Patent Publication Number: US-11655788-B2

Title: Charge forming device with throttle valve

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/842,795 filed on May 3, 2019 the entire contents of which are incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to a throttle valve associated with a rotary position sensor. 
     BACKGROUND 
     Fuel systems including electronic fuel injectors typically provide fuel at relatively high pressure to and from the fuel injectors. The injection pressure may be constant so that the duration over which the injector is open determines the amount of fuel discharged from the injector. Such systems may be relatively complex and require multiple sensors some of which may be relatively costly, like oxygen sensors in an exhaust gas, and high pressure pumps to provide fuel to the injectors at the high pressure. Such fuel systems are too expensive and complex for a wide range of engine applications. 
     SUMMARY 
     In at least some implementations, a charge forming device includes a body that has a throttle bore, a throttle valve associated with the throttle bore, a coupler and an actuator. The throttle has a valve head received within and movable relative to the throttle bore, and a valve shaft to which the valve head is coupled. The coupler is connected to the valve shaft and carries or includes a sensor element. And the actuator has a drive shaft coupled to the coupler so that rotation of the drive shaft is transmitted to the coupler and the valve shaft. 
     In at least some implementations, the coupler includes a first drive feature engaged with the drive shaft and a second drive feature engaged with the valve shaft. In at least some implementations, the coupler includes an anti-rotation feature and the sensor element includes an anti-rotation feature that is engaged with the anti-rotation feature of the coupler to prevent rotation of the sensor element relative to the coupler. The anti-rotation features of both the coupler and the sensor element may be defined by at least one flat surface. The coupler may include a cavity in which the sensor element is at least partially received, and the anti-rotation feature of the coupler may be defined by a surface that defines the cavity. 
     In at least some implementations, the coupler is flexible and may twist to permit movement of drive shaft relative to the throttle valve shaft when sufficient force is applied to the coupler. And the coupler is resilient so that the coupler untwists when the force causing the twisting is decreased sufficiently to permit untwisting of the coupler. 
     In at least some implementations, the device includes a circuit board and a sensor on the circuit board that is responsive to movement of the sensor element, and the coupler is mounted to an end of the throttle valve shaft that is closest to the circuit board. The throttle valve shaft or the drive shaft may extend through a void in the circuit board. The actuator may be located adjacent to a first side of the circuit board and the coupler may be located adjacent to a second side of the circuit board that is opposite to the first side. 
     In at least some implementations, a charge forming device includes a fuel injector having an electrically actuated valve and an outlet port, and fuel flows through the outlet port when the valve is open, and a pressure sensor arranged so that the pressure sensor is communicated with the pressure in the area of the outlet port. 
     In at least some implementations, the device also includes a controller communicated with the pressure sensor, and wherein the controller controls opening of the valve at least in part as a function of the pressure at the pressure sensor. 
     In at least some implementations, the device also includes a body having a throttle bore, and wherein the outlet port opens into the throttle bore and the body includes a passage that opens into the throttle bore in the area of the outlet port. The passage is communicated with the pressure sensor so that an output of the pressure sensor is indicative of the pressure within the passage. In at least some implementations, the throttle bore has an axis and a plane perpendicular to the axis and intersecting the outlet port is within one inch of an end of the passage that is open to the throttle bore. 
     In at least some implementations, the device also comprises a body having a throttle bore with a venturi located within the throttle bore, and wherein the outlet port opens into the venturi, and wherein the pressure sensor is responsive to the pressure within the area of the venturi. The body may include a passage that has a first end that is open to the throttle bore within one inch of the venturi and wherein the passage is communicated with the pressure sensor. 
