Parallel Pilot Valves With Different Overlaps for Disturbance Robustness

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Solution Overview

Problem

Existing hydraulic systems with pilot-operated pressure control valves exhibit low robustness against disturbances such as contamination, jamming, vibrations, and changes in friction coefficients, leading to undesirable disruptions in hydraulic function.

Innovation Solution

A hydraulic system with at least two pilot-operated pressure control valves connected in parallel, featuring different valve overlaps and configurations to enhance robustness, allowing one valve to compensate for the failure of the other, ensuring continuous operation even if one valve becomes stuck.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If pressure control valves with identical characteristics are used, then manufacturing complexity is reduced, but robustness against disturbances deteriorates

Engineering Contradiction:
Improvemanufacturing simplicityVSAvoidrobustness against disturbances
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies local quality by assigning different valve overlaps to different pressure control valves. Specifically, the first pressure control valve has a first valve overlap while the second pressure control valve has a second valve overlap that differs from the first. This creates local differentiation in the redundant valves, making them respond differently to disturbances and reducing the likelihood that both valves will fail simultaneously due to the same disturbance.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent implements parameter changes by varying the valve overlap parameter between different pressure control valves. The first valve overlap and second valve overlap are deliberately made different, which changes the flow characteristics and response behavior of each valve. This parameter differentiation enhances robustness against disturbances while maintaining relatively simple manufacturing processes.

Inventive Principle:
Principle #35Parameter changes

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

The system achieves high robustness against disturbances and operational costs, allowing one to maintain continuous operation even if one valve becomes stuck, the other pressure control valves can still fulfill most of the functional requirements of the hydraulic system.

Implementation Method 1

Each pressure control valve has at least one valve spool, which is guided longitudinally within valve bodies... A high-pressure line is connected to the high-pressure valve pockets, a working-pressure line to the working-pressure valve pockets, and a low-pressure line to the low-pressure valve pockets of the pressure control valves

Methodology Applied
Scientific EffectHydraulic pressure: Pressure Gradient

Data Source

PatentEP4448988B1Hydraulic system with at least two pressure-regulating pilot valves
Publication Date: 2025.12.17 ZF FRIEDRICHSHAFEN AG
  • EP4448988B1 patent drawingFigure 1
  • EP4448988B1 patent drawingFigure 2
  • EP4448988B1 patent drawing

AI summary

The invention relates to a hydraulic system (1) with at least two pressure-regulating pilot valves (2, 3) in a parallel circuit in order to set a working pressure (p_A). Each of the pressure-regulating valves (2, 3) has a valve slide (2A, 3A), each of which is guided in valve housings (2B, 3B) in a longitudinally movable manner. A high-pressure line (5) is connected to a respective high-pressure valve pocket (2B1, 3B1), a working pressure line (4) is connected to a respective working-pressure valve pocket (2B2, 3B2), and a low-pressure line (6) is connected to a respective low-pressure valve pocket (2B3, 3B3) of the pressure-regulating valves (2, 3). The pressure-regulating valves (2, 3) are designed with different valve laps (Udk2, Udk3).