Abstract:
An adjustable camshaft system for an automotive engine includes a camshaft having machined and fabricated axially-directed control passages combined with an oil-activated camshaft phaser. The fabricated oil control passages are formed within a portion of the camshaft having an outside diameter which is substantially equal to the outside diameter of other portions of the camshaft fitted within bearings carried within the engine&#39;s cylinder head.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a camshaft which is specially fabricated for use with an oil-controlled camshaft phaser capable of changing the timing relationship between the crankshaft and camshaft of a reciprocating internal combustion engine.  
       BACKGROUND  
       [0002]     Oil-controlled camshaft phasers are known in the art. Such devices allow camshaft timing to be continuously adjusted by a closed loop control system. Usually, actuation is controlled by engine oil, which is ported to the phaser at a control pressure. The actual phase angle of the camshaft with respect to the crankshaft is determined by means of sensors which monitor both crankshaft and camshaft position in real time. Oil is caused to be directed by a control valve to either a retard port or an advance port of the phaser to achieve the necessary adjustment in camshaft position. It is known to run oil through camshaft itself to achieve adjustment. U.S. Pat. No. 5,138,985 and 6,026,772 disclose systems in which oil is run about the camshaft itself. Each of the systems of the &#39;985 and &#39;772 patents are characterized by very large camshaft diameters in the area in which the oil is furnished to the camshaft phaser. Also, these designs rely on passages which are machined into the interior of the camshaft, and this presents problems because axial drillings are difficult both to machine and to clean after the machining process. Unfortunately, the presence of foreign material may cause a camshaft phaser to fail.  
         [0003]     The present system uses a sleeve and axially directed grooves machined through the surface and into a subdiametral portion of the camshaft. The grooves and sleeve, taken together make up axially directed oil control passages.  
       SUMMARY  
       [0004]     An adjustable camshaft system for an automotive engine includes a camshaft mounted within a cylinder head upon a plurality of camshaft bearings, including a front bearing. The camshaft has a driven end extending from the front bearing. An oil-activated camshaft phaser is attached to the driven end of the camshaft. The phaser has at least one timing advance port and at least one timing retard port. A plurality of axially directed control passages, which are operably associated with the driven end of the camshaft, extend from the front camshaft bearing to the camshaft phaser. Each of these control passages includes an axially directed groove formed in a cylindrical surface of the driven end of the camshaft. The grooves are capped by a cylindrical sleeve applied to the driven end. A plurality of control ports formed in the cylindrical sleeve is in registry with the previously described axially directed grooves. The control ports themselves are in axial registry with a plurality of oil control passages extending radially through the front camshaft bearing. At least one exterior signal port is formed in the cylindrical sleeve and extends from one of the control passages. This exterior signal port is in axial registry with one of the phaser&#39;s timing advance port and the timing retard port. At least one interior signal port is formed within an inner annular wall of the camshaft and extends from one of the axially directed control passages. The interior signal port is in axial registry with an annular passage extending to one of the timing advance port and the timing retard port.  
         [0005]     The compactness of the present unit is promoted by the fact that the cylindrical sleeve which forms one portion of the control passages within the camshaft has an outside diameter which approximates the outside diameter of other camshaft bearing surfaces formed on the camshaft.  
         [0006]     Each of the axially directed grooves formed in the driven end of the camshaft has a generally rectilinear cross section. This means that the grooves are at least predominantly parallel-sided. This configuration results from the milling or grinding processes used to form the grooves in the camshaft.  
         [0007]     According to another aspect of the present invention, a method for manufacturing an internal combustion engine camshaft for use with an oil-activated camshaft phaser includes the steps of machining a plurality of camshaft bearing surfaces to a common diameter, machining a front bearing portion of the camshaft to a diameter less than the common diameter, cutting a plurality of generally parallel-sided, axially-directed control passage grooves within the front bearing portion of the camshaft, and applying a ported sleeve, having an external camshaft bearing surface with a diameter proximate said common diameter, to the front bearing portion of the camshaft, thereby capping the grooves and forming a plurality of axially directed control passages within the camshaft.  
         [0008]     It is an advantage of a camshaft and oil-controlled phaser according to the present invention that the fabricated front portion of the camshaft is of a sufficiently small diameter so as to reduce the package dimension, weight, and inertia of not only the camshaft, but also a phaser mounted upon the camshaft.  
         [0009]     It is a further advantage of a camshaft and phaser system according to the present invention that fabricated passages in the camshaft permit excellent inspection and cleaning of the passages during manufacturing of the camshaft, thereby promoting reliability of the camshaft system once it is installed within an engine.  
