JPS643015Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to an oil seal, and more specifically, to an oil seal suitable for use under conditions where foreign substances such as muddy water and sludge are present.

(Prior Art) In a conventional oil seal, as shown in FIG. 1, a lip portion 1 that makes sliding contact with the circumferential surface of a shaft is made of rubber, and a circumferential groove 1a is formed in the outer peripheral portion of this lip portion 1. The coil spring 2 is tied to the circumferential groove 1a in an exposed state, and the coil spring 2 is
It functions to compensate for the reduction in interference of the lip portion 1 due to wear and deformation of the rubber, and to improve the ability of the lip portion 1 to follow shaft runout.

(Problems to be Solved by the Invention) However, such a structure has the following problems, and improvements have been desired.

That is, as shown in FIG. 2, when the oil seal is fitted and assembled onto the shaft 3, the lip portion 1 of the oil seal changes from the state shown by the imaginary line (the state before assembly) to the state shown by the solid line. The diameter is expanded and deformed to the state shown (the state after assembly) by the amount of interference. Due to this diameter-expanding deformation, the coil spring 2 also expands by the amount of this diameter-expanding deformation, creating a gap between the spring wires.

Therefore, when this oil seal is used in an external environment where it is exposed to muddy water or sludge, mud or sludge may be present in the gap between the spring wires of the coil spring 2, as shown in FIG. Foreign matter A such as the following will enter.

However, in the lever state, even if the interference decreases in the lip part 1 due to wear of the lip part 1, the contraction of the coil spring 2 is inhibited due to the foreign matter A that has entered between the spring wires. As a result, sufficient contraction cannot be performed to compensate for the decrease in interference, resulting in early deterioration of sealing performance.

(Means for solving the problem) The present invention solves such conventional problems and
The purpose of this invention is to provide an oil seal that is not affected by foreign substances such as sludge even when used under conditions where such foreign substances are present, and that can maintain sealing performance over a long period of time. .

To achieve this purpose, the oil seal of the present invention has a coil spring tied to the outer circumference of the rubber lip of the seal body, and the exposed portion of the coil spring is covered with a rubber coating. In this case, the coil spring 4 is a pipe-shaped spring with a small spacing between spring wires, an adhesive is applied to the outer peripheral surface of the coil spring 4, and the inner half body of the coil spring 4 is connected to the seal body. The seal body 7 is embedded in the outer circumference of the lip portion 9 of the seal body 7, and its outer half body is covered with a thin rubber coating 5 that allows the coil spring 4 to expand and contract normally, so that the coil spring 4 and the seal body 7 are integrated. It is characterized in that a recess 9 is formed over the entire circumference of the axially distal end portion of the lip portion 6 at a portion located radially inward from the center of the coil spring 4.

(Function) The inner half of the coil spring 4, which is a pipe-shaped spring with a small spacing between spring wires, is buried in the outer circumference of the lip portion 6 of the seal body 7, and the outer half of the coil spring 4 is embedded in the outer circumference of the lip portion 6 of the seal body 7. The coil spring 4 is coated with a thin rubber coating 5 that allows normal expansion and contraction, and the coil spring 4 and the seal body 7 are integrally molded. It is not exposed and is completely unaffected by foreign substances such as muddy water and sludge.

Furthermore, by integrally molding the coil spring 4 and the seal body 7, the manufacturing process can be facilitated and simplified.

Adhesive is applied to the outer circumferential surface of the coil spring 4, and the outer circumference is coated with rubber, forming a uniform thin rubber coating on the outer circumferential surface of the coil spring 4;
This enables the coil spring 4 to exhibit stable performance.

Furthermore, in the axial tip portion of the lip portion 6, a recess 9 is formed around the entire circumference at a portion located on the inner diameter side from the center of the coil spring 4, and an oil seal is integrally molded with a mold. When doing,
The coil spring 4 is reliably positioned by the portion corresponding to the recess 9 of the mold.

(Example) An example of the present invention will be described below based on FIGS. 4 and 5.

As shown in FIG. 4, the oil seal of the present invention has a structure in which a coil spring 4 and a seal body 7 are integrally molded.

That is, the inner half of the coil spring 4 is buried in the lip portion 6 of the seal body 7, and the outer half of the coil spring 4 is covered with a thin rubber coating 5, so that it is integrated with the seal body 7. Molded.

As the coil spring 4, a pipe-shaped spring is used in which the gap between the spring wires (spring wire spacing) is set small, and in the illustrated example, the spring wire spacing is set to zero as shown in FIG. In addition, a pipe-shaped spring without a gap is preferably used.

