JP2011170051A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a time required for a nip portion between a fixing roller and a pressure roller to reach a fixation temperature. <P>SOLUTION: The fixing device configured to heat a developer and fix the developer on a medium includes: a fixing member configured to supply heat to the developer and the medium; a heating element configured to heat the fixing member; a support member configured to support the heating element; a pressure member configured to press the fixing member to the heating element; a second pressure member that comes into contact with the fixing member; and a third pressure member that comes into contact with the fixing member. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device in an image forming apparatus such as an electrophotographic printer, a copying machine, and a facsimile.

  A conventional fixing device in an image forming apparatus such as a printer, a copying machine, or a facsimile that forms a monochrome image or a color image is provided inside a fixing belt, and a fixing roller that presses the fixing belt is opposed to the fixing roller. A nip portion (contact area) is formed by a pressure roller that contacts the outer peripheral surface of the fixing belt, and the fixing belt is heated by a sheet heater supported by a support member. (See, for example, Patent Document 1).

JP 2007-322888 (paragraph “0015” to “0026”, FIG. 2)

  However, in the above-described conventional technology, the fixing belt is heated by the planar heating member having a small contact area with the fixing belt, so that the heat transfer efficiency to the fixing belt is low, and the nip between the fixing roller and the pressure roller is low. There is a problem that it takes a long time for the portion to reach the fixing temperature.

  An object of the present invention is to solve such a problem, and an object of the present invention is to shorten the time until the nip portion between the fixing roller and the pressure roller reaches the fixing temperature.

  Therefore, the present invention provides a fixing device that heats a developer and fixes it on a medium, a fixing member that supplies heat to the developer and the medium, a heating element that heats the fixing member, and the heating element. A supporting member that supports the pressing member; a pressing member that presses the fixing member against the heating element; a second pressing member that contacts the fixing member; and a third pressing member that contacts the fixing member. It is characterized by.

  According to the present invention as described above, it is possible to shorten the time until the nip portion between the fixing roller and the pressure roller reaches the fixing temperature.

Sectional drawing which shows the structure of the fixing device in a 1st Example. Explanatory drawing which shows the structure of the image forming apparatus in 1st Example. Sectional explanatory drawing of the fixing roller and the pressure roller in the first embodiment Cross-sectional explanatory drawing of the pressure member in the first embodiment Sectional explanatory drawing of the fixing belt in the first embodiment Cross-sectional explanatory drawing of the planar heating element in the first embodiment Exploded perspective view of a planar heating element in the first embodiment The perspective view of the planar heat generating body and support body in 1st Example Sectional drawing which shows the structure of the fixing device in a 1st Example. Sectional drawing which shows the structure of the fixing device in 2nd Example. Perspective view of planar heating element and support in the second embodiment Perspective view of a sheet heating element and a support in the second embodiment (modified example) Sectional drawing which shows the structure of the fixing device in 3rd Example. The perspective view which shows the structure of the fixing device in a 3rd Example. Sectional drawing of the fixing pad in 3rd Example Exploded perspective view of a planar heating element in the third embodiment Side view and perspective view of support member in third embodiment Explanatory drawing of the fixing belt in the third embodiment Side view of the fixing device according to the third embodiment. Sectional drawing which shows the structure of the fixing device in a 4th Example. Sectional drawing of the principal part showing the configuration of the fixing device in the fourth embodiment

  Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings.

  FIG. 2 is an explanatory diagram showing the configuration of the image forming apparatus in the first embodiment.

  In FIG. 2, a printer 20 as an image forming apparatus forms a toner image corresponding to a recording light, a paper conveying unit 24 that conveys a paper (recording medium), an LED (Light Emitting Diode) head 23 as a recording light exposure member, and the recording light. And a fixing device 26 that conveys a sheet on which a toner image (developer image) is formed and heats the sheet and toner to fix the toner image on the sheet.

  The toner image forming unit 25 and the fixing device 26 are arranged in the order in which the sheets are conveyed by the sheet conveying unit 24. The LED head 23 is disposed adjacent to the toner image forming unit 25.

  When a control unit (not shown) receives a print instruction, the paper transport unit 24 transports the paper to the toner image forming unit 25 in accordance with the timing of image formation.

  The LED head 23 irradiates the toner image forming unit 25 with recording light corresponding to the printing information based on the printing instruction, and the toner image forming unit 25 conveys the toner image corresponding to the irradiated recording light by the paper conveying unit 24. Form on paper.

  Thereafter, when the paper is transported to the fixing device 26 by the paper transport unit 24, the paper is discharged out of the device after the toner image on the paper is fixed by the heat and pressure of the fixing device 26.

  Each operation of the image forming apparatus is controlled based on a control program (software) stored in a storage unit such as a memory by a control unit such as a CPU (Central Processing Unit) (not shown) and a control unit as a calculation unit. The

  FIG. 1 is a cross-sectional view showing the configuration of the fixing device in the first embodiment.

  In FIG. 1, a fixing device 26 moves with a sheet to convey the sheet, and includes an endless fixing belt 2 as a fixing member that supplies heat to the sheet and toner as a developer, and a fixing belt 2 that contacts the fixing belt 2. A sheet heating element 4 as a heating means for heating, a support 3 as a support member for supporting the sheet heating element 4, a stabilizing means for stabilizing the contact between the fixing belt 2 and the sheet heating element 4, and the fixing belt 2 are provided. An auxiliary roller 8 as a pressing means (pressing member) that presses the sheet heating element 4 against the support 3 via the auxiliary roller 8 is arranged downstream of the auxiliary roller 8 in the moving direction of the fixing belt 2 and contacts one surface of the fixing belt 2. A pressure member (pressure pad) 9 as a first pressure member, a fixing roller 1 as a second pressure member, and a fixing belt 2 are disposed opposite to the pressure member 9 and the fixing roller 1 for fixing. bell 2 consists pressure roller 5 as a third pressure member for pressing the paper to fix the unfixed toner 6 on the paper 7 being conveyed in the medium conveyance direction indicated by an arrow in FIG.