     In at least some implementations, a method of controlling fuel injection events includes sensing the pressure at or near a fuel injector outlet and opening a valve of the fuel injector when the pressure at or near the fuel injector is a negative relative pressure. In at least some implementations, the method also includes determining the portion of a negative pressure signal in which to open the valve. In at least some implementations, the method also comprises comparing the sensed pressure to a threshold and opening the valve when the pressure exceeds the threshold. In at least some implementations, opening of the valve is controlled as a function of the magnitude of the pressure at or near the outlet of the fuel injector. And in at least some implementations, the pressure is continuously measured or sensed, or sampled at fixed rate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of certain embodiments and best mode will be set forth with reference to the accompanying drawings, in which: 
         FIG.  1    is a perspective view of a throttle body assembly having multiple bores from which a fuel and air mixture may be delivered to an engine, a main body of the throttle body assembly is shown transparent to show certain internal components and features; 
         FIG.  2    is another perspective view of the throttle body assembly; 
         FIG.  3    is another perspective view of the throttle body assembly with a vapor separator cover removed; 
         FIG.  4    is a perspective sectional view of a throttle body assembly; 
         FIG.  5    is a perspective sectional view of a throttle body assembly; 
         FIG.  6    is an enlarged, fragmentary perspective view of a portion of a throttle body assembly showing an air induction path and valve; 
         FIG.  7    is a fragmentary sectional view of a throttle body assembly including an actuator driven throttle valve and a position sensing arrangement; 
         FIG.  8    is a perspective view of a coupler; 
         FIG.  9    is another perspective view of the coupler; 
         FIG.  10    is a fragmentary sectional view of a throttle body assembly having two throttle bores; and 
         FIG.  11    is a graph showing waveforms associated with ignition events, pressure near an injector carried by the throttle body and injector events. 
     
    
    
     DETAILED DESCRIPTION 
     Referring in more detail to the drawings,  FIGS.  1 - 3    illustrate a charge forming device  10  that provides a combustible fuel and air mixture to an internal combustion engine  12  (shown schematically in  FIG.  1   ) to support operation of the engine. The charge forming device  10  may be utilized on a two or four-stroke internal combustion engine, and in at least some implementations, includes a throttle body assembly  10  from which air and fuel are discharged for delivery to the engine. 
     The assembly  10  includes a housing having a throttle body  18  that has more than one throttle bore  20  (shown as two separate bores extending through the body parallel to each other) each having an inlet  22  ( FIG.  2   ) through which air is received into the throttle bore  20  and an outlet  24  ( FIG.  1   ) connected or otherwise communicated with the engine (e.g. an intake manifold  26  thereof). The inlets may receive air from an air filter (not shown), if desired, and that air may be mixed with fuel provided from separate fuel metering valves  28 ,  29  carried by or communicated with the throttle body  18 . The intake manifold  26  generally communicates with a combustion chamber or piston cylinder of the engine during sequentially timed periods of a piston cycle. For a four-stroke engine application, as illustrated, the fluid may flow through an intake valve and directly into the piston cylinder. Alternatively, for a two-stroke engine application, typically air flows through the crankcase (not shown) before entering the combustion chamber portion of the piston cylinder through a port in the cylinder wall which is opened intermittently by the reciprocating engine piston. 
     The throttle bores  20  may have any desired shape including (but not limited to) a constant diameter cylinder or a venturi shape wherein the inlet leads to a tapered converging portion that leads to a reduced diameter throat that in turn leads to a tapered diverging portion that leads to the outlet  24 . The converging portion may increase the velocity of air flowing into the throat and create or increase a pressure drop in the area of the throat. In at least some implementations, a secondary venturi, sometimes called a boost venturi  36  may be located within one or more of the throttle bores  20  whether the throttle bore  20  has a venturi shape or not. The boost venturis may be the same, if desired, and only one will be described further. The boost venturi  36  may have any desired shape, and as shown in  FIGS.  1  and  4   , has a converging inlet portion that leads to a reduced diameter intermediate throat that leads to a diverging outlet. The boost venturi  36  may be coupled the to throttle body  18  within the throttle bore  20 , and in some implementations, the throttle body may be cast from a suitable metal and the boost venturi  36  may be formed as part of the throttle body, in other words, from the same piece of material cast as a feature of the throttle body when the remainder of the throttle body is formed. The boost venturi  36  may also be an insert coupled in any suitable manner to the throttle body  18  after the throttle body is formed. In the example shown, the boost venturi  36  includes a wall  44  that defines an inner passage  46  that is open at both its inlet and outlet to the throttle bore  20 . A portion of the air that flows through the throttle body  18  flows into and through the boost venturi  36  which increases the velocity of that air and decreases the pressure thereof. The boost venturi  36  may have a center axis  48  ( FIG.  4   ) that may be generally parallel to a center axis  50  ( FIG.  4   ) of the throttle bore  20  and radially offset therefrom, or the boost venturi  36  may be oriented in any other suitable way. 
