Electro-hydraulic Drive Unit Decompression Module
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Solution Overview
Problem
Electrohydraulic drive units face challenges in achieving smooth and reproducible piston movement reversal, particularly at the bottom dead center, where high pressures and counterforces can lead to stress on the workpiece and discontinuities in the work cycle.
Innovation Solution
Incorporating a hydraulic decompression module with a hydraulic accumulator connected to the second hydraulic working chamber via a charging/discharging valve, allowing for controlled decompression and separation from the cylinder-piston arrangement, enabling a gentle and continuous return stroke without switching valves, thus reducing the influence of workpiece springback and machine deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the hydraulic pump reverses direction to decompress the first hydraulic working chamber at bottom dead center, then the pressure in the first working chamber is reduced, but this causes discontinuities and stress on the workpiece due to the reversal operation
Solution Approach 1:
The patent segments the decompression function from the main hydraulic pump by introducing a separate second hydraulic pump dedicated to supplying the second hydraulic working chamber. This allows the first pump to focus on decompressing the first chamber while the second pump independently controls the second chamber, eliminating the need for the first pump to reverse direction and causing discontinuities.
Solution Approach 2:
The patent introduces a decompression valve as an intermediary component that enables controlled decompression of the first hydraulic working chamber without requiring the hydraulic pump to reverse direction. The valve provides a dedicated pathway for fluid discharge, allowing smooth pressure reduction while maintaining continuous pump operation.
2Ease of operation
If switching valves are used to reverse hydraulic fluid flow for piston reversal, then the piston can be moved in either direction, but switching valves cause discontinuities in the work cycle
Solution Approach 1:
The patent divides the hydraulic control system into separate functional segments: a first hydraulic pump with a decompression valve for the first working chamber, and a second hydraulic pump for the second working chamber. This segmentation eliminates the need for switching valves to reverse flow direction, as each pump independently controls its designated chamber without requiring flow reversal.
Solution Approach 2:
Instead of using switching valves to reverse hydraulic fluid flow direction for piston reversal, the patent inverts the approach by using a dedicated second pump to supply the second chamber while the first pump handles decompression through a decompression valve. This eliminates the need for flow reversal and associated valve switching.
3Speed
If the hydraulic pump operates in brake mode to slow piston descent, then the piston can be controlled during rapid traverse, but this creates stress on the workpiece during the switching phase
Solution Approach 1:
The patent segments the hydraulic control functions by dedicating the first hydraulic pump to decompression and braking operations on the first working chamber, while the second hydraulic pump independently manages the second working chamber. This segmentation allows smooth transitions between operating phases without requiring switching valves that cause workpiece stress.
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 enhances the reproducibility and gentleness of the work cycle, achieving a constant and jerk-free movement, reducing errors and reject rates, and is suitable for applications like powder presses and press brakes by allowing controlled decompression and reducing the impact of workpiece springback.
Implementation Method 1
a hydraulic decompression module (9), in particular a decompression module, comprising a hydraulic accumulator (10), which can be connected to the second hydraulic working chamber (6)
Implementation Method 2
connected to the second hydraulic working chamber (6) via a charging/discharging valve (14)
Data Source
Figure 1
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AI summary
The invention relates to an electro-hydraulic drive unit comprising a cylinder-piston arrangement (1) having a piston-side first hydraulic operating chamber (5) and a piston-rod-side second hydraulic operating chamber (6), a tank (4), a variable-speed-driven hydraulic pump (3) having a tank connection (T) and an operating connection (P), a valve arrangement connected between the operating connection (P) of the hydraulic pump (3) and between the cylinder-piston arrangement (1), a feeder valve (8) connected between the tank (4) and the first hydraulic operating chamber (5), and a machine control. By means of said machine control, switch valves (S1-S6) of the valve arrangement can be switched between an application of the first hydraulic operating chamber (5) and of the second hydraulic operating chamber (6) of the cylinder-piston arrangement (1) in the pump operation of the hydraulic pump (3) from the operating connection (P) thereof. According to the invention, a hydraulic decompression module (9) having a hydraulic accumulator (10) is provided, which can be connected via a line arrangement (L) to a the second hydraulic operating chamber (6) by means of a charging/discharging valve (14) arranged therein.