JP2005156918A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the life of a fixing device which employs a metallic sleeve by preventing sleeve ends from cracking. <P>SOLUTION: An end ring of a fixing sleeve unit is coated with a lubricant such as dry surf. Alternatively fixing sleeve end surface are protected through lubricating sheet to reduce the load resulting from friction between the fixing sleeve and end ring. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device that heats a heated material by passing the heated material through a pressure nip portion between a heating member and a pressure member and nipping and conveying the heated material.

  More specifically, the fixing device includes a film-like rotator, a guide member that guides the rotator, and a heating unit that heats a transfer material conveyed in the nip as the rotator rotates with respect to the guide member. About.

  In an image forming apparatus such as an electrophotographic copying machine or a printer, an unfixed toner image formed or supported directly (transferred) or directly on a transfer material (paper) by an appropriate image forming process means such as an electrophotographic process As a fixing device for heat fixing as a permanently fixed image, a heat roller type heat fixing device has been widely used.

  In recent years, a film heating type fixing device has been put into practical use from the viewpoint of quick start and energy saving. There has also been proposed an electromagnetic induction heating type heating device for generating heat from a metal film itself.

a) Film-type fixing device A film-heating-type fixing device is proposed in, for example, JP-A-63-313182, JP-A-2-157878, JP-A-4-44075, and JP-A-4-204980. Has been.

  That is, a heat-resistant film (hereinafter referred to as a fixing film) is sandwiched between a ceramic heater as a heating body and a pressure roller as a pressure member to form a pressure nip (hereinafter referred to as a fixing nip portion), and the fixing By introducing a transfer material that forms and supports an unfixed toner image between the fixing film and the pressure roller at the nip, and transporting it with the fixing film, the heat of the ceramic heater is transferred through the fixing film. The unfixed toner image is fixed on the surface of the transfer material by applying pressure at the fixing nip portion.

  This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a film having a low heat capacity member, and energizes the ceramic heater as a heat source only at the time of image formation to have a predetermined fixing temperature. Heat generation, and there is an advantage that the waiting time from the power-on of the image forming apparatus to the image forming executable state is short, and the power consumption during standby is significantly reduced.

b) Fixing device using metal film (fixing belt) In recent years, with the increase in speed and colorization of image forming devices, a film heating type fixing device uses a metal film such as SUS or nickel as the fixing film, Further, a fixing device using a belt-like member (hereinafter, a fixing belt) in which an elastic layer is provided on a metal film has been proposed.

  Conventionally, heat-resistant resins have been used as the base material for fixing films. However, as the speed of image forming devices increases, the thermal conductivity of the fixing film increases and the heat of the ceramic heater is transferred more efficiently. It became necessary to tell to. For this reason, it is preferable to use a metal having a higher thermal conductivity than the resin as the fixing film substrate. A fixing device using such a metal fixing film is disclosed in Japanese Patent Application Laid-Open No. 2003-045615, Japanese Patent Application Laid-Open No. 2003-156554, and the like.

  Also, with the colorization of image forming apparatuses, it has become necessary to provide an elastic layer on the base material of the fixing film. Examples of such a fixing belt and an image forming apparatus are disclosed in JP-A-10-10893, JP-A-11-15303, and the like.

  This is because when the toner image passes through the fixing nip portion, the conventional film fixing device cannot follow the shape of the toner image transferred in multiple layers of the color image, and partially fixes the toner image. This is because unevenness of sex occurs. Unevenness of fixing property appears as unevenness in gloss of an image, or becomes non-transparent in OHT (transparent sheet for overhead projector), and unevenness of transparency appears as an image defect when projected. there were.

  By providing an elastic layer on the fixing film, the elastic layer is deformed along the toner layer, so that the toner that is unevenly placed on the image is encased in the elastic layer and uniformly heated by applying heat uniformly. Fixing is achieved.

  However, since the thermal conductivity of the fixing film is inferior due to the provision of the elastic layer, it is necessary to give an extra amount of heat. In particular, in order to ensure the on-demand property of the fixing device, it is necessary to quickly raise the fixing device to a predetermined temperature. Therefore, by making the base material a metal film rather than a normal fixing film, the thermal conductivity can be reduced. The use of an improved fixing belt is advantageous.

c) Electromagnetic induction heating type fixing device Japanese Utility Model Laid-Open No. 51-109739 discloses an induction overheating fixing device that induces eddy currents in a metal layer (heating layer) of a fixing film by magnetic flux and generates heat by its Joule heat. It is disclosed. This makes it possible to directly heat the fixing film by using the generation of induced current, and achieves a fixing process that is more efficient than a heat roller type fixing device using a halogen lamp as a heat source.

