JP6227097B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus that thermally adjusts the surface of a rotating body by bringing a belt member into contact with the rotating body, and more specifically, a plurality of supporting rotating bodies that stretch the belt member are rotated by forming a twist angle. The present invention relates to a structure for copying a belt member on a curved surface of a body.

  An image forming apparatus that transfers a toner image carried on an image carrier onto a recording material, and heats and presses the recording material onto which the toner image has been transferred by a fixing device, which is an example of an image heating device, to fix the image on the recording material. Widely used.

  In recent years, with the increase in image formation speed, an external heating mechanism for heating the fixing roller from the outside is being adopted. An image heating apparatus using a belt member as such an external heating mechanism has been proposed (Patent Documents 1 and 2).

  In the apparatus described in Patent Document 1, an external heating belt stretched around three support rollers is brought into contact with the outer peripheral surface of the fixing roller. In the apparatus described in Patent Document 2, an external heating belt stretched between two support rollers is brought into contact with the outer peripheral surface of the fixing roller.

JP 2004-198659 A JP 2007-2112896 A

  Incidentally, it is practically difficult to assemble and maintain the support rollers that stretch the external heating belt in parallel with high accuracy. However, if the parallelism between the support rollers is not ensured, the external heating belt may move in the width direction during running and may be displaced, and as a result, it may not run stably. Therefore, in order to stably run the external heating belt, steering control has been proposed in which one support roller is tilted with respect to another support roller to dynamically adjust the deviation of the external heating belt. However, in this case, if an excessive twist angle is formed between the plurality of support rollers, there is a possibility that a part of the region to be contacted by the external heating belt is separated from the fixing roller.

  An object of the present invention is to provide an image heating apparatus that can suppress an excessive twist angle between support rollers.

  An image heating apparatus according to the present invention includes a heating rotator that heats a toner image on a recording material, an endless belt member that contacts the heating rotator and heats the heating rotator, and an inner periphery of the belt member. A belt unit having a first support member and a second support member that rotatably support the belt member from the surface side and press the belt member toward the heating rotator, and a width direction orthogonal to the rotation direction of the belt member A detector that detects that the belt member is out of a predetermined range; and a rotation mechanism that rotates the belt unit in a direction to return the belt member to the predetermined range in response to detection by the detector. Along with the rotation of the belt unit by the rotation mechanism, the force by which the first support member presses the belt member toward the heating rotator is applied to both ends of the belt member in the width direction. The first support member is allowed to displace in a direction equal to the same, and the force by which the second support member presses the belt member toward the heating rotator is applied to both ends of the belt member in the width direction. A displacement mechanism that allows the second support member to displace in a direction that is equal to each other; and a limit mechanism that limits a displacement amount of the first support member and the second support member that the displacement mechanism allows to a predetermined amount; , Comprising.

  An image heating apparatus according to the present invention includes a heating rotator that heats a toner image on a recording material, an endless belt member that contacts the heating rotator and heats the heating rotator, and an inner periphery of the belt member. A belt unit having a first support member and a second support member that rotatably support the belt member from the surface side and press the belt member toward the heating rotator, and a width direction orthogonal to the rotation direction of the belt member A detector that detects that the belt member is out of a predetermined range; and a rotation mechanism that rotates the belt unit in a direction to return the belt member to the predetermined range in response to detection by the detector. As the belt unit is rotated by the rotation mechanism, the first support member and the second support member are arranged such that the rotation axes of the first support member and the second support member are in a twisted positional relationship. A displacement mechanism that allows the holding member to be displaced; and a restriction mechanism that limits a displacement amount of the first support member and the second support member allowed by the displacement mechanism to a predetermined amount. To do.

  In the image heating apparatus of the present invention, since the limiting mechanism limits the amount of displacement of the first support member and the second support member to a predetermined amount, an excessive twist angle is generated between the first support member and the second support member. Can be suppressed.

1 is an explanatory diagram of a configuration of an image forming apparatus. FIG. 3 is an explanatory diagram of a configuration of a fixing device according to the first exemplary embodiment. It is explanatory drawing of the contact-and-separation mechanism of an external heating belt. It is explanatory drawing of the rotation mechanism of a holding frame. It is explanatory drawing of the crossing angle of the bus of a fixing roller, and the bus of an external heating belt. It is explanatory drawing of the cancellation effect of the applied pressure difference by a twist angle. It is explanatory drawing of the steering mechanism of an external heating belt. It is explanatory drawing of the drive part of a steering mechanism. It is an enlarged view of the drive part of a steering mechanism. It is explanatory drawing of arrangement | positioning of a belt position detection sensor. It is explanatory drawing of the relationship between a belt shift direction and the rotation direction of a sensor flag. It is explanatory drawing of the fixing apparatus of a comparative example. It is explanatory drawing of arrangement | positioning of the control part in Example 1. FIG. It is explanatory drawing of operation | movement of a holding | maintenance frame. It is a perspective view of a control part. It is explanatory drawing of operation | movement of a control part. It is explanatory drawing of the relative rotation angle of a holding frame. It is explanatory drawing of the control angle of the relative rotation of a holding frame. It is explanatory drawing of the effect of Example 1. FIG. It is explanatory drawing of arrangement | positioning of the control part in Example 2. FIG. 6 is an explanatory diagram of the thermistor arrangement in Embodiment 2. FIG. It is explanatory drawing of the rotation stop structure of the sensor support shaft with respect to a holding frame. It is explanatory drawing at the time of relative rotation of a holding | maintenance frame. It is explanatory drawing of operation | movement of the control part in Example 2. FIG. It is explanatory drawing of the control part of Example 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
FIG. 1 is an explanatory diagram of the configuration of the image forming apparatus. As shown in FIG. 1, the image forming apparatus 100 is a tandem intermediate transfer type full color printer in which image forming portions Pa, Pb, Pc, and Pd of yellow, magenta, cyan, and black are arranged along an intermediate transfer belt 130. is there.

  In the image forming portion Pa, a yellow toner image is formed on the photosensitive drum 3 a and is primarily transferred to the intermediate transfer belt 130. In the image forming unit Pb, a magenta toner image is formed on the photosensitive drum 3 b and is primarily transferred to the intermediate transfer belt 130. In the image forming portions Pc and Pd, a cyan toner image and a black toner image are formed on the photosensitive drums 3c and 3d, respectively, and sequentially transferred onto the intermediate transfer belt 130.

  The recording material P is taken out from the recording material cassette 10 one by one and waits on the registration roller 12. The registration roller 12 feeds the recording material P to the secondary transfer portion T2 in time with the toner image on the intermediate transfer belt 130. The recording material P that has been transported through the secondary transfer portion T2 and secondarily transferred the four color toner images from the intermediate transfer belt 130 is transported to the fixing device 9 and is heated and pressed by the fixing device 9 to form a toner image. After fixing, the paper is discharged to a tray 7 outside the machine body.

