Displacement Control Valve for Meterless Hydraulic System Stability
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Solution Overview
Problem
Conventional hydraulic systems face inefficiencies due to fluid restriction for speed control, and meterless systems suffer from instabilities, pump overspeeding, and pressure spikes during transitional operations.
Innovation Solution
A hydraulic system incorporating a displacement control valve with a movable cage portion to selectively restrict fluid flow through actuator passages, a regeneration valve for pump overspeed prevention, and load-holding valves for pressure management, enhancing efficiency and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fluid restriction is used to control actuator speed, then actuator speed can be independently controlled, but flow losses increase and overall hydraulic system efficiency decreases
Solution Approach 1:
The invention extracts the speed control function from the actuator circuit and relocates it to the pump displacement control. By controlling the pump's displacement, the system determines actuator speed without restricting fluid flow in the actuator line, thereby eliminating the energy losses associated with throttling while maintaining independent speed control capability.
Solution Approach 2:
The system employs feedback mechanisms where the actuator's position or speed information is used to adjust pump displacement dynamically. This closed-loop control ensures that the pump delivers exactly the flow needed for desired actuator speed, preventing both excessive flow (energy waste) and insufficient flow (performance degradation).
2Loss of energy
If meterless hydraulic system operates in transitional modes, then efficiency is improved, but instabilities and pressure spikes occur
Solution Approach 1:
The invention incorporates cushioning elements and controlled compression chambers that anticipate and dampen pressure spikes before they propagate through the system. During transitional operations, these pre-positioned cushioning mechanisms absorb pressure transients and stabilize flow, allowing the meterless system to maintain high efficiency without suffering from instability or damaging pressure spikes.
Solution Approach 2:
The system introduces intermediary components such as accumulators, compliance chambers, or damping valves that act as buffers between the pump and actuator during transitional modes. These intermediaries smooth out pressure fluctuations and provide hydraulic cushioning, enabling the system to operate efficiently in transitional states without experiencing instabilities.
Data Source
AI summary
A hydraulic system is disclosed. The hydraulic system may have a pump, a tank, a displacement actuator having first and second chambers, a regeneration valve, and a load-holding valve. The hydraulic system may also have a displacement control valve including a valve element, and a stationary cage portion at least partially forming a high-pressure passage fluidly connecting the pump and valve element, a low-pressure passage fluidly connecting the valve element and tank, a first displacement actuator passage fluidly connecting the valve element and first chamber, a second displacement actuator passage fluidly connecting the valve element and second chamber, a load-holding control passage fluidly connecting the valve element and load-holding valve, and a regeneration control passage fluidly connecting the valve element and regeneration valve. The displacement control valve may also include a movable cage portion that is movable to selectively restrict fluid flow through only the first and second displacement actuator passages.