Telescoping Steering Spindle Sliding Sleeve Friction Control
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Solution Overview
Problem
Existing telescoping steering spindles fail to permanently reduce the stick-slip effect and associated noise, while also being costly and complex to manufacture, due to inefficiencies in torque transmission and friction reduction.
Innovation Solution
A telescoping steering spindle with a sliding sleeve made of a mixture of PEEK, PTFE, graphite, and carbon fibers, combined with a lubricant of specific dynamic viscosity, applied to steel surfaces with controlled roughness, to reduce static and sliding friction differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a plastic sleeve is provided between the two shaft parts to reduce friction, then the sliding properties are improved, but the stick-slip effect and associated noise are not permanently reduced
Solution Approach 1:
The patent applies composite materials by combining PEEK with specific proportions of PTFE (7-13% by volume), graphite (7-13% by volume), and carbon fibers (25-35% by volume) to create a sliding sleeve material that permanently reduces the stick-slip effect. This composite formulation addresses the limitation of simple plastic sleeves by integrating multiple materials with complementary friction-reducing properties, thereby eliminating noise while maintaining reliable sliding characteristics.
Solution Approach 2:
The patent changes the material parameters of the sliding sleeve by precisely controlling the volume percentages of each component (PEEK, PTFE, graphite, carbon fibers). This parameter optimization ensures that the material achieves the right balance between friction reduction and structural integrity, permanently eliminating the stick-slip effect while maintaining torque transmission capability.
2Reliability
If targeted roughening of the sliding sleeve is applied to improve sliding properties, then friction is reduced, but the solution becomes more complex and less durable
Solution Approach 1:
The patent replaces complex surface treatment processes with a cost-effective composite material formulation. Instead of applying expensive and complex roughening treatments that reduce durability, the invention incorporates friction-reducing properties directly into the sliding sleeve material itself through the PEEK-PTFE-graphite-carbon fiber composite, simplifying manufacturing while enhancing long-term durability.
3Reliability
If additional lubricants and complex material combinations are used to reduce friction, then sliding properties are improved, but manufacturing costs increase
Solution Approach 1:
The patent merges multiple friction-reducing materials (PTFE, graphite, carbon fibers) into a single composite sliding sleeve material that can be manufactured as one integrated component. This eliminates the need for separate lubricant applications and complex assembly steps, reducing manufacturing costs while achieving permanent friction reduction and stick-slip effect elimination.
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 durable and low-friction sliding connection that significantly reduces the stick-slip effect, maintaining service life and minimizing force differences between static and sliding friction, thus enhancing the operational reliability and durability of the steering spindle.
Implementation Method 1
a sliding sleeve (5) made of a mixture of the material PEEK and additionally the material PTFE with a percentage by volume in the range of 7% to 13% and additionally the Material graphite with a volume fraction of 7% to 13%
Implementation Method 2
the difference between static friction and sliding friction can also be reduced
Implementation Method 3
the combination of materials increases the durability of the sliding sleeve (5) and the sliding connection formed with it
Data Source
Figure 1
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AI summary
The spindle (1) has inner and outer spindles (2, 3) between which an intermediate space is provided, where a sliding bush containing thermoplastic is provided in the space. The bush has a mixture containing polyetheretherketone, PTFE with volume portion in range of 7 percent to 13 percent, graphite with volume portion of 7 percent to 13 percent and carbon fibers with volume portion of 25 to 35 percent. A lubrication agent (11) is arranged in sliding contact between the bush and the outer and/or inner spindles. The lubrication agent has dynamic viscosity in range of 2000 to 4000 millipascal seconds at temperature of 25 degrees Celsius, in range of 600 to 1200 millipascal seconds at temperature of 80 degrees Celsius and in range of 150000 to 220000 millipascal seconds at temperature of minus 20 degrees Celsius.