JP2009229679A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the variation of the separation distance between a peeling member and the surface of an endless-like fixing rotating body. <P>SOLUTION: In a fixing device 100, a pressing pad 116 is provided inside a fixing belt 102 and a positioning portion 120 is projectingly provided in the side surface of the pressing pad 116. The positioning portion 120 is arranged to face a peeling plate 124 for peeling a recording paper P from the fixing belt 102. Even if the fixing belt 102 is dented inward when an adjusting plate 158 with a predetermined thickness is brought into contact with the surface of the fixing belt 102 and further the peeling plate 124 is pressed against the adjusting plate 158, to adjust the separation distance between the fixing belt 102 and the peeling plate 124, the fixing belt 102 comes into contact with the positioning portion 120, to be supported, so that a deformation amount is prevented. Accordingly, the variation of the separation distance between the peeling plate 124 and the surface of the fixing belt 102 is prevented compared with the case when the positioning portion 120 does not exist inside the fixing belt 102. <P>COPYRIGHT: (C)2010,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 copying machine, a toner image transferred onto a recording sheet (recording medium) is passed through a nip portion formed by a fixing belt heated by a heat source and a pressure roll. A fixing device that melts and fixes toner by the action of heat and pressure is used.

Here, as an example of a fixing device using a fixing belt and a pressure roll, a thin fixing belt is disposed in a diametrically stretched state, and the recording paper is peeled off near the exit side of the nip portion of the fixing belt. There is one provided with a peeling member to be made (see, for example, Patent Document 1).
JP 2007-087827 A

  An object of the present invention is to provide a fixing device that can suppress variations in the separation distance between the peeling member and the surface of the endless fixing rotating body.

  According to a first aspect of the present invention, there is provided a fixing device comprising: an endless fixing rotator for heating and fixing a developer on a recording medium; a pressure member for applying pressure to an outer peripheral surface of the fixing rotator; and the fixing rotation. A pressing member that is provided on the inside of the body and presses the fixing rotator toward the pressure member; and a recording medium on which the developer is fixed, disposed opposite to the surface of the fixing rotator with a gap. It is characterized by having a peeling member for peeling from the fixing rotator, and a positioning member for positioning the peeling member, facing the peeling member inside the fixing rotator.

  The fixing device according to claim 2 of the present invention is characterized in that the positioning member is provided at a position in contact with the inner peripheral surface of the fixing rotator when the fixing rotator is not rotated and is not heated. .

  According to a third aspect of the present invention, there is provided a fixing device comprising: an endless fixing rotator for heating and fixing a developer on a recording medium; a pressure member that applies pressure to an outer peripheral surface of the fixing rotator; and the fixing rotation. A pressing member that presses the fixing rotator toward the pressure member, contact / separation means that contacts and separates the fixing rotator and the pressure member, and a surface of the fixing rotator. And a separation member that separates the recording medium on which the developer is fixed from the fixing rotator, and is disposed opposite the separation member inside the fixing rotator to position the separation member. And a positioning member.

  In the fixing device according to a fourth aspect of the present invention, the positioning member is configured such that the contact / separation unit separates the fixing rotator and the pressure member, and the fixing rotator is not rotated and heated. It is provided at a position in contact with the inner peripheral surface of the fixing rotator.

  The fixing device according to claim 5 of the present invention is characterized in that the positioning member is provided at a position that is not in contact with the inner peripheral surface of the fixing rotator when the fixing rotator rotates.

  The fixing device according to a sixth aspect of the present invention is characterized in that the positioning member is provided at a position that is not in contact with the inner peripheral surface of the fixing rotator when the fixing rotator is heated.

  In the fixing device according to claim 7 of the present invention, the positioning member is not in contact with the inner peripheral surface of the fixing rotator when the contacting / separating means contacts the fixing rotator and the pressure member. It is characterized by being provided at the position.

  The fixing device according to an eighth aspect of the present invention is characterized in that the positioning member is provided on the pressing member.

  The fixing device according to claim 9 of the present invention is characterized in that the positioning member and the pressing member are integrated.

  The fixing device according to a tenth aspect of the present invention is characterized in that the positioning member is provided at a plurality of positions spaced apart in the longitudinal direction of the fixing rotating body.

  In the fixing device according to an eleventh aspect of the present invention, when the heat capacity body that absorbs heat of the fixing rotator is inside the fixing rotator, the positioning member is arranged in the longitudinal direction of the fixing rotator. It is characterized by being provided at a different position.

  The fixing device according to a twelfth aspect of the present invention is characterized in that the positioning member is provided outside a recording medium passage region of the fixing rotator.

  The fixing device according to a thirteenth aspect of the present invention is characterized in that the positioning member has a curved surface having a curvature radius smaller than the curvature radius of the inner peripheral surface of the fixing rotating body.

  An image forming apparatus according to a fourteenth aspect of the present invention is the fixing device according to any one of the first to thirteenth 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.

  According to the first and third aspects of the present invention, variation in the separation distance between the peeling member and the surface of the endless fixing rotator can be suppressed as compared with the case where there is no positioning member inside the fixing rotator.

  According to the second and fourth aspects of the present invention, the variation in the separation distance between the peeling member and the surface of the endless fixing rotator can be further reduced as compared with the case where the fixing rotator and the positioning member do not contact each other. .

  According to the fifth aspect of the present invention, the wear of the fixing rotator can be suppressed as compared with the case where the fixing rotator and the positioning member are in contact with each other during the rotation of the fixing rotator.

  According to the sixth aspect of the present invention, the temperature reduction of the fixing rotator can be suppressed as compared with the case where the fixing rotator and the positioning member are in contact with each other when the fixing rotator is heated.

  According to the seventh aspect of the present invention, wear can be suppressed during rotation of the fixing rotator, and temperature drop can be suppressed during heating of the fixing rotator, as compared with the case where the fixing rotator and the positioning member are in contact.

  In the invention of claim 8, it is not necessary to separately provide a member for supporting the positioning member.

  According to the ninth aspect of the present invention, the dimensional accuracy and the mounting accuracy of the member are improved as compared with the case where the positioning member and the pressing member are mounted separately.

