Electro-Hydraulic Drive Architecture for Closed-Open Circuit Switching
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Solution Overview
Problem
Conventional hydraulic systems for work machines, such as excavators and wheel loaders, suffer from inefficiencies due to large power losses through throttling and the provision of constant fluid flow regardless of actuator usage, leading to poor efficiency and increased energy consumption.
Innovation Solution
A dual architecture electro-hydraulic drive system that dynamically switches between closed-circuit and open-circuit modes of operation, utilizing electric motor-driven hydrostatic pumps and a valve assembly to optimize fluid flow and eliminate the need for a separate boost pump, enabling on-demand energy use and flow sharing between actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hydraulic pump provides constant fluid flow to actuators, then the actuators can operate reliably, but the system experiences poor efficiency and high energy consumption
Solution Approach 1:
The patent implements a variable displacement pump that dynamically adjusts its fluid flow output based on the actual demand of hydraulic actuators. The pump's displacement is varied in response to feedback from the hydraulic system, allowing the system to provide reliable actuator operation while consuming only the energy actually needed, eliminating the waste associated with constant flow provision.
2Ease of operation
If conventional valves are used to control fluid flow to actuators, then the actuators can be precisely controlled, but large power losses occur due to throttling
Solution Approach 1:
The patent replaces conventional mechanical throttling valves with an electro-hydraulic control system. This substitution uses electronic control signals to regulate pump displacement and fluid flow, eliminating the need for mechanical throttling that causes power losses. The electro-hydraulic system maintains precise actuator control while significantly reducing energy dissipation.
3Productivity
If a separate boost pump is added to the hydraulic system, then excess flow capacity and system performance are improved, but device complexity and component size increase
Solution Approach 1:
The patent makes the main hydraulic pump multi-functional by enabling it to operate in both constant displacement mode for providing excess flow capacity and variable displacement mode for precise flow control. This eliminates the need for a separate boost pump, as the single pump can adapt its output to meet all system demands, thereby reducing component count and system complexity while maintaining productivity.
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 approach enhances efficiency by reducing excess flow capacity and component size, lowering energy consumption, and allowing for hydraulic-to-electric energy recovery, thereby reducing the size of hybrid engines and battery costs while maintaining system performance.
Implementation Method 1
a pump configured to be a fluid flow source driven by an electric motor to provide fluid flow to the hydraulic actuator
Implementation Method 2
a valve assembly configured to operate in a plurality of states comprising at least: (a) a first state in which the valve assembly blocks flow path between the inlet port of the pump and the reservoir, thereby allowing the pump to operate in a closed-circuit configuration
Data Source
AI summary
An example hydraulic system includes a hydraulic actuator; a pump driven by an electric motor and having an inlet port and an outlet port; a boost flow line configured to provide boost fluid flow or receive excess fluid flow; a reservoir fluid line fluidly coupled to a reservoir; and a valve assembly configured to operate in a plurality of states to allow the pump to operate in a closed-circuit configuration in which fluid discharged from the hydraulic actuator is provided to the inlet port of the pump or an open-circuit configuration in which fluid discharged from the hydraulic actuator is provided to the reservoir.