JP2008287024A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of shortening the warmup time of a heat roller by enhancing heat insulating property between base material and a planar heating element, while taking space saving into consideration. <P>SOLUTION: In the fixing device 11 equipped with the heat roller 12, the heat roller is equipped with the base material 21 formed into a cylindrical shape, and the planar heating element 22 stuck to the outer surface of the base material via a heat insulating layer 26 to be integrated therewith. The heat-insulating layer includes an air layer 26a, made of heat resistant material and constituted of many linear minute spaces in which air is accumulated in its thickness, and the linear minute space is formed extending over both ends, in the longitudinal direction of the base material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device including a heat roller, and more particularly to a fixing device that fixes a toner image on a recording medium.

  Conventionally, as an image forming apparatus using a fixing device for recording image information such as characters and figures on a recording medium such as recording paper, an electrophotographic copying machine, a facsimile machine, a printer, or these functions have been provided. A so-called multifunction machine or the like is known. In such an image forming apparatus, a corona charging system charger, an exposure device composed of an LED, a developing device, a transfer roller (transfer device), and a cleaning device for residual transfer toner are arranged in this order around the photosensitive drum. Some of them are composed of an arranged process unit and a fixing device downstream thereof. When an optical image based on the image information is irradiated onto the surface of the photosensitive drum by the exposure device and an electrostatic latent image is formed on the surface of the photosensitive drum, the electrostatic latent image is sequentially generated by a biased developing device. The developed toner image reaches a mating portion between the photosensitive drum and the transfer roller as a toner image. The transfer roller nip conveys the recording paper together with the photosensitive drum while being driven to rotate, and during this time, the toner image on the surface of the photosensitive drum is transferred to the recording paper. After that, the recording paper conveyed to the fixing device reaches the mating portion between the heat roller and the press roller, and when the recording paper is heated and pressurized when conveyed in the nip, the toner image is transferred onto the recording paper. Has become established.

  A conventional heat roller in the fixing device as described above is a cylindrical roller made of a metal such as aluminum or stainless steel as its base material, and a heat roller is inserted by inserting a halogen lamp as a heat source into the hollow base material. Is supposed to heat. However, the structure in which the heat roller is heated from the inside through the air layer in the hollow base material has poor thermal efficiency, so that the surface of the heat roller reaches the temperature required for fixing the toner image (approximately 180 ° C.). The problem is that the rise time (warm-up time) is long.

Therefore, in Patent Document 1 (see FIG. 3) and Patent Document 2 described below, a heat generating layer, a heat generating layer, a release layer, and the like are provided on the outer peripheral surface of the base material of the heat roller, and a planar heating element is used as the heat generating layer. According to these, it is said that the warm-up time can be shortened by directly heating the surface of the heat roller.
JP 2001-343850 A JP 2004-46081 A

Since the planar heating element as described above has a high temperature of 180 ° C. or higher, the substrate itself is required to have heat resistance, and the heat generated by the planar heating element is not taken away by the substrate, and the outside of the heat roller. Often, a heat insulating layer is interposed between the base material and the planar heating element so that heat is radiated from the surface.
The fixing devices of Patent Documents 1 and 2 have such a structure. In Patent Document 1, a heat-resistant film is stacked in multiple layers, and holes are formed in each heat-resistant film, or a porous heat-resistant film. Patent Document 2 discloses a heat insulating layer using a resinous resin film and a heat insulating layer using a resin hollow structure or a foamed member obtained by foaming a resin.

In these Patent Documents 1 and 2, the heat insulating property is enhanced by providing an air layer in the heat insulating layer. However, the temperature of the base material of the heat roller may increase depending on the use for a long time. In this case, since the base material of the heat roller is formed in a cylindrical shape, it easily expands in the diameter expansion direction as the temperature rises. When the base material is thus thermally expanded, it is attached to the surface and integrated. There is a concern that a tensile force in the surface area direction along the circumferential direction acts on the planar heating element to cause disconnection or the like.
However, the heat insulating layers described in Patent Document 1 and Patent Document 2 are provided with an air layer to enhance heat insulating properties, and this air layer expands the base material, particularly in the diameter expansion direction (circumferential direction). It is not intended to function to absorb. Therefore, it cannot be said that concerns such as disconnection of the planar heating element are still eliminated.
On the other hand, if the heat insulating layer provided between the base material and the planar heating element is thick to enhance the heat insulating property, or an elastic layer is provided to provide cushioning properties, There has been a problem that the outer diameter of the roller becomes large and cannot meet the demand for space saving.

