Abstract:
Pressure balanced spool poppet valves with printed actuator coils minimize valve leakage and facilitate efficient manufacturing and reliable operation. The spool poppet valves may be configured like a conventional spool valve, but further include a poppet valve at one end of the spool to proved much better sealing when the poppet valve is closed. Various features are disclosed, including pressure balancing for high pressure operation. The printed actuator coils for the spool poppet valves are formed by the interconnection of conductive coils on each of multiple layers of a multiple layer printed circuit board, which circuit board may have a hole there through for accommodation of mechanical and/or magnet requirements, and may include similar printed actuator coils for one or more additional spool poppet valves as well as electronic devices associated with the operation thereof. The spool poppet valves may be advantageously constructed without printed actuator coils, and the printed actuator coils may be advantageously used in actuators of other designs.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/738,859 filed Nov. 21, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to the field of valves, and systems using a plurality of solenoid actuators.  
         [0004]     2. Prior Art  
         [0005]     Embodiments of the present invention provide improved devices for fluid control in various applications. Typical examples include the control of a high pressure fuel injector, and hydraulic engine valve actuation systems. Two-way poppet valves (open and closed) are often used due to their low leakage characteristics. In many applications, it is highly desirable to use a three-way valve for improved performance and control, but this is difficult due to a three-way valve&#39;s inability to pressure balance completely unless it is a spool valve, which leaks excessively. For purposes of this disclosure, a three-way valve will be described as a valve coupling a source (S) passage to a control (C) passage or coupling the control passage to a vent (V), though other port identifications may be more appropriate depending on the use of the three-way valve.  
         [0006]     The choices for a three-way valve are:  
         [0007]     Spool valve. A spool valve can create the required hydraulic paths, but while in either position (S-C or C-V) the valve has a very short leak (seal) path from a high-pressure area to a vented area, which can lead to high system parasitic losses. This valve can be designed to have a hydraulic short circuit (momentarily coupling of source and vent when transitioning from one position to the other) or not, depending on the application. The advantages are primarily in its pressure balance, thereby requiring very low actuation forces, and in the ability to be designed to avoid the short circuit.  
         [0008]     Three-way hard-seat valve (Poppet). This type of valve can have no leakage in either position, but when the valve is transitioning from one position to the other, there necessarily exists a direct flow path between the source and the vent that could lead to large losses of energy and system noise. This type of valve cannot be completely pressure balanced, and therefore requires greater actuating forces than a typical pressure balanced spool valve.  
         [0009]     Two two-way hard-seat valves (Poppet). This option has no leakage and can have a direct flow path between the source and the vent or not, depending on control of the system. The disadvantage of this system is that twice as many control valves are needed to achieve three-way control, adding system and control complexity, and further requiring more room to package.  
         [0010]     Thus the current choices and their disadvantages are:  
         [0011]     Spool Valve: High static leakage.  
         [0012]     Three-way hard-seat valve: High actuating force requirements (due to pressure imbalance) and short circuit loss.  
         [0013]     Two, two-way hard seat valves: Cost and complexity.  
         [0014]     Solenoid actuators for valves of various types are also well known. Such actuators may be single coil spring return, with or without magnetic latching or double coil, with or without magnetic latching (see U.S. Pat. Nos. 3,743,898 and 5,640,987). However configured, solenoid actuators generally have a relatively simple mechanical configuration, with the solenoid coils being relatively inexpensive to wind. However, in certain applications, the number of solenoid actuated valves preferably used may be relatively large, giving rise to quite a substantial wiring problem. Superimposed on this in certain applications is a combination of heat and vibration that can cause premature wiring failure, and thus possibly giving rise to unsatisfactory reliability of the system. One such application to which preferred embodiments of the present invention are directed is in diesel engines, and more specifically, to hydraulic engine valve actuation systems as are currently in development, and diesel engine fuel injection systems, as well as fuel air cells incorporating both hydraulic engine valve actuation and fuel injection in a single assembly for each engine cylinder. Because most diesel engines are multiple cylinder engines, such as 6 and 8 cylinder engines, each having intake valves, exhaust valves and a fuel injector, all three of which must be independently controlled for each cylinder, and preferably for greater flexibility each engine valve actuator and each fuel injector will have more than one solenoid valve, the number of solenoid valves preferably used in a multi-cylinder engine can be quite substantial. Accordingly, wiring of the individual solenoid coils to a harness for connection to a control box would be complicated and expensive and may not have the reliability inherent in the rest of the diesel engine.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a cross section of one embodiment of pressure balanced spool poppet valve in accordance with the present invention.  
