Belt Pretensioner Bushing for Cable Protection
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Solution Overview
Problem
Existing belt pretensioner designs with linear drives face complexity in housing design and sealing due to the need for an annular sleeve extending into the cavity to protect the cable from hot pressurized gas, which complicates the sealing mechanism and requires the sealing to withstand both thermal and mechanical loads.
Innovation Solution
A bushing made of aluminum, with a radial flange and second flanges, is used to surround the cable, providing direct protection and sealing at different sections, eliminating the need for an annular sleeve and ensuring the sealing is not loaded by the pressurized gas, while the bushing is fixed in position and minimizes noise and heat absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an annular sleeve is integrated into the housing to protect the cable from hot pressurized gas, then cable protection is improved, but housing design complexity increases and sealing becomes more difficult
Solution Approach 1:
The protective function is extracted from the housing structure and implemented as a separate bushing component. This bushing is inserted into the cavity to protect the cable from hot pressurized gas, while the housing itself remains simple without integrated annular sleeves. The sealing is also separated as an independent element within the bushing rather than being integrated into the housing structure.
Solution Approach 2:
The protective system is segmented into distinct functional components: the bushing for cable protection, the sealing element for gas sealing, and the housing for structural support. This segmentation allows each component to be optimized independently - the bushing handles thermal protection while the sealing handles gas containment, simplifying the overall housing design.
2Object-affected harmful factors
If sealing is arranged between the annular sleeve and cable to protect from hot gas, then cable sealing is improved, but the sealing must withstand both thermal and mechanical loads increasing complexity
Solution Approach 1:
The sealing function is extracted from the housing-sealing interface and relocated to the bushing-cable interface. The sealing element is arranged between the bushing and the cable, allowing it to handle only the cable sealing function rather than both housing sealing and cable protection simultaneously. This reduces the thermal and mechanical loads on the sealing.
Solution Approach 2:
The bushing acts as an intermediary component between the hot pressurized gas environment and the cable. It provides a protective barrier while the sealing element provides the actual seal at the cable-bushing interface. This intermediary structure separates the thermal protection function from the sealing function, simplifying the sealing design.
3Manufacturing precision
If the bushing is fixed at the abutment with direct contact, then positioning precision is improved, but noise increases due to direct contact
Solution Approach 1:
The bushing design uses local quality differentiation: the first flange provides rigid fixed contact with the abutment for precise positioning, while the second flanges provide spaced contact points that reduce noise transmission. The selective engagement of different flange sections with the cavity wall allows simultaneous achievement of positioning precision and noise reduction.
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 enhances cable protection from hot pressurized gas, simplifies the housing design, and improves the pretensioner's efficiency by allowing quicker pressure buildup and reduced noise, as the bushing is in direct contact with the cable and housing, and the second flanges facilitate faster gas passage to drive the piston.
Implementation Method 1
a pressurized gas generated by a gas generator when the belt pretensioner is activated. The piston is driven by the pressurized gas
Implementation Method 2
the bushing is in direct contact with the cable and housing, and the second flanges facilitate faster gas passage to drive the piston
Data Source
Figure 1
Figure 2
AI summary
Belt pretensioner with a linear drive comprising -a housing (1) with a cavity (5), and -a gas generator (3) fixed in the housing (1), which loads the cavity (5) with a pressurized gas when activated, and -a cable (2), which runs through the cavity (5) and is guided in a guidance (10) arranged in the housing (1) and -a piston/cylinder unit, wherein -the piston/cylinder unit is attached at the housing (1) and closes the cavity (5) in the housing (1), wherein -the cable (2) is connected with one end with the piston (6) and with the other end with one part of a seatbelt device, wherein -a sealing (9) is provided which is arranged between the cable (2) and the housing (1), wherein -the cable (2) is protected at least partially in the section running through the cavity (5) by a shielding, wherein -the sealing (9) is arranged in the guidance (10) of the housing (1), and -the shielding is realized by a bushing (11) surrounding the cable (2), and -the bushing (11) abuts with its first face side, which is directed towards the guidance (10) in axial direction at an abutment (15) of the housing (1).