  Such an electromagnetic induction type heat fixing apparatus uses a thin metal of about 50 μm as a fixing film. Further, when an electromagnetic induction heating type fixing device is applied to a color image forming apparatus, a fixing belt having an elastic layer on a metal layer is used.

d) Conventional fixing belt end crack countermeasures As described above, in the fixing method using a film-like thin metal rotating body, cracks occur at the end of the fixing belt by repeatedly using the rotating state, There was a problem of destruction. This is because although the fixing belt itself has high rigidity, in the fixing belt manufacturing process, when the fixing belt is cut into an appropriate length for the fixing device, burrs and minute cracks are generated and used repeatedly in a rotating state. When the end surface of the fixing belt was rubbed, a crack originated from such burrs and minute cracks.

  In order to prevent such cracks at the end of the fixing belt, in Japanese Patent Application Laid-Open No. 2002-231419, a flange supporting the end of the fixing belt is supported from the outer peripheral surface of the fixing sleeve, and is configured to rotate together with the fixing sleeve. Thus, a configuration for preventing the rubbing between the fixing belt end and the fixing device is disclosed.

  FIG. 7 is a cross-sectional view of an example of a configuration in which the fixing flange is supported from the outer peripheral surface of the fixing sleeve and rotated together with the fixing sleeve, as viewed from the longitudinal direction.

  The inner diameter of the fixing flange 702 is set to be larger than the outer diameter of the fixing belt 701. When the fixing belt 701 is pressed by the pressure roller 703, the inner surface of the fixing belt 701 comes into contact with the inner surface of the fixing flange 702. By generating a frictional force, the fixing flange 702 rotates as the fixing belt 701 rotates.

The fixing flange 702 is supported by a receiving portion (not shown) and prevents the fixing belt 701 from falling off the fixing flange 702 even when the fixing belt 701 is shifted in the longitudinal direction.
Japanese Patent Laid-Open No. 2002-231419

  However, as the fixing belt 701 rotates, the fixing belt 701 is deformed by the pressure roller 703 and repeats vertical movement with respect to the fixing flange 702. Therefore, even if the fixing flange 702 rotates together with the fixing belt 701, a certain amount of friction between the end surface of the fixing belt 701 and the fixing flange 702 is unavoidable.

  Also in the conventional fixing flange 702 disclosed in Japanese Patent Application Laid-Open No. 2002-231419, as shown in a cross-sectional view seen from a direction perpendicular to the longitudinal direction shown in FIG. The angle θ between the longitudinal extension line of the fixing belt 701 and the surface of the fixing flange 702 contacting the end surface of the fixing belt 701 is set to 90 ° or more, so that the fixing belt 701 is deformed by the pressure roller 703 as the fixing belt 701 rotates. In response, a configuration for preventing the rubbing on the end surface of the fixing flange 702 has been proposed. However, there is always a place where the end surface of the fixing belt and the fixing flange come into contact with each other on the side where the fixing belt 701 approaches. The rubbing accompanying 701 rotation is inevitable.

  Further, on the side where the fixing belt 701 approaches, a frictional force is generated at the receiving portion of the fixing flange 702, and the fixing flange 702 may not rotate in synchronization with the rotation of the fixing belt 701. In such a case, since the rotation speeds of the fixing flange 702 and the fixing belt 701 are different from each other, the same friction as that of the fixing device without the fixing flange 702 is generated, and the fixing belt 701 is cracked. There was a case.

  Furthermore, when θ is set large, the fixing flange is pulled in the direction of the arrow in FIG. 8 due to the shifting force in the longitudinal direction of the fixing belt 701, and the fixing belt 701 is distorted in the longitudinal direction. Since the stress increases, there is a problem that the fixing belt 701 causes fatigue failure.

  In particular, in the fixing belt 701 in which the fixing belt 701 base layer is formed by plastic processing such as ironing, the residual stress of the metal layer is large, and the fixing belt 701 is rubbed by the end surface of the fixing belt 701 and distortion in the longitudinal direction. Cracks starting from minute cracks on the end face are likely to occur, and fatigue failure is likely to occur.

  In particular, in the color image forming apparatus, it is necessary to increase the pressure in the fixing nip portion as compared with the monochrome image forming apparatus. This is because a color image is formed by superimposing a plurality of colors of toner, so that the toner image height is higher than that of a black and white image forming apparatus, and a higher pressure is required in order to obtain a uniformly smooth image in the fixing unit. Is necessary.

  When the pressure at the fixing nip portion is increased, the force that the fixing belt approaches in the longitudinal direction also increases, so that cracking due to buckling of the fixing belt is likely to occur.

