Directional Valve Damping for Hydraulic Torsional Oscillation Control
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Solution Overview
Problem
Conventional load-sensing directional valves in oscillation-prone applications, such as mobile machinery, face challenges with significant and difficult-to-contain torsional oscillations due to sudden opening, leading to unintended pressure losses and instability, as existing damping methods either reduce volume flow or require additional costly valves.
Innovation Solution
The valve design connects the supply pressure at the pressure supply connector to a control channel via an orifice plate, which is then connected to the return flow connection, using the swivel angle pump's load-sensing pressure to control the pressure compensator, and includes a bypass connection to increase pressure upstream of the return flow orifice, preventing overshooting without withdrawing volume flow from the load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional load-sensing directional valves are used in oscillation-prone applications, then the valve can control hydraulic motors for slewing gears, but sudden opening of the control slide causes significant torsional oscillations and system instability
Solution Approach 1:
A damping system is introduced as an intermediary element between the control slide and the hydraulic circuit. This damping system includes a damping orifice that mediates the fluid flow, preventing sudden pressure changes and oscillations while maintaining the valve's primary control function. The damping orifice acts as a buffer that smooths out rapid fluctuations in the hydraulic system.
Solution Approach 2:
The damping system is designed to provide beforehand cushioning by pre-establishing a controlled resistance to fluid flow through the damping orifice. This cushioning effect is always present in the system, preparing it to absorb and dampen oscillations before they can develop into significant torsional vibrations, thereby maintaining system stability.
2Reliability
If lowering brake check valves are installed in the return line to ensure constant volume flow, then return line flow stability is improved, but the degree of dampening of the PT2-element is not changed and extra expenses are incurred
Solution Approach 1:
The damping function is merged with the existing directional valve structure by integrating a damping orifice into the valve body or control slide assembly. This combines the flow control function with the damping function in a single component, eliminating the need for separate lowering brake check valves while achieving both return line stability and oscillation dampening.
Solution Approach 2:
The damping orifice serves multiple functions simultaneously: it provides damping for the PT2-element, stabilizes return line flow, and prevents torsional oscillations. This multi-functionality replaces the need for multiple specialized valves, reducing device complexity while maintaining comprehensive system control.
3Reliability
If load-feedback connections are used to reduce load pressure to control the opposite end face of the control slide, then damping is achieved, but volume flow is withdrawn from the load-sensing signal reducing control precision
Solution Approach 1:
The hydraulic circuit is segmented into separate functional paths: one path handles the load-sensing signal for precise speed control, while another path through the damping orifice provides damping without interfering with the load-sensing signal. This segmentation allows both damping and precise speed control to operate independently without compromising either function.
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 effectively dampens oscillations in hydraulic systems, allowing for precise speed control and accurate position sensing of the control slide, reducing overshooting and maintaining system stability without affecting the pressure compensator, and is applicable to both load-sensing and throttle valves.
Implementation Method 1
the supply pressure at the pressure supply connector is connected to control a user that is connected to the respective service connection of the valve via an orifice plate to a control channel
Implementation Method 2
The valve design connects the supply pressure at the pressure supply connector to a control channel via an orifice plate, which is then connected to the return flow connection, using the swivel angle pump's load-sensing pressure to control the pressure compensator
Data Source
AI summary
A valve includes a valve housing (33), which has at least one service connection (A, B), a pressure supply connection (P) and a return connection (T). In the valve housing (33), a control slide (STS) is guided so as to be movable longitudinally to control these individual connections. The supply pressure, which is applied to the pressure connection (P) to control a consumer (10, 12), connected to the service connection (A; B), is guided across at least one control side (56) of the control slide (STS) via an orifice plate (54) and a control channel (50). The control side (56) is positioned in a control chamber (58) in the valve housing (33) such that it can move. The control chamber (58) is connected to the return connection (T) via an additional orifice plate (59).