JP2018054729A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of reducing the warpage of a separation guide by suppressing a temperature difference between a first position and a second position in the conveyance direction of a recording material in the separation guide and capable of improving separation performance by making the separation guide closer to a fixing member.SOLUTION: The fixing device includes a rotation body, an opposing body which faces the rotation body and forms a nip part where the recording material carrying a toner image is held and conveyed in a state of being pressurized together with the rotation body, a heating body which heats the rotation body, the separation guide which separates the recording material passing through the nip part from the rotation body, and a heat conduction member which comes into contact with the separation guide so as to suppress the temperature difference between the first position in the conveyance direction of the recording material in the separation guide and the second position further away from the nip part than the first position. The separation guide includes a first area which comes into contact with the heat conduction member in the first position and a second area which comes into contact with the heat conduction member in the second position and is wider than the first area.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a fixing device and is suitable for an electrophotographic image forming apparatus capable of forming an image on a sheet, such as a multifunction machine, a copying machine, a printer, and a fax machine.

  As a fixing device mounted on an electrophotographic copying machine or printer, a film heating method is known. The fixing device of the film heating system includes, for example, a fixing nip portion by sandwiching a flexible thin fixing film as a heat transfer member between a ceramic heater as a heating member and a pressure roller as a pressure member. To form.

  Then, a recording material on which an unfixed toner image is formed and supported is introduced between the fixing film and the pressure roller in the fixing nip portion, and is nipped and conveyed together with the fixing film. As a result, the unfixed toner image is fixed on the recording material surface by the pressure of the fixing nip portion while applying heat from the ceramic heater through the fixing film.

  However, when the toner image is heated and melted by receiving heat from the fixing film, the heat-melted toner image becomes sticky, and the recording material adheres to the outer peripheral surface (surface) of the fixing film and wraps around. There is. Therefore, in order to prevent the recording material from being wrapped around the surface of the fixing film, a technique for separating the recording material by providing a separation guide has been proposed (Patent Document 1).

  In recent years, along with the need for thin paper as a recording material, there is an increasing need to minimize the leading margin of the recording material. On the other hand, a low-cost resinous separation guide has been used for cost reduction. .

JP 2011-27899 A

  However, in a separation guide made of a material having low thermal conductivity and high thermal expansion like resin, the tip side near the fixing film becomes high temperature due to the radiant heat received from the fixing film, and the rear end side far from the fixing film is on the tip side. The temperature is lower than that. And the problem that the center part of the longitudinal direction in the front end side of a separation guide warps in the direction approaching a fixing film by the thermal expansion difference of a front end side and a rear end side.

  Therefore, if the separation guide is disposed away from the fixing film in order to prevent the fixing film and the leading end of the separation guide from coming into contact with each other due to the warpage, the separation performance is lowered.

  An object of the present invention is to suppress the temperature difference between the first position and the second position in the recording material conveyance direction in the separation guide, thereby reducing the warp of the separation guide and separating the separation guide closer to the fixing member. An object of the present invention is to provide a fixing device capable of improving the performance.

  In order to achieve the above object, a fixing device according to the present invention includes a rotating body and a nip portion that faces the rotating body and is nipped and conveyed in a state where a recording material bearing a toner image is pressed. A counter body formed together with the heating body for heating the rotating body, a separation guide for separating the recording material passing through the nip portion from the rotating body, and a first position in the recording material conveyance direction in the separation guide And a heat conduction member that contacts the separation guide so as to suppress a temperature difference between the first position and a second position that is further away from the nip portion than the first position. A first area in contact with the heat conducting member at a position 1 is provided, and a second area wider than the first area in contact with the heat conducting member at the second position is provided.

  Another fixing device according to the present invention includes a heating body, a fixing rotator heated by the heating body, a pressure member that presses against the fixing rotator to form a nip portion, and the fixing rotator. And a resin separation guide positioned on the metal frame, and one end of the resin separation guide is disposed at a position close to the fixing rotator. In the fixing device configured as described above, the separation guide is positioned so as to be thermally expandable in a longitudinal direction that is a direction orthogonal to a direction in which the recording material is conveyed to the metal frame. The metal frame has a contact portion, and is configured such that the area of the contact portion becomes wider as going away from the fixing rotating body.

