JP2006322996A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect the temperature of a rotating member by a non-contact temperature detection means. <P>SOLUTION: The heating device has the temperature detection means 18 for detecting the temperature of the rotating member 20 in a non-contact state so as to control a heating body 16, and a backup member 32 opposed to the temperature detection means through the rotating member and coming into contact with the rotating member so that the conveyance of the rotating member relative to the temperature detection means may be stable in the downstream area of a nip part N in the rotating direction of the rotating member 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating apparatus suitable for use as an image heating and fixing apparatus of an electrophotographic or electrostatic recording type image forming apparatus.

  In an image forming apparatus such as an electrophotographic copying machine, a printer, or a facsimile, an image heating and fixing apparatus for heating and fixing an unfixed toner image corresponding to target image information formed and supported on a recording material by an image forming process unit Is installed. As this image heating and fixing apparatus, a film heating type heating apparatus is put to practical use as an image heating and fixing apparatus.

  Patent Documents 1 to 4 propose a film heating type heating device. That is, a fixing nip portion is formed by sandwiching a heat resistant film (fixing film, fixing belt) as a rotating member between a ceramic heater as a heating body and a pressing roller as a pressing member. In the fixing nip portion, a recording material as a heated material on which an unfixed toner image is formed and supported is introduced between the fixing film and the pressure roller, and is nipped and conveyed together with the fixing film. As a result, the heat of the ceramic heater is applied to the recording material through the fixing film in the fixing nip portion, and the unfixed toner image is fixed on the recording material surface by the applied pressure of the fixing nip portion.

  Such a film heating type heating apparatus can use a heating element with a low heat capacity or a thin heat-resistant film that is rapidly heated. For this reason, there are advantages such as power saving and shortening of the wait time (quick start performance), and an in-machine temperature rise of the apparatus such as an image forming apparatus can be reduced. is there.

  FIG. 10 shows an example of a conventional image heat fixing apparatus. FIG. 10 is a cross-sectional side view of a film fixing device 201 using a fixing film 203 having an elastic layer as a rotating member.

  Reference numeral 202 denotes a fixing film unit, which includes a heater holder 207 having a substantially semicircular arc shaped cross-sectional cross section, a heater holder 207 having a fixing heater 204, and an endless belt-like (cylindrical) flexible thin-layer fixing belt 203 ( A fixing film). The fixing heater 204 is fixed to the lower surface of the heater holder 207 along the length of the heater holder (perpendicular to the drawing). The fixing film film 203 is loosely fitted on the heater holder 207 with the fixing heater.

  Reference numeral 205 denotes an elastic pressure roller (hereinafter referred to as a pressure roller), which has a heat-resistant elastic layer 205b around a core metal 205a. The pressure roller 205 is disposed such that both ends of the cored bar 205a are rotatably supported between side plates (not shown) of the fixing device.

  The fixing film unit 202 is arranged on the upper side of the pressure roller 205 and in parallel with the pressure roller with the fixing heater 204 side facing downward, and both end portions of the heater holder 207 are pushed down with a predetermined pressing force by an urging means (not shown). It is in a state. Accordingly, the lower surface of the fixing heater 204 is pressed against the upper surface of the pressure roller 205 across the fixing film 203 against the elasticity of the pressure roller to form a fixing nip portion 206 having a predetermined width.

  The pressure roller 205 is driven to rotate at a predetermined peripheral speed in the direction of the arrow by a drive mechanism (not shown). By the rotational driving of the pressure roller 205, a rotational force acts on the fixing film by the frictional force between the pressure roller and the outer surface of the fixing film 203 in the fixing nip portion 206. As a result, the fixing film 203 has a peripheral speed substantially corresponding to the peripheral speed of the elastic pressure roller 205 in the direction of the arrow while the inner peripheral surface of the fixing film 203 slides in close contact with the lower surface of the fixing heater 204 at the fixing nip portion 206. It becomes a driven rotation state on the outer periphery of.

  The fixing film 203 uses an endless belt made of a heat-resistant resin having a thickness of about 50 μm as a base layer, has an elastic rubber layer having a thickness of 300 μm on its surface, and a release layer having a thickness of several μm on its outer surface layer. (Coating layer of fluororesin etc.) is formed. Further, a sleeve having a metal on an endless belt may be used for the base layer of the fixing film 203 in order to reduce the heat capacity and increase the thermal conductivity.

  The fixing heater 204 is formed by forming an energization heating resistor on a ceramic substrate. A temperature detection unit 209 is disposed in contact with the back surface of the fixing heater 204, and the temperature of the fixing heater 204 is detected by the temperature detection unit. The temperature detected by the temperature detection means 209 is taken into a control means (not shown). Then, the power supplied to the fixing heater 204 is controlled by the control means so that the surface temperature of the fixing film 203 becomes a desired temperature (target temperature), and the temperature of the fixing heater is controlled.

