JPS6116447Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an oil seal device for a piston rod in a hydraulic shock absorber. The present invention relates to an oil seal device capable of ensuring sufficiently reliable sealing performance under various operating temperature conditions.

Conventionally, single-type high-pressure oil seal devices have been widely used in hydraulic shock absorbers for motorcycles, four-wheeled vehicles, and the like. However, when this single-type oil seal device has a single seal lip, the pressure distribution of the seal lip changes when the pressure is high, making it difficult to maintain a sealed state and easily causing oil leakage. Furthermore, even if multiple seal lips are used as an improvement to a single seal lip, since the base of the seal device is shared, each seal lip does not perform its sealing function independently and is influenced by other seal lips. However, it was not yet sufficient to improve the pressure resistance and the follow-up sealing performance against the piston rod.

Furthermore, in order to improve the various shortcomings of the conventional single-type oil seal device, an oil seal device (Utility Model Open 1989-1983) was developed in which composite seal members are arranged in multiple stages in order to satisfy the requirements of pressure resistance and followability to the piston rod. 24449) is provided. However, since such oil seal devices do not take temperature conditions into consideration, sufficient effects cannot be obtained at room temperature in terms of oil leakage, pressure resistance, and ability to follow the piston rod.

That is, not only the single oil seal device but also the multi-stage oil seal device,
Since the seal rubber material is the same material, there are limits to the operating temperature conditions of the rubber material, such as the cold temperature at which it can exhibit elasticity and the heat resistance temperature at which it does not cause heat aging, and therefore it can be covered normally with the same material. Oil leakage could not be avoided under temperature conditions exceeding the normal operating temperature range, for example, at low temperatures below -30°C and high temperatures above 160°C.

The present invention was developed in view of the conventional problems, and includes nitrile rubber, which is a low-temperature rubber material with excellent cold resistance that does not lose its elasticity even at low temperatures, and nitrile rubber, which does not cause heat aging even at high temperatures. By combining sealing members made of fluorine rubber, which is a high-temperature rubber material with excellent heat resistance, and arranging them in parallel in the cylinder, sufficiently reliable sealing performance can be obtained even under a wide range of operating temperature conditions. An oil seal device is provided.

FIG. 1 is a sectional view of essential parts showing an embodiment of the oil seal device of the present invention. This oil seal device has a sealing member 7 made of nitrile rubber, which is a low-temperature rubber material with a low glass transition point and excellent cold resistance, on the axially inner side of the cylinder 6, and a sealing member 7 made of nitrile rubber, which is a low-temperature rubber material with a low glass transition point and excellent cold resistance, and a sealing member 7 on the axially outer side at a temperature that causes heat aging. The sealing member 1 is made of fluororubber, which is a high-temperature rubber material with excellent heat resistance.

To explain in more detail, 1 is, for example, -10℃ to 200℃
A ring-shaped sealing member made of, for example, fluororubber, which is a high-temperature rubber material, and which has sufficient elasticity between It is baked onto the gold 2 upright piece 2a.

The seal member 1 branches into a dust seal lip 3 and an oil seal lip 4 from a portion where the upright piece 2a is located, and these are in elastic contact with the outer peripheral surface of the piston rod 5. On the other hand, the seal member 1
In the lower part of the cylinder 6, that is, further inside the cylinder 6,
A cylindrical portion 7a of a ring-shaped sealing member 7 made of a low-temperature rubber material, for example, nitrile rubber having sufficient elasticity between -40°C and 100°C, is fitted and fixed. This sealing member 7 is also integrated with the L-shaped core metal 8 by baking. The cylindrical portion 8b of the core metal 8 is held on the inner circumferential surface of the cylinder 6 together with the cylindrical portion 7a, and an oil seal lip 9 is provided protruding from the end side of the upright piece 8a of the core metal 8. In addition, a plurality of through holes 10 are provided in the center of the upright piece 8a of the core bar 8.
A through hole 11 is provided in the sealing member 7 on the upper part of the core bar 8 facing these through holes 10.
The lower seal member 7 is provided with an opening/closing flap piece 12 formed by cutting a portion of the lower seal member 7. In addition, 13 and 14 are the respective oil seal lips 4,
This is a garter spring that urges the piston rod 9 toward the piston rod 5 side.

