JP2009271097A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which prevents contact between the guide members and temperature detecting sensors even when the guide members thermally expand, without enlarging the device in the width direction and without deteriorating the function of guide members even if a temperature detecting sensor is installed near a nip, and to provide an image forming apparatus. <P>SOLUTION: The fixing device includes the temperature detecting sensors 61 and 62 for detecting the surface temperature of a width direction end of a fixing member 20 or pressure member 30. In a frame 60, female screws 60a to 60c for fastening and holding the guide members 41 and 42 are formed at both ends in the width direction. The guide members 41 and 42 includes: positioning circular holes 41a and 42a aligned with the female screw 60a on one width direction end on which the temperature detecting sensors 61 and 62 are installed; and long holes 41b and 42b aligned with the female screw 60b on the other width direction end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing device installed there.

  2. Description of the Related Art Conventionally, in a fixing device in an image forming apparatus such as a copying machine or a printer, a technique for installing a guide member for guiding a recording medium fed into a nip portion or a recording medium sent out from the nip portion, a fixing roller, etc. A technique for detecting a surface temperature of a pressure member such as a fixing member or a pressure roller with a temperature detection sensor and controlling a heating unit such as a heater based on the detection result is widely known (for example, Patent Document 1). reference.).

In Patent Document 1 or the like, an inlet guide plate (guide member) is installed at a position upstream of the nip portion in the conveyance direction of the recording medium and facing the non-fixing surface of the recording medium. Then, the recording medium conveyed toward the nip portion is smoothly fed into the nip portion while being guided by the inlet guide plate.
A thermistor (temperature detection sensor) is in contact with the surface of the fixing roller. Then, the surface temperature (fixing temperature) of the fixing roller is detected by the thermistor, and based on the detection result, the output of the heater provided in the fixing roller is controlled so that the fixing temperature becomes a desired value.

JP 2006-178162 A

In the conventional fixing device described above, the temperature detection sensor cannot be installed in the vicinity of the nip portion in order to avoid contact with the guide member installed in the vicinity of the nip portion.
Specifically, the fixing process is performed at the nip portion, and the surface temperature of the fixing member (or pressure member) varies greatly during one rotation of the fixing member (or pressure member). In order to perform good fixing temperature control with high stability and stability, it is desirable to detect the fixing temperature by installing a temperature detection sensor at a position as close as possible to the nip portion upstream of the nip portion. However, the guide member needs to reliably guide the recording medium fed into the nip portion (or the recording medium sent out from the nip portion) toward the nip portion. It was installed in. For this reason, in order to avoid a malfunction in which the temperature detection sensor is damaged or malfunctions due to contact with a guide member installed in the vicinity of the nip portion (particularly, a guide member installed on the inlet side of the nip portion), The detection sensor could not be installed near the nip.

  In order to solve such a problem, a temperature detection sensor is installed at a position away from the width direction end of the guide member to detect the surface temperature of the width direction end of the fixing member (or pressure member). Can be considered. However, in such a case, in the fixing device that reaches a high temperature, it is necessary to reliably prevent the guide member from thermally expanding and coming into contact with the temperature detection sensor. Further, if the temperature detection sensor is installed at a position far away from the guide member, the fixing device becomes large in the width direction.

  The present invention has been made to solve the above-described problems, and even when the temperature detection sensor is installed in the vicinity of the nip portion, the function of the guide member does not increase in size in the width direction. An object of the present invention is to provide a fixing device and an image forming apparatus that do not come into contact with a temperature detection sensor even if a guide member is thermally expanded without impairing the above.

  According to a first aspect of the present invention, a fixing device forms a fixing member that heats and melts a toner image and fixes the toner image on a recording medium, and a nip portion that is pressed against the fixing member and the recording medium is conveyed. A pressurizing member, a guide member that is disposed at a position facing the recording medium fed into or sent out from the nip portion, guides the recording medium, a frame that holds the guide member, and the fixing A temperature detection sensor that detects a surface temperature of a member or the end portion in the width direction of the pressure member, and the frame has female screw portions for fastening and holding the guide member at both ends in the width direction. Each of the guide members includes a circular hole for positioning that is aligned with the female screw portion on the side of the width direction end where the temperature detection sensor is installed, and a side of the other width direction end. Located in the female screw part of A long hole being Align, those provided with the.

