Abstract:
A valve assembly for an exhaust gas recirculation (EGR) system which provides emission control, regulates flow of exhaust gases, and is suitable for gasoline or diesel applications. The EGR valve assembly is a latching valve assembly which reduces power consumption (i.e., continuous electric draw) from the battery while the valve is either being held open or closed, and reduces electrical interference inherent with integrated position sensors. The valve assembly includes a latching mechanism controlled by an actuator which allows a valve to latch open or closed. The valve may be a single stage valve or a multi-stage valve, which includes a latching mechanism that allows for intermediate open positions, and uses of only a short, single pulse of voltage, to change the state of the valve. The actuator may also be held energized at full extend, maintaining a maximum valve open position, creating additional flow capability of the valve assembly.

Description:
FIELD OF THE INVENTION 
     The invention relates generally to an internal combustion exhaust system having an exhaust gas recirculation (EGR) valve assembly, where the EGR valve assembly includes a latching mechanism which maintains the EGR valve assembly in an open position or closed position when no electric power is used. 
     BACKGROUND OF THE INVENTION 
     Exhaust Gas Recirculation (EGR) provides an effective means to reduce nitrous oxide emissions (NOx) from the vehicle. The reintroduction rate of exhaust gases is controlled by an EGR valve. The exhaust gases displace available oxygen (O 2 ) to slow the fuel burn rate, and thus the peak combustion temperature is reduced. The byproduct of the cooler combustion temperature is reduction in thermally sensitive emissions of NOx. 
     One of the requirements for proper operation of an EGR system is that the EGR valve must seal in the normally closed position, preventing exhaust gases from leaking into the intake manifold. The EGR valve must also regulate the flow of exhaust gases, which is typically achieved using a linear-style valve. Regulation of the flow rate is typically achieved with a positional feedback sensor. This duality of sensory feedback and variable power consumption may be significant for variable speed (rpm) engines. 
     Accordingly, there exists a need for a valve assembly which is able to remain in an open position or closed position to regulate the flow of exhaust gas, while at the same time minimizing the amount of energy used to maintain the valve in the open position. There is also a need for a valve assembly which meets current packaging requirements, and is capable of performing multi-stage regulation of exhaust gas flow. 
     SUMMARY OF THE INVENTION 
     The present invention is a valve assembly for an exhaust gas recirculation (EGR) system which provides emission control, and regulates flow of exhaust gases reintroduced into the engine intake manifold. The valve assembly of the present invention is suitable for gasoline or diesel applications. 
     The EGR valve assembly of the present invention is a latching valve assembly which reduces power consumption (i.e., continuous electric draw) from the battery while the valve is either being held open or closed, and reduces electrical interference inherent with integrated position sensors. 
     In an embodiment, the valve assembly of the present invention includes a latching mechanism controlled by an actuator which allows a valve to latch open, or closed. In one embodiment, the valve may be a single stage valve, and uses only a short, single pulse of voltage, to change the state of the valve. In another embodiment, the present invention is a multi-stage valve which includes a latching mechanism that allows for intermediate open positions, and again uses only a short, single pulse of voltage, to change the state of the valve. Because of the use of only a short, single pulse of voltage to change the position of the valve assembly, the valve assembly of the present invention is physically smaller as compared to a large dynamic linear solenoid required of typical electronic EGR systems. In yet other embodiments, the actuator is also held energized at full extend, maintaining a maximum valve open position, in effect creating additional flow capability of the valve assembly. A secondary pulsed signal (PWM signal) effectually holds the valve in the maximum open state with reduced power consumption after being energized (i.e., a peak-and-hold signal). 
     In one embodiment, the present invention is a valve assembly having an upper housing which includes a cavity, a lower housing which includes an exhaust cavity, and an actuator and latching mechanism disposed in the cavity of the upper housing. The latching mechanism includes an index mechanism and a guide selectively engaged with the index mechanism. A valve seat is located in the lower housing and is in fluid communication with the exhaust cavity formed as part of the lower housing. A valve member is connected to and controlled by the actuator, such that he valve member is selectively in contact with the valve seat. The latching mechanism places the valve member in a closed position such that the valve member is in contact with the valve seat and the index mechanism is disengaged from the guide, preventing exhaust gas from flowing through the exhaust cavity formed as part of the lower housing. The latching mechanism also places the valve member in one of a plurality of open positions, where the valve member is moved away from the valve seat and the index mechanism is engaged with the guide, allowing exhaust gas to flow through the exhaust cavity of the lower housing. 
