Closed-Circuit Swing Hydraulics for Faster Deceleration Response

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Solution Overview

Problem

In construction machines with hydraulic closed circuits, the swing deceleration responsiveness is compromised due to the pressure loss in the flushing valve, which is exacerbated by the smaller flow rate discharged from the flushing valve when driving a swing motor compared to a single rod cylinder.

Innovation Solution

The construction machine is configured with a hydraulic closed circuit system where the minimum passage area from the second flushing valve to the tank is smaller than that of the first flushing valve, allowing for a larger pressure loss and quicker switching of the flushing valve during swing deceleration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the flushing valve is designed with a larger minimum passage area to reduce pressure loss, then the pressure loss at the flushing valve is reduced, but the swing deceleration responsiveness is lowered

Engineering Contradiction:

Improvepressure loss at flushing valveVSAvoidswing deceleration responsiveness

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The patent applies different minimum passage area specifications to different flushing valves based on their specific application requirements. The first flushing valve (for cylinder closed circuit) has a larger minimum passage area to handle high flow rates, while the second flushing valve (for swing closed circuit) has a smaller minimum passage area to generate sufficient pressure loss for rapid switching and improve swing deceleration responsiveness.

Inventive Principle:

Principle #3Local quality

2Loss of time

If the flushing valve switches over quickly to connect the low pressure side to the tank, then the swing deceleration responsiveness is improved, but the pressure loss increases

Engineering Contradiction:

Improveswitching time of flushing valveVSAvoidpressure loss at flushing valve

Core Design Contradiction:

Loss of timeVSLoss of energy

Solution Approach 1:

The patent changes the key parameter of the flushing valve (minimum passage area) to achieve the desired performance. By specifying a smaller minimum passage area for the second flushing valve, the system generates sufficient pressure loss to enable rapid switching and improve swing deceleration responsiveness, accepting the trade-off of increased pressure loss as necessary for the application.

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

This configuration enhances swing deceleration responsiveness by reducing the time it takes for the pressure to reach the relief pressure, thereby improving the operability of the swing mechanism.

Implementation Method 1

allowing for a larger pressure loss and quicker switching of the flushing valve during swing deceleration

Methodology Applied

Scientific EffectPressure loss: Pressure Drop

Data Source

PatentEP3835598B1Construction machine

Publication Date: 2025.05.07 HITACHI CONSTRUCTION MACHINERY CO LTD

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AI summary

Provided is a construction machine on which a hydraulic closed circuit for driving a single rod-type hydraulic cylinder and a swing hydraulic motor is mounted and that has good swing deceleration responsiveness. In this construction machine that drives each of a single rod-type hydraulic cylinder and a swing hydraulic motor in a closed circuit, a minimum passage area from a second flushing valve to a tank in a case the second flushing valve is fully open is smaller than a minimum passage area from a first flushing valve to the tank in a case the first flushing valve is fully open.