JP2007025379A - Heat insulating sleeve, fixing device and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat insulating sleeve capable of reducing the occurrence of abnormal sounds due to slip between a shaft part and a bearing member of a heat roller and stress to a rotational drive delivering member due to torsion in an axial direction, and a fixing device and an image forming apparatus provided with the same. <P>SOLUTION: With respect to a heat insulating sleeve 60 which is disposed between a bearing member 70 rotatably supporting a shaft part 50 of a heating rotating member 44 incorporating a heater 48 and the shaft part 50 and can be expanded in a radial direction by formation of a slit S, an engaging projection 63 being short in a width direction and long in a circumferential direction is formed in the vicinity of one end part 64 out of end parts on both sides of the slit S, and an engaging projection 62 being short in a circumferential direction and long in a width direction is formed in the vicinity of the other end part 66, and the engaging projections 62 and 63 are engaged with parts 58 and 59 to be engaged, which are formed on the shaft part 50 of the heating rotating member 44. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, a fixing device used in the image forming apparatus, and a heat insulating sleeve used in the fixing device.

  In general, in an image forming apparatus such as a copying machine or a printer employing an electrophotographic method, the surface of the photosensitive drum is uniformly charged by a charging device, and then the surface of the photosensitive drum is irradiated with image light to electrostatically A latent image is formed, and the electrostatic latent image is developed by a developing device to form a toner image. Then, after the toner image is transferred onto the paper, the toner image on the paper is fixed by heating and pressing with a fixing device, thereby forming an image.

  The fixing device includes a heating roller with a built-in heater therein, and a pressure roller that presses the sheet against the heating roller. Then, the paper carrying the toner image is passed between the heating roller and the pressure roller, and the toner image is melted by heating and pressurizing and fixed on the paper.

In such a fixing device, when the process speed is increased and the heating temperature is set to a high temperature, there is a demand to improve the thermal efficiency in order to suppress the power consumption of the heater. Therefore, an insulating sleeve is interposed between the shaft portion of the heating roller provided with a heater inside and a ball bearing (bearing member) that rotatably supports the heating roller, so that the heat of the heating roller is transmitted to the ball bearing. I try to prevent it. In addition, the heat insulation sleeve is formed with a slit along the axial direction, and is configured to be able to absorb the thermal expansion of the shaft portion of the heating roller (for example, see Patent Document 1).
JP 2001-56020 A

  However, in such a fixing device, the thermal expansion can be absorbed by the slit (gap) of the heat insulating sleeve being widened against the thermal expansion of the shaft portion of the heating roller. There is a problem that slippage (sliding) occurs between the sleeve and the heat insulation sleeve and between the ball bearing and the heat insulation sleeve, and abnormal noise is generated due to the slippage.

  Therefore, an engagement boss portion is provided on the inner peripheral surface of the heat insulating sleeve, and this boss portion is engaged with an opening-shaped groove formed in the shaft portion of the heating roller so that the shaft portion of the heating roller and the heat insulating sleeve are And slip between the ball bearing and the insulating sleeve. In this case, slipping between the heat insulating sleeve and the shaft portion and between the heat insulating sleeve and the ball bearing is prevented, so that abnormal noise is unlikely to occur, but the heat insulating sleeve against thermal expansion of the shaft portion of the heating roller. Had the problem of being stressed.

  Moreover, the heat by the heater in a heating roller leaks from an opening-shaped groove hole, and there existed a problem that thermal efficiency fell. Further, when the heat insulating sleeve rotates, the circumferential end formed by the slit twists in the axial direction (especially the upstream side in the rotational direction protrudes outward in the axial direction), and the end of the heating roller shaft (outside the heat insulating sleeve) There is a problem in that stress is applied to the rotation drive gear (rotation drive transfer member) provided in (rotates the rotation drive gear outward).

  Therefore, in view of the above problems, the present invention is not limited to stress due to thermal expansion of the heating roller, but also to generation of abnormal noise due to slippage between the shaft portion of the heating roller and the bearing member, and torsion in the axial direction. It is an object of the present invention to obtain a heat insulating sleeve that can reduce the stress caused to the rotational drive transfer member, and a fixing device and an image forming apparatus provided with the heat insulating sleeve.

  In order to achieve the above object, a heat insulating sleeve according to claim 1 of the present invention is provided between a bearing member that rotatably supports a shaft portion of a heating rotating member in which a heater is built, and the shaft portion. In the heat insulating sleeve that is arranged in the slit and can be expanded in the radial direction by forming a slit, the plate thickness at one end across the slit is formed thinner than the plate thickness at the other end. It is characterized by having.

  According to the first aspect of the present invention, even if the shaft portion of the heating rotary member is thermally expanded, the heat insulating sleeve is expanded in the radial direction by the slits, and thus is not subjected to stress. Moreover, since the plate | board thickness of one edge part on both sides of a slit is formed thinner than the plate | board thickness of the other edge part, a contact area with a shaft part or a bearing member can be reduced. That is, it is possible to suppress the generation of abnormal noise due to the sliding between the heat insulating sleeve and the shaft portion and between the heat insulating sleeve and the bearing member.

  Further, the heat insulation sleeve according to claim 2 is the heat insulation sleeve according to claim 1, wherein the one end portion has a tapered shape when viewed from the axial direction so that the surface side receiving the force by the rotation of the heating rotating member is. It is characterized by being.

  The heat insulation sleeve according to claim 3 is characterized in that, in the heat insulation sleeve according to claim 1, the one end is tapered at least on the bearing member side when viewed from the axial direction. Yes.

  According to the invention described in claim 2 or claim 3, since the contact area between the heat insulating sleeve and the shaft portion and between the heat insulating sleeve and the bearing member is suitably reduced, abnormal noise caused by slippage between them is reduced. Occurrence can be prevented. In addition, the surface side which receives force by rotation of a heating rotation member is the inner peripheral surface side and / or outer peripheral surface side of a heat insulation sleeve.

