JP2008052182A - Fixing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing unit and an image forming apparatus which can suppress deterioration in strength of an insulating sleeve. <P>SOLUTION: The fixing unit provided in a laser printer is provided with a heat roller 41 heated by a halogen heater HH, a first bearing 60 supporting an end part 41b of the heat roller 41 to be able to be rotated and a second insulating sleeve 65 intervening between the end part 41b of the heat roller 41 and the first bearing 60. Then, a portion along an inner periphery surface of the first bearing 60 of a first insulating sleeve 64 is projected from both sides of the first bearing 60 in an axial direction of the heat roller 41. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fixing device that thermally fixes a developer image on a sheet (recording sheet), and an image forming apparatus including the fixing device.

  Generally, an image forming apparatus such as a laser printer is provided with a fixing device for thermally fixing a developer image transferred from a photosensitive member to a sheet. As such a fixing device, conventionally, there are a heating roller, a pressure roller pressed against the heating roller, a bearing that rotatably supports a rotating shaft of the heating roller, and a bearing and a rotating shaft of the heating roller. The thing provided with the heat insulation sleeve arrange | positioned between is known (refer patent document 1). According to this technique, since the heat of the heating roller is blocked by the heat insulating sleeve, it is possible to reduce the influence of the heat on the bearing. In addition, as represented by the invention disclosed in this document and the prior art, the portion of the heat insulating sleeve that contacts the inner peripheral surface of the bearing is approximately the same as the width (axial length) of the bearing. It was generally short.

Japanese Patent Laid-Open No. 54-59549 (FIG. 2)

  However, when the heat insulating sleeve is arranged as described above, when the heating roller expands and contracts in the axial direction due to heat, the heat insulating sleeve and the bearing may be displaced from each other in the axial direction. There was a risk that the contact area between the heat insulating sleeve and the bearing would decrease. If the contact area between the heat insulating sleeve and the bearing is reduced as described above, the heat insulating sleeve may be worn out and the strength of the heat insulating sleeve may be reduced.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing device and an image forming apparatus capable of suppressing a decrease in strength of a heat insulating sleeve.

  The present invention that solves the above problems is a fixing device that thermally fixes a developer image onto a recording sheet onto which the developer image has been transferred, and includes a heating roller that is heated by a heat source, and a pressure toward the heating roller. A pressure roller, a bearing that rotatably supports an end portion of the heating roller, a heat insulating sleeve interposed between the end portion of the heating roller and the bearing, the heating roller, and the pressure And a portion of the heat insulating sleeve along the inner peripheral surface of the bearing protrudes on both sides of the bearing in the axial direction of the heating roller.

  Here, the “part along the inner peripheral surface of the bearing” refers to a part that can come into contact with the inner peripheral surface of the bearing and can face the inner peripheral surface of the bearing.

  According to the present invention, since the portion along the inner peripheral surface of the bearing of the heat insulating sleeve protrudes on both sides of the bearing in the axial direction of the heating roller, even if the heating roller expands and contracts in the axial direction due to heat, the heat insulating sleeve It is possible to prevent the bearings from shifting in the axial direction and reducing their contact area. The fixing device as described above is provided in the image forming apparatus.

  According to the present invention, since it is possible to suppress a decrease in the contact area between the heat insulating sleeve and the bearing, it is possible to suppress wear of the heat insulating sleeve and to suppress a decrease in strength of the heat insulating sleeve.

[First Embodiment]
<Overall configuration of laser printer>
First, the overall configuration of a laser printer as an example of the image forming apparatus of the present invention will be briefly described. In the drawings to be referred to, FIG. 1 is a side sectional view showing a first embodiment of a laser printer as an example of an image forming apparatus of the present invention.
As shown in FIG. 1, the laser printer 1 includes a feeder unit 4 for feeding a sheet 3 into a main body casing 2, an image forming unit 5 for forming an image on the fed sheet 3, and the like. ing.

