Hydraulic Driving System Smooth Cylinder Extension
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Solution Overview
Problem
In hydraulic driving systems for machines like hydraulic excavators, the integration of closed and open circuits can lead to uneven hydraulic fluid flow rates, causing pressure differences that impair the smooth operation of single rod hydraulic cylinders, particularly during extension and retraction.
Innovation Solution
A hydraulic driving system with a closed circuit and an open circuit configuration, featuring a control unit with inlet and outlet ports connected annularly to the hydraulic cylinder, and a control device that manages the flow of hydraulic fluid through opening and closing devices to regulate pressure differences between the circuits, ensuring smooth extension and retraction of the single rod hydraulic cylinder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hydraulic fluid from open circuit and closed circuit are merged through distribution circuit, then the single rod hydraulic cylinder can be driven, but smooth motion is impaired due to sudden change in inlet-flow rate caused by pressure difference
Solution Approach 1:
The control device performs preliminary action by controlling the opening and closing timing of the first opening and closing device before the hydraulic fluids are merged. By advancing the timing of opening the first opening and closing device, the system prepares the flow path in advance to accommodate the pressure difference, preventing sudden flow rate changes and ensuring smooth cylinder motion.
Solution Approach 2:
The control device uses feedback by monitoring the pressure difference between the open circuit and closed circuit, and adjusts the timing of the first opening and closing device accordingly. This closed-loop control ensures that the inlet-flow rate changes smoothly by responding to actual pressure conditions in real-time.
2Reliability
If check valve is used to prevent backward flow from open circuit to closed circuit, then backward flow is prevented, but pressure difference causes sudden inlet-flow rate change
Solution Approach 1:
The control device performs preliminary action by controlling the timing of the first opening and closing device to open before the pressure difference becomes problematic. This preemptive timing adjustment prevents the sudden flow rate change that would otherwise occur when hydraulic fluids merge, while the check valve continues to provide reliable backward flow prevention.
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
The system ensures smooth operation of the single rod hydraulic cylinder by regulating hydraulic fluid flow and pressure differences, improving the starting characteristics and speed of extension and retraction processes.
Implementation Method 1
a hydraulic pump (P1, P2, P3, P4), a single rod hydraulic cylinder (A1, A2, A3, A4) and a control device (S1, S2, S3, S4)
Data Source
AI summary
To provide a hydraulic driving device configured to smoothly extend a hydraulic cylinder. The present invention includes the open circuit E, the closed circuit A, a control device 57, and a control lever 56a. The open circuit E is provided with a flow passage 202 for connecting an outlet port of the open circuit pump 13 and a head chamber 1a of the boom cylinder 1, a selector valve 44a provided in the flow passage 202, a discharge flow passage 404 for connecting a hydraulic fluid tank 25 and a flow passage 200, and a bleed-off valve 64 provided in the discharge flow passage 404. The control device 57 is configured in such a manner that when a manipulate signal for extending the boom cylinder 1 is input from the control lever 56a, the bleed-off valve 64 is closed, the selector valve 44a is subsequently opened, and the open circuit pump 13 is controlled.