JPS63296915A - Molding method for boot made of short-fiber reinforced rubber - Google Patents

Abstract

PURPOSE:To obtain stably desired high rigidity by making an orientation direction of a fiber uniform, by casting a short-fiber added rubber material through an end of a longitudinal direction of a boot-shaped casting space by making the whole circumference of its end fringe into a gate. CONSTITUTION:A rubber material in a fluidized state is injected into a connecting port 15 of a molding device 10 from an injection device 14 through turning of its screw. The rubber material cast into the molding device 10 is supplied to a gate 17 having an opening running along a cylindrical fringe through a sprue 16 and cast within a casting space 18 through the gate 17. The rubber material and short fiber advance symmetrically with a boot axis as its center and flow radially toward an end part of the major axis side from that of the minor axis side of bellows. Therefore, the short fiber is oriented uniformly along a longitudinal direction of the bellows and the short fiber arranged in a circumferential direction of the boot is quite rare, in molded products obtained by solidifying the rubber material.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a short fiber reinforced rubber boot that is made of short fiber reinforced rubber reinforced by adding short fibers and is used to form a boot to be attached to an automobile drive shaft, etc. Concerning a molding method.

[Prior Art] For example, an automobile drive shaft is provided with a universal joint on the final reduction gear side and the wheel side, and this joint has a boot for trapping grease inside the joint. It is arranged to cover.

FIG. 2 is a schematic diagram showing a portion of this drive shaft. A driving force is transmitted to the drive shaft 1 from a final reduction gear unit 3 via an inner joint 2, and this driving force is transmitted to an axle hub and a wheel 5 via an outboard joint 4. And each joint 2
．． A bellows-shaped boot 6 is disposed at 4.

This boot 6 has a small diameter end that is connected to the drive shaft 1.
The large diameter end is attached to each joint. The inside of the boot 6 is filled with grease to lubricate the joint portion.

By the way, since this boot 6 is molded from a rubber material, if its rigidity is low, it may bulge in the radial direction due to the high speed rotation of the drive shaft 1, and may come into contact with surrounding members and break.

When the boot 6 is torn in this manner, the internal grease leaks out, and chips and the like enter the boot, causing joint wear. Incidentally, in order to increase the rigidity of the boot 6, the thickness of the rubber material may be increased, but this increases the size of the boot, which is contrary to the recent demand for miniaturization of parts.

Therefore, in order to increase the rigidity of the boots while keeping the wall thickness thin, boots made of short fiber-reinforced rubber, which is reinforced by adding short fibers to the rubber material, have recently been developed (Japanese Unexamined Patent Application Publication No. 1983-1993). -10170 etc.).

By the way, conventionally, this bellows-shaped boot 6 has a bellows-shaped injection space formed between an outer mold 9 and a middle sesame 8, as shown schematically in FIG. It is molded by injecting the rubber material through an injection lower provided at the edge (in the illustrated example, the edge on the large diameter side).

[Problems to be Solved by the Invention] However, when short fiber-added rubber material is injected through a dotted injection lower as in the past, the direction of fiber orientation is non-uniform in the boot molded product after solidification. becomes. For this reason, even though short fibers are added to the matrix rubber material for the purpose of improving rigidity, the resulting molded products often do not have the desired high rigidity. Further, there are problems such as large variations in rigidity in molded products and low product yield.

The present invention has been made in view of the above circumstances, and provides a method for forming short fiber-reinforced rubber boots that can uniformize the orientation direction of fibers and stably obtain desired high rigidity. The purpose is to

[Means for Solving the Problems] The method for molding short fiber-reinforced rubber boots according to the present invention involves injecting a rubber material to which short fibers have been added into the gap between the outer mold and the inner sesame to form a bellows-shaped boot. A method for forming boots made of short fiber-reinforced rubber, characterized in that a short fiber-added rubber material is injected from one longitudinal end of a boot-shaped injection space using the entire circumference of the edge as a gate. .

[Operation] In the present invention, the short fiber-added rubber material is injected from one end in the longitudinal direction of the bellows-shaped boot-shaped injection space.

In this case, since the edge of the bellows-shaped injection space has a circumferential shape, the short fiber-added rubber material is injected using the entire circumference as a gate.

