Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2001-10-22
2003-09-09
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
C508S186000, C508S272000, C508S391000, C508S436000
Reexamination Certificate
active
06617287
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to lubricants for manual transmissions with improved performance with sintered synchromesh components. Problems occur with synchromesh parts in a manual transmission with many oils having too low friction or high wear of the components leading to synchromesh damage and poor or failed gear shifts.
The synchronizer is one of the more important components of any manual gearbox. Increasing performance, reducing shift force and minimizing the between-the-gears energy losses are the primary objectives for a new generation of synchronizer systems. Improvements in the capacity of the brass system and the introduction of formed sintered cones are allowing economical re-engineering of existing synchronizer designs into more efficient designs (see Hoerbiger and Co. Engineering Report 32). The chemistry of manual transmission lubricating oils needs to be reformulated for these designs to be able to maintain adequate friction between the sintered cones and protect these parts from wear.
Conventional gear oils or manual transmission oils typically contain chemical components, such as active sulfur and surface-active amine organophosphates. While excellent as additives to provide extreme pressure lubrication, in the usual amounts these additives alone are too slippery and do not adequately protect the sintered surfaces from abrasive or corrosive wear.
Poat et al. in U.S. Pat. No. 5,691,283 disclose a method of operating a vehicle having a manual transmission with a cone synchronizer using fluids with improved friction characteristics containing mineral or synthetic oils, one or more Mannich dispersants including borated Mannich dispersants, metal free sulfur containing antiwear and/or extreme pressure agents, one or more phosphorus containing and nitrogen containing antiwear and/or extreme pressure agents, and overbased alkali metal or alkaline earth metal detergents. The method may employ a finished lubricant in which all or a portion of the base oil is a polyalphaolefin (PAO). Other potential additives are listed including Cu corrosion inhibitors, which may be synonymous with “metal deactivators.” No specific ones are named. There is no mention of a synchronizer with sintered metal parts but instead the emphasis is on steel units with molybdenum-based plasma spray coatings. Poat et al. in EP 0 767 236 disclose improving the frictional characteristics of manual transmissions of the synchronizer type with compositions of more than 40% hydrogenated poly-a-olefins and 0.01-2% of an overbased alkaline earth metal sulfurized phenate or salicylate. Additive packages are described as generally containing a sulfur-phosphorus antiwear or extreme-pressure additive system, one or more antioxidants, one or more corrosion inhibitors and an antifoam additive and may, preferably contain a dispersant additive. There is no mention of a specific metal deactivator, and there is no mention of sintered metal parts.
Wallace et al., in U.S. Pat. No. 5,492,638, disclose a method similar to the Poat et al. patent, disclosing the same list of required components but as a method of improving gear shift performance.
Schwind et al. in U.S. Pat. No. 4,792,410 disclose the synchromesh manual transmission fluids. A composition is disclosed in Example IV for a manual transmission fluid containing a mixture of synthetic materials including a majority of PAO as the base stock, a zinc dithiophosphate and dioleylphoshite as extreme pressure (EP)/antiwear agents, a sulfurized olefin EP agent, a magnesium sulfonate detergent, and a borated carbonate overbased sodium sulfonate. Schwind et al. in WO 87/05927 disclose similar examples and claims alkaline earth metal detergents with synthetic oils for manual transmission fluids. No metal deactivators or amine phosphates are disclosed in either and the only boron is in the form of the borated detergent not a borated dispersant. Synchromesh with sintered parts is not disclosed.
Teqjui et al. in EP 0976813 disclose high synchromesh durability performance and gear protection of a manual transmission gearbox. Metal detergents are presented as a required component as overbased salicylates and a calcium sulfonate is shown in the comparative examples. Metal deactivators are described as optional components at up to 7%, with specific mention of up to 3.5% of a dimercaptothiadiazole derivative. The patent discloses specific metal borate containing formulations for manual transmission fluids. The synchromesh durability testing shown involves brass or Mo/steel synchronizers, not sintered metal. No synthetic oil is disclosed.
Shubken et al. in U.S. Pat. No. 4,172,855 disclose a process for manufacturing alpha olefin oligomers useful as synthetic lubricant base oils. Example 2 shows the combination of the PAO with a calcium sulfonate with other additives in an engine crankcase lubricant.
Similarly, Howie et al. in U.S. Pat. No. 4,525,289 in Example IIC disclose a formulation that has a PAO in combination with a overbased calcium sulfonate and an overbased magnesium sulfonate as a crankcase lubricant.
In a paper by O'Connor et al., entitled
Axle Efficiency Response to Synthetic Lubricant Components
(SAE Paper No. 821181), presented at the Fuels and Lubricants Meeting in Toronto, Ontario, Canada, in October 1982) the authors state that “investigations with both partial- and full-synthetic base formulations have shown improvements compared to conventional petroleum based gear oils. Maximum benefits are gained with total synthetic base type formulations.” This paper teaches the value of synthetic oils for axle efficiency that would result in fuel savings. The chemistry is not disclosed. The paper mentions that there is a 50% over-treatment of the EP additive to insure GL-5 quality, the gear oil performance standard, and that all EP additives used were commercial SP types. (This would typically mean sulfur(S) as sulfurized olefins and phosphorous(P) as amine phosphates.) There is no disclosure that basic metal detergents would also be present and there is no discussion of manual transmissions, or synchromesh manual transmissions, or the latter with sintered metal parts.
All of the above prior art references reveal the use of the various components in lubricants in some capacity and even some combinations in manual transmissions. None of the references teach the specified combinations of this invention or the advantages of these combinations in manual transmission fluids with sintered metal synchronizers. None of the references address the problems of wear or low friction of fluids in synchromesh manual transmissions with sintered metal parts.
The present invention solves the problem of wear and too low friction in a manual transmission with sintered metal parts in the synchronizer of the transmission by using a lubricating oil formulated with a high level of an alkaline earth sulfonate in combination with amine phosphates.
SUMMARY OF THE INVENTION
The present invention provides a composition suitable for lubricating a manual transmission designed with sintered metal surfaces in the synchronizer, comprising:
(a) at least about 70% by weight of oil of lubricating viscosity of API Group III, IV, V or mixtures thereof,
(b) about 0.01 to about 2% by weight of an amine salt of a phosphorus containing acid,
(c) at least about 0.5% by weight of a basic metal salt of an organic acid,
(d) about 0% to about 0.7% by weight of a metal deactivator compound, and
(e) about 0% to about 3% by weight of a boron-containing dispersant.
The present invention further provides a method for preventing wear of sintered metal surfaces in the synchronizer of a manual transmission and improving performance by using a lubricant of the composition of the present invention. The lubricating composition is characterized by the selection of a stable base oil and high levels of metal detergents, an amine phosphate extreme-pressure agent and other gear oil additives. The method further enhances performance with the addition of either or both of the metal deactivator compou
Gahagan Michael P.
O'Connor Brian M.
Esposito Michael F.
Gilbert Teresan W.
Howard Jacqueline V.
The Lubrizol Corporation
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