JP2010152053A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device in which a heating element is disposed inside a fixing belt, the fixing device suppressing excessive deformation of the heating element, which is caused by thermal expansion of the heating element. <P>SOLUTION: The heating element 25 is processed in a curved shape along the internal circumferential surface of the fixing belt 21 and disposed in contact with the fixing belt along the circumferential direction thereof. In addition, a plate-like heat conductive member 26 is superposed on the back of the heating element. The heating element and heat conductive member are supported at both width-direction ends of the fixing belt, and both circumferential-direction ends of the fixing belt are supported by plate springs 27 and 28. On the upstream side of the fixing belt in the moving direction thereof, the heating element and heat conductive member are fixed to and supported by the plate spring 27 by means of a rivet 35. On the downstream side thereof, a long hole 38 is formed, and the heating element and heat conductive member are joined to the plate spring 28 by means of a pin 36. The heating element and heat conductive member can be circumferentially displaced within the range of the long diameter of the long hole so as to permit relative displacement of the heating element and heat conductive member. In addition, the displacement perpendicular to the surface of the fixing belt on the downstream side is suppressed by the pin 36. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  2. Description of the Related Art In image forming apparatuses that use powdered toner, fixing devices that widely apply heat and pressure to a toner image on a recording medium are widely used. Such a fixing device includes a fixing member (heating member) that heats an endless peripheral surface, and a pressure member that is pressed against the fixing member. Then, a sheet-like recording medium is sandwiched between them, and the recording medium is conveyed along with the circumferential movement of the endless peripheral surface, and the toner image on the recording medium is heated and pressurized.

  As a means for heating the peripheral surface of the fixing member, for example, as described in Patent Document 1, a conductive layer is provided along the peripheral surface of the fixing member, and an exciting coil is disposed so as to face each other. Some supply high-frequency current. An eddy current is generated in the conductive layer by the magnetic field generated by the high-frequency current, and heat is generated.

In addition, the fixing device described in Patent Document 2 has a heating element disposed inside a fixing member that is hollow and has an endless outer peripheral portion, and the heating element is brought into contact with the fixing member. An electromagnetic induction heating coil is disposed at a position facing the heating element via the fixing member, and an eddy current is induced in the heating element by the action of the generated high-frequency magnetic field to heat and heat the fixing member that contacts. It is supposed to be.
JP 2000-187406 A JP 2008-164783 A

  An object of the present invention is to provide a fixing device in which excessive deformation due to thermal expansion of a heating element is suppressed, and an image forming apparatus using the fixing device.

  In order to solve the above-described problems, the invention according to claim 1 is directed to an endless belt-like fixing member whose outer peripheral surface is pressed against a recording medium on which an image is recorded, and an inner peripheral surface of the fixing member. A pressing member that presses the outer peripheral surface of the fixing member against the recording medium from the inner peripheral surface, a support that supports the pressing member, and is pressed against the pressing member via the fixing member and rotates. A pressure rotating body that is disposed to face the peripheral surface of the fixing member, and a magnetic field generating unit that generates a magnetic field, and is disposed at a position facing the magnetic field generating unit, and is disposed on the inner peripheral surface of the fixing member. And a heating element that is bent into a curved shape along the plate and that is in contact with the fixing member, and a plate-like heat conduction member that is superimposed on the opposite side of the surface of the heating element that contacts the fixing member. The heating element and the heat transfer The guide member is fixedly supported at one end in the circumferential direction of the fixing member, and the other end is displaced in the circumferential direction and relative to the circumferential direction between the heating element and the heat conducting member. A fixing device is provided which is supported so as to allow a general displacement.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the heating element is supported by an elastic member, and can be displaced in a direction to advance and retreat with respect to the fixing member by deformation of the elastic member. It shall be.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the both ends of the fixing member in the width direction are respectively supported at both ends in the circumferential direction of the fixing member. To do.

  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, the heating element includes a portion corresponding to a passing range of the recording medium in a width direction of the fixing member. It is assumed that a range in contact with the fixing member in the circumferential direction is larger than a portion not corresponding to the passing range.

  According to a fifth aspect of the present invention, in the fixing device according to any one of the first to fourth aspects, the heating element is formed of a temperature-sensitive magnetic material that becomes weak in magnetism when the temperature rises. Shall.

