Hydraulic Excavator Drive System Cavitation Prevention

Solution Overview

Problem

In hydraulic excavator drive systems, the risk of cavitation and temporary stopping of arm or bucket movement occurs due to the weight distribution, leading to inefficiencies and energy wastage, particularly during arm crowding or bucket-in operations.

Innovation Solution

A hydraulic excavator drive system with a bypass line and restrictor mechanism, controlled by a load detector and controller, adjusts the opening area of control valves to prevent cavitation and optimize energy usage by blocking the bypass line when the arm or bucket is moved in the air and opening it during excavation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the opening area of the control valve for returning hydraulic oil to the tank is reduced to prevent cavitation, then cavitation is prevented, but the discharge pressure of the hydraulic pump increases and energy consumption increases

Engineering Contradiction:

Improvecavitation preventionVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The hydraulic oil return path is segmented into two separate paths: (1) through the control valve with reduced opening area for cavitation prevention, and (2) through the bypass line with larger capacity for energy efficiency. This segmentation allows each path to serve different functions simultaneously, resolving the contradiction between reliability and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass line acts as an intermediary path that provides an alternative route for hydraulic oil return. By introducing this intermediate element, the system can maintain the restricted flow through the control valve while allowing excess oil to bypass through the lower-resistance path, thereby preventing cavitation without excessive energy consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If the opening area of the control valve is large to reduce energy consumption, then energy consumption is reduced, but cavitation occurs at the head side of the cylinder

Engineering Contradiction:

Improveenergy consumptionVSAvoidcavitation

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The hydraulic oil return path is segmented into two separate paths: (1) through the control valve with reduced opening area for cavitation prevention, and (2) through the bypass line with larger capacity for energy efficiency. This segmentation allows each path to serve different functions simultaneously, resolving the contradiction between reliability and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass line acts as an intermediary path that provides an alternative route for hydraulic oil return. By introducing this intermediate element, the system can maintain the restricted flow through the control valve while allowing excess oil to bypass through the lower-resistance path, thereby preventing cavitation without excessive energy consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the opening area of the control valve is reduced to prevent cavitation, then cavitation is prevented, but the swinging of the arm or bucket temporarily stops

Engineering Contradiction:

Improvecavitation preventionVSAvoidswinging continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The hydraulic oil return path is segmented into two separate paths: (1) through the control valve with reduced opening area for cavitation prevention, and (2) through the bypass line with larger capacity for energy efficiency. This segmentation allows each path to serve different functions simultaneously, resolving the contradiction between reliability and energy loss.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bypass line acts as an intermediary path that provides an alternative route for hydraulic oil return. By introducing this intermediate element, the system can maintain the restricted flow through the control valve while allowing excess oil to bypass through the lower-resistance path, thereby preventing cavitation without excessive energy consumption.

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

This configuration prevents cavitation and temporary stopping while minimizing energy consumption by allowing hydraulic oil to return through the bypass line during high-pressure operations, reducing the discharge pressure of the hydraulic pump.

Implementation Method 1

there is a risk that cavitation occurs at the head side of the cylinder due to the above-described influence of the weight of the arm or bucket

Methodology Applied

Scientific EffectCavitation: Cavitation

Data Source

PatentUS10167611B2Hydraulic excavator drive system

Publication Date: 2019.01.01 KAWASAKI JUKOGYO KK

AI summary

A hydraulic excavator drive system includes: a cylinder that drives a moving part that is an arm or a bucket. Hydraulic oil is supplied from a hydraulic pump to the cylinder via a control valve. A bypass line branches off from a rod-side supply/discharge line. The bypass line is blocked and opened by a restrictor. The restrictor is controlled by a controller such that, when the hydraulic oil is supplied to the cylinder through a head-side supply/discharge line, the restrictor blocks the bypass line if a pressure detected by a load detector is lower than a predetermined value, and opens the bypass line if the pressure detected by the load detector is higher than or equal to the predetermined value.