Middle phase continuously variable valve timing system with intermediate lock pin and cam torque response control and method thereof

Abstract

A method of controlling an intermediate lock pin and cam torque response for a continuously variable valve timing system with is disclosed. The method includes entering a cam phaser control mode for controlling the middle phase CVVT when an engine starts, or performing lock pin chattering of a lock pin locking a cam at a middle position which is between an advanced position and a retarded position, by an oil pressure. A cam torque response control mode for controlling the middle phase CVVT is entered. The lock pin chattering occurs due to an intermittent oil flow supplying to the lock pin.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority to Korean Patent Application No. 10-2014-0078259, filed on Jun. 25, 2014 which is incorporated herein by reference in its entirety.TECHNICAL FIELD[0002]The present disclosure relates to a continuously variable valve timing system, and more particularly, relates to a middle phase continuously variable valve timing system with intermediate lock pin and cam torque response control.BACKGROUND[0003]Due to increasing demand for fuel efficiency improvement, exhaust gas reduction, low-speed torque increase, and output improvement, there is a need to improve performance of a continuously variable valve timing system (CVVT) or camshaft phaser system capable of optimally controlling intake / exhaust valve opening and closing timing thereof according to an engine revolutions per minute (RPM).[0004]To improve the performance of the conventional CVVT, a middle phase CVVT has been developed to reduce a syste...

AI Technical Summary

Benefits of technology

The present invention is directed to a middle phase continuously variable valve timing (CVVT) system with intermediate lock pin and cam torque response control. The invention aims to reduce the delay in unlocking the lock pin in response to a rapidly changing condition, such as an open loop response time at high engine speed and low oil temperature. The invention achieves this by using two control modes, namely, a cam phaser control mode and a cam torque response control mode. The cam torque response control mode rapidly unlocks the lock pin prior to the cam phaser control mode to ensure quick response to the changing condition. The execution condition may also include an open loop response time at high engine speed for emission effect.

Problems solved by technology

However, the middle phase CVVT maintains a cam middle phase by using a lock pin, and therefore, a delay of unlocking [locking→unlocking] of the lock pin may occur.

For example, the lock pin needs to be rapidly unlocked at all times when controlling the middle phase CVVT, but the unlocking of the lock pin is delayed under a specific condition that an engine RPM is reduced to about 500 RPM to 1000 RPM and an engine oil temperature is about 110° C. to 130° C., and thus, a response delay occurs.

The response delay of the lock pin mainly occurs when the middle phase CVVT is controlled under the condition of an open loop response time (OLRT) at 100° (crank angle) / sec after an engine initiates, thus decreasing efficiency of emission effect which reduces harmful substances.

The middle phase CVVT is regulated to satisfy operation functions at an oil temperature of −10° C. to 130° C. and an engine RPM equal to or more than 500 RPM, such that the response delay of the lock pin under specified low-speed and high-temperature conditions may reduce reliability of the operational performance of the middle phase CVVT.

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