  The present invention has been made in view of the above circumstances, and while considering space saving, it is possible to improve the heat insulation between the base material and the sheet heating element and to shorten the warm-up time of the heat roller. An object of the present invention is to provide a fixing device that can be used.

  The heat roller in the fixing device of the present invention includes a base material having a cylindrical shape, and a planar heating element attached to and integrated with an outer surface of the base material via a heat insulating layer, and the heat insulating layer. Includes an air layer made of a heat-resistant material and having a large number of linear fine spaces in which air stays within the thickness, and the linear fine spaces are along the longitudinal direction of the base material and between both ends thereof. It is characterized by being formed over.

  In the present invention, the heat insulating layer is formed of a sheet body in which a large number of cylindrical tubes made of a heat resistant resin having an outer diameter of 1.0 mm or less are arranged in parallel in the surface area direction, and the linear fine space is It can consist of the hollow part of a cylindrical tube. The heat insulating layer is formed of a sheet body having a thickness of 1.0 mm or less in which the corrugated heat-resistant resin sheet and the flat heat-resistant resin sheet are laminated, and the linear fine space is laminated by the two sheets. It can also consist of space.

According to the heat roller in the fixing device of the present invention, the heat roller includes a planar heating element that is attached to and integrated with the outer surface of the base material via a heat insulating layer. Since the air layer is composed of a large number of linear fine spaces in which air stays within the thickness, the heat insulation effect is enhanced by the large number of linear fine spaces constituting the air layer, and a planar heating element is emitted from the substrate. The surface of the heat roller can be effectively heated without taking heat away. Therefore, the temperature of the surface of the heat roller can be rapidly increased, and the warm-up time can be significantly shortened. Further, heat conduction from the planar heating element to the base material is effectively blocked by an air layer composed of a linear fine space formed along the longitudinal direction of the base material and between both end portions thereof. The thermal expansion of the material can be prevented. Furthermore, even if the temperature of the base material rises due to use for a long time and the base material expands somewhat in the diameter expansion direction (circumferential direction), the linear fine space of the air layer extends along the longitudinal direction of the base material, and Since it forms over both ends, this bears the role of a cushion and can absorb expansion | swelling of the diameter expansion direction (circumferential direction) of a base material.
As a result, the planar heating element is formed of a conductor pattern without applying a tensile force in the plane direction to the planar heating element attached to the outer surface of the base material and integrated. However, it is possible to prevent disconnection of the conductor pattern, and it is possible to configure a highly reliable fixing device that can stably heat the heat roller without failure.

According to the heat roller in the fixing device of the present invention, the heat insulating layer is formed of a sheet body in which a large number of cylindrical tubes made of a heat resistant resin having an outer diameter of 1.0 mm or less are arranged in parallel in the surface area direction. Or a sheet body having a thickness of 1.0 mm or less integrated by laminating a corrugated heat-resistant resin sheet and a flat heat-resistant resin sheet. However, the outer diameter of the heat roller is not increased, and the demand for space saving can be met.
Further, the linear fine space is composed of a hollow portion of a cylindrical tube or a laminated space composed of a corrugated heat-resistant resin sheet and a flat heat-resistant resin sheet. As described above, disconnection or the like of the planar heating element can be prevented.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view showing an embodiment of an image forming apparatus provided with a fixing device of the present invention, FIG. 2 is an enlarged view of a main part of the ID fixing device, and FIG. FIG. 4 is a partial cutaway perspective view and an enlarged view of the Y portion, and FIG. 4 is a view corresponding to the Y portion of FIG.

The image forming apparatus X shown in FIG. 1 is illustrated by taking a printer having an electrophotographic recording unit as an example. However, the image forming apparatus X is not limited to this. The fixing device according to the present embodiment may be applied to various apparatuses including a recording unit of various color recording methods without being limited to a monochrome electrophotographic recording unit. Is possible.
In the figure, the apparatus main body 1 of the image forming apparatus X includes a recording paper (recording medium) paper feeding section 2, an electrophotographic image recording section 3, and a recording paper discharge section 4 after printing in this order. It is constructed by layering in the height direction.

