Patent Publication Number: US-7584727-B2

Title: Permanent magnet electromagnetic actuator for an electronic valve actuation system of an engine

Description:
This application is a continuation of U.S. patent application Ser. No. 10/811,085, filed Mar. 25, 2004, the entire contents of which are incorporated herein by reference. 

   FIELD 
   The field of the disclosure relates to electromechanical actuators coupled to cylinder valves of an internal combustion engine, and more particularly to a dual coil valve actuator. 
   BACKGROUND AND SUMMARY 
   Electromechanical valve actuators for actuating cylinder valves of an engine have several system characteristics to overcome. First, valve landing during opening and closing of the valve can create noise and wear. Therefore, valve landing control is desired to reduce contact forces and thereby decrease wear and noise. However, in some prior art actuators, the rate of change of actuator magnetic force between an armature and a core with respect to changes in the airgap length (dF/dx) can be high when the air gap is small (e.g., at landing). As such, it can be difficult to accurately control the armature and/or seat landing velocity. 
   Second, opening and closing time of the valve can be limited to, for example, to greater than a desired value of about 3 msec. In other words, due to limited force producing capability, the transition time of some previous systems may be insufficient, and therefore result in reduced engine peak power. 
   Third, the power consumption of an electric valve actuation (EVA) system can have an impact on vehicle fuel economy, engine peak power, and the size/cost of the electrical power supply system. Therefore, reducing power consumption of the actuator, without sacrificing performance, can be advantageous. 
   One approach for designing an electromechanical valve actuator of an engine with a permanent magnet is described in JP 2002130510A. Various figures show what appears to be a permanent magnet located below coils having an adjacent air gap. The objective of this reference appears to be to increase the flux density in the core poles by making the permanent magnet width (“Wm” in  FIG. 4 ) wider than the center pole width (“Di” in  FIG. 4 ). The air gaps  39  by the two sides of the permanent magnet appear to be introduced to limit the leakage flux. Apparently, to further increase the flux density in the core pole, the permanent magnet cross section shape is changed from flat to V-shaped in  FIG. 9 . 
   Such a configuration therefore results in the bottom part of the center pole (Wm) being wider than the top part (Di) to accommodate the permanent magnet, which is placed below the coil. The inventors herein have recognized that these two features give rise to several disadvantages. 
   As a first example, such a configuration can result in increased coil resistance or actuator height requirements. In other words, to provide space for the permanent magnet, either the height of the actuator is increased (to compensate the loss of the space for the coil), or the resistance of the coil is higher if the height of the core is kept constant. 
   As a second example, the flux enhancing effect may also be limited by actuator height. In other words, the amount of space below the coils available for the permanent magnet is limited due to packaging constraints, for example. Therefore, while some flux enhancement may be possible, it comes at a cost of (as is limited by) height restrictions. 
   Other attempts have also been made to improve the actuator performance by using a permanent magnet. For example, U.S. Pat. No. 4,779,582, describes one such actuator. However, the inventors herein have also recognized that while such an approach may produce a low dF/dx, it still produces low magnetic force due to the magnetic strength limit of the permanent magnet material. Alternatively, other approaches, such as in U.S. application Ser. No. 10/249,328 may increase the magnetic force, but may not reduce the dF/dx for armature and valve landing speed control. 
   In one example, the above disadvantages can be at least partially overcome by a valve actuator for an internal combustion engine, comprising: at least one electromagnet having a coil wound about a core; an armature fixed to an armature shaft extending axially through the core, and axially movable relative thereto; and at least one permanent magnet extending at least partially into an interior portion of the core. 
   In this way, there is increased space for the permanent magnet (between the coils), and the actuator height is not required to be increased (although it can be, if desired). Additionally, since coil space is not necessarily reduced, increased coil resistance can be avoided or reduced. 
   In one specific example, such an approach can be used so that the area of the permanent magnet surface contacting the core is larger than the center pole area facing the armature. As a result, the flux density in the center pole surface may be significantly higher than the flux density in the permanent magnet material&#39;s surface, which is limited by the permanent magnet material property. Further, since the magnetic force is proportional to the square of the flux density, this embodiment can increase (significantly in some examples) the force, without necessarily increasing the size of the actuator. And since the permanent magnet is in the path of the flux produced by the current, in one example, the actuator can have a low dF/dx and dF/di (rate of change of force with respect to changes in current), which can be beneficial for landing speed control. 