<Configuration of feeder section>
The feeder unit 4 includes a paper feed tray 6 that is detachably attached to the bottom of the main casing 2 and a paper pressing plate 7 provided in the paper feed tray 6. The feeder unit 4 includes a sheet feeding roller 8 and a sheet feeding pad 9 provided above one end of the sheet feeding tray 6, and a sheet provided downstream of the sheet feeding roller 8 in the conveying direction of the sheet 3. Powder removing rollers 10 and 11 are provided. Further, the feeder unit 4 includes a registration roller 12 provided on the downstream side with respect to the paper dust removing rollers 10 and 11. In the following description, the downstream side or the upstream side in the conveyance direction of the paper 3 may be simply referred to as the downstream side or the upstream side.

  In the feeder section 4 configured as described above, the paper 3 in the paper feed tray 6 is brought close to the paper feed roller 8 side by the paper pressing plate 7 and sent out by the paper feed roller 8 and the paper feed pad 9. Then, after passing through the various rollers 10 to 12, they are conveyed one by one to the image forming unit 5.

<Configuration of image forming unit>
The image forming unit 5 includes a scanner unit 16, a process cartridge 17, a fixing device 18, and the like.

<Configuration of scanner unit>
The scanner unit 16 is provided at an upper portion in the main body casing 2 and includes a laser light emitting unit (not shown), a polygon mirror 19 that is rotationally driven, lenses 20, 21 and reflecting mirrors 22, 23, 24, and the like. . As indicated by the chain line, the laser beam based on the image data emitted from the laser emission unit passes or reflects in the order of the polygon mirror 19, the lens 20, the reflecting mirrors 22, 23, the lens 21, and the reflecting mirror 24, and the process cartridge. The surface of the 17 photosensitive drums 27 is irradiated by high-speed scanning.

<Process cartridge configuration>
The process cartridge 17 is disposed below the scanner unit 16 and is configured to be detachably attached to the main body casing 2. A developing cartridge 28, a photosensitive drum 27, a scorotron charger 29, and a transfer roller 30 are mainly provided in a hollow casing 51 that constitutes the outer frame of the process cartridge 17.

  The developing cartridge 28 is detachably attached to the housing 51 and includes a developing roller 31, a layer thickness regulating blade 32, a supply roller 33, and a toner hopper 34. The toner in the toner hopper 34 is supplied to the developing roller 31 by the rotation of the supply roller 33 in the arrow direction (counterclockwise direction). At this time, the toner is positively frictionally charged between the supply roller 33 and the developing roller 31. Is done. The toner supplied onto the developing roller 31 enters between the layer thickness regulating blade 32 and the developing roller 31 as the developing roller 31 rotates in the arrow direction (counterclockwise), and has a constant thickness. It is carried on the developing roller 31 as a thin layer.

  The photosensitive drum 27 is supported by the housing 51 so as to be rotatable in the arrow direction (clockwise). The photosensitive drum 27 is formed of a positively chargeable photosensitive layer made of polycarbonate, while the drum body is grounded.

  The scorotron charger 29 is disposed above the photosensitive drum 27 so as to face the photosensitive drum 27 with a predetermined interval therebetween. The scorotron charger 29 is a positively charged scorotron charger that generates corona discharge from a charging wire such as tungsten, and is configured to uniformly charge the surface of the photosensitive drum 27 to a positive polarity. ing.

  The transfer roller 30 is disposed below the photosensitive drum 27 so as to face and contact the photosensitive drum 27, and is supported by the housing 51 so as to be rotatable in the arrow direction (counterclockwise direction). The transfer roller 30 is configured by covering a metal roller shaft with a conductive rubber material. A transfer bias is applied to the transfer roller 30 at the time of transfer.

  The surface of the photosensitive drum 27 is uniformly positively charged by the scorotron charger 29 and then exposed by high-speed scanning of the laser beam from the scanner unit 16. Thereby, the potential of the exposed part is lowered, and an electrostatic latent image based on the image data is formed. Here, the “electrostatic latent image” refers to an exposed portion of the surface of the photosensitive drum 27 that is uniformly positively charged and exposed to a laser beam to have a lowered potential. Next, the rotation of the developing roller 31 causes the toner carried on the developing roller 31 to be supplied to an electrostatic latent image formed on the surface of the photosensitive drum 27 when it contacts and faces the photosensitive drum 27. The The toner is visualized by being selectively carried on the surface of the photosensitive drum 27, whereby a toner image is formed by reversal development.