         [0010]     It is another advantage of the present invention that because the oil passages immediately underlie the surface of the camshaft, less pumping work is required to move control oil through the camshaft.  
         [0011]     Other advantages, as well as features and objects of the present invention will become apparent to the reader of the specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a perspective view of a camshaft and phaser system according to the present invention.  
         [0013]      FIG. 2  is a sectional view of a phaser and camshaft according to the present invention.  
         [0014]      FIG. 3  is a plan view cutaway of a phaser according to the present invention taken along the line  3 - 3  of  FIG. 1 .  
         [0015]      FIG. 4  is an end view of the driven end of a camshaft according to the present invention taken along the line  4 - 4  of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     As shown in  FIG. 1 , camshaft  10  has a number of camshaft bearing surfaces,  12 , which allow camshaft  10  to be mounted to cylinder head  16  by means of camshaft bearings  20 . Camshaft  10  operates a number of poppet valves,  17 , which control the gasses flowing into and out of the cylinders of an engine. Camshaft journals  20  are mounted on camshaft saddles  20   g , ( FIG. 2 ) by means of a plurality of bearing caps  20   f  (one shown). Camshaft position identification wheel  48  is locked to camshaft  10 .  
         [0017]      FIG. 1  also shows oil-activated camshaft phaser  40 , which has a drive sprocket,  42 , for connection with the engine&#39;s crankshaft by means of a timing chain (not shown).  
         [0018]     Moving now to  FIG. 2 , camshaft  10  is shown as having at least two control passages,  22 , which are axially directed and formed in the front, or driven, end,  14 , of camshaft  10 . Driven end  14  is said to be subdiametral because diameter D 2 , which is the diameter to which driven end  14  is reduced during machining of the camshaft, has a lesser dimension, and in fact, is smaller than diameter D 1 . This latter diameter, D 1 , characterizes both the diameter of the parent camshaft through the remaining cam bearings of the engine, as well as the outside diameter of cylindrical sleeve  26 , which will be discussed in further detail below.  
         [0019]      FIG. 2  shows the manner in which sleeve  26  cooperates with a plurality of axially directed grooves,  24 , to form oil control passages  22 . Control passages  22  extend from cam bearing cap  20   f  and saddle  20   g  into camshaft phaser  40 . As shown in  FIG. 2 , control port  28   a  formed in sleeve  26  is a retard control port. Port  28   a  picks up an oil pressure signal from oil control passage  18   a  and allows oil to flow through connected control passage  22   a  to interior signal port  32 . Control port  28   b , an advance control port formed within sleeve  26 , picks up an oil pressure signal from oil control passage  18   b  formed in camshaft bearing saddle  20   g  and transmits the signal through control passage  22   b.    
         [0020]     Oil flowing through control port  28   b , the advance control port, flows forward an associated passage  22  and leaves such passage  22  through exterior signal port  30 . Upon leaving exterior port  30 , the oil enters oil activated phaser  40  through timing advance ports  44 . The control oil then flows from timing advance ports  44  into a plurality of timing advance chambers  46 . Timing advance chambers  46  cause rotor  41  to move in a direction tending to advance the timing of camshaft  10  with respect to the engine&#39;s crankshaft. If, however, oil flows through interior signal port  32  which is formed in inner annular wall  36  of camshaft  10 , the oil will then flow through annular passage  34  and into timing retard ports  50  of camshaft phaser  40 . Timing retard chambers  52  within phaser  40  are connected with timing retard ports  50 , and oil pressure applied within timing retard ports  52  will cause rotor  41  to move in a direction tending to retard camshaft  10  with respect to the engine&#39;s crankshaft.  
         [0021]      FIG. 4  shows clearly that axially directed grooves  24  have parallel sides resulting from the machining of the grooves themselves. Those skilled in the art will appreciate in view of this disclosure that grooves  24  could be formed by any one of a number of machining processes, used either singly, or in combination with others. For example, grooves  24  could be made by milling, grinding, or other processes. The generally parallel sides allow for excellent inspection and cleaning of grooves  24  during the manufacturing process.  
         [0022]     From the foregoing it is thus seen that sleeve  26  functions not only as an integral part of control passages  22 , but also as a bearing surface for camshaft  10 . This allows one wishing to employ the present invention to discard the need for axial drillings of the camshaft, which as explained above, are fraught with expense and manufacturing problems.  
         [0023]     While particular embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Accordingly, it is intended that the invention be limited only in terms of the appended claims.