JP2007213000A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus, in which enve if a temperature sensor of a non-contact type is used, size and cost reductions are achieved, the gap of a thermister element is highly accurately set, and variations in the detection of the temperature of the fixing member are prevented. <P>SOLUTION: The fixing device 19 fixes a toner image T to a recording medium P. The fixing device 19 includes: a fixing member 60 that melts the toner image T; a temperature sensor 80 having a thermister element 81 that detects the temperature of the fixing member 60 without being in contact with it; and a holding member 70 that holds the temperature sensor 80 and determines the gap G of the thermister element 81 relative to the fixing member 60. The temperature sensor 80 includes: a first part 84a1 held by the first holding part 70a of a holding member 70, and a second part 84c1 held by the second holding part 70b of the holding member 70. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine thereof, and a fixing device installed therein, and in particular, a fixing device and an image forming apparatus equipped with a non-contact type temperature sensor. It is about.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer, a technique using a temperature sensor (non-contact type thermistor) that detects the temperature (fixing temperature) of a fixing member in a fixing device in a non-contact manner (for example, , See Patent Document 1).

  The fixing device includes a fixing member such as a fixing roller and a fixing belt, a pressure member such as a pressure roller that presses against the fixing member to form a nip portion, a heating unit that directly or indirectly heats the fixing member, and a fixing member It comprises a temperature sensor that detects the temperature. Heating means for heating the fixing member includes a heater lamp heating method using a heat source such as a heater, and an electromagnetic induction heating method using an exciting coil.

Then, a toner image (image) is transferred onto the surface of the recording medium that moves along the conveyance path of the image forming apparatus at the image forming unit. Thereafter, the recording medium carrying the unfixed image further moves along the conveyance path and reaches the fixing device. The recording medium that has reached the fixing device is fed between the fixing member and the pressure member (a nip portion). The toner image is melted by the heat received from the fixing member, and the toner image is fixed on the recording medium by the pressure received from both members. The recording medium on which the toner image is fixed is sent out from the nip portion and then discharged as an output image outside the image forming apparatus.
In such a fixing device, it is necessary to optimize the surface temperature of the fixing member in order to ensure stable fixing properties. For this purpose, the temperature of the fixing member is detected by a temperature sensor, and the amount of heating by the heating means is adjusted and controlled based on the detection result.

  The non-contact temperature sensor disclosed in Patent Document 1 and the like includes a thermistor element that detects the temperature of the fixing member in a non-contact manner. That is, the non-contact temperature sensor is disposed with a predetermined gap with respect to the fixing member. Therefore, the durability is higher than that of a contact-type temperature sensor that comes into contact with the fixing member, and the problem of damaging the surface of the fixing member does not occur. Furthermore, it is smaller and less expensive than a non-contact sensor such as a thermopile.

JP 2004-205417 A

  In the non-contact type temperature sensor disclosed in Patent Document 1 or the like, the gap between the thermistor element and the fixing member cannot be set with high accuracy, and the temperature detection by the temperature sensor varies. Therefore, the temperature control of the fixing device may become unstable.

Specifically, in the non-contact type temperature sensor disclosed in Patent Document 1 or the like, a case (base) that holds the thermistor element or the like is fastened to a holding member (fixing plate) of the fixing device body, and the entire sensor is separated. Due to the support being held, the gap of the thermistor element with respect to the fixing member varies depending on the temperature sensor assembly state (assembly error) and component accuracy. Therefore, the temperature detection by the temperature sensor varies for each fixing device (image forming apparatus).
Furthermore, the non-contact type temperature sensor disclosed in Patent Document 1 or the like has a warp in the film member (infrared transparent film) that holds the thermistor element and the lead wire and the frame body (fixing frame), In some cases, the gap between the thermistor element and the fixing member varies over time. For this reason, even when the gap of the thermistor element is initially set to a target value, the gap has changed over time, resulting in variations in temperature detection by the temperature sensor.

  In order to perform highly accurate temperature control using a non-contact type temperature sensor, it is necessary to accurately set the gap of the temperature sensor with respect to the detection target. The temperature of the fixing member (fixing temperature) in the fixing device greatly affects the image quality (fixability) in the output image. Therefore, when the non-contact type temperature sensor is used as the temperature sensor in the fixing device, the above-described problem cannot be particularly ignored.

