Hydraulic Pump Relief Pressure Control for Multi-Cylinder Industrial Vehicles
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Solution Overview
Problem
Conventional hydraulic drive devices for industrial vehicles have a fixed upper limit pressure for hydraulic oil discharge, regardless of the operated hydraulic cylinder, which limits adaptability and efficiency in varying operational demands.
Innovation Solution
A hydraulic drive device with a variable capacity pump, a capacity control valve, and a relief valve system that adjusts the relief pressure based on the operation state of the tools, allowing the upper limit pressure of hydraulic oil discharge to be dynamically controlled according to the specific hydraulic cylinder in use, ensuring optimal pressure distribution and preventing overloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the upper limit pressure of hydraulic oil discharged from the hydraulic pump is determined by adjusting an adjust screw disposed in the control valve, then the upper limit pressure is constant regardless of the operated hydraulic cylinder, but this limits adaptability to varying operational demands
Solution Approach 1:
The relief pressure setting portion dynamically adjusts the relief pressure of the relief valve based on which hydraulic cylinder is operating. The control unit receives operation state signals from operation detecting portions and automatically changes the relief pressure setting, transforming a static pressure control system into a dynamic one that adapts to different operational conditions without requiring manual intervention or complex mechanical adjustments.
Solution Approach 2:
The system changes the relief pressure parameter according to the operated hydraulic cylinder. When different hydraulic cylinders are detected as operating, the control unit modifies the relief pressure setting parameter accordingly, allowing the upper limit pressure to vary based on operational requirements while maintaining a relatively simple overall system structure.
2Productivity
If a fixed upper limit pressure is used for all hydraulic cylinders, then the control system is simple, but operational efficiency is reduced when varying pressure is needed
Solution Approach 1:
The system performs self-service by automatically detecting which hydraulic cylinder is operating through operation detecting portions and autonomously adjusting the relief pressure setting via the relief pressure setting portion. The control unit processes operation state signals and automatically modifies pressure parameters without requiring external intervention, thereby improving operational efficiency while maintaining system simplicity through automated decision-making.
Solution Approach 2:
The system implements feedback control by continuously monitoring the operation state of hydraulic cylinders through operation detecting portions and using this information to adjust the relief pressure setting. The control unit receives feedback signals about which cylinder is operating and automatically modifies the pressure parameter accordingly, creating a closed-loop control system that optimizes operational efficiency.
3Reliability
If the relief pressure is fixed, then the system is simple to control, but it cannot prevent overloading for specific hydraulic cylinders requiring lower pressure
Solution Approach 1:
The system applies preliminary anti-action by preemptively adjusting the relief pressure setting based on which hydraulic cylinder is detected as operating. Before overloading can occur, the control unit has already configured the appropriate relief pressure level for the specific cylinder in use, preventing excessive pressure buildup and potential damage while maintaining relatively simple relief valve hardware.
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 solution enables the hydraulic drive device to adjust the upper limit pressure of hydraulic oil discharge in real-time, enhancing operational efficiency and protecting hydraulic components by ensuring the pressure is appropriate for the specific operation, thus improving the overall performance and longevity of the system.
Implementation Method 1
a hydraulic pump 4 that is of a variable capacity type, driven by an engine and discharges hydraulic oil stored in the tank
Implementation Method 2
a relief valve 40 disposed between the pilot line 30 and the tank 3, and that opens when the pilot pressure generated in the pilot line is equal to or greater than a relief pressure
Implementation Method 3
The capacity control valve controls the hydraulic pumps so that a differential pressure between a discharge pressure of the hydraulic pump and the pilot pressure of the pilot line is to be a predetermined pressure
Data Source
AI summary
A hydraulic drive device for an industrial vehicle includes a tank, a hydraulic pump, a capacity control valve, a plurality of hydraulic cylinders, a plurality of direction switching valves, a first hydraulic oil passage, a second hydraulic oil passages, a pilot line, a relief valve, a relief pressure setting portion, a plurality of operation detecting portions, and a control unit. The control valve controls the hydraulic pumps so that a differential pressure between a discharge pressure of the hydraulic pump and a pilot pressure of the pilot line is to be a predetermined pressure. The control unit controls the relief pressure setting portion.