Hydraulic Flow Management System for Electro-Hydrostatic Actuation
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Solution Overview
Problem
Existing hydraulic systems using electro-hydrostatic actuation with unbalanced cylinders face challenges in maintaining elevated inlet pressure, leading to cavitation and pitting, and require large, heavy accumulators that incur maintenance and leakage issues, while also wasting energy due to inefficient flow management and cooling systems.
Innovation Solution
A flow management system that uses a single electric motor-driven boost pump to maintain constant elevated pressure in the hydraulic fluid supply, eliminating the need for accumulators and optimizing fluid flow by recirculating hydraulic fluid for cooling and energy recovery, with a controller managing the boost pump to anticipate pressure demands and minimize energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pressurized accumulator is installed in the closed hydraulic circuit to maintain elevated inlet pressure, then cavitation and pitting are prevented, but the physical size and weight of the system increase undesirably
Solution Approach 1:
The patent removes the accumulator from the hydraulic circuit and replaces it with a tank open to the atmosphere. The boost pump directly supplies pressurized hydraulic fluid to the actuation system pump inlet, eliminating the need for an accumulator while maintaining elevated inlet pressure to prevent cavitation and pitting.
Solution Approach 2:
The patent introduces a boost pump as an intermediary device between the atmospheric tank and the actuation system pump. This boost pump generates the required elevated inlet pressure dynamically, replacing the static pressure storage function of the accumulator and enabling compact system design without compromising reliability.
2Stability of the object's composition
If a large volume of hydraulic fluid is stored in the accumulator to compensate for thermal expansion and leakage, then system pressure is maintained, but the accumulator size and weight increase
Solution Approach 1:
The patent replaces the static pressure storage of the accumulator with a dynamic pressure generation system. The boost pump continuously or intermittently supplies pressurized fluid to the actuation system, adapting to changing pressure demands without requiring large fluid storage volumes. This dynamic approach maintains pressure stability while minimizing system volume.
Solution Approach 2:
The boost pump operates to continuously maintain elevated inlet pressure in the hydraulic circuit, ensuring stable operation of the actuation system. By providing continuous pressurization rather than relying on pre-stored fluid volume, the system achieves pressure stability with minimal accumulator size or alternative volume.
3Temperature
If the hydraulic system uses a traditional cooling system with separate components, then cooling function is provided, but system complexity and energy loss increase
Solution Approach 1:
The patent merges the cooling function with the existing hydraulic circuit by routing hydraulic fluid through the electric motor housing that serves as a heat exchanger. The hydraulic fluid absorbs heat from the motor during operation, providing cooling without requiring separate cooling components. This integration reduces system complexity while maintaining effective temperature control.
Solution Approach 2:
The electric motor housing serves dual functions: as the motor housing itself and as a heat exchanger for cooling the hydraulic fluid. The system uses its own operational heat generation to provide cooling, eliminating the need for external cooling systems and reducing overall system complexity and energy loss.
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
This solution reduces cavitation and pitting, minimizes system size and weight, eliminates maintenance issues related to accumulators, and recovers energy that would otherwise be wasted, while providing efficient cooling and fluid management for hydraulic systems.
Implementation Method 1
maintain a constant elevated pressure in the hydraulic fluid supply... hydraulic fluid is exposed to sharp and rapid pressure drops resulting from the demands of highly responsive actuators
Implementation Method 2
The boost pump also can be operated to circulate hydraulic fluid through at least a part of the electric drive system for cooling purposes
Implementation Method 3
or to direct fluid flow through the boost pump to drive an electric motor for energy recovery purposes
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
A flow management system (270) capable of providing adjustable hydraulic fluid flow or pressure at a common line to supply bidirectional pumps in electro-hydrostatic actuation systems and conditioning re-circulated hydraulic fluid. The system enables flow sharing between multiple actuation systems (271,272) and minimization of energy consumption by a power- on-demand approach and/or electrical energy regeneration while eliminating the need for an accumulator. The system has particular application to electro-hydrostatic actuation systems that typically include bi-directional electric motor driven pumps (276) and unbalanced hydraulic actuators (225,227) connected within closed circuits to provide work output against external loads and reversely recover energy from externally applied loads.