  The present invention has been made to solve the above-described problems. Even when a non-contact type temperature sensor is used, the gap of the thermistor element can be set with high accuracy even if it is small and inexpensive. It is an object of the present invention to provide a fixing device and an image forming apparatus that do not cause variations in temperature detection of a fixing member.

  According to a first aspect of the present invention, there is provided a fixing device for fixing a toner image on a recording medium, a fixing member for melting a toner image, and a thermistor for detecting the temperature of the fixing member in a non-contact manner. A temperature sensor having an element, and a holding member that holds the temperature sensor and defines a gap of the thermistor element with respect to the fixing member, the temperature sensor being held in a first holding portion of the holding member. 1 holding | maintenance part and the 2nd to-be-held part hold | maintained at the 2nd holding | maintenance part of the said holding member are comprised.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the first held portion and the second held portion are spaced apart so as to sandwich the thermistor element. It is formed.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, at least one of the first held portion and the second held portion is a plane. The other is formed so as not to be disposed on the same plane as the plane.

  According to a fourth aspect of the present invention, there is provided the fixing device according to any one of the first to third aspects, wherein the first held portion is a lead wire having one end connected to the thermistor element. It is provided in the accommodating part which accommodates the other end side.

  According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the distance between the second held portion and the fixing member is that of the first held portion with respect to the fixing member. It is formed so as to be larger than the distance.

  According to a sixth aspect of the present invention, in the fixing device according to the fourth or fifth aspect, the first held portion is a plane, and the temperature sensor includes the thermistor element. It is formed so as to be disposed on the same plane as the plane.

  The fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the fourth to sixth aspects, wherein the temperature sensor includes a frame body integrated with the housing portion, and the frame. A film-like member that is adhered to a body and holds the thermistor element and the lead wire, and the second held portion is formed integrally with the frame.

  The fixing device according to an eighth aspect of the present invention is the fixing device according to the seventh aspect, wherein the second held portion has a notch.

  The fixing device according to a ninth aspect of the present invention is the fixing device according to any one of the fourth to eighth aspects, wherein the second held portion is connected to the second holding portion of the holding member. It is formed so as to be held in contact.

  According to a tenth aspect of the present invention, in the fixing device according to any one of the fourth to ninth aspects, the first holding portion and the second holding portion are integrated in the holding member. The first holding portion is a flat surface, and the second holding portion is a cut surface formed in a plane inclined within a range of 30 to 120 ° with respect to the flat surface. It is a lower end of a notch part, Comprising: The said 2nd to-be-held part penetrates the said notch part.

  According to an eleventh aspect of the present invention, in the fixing device according to any one of the first to tenth aspects, the temperature sensor is a second thermistor that detects an ambient temperature in the vicinity of the thermistor element. It further has an element.

  The fixing device according to a twelfth aspect of the present invention is the fixing device according to the eleventh aspect, wherein the second thermistor element has a distance to the fixing member larger than a distance of the thermistor element to the fixing member. It is arrange | positioned so that it may become.

  The fixing device according to a thirteenth aspect of the present invention is the fixing device according to the eleventh or twelfth aspect of the present invention, wherein the second thermistor element includes the first held portion and the second held portion. Between them.

  According to a fifteenth aspect of the present invention, in the fixing device according to any one of the eleventh to thirteenth aspects, the first held portion includes each of the thermistor element and the second thermistor element. The second thermistor element is provided on a side surface of the housing portion. The second thermistor element is provided on the housing portion for housing the lead wire connected to the housing.

  According to a fifteenth aspect of the present invention, in the fixing device according to any one of the first to fourteenth aspects, the thermistor element is held on a heat resistant film.

  According to a sixteenth aspect of the present invention, in the fixing device according to the fifteenth aspect, the heat-resistant film is made of polyimide or / and polytetrafluoroethylene.

  According to a seventeenth aspect of the present invention, an image forming apparatus includes the fixing device according to any one of the first to sixteenth aspects.

