Internal Combustion Engine Variable Valve Mechanism Rocker Arm Design
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Solution Overview
Problem
The use of torsion coil springs as lost motion springs in variable valve mechanisms increases the size and weight of rocker arms, and thin, long compression coil springs used as alternatives can bend, leading to unstable operation, reduced fuel efficiency, and increased size due to interference with other components, along with potential surging at high speeds.
Innovation Solution
An internal combustion engine design incorporating a compression coil spring separate from the rocker arm, with a shaft and retainer system that restricts bending and prevents interference, allowing stable force output and reduced size and weight, while the compression coil spring contacts the shaft to attenuate surging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a torsion coil spring is used as a lost motion spring, then the rocker arm can be compact, but the size and weight of the rocker arm increase due to attachment portions
Solution Approach 1:
The patent extracts the lost motion spring function from the rocker arm assembly by using a separate compression coil spring positioned in the valve mechanism. This eliminates the need for attachment portions on the rocker arm, thereby reducing rocker arm weight and complexity while maintaining the lost motion function.
2Area of stationary object
If a thin and long compression coil spring is used, then the winding diameter can be kept small to avoid interference, but the spring bends relative to the winding axis causing unstable operation
Solution Approach 1:
The patent introduces a guide member as an intermediary component that constrains the compression coil spring to prevent bending relative to the winding axis. This guide member ensures the spring maintains its intended geometry and force output characteristics, thereby ensuring stable valve operation while allowing the use of a thin, long spring with small winding diameter.
3Area of stationary object
If a thin and long compression coil spring is used, then the winding diameter is reduced, but clearance with other members must be increased to avoid contact
Solution Approach 1:
The guide member serves as a mediator that organizes the spatial arrangement of components. It provides a defined path for the compression coil spring, ensuring proper clearance relationships with other members without requiring excessive overall space in the variable valve mechanism.
4Area of stationary object
If a thin and long compression coil spring is used, then the spring is compact, but surging occurs at high engine speeds
Solution Approach 1:
The guide member acts as a damping intermediary that restricts lateral movement and vibration of the compression coil spring. By constraining the spring to move primarily in the axial direction, the guide member suppresses surging behavior that would otherwise occur at high engine speeds, enabling stable operation across the full speed range.
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 design stabilizes valve operation, maintains fuel efficiency, reduces the size and weight of the rocker arm, and prevents surging at high speeds, thereby addressing the issues of size, weight, and operational stability.
Implementation Method 1
a compression coil spring which is separate from the rocker arm and outputs a force to the second arm
Implementation Method 2
a shaft which is arranged on an inner side of the compression coil spring and extends along a winding axis of the compression coil spring
Implementation Method 3
the compression coil spring contacts the shaft to attenuate surging
Data Source
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AI summary
An object is to provide an internal combustion engine with which it is possible to suppress a decrease in the fuel efficiency and an increase in the size of the variable valve mechanism, while surging is unlikely to occur while running at a high speed, wherein it is possible to reduce the size or the weight of the rocker arm. An internal combustion engine (10) includes, as a lost motion spring that urges a rocker arm (40) toward a cam (23A), a compression coil spring (68) supported on a cylinder head (12). A shaft (70) is arranged on an inner side of the compression coil spring (68) and extends along a winding axis (68d) of the compression coil spring (68).