Variable valve opening for an internal combustion engine

Abstract

An intake or exhaust valve for an internal combustion engine has a rocker arm with a pivot between its ends, one end of which is engaged by the pushrod, and the other end engages the valve stem. An adjustable stop has two positions for the rocker arm pivot; a rest position where there is no movement of the pivot, and an upper lock position where the pivot moves in response to the pushrod, and there is a reduction in the opening of the valve. A progressive rate spring compresses as the pivot moves towards the upper lock position, thereby modulating valve opening for relatively slow start (or stop) of valve stroke with accelerating (or decelerating stroke), as the progressive rate spring compresses (or expands). Relatively thinner and thicker Belleville springs are used in series to produce a progressive rate spring. The lock position of the pivot elevated above the rest position is determined by a hydraulic block trapping oil in a closed chamber. One or more intermediate lock positions can be provided by varying the available volume of the closed chamber. An inner sleeve is rotated to obstruct one or more holes for fluid passage and an outer sleeve moves longitudinally to hit hydraulic block when an end passes the highest of such holes.

What is claimed is:  
     
         1 . An internal combustion engine having intake and exhaust valves comprising: 
 a pushrod;    a rocker arm having a pivot between its ends and having one end engaged by the pushrod;    a valve stem engaging the other end of the rocker arm;    an adjustable stop having at least two positions for the rocker arm pivot, a lock position elevated above a rest position; and    a progressive rate spring which is deformed before the pivot reaches the lock position, a first portion of the stroke of the spring being smoothly continuous with a relatively lower force/displacement slope and a second portion of the stroke of the spring being smoothly continuous with a relatively higher force/displacement slope    
     
     
         2 . An internal combustion engine according to  claim 1  wherein the lock position comprises a hydraulic block.  
     
     
         3 . An internal combustion engine according to  claim 1  wherein the lock position is enabled by rotation.  
     
     
         4 . An internal combustion engine according to  claim 1  wherein the adjustable stop comprises: 
 an at least partially hollow member on which the rocker arm pivot is free to slide;  
 an outer sleeve engaging the rocker arm pivot and free to slide on the outside of the member;  
 an annular chamber between the outside of the member and the inside of the outer sleeve;  
 a hole through a wall of the member between the inside of the member and the annular chamber; and  
 an obstruction which permits flow or blocks flow through the hole.  
 
     
     
         5 . An internal combustion engine according to  claim 4  wherein the obstruction comprises an inner sleeve in the member with an end portion adjacent to the hole and the end portion configured to either open or close the hole.  
     
     
         6 . An internal combustion engine according to  claim 1  further comprising an additional lock position between the lock position and the rest position.  
     
     
         7 . An internal combustion engine according to  claim 6  wherein the rest and two lock positions are selected by rotation.  
     
     
         8 . An internal combustion engine having intake and exhaust valves comprising: 
 a pushrod;    a rocker arm pivoted between its ends and having one end engaged by the pushrod;    a valve stem engaging the other end of the rocker arm;    a selectively movable pivot supporting the rocker arm, the movable pivot having a lower rest position and an upper lock position, the upper lock position being determined by liquid trapped in a volume which is closed in response to upward movement of the pivot; and    the pivot having an intermediate lock position between the rest position and the upper lock position.    
     
     
         9 . An internal combustion engine according to  claim 8  wherein the intermediate lock position is also determined by liquid trapped in a volume which is closed in response to upward movement of the pivot.  
     
     
         10 . An internal combustion engine according to  claim 8  wherein the pivot is retained in the rest position by liquid trapped in a volume which is closed.  
     
     
         11 . An internal combustion engine according to  claim 8  comprising: 
 a radially extending passage through which liquid can pass;  
 a first sleeve controllably movable for closing or opening one end of the passage; and  
 a second sleeve movable in response to movement of the pivot for closing or opening the other end of the passage.  
 
     
     
         12 . An internal combustion engine according to  claim 11  wherein the first sleeve is rotatable and the second sleeve moves longitudinally.  
     
     
         13 . An internal combustion engine according to  claim 11  further comprising a second radially extending passage through which liquid can pass, one of the passages having an upper edge further from the pivot than the upper edge of the other passage.  
     
     
         14 . An internal combustion engine having intake and exhaust valves comprising: 
 a pushrod;    a rocker arm having a pivot between its ends and having one end engaged by the pushrod;    a valve stem engaging the other end of the rocker arm;    an adjustable stop having at least two positions for the rocker arm pivot, namely a lock position elevated above a rest position; and    means for gradually starting valve opening before or upon the pivot reaching the lock position.    
     
     
         15 . An internal combustion engine according to  claim 14  further comprising an additional lock position for the pivot between the rest position and the lock position.  
     
     
         16 . An internal combustion engine according to  claim 14  wherein the lock position is reached when hydraulic block occurs in a closed chamber.  
     
     
         17 . An internal combustion engine according to  claim 16  wherein a selection is made between the rest position and the lock position of the pivot by rotating a member for changing the volume of the closed chamber  
     
     
         18 . An internal combustion engine according to  claim 17  comprising: 
 a servo motor connected to the rotating member;  
 means for sensing engine rotational speed; and  
 a computer control for moving the servo motor in response to engine rotational speed.  
 
     
     
         19 . A method of operating an internal combustion engine having intake and exhaust rocker arms mounted on pivots for opening engine valves comprising moving a rocker arm pivot against a progressive rate spring in response to movement of a pushrod.  
     
     
         20 . A method of operating an internal combustion engine having intake and exhaust rocker arms mounted on pivots for opening engine valves, each rocker arm engaged by a pushrod at one end and a valve stem at the opposite end, comprising: 
 moving a rocker arm pivot in response to movement of a pushrod without significant movement of the corresponding valve stem;    moving both the valve stem and the pivot in response to further movement of the pushrod; and    moving only the valve stem in response to further movement of the pushrod.    
     
     
         21 . A method of operating an internal combustion engine having intake and exhaust rocker arms mounted on pivots for opening engine valves, each rocker arm engaged by a pushrod at one end and a valve stem at the opposite end, comprising: 
 moving a rocker arm pivot in response to movement of a pushrod; and    selecting presence or absence of movement of the rocker arm pivot by rotation of a control member.    
     
     
         22 . A method of operating an internal combustion engine having intake and exhaust rocker arms mounted on pivots for opening engine valves, each rocker arm engaged by a pushrod at one end and a valve stem at the opposite end, comprising: 
 moving a rocker arm pivot in response to movement of a pushrod; and    using a hydraulic block to hold the rocker arm pivot in or near a rest position;    using a hydraulic block to stop the pivot movement at an upper lock position; and    using a hydraulic block to stop the pivot movement at an intermediate lock position between the rest position and the upper lock position.