Variable Valve Rocker Arm Asymmetry for Cam Stability
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Solution Overview
Problem
The existing cam-changing variable valve mechanism experiences unexpected sliding of the cam unit due to valve spring reaction forces, caused by manufacturing tolerances leading to inclination between cams and rocker arms, resulting in friction-induced sliding forces.
Innovation Solution
The mechanism incorporates a configuration where two rocker arms for each cylinder are intentionally inclined in opposite directions, with their support and pressing portions offset in the axial direction, canceling out valve spring reaction forces and reducing friction resistance, thereby suppressing the unexpected slide of the cam unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rocker arms are arranged perpendicular to the cam axial direction, then the valve actuating system operates smoothly, but manufacturing tolerances cause inclination between cams and rocker arms, leading to unexpected sliding of the cam unit
Solution Approach 1:
The patent applies asymmetry by intentionally designing the rocker arms to be inclined at specific angles (first inclination angle and second inclination angle) relative to the cam axial direction. This asymmetric arrangement allows the opposing rocker arms to generate counteracting horizontal forces that cancel each other out, preventing unexpected cam unit sliding while compensating for manufacturing tolerances.
Solution Approach 2:
The patent uses the counterweight principle by arranging two rocker arms on opposite sides of the cam unit with equal but opposite inclination angles. The horizontal components of the valve spring reaction forces from these two rocker arms act in opposite directions and cancel each other out, effectively counterbalancing the sliding forces that would otherwise cause unexpected cam unit displacement.
2Reliability
If rocker arms are inclined to cancel valve spring reaction forces, then friction resistance is reduced and cam unit sliding is suppressed, but the support portion and pressing portion must be offset in the axial direction
Solution Approach 1:
The patent applies asymmetry by intentionally designing the rocker arms to be inclined at specific angles (first inclination angle and second inclination angle) relative to the cam axial direction. This asymmetric arrangement allows the opposing rocker arms to generate counteracting horizontal forces that cancel each other out, preventing unexpected cam unit sliding while compensating for manufacturing tolerances.
Solution Approach 2:
The patent resolves the structural complexity issue by utilizing the axial dimension. The support portion and pressing portion of each rocker arm are offset in the axial direction, which allows the rocker arm to be inclined without interfering with the cam unit operation. This dimensional approach transforms a potential two-dimensional conflict into a three-dimensional solution.
3Reliability
If two rocker arms are arranged to cancel sliding forces, then friction resistance is reduced, but the configuration must avoid interference with intake ports
Solution Approach 1:
The patent resolves the structural complexity issue by utilizing the axial dimension. The support portion and pressing portion of each rocker arm are offset in the axial direction, which allows the rocker arm to be inclined without interfering with the cam unit operation. This dimensional approach transforms a potential two-dimensional conflict into a three-dimensional solution.
Solution Approach 2:
The patent applies local quality by making the inclination and axial offset specific to each rocker arm's position and function. The first rocker arm has a first inclination angle and the second rocker arm has a second inclination angle, with their support and pressing portions offset in the axial direction. This localized configuration allows the system to cancel sliding forces while adapting to the specific spatial constraints of the engine layout and avoiding interference with intake ports.
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 effectively cancels out sliding forces acting on the cam unit, reducing friction and preventing unexpected sliding, while maintaining the flexibility of the valve actuating system and avoiding interference with intake ports.
Implementation Method 1
the cam 41 is dragged in the direction of the axis X (not shown in FIG. 7) under the friction resistance between the cam 41 and the rocker arm 15
Data Source
AI summary
For example, two intake valves for each cylinder each are driven by a selected one of cams via a corresponding rocker arm. Each rocker arm includes a support portion and a pressing portion (distal end portion). The support portion is rockably supported by a cylinder head. The pressing portion is configured to press a stem of the corresponding intake valve. The support portion of one of the rocker arms deviates to one side in an axis X direction (cam axial direction) with respect to the distal end portion. The support portion of the other one of the rocker arms deviates to the other side in the axis X direction with respect to the distal end portion.