  The image forming portions Pa, Pb, Pc, and Pd are configured substantially the same except that the color of toner used in the developing devices 1a, 1b, 1c, and 1d is different from yellow, magenta, cyan, and black. In the following, the image forming unit Pa will be described, and redundant description regarding the image forming units Pb, Pc, and Pd will be omitted.

  In the image forming portion Pa, a charging roller 2a, an exposure device 5a, a developing device 1a, a primary transfer roller 6a, and a drum cleaning device 4a are arranged around the photosensitive drum 3a. The photosensitive drum 3a has a photosensitive layer formed on the surface of an aluminum cylindrical material.

  The charging roller 2a charges the surface of the photosensitive drum 3a to a uniform potential. The exposure device 5a scans the laser beam and writes an electrostatic image of the image on the photosensitive drum 3a. The developing device 1a develops the electrostatic image and forms a toner image on the photosensitive drum 3a. The primary transfer roller 6 a is applied with a voltage to primarily transfer the toner image on the photosensitive drum 3 a to the intermediate transfer belt 130.

  The drum cleaning device 4a rubs the photosensitive drum 3a with a cleaning blade to collect the transfer residual toner attached to the photosensitive drum 3a by escaping from the transfer to the intermediate transfer belt 130. The belt cleaning device 15 collects the transfer residual toner attached to the intermediate transfer belt 130 by escaping from the transfer to the recording material at the secondary transfer portion T2.

<Example 1>
As shown in FIG. 2, the fixing roller 101, which is an example of a heating rotator, rotates in contact with the recording material and can heat the toner image on the recording material. An external heating belt 105, which is an example of an endless belt member, rotates in contact with the fixing roller 101 in order to perform thermal adjustment of the fixing roller 101. A first support roller 103, which is an example of a first support member, and a second support roller 104, which is an example of a second support member, are rotatably supported from the inner peripheral surface side so as to stretch the external heating belt 105. The thermistor 123 contacts the external heating belt 105 and detects the temperature.

  As shown in FIG. 3, the holding frame 206a, which is an example of a first holding member (which is also a part of a displacement mechanism described later), has end portions (one end) on one end side of the first support roller 103 and the second support roller 104. Each part) is swingably held. A holding frame 206b, which is an example of a second holding member (which is also a part of a displacement mechanism described later), swings the other end portion (the other end portion) of the first support roller 103 and the second support roller 104, respectively. Hold freely. An intermediate frame 208, which is an example of a displacement mechanism (twist mechanism), can relatively rotate the holding frame 206a and the holding frame 206b so as to form a twist angle in the first support roller 103 and the second support roller 104. To support.

  As shown in FIG. 7, the worm wheel 118, which is an example of a rotation mechanism, controls the lateral movement of the external heating belt 105 along the first support roller 103 and the second support roller 104. The worm wheel 118 rotates the intermediate frame 208 so as to form an intersection angle between the bus of the external heating belt 105 and the bus of the fixing roller 101. Photointerrupters 133 and 134, which are examples of detectors, are positioned in the width direction of the external heating belt 105 along the first support roller 103 and the second support roller 104 (direction perpendicular to the rotation direction of the external heating belt 105). Detect (shift position). The control unit 140 that is also a part of the rotation mechanism described above operates the worm wheel 118 based on the detection outputs of the photo interrupters 133 and 134 to control the lateral movement of the external heating belt 105.

  As shown in FIG. 15, the restriction portions 300A and 300B, which are examples of the restriction mechanism, restrict the maximum relative rotation angle (displacement amount) between the holding frame 206a and the holding frame 206b to a predetermined angle (predetermined amount) and beyond. It can function as a stopper that disables relative rotation of the lens. As shown in FIG. 18, the predetermined angle (γ) is larger than the maximum relative rotation angle (βmax) of the holding frame 206a and the holding frame 206b that is generated in accordance with the control of the lateral movement of the external heating belt 105.

  As shown in FIG. 15, the bent portion 301a, which is an example of the first contact portion, extends along the first support roller 103 and the second support roller 104 from the holding frame 206a toward the holding frame 206b. The flat surface portion 302a, which is an example of the second contact portion, extends along the first support roller 103 and the second support roller 104 from the holding frame 206b toward the holding frame 206a. The bent portion 301a and the flat portion 302a are in a positional relationship that overlaps with the relative rotation of the holding frame 206a and the holding frame 206b. The bent portions 301a and 301b and the flat portions 302a and 302b are arranged one by one at a distance in the stretching direction of the external heating belt 105.

  As shown in FIG. 14, a plate spring 123m, which is an example of a first urging member, has a thermistor 123a as a first temperature detecting means fixed to one end and the other end fixed to a holding frame 206a. The thermistor 123a is caused to follow the external heating belt 105 by the deformation. A plate spring 123n, which is an example of a second urging member, has a thermistor 123b as a second temperature detecting means fixed to one end and the other end fixed to a holding frame 206b. The thermistor 123b is fixed by a cantilever elastic deformation. Contact with the external heating belt 105. The predetermined angle (γ) is smaller than the maximum relative rotation angle of the holding frame 206a and the holding frame 206b that can cause the thermistors 123a and 123b to follow the external heating belt 105 by cantilever elastic deformation of the leaf springs 123m and 123n. .

(Fixing device)
FIG. 2 is an explanatory diagram of a configuration of the fixing device according to the first exemplary embodiment. As shown in FIG. 2, the fixing device 9 presses the pressure roller 102 against the fixing roller 101 to form a nip portion N of the recording material. The nip portion N sandwiches and conveys the recording material P carrying the unfixed toner K, melts the toner, and fixes the image on the recording material P.

  In the fixing roller 101, an elastic layer 101b is disposed on the outer peripheral surface of a cored bar 101a, and the surface of the elastic layer 101b is covered with a release layer 101c. The fixing roller 101 is driven by a driving mechanism 141 including a gear train (not shown), and rotates in the direction of arrow A at a process speed of 300 mm / sec.

  In the pressure roller 102, an elastic layer 102b is disposed on the outer peripheral surface of the cored bar 102a, and the surface of the elastic layer 102b is covered with a release layer 102c. The pressure roller 102 is driven by the drive mechanism 141 and rotates in the arrow B direction. The pressure roller 102 is driven by a pressure mechanism (not shown) using an eccentric cam and is brought into contact with and separated from the fixing roller 101. A pressure mechanism (not shown) presses the pressure roller 102 to the fixing roller 101 with a predetermined pressure, and forms a nip portion N between the fixing roller 101 and the pressure roller 102.

  The halogen heater 111 is non-rotatably disposed inside the cored bar 101 a of the fixing roller 101. The thermistor 121 is disposed in contact with the fixing roller 101 and detects the surface temperature of the fixing roller 101. The control unit 140 performs ON / OFF control of the halogen heater 111 according to the temperature detected by the thermistor 121 to maintain the surface temperature of the fixing roller 101 at a predetermined target temperature corresponding to the type of recording material.