  According to the present invention, since the first held portion and the second held portion are provided in the non-contact type temperature sensor, the gap between the thermistor elements can be set with high accuracy, and the temperature of the fixing member can be reduced. It is possible to provide a fixing device and an image forming apparatus that do not cause variations in detection.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a tandem type color printer as an image forming apparatus, 7 is a paper feeding unit for storing a recording medium P such as transfer paper, and 10 is a full-color toner image (image) based on input image information. 11Y, 11M, 11C, and 11BK are photosensitive drums on which toner images of various colors (yellow, magenta, cyan, and black) are formed, and 17 is a primary that is formed by superimposing a plurality of color toner images. An intermediate transfer belt to be transferred, 18 is a transfer roller for secondary transfer of a toner image superimposed and carried on the intermediate transfer belt 17 to the recording medium P, and 19 is a fixing device for fixing an unfixed image on the recording medium P. Indicates.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, image information of each color of yellow, magenta, cyan, and black is transmitted from the host computer to a writing unit (not shown). Then, laser light (exposure light) based on the image information of each color is emitted from the writing unit toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing a charging unit (not shown) (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit, laser beams corresponding to the image signals are emitted from the four light sources corresponding to the respective colors. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y after being charged by the charging unit.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing a developing unit (not shown). Then, each color toner is supplied from each developing unit onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (developing process). ).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller is installed at each of the opposed portions so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photoconductive drums 11Y, 11M, 11C, and 11BK are sequentially transferred to the intermediate transfer belt 17 at the position of the transfer bias roller (primary transfer process). .)

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the primary transfer process reach positions facing a cleaning unit (not shown). Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

  On the other hand, the surface of the intermediate transfer belt 17 on which the toner images of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred in an overlapping manner travels in the direction of the arrow in the figure and reaches a position facing the transfer roller 18. . Then, the full-color toner image on the intermediate transfer belt 17 is secondarily transferred onto the recording medium P at a position facing the transfer roller 18 (secondary transfer process).

Here, the recording medium P transported to a position (contact position) between the transfer roller 18 and the intermediate transfer roller 17 is transported from the paper feeding unit 7 via a transport guide, a registration roller, and the like. is there.
Specifically, the transfer paper P fed by the paper feed roller from the paper feed unit 7 that stores the recording medium P passes through the transport guide and is guided to the registration roller. The recording medium P that has reached the registration roller is conveyed toward the position of the transfer roller 18 in synchronization with the toner image on the intermediate transfer belt 17.

Thereafter, the recording medium P on which the full color image is transferred is guided to the fixing device 19. In the fixing device 19, the color image (toner) is fixed on the recording medium P at the nip between the fixing belt and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 19 installed in the image forming apparatus main body 1 will be described in detail.
As shown in FIG. 2, the fixing device 20 mainly includes a fixing belt 60 as a fixing member, a support roller 40, a heater 41 that is provided in the support roller 40 and functions as a heating unit, a fixing auxiliary roller 50, and a pressure member. The pressure roller 30, the tension roller 61, the temperature sensor 80, the holding member 70 that holds the temperature sensor 80, and the like.

Here, the fixing auxiliary roller 50 is formed by forming an elastic layer such as silicone rubber on the surface of a cored bar made of stainless steel or the like. The elastic layer of the auxiliary fixing roller 50 is formed so as to have a thickness of 1 to 5 mm and an Asker hardness of 30 to 60 degrees.
The support roller 40 is a thin cylindrical body that rotates counterclockwise in FIG. 2, and a heater 41 is fixed therein as a heat source.

The heater 41 is a rod-shaped heater having a heating wire inside, and both ends thereof are fixed to the side plate of the fixing device 19. In the first embodiment, two heaters 41a and 41b having different heating ranges are installed, and when fixing a small-sized recording medium P, power is supplied to only one heater 41a, and a large amount of heat is supplied. When fixing a recording medium P having a size, electric power is supplied to both heaters 41a and 41b.
The fixing belt 60 is heated via the support roller 40 by the heater 41 whose output is controlled by the power supply unit of the apparatus main body 1. Then, heat is applied to the toner image T on the recording medium P from the surface of the fixing belt 60 to melt the toner image.

The output control of the heater 41 is performed based on the detection result of the belt surface temperature by the temperature sensor 80 that faces the fixing belt in a non-contact manner. And by such output control of the heater 41, the temperature of the fixing belt 60 (fixing temperature) can be maintained at a desired temperature.
Here, the temperature sensor 80 is held by the holding member 70, and the gap G of the thermistor element 81 with respect to the fixing belt 60 is determined. This will be described in detail later.

  The fixing belt 60 is stretched and supported by a support roller 40, a fixing auxiliary roller 50, and a tension roller 61. The fixing belt 60 has a base layer, an elastic layer made of silicone rubber, and a release layer made of a fluorine compound laminated from the inner peripheral surface side. By providing the release layer on the surface of the fixing belt 60, the releasability (peelability) for the toner T (toner image) is secured. The fixing belt 60 travels counterclockwise in FIG.