  The temperature of the fixing belt 2 is detected by a temperature detection unit (not shown), and is maintained at a predetermined temperature by a control unit (not shown). The temperature detecting means (not shown) may be in contact with the outer or inner surface of the fixing belt 2 or non-contact with a minute gap.

  The fixing belt 2 is stretched around the sheet heating element 4, the pressure member 9, the fixing roller 1, and the support 3, and the pressure roller 5 is in contact with the pressure member 9 and the fixing roller 1 through the fixing belt 2. is doing. The fixing belt 2 may be bent without being in close contact with the sheet heating element 4, the pressure member 9, the fixing roller 1, and the support 3.

  The fixing roller 1 and the pressure roller 5 are composed of an elastic layer 32 and a cored bar 31 as shown in FIG. Further, the fixing roller 1 and the pressure roller 5 may be formed by forming a release layer 33 on the elastic layer 32 as shown in FIG.

  The elastic layer 32 is usually made of a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber. The cored bar 31 is made of a metal pipe or shaft such as aluminum, iron or stainless steel in order to maintain a certain rigidity.

  As shown in FIG. 4, the pressing member 9 includes a surface layer 41, an elastic layer 42, and a base material 43. For the surface layer 41 in contact with the fixing belt 2, a resin material having a high heat resistance and a low surface friction resistance is usually used, such as a silicon resin or a fluorine resin. The elastic layer 42 is usually made of a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber. The base material 43 is made of a metal material such as aluminum, iron or stainless steel in order to maintain a certain rigidity.

  The pressure roller 5 is rotatably held by a frame (not shown) via a bearing, and has a gear (not shown). When this gear is driven to rotate from the paper transport unit 24, the pressure roller 5 rotates in the direction indicated by the arrow A in FIG. 1, and the fixing belt 2 is driven by the frictional force with the pressure roller 5, so that the fixing roller 1 1 is driven to rotate in the direction indicated by arrow B in FIG.

  Note that the fixing roller 1 may be driven to rotate from the paper transport unit 24. Alternatively, both the fixing roller 1 and the pressure roller 5 may be rotationally driven from the paper transport unit 24.

  The fixing roller 1 and the pressure member 9 are pressed in a direction to come into pressure contact with the pressure roller 5 by an elastic body (not shown) such as a spring. The pressure roller 5 is in contact with the fixing roller 1 at a position facing the fixing roller 1 through the fixing belt 2. Further, the pressure roller 5 is in contact with the pressure member 9 at a position facing the pressure member 9 through the fixing belt 2. Thus, a nip portion where the pressure roller 5 contacts the fixing roller 1 via the fixing belt 2 and a nip portion where the pressure roller 5 contacts the pressure member 9 via the fixing belt 2 are formed. .

  As shown in FIG. 5A, the fixing belt 2 has a thin base 51 (in the case of a base made of nickel, polyimide, stainless steel, etc.), and preferably has a thickness of about 30 to 150 μm in order to achieve both strength and flexibility. In addition, silicon rubber (thickness is preferably 50 to 300 μm to achieve both low hardness and high thermal conductivity) or fluorine resin (thickness is preferred to achieve both thinning due to wear and high thermal conductivity) as the elastic layer 52. 10 to 50 μm) may be thinly formed, and the release layer 53 may be provided on the elastic layer 52, or the release layer 53 may be provided on the base 51 as shown in FIG. The fixing roller 1, the support 3, and the pressure member 9 are stretched with the release layer 53 outside.

  The release layer 53 is a resin having high heat resistance and low surface free energy after molding, such as PTFE (polytetrafluoroethylene), PFA (partite), like the release layer 33 of the fixing roller 1 or the pressure roller 5. Typical fluorine-based resins (thickness is preferably 10 to 50 μm) such as fluoroalkoxyalkane) and FEP (perfluoroethylene-propene copolymer) can be used.

  The support 3 is made of a metal having high thermal conductivity and workability such as aluminum or copper, or an alloy containing these as a main component, or iron, iron-based alloys, stainless steel, etc. having high heat resistance and rigidity. .

  As shown in FIG. 6A or 6B, the sheet heating element 4 is placed on the support 3 without being bonded to the upstream end of the support 3 in the rotation direction of the fixing belt. The side surface of the planar heating element 4 is locked by a locking member (not shown) formed on the support 3 so that it does not shift. Further, a sliding surface (curved surface) that comes into contact with the fixing belt is formed on the support body 3 on the downstream side (between the auxiliary roller 8 and the pressure roller 5) from the planar heating element 4. Therefore, this sliding surface is provided on the downstream side of the planar heating element 4 in the rotation direction of the fixing belt. In addition, the edge part of the support body 3 means that the planar heating element 4 is not arrange | positioned in the center part of the support body 3, as shown in FIG.6 (c).

  Further, the support 3 and the planar heating element 4 are integrated by pressing the planar heating element 4 against the support 3 via the fixing belt 2 by the auxiliary roller 8, and the heat of the planar heating element 4 is supported by the support. 3 is transmitted.