  According to a fourth aspect of the present invention, in the thermal insulation sleeve according to the second or third aspect, the one end portion having the tapered shape is bent and deformed by the rotation of the heating rotary member. The shaft portion and / or the bearing member are not contacted.

  According to the fourth aspect of the present invention, even if one of the tapered end portions is bent and deformed by the rotation of the heating rotating member, it does not contact the shaft portion and / or the bearing member, so that abnormal noise is generated. do not do.

  According to a fifth aspect of the present invention, there is provided a heat insulation sleeve according to the present invention, wherein the heat insulation sleeve is disposed between the shaft member and a bearing member that rotatably supports the shaft portion of the heating rotary member in which the heater is built, and a slit is formed. In the heat insulating sleeve that can be expanded in the radial direction, the plate width of one end portion sandwiching the slit is narrower than the plate width of the other end portion. .

  According to the fifth aspect of the present invention, even if the shaft portion of the heating rotary member is thermally expanded, the heat insulating sleeve is expanded in the radial direction by the slit, so that it is not subjected to stress. In addition, since the plate width of one end portion sandwiching the slit is formed narrower than the plate width of the other end portion, even if the heat insulating sleeve is twisted, the rotational drive transfer member provided on the outer shaft portion The pressing force (stress) against can be reduced.

  Further, the heat insulation sleeve according to claim 6 is the heat insulation sleeve according to claim 5, wherein the one end portion is at least tapered when viewed from a direction orthogonal to the axial direction. It is characterized by being.

  According to the sixth aspect of the present invention, even if the heat insulating sleeve is twisted, it is possible to further reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the outer shaft portion.

  According to a seventh aspect of the present invention, there is provided a heat insulation sleeve according to the present invention, wherein the heat insulation sleeve is disposed between a bearing member that rotatably supports a shaft portion of a heating rotary member in which a heater is incorporated, and the shaft portion, and a slit is formed. In the heat insulating sleeve that can be expanded in the radial direction, one end portion sandwiching the slit is offset to the center side of the heating rotating member with respect to the other end portion. It is said.

  According to the seventh aspect of the present invention, even if the shaft portion of the heating rotating member is thermally expanded, the heat insulating sleeve is expanded in the radial direction by the slits, and thus is not subjected to stress. In addition, since one end portion sandwiching the slit is offset in advance to the center side of the heating rotary member with respect to the other end portion, even if the heat insulating sleeve is twisted, the rotational drive provided on the outer shaft portion The pressing force (stress) on the transfer member can be reduced.

  In addition, the heat insulating sleeve according to claim 8 is the heat insulating sleeve according to any one of claims 1 to 7, wherein the heat insulating sleeve is engaged with an engaged portion formed on a shaft portion of the heating rotating member. Thus, an engagement portion that makes the heat insulating sleeve relatively unrotatable with respect to the shaft portion is formed in the vicinity of the other end portion that is downstream in the rotation direction of the heating rotation member. .

  And the heat insulation sleeve of Claim 9 is engaged with the to-be-engaged part formed in the axial part of the said heating rotation member in the heat insulation sleeve of any one of Claim 1 thru | or 7. Accordingly, an engaging portion that makes the heat insulating sleeve relatively unrotatable with respect to the shaft portion is formed across the slit.

  According to invention of Claim 8 or Claim 9, since the fixation strength of the heat insulation sleeve with respect to a shaft part can be improved, the twist of a heat insulation sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  Further, the heat insulating sleeve according to claim 10 is the heat insulating sleeve according to claim 8 or 9, wherein the engaging portion is formed to have a length in the width direction longer than a length in the circumferential direction. It is characterized by.

  According to the tenth aspect of the present invention, since the engaging portion is formed so that the length in the width direction is longer than the length in the circumferential direction, between the heat insulating sleeve and the shaft portion, and between the heat insulating sleeve and the bearing member. Slip between the two is preferably prevented. Therefore, it is possible to suppress the occurrence of abnormal noise due to the slip.

  The heat insulating sleeve according to claim 11 is the heat insulating sleeve according to claim 8 or 9, wherein the engaging portion has a longer length in the circumferential direction than a length in the width direction. It is characterized in that it is formed closer to the end of the shaft than the center in the width direction.

  According to the eleventh aspect of the present invention, the engaging portion is longer in the circumferential direction than in the width direction, and is formed closer to the end of the shaft portion than the central portion in the width direction of the heat insulating sleeve. Therefore, twisting of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  According to a twelfth aspect of the present invention, the heat insulating sleeve according to the present invention is disposed between a shaft member and a bearing member that rotatably supports a shaft portion of a heating rotary member in which a heater is built, and a slit is formed. In the heat insulating sleeve that can be expanded in the radial direction, the heat insulating sleeve is made relatively to the shaft portion by engaging with the engaged portion formed on the shaft portion of the heating rotating member. The engaging portion that is non-rotatable is longer in the circumferential direction than the length in the width direction, and is formed closer to the end of the shaft portion than the center portion in the width direction of the heat insulating sleeve. .

  The heat insulating sleeve according to claim 13 is the heat insulating sleeve according to claim 12, wherein the engaging portion is formed in the vicinity of the end portion on the downstream side in the rotation direction of the heating rotary member with the slit as a boundary. It is characterized by being.

  According to the twelfth and thirteenth aspects of the present invention, even if the shaft portion of the heating rotary member is thermally expanded, the heat insulating sleeve is expanded in the radial direction by the slits, and thus is not subjected to stress. In addition, the engagement portion is longer in the circumferential direction than in the width direction, and is formed closer to the end of the shaft portion than the central portion in the width direction of the heat insulation sleeve, thereby suppressing twisting of the heat insulation sleeve. can do. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  The heat insulation sleeve according to claim 14 is characterized in that, in the heat insulation sleeve according to claim 12, the engaging portion is formed across the slit.