  For these reasons, further improvement in durability has been demanded.

  The present invention for solving the above-described problems includes a film-like fixing belt, a guide member that guides the fixing belt, a pressure member that forms a pressure nip with respect to the guide member via the fixing belt, and the fixing In the fixing device having a heating means for heating the transfer material heated in the nip as the fixing belt rotates, the total length of the fixing belt is larger than the contact surface length of the pressure member. The fixing belt has a structure in which both end portions thereof are supported by flanges which are support members from the outer peripheral surface side, and the flange is subjected to a treatment for improving lubricity. And

  By adopting the above configuration, it is possible to more effectively prevent cracks originating from minute cracks on the fixing belt end surface by reducing the resistance when the fixing belt end surface and the fixing flange rub against each other. As a result, the fixing device and the image forming apparatus can be further extended in service life.

  Hereinafter, embodiments of the present invention will be described in detail.

(Image forming device)
FIG. 1 is a cross-sectional view of an image forming apparatus provided with a fixing device in Embodiment 1 of the present invention.

  In this embodiment, a full color image forming apparatus employing a color on demand fixing device will be described.

  The image forming apparatus according to the present exemplary embodiment is a full-color image forming apparatus that obtains a full-color image by superimposing toner images of four colors of yellow, cyan, magenta, and black using an electrophotographic method. Is incorporated.

  In the present embodiment, the process speed of the full-color image forming apparatus is 90 mm / sec, and the number of printed sheets per minute is 16 US letter size paper. Further, the time (FPOT) to the first print (First Page Out) is about 15 seconds.

  The configuration of the color image forming apparatus according to the present invention will be described with reference to FIG. In the color image forming apparatus of the present invention, a photosensitive drum (1Y, 1C, 1M, 1K) as an image carrier, a charging roller (2Y, 2C, 2M, 2K) as a charging unit, and an electrostatic latent image are visualized. For this purpose, a so-called all-in-one cartridge is used in which developing means (3Y, 3C, 3M, 3K) and cleaning means for photosensitive drums (4Y, 4C, 4M, 4K) and the like are collected in one container.

  Develop yellow cartridge with yellow (Y) toner in developer, magenta cartridge with magenta (M) toner in developer, cyan cartridge with cyan (C) toner in developer, and black (K) toner Four cartridges of black cartridge filled in the container are used.

  In the image forming apparatus of this embodiment, the optical system 5 that forms an electrostatic latent image by exposing the photosensitive drums (1Y, 1C, 1M, and 1K) corresponds to the four color toner cartridges. Is provided. A laser scanning exposure optical system is used as the optical system.

  The scanning light based on the image data is exposed from the optical system 5 on the photosensitive drum (1Y, 1C, 1M, 1K) uniformly charged by the charging means (2Y, 2C, 2M, 2K). Then, an electrostatic latent image corresponding to the image is formed on the surface of the photosensitive drum (1Y, 1C, 1M, 1K). By setting the developing bias applied to the developing roller (3Y, 3C, 3M, 3K) from a bias power source (not shown) to an appropriate value between the charged potential and the latent image (rear exposure) potential, the negative polarity The toner charged on the surface is selectively attached to the electrostatic latent image on the photosensitive drum (1Y, 1C, 1M, 1K), whereby development is performed.

  The single color toner image developed on the photosensitive drum (1Y, 1C, 1M, 1K) is synchronized with the photosensitive drum (1Y, 1C, 1M, 1K) on the intermediate transfer member that rotates at a substantially constant speed. Is transferred to. In this embodiment, an intermediate transfer belt 6 is used as an intermediate transfer member, which is driven by a driving roller 7 and stretched by a tension roller 8. Primary transfer rollers (9Y, 9C, 9M, 9K) are used as primary transfer means for transferring the toner image on the photosensitive drum (1Y, 1C, 1M, 1K) to the intermediate transfer belt 6. The primary transfer roller (9Y, 9C, 9M, 9K) is applied with a primary transfer bias having a polarity opposite to that of the toner from a bias power source (not shown), whereby the toner image is primarily transferred to the intermediate transfer belt 6. Is done.

  After the primary transfer, the toner remaining as a transfer residue on the photoreceptor (1Y, 1C, 1M, 1K) is removed by the cleaning means (4Y, 4C, 4M, 4K). In this embodiment, blade cleaning using a urethane blade is used as the cleaning means.

  The above process is performed for each color of yellow, magenta, cyan, and black in synchronization with the rotation of the intermediate transfer belt 6, and the primary transfer toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 6. At the time of image formation of only a single color (monochrome mode), the above process is performed only for the target color.

