Variable Camshaft Timing for Cylinder Deactivation

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Solution Overview

Problem

Existing cylinder deactivation systems in engines face challenges with valve overlap control, leading to inefficient fuel economy and combustion stability, particularly at varying engine loads, due to limitations in valve timing adjustment and unintended gas flow between intake and exhaust systems.

Innovation Solution

A mechanical cam phasing device is used to adjust the timing of intake and exhaust valves symmetrically about the bottom center position of the piston, ensuring substantially no valve overlap and equal gas exchange, thereby eliminating net gas flow and maintaining consistent pressure within cylinders.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional valve deactivation systems are used with fixed cam timing, then cylinder deactivation can be achieved, but valve overlap cannot be controlled leading to inefficient fuel economy and combustion stability

Engineering Contradiction:

Improvefuel economyVSAvoidvalve timing control

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent implements variable camshaft timing mechanisms that dynamically adjust the phase relationship between crankshaft and camshaft lobes. This allows the valve timing to be continuously varied based on operating conditions, enabling optimal control of valve overlap during cylinder deactivation to improve fuel economy while maintaining combustion stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the timing parameters of intake and exhaust valve events by adjusting camshaft phase angles. By varying these timing parameters, the system can control valve overlap duration and timing, allowing optimized deactivation operation across different engine loads and speeds to reduce energy loss.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If valve deactivators are used to deactivate cylinders, then fuel economy can be improved, but reliability issues arise with latching and ensuring deactivation within one engine cycle at high speeds

Engineering Contradiction:

Improvefuel economyVSAvoidvalve deactivation reliability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent replaces mechanical valve deactivators with a camshaft-based valve actuation system. The camshaft lobes directly control valve opening and closing through hydraulic actuators, eliminating the need for separate deactivator mechanisms. This substitution improves reliability by removing latching mechanisms while maintaining the ability to deactivate cylinders for fuel economy improvement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If both camshafts are linked together with one phase for normal operation, then valve events are optimized for normal operation, but valve overlap cannot be adjusted for deactivated operation leading to harmful gas flow from exhaust to intake

Engineering Contradiction:

Improvecamshaft linkage simplicityVSAvoidexhaust gas flow into intake

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The patent segments the control of intake and exhaust camshafts by providing independent phase adjustment capability for each camshaft relative to the crankshaft. This segmentation allows the exhaust camshaft timing to be independently optimized to prevent harmful exhaust gas flow into the intake system during cylinder deactivation, while maintaining simple linked operation during normal operation.

Inventive Principle:

Principle #1Segmentation

4Stability of the object's composition

If intake and exhaust valve events are retarded symmetrically about bottom center, then gas exchange is equalized and net gas flow is eliminated, but device complexity increases with mechanical adjustment mechanisms

Engineering Contradiction:

Improvecylinder pressure stabilityVSAvoidcam timing adjustment mechanism

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent implements a universal camshaft timing control system that performs multiple functions: normal operation with linked camshafts, cylinder deactivation with independent timing adjustment, and optimization of valve overlap control. This multi-functional system achieves stable cylinder pressure during deactivation while using integrated hydraulic actuators that reduce overall device complexity compared to separate adjustment mechanisms.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8042504B2Adjusting valve timing to deactivate engine cylinders for variable displacement operation

Publication Date: 2011.10.25 FORD GLOBAL TECH LLC

AI summary

An internal combustion engine having two cylinder banks and adjustable camshaft timing is disclosed in which the camshafts in one cylinder bank are adjusted so that there is no net flow from the cylinders to effectively disable the cylinder bank. In particular, exhaust valve timing is advanced so that the maximum valve lift occurs approximately at bottom center between expansion and exhaust strokes and intake valve timing is advanced so that maximum valve lift occurs approximately at bottom center between intake and compression strokes. Also disclosed is an engine in which an intake and an exhaust camshaft on a single bank are coaxial with valve timings adjusted by rotating the inner of the two camshafts with respect to the outer of the two camshafts.