JP2009162975A - Fixing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of abnormal noise, such as, stick-slip abnormal noise, caused by the difference in the heat expansion in a fixing unit in with both end sections of a roller shaft of a heat roller integrating a heat source is supported by a supporting frame via a bearing. <P>SOLUTION: In the fixing unit 34 has the fixing roller (heat roller) 41 integrating a heater (the heat source) 40, supported by a fixing frame (support frame) 45a via the bearing 44, a space S is provided between an outer wheel 46 and an inner wheel 48 of the bearing so that the fixing roller can be slid in the axial direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that records a toner image on a recording material such as paper or a resin film using an electrophotographic process, such as a copying machine, a printer, a facsimile, or a complex machine thereof. The present invention also relates to a fixing device for fixing an unfixed toner image on a recording material by passing the recording material through a fixing nip between the fixing member and the pressure member and applying pressure together with heating in such an image forming apparatus.

  Conventionally, in a fixing device provided in an electrophotographic image forming apparatus, as shown in FIG. 7, for example, a fixing roller 1 incorporating a heater (not shown) as a heat source and pressed against the fixing roller 1 by a biasing member 2, 1 is provided with a pressure roller 3 that is driven to rotate. The fixing roller 1 is obtained by coating a rubber layer on the outer periphery of a cylindrical core metal with a coating such as Teflon (registered trademark). The fixing roller 1 and the pressure roller 3 are rotatably supported by the fixing frames 6a and 6b or the pressure frames 7a and 7b through the bearings 4a, 4b, 5a, and 5b, respectively. It was.

  By the way, as the bearings 4a and 4b of the fixing roller 1 incorporating the heater, as shown in FIGS. 8A and 8B, a ball bearing having a ball t between the outer ring 8 and the inner ring 9 is used. It had been. Reference numeral 1 </ b> A in the drawing is a roller shaft of the fixing roller 1.

Japanese Patent Laid-Open No. 11-73052 JP 2005-292644 A

  However, as described above, in the conventional fixing device, since the outer ring 8 and the inner ring 9 do not slide in the roller shaft 1A direction, the fixing roller is fixed with a heater in order to fix the toner on the recording material such as paper. 1 is heated, a difference in thermal expansion occurs between the fixing roller 1 and the fixing frames 6a and 6b. The difference in thermal expansion cannot be absorbed, and a between the outer ring 8 and the fixing frames 6a and 6b and between the fixing roller 1 and the inner ring. Stick-slip noise was generated between 9 and b due to axial slip.

  In view of this, a first object of the present invention is to solve the above-described problem, in a fixing device in which both end portions of a roller shaft of a heat roller incorporating a heat source are supported by a support frame via a bearing. It is to prevent the occurrence of abnormal noise such as stick-slip abnormal noise.

  The second object of the present invention is to completely prevent the occurrence of abnormal noise by completely absorbing the difference in thermal expansion with a bearing.

  A third object of the present invention is to make the inner ring move smoothly with respect to the outer ring, and to further reduce the occurrence of abnormal noise.

  A fourth object of the present invention is to make the inner ring rotate integrally with the heat roller to further suppress the generation of abnormal noise.

  The fifth object of the present invention is to further suppress the generation of abnormal noise caused by slipping between the outer ring and the heat roller.

  A sixth object of the present invention is to further suppress the generation of abnormal noise caused by slipping between the outer ring and the heat roller.

  A seventh object of the present invention is to prevent wear of the heat roller and suppress the occurrence of abnormal noise due to stick slip between the bearing and the heat roller.

  An eighth object of the present invention is to fix the bearing to the heat roller with a small number of parts and suppress the occurrence of abnormal noise.

  A ninth object of the present invention is to prevent wear of the heat roller, more securely fix the bearing to the heat roller, and suppress the occurrence of abnormal noise.

  A tenth object of the present invention is to reduce the change in the outer diameter of the heat roller during endurance so that the press-fitted state can be maintained and to suppress the occurrence of abnormal noise.

  An eleventh object of the present invention is to provide a stick-slip noise caused by a difference in thermal expansion in an image forming apparatus including a fixing device in which both end portions of a roller shaft of a heat roller incorporating a heat source are supported by a support frame via a bearing. It is to prevent the occurrence of abnormal sounds such as.

  Therefore, in order to achieve the first object described above, the invention according to claim 1 is a fixing device in which a heat roller incorporating a heat source is supported by a support frame via a bearing, and an outer ring and an inner ring of the bearing. Between the two, a gap is provided to allow the heat roller to slide in the axial direction.

