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.

What is claimed is: 
     
         1 . A method of controlling an intermediate lock pin and cam torque response for a middle phase continuously variable valve timing (CVVT) system, the method comprises steps of:
 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 a position between an advanced position and a retarded position, by an oil pressure; and   entering a cam torque response control mode for controlling the middle phase CVVT,   wherein the lock pin chattering occurs due to an intermittent oil flow supplying to the lock pin.   
     
     
         2 . The method of  claim 1 , wherein the intermittent oil flow is formed by intermittently turning on/off an oil-flow control valve (OCV) which controls the oil. 
     
     
         3 . The method of  claim 1 , wherein the cam torque response control mode is entered when a target value of the cam is the same as a current value of the cam and the cam phaser control mode is entered when the target value of the cam is different from the current value of the cam. 
     
     
         4 . The method of  claim 3 , wherein an execution condition of the cam torque response control mode includes an engine revolutions per minute (RPM) of 500 to 1000 RPM and an oil temperature of 110° C. to 130° C. 
     
     
         5 . The method of  claim 4 , wherein the execution condition of the cam torque response control mode further includes an open loop response time (OLRT) at 100° (crank angle)/sec for an emission effect. 
     
     
         6 . The method of  claim 1 , wherein the cam torque response control mode is executed by steps of:
 determining whether an unlocking of the lock pin is delayed by a first fast unlocking condition;   determining whether the lock pin chattering is performed by a second fast unlocking condition after the delay of unlocking the lock pin is determined; and   performing the lock pin chattering by controlling the cam torque response when controlling the middle phase CVVT.   
     
     
         7 . The method of  claim 6 , wherein the first fast unlocking condition includes an oil temperature, an engine RPM, and a voltage. 
     
     
         8 . The method of  claim 7 , wherein determination conditions of the first fast unlocking includes oil temperature>TH — 0 (oil temperature threshold), engine RPM<TH_R (engine RPM threshold), and voltage<TH_L (voltage threshold), and the unlocking delay of the lock pin is determined when all the determination conditions are satisfied. 
     
     
         9 . The method of  claim 8 , wherein the oil temperature is 110° C. to 130° C., the engine RPM is 500 RPM to 1000 RPM, and the voltage is a voltage of an oil-flow control valve (OCV) controlling the oil of the middle phase CVVT. 
     
     
         10 . The method of  claim 8 , further comprising a step of:
 terminating the unlocking delay determination of the lock pin and entering the cam phaser control mode for performing the control of the middle phase CVVT when any one of the determination condition of the oil temperature, the determination condition of the engine RPM, and the determination condition of the voltage is not satisfied.   
     
     
         11 . The method of  claim 6 , further comprising steps of:
 determining the lock pin chattering when a negative cam torque is generated and an intake valve opens; and   dividing the oil temperature into a first oil temperature of a region of 110° C. and a second oil temperature of a region of 130° C., and performing the lock pin chattering at the first oil temperature and the second oil temperature, respectively,   wherein the second fast unlocking condition includes crank signal synchronization, an opening timing determination of the intake valve for each cylinder, a cam torque determination, an oil temperature check, and a cam torque phase determination.   
     
     
         12 . The method of  claim 11 , further comprising a step of:
 terminating the lock pin chattering and entering the cam phaser control mode for immediately performing the control of the middle phase CVVT when a positive cam torque is generated and the intake valve closes.   
     
     
         13 . The method of  claim 6 , wherein in the cam torque response control, the lock pin chattering is a pulse width modulation (PWM) duty signal supplied to an OCV, in which the PWM duty signal is divided into a first oil temperature of a region of 110° C. and a second oil temperature of a region of 130° C. under the second fast unlocking condition, and an output of the PWM duty signal is generated at a negative cam torque phase when the intake valve opens under the second fast unlocking condition. 
     
     
         14 . A middle phase continuously variable valve timing (CVVT) system, the system comprising:
 a controller configured to control a middle phase CVVT when an engine runs, the controller including: a cam torque sensor, a cam phaser control determiner, a cam torque control determiner, and a cam phaser controller,   wherein the cam torque sensor is configured to use a crank signal, a cooling water temperature, an oil-flow control valve (OCV) voltage as a cam torque sensing data, configured to detect a cam torque phase by a negative cam torque generated when an intake valve opens and a positive cam torque generated when the intake valve closes, and configured to output a negative cam torque signal to the cam phaser controller,   the cam phaser control determiner is configured to use a difference between a target value of a cam and a current value of the cam calculated based on the cam torque as a cam phaser control data and configured to output the signal based on the difference between the target value of the cam and the current value of the cam to the cam phaser controller,   the cam torque control determiner is configured to use an oil temperature for oil temperature data, is configured to divide the oil temperature into a first oil temperature and a second oil temperature, and configured to output the divided oil temperature to the cam phaser controller, and   the cam phaser controller configured to output a pulse width modulation (PWM) duty signal generated by the first oil temperature and the second oil temperature when the cam torque phase is a negative phase and configured to output the PWM duty signal to the OCV controlling an oil of the middle phase CVVT.   
     
     
         15 . The middle phase CVVT system of  claim 14 ,
 wherein the OCV is connected to an oil pressure circuit, and the oil pressure circuit is connected to the cam which controls an intake valve and an exhaust valve,   the oil pressure circuit is provided with a lock pin locking the cam at a middle position between a most retarded position and a most advanced position, and   lock pin chattering is generated in the lock pin by repeatedly turning on/off the OCV by the PWM duty signal.   
     
     
         16 . The middle phase CVVT system of  claim 15 , wherein the OCV controls the oil at an oil temperature of −10° C. to 130° C. and an engine RPM equal to or more than 500 RPM. 
     
     
         17 . The middle phase CVVT system of  claim 14 , wherein the cam torque sensor, the cam phaser control determiner, and the cam torque control determiner are integrated into a single block so that each output line is connected to the cam phaser controller. 
     
     
         18 . The middle phase CVVT system of  claim 14 , wherein the controller is an engine control unit (ECU) controlling the engine. 
     
     
         19 . The middle phase CVVT system of  claim 14 , wherein the first oil temperature is in a region of 110° C., and the second oil temperature is in a region of 130° C. 
     
     
         20 . A non-transitory computer-readable recording medium comprising computer executable instructions which cause a controller to perform the method according to  claim 1 .