Abstract:
A vehicle engine includes: a cylinder head; a cam housing fixed to a top of the cylinder head; a cam cap fixed to a top of the cam housing; a camshaft rotatably supported between the cam housing and the cam cap, the camshaft supporting a cam; a rocker arm configured to be pushed by the cam; and a valve configured to operate by being pushed by the rocker arm; and an oil pipe that is formed integrally with the cam cap. Lubricant oil is supplied through the oil pipe to a contact point between the cam and the rocker arm.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from Japanese Patent Application No. 2009-236226 filed on Oct. 13, 2009. The entire content of this priority application is incorporated herein by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a vehicle engine. 
       BACKGROUND 
       [0003]    A typical vehicle engine includes a cylinder head, a cam housing, a cam cap, camshafts, rocker arms, and valves. The cam housing is fixed to a top of the cylinder head. The cam cap is fixed to a top of the cam housing. The camshafts are rotatably supported between the cam housing and the cam cap. Each camshaft supports cams. The cams push the rocker arms, while the rocker arms push the valves so that the valves operate. One of such typical vehicle engines further includes a shower pipe wherethrough lubricant oil is supplied to contact points between the cams and the rocker arms. 
         [0004]    The shower pipe is generally a separate part attached to the cam cap or to a head cover that covers the top of the cam cap. That is, a part separate from the cam cap or from the head cover is necessary as the shower pipe. The parts count of the vehicle engine is higher accordingly. 
         [0005]    Thus, there is a need for a vehicle engine with a lower parts count. 
       SUMMARY 
       [0006]    An aspect in accordance with the present invention is a vehicle engine including: a cylinder head; a cam housing fixed to a top of the cylinder head; a cam cap fixed to atop of the cam housing; a camshaft rotatably supported between the cam housing and the cam cap, the camshaft supporting a cam; a rocker arm configured to be pushed by the cam; a valve configured to operate by being pushed by the rocker arm; and an oil pipe configured to supply lubricant oil to a contact point between the cam and the rocker arm. The oil pipe is formed integrally with the cam cap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a sectional view of a vehicle engine of a first embodiment, illustrating a state before the cam cap is mounted to the cam housing; 
           [0008]      FIG. 2  is a sectional view of the vehicle engine of the first embodiment, illustrating a state after the cam cap is mounted to the cam housing; 
           [0009]      FIG. 3  is a perspective view of the cam housing, a camshaft, and the cam cap of the first embodiment; 
           [0010]      FIG. 4  is a sectional view of a vehicle engine of a second embodiment, illustrating a state before a cam cap is mounted to the cam housing; 
           [0011]      FIG. 5  is a sectional view of the vehicle engine of the second embodiment, illustrating a state after the cam cap is mounted to the cam housing; and 
           [0012]      FIG. 6  is a perspective view of the cam housing, a camshaft, and a cam cap of the second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
     &lt;First Embodiment&gt; 
       [0013]    A first embodiment in accordance with the present invention will be described with the drawings. 
         [0014]    As illustrated in  FIGS. 1 and 2 , a vehicle engine  10  of this embodiment includes a cylinder head (not illustrated in the drawings), a cam housing  12 , a cam cap  14 , camshafts  16 , rocker arms  20 , and valves  22 . The cam housing  12  is fixed to a top of the cylinder head. The cam cap  14  is fixed to a top of the cam housing  12 . Each camshaft  16  is rotatably supported between the cam housing  12  and the cam cap  14 . The camshaft  16  supports cams  18 . The cams  18  push the rocker arms  20 . The rocker arms  20  push the valves  22  so that the valves  22  operate. The vehicle engine  10  is a so-called DOHC engine, including the left and right camshafts  16  for operating the intake and exhaust valves  22 , respectively. 
         [0015]    The cam housing  12  is bolted on the top of the cylinder head. The cam housing  12  accommodates the rocker arms  20 , the valves  22 , lash adjusters  24 , and valve springs  26 . An end of each rocker arm  20  is supported from below by the corresponding lash adjuster  24 , while the other end contacts a stem  22   a  of the corresponding valve  22  from above. As a crankshaft (not illustrated in the drawings) rotates, the camshafts  16  rotate so that the cams  18  push down rollers  20   a  of the rocker arms  20 . Then, the rocker arms  20  swing up and down about top ends of the lash adjusters  24  while reciprocating the valves  22  up and down against the elastic forces of the valve springs  26 . Thus, the camshafts  16 , the cams  18 , the rocker arms  20 , the lash adjusters  24 , and the valve springs  26  are accommodated in the cam housing  12  and configure a valve train for operating the valves  22 . 
         [0016]    The cam cap  14  is bolted on the top of the cam housing  12 . The cam housing  12  and the cam cap  14  are made of metal such as aluminium alloy. The cam housing  12  and the cam cap  14  can be manufactured by, for example, die casting. 
         [0017]    As illustrated in  FIG. 3 , the cam housing  12  includes a rectangular outer frame  12   a  and partitions  12   b.  The outer frame  12   a  defines a space, while the partitions  12   b  partition the space into a plurality of subspaces. Similar to this, the cam cap  14  includes a rectangular outer frame  14   a  and partitions  14   b.  The outer frame  14   a  defines a space, while the partitions  14   b  partition the space into a plurality of subspaces. Each of the subspaces defined by the partitions  12   b,    14   b  accommodates the valve train components for operating the cylinder valves  22  of the vehicle engine  10 . 
         [0018]    Each camshaft  16  is a round bar made with metallic material such as JIS STKM (Carbon Steel Tubes for Machine Structural Purposes). The plurality of cams  18  are integrally provided on the circumference of the camshaft  16 . The cams  18  are arranged in the axial direction of the camshaft  16 . 