  According to a sixth aspect of the present invention, there is provided an image forming unit that forms a toner image by attaching toner to a latent image due to a difference in electrostatic potential, and directly transfers the toner image to a transported recording medium or an intermediate A transfer device that transfers the toner image transferred to the recording medium by heating and fixing the toner image transferred to the recording medium after the transfer to the transfer medium; An image forming apparatus which is a fixing device according to any one of claims 1 to 5 is provided.

  According to the first aspect of the present invention, it is possible to suppress excessive deformation of the heating element as compared with the case where the present configuration is not provided.

  According to the second aspect of the present invention, the adhesion with the fixing member is improved as compared with the case where the present configuration is not provided.

  According to the third aspect of the present invention, when the support is deflected, the influence of the deflection on the heating element is reduced as compared with the case where the present configuration is not provided, and the heating element is arranged along the fixing member. Adhering shape is maintained.

  According to the fourth aspect of the present invention, the amount of heat transfer to the fixing member is increased in the area where the fixing member is in contact with the recording medium than in the area where the fixing member is not in contact as compared with the case where the present configuration is not provided. It becomes possible.

  According to the fifth aspect of the present invention, it is possible to suppress an excessive temperature rise of the heating element as compared with the case where the present configuration is not provided.

  According to the invention described in claim 6, it is possible to suppress excessive deformation of the heating element as compared with the case where the present configuration is not provided.

Hereinafter, embodiments of the invention according to the present application will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention.
The image forming apparatus includes a cylindrical photosensitive drum 1 on which a latent image is formed by irradiating image light after uniform charging. Around the photosensitive drum 1, the photosensitive drum 1 is provided. A charging device 2 that uniformly charges the surface of the photosensitive drum 1, an exposure device 3 that irradiates the photosensitive drum 1 with image light to form a latent image on the surface, and an electrostatic latent image on the photosensitive drum 1 is selected by toner. A transfer roll 5 for transferring a toner image on the photosensitive drum to a recording medium by an electric field formed by applying a transfer bias voltage between the developing device 4 and the photosensitive drum 1 that are visualized by a specific adhesion; And a cleaning device 6 for removing toner remaining on the photosensitive drum 1 after the image is transferred.

  Further, a paper feed tray 7 that stores a recording medium to which the toner image is transferred, and a recording medium fed one by one from the paper feed tray 7 are transferred to the press contact portion 5a where the photosensitive drum 1 and the transfer roll 5 face each other. And a fixing device 20 that heats and presses the toner image transferred to the recording medium, and a discharge roller 9 that sends the recording medium on which the toner image is fixed to the discharge tray 10. It has been.

  In the image forming apparatus as described above, the photosensitive drum 1 is charged to a substantially uniform negative polarity by the charging device 2. The exposure device 3 irradiates the charged surface of the photosensitive drum 1 with image light based on the image data. The exposed portion of the exposed surface of the photosensitive drum 1 has a reduced charging potential, and a non-exposed portion. A latent image is formed due to the potential difference between the two. The developing device 4 holds toner having a negative charge on the peripheral surface of the developing roll 4 a by thinning the toner, and the toner thinned by the rotation of the developing roll 4 a is the peripheral surface of the photosensitive drum 1. It is conveyed to the position facing. An electric field is generated between the photosensitive drum 1 and the developing roll 4a by the developing bias voltage applied between the two, and the toner having a negative charge is transferred to the exposed portion. The toner image formed in this way is conveyed to the transfer pressure contact portion 5a to which the transfer roll 5 is pressed by the rotation of the photosensitive drum 1.

  On the other hand, the recording medium sent out one by one from the paper tray 7 is sent to the transfer pressure contact portion 5a at the timing of contact with the toner image on the photosensitive drum 1. The recording medium contacts the surface of the photosensitive drum 1 on the upstream side of the transfer pressure contact portion 5a, and passes through the transfer pressure contact portion 5a in a close contact state. An electric field is formed by a transfer bias voltage in the transfer pressure contact portion 5a and its periphery, and the toner image is transferred to the recording medium in the electric field.

