Oil supply structure for reducing friction of cam shaft

Abstract

An oil supply structure for reducing friction of a cam shaft attached to a valve train of an automotive engine is disclosed. An oil supply hole formed in a cam shaft is, repeatedly connected and disconnected to a cylinder head oil supply hole during the rotation of the cam shaft. An oil pocket is established in the form of a concave groove in a section in the circumferential direction on an inner circumferential surface of a cam cap assembled on the top of the cam shaft so as to supply oil to the oil pocket only when the cylinder head oil supply hole is connected to the cam shaft oil supply hole. It is thus possible to supply oil to the oil pocket through the cam shaft oil supply hole at specific points of time and, simultaneously, to sufficiently ensure the sealing width in other regions than the oil pocket, thus reducing oil loss and obtaining a more efficient friction reduction.

1 . An oil supply path for reducing friction of a cam shaft, comprising:
 a cylinder head oil supply hole, defined inside a cylinder head having an outlet positioned on an inner circumferential surface of a journal part bearing-supporting the cam shaft and an inlet is connected to an oil gallery in the cylinder head;   a cam shaft oil supply hole formed on the cam shaft supported by the journal part of the cylinder head and penetrating at a position to communicate with the outlet of the cylinder head oil supply hole; and   an oil pocket formed with a predetermined length in the circumferential direction on an inner circumferential surface, which is a friction surface with the cam shaft, of a semicircular cam cap assembled on the cylinder head over the cam shaft, so as to connect opening portions on one end and on the other end of the cam shaft oil supply hole with each other, thus supplying oil to the oil pocket from the cam shaft oil supply hole.   
   
   
       2 . The oil supply path for reducing friction of a cam shaft as recited in  claim 1 , wherein the oil pocket is arranged to connect the opening portion on one end of the cam shaft oil supply hole to the opening portion on the other end of the cam shaft oil supply hole when the opening portion on one end of the cam shaft oil supply hole is coupled to the outlet of the cylinder head oil supply hole. 
   
   
       3 . The oil supply path for reducing friction of a cam shaft as recited in  claim 1  or  claim 2 , wherein the oil pocket is established in the inner circumferential surface of the semicircular cam cap from a position, which meets a hole central extension line of the opening portion on one end of the cam shaft oil supply hole at the point of time when the opening portion on the other end of the cam shaft oil supply hole meets the outlet of the cylinder head oil supply hole, to a position, which meets the hole central extension line of the opening portion on one end of the cam shaft oil supply hole at the point of time when the opening portion on the other end of the cam shaft oil supply hole is completely out of the outlet of the cylinder head oil supply hole. 
   
   
       4 . The oil supply path for reducing friction of a cam shaft as recited in  claim 3 , wherein the oil pocket is arranged in a specific section between a position corresponding to an angle of about 55° and a position corresponding to angle of about 85° from an end point in the inner circumferential surface of the semicircular cam cap. 
   
   
       5 . An oil supply structure for an engine having a cam shaft carried in a journal between a cam cap and cylinder head, the oil supply structure comprising:
 a first oil supply hole defined in the cylinder head and communicating between said journal and an oil gallery;   a second oil supply hole defined through said cam shaft and positioned to periodically align with the first oil supply hole upon rotation of the cam shaft, and   an oil pocket formed in said cam cap and positioned to periodically receive oil from said oil gallery through the first and second oil supply holes upon rotation of the cam shaft.   
   
   
       6 . The oil supply structure of  claim 5 , wherein:
 the second oil supply hole has a diameter and the oil pocket has a width substantially the same as the diameter of the second oil supply hole; and   the oil pocket has a length that extends around a part of an inner circumference of the journal in the cam cap.   
   
   
       7 . The oil supply structure of  claim 6 , wherein said length of the oil pocket is greater than said diameter of the oil pocket. 
   
   
       8 . The oil supply structure of  claim 7 , wherein the oil pocket extends for a length of about 30° around an inner circumference of the cam cap. 
   
   
       9 . The oil supply structure of  claim 8 , wherein the length of the oil pocket extends from a position about 55° from an end point of the cam cap to a position about 85° from said end point. 
   
   
       10 . The oil supply structure of  claim 6 , wherein said cam shaft, cylinder head and cam cap include plural aligned oil supply holes and oil pockets. 
   
   
       11 . An oil supply structure for an engine, comprising:
 a cylinder head defining a first oil supply hole therein communicating with an oil gallery;   a cam shaft journal formed in the cylinder head, said first oil supply hole communicating with said journal;   a cam shaft disposed in said journal and defining a second oil supply hole extending therethrough in apposition disposed to periodically align with the first oil supply hole upon rotation of the cam shaft; and   a cam cap covering the cam shaft and forming an upper journal portion around said cam shaft, said cam cap defining an oil pocket therein disposed to periodically communicate with the oil gallery through said first and second oil supply holes upon rotation of the cam shaft and second oil supply hole therein.   
   
   
       12 . The oil supply structure of  claim 11 , wherein:
 the second oil supply hole has a diameter and the oil pocket has a width substantially the same as the diameter of the second oil supply hole; and   the oil pocket has a length that extends around a part of an inner circumference of the journal in the cam cap.   
   
   
       13 . The oil supply structure of  claim 12 , wherein the oil pocket extends for a length of about 30° around an inner circumference of the cam cap. 
   
   
       14 . The oil supply structure of  claim 13 , wherein the length of the oil pocket extends from a position about 55° around an inner circumference of the cam cap from point were the cam cap meets the cylinder head to a a position about 85° from said point. 
   
   
       15 . The oil supply structure of  claim 14 , wherein said cam cap meets said cylinder head along a substantially horizontal plan that substantially bisects the cam shaft. 
   
   
       16 . The oil supply structure of  claim 11 , wherein said cam shaft, cylinder head and cam cap define plural sets of aligned first and second oil supply holes and oil pockets, each said set spaced longitudinally along the cam shaft, cylinder head and cam cap.