  The pressure roller 205 is driven to rotate, the fixing film 203 is driven to rotate, and the fixing heater 204 rises to a predetermined temperature and temperature control is performed. In this state, the recording material P carrying the unfixed toner image t is introduced between the fixing film 203 and the pressure roller 205 in the fixing nip portion 206. The recording material P is nipped and conveyed through the fixing nip 206 together with the fixing film with the carrying surface of the unfixed toner image in close contact with the outer surface of the fixing film 203. In the nipping and conveying process, heat of the fixing heater 204 is applied to the recording material P through the fixing film 203 and receives pressure from the fixing nip portion 206. As a result, the unfixed toner image t is fixed on the recording material P as a permanently fixed image by heat and pressure. The recording material P passes through the fixing nip portion 206 and is discharged after being separated from the surface of the fixing film 203 with a curvature.

The above-described fixing device is configured to detect the fixing heater temperature by arranging the temperature detecting means on the back surface of the fixing heater. In the above fixing device, the temperature detecting means may be brought into contact with the surface or the inner surface of the fixing film to detect the temperature of the fixing film.
JP-A-63-313182 Japanese Patent Laid-Open No. 1-263679 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075

  (1): In the above fixing device, when the temperature detecting means is brought into contact with the surface of the fixing film, the release layer formed on the surface of the fixing film is generally damaged by coating with a fluororesin or the like. There is a possibility that. If the release layer is scratched, the toner on the surface of the recording material is peeled off, which may cause image defects. Further, the unfixed toner slightly existing on the surface of the fixing film gradually accumulates in the temperature detection unit (contact portion of the temperature detection unit with the fixing film surface) according to the number of recording materials introduced into the fixing nip portion. . There is a possibility that toner accumulated on the temperature detection unit is occasionally discharged onto the image on the surface of the recording material via the fixing film, thereby causing toner contamination on the image.

  As a countermeasure, a method using a non-contact type temperature detecting means as the temperature detecting means can be considered. When using non-contact type temperature detection means, the detection temperature is greatly affected by the fluctuation (change) in the distance between the detection element and the fixing film as the temperature detection object, so it is important to stabilize this distance accurately. It is. That is, the temperature detection means varies (detection temperature fluctuation) in accordance with the change in the distance between the temperature detection means and the fixing film as the detection object, so that the distance between the temperature detection means and the fixing film can be accurately set. It is necessary to stabilize. By keeping the distance between the temperature detecting means and the fixing film constant, fluctuation of the detected temperature of the temperature detecting means can be reduced, and the temperature control of the ceramic heater can be accurately controlled.

  However, when the non-contact type temperature detecting means is employed in a fixing device having a flexible fixing film as a rotating member, the fluctuation of the detected temperature becomes very large, so that it cannot be practically used.

  (2): On the other hand, when a non-contact type temperature detecting means is used for the inner surface of the fixing film, the interval between the temperature detecting means and the fixing film can be stabilized with high accuracy as in the case of (1). Difficult, the fluctuation of the detection temperature becomes very large. Furthermore, since a ceramic heater or the like that is a heating element is arranged inside the film, the arrangement of the temperature detection element is restricted, and it becomes difficult to detect the temperature in a portion closer to the heating element.

  Further, it is assumed that the temperature detecting means is brought into contact with the inner surface of the fixing film, and the heat generating portion (energizing heat generating resistor) of the heater is disposed on the surface on which the ceramic heater and the fixing film slide. In this case, since the fixing film is regarded as a conductor depending on the material of the base layer, at least the energization heating resistor and the temperature detecting means are electrically connected. In order to avoid this, it is necessary to use a method in which aluminum nitride having high thermal conductivity is used as the heater and the energization heating resistor is provided on the surface opposite to the surface on which the fixing film and the heater slide. For this reason, it has been impossible to employ a ceramic heater using an inexpensive alumina substrate that has been conventionally used.

  (3): Furthermore, when a fixing film having an elastic layer is used, the following problem may occur. That is, the thermal conductivity of silicone rubber or the like used as an elastic layer is not so high, and a member such as a ceramic substrate is disposed between the fixing film surface and the temperature detecting means provided on the back surface of the ceramic heater. The For this reason, the thermal responsiveness is poor, and it is difficult to control the heater temperature based on the temperature detected by the temperature detecting means provided on the back surface of the ceramic heater. In particular, it is difficult for the temperature detection means on the back side of the heater to detect that the recording material has passed through the fixing device and took the heat of the surface of the fixing film to reduce the temperature of the surface of the fixing film. There is a possibility that problems such as passing will occur.

  On the other hand, if the temperature detection means moved to the surface or inner surface of the fixing film detects the temperature of the fixing film in a non-contact manner, and the heater drive is controlled based on the detected temperature, the heater There is an advantage that the temperature can be accurately controlled. However, when the temperature detecting means is moved to the surface or the inner surface of the fixing film, the problem of fluctuation of the detected temperature remains as shown in the above (1) and (2). It was difficult to use.

