sheet to which the toner image 25 is attached is sent in the medium conveyance direction indicated by the arrow X1 and rotated in the direction indicated by the arrow X2, and the recording medium 1 indicated by the arrow X3. It is inserted into the pressure contact portion with the pressure roller 40 rotating in the direction. As shown in FIG. 10, in the fixing device 10 of the electrophotographic printer, the distance c of the leading end 1b between the leading end Q of the recording medium 1 and the front end P of the printing area 1a on the recording medium 1 is set to a predetermined value. Has been. The leading edge 1b is called a blank area (top margin), and printing is prohibited at a position closer to the leading edge Q of the recording medium 1 than this. In other words, the toner image 25 is not transferred to the blank area of the leading end 1 b to prevent the vicinity of the leading end 1 b of the recording medium 1 from sticking to the fixing roller 30.

  The gap d between the separation member 50 and the outer peripheral surface of the fixing roller 30 needs to be set smaller than the distance c of the leading end portion 1b of the recording medium 1 that is separated from the outer peripheral surface of the fixing roller 30 (d). <C). The distance at which the front end 1b of the recording medium 1 is separated from the fixing roller 30 varies depending on the type of the recording medium 1, particularly the waist strength. Therefore, the front end 1b of the recording medium 1 having the weakest waist among the recording media 1 to be handled. Is set smaller than the distance away from the fixing roller 30. Specifically, when the recording medium 1 with the lowest stiffness is a continuous amount of 50 kg (the continuous amount is the weight of the recording medium 1 per 1000 sheets), the outer peripheral surfaces of the separation member 50 and the fixing roller 30 The gap d is preferably set to about 1 mm from the actually measured value. A transport plate 26 is provided on the downstream side of the separation member 50 in the medium transport direction.

(Overall Operation of Image Forming Apparatus of Embodiment 1)
In the image forming apparatus shown in FIG. 2, when the print control unit 6 receives a print instruction from a host device (not shown) or the like, recording is performed in accordance with the timing of image formation by the recording medium transport unit 3 controlled by the print control unit 6. The recording medium 1 in the medium cassette 2 is conveyed to the toner image forming unit 4. When the LED head 5 irradiates the toner image forming unit 4 with recording light corresponding to the printing information, the toner image forming unit 4 applies the toner image 25 in FIG. 8 corresponding to the irradiated recording light onto the recording medium 1. Form. When the recording medium 1 on which the toner image 25 is formed is conveyed to the fixing device 10 by the recording medium conveying unit 3, the toner image 25 on the recording medium 1 is fixed by the heat and pressure of the fixing device 10. Thereafter, the recording medium 1 on which the toner image 25 is fixed is discharged to the outside by the recording medium transport unit 3.

(Operation of Fixing Device of Example 1)
The fixing operation of the fixing device 10 shown in FIGS. 1, 3, and 8 will be described.

  For example, the fixing roller 30 is rotated in the direction of the arrow X2 in FIG. 8 by a drive motor (not shown). The pressure roller 40 to which the rotation is transmitted rotates in the direction of the arrow X3 in FIG. The recording medium 1 to which the unfixed toner image 25 is transferred is conveyed in the medium conveyance direction indicated by the arrow X1 in FIG. When the recording medium 1 is inserted into a pressure contact portion between the fixing roller 30 and the pressure roller 40 and heated by the heat source 34 in the fixing roller 30 and is pressed by the pressure contact portion, an unfixed toner image is obtained. 25 is melted and fixed on the recording medium 1.

Next, the separation operation of the recording medium 1 will be described with reference to FIGS.
The melted toner image 25 has adhesiveness and sticks to the outer peripheral surface of the fixing roller 30. Therefore, the recording medium 1 that has passed through the pressure contact portion between the fixing roller 30 and the pressure roller 40 is conveyed in a state of being attached to the outer peripheral surface of the fixing roller 30. However, since the unfixed toner image 25 is not transferred to the leading end 1 b of the recording medium 1 and the recording medium 1 is stiff, the leading end 1 b of the recording medium 1 is stuck to the fixing roller 30. Not attached. That is, a relatively weak portion of the recording medium 1 sticks to the outer peripheral surface of the fixing roller 30, but the leading end 1 b of the recording medium 1 is away from the outer peripheral surface of the fixing roller 30.

