Patent Publication Number: US-10329971-B2

Title: Sliding camshaft barrel position sensing

Description:
TECHNICAL FIELD 
     The present invention generally relates to camshaft position sensing systems for an internal combustion engine, and more particularly relates to a system and method for direct sensing of a sliding camshaft barrel position based on barrel features. 
     BACKGROUND 
     Internal combustion engines include intake and exhaust valves that can be actuated by cams of at least one camshaft. In some configurations the camshafts are constructed with sliding camshaft lobes having at least one camshaft barrel. Each camshaft barrel is configured to select at least two shift positions per cylinder. The sliding camshaft lobes are rotationally locked but can move in the axial direction on a base shaft that is controlled and driven like a standard camshaft on the internal combustion engine. 
     At least one actuator unit is fixed on the internal combustion engine for displacing each of the sliding camshaft lobes. Particularly, at least one actuator pin of an actuator unit is operative to selectively engage displacement grooves arranged symmetrically opposite to each other on the periphery of the camshaft barrels of the sliding camshaft lobes. As the camshaft rotates, an actuator pin is selected to move into a displacement groove of the camshaft barrel which causes the sliding camshaft lobe to shift into a different axial position along the camshaft axis. When a sliding camshaft lobe shifts position, the intake and/or exhaust valves associated with it may be caused to actuate differently which in turn will cause the engine operation to be different. 
     To ensure the sufficient performance and reliability of engine operation it is important to know the state and position of the sliding camshaft lobes, particularly the camshaft barrels, over the full operating range of the engine. Thus, there is a need for a reliable means of determining the position of a sliding camshaft barrels at all times during engine operation. 
     BRIEF SUMMARY 
     One or more exemplary embodiments address the above issue by providing a system and method for sliding camshaft barrel position sensing. More particularly, disclosed are exemplary embodiments that relate to a system and method for direct sensing of a sliding camshaft barrel position based on barrel features. 
     According to an aspect of an exemplary embodiment, a system for direct sensing of a sliding camshaft barrel position based on barrel features includes at least one sliding camshaft having at least one camshaft barrel. Still another aspect as according to the exemplary embodiment includes at least one position shifting slot disposed in the at least one camshaft barrel. And another aspect includes at least one actuator for engaging the at least one position shifting slot and shifting position of the at least one camshaft barrel. And yet another aspect of the exemplary embodiment includes at least one sensor for detecting the shifted position of the at least one camshaft barrel. 
     Still another aspect of the exemplary embodiment wherein at least one sliding camshaft is an intake camshaft. And another aspect wherein at least one sliding camshaft is an exhaust camshaft. And a further aspect wherein the intake camshaft has two sliding lobes each having two camshaft barrels. Yet a further aspect wherein the exhaust camshaft has two sliding lobes barrels each having one camshaft barrel. 
     Another aspect in accordance with the exemplary embodiment wherein two actuators are used for shifting the position of the two intake camshaft sliding lobes. Still another aspect wherein two actuators are used for shifting the position of the two exhaust camshaft sliding lobes. And another aspect wherein the at least one sensor is a Hall Effect sensor. 
     Yet another aspect of the exemplary embodiment wherein the intake camshaft positions can be shifted between high lift, low lift and deactivated (also referred to as Active Fuel Management (AFM)) positions. And still another aspect in accordance with the embodiment wherein the exhaust camshaft position can be shifted between high lift and deactivated (AFM) positions. 
     Another aspect in accordance with a method for sensing camshaft barrel position of a sliding camshaft includes rotating at least one sliding camshaft having at least one camshaft barrel. 
     Still in accordance with the exemplary embodiment, the method includes activating at least one actuator for engaging at least one position shifting slot in the at least one camshaft barrel to shift position of the at least one camshaft barrel. Yet another aspect includes detecting the shifted position of the at least one camshaft barrel of the at least one sliding camshaft using at least one sensor. 
