JPH0934294A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a bearing from being pulled out from a fixing roller without increasing a cost. SOLUTION: One end part 2a of the fixing roller 2 is constituted by having a larger diameter than the other part. The bearing 6a is arranged at the inside of a large diameter part 2a, so that the bearing is prevented from falling off. The bearing 6a is positioned by the end surface of the large diameter part 2a and a device frame 4. The bearing 6b on an opposite side is prevented from falling off by a fixing gear 7 pressed by the flange 8a of a driving gear 8, so that it is positioned by the device frame 4 and the fixing gear 7. A stopper is unnecessitated for preventing the bearing from falling off, so that parts cost and assembling cost are reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device mounted on an image forming apparatus such as a copying machine or a printer to fix an unfixed toner image on a recording medium.

[0002]

2. Description of the Related Art An unfixed image (an image formed by toner made of heat-meltable resin) mounted on an image forming apparatus such as a copying machine, a printer or a facsimile and transferred onto a recording medium such as transfer paper. As a fixing device for heating and fixing on a recording medium, a fixing roller (heating roller) with a built-in heater is brought into pressure contact with a pressure roller, and the recording medium is passed between both rollers to generate heat and pressure. A heat roller type fixing device for fixing an unfixed toner image on a recording medium is well known.

In a conventional heat roller type fixing device, a fixing roller is supported by a device frame via a bearing. The bearing is usually prevented from coming out by a stopper (retaining ring) such as a C ring or an E ring. In addition, the inward positioning is generally performed by a device frame. Recently, in order to reduce costs, the number of cases where a semicircular bearing is used as a bearing for supporting the fixing roller is increasing.

FIG. 4 is an exploded perspective view for explaining an example of a conventional fixing device. FIG. 4A shows a fixing roller.
The device frame and the pressure roller are shown in FIG. The fixing roller 12 shown in this figure is rotatably supported by the fixing frame 14 by a sliding bearing 16. That is, the fixing roller 12 is inserted into the frame 14 and the fixing roller 1
The sliding bearings 16 are fitted into the rollers 12 from both sides of the device 2 and supported by the device frame 14. Then, the fixing gear 17 is fitted to the outer side of the bearing 16 at one roller end, and the retaining ring 15 is fitted into the fixing roller 12 from the outer side to prevent the bearing 16 and the fixing gear 17 from coming off. On the opposite side of the fixing roller 12, a retaining ring 15 is fitted and inserted just outside the bearing 16 to prevent the bearing 16 from coming off. The retaining ring 15 is the fixing roller 1.
2 is fitted into and held in a groove 12a provided on the outer peripheral surface near both ends of the second member. The bearings 16 on both sides of the roller are positioned with their flange surfaces contacting the frame 14 so that their movement inside the roller is restricted. A pressure roller 13 is located below the fixing roller 12 in the frame 14 and is pressed by a pressure mechanism (not shown).
Is pressed against the fixing roller 12. Further, the paper loading and unloading ports of the frame 14 are not shown.

As described above, in the conventional fixing device, C
A retaining ring such as a ring or an E ring is used to prevent the bearing from coming off the fixing roller.

[0006]

However, in the conventional fixing device as described above, there is a problem that the use of the retaining ring increases the cost of parts, and the number of assembling steps increases, so that the manufacturing cost also increases. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the conventional fixing device and to provide a fixing device capable of preventing the bearing from coming off from the fixing roller without increasing the cost. .

[0008]

According to the present invention, the above-mentioned problems include a fixing roller having a built-in heat source and a pressure roller pressed against the fixing roller, and an unfixed image is carried between the rollers. A fixing device for fixing an unfixed image on a recording medium by passing through the recording medium, wherein a device frame is divided into an upper frame supporting the fixing roller and a lower frame supporting the pressure roller. In a fixing device in which the fixing roller is supported by the upper frame via substantially semicircular bearings mounted near both ends of the roller, the fixing roller has an outer diameter of at least one roller end portion. Is larger than the roller outer diameter of the bearing mounting portion, and the bearing is prevented from coming off.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded perspective view showing a fixing device according to an embodiment of the present invention. In the fixing device 1 shown in this figure, the frame of the fixing device is divided into an upper frame 4 and a lower frame 5. A fixing roller 2 is arranged in the upper frame 4, and a pressure roller 3 is arranged in the lower frame 5. The pressure roller 3 is urged upward by a pressure mechanism (not shown) and brought into pressure contact with the fixing roller 2. Therefore, the fixing roller 2
Is placed on the pressure roller 3.

As shown in FIG. 2, the fixing roller 2 is supported on the upper frame 4 by flanged sliding bearings 6a and 6b. The sliding bearings 6a and 6b have a semicircular shape as shown in FIG. 3, and a semicircular cutout portion (see FIG. 1) of the upper frame 4 is fitted into the flange portion thereof. The pressure roller 3 is urged upward from below the fixing roller 2 by a pressure mechanism (not shown).
Is rotatably supported by the pressure roller 3 and the sliding bearings 6a and 6b.