  The recording medium onto which the toner image has been transferred is sent to the fixing device 20 while holding the toner image. The fixing device 20 heats and presses the toner image on the recording medium and fixes the toner image on the recording medium.

FIG. 2 is a schematic cross-sectional view of the fixing device according to an embodiment of the present invention.
The fixing device 20 is provided so as to face a fixing belt 21 having an endless peripheral surface, a pressure roll 22 in contact with an outer peripheral surface of the fixing belt 21, and an outer peripheral surface of the fixing belt 21, An electromagnetic induction heating device 30 for heating the fixing belt 21, a pressing member 23 that contacts the inner peripheral surface of the fixing belt 21 and presses the pressure roll 22 through the fixing belt, and supports the pressing member 23. The support 24, the heating element 25 arranged in contact with the inner peripheral surface of the fixing belt 21, and the heat conducting member 26 arranged in contact with the inside of the heating element 25 constitute a main part. Yes. And the said heat generating body 25 and the heat conductive member 26 are supported by the support body 24 via the leaf | plate springs 27 and 28 in the state piled up.

  The fixing belt 21 functions as a fixing member, and is an endless flexible belt having a thin conductive layer. And it is supported so that the circular movement to the circumferential direction (the direction of the arrow A shown in FIG. 2) is attained. As shown in FIG. 3, the fixing belt includes a base layer 21a made of a sheet-like member having high heat resistance from the inside, a conductive layer 21b laminated on the base layer, and a surface release layer 21c that is the uppermost layer. It consists of and. Further, a lubricant such as silicon oil or fluorine oil is applied to the inner surface of the base layer 21 a, that is, the inner peripheral surface 21 d of the fixing belt 21, so that the circumferential movement of the fixing belt 21 is made smooth.

The base layer 21a may be made of a synthetic resin having high heat resistance such as polyimide or polyimide amide.
The conductive layer 21b is a layer that generates heat by electromagnetic induction action of a magnetic field generated by the electromagnetic induction heating device 30, and a metal layer of iron, cobalt, nickel, copper, aluminum, chrome, etc. with a thickness of about 1 to 50 μm. What was formed is used.
Since the surface release layer 21c is a layer that is in direct contact with the unfixed toner image transferred onto the recording medium, a material having good release properties is used.

  In the present embodiment, the fixing belt 21 has a circular cross section with an inner diameter of about 30 mm in an unconstrained state, and the base layer 21a has a rigidity of 75 μm so as not to buckle or the like in the width direction. Polyimide is used. The conductive layer 21b is preferably a thin layer so that permanent deformation and cracks do not occur even when the curvature of the fixing belt 21 is large. The conductive layer 21b has a thickness of 10 μm formed on the base layer 21a by means such as vapor deposition or plating. A copper layer is employed. Further, a perfluoroalkoxy fluororesin (PFA) having a thickness of 50 μm is laminated on the conductive layer 21b as the surface release layer 21c.

The pressing member 23 is flexibly deformed by the pressure of the pressure roll 22, and the fixing belt 21 is sandwiched between the pressure roll 22 and the fixing belt 21 and the pressure roll 22 are arranged along the circumferential direction. A fixing nip to be pressed is formed.
The support 24 is formed by combining steel plates, and is fixedly supported on a base portion that supports each member of the fixing device 20 at both ends in the axial direction, that is, in the width direction of the fixing belt 21. And it supports the pressing member 23 and opposes the pressing force from the pressure roll 22.

The pressure roll 22 functions as a pressure rotator, and a metal cylindrical cored bar 22a is used as a core, and a surface release layer 22b is provided on the surface of the cylindrical cored bar. Then, the fixing belt 21 is held between the pressing member 23 and is driven to rotate in the direction of arrow B shown in FIG. Therefore, when the recording medium P on which the unfixed toner image is transferred is sent to the fixing nip where the fixing belt 21 and the pressure roll 22 are pressed, the recording medium is conveyed and heated and pressurized.
In the present embodiment, as the pressure roll 22, a surface of a cylindrical cored bar 22a having a diameter of 28 mm is coated with PFA having a thickness of 30 μm as the surface release layer 22b.