  An object of the present invention is to provide a heating apparatus that can accurately detect the temperature of a rotating member by a non-contact temperature detecting means.

  A representative configuration of the heating device according to the present invention includes a rotating member, a heating body that heats the rotating member, and a pressure member that forms a nip portion with the heating body and the rotating member interposed therebetween. In the heating apparatus that heats the material to be heated while being nipped and conveyed at the nip portion, the temperature of the rotating member is not controlled in order to control the heating body in the downstream area of the nip portion in the rotation direction of the rotating member. Temperature detecting means for detecting contact; and a backup member that opposes the temperature detecting means via the rotating member and that contacts the rotating member and stabilizes conveyance of the rotating member with respect to the temperature detecting means. It is characterized by.

  According to the present invention, since the rotating member comes into contact with the backup member in the downstream area of the nip portion in the rotating direction and stably conveys the rotating member to the non-contact temperature detecting means, the temperature detecting means not contacting the rotating member. Can be kept constant. Thereby, the temperature of the rotating member can be detected with high accuracy by the non-contact temperature detecting means.

  Exemplary embodiments of the present invention will be described in detail below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not intended that the scope of the present invention be limited to the following examples.

(1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram showing an example of a color image forming apparatus in which the heating apparatus according to the present invention can be mounted as an image heating and fixing apparatus.

  The image forming apparatus of this embodiment is an electrophotographic tandem type full-color printer.

  The image forming apparatus includes an image forming unit 1Y that forms a yellow image and an image forming unit 1M that forms a magenta image. Furthermore, an image forming unit 1C that forms a cyan image and an image forming unit 1Bk that forms a black image are provided. The four image forming units (image forming units) are arranged in a line at a constant interval.

  Photosensitive drums 2a, 2b, 2c, and 2d are installed in the image forming units 1Y, 1M, 1C, and 1Bk, respectively. Around each photosensitive drum 2a, 2b, 2c, and 2d, charging rollers 3a, 3b, 3c, and 3d, developing devices 4a, 4b, 4c, and 4d, transfer rollers 5a, 5b, 5c, and 5d, and drum cleaning Devices 6a, 6b, 6c and 6d are installed. Exposure devices 7a, 7b, 7c, and 7d are installed above the charging rollers 3a, 3b, 3c, and 3d and the developing devices 4a, 4b, 4c, and 4d, respectively. The developing devices 4a, 4b, 4c, and 4d store yellow toner, magenta toner, cyan toner, and black toner, respectively.

  First, when an image forming operation start signal (print start signal) is issued, the photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk are rotationally driven at a predetermined process speed. The photosensitive drums 2a, 2b, 2c, and 2d of the image forming units 1Y, 1M, 1C, and 1Bk are uniformly charged to negative polarity by the charging rollers 3a, 3b, 3c, and 3d, respectively.

  Then, the exposure devices 7a, 7b, 7c, and 7d convert the input color-separated image signals into optical signals by a laser output unit (not shown), respectively. Then, an electrostatic latent image is formed by performing scanning exposure on each of the charged photosensitive drums 2a, 2b, 2c, and 2d with laser light that is a converted optical signal.

  Next, yellow toner is charged on the surface of the photosensitive member by the developing device 4a in which a developing bias having the same polarity as the charging polarity (negative polarity) of the photosensitive drum is applied on the photosensitive drum 2a on which the electrostatic latent image is formed. The electrostatic latent image is visualized with toner by electrostatic adsorption according to the potential.

  This yellow toner image has a primary transfer bias (a reverse polarity (positive polarity) to the toner) at the primary transfer portion N where the photosensitive drum 2a and the endless belt-shaped intermediate transfer body 40 as a transfer medium are in contact with each other. The image is primarily transferred onto the intermediate transfer belt 40 by the applied transfer roller 5a.

  Here, the intermediate transfer belt 40 is stretched around a drive roller 41, a support roller 42, and a secondary transfer counter roller 43. The intermediate transfer belt 40 to which the yellow toner image has been transferred is rotated (moved) in the direction of the arrow (clockwise) by driving the drive roller 41, and is rotated toward the image forming unit 1M.

  Also in the image forming unit 1M, the magenta toner image formed on the photosensitive drum 2b in the same manner as described above is superimposed on the yellow toner image on the intermediate transfer belt 40 and transferred by the primary transfer unit N. The

  In the same manner, cyan and black toner images formed on the photosensitive drums 2c and 2d of the image forming units 1C and 1Bk on the yellow and magenta toner images superimposed and transferred onto the intermediate transfer belt 40 in the same manner are respectively primary. The images are sequentially overlapped at the transfer portion N. As a result, a full-color toner image is formed on the intermediate transfer belt 40.

