Pressure-Adaptive Piston-Bushing Interface for Low-Leakage Sealing
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Solution Overview
Problem
The piston-cylinder interface in axial piston machines faces challenges in achieving efficient sealing and load-bearing functions simultaneously, leading to high energy dissipation and leakage, which existing technologies have not adequately addressed without expensive manufacturing processes or micro-surface shaping.
Innovation Solution
A novel piston-cylinder interface design featuring a cylindrical bushing with a circumferential groove that deflects under pressure to create a fluid-dynamic seal, reducing frictional losses and energy dissipation while maintaining effective sealing, and does not require micron-level manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight seal is created in the piston-cylinder interface to prevent leakage, then sealing performance is improved, but frictional losses increase leading to higher energy dissipation
Solution Approach 1:
The piston crown is designed with a flexible or deformable section that dynamically adjusts the clearance between piston and cylinder bore based on operating conditions. This dynamic adaptation allows the system to maintain optimal balance between sealing performance and frictional losses, rather than relying on a fixed tight seal throughout all operating phases
Solution Approach 2:
The invention changes the physical parameters of the piston-cylinder interface by introducing variable clearance through flexible materials or deformable structures. This allows the clearance parameter to vary during operation, enabling the system to achieve both effective sealing and reduced frictional losses at different stages of the operational cycle
2Reliability
If micro-surface shaping is applied to the cylinder bore to improve sealing, then sealing performance is improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of complex micro-surface shaping of the rigid cylinder bore, the invention employs a flexible piston crown or thin film structure that naturally conforms to the cylinder bore. This flexible element achieves sealing through its ability to deform and adapt to surface irregularities, avoiding the need for expensive precision micro-machining processes
Solution Approach 2:
The invention transitions from rigid, precision-machined surfaces to a system where the sealing parameter (clearance) can dynamically change. This is achieved through flexible materials or deformable structures that adapt their geometry based on operating conditions, eliminating the need for complex micro-surface shaping manufacturing processes
3Reliability
If clearance between piston and cylinder is reduced to improve sealing, then leakage is reduced, but viscous dissipation increases leading to higher energy loss
Solution Approach 1:
The system employs dynamic clearance adjustment where the piston crown or cylinder bore can change its geometry during operation. This allows the clearance to be larger during phases where viscous dissipation would be problematic and smaller during phases where sealing is critical, achieving both goals without compromise
Solution Approach 2:
The flexible piston crown or deformable structure undergoes periodic deformation synchronized with the operational cycle. This periodic action creates optimal sealing clearance at critical moments while maintaining larger clearance during other phases to minimize viscous dissipation and energy loss
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 design reduces energy dissipation and leakage by optimizing the sealing function without stringent manufacturing tolerances, achieving performance equivalent to a baseline interface at reduced clearance, thus lowering manufacturing costs and maintaining structural integrity.
Implementation Method 1
creating a fluid-dynamic seal between the piston and the cylindrical bushing, creating fluid-dynamic buildup of pressure therebetween
Implementation Method 2
the pressure inside the gap between the piston and the cylinder bore fluid-dynamically balances the side load acting on the piston due to the reaction from the swashplate
Data Source
AI summary
A piston and cylinder assembly of an axial piston machine is disclosed which includes a cylinder having a uniform internal diameter, a cylindrical bushing press-fit against the inner surface of the cylinder and extending at least partially therein, the bushing comprising at least one circumferential groove formed on an outer surface of the bushing against the inner surface of the cylinder, a piston reciprocably disposed within the cylindrical bushing, generating a piston-bushing-interface, the piston and the bushing defining a diametrical clearance therebetween, the diametrical clearance defining a lubrication gap and a fluid-dynamic seal between the piston and the cylindrical bushing.