  The pressure roller 30 as a pressure member mainly includes a cored bar and a plurality of elastic layers formed on the outer peripheral surface of the cored bar via an adhesive layer. The elastic layer of the pressure roller 30 is made of a material such as fluorine rubber, silicone rubber, or foamable silicone rubber. A thin release layer is provided on the surface of the elastic layer. As the material of the release layer, a single layer film of heat-resistant resin such as polyimide, polyetherimide, PES (polyether sulfide), PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), or a film having a thickness of 20 μm The composite layer film etc. which gave the release coat layer which added the electrically conductive material to fluororesins, such as PTFE (tetrafluoroethylene resin) and PFA, in the surface layer side of 10-30 micrometers can be used.

The pressure roller 30 is pressed against the auxiliary fixing roller 50 via the fixing belt 60 by a not-shown pressure mechanism. In this way, a desired nip portion is formed between the pressure roller 30 and the fixing belt 60.
In addition, guide plates 21 and 22 for guiding the conveyance of the recording medium P are disposed on the entrance side and the exit side of the contact portion (nip portion) between the fixing belt 60 and the pressure roller 30, respectively. ing. The guide plates 21 and 22 are fixed to the side plate of the fixing device 19.
Further, a separation plate 23 for assisting separation of the recording medium P after the fixing step from the fixing belt 60 is disposed in the vicinity of the exit side of the nip portion.

The fixing device 19 configured as described above operates as follows.
By the rotation driving of the fixing auxiliary roller 50, the fixing belt 60 rotates counterclockwise in FIG. 2, the support roller 40 also rotates counterclockwise, and the pressure roller 30 also rotates clockwise. The fixing belt 60 is heated at the position of the support roller 40.
Thereafter, the surface of the heated fixing belt 60 reaches a contact portion with the pressure roller 30. Then, the toner image T (toner) on the conveyed recording medium P is heated and melted. The surface of the fixing belt 60 that has passed through the fixing position then reaches the position of the support roller 40 again.
Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

Hereinafter, the temperature sensor 80 and the holding member 70 characteristic of the first embodiment will be described in detail.
3 is a perspective view showing the temperature sensor 80, FIG. 4 is a side view showing the temperature sensor 80, and FIG. 5 is a bottom view showing the temperature sensor 80. 6A is a side view showing the holding member 70 in a state where the temperature sensor 80 is held, and FIG. 6B is a front view showing the holding member 70.

3 to 5, the temperature sensor 80 includes a thermistor element 81, a lead wire 82, a film-like member 88, a case 84, a cover 85, a harness 87, and the like.
The thermistor element 81 is a thermosensitive element with high thermal response that detects the temperature (surface temperature) of the fixing belt 60 as a temperature detection object in a non-contact manner. One end of each of the two lead wires 82 is connected to the thermistor element 81. The other end of the lead wire 82 is accommodated in the accommodating portion 84 a of the case 84. In the housing part 84a, the other end of the lead wire 82 and the harness 87 are electrically connected, and a cover 85 is provided above the housing part 84a. Then, the harness 87 is connected to a power supply board portion (not shown) of the apparatus main body 1, and the temperature of the fixing belt 60 is detected by the voltage change of the thermistor element 81.

  The thermistor element 81 and the lead wire 82 are fixed on a film-like member 88 that is attached to the frame body 84b (integrated with the above-described housing portion 84a) of the case 84 from the lower surface side. Here, the film-like member 88 is a thin film having heat resistance such as polyimide (for example, “Kapton (registered trademark)”), and prevents the thermistor element 81 and the lead wire 82 from being thermally damaged.

Referring to FIG. 3, the case 84 includes an accommodation portion 84 a, a frame body 84 b, and a frame body tip portion 84 c. The case 84 is formed of a heat-resistant resin material by integrally forming a housing portion 84a, a frame body 84b, and a frame body tip portion 84c.
In the housing portion 84a of the case 84, the other end of the lead wire 82 and the harness 87 are electrically connected. A cover 85 is provided above the accommodating portion 84a. Further, the accommodation portion 84a and the cover 85 are formed with through holes 85a for inserting the screws 90 (the insertion of screws in the direction of the arrow in FIG. 4). The temperature sensor 80 is fastened to the holding member 70 by a screw 90 through the through hole 85a.

