Off-Axis Vane Pump for Automatic Transmission
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Solution Overview
Problem
Existing hydraulic pumps for automatic transmissions face challenges in achieving high efficiency, small size, and self-priming capabilities, especially under cold start conditions with high viscosity transmission fluid, which affects gear shifting and operational efficiency.
Innovation Solution
A vane pump design featuring a housing off-axis from the transmission input shaft, driven by a chain or gear train, with a cylindrical chamber and eccentrically disposed rotor having radial slots and a single vane ring, enhancing self-priming and reducing size and leakage through tight tolerances and pressurization of vanes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the pump is mounted concentric to the engine axis, then the size is reduced, but the efficiency and self-priming capability deteriorate
Solution Approach 1:
The pump is positioned off-axis relative to the engine centerline, creating an asymmetric arrangement that improves suction characteristics and self-priming capability while maintaining compact dimensions through optimized spatial layout
2Loss of energy
If the vanes are pressed tightly against the chamber wall, then leakage is reduced, but friction and wear increase
Solution Approach 1:
Hydraulic pressure is used to dynamically adjust the contact pressure between vanes and chamber wall, increasing it during high-pressure operation to reduce leakage while maintaining lower average pressure to minimize wear and friction
3Device complexity
If the pump is driven directly at engine speed, then the complexity is reduced, but the efficiency under varying engine conditions deteriorates
Solution Approach 1:
A chain drive mechanism serves as an intermediary between the engine and pump, allowing flexible power transmission that can optimize pump speed independent of engine speed variations, thereby maintaining high efficiency across different operating conditions
4Strength
If the transmission fluid has high viscosity during cold start, then the lubrication is improved, but the pump efficiency and gear shifting capability deteriorate
Solution Approach 1:
The pump's off-axis positioning and suction port design enable it to automatically draw fluid from the transmission pan during cold start, creating self-priming action that overcomes high viscosity effects and establishes hydraulic pressure for gear shifting without external assistance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves high efficiency, self-priming capabilities, and improved cold start performance by maintaining vane close proximity to the chamber wall, reducing leakage, and allowing flexible mounting, suitable for both front and rear wheel drive transmissions.
Implementation Method 1
The rotor includes two halves that define a central chamber. The rotor also includes a plurality of radial slots which receive a like plurality of vanes. The outer ends of the vanes are in contact with the wall of the cylindrical chamber and the inner ends are in contact with a single vane ring received within the central chamber.
Implementation Method 2
maintaining vane close proximity to the chamber wall, reducing leakage
Data Source
AI summary
A vane pump for an automatic transmission includes a housing which may be spaced from the axis of the transmission input shaft axis and driven by a chain or gear train driven by the torque converter hub or disposed on and about the axis of the transmission input shaft and driven at engine speed. The vane pump includes a pair of port plates which reside on the end faces of a pump body having a cylindrical chamber which receives an eccentrically disposed rotor that is coupled to a stub shaft. The rotor includes two halves that define a central chamber. The rotor also includes a plurality of radial slots which receive a like plurality of vanes. The outer ends of the vanes are in contact with the wall of the cylindrical chamber and the inner ends are in contact with a single vane ring received within the central chamber.