JP4673665B2 - Fixing device - Google Patents

Description

The present invention relates to a fixing device disposed in an electrophotographic image forming apparatus such as a copying machine, a laser printer, or a facsimile, and more particularly, a fixing device including a heat roller heated by a heat member such as a halogen lamp. About.

A pair of side walls spaced from each other, a heat roller rotatably supported through a bearing between the side walls, and a hollow tube, and passing through the center of the heat roller A fixing device including a heater member arranged so as to extend is well known in, for example, Japanese Patent Application Laid-Open No. H10-228707. An example of such a fixing device will be described more specifically with reference to FIGS.

The illustrated fixing device 2 disposed in the main body of the image forming apparatus (not illustrated) includes a pair of side walls 4 and 6 disposed at a distance from each other, and bearings 8 and 10 between the side walls 4 and 6. A heat roller (fixing roller) 12 supported rotatably via the heater, a heater member 14, and cover members 16 and 18 mounted on the outer sides of the side walls 4 and 6, respectively. The side walls 4 and 6 are formed from a metal plate. The heat roller 12 is formed from a hollow tube. More precisely, a metal hollow tube and a heat-resistant rubber layer attached to the outer peripheral surface of the hollow tube are provided. Cover members 16 and 18 formed of appropriate synthetic resin are arranged so as to cover both ends of the heat roller 12 with a gap therebetween. The heater member 14 is made of, for example, a halogen lamp, extends through the center portion of the heat roller 12, and both end portions are supported by cover members 16 and 18, respectively. One end portion (right end portion in FIG. 5) of the heat roller 12 is protruded to the outside of one side wall 14 disposed on the right side in FIG. 5, and the driven gear 20 is provided at the one end portion of the heat roller 12. It arrange | positions so that it can rotate integrally. The driven gear 20 formed of an appropriate synthetic resin includes a ring plate-like web 24 having both surfaces orthogonal to the axis of the driven gear 20 (the axis common to the heat roller 12), and the one cover member 16 are arranged to face each other with an interval. A cooling fan 22 composed of an axial fan is disposed outside the one cover member 16 (to the right in FIGS. 5 and 6). The cooling fan 22 is disposed in a main body of an image forming apparatus (not shown) in which the fixing device 2 is disposed. The cooling fan 22 discharges air around the fixing device 2 and air in the apparatus main body to the outside. It has the function of not excessively increasing the ambient temperature in the body.

During fixing, the heater member 14 is energized and the heat roller 12 is heated from the inside. The cooling fan 22 is driven to rotate, and air flows from left to right in FIGS. 5 and 6. The heat roller 12 is formed of a hollow tube and is open at both ends. Between the one end of the heat roller 12 and the one cover member 16 and between the driven gear 20 and the one cover member 16, There is a gap that leads to the outside of the fixing device 2, and a through hole 18a is formed in the center of the other cover member 18, and the other end (left end in FIG. 5) of the heat roller 12 and the other cover. Due to the fact that the outside of the member 18 communicates with the outside through the through hole 18a, the air sucked by the cooling fan 22 flows as indicated by arrows in FIGS.

That is, in the fixing device 2, the air flows into the heat roller 12 through the through hole 18a of the other cover member 18 and the other end of the heat roller 12, and is discharged from one end of the heat roller 12. The heat roller 12 is discharged to the outside of the fixing device 2 through a gap between one end of the heat roller 12 and the one cover member 16 and a gap between the driven gear 20 and the one cover member 16.

As a result, the fixing device 2 has the following problems.
(1) As the air moves, heat moves in the heat roller 12 and is released to the outside, so that heat loss of the heat roller 12 increases and fixing efficiency decreases.
(2) As indicated by the temperature gradient line L1 in FIG. 5, the temperature in the heat roller 12 rises from the upstream to the downstream in the direction in which the air flows, and thus the direction in which the heat moves. As a result, the surface temperature distribution of the heat roller 12 becomes non-uniform, which may cause image defects.
(3) Moreover, since the molybdenum foil is used for the both-ends sealing part of the filament in the heater member 14 comprised from a halogen lamp, it was arrange | positioned in the downstream edge part from which the heat | fever in the heat roller 12 is discharged | emitted. If the temperature of the molybdenum foil rises excessively, the durability of the heater member 14 may be impaired, and the life may be shortened.
(4) Further, it is necessary to form the bearing 8 and the driven gear 20 disposed at the downstream end where the heat in the heat roller 12 is discharged from a material having higher heat resistance than usual, and the cost. It will be up.
JP 06-149107 A

The object of the present invention is to prevent the movement and non-uniformity of the temperature in the heat roller, thereby reducing the heat loss of the heat roller and improving the fixing efficiency, ensuring the durability of the heater member, and reducing the cost. It is an object of the present invention to provide a novel fixing device that makes it possible.

