JP2008224875A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a lubricant from leaking from width-directional end parts of a fixing belt, when the fixing belt is driven. <P>SOLUTION: On an end surface of a heating body 110 in the rotating direction of the fixing belt 102, a slope portion 132 is provided which tilts to the downstream side in the rotating direction of the fixing belt 102 from a corner part of the end surface to the center. A lubricant L carried sticking on an inner peripheral surface of the fixing belt 102 comes into contact with the end surface of the heating body 110, to moves from both end parts to the center part along the slope part 132. The lubricant L enters the gap between the fixing belt 102 and heating body 110 so as to spread from the center part to both the end parts. Consequently, the lubricant L on the reverse surface of the fixing belt 102 is leveled uniformly at the center part and both end parts, so that the lubricant L will not leak from the width-directional end parts of the fixing belt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer or a copier, a toner image transferred onto a recording sheet is passed through a nip formed by a fixing belt having a heat source and a pressure roller, and the action of heat and pressure is applied. A belt-type fixing device that melts and fixes toner is used.

  As a heat source of the belt-type fixing device, a heating roller including a halogen heater or a heating element that generates heat by electromagnetic induction is used.

As an example of a belt-type fixing device, an endless fixing belt having grease coated on the inner surface is stretched between a heating roller and a nip forming member, and the grease is guided from both ends in the width direction of the fixing belt to the center portion. There is one provided with a member (for example, see Patent Document 1).
JP 2006-038990

  An object of the present invention is to prevent the lubricant from leaking from the end in the width direction of the fixing belt when the fixing belt is driven.

  A fixing device according to claim 1 of the present invention includes an endless fixing member that is rotatably supported at both ends, a heating element that is disposed inside the fixing member, and generates heat to heat the fixing member. A support disposed inside the fixing member; a pressure member that presses the fixing member against the support; and a frictional force applied to the back surface of the fixing member between the heating element and the support. In the fixing device having a lubricant, an inclined portion inclined toward the downstream side in the rotation direction of the fixing member from the corner portion to the center of the end surface of the heating element on the upstream side in the rotation direction of the fixing member. It is characterized by providing.

  The fixing device according to a second aspect of the present invention is characterized in that an R surface or a C surface is formed on the fixing member side of the corner portion of the inclined portion.

  A fixing device according to a third aspect of the present invention is characterized in that a groove portion for storing the lubricant is provided across a width direction on a surface where the heating element contacts the fixing member.

  The fixing device according to a fourth aspect of the present invention is characterized in that an R surface or a C surface is formed at the opening edge of the groove.

  According to a fifth aspect of the present invention, there is provided a fixing device including an electromagnetic induction coil that generates a magnetic field and generates heat by electromagnetic induction, and the groove portion is disposed in an air core portion where the electromagnetic induction coil does not exist. It is a feature.

  An image forming apparatus according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, an exposure unit that emits exposure light, and a latent image formed by the exposure light. Is developed with a developer to form a developer image, a transfer unit that transfers the developer image made visible at the development unit onto a recording medium, and the developer image is transferred at the transfer unit. And a transport unit that transports the recorded recording medium to the fixing device.

In the first aspect of the invention, since the lubricant is present uniformly from the center to the both ends of the back surface of the fixing belt, the lubricant does not come from the end in the width direction of the fixing belt when the fixing belt is driven. Compared to the case where this configuration is not provided, the lubricant easily enters the sliding surface between the fixing member and the heating element along the R surface or the C surface. Is less likely to be scraped off.

  According to the third aspect of the present invention, since the lubricant is always present on the surface of the heating element, the deterioration of the surface of the heating element due to the friction between the fixing member and the heating element can be suppressed as compared with the case where this configuration is not provided.

  In the invention of claim 4, since the lubricant moves along the R surface or the C surface formed at the opening edge of the groove portion as compared with the case where this configuration is not provided, the gap between the fixing member and the heating element is increased. It is easy for the lubricant to enter the fixing member, and it is difficult to apply a load to the fixing member.

  The invention according to claim 5 can suppress the deterioration of the lubricant due to the heat generated by the heating element, as compared with the case where this configuration is not provided.

  According to the sixth aspect of the present invention, the paper wrinkles and the deterioration of the fixing member are reduced and the fixing property can be maintained as compared with the case where the present configuration is not provided.

  A first embodiment of a fixing device and an image forming apparatus of the present invention will be described with reference to the drawings.

  FIG. 1 shows a printer 10 as an image forming apparatus.

  In the printer 10, optical scanning that emits a light beam corresponding to each toner of yellow (Y), magenta (M), cyan (C), and black (K) in a housing 12 constituting the main body of the printer 10. Devices 14Y, 14M, 14C and 14K are fixed. A control unit 70 that controls the operation of each unit of the printer 10 is provided at a position adjacent to the optical scanning device 14K.