  Another fixing device according to the present invention includes a heating body, a fixing rotator heated by the heating body, a pressure member that presses against the fixing rotator to form a nip portion, and the fixing rotator. A resin separation guide positioned in a casing for positioning (101), and one end of the resin separation guide is disposed at a position close to the fixing rotating body. The apparatus is characterized in that a high thermal conductive member (401) having a thermal traditional rate of 2 times or more of copper thermal conductivity 398 W / (m · K) is attached to the separation guide.

  According to the present invention, an object of the present invention is to reduce the warp of the separation guide by suppressing the temperature difference between the first position and the second position in the recording material conveyance direction in the separation guide, and to the fixing member. The separation guide can be brought closer and the separation performance can be improved.

1 is a cross-sectional view of an image forming apparatus equipped with a fixing device according to an embodiment of the invention. Sectional drawing explaining schematic structure of the fixing apparatus which concerns on embodiment of this invention. The perspective view explaining the isolation | separation guide and metal frame of 1st Embodiment (A) is a figure explaining a prior art example, (b) is a figure explaining the contact part of the separation guide and metal frame of 1st Embodiment. Sectional drawing explaining the temperature measurement part of the separation guide and metal frame of 1st Embodiment The graph explaining the temperature and curvature amount of the separation guide and metal frame of the first embodiment The graph which showed the curvature amount of the separation guide explaining the effect of 1st Embodiment The figure explaining the separation guide and graphite sheet of 2nd Embodiment The graph explaining the temperature and the amount of warping of the separation guide of the second embodiment Diagram showing deformation direction of separation guide

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

<< First Embodiment >>
(Image forming device)
FIG. 1 is a cross-sectional view of an image forming apparatus 500 equipped with a fixing device according to an embodiment of the present invention. Four cartridges 7 (7a to 7d) arranged in parallel in an oblique direction (angle β with respect to the horizontal plane T) are photosensitive drum units 26 (26a to 26d) each having a photosensitive drum 1 (1a to 1d) as an electrophotographic photosensitive member. And a developing unit 4 (4a to 4d).

  The photosensitive drum 1 is driven to rotate clockwise (Q direction) in the figure by a driving member (not shown). Further, around the photosensitive drum 1, a cleaning member 6 (6a to 6d), a charging roller 2 (2a to 2d), and a developing unit 4 are arranged in the order of the rotation direction.

  The cleaning member 6 removes the toner agent remaining on the photosensitive drum 1 after transferring the toner image formed on the photosensitive drum 1 onto the intermediate transfer belt 5. The toner agent removed by the cleaning member 6 is collected in a removed toner chamber in the photoreceptor unit 26 (26a to 26d).

  The charging roller 2 charges the surface of the photosensitive drum 1 uniformly. After the surface of the photosensitive drum 1 is charged by the charging roller 2, laser light is exposed on the surface of the photosensitive drum 1 from the scanner unit (exposure means) 3 through the unit openings 32 (32 a to 32 d). As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 1. In the present embodiment, the scanner unit 3 is disposed below the cartridge 7.

  The developing unit 4 supplies toner agent to the electrostatic latent image formed on the photosensitive drum 1 and develops the electrostatic latent image as a toner image. The developing unit 4 includes a developing roller 25 (25a to 25d) that contacts the photosensitive drum 1 and supplies a toner agent to the surface of the photosensitive drum 1. Further, a supply roller 34 (34 a to 34 d) that contacts the developing roller 25 and supplies a toner agent to the developing roller 25 is provided.

  When forming an image on the recording material (recording paper) S, first, the electrostatic latent image formed on the surface of the photosensitive drum 1 by the scanner unit 3 is developed as a toner image by the cartridge 7 and transferred to the intermediate transfer belt 5. Is done.

  The intermediate transfer belt 5 is stretched around a driving roller 10 and a tension roller 11 and is driven in the direction of arrow R shown in FIG. Further, a primary transfer roller 12 (12a to 12d) is disposed inside the intermediate transfer belt 5 so as to face each photosensitive drum 1, and a transfer bias is applied by a bias applying unit (not shown). It has become. For example, when a negatively charged toner agent is used, a toner image is sequentially primary transferred onto the intermediate transfer belt 5 by applying a positive bias to the primary transfer roller 12. Then, the four-color toner images are conveyed to the secondary transfer unit 15 in a state where the intermediate transfer belt 5 is overlaid.