  According to the invention described in claim 14, since the fixing strength of the heat insulating sleeve with respect to the shaft portion can be improved, the twist of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  Further, the heat insulation sleeve according to claim 15 of the present invention is disposed between the shaft portion and the bearing member that rotatably supports the shaft portion of the heating rotation member in which the heater is built, and a slit is formed. In the heat insulating sleeve that can be expanded in the radial direction, the heat insulating sleeve is made relatively to the shaft portion by engaging with the engaged portion formed on the shaft portion of the heating rotating member. It is characterized in that at least one engaging portion that cannot be rotated is independently formed in the vicinity of one end portion and the other end portion with the slit interposed therebetween.

  According to the fifteenth aspect of the present invention, since the fixing strength of the heat insulating sleeve with respect to the shaft portion can be improved, twisting of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve. Further, since slip between the heat insulating sleeve and the shaft portion and between the heat insulating sleeve and the bearing member can be prevented, generation of abnormal noise due to the slip can be suppressed.

  The heat insulation sleeve according to claim 16 is the heat insulation sleeve according to claim 15, wherein the other end is downstream in the rotation direction of the heating rotary member, and is formed at the other end. The engaging portion is longer in the width direction than the circumferential length, and the engaging portion formed at the one end is longer in the circumferential direction than in the width direction, and the circumferential direction thereof. This length is shorter than the circumferential length of the engaged portion.

  According to the invention described in claim 16, since the fixing strength of the heat insulating sleeve with respect to the shaft portion can be improved, twisting of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve. Further, since slip between the heat insulating sleeve and the shaft portion and between the heat insulating sleeve and the bearing member can be prevented, generation of abnormal noise due to the slip can be suppressed. Further, even if the heat insulating sleeve is bent and deformed so as to be squeezed, the circumferential length of the engaging portion is shorter than the circumferential length of the engaged portion. acceptable.

  Further, the heat insulation sleeve according to claim 17 is the heat insulation sleeve according to claim 16, wherein the engagement portion formed at the one end is more at the end of the shaft portion than at the center in the width direction of the heat insulation sleeve. It is formed on the part side.

  According to the seventeenth aspect of the present invention, twisting of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  Moreover, the heat insulation sleeve of Claim 18 is a heat insulation sleeve of any one of Claims 1 thru | or 17, The inner peripheral surface which faces the said axial part is polygonal shape seeing from an axial direction. It is characterized by being.

  According to the invention described in claim 18, since the contact area of the heat insulating sleeve with respect to the shaft portion can be reduced, generation of abnormal noise due to slippage between the heat insulating sleeve and the shaft portion can be suppressed. .

  According to a nineteenth aspect of the present invention, there is provided the fixing device according to any one of the eighth to eighteenth aspects, wherein the heat insulating sleeve according to any one of the eighth to eighteenth aspects is attached to a shaft portion and heated by a built-in heater. A member, a bearing member provided on the outer peripheral surface of the heat insulating sleeve and rotatably supporting the heat insulating sleeve, and provided on the end side of the shaft portion relative to the shaft portion so as not to rotate relative to the shaft portion. And a rotation drive transfer member that rotates the heating rotation member, wherein the rotation drive transfer member has a rotation preventing portion that fits into a rotation-stopped portion formed in the shaft portion. The rotation preventing portion, the to-be-rotated prevention portion, and the engagement portion are arranged in a straight line.

  According to the nineteenth aspect of the present invention, since the rotation preventing portion, the to-be-rotated portion, and the engaging portion are arranged on a straight line, the number of processing steps can be reduced. Therefore, the manufacturing cost can be reduced.

  The fixing device according to claim 20 is the fixing device according to claim 19, wherein the anti-rotation portion and the engaging portion are convex portions, and the anti-rotation portion can also insert the engaging portion. It is characterized by being a concave or notched portion.

  According to invention of Claim 20, a processing man-hour can further be reduced. Therefore, the manufacturing cost can be reduced.

  The fixing device according to a twenty-first aspect is the fixing device according to the nineteenth or twentieth aspect, wherein the engaging portion is formed across the slit.

  According to the twenty-first aspect of the present invention, since the fixing strength of the heat insulating sleeve with respect to the shaft portion can be improved, twisting of the heat insulating sleeve can be suppressed. Therefore, it is possible to reduce the pressing force (stress) with respect to the rotational drive receiving member provided on the shaft portion outside the heat insulating sleeve.

  According to a twenty-second aspect of the present invention, there is provided the fixing device according to any one of the eighth to eighteenth aspects, wherein the heat insulating sleeve according to any one of the eighth to eighteenth aspects is attached to a shaft portion and heated by a built-in heater. In a fixing device including a member and a bearing member provided on an outer peripheral surface of the heat insulating sleeve and rotatably supporting the heat insulating sleeve, the heat insulating sleeve is regulated from both sides in the width direction on the shaft portion. It is characterized in that a step portion that can be formed is formed.

  According to the twenty-second aspect of the present invention, it is possible to suppress twisting of the heat insulating sleeve without forming the engaging portion and the engaged portion. Therefore, stress (pressing force) is not applied to the rotation drive transfer member provided on the shaft portion outside the heat insulating sleeve. Further, it is possible to prevent the grease that is between the heat insulating sleeve and the shaft portion from seeping out.

  An image forming apparatus according to a twenty-third aspect of the present invention includes the fixing device according to any one of the nineteenth to twenty-second aspects.

  According to the twenty-third aspect of the present invention, since the stress due to the thermal expansion of the heating roller can be prevented when the image forming apparatus is driven, the heat insulating sleeve can be prevented from being damaged. Further, it is possible to reduce the occurrence of abnormal noise due to the sliding of the heat insulating sleeve and the stress on the rotational drive giving / receiving member due to twisting.

  As described above, according to the present invention, in addition to the stress due to the thermal expansion of the heating roller, the abnormal noise caused by the sliding between the shaft portion and the bearing member of the heating roller and the torsion in the axial direction are caused. It is possible to provide a heat insulating sleeve that can reduce the stress caused to the rotational drive giving and receiving member, and a fixing device and an image forming apparatus including the heat insulating sleeve.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS The best mode for carrying out the present invention will be described below in detail based on the embodiments shown in the drawings. First, an image forming apparatus 10 provided with a fixing device according to the present invention will be described with reference to FIG. The fixing device is configured as a fixing unit 40 that can be attached to and detached from the image forming apparatus main body 12.

