JPS6359847B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to resin hydraulic cylinders for brakes or clutches used in automobiles, etc. More specifically, when manufacturing hydraulic cylinders, injection molding is performed using polyamide filled with inorganic materials such as glass fiber. The present invention relates to a material composition for improving the surface roughness of the inner surface of a cylinder when molded by a molding method. When molding a resin hydraulic cylinder using the injection molding method, it is an important issue to achieve the best uniform surface roughness on the inner surface of the cylinder. Methods for improving the cylinder surface roughness of manufactured hydraulic cylinders by molding from the viewpoint of material composition include: (1) Decreasing the amount of glass fiber filled into polyamide. (2) Fill with relatively short glass fibers. (3) Use low viscosity polyamide. However, methods (1) to (3) above have the disadvantage that the strength of the material decreases, resulting in a decrease in the pressure resistance and rigidity of the hydraulic cylinder.
Also, JP-A No. 59-033127 "Resin Hydraulic Cylinder"
describes a method of adding copolymerized nylon, but in this method, by adding copolymerized nylon in an amount of 2 to 15% by weight, the surface roughness of the hydraulic cylinder can be increased from 1.4 μRZ to 2.0 μRZ. μRZ
(previously it was approx.
5.6 μRZ), but the tensile strength of the material containing 5% 6,66 copolymer nylon was approximately 10% lower than that of the conventional 66 nylon GF containing 45%. The present invention solves the above-mentioned drawbacks by ensuring a surface roughness of 1.4 μRZ to 3.0 μRZ for the hydraulic cylinder.
Moreover, the present invention provides a hydraulic cylinder having tensile strength almost the same as that of the 66 nylon GF45%. That is, in the production of hydraulic cylinders, a compound having two stearamide groups, such as ethylene bisstearamide, is particularly added to polyamide filled with an inorganic material such as glass fiber. That is, the melting point of the stearamide compound is 100-
Because the temperature is 145°C, when polyamide is molded, it becomes liquid due to the heat of the injection cylinder, and this acts as a wax agent between the polyamide molecules or between the polyamide and the mold, improving fluidity, and as a result, the melted polyamide and Due to the difference in the flow resistance of the inorganic material dispersed in the polyamide, the inorganic material tends to be left behind compared to the flow of the polyamide. As the amount of inorganic substances on the surface of the molded product is extremely small, the surface roughness of the molded product is significantly improved, and the reinforcing glass fiber is made of polyamide. This improves tensile strength. As described above, by carrying out the present invention, it is possible to easily manufacture a resin hydraulic cylinder having excellent surface roughness and excellent strength. The following is a detailed explanation of Figures 1 to 4 based on examples.
This will be explained using figures. 1 is a hydraulic cylinder, 2 is a cylinder, 2a is an inner surface of the cylinder, 3 is a flange, 4 is a piston, 5 is a piston cup, 6 is an inner surface of the cylinder 2a,
In particular, this is the part on which the piston cup slides, and in a resin cylinder, the surface roughness number 6 on the inner surface of the cylinder is the most important. 3 is a mold 7, an injection molding machine 8, a gate 9, a lower part of the cylinder 10, and a mold 11 on the opening side of the hydraulic cylinder. FIG. 3 shows the injection molding of the hydraulic cylinder. Using an injection molding machine 8, 0, 0.3, 0.5, 0, 0.3, 0.5,
Hydraulic cylinders were molded by mixing at 1.0WET%. An enlarged view of the molded state of the cylinder in this case is shown in FIG. 4B. 20 is glass fiber, and 21 is a resin made by adding ethylene bisstamide to polyamide, which is heated to about 230 to 290°C by an injection molding machine to become liquid. If this resin is injection molded, the glass fibers 20 are left in the center of the thickness of the cylinder and 21a, 21b, 21
As shown in c, the flow of the resin progresses and it adheres to the surfaces 7 and 11 of the mold, and the surface of the molded product has very little inorganic filling, especially since surface roughness is the most important. The area around the inner surface of the cylinder 6 is significantly improved. FIG. 4A shows a conventional example in which, when the resin has viscosity, the glass fibers and the resin flow as one and move forward, causing the glass fibers to rise to the surface of the mold. Table 1 shows the surface roughness at the arrow points of the hydraulic cylinder shown in FIG.

[Table] Table 2 shows the tensile strength used in hydraulic cylinders.

[Table] From Table 2, the examples according to the present invention have almost the same tensile strength as 66 nylon containing 45% GF.

[Table] Table 3 shows the surface roughness at the arrow point of the hydraulic cylinder in the case where methylene bisstearamide was blended as another example. It can be seen that blending methylene bis stearamide has the same effect of improving surface roughness as ethylene bis stearamide.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hydraulic cylinder, and FIG. 2 is a sectional view of an injection molded cylinder. Fig. 3 is a cross-sectional view of a mold for a hydraulic cylinder, and Fig. 4 shows the flow of resin during cylinder molding, where A is an explanatory diagram of a conventional example and B is an explanatory diagram of an embodiment based on the present invention. It is a diagram. 1...Hydraulic cylinder, 2...Cylinder, 20...
...Glass fiber, 21... Molding material.

Claims (1)

[Claims] 1 Stearamide groups are added to a polyamide molding material filled with 15 to 60% by weight of inorganic materials such as glass fibers.
A resin hydraulic cylinder shaped by injection molding using a molding material containing 0.3 to 1.5% by weight of a compound containing: