CVT Fluid Friction Modifiers for Shudder Durability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Continuously variable transmissions (CVTs) face a challenge in maintaining high metal friction for optimal performance while preventing shudder issues, as existing fluids often sacrifice wet clutch performance to achieve high metal friction.
Innovation Solution
A lubricant composition comprising an oil of lubricating viscosity, nitrogen-containing materials such as amides and tertiary amines, functionalized dispersants treated with 2,5-dimercapto-1,3,4-thiadiazole and borating agents, and hydrocarbyl phosphite, which balances metal friction and anti-shudder durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If CVT fluids are designed to provide high metal friction for belt/pulley assembly, then metal-on-metal friction coefficient is improved, but wet clutch performance deteriorates causing shudder
Solution Approach 1:
The patent changes the chemical composition parameters of the lubricant by incorporating specific friction modifiers (amines with hydroxy acid, tertiary amines with polyol-containing alkyl groups) and multifunctional dispersants (borated and phosphated). This chemical parameter adjustment allows the fluid to maintain high metal friction (0.10-0.15 coefficient) while providing anti-shudder protection for wet clutches, resolving the contradiction between these two opposing requirements
Solution Approach 2:
The patent creates a composite lubricant formulation combining multiple additive packages: friction modifiers (amines and tertiary amines), multifunctional dispersants (borated and phosphated), and their interaction products. This composite approach allows simultaneous achievement of high metal friction and wet clutch protection, as the different components work synergistically to address both the belt/pulley and clutch requirements
2Reliability
If friction modifiers are added to reduce wet clutch friction, then anti-shudder performance is improved, but metal friction for belt/pulley assembly decreases
Solution Approach 1:
The patent carefully controls the concentration and type of friction modifiers, using specific amine structures (R1R2NR3 where R1 and R2 are hydrocarbyl groups of at least 6 carbon atoms and R3 is a polyol-containing alkyl group) at optimized levels. This parameter optimization ensures sufficient anti-shudder durability without excessively reducing the metal friction coefficient below the required 0.10-0.15 range for proper belt/pulley operation
3Force
If lubricant provides high metal friction for clamping force, then belt/pulley performance is improved, but wet clutch shudder increases after high mileage
Solution Approach 1:
The patent incorporates multifunctional dispersants (borated and phosphated) that proactively protect wet clutch surfaces from wear and deposit formation before shudder can develop. These dispersants prevent the buildup of friction-increasing contaminants during high-mileage operation, maintaining stable clutch friction characteristics and preventing shudder development over time while preserving the high metal friction needed for clamping force
Solution Approach 2:
The patent uses specific amine and tertiary amine structures with controlled carbon chain lengths (at least 6 carbon atoms) and functional groups (polyol-containing alkyl groups) that provide long-term stability. These chemical parameter selections ensure the lubricant maintains both high metal friction for clamping force and sustained anti-shudder durability through extended service life
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The lubricant composition maintains or improves metal friction performance while enhancing anti-shudder durability, ensuring stable metal-metal friction coefficients and reducing shudder occurrence in CVTs.
Implementation Method 1
at least two nitrogen-containing materials, comprising at least one each of: (i) at least one amide represented by the formula R3C(O)NR1R2... (ii) at least one tertiary amine being represented by the formula R4R5NR6...
Implementation Method 2
The lubricant must provide the appropriate degree of friction between the belt and pulley assembly, to avoid the problem of slippage on one hand, and binding on the other
Implementation Method 3
published U.S. application US-2005-0041395, Feb. 24, 2005, Tipton et al., discloses a multifunctional dispersant prepared by heating together (a) a dispersant and (b) 2,5-dimercapto-1,3,4-thiadiazole or a hydrocarbyl-substituted 2,5-dimercapto-1,3,4-thiadiazole which is substantially insoluble in a hydrocarbon oil of lubricating viscosity at 25° C., and further either (c) a borating agent or (d) an inorganic phosphorus compound, or both (c) and (d)
Data Source
AI summary
A lubricant composition comprising (a) an oil of lubricating viscosity; (b) at least two nitrogen-containing materials, comprising (i) at least one amide of the formula R3C(O)NR1R2 and (ii) at least one tertiary amine being represented by the formula R4R5NR6 where R4 and R5 are alkyl groups of at least 6 carbon atoms and R6 is a polyhydroxyl-containing alkyl group or a polyhydroxyl-containing alkoxyalkyl group; (c) a functionalized dispersant component, and (d) at least one diallyl phosphite, provides good lubricant performance for a continuously variable transmission.