   As such, various advantages can be achieved in some cases, such as decreased resistance, decreased height requirements, and increased force output, while maintaining reduced dF/dx and dF/di (which can help valve landing control). 
   In another example embodiment, the valve actuator can comprise a core having a wound coil located therein, said core further having at least one permanent magnet located at least partially below said coil and positioned at an angle relative to a direction of movement of an armature, with an inner part of said permanent magnet being located closer to said coil than an outer part of said permanent magnet, where said inner part of said permanent magnet is closer to a center of said core than said outer part of said permanent magnet. Further, the valve actuator can further comprise a first gap at said inner part of said permanent magnet and a second gap at said outer part of said permanent magnet. 
   By having such a configuration, it is also possible to obtain improved actuator force performance, while reducing coil resistance and improving valve manufacturability. Further, in some examples using gaps near selected areas of the permanent magnet, flux leakage can be reduced. 
   The above advantages and other advantages and features will be readily apparent from the following detailed description or from the accompanying drawings, taken alone or in combination. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages described herein will be more fully understood by reading an example of an embodiment, referred to herein as the Description of Example Embodiments, with reference to the drawings wherein: 
       FIG. 1  is a block diagram of an engine illustrating various components; 
       FIG. 2  is a cross-section illustrating one embodiment of a valve actuator assembly for an intake or exhaust valve of an internal combustion engine; 
       FIG. 3  is a graph showing magnetic force of an actuator as a function of the air gap for a prior art system; 
       FIG. 4  is a cross-section illustrating an embodiment of a valve actuator; 
       FIG. 5  is a graph showing magnetic force of an actuator as a function of the air gap for a prior art system compared with one example embodiment of the present disclosure; and 
       FIGS. 6-23  are cross-sections of alternative embodiments of a valve actuator. 
   

   DESCRIPTION OF EXAMPLE EMBODIMENTS 
   This disclosure outlines an electromagnetic actuator that can provide advantageous operation, especially when used to actuate a valve of an internal combustion engine, as shown by  FIGS. 1-2 . This improved actuator may result in a lower cost and lower component requirements, while maintaining desired functionality. 
   As a general background, several of the hurdles facing electromechanical actuators for valve engine are described. 
   A first example issue relates to engine noise and valve durability. For every two engine crank-shaft cycles the armature of the EVA actuator of each engine valve “lands” on the upper and lower core once, the armature stem lands on the valve stem once, and the valve lands on the valve seat once (4 impacts). To meet the engine noise requirements the landing speeds of the armature and valve have to be controlled not to exceed a certain level. However, due to the fact that the rate of change of the actuator magnetic force between the armature and the core with respect to changes in the airgap length (dF/dx) is high when the air gap is small, as shown in  FIG. 3  for prior art approaches, it can be difficult to control the armature and seat landing velocity. As a result, some EVA systems can have increased noise unless a complicated control algorithm is implemented. Another issue caused by the high armature and valve landing speed relates to valve durability. Because the EVA actuators have to go through millions of cycles in the life of the vehicle, high armature and valve landing speed may lead to short EVA life. 
   A second example issue relates to transition time of valve opening/closing. In some situations, to meet the engine peak power requirements, the transition time of the valve opening and closing should be shorter than a certain value (e.g., ˜3 msec). Due to some prior art actuator&#39;s limited force producing capability, the transition times may not meet these requirements. As a result, engines equipped with EVA may produce less peak power. 
   A third example issue relates to power consumption of the EVA system. The power consumption of the EVA system can have a direct impact on the vehicle fuel economy, engine peak power, and the size/cost of the electrical power supply system. It is therefore desired to minimize or reduce the power consumption of the EVA system. 
   Various embodiments are described below of a valve actuator for addressing the above issues, as well as for providing other advantages. In one example, at least some of the above issues are addressed by utilizing permanent magnet (PM) material in unique arrangements so that the dF/dx, transition time and power consumption of the actuator are reduced, while the force capability of the actuator is increased. 