         [0016]      FIG. 2  is an exploded perspective view of a multilayer printed circuit board having printed coils on each layer of the board.  
         [0017]      FIG. 3  is a face view of the multilayer printed circuit board of  FIG. 2 .  
         [0018]      FIG. 4  is a schematic diagram of an exemplary application of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     First referring to  FIG. 1 , a cross-section of a spool poppet valve in accordance with an embodiment of the present invention may be seen. The valve shown is a three-way valve, in that it may connect a control port C to a supply port S or to a vent port V. The valve includes a housing  20  and cap  22 , both of which are of magnetic materials, and an end cap  24 , which may or may not be fabricated of a magnetic material. Located within the housing  20  is a spool  26  having a poppet valve  28  at the left end thereof, with a coil spring  30  encouraging the spool and poppet valve to the right position, as shown. In this position, the control port C is coupled to the vent port V, with the poppet valve being firmly seated on seat  32  on the housing to seal the high pressure fluid in the source port S from the control port C.  
         [0020]     At the right end of spool  26  is a magnetic armature  28  urged against end  34  of the spool by a pressure balance piston  36 , the right end of which is also subjected to the fluid pressure of the supply S. The diameter of the pressure balance piston  36  is the same as the outer diameter of the spool  26 , thus substantially equal to the inner diameter of the housing  20  and cap  22 . This, coupled with the fact that the angle of the valve seat  32  is slightly greater than the angle of the poppet valve  28  so that the poppet valve seals on the edge of the bore in the housing  20 , means that the spool poppet valve is pressure balanced, the pressure of the supply S on the poppet valve  28  acting over the same area as the fluid in supply S acting on the end of pressure balance piston  36 .  
         [0021]     When a current is passed through coil  38 , the armature  28  is attracted to the left, overcoming the force of spring  30  to move the spool to a left-most position when the armature  28  is attracted flat against the end of housing  20 . In this position, a magnetic circuit is established through housing  20  and armature  28  that has a substantially zero air gap. Thus in this position, the armature  28  may be retained by residual magnetism in the housing  20  and armature  28 , or alternatively, by a small holding current in coil  38 , depending on the relative forces between spring  30  and the holding force of the residual magnetism. Obviously, when the spool moves to the left position, in this embodiment the coupling from the control C to the vent V is first discontinued as poppet valve opens, and then coupling from the control port C to the supply port S is opened by the spool. Alternatively, if one wanted, one could simultaneously close one port and open the other, or as a further alternative, open the coupling between the control port C and the supply port S before closing the coupling between the control port C and the vent, though usually this is undesirable because of the loss of energy by the momentary coupling of the supply port S directly to the vent port V.  
         [0022]     An advantage of the spool poppet valve of  FIG. 1  is the fact that when the poppet valve is closed, the leakage characteristic of a spool valve is grossly reduced. This is of particular advantage in applications where the fluid pressure in the supply S is quite high and/or when the valve is used in an application where the valve is used to couple the high pressure fluid in supply port S to the control port C only a relatively small percentage of the overall time of use of the valve. By way of specific example, a valve in accordance with  FIG. 1  might be used to control the fluid pressure over an intensifier in an intensifier-type fuel injector. In such an application, in a four-cycle diesel engine, the control port C would be coupled to the supply port S over a crankshaft angle of perhaps 90° or less during each 720° rotation of the crankshaft. Thus in such applications, the leakage from supply to vent is grossly reduced by the poppet valve. In that regard, when the valve is actuated, the supply pressure in supply port S will be communicated to the control port C, with leakage past the spool to the vent port V, though as stated before, that will occur only for a relatively small percentage of the use of the valve. There will, of course, also be leakage from the supply port S past the pressure balance piston  36  to vent V, although because of the length of the leakage area, this leakage is also grossly reduced in comparison to that of a relatively short stroke ordinary spool valve.  
