JP6834603B2 - Fixing device and image forming device - Google Patents

Description

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

In image forming devices such as copiers, printers, and facsimiles, a heat fixing method is widely adopted as a method for fixing an unfixed toner image transferred to a recording medium such as paper on paper. As a fixing device, a pressure roller and an endless fixing belt that rotates in contact with the pressure roller are known. Further, this fixing device has a heater that heats the fixing belt and a nip forming portion that contacts the inner surface of the fixing belt to form a fixing nip portion between the pressurizing roller and the fixing belt.

Further, in order to prevent fixing and ignition due to abnormal energization of the heater, in the conventional fixing device, the energization is cut off when the temperature reaches a predetermined temperature by the thermostat. In recent years, the heating rate of the fixing member (fixing belt) has become faster due to the lower heat capacity of the fixing device for energy saving, detection and operation are not in time when the temperature rises abnormally, and it already ignites when the power supply to the heater is cut off. There was a problem that the temperature became high, which is dangerous.

In order to lower the temperature at which the thermostat operates, it is generally practiced to install the temperature detecting means closer to the fixing member. However, if they are brought too close to each other, the thermostat will operate and the fixing device cannot be used due to excessive temperature rise at the edges during small-sized paper passing or temporary temperature rise during jam processing, which is not an abnormality in energization of the heater. Further, when the thermostat is arranged inside the fixing belt, the diameter of the fixing belt becomes large, and the detection sensitivity may deteriorate due to the entry of sliding members, grease, etc. inside the fixing belt.

In order to supplement the responsiveness of the temperature detecting means, as a conventional technique, the fixing belt approaches the temperature detecting member according to the temperature. For example, when the temperature rises abnormally, the layers are delaminated using the difference in the coefficient of thermal expansion between the elastic layer and the base layer of the fixing belt, and the separated surface layer portion approaches the safety device to detect the abnormal temperature rise of the fixing belt and the heater. A fixing device having a configuration for shutting off the energization of the belt has already been proposed (see, for example, Patent Document 1).

Further, a fixing device has already been proposed in which the fixing belt is pressed and regulated in the axial direction from the end of the fixing belt, and the energization is cut off by approaching or contacting the temperature detecting member when the belt breaks (for example). , Patent Document 2).

JP-A-2010-107557 Japanese Unexamined Patent Publication No. 2016-90885

In the fixing device described in Patent Document 1, if the fixing belt is rotating, the peeled portion may come close to or come into contact with the temperature detection member, but when the delamination is performed when the belt is stopped, the delamination position is uncertain. It is not always near the temperature detection member. Therefore, if the fixing belt does not approach the temperature detecting member, accurate temperature detection cannot be performed, which causes a problem.

In the method described in Patent Document 2, the buckling shape of the belt differs depending on the strength of the fixing belt at high temperature and the presence or absence of rotation, and the belt breaking position changes. Therefore, the belt does not always break at the target temperature and position, and the reverse is true. There is a possibility of moving away from the belt, which is a problem.

Therefore, the present invention provides a fixing device capable of more reliably detecting the abnormal temperature rise by the temperature detecting means and shutting off the energization of the heater when the fixing belt rises abnormally, and an image forming device provided with the fixing device. With the goal.

In order to achieve the above object, the present invention has a pressure roller, an endless fixing belt that rotates in contact with the pressure roller, a heating portion for heating the fixing belt, and the inside of the fixing belt. A nip that has a pad that is arranged to face the pressure roller and comes into contact with the inner surface of the fixing belt and a pad support member that supports the pad, and forms a fixing nip portion between the pressure roller and the fixing belt. A fixing device having a forming portion and a temperature detecting member arranged on the outer periphery of the fixing belt and shutting off energization to the heating portion when an abnormal temperature rise of the fixing belt is detected, and the abnormal temperature rise of the fixing belt. It is characterized by providing a belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member.

According to the above configuration, when the temperature of the fixing belt rises abnormally, the fixing belt is deformed so as to be closer to the temperature detection member side, so that the trajectory of the fixing belt is compared with the case where the temperature detection member is brought closer to the fixing belt side. Is stable, so that the distance between the fixing belt and the temperature detecting member can be stably brought close to each other. Therefore, when the fixing belt rises abnormally, it is possible to obtain a fixing device capable of more reliably detecting the abnormal temperature rise and cutting off the energization of the heater.

Further, in the fixing device having the above-described configuration, the belt urging means is arranged inside the fixing belt as the urging member, and hits the inner peripheral surface of the fixing belt when the temperature of the fixing belt rises abnormally. A configuration having an internal urging member that is in contact with the fixing belt to urge the fixing belt to be deformed is preferable, and the belt urging means is arranged as the urging member on the outer peripheral portion of the fixing belt, and the fixing belt has a structure. It may have a configuration having an external urging member that abuts on the outer peripheral surface of the fixing belt and urges the fixing belt to deform when the temperature rises abnormally, or may have a configuration including both of them.

Further, in the fixing device having the above configuration, the belt urging means includes, as the urging member, an internal urging member provided with an arcuate abutting portion that abuts and urges the inner peripheral portion of the belt. Further, it has a holding member made of a magnet or a magnetic material of a temperature-sensitive material that attracts and holds the internal urging member in a non-contact state with the belt, and when the fixing belt rises abnormally, the holding member It is preferable that the magnetic force of the belt is reduced to release the holding of the internal urging member, and the arcuate contact portion abuts on the inner peripheral portion of the belt to urge the belt.

Further, in the fixing device having the above configuration, the belt urging means is an internal urging member provided with an arc-shaped contact portion that abuts and urges the inner peripheral portion of the fixing belt as the urging member. A holding member made of a magnet or a magnetic material of a temperature-sensitive material that attracts and holds the internal urging member in a non-contact state with the fixing belt, and the internal urging member from the outside of the fixing belt. It has a magnet made of a temperature-sensitive material that attracts by magnetic force or an attractive member made of a magnetic material, and when the fixing belt rises abnormally, the magnetic force of the holding member becomes small, and the magnetic force of the attractive member does not become small. The structure may be such that the arc-shaped contact portion abuts on the inner peripheral portion of the fixing belt and is urged by exerting a magnetic force that attracts the internal urging member.

Further, in the fixing device having the above-described configuration, the belt urging means is a main body serving as the urging member, which is an arc-shaped contact portion and a heat collecting portion that abut and urge the inner peripheral portion of the fixing belt. It has an internal urging member made of a shape memory fitting member provided with a portion, and when the temperature rise of the fixing belt abnormally, the shape memory fitting member is thermally deformed and the arcuate contact portion is inside the fixing belt. It is preferable that the main body portion serving as a heat collecting portion is installed on the pad support member arranged inside the fixing belt.

Further, in the fixing device having the above-described configuration, the belt urging means holds the fixing belt as the urging member in two portions separated from the portion facing the temperature detection member on both sides. It has an external urging member which is arranged at at least two places on the outer peripheral portion of the belt and is composed of a heat-deforming member which is deformed when the temperature of the fixing belt rises abnormally. The fixing belt may be urged so as to approach the direction of the temperature detecting means when the temperature is raised.

