CV Joint Grease Composition for Low-Temperature Noise Suppression
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Solution Overview
Problem
Existing grease compositions for outboard constant velocity joints fail to effectively suppress noise at low temperatures due to deteriorated grease fluidity and increased rolling and sliding speeds, leading to stick-slip and high sound pressure.
Innovation Solution
A grease composition comprising a diurea-based thickener and a base oil with specific kinematic viscosities at -20°C and 100°C, combined with additives like molybdenum dialkyldithiocarbamate and overbased Ca sulfonate, to enhance noise suppression and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional grease compositions are used in outboard constant velocity joints at low temperatures, then the grease provides basic lubrication, but the grease fluidity deteriorates when completely cooled, causing noise due to stick-slip at high operating angles
Solution Approach 1:
The invention changes the chemical composition parameters of the grease by incorporating specific additives (molybdenum dialkyldithiocarbamate sulfide and zinc dialkyldithiocarbamate) in optimized proportions (0.1-5% and 0.1-5% respectively) along with a urea thickener (5-20%). This compositional parameter change enables the grease to maintain appropriate fluidity at low temperatures while providing effective lubrication, thereby suppressing noise without sacrificing operational performance.
Solution Approach 2:
The invention creates a composite grease formulation by combining multiple components with complementary functions: base oil for lubrication, urea thickener for viscosity control, and specific additives (molybdenum dialkyldithiocarbamate sulfide, zinc dialkyldithiocarbamate, and zinc dithiophosphate) for extreme pressure protection and fluidity maintenance. This composite material approach allows the grease to exhibit improved low-temperature fluidity and noise suppression characteristics that individual components cannot achieve alone.
2Adaptability or versatility
If the operating angle of the outboard constant velocity joint is increased, then the joint can accommodate larger steering angles, but the rolling and sliding speed and load between balls and transfer surfaces become significantly large, making it difficult to form a lubricating film and generating noise
Solution Approach 1:
The invention modifies the lubricant's chemical composition parameters by adding molybdenum dialkyldithiocarbamate sulfide and zinc dialkyldithiocarbamate in specific concentrations (0.1-5% each). These compositional changes enhance the lubricant's film-forming capability under high load and high-speed conditions, enabling reliable lubrication even at large operating angles where conventional greases fail to maintain adequate film thickness.
Solution Approach 2:
The grease composition acts as an intermediary substance that mediates between the metal surfaces of the constant velocity joint under extreme operating conditions. The specific additive package (molybdenum and zinc compounds) creates a protective intermediary layer that prevents direct metal-to-metal contact, reduces friction, and maintains lubricating film integrity even when high rolling and sliding speeds occur at large operating angles.
3Ease of operation
If a car is left outdoors for a long time during periods of severe cold, then the vehicle remains stationary, but the fluidity of the grease in the CVJs deteriorates further when completely cooled, causing high sound pressure and prolonged noise when the car is started with a large operating angle
Solution Approach 1:
The invention changes the grease's physical and chemical parameters by incorporating a urea thickener (5-20%) combined with specific additives. This parameter modification ensures the grease maintains suitable fluidity even after prolonged exposure to severe cold temperatures, preventing the deterioration that leads to high noise during cold starts with large operating angles.
Solution Approach 2:
The grease composition provides beforehand cushioning by maintaining adequate fluidity and lubrication properties even after extended periods in severe cold conditions. The specific additive package (molybdenum dialkyldithiocarbamate sulfide, zinc dialkyldithiocarbamate, and zinc dithiophosphate) creates a protective effect that cushions against the adverse effects of low-temperature stiffening, ensuring quiet operation during cold starts without requiring vehicle movement or warming up.
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 grease composition significantly reduces noise generation and improves durability by maintaining grease fluidity and preventing metal contact at low temperatures, ensuring quiet operation.
Implementation Method 1
a base oil containing a synthetic oil and having a kinematic viscosity at a temperature of -20°C measured according to JIS K 2283 of 3,000 to 20,000 mm 2
Implementation Method 2
the rolling and sliding speed and the load between the balls and the transfer surfaces of the inner and outer rings become significantly large, making it difficult to form a lubricating film
Data Source
AI summary
A grease composition for outboard constant velocity joints, comprising (a) a diurea-based thickener and (b) a base oil containing a synthetic oil and having a kinematic viscosity at a temperature of -20°C measured according to JIS K 2283 of 3,000 to 20,000 mm2/s.