Hydrostatic Shaft Bearing in Gear Pumps With Isolated Case Drain
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Solution Overview
Problem
Gear pumps face challenges in operating at zero discharge flow with high pressure, leading to high shaft bearing loads at low speeds, which traditional journal bearings cannot adequately support, and roller element bearings are costly and heavy.
Innovation Solution
A gear pump configuration with hydrostatic bearings that utilize high-pressure leakage fluid to support the pump shaft via a hydrostatic bearing, with the leakage fluid directed to an isolated case drain to cool the internal components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional journal bearings are used to support the pump shaft at low speeds, then the bearing structure is simple, but the bearing cannot adequately support high shaft bearing loads
Solution Approach 1:
The patent applies hydraulics by using high-pressure leakage fluid to create a hydrostatic bearing that supports the pump shaft. The leakage fluid from the gear pump is directed to a bearing surface, where it generates hydrostatic pressure to support the shaft load, enabling reliable operation at low speeds where traditional journal bearings fail.
2Force
If roller element bearings are used to support the pump shaft at low speeds, then the bearing can support high loads, but the bearing becomes costly and heavy
Solution Approach 1:
The patent replaces heavy roller element bearings with a hydrostatic bearing that uses leakage fluid to generate supporting pressure. This hydraulic approach eliminates the need for heavy rolling elements while maintaining the capability to support high shaft loads at low speeds.
Solution Approach 2:
The patent uses a simple hydrostatic bearing structure that is less expensive than roller element bearings. The bearing relies on fluid pressure rather than complex mechanical rolling elements, reducing both cost and weight while achieving the required load support capability.
3Force
If leakage fluid is used to support the pump shaft, then the shaft bearing load is reduced, but the leakage fluid must be drained to prevent recirculation and maintain high pressure
Solution Approach 1:
The patent extracts the leakage fluid from the gear pump and directs it to the hydrostatic bearing through a dedicated passage. The fluid is then drained through a separate case drain that is isolated from the inlet chamber, preventing recirculation and maintaining the high pressure needed for both pumping and bearing support functions.
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 solution provides effective, low-cost, and weight-efficient support for the pump shaft at low speeds, enhancing efficiency and cooling while preventing recirculation of leakage fluid, thus maintaining high pressure and reducing power loss.
Implementation Method 1
fluid in the pocket to apply a supporting force to the pump shaft
Implementation Method 2
cool the internal components of the pump
Data Source
AI summary
An example gear pump includes a pump ring gear; a pump shaft; a pump pinion mounted to the pump shaft and disposed within the pump ring gear, such that external teeth of the pump pinion engage with internal teeth of the pump ring gear, wherein the pump shaft is configured to rotate the pump pinion, thereby rotating the pump ring gear engaged therewith to displace fluid from an inlet chamber to an outlet chamber; one or more cross-holes; a bushing disposed about the pump shaft; and a pocket formed about a portion of the bushing, wherein the one or more cross-holes fluidly couple the outlet chamber to the pocket, thereby causing fluid in the pocket to apply a supporting force to the pump shaft.