Hydraulic Actuator Valve Pre-Opening for Low-Temperature Start-Up

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Solution Overview

Problem

In working machines with closed center load sensing hydraulic systems, the generation of the required flow rate for hydraulic actuators is delayed at low temperatures, leading to sudden movements of actuators and potential shocks, especially at start-up, due to delayed LS differential pressure generation.

Innovation Solution

Implement preliminary control to limit the hydraulic fluid flow rate to an inching flow rate before full drive control, adjusting the maintaining period based on hydraulic fluid temperature, and using a controller to switch to drive control when the actuator operation is detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the control valve is opened by a large opening amount during drive control, then the required flow rate for the hydraulic actuator is achieved, but a shock occurs at low temperatures due to delayed LS differential pressure generation

Engineering Contradiction:

Improveflow rateVSAvoidshock

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The controller performs preliminary control by opening the control valve to a preliminary opening amount (less than the opening amount during drive control) before executing drive control. This preliminary action allows the LS differential pressure to be generated in advance, especially under low temperature conditions where pressure buildup is delayed, preventing sudden actuator movement and shock when full drive control commences

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The control valve opening amount is made dynamic and adaptive based on temperature conditions. The controller adjusts the opening amount between a preliminary opening amount (for low temperature conditions) and a larger opening amount (for normal conditions), allowing the system to optimize performance and prevent shock based on real-time temperature sensing

Inventive Principle:

Principle #15Dynamics

2Speed

If the control valve is opened quickly to achieve required flow rate, then actuator response speed is improved, but hunting occurs due to sudden cylinder pressure change

Engineering Contradiction:

Improveactuator response speedVSAvoidcylinder pressure stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The controller executes preliminary control to open the control valve to a preliminary opening amount before drive control begins. This preliminary action allows cylinder pressure to build up gradually and stabilizes the pressure conditions, preventing hunting when the actuator starts moving while still enabling responsive operation when needed

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12590596B2Working machine and control method therefor

Publication Date: 2026.03.31 KUBOTA CORP

AI summary

A working machine includes a driver, a control valve, and a controller. The driver includes a hydraulic actuator and a driven body to be driven by the hydraulic actuator. The control valve regulates a hydraulic fluid to operate the hydraulic actuator. The controller is configured or programmed to control the control valve. Before starting to execute drive control for the driven body, the controller is configured or programmed to perform preliminary control to open the control valve by an opening amount that is less than an opening amount during the drive control.