  As shown in FIG. 1, the image forming apparatus 10 has an opening / closing cover 14 rotatably attached to the image forming apparatus main body 12, and the image forming apparatus is opened by opening the opening / closing cover 14. A fixing unit 40 can be loaded in the main body 12. When the fixing unit 40 is loaded into the image forming apparatus main body 12, the connector 42 of the fixing unit 40 is coupled to the connector 16 of the image forming apparatus main body 12 at the same time so that power can be supplied to the fixing unit 40 and fixing is performed. Completion of loading of the unit 40 is detected. After the fixing unit 40 is loaded in the image forming apparatus main body 12, the image forming apparatus 10 becomes operable by closing the open / close cover 14.

  Further, the image forming apparatus main body 12 is provided with a process cartridge 18 in which an image forming unit is integrated into a unit. A photosensitive drum 20 that rotates in a certain direction is provided inside the process cartridge 18. Around the photosensitive drum 20, from the upstream side in the rotation direction, a charging roller 22 that uniformly charges the photosensitive drum 20 and a developing roller 24 that develops the electrostatic latent image formed on the photosensitive drum 20 are provided. And a transfer roller 26 for transferring the developed toner image on the photosensitive drum 20 to a sheet.

  Further, a cleaning member 28 for cleaning the surface of the photosensitive drum 20 after transfer is provided on the downstream side of the transfer roller 26 in the rotation direction of the photosensitive drum 20. The image forming apparatus main body 12 is provided with an exposure device 30 that irradiates the photosensitive drum 20 with image light between the charging roller 22 and the developing roller 24.

  A paper feed cassette 32 that accommodates paper is disposed in the lower part of the image forming apparatus main body 12 so that the paper can be pulled out. The paper feed cassette 32 takes out the paper one by one at the paper take-out position. A paper feed roller 34 for conveyance is provided. In addition, a plurality of transport roller pairs 36 that transport the paper supplied from the paper feed roller 34 to a position where the photosensitive drum 20 and the transfer roller 26 face each other are provided. A fixing unit 40 is disposed (loaded) on the downstream side of the transfer roller 26 in the sheet conveyance direction, and a discharge unit for discharging the sheet after toner image fixing is disposed on the downstream side of the fixing unit 40. A paper tray 38 is provided.

  In such an image forming apparatus 10, the surface of the photosensitive drum 20 is uniformly charged by the charging roller 22, and image light is irradiated from the exposure device 30, thereby forming an electrostatic latent image on the surface. . This electrostatic latent image is developed by the developing roller 24, and a toner image is formed on the photosensitive drum 20.

  On the other hand, the paper is supplied from the paper supply cassette 32 by the paper supply roller 34, and is conveyed to the position where the photosensitive drum 20 and the transfer roller 26 are opposed by the conveyance roller pair 36. Then, the toner image on the photosensitive drum 20 is transferred onto the paper by the transfer roller 26. The sheet on which the toner image has been transferred is conveyed to the fixing unit 40 and heated and pressed between the heating roller 44 and the pressure roller 46, whereby the toner image is melted and fixed on the sheet. . Thereafter, the paper on which the image is formed is discharged to the paper discharge tray 38.

  In the image forming apparatus 10 as described above, the fixing unit 40 (fixing apparatus) according to the present invention will be described next. As shown in FIGS. 2 and 3, the fixing unit 40 includes a heating roller 44 that is heated to a predetermined temperature and a pressure roller 46 that presses the sheet against the heating roller 44. The pressure roller 46 includes a stainless steel or iron core bar and a heat-resistant elastic layer (silicon sponge, Asker C hardness 40 °), and a surface layer of a release layer having a low friction coefficient (PFA having a film thickness of 30 μm). ) Is provided.

  On the other hand, the heating roller 44 is a hollow cored bar (thickness 0.5 mm to 1.5 mm iron or aluminum base tube) provided with a release layer (tube made of PFA with a film thickness of 30 μm) having a low friction coefficient on the surface. The lamp heater 48 is arranged inside. As shown in FIG. 7A, the lamp heater 48 is offset to the inner peripheral surface side from the center (axial center) of the heating roller 44, and the temperature is detected by a temperature sensor (not shown). Yes. Thereby, it is the structure controlled so that the heating roller 44 does not overheat.

  As shown in FIGS. 4 and 5, the shaft portion 50 of the heating roller 44 meshes with a rotation driving gear (not shown) of the image forming apparatus main body 12 to transmit the rotation driving force to the heating roller 44. The rotation drive gear 52 (rotation drive giving / receiving member) is inserted into the shaft portion 50 so as not to rotate. That is, the rotary drive gear 52 has a key groove 56 formed by a U-shaped protrusion 54 (rotation preventing portion) projecting on the inner peripheral surface thereof being cut out in a U-shape at the end of the shaft portion 50. The rotation is prevented from rotating with respect to the shaft portion 50 by being fitted into the rotation-preventing portion (see FIG. 6).

  Both end portions of the heating roller 44 are formed as a shaft portion 50 that is formed to have a small diameter by drawing, and a ball bearing 70 (bearing member) is fitted to the shaft portion 50 via a heat insulating sleeve 60 described later. Has been. Further, as shown in detail in FIG. 6, the shaft portion 50 of the heating roller 44 is formed with a substantially rectangular recess 58 (engaged portion) that is long in the circumferential direction. Specifically, the recess 58 is formed on the tube wall of the heating roller 44 by drawing or the like, and the engagement protrusion 62 (engagement portion) of the heat insulating sleeve 60 can be engaged therewith.