  Further, the transfer material P set in the transfer material cassette 10 serving as a transfer material supply unit is fed by a feed roller 11 and is transferred to the secondary transfer unit at a predetermined timing by the registration roller 12 and the intermediate transfer belt 6. It is conveyed to the nip portion with the secondary transfer means.

  The primary transfer toner image formed on the intermediate transfer belt 6 is applied onto the transfer material P by a bias having a polarity opposite to that of the toner, which is applied to a secondary transfer roller 13 as a secondary transfer unit by a bias applying unit (not shown). Are collectively transferred. Reference numeral 14 denotes a secondary transfer roller facing roller.

  The secondary transfer residual toner remaining on the intermediate transfer belt 6 after the secondary transfer is removed by the intermediate transfer belt cleaning unit 15. In the present embodiment, the intermediate transfer member is cleaned by the urethane blade in the same manner as the photosensitive drum cleaning means.

  The toner image secondarily transferred onto the transfer material P passes through the fixing device F serving as a fixing unit, so that the toner image is melted and fixed onto the transfer material P and becomes an output image of the image forming apparatus.

  In addition, the image forming apparatus according to the present exemplary embodiment uses the same power control circuit as that according to the first exemplary embodiment to control the power supplied to the heater 700.

(Fixing device F)
FIG. 2 is a cross-sectional view of the fixing device in this embodiment.

  The fixing device in this embodiment includes a heater 700, a heater holder 17, a thermistor 18, a fixing belt 20, a pressure roller 22, and an entrance guide 23.

  The heater holder 17 is formed of a liquid crystal polymer resin having high heat resistance, plays a role of holding the heater 700 and guiding the fixing belt 20.

  In this example, DuPont Zenite 7755 (trade name) was used as the liquid crystal polymer. The maximum usable temperature of Zenite 7755 is about 270 ° C.

  The thermistor 18 is disposed to detect the temperature of the inner surface of the fixing belt 20 and perform temperature control.

  The thermistor 18 has a thermistor element attached to the tip of a stainless steel arm, and the thermistor element always contacts the inner surface of the fixing belt 20 even when the movement of the inner surface of the fixing belt 20 becomes unstable due to the swing of the arm. Kept in a state.

  The thermistor 18 is connected to the CPU 117, and the CPU 117 determines the temperature control content of the heater 700 based on the output of the thermistor 18 and controls the energization of the heater 700.

  The fixing belt 20 is formed by forming an elastic layer and a release layer on a metal base layer. The fixing belt configuration will be described in detail later.

  The pressure roller 22 is formed by forming a silicone rubber layer having a thickness of about 3 mm on a stainless steel core by injection molding and coating a PFA resin tube having a thickness of about 40 μm thereon.

  The entrance guide 23 serves to guide the transfer material so that the transfer material P that has passed through the secondary transfer nip is accurately guided to the fixing nip portion. The entrance guide of the present embodiment is made of polyphenylene sulfide (PPS) resin.

  The pressure roller 22 and the entrance guide 23 are each assembled to a frame 24, and a fixing belt 20 including a fixing heater 16 bonded to the heater holder 17 is placed thereon. Pressurized with a force of 10 kgf on one side. The pressure mechanism has a pressure release mechanism (not shown), and is configured such that the pressure is released and the transfer material P can be easily removed during jam processing or the like.

  In the fixing device of this embodiment, the fixing belt 20 is driven to rotate as the pressure roller 22 rotates. At that time, the inner surface of the fixing belt 20 and the heater holder 17 are configured to slide. Grease is applied to the inner surface of the fixing belt 20 to ensure slidability between the heater holder 17 and the inner surface of the fixing belt 20.

  In normal use, the rotation of the fixing belt 20 starts with the rotation of the fixing device, and the temperature of the inner surface of the fixing belt 20 increases as the temperature of the heater 700 increases.

(Fixing belt 20)
FIG. 3 shows a cross-sectional view of the fixing belt 20 used in this embodiment.

The fixing belt 20 is formed by forming a silicone rubber layer 20b by a ring coating method on a SUS belt 20a formed into a seamless belt shape having a thickness of 50 [mu] m by drawing a SUS base tube, and releasing properties. The layer 20c is formed by covering a PFA resin tube having a thickness of 30 μm. For the silicone rubber layer 20b, it is desirable from the viewpoint of temperature rise to use a material having as high a thermal conductivity as possible and to reduce the heat capacity of the fixing belt 20. In this example, a material having a thermal conductivity of about 1.0 × 10 ⁻³ cal / sec · cm · K and a silicone rubber having a high thermal conductivity were used.