  The halogen heater 112 is disposed in a non-rotating manner inside the cored bar 102 a of the pressure roller 102. The thermistor 122 is disposed in contact with the pressure roller 102 and detects the surface temperature of the pressure roller 102. The control unit 140 controls ON / OFF of the halogen heater 112 according to the temperature detected by the thermistor 122, and maintains the surface temperature of the pressure roller 102 at a predetermined target temperature.

(External heating belt)
As shown in FIG. 2, the image forming apparatus is required to have high productivity (number of printed sheets per unit time) even for a recording material having a large basis weight (weight per unit area) such as cardboard. In order to increase productivity with a recording material having a large basis weight, it is necessary to speed up the heat treatment in the fixing device 9. However, since a recording material having a large basis weight takes away a lot of heat, the amount of heat required for fixing becomes larger than that of a recording material having a low basis weight. Therefore, the fixing device 9 is arranged so that the external heating belt 105 can be brought into contact with / separated from the fixing roller 101. The external heating belt 105 increases the contact area for conducting heat from the first support roller 103 and the second support roller 104 to the fixing roller 101, and increases the heating efficiency of the fixing roller 101.

  The external heating belt 105 abuts on the outer peripheral surface of the fixing roller 101 to form a nip portion Ne and heats the fixing roller 101 externally. The external heating belt 105 has a base layer made of metal such as stainless steel or nickel, or a base layer made of resin such as polyimide. The surface of the base layer is covered with a heat-resistant sliding layer using a fluorine-based resin in order to prevent toner adhesion. The external heating belt 105 is frictionally driven with the rotation of the fixing roller 101 and is driven to rotate in the direction of arrow C.

  The first support roller 103 is made of a metal having high thermal conductivity such as aluminum, iron, and stainless steel. A halogen heater 113 is disposed non-rotatingly through the center of the first support roller 103. The thermistor 123 is in contact with the external heating belt 105 supported by the first support roller 103 and detects the temperature. The control unit 140 controls ON / OFF of the halogen heater 113 according to the temperature detected by the thermistor 123, and maintains the temperature of the first support roller 103 at a predetermined target temperature.

  The second support roller 104 is formed of a metal having high thermal conductivity such as aluminum, iron, and stainless steel. The halogen heater 114 is disposed non-rotatingly through the center of the second support roller 104. The thermistor 124 is in contact with the external heating belt 105 supported by the second support roller 104 and detects the temperature. The control unit 140 controls ON / OFF of the halogen heater 114 according to the temperature detected by the thermistor 124, and maintains the temperature of the second support roller 104 at a predetermined target temperature.

  The target temperature for temperature adjustment of the first support roller 103 and the second support roller 104 is set higher than the target temperature for temperature adjustment of the fixing roller 101. If the surface temperature of the first support roller 103 and the second support roller 104 is kept higher than the surface temperature of the fixing roller 101, heat can be supplied efficiently with respect to a decrease in the surface temperature of the fixing roller 101. It is. During continuous image formation of thick paper, the target temperature of the first support roller 103 and the second support roller 104 is set to 230 ° C. with respect to the target temperature of 165 ° C. of the fixing roller 101. The surface temperatures of the first support roller 103 and the second support roller 104 are kept 75 ° C. higher than the surface temperature of the fixing roller 101.

  The surface layer of the external heating belt 105 becomes dirty due to adhesion of foreign matters such as toner and paper powder transferred (offset) from the recording material. The cleaning roller 108 adsorbs foreign matters such as toner and paper dust to a silicon rubber layer provided on the surface. The cleaning roller 108 is pressed by the external heating belt 105 with a predetermined pressure and is rotated to clean the surface of the external heating belt 105.

  The fixing device 9 waits for the next image forming job in a state where the external heating belt 105 is separated from the fixing roller 101. When an image forming job is transmitted to the image forming apparatus, a preparation operation is started in each device in the image forming apparatus, and a heating operation is started in the fixing device 9. When the fixing roller 101, the pressure roller 102, and the external heating belt 105 reach their target temperatures in the heating operation, the external heating belt 105 is pressed against the fixing roller 101 and an image forming job is started. Thereafter, when the image forming job is completed, the external heating belt 105 is separated from the fixing roller 101 and is held until the next image forming start.

(Torsion angle of support roller)
FIG. 3 is an explanatory diagram of an external heating belt contact / separation mechanism. FIG. 4 is an explanatory view of a holding frame turning mechanism. FIG. 5 is an explanatory diagram of the crossing angle between the bus of the fixing roller and the bus of the external heating belt. FIG. 6 is an explanatory diagram of the effect of canceling the pressure difference due to the twist angle.

  As shown in FIG. 3, the external heating unit 150 as a belt unit stretches and stretches the external heating belt 105 between the first support roller 103 and the second support roller 104. Since the external heating belt 105 is rotatably supported by the first support roller 103 and the second support roller 104, it rotates following the rotation of the fixing roller 101.

  The external heating belt 105 can be brought into contact with / separated from the fixing roller 101 by the contact / separation mechanism 200. The contact / separation mechanism 200 also serves as a pressure contact mechanism that presses the first support roller 103 and the second support roller 104 against the fixing roller 101 via the external heating belt 105. The pressure frame 201 is rotatable with respect to the housing frame 9 f of the fixing device 9 about the support shaft 203.

  A pressure spring 204 is disposed between the rotating end of the pressure frame 201 and the housing frame 9 f of the fixing device 9. The pressure spring 204 pushes down the rotation end of the pressure frame 201 and biases the intermediate frame 208 toward the fixing roller 101. The intermediate frame 208 is rotatably supported with respect to the pressurizing frame 201 by a pair of intermediate rollers 210 disposed on the front side and the back side. In a state where the first support roller 103 and the second support roller 104 are in pressure contact with the fixing roller 101 via the external heating belt 105, the pressure spring 204 causes the first support roller 103 and the second support roller 104 to have a total pressure of 392N ( Pressurize at about 40 kgf).

  The pressure release cam 205 is in contact with the lower surface of the rotating end of the pressure frame 201. The control unit 140 controls the motor 211 to rotate the pressure release cam 205 about the rotation shaft 205a, thereby moving the rotation end of the pressure frame 201 up and down. When the pressure release cam 205 is separated from the pressure frame 201, the pressure spring 204 pushes down the rotating end of the pressure frame 201 and presses the external heating belt 105 against the fixing roller 101. When the pressure release cam 205 contracts the pressure spring 204 and pushes up the pressure frame 201, the external heating belt 105 is separated from the fixing roller 101.

