Coaxial Screw-Spring Retention for Motor Vehicle Closure Linear Drives
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Solution Overview
Problem
Existing linear drives for motor vehicle closures are either unsafe in the event of a fire due to guide elements melting and allowing the screw spring to escape, or they have a less compact design by positioning the screw spring radially outside the outer tube.
Innovation Solution
A compact linear drive design with a screw spring clamped coaxially between inner and outer support elements, secured by a securing element with a larger radial diameter than the screw spring, and further secured by a ring washer, ensuring the screw spring remains in place even under high temperatures, and guided by support elements made of plastic to minimize friction and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the screw spring is arranged radially outside the outer tube, then the safety in the event of fire is improved, but the compactness of the linear drive deteriorates
Solution Approach 1:
The screw spring is arranged radially inside the outer tube and clamped between the inner support element and outer support element, nesting the spring within the existing structure. This eliminates the need for radial external arrangement while maintaining safety through the fire-resistant metal support elements that prevent spring escape even at high temperatures.
Solution Approach 2:
The linear drive uses metal support elements (inner support element and outer support element) with different fire resistance properties than plastic guide elements. These metal components ensure the screw spring remains secured during fire conditions, achieving safety without requiring radial external placement.
2Ease of manufacture
If plastic guide elements are used to support the screw spring, then the manufacturing cost is reduced, but the reliability in the event of fire deteriorates
Solution Approach 1:
The linear drive employs metal support elements (inner support element and outer support element) instead of plastic guide elements. These metal components maintain structural integrity and fire resistance while providing the necessary support for the screw spring, solving the reliability issue without significantly complicating manufacturing.
Solution Approach 2:
The support elements are designed with specific geometric parameters including a radial diameter larger than the screw spring's radial diameter. This parameter change ensures the support elements can physically contain the screw spring even under thermal stress, preventing escape during fire conditions.
3Volume of moving object
If the inner element is fully insertable into the outer tube, then the compactness is improved, but the friction and noise increase
Solution Approach 1:
The support elements act as intermediary components between the inner element and outer tube, providing a controlled interface that reduces direct metal-to-metal contact. This intermediary structure maintains full insertability for compactness while minimizing friction and noise through the designed contact surfaces.
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 design provides a safe and compact linear drive that prevents the screw spring from escaping during a fire and reduces friction and noise, maintaining functionality and safety without additional components.
Implementation Method 1
the screw spring can support the inner element being pulled out of the outer tube or the inner element being pushed into the outer tube
Implementation Method 2
guided by support elements made of plastic to minimize friction and noise
Data Source
AI summary
A linear drive (100) for moving a closure element of a motor vehicle relative to a body of the motor vehicle. The linear drive (100) includes an outer tube (110), an inner element (120) arranged in the outer tube (110), wherein the inner element (120) is telescopically extendable along a drive axis (A) of the linear drive (100) from an outlet end of the outer tube (110), and wherein an inner connecting element (128) is fixed to the end of the inner element (120) which is extendable from the outer tube (110), a screw spring (130) is disposed between the inner element (120) and the outer tube (110), an inner support element (122) is fixed to the inner element (120) and an outer support element (111) is fixed to the outer tube (110).