  The optical scanning devices 14Y, 14M, 14C, and 14K scan the light beam emitted from the light source with a rotating polygon mirror (polygon mirror) (not shown) and reflect the light beam with a plurality of optical components such as a reflection mirror to each toner. Corresponding light beams 16Y, 16M, 16C, and 16K are emitted.

  The light beams 16Y, 16M, 16C, and 16K are guided to the corresponding photosensitive drums 18Y, 18M, 18C, and 18K, respectively. Each of the photosensitive drums 18Y, 18M, 18C, and 18K is rotated in the direction of arrow A by driving means including a motor and a gear (not shown).

  Chargers 20Y, 20M, 20C, and 20K that charge the surfaces of the photosensitive drums 18Y, 18M, 18C, and 18K are provided on the upstream side in the rotation direction of the photosensitive drums 18Y, 18M, 18C, and 18K.

  Further, on the downstream side in the rotation direction of the photosensitive drums 18Y, 18M, 18C, and 18K, developing units 22Y and 22M that develop the Y, M, C, and K toners on the photosensitive members 18Y, 18M, 18C, and 18K, respectively. , 22C and 22K are provided.

  An intermediate transfer belt 28 to which the developed toner images are primarily transferred is disposed downstream of the developing units 22Y, 22M, 22C, and 22K in the rotational direction of the photosensitive drums 18Y, 18M, 18C, and 18K.

  The intermediate transfer belt 28 is constituted by a film-like endless belt in which an appropriate amount of an antistatic agent such as carbon black is contained in a resin such as polyimide or polyamide. And the volume resistivity is formed so that it may become 106-1014 ohm-cm, The thickness is comprised by about 0.1 mm, for example.

  Each color toner image formed on the photosensitive drums 18Y, 18M, 18C, and 18K is intermediately transferred to the inner side of the intermediate transfer belt 28 at a position where the photosensitive drums 18Y, 18M, 18C, and 18K face each other. Primary transfer rolls 24Y, 24M, 24C, and 24K that transfer to the belt 28 are disposed. The primary transfer rolls 24Y, 24M, 24C, and 24K constitute a primary transfer unit 25 that performs primary transfer from the photosensitive drums 18Y, 18M, 18C, and 18K to the intermediate transfer belt 28.

  The primary transfer rolls 24Y, 24M, 24C, and 24K have a shaft (not shown) and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll made of a blend rubber of NBR, SBR, and EPDM blended with a conductive agent such as carbon black and having a volume resistivity of 107.5 to 108.5 Ωcm.

  The primary transfer rolls 24Y, 24M, 24C, and 24K are pressed against the photosensitive drums 18Y, 18M, 18C, and 18K with the intermediate transfer belt 28 interposed therebetween. The primary transfer rolls 24Y, 24M, 24C, and 24K are applied with a voltage (primary transfer bias) having a polarity opposite to the charging polarity (negative polarity; the same applies hereinafter) of each toner by a voltage applying unit (not shown). It has become. As a result, the toner images on the respective photoconductive drums 18Y, 18M, 18C, and 18K are electrostatically attracted sequentially to the intermediate transfer belt 28, and a superimposed toner image is formed on the intermediate transfer belt 28. ing.

  Further, drum cleaners 26Y, 26M, 26C, and 26K for removing residual toner on the photosensitive drums 18Y, 18M, 18C, and 18K are provided on the downstream side in the rotation direction of the photosensitive drums 18Y, 18M, 18C, and 18K. ing.

  Inside the intermediate transfer belt 28, a drive roll 30 that is driven by a motor (not shown) having excellent constant speed to move the intermediate transfer belt 28 and an array of the photosensitive drums 18Y, 18M, 18C, and 18K A support roll 32 that extends substantially linearly in the direction and supports the intermediate transfer belt 28 is provided. Thereby, the intermediate transfer belt 28 is driven to circulate at a predetermined speed in the arrow B direction.

  A tension roll 34 is provided inside the intermediate transfer belt 28 to apply a constant tension to the intermediate transfer belt 28 and prevent the intermediate transfer belt 28 from meandering.

  A secondary transfer portion 42 that transfers the toner image on the fixing belt 28 onto the recording paper P is provided on the downstream side in the moving direction of the intermediate transfer belt 28.

  The secondary transfer unit 42 includes a secondary transfer roll 38 disposed on the toner image carrying surface side of the intermediate transfer belt 28 and a backup roll 36.

