Transaxle Case Overhanging Rib Reduces Stirring Resistance
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Solution Overview
Problem
In power transfer devices, oil from the storage chamber leaks into the differential chamber due to clearance between the reservoir plate and the case, increasing stirring resistance on the differential ring gear.
Innovation Solution
The power transfer device incorporates a case design with an overhanging portion and an extending rib on the second case member, forming a splattering space where oil is splattered and pushed back into the storage chamber, reducing oil residence in the differential chamber and lowering stirring resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a differential partitioning member with a reservoir plate is used to partition the differential chamber and storage chamber, then the structure is simple and easy to manufacture, but oil leaks from the storage chamber into the differential chamber through clearances, increasing stirring resistance
Solution Approach 1:
The case is divided into a first case member and a second case member with different functions. The first case member forms the storage chamber with a relatively simple structure, while the second case member forms the differential chamber with an overhanging portion that creates a unidirectional flow path. This segmentation allows each part to be optimized for its specific function while maintaining ease of manufacture.
Solution Approach 2:
Instead of trying to prevent oil from entering the differential chamber entirely (which would require complex sealing), the invention inverts the approach by allowing oil to enter but designing the overhanging portion to prevent oil from returning to the storage chamber. This inversion transforms a sealing problem into a flow direction control problem, maintaining manufacturing simplicity while reducing stirring resistance.
2Object-affected harmful factors
If the reservoir plate is designed to tightly contact the rib member to suppress oil inflow, then oil leakage is reduced, but manufacturing precision becomes difficult to achieve and maintain
Solution Approach 1:
The invention extracts the sealing function from the reservoir plate-contact interface and relocates it to the overhanging portion structure. By taking out the requirement for tight contact between the reservoir plate and rib member, the design eliminates the need for high manufacturing precision at that interface while still achieving effective oil flow control through the overhanging portion's geometric design.
Solution Approach 2:
The invention changes the critical parameter from contact tightness (which requires high precision) to the geometric dimensions of the overhanging portion (which can be manufactured with standard tolerances). By changing which parameter controls the oil flow behavior, the design achieves effective sealing without requiring difficult-to-maintain manufacturing precision.
3Reliability
If more working oil is allowed to reside in the differential chamber for adequate lubrication, then lubrication is improved, but stirring resistance increases and operational efficiency decreases
Solution Approach 1:
The invention creates a dynamic oil flow system where oil continuously circulates from the storage chamber through the differential chamber and back. The overhanging portion acts as a one-way gate that maintains adequate oil levels for lubrication while preventing oil accumulation that would increase stirring resistance. This dynamic approach balances lubrication needs with efficiency requirements.
Solution Approach 2:
The design ensures continuous oil circulation through the differential chamber, providing constant lubrication to the differential gear components. The overhanging portion maintains a continuous oil supply path while preventing oil from stagnating in the differential chamber, thus maintaining both adequate lubrication and low stirring resistance through continuous flow.
Data Source
AI summary
A transaxle case with an overhanging portion that overhangs outward relative to a vertical line (a tangential line) that extends upward from a 90-degree rotated portion at a location rotated from the vertically lower portion of a differential ring gear by 90 degrees, and an extending rib that extends from the overhanging portion toward the center of rotation of the differential ring gear to the vicinity of the outer periphery of the differential ring gear, and the overhanging portion and the extending rib constitute a splattering space. The lower surface of the extending rib is formed as an inclined surface such that working oil is pushed toward a converter housing when working oil splattered to the splattering space collides against the lower surface. Consequently, working oil is caused to be splattered to the splattering space, collides against the lower surface of the extending rib, and pushed toward the converter housing.