JP2008310155A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of surely preventing a gear from falling off a fixing roller, and also, controlling the movement of the fixing roller in an axial direction, to attain improvement in the positional accuracy of the fixing roller and stabilization of the driving torque. <P>SOLUTION: The fixing device includes: the rotationally driven fixing roller 2; and a pressure roller as a follower rotating roller in contact with the fixing roller 2, wherein the gear 7 is fitted on the outer periphery of one axial end of the fixing roller 2, and also, a protrusion 7a protruded on the inner peripheral surface of the gear 7 is fitted into a recessed groove 2a formed on the outer periphery of one axial end of the fixing roller 2. At least the driving-side end faces of the protrusion 7a of the gear 7 and the recessed groove 2a of the fixing roller 2 are inclined in the driving direction against the axial direction of the fixing roller 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing process including a fixing roller that rotates by receiving a drive from a gear attached to one end in an axial direction, and a pressure roller that rotates in contact with the fixing roller.

  2. Description of the Related Art Image forming apparatuses such as copiers and printers that form an image through an electrophotographic process are provided with a fixing device for fixing a toner image transferred from an image carrier such as a photosensitive drum to a sheet. As this fixing device, a two-roller system including a fixing roller and a pressure roller rotating in contact with each other and a belt system using an endless fixing belt as a heating member are known.

  For example, in a fixing device that employs a two-roller system, the fixing roller is rotated by receiving a drive from a gear attached to the outer periphery of one end in the axial direction, and the pressure roller is pressed by the fixing roller to be driven and rotated. As the paper passes through the fixing nip formed between the rollers, the toner image transferred onto the paper is heated and pressurized, and the toner image is fixed on the paper as a permanent image.

  In such a fixing device, as shown in FIG. 8, a concave groove (key groove) 102a is formed on the outer peripheral portion of one end of the fixing roller 102, and a convex portion (key) 107a is formed on the inner peripheral surface of the gear 107. The gear 107 is attached to the fixing roller 102 by fitting the gear 107 to the outer periphery of one end of the fixing roller 102 while fitting the convex portion 107a of the gear 107 into the concave groove 102a formed in the fixing roller 102. ing.

  By the way, conventionally, the snap ring fitted on the outer periphery of the fixing roller prevents the gear from coming off from the fixing roller, and the fixing roller has a stopper means such as a thrust bearing or a rib provided at both axial ends of the fixing roller. A configuration that regulates axial backlash is employed.

  Japanese Patent Application Laid-Open No. 2004-228867 proposes partially reinforcing the gear fitting portion of the fixing roller for the purpose of preventing damage to the gear fitting portion of the fixing roller.

Further, Patent Documents 2 and 3 propose that a T-shaped or L-shaped groove (locking groove) is formed on the outer periphery of the fixing roller in order to prevent the gear from coming off from the fixing roller.
JP-A-8-248798 JP-A-8-160793 Japanese Patent Laid-Open No. 5-188817

  By the way, since the fixing roller is provided with a heating source such as a heater, it is necessary to secure a large axial play in the fixing roller in consideration of thermal expansion. There was a problem of lowering.

  In the conventional method of regulating the axial backlash of the fixing roller by means of stoppers such as thrust bearings and ribs provided at both ends in the axial direction of the fixing roller, the stopper means such as a non-sliding rib and the end face of the gear However, there is a problem in that the driving torque varies greatly depending on whether or not both are in sliding contact.

  In the conventional gear coupling structure shown in FIG. 8, the gear 107 is a spur gear, and the convex portion 107 a on the gear 107 side and the concave groove 102 a on the fixing roller 102 side are formed in parallel to the axial direction of the fixing roller 102. Therefore, there is a problem that the gear 107 may come off from the fixing roller 102 and the axial movement of the fixing roller 102 cannot be restricted.

  Therefore, a method is considered in which the gear is composed of a helical gear to generate a thrust force, and the axial movement of the fixing roller is regulated by this thrust force, but the thrust force is excessive. In such a case, there arises a problem that the snap ring fitted to the fixing roller is detached or the driving torque is significantly increased.

  Further, the configuration proposed in Patent Document 1 cannot solve the above problem. In the configurations proposed in Patent Documents 2 and 3, although the gear is prevented from coming off, the axial movement of the fixing roller is restricted. There is a problem that you can't.

  The present invention has been made in view of the above problems, and the object of the present invention is to reliably prevent the gear from coming off from the fixing roller and to restrict the axial movement of the fixing roller to thereby improve the positional accuracy of the fixing roller. An object of the present invention is to provide a fixing device capable of improving and stabilizing the driving torque.

