Spark Ignition Engine EGR Control for Cylinder Uniformity

Solution Overview

Problem

In spark ignition internal combustion engines with variable compression ratio and intake valve timing mechanisms, excessive blowback of intake gas leads to uneven EGR distribution among cylinders, causing variations in air-fuel ratio and intake resistance, which deteriorate combustion efficiency and fuel efficiency.

Innovation Solution

Implementing a control mechanism that adjusts the EGR valve opening degree based on the intake valve closing timing, engine load, speed, coolant temperature, and ethanol concentration to minimize EGR gas variation among cylinders, ensuring consistent air-fuel ratio and reduced intake resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the closing timing of the intake valve is retarded to reduce intake air amount, then fuel efficiency is improved through higher expansion ratio, but blowback of intake gas becomes excessive causing uneven EGR distribution among cylinders

Engineering Contradiction:

Improvefuel efficiencyVSAvoidEGR distribution uniformity

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies dynamic control by making the EGR valve opening degree variable based on intake valve closing timing. Instead of a fixed EGR rate, the system dynamically adjusts the EGR valve opening degree in response to changes in intake valve closing timing, ensuring that EGR distribution remains uniform across cylinders even when intake valve timing is retarded to improve fuel efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a feedback control mechanism where the EGR valve opening degree is determined based on the actual intake valve closing timing. The control system monitors the intake valve closing timing and adjusts the EGR valve opening degree accordingly, creating a closed-loop control that maintains uniform EGR distribution while allowing optimization of fuel efficiency through variable intake timing.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If the closing timing of the intake valve is extremely retarded to achieve very high expansion ratio, then heat efficiency is maximized, but blowback becomes so strong that EGR gas is unevenly distributed among cylinders

Engineering Contradiction:

Improveheat efficiencyVSAvoidair-fuel ratio consistency

Core Design Contradiction:

Loss of energyVSManufacturing precision

Solution Approach 1:

The patent applies dynamic control by making the EGR valve opening degree variable based on intake valve closing timing. Instead of a fixed EGR rate, the system dynamically adjusts the EGR valve opening degree in response to changes in intake valve closing timing, ensuring that EGR distribution remains uniform across cylinders even when intake valve timing is retarded to improve fuel efficiency.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent implements a feedback control mechanism where the EGR valve opening degree is determined based on the actual intake valve closing timing. The control system monitors the intake valve closing timing and adjusts the EGR valve opening degree accordingly, creating a closed-loop control that maintains uniform EGR distribution while allowing optimization of fuel efficiency through variable intake timing.

Inventive Principle:

Principle #23Feedback

3Quantity of substance

If EGR operation is carried out with large and strong blowback, then exhaust gas recirculation is achieved, but distribution of EGR gas among cylinders deteriorates causing variation in air-fuel ratio

Engineering Contradiction:

ImproveEGR gas flow amountVSAvoidair-fuel ratio uniformity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by adjusting the EGR valve opening degree as a control parameter in response to intake valve closing timing. By changing the EGR valve opening degree parameter based on the timing conditions, the system maintains appropriate EGR gas flow distribution even when blowback conditions change, thereby preserving air-fuel ratio uniformity across all cylinders.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8613274B2Spark ignition type internal combustion engine

Publication Date: 2013.12.24 TOYOTA JIDOSHA KK

AI summary

A spark ignition type internal combustion engine of the present invention comprises a variable closing timing mechanism able to change a closing timing of an intake valve after intake bottom dead center and an EGR mechanism making a part of the exhaust gas flow again into a combustion chamber as EGR gas. The EGR mechanism is controlled so that the amount of EGR gas is reduced when the closing timing of the intake valve is at a retarded side, compared with when it is at an advanced side. Due to this, occurrence of variation among cylinders in the air-fuel ratio and intake resistance along with blowback of intake gas can be suppressed.