Variable Valve System For Internal Combustion Engine

Abstract

The invention relates to a variable valve system for an internal combustion engine including an electric motor that can be rotated in any one of a normal rotation direction and a reverse rotation direction; a first cam that is driven by the electric motor; a second cam that has a same shape as the first cam, that is driven by the electric motor, and that differs from the first cam in a rotation phase; a first valve that is opened and closed by the first cam; a second valve that is opened and closed by the second cam; and a control unit that controls rotation of the electric motor. Each of the first cam and the second cam is symmetric with respect to a straight line passing a cam center and a cam nose.

1 . A variable valve system for an internal combustion engine, comprising:
 an electric motor that can be rotated in any one of a normal rotation direction and a reverse rotation direction;   a first cam that is driven by the electric motor;   a second cam that has a same shape as the first cam, that is driven by the electric motor, and that differs from the first cam in a rotation phase;   a first valve that is provided to a first cylinder and that is opened and closed by the first cam;   a second valve that is provided to a second cylinder and that is opened and closed by the second cam; and   a control unit that controls rotation of the electric motor, wherein   each of the first cam and the second cam is symmetric with respect to a straight line passing a cam center and a cam nose.   
   
   
       2 . The variable valve system for an internal combustion engine according to  claim 1 , wherein
 the control unit alternately switches a rotation direction of the electric motor between the normal rotation direction and the reverse rotation direction such that the first valve is opened and closed using, from among two ramp portions of the first cam, the ramp portion used to open the first valve when the electric motor is rotated in a given direction, and the second valve is opened and closed using, from among two ramp portions of the second cam, the ramp portion used to close the second valve when the electric motor is rotated in the given direction.   
   
   
       3 . The variable valve system for an internal combustion engine according to  claim 1 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at a start time of an open period of the first valve is higher than the rotation speed at an end time of the open period of the first valve, and the rotation speed at a start time of an open period of the second valve is higher than the rotation speed at an end time of the open period of the second valve.   
   
   
       4 . The variable valve system for an internal combustion engine according to  claim 1 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at an end time of an open period of the first valve is lower than the rotation speed at a start time of the open period of the first valve, and the rotation speed at an end time of an open period of the second valve is lower than the rotation speed at a start time of the open period of the second valve.   
   
   
       5 . The variable valve system for an internal combustion engine according to  claim 1 , further comprising:
 a camshaft used to take air into cylinders or discharge exhaust gas from the cylinders, wherein   the camshaft is driven by the electric motor controlled by the control unit,   the electric motor drives the first cam provided onto the camshaft; and   the electric motor drives the second cam provided onto the camshaft.   
   
   
       6 . A variable valve system for an internal combustion engine, comprising:
 an electric motor that can be rotated in any one of a normal rotation direction and a reverse rotation direction;   multiple cams that are driven by the electric motor;   multiple valves that are provided to take air into cylinders or discharge exhaust gas from the cylinders and that are opened and closed by the respective cams; and   a control unit that controls rotation of the electric motor, wherein   each of the cams is symmetric with respect to a straight line passing a cam center and a cam nose.   
   
   
       7 . The variable valve system for an internal combustion engine according to  claim 6 , wherein
 the control unit alternately switches a rotation direction of the electric motor between the normal rotation direction and the reverse rotation direction such that the cam opens and closes the valve using only one of two ramp portions of the cam.   
   
   
       8 . The variable valve system for an internal combustion engine according to  claim 6 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at a start time of an open period of the valve is higher than the rotation speed at an end time of the open period of the valve.   
   
   
       9 . The variable valve system for an internal combustion engine according to  claim 6 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at an end time of an open period of the valve is lower than the rotation speed at a start time of the open period of the valve.   
   
   
       10 . The variable valve system for an internal combustion engine according to  claim 2 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at a start time of an open period of the first valve is higher than the rotation speed at an end time of the open period of the first valve, and the rotation speed at a start time of an open period of the second valve is higher than the rotation speed at an end time of the open period of the second valve.   
   
   
       11 . The variable valve system for an internal combustion engine according to  claim 2 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at an end time of an open period of the first valve is lower than the rotation speed at a start time of the open period of the first valve, and the rotation speed at an end time of an open period of the second valve is lower than the rotation speed at a start time of the open period of the second valve.   
   
   
       12 . The variable valve system for an internal combustion engine according to  claim 7 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at a start time of an open period of the valve is higher than the rotation speed at an end time of the open period of the valve.   
   
   
       13 . The variable valve system for an internal combustion engine according to  claim 7 , wherein
 the control unit controls a rotation speed of the electric motor such that the rotation speed at an end time of an open period of the valve is lower than the rotation speed at a start time of the open period of the valve.