  As a result, the leading end portion 1 b of the recording medium 1 that has been conveyed through the press contact portion is separated by the separation member 50 so as not to enter the gap d between the outer peripheral surface of the fixing roller 30 and the separation member 50. As a result, the part to which the recording medium 1 is attached is peeled off along with the separated tip 1b, and the entire recording medium 1 is separated from the fixing roller 30. The separated recording medium 1 is discharged along the transport plate 26.

(Modification of Example 1)
In the first embodiment, the constituent members of the fixing device 10 may be modified as shown in the following (1) to (3).

  (1) In FIGS. 8 and 9, the pressure roller 40 may be rotationally driven in the direction of the arrow X3, and thereby the fixing roller 30 may be rotated in the direction of the arrow X2.

  (2) In FIG. 6, a heat source such as a halogen heater (not shown) may be provided inside the pressure roller 40 instead of the heat source 34 in the fixing roller 30. Alternatively, in order to accelerate the temperature rise on the surface of the member, a heat source 34 may be provided inside the fixing roller 30 and a heat source (not shown) may be provided inside the pressure roller 40.

  (3) Although the wire-shaped separation member 50 shown in FIG. 7 has a smooth shape with a circular cross section, the cross section may be deformed into another shape such as an ellipse or a polygon. Or you may deform | transform into a shape as shown in FIG.

FIG. 11 is a view showing a modification of the separation member 50 of FIG.
A wire-shaped separation member 50A shown in FIG. 11 has a twisted shape. Further, although not shown, the separating member 50A may be deformed into a knitted shape by a plurality of the same members or a plurality of different members.

(Effect of Example 1)
The fixing device 10 according to the first exemplary embodiment and the image forming apparatus including the same have the following effects (a) to (h).

  (A) A separation member 50 is provided with a gap d with respect to the outer peripheral surface of the fixing roller 30, and the recording medium 1 is separated from the fixing roller 30 by the separation member 50. For this reason, the fixing roller 30 is not damaged, and it is possible to accurately prevent a printing defect caused by a separation member including a separation plate as in the related art coming into contact with the fixing roller. Therefore, it is possible to form an image with high accuracy without causing problems such as printing defects.

  (B) Since the wire-shaped separating member 50 is used to separate the recording medium 1, the surface area is small, and the fixing roller 30 is not surrounded as in the conventional case, so that water vapor generated from the recording medium 1 escapes. It becomes easy. Thereby, water vapor does not stay around the separation member 50. No condensation occurs and no water droplets adhere when the recording medium 1 is discharged.

  (C) Since the separation member 50 for separating the recording medium 1 is supported by the side plates 21 and 22 of the frame 20 in the same manner as the fixing roller 30, the number of parts is reduced compared to the conventional case and the cost is low. The gap d between the fixing roller 30 and the outer peripheral surface of the separating member 50 can be obtained with high accuracy.

  (D) When the frame 20 is grounded and the separating member 50 stretched on the frame 20 is formed of a conductive material, the recording medium 1 can be gradually charged with charges such as static electricity. 1 can be discharged accurately.

  (E) When the separation member 50 is formed of a material of 18.0 × E-6, for example, in an environment where the linear expansion coefficient is 300 ° C. or less, it is possible to accurately prevent loosening due to heat.

  (F) Since the surface peeling layer 52 made of fluorine resin or the like is formed on the surface of the separating member 50, toner adhesion can be prevented.

  (G) Since the length of the separating member 50 is larger than the length of the fixing roller 30 in the rotation axis direction, the recording medium 1 can be accurately separated from the fixing roller 30 even if the recording medium 1 is obliquely displaced during fixing.

  (H) As shown in FIG. 11, when the separating member 50 </ b> A has a twisted shape or a braided shape, the contact area with the recording medium 1 becomes small, so that the separation with respect to the recording medium 1 is improved.

(Configuration of Example 2)
FIG. 12 is a perspective view illustrating an appearance of the fixing device according to the second exemplary embodiment of the present invention. Further, FIG. 13 is an enlarged perspective view of a portion B in FIG. 12 and 13, elements common to those in FIGS. 1 and 3 showing the fixing device 10 according to the first embodiment are denoted by common reference numerals.

  In the fixing device 10 </ b> A of the second embodiment, in the wire-like separation member 50 similar to that of the first embodiment, elastic members (for example, leaf springs) 60 for applying tension in the longitudinal direction are provided on both side plates of the frame 20. 21 and 22, respectively.