         [0019]    Each camshaft  16  is rotatably supported between the cam housing  12  and the cam cap  14 . Specifically, the camshaft  16  is rotatably supported between bearing recesses  28  and bearing recesses  30 . Each of the bearing recesses  28 ,  30  is generally semicircular in cross section. The bearing recesses  28  are formed in the top face of the cam housing  12 . The bearing recesses  30  are formed in the bottom face of the cam cap  14  (see  FIG. 1 ). 
         [0020]    Two oil pipes  32  are integral parts of the cam cap  14 . Through the oil pipes  32 , lubricant oil (hereinafter simply referred to as “oil”) is supplied to the contact points between the cams  18  and the rollers  20   a  of the rocker arms  20 . The oil pipes  32  can be formed integrally with the cam cap  14  in, for example, a die-casting process for manufacturing the cam cap  14 . The oil pipes  32  extend substantially parallel to the axial direction of the camshafts  16  and through the thicknesses of the partitions  14   b.  The oil pipe  32  has a center hole  34  running through the axis thereof. The center hole  34  is bored with a tool such as a drill. The center hole  34  is an oil flow path. 
         [0021]    The oil pipe  32  has a plurality of oil holes  36  arranged at predetermined intervals in the axial direction of the oil pipe  32 . Each oil hole  36  is approximately from  1  mm to  2  mm in diameter. The oil hole  36  runs through the thickness of the pipe wall of the oil pipe  32 , obliquely downward from the center hole  34 . 
         [0022]    An oil pump pumps up oil from an oil pan. The oil is then forced through an oil gallery (not illustrated in the drawings) in the cam housing  12  and in the cam cap  14  to the oil pipes  32 , and then is injected from the oil holes  36  toward the cams  18  and the rocker arms  20 . Thus, oil is supplied to the contact points between the cams  18  and the rocker arms  20 . 
         [0023]    In a state where the cam cap  14  is mounted to the cam housing  12  as illustrated in  FIG. 2 , the oil pipes  32  are located above the cams  18 . Accordingly, even in the event of lower oil pressure in the oil pipes  32  due to oil pump trouble etc., the oil in the oil pipes  32  can fall by its own weight from the oil holes  36 . Oil can thus be continuously supplied to the contact points between the cams  18  and the rocker arms  20 . 
         [0024]    As described above, the vehicle engine  10  of this embodiment includes the oil pipes  32  that are provided integrally with the cam cap  14 . Therefore, no member separate from the cam cap  14  or from the head cover is necessary as the oil pipes  32 . The parts count of the vehicle engine  10  can be lower accordingly. 
       &lt;Second Embodiment&gt; 
       [0025]    A second embodiment in accordance with the present invention will be described with reference to the drawings. 
         [0026]    A vehicle engine  50  of this embodiment differs from the engine  10  of the first embodiment in the configuration of the cam cap and the oil pipe. The other configurations are similar to the first embodiment. Accordingly, the components similar to those of the first embodiment will be designated with the same reference characters, while the description will be omitted. 
         [0027]    As illustrated in  FIGS. 4 through 6 , the vehicle engine  50  includes a plurality of plate-like bodies  54  that configure a cam cap  52 . The plate-like bodies  54  are bolted on a top of the cam housing  12 . The plate-like bodies  54  partition the plurality of cams  18  into groups of two cams  18 . The plate-like bodies  54  are made by metallic material such as aluminium alloy. The plate-like bodies  54  can be manufactured by, for example, die casting. 
         [0028]    Each camshaft  16  is rotatably supported between the cam housing  12  and the cam cap  52 . Specifically, the camshaft  16  is rotatably supported between the bearing recesses  28  and bearing recesses  58 . Each of the bearing recesses  28 ,  58  is generally semicircular in cross section. The bearing recesses  28  are formed in the top face of the cam housing  12 . The bearing recesses  58  are formed in the bottom faces of the plate-like bodies  54 . 
         [0029]    Oil pipes  60  are integral parts of the respective plate-like bodies  54 . The oil pipes  60  are disposed on the top face of the respective plate-like bodies  54 . Through the oil pipes  60 , oil is supplied to the contact points between the cams  18  and the rollers  20   a  of the rocker arms  20 . The oil pipe  60  can be formed integrally with the plate-like bodies  54  in, for example, a die-casting process for manufacturing the plate-like bodies  54 . The oil pipes  60  extend substantially parallel to the axial direction of the camshafts  16 . The oil pipe  60  has a center hole  62  running through the axis thereof. The center hole  62  is bored with a tool such as a drill. The center hole  62  is an oil flow path. The center hole  62  is open-ended in the two ends of the oil pipe  60 . 
         [0030]    The oil pump pumps up oil from an oil pan. The oil is then forced through the oil gallery (not illustrated in the drawings) in the cam housing  12  and in the cam cap  52  to the oil pipes  60 , and then falls from both ends of the oil pipes  60  toward the cams  18  and the rocker arms  20 . Thus, oil is supplied to the contact points between the cams  18  and the rocker arms  20 . 
         [0031]    In the state where the cam cap  52  is mounted to the cam housing  12  as illustrated in  FIG. 5 , the oil pipes  60  are located above the cams  18 . Accordingly, even in the event of lower oil pressure in the oil pipes  60  due to oil pump trouble, the oil in the oil pipes  60  can fall by its own weight from the both ends of the oil pipes  60 . Oil can thus be continuously supplied to the contact points between the cams  18  and the rocker arms  20 . 
         [0032]    As described above, the vehicle engine  50  of this embodiment includes the oil pipes  60  that are provided integrally with the cam cap  52 . Therefore, no member separate from the cam cap  52  or from the head cover is necessary as the oil pipes  60 . The parts count of the vehicle engine  50  can be lower accordingly.