Elliptical Gear Valvetrain for Variable Valve Timing

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Solution Overview

Problem

Existing engine valvetrains with variable valve timing and lift mechanisms face challenges in achieving precise control and reducing friction due to complex gear systems and multiple sliding contacts, which affect the cyclic variation of cam speeds and valve lift events.

Innovation Solution

The engine employs noncircular, specifically elliptical, gears that are eccentrically mounted to vary the rotational speed of the cam cyclically with the crankshaft speed constant, allowing for adjustable valve lift timing and duration by altering the gear relationships and cam follower interactions, thereby reducing parts and friction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If prior art variable valve timing and lift mechanisms are used, then valve timing control is achieved, but device complexity increases due to complex gear systems and multiple sliding contacts

Engineering Contradiction:

Improvevalve timing controlVSAvoidgear systems

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs noncircular, specifically elliptical, gears that are eccentrically mounted to vary the rotational speed of the cam cyclically with the crankshaft speed constant. This asymmetric gear design enables precise control over valve lift timing and duration while reducing parts and friction compared to traditional symmetric gear systems.

Inventive Principle:

Principle #4Asymmetry

2Adaptability or versatility

If prior art variable valve timing mechanisms are used, then valve timing adjustment is possible, but friction increases due to multiple sliding contacts

Engineering Contradiction:

Improvevalve timing adjustmentVSAvoidfriction

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The elliptical gears with eccentric mounting provide variable valve timing adjustment while reducing the number of sliding contacts through the optimized gear geometry, thereby reducing friction.

Inventive Principle:

Principle #4Asymmetry

3Measurement precision

If noncircular eccentric gears are used to vary cam speed cyclically, then precise control over valve lift timing and duration is achieved, but manufacturing precision requirements increase

Engineering Contradiction:

Improvevalve lift timing controlVSAvoidgear geometry

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The elliptical gear design provides precise control over valve lift timing and duration through its asymmetric geometry. The eccentric mounting allows the cam speed to vary cyclically while maintaining a constant crankshaft speed, achieving precise timing control.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent specifically employs elliptical (curved) gear geometry instead of straight or circular profiles. This curvature enables the cyclic variation of cam speed while maintaining manufacturability through standard elliptical machining processes.

Inventive Principle:

Principle #14Spheroidality (Curvature)

4Adaptability or versatility

If traditional variable valve timing systems are used, then basic timing control is achieved, but productivity is reduced due to more parts and higher friction

Engineering Contradiction:

Improvetiming controlVSAvoidengine efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The asymmetric elliptical gear design achieves advanced engine operation strategies like late intake valve closing and early intake valve opening, improving power and efficiency while using fewer parts and reducing friction compared to traditional systems.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent enables dynamic control of valve lift timing and duration by altering the relationship between the speed cycle of the cam and the rotational position of the cam relative to the valve or cam follower, allowing the system to adapt to different operating conditions for optimal productivity.

Inventive Principle:

Principle #15Dynamics

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

This configuration provides more precise control over valve lift events, reduces friction, and enables advanced engine operation strategies like late intake valve closing and early intake valve opening, improving power and efficiency while maintaining fewer parts and sliding contacts.

Implementation Method 1

noncircular, specifically elliptical, gears that are eccentrically mounted to vary the rotational speed of the cam cyclically with the crankshaft speed constant

Methodology Applied

Scientific EffectEccentric mechanism: Excentric

Data Source

PatentUS7614371B2Engine valvetrain having variable valve lift timing and duration

Publication Date: 2009.11.10 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An engine includes a crankshaft, a first noncircular gear operatively connected to the crankshaft to be driven thereby, a second noncircular gear meshingly engaged with the first noncircular gear, a cam operatively connected to the second noncircular gear to be driven thereby, and a valve operatively connected to the cam for movement between open and closed positions. The noncircular gears enable the speed of the cam to vary cyclically with constant rotation of the crankshaft speed. Valve lift timing and duration may be variable by moving the second noncircular gear with respect to the first noncircular gear while maintaining meshing engagement therebetween.