  According to a second aspect of the present invention, in order to achieve the second object described above, in the fixing device according to the first aspect, the gap is a difference in thermal expansion between the heat roller and the support frames at both ends thereof. It is characterized by being formed larger.

  According to a third aspect of the present invention, in order to achieve the third object described above, in the fixing device according to the first or second aspect, the bearing is a ball bearing in which a plurality of balls are arranged side by side as rolling elements. It is characterized by.

  According to a fourth aspect of the present invention, in order to achieve the fourth object described above, in the fixing device according to the third aspect, the plurality of balls provided side by side are smaller at the end than at the center. It is characterized by that.

  According to a fifth aspect of the present invention, in order to achieve the third object described above, in the fixing device according to the first or second aspect, the bearing is a roller bearing.

  According to a sixth aspect of the present invention, in order to achieve the fourth object described above, in the fixing device according to the fifth aspect, the roller of the roller bearing has a shape with a large diameter at the center. It is characterized by.

  According to a seventh aspect of the present invention, in order to achieve the fifth object described above, in the fixing device according to any one of the first to sixth aspects, the outer ring of the bearing is screwed to the support frame. It is fixed.

  According to an eighth aspect of the present invention, in order to achieve the sixth object described above, in the fixing device according to any one of the first to seventh aspects, the outer ring of the bearing is different from the flange portion of the outer ring. It is fixed to the support frame by pressing it down.

  According to a ninth aspect of the present invention, in order to achieve the seventh object described above, in the fixing device according to any one of the first to eighth aspects, the bearing is mounted on the heat roller using a ring attached to the heat roller. It is fixed to a roller.

  According to a tenth aspect of the present invention, in order to achieve the eighth object described above, in the fixing device according to the ninth aspect, the bearing includes the ring attached to the heat roller and a step provided on the heat roller. It is fixed to a roller.

  According to an eleventh aspect of the present invention, in order to achieve the ninth object described above, in the fixing device according to any one of the first to eighth aspects, the bearing is fixed onto the heat roller by press fitting. It is characterized by that.

  According to a twelfth aspect of the present invention, in order to achieve the tenth object described above, in the fixing device according to the eleventh aspect, the hardness of the roller shaft of the heat roller is 70 HV or more.

  According to a thirteenth aspect of the present invention, there is provided an image forming apparatus including the fixing device according to any one of the first to twelfth aspects to achieve the eleventh object described above.

  According to the first aspect of the present invention, in the fixing device in which both end portions of the roller shaft of the heat roller incorporating the heat source are supported by the support frame via the bearing, the heat roller is disposed between the outer ring and the inner ring of the bearing. Since there is a gap that allows sliding in the axial direction, the gap absorbs the difference in thermal expansion between the heat roller and the support frame by the smooth movement of the inner ring relative to the outer ring, resulting from the difference in thermal expansion. Generation of abnormal noise such as stick-slip abnormal noise can be prevented.

  According to the second aspect of the present invention, since the gap is formed larger than the thermal expansion difference between the heat roller and the support frames at both ends thereof, the thermal expansion difference is completely absorbed by the bearing, and abnormal noise is generated. The generation of abnormal noise can be suppressed by reliably preventing the occurrence and reducing the axial play of the heat roller.

  According to the invention described in claim 3, since the bearing is a ball bearing in which a plurality of balls are arranged side by side as rolling elements, the contact area between the rolling elements and the inner and outer rings is reduced, and the inner ring moves smoothly with respect to the outer ring. Thus, the occurrence of abnormal noise can be further reduced.

  According to the fourth aspect of the invention, the plurality of balls arranged side by side are smaller in size than the center one, so that the inner ring rotates integrally with the roller shaft of the heat roller inclined by bending. And the occurrence of abnormal noise can be further suppressed.

  According to the fifth aspect of the present invention, since the bearing is a roller bearing, the inner ring moves smoothly with respect to the outer ring, and the generation of abnormal noise can be further suppressed.

  According to the sixth aspect of the present invention, since the roller of the roller bearing has a shape with a large diameter at the central portion, the inner ring can rotate integrally with the roller shaft of the heat roller inclined by bending. The occurrence of abnormal noise can be suppressed.

  According to the seventh aspect of the present invention, since the outer ring of the bearing is fixed by screwing to the support frame, the outer ring is fixed and the generation of abnormal noise due to slippage between the outer ring and the thermal frame is further suppressed. be able to.