In such an oil seal device, the high-temperature seal member 1 performs a sufficient sealing action at the above-mentioned high temperature within a temperature range that does not cause thermal aging, and the low-temperature seal member 7 has a strain that does not impair its elasticity. It achieves sufficient sealing action in the above-mentioned low temperature range within the 10% recovery point (TR50/10) temperature, and as a result, it can be used over a wide range of operating temperature conditions (-40℃ to 200℃) that cannot be covered by a single material. ) can be satisfied. In this case, when the piston rod 5 slides, the oil scraped off by the oil seal lips 4 and 9 is accommodated in the gap A between the seal members 1 and 7. When the oil pressure or the amount of oil in A exceeds a predetermined value, the flap 12 bends inside the cylinder 6, opens the through holes 10 and 11, and the oil is returned to the inside of the cylinder 6 (when the piston is lowered), filling the air gap. The pressure inside part A can be released. Thereby, the sealing action of each oil seal lip 4, 9 can be made smooth.

By the way, the seal member 1 for high temperatures is provided outside the cylinder 6 with respect to the seal member 7 for low temperatures. This was done in view of the fact that such an oil seal device is effective when the operating temperature cycle exceeding the normal operating temperature range is normal temperature→low temperature→high temperature. That is, at low temperatures, the inner seal member 7 is effective and oil does not leak into the gap A on the outer seal member 1 side. Therefore, at low temperatures, the outer high temperature seal member 1 hardens and loses its elasticity. Even if it loses its follow-up sealing properties, there is no need to worry about leakage to the outside. On the other hand, even if the sealing member 7 on the low-temperature side loses its sealing properties due to thermal aging and oil leaks into the gap A after the temperature reaches high temperature, the outer high-temperature sealing member 1 is effective, so the external Reliably prevents oil leakage.

However, in the above operating temperature cycle, if the seal member 7 for low temperature and the seal member 1 for high temperature are arranged in reverse order, the inner seal member will harden at low temperature and lose its sealing properties, causing the above-mentioned void. After an oil leak occurs in part A and the temperature rises, the outer low-temperature sealing member loses its sealing properties due to heat aging, so the oil that leaked into gap part A during the previous low temperature is transferred to cylinder 6. This will cause leakage to the outside of the
If the arrangement is reversed in the above operating temperature cycle exceeding the normal operating temperature range, oil leaks to the outside. That is, it is necessary to provide the low-temperature sealing member 7 inside the high-temperature sealing member 1, especially in order to improve the low-temperature sealing performance.

In addition, if the operating temperature cycle exceeding the normal operating temperature is normal temperature → high temperature → low temperature, if the low temperature seal member 7 causes thermal aging phenomenon under high temperature, then at low temperature, The sealing function is equivalent to that of an oil seal device made of a single material.

FIG. 2 shows another embodiment of the oil seal device of the present invention. This is different from what is shown in FIG. 1, in that the core bar 2' is extended downward along the inner circumferential surface of the cylinder 6, and upright pieces 2a' and 8a' are provided in two stages on this. The seal member 1 for high temperature and the seal member 7 for low temperature are baked,
The base of the sealing member 7' is a thin flap piece 15. This flap piece 15 is normally in contact with the sealing member 1' portion that is fitted and fixed to the cylinder 6 due to its own elastic force, and when the amount of oil leaking into the gap A' reaches a predetermined value, the chain line It is designed to be opened as shown in .

Even with such an oil seal device, the oil sealing action at high and low temperatures can be achieved in a wide range of operating temperature conditions. Furthermore, when the pressure of the oil pushed into the cavity A' by each oil seal lip 4', 9' reaches a predetermined level, the flap piece 15 can be opened and returned to the cylinder 6. can.

As explained in detail above, according to the present invention, an oil seal device for a piston rod in a hydraulic shock absorber uses nitrile, a low-temperature rubber with excellent cold resistance that does not lose its elasticity even at low temperatures. A low-temperature sealing member made of rubber and a high-temperature sealing member made of fluororubber, which is a high-temperature rubber material with excellent heat resistance that does not cause heat aging even at high temperatures, are arranged in two stages inside and outside the cylinder in the axial direction. By arranging them in parallel, it is possible to obtain an oil seal device that is effective and has sufficient elasticity and sealing performance even in a wide range of operating temperatures exceeding normal operating temperatures. In this way, conventional single-type oil seal devices made of a single material or two-stage oil seal devices that exhibit a sealing effect at normal operating temperatures could not cope with the problem of oil at low or high temperatures exceeding the normal operating temperature. This eliminates leakage, which is extremely beneficial in practice.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an oil seal device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a main part of another embodiment. 1, 1'...High temperature side sealing member, 5...Piston rod, 6...Cylinder, 7,
7'...Sealing member on the low temperature side.

Claims (1)

[Scope of utility model registration request] An oil seal device for a piston rod in a hydraulic shock absorber, characterized in that a sealing member made of nitrile rubber is provided on the axially inner side of the cylinder, and a sealing member made of fluorine rubber is similarly provided on the axially outer side of the cylinder. sealing device.