JPH08101596A - Thermal roller fixing device - Google Patents

Abstract

PURPOSE: To eliminate friction between shafts of a heat resistant bush and a fixing roller, and to prevent generation of a noise and formation of a flaw, by providing the heat resistant bush fixed to the shaft of the fixing roller in between the fixing roller and the bearing. CONSTITUTION: The heat resistant bush 5 is put in the shaft 4 of the fixing roller and the heat resistant bush 5 is put in the inner ring of the ball bearing 6. The shaft 4 of the fixing roller is formed in a shape of D type by grinding. Moreover, the heat resistant bush 5 is composed with use of the heat resistive resin, and the inside shape is formed in the D type so as to fit on the shaft 4 of the fixing roller and the outside shape is formed in the state of a ring type so as to fit on the inner ring of the ball bearing 6. Then, the heat resistant bush 5 provided with the D type inside shape is fit on the shaft 4 of the fixing roller provided with the D type shape and put in the ball bearing 6 as the bearing, by this way, at the rotating time of the fixing roller 8, the heat resistant bush 5 is rotated with the shaft 4 of the fixing roller 5 without the rotary slip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to a fixing device for an image forming apparatus such as a facsimile. More specifically, the present invention relates to a heat roller fixing device of an image forming apparatus that performs fixing by passing a transfer material carrying an unfixed toner image between a pair of fixing rollers.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine or a printer using this type of electrophotographic system, a corona discharger such as an optical section, a photosensitive drum, a charger, a transfer unit, a static eliminator,
It is composed of a developing device, a cleaner, a fixing device, a paper feeding / conveying unit and the like. In the process around the photoconductor drum, first, the surface of the photoconductor is uniformly charged by a charger in a dark place. Next, light is applied to the photoconductor by the exposure device to remove the charged electric charge in the exposed part to form an electrostatic latent image. In the developing device, the toner charged to the opposite polarity to the electrostatic latent image is superposed on the electrostatic latent image, visualized and sent to the transfer device. In the transfer device, the polarity opposite to the charge polarity of the toner is applied from the back side of the transfer material. Is applied to the transfer material, and the toner image is transferred to the transfer material by electrostatic force. The latent image charges on the photoconductor drum after transfer are removed by a charge remover. Further, the residual toner remaining on the photosensitive drum without being transferred is removed by a cleaner. Next, the transfer material carrying the toner image is conveyed to the fixing device. The fixing device of the image forming apparatus is composed of a heating roller having a built-in heat source and a pressure roller in pressure contact with the heating roller, and these are generally called fixing rollers. The heating roll
A transfer material carrying an unfixed toner image is passed through a contact portion between the roller and the pressure roller, that is, a nip portion, and fixing is performed by heat and pressure. At this time, it is an essential condition that the heating roller and the pressure roller are maintained at a high temperature. Therefore, in order to prevent heat from being released from the shaft portions at both ends of the heating roller and the pressure roller, as shown in FIG. 5, a bush-shaped bush is formed between the shaft 1 of each roller and the bearing 2. The heat insulating member 3 was interposed.

[0003]

However, in the structure in which the bush-shaped heat insulating member is interposed between the shaft and the bearing of the fixing roller pair consisting of the heating roller and the pressure roller, each roller rotates. Then, due to a gap due to a difference in thermal expansion between the shaft of each roller, the heat insulating member, and the bearing, and a dimensional error, slip occurs between the shaft and the heat insulating member, and friction occurs. Not only will this cause damage, but it will also cause damage to the shaft and the heat insulating member. When such a scratch occurs,
The gap between the shaft and the heat insulating member is further amplified, and it becomes difficult to maintain stable rotation of each roller. Furthermore, the scratches on the shaft require unintentional replacement of the rollers themselves without depending on the aging of the functions of the rollers (deterioration of surface properties of the rollers, etc.), leading to an increase in cost. Further, due to the deformation of the shaft and the difficulty of fitting, it becomes difficult to reuse each roller, the reuse rate decreases, and it becomes out of the trend of recycling in recent years.

[0004]

In order to solve the above problems, the present invention provides a heat roller fixing device for heating and fixing by passing a transfer material carrying an unfixed toner image between a pair of fixing rollers. A heat-resistant bush is disposed between the shaft and the bearing of at least one of the fixing rollers of the fixing roller so as to be fixed to the shaft, and the heat-resistant bush is not rotated with respect to the shaft.