  According to the invention described in claim 8, since the outer ring of the bearing is fixed to the support frame by pressing the flange portion of the outer ring with a separate part, the outer ring is securely fixed and the outer ring and the thermal frame are fixed. Generation of abnormal noise due to slipping can be further suppressed.

  According to the ninth aspect of the present invention, since the bearing is fixed to the heat roller using the ring attached to the heat roller, the heat roller is prevented from being worn, and abnormal noise due to stick slip between the bearing and the heat roller is prevented. Can be suppressed.

  According to the tenth aspect of the present invention, since the bearing is fixed to the heat roller by the ring attached to the heat roller and the step provided on the heat roller, the bearing is fixed to the heat roller with a small number of parts, and abnormal noise is reduced. Occurrence can be suppressed.

  According to the eleventh aspect of the present invention, since the bearing is fixed on the heat roller by press fitting, the heat roller is prevented from being worn, and the bearing is more securely fixed to the heat roller, thereby suppressing abnormal noise. be able to.

  According to the twelfth aspect of the present invention, since the hardness of the roller shaft of the heat roller is 70 HV or more, the change in the outer diameter of the heat roller during the endurance can be reduced to maintain the press-fitted state, and abnormal noise is generated. Can be suppressed.

  According to the thirteenth aspect of the present invention, since the image forming apparatus includes the fixing device according to any one of the first to twelfth aspects, both ends of the roller shaft of the heat roller incorporating the heat source are bearings. In the image forming apparatus provided with the fixing device supported by the support frame via the support, it is possible to prevent the occurrence of abnormal noise such as stick-slip abnormal noise due to the difference in thermal expansion.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 shows an overall schematic configuration of an internal mechanism of a color copying machine which is an example of a tandem image forming apparatus.

  In the figure, reference numeral 100 is a copying machine body, 200 is a scanner mounted on the copying machine body 100, and 300 is an automatic document feeder (ADF) mounted on the scanner.

  In the copying machine main body 100, an endless belt-like intermediate transfer member 10 is stretched substantially horizontally around a driving roller 11 and a driven roller 12 in the illustrated example, and extends in the direction of arrow A in the figure. It is provided so that it can rotate. Of course, the intermediate transfer member 10 may be wound around three or more rollers.

  On the intermediate transfer body 10, four image forming stations 20 are arranged in the order of, for example, black (20K), yellow (20Y), magenta (20M), and cyan (20C) from the upstream side to the downstream side. They are arranged in tandem style. Each image forming station 20 is provided with a drum-shaped image carrier 21 so as to be in contact with the intermediate transfer member 10, and around the image carrier 21, a charging device 22, a developing device 23, and an intermediate transfer member. A primary transfer device 24, a primary cleaning device 25, and the like are arranged with 10 therebetween. A secondary cleaning device 14 is installed upstream of the most upstream black image forming station 20K. An exposure device 15 is provided on the four image forming stations 20.

  On the other hand, at the bottom of the copying machine main body 100, a paper feed tray 16 for storing a recording material such as paper is detachably provided. A paper feed roller 17 and a separation pad 18 are provided on the upper right side of the paper feed tray 16 in the figure, and a recording material conveyance path 30 is formed upward therefrom. In the recording material conveyance path 30, the secondary transfer device 33, the fixing device 34, and the registration roller pair 32, the intermediate transfer member 10, and the drive roller 11 are disposed in order from the positions of the paper feed roller 17 and the separation pad 18. A pair of paper discharge rollers 35 and the like are arranged and continue to the paper discharge tray 36 on the copying machine main body 100.

  On the right side of the recording material conveyance path 30 in the figure, the recording material that has exited the fixing device 34 is switched back by the paper discharge roller pair 35, conveyed by the conveyance roller pair 37, and again to the upstream position of the registration roller pair 32. A double-sided conveyance path 38 is provided.

  Now, when making a color copy using this color copying machine, a document is set on the document table of the automatic document feeder 300. Alternatively, the automatic document feeder 300 is opened, a document is set on the contact glass of the scanner 200, and the automatic document feeder 300 is closed and pressed by it.

  When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 300, the document is transported and moved onto the contact glass, and then the scanner 200 is driven to read the document content. . When a document is set on the contact glass, the content of the document is read by the scanner 200 as it is.