  As in the first embodiment, holes 21a and 22a for the separation member 50 are formed in both side plates 21 and 22 constituting the frame 20, respectively. Both ends of the separating member 50 are inserted into the holes 21a and 22a, respectively.

FIG. 14 is an enlarged view showing the end shape of the separating member 50 in FIG. 13.
Both end portions of the separating member 50 have a hook shape 50c.

FIG. 15 is a perspective view showing the vicinity of the leaf spring 60 in FIG.
In the both side plates 21 and 22 constituting the frame 20, leaf springs 60 having attachment holes 60 a are respectively attached to the attachment portions of the bearings 35 and 36 that support both ends of the fixing roller 30. Each leaf spring 60 is fixed to both side plates 21 and 22 by screws 61 and 62, respectively. Both end portions of the separating member 50 are inserted into the holes 21 a and 22 a of the side plates 21 and 22, respectively, and hook shapes 50 c at both end portions of the separating member 50 are respectively hooked into the mounting holes 60 a of the leaf springs 60. . The separating member 50 is pulled from both ends by the elastic force of each leaf spring 60 so as to follow the shape of the holes 21 a and 22 a of the side plates 21 and 22 to which the fixing roller 30 is attached.

FIG. 16 is a plan view of the vicinity of the leaf spring 60 shown in FIG.
The direction in which the separating member 50 is pulled by the elastic force of the leaf spring 60 is a direction toward the rotation center 30 a of the fixing roller 30. This is because the separation member 50 is stretched in parallel to the fixing roller 30 with a predetermined gap d from the fixing roller 30.

  FIG. 17 is an enlarged cross-sectional view of the leaf spring 60 before the separation member 50 is attached as viewed from the arrows Y1 and Y2 in FIG. Further, FIG. 18 is an enlarged cross-sectional view of the leaf spring 60 in a state having an elastic force after the separation member 50 is attached as viewed from the arrows Y1 and Y2 in FIG.

  The leaf spring 60 has an elastic force in the direction of arrow Z in FIG. 18 and pulls both ends of the separating member 50. Therefore, the separation member 50 is stretched so as to be parallel to the rotation axis of the fixing roller 30. Further, the separation member 50 is not in contact with the outer peripheral surface of the fixing roller 30 and is maintained in a state where there is an appropriate gap d (for example, about 1 mm). A transport plate 26 as shown in FIGS. 8 and 9 is provided at a position away from the separation member 50 on the outer peripheral surface of the fixing roller 30.

  Other configurations of the fixing device 10A and the image forming apparatus in the second embodiment are the same as those of the fixing device 10 and the image forming apparatus in the first embodiment.

(Operation of Fixing Device of Example 2)
As in the first embodiment, in FIGS. 8, 9 and 12, when the fixing roller 30 is rotated in the direction of the arrow X2 in FIG. Rotate in the direction of arrow X3 in FIG. The recording medium 1 to which the unfixed toner image 25 is transferred is conveyed in the medium conveying direction indicated by the arrow X1 in FIG. When the recording medium 1 is inserted into a pressure contact portion between the fixing roller 30 and the pressure roller 40 and heated by the heat source 34 in the fixing roller 30 and is pressed by the pressure contact portion, an unfixed toner image is obtained. 25 is melted and fixed on the recording medium 1.

  Next, in the separation operation of the recording medium 1, the fused toner image 25 is attached to the outer peripheral surface of the fixing roller 30 as in the first embodiment. Therefore, the recording medium 1 that has passed through the pressure contact portion between the fixing roller 30 and the pressure roller 40 is conveyed in a state of being attached to the outer peripheral surface of the fixing roller 30. However, since the unfixed toner image 25 is not transferred to the leading end 1 b of the recording medium 1 and the recording medium 1 is stiff, the leading end 1 b of the recording medium 1 is stuck to the fixing roller 30. Not attached. As a result, the leading end portion 1 b of the recording medium 1 that has been conveyed through the press contact portion is separated by the separation member 50 so as not to enter the gap d between the outer peripheral surface of the fixing roller 30 and the separation member 50. As a result, the part to which the recording medium 1 is attached is peeled off along with the separated tip 1b, and the entire recording medium 1 is separated from the fixing roller 30. The separated recording medium 1 is discharged along the transport plate 26.