     The latching mechanism also includes an indexing latch connected to the actuator, a first plurality of teeth formed as part of the indexing latch, a second plurality of teeth formed as part of the guide, a plurality of vertexes, each of which is located in between two of the second plurality of teeth, and a plurality of indexing teeth formed as part of the index mechanism. The first plurality of teeth is engaged with the indexing teeth when the valve member is in the closed position. The second plurality of teeth is configured such that a portion of the plurality of vertexes are located at a first distance from the valve seat, and a second portion of the plurality of vertexes are located at a second distance from the valve seat. Each one of the plurality of indexing teeth is engaged with a corresponding one of the first portion of the plurality of vertexes when the valve member is in the first of the plurality of open positions, and each one of the plurality of indexing teeth is engaged with a corresponding one of the second portion of the plurality of vertexes when the valve member is in the second of the plurality of open positions. 
     A plurality of slots is formed as part of the guide, and each of the plurality of indexing teeth are disposed in a corresponding one of the plurality of slots and engaged with the first plurality of teeth when the valve is in the closed position, and the plurality of indexing teeth are removed from the plurality of slots, and disengaged from the first plurality of teeth when the valve is in one of the plurality of open positions. 
     A load spring biases the index mechanism such that the valve is biased towards the valve seat (i.e., closed), and a return spring substantially surrounds part of the armature such that the return spring is in contact with part of the armature. The return spring biases the index mechanism such that the valve is biased towards the valve seat, and the actuator is activated to move the armature and the valve member against the force of the load spring and the return spring, and the valve member away from the valve seat, when the valve is in the closed position. 
     The first plurality of teeth are engaged with the indexing teeth when the valve is in the closed position, and when the actuator is activated, the armature moves the indexing latch and valve, causing the first plurality of teeth to engage with the indexing teeth and move the index mechanism such that the index mechanism rotates about the armature. When the actuator is then deactivated, the first plurality of teeth engage with the second plurality of teeth, further rotating the index mechanism about the armature and engaging the indexing teeth with a first portion of the vertexes. The indexing latch then disengages from the first plurality of teeth, placing the valve in a first of the plurality of open positions. 
     In one embodiment, the valve assembly is a multi-stage valve assembly, where the actuator is again activated when the valve is in the first of the plurality of open positions, such that the armature again moves the indexing latch and valve, causing the first plurality of teeth to engage with the indexing teeth and move the index mechanism such that the index mechanism disengages from the guide and rotates about the armature. When the actuator is deactivated, the indexing teeth reengage with the second plurality of teeth such that the index mechanism further rotates about the armature and the indexing teeth engage with a second portion of the vertexes, and the first plurality of teeth disengage from the index mechanism, placing the valve in a second of the plurality of open positions. The actuator is again activated when the valve is in the second of the plurality of open positions, such that the armature again moves the indexing latch and valve, causing the first plurality of teeth to engage with the indexing teeth and move the index mechanism such that the indexing teeth disengage from the second portion of the plurality of vertexes and the index mechanism rotates about the armature. When the actuator is again deactivated, the indexing latch and the index mechanism moves such that the valve member is placed back in the closed position. 
     In another embodiment, the valve assembly is a multi-stage valve assembly having incremental stops, where the actuator is again activated when the valve is in the first of the plurality of open positions, such that the armature again moves the indexing latch and valve, causing the first plurality of teeth to engage with and the indexing teeth and move the index mechanism such that the indexing teeth disengage from the first portion of the plurality of vertexes and the indexing mechanism rotates about the armature. When the actuator is deactivated, the indexing latch and the index mechanism move such that the valve member is placed back in the closed position. When the actuator is again activated and the valve is in the closed position, the armature again moves the indexing latch and valve, causing the first plurality of teeth to engage with the indexing teeth and move the index mechanism such that the index mechanism rotates about the armature, and when the actuator is again deactivated, the indexing teeth engage with the second plurality of teeth, and the index mechanism further rotates about the armature and the indexing teeth engage with a second portion of the vertexes, and the first plurality of teeth disengage from the index mechanism, placing the valve in a second of the plurality of open positions. 
