Circumferential Grooves for Hydrostatic Balancing in Piston-Cylinder Interfaces
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Solution Overview
Problem
Conventional axial piston machines are limited to operating pressures of approximately 200 bar when using low-viscosity working fluids like water due to high leakage rates and difficulty in maintaining a hydrodynamic seal, leading to potential metal-to-metal contact and catastrophic component failure.
Innovation Solution
Incorporating circumferential grooves within the piston-cylinder lubrication interfaces to promote hydrostatic balancing of pressure, increasing the load-carrying capacity of the working fluid and reducing the likelihood of metal-to-metal contact, allowing operation at pressures up to 300 bar with low viscosity fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water is used as working fluid in axial piston machines, then environmental friendliness and thermal conductivity are improved, but leakage rates increase and hydrodynamic seal maintenance becomes difficult
Solution Approach 1:
The patent applies preliminary action by introducing circumferential grooves in the piston-cylinder lubrication interface before operation begins. These grooves pre-establish hydrostatic pressure balancing capabilities, allowing the system to maintain reliable hydrodynamic sealing with water from the start of operation rather than relying on water's natural viscosity properties.
Solution Approach 2:
The patent applies hydraulics by utilizing the working fluid itself (water) to create hydrostatic pressure within the circumferential grooves. This hydrostatic pressure actively balances the load-carrying requirements, replacing the need for hydrodynamic sealing that would normally rely on fluid viscosity. The water is pressurized within the grooves to maintain the bearing function.
2Power
If operating pressure is increased beyond 200 bar with low-viscosity fluids, then power and productivity are improved, but metal-to-metal contact occurs and component failure risk increases
Solution Approach 1:
The circumferential grooves are pre-configured in the piston-cylinder interface to provide hydrostatic pressure balancing before high-pressure operation begins. This preliminary structural arrangement enables the system to safely handle pressures up to 300 bar by preventing metal-to-metal contact through proactive pressure distribution, rather than relying on reactive measures after contact occurs.
Solution Approach 2:
The patent changes the pressure distribution parameters within the lubrication interface by introducing circumferential grooves. These grooves create localized hydrostatic pressure zones that balance the load-carrying requirements, fundamentally altering how pressure is distributed across the piston-cylinder interface. This parameter change allows safe operation at higher pressures without increasing component failure risk.
3Device complexity
If conventional piston-cylinder interfaces are used without grooves, then device complexity is minimized, but load-carrying capacity of the working fluid is insufficient for high-pressure operation
Solution Approach 1:
The patent applies segmentation by dividing the continuous piston-cylinder lubrication interface into distinct zones using circumferential grooves. These grooves segment the interface into load-bearing regions and hydrostatic pressure balancing regions. This segmentation allows the working fluid to effectively carry higher loads by distributing pressure across multiple zones rather than relying on a uniform interface.
Solution Approach 2:
The patent applies local quality by creating circumferential grooves at specific locations within the piston-cylinder interface. These grooves are strategically positioned to provide local hydrostatic pressure balancing where needed most. The local modification of the interface structure (adding grooves only in critical areas) increases load-carrying capacity without requiring complete redesign of the entire interface, thus maintaining reasonable device complexity.
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 implementation of circumferential grooves enhances the load-carrying capacity of the working fluid, enabling axial piston machines to operate safely at higher pressures with low viscosity fluids like water without significant metal-to-metal contact, thereby extending the operational pressure limit.
Implementation Method 1
The grooves promote hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interfaces and increase a load-carrying capacity of the working fluid within the piston-cylinder lubrication interfaces during operation
Implementation Method 2
Within this lubrication gap, a continuous film of the working fluid is preferably always present to provide a bearing function that prevents direct contact between the piston and bore wall
Data Source
AI summary
Positive displacement machines and methods therefor capable of increasing a load-carrying capacity of a piston-cylinder lubrication interface of positive displacement machines having a cylinder block, a cylindrical bore defined in the cylinder block, a piston reciprocably disposed within the cylindrical bore, and a working fluid within the piston-cylinder lubrication interface to provide a load-bearing function between the piston and the bore wall of the cylinder bore. The method includes providing at least one circumferential groove on a bore wall of the cylindrical bore within the piston-cylinder lubrication interface having an opening facing the piston and that is in fluidic communication with the piston-cylinder lubrication interface so as to contain a portion of the working fluid, and operating the positive displacement machine such that the working fluid enters the cylindrical groove and promotes hydrostatic balancing of pressure of the working fluid within the piston-cylinder lubrication interface.