Further, in the fixing device having the above configuration, the Curie temperature of the magnet or magnetic material used for the holding member is preferably higher than the heating temperature of the fixing device, and the belt urging means is used at both ends of the fixing belt. It is preferable to urge only the magnet, and it is more preferable to provide a belt position regulating member inside the fixing belt and in the vicinity of the heater to prevent the fixing belt from getting too close to the heater.

Further, the present invention may be an image forming apparatus provided with the fixing apparatus having the above configuration.

According to the present invention, when the fixing belt rises abnormally, the temperature detecting means can more reliably detect the abnormal temperature rise and obtain a fixing device capable of cutting off the energization of the heater and an image forming device provided with the fixing device. Can be done.

It is a partial vertical sectional front view of the image forming apparatus which concerns on embodiment of this invention. It is a side view of the fixing device included in the image forming apparatus shown in FIG. It is sectional drawing of the fixing apparatus of 1st Embodiment. It is sectional drawing of the fixing apparatus of 1st Embodiment. It is sectional drawing of the fixing apparatus of 2nd Embodiment. It is sectional drawing of the fixing apparatus of 2nd Embodiment. It is sectional drawing of the fixing apparatus of 3rd Embodiment. It is sectional drawing of the fixing apparatus of 4th Embodiment. It is sectional drawing of the fixing apparatus of 5th Embodiment. It is a perspective view which shows an example of an internal urging member. It is sectional drawing of the fixing apparatus of another embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. Further, the same reference numerals are used for the same constituent members, and duplicate description will be omitted as appropriate.

First, the image output operation of the image forming apparatus according to the embodiment of the present invention will be described while explaining the outline of the structure with reference to FIG. FIG. 1 is an example of a partial vertical cross-sectional front view of the image forming apparatus. The alternate long and short dash line with an arrow in FIG. 1 indicates the paper transport path and transport direction. Further, the vertical direction, the horizontal direction, and the paper surface depth direction in FIG. 1 are the vertical direction, the horizontal direction, and the depth direction of the image forming apparatus.

As shown in FIG. 1, the image forming apparatus 1 is a so-called tandem type color copier, and includes an image reading unit 2 for reading an image of a document, a printing unit 3 for printing the read image on a transfer material such as paper, and the like. It includes an operation unit 4 for inputting print conditions and displaying an operating status, and a main control unit 5.

The image reading unit 2 is a known one that reads an image of a document placed on the upper surface of a platen glass by moving a scanner (not shown). The image of the manuscript is color-separated into three colors of red (R), green (G), and blue (B), and converted into an electric signal by a CCD (Charge Coupled Device) image sensor (not shown). As a result, the image reading unit 2 obtains image data for each color of red (R), green (G), and blue (B).

The color-coded image data obtained from the original by the image reading unit 2 is subjected to various processing by the main control unit 5, and the reproduced colors of yellow (Y), magenta (M), cyan (C), and black (K) are reproduced. It is converted into image data and stored in a memory (not shown) of the main control unit 5. The image data for each reproduction color stored in the memory is processed for correcting the misalignment, and then the scanning line is synchronized with the paper transfer in order to perform optical scanning on the photoconductor drum 21 which is an image carrier. It is read out every time.

The printing unit 3 forms an image by an electrophotographic method, transfers the image to paper, and prints the image. The printing unit 3 includes an intermediate transfer belt 11 in which the intermediate transfer body is formed as an endless belt. The intermediate transfer belt 11 is wound around the drive roller 12, the driven rollers 13, and 14. The intermediate transfer belt 11 is rotationally moved counterclockwise in FIG. 1 by the drive roller 12.

The drive roller 12 presses against and contacts the secondary transfer roller 15 facing the intermediate transfer belt 11 with the intermediate transfer belt 11 interposed therebetween. At the location of the driven roller 14, the intermediate transfer cleaning unit 16 provided so as to face the driven roller 14 with the intermediate transfer belt 11 interposed therebetween comes into contact with the outer peripheral surface of the intermediate transfer belt 11. After the toner image formed on the outer peripheral surface of the intermediate transfer belt 11 is transferred to the paper, the intermediate transfer cleaning unit 16 removes and cleans the deposits such as toner remaining on the outer peripheral surface of the intermediate transfer belt 11.

Image forming portions 20Y, 20M, 20C, and 20K corresponding to the reproduction colors of yellow (Y), magenta (M), cyan (C), and black (K) are provided below the intermediate transfer belt 11. In this description, unless it is particularly necessary to limit the description, the description of the identification symbols of "Y", "M", "C", and "K" is omitted, and the term "image forming unit 20" is generically referred to. Sometimes. The four image forming portions 20 are arranged in a line from the upstream side to the downstream side in the rotational direction along the rotational direction of the intermediate transfer belt 11. The four image forming units 20 have the same configuration, and a charging unit, an exposure unit, a developing unit, a drum cleaning unit, and a primary transfer roller are arranged around the photoconductor drum 21 that rotates clockwise in FIG. Be prepared.

Above the intermediate transfer belt 11, a toner bottle 31 and a toner hopper 32 corresponding to the image forming portions 20 of each of the four reproduction colors are provided. The developing unit and the toner hopper 32 are provided with a remaining amount detecting unit (not shown) for detecting the remaining amount of toner inside each of the developing unit and the toner hopper 32. Further, a toner replenishing device (not shown) is provided between the developing unit and the toner hopper 32 and between the toner hopper 32 and the toner bottle 31. When the remaining amount detecting unit detects a decrease in the remaining amount of toner inside the developing unit, the replenishing device drives the toner hopper 32 to replenish the toner to the developing unit. Further, when the remaining amount detecting unit detects a decrease in the remaining amount of toner inside the toner hopper 32, the replenishing device drives the toner bottle 31 to replenish the toner hopper 32. The toner bottle 31 is detachably provided with respect to the main body of the apparatus and can be replaced with a new one as appropriate.

A scanning optical device 23, which is an exposure unit, is arranged below the image forming unit 20. The scanning optical device 23 has one light source such as four semiconductor lasers (not shown) corresponding to each of the four image forming units 20 and individually corresponding to each of the four photoconductor drums 21. The scanning optical device 23 modulates the four semiconductor lasers according to the image gradation data of each reproduction color, and emits the laser light corresponding to each reproduction color individually to the four photoconductor drums 21.

A paper supply device 91 is provided below the scanning optical device 23. The paper supply device 91 loads and accommodates a plurality of paper Ps therein, and sends the papers P one by one to the paper transport path Q in order from the top layer of the paper bundle. The paper P sent out from the paper loading device 91 to the paper transport path Q reaches the position of the resist roller pair 94. Then, the resist roller pair 94 corrects (skew correction) the diagonal feed of the paper P and synchronizes with the rotation of the intermediate transfer belt 11, so that the contact portion (secondary transfer) between the intermediate transfer belt 11 and the secondary transfer roller 15 is formed. Paper P is sent out toward the nip portion).

In the image forming unit 20, an electrostatic latent image is formed on the surface of the photoconductor drum 21 by the laser light emitted from the scanning optical device 23, and the electrostatic latent image is visualized as a toner image by the developing unit. The toner image formed on the surface of the photoconductor drum 21 is primarily transferred to the outer peripheral surface of the intermediate transfer belt 11 at a position where the photoconductor drum 21 faces the primary transfer roller with the intermediate transfer belt 11 interposed therebetween. Then, as the intermediate transfer belt 11 rotates, the toner image of each image forming unit 20 is sequentially transferred to the intermediate transfer belt 11 at a predetermined timing, so that the outer peripheral surface of the intermediate transfer belt 11 is yellow, magenta, cyan, and black. A color toner image (printed image) is formed by superimposing the toner images of the four colors.