  On the other hand, it is desirable that the silicone rubber layer 20b of the fixing belt 20 be made as thick as possible from the viewpoint of image quality such as OHT permeability and “s” (small gloss unevenness) on the image. According to the study by the present inventors, it has been found that a rubber thickness of 200 μm or more is necessary to obtain a satisfactory level of image quality.

  The silicone rubber layer 20b in the present example has a thickness of 250 μm. Further, the outer diameter of the fixing belt 20 in this embodiment is 24 mm.

When the heat capacity of the fixing belt 20 thus formed was measured, it was 2.8 × 10 ⁻² cal / cm ² K (heat capacity per 1 cm ^{2 of the} fixing belt). Generally, when the heat capacity of the fixing belt 20 is 1.0 cal / cm ² K or more, the temperature rise becomes dull and the on-demand property is impaired. On the other hand, if it is attempted to be 1.0 × 10 ⁻² cal / cm ² K or less, the rubber layer of the fixing belt 20 has to be extremely thin, and the image quality such as the OHT permeability and the level of “su” is increased. The thickness of the rubber layer necessary to maintain the thickness cannot be secured. Therefore, it can be seen that the heat capacity of the fixing belt 20 that satisfies both on-demand characteristics and image quality is included in the range of 1.0 × 10 ⁻² cal / cm ² K to 1.0 cal · cm ² K. .

  Further, by providing a fluororesin layer on the surface of the fixing belt 20, the surface releasability is improved, and the offset phenomenon that occurs when the toner once adheres to the surface of the fixing belt 20 and moves to the transfer material P again is prevented. can do.

  Further, by using a PFA tube as the releasable layer 20c on the surface of the fixing belt 20, a uniform releasable layer can be formed more easily.

(Fusing flange)
The fixing flange in this embodiment will be described in detail with reference to FIGS. 4a and 4b.

  4A is a view of the fixing flange 400, the fixing belt 20, and the pressure roller 22 as viewed from the same direction as the cross-sectional view of FIG. 4B is a cross-sectional view of the fixing belt 20 and the fixing flange 400 taken along a plane perpendicular to the longitudinal direction.

  As shown in FIG. 4 a, the fixing flange 400 has an inner diameter larger than the outer diameter of the fixing belt 20, and the fixing belt 20 deformed by the pressure roller 22 is inscribed in the fixing flange 400 to generate a frictional force. The belt 20 and the fixing flange 400 rotate together to prevent the end face of the fixing belt 20 from rubbing.

  The fixing flange 400 is made of PPS (polyphenylene sulfide) resin. In this embodiment, the inner diameter is 25.5 mm.

  If the inner diameter of the fixing flange 400 that holds the outer peripheral surface of the fixing belt 20 is too small, the fixing belt 20 cannot be deformed in the fixing flange 400 at all, and the fitting portion with the fixing flange 400 and the contact portion of the pressure roller 22 ( In the nip forming portion), the fixing belt 20 is distorted in the longitudinal direction, and stress due to pressure and heating is greatly applied to the fixing belt 20 during durable use, causing the fixing belt 20 to undergo fatigue failure.

  On the other hand, if the inner diameter of the fixing flange 400 is too large, sufficient frictional force is not generated between the surface of the fixing belt 20 and the inner surface of the fixing flange 400, the fixing belt 20 and the fixing flange 400 slip, and the fixing flange 400 is scraped. This causes problems such as breakage and cracks at the end of the fixing belt 20 due to rubbing.

  By maintaining an appropriate relationship between the outer diameter of the fixing belt 20 and the inner diameter of the fixing flange 400, a frictional force is generated between the surface of the fixing belt 20 and the inner surface of the fixing flange 400, and damage to the fixing belt 20 is not increased. A rotational force can be applied to the fixing flange 400.

  Further, a lubricant is applied to the fixing flange 400 in this embodiment.

  As a lubricant, based on a volatile solvent, a liquid lubricant that combines an oil component with good low-temperature fluidity and an ultrafine fluororesin, specifically, is provided by Harves Co., Ltd. Drysurf HF-1800 (trade name) was used. This lubricant is called a dry film lubricant and has an opaque white appearance, no flash point (open type), a use temperature range of −30 to 120 ° C., and a specific gravity of 1.53 (25 Degree), the surface after application is semi-wet, and the ozone depletion coefficient is also “0”.

  In this embodiment, the fixing flange 400 is dipped and dried in the dry surf HF-1800 solution to form a dry surf film having a thickness of about 10 μm on the entire surface of the fixing flange 400. Increases lubricity.