     Referring to  FIG.  1   , the air flow rate through the throttle bore  20  and into the engine is controlled at least in part by one or more throttle valves  52 . In at least some implementations, the throttle valve  52  includes multiple heads  54  received one in each bore  20 , each head may include a flat plate coupled to a rotating throttle valve shaft  56 . The shaft  56  extends through a shaft bore  58  formed in the throttle body  18  that intersects and may be generally perpendicular to the throttle bores  20 . The throttle valve  52  may be driven or moved by an actuator  60  between an idle position wherein the heads  54  substantially block air flow through the throttle bores  20  and a fully or wide-open position wherein the heads  54  provide the least restriction to air flow through the throttle bores  20 . In one example, the actuator  60  may be an electrically driven motor  62  coupled to the throttle valve shaft  56  to rotate the shaft and thus rotate the valve heads  54  within the throttle bores  20 . In another example, the actuator  60  may include a mechanical linkage, such as a lever attached to a throttle valve shaft  56  to which a Bowden wire may be connected to manually rotate the shaft  56  as desired and as is known in the art. In this way, multiple valve heads may be carried on a single shaft and rotated in unison within different throttle bores. A single actuator may drive the throttle valve shaft, and a single throttle position sensor may be used to determine the rotary position of the throttle valve (e.g. the valve heads  54  within the throttle bores  20 ). 
     The fuel metering valves  28  may be the same for each bore  20  and so only one is described further. The fuel metering valve  28  may have an inlet  66  to which fuel is delivered, a valve element  68  (e.g. a valve head) that controls fuel flow rate and an outlet  70  downstream of the valve element  68 . To control actuation and movement of the valve element  68 , the fuel metering valve  28  may include or be associated with an electrically driven actuator  72  such as (but not limited to) a solenoid. Among other things, the solenoid  72  may include an outer casing  74  received within a cavity  76  in the throttle body  18 , a coil  78  wrapped around a bobbin  80  received within the casing  74 , an electrical connector  82  arranged to be coupled to a power source to selectively energize the coil  78 , and an armature  84  slidably received within the bobbin  80  for reciprocation between advanced and retracted positions. The valve element  68  may be carried by or otherwise moved by the armature  84  relative to a valve seat  86  that may be defined within one or both of the solenoid  72  and the throttle body  18 . When the armature  84  is in its retracted position, the valve element  68  is removed or spaced from the valve seat  86  and fuel may flow through the valve seat. When the armature  84  is in its extended position, the valve element  68  may be closed against or bears on the valve seat  86  to inhibit or prevent fuel flow through the valve seat. In the example shown, the valve seat  86  is defined within the cavity  76  of the throttle body  18  and may be defined by a feature of the throttle body or by a component inserted into and carried by the throttle body or the solenoid casing  74 . The solenoid  72  may be constructed as set forth in U.S. patent application Ser. No. 14/896,764. The inlet  68  may be centrally or generally coaxially located with the valve seat  86 , and the outlet  70  may be radially outwardly spaced from the inlet and generally radially outwardly oriented. Of course, other metering valves, including but not limited to different solenoid valves or commercially available fuel injectors, may be used instead if desired in a particular application. 