[0005]

According to the fixing device constructed as described above, the heat-resistant bush is provided between the shaft and the bearing of the fixing roller so as to be fixed to the shaft of the roller. The bush also rotates without rotating slip with the axis of the roller.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 are a side view and a cross-sectional view around a fixing roller shaft. A heat resistant bush 5 is fitted into the shaft 4 of the fixing roller, and the heat resistant bush 5 is fitted into the inner ring of the ball bearing 6. The heat resistant bush 5 is fixed by a retaining ring 7 so as not to shift in the axial direction. The shaft 4 of the fixing roller is ground and formed into a D shape. Here, in the conventional fixing roller shaft, the surface of the roller shaft is ground to a roughness of about 1.6a in order to suppress friction between the roller shaft and the bearing or between the roller shaft and the bush. However, in the present invention, since the roller shaft and the bearing or the roller shaft and the bush are fixed so as not to cause rotational slip, a rough state of about 1.6a to 6.3a is sufficient. . The heat-resistant bush 5 is made of heat-resistant resin, and has an inner shape of D shape for fitting with the shaft 4 of the fixing roller and an outer shape of a ring shape that fits with the inner ring of the ball bearing 6. To do. The heat resistant bush 5 has a brim shape for positioning in the thrust direction. If a material is selected such that the coefficient of thermal expansion of the shaft 4 of the fixing roller and the heat resistant bush 5 is smaller than that of the heat resistant bush, the shaft of the fixing roller 8 is heated when the fixing device is used. Due to the thermal expansion of the portion, the clearance between the heat resistant bush 5 and the shaft 4 of the fixing roller decreases. Further, at the time of designing, the fitting tolerance between the shaft 4 of the fixing roller and the heat resistant bush 5 can be made large, and the surface of the shaft 4 of the fixing roller can be made rough. Therefore, at the time of assembly, Improves its assemblability. By fitting the heat-resistant bush 5 having the D-shape on the inside to the shaft 4 of the D-shaped fixing roller and fitting it into the ball bearing 6 which is a bearing, the heat-resistant bush is rotated when the fixing roller 8 is rotated. Reference numeral 5 rotates without rotating slip with the shaft 4 of the fixing roller. (It does not rotate with respect to the shaft 4 of the fixing roller.) Therefore, since no friction is generated between the shaft 4 of the fixing roller and the heat resistant bush 5, the shaft 4 of the fixing roller and the heat resistant bush 5 None of the bushes 5 is scratched, and no abnormal noise due to rubbing occurs. Further, since the shaft portion is not damaged or deformed, if the fluorine coating on the surface of the fixing roller 8 is deteriorated, it can be easily reused by once removing it, peeling the film, and recoating. , Also contribute to recycling.

Further, as shown in FIGS. 3 and 4, if the heat resistant bush is a drive gear and heat resistant bush 9 integrated with the drive gear of the fixing roller, the number of parts can be reduced. As described above, in the present embodiment, the inside of the shaft portion and the heat-resistant bush is a D-shaped detent, but it is applied to a spline-shaped detent, an oval detent, and a detent with a key and a key groove. It is possible. By installing these detents between the heat insulating bush and the inner ring of the ball bearing, the inner ring of the ball bearing and the heat resistant bush also rotate together without slipping. Also, it is possible to prevent scratches and abnormal noise from being generated on the shaft portion due to frictional rubbing, and it is possible to prolong the service life and reuse.

[0008]

As described above, since the heat resistant bush is provided between the shaft and the bearing of the fixing roller so as to be fixed to the shaft of the fixing roller, the heat resistant bush is also fixed as the fixing roller rotates. Since it rotates without causing rotational slip with the roller shaft, friction between the heat-resistant bush and the fixing roller shaft is eliminated, and noise is generated due to friction.
It is possible to prevent damages on the roller shaft and the heat insulating member. Further, the rotation of the roller is kept stable by preventing the generation of scratches, and the reuse of the roller is facilitated.

[0009]

[Brief description of drawings]

FIG. 1 is a side view around a shaft portion of a fixing roller according to an exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view around a shaft portion of a fixing roller according to an exemplary embodiment of the present invention.

FIG. 3 is a side view around a shaft portion of a fixing roller according to another embodiment of the present invention.

FIG. 4 is a sectional view around a shaft portion of a fixing roller according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view around a shaft portion of a conventional fixing roller.

[Explanation of symbols]

 4 Fixing roller shaft 5 Insulating bush 6 Ball bearing 7 Primary coil

Claims (4)

[Claims] 1. A thermal roller fixing device for heating and fixing a toner image on a transfer material by passing between a pair of fixing rollers,
Between the shaft and the bearing of at least one roller of the fixing roller, a heat resistant bush is arranged so as to be fixed to the shaft,
The heat roller fixing device, wherein the heat resistant bush is not rotated with respect to the shaft. 2. The heat roller fixing device according to claim 1, wherein the bearing is a ball bearing, and the heat resistant bush is non-rotating with respect to the inner ring of the ball bearing. 3. The heat roller fixing device according to claim 1, wherein a surface roughness of a contact surface of the shaft with the heat resistant bush is a center average roughness of 1.6a or more. 4. The heat roller fixing device according to claim 1, wherein the heat resistant bush has a coefficient of thermal expansion equal to or less than a coefficient of thermal expansion of the shaft.