Steering Column Driving Member Shear and Deformation
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Solution Overview
Problem
Existing steering column devices require highly accurate dimensional relations to set proper sliding frictional resistance for collision energy absorption, leading to increased machining costs.
Innovation Solution
A steering column device with a driving member featuring a first protrusion that shears under impact and a second protrusion that elastically deforms to absorb impact load, allowing for separate uncoupling and energy absorption, reducing the need for precise dimensional settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the width of the impact-load-input-time engaging section is reduced to be narrower than the diameter of the normal-time engaging section, then the sliding frictional resistance increases to provide proper collision energy absorption, but the machining cost increases due to the need for highly accurate dimensional setting
Solution Approach 1:
The driving member is divided into two distinct protrusions: a first protrusion for normal-time engagement and a second protrusion for impact-load engagement. This segmentation allows each protrusion to have optimized dimensions for its specific function, with the second protrusion having a smaller cross-sectional area to generate higher sliding frictional resistance for collision energy absorption, while the first protrusion maintains larger dimensions for normal operation. The segmented design eliminates the need for highly accurate dimensional setting across the entire engaging section.
Solution Approach 2:
Different sections of the driving member are given different local qualities: the first protrusion has larger cross-sectional area for normal engagement, while the second protrusion has smaller cross-sectional area specifically positioned to engage during impact loads. The long hole in the inner column is also designed with different sections - a normal-time engaging section and an impact-load-input-time engaging section - where the latter has a narrower width to increase sliding frictional resistance. This local quality differentiation allows proper collision energy absorption without requiring highly accurate dimensional setting throughout the entire structure.
2Reliability
If the sliding frictional resistance is set to proper resistance for collision energy absorption, then the collision energy absorption performance improves, but the dimensional relation between the sleeve and the impact-load-input-time engaging section must be set highly accurately, increasing machining cost
Solution Approach 1:
The driving member is divided into two distinct protrusions: a first protrusion for normal-time engagement and a second protrusion for impact-load engagement. This segmentation allows each protrusion to have optimized dimensions for its specific function, with the second protrusion having a smaller cross-sectional area to generate higher sliding frictional resistance for collision energy absorption, while the first protrusion maintains larger dimensions for normal operation. The segmented design eliminates the need for highly accurate dimensional setting across the entire engaging section.
Solution Approach 2:
The cross-sectional area of the second protrusion is specifically designed to be smaller than that of the first protrusion, changing the geometric parameter to increase sliding frictional resistance. The narrower width of the impact-load-input-time engaging section relative to the normal-time engaging section creates a parameter change that generates the required frictional resistance for collision energy absorption. These parameter changes are deliberately designed to achieve proper resistance without requiring highly accurate dimensional relationships.
3Device complexity
If a single protrusion is used for both normal engagement and impact absorption, then the device structure is simpler, but the uncoupling and impact absorption functions cannot be separately optimized
Solution Approach 1:
The driving member is divided into two distinct protrusions: a first protrusion for normal-time engagement and a second protrusion for impact-load engagement. This segmentation allows each protrusion to have optimized dimensions for its specific function, with the second protrusion having a smaller cross-sectional area to generate higher sliding frictional resistance for collision energy absorption, while the first protrusion maintains larger dimensions for normal operation. The segmented design eliminates the need for highly accurate dimensional setting across the entire engaging section.
Solution Approach 2:
The impact absorption function is extracted from the normal engagement function by separating the second protrusion from the first protrusion. The second protrusion is specifically designed to be engaged only during impact loads, while the first protrusion handles normal operational engagement. This extraction allows the uncoupling function (first protrusion) and impact absorption function (second protrusion) to be independently optimized without compromising either function.
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 design enables easy setting of energy absorption during collisions while reducing machining costs by using a resin driving member with a lower Young's modulus than the metal inner column, allowing for stable impact absorption and uncoupling.
Implementation Method 1
The first protrusion is pressed against the engaging hole and sheared when the inner column receives an impact load toward a vehicle body forward direction
Implementation Method 2
The second protrusion relatively moves in the long hole while being elastically deformed and receiving sliding frictional resistance toward the vehicle body front-rear direction when the inner column receives the impact load
Implementation Method 3
the second protrusion relatively moves in the long hole while being elastically deformed and receiving sliding frictional resistance
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A motor (11) is attached to an outer column (5) which is mounted on a vehicle body. A driving force of the motor (11) is transmitted to an inner column (7) by a driving member (15) via a screw shaft (13). The driving member (15) includes a first protrusion (23b) engaged in and fixed to an engaging hole (7a) of the inner column (7) and a second protrusion (23c) inserted into a long hole (7b) of the inner column (7). The first protrusion (23b) is pressed against the engaging hole (7a) and sheared when the inner column (7) receives an impact load toward a vehicle body forward direction. The second protrusion (23c) relatively moves in the long hole (7b) while receiving sliding frictional resistance toward a vehicle body rearward direction and being elastically deformed when the inner column (7) receives the impact load toward the vehicle body forward direction.