JPH0458368B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for manufacturing a composite bearing using fluororesin. [Prior art] Although fluororesin cannot be injection molded, extrusion molding is possible. Therefore, an extruded tube is cut to the required length, and a required synthetic resin having mechanical strength is injection molded around the outer circumference of the extruded tube. A method of manufacturing bearings using
(Refer to Publication No. 81221). [Problems to be solved by the invention] Fluororesin extruded tubes are molded and fired at high temperatures of 300°C or higher, and the resin itself has a very high shrinkage rate (3 to 5%). There is a large variation in the inner diameter dimensions of the tubes.
It cannot be used as a bearing that requires proper clearance. Therefore, in conventional manufacturing methods, an extruded tube is formed to be thicker than the required finished dimensions, the inner diameter of the tube is machined and finished, and then synthetic resin is injection molded around the outer circumference. Ta. However, such a manufacturing method requires a machining process and has the problem that the fluororesin material that is cut by the machining process is wasted. SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a manufacturing method that does not require machining and can save materials. [Means for Solving the Problems] A method for manufacturing a composite bearing according to the present invention will be described with reference to the drawings. In this manufacturing method, a fluororesin extruded tube 1 is cut to a required length to form a cylindrical bearing member 2. The inner diameter a of the extruded tube 1, and hence the inner diameter a of the bearing member 2, is slightly smaller than the outer diameter b of the core 3 of the injection molding apparatus. Therefore, when the above-mentioned bearing member 2 is placed over the outer periphery of the core 3, the bearing member 2 is stretched in the direction in which its diameter increases. FIG. 3 shows the injection molding process, in which the core 3 covered with the bearing member 2 is replaceably attached to one mold 4, and the other mold 5 is fitted around the bearing member 2. A molded cavity is formed in the molded cavity, and a synthetic resin having the required mechanical strength is injection molded into the cavity to form the bearing exterior member 6.
Become one with. In this way, as shown in FIG. 4, a composite bearing 7 is obtained which has a bearing member 2 made of fluororesin on its inner periphery and has a required bearing exterior member 6 made of synthetic resin integrated on its outer periphery. . It should be noted that, as shown in FIG. 6, on the outer circumferential surface of the extruded tube 1 or bearing member 2, longitudinal slits 8 are provided at regular intervals to facilitate stretching, and also to allow the tube to be pulled inward during cooling. The advantage is that the force is weaker and the amount of contraction is smaller. Further, the cross-sectional shape of the core 3 is not necessarily circular, and may be non-circular such as an ellipse or an oblong. In addition, the composite bearing manufactured as described above was divided into two parts as shown in FIG. 7, and a half-shaped composite bearing 9
It is also possible to do this. Examples of the fluororesin include tetrafluoroethylene resin, fluoroethylene propylene resin, tetrafluoroethylene/ethylene copolymer resin, and tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer resin. In addition, examples of the synthetic resin forming the bearing exterior member 6 include glass fiber-filled polycarbonate resin, polypropylene resin, ABS resin, polyphenylene sulfide resin, polyether sulfone resin,
Examples include phenolic resin, unsaturated polyester resin, nylon, and polyacetal resin. [Example] Composite bearings were manufactured by the method of the present invention using extruded fluororesin tubes with wall thicknesses of 0.3 mm and 0.5 mm. Tetrafluoroethylene resin is used as the fluororesin, and the outer peripheral surface of the bearing member 2 manufactured using this resin is treated to enable adhesion, and the outer periphery of the bearing member is coated with glass fiber-containing polyphenylene sulfide resin. 6 was formed by injection molding. The inner diameter a of the tube 1, the outer diameter b of the core 3, and the inner diameter c of the product 7 were measured for 30 to 50 test pieces thus produced, and the results are shown in Table 1.

〔effect〕

As described above, in this invention, a bearing member made of fluororesin is stretched in the direction of diameter expansion and placed over a core, and then a bearing exterior member is formed by injection molding. The dimensional accuracy of the bearing member depends on the dimensional accuracy of the outer peripheral surface of the core. Since the outer circumferential surface of the core can be finished with sufficiently high dimensional accuracy, a bearing with high dimensional accuracy can be manufactured even if the finishing step by machining after injection molding is omitted. Also, since no finishing is done by machining,
As the fluororesin tube needs to be made thinner than conventional tubes by the amount of cutting allowance, it is possible to save on materials and it is also easier to stretch when covering the core. can. Furthermore, the composite bearing obtained by the method of the present invention allows the tube to be formed thinner than conventional bearings in which the tube is machined, so it has a small amount of creep and a high final roundness, and is also heat resistant. Since it is easy to dissipate, it can provide excellent quality, such as a longer life.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a fluororesin extrusion tube.
Figure 2 is a sectional view of the bearing member, Figure 3 is a sectional view during injection molding, Figure 4 is a sectional view of the product, Figure 5 is a perspective view of the product, and Figure 6 is another example of the bearing member. end view,
FIG. 7 is a perspective view of another product. DESCRIPTION OF SYMBOLS 1... Fluorine resin extrusion tube, 2... Bearing member, 3... Core, 6... Bearing exterior member, 7... Composite bearing, 8... Slit, 9... Half-split type composite bearing.

Claims (1)

[Scope of Claims] 1. A cylindrical bearing member of a required length is formed using an extruded tube made of fluororesin, and the bearing member is placed on the core of an injection molding machine, and then the outer periphery of the bearing member is molded into the required machine. In the manufacturing method of a composite bearing, the inner circumference of the bearing member is formed shorter than the outer circumference of the core, and the bearing member is stretched in a radial direction. A method for manufacturing a composite bearing, characterized by covering the core. 2. Claim 1, characterized in that a longitudinal slit is formed on the outer peripheral surface of the bearing member.
The manufacturing method of the composite bearing described in .