Patent Application
20140161498
1. Field of the Invention
The present invention relates to an image heating apparatus to be used in an image forming apparatus, such as a copier and a laser beam printer (LBP), which adopts an image forming process of an electrophotographic system or an electrostatic recording system. As such an image heating apparatus, there is known a fixing apparatus for heating and fixing an unfixed toner image formed on a recording material (transfer material, printing paper, photosensitive paper, electrostatic recording paper, etc.) as a fixed image. Further, there is known a glossiness enhancing apparatus for enhancing glossiness of an image by heating the image fixed to a recording material.
2. Description of the Related Art
Hitherto, as a fixing apparatus provided in an image forming apparatus such as a copier, a printer, and a facsimile of an electrophotographic system, a contact heating type heat roller system having satisfactory thermal efficiency and a film heating system having quick start property (on-demand property) have been used. The fixing apparatus of a film heating system can realize small heat capacity and suppress power consumption during standby through use of a heat-resistant film or a metal sleeve (hereinafter referred to as “fixing sleeve”) serving as a hollow rotatable heating rotary member which is heated by a heating source, and hence this fixing apparatus is excellent in energy saving property. Specifically, Japanese Patent Application Laid-Open No. H04-44075 discloses a fixing apparatus of a film heating system.
In the fixing apparatus as described above, a recording material bearing an image is conveyed to a nip portion formed between a heating rotary member and a pressure member, and is nipped therebetween to heat the image. The fixing apparatus includes a holding member provided at an end portion in a rotation axis direction of a fixing sleeve serving as the heating rotary member, and the holding member includes a regulation surface for holding an inner surface of the fixing sleeve at a position on an upstream side of the nip portion, and a regulation surface for regulating the movement in the rotation axis direction of the fixing sleeve. Specifically, a fixing flange includes a regulation surface serving as a shift regulation member as well as a regulation surface serving as a holding member to be brought into internal contact with a fixing sleeve end portion to stabilize the shape of the fixing sleeve during rotation.
However, in the above-mentioned related art, when movement force (shift force) in the rotation axis direction (thrust direction) of the fixing sleeve is too strong, there is a risk in that the end surface of the fixing sleeve and the shift regulation member strongly rub against each other to shave and damage the shift regulation member and the metal sleeve. Alternatively, there is a risk in that the end portion of the fixing sleeve buckles to be damaged.
According to an aspect of the invention, the purpose of the invention is to provide a fixing apparatus for fixing a toner image onto a recording material by heating the recording material bearing the toner image while conveying the recording material through a nip portion, wherein the fixing apparatus including a sleeve, a nip portion forming member that contacts an inner surface of the sleeve, a pressure member that forms the nip portion together with the nip portion forming member through the sleeve, and a regulation member that regulates movement of the sleeve, the regulation member including a first surface opposed to an inner surface of an end portion of the sleeve in a generatrix direction of the sleeve, and a second surface opposed to an end surface of the sleeve in the generatrix direction of the sleeve, wherein the regulation member does not rotate together with the sleeve wherein the first surface on an upstream side of the nip portion in a conveyance direction of the recording material includes a region in which a distance between the inner surface of the sleeve and the first surface in a radial direction of the sleeve increases toward a center portion of the sleeve in the generatrix direction, and wherein the end surface of the sleeve contacts the region when the sleeve moves in the generatrix direction of the sleeve.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Image Forming Apparatus
The entire configuration of an image forming apparatus is described together with an image forming operation with reference to
The color laser printer includes toner cartridges 1a, 1b, 1c, and 1d removably mounted on an image forming apparatus main body. These four toner cartridges 1a, 1b, 1c, and 1d have the same structure except for formation of images with toners of different colors, that is, yellow, magenta, cyan, and black.