According to the present invention, a pair of side walls disposed at a distance from each other, a heat roller rotatably supported through a bearing between the side walls and formed from a hollow tube, A fixing device comprising: a cover member mounted on the outside of each side wall so as to cover both ends; and a heater member extending through the center portion of the heat roller and having both end portions supported by the cover member. In
One cover member is provided with a closing member that closes a gap between one end of the heat roller and the one cover member.
A fixing device is provided.
One end portion of the heat roller is projected to the outside of one side wall, and the one end portion is a driven gear having a ring-plate-shaped web so as to face the one cover member with a space therebetween. The arranged driven gear is arranged so that it can rotate integrally, and on one of the cover members, a cylindrical boss extending toward the driven gear is arranged on the same axis as the driven gear, The boss is fitted and supported by the boss so that the substantially cylindrical closure member cannot rotate relative to the boss and is movable in the axial direction. One side of the closure member is opposed to the one side. Between the inner surface of the cover member, spring means for urging the closing member toward the driven gear is disposed, and the other side surface of the closing member is rotated relative to the web of the driven gear by the spring means. It is preferred that it be pressed as possible.
A plurality of locking projections extending from the one side surface toward the inner side surface of the one cover member are formed on the one side surface of the closing member at intervals in the circumferential direction. A holding recess that extends in a direction opposite to the locking projection is disposed on the inner surface that is opposite to the locking projection, and the spring means has one end on each of the holding recesses. Each of the compression coil springs is fitted and locked to the corresponding locking protrusion disposed on the one side surface of the closing member. It is preferable.
An anti-rotation protrusion that extends radially outward is formed on the outer peripheral surface of the closing member, and an anti-rotation recess that extends radially outward on the inner peripheral surface of the boss disposed on the one cover member. It is preferable that the anti-rotation protrusion is fitted to the anti-rotation recess so as to be movable in the axial direction.

Hereinafter, an embodiment of a fixing device 100 configured according to the present invention will be described in detail with reference to FIGS. 1 to 4, substantially the same parts as those in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof is omitted.

1 to 4, in the fixing device 100 according to the present invention, a closing member 30 that closes a gap between one end of the heat roller 12 and the one cover member 16 is disposed on one cover member 16. It is important that A cylindrical boss 40 extending toward the driven gear 20 is disposed on one cover member 16 on the same axis as the driven gear 20. The substantially cylindrical closing member 30 is fitted and supported on the boss 40 so as not to be relatively rotatable and movable in the axial direction. Spring means for urging the closing member 30 toward the driven gear 20 between the one side surface 31 in the axial direction of the closing member 30 and the inner side surface 17 of the one cover member 16 facing the one side surface 31. In the embodiment, three compression coil springs 42 are disposed (only one compression coil spring 42 is shown in FIG. 2). The other axial side surface 32 of the closing member 30 is pressed against the web 24 of the driven gear 20 by each of the compression coil springs 42 so as to be relatively rotatable.

More specifically, the closing member 30 includes a cylindrical main body 33 and an annular protrusion 34 that extends radially inward from the axial end of the cylindrical main body 33 (the right end in FIG. 4) with a certain axial width. Are integrally formed. One side surface 31 of the closing member 30 is formed by an end surface in the axial direction of the cylindrical body 33 and an end surface in the axial direction of the annular protrusion 34 that continuously extend in a direction perpendicular to the axis of the closing member 30. The other side surface 32 of the closing member 30 is formed from the other end surface in the axial direction of the cylindrical body 33 extending in a direction perpendicular to the axis of the closing member 30. The one side 31 of the closing member 30 has a plurality of locking projections 35 extending in the axial direction from the one side 31 toward the inner side 17 of the one cover member 16, and in the embodiment, three pin-like lockings. The protrusions 35 are formed at intervals in the circumferential direction.

On the inner side surface 17 of one cover member 16, which is opposite to each of the locking projections 35, a holding recess 44 is provided that extends in the opposite direction to each of the locking projections 35. (Only one holding recess 44 is shown in FIG. 2). Each of the holding recesses 44 includes a circular inner peripheral surface having a constant diameter (a diameter larger than that of the compression coil spring 42). Since the bottom part and the inner peripheral surface of each holding recess 44 are continuous with the inner side surface 17 of one cover member 16, it can be said that they constitute a part of the inner side surface 17. One end of each compression coil spring 42 is inserted and held in the corresponding holding recess 44, and the other end is engaged with a corresponding locking protrusion 35 disposed on one side surface 31 of the closing member 30. Stopped. A detent 36 is formed on the outer peripheral surface of the closing member 30 so as to extend outward in the radial direction. Corresponding to this, an anti-rotation recess 46 extending outward in the radial direction is formed on the inner peripheral surface of the boss 40 disposed on one cover member 16. The closing member 30 is fitted so that the outer peripheral surface of the cylindrical main body 33 is movable in the axial direction with respect to the inner peripheral surface of the boss 40 in the one cover member 16, and the anti-rotation protrusion 36 is an anti-rotation recess of the boss 40. By being fitted to 46 so as to be movable in the axial direction, the boss 40 is fitted and supported so as not to be relatively rotatable and movable in the axial direction.