The color toner image primaryly transferred to the outer peripheral surface of the intermediate transfer belt 11 is formed by contacting the intermediate transfer belt 11 and the secondary transfer roller 15 with the paper P sent synchronously by the resist roller pair 94. It is transferred at the secondary transfer nip.

A fixing device 40 is provided above the secondary transfer nip portion. The paper P on which the unfixed toner image is transferred at the secondary transfer nip portion is sent to the fixing device 40, and the toner image is heated and pressurized to be fixed on the paper P. The paper P that has passed through the fixing device 40 is discharged to the paper ejection unit 96 provided above the intermediate transfer belt 11.

The operation unit 4 is provided on the front side of the upper part of the image forming apparatus 1. The operation unit 4 includes a display unit 4w having a touch panel. The operation unit 4 inputs settings such as printing conditions such as the type and size of paper P used for printing by the user, enlargement / reduction, and presence / absence of double-sided printing, and input of settings such as a fax number and sender name in facsimile transmission. Accept. In addition, the operation unit 4 also serves as a notification unit for notifying the user of, for example, the state of the device, precautions, error messages, etc. by displaying them on the display unit 4w.

Further, the image forming apparatus 1 is provided with a main control unit 5 composed of a CPU (not shown), an image processing unit, and other electronic components (not shown) in order to control the operation of the entire image forming apparatus 1. The main control unit 5 uses a CPU, which is a central processing unit, and an image processing unit, and is a printing unit 3 including an image forming unit 20 and a fixing device 40 based on programs and data stored and input in a memory, and an image reading unit. A series of image forming operations and printing operations are realized by controlling components such as part 2.

Subsequently, the detailed configuration of the fixing device 40 will be sequentially described with reference to FIGS. 2 to 11. FIG. 2 is a side view showing the basic configuration of the fixing device 40 according to the present embodiment.

As shown in FIG. 2, the fixing device 40 includes a pressure roller 41, a guide member 42, a fixing belt 43, a heating part (heater 44), and a nip forming part 50.

The pressurizing roller 41 has a cylindrical shape, and the rotation axis extends in the paper width direction, that is, in the front-rear direction of the image forming apparatus 1. The pressurizing roller 41 has a length longer than the entire area of the paper transport path Q in the paper width direction. The pressure roller 41 has a laminated structure having an elastic layer or the like whose surface is coated with, for example, a release layer made of fluorine (PFA).

A predetermined pressure is applied to the pressure roller 41 by a pressure mechanism using a pressure spring or the like. The pressurizing mechanism pressurizes the rotating shaft 41a of the pressurizing roller 41 toward the fixing belt 43 on the outer side in the axial direction of the pressurizing roller 41. The peripheral surface of the pressure roller 41 presses and contacts the nip forming portion 50 via the fixing belt 43 to form the fixing nip portion N. In the fixing nip portion N, for example, the pressure roller 41 is in a state of being recessed inward in the radial direction. The fixing device 40 heats and pressurizes the paper P at the fixing nip portion N where the pressurizing roller 41 and the nip forming portion 50 come into contact with each other across the fixing belt 43, and transfers the unfixed toner image transferred to the paper P to the paper P. Is melted and fixed.

The rotating shaft 41a of the pressurizing roller 41 is rotatably supported by a bearing provided in a housing portion (not shown) of the fixing device 40. The pressurizing roller 41 receives power from a fixing motor (not shown) and rotates clockwise in FIG.

The fixing belt 43 is wound around the nip forming portion 50 and formed in an endless shape. The fixing belt 43 is sandwiched between the pressure roller 41 and the nip forming portion 50 at the fixing nip portion N. The fixing belt 43 comes into contact with the pressure roller 41 and rotates counterclockwise in FIG. 2, and the fixing belt 43 has a length longer than the entire area of the paper transport path Q in the paper width direction.

The fixing belt 43 is a cylindrical member and is composed of a base material layer, an elastic layer, and a mold release layer from the inside of the cylinder. The base material layer is arbitrarily selected from heat resistance, strength, flexibility, and the like. For example, metals such as Ni, SUS, Al, PI, PPS, etc. are desirable. The thickness depends on the material strength, but is about 30 to 100 μm. The elastic layer is made of Si rubber, fluororubber, etc., has a thickness of about 50 to 100 μm, and has an elastic modulus of about 0.03 to 100 MPa. For the release layer, it is desirable to use PFA, PTFE, etc., which are fluororesins, in consideration of the releasability with the toner. The thickness is arbitrary, but it is about 10 to 70 μm.

The fixing device 40 according to the present embodiment has a free belt configuration, and guide members 42 are interposed at both ends of the fixing belt 43 in the width direction, and the intermediate portion in the width direction is free. The fixing belt 43 has a cylindrical shape, and a heater 44 is housed inside the fixing belt 43 as a heating unit for heating the fixing belt 43. As the heater 44, a halogen heater, a ceramic heater, or the like can be used. Then, the cylindrical rotatable fixing belt 43 is directly heated by the radiant heat from the heater 44. The contact portion of the guide member 42 with the fixing belt 43 preferably includes a peripheral surface made of a low friction member that slidably and rotatably supports the fixing belt 43. Further, the guide member 42 itself may be rotatably supported.

The nip forming portion 50 is arranged inside the fixing belt 43 so as to face the pressure roller 41, and contacts the inner surface of the fixing belt 43 to form a fixing nip portion N between the pressure roller 41 and the fixing belt 43. The nip forming portion 50 includes a pad 51 and a pad support member 52.

The pad 51 is arranged immediately inside the fixing nip portion N of the fixing belt 43. The pad 51 has a longitudinal shape that extends longer than the fixing belt 43 in the paper width direction. The pad 51 is pressurized by the pressurizing roller 41 via the fixing belt 43 and comes into contact with the inner surface of the fixing belt 43 at the fixing nip portion N. Heat-resistant resin, metal, or the like is used for the pad 51 and the pad support member 52. Further, a sliding sheet is provided on the surface of the fixing belt 43 that slides on the inner peripheral surface. A sliding sheet coated and impregnated with a slidable material on the surface is arranged on the sliding portion of the pad 51 and the fixing belt 43, but a similar coat layer may be provided on the surface.

The pad support member 52 is arranged in a region separated from the fixing nip portion N across the pad 51. One side of the pad support member 52 opposite to the fixing nip portion N side of the pad 51 is attached to support the pad 51. The pad support member 52 of the present embodiment is made of a heat-resistant sheet metal having a substantially L-shaped cross section when viewed from the paper width direction and extending in the paper width direction. The pad support members 52 are fixed to the side plates of the housing portion of the fixing device 40 on both ends in the paper width direction.

