Steering Column Telescopic Sleeve-Wedge Structure for Low Backlash
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Solution Overview
Problem
Existing telescopic structures in steering columns face issues with radial backlash, high sliding force, and limited rigidity due to metal-on-metal contact and dependence on spring force, leading to increased wear and slow operation speeds.
Innovation Solution
A telescopic structure with an interface structure comprising a sleeve, a wedge, and a biasing member, where the wedge is biased to engage between the outer and inner tubes, eliminating backlash and reducing sliding force by preventing friction between the wedge and the second tube, allowing the sleeve and wedge to support the inner tube without backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring presses a plastic member against the inner tube to eliminate clearance, then radial backlash is reduced and rigidity is improved, but the sliding force increases significantly and wear on the motor increases
Solution Approach 1:
The interface structure is segmented into distinct functional components: a sleeve that provides the sliding surface, wedge members that apply radial force, and a biasing member that maintains contact pressure. This segmentation allows each component to be optimized independently - the sleeve provides a large sliding area with the inner tube while the wedges apply force efficiently through inclined surfaces.
Solution Approach 2:
The sleeve acts as an intermediary component between the inner tube and the wedge members. It transfers the radial force from the wedges to the inner tube while providing a dedicated sliding surface that reduces friction. The biasing member serves as an intermediary that maintains constant contact pressure between the wedges and the sleeve without requiring direct metal-to-metal contact.
2Reliability
If a large spring force is used to ensure good rigidity, then backlash is eliminated, but the sliding force increases to approximately 400N causing increased wear and slower operation
Solution Approach 1:
The interface structure uses dynamic elements including a biasing member that maintains adaptive contact pressure, and wedge members that can move radially to accommodate manufacturing tolerances and wear. This dynamic design allows the system to maintain backlash-free operation while reducing the peak forces required compared to static rigid connections.
Solution Approach 2:
The design changes the force application parameters by using inclined surfaces on the wedge members to convert axial spring force into radial clamping force. This mechanical advantage allows a smaller biasing member force to generate sufficient radial pressure to eliminate backlash, thereby reducing the sliding force and improving operation speed.
3Device complexity
If metal-on-metal contact is used between the outer tube and inner tube, then structural simplicity is maintained, but sliding force increases and grease is required
Solution Approach 1:
The sleeve acts as an intermediary sliding component between the inner tube and the external environment. It provides a dedicated low-friction sliding surface that contacts the inner tube, while the outer tube contacts the wedge members through the sleeve. This intermediary structure eliminates direct metal-to-metal sliding between the tubes while maintaining structural simplicity.
Solution Approach 2:
The interface structure combines different materials strategically: the sleeve is made of plastic or composite material to provide low-friction sliding against the inner tube, while the wedge members and biasing member can be metal. This composite approach reduces sliding force and eliminates the need for grease while maintaining structural integrity.
4Ease of manufacture
If the contact surface of the sliding interface is not clearly defined, then manufacturing is simpler, but it becomes difficult to control natural frequency, rigidity, and low-temperature sliding force
Solution Approach 1:
The sliding interface is segmented into dedicated surfaces: the inner circumferential surface of the sleeve and the outer surface of the inner tube. This segmentation creates clearly defined contact areas that can be precisely controlled during manufacturing while keeping the overall design simple. Each component has specific surfaces optimized for their function.
Solution Approach 2:
The sleeve and inner tube have locally optimized surfaces at their contact interface. The sleeve's inner circumferential surface and the inner tube's outer surface are specifically designed with appropriate finish, hardness, and geometric tolerances to control sliding characteristics, natural frequency, and rigidity, while the rest of the components maintain manufacturing simplicity.
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 achieves reduced sliding force, increased rigidity, and improved operation speed by eliminating backlash and minimizing friction, enhancing the comfort and performance of the steering wheel operation.
Implementation Method 1
a biasing member (for example, a spring) arranged between the outer tube and the inner tube and configured to bias the wedge in the first direction
Implementation Method 2
a wedge arranged between the outer tube and the inner tube and configured to be engaged between the outer tube and the inner tube in response to the biasing of the wedge by the biasing member
Implementation Method 3
allowing the sleeve and the inner tube to slide on each other
Data Source
AI summary
An interface structure includes a sleeve, a wedge and a biasing member. The sleeve is arranged between the inner circumferential surface of the outer tube and the outer circumferential surface of the inner tube. The sleeve includes at least one fixing portion fixed to a first tube that is one of the outer tube and the inner tube, at least one contact surface configured to come into contact with a second tube that is the other of the outer tube and the inner tube, and a wedge mating surface configured to be mated with the wedge. The wedge is arranged between the first tube and the sleeve and is mated with the wedge mating surface of the sleeve. The biasing member biases the wedge so as to engage the wedge between the first tube and the sleeve while allowing the sleeve and the second tube to slide on each other.