Variable Valve Rocker Arm Segmentation for Friction Reduction
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Solution Overview
Problem
Existing variable valve apparatuses for internal combustion engines face challenges in reducing the size of the rocker arm and minimizing friction when a hydraulic lash adjuster is integrated, leading to increased size and moment of inertia, which necessitates higher valve spring load and friction.
Innovation Solution
A variable valve apparatus design featuring a low lift cam with a smaller base circle radius, a hydraulic lash adjuster positioned closer to the rocking center, and a switching mechanism that uses a force other than hydraulic pressure to displace the pin, allowing for a compact oil supply path and reduced friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic lash adjuster is arranged in a rocker arm with a roller and pin in the center part, then the valve mechanism can maintain proper valve clearance, but the rocker arm size must be increased and the camshaft position raised to secure installation space
Solution Approach 1:
The invention divides the rocker arm into two functional segments: a first rocker arm with a roller for cam contact, and a second rocker arm with a hydraulic lash adjuster for valve clearance control. This segmentation allows each component to be optimized independently, placing the lash adjuster at the end of the second rocker arm rather than requiring it to share space with the roller and pin in the center part.
2Volume of moving object
If the rocker arm length is increased to accommodate the hydraulic lash adjuster, then the installation space is secured, but the moment of inertia of the rocker arm increases
Solution Approach 1:
Instead of increasing the length of the rocker arm in the traditional sense, the invention positions the hydraulic lash adjuster at the end of the second rocker arm, utilizing the spatial arrangement in a different dimension. The second rocker arm is arranged next to the first rocker arm, and the lash adjuster is placed at its end away from the rocking center, effectively using available space without proportionally increasing moment of inertia.
3Reliability
If the rocker arm size and moment of inertia are increased, then the hydraulic lash adjuster can be installed, but the equivalent inertia mass of the valve mechanism system increases
Solution Approach 1:
By segmenting the rocker arm function into two separate arms (first rocker arm for cam contact, second rocker arm for valve clearance), the invention avoids concentrating all components in a single enlarged arm. This segmentation allows the hydraulic lash adjuster to be installed without requiring a proportionally larger equivalent inertia mass for the entire valve mechanism system.
4Reliability
If the valve spring load is increased to compensate for the larger inertia mass, then the valve operation is maintained, but friction increases
Solution Approach 1:
The segmentation of the rocker arm system allows each component to be sized appropriately for its specific function rather than requiring oversized components to handle maximum possible loads. The second rocker arm with the hydraulic lash adjuster can be optimized for clearance control without needing to accommodate the entire valve mechanism's maximum inertia mass, thereby reducing friction.
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 reduces the size and moment of inertia of the rocker arm, minimizes friction, and prevents 'pump-up' actions, while maintaining effective valve operation and reducing the need for high hydraulic pressure, thus enhancing the efficiency and performance of the valve mechanism.
Implementation Method 1
a hydraulic lash adjuster arranged at an end on an opposite side to a rocking center of the second rocker arm
Implementation Method 2
the necessity sometimes arises to lengthen the rocker arm and raise the position of the camshaft in order to secure installation space for the hydraulic lash adjuster itself and installation space for an oil supply path for supplying a hydraulic pressure
Implementation Method 3
an oil supply path that is formed inside the second rocker arm and that supplies oil to the hydraulic lash adjuster
Implementation Method 4
a roller for reducing frictional resistance with a cam
Implementation Method 5
a cam provided on a camshaft that rotates; a first rocker arm that contacts the cam, and that is rocked by rotation of the cam
Data Source
AI summary
A variable valve apparatus of an internal combustion engine includes a first rocker arm that contacts a cam, a low lift cam provided coaxially with the cam, and a second rocker arm capable of contacting the low lift cam. The apparatus also includes a switching mechanism capable of connecting the first rocker arm and the second rocker arm to each other through pins, valves that open by being pressed by the second rocker arms via hydraulic lash adjusters arranged in the second rocker arms, and an oil supply path formed inside the second rocker arms that supplies oil to the hydraulic lash adjusters. A radius of a base circle of the low lift cam is smaller than a radius of a base circle of the cam.