  In order to achieve the above object, the invention described in claim 1 is provided with a fixing roller that is rotationally driven and a pressure roller that rotates in contact with the fixing roller, and a gear is fitted to the outer periphery of one end in the axial direction of the fixing roller. In addition, in a fixing device in which a convex portion protruding from the inner peripheral surface of the gear is fitted into a concave groove formed on the outer periphery of one end in the axial direction of the fixing roller, the convex portion of the gear and the fixing roller It is characterized in that at least the driving side end face of the concave groove is inclined with respect to the axial direction of the fixing roller.

  According to a second aspect of the present invention, in the first aspect of the invention, at least the driving side end surfaces of the convex portion of the gear and the concave groove of the fixing roller are inclined in the driving direction with respect to the axial direction of the fixing roller. It is characterized by.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a retaining rib is projected from the end surface of the gear on the side opposite to the fixing roller.

  According to the first aspect of the present invention, since at least the driving side end surfaces of the gear convex portion and the concave groove of the fixing roller are inclined with respect to the axial direction of the fixing roller, the gear is reliably prevented from coming off from the fixing roller. In addition, the component force of the driving reaction force acts on the fixing roller as an axial thrust force, so that the fixing roller is moved toward one end in the axial direction to restrict axial movement, and its positional accuracy is improved. .

  According to the second aspect of the present invention, since at least the driving side end surfaces of the gear convex portion and the concave groove of the fixing roller are inclined in the driving direction with respect to the axial direction of the fixing roller, the fixing roller has an anti-gear direction. The fixing roller is moved toward the non-gear side due to the thrust force, and the end face of the gear is not selectively slidably contacted with the stopper means on the image forming apparatus side, the driving torque is kept low, and the torque fluctuation is suppressed. This stabilizes the driving torque.

  According to the third aspect of the present invention, since the retaining rib is protruded on the end surface of the gear on the side opposite to the fixing roller, even if the gear moves relative to the fixing roller, it is formed on the end surface. Since the rib is in contact with the main body frame or the like and the axial movement of the gear is restricted, the gear is prevented from coming off from the fixing roller.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a side sectional view of a fixing device according to the present invention, FIG. 2 is a front sectional view showing a support structure of a fixing roller of an identification fixing device, and FIG. 3 is a plan view of a gear and a fixing roller end before binding. 4 is a plan view of an end portion of the fixing roller to which the gear is bound, FIG. 5 is a cross-sectional view taken along line AA in FIG. 4, and FIG. 6 is a cross-sectional view taken along line BB in FIG.

  A fixing device 1 shown in FIG. 1 fixes a toner image transferred onto a sheet in a transfer process, and includes a fixing roller 2 that is rotationally driven and a pressure roller 3 that rotates in contact with the fixing roller 2. The toner image carried on the paper is heated and pressed in the process of passing through the fixing nip formed between the fixing roller 2 and the pressure roller 3 and fixed as a permanent image on the paper. Is done. The sheet on which the toner image is fixed is discharged out of the fixing device 1, discharged to the outside of the apparatus through a conveyance path (not shown), and stacked on a discharge tray (not shown).

  Here, as shown in FIG. 2, the fixing roller 2 is formed of a cylindrical member, and as shown in FIG. 1, a heat source 10 such as a halogen heater is disposed at the center thereof. One end of the fixing roller 2 in the axial direction (left end in FIG. 2) is rotatably supported on the frame 5 by the thrust bearing 4, and the other end (right end in FIG. 2) is rotatably supported by the frame 5 by the bearing 6. Yes. A gear 7 is attached to the outer periphery of the end of the fixing roller 2 that protrudes outward from the bearing 6, and when a driving force is transmitted from a motor (not shown) to the gear 7, the fixing roller together with the gear 7 is fixed. 1 is rotated at a predetermined speed, and the pressure roller 3 shown in FIG. 1 pressed against the fixing roller 2 is driven to rotate to perform a required fixing process.

  By the way, a retaining rib 8 protrudes from the end surface of the gear 7 on the fixing roller 2 side (the right end surface in FIG. 2). In a normal operation state, the retaining rib 8 and the rib 9 of the main body frame are provided. Is formed with an axial gap δ shown in the figure.

  Next, the coupling structure of the gear 7 to the fixing roller 2 will be described with reference to FIGS.

  As shown in FIG. 3, a concave groove 2 a having a constant width is formed on the outer periphery of the end portion of the fixing roller 2 so as to be inclined by a predetermined angle α on the driving direction side with respect to the axial direction of the fixing roller 2. Further, a convex portion 7 a having a constant width (actually a key separate from the gear 7) is formed on the inner diameter portion of the gear 7 in the axial direction of the fixing roller 2 in the same manner as the concave groove 2 a formed in the fixing roller 2. On the other hand, it is inclined to the drive direction side by an angle α.

