U-Cup Piston Ring Geometry for Low-Crevice Cylinder Sealing
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Solution Overview
Problem
The existing piston rings in internal combustion engines fail to effectively reduce crevice volume at the top land, leading to increased emissions and reduced efficiency due to incomplete combustion of fuel, as they are not adequately sealed at high RPMs and are prone to being pushed away from the cylinder walls by pressurized gases.
Innovation Solution
A U-cup shaped piston ring with a radial contact surface and fluid-pressure receiving surfaces, designed to be loaded radially against the cylinder wall and axially against the piston, ensuring a net outward force for sealing, and featuring retaining tabs and a secondary seal to maintain positioning and prevent leakage, even at varying engine speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a U-cup shaped piston ring is used to reduce crevice volume, then emissions are reduced and efficiency is improved, but the piston ring is pushed away from the cylinder walls by pressurized gases at high RPMs
Solution Approach 1:
The invention changes the geometric parameters of the piston ring by providing asymmetric radial contact surfaces with different areas. The first radial contact surface has a larger area than the second radial contact surface, creating an asymmetric pressure distribution that generates a net outward force to maintain sealing at high RPMs while reducing crevice volume for lower emissions
Solution Approach 2:
The piston ring employs asymmetric design in its radial contact surfaces, where the first radial contact surface extending from the top land has a larger area than the second radial contact surface. This asymmetry creates differential pressure forces that push the piston ring outward against the cylinder wall, preventing it from being pushed away by pressurized gases during high RPM operation
2Stability of the object's composition
If the piston ring is designed with equal projection areas on both sides, then the ring remains stable, but it cannot generate sufficient outward force to maintain sealing against pressurized gases
Solution Approach 1:
The invention deliberately introduces asymmetry in the radial contact surface areas to generate the necessary outward sealing force. The first radial contact surface has a larger area than the second, creating a net outward force that overcomes the inward pressure from gases while maintaining operational stability through controlled asymmetric pressure distribution
3Reliability
If mechanical force is applied to urge the piston ring towards the cylinder wall, then sealing is improved, but the device complexity increases with additional components
Solution Approach 1:
The piston ring design enables self-service by using the engine's own operating conditions (fluid pressure differentials across asymmetric surfaces) to automatically generate the outward forcing force needed for sealing. The asymmetric radial contact surfaces convert the existing pressure field into a self-regulating sealing mechanism that adapts to varying engine loads and speeds without additional mechanical components
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 solution effectively reduces crevice volume, ensuring reliable sealing and improved engine efficiency by maintaining contact with the cylinder wall under fluid pressure, reducing emissions and fuel consumption, and enhancing the piston ring's stability and sealing performance across all engine loads and speeds.
Implementation Method 1
the fluid pressure causes a net force by which the radial contact surface is urged radially against the cylinder wall
Data Source
AI summary
Embodiments of a combination piston and piston ring to reduce the volume of a crevice defined between the circumferential wall of a cylinder and a portion of the outer wall of a piston within the cylinder, the portion extending down from the top of the piston. The combination piston and piston ring is configured such that pressurized fluid within the cylinder reliably urges a radial face of the piston ring to sealingly engage the circumferential wall of the cylinder, even as the piston reciprocates within the cylinder.