  Thereafter, the photosensitive drum 27 and the transfer roller 30 are rotationally driven so as to sandwich and convey the sheet 3 between them, and the sheet 3 is conveyed between the photosensitive drum 27 and the transfer roller 30, so that the photosensitive drum 27 and the transfer roller 30 are photosensitive. The toner image carried on the surface of the drum 27 is transferred onto the paper 3.

<Configuration of fixing device>
The fixing device 18 is disposed on the downstream side of the process cartridge 17, and is provided on the downstream side of the heating roller 41, the pressure roller 42 pressed against the heating roller 41, and the heating roller 41 and the pressure roller 42. A pair of transport rollers 43 is provided. In the fixing device 18 configured as described above, the toner image transferred onto the sheet 3 is thermally fixed while the sheet 3 passes between the heating roller 41 and the pressure roller 42. Thereafter, the sheet 3 is transported to the paper discharge path 44 by the transport roller 43. The paper 3 sent to the paper discharge path 44 is discharged onto a paper discharge tray 46 by a paper discharge roller 45.

<Details of fixing device structure>
Next, details of the structure of the fixing device will be described. In the drawings to be referred to, FIG. 2 is a schematic configuration diagram showing the relationship between the components constituting the fixing device of the laser printer shown in FIG. 1, and FIG. It is a side view which shows a relationship. It should be noted that the structure of the fixing device shown in FIG. 1 is omitted as appropriate for convenience of explanation.

  As shown in FIG. 2, the fixing device 18 mainly includes the heating roller 41 and the pressure roller 42 described above, a first bearing 60 for the heating roller 41, and a second bearing 61 for the pressure roller 42. A housing 62 and a pressure arm 63 are provided.

  The heating roller 41 is a part formed in a hollow cylindrical shape, and is heated by a halogen heater HH disposed therein. The heating roller 41 is rotatably supported by the housing 62 via the first bearing 60 (the support portion is not shown). As the first bearing 60, it is desirable to employ a ball bearing that can sufficiently withstand the pressing force from the pressure roller 42.

  Further, a gear G is fixed to one end of the heating roller 41, whereby a driving force from a driving device (not shown) is transmitted to the heating roller 41 through the gear G so that the heating roller 41 rotates. It has become. Between the both end portions of the heating roller 41 and the first bearing 60, a first heat insulating sleeve 64 and a second heat insulating sleeve 65 for suppressing heat transfer from the heat roller 41 to the first bearing 60 are interposed. Has been. The details of the structure of the first heat insulating sleeve 64 and the second heat insulating sleeve 65 will be described later.

  The pressure roller 42 is a part formed in a columnar shape, and a rotation shaft 42a is provided so as to protrude outward from the center of both ends thereof. The rotating shaft 42 a is rotatably supported by the second bearing 61.

  As shown in FIG. 3, the pressure arm 63 is urged toward the heating roller 41 by the pulling spring S, thereby pressing (urging) the pressure roller 42 toward the heating roller 41. It is a part. The pressure arm 63 has one end 63a rotatably supported by the housing 62, the second bearing 61 supported by the substantially central portion, and the other end urged by the tension spring S. ing.

  As shown in FIG. 2, the housing 62 includes a pair of side walls 62 a and 62 b that face the end face of the heating roller 41, and an upper wall 62 c that is disposed on the opposite side of the pressure roller 42 across the heating roller 41. It has a structure mainly equipped with. The housing 62 holds the heating roller 41 via the first bearing 60 (see FIG. 5) and holds the pressure roller 42 via the pressure arm 63. A first electrode 66 connected to one end of the halogen heater HH is provided on one of the side walls 62a and 62b, and the other end of the halogen heater HH is provided on the other side wall 62b. The 2nd electrode 67 connected to is provided.