     Fuel that flows through the valve seat  86  (e.g. when the valve element  68  is moved from the valve seat by retraction of the armature  84 ), flows to the metering valve outlet  70  for delivery into the throttle bore  20 . In at least some implementations, fuel that flows through the outlet  70  is directed into the boost venturi  36 , when a boost venturi  36  is included in the throttle bore  20 . In implementations where the boost venturi  36  is spaced from the outlet  70 , an outlet tube  92  ( FIG.  4   ) may extend from a passage or port defining at least part of the outlet  70  and through an opening in the boost venturi wall  44  to communicate with the boost venturi passage  46 . The tube  92  may extend into and communicate with the throat  40  of the boost venturi  36  wherein a negative or subatmospheric pressure signal may be of greatest magnitude, and the velocity of air flowing through the boost venturi  36  may be the greatest. Of course, the tube  92  may open into a different area of the boost venturi  36  as desired. Further, the tube  92  may extend through the wall  44  so that an end of the tube projects into the boost venturi passage  46 , or the tube may extend through the boost venturi passage so that an end of the tube intersects the opposite wall of the boost venturi and may include holes, slots or other features through which fuel may flow into the boost venturi passage  46 , or the end of the tube may be within the opening  94  and recessed or spaced from the passage (i.e. not protruding into the passage). 
     Further, as shown in  FIGS.  4  and  6   , air induction passages  172 ,  173  may be used with each or any one of multiple metering valves  28  when more than one metering valve is used. The air induction passages  172 ,  173  may extend from a portion of the throttle bores  20  upstream of the fuel outlet of the metering valve with which it is associated and may communicate with the fuel passage leading to the fuel outlet of the metering valve. In the example shown, the air induction passages  172 ,  173  lead from an inlet end  22  of the throttle body  18  and to the fuel outlet passages. 
     In the example where a fuel tube  92  extends into a boost venturi  36 , the induction passages  172 ,  173  may extend into or communicate with the fuel tube (as shown in  FIG.  6   ) to provide air from the induction passages and fuel from the metering valves  28  into the fuel tubes  92  where it may be mixed with air flowing through the throttle bores  20  and boost venturis  36 . 
     A jet of other flow controller may be provided in the induction passages  172 ,  173  to control the flow rate of air in the passages, if desired. In addition to or instead of a jet or other flow controller, the flow rate through the induction passages  172 ,  173  may be controlled at least in part by a valve. The valve could be located anywhere along the passages  172 ,  173 , including upstream of the inlet of the passages. In at least one implementation, the valve may be defined at least in part by the throttle valve shaft  56 . In this example, the induction passage  172  intersects or communicates with the throttle shaft bore so that air that flows through the induction passages flows through the throttle shaft bore before the air is discharged into the throttle bore. Separate voids, like holes  174  or slots, may be formed in the throttle valve shaft  56  (e.g. through the shaft, or into a portion of the periphery of the shaft) and aligned with the passages  172 ,  173 , as shown in  FIG.  6   . As the throttle valve shaft  56  rotates, the extent to which the void is aligned or registered with the induction passage changes. Thus, the effective or open flow area through the valve changes which may change the flow rate of air provided from the induction passage. If desired, in at least one position of the throttle valve, the voids may be not open at all to the induction passages such that air flow from the induction passages past the throttle valve bore does not occur or is substantially prevented. Hence, the air flow provided from the induction passages to the throttle bore may be controlled at least in part as a function of the throttle valve position. 
     Fuel may be provided from a fuel source to the metering valve inlet  66  and, when the valve element  68  is not closed on the valve seat  86 , fuel may flow through the valve seat and the metering valve outlet  70  and to the throttle bore  20  to be mixed with air flowing therethrough and to be delivered as a fuel and air mixture to the engine. The fuel source may provide fuel at a desired pressure to the metering valve  28 . In at least some implementations, the pressure may be ambient pressure or a slightly superatmospheric pressure up to about, for example, 6 psi above ambient pressure. 
