Variable Valve Train Cylinder Balance Control

Solution Overview

Problem

Internal combustion engines with variable valve trains face issues of uneven running and reduced ride comfort due to manufacturing tolerances in the valve train and valves, particularly in the lower load range and during idling, leading to noticeable torque differences between cylinders.

Innovation Solution

A method for controlling the variable valve train by determining cylinder-specific fuel quantity reductions and valve lift deviations, optimizing fuel delivery and valve lift to minimize uneven running, using a control device that adjusts the valve train to equalize cylinder-specific intake air quantities and compensate for fuel delivery errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If variable valve lift control is used to enable unthrottled operation in lower and medium load range, then fuel consumption is reduced, but manufacturing tolerances in valve train and valves cause errors in cylinder filling leading to noticeable torque differences and reduced ride comfort

Engineering Contradiction:

Improvefuel consumptionVSAvoidcylinder filling accuracy

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies local quality by determining cylinder-specific deviations of inlet valve lift from a valve reference value and adjusting fuel delivery individually for each cylinder based on its specific deviation. This allows each cylinder to be optimized for its actual performance characteristics, compensating for manufacturing tolerances while maintaining overall fuel efficiency benefits.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements feedback by measuring actual cylinder filling through fuel delivery adjustments and monitoring torque differences, then using this information to determine cylinder-specific valve lift deviations and adjust fuel delivery accordingly. This closed-loop control continues until torque differences are within an acceptable range, ensuring both fuel efficiency and ride comfort.

Inventive Principle:

Principle #23Feedback

2Loss of energy

If small inlet valve lift is used in lower load range and during idling, then charge exchange losses are reduced, but manufacturing tolerances cause noticeable torque differences that restrict ride comfort

Engineering Contradiction:

Improvecharge exchange lossesVSAvoidride comfort

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent applies local quality by determining cylinder-specific deviations of inlet valve lift from a valve reference value and adjusting fuel delivery individually for each cylinder based on its specific deviation. This allows each cylinder to be optimized for its actual performance characteristics, compensating for manufacturing tolerances while maintaining overall fuel efficiency benefits.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements feedback by measuring actual cylinder filling through fuel delivery adjustments and monitoring torque differences, then using this information to determine cylinder-specific valve lift deviations and adjust fuel delivery accordingly. This closed-loop control continues until torque differences are within an acceptable range, ensuring both fuel efficiency and ride comfort.

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If cylinder-specific control of inlet valve lift is implemented, then cylinder filling accuracy is improved, but device complexity increases

Engineering Contradiction:

Improvecylinder filling accuracyVSAvoidvalve train control complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies copying by using a valve reference value that represents the expected valve lift behavior, and by determining deviations from this reference rather than controlling each valve independently with complex mechanisms. This allows cylinder-specific optimization while maintaining a relatively simple base valve train design that can be adjusted through control algorithms.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS9309814B2Method and device for controlling a variable valve train of an internal combustion engine

Publication Date: 2016.04.12 VITESCO TECHNOLOGIES GMBH

AI summary

A method for controlling a variable valve train of an internal combustion engine including multiple cylinders is disclosed. At a first operating point of the engine, an intake air amount is determined and cylinder-individual values for a fuel amount reduction are determined by successively reducing the respectively supplied fuel amount for each cylinder until a characteristic representing uneven running of the engine has reached a predetermined uneven running threshold value. A ratio of a change in the intake valve lift to the resulting change in the intake air amount is determined for the first operating point. Cylinder-individual deviations of the intake valve lift from a reference value are determined based on the ratio, the intake air amount at the first operating point, and the associated value for the fuel amount reduction. The variable valve train is then controlled on the basis of the cylinder-individual deviations of the intake valve lift.