  The surface heating element 4 has a flat surface or a circular arc surface in contact with the inner surface of the fixing belt 2, and a ceramic heater, a stainless steel heater, or the like is used. FIG. 7A is an exploded perspective view in the case where the planar heating element 4 has a flat plate shape. The planar heating element 4 is a thin glass film as an electrical insulating layer 71 on a substrate 70 such as stainless steel (SUS430). A resistance heating element 73 is formed in a paste form by screen printing with a powder of nickel-chromium alloy or silver-palladium alloy, and a chemically stable metal having a low electrical resistance, such as silver. The electrode 74 is formed of a refractory metal such as tungsten, and glass or a typical material such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene-propene copolymer) is formed thereon. Those protected by a protective layer 75 made of fluorine resin are used. In this case, the surface contacting the inner surface of the fixing belt 2 may be either the resistance heating element 73 side or the opposite surface. FIG. 7B is an exploded perspective view in the case where one surface of the sheet heating element 4 has an arc shape, and one surface of the substrate 76 is curved in a convex shape, and this surface is the inner surface of the fixing belt 2. Contact with.

  The surface of the auxiliary roller 8 is provided with an elastic layer like the fixing roller 1 or the pressure roller 5, and a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber is used. Similarly, a metal pipe such as aluminum, iron, or stainless steel or a shaft is used for the metal core in order to maintain a certain rigidity. Further, as a release layer on the elastic layer, for example, a typical fluorine resin (thickness is preferable) such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene-propene copolymer), etc. 10 to 50 μm) may be formed. Alternatively, a sponge material or felt for applying a release agent such as silicon oil or fluorine oil instead of the elastic layer may be used.

  FIG. 8 is a perspective view of the sheet heating element and the support in the first embodiment, and shows a state in which the support 3 and the sheet heating element 4 are integrated. Here, the contact length L1 (mm) of the support 3 with the planar heating element 4 and the length L2 (mm) of the heating region of the planar heating element 4 have a relationship of L1 ≦ L2.

  The operation of the above configuration will be described.

  In FIG. 1, the fixing belt 2 is rotationally driven in the direction indicated by the arrow B by the pressure roller 5 while sliding with respect to the support 3 and the sheet heating element 4, and electric power is supplied to the sheet heating element 4. Thus, the contact portion with the planar heating element 4 is heated. The surface temperature of the fixing belt 2 is detected by a temperature detection means (not shown), and the power supplied to the planar heating element 4 is controlled by a control unit (not shown) based on this, so that the surface of the fixing belt 2 is maintained at an appropriate temperature. The

  The recording medium 7 onto which the toner 6 has been transferred is conveyed through a nip formed on the fixing belt 2, and the toner 6 on the recording medium 7 is heated and pressed by the fixing belt 2 and the pressure roller 5 onto the recording medium 7. It is fixed.

  1 and FIG. 9 respectively show the upstream side (FIG. 1) or the downstream side (FIG. 9) of the sliding surface on which the planar heating element 4 is formed on the supports 3 and 9 with respect to the rotation direction of the fixing belt 2. The case where it is arrange | positioned is shown. In the fixing device that vertically feeds the A4 size print medium in the two types of configurations, the temperature at the center of the fixing belt 2 that fixes the toner at the center in the transport direction of the A4 size print medium, and the A4 size print medium When the temperature of the end portion of the fixing belt 2 for fixing the toner at the side end portion in the conveyance direction of the toner is measured, the temperature difference between the center portion and the end portion indicates that the sheet heating element 4 is located upstream of the support 3. In the case of FIG. 1 arranged at the end, the temperature is 10 ° C. or lower, and in the case of FIG. 9 where the planar heating element 4 is arranged at the downstream end of the support 3, the temperature is 20-30 ° C.

  The measurement conditions are shown below.

The fixing belt 2 has an inner diameter of 40 mm, the base is polyimide (thickness 80 μm), the elastic layer is silicon rubber (thickness 150 μm), the release layer is PFA (thickness 30 μm),
The fixing roller 1 has a φ16 elastic layer made of silicon sponge (thickness 1 mm), ASKER C hardness 80 degrees,
The pressure roller 5 has a φ36 elastic layer made of silicon rubber (thickness 1 mm), ASKER C hardness 80 degrees,
The pressure member 9 has an elastic layer made of silicon rubber 1 mm JIS-A hardness 20 degrees,
The pressing force of the pressure member 9 is 20 kg · f,
The planar heating element 4 is a stainless steel heater with a width of 12 mm and an output of 1200 W.
The auxiliary roller 8 has a φ14 elastic layer made of silicon sponge (thickness 4 mm) ASKER C hardness 35 degrees, pressing load 1.5 kg · f,
The support 3 is made of aluminum and has a thickness of 1.5 mm. The length of the sliding portion with the fixing belt 2 is 18 mm, both of which have the same volume and heat capacity.
The target temperature of the fixing belt 2 is 160 ° C. (heated from 20 ° C. to 160 ° C.),
The width of the nip portion in the conveyance direction of the print medium is 13 mm,
The peripheral speed of the fixing belt 2 was 75 mm / s.

  The reason why the temperature difference between the central portion and the end portion of the fixing belt is different will be described below.

  As shown in FIG. 9, in the configuration in which the sheet heating element 4 is arranged on the downstream side of the sliding surface formed on the support 91 with respect to the rotation direction of the fixing belt 2, the auxiliary roller 8 passes through the fixing belt 2. The portion where the sheet heating element 4 is pressed against the support 91 and the nip portion formed by pressing the fixing roller 1 and the pressure member 9 against the pressure roller 5 via the fixing belt 2 are the fixing belt 2. 9 rotates in the direction indicated by the arrow B in FIG. 9, the fixing belt 2 is in a positional relationship of bending, so that the fixing belt 2 is separated from the sliding surface of the support 91 and heat is transferred from the support 91 to the fixing belt 2. Is not transmitted.

  On the other hand, as shown in FIG. 1, in the configuration in which the planar heating element 4 is arranged at the upstream end of the sliding surface formed on the support 3 with respect to the rotation direction of the fixing belt 2, the auxiliary roller 8 A portion where the sheet heating element 4 is pressed against the support 3 via the fixing belt 2, and a nip portion formed by pressing the fixing roller 1 and the pressure member 9 against the pressure roller 5 via the fixing belt 2. Means that when the fixing belt 2 rotates in the direction indicated by the arrow B in FIG. 1, the fixing belt 2 is in a tensioned positional relationship, so that the fixing belt 2 comes into contact with the sliding surface (curved surface) of the support 3 and is supported. Heat is efficiently transferred from the body 3 to the fixing belt 2.