  The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the frame has at least a female screw portion for fastening and holding the guide member at a central portion in the width direction. The guide member further includes an elongated hole portion that is aligned with the female screw portion at the central portion in the width direction.

  The fixing device according to a third aspect of the present invention is the fixing device according to the first or second aspect, wherein the guide member uses a fixing screw at a position of the circular hole portion for positioning. Screws are fastened to the frame using stepped screws at the positions of the long holes.

  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 temperature detection sensor is provided in a conveyance area of the recording medium conveyed to the nip portion. It is arranged outside.

  The fixing device according to a fifth aspect of the present invention is the fixing device according to any one of the first to fourth aspects, wherein the temperature detection sensor is upstream of the nip portion in the conveyance direction of the recording medium. A contact-type temperature detection sensor that is disposed close to the nip portion and contacts the surface of the fixing member or the pressure member, and the guide member is fed into the nip portion. It is disposed at a position facing the recording medium.

  The fixing device according to a sixth aspect of the present invention is the fixing device according to any one of the first to fifth aspects, wherein the temperature detection sensor is provided close to an end in the width direction of the guide member. Is.

  A fixing device according to a seventh aspect of the present invention is the fixing device according to any one of the first to sixth aspects, wherein the temperature detection sensor is held by the frame.

  The fixing device according to an eighth aspect of the present invention is the fixing device according to any one of the first to seventh aspects, wherein the guide member is formed of a thermoreversible resin material or a metal material. is there.

  An image forming apparatus according to a ninth aspect of the present invention includes the fixing device according to any one of the first to eighth aspects.

  In the present invention, a circular hole for positioning is formed on the guide member on the side of the width direction end where the temperature detection sensor is installed, and a long hole is formed on the side of the other width direction end. Yes. Thus, even when the temperature detection sensor is installed in the vicinity of the nip portion, the temperature detection sensor does not increase in size in the width direction, does not impair the function of the guide member, and the guide member is thermally expanded. It is possible to provide a fixing device and an image forming apparatus that do not come into contact with each other.

Embodiment.
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.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is the main body of a tandem type color copier as an image forming apparatus, 2 is a writing unit that emits laser light based on input image information, 4 is a document reading unit that reads image information of a document D, and 7 is A paper supply unit for storing a recording medium P such as transfer paper, 11Y, 11M, 11C, and 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, and 12 is a photosensitive drum. 11Y, 11M, 11C, and 11BK are charged. 13 is a developing unit that develops an electrostatic latent image formed on each photoconductor drum 11Y, 11M, 11C, and 11BK, and 15 is each photoconductor drum 11Y. A cleaning unit that collects untransferred toner on 11M, 11C, and 11BK is shown.
Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred, and 18 a color image formed on the intermediate transfer belt 17 as a recording medium. A secondary transfer roller 19 for transferring the toner image onto P is an electromagnetic induction heating type fixing device for fixing a toner image (unfixed image) on the recording medium P.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, image information of the document D placed on the contact glass 5 is optically read by the document reading unit 4. Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.
Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color 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 photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (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 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. 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 rotational 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 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated to 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 the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development 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 (not shown) is installed at each facing portion so as to abut on 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 the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (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.

Thereafter, the intermediate transfer belt 17 on which the toner images of the respective colors are transferred in a superimposed manner reaches a position facing the secondary transfer roller 18. At this position, the secondary transfer backup roller sandwiches the intermediate transfer belt 17 between the secondary transfer roller 18 and forms a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 17 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip (secondary transfer process). At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 17.
Thereafter, the intermediate transfer belt 17 reaches the position of the intermediate transfer cleaning unit 16. At this position, the untransferred toner on the intermediate transfer belt 17 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 17 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip passes through a transport path K1 in which a paper feed roller 8, a registration roller, and the like are installed from a paper feed unit 7 disposed below the apparatus main body 1. It was transported via.
Specifically, a plurality of recording media P are stored in the paper supply unit 7 in a stacked manner. When the paper feed roller 8 is rotationally driven counterclockwise in FIG. 1, the uppermost recording medium P is fed toward the transport path K1.