     The EGR system includes an exhaust recirculation conduit and an intake conduit, both of which are in fluid communication with the exhaust cavity formed as part of the lower housing. The valve member is changed between the closed position and one of the plurality of open positions to control the flow of exhaust gas through the exhaust cavity formed as part of the lower housing. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a diagram of an exhaust gas recirculation system for a gasoline engine having at least one valve incorporating a latching mechanism, according to embodiments of the present invention; 
         FIG. 2  is a perspective sectional view of a latching exhaust gas recirculation valve assembly, according to embodiments of the present invention; 
         FIG. 3  is a graph depicting the voltage versus valve position of an exhaust gas recirculation valve assembly, according to embodiments of the present invention; 
         FIG. 4  is a sectional side view of a latching exhaust gas recirculation valve assembly, according to embodiments of the present invention; 
         FIG. 5A  is a perspective view of a latching mechanism, used as part of an exhaust gas recirculation valve assembly, according to embodiments of the present invention; 
         FIG. 5B  is a perspective sectional view of a latching mechanism, used as part of an exhaust gas recirculation valve assembly, according to embodiments of the present invention; 
         FIG. 6A  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted prior to actuation, and the exhaust gas recirculation valve assembly is in a closed position, according to embodiments of the present invention; 
         FIG. 6B  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is partially extended as the exhaust gas recirculation valve assembly is moved to an open position, according to embodiments of the present invention; 
         FIG. 6C  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted after actuation, and exhaust gas recirculation valve assembly is held in an open position, according to embodiments of the present invention; 
         FIG. 6D  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is partially extended as the exhaust gas recirculation valve assembly is being released from an open position, according to embodiments of the present invention; 
         FIG. 6E  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully extended as the exhaust gas recirculation valve assembly is being released from an open position, according to embodiments of the present invention; 
         FIG. 6F  is a diagram of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted after actuation, and exhaust gas recirculation valve assembly is in a closed position, according to embodiments of the present invention; 
         FIG. 7A  is a diagram of a second embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted prior to actuation, and exhaust gas recirculation valve assembly is in a closed position, according to embodiments of the present invention; 
         FIG. 7B  is a diagram of a second embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted after the exhaust gas recirculation valve assembly is moved to one of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 7C  is a diagram of a second embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted, and the exhaust gas recirculation valve assembly is held in one of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 7D  is a diagram of a second embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully extended as the exhaust gas recirculation valve assembly is being released from one of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 7E  is a diagram of a second embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted and the after actuation, and the exhaust gas recirculation valve assembly is in the closed position, according to embodiments of the present invention; 
         FIG. 8A  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where latching mechanism is configured such that the indexing latch is fully retracted prior to actuation, and the exhaust gas recirculation valve assembly is in a closed position, according to embodiments of the present invention; 
         FIG. 8B  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully extended as the exhaust gas recirculation valve assembly is moved to one of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 8C  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted and the exhaust gas recirculation valve assembly is held in a first of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 8D  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully extended as the exhaust gas recirculation valve assembly is being released from one of a plurality of open positions, according to embodiments of the present invention; 
         FIG. 8E  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted after actuation, and the exhaust gas recirculation valve assembly is in a closed position, according to embodiments of the present invention; and 
         FIG. 8F  is a diagram of a third embodiment of a latching mechanism used as part of an exhaust gas recirculation valve assembly, where the latching mechanism is configured such that the indexing latch is fully retracted, and the exhaust gas recirculation valve assembly is in a second of a plurality of open positions, according to embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     A diagram of an air flow system having an exhaust gas recirculation (EGR) valve according to the present invention is shown in  FIG. 1  generally at  10 . The system  10  includes an air filter  12  connected to an intake conduit  14 . The intake conduit  14  is connected to an intake manifold  16  of an engine, shown generally at  18 . Disposed within the intake conduit  14  is a manifold absolute pressure (MAP) sensor, shown generally at  20 , a throttle control valve, shown generally at  22 , and an exhaust gas recirculation (EGR) valve assembly, shown generally at  24 . 
     The engine  18  also includes an exhaust manifold  26 , connected to the exhaust manifold  26  is an exhaust conduit  28 , and disposed in the exhaust conduit  28  is a first catalyst  30  and a second catalyst  32 . Connected to the exhaust conduit  28  is a recirculation conduit  34 , where the recirculation conduit  34  is connected to the exhaust conduit  28  in an area of the exhaust conduit  28  located between the catalysts  30 , 32 . The system  10  also includes a fuel vapor purge system, shown generally at  36 , which is used for controlling the flow of air and purge vapor into the intake conduit  14 . 
     Referring to  FIGS. 2-6F , the EGR valve assembly  24  includes a first port, which in this embodiment is an exhaust gas inlet port  74  connected to the recirculation conduit  34 , and the inlet port  74  is formed as part of a lower housing  76 . The lower housing  76  is connected to a thermal isolator  38 , and the thermal isolator  38  is connected to an upper housing  80 . Formed as part of the lower housing  76  is an exhaust cavity  82 , and in fluid communication with the exhaust cavity  82  is a second port, or outlet port  84 . The outlet port  84  is connected to and in fluid communication with the intake conduit  14 . 