  At this time, the toner agent remaining on the intermediate transfer belt 5 after the secondary transfer to the recording material S is removed by the transfer belt cleaning device 23, and the removed toner agent is used as a waste toner conveyance path (not shown). And is collected in a waste toner collecting container (not shown).

  On the other hand, in synchronization with the image forming operation described above, the recording material S is fed toward the secondary transfer unit 15 by a conveyance mechanism including the feeding device 13 and the registration roller pair 17. The feeding device 13 includes a feeding cassette 24 that stores a plurality of recording materials S, a feeding roller 8 that feeds the recording materials S, and a transport roller pair 16 that transports the fed recording materials S. doing. The feeding cassette 24 is configured to be detachable from the image forming apparatus 500. The user pulls out the feeding cassette 24 and removes it from the image forming apparatus 500. Then, the user sets the recording material S and inserts it into the image forming apparatus 500, whereby the replenishment of the recording material S is completed.

  Among the recording materials S stored in the feeding cassette 24, the feeding roller 8 is pressed against the recording material S located at the uppermost position, and is separated one by one by the separation pad 9 as the feeding roller 8 rotates. (Friction piece separation method) The recording material S is conveyed. The recording material S conveyed from the feeding device 13 is conveyed to the secondary transfer unit 15 by the registration roller pair 17.

  In the secondary transfer unit 15, a four-color toner image on the intermediate transfer belt 5 can be secondarily transferred onto the conveyed recording material S by applying a positive bias to the secondary transfer roller 18. Is possible.

  Then, the recording material S is fed from the secondary transfer unit 15, conveyed to the fixing device 40, and heat and pressure are applied to the image transferred to the recording material S to fix the toner image on the recording material S. . Thereafter, the recording material S on which the toner image is fixed is discharged to the discharge tray 20 by the discharge roller pair 19.

(Fixing device)
Next, the fixing device 40 will be described in detail with reference to FIG. The fixing device 40 is a film heating type heating device. The fixing device 40 includes a pressure roller 106 as a pressure member, a ceramic heater (heater) 100 as a heating member, and a cylindrical fixing film 101 as a fixing member. Then, a nip portion N is formed between the heater 100 and the pressure roller 106 as a counter body with the fixing film 101 as a rotating body interposed therebetween. The recording material carrying the toner image is nipped and conveyed at the nip portion in a pressurized state.

  The fixing device 40 includes a fixing film supporting member (supporting member) 103 that restricts the trajectory of the fixing film 101 and a fixing flange 104 that restricts the end of the fixing film 101 in the longitudinal direction. Here, the longitudinal direction is a direction orthogonal to the recording material conveyance direction and the recording material thickness direction. Further, the fixing device 40 is disposed so that the pressure stay 102 disposed on the inner surface side of the fixing film 101 in order to ensure the strength of the support member 103 and the discharged recording material S are not wrapped around the fixing film 101. The separation guide 201 is provided. Details of each will be described below.

  The heater 100 as a heating means is basically composed of a thin and thin plate-like ceramic substrate and an energization heating resistor layer provided on the surface of the substrate, and has a steep rise characteristic as a whole by energization of the heating resistor layer. It is a low heat capacity heater that raises the temperature. The heater 100 is fitted and supported in a fitting groove 103 a provided on the lower surface of the support member 103 along the longitudinal direction.

  The fixing film 101 is a heat-resistant cylindrical member that transfers heat to the recording material, and is externally fitted to the support member 103. The fixing film 101 is a film having a four-layer composite structure including a release layer, an elastic layer, a base layer, and an inner surface coating layer. As the release layer, a fluororesin material having a thickness of 100 μm or less, preferably 20 to 70 μm can be used. Examples of the fluororesin layer include PTFE and PFA. The elastic layer can be made of a rubber material having a thickness of 1000 μm or less, preferably 500 μm or less in order to reduce the heat capacity. For example, silicone rubber, fluorine rubber and the like can be mentioned.

  As the base layer, a heat-resistant material having a thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more can be used. For example, a metal film such as SUS or nickel, or a resin material such as polyimide can be used. The inner surface coat layer is a resin layer having heat resistance. For example, polyimide, polyimide amide, PEEK, PTFE, FEP, PFA and the like can be mentioned.

