Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
1999-11-24
2001-05-15
McAvoy, Ellen M. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S293000, C508S294000, C508S441000, C508S442000, C508S551000, C508S554000
Reexamination Certificate
active
06232275
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lubricating oil composition for automatic transmissions. More particularly, the present invention is concerned with a lubricating oil composition for automatic transmissions which is excellent in the performance of preventing shudder of friction materials in a clutch portion for automatic transmissions, enhanced in the capacity of transmission torque, and at the same time capable of maintaining the performance of preventing said shudder and the enhanced capacity of transmission torque for a long period of time.
2. Description of the Related Arts
There has been introduced in recent years, a slip control system of operating a lockup mechanism even in the region of low velocity of automobile transmissions in order to decrease a power transmission loss in automatic transmissions and improve fuel consumption. In the case, however, where a lockup mechanism is operated in the region of low velocity of automobile transmissions, there is frequently caused the problem that abnormal vibration of an automobile body called shudder takes place in lockup friction surfaces. In such circumstances, there is eagerly desired the development of a lubricating oil composition for automatic transmissions which is capable of preventing said shudder and maintaining the transmission torque at a high level for a long period of time.
It is known that in order to prevent the above-mentioned shudder, there is required such a &mgr; (friction coefficient) —V (sliding velocity) characteristics that the friction coefficient increases with an increase in the sliding velocity. There has heretofore been suggested the use of a friction modifying agent such as a phosphoric acid ester and an amidocarboxylic acid. For instance, Japanese Patent Application Laid-Open Number 305082/1995 (Heisei-7) discloses a lubricating oil composition for automatic transmissions which comprises a base oil blended with {circle around (1)} a zinc dithiophosphate and/or a basic zinc dithiophosphate, {circle around (2)} at least one compound selected from the group consisting of phosphoric acid esters, acidic phosphoric acid esters and phosphorous acid esters and {circle around (3)} an organic friction modifying agent in which a specific bond and/or a functional group are introduced in its molecules. The aforesaid composition, although being favorable in the initial performance of preventing shudder, suffers from the disadvantage that in the case of long-term usage, the zinc dithiophosphate is stuck to the surface of a wet clutch and markedly shorten the duration of preventing the shudder, thus making it impossible to maintain the initial performance. In addition, Japanese Patent Application Laid-Open Number 254196/1988 (Showa-63) discloses the use of a friction modifying agent such as a phosphoric acid ester, a fatty acid ester or a fatty acid amide as an additive for a lubricating oil composition for automatic transmissions. The above-mentioned composition, however, is insufficient in the initial performance of preventing the shudder.
That is to say, the use of the above-disclosed compound brings about such problems as insufficiency in the performance of preventing shudder, lowering of the friction coefficient (&mgr;) in a wet clutch portion and/or the shortage of capacity of transmission torque. Further, the problems still remain unsolved in that persistency of favorable &mgr; -V characteristics is insufficient as compared with the service lifetime of automobile bodies, and frequent renewal of lubricating oil is forced to carry out.
SUMMARY OF THE INVENTION
Under such circumstances, a general object of the present invention is to reconcile both the performance of preventing shudder vibration and the capacity of transmission torque, and thereby provide a lubricating oil composition for automatic transmissions which has a long service lifetime.
Other objects of the present invention will be obvious from the text of this specification hereinafter disclosed.
In view of the foregoing, intensive extensive research and investigation were accumulated by the present inventors in order to achieve the objects. As a result, it has been found that the objects can be effectively attained by a method in which a specific base oil is blended with non-boron based and boron based succinic acid imides, a condensation product of a branched chain fatty acid and an amine, and a dialkyl hydrogenphosphite. The present invention has been accomplished by the foregoing findings and information.
Specifically, the present invention provides a lubricating oil composition for automatic transmissions which comprises a base oil comprising at least one oil selected from the group consisting of a mineral oil and a synthetic oil each having a kinematic viscosity at 100° C. of 1 to 30 mm
2
/sec and a % C
A
(aromatic carbon content in percentage when measured by an n-d-M ring analysis method) of at most 20; (A) a non-boron based succinic acid imide and a boron based succinic acid imide each in an amount of 0.1 to 5% by weight based on the whole composition; (B) a condensation product of a branched chain fatty acid having 8 to 30 carbon atoms and an amine in an amount of 0.05 to 2% by weight based on the whole composition ; and (C) a dialkyl hydrogenphosphite in an amount of 0.1 to 1% by weight based on the whole composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lubricating oil composition for automatic transmissions comprises a base oil, (A) a non-boron based succinic acid imide and a boron based succinic acid imide, (B) a condensation product of a branched chain fatty acid and an amine, and (C) a dialkyl hydrogenphosphite.
It is possible to employ any of a mineral oil and a synthetic oil as the base oil for the lubricating oil composition according to the present invention. There are usable, as the mineral oil, a variety of well known conventional mineral oils that are exemplified by paraffin base mineral oil, intermediate base mineral oil and naphthene base mineral oil. Specific examples thereof include a light neutral oil produced by solvent refining or hydrorefining, an intermediate neutral oil, a heavy neutral oil and bright stock.
There are usable, as the synthetic oil, a variety of well known conventional synthetic oils that are exemplified by poly&agr;-olefin (including &agr;-olefin copolymer), polybutene, polyol esters, dibasic esters, phosphoric acid esters, polyphenyl ethers, alkylbenzenes, alkylnaphthalenes, polyoxyalkylene glycols, neopentyl glycol, silicone oil, trimethylol propane, pentaerythritol and hindered esters. Any of the above-exemplified oils may be used alone or in combination with at least one other oil, for instance, the combination of a mineral oil and a synthetic oil.
It is necessary for the above-mentioned base oil to have a kinematic viscosity at 100° C. of 1 to 30 mm
2
/sec and a % C
A
of at most 20. A a kinematic viscosity at 100° C. thereof, when being less than 1 mm
2
/sec, leads to an increased friction at the sliding portions of a gear bearing and a clutch in the automatic transmission, whereas said kinematic viscosity, when being more than 30 mm
2
/sec, brings about such inexpedience as the deterioration of low temperature characteristics of the oil. In view of the foregoing, the above-mentioned kinematic viscosity at 100° C. is preferably 2 to 20 mm
2
/sec, more preferably 3 to 10 mm
2
/sec. Moreover, the % C
A
thereof is preferably at most 10, since the % C
A
of more than 20 results in the deterioration of low temperature characteristics of the oil.
In the composition according to the present invention, there are used a general succinic acid imide ( non-boron based succinic acid imide ) and a boron-containing succinic acid imide (boron based succinic acid imide) in combination as the component (A) for the main purpose of improving dispersibility of sludge to be formed.
As the non-boron based succinic acid imide in particular, there is preferably used the succinic acid imide represented by the general formula:
wherein R
1
is an alkyl
Ichihashi Toshihiko
Ishikawa Takao
Kato Masayuki
Murakami Yasuhiro
Umesato Kazuo
Idemitsu Kosan Co. Ltd.
McAvoy Ellen M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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