Nested Rocker Arm Assembly for Variable Valve Actuation
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Solution Overview
Problem
Current variable valve actuation systems for internal combustion engines face challenges in fitting existing cylinder head designs due to increased width, which leads to interference with spark plug tubes and cam towers, requiring costly modifications and assembly clearance issues.
Innovation Solution
The development of a modified rocker arm assembly with a latch and latch seat design that compensates for manufacturing tolerances, allowing for a predefined lash and accommodating obstructed sides, enabling the system to fit within existing engine head designs without significant modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable valve actuation system with inner and outer rocker arms is implemented, then advanced valve lift control and cylinder deactivation capabilities are achieved, but the width of the rocker arm assembly increases causing interference with spark plug tubes and cam towers
Solution Approach 1:
The patent implements nesting by placing the inner rocker arm inside the outer rocker arm assembly. The inner rocker arm with its cam lobe interface is positioned within the outer rocker arm structure, allowing both components to occupy the same spatial envelope. This nested configuration enables the variable valve actuation system to achieve advanced control capabilities while minimizing the overall width of the assembly to avoid interference with surrounding engine components.
Solution Approach 2:
The patent transitions from a conventional side-by-side or stacked rocker arm configuration to a nested three-dimensional arrangement. By utilizing the vertical and radial dimensions rather than only horizontal spacing, the design accommodates both inner and outer rocker arms within a compact footprint. This dimensional reorganization allows the assembly to fit within existing engine head clearances while maintaining full functionality.
2Area of stationary object
If the rocker arm assembly width is reduced to fit existing engine heads, then compatibility with spark plug tubes and cam towers is maintained, but manufacturing tolerances become more critical and assembly clearance becomes tighter
Solution Approach 1:
The patent incorporates a latch mechanism with a latch seat that is designed to compensate for manufacturing tolerances. The latch seat includes features such as recesses, clearance zones, or adjustable positioning elements that absorb dimensional variations from the inner and outer rocker arms. This beforehand cushioning approach ensures that even with tighter assembly clearances, the latch can still achieve proper engagement and maintain reliable operation without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The patent utilizes parameter changes in the latch seat design, such as varying the depth, width, or orientation of the latch receptacle, to accommodate tolerance stacks. By making the latch seat geometry adjustable or optimized within a range of parameters, the system can compensate for manufacturing variations while maintaining the reduced overall width needed for engine head compatibility.
3Area of stationary object
If the rocker arm assembly width is reduced to fit existing engine heads, then compatibility with spark plug tubes and cam towers is maintained, but assembly complexity and cost of modifications increase
Solution Approach 1:
The patent merges the latch mechanism with the existing rocker arm structure rather than treating it as a separate additive component. The latch seat is integrated into the outer rocker arm, and the latch pin or actuating mechanism is combined with the inner rocker arm assembly. This merging approach consolidates multiple functions into unified components, reducing the overall part count and assembly complexity despite the advanced functionality provided.
Solution Approach 2:
The latch mechanism is designed to serve multiple functions: it provides the variable valve actuation switching capability, maintains the nested rocker arm configuration, and compensates for manufacturing tolerances. By making the latch system multi-functional, the patent reduces the need for additional separate components that would increase complexity and cost, achieving tolerance compensation and width reduction through the same structural elements.
Data Source
Figure 1A~1B
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AI summary
A novel cylinder head arrangement is described for an in-line four cylinder or eight cylinder engine with each head having two end cylinders and two middle cylinders. A modified arrangement allows additional space for the installation of wider rocker arm assemblies used for variable valve lift (VVL), cylinder deactivation (CDA) and other types of variable valve actuation (VVA) in these existing cylinder head designs. In the first embodiment, cam towers of conventional designs adjacent the end two cylinders are not used. At least one end support is used which may be an outboard bearing on a camshaft for each end. The wider rocker assemblies may then be installed. In an alternative embodiment, the cam towers adjacent the inner two cylinders are eliminated and a single camshaft support piece with a support bearing is installed between the inner cylinders to provide support for the camshafts. The wider rocker assemblies may then be installed on at least one of the middle cylinders. The system also includes a novel oil control valve that operates latches in switching rocker arm assemblies.