Abstract:
A rotary position sensing assembly for an internal combustion engine includes a mounting socket rigidly attached to a structural support of a rotating component and a position sensor slidably engaged with the socket. A slidably engageable retainer maintains the sensor within the socket at a predetermined distance from the rotating component.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a position sensing assembly for determining the rotating position of such engine parts as camshafts or crankshafts.  
           [0003]    2. Disclosure Information  
           [0004]    Electronic engine control systems have been in widespread use for a number of years in the automotive industry. The control of fuel injection and spark timing require precise information regarding the position of the engine&#39;s internal parts i.e. crankshaft, pistons, valves, etc. as the engine progresses through the usual 2 or 4-stroke cycles. The need for precise information as to the location of a camshaft is increasingly underscored by the use of such devices as variable camshaft timing. This has in turn necessitated the use of camshaft position sensors. A problem with automotive engines arises because packaging considerations do not always allow for a sensor to be mounted on the front of the engine, for example, to promote easy accessibility for service. Mounting of a camshaft sensor through a camshaft cover, as illustrated in FIG. 1, is a known attempt to provide a solution to the packaging problem.  
           [0005]    The sensor shown at  10  in FIG. 1 is mounted and retained through camshaft cover  16  and retained within the cover by means of bolt  12 . The sensor is mounted within aperture  14  formed in cam cover  16 . Accurate operation of sensor  10  requires that the air gap between sensor  10  and the teeth contained on wheel  18 , which is mounted to a camshaft, be accurately maintained at relatively small distance of 0.5-2.0 mm. Unfortunately, tolerance stack-up in the cam cover system, including cover  16  and any associated gasketing will impair the ability to accurately measure the position of the camshaft. This occurs because tolerance growth or other tolerance uncertainty will cause the position of sensor  10  with respect to wheel  18  to be unpredictable, and as a result the output of sensor  10  will not be reliable over long engine production runs.  
           [0006]    The present invention solves the difficulties engendered by prior art position sensing systems, while providing a mounting system which requires only that the sensor be snapped into place by the production operator. This allows quick, error-free mounting of the sensor, while at the same time providing a seal which simultaneously prevents fluid from escaping from the engine, while preventing dirt from ingressing into the engine.  
         SUMMARY OF THE INVENTION  
         [0007]    A rotary position sensing assembly for an internal combustion engine includes a mounting socket rigidly attached to a structural support of a rotating component and a position sensor slidably engaged with the socket. A slidably engageable retainer maintains the sensor within the socket at a predetermined distance from the rotating component. A structural support according to the present invention may comprise a component part of a cylinder head, a cylinder block, or other type of rigid support for a rotating component such as a crankshaft or camshaft. For example, a sensor according to the present invention may be mounted upon a camshaft tower within a cylinder head.  
           [0008]    According to another aspect of the present invention, a position sensor may comprise a variable reluctance or Hall Effect sensor, or other type of sensor known to those skilled in the art and suggested by this disclosure. The position of the sensor within the socket is reliably, repeatably, and precisely maintained through the use of a shoulder and retainer system, wherein the mounting socket has a shoulder adapted to abuttingly receive the position sensor when the sensor is mounted within the socket and the position sensor engages and abuts the shoulder. As explained above, a retainer maintains the sensor abutted with the shoulder so as to station the sensor at a predetermined distance from a rotating component which could comprise, for example, a camshaft having a multi-tooth sensor wheel incorporated therein.  
           [0009]    According to another aspect of the present invention, a method for installing a position sensor within a position sensing assembly for tracking the rotary position of a rotating component incorporated within an internal combustion engine includes the steps of providing a sensor mounting socket within a support structure for the rotating component, and providing a cover for the rotating component, with the cover incorporating a seal for allowing the insertion of a sensor into the mounting socket. The method further includes the step of providing an axially activated retainer adapted for interposition between the sensor mounting socket and a sensor and, finally, axially inserting a position sensor through the seal and into the retention socket until the axially activated lock engages the sensor. Positive retention and placement of the sensor are established because the sensor will abut at least a portion of the socket when the axially activated lock or retainer is engaged with the sensor.  
           [0010]    It is an advantage of the present invention that a position sensor assembly and method according to this invention provides a speedy and error-free system for mounting a rotary position sensor.  
