Steering Gear Grease Composition for Mixed-Surface Wear Control
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Solution Overview
Problem
Existing grease compositions for steering gear devices fail to adequately lubricate both the meshing portion between rack and pinion teeth and the sliding contact portion between the rack shaft and the rack guide mechanism, leading to wear and reduced steering performance over time.
Innovation Solution
A grease composition comprising trimellitate ester, poly-α-olefin, lithium 12-hydroxystearate, lithium stearate, and molybdenum dialkyl dithiocarbamate, which forms a tribo-reaction film to enhance lubrication and suppress wear on friction faces, including those made of resin and steel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing grease compositions are used for lubrication, then the meshing portion between rack and pinion teeth can be lubricated, but the sliding contact portion between rack shaft and rack guide mechanism is not adequately lubricated, leading to wear
Solution Approach 1:
The grease composition is designed to perform multiple lubrication functions simultaneously: it lubricates both the meshing portion between rack and pinion teeth (gear contact) and the sliding contact portion between rack shaft and rack guide mechanism (sliding contact). This is achieved by formulating a composite grease containing lithium 12-hydroxystearate as thickener combined with specific additives that provide both extreme pressure protection and anti-wear properties suitable for different types of friction surfaces
Solution Approach 2:
The grease uses a composite formulation combining lithium 12-hydroxystearate thickener with multiple additives including extreme pressure additives and anti-wear additives. This composite material approach allows the grease to exhibit multiple protective functions simultaneously, addressing both gear meshing lubrication and sliding contact lubrication needs in the steering gear device
2Reliability
If grease is applied to reduce wear, then the clearance between rack teeth and pinion teeth can be maintained, but the grease must also lubricate the sliding contact portion between rack shaft and rack guide mechanism
Solution Approach 1:
The grease composition is designed as a multi-functional lubricant that simultaneously protects both the gear meshing interface (rack and pinion teeth) and the sliding contact interface (rack shaft and rack guide mechanism). This eliminates the need for separate lubrication systems or multiple grease applications, simplifying the overall lubrication strategy while maintaining comprehensive wear protection across all friction surfaces in the steering gear device
3Ease of manufacture
If a simple grease composition is used, then the formulation is easy to manufacture, but it fails to provide adequate lubrication for both meshing and sliding contact portions
Solution Approach 1:
The grease formulation uses specific parameter ranges to achieve optimal performance: lithium 12-hydroxystearate content is controlled at 80-95 mass% of the total thickener, extreme pressure additive content is maintained at 0.1-5 mass% of the grease, and anti-wear additive content is kept at 0.1-5 mass% of the grease. These controlled parameter ranges ensure consistent lubrication performance for both gear meshing and sliding contact while maintaining manufacturability through standardized production processes
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 effectively lubricates both meshing and sliding contact portions, reducing wear and maintaining steering performance over a long period by forming a stable tribo-reaction film.
Implementation Method 1
A grease composition... which forms a tribo-reaction film to enhance lubrication and suppress wear on friction faces
Data Source
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AI summary
A grease composition includes a base oil, a thickener, and an extreme pressure additive. The base oil contains trimellitate ester and poly-α-olefin. A proportion of the trimellitate ester to a total amount of the trimellitate ester and the poly-α-olefin is 10.0 mass% or more and 60.0 mass% or less. The thickener contains lithium 12-hydroxystearate and lithium stearate. A proportion of the lithium 12-hydroxystearate to a total amount of the lithium 12-hydroxystearate and the lithium stearate is 5.0 mass% or more and 95.0 mass% or less. The extreme pressure additive contains molybdenum dialkyl dithiocarbamate. A proportion of the molybdenum dialkyl dithiocarbamate to a total amount of the trimellitate ester, the poly-α-olefin, the lithium 12-hydroxystearate, the lithium stearate, and the molybdenum dialkyl dithiocarbamate is 0.6 mass% or more and 16.0 mass% or less.