Transmission Shaft Bore Layout for Fluid Routing and Strength
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Solution Overview
Problem
Motor vehicle transmission shafts with multiple bore holes face challenges in maintaining strength while minimizing outer diameter and preventing hydraulic short circuits due to varying high pressures and potential breakthroughs between bore holes.
Innovation Solution
A shaft design with four axial bore holes, where the central axis of each bore hole is offset from the axis of rotation, and the radial distance and bore diameters are varied to optimize wall thickness and strength, ensuring consistent radial distribution and uniform arrangement of bore holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If four axial bore holes are provided in the shaft for fluid supply, then fluid conductivity is improved, but shaft strength deteriorates
Solution Approach 1:
The patent applies asymmetry by arranging the four bore holes at different radial distances from the shaft axis. Specifically, two bore holes are positioned at a first radial distance while the other two are positioned at a second radial distance, creating an asymmetric distribution pattern. This asymmetric arrangement optimizes the balance between providing sufficient fluid supply paths and maintaining adequate wall thickness for shaft strength, resolving the contradiction between fluid conductivity and structural integrity.
2Area of stationary object
If the outer diameter of the shaft is reduced, then bearing and sealing element sizes are minimized, but wall thickness between bore holes decreases leading to hydraulic short circuits
Solution Approach 1:
The patent applies local quality by varying the wall thickness distribution around the bore holes based on their radial positions. Bore holes at different radial distances create zones with different wall thickness characteristics, allowing the shaft to maintain adequate hydraulic isolation in critical areas while keeping the overall outer diameter small. This localized optimization of wall thickness ensures reliability prevents hydraulic short circuits between adjacent bore holes.
3Quantity of substance
If deep bore holes are drilled, then fluid supply capability is improved, but drilling axis obliquity reduces wall thickness between bore holes
Solution Approach 1:
The patent applies preliminary action by pre-planning and pre-positioning the bore holes at specific radial distances from the shaft axis before the actual drilling process. The asymmetric arrangement with two bore holes at a first radial distance and two at a second radial distance is designed in advance to account for potential drilling axis obliquity. This preliminary positioning strategy ensures that even with manufacturing tolerances, the wall thickness between bore holes remains sufficient to prevent hydraulic short circuits.
Data Source
AI summary
A shaft (W) for a motor vehicle transmission (G) includes four axial bore holes (B1, B2, B3, B4) for conducting fluid within the shaft (W). A central axis of each of the four bore holes (B1, B2, B3, B4) is spaced apart from an axis of rotation (WA) of the shaft (W). A radial distance (r1) between the central axis of at least two of the four bore holes (B1, B2, B3, B4) and the axis of rotation (WA) differs from a radial distance (r2) between the central axis of one of the remaining bore holes and the axis of rotation (WA). A transmission (G) for a motor vehicle with a shaft (W) is also provided.