The thin rubber coating 5 is formed into a thin film having a thickness sufficient to allow the coil spring 4 to expand and contract normally.

A specific method for forming the thin rubber coating 5 is to set the coil spring 4 coated with adhesive in advance in a mold (not shown), and fill the space between the mold and the coil spring 4 with rubber. Apply pressure. Due to this pressurization, the filled rubber flows along the adhesive-coated surface of the coil spring 4 and becomes a thin film, and is tightly adhered to the adhesive-coated surface.
This is done simultaneously with the vulcanization molding of the oil seal.

The adhesive is essential for forming a uniform thin rubber coating 5 on the outer circumferential surface of the coil spring 4 and for stably exhibiting a predetermined performance of the coil spring 4. By the way, even if you try to form the thin rubber coating 5 without using this adhesive,
It has been confirmed that the flow of the rubber itself tends to be uneven over the entire outer peripheral surface of the coil spring 4, making it difficult to form the thin rubber coating 5, and that the coil spring 4 does not exhibit its intended performance. ing.

Further, as shown in FIG. 4, in the axial tip end of the lip portion 6, a recess 9 is formed around the entire circumference at a portion located on the inner diameter side from the center of the coil spring 4. It is said that

The recess 9 is formed when the oil seal is integrally molded with the mold, and when the oil seal is integrally molded with the mold, the portion corresponding to the recess 9 of the mold is formed with the coil spring. It can be used to ensure positioning in step 4.

In connection with this, the cross-sectional shape of the lip portion 6 of the seal body 7 is as shown in FIG. It is said to have a shape. That is, the axially protruding part 8 is formed at the tip of the lip part 6 on the axially open end side, and the outer circumferential surface of this axially protruding part 8 is shaped so as to be located radially inward from the center of the coil spring 4. Further, the recess 9 is formed at the connection portion between the base of the axial protrusion 8 and the thin rubber coating 5.

Therefore, even when the oil seal configured as described above is used in an external environment where it is exposed to muddy water or sludge, the coil spring 4
The entire outer periphery of the tank is covered and is not exposed to the outside, so it is completely unaffected by foreign substances such as muddy water and sludge.

Therefore, even if the lip portion 6 of the seal body 7 suffers a reduction in interference over time due to wear or the like, the coil spring 4 will have sufficient strength to compensate for this loss of interference. It is possible to perform precise contraction and maintain stable sealing performance over a long period of time.

Next, in order to investigate the performance of the oil seal according to the present invention, the results of a performance test comparing it with a conventional oil seal will be explained.

First, both the oil seal of the above embodiment and the conventional oil seal shown in Fig. 1 were mounted on a shaft and immersed in muddy water, and their inner diameters were measured to examine changes in interference due to foreign matter adhesion. In the conventional example,
As shown by the broken line in Figure 6, the actual interference decreased with the passage of immersion time, whereas in the oil seal of the example, it was confirmed that the initial interference was maintained regardless of the passage of immersion time. It was done.

In addition, as shown in Fig. 7, one side of the shaft B on which the oil seal S is attached is set as a muddy area, and the other side is set as an air area, and the sealing performance is measured for the oil seal of the above embodiment and the conventional oil seal. did.
As a result, as shown in FIG. 8, it was confirmed that the oil seal of the example had almost twice the lifespan of the conventional oil seal in terms of muddy water resistance.

(Effects of the invention) As detailed above, according to the invention, various effects as listed below can be obtained, and the oil seal is optimal for use under conditions where foreign substances such as muddy water and sludge are present. can be provided.

(1) The coil spring 4 is made of a pipe-shaped spring with a small spacing between spring wires, and its inner half body is connected to the seal body 7.
It is buried in the outer peripheral part of the lip part 6, and
Since its outer half body is covered with a thin rubber coating 5 that allows the coil spring 4 to expand and contract normally, and is integrally molded with the seal body 7, the entire outer periphery of the coil spring 4 is covered. , is not exposed to the outside and is completely unaffected by foreign substances such as muddy water and sludge.

Therefore, even when used under conditions where foreign matter such as muddy water or sludge is present, it is possible to completely prevent foreign matter from entering the gap between the coil spring wires, and this reduces the interference of the lip portion of the coil spring. can perform enough contraction to compensate for the
Seal performance can be maintained over a long period of time.

(2) Since adhesive is applied to the outer peripheral surface of the coil spring 4 and the outer periphery is covered with rubber,
A uniform thin rubber coating can be formed on the outer peripheral surface of the coil spring 4.

