JPH0421570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an oil seal used in a bearing part of a mechanical device, and more specifically, it presents a means for molding a rubber portion of an oil seal. It is something.

(Prior Art) As shown in FIG. 3, an oil seal used in a bearing part of a mechanical device consists of a cylindrical part 2 and a radial part 3, and a mounting part 1 reinforced by a reinforcing ring 4.
a waist part 5 joined to the end of the radial part 3 and formed to be deformable; a seal lip 7 connected to the waist part 5 and sealingly sliding against the other peripheral surface at the tip;
It has a seal piece 6 with a spring insertion groove 8 for holding a garter spring added to appropriately apply contact pressure to the mating circumferential surface, and extends from the waist part 5 to the opposite side of the seal piece 6. Some are equipped with a dust seal piece 9.

As shown in FIG. 4, the rubber part of the oil seal described above is molded downward so as to correspond to the annular space sandwiched between the cylindrical part 2 of the mounting part 1, the waist part 5, and the seal piece 6. A reinforcing ring 4 having a substantially L-shaped cross section and an annular molding material piece 13 are placed on an annular protrusion 11 provided on a mold 10, and the waist portion 5, seal piece 6, and dust seal are placed. The upper mold 15 having a molding surface corresponding to the shape of the piece 9 is stacked, and then, as shown in FIG. 5, the upper mold 15 and the lower mold 10 are pressurized and heated. Following this molding process, as shown in FIG. 6, a mold release process is carried out in which the upper mold 15 and the lower mold 10 are separated to take out the molded product.

(Problems to be Solved by the Invention) In order to maintain the sealing function, the oil seal having the above-mentioned shape has a waist part in order to ensure that the seal piece 6 and the dust seal piece 9 follow the mating peripheral surfaces. 5 and the seal piece 6, the side walls of the dust seal piece 9 and the spring insertion groove 8 are formed thin, and the rubber portion consisting of the waist part 5, the seal piece 6, and the dust seal piece 9 has a complicated cross-sectional shape. Both upper and lower molds 1
The shape of the cavity formed by 0,15 is
During the transition from the state shown in FIG. 4 to the state shown in FIG. 5, and during the transition from the state shown in FIG. 5 to the state shown in FIG. 6,
During the former molding process, extremely complex stress is applied to the flowing molding material and affects the molded product, and during the latter mold release process, the stress is extremely complex. Since complex tensile stress, bending stress, etc. are applied to each thin-walled part, when the mold is released, cracks may occur in the part affected by the concentrated stress during the molding process. The risk of cracking in the thin-walled parts mentioned above varies depending on the rubber material, and it has been found that in oil seals made of fluorocarbon rubber, stress concentration due to changes in material flow during molding is extremely large. ing.

(Means for Solving the Problem) The inventors have proposed that the surface of the mold be applied to the surface of the mold corresponding to the thin rubber parts such as the joint between the waist part and the seal part, the dust seal part, and the side part of the spring insertion groove. It has been confirmed that by applying knurling, it is possible to prevent abnormal concentration of stress on the flow of the molding material during pressure molding as described above, and as a result, it is possible to prevent the occurrence of cracks during mold release.

Suitable groove shapes for knurling include multiple screw shapes, lattice stripes that intersect with each other at an angle, or intersect vertically and horizontally, and the cross-sectional shape of the narrow grooves formed by knurling can be arbitrary, such as triangular, trapezoidal, semicircular, etc. The protrusion formed on the surface of the oil seal by knurling maintains the flexibility of the seal piece, dust seal piece, etc. so that it does not affect the sealing function. Therefore, good results were obtained even when the height was kept to a microscopic level of about 0.1 mm and the apex angle was set at about 90 to 120 in the case of a triangular cross section.

(Function) As mentioned above, knurling is applied to the mold surface corresponding to the joint between the waist of the oil seal and the seal lip piece, the inner and side parts of the spring insertion groove, and the thin-walled parts such as the dust seal piece. When molding the rubber part of the oil seal using a mold,
When the piece of molding material placed on the lower mold together with the reinforcing ring flows into the molding cavity, which deforms as the upper and lower molds are pressurized, the thin grooves on the mold surface cause the material to deform. acts to regulate the flow of
Prevents the generation of concentrated stress during flow.

(Example) Fig. 1 shows an example of the structure of a mold used in the method of manufacturing an oil seal according to the present invention, and shows the mold surface corresponding to the joint between the waist part of the lower mold 10 and the seal lip part, and the spring insertion part. For example, on the mold surface corresponding to the inner surface and side portions of the groove and the mold surface corresponding to the dust seal lip portion of the upper mold 15, a second mold is applied.
It is knurled to form a narrow groove with a cross-sectional shape as shown in the figure.

(Effects) As described above, in the method for manufacturing an oil seal according to the present invention, a mold is formed that corresponds to thin-walled parts such as the joint part between the waist part and the seal lip part, the inner and side parts of the spring insertion groove, and the dust seal lip part. The rubber part is formed using a mold with knurling on the surface of the mold, which allows the flow of molding material to flow into the molding cavity due to the clamping pressure of both the upper and lower molds. However, the above-mentioned knurling process reduces the concentration of stress on the flowing material, thereby preventing cracks on the surface of the thin wall part during the mold release process that were observed in the conventional oil seal manufacturing method. Occurrence is completely prevented.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a mold used in the method for manufacturing an oil seal according to the present invention, and FIG.
The figure is a sectional view showing an example of the shape of a shallow groove formed by knurling, FIG. 3 is a sectional view showing an example of an oil seal to which the present invention applies, and FIGS. Figure 4 is a cross-sectional view showing the manufacturing process; Figure 5 is a cross-sectional view showing the situation at the time of completion of the molding process; Figure 6 is a cross-sectional view showing the mold release process. be. DESCRIPTION OF SYMBOLS 1... Mounting part, 2... Cylindrical part, 3... Radial part, 4... Reinforcement ring, 5... Waist part, 6... Seal piece, 7... Seal lip, 8... Spring insertion groove, 9 ... Dust seal piece, 10 ... Lower mold, 11 ... Annular protrusion, 13 ... Molding material piece,
15...Upper mold.

Claims (1)

[Claims] 1. In a method for manufacturing an oil seal having a waist portion 5 coupled to a radial end of the mounting portion 1 and seal pieces 6, 9 extending from the waist portion 5, the oil seal corresponds to the thin-walled portion of the rubber portion. A method for manufacturing an oil seal, the method comprising using a mold having a knurled surface. 2. A lower mold 10 whose mold surface corresponding to the joint between the waist portion 5 and the seal piece 6 is knurled.
A method for manufacturing an oil seal according to claim 1, which uses the following. 3. The method of manufacturing an oil seal according to claim 1, which uses a lower mold 10 whose mold surface corresponding to the inner surface of the spring insertion groove 8 is knurled. 4. The method for manufacturing an oil seal according to claim 1, which uses a lower mold 10 whose mold surface corresponding to the outer surface of the spring insertion groove 8 is knurled. 5. The method of manufacturing an oil seal according to claim 1, which uses an upper mold 15 whose mold surface corresponding to the dust seal piece 9 is knurled.