That is, the rubber material is injected into the bellows-shaped injection space through a linear (for example, circumferential) gate rather than a dot-shaped gate as in the conventional method. This ensures that the material flow is uniform around the boot axis, thereby avoiding non-uniform orientation.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a sectional view showing a molding apparatus 10 used for carrying out a molding method according to an embodiment of the present invention. This molding apparatus 10 has an upper mold 11 and a lower mold 12, and the upper mold 11 and the lower mold 12 are formed with a recess corresponding to the bellows-shaped outer shape of the boot to be manufactured. Moreover, the inner separator 13 has a shape that matches the bellows-shaped inner shape of the boot, and the inner separator 13 is fitted into the recesses of the upper mold 11 and the lower mold 12 to connect the upper mold 11 and the lower mold 12. This molding device 10 is assembled by overlapping them. Then, a rubber material injection space 1 is opened between the upper mold 11, the lower mold 12, and the middle sesame 13.
8 (boot cavity) is formed. A connecting port 15 is provided on the upper surface of the upper mold 11 for injecting the fluidized rubber material from the injection device 14 into the molding device 10. and,
A gate 17 is formed in the center of the molding device 10 for supplying the rubber material to the bellows-shaped injection space 18 of the boot, and the gate 17 and the connecting port 15 are connected by a runner 16.

In this embodiment, the gate 17 is provided at the end of the boot on the small diameter side in the longitudinal direction, and has a circumferential opening along the edge of the small diameter side. As a result, runner 16
The rubber material supplied to the gate 17 is injected into the injection space 18 (boot cavity) in a cylindrical shape from the edge on the small diameter side of the boot.

In the molding method according to this embodiment, fluid rubber material is injected from the injection station 14 into the connecting port 15 of the molding device 10 by rotation of the screw.

This rubber material is, for example, chlorinated polyethylene (CPE
) is used as the base (matrix) rubber material, and nylon 6 is added as short fibers to this to create short fiber reinforced rubber (CF
RR; Chopped Fiber Reinfor
ced Rubber).

The rubber material injected into the molding device 10 is supplied via the runner 16 to a gate 17 having an opening along the cylindrical edge, and is injected from the gate 17 into the injection space 18 . The rubber material then flows within the injection space 18 towards the larger diameter end of the boot. In this case, unlike the case where the gate is dot-shaped, in this example the gate is circumferential, so the rubber material and short fibers extend along the peaks and valleys of the bellows from the small diameter side to the long diameter side. The velocity component in the circumferential direction of the bellows is extremely small. That is, the rubber material and short fibers advance symmetrically about the boot axis and flow radially from the small diameter end of the bellows toward the long diameter end. Therefore, in the molded product obtained by solidifying this rubber material, the short fibers are uniformly oriented along the longitudinal direction of the bellows, and very few short fibers are arranged in the circumferential direction of the bellows.

This results in a CFRR boot with extremely high radial rigidity. Therefore, when this boot is installed on an automobile drive shaft, the
Since the boot is prevented from swelling in the radial direction even when subjected to high-speed rotation of pm, durability is improved and the life of the boot is extended.

In the above embodiment, the gate is provided at the edge of the small diameter side of the boot, but the gate is not limited thereto, and the rubber material may be injected from the edge of the large diameter side. However, in consideration of the amount of unnecessary parts to be cut off after molding, it is preferable to inject from the short edge on the small diameter side where the circumference is short.

[Effects of the Invention] According to the present invention, the flow of the rubber material in the molding device is symmetrical around the boot axis, so the added short fibers are aligned uniformly, and are extremely aligned with respect to the boot radial direction. A boot molded product with high rigidity can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a molding device showing an embodiment of the present invention;
The figure is a schematic diagram showing a boot attached to an automobile drive shaft, and FIG. 3 is a schematic diagram illustrating a conventional method. 10; Molding device, 11; Upper mold, 12; Lower mold, 13; Middle sesame, 14; Injection device, 17; Gate, 18; Injection space

Claims (1)

[Claims] In a method for forming short fiber-reinforced rubber boots, in which a rubber material added with short fibers is injected into the gap between the outer mold and the inner sesame to form a bellows-shaped boot, the longitudinal direction of the injection space in the boot shape is A method for forming short fiber-reinforced rubber boots, characterized by injecting short fiber-added rubber material from one end using the entire circumference of the edge as a gate.