Variably operated valve system for internal combustion engine

Abstract

A variably operated valve system for an internal combustion engine, a valve stop mechanism ( 11 ) makes at least one of a pair of fulcrum members lost motion to stop open-and-closure drives for one of two engine valves per cylinder and a stop of open-and-closure drives for the one of the engine valves is inhibited, in a case where a lost motion quantity of the valve stop mechanism exceeds a predetermined value (M3).

What is claimed is: 
     
         1 . A variably operated valve system comprising:
 a drive shaft to which a rotation driving force is transmitted from an engine crankshaft and on an outer periphery of which drive cams are disposed;   two swing cams that operate two engine valves per engine cylinder to open against spring forces of respective valve springs;   a transmission mechanism that converts rotation motions of the drive cams into swing motions and transmits the converted swing motions to the respective swing cams;   a pair of swing arms interposed between the respective swing cams and the respective engine valves to operate the respective engine valves to open or close;   a pair of fulcrum members each of which provides a swing fulcrum of each of the swing arms;   a control mechanism that varies a posture of the transmission mechanism to variably control a lift quantity of each of the engine valves;   a valve stop mechanism that makes at least one of the pair of fulcrum members lost motion to stop open-and-closure drives for one of the two engine valves; and   valve stop inhibit means for inhibiting a stop of open-and-closure drives for the one of the engine valves, in a case where a lost motion quantity of the valve stop mechanism exceeds a predetermined value.   
     
     
         2 . A variably operated valve system for an internal combustion engine, comprising:
 drive cams to which a rotational force is transmitted from a crankshaft;   engine valves, two of the engine valves being mounted in each of engine cylinders and each engine valve being biased toward a valve closure direction by means of a spring force of a corresponding one of valve springs;   swing cams that make the respective engine valves open operation against spring forces of valve springs;   a transmission mechanism that converts rotation motions of the drive cams into swing motions and transmits the converted swing motions to the swing cams;   a control mechanism that varies a posture of the transmission mechanism to variably control a lift quantity of each of the engine valves;   a pair of operational members that swing in accordance with the swing motions of the swing cams to operate the respective engine valves to open or close;   a valve stop mechanism that absorbs a swing quantity of one of the pair of operational members to stop open-and-closure operations of one of the two engine valves; and   valve stop inhibiting means for inhibiting an absorption of a swing motion of the valve stop mechanism in a case where the swing quantity of each of the pair of the operational members exceeds a predetermined quantity.   
     
     
         3 . A variably operated valve system for an internal combustion engine, comprising:
 a drive cam rotationally driven through a crankshaft;   a pair of engine valves, each engine valve being biased toward a closure direction by means of a spring force of a valve spring;   a pair of swing cams that swing to drive the pair of engine valves via a pair of operational members;   a transmission mechanism that converts a rotation motion of the drive cam into a swing motion and transmits the converted swing motion to the pair of swing cams;   a control mechanism that varies a posture of the transmission mechanism to vary operation characteristics of the pair of the engine valves; and   a valve stop mechanism disposed on at least one of the pair of operational members to make a lost motion to stop a drive of one of the pair of engine valves, wherein, in a case where a valve lift quantity of one of the pair of engine valves exceeds a predetermined value, an operation of a valve stop through the valve stop mechanism is inhibited.   
     
     
         4 . The variably operated valve system for the internal combustion engine as claimed in  claim 1 , wherein the valve stop mechanism includes: a retaining hole that holds one of the pair of fulcrum members movable; and a basing member that biases the one of the pair of fulcrum members toward a direction of a corresponding one of the pair of swing arms and the lost motion is made by moving the one of the pair of fulcrum members against the biasing member. 
     
     
         5 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein the pair of fulcrum members are hydraulic pressure rush adjusters. 
     
     
         6 . The variably operated valve system for the internal combustion engine as claimed in  claim 1 , wherein the valve stop mechanism is disposed only in one of the pair of fulcrum members and, when the lost motion quantity is equal to or below the predetermined value, only one of the two engine valves corresponding to the one of the pair of fulcrum members is allowed to be stopped through the valve stop mechanism. 
     
     
         7 . The variably operated valve system for the internal combustion engine as claimed in  claim 1 , wherein the valve stop mechanism is disposed in both of the pair of fulcrum members and, when the lost motion quantity is equal to or below the predetermined quantity, both of the two engine valves are allowed to be stopped through the valve stop mechanism. 
     