  Thus, as shown in FIGS. 4 to 6, the gear 7 has the inner diameter portion thereof fixed to the fixing roller 2 in a state where the convex portion 7 a provided on the inner diameter portion is fitted in the concave groove 2 a of the fixing roller 2. It is bound to the fixing roller 2 by being fitted to the outer periphery of the end portion.

  In the above state, when the gear 7 is driven to rotate, a reaction force F of the driving force is applied to the driving-side end surface (contact surface) of the convex portion 7 a of the gear 7 and the concave groove 2 a of the fixing roller 2. The axial component Fx of the reaction force F acts on the gear 7 in a direction that prevents the gear 7 from coming off from the fixing roller 2 (direction in which the gear 7 is pressed against the fixing roller 2). Further, the fixing roller 2 is pressed to the counter gear side (left direction in FIG. 2) by the axial component Fx of the reaction force F, and the counter gear side end surface of the fixing roller 2 is received by the thrust bearing 4.

  In this embodiment, since the convex portion 7a of the gear 7 and the concave groove 2a of the fixing roller 2 are inclined in the driving direction with respect to the axial direction of the fixing roller 2, the gear 7 is reliably prevented from coming off from the fixing roller 2. In addition, since the component force Fx of the driving reaction force F acts on the fixing roller 2 as an axial thrust force, the fixing roller 2 is brought close to the non-gear side to restrict axial movement, and its positional accuracy Is increased. Further, since the fixing roller 2 is moved toward the non-gear side and the axial movement is restricted, the end surface of the gear 7 is not selectively slidably contacted with the rib 9 of the main body freem, and the driving torque is kept low. The fluctuation is suppressed and the driving torque is stabilized.

  In this embodiment, since the retaining rib 8 protrudes from the end surface of the gear 7 on the side opposite to the fixing roller, even if the gear 7 moves relative to the fixing roller 2, it is formed on the end surface. Since the stopping rib 8 abuts against the rib 9 of the main body frame and the axial movement of the gear 7 is restricted, the gear 7 is reliably prevented from coming off from the fixing roller 2.

  In order to obtain the above effect, at least the driving side end surfaces of the convex portion 7a of the gear 7 and the concave groove 2a of the fixing roller 2 may be inclined with respect to the axial direction of the fixing roller 2. As shown in FIG. 7, only the driving side end surface 2a-1 of the concave groove 2a of the fixing roller 2 is inclined with respect to the axial direction of the fixing roller 2, and the non-driving side end surface 2a-2 is the shaft of the fixing roller 2 as usual. The same effect as described above can be obtained even when the surface is parallel to the direction. Further, the gear 7 and the convex portion 7a can be integrally formed by making the width of the gear 7a narrower than the entrance width of the groove 2a provided in the fixing roller 2 in the same manner as the inclination angle α of the driving side end face. It becomes.

1 is a side sectional view of a fixing device according to the present invention. FIG. 3 is a front sectional view showing a support structure of a fixing roller of the fixing device according to the present invention. FIG. 3 is a plan view of a gear and a fixing roller end portion before binding of the fixing device according to the present invention. FIG. 4 is a plan view of an end portion of a fixing roller to which a gear of the fixing device according to the present invention is bound. It is the sectional view on the AA line of FIG. It is the BB sectional view taken on the line of FIG. FIG. 9 is a plan view of an end portion of a fixing roller showing a modification of the present invention. FIG. 6 is a plan view of a gear and a fixing roller end portion before binding of a conventional fixing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing roller 2a Concave groove 2a-1 Concave groove driving side end surface 2a-2 Concave groove non-driving side end surface 3 Pressure roller 4 Thrust bearing 5 Frame 6 Bearing 7 Gear 7a Gear convex part 8 Retaining rib 9 Body frame rib 10 Heat source

Claims (3)

A fixing roller that is driven to rotate, and a pressure roller that rotates in contact with the fixing roller. A gear is fitted to the outer periphery of one end in the axial direction of the fixing roller, and a convex portion that protrudes from the inner peripheral surface of the gear. In a fixing device formed by fitting in a groove formed on the outer periphery of one end in the axial direction of the fixing roller,
The fixing device according to claim 1, wherein at least a driving side end surface of the convex portion of the gear and the concave groove of the fixing roller is inclined with respect to the axial direction of the fixing roller.   2. The fixing device according to claim 1, wherein at least a driving side end surface of the convex portion of the gear and the concave groove of the fixing roller is inclined in the driving direction with respect to the axial direction of the fixing roller. The fixing device according to claim 1, wherein a retaining rib protrudes from an end surface of the gear on the side opposite to the fixing roller.

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