  The pressure stay 102 is a member for imparting strength in the longitudinal direction to the support member 103 by pressing against the back surface of the support member 103 and correcting the support member 103. The support member 103 is a heat and heat insulating member provided inside the fixing film 101. Specifically, materials having good insulation and heat resistance such as phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, and LCP resin are used.

  The support member 103 is provided with a fitting groove 103 a so as to support the heater 100, and the heater 100 presses the pressure roller 106 through the fixing film 101 to form the nip portion N.

  The fixing flanges 104 are fitted to both ends of the pressure stay 102 in the longitudinal direction to guide the rotation of the fixing film 101 and prevent the fixing film 101 from coming off. The fixing flange 104 is fitted and held on a side plate (not shown).

  The pressure roller 106 as a pressure member includes a cored bar 106a, a heat-resistant / elastic material layer 106b made of silicone rubber, fluororubber, fluororesin, or the like, which is concentrically molded and coated around the cored bar. The release layer is provided on the surface layer. For example, for the release layer, a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP can be selected.

  Bearing members (not shown) made of a heat-resistant resin such as PEEK, PPS, liquid crystal polymer, and the like are attached to both ends in the longitudinal direction of the cored bar, and are arranged to be rotatably held on a side plate (not shown). Further, the pressure roller 106 is rotationally driven by the driving means 24 controlled by the control unit 45 through a gear (not shown) attached to the end portion in the longitudinal direction. The fixing film 101 is driven to rotate by the pressure roller 106.

(Separation guide and heat conduction member)
Next, the separation guide 201 and the metal frame 202 as a metal member which is a heat conducting member will be described in detail with reference to FIG. The recording material S is nipped and conveyed by the fixing film 101 and the pressure roller 106 at the nip portion N, and the toner image t is heated and fixed on the recording material S by receiving heat and pressure in the conveyance process. The recording material S adheres to the surface of the fixing film 101 by heating and melting the toner image t at the nip portion N, and is separated by the separation guide 201 even if it is conveyed along with the rotation of the fixing film 101.

  That is, the recording material S is separated from the surface of the fixing film 101 when the leading edge Se of the recording material S abuts against the leading edge 201 a of the separation guide 201.

  As described above, the separation guide 201 is disposed so as to prevent the recording material S discharged and conveyed from being wound around the fixing film 101 and not to be damaged by coming into contact with the fixing film 101. That is, based on the rotation trajectory of the fixing film 101, the gap between the surface layer of the fixing film 101 and the separation guide tip 201a is arranged on the downstream side of the conveyance with a gap a. In this embodiment, PBT + ABS that is a resin material is used as the material of the separation guide 201.

  The separation guide 201 is fixed (positioned) to the metal frame 202, and the metal frame 202 is supported (positioned) on a side plate (not shown) as a casing for positioning the fixing film 101, similarly to the fixing flange 104. ing. In this embodiment, iron is used as the material of the metal frame 202.

  Next, a method for fixing the separation guide 201 and the metal frame 202 will be described in detail with reference to the perspective view of FIG. The separation guide 201 has claw portions 201d and 201e formed in a key shape, and is fitted and fixed in square holes 202d and 202e provided in the metal frame 202 in the H direction in the drawing, which is the recording material conveyance direction. Yes. Further, in the longitudinal direction perpendicular to the recording material conveyance direction, the central portion of the separation guide 201 is fixed (positioned) to the metal frame 202 at one point by a screw 301 as shown in FIG.

  At this time, since the square holes 202d and 202e of the metal frame 202 are made larger than the claw portions 201d and 201e in the longitudinal direction, the separation guide 201 has a J-direction and a K Thermal expansion is possible in the direction. The metal frame 202 has bent portions 202f and 202g, and is supported by a side plate (not shown).

  FIG. 4 is a view when the separation guide 201 is viewed from the arrow Y direction in FIG. 4A shows a conventional contact portion 201m between the separation guide and the metal frame, and FIG. 4B shows a contact portion 201n between the separation guide and the metal frame of the present embodiment. The separation guide 201 includes a plurality of contact portions 201m (FIG. 4A) and 201n (FIG. 4B) with the metal frame in the longitudinal direction. The contact portion 201n of the present embodiment is formed in a triangular shape as shown in FIG. 4B, and the contact portion 201n extends from the 201a portion on the upstream side in the recording material conveyance direction H to the 201b portion on the downstream side. It is formed so that the area increases.