The toner cartridges 1a, 1b, 1c, and 1d respectively include developing units 7a, 7b, 7c, and 7d and image bearing member units 8a, 8b, 8c, and 8d. The developing units 7a, 7b, 7c, and 7d respectively include developing rollers 4a, 4b, 4c, and 4d. The image bearing member units 8a, 8b, 8c, and 8d respectively include photosensitive drums 2a, 2b, 2c, and 2d serving as image bearing members, charging rollers 3a, 3b, 3c, and 3d, drum cleaning blades 5a, 5b, 5c, and 5d, and waste toner containers.
A scanner unit 6 is provided below the toner cartridges 1a, 1b, 1c, and 1d, and exposes the photosensitive drums 2a, 2b, 2c, and 2d with light based on an image signal. That is, the photosensitive drums 2a, 2b, 2c, and 2d are charged at a predetermined negative potential respectively by the charging rollers 3a, 3b, 3c, and 3d. Then, electrostatic latent images are formed by the scanner unit 6. Toners of negative polarity adhere to the electrostatic latent images through reverse development by the developing units 7a, 7b, 7c, and 7d. In this way, toner images of yellow, magenta, cyan, and black are formed.
An intermediate transfer belt unit 30 includes an intermediate transfer belt 31 stretched around a drive roller 32, a secondary transfer opposed roller 36, and a tension roller 33, and the tension roller 33 applies tension in the arrow B direction. Primary transfer rollers 34a, 34b, 34c, and 34d are arranged on an inside of the intermediate transfer belt 31 so as to face the photosensitive drums 2a, 2b, 2c, and 2d, and a transfer shift is applied from a shift applying unit (not shown).
The toner images formed on the photosensitive drums 2a, 2b, 2c, and 2d are sequentially primarily transferred onto the intermediate transfer belt 31 when each of the photosensitive drums 2a, 2b, 2c, and 2d rotates in an arrow direction and the intermediate transfer belt 31 rotates in the arrow A direction. Specifically, when a positive shift is applied to the primary transfer rollers 34a, 34b, 34c, and 34d, the toner images on the photosensitive drums 2a, 2b, 2c, and 2d are primarily transferred onto the intermediate transfer belt 31 sequentially in an order from the toner image on the photosensitive drum 2a, and the toner images of four colors superimposed on each other are conveyed to a secondary transfer nip potion 37.
A feeding and conveying device 20 includes a sheet feed roller 22 for feeding a transfer material P from a sheet feed cassette 21 receiving the transfer material P and conveyance rollers 24 for conveying the fed transfer material P. Then, the transfer material P conveyed from the feeding and conveying device 20 is substantially vertically conveyed to the secondary transfer nip portion by a registration roller pair 23. In the secondary transfer nip portion 37, a positive shift is applied to a secondary transfer roller 35, with the result that the toner images of four colors on the intermediate transfer belt 31 are secondarily transferred onto the conveyed transfer material P.
The transfer material P with the toner images transferred thereto is conveyed to a fixing apparatus 40, and heated and pressurized by a fixing sleeve 41 serving as a heating rotary member and a pressure roller 42, with the result that the toner images are fixed onto the surface of the transfer material P. The transfer material P with the toner images fixed thereto is delivered to a discharge toray 44 by a discharge roller pair 43.
Toner remaining on the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d after the toner image transfer is removed by cleaning blades 5a, 5b, 5c, and 5d. Further, toner remaining on the intermediate transfer belt 31 after the secondary transfer to the transfer material P is removed by a cleaning blade 51 of a transfer belt cleaning device 50, and the removed toner passes through a waste toner conveyance path 52 to be collected to a waste toner collecting container (not shown).
Image Heating Apparatus
The fixing apparatus 40 according to the first embodiment includes the fixing sleeve 41 serving as a flexible belt member, the pressure roller 42 serving as a pressure member, and a heater 60 serving as a heating source, and causes the pressure roller 42 to pressurize the heater 60. Further, the friction force between the heater and the fixing sleeve 41 is reduced by interposing a fixing grease (not shown) therebetween so that the fixing sleeve 41 is driven to rotate smoothly. In the fixing apparatus 40 as described above, a recording material bearing an image is conveyed to the nip portion N formed between the fixing sleeve 41 and the pressure roller 42, and is nipped therebetween to heat the image.