The recording paper feeding unit 2 includes a detachable paper feeding cassette 2a capable of accumulating and storing a large number of recording papers, a separation paper feeding roller 2b installed at the front end in the paper feeding direction of the paper feeding cassette 2a, The separation pad 2c is elastically contacted with the peripheral surface of the separation sheet feeding roller 2b.
It should be noted that a similar cassette can be stacked under the paper feed cassette 2a to form a multi-stage cassette, or an optional cassette (not shown) can be installed. Further, a retard roller may be used instead of the separation pad 2c.

  The image recording unit 3 includes a corona charging type charger (corona discharger) 6, an exposure unit 7 including an LED, a developing unit 8, a transfer roller (transfer unit) 9, and a transfer residual toner around the photosensitive drum 5. The cleaning unit 10 is arranged in this order, and a fixing unit 11 described later on the downstream side thereof. These process units, except for the exposure unit 7 and the transfer roller 9, are a drum unit 50 in which the photosensitive drum 5, the charger 6 and the cleaning device 10 are integrated, a developing unit housing 81, stirring and conveying screws 82 and 83, a supply paddle 84, The developing unit 80 is a process unit including the developing roller 85 and the like.

The developing unit 80 shown in the figure is a developing unit using a two-component developer, and stores toner and a carrier in a developing device housing 81 that also serves as a resin-molded developer container. The developer is supplied to the developing roller 85 biased by the supply paddle 84 while being stirred and transported by the stirring and transporting screws 82 and 83. A magnetic sensor 86 is attached to the outer surface of the developing device housing 81 to detect the toner density (mixing ratio of toner and carrier) in the developing device housing 81. The toner tank 14 and the toner hopper 15 are installed at a position apart from the developing device unit 80. When the magnetic sensor 86 detects that the toner concentration in the developing device housing 81 is lowered, the toner hopper 15 The toner is supplied into the developing device housing 81 via the conveyor (pipe screw) 16. The toner is supplied to the toner hopper 15 by the toner tank 14.
In this embodiment, the developing device using the two-component developer is exemplified as described above. However, the developing device is not limited to this and can be applied to a one-component method.

  The drum unit 50 and the developing device unit 80 are detachably attached to the apparatus main body 1 from the front side thereof individually or in a state where both are connected by some connecting means. It is also possible to make all the process parts except the exposure device 7 and the transfer roller 9 collectively a process unit. Further, a toner cartridge 18 formed by integrating a waste toner tank 17 and a toner tank 14 which will be described later is also detachably attached to the apparatus main body 1 from the front side. The process units 50 and 80 and the toner cartridge 18 are appropriately replaced with new ones as consumables. Here, the front side of the apparatus main body 1 refers to the front side of the sheet in FIG.

  On the downstream side of the fixing device 11, a switching gate 4b, a discharge roller pair 4c, and a discharge tray 4d are connected in series, and the discharge unit 4 is configured by these. A registration roller pair 4a is disposed in the vicinity of the upstream side of the process section, and the recording paper (paper) separated and fed from the paper feed cassette 2a one by one by the action of the separation paper feed roller 2b and the separation pad 2c. Is registered by the registration roller pair 4 a and introduced into the mating portion between the photosensitive drum 5 and the transfer roller 9. The surface of the photosensitive drum 5 is negatively charged by the charger 6 while rotating in the direction of the arrow in FIG. 1, and an optical image based on the image information is irradiated to the surface of the photosensitive drum 5 by the exposure device 7. An electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is formed by changing the potential of the light irradiated portion and maintaining the potential of other portions depending on the characteristics of the photoconductor on the surface of the photosensitive drum 5.

  The electrostatic latent image is successively developed by a developing device 8 to which a bias is applied, and reaches a matching portion between the photosensitive drum 5 and the transfer roller 9 as a toner image. During this development, toner is attracted to the photosensitive drum 5 due to a potential difference with the developing unit 8 at a portion where the potential has changed due to light irradiation, so that a black portion is formed. As a result, a black and white toner image based on the image information is formed. The registration roller pair 4a is rotationally driven under registration control so that the recording paper is introduced into the mating portion in synchronization with the toner image on the surface of the photosensitive drum 5.

