Excavator Control Valve Layout for Faster Bleed-Off Response

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Solution Overview

Problem

The responsiveness of hydraulic circuits in bleed-off control is decreased when bleed-off valves are positioned further downstream of directional control valves in center bypass oil passages, leading to increased load on hydraulic pumps and reduced pressure reduction efficiency.

Innovation Solution

The control valve device places bleed-off valves upstream of directional control valves in the center bypass oil passages, allowing for immediate pressure reduction by minimizing the influence of residual pressures from directional control valves, and maintains the center bypass oil passage open regardless of spool positions to ensure consistent hydraulic oil supply to multiple directional control valves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If bleed-off valves are positioned downstream of directional control valves in center bypass oil passages, then pressure loss in center bypass oil passages is reduced, but responsiveness of bleed-off control decreases

Engineering Contradiction:

Improvepressure lossVSAvoidresponsiveness of bleed-off control

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The patent inverts the conventional arrangement by positioning bleed-off valves upstream of directional control valves instead of downstream. This reversal allows the bleed-off valves to directly reduce pressure in the center bypass oil passage before the hydraulic oil reaches the directional control valves, eliminating the delay caused by residual pressures and immediately reducing the load on the hydraulic pump.

Inventive Principle:

Principle #13The other way round (Inversion)

2Loss of energy

If bleed-off valves are positioned downstream of directional control valves, then pressure loss is reduced, but load on hydraulic pump increases due to residual pressures

Engineering Contradiction:

Improvepressure lossVSAvoidload on hydraulic pump

Core Design Contradiction:

Loss of energyVSPower

Solution Approach 1:

By reversing the position of bleed-off valves to be upstream of directional control valves, the system eliminates residual pressures that would otherwise cause the hydraulic pump to work harder. The bleed-off valves directly reduce pressure in the center bypass oil passage, preventing the accumulation of residual pressures that increase pump load.

Inventive Principle:

Principle #13The other way round (Inversion)

3Loss of energy

If bleed-off valves are positioned downstream of directional control valves, then pressure loss in center bypass oil passages is reduced, but pressure reduction efficiency decreases

Engineering Contradiction:

Improvepressure lossVSAvoidpressure reduction efficiency

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The inverted positioning of bleed-off valves upstream of directional control valves enables direct and immediate pressure reduction in the center bypass oil passage. This eliminates the intermediate step where residual pressures would otherwise persist, thereby improving pressure reduction efficiency while maintaining reduced pressure loss.

Inventive Principle:

Principle #13The other way round (Inversion)

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 the responsiveness of bleed-off control by reducing the impact of residual pressures from directional control valves, enabling swift pressure adjustments and improved operability of hydraulic actuators.

Implementation Method 1

by performing bleed-off control with the bleed-off valves, pressure loss in the center bypass oil passages can be reduced

Methodology Applied

Scientific EffectHydraulic pressure reduction through bypass flow: Pressure Drop

Data Source

PatentEP3492661B1Excavator, and control valve for excavator

Publication Date: 2023.11.01 SUMITOMO CONSTRUCTION MACHINERY

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AI summary

A shovel, etc., that can suppress a decrease in the responsiveness of bleed-off control in the case of supplying hydraulic oil to multiple directional control valves in parallel through a center bypass oil passage is provided. Therefore, a hydraulic pump, multiple hydraulic actuators, a center bypass oil passage supplied with hydraulic oil discharged from the hydraulic pump, multiple directional control valves arranged in tandem in the center bypass oil passage and configured to supply the hydraulic actuators with the hydraulic oil from the center bypass oil passage, wherein at least a directional control valve other than the most downstream directional control valve opens the center bypass oil passage, and a bleed-off valve connected to part of the center bypass oil passage upstream of at least one of the directional control valves are included.