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It is clear that excessive lip wear is one of the origin of oil seal leakage in the market. In this paper, follows are discussed; Oil seals used for the rear side of automotive mission gear case have excessive lip wear as typical failure mode, and the sealing characteristics of oil seals is influenced by reciprocating motion of rotational shaft with rough surface.

It has recently become popular to enclose gas in shock absorbers in order to improve thier performance. The operating condition of oil seals for shock absorbers, therefore, has been changing, and some problems with frictional characteristics and sealing performance have newly been observed. This paper discusses how the problems are solved experimentally and reviews the countermeasures to prevent such problems before they actually happen.

Improvement of automotive fuel consumption is subject of saving energy today. Oil seals with low friction for automobile are required in the market. In this report, an idea for decreasing the friction of seals and its concreate countermeasure are discussed. It becomes clear that developed low friction seals have good sealing performance as same as present seals.

New type oil seals - nonwoven fabric secondary lip type oil seals are recently widely used for one of the sealing apparatus for automotive application. Basic improvement of this type of seals is in a secondary lip which prevents solid foreign matters such as dust and sand from entering into the rubbing portion between a primary lip of oil seals and a shaft. This secondary lip is superior in anti-dust property, wear resistance, following ability to the shaft eccentricity and air permeability to the conventional secondary lip of rubber. And the sealing performance of new type seals with the secondary lip made of special nonwoven fabrics is more stable than that of the conventional rubber seals.

Fine solid particles in a lubricating oil affect the sealing characteristics of oil seals, and their lives are shortened by the wear of oil seals and shafts created by the particles. Tests were carried out by using various kinds of foreign matters. The results showed that foreign matters in oil film between the sealing lip and the shaft surface directly caused the leakage. Consequently, it was reconfirmed that the practical application of dust lip and the countermeasure in the construction of seals or their housings were indispensable to obtain the long life and the stable operation of oil seals.

For purpose of clarifying the effect of quantity of lubricating oil supplied to the seal lip portion on sealing characteristics of oil seals, relations between the typical constructional applications of the fitting portion for oil seals and the quantity of the lubricating oil supplied to the oil seals are discussed. Then the necessary minimum quantity of the lubricating oil for preventing the seal lip from wear is investigated. And it is clarified that the decrease in sealing characteristics occurs when the lubricating oil is supplied insufficiently to the seal lip portion and, finally, the countermeasure is discussed.

Through the market experience and information analysis, the importance of Sealing Reliability Activity, especially at the beginning step of determining temporary design specification of oil seal and at the step of evaluation of prototype seals produced according to the temporary design specifications, is discussed.

In order to improve the reliability of seals for automotive application in practical use, it is considered that further basic investigations concerning sealing characteristics of seals are necessary. However, it has been found, from analyzing seals decided in the market as defective parts, that the troubles of seals in the market are mainly caused by both wrong handling for seals and the use under wrong operating condition which has not been expected by manufacturers of seals. Therefore, in order to improve the reliability of seals, it is important to investigate in detail troubles on functional characteristics of seals and their countermeasures. In this paper, on oil seals, O-rings, water pump seals and dust cover seals as seals for automotive application, the results of investigations are discussed.