As described above, in the fixing device 40 according to the present embodiment, the heater 44 is arranged inside the cylindrical fixing belt 43, and a part of the inner peripheral surface of the fixing belt 43 is heated. Further, a nip forming member (pad 51) and a pad supporting member 52 for supporting the nip forming member (pad 51) are also arranged inside the belt, and a fixing nip portion N is formed together with a pressing member (pressurizing roller 41) arranged on the outer circumference of the belt to form a fixing nip portion N on paper. The formed toner image is fixed. A thermostat 70 is arranged at a predetermined distance as a temperature detecting member on the outer peripheral portion of the fixing belt 43. Further, the thermostat 70 has a function of cutting off the energization of the heater 44.

That is, the fixing device 40 according to the present embodiment is arranged on the outer periphery of the fixing belt 43, and has a temperature detecting member (thermostat 70) that shuts off energization to the heating unit (heater 44) when an abnormal temperature rise of the belt is detected. Have. Further, a belt urging means 60 having an urging member that urges the fixing belt 43 when the temperature of the fixing belt 43 rises abnormally to approach the temperature detecting member is provided.

The belt urging means 60 is an urging member (internal urging member) including, for example, an arcuate contact portion 61a (see FIG. 3) that abuts and urges the inner peripheral portion of the fixing belt 43 as an urging member. 61), and further includes a holding member 62 made of a magnet or a magnetic material of a temperature-sensitive material that attracts and holds the internal urging member 61 in a non-contact state with the fixing belt 43. Further, the internal urging member 61 may be provided with a suction member 63 made of a magnet of a temperature-sensitive material or a magnetic material that attracts the internal urging member 61 from the outside of the fixing belt 43 by a magnetic force.

In any case, when the temperature of the fixing belt 43 rises abnormally, the urging member (internal urging member 61) comes off from the holding member 62, and the arcuate contact portion 61a abuts on the inner peripheral portion of the fixing belt 43 to urge. Any configuration may be used. Therefore, the urging member (internal urging member 61) may be a hinged rotating drop type to bend the fixing belt 43 by its own weight, or may be elastically deformed to urge the fixing belt 43 with a leaf spring structure. , A configuration using a bimetal, a shape memory alloy, or the like that deforms in a predetermined direction when heated may be used.

Further, in consideration of the position fluctuation of the belt, the fixing belt 43 and the detection surface of the thermostat 70 are usually arranged at a distance of about several mm (for example, 3 mm). Further, the amount of movement of the fixing belt in the thermostat direction when the belt is urged by the urging member is adjusted to 3 mm, and the fixing belt 43 and the thermostat detection surface are arranged so as to come into contact with each other during urging.

<First Embodiment>
Next, the belt urging means 60 of the first embodiment will be described with reference to FIGS. 3 and 4. 3 and 4 are schematic cross-sectional views of the fixing device of the first embodiment. Further, for convenience, the posture in which the fixing belt 43 is arranged above the pressure roller 41 is shown, but this arrangement may be horizontal or diagonal as shown in FIG. 2, and is not particularly limited.

The belt urging means 60 of the present embodiment has an internal urging member 61 and a holding member 62 arranged inside the fixing belt 43. FIG. 3 shows an operating state in which the internal urging member 61 urges and deforms the fixing belt 43, and FIG. 4 shows the internal urging member 61 being held inside the fixing belt 43 by the holding member 62. Indicates the standby state.

That is, the belt urging means 60 according to the present embodiment is arranged inside the fixing belt 43 as an urging member, and abuts on the inner peripheral surface of the fixing belt 43 when the temperature of the fixing belt 43 rises abnormally. It is characterized by having an internal urging member 61 that urges the belt to deform. With this configuration, by urging the fixing belt 43 from the inside to the outside via the internal urging member 61, the fixing belt 43 can be easily deformed in the direction approaching the temperature detecting member. .. Further, if the fixing device has a free belt configuration, the fixing belt 43 can be greatly deformed even with a weak urging force. Therefore, it is better to place the fixing belt inside the belt closer to the temperature detection member and closer to the heat source for thermal deformation. It has good responsiveness and is the most efficient configuration.

The holding member 62 is made of a temperature-sensitive magnet attached to a long side portion having an L-shaped cross section that does not hold the pad 51 of the pad support member 52, and the internal urging member 61 is made of this temperature-sensitive magnet. It is made of an iron material that magnetizes the holding member 62.

Further, the internal urging member 61 is, for example, an urging member having a spring property (for example, a leaf spring), and is elastically displaceable in a direction of contacting the inner peripheral surface of the fixing belt 43 when separated from the holding member 62. There is. Therefore, when the holding member 62 maintains a high magnetic force, the internal urging member 61 can be magnetically held against the spring force of the internal urging member 61, but the magnetic force of the holding member 62 disappears. When it becomes weak or weak, the spring force of the internal urging member 61 becomes relatively strong, and the arcuate contact portion 61a of the internal urging member 61 separates from the holding member 62 and becomes the inner peripheral surface of the fixing belt 43. Abut.

In this embodiment, a neodymium magnet having a Curie temperature of about 300 ° C. is used as the temperature-sensitive magnet material. Further, it is mounted on the opposite side of the heater 44 of the pad support member 52, and is configured to be heated before the fixing belt 43 by the heat of the heater 44.

Since the belt temperature of the fixing device 40 during normal use is 150 ° C. to 180 ° C., the magnetic force of the holding member 62 made of a neodymium magnet having a Curie temperature of about 300 ° C. is maintained in this state. Further, since the internal urging member 61 is made of an iron material, the Curie temperature is about 770 ° C., and the magnetic permeability does not decrease.

Therefore, during the normal operation of the fixing device 40, the internal urging member 61 is attracted by the magnetic force of the magnet, and the internal urging member 61 is not urged by the fixing belt 43 (FIG. 3). When the inside of the fixing belt 43 exceeds the Curie temperature (about 300 ° C.) of the magnet, the magnetic force disappears, the internal urging member 61 is urged to the fixing belt 43 by its own weight and elasticity, and the distance between the thermostat 70 and the fixing belt 43 is close. Alternatively, the energization is cut off by the operation of the thermostat 70 that contacts and detects the abnormal temperature rise of the fixing belt 43.

The magnetic force of the magnet does not necessarily disappear, and the fixing belt 43 can be urged even if the magnetic permeability of the internal urging member 61 side decreases. In that case, it is preferable to use a magnetic material whose magnetic permeability changes at a desired temperature as the material of the internal urging member 61. Further, a magnetic material may be used only for a portion that attracts the magnet, and a non-magnetic member may be used for the other portion.

The same effect can be obtained by using a temperature-sensitive member such as bimetal or shape memory alloy instead of magnetic force, but while bimetal has linear temperature and displacement (first-order proportional), magnet has temperature and magnetic force. Alternatively, since the relationship between the magnetic permeability is non-linear, it is possible to make a configuration that rapidly approaches at the target temperature, so magnetic force is preferable.

The set temperature of the fixing belt 43 required for fixing is about 200 ° C. or lower, but the temperature rises to about 250 ° C. when a small size paper is passed or a paper jam is stopped during continuous paper passing. That is, since the normal heating temperature of the fixing belt 43 rises to about 250 ° C., the operating temperature of the urging means using the temperature-sensitive material is 250 ° C. or higher, and about 300 ° C. is desirable to prevent smoke and ignition. ..

<Second Embodiment>
Since the fixing belt 43 can be brought closer to the thermostat 70 by arranging the urging member externally, this embodiment will be described with reference to FIGS. 5 and 6 as the second embodiment.

