Variable valve system of internal combustion engine

Abstract

A variable valve system of an internal combustion engine includes a first mechanism that varies an operation angle of an intake valve in accordance with a conversion actuation force applied thereto and a second mechanism that varies an operation angle of an exhaust valve in accordance with the conversion actuation force applied thereto, wherein the first and second mechanisms force mechanically the intake and exhaust valves to take smaller and larger operation angles respectively when the conversion actuation forces are not applied to the first and second mechanisms respectively.

What is claimed is: 
     
         1 . A variable valve system of an internal combustion engine, comprising:
 an intake valve operation angle varying mechanism that varies an operation angle of an intake valve in accordance with a conversion actuation force applied thereto; and   an exhaust valve operation angle varying mechanism that varies an operation angle of an exhaust valve in accordance with the conversion actuation force applied thereto,   wherein the intake valve operation angle varying mechanism forces mechanically the intake valve to take a smaller operation angle when receiving no conversion actuation force; and   wherein the exhaust valve operation angle varying mechanism forces mechanically the exhaust valve to take a larger operation angle when receiving no conversion actuation force.   
     
     
         2 . A variable valve system of an internal combustion engine as claimed in  claim 1 , further comprising:
 an exhaust valve operation phase varying mechanism that varies an exhaust valve operation phase at the time when the exhaust valve assumes its peak lift,   wherein the exhaust valve operation phase varying mechanism forces mechanically the exhaust valve operation phase to take a retarded side when receiving no conversion actuation force.   
     
     
         3 . A variable valve system of an internal combustion engine as claimed in  claim 1 , further comprising:
 an intake valve operation phase varying mechanism that varies an intake valve operation phase at the time when the intake valve assumes its peak lift,   wherein the intake valve operation phase varying mechanism forces mechanically the intake valve operation phase to take a retarded side when receiving no conversion actuation force.   
     
     
         4 . A variable valve system of an internal combustion engine as claimed in  claim 1 , further comprising:
 an intake valve operation phase varying mechanism that varies an intake valve operation phase at the time when the intake valve assumes its peak lift; and   an exhaust valve operation phase varying mechanism that varies an exhaust valve operation phase at the time when the exhaust valve assumes its peak lift,   wherein the intake and exhaust valve operation phase varying mechanisms force mechanically the intake and exhaust valve operation phases to take a retarded side when receiving no conversion actuation forces respectively.   
     
     
         5 . A variable valve system of an internal combustion engine as claimed in  claim 1 , in which at least one of the conversion actuation forces respectively applied to the intake and exhaust valve operation angle varying mechanisms is a hydraulic force. 
     
     
         6 . A variable valve system of an internal combustion engine as claimed in  claim 1 , in which at least one of the conversion actuation forces respectively applied to the intake and exhaust valve operation angle varying mechanisms is an electric force. 
     
     
         7 . A variable valve system of an internal combustion engine as claimed in  claim 1 , in which one of the conversion actuation forces respectively applied to the intake and exhaust valve operation angle varying mechanisms is a hydraulic force and the other of the conversion actuation forces is an electric force. 
     
     
         8 . A variable valve system of an internal combustion engine as claimed in  claim 1 , in which:
 when receiving the conversion actuation force, the intake valve operation angle varying mechanism forces the intake valve to take an operation angle larger than that taken when receiving no conversion actuation force.   
     
     
         9 . A variable valve system of an internal combustion engine as claimed in  claim 8 , in which:
 when receiving the conversion actuation force, the exhaust valve operation angle varying mechanism forces the exhaust valve to take an operation angle smaller than that taken when receiving no conversion actuation force.   
     
     
         10 . A variable valve system of an internal combustion engine as claimed in  claim 9 , in which:
 the intake and exhaust valve operation angle varying mechanisms selectively vary the respective operation angles of the intake and exhaust valves based on a fact whether or not the conversion actuation forces are applied to the mechanisms respectively.   
     
     
         11 . A variable valve system of an internal combustion engine as claimed in  9 , in which:
 the intake and exhaust valve operation angle varying mechanisms continuously vary the respective operation angles of the intake and exhaust valves in accordance with an operation amount of the conversion actuating forces respectively.   
     
     
         12 . A variable valve system of an internal combustion engine, comprising:
 an intake valve operation angle varying mechanism that varies an operation angle of an intake valve by using a hydraulic force or electric force as a conversion actuation force; and   an exhaust valve operation angle varying mechanism that varies an operation angle of an exhaust valve by using a hydraulic force or electric force as a conversion actuation force;   wherein when receiving no conversion actuation force, the intake valve operation angle varying mechanism forces the intake valve to take and hold an operation angle smaller than that taken when receiving the conversion actuation force, and   wherein when receiving no conversion actuation force, the exhaust valve operation angle varying mechanism forces the exhaust valve to take and hold an operation angle larger than that taken when receiving the conversion actuation force.   
     
     
         13 . A variable valve system of an internal combustion engine as claimed in  claim 12 , further comprising:
 an exhaust valve operation phase varying mechanism that varies an exhaust valve operation phase at the time when the exhaust valve assumes its peak lift,   wherein the exhaust valve operation phase varying mechanism forces mechanically the exhaust valve operation phase to take a retarded side when receiving no conversion actuation force.   
     
     
         14 . A variable valve system of an internal combustion engine as claimed in  claim 12 , further comprising:
 an intake valve operation phase varying mechanism that varies an intake valve operation phase at the time when the intake valve assumes its peak lift,   wherein the intake valve operation phase varying mechanism forces mechanically the intake valve operation phase to take a retarded side when receiving no conversion actuation force.   
     
     
         15 . A variable valve system of an internal combustion engine as claimed in  claim 12 , further comprising:
 an intake valve operation phase varying mechanism that varies an intake valve operation phase at the time when the intake valve assumes its peak lift; and   an exhaust valve operation phase varying mechanism that varies an exhaust valve operation phase at the time when the exhaust valve assumes its peak lift,   wherein the intake and exhaust valve operation phase varying mechanisms force mechanically the intake and exhaust valve operation phases to take a retarded side when receiving no conversion actuation force.   
     
     
         16 . A variable valve system of an internal combustion engine, comprising:
 a first means that varies an operation angle of an intake valve in accordance with a conversion actuation force applied thereto; and   a second means that varies an operation angle of an exhaust valve in accordance with the conversion actuation force applied thereto,   wherein the first means forces mechanically the intake valve to take a smaller operation angle when receiving no first conversion actuation force; and   wherein the second means forces mechanically the exhaust valve to take a larger operation angle when receiving no second conversion actuation force.   
     
     
         17 . In a variable valve system of an internal combustion engine which comprises an intake valve operation angle varying mechanism that varies an operation angle of an intake valve in accordance with a conversion actuation force applied thereto and an exhaust valve operation angle varying mechanism that varies an operation angle of an exhaust valve in accordance with the conversion actuation force applied thereto,
 a method for controlling the variable valve system comprising:   controlling the intake valve operation angle varying mechanism to force mechanically the intake valve to take a smaller operation angle when no conversion actuation force is applied to the intake valve operation angle varying mechanism; and,   controlling the exhaust valve operation angle varying mechanism to force mechanically the exhaust valve to take a larger operation angle when no conversion actuation force is applied to the exhaust valve operation angle varying mechanism.