  Next, the measurement points of the temperature of the separation guide 201 and the metal frame 202 (FIG. 5), the temperature change graph of the measurement points, the displacement of the separation guide 201 (FIG. 6), the deformation principle and the deformation direction of the separation guide 201 (FIG. 10) will be described.

  In FIG. 5, the temperature on the front end side near the fixing film 101 where the separation guide 201 is a heat source is Tma, and the temperature on the far rear end side is Tmb. Further, the temperature on the front end side close to the fixing film 101 where the metal frame 202 is a heat source is Tpa, and the temperature on the far rear end side is Tpb. Graph 6 shows the temperature change at each point when the horizontal axis is timed and the fixing film 101 is heated from room temperature.

  FIG. 6A is a graph when the temperature is measured with the conventional separation guide 201 and the metal frame 202, and the contact portion between the separation guide 201 and the metal frame 202 is in the state of FIG. 4A. FIG. 6B is a graph when the temperature is measured with the separation guide 201 and the metal frame 202 of the present embodiment, and the contact portion between the separation guide 201 and the metal frame 202 is in the state of FIG.

  The separation guide 201 is arranged so that one end in the recording material conveyance direction (H direction) is close to the fixing film 101 heated to 170 ° C. by the heater 100. For this reason, in FIG. 6A, the tip temperature Tma of the separation guide 201 receives radiant heat from the fixing film 101 and rises to about 85 ° C. when the heating time is 300 seconds. On the other hand, since the rear end portion 201b of the separation guide 201 is farther from the fixing film 101 than the front end portion 201a, the temperature rise due to the influence of the radiant heat of the fixing film 101 is less than that of the front end portion 201a, and the rear end temperature Tmb. Is about 45 ° C.

Therefore, in the conventional separation guide 201 and the metal frame 202, a temperature difference of about 40 ° C. occurs between the front end portion 201a and the rear end portion 201b of the separation guide 201. Here, the thermal expansion coefficient of PBT + ABS, which is the material of the separation guide 201, is 3.0 × 10 ⁻⁵ mm / K, and the longitudinal length (longitudinal width) of the separation guide 201 is 330 mm. At the end, the expansion difference is 0.4 mm in the longitudinal direction.

  In the separation guide 201 in which the conventional separation guide tip 201a shown in FIG. 4A is connected in a straight line, the difference in thermal expansion is the direction in which the separation guide 201 approaches the fixing film 101 in the recording material conveyance direction H shown in FIG. The warpage was 0.45 mm. The amount of deformation due to warping of the separation guide 201 at that time is shown as a guide displacement in FIG. As described above, in the conventional separation guide 201 and the metal frame 202, it is necessary to determine the gap between the separation guide 201 and the fixing film 101 in consideration of the warpage of 0.45 mm.

  Hereinafter, this embodiment will be described. Also in this embodiment, as described above, the separation guide 201 is disposed close to the fixing film 101 heated to 170 ° C. by the heater 100. For this reason, in FIG. 6B, the tip temperature Tma of the separation guide 201 receives radiant heat from the fixing film 101 and rises to about 85 ° C. when the heating time is 300 seconds. On the other hand, the rear end temperature Tmb is about 75 ° C. as will be described later.

Therefore, in the separation guide 201 and the metal frame 202 of the present embodiment, a temperature difference of about 10 ° C. occurs between the front end portion 201a and the rear end portion 201b of the separation guide 201. Here, the thermal expansion coefficient of PBT + ABS, which is the material of the separation guide 201, is 3.0 × 10 ⁻⁵ mm / K, and the longitudinal length (longitudinal width) of the separation guide 201 is 330 mm. The end portion has an expansion difference of 0.1 mm in the longitudinal direction.

  In the separation guide 201 in which the separation guide tip 201a of this embodiment shown in FIG. 4B is connected in a straight line as shown in FIG. 4B, the separation guide 201 moves to the fixing film 101 in the recording material conveyance direction H shown in FIG. The warpage was 0.25 mm in the approaching direction. The amount of deformation due to warping of the separation guide 201 at that time is shown as a guide displacement in FIG. In this manner, in the separation guide 201 and the metal frame 202 of the present embodiment, the separation guide 201 may determine the gap with the fixing film 101 in consideration of the warpage of 0.25 mm.