  Further, in the fixing flange 400 in this embodiment, the angle θ between the surface in contact with the outer peripheral surface of the fixing sleeve 20 and the surface in contact with the end surface of the fixing sleeve 20 is set to 90 °.

(An endurance test)
A durability test was performed using the fixing device of this example.

  The durability test was performed by setting the fixing device in the present example in the image forming apparatus and performing paper feeding. After repeating the output pattern of 6 seconds after passing the two transfer materials, 150,000 sheets of the transfer material were put through, and the fixing flanges 400 at both ends continued to rotate at the same speed as the fixing belt 20. . At this time, the fixing belt 20 was not damaged and the fixing performance was not deteriorated.

  Further, when the surface of the fixing flange 400 after the end of the durability was observed, the dry surf film was maintained, and the slidability was also secured at the receiving portion of the fixing flange 400. In addition, slidability on the contact surface between the end surface of the fixing belt 20 and the fixing flange 400 is also ensured.

  By forming a film by dry surf on the surface of the fixing flange 400, even when the fixing belt 20 is shifted in the longitudinal direction, the rotation of the fixing flange 400 can be maintained. Even when the fixing flange 400 is rubbed, the load applied to the minute cracks on the end face of the fixing belt 20 can be reduced, and there is an effect of preventing the cracks from expanding due to the rub.

(Comparative example)
As a comparative example, a fixing device similar to that of Example 1 was prepared and the durability test similar to that of Example 1 was performed, except that dry surf was not applied to the fixing flange 400.

  When the rotating fixing device was observed at the time when 50,000 sheets were passed, the fixing flange 400 on the side where the fixing belt 20 approached was not rotated.

  Further, when 80,000 sheets were passed, one crack having a length of about 2 cm occurred at the end of the fixing belt 20. If the durability was further continued, the number of cracks increased to 6 at the time of 85,000 sheets. At the time when 90,000 sheets were passed, the crack length reached 15 cm, and defects were generated as uneven fixing properties on the image. When 100,000 sheets were passed, the fixing belt 20 was completely destroyed, and the fixing device became unusable.

  This is because the slidability of the fixing flange 400 is insufficient, and a fixing force in the longitudinal direction is applied to the fixing belt 20 so that the fixing flange 400 is strongly pressed against the receiving portion, and the frictional force between the fixing flange 400 and the receiving portion. This is because the fixing flange does not rotate, and the end surface of the fixing belt 20 is rubbed against the inner surface of the fixing flange 400, thereby exerting a force for expanding micro cracks existing on the end surface of the fixing belt 20. In particular, the fixing belt 20 formed by plastic working has a large residual stress and is liable to cause expansion of cracks due to rubbing. For this reason, in the state where the slidability between the end surface of the fixing belt 20 and the fixing flange 400 is not secured, the fixing belt 20 is damaged.

  In this embodiment, the slidability of the fixing belt and the fixing flange is improved by applying dry surf to the fixing flange, but not limited to dry surf, a method of forming a lubricating film such as powder coating, Arbitrary lubrication treatments such as a method of applying a paste containing a solid lubricant, grease application, oil application, etc. can be performed.

  In this embodiment, the color image forming apparatus has been described in detail. However, the present invention may be applied to a black and white image forming apparatus. Also in a black and white image forming apparatus, the use of a metal belt is effective for speeding up, and further, by providing an elastic layer on the fixing belt, it is possible to improve the image level such as uneven gloss.

  This embodiment is substantially the same as the first embodiment, but instead of applying a lubricant to the fixing flange, a lubricating sheet or the like is interposed between the fixing belt and the fixing flange sliding surface in the same manner as the first embodiment. The effect of preventing damage to the fixing belt is obtained.

  FIG. 5 shows an example of such a lubricating sheet.

  The lubricating sheet 500 may be of any type as long as it has a lubricating property such as a glass cloth impregnated with silicone oil or fluorine oil, a glass cloth impregnated / fired with a fluorine resin, or the like.

  In this example, NITOFLON (registered trademark) impregnated glass cloth (product No. 970-2LL, manufactured by Nitto Denko) was used as a material.

  Such a lubricating sheet 500 is formed in a donut shape having the same diameter as the inner diameter of the fixing flange 400, and is interposed between the sliding surfaces of the fixing flange 400 and the fixing belt 20, and between the fixing flange 400 and the receiving portion. . At this time, the lubricating sheet 500 may be attached to the fixing flange 400.

  When the same durability test as in Example 1 was performed using the fixing device of this example, the fixing belt was not damaged even when 150,000 sheets were passed, and the fixing performance was not deteriorated.

  In this embodiment, an electromagnetic induction heating type fixing device is used as the fixing device.

