LS Control Arrangement for Hydraulic Oscillation
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Solution Overview
Problem
Existing LS control arrangements for hydraulic consumers, particularly those used in mobile work equipment, tend to oscillate due to the dependency of the lowering brake valve on inlet pressure, leading to fluctuations that affect the pressure compensator and variable displacement pump, making them susceptible to vibration.
Innovation Solution
An LS control arrangement with a simplified structure that integrates a pressure divider between a throttle sequence on the inlet and outlet sides, allowing the load-sensing chamber to be connected via axial and radial bores, eliminating the need for separate signaling channels for each valve slide direction, thereby preventing undesired closing of the pressure compensator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lowering brake valve controlled by inlet pressure is used to control hydraulic consumers, then the lowering function is achieved, but the system becomes susceptible to oscillation and vibration
Solution Approach 1:
A pressure divider with constant and variable nozzles is introduced as an intermediary device between the inlet and the pressure compensator. This mediator transforms the inlet pressure signal into a stabilized reporting pressure that acts on the pressure compensator, preventing direct coupling between the lowering brake valve and the pressure compensator that causes oscillation.
Solution Approach 2:
The pressure divider creates a feedback mechanism where the reporting pressure is continuously adjusted based on the inlet pressure and load conditions. The variable nozzle modifies the feedback signal to maintain stable operation of the pressure compensator during lowering operations, preventing oscillatory behavior.
2Manufacturing precision
If separate signaling channels are provided for each valve slide direction, then precise pressure control is achieved, but the manufacturing complexity increases
Solution Approach 1:
The pressure divider is designed as a universal component that handles both lifting and lowering operations through a single integrated structure. The constant and variable nozzles work together in one device to provide the necessary pressure signaling for both valve slide directions, eliminating the need for separate signaling channels.
Solution Approach 2:
Multiple pressure signaling functions are merged into a single pressure divider component. The device combines the functions of pressure sensing, signal modulation, and directional control in one integrated structure, simplifying the overall valve design while maintaining precise pressure control.
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 the tendency for oscillation when lowering a load by maintaining a constant pressure drop across the inflow measuring orifice, simplifying the manufacturing of the directional control valve, and ensuring stable operation by regulating the signaling pressure acting on the pressure compensator.
Implementation Method 1
the pressure compensator, which is acted upon in the opening direction by the force of a spring and a pressure corresponding to the load pressure downstream of the inflow measuring orifice and in the closing direction by the pressure upstream of the inflow measuring orifice
Implementation Method 2
A variable displacement pump (24) supplies pressure medium to a pressure line (22). An inflow measuring orifice (27) is arranged in an inlet channel (27) of a directional control valve (16), via which a hydraulic consumer is supplied with pressure medium
Implementation Method 3
a lowering brake valve is often assigned to it on the outflow side. Such a lowering brake valve is in principle a check valve that can be unlocked by the pressure in the inlet and allows controlled lowering when the load is pressing
Data Source
Figure 1
Figure 2
Figure 3A1~3A3
AI summary
An LS control arrangement is disclosed, having an inlet metering orifice and a pressure regulator (18), via which the pressure drop can be maintained constant across the inlet metering orifice. The reporting pressure acting on the pressure regulator (18) in the opening direction can be varied as a function of the lift in order to avoid any oscillation of the system in case of a negative load.