   Referring to  FIG. 1 , internal combustion engine  10  is shown. Engine  10  is an engine of a passenger vehicle or truck driven on roads by drivers. Engine  10  can coupled to torque converter via crankshaft  13 . The torque converter can also be coupled to transmission via a turbine shaft. The torque converter has a bypass clutch which can be engaged, disengaged, or partially engaged. When the clutch is either disengaged or partially engaged, the torque converter is said to be in an unlocked state. The turbine shaft is also known as transmission input shaft. The transmission comprises an electronically controlled transmission with a plurality of selectable discrete gear ratios. The transmission also comprises various other gears such as, for example, a final drive ratio. The transmission can also be coupled to tires via an axle. The tires interface the vehicle to the road. 
   Returning again to  FIG. 1 , internal combustion engine  10  comprises a plurality of cylinders, one cylinder of which is shown. The engine is controlled by electronic engine controller  12 . Engine  10  includes combustion chamber  30  and cylinder walls  32  with piston  36  positioned therein and connected to crankshaft  13 . Combustion chamber  30  communicates with intake manifold  44  and exhaust manifold  48  via respective intake valve  52  and exhaust valve  54 . Exhaust gas oxygen sensor  16  is coupled to exhaust manifold  48  of engine  10  upstream of catalytic converter  20 . In one example, converter  20  is a three-way catalyst for converting emissions during operation about stoichiometry. In one example, at least one of, and potentially both, of valves  52  and  54  are controlled electronically via apparatus  210 . 
   Intake manifold  44  communicates with throttle body  64  via throttle plate  66 . Throttle plate  66  is controlled by electric motor  67 , which receives a signal from ETC driver  69 . ETC driver  69  receives control signal (DC) from controller  12 . In an alternative embodiment, no throttle is utilized and airflow is controlled solely using valves  52  and  54 . Further, when throttle  66  is included, it can be used to reduce airflow if valves  52  or  54  become degraded, or to create vacuum to draw in recycled exhaust gas (EGR), or fuel vapors from a fuel vapor storage system having a valve controlling the amount of fuel vapors. 
   Intake manifold  44  is also shown having fuel injector  68  coupled thereto for delivering fuel in proportion to the pulse width of signal (fpw) from controller  12 . Fuel is delivered to fuel injector  68  by a conventional fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). 
   Engine  10  further includes conventional distributorless ignition system  88  to provide ignition spark to combustion chamber  30  via spark plug  92  in response to controller  12 . In the embodiment described herein, controller  12  is a conventional microcomputer including a microprocessor unit  102 , input/output ports  104 , electronic memory chip  106 , which is an electronically programmable memory in this particular example, random access memory  108 , and a conventional data bus. 
   Controller  12  receives various signals from sensors coupled to engine  10 , in addition to those signals previously discussed, including measurements of inducted mass air flow (MAF) from mass air flow sensor  110  coupled to throttle body  64 ; engine coolant temperature (ECT) from temperature sensor  112  coupled to cooling jacket  114 ; a measurement of manifold pressure from MAP sensor  129 , a measurement of throttle position (TP) from throttle position sensor  117  coupled to throttle plate  66 ; a measurement of transmission shaft torque, or engine shaft torque from torque sensor  121 , a measurement of turbine speed (Wt) from turbine speed sensor  119 , where turbine speed measures the speed of shaft  17 , and a profile ignition pickup signal (PIP) from Hall effect sensor  118  coupled to crankshaft  13  indicating an engine speed (N). Alternatively, turbine speed may be determined from vehicle speed and gear ratio. 
   Continuing with  FIG. 1 , accelerator pedal  130  is shown communicating with the driver&#39;s foot  132 . Accelerator pedal position (PP) is measured by pedal position sensor  134  and sent to controller  12 . 
   In an alternative embodiment, where an electronically controlled throttle is not used, an air bypass valve (not shown) can be installed to allow a controlled amount of air to bypass throttle plate  62 . In this alternative embodiment, the air bypass valve (not shown) receives a control signal (not shown) from controller  12 . 
   Also, in yet another alternative embodiment, intake valve  52  can be controlled via actuator  210 , and exhaust valve  54  actuated by an overhead cam, or a pushrod activated cam. Further, the exhaust cam can have a hydraulic actuator to vary cam timing, known as variable cam timing. 
   In still another alternative embodiment, only some of the intake valves are electrically actuated, and other intake valves (and exhaust valves) are cam actuated. 