  Here, the second electrode 67 is formed in an L shape in sectional view by a connection portion 67a connected to the halogen heater HH and a first conductive portion 67b provided along the inner surface of the side wall 62b. Further, the first conductive portion 67 b of the second electrode 67 is integrally formed with a second conductive portion 68 that transmits electricity from an external power source to the second electrode 67 in order to supply power to the second electrode 67. ing. The second conductive portion 68 is provided along the inner surface of the upper wall 62c of the housing 62. The halogen heater HH is activated by supplying electric power to the second conductive portion 68 and the first electrode 66 from an external power source through a path such as an electric wire (not shown).

  Further, the second conductive portion 68 is appropriately provided with a thermal fuse (not shown) that is disconnected when the temperature of the heating roller 41 reaches a predetermined value or more. In the present embodiment, the second conductive portion 68 and the thermal fuse are cited as examples of the power supply member. However, the present invention is not limited to this example. For example, in addition to the second conductive portion 68 and the thermal fuse, A power supply member may be added with a thermostat for current control.

<Details of insulation sleeve structure>
Next, the detail of the structure of the 2nd heat insulation sleeve used as the characterizing part of this invention is demonstrated. In the drawings to be referred to, FIG. 4 is a cross-sectional view showing the structure around the first heat insulation sleeve, and FIG. 5 is a cross-sectional view showing the structure around the second heat insulation sleeve.

  As shown in FIG. 4, the first heat insulating sleeve 64 has a cylindrical main body portion 64a that fits into an end portion 41b having a smaller diameter than the central portion 41a of the heating roller 41, and a radial direction from one end portion of the main body portion 64a. And a flange portion 64b protruding outward. The first heat insulating sleeve 64 protrudes outward from both end surfaces 60 a and 60 b of the first bearing 60 when both ends of the first heat insulating sleeve 64 are attached to the end 41 b of the heating roller 41. Further, at this time, the flange portion 64b is arranged at a position facing the inner end surface 60a of the first bearing 60, so that even if the heating roller 41 expands in the axial direction, the first heat insulating sleeve 64 is The first bearing 60 is not displaced.

  The length of the first heat insulating sleeve 64 in the axial direction, the amount of protrusion from the first bearing 60, and the initial attachment position to the end 41b of the heating roller 41 take into account the expansion / contraction state of the heating roller 41. It may be determined appropriately by experiment or simulation. In addition, the material of the first heat insulating sleeve 64 may be a conductive material or an insulator.

  Further, the above-described gear G is fixed to the outside of the end portion 41b of the heating roller 41 where the first heat insulating sleeve 64 is attached. Then, on the inner end face of the gear G, a restricting portion Ga that restricts the displacement of the first bearing 60 outward in the axial direction is formed so as to protrude toward the first bearing 60 side. Further, the axial displacement of the first heat insulating sleeve 64 is restricted by the step surface between the central portion 41 a and the end portion 41 b of the heating roller 41. Therefore, in the structure around the gear G, the first heat insulating sleeve 64 has a structure that hardly deviates with respect to the first bearing 60.

  As shown in FIG. 5, the second heat insulating sleeve 65 is formed of an insulator, and has a cylindrical main body 65 a that fits into the end 41 b of the heating roller 41, and a radial direction from one end of the main body 65 a. A flange portion 65b that protrudes outward is mainly provided. Furthermore, the second heat insulating sleeve 65 includes a cover portion 65c that protrudes radially inward from the end opposite to the flange portion 65b. And the outer peripheral surface 65d used as the site | part along the inner peripheral surface of the 1st bearing 60 of this 2nd heat insulation sleeve 65 protrudes toward the axial direction outer side from the both end surfaces 60a and 60b of the 1st bearing 60.

  The length of the second heat insulating sleeve 65 in the axial direction, the amount of protrusion from the first bearing 60, and the initial attachment position to the end 41b of the heating roller 41 take into account the expansion / contraction state of the heating roller 41. It may be determined appropriately by experiment or simulation. For example, as an example of the amount of protrusion from the first bearing 60, a form in which the protruding amount X1 inward in the axial direction is 2 mm and the protruding amount X2 in the axially outward direction is 0.1 mm at room temperature. .

