Piston Rod Oil Passage Layout to Reduce Communication Hole Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing compression ratio varying mechanisms experience stress concentration in communication holes due to combustion pressure, which can lead to material failure and inefficiencies in engine operation.
Innovation Solution
A compression ratio varying mechanism is designed with communication holes that have first and second openings positioned apart in the stroke direction to reduce stress concentration, featuring a large-diameter and small-diameter portion configuration and seal members to manage hydraulic pressure and oil flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a communication hole is formed in the piston rod to allow cooling oil flow, then cooling efficiency is improved, but stress concentration occurs due to combustion pressure
Solution Approach 1:
The communication hole is designed to be inclined rather than perpendicular to the piston rod axis, changing the dimensional orientation of the hole. This inclination angle causes the opening to be positioned apart in the stroke direction, distributing stress more effectively while maintaining cooling oil flow capability
Solution Approach 2:
The piston rod structure is optimized locally around the communication hole by positioning the opening apart in the stroke direction and using specific inclination angles. This creates a localized stress distribution pattern that reduces concentration at critical points while preserving the overall structural integrity
2Temperature
If the communication hole opening is positioned to allow easy cooling oil introduction, then cooling performance is improved, but stress concentration increases due to combustion pressure application
Solution Approach 1:
The communication hole is inclined at a specific angle relative to the piston rod axis, changing the spatial dimension of the opening. This inclination positions the opening apart in the stroke direction, allowing cooling oil introduction while reducing stress concentration through optimized geometric orientation
Solution Approach 2:
The inclination angle of the communication hole is optimized as a geometric parameter to balance two competing requirements: sufficient opening area for cooling oil flow and appropriate orientation to minimize stress concentration under combustion pressure
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 reduces stress concentration in communication holes, enhancing the durability and efficiency of the engine by alleviating stress and improving the flow of cooling oil and working oil.
Implementation Method 1
the cooling oil is introduced from the outside of the piston rod to the cooling oil passage through the communication hole
Implementation Method 2
a seal arranged on the outer peripheral side surface of the piston rod, between the first opening and the second opening in the stroke direction
Implementation Method 3
A top dead center position of a piston is changed by supplying or discharging working oil to or from the hydraulic chamber
Data Source
AI summary
Provided is a compression ratio varying mechanism, including a communication hole including: a first opening opened in an outer peripheral side surface of a piston rod; and a second opening, which is prevented from being opposed to the first opening in a radial direction of a piston rod, and is connected to an oil passage at a position apart from the first opening in a stroke direction.