     Disposed within the upper housing  80  is an actuator, which in this embodiment is a solenoid assembly, shown generally at  86 , which is part of the EGR valve assembly  24 . The solenoid assembly  86  is disposed within a cavity, shown generally at  88 , formed as part of the upper housing  80 . Also forming part of the cavity  88  is an outer wall portion  92  of the upper housing  80 . 
     The solenoid assembly  86  includes a lower stator  94 , where the lower stator  94  has a flange portion  42  which is in contact with a lip portion  98  formed as part of the upper housing  80 . The flange portion  42  of the lower stator  94  is in contact with a bobbin  100 , and a stator core  44  of the lower stator  94  is surrounded by the bobbin  100 , best shown in  FIGS. 2 and 4 . The outer wall portion  92  forms part of the upper housing  80 . The bobbin  100  is surrounded by a coil (not shown for demonstrative purposes), which is located in a cavity, shown generally at  102 . There is an aperture  78  formed as part of the lower stator  94 , and extending through the aperture  78  is a valve stem  40 , and connected to the valve stem  40  is a moveable armature  54 . The valve stem  40  extends through an aperture  46  formed as part of a stem shield  48 , and the stem shield  48  is connected to a bushing  112 , also having an aperture  112   a , where the valve stem  40  also extends through the aperture  112   a . The bushing  112  is connected to and partially surrounded by the thermal isolator  38 , partially surrounded by the upper housing  80 , and is in contact with the lower stator  94 . 
     The armature  54  includes a large diameter magnetic portion  106  which extends into the solenoid assembly  86 , and is partially surrounded by a bearing sleeve  90 , and the bearing sleeve  90  is partially surrounded by an upper stator  166  and the bobbin  100 . The large diameter magnetic portion  106  also includes a magnetic tapered section  108  which selectively moves towards and away from a stator cone  110  formed as part of the lower stator  94 . Disposed between an outer flange portion  166 A formed as part of the upper stator  166  and the bobbin  100  is an upper stator washer  170 . There is a load spring  64  in contact with the upper stator washer  170 , such that an end of the load spring  64  surrounds the outer flange portion  166 A of the upper stator  166 . The outer flange portion  166 A is integrally formed with a central base portion  166 B of the upper stator  166 . The central base portion  166 B of the upper stator  166  is partially surrounded by the bobbin  100 , partially surrounded by the upper stator washer  170 , and surrounds part of the bearing sleeve  90 . The bearing sleeve  90  is in sliding contact with and is supported by the central base portion  166 B, and the armature  54  is able to move relative to the central base portion  166 B. 
     The armature  54  also includes a small diameter portion  116  which is integrally formed with the large diameter magnetic portion  106 . The small diameter portion  116  is connected to a stopper cap  118 . There is also a cap sleeve  117  surrounding the small diameter portion  116 , and located between the stopper cap  118  and the indexing latch  56 . The valve stem  40  is integrally formed with a valve member, shown generally at  120 . The valve member  120  is selectively in contact with a valve seat  128 , where the valve seat  128  is formed as part of an insert  124 . The insert  124  is connected to the lower housing  76  through any suitable manner, such as a press-fit. The stopper cap  118 , the armature  54 , the valve stem  40  and valve member  120  move together as the valve member  120  is changed between an open position and a closed position. There is also a flange (not shown) which is located on a lip portion  174  formed as part of the outer wall portion  92 . The contact between the magnetic tapered section  108  and the stator cone  110 , and the contact between the valve member  120  and the valve seat  128  controls the travel of the valve member  120  between the open position and the closed position. The flange has an aperture through which the stopper cap  118  extends, and a flange portion  118 A which is formed as part of the stopper cap  118 . 
     Also disposed within the upper housing  80  is a latching mechanism, shown generally at  52  in  FIGS. 4, 5A-5B, and 6A-6F . The latching mechanism  52  is used with the armature  54  to hold the valve member  120  in an open position even if the coil is not energized. The armature  54  is part of the solenoid assembly  86 , and a current is applied to the coil to energize the coil, and move the armature  54  and the valve member  120  away from the valve seat  128 . 