     To provide fuel to the metering valve inlet  66 , the throttle body assembly  10  may include an inlet chamber  100  ( FIG.  3   ) into which fuel is received from a fuel supply, such as a fuel tank. The throttle body assembly  10  may include a fuel inlet  104  leading to the inlet chamber  100 . In a system wherein the fuel pressure is generally at atmospheric pressure, the fuel flow may be fed under the force of gravity to the inlet chamber  100 . In at least some implementations, as shown in  FIGS.  3  and  4   , a valve assembly  106  may control the flow of fuel into the inlet chamber  100 . The valve assembly  106  may include a valve element  108  and may include or be associated with a valve seat so that a portion of the valve element  108  is selectively engageable with the valve seat to inhibit or prevent fluid flow through the valve seat, as will be described in more detail below. The valve element  108  may be coupled to an actuator  112  that moves the valve  108  relative to the valve seat, as will be set forth in more detail below. A vent port or passage  102  ( FIGS.  4  and  5   ) may be communicated with the inlet chamber and with the engine intake manifold or elsewhere as desired so long as the desired pressure within the inlet chamber  100  is achieved in use, which may include atmospheric pressure. The level of fuel within the inlet chamber  100  provides a head or pressure of the fuel that may flow through the metering valve  28  when the metering valve is open. 
     To maintain a desired level of fuel in the inlet chamber  100 , the valve  108  is moved relative to the valve seat by the actuator  112  which, in the example shown, includes or is defined by a float that is received in the inlet chamber and is responsive to the level of fuel in the inlet chamber. The float  112  may be buoyant in fuel and provide a lever pivotally coupled to the throttle body  18  or a cover  118  coupled to the body  18  on a pin and the valve  108  may be connected to the float  112  for movement as the float moves in response to changes in the fuel level within the inlet chamber  100 . When a desired maximum level of fuel is present in the inlet chamber  100 , the float  112  has been moved to a position in the inlet chamber wherein the valve  108  is engaged with and closed against the valve seat, which closes the fuel inlet  104  and prevents further fuel flow into the inlet chamber  100 . As fuel is discharged from the inlet chamber  100  (e.g. to the throttle bore  20  through the metering valve  28 ), the float  112  moves in response to the lower fuel level in the inlet chamber and thereby moves the valve  108  away from the valve seat so that the fuel inlet  104  is again open. When the fuel inlet  104  is open, additional fuel flows into the inlet chamber  100  until a maximum level is reached and the fuel inlet  104  is again closed. 
     The inlet chamber  100  may be defined at least partially by the throttle body  18 , such as by a recess formed in the throttle body, and a cavity in the cover  118  carried by the throttle body and defining part of the housing of the throttle body assembly  10 . Outlets  120  ( FIG.  5   ) of the inlet chamber  100  leads to the metering valve inlet  66  of each metering valve  28 ,  29 . So that fuel is available at the metering valve  28  at all times when fuel is within the inlet chamber  100 , the outlet  120  may be an open passage without any intervening valve, in at least some implementations. The outlet  120  may extend from the bottom or a lower portion of the inlet chamber so that fuel may flow under atmospheric pressure to the metering valve  28 . 
     In use of the throttle body assembly  10 , fuel is maintained in the inlet chamber  100  as described above and thus, in the outlet  120  and the metering valve inlet  66 . When the metering valve  28  is closed, there is no, or substantially no, fuel flow through the valve seat  86  and so there is no fuel flow to the metering valve outlet  70  or to the throttle bore  20 . To provide fuel to the engine, the metering valve  28  is opened and fuel flows into the throttle bore  20 , is mixed with air and is delivered to the engine as a fuel and air mixture. The timing and duration of the metering valve opening and closing may be controlled by a suitable microprocessor or other controller. The fuel flow (e.g. injection) timing, or when the metering valve  28  is opened during an engine cycle, can vary the pressure signal at the outlet  70  and hence the differential pressure across the metering valve  28  and the resulting fuel flow rate into the throttle bore  20 . Further, both the magnitude of the engine pressure signal and the airflow rate through the throttle valve  52  change significantly between when the engine is operating at idle and when the engine is operating at wide open throttle. In conjunction, the duration that the metering valve  28  is opened for any given fuel flow rate will affect the quantity of fuel that flows into the throttle bore  20 . 
     The inlet chamber  100  may also serve to separate liquid fuel from gaseous fuel vapor and air. Liquid fuel will settle into the bottom of the inlet chamber  100  and the fuel vapor and air will rise to the top of the inlet chamber where the fuel vapor and air may flow out of the inlet chamber through the vent passage  102  or vent outlet (and hence, be delivered into the intake manifold and then to an engine combustion chamber). To control the venting of gasses from the inlet chamber  100 , a vent valve  130  may be provided at the vent passage  102 . The vent valve  130  may include a valve element  132  that is moved relative to a valve seat to selectively permit fluid flow through the vent or vent passage  102 . To permit further control of the flow through the vent passage  102 , the vent valve  130  may be electrically actuated to move the valve element  132  between open and closed positions relative to the valve seat  134 . 