  The cover portion 65 c of the second heat insulating sleeve 65 covers the end surface 41 c of the heating roller 41 by being formed to protrude radially inward from the inner surface of the end portion 41 b of the heating roller 41. As a result, even if the distance between the end surface 41c of the heating roller 41 and the second electrode 67 disposed opposite to the end surface 41c is reduced, it is possible to prevent the electric discharge generated therebetween.

  Further, the second conductive portion 68 disposed to face the outer peripheral surface 41d of the heating roller 41 is a distance L longer than the thickness D of the main body portion 65a of the second heat insulating sleeve 65 from the outer peripheral surface 41d of the heating roller 41. It is arrange | positioned so that it may leave only. Here, the distance L refers to the distance from the outer peripheral surface 41 d of the heating roller 41 to the second conductive portion 68 in the radial direction of the heating roller 41. In addition, the thickness D of the main body portion 65 a of the second heat insulating sleeve 65 refers to the thickness of the main body portion 65 a in the radial direction of the second heat insulating sleeve 65.

Next, the operation of the second heat insulating sleeve 65 will be described.
When the heating roller 41 expands and contracts in the axial direction due to the influence of heat, the second heat insulating sleeve 65 shown in FIG. 5 moves in the axial direction together with the end portion 41 b of the heating roller 41. At this time, the relative position between the first bearing 60 and the second heat insulating sleeve 65 changes. However, since the outer peripheral surface 65d of the second heat insulating sleeve 65 protrudes on both sides of the first bearing 60, the second The heat insulating sleeve 65 is always in contact with the entire width of the first bearing 60. That is, the contact area between the second heat insulating sleeve 65 and the first bearing 60 is always kept constant. In addition, as for the 1st heat insulation sleeve 64, since the relative position of the 1st bearing 60 and the 1st heat insulation sleeve 64 does not shift | deviate by gear G etc. as mentioned above, the contact area is always kept constant.

Next, the relationship between the heating roller 41 and the second conductive portion 68 when the second heat insulating sleeve 65 is melted by heat will be described.
As shown in FIG. 5, if the second heat insulating sleeve 65 is melted due to an abnormal temperature rise of the end portion 41 b of the heating roller 41, the heating roller 41 is not supported by the second heat insulating sleeve 65. 41 becomes movable in the radial direction. However, since the movement of the heating roller 41 is regulated by the inner peripheral surface of the first bearing 60, the maximum distance that the heating roller 41 can move in the radial direction is the thickness D of the main body portion 65a of the second heat insulating sleeve 65. The distance of minutes. Therefore, even if the heating roller 41 rattles in the radial direction in this way, the second distance L is separated from the outer peripheral surface 41d of the heating roller 41 by a distance L longer than the thickness D of the main body portion 65a of the second heat insulating sleeve 65. The outer peripheral surface 41 d of the heating roller 41 does not contact the conductive portion 68.

According to the above, the following effects can be obtained in the present embodiment.
Since the outer peripheral surface 65d of the second heat insulating sleeve 65 protrudes from both end surfaces 60a and 60b of the first bearing 60, the second heat insulating sleeve 65 is always attached to the second heat insulating sleeve 65 even when the heating roller 41 expands and contracts due to the influence of heat. The entire inner surface of the one bearing 60 can be kept in contact. That is, since the decrease in the contact area between the second heat insulating sleeve 65 and the first bearing 60 can be suppressed, the wear of the second heat insulating sleeve 65 can be suppressed and the decrease in the strength of the second heat insulating sleeve 65 can be suppressed. .

Since the second heat insulating sleeve 65 is formed of an insulator and covers the end surface 41c of the heating roller 41 with the cover portion 65c, the second electrode 67 is brought closer to the end surface 41c side, and the fixing device 18 is reduced in size. be able to.
Since the second conductive portion 68 is separated from the outer peripheral surface 41d of the heating roller 41 by a distance greater than the thickness D of the main body portion 65a of the second heat insulating sleeve 65, even if the second heat insulating sleeve 65 is melted. Further, it is possible to prevent a short circuit due to contact between the heating roller 41 and the second conductive portion 68.