  The bottom surface of the accommodating portion 84a is a first held portion 84a1 that is held by the first holding portion 70a (see FIGS. 2 and 6) of the holding member 70 (see FIGS. 2 and 4). .) The first held portion 84a1 is a flat surface and serves as a reference surface (fastening surface) for holding (fastening) the temperature sensor 80 on the holding member 70. Further, the thermistor element 81 is disposed on the same plane as the first held portion 84a1 (on the film-like member 88 attached to the frame body 84b). With such a configuration, the gap G of the thermistor element 81 with respect to the fixing belt 60 can be easily determined.

  Referring to FIGS. 3 to 5, frame body distal end portion 84 c of case 84 is formed so as to protrude from housing portion 84 a and frame body 84 b (formed in a direction away from fixing belt 60). . And the 2nd to-be-held part 84c1 hold | maintained at the 2nd holding | maintenance part 70b (refer FIG. 2, FIG. 6) of the holding member 70 is formed in the bottom face of the frame front-end | tip part 84c (FIG. 2). Reference can be made to FIG.

  Here, the holding member 70 is sandwiched between side plates (a support roller 40, a fixing auxiliary roller 50, and a pressure roller 30 are supported via bearings) provided at both ends in the width direction of the fixing device 19. This is a stay as a plate-shaped member. A part of the holding member 70 (the position on the end side in the width direction) is bent to hold the temperature sensor 80 and determine the gap G of the thermistor element 81. 70a and a second holding part 70b are formed.

  Referring to FIG. 6B, the second holding portion 70b is a lower end of a notch portion 70b1 formed in a plane inclined substantially perpendicular to the first holding portion 70a (which is a plane). And the 2nd to-be-held part 84c1 (frame front-end | tip part 84c) of the temperature sensor 80 penetrates into this notch part 70b1, and the 2nd to-be-held part 84c1 is hold | maintained at the lower end of the notch part 70b1 (substantially line contact). It will be.) With such a configuration, the contact area between the second held portion 84c1 and the second holding portion 70b is reduced, so that the heat capacity around the thermistor element 81 is reduced. That is, the occupied space of the second held portion 84c1 and the second holding portion 70b installed around the thermistor element 81 can be reduced. Therefore, the temperature detection error of the temperature sensor 80 due to the difference in heat capacity around the thermistor element 81 is suppressed.

  In the first embodiment, the plane on which the second holding portion 70b is formed is inclined substantially at right angles to the first holding portion 70a, but the plane on which the second holding portion 70b is formed is the first holding. It can also be made to incline in the range of 30-120 degrees with respect to the part 70a. Also in this case, the second held portion 84c1 can be reliably held with a small contact area, and the heat capacity around the thermistor element 81 can be reduced.

  Referring to FIG. 4, in the first embodiment, first held portion 84a1 and second held portion 84c1 are arranged so as not to be on the same plane (virtual plane). . Specifically, the second held portion 84c1 is formed such that the distance from the fixing belt 60 is larger than the distance from the first held portion 84a1 to the fixing belt 60. With such a configuration, since the distance between the second held portion 84c1 and the thermistor element 81 can be set long, the heat capacity around the thermistor element 81 is reduced. Therefore, the temperature detection error of the temperature sensor 80 due to the difference in heat capacity around the thermistor element 81 is suppressed. Further, providing a step between the first held portion 84a1 and the second held portion 84c1 makes it difficult for the case 84 to be warped. Furthermore, the installation property of the temperature sensor 80 with respect to the holding member 70 is improved by setting the distance of the second held portion 84 c 1 with respect to the fixing belt 60 large.

With reference to FIG.3 and FIG.5, in this Embodiment 1, the notch 84c2 (through-hole) is formed in the frame front-end | tip part 84c (2nd to-be-held part 84c1). With such a configuration, the contact area between the second held portion 84c1 and the second holding portion 70b is reduced, so that the heat capacity around the thermistor element 81 is reduced. That is, the occupied space of the second held portion 84c1 and the second holding portion 70b installed around the thermistor element 81 can be reduced. Therefore, as shown in FIG. 7, the temperature detection accuracy when the cutout 84c2 is formed in the second held portion 84c1 (solid line S1) is the temperature detection accuracy when the cutout 84c2 is not formed (broken line S2). Compared to).) That is, the temperature detection error of the temperature sensor 80 due to the heat capacity difference around the thermistor element 81 is suppressed.
In the first embodiment, the bottom portion of the frame body tip portion 84c on which the second held portion 84c1 is formed is a flat surface. However, two cylinders are provided on the frame body tip portion 84c and these are attached to the second object. The holding portion 84c1 may be used.

