Nested Servo Valve Control for High-Flow Precision Positioning

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Solution Overview

Problem

Current servo valves for high volume flow requirements are complex and require precise position control, which is effort-intensive and prone to wear, making them less efficient and reliable.

Innovation Solution

A self-regulating servo valve design featuring a controller housing, pilot stage with a proportional magnet and damping spring, and a main stage with a spring-mounted main control piston, where the pilot piston is slidably mounted within the main control piston, and includes axial fluid passages and grooves for precise control, minimizing flow force influence on the main control piston.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional servo valves are used for high volume flow requirements, then position control precision can be achieved, but the system complexity and component wear increase significantly

Engineering Contradiction:
Improveposition control precisionVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements a nested structure where the pilot control piston is positioned inside the main control piston, and the main control piston is positioned inside the bushing. This nested arrangement allows multiple control functions to be integrated in a compact configuration, reducing overall system complexity while maintaining precise position control through the hierarchical control mechanism.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The servo valve is divided into distinct functional segments: the pilot stage with the pilot control piston, the main stage with the main control piston, and the bushing. Each segment performs a specific function in the control hierarchy, allowing the system to achieve precise control through distributed functionality rather than requiring a single complex component.

Inventive Principle:
Principle #1Segmentation

2Measurement precision

If conventional servo valves are used for high volume flow requirements, then position control precision can be achieved, but the system requires greater effort and wear-prone components

Engineering Contradiction:
Improveposition control precisionVSAvoidcomponent wear
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The spring-mounted main control piston and pilot control piston create a self-regulating mechanism that automatically adjusts to flow conditions. The springs provide continuous contact force to maintain play-free operation between the nested pistons, eliminating the need for external adjustment mechanisms and reducing wear through consistent self-lubrication and pressure distribution.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The damping spring mounted on the pilot control piston and the spring mounted on the main control piston provide cushioning forces that prevent impact loads and reduce wear during operation. These springs absorb shocks and maintain smooth operation of the nested pistons, extending component life while maintaining precision control.

Inventive Principle:
Principle #11Beforehand cushioning (Prior cushioning)

3Device complexity

If a compact design is implemented, then the system becomes simpler, but achieving precise position control with high volume flow becomes more difficult

Engineering Contradiction:
Improvesystem simplicityVSAvoidposition control precision
Core Design Contradiction:
Device complexityVSMeasurement precision

Solution Approach 1:

The nested arrangement of the pilot control piston inside the main control piston inside the bushing achieves compactness while maintaining precise control. The hierarchical control mechanism allows the smaller pilot piston to control the position of the larger main piston, enabling high-volume flow control in a compact configuration without sacrificing precision.

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent utilizes the axial dimension within the nested structure to accommodate multiple control functions. The axial fluid passages and grooves are arranged along the axial direction, allowing complex fluid control paths to be implemented within the compact radial space of the nested pistons, maintaining precision control without increasing overall system size.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 design enables precise position control with reduced complexity and wear, allowing for efficient high volume flow management with low drive power and minimal influence from flow forces, resulting in a compact and simplified system.

Implementation Method 1

position control of the main control piston is already achieved by the pilot control piston... The pilot stage comprising a proportional magnet and a pilot piston mounted on a damping spring

Methodology Applied
Scientific EffectMagnetic force: Lorentz Force

Implementation Method 2

pilot piston mounted on a damping spring

Methodology Applied
Scientific EffectDamping: Damping

Implementation Method 3

a play-free spring being provided between the pilot piston and the main control piston

Methodology Applied
Scientific EffectSpring force: Spring

Implementation Method 4

main stage comprising a main control piston mounted on a spring... at least one axial fluid passage with at least three inlets spaced axially from one another

Methodology Applied
Scientific EffectHydraulic pressure: Pressure Gradient

Data Source

PatentEP3207436B1Self-controlling servo valve
Publication Date: 2021.05.05 LIEBHERR MACHINES BULLE
  • EP3207436B1 patent drawingFigure 1
  • EP3207436B1 patent drawingFigure 2
  • EP3207436B1 patent drawingFigure 3

AI summary

The invention relates to a self-controlling servo valve, comprising a controller housing, a pilot control stage, a main stage, and a sleeve, wherein the pilot control stage comprises a proportional magnet and a pilot control piston, which is supported on a damping spring, wherein the main stage comprises a main control piston supported on a spring, wherein the main control piston is supported in a sildeable manner within the sleeve and the pilot control piston is supported in a slideable manner within the main control piston, wherein a play-free spring is provided between the pilot control piston and the main control piston, and wherein the pilot control piston comprises at least one axial fluid feed-through having at least three feeds axially spaced apart from each other. The invention further relates to a device, in particular a hydraulic device, comprising a corresponding servo valve.