Transmission Input Shaft Geometry for Seal-Safe Torque Converter Assembly
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Solution Overview
Problem
The existing automatic transmission assembly process risks damaging the seal ring during the assembly of the torque converter and input shaft due to misalignment, which can cause the small diameter portion of the input shaft to catch in the seal ring protruding from the support member.
Innovation Solution
A transmission design that includes a torque converter with a hollow shaft, a transmission input shaft with a large diameter portion and a small diameter portion, a seal member, and a bush positioned between the hollow shaft and the input shaft, where the seal member has a larger diameter than the bush, and the small diameter portion's axial length is set to be longer than the bush's insertion length, allowing axis alignment without initial contact between the seal member and the large diameter portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the small diameter portion of the input shaft is inserted into the support member before axis alignment is completed, then the assembly process can proceed, but the seal ring may be damaged due to misalignment
Solution Approach 1:
The input shaft is segmented into two distinct portions: a small diameter portion for initial insertion through the bush, and a large diameter portion for subsequent contact with the seal ring. This segmentation allows the assembly process to proceed in stages - first inserting the small diameter portion for alignment, then engaging the large diameter portion with the seal ring to complete the assembly without damaging the seal ring
Solution Approach 2:
The small diameter portion of the input shaft is designed to be inserted into the bush before axis alignment is completed. This preliminary insertion action allows the components to be positioned and aligned properly before the seal ring engages with the large diameter portion, preventing seal ring damage while maintaining assembly continuity
2Reliability
If the seal ring protrudes from the support member to contact the input shaft, then sealing function is achieved, but the seal ring is vulnerable to damage during assembly
Solution Approach 1:
Different portions of the input shaft have different diameters tailored for different functions: the small diameter portion is designed for insertion through the bush during alignment, while the large diameter portion is designed to contact the seal ring. This local quality differentiation ensures that the seal ring only contacts the robust large diameter portion, protecting it from damage while maintaining the sealing function
Solution Approach 2:
The assembly process is designed so that the small diameter portion is inserted first for alignment purposes, and only after proper alignment is achieved does the large diameter portion contact the seal ring. This preliminary alignment action prevents misalignment-related damage to the seal ring while ensuring the sealing function is properly established
Data Source
AI summary
A transmission includes: a torque converter; a transmission input shaft; a seal member sandwiched between the hollow shaft and the transmission input shaft; and a bush, the transmission input shaft including a large diameter portion abutted on the seal member, and a small diameter portion which is positioned on the tip end side of the large diameter portion, and which has a diameter smaller than a diameter of the large diameter portion, the seal member having a diameter larger than a diameter of the bush, and the small diameter portion having an axial length set to be longer than a length from an insertion inlet of the transmission input shaft of the bush to the seal member.