     In  FIGS. 4 and 6A , the valve member  120  is in a closed position. The mechanism  52  also includes an indexing latch  56  connected to the armature  54  such that the latch  56  moves with the armature  54 , as shown in  FIG. 4 , and the latch  56  includes a first plurality of teeth  58  and several indexing splines  68 . The mechanism  52  also includes several slots  60  formed as part of a guide  142 , where the guide  142  also includes a second plurality of teeth  66 . The mechanism  52  also includes an index mechanism  62  having at least one indexing tooth  62 A (in this embodiment, the mechanism  62  has multiple teeth  62 A, but only one is shown in  FIGS. 6A-6F  for demonstrative purposes), where the index mechanism  62  also surrounds the small diameter portion  116  of the armature  54 , but is able to slide and move relative to the small diameter portion  116  of the armature  54 . Force is applied to the index mechanism  62  by the load spring  64 . The index mechanism  62  is also adjacent a spring cup, shown generally at  132 . More specifically, the spring cup  132  includes an inner cylindrical portion  134  located next to the index mechanism  62 . The inner cylindrical portion  134  also surrounds the small diameter portion  116 , but is not connected to the small diameter portion  116  such that the spring cup  132  is also able to slide and move relative to the small diameter portion  116 . The inner cylindrical portion  134  is connected to an outer cylindrical portion  136  with a central flange  138 . Part of the load spring  64  surrounds the outer cylindrical portion  136  and is in contact with an outer flange  140  integrally formed with the outer cylindrical portion  136 . 
     In addition to the load spring  64 , there is also a return spring  144  which surrounds the small diameter portion  116 , and is located between the spring cup  132  and the large diameter magnetic portion  106  of the armature  54 . More specifically, the return spring  144  is between the inner cylindrical portion  134  of the spring cup  132  and the large diameter magnetic portion  106  of the armature  54 , and the return spring  144  biases the spring cup  132  away from the large diameter magnetic portion  106  of the armature  54 . The load spring  64  is between the outer flange  140  and the bobbin  100 , and biases the spring cup  132  and the index mechanism  62  away from the bobbin  100 . Depending on the configuration of the latching mechanism  52 , the load spring  64  causes the spring cup  132  and index mechanism  62  to apply force to the latch  56  or the guide  142 . Therefore, the latching mechanism  52  is biased in two different ways, one way is the return spring  144  biasing the spring cup  132  and the index mechanism  62  away from the large diameter magnetic portion  106  of the armature  54  (which is movable), and the other is the load spring  64  biasing the spring cup  132  and the index mechanism  62  away from the bobbin  100  (which is stationary). 
     In addition to the slots  60  and the teeth  66 , the guide  142  also includes an inner housing  146  which partially surrounds the indexing latch  56  and the index mechanism  62 . Part of the inner housing  146  is surrounded by the spring cup  132 . The inner housing  146  is integrally formed with several support members  150 , and the support members  150  are integrally formed with a circumferential flange member  152 . There are apertures, shown generally at  154 , between each of the support members  150 . The circumferential flange member  152  is connected to the upper stator washer  170  through any suitable method, such as spot welding, use or an adhesive, or the like. The connection of the circumferential flange portion  152  to the upper stator washer  170  properly positions the guide  142 . 
     The latching mechanism  52  functions to hold the valve member  120  in an open position, even when the coil is not energized. Referring to  FIGS. 4 and 6A , the latching mechanism  52  is shown in a position which corresponds to the valve member  120  being in a closed position. When the coil is energized enough to generate a magnetic force to overcome the force from the springs  64 , 144 , the armature  54  and the indexing latch  56  move toward the lower stator  94 , moving the valve member  120  away from the valve seat  128 , placing the valve member  120  in an open position. The movement of the armature  54  toward the lower stator  94  causes force to be applied to the teeth  62 A of the index mechanism  62  from at least one of the first plurality of teeth  58  formed as part of the indexing latch  56 . The movement of the indexing latch  56  is guided by the movement of the indexing splines  68  moving in the slots  60 . The force applied to the index mechanism  62  from the indexing latch  56  overcomes the force applied to the index mechanism  62  from the springs  64 , 144  by way of the spring cup  132  and moves each tooth  62 A of the index mechanism  62  out of a corresponding slot  60 , as shown in  FIG. 6B . 
     It is shown in  FIGS. 6A-6F  that the vertexes  58 A of the first plurality of teeth  58  are not in alignment with the vertexes  66 A of the second plurality of teeth  66 , which facilitates the rotation of the index mechanism  62 . Each of the teeth  62 A has an angled portion  62 B which also facilitates the rotation of the index mechanism  62 . The coil is energized to move the armature  54  and the indexing latch  56  toward the lower stator  94  enough to move the teeth  62 A of index mechanism  62  out of the slots  60 . Once the indexing latch  56  has moved the teeth  62 A of the index mechanism  62  out of the slots  60 , the pressure applied to the index mechanism  62  from the spring cup  132  and the load spring  64  and the return spring  144  pushes each tooth  62 A towards a corresponding vertex  58 A. This causes the index mechanism  62  to move (i.e., rotate about the small diameter portion  116  of the armature  54 ) as each tooth  62 A slides towards one of the vertexes  58 A in between two of the first plurality of teeth  58 , as shown in  FIG. 6B . 
