Abstract:
A switchable fluid control valve assembly having a regulating spool and a pilot spool disposed within a common bore. A regulating spring urges the regulating spool toward a rest position wherein an oil supply port is fully uncovered. Supply oil entering the assembly causes the regulating spool to assume a position wherein oil flow is throttled to a downstream pressure insufficient to activate an associated valve deactivation mechanism but sufficient to provide lubrication to the engine. When activation of the mechanism is desired, a solenoid moves the pilot spool wherein oil at full pressure is engaged against the regulating spool, de-throttling the flow of oil to the mechanism. When the solenoid is again deactivated, a dump port is opened into the oil flow path, immediately reducing the pressure on the regulating spool which then moves to eclipse the supply port and open a path from the mechanism to drain. DP-30941 6

Description:
RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS  
       [0001]    The present application draws priority from a pending US Provisional Application, Serial No. 60/432,474, filed Dec. 11, 2002. 
     
    
     
       TECHNICAL FIELD  
         [0002]    The present invention relates to spool-type valves; and more particularly, to such valves as are commonly employed for switching and controlling flow of activation and lubricating fluids to various components of internal combustion engines; and most particularly, to a switchable oil control spool valve system having a regulating spool for regulating oil pressure and activation flow, and a pilot spool for switching between a high pressure activation mode and a low pressure regulating mode, both spools being disposed in a common bore in a common housing.  
         BACKGROUND OF THE INVENTION  
         [0003]    Spool-type valves for controllably diverting the flow of fluids are well known. In a typical spool valve, a hollow piston, or “spool,” having a plurality of radial ports through the spool wall is slidably disposed within a cylindrical body that is also provided with a plurality of internal annular grooves and radial ports extending through the body wall. The spool is variably positionable within the body to cause selected ports in the spool to be aligned with grooves and ports in the body, thereby permitting flow of fluid from outside the body through first aligned ports into the interior of the spool and out through second aligned ports. A plurality of different flow paths typically is possible by positioning the spool at a plurality of different axial positions within the body. Typically, the spool is connected to a linear solenoid actuator, whereby the spool may be axially positioned by signals from a controller such as a computerized engine control module, although other actuations such as pneumatic and hydraulic are within the scope of the invention as described below.  
           [0004]    A common usage for an oil-control spool valve is to variably actuate engine control subsystems such as camshaft phasers and variable valve activation (VVA) mechanisms, and multi-step or valve deactivation mechanisms. In a two step valve mechanism, for example, the mechanism selects the lift profile (low or high) of an intake valve camshaft using a hydraulically activated roller finger follower (RFF).  
           [0005]    In a simple configuration of this example, a spool valve supplies high pressure oil, typically from an engine-driven oil pump, to activate the RFF, and shuts off the oil supply to deactivate and drain pressure from the RFF. However, it is desirable that in RFF-deactivation mode the oil supply not be completely shut off, as other components of the valve train, such as camshaft lobes and rocker arms, continue to require flow of oil for lubrication. In the prior art, continued lubrication may require separate valving and/or complicated porting.  
           [0006]    What is needed is an oil control valve assembly that is switchable not simply between on and off modes but between a pressure high enough for RFF activation and a controlled pressure low enough for lubrication but insufficient for RFF activation.  
           [0007]    What is needed further is means for instantaneously switching of the oil supply from high-pressure mode to low-pressure mode.  
