On-Off Valve Lag Monitoring for Hydraulic Drive Reliability
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Solution Overview
Problem
Existing hydraulic drive systems in work machines fail to accurately predict the lifetime of on/off valves, leading to unnecessary maintenance and increased costs due to premature replacement of functional valves.
Innovation Solution
A hydraulic drive system that includes a controller to compute valve-opening and valve-closing lag times to determine the deterioration state of on/off valves, allowing for precise estimation of valve condition and timely replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lifetime prediction is based on number of operations and use time without considering individual valve differences, then prediction can be executed for all valves, but prediction accuracy varies on each valve basis leading to premature replacement
Solution Approach 1:
The patent replaces mechanical/lifetime-based prediction methods with electrical signal-based measurement. By substituting the mechanical operation counting system with electrical signal analysis (measuring voltage changes across the valve coil), the system achieves higher prediction accuracy while maintaining ease of implementation through existing electrical infrastructure.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using voltage signal characteristics as a mediator between the valve's operational state and its deterioration condition. Instead of directly measuring wear or lifetime, the system measures electrical properties (voltage, current, resistance) that correlate with valve health, enabling accurate prediction without complex mechanical sensors.
2Reliability
If replacement timing is set earlier than the end of predicted lifetime to ensure reliability, then valve failure is prevented, but maintenance cost increases due to replacement of valves that have not reached lifetime limit
Solution Approach 1:
The patent enables preliminary detection of valve deterioration through electrical signal analysis before actual failure occurs. By monitoring voltage and current characteristics in real-time, the system identifies valves that are approaching failure, allowing maintenance to be scheduled precisely when needed rather than using conservative early replacement schedules.
Solution Approach 2:
The patent changes the monitoring parameter from simple operational counts to electrical signal characteristics (voltage, current, resistance). This parameter change enables continuous assessment of valve health state, allowing the system to distinguish between valves that are truly deteriorating and those that are still functional, thereby optimizing replacement timing.
3Difficulty of detecting and measuring
If pressure difference measurement is used to determine valve stuck state, then valve status can be detected, but the problem arises that driving of the actuator is limited or impossible when valve is stuck
Solution Approach 1:
The patent replaces mechanical pressure-based detection with electrical signal-based detection. By measuring voltage and current characteristics across the valve coil, the system can detect valve stuck conditions electrically before they manifest as pressure problems or actuator failures, enabling early warning without affecting actuator operation.
Solution Approach 2:
The patent implements feedback by continuously monitoring electrical signals from the valve and using this information to predict deterioration and detect stuck conditions. This feedback mechanism allows the system to warn operators of impending valve failure before it affects actuator productivity, enabling preventive maintenance scheduling.
Data Source
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AI summary
An object of the present invention is to provide a hydraulic drive system that can accurately estimate a deterioration state of an on/off valve that opens and closes a hydraulic line that connects a hydraulic pump to an actuator. To this end, a controller computes a first valve-opening lag time from output of a first valve opening command signal (valve opening command value) instructing a first on/off valve to open to opening of the first on/off valve, and computes a first valve-closing lag time from output of a first valve closing command signal (valve closing command value) instructing the first on/off valve to close to closing of the first on/off valve. The controller determines a deterioration state of the first on/off valve on the basis of the first valve-opening lag time and the first valve-closing lag time.