         [0023]     Another aspect of the present invention is a construction of the actuator coils  38  in the valve of  FIG. 1 , and for that matter, their construction as it relates to systems using a plurality of solenoid actuated valves, including but not necessary limited to, valves of the specific type shown in  FIG. 1 . In particular, in some applications, it may be desirable to use printed coils (copper traces as in a printed circuit) for the actuator printed on the same printed circuit board as the coils for other actuators and/or on the same circuit board as electronic components used for such purposes as control of the actuator coils.  
         [0024]     By way of specific example, an exploded view of a portion of a multi-layer printed circuit board can be seen in  FIG. 2 . As shown therein, in this embodiment, each printed coil  38  has first and second contacts  40  and  42 . As may be seen in  FIG. 2 , alternate layers of the windings are printed in an opposite sense. Also, terminal  42  of an upper layer is aligned with terminal  42  of the next layer, though terminal  40  of that next layer is rotated 90° from terminal  40  of the upper layer. However, terminal  40  of the second layer is aligned with terminal  40  of the third layer, etc. Consequently, drilling through holes 90° apart and plating through the through holes will connect the coils of adjacent layers to provide a continuous coil of one winding sense through the multi-layer printed circuit board  44 . Actually, the start connection on the upper layer and the finish connection on the lower layer must be offset from each other if they are to be brought out from the same layer to avoid connecting the end terminals of the resulting composite coil together. Thus terminal  40  on the upper layer and terminal  40  on the lower layer would be offset, typically circumferentially, from each other. With the specific configuration shown in  FIG. 2 , eight coil layers would be provided, with the four plated through hole pattern within the inner diameter of the individual coil being offset 45° from the hole pattern of contacts  40  outside the outer diameter of the individual coils.  
         [0025]     The coils shown in  FIG. 2  are shown as spirals, though as one alternative, each coil may be a circular arc of somewhat less than 360° stepping inward (or outward) radially to the next circular arc coil. Also, while plated through holes are used in a preferred embodiment to contact the coils in adjacent layers, other means of providing such inner connection may be used if desired. Further, while in the embodiment disclosed, the overall start and finish contacts for the final coil of interconnected windings are made available at the upper layer, such contacts may be brought out on the layer on which they occur, with contact made thereto at some other positions on the board away from the coils themselves. This avoids the need for angularly offsetting the start and finish connections.  
         [0026]      FIG. 2  shows slightly over three turns per printed coil, for a total of  25  turns for eight layers of printed coils. This of course is schematic only, as the number of turns per layer and the number of layers used may be chosen as desired or required for a particular application. In applications for preferred embodiments of the invention, the spool poppet valves are fast acting, so while a high current pulse though the coil is used for actuation of the solenoid actuator, that pulse is of very short duration, and with quite a low duty cycle, so that coil heating may be kept relatively low. Also, if a holding current is used instead of magnetic latching, the holding current may be quite low because of the substantially zero air gap in the magnetic circuit when the solenoid actuator is actuated, so it causes very little coil heating. If desired or necessary for a particular application, high thermal conductivity printed circuit board materials are commercially available that could be used.  
         [0027]      FIG. 3  shows a multi-layer board with eight or more layers having eight windings, each comprised of eight individual windings, such as is illustrated in  FIG. 2 . Thus, visible in  FIG. 3  are the plated through holes  40  around the OD of each coil, as well as the plated through holes  42  around the ID of each printed coil. Also visible in  FIG. 3 , as well as  FIG. 2 , is a central hole  46  in each of the eight coils for the end  34  of the spool  26  for the embodiment of the spool poppet valve shown in  FIG. 1 . In that regard, the housing  20  and cap  22  shown in  FIG. 1  may have a circular or rectangular outer surface, or other shapes as desired. However, printed circuit board  40  extends beyond or out of the housing  20  and cap  22  in a direction perpendicular to the plane of the view of  FIG. 1 , so that the same multi-layer circuit board may provide solenoid coils for multiple solenoid actuated valves, whether of the configuration of  FIG. 1  or of other configurations and types. In that regard, if eight individual coils, as illustrated in  FIG. 2 , are used on an eight layer board, one coil layer, normally the top coil layer, would be exposed. Accordingly, depending on the overall configuration used, it may be necessary to insulate this layer from housing  20  or armature  28 , which may be done in various ways, including the use of an insulator which may also serve as a seal to assure that any leakage past pressure balance pin  36  is exhausted through the vent and cannot leak out along the printed circuit board.  