Referring to FIGS. 1 and 2, during fixing, heater member 14 is energized and heat roller 12 is heated from the inside. The cooling fan 22 is driven to rotate, and air flows from left to right in FIGS. 1 and 2. In the fixing device 100 according to the present invention, the cover member 16 on one side is provided with a closing member 30 that closes the gap between the one end of the heat roller 12 and the cover member 16 on the one side. There is no air flow. That is, the outer peripheral surface of the closing member 30 is fitted to the inner peripheral surface of the boss 40 in one cover member 16, and the annular other side surface 32 of the closing member 30 is driven by the driven coil 20 by each of the compression coil springs 42. Since the web 24 is pressed against the web 24 so as to be relatively rotatable, the one end portion of the heat roller 12 is substantially closed. As a result, the fixing device 100 according to the present invention achieves the following effects.
(1) Since heat does not move in the heat roller 12, heat loss of the heat roller 12 is reduced, and fixing efficiency is improved.
(2) The temperature inside the heat roller 12 is substantially constant in the axial direction as shown by the temperature gradient line L2 in FIG. 1, and the surface temperature distribution of the heat roller 12 becomes uniform, which may cause image defects. Is resolved.
(3) The temperature of the molybdenum foil used for the filament sealing portion in the heater member 14 is kept substantially the same at both ends of the heater member 14, and one of them does not rise excessively. Durability is ensured.
(4) Since the bearings 8 and 10 and the driven gear 20 disposed at both ends of the heat roller 12 can be formed of a normal heat-resistant material, the cost can be reduced.

1 is a cross-sectional view showing an embodiment of a fixing device configured according to the present invention. FIG. 2 is an enlarged cross-sectional view showing a right end portion of the fixing device shown in FIG. FIG. 3 is a view of the center portion of the cover member shown in FIG. 2 as viewed from the left in FIG. It is AA arrow sectional drawing of FIG. It is sectional drawing which shows an example of the conventional fixing device. FIG. 6 is an enlarged cross-sectional view illustrating a right end portion of the fixing device illustrated in FIG. 5.

Explanation of symbols

2, 100: fixing device 4, 6: side wall 8, 10: bearing 12: heat roller 14: heater member 16, 18: cover member 18a: through hole 20: driven gear 22: cooling fan 24: web 30: closing member 35: Locking projection 36: Anti-rotation projection 40: Boss 42: Compression coil spring 44: Holding recess 46: Anti-rotation recess

Claims (4)

A pair of side walls spaced apart from each other, a heat roller rotatably supported through a bearing between each of the side walls, and a side wall so as to cover both ends of the heat roller In a fixing device comprising a cover member mounted on each outer side, and a heater member extending through the center of the heat roller and having both ends supported by the cover member,
One cover member is provided with a closing member that closes a gap between one end of the heat roller and the one cover member.
A fixing device. One end portion of the heat roller is projected to the outside of one side wall, and the one end portion is a driven gear having a ring-plate-shaped web so as to face the one cover member with a space therebetween. The arranged driven gear is arranged so that it can rotate integrally, and on one of the cover members, a cylindrical boss extending toward the driven gear is arranged on the same axis as the driven gear, The boss is fitted and supported by the boss so that the substantially cylindrical closure member cannot rotate relative to the boss and is movable in the axial direction. One side of the closure member is opposed to the one side. Between the inner surface of the cover member, spring means for urging the closing member toward the driven gear is disposed, and the other side surface of the closing member is rotated relative to the web of the driven gear by the spring means. The fixing device according to claim 1, wherein the fixing device can be pressed. A plurality of locking projections extending from the one side surface toward the inner side surface of the one cover member are formed on the one side surface of the closing member at intervals in the circumferential direction. A holding recess that extends in a direction opposite to the locking projection is disposed on the inner surface that is opposite to the locking projection, and the spring means has one end on each of the holding recesses. Each of the compression coil springs is fitted and locked to the corresponding locking protrusion disposed on the one side surface of the closing member. The fixing device according to claim 2. An anti-rotation protrusion that extends radially outward is formed on the outer peripheral surface of the closing member, and an anti-rotation recess that extends radially outward on the inner peripheral surface of the boss disposed on the one cover member. The fixing device according to claim 3, wherein the anti-rotation protrusion is fitted to the anti-rotation recess so as to be movable in the axial direction.

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