  The recording medium P transported to the transport path K1 temporarily stops at the position of the roller nip of the registration roller (not shown) that has stopped rotating. Then, the registration roller is driven to rotate in synchronization with the color image on the intermediate transfer belt 17, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 19. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing roller and the pressure roller.
The recording medium P after the fixing process is discharged as an output image by the paper discharge roller 9 to the outside of the apparatus main body 1 (moving in the direction indicated by the broken line arrow), and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 19 detachably installed in the image forming apparatus main body 1 will be described in detail.
As shown in FIG. 2, the fixing device 19 includes an induction heating unit 25 (magnetic flux generating means), a fixing roller 20 as a fixing member facing the induction heating unit 25, and a pressure as a pressure member that presses against the fixing roller 20. The roller 30, the inlet guide plate 41 (guide member), the spur guide plate 42 (guide member), the separation guide plate 43, the outlet guide plate 50, thermistors 61 and 62 as temperature detection sensors, the frame 60, and the like.

Here, the fixing roller 20 as a fixing member is formed by sequentially laminating a heat insulating elastic layer 22 made of foamed silicone rubber or the like and a sleeve layer 21 on a cored bar 23 made of iron or stainless steel, The outer diameter is about 40 mm.
The sleeve layer 21 of the fixing roller 20 is a multilayer structure in which a base material layer, a first antioxidant layer, a heat generating layer, a second antioxidant layer, an elastic layer, and a release layer are sequentially laminated from the inner peripheral surface side. Specifically, the base material layer is formed of stainless steel having a layer thickness of about 40 μm, and the first antioxidant layer and the second antioxidant layer are formed by strike plating treatment of nickel having a layer thickness of 1 μm or less. The heating layer is made of copper having a layer thickness of about 10 μm, the elastic layer is made of silicone rubber having a layer thickness of about 150 μm, and the release layer has a layer thickness of about 30 μm. It is formed of PFA (tetrafluoroethylene / barfluoroalkyl vinyl ether copolymer).
In the fixing roller 20 configured as described above, the heat generating layer of the sleeve layer 21 is electromagnetically heated by the magnetic flux generated from the induction heating unit 25. The configuration of the fixing roller 20 is not limited to that of the present embodiment, and for example, the sleeve layer 21 can be separated without being bonded to the heat insulating elastic layer 22 (fixing auxiliary roller). However, when the sleeve layer 21 (fixing sleeve) is separated, it is preferable to install a member for preventing the sleeve layer 21 from moving in the width direction (thrust direction) during operation.

Here, a spur guide plate 42 (guide member) in which a plurality of spurs are arranged in parallel in the width direction is installed at a position facing the fixing roller 20 and upstream of the nip portion (upstream in the transport direction). ing. The spur guide plate 42 as a guide member is disposed at a position facing the fixing surface (the surface on which the image is fixed) of the recording medium P fed into the nip portion, and the recording medium P is placed in the nip portion. To guide you. The spur guide plate 42 is formed in a sawtooth shape so that a spur does not rub even if the spur contacts an unfixed image on the recording medium P.
A separation guide plate 43 is provided at a position facing the fixing roller 20 and facing the fixing surface of the recording medium P sent from the nip (on the downstream side in the conveyance direction of the nip). Has been. The separation guide plate 43 is for preventing a problem that the recording medium P after the fixing process sent out from the nip portion is attracted to and wound around the fixing roller 20. That is, when the recording medium P after the fixing process is attracted to the fixing roller 20, the separation guide plate 43 comes into contact with the leading end of the recording medium P to forcibly separate the recording medium P from the fixing roller 20. .

Further, a thermistor 62 as a contact-type temperature detection sensor that contacts the fixing roller 20 is disposed upstream of the nip (on the upstream side in the conveyance direction of the recording medium P) and close to the nip. It is installed. 4, the thermistor 62 as a temperature detection sensor is disposed at the end portion in the width direction on the drive units 75 and 76 side, and detects the surface temperature at the end portion in the width direction of the fixing roller 20.
Although not shown, a thermopile (non-contact type temperature detection sensor) is disposed at a position facing the center in the width direction of the fixing roller 20.
Then, the temperature on the fixing roller 20 (fixing temperature) is detected by the thermistor 62 and the thermopile, and the heating amount by the induction heating unit 25 is adjusted based on the detection result by the thermistor 62 and the thermopile.