  According to the tenth aspect of the present invention, the variation in the longitudinal direction of the separation distance between the fixing rotary member and the peeling member can be suppressed as compared with the positioning member provided at one place in the longitudinal direction of the fixing rotary member.

  According to the eleventh aspect of the present invention, the temperature reduction of the fixing rotating body can be suppressed as compared with the case where the heat capacity body and the positioning member are arranged at the same position in the longitudinal direction.

  According to the twelfth aspect of the present invention, it is possible to prevent a temperature drop in the passage area of the recording medium as compared with the case where the positioning member is in the passage area of the recording medium.

  According to the thirteenth aspect of the present invention, the surface of the positioning member and the inner surface of the fixing rotator are less likely to be worn as compared with the case where this configuration is not provided.

  According to the fourteenth aspect of the present invention, it is possible to suppress the winding of the recording medium around the fixing rotator of the fixing device and the contact of the peeling member to the fixing rotator as compared with the case where this 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. The printer 10 performs optical scanning in which a light beam corresponding to each toner of yellow (Y), magenta (M), cyan (C), and black (K) is emitted into 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 photoreceptors 18Y, 18M, 18C, and 18K, respectively. Each of the photoconductors 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 photoreceptors 18Y, 18M, 18C, and 18K are provided on the upstream side in the rotation direction of the photoreceptors 18Y, 18M, 18C, and 18K. Further, on the downstream side in the rotation direction of the photoconductors 18Y, 18M, 18C, and 18K, developing units 22Y, 22M that develop the Y, M, C, and K toners on the photoconductors 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 rotation direction of the photoreceptors 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.

  At the position where the photoconductors 18Y, 18M, 18C, 18K and the intermediate transfer belt 28 face each other, the respective color toner images formed on the photoconductors 18Y, 18M, 18C, 18K are placed on the inner side of the intermediate transfer belt 28. Primary transfer rolls 24Y, 24M, 24C, and 24K that transfer to the toner are disposed. The primary transfer rolls 24Y, 24M, 24C, and 24K constitute a primary transfer unit 25 that performs primary transfer from the photoreceptors 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 cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black.

  The primary transfer rolls 24Y, 24M, 24C, and 24K are in pressure contact with the photoreceptors 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 photoconductors 18Y, 18M, 18C, and 18K are sequentially electrostatically attracted to the intermediate transfer belt 28, and a superimposed toner image is formed on the intermediate transfer belt 28. Yes. Cleaners 26Y, 26M, 26C, and 26K for removing residual toner on the photoconductors 18Y, 18M, 18C, and 18K are provided on the downstream side in the rotation direction of the photoconductors 18Y, 18M, 18C, and 18K.

  Inside the intermediate transfer belt 28, a driving roll 30 that is driven by a motor (not shown) having excellent constant speed to move the intermediate transfer belt 28, and the arrangement directions of the photoreceptors 18Y, 18M, 18C, and 18K. A support roll 32 that extends in a substantially straight line 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 unit 42 that transfers the toner image on the intermediate transfer 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 cylindrical roll formed of a blend rubber of NBR, SBR, and EPDM containing a conductive agent such as carbon black.

  The secondary transfer roll 38 is disposed in pressure contact with the backup roll 36 with the intermediate transfer belt 28 interposed therebetween. 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. The hardness is set to 70 ° (Asker C), for example.

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

  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.

  A home position sensor 48 is provided on the upstream side of the primary transfer roll 24Y corresponding to the yellow toner and inside the intermediate transfer belt 28 for generating a signal serving as a reference for adjusting the timing of image formation corresponding to each toner. Yes.

  The home position sensor 48 detects a predetermined mark provided on the back side of the intermediate transfer belt 28 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, 56 that are rotationally driven by a drive 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 section 42 described above. Is provided. A conveyance chute 58 for feeding the recording paper P to the secondary transfer unit 42 is provided on the downstream side of the conveyance roll 56 in the conveyance direction of the recording paper P.

  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.

  Next, 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 photoconductors 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 photoreceptors 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. Is done. 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 photoconductors 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. 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. After fixing, the recording paper P is discharged in the direction of arrow C and collected on the paper stacking tray 64.

  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 is removed from the intermediate transfer belt 28. The 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 housing 106 in which an opening for entering or discharging the recording paper P is formed. Inside the housing 106, cap-like support members (not shown) are fitted at both ends, and an endless fixing belt 102 supported rotatably in the direction of arrow D is provided.

  A bobbin 108 made of an insulating material is disposed at a position facing the outer peripheral surface of the fixing belt 102. The bobbin 108 is formed in a substantially arc shape that follows the outer peripheral surface of the fixing belt 102, and has a protruding portion 108 </ b> A protruding toward the opposite side of the fixing belt 102. The distance between the bobbin 108 and the fixing belt 102 is 1 to 3 mm.

  An excitation coil 110 that generates a magnetic field H when energized is wound around the bobbin 108 a plurality of times in the axial direction (the depth direction in FIG. 2) around the convex portion 108A. A magnetic path forming member 112 made of a magnetic material such as ferrite formed in a substantially arc shape following the arc shape of the bobbin 108 is disposed at a position opposite to the fixing belt 102 and facing the exciting coil 110. It is supported by.

  Here, as shown in FIG. 3A, the fixing belt 102 includes a base layer 130, a heat generating layer 132, a protective layer 134, an elastic layer 136, and a release layer 138 from the inside to the outside. These are laminated and integrated.

  The base layer 130 serves as a base (base) for maintaining the strength of the fixing belt 102, and polyimide having a thickness of 50 to 200 μm is used. In addition to the resin such as polyimide, the base layer 130 is made of a metal soft magnetic material composed of a metal such as iron, nickel, silicon, boron, niobium, copper, zirconium, cobalt, or an alloy thereof. Also good.