  Even though the length of the portion of the support 3 on which the fixing belt 2 slides is the same and the width of the sheet heating element 4 is the same, the center of the A4 size print medium related to the rise time of the fixing device is provided. The difference between the temperature at the center portion of the fixing belt 2 that contacts the end portion of the fixing belt 2 that contacts the end portion of the A4 size printing medium appears in the configuration shown in FIG. This is because the tension of 2 promotes the contact of the fixing belt 2 with the support 3, the contact area between the fixing belt 2 and the support 3 is increased, and the heat transfer efficiency from the support 3 to the fixing belt 2 is increased. .

  As described above, in the first embodiment, the planar heating element is arranged on the upstream side of the sliding surface as the sliding portion formed on the support in the rotation direction of the fixing belt, so that The heat transfer efficiency can be increased, and the time until the nip portion between the fixing roller and the pressure roller reaches the fixing temperature can be shortened.

  The configuration of the second embodiment is different from the first embodiment in the configuration of the support.

  FIG. 10 is a cross-sectional view showing the configuration of the fixing device in the second embodiment, and FIG. 11 is a perspective view of the sheet heating element and the support in the second embodiment. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  10 and 11, the support 92 is formed such that the distance between the central portion where the fixing belt 2 as the fixing member slides and the distance between both ends are different. The relationship between the distance Lc at the center of the support 92 on which the fixing belt 2 slides, the distance Lf (left in the figure) and the distance Lr (right in the figure) at both ends is Lc ≧ Lf and Lc ≧ Lr It has become. Other configurations are the same as those of the support 3 in the first embodiment.

  As shown in FIG. 12, the relationship between the distance Lc of the central portion where the fixing belt 2 of the support 93 slides, the distance Lf (left in the figure) and the distance Lr (right in the figure) of both ends is expressed as Lc. ≦ Lf and Lc ≦ Lr may be satisfied.

  When an alloy mainly composed of aluminum having high thermal conductivity and workability is used for the support 92, a unique extruded material having a curved surface formed of the alloy is used, and parts other than the curved surface are pressed and molded. Alternatively, an alloy plate material mainly composed of aluminum may be pressed to form the whole.

  The operation of the above configuration will be described.

  When the distance of the central portion of the support where the fixing belt 2 slides is Lc, and the distance between both ends is Lf (left in the figure) and Lr (right in the figure), the support 92 of this embodiment shown in FIG. Is different from the support 3 of the first embodiment shown in FIG. 1 in which Lc ≧ Lf and Lc ≧ Lr, and Lf = Lc = Lr.

  The volume and heat capacity of the support 3 shown in FIG. 1 and the support 92 shown in FIG. 11 are the same, and the distance (Lc, Lf, Lr) that the support and the fixing belt 2 slide is different.

  In the fixing device that vertically feeds the A4 size print medium in the two types of configurations, the temperature at the center of the fixing belt 2 that fixes the toner at the center in the transport direction of the A4 size print medium, and the A4 size print medium When the temperature at the end of the fixing belt 2 for fixing the toner at the side end in the transport direction of the toner is measured, the temperature at the center of the fixing belt 2 for fixing the toner at the center of the A4 size printing medium and the A4 size The temperature difference between both ends of the fixing belt 2 for fixing the toner at the end of the print medium is 5 ° C. or less when the support 92 of this embodiment is provided, and the support 3 of the first embodiment is When provided, the temperature was 10 ° C. or lower.

  The measurement conditions are shown below.

The fixing belt 2 has an inner diameter of 40 mm, the base is polyimide (thickness 80 μm), the elastic layer is silicon rubber (thickness 150 μm), the release layer is PFA (thickness 30 μm),
The fixing roller 1 has a φ16 elastic layer made of silicon sponge (thickness 1 mm), ASKER C hardness 80 degrees,
The pressure roller 5 has a φ36 elastic layer made of silicon rubber (thickness 1 mm), ASKER C hardness 80 degrees,
The pressure member 9 has an elastic layer made of silicon rubber (thickness 1 mm) JIS-A hardness 20 degrees,
The pressing force of the pressure member 9 is 20 kg · f,
The planar heating element 4 is a stainless steel heater with a width of 12 mm and an output of 1200 W.
The auxiliary roller 8 has a φ14 elastic layer made of silicon sponge (thickness 4 mm) ASKER C hardness 35 degrees, pressing load 1.5 kg · f,
The support 3 is made of aluminum and has a thickness of 1.5 mm. The area of the sliding portion with the fixing belt 2 is 4,000 mm ² , both of which have the same volume and heat capacity.
The target temperature of the fixing belt 2 is 160 ° C. (heated from 20 ° C. to 160 ° C.),
The width of the nip portion in the conveyance direction of the print medium is 13 mm,
The peripheral speed of the fixing belt 2 was 75 mm / s.

  From the above, according to the present embodiment, by adjusting the distance in which the fixing belt 2 of the support 92 slides in the configuration shown in FIGS. 10 and 11 at the position in the width direction in the conveyance direction of the print medium, A4 The temperature difference between the central portion of the fixing belt 2 for fixing the toner at the central portion in the conveyance direction of the size printing medium and the both ends of the fixing belt 2 for fixing the toner at the side edge in the conveyance direction of the A4 size printing medium. It is possible to control.

  Note that the amount of heat radiation at the center and end of the fixing belt 2 varies depending on the surrounding environment such as the air flow around the fixing device 26 in the image forming apparatus. You may make it control the temperature difference with both ends.