  The secondary transfer roll 38 includes a shaft (not shown) and a sponge layer as an elastic layer fixed around the shaft. The shaft is a cylindrical bar made of metal such as iron or SUS. The sponge layer is a sponge-like cylindrical roll made of a blend rubber of NBR, SBR, and EPDM blended with a conductive agent such as carbon black and having a volume resistivity of 107.5 to 108.5 Ωcm.

  The secondary transfer roll 38 is disposed in pressure contact with the backup roll 36 with the intermediate transfer belt 28 interposed therebetween. Here, the secondary transfer roll 38 is grounded and a secondary transfer bias is applied between the secondary transfer roll 38 and the backup roll 36, and the toner image is secondarily transferred onto the recording paper P conveyed to the secondary transfer unit 42. It is like that.

  The backup roll 36 is composed of a EPDM and NBR blend rubber tube with carbon dispersed on the surface, and an EPDM rubber inside. And it forms so that surface resistivity may become 107-1010 ohms / square, and hardness is set to 70 degrees (Asker C), for example.

  The backup roll 36 is disposed on the back surface side of the intermediate transfer belt 28 to form a counter electrode of the secondary transfer roll 38, and the backup roll 36 is connected to the backup roll 36 through a metal power supply roll 40 disposed in contact with the backup roll 36. The next transfer bias is applied stably.

  An intermediate transfer belt cleaner 46 that removes residual toner and paper dust on the intermediate transfer belt 28 after the secondary transfer is provided downstream of the secondary transfer portion 42 in the moving direction of the intermediate transfer belt 28. It is provided so that it can contact and separate. A cleaning backup roll 44 is provided inside the intermediate transfer belt 28 in the intermediate transfer belt cleaner 46.

  On the other hand, on the upstream side of the primary transfer roll 24Y corresponding to yellow toner, a home position sensor 48 that generates a signal serving as a reference for matching the timing of image formation corresponding to each toner is provided.

  The home position sensor 48 detects a predetermined mark provided on the back side of the intermediate transfer belt 15 and generates a reference signal. Based on the reference signal, the control unit 70 operates each unit of the printer 10 to start image formation.

  An image density sensor 43 for adjusting image quality is provided on the downstream side of the primary transfer roll 24K corresponding to black toner.

  On the other hand, a paper tray 50 for storing the recording paper P is provided below the printer 10. A pickup roll 52 is provided at one end of the paper tray 50 to take out and transport the recording paper P at a predetermined timing.

  Above the pick-up roll 52, a plurality of transport rolls 54 that are driven to rotate by a driving means including a motor and gear (not shown) and transport the recording paper P delivered by the pick-up roll 52 to the secondary transfer unit 42 described above, 56 is provided.

  On the downstream side of the conveyance roll 56 in the conveyance direction of the recording paper P, a conveyance chute 58 for feeding the recording paper P to the secondary transfer unit 42 is provided.

  A conveying belt 60 that conveys the recording paper P, on which the secondary transfer of the toner image has been completed, to the fixing device 100 is provided in the sending direction of the recording paper P in the secondary transfer unit 42. The transport belt 60 is stretched by stretch rolls 57 and 59, and is provided so as to be movable by a driving means including a motor and a gear (not shown).

  A guide 62 for guiding the recording paper P to the fixing device 100 is provided on the inlet side of the fixing device 100. A paper stacking tray 64 fixed to the casing 12 of the printer 10 is provided on the exit side of the fixing device 100.

  Here, image formation of the printer 10 will be described.

  First, image data output from an image reading device (not shown) or a personal computer is subjected to predetermined image processing by an image processing device (not shown). The image processing apparatus performs predetermined image processing such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color editing, moving editing, and other various image editing on the input reflectance data. Is given. The image data subjected to the image processing is converted into color material gradation data of four colors Y, M, C, and K, and is output to the optical scanning devices 14Y, 14M, 14C, and 14K.

  The optical scanning devices 14Y, 14M, 14C, and 14K irradiate the respective photoconductive drums 18Y, 18M, 18C, and 18K with the light beams 16Y, 16M, 16C, and 16K according to the input color material gradation data.

  The surfaces of the photosensitive drums 18Y, 18M, 18C, and 18K are charged in advance by the chargers 20Y, 20M, 20C, and 20K, and the surfaces are exposed by the light beams 16Y, 16M, 16C, and 16K, and an electrostatic latent image is formed. It is formed. The formed electrostatic latent images are developed as toner images of respective colors Y, M, C, and K by developing units 22Y, 22M, 22C, and 22K.