     And yet other aspects in accordance with the exemplary embodiment wherein detecting includes tracking features of the at least one camshaft barrel indicative of at least one of a high lift, low lift, or deactivated (AFM) camshaft barrel position. 
     Still another aspect of the exemplary embodiment wherein detecting includes tracking at least one position shifting slot of the at least one camshaft barrel that is indicative of at least one of a high lift, low lift, or deactivated camshaft barrel position. And further aspects wherein detecting includes using a Hall Effect sensor for tracking the at least one position shifting slot of the at least one camshaft barrel. 
     Yet further aspects in accordance with the exemplary embodiment also includes performing at least one remedial action when the at least one camshaft barrel remains in an unshifted position in response to activating at least one actuator. And yet another aspect wherein the remedial action is restoring at least one other camshaft barrel to the unshifted position of the at least one camshaft barrel. 
     Still another aspect further includes setting a fault code and service indicator lamp. And one other aspect wherein activating includes activating two actuators for shifting position of the at least one camshaft barrel. Yet a further aspect wherein rotating includes an intake sliding camshaft and an exhaust sliding camshaft. 
     And another aspect wherein detecting the shifted position of the intake sliding camshaft includes high lift, low lift, and deactivated positions. Still another aspect wherein detecting the shifted position of the exhaust camshaft includes high lift and deactivated positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present exemplary embodiment will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  is an illustration of an intake and an exhaust sliding camshaft configuration for a 4 cylinder internal combustion engine in accordance with aspects of an exemplary embodiment; 
         FIG. 2  is an illustration of an intake sliding camshaft configuration with position shifting actuators in accordance with aspects of the exemplary embodiment; 
         FIG. 3  is an illustration of an exhaust sliding camshaft configuration with position shifting actuators in accordance with aspects of the exemplary embodiment; 
         FIG. 4  is an illustration of a sliding camshaft cover with position shifting actuators and detection sensors in accordance with aspects of the exemplary embodiment; 
         FIG. 5 a    is an illustration of a lobe of an intake sliding camshaft in a high lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 5 b    is an illustration of a lobe of an intake sliding camshaft in transition from a high lift to low lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 5 c    is an illustration of a lobe of an intake sliding camshaft in low lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 5 d    is an illustration of a lobe of an intake sliding camshaft in transition from a low lift to deactivated position in accordance with aspects of the exemplary embodiment; 
         FIG. 5 e    is an illustration of a lobe of an intake sliding camshaft in a deactivated position in accordance with aspects of the exemplary embodiment; 
         FIG. 6 a    is an illustration of a lobe of an intake sliding camshaft in transition from a deactivated to low lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 6 b    is an illustration of a lobe of an intake sliding camshaft a low lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 6 c    is an illustration of a lobe of an intake sliding camshaft in transition from a low lift to a high lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 6 d    is an illustration of a lobe of an intake sliding camshaft in a high lift position in accordance with aspects of the exemplary embodiment; 
         FIG. 7 a    is an illustration of a surface area view of an intake camshaft barrel with position shifting slots and position tracking lines in accordance with aspects of the exemplary embodiment; 
         FIG. 7 b    is a graph of position sensor outputs when detecting the position of the intake camshaft barrel in accordance with aspects of the exemplary embodiment; 
         FIG. 7 c    is an illustration of a surface area view of an exhaust camshaft barrel with position shifting slots and position tracking lines in accordance with aspects of the exemplary embodiment; 
         FIG. 7 d    is a graph of position sensor outputs when detecting the position of the exhaust camshaft barrel in accordance with aspects of the exemplary embodiment; and 
         FIG. 8  is an illustration of an algorithm for sliding camshaft barrel position sensing using camshaft barrel features in accordance with the exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the embodiment or the application and uses thereof. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
     In accordance with the disclosed embodiment,  FIG. 1  is an illustration of an intake and an exhaust sliding camshaft configuration for a 4 cylinder internal combustion engine  10  in accordance with aspects of an exemplary embodiment. It is appreciated that the 4 cylinder embodiment is merely exemplary and the concept of sliding camshaft barrel position sensing may be applied to other multiple cylinder engine configurations, e.g., 5, 6, 8, 9, or 12, without exceeding the scope of the invention. 