  As described above, in the second embodiment, in addition to the effects of the first embodiment, by adjusting the distance between the center portion and the end portion of the support on which the fixing belt slides, the medium width of the fixing belt is adjusted. The effect that the temperature in the direction can be controlled is obtained.

  The configuration of the third embodiment is different from that of the first embodiment in the configuration of the fixing device, and the other configurations are the same as those of the first embodiment. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  FIG. 13 is a cross-sectional view showing the configuration of the fixing device in the third embodiment, and FIG. 14 is a perspective view showing the configuration of the fixing device in the third embodiment.

  13 and 14, the fixing device 26 is an endless fixing belt that is wound around the fixing roller 1 and a plurality of members, moves with the sheet to convey the sheet, and supplies heat to the sheet and toner. 2, a planar heater (planar heating element) 104 as a heat source for heating the fixing belt 2, a supporting member (supporting body) 103 that supports the planar heater 104, and a planar heater supported by the supporting member 103. A pressing roller 108 as a pressing member that presses 104 to the support member 103 via the fixing belt 2, and is fixed to an end of the supporting member 103 and is arranged downstream of the pressing roller 108 in the moving direction of the fixing belt 2, A fixing pad 109 as a pressure member (nip forming member) that contacts one surface of the fixing belt 2 and downstream of the pressing roller 108 in the moving direction of the fixing belt 2. A pressure roller 5 is provided as a third pressure member that is disposed opposite to the fixing pad 109 and the fixing roller 1 and presses the fixing belt 2 against the fixing pad 109 and the fixing roller 1. Unfixed toner 6 is fixed on the sheet 7 conveyed in the medium conveying direction.

  The pressure roller 5 may have a halogen heater (not shown) in order to accelerate the temperature rise on the roller surface.

  The temperature of the fixing belt 2 is detected by a temperature detection unit (not shown), and is maintained at a predetermined temperature by a control unit (not shown). The temperature detecting means (not shown) may be in contact with the outer or inner surface of the fixing belt 2 or non-contact with a minute gap.

  The support member 103 is held by the lever 120, and the fixing pad 109 fixed to the support member 103 is pressed against the pressure roller 5 by using an elastic body (not shown) such as a spring with the fulcrum 120 a of the lever 120 as a fulcrum. It is pressed in the direction indicated by the arrow G in FIG.

  The fixing roller 1 is rotatably held by a lever 121 having the same fulcrum 120a as that of the lever 120 via a bearing (not shown), and is pressed against the pressure roller 5 by an elastic body (not shown) such as a spring with the fulcrum 120a as a fulcrum. It is pressed in the direction indicated by the arrow H in FIG.

  The pressure roller 108 is rotatably held by a lever 121 that holds the fixing roller 1 via a bearing (not shown), and is attached to the sheet heater 104 via the fixing belt 2 by an elastic body (not shown) such as a spring. It is pressed in the direction indicated by the arrow J in FIG.

  The product hardness of the pressing roller 108 is 35 ° ± 5 ° in terms of ASKER-C hardness, and the pressing load is 1.5 kg · f ± 0.5 kg · f.

  Further, as shown in FIG. 14, the width L 18 in the width direction of the pressure roller 108, the length L 14 in the width direction of the sheet heater 104, the length L 13 in the width direction of the support member 103, and the width direction of the fixing belt 2. The relationship of the length L12 is L14 ≧ L18 ≧ L12 ≧ L13 in order to stably heat the fixing belt 2.

  Further, the pressing roller 108 is pressed against the sheet heater 104 via the fixing belt 2, and the sheet heater 104 is pressed against and integrated with the support member 103 by this pressing force, so that one of the sheet heaters 104 is integrated. The fixing belt 2 is heated on this surface, and the support member 103 is heated on the other surface.

  The pressure roller 5 is in contact with the fixing pad 109 and the fixing roller 1 through the fixing belt 2 at positions facing each other.

  As a result, the first nip portion where the pressure roller 5 is in contact with the fixing pad 109 via the fixing belt 2 and the contact between the pressure roller 5 and the fixing roller 1 via the fixing belt 2 are contacted. A second nip portion that is a contact area is formed.

  The configurations of the fixing roller 1 and the pressure roller 5 are the same as those in the first embodiment.

  As shown in FIG. 15, the fixing pad 109 includes a surface layer 109a and an elastic layer 109b, and is fixed to the support member 103 with an adhesive, for example. For the surface layer 109a in contact with the fixing belt 2, a resin material having high heat resistance and low surface friction resistance, such as silicon resin or fluorine resin, is usually used. For the elastic layer 109b, a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber is usually used.

  As shown in FIG. 5A, the fixing belt 2 is a thin base 51 (in the case of a base made of nickel, polyimide, stainless steel, etc.), and the thickness is preferably about 30 to 150 μm in order to achieve both strength and flexibility. In addition, as the elastic layer 52, silicon rubber (thickness is preferably 50 to 300 μm in order to achieve both low hardness and high thermal conductivity) or fluorine resin (in order to achieve both thinning due to wear and high thermal conductivity) Is preferably 10 to 50 μm, and a release layer 53 is formed on the elastic layer 52. Further, as shown in FIG. 5B, a release layer 53 may be provided on the base 51, and the release layer 53 is disposed outside the fixing roller 1, the support member 103, and the fixing pad 109. Yes.

  Like the release layer 33, the release layer 53 is a resin having high heat resistance and low surface free energy after molding, such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluorocarbon). Typical fluorine-based resins (thickness is preferably 10 to 50 μm) such as ethylene-propene copolymer) can be used.

  The outer surface roughness is Ra: 0.6 (μm) or less, and the inner surface roughness is Ra: 5.0 (μm) or less.

