Variable Displacement Pump-Motor Hydromechanical Control
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Solution Overview
Problem
Variable displacement pumps and motors face issues with friction and leakage losses, as well as complexity and cost due to exposure to high pressure fluids throughout the cycle, and the need for complex electrical valve control and algorithms to manage fluid flow.
Innovation Solution
A hydromechanical fluid control system using a pilot spool valve with helical coding to control main stage valves, minimizing exposure to high pressure fluid and reducing friction and leakage, while maintaining full piston stroke length and adjusting displacement efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If electrical valve control with main stage valves is used to control cylinder opening to high pressure fluid, then displacement can be adjusted, but device complexity and cost increase due to complex control logic and instrumentation
Solution Approach 1:
The patent replaces electrical valve control systems with a purely mechanical control mechanism. A pilot spool valve with helical grooves mechanically controls the timing and duration of main stage valve openings through rotational movement, eliminating the need for electrical actuators, control algorithms, and associated instrumentation while maintaining variable displacement capability
Solution Approach 2:
The pilot spool valve automatically controls the main stage valves through its own rotational position and helical groove geometry. The system self-regulates the timing and duration of high pressure fluid admission to each cylinder based on the spool's rotational angle, without requiring external electrical control signals or complex control logic
2Productivity
If pistons are exposed to high pressure fluid throughout the pumping stroke, then fluid flow is maintained, but friction and leakage losses increase even at low displacements
Solution Approach 1:
The main stage valves open and close periodically based on the rotational position of the pilot spool valve, creating discrete intervals of high pressure fluid admission to each cylinder. This periodic action allows the pistons to be exposed to high pressure fluid only during the necessary portion of their stroke, reducing friction and leakage losses while maintaining fluid flow productivity
Solution Approach 2:
The duration and timing of high pressure fluid exposure to each piston is dynamically adjusted by rotating the pilot spool valve to different angular positions. This dynamic control allows optimization of the balance between maintaining sufficient fluid flow and minimizing energy losses from friction and leakage
3Adaptability or versatility
If the duration of cylinder opening to high pressure fluid is increased, then displacement increases, but friction and leakage losses increase
Solution Approach 1:
The system uses periodic opening and closing of main stage valves controlled by the rotating pilot spool to achieve variable displacement. By adjusting the rotational position of the spool, the duration of each valve opening event is varied, allowing displacement control without continuously prolonged exposure to high pressure fluid, thereby limiting friction and leakage losses
Data Source
AI summary
A variable displacement pump-motor includes a pump-motor having a plurality of cylinders and pistons, and further including a main shaft rotatable relative to the system body. A hydro mechanical control system includes a plurality of main stage valves in communication with the plurality of cylinders. Each of the main stage valves is configured to open and close a cylinder of the plurality of cylinders to one or more of high or low pressure fluid sources. A pilot spool valve is in selective communication with each of the main stage valves. The pilot spool rotates with the main shaft. The pilot spool includes coding configured to operate each of the main stage valves to open and close the respective cylinders to the one or more high and low pressure fluid sources according to a translational position of the pilot spool and rotation of the pilot spool by the main shaft.