  In such a fixing unit 40, the heat insulating sleeve 60 is attached to the shaft portion 50 of the heating roller 44 as described above. At this time, the heat insulating sleeve 60 is expanded in the radial direction by the slit S and fitted into the shaft portion 50, and the engaging protrusion 62 is engaged with the concave portion 58. Thereby, the heat insulation sleeve 60 is fixed to the shaft part 50, and the drop-off from the shaft part 50 of the heat insulation sleeve 60 is prevented. In this way, since the heat insulating sleeve 60 can be fixed to the shaft portion 50 without using a retaining ring such as a ring separately, the number of parts can be reduced, and the fixing unit 40 can be reduced in size and space. Can be achieved.

  A ball bearing 70 is fitted on the outer periphery of the heat insulating sleeve 60 (see FIG. 3), and the heating roller 44 is rotatably supported. Then, when the rotational driving force is transmitted from the rotational driving gear (not shown) of the image forming apparatus main body 12 to the rotational driving gear 52, the heating roller 44 rotates in a predetermined direction at a constant speed. That is, in the fixing unit 40, the heating roller 44 and the pressure roller 46 are rotationally driven at a constant speed in opposite directions.

  Next, in the fixing unit 40 as described above, the heat insulating sleeve 60 will be described in detail. The heat insulating sleeve 60 is arranged to prevent heat from being transferred to the ball bearing 70 having a larger heat capacity due to heat from the heating roller 44, and is made of heat resistant synthetic resin such as polyimide resin. Molded integrally. In addition, the shape of the recessed part 58 and the engagement protrusion 62 is not limited to the substantially rectangular shape of illustration, For example, a substantially elliptical shape etc. may be sufficient.

  Further, as shown in FIG. 7A, the heat insulating sleeve 60 is provided with a slit S so as to be substantially C-shaped when viewed from the axial direction, and the thermal expansion of the shaft portion 50 is caused by the slit S. Accordingly, it can be expanded in the radial direction. Therefore, when the image forming apparatus 10 is driven, even if the shaft portion 50 of the heating roller 44 expands in the radial direction due to thermal expansion, the heat insulating sleeve 60 is not subjected to stress. That is, since the heat insulating sleeve 60 can absorb the thermal expansion of the heating roller 44, there is no problem that the heat insulating sleeve 60 is damaged.

<First Embodiment>
In the heat insulating sleeve 60 having such a configuration, the first embodiment will be described first. In the heat insulating sleeve 60 of the first embodiment, the concave portion 58 is located near the slit S and downstream of the heating roller 44 in the rotation direction (hereinafter sometimes simply referred to as “downstream side”). In addition, a substantially rectangular engagement protrusion 62 having a slightly smaller dimension and extending in the circumferential direction is provided.

  When the engagement protrusion 62 is engaged with the recess 58, the heat insulating sleeve 60 is attached to the shaft portion 50 in a non-rotating state. However, if the engagement protrusion 62 is elongated in the circumferential direction, Since the length (width) in the axial direction can be minimized, there is an advantage that the space in the axial direction (width direction) of the heating roller 44 can be saved.

  As shown in FIGS. 4 and 5, the engagement protrusion 62 of the heat insulating sleeve 60 is formed on the end side (outside side) of the heating roller 44 with respect to the central portion in the width direction. Thereby, it is the structure by which the twist of the heat insulation sleeve 60 is suppressed.

  That is, in the heat insulating sleeve 60, the engagement protrusion 62 is not formed on the upstream side in the rotation direction of the heating roller 44 (hereinafter sometimes simply referred to as “upstream side”) with the slit S as a boundary. When the heat insulating sleeve 60 rotates with the rotation of the roller 44, the upstream end 64 may be displaced outward due to friction between the outer peripheral surface of the heat insulating sleeve 60 and the inner peripheral surface of the ball bearing 70. .

  Normally, the outward twist of the upstream end portion 64 in the heat insulating sleeve 60 is restricted by the rotational drive gear 52. If the amount of twist is large, stress (pressing force) is applied to the rotational drive gear 52. Will give a result. Therefore, the position where the engagement protrusion 62 is formed is set to the above-described position so that the twisting of the upstream end portion 64 of the heat insulating sleeve 60 toward the outer side is suppressed. That is, this reduces the stress on the rotational drive gear 52 by the heat insulating sleeve 60.

  Further, as shown in FIG. 7B, the recess 58 formed in the shaft portion 50 of the heating roller 44 has a heat insulating portion at the portion contacting the engaging protrusion 62 in the rotation direction (the engaging surface with the engaging protrusion 62). The inclined surface 58A is widened toward the outer periphery of the sleeve 60, and the engaging protrusion 62 is also formed with an inclined surface 62A in accordance with this shape. Therefore, when the rotational force acts on the engaging projection 62 of the heat insulating sleeve 60 from the recess 58, a force acts in the direction of expanding the heat insulating sleeve 60 outward, whereby the downstream end 66 of the heat insulating sleeve 60 is moved to the ball bearing. 70 is in pressure contact state.

  That is, when the heat insulating sleeve 60 rotates in this state, the upstream end portion 64 of the heat insulating sleeve 60 is bent and deformed in a direction in which the shaft portion 50 is tightened. For this reason, the heat insulating sleeve 60 is maintained in the state of being attached to the shaft portion 50, but due to this tightening, an abnormality is caused between the upstream end portion 64 of the heat insulating sleeve 60 and the shaft portion 50 and / or the ball bearing 70. Sound is generated.

  That is, when the heat insulating sleeve 60 is rotated with the rotation of the heating roller 44, the upstream end portion 64 is bent and deformed so that the upstream end portion 64 is squeezed by friction with the ball bearing 70 (so that the interval between the slits S is reduced). Do (tighten). Then, the inner peripheral surface of the upstream end portion 64 slides with respect to the outer peripheral surface of the shaft portion 50, or the outer peripheral surface of the upstream end portion 64 slides with respect to the inner peripheral surface of the ball bearing 70. An abnormal noise occurs.