  The fixing belt 2 has a width direction dimension of 320 mm and a thickness of 260 μm. The fixing belt 2 rotates at a peripheral speed of 200 mm / s, and a color image is 40 sheets of A4 size paper laterally fed per minute. To settle.

  The support member 103 is made of a metal having high thermal conductivity and workability such as aluminum or copper, or an alloy containing these as a main component, or iron, iron-based alloys, stainless steel, or the like having high heat resistance and rigidity. .

  The sheet heater 104 is placed on the support member 103 without being bonded to the upstream end of the support member 103 with respect to the rotation direction of the fixing belt 2, and the sheet heater 104 is formed on the support member 103. The side surfaces are locked by a locking member (not shown) so as not to be displaced.

  Further, the support member 103 and the planar heater 104 are integrated by pressing the planar heater 104 against the support member 103 via the fixing belt 2 by the pressing roller 108, and the heat of the planar heater 104 is transmitted to the support member 103. It is supposed to be.

  The support member 103 is formed with a curved portion (curved surface) that contacts the fixing belt 2 between the pressing roller 108 and the pressure roller 5, and the contact surface with the fixing belt 2 has a sliding property. Fluorine resin may be formed in order to increase the resistance. The length of the support member 103 in the width direction is 315 mm, and the radius of the curved portion is 22.5 mm ± 1.0 mm, which is substantially equal to the inner diameter of the fixing belt 2 in the initial state.

  Further, the contact surface of the support member 103 with the fixing belt 2 is smooth in consideration of slidability and heat transfer, and the surface roughness is Ra: 6.3 (μm) or less. The portion that supports the planar heater 104 is concave or L-shaped.

  The planar heater 104 is a heating element that generates heat when an electric current flows. The surface that contacts the inner surface of the fixing belt 2 is a flat surface, and a ceramic heater, a stainless steel heater, or the like is used. FIG. 16 is an exploded perspective view of the planar heater 104. In the planar heater 104, a thin glass film is formed as an electrical insulating layer 161 on a substrate 160 such as stainless steel (SUS430), and nickel- A resistance heating element 163 is formed in a paste form by screen printing of a chromium alloy or silver-palladium alloy powder, and an electrode is formed of a chemically stable and low electrical resistance metal such as silver or a high melting point metal such as tungsten at the end. 164 is formed thereon, and is protected with a protective layer 165 made of glass or a typical fluorine resin such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), and FEP (perfluoroethylene-propene copolymer). Used.

  In this case, the surface in contact with the inner surface of the fixing belt 2 may be either the surface on the resistance heating element 163 side or the surface protected by the protective layer 165 on the opposite side. The planar heater 104 heats the fixing belt 2 and the support member 103 in order to efficiently heat the fixing belt 2. The length in the width direction is 375 mm, the length of the heat generating part is 330 mm, and the output is 1200 W at 350 ° C.

  The surface of the pressure roller 108 is provided with an elastic layer like the fixing roller 1 or the pressure roller 5, and a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber is used.

  The metal core of the pressure roller 108 is also made of a metal pipe or shaft such as aluminum, iron or stainless steel in order to maintain a certain rigidity like the fixing roller 1 or the pressure roller 5.

  Moreover, as a release layer on the elastic layer, for example, a typical fluorine resin (thickness) such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene-propene copolymer), etc. Preferably, 10 to 50 μm) may be formed. Alternatively, a sponge material or felt for applying a release agent such as silicon oil or fluorine oil instead of the elastic layer may be used.

  The pressure roller 5 is rotatably held by a frame (not shown) via a bearing, and has a gear (not shown). When this gear is rotationally driven from the paper transport unit 24, the pressure roller 5 rotates in the direction indicated by the arrow C in FIG. 13, and the fixing belt 2 is connected to the pressure roller 5 and the fixing roller 1 is connected to the fixing belt 2. By being driven by the frictional force, it is rotationally driven in the direction indicated by the arrow D in FIG.

  Note that the fixing roller 1 may be driven to rotate from the paper transport unit 24. Alternatively, both the fixing roller 1 and the pressure roller 5 may be rotationally driven from the paper transport unit 24.

  Further, a part of the fixing belt 2 includes a portion where no tension is applied in order to reduce driving torque.

  Further, when the pressure roller 5 rotates in the direction indicated by the arrow C in FIG. 13, the fixing belt 2 is pulled in the direction indicated by the arrow D toward the nip portion. Further, since the fixing belt 2 is in pressure contact with the pressing roller 108 and the sheet heater 104, the fixing belt 2 is pulled in the direction indicated by the arrow E, and a force is applied to the fixing belt 2 in the direction indicated by the arrow F, so Contact with.

  FIGS. 17A and 17B are a side view and a perspective view of a support member according to the third embodiment, in which FIG. 17A is a side view and FIG. 17B is a perspective view.

  In FIG. 17, a part of the shape of the support member 103 has an arcuate shape r <b> 1 and forms a belt sliding portion (curved portion) in contact with the fixing belt 2, that is, a substantially semi-cylindrical curved surface. The radius of the shape r1 is desirably substantially equal to the radius of the inner diameter R of the initial cylindrical shape of the fixing belt 2 shown in FIG. 18 in order to stabilize the contact between the fixing belt 2 and the support member 103.

  In this embodiment, since the radius of the fixing belt 2 is 22.5 mm, the radius of the arc-shaped belt sliding portion of the support member 103 is also 22.5 mm. However, in consideration of stable heat transfer to the fixing belt 2, the radius of the belt sliding portion of the support member 103 can be allowed to be 15 to 30 mm. In addition, said dimension is a dimension managed at normal temperature.