  The electromagnetic induction heating device 30 includes a coil support member 31 disposed so that a concavely curved surface faces the outer peripheral surface of the fixing belt 21 with a gap, and a convex shape of the plate-like coil support member 31. The main part is composed of an excitation coil 32 supported on a curved surface and supplied with a high-frequency current by an excitation circuit 34 and a magnetic shielding member 33 provided outside the excitation coil 32. By supplying a high frequency current to the exciting coil 32, a magnetic field is generated, and an eddy current is induced in the conductive layer 21b and the heating element 25 of the fixing belt 21 facing each other to generate heat.

  The heating element 25 is a plate-like member bent into a curved shape following the inner peripheral surface of the fixing belt 21. The heating element 25 is in contact with the inner peripheral surface of the fixing belt 21 and the electromagnetic induction heating via the fixing belt 21. It arrange | positions so that the apparatus 30 may be opposed. For example, iron, nickel, cobalt, SUS, or an alloy thereof can be used, which is formed of a metal material that generates heat due to an eddy current induced by a high-frequency magnetic field. Further, a nickel (Ni) -iron (Fe) system having a Curie point in a range not lower than a heat resistance temperature of the fixing belt but not higher than a set temperature for heating the fixing belt, for example, a range from 170 ° C. to 250 ° C., nickel Ni A chromium-chromium-iron-Fe-based magnetic shunt alloy, that is, a temperature-sensitive magnetic material can also be used. By using these magnetic shunt alloys, an excessive temperature rise of the heating element can be suppressed.

  It is desirable that the heating element 25 be formed as thin as possible in order to make the temperature rise during heat generation rapid. However, the magnetic field passes through the heating element 25 and reaches the heat conducting member 26 disposed on the back surface of the heating element 25 (the surface opposite to the contact surface with the fixing belt 21), and the heat conducting member 26 generates heat. It is desirable to avoid this, and the thickness should be greater than the skin depth. From such a viewpoint, in the present embodiment, the thickness of the heating element 25 is set to 0.3 mm.

The heat conducting member 26 is a plate-like member formed following the shape of the inner surface of the heating element 25, and is slidably disposed on the back surface of the heating element 25. Then, the heat conduction from the heating element 25 promotes the uniform temperature of the heating element 25. The heat conductive member 26 is made of a material having a thermal conductivity higher than that of the heating element 25 and can be formed of a metal such as silver, copper, gold, aluminum, or an alloy thereof.
In this embodiment, aluminum is employed and the thickness is 0.4 mm.

The heating element 25 and the heat conducting member 26 are supported at both ends in the width direction of the fixing belt 21 in a state of being overlapped as shown in FIG. 4, and the periphery of the fixing belt 21 at each end. The upstream portion and the downstream portion in the direction are joined to the leaf springs 27 and 28. Therefore, the curved plate-like heating element 25 and the heat conducting member 26 are supported by the joint portions 25a, 25b, 26a, and 26b (see FIG. 5) provided at the four corner portions.
As shown in FIG. 4, the joints 25 a, 25 b, 26 a, and 26 b are bent inward from the curved surface that contacts the fixing belt 21, with slits 25 c provided between the portions that contact the fixing belt 21. It is put. The joint portions 25a, 25b, 26a, and 26b are substantially flat as shown in FIG. 5, and are supported by being overlapped with the leaf springs 27 and 28.

  As shown in FIG. 4 or FIG. 5, the leaf springs 27 and 28 are paired on both side surfaces at both ends of the support 24 arranged so that the axis line is in the width direction of the fixing belt 21. It is fixed. Further, there are projecting portions 27a and 28a projecting to both sides in a direction that advances and retreats with respect to the fixing belt 21 at the center portion in the circumferential direction of the heating element 25, that is, a direction substantially perpendicular to the direction indicated by the arrow C in FIG. .

  Supporting portions 27b and 28b for supporting the heating element 25 and the heat conducting member 26 are continuously provided on the distal end sides of the overhanging portions 27a and 28a, and the joining portions 25a and 25b of the heating element 25 and the heat conduction are provided. It is bent so as to be substantially parallel to the joint portions 26a and 26b of the members. The support portions 27b and 28b are superposed on the heat-generating member joint portions 25a and 25b and the heat conductive member joint portions 26a and 26b, respectively, and are supported by them. As a result, the heating element 25 and the heat conducting member 26 are supported so as to be displaceable by bending deformation of the projecting portions 27 a and 28 a of the leaf spring, and can follow the fixing belt 21 elastically. ing.