  Subsequently, the toner images formed on the photosensitive drums 18Y, 18M, 18C, and 18K are transferred onto the intermediate transfer belt 28 in the primary transfer unit 25. In this transfer, the primary transfer rolls 24Y, 24M, 24C, and 24K apply a voltage (primary transfer bias) opposite to the toner charging polarity (minus polarity) to the intermediate transfer belt 28, and the toner image is transferred to the intermediate transfer belt 28. This is done by sequentially superimposing on the surface.

  Subsequently, the intermediate transfer belt 28 onto which the toner image has been transferred is conveyed to the secondary transfer unit 42.

  On the other hand, the pickup roll 52 rotates in accordance with the timing at which the toner image is conveyed to the secondary transfer unit 42, and a recording paper P having a predetermined size is sent from the paper tray 50.

  The recording paper P sent out by the pickup roll 52 is transported by the transport rolls 54 and 56, and reaches the secondary transfer unit 42 through the transport chute 58. Before reaching the secondary transfer portion 42, the recording paper P is temporarily stopped, and a registration roll (not shown) rotates in accordance with the movement timing of the intermediate transfer belt 28 on which the toner image is carried. The position of P and the position of the toner image are aligned.

  In the secondary transfer unit 42, the secondary transfer roll 38 is pressed against the backup roll 36 via the intermediate transfer belt 28. At this time, the recording paper P conveyed at the same timing is sandwiched between the intermediate transfer belt 28 and the secondary transfer roll 38.

  At this time, a voltage (secondary transfer bias) having the same polarity as the toner charging polarity (negative polarity) is applied from the power supply roll 40, and a transfer electric field is formed between the secondary transfer roll 38 and the backup roll 36. The The unfixed toner image carried on the intermediate transfer belt 28 is pressed by the secondary transfer roll 38 and the backup roll 36 and is electrostatically transferred onto the recording paper P at once.

  Subsequently, the recording paper P on which the toner image has been electrostatically transferred is conveyed as it is while being peeled off from the intermediate transfer belt 28 by the secondary transfer roll 38, and is conveyed to the conveyance belt 60.

  The conveyance belt 60 conveys the recording paper P to the fixing device 100 in accordance with the optimum conveyance speed in the fixing device 100. The unfixed toner image on the recording paper P conveyed to the fixing device 100 is fixed on the recording paper P by the fixing device 100.

  The recording paper P on which the fixed image is formed is discharged to the paper stacking tray 64 and stacked.

  On the other hand, after the transfer onto the recording paper P is completed, the residual toner remaining on the intermediate transfer belt 28 is conveyed to the intermediate transfer belt cleaner 46 as the intermediate transfer belt 28 rotates, and from the intermediate transfer belt 28. Removed.

  In this way, image formation by the printer 10 is performed.

  Next, the fixing device 100 will be described.

  As shown in FIG. 2, the fixing device 100 includes a fixing belt 102 having an endless peripheral surface inside a housing 106 made of heat-resistant resin and the like, and a fixing belt 102 that is in pressure contact with the outer peripheral surface of the fixing belt 102. The pressure roll 104 that is driven to rotate is arranged.

  Inside the fixing belt 102, a pressing pad 116 that is pressed against the pressure roll 104 via the fixing belt 102, and a pad support member 114 that supports the pressing pad 116 and the like are provided.

  Outside the fixing belt 102, an electromagnetic induction heating unit 118 that generates a magnetic field and electromagnetically heats the fixing belt 102 in the longitudinal direction is provided.

  Further, a ferrite member 124 that is formed following the shape of the peripheral surface of the fixing belt 102 and strengthens the magnetic field generated by the electromagnetic induction heating unit 118 is disposed so as to form a predetermined gap. The ferrite member 124 increases the magnetic field and increases the heating efficiency of the fixing belt 102.

  On the other hand, a separation claw (not shown) for preventing the recording paper P from being wrapped around the fixing belt 102 is provided in the vicinity of the fixing belt 102 on the discharge side of the recording paper P.

  The fixing belt 102 is configured by laminating a base layer, an elastic layer, and a release layer (not shown) in order from the inner peripheral side. In addition, a primer layer for adhesion may be provided between the layers.

  The base layer is made of a flexible, excellent mechanical strength, heat-resistant material such as fluororesin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, PFA resin, PTFE resin, FEP resin, etc. Used for. The thickness is 10 to 150 μm, preferably 30 to 100 μm. If the thickness is less than 10 μm, the strength of the fixing belt 61 cannot be obtained, and if the thickness is greater than 150 μm, the flexibility is impaired, and the heat capacity increases and the temperature rise time becomes longer. is there. In the present embodiment, a sheet-like member made of polyimide resin having a thickness of 80 μm is used.