  Here, in the second embodiment, as in the first embodiment, the gap d between the separating member 50 and the fixing roller 30 is the distance that the leading end 1b of the recording medium 1 that is the weakest is separated from the outer peripheral surface of the fixing roller 30. (For example, d is about 1 mm). In addition, both ends of the separating member 50 are pulled by the leaf spring 60. Therefore, the deflection of the separating member 50 corresponding to the thermal expansion is absorbed, and the gap d between the separating member 50 and the outer peripheral surface of the fixing roller 30 maintains the set planting. Thereby, the recording medium 1 can be accurately separated from the fixing roller 30.

(Modification of Example 2)
In the second embodiment, the constituent members of the fixing device 10A may be modified in the same manner as the modifications (1) to (3) of the first embodiment.

  Furthermore, in the second embodiment, the example in which the leaf spring 60 is used as the elastic member that applies tension to the separation member 50 has been described. However, the elastic member may be realized by using a compression spring, a tension spring, or the like.

FIG. 19 is a schematic cross-sectional view showing a modification of the leaf spring 60 in the second embodiment of the present invention.
In this modification, compression coil springs 71 and 72 are used in place of the leaf spring 60 in FIG. Both ends of a wire-like separation member 50 are inserted into the holes 21a and 22a of the side plates 21 and 22 constituting the frame 20, and disc-shaped locking members 73 and 74 are welded to the both ends. It is fixed. A compression coil spring 71 is mounted between one side plate 21 and the locking member 73, and a compression coil spring 72 is mounted between the other side plate 22 and the locking member 74. Yes.

  Both compression coil springs 71 and 72 have elasticity in the directions of arrows Z1 and Z2 in FIG. 19 and pull both ends of the separating member 50. Therefore, as in the second embodiment, the deflection of the separation member 50 due to thermal expansion is absorbed, and the gap d between the separation member 50 and the outer peripheral surface of the fixing roller 30 maintains the set planting. Thereby, the recording medium 1 can be accurately separated from the fixing roller 30.

(Effect of Example 2)
According to the fixing device 10A of the second embodiment and the image forming apparatus including the same, there are the same effects as the effects (a) to (h) of the first embodiment. Furthermore, according to the second embodiment, both ends of the separation member 50 are pulled by elastic members such as the leaf spring 60 and the compression coil springs 71 and 72, so that even when the separation member 50 is thermally expanded, the separation member It is possible to stably maintain the gap d between the fixing roller 30 and the outer peripheral surface of the fixing roller 30, and there is an effect that a constant separation performance can be always secured.

(Configuration of Example 3)
FIG. 20 is a cross-sectional view showing the configuration of the fixing device according to the third embodiment of the present invention. The fixing device 10 according to the first embodiment is shown in common with the components in FIGS. 1, 3, 8, and 9. Are marked with a common reference.

  When the recording medium 1 on which the toner image 25 is formed is sent from the medium conveyance direction indicated by the arrow X1, the fixing device 10B according to the third exemplary embodiment fixes the toner image 25 to the recording medium 1 by heating and pressing. This is a belt type fixing device, and has an endless fixing belt 81 for supplying heat to the recording medium 1 and further conveying it.

  Inside the fixing belt 81, the fixing belt 81 is stretched and heated, a fixing member 82 that rotates the fixing belt 81, the fixing roller 30 that rotates the fixing belt 81, and the fixing belt 81 with respect to the rotation direction indicated by the arrow X2. A fixing pad 83 that is disposed upstream of the roller 30 and presses the fixing belt 81 from the inner peripheral surface toward the outer peripheral surface of the arrow X4, and fixing with respect to the rotation direction of the fixing belt 81 in the direction of the arrow X2. A guide member 84 is provided on the upstream side of the pad 83 and on the downstream side of the stretching member 82 and guides the rotation of the fixing belt 81.

  A pressure roller 40 as a pressure member is provided outside the fixing belt 81 so as to face the fixing roller 30 and the fixing pad 83. The pressure roller 40 presses the fixing pad 83 in the direction opposite to the arrow X4 with the fixing belt 81 interposed therebetween, thereby forming the first nip portion N1 that is a contact range and fixing with the fixing belt 81 interposed therebetween. By pressing the roller 30 in the direction of the arrow X5, a second nip portion N2 that is a contact range is formed.

  A holder 85 is disposed below the tension member 82. A pressure member 87 is attached to the holder 85 via a spring 86. The tension member 82 is attached on the pressure member 87 via a planar heater 88 as a heat source for heating the tension member 82. The pressurizing member 87 pressurizes the tension member 82 in the upward direction of the arrow X6 through the planar heater 88 by the biasing force of the spring 86. The fixing belt 81, the fixing roller 30, the fixing pad 83, the sheet heater 88, and the like constitute a fixing member.