  When a start switch (not shown) is pressed, the drive roller 11 is driven to rotate by a drive motor (not shown), the driven roller 12 is driven to rotate, and the intermediate transfer member 10 is rotated in the direction of arrow A. At the same time, the image carrier 21 is rotated at each image forming station 20. Then, along with the rotation of the image carrier 21, the surface of the image carrier 21 is first uniformly charged by the charging device 22, and then the writing light from the exposure device 15 described above according to the reading content of the scanner 200 by a laser, LED, or the like. L is irradiated to form an electrostatic latent image on the image carrier 21.

  Thereafter, toner is attached by the developing device 23 to visualize the electrostatic latent image, and the visible image is transferred onto the intermediate transfer member 10 by the primary transfer device 24. The surface of the image carrier 21 after the image transfer is cleaned and initialized by removing residual toner by the primary cleaning device 25, and is prepared for another image formation. The black, yellow, magenta, and cyan single-color images formed on the respective image carriers 21 are sequentially primary-transferred along with the conveyance of the intermediate transfer body 10 and are superimposed on the intermediate transfer body 10 to form a composite color image. The

  Further, when a start switch (not shown) is pressed, the sheet feeding roller 17 is rotated at an appropriate timing, and the recording materials are fed out from the sheet feeding tray 16 and separated one by one by the separation pad 18. It is put in the conveyance path 30 and the front end abuts against the registration roller pair 32 and is stopped.

  Then, the registration roller pair 32 is rotated in synchronization with the composite color image on the intermediate transfer member 10, and a recording material is sent between the intermediate transfer member 10 and the secondary transfer device 33. The composite color image on the intermediate transfer member 10 is secondarily transferred at once to form a color image on the recording material.

  The recording material after the secondary transfer is transported by the secondary transfer device 33 and sent to the fixing device 34. After the transfer image is fixed by applying heat and pressure by the fixing device 34, the discharge roller pair 35 is discharged. Are discharged and stacked on the discharge tray 36. Alternatively, the sheet is put into the double-sided conveyance path 38, reversed there and led again to the secondary transfer position, and an image formed separately is formed on the back side, and then discharged onto the discharge tray 36 by the discharge roller pair 35. Is done.

  On the other hand, the intermediate transfer body 10 after the secondary transfer is initialized by removing residual toner remaining on the intermediate transfer body 10 after the image transfer by the secondary cleaning device 14, and is ready for image formation again.

  Further, when making a monochrome or two-color copy using this color copying machine, an image is formed by appropriately selecting one or two image forming stations 20.

  Incidentally, the fixing device 34 includes a fixing roller 41 that is a heat roller including a heater 40 as a heat source, and a pressure roller 42 that is pressed against the fixing roller to form a fixing nip N, and is a fixing member. By passing the recording material through a fixing nip N between the fixing roller 41 and the pressure roller 42 as a pressure member and applying pressure with heating, an unfixed toner image is fixed on the recording material.

FIG. 2A shows an internal structure on one end side of the fixing device 34. FIG. 5B shows a cross section of the bearing portion of the fixing roller 41.
As shown in the figure, the fixing roller 41 is held by supporting both end portions of the roller shaft 43 with left and right fixing frames 45 a and 45 b (not shown) via bearings 44. As shown in (B), the bearing 44 has a certain gap between the outer ring 46 and the rolling element 47 and between the inner ring 48 and the rolling element 47 so that the fixing roller 41 can slide in the axial direction. S is provided.

  As a result, the inner ring 48 can slide in the axial direction with respect to the outer ring 46 through the gap S, and the inner ring 48 can be compared with the outer ring 46 with respect to the difference in thermal expansion between the fixing roller 41 and the fixing frames 45a and 45b as the support frames. Absorbing by moving smoothly, abnormal noise such as stick-slip noise can be suppressed.

  Here, the sum of the gaps S between the left and right bearings 44 of the fixing roller 41 is larger than the difference in thermal expansion between the fixing roller 41 and the fixing frames 45a and 45b at both ends thereof. As a result, the difference in thermal expansion can be completely absorbed by the bearing 44 to reliably prevent the occurrence of abnormal noise, and the axial play of the fixing roller 41 can be reduced to suppress the occurrence of abnormal noise.

