Vehicular Drive Device Casing Segmentation for Noise Reduction
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Solution Overview
Problem
Vehicular drive systems with electric motors and helical gear portions face issues with operating noise and performance due to variations in the air gap between stators and rotors, caused by meshing reaction forces, which also lead to increased weight and cost when attempting to address these issues with additional casing rigidity.
Innovation Solution
A vehicular drive system design where the stator of each electric motor is fixed to a first casing member, and the rotor is supported by both the first and second casing members, allowing the meshing reaction force to be transmitted to the second casing member, reducing the variation in the stator's fixing position and eliminating the need for additional support members, thus minimizing air gap variations and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the stator is fixed to the same casing member that supports the helical gear portion, then the structure is simplified, but the meshing reaction force causes deformation and air gap variation leading to increased noise and reduced performance
Solution Approach 1:
The casing is divided into two separate casing members: a first casing member that supports the stator and a second casing member that supports the helical gear portion. This segmentation isolates the sources of vibration and deformation, preventing the meshing reaction force from affecting the stator fixing position and thus maintaining consistent air gap and reducing operating noise.
Solution Approach 2:
A support portion is introduced as an intermediary element between the second casing member and the helical gear portion. This support portion is specifically designed to bear the meshing reaction force, acting as a mediator that protects the casing structure from deformation and prevents air gap variation, thereby reducing noise while maintaining structural simplicity.
2Reliability
If the air gap is increased to avoid sliding contact, then reliability is improved, but operation performance is reduced
Solution Approach 1:
The patent introduces a support portion that beforehand cushions and absorbs the meshing reaction force generated by the helical gear portion. By providing this preliminary protection against deformation, the air gap can be maintained at an optimal small size without risk of sliding contact, thus preserving both reliability and operation performance.
3Stability of the object's composition
If ribs are added to increase casing rigidity, then stability is improved, but weight and size increase leading to deteriorated fuel economy and increased manufacturing cost
Solution Approach 1:
Instead of adding ribs to the entire casing structure, the patent segments the casing into two members with the support portion strategically positioned to handle the meshing reaction force. This targeted approach provides necessary rigidity and stability only where needed, avoiding unnecessary weight and complexity throughout the entire structure.
Data Source
AI summary
A vehicular drive system is provided with at least one electric motor and a helical gear portion which are accommodated within a casing formed by a plurality of casing members fixed to each other, wherein: said casing includes a first casing member to which a stator of each of said at least one electric motor is fixed, and a second casing member which is fixed to said first casing member so as to cooperate with said first casing member to form a space accommodating said at least one electric motor and which has a support portion supporting said helical gear portion; and a rotor of said each electric motor is rotatably supported at opposite ends thereof by said first casing member and said second casing member, respectively, while said helical gear portion is rotatably supported by said second casing member through said support portion.