Controller of variable valve actuator

Abstract

The present invention provides a variable valve mechanism control device that is capable of reducing the power consumption and rating of an electric motor by allowing camshaft rotary inertia torque to reduce spring reaction force during a valve lift. Camshaft rotary inertia force is increased to a value not smaller than a predetermined value before the start of a valve lift. During the time interval between the instant at which the valve lift starts and the instant at which the maximum lift is provided, the spring reaction force of a valve spring is used as deceleration torque for the camshaft rotary inertia force. During the time interval between the instant at which the maximum lift is provided and the instant at which the valve lift terminates, the spring reaction force is used as acceleration torque for the camshaft rotary inertia force. The camshaft rotary inertia force cancels the spring reaction force so that motor torque generated during a valve lift is composed of counter-friction torque only.

1 . A variable valve mechanism control device for an internal combustion engine, comprising:
 a camshaft on which a cam is mounted to drive a valve that is biased by a valve spring;   an electric motor which rotationally drives the camshaft; and   control means for exercising drive control over the electric motor;   wherein the control means controls the rotary inertia force of the camshaft so as to be equal to or more than a predetermined value at the beginning of a valve lift so that the rotary inertia force cancels the spring reaction force of the valve spring.   
   
   
       2 . The variable valve mechanism control device according to  claim 1 , wherein the control means controls the rotational position of the electric motor so that the rotation speed of the camshaft is decreased by the spring reaction force exerted during the time interval between the instant at which a valve lift starts and the instant at which the maximum lift position is reached, and that the rotation speed of the camshaft is increased by the spring reaction force exerted during the time interval between the instant at which the maximum lift position is reached and the instant at which the valve lift terminates. 
   
   
       3 . The variable valve mechanism control device according to  claim 1 , wherein the control means employs the spring reaction force exerted during the time interval between the instant at which the valve lift starts and the instant at which the maximum lift position is reached as deceleration torque for the rotary inertia force, while employing the spring reaction force exerted during the time interval between the instant at which the maximum lift position is reached and the instant at which the valve lift terminates as acceleration torque for the rotary inertia force. 
   
   
       4 . The variable valve mechanism control device according to  claim 1 , wherein, when the rotary inertia force exerted at the end of the valve lift is smaller than the predetermined value, the control means requires during a cam base circle slide to the electric motor to generate such torque that causes said rotary inertia force to be equal to or more than the predetermined value. 
   
   
       5 . The variable valve mechanism control device according to  claim 1 , wherein the control means inhibits the electric motor to generate torque opposing the spring reaction force and requires the electric motor to generate only torque opposing the friction of the cam and valve during a valve lift. 
   
   
       6 . The variable valve mechanism control device according to  claim 1 , further comprising:
 engine speed change means which raises an engine speed to a value equal to or more than a predetermined value when a requested engine output value is equal to or more than a predetermined value and the engine speed is in a low rotation speed region where the engine speed is equal to or lower than the predetermined value.   
   
   
       7 . The variable valve mechanism control device according to  claim 1 , further comprising:
 an inertia force increase member which is installed in a cam drive system having the camshaft and the electric motor to increase the camshaft rotary inertia force;   wherein the inertia force increase member adjusts the enlargement range for an actual operating angle in a low rotation speed region where an engine speed is equal to or lower than a predetermined value.   
   
   
       8 . The variable valve mechanism control device according to  claim 1 , further comprising:
 an inertia force change mechanism which can change the camshaft rotary inertia force when the operating angle of the valve is to be changed within a low rotation speed region where an engine speed is equal to or lower than a predetermined value.   
   
   
       9 . The variable valve mechanism control device according to  claim 1 , wherein, when the cam is to be driven from a stopped state, the control means requires the electric motor to generate such torque that causes the rotary inertia force to be equal to or more than a predetermined value during a cam base circle slide before the start of a valve lift. 
   
   
       10 . The variable valve mechanism control device according to  claim 1 , wherein, when the cam is to be driven from a stopped state, the control means requires the electric motor to generate such torque that causes the rotary inertia force to reach a predetermined initial value during a cam base circle slide before the start of a valve lift, and then requires the electric motor to generate such torque that causes the rotary inertia force at the end of the valve lift to reach a predetermined value greater than the predetermined initial value. 
   
   
       11 . The variable valve mechanism control device according to  claim 1 , wherein, when the cam is to be driven in a normal rotation direction, the control means changes the rotation speed of the camshaft during a cam base circle slide in accordance with an engine speed so that the rotation of the camshaft synchronizes with the rotation of a crankshaft. 
   
   
       12 . A variable valve mechanism control device for an internal combustion engine, comprising:
 a camshaft on which a cam is mounted to drive a valve that is biased by a valve spring;   an electric motor which rotationally drives the camshaft; and   control means for exercising drive control over the electric motor;   wherein the control means controls the rotational position of the electric motor so that the cam rotation speed during a valve lift is equal to or lower than the cam rotation speed during a cam base circle slide.   
   
   
       13 . The variable valve mechanism control device according to  claim 1 , wherein the control means increase the rotary inertia force to a value equal to or more than a predetermined value by imparting torque of the electric motor during a cam base circle slide so as to swingingly drive the cam, and then synchronizes the rotation of the camshaft with the rotation of a crankshaft. 
   
   
       14 . The variable valve mechanism control device according to  claim 13 , further comprising:
 startup request acquisition means for acquiring a startup request for the internal combustion engine;   wherein the control means changes the period for swingingly driving the cam to increase the rotary inertia force in compliance with the startup request acquired by the startup request acquisition means.   
   
   
       15 . The variable valve mechanism control device according to  claim 14 , wherein the control means includes judgment means for determining the degree of requested acceleration indicated by the startup request, applies the torque of the electric motor only during a cam base circle slide if the degree of requested acceleration is smaller than a predetermined value, and applies the torque of the electric motor not only during a cam base circle slide but also during a valve lift if the degree of requested acceleration is equal to or more than the predetermined value. 
   
   
       16 . A variable valve mechanism control device for an internal combustion engine, comprising:
 a camshaft on which a cam is mounted to drive a valve that is biased by a valve spring;   an electric motor which rotationally drives the camshaft; and   a control unit for exercising drive control over the electric motor;   wherein the control unit controls the rotary inertia force of the camshaft so as to be equal to or more than a predetermined value at the beginning of a valve lift so that the rotary inertia force cancels the spring reaction force of the valve spring.   
   
   
       17 . A variable valve mechanism control device for an internal combustion engine, comprising:
 a camshaft on which a cam is mounted to drive a valve that is biased by a valve spring;   an electric motor which rotationally drives the camshaft; and   a control unit for exercising drive control over the electric motor;   wherein the control unit controls the rotational position of the electric motor so that the cam rotation speed during a valve lift is equal to or lower than the cam rotation speed during a cam base circle slide.