         [0028]     An exemplary application of this embodiment of the present invention is schematically shown in  FIG. 4 . In this application, a hydraulic engine valve actuation system for a four-cylinder engine or for each bank of four cylinders of a V8 engine is schematically shown. Here, eight valves (as well as other components of the valve actuation system), such as valves  18  of  FIG. 1 , are shown, four for controlling hydraulic actuators  48  for engine intake valves, and four for controlling hydraulic valve actuators  50  for engine exhaust valves. Such an assembly, by way of example, may be provided on some interconnecting structure  52  for bolting to a engine head over the intake and exhaust valves with spring return, respectively. In that regard, hydraulic engine valve actuation systems and methods of operating such systems are known in the prior art. See, for instance, U.S. Pat. No. 6,739,293, which discloses a two-stage system, though single-stage systems wherein a solenoid actuated valve directly controls hydraulic fluid as applied to the hydraulic valve actuators are also known. In any event, in the system shown in  FIG. 4 , printed circuit board  40  spans all eight valves  18 , and not only provides connections to the eight coils and the interconnection of layers making up each coil, but further provides printed circuit board space for various electronic components  54  to provide solenoid coil drivers, signal processing if engine valve position sensors are used, and various other tasks. Preferably in such an embodiment, a single cable  56  is used to provide power to the printed circuit board as well as such purposes as providing control signals to the board, and if sensors are used, sensor signals from the board. In that regard, preferably, communication to and from the board is through a serial bus, with the electronic components  54  on the printed circuit board  40  also including appropriate bus interfaces.  
         [0029]     The advantage of an embodiment of the general type shown in  FIG. 4  may be appreciated by recognizing that a multi-layer board in such applications is already required, so that the use of such a multi-layer board to achieve not only the multiple solenoid coils required in such a system, but to also make connections between the coils and the electronic circuits on the multi-layer board is achieved with little increase in cost.  
         [0030]     The printed solenoid coil aspect of the present invention has been illustrated herein schematically. By way of example,  FIG. 3  shows a multi-layer printed circuit board that has a rectangular planform and provision for eight actuator coils laid out in a linear array. Obviously in typical applications, the printed circuit board may not be rectangular, but may have regions of increased and decreased width, have holes for access to bolts there below, may have a larger or smaller number of printed solenoid coil layers and/or have printed solenoid coils that are not laid out in a linear array, depending on the specific application. By way of further example, each cylinder of a multiple cylinder engine, such as a diesel engine, may have one solenoid actuator for a valve controlling the engine intake valves, a second solenoid actuator for the engine exhaust valves and one or more additional solenoid actuators for controlling the fuel injector, all of which may be laid out on a printed circuit board, like printed circuit board  40 , to provide the desired interconnection as well as electronics on the multi-layer printed circuit board. In that regard, the printed circuit board may or may not include a central control processor and associated memory, though if it does, cable  56  ( FIG. 4 ) would still provide power and signal information at least to and perhaps from the printed circuit board, such as crankshaft angle, engine operating conditions and environmental conditions. Including the central control processor on the board can reduce costs by both taking full advantage of the multilayer board and by minimizing the communication needed to and from the board.  
         [0031]     Thus the present invention has a number of aspects, which aspects may be practiced alone or in various combinations or sub-combinations, as desired. Also while certain preferred embodiments of the present invention have been disclosed and described herein for purposes of illustration and not for purposes of limitation, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.