  The full-color toner image superimposed and transferred on the intermediate transfer belt 40 in this way is formed by the secondary transfer counter roller 43, the intermediate transfer belt 40, and the secondary transfer roller 44 as the intermediate transfer belt 40 rotates. Reaches the secondary transfer portion M.

  The recording material (transfer material) P as a heated material is transferred by the registration roller 46 in accordance with the timing at which the front end of the full color toner image on the intermediate transfer belt 40 is moved to the secondary transfer portion M. Transport to. A full-color toner image is secondarily transferred collectively to the recording material P by a secondary transfer roller 44 to which a secondary transfer bias (opposite polarity (positive polarity) with respect to toner) is applied.

  The recording material P on which the full-color toner image is formed is conveyed to the fixing device 12 installed on the downstream side in the conveyance direction of the recording material P. Then, a full-color toner image is heated and pressed at the fixing nip portion between the fixing belt 20 and the pressure roller 22 to be melted and fixed on the surface of the recording material P, and then discharged to the outside to become an output image of the image forming apparatus.

  On the other hand, the primary transfer residual toner remaining on the photosensitive drums 2a, 2b, 2c, and 2d during the primary transfer is removed and collected by the drum cleaning devices 6a, 6b, 6c, and 6d. The secondary transfer residual toner remaining on the intermediate transfer belt 40 after the secondary transfer is removed by the belt cleaning device 45 and used again for image formation.

  The image forming apparatus includes an environment sensor 50, and charging, developing, primary transfer, secondary transfer bias and fixing conditions are changed according to the atmosphere environment (temperature, humidity) in the image forming apparatus. It has a possible configuration. The environment sensor 50 is used for adjusting the density of the toner image formed on the recording material P and for achieving optimum transfer and fixing conditions.

  Further, the image forming apparatus has a media sensor 51, and by determining the recording material P, the transfer bias and the fixing conditions can be changed according to the recording material. The media sensor 51 is used to achieve optimum transfer and fixing conditions for the recording material P.

(2) Fixing device 12
2 is a cross-sectional side view of the fixing device 12 according to the present embodiment, FIG. 3 is a front view of the device with an intermediate portion omitted, and FIG. 4 is a longitudinal cross-sectional view of the device with an intermediate portion omitted.

  The fixing device 12 of this embodiment is a heating device of a fixing belt heating method and a pressure rotating body driving method (tensionless type).

  In the following description, the longitudinal direction is a direction perpendicular to the conveyance direction of the recording material P and parallel to the surface of the recording material.

  Reference numeral 20 denotes a fixing belt as a rotating member (first rotating body), which is a thin-layered flexible (endless belt-like, sleeve-like) member in which an elastic layer is provided on the belt-like member. .

  First, an endless belt (sleeve) in which a SUS material is formed in a cylindrical shape with a thickness of 50 μm is used for a base layer 20a of a fixing belt (hereinafter referred to as a fixing film) 20. In practice, a resin such as polyimide can be used, but a metal such as SUS or nickel has a thermal conductivity 10 times that of polyimide, so that higher on-demand characteristics can be obtained. Therefore, in the present embodiment, SUS, which is a metal, is used for the base layer 20a of the fixing film 20.

On the belt (sleeve) member made of SUS, a silicone rubber having a relatively high thermal conductivity is formed as an elastic layer 20b in a layer having a thickness of about 300 μm by a ring coating method. The specific heat of the silicone rubber used in the present embodiment is about 12.2 × 10 ⁻¹ J / g · ° C.

  Finally, in the outermost layer, a release layer (outermost surface layer) 20c having a thickness of 30 μm is formed of a fluororesin material having high releasability. Thereby, it is possible to prevent the offset phenomenon that occurs when the toner once adheres to the surface and moves to the recording material P again. Further, when the fluororesin layer on the surface of the fixing belt 20 is a PFA tube, a uniform fluororesin layer can be formed more easily.

  Reference numeral 17 denotes a heater holder having a semicircular arc shaped heat resistance and rigidity as a heating body holding member.

  Reference numeral 16 denotes a fixing heater as a heating body (heat source), which is disposed on the lower surface of the heater holder 17 along the length of the holder.

  The heater holder 17 is formed of a liquid crystal polymer resin having high heat resistance, plays a role of holding the fixing heater 16 and guiding the fixing film 20. The fixing film 20 is loosely fitted on the heater holder 17.

  In this embodiment, a liquid crystal polymer “DuPont Xenite 7755 (trade name)” was used as a material for the heater holder 17. The maximum usable temperature of this liquid crystal polymer is about 270 ° C.

  Reference numerals 21a and 21b denote flange members as regulating members, which are assembled by inserting the longitudinal end portions of the fixing heater 16 and the heater holder 17. The interval between the flange members 21 a and 21 b is set slightly wider than the longitudinal dimension of the fixing film 20. As a result, the flange members 21a and 21b position the ends of the fixing film 20 loosely and regulate them.