  The elastic layer has a thickness of 10 to 500 [mu] m, preferably 50 to 300 [mu] m, and silicone rubber, fluorine rubber, fluorosilicone rubber, etc. excellent in heat resistance and heat conductivity are used. In the present embodiment, silicone rubber having a rubber hardness of 15 ° (JIS-A: JIS-KA type tester) and a thickness of 200 μm is used.

  Since the release layer is a layer that is in direct contact with the unfixed toner image transferred onto the recording paper P, it is necessary to use a material having excellent release properties and heat resistance. Therefore, as the material constituting the release layer, for example, tetrafluoroethylene perfluoroalkyl vinyl ether polymer (PFA), polytetrafluoroethylene (PTFE), fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, etc. Are preferably used. The thickness of the release layer is preferably 5 to 50 μm.

  On the other hand, the pressure roll 104 has a metal cylindrical member 108 as a core material (core), and is laminated on the surface of the cylindrical member 108 and has heat resistance such as silicone rubber, foamed silicone rubber, fluororubber, and fluororesin. It has an elastic layer and a release layer on the outermost surface.

  The pressure roll 104 is disposed in parallel with the rotation axis of the fixing belt 102, and both ends thereof are urged and supported by the fixing belt 102 by spring members (not shown). The pressure roll 104 is biased by the pressing pad 116 through the fixing belt 102 so as to have a total load of 294N (30 kgf).

  Here, the pressing roll 104 is rotated in the arrow Y direction by a driving means such as a motor and a gear (not shown). Further, the fixing belt 102 is driven to rotate in the direction of the arrow X by the rotational drive of the pressure roll 104.

  The pressing pad 116 is made of an elastic material such as silicone rubber or fluororubber, a heat resistant resin such as polyimide resin, polyphenylene sulfide (PPS), polyethersulfone (PES), or liquid crystal polymer (LCP). Further, the pressing pad 116 is disposed over an area slightly wider than the area (sheet passing area) through which the recording paper P passes in the width direction of the fixing belt 102, and the pressing pad 116 has a substantially entire length in the longitudinal direction. It is comprised so that the pressure roll 104 may be pressed over.

  The contact surface between the pressing pad 116 and the fixing belt 102 is formed as a concave curved surface following the outer surface shape of the pressure roll 104. Therefore, a sufficiently wide nip width can be formed with the pressure roll 104 via the fixing belt 102.

  A lubricant is applied to the inner peripheral surface (base layer side) of the fixing belt 102. As the lubricant, amino-modified silicone oil, dimethyl silicone oil, or the like is used. Accordingly, the frictional resistance between the fixing belt 102 and the pressing pad 116 is reduced, and the fixing belt 102 can be smoothly rotated.

  The pad support member 114 is a rod-shaped member having an axis in the width direction of the fixing belt 102. A pressing pad 116 is attached to a portion of the pad support member 114 facing the pressure roll 104, and the pressing force acting on the pressing pad 116 from the pressure roll 104 via the fixing belt 102 is applied by the pad support member 114. I bear it.

  As a material constituting the pad support member 114, a material having such a rigidity that the bending amount when receiving the pressing force from the pressure roll 104 is not more than a predetermined level, preferably not more than 1 mm is used.

  Further, the material of the pad support member 114 needs to be hardly affected by the magnetic flux generated by the electromagnetic induction heating unit 118 described above. For this reason, as the pad support member 114, for example, a heat-resistant resin such as PPS containing glass fiber, phenol, polyimide, or a liquid crystal polymer, heat-resistant glass, or a metal such as aluminum that has low specific resistance and is not easily affected by induction heating is used. In the present embodiment, the pad support member 114 is made of aluminum formed to have a rectangular cross-sectional shape having a long axis in the pressing force direction from the pressure roll 104.

  On the other hand, a temperature sensor 126 is provided at a predetermined distance from the outer peripheral surface of the fixing belt 102. The temperature sensor 126 is a non-contact type sensor that detects the temperature of the fixing belt 102 by absorbing infrared rays.

  Next, the electromagnetic induction heating unit 118 will be described.

  The electromagnetic induction heating unit 118 includes a pedestal 120 having a curved surface that follows the shape of the outer peripheral surface of the fixing belt 102 along the width direction of the fixing belt 102, an excitation coil 122 supported by the pedestal 120, and the excitation coil 122. The main part is composed of an excitation circuit (not shown) for supplying a high-frequency current.

  The pedestal 120 is made of a material having insulating properties and heat resistance. For example, a phenol resin, a polyimide resin, a polyamide resin, a polyamideimide resin, a liquid crystal polymer resin, or the like can be used.