  Also in this embodiment, the fixing belt 20 end and the fixing flange 400 are configured in the same manner as in the first embodiment.

  FIG. 6 shows a cross-sectional view of an electromagnetic induction heating type fixing device.

  The magnetic field generating means includes magnetic cores 62 a, 62 b, 62 c and an excitation coil 63.

  The magnetic cores 62a, 62b, and 62c are high magnetic permeability members, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite having a low loss even at 100 kHz or higher.

  Reference numeral 67 denotes a high-frequency transmission circuit unit which is a power supply unit (power supply unit), which can generate a high frequency of 20 kHz to 500 kHz by a switching power supply. The exciting coil 63 generates an alternating magnetic flux by the alternating current (high-frequency current) supplied from the power supply unit 67.

  Reference numerals 61a and 61b are saddle-shaped belt guide members having a substantially semicircular cross-sectional shape. The fixing belts (fixing sleeves) are cylindrical electromagnetic induction heating belts on the outer side. The first rotating body 20 is externally fitted loosely. The belt guide member 61a holds magnetic cores 62a, 62b and 62c as magnetic field generating means and an exciting coil 63 on the inside. A sliding member 65 is disposed on the belt guide member 61 a on the inner surface of the fixing belt 20 on the side of the nip portion 27 facing the pressure roller 22.

  Reference numeral 64 denotes a laterally long pressurizing rigid stay disposed in contact with the inner surface flat portion of the belt guide member 61b.

  Reference numeral 66 denotes an insulating member for insulating the magnetic cores 62 a, 62 b, 62 c and the exciting coil 63 from the pressurizing rigid stay 64.

  The pressing rigid stay 64 applies a pressing force by a pressing mechanism (not shown). As a result, the sliding member 65 on the lower surface of the belt guide member 61a and the pressure roller 22 are pressed against each other with the fixing belt 20 interposed therebetween to form a fixing nip portion 27 having a predetermined width.

  The pressure roller 22 is rotationally driven in a counterclockwise direction indicated by an arrow by a driving means (not shown). A rotational force acts on the fixing belt 20 by the frictional force between the pressure roller 22 and the outer surface of the fixing belt 20 by the rotational driving of the pressure roller 22, and the inner surface of the fixing belt 20 is a sliding member in the fixing nip 27. The belt guide members 61a and 61b are rotated around the outer periphery of the belt guide member 61a and 61b in a clockwise direction indicated by an arrow while being in close contact with the lower surface of the roller 65 at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 22. In this case, in order to reduce the mutual sliding frictional force between the lower surface of the sliding member 65 and the inner surface of the fixing belt 20 in the fixing nip portion 27, the lower surface of the sliding member 65 and the inner surface of the fixing belt 20 are fixed. A lubricant such as heat-resistant grease can be interposed between the two.

  The alternating magnetic flux guided to the magnetic cores 62a, 62b, and 62c is an electromagnetic induction heating layer as a heating body of the fixing belt 20 between the magnetic cores 62a and 62b and between the magnetic cores 62a and 62c. An eddy current is generated (not shown). This eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heat generating layer due to the specific resistance of the electromagnetic induction heat generating layer in the fixing belt 20 described later. Here, the heat generation region is defined as a region where the heat generation amount is Q / e or more, where Q is the maximum heat generation amount. This is a region where the amount of heat generated for fixing can be obtained.

  In the electromagnetic induction heating type fixing device shown in this embodiment, the fixing belt 20 used here is a heating layer (not shown) made of a metal belt or the like as a base layer of the electromagnetic induction heat-generating fixing belt 20. The composite layer structure has an elastic layer (not shown) laminated on the outer surface and a release layer (not shown) laminated on the outer surface. For adhesion between the heat generating layer and the elastic layer and adhesion between the elastic layer and the release layer, a primer layer (not shown) may be provided between the layers. In the fixing belt 20 having a substantially cylindrical shape, the heat generating layer is on the inner surface side, and the release layer is on the outer surface side. As described above, when an alternating magnetic flux acts on the heat generating layer, an eddy current is generated in the heat generating layer, and the heat generating layer generates heat. The heat heats the fixing nip portion 27 through the elastic layer / release layer, and heats the recording material P as a material to be heated that is passed through the fixing nip portion 27 to heat and fix the toner image. .

