Gear Case Layout for Compact EV Drive Lubrication
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Solution Overview
Problem
Conventional driving force transmission devices with gear systems and lubricating oil face challenges in reducing the size of the transmission case due to the accommodation of components within it.
Innovation Solution
The drive device incorporates a motor, output part, gear part, and housing with a gear case design that includes a wall part extending radially and a circumferentially penetrating opening, allowing for efficient torque transmission and reduced size through the use of a support member and bearing parts, and a lubricant system that minimizes lubricant scattering and temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the accommodating part is accommodated inside the transmission case, then the gear is protected and lubricated, but the size of the transmission case cannot be reduced
Solution Approach 1:
The transmission case is divided into a housing and a separate gear case. The gear case accommodates the gear and lubricating oil, while the housing provides structural support and mounting for the motor. This segmentation allows the gear case to be optimized for compactness while the housing maintains overall structural integrity, thereby reducing the total size while preserving gear protection and lubrication functions.
Solution Approach 2:
The gear case is positioned such that it partially overlaps with the housing in the axial direction, with the gear case located on the downstream side. This nested arrangement allows the gear case to be integrated into the existing housing structure, maximizing space utilization and reducing the overall transmission case size while maintaining proper gear accommodation and lubrication.
2Reliability
If the gear case is positioned on the upstream side, then lubrication is effective, but lubricant scatters to the housing and temperature rises
Solution Approach 1:
The gear case is extracted from the traditional upstream position and relocated to the downstream side of the housing. This extraction removes the source of lubricant scattering from the housing, thereby reducing temperature rise. The gear case maintains its lubrication function through dedicated lubricant supply channels while preventing harmful thermal effects on the housing.
Solution Approach 2:
A seal member is introduced as an intermediary between the gear case and the housing. This seal member prevents lubricant from scattering to the housing while allowing the gear case to maintain effective lubrication. The seal member acts as a barrier that isolates the lubricant within the gear case, preventing thermal transfer to the housing and reducing overall temperature rise.
3Volume of moving object
If the gear case overlaps the housing in the axial direction, then space is utilized efficiently, but the gear case must be precisely positioned
Solution Approach 1:
Positioning protrusions and positioning recesses are designed into the gear case and housing respectively before assembly. The positioning protrusions on the gear case fit into the positioning recesses on the housing, establishing precise relative positioning in advance. This preliminary positioning action ensures accurate alignment when the gear case overlaps the housing in the axial direction, eliminating the need for complex post-assembly adjustments.
Solution Approach 2:
The positioning protrusions and recesses are designed with tolerances that allow the gear case to self-align with the housing during assembly. The overlapping configuration combined with these self-aligning features enables the components to find their correct relative positions automatically, reducing the need for high-precision manual positioning while maintaining efficient space utilization.
Data Source
AI summary
A drive device includes a motor, an output part outputting torque to the outside, a gear part transmitting torque of the motor to the output part, and a housing having an internal space. The gear part includes at least one gear shaft extending in an axial direction, to which at least one gear is fixed, and a gear case accommodating the gear. The gear case includes a wall part facing an outer circumferential surface of the accommodated gear in a radial direction and extending in a circumferential direction and an opening adjacent to the wall part in the circumferential direction and penetrating in the radial direction. The opening faces the housing in the radial direction, and in a rotation direction of the gear, the wall part includes a front end disposed on a front side of the opening and adjacent to the opening. The front end contacts the housing.