Steering Column Shearable Jacket Connector Design
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Solution Overview
Problem
Collapsible steering column assemblies face challenges in maintaining the upper and lower jackets fixed relative to each other during normal operational use while allowing for telescopic movement during a collision event, requiring a mechanism to restrain the jackets axially until a predetermined load is applied.
Innovation Solution
A jacket connector with pre-determined shear resistance is used to securely attach the jackets during normal conditions and permit telescopic movement upon exceeding the shear resistance, allowing the upper jacket to collapse relative to the lower jacket.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the upper jacket and lower jacket are rigidly attached during normal operational use, then the structural stability and rigidity are improved, but the ability to collapse during collision events deteriorates
Solution Approach 1:
The jacket connector transitions from a static rigid connection to a dynamic shearable connection. The connector is designed with a predetermined shear strength that allows it to remain rigid during normal operation but fail in a controlled manner when subjected to collision forces exceeding the shear threshold, enabling the upper jacket to collapse relative to the lower jacket
Solution Approach 2:
The connector's mechanical properties are specifically engineered with a predetermined shear resistance parameter. This parameter is selected to be higher than normal operational loads but lower than forces required to damage the energy absorption device, creating a controlled failure point that enables collapse while maintaining structural integrity during normal use
2Adaptability or versatility
If a shearable jacket connector is used to enable collapse during collisions, then the collapse capability is improved, but the structural strength during normal operational use deteriorates
Solution Approach 1:
The connector is designed with optimized geometric parameters and material properties to achieve a specific shear strength that falls within a predetermined range. This careful parameter selection ensures the connector is strong enough to maintain structural integrity during normal operation but weak enough to shear during collision events, resolving the strength-collapse capability contradiction
3Loss of energy
If traditional energy absorption devices are used without a shearable connector, then the energy absorption capability is improved, but the complexity of the device increases
Solution Approach 1:
The invention extracts the collapse initiation function from the energy absorption device and places it in the jacket connector. The connector's shearable design automatically initiates collapse when forces exceed the shear threshold, eliminating the need for additional mechanisms within the energy absorption device and simplifying the overall system while maintaining energy absorption capability
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
This solution provides a cost-effective mechanism for axial restraint during normal conditions and enables telescopic movement in response to sufficient axial loads, enhancing safety by allowing energy absorption and reducing driver injury during collisions.
Implementation Method 1
The jacket connector includes a pre-determined shear resistance for shearing between the first jacket and the second jacket
Implementation Method 2
The jacket connector shears in response to an axial load applied to one of the first jacket and the second jacket greater than the pre-determined shear resistance
Data Source
AI summary
A steering column assembly includes a first jacket defining a first bore and a second jacket defining a second bore aligned with the first bore prior to collapse of the first jacket and the second jacket. A jacket connector extends through the bores to interconnect the first jacket and the second jacket. The jacket connector includes a pre-determined shear resistance, above which the jacket connector is sheared to permit telescopic movement between the first jacket and the second jacket. Accordingly, in response to an axial load greater than the pre-determined shear resistance of the jacket connector being applied to one of the first jacket and the second jacket, the jacket connector shears, permitting the telescopic movement. The jacket connector includes a pin defining a pin bore. The pin bore defines a cross sectional area, with the pre-determined shear resistance depending upon the cross sectional area of the pin bore.