  The temperature of the fixing belt 20 is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 63 by the temperature control systems 21 and 67 including the main thermistor 18 and the sub-thermistor 19 as temperature detecting means. It is adjusted. That is, the main thermistor 18 is a temperature detecting means for detecting the temperature of the fixing belt 20, and in this embodiment, the main thermistor 18 is exposed to the heat generation area H of the inner surface of the fixing belt 20 on the outer surface of the belt guide member 61a. It is arranged. The main thermistor 18 contacts the inner surface of the fixing belt 20 and detects the temperature of the fixing belt 20. The temperature information of the fixing belt 20 measured by the main thermistor 18 is input to the control circuit CPU21. The control circuit CPU 21 controls current supply from the power supply unit 67 to the exciting coil 63 based on the input temperature information, and adjusts the temperature of the fixing belt 20, that is, the temperature of the fixing nip portion 27 to a predetermined temperature.

  Thus, the fixing belt 20 rotates, and the electromagnetic induction heat generation of the fixing belt 20 is performed as described above by the power supply from the power supply unit 67 to the excitation coil 63, and the fixing nip portion 27 rises to a predetermined temperature to control the temperature. In this state, the recording material P on which the unfixed toner image t conveyed from the image forming unit is formed has an image surface facing upward between the fixing belt 20 and the pressure roller 22 of the fixing nip 27, that is, fixing. The toner is introduced so as to face the belt surface, and in the fixing nip portion 27, the image surface is in close contact with the outer surface of the fixing belt 20, and the fixing nip portion 27 is nipped and conveyed together with the fixing belt 20. In the process in which the recording material P is nipped and conveyed together with the fixing belt 20 through the fixing nip portion 27, the fixing belt 20 is heated by electromagnetic induction heat generation, and the unfixed toner image t on the recording material P is heated and fixed. When the recording material P passes through the fixing nip portion 27, it is separated from the outer surface of the fixing belt 20 and discharged and conveyed. The heat-fixed toner image on the recording material is cooled to a permanent fixed image after passing through the fixing nip.

  When the same durability test as in Example 1 was performed using the fixing device of this example, the fixing belt was not damaged even when 150,000 sheets were passed, and the fixing performance was not deteriorated.

  The present invention is not limited to a fixing device mounted on an electrophotographic image forming apparatus, but can also be applied to a fixing device mounted on an image forming apparatus of another recording system such as an electrostatic recording system.

1 is a cross-sectional view of an image forming apparatus according to Embodiment 1 of the present invention. 1 is a cross-sectional view of a fixing device according to Embodiment 1 of the present invention. FIG. 3 is an enlarged view of a fixing belt and a fixing flange portion in Embodiment 1 of the present invention. FIG. 3 is a diagram of the fixing belt and the fixing flange portion according to Embodiment 1 of the present invention when viewed from a direction perpendicular to the longitudinal direction. 7 is a slidable sheet interposed between the fixing belt and the fixing flange in Embodiment 2 of the present invention. FIG. 9 is a cross-sectional view of a fixing device according to Embodiment 3 of the present invention. FIG. 6 is a configuration diagram of a fixing flange portion in a conventional fixing device. The figure which looked at the fixing belt and the fixing flange part in the conventional fixing device from the longitudinal orthogonal direction.

Explanation of symbols

20 fixing belt 22 pressure roller 400 fixing flange 500 sliding sheet

Claims (11)

A film-like fixing belt, a guide member for guiding the fixing belt, a pressure member for forming a pressure nip with the guide member via the fixing belt, and heating the fixing belt to rotate the fixing belt And a heating device for heating the transfer material conveyed in the nip,
The total length of the fixing belt is set to be larger than the contact surface length of the pressure member, and the fixing belt has a structure in which both end portions are supported from the outer peripheral surface side by flanges as support members, A fixing device, wherein the flange is subjected to a treatment for improving lubricity.   The fixing device according to claim 1, wherein the process for improving the lubricity is performed by applying a lubricant to the flange.   3. The fixing device according to claim 2, wherein a powdery lubricant dispersed in a solvent is used as the lubricant.   The fixing device according to claim 2, wherein silicone oil or fluorine oil is used as the lubricant.   The fixing device according to claim 2, wherein grease is used as the lubricant.   The fixing device according to claim 2, wherein a surface coating material is used as the lubricant.   2. The fixing device according to claim 1, wherein the treatment for improving the lubricity is performed by interposing a sheet-like member having excellent lubricity between the flange and the fixing belt.   The angle θ formed by the support surface on the outer peripheral surface side of the fixing belt and the sleeve longitudinal support surface of the flange in the longitudinal sectional shape of the flange is approximately 90 °. Fixing device.   The fixing device according to claim 1, wherein the fixing belt includes at least one metal layer.   The fixing device according to claim 9, wherein the metal layer is stainless steel, nickel, or an alloy containing any one of them. The fixing device according to claim 9, wherein the metal layer is formed by plastic working.

Images