A bias is applied to the transfer roller 9, and the recording paper is nip-conveyed while being paired with the photosensitive drum 5 and being rotationally driven in the direction indicated by the arrow (with respect to the photosensitive drum 5). The toner image is transferred onto the recording paper. Toner remaining on the surface of the photosensitive drum 5 (which may include paper dust) is removed and collected by the cleaning device 10. The recording sheet onto which the toner image has been transferred is introduced into the fixing device 11 and fixed as a permanent image, and then the switching gate 4b is pushed up and discharged onto the discharge tray 4d through the discharge roller pair 4c. This series of recording paper feeds rises substantially vertically (vertically) immediately after feeding from the paper feed cassette 2a, and the discharge roller pair 4c makes a U-turn in a direction of about 180 degrees from the feed direction from the paper feed cassette 2a. This is done along the main feeding path P. With such a layout configuration, the entire apparatus can be made compact.
Waste toner removed and collected by the cleaning device 10 is stored in a waste toner tank 17 constituting a toner cartridge 18 via a screw conveyor 19.

The image forming apparatus X shown in the figure is further provided with a double-sided recording function, and circulates from the attachment position of the switching gate 4b of the main feeding path P to the main feeding path P on the upstream side of the registration roller pair 4a. The recording paper is conveyed along the reverse feed path P1 that merges.
In the figure, reference numeral 1a denotes a manual paper feed tray constituting a manual paper feed function, and reference numeral 1b denotes a case where a paper jam occurs in the main feeding path P and the reverse feeding path P1. It is a jam access cover that opens and closes.

The fixing device according to this embodiment will be described in detail with reference to FIG.
The fixing device 11 is disposed on the downstream side of the drum unit 50 (see FIG. 1), and includes a heat roller 12 and a press roller 13 that are in pressure contact with each other in a resin-molded fixing device housing 11a.
An upstream opening 11b for receiving the recording paper conveyed along the main feeding path P is opened on the upstream side of the fixing device housing 11a in the recording paper conveyance direction (below the paper surface, hereinafter sometimes referred to as the upstream side). A downstream opening 11c is provided on the downstream side in the recording paper conveyance direction (upward on the paper surface, hereinafter sometimes referred to as the downstream side) for discharging the recording paper on which the toner image is fixed toward the discharge unit 4. .
As shown in FIG. 1, the fixing device 11 is arranged so that the nip portion n between the heat roller 12 and the press roller 13 is along the main feeding path P, while being attached to the apparatus main body 1.

In the fixing device housing 11a, a separation claw 11d for separating the recording paper to be conveyed from the heat roller 12 and guide ribs 11e for guiding the conveyance of the recording paper are disposed at a plurality of locations along the roller axial direction. Yes.
The peeling claw 11d is configured to be swingable with a base end portion pivotally supported, and is always urged by a torsion spring or the like so that the tip end abuts against the outer surface of the heat roller 12.

Further, the fixing device housing 11a has an electrode plate 11k connected to an AC power source (not shown) for supplying power to the sheet heating element 22 of the heat roller 12, a brush urging means 11j, and a power supply brush 11i. Is provided. The brush urging means 11j is composed of a compression coil spring, a leaf spring, or the like, and urges the power supply brush 11i toward the annular electrode member 24 with a predetermined pressing force.
The electrode plate 11k and the brush urging means 11j may be formed of phosphor bronze, and the power supply brush 11i may be formed of copper, graphite alloy, or the like.

  The annular electrode member 24 is an electrode member formed in a ring shape, that is, a power feeding portion, and is made of copper, graphite alloy, or the like, and is electrically connected to the AC power source through the electrode plate 11k, the brush urging means 11j, and the power feeding brush 11i. It is connected to the. A total of two annular electrode members 24 are provided, one on each side so as to be attached to a conduction portion (not shown) of the heater layer of the planar heating element 22. Here, an example in which an annular electrode member is used as a power feeding portion is shown, but the present invention is not limited to this, and any power supply can be used as long as it can feed power to the planar heating element 22.

  On the outer surface of the heat roller 12, a temperature sensor 11f such as a thermostat for measuring the surface temperature is placed in contact (sliding contact) or close to the heat roller 12, and the heat sensor 12f is heated based on the temperature measured by the temperature sensor 11f. The heating part of the planar heating element 22 to be described later is controlled so that the outer surface of the roller 12 is maintained at an optimum temperature.

