Abstract:
A camshaft may include a first shaft, a bearing sleeve member located on and fixed to the first shaft, and a first lobe member located on the first shaft and displaceable between first and second positions. The first lobe member may be axially offset relative to the bearing sleeve member when in the first position to allow for machining of an outer surface of the bearing sleeve member and removal of machining debris from the outer surface. The first lobe member may be axially aligned with and bearingly supported on the bearing sleeve member when in the second position.

Description:
FIELD 
       [0001]    The present disclosure relates to engine camshaft assemblies, and more specifically to concentric camshaft assemblies. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Engines typically include a camshaft to actuate intake and exhaust valves. Some camshafts are concentric camshafts that provide for relative rotation between the intake and exhaust lobes. The intake lobes may be fixed to an outer shaft for rotation with the shaft and the exhaust lobes may be rotatably supported on the shaft. Alternatively, the exhaust lobes may be fixed to the outer shaft for rotation with the shaft and the intake lobes may be rotatably supported on the shaft. In either arrangement, the lobes that are rotatably supported on the shaft may use an outer surface of the shaft as a bearing surface. 
       SUMMARY 
       [0004]    A camshaft may include a first shaft, a bearing sleeve member located on and fixed to the first shaft, and a first lobe member located on the first shaft and displaceable between first and second positions. The first lobe member may be axially offset relative to the bearing sleeve member when in the first position to allow for machining of an outer surface of the bearing sleeve member and removal of machining debris from the outer surface. The first lobe member may be axially aligned with and bearingly supported on the bearing sleeve member when in the second position. 
         [0005]    An engine assembly may include an engine structure, a camshaft supported on the engine structure, and a cam phaser coupled to the camshaft. The camshaft may include a first shaft, a bearing sleeve member located on and fixed to the first shaft, and a first lobe member located on the first shaft and displaceable between first and second positions. The first lobe member may be axially offset relative to the bearing sleeve member when in the first position to allow for machining of an outer surface of the bearing sleeve member and removal of machining debris from the outer surface. The first lobe member may be axially aligned with and bearingly supported on the bearing sleeve member when in the second position. The cam phaser may be coupled to the camshaft and may selectively rotate the first lobe member on the bearing sleeve member when the first lobe member is in the second position. 
         [0006]    A method may include fixing a first lobe member to a first shaft of an engine camshaft, fixing a bearing sleeve member to the first shaft, locating a second lobe member on the first shaft, fixing a third lobe member on the first shaft after the locating. The second lobe member may be disposed between the first and third lobe members. The method may further include displacing the second lobe member axially with respect to the bearing sleeve member to expose an outer surface of the bearing sleeve member and performing a finishing process on the outer surface of the second lobe member after the displacing. 
         [0007]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0008]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0009]      FIG. 1  is a schematic illustration of an engine assembly according to the present disclosure; 
           [0010]      FIG. 2  is a perspective exploded view of the camshaft of  FIG. 1 ; 
           [0011]      FIG. 3  is a section view of the camshaft of  FIG. 1  showing a lobe member in a first orientation; and 
           [0012]      FIG. 4  is a section view of the camshaft of  FIG. 1  showing a lobe member in a second orientation. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
         [0014]    Referring now to  FIG. 1 , an exemplary engine assembly  10  is schematically illustrated. The engine assembly  10  may include an engine  12  including a plurality of cylinders  14  having pistons  16  disposed therein. The engine  12  may further include an intake valve  18  and an exhaust valve  20  for each cylinder  14 , as well as a camshaft  26  and a cam phaser  28 . While the engine assembly  10  is illustrated as a single overhead cam engine, it is understood that the present disclosure may be applicable to a variety of other engine configurations as well. 
         [0015]    With reference to  FIGS. 2-4 , the camshaft  26  may include first and second shafts  32 ,  34 , a first set of lobe members  36 ,  38 ,  40 ,  42 , a second set of lobe members  44 ,  46 ,  48 ,  50 , a locating member  52 , bearing sleeves  54 , and drive pins  56 . In the present example, the first set of lobe members  36 ,  38 ,  40 ,  42  may form an intake lobe set and the second set of lobe members  44 ,  46 ,  48 ,  50  may form an exhaust lobe set. However, it is understood that alternate arrangements may be provided where the first set of lobe members  36 ,  38 ,  40 ,  42  may form an exhaust lobe set and the second set of lobe members  44 ,  46 ,  48 ,  50  may form an intake lobe set. 
         [0016]    The second shaft  34  may be rotatably disposed within the first shaft  32 . The first shaft  32  may include slots  58  therethrough and the second shaft  34  may include apertures  60 . The pins  56  may extend through the slots  58  and apertures  60  and may be engaged with the second set of lobe members  44 ,  46 ,  48 ,  50  to couple the first set of lobe members  36 ,  38 ,  40 ,  42  for rotation with the second shaft  34 . The slots  58  in the first shaft  32  may generally allow for a rotational travel of the pins  56  therein. 