     As shown in  FIGS.  4  and  5   , to control actuation and movement of a valve element  132 , the vent valve  130  may include or be associated with an electrically driven actuator such as (but not limited to) a solenoid  136 . Among other things, the solenoid  136  may include an outer casing received within a cavity in the throttle body  18  or cover  118  and retained therein by a retaining plate or body, a coil wrapped around a bobbin received within the casing, an electrical connector  146  arranged to be coupled to a power source to selectively energize the coil, an armature slidably received within the bobbin for reciprocation between advanced and retracted positions and an armature stop. The valve element  132  may be carried by or otherwise moved by the armature relative to a valve seat that may be defined within one or more of the solenoid  136 , the throttle body  18  and the cover  118 . When the armature is in its retracted position, the valve element  132  is removed or spaced from the valve seat and fuel may flow through the valve seat. When the armature  148  is in its extended position, the valve element  132  may be closed against or bears on the valve seat  134  to inhibit or prevent fuel flow through the valve seat. The solenoid  136  may be constructed as set forth in U.S. patent application Ser. No. 14/896,764. Of course, other valves, including but not limited to different solenoid valves (including but not limited to piezo type solenoid valves) or other electrically actuated valves may be used instead if desired in a particular application. 
     The vent passage  102  or vent outlet could be coupled to a filter or vapor canister that includes an adsorbent material, such as activated charcoal, to reduce or remove hydrocarbons from the vapor. The vent passage  102  could also or instead be coupled to an intake manifold of the engine where the vapor may be added to a combustible fuel and air mixture provided from the throttle bore  20 . In this way, vapor and air that flow through the vent valve  130  are directed to a downstream component as desired. In the implementation shown, an outlet passage  154  extends from the cover  118  downstream of the valve seat  134  and to an intake manifold of the engine (e.g. via the throttle bores  20 ). While the outlet passage  154  is shown as being defined at least in part in a conduit that is routed outside of the cover  118  and throttle body  18 , the outlet passage  154  could instead be defined at least in part by one or more bores or voids formed in the throttle body and/or cover, and or by a combination of internal voids/passages and external conduit(s). 
     In at least some implementations, the cover  118  defines part of the inlet chamber  100  and the vent passage  102  extends at least partially within the cover and communicates at a first end with the inlet chamber  100  and at a second end with an outlet from the throttle body (e.g. the cover). The vent valve  130  and valve seat  132  are disposed between the first and second ends of the vent passage  102  so that the vent valve controls the flow through the vent passage. In the implementation shown, the vent passage  102  is entirely within the cover  118 , and the vent valve  130  is carried by the cover, e.g. within the cavity formed in the cover. 
     In at least some implementations, a pressure in the vent passage  102  can interfere with the fuel flow from the inlet chamber  100  to the fuel metering valve  28  and throttle bore  20 . For example, when the vent passage  102  is communicated with the intake manifold or with an air cleaner box/filter, a subatmospheric pressure may exist within the vent passage. The subatmospheric pressure, if communicated with the inlet chamber  100 , can reduce the pressure within the inlet chamber and reduce fuel flow from the inlet chamber. Accordingly, closing the vent valve  130  can inhibit or prevent communication of the subatmospheric pressure from the vent passage  102  with the inlet chamber  100 . A pressure sensor responsive to pressure in the vent passage  102  or in, for example, the intake manifold, may provide a signal that is used to control, at least in part, the actuation of the vent valve  130  as a function of the sensed pressure to improve control over the pressure in the inlet chamber. Also or instead, the vent valve  130  may be closed to permit some positive, superatmospheric pressure to exist within the inlet chamber  100  which may improve fuel flow from the inlet chamber to the throttle bore  20 . And the vent valve  130  may be opened to permit engine pressure pulses (e.g. from the intake manifold) to increase the pressure within the inlet chamber  100 . As noted above, the opening of the vent valve  130  may be timed with such pressure pulses by way of a pressure sensor or otherwise. These examples permit better control over the fuel flow from the inlet chamber  100  and thus, better control of the fuel and air mixture delivered from the throttle bore  20 . In this way, the vent valve  130  may be opened and closed as desired to vent gasses from the inlet chamber  100  and to control the pressure within the inlet chamber. 