     The engine  10  includes at least one sliding camshaft having at least one camshaft barrel. In the case, the engine  10  includes an intake sliding camshaft  12  and an exhaust sliding camshaft  14 . For shifting the position of the intake  12  and exhaust  14  sliding camshafts, at least one actuator  16  is provided in selective communication to the camshafts and commanded on and off by a control module, e.g., engine control module (not shown). Particular to this embodiment, engine  10  includes a plurality of actuators ( 16   a - 16   f ) with actuators ( 16   a - 16   d ) being operative for shifting the intake sliding camshaft  12 , and actuators ( 16   e - 16   f ) being operative for shifting the exhaust sliding camshaft  14  when commanded by the controller. 
     Referring now to  FIG. 2 , the intake sliding camshaft  12  includes two sliding lobes,  18  and  20 . Each sliding lobe ( 18 ,  20 ) includes two camshaft barrels. Camshaft barrels  22  and  24  are fixed on the sliding lobe  18 , and the camshaft barrels  26  and  28  are fixed to sliding lobe  20  in accordance with the exemplary embodiment. Referring to the enlarged view of the sliding lobe  18 , included is a high lift position  29 , a low lift position  30 , and a deactivated position  31 . The high lift position  29  refers to the air intake valves ( 34   a - 40   a ) being opened to the maximum position each time the intake sliding camshaft  12  rotates 360° while in this position. The low lift position  30  refers to the air intake valves being opened to a less than maximum position each time the intake sliding camshaft  12  rotates 360° and the deactivated position  31  refers to the air intake valves not be opened at all each time the intake sliding camshaft  12  rotates 360°. The intake sliding camshaft  12  also includes pipe journals  32  for at least maintaining spacing between sliding lobes. 
     Referring now to  FIG. 3 , the exhaust sliding camshaft  14  includes two sliding lobes  42  and  44 . Each sliding lobe ( 42 ,  44 ) includes one camshaft barrel. Camshaft barrel  46  is fixed on the sliding lobe  42 , and the camshaft barrel  48  is fixed to sliding lobe  44  in accordance with the exemplary embodiment. Referring to the enlarged view of the sliding lobe  42 , included is only a high lift position  47  and a deactivated position  50  in accordance with the exemplary embodiment. As noted above, the high lift position and deactivated position of the sliding exhaust lobe  42  are for opening the air exhaust valves ( 34   b - 40   b ) to a maximum position or not opening the valves at all, respectively. Valves  34   b  and  40   b  are only operable to be opened to a high lift position while valves  36   b  and  38   b  are operable in a high lift  47  and a deactivated position  50 . In accordance with the exemplary embodiment, it requires the activation of at least two position shifting actuators to shift the lobes ( 18 ,  20 ,  422 ,  44 ) of the sliding camshafts ( 12 ,  14 ). 
     Referring now to  FIG. 4 , an illustration of a sliding camshaft cover  54  with position shifting actuators ( 16   a - 16   f ) and position detection sensors  52  in accordance with aspects of the exemplary embodiment is provided. The sliding camshaft cover  54  shrouds the intake  12  and exhaust  14  sliding camshafts as protection from the outside environment containments and retain oil splatter produced by the operation of the engine. The position detection sensors  52  are disposed in the sliding camshaft cover  54  proximate to at least one position shifting slot such that the position of at least one camshaft barrel, e.g., camshaft barrel ( 22 , 24 ), can be detected by the position detection sensor(s)  52  (See  18 ). The position detection sensors  52  may be of the type that are used for position detection suitable for an engine environment including, but not limited to, a Hall Effect sensor. 
