Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2002-04-19
2003-03-04
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
C508S273000
Reexamination Certificate
active
06528458
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a lubricant and a method for lubricating a transmission having a plurality of wet clutches and a plurality of partial power transmission shafts, all elements being lubricated by a common fluid, that is, in a dual clutch transmission.
Dual clutch transmissions, also known as double clutch or twin clutch transmissions, of a variety of types are known. For example, “Transmission Options,” in
Automotive Engineering International,
July, 2001, discusses on pages 67-68 double-clutch transmissions and certain of their limitations. Double clutch transmission are known with either dry or wet clutches, the latter having hydrodynamic torque converters.
European publication EP 1 052 421 A, Nov. 15, 2000, discloses a multiple clutch system for a transmission, with two multi-disk clutches that are coaxial with each other, and each clutch is assigned to one of two shafts. The two clutches are arranged in a sealed chamber which contains lubricating oil.
U.S. Pat. No. 6,251,840, Ward et al., Jun. 26, 2001, priority Sep. 12, 1995, equivalent to EP 761 805 A, Mar. 12, 1997, discloses lubricating compositions for use in automatic transmission fluids, tractor hydraulic fluids, manual transmission fluids, continuously variable transmission fluids, wet brake and wet clutch fluids, hydraulic fluids and the like. The compositions embody sulfur and boron-containing components as well as antifoam agents in an oil of lubricating viscosity. Included in the oil of lubricating viscosity is 0.025-5 weight percent on an oil-free basis based on the weight of the lubricating composition of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) or derivatives thereof. The compositions reduce wear in the device in which they are used.
U.S. Pat. No. 4,136,043, Davis, Jan. 23, 1979, discloses compositions which form homogeneous blends with lubricating oils and the like, produced by preparing a mixture of an oil-soluble dispersant (preferably a substantially neutral or acidic carboxylic dispersant) and a dimercaptothiadiazole, and heating the mixture above about 100° C. The additive is useful for the inhibition of copper activity and “lead paint” deposition in lubricants. Automatic transmission fluids, transaxle lubricants and other lubricating oil and grease compositions can benefit from the incorporation of the disclosed invention.
U.S. Pat. No. 6,232,275 B, Ichihashi et al., May 15, 2001, filed Nov. 24, 1999, discloses a lubricating oil composition for automatic transmissions which comprises a base oil, a non-boron based succinic acid imide and a boron based succinic acid imide, a condensation product of a branched chain fatty acid and an amine, and a dialkyl hydrogen phosphite, and optionally at least one member selected from viscosity index improvers, antioxidants, metal deactivators, defoaming agents, detergents, extreme pressure agents, and rust preventive. In examples, one of the other additives is a thiadiazole compound.
U.S. Pat. No. 6,103,673, Sumiejski et al., Aug. 15, 2000, discloses compositions for continuously variable transmissions, comprising an oil of lubricating viscosity, a shear stable viscosity modifier, an overbased metal salt, a phosphorus compound, and a combination of at least two friction modifiers. At least one of the friction modifiers is selected from zinc salts of fatty acids, hydrocarbyl imidazolines, and borated epoxides. Optional materials include dispersants, of which amine dispersants, a mixture of borated, non-reacted, and species reacted with CS
2
, are disclosed.
The present invention, therefore, solves the problem of fulfilling the requirements of smooth and efficient lubrication of a dual clutch transmission (“DCT”). A single lubricant, as described herein, simultaneously satisfies the multiple requirements of such a transmission, including lubrication of gearing, typical of a manual transmission, and lubrication of gear synchronizers, also typical of a manual transmission, while also lubricating the wet clutch component, that is, a slipping start-up clutch, which is typical of an automatic transmission with all the challenging requirements associated therewith. In particular, the gears of the DCT require pitting protection; the synchronizers require a fluid that provides good durability of shifting as well as having the proper friction curve parameters; and the two start-up clutches for the two parallel input shafts contaiing the gears require proper lubrication.
SUMMARY OF THE INVENTION
The present invention provides a method for lubricating a transmission having a plurality of wet clutches and a plurality of partial power transmission shafts, wherein shifting of gears occurs by a process comprising synchronization of an engaged and a non-engaged partial transmission shaft and engagement of a wet clutch; said method comprising supplying to said transmission a lubricating composition comprising: (a) an oil of lubricating viscosity; (b) 2,5-dimercapto-1,3,4-thiadiazole (DMTD), a derivative of DMTD, or mixtures thereof; (c) a friction modifier other than a species of (b); and (d) a dispersant other than a species of (b).
The present invention also provides a composition suitable for lubricating a transmission having a plurality of wet clutches and a plurality of partial power transmission shafts, comprising or prepared by mixing: (a) an oil of lubricating viscosity; (b) a reaction product of 2,5-dimercapto-1,3,4-thiadiazole and a nitrogen-containing dispersant; (c) a friction modifier which is a condensation product of a C
6
to C
24
aliphatic carboxylic acid and a polyalkylenepolyamine; and (d) a phosphorus compound.
DETAILED DESCRIPTION OF THE INVENTION
Various preferred features and embodiments will be described below by way of non-limiting illustration.
The lubricating compositions useful in the present invention are based on diverse oils of lubricating viscosity, including natural and synthetic lubricating oils and mixtures thereof. The oil of lubricating viscosity is generally present in a major amount (i.e. an amount greater than about 50 percent by weight). Typically, the oil of lubricating viscosity is present in an amount of 75 to 95 percent by weight, and often greater than about 80 percent by weight of the composition.
Natural oils useful in making the inventive lubricants and functional fluids include animal oils and vegetable oils as well as mineral lubricating oils such as liquid petroleum oils and solvent treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic
aphthenic types which may be further refined by hydrocracking and hydrofinishing processes.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins, also known as polyalpha olefins; polyphenyls; alkylated diphenyl ethers; and alkylated diphenyl sulfides; and the derivatives, analogs and homologues thereof. Also included are alkylene oxide polymers and interpolymers and derivatives thereof, in which the terminal hydroxyl groups may have been modified by esterification or etherification. Also included are esters of dicarboxylic acids with a variety of alcohols, or esters made from C
5
to C
12
monocarboxylic acids and polyols or polyol ethers. Other synthetic oils include silicon-based oils, liquid esters of phosphorus-containing acids, and polymeric tetrahydrofurans.
Unrefined, refined and rerefined oils, either natural or synthetic, can be used in the lubricants of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. Refined oils have been further treated in one or more purification steps to improve one or more properties. They can, for example, be hydrogenated, resulting in oils of improved stability against oxidation.
In one embodiment, the oil of lubricating viscosity is a Group II or a Group III oil, or a synthetic oil, or mixtures thereof. Group II and Group III oils are classifications established by the API Base Oil Interchangeability Gu
Tagliamonte Thomas A.
Tipton Craig D.
Ward, Jr. William C.
Esposito Michael F.
Howard Jacqueline V.
Shold David M.
The Lubrizol Corporation
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