Hydrostatic Drive Accumulator Valve Control for Cavitation Prevention
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Solution Overview
Problem
Existing hydrostatic drives for starting internal combustion engines face challenges in quickly adjusting from negative to positive swept volumes without causing component damage due to cavitation, as they often rely solely on restoring springs, which can lead to excessive load on the engine during startup.
Innovation Solution
The hydrostatic drive incorporates an electronic control unit that manages the accumulator shut-off valve to maintain a fluid connection to the high-pressure accumulator during adjustments, utilizing both the pressure force and restoring spring force to facilitate quick adjustments from negative to zero swept volume, thereby preventing cavitation and reducing engine load during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the hydraulic machine is adjusted quickly from negative swept volume to positive swept volume using only a restoring spring, then the adjustment speed is improved, but excessive load is placed on the engine and cavitation may occur
Solution Approach 1:
The accumulator shut-off valve is switched to the second position (disconnecting the accumulator) before the hydraulic machine reaches zero swept volume during the adjustment from negative to positive swept volume. This preliminary action prevents the hydraulic machine from evacuating the pressure line and causes cavitation, thereby protecting components from damage while maintaining quick adjustment speed
Solution Approach 2:
The patent converts the potentially harmful effect of rapid adjustment (which could cause cavitation and component damage) into a beneficial outcome by using the electronic control unit to precisely time the valve switching. The rapid adjustment is maintained, but the harmful cavitation is prevented by disconnecting the accumulator at the optimal moment, thus converting a harmful side effect into a controlled protective measure
2Reliability
If the accumulator shut-off valve switches early during adjustment, then cavitation is prevented, but the fluidic connection is lost prematurely
Solution Approach 1:
The electronic control unit monitors the swept volume of the hydraulic machine in real-time and uses this feedback information to determine the optimal moment to switch the accumulator shut-off valve. By continuously monitoring the adjustment position, the control unit ensures the valve switches at the precise moment when the hydraulic machine reaches or approaches zero swept volume, maximizing the fluidic connection duration while preventing cavitation
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 ensures rapid and efficient adjustment of the hydraulic machine out of the negative swept volume range without causing cavitation, allowing the internal combustion engine to start quickly and reach idle rotational speed without undue load, thus enhancing the reliability and efficiency of the hydrostatic drive system.
Implementation Method 1
charge a hydropneumatic high-pressure accumulator and supply pressure medium to further hydraulic consumers
Implementation Method 2
at least one restoring spring, under the action of which the hydraulic machine is set to a predetermined swept volume when a pressurization of the adjustment chambers is ended
Implementation Method 3
the hydraulic machine can, for operation as a hydraulic motor, be supplied with pressure medium via a pressure line which runs between a pressure port of the hydraulic machine and the high-pressure accumulator
Data Source
AI summary
A hydrostatic drive includes a hydraulic machine, a hydraulic adjusting device, a high-pressure accumulator, an accumulator-closing valve, and an electronic control unit. The hydraulic machine has a swept volume that is adjustable via the hydraulic adjusting device from a maximum positive swept volume to a maximum negative swept volume via a zero swept volume. The hydraulic machine is operated as a pump with positive swept volume and as a motor with negative swept volume. The high-pressure accumulator supplies the hydraulic machine with pressure medium for operation as a motor via a pressure line. The accumulator-closing valve has a first position and a second position and is arranged in the pressure line. A fluidic connection from the high-pressure accumulator to the hydraulic machine is open in the first position and closed in the second position. The accumulator-closing valve is actuated in accordance with signals from the electronic control unit.