(a) Field of Invention
The present invention relates to a continuously variable valve timing device, and more particularly, to a continuously variable valve timing device that maintains internal pressure of an electric variable valve timing mechanism cover partitioned by a seal ring, at atmospheric pressure to preserve function and durability of the seal ring, and prevent malfunction of an electricity driven motor.
(b) Description of Related Art
In general, an internal combustion engine is an apparatus that generates power by suctioning air and fuel from the exterior of a vehicle, and combusting fuel in a combustion chamber, and has an intake valve configured to suction air and fuel into the combustion chamber, and an exhaust valve configured to discharge explosion gas combusted in the combustion chamber, and the intake and exhaust valves are opened and closed in conjunction with rotation of a camshaft.
Optimum opening and closing timing of the intake and exhaust valves may be varied based on an engine revolution per minute (RPM), an engine load, and the like. Therefore, a technology, which properly controls valve timing based on a driving state of the engine by having a displacement within a set range without definitely setting the rotation of the camshaft based on rotation of a crankshaft, has been developed, and this technology is referred to as a variable valve timing (VVT) device. In addition, the continuously variable valve timing (CVVT) device is a type of variable valve timing device, and has a configuration that may control valve timing with an arbitrary value within a predetermined displacement.
The continuously variable valve timing device includes a cam sprocket connected to the camshaft to rotate the camshaft, an electric variable valve timing mechanism connected with the cam sprocket and driven by a motor, a chain cover configured to protect the cam sprocket and a chain system from foreign substances, an electric variable valve timing mechanism cover configured to protect the electric variable valve timing mechanism from foreign substances, a seal ring mounted between the electric variable valve timing mechanism and the electric variable valve timing mechanism cover, and partitions an internal space of the electric variable valve timing mechanism cover to block oil from flowing toward a brush of a connector installed on a slip ring of the electric variable valve timing mechanism and the electric variable valve timing mechanism cover, and a rubber plug mounted in a mounting aperture formed within the electric variable valve timing mechanism cover to prevent an inflow of foreign substances such as moisture and dust.
However, in the aforementioned continuously variable valve timing device in the related art, pressure in the internal space of the electric variable valve timing mechanism cover may be varied due to a variation in temperature of the engine and due to an oil seal structure that seals a contact portion of a rotating body, a seal line of the seal ring may be damaged when pressure increases due to the variation in pressure, durability such as an increase in frictional force of the oil seal may occur pressure is reduced, oil may flow from the engine side through a gap in the damaged seal ring, and as a result, a malfunction may occur on the motor that drives the electric variable valve timing mechanism.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.