   Referring now to  FIG. 2 , a cross-section illustrating a valve actuator assembly for an intake or exhaust valve of an internal combustion engine is shown. Valve actuator assembly  210  includes an upper electromagnet  212  and a lower electromagnet  214 . As used throughout this description, the terms “upper” and “lower” refer to positions relative to the combustion chamber or cylinder with “lower” designating components closer to the cylinder and “upper” referring to components axially farther from the corresponding cylinder. An armature  216  is fixed to, and extends outward from, an armature shaft  218 , which extends axially through a bore in upper electromagnet  212  and lower electromagnet  214 , guided by one or more bushings, represented generally by bushing  220 . Armature shaft  218  is operatively associated with an engine valve  230  that includes a valve head  232  and valve stem  234 . Depending upon the particular application and implementation, armature shaft  218  and valve stem  234  may be integrally formed such that armature  216  is fixed to valve stem  234 . However, in the embodiment illustrated, shaft  218  and valve stem  234  are discrete, separately moveable components. This provides a small gap between shaft  218  and valve stem  234  when armature  216  is touching upper core  252 . Various other connecting or coupling arrangements may be used to translate axial motion of armature  216  between upper and lower electromagnets  212 ,  214  to valve  230  to open and close valve  230  to selectively couple intake/exhaust passage  236  within an engine cylinder head  238  to a corresponding combustion chamber or cylinder (not shown). 
   Actuator assembly  210  also includes an upper spring  240  operatively associated with armature shaft  218  for biasing armature  216  toward a neutral position away from upper electromagnet  212 , and a lower spring  242  operatively associated with valve stem  234  for biasing armature  216  toward a neutral position away from lower electromagnet  214 . 
   Upper electromagnet  212  includes an associated upper coil  250  wound through two corresponding slots in upper core  252  encompassing armature shaft  218 . One or more permanent magnets  254 ,  256  are positioned substantially between the slots of coil  250 . The various orientations of the permanent magnet(s) are explained in greater detail with reference to  FIGS. 4-20 . As described, the various orientations provide for increased performance in various respects, without requiring additional actuator height and without reducing the available space for the coils (although each can be done, if desired). 
   Lower electromagnet  214  includes an associated lower coil  260  wound through two corresponding slots in lower core  262  encompassing armature shaft  218 . One or more permanent magnets  264 ,  266  are positioned substantially between the slots of lower coil  60 . As noted above, the various orientations of the permanent magnet(s) are explained in greater detail with reference to  FIGS. 4-20 . 
   During operation of actuator  210 , the current in lower coil  260  is turned off or changed direction to close valve  230 . Bottom spring  242  will push valve  230  upward. Upper coil  250  will be energized when armature  216  approaches upper core  252 . The magnetic force generated by upper electromagnet  212  will hold armature  216 , and therefore, valve  230  in the closed position. To open valve  230 , the current in upper coil  250  is turned off or changed direction and upper spring  240  will push armature shaft  218  and valve  230  down. Lower coil  260  is then energized to hold valve  230  in the open position. 
   As will be appreciated by those of ordinary skill in the art, upper and lower electromagnets  212 ,  214  are preferably identical in construction and operation. However, upper and lower components of the actuator may employ different electromagnet constructions depending upon the particular application. Likewise, the approaches described may be used for either the upper or lower portion of the actuator with a conventional construction used for the other portion, although such asymmetrical construction may not provide the benefits or advantages to the same degree as a construction (symmetrical or asymmetrical) that uses the approaches herein 
   As illustrated above, the electromechanically actuated valves in the engine can be designed to remain in the open or close position when the actuators are de-energized, with the armature held in place by the flux produced by the permanent magnet. The electromechanically actuated valves in the engine can also be designed to remain in the half open position when the actuators are de-energized. In this case, prior to engine combustion operation, each valve goes through an initialization cycle. During the initialization period, the actuators are pulsed with current, in a prescribed manner, in order to establish the valves in the fully closed or fully open position. Following this initialization, the valves are sequentially actuated according to the desired valve timing (and firing order) by the pair of electromagnets, one for pulling the valve open (lower) and the other for pulling the valve closed (upper). 
   The magnetic properties of each electromagnet are such that only a single electromagnet (upper or lower) needs be energized at any time. Since the upper electromagnets hold the valves closed for the majority of each engine cycle, they are operated for a much higher percentage of time than that of the lower electromagnets. 