FIG. 5 is a schematic cross-sectional view of the fixing device of the second embodiment, in which the external urging members 64 (64A, 64B) as urging members are thermally deformed to urge and deform the fixing belt 43. FIG. 6 shows a standby state in which the external urging members 64 (64A, 64B) are held at a position where they are not deformed and do not interfere with the fixing belt 43.

The external urging member 64 (64A, 64B) according to the present embodiment is made of, for example, a bimetal. Since the shape of the bimetal gradually displaces with respect to temperature, it is installed outside the fixing belt 43 which is in a non-contact state with the fixing belt 43 before heating. Further, in order to displace the fixing belt 43 in the direction of the thermostat 70, the bimetal that displaces the fixing belt 43 at two positions between the pad 51 and the thermostat 70 when the temperature rises abnormally and urges the outer peripheral surface of the fixing belt 43. An external urging means 64 is arranged.

That is, in the present embodiment, as the urging member, the fixing belt 43 is arranged at at least two places on the outer peripheral portion of the fixing belt 43 so as to sandwich two parts separated from the portion facing the temperature detection member on both sides, and is fixed. It has external urging members 64 (64A, 64B) made of a heat-deformable member that deforms when the belt 43 is abnormally heated, and through the deformation of the heat-deformable member, the fixing belt 43 is moved when the fixing belt 43 is abnormally heated. It is characterized by urging it so that it approaches the direction of the temperature detecting means. With this configuration, when the temperature of the fixing belt 43 rises abnormally, the fixing belt 43 can be urged from two locations on the outer peripheral portion of the fixing belt 43 to bring the fixing belt 43 closer to the temperature detecting means.

As described above, according to the present embodiment, the temperature at the time of fixing (paper passing) (150 ° C to 160 ° C) is abnormally raised in a non-contact state with the fixing belt 43, and the temperature of the central portion exceeds 300 ° C. The external urging member 64 (64A, 64B) is deformed, the fixing belt 43 is pushed to the point where the fixing belt 43 and the detection surface of the thermostat 70 come into contact with each other, and the thermostat 70 detects an abnormal temperature rise of the fixing belt 43. The energization is cut off by the operation.

Further, the belt urging means 60 may be configured to include both the internal urging member 61 described in the first embodiment and the external urging means 64 described in the second embodiment. In this case, the fixing belt 43 is deformed from the inside of the portion of the fixing belt 43 facing the temperature detecting member toward the temperature detecting member via the internal urging member 61, and at the same time, the temperature detecting member of the fixing belt 43 is deformed. The fixing belt 43 can be deformed in a direction approaching the temperature detecting member from the outside on both sides of the portion facing the temperature detecting member via the external urging members 64 (64A, 64B).

<Third Embodiment>
In addition to the configuration of the first embodiment, a configuration including a suction member that sucks and holds the internal urging member 61 from the outside of the fixing belt 43 will be described as the third embodiment with reference to FIG. 7. FIG. 7 is a schematic cross-sectional view of the fixing device of the third embodiment.

As shown in FIG. 7, the present embodiment has, as an urging member, an internal urging member 61 made of an iron material having an arcuate abutting portion 61a that abuts and urges the inner peripheral portion of the fixing belt 43. Further, the holding member 62 made of a magnet made of a temperature-sensitive material that attracts and holds the internal urging member 61 in a non-contact state with the fixing belt 43 and the internal urging member 61 are attracted by magnetic force from the outside of the fixing belt 43. It is configured to have an attractive member 63 made of a magnet made of a temperature-sensitive material. Then, when the temperature of the fixing belt 43 rises abnormally, the magnetic force of the holding member 62 becomes small, and the magnetic force of the suction member 63 does not become small, but exerts the magnetic force of attracting the internal urging member 61, so that the internal urging member 61 The arc-shaped contact portion abuts on the inner peripheral portion of the fixing belt 43 and urges the fixing belt 43.

The internal urging member 61 of the present embodiment may be a rotary drop type or a leaf spring type that urges the fixing belt 43 by its own weight. In any case, when the temperature of the fixing belt 43 rises abnormally, the holding force of the holding member 62 becomes small to release the holding of the internal urging member 61, and in addition, the internal urging member 61 is sucked by the suction member 63. By the action, it becomes possible to approach the temperature detection member (thermostat 70) more reliably and stably.

Further, the suction member 63 is preferably installed at a position where the fixing belt 43 can come into contact with the thermostat detection surface when the internal urging member 61 urges the suction member 63.

The magnetic force relationship of the magnet in this case is
The magnetic force of the holding member 62> the magnetic force of the suction member 63 so that the belt is not urged during normal operation. Further, the Curie temperature of the magnet of the temperature-sensitive material of the inner holding member 62 is set to about 450 ° C, which is higher than the Curie temperature of the magnet of the temperature-sensitive material of the outer suction member 63. ing.

Therefore, a neodymium magnet is used for the inner holding member 62, but a ferrite magnet (Curie temperature 450 ° C.) is used for the outer suction member 63. As described above, the internal urging member 61 is made of an iron material having a Curie temperature of about 770 ° C. Further, the magnetic force may be adjusted by the size of the magnet.

As described above, when the internal urging member 61 made of an iron material is adopted as the urging member and the magnet of the temperature-sensitive material is adopted as the inner holding member 62 and the outer suction member 63, the Curie temperature of those members As a relationship,
The magnet of the holding member 62 <the magnet of the suction member 63 ≤ the internal urging member, which is a condition for the internal urging member 61 to be attracted to the magnet of the suction member 63 at the time of abnormal temperature rise.

Since there is a relationship of the magnetic force of the holding member 62> the magnetic force of the suction member 63 during normal paper passing, the magnet of the holding member 62 arranged on the pad support member 52 holds the internal urging member 61 by the magnetic force. It is pulled to the side and is in a non-contact state with the fixing belt 43. When the temperature inside the fixing belt 43 rises to 300 ° C. or higher and exceeds the Curie temperature of the magnet of the holding member 62, the magnet loses its magnetic force. At this time, the temperature of the magnet of the attraction member 63 on the outside of the fixing belt 43 has not reached the Curie temperature (450 ° C.), and the Curie temperature of the iron material is much higher than the operating temperature (770 ° C.). Both the magnet of the member 63 and the internal urging member 61 retain their magnetic properties, and the internal urging member 61 is attracted to the magnet side of the outer attractive member 63 to urge the fixing belt 43.

<Fourth Embodiment>
In order to further increase the sensitivity of the temperature-sensitive member to the temperature, a more effective effect can be obtained by arranging a heat collecting portion as a part of the urging means. Therefore, an embodiment in which a heat collecting portion made of a material having good thermal conductivity such as copper or aluminum is provided will be described as a fourth embodiment with reference to FIG.

FIG. 8 is a schematic cross-sectional view of the fixing device of the fourth embodiment. A heat collecting portion made of an aluminum material having good thermal conductivity is provided on the surface of the pad support member 52 facing the thermostat 70, and an internal urging member 61A provided with an urging member made of a shape memory alloy member is provided. It is preferable that the heat collecting portion is integrally formed with the main body portion 61Ab of the internal urging member 61A.