  Further, the arc shape of the support member 103 is such that, as in the support member 193 shown in FIG. 19, the unfixed toner 6 on the recording medium 7 is moved to the first nip portion by the wavy or slack of the fixing belt 2 or the recording medium 7. In order to secure the angle θ1 so that the image is not disturbed by contact with the fixing belt 2 in front of the fixing belt 2 and to bring the fixing belt 2 closer to a natural shape, the radius of the shape r2 on the upstream side in the rotation direction of the fixing belt 2 is larger. It is also desirable to reduce the radius of the shape r3 near the first nip entrance on the downstream side.

  The operation of the above configuration will be described.

  In FIG. 13, during the printing operation, that is, when the fixing belt 2 is rotationally driven by the pressure roller 5 in the direction indicated by the arrow D, the fixing belt 2 includes the fixing pad 109 as the pressure member and the pressure roller 5. The first nip portion is stretched between the pressing roller 108 and the pressure contact portion of the planar heater 104, contacts the curved portion of the support member 103, and slides relative to the planar heater 104 and the support member 103. Rotates while moving.

  The sheet heater 104 that is supplied with power and generates heat heats the fixing belt 2 that is pressed against the sheet heater 104 by the pressure roller 108 and the support member 103 that is in contact with the sheet heater 104. .

  The heated support member 103 heats the fixing belt 2 that is in contact with the rotating support member 103. The surface temperature of the fixing belt 2 is detected by a temperature detection unit (not shown), and the power supplied to the planar heater 104 is controlled by a control unit (not shown) based on this temperature to maintain the surface of the fixing belt 2 at an appropriate temperature.

  The fixing belt 2 is sandwiched by both the third nip portion between the pressing roller 108 and the planar heater 104 and the first nip portion between the fixing pad 109 and the pressure roller 5, and contacts the pressure roller 5 side. When the fixing belt 2 starts to be driven to rotate by the surface, the third nip portion is driven through the fixing belt 2 after the first nip portion is rotationally driven, so that the fixing belt is interposed between the first and third nip portions. 2 is pulled, and the fixing belt 2 is wound around the sliding surface of the curved portion of the support member 103.

  In order to effectively wind the fixing belt 2 around the support member 103, the first and third nip portions have a positional relationship of 90 degrees or more with the rotation of the fixing belt 2 as the center. To do.

  The recording medium 7 onto which the toner 6 has been transferred is conveyed through a nip formed on the fixing belt 2, and the toner 6 on the recording medium 7 is heated and pressed by the fixing belt 2 and the pressure roller 5 to record the recording medium. 7 is fixed.

  In the nip portion, the elastic layer 52 of the fixing belt 2, the elastic layer 109b of the fixing pad 109, and the elastic layer 32 of the fixing roller 1 are stepped due to unevenness on the surface of the recording medium 7, and toner if it is a color image. 6 follows the step generated due to the multilayer by elastically deforming, and performs good fixing without uneven fixing.

  In this way, the fixing belt 2 is pressed against the support member 103 by the pressing roller 108, and the support member 103 and the planar heater 104 are integrated to stabilize the fixing belt 2 and the support member 103 with the planar heater 104. Heating was possible.

  Further, when the fixing belt 2 rotates, the fixing belt 2 is stretched between the fixing pad 109 as a pressure member and the nip portion of the pressure roller 5, and the pressure contact portion of the sheet heater 104 and the pressure roller 108. In addition, by making contact with the sliding surface of the curved portion of the support member 103, heat can be transferred from the support member 103 heated by the planar heater 104 to the fixing belt 2, and the fixing belt 2 is heated. It became possible to lengthen the time to do.

  By providing the pressure roller 108 in this manner, the fixing belt 2 can be stably brought into contact with the planar heater 104, and the planar heater 104 can be pressed and integrated with the support member 103, and the fixing can be performed. The belt 2 is stretched between the nip portion between the fixing pad 109 and the pressure roller 5 and the pressure contact portion between the sheet heater 104 and the pressure roller 108, so that the rotating fixing belt 2 is attached to the curved portion of the support member 103. Since the contact can be achieved, the heat transfer efficiency is increased, and the heating time of the fixing belt 2 can be shortened.

  In this embodiment, a pressing roller is used as a pressing member for stably bringing the fixing belt 2 into contact with the planar heater 104, but any member that can press the fixing belt 2 against the planar heater 104 is used. Alternatively, a pad that presses the fixing belt by a biasing means such as a spring may be used.

  As described above, in the third embodiment, the pressing roller that presses the planar heater against the support member via the fixing belt is provided, the heat of the planar heater is transmitted to the support member, and the support member rotates. By bringing the fixing belt into contact with each other, it is possible to increase the heat transfer efficiency and to shorten the heating time of the fixing belt.

  FIG. 20 is a cross-sectional view showing the structure of the fixing device in the fourth embodiment. The same parts as those in the first and third embodiments described above are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 20, the fixing device 26 includes a tension roller 201 as a biasing unit that stretches the fixing belt 2 and biases the fixing belt 2 from the inside.

  The tension roller 201 is rotatably supported by a lever (not shown) via a bearing, and the fixing belt 2 is in a direction in which the fixing belt 2 comes into contact with the support member 103 by an elastic body (not shown) such as a spring. 21, that is, the angle θ2 formed by the fixing belt 2 and the contact surface between the planar heater 104 and the fixing belt 2 shown in FIG. It is biased in the direction indicated by the arrow K in FIG.

  The surface of the tension roller 201 is provided with an elastic layer like the fixing roller 1 or the pressure roller 5, and a rubber material having high heat resistance such as silicon rubber, sponge-like silicon rubber, or fluorine rubber is used. Similarly, a metal pipe such as aluminum, iron, or stainless steel or a shaft is used for the metal core in order to maintain a certain rigidity. Further, as a release layer on the elastic layer, for example, a typical fluorine resin (thickness is preferable) such as PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxyalkane), FEP (perfluoroethylene-propene copolymer), etc. 10 to 50 μm) may be formed.

  The operation of the above configuration will be described.

