Piston Concave Surface Layout for High-Speed Stability
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Solution Overview
Problem
The issue of piston inclination and potential contact with the rotation axle due to oil entrainment at high rotational speeds in fluid working machines, particularly in hydraulic pump motors, is not adequately addressed by existing technologies.
Innovation Solution
The design incorporates a piston with an opposing concave portion that receives fluid via a communication path, positioning the center of gravity of the reaction force from the fluid upstream of the rotation axle, stabilizing the piston's movement and preventing inclination by ensuring effective lubrication and oil entrainment between the piston and the sliding surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation axle rotates at high speed, then the productivity of the fluid working machine is improved, but the piston may tilt and come into contact with the rotation axle due to oil entrainment
Solution Approach 1:
The opposing portion of the piston is given a different local quality by providing a concave portion with a specific center of gravity position. This local modification creates an asymmetric force distribution that counteracts the oil entrainment effect, allowing the piston to remain stable even at high rotational speeds without requiring a complete redesign of the piston structure.
2Force
If oil is supplied to the sliding surface for lubrication, then friction is reduced, but the oil may push the piston from the side causing inclination
Solution Approach 1:
The concave portion in the opposing surface of the piston creates an asymmetric geometry that deliberately positions the center of gravity of the oil force upstream of the rotation axle. This asymmetric design allows the oil to exert a stabilizing moment rather than a tilting moment, converting the harmful side-push effect into a beneficial stabilizing force that maintains piston orientation during high-speed operation.
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 configuration effectively suppresses piston inclination and contact with the sliding surface, reducing wear and ensuring smooth operation even at high rotational speeds by maintaining stable piston alignment and lubrication.
Implementation Method 1
an opposing concave portion provided in an opposing portion that faces a sliding surface of the rotation axle, and to which the fluid is supplied from the housing portion via the communication path
Implementation Method 2
The oil entrained by the sliding surface of the rotation axle normally enters between the piston and the rotation axle (referred to as 'dynamic pressure effect')
Data Source
AI summary
A fluid working machine includes a cylinder that has a housing portion for accommodating a fluid, a piston that reciprocates in the cylinder, and a crankshaft that performs rotational motion in conjunction with reciprocating motion of the piston. The piston has an opposing concave portion provided in an opposing portion that faces a sliding surface of the crankshaft, and to which the fluid is supplied from the housing portion via the communication path. The opposing concave portion is provided in the opposing portion such that the center of gravity position of a force acting on the piston from the fluid in the opposing concave portion is located upstream of the crankshaft in the rotation direction when viewed from a central axis of the piston.