  The heat generating layer 132 is made of 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 described above. Further, the heat generating layer 132 needs to be configured to be thinner than the so-called skin depth in order to penetrate the magnetic flux of the magnetic field H. Here, as a metal material used as the heat generating layer 132, for example, a metal material of gold, silver, copper, aluminum, zinc, tin, lead, bismuth, beryllium, antimony, or an alloy thereof can be used. In the present embodiment, copper having a thickness of 10 μm is used as the heat generating layer 132.

  The protective layer 134 has a higher mechanical strength than the heat generating layer 132 and is preferably a material that is resistant to repeated strain, and is preferably a material that is resistant to rust and corrosion. In this embodiment, nickel having a thickness of 10 μm is used.

  The elastic layer 136 is made of silicon rubber or fluorine rubber from the viewpoint of obtaining excellent elasticity and heat resistance. In this embodiment, silicon rubber having a thickness of 200 μm is used. The elastic layer 136 preferably has a thickness of 200 to 600 μm.

  The release layer 138 is provided to weaken the adhesive force with the toner T (see FIG. 2) melted on the recording paper P so that the recording paper P can be easily separated from the fixing belt 102. In order to obtain excellent surface release properties, a fluororesin, a silicon resin, or a polyimide resin is used as the release layer 138. In this embodiment, PFA (tetrafluoroethylene / perfluoroalkoxyethylene copolymer resin) is used. Is used. The thickness of the release layer 138 is 30 μm.

  On the other hand, as shown in FIG. 2A, on the inner side of the fixing belt 102, prismatic pillars 114 made of aluminum, which is a nonmagnetic material, are arranged in a non-contact manner with the width direction of the fixing belt 102 as the longitudinal direction. Both ends are fixed to the casing 106 of the fixing device 100.

  The support column 114 has a concave portion 114A formed along the longitudinal direction on the bottom surface side, and a convex portion 114B having a substantially trapezoidal cross section projecting outward from the right side surface. A resin-made pressing pad 116 for pressing the fixing belt 102 outward at a predetermined pressure is fixed to the recess 114A. One end surface of the pressing pad 116 is in contact with the inner peripheral surface of the fixing belt 102 to press the fixing belt outward.

  A temperature sensor 118 that detects the temperature of the surface of the fixing belt 102 in contact with the inner peripheral surface of the fixing belt 102 is disposed on the convex portion 114B. The temperature sensor 118 measures the temperature of the surface of the fixing belt 102 by changing the resistance value according to the amount of heat applied from the surface of the fixing belt 102. The temperature sensor 118 is fixed to the distal end portion of a leaf spring 119 made of a resin such as polyimide, and the base end portion of the leaf spring 119 is fixed to the convex portion 114B with a screw (not shown).

  As shown in FIG. 3B, the temperature sensor 118 is connected to a control circuit 142 provided inside the aforementioned control unit 70 (see FIG. 1) via a wiring 140. The control circuit 142 is connected to the energizing circuit 146 via the wiring 144, and the energizing circuit 146 is connected to the above-described exciting coil 110 via the wirings 148 and 150. The energization circuit 146 is driven or stopped based on an electric signal sent from the control circuit 142, and supplies or stops supplying an alternating current having a predetermined frequency to the exciting coil 110 via the wires 148 and 150. .

  Here, the control circuit 142 measures the temperature on the inner peripheral side of the fixing belt 102 based on the amount of electricity sent from the temperature sensor 118, converts the temperature to the temperature on the outer peripheral side, and stores the converted temperature in advance. The fixing set temperature (170 ° C. in the present embodiment) is compared. When the converted temperature is lower than the fixing set temperature, the energizing circuit 146 is driven to energize the exciting coil 110 and generate a magnetic field H (see FIG. 2) as a magnetic circuit. When the converted temperature is higher than the fixing set temperature, the energization circuit 146 is stopped.

  As shown in FIG. 2A, a thermostat 129 connected to the above-described control unit 70 (see FIG. 1) by a wiring (not shown) is arranged inside the fixing belt 102 and downstream of the temperature sensor 118. Yes. The thermostat 129 is attached to a substantially L-shaped support member 127, and the support member 127 is fixed to the support column 114. Here, the thermostat 129 is in contact with the inner peripheral surface of the fixing belt 102, and when the fixing belt 102 reaches a predetermined temperature (for example, 200 ° C.), the internal switch is turned on. Thereby, the energization to the exciting coil 110 is cut off, and an excessive temperature rise of the fixing belt 102 is suppressed.

  Next, as shown in FIG. 2B, the pressing pad 116 is provided with a positioning portion 120 having a substantially fan-shaped cross section protruding from the side surface 116 </ b> A to the outside (the inner peripheral surface side of the fixing belt 102). The positioning part 120 is arranged at two positions (120A, 120B) at a predetermined interval in the longitudinal direction of the pressing pad 116, and each positioning part 120A, 120B is in contact with the inner peripheral surface of the fixing belt 102, respectively. Curved portions 122A and 122B are formed.

  On the other hand, as shown in FIG. 2A, the fixing belt 102 is pressed toward the pressing pad 116 at a position facing the outer peripheral surface of the fixing belt 102, and a drive motor 154 (see FIG. 4) and not shown. A pressure roll 104 that is rotated in the direction of arrow E by a drive mechanism including a gear is disposed.

  The pressure roll 104 has a configuration in which silicon rubber and PFA are coated around a cored bar 105 made of a metal such as aluminum. Here, the pressure roll 104 presses the fixing belt 102 toward the pressing pad 116, and a nip portion 107 that is a contact portion between the fixing belt 102 and the pressure roll 104 is formed.

  In the vicinity of the exit side of the nip portion 107 (downstream in the rotation direction of the fixing belt 102), a peeling plate 124 is provided at a position facing the positioning portion 120 with the fixing belt 102 interposed therebetween with a predetermined interval. . The peeling plate 124 is formed in a rectangular shape having a width substantially equal to the width in the longitudinal direction of the fixing belt 102, and a plate material 125 is erected on the upper surface.

  A through hole 126 penetrating along the longitudinal direction of the fixing belt 102 is formed in the upper portion of the plate material 125. The through hole 126 is a long hole substantially parallel to the in-plane direction of the peeling plate 124, and the screw 128 is inserted therethrough. Here, the plate member 125 is fastened to the bracket (not shown) attached to the housing 106 with screws 128, whereby the peeling plate 124 is fixed to the housing 106.