  Therefore, as shown in FIGS. 8 to 11, the plate thickness of the upstream end portion 64 is formed thinner than the plate thickness of the downstream end portion 66. That is, at the upstream end portion 64 of the heat insulating sleeve 60, at least the outer peripheral surface side facing the inner peripheral surface of the ball bearing 70 is a tapered surface 64A that becomes narrower toward the tip (slit S side) when viewed from the axial direction. ing.

  According to this, between the outer peripheral surface of the upstream end portion 64 of the heat insulating sleeve 60 and the inner peripheral surface of the ball bearing 70, and further between the inner peripheral surface of the upstream end portion 64 of the heat insulating sleeve 60 and the outer peripheral surface of the shaft portion 50. Since the contact area can be reduced, abnormal noise caused by slippage (sliding) occurring between them can be suppressed.

  In addition, as shown in FIG. 12, when the shape of the recessed part 58 and the engagement protrusion 62 is made long in the width direction, the fixing strength of the heat insulating sleeve 60 with respect to the shaft part 50 can be improved, and the resistance in the tightening direction can be increased. As a result, the generation of abnormal noise can be further suppressed. Further, as shown in FIGS. 10 and 11, when the tapered surface 64 </ b> A is formed on the inner peripheral surface and the outer peripheral surface of the upstream end portion 64, the upstream end portion 64 winds the shaft portion 50. Even if it bends and deforms in the tightening direction, it does not come into contact with the shaft portion 50 and the ball bearing 70, so that it is possible to prevent the generation of abnormal noise.

  Moreover, as shown in FIG. 13, the engaging protrusion 62 may be formed across the slit S. With such a configuration, not only abnormal noise but also the above-described twist can be suitably suppressed. Furthermore, as a method of suppressing (preventing) the twist, as shown in FIGS. 14 and 15, the upstream end 64 of the heat insulating sleeve 60 is narrowed in the width direction when viewed from the direction orthogonal to the axial direction. It may be configured.

  That is, at least the width direction outer side (end portion side of the shaft portion 50) of the upstream end portion 64 of the heat insulating sleeve 60 is formed into a tapered surface 64B that becomes thinner as going to the tip end (slit S side). With such a configuration, even if the twist described above occurs, the pressing force to the rotation drive gear 52 is reduced, so that no stress is applied to the rotation drive gear 52.

  As a method for reducing stress (pressing) on the rotational drive gear 52, as shown in FIG. 16, the upstream end 64 of the heat insulating sleeve 60 is inwardly indicated by the arrow X with respect to the downstream end 66. A configuration in which the heat insulating sleeve 60 is formed in a spiral shape in advance so as to be offset to the side (cylindrical portion 44A side) may be employed.

  According to this, since the upstream end portion 64 is shifted (offset) from the beginning to the cylindrical portion 44A side (center side of the heating roller 44), even if the upstream end portion 64 is twisted outward. The pressing force to the rotation drive gear 52 is reduced. Therefore, stress can be prevented from being applied to the rotation drive gear 52.

Second Embodiment
Next, a second embodiment will be described. As shown in FIG. 12, when the recess 58 and the engagement protrusion 62 are formed in a shape that is long in the width direction (short in the circumferential direction), the resistance to the tight tightening (force applied in the circumferential direction) of the heat insulating sleeve 60 can be increased. Therefore, the generation of abnormal noise can be suppressed. However, with such a shape, resistance to the twist (force applied in the axial direction) of the upstream end portion 64 of the heat insulating sleeve 60 is low.

  Therefore, in the heat insulating sleeve 60 of the second embodiment, as shown in FIG. 17, a substantially rectangular engagement protrusion 62 that is short in the circumferential direction and long in the width direction is formed on the downstream end portion 66. A substantially rectangular engagement protrusion 63 that is short in the width direction and long in the circumferential direction is formed in 64. The shaft portion 50 is also formed with recesses 58 and 59 corresponding to the engagement protrusions 62 and 63, respectively.

  With such a configuration, it is possible to increase the resistance against the tight tightening (force applied in the circumferential direction) of the heat insulating sleeve 60 and to the twist (force applied in the axial direction) of the upstream end portion 64 of the heat insulating sleeve 60. Can also increase resistance. That is, it is possible to prevent the generation of abnormal noise due to tight tightening of the heat insulating sleeve 60 and to prevent stress on the rotational drive gear 52 due to twisting.

  Note that the circumferential length of the engaging protrusion 63 formed on the upstream end 64 is shorter than the circumferential length of the recess 59 (the illustrated one is about half the length). ). Therefore, even when the engagement protrusion 63 moves in the circumferential direction with respect to the recess 59 when the upstream end 64 is tightened, the movement is allowed.

  In FIG. 17, the engaging protrusion 63 is formed at the center in the width direction of the heat insulating sleeve 60, but the engaging protrusion 63 is formed on the shaft portion 50 more than the center in the width direction of the heat insulating sleeve 60 as shown in FIG. 18. It is preferable to form it on the end side (outside side) because resistance to twisting can be further improved.

<Third Embodiment>
Next, a third embodiment will be described. An engagement protrusion 62 is not formed on the heat insulating sleeve 60 of the third embodiment. That is, the concave portion 58 is not formed in the shaft portion 50. In the third embodiment, the heat insulating sleeve 60 is prevented from being twisted by devising the shape of the shaft portion 50.

  That is, as shown in FIG. 19, a stepped portion 68 to which the heat insulating sleeve 60 can be fitted is formed on the shaft portion 50 so that the heat insulating sleeve 60 can be regulated from both sides in the width direction. With such a configuration, the heat insulating sleeve 60 can be prevented from being twisted without devising the shape of the heat insulating sleeve 60, and the rotary drive gear 52 provided on the shaft portion 50 on the outer side of the heat insulating sleeve 60. It is possible to prevent stress (pressing force) from being applied.

  In addition, since the number of processing steps can be reduced with such a configuration, the manufacturing cost including the heat insulating sleeve 60 can be reduced. Further, it is possible to prevent the grease applied between the heat insulating sleeve 60 and the shaft portion 50 from bleeding. Although not shown, it goes without saying that the same effect can be obtained even if a step portion is formed on the inner peripheral surface of the ball bearing 70 and the heat insulating sleeve 60 can be regulated from both sides in the width direction.