  Specifically, in the fixing device 34 in which the dimension between the fixing frames 45a and 45b is 250 mm, the heating by the heater 40 causes the fixing roller 41 to be 250 ° C. and the fixing frames 45a and 45b to be 70 ° C. Is 1.3 mm for the fixing roller 41 made of aluminum and 0.2 mm between the fixing frames 45a and 45b made of iron, so the difference in thermal expansion between them is 1.1 mm. Therefore, when the clearances of the bearings 44 are 1.2 mm in total, the thermal expansion amount of the fixing roller 41 is absorbed by the clearances S in the bearing 44, and the fixing between the roller shaft 43 and the inner ring 48 of the fixing roller 41 or the outer ring 46 and the fixing. Occurrence of abnormal noise such as stick slip due to axial slip between the frames 45a and 45b can be eliminated. Further, if the gap S is formed in the bearings 44 at both ends, the gap between the bearings 44 on one side may be 0.6 mm and the gap at both ends may be 1.2 mm.

  In the example shown in FIGS. 2A and 2B, the bearing 44 is a roller bearing using a roller as the rolling element 47. As described above, when the bearing 44 is a roller bearing, the inner ring 48 moves smoothly with respect to the outer ring 46, and the occurrence of abnormal noise can be further suppressed. At this time, if the roller of the roller bearing has a shape with a large diameter at the center, the inner ring 48 can rotate integrally with the roller shaft 43 of the fixing roller 41 inclined by bending, thereby suppressing the occurrence of abnormal noise. Can do.

FIG. 3A shows an example of the shape of a roller bearing, and FIG. 3B shows an example in which the bearing 44 is a ball bearing in which a plurality of balls are arranged as rolling elements 47.
When the bearing 44 is a ball bearing in which a plurality of balls are arranged side by side as the rolling element 47, the contact area between the rolling element 47 and the inner and outer rings 46 and 48 is reduced, and the inner ring 48 moves smoothly with respect to the outer ring 46, thereby causing abnormal noise. Can be further reduced.

  Also, as shown in the figure, when the diameter of the plurality of balls arranged side by side is smaller than that at the center, the inner ring 48 can rotate integrally with the roller shaft 43 of the fixing roller 41 inclined by bending. The occurrence of abnormal noise can be further suppressed.

FIG. 4 shows another example of a support structure for the fixing roller 41.
As shown in the figure, the outer ring 46 of the bearing 44 may be fixed to fixing frames 45a and 45b (not shown) by, for example, two fixing screws 50. In this way, the outer ring 46 is fixed, and the generation of abnormal noise due to slippage between the outer ring 46 and the fixing frames 45a and 45b can be further suppressed. 4 denotes a pressure frame that supports the roller shaft 52 of the pressure roller 42 via a bearing 53.

FIG. 5A shows another example of the support structure of the fixing roller 41, and FIG. 5B shows a cross section of the bearing portion of the fixing roller 41. FIG.
A fixing member 50 is screwed to the fixing frames 45a and 45b to fix another member 55, and the outer ring 46 is fixed to the fixing frames 45a and 45b by pressing the flange portion 54 of the outer ring 46 with the other member 55. It has become. Therefore, the outer ring 46 is securely fixed, and generation of abnormal noise due to slippage between the outer ring 46 and the fixing frames 45a and 45b can be further suppressed.

FIG. 6A shows still another example of the support structure of the fixing roller 41, and FIG. 6B shows still another example.
In (A), the inner ring 48 is fixed to the fixing roller 41 so as not to move on the roller shaft 43 in the axial direction by using rings 56 attached to the outer periphery of the roller shaft 43 of the fixing roller 41 on both sides of the inner ring 48. Accordingly, it is possible to prevent the fixing roller 41 from being worn, and to suppress the occurrence of abnormal noise due to stick-slip between the bearing 44 and the fixing roller 41. In (B), the inner ring 48 is a roller shaft by a ring 56 attached to the outer periphery of the roller shaft 43 of the fixing roller 41 on one side of the inner ring 48 and a step 57 provided on the outer periphery of the roller shaft 43 of the fixing roller 41 on the other side of the inner ring 48. 43 is fixed to the fixing roller 41 so as not to move in the axial direction. Thereby, the bearing 44 can be fixed to the fixing roller 41 with a small number of parts, and the occurrence of abnormal noise can be suppressed.

  In the above-described example, a ring 56 attached to the fixing roller 41 is provided, or a step 57 is provided on the outer periphery of the roller shaft 43 of the fixing roller 41 so that the bearing 44 does not move on the roller shaft 43 in the axial direction. It is fixed to the roller 41. However, the bearing 44 may be fixed on the fixing roller 41 by press-fitting the inner ring 48 of the bearing 44 on the outer periphery of the roller shaft 43. In this way, it is possible to prevent the fixing roller 41 from being worn and more reliably fix the bearing 44 to the fixing roller 41 and suppress the occurrence of abnormal noise.

