Abstract:
A hydraulic control valve is provided having a solenoid body, an energizable coil, and an armature positioned adjacent the coil. A valve stem extends from the armature. The coil is energizable to move the armature and the valve stem from a first position to a second position. The valve body, the armature and the valve stem are configured so that the armature and the valve stem are biased to the first position by pressurized fluid, allowing the armature to operate without a biasing spring.

Description:
TECHNICAL FIELD 
     The present invention relates to an electrically operated hydraulic control mechanism such as a solenoid valve. 
     BACKGROUND OF THE INVENTION 
     Solenoid control valves for hydraulic control systems are used to control oil under pressure that may be used to switch latch pins in switching lifters and lash adjusters in engine valve systems. Valve lifters are engine components that control the opening and closing of exhaust and intake valves in an engine. Lash adjusters may also be used to deactivate exhaust and intake valves in an engine. Engine valves may be selectively deactivated or locked out to disable operation of some cylinders in an engine when power demands on an engine are reduced. By deactivating cylinders, fuel efficiency of an engine may be improved. 
     Engine deactivating solenoid control valves must operate with minimum response times to maximize engine efficiency. Valve response times include valve activation response times and deactivation response times. Solenoid control valves apply a magnetic force to an armature that moves a control valve stem by activating a coil to move the armature against a biasing force that is typically provided by a spring. The magnetic force applied by the solenoid to the armature and in turn to the control valve stem should be maximized to reduce response time. The magnetic force applied by the coil can be increased by increasing the size of the coil. However, cost and weight reduction considerations tend to limit the size of the coil. Deactivation response times are adversely impacted by valve closure biasing springs, the force of which must be overcome before the valve is opened. While this delay in response times in most applications is minimal, in variable valve actuation systems, the limited time window for valve activation and deactivation is critical and must be minimized. 
     SUMMARY OF THE INVENTION 
     A hydraulic control valve is provided having a solenoid body, an energizable coil, and an armature positioned adjacent the coil. A valve stem extends from the armature. The coil is energizable to move the armature and the valve stem from a first position to a second position. The first position may be a deenergized, closed position, and the second position may be an energized, open position. The valve body, the armature and the valve stem are configured so that the armature and the valve stem are biased to the first position by pressurized fluid, allowing the armature to operate without a biasing spring. Thus, the armature is configured so that the net fluid forces contribute to closing the valve, providing a relatively quick valve actuation response time. If no biasing spring is used, cost and assembly time, as well as response time, are minimized. Additionally, the solenoid may be weaker, and therefore less expensive, as no spring biasing force needs to be overcome. 
     In one embodiment, the armature and the valve stem include a first poppet and a second poppet, and the valve body defines a supply chamber with a first seat, a second seat, and a control chamber between the first and second seats. The first poppet is configured to sit at the first seat and the second poppet is configured to be spaced from the second seat in the first position to prevent pressurized fluid flow past the first seat and to exhaust fluid from the control chamber past the second seat. The first poppet is configured to be spaced from the first seat and the second poppet is configured to sit at the second seat in the second position to permit flow of pressurized fluid from the supply chamber to the control chamber and prevent flow from the control chamber to the exhaust chamber. 
     The hydraulic control valve may be mounted to an engine such that the armature falls to the second position when the engine is off and the coil is not energized, thereby moving the first poppet off of the seat to open the supply chamber to the control chamber. Thus, due to gravity, the armature is in the same position as the energized, engine—on position when the engine is off and the coil is not energized. When the engine is subsequently restarted, with the coil still deenergized, air can thereby expel from the supply chamber to the control chamber, and further to the exhaust when the armature and valve stem move to the first position due to pressurized oil acting on the second poppet. Expelling any air in the system enables a quicker, more controlled response of the valve. 
     A hydraulic control circuit is provided with an electromagnetic actuator selectively actuatable to create a flux path, a valve body having a seat past which a fluid under pressure is selectively permitted to flow, and an armature that is selectively moved in a first direction by electromagnetic flux. The armature defines a poppet that is moved in the first direction relative to the seat from a closed position in which fluid flow past the seat is prevented to an open position in which fluid flow past the seat is permitted, the armature being biased to the closed position by operation of the fluid under pressure. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a solenoid valve; 
         FIG. 2  is an exploded perspective view of the solenoid valve shown in  FIG. 1 ; 
         FIG. 3  is a partial cross-sectional view taken along the plane of section line  3 - 3  in  FIG. 1  showing the valve in a first, closed and deenergized position; and 
         FIG. 4  is a partial cross-sectional view similar to  FIG. 3  of the valve in a second, open and energized position. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a solenoid valve  10 , for example, such as that used to deactivate lifters or operate a dual lift system in an internal combustion engine or diesel engine is illustrated. The solenoid valve  10  may also be referred to as an electromagnetic actuator. The solenoid valve  10  is installed in an engine  12 . The solenoid valve  10  includes a solenoid portion  16  and a valve body  18 . 
