Hydraulic Control Valve Pre-Opening for Low-Temperature Start-Up Stability
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Solution Overview
Problem
In working machines with closed center load sensing hydraulic systems, the rising of delivery pressure and load pressure is delayed at low temperatures, leading to delayed generation of the LS differential pressure, which can cause shocks and hunting when the control valve flow rate is increased suddenly.
Innovation Solution
Implement preliminary control to limit the hydraulic fluid flow rate to an inching flow rate before drive control, with the flow rate maintained for extended periods at lower temperatures, and switch to drive control upon operation detection or temperature rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the control valve is opened at a large opening degree to provide high flow rate, then the productivity is improved, but a shock occurs at low temperatures due to delayed pressure generation
Solution Approach 1:
The controller performs preliminary control by limiting the control valve opening degree to a predetermined value before executing drive control. This preliminary action allows pressure to build up gradually in the hydraulic system, especially at low temperatures where pressure generation is delayed, preventing sudden shock when full flow is eventually required
Solution Approach 2:
The control valve opening degree is dynamically adjusted based on temperature conditions. At low temperatures, the opening is initially limited to a predetermined value, then gradually increased to the target opening degree. This dynamic adjustment adapts the system behavior to temperature-dependent hydraulic characteristics, preventing shock while maintaining productivity
2Productivity
If the control valve opening degree is increased suddenly to meet high flow demand, then the productivity is improved, but hunting occurs due to sudden cylinder pressure change
Solution Approach 1:
Before executing drive control that requires high flow rates, the controller first applies preliminary control to open the control valve only to a predetermined extent. This preliminary action prepares the hydraulic system by allowing pressure to stabilize gradually, preventing sudden pressure changes that would cause hunting in the hydraulic actuator
Solution Approach 2:
The controller monitors the operation state of the hydraulic actuator and adjusts the control valve opening degree accordingly. When the actuator starts moving during preliminary control, the controller increases the opening degree to the target value, using feedback from actuator movement detection to smoothly transition from limited to full flow without causing pressure instability
Data Source
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AI summary
A working machine (1) includes a drive device (8), a control valve (30), and a controller (11). The drive device (8) includes a hydraulic actuator (HA) and a drive member (DM) to be driven by the hydraulic actuator (HA). The control valve (30) regulates a hydraulic fluid for operating the hydraulic actuator (HA). The controller (11) controls the control valve (30). Before starting to execute drive control for the drive member (DM), the controller (11) performs preliminary control to open the control valve (30) by an opening degree which is less compared with that used in the drive control.