  At this time, by setting the hardness of the roller shaft 43 of the fixing roller 41 to 70 HV or more, the outer diameter change of the fixing roller 41 during durability can be reduced to maintain the press-fitted state, and the occurrence of abnormal noise can be suppressed. Can do.

  In the above-described example, the case where the fixing member is the fixing roller 41 including the heater 40 as a heat source, and the fixing roller 41 is a heat roller has been described. However, when the fixing member is a fixing belt that hangs between a plurality of support rollers, and the fixing belt is heated by a heat source built in the support roller, the support roller containing the heat source is used as a heat roller. The heat roller may be supported by a support frame via a bearing, and a gap that allows the heat roller to slide in the axial direction may be provided between the outer ring and the inner ring of the bearing.

  Further, not only the fixing member but also a pressure roller that presses against the fixing member has a structure that incorporates a heat source, the pressure roller may be a heat roller.

1 is an overall schematic configuration diagram of an internal mechanism of a color copying machine which is an example of a tandem image forming apparatus. (A) is a perspective view showing an internal structure of one end side of a fixing device provided in the color copying machine, and (B) is a sectional view of a bearing portion of a fixing roller provided in the fixing device. (A) is a cross-sectional view of the bearing portion of the fixing roller in an example in which the roller of the roller bearing of the fixing roller is shaped like a roller, and (B) is an example in which the bearing is a ball bearing. FIG. 6 is a perspective view showing an internal structure on one end side of a fixing device showing another example of a supporting structure of a fixing roller. (A) is a perspective view showing an internal structure of one end side of a fixing device showing still another example of a fixing roller support structure, and (B) is a sectional view of a bearing portion of the fixing roller. (A) is still another example of a fixing roller support structure, and (B) is a sectional view of a bearing portion of a fixing roller of still another example. It is a perspective view which shows the internal structure of the conventional fixing device. (A) is a perspective view showing an internal structure on one end side of the conventional fixing device, and (B) is a sectional view of a bearing portion of a fixing roller provided in the fixing device.

Explanation of symbols

34 Fixing device 40 Heater (heat source)
41 Fixing roller (heat roller)
42 Pressure roller 43 Roller shaft 44 Bearing 45a Fixing frame (support frame)
46 outer ring 47 rolling element 48 inner ring 50 fixing screw 54 flange of outer ring 55 separate parts 56 ring 57 step S gap

Claims (13)

In a fixing device in which a heat roller incorporating a heat source is supported by a support frame via a bearing,
A fixing device, wherein a gap is provided between the outer ring and the inner ring of the bearing so that the heat roller can slide in the axial direction. The fixing device according to claim 1,
The fixing device, wherein the gap is formed larger than a difference in thermal expansion between the heat roller and the support frames at both ends thereof. The fixing device according to claim 1 or 2,
The fixing device, wherein the bearing is a ball bearing provided with a plurality of balls arranged as rolling elements. The fixing device according to claim 3.
A fixing device in which a plurality of balls provided side by side are smaller at the end than at the center. The fixing device according to claim 1 or 2,
The fixing device, wherein the bearing is a roller bearing. The fixing device according to claim 5.
The fixing device according to claim 1, wherein the roller of the roller bearing has a shape having a large diameter at the center. The fixing device according to any one of claims 1 to 6,
An outer ring of the bearing is fixed to the support frame by screwing. In the fixing device according to any one of claims 1 to 7,
The fixing device, wherein an outer ring of the bearing is fixed to the support frame by pressing a flange portion of the outer ring with a separate part. In the fixing device according to any one of claims 1 to 8,
The fixing device, wherein the bearing is fixed to the heat roller using a ring attached to the heat roller. The fixing device according to claim 9.
The fixing device, wherein the bearing is fixed to the heat roller by a ring attached to the heat roller and a step provided on the heat roller. In the fixing device according to any one of claims 1 to 8,
The fixing device, wherein the bearing is fixed on the heat roller by press-fitting. The fixing device according to claim 11.
The fixing device according to claim 1, wherein a hardness of a roller shaft of the heat roller is 70HV or more.   An image forming apparatus comprising the fixing device according to claim 1.

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