As described above, the temperature sensor 80 includes the first held portion 84a1 held by the first holding portion 70a and the second held portion 84c1 held by the second holding portion 70b. . As a result, the gap G of the thermistor element 81 can be set with higher accuracy than when the non-contact type temperature sensor 80 is cantilevered.
Specifically, the gap G of the thermistor element 81 with respect to the fixing belt 60 is less likely to vary depending on the state of assembly of the temperature sensor 80 (assembly error) and component accuracy. Therefore, variations in temperature detection by the temperature sensor 80 for each fixing device 19 (image forming apparatus 1) do not occur.
Furthermore, the problem that the warp occurs in the film member 88 and the frame body 84b holding the thermistor element 81 and the lead wire 82 and the gap G of the thermistor element 81 with respect to the fixing belt 60 varies over time is also reduced. Therefore, the gap G of the thermistor element 81 can be stably maintained at the target value from the initial stage to the passage of time. And the gap G changes with time, and the malfunction which the variation in the temperature detection by the temperature sensor 80 does not arise.

  In the first embodiment, the first held portion 84a1 and the second held portion 84c1 are formed so as to be separated so as to sandwich the thermistor element 81 therebetween. In other words, the thermistor element 81 is disposed between the first held portion 84a1 and the second held portion 84c1 when viewed from above. Accordingly, the temperature sensor 80 is held by the holding member 70 by the first held portion 84a1 and the second held portion 84c1 in a well-balanced manner without causing warpage. Therefore, the gap G of the thermistor element 81 can be set with high accuracy.

  As described above, in the first embodiment, since the first held portion 84a1 and the second held portion 84c1 are provided in the non-contact type temperature sensor 80, the thermistor element 81 is small and inexpensive. Thus, it is possible to provide a fixing device and an image forming apparatus in which the gap G can be set with high accuracy and the temperature detection of the fixing belt 60 (fixing member) does not vary.

  In the first embodiment, the present invention is applied to the fixing device 19 using the fixing belt 60 as a fixing member. However, the present invention is also applied to a fixing device using a fixing roller as a fixing member. be able to. In the first embodiment, the present invention is applied to the heater lamp heating type fixing device 19, but the present invention can also be applied to an electromagnetic induction heating type fixing device. In these cases, the same effect as in the first embodiment can be obtained by providing the first held portion 84a1 and the second held portion 84c1 in the non-contact type temperature sensor 80.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 8 is a perspective view showing a temperature sensor 80 installed in the fixing device according to the second embodiment, and FIG. 9 is a side view showing the temperature sensor 80. The temperature sensor in the second embodiment is different from that in the first embodiment in that a second thermistor element 83 that detects the ambient temperature in the vicinity of the thermistor element 81 is provided.

Referring to FIGS. 8 and 9, the temperature sensor 80 according to the second embodiment includes a thermistor element 81 (first thermistor element), a lead wire 82, a heat resistant film 88 (film-like member), a second thermistor element 83, A case 84, a cover 85, a harness 87, and the like are included.
Similar to the first embodiment, the thermistor element 81 is a temperature-sensitive element with high thermal responsiveness that detects the temperature (surface temperature) of the fixing belt 60 serving as a temperature detection object in a non-contact manner. The thermistor element 81 is held on the heat resistant film 88 so as to face the fixing belt 60 with the heat resistant film 88 interposed therebetween. Specifically, the thermistor element 81 and the lead wire 82 are fixed on a heat-resistant film 88 attached to the frame body 84b (integrated with the above-described housing portion 84a) of the case 84 from the lower surface side. . Here, the heat-resistant film 88 is a thin film (having a thickness of several μm) having heat resistance such as polyimide (for example, “Kapton (registered trademark)”), and the thermistor element 81 and the lead wire 82. In addition to preventing thermal breakage, the radiant heat (infrared rays) emitted from the fixing belt 60 is transmitted to enable highly accurate temperature detection.
In addition, as a material of the heat-resistant film 88, polytetrafluoroethylene (for example, “Teflon (registered trademark)”) can be used in addition to polyimide, or a composite material of polyimide and polytetrafluoroethylene is used. You can also.

