Variable Valve Rocker Arm Positioning Mechanism
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Solution Overview
Problem
Existing variable valve mechanisms for engines face challenges in achieving smooth rocker arm operation while downsizing the engine, as they often result in increased engine size due to friction and the need for larger cylinder heads to accommodate rocker arm positioning and bearing structures.
Innovation Solution
A variable valve mechanism featuring a rocker shaft with first and second rocker arms, where the first rocker arm has recessed portions to restrict movement by the valve stem, and the second rocker arm is positioned by the first rocker arm, eliminating the need for direct contact with the cylinder head and reducing friction, allowing for a compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the high-speed rocker arm abuts against the cylinder head for positioning, then the rocker arm can be restricted from displacement in the arrow C direction, but friction occurs at the contact part and smooth operation of the rocker arm is hindered
Solution Approach 1:
The patent introduces a positioning structure on the rocker shaft that acts as an intermediary element between the rocker arm and the cylinder head. This positioning structure provides the necessary restriction of displacement without requiring direct contact between the rocker arm and cylinder head, thereby eliminating friction at the contact part while maintaining positioning stability.
2Stability of the object's composition
If the cylinder head is increased in width to accommodate the positioning structure and bearing portion, then the rocker arm can be properly positioned and supported, but the engine as a whole is increased in size
Solution Approach 1:
The patent merges the positioning function and the bearing support function into a single integrated positioning structure on the rocker shaft. This structure simultaneously provides positioning for the rocker arm and support for the bearing, eliminating the need for separate structures that would require additional space in the cylinder head, thereby maintaining compact engine size while ensuring accurate positioning.
Data Source
AI summary
A variable valve mechanism for an engine includes: a rocker shaft; a first rocker arm rotatably supported by the rocker shaft, for transmitting displacement of a first cam to a valve; a second rocker arm rotatably supported by the rocker shaft, for transmitting a displacement of a second cam to the valve; and a switching mechanism for switching a transmitting state and a non-transmitting state. The first rocker arm has a pair of first arm portions and a recess portion in which an upper end of the valve is inserted at an end portion of each of the first arm portions. The second rocker arm has a second arm portion disposed between the first arm portions. The first rocker arm is restricted from movement in an axis direction of the rocker shaft when an inner sidewall of the recess portion is in contact with the upper end of the valve. The second rocker arm is restricted from movement in the axis direction when the second arm portion is in contact with the first rocker arm.