  The fixing heater 16, the heater holder 17, the fixing film 20, and the flange members 21a and 21b are integrally assembled as a fixing film unit. Then, the fixing heater 16 side is directed downward, and the flange members 21a and 21b are held by the pair of side plates 24a and 24b on the back side and the near side of the apparatus frame.

  Reference numeral 22 denotes a pressure roller as a pressure member (second rotating body). The pressure roller 22 is formed by forming a silicone rubber layer (elastic layer) 22b having a thickness of about 3 mm on a stainless steel core 22a by injection molding and coating a PFA resin tube 22c having a thickness of about 40 μm thereon. . The pressure roller 22 is disposed below the fixing belt 20 in parallel with the fixing belt 20, and both ends of the cored bar 22a are connected to the pair of side plates 24c and 24d on the back side and the front side of the apparatus frame, and bearings 25a and 25b. It is made to rotate freely through.

  Both ends of the heater holder 17 are biased in the axial direction of the pressure roller 22 by a pressure mechanism including pressure springs 26a and 26b with a force of 98N (10 kgf) on one side and a total pressure of 196N (20 kgf). With this pressure mechanism, the downward surface of the fixing heater 16 is brought into pressure contact with the elastic layer 22b of the pressure roller 22 via the fixing film 20 with a predetermined pressing force against the elasticity of the elastic layer, and a predetermined required for heat fixing. A fixing nip portion (hereinafter referred to as a nip portion) N having a width is formed. Here, W is the maximum width dimension of the recording material P introduced into the nip N. The pressurizing mechanism includes a pressure releasing mechanism, and has a configuration in which the pressurization is released and the recording material P can be easily removed at the time of jam processing or the like.

  Here, in a state where the recording material P is not introduced into the nip portion N, the driving gear G provided at one end of the cored bar 22a of the pressure roller 22 is rotated in a predetermined direction by driving means (not shown). When driven, the pressure roller 22 is rotationally driven in the direction of the arrow at a predetermined peripheral speed. At this time, the fixing film 20 is driven to rotate in the direction of the arrow by receiving a sliding frictional force corresponding to the rotational driving of the pressure roller 22 through the nip portion N.

  In this embodiment, the fixing heater 16 is formed by coating a conductive paste containing silver / palladium alloy on an alumina substrate into a film having a uniform thickness by a screen printing method, forming a resistance heating element, and then forming a pressure-resistant glass. A ceramic heater with a glass coating is used.

  FIG. 5 is a structural model diagram of an example of such a ceramic heater, where (a) is a partially cutaway surface model diagram, (b) is a back surface model diagram, and (c) is an enlarged cross-sectional model diagram.

The fixing heater 16 includes the following (i) to (v).
(I): It has a horizontally long alumina substrate a as a substrate having a direction perpendicular to the conveying direction of the recording material P as a longitudinal direction.
(Ii): a conductive paste containing silver palladium (Ag / Pd) alloy, which is applied to the surface side of the above-mentioned alumina substrate a in a linear or strip shape by screen printing along the length, and generates heat when current flows. And a resistance heating element layer b as a resistance heating element. The resistance heating element layer b is formed to have a thickness of about 10 μm and a width of about 1 to 5 mm.
(Iii): First and second electrode parts c and d and an extended electric circuit part similarly formed by patterning silver paste screen printing or the like on the surface side of the alumina substrate a as a power supply pattern for the resistance heating element layer b. e · f.
(Iv): Thickness of 10 μm capable of withstanding rubbing with the fixing film 20 formed on the resistance heating element layer b and the extension electric circuit portions e and f to ensure protection and insulation. It has a thin glass coat g.
(V): A sub thermistor 19 as a second temperature detecting means is provided on the back side of the alumina substrate a.

  The fixing heater 16 is exposed to the surface side downward and is fixedly supported on the heater holder 17 as described above.

  As shown in FIG. 5, the sub-thermistor 19 is disposed near the end of the fixing heater 16 and is disposed so as to contact the back surface of the fixing heater 16.

  The sub-thermistor 19 serves as a safety device that detects the temperature of the fixing heater 16 as a heating body and monitors the temperature of the fixing heater so as not to exceed a predetermined temperature.

  Further, the sub-thermistor 19 monitors the overshoot of the temperature of the fixing heater 16 at the start-up and the temperature rise at the end. For example, when the temperature at the end of the fixing heater 20 exceeds a predetermined temperature due to temperature rise at the end, control is performed such as reducing the throughput so that the temperature rise at the end is not further deteriorated. Used for judgment.

  A power supply connector 30 is attached to the first and second electrode portions c and d of the fixing heater 16, and the first and second electrode portions c are supplied from the heater drive circuit portion 28 via the power supply connector 30. When the electric power is supplied to d, the resistance heating element layer b generates heat, and the fixing heater 16 is quickly heated.

