Excavator Pilot Line Bypass for Area Limit Control Response

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Solution Overview

Problem

In hydraulic excavators, area limiting control is compromised due to pressure loss and leakage flow in solenoid proportional valves, leading to reduced response of the work implement, especially when the temperature of stagnant hydraulic fluid in the pilot line drops, which is not effectively detected by existing temperature monitoring systems.

Innovation Solution

A work machine design that includes a changeover valve capable of bypassing the solenoid proportional valve, with a controller that determines the fluid temperature and adjusts the changeover valve position to maintain hydraulic fluid temperature and enable area limiting control while ensuring response, by using a first fluid temperature detection device and a control changeover switch to specify enabling or disabling of area limiting control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the solenoid proportional valve is used for area limiting control, then the work implement can be controlled not to enter a predetermined area, but the response of the work implement is reduced due to pressure loss and leakage flow

Engineering Contradiction:

Improvearea limiting control precisionVSAvoidresponse speed

Core Design Contradiction:

Manufacturing precisionVSSpeed

Solution Approach 1:

The system dynamically switches between two operational modes: area limiting control mode (using solenoid proportional valve for precision) and normal control mode (direct pilot pressure for speed). The control device detects temperature conditions and work requirements to determine which mode to activate, making the system adaptable to different operational needs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The changeover valve acts as an intermediary that directs pilot pressure through different paths. When area limiting control is needed, it routes pressure through the solenoid proportional valve; when response speed is prioritized, it bypasses the solenoid proportional valve. This intermediary component enables flexible control over the pressure path.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If the pilot pressure is guided through the solenoid proportional valve for area limiting control, then the work implement can be precisely controlled, but the temperature of stagnant hydraulic fluid in the pilot line decreases, reducing response further

Engineering Contradiction:

Improvearea limiting control precisionVSAvoidhydraulic fluid temperature

Core Design Contradiction:

Manufacturing precisionVSTemperature

Solution Approach 1:

The control device detects temperature conditions in advance and switches to normal control mode (bypassing the solenoid proportional valve) when low temperature is detected, preventing the response degradation before it occurs. This preliminary detection and response maintains system performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hydraulic system uses its own operating conditions (temperature, work type) to automatically determine the appropriate control mode. The control device monitors system state and adjusts the changeover valve position accordingly, allowing the system to self-regulate between precision and speed modes based on real-time conditions.

Inventive Principle:

Principle #25Self-service

3Speed

If the changeover valve bypasses the solenoid proportional valve to improve response, then the response of the work implement is improved, but the area limiting control cannot be performed

Engineering Contradiction:

Improveresponse speedVSAvoidarea limiting control capability

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control device changes the operational parameters of the hydraulic system by adjusting the changeover valve position. This switches the pilot pressure path between two configurations: one optimized for precision (through solenoid proportional valve) and one optimized for speed (bypassing solenoid proportional valve).

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10961690B2Work machine

Publication Date: 2021.03.30 HITACHI CONSTRUCTION MACHINERY CO LTD

AI summary

A work machine is provided. The work machine includes a changeover valve capable of disabling area limiting control by bypassing an area limiting control solenoid proportional valve disposed in a pilot line through which pilot pressure generated by a hydraulic pilot type operation device is guided to a directional control valve and the work machine can perform the area limiting control while ensuring response of a work implement. When a first fluid temperature T1 is higher than a first predetermined temperature Ta and a control changeover switch 66 specifies disabling of the area limiting control, a controller brings a plurality of changeover valves into a bypass position. When the first fluid temperature T1 is equal to or lower than the first predetermined temperature Ta, the controller brings the changeover valves into a communication position and places the solenoid proportional valves in a fully open position.