The present invention is not limited to the first embodiment, and can be used in various forms as exemplified below.
In the first embodiment, two types of heat insulating sleeves such as the first heat insulating sleeve 64 and the second heat insulating sleeve 65 are provided at each end of the heating roller 41, but the present invention is not limited to this. Absent. For example, the first heat insulating sleeve 64 is provided at both ends of the heating roller 41, and in the structure on the opposite side of the gear G, the outer peripheral surface of the main body 64 of the first heat insulating sleeve 64 is the both end surfaces 60 a and 60 b of the first bearing 60. You may make it protrude from. In this case, the number of parts can be reduced.

  In the first embodiment, the second conductive portion 68 is disposed inside the housing 62 and is separated from the outer peripheral surface 41d of the opposed heating roller 41 by a predetermined distance. However, the present invention is not limited to this. is not. For example, as shown in FIG. 6, the second conductive portion 68 may be disposed outside the housing 62 ′, and the outer surface of the second conductive portion 68 may be covered with a cover 69. According to this, even if the second heat insulating sleeve 65 is melted, the heating roller 41 can only come into contact with the second conductive portion 68 outside the housing 62 ′ only by rattling in the housing 62 ′. Absent. Furthermore, even if the first bearing 60 is formed of resin and the first bearing 60 is melted together with the second heat insulating sleeve 65, the contact between the second conductive portion 68 and the heating roller 41 is as follows. It is reliably prevented by the housing 62 '. Therefore, according to this structure, a short circuit due to contact between the heating roller 41 and the second conductive portion 68 can be reliably prevented by the housing 62 '. In addition, since the outer side of the second conductive portion 68 is covered with the cover 69, it is possible to suppress problems due to the influence of dust and the like.

[Second Embodiment]
Next, a second embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In addition, since this embodiment changes a part of the 1st heat insulation sleeve 64 which concerns on above-described 1st Embodiment, the same code | symbol is attached | subjected about the component similar to 1st Embodiment. The description will be omitted. In the drawings to be referred to, FIG. 7 is a cross-sectional view showing a first heat insulating sleeve according to the second embodiment.

  As shown in FIG. 7, the third heat insulating sleeve 64 ′ according to the second embodiment includes a main body portion 64a similar to the first heat insulating sleeve 64 according to the first embodiment, and one end of the main body portion 64a. The extension part 64c integrally formed in the part is provided. And this extension part 64c is the surface of the heating roller 41 so as to extend inward in the axial direction from the step surface 41e between the end part 41b and the central part 41a of the heating roller 41 and cover a part of the central part 41a. It is formed along.

According to the above, the following effects can be obtained in the second embodiment.
Since the extension portion 64c of the third heat insulating sleeve 64 ′ extends inward in the axial direction from the step surface 41e of the heating roller 41, the first bearing 60 can be moved toward the step surface 41e. For this reason, the third heat insulating sleeve 64 ′ and the tip end surface of the end portion 41b of the heating roller 41 can be moved inward as much as the first bearing 60 is moved toward the stepped surface 41e. It can be miniaturized in the direction.

The present invention is not limited to the second embodiment, and can be used in various forms as exemplified below.
In 2nd Embodiment, although the extension part 64c was provided instead of the flange part 64b of the 1st heat insulation sleeve 64 which concerns on 1st Embodiment, this invention is not limited to this. For example, instead of the flange portion 65b of the second heat insulating sleeve 65 according to the first embodiment, an extension portion 64c may be provided.

The present invention is not limited to the above-described embodiments, and can be used in various forms as exemplified below.
In each of the above embodiments, the present invention is applied to the laser printer 1, but the present invention is not limited to this, and the present invention may be applied to other image forming apparatuses such as a copying machine and a multifunction machine.

In each of the above embodiments, the transfer roller 30 is used as an example of the transfer unit. However, the present invention is not limited to this, and a non-contact type, for example, may be used.
In each of the embodiments, the paper 3 such as a thick paper, a postcard, and a thin paper is used as an example of the recording sheet. However, the present invention is not limited to this, and may be an OHP sheet, for example.