         [0017]    The second set of lobe members  44 ,  46 ,  48 ,  50  may be fixed for rotation with the first shaft  32 . The engagement between the second set of lobe members  44 ,  48 ,  50 ,  52  and the first shaft  32  may include a friction fit engagement. The first set of lobe members  36 ,  38 ,  40 ,  42  may be similar to one another. The second set of lobe members  44 ,  46 ,  48 ,  50  may additionally be similar to one another. Therefore, the lobe member  36  will be described with the understanding that the description applies equally to the remainder of the first set of lobe members  38 ,  40 ,  42  and lobe member  44  will be described with the understanding that the description applies equally to the remainder of the second set of lobe members  46 ,  48 ,  50 . The lobe member  36  may include a bore  62  defining a first inner diameter (D 1 ) and the lobe member  44  may include a bore  64  defining a second inner diameter (D 2 ). The second diameter (D 2 ) may be less than the first diameter (D 1 ). 
         [0018]    The locating member  52  may be fixed to an end of the first shaft  32  near the cam phaser  28 . The locating member  52  may be fixed to the first shaft  32  in a manner similar to the second set of lobe members  44 ,  46 ,  48 ,  50 , such as through a friction fit engagement. The locating member  52  may include first and second end portions  66 ,  68  and a bearing portion  70  extending between the first and second end portions  66 ,  68 . The bearing portion  70  may be rotatably supported by the engine  12  and the first and second end portions  66 ,  68 . The first end portion  66  may be coupled to the cam phaser  28  and the second end portion  68  may form a stop, as discussed below. 
         [0019]    The bearing sleeves  54  may be fixed to first shaft  32  and may include a slot  72  generally aligned with the slot  58  in the first shaft  32 . The bearing sleeve  54  may include an outer surface  74  defining an outer diameter (D 3 ) that is greater than the first inner diameter (D 1 ) and less than the second inner diameter (D 2 ). The bearing sleeve  54  may include first and second portions  76 ,  78 . The lobe member  36  may be rotatably disposed on the first portion  76 . The second portion  78  may extend axially from the first portion  76  and the lobe member  44  to form a bearing surface for the camshaft  26 . The axial spacing (L 1 ) between adjacent ones of the bearing sleeves  54  and the second set of lobe members  44 ,  46 ,  48 ,  50  and the axial spacing (L 2 ) between the bearing sleeve  54  and the locating member  52  may each be greater than the axial extent (L 3 ) of each of the first set of lobe members  36 ,  38 ,  40 ,  42 . 
         [0020]    With reference to  FIGS. 3 and 4 , assembly of the camshaft  26  will now be discussed. The first set of lobe members  36 ,  38 ,  40 ,  42 , the second set of lobe members  44 ,  46 ,  48 ,  50 , the locating member  52 , and the bearing sleeves  54  may be located on the first shaft  32  in the arrangement shown in  FIG. 3  where the first set of lobe members  36 ,  38 ,  40 ,  42  are displaced from the bearing sleeves  54  to expose the outer surfaces  74 . The first set of lobe members  36 ,  38 ,  40 ,  42  and the second set of lobe members  44 ,  46 ,  48 ,  50  may be completely finished (i.e., no more machining processes required) before being placed on the first shaft  32 . Next, the second set of lobe members  44 ,  46 ,  48 ,  50 , the locating member  52 , and the bearing sleeves  54  may be fixed to the first shaft  32 . The second set of lobe members  44 ,  46 ,  48 ,  50  the locating member  52 , and the bearing sleeves  54  may be fixed to the first shaft  32  in a variety of ways. For example, a radially outward force may be applied from within the first shaft  32  to provide the frictional engagement between the second set of lobe members  44 ,  46 ,  48 ,  50 , the locating member  52 , and the bearing sleeves  54  and the first shaft  32 . The radially outward force may be applied in a variety of ways including a ballizing process. 
         [0021]    Once the second set of lobe members  44 ,  46 ,  48 ,  50  the locating member  52 , and the bearing sleeves  54  are fixed to the first shaft  32 , the outer surfaces  74  of the bearing sleeves  54  may be machined to a desired finish. The machining may include grinding the outer surfaces  74  to the desired finish. The first set of lobe members  36 ,  38 ,  40 ,  42  may be isolated from the bearing sleeves  54  during the machining process, preventing exposure of the bore  62  of the first set of lobe members  36 ,  38 ,  40 ,  42  to debris from the machining operation. Once the machining operation is completed, the debris may then be cleaned from the outer surfaces  74  of the bearing sleeves  54 . The first set of lobe members  36 ,  38 ,  40 ,  42  may then be located on the bearing sleeves  54  and fixed to the second shaft  34  for rotation on the bearing sleeves  54 .