         SUMMARY OF THE INVENTION  
         [0008]    A switchable oil control valve system in accordance with the invention comprises a spool valve assembly having a regulating spool and a pilot spool disposed within a common bore in the valve housing. An apertured stop fixedly disposed in the bore between the spools separates the bore into a regulating chamber and a pilot chamber and defines a spring seat for both a regulating spring and a pilot spring. The regulating spring urges the regulating spool toward a rest position wherein an oil supply port in the housing is fully uncovered. In operation, supply oil entering the valve is available to a first pressure face of the regulating spool such that, with proper selection of regulating spring strength, the regulating spool assumes an intermediate position wherein supply oil flow is throttled to a pressure insufficient to activate an associated deactivatable RFF but is sufficient to provide lubrication to moving parts in the mechanical valve train. The regulating spool and spring in the housing thus comprise a self-regulating hydraulic governor for oil flow and pressure through the spool valve. The pilot spool is actuable through an end of the housing by a linear solenoid. When activation of the RFF is desired, the solenoid is energized, urging the pilot spool to a first position wherein oil at full engine pressure is admitted to the pilot chamber. The oil flows through the apertured stop into the regulating chamber, and brings high oil pressure against a second and opposing pressure face of the regulating spool. The regulating spool is displaced thereby, fully opening the supply port and sending high pressure oil to activate the RFF. When deactivation of the RFF is desired, the solenoid is de-energized. The pilot spring urges the pilot spool to a second position wherein a dump port is opened into the oil flow path, immediately reducing to zero the pressure on the face of the regulating spool adjacent the stop. Residual pressure on the opposite face of the regulating spool causes the spool to move against the regulating spring to a new position wherein the inlet port is eclipsed and a path from the RFF to drain is opened via the pilot spool. As the residual pressure is gradually reduced via a sensing port in the regulating spool, the regulating spool returns to the first position wherein the drain path is closed and the throttling/regulating function for lubrication is resumed, awaiting the next call for RFF activation.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 is a cross-sectional view of a piloted control valve assembly in accordance with the invention, showing the principal components thereof;  
         [0011]    [0011]FIG. 2 is a cross-sectional view similar to the view shown in FIG. 1, showing the valve assembly in regulating mode;  
         [0012]    [0012]FIG. 3 is a cross-sectional view showing the path of oil flow through the valve assembly from the supply port to the control port during regulating (low pressure) mode, as shown in FIG. 2;  
         [0013]    [0013]FIG. 4 is a cross-sectional view similar to the view shown in FIGS. 1 and 2, showing the valve assembly in high pressure mode;  
         [0014]    [0014]FIG. 5 is a cross-sectional view similar to the view shown in the previous drawings, showing the valve assembly in dump mode; and  
         [0015]    [0015]FIG. 6 is a cross-sectional view showing the path of oil flow through the valve assembly from the control port to the dump port during dump mode, as shown in FIG. 5. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Referring to FIG. 1, an integrated oil control valve assembly  10  in accordance with the present invention is shown. Valve assembly  10  includes spool valve assembly  12  and solenoid valve assembly  14 . Spool valve assembly  12  includes generally cylindrical housing  16 , regulating spool  18 , pilot spool  20  and regulating and pilot springs  22 , 24 , respectively. In operation, the axial position of regulating spool  18  within housing  16  regulates the pressure of oil flowing to an associated oil-actuated device such as a roller finger follower (not shown), and also to lubrication-requiring elements such as camshaft bearings and cam lobe surfaces. The axial position of pilot spool  20  determines the unregulated oil pressure in the system, either high pressure or zero pressure.  
         [0017]    Regulating spool  18  defines first pressure end face  26 , counter bore  28 , flow annulus  30  disposed between a first end  32  and a second pressure end face  34  of regulating spool  18 , and spring bore  36 . Regulating spool  18  further defines central axis A wherein counter bore  18 , flow annulus  30  and spring bore  36  are concentric with central axis A. Further included in regulating spool  18  are at least one radial sense port  38  fluidly connecting annulus  30  with counter bore  28  and at least one radial dump port  40  (3 are shown) fluidly connecting outside surface  42  of regulating spool  18  with spring bore  36 .  
         [0018]    Still referring to FIG. 1, cupped-shaped pilot spool  20  includes open end  50  and closed end  52 . Pilot spool  20  defines spring pocket  54 , at least one radial pressure port  56  and at least one dump/vent port  58 . (In both cases, 3 are shown). Both the pressure ports and the dump/vent ports fluidly connect an outside surface  60  of pilot spool  20  with spring pocket  54 . Pilot spool  20  further defines central axis B.  