  The fixing roller 30 is rotatably attached to a frame (not shown) via a bearing (not shown). On the downstream side in the recording medium conveyance direction at 81 fixing belts that are in contact with the fixing roller 30, substantially in the same manner as in the first embodiment, with a predetermined gap d with respect to the 81 fixing belts that are in contact with the fixing roller 30. A wire-shaped separating member 50 is disposed in parallel. A transport plate 26 is provided at a position away from the separating member 50 at 81 fixing belts in contact with the fixing roller 30.

  The fixing pad 83 is held by a lever 89. The fixing pad 83 is pressed by a spring 91 supported by a holder 90 held by a frame (not shown) with the fulcrum 89a of the lever 89 as an axis in the direction of an arrow X4 that presses against the pressure roller 40. The pressure roller 40 is rotatably attached to the lever 92 via a bearing (not shown). This pressure roller 40 is pressed by an elastic member such as a spring (not shown) around the fulcrum 92a of the lever 92 in the direction of the arrow X5 pressed against the fixing roller 30, and via the fixing belt 81, the fixing pad 83. Are in contact with each other at positions facing the fixing roller 30.

  The guide member 84 is fixed to a holder 90 that is held by a frame (not shown), and a part of the guide member 84 has an arc shape in order to stabilize the rotation of the fixing belt 81.

  A pair of flanges 93 are fixed to the holder 90 in order to restrict the movement of both ends in the width direction of the fixing belt 81 (that is, the direction orthogonal to the rotation direction of the fixing belt 81). Each flange 93 has an arcuate part of the inner shape of the fixing belt 81 in order to stabilize the rotation of both ends of the fixing belt 81. Further, the outer side of the fixing belt 81 in each flange 93 has a shape larger than the inner diameter of the fixing belt 81 in order to restrict movement of the fixing belt 81 in the width direction.

  Note that a heat source such as a halogen heater (not shown) may be provided inside the fixing roller 30 or the pressure roller 40 in order to accelerate the temperature rise on the roller surface, as in the first embodiment.

(Operation of Example 3)
In the fixing device 10B according to the third exemplary embodiment, the fixing roller 30 is rotationally driven from the medium conveyance unit 3 in FIG. 2 via a gear (not shown). As a result, the fixing belt 81 is driven by the fixing roller 30 and the pressure roller 40 is driven by the frictional force with the fixing belt 81, so that the fixing belt 81 is rotationally driven in the direction of the arrow X2 in FIG. . Note that the pressure roller 40 may be rotationally driven from the recording medium conveyance unit 3. When the fixing roller 30 rotates in the direction of the arrow X2 in FIG. 20, the fixing belt 81 is pulled by the first nip portion N1. Further, since the fixing belt 81 is stretched in the direction of the arrow X6 in FIG. 20 by the stretching member 82, the fixing belt 81 rotates while sliding with respect to the guide member 84.

  When the fixing belt 81 is rotationally driven by the fixing roller 30 in the direction of the arrow X2 in FIG. 20 during the printing operation, the fixing belt 81 is connected to the fixing pad 83, the first nip portion N1 of the pressure roller 40, and the tension. It is stretched by the frame member 82 and rotates while sliding with respect to the guide member 84. At this time, the tension member 82 is heated and the fixing belt 81 is heated by the planar heater 88 in a state where electric power is supplied and heat is generated.

  The surface temperature of the fixing belt 81 is detected by a temperature sensor (not shown), and based on the detection result, the power supplied to the sheet heater 88 is controlled by the print control unit 6 in FIG. Maintained. The recording medium 1 on which the toner image 25 is formed is conveyed through the nip portions N1 and N2 formed on the fixing belt 81, and the toner image 25 on the recording medium 1 is formed by the fixing belt 81 and the pressure roller 40. It is fixed on the recording medium 1 by heating and pressing.

