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Boron Additives for Improved Anti-Pitting in Automatic Transmissions

IP.com Disclosure Number: IPCOM000020407D
Publication Date: 2003-Nov-20
Document File: 2 page(s) / 24K

Publishing Venue

The IP.com Prior Art Database

Related People

William C. Ward, Jr.: AUTHOR [+2]

Abstract

Boron-containing formulations suitable for use as fluids for automatic transmissions, including continuously variable transmissions, provide improved gear pitting, friction, and antiwear performance. The use of a high level of boron effectively improves the gear pitting characteristics while maintaining high static and dynamic clutch coefficients of friction and metal-on-metal friction, compared with formulations using traditional alkenyl succinimide dispersants. The formulations also show excellent response with an optimum low treatment of phosphorus extreme pressure/anti-wear compounds.

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Boron Additives for Improved Anti-Pitting in Automatic Transmissions

The present invention relates to boron-containing formulations suitable for use as fluids for automatic transmissions (ATs), including continuously variable transmissions (CVTs), providing improved gear pitting, friction, and antiwear performance.

         The use of a high level of boron effectively improves the gear pitting characteristics of fluids for CVTs and ATs, while maintaining high static and dynamic clutch coefficients of friction and metal-on-metal friction, compared with formulations using traditional alkenyl succinimide dispersants. The present formulations also show excellent response with an optimum low treatment of phosphorus extreme pressure/anti-wear compounds.

         Gear performance is an important parameter for both ATs and CVTs. Pitting of gear teeth harms the durability of ATs and CVTs. Such devices must also simultaneously exhibit high and stable wet clutch capacity and high metal on metal friction (needed for the element/variator in the CVT). Fluids containing higher boron content, and formulated predominantly with borated alkenyl succinimide dispersant, are superior to fluid formulated predominantly with non-borated alkenyl succinimide dispersants. Such fluid provide improved gear antipitting while maintaining sufficiently high friction performance to make them suitable for use both in ATs and CVTs.

         Test formulations are prepared in an API Group II / III base oil with a polymethacrylate viscosity modifier and a pour point depressant. Conventional amounts of dialkyl hydrogen phosphite, and 85% phosphoric acid are included, as well as various antioxidants, thiadiazole corrosion inhibitor, fatty amine friction modifier, seal swell agent, antifoam agents, and overbased calcium sulfonate detergents. Borated and non-borated succinimide dispersants are included in the percentage amounts as indicated in the following table:

Ex:                            1         2         3         4         5        

Polyisobutenyl succinimide                  1.74                  1.74

dispersant, CS2 treated

Polyiosbutenyl succinimide         0.28                  1.71                  1.71

dispersant

Borated polyisobutenyl         2.01         0.34         0.34         0.34         0.34

succinimide dispersant

% B in composition                  0.038         0.006 0.006         0.006         0.006

Each of the dispersants as reported contain the conventional amount of diluent oil. The borated polyisobutenyl dispersant composition is the product of polyisobutenylsuccinic anhydride with polyethyleneamines and boric acid. It contains 1.9% by weight boron and 33% diluent oil.

         In an LFW-1 Block-on-Ring friction test, each of the formulations gives a high...