Hydrostatic Piston Machine Pressure Sensor Placement
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Solution Overview
Problem
Existing hydrostatic piston machines face challenges in reliably and simply detecting state variables, particularly the displacement volume, due to limitations in pressure sensor placement and potential cavitation effects, which affect the accuracy and resolution of measurements.
Innovation Solution
The solution involves determining state variables by analyzing pressure profiles within switching regions, using a pressure sensor to detect pressure variations in displacement chambers and a fluid volume, which allows for the determination of the adjusting element's position and displacement volume, even with a small dead volume and optimal fluid volume to displacement chamber ratio for improved resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is placed directly in the switching region to detect pressure variations, then measurement accuracy is improved, but cavitation effects occur and installation space is enlarged
Solution Approach 1:
The patent introduces a fluid volume as an intermediary between the displacement chamber and the pressure sensor. The pressure sensor detects pressure variations in the fluid volume, which indirectly reflects the displacement chamber volume changes without requiring direct placement in the switching region, thereby avoiding cavitation effects while maintaining measurement accuracy.
Solution Approach 2:
The patent segments the measurement system into two distinct parts: the displacement chamber where pressure variations occur, and the fluid volume where the pressure sensor is placed. This segmentation allows the sensor to be positioned away from the harmful switching region while still detecting the relevant pressure signals through the coupled fluid volume.
2Measurement precision
If the dead volume of the displacement chamber is reduced to improve resolution, then measurement resolution is improved, but the system becomes more sensitive to pressure variations
Solution Approach 1:
The fluid volume acts as a buffer that mediates between the displacement chamber and the pressure sensor. It allows the system to maintain small dead volume in the displacement chamber for high resolution while the fluid volume absorbs and stabilizes pressure variations, preventing excessive sensitivity that would compromise reliability.
3Measurement precision
If opto-electronic or inductive measuring systems are used to detect swashplate position, then non-contact measurement is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex opto-electronic or inductive measuring systems with a simpler pressure-based detection method. By using a pressure sensor to detect pressure variations in the fluid volume that correspond to displacement chamber volume changes, the system achieves the same measurement function with significantly reduced complexity.
Solution Approach 2:
Instead of directly measuring the swashplate position, the patent creates a copy of the volume information through pressure variations in the fluid volume. The pressure sensor detects these variations, which represent the displacement chamber volume state, providing an indirect but accurate measurement without complex positioning sensors.
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 method enables accurate and reliable detection of displacement volume, rotating speed, and high pressure in hydrostatic piston machines using a simple pressure sensor, enhancing measurement resolution and accuracy without enlarging the installation space or being affected by cavitation.
Implementation Method 1
a fluid volume which serves as a pre-compression volume (PCV)... in which a pressure variation, based solely on the compressibility of the pressure medium, is associated with an inflow or outflow of a pressure medium
Data Source
AI summary
A hydrostatic piston machine has an adjustment element that is adjustable for varying a displacement volume, and a rotating cylinder part having a plurality of cylinder bores with pistons that are supported on the adjustment element and delimit a displacement chamber. Each displacement chamber is moved in an alternating manner by a connecting opening to overlap a low-pressure control opening situated on a low-pressure side of a stationary control part and a high-pressure control opening situated on a high-pressure side of the control part. Two switching regions are situated between the low-pressure control opening and the high-pressure control opening, the pistons changing direction at a dead center within the switching regions. The position of the adjustment element is determined from a pressure profile which is a function of the variable size of the displacement chambers in a switching region, the variable size depending on the position of the adjustment element.