   One approach that can be used to control valve position includes position sensor feedback for potentially more accurate control of valve position. This can be used to improve overall position control, as well as valve landing, to possibly reduce noise and vibration. 
   Note that the above system is not limited to a dual coil actuator, but rather it can be used with other types of actuators. For example, the actuator  210  can be a single coil actuator. 
     FIG. 4  illustrates one embodiment of an improved actuator design. Note that  FIG. 4  shows the system without an armature shaft (such as  218 ) for clarity. Specifically,  FIG. 4  shows core  410  with coil  412 . Further, an angled permanent magnet cross section  414  is shown having air gaps  416  and  418 . In one example, the air gaps are adjacent to the permanent magnet, such as, for example, immediately adjacent the magnet with core material separating the coils from the air gap(s). Finally, armature  420  is also illustrated in  FIG. 4 . The inside surface of the permanent magnet  414  is NORTH (N), while the exterior surface (facing the coil), is SOUTH (S).  FIG. 4  shows a cross-sectional view (since the actuator isn&#39;t round the magnets wouldn&#39;t form a conical shape). In this cross-sectional view, the two magnet sections are of a linear, rectangular shape angled relative to the axial motion of the armature, with each section angled toward the center of the core across the height of the coil, with the outer ends toward the bottom of the core (armature side). As shown in Figures below, the orientation of the magnets could alternatively be that they come together near the armature side of the coils. 
   As a result, the inner core material is thinner between the interior of the coil and the exterior of the magnet sections at the armature side of the coil as compared with the opposite (upper) side. Likewise, the inner core material is thicker between the interior of the magnet sections at the armature side of the coil as compared with the opposite (upper) side. 
   Note also that multiple magnets could be used and also that the top air gap  416  could be eliminated. Also note that various other shapes can be used having at least a portion of the permanent magnet angled relative to the direction of motion of the armature. 
   As illustrated in  FIG. 4 , permanent magnet  414  is angled relative to the motion of armature  420 .  FIG. 4  shows an angle of approximately 30 degrees, although various other angles could be used, such as 5-10, 5-20, 5-80, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, or therebetween. Adjusting the angle varies the amount of improved operation, but also can affect the width of the actuator, and/or the amount of permanent magnet material utilized. 
   One advantageous feature of the embodiment of  FIG. 4  is that the permanent magnets are arranged in such as manner so that the area of the permanent magnet surface contacting the core is larger than the center pole area facing the armature. As a result, the flux density in the center pole surface may be significantly higher than the flux density in the permanent magnet material&#39;s surface, which is limited by the permanent magnet material property. Further, since the magnetic force is proportional to the square of the flux density, this embodiment can increase (significantly in some examples) the force, without necessarily increasing the size of the actuator. 
   Further, by positioning a permanent magnet at an angle and/or at least partially between the slots of coil  412 , it is possible to use more permanent magnet material, without requiring a larger (longer) actuator for a given specification. Further, more height is available for permanent magnet material than if the magnet was positioned below the coils, without requiring the overall height of the core to be increased. In other words, it is possible to get more magnetic material for a given height. By having greater magnetic material, it is possible to further increase the flux density in the core, thereby increasing the magnetic force for a given set of conditions. 
   Additionally, by positioning a permanent magnet at least partially between the slots of coil  412 , this also enables more space for coil  412 , thereby allowing more copper to be used in the coil, which can lower resistance and power loss, as well as heat generation. Thus, compared with approaches that place the permanent magnet below the coil, increased space is available to use as slot area for the coil. Therefore, for the same core height, prior approaches would have higher coil resistance because of the smaller slot area. 
   Additionally, the leakage flux produced by the permanent magnet  414  can be reduced by the placement of air-gaps as shown in  FIG. 4 . In one example, the upper air gaps  416  can be used to reduce flux leakage near the peak of the magnet, although these can be deleted in some cases. Likewise, the lower air gap  418  can also be used to reduce flux leakage, without requiring increased actuator height, although these can be deleted in some cases. 
   In one example, the material separating air-gap  416 , termed bridge material  430 , between gap  416 , should be as thin as mechanically possible to reduce flux leakage. Likewise, for air-gaps  418 , in one example, the bridge areas on the side ( 432 ) and bottom ( 434 ) are also designed to be as thin as mechanically possible. 