Fixing Sleeve
The fixing sleeve 41 serving as the hollow rotatable heating rotary member has a configuration in which an elastic layer 41b is formed on the outer periphery of a base layer 41a (
It is desired that a material having as high thermal conductivity as possible be used for the elastic layer 41b from the viewpoint of achieving quick start. Thus, in the first embodiment, silicone rubber having a thermal conductivity of about 1.0×10−3 cal/(sec·cm·K) having a thickness of about 250 μm was used for the elastic layer 41b.
The releasing layer 41c is provided so as to prevent an offset phenomenon which occurs when toner temporarily adheres to the surface of the fixing sleeve 41 and moves to the transfer material P again. As a material for the releasing layer 41c, a fluorine resin such as polytetrafluoroethylene (PTFE) and perfluoroalkoxy (PFA) (PA), a silicone resin, or the like is used. In the first embodiment, the releasing layer 41c is formed as a PFA tubing having a thickness of about 30 μm, and the outer circumferential surface of silicone rubber serving as the elastic layer 41b is covered with the PFA tubing.
Pressure Roller
The pressure roller 42 serving as a pressure member has a configuration in which a conductive silicone rubber layer having a thickness of about 3 mm is formed as an elastic layer 42b on the outer circumferential surface of a metallic cored bar 42a (
The pressure roller 42 is rotated by a driving unit M at a circumferential speed of 135 mm/sec in the arrow direction. The fixing sleeve 41 is driven to rotate around a heater holder 61 at the same speed as the rotation speed of the pressure roller 42 due to the friction force between the fixing sleeve 41 and the pressure roller 42.
Heater
The heater 60 serving as a heating source includes an elongated substrate 60a (
A heat resistive layer 60b serving as a heat generator is formed in the longitudinal direction of the substrate 60a on a back surface of the substrate 60a. The heat resistive layer 60b contains an AgPd alloy, a NiSn alloy, a RuO2 alloy, and the like as main components, and is molded so as to have a thickness of about 10 μm, a length of 310 mm, and a width of 4 mm. The heat resistive layer 60b generates heat by being supplied with a current from a power source (not shown) through both end portions.
An insulating glass layer 60c ensures insulation from an external conductive member by overcoating the heat resistive layer 60b. In addition, the insulating glass layer 60c has a corrosion-resistant function for preventing a change in resistance due to oxidation or the like of the heat resistive layer 60b and serves to prevent mechanical damages. Note that, the insulating glass layer 60c has a thickness of 30 μm.
A sliding layer 60d is a layer having a thickness of 6 μm containing an imide-based resin such as polyimide and polyamideimide as a component, and is provided on a surface of the substrate 60a that slides against an inner circumferential surface of the fixing sleeve 41. The sliding layer 60d has a function excellent in heat resistance, lubricity, and abrasion resistance and imparts smooth sliding property with respect to an inner circumferential surface of the fixing sleeve 41.
Heater Holder
The heater holder 61 serving as a backup member is formed of a heat-resistant resin such as a liquid crystal polymer resin having high heat resistance so as to have a semi-circular trough pail shape in lateral cross-section. Then, the fixing sleeve 41 is loosely fitted onto the outer periphery of the heater holder 61.
Pressure Stay
A pressure stay 62 serving as a skeletal member is formed of a material such as a metal having stiffness so as to have an inverted U-shape in lateral cross-section. The pressure stay 62 is disposed on a surface of the heater holder 61 opposite to the pressure roller 42 on an inner side of the fixing sleeve 41. The pressure stay 62 brings the heater 60 into abutment against the pressure roller 42 with the fixing sleeve 41 interposed therebetween through the intermediation of the heater holder 61 by the fixing flanges 63 and pressure springs 64 described later.