     Once each tooth  62 A is in contact with one of the vertexes  58 A of the first plurality of teeth  58 , each tooth  62 A of the index mechanism  62  is also positioned such that each tooth  62 A is between two of the second plurality of teeth  66  formed as part of the guide  142 , also shown in  FIG. 6B . The coil is then de-energized, but the valve member  120  remains in the open position because the index mechanism  62  (and therefore the spring cup  132  and armature  54 ) is held in place by the guide  142 . More specifically, after the coil is de-energized, the indexing latch  56 , moves away from the index mechanism  62  enough to allow the teeth  58  of the indexing latch  56  to disengage from the teeth  62 A of the index mechanism  62 , while at the same time, the force of the springs  64 , 144  causes the armature  54  to move a small amount away from the lower stator  94  such that the teeth  62 A move toward the vertexes  66 A of the second plurality of teeth  66  formed as part of the guide  142 , as shown in  FIG. 6C , again rotating the index mechanism  62 . Since the guide  142  is stationary, and the teeth  62 A of the index mechanism  62  are interlocked with the teeth  66  of the guide  142 , the index mechanism  62 , spring cup  132 , and armature  54  are not allowed to move to place the valve member  120  back in the closed position, but rather are held in place by the guide  142  (and the teeth  58  of the indexing latch  56  are disengaged from the teeth  62 A of the index mechanism  62 ), to maintain the valve member  120  in the open position. This allows the exhaust gas to flow from the recirculation conduit  34  through the EGR valve assembly  24  and into the intake conduit  14  as the valve member  120  is held in the open position, but does not draw any power from the vehicle battery to maintain the position of the valve member  120  in the open position since the coil is not energized. 
     Once the valve member  120  is in the open position (i.e., the valve member  120  is no longer in contact with the valve seat  128 ), the exhaust gas is able to flow through the first port  74  from the recirculation conduit  34 , through the valve seat  128 , and into the exhaust cavity  82 . The exhaust gas then flows from the exhaust cavity  82  and out of the second port  84  into the intake conduit  14 . 
     Once it is desired to change the valve member  120  from the open position back to the closed position, the coil is again energized, moving the armature  54  and the indexing latch  56  toward the lower stator  94  such that the first plurality of teeth  58  again engage and apply force to the teeth  62 A of the index mechanism  62  to overcome the force applied to the index mechanism  62  from the springs  64 , 144  and lift the index mechanism  62  away from the second plurality of teeth  66 . As mentioned above, the vertexes  58 A of the first plurality of teeth  58 A are not in alignment with the vertexes  66 A of the second plurality of teeth  66 . When the valve member  120  is in the open position, and the teeth  62 A of the index mechanism  62  are held in place by the teeth  66  of the guide  142 , the teeth  62 A of the index mechanism  62  are not in alignment with the vertexes  58 A of the first plurality of teeth  58 , shown in  FIG. 6C . Once the teeth  62 A of the index mechanism  62  have disengaged from the second plurality of teeth  66 , and are only engaged with the first plurality of teeth  58 , the teeth  62 A move toward the corresponding vertexes  58 A (because of the force from the springs  64 , 144 ), causing the index mechanism  62  to rotate, such that the teeth  62 A are no longer in alignment with the vertexes  66 A of the second plurality of teeth  66 . The coil is then again de-energized, and the armature  54  and indexing latch  56  move away from the lower stator  94 , and the teeth  62 A reengage with the second plurality of teeth  66  of the guide  142 , as shown in  FIG. 6E . However, instead of moving towards the vertexes  66 A due to the force of the springs  64 , 144 , the each tooth  62 A moves towards a corresponding slot  60 , allowing the index mechanism  62  to move further away from the lower stator  94 , and each tooth  62 A to move into a corresponding slot  60 , as shown in  FIG. 6F , which also results in the force from the springs  64 , 144  moving the armature  54 , indexing latch  56 , index mechanism  62 , and spring cup  132  further away from the lower stator  94 , and the valve member  120  to move back to the closed position, as shown in  FIGS. 4, 6A, and 6F . 
     The solenoid assembly  86  and therefore the coil is only energized when the valve member  120  is being changed between the open position and the closed position. Once the valve member  120  is in the open position, the coil is de-energized. Furthermore, once the valve member  120  is in the closed position, the coil is de-energized. An example of this is shown in  FIG. 3 , where voltage  70  of the solenoid assembly  86  and the position  72  of the valve member  120  are shown. The voltage  70  is applied to the coil, and therefore the armature  54 , as a single, short pulse, for about 30 milliseconds, the armature  54  moves the indexing latch  56  and the index mechanism  62 , allowing the valve member  120  to change to the open position, as described above. Once the valve member  120  is in the open position, the coil is then de-energized, the voltage  70  then drops to zero, and the valve member  120  is held in the open position by the latching mechanism  52 . The voltage  70  is then re-applied as a short, single pulse to the coil, which then re-energizes the coil, and the latching mechanism  52  is actuated to change the valve member  120  from the open position to the closed position. The function of the latching mechanism  52  allows to the coil of the solenoid assembly  86  to be de-energized, and therefore no power is drained from the battery of the vehicle, while still providing the capability of the valve member  120  to be held in the open position or closed position. Energy is only used in intervals of about 30 milliseconds when changing the valve member  120  between the open and closed positions, as shown in  FIG. 3 , and energy is not used when the valve member  120  is held in the open position or the closed position. 
