Variable Compression Ratio Engine Control for Piston-Valve Collision Prevention

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Solution Overview

Problem

Existing methods for controlling compression ratio and valve characteristics in internal combustion engines to prevent piston-valve collisions often compromise engine efficiency and fuel economy, as reducing valve lift or retarding intake valve timing decreases charge efficiency, while minimizing compression ratio reduces air-fuel mixture temperature.

Innovation Solution

Implementing a variable compression ratio mechanism and valve characteristics control system that determines an upper variation limit compression ratio to prevent collisions by limiting the target compression ratio when it exceeds this limit, allowing the engine to operate efficiently and economically by avoiding piston-valve collisions while maintaining optimal compression ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the compression ratio is increased to improve engine efficiency, then the engine efficiency improves, but the piston and valves may collide with each other

Engineering Contradiction:

Improveengine efficiencyVSAvoidcollision prevention

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies dynamics by making the compression ratio variable rather than fixed. The compression ratio is dynamically adjusted based on engine operating conditions through a variable compression ratio mechanism that changes the combustion chamber capacity. This allows the system to optimize engine efficiency by increasing compression ratio when safe, while preventing collisions by reducing compression ratio when valve-piston clearance becomes insufficient, thus resolving the contradiction between efficiency improvement and collision prevention.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the valve lift is reduced or intake valve timing is retarded to prevent collision, then collision is prevented, but the charge efficiency of air-fuel mixture decreases

Engineering Contradiction:

Improvecollision preventionVSAvoidcharge efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

3Reliability

If the compression ratio is reduced towards the minimum to prevent collision, then the distance between piston top dead center and valve increases, but the temperature of air-fuel mixture does not sufficiently increase

Engineering Contradiction:

Improvecollision preventionVSAvoidair-fuel mixture temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

4Reliability

If the target compression ratio is limited to prevent collision, then collision is prevented, but the engine cannot operate at optimal compression ratio

Engineering Contradiction:

Improvecollision preventionVSAvoidengine efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7278383B2Internal combustion engine with variable compression ratio and valve characteristics

Publication Date: 2007.10.09 TOYOTA JIDOSHA KK

AI summary

When controlling the valve characteristics of an intake valve and changing the compression ratio, an upper variation limit compression ratio, which is the upper limit of the variation of compression ratio, is determined according to the actual valve characteristics of the intake valve characteristics control. The upper variation limit compression ratio is set to a valve at which the intake valve does not collide with the piston. When a target compression ratio corresponding to the operation state of the engine is larger than the upper variation limit compression ratio, the compression ratio is set to the upper variation limit compression ratio that is smaller than the target compression ratio. Thus, collision between the intake valve and the piston can be prevented while allowing the compression ratio to be increased up to the maximum compression ratio of the range where the collision does not occur.