  As the exciting coil 122, for example, a long litz wire in which a plurality of copper wires having a diameter of 0.1 to 0.5 mm, which are insulated from each other by a heat-resistant insulating material (for example, polyimide resin, polyamideimide resin, etc.) is bundled. A closed loop shape such as a circular shape, an elliptical shape, or a rectangular shape is used that is wound a plurality of times (for example, 11 turns). And the excitation coil 122 is being fixed to the base 120, maintaining the shape by being hardened with the adhesive agent.

  In the electromagnetic induction heating unit 118, when a high frequency current is supplied from the excitation circuit (not shown) to the excitation coil 122, the magnetic flux repeatedly generates and disappears around the excitation coil 122. Thereby, the magnetic field H is formed. Here, the frequency of the high-frequency current is set to 10 to 500 kHz, for example, but is set to 20 to 100 kHz in the present embodiment.

  On the other hand, on the inner side of the fixing belt 102, a heating element 110 that is in surface contact with the inner peripheral surface of the fixing belt 102 and generates heat to raise the temperature of the fixing belt 102 to a preset fixing temperature is provided.

  Here, based on the measurement value of the temperature sensor 126, the control unit 70 (see FIG. 1) of the image forming apparatus controls the amount of power to be supplied to the exciting coil 122 or the supply time of the high-frequency current, thereby generating heat. The heat generation amount of the body 110 is controlled so that the temperature of the fixing belt 102 is maintained at a predetermined temperature.

  Next, the heating element 110 will be described.

  The heating element 110 is a metal material that generates heat by an electromagnetic induction effect in which an eddy current flows so as to generate a magnetic field that cancels the magnetic field H. For example, iron, nickel, manganese, gold, silver, copper, aluminum, zinc, or these A metal material of an alloy of the above can be used. In the present embodiment, iron is used as the heating element 110 from the viewpoint of efficiently obtaining a necessary calorific value and low cost.

  As shown in FIG. 3 a, the heating element 110 has a convex curved shape, and the outer peripheral surface 130 is in contact with the inner peripheral surface of the fixing belt 102. An entrance 112 is formed on the end surface 132 of the heating element 110 on the upstream side in the rotation direction of the fixing belt 102 by chamfering the C surface. The entrance 112 allows the aforementioned lubricant to enter the gap between the fixing belt 102 and the heating element 110 from the entrance 112 as the fixing belt 102 rotates.

  FIG. 3 b shows a state where the heating element 110 of FIG. 3 a is viewed from the direction of the arrow X.

  As shown in FIG. 3 b, an inclined portion 132 is formed on the end surface of the heating element 110 so as to have an angle θ toward the downstream side in the rotation direction of the fixing belt 102 from the corner portion of the end surface toward the center portion. . The inclined portion 132 has a mountain shape so that the center portion is located on the downstream side in the rotation direction of the fixing belt 102 with respect to both end portions of the heating element 110.

  Next, the operation of the first embodiment of the present invention will be described.

  First, a case where the heating element 202 is used will be described as a comparative example with the first embodiment of the present invention.

  As shown in FIG. 4 a, the fixing belt 200 made of the same material as the above-described fixing belt 102 rotates in the direction of the arrow X while being in contact with the heating element 202. The lubricant (L) is applied to the inner peripheral surface of the fixing belt 200.

  Further, the end surface 204 of the heating element 202 on the upstream side in the rotation direction of the fixing belt 200 is a surface in the normal direction with respect to the inner peripheral surface of the fixing belt 200. For this reason, the gap between the fixing belt 200 and the heating element 202 is narrow.

  Here, as shown in FIG. 4b, the lubricant that adheres to the inner peripheral surface of the fixing belt 200 (not shown) and is conveyed in the direction of arrow A is scraped off by the end surface 204, and most of the lubricant is a heating element. It moves in the direction of arrow B or arrow C along the end face 204 of 202. A small amount of lubricant enters the gap between the heating element 202 and the fixing belt 200 and is conveyed in the direction of arrow D.

  For this reason, when the fixing belt 200 continues to rotate, the amount of lubricant in the center of the fixing belt 200 becomes very small, and the amount of lubricant in the gap between the heating element 202 and the fixing belt 200 also decreases. Then, the frictional force between the heating element 202 and the fixing belt 200 increases, and the load when the fixing belt 200 moves is increased.

  When the load of the fixing belt 200 increases, the fixing belt 200 cannot be rotated (moved) at a predetermined speed, and the toner image at the time of fixing is disturbed or paper wrinkles are generated.

  On the other hand, as shown in FIGS. 5 a and 5 b, in the first embodiment of the present invention, the lubricant L attached to the inner peripheral surface of the fixing belt 102 and conveyed in the direction of arrow A is the end of the heating element 110. And moves from the corner toward the center along the inclined portion 132 (in the directions of arrows E and F).