     Another embodiment of the EGR valve assembly  24  is shown in  FIGS. 7A-7E , with like numbers referring to like elements. However, in this embodiment, the latching mechanism  52  is constructed to provide multiple open positions. The guide  142  includes teeth  66  which are different sizes and have vertexes  66 A,B at varying distances from the valve seat  128 , which allows for the latching mechanism  52  to be placed in multiple configurations, and the valve member  120  to be placed in multiple open positions, or to function as a multi-stage valve. The valve member  120  is in the closed position when the latching mechanism  52  is configured as shown in  FIG. 7A . The coil is energized in the same manner as in the previous embodiment. When the coil is energized and then de-energized as previously described, the indexing teeth  62 A of the index mechanism  62  change from being engaged with the teeth  58  of latch  56  shown in  FIG. 7A  to being engaged with the teeth  66  of the guide  142 , placing the latching mechanism  52  in a first configuration, as shown in  FIG. 7B , and placing the valve member  120  in a first open position. More specifically, the tooth  62 A shown in  FIG. 7B  is engaged with the first vertex  66 A of the guide. When it is desired to change the valve member  102  to a second open position, the coil is again energized and de-energized as described in the previous embodiment, changing the location of the indexing teeth  62 A from being engaged with the first vertex  66 A of the guide  142 , as shown in  FIG. 7B , to being engaged with the second vertex  66 B of the guide  142 , placing the latching mechanism  52  in a second configuration, as shown in  FIG. 7C . When the teeth  62 A are engaged with the second vertex  66 B, the valve member  120  is then placed in the second open position. 
     In the embodiment shown in  FIGS. 7A-7E , a portion of the teeth  66  have vertexes  66 A which are located at a first distance from the valve seat  128 , and another portion of the teeth  66  have vertexes  66 B which are located at a second distance from the valve seat  128 . The second distance is less than the first distance from the valve seat  128 , and therefore a greater amount of exhaust gas is able to flow from the recirculation conduit  34  to the intake conduit  14  when the valve member  120  is in one of the open positions. 
     When it is desired to place the valve member  120  back in the closed position, the coil  120  is then energized and de-energized as described in the previous embodiment, and the tooth  62 A changed from being engaged with the second vertex  66 B, shown in  FIG. 7C , to being located in the slot  60 , as shown in  FIG. 7E . The tooth  62 A is shown transitioning between the vertex  66 B and the slot  60  in  FIG. 7D . 
     Yet another embodiment of the present invention is shown in  FIGS. 8A-8F . In this embodiment, the latching mechanism  52  is also constructed to have multiple open positions, but is also able to place the valve member  120  in the closed position in between each open position. 
     The coil is again energized in the same manner as in the previous embodiments. The valve member  120  is in the closed position when the latching mechanism  52  is configured as shown in  FIG. 8A . When the coil is energized, the indexing latch  56  moves towards the lower stator  94 , moving the tooth  62 A out of the slot  60 , as shown in  FIG. 8B , and the index mechanism  62  rotates such that each tooth  62 A moves to a corresponding vertex  58 A of the teeth  58 , as previously described, such that when the coil is de-energized, the latch  56  moves away from the lower stator  94  such that each tooth  62 A engages with a corresponding tooth  66  of the guide  142 , which causes the index mechanism  62  to rotate further, and each tooth  62 A to move towards and engage a corresponding vertex  62 B, placing the latching mechanism  52  in a second configuration and the valve member  120  in one of the open positions, as shown in  FIG. 8C . 