     Still further, it may be desirable to close the vent passage  102  to avoid the fuel in the inlet chamber  100  from going stale over time (due to evaporation, oxidation or otherwise), such as during storage of the device with which the throttle body assembly  10  is used. In this way, the vent valve  130  may be closed when the device is not being used to reduce the likelihood or rate at which the fuel in the throttle body assembly  10  becomes stale. 
     Finally, when the vent valve strokes from open to closed, the armature and valve element  132  movement displace air/vapor in the vent passage  102  toward and into the inlet chamber  100  which may raise the pressure in the inlet chamber. Repeated actuations of the vent valve  130  may then provide some pressure increase, even if relatively small, that facilitates fuel flow from the inlet chamber  100  to the throttle bore  20 . 
     In at least some implementations, the pressure within the inlet chamber  100  may be controlled by actuation of the vent valve  130 , to be between 0.34 mmHg to 19 mmHg. In at least some implementations, the vent valve  130  may be opened and closed repeatedly with a cycle time of between 1.5 ms to 22 ms. And in at least some implementations, the vent valve  130  may be controlled at least when the throttle valve is at least 50% of the way between its idle and wide open positions (e.g. between 50% and 100% of the angular rotation from idle to wide open), for example, because the intake manifold pressure may be greater in that throttle position range and thus, more likely to interfere with the pressure in the inlet chamber. 
     The vent valve  130  may be actuated by a controller  162  ( FIGS.  1 ,  4  and  5   ) that controls when electrical power is supplied to the solenoid  136 . The controller  162  may be the same controller that actuates the fuel metering valve  28  or a separate controller. Further, the controller  162  that actuates one or both of the vent valve  130  and the fuel metering valve  28  may be mounted on or otherwise carried by the throttle body assembly  10 , or the controller may be located remotely from the throttle body assembly, as desired. In the example shown, the controller  162  is carried within a sub-housing  164  that is mounted to the throttle body  18  and/or cover  118 , or otherwise carried by the housing (e.g. the body and/or cover), and which may include a printed circuit board  166  and a suitable microprocessor  168  or other controller for actuation of the metering valve  28 , vent valve  130  and/or the throttle valve (e.g. when rotated by a motor  62  as shown and described above). Further, information from one or more sensors may be used to control, at least in part, operation of the vent valve, and the sensor(s) may be communicated with the controller that controls actuation of the vent valve. 
     The dual bore throttle body and fuel injection assembly may be used to provide a combustible fuel and air mixture to a multi-cylinder engine. The assembly may improve cylinder to cylinder air-fuel ratio balancing, engine starting, and overall run quality and performance compared to an assembly having a single throttle bore and a single fuel injector or point/location of fuel injection. 
     The system or assembly may include a low pressure fuel injection system described above with the any following additional options: a single throttle body assembly with a plurality of throttle bores; one or more vapor separators integrated into the throttle body assembly; at least one injector per throttle bore; optional boost venturi for the injector(s); a single engine control module/controller; a single throttle shaft including multiple throttle valve heads on the shaft, one in each throttle bore; a single throttle position sensor; may include a single throttle actuator which may be electronically controlled; may include two ignition coils or a double-ended ignition coil. 
     As shown in  FIG.  7    a throttle body or other charge forming device may include one or more throttle bores  20 , and a throttle valve  52  associated with each throttle bore  20 . The throttle valves  52  may be separate or a single throttle valve shaft  56  may include multiple valve heads  54  that rotate with the shaft  56  between a first or idle position and a second or open position which may be a wide open or fully open position. In the example shown in  FIG.  4   , the throttle valve shaft  56  has two valve heads  54  mounted thereon, which are shown as thin discs in a dual butterfly valve arrangement. In the first position, the valve heads  54  are generally perpendicular to fluid flow through the throttle bores  20  and provide a maximum restriction to fluid flow through the throttle bores  20  (where generally perpendicular includes perpendicular and orientations within 15 degrees of perpendicular). In the second position, the valve heads  54  are generally parallel to fluid flow through the throttle bores  20  and may provide a minimum restriction to fluid flow through the throttle bores  20  (where generally parallel includes parallel and orientations within 15 degrees of parallel). 
     As noted above, the throttle valve  52  may be driven or moved by the actuator  60  which may be an electrically driven motor  62  coupled to the throttle valve shaft  56  to rotate the shaft and thus rotate the valve heads  54  within the throttle bores  20 . As shown in  FIG.  4   , a coupler  180  may drivingly connect the actuator  60  to the throttle valve shaft  56 . The coupler  180  may include a first recess  182  in which an end  184  of the throttle valve shaft  56  is received and a second recess  185  in which a drive shaft  186  of the actuator  60  is received. Thus, the coupler  180  in at least some implementations may be a component formed separately from the throttle valve shaft  56  and the drive shaft  186 . Suitable anti-rotation features may be provided between the coupler  180  and shafts  56  and  186  (e.g. complementary noncircular portions or surfaces) so that the throttle valve shaft  56  is rotated when the drive shaft  186  rotates. If desired, the coupler may be flexible, that is, it may twist or flex somewhat to reduce impulse forces from rapid movements (e.g. larger accelerations or decelerations) of the assembly. And the coupler  180  may be resilient so that it untwists or unflexes so that the amount of commanded rotation of the throttle valve  52  is achieved when the force causing the twisting is removed or sufficiently reduced (that is, the rotation of the actuator  60  is accurately transmitted to and results in the same amount of rotation of the throttle valve  52 ). 
     In  FIG.  4   , the coupler  180  is arranged on the end  184  of the valve shaft  56  opposite to and end  188  of the valve shaft  56  that is adjacent to the circuit board  166 . That end  188  of valve shaft  56  includes or is connected to a second coupler  190  that carries a sensor element  192  that rotates with the valve shaft  56 . A sensor  194  responsive to the movement of the sensor element  192  may be mounted to the circuit board  166  or elsewhere as desired. In at least some implementations, the sensor element  192  is a magnet and the sensor  194  is responsive to movement of the magnetic field of the magnet  192  when the valve shaft  56  is rotated. This provides a non-contact sensor arrangement that enables accurate determination of the rotary or angular position of the throttle valve. 
     In  FIG.  7   , a coupler  200  interconnects the actuator  60  with the valve shaft  56  and also carries or otherwise includes the sensor element  192 . This coupler  200  is mounted on the end  188  of the valve shaft  56  that is adjacent to the circuit board  166  and/or the sensor  194 . As shown in  FIGS.  7 - 9   , the coupler  200  has a first drive feature  202  engaged with the drive shaft  186  of the actuator  60  for co-rotation of the coupler  200  with the drive shaft  186 , and a second drive feature  204  engaged with the valve shaft  56  for co-rotation of the valve shaft  56  and coupler  200 . The drive features  202 ,  204  may include recesses or sockets into which portions of the shafts  56 ,  186  extend, with non-circular portions or surfaces that prevent relative rotation of the coupler  200  relative to either shaft  56 ,  186 , or the coupler may include projections that are received in sockets or cavities in the shafts  56 ,  186  or some combination of such features. In the example shown, the first drive feature  202  includes two oppositely facing flat surfaces  205  ( FIG.  9   ) and the drive shaft end  188  is complementarily shaped, and the second drive feature  204  includes one flat surface  206  ( FIG.  8   ), is generally D-shaped and the drive shaft  186  is complementarily shaped. Of course, other noncircular shapes and arrangements may be used as desired. The drive features  202 ,  204  could also be circular, if desired, and also if desired, an adhesive, set screw or other connection may be provided between the shafts  56 ,  186