The heat roller 12 is rotatably supported in the fixing device housing 11a by a bearing (not shown) or the like via roller shaft members 25 attached to both ends, and is driven by driving means (not shown) such as a motor. Thus, rotation driving is performed.
The roller shaft member 25 includes a columnar shaft portion 25a concentric with the center of the base 21 and a disc-shaped flange portion 25c, which are integrally formed of a metal material or a resin material. Yes. The roller shaft member 25 is fitted into openings at both ends in the axial direction of the base material 21, and a step (not shown) is formed in the opening of the base material 21 so as to be fitted with the flange portion 25 c at this time. Yes. In the figure, reference numeral 25 b denotes an air vent hole formed in the roller shaft member 25.
When the heat roller 12 is rotationally driven in the direction of the arrow in FIG. 2, the press roller 13 is driven to rotate, and the recording paper introduced into the nip portion n is nipped and the recording paper passes through the nip portion n. The transferred toner image is fixed on the recording paper by thermocompression bonding. Then, the nip is conveyed to the discharge unit 4 side.

The press roller 13 includes a press roller shaft 13a formed of a metal material such as a steel material, and a cylindrical elastic member 13b that covers the outer peripheral surface of the press roller shaft 13a. The cylindrical elastic member 13b is made of a rubber body such as silicone or urethane or a sponge body, and is attached to the press roller shaft 13a via an adhesive or the like.
The cylindrical elastic member 13b is covered with a fluorine resin tube 13c such as a tetrafluoroethylene / perfluoroalkylvinyl copolymer as a release layer for enhancing the releasability of recording paper and toner.
In addition, as a metal material applied to the press roller shaft 13a, a steel material such as SUM24L or S20C may be plated with nickel. The thickness of the fluororesin tube 13c is preferably about 30 μm to 50 μm.

Both ends of the press roller shaft 13a are rotatably supported by bearing bodies 11g. The bearing body 11g is slidably provided with respect to the fixing device housing 11a, and is urged by roller urging means 11h including a coil spring fixed to the fixing device housing 11a.
By this roller urging means 11h, the press roller 13 is pressed against the heat roller 12 to form a nip portion n.

The roller urging means 11h is fixedly supported by a metal chassis (not shown) fixed in the fixing device housing 11a.
The roller urging means 11h is not limited to a coil spring, and any urging means that can urge the press roller 13 against the heat roller 12 may be used.
Further, although not shown, in the fixing device 11, a nip releasing mechanism that releases the nip between the heat roller 12 and the press roller 13, a cleaning roller or a cleaning blade that removes paper dust and toner adhering to the surface of the heat roller 12. Etc.

Next, an example of the heat roller provided in the fixing device according to the present embodiment will be described in detail with reference to FIG. 3 is an enlarged view of the Y portion. For the sake of explanation, FIG. 3 partially cuts the heat roller 12 and omits the illustration of the annular power supply member 24 and the roller shaft member 25.
The heat roller 12 includes a base material 21 made of a hollow cylinder, a heat insulating layer 26 formed on the outer peripheral surface of the base material 21, a planar heating element 22, and a release layer 23 covering the outer peripheral surface of the planar heating element 22. The roller body 20, the above-described annular electrode member 24, and the roller shaft member 25 are configured.
The base material 21 is configured by molding a resin having electrical insulation properties, for example, polyphenylene sulfide (hereinafter abbreviated as PPS) resin into a hollow cylindrical shape.
PPS resin is excellent in heat resistance, strength, dimensional stability, and the like, and is suitable as the base material 21 of the heat roller 12. In addition, other heat-resistant resin materials and metals having at least an outer peripheral surface electrically insulating. It may be composed of a material.

The planar heating element 22 has a three-layer structure in which a heater layer 22a, an insulating layer 22b, and a heat transfer layer 22c are laminated in this order outward in the radial direction.
Examples of the insulating layer 22b include a polyimide film, examples of the heat transfer layer 22c include a copper foil, and the sheet heating element 22 includes, for example, a copper foil on one surface of an insulating layer 22b made of a polyimide film. A heat transfer layer 22c is attached, and a foil-like material made of stainless steel or nickel chrome is heat-pressed with a heat-resistant adhesive such as polyimide resin or silicone resin on the other surface, and a known method such as wet etching Thus, the heater layer 22a is formed by processing into a pattern shape having a plurality of lines.
With the configuration as described above, the planar heating element 22 is wound around the outer peripheral surface of the base material 21 via a heat insulating layer 26 described later on the outer peripheral surface of the base material 21 as a flexible sheet-like heater. It is done.