Flange
The fixing flanges 63 formed of a heat-resistant resin such as a liquid crystal polymer having high heat resistance (
The fixing flanges 63 are provided at both end portions in the longitudinal direction of the fixing sleeve (generatrix direction of the fixing sleeve 41) and regulate the movement of the fixing sleeve 41 in a radial direction and the generatrix direction of the fixing sleeve 41. That is, the fixing flanges 63 respectively include a regulation surface 63a (first surface) opposed to an inner surface of the fixing sleeve 41 and a regulation surface 63c (second surface) opposed to an end surface in a rotation axis direction (longitudinal direction) of the fixing sleeve 41.
Further, the regulation surface 63c of the fixing flange 63 regulates the shift of the fixing sleeve 41 in the generatrix direction of the fixing sleeve 41. In the first embodiment, the force to reduce the shift described below is generated. In the case where the shift force of the fixing sleeve 41 is larger than the force to reduce the shift, the end surface of the fixing sleeve 41 is regulated by the regulation surface 63c of the fixing flange 63. In this case, the regulation surface 63c has a second tapered shape in which the distance between the end surface of the fixing sleeve 41 and the regulation surface 63c in the generatrix direction of the sleeve increases toward a downstream side in the conveyance direction of a recording material as illustrated in
Sleeve Shift Force Control Mechanism
The shift force of the fixing sleeve 41 is controlled through use of the shape of the regulation surface 63a of the fixing flange 63 for regulating the inner surface of the fixing sleeve 41 (in particular, the component 63s illustrated in
On the other hand,
The force exerted by the pressure roller 42 is generated in up and down directions in
The magnitude of the force to reduce the shift to the longitudinal direction center portion side is as follows. That is, a force F sin θ2 to reduce the shift of the fixing sleeve 41 is expressed by (F×(A−A′)sin θ1)/L, where θ1 represents a tapered angle of the regulation surface 63a of the fixing flange 63, L represents the length of the fixing sleeve 41, and θ2 represents a crossing angle of the fixing sleeve 41 and the pressure roller 42.
Therefore, the crossing angle θ2 increases as the shift becomes larger, with the result that the force to reduce the shift of the fixing sleeve 41 increases to reduce the shift force. Further, the force to reduce the shift of the fixing sleeve 41 increases as the tapered angle θ1 of the fixing flange 63 becomes larger, with the result that the shift force can be reduced. On the other hand, when the tapered angle θ1 of the fixing flange 63 is too large, the force to push up the end portion of the fixing sleeve 41 from the inner surface increases in the case where the fixing sleeve 41 is shifted, and there is a risk in that the end surface of the fixing sleeve 41 is ripped in a trumpet shape.
Therefore, it is necessary to set the tapered angle θ1 of the fixing flange 63 so that the effect of reducing shift of the fixing sleeve 41 is kept and the end surface of the fixing sleeve 41 is prevented from being ripped in a trumpet shape.
Further, in the case where the shift force of the fixing sleeve 41 is larger than the force F sin θ2 to reduce the shift of the fixing sleeve 41, the end surface of the fixing sleeve 41 is regulated by the regulation surface 63c. The regulation surface 63c of the fixing flange 63 has a tilt of (90−θ2Max)° with respect to an axial line of the pressure roller 42, where θ2Max represents a crossing angle between the fixing sleeve 41 and the pressure roller 42 when the fixing sleeve 41 is brought into contact with the regulation surface 63c. When the end surface of the fixing sleeve 41 collides with the regulation surface 63c having the tilt described above, buckling or the like in the fixing sleeve 41 is prevented, which may occur in the case where the shift force is concentrated in one place when the fixing sleeve 41 collides with the regulation surface 63c in
Effect Confirmation Test
The effect of reducing the shift of the fixing sleeve and the ripping of the fixing sleeve 41 which is a harmful effect were confirmed by changing the tapered angle θ1 of the fixing flange 63. As a comparative example, the similar confirmation was also performed with respect to a tapered angle of 0°. Note that, a crossing angle between the pressure roller 42 and the fixing sleeve 41 formed due to an outer diameter difference and a component tolerance of the pressure roller 42 was set so that the shift is likely to occur in the fixing sleeve 41. Table 1 shows effect confirmation test results obtained by observing the state of the image heating apparatus after 75,000 recording materials of an A3 (297×420 mm) size were printed continuously.
