Abstract:
A camshaft system for internal combustion engine includes a camshaft having a thrust ring which is lubricated by oil from a control valve which operates a camshaft phaser with lubricating oil, and with the lubricating oil being furnished to the camshaft at crankcase pressure after the oil leaves the camshaft phaser.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    None. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a camshaft system for operating cylinder poppet valves incorporated within internal combustion engine, where the camshaft has a controlled timing or phasing, and with lubricating oil serving the dual function of not only operating camshaft phaser, but also providing lubrication for a portion of the camshaft. 
         [0004]    2. Background Information 
         [0005]    The lubrication of moving parts within an internal combustion engine is both necessary and costly. Of course, lubrication must be furnished to prevent undue wear of moving parts, but also to provide a mechanism for facilitating heat transfer. Lubrication is costly because a pump and a transfer network must be provided, with the pump having sufficient capacity to service a wide variety of moving parts and engine operating regimes. In the case of moving parts such as a camshaft, this lubrication requirement extends to lubrication of the camshaft&#39;s thrust faces. Usually, camshaft lubrication needs dictate that drilled passages be provided in opposing sides of the structures to which the camshaft&#39;s thrust surfaces abut. However, this necessitates that the oil pump be sized for a significant leakage path; this means that the pump must have greater capacity and, also, that the pump will absorb more power. 
         [0006]    It would be desirable to be able to furnish lubrication to camshaft thrust faces without the need of providing additional oil pump capacity and without the need for providing specialized drilled or cored passages within a cylinder head of an overhead cam engine. 
       SUMMARY OF THE INVENTION 
       [0007]    A camshaft system for an internal combustion engine includes a cylinder head, with a camshaft mounted upon a number of bearing surfaces contained in the cylinder head. A thrust ring is incorporated in the camshaft. A combination lubricant reservoir and thrust reactor is formed in the cylinder head and receives the thrust ring. A control valve for operating a camshaft phaser is connected with the cylinder head. The control valve furnishes lubricating oil under pressure to the camshaft phaser. At least one lubricant drain passage conducts lubricating oil from the control valve. The oil first enters the phaser, and is then conducted to the combination lubricant reservoir and thrust reactor. 
         [0008]    According to another aspect of the present invention lubricating oil leaves the control valve and entering the lubricant reservoir and thrust reactor at crankcase pressure. 
         [0009]    According to another aspect of the present invention, the combination lubricant reservoir and thrust reactor includes a generally semi-circular pocket having front and rear axial thrust faces for engaging the camshaft&#39;s thrust ring. 
         [0010]    According to another aspect of the present invention, two camshafts may be provided with lubricant for their thrust rings by a single control valve operating a single camshaft phaser mounted to one of the camshafts. 
         [0011]    It is an advantage of the present invention that because lubricant which is provided to the camshaft thrust surfaces is at crankcase pressure, maximum oil pressure is available to operate the camshaft phaser supplied with oil by the control valve. 
         [0012]    It is a further advantage of a system according to the present invention that oil pump capacity may be reduced because of the lack of a need to provide oil under pressure for the camshaft&#39;s thrust surfaces. 
         [0013]    Yet another advantage of a system according to the present invention resides in the notion that a single camshaft phaser control valve may be used for providing camshaft thrust surface lubrication for both of the camshafts found in a single cylinder head of a dual overhead camshaft engine. 
         [0014]    Other advantages, as well as features of the present invention, will become apparent to the reader of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a perspective view of a portion of a cylinder head having a control valve and camshaft arrangement according an aspect of the present invention. 
           [0016]      FIG. 2  is a plan view of a portion of a cylinder head similar to that shown in  FIG. 1 . 
           [0017]      FIG. 3  is a perspective view of a cylinder head having dual overhead camshafts and two camshaft phasers and control valves according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0018]    As shown in  FIG. 1 , an engine cylinder head,  10 , has a camshaft,  14 , mounted therein upon a number of camshaft bearings, with one bearing,  46 , being illustrated. Camshaft  14  incorporates an integral, one-piece camshaft thrust ring,  18 , which has a rear thrust face,  22 , and a front thrust face,  26 , with the latter being best shown in  FIG. 2 . 
         [0019]      FIG. 1  also shows an oil control valve,  50 , which provides lubricating oil under pressure to camshaft phaser,  58 , which is shown in  FIGS. 1 and 2 .  FIG. 2  also shows a camshaft sprocket,  62 , which is mounted upon camshaft phaser,  58 , and which powers camshaft  14  through either an elastomeric, fiber-reinforced belt, or a chain, or for that matter, a gear drive. 
         [0020]    Control valve  50  receives oil ported through a supply passage,  54 , formed in cylinder head  10  ( FIG. 3 ), and provides oil to camshaft phaser  58  such that oil is constantly flowing through control valve  50 . As a result, a stream of “used oil” continually flows through ports  68  formed in control of the body of control valve  50 ; ports  68 , which function as drain passages for valve  50 , are shown in  FIGS. 1 ,  2  and  3 . It is a feature of commonly used camshaft phaser control valves that oil flows from the valves and is not merely deadheaded at the camshaft phaser. In other words, whether the camshaft timing is advanced or retarded fully, or somewhere in between, oil will leave ports  68 . The present invention takes advantage of this continuous flow of oil, but without adding further burden to the engine&#39;s oil pump. The latter advantage is achieved by using post-phaser oil, at crankcase pressure, to lubricate one or more camshafts. 
         [0021]    Oil which flows from ports  68  ultimately flows across cylinder head  10  and into a combination lubricant reservoir and thrust reactor,  28  ( FIGS. 1 ,  2 , and  3 ). This combination device includes a semicircular pocket,  30 , into which lubricant flows at crankcase pressure. Pocket  30  has a rear axial thrust face,  38 , which is shown in  FIGS. 1 ,  2  and  3 , and a front axial thrust face,  42 , which is best shown in  FIG. 2 . Because oil flows constantly from ports  68  of control valve  50  whenever the engine is operating, oil flows into pocket  30  and fills the pocket to the extent it is permitted by virtue of the semi-annular wall which defines rear thrust face  38 . 
         [0022]    As is clearly shown in  FIG. 2 , pocket  30  has an overall diameter which exceeds the diameter of camshaft thrust ring  18  and this situation provides a ready passage for oil leaving lubricant drain passages  68  on control valve  50 .  FIG. 2  also shows an electrical connector,  52 , for control valve  50 . 
         [0023]    Although  FIG. 3  shows two control valves, namely valve  50  and valve  66 , which are attached to cylinder head  10 , and which both serve to lubricate camshaft thrust rings, it should be appreciated that the present oiling system may be employed with a single control valve, usually on the intake side of the engine, which in this case would be valve  50 . It has been determined that sufficient lubrication for camshaft thrust ring  20  of camshaft  16  will flow across cylinder head  10 , particularly with a V-type engine in which the cylinder heads are inclined at a negative angle to the horizontal. This inclination allows oil to overflow from pocket  30  and down into a second pocket,  34 , shown in  FIG. 3 , so as to provide lubrication to camshaft thrust ring  20 , which is located upon a second camshaft,  16 . In this manner, the thrust rings of both camshafts  14  and  16  may be lubricated with oil coming from a single control valve, namely valve  50 , thereby disposing with the need for drillings within cylinder heads to provide either of thrust rings  18  or  20  with lubrication. 
         [0024]    The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Accordingly the scope of legal protection afforded this invention can only be determined by studying the following claims.