  Further, the lubricant L moves along the inclined portion 132 to the central portion and also moves along the inclined surface of the entrance 112, and enters the gap between the fixing belt 102 and the heating element 110 (in the direction of arrow G).

  The lubricant L that has entered the gap between the fixing belt 102 and the heating element 110 is divided into two upper and lower layers, a part close to the inner peripheral surface of the fixing belt 102 flows and moves, and is closer to the outer peripheral surface 130 of the heating element 110. A part remains on the surface of the heating element 110. Further, by being sandwiched between the fixing belt 102 and the heating element 110, the fixing belt 102 spreads over the entire width direction.

  As a result, the lubricant L on the back surface of the fixing belt 102 is evenly distributed at the center and both ends during one rotation of the fixing belt 102, so that the lubricant L leaks from the end in the width direction of the fixing belt. Absent. Further, the lubricant L is always present in the gap between the fixing belt 102 and the heating element 110, and it is difficult to apply an extra load to the fixing belt 102.

  FIG. 6 shows the rotational torque (B) of the fixing belt when the heating element and the fixing belt of the comparative example are used, and the fixing belt when the heating element 110 and the fixing belt 102 of the first embodiment of the present invention are used. It is the graph which compared rotational torque (A).

  As shown in FIG. 6, in the graph A in the case where the heating element 110 of the present invention is used, the torque can be suppressed to about 0.6 N · m even when the number of fixed sheets (the number of copies) of the recording paper P becomes 200K. Thus, the torque is about ½ of the torque shown in graph B when the heating element of the comparative example is used.

  Next, a second embodiment of the fixing device and the image forming apparatus of the present invention will be described with reference to the drawings.

  Note that components that are basically the same as those in the first embodiment described above are given the same reference numerals as those in the first embodiment, and descriptions thereof are omitted.

  As shown in FIG. 7, in the second embodiment of the present invention, a heating element 142 is provided instead of the heating element 110 in the fixing apparatus 100 of the first embodiment (fixing apparatus 140). The heating element 142 is made of the same material as the heating element 110 (see FIG. 2) described above.

  As shown in FIG. 8 a, the heating element 142 has a convex curved shape, and the outer peripheral surface 146 is in contact with the inner peripheral surface of the fixing belt 102.

  An entrance 144 is formed by chamfering the C surface on the end surface of the heating element 142 on the upstream side in the rotation direction of the fixing belt 102. As a result, the lubricant L described above enters the gap between the fixing belt 102 and the heating element 142 from the entrance 144 as the fixing belt 102 moves.

  The end surface of the heating element 142 is provided with an inclined portion 145 inclined toward the downstream side in the rotation direction of the fixing belt 102 from the corner portion to the central portion of the end surface (see FIG. 8c).

  On the other hand, a groove 148 is formed at the curved top portion of the heating element 142 along the width direction of the heating element 142 (the direction from the front to the back of FIG. 8A).

  The groove portion 148 is disposed at a position where the exciting coil 122 (see FIG. 7) faces the air core portion, and stores a part of the lubricant L carried by the movement of the fixing belt 102. . Here, the air core portion corresponds to the center convex portion position of the pedestal 120 and indicates a central space portion (a portion where the excitation coil 122 does not exist) of the excitation coil 122 wound a plurality of times.

  Note that a predetermined amount (for example, an amount that is 3/4 of the entire depth of the groove portion 148) of the lubricant L is stored in the groove portion 148 in advance.

  As shown in FIG. 8 b, an entrance 150 that is chamfered in a C-shape is formed in the upper portion (opening edge) of the groove portion 148 on the downstream side in the rotation direction of the fixing belt 102. Accordingly, a part of the lubricant L stored in the groove portion 148 enters the gap between the fixing belt 102 and the heating element 142 through the entrance 150 as the fixing belt 102 rotates.

  Next, the operation of the second embodiment of the present invention will be described.

  First, as shown in FIGS. 8 a to 8 c, the lubricant L conveyed in the direction of arrow A by the rotation of the fixing belt 102 contacts the end surface of the heating element 142, and along the inclined portion 145, the corner portion of the end surface To the center (arrow E, F direction).

  Further, the lubricant L moves along the inclined portion 145 to the central portion and also moves along the slope of the entrance 144, and enters the gap between the fixing belt 102 and the heating element 142 (in the direction of arrow G).

  Subsequently, a part of the lubricant L that has entered the gap between the fixing belt 102 and the heating element 142 remains on the outer circumferential surface 146 of the heating element 142, and the rest moves along the outer circumferential surface 146 due to the rotation of the fixing belt 102. And stored in the groove 148.

