Variable valve device and control method thereof

Abstract

A variable valve device has a hydraulic actuator that implements discharge of operating oil in a pressure chamber and a hydraulic control valve that controls supply and discharge of the operating oil to and from the hydraulic actuator by opening and closing, thereby preventing the closing movement of the intake valve. After a signal that closes the hydraulic control valve in a current engine control cycle is output at a prescribed crank angle, the crank angle of a crankshaft, when surge pressure in the pressure chamber has exceeded a prescribed threshold value resulting from closing of the hydraulic control valve, is determined, and at least either an output crank angle or a waveform of the signal that closes the hydraulic control valve is corrected based on the operation start crank angle, and the corrected signal is output to the hydraulic control valve in a next control cycle.

1 . A hydraulically driven variable valve device that has a valve train that opens or closes an intake port by moving an intake valve of an engine, and varies a crank angle at which the intake port is fully closed by the valve train,
 the valve device comprising:   a hydraulic actuator that is activated by movement of the intake valve and discharges, using a closing movement of the intake valve, operating oil in a pressure chamber provided in a cylinder;   a hydraulic control valve that controls supply and discharge of operating oil to and from the hydraulic actuator by opening and closing, and prevents outflow of the operating oil from a pressure chamber of the hydraulic actuator when closing is implemented, thereby preventing the closing movement of the intake valve;   a crank angle detection sensor that detects a crank angle indicating an angle of rotation of the engine crankshaft;   a TDC detection sensor that detects that each cylinder of the engine has reached a top dead center (TDC);   hydraulic pressure detecting means that detects hydraulic pressure of the pressure chamber of the hydraulic actuator; and   a controller that stops, during implementation of the closing movement of the intake valve, the closing movement of the intake valve and outputs a signal that closes the hydraulic control valve in order to maintain an open state of the intake port at a prescribed opening for a prescribed amount of time when a prescribed crank angle is determined to have been reached based on a detection signal from the TDC detection sensor and a detection signal from the crank angle detection sensor, wherein   after outputting a signal that closes the hydraulic control valve at the prescribed crank angle in a current control cycle, the controller monitors hydraulic surge pressure of the pressure chamber resulting from closing of the hydraulic control valve in use of a detection signal of the hydraulic pressure detecting means, determines an operation start crank angle of the hydraulic control valve based on the surge pressure, corrects at least either an output crank angle or waveform of a signal that closes the hydraulic control valve based on the operation start crank angle, and outputs the corrected signal to the hydraulic control valve in a next control cycle.   
     
     
         2 . The variable valve device according to  claim 1 , wherein the controller corrects at least either the output crank angle or waveform of the signal that closes the hydraulic control valve so that the crank angle, at which the intake port is fully closed when the closing movement of the intake valve is completed, is within a prescribed range after the signal that closes the hydraulic control valve is switched off. 
     
     
         3 . A control method for a variable valve device that varies a crank angle at which an intake port is fully closed by opening or closing the intake port by moving an intake valve of an engine by a valve train, and activating a hydraulic actuator by moving the intake valve, and moreover preventing outflow of operating oil from a pressure chamber provided in a cylinder of the hydraulic actuator by a variable valve device,
 the method comprising:   in a current control cycle,   implementing discharge of the operating oil in the pressure chamber of the hydraulic actuator by activating the hydraulic actuator by closing movement of the intake valve;   closing a hydraulic control valve that controls supply and discharge of the operating oil to and from the hydraulic actuator when a crank angle reaches a prescribed angle during closing movement of the intake valve after each cylinder of an engine reaches a top dead center, and preventing outflow of the operating oil from the pressure chamber, thereby preventing closing movement of the intake valve;   stopping the closing movement of the intake valve by closing the hydraulic control valve for a prescribed amount of time, and maintaining an open state of the intake port at a prescribed opening for a prescribed amount of time;   monitoring surge pressure of hydraulic pressure of the pressure chamber resulting from prevention of outflow of the operating oil from the pressure chamber, and determining timing of the start of actual variable valve actuation (VVA) based on the surge pressure,   correcting at least either an output crank angle or a waveform of a signal that closes the hydraulic control valve based on the actual VVA starting timing; and   outputting the corrected signal to the hydraulic control valve in a next control cycle.   
     
     
         4 . The control method for a variable valve device according to  claim 3 , comprising:
 comparing the actual VVA starting timing with a preset prescribed VVA starting timing; and   carrying out, when the actual VVA starting timing comes after the prescribed VVA starting timing, at least either correction in which an output crank angle of the signal that closes the hydraulic control valve of the next control cycle is made to be earlier than the current output crank angle, or correction in which an output value of the signal that closes the hydraulic control valve of the next control cycle is made to be larger than the current output value, while on the other hand,   carrying out, when the actual VVA starting timing comes before the prescribed VVA starting timing, at least either correction in which the output crank angle of the signal that closes the hydraulic control valve of the next control cycle is made to be later than the current output crank angle, or correction in which the output value of the signal that closes the hydraulic control valve of the next control cycle is made to be smaller than the current output value, is carried out.   
     
     
         5 . The control method for a variable valve device according to  claim 3 , comprising:
 comparing the actual VVA starting timing with the preset prescribed VVA starting timing; and   carrying out, when the actual VVA starting time comes after the prescribed VVA starting timing, at least either correction in which, an output time of the signal that closes the hydraulic control valve of the next control cycle is made to be longer than the current output time and an output crank angle is made to be earlier than the current output crank angle, or correction in which the output time of the signal that closes the hydraulic control valve of the next control cycle is made to be longer than the current output time and an output value is made to be larger than the current output value, while on the other hand,   carrying out, when the actual VVA starting timing comes before the prescribed VVA starting timing, at least either correction in which the output time of the signal that closes the hydraulic control valve of the next control cycle is made to be shorter than the current output time and the output crank angle is made to be later than the current output crank angle, or correction in which the output time of the signal that closes the hydraulic control valve of the next control cycle is made to be shorter than the current output time and the output value is made to be smaller than the current output value.