Work Machine Hydraulic Valve Circuit for Load Pressure Retention

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Solution Overview

Problem

The existing hydraulic systems for work machines face inefficiencies in load pressure management, leading to excessive return of operation fluids and reduced load pressures in transmission fluid tubes, which affects the overall performance and operability of the machines.

Innovation Solution

The hydraulic system incorporates a first switch valve with a confluent and isolation position to connect and disconnect operation fluid and transmission fluid tubes, utilizing a first return circuit at the isolation position and a second return circuit at both positions to control fluid return and maintain increased load pressures by ensuring only necessary fluid return to the tank.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If the first transmission fluid tube and second transmission fluid tube are connected at the confluent position, then the hydraulic system can operate the operation device with unified pressure control, but excessive fluid return occurs reducing the load pressure

Engineering Contradiction:
Improveoperability of hydraulic systemVSAvoidload pressure in transmission fluid tube
Core Design Contradiction:
Ease of operationVSStress or pressure

Solution Approach 1:

The first return circuit is dynamically connected or disconnected based on the position of the first switch valve. When the first switch valve is at the isolation position, the first return circuit is connected to return fluid from the first transmission fluid tube. When the first switch valve is at the confluent position, the first return circuit is disconnected to prevent excessive fluid return and maintain load pressure in the connected transmission fluid tubes.

Inventive Principle:
Principle #15Dynamics

2Adaptability or versatility

If the first switch valve is at the isolation position to operate travel device separately, then the travel device can be controlled independently, but the first transmission fluid tube requires separate fluid return path

Engineering Contradiction:
Improveindependent control capabilityVSAvoidfluid return circuit configuration
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The first return circuit serves multiple functions: it returns fluid from the first transmission fluid tube when the first switch valve is at the isolation position (independent travel device operation), and it disconnects when the first switch valve is at the confluent position to prevent excessive fluid return. This multi-functional design allows the system to adapt to different operational modes without requiring entirely separate return circuits for each mode.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 configuration prevents excessive fluid return, thereby increasing load pressures in the transmission fluid tubes, enhancing the flow rate control and operability of the hydraulic system, particularly when the first transmission fluid tube is connected to the second transmission fluid tube.

Implementation Method 1

a first return circuit configured to be connected to the first transmission fluid tube and to return the operation fluid in the first transmission fluid tube to the tank at the isolation position

Methodology Applied
Scientific EffectHydraulic pressure differential: Pressure Gradient

Data Source

PatentEP3225752B1Hydraulic system for work machine
Publication Date: 2021.11.03 KUBOTA CORP
  • EP3225752B1 patent drawingFigure 1
  • EP3225752B1 patent drawingFigure 2
  • EP3225752B1 patent drawingFigure 3

AI summary

A hydraulic system for a work machine includes a first switch valve and a first return circuit. The first switch valve has a confluent position to connect a first operation fluid tube to a second operation fluid tube and to connect a first transmission fluid tube to a second transmission fluid tube and an isolation position to release the connection between the first operation fluid tube and the second operation fluid tube and to release the connection between the first operation fluid tube and the second operation fluid tube, the first switch valve being configured to be switched to the confluent position and to the isolation position.