Variable Compression Ratio Control via Eccentric Cam Plungers
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Solution Overview
Problem
Existing variable compression ratio systems face limitations in precision control and power loss due to complex oil paths and high oil pressure losses, which affect fuel efficiency and engine performance.
Innovation Solution
A variable compression ratio apparatus utilizing a piston pin, small and large diameter eccentric cams, and oil-jet injection nozzles to control the compression ratio in multiple steps with reduced oil paths, minimizing power loss and improving control accuracy through hydraulic pressure management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable compression ratio apparatus uses complex oil paths to control compression ratio, then compression ratio control is achieved, but power loss increases due to high oil pressure losses
Solution Approach 1:
The patent divides the compression ratio control into multiple discrete steps (e.g., 4 steps) using separate plungers for each compression ratio level. Each plunger controls a specific compression ratio by blocking or opening corresponding oil passages, allowing precise control while minimizing unnecessary oil flow and pressure loss compared to continuous control systems.
Solution Approach 2:
The patent implements localized oil control at specific positions within the piston pin bore. Each plunger controls oil flow to specific chambers (first/second chambers for small diameter eccentric cam, third/fourth chambers for large diameter eccentric cam) independently, allowing precise local control of eccentric cam rotation positions with minimal overall oil pressure loss.
2Measurement precision
If a variable compression ratio apparatus uses multiple oil paths for precise control, then compression ratio precision is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple control functions into a compact piston pin structure that houses all plungers, eccentric cams, and oil passages within the existing connecting rod assembly. The first and second plungers work together with the small and large diameter eccentric cams in an integrated manner, controlling compression ratio through coordinated rotation of both cams simultaneously, thereby achieving precise multistep control without proportionally increasing overall system complexity.
Solution Approach 2:
The piston pin structure serves multiple functions: it connects the piston to the connecting rod, houses the plunger mechanisms for compression ratio control, contains the eccentric cams for position adjustment, and manages all oil flow paths. This multi-functionality allows precise compression ratio control to be achieved within an existing component, avoiding the need for separate dedicated control mechanisms that would increase device complexity.
3Power
If ignition timing is advanced at high compression ratio, then thermal efficiency increases, but abnormal combustion occurs and engine may be damaged
Solution Approach 1:
The patent implements dynamic compression ratio adjustment capability that allows the compression ratio to change based on operating conditions. By using movable plungers that can rotate the eccentric cams to different positions, the system can dynamically select from multiple compression ratio steps (e.g., 8:1 to 14:1), enabling optimal compression ratio selection for each operating condition to prevent knocking while maintaining high thermal efficiency when appropriate.
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 apparatus achieves improved fuel efficiency and reduced power loss by precisely controlling the compression ratio in multiple steps, enhancing engine performance and simplifying oil path management.
Implementation Method 1
controlling the control position of the first and second plungers by supplying hydraulic pressure to an end portion of the first plunger and the other portion of the second plunger through first and second guide passages formed inside the piston by injecting oil to the lower portion of the piston
Implementation Method 2
a first plunger movably disposed in a first plunger space formed at a side inside the piston pin so as to control a rotational position of the small diameter eccentric cam by controlling oil supplied to first and second chambers formed between the outer circumference surface of the small diameter eccentric cam and an inner circumference surface of the large diameter eccentric cam
Data Source
AI summary
A variable compression ratio apparatus may include: a piston pin; a small diameter eccentric cam disposed on a piston; a large diameter eccentric cam disposed between the small diameter eccentric cam and a small end portion of a connecting rod; a first plunger movably disposed in a first plunger space inside the piston pin; a second plunger movably disposed in a second plunger space formed inside the piston pin; and first and second oil injection nozzles disposed at a lower portion of the piston. In particular, the first and second oil injection nozzles control a control position of the first and second plungers by supplying hydraulic pressure to an end portion of the first plunger and the other portion of the second plunger through first and second guide passages formed inside the piston by injecting oil to the lower portion of the piston.