Piston Thermal Barrier with Localized Heat Insulation
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Solution Overview
Problem
The existing heat insulating films on piston top surfaces in internal combustion engines, composed of anodized aluminum and Y2O3-stabilized ZrO2, have low thermal conductivity and heat capacity, leading to increased followability of piston top surface temperature but also cause knocking due to heat spot generation at cavity and edge portions.
Innovation Solution
A piston design featuring a low heat insulation film on cavity and edge portions, composed of alumina with open pores, and a high heat insulation film on surrounding surfaces, with a sealer covering the pores, to manage heat distribution and prevent heat spot formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat insulating film with low thermal conductivity and low heat capacity is formed on the entire piston top surface, then the followability of piston top surface temperature to gas temperature is improved, but knocking easily occurs due to heat spot generation at cavity edge portions
Solution Approach 1:
The patent applies different heat insulating film types to different regions of the piston top surface. Specifically, a first heat insulating film (with lower heat insulation performance) is applied to cavity edge portions where heat spots easily generate, while a second heat insulating film (with higher heat insulation performance) is applied to other portions. This local differentiation resolves the contradiction by preventing knocking at critical locations while maintaining overall temperature followability.
2Loss of energy
If a heat insulating film is formed on the piston top surface, then cooling loss is reduced, but heat spots generate at cavity edge portions leading to knocking
Solution Approach 1:
The patent differentiates heat insulating film application by location: cavity edge portions receive a first heat insulating film with lower insulation performance to prevent heat spot accumulation, while other areas receive a second heat insulating film with higher insulation performance to reduce cooling loss. This spatially varying approach balances energy retention with heat spot prevention.
Solution Approach 2:
The heat insulating film is segmented into two distinct types applied to different regions of the piston top surface. The first film (lower insulation) targets cavity edge portions prone to heat spots, while the second film (higher insulation) covers other areas. This segmentation allows simultaneous optimization of local heat management and overall thermal efficiency.
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 design enhances heat escape to the piston base material, reducing the likelihood of knocking while maintaining followability of piston top surface temperature with the combustion chamber gas temperature.
Implementation Method 1
a low heat insulation film that is formed on a cavity edge portion forming a boundary between the cavity and the top surface and is composed of alumina having a number of pores that are opened to the top surface
Implementation Method 2
The heat insulating film is composed of a porous layer that is obtained by anodizing a surface of a piston base material of an aluminum alloy
Data Source
AI summary
On a piston top surface, a cavity and two valve recesses are formed. On the piston top surface, a first heat insulating film is formed. However, on edge portions, a second heat insulating film different from the first heat insulating film is formed. The second heat insulating film is formed along the edge portions. The first heat insulating film is composed of porous alumina and a sealer. The second heat insulating film is composed of only porous alumina.