     Referring to  FIGS. 2 and 3 , the solenoid valve  10  is shown to include a solenoid can  20  that houses a coil  22  that powers the solenoid valve  10 . A pole piece  24  is assembled within the solenoid can  20 . The pole piece  24  defines part of the flux path for the coil  22 . A flux collector insert  26  is disposed within the solenoid can  20  and also forms part of the flux path for the coil  22 . 
     An armature  28  is acted upon by the flux created by energizing the coil  22  to shift the solenoid valve  10  from a normally closed position as shown in  FIG. 3  to the open position as shown in  FIG. 4 . An air gap  30  is provided between a radially-extending face  31  of the pole piece  24  and a radially-extending face  33  of the armature  28 . The air gap  30  may be adjusted by adjusting the pole piece  24  relative to the armature  28 . A relief groove  34 , shown in  FIG. 2 , is provided in the armature  28  that facilitates flow of oil under pressure axially across the armature  28 . The relief groove  34  is also referred to as a conduit. Alternatively, a conduit may be formed in the valve body  18  adjacent the armature  28  to provide flow of pressurized oil across the armature  28 . The flux collector insert  26  may be inserted adjacent to the coil  22  and the valve body  18  in a molded one-piece or multiple-piece body  40 . 
     The valve body  18  defines an oil intake chamber  41 , also referred to as a supply chamber, in which the armature  28  is disposed and that initially receives oil under pressure. The valve body also defines an intermediate chamber  42 , also referred to as a control chamber. A plurality of O-ring grooves  43  are provided on the exterior of the valve body  18  that each receives one of a plurality of seals  44 . The seals  44  establish a seal between the valve portion  18  and the engine  12 . The molded body  40  defines an internal coil receptacle  46 , or bobbin, that extends into the solenoid portion  16 . The coil  22  is shown only in part, but it is understood that the coil  22  fills the coil receptacle  46 . The body  40  may be formed as a one-piece integral plastic molded part, as illustrated, or could be formed in pieces and assembled together. The coil  22  is wrapped around the coil receptacle  46 . 
     A valve stem  48  has a portion  50  that is received within an opening  52  in the armature  28 . The position of the control valve stem  48  may be adjusted relative to the armature  28  by a threaded connection or by a press-fit between the stem  48  and the armature  28 . The armature  28  includes a poppet  54  that is moved relative to the valve seat  56  in response to pressure changes, as will be more fully described below. An exhaust poppet  60  is provided on one end of the control valve stem  48  to move relative to a valve seat  62  to open and close an exhaust port  70 . 
     A supply gallery  64  is provided in the engine  12  to provide pressure P 1  to the oil intake chamber  41  that is defined in the valve body  18 . A control gallery  68  is provided in the engine  12  that is normally maintained at control pressure P 2 . An exhaust gallery  71 , also provided in the engine, is in communication with the exhaust port  70  and is ported to ambient pressure and may be referred to as “P 0 ”. The intermediate chamber  42  goes to Pressure P 0  when the exhaust port  70  is opened. 
     Referring to  FIG. 4 , the solenoid valve  10  is shown in the open position. The coil  22  is energized to retract the armature  28  toward the coil  22 . The poppet  54  opens the valve seat  56  to provide pressure P 1  from the oil intake chamber  41  to the intermediate chamber  42 , and the exhaust poppet  60  sits at seat  62  to close the exhaust port  70 . 
     Referring to  FIGS. 2-4 , the valve body  18  includes a supply opening  63  that receives oil under pressure from a supply gallery  64  that is in communication with the oil intake chamber  41  and the valve seat  56 . When the valve seat  56  is open, the intake chamber  41  is in communication with the intermediate chamber  42 . Oil under pressure is provided through an outlet opening  66 , also referred to as a control port, and to a control gallery  68 . An exhaust port  70  is provided at the inboard end of the valve body  40 . Exhaust port  70  is in communication with exhaust gallery  71 . 