  In addition, since the through-hole 126 is a long hole, the position of the peeling plate 124 can be adjusted in a substantially horizontal direction (front-rear direction) by loosening the screw 128. The housing 106 is provided with a removable cover member (not shown) in part. The cover member is removed when the position of the peeling plate 124 is adjusted, and the cover member is removed after the position of the peeling plate 124 is adjusted. It can be attached to the body 106.

  Here, the mounting position of the positioning portion 120 and the amount of protrusion from the pressing pad 116 are the positions where the curved surface portions 122A and 122B are in contact with the inner peripheral surface of the fixing belt 102 or the vicinity thereof when the fixing belt 102 is not rotating and not heated ( The position is set so that the fixing belt 102 and the positioning unit 120 are not in contact with each other when the fixing belt 102 is rotated or rotated and heated. Has been.

  The mounting position of the positioning unit 120 (including the amount of protrusion from the pressing pad 116) and the disposition setting of the peeling plate 124 are set in such a manner that the fixing belt 102 rotates when the pressure roll 104 presses the fixing belt 102. The amount of deformation ΔR1 in the radial direction as seen from the shape of the fixing belt 102 when it is not heated and not rotated, and the fixing belt 102 when it is rotated and heated (fixing set temperature) when it is not heated and rotated The amount of deformation ΔR2 in the radial direction viewed from the shape of the image is measured in advance, the amount of deformation ΔR1 and the amount of deformation ΔR2, the necessary separation distance D (standard value) when fixing the fixing belt 102 and the peeling plate 124, and fixing. It is set based on the thickness dt of the belt 102.

  For example, assuming that ΔR1 <ΔR2, the required distance L from the curved surface portions 122A and 122B to the tip of the peeling plate 124 is L = ΔR2 + dt + D. The arrangement of 120 and the peeling plate 124 is set. In this embodiment, the pressing pad 116 and the positioning portion 120 are integrally formed. However, they may be formed independently and the positioning portion 120 may be attached to the pressing pad 116.

  Next, the connection configuration of the control unit 70 will be described.

  As shown in FIG. 4, the control unit 70 is measured by a central processing unit (CPU) 71 that performs various controls of the printer 10, a program storage unit (ROM) 72 that stores various control programs, and a temperature sensor 118. The data storage unit (RAM) 74 that temporarily stores or deletes the temperature measurement data or other measurement data, and the timer 76 that operates at a predetermined clock. The control unit 70 includes a control circuit 142 (see FIG. 3B).

  The control unit 70 is connected to an input / output interface 80 through which various signals are input / output. Via the input / output interface 80, the temperature sensor 118, the switch 82, a user interface (UI) 84, a thermostat 129, and a drive. The motor 154 and the energization circuit 146 are connected.

  The switch 82 is a switch for turning on / off the power of the printer 10, and the user interface 84 is configured by an input panel or the like for the user to directly instruct execution of image formation or the like. The drive motor 154 is a part of a drive mechanism that rotates the pressure roll 104.

  Here, signals are input to the CPU 71 from the temperature sensor 118, the switch 82, the user interface 84, and the thermostat 129 via the input / output interface 80. On the other hand, a control signal from the CPU 71 is output to the drive motor 154 and the energization circuit 146 via the input / output interface 80. The drive motor 156 is used in a third embodiment to be described later and is not used in the first embodiment.

  Next, the fixing operation of the fixing device 100 will be described.

  As shown in FIGS. 1 to 4, the recording paper P (or envelope) onto which the toner T has been transferred is sent to the fixing device 100 through the image forming process of the printer 10 described above. In the fixing device 100, a drive motor (not shown) is driven by the control unit 70, the pressure roll 104 rotates in the arrow E direction, and the fixing belt 102 is driven to rotate in the arrow D direction. At this time, the energization circuit 146 is driven based on the electrical signal from the control circuit 142, and an alternating current is supplied to the excitation coil 110.

  When an alternating current is supplied to the exciting coil 110, the magnetic field H as a magnetic circuit repeats generation and disappearance around the exciting coil 110. When the magnetic field H crosses the heat generating layer 132 of the fixing belt 102, an eddy current is generated in the heat generating layer 132 so as to generate a magnetic field that prevents the magnetic field H from changing. The heat generating layer 132 generates heat in proportion to the skin resistance of the heat generating layer 132 and the magnitude of the eddy current flowing through the heat generating layer 132, whereby the fixing belt 102 is heated.

  The temperature of the surface of the fixing belt 102 is detected by the temperature sensor 118, and when the fixing temperature has not been reached, the control circuit 142 drives and controls the energizing circuit 146 to energize the exciting coil 110 with an alternating current of a predetermined frequency. To do. When the fixing set temperature is reached, the control circuit 142 controls the energization circuit 146 so that the temperature can be maintained.

  Subsequently, the recording paper P sent to the fixing device 100 is heated and pressed by the fixing belt 102 having a predetermined fixing set temperature and the pressure roll 104, and the toner image is fixed on the surface of the recording paper P. . Then, the fixed recording paper P is discharged to the paper stacking tray 64.

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

  FIG. 5A to FIG. 5D show the adjustment process of the separation distance between the fixing belt 102 and the tip of the peeling plate 124. The casing 106, the excitation coil 110, and the like are not shown.

  As shown in FIG. 5A, it is assumed that the distance between the fixing belt 102 and the peeling plate 124 is d1 and is not adjusted. At this time, the screw 128 (see FIG. 2A) of the peeling plate 124 is loosened. Here, in order to adjust the separation distance, an adjustment plate 158 having a thickness t is inserted between the fixing belt 102 and the peeling plate 124 and is brought into contact with the surface of the fixing belt 102 and positioned. It is assumed that the thickness t is set in advance to t = D + ΔR2 using the necessary separation distance D and the deformation amount ΔR2, and t> ΔR2.