Referring to FIG. 2, a pressure roller 30 as a pressure member is formed on a cylindrical member 32 made of aluminum, copper or the like, an elastic layer 31 made of silicone rubber or the like, a release layer made of PFA or the like (not shown). Is formed). The elastic layer 31 of the pressure roller 30 is formed to have a thickness of 1 to 5 mm. The release layer of the pressure roller 30 is formed so that the layer thickness is 20 to 50 μm. The pressure roller 30 is in pressure contact with the fixing roller 20. Then, the recording medium P is conveyed to a pressure contact portion (a nip portion) between the fixing roller 20 and the pressure roller 30.
In the present embodiment, a heater 33 such as a halogen heater is provided in the pressure roller 30 in order to increase the heating efficiency of the fixing roller 20. By supplying electric power to the heater 33, the pressure roller 30 is heated by the radiant heat of the heater 33, and the surface of the fixing roller 20 is heated via the pressure roller 30.

A thermistor 61 as a contact-type temperature detection sensor that contacts the pressure roller 30 is located upstream of the nip portion (on the upstream side in the conveyance direction of the recording medium P) and close to the nip portion. It is arranged. The thermistor 61 as the temperature detection sensor is disposed at the end in the width direction on the side of the drive units 75 and 76 with reference to FIG. 4, and detects the surface temperature at the end in the width direction of the pressure roller 30. .
Although not shown, a thermopile (non-contact type temperature detection sensor) is disposed at a position facing the central portion in the width direction of the pressure roller 30.
Then, the temperature on the pressure roller 30 is detected by the thermistor 61 or the thermopile, and the heating amount by the heater 33 is adjusted based on the detection result by the thermistor 61 or the thermopile.

Here, at a position facing the pressure roller 30 and facing the non-fixing surface of the recording medium P fed into the nip portion (on the upstream side of the nip portion), a guide member is provided. An inlet guide plate 41 is installed. The inlet guide plate 41 guides the recording medium P fed into the nip portion to the nip portion. The configuration and operation of the inlet guide plate 41 as a guide member will be described later in detail with reference to FIGS.
Further, an exit guide plate 50 is installed at a position facing the pressure roller 30 and facing the non-fixing surface of the recording medium P sent from the nip portion (on the downstream side of the nip portion). Has been. The exit guide plate 50 is for guiding the recording medium P after the fixing process sent from the nip portion toward the conveyance path after the fixing process.
With reference to FIG. 3, a grip portion 70 is installed on the outlet guide plate 50. Then, an operator such as a user or a serviceman moves the main part of the fixing device 19 when the jam of the recording medium P occurs at the position of the fixing device 19 (this is a phenomenon in which the recording medium P being conveyed is clogged). After taking out and gripping the grip portion 70, the exit guide plate 50 is rotated about the rotation shaft portion 50a (rotation in the direction of the arrow in FIG. 2), and the jam paper is nipped in a state where the nip portion is exposed. It will be pulled out and removed from the part.

The induction heating unit 25 includes a coil unit 26 (excitation coil), a core unit 27 (excitation coil core), a coil guide 28, and the like. The coil portion 26 is wound in the width direction (in the direction perpendicular to the paper surface of FIG. 2) by winding a litz wire bundled with thin wires on a coil guide 28 disposed so as to cover a part of the outer peripheral surface of the fixing roller 20. It is extended. The coil guide 28 is made of a resin material having high heat resistance and holds the coil portion 26 on the side facing the fixing roller 20. The core portion 27 is made of a ferromagnetic material such as ferrite (having a relative magnetic permeability of about 2500), and is used to form an efficient magnetic flux toward the heat generating layer of the fixing roller 20, and includes an arch core and a center core. It is composed of a side core and the like.
The induction heating unit 25 is configured to be separable from the main part of the fixing device 19. Then, the main part (the unit shown in FIG. 3) of the fixing device 19 is separated from the induction heating unit 25 and taken out from the image forming apparatus main body 1 with the door 100 being opened (see FIG. 3). (The movement to the right in FIG. 1).