  In FIG. 2, reference numeral 40 denotes an entrance guide, and the recording material P that has passed through the secondary transfer nip M is accurately guided to the nip portion N that is the pressure contact portion between the fixing film 20 and the pressure roller 22 in the fixing heater 16 portion. It plays a role of guiding the recording material. The entrance guide 40 of this embodiment is made of polyphenylene sulfide (PPS) resin. Reference numeral 41 denotes a fixing discharge roller.

  As described above, when the pressure roller 22 is driven to rotate, the cylindrical fixing film 20 is rotated, the fixing heater 16 is energized, and the temperature is raised to a predetermined temperature. The recording material P carrying t is introduced into the nip N by the entrance guide 23. Then, the toner image carrying surface side of the recording material P is in close contact with the outer surface of the fixing film 20 in the nip portion N, and the nip portion is nipped and conveyed together with the fixing film. In this nipping and conveying process, the heat of the fixing heater 16 is applied to the recording material P through the fixing film 20, and the unfixed toner image t on the recording material is heated and pressurized on the recording material to be melted and fixed. Thereafter, the recording material P that has passed through the nip portion N is separated from the surface of the fixing film 20 by the curvature, and is discharged by the fixing discharge roller 41.

(3) Description of Main Thermistor 18 In this embodiment, as a means for controlling the temperature of the fixing heater 16, a main thermistor 18 as a first temperature detecting means is used in addition to the sub-thermistor 19 described above. One of the features of the present invention is that a non-contact type temperature detecting element is used as the main thermistor 18.

  FIG. 6A shows a perspective view of the main thermistor 18.

  The main thermistor 18 includes a temperature detection element 18-1, a polyimide tape 18-2, a holder 18-3, a lead wire 18-4, and the like. The temperature detection element 18-1 is covered with a polyimide tape 18-2 and supported by a holder 18-3. Since the holder 18-3 needs to stabilize the position of the temperature detecting element 18-1, a PPS resin material is used in this embodiment, and the position accuracy is not changed even within the operating temperature. The temperature detecting element 18-1 is connected to a lead wire 18-4 through a lead terminal 18-1a. The temperature detected by the temperature detection element 18-1 is sent as an electrical signal to the control circuit unit 29 (FIG. 5) via the lead wire 18-4.

  FIG. 7 is a perspective view showing an arrangement of a main thermistor 18 and a backup member 32 described later in the fixing film 20.

  As shown in FIGS. 2 and 7, the main thermistor 18 is disposed in the downstream direction of the nip portion N in the rotation direction of the fixing film 20 in the longitudinal center of the fixing film or in the vicinity thereof so as not to contact the fixing film surface. An end of a planar U-shaped fixing member 35 parallel to the fixing film 22 is attached to the longitudinal end of the heater holder 17, and the holder 18-3 of the main thermistor 18 (FIG. 6A) is attached to the fixing member 35. ) Is supported. That is, the main thermistor 18 stabilizes the distance from the surface of the fixing film 20 by fixing and supporting the holder 18-3 on the fixing member 35 with the longitudinal end of the heater holder 17 as a reference.

  Since this non-contact type main thermistor 18 is not in contact with the fixing film 20 as a temperature measurement object, there is an advantage that a rotating member such as a fixing film is not damaged. On the other hand, as described above, if the distance from the fixing film 20 is not kept constant, there is a problem that the variation in the detected temperature becomes large.

  In the film fixing apparatus as in this embodiment, the heat capacity of the fixing film 20 itself is slightly large. Therefore, the temperature of the fixing film 16 is measured to control the temperature of the fixing heater 16 (temperature control). good. In particular, it is preferable to measure the temperature in the portion closest to the nip portion N, that is, in the downstream region of the nip portion. The downstream area of the nip portion N is a position where the sliding frictional force that conveys the fixing film 20 is released, so that the rotation trajectory of the fixing film 20 is the most unstable position, and the main thermistor 18 and the surface of the fixing film 20 It was difficult to keep the interval constant. Therefore, the fluctuation of the detected temperature is also large.

  Therefore, in order to minimize variations in the detected temperature of the main thermistor 18, a backup member 32 is provided on the inner surface side of the fixing film 20 facing the detection point of the main thermistor (FIGS. 2 and 7).

(4) Description of Backup Member 32 FIG. 6B shows a perspective view of the backup member 32.

  In this embodiment, the backup member 32 includes a cylindrical roller portion 32a formed of a liquid crystal polymer having the same heat resistance and heat insulation as the heater holder 17, and shafts 32b provided at both ends of the roller portion. ing. The roller portion 32a has a length of 10 mm and an outer diameter Φ6.

