Hydrostatic Piston Mounting for Friction Reduction
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Solution Overview
Problem
Hydrostatic positive displacement machines face issues with high friction and wear in the adjusting device due to tribological contact between the adjusting piston and the cylinder, particularly caused by transverse forces during operation.
Innovation Solution
The adjusting piston is mounted hydrostatically with uniformly distributed pressure pockets on its bearing surface, each connected via a fixed throttle and a variable bearing gap, allowing pressure fluid to flow in and out, which balances forces to maintain a constant bearing gap width, reducing friction and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the adjusting piston is mounted with direct frictional contact (tribological contact), then the structure is simple, but friction and wear increase significantly
Solution Approach 1:
The adjusting piston is mounted hydrostatically using pressure fluid in pressure pockets to create a floating bearing surface. The pressure fluid is supplied through fixed throttles to multiple pressure pockets distributed over the bearing surface, forming a hydrostatic film between the adjusting piston and cylinder, thereby eliminating direct frictional contact and reducing wear.
2Reliability
If hydrostatic mounting with pressure pockets is implemented, then friction and wear are reduced, but the quantity of pressure fluid increases
Solution Approach 1:
The bearing surface is divided into multiple discrete pressure pockets distributed uniformly over the circumference. Each pressure pocket is supplied with pressure fluid through individual fixed throttles. This segmentation allows the pressure fluid to be distributed efficiently across the bearing surface, maintaining hydrostatic support while minimizing the total quantity of pressure fluid required.
Solution Approach 2:
Pressure pockets are positioned specifically in regions where they are most effective for maintaining the bearing gap, particularly at locations where the bearing gap width tends to increase. The fixed throttles are designed to provide the optimal pressure distribution locally, ensuring minimal pressure fluid consumption while maintaining reliable hydrostatic mounting.
3Ease of operation
If the bearing gap width varies during operation, then the adjusting piston can move freely, but friction and wear increase
Solution Approach 1:
The hydrostatic mounting system dynamically adjusts the pressure distribution in the pressure pockets based on the position of the adjusting piston. When the piston moves toward one side, the bearing gap increases on that side, causing pressure fluid to flow more readily through the bearing gap, which reduces pressure in those pockets and creates a restoring force. This dynamic pressure adjustment maintains constant bearing gap width while allowing free piston movement.
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 arrangement significantly reduces friction and wear in the adjusting device, maintaining a constant bearing gap width and minimizing the pressure fluid required for hydrostatic mounting, thus enhancing the operational efficiency and longevity of the machine.
Implementation Method 1
pressure fluid flows into each pressure pocket via a fixed throttle, which is assigned only to the respective pressure pocket, and flows out of each pressure pocket via the bearing gap
Implementation Method 2
The adjusting piston is mounted hydrostatically, wherein at least three pressure pockets are distributed uniformly in a row over the circumference of a bearing surface
Implementation Method 3
If the bearing gap width increases on a first side of the adjusting piston, because the adjusting piston moves toward the opposite, second side, the throughflow cross section of the variable throttle(s) becomes greater on the first side and the pressure in the pressure pockets on the first side drops
Data Source
AI summary
A hydrostatic positive displacement machine has an adjustable swept volume, and has a lifting element, a rotor with positive displacement elements supported on the lifting element, and a hydraulic adjusting device that adjusts the swept volume and includes an adjusting piston that is mounted in or on a cylinder, is movable axially rectilinearly in relation to the cylinder, and is adjacent to a pressurizable adjusting chamber. A bearing gap is formed between a circular-cylindrical bearing surface of the adjusting piston and a circular-cylindrical bearing surface of the cylinder. The adjusting piston is mounted hydrostatically, wherein at least three pressure pockets are distributed uniformly in a row over the circumference of a bearing surface. Pressure fluid flows into each pressure pocket via a fixed throttle, which is assigned only to the respective pressure pocket, and flows out of each pressure pocket via the bearing gap.