Tie Rod End Lubrication Coating Torque Management
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Solution Overview
Problem
Existing tie rod end ball joints face a tradeoff between initial frictional resistance and long-term durability, with coatings either providing excessive initial resistance or wearing off prematurely, leading to undesirable 'feel' and reduced life.
Innovation Solution
A tie rod end with a stud and bearing assembly featuring a lubrication groove and a bonded lubrication coating, such as Sunoloy, which reduces initial torque and wears away over time to maintain a desirable torque level after 1 million cycles, ensuring extended life and reduced wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a lubrication coating is applied to reduce initial frictional resistance, then the initial torque is reduced to a desirable level, but the coating wears away over time causing the frictional resistance to increase again
Solution Approach 1:
The lubrication coating is applied in advance to the ball or bearing surface before assembly, creating a preliminary lubricated state that reduces initial frictional resistance and torque. The coating is designed to be consumed or worn away over a predetermined number of cycles, after which the joint operates with the original friction characteristics.
Solution Approach 2:
The frictional resistance parameter is changed over time through the controlled consumption of the lubrication coating. Initially, the coating provides low friction and low torque. As the coating wears away over the predetermined number of cycles, the frictional resistance increases back to the original level, creating a time-dependent parameter change that resolves the contradiction between initial ease of operation and long-term durability.
2Reliability
If the tie rod end is assembled with high frictional resistance, then the joint provides long-term durability, but the initial torque is too high causing a poor perceived feel
Solution Approach 1:
The lubrication coating is applied in advance to create a preliminary low-friction state that masks the inherently high frictional resistance of the joint design. This allows the joint to be assembled with desirable low initial torque and perceived feel, while the underlying high frictional resistance characteristics remain to provide long-term durability once the coating is consumed.
Solution Approach 2:
The lubrication coating acts as a disposable, consumable element that is intentionally designed to wear away after a predetermined number of cycles. This short-lived coating component enables the joint to achieve desirable initial operational characteristics, while the permanent joint structure maintains high frictional resistance for long-term durability.
3Ease of operation
If a lubrication coating is applied to reduce initial torque, then the perceived quality is improved, but the coating may be prematurely scraped off the surface
Solution Approach 1:
The coating is designed with specific material parameters and thickness characteristics that enable it to be consumed through controlled wear rather than premature scraping. The coating parameters are optimized to withstand the operational conditions for the predetermined number of cycles, transitioning from a potential adhesion problem to a controlled consumption mechanism that reliably reduces initial torque.
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 solution provides a tie rod end with an initial desirable torque setting that decreases over time, maintaining a low torque level after 1 million cycles, comparable to non-coated joints, while extending the component's life and reducing wear, thus addressing the tradeoff between initial resistance and durability.
Implementation Method 1
A wearable friction-reducing coating is applied to at least one of the ball and bearing surface
Implementation Method 2
The coating is provided to be substantially consumed on a high contact area of the tie rod end in use
Data Source
AI summary
A tie rod end includes a stud with a spherical ball at one end and a bearing having a concave spherical bearing running surface for sliding abutment with the ball. The contact area of the ball or the bearing running surface has a lubrication groove to facilitate channeling grease, wherein the grooved member is coated with a bonded lubrication coating. The lubrication coating reduces the initial preload torque from that which would be ordinarily be perceived as undesirable to a torque that is perceived as desirable. The lubrication coating is substantially consumed on the high contact area over about 100 to 500 thousand cycles, with the resulting torque being remaining greater than zero, which is also perceived as being desirable.