  In FIG. 20, during the printing operation, the fixing belt 2 that is in contact with the support member 103 by the stretching roller 201 and is not separated from the planar heater 104 is fixed to the support member 103 and the planar heater 104. While being slid, the pressure roller 5 is rotationally driven in the direction indicated by the arrow D.

  The fixing belt 2 pressed against the planar heater 104 by the pressing roller 108 energized by supplying electric power to the planar heater 104 and the support member 103 integrated with the planar heater 104 are heated. . The heated support member 103 heats the fixing belt 2 that slides and rotates.

  Since the tension roller 201 is provided in this manner, the fixing belt 2 can be stably brought into contact with the support member 103. Therefore, the heat transfer efficiency is higher than that in the third embodiment, and the fixing belt It became possible to further shorten the heating time of 2.

  As described above, in the fourth embodiment, by providing the stretching roller, the fixing belt can be stably brought into contact with the support member, further improving the heat transfer efficiency and reducing the heating time of the fixing belt. Furthermore, the effect that it can shorten is acquired.

  In the first to fourth embodiments, the image forming apparatus has been described as a printer. However, the image forming apparatus is not limited to this, and may be a multi function peripheral (MFP), a facsimile, or a copying apparatus. .

  Further, although the fixing belt has been described as an endless belt, it may have an end.

  Further, the fixing belt can be heated more efficiently by combining the configurations of the first to fourth embodiments.

DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Fixing belt 3, 103 Support body (support member)
4, 104 Planar heating element (planar heater)
5 Pressure roller 6 Toner 7 Paper (recording medium)
8 Auxiliary roller 9, 109 Pressure member (fixing pad)
20 Printer (image forming device)
23 LED head 24 Paper transport unit 25 Toner image forming unit 26 Fixing device 108 Pressure roller 120, 121 Lever 201 Tension roller

Claims (18)

In a fixing device that heats and fixes a developer on a medium,
A fixing member for supplying heat to the developer and the medium;
A heating element for heating the fixing member;
A support member for supporting the heating element;
A pressing member that presses the fixing member against the heating element;
A second pressure member in contact with the fixing member;
A fixing device comprising: a third pressure member in contact with the fixing member. The fixing device according to claim 1.
The fixing member is a fixing belt that moves together with the medium and supplies heat to the developer and the medium;
The pressing member presses the heating element to the support member via the fixing belt,
The second pressure member contacts one surface of the fixing belt downstream of the pressing member in the moving direction of the fixing belt;
The third pressure member is a pressure roller that is disposed to face the second pressure member across the fixing belt and presses the medium against the fixing belt.
The fixing device, wherein the support member is in contact with the fixing belt between the pressing member and the pressure roller. The fixing device according to claim 2.
The fixing device, wherein the fixing belt is an endless belt. The fixing device according to claim 3.
The fixing device, wherein the fixing belt is stretched between the pressing member and the pressure roller when rotating, and contacts the support member. The fixing device according to claim 2, 3 or 4,
The fixing device, wherein a length of a contact portion with the fixing belt in a moving direction of the fixing belt is constant in a direction orthogonal to the moving direction. The fixing device according to claim 2, 3 or 4,
The fixing device according to claim 1, wherein the length of the contact portion with the fixing belt in the moving direction of the fixing belt is different between a central portion and an end portion in a direction orthogonal to the moving direction. The fixing device according to any one of claims 1 to 6,
The fixing device, wherein the second pressure member is a fixing roller. The fixing device according to any one of claims 1 to 7,
The fixing device is characterized in that the support member is molded by an extrusion process. The fixing device according to any one of claims 1 to 7,
The fixing device is characterized in that the support member is molded from a plate material by press working. In a fixing device that heats and fixes a developer on a medium,
A fixing member that supplies heat to the developer and the medium and moves in a predetermined direction;
A heating element for heating the fixing member;
A support member that supports the heating element and has a sliding portion that slides on the fixing member;
A pressing member that presses the fixing member against the heating element;
A second pressure member in contact with the fixing member;
A third pressure member in contact with the fixing member;
The fixing device according to claim 1, wherein the sliding portion is disposed on the downstream side of the heating element in the moving direction of the fixing member. The fixing device according to claim 10.
The fixing member is a fixing belt that moves together with the medium and supplies heat to the developer and the medium;
The pressing member presses the heating element to the support member via the fixing belt,
The second pressure member contacts one surface of the fixing belt downstream of the pressing member in the moving direction of the fixing belt;
The third pressure member is a pressure roller that is disposed to face the second pressure member across the fixing belt and presses the medium against the fixing belt.
The fixing device is characterized in that the support member has a substantially semi-cylindrical curved surface, and the curved surface is in contact with the fixing belt between the pressing member and the second pressure member. The fixing device according to claim 11.
The fixing device, wherein the second pressure member is formed on the support member. The fixing device according to claim 11 or 12,
The fixing belt is an endless belt,
A fixing device, wherein a radius of the curved surface is substantially equal to a radius of the fixing belt. The fixing device according to claim 11 or 12,
The fixing belt is an endless belt,
A fixing device, wherein a radius of the curved surface on the downstream side in the moving direction of the fixing belt is smaller than a radius of the curved surface on the upstream side. The fixing device according to claim 13 or 14,
The fixing device, wherein the fixing belt is stretched between the pressing member and the pressure roller when rotating, and contacts the curved surface. The fixing device according to any one of claims 13 to 15,
A tension roller is provided to stretch the fixing belt;
The fixing device, wherein the fixing belt is in contact with the curved surface. The fixing device according to claim 16.
The fixing device, wherein the tension roller is urged in a direction in which the fixing belt is brought into contact with the curved surface and in a direction in which the belt is brought into contact with the heating element. An image forming apparatus comprising the fixing device according to claim 1.

Images