That is, by using the above adhesive, the flow of the rubber itself over the entire outer circumferential surface of the coil spring 4 becomes uniform during molding, and the coil spring 4 is buried in the rubber coating, and the rubber coating and the coil spring 4 are bonded together. The thin rubber coating 5 is reliably formed in close contact with the thin rubber coating 5 without any separation. Furthermore, after the oil seal is formed, the coil spring 4 will not fall off.

Furthermore, when a rubber coating is formed directly on the outer periphery of a coil spring, if the rubber coating becomes scratched due to the tension applied to the rubber coating, there is a risk that the rubber coating will burst and the coil spring will be exposed. Since adhesive is applied to the outer peripheral surface of the coil spring 4 and the outer periphery is coated with rubber, even if the rubber coating is damaged, the rubber coating will not be torn and there is no risk of the coil spring being exposed. .

As a result, the coil spring 4 exhibits stable performance.

In addition, since the thin rubber coating 5 is entirely adhered to the outer circumferential surface of the coil spring 4, it expands and contracts in accordance with the expansion and contraction of the coil spring 4, allowing the coil spring 4 to expand and contract normally. Therefore, due to the formation of the thin rubber coating 5, the normal operation of the coil spring 4 is not inhibited and its function is not impaired.

Moreover, the entire thin rubber coating 5 is the coil spring 4.
If the coil spring 4 is bonded to the outer circumferential surface of the coil spring 4, even if a part of it is damaged, the thin rubber coating will not be torn and the coil spring 4 will not be exposed to the outside. Entry between the coil spring wires can be completely prevented, and the coil spring 4
Its stable performance is demonstrated over a long period of time.

(3) Since the coil spring 4 and the seal body 7 are integrally molded, the manufacturing process is easy and simple.
As a result, product costs can be reduced.

(4) At the tip of the lip portion 6 in the axial direction, a portion located on the inner diameter side from the center of the coil spring 4,
Since the recess 9 is formed over the entire circumference, when integrally molding the oil seal with a mold, it is possible to accurately position the coil spring 4 at a portion of the mold corresponding to the recess 9. ensured that
In this respect as well, the desired performance of the coil spring 4 can be obtained.

(5) Furthermore, due to the presence of the recess 9, the range of the thin rubber coating 5 formed on the outer periphery of the coil spring 4 can be made as large as possible, thereby improving the function of the coil spring 4. In addition to reducing the influence of the rubber part, it is possible to reduce costs by reducing the amount of rubber used.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the structure of the lip part of a conventional oil seal, Figure 2 is an explanatory diagram showing the oil seal installed on the shaft, and Figure 3 is a diagram showing the possibility of foreign matter entering between the coil spring wires of the oil seal. 4 is a cross-sectional view showing the structure of the lip portion of an oil seal according to an embodiment of the present invention, FIG. 5 is a cross-sectional view showing an enlarged coil spring portion of the oil seal, and FIG. A graph showing a comparison of interference changes due to foreign matter adhesion between the oil seal of the same example and a conventional oil seal. Figure 7 shows the settings for a comparison test regarding the muddy water resistance of the oil seal of the same example and the conventional oil seal. FIG. 8 is a graph showing the comparative test results. 4...Coil spring, 5...Thin rubber coating, 6...
... lip portion, 7 ... seal body, 8 ... axial protrusion, 9 ... recess.

Claims (1)

[Claims for Utility Model Registration] (1) An oil seal in which a coil spring is tied to the outer periphery of a rubber lip of a seal body, and the exposed portion of the coil spring is covered with a rubber coating, The coil spring 4 is a pipe-shaped spring with a small spacing between spring wires, an adhesive is applied to the outer peripheral surface of the coil spring 4, and the inner half of the coil spring 4 is attached to the lip of the seal body 7. The seal body 7 is embedded in the outer peripheral portion of the seal body 6, and its outer half body is covered with a thin rubber coating 5 that allows the coil spring 4 to expand and contract normally, and the coil spring 4 and the seal body 7 are integrally molded. At the axial tip end portion of the lip portion 6,
An oil seal characterized in that a recess 9 is formed around the entire circumference of the coil spring 4 at a portion located on the inner diameter side from the center. (2) the recess 9 is formed at the connection portion between the base of the axial protrusion 8 formed at the tip of the lip portion 6 of the seal body 7 and the thin rubber coating 5 of the coil spring 4; The oil seal according to claim 1, wherein the outer circumferential surface of the axial protrusion 8 is located radially inward from the center of the coil spring 4.