  Subsequently, as shown in FIG. 5B, the peeling plate 124 is slid in the direction of the arrow F, and is brought into contact with the adjustment plate 158 to be positioned. In this state, the screw 128 is fastened, and the separation plate 124 is fixed.

  Subsequently, as shown in FIG. 5C, the adjustment plate 158 is pulled out, and a gap of a distance d <b> 2 is formed between the fixing belt 102 and the separation plate 124. Immediately after the adjustment plate 158 is pulled out, the distance d2 is equal to the plate thickness of the adjustment plate 158, so d2 = t.

  Subsequently, as shown in FIG. 5D, when the fixing operation of the fixing device 100 is started and the fixing belt 102 is rotated and heated in the direction of the arrow D, the fixing belt 102 bends outward and is positioned. A gap of a distance d4 is formed between 120 (curved surface portions 122A and 122B) and the inner peripheral surface of the fixing belt 102. The distance d4 is a distance substantially equal to the aforementioned ΔR2.

  On the other hand, the separation distance d3 between the surface of the fixing belt 102 and the tip of the separation plate 124 is d3 = d2−d4 = t−ΔR2 = D, which is a necessary separation distance. Do not contact with. Further, even when the recording paper P (see FIG. 2) is likely to wrap around the surface of the fixing belt 102 when being discharged from the nip portion 107, the leading edge contacts the leading edge of the separation plate 124 and is separated from the fixing belt 102. Therefore, winding around the fixing belt 102 is difficult to occur.

  Note that when the fixing belt 102 is heated, the positioning unit 120 is not in contact with the inner peripheral surface of the fixing belt 102, so that the temperature of the fixing belt 102 decreases due to heat conduction to the positioning unit 120. Absent.

  FIG. 6A and FIG. 6B show results of measuring variations in the adjustment value of the separation distance between the fixing belt 102 and the separation plate 124 using the fixing device with n = 20 in the conventional example and this embodiment. is there. The separation distance is obtained by measuring the difference (step) in height between the surface of the fixing belt 102 and the separation plate 124 using a laser displacement meter and subtracting the thickness of the separation plate 124 from this measured value. The fixing device 100 without the positioning unit 120 is a conventional example.

  Here, when the required separation distance D is set to the center value of 0.5 mm, the allowable adjustment error is set to 0.2 mm, and 0.3 mm <D <0.5 mm is set as a standard, the conventional example is out of specification at a rate of about 40%. It became. This is because when the adjustment plate 158 contacts the fixing belt 102 or when the separation plate 124 contacts the adjustment plate 158, the fixing belt 102 is deformed inward, and the degree of deformation of the adjustment plate 158 causes the fixing belt 102 to be deformed. It is expected to vary depending on the force applied to the surface. In particular, when the fixing belt 102 is stretched in the radial direction in the sheet passing region, the variation is considered to be larger.

  On the other hand, in the fixing device 100 of the present embodiment, all are within the standard, and the average value is 0.49 mm which is close to the center of the standard. This is considered to be because when the positioning portion 120 is present as in the present embodiment, the variation in the degree of deformation inward of the fixing belt 102 is suppressed to be small compared to the conventional example. Therefore, the variation in the separation distance between the separation plate 124 and the surface of the fixing belt 102 can be further suppressed as compared with the conventional example, and the separation failure of the recording paper P due to the separation of the fixing belt 102 and the separation plate 124 is caused. The occurrence of flaws on the fixing belt due to the contact between the belt 102 and the peeling plate 124 can be further reduced.

  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.

  7A and 7B show the fixing device 160. FIG. The fixing device 160 is obtained by replacing the pressing pad 116 and the positioning unit 120 of the above-described fixing device 100 (see FIG. 2) with a pressing pad 162 and a positioning member 164. The pressing pad 162 is made of resin, and the pressing pad 162 and the positioning member 164 are configured separately. Further, the positioning member 164 is formed with a curved surface portion 164A having a curvature radius R1.

  The position of the positioning member 164 is set in advance so that the separation distance between the fixing belt 102 and the separation plate 124 becomes a necessary separation distance D = d5 when fixing by the fixing device 160 after the position of the separation plate 124 is adjusted. Note that the radius of curvature of the fixing belt 102 is R2, and R1 <R2.

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

  As shown in FIG. 7A, an adjustment plate 166 having a predetermined plate thickness is inserted between the fixing belt 102 and the peeling plate 124 in order to adjust the separation distance between the fixing belt 102 and the peeling plate 124. The surface of the belt 102 is contacted. When the adjustment plate 166 comes into contact with the fixing belt 102, the fixing belt 102 tends to be recessed inside, but is supported by the positioning member 164 so that the degree of deformation to the inside is larger than when the positioning member 164 is not present. Variations can be reduced. Thereby, the adjustment plate 166 is positioned.

  Subsequently, the peeling plate 124 is slid and moved in contact with the adjustment plate 166 and positioned. After the adjustment plate 166 and the release plate 124 come into contact with each other, the screw 128 (see FIG. 2) is fastened, and the release plate 124 is fixed. Then, the adjustment plate 166 is pulled out, and a gap of a predetermined distance is formed between the fixing belt 102 and the peeling plate 124.

  Subsequently, as shown in FIG. 7B, when the fixing operation is started and the fixing belt 102 is rotated and heated in the direction of the arrow D, the fixing belt 102 bends outward. Here, the radius of curvature R1 of the curved surface portion 164A is not changed, but the radius of curvature of the fixing belt 102 is further increased from R2, so that the fixing belt 102 is separated from the curved surface portion 164A and the distance between the positioning member 164 and the fixing belt 102 is reached. A gap d6 is formed.

  At this time, the separation distance between the fixing belt 102 and the separation plate 124 is d5, which is a necessary separation distance, so that the separation plate 124 does not contact the surface of the fixing belt 102. Further, when the recording paper P (see FIG. 2) is discharged from the nip portion 107, even if the recording paper P is likely to be wound around the surface of the fixing belt 102, the leading end contacts the leading end of the peeling plate 124 and is separated from the fixing belt 102. Therefore, the winding around the fixing belt 102 hardly occurs.

  Next, a third 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.

