Vehicle Power Transmission Case Crack Propagation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In vehicle power transmission apparatuses, collisions can cause deformation of vehicle members, leading to loads being applied to mounts, which are then transmitted to the case via bolts, resulting in crack propagation and potential breakage holes that expose internal components like motors.
Innovation Solution
The power transmission apparatus incorporates auxiliary holes between bolt tightening holes, aligned parallel to them, which redirect crack propagation outward, preventing breakage holes from forming between the inside and outside of the case.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the case is made strong to prevent crack propagation, then reliability improves, but weight and manufacturing complexity increase
Solution Approach 1:
The case is segmented into regions with different thicknesses: a thicker first case portion at the mount fastening portion for crack resistance, and a thinner second case portion elsewhere to reduce weight and complexity. This segmentation allows the case to provide enhanced protection where needed without uniformly increasing complexity throughout the entire structure.
Solution Approach 2:
The case employs local quality by varying the thickness of different portions: the first case portion has greater thickness to resist crack propagation from collision loads, while the second case portion has reduced thickness to minimize weight. This localized differentiation of structural properties allows the case to achieve high reliability at critical locations without overall complexity increase.
2Weight of moving object
If the case wall is made thin to reduce weight, then weight decreases, but crack propagation risk increases
Solution Approach 1:
The case wall is segmented into different thickness zones: a thicker first case portion at the mount fastening portion where collision loads are transmitted, and a thinner second case portion in other areas. This segmentation enables weight reduction in non-critical areas while maintaining crack resistance at critical locations through the thicker wall design.
Solution Approach 2:
The case employs local quality by providing different wall thicknesses in different locations: the first case portion has increased thickness to prevent crack propagation under collision loads, while the second case portion has reduced thickness to minimize overall weight. This localized structural differentiation resolves the contradiction between weight reduction and crack resistance.
3Reliability
If auxiliary holes are added to redirect cracks, then reliability improves, but manufacturing complexity increases
Solution Approach 1:
The case is segmented by incorporating auxiliary holes that divide the case into multiple regions (first case portion, second case portion, and third case portion). These holes create natural barriers that segment crack propagation paths, forcing cracks to follow predetermined routes away from critical internal components. The segmentation approach controls crack behavior without requiring complex additional structures.
Solution Approach 2:
The auxiliary holes act as intermediary elements that mediate crack propagation. By introducing these holes between the mount fastening portion and the motor, they serve as crack arrestors that redirect crack paths along the case wall rather than allowing direct propagation toward internal components. This intermediary structure provides simple yet effective crack control.
Data Source
Figure 1~3
Figure 4~6
Figure 7~9
AI summary
A power transmission apparatus (14) is used in a vehicle and mounted on a vehicle member (16) via a mount (22). The power transmission apparatus includes a case (24). The case includes a motor (26) provided inside the case. The case includes a mount fastening portion (36, 82) for fastening the mount with a plurality of bolts. The mount fastening portion has a plurality of bolt tightening holes (40). The plurality of bolt tightening holes are provided so that the plurality of bolts are tightened into the plurality of bolt tightening holes. The bolt tightening holes have axial directions parallel to each other. A space isolated from an inside of the case is formed by a wall of the case in a region connecting two adjacent bolt tightening holes when the mount fastening portion is viewed in the axial directions of the plurality of bolt tightening holes.