  The second thermistor element 83 is a temperature-sensitive element with high thermal responsiveness that detects the ambient temperature in the vicinity of the thermistor element 81. One end of two lead wires (not shown) is also connected to the second thermistor element 83. The lead wire of the second thermistor element 83 is accommodated in the accommodating portion 84 a of the case 84. In the housing part 84a, the other end of the lead wire of the second thermistor element 83 and the harness 87 are electrically connected. Then, the ambient temperature is detected by the voltage change of the second thermistor element 83, and the detection result is substituted (or verified) into the relational expression (or conversion table) stored in the control unit, so that the detected temperature of the thermistor element 81 is changed. It is corrected.

The second thermistor element 83 is held at a position farther from the fixing belt 60 than the thermistor element 81 and relatively close to the thermistor element 81. Specifically, the second thermistor element 83 is held on the side surface (the side surface close to the thermistor element 81) of the housing portion 84a (cover 85) of the case 84. 9, the distance (gap) D of the second thermistor element 83 to the fixing belt 60 is set to be larger than the distance (gap) G of the thermistor element 81 to the fixing belt 60. (D> G).
With such a configuration, variation in the detection result of the temperature sensor 80 (correction of the detection temperature of the thermistor element 81) is reduced. That is, the second thermistor element 83 can accurately detect the ambient temperature in the vicinity of the thermistor element 81 without being affected by the heat generated from the fixing belt 60.

In addition, the case 84 in the present second embodiment is also configured with a housing portion 84a, a frame body 84b, and a frame body tip portion 84c, as in the first embodiment. The bottom surface of the housing portion 84 a is a first held portion 84 a 1 that is held by the first holding portion 70 a of the holding member 70. A second held portion 84c1 that is held by the second holding portion 70b of the holding member 70 is formed on the bottom surface of the frame front end portion 84c.
The temperature sensor 80 includes a first held portion 84a1 held by the first holding portion 70a and a second held portion 84c1 held by the second holding portion 70b. As a result, the gap G of the thermistor element 81 can be set with higher accuracy than when the non-contact type temperature sensor 80 is cantilevered.

  Here, in the second embodiment, the first held portion 84a1 and the second held portion 84c1 are formed so as to be separated so as to sandwich the second thermistor element 83. In other words, as viewed from above, the second thermistor element 83 is disposed between the first held portion 84a1 and the second held portion 84c1. Accordingly, the temperature sensor 80 is held by the holding member 70 by the first held portion 84a1 and the second held portion 84c1 in a well-balanced manner without causing warpage. Therefore, the gap D of the second thermistor element 83 can be set with high accuracy. In other words, the second thermistor element 83 that detects the ambient temperature in the vicinity of the thermistor element 81 can be positioned with high accuracy. And the variation in the temperature detection in the temperature sensor 80 is suppressed.

Finally, the relationship between the installation position of the second thermistor element 83 and the detection accuracy of the temperature sensor 80 will be described with reference to FIGS.
FIG. 10 is a side view showing the temperature sensor 80 (corresponding to FIG. 9), in which the installation position of the second thermistor element 83 is changed. Specifically, the second thermistor element 83A installed at the same position as the installation position in the second embodiment, the second thermistor element 83B installed on the upper surface of the accommodating portion 84a (cover 85), and the accommodating portion 84a ( The difference in detection accuracy of the temperature sensor by the second thermistor element 83C installed in the vicinity of the lower surface of the cover 85) was experimentally confirmed. The second thermistor element 83B and the second thermistor element 83C are disposed at a position farther from the thermistor element 81 than the second thermistor element 83A.

  FIG. 11 is a graph showing the experimental results. The solid line Q1 shows the detection accuracy of the temperature sensor when the second thermistor 82A of FIG. 10 is used, and the broken line Q2 uses the second thermistor 82B of FIG. In this case, the detection accuracy of the temperature sensor is shown, and the alternate long and short dash line Q3 shows the detection accuracy of the temperature sensor when the second thermistor 82C of FIG. 10 is used. In the experiment, the temperature of the detection object set at 160 ° C. is detected for a certain period of time.

  From FIG. 11, it can be seen that the variation in the detection result of the temperature sensor 80 varies greatly depending on the installation positions of the second thermistor elements 83 </ b> A to 82 </ b> C that detect the ambient temperature in the vicinity of the thermistor element 81. And according to the structure in this Embodiment 2, it turns out that the variation in the detection result in the temperature sensor 80 is almost lost.

  As described above, also in the second embodiment, the first held portion 84a1 and the second held portion 84c1 are provided in the non-contact type temperature sensor 80 as in the first embodiment. In addition, it is possible to provide a fixing device and an image forming apparatus that are small and inexpensive, can set the gap G of the thermistor element 81 with high accuracy, and do not cause variations in temperature detection of the fixing belt 60 (fixing member). .