  FIG. 8 shows the fixing device 170. The fixing device 170 is provided with a retract mechanism unit 172 that contacts or separates the pressure roll 104 of the above-described fixing device 100 (see FIG. 2) from the fixing belt 102.

  The retract mechanism 172 is formed of a substantially U-shaped sheet metal, and includes an arm member 174 to which a bearing (not shown) that rotatably supports both ends of the pressure roll 104 is fixed. The arm member 174 is attached to a pair of side plates 176 provided upright at both ends of the pressure roll 104 inside the casing 106 (not shown) of the fixing device 170 by columnar support pins 178, and is in the direction of arrow R1. Is swingable.

  Bolts 180 are provided on the side surface of the side plate 176 substantially parallel to the side surface of the side plate 176. The front end of the bolt 180 is fastened to a hole 184 of a plate-like fixing portion 182 protruding from the side plate 176, and the rear end is bonded to an engaging portion (not shown) and fixed to the side plate 176. It is like that. Further, a plate-like urging portion 188 formed with a hole 186 having a size through which the bolt 180 can be inserted projects from the end of the arm member 174 opposite to the support pin 178.

  Here, the bolt 180 is inserted into the hole 186 of the urging portion 188, a spring 190 having a predetermined elastic force is externally inserted into the bolt 180, and the tip of the bolt 180 is fastened to the hole 184. Thus, the spring 190 is disposed between the fixing portion 182 and the biasing portion 188. Accordingly, when the arm member 174 is urged downward by the urging force of the spring 190, the pressure roll 104 is separated from the fixing belt 102.

  On the other hand, an eccentric cam 194 is provided in the vicinity of the arm member 174. The eccentric cam 194 swings in the arrow R2 direction about a substantially cylindrical support pin 192 as an axis. The eccentric cam 194 is provided with a gear portion 196 having a predetermined number of teeth. A drive gear 198 having a predetermined number of teeth meshes with the gear portion 196. The drive gear 198 swings the eccentric cam 194 by forward rotation (clockwise) and reverse rotation (counterclockwise) of the drive motor 200 driven by a power source (not shown).

  Here, when the drive motor 200 is turned forward and the drive gear 198 rotates in the forward direction, the eccentric cam 194 swings upward. As a result, the tip of the eccentric cam 194 comes into contact with the contact portion 202 of the arm member 174, swings the arm member 174 toward the fixing belt 102, and the pressure roll 104 contacts the fixing belt 102.

  Further, when the drive motor 200 is turned on in reverse and the drive gear 198 rotates in the reverse direction, the eccentric cam 194 swings downward. As a result, the eccentric cam 194 is separated from the contact portion 202 of the arm member 174, the arm member 174 is urged downward by the spring 190, and the pressure roll 104 is separated from the fixing belt 102.

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

  As shown in FIG. 9A, with the fixing belt 102 and the pressure roll 104 separated from each other and the fixing belt 102 and the release plate 124 separated from each other by a distance d7, the adjustment plate 204 having a predetermined plate thickness is fixed. It is inserted between the belt 102 and the peeling plate 124. Then, the adjustment plate 204 is brought into contact with the surface of the fixing belt 102. At this time, the fixing belt 102 tends to be recessed inward, but by being supported by the positioning portion 120, variation in the degree of inward deformation can be suppressed as compared with the case where the positioning portion 120 does not exist. Thereby, the adjustment plate 204 is positioned.

  Subsequently, as shown in FIG. 9B, the peeling plate 124 is slid in the direction of the arrow F and positioned in contact with the adjustment plate 204. After the adjustment plate 204 and the peeling plate 124 come into contact with each other, a screw 128 (see FIG. 2) is fastened to fix the peeling plate 124. Thereafter, the adjustment plate 204 is pulled out, and a gap of a predetermined separation distance is formed between the fixing belt 102 and the peeling plate 124.

  Subsequently, when the warm-up of the fixing device is started, the fixing belt 102 is rotated and heated while the fixing belt 102 and the pressure roll 104 are separated from each other. By warming up in a separated state, it is possible to further shorten the warm-up time.

  Subsequently, as shown in FIGS. 8 and 9C, the drive motor 200 of the retract mechanism 172 is turned forward, the drive gear 198 rotates in the forward direction, and the eccentric cam 194 swings upward. Move. As a result, the arm member 174 swings upward, and the pressure roll 104 comes into contact with the fixing belt 102. Here, the fixing belt 102 is deformed by being pressed by the pressure roll 104, and a gap of a distance d 9 is formed between the positioning unit 120 and the fixing belt 102, and the surface of the fixing belt 102 and the peeling plate 124 are formed. A gap having a necessary separation distance D is formed between the tips of the two. For this reason, the separation plate 124 does not contact the surface of the fixing belt 102. Further, when the recording paper P (see FIG. 2) is discharged from the nip portion 107, even if the recording paper P is likely to be wound around the surface of the fixing belt 102, the leading end comes into contact with the leading end of the peeling plate 124 and comes from the fixing belt 102. Since they are separated, the winding around the fixing belt 102 hardly occurs.

  Next, a fourth 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.

  FIG. 10A shows the fixing device 210. The fixing device 210 is provided with resin positioning portions 212 (212A, 212B, 212C) at equal intervals in the longitudinal direction of the pressing pad 116, instead of the positioning portion 120 in the fixing device 170 of the above-described third embodiment. ing. The positioning parts 212A and 212C are respectively arranged on the end side, and the positioning part 212B is arranged in the center part. The curvature radii of the curved surfaces of the positioning portions 212 </ b> A to 212 </ b> C are smaller than the curvature radius of the fixing belt 102.

  Further, two temperature sensors 118 (118A, 118B) are provided at predetermined intervals in the width direction (longitudinal direction) of the fixing belt 102, and the thermostat 129 is disposed between the temperature sensor 118A and the temperature sensor 118B. ing. Here, in the width direction of the fixing belt 102, the positioning positions of the positioning portions 212A, 212B, 212C, the temperature sensor 118A, the thermostat 129, and the temperature sensor 118B are A, B, C, D, E, and F, respectively.