In each of the above embodiments, the tension spring S is employed as an example of the urging means. However, the present invention is not limited to this, and may be, for example, a push spring, a torsion spring, or the like.
In each of the above embodiments, the halogen heater HH is adopted as an example of the heat source. However, the present invention is not limited to this, and for example, an induction heating type IH (Induction Heating) heater or a heating resistor may be adopted.

  In each of the embodiments, the toner is used as an example of the developer, the developing cartridge 28 is used as an example of the developing unit, the scanner unit 16 is used as an example of the exposure device, and the photosensitive drum 27 is used as an example of the photoconductor. Is not to be done. That is, it goes without saying that materials and structures can be changed as appropriate without departing from the spirit of the present invention.

1 is a side cross-sectional view showing a first embodiment of a laser printer as an example of an image forming apparatus of the present invention. It is a schematic block diagram which shows the relationship of each component which comprises the fixing device of the laser printer shown in FIG. It is a side view which shows the relationship of each component which comprises the fixing device of the laser printer shown in FIG. It is sectional drawing which shows the structure around a 1st heat insulation sleeve. It is sectional drawing which shows the structure around the 2nd heat insulation sleeve. It is sectional drawing which shows the form which provided the 2nd electroconductive part in the outer side of the housing | casing. It is sectional drawing which shows the 1st heat insulation sleeve which concerns on 2nd Embodiment.

Explanation of symbols

1 Laser printer (image forming device)
3 paper (recording sheet)
16 Scanner unit (exposure device)
18 Fixing Device 27 Photosensitive Drum (Photoconductor)
28 Developing cartridge (developing means)
30 Transfer roller (transfer means)
41 Heating roller 41a Central portion 41b End portion 41c End surface 41d Outer peripheral surface 41e Stepped surface 42 Pressure roller 42a Rotating shaft 60 First bearing 60a End surface 62 Housing 63 Pressure arm 64 First heat insulating sleeve 64a Body portion 64b Flange portion 65 First 2 heat insulation sleeve 65a body part 65b flange part 65c cover part 66 1st electrode 67 2nd electrode 67a connection part 67b 1st electroconductive part 68 2nd electroconductive part (power supply member)
69 Cover HH Halogen heater (heat source)

Claims (6)

A fixing device for thermally fixing the developer image to a recording sheet onto which the developer image has been transferred;
A heating roller heated by a heat source;
A pressure roller pressed against the heating roller;
A bearing that rotatably supports an end of the heating roller;
A heat insulating sleeve interposed between an end of the heating roller and the bearing;
A housing that holds the heating roller and the pressure roller;
A portion of the heat insulating sleeve along the inner peripheral surface of the bearing protrudes on both sides of the bearing in the axial direction of the heating roller. An electrode connected to the heat source;
A power supply member for supplying power to the electrode,
The electrode is disposed to face the end surface of the heating roller,
The fixing device according to claim 1, wherein the heat insulating sleeve is formed of an insulator and covers an end surface of the heating roller.   The power supply member is disposed so as to face the outer peripheral surface of the heating roller, and is disposed so as to be separated from the outer peripheral surface of the heating roller by a distance longer than the thickness of the heat insulating sleeve. The fixing device according to claim 1 or 2. The power supply member is disposed outside the housing,
The fixing device according to claim 1, wherein an outer surface of the power supply member is covered with a cover. The heating roller has a central portion sandwiched between both ends and a larger diameter than the both ends,
The fixing device according to claim 1, wherein the heat insulating sleeve extends inward from a stepped surface between both end portions and a central portion of the heating roller. An image forming apparatus for forming an image on a recording sheet,
An exposure device that scans a laser beam in accordance with the input image signal;
A photoconductor on which an electrostatic latent image is formed by scanning laser light with the exposure device;
Developing means for supplying a developer to the photoreceptor;
Transfer means for transferring a developer image formed with the developer onto the recording sheet;
An image forming apparatus comprising: the fixing device according to claim 1.

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