         [0019]    Generally cylindrical housing  16  of spool valve assembly  12  includes first end  62 , second end  64 , outer surface  66  and internal bore  68 . Internal bore  68  defines a regulating chamber  70  having a first diameter, a pilot chamber  72  having a second diameter, and step  74  therebetween. The diameter of regulating chamber  70  is slightly larger than the diameter of pilot chamber  72  and both are concentric with central axis C of housing  16 . Housing  16  also includes radial supply port  76  and radial control port  78 , both fluidly connecting outside surface  66  of housing  16  with regulating chamber  70  of internal bore  68 . Housing  16  further defines a first internal annular groove  80  disposed along the regulating chamber  70  of internal bore  68 , a second internal annular groove  82  and a third annular groove  84  disposed along pilot chamber  72  of internal bore  68 . Pilot port  86  intersects and is in fluid connection with second internal annular groove  82 . Vent orifice  88  intersects with third internal annular groove  84  and fluidly connects groove  84  with outside surface  66  of housing  16 .  
         [0020]    Pilot spool  20  is slidably disposed in housing  16  so that its outside surface  60  is in close contact, i.e., substantially fluid tight, with the wall of pilot chamber  72  of housing  16 . Regulating spool  18  is slidably disposed in housing  16  so that its outside surface  42  is in close contact, i.e., substantially fluid tight, with the wall of regulating chamber  70  of housing  16 . Central axes A, B, and C are coincidentally aligned. Stop  90  having a central aperture  122  (FIG. 4) is fixedly positioned against step  74  to be held in place such as by, for example, press fit or welding.  
         [0021]    A first end of pilot spring  24  is in contact with stop  90  so as to bias pilot spool  20  to the right, as shown in FIGS. 1 and 2.  
         [0022]    A first end of regulating spring  22  is in contact with stop  90  so as to bias regulating spool  18  to the left as shown in FIG. 2. First end  62  of housing  16  is closed off in a fluid tight manner by plug  92  as known in the art. When thus assembled, plug  92 , internal bore  68  of housing  16 , and first pressure end face  26  of regulating spool  18  conjunctively form an actuating chamber  94 .  
         [0023]    Still referring to FIG. 1, solenoid valve assembly  14  includes a frame  96  containing primary plate  98  and a plurality of windings  99  in bobbin assembly  100 . A ferromagnetic plunger  102  is slidably disposed within an axial bore  104 , plunger  102  defining a solenoid armature for cooperating electromagnetically with windings  99 . An actuating shaft  108  is axially disposed and retained within plunger  102  and extends through axial bore  110  of primary plate  98  for connection with pilot spool  20 . A generally cylindrical non-magnetic can  106  surrounds plunger  102  for slidably guiding and centering the plunger axially of primary plate  98 . Electrical connector  112  is fixed to frame  96  by retainer ring  114 , as is known in the art, and electrical leads (not shown) connect windings  99  to terminals  116 , as also is known in the art. Solenoid assembly  14  is sealed against spool assembly  12  with O-ring seal  118 , or the like, and rigidly fixed thereto by, for example, crimping the end of frame  96  over a mating end surface of second end  64  of housing  16 .  
         [0024]    Referring to FIGS. 2 through 6, the operation of integrated oil control assembly  10  will now be discussed. In the view shown in FIGS. 2 and 3, control assembly  10  is in its regulating mode. That is, solenoid valve assembly  14  is in its de-energized or “off”position, and pilot spring  24  is shown biasing pilot spool  20  to the right, (as shown in the figure). Thus, pilot spool  20  is not involved in regulating flow of oil to the RFF when the solenoid is de-energized.  
         [0025]    Oil  21 , fed under pressure as by the engine oil pump (not shown), is directed to supply port  76 , flow annulus  30 , through sense port  38 , and into actuating chamber  94  where it presents hydraulic pressure  95  against first pressure face  26  of regulating spool  18 . Oil also is directed around flow annulus  30  to control port  78 , where the oil is directed through passages (not shown) to operate a  2 -step roller finger follower of a corresponding  2 -step valve activating mechanism  79  or other switchable control device (not shown) of internal combustion engine  81 . In the pressure regulating mode, oil directed to the RFF is under relatively low pressure and, therefore, the RFF is positioned to operate in its “deactivated” mode. In this mode, oil can still flow to lubrication-requiring elements.  