In the case where the tapered angle θ1 of the fixing flange 63 is 0°, there is no effect of reducing the shift of the fixing sleeve 41. In this case, the fixing sleeve 41 rotates while the end surface of the fixing sleeve 41 and the regulation surface 63c of the fixing flange 63 rub against each other strongly. Therefore, a great amount of shavings of the fixing flange 63 and the fixing sleeve 41 was generated.
On the other hand, in the case where the tapered angle θ1 of the fixing flange 63 is 10° or 20°, the force to reduce the shift of the fixing sleeve 41 acts to reduce the rubbing force. That is, although the fixing sleeve 41 rotates while rubbing against the regulation surface 63c of the fixing flange 63 after 75,000 recording materials are printed, the rubbing force between the fixing sleeve 41 and the regulation surface 63c of the fixing flange 63 is reduced by the force to reduce the shift. Thus, the amount of shavings of the fixing sleeve 41 and the fixing flange 63 was reduced compared to the case where the tapered angle θ1 was 0°. Further, there was no problem of ripping of the fixing sleeve 41 which might occur due to an increase in tapered angle.
In the case where the tapered angle θ1 of the fixing flange 63 is 30°, the amount of shavings of the fixing sleeve 41 and the fixing flange 63 was reduced in the same way as in the case where the tapered angle θ1 was 10° or 20°. However, ripping of the end portion of the fixing sleeve 41 in a trumpet shape occurred.
From the results described above, in the first embodiment, the shaving of the fixing flange 63 and the fixing sleeve 41 can be suppressed by setting the tapered angle θ1 of the fixing flange 63 to 10° or 20°. It was also confirmed that ripping of the end portion of the fixing sleeve 41 which might occur as a harmful effect does not occur. Thus, the shift force of the fixing sleeve 41 can be reduced without strictly setting the size tolerance of the fixing member related to a crossing angle between the pressure roller 42 and the fixing sleeve 41.
A fixing flange that is not included in the first embodiment is now described. A fixing apparatus illustrated in
A second embodiment of the present invention is hereinafter described. In the first embodiment, in the case where the shift force of the fixing sleeve 41 is larger than the force to reduce the shift, the shift force is finally regulated by the regulation surface 63c of the fixing flange 63. In the second embodiment, the shift is regulated by setting the diameter of an inner receiving portion of the fixing sleeve 41 to be larger than the inner diameter of the fixing sleeve 41.
In the fixing flange 63 of the second embodiment, the regulation surface 63a has a first tapered shape, and the regulation surface 63c has a second tapered shape in the same way as in the first embodiment.
The second embodiment has a feature in that, as illustrated in
When the above-mentioned relationship is satisfied, there is no possibility that the regulation surface 63c of the fixing flange 63 and the end surface of the fixing sleeve 41 may rub against each other. Further, the inner surface of the fixing sleeve 41 is supported at two positions: the regulation surface 63a on the upstream side and the tip end of the regulation surface 63b on the downstream side. According to this configuration, the force which the fixing sleeve 41 moves to receive from the fixing flange 63 can be dispersed into the above-mentioned two positions, and hence ripping of the fixing sleeve 41 can be prevented.
