JPS6347603B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin hydraulic cylinder for brakes or clutches used in automobiles, etc.
More specifically, the present invention relates to a material composition for improving the surface roughness of the inner surface of a hydraulic cylinder when the cylinder is molded by injection molding using polyamide filled with an inorganic material such as glass fiber. 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 from the viewpoint of material composition include (1) reducing the amount of glass fiber filled in polyamide; (2) Fill with relatively short glass fibers. (3) Fill with an inorganic substance that does not easily obstruct the flow of glass beads, etc. (4) 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.
In method (4), the overall strength of the material decreases, and
This had the disadvantage that durability such as fatigue resistance and heat resistance decreased, resulting in a decrease in the durability of the hydraulic cylinder. Next, regarding the surface roughness of the inner surface of the cylinder when molding a resin hydraulic cylinder using the injection molding method, there are problems in molding. The surface roughness of the inner surface of the cylinder where the meat part is attached deteriorates due to insufficient cavity pressure, resulting in the disadvantage that inorganic materials such as glass fibers are exposed on the surface. The present invention solves the above-mentioned drawbacks, without reducing the filling amount of inorganic materials such as glass fiber as in (1) above, and by selecting a special filler as in (2) and (3). There is no need to mix polyamides, there is no need to select a low viscosity polyamide as in (4), and there is no reduction in the pressure resistance and durability of the hydraulic cylinder, and the cylinder surface roughness is excellent. A hydraulic cylinder having uniform surface roughness is provided. In the present invention, a resin hydraulic cylinder manufactured by injection molding is made of polyamide filled with an inorganic material such as glass fiber, and a copolymer nylon (hereinafter referred to as 6, 66
copolymer nylon), or copolymer nylon consisting of caproamide and hexamethylene sebaamide (hereinafter referred to as 6,610 copolymer nylon), or ternary copolymer nylon consisting of caproamide, hexamethylene adipamide, and hexamethylene sebaamide. A polyamide molding material containing 2 to 15% by weight of copolymer nylon (hereinafter referred to as 6, 66, 610 ternary copolymer nylon) is used to achieve a surface roughness that prevents glass fibers from being exposed on the surface. This provides a hydraulic cylinder with excellent characteristics. Generally, the cylinder surface roughness of a hydraulic cylinder manufactured from polyamide filled with an inorganic substance is the best when the molten resin in the cylinder part solidifies under sufficient cavity pressure. However, areas away from the gate or areas with thick walls tend to lack cavity pressure during solidification due to solidification of the resin between the gate and the surface roughness of these areas. Deteriorate. According to the present invention, the solidification of the resin between the gate and the gate is delayed due to the action of the 6,66 copolymerized nylon etc., which is especially blended. The time during which the injection pressure is applied to the part becomes longer, and a lack of cavity pressure can be prevented, and as a result, the cylinder surface roughness of the hydraulic cylinder can be dramatically improved. The following will be specifically explained based on examples.
In Figures 1 to 3, 1 is a hydraulic cylinder, 2 is a hydraulic cylinder, and 2 is a hydraulic cylinder.
is the cylinder, 2a is the inner surface of the cylinder, 3 is the reservoir, 4 is the flange, 5 is the piston, 6 is the piston cup, and 7 is the part of the cylinder inner surface 2a where the piston cup especially slides, especially in a resin cylinder. The surface roughness of the part 7 on the inner surface of the cylinder is the most important. 8 is a mold, 9 is an injection molding machine, 10 is a gate, 11 is a cylinder bottom, 12 is a cylinder opening, and injection molding of a hydraulic cylinder is carried out at the second stage.
As shown in the figure, molding is performed with the bottom of the hydraulic cylinder communicating with the gate. When the injection molding machine 9 molds glass fiber reinforced polyhexamethylene adipamide (hereinafter referred to as 66 nylon) with a blend material such as 6,66 copolymer nylon, the molten resin material passes through the gate 10. The resin material advances from the cylinder bottom wall 11 to the cylinder opening 12 and reservoir 13. In this case, the resin material is 6,66 copolymerized nylon, and sufficient injection pressure is applied to delay the solidification of the resin, but it takes a long time. Therefore, insufficient cavity pressure can be prevented, and the surface roughness of the inner surface of the cylinder, especially near the cup sliding portion 7, can be improved. Next, as a specific example, the cylinder shown in FIG. 3 will be explained based on data obtained using the method of the present invention. In other words, the following is an example comparing the inner surface roughness of the conventional glass fiber reinforced 66 nylon alone and the inner surface roughness of the cylinder formed by blending it with a blend material such as 6,66 copolymer nylon. It is shown in Table 1. The measured position P is L = 25mm from the cylinder opening.
This is the point.

[Table] From Table 1, the conventional example No. 1 has a surface roughness of 5.6 μRZ, and the surface roughness of No. 2 and No. 3, which are examples of the present invention, are 1.4 μRZ and 1.3 μRZ. Approximately 1/3 to 1/4 of
It is. Figure 4 is an enlarged view of the situation in Table 1, where A is No. 1.
This is a 2000 times enlarged view of the vicinity of point P of glass fiber-reinforced 66 nylon in the conventional example, and the solid line is the surface roughness of the inner surface of the cylinder. B is Example No. 2, which is a mixture of glass fiber-reinforced 66 nylon and 5% by weight of 6,66 copolymerized nylon as a blend material.
This is a double enlarged view. C is Example No. 3, which is a mixture of glass fiber-reinforced 66 nylon and 10% by weight of 6,66 copolymerized nylon as a blend material.
This is a 5000x enlarged view. As described above, the present invention uses 2 to 15 weight percent of 6,66 copolymer nylon, 6,610 copolymer nylon, or 6,66,610 ternary copolymer nylon to a polyamide molding material filled with 15 to 60 weight percent of inorganic materials such as glass fibers. %
By using the blended molding material, a cylinder with extremely excellent surface roughness can be molded.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a master cylinder, Fig. 2 is a sectional view of a mold of a cylinder injection molding device, Fig. 3 is a partially omitted sectional view of a cylinder of an embodiment, and Fig. 4 is a sectional view of a cylinder injection molding device.
The figures show the unevenness of the inner surface of the cylinder of the example. A is a 2000 times enlarged view of the conventional product, B is a 5000 times enlarged view of the example, and C is another example.
This is a 5000x enlarged view. 1...Hydraulic cylinder, 2...Cylinder, 2a...
...Cylinder inner surface, 9...Injection molding machine.

Claims (1)

[Claims] 1 A polyamide homocopolymer filled with 15 to 60% by weight of an inorganic substance such as glass fiber is mixed with a copolymer nylon consisting of caproamide and hexamethylene adipamide, or a copolymer consisting of hexamethylene adipamide and hexamethylene sebaamide. A resin hydraulic cylinder containing 2 to 15% by weight of polymer nylon or ternary copolymer nylon consisting of caproamide, hexamethylene adipamide, and hexamethylene sebacamide and shaped by injection molding.