The fixing device 19 configured as described above operates as follows.
The fixing roller 20 is driven to rotate counterclockwise in FIG. 2 by a drive motor (not shown), and the pressure roller 30 is rotated clockwise accordingly. The sleeve layer 21 (heat generation layer) of the fixing roller 20 is heated by the magnetic flux generated from the induction heating unit 25 at a position facing the induction heating unit 25.

  Specifically, the oscillation circuit causes a high-frequency alternating current of 10 kHz to 1 MHz (preferably 20 kHz to 800 kHz) to flow from the coil unit 26 to a coil unit 26 from a power supply unit (not shown) whose frequency is variable. The magnetic field lines are formed so as to alternately switch in both directions toward the sleeve layer 21 of the fixing roller 20. By forming an alternating magnetic field in this manner, an eddy current is generated in the heat generating layer of the sleeve layer 21, and the heat generating layer generates Joule heat due to its electric resistance and is induction-heated. Thus, the sleeve layer 21 (fixing roller 20) is heated by induction heating of its own heat generation layer.

Thereafter, the surface of the fixing roller 20 heated by the induction heating unit 25 reaches a contact portion (nip portion) with the pressure roller 30. Then, the toner image T (toner) on the conveyed recording medium P is heated and melted.
Specifically, the recording medium P carrying the toner image T through the image formation process described above is guided between the entrance guide plate 41 (or the spur guide plate 42) and between the fixing roller 20 and the pressure roller 30 ( (It is a nip portion)) (the movement in the transport direction of the arrow Y1). The toner image T is fixed on the recording medium P by the heat received from the fixing roller 20 and the pressure received from the pressure roller 30, and the recording medium P is sent out between the fixing roller 20 and the pressure roller 30 ( This is the movement in the transport direction of the arrow Y2.)
The surface of the fixing roller 20 that has passed through the nip portion then reaches the position facing the induction heating unit 25 again.
Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

Hereinafter, the configuration and operation of the fixing device 19 which are characteristic in the present embodiment will be described in detail with reference to FIGS.
FIG. 4 is a schematic bottom view showing the fixing device 19. FIG. 5 is a cross-sectional view showing a circular hole 41a for positioning the inlet guide plate 41, as viewed from the direction X1 in FIG. 6 is a cross-sectional view showing the elongated holes 41b and 41c of the inlet guide plate 41. FIG. 6 (A) is a view as seen from the direction X2 in FIG. 4, and FIG. It is the figure seen from the viewing direction. In FIG. 4, the illustration of the fixing screw 71, the stepped screw 72, the female screw portions 60 a to 60 c, and the like is omitted for easy viewing of the drawing.

As shown in FIG. 4, the inlet guide plate 41 as a guide member is held by a frame 60 (housing) of the fixing device 19.
Specifically, referring to FIGS. 4 to 6, the frame 60 has female screw portions 60 a to 60 c for fastening and holding the inlet guide plate 41 with screws between the width direction both end portions and the width direction center portion. It is formed in three places. The inlet guide plate 41 is formed with one positioning circular hole 41a and two elongated holes 41b and 41c at positions corresponding to the female screw portions 60a to 60c of the frame 60. Specifically, the circular hole portion 41a (positioning circular hole portion) of the inlet guide plate 41 is the width direction end portion side where the thermistor 61 (temperature detection sensor) is installed (the left end portion in FIG. 4). ) And the female screw portion 60a. Further, the two long hole portions 41a and 41c of the inlet guide plate 41 are respectively the female screw portion 60b on the other width direction end portion side (the right end portion in FIG. 4) and the width direction center portion. It is formed so as to be aligned with the female screw portion 60c.