  As shown in FIG. 4, the front ends of the first support roller 103 and the second support roller 104 are supported by the holding frame 206a. The front holding frame 206a is swingably supported by the intermediate frame 208 by support shafts 207a and 207b. The holding frame 206a rotatably supports the front end portions of the first support roller 103 and the second support roller 104 via a heat insulating bush and a bearing (not shown). One end of the first support roller 103 and the second support roller 104 is rotatably supported by a bearing (not shown) fixed to the holding frame 206a.

  The inner ends of the first support roller 103 and the second support roller 104 are supported by the holding frame 206b. The rear holding frame 206b is swingably supported by the intermediate frame 208 by support shafts 207c and 207d. The holding frame 206b rotatably supports end portions of the first support roller 103 and the second support roller 104 via a heat insulating bush and a bearing (not shown). The other ends of the first support roller 103 and the second support roller 104 are rotatably supported by a bearing (not shown) fixed to the holding frame 206b. As shown in FIG. 4, the support shafts 207a to 207d are located on a common axis. That is, the holding frame 206a and the holding frame 206b can swing around a common axis.

  As shown in FIG. 4, pressure springs 204 a and 204 b are disposed at both ends of the pressure frame 201 in the longitudinal direction. The pressure spring 204 brings the external heating belt 105 into contact with the outer peripheral surface of the fixing roller 101 with a predetermined pressure via the first support roller 103 and the second support roller 104. A straight line connecting the support shafts 207a, 207b, 207c, and 207d and the center of the fixing roller 101 is a straight line connecting the centers of the first support roller 103 and the second support roller 104 with the external heating belt 105 in close contact with the fixing roller 101. This is a vertical bisector.

  As shown in FIG. 5, when the bus of the external heating belt 105 and the bus of the fixing roller 101 have an intersection angle θ, one of the first support roller 103 and the second support roller 104 precedes at the end on the back side. Then, pressurization of the fixing roller 101 is started. At the same time, at the end on the near side, the other of the first support roller 103 and the second support roller 104 starts to press the fixing roller 101 in advance. One end of the first support roller 103 (second support roller 104) in the longitudinal direction bites into the fixing roller 101, and the other end separates from the fixing roller 101. For this reason, the distribution of the nip pressure between the fixing roller 101 and the external heating belt 105 in the longitudinal direction of the fixing roller 101 becomes non-uniform.

  As shown in FIG. 6 (a), the pressure difference between the first support roller 103 and the second support roller 104 causes the front holding frame 206a and the rear holding frame 206b to autonomously rotate. The pressure difference between the first support roller 103 and the second support roller 104 is canceled out. The holding frame 206a on the near side and the holding frame 206b on the back side rotate relative to each other, and the first support roller 103 and the second support roller 104 are positioned at a twisted position corresponding to the curved surface of the fixing roller 101. Since the relative twist angle between the first support roller 103 and the second support roller 104 is free, the postures of the first support roller 103 and the second support roller 104 are autonomously moved to the twist position corresponding to the curved surface of the fixing roller 101. The external heating belt 105 comes into close contact with the fixing roller 101.

  As shown in FIG. 6B, on the front side, the holding frame (206a) rotates about the support shafts 207a and 207b to cancel the pressure difference between the first support roller 103 and the second support roller 104. . As shown in FIG. 6C, on the back side, the holding frame (206b) rotates about the support shafts 207c and 207d to cancel the pressure difference between the first support roller 103 and the second support roller 104. . That is, the holding frame (206a) and the holding frame (206b) swing in opposite directions around a common axis. For this reason, the distribution of the nip pressure between the fixing roller 101 and the external heating belt 105 when the crossing angle θ is changed in accordance with the control of the lateral movement of the external heating belt 105 becomes uniform.

  As a result of both the first support roller 103 and the second support roller 104 being evenly pressed against the fixing roller 101, the first support roller 103 and the second support roller 104 are passed through the external heating belt 105 on the front side and the back side. Thus, sufficient external heating is performed on the fixing roller 101.

(Steering mechanism)
FIG. 7 is an explanatory view of the steering mechanism of the external heating belt. FIG. 8 is an explanatory diagram of a drive unit of the steering mechanism. FIG. 9 is an enlarged view of the drive unit of the steering mechanism.

  As shown in FIG. 2, the fixing device 9 rotates the external heating unit 150 while keeping the positional relationship between the first support roller 103 and the second support roller 104 constant, and the first support roller 103 and the second support roller. The lateral movement of the external heating belt 105 along 104 is controlled.

  As shown in FIG. 5, when the external heating belt 105 and the fixing roller 101 come into contact with each other at an intersecting angle θ, the first support roller 103 and the second support roller with respect to the external heating belt 105 are rotated by the rotation of the fixing roller 101. A shifting force along 104 is generated. Using this principle, the fixing device 9 intentionally changes the crossing angle θ to forcibly set the direction of the lateral movement of the external heating belt 105.

  The external heating belt 105 moves along the first support roller 103 and the second support roller 104 during the rotation operation. The cause of the shift is the shift in parallelism between the first support roller 103 and the second support roller 104, the above-described crossing angle θ, and the like.

  As shown in FIG. 7, a rotation shaft 209 is arranged in the normal direction to the contact surface where the fixing roller 101 and the external heating belt 105 are in contact with each other. The rotation shaft 209 is a rotation center that changes the intersection angle θ between the external heating belt 105 and the fixing roller 101. Since the rotation shaft 209 is disposed at the center of the external heating unit 150, the nip pressure balance between the front side and the back side in the longitudinal direction of the fixing roller 101 is stabilized.

  The controller 140 integrally tilts the first support roller 103 and the second support roller 104 about the rotation shaft 209 to change the intersection angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101. Thus, the direction of the external heating belt 105 is controlled. The controller 140 forcibly changes the crossing angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101 from the outside, reverses the shift of the external heating belt 105, and shifts the external heating belt 105. Keep the range within the predetermined range.

  Both ends of the support shaft 203 of the pressure frame 201 are fixed to the main body side plate 202. The intermediate frame 208 and the external heating belt 105 can be integrally rotated with respect to the pressure frame 201 around the rotation shaft 209. The support shaft 207a fixed to the intermediate frame 208 is held with a clearance with the main body side plate 202, and can move in the directions of arrows H and J within the clearance range as the arm portion 118a moves.

  A fan-shaped worm wheel 118 that can rotate around the rotation shaft 119 meshes with the worm gear 120. When the motor 125 rotates in the forward direction and the worm wheel 118 rotates in the arrow G direction, the arm portion 118a moves in the arrow H direction and moves the support shaft 207a in the arrow H direction. When the motor 125 rotates in the reverse direction and the worm wheel 118 rotates in the direction of arrow I, the arm portion 118a moves in the direction of arrow J and moves the support shaft 207a in the direction of arrow J (see FIGS. 7 and 8). .

