Shift Device Non-Uniform Press-Fit Sealing
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Solution Overview
Problem
Existing shift lever devices face challenges in achieving improved sealing performance due to the contact force between the shift body and the press-fit hole, which affects the sealing efficiency.
Innovation Solution
The shift device features a press-fit hole with a larger interference amount at the intermediate side compared to the end portions, allowing for reduced contact force and enhanced sealing performance, and includes a catch section for easier assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the press-fit interference amount is increased to improve sealing performance, then the sealing performance improves, but the contact force between the shift body and the press-fit hole increases causing deformation
Solution Approach 1:
The press-fit hole is designed with non-uniform interference distribution along its length direction. The intermediate portion has a larger interference amount than the end portions, creating localized sealing zones where high contact pressure is needed while maintaining lower contact pressure in other areas to prevent deformation. This local quality variation resolves the contradiction by applying high interference only where sealing is critical rather than uniformly throughout.
Solution Approach 2:
The press-fit hole is segmented into different interference zones: end portions with smaller interference and an intermediate portion with larger interference. This segmentation allows different functional requirements to be met in different regions - the end portions accommodate the shift body with minimal deformation while the intermediate portion provides enhanced sealing through higher contact force.
2Reliability
If the press-fit interference amount is increased to improve sealing performance, then the sealing performance improves, but the assembly difficulty increases
Solution Approach 1:
By concentrating the larger interference amount in the intermediate portion rather than distributing it uniformly, the design achieves effective sealing at the critical mid-section while maintaining easier assembly at the end portions. The gradual transition from smaller to larger interference facilitates progressive assembly while ensuring sealing at the most critical location.
3Reliability
If the press-fit hole is made rigid to maintain seal integrity, then the sealing performance improves, but the hole cannot accommodate movement of the shift body
Solution Approach 1:
The press-fit hole is designed to be movable relative to the shift body, accommodating the movement of the shift body while maintaining sealing. The elastic boot material provides dynamic sealing capability, allowing the hole to move with the shift body while the elastic material continuously maintains contact and sealing integrity throughout the movement range.
Solution Approach 2:
The press-fit hole is formed in an elastic boot body, which uses the flexibility of the elastic material to accommodate movement while maintaining seal integrity. The elastic material deforms to allow movement of the shift body but maintains continuous contact to preserve the sealing function throughout the movement cycle.
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 configuration reduces contact force between the shift body and the press-fit hole, thereby improving the sealing performance and facilitating easier assembly by distributing the interference amount gradually across the length of the press-fit hole.
Implementation Method 1
an elastic boot body, and the rectangular hole pivots when the shift lever is pivoted. The elastic boot body forms a seal between the upper and lower sides of the rectangular hole.
Implementation Method 2
a press-fit interference amount between the shift body and the press-fit hole
Data Source
AI summary
A shift device in which a press-fit column of a control lever is press-fitted into and passed through a press-fit hole in a boot such that the boot forms a seal between the upper side and the lower side of the press-fit hole. A press-fit interference amount between the press-fit column and the press-fit hole is larger at a length direction intermediate side of the press-fit hole than at a length direction end portion side of the press-fit hole. This enables a reduction in the contact force between the press-fit column and a peripheral face of the press-fit hole at the length direction intermediate side of the press-fit hole to be suppressed, enabling the sealing performance of the press-fit hole in the boot to be improved.