Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Sulfurized compound of indeterminate structure – which is a...
Patent
1997-06-05
1998-08-11
Howard, Jacqueline V.
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Sulfurized compound of indeterminate structure, which is a...
508408, 508441, 508442, 508586, C10M14108, C10M14110
Patent
active
057927316
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a lubricant composition for continuous variable transmissions and also to a method for lubricating continuous variable transmissions with said lubricant composition. This lubricant composition is superior in wear resistance and extreme pressure properties and is capable of keeping the coefficient of friction high for a long period of time and of transmitting a large amount of torque. It is particularly suitable for transmissions of metal belt type.
BACKGROUND ART
The conventional automotive automatic transmission consists of a torque converter and a finitely variable transmission comprising several gear trains. The transmission of this type has a problem with low efficiency due to slip loss in the torque converter and torque loss at the time of speed change. To address this problem, there has recently been developed an automotive continuous variable transmission that employs a steel belt. It is now in practical use.
This transmission, however, suffers the disadvantage that the coefficient of friction decreases so much under a high load that it cannot transmit a large torque and the belt slips at the time of rapid acceleration, resulting in a low ratio of torque transmission. This disadvantage arises from the fact that it is lubricated with the conventional lubricant (so-called ATF) for finitely variable transmissions. For this reason, the above-mentioned continuous variable transmission is used only for automobiles with a small-capacity engine (generating a small torque).
With a view to overcoming this disadvantage, attempts have been made to improve the ratio of torque transmission from the standpoint of mechanism. However, it has been found that improvement in torque transmission is incompatible with improvement in wear resistance, because torque transmission is always accompanied by slight slipping (which is inherent in the mechanism employed).
It is an object of the present invention to provide a lubricant composition and a method for lubrication with said lubricant composition. The lubricant composition of the present invention is superior in wear resistance and extreme pressure properties, capable of keeping a coefficient of friction high for a long period of time, and capable of transmitting a large amount of torque. It is particularly suitable for transmissions of metal belt type.
DISCLOSURE OF THE INVENTION
The present inventors carried out a series of researches to develop a lubricant composition for continuous variable transmissions which meets the above-mentioned requirements. As a result, it was found that a lubricant keeps the coefficient of friction higher than 0.10 for a long period time if its base oil is incorporated with a sulfur-based extreme pressure additive, a phosphorus-based extreme pressure additive, and an alkaline earth metal-based detergent as essential ingredients. This finding led to the present invention.
It is an object of the present invention to provide a lubricant composition for continuous variable transmissions which comprises a base oil, a sulfur-based extreme pressure additive (A), a phosphorus-based extreme pressure additive (B), and an alkaline earth metal-based detergent (C).
It is another object of the present invention to provide a method for lubricating continuous variable transmissions with said lubricant composition.
The preferred embodiments of the present invention are as follows.
A lubricant composition for continuous variable transmissions as defined above, wherein the sulfur-based extreme pressure additive is at least one species selected from sulfurized oils and fats, thiocarbamates, and thioterpenes.
A lubricant composition for continuous variable transmissions as defined above, wherein the phosphorus-based extreme pressure additive is at least one species selected from tricresyl phosphate and amine salts of alkyl or alkenyl acid phosphate ester.
A lubricant composition for continuous variable transmissions as defined above, wherein the alkaline earth metal-based detergent is calcium phenate.
A lu
REFERENCES:
patent: 3652410 (1972-03-01), Hollinghurst et al.
patent: 5492638 (1996-02-01), Wallace et al.
Ichihashi Toshihiko
Igarashi Hideo
Sonoda Noboru
Howard Jacqueline V.
Idemitsu Kosan Co. Ltd.
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