  When the near side of the intermediate frame 208 moves in the direction of arrow H or J, the first support roller 103 and the second support roller 104 rotate around the rotation shaft 209, and the fixing roller 101 and the first support roller 103 An intersection angle θ is set between the second support rollers 104. There is a relationship between the crossing angle θ between the fixing roller 101 and the external heating belt 105 and the shifting speed of the external heating belt 105. The shifting force of the external heating belt 105 changes according to the amount of movement of the arm portion 118a, and the direction and shifting speed of the external heating belt 105 along the first support roller 103 and the second support roller 104 are controlled. .

  When the support shaft 207a moves in the H direction from the point of zero offset force, the offset force that moves the external heating belt 105 to the back side (in the arrow M direction) of the fixing roller 101 increases. When the support shaft 207a moves in the J direction from the point of zero offset force, the offset force that moves the external heating belt 105 toward the front side (arrow L direction) of the fixing roller 101 increases. Thus, by moving the support shaft 207a in the directions of arrows H and J, the direction in which the external heating belt 105 approaches can be controlled in the directions of arrows M and L.

  In the present embodiment, the support shaft 207 a is fixed by the worm wheel 118 with the position where the external heating unit 150 is mounted so as to be parallel to the fixing roller 101 as the home position. The home position is detected by the photo interrupter 135 attached to the worm wheel 118.

  When the fixing roller 101 rotates, the external heating belt 105 is driven to rotate, and the external heating belt 105 approaches either the front side or the back side in the longitudinal direction. The controller 140 shifts the position of the support shaft 207a so that a force is applied in a direction opposite to the direction in which the external heating belt 105 approaches.

(Belt position detection sensor)
FIG. 10 is an explanatory diagram of the arrangement of the belt position detection sensor. FIG. 11 is an explanatory diagram of the relationship between the belt shift direction and the rotation direction of the sensor flag. As shown in FIG. 10B, the arm 129 and the roller 128 rotate together around the rotation axis 136. The sensor flag 132 rotates around the rotation shaft 137.

  As shown in FIG. 10A, the arm 129 and the sensor flag 132 are engaged by a link portion 138 to transmit rotation. The roller 128 is in contact with the belt edge of the external heating belt 105. The torsion spring 131 applies torque to the arm 129 to urge the roller 128 in the direction of arrow Q.

  Therefore, as shown in FIG. 10B, when the external heating belt 105 is moved in the arrow Q direction, the link portion 138 is moved in the arrow W direction. When the external heating belt 105 approaches the arrow R direction, the link portion 138 moves in the arrow O direction.

  As shown in FIG. 11A, photointerrupters 133 and 134 are arranged along the sensor flag 132. The photo interrupters 133 and 134 detect the four edges of the two slits formed in the sensor flag 132 and invert the outputs. Corresponding positions of the external heating belt 105 are defined in correspondence with the four edges of the sensor flag 132. As an example, the photo interrupters 133 and 134 are arranged so that the external heating belt 105 repeats the shifting with an amplitude of 5 mm. When the external heating belt 105 approaches the arrow R direction, the arm 129 rotates in the arrow S direction, the sensor flag 132 rotates in the arrow T direction, the photo interrupter 133 is turned off, and the photo interrupter 134 is turned on.

  As shown in FIG. 11B, when the external heating belt 105 approaches the arrow Q direction, the arm 129 rotates in the arrow U direction, the sensor flag 132 rotates in the arrow V direction, and the photo interrupter 133 is turned on. Then, the photo interrupter 134 is turned off.

(Comparative example)
FIG. 12 is an explanatory diagram of a fixing device of a comparative example.

  As shown in FIG. 7, the external heating unit 150 supplies the amount of heat directly to the surface of the fixing roller 101 by bringing the external heating belt 105 into contact therewith. The external heating unit 150 controls the shift of the external heating belt 105 by rotating around the rotation shaft 209 and changing the crossing angle θ between the bus of the external heating belt 105 and the bus of the fixing roller 101. In addition, the holding frames 206a and 206b rotate relative to the support shafts 207a, 207b, 207c, and 207d as the external heating belt 105 moves, and the first support roller 103 and the second support roller 104 A twist angle is formed between the two. Thereby, the nip pressure distribution with the fixing roller 101 along the first support roller 103 and the second support roller 104 is made uniform on the front side and the back side in the longitudinal direction.

  Here, in the case where the twist angle of the first support roller 103 and the second support roller 104 can be set to be unlimited, the twist angle is increased when the external heating unit 150 is assembled or when the external heating unit 150 is lifted alone. It can be excessive.

  As shown in FIG. 12A, the surface temperature of the external heating belt 105 is detected by a thermistor 123 (123a, 123b) that contacts the contact area between the first support roller 103 and the external heating belt 105. And when the twist angle between the first support roller 103 and the second support roller 104 becomes excessive, the distance between the thermistors 123a, 123b and the external heating belt 105 becomes closer than expected when it occurs during control, To leave.

  As shown in FIG. 12B, the effect is particularly great with respect to the thermistor 123a arranged near the center in the longitudinal direction in order to detect the temperature at the center of the external heating belt 105. If the leaf spring 123m that supports the thermistor 123a is plastically deformed in accordance with the torsion angle between the first support roller 103 and the second support roller 104, the thermistor 123a may not contact the surface of the external heating belt 105.

  Therefore, in the following embodiment, a limiter is provided at the twist angle between the first support roller 103 and the second support roller 104 to solve the problem of the comparative example. The limiter regulates the twist angle between the first support roller 103 and the second support roller 104, so that the displacement amount of the plate spring 123m of the thermistor 123a that detects the surface temperature of the external heating belt 105 by contacting the external heating belt 105 is reduced. It is reduced.

  FIG. 13 is an explanatory diagram of the arrangement of the restricting portions in the first embodiment. FIG. 14 is an explanatory diagram of the operation of the holding frame. FIG. 15 is a perspective view of the restricting portion. FIG. 16 is an explanatory diagram of the operation of the restricting unit.

  As shown in FIG. 13, the external heating unit 150 is divided into an upper portion 150U and a lower portion 150D. The upper portion 150U rotates the intermediate frame 208 around the rotation shaft 209 with respect to the pressure frame 201. The lower portion 150D is supported by being rotatably suspended by shafts 207a, 207b, 207c, and 207d installed on the intermediate frame 208. The lower portion 150D rotatably supports one end portions of the first support roller 103 and the second support roller 104 by the holding frame 206a, and the other end portion of the first support roller 103 and the second support roller 104 by the holding frame 206b. Support for rotation.

  As shown in FIG. 14, the lower portion 150D rotates the holding frame 206a and the holding frame 206b relatively to twist the holding frame 206a and the holding frame 206b. Thereby, a torsion angle is set between the first support roller 103 and the second support roller 104, and the pressure distribution in the nip portion with the fixing roller 101 in the longitudinal direction of the external heating belt 105 is set as shown in FIG. Will be leveled evenly autonomously.