  Here, in the present embodiment, the fact that the rear end temperature Tmb rises to about 75 ° C. will be described below. In the present embodiment, as shown in FIG. 4B, the contact portion 201n between the separation guide 201 and the metal frame 202 is formed in a triangular shape. That is, the area of the contact portion 201n is increased from the 201a portion on the upstream side in the recording material conveyance direction H to the 201b portion on the downstream side.

  In FIG. 6B, when the heating time is 300 seconds, the tip temperature Tpa of the metal frame 202 rises to about 100 ° C. On the other hand, the rear end temperature Tpb of the metal frame 202 rises to about 95 ° C. The reason why there is not much temperature difference between the front end and the rear end of the metal frame 202 is that the metal frame 202 has a high thermal conductivity. Iron is used as the material of the metal frame 202, the thermal conductivity is 84 W / (m · K), and the thermal conductivity of PBT + ABS, which is the material of the separation guide 201, is 0.29 W / (m · K). Therefore, iron has a thermal conductivity approximately 290 times higher than that of PBT + ABS resin.

  In addition, since the thermal conductivity of air is 0.02 W / (m · K) and the thermal conductivity is very low, it is naturally easier to transfer heat by direct contact than heat transfer by radiation.

  As described above, in this embodiment, the contact area of the separation guide 201 that contacts the metal frame 202 with little temperature change on the upstream side and the downstream side is made wider on the downstream side than the upstream side, so that the rear end of the separation guide The temperature Tmb could be increased. As a result, as shown in FIG. 7, the amount of warpage can be greatly reduced from the conventional 0.45 mm to 0.25 mm, and the gap a between the fixing film 101 and the separation guide tip 201a can be made smaller than the conventional one. Therefore, the separation performance could be improved.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described. In the present embodiment, the heat that contacts the separation guide so as to suppress the temperature difference between the first position in the recording material conveyance direction of the separation guide and the second position that is farther from the nip portion than the first position. A graphite sheet having a very high thermal conductivity is used as the conductive member. This graphite sheet is a high thermal conductive member having a thermal traditional rate of more than twice the thermal conductivity of copper, 398 W / (m · K).

  FIG. 8 is a view for explaining the arrangement of the separation guide 201 and the graphite sheet 401, and is a view when the separation guide 201 is viewed from the direction of the arrow Z in FIG. The graphite sheet is graphite having a structure close to a single crystal produced by a method of graphitizing a polymer film by thermal decomposition, and has high thermal conductivity.

  The thermal conductivity of the graphite sheet 401 used in this embodiment is 1500 W / (m · K), about 17 times that of iron, which is the material of the metal frame 202, and 5172 times that of PBT + ABS, which is the material of the separation guide 201. . In the present embodiment, the graphite sheet 401 is directly attached to the entire surface between the ribs of the separation guide 201 in the longitudinal direction as shown in FIG. The graphite sheet 401 has orientation, and in this embodiment, the graphite sheet 401 is attached so as to have orientation in a direction parallel to the recording material conveyance direction H.

  In FIG. 9, the front end temperature Tma and the rear end temperature Tmb of the separation guide 201 when the graphite sheet 401 is pasted, and the warp amount (guide displacement) are shown. When the heating time was 300 sec, the separation guide front end temperature Tma was 54 ° C., and the rear end temperature Tmb was 51 ° C. This is because the thermal conductivity of the graphite sheet 401 is very high, so that there was almost no temperature difference. Moreover, since there is a heat dissipation effect from the graphite sheet 401, the temperature of the separation guide 201 is lowered as a whole.

  By contacting a material having very high thermal conductivity with the separation guide 201 as in the present embodiment, the temperature difference between the front end portion 201a and the rear end portion 201b of the separation guide 201 is reduced, and the amount of warpage of the separation guide 201 is reduced. Can be reduced to 0.05 mm. As a result, the gap a between the fixing film 101 and the separation guide tip 201a can be made smaller than before, so that the separation performance can be improved.

(Modification)
In the above-described embodiment, the preferred embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications can be made within the scope of the present invention.

(Modification 1)
In the embodiment described above, the fixing film 101 is used as the fixing rotating body (rotating body) and the ceramic heater 100 is used as the heating body. However, the present invention is not limited to this. For example, an electromagnetic induction exothermic film may be used as the fixing film, and an exciting coil and a magnetic core that generate heat by applying a magnetic flux to the electromagnetic induction exothermic film as a heating element may be used. Further, a system in which a fixing film or a fixing roller is heated using a halogen heater as a heating body may be used.

