Abstract:
An oil control valve for a variable cam phaser has a secure steel-to-steel fit between the secondary plate of the bobbin and the frame owing to a shoulder formed in the frame against which the secondary plate abuts, and also owing to an o-ring disposed between the bobbin and frame. This prevents oil from leaking into the electrical connector of the valve, which advantageously can be oriented parallel to the axis of the valve.

Description:
I. FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to oil control valves for variable cam phasers. 
       II. BACKGROUND OF THE INVENTION 
       [0002]    A Variable Cam Phaser (VCP) replaces the standard pulley, sprocket or gear in a gasoline engine&#39;s valve train. It enables the cam lobe (lift event) timing to crank shaft timing to be changed while the engine is operating, based on the parameters of the engine. Variable cam phasing changes the timing of the valve lift event, and can be used to shift the intake cam, the exhaust cam, or both on dual overhead cam engines. This helps increase engine efficiency, improving idle stability while delivering more torque and horsepower. It also helps boost fuel economy and reduces hydrocarbon emissions. 
         [0003]    The cam lobe angular position of the VCP (i.e., its phase relationship), is controlled by an internal vane mechanism of the VCP that in turn is established by an oil control valve. More specifically, commands from the engine control module (ECM) of the vehicle adjust the position of the oil control valve, which can be mounted in the cylinder head to regulate engine oil flow to either side of the vanes to advance or retard the camshaft position. 
         [0004]    Typically, the oil control valve has a fluid control portion that is driven by an electromagnetic solenoid. The fluid control portion includes a valve body and an internal spool, with two separate openings being formed in the valve body that are in fluid connection with two separate sides of the VCP. The internal spool has an oil inlet and two separate outlets that correspond to and overlap with the two openings in the valve body. With this structure, pressurized engine oil can be made to flow through the valve to the two sides of the variable cam phaser as appropriate for the desired VCP configuration. 
         [0005]    The electromagnetic solenoid of the oil control valve is comprised mainly of a bobbin, which has metal and plastic sections. Currently, the bobbin of the electromagnetic solenoid can become dislodged or loose over time due to the differing thermal expansion of its metal and plastic components caused by the heat of the engine. After becoming dislodged or loose, oil from the fluid control portion of the oil control valve can leak through the bobbin into the electromagnetic solenoid. This effect may cause the oil control valve to malfunction. 
         [0006]    In an attempt to remedy the present situation, manufacturers have attempted various solutions to minimize oil leakage and ensure a permanent fit between the metal and the plastic components of the bobbin. Some of these solutions include press fits, spring washers, and crimping steel to steel surfaces on the bobbin. However, these solutions prove to be expensive. Other solutions have also been implemented, but only retard the loosening effect and do not ensure a permanent fit. The present invention provides a method for achieving a cost-effective permanent fit between the metal and plastic sections of the bobbin. 
       SUMMARY OF THE INVENTION 
       [0007]    An oil control valve for a variable cam phaser includes a metal frame that is formed with a radially enlarged part with a first inside diameter and a radially smaller part with a second inside diameter less than the first inside diameter. The two parts are coaxial with each other such that a shoulder is established between them. More specifically, the shoulder defines an annular surface that is perpendicular to the axis of the parts. A bobbin that is partially metal is disposed within the frame with the bobbin abutting the surface of the shoulder. An o-ring is disposed between the bobbin and frame. The combination of the o-ring and bobbin abutting the surface of the shoulder substantially prevents oil from leaking to a connector associated with the valve. 
         [0008]    In non-limiting implementations the connector is substantially coaxial with the axis of the frame and bobbin. The bobbin may include a secondary plate engaged with a plastic body by means of overmolding the plastic body onto the secondary plate, and the secondary plate abuts the surface of the shoulder. In some applications the valve can be engaged with the variable cam phaser. 
         [0009]    In another aspect, an assembly for a vehicle includes a variable cam phaser and an oil control valve engaged with the phaser to selectively port oil to the phaser. The oil control valve has a shoulder defining a metal-to-metal interface between two metal parts of the valve to inhibit oil leakage into an electrical connector of the valve. 
         [0010]    In yet another aspect, an oil control valve includes an electrical connector and a bobbin including a metal secondary plate. A frame surrounds the bobbin. As set forth further below, the frame defines an axis and an annular surface substantially perpendicular to the axis, with the secondary plate abutting the surface. 
         [0011]    The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a block diagram of a non-limiting environment of the present oil control valve; and 
           [0013]      FIG. 2  is a cut-away side view of an exemplary non-limiting embodiment of the present valve. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring initially to  FIG. 1 , an internal combustion engine  5  is shown with a controller  10 . The engine  5  is operably coupled to a variable cam phaser  14  that is controlled by an oil control valve  12 , the details of which are further described below. 