  As shown in FIG. 13, restricting portions 300A and 300B are formed on the holding frames 206a and 206b. The restricting portions 300A and 300B restrict the torsion angle (displacement amount) between the first support roller 103 and the second support roller 104 by restricting the relative rotation angle of the holding frame 206a and the holding frame 206b.

  As shown in FIG. 15, the holding frame 206a is formed with two bent portions 301a and 301b bent in two stages at the center end portion with the shaft 207b interposed therebetween. The holding frame 206b is formed with two flat portions 302a and 302b protruding from the central end portion with the shaft 207c interposed therebetween. In the restricting portion 300A, the bent portion 301a formed on the holding frame 206a extends to above the flat portion 302a formed on the holding frame 206b, and the bent portion 301a and the flat portion 302a overlap in the longitudinal direction. In the restricting portion 300B, the bent portion 301b formed on the holding frame 206a extends to above the flat portion 302b formed on the holding frame 206b, and the bent portion 301b and the flat portion 302b overlap in the longitudinal direction.

  As shown in FIG. 16A, when the holding frame 206b rotates relative to the holding frame 206a in the direction of arrow A, the flat portion 302b of the holding frame 206b comes into contact with the bent portion 301b of the holding frame 206a. The above relative rotation is restricted.

  As shown in FIG. 16B, when the holding frame 206b rotates relative to the holding frame 206a in the direction of the arrow B, the flat portion 302a of the holding frame 206b comes into contact with the bent portion 301a of the holding frame 206a. The above relative rotation is restricted.

  In this way, the bent portions 301a and 301b formed on the holding frame 206a and the flat portions 302a and 302b formed on the holding frame 206b are in contact with each other, so that the gap between the first support roller 103 and the second support roller 104 is between them. An excessive twist angle is not generated.

(Relative rotation angle of holding frame)
FIG. 17 is an explanatory diagram of the relative rotation angle of the holding frame. FIG. 18 is an explanatory diagram of a restriction angle of the relative rotation of the holding frame. FIG. 19 is an explanatory diagram of the effect of the first embodiment.

  As shown in FIG. 17A, the first support roller 103 and the second support roller 104 are changed by changing the crossing angle of the bus of the external heating belt 105 with respect to the bus of the fixing roller 101 around the rotation shaft 209. The lateral movement of the external heating belt 105 along the axis is controlled. Let α be the crossing angle of the fixing roller 101 and the external heating belt 105 in the control of the lateral movement of the external heating belt 105. The intersection angle α is controlled in accordance with a change in the shifting speed of the external heating belt 105, a change in the shifting position, and the like. The intersection angle α is set to be equal to or less than a certain upper limit value, and an error message is displayed when the shift cannot be controlled even with the upper limit value. In the first embodiment, the upper limit value αmax of the intersection angle α is set to 2 degrees.

  As shown in FIG. 17B, when the crossing angle α between the external heating belt 105 and the fixing roller 101 is changed, the first support roller 103 and the second support roller 104 that stretch the external heating belt 105 are mutually connected. The rotational axis of is the torsional positional relationship. Accordingly, the relative rotation angle formed by the holding frame 206a and the holding frame 206b is β. The relative rotation angle β between the holding frame 206a and the holding frame 206b when the crossing angle of the bus of the external heating belt 105 with respect to the bus of the fixing roller 101 is the upper limit αmax is set to the upper limit βmax. In the first embodiment, the upper limit value βmax is set to 6 degrees.

As shown in FIG. 18, the relative rotation angle between the holding frame 206a and the holding frame 206b, which is regulated by contact between the bent portion 301b of the holding frame 206a and the flat portion 302b of the holding frame 206b, is γ. In Example 1, the relationship between the relative rotation angle γ and the upper limit value βmax was set as follows.
γ ≧ βmax

  Since the angle γ varies depending on the component tolerance, it is desirable to design with γ> βmax as a design value. When the relative rotation angle γ is smaller than the upper limit value βmax, the twist angles of the first support roller 103 and the second support roller 104 are insufficient when the lateral movement of the external heating belt 105 is controlled, and the external heating belt 105 and the fixing roller 101 are moved. The nip pressure distribution in the longitudinal direction becomes non-uniform.

  In Example 1, the angle γ was set to 8 degrees, which is larger than the upper limit value βmax of 6 degrees. For this reason, when the lateral movement of the external heating belt 105 is controlled, the longitudinal nip pressure distribution between the external heating belt 105 and the fixing roller 101 is not affected. When the external heating belt 105 is assembled or when the external heating unit 150 is lifted alone, the first support roller 103 and the second support roller 104 that suspend the external heating belt 105 are not greatly twisted.

  As shown in FIG. 19A, in Comparative Example 1, since the distance between the external heating belt 105 and the thermistor 123a is large as the first support roller 103 is twisted, the leaf spring 123m is bent and plastically deformed. there's a possibility that. As shown in FIG. 19B, in Example 1, since the change in the distance between the external heating belt 105 and the thermistor 123a is restricted to a small extent as the first support roller 103 is twisted, the leaf spring 123m is bent. Therefore, plastic deformation is not necessary.

  According to the first embodiment, when the crossing angle θ between the fixing roller 101 and the external heating belt 105 is changed to control the shift of the external heating belt 105, the required relative rotation angle between the holding frame 206a and the holding frame 206b is set. Sufficiently secured. The distribution of the nip pressure with the fixing roller in the longitudinal direction of the external heating belt 105 can be kept uniform without affecting the control of the lateral movement of the external heating belt 105. In addition, the relative rotation angle between the holding frame 206a and the holding frame 206b is regulated so that the torsion angles of the first support roller 103 and the second support roller 104 are within an allowable range, so that the displacement of the plate spring 123m of the thermistor 123a The amount is reduced.

  According to the first embodiment, when the external heating belt 105 is replaced or when the external heating unit 150 is lifted up alone, the first support roller 103 and the second support roller 104 do not have to be greatly twisted.

  In the first embodiment, the rotation shaft 209 is provided in the external heating unit 150 and the crossing angle with the fixing roller 101 is changed to control the shift of the external heating belt 105. The first support roller 103 that stretches the external heating belt 105 and the holding frames 206 a and 206 b that hold the ends of the second support roller 104 are twisted.

  However, since the twist is restricted by an angle larger than the maximum value of the twist angle used in the shift control, the temperature is detected by contacting the surface of the external heating belt 105 without affecting the shift control of the external heating belt 105. The amount of displacement of the thermistor 123a can be regulated. For this reason, when the external heating belt 105 is assembled, the first support roller 103 and the second support roller 104 are not greatly twisted, and the thermistor 123a that contacts the surface of the external heating belt 105 and detects the temperature is not greatly displaced. .

