JP2553701B2 - Bearing device and developing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device that can be used in the general mechanical field, and to a developing device in the electrophotographic recording field as an application example thereof.

2. Description of the Related Art Generally, in mechanical design, soft metal such as aluminum, aluminum alloy, or copper metal is not directly rotatably supported by a slide bearing. The reason is that these soft metals are likely to cause wear and pseudo-attachment in the bearing portion. However, in order to take advantage of the high-precision machinability of these soft metals and the lightness of aluminum-based metals, it is sometimes possible to directly rotate and support these soft metals. Hereinafter, as such an example, a developing device of an electrophotographic recording apparatus will be described as an example. From the viewpoint of the developer used, the electrophotographic recording dry development method is classified into magnetic and non-magnetic depending on the presence or absence of magnetism of the toner, and one-component development method and second-generation development method depending on whether the carrier is included or not. To be done. Among them, the non-magnetic one-component developing method has attracted attention as a developing method suitable for colorization of recent electrophotography. In particular, the non-magnetic one-component developer is used, and the developer on the developer carrier (hereinafter also referred to as a developing roll) and the electrostatic latent image carrier (hereinafter, referred to as a photoconductor) are not in contact with each other. The non-magnetic one-component non-contact developing method in which development is carried out while maintaining the ability to superimpose toner images of different colors on a photoconductor is of particular interest. The main constitution of this non-magnetic one-component non-contact developing method is shown in FIG. In FIG. 7, reference numeral 1 is an electrostatic latent image carrier (hereinafter also referred to as a photosensitive drum), which is formed by coating selenium 3 or the like on the surface of a rough aluminum tube 2. Reference numeral 4 is a non-magnetic one-component developing device, and one-component developer (hereinafter also referred to as toner) 5 in a hopper is elastic member 8 which is a developer supplying means through an opening 7 by a conveying mechanism 6 which rotates in the arrow direction. Be transported to. Then, a part of the toner 5 carried on the elastic body roller 8 is supplied to a developer carrying body 9 (hereinafter also referred to as a developing roller) which rubs against the elastic body roller 8. Further, due to the rubbing at this time, the toner is triboelectrically charged to have an appropriate polarity. The toner 10 carried on the developing roller 9 in a non-contact manner with the photosensitive drum 1 acts under the action of an electric field formed by an external power source 11 connected between the photosensitive drum 1 and the developing roller 9. , Fly from the developing roller 9 to the photosensitive drum 1 to develop the latent image. FIG. 8 is a view of FIG. 7 seen from the direction of arrow A. In FIG. 8, the vicinity of the rotation support shaft 14 at both ends of the developing roller 9 is shown in partial cross section. In FIG. 8, 13 is a spacer ring, which is rotatably mounted on the rotation support shaft 14 of the developing roller 9. The outer diameter of the spacer ring 13 is set to the developing roller 9
By setting the outer peripheral surface of the spacer ring 13 against the photosensitive drum 1 by making it about 0.3 mm larger than that, the surface of the developing roller 9 is in a non-contact state with a slight gap from the surface of the photosensitive drum 1. To be kept in position. The developing roller 9
The rotary support shafts 14 at both end portions are integrally processed with the central developer carrying portion. The rotary support shaft 14 is made of a resin-made sliding bearing 15 press-fitted and held in the housing of the developing device.
It is rotatably supported by. In the non-magnetic one-component non-contact development thus constructed, it is important to stabilize the gap between the surface of the developing roller and the surface of the photosensitive drum, so-called developing gap G, in order to stabilize the developing characteristics. It is one of the important points. In particular, it is important for stabilizing the developing characteristics in the region from the highlight to the halftone. The fluctuation of the developing gap G causes the fluctuation of the developing electric field, and the amount of toner flying on the photosensitive drum 1 also fluctuates according to the fluctuation, which causes unevenness in the image density. The most important control items for suppressing the fluctuation of the developing gap G within the allowable value are the runout accuracy when the developing roller 9 is rotated and the coaxiality of the inner and outer diameters of the spacer ring with respect to the rotation support shaft 14. . And these are both 10μ
It is desirable to suppress the accuracy to m or less. From the viewpoint of such accuracy requirement or weight reduction, the developing roller 9 is
Rotating shaft made of aluminum or aluminum alloy
Often integrated with 14. In particular, the developing roller is often manufactured from an A2011 series (JIS classification) aluminum material, which has excellent machinability from the viewpoint of processing accuracy.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Now, in such a conventional example, there is a problem in reliability of the bearing portion of the rotary support shaft 14 of aluminum or aluminum alloy and the sliding bearing 15 made of resin. .
That is, abnormal wear may occur between the rotary support shaft 14 and the bearing 15. As is well known, when supporting a soft metal such as aluminum, aluminum alloy, or copper-based metal with a sliding bearing, carefully select the bearing material and control the clearance between the shaft and the inner surface of the bearing. There is a need. Above all, the most important point is the choice of bearing material. For example, polyacetal-based material is a relatively common material as a sliding bearing material,
When these are used as the bearing material of the above-mentioned soft metal, remarkable pseudo attachment and galling occur in the bearing portion. For these soft metals, a bearing material using Poly Phenylene Sulfide as a base material is suitable, and is commercially available, for example, under the trade name of Polymex (NSK). Certainly, it is recognized that the bearing based on polyphenylene sulfide is significantly improved in reliability with respect to soft metals as compared with bearings made of other materials, but as described above, in the bearing portion, Occasionally, wear and scratches on bearing materials and rotating shafts occurred. Due to such wear of the bearing portion, the load resistance of the bearing portion remarkably increases, and the normal operation of the developing device cannot be performed. Alternatively, abrasion powder adheres to the outer peripheral surface of the spacer ring 13 and causes the development gap G
However, there is a problem in that the image quality is remarkably deteriorated due to the large fluctuation of