<Fourth embodiment>
Next, a fourth embodiment will be described. As shown in FIG. 20, the heat insulating sleeve 60 of the fourth embodiment is formed with a substantially elliptical engagement protrusion 65 that is long in the width direction. That is, before the U-shaped key groove 56 formed in the shaft portion 50 is extended inward (cylindrical portion 44 </ b> A side) and the U-shaped protrusion 54 of the rotary drive gear 52 is fitted into the key groove 56. The engagement protrusion 65 of the heat insulating sleeve 60 can be fitted into the key groove 56. That is, the U-shaped protrusion 54, the engaging protrusion 65, and the key groove 56 are arranged on a straight line.

  With such a configuration, the key groove 56 for preventing the rotation of the rotation drive gear 52 with respect to the shaft portion 50 can be used for the engagement of the engagement protrusion 65 of the heat insulating sleeve 60, thereby improving the moldability of the shaft portion 50. Can be made. That is, since it is not necessary to separately form the concave portion 58, the processing man-hour of the shaft portion 50 can be reduced, and thereby the manufacturing cost of the heating roller 44 can be reduced.

  In this case, the shape of the engagement protrusion 65 is a substantially elliptical shape that is long in the width direction in order to match the U-shaped key groove 56. That is, the shape of the engagement protrusion 65 is appropriately changed according to the shape of the key groove 56. Further, as shown in FIG. 21, the engaging protrusion 65 may be formed across the slit S. According to this, since the fixing strength of the heat insulation sleeve 60 with respect to the axial part 50 can be improved, the twist of the heat insulation sleeve 60 can be suppressed.

<Fifth Embodiment>
Finally, a fifth embodiment will be described. In the heat insulating sleeve 60 of the fifth embodiment, as shown in FIG. 22, the inner peripheral surface facing the outer peripheral surface of the shaft portion 50 of the heating roller 44 is formed in a polygonal shape when viewed from the axial direction. With this configuration, the gap D is formed between the outer peripheral surface of the shaft portion 50 and the inner peripheral surface of the heat insulating sleeve 60, and the contact area of the inner peripheral surface of the heat insulating sleeve 60 with respect to the outer peripheral surface of the shaft portion 50 is reduced. Since it can reduce, generation | occurrence | production of the abnormal sound resulting from the slip (sliding) between the heat insulation sleeve 60 and the axial part 50 can be suppressed.

  As described above, the heat insulating sleeve 60 (shaft portion 50) according to the present invention has been described based on the first to fifth embodiments. However, it goes without saying that the contents described in each embodiment may be appropriately combined. Yes. For example, the tapered surface 64B may be formed on the outer side in the width direction of the heat insulating sleeve 60 formed in a spiral shape shown in FIG. 16, and the outer side in the width direction of the heat insulating sleeve 60 shown in FIGS. A tapered surface 64B may be formed on the side.

  In addition, it is preferable that the heat insulating sleeve 60 is toned in white in order to make it difficult to take the heat of the heating roller 44. Further, in order to make it easy to absorb the radiant heat from the lamp heater 48 on the inner peripheral surface of the shaft portion 50 excluding the vicinity of the cylindrical portion 44A and the concave portion 58 of the heating roller 44, the black paint B (FIG. )) Is preferred. Further, the concave portions 58 and 59 of the shaft portion 50 may be formed as an open slot, but it is preferable that the recess is not a slot because thermal efficiency does not decrease.

Schematic side view showing configuration of image forming apparatus Schematic perspective view showing the fixing unit Schematic perspective view showing the inside of the fixing unit Schematic perspective view showing the configuration of the heating roller Schematic front view showing the configuration of the heating roller Schematic front view showing the shaft of the heating roller (A) Schematic sectional view showing a state in which a heat insulating sleeve is inserted into the shaft portion of the heating roller, (B) Schematic sectional view showing a concave portion and an engaging projection. Schematic sectional view showing the insulation sleeve Schematic sectional view showing a state in which a heat insulating sleeve is inserted into the shaft portion of the heating roller and a ball bearing is inserted into the heat insulating sleeve. Schematic sectional view showing the insulation sleeve Schematic sectional view showing a state in which a heat insulating sleeve is inserted into the shaft portion of the heating roller and a ball bearing is inserted into the heat insulating sleeve. Schematic front view showing shaft and heat insulating sleeve of heating roller Schematic sectional view showing the insulation sleeve Schematic front view showing insulation sleeve Schematic front view showing insulation sleeve Schematic front view showing insulation sleeve Schematic front view showing shaft and heat insulating sleeve of heating roller Schematic front view showing shaft and heat insulating sleeve of heating roller (A) The schematic perspective view which shows the axial part of a heating roller, (B) The schematic sectional drawing which shows the axial part of a heating roller Schematic perspective view showing shaft portion of heat roller, heat insulating sleeve and rotation drive gear Schematic perspective view showing shaft portion of heat roller, heat insulating sleeve and rotation drive gear Schematic sectional view showing a state in which a heat insulating sleeve is inserted into the shaft portion of the heating roller and a ball bearing is inserted into the heat insulating sleeve.