<Example 2>
FIG. 20 is an explanatory diagram of the arrangement of the restricting portions in the second embodiment. FIG. 21 is an explanatory diagram of the thermistor arrangement in the second embodiment. FIG. 22 is an explanatory diagram of a structure for preventing rotation of the sensor support shaft with respect to the holding frame. FIG. 23 is an explanatory view at the time of relative rotation of the holding frame. FIG. 24 is an explanatory diagram of the operation of the restriction unit in the second embodiment. As shown in FIG. 21, the sensor support shaft 303, which is an example of a both-supported beam member, is arranged so as to span between the holding frame 206a and the holding frame 206b. The sensor support shaft 303 forms a twist angle with respect to the first support roller 103 and the second support roller 104 as the holding frame 206a and the holding frame 206b rotate relative to each other.

  As shown in FIG. 12, in Example 1, when the holding frames 206a and 206b are relatively rotated and are in a twisted positional relationship, the distance between the horizontal portion of the holding frame 206a and the surface of the first support roller 103 is large. fluctuate. For this reason, the leaf spring 123m whose root is fixed to the horizontal portion of the holding frame 206a needs to absorb a large amount of displacement of the thermistor 123a by deformation.

  As shown in FIG. 20, in Example 2, when the holding frames 206a and 206b are relatively rotated and are in a torsional positional relationship, the root of the leaf spring 123m moves up and down, and the root of the leaf spring 123m and the thermistor 123a. Reduce the amount of displacement. For this reason, the displacement amount of the distance between the thermistors 123a and 123b and the surface of the first support roller 103 is small when the first support roller 103 and the second support roller 104 are in a twisted positional relationship.

  As shown in FIG. 20, in the second embodiment, a sensor support shaft 303 is arranged in parallel with the first support roller 103 between the holding frame 206 a and the holding frame 206 b, and the sensor is supported in parallel with the second support roller 104. An axis 304 is arranged. Then, the thermistors 123a and 123b are arranged to be supported by the sensor support shaft 303, and the thermistors 124a and 124b are arranged to be supported by the sensor support shaft 304.

  A holding frame 206 a that rotatably holds one end of the first support roller 103 and the second support roller 104 is rotatably supported by a shaft 207 a disposed on the intermediate frame 208. Holding frames 206a and 206b that rotatably hold the other ends of the first support roller 103 and the second support roller 104 are rotatably supported by a shaft 207b disposed on the intermediate frame 208.

  As shown in FIG. 21, the sensor support shafts 303 and 304 are disposed so as to connect the holding frame 206a and the holding frame 206b and penetrate the holding frame 206a and the holding frame 206b. The base sides of the leaf springs 123m and 123n are fixed to the sensor support shaft 303, and the thermistors 123a and 123b are fixed to the distal ends of the leaf springs 123m and 123n. The base sides of leaf springs 124m and 124n as other urging members are fixed to the sensor support shaft 304, and thermistors 124a and 124b as other temperature detection means are fixed to the distal ends of the leaf springs 124m and 124n. .

  As shown in FIG. 22, the end portions of the sensor support shafts 303 and 304 inserted into the holding frame 206a are cut into a D shape, and the rotation is restricted with respect to the holding frame 206a. The end portions of the sensor support shafts 303 and 304 are rotatable with respect to the holding frame 206b. The sensor support shafts 303 and 304 are fitted with retaining rings 305 at positions protruding from the holding frames 206a and 206b with respect to the holding frames 206a and 206b.

  As shown in FIG. 23A, the holding frames 206a and 206b rotate relative to each other in accordance with the control of the lateral movement of the external heating belt 105, so that the first support roller 103 and the second support roller 104 are in a twisted positional relationship. Become. At the same time, the sensor support shafts 303 and 304 are also in a twisted positional relationship, and the first support roller 103 and the sensor support shaft 303 are maintained in a substantially parallel positional relationship, and the second support roller 104 and the sensor support shaft are maintained. 304 maintains a substantially parallel positional relationship. For this reason, the displacement amount of the distance between the thermistors 123a and 123b and the first support roller 103 due to the relative rotation of the holding frame 206a and the holding frame 206b is smaller than that in the first embodiment. At the same time, the displacement amount of the distance between the thermistors 124a and 124b and the second support roller 104 due to the relative rotation of the holding frame 206a and the holding frame 206b is also smaller than that in the first embodiment.

  As shown in FIGS. 23B and 23C, even if the first support roller 103 and the second support roller 104 are twisted, a parallel positional relationship between the sensor support shaft 303 and the first support roller 103, and The parallel positional relationship between the sensor support shaft 304 and the second support roller 104 does not change. Since the sensor support shafts 303 and 304 are prevented from coming off from the holding frames 206a and 206b, the first support roller 103 and the sensor support shaft 303 are twisted in the same direction, and the second support roller 104 and the sensor support shaft 304 are twisted. This is because it twists in the same direction.

  Accordingly, the thermistors 123a, 123b, 124a, 124b attached to the sensor support shafts 303, 304 via the leaf springs 123m, 123n, 124m, 124n are in contact positions with the first support roller 103 and the second support roller 104. The shift is small. The plastic deformation of the leaf springs 123m, 123n, 124m, and 124n accompanying the shift control of the external heating belt 105 is less likely to occur than in the first embodiment.

  However, also in the second embodiment, when the external heating unit 150 is assembled or when the external heating unit 150 is lifted up alone, the first support roller 103 and the second support roller 104 are largely twisted, and the leaf spring 123m is plastic. There is a possibility of deformation.

  Therefore, as shown in FIG. 20, flat portions 305a and 305b are arranged on the front side of the intermediate frame 208 to limit the rotation angle of the holding frame 206a. Flat portions 306a and 306b are arranged on the back side of the intermediate frame 208 to limit the rotation angle of the holding frame 206b.

  As shown in FIG. 24, on the front side, the flat portions 305a and 305b fixed to the intermediate frame 208 abut against the holding frame 206a, and the twist angle of the holding frame 206a with respect to the intermediate frame 208 is restricted within a predetermined range. On the back side, the flat portions 306a and 306b fixed to the intermediate frame 208 abut against the holding frame 206b, and the twist angle of the holding frame 206b with respect to the intermediate frame 208 is restricted within a predetermined range. As in the first embodiment, the predetermined range of each twist angle is set to an angle slightly larger than the twist angle generated by the control of the shift of the external heating belt 105 so as not to hinder the control of the shift. ing. FIG. 24 shows the holding frame 206a, but the holding frame 206b has the same configuration.

  In the second embodiment, since the displacement amounts of the thermistors 123a, 123b, 124a, and 124b are smaller than those in the first embodiment, the reproducibility of temperature detection by the thermistors 123a, 123b, 124a, and 124b is increased. In the second embodiment, as compared with the first embodiment, the torsion of the external heating unit 150 is somewhat inhibited by the sensor support shafts 303 and 304, but the temperature detection error due to the plastic deformation of the leaf springs 123m, 123n, 124m, and 124n. Can be greatly reduced.

