Actuator and Control Method For Variable Valve Timing (Vvt) Mechanism

Abstract

A variable valve timing system includes a toothed rotating sleeve, a rack, and an actuator. The rack has a first end, a second end with a plurality of teeth in meshing contact with the teeth of rotating sleeves of the valve and being linearly moveable to rotate the sleeves. The actuator includes a housing, a control valve, and at least one check valve. The housing slidably receives a piston coupled to the rack separating a chamber in the housing into first and second chambers. The control valve selectively directs fluid from the first to the second chamber or vice versa. When the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, pressurizing the first or the second chamber and under control of the control valve, fluid recirculates from the first or the second chamber to the other chamber.

1 . A variable valve timing system for altering valve timing of an internal combustion engine having at least one camshaft and a plurality of valves having a valve stem with a valve head, the valve timing system comprising:
 a toothed rotating sleeve having a plurality of teeth around at least part of its circumference, rotatably mounted on each valve stem about an axis, having a valve lifter mounted on an upper surface off of an axis of rotation;   a rack having a first end, a second end comprising a plurality of teeth in meshing contact with the teeth of the rotating sleeves of the valves, and being linearly moveable to rotate the rotating sleeves;   an actuator comprising:
 a housing having a chamber for slidably receiving a piston coupled to the rack, wherein the piston separates the chamber into a first chamber and a second chamber, 
 a control valve in connection with the first chamber and the second chamber for directing fluid flow between the first chamber and the second chamber, selectively directing fluid from the first chamber to the second chamber or vice versa; and 
 at least one check valve between the first chamber and the second chamber and the control valve for blocking reverse fluid flow; 
   wherein when the rack is shifted linearly by vibrational impulses from the engine, the piston moves linearly within the housing, the first chamber or the second chamber is pressurized and under control of the control valve, and fluid recirculates from the first chamber or the second chamber to the other chamber.   
   
   
       2 . The system of the  claim 1 , further comprising a passage in fluid communication with a pressurized fluid source for providing makeup fluid only. 
   
   
       3 . The system of  claim 2 , further comprising a check valve in the passage. 
   
   
       4 . The system of  claim 1 , wherein the housing is split into a first housing and a second housing. 
   
   
       5 . The system of  claim 4 , further comprising a second piston. 
   
   
       6 . The system of  claim 1 , wherein the control valve is spool valve. 
   
   
       7 . The system of  claim 1 , wherein the control valve is split into a first control valve and a second control valve. 
   
   
       8 . The system of  claim 7 , wherein the first control valve and the second control valve are solenoid valves. 
   
   
       9 . The system of  claim 1 , wherein each lobe on the camshaft has a varying contour a long a length. 
   
   
       10 . A method of altering the valve timing of an internal combustion engine having at least one camshaft and a plurality of valves having a valve stem with a valve head using a valve timing system comprising: a toothed rotating sleeve having a plurality of teeth around at least part of its circumference, rotatably mounted on each valve stem about an axis, having a valve lifter mounted on an upper surface off of an axis of rotation; a rack having an end with a plurality of teeth in meshing contact with the teeth of the rotating sleeves of the valves being linearly moveable rotate the rotating sleeves; and an actuator having a housing having a chamber for slidably receiving a piston coupled to the rack, wherein the piston separates the chamber into a first chamber and a second chamber, a control valve in connection with the first chamber and the second chamber for directing fluid flow between the first chamber and the second chamber, selectively directing fluid from the first chamber to the second chamber or vice versa; and at least one check valve between the first chamber and the second chamber and the control valve for blocking reverse fluid flow, comprising the steps of:
 a) determining the position of rack;   b) sending the position of the rack to an engine control unit;   c) sending a signal based on the position of the rack from the engine control unit to the actuator and moving a control valve of the actuator to a first position, a second position, or a third position; and   d) pressurizing a first chamber or a second chamber of the actuator based on the position of the rack and the control valve of the actuator, allowing flow of fluid from the pressurized chamber to the other chamber and blocking reverse flow.   
   
   
       11 . The method of  claim 10 , wherein the third position of the spool is a null position.