Variable Valve Mechanism Cylinder Head Height Reduction
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Solution Overview
Problem
Conventional variable valve mechanisms have a large overall height due to the placement of the control shaft above the camshaft, leading to increased cylinder head height.
Innovation Solution
A variable valve mechanism with a rocker shaft parallel to the camshaft, featuring a main arm, cam arm, control cam, and displacement member that changes the relative phase between the arms by varying the distance from the shaft center, reducing overall height by minimizing the need for additional vertical space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control shaft is placed above the camshaft, then the variable valve mechanism can function properly, but the overall height of the cylinder head increases
Solution Approach 1:
The control shaft is repositioned from a vertical arrangement (above the camshaft) to a horizontal arrangement (parallel to the camshaft). This dimensional change allows the variable valve mechanism to maintain its functionality while reducing the vertical space required in the cylinder head, thereby solving the contradiction between mechanism reliability and compactness.
Solution Approach 2:
The variable valve mechanism components (control cam, displacement member, main arm, cam arm) are nested within the existing cylinder head structure alongside the camshaft and valve train. This nesting arrangement allows the control shaft to be positioned parallel to the camshaft rather than above it, reducing overall height while maintaining all necessary functional relationships between components.
2Length of stationary object
If the control shaft is positioned parallel to the camshaft, then the overall height is reduced, but the mechanism complexity increases
Solution Approach 1:
The control cam on the control shaft performs multiple functions: it controls the displacement member to adjust valve lift, and its varying radius profile automatically provides the necessary phase displacement between the main arm and cam arm. This multi-functionality reduces the need for additional separate components, thereby managing complexity while achieving compact dimensions.
Solution Approach 2:
The functions of controlling valve lift and adjusting timing phase are merged into a single control cam structure. The control cam's varying radius profile simultaneously controls both the displacement of the valve mechanism and the relative phase between arms, reducing the number of separate control components needed and managing overall system complexity.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
The present invention provides a variable valve mechanism (10) which includes a camshaft (12) having a drive cam (14), a rocker shaft (25), and a variable mechanism (30) that is provided on the rocker shaft (25), and that changes an opening/closing amount of the valve (13). The variable mechanism (30) includes a main arm (35) that engages with the drive cam (14), a cam arm (40) that has a cam surface (41) pressing the valve (13), a control cam (31) that has an outer peripheral surface (32) whose distance from a shaft center (26) of the rocker shaft (25) varies gradually, and a displacement member (48) whose distance from the shaft center (26) is changed by turning of the control cam (31). A relative phase between the main arm (35) and the cam arm (40) is displaced as the distance between the displacement member (48) and the shaft center (26) changes.