         [0026]    A self-regulated oil pressure is maintained by oil control valve assembly  10 , as follows. As oil pressure at supply port  76  increases, pressure builds up against end face  26  causing regulating spool  18  to move to the right against regulating spring  22 . As shown in FIG. 2, with movement of regulating spool  18  to the right, shoulder  120  of regulating spool  18  progressively eclipses supply port  76  and thereby progressively restricts the flow of oil through supply port  76 , thereby reducing the amount and pressure of the oil flowing through flow annulus  30  and to the RFF through control port  78 , until the hydraulic force produced by the control pressure balances the extensive force of regulating spring  22 . Thus, the flow and pressure of oil to the RFF during deactivation thereof is self-governing. The resulting relatively low oil pressure is satisfactory general lubrication of related mechanical surfaces not involved in activation and deactivation, for example, the cam surfaces and camshaft bearings.  
         [0027]    Any small amount of oil leaking past regulating spool  18  toward pilot spool  20  is vented out of the assembly dump/vent port  58 , third internal annular groove  84  and vent orifice  88 , as shown in FIG. 1. Since pilot port  86 , which also receives oil under pressure from the engine oil pump, is closed-off by pilot spool  20  being positioned to the right, oil under pressure is not directed to second pressure end face  34  of regulating spool  18  to augment the extensive force of regulating spring  22 . Thus, a relatively low oil pressure to the  2 -step RFF is maintained, keeping the WA in deactivation mode.  
         [0028]    The high pressure mode is shown in FIG. 4. In this mode, solenoid valve assembly  14  is in its energized or “on” position, and pilot spool  20  is moved to the left, as shown in the figure. Oil flow from dump/vent ports  58  is prevented from flowing into third internal annular groove  84  and out vent orifice  88 . However, pressurized oil from the oil pump is permitted to flow into the assembly through pilot port  86 , second internal annular groove  82  and pressure ports  56  where it communicates through stop aperture  122  and against second pressure face  34  of regulating spool  18 . This pressure, coupled with the biasing force of regulating spring  22 , overcomes the regulated hydraulic oil pressure  95  in chamber  94  and forces regulating spool  18  to move to the left as shown. This fully opens supply port  76  to flow annulus  30  and thereby imparts full, unregulated oil pressure to control port  78  and to the RFF to place the  2 -step RFF in its activated or high-step mode. Of course, pressure in chamber  94  against first pressure face  26  will also increase to the full engine pump pressure, but it is offset by equal pressure against second pressure face  34  exerted by high pressure oil from supply port  86 ; thus, if faces  26 , 34  have equal areas, only the spring force is a factor in dictating the position of the regulating spool.  
         [0029]    [0029]FIGS. 5 and 6 show oil control assembly  10  in its dump mode. In this mode, the assembly rapidly returns the pressure of oil fed to the  2 -step RFF from a high pressure for activating the RFF to a regulated pressure for deactivating the RFF. Solenoid valve assembly  14  is shown in its de-energized or “off”position again. Plunger  102  and pilot spool  20  are moved to the right, as shown in the figures. Oil flow from pilot port  86  is immediately blocked and flow of oil from dump/vent ports  58  into third internal annular groove  84  and out vent orifice  88  is again permitted, thereby instantaneously reducing the oil pressure against second end  34  of regulating spool  18 . Since the oil pressure in actuating chamber  94  is still high, regulating spool  18  immediately moves full travel to the right against regulating spring  22  and against stop  90 . In this position, oil flow through supply port  76  is blocked. Moreover, oil  21 , under high pressure from the 2-step RFF flows back through control port  78 , around flow annulus  30  where it is permitted to communicate through radial dump port  40  in regulating spool  18  via first internal annular groove  80  into spring bore  36 , through stop aperture  122 , into spring pocket  54 , and out through dump/vent ports  58 , third internal annular groove  84  and vent orifice  88 . Thus, oil pressure is bled from the  2 -step RFF to orifice  88  to immediately return the RFF from a high pressure, activated mode to a low-regulated pressure, deactivated mode. As pressure  95  in chamber  94  decays via oil flow out of actuation chamber  94  via sense port  38 , regulating spring  22  urges regulating spool  18  to the left, causing the partial reopening of supply port  76 , as assembly  10  is returned to the low pressure control mode shown in FIG. 2. Assembly  10  is now ready for reactivation to high pressure mode when needed.  
         [0030]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.