Rotary Valve Construction

Abstract

An axial flow rotary valve ( 1 ) for an internal combustion engine and method of manufacture thereof. The valve comprising a centre portion ( 5 ) having a cylindrical periphery, inlet and exhaust portions ( 9, 16 ) both smaller in diameter than the centre portion, and an inlet port ( 3 ) and an exhaust port ( 4 ) terminating respectively as an inlet opening ( 6 ) and an exhaust opening ( 7 ) in the periphery of the centre portion. The centre portion having at least one elongate passage ( 21 ) communicating between the inlet portion and the exhaust portion, the whole of the passage being disposed circumferentially outside the openings and radially outside at least one of the inlet and exhaust portions.

1 . An axial flow rotary valve for an internal combustion engine, said valve being adapted to rotate about an axis within a bore in the cylinder head of said engine, one end of said valve being an inlet end and the other end being an exhaust end, said valve comprising a centre portion having a cylindrical periphery, an inlet portion smaller in diameter than said centre portion, extending between said centre portion and said inlet end, an exhaust portion smaller in diameter than said centre portion, extending between said centre portion and said exhaust end, an inlet port extending from said inlet end and terminating as an inlet opening in the periphery of said centre portion, and an exhaust port extending from said exhaust end and terminating as an exhaust opening in the periphery of said centre portion, characterised in that said centre portion has at least one elongate passage communicating between said inlet portion and said exhaust portion, said passage being disposed circumferentially outside said openings and radially outside at least one of said inlet and exhaust portions.  
   
   
       2 . A rotary valve as claimed in  claim 1  wherein said passage has an aspect ratio smaller than 10:1.  
   
   
       3 . A rotary valve as claimed in  claim 1  wherein at least one end of said centre portion has an annular valve seat extending radially inwards from said cylindrical periphery and at least a portion of said passage is radially outside the inside diameter of said annular valve seat.  
   
   
       4 . A rotary valve as claimed in  claim 3  wherein said centre portion has at least one annular cavity, axially outside said inlet and exhaust openings, having an annular opening radially inside of said annular valve seat, and an end of said passage terminates at said cavity.  
   
   
       5 . A rotary valve as claimed in  claim 1  wherein said at least one elongate passage comprises a plurality of circumferentially spaced apart elongate passages.  
   
   
       6 . A rotary valve as claimed in  claim 5  wherein at least one of said passages is adjacent the trailing edge of said exhaust opening.  
   
   
       7 . A rotary valve as claimed in  claim 5  wherein each of said passages has a substantially circular section and extends in a substantially axial direction.  
   
   
       8 . A rotary valve as claimed in  claim 1  wherein said inlet and exhaust ports are separated by a common wall having no internal passages.  
   
   
       9 . A rotary valve as claimed in  claim 1  wherein said elongate passage is a coolant passage.  
   
   
       10 . A rotary valve as claimed in  claim 1  wherein said valve is manufactured from a single solid piece of material.  
   
   
       11 . A rotary valve as claimed in  claim 1  wherein said valve is manufactured from an inner body and at least one outer body, said outer body at least partially surrounding said inner body and attached thereto such that said passage is formed at the interface between said bodies.  
   
   
       12 . A method of manufacturing a rotary valve as claimed in  claim 4 , from an unfinished valve having an oversize centre portion stepping radially inwards at both ends, comprising the steps of: 
 a. machining said oversize centre portion to form said elongate passage and an annular groove in the end face of at least one end of said oversize centre portion;    b. deforming said end of said oversize centre portion radially inwards such that said annular groove becomes said annular cavity; and    c. machining said end face to form said annular valve seat and machining the outside diameter of said oversize centre portion to form said centre portion.    
   
   
       13 . A rotary valve assembly for an internal combustion engine, comprising a rotary valve as claimed in  claim 1 , a cylinder head having a bore in which said valve is supported by bearing means and rotates with a small predetermined clearance between said bore and said centre portion of said valve, said inlet and exhaust openings of said valve periodically communicating with a window in said bore, and first and second sealing rings flexibly sealed to said bore and biased axially inwards against first and second valve seats respectively formed by opposite ends of said centre portion.  
   
   
       14 . A rotary valve assembly as claimed in  claim 13  further comprising a heat insulation barrier in the exhaust port of said valve covering at least a portion of the common wall separating said inlet and exhaust ports of said valve.  
   
   
       15 . A rotary valve assembly as claimed in  claim 13  wherein there is an air gap between said insulation barrier and said common wall.