  The groove portion 148 is in a region that does not face the exciting coil 122, and the side wall and the periphery of the groove portion 148 do not generate heat even when the exciting coil 122 is energized to generate heat. For this reason, the lubricant L stored in the groove 148 is not heated more than necessary.

  Subsequently, when the amount of the lubricant L stored in the groove portion 148 increases and the amount of the lubricant L at the entrance 150 increases, the lubricant L flows along the inclined surface of the entrance 150 with the fixing belt 102 and the heating element. Enter the gap 142.

  Part of the lubricant L that has entered the gap between the fixing belt 102 and the heating element 142 remains on the outer peripheral surface 146 of the heating element 142, and the rest moves on the heating element 142. Further, the lubricant L moves from the central portion to both ends by being sandwiched between the fixing belt 102 and the heating element 142, and spreads evenly on the back surface of the fixing belt 102.

  In addition, this invention is not limited to said embodiment.

  The printer 10 may use a liquid developer as well as a dry electrophotographic system using a solid developer.

  The heating elements 110 and 142 are not limited to those that generate heat by electromagnetic induction heating, but may be heating elements that self-heat, such as a ceramic heater.

  The chamfers of the entrances 112 and 144 may be formed not only by the C plane but also by the R plane. Further, the chamfering may be inclined and curved so that the opening width of the central portion is the widest.

  The shapes of the inclined portions 132 and 145 may be linear or curved.

  The fixing belt 102 may have a heat generating layer.

1 is an overall view of an image forming apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view of a fixing device according to a first embodiment of the present invention. It is sectional drawing of the heat generating body which concerns on 1st Embodiment of this invention. (B) It is a front view of the heat generating body which concerns on 1st Embodiment of this invention. It is a schematic diagram which shows the moving direction of the lubricant in the heat generating body of the conventional example. It is a schematic diagram which shows the moving direction of the lubricant in the heat generating body which concerns on 1st Embodiment of this invention. 6 is a graph comparing the driving torque of the fixing belt of the comparative example and the driving torque of the fixing belt according to the first embodiment of the present invention. FIG. 6 is a cross-sectional view of a fixing device according to a second embodiment of the present invention. It is a schematic diagram which shows sectional drawing of the heat generating body which concerns on 2nd Embodiment of this invention, and the moving direction of a lubricant.

Explanation of symbols

10 Printer (image forming device)
14 Optical scanning device (exposure unit)
22 Developer (Developer)
25 Primary transfer section (transfer section)
42 Secondary transfer section (transfer section)
60 Conveyor belt (conveyor)
100 Fixing device (fixing device)
102 Fixing belt (fixing member)
104 Pressure roll (Pressure member)
110 Heating element (heating element)
112 Entrance (C side)
116 Press pad (support)
122 Excitation coil (electromagnetic induction coil)
132 Inclined part (inclined part)
140 Fixing device (fixing device)
142 Heating element (heating element)
144 Entrance (C side)
145 Inclined part (inclined part)
148 Groove (groove)
150 entrance (opening edge)
H Magnetic field (magnetic field)
L Lubricant (Lubricant)
P Recording paper (recording medium)
T Toner (Developer)

Claims (6)

An endless fixing member having both ends rotatably supported;
A heating element disposed inside the fixing member and generating heat to heat the fixing member;
A support disposed inside the fixing member;
A pressure member that pressurizes the fixing member against the support;
A lubricant applied to the back surface of the fixing member to reduce the frictional force between the heating element and the support;
In a fixing device having
A fixing device characterized in that an inclined portion is provided on an end face of the heat generating element on the upstream side in the rotation direction of the fixing member, and is inclined toward the downstream side in the rotation direction of the fixing member from a corner portion to the center of the end face. .   The fixing device according to claim 1, wherein an R surface or a C surface is formed on the fixing member side of the corner portion of the inclined portion.   The fixing device according to claim 1, wherein a groove portion for storing the lubricant is provided across a width direction on a surface where the heating element contacts the fixing member.   The fixing device according to claim 3, wherein an R surface or a C surface is formed at an opening edge of the groove portion.   The electromagnetic induction coil which generates a magnetic field and heats the heating element by electromagnetic induction is provided, and the groove portion is arranged in an air core portion where the electromagnetic induction coil does not exist. Fixing device. A fixing device according to any one of claims 1 to 5,
An exposure unit that emits exposure light; and
A developing unit that exposes the latent image formed by the exposure light with a developer to form a developer image; and
A transfer unit that transfers the developer image made visible in the developing unit onto a recording medium;
A transport unit that transports the recording medium onto which the developer image has been transferred in the transfer unit to the fixing device;
An image forming apparatus comprising:

Images