Variable Valve Drive Rocker Lever Contour Adjustment
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Solution Overview
Problem
Conventional variable valve drives for internal combustion engines cannot continuously vary valve opening and closing times and lifts, and existing solutions require changes to peripheral components to achieve variability.
Innovation Solution
A variable valve drive utilizing a switchable rocker lever arrangement with a transmission rocker lever and a valve rocker lever, where the contour surface of the transmission rocker lever defines the valve lift by varying the rolling region, allowing continuous adjustment of valve opening and closing times and lifts without altering the rocker lever and camshaft construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple cams with different contours are arranged on the camshaft to achieve variable valve timing and lift, then valve opening and closing times can be varied, but the device complexity increases and peripheral components must be changed
Solution Approach 1:
The transmission rocker lever is divided into two segments: a first lever that engages with the cam and a second lever with the contour surface. These segments can rotate relative to each other about the rocker lever axle, allowing independent adjustment of the contour surface position without changing the camshaft or other peripheral components. This segmentation enables variability while maintaining simplicity of the overall system.
Solution Approach 2:
The transmission rocker lever transitions from a fixed configuration to a dynamic, adjustable configuration. The contour surface can be rotated to different positions during operation, allowing continuous variation of valve timing and lift characteristics. This dynamic adjustment capability provides versatility without requiring multiple separate cams or complex peripheral components.
2Adaptability or versatility
If the camshaft is axially displaced to switch between different cam contours, then different valve profiles can be selected, but the moving masses increase and the system becomes less robust
Solution Approach 1:
Instead of moving the camshaft axially to switch between different cam contours, the invention inverts the approach by keeping the camshaft stationary and rotating the contour surface on the transmission rocker lever. This inversion eliminates the need for axial displacement mechanisms and reduces moving masses while maintaining the ability to switch between different valve profiles.
Solution Approach 2:
The variability function is extracted from the camshaft assembly and transferred to the transmission rocker lever. By taking out the adjustment mechanism from the camshaft and placing it on the rocker lever, the heavy camshaft remains stationary while only the lighter rocker lever components need to be adjusted, significantly reducing moving masses.
3Adaptability or versatility
If an adjustment member with hydraulic or pneumatic piston-cylinder unit is used to displace the cam block, then continuous variability can be achieved, but the device complexity and moving masses increase
Solution Approach 1:
The complex hydraulic or pneumatic piston-cylinder adjustment mechanism is replaced with a simpler mechanical rotation mechanism. The contour surface is rotated to different positions using a straightforward rotational movement about the rocker lever axle, eliminating the need for pistons, cylinders, and associated fluid systems while achieving continuous variability.
Solution Approach 2:
Instead of using a complex actuating mechanism to change valve parameters, the invention changes the position parameter of the contour surface by rotation. This simple parameter change (angular position of the contour surface) directly controls valve timing and lift characteristics, achieving continuous variability with minimal mechanical complexity.
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
Enables continuous variation of valve opening and closing times and lifts, maintaining the construction of conventional valve drives and minimizing moving masses, resulting in a robust and fully variable control suitable for utility and industrial engines.
Implementation Method 1
At a second end, the transmission rocker lever is operatively connected by way of a contour surface, in particular a valve-lift-defining contour surface, to the roller of the valve rocker lever, in such a way that a rocking movement of the transmission rocker lever generates a corresponding rocking movement of the valve rocker lever, in the case of which the roller of the valve rocker lever rolls on the contour surface.
Data Source
AI summary
A variable valve drive for a lifting valve, such as a charge-exchange valve of an internal combustion engine, that is periodically movable between closed and open positions indirectly by way of a cam via a rocker lever. The variable valve drive includes a switchable rocker lever arrangement for the actuation of the lifting valve, having a transmission rocker lever and a valve rocker lever which are mounted pivotably on different rocker lever axles parallel to the camshaft axis. The valve rocker lever, is in operative contact with the lifting valve at a first end, and has a roller, at a second end. The transmission rocker lever, is in engagement with a cam of the camshaft and, is operatively connected to the roller of the valve rocker lever.