     Referring to  FIG. 5 a   , an illustration of a lobe  18  of an intake sliding camshaft  12  in a high lift position  29  prior to being shifted by the position shifting actuators ( 16   a - 16   b ) in accordance with aspects of the exemplary embodiment. The lobe  18  includes camshaft barrels  22  and  24  with each barrel having at least one position shifting slot  56  and  58 , respectively. The position shifting actuators ( 16   a - 16   b ) are operative to engage the at least one position shifting slot ( 56 ,  58 ) of the camshaft barrel ( 22 ,  24 ) when commanded on by the engine controller (not shown). 
     As the intake sliding camshaft  12  rotates towards direction  60 , a position shifting actuator  16   a  or  16   b  may be commanded on to engage the at least one position shifting slot  56  or  58 , respectively, to cause the lobe  18  of the intake sliding camshaft  12  to shift along the camshaft axis in direction  62 . The position detection sensor  52  continuously detects the position of the camshaft barrel ( 22 ,  24 ) and communicates the position to the engine controller. 
     Referring now to  FIGS. 5 b  and 5 c   , when the position shifting actuator  16   a  engages the position shifting slot  56 , the lobe  18  shifts along the camshaft axis in the direction  62  such that the intake valves  64  transition from the high lift position  29  to the low lift position  30 . In addition, the position detection sensors  52  now detect distinct features on the camshaft barrel ( 22 ,  24 ) indicative of the low lift position  30  which is communicated to the engine controller. 
     Referring now to  FIGS. 5 d  and 5 e   , when the position shifting actuator  16   a  is commanded to engage the position shifting slot  56  again, the lobe  18  is caused to shift along the camshaft axis in the direction  62  such that the intake valves  64  transition from the low lift position  30  to the deactivated position  31 . In addition, the position detection sensors  52  now detect distinct features on the camshaft barrel ( 22 ,  24 ) indicative of the deactivated position  31 . In accordance with the exemplary embodiment, the position detection sensors  52  detect the high lift position  29  of the lobe  18  rather than distinct features of the camshaft barrel ( 22 ,  24 ) as being indicative of the transition from the low lift position  30  to the deactivated position  31 . It is appreciated that the camshaft barrel ( 22 ,  24 ) or the lobe  18  could be constructed to include additional features indicative of a transition to the deactivated position  31  without exceeding the scope of the invention. 
     Referring to  FIGS. 6 a  and 6 b   , when the position shifting actuator  16   b  is commanded to engage the position shifting slot  58 , the lobe  18  is caused to shift along the camshaft axis in the opposite direction  62  such that the intake valves  64  transition from the deactivated position  31  to the low lift position  30 . In addition, the position detection sensors  52  once again detect distinct features on the camshaft barrel ( 22 ,  24 ) indicative of the low lift position  30 . 
     Referring now to  FIGS. 6 c  and 6 d   , when the position shifting actuator  16   b  is again commanded to engage the position shifting slot  58 , the lobe  18  is caused to shift along the camshaft axis in the opposite direction  62  such that the intake valves  64  transition from the low lift position  30  to the high lift position  29 . Additionally, the position detection sensors  52  now detect distinct features on the camshaft barrel ( 22 ,  24 ) indicative of the high lift position  29 . It is appreciated that the lobes of the intake  12  and exhaust  14  sliding camshafts are shifted into the various positions in a manner consistent with the shifting of lobe  18  in accordance with aspects of the exemplary embodiment. 
     Referring to  FIG. 7 a   , an illustration of a surface area view of an intake camshaft barrel  22  having a barrel surface  70 , position shifting slots  72 , and position tracking lines ( 74 ,  76 ,  78 ) in accordance with aspects of the exemplary embodiment is provided. The camshaft barrel surface  70  is form of metallic material capable of being detected by a suitable sensing device such as, but not limited to, a Hall Effect sensor as the camshaft barrel  22  rotates. It is appreciated that we will use suitable sensing devices to detect unique features of the camshaft barrels for identifying the distinct positions of the sliding camshafts ( 12 , 14 ). Accordingly, when the position detection sensor  52  senses the barrel surface  70  a high output signal sent to the engine controller, and when a position shifting slot  72  is detected a low output signal will be sent to the engine controller. 