         [0015]    In general overview, the engine  5  has at least one camshaft  16  with the variable cam phaser  14  attached thereto and a cam position sensor  13 . The cam phaser  14  is fluidly connected to the oil control valve  12 , which in turn is fluidly connected to a pressurized supply of oil from the engine  5  or other source. In non-limiting exemplary implementations the controller  10  is operably connected to an engine torque management system such as the one described in U.S. Pat. No. 6,367,462, incorporated by reference. 
         [0016]    The controller  10  is also operably connected to at least one sensor that is used to monitor engine operation. The engine torque management system may also include a fuel injection system, an ignition system, an electronic throttle control system, an exhaust gas recirculation system, an evaporative control system (not shown), along with the variable cam phaser  14  with the oil control valve  12 . Without limitation and in accordance with principles known in the art, the sensor may include an engine speed sensor, a manifold absolute pressure sensor, a throttle position sensor, an oxygen sensor, intake air sensor, mass air flow sensor, EGR position sensor, exhaust pressure sensor, exhaust gas sensor, torque sensor, combustion sensor, or others (not shown), and/or the cam position sensor  13 . In any case, the controller  10  collects information from the sensors and control output systems, including the engine torque management system, using control algorithms and calibrations internal to the controller  10 . 
         [0017]    With particular regard to elements of the oil control valve  12  that are the subject of further disclosure below, the valve  12  includes an electromagnetic solenoid  30  and a valve  32 . The valve advantageously may be a spool valve  32  with a single inlet  34  of oil and two outlets of oil  36 ,  38 . A spool  31  is attached to an armature (not shown) of the electromagnetic solenoid  30 , and the spool  31  is contained within a valve body  33  coaxial to the longitudinal axis of the body  33 . 
         [0018]    Each of the two outlets  36 ,  38  of oil is attached to one of the inlets of the cam phaser  14 , as described above. In some embodiments, the electromechanical solenoid  30  is driven by a pulsewidth-modulated (PWM) signal  40  sent from the controller  10 . In operation, a PWM signal  40  is sent to the electromagnetic solenoid  30  to cause the armature (not shown in  FIG. 1 ) and attached spool  31  to move linearly along the longitudinal axis within the valve body  33 . 
         [0019]    The position of the spool  31  in conjunction with the designs of the spool  31  and the valve body  33  determines the oil flow through the valve  32  from the fluid inlet  34  to each of the two fluid outlets  36 ,  38 . The oil control valve  12  provides sufficient oil flow rate through the valve  32  so that the response time of the cam phaser  14  and corresponding combustion efficiency of the engine  5  can be optimized at typical oil pressures, temperatures and voltage levels. 
         [0020]    Moving to  FIG. 2 , relevant details of the electromagnetic end of the valve  12  are shown. The electromagnetic solenoid  30  shown in  FIG. 1  is wound around a bobbin  42  that extends past the solenoid and that defines an axis  44 . The electromagnetic solenoid in  FIG. 1  is electrically connected to a connector  46 , which is disposed in a connector cavity  48  formed in the bobbin  42 . As shown in  FIG. 2 , the connector cavity  48  is coaxial with the axis  44  of the bobbin  42  and the connector pin  46  is parallel to and if desired coaxial with the axis  44 . 
         [0021]    The bobbin  42 , which may be hollow such that it forms a bobbin chamber  50  as shown, is surrounded by a metal frame  52 . In accordance with present principles, the frame  52  is formed with a radially enlarged part  54  with a first inside diameter D 1  and a radially smaller part  56  with a second inside diameter D 2  which is less than the first inside diameter D 1 . The radially enlarged part  54  and the radially smaller part  56  are coaxial with each other and with the connector  46 . 
         [0022]    As shown in  FIG. 2 , a shoulder  58  is established between the radially enlarged part  54  and the radially smaller part  56 . The shoulder  58  defines an annular surface  60  that is perpendicular to the axis  44  of the bobbin  42 . Further, the bobbin  42  abuts the surface of the shoulder  58  and is at least partially disposed within the frame  52 . 
         [0023]    More specifically, the bobbin  42  includes a hollow metal secondary plate  62  that is engaged with the plastic body of the bobbin  42  by means of, e.g., overmolding the plastic body onto the secondary plate  62 , and a portion of the secondary plate  62  abuts the surface of the shoulder  58 , creating a metal-to-metal interface. By way of the metal-to-metal interface, oil is in part prevented from leaking through the bobbin  42  into the connector  46  because the thermal expansion of both metal components will remain equal and the seal between the metal interfaces will remain secure, thereby inhibiting oil from leaking up through the bobbin. 
         [0024]    A further seal between the bobbin and the frame is created through the existence of an O-ring  64 . The O-ring  64  is disposed between the bobbin  42  and frame  52  in a circular groove  66  that is formed in the bobbin  42  as shown. Any oil leaking past the metal-to-metal interface described above will be further impeded by the O-ring  64 , which acts as a secondary barrier to ensure that oil does not leak into the connector  46 . 
         [0025]    While the particular OIL CONTROL VALVE FOR VARIABLE CAM PHASER is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.