The inlet guide plate 41 is screwed to the frame 60 using a fixing screw 71 at the position of the circular hole 41a and a stepped screw 72 at the positions of the long holes 41b and 41c.
Specifically, referring to FIG. 5, fixing screw 71 is screwed into female screw portion 60 a (a female screw portion formed at an end portion on the thermistor 61 side) with inlet guide plate 41 interposed therebetween. . Here, the circular hole portion 41 a is formed so that its hole diameter is substantially equal to the diameter of the male screw portion of the fixing screw 71, and the position of the inlet guide plate 41 is determined.
Referring to FIG. 6, the stepped screw 72 is screwed into the female screw portions 60b and 60c with the inlet guide plate 41 interposed therebetween. Here, the hole shapes of the long hole portions 41b and 41c are formed such that the length in the short direction (the vertical direction in FIG. 4) is equal to the outer diameter of the step portion of the step screw 72, and the long direction (see FIG. 4) is sufficiently larger than the outer diameter of the stepped portion of the stepped screw 72, and is sufficiently smaller than the outer diameter of the head portion of the stepped screw 72. That is, the inlet guide plate 41 is restricted only in the direction (vertical direction in FIG. 4) perpendicular to the width direction by the elongated holes 41b and 41c.

With such a configuration, even if the inlet guide plate 41 thermally expands in the fixing device 19 that reaches a high temperature during operation, the inlet guide plate 41 is hardly displaced to the thermistor 61 side (circular hole 41a side). The other end (the right end in FIG. 4) is displaced (expanded) along the shape of the elongated holes 41b and 41c.
Therefore, in order to prevent the fixing device 19 from increasing in size in the width direction, the thermistor 61 is provided close to the end portion in the width direction of the inlet guide plate 41 (when installed at a slight distance). Even so, the problem that the inlet guide plate 41 contacts the thermistor 61 due to the thermal expansion of the inlet guide plate 41 is suppressed.
In the present embodiment, since the thermistor 61 is installed on the upstream side of the nip portion and as close as possible to the nip portion, the heating control of the pressure roller 30 (heater 33) is stable and highly responsive. Can be done well. Further, since the entrance guide plate 41 is installed as close as possible to the nip portion, the recording medium P fed into the nip portion can be smoothly guided toward the nip portion.

Here, in Embodiment 1, the inlet guide plate 41 is formed of a thermoreversible resin material. When the inlet guide plate 41 is formed of a resin material as described above, even when the inlet guide plate 41 is warped, a gap is formed between the inlet guide plate 41 and the function as the inlet guide plate 41. In order not to be damaged, it is desirable to arrange the long hole portion in the center portion in the width direction in addition to the end portion in the width direction (this is the configuration of the present embodiment). In that case, the number of the long hole portions 41c provided in the central portion in the width direction may be two or more.
On the other hand, when the inlet guide plate 41 is formed of a metal material, the inlet guide plate 41 is less likely to warp. Therefore, as shown in FIG. 7, the long hole portion 41b is disposed only at the end in the width direction. can do. When the inlet guide plate 41 is formed of a metal material, in order to improve the slidability with the recording medium P, the surface thereof has a heat resistant low friction such as Teflon (registered trademark), oflon (trade name) or the like. It is preferred to coat the material.

The thermistor 61 is held by the frame 60 on the side of a drive unit (configured by a drive motor 75 and a gear train 76) that drives the fixing roller 20 and the pressure roller 30.
Further, the thermistor 61 is disposed outside the non-sheet passing area of the recording medium P conveyed to the nip portion. As a result, even if the surface of the pressure roller 30 is worn due to the contact of the thermistor 61, problems such as a decrease in the transportability of the recording medium P and a defect in which the output image is damaged are suppressed.

  In the present embodiment, the spur guide plate 42 as a guide member is also configured in the same manner as the entrance guide plate 41. That is, the spur guide plate 42 as a guide member has a circular hole portion 42a formed on the thermistor 62 side, and elongated hole portions 42b and 42c formed on the other end side and the central portion. Is held in. As a result, the spur guide plate 42 and the thermistor 62 also have the same effects as those of the inlet guide plate 41 and the thermistor 61 described above.

