Pump Bearing Arrangement With Shaft Extender for Higher Radial Loads
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Solution Overview
Problem
Conventional bearing arrangements in variable displacement vane pumps are limited by high hydraulic radial loading, restricting their application to low pressure rise and low displacement, and larger bearings are unsuitable due to rotor vane slot limitations.
Innovation Solution
A pump design incorporating a shaft extender with a conical portion complementary to the input shaft, secured by a retaining nut and key slots, and enclosed by end caps to enhance bearing support, allowing for increased radial load capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If larger bearings are used to carry more load, then radial load capacity is improved, but the bearing diameter is limited by the rotor vane slots
Solution Approach 1:
The bearing support system is segmented into two functional parts: the bearing itself (which can be larger for load capacity) and the shaft extender (which bridges the gap between the limited-diameter shaft and the larger bearing). This allows the bearing to be sized for load capacity while the shaft diameter remains constrained by rotor vane slot requirements.
Solution Approach 2:
The shaft extender acts as an intermediary component between the input shaft and the bearing. It has a first portion that interfaces with the input shaft and a second portion that supports the bearing, allowing the bearing to be larger than the shaft diameter while maintaining proper load transmission.
2Ease of manufacture
If the shaft extender fit loosens during rotation, then manufacturing tolerances are relaxed, but the shaft extender may disengage from the input shaft
Solution Approach 1:
The retaining nut is installed beforehand to prevent the shaft extender from disengaging if the conical fit loosens during operation. This preemptive measure ensures that even if manufacturing tolerances allow for some play in the conical interface, the shaft extender remains securely retained.
Solution Approach 2:
The retention mechanism transitions from relying solely on the conical mechanical fit to using a threading mechanism (retaining nut with threads engaging the input shaft). This substitution provides additional retention security independent of the conical interface fit quality.
3Device complexity
If conventional bearing arrangements are used, then the design is simple, but high hydraulic radial loading limits pressure rise and displacement applications
Solution Approach 1:
The bearing arrangement is segmented into conventional components (bearing, shaft extender, retaining nut, end caps) that can be manufactured and assembled using standard processes. This segmentation allows the system to handle high hydraulic loads while maintaining relative simplicity in manufacturing and assembly.
Solution Approach 2:
The solution addresses the load capacity limitation by extending the shaft in the radial dimension through the shaft extender, which allows the bearing to be positioned farther from the rotor, effectively increasing the moment arm and load capacity without increasing the rotor diameter.
Data Source
AI summary
In accordance with at least one aspect of this disclosure, a pump comprises a pump rotor having a plurality of vanes therein configured to pump a fluid from a pump inlet to a pump outlet through rotation of the rotor about a rotational axis, an input shaft operatively connected to drive rotation of the rotor, and a bearing operatively connected to the input shaft configured to facilitate rotation of the input shaft. A shaft extender is operatively connected radially between the input shaft and the bearing. The input shaft includes a conical portion and the shaft extender includes a conical portion complementary to the conical portion of the input shaft. The shaft extender interfaces with at least the conical portion of the input shaft, when on the input shaft.