Coaxial Vehicle Drive Case Structure for Helical Gear Thrust Isolation
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Solution Overview
Problem
In existing vehicle drive devices, the thrust forces acting on helical gears can cause distortion in the stator support portion, leading to a decrease in the performance of the rotary electric machine.
Innovation Solution
The vehicle drive device includes a rotary electric machine, a transmission with helical gears, and a case structured with separate members to isolate thrust forces, preventing distortion in the stator support portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the support member supports both the first helical gear and the rotor bearing, then the device can be downsized, but the thrust force may be transmitted to the first case member causing stator support portion distortion
Solution Approach 1:
The case is divided into two separate members: the first case member that houses the rotary electric machine and the second case member that houses the transmission. This segmentation isolates the thrust force transmission path to the second case member, preventing it from reaching the stator support portion on the first case member, thereby resolving the contradiction between downsizing and maintaining stability.
Solution Approach 2:
The support member acts as an intermediary that is fixed to the second case member rather than the first case member. This intermediary arrangement allows the support member to bear thrust forces from the helical gear while preventing these forces from being transmitted to the stator support portion, enabling both compact design and structural stability.
2Device complexity
If the support member is fixed to the first case member, then the structure is simpler, but the thrust force causes distortion in the stator support portion leading to decreased rotary electric machine performance
Solution Approach 1:
The case is segmented into two separate members with distinct functions. The first case member provides a stable mounting for the stator support portion, while the second case member absorbs the thrust forces from the helical gear. This segmentation prevents force transmission that would compromise rotary electric machine performance.
Solution Approach 2:
The support member is extracted from the first case member and repositioned to be fixed to the second case member. This extraction removes the harmful coupling between the thrust force transmission path and the stator support portion, thereby protecting rotary electric machine performance while maintaining structural integrity.
3Stability of the object's composition
If the first case member and second case member are separate members, then thrust forces are isolated from the stator support portion, but the device structure becomes more complex
Solution Approach 1:
The case is divided into two functionally distinct members: the first case member dedicated to housing the rotary electric machine with a stable stator support portion, and the second case member housing the transmission and bearing the support member. This segmentation achieves force isolation while maintaining reasonable structural complexity.
Solution Approach 2:
The second case member serves multiple functions: it houses the transmission components and provides the mounting structure for the support member that bears thrust forces. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in overall device complexity while achieving the desired stability.
Data Source
AI summary
A rotary electric machine, a transmission, and a differential gear device are disposed coaxially. The transmission includes a first helical gear and a second helical gear that meshes with the first helical gear. A case includes a first case member including a stator support portion that supports a stator of the rotary electric machine, a second case member that is structured as a separate member from the first case member and forms a gear chamber that houses the transmission and the differential gear device, and a support member that supports the first helical gear in an axial direction. The support member rotatably supports a rotor of the rotary electric machine via a rotor bearing, and is fixed to the second case member.