That is, the belt urging means 60 according to the present embodiment includes, as urging members, an arc-shaped contact portion 61Aa that abuts and urges the inner peripheral portion of the fixing belt 43 and a main body portion 61Ab provided with a heat collecting portion. The internal urging member 61A made of the shape memory alloy member provided is provided, and when the fixing belt 43 is abnormally heated, the internal urging member 61A made of the shape memory alloy member is thermally deformed and the arcuate contact portion 61Aa is formed. It is characterized in that it abuts on the inner peripheral portion of the fixing belt 43 and urges it. With this configuration, even if an urging member (internal urging member 61A) made of a shape memory alloy member provided with an arcuate contact portion 61Aa is used, the temperature of the fixing belt 43 is detected when the temperature of the fixing belt 43 rises abnormally. It can be easily deformed in the direction approaching the member (thermostat 70).

In the present embodiment shown in FIG. 8, when a shape memory alloy member is used as the temperature sensitive member, a heat collecting portion (main body portion 61Ab) is provided as a part of the shape memory alloy member, and contact with the pad support member 52. The area is increasing. Therefore, since the heat of the heater 44 is not the portion that directly hits the belt but the back side of the pad support member 52, the heating of the fixing belt 43 is not blocked, and the pad support member 52 is directly heated by the heater 44, so that the temperature is high. Therefore, the temperature of the shape memory alloy can be effectively raised.

<Fifth Embodiment>
Further, the configuration in which the magnet of the inner holding member 62 described in the first embodiment and the third embodiment is used as the heat collecting portion will be described with reference to FIG. 9 as the fifth embodiment.

FIG. 9 is a schematic cross-sectional view of the fixing device of the fifth embodiment, showing a configuration in which the magnet of the holding member 62 is provided at a portion directly heated by the heater 44.

As shown in FIG. 9, this is an example in which a part of the holding member 62 of the magnet of the temperature sensitive member is arranged in a portion directly exposed to light or heat from the heater 44, and one surface of the magnet is used as a heat collecting portion. With this configuration, when the rotation of the fixing belt 43 is stopped, the temperature of the magnet rises faster when it is directly heated by radiant heat in order to detect an abnormal temperature rise while the heater 44 remains lit. The operating time can be shortened.

<Other Embodiments>
Next, other embodiments will be described with reference to FIG. FIG. 10 is a perspective view showing an example of the internal urging member.

As shown in FIG. 10, it is preferable that the internal urging member 61 (61A) urges only both ends of the fixing belt 43 (inside that does not interfere with the guide member 42). With this configuration, the heat capacity of the image region can be reduced by providing the urging members (internal urging members 61, 61A) only at the end of the fixing belt 43 so as not to affect the warm-up time. Can be configured in.

For example, when the internal urging member 61A made of bimetal is provided, the urging member is arranged inside the fixing belt 43, and the heat capacity becomes large, so that the temperature rising time becomes long. Further, even when the external urging member 64 made of bimetal is arranged outside, the temperature rise of the fixing belt 43 is hindered in the contact state, so that the urging member needs to have a minimum heat capacity.

The urging member at the end (arc-shaped contact portion 61Aa) is arranged outside the paper passing region, and in this embodiment, the maximum paper passing width is A3 size (297 mm), so the interval between the urging parts is set to 300 mm. An urging member with a width of 10 mm was formed in the area outside the paper. Further, the urging member is integrally formed and is fixed to the pad support member 52 via a heat collecting portion (main body portion 61Ab). Therefore, since the arcuate contact portions 61Aa at both ends are at the same temperature due to heat conduction, even if they are arranged at both ends, they can be deformed at the same time and the urging operation can be performed at the same time. The urging members (arc-shaped contact portion 61Aa) at both ends may be composed of separate members, but in that case, it is desirable to fix them to members having the same temperature, such as a holding member, so that the urging operations are performed at the same time. ..

By arranging the position of the urging member (arc-shaped contact portion 61Aa) at the end of the belt (non-passing area), the heat capacity of the passing area can be reduced, so that the warm-up time can be shortened and the thermostat 70 can be used. It is possible to improve both sensitivity.

Further, as shown in FIG. 11 which is a schematic cross-sectional view of another embodiment, a belt position regulating member 71 for suppressing the fixing belt 43 from getting too close to the heater 44 is provided inside the fixing belt 43 and in the vicinity of the heater 44. It is preferable to provide. With this configuration, even if the fixing belt 43 is deformed in the direction approaching the temperature detecting member via the internal urging members 61, 61A and the external urging member 64, the fixing belt 43 can be formed via the belt position regulating member 71. It is possible to prevent the fixing belt 43 from smoking or igniting by suppressing the heater 44 from getting too close to the heater 44.

When the fixing belt 43 is brought closer to the thermostat 70 side, the belt on the opposite side, which is not urged by the urging member, is deformed toward the inside and approaches the member inside the belt. Further, in a transient state in which the urging member does not completely urge the fixing belt 43, the position of the belt becomes unstable. In the present embodiment, the belt between the pad 51 on the side opposite to the urged side and the internal urging members 61, 61A approaches the heater 44 side, and the fixing belt is before the power supply of the heater 44 is cut off. 43 becomes hot.

Therefore, a position regulating member 71 that regulates the deformation position of the fixing belt 43 is arranged in the vicinity of the heater 44 between the pad 51 inside the belt on the side opposite to the urged side and the internal urging members 61 and 61A. As a result, when the urging members (internal urging members 61, 61A) urge the fixing belt 43, the fixing belt 43 is regulated at three points in the circumferential direction, so that the traveling position of the fixing belt 43 is stable and transient. In the state, the belt position does not come too close to the heater 44, and the position of the fixing belt 43 is stable.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the gist of the invention. For example, although the belt urging means 60 having the internal urging member 61 and the holding member 62 is attached to the pad support member 52 having an L-shaped cross section, a support member provided separately from the pad support member 52 is interposed. You may. Further, although the internal urging member 61 has been described as having an arcuate contact portion, it may be a smooth surface such as a chamfered surface or a wavy surface. Further, the internal urging member 61 is made of an iron material, and the holding member 62 and the suction member 63 are made of a magnet. However, even if the combination of the magnet and the magnetic material is different, the internal urging member can be attracted and urged by magnetic force. It doesn't matter.

As described above, the present invention includes a pressure roller 41, an endless fixing belt 43 that rotates in contact with the pressure roller 41, a heating unit (heater 44) that heats the fixing belt 43, and a fixing belt 43. A pad 51 that is arranged to face the pressure roller 41 and comes into contact with the inner surface of the fixing belt 43 and a pad support member 52 that supports the pad 51 are provided between the pressure roller 41 and the fixing belt 43. Fixing having a nip forming portion 50 forming the fixing nip portion N and a temperature detecting member (thermostat 70) arranged on the outer periphery of the fixing belt 43 and shutting off energization to the heating portion when an abnormal temperature rise of the fixing belt 43 is detected. The apparatus 40 is characterized in that the belt urging means 60 having an urging member that urges and deforms the fixing belt 43 to bring it closer to the temperature detecting member when the temperature of the fixing belt 43 rises abnormally is provided.