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

  As shown in FIG. 10B, an adjustment plate 158 is inserted between the fixing belt 102 and the peeling plate 124 to adjust the separation distance between the fixing belt 102 and the peeling plate 124, and is placed on the surface of the fixing belt 102. Touched. When the adjustment plate 158 comes into contact with the fixing belt 102, the fixing belt 102 tends to be recessed inward, but is supported by the three positioning portions 212A, 212B, and 212C, so that the inner side is compared with the case where no positioning portion is present. The variation in the degree of deformation to is reduced. Thereby, the adjustment plate 158 is positioned.

  Moreover, since the positioning part 212 is provided in several places, compared with the case where the positioning part is partially provided one place, the inclination of the longitudinal direction of the adjustment board 158 is suppressed. As a result, when the peeling plate 124 is slid and brought into contact with the adjustment plate 158 and the peeling plate 124 is fixed, the fixing belt 102 and the peeling plate 124 are fixed at each longitudinal portion (both ends and central portion) of the fixing belt 102. Variation in the separation distance can be suppressed.

  Subsequently, when the fixing operation is started and the fixing belt 102 is rotated and heated, the fixing belt 102 bends outward, and the separation distance between the surface of the fixing belt 102 and the tip of the peeling plate 124 is the necessary separation distance. Become. At this time, the positioning portions 212A, 212B, and 212C are not in contact with the inner peripheral surface of the fixing belt 102.

  Here, in FIG. 11A, the positioning portions 212A to 212C are positioned as a fixing belt temperature graph (T1) in a non-contact state (this embodiment) with the inner peripheral surface of the fixing belt 102, and as a comparative example. A graph (T2) of the fixing belt temperature when the portions 212A to 212C are in contact with the inner peripheral surface of the fixing belt 102 is shown.

  In FIG. 11A, in the graph T2 in the contact state, a temperature drop is observed at the arrangement positions A, B, and C of the positioning portions 212A, 212B, and 212C. This is because the heat quantity of the fixing belt 102 is absorbed by the contact of the positioning portions 212A to 212C which are heat capacity members.

  On the other hand, in the graph T1 in the non-contact state, the temperature decrease is observed at the placement positions D, F, and E of the temperature sensors 118A and 118B and the thermostat 129, as in the graph T2, but the placement positions A, B, and C The temperature drop is smaller than the temperature drop in the graph T2, and the variation in temperature distribution in the entire fixing belt width direction is also smaller than that in the graph T2. In this manner, the positioning portions 212A to 212C are not in contact with the fixing belt 102, so that a decrease in fixing temperature is suppressed.

  FIG. 11B shows the fixing belt temperature graph (T1) of the present embodiment and, as a comparative example, positioning portions 212A and 212B on the upstream side of the same arrangement positions D and F as the temperature sensors 118A and 118B. A graph (T3) of the fixing belt temperature when placed in contact is shown.

  In FIG. 11B, in the graph T3, the temperature sensor 118A and the positioning unit 212A or the temperature sensor 118B and the positioning unit 212B are in contact with each other on the same inner circumference of the fixing belt 102. A temperature drop is observed.

  On the other hand, in the graph T1 in the non-contact state, although temperature drops are observed at the placement positions D, F, and E of the temperature sensors 118A and 118B and the thermostat 129, the positioning units 212A to 212C, the temperature sensors 118A and 118B, and the thermostat Since the arrangement position is different from that of 129, the temperature drop is small compared to the graph T3.

  Next, a fifth 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.

  FIG. 12A shows the fixing device 220. The fixing device 220 includes positioning portions 222A and 222B in place of the positioning portion 120 in the fixing device 170 of the third embodiment described above. Here, when the passing area of the recording sheet P of the fixing belt 102 is W2, and the non-passing areas (outside of W2) are W1 and W3, the positioning part 222A is the non-passing area W1, and the positioning part 222B is the non-passing area W3. Is arranged. The curvature radii of the curved surfaces of the positioning portions 222A and 222B are smaller than the curvature radii of the fixing belt 102.

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

  As shown in FIG. 12B, an adjustment plate 158 is inserted between the fixing belt 102 and the peeling plate 124 in order to adjust the separation distance between the fixing belt 102 and the peeling plate 124, and is placed on the surface of the fixing belt 102. Touched. When the adjusting plate 158 comes into contact with the fixing belt 102, the fixing belt 102 tends to be recessed inward, but is supported by the two positioning portions 222A and 222B, so that the fixing belt 102 is inward compared with the case where the positioning portion does not exist. Variations in the degree of deformation can be further reduced. Thereby, the adjustment plate 158 is positioned.

  Further, since the positioning portion 222 is provided at a plurality of locations (222A, 222B), the inclination of the adjustment plate 158 in the longitudinal direction can be suppressed as compared with the case where the positioning portion is partially provided at one location. As a result, when the peeling plate 124 is slid and brought into contact with the adjustment plate 158 and the peeling plate 124 is fixed, the fixing belt 102 and the peeling plate 124 are fixed at each longitudinal portion (both ends and central portion) of the fixing belt 102. Variation in the separation distance can be suppressed.

  Subsequently, when the fixing operation is started and the fixing belt 102 is rotated and heated, the fixing belt 102 bends outward, and the separation distance between the surface of the fixing belt 102 and the tip of the peeling plate 124 is the required separation distance. Become. At this time, even if the positioning portions 222A and 222B may come into contact with the inner circumferential surface of the fixing belt 102, the positioning portions 222A and 222B are outside the non-passing area of the recording paper P passing area W2 where fixing is performed. W1 and W3), the influence of the passing area W2 on the fixing temperature is smaller than when the positioning portion is inside the passing area W2.

  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. Further, a thermocouple may be used in place of the temperature sensor 118 as means for detecting the temperature of the fixing belt 102.

  The positioning unit 120 may be a single member that extends in the longitudinal direction of the fixing belt 102. In this case, it is necessary to dispose the fixing belt 102 and the positioning unit 120 in a non-contact state at the time of fixing.