     The coil is then energized to actuate the latching mechanism  52  as shown in  FIG. 8D  to transition the valve member  120  between one of the plurality of open positions and the closed position, and then de-energized to configure the latching mechanism  52  such that each tooth  62 A moves into a corresponding slot  60 , as shown in  FIG. 8E , and the valve member  120  is back in the closed position. This process is repeated to change the valve member  120  from the closed position shown in  FIG. 8E  to another open position, shown in  FIG. 8F , where the latching mechanism  52  is in a first configuration, and each tooth  62 A is engaged with a corresponding vertex  66 A. It is therefore shown in  FIGS. 8A-8F  that the valve member  120  is able to be placed in multiple open positions, and placed in a closed position in between each of the open positions. Again, the vertexes  66 A of the teeth  66  are located at a first distance from the valve seat  128 , and the vertexes  66 B of the teeth  66  are located at a second distance from the valve seat  128 . The second distance is less than the first distance, and therefore a greater amount of exhaust gas is able to flow from the recirculation conduit  34  to the intake conduit  14  when the valve member  120  is in the larger of the open positions, and each tooth  62 A is engaged with a vertex  66 B. However, the valve member  120  is placed in the closed position in between the open positions. 
     Another feature of the present invention is that in all of the embodiments above, the coil may be held energized at full extend, such that the valve member  120  is the furthest away from the valve seat  128 , maintaining a maximum open position, in effect creating additional flow capability of the valve assembly  24 . A secondary pulsed signal (i.e., PWM signal) effectually holds the valve member  120  in the maximum open state with reduced power consumption after being energized (i.e., a peak-and-hold signal). In all of the embodiments, the position of the valve member  120  is changed to control the flow of exhaust gas from through the first port  74  from the recirculation conduit  34 , through the valve seat  128 , into the exhaust cavity  82 , and out of the second port  84  into the intake conduit  14 . 
     Another feature of the present invention is the ability to detect the position of the valve assembly  24 , and more specifically the position of the valve member  120 , by detecting the current applied to the coil. This feature is also described in U.S. patent application Ser. No. 14/708,354, the entire specification of which is incorporated herein by reference. 
     The position of the armature  54 , and therefore the valve member  120  is detected by measuring current. The change in current is measured by emitting a 12 Volt pulse through the coil. In one embodiment, the voltage pulse typically lasts between 5-15 milliseconds, and is therefore not long enough, or strong enough, to move the armature  54 , but is significant enough to cause a change in current in the coil that is measurable. It should be noted that it is within the scope of the invention that the voltage pulse used to detect the position of the valve member  120  may last for longer or shorter time intervals, as long as the armature  54  and valve member  120  remain stationary. Because the change in current in the coil is measured, and the level of current change depends on the location of the armature  54  and corresponds to the location of the valve member  120  and the armature  54 , the location of the valve member  120  and the armature  54  is therefore detected and used to identify the position of the latching mechanism  52 . 
     In this embodiment, the current of the coil is measured when the valve member  120  is in either one of the open positions or the closed position, and is stationary (i.e., not transitioning between one of the open positions and closed position). In this embodiment, a 12 Volt pulse is emitted through the coil, and a measurement of the current of the coil is then taken. The current of the coil changes, depending upon the location of the armature  54 . 
     The position of the valve member  120  is able to be detected when the valve member  120  is in either one of the open position or the closed position. To detect the position of the valve member  120  and the armature  54 , a voltage pulse is sent across a sense resistor (not shown), and into the coil of the solenoid assembly  86 . The voltage pulse is not large enough or long enough to move the armature  54 , but creates a voltage across the sense resistor that is measured, which then corresponds to the current flowing through the sense resistor. This value of the current varies depending on the location of the armature  54 , and valve member  120 . Although in this embodiment, a sense resistor is used to detect the position of the valve member  120  and armature  54 , it is within the scope of the invention that other electrical components in circuits having different configurations may be used. 
     The peak current measurement taken during a first voltage pulse is compared to the peak current measurement taken during a second voltage pulse. The higher of the two current measurements indicates that the armature  54  and valve member  120  are in the closed position, and the lower of the two current measurements indicates that the armature  54  and valve member  120  are in the closed position. In the embodiments shown in  FIGS. 7A-7E  and  FIGS. 8A-8F , there are different current measurements that correspond to the multiple open positions of the valve member  120 . The higher the current measurement, the further open the valve member  120 . 
     Additionally, the voltage pulse being applied for different lengths of time produces different current measurements, which also depends on whether the valve member  120  is in the open position or closed position. The current measurement, and therefore the position of the valve member  120  and armature  54 , is therefore detected by measuring the current in the coil after applying the voltage pulse to the coil for a specified time period. The specified time period of the voltage pulse may be any desired time period, as long as the valve member  120  and armature  54  remain stationary during the application of the voltage pulse. 
     Although the present invention is shown as being used with an exhaust gas recirculation system  10 , it is within the scope of the invention that the valve assembly  24  may be configured for use with other applications requiring a latching valve which may be deactivated when in open or closed positions. Such other applications may include, but are not limited to, fuel vapor purge systems, air intake valves for fuel cell powered vehicles, and the like. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.