Explanation of symbols

10 Image forming apparatus 40 Fixing unit (fixing device)
44 Heating roller (heating rotating member)
46 Pressure roller 48 Lamp heater (heater)
50 Shaft 52 Rotation Drive Gear (Rotation Drive Transfer Member)
54 Protrusion (non-rotating part)
56 Keyway (Non-rotating part)
58, 59 Recess (engaged part)
60 Thermal insulation sleeve 62, 63 Engagement protrusion (engagement part)
64 Upstream end 66 Downstream end 68 Stepped portion 70 Ball bearing (bearing member)
S slit

Claims (23)

In a heat insulating sleeve that is arranged between a bearing member that rotatably supports a shaft portion of a heating rotating member with a built-in heater, and the shaft portion, and that can be expanded in a radial direction by forming a slit. ,
A heat insulating sleeve, wherein a thickness of one end portion sandwiching the slit is formed thinner than a thickness of the other end portion.   2. The heat insulating sleeve according to claim 1, wherein the one end portion has a tapered shape when viewed from the axial direction on a surface side that receives a force by the rotation of the heating rotating member.   2. The heat insulating sleeve according to claim 1, wherein at least the bearing member side of the one end portion is tapered as viewed from the axial direction.   4. The taper-shaped one end portion does not contact the shaft portion and / or the bearing member even if the one end portion is bent and deformed by the rotation of the heating rotating member. Insulation sleeve as described. In a heat insulating sleeve that is arranged between a bearing member that rotatably supports a shaft portion of a heating rotating member with a built-in heater, and the shaft portion, and that can be expanded in a radial direction by forming a slit. ,
A heat insulating sleeve characterized in that a plate width of one end portion sandwiching the slit is formed narrower than a plate width of the other end portion.   6. The heat insulating sleeve according to claim 5, wherein at least one end of the one end is tapered when viewed from a direction orthogonal to the axial direction. In a heat insulating sleeve that is arranged between a bearing member that rotatably supports a shaft portion of a heating rotating member with a built-in heater, and the shaft portion, and that can be expanded in a radial direction by forming a slit. ,
One heat-insulating sleeve characterized in that one end portion sandwiching the slit is offset toward the center of the heating rotary member with respect to the other end portion.   By engaging with an engaged portion formed on the shaft portion of the heating rotating member, an engaging portion that makes the heat insulating sleeve relatively unrotatable with respect to the shaft portion is downstream in the rotation direction of the heating rotating member. The heat insulating sleeve according to any one of claims 1 to 7, wherein the heat insulating sleeve is formed in the vicinity of the other end which is a side.   By engaging with an engaged portion formed on the shaft portion of the heating rotary member, an engagement portion that makes the heat insulation sleeve relatively unrotatable with respect to the shaft portion is formed across the slit. The heat insulation sleeve according to any one of claims 1 to 7, wherein the heat insulation sleeve is provided.   The heat insulating sleeve according to claim 8 or 9, wherein the engaging portion is formed to have a length in the width direction longer than a length in the circumferential direction.   The length of the circumferential direction is longer than the length of the width direction, and the said engaging part is formed in the edge part side of the said axial part rather than the width direction center part of the heat insulation sleeve. Or the heat insulation sleeve of Claim 9. In a heat insulating sleeve that is arranged between a bearing member that rotatably supports a shaft portion of a heating rotating member with a built-in heater, and the shaft portion, and that can be expanded in a radial direction by forming a slit. ,
By engaging the engaged portion formed on the shaft portion of the heating rotating member, the engaging portion that makes the heat insulating sleeve relatively unrotatable with respect to the shaft portion is more circumferential than the length in the width direction. The heat insulating sleeve is characterized in that the length of the heat insulating sleeve is long, and the heat insulating sleeve is formed closer to the end of the shaft portion than the central portion in the width direction of the heat insulating sleeve.   The heat insulating sleeve according to claim 12, wherein the engaging portion is formed in the vicinity of an end portion on the downstream side in the rotation direction of the heating rotating member with the slit as a boundary.   The heat insulating sleeve according to claim 12, wherein the engagement portion is formed across the slit. In a heat insulating sleeve that is arranged between a bearing member that rotatably supports a shaft portion of a heating rotating member with a built-in heater, and the shaft portion, and that can be expanded in a radial direction by forming a slit. ,
By engaging with the engaged portion formed on the shaft portion of the heating rotating member, an engaging portion that makes the heat insulating sleeve relatively unrotatable with respect to the shaft portion is sandwiched by one of the slits. A heat insulating sleeve, wherein at least one is formed independently in the vicinity of the end and in the vicinity of the other end.   The other end is on the downstream side in the rotation direction of the heating rotary member, and the engaging portion formed on the other end has a length in the width direction longer than a length in the circumferential direction, and the one end The engaging portion formed in the portion is longer in the circumferential direction than the width in the width direction, and the circumferential length is shorter than the circumferential length of the engaged portion. The heat insulation sleeve according to claim 15.   The heat insulating sleeve according to claim 16, wherein the engaging portion formed at the one end portion is formed closer to the end portion side of the shaft portion than the center portion in the width direction of the heat insulating sleeve.   The heat insulating sleeve according to any one of claims 1 to 17, wherein an inner peripheral surface facing the shaft portion has a polygonal shape when viewed in the axial direction. The heat insulating sleeve according to any one of claims 8 to 18, wherein the heat insulating sleeve is attached to the shaft portion and heated by a built-in heater;
A bearing member provided on an outer peripheral surface of the heat insulating sleeve and rotatably supporting the heat insulating sleeve;
A rotation drive transfer member that is provided on the end side of the shaft portion relative to the shaft portion rather than the heat insulating sleeve so as not to rotate relative to the shaft portion, and rotates the heating rotation member;
In the fixing device provided with
The rotation drive receiving member has a rotation preventing portion that fits into a rotation prevented portion formed in the shaft portion, and the rotation preventing portion, the rotation prevented portion, and the engagement portion are arranged in a straight line. A fixing device.   The fixing device according to claim 19, wherein the detent portion and the engaging portion are convex portions, and the detent portion is a concave portion or a notch portion into which the engaging portion can also be inserted. .   The fixing device according to claim 19, wherein the engaging portion is formed across the slit. The heat insulating sleeve according to any one of claims 8 to 18, wherein the heat insulating sleeve is attached to the shaft portion and heated by a built-in heater;
A bearing member provided on an outer peripheral surface of the heat insulating sleeve and rotatably supporting the heat insulating sleeve;
In the fixing device provided with
A fixing device characterized in that the shaft portion is formed with a step portion that can regulate the heat insulating sleeve from both sides in the width direction.   An image forming apparatus comprising the fixing device according to any one of claims 19 to 22.

Images