  As shown in FIGS. 2 and 7, the heater holder 17 has a semicircular recess 17 a at a position facing the main thermistor 18. The roller portion 32 a of the backup member 32 is loosely fitted into the recess 17 a so that the outer peripheral surface thereof protrudes from the surface of the heater holder 17. The shafts 32b at both ends of the roller part are rotatably held in bearing recesses 17b provided in the backup member 17 on both sides of the recesses 17a. Therefore, the backup member 32 is configured such that the surface of the roller portion 32a protruding from the surface of the heater holder 17 is in contact with the fixing film 20, and can be rotated around the shafts 32b at both ends in this state. As a result, the backup member 32 is driven to rotate as the fixing film 20 rotates. Then, the fixing film 20 is rotated so as to follow the backup member 32.

  Thus, since the roller portion 32a of the backup member 32 contacts and rotates on the inner peripheral surface of the fixing film 20 at a position facing the main thermistor 18, the conveyance of the fixing film, that is, the rotation trajectory can be stabilized. Thereby, the space | interval of the main thermistor 18 and the fixing film 20 surface can be kept constant.

  Further, the backup member 32 is made of a highly heat-insulating material so that the heat of the fixing film 20 is not absorbed. As a result, uneven gloss caused by uneven temperature of the fixing film 20 can be prevented.

  Further, by making the shape of the backup member 32 into a roller shape, the rotation of the fixing film 20 is not hindered, and at the same time, the positional relationship with the main thermistor 18 is increased by positioning the heater holder 17 as a reference. Yes. As a result, it is possible to increase the distance / position accuracy between the surface of the fixing film 20 and the main thermistor 18 and to prevent fluctuations in the detected temperature of the fixing film 20 by the main thermistor.

  In such a configuration, the method for controlling the temperature of the fixing film 20 using the non-contact main thermistor 18 and the sub-thermistor 19 is as follows.

  The detection output of the main thermistor 18 is taken into a control circuit unit (CPU) 29 (FIG. 5) via an A / D converter (not shown). The control circuit unit 29 determines the temperature control content of the fixing heater 16 based on the outputs of the main thermistor 18 and the sub-thermistor 19, and controls the energization of the fixing heater 16 by the heater drive circuit unit 28 as power supply means. .

  In normal use, the rotation of the fixing film 20 starts as the pressure roller 22 starts rotating, and the temperature of the inner surface of the fixing film increases as the temperature of the fixing heater 16 increases. The energization to the fixing heater 16 is controlled by PID control, and the input power is controlled so that the surface temperature of the fixing film 20, that is, the detected temperature of the main thermistor 18 becomes 190 ° C.

  As described above, according to the fixing device 27 of the present embodiment, since the behavior of the fixing film 20 in the downstream area of the nip portion N can be suppressed, the fluctuation of the detected temperature of the fixing film detected by the main thermistor 18 is suppressed. It becomes possible to suppress. Accordingly, the temperature of the surface of the fixing film 20 can be detected with high accuracy without scratching the surface of the fixing film and without causing toner contamination.

  As a result, the temperature control of the fixing heater 16 can be performed with higher accuracy than before, and a stable fixed image can be obtained stably.

  FIG. 8 is a schematic cross-sectional side view of the fixing device of this embodiment, and FIG. 9 is a perspective view showing the arrangement of the main thermistor and the backup member in the fixing film.

  In the present embodiment, the same members and portions as those of the fixing device 12 of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In this embodiment, the case where the main thermistor 18 cannot be disposed on the surface of the fixing film 20 due to the configuration of the path (conveyance path) of the recording material P and the fixing device 12 will be described.

  As shown in FIGS. 8 and 9, the main thermistor 18 is disposed on the inner surface side of the fixing film 20. When the main thermistor 18 is disposed on the inner surface side of the fixing film 20, it is necessary to secure a distance between the power supply pattern for the resistance heating element layer b of the ceramic heater 16 and the main thermistor 18 to ensure safety.

  In particular, when the fixing film 20 having a metal film (sleeve) as a base layer is used, the inner surface of the fixing film is conductive. Can happen. That is, current may flow directly from the resistance heating element layer b on the primary circuit side to the main thermistor 16 due to breakage of the ceramic heater 16, and the device itself may be destroyed.

  Therefore, when the non-contact main thermistor 18 is disposed on the inner surface of the fixing film 20, even if the fixing heater 16 is damaged, the fixing film 20 and the main thermistor 18 are not in contact with each other. Is very effective.

  As described in the first embodiment, the main thermistor 18 needs to keep a constant distance from the fixing film 20. Therefore, also in this embodiment, the main thermistor 18 is disposed in the longitudinal center of the fixing film or in the vicinity thereof in the downstream area of the nip portion N in the rotation direction of the fixing film 20. That is, the main thermistor 18 is disposed so that the holder 18-3 is fixedly supported by the heater holder 17 and the temperature detecting element 18-1 is not in contact with the inner surface of the fixing film.