  The release layer 23 which becomes the outermost periphery of the heat roller 12 is for reducing adhesion of toner and paper powder, and for example, the thickness is preferably about 30 μm. As a material for the release layer 23, a fluorine resin such as tetrafluoroethylene / perfluoroalkylvinyl copolymer is used.

A heat insulating layer 26 is interposed between the base material 21 and the planar heating element 22 so that heat generated by the planar heating element 22 is not taken away by the base material 21.
The heat insulating layer 26 is made of a heat-resistant resin material such as a Teflon (registered trademark) or fluorine-based heat resistant resin material or the above-described PPS resin, and is composed of a large number of linear fine spaces in which air stays within the thickness. The air layer 26a is formed. If a material having elasticity is used as the heat resistant resin material, the cushioning property of the sheet body 26c described later can be further improved, which is preferable.

The heat insulating layer 26 shown in this embodiment is formed of a sheet body 26c in which a large number of cylindrical tubes 26b having a substantially circular cross section are connected in parallel and integrated by welding or the like, and the hollow of the cylindrical tube 26b is formed. The part becomes an air layer 26a composed of a linear fine space, and air is retained in the hollow part. In other words, the cylindrical tube 26b is arranged along the longitudinal direction of the base material 21 and continuously over both ends thereof, whereby the heat insulating layer 26 including the air layer 26a composed of a large number of linear fine spaces is formed. Is done. The linear fine space formed here is made of a hollow portion of the cylindrical tube 26b, so that it can absorb deformation due to thermal expansion of the base material 21 as compared to a heat insulating layer made of a flat sheet body. Can be provided.
The heat insulating layer 26 is wound around the outer surface of the base material 21 and attached with an adhesive so as to be integrated. At this time, if a heat-resistant adhesive such as epoxy is used as the adhesive, the heat insulation effect can be further enhanced.
Further, the outer diameter d of the tube 26b of the heat insulating layer 26 constituted by the sheet body 26c is set to 1.0 mm or less in order to meet the demand for space saving so that the outer diameter of the heat roller 12 is not increased.

According to this, the heat generated by the sheet heating element 22 is blocked by the air layer 26 a formed in the heat insulating layer 26, the heat insulating effect is enhanced, and the heat generated by the sheet heating element 22 is deprived of the base material 21. The surface of the heat roller 12 can be effectively heated. Therefore, the temperature of the surface of the heat roller 12 can be rapidly increased, and the warm-up time can be significantly shortened.
In addition, heat conduction from the planar heating element 22 to the base material 21 is effectively blocked by the air layer 26a formed of a linear fine space, and thermal expansion of the base material 21 can be prevented. Furthermore, even if the temperature of the base material 21 rises and the base material 21 expands somewhat in the diameter-expanding direction due to long-time use, the linear fine space of the air layer 26a is along the longitudinal direction of the base material 21, and the Since it forms over both ends, this bears the role of a cushion and can absorb expansion of the base material 21 in the diameter expansion direction (circumferential direction).
Thereby, since the tensile force in the surface area direction is not applied to the planar heating element 22 that is attached to the base material 21 and integrated, the conductor pattern formed on the heater layer 22a, particularly each line pattern, is It is possible to prevent disconnection of connecting conduction parts (not shown). Therefore, it is possible to configure the highly reliable fixing device 11 that is free from failure and can stably heat the heat roller 12.

  In addition, the structure of the heat insulation layer 26 is not limited to this, What is necessary is just to include the air layer 26a which consists of many linear fine space in which air stagnates. For example, it is good also as a sheet | seat body comprised by pinching | interposing the upper and lower sides of the sheet | seat body 26c which arranged the cylindrical tube 26b shown in FIG. According to this, since both the outer surface and inner surface of the heat insulation layer 26 are flat, the adhesiveness with the base material 21 and the planar heating element 22 can be improved.