  A through hole is cut in each of the positions where the leaf spring support portion 27b, the heating element joining portion 225a, and the heat conducting member joining portion 26a overlap each other on the upstream side in the rotation direction of the fixing belt 21. The heating element 25 and the heat conducting member 26 are fixed to the leaf spring 27 by a rivet 35 inserted through the hole.

On the other hand, on the support portion 28b of the leaf spring disposed on the downstream side in the rotation direction of the fixing belt 21, the joining portion 25a of the heating element and the joining portion 26b of the heat conducting member are slidably overlapped. The long holes 37 having a long diameter in the circumferential direction are respectively cut at positions corresponding to. Pins 36 whose diameters are enlarged at both ends are inserted into the long holes 37 to maintain the overlapping state, and the heating element 25, the heat conduction member 26, and the leaf spring 28 are allowed to be relatively displaced in the circumferential direction. It is supposed to be. Therefore, the heating element 25 and the heat conducting member 26 can move in the circumferential direction in the range of the long diameter of the long hole 37 with respect to the leaf spring 28, and the heating element 25 and the heat conducting member 26 are displaced within this range. At the same time, relative displacement caused by sliding between the heating element 25 and the heat conducting member 26 is allowed. Thereby, even if the temperature of the heat generating body 25 and the heat conductive member 26 rises and each expands with a different linear expansion coefficient, the restraint of strain is relaxed. Further, due to the rotation of the fixing belt 21 and the force applied to the outer peripheral surface of the heating element 25, the heating element 25 is easily deformed along the curvature of the fixing belt 21 during rotation. Therefore, the possibility that the end portions in the circumferential direction particularly damage the inner peripheral surface of the fixing belt 21 due to thermal expansion of the heating element 25 and the heat conducting member 26 is reduced.
The heating element 25 and the heat conducting member 26 may be restrained from displacement in the width direction of the fixing belt with respect to the leaf spring 28, but are preferably supported so as to allow the displacement.

  As described above, the region where the heating element 25 is supported by the leaf springs 27 and 28 is a non-sheet-passing region in which the recording medium does not pass in the width direction of the fixing belt 21, and the fixing belt 21 and the heating element 25 are separated from each other. Even if they are separated from each other, the fixing of the image is not affected.

  Further, in the sheet passing area, the heating element 25 and the heat conducting member 26 maintain a shape following the fixing belt 21 that circulates in almost the entire area in the circumferential direction. In this area, the heating element 25 is substantially in the entire area in the circumferential direction. In contact with the fixing belt 21. Therefore, the area in contact with the fixing belt 21 is larger than both end portions in the width direction of the fixing belt 21, that is, the region where the recording medium does not pass, thereby giving a sufficient amount of heat to the fixing belt 21 and making the temperature uniform. It is like that.

Next, the operation of such a fixing device 20 will be described.
When the pressure roll 22 is driven to rotate, the contacting fixing belt 21 is driven in the circumferential direction, and the recording medium P holding the toner image is sent between the pressure roll 22 and the fixing belt 21.
On the other hand, a high-frequency current is supplied from the excitation circuit 34 to the excitation coil 32 of the electromagnetic induction heating device 30, and the magnetic flux repeatedly generates and disappears around the excitation coil 32. When this magnetic flux crosses the conductive layer 21b of the fixing belt 21, an eddy current is generated in the conductive layer of the fixing belt 21 so as to generate a magnetic field that hinders the change of the magnetic field, and Joule heat is generated.
Further, the heating element 25 arranged in contact with the inner peripheral surface of the fixing belt 21 also generates heat by the action of the magnetic field, and heats the fixing belt 21. Further, the heat conducting member 26 disposed so as to overlap the back surface of the heat generating element 25 makes the temperature of the heat generating element 25 uniform by heat conduction from the heat generating element 25.

