Chain Cover Rigidity for Variable Valve Timing
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Solution Overview
Problem
Conventional internal combustion engines with variable valve timing mechanisms experience decreased support rigidity due to vibrations, as the surface rigidity of the cover member at the mount attachment portion is compromised, leading to potential vibrations and reduced engine stability.
Innovation Solution
The design incorporates a chain cover with a bulging mount attachment portion and a recessed exhaust side wall, along with a step portion, to enhance the surface rigidity and absorb vibrations, while maintaining the responsiveness of the variable valve devices by adjusting the dimensions and vane configurations of the intake and exhaust variable valve devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat cover member is used with the mount attachment portion, then the manufacturing is simple, but the surface rigidity at the attachment position decreases and vibration occurs
Solution Approach 1:
The cover member is designed with a curved outer peripheral surface instead of a flat surface. Specifically, the outer peripheral surface is curved in the radial direction of the camshaft, creating a bulging shape that provides structural reinforcement. This curvature increases the surface rigidity at the mount attachment portion while maintaining manufacturing feasibility through standard forming processes.
2Length of moving object
If the exhaust variable valve device is positioned closer to the engine main body, then the exhaust camshaft length is reduced, but the exhaust side wall portion must be recessed which complicates the structure
Solution Approach 1:
The exhaust side wall portion is designed to be recessed in the axial direction of the camshaft, creating a stepped structure. This dimensional change allows the exhaust variable valve device to be positioned closer to the engine main body, reducing the exhaust camshaft length, while the recessed wall portion provides the necessary structural support and mounting surface.
3Device complexity
If the intake and exhaust variable valve devices are positioned at the same axial location, then the layout is simple, but the mount attachment portion surface rigidity decreases
Solution Approach 1:
The intake and exhaust variable valve devices are positioned asymmetrically along the camshaft axis. The exhaust variable valve device is positioned closer to the engine main body than the intake variable valve device. This asymmetric arrangement, combined with the curved outer peripheral surface, creates structural reinforcement at the mount attachment portion while maintaining a relatively simple overall layout.
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 increases the support rigidity of the engine by suppressing vibrations at the mount attachment portion and maintaining the operational efficiency of the variable valve timing mechanism, even with shorter exhaust camshaft dimensions.
Implementation Method 1
the surface rigidity of the cover member at the attachment position of the mount attachment portion may decrease, the mount attachment portion may be likely to vibrate due to the vibration of the engine
Implementation Method 2
The intake side actuator and the exhaust side actuator are operated by an operating fluid supplied from a hydraulic control valve to change rotation phases of the intake cam shaft and the exhaust cam shaft with respect to a crankshaft
Data Source
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AI summary
A chain cover 20 with a mount attachment portion 21 includes an intake side wall portion 20A facing an intake variable valve device 15 and an exhaust side wall portion 20B facing an exhaust variable valve device 16. A right end surface of the exhaust variable valve device facing the chain cover 20 is located to be closer to an engine main body 2 than that of the intake variable valve device. The exhaust side wall portion of the chain cover is recessed to be closer to the engine main body than the intake side wall portion is. The mount attachment portion is provided on the intake side wall portion, the exhaust side wall portion, and a step portion 20C connecting therebetween.