(Modification 2)
In the embodiment described above, the separation guide 201 is made of resin. However, the present invention is not limited to this, and various materials having lower thermal conductivity than aluminum can be used.

(Modification 3)
In the above-described embodiment, the separation guide 201 is supported on the side plate (not shown). However, the present invention is not limited thereto, and the separation guide 201 may be supported on the fixing flange 104.

(Modification 4)
In the embodiment described above, the recording paper has been described as the recording material. However, the recording material in the present invention is not limited to paper. Generally, a recording material is a sheet-like member on which a toner image is formed by an image forming apparatus. For example, regular or irregular plain paper, cardboard, thin paper, envelope, postcard, seal, resin sheet, OHP sheet, Includes glossy paper.

(Modification 5)
In the above-described embodiment, the fixing device that fixes an unfixed toner image to a sheet has been described as an example. However, the present invention is not limited to this, and the toner image that is supposedly attached to the sheet is used to improve the gloss of the image. The present invention can be similarly applied to a device for heating and pressing (also called a fixing device in this case).

100 .. Ceramic heater, 101 .. Fixing film, 106 .. Pressure roller, 201 .. Separation guide, 202 .. Metal frame, 401. S ... Recording material

Claims (15)

A rotating body,
A counter body that forms a nip portion that is opposed to the rotating body and is nipped and conveyed in a state where the recording material carrying the toner image is pressurized, and the rotating body;
A heating body for heating the rotating body;
A separation guide for separating the recording material passing through the nip portion from the rotating body;
A heat conducting member in contact with the separation guide so as to suppress a temperature difference between a first position in the recording material conveyance direction in the separation guide and a second position separated from the nip portion from the first position. When,
Have
The separation guide has a first area that contacts the heat conducting member at the first position, and a second area that is wider than the first area that contacts the heat conducting member at the second position. A fixing device comprising: a fixing device;   The fixing device according to claim 1, wherein the separation guide is made of a material having a lower thermal conductivity than aluminum.   The fixing device according to claim 2, wherein a material of the separation guide is resin.   The fixing device according to claim 1, wherein the heat conducting member is a metal member.   The fixing device according to claim 4, wherein the metal member is a metal frame positioned in a casing for positioning the rotating body.   The fixing device according to claim 5, wherein the separation guide is positioned on the metal frame.   4. The fixing device according to claim 1, wherein the heat conductive member has a heat conductivity that is twice or more that of copper. 5.   The fixing device according to claim 1, wherein the heat conducting member is a graphite sheet.   The fixing device according to claim 8, wherein the graphite sheet has orientation in a direction parallel to the recording material conveyance direction.   The fixing device according to claim 1, wherein the separation guide is positioned so as to be capable of thermal expansion in a longitudinal direction orthogonal to the recording material conveyance direction.   The fixing device according to claim 10, wherein the separation guide is fixed at one point in a longitudinal direction orthogonal to the recording material conveyance direction.   The fixing device according to claim 11, wherein the separation guide is fixed at a central portion in a longitudinal direction orthogonal to the recording material conveyance direction.   The fixing device according to claim 1, wherein the separation guide is disposed at a position where one end in the recording material conveyance direction is close to the rotating body. A heating element;
A fixing rotating body heated by the heating body;
A pressure member that forms a nip portion in pressure contact with the fixing rotator;
A metal frame positioned in a housing for positioning the fixing rotating body;
A resin separation guide positioned on the metal frame,
In the fixing device configured so that one end of the resin separation guide is disposed at a position close to the fixing rotating body,
The separation guide is positioned so as to be thermally expandable in a longitudinal direction that is a direction orthogonal to a direction in which the recording material is conveyed to the metal frame,
The fixing device is characterized in that the separation guide and the metal frame have a contact portion, and the area of the contact portion is configured to increase as it goes away from the fixing rotating body. A heating element;
A fixing rotating body heated by the heating body;
A pressure member that forms a nip portion in pressure contact with the fixing rotator;
A resin separation guide positioned in a housing for positioning the fixing rotating body;
Have
In the fixing device configured so that one end of the resin separation guide is disposed at a position close to the fixing rotating body,
A fixing device, wherein a high heat conductive member having a heat traditional rate of 2 times or more of copper thermal conductivity of 398 W / (m · K) is attached to the separation guide.