  At this time, thermal expansion occurs in the heating element 25 and the heat conducting member 26, and the amount of distortion differs depending on the material formed. In the present embodiment, the distortion of the heat conducting member 26 increases. However, in the heating element 25 and the heat conducting member 26, the joint portions 25a and 26a are fixedly supported by the leaf spring 27 on the upstream side in the circumferential movement direction of the fixing belt 21, and the downstream joint portions 25b and 26b are in the circumferential direction. Are supported so as to allow displacement, and are slidable between each other. Thereby, the joint part on the downstream side of the heating element 25 and the heat conducting member 26 is allowed to be displaced in the circumferential direction (in the direction of arrow E shown in FIG. 5) due to thermal expansion, and parallel to these contact surfaces. Relative to each other (direction of arrow F shown in FIG. 5) occurs, and bending deformation caused by restraining the thermal expansion strain is suppressed. Further, the joint portion on the downstream side of the heating element 25 and the heat conducting member 26 is restrained from being displaced in a direction perpendicular to the surface of the heating element 25 (in the direction of arrow D shown in FIG. 5), and the temperature rises. It is possible to suppress the displacement from being pushed out to the fixing belt side. By suppressing the displacement and deformation in this way, the heat generating element 25 and the heat conducting member 26 are excessively deformed so that even if the temperature rises, the driving of the fixing belt is hindered or the fixing belt is damaged. Is suppressed.

Further, since the heat generating body 25 and the heat conducting member 26 are supported at both ends in the axial direction, that is, the width direction of the fixing belt, the support 24 is fixed to the fixing belt by pressing the pressure roll 22 against the pressing member 23. Even if it bends in the width direction of 21, it does not follow the bending of the support 24, and the adhesion to the fixing belt 21 is maintained.

  As described above, even if the heating element 25 and the heat conducting member 26 are thermally expanded, the contact state with the fixing belt 21 is not greatly affected, and the fixing belt 21 is heated to a temperature suitable for fixing the toner image. . Then, the fixing belt 21 heated in this manner is superimposed on the recording medium P that holds the toner image on the surface and is fed between the pressing member 23 and the pressure roll 22, and the toner image is heated and pressed. And pressed onto the recording medium. The recording medium that has passed through the pressure contact portion of the pressure roll 22 is peeled off from the fixing belt 21 and the pressure roll 22 and conveyed to the paper discharge roll 10.

  In addition, since the thermal expansion coefficients of the heating element 25 and the heat conducting member 26 are different from each other, the respective curvatures in the circumferential direction are changed, and a force for separating the heating element 25 and the heat conducting member 26 from each other acts. There is. However, when the fixing belt 21 rotates in the direction of the arrow A, a force in the direction of the arrow G shown in FIG. 5 acts to suppress the heating element 25 and the heat conducting member 26 from being separated, and fixing. Adhesiveness with the belt 21, the heating element 25, and the heat conducting member 26 is maintained.

In the embodiment described above, the fixing belt has a three-layer structure, but an elastic layer for improving the fixing property and image quality of the toner image is provided between the conductive layer and the surface release layer. An adhesive layer or a protective layer for each layer may be provided. Alternatively, a heat resistant resin layer may be laminated on the conductive layer, and the conductive layer may be sandwiched between the two heat resistant resin layers.
Furthermore, a fixing belt having a two-layer structure that does not have a conductive layer may be used. At this time, the fixing belt is heated only by heat conduction from the heating element.

  The fixing member for fixing the heating element 25 and the heat conducting member 26 to the leaf spring 27 uses the rivet 35 in the above embodiment, but other fixing members or other fixing structures can be adopted. In addition, the member to be joined to the leaf spring 28 on the downstream side in the circumferential direction is a member other than the above pins as long as it allows displacement of the heating element and the heat conducting member in the circumferential direction and can be supported by the leaf spring. It is also possible to use other joint structures.

  On the other hand, the heating element and the heat conduction member can be fixedly supported downstream in the circumferential movement direction of the fixing belt, and the heating element and the heat conduction member can be supported movably in the circumferential direction on the upstream side. Considering the force to the heating element acting by the movement, it is preferable to fix and support the heating element on the upstream side because adhesion between the fixing belt and the heating element is increased.