  An end portion of a planar U-shaped fixing member 36 parallel to the fixing film 22 is attached to the longitudinal end portion of the heater holder 17, and the backup member 32 is rotatably supported by the fixing member 36. The fixing member 36 has bearing portions 36a on both sides of the position facing the main thermistor 18, and the roller portion 32a of the backup member 32 is disposed between the bearing portions 36a so that the shaft 32b is rotatably supported by the bearing portion. Yes. Accordingly, the backup member 32 is configured such that the surface of the roller portion 32a protruding from the bearing portion 36a contacts the surface of the fixing film 20 and can rotate around the shafts 32b at both ends in this state. As a result, the backup member 32 is driven to rotate as the fixing film 20 rotates. Then, the fixing film 20 is rotated so as to follow the backup member 32. That is, the backup member 32 is fixedly supported by the fixing member 36 based on the longitudinal end portion of the heater holder 17 so that the roller portion 32 a is in contact with the surface of the fixing film 20. Thus, a gap (interval) that can ensure safety is formed between the inner surface of the fixing film 20 and the main thermistor 33, and at the same time, the gap can be stably maintained.

  The backup member 32 employed in the present embodiment is basically the same material / shape as shown in the first embodiment, but since there is a high possibility that toner will adhere to the surface, fluorine such as PFA / PTFE / ETFE is used. It is necessary to coat with a resin material. Actually, in this embodiment, a material coated with a PTFE material is used.

  Further, since the surface of the fixing film 20 is brought into contact with the surface of the fixing film 20, the surface of the fixing film 20 is rotated so as to follow the rotation of the fixing film 20 in the same manner as in the first embodiment.

  In the fixing device of this embodiment, since the roller portion 32a of the backup member 32 contacts and rotates on the outer peripheral surface of the fixing film 20 at a position facing the main thermistor 18 on the inner surface side of the fixing film 20, the fixing film is conveyed or rotated. The orbit can be stabilized. As a result, the distance between the main thermistor 18 and the inner surface of the fixing film 20 can be kept constant. Therefore, similarly to the fixing device shown in the first embodiment, the temperature of the fixing film 20 can be accurately detected using the non-contact main thermistor 18. Therefore, there are no problems such as fixing flaws and toner stains as described above, and stable fixing can always be performed.

[Other]
1) In each embodiment, the backup member 32 has a roller portion 32a having a length of 10 mm in contact with the inner surface of the fixing film 20, but is not limited thereto, and is in contact with the entire length of the fixing film. There may be.

  2) The heating body is not limited to a ceramic heater, and an electromagnetic induction heating body including a magnetic core and an exciting coil wound around the magnetic core can be used.

  3) The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but an image heating device that heats a recording material carrying an image to improve surface properties such as gloss, and image heating that is supposed to be worn Can be used as a device. In addition, it can be widely used as a means / device for heat-treating a material to be heated, such as a heating / drying device, a heating laminating device, and a heating / pressurizing wrinkle removing device.

Schematic configuration diagram showing an example of an image forming apparatus Side cross-sectional side model diagram of the fixing device of Example 1, Front model of the device with the middle part omitted Longitudinal cross section model of the device with the middle part omitted Structural model diagram of an example of a ceramic heater (A) is a perspective view of a main thermistor, (b) is a perspective view of a backup member. The perspective view which shows the arrangement | positioning form of the main thermistor and backup member in a fixing film FIG. 9 is a perspective view showing an arrangement form of a main thermistor and a backup member in a fixing film. The perspective view which shows the arrangement | positioning form of the main thermistor and backup member in a fixing film FIG. 6 is a schematic cross-sectional view showing a conventional film fixing device configuration.

Explanation of symbols

12. Fixing device 16 Ceramic heater 17 Heater holder 18 Main thermistor 19 Subthermistor 20 Fixing film 22 Pressure roller 29 Control circuit (CPU)
32 ... Backup material P ... Recording material

Claims (6)

A rotating member; a heating member that heats the rotating member; and a pressure member that forms a nip portion across the heating member and the rotating member, while conveying and sandwiching the material to be heated in the nip portion. In a heating device for heating,
A temperature detecting means for detecting the temperature of the rotating member in a non-contact manner in order to control the heating body in the downstream area of the nip portion in the rotation direction of the rotating member, and via the temperature detecting means and the rotating member And a backup member that contacts the rotating member and stabilizes the conveyance of the rotating member with respect to the temperature detecting means.   The rotating member is a flexible member, the temperature detecting means is provided on the outer peripheral surface side of the flexible member, and the backup member is provided on the inner peripheral surface side of the flexible member. The heating apparatus according to claim 1.   The rotating member is a flexible member, the temperature detecting means is provided on the inner peripheral surface side of the flexible member, and the backup member is provided on the outer peripheral surface side of the flexible member. The heating apparatus according to claim 1.   The heating device according to claim 2 or 3, wherein the flexible member includes at least a metallic sleeve as a base layer and an elastic layer on a surface of the base layer.   The heating apparatus according to claim 1, wherein the heating body includes a substrate and a resistance heating element disposed on the substrate.   The heating device according to claim 1, wherein the heating body includes a magnetic core and an exciting coil wound around the magnetic core.

Images