   Alternatively, air gap  416  (or  418 ) can be deleted to eliminate the leakage flux at that area, so that magnet  414  comes together in the cross sectional view at the peak. 
     FIG. 5  illustrates example improvements made by this embodiment over the permanent magnet actuator according to U.S. Pat. No. 4,829,947. It can be seen from  FIG. 5  that the magnetic force is increased significantly when the current is positive. When the magnetic force needs to be reduced for armature release, the magnetic force of the actuator according to this embodiment is reduced faster than the previous permanent magnet actuator. Since the permanent magnet is in the path of the flux produced by the current, the actuator can have a low dF/dx and dF/di (rate of change of force with respect to changes in current), which can be beneficial for landing speed control. As a result of higher force for the same current, the actuator of this embodiment can enable the utilization of stronger springs to reduce the transition time and/or reduce current for the same force to reduce actuator power consumption, without requiring a larger actuator height. 
   As such, another advantage, with respect to prior designs, is that such an approach can achieve its benefits without requiring an increase in the actuator size (height). 
     FIG. 5  shows a force comparison of the above embodiment compared with a prior art approach using modeled results. 
   Various modifications can be made to the above embodiment, some of which are illustrated by the example alternative embodiments of  FIGS. 6-20 . 
   Referring now to  FIG. 6 , an alternative embodiment is shown where the permanent magnet  614  extends only along a portion of the height of the coil, and an alternative air gap  616  at the upper junction of the magnet is used. The remainder of the actuator is similar to  FIG. 4 . Such a configuration can be used to improve manufacturability in some cases. 
   Referring now to  FIG. 7 , an alternative embodiment is shown where the orientation of permanent magnet  714  is rotated relative to that of  FIG. 4 , and an alternative air gap  716  at the lower junction of the magnet is used, along with the air gap  718  at the upper ends away from the armature side of the core. The remainder of the actuator is similar to  FIG. 4 . 
   Still other alternatives are described below with regard to the schematic diagrams of  FIGS. 8-21 .  FIG. 8  again illustrates an embodiment similar to  FIG. 7 , except that no air gaps are used, and a common permanent magnet  814  is used. Specifically, the Figure shows core  810 , coil  812 , and armature  820 , along with the permanent magnet  814 . 
   The permanent magnet can alternatively be placed at a lower position as shown by  914  in  FIG. 9 , extending past the coil on the non-armature side, to provide increased magnetic material to enhance actuator operation. Further, the Figure shows core  910 , coil  912 , and armature  920 , along with the permanent magnet  914 . 
   To improve manufacturability, bridges can be introduced to make the core a one-piece core, as shown in  FIG. 10  (and also illustrated in other examples above). Holes  1016  and  1018  are also shown, which can be either filled with epoxy to improve the core integrity or left open for simpler manufacturing. Note also that any of the air gaps above and/or below can also be filled with epoxy. Further, the Figure shows core  1010 , coil  1012 , and armature  1020 , along with the permanent magnet  1014 . 
   The permanent magnet in the above embodiments can also be flipped to create still other embodiments.  FIG. 11  shows an example, which is a version based on  FIG. 10  with the orientation of the magnet  1114  rotated by 180 degrees in the cross-sectional view compared with  1014 , so that the magnet extends outwardly toward the non-armature end. Further, the Figure shows core  1110 , coil  1112 , and armature  1120 , along with the permanent magnet  1114 . 
   Further, one or more layers of permanent magnet material can be added to any of the above embodiments to create still other embodiments, as shown in  FIG. 12 . Specifically,  FIG. 12  shows first permanent magnet layer  1214  and second layer  1215 , both having at least a portion of the permanent magnet, or all of the permanent magnet, located between the slots of the coil. Further, the Figure shows core  1210 , coil  1212 , and armature  1220 . Also, air gaps could be added, if desired as shown in various other embodiments. 
   Also, the permanent magnet can have different shapes, while still providing some improved performance.  FIG. 13  shows one example, while still providing at least some angled portions of the magnet relative to the axial motion of the armature. In this example, permanent magnet  1314  is shown with core  1310 , coil  1312 , and armature  1320 . Permanent magnet  1314  has a U-shaped cross section, with the ends of the U toward the armature. 