     Referring to  FIG. 7 b   , a graph of position detection sensor  52  outputs indicative of the position of the intake camshaft barrel  22  in accordance with aspects of the exemplary embodiment is provided. Graph line  74   a  relates to position tracking line  74  and is indicative of the intake sliding camshaft  12  being in the high lift position  29  which causes the intake valves to be opened to maximum position as the camshaft rotates. Graph line  76   a  relates to position tracking line  76  and is indicative of the intake sliding camshaft  12  being in the low lift position  30  which causes the intake valves to be opened to a level less than the maximum position as the camshaft rotates. Graph line  78   a  relates to position tracking line  78  and is indicative of the intake sliding camshaft  12  being in the deactivated position  31  which causes the intake valves to be in a closed position as the camshaft rotates. Accordingly, the three distinct graph lines ( 74   a - 78   a ) can be used to at all times determine the position of the intake sliding camshaft or lobes thereof. 
     Referring now to  FIG. 7 c   , an illustration of a surface area view of an exhaust camshaft barrel  46  having a barrel surface  80 , position shifting slots  82 , and position tracking lines ( 84 ,  86 ) in accordance with aspects of the exemplary embodiment is provided.  FIG. 7 d    presents a graph of position detection sensor  52  outputs indicative of the position of the exhaust camshaft barrel  46 . Graph line  84   a  relates to position tracking line  84  and is indicative of the exhaust sliding camshaft  14  being in the high lift position  47  which causes the exhaust valves to be opened to maximum position as the camshaft rotates. Graph line  86   a  relates to position tracking line  86  and is indicative of the exhaust sliding camshaft  12  being in the deactivated position  50  which causes the exhaust valves to be in a closed position as the camshaft rotates. Accordingly, the two distinct graph lines ( 84   a - 86   a ) can be used to at all times determine the position of the exhaust sliding camshaft or lobes thereof. 
     Referring now to  FIG. 8 , an illustration of an algorithm  100  for sliding camshaft barrel ( 12 , 14 ) position sensing using camshaft barrel features in accordance with the exemplary embodiment is provided. At block  110 , the process begins with rotating at least one sliding camshaft ( 12 , 14 ) having at least one camshaft barrel and detecting the current position of the camshaft barrel. At block  120 , the process continues with activating at least one actuator ( 16   a - 16   f ) for engaging at least one position shifting slot in the at least one camshaft barrel to shift position of the at least one camshaft barrel. 
     At block  130 , the process continues with detecting the shifted position of the at least one camshaft barrel of the at least one sliding camshaft ( 12 , 14 ) using at least one sensor. In accordance with the exemplary embodiment, a Hall Effect sensor is used for detecting the shifted position of the at least one camshaft. 
     At block  140 , the process continues with determining if the at least one camshaft barrel shifted position as commanded. If it is determined that the at least one camshaft barrel shifted position as commanded then the process returns to block  120 . 
     At block  150 , the process continues with performing at least one remedial action when the at least one camshaft barrel remains in an unshifted position in response to activating the at least one actuator. In this case, if an actuator was commanded to shift the at least one camshaft barrel position from high lift to low lift, and then the at least one camshaft barrel did not shift as commanded, the remedial action would be to command at least one other camshaft barrel(s) back to the high lift position to be in synchronous with the unshifted camshaft barrel. In other words, the camshaft barrels that in fact shifted position from high lift to low lift as commanded will be shifted back to the low lift position to be in the same state as the unshifted camshaft barrel. 
     At block  160 , further remedial actions may include, but not limited to, setting a fault code in the engine controller, activating an alarm, and/or illuminating indicator lamp to alert the vehicle operator that service is required 
     The detailed description provides those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.