According to the above configuration, when the temperature of the fixing belt 43 rises abnormally, the fixing belt 43 is brought closer to the temperature detecting member side via the belt urging means 60, as compared with the case where the temperature detecting member is brought closer to the belt side. Since the trajectory of the fixing belt 43 is stable, the distance between the fixing belt 43 and the temperature detecting member can be stably brought close to each other. Therefore, when the fixing belt 43 abnormally rises in temperature, it is possible to obtain a fixing device 40 capable of more reliably detecting the abnormal temperature rise by the temperature detecting means and cutting off the energization of the heater 44.

Further, in the fixing device 40 having the above-described configuration, the belt urging means 60 is arranged inside the fixing belt 43 as an urging member, and is placed on the inner peripheral surface of the fixing belt 43 when the temperature of the fixing belt 43 rises abnormally. It is characterized by having an internal urging member 61 that abuts and urges the fixing belt 43 to deform. According to this configuration, by urging the fixing belt 43 from the inside to the outside via the internal urging member 61, the fixing belt 43 can be easily deformed in the direction approaching the temperature detecting member. Further, if the fixing device has a free belt configuration, the fixing belt 43 can be greatly deformed even with a weak urging force. Therefore, it is better to place the fixing belt inside the belt closer to the temperature detection member and closer to the heat source for thermal deformation. It has good responsiveness and is the most efficient configuration.

Further, in the fixing device 40 having the above configuration, the belt urging means 60 is arranged on the outer peripheral portion of the fixing belt 43 as an urging member, and is placed on the outer peripheral surface of the fixing belt 43 when the temperature of the fixing belt 43 rises abnormally. It is characterized by having an external urging member 64 that abuts and urges the fixing belt 43 to deform. According to this configuration, when the temperature of the fixing belt 43 rises abnormally, the fixing belt 43 can be brought closer to the temperature detecting member via the external urging member 64. Further, since the belt urging means 60 is arranged outside the fixing belt 43, the diameter of the fixing belt 43 can be made smaller and the heat capacity of the fixing device can be reduced.

Further, in the fixing device 40 having the above configuration, the belt urging means 60 is internally attached as an urging member, which includes an arc-shaped contact portion 61a that abuts and urges the inner peripheral portion of the fixing belt 43. It has a urging member 61, and further has a holding member 62 made of a magnet or a magnetic material of a temperature-sensitive material that attracts and holds the internal urging member 61 in a non-contact state with the fixing belt 43, and abnormally raises the fixing belt 43. When warm, the magnetic force of the holding member 62 becomes small to release the holding of the internal urging member 61, and the arcuate contact portion 61a abuts on the inner peripheral portion of the fixing belt 43 to urge the fixing belt 43. According to this configuration, since the holding member 62 that attracts and holds the internal urging member 61 provided with the arcuate contact portion 61a is made of a magnet or a magnetic material as a temperature-sensitive material, the temperature rise of the fixing belt 43 abnormally rises. Occasionally, the fixing belt 43 can be deformed so as to be closer to the temperature detecting member only by releasing the holding of the internal urging member 61.

Further, in the fixing device 40 having the above-described configuration, the belt urging means 60 is internally attached as an urging member, which includes an arc-shaped contact portion 61a that abuts and urges the inner peripheral portion of the fixing belt 43. A holding member 62 made of a magnet or magnetic material of a temperature-sensitive material that has a urging member 61 and further attracts and holds the internal urging member 61 in a non-contact state with the fixing belt 43, and an internal urging member 61 are fixed. It has a magnet of a temperature-sensitive material or a suction member 63 made of a magnetic material that attracts from the outside of the belt 43 by magnetic force, and when the temperature rise of the fixing belt 43 abnormally, the magnetic force of the holding member 62 becomes small, and the attraction member 63 It is characterized in that the arc-shaped contact portion 61a abuts on the inner peripheral portion of the fixing belt 43 and is urged by exerting a magnetic force that attracts the internal urging member 61 without reducing the magnetic force. According to this configuration, in addition to releasing the holding of the internal urging member 61 by the holding member 62 when the temperature of the fixing belt 43 rises abnormally, the suction action of the internal urging member 61 by the suction member 63 further ensures the temperature. It becomes possible to get closer to the detection member.

Further, in the fixing device 40 having the above configuration, the belt urging means 60 has an arc-shaped contact portion 61Aa and a heat collecting portion that abut and urge the inner peripheral portion of the fixing belt 43 as urging members. It has an internal urging member 61A made of a shape memory alloy member having a main body portion 61Ab, and when the temperature rise of the fixing belt 43 is abnormal, the shape memory alloy member is thermally deformed and the arcuate contact portion 61Aa is the fixing belt. It is characterized in that it abuts on the inner peripheral portion of 43 and urges it. According to this configuration, even if the belt urging means 60 provided with the internal urging member 61A made of the shape memory alloy member provided with the arcuate contact portion 61Aa is used, the fixing belt 43 is used when the temperature of the fixing belt 43 rises abnormally. It can be easily deformed in the direction approaching the temperature detecting member.

Further, in the fixing device 40 having the above-described configuration, the belt urging means 60 uses the fixing belt 43 as an urging member so as to sandwich two portions separated from the portion facing the temperature detection member on both sides. The fixing belt 43 has an external urging member 64 which is arranged at at least two locations on the outer peripheral portion of the 43 and is composed of a heat deforming member which deforms when the temperature of the fixing belt 43 rises abnormally. It is characterized in that the fixing belt 43 is urged so as to approach the direction of the temperature detecting means when the temperature is raised. According to this configuration, when the temperature of the fixing belt 43 rises abnormally, the fixing belt 43 can be urged from two places on the outer peripheral portion of the fixing belt 43 to bring the fixing belt 43 closer to the temperature detecting means.

Further, the present invention is characterized in that, in the fixing device 40 having the above configuration, the main body portion 61Ab serving as a heat collecting portion is installed on a pad support member 52 arranged inside the fixing belt 43. According to this configuration, the belt urging means 60 made of a shape memory alloy member can be easily attached via the pad support member 52 that supports the pad 51. Further, the heat collecting portion and the operating portion can be freely arranged, and for example, the heat collecting portion can be provided in the central portion where the temperature tends to be high.

Further, the present invention is characterized in that, in the fixing device 40 having the above configuration, the Curie temperature of the magnet or magnetic material used for the holding member 62 is higher than the normal heating temperature of the fixing belt 43. According to this configuration, the magnetic force of the holding member 62 is maintained during the normal operation of the fixing device 40, and when the fixing belt 43 abnormally rises above the normal heating temperature, the magnetic force of the holding member becomes small and is internally attached. The force member 61 can be pressed against the fixing belt 43.

Further, the present invention is characterized in that, in the fixing device 40 having the above configuration, the belt urging means 60 urges only both ends of the fixing belt 43. According to this configuration, the heat capacity of the image region can be reduced by providing the urging member only at the end of the fixing belt 43, and the warm-up time can be not affected.

Further, in the fixing device 40 having the above configuration, the fixing belt 43 is provided with a belt position regulating member 71 for preventing the fixing belt 43 from getting too close to the heating part inside the fixing belt 43 and in the vicinity of the heating part (heater 44). It is characterized by. According to this configuration, when the fixing belt 43 is deformed by the belt urging means 60, the fixing belt 43 is suppressed from approaching the heater 44 via the belt position regulating member 71, and the fixing belt 43 emits smoke and ignites. You can prevent it from happening.