By the way, the roller diameter of one end portion (left end portion in FIG. 2) of the fixing roller 2 is made larger than the roller diameters of the other portions. The outer surface of the sliding bearing 6a is brought into contact with the end surface of the step between the large diameter portion 2a and the small diameter portion to prevent the sliding bearing 6a from coming off the fixing roller 2. The sliding bearing 6a is positioned to the right in FIG. 2 by the upper frame 4. Therefore, the sliding bearing 6a is positioned with the movement of the fixing roller 2 in the roller axial direction restricted. At the same time, the fixing roller 2 is restricted from moving to the right in FIG.

A fixing gear 7 for driving the fixing roller is fitted to the right end portion of the fixing roller 2 in FIG.
Then, the drive gear 8 is meshed with the fixing gear 7,
The rotation of a motor (not shown) is transmitted to the fixing roller 2 and the fixing roller 2 is rotationally driven. The end portion of the fixing roller 2 on the gear 7 side is not made large in diameter but has the same roller diameter as the central portion. This is because the fixing gear 7 is fitted into the fixing roller 2. Further, the drive gear 8 is a gear with a flange, and the flange 8a of the gear 8 presses the side surface of the fixing gear 7 to prevent the fixing gear 7 from coming off the fixing roller 2. As the fixing gear 7 is prevented from coming off, the sliding bearing 6b contacting the side surface of the fixing gear 7 is also prevented from coming off from the fixing roller 2. Further, the sliding bearing 6b is restricted from moving to the left in FIG. 2 by the upper frame 4.

In this way, the slip bearings 6a and 6b are prevented from coming off. Therefore, in this embodiment, it is not necessary to use a retaining ring such as a C ring or an E ring to prevent the bearing from coming off, and it is possible to reduce the component cost and the assembly cost.

In the present embodiment, the fixing gear 7 is prevented from coming off from the fixing roller 2 by the flanged gear 8 meshed with the fixing gear 7. A retaining ring such as a C ring or an E ring may be used on the outside of the gear 7. In this case, the retaining ring is omitted only on the one end side of the fixing roller, but even in that case, the cost can be reduced.

In this embodiment, the end portion (one end portion) of the fixing roller 2 has a larger diameter than the bearing mounting portion and the fixing portion in order to prevent the bearing from coming off. By making the roller so that only the bearing mounting part (the part where the sliding bearing fits) has a smaller diameter than the other parts, the roller end is not made larger than the bearing mounting part and the fixing part. The outer diameter of the portion may be larger than the outer diameter of the bearing mounting portion. In this case, the bearing can be prevented from coming off without hindering the fitting and insertion of the fixing gear, so that the retaining rings on both sides of the roller can be omitted and the cost can be reduced. For example, the end portion of the fixing roller and the fixing portion (pressure roller)
It is also possible to make the outer diameter of the portion (which is pressed against the roller) the same and to make the bearing mounting portion smaller in diameter than the roller end portion and the fixing portion.

[0016]

As described above, according to the fixing device of the present invention, the outer diameter of the roller end portion on at least one side is larger than the outer diameter of the roller of the bearing mounting portion to prevent the bearing from coming off. Therefore, even if the retaining ring on at least one side is omitted, the bearing can be prevented from coming off and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention.

FIG. 2 is a side view showing a method of supporting a fixing roller of the fixing device.

FIG. 3 is a front view showing a bearing that supports a fixing roller of the fixing device.

FIG. 4 is an exploded perspective view showing an example of a conventional fixing device, (a) shows a fixing roller, and (b) shows an apparatus frame and a pressure roller.

[Explanation of symbols]

 1 Fixing Device 2,12 Fixing Roller 2a Large Diameter Part 3,13 Pressurizing Roller 4 Upper Frame 5 Lower Frame 6,16 Sliding Bearing 7,17 Fixing Gear 8 Drive Gear 14 Fixing Frame 15 Stop Ring (Stopper)

Claims (1)

[Claims] 1. An unfixed image is recorded on a recording medium by passing a recording medium carrying an unfixed image between the two rollers, the fixing roller having a built-in heat source and a pressure roller pressed against the fixing roller. In a fixing device for fixing, a device frame is divided into an upper frame supporting the fixing roller and a lower frame supporting the pressure roller, and the fixing roller is mounted near both ends of the roller. In the fixing device supported by the upper frame via a substantially semi-circular bearing, the fixing roller has a roller end outer diameter on at least one side larger than a roller outer diameter of the bearing mounting portion. Is
A fixing device characterized in that the bearing is prevented from coming off.