     In operation, the valve  10  is normally closed as shown in  FIG. 3  and is shifted to its open position as shown in  FIG. 4  by energizing the coil  22 . The coil  22 , when energized, reduces the air gap  30  formed between the pole piece  24  and the armature  28 . The armature  28  is shifted toward the pole piece  24  by electromagnetic flux created by the coil  22 . Oil in chamber  41  is in communication with the gap  30  through the relief groove  34 . 
     When in the normally closed position shown in  FIG. 3 , the poppet  54  closes the valve seat  56 , isolating the oil intake chamber  41 , which is at P 1 , from the intermediate chamber  42 , which is at P 2 . The oil under pressure in the oil intake chamber  41  biases the poppet  54  against the valve seat  56 . The area of the armature  28  affected by P 1  biases the armature to the closed position as P 1  acts on the larger surface area of face  33  of the armature  28  at the gap  30  to provide biasing force in one direction (i.e., in a direction to seat the poppet  54  at the seat  56 , while pressurized fluid at P 1  acts on a smaller surface area  73  of the armature in the chamber  41  in an opposing direction. The biasing force applied to the poppet  54  is intended to eliminate the need for a spring. Alternatively, a spring (not shown) may be incorporated to increase the biasing force applied to the poppet  54 . 
     When the coil  22  is energized, flux through the pole piece  24  and flux collector insert  26  pulls the armature  28  toward the pole piece  24 , as shown in  FIG. 4 . The face-to-face orientation of the armature  28  relative to the pole piece  24  subjects the armature  28  to exponentially greater magnetic force. Shifting the armature  28  causes the poppet  54  to open relative to the valve seat  56 , thereby providing pressure P 1  from the oil intake chamber  41  to the intermediate chamber  42 . The intermediate chamber  42  is normally maintained at pressure P 2  but is increased to P 1  when the poppet  54  opens the valve seat  56  and the poppet  60  closes valve seat  62  to close off the exhaust port  70 . Thus, P 1  acts on the surface area of face  33  of the armature  28  and the surface area  72  of the poppet  54  in one direction and on annular surface area  73  and surface area  74  of poppet  54  in an opposing direction. Because the affected surface area  33  is equal to the combined surface areas  73  and  74 , the net force is that on surface area  72 . This change in pressure increases the hydraulic pressure supplied to the engine valve system to P 1 . When the pressure provided to the engine valve system changes to P 1 , selected engine valves may be deactivated by latch pins, lash adjusters or another controlled device (not shown) to thereby deactivate selected cylinders of the engine. 
     When the coil  22  is subsequently deenergized, with the forces due to the flux removed (i.e., the net force pulling the armature  28  toward the pole piece  24 ), the net fluid pressure on surface area  33  drives the armature  28  to the normally closed, deenergized position of  FIG. 3 . Thus, the armature  28  is configured so that the net fluid forces (i.e., net downward force acting on face  72 ) contributes to closing the valve  10 , with the chamber  42  exhausting to exhaust port  70 , thereby providing relatively quick valve actuation response time from the energized to the deenergized position. 
     The valve  10  is provided with an air purging and self-cleaning feature. Specifically, the armature  28  is formed with a bypass slot  53 , also referred to as a bypass channel, to permit a limited amount of oil to move from chamber  41  to chamber  42  when the valve  10  is closed, bypassing the seat  56 . Alternatively, the bypass slot may be provided in the body  18  adjacent the seat  56 . The slot  53  also allows particles of dirt to be expelled from chamber  41  with the oil, and thus functions as a “self-cleaning” feature of the valve. Additionally, air is purged from the chamber  41  through slot  53 , thus preventing an air cushion acting against valve  10  moving to the energized position of  FIG. 4  when the coil  22  is subsequently energized. This allows quick transitioning from the deenergized to the energized position. 
     When the engine  12  is off so that no fluid pressure is provided in the valve  10  and the coil  22  is deenergized, assuming that the valve  10  is installed in the engine  12  with the armature  28  above the pole piece plug  24  (i.e., upside down with respect to the view shown in  FIGS. 3 and 4 ), gravity will cause the armature  28  to fall to the energized position of  FIG. 4  (although the coil is not energized). Thus, when the engine  12  is started, pressurized oil will come up the supply gallery  64  and force any air ahead of it out of the supply chamber  41  to the control chamber  42 , past the open seat  56  as the oil proceeds into chamber  41  and gap  30 , biasing the armature  28  to the closed, deenergized position of  FIG. 3 . The air is expelled from chamber  42  to exhaust port  70  as the poppet  62  unseats. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.