     
         8 . The variably operated valve system for the internal combustion engine as claimed in  claim 6 , wherein the pair of swing cams are integrally formed. 
     
     
         9 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein the swing fulcrum of each of the pair of each of the pair of swing arms is formed by a spherical recess section disposed on a corresponding one of the pair of swing arms and a spherical convex section engaged with the recess section. 
     
     
         10 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein, when the valve stop inhibiting means mechanically inhibits the lost motion of the one of the pair of fulcrum members when the lost motion quantity exceeds the predetermined value. 
     
     
         11 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein the control shaft includes a control cam that is in an eccentricity state to an axial center of the control shaft, the control cam is inserted through the transmission mechanism, and the posture of the transmission mechanism is varied according to a rotation of the control cam. 
     
     
         12 . The variably operated valve system for the internal combustion engine as claimed in  claim 10 , wherein a limitation of the lost motion is made by a limitation of a movement of the one of the pair of fulcrum members by means of a projection section in a movable range of the one of the pair of fulcrum members. 
     
     
         13 . The variably operated valve system for the internal combustion engine as claimed in  claim 10 , wherein the valve stop inhibit means is constituted by a movement purpose hole and a limitation purpose hole, both of the movement purpose and limitation purpose holes being disposed in the one of the pair of fulcrum members and in an inner wall of the retaining hole, and a limitation pin movably disposed across the movement purpose hole and the limitation purpose hole and a state in which the one of the pair of fulcrum members is in a locked state by disposing the limitation pin across the movement purpose hole and the limitation purpose hole and another state in which the limitation pin is housed in the movement purpose hole to enable the one of the pair of fulcrum members to make the lost motion are controlled. 
     
     
         14 . The variably operated valve system for the internal combustion engine as claimed in  claim 13 , wherein the valve stop inhibiting means includes another biasing member disposed in the movement purpose hole of the one of the pair of fulcrum members to bias the limitation pin toward a direction of the limitation purpose hole and a hydraulic pressure circuit that supplies a hydraulic pressure to press under pressure the limitation pin in another direction of the movement purpose hole of the one of the pair of fulcrum members against the biasing force of the other biasing member. 
     
     
         15 . The variably operated valve system for the internal combustion engine as claimed in  claim 14 , wherein the hydraulic pressure circuit includes: oil passage holes disposed at a bearing section of the control shaft and a communication hole penetrated through a diameter direction of the control shaft to appropriately communicate with the oil passage holes and wherein, when the control shaft is rotated through an angle equal to or below a predetermined rotation angle, both of the oil passage holes and the communication hole are communicated with each other and, when the control shaft exceeds the predetermined rotation angle, the communication between the oil passage holes and communication hole is interrupted. 
     
     
         16 . The variably operated valve system for the internal combustion engine as claimed in  claim 14 , wherein, when the lost motion quantity is smaller than the predetermined value of the lost motion quantity of the one of the pair of fulcrum members, a hydraulic pressure is supplied to move the limitation pin toward the direction of the movement purpose hole against a biasing force of the other biasing member and, when the lost motion quantity exceeds the predetermined value, the biasing force of the other biasing member causes the limitation pin toward the direction of the limitation purpose hole. 
     
     
         17 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein an angle which is a subtraction of 90° from an angle formed between the corresponding one of the pair of swing arms and the one of the pair of fulcrum members when the lost motion quantity of the fulcrum member is at the predetermined value is smaller than an angle formed between the corresponding one of the pair of swing arms and the one of the pair of fulcrum members when the engine valves are open at a time of a maximum lift control. 
     
     
         18 . The variably operated valve system for the internal combustion engine as claimed in  claim 4 , wherein the valve stop inhibiting means includes a limitation member that limits the lost motion by biasing the one of the pair of fulcrum members toward a direction of the corresponding one of the pair of swing arms, when the lost motion quantity of the one of the pair of fulcrum members exceeds the predetermined value. 
     
     
         19 . The variably operated valve system for the internal combustion engine as claimed in  claim 14 , wherein the valve stop inhibiting means includes a valve stop inhibit circuit constituted by a control unit that interrupts the supply of the hydraulic pressure via an electromagnetic switching valve of the hydraulic pressure circuit. 
     
     
         20 . The variably operated valve system for the internal combustion engine as claimed in  claim 19 , wherein the predetermined value of the lost motion quantity can arbitrarily be set according to a driving condition of the engine.