Further, the following effect is also obtained owing to the tapered shape of the regulation surface 63b of the fixing flange 63 on the downstream side of the fixing nip portion. That is, in the case where the fixing sleeve 41 is shifted on a side opposite to the fixing flange 63 as illustrated in
In the case where a recording material jammed in the fixing nip is pulled out from the upstream side to clear the jam, the fixing sleeve 41 rotates while the inner surface thereof is regulated by the regulation surface 63b of the fixing flange 63 on the downstream side. When the distance between the inner surface of the fixing sleeve 41 and the fixing flange 63 on the downstream side is large, a deformation amount of the end portion of the fixing sleeve 41 becomes large, and the fixing sleeve 41 is damaged. The distance between the inner surface of the fixing sleeve 41 and the fixing flange 63 on the downstream side can be reduced from d2 to d1 by forming the fixing flange 63 on the downstream side in a tapered shape, and hence the deformation of the fixing sleeve 41 that may be caused by clearing the jam is suppressed to alleviate damage.
A third embodiment of the present invention is hereinafter described. The third embodiment is preferred in the case of using a fixing sleeve having different ripping strengths at both ends due to the difference in a processing method or the like. In the foregoing embodiments, the fixing flanges 63 at both end portions have the first tapered angle θ1. In the third embodiment, a fixing flange at one end portion is provided with the first tapered angle θ1. That is, in the third embodiment, both ends of the fixing sleeve 41 have different ripping strengths, and only the fixing flange serving as a holding member at one end portion having ripping strength higher than that of the other end portion is provided with the first tapered shape (angle θ1).
According to the above-mentioned configuration, the first tapered angle θ1 of the fixing flange 63 enables a force for causing ripping of the fixing sleeve 41 to be applied to only the side of the fixing sleeve 41 having higher strength. Therefore, the end portion of the fixing sleeve 41 can be prevented from being ripped. The mechanism of the force to reduce the shift of the fixing sleeve 41 is described in the first embodiment, and hence the description thereof is omitted here.
As means for enhancing the ripping strength on one side of the fixing sleeve 41, there are provided a method involving reinforcing the end portion with a reinforcing tape, a method involving setting the thickness of the fixing sleeve 41 to be larger, and the like. Further, in the third embodiment, although the fixing flange 63 described in the first embodiment is used, the fixing flange 63 described in the second embodiment may be used.
The first to third embodiments have been described above. However, the present invention is not limited thereto, and the technical matters disclosed in the respective embodiments may be appropriately combined and variously modified as exemplified below within the scope of the present invention.
In the above-mentioned embodiments, the regulation surface 63a of the fixing flange 63 serving as a holding member at the upstream side of the nip portion in the conveyance direction of a recording material has the first tapered shape, and the regulation surface 63c has the second tapered shape. However, the regulation surface 63c may be parallel to the end surface of the sleeve.
Although the first tapered shape of the regulation surface 63a illustrated in
The scope of the present invention is not limited to the material, shape, and relative arrangement of constituent components described in the foregoing embodiments unless otherwise specified. For example, in the foregoing embodiments, although SUS is used as a material for the base layer 41a of the fixing sleeve 41, a metal other than SUS such as Ni and Al or a resin such as polyimide may be used.
Further, the fixing sleeve 41 is not limited to those heated by a heater as described in the foregoing embodiments. The fixing sleeve 41 may be those which include an electric conduction part and perform self-heating or those which generate heat through electromagnetic induction.
Further, in the foregoing embodiments, although the pressure roller 42 serving as a driving roller is used as a pressure member, a fixed pressure pad serving as a pressure member can also be used in the case where the fixing sleeve 41 is mounted through the intermediation of another driving roller and is capable of rotating.
Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions recorded on a storage medium (e.g., non-transitory computer-readable storage medium) to perform the functions of one or more of the above-described embodiment(s) of the present invention, and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more of a central processing unit (CPU), micro processing unit (MPU), or other circuitry, and may include a network of separate computers or separate computer processors. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-270301, filed Dec. 11, 2012, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-270301 | Dec 2012 | JP | national |