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view showing a fixing device installed in the image forming apparatus of FIG. 1. It is a perspective view which shows a temperature sensor. It is a side view which shows a temperature sensor. It is a bottom view which shows a temperature sensor. They are (A) side view and (B) front view which show a holding member. It is a graph which shows the detection accuracy of a temperature sensor. It is a perspective view which shows the temperature sensor in Embodiment 2 of this invention. It is a side view which shows the temperature sensor of FIG. It is the figure which changed the installation position of the 2nd thermistor element. It is a graph which shows the relationship between the installation position of a 2nd thermistor element, and the detection accuracy of a temperature sensor.

Explanation of symbols

1 image forming apparatus body (apparatus body),
7 paper feeding unit, 10 image forming unit,
11BK, 11Y, 11M, 11C photosensitive drum,
17 Intermediate transfer belt, 18 Transfer roller,
19 fixing device,
40 support rollers, 41, 41a, 41b heaters,
50 fixing auxiliary roller,
60 fixing belt (fixing member),
70 holding member (plate-like member), 70a first holding part,
70b 2nd holding | maintenance part, 70b1 notch part,
80 temperature sensor, 81 thermistor element, 82 lead wire,
83 second thermistor element,
84 case, 84a accommodating part,
84a1 first held portion, 84b frame,
84c frame body front end part, 84c1 second held part, 84c2 notch,
85 cover, 85a through hole,
87 Harness, 88 Film-like member (heat-resistant film), 90 screws.

Claims (17)

A fixing device for fixing a toner image on a recording medium,
A fixing member for melting the toner image;
A temperature sensor having a thermistor element for detecting the temperature of the fixing member in a non-contact manner;
A holding member that holds the temperature sensor and defines a gap of the thermistor element with respect to the fixing member,
The temperature sensor includes a first held portion held by a first holding portion of the holding member and a second held portion held by a second holding portion of the holding member. Fixing device to do.   The fixing device according to claim 1, wherein the first held portion and the second held portion are formed so as to be spaced apart so as to sandwich the thermistor element.   2. The first held portion and the second held portion are formed so that at least one is a flat surface and the other is not disposed on the same plane as the flat surface. The fixing device according to claim 2.   The said 1st to-be-held part was provided in the accommodating part which accommodates the other end side of the lead wire by which the one end was connected to the thermistor element, The Claim 1 characterized by the above-mentioned. Fixing device.   The fixing device according to claim 4, wherein the second held portion is formed such that a distance of the second held portion with respect to the fixing member is larger than a distance of the first held portion with respect to the fixing member. The first held portion is a plane,
The fixing device according to claim 4, wherein the temperature sensor is formed such that the thermistor element is disposed on the same plane as the plane. The temperature sensor includes a frame integrated with the housing, and a film-like member that is attached to the frame and holds the thermistor element and the lead wire,
The fixing device according to claim 4, wherein the second held portion is formed integrally with the frame body.   The fixing device according to claim 7, wherein the second held portion has a notch.   The fixing device according to claim 4, wherein the second held portion is formed so as to be held in line contact with the second holding portion of the holding member. . The holding member is a plate-like member in which the first holding portion and the second holding portion are integrally formed,
The first holding part is a plane,
The second holding part is a lower end of a notch part formed in a plane inclined in a range of 30 to 120 ° with respect to the plane,
The fixing device according to claim 4, wherein the second held portion is inserted into the notch portion.   The fixing device according to claim 1, wherein the temperature sensor further includes a second thermistor element that detects an ambient temperature in the vicinity of the thermistor element.   The fixing device according to claim 11, wherein the second thermistor element is disposed such that a distance of the second thermistor element to the fixing member is larger than a distance of the thermistor element to the fixing member.   The fixing device according to claim 11, wherein the second thermistor element is disposed between the first held portion and the second held portion. The first held portion is provided in an accommodating portion that accommodates a lead wire connected to each of the thermistor element and the second thermistor element,
The fixing device according to claim 11, wherein the second thermistor element is held on a side surface of the housing portion.   The fixing device according to claim 1, wherein the thermistor element is held on a heat resistant film.   The fixing device according to claim 15, wherein the heat-resistant film is made of polyimide or / and polytetrafluoroethylene. An image forming apparatus comprising the fixing device according to claim 1.

Images