  The cross-sectional shape of the positioning part 120 is not limited to an arc shape, and may be a polygonal shape. Further, when the adjustment plate 158 is brought into contact with the surface of the fixing belt 102, the positioning unit 120 does not necessarily need to be in contact with the inner peripheral surface of the fixing belt 102, and is slightly in the allowable adjustment range. And may be separated from each other.

  Further, the mounting position of the positioning portion 120 is not limited to the side surface 116A of the pressing pad 116, but, for example, a frame member is provided on the side surface of the support column 114 or the pressing pad according to the size and arrangement position of each member. You may make it attach to a frame member.

1 is an overall view of an image forming apparatus according to a first embodiment of the present invention. 1A is a cross-sectional view of a fixing device according to a first embodiment of the present invention. (B) It is a perspective view of the press member and positioning member which concern on 1st Embodiment of this invention. (A) It is sectional drawing of the fixing belt which concerns on 1st Embodiment of this invention. (B) It is a connection diagram of the control circuit and energization circuit concerning a 1st embodiment of the present invention. FIG. 2 is a block diagram illustrating a connection state of each unit including a control unit of the image forming apparatus according to the first embodiment of the present invention. It is process drawing which shows the adjustment procedure of the space | interval of the fixing belt and peeling plate which concerns on 1st Embodiment of this invention. (A) It is a bar graph which shows the distance data after adjustment of the fixing belt and peeling plate of a prior art example. (B) It is a bar graph which shows the distance data after adjustment of the fixing belt and peeling plate of the fixing device which concerns on 1st Embodiment of this invention. FIG. 6 is a partial cross-sectional view of a fixing device according to a second embodiment of the present invention. It is the block diagram which showed the retract mechanism part which concerns on 3rd Embodiment of this invention. It is process drawing which shows the adjustment procedure of the space | interval of the fixing belt and peeling plate which concerns on 3rd Embodiment of this invention. (A) It is an arrangement plan of positioning members etc. concerning a 4th embodiment of the present invention. (B) It is a fragmentary sectional view of the fixing device concerning a 4th embodiment of the present invention. 6 is a graph showing a relationship between a fixing belt width direction position and a fixing belt temperature in a fixing device according to a fourth embodiment of the present invention, together with a comparative example. (A) It is an arrangement plan of positioning members etc. concerning a 5th embodiment of the present invention. (B) It is a fragmentary sectional view of the fixing device concerning a 5th embodiment of the present invention.

Explanation of symbols

10 Printer (image forming device)
14 Optical scanning device (exposure unit)
22 Developer (Developer)
42 Secondary transfer section (transfer section)
60 Conveyor belt (conveyor)
100 Fixing device (fixing device)
102 Fixing belt (fixing rotating body)
104 Pressure roll (Pressure member)
116 Press pad (press member)
118 Temperature sensor (heat capacity body)
120 Positioning part (positioning member)
122A Curved surface (curved surface)
122B Curved surface (curved surface)
124 Peeling plate (peeling member)
129 Thermostat (heat capacity body)
160 Fixing device (fixing device)
164 Positioning member (positioning member)
164A Curved surface (curved surface)
170 Fixing device (fixing device)
172 Retract mechanism (contact / separation means)
210 Fixing device (fixing device)
220 Fixing device (fixing device)
P Recording paper (recording medium)
T Toner (Developer)

Claims (14)

An endless fixing rotator for heating the developer to fix it on the recording medium;
A pressure member that applies pressure to the outer peripheral surface of the fixing rotating body;
A pressing member that is provided inside the fixing rotator and presses the fixing rotator toward the pressure member;
A peeling member that is disposed to face the surface of the fixing rotator with a gap and peels the recording medium on which the developer is fixed from the fixing rotator;
A positioning member that is disposed opposite to the peeling member inside the fixing rotator and positions the peeling member;
A fixing device.   The fixing device according to claim 1, wherein the positioning member is provided at a position in contact with an inner peripheral surface of the fixing rotator when the fixing rotator is not rotated and heated. An endless fixing rotator for heating the developer to fix it on the recording medium;
A pressure member that applies pressure to the outer peripheral surface of the fixing rotating body;
A pressing member that is provided inside the fixing rotator and presses the fixing rotator toward the pressure member;
Contact / separation means for contacting / separating the fixing rotator and the pressure member;
A peeling member that is disposed to face the surface of the fixing rotator with a gap and peels the recording medium on which the developer is fixed from the fixing rotator;
A positioning member that is disposed opposite to the peeling member inside the fixing rotator and positions the peeling member;
A fixing device.   The positioning member is located at a position where the contact / separation means contacts the inner peripheral surface of the fixing rotator when the fixing rotator and the pressure member are separated and the fixing rotator is not rotated and heated. The fixing device according to claim 3, wherein the fixing device is provided.   5. The positioning device according to claim 1, wherein the positioning member is provided at a position that is not in contact with an inner peripheral surface of the fixing rotator when the fixing rotator is rotated. 6. Fixing device.   The fixing device according to claim 5, wherein the positioning member is provided at a position that is not in contact with an inner peripheral surface of the fixing rotator when the fixing rotator is heated.   The positioning member is provided at a position that is not in contact with the inner peripheral surface of the fixing rotator when the contacting / separating means contacts the fixing rotator and the pressure member. The fixing device according to any one of claims 3 to 6.   The fixing device according to claim 1, wherein the positioning member is provided on the pressing member.   The fixing device according to claim 1, wherein the positioning member and the pressing member are integrated.   10. The fixing device according to claim 1, wherein a plurality of the positioning members are provided at intervals in a longitudinal direction of the fixing rotating body.   When there is a heat capacity body that absorbs heat of the fixing rotator inside the fixing rotator, the positioning member is provided at a position different from the heat capacity body in the longitudinal direction of the fixing rotator. The fixing device according to claim 1, wherein the fixing device is a fixing device.   The fixing device according to claim 1, wherein the positioning member is provided outside a recording medium passage region of the fixing rotator.   The fixing device according to claim 1, wherein the positioning member has a curved surface having a smaller radius of curvature than a radius of curvature of an inner peripheral surface of the fixing rotating body. . A fixing device according to any one of claims 1 to 13,
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