Valve actuation controlling apparatus and method for engine

Abstract

After commanding an engine to stop, an electronic controller controls a variable working-angle control mechanism to increase the working angle of an intake valve in preparation for restarting of the engine. In the case of an automatic stop, which is followed by restarting of the engine in a relatively short time, the working angle of the intake valve is set to the maximum working angle of the variable working-angle control mechanism, which maximizing decompression. In a manual stop, it is necessary to allow for both hot start and cold start. Also, in the manual stop, a target working angle when the engine is stopped is set less than that of a case of the automatic stop. Thus, the starting characteristic is prevented from being degraded by increased friction of engine parts during a cold start, and knocking is prevented from occurring due to a high compression ratio in a cylinder during a hot start.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to a valve actuation controlling apparatus and method applied to an engine equipped with a variable working-angle control mechanism which varies the working angle of intake valves. [0002] Engines such as vehicle engines are equipped with variable valve mechanisms which vary valve characteristics of intake valves and exhaust valves. Among variable valve mechanisms proposed recently, there are variable valve lift and working-angle control mechanisms which vary valve lifts and working angles of intake and exhaust valves. [0003] Japanese Laid-Open Patent Publications No. 2002-89303 and No. 2002-61522 each disclose a valve actuation controlling apparatus that presets the valve actuation of intake valves to be suitable for securing engine starting characteristics immediately before the engine stops, thereby preparing for a next engine start. As shown in FIG. 8, immediately before the engine stops, that is after commanding th...

AI Technical Summary

Benefits of technology

[0006] Accordingly, it is an objective of the present invention to provide valve actuation controlling apparatus and method that improve engine starting characteristics.

Problems solved by technology

However, the above setting of the valve actuation of intake valves does not always ensure proper engine starting characteristics depending on engine starting conditions.

For example, during a very cold start in which engine parts encounter high friction, working angle θ that is less than that of idling may result in a shortage of intake air, making it impossible to generate sufficient torque to counteract the increased friction.

On the other hand, an attempt to intensify air flow in the cylinder will cause heat from friction between air and the intake valve, etc. to raise compression end temperature (temperature at the top dead center) of the air drawn into the cylinder, increasing the likelihood of knocking during a hot start.

Thus, reducing the lift and working angle θ of the intake valves immediately before the engine stops do not always ensure proper engine starting characteristics.

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