Next, another embodiment will be described in detail with reference to FIG. Portions common to the above-described embodiment are denoted by common reference numerals, and description of the common portions is omitted.
In this embodiment, the heat insulation layer 26 is formed by a sheet body 26c formed by laminating a corrugated heat resistant resin sheet 26e and a flat heat resistant resin sheet. Specifically, the heat insulating layer 26 shown here has a so-called cardboard structure, and a laminated space formed by a corrugated heat resistant resin sheet 26e sandwiched between two flat heat resistant resin sheets 26d has a linear shape. An air layer 26 a composed of a fine space is formed, where air stays and is configured as a heat insulating layer 26. The crests and troughs of the corrugated heat-resistant resin sheet 26e sandwiched between the two flat heat-resistant resin sheets 26d are formed along the longitudinal direction of the base material 21 and over both ends thereof. Therefore, compared with the heat insulation layer which consists only of a flat sheet body, it can be equipped with the elasticity which can absorb the deformation | transformation etc. by the thermal expansion of the base material 21. FIG.
The thickness of the heat insulating layer 26 composed of the sheet body 26c is set to 1.0 mm or less in order to meet the demand for space saving so that the outer diameter of the heat roller 12 is not increased.

According to this, the heat generated by the sheet heating element 22 is blocked by the air layer 26 a formed in the heat insulating layer 26, the heat insulating effect is enhanced, and the heat generated by the sheet heating element 22 is deprived of the base material 21. The surface of the heat roller 12 can be effectively heated. Therefore, the temperature of the surface of the heat roller 12 can be rapidly increased, and the warm-up time can be significantly shortened.
In addition, heat conduction from the planar heating element 22 to the base material 21 is effectively blocked by the air layer 26a formed of a linear fine space, and thermal expansion of the base material 21 can be prevented. Furthermore, even if the temperature of the base material 21 rises due to long-term use and the base material 21 expands somewhat in the diameter increasing direction, the linear fine space of the air layer 26a is along the longitudinal direction of the base material and both ends thereof Since it is formed between the parts, this serves as a cushion and can absorb expansion of the base material 21 in the diameter increasing direction (circumferential direction).
Thereby, since the tensile force in the surface area direction is not applied to the planar heating element 22 that is attached to the base material 21 and integrated, the conductor pattern formed on the heater layer 22a, particularly each line pattern, is It is possible to prevent disconnection of connecting conduction parts (not shown). Therefore, it is possible to configure the highly reliable fixing device 11 that is free from failure and can stably heat the heat roller 12.
In addition, the structure of the heat insulation layer 26 is not limited to this, The point which should just contain the air layer 26a which consists of many linear fine space in which air stagnates is the same as the above-mentioned.

1 is a schematic longitudinal sectional view showing an embodiment of an image forming apparatus including a fixing device of the present invention. FIG. 2 is an enlarged view of a main part of the fixing device. FIG. 2 is a partially broken perspective view of a heat roller and an enlarged view of a Y portion in the fixing device. It is other embodiment of the same heat roller, Comprising: It is a figure corresponded to the Y section of FIG.

Explanation of symbols

X Image forming apparatus 11 Fixing apparatus 12 Heat roller 21 Base material 22 Planar heating element 26 Heat insulation layer 26a Air layer 26b Cylindrical tube 26c Sheet body 26d Flat heat resistant resin sheet 26e Corrugated heat resistant resin sheet

Claims (3)

A fixing device including a heat roller,
The heat roller includes a base material having a cylindrical shape, and a planar heating element that is attached to and integrated with an outer surface of the base material via a heat insulating layer,
The heat insulating layer includes an air layer made of a heat-resistant material and including a large number of linear fine spaces in which air stays within the thickness, and the linear fine spaces extend along the longitudinal direction of the base material and A fixing device formed between both end portions. The fixing device according to claim 1,
The heat insulating layer is formed of a sheet body in which a large number of cylindrical tubes made of a heat-resistant resin having an outer diameter of 1.0 mm or less are arranged in parallel in the surface area direction, and the linear fine space is formed by the cylindrical tube. A fixing device comprising a hollow portion. The fixing device according to claim 1,
The heat insulation layer is formed of a sheet body having a thickness of 1.0 mm or less in which a corrugated heat-resistant resin sheet and a flat heat-resistant resin sheet are laminated and integrated, and the linear fine space is laminated by the two sheets. A fixing device comprising a space.

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