Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2003-04-10
2004-12-07
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
C508S226000, C508S228000, C508S231000, C508S242000, C508S291000, C508S390000, C508S518000, C508S538000, C508S586000, C252S077000, C252S078100, C252S078500
Reexamination Certificate
active
06828286
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to lubricant compositions, and more particularly to lubricant compositions which are not decreased in anti-shudder property over an extended period of time and have an enhanced transmission torque capacity for wet clutches and/or wet brakes, suitable for automatic transmissions and continuously variable transmissions.
2. Description of the Prior Art
Most of the automatic transmissions and continuously variable transmissions equipped in automobiles are provided with torque converters which transmit engine torque via a lubricant to the transmissions. The torque converters is so structured that the power can not be transmitted if the difference in rotation between the input side (the engine side) and the output side (the transmission side) is not developed. This rotation difference causes the transmission to be decreased in power transmitting efficiency. With the background of the issues concerning environments, demands have been increasing for automobiles which are fuel efficient for the purpose of reducing the amount of carbon dioxide gas discharged. In connection with this, the transmissions are required to be more increased in power transmitting efficiency. Recently, as one of the measures, there have been used torque converters equipped with wet clutch hereinafter referred to as “torque converter clutch” which in addition to fluid coupling, transmit the engine torque directly to the transmission mechanism variously according to the running conditions.
However, while the torque converter clutch is working, the comfort on driving is greatly affected at the change of engine torque. Therefore, in the conventional mechanisms, the torque converter clutch is worked only at high road speeds at which the changes of the engine torque are lessen, and is not worked at low road speeds. For this reason, the transmission loss in the torque converters can not be avoided at low road speeds as well as at the time of starting and thus the improvement of fuel economy as expected can not be achieved.
Recently, in order to reduce such a transmission loss, there has been developed and introduced a so-called slipping controlling system in which the torque converter clutch works at low road speeds as well and absorbs the vibration resulting from the change of engine torque, by relative slippage of the clutch.
However, abnormal vibration, known as shudder, in the vehicle frequently occurs at the torque converter clutch's friction surface when the slip-control of the clutch operates, and discomforts the driving conditions. In order to prevent the shudder phenomenon, it is highly demanded to provide a lubricant which has an excellent durability of anti-shudder performance resulting from the improvement of friction coefficient (&mgr;)-sliding velocity (V) characteristics so as to have a friction coefficient (&mgr;) which increases as sliding velocity (V) increases.
The further improvement of anti-shudder durability has been demanded because of the progressed enlargement of the low-speed range in which the slip-controlling mechanism operates.
The automatic transmissions and continuously variable transmissions have wet clutches in their gear-change mechanism and front and rear drive switching mechanism. If the friction property of such clutches is poor, a transmission shock occurs at the change of speed, resulting in discomfort of driving. Therefore, a lubricant for automatic transmissions is required to have an excellent shifting property so as to decrease the shock occurring at the time of clutch engagement.
As one of the measures for improving the anti-shudder durability and shifting property of the lubricant, it has been proposed to blend therewith large amounts of friction modifiers. However, depending on the type of friction modifier, the addition thereof would extremely decrease the friction coefficient of the wet clutch and fail to attain a transmission torque capacity.
The anti-shudder durability and shifting property and the transmission torque capacity are in a trade-off relation. Therefore, it is desired to develop a lubricant composition having all of these properties.
With the background of the foregoing, the object of the present invention is to provide a novel lubricant composition which can retain an anti-shudder durability for extended periods and has a high transmission torque capacity and improved shifting property.
BREIF SUMMARY OF THE INVENTION
After intensive research efforts made to solve the foregoing problems, it was found that the problems can be solved with a lubricant composition comprising a lubricant base oil blended with compounds obtained by modifying specific succinimides.
That is, the present invention provides a lubricant composition which comprises a lubricant base oil and one or more compounds selected from the group consisting of those resulting from the modification of succinimides represented by formula (1) or (2)
wherein R
1
and R
2
may be the same or different and are each independently a hydrocarbon group having 8 to 30 carbon atoms, R
3
and R
4
may be the same or different and are each independently a hydrocarbon group having 1 to 4 carbon atoms, R
5
is hydrogen or a hydrocarbon group having 1 to 30 carbon atoms, and n is an integer from 1 to 7.
R
1
and R
2
in formula (1) or (2) are preferably branched hydrocarbon groups having 8 to 30 carbon atoms.
In formula (1) or (2), n is preferably an integer from 1 to 3.
The modified succinimide compounds are preferably those resulting from the modification of succinimides of formula (1) or (2) with one or more compounds selected from the group consisting of boric acids, phosphoric acids, carboxylic acids, and derivatives thereof.
The lubricant composition further contains one or more friction modifiers and/or metal-based detergents.
The lubricant composition is preferably used in automatic transmissions and/or continuously variable transmissions.
The lubricant composition is preferably used in transmissions equipped with a wet clutch and/or a wet break.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more details below.
Lubricating base oils useful in this invention are any mineral oils and/or synthetic oils which are usually used as lubricant base oils.
Specific examples of the mineral oils include paraffinic- and naphthenic-mineral oils which are produced by subjecting lubricant fractions resulting from the atmospheric distillation and the vacuum distillation of crude oil to one or more refining processes such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, catalytic dewaxing, hydro-refining, sulfuric acid washing, and clay treatment in suitable combination; and n-paraffins. Particularly preferred are those improved in low-temperature flowability by dewaxing after solvent- or hydro-refining. With the objective of improving low temperature flowability and oxidation stability of the resulting composition, it is preferred to use mineral oils of which %Cp specified by the n-d-m method of ASTM-D 3238-80 is 60 or greater and preferably 70 or greater, %CA specified by the same is 10 or less and preferably 5 or less, and viscosity index is 95 or greater and preferably 100 or greater.
Although not restricted, examples of synthetic oils are one or more compounds selected from poly-&agr;-olefins such as 1-octene oligomer, 1-decene oligomer, and ethylene-propylene oligomer, and hydrides thereof; isobutene oligomers and hydrides thereof; isoparaffins; alkylbenzenes; alkylnaphthalenes; diesters such as ditridecyl glutarate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, and di-2-ethylhexyl sebacate; polyol esters such as trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethyl hexanoate, and pentaerythritol pelargonate; polyoxyalkylene glycols; dialkyldiphenyl ethers; and polyphenyl ethers. When consideration is given to the solubility of additives, these synthetic oils are preferably used in the form of mixtures thereof or mix
Arimoto Naozumi
Ishida Noboru
Komiya Kenichi
Morita Eitaro
Shirahama Shinichi
Akin Gump Strauss Hauer & Feld & LLP
McAvoy Ellen M.
Nippon Mitsubishi Oil Corporation
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