Means for Solving the Problems Means for solving the above problems, the surface of the rotating shaft of a soft metal, and finishing by grinding to have a predetermined surface roughness or less.

Action The action of the above means has not yet been clearly determined. However, it is well known that the wear of the bearing depends on its surface condition. Therefore, even if the surface roughness is the same, the wear condition of the bearing changes depending on the surface processing method. That is quite conceivable. Hereinafter, in the examples, the validity of the above means for solving the problems will be clarified by experimental data. At the same time, its action will be considered.

Example FIG. 1 shows a comparison of the wear states of the bearings when the rotary shaft was turned and when it was ground. The base material of the sliding bearing material is polyphenylene sulfide. Fig. 2 is a schematic diagram of the equipment used for this wear test. 20 is a rotating shaft, 21 is a sliding bearing that supports the rotating shaft 20, 22 is a rolling bearing fitted to the rotating shaft 20, and 23 is a sliding bearing. Reference numeral 21 is a housing that is press-fitted and supported. The rolling bearing 22 is pressed by the leaf spring 24 in the arrow direction, and the pressure on the inner peripheral surface of the sliding bearing 21 can be varied by adjusting the pressing force. Further, the rotary shaft 20 is connected to a variable speed rotating means (not shown) and driven to rotate. With this experimental device, the frequency of occurrence of visually recognizable wear and damage on the surface of the rotary shaft 20 or the inner surface of the bearing 21 at the two bearing portions on both ends was repeated 250 times. There is a problem (the number of bearings evaluated is therefore 250 × 2 = 500, as shown in FIG. 1). Now, as shown in FIG. 1, when the grinding process is performed, the probability of occurrence of wear and scratches is zero in this test, which is clearly superior to the turning process. Next, an experiment was conducted using the apparatus shown in FIG. 2 to find out to what extent the surface roughness of the rotary support shaft could be allowed when it was ground. FIG. 3 shows the results. FIG. 3 shows how the surface roughness of the rotary shaft 20 deteriorates due to the accumulated rotation time. As is clear from this figure, when grinding is performed, there is no problem even if the surface roughness is about 10 μmRz. Next, the developing device shown in FIG. 4 to which this bearing device is applied will be described. The difference from the conventional developing device lies in the processing method of the surface of the rotary support shaft 14 (therefore, there is no difference in the drawings between FIGS. 4 and 7).
Further, in the conventional developing device, the rotary shaft was machined by turning, but based on the above result, in the embodiment shown in FIG. The surface of the support shaft is finished to 10 μm Rz by grinding. When the electrophotographic apparatus was actually operated using the developing apparatus of the present example, no abrasion or abrasion powder was found in the bearing portion even after copying 100,000 sheets. As a result, in this example, no increase in the load on the developing device or variation in the developing gap was observed, and the developing characteristics were stable and extremely good. By grinding the surface in this way, the reliability of the bearing portion can be greatly improved, but the following may be considered as the reason why the wear state differs depending on the processing method. As shown in FIG. 5, the surface shape of the turning process has a