Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-06-05
2003-07-15
Howard, Jacqueline V. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S199000, C508S391000
Reexamination Certificate
active
06593281
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a lubricating oil composition for automatic transmissions.
BACKGROUND OF THE INVENTION
The lubricating oil for automatic transmission is one that is used for automatic transmissions such as those of automobiles and the like having a torque converter, a gearing, a hydraulic mechanism, a wet clutch built therein. The lubricating oil for automatic transmission is required to have many functions as a transmission medium of power against a torque converter, a hydraulic system, a control system and the like, a lubricating medium or a heating medium for temperature control against gearings, bearings, a wet clutch and the like, and also as a lubricating medium or a friction characteristic lock-up medium or the like for friction plates.
A lock-up clutch that is effective in improving a fuel cost has been recently adopted for an automotive automatic transmission. Under this arrangement, the transmission is built in a torque converter. The lock-up clutch functions to transmit the drive power of an engine directly to the transmission depending on the travelling conditions and effect the change over between the drive of the torque converter and the direct drive at an appropriate timing, thereby improving the efficiency of the torque converter.
The lubricating oil required for such an automatic transmission as set out hereinabove should be one that has a good &mgr; (coefficient of friction)-V (sliding velocity) characteristic, i.e. the degree in reduction of the coefficient of friction depending on the increase in relative sliding velocity is small, or the oil has such a friction characteristic of a positive gradient that the coefficient of friction increases with an increasing sliding velocity.
In the lubricating oil for automatic transmission, there has been hitherto proposed the use, as a friction modifier, of phosphoric esters, fatty acid esters, fatty acid amides and the like as set out, for example, in Japanese Patent Application Laid-open No. Sho 63-2544196. However, the formation of such a friction modifier as mentioned above has a difficulty in that the coefficient of friction is lowered within a range of a low sliding velocity of the lock-up clutch, thereby causing a transmission torque capacity to become insufficient at the time of clutch coupling.
For the purpose of increasing the transmission torque capacity, we have already proposed the use of at least one of a metal alkylphenate and a metal alkylphenate sulfide in Japanese Patent Application Laid-open No. Hei 5-105892, the use in combination of a metal salt of an organic acid such as calcium sulfonate or the like with a specific type of polyamide compound in Japanese Patent Application Laid-open No. Hei 8-319494, and the formulation, in a base oil, of a metal salt of an organic acid, a specific type of polyamide compound, and an acidic phosphoric ester, etc. in Japanese Patent Application Laid-open No. Hei 10-265793.
Further, there have been proposed, in Japanese Patent Application Laid-open No. Hei 9-328697, a lubricating oil composition for automatic transmission having excellent shudder proofness wherein a sulfur-containing antioxidant, phosphoric esters and a reaction product between a carboxylic acid and an amine are formulated in a base oil, in Japanese Patent Application Laid-open No. Hei 10-306292, a lubricating oil composition for automatic transmission having excellent shudder proofness wherein Ca-sulfonate having a specified total base number and phosphites are formulated, and, in Japanese Patent Application Laid-open No. Hei 11-116982, a lubricating oil composition having excellent shudder proofness wherein calcium sulfonate, etc., zinc dithiophosphate and a bisphenol antioxidant are formulated.
However, in spite of these proposals, the friction plate of wet clutch is clogged when used over a long time, with the attendant problem that the coefficient of friction at the lock-up clutch lowers and a friction characteristic such as a &mgr;-V characteristic is worsened. The clogging of the friction plate is considered, as one factor, to result from the formation, in a lubricating oil, of a precipitate insoluble in the lubricating oil. Especially, in order to obtain both a high torque capacity of a wet clutch and a good &mgr;-V characteristic, it is effective to formulate a boron-containing succinimide ashless dispersant. In the use of the dispersant, a precipitate may be formed, in some case, in a lubricating oil when moisture is present, thus leading to the problem on the possibility of the clogging of the friction plate and the blocking of a lubricating oil path.
SUMMARY OF THE INVENTION
The invention provides a lubricating oil composition for automatic transmission, which has both a high wet clutch torque capacity and a good &mgr;-V characteristic (i.e., positive with respect to the gradient thereof) and enhanced storage stability in a high humidity environment. Herein &mgr; means coefficient of friction and V means sliding velocity.
Applicants have found that when at least three additives including a friction modifier (A), a metal detergent (B), and a specific type of ashless dispersant (C) are formulated in a lubricating base oil as essential components, there can be obtained a lubricating oil composition for automatic transmission which has both a high torque capacity of a wet clutch, i.e., a satisfactory coefficient of friction in a high sliding velocity region, and such a property that the &mgr;-V characteristic is positive in gradient, both required for the lubricating oil for automatic transmission and which also has excellent storage stability in a high humidity environment.
More particularly, according to an embodiment of the invention, there is provided a lubricating oil composition of automatic transmission of the type wherein a friction modifier (A), a metal detergent (B), and a specific type of ashless dispersant (C) are formulated in a lubricating base oil made of a mineral oil and/or a synthetic oil, characterized in that said ashless dispersant consists of a succinimide containing boron at a rate of three or less atoms in one molecule of the ashless dispersant.
As stated above, the invention relates to a lubricating oil composition wherein at least three specific types of compounds are formulated in a lubricating base oil. Preferred embodiments include those set forth below.
(1) A lubricating oil composition for automatic transmission, wherein the amount of the friction modifier ranges from 0.01-5 wt % based on the total weight of the composition.
(2) A lubricating oil composition for automatic transmission, wherein the amount of the metal detergent ranges from 0.1-7 wt % based on the total weight of the composition.
(3) A lubricating oil composition for automatic transmission, wherein the amount of the ashless dispersant ranges from 0.1-10 wt % based on the total weight of the composition.
(4) A lubricating oil composition for automatic transmission, wherein the friction modifier is made of an amine friction modifier and/or a boron-containing alcohol friction modifier.
(5) A lubricating oil composition for automatic transmissions, wherein the metal detergent is an alkaline earth metal salt of an alkylbenzene or alkylnaphthalenesulfonic acid, an alkaline earth metal salt of an alkylphenol sulfide or an alkaline earth metal salt of an alkylsalicyclic acid.
(6) A lubricating oil composition for automatic transmission, wherein the metal detergent has a total base number ranging 100-400 mg KOH/g.
(7) A lubricating oil composition for automatic transmission, wherein the ashless dispersant is made of a succinimide having boron at a rate of 1.5 atoms or less per molecule of the ashless dispersant.
The present invention may comprise, consist or consist essentially of the elements or steps disclosed and may be practiced in the absence of a step or element not disclosed as required and includes the products produced by the processes disclosed herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of invention are described in detail below.
Lu
Kugimiya Takanori
Sato Takehisa
Howard Jacqueline V.
Scuorzo Linda M.
TonenGeneral Sekiyu K.K.
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