<Example 3>
FIG. 25 is an explanatory diagram of a restriction unit according to the third embodiment. As shown in FIG. 25, the configuration for limiting the relative rotation angle of the holding frames 206a and 206b may be arranged in one place. Other configurations are the same as those of the first embodiment.

  In each of the above-described examples, as long as the maximum relative rotation angle between the first holding member and the second holding member is regulated to a predetermined angle so that an excessive load is not applied to the predetermined component, a part of the configuration of the embodiment or Other embodiments may be implemented in which all are replaced with the alternative configuration.

  Therefore, the heating means for the heating rotator and the belt member is not limited to the halogen heater. An induction heating layer may be provided on the heating rotator and the belt member, and induction heating may be performed by an alternating magnetic flux. The heating rotator is not limited to the fixing roller, and may be a pressure roller that heats the back surface of the image surface of the recording material.

  In addition to the fixing device, the image heating device includes a surface heating device that adjusts the gloss and surface properties of a semi-fixed or fixed image. Also included is a decurling device for the recording material on which the fixed image is formed. In addition to being incorporated in the image forming apparatus, the image heating apparatus can be implemented as a single apparatus or component unit that is installed and operated independently. The image forming apparatus can be implemented without distinction between monochrome / full color, sheet-fed type / recording material conveyance type / intermediate transfer type, toner image forming method, and transfer method. The present invention can be implemented in image forming apparatuses for various uses such as a printer, various printing machines, a copying machine, a FAX, and a multifunction machine, in addition to necessary equipment, equipment, and a housing structure.

DESCRIPTION OF SYMBOLS 9 Fixing device, 11 Secondary transfer roller 101 Fixing roller, 102 Pressure roller 103 First support roller, 104 Second support roller 105 External heating belt, 108 Cleaning roller 111 (112, 113, 114) Halogen heater 117 Pressure arm 118 worm wheel,
123a (123b, 124a, 124b) Thermistor 123m (123n, 124m, 124n) Leaf spring, 125 motor,
130 intermediate transfer belt, 133 (134, 135) photo interrupter 150 external heating unit, 201 pressure frame, 204 pressure spring 205 pressure release cam, 206 holding frame 207 axis, 208 intermediate frame, 209 rotation axis 211 rotation regulating member, 300 restricting portion, 301 bending portion 302 flat portion, 303 (304) sensor support shaft K toner, P recording material, Pa, Pb, Pc, Pd image forming portion

Claims (11)

A heating rotator for heating the toner image on the recording material;
An endless belt member that contacts the heating rotator and heats the heating rotator, and supports the belt member rotatably from the inner peripheral surface side, and presses the belt member toward the heating rotator. A belt unit having a first support member and a second support member;
A detector for detecting that the belt member is out of a predetermined range in a width direction perpendicular to the rotation direction of the belt member;
A rotation mechanism for rotating the belt unit in a direction to return the belt member to the predetermined range in response to detection by the detector;
A direction in which the force by which the first support member presses the belt member toward the heating rotating body becomes equal at both ends in the width direction of the belt member as the belt unit is rotated by the rotation mechanism. Direction in which the first support member is allowed to displace and the force by which the second support member presses the belt member toward the heating rotator is equal to each other at both ends in the width direction of the belt member. A displacement mechanism that allows the second support member to be displaced;
A limiting mechanism that limits the amount of displacement of the first support member and the second support member allowed by the displacement mechanism to a predetermined amount,
An image heating apparatus. A heating rotator for heating the toner image on the recording material;
An endless belt member that contacts the heating rotator and heats the heating rotator, and supports the belt member rotatably from the inner peripheral surface side, and presses the belt member toward the heating rotator. A belt unit having a first support member and a second support member;
A detector for detecting that the belt member is out of a predetermined range in a width direction perpendicular to the rotation direction of the belt member;
A rotation mechanism for rotating the belt unit in a direction to return the belt member to the predetermined range in response to detection by the detector;
As the belt unit is rotated by the rotation mechanism, the first support member and the second support member are arranged such that the rotational axes of the first support member and the second support member are in a twisted positional relationship. A displacement mechanism that allows displacement;
A limiting mechanism that limits the amount of displacement of the first support member and the second support member allowed by the displacement mechanism to a predetermined amount,
An image heating apparatus. The restriction mechanism has a stopper that abuts against the displacement mechanism when the first support member and the second support member are displaced beyond a range in which the first support member and the second support member can be displaced along with the rotation of the belt unit by the rotation mechanism.
The image heating apparatus according to claim 1, wherein the apparatus is an image heating apparatus. A temperature detecting means for detecting the temperature of the belt member; and a direction in which one end is fixed to the displacement mechanism and the temperature detecting means is supported at the other end, and the belt member is sandwiched between the first supporting member A biasing member for biasing the temperature detecting means;
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. Another temperature detecting means for detecting the temperature of the belt member, one end of which is fixed to the displacement mechanism and supporting the other temperature detecting means at the other end; and the belt member is connected to the second support member Comprising another urging member for urging the another temperature detecting means in the direction of being sandwiched between,
The image heating apparatus according to claim 4. The displacement mechanism holds each end portion on one end side in the width direction of the first support member and the second support member, and the first support member as the belt unit is rotated by the rotation mechanism. And a first holding member that is swingable in a direction in which respective forces pressing the one end side of the belt member toward the heating rotator are equal to each other,
While holding each edge part of the other end side of the width direction of the 1st support member and the 2nd support member, with the rotation of the belt unit by the rotation mechanism, the 1st support member and the 2nd A support member having a second holding member that can swing in directions in which respective forces pressing the other end side of the belt member toward the heating rotator are equal to each other;
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. The first holding member and the second holding member are swingable around a common axis.
The image heating apparatus according to claim 6. The first holding member and the second holding member rotate in opposite directions around the common axis as the belt unit is rotated by the rotation mechanism.
The image heating apparatus according to claim 7. First temperature detecting means for detecting the temperature of the belt member;
One end of the first holding member is fixed to the first holding member and the first temperature detecting unit is supported by the other end, and the first temperature detecting unit is attached in a direction to sandwich the belt member with the first supporting member. A first biasing member
Second temperature detecting means for detecting the temperature of the belt member;
One end of the second holding member is fixed to the second holding member, and the second temperature detecting unit is supported by the other end, and the second temperature detecting unit is attached in a direction to sandwich the belt member with the second supporting member. A second biasing member for biasing,
The image heating apparatus according to claim 6, wherein the image heating apparatus is an image heating apparatus. A drive mechanism for driving the heating rotator,
The belt member is driven to rotate by the heating rotator.
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus. The first support member and the second support member each have a heater.
The image heating apparatus according to claim 1, wherein the image heating apparatus is an image heating apparatus.

Images