Further, in the above embodiment, the heating element is heated by the electromagnetic induction heating device 30, but a planar heating element that generates heat when directly energized can also be used. When such a planar heating element is used, it is desirable to provide a power supply device that supplies power to the planar heating element, and this power supply device includes a power storage unit including a battery, a capacitor, and the like. The power storage unit is set so as to be charged except during fixing, and power is supplied from the power storage unit to the sheet heating element during fixing when a large amount of power is supplied to the electromagnetic induction heating device. This suppresses the amount of power used during fixing.
Further, even in such a planar heating element, similarly to the present embodiment, the end portion on the upstream side in the circumferential movement direction of the fixing belt is firmly fixed and supported to the leaf spring together with the heat conduction member, On the downstream side, it can be supported to allow displacement in the circumferential direction. Thereby, the excessive deformation | transformation of the heat generating body and heat conductive member by thermal expansion is suppressed.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a fixing device that is used in the image forming apparatus illustrated in FIG. 1 and is an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of a fixing belt used in the fixing device shown in FIG. 2. FIG. 3 is a schematic perspective view showing a heating element used in the fixing device shown in FIG. 2. FIG. 3 is an enlarged sectional view showing a part of the fixing device shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1: Photosensitive drum, 2: Charging apparatus, 3: Exposure apparatus, 4: Developing apparatus, 5: Transfer roll, 5a: Transfer press-contact part, 6: Cleaning apparatus, 7: Paper tray, 8: Conveyance path, 9: Ejection Paper roll, 10: paper output tray,
20: fixing device, 21: fixing belt, 22: pressure roll, 23: pressing member, 24: support, 25: heating element, 25a, 25b: junction of heating element, 26: heat conducting member, 26a, 26b : Joint part of heat conduction member, 27, 28: Leaf spring, 27a, 28a: Overhang part of leaf spring, 27b, 28b: Support part of leaf spring,
30: Electromagnetic induction heating device, 31: Coil support member, 32: Excitation coil, 33: Magnetic shielding member, 34: Excitation circuit, 35: Rivet, 36: Pin, 37: Long hole, P: Recording medium

Claims (6)

An endless belt-like fixing member whose outer peripheral surface is pressed against a recording medium on which an image is recorded;
A pressing member that is disposed in contact with the inner peripheral surface of the fixing member and presses the outer peripheral surface of the fixing member against the recording medium from the inner peripheral surface;
A support that supports the pressing member;
A pressure rotating body that is pressed against the pressing member via the fixing member and rotates;
A magnetic field generating means arranged to face the peripheral surface of the fixing member and generating a magnetic field;
A heating element disposed at a position facing the magnetic field generating means, bent into a curved shape along the inner peripheral surface of the fixing member, and in contact with the fixing member;
A plate-like heat conducting member superimposed on the opposite side of the surface of the heating element that contacts the fixing member,
The heating element and the heat conducting member are supported by fixing one end portion in the circumferential direction of the fixing member, and the other end portion is displaced in the circumferential direction and the heating element and the heat conducting member. The fixing device is supported so as to allow relative displacement in the circumferential direction.   The fixing device according to claim 1, wherein the heating element is supported by an elastic member, and can be displaced in a direction to advance and retreat with respect to the fixing member by deformation of the elastic member.   3. The heat generating member and the heat conducting member are supported at both ends in the circumferential direction of the fixing member at both ends in the width direction of the fixing member, respectively. The fixing device described.   In the heating element, the portion corresponding to the passing range of the recording medium in the width direction of the fixing member has a larger range in contact with the fixing member in the circumferential direction than the portion not corresponding to the passing range. The fixing device according to any one of claims 1 to 3, wherein   The fixing device according to any one of claims 1 to 4, wherein the heating element is formed of a temperature-sensitive magnetic material that becomes weak in magnetism when the temperature rises. An image forming unit that forms a toner image by attaching toner to a latent image due to a difference in electrostatic potential;
A transfer device that directly transfers the toner image to a transported recording medium or transfers the toner image to an intermediate transfer member, and then transfers the toner image to a transported recording medium;
A fixing device that heats and fixes the toner image transferred to the recording medium to the recording medium,
6. The image forming apparatus according to claim 1, wherein the fixing device is a fixing device according to any one of claims 1 to 5.

Images