triangular shape when viewed microscopically by transferring the tip shape of the cutting tool. The surface of the rotary support shaft 14 contacts the inner peripheral surface 32 of the bearing 15 at the apex 31 of the triangular shape. Therefore, in the case of turning, microscopically, a high pressure is concentrated on the apex portion 31, and the sliding bearing 15 is rubbed against the apex portion 31, and it is considered that abrasion is generated from the apex portion 31. On the other hand, in the case of grinding, it is considered that the shape will be as shown in FIG. In this case, the rotation support shaft
Since the outer peripheral surface of 14 is relatively in uniform contact with the inner peripheral surface 32 of the bearing 15, the concentration of pressure unlike in the case of turning processing does not occur, and as a result, it is presumed that the bearing portion functions normally. It In the above embodiments, the developing device of the electrophotographic recording apparatus is taken up for description, but the bearing device of the present invention is not limited to the above embodiments, and it is obvious that it can be widely applied to the mechanical structure field. is there.

In the above description, the case of the rotary shaft has been described as an example, but it is clear that the bearing structure of the present invention also has the same effect in the linear sliding shaft and the sliding bearing supporting the linear sliding shaft. .

EFFECTS OF THE INVENTION As described above, the present invention greatly improves the requestability of a mechanical element called a bearing device. Therefore, the present invention is not limited to application to a developing device and exerts great effects over a wide range of fields.

[Brief description of drawings]

FIG. 1 is a comparative view showing the superiority of a bearing device according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a main part of the experimental device of FIG. 1, and FIG. 3 is a surface roughness of the bearing device of the present embodiment. FIG. 4 is a sectional view showing the main part of the developing device to which the coaxial receiving device is applied, FIGS. 5 and 6 are explanatory views of the operation of this embodiment, and FIGS. FIG. 11 is a cross-sectional view of a main part of a conventional developing device. 14 …… Rotary support shaft, 15 …… Bearing, 20 …… Rotary shaft, 21…
… Slip bearings.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yuuji Sakamoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 63-44680 (JP, A) JP 61- 144469 (JP, A) JP-A-63-211150 (JP, A) JP-A-63-272454 (JP, A) JP-B-50-20293 (JP, B1)

Claims (3)

(57) [Claims] 1. A rotating shaft or a linear sliding shaft made of aluminum, an aluminum alloy, or a copper-based metal,
In a bearing device constituted by a sliding bearing made of resin for rotatably supporting or slidingly supporting the rotating shaft or the sliding shaft, the shaft surface that rubs against the sliding bearing is made to have a surface roughness of 10 μmRz or less by grinding. At the same time, the bearing device is characterized in that the material of the resin-made sliding bearing includes Poly Phenylene Sulfide. 2. The bearing device according to claim 1, wherein the aluminum or aluminum alloy corresponds to JIS classification A2011. 3. A developing device having a cylindrical developer carrier for rotatably supporting a developer on a surface thereof and supplying the developer to a latent image carrier, wherein the developer carrier is an aluminum. Alternatively, the developing device is formed of an aluminum alloy and is rotatably supported by the bearing device according to claim 1.