Variable Valve Timing Groove Layout for Oil Leakage Control
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Solution Overview
Problem
Existing variable valve timing systems face challenges with oil leakage along the oil path from the oil control valve to the variable valve device, particularly due to high hydraulic pressure requirements for advancing the camshaft, which affects the stability and efficiency of the system.
Innovation Solution
A hydraulically controlled variable valve timing system with a camshaft featuring an advance groove, a retard groove, and an accommodation groove on its bearing surface, where the advance groove is positioned between the retard groove and the accommodation groove, generating counter hydraulic pressure to suppress oil leakage and maintain stable operation, even if some oil leaks from the retard groove.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil is supplied to the variable valve device through the camshaft, then the variable valve device can be actuated, but oil leakage occurs from between the camshaft and bearing
Solution Approach 1:
The bearing surface is segmented into multiple grooves (advance groove, retard groove, accommodation groove) that are positioned at different locations. This segmentation allows the oil path to be divided into separate channels, preventing oil leakage by containing the oil flow within specific grooves rather than allowing it to escape from the camshaft-bearing interface.
2Force
If higher hydraulic pressure is applied to advance the camshaft, then the variable valve device can overcome oil leakage, but oil leakage increases from the advance groove
Solution Approach 1:
The accommodation groove acts as an intermediary structure that receives the thrust stopper. This groove provides a dedicated space for the thrust stopper to contact the bearing surface, creating a mechanical stop that prevents excessive axial movement of the camshaft. This intermediary structure allows the system to use higher hydraulic pressure for advancing the camshaft without causing oil leakage, as the thrust stopper confines the pressure within the accommodation groove rather than allowing it to escape through the advance groove.
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 ensures stable operation of the variable valve device by suppressing oil leakage and maintaining appropriate hydraulic pressure, allowing the system to function effectively despite the higher hydraulic pressure required for advancing the camshaft.
Implementation Method 1
a variable valve device configured to advance or retard the camshaft by a hydraulic pressure
Implementation Method 2
an oil control valve configured to control the hydraulic pressure with respect to the variable valve device
Data Source
AI summary
There is provided a variable valve timing system, including: a camshaft rotatably supported by a support wall of an engine; a variable valve device configured to advance or retard the camshaft by a hydraulic pressure; and an oil control valve. A thrust stopper is formed on an outer peripheral surface of the camshaft. A bearing surface of the support wall is formed with an advance groove through which oil for advancing the camshaft is to pass, a retard groove through which oil for retarding the camshaft is to pass, and an accommodation groove configured to accommodate the thrust stopper. At the bearing surface, the retard groove is positioned on one wall surface side of the support wall, the accommodation groove is positioned on the other wall surface side of the support wall, and the advance groove is positioned between the retard groove and the accommodation groove.