Hydraulic Circuit Isolation for Precise Construction Machine Control

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Solution Overview

Problem

Hydraulic systems in work machines like excavators face interference and reduced motion accuracy due to pressure and restriction differences in hydraulic circuits, especially during operations requiring high precision like grading.

Innovation Solution

A controller for the hydraulic system that independently controls first and second actuators using separate pumps, and adjusts valve settings to reallocate fluid flow, isolating actuators from cross-pump control during precision operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple pumps are used to control multiple actuators through shared hydraulic circuits, then the hydraulic system can operate concurrently and independently for different functions, but pressure and restriction differences cause interference that reduces motion accuracy

Engineering Contradiction:
Improveconcurrent independent operationVSAvoidmotion accuracy
Core Design Contradiction:
Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The hydraulic system is segmented into primary and secondary circuits for each actuator, with each circuit controlled by a dedicated pump during precision operations. This segmentation isolates the hydraulic circuits to eliminate cross-talk and interference between actuators, thereby maintaining motion accuracy while preserving the ability to operate functions independently when needed.

Inventive Principle:
Principle #1Segmentation

2Device complexity

If a single pump controls multiple actuators through shared hydraulic circuits, then the system structure is simpler, but the velocities of hydraulic circuits become imbalanced resulting in reduced motion accuracy

Engineering Contradiction:
Improvesystem structureVSAvoidmotion accuracy
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The system dynamically reconfigures the hydraulic circuit architecture based on operational requirements. During precision operations, the controller activates a second pump and closes valves to create independent primary circuits for each actuator. During non-critical operations, the system reverts to a simpler configuration with fewer active components, thus balancing structural simplicity with motion accuracy requirements.

Inventive Principle:
Principle #15Dynamics

3Ease of operation

If hydraulic circuits share common pump control, then the system is easier to operate, but cross-talk between circuits causes deviation from desired fluid flow and reduces precision

Engineering Contradiction:
Improvesystem controlVSAvoidfluid flow precision
Core Design Contradiction:
Ease of operationVSMeasurement precision

Solution Approach 1:

Electronically controllable valves serve as intermediaries between the pumps and hydraulic circuits. These valves are controlled by a controller that monitors operational requirements and activates/deactivates specific circuits as needed. This intermediary layer allows the system to maintain ease of operation through centralized control while achieving fluid flow precision by isolating circuits when high accuracy is required.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

Improves motion accuracy and precision of hydraulic actuators by minimizing cross-talk between hydraulic circuits, enabling high-precision operations such as grading with reduced fluid flow deviations.

Implementation Method 1

a first pump to cause fluid to flow through the first primary hydraulic circuit and the second secondary hydraulic circuit

Methodology Applied
Scientific EffectHydraulic fluid flow: Hydraulic Press

Implementation Method 2

a second pump to cause fluid to flow through the second primary hydraulic circuit and the first secondary hydraulic circuit

Methodology Applied
Scientific EffectHydraulic fluid flow: Hydraulic Press

Implementation Method 3

closing of a first valve that controls fluid flow through the first secondary hydraulic circuit

Methodology Applied
Scientific EffectFluid flow control: Valve

Implementation Method 4

closing of a second valve that controls fluid flow through the second secondary hydraulic circuit

Methodology Applied
Scientific EffectFluid flow control: Valve

Data Source

PatentEP4381141B1Control of a hydraulic system of a construction machine
Publication Date: 2025.05.07 CATERPILLAR INC
  • EP4381141B1 patent drawingFigure 1
  • EP4381141B1 patent drawingFigure 2
  • EP4381141B1 patent drawingFigure 3

AI summary

A hydraulic system may include a first actuator to control a first linkage member, a second actuator to control a second linkage member, a first primary hydraulic circuit and a first secondary hydraulic circuit that include the first actuator, a second primary hydraulic circuit and a second secondary hydraulic circuit that include the second actuator, a first pump to cause fluid to flow through the first primary hydraulic circuit and the second secondary hydraulic circuit, a second pump to cause fluid to flow through the second primary hydraulic circuit and the first secondary hydraulic circuit, and a controller. The controller may be configured to determine that an operator assistance mode is enabled, and cause closing of a first valve that controls fluid flow through the first secondary hydraulic circuit and a second valve that controls fluid flow through the second secondary hydraulic circuit.