  As described above, in the present embodiment, the width direction end portion side where the thermistors 61 and 62 (temperature detection sensors) are installed on the inlet guide plate 41 (guide member) and the spur guide plate 42 (guide member). Are formed with circular hole portions 41a and 42a for positioning, and elongated hole portions 41b and 42b are formed on the other width direction end portion side. Accordingly, even when the thermistors 61 and 62 are installed in the vicinity of the nip portion, the fixing device 19 does not increase in size in the width direction, and the functions of the entrance guide plate 41 and the spur guide plate 42 are not impaired. Even if the guide plate 41 and the spur guide plate 42 are thermally expanded, it is possible to reliably suppress the problem of contacting the thermistors 61 and 62.

In the present embodiment, the present invention is applied to the electromagnetic induction heating type fixing device 19 using the exciting coil 26 as the heating means. However, an electrophotography such as a fixing device using a heater as the heating means. Naturally, the present invention can be applied to all the fixing devices used in the image forming apparatus of the type.
In the present embodiment, the present invention is applied to a fixing device using the fixing roller 20 as the fixing member and the pressure roller 30 as the pressure member. However, a fixing belt or a fixing film is used as the fixing member. The present invention can also be applied to a conventional fixing device and a fixing device using a pressure belt or a pressure pad as a pressure member.
In these cases, the same effect as in the present embodiment can be obtained by configuring the guide member and the temperature detection sensor in the same manner as in the present embodiment.

  In the present embodiment, the present invention is applied to the inlet guide plate 41 and the spur guide plate 42 installed on the inlet side of the nip portion, but the outlet guide plate 50 installed on the outlet side of the nip portion The present invention can also be applied to the separation guide plate 43.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. Further, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a fixing device. FIG. 2 is a perspective view showing a fixing device. It is a bottom view showing the fixing device. It is sectional drawing which shows the circular hole part for positioning of a guide member. It is sectional drawing which shows the long hole part of a guide member. It is a bottom view showing another fixing device.

Explanation of symbols

1 image forming apparatus body (apparatus body),
19 fixing device (device unit),
20 fixing roller (fixing member),
25 induction heating unit,
30 pressure roller (pressure member),
41 Entrance guide plate (guide member),
41a Circular hole (positioning circular hole),
41b, 41c slot,
42 Spur guide plate (guide member),
42a circular hole (positioning circular hole),
42b, 42c long hole part,
60 frames,
60a-60c female thread part,
61, 62 thermistor (temperature detection sensor),
71 fixing screws,
72-stage screw.

Claims (9)

A fixing member that heats and melts the toner image and fixes the toner image on the recording medium;
A pressure member that forms a nip portion to which the recording medium is conveyed in pressure contact with the fixing member;
A guide member that is disposed at a position facing the recording medium fed into or sent out from the nip portion and guides the recording medium;
A frame for holding the guide member;
A temperature detection sensor for detecting a surface temperature of an end portion in the width direction of the fixing member or the pressure member;
With
The frame includes female screw portions for fastening and holding the guide member at both ends in the width direction,
The guide member includes a circular hole for positioning that is aligned with the female screw portion on the width direction end portion on which the temperature detection sensor is installed, and the female screw on the other width direction end portion side. A fixing device comprising: a long hole portion aligned with the portion. The frame further includes at least one female screw portion for fastening and holding the guide member at the center in the width direction,
The fixing device according to claim 1, wherein the guide member further includes a long hole portion that is aligned with the female screw portion at a central portion in the width direction.   2. The guide member according to claim 1, wherein the guide member is screwed to the frame using a fixing screw at a position of the circular hole for positioning and a step screw at a position of the elongated hole. The fixing device according to claim 2.   The fixing device according to claim 1, wherein the temperature detection sensor is disposed outside a conveyance area of a recording medium conveyed to the nip portion. The temperature detection sensor is disposed on the upstream side of the nip portion in the recording medium conveyance direction and close to the nip portion, and is in contact with the surface of the fixing member or the pressure member. A temperature detection sensor,
The fixing device according to claim 1, wherein the guide member is disposed at a position facing a recording medium fed into the nip portion.   The fixing device according to claim 1, wherein the temperature detection sensor is provided close to an end in a width direction of the guide member.   The fixing device according to claim 1, wherein the temperature detection sensor is held by the frame.   The fixing device according to claim 1, wherein the guide member is formed of a thermoreversible resin material or a metal material.   An image forming apparatus comprising the fixing device according to claim 1.

Images