   Also,  FIG. 14  shows an embodiment with bridges introduced to the embodiment shown in  FIG. 13 , thereby illustrating that such bridges and air gaps can be used in any of the embodiments described herein. Specifically, air gaps  1418  are shown at the ends of the U of U-shaped permanent magnet  1416 , along with core  1410 , coil  1412 , and armature  1420 . 
   Further,  FIGS. 15-16  show the embodiments based on the embodiment shown in  FIGS. 13-14 , with an alternative orientation of the permanent magnet (flipped). Specifically,  FIG. 15  shows core  1510 , coil  1512 , and armature  1520  with inverted permanent magnet  1516  having the ends of the U-shaped cross section located away from the armature end.  FIG. 16  shows core  1610 , coil  1612 , and armature  1620  with inverted permanent magnet  1616  having the ends of the U-shaped cross section located away from the armature end. Further, air gaps  1618  are also shown at the end of the U-shaped cross section of magnet  1616 . 
   In still another alternative embodiment, the permanent magnet can be segmented as shown in  FIG. 17 , yet still have at least one permanent magnet located at least partially inside said coil and positioned at an angle relative to a direction of movement of an armature. Specifically, first permanent magnet segment  1714  is shown between the slots of coil  1712  and between the second permanent magnet segment  1715 . Further, in one example, gaps  1716  and  1718  (or holes, or epoxy filled holes) can be positioned between the segments, and at the external ends of the segments. In this example, gap  1716  is located between segments  1714  and  1715 , while gap  1716  is located between segment  1715  and coil  1712 . Also, the Figure shows armature  1720  and core  1710 . By segmenting the permanent magnet, it can be possible to improve manufacturability, and more easily obtain alternative angles for different magnet segments, along with alternative cross-sectional shapes. 
   In the example of  FIG. 17 , segment  1715  is angled relative to the axial motion of armature  1720 , while segment  1714  is located perpendicular to the axial motion of the armature  1720 . Also, while the Figure shows the segments fully contained within coil  1712 , in an alternative embodiment segment  1715  can be only partially located within coil  1712 , and segment  1714  located within coil  1712 . 
     FIGS. 18-20  are still further variations based on the embodiment shown in  FIG. 17 , illustrating different orientations of the segmented permanent magnet at different locations within the coil. For example,  FIG. 18  shows segments  1814  and  1815  located away from armature  1820  at the non-armature end of core  1810 , while still between the slots of coil  1812 . Further, air gaps  1816  and  1818  are also shown.  FIG. 19  shows segments  1914  and  1915  located at the armature  1920  end of core  1910 , while still between the slots of coil  1912 . However, in  FIG. 19 , segment  1915  is inwardly angled away from armature  1920 , whereas in  FIGS. 17 and 18 , segments  1815  and  1715  are both outwardly angled away from the armatures.  FIG. 19  also shows gaps  1916  and  1918 . 
     FIG. 20  is similar to that of  FIG. 19 , except shows an alternative location of segments  2014  and  2015  closer to a non-armature end of core  2010 .  FIG. 20  also shows coil  2012 , armature  2020 , along with air gaps  2016  and  2018 . 
     FIG. 21  shows still another alternative embodiment illustrating that benefits can also be achieved over prior approaches without requiring permanent magnet to be located within the coil  2112 , while still positioning the permanent magnet  2114  at an angle relative to the motion of armature  2120 . Also, optional air gaps  2116  and  2118  at the inward and outward ends of the magnet, respectively, are also shown. The figure also illustrates the internal side is NORTH (N), while the external side of the magnet is SOUTH (S). 
   Such a configuration can be beneficial in that it can provide increased internal area for a through-shaft. In other words, because magnet  2114  has a cross section that avoids having a center area in the center of the core  2110 , more area is available for the coil and/or shaft. 
   As note above, the above configuration show various ways the configuration of the actuator can be changed. Each variation can be used with any other variation. For example, multiple layers of permanent magnet can be used in any of the shapes or configurations discussed above. 
   It will be appreciated that the configurations disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above actuator technology can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. Also, the approach described above is not specifically limited to a dual coil valve actuator. Rather, it could be applied to other forms of actuators, including ones that have only a single coil per valve actuator The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein. 
   The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.