  Next, in the separation operation of the recording medium 1, the melted toner image 25 adheres to the outer peripheral surface of 81 fixing belts that are in contact with the fixing roller 30 in substantially the same manner as in the first embodiment. For this reason, the recording medium 1 that has passed the pressure contact portion between the fixing roller 81 and the pressure roller 40 that contacts the fixing roller 30 is conveyed while being adhered to the outer peripheral surface of the fixing belt 81 that contacts the fixing roller 30. To go. However, since the unfixed toner image 25 is not transferred to the leading end 1 b of the recording medium 1 and the recording medium 1 is stiff, the leading end 1 b of the recording medium 1 is stuck to the fixing belt 81. Not attached. As a result, the leading end 1b of the recording medium 1 conveyed through the pressure contact portion is separated so as not to enter the gap d between the outer peripheral surface of the fixing belt 81 in contact with the fixing roller 30 and the separation member 50. Separated by member 50. As a result, the part to which the recording medium 1 is adhered is peeled off along with the separated leading end 1 b, and the entire recording medium 1 is separated from the fixing belt 81. The separated recording medium 1 is discharged along the transport plate 26.

(Modification of Example 3)
In the third embodiment, the fixing device 10B may be modified as follows (i) to (iii).

  (I) The constituent members of the fixing device 10B may be modified in the same manner as the modifications (1) to (3) of the first embodiment.

  (Ii) As in the second embodiment or its modification, an elastic member such as a leaf spring 60, a compression spring, or a tension spring may be provided to apply tension to the separation member 50.

  (Iii) In FIG. 20, the fixing belt 81, the fixing pad 83, the sheet heater 88, and the like may be provided not on the fixing roller 30 side but on the pressure roller 40 side.

(Effect of Example 3)
According to the fixing device 10B and the image forming apparatus including the same according to the third exemplary embodiment, the wire-like separation member 50 is disposed with a gap d with respect to the outer peripheral surface of 81 fixing belts that are in contact with the fixing roller 30. In addition, since the recording medium 1 is separated from the fixing belt 81 by the separation member 50, there are substantially the same effects as those of the first and second embodiments.

(Other variations)
The present invention is not limited to the first to third embodiments and their modifications, and various other forms of use and modifications are possible. For example, there are the following forms (I) and (II) as usage forms and modifications.

  (I) The fixing member constituted by the fixing roller 30 or the like, or the pressure member constituted by the pressure roller 40 or the like may be modified to a configuration other than that illustrated.

  (II) In the first to third embodiments, an electrophotographic printer has been described as an example of the image forming apparatus. However, the image forming apparatus of the present invention is not limited to this, and may be a facsimile machine, a copying machine, The present invention can also be applied to a multifunction peripheral (MFP).

DESCRIPTION OF SYMBOLS 1 Recording medium 4 Toner image formation part 5 LED head 10, 10A, 10B Fixing device 20 Frame 25 Toner image 30 Fixing roller 40 Pressure roller 50, 50A Separation member 60 Leaf spring 72, 73 Compression coil spring 81 Fixing belt 88 Planar shape heater

Claims (10)

When the recording medium having the developer image attached thereto is sent from the upstream side in the recording medium conveyance direction, a pressure member that is in pressure contact with the recording medium;
A fixing member that rotatably contacts the pressure member via the recording medium, fixes the developer image attached to the recording medium, and sends the developer image downstream in the recording medium conveyance direction;
A wire-like separation member disposed at a predetermined interval with respect to the fixing member on the downstream side of the fixing member;
A fixing device. The fixing device according to claim 1 further includes:
A frame that supports the fixing member and the separating member;
Both ends of the rotation shaft of the fixing member are rotatably attached to the frame,
The fixing device is characterized in that the separating member is disposed substantially parallel to the rotation shaft of the fixing member, and both ends thereof are attached to the frame. The fixing device according to claim 2 further includes:
A fixing device having an elastic member attached to an end portion of the separation member and applying tension in a longitudinal direction of the separation member.   The fixing device according to claim 1, wherein the separation member has conductivity.   4. The separation member according to claim 1, wherein the separation member is formed of a material of 18.0 × E-6 in an environment having a linear expansion coefficient of 300 ° C. or less. Fixing device.   The fixing device according to claim 1, wherein a surface peeling layer is formed on a surface of the separating member.   The fixing device according to claim 1, wherein the separation member has a twisted shape.   The fixing device according to claim 1, wherein the separating member has a braided shape formed by a plurality of identical members or a plurality of separate members.   The fixing device according to claim 1, wherein a length of the separating member is larger than a length of the fixing member in a rotation axis direction. A fixing device according to any one of claims 1 to 10,
A developer image forming unit for forming the developer image and attaching the developer image to the recording medium, and supplying the recording medium to which the developer image is attached to the fixing device;
An image forming apparatus comprising:

Images