That is, according to the present invention, when the fixing belt 43 abnormally rises in temperature, it is possible to realize a fixing device 40 capable of more reliably detecting the abnormal temperature rise and cutting off the energization of the heater 44. become.

Further, in the image forming apparatus 1 provided with the fixing device 40 according to the present embodiment, since the abnormal temperature rise of the fixing belt 43 can be detected more reliably, the fixing member (the fixing member () by reducing the heat capacity of the fixing device for energy saving. Even when the heating rate of the fixing belt) becomes high, the energization of the heater 44 can be cut off before the fixing belt 43 emits smoke or ignites.

As described above, according to the present invention, when the fixing belt rises abnormally, the temperature detecting means can more reliably detect the abnormal temperature rise and cut off the energization of the heater, and an image provided with the fixing device. A forming device can be obtained.

Therefore, the fixing device according to the present invention can be suitably applied to an energy-saving type image forming device or the like, which is required to detect an abnormal temperature rise of the fixing belt at an early stage.

1 Image forming device 40 Fixing device 41 Pressurizing roller 43 Fixing belt 44 Heater (heating part)
50 Nip forming part 51 Pad 52 Pad support member 60 Belt urging means 61 Internal urging member 61A Internal urging member (shape memory alloy member)
61a, 61Aa Arc-shaped contact part 62 Holding member 63 Suction member 64, 64A, 64B External urging member (shape memory alloy member)
70 Thermostat (temperature detection member)
71 Belt position regulation member N Fixing nip part P Paper

Claims (9)

The pressure roller, the endless fixing belt that rotates in contact with the pressure roller, the heating portion that heats the fixing belt, and the fixing belt that is arranged inside the fixing belt so as to face the pressure roller. A nip forming portion having a pad in contact with the inner surface of the pad and a pad supporting member supporting the pad to form a fixing nip portion between the pressure roller and the fixing belt, and a nip forming portion arranged on the outer periphery of the fixing belt. A fixing device having a temperature detecting member that shuts off energization of the heating portion when an abnormal temperature rise of the fixing belt is detected.
A belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member when the temperature of the fixing belt rises abnormally is provided .
The belt urging means is arranged as the urging member on the outer peripheral portion of the fixing belt, and is attached so as to abut on the outer peripheral surface of the fixing belt and deform the fixing belt when the temperature rises abnormally. A fixing device characterized by having an external urging member to be urged. The belt urging means is arranged inside the fixing belt as the urging member, and is attached so as to abut on the inner peripheral surface of the fixing belt and deform the fixing belt when the temperature of the fixing belt rises abnormally. The fixing device according to claim 1, further comprising an internal urging member for urging. The pressure roller, the endless fixing belt that rotates in contact with the pressure roller, the heating portion that heats the fixing belt, and the fixing belt that is arranged inside the fixing belt so as to face the pressure roller. A nip forming portion having a pad in contact with the inner surface of the pad and a pad supporting member supporting the pad to form a fixing nip portion between the pressure roller and the fixing belt, and a nip forming portion arranged on the outer periphery of the fixing belt. A fixing device having a temperature detecting member that shuts off energization of the heating portion when an abnormal temperature rise of the fixing belt is detected.
A belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member when the temperature of the fixing belt rises abnormally is provided.
The belt urging means has, as the urging member, an internal urging member having an arcuate contact portion that abuts and urges the inner peripheral portion of the fixing belt, and further, the internal urging member. It has a holding member made of a magnet or a magnetic material of a temperature-sensitive material that attracts and holds the fixing belt in a non-contact state, and when the fixing belt is abnormally heated, the magnetic force of the holding member becomes small and the biasing is performed. to release the holding member, the arcuate contact portion you characterized in that biasing contact with the inner peripheral portion of the fixing belt constant Chakusochi. The pressure roller, the endless fixing belt that rotates in contact with the pressure roller, the heating portion that heats the fixing belt, and the fixing belt that is arranged inside the fixing belt so as to face the pressure roller. A nip forming portion having a pad in contact with the inner surface of the pad and a pad supporting member supporting the pad to form a fixing nip portion between the pressure roller and the fixing belt, and a nip forming portion arranged on the outer periphery of the fixing belt. A fixing device having a temperature detecting member that shuts off energization of the heating portion when an abnormal temperature rise of the fixing belt is detected.
A belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member when the temperature of the fixing belt rises abnormally is provided.
The belt urging means has, as the urging member, an internal urging member having an arcuate contact portion that abuts and urges the inner peripheral portion of the fixing belt, and further, the internal urging member. A magnet made of a temperature-sensitive material or a magnetic material that attracts and holds the magnet in a non-contact state with the fixing belt, and a magnet made of a temperature-sensitive material that magnetically attracts the internal biasing member from the outside of the fixing belt. It has an attractive member made of a magnetic material, and when the temperature of the fixing belt rises abnormally, the magnetic force of the holding member becomes small, and the magnetic force of the attractive member does not decrease and exerts a magnetic force that attracts the internal urging member. to constant Chakusochi you characterized by biasing the arcuate contact portion is brought into contact with the inner peripheral portion of the fixing belt. The pressure roller, the endless fixing belt that rotates in contact with the pressure roller, the heating portion that heats the fixing belt, and the fixing belt that is arranged inside the fixing belt so as to face the pressure roller. A nip forming portion having a pad in contact with the inner surface of the pad and a pad supporting member supporting the pad to form a fixing nip portion between the pressure roller and the fixing belt, and a nip forming portion arranged on the outer periphery of the fixing belt. A fixing device having a temperature detecting member that shuts off energization of the heating portion when an abnormal temperature rise of the fixing belt is detected.
A belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member when the temperature of the fixing belt rises abnormally is provided.
The belt urging means is arranged as the urging member at at least two locations on the outer peripheral portion of the fixing belt so as to sandwich two portions of the fixing belt separated from the portion facing the temperature detecting member on both sides. The fixing belt has an external urging member made of a heat-deformable member that deforms when the fixing belt rises abnormally, and the fixing belt is subjected to temperature detection means when the fixing belt rises abnormally through deformation of the heat-deforming member. constant Chakusochi it characterized by biasing such that approach the direction. The fixing device according to claim 3 or 4 , wherein the Curie temperature of the magnet or magnetic material used for the holding member is higher than the normal heating temperature of the fixing belt. The pressure roller, the endless fixing belt that rotates in contact with the pressure roller, the heating portion that heats the fixing belt, and the fixing belt that is arranged inside the fixing belt so as to face the pressure roller. A nip forming portion having a pad in contact with the inner surface of the pad and a pad supporting member supporting the pad to form a fixing nip portion between the pressure roller and the fixing belt, and a nip forming portion arranged on the outer periphery of the fixing belt. A fixing device having a temperature detecting member that shuts off energization of the heating portion when an abnormal temperature rise of the fixing belt is detected.
A belt urging means having an urging member that urges and deforms the fixing belt to bring it closer to the temperature detecting member when the temperature of the fixing belt rises abnormally is provided.
Constant Chakusochi said belt urging means you characterized by biasing only both end portions of the fixing belt. The invention according to any one of claims 1 to 7 , wherein a belt position regulating member for preventing the fixing belt from getting too close to the heating portion is provided inside the fixing belt and in the vicinity of the heating portion. Fixing device. An image forming apparatus comprising the fixing apparatus according to any one of claims 1 to 8.