Methods for improved power transmission performance and compositions therefor

Abstract

Advanced methods are provided for achieving improved power transmission performance, and unique fluid compositions useful for practicing such methods are also presented. In particular a method and related composition is provided for reducing NVH in a power transmission apparatus having a friction torque transfer apparatus, such as, e.g., a shifting clutch, comprising maintaining a negative ∂μ / ∂T slope, and / or a negative ∂μ / ∂P slope, during engagement of the friction torque transfer apparatus.

Description

[0001] This application claims the benefit of priority of U.S. Provisional Application No. 60 / 695,183, filed on Jun. 30, 2006.FIELD OF THE INVENTION [0002] The present disclosure relates to methods for providing improved power transmission performance and fluid compositions suitable for use in power transmission applications. BACKGROUND OF THE INVENTION [0003] An automatic transmission in a vehicle generally includes a multiple disk clutch in which a plurality of friction plates, each having a friction material bonded to a surface of a metal substrate (core plate), and a plurality of separator plates, each constituted by a single plate or more, are arranged in an alternating sequence. In an automatic transmission lubricated with transmission fluid, these plates are frictionally connected / disconnected to / from one another so that driving force is transmitted / released. Wet friction materials used in transmission clutches have included paper friction materials, carbon fiber friction mat...

AI Technical Summary

Benefits of technology

[0140] The fluids of the present embodiments may also optionally include conventional additives of the type used in power transmission fluid formulations and gear lubricants in addition to the extreme pressure and antiwear performance improving co-additives described above. Such additives include, but are not limited to, metallic detergents, dispersants, friction modifiers, antioxidants, viscosity index improvers, copper corrosion inhibitors, anti-rust additives, antiwear additives, antifoamants, pour point depressants, seal swell agents, colorants, metal deactivators, and / or air expulsion additives. It will be appreciated that various required and optional additives described herein may have additional other advantageous effects in the finished fluids.

[0142] Component (G) comprises at least one oil-soluble supplemental dispersant. Suitable dispersants may include ashless dispersants such as succinic dispersants, Mannich base dispersants, and polymeric polyamine dispersants. Hydrocarbyl-substituted succinic acylating agents are used to make hydrocarbyl-substituted succinimides. The hydrocarbyl-substituted succinic acylating agents include, but are not limited to, hydrocarbyl-substituted succinic acids, hydrocarbyl-substituted succinic anhydrides, the hydrocarbyl-substituted succinic acid halides (especially the acid fluorides and acid chlorides), and the esters of the hydrocarbyl-substituted succinic acids and lower alcohols (e.g., those containing up to 7 carbon atoms), that is, hydrocarbyl-substituted compounds which can function as carboxylic acylating agents.

[0143] Hydrocarbyl substituted acylating agents are made by reacting a polyalkyl olefin or chlorinated polyalkyl olefin of appropriate molecular weight with maleic anhydride. Similar carboxylic reactants can be used to make the acylating agents. Such reactants may include, but are not limited to, maleic acid, fumaric acid, malic acid, tartaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, mesaconic acid, ethylmaleic anhydride, dimethylmaleic anhydride, ethylmaleic acid, dimethylmaleic acid, hexylmaleic acid, and the like, including the corresponding acid halides and lower aliphatic esters.

[0144] The molecular weight of the olefin can vary depending upon the intended use of the substituted succinic anhydrides. Typically, the substituted succinic anhydrides will have a hydrocarbyl group of from about 8 to about 500 carbon atoms. However, substituted succinic anhydrides used to make lubricating oil dispersants will typically have a hydrocarbyl group of about 40 to about 500 carbon atoms. With high molecular weight substituted succinic anhydrides, it is more accurate to refer to number average molecular weight (Mn) since the olefins used to make these substituted succinic anhydrides may include a mixture of different molecular weight components resulting from the polymerization of low molecular weight olefin monomers such as ethylene, propylene, and isobutylene.

[0145] The mole ratio of maleic anhydride to olefin can vary widely. It may vary, for example, from about 5:1 to about 1:5, or for example, from about 1:1 to about 3:1. With olefins such as polyisobutylene having a number average molecular weight of about 500 to about 7000, or as a further example, about 800 to about 3000 or higher and the ethylene-alpha-olefin copolymers, the maleic anhydride may be used in stoichiometric excess, e.g. about 1.1 to about 3 moles maleic anhydride per mole of olefin. The unreacted maleic anhydride can be vaporized from the resultant reaction mixture.

[0146] The polyalkyl or polyalkenyl substituent on the succinic anhydrides employed herein is generally derived from polyolefins, which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, and butylene. The mono-olefin employed may have about 2 to about 24 carbon atoms, or as a further example, about 3 to about 12 carbon atoms. Other suitable mono-olefins include propylene, butylene, particularly isobutylene, 1-octene, and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.

Problems solved by technology

The present investigators also have discovered that merely using a transmission fluid in the operation of a power transmission which yields a positive slope of coefficient of friction (μ) versus sliding velocity (v) is inadequate to significantly suppress and control NVH.

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