Servohydraulic Drive Stroke Control Independent of Load Pressure
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Solution Overview
Problem
Existing servohydraulic drives cannot actively and independently adjust the stroke volume of the hydrostatic displacement machine, especially at high load pressures, which can negatively impact workpiece quality due to excessive torque production.
Innovation Solution
A supply unit that provides pressurized fluid to the adjustment device regardless of working line pressures, using a switching valve to control the actuating pressure between a minimum and maximum stroke volume, with an auxiliary pump and hydraulic accumulator system to maintain necessary pressures without energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the stroke volume is adjusted only after a rise in load pressure, then the adjustment device can be supplied with necessary actuating pressure, but the quality of the workpiece is negatively affected due to delayed adjustment
Solution Approach 1:
The supply unit proactively supplies pressurized fluid to the adjustment device before load pressure rises, enabling the stroke volume to be adjusted immediately when needed rather than waiting for pressure conditions to become favorable. This preliminary action eliminates the adjustment delay that previously degraded workpiece quality.
2Power
If the stroke volume is not adjusted at high load pressures, then the system operates simply, but the torque produced by the electric motor becomes excessively large
Solution Approach 1:
The stroke volume of the displacement machine is made dynamically adjustable through the supply unit and switching valve, allowing the system to adapt the motor torque to actual load conditions. At high load pressures, the stroke volume can be reduced to prevent excessively large torque, while at lower pressures the full stroke volume is available.
3Adaptability or versatility
If a supply unit with auxiliary pump is used to provide pressurized fluid independently, then the stroke volume can be adjusted actively and independently of load pressure, but the device complexity increases
Solution Approach 1:
The supply unit with auxiliary pump serves multiple functions: it provides pressurized fluid for active stroke volume adjustment, maintains system pressure during operation, and enables independent adjustment regardless of main circuit conditions. This multi-functionality justifies the added complexity by providing adjustment independence.
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
Enables active and load-pressure-independent adjustment of the stroke volume, reducing energy losses and ensuring consistent workpiece quality by allowing precise control between maximum and minimum stroke volumes.
Implementation Method 1
a hydraulic accumulator which is preset to a low pressure and which is fluidically connected via a valve assembly in each case to the working line in which the lower pressure prevails
Implementation Method 2
if the supply unit comprises an auxiliary pump having a pressure port by which the adjustment device can be supplied with pressurized fluid, and having a suction port which is connected to the low-pressure hydraulic accumulator
Data Source
AI summary
A servohydraulic drive includes a hydrostatic displacement machine, an electric machine that is mechanically speed-coupled with the displacement machine, a hydraulic cylinder that is fluidically connected to the displacement machine via first and second working lines, a hydraulic accumulator, and a supply unit. The displacement machine has a stroke that is adjustable via a hydraulic adjustment device. The cylinder is configured to be activated by reversal of the fluid flow through the displacement machine in opposite directions. The accumulator is preset to a low pressure and is fluidically connected via a valve assembly in each case to the lower pressure working line. The supply unit is configured to supply the adjustment device with pressurized fluid under the necessary pressure for the adjustment regardless of the present pressure in the working lines such that the displacement machine is configured for an active and load pressure-independent adjustment of its stroke volume.