           [0011]    It is another advantage of the present invention that the present mounting system and method will precisely locate a position sensor with respect to a rotating component, obviating problems associated with prior art cam cover mounting systems. The present system allows mounting of a sensor through a cam cover notwithstanding stack up changes or tolerance changes in the distance between the cam cover and a rotating component which is being monitored.  
           [0012]    Other advantages as well as objects and features of the present invention will become apparent to the reader of this specification. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is a schematic representation of a prior art rotary position sensor used in an internal combustion engine.  
         [0014]    [0014]FIG. 2 is a partially schematic representation of a rotary position sensor and assembly according to the present invention.  
         [0015]    [0015]FIG. 3 is a partially schematic representation of a second form of a rotary position sensing assembly according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    As shown in FIG. 2, rotary position sensing assembly includes sensor  32  which may comprise either a Hall Effect or a variable reluctance sensor, or other type of sensor known to those skilled in the art and suggested by this disclosure. In any event, sensor  32  is mounted within socket  34  which is rigidly attached to cylinder block  36 . In a preferred embodiment, socket  34  is formed as a bore within cylinder block  36 . Socket  34  is located such that sensor  32  is in sufficient proximity with sensor wheel  38  so as to establish a 0.5-2.0 mm air gap extending between sensor  32  and the proximal end of each tooth,  39 , attached to sensor wheel  38 . Shaft  42  may comprise either a crankshaft, or a camshaft, or another type of rotating assembly. The assembly of FIG. 2 also includes seal  44  which is attached to an outer portion of socket  34  and which serves to retain lubricant or other engine fluid, while excluding contaminants from the interior of socket  34 . Finally, the sensing assembly of FIG. 2 also includes retainer  46  which is shown with further detail as item  64  in FIG. 3, and which is housed within bore or socket  34 . Retainer  46  is slidably engageable, or in other words, axially activated, because all that need be done to engage retainer  46  is to push sensor  32  into contact with abutment  40  within socket  34 . Thereafter, retainer  46  serves to maintain sensor  32  abutted with abutment  40 , so as to maintain the precise air gap required for proper operation of sensor  32 .  
         [0017]    The abutting relationship between the sensor and its mounting socket is shown in greater detail in FIG. 3. Retainer  64  may comprise a split, or snap ring type of retainer which engages retainer groove  66 , which is formed within the wall of socket  56 . Alternatively, retainer  64  may comprise a wireformed ring or other similar type of spring or snap ring type of retainer known to those skilled in the art and suggested by this disclosure.  
         [0018]    Retainer  64  is preferably mounted upon sensor  54  prior to insertion of sensor  54 . This allows sensor  54  and retainer  64  to be pushed into socket  56  until retainer  64  engages retainer groove  66 . At this point sensor  54  will have been pushed into registry abutment with shoulder  72  which is formed in socket  56 . This permits sensor  54  to be snapped into position within socket  56  without the need of any special tools.  
         [0019]    [0019]FIG. 3 further illustrates the use of a sensing assembly according to the present invention in which the sensor portion,  54 , of the sensing assembly is inserted through cover  60  which encloses an engine structure such as cylinder head  58 . Sensor  54  passes through seal  62 , which is mounted within aperture  61  formed in cover  60 . Although seal  62  is shown as having a garter spring  74  for purposes of enhancing its sealing capability, those skilled in the art will appreciate in view of this disclosure that seal  62  could be selected from any one of a number of different types of seals known to those skilled in the art and suggested by this disclosure.  
         [0020]    Sensor  54  is precisely located axially by the present mounting system, so as to maintain the air gap, G, required for any particular sensor being employed according to the present invention. As before, sensor  54  is intended to detect the position of a rotating assembly (not shown) which has a sensor wheel with at least one tooth  70  incorporated therein.  
         [0021]    Sensor  54  has integral abutment  68  formed about the periphery of sensor  54 . This abutment  68  abuts a shoulder  72  formed as a portion of socket  56 . Thus, when abutment  68  and shoulder  72  are in contact with each other, sensor  54  is prevented from sliding any further into the engine. Moreover, retainer  64  which is mounted within retainer groove  66  formed in socket  56 , and a similar groove  76  formed in the outer periphery of sensor  54 , serves to prevent unwanted movement outward of sensor  54  in a direction away from sensor wheel  70 . As a result, the present inventive mounting system will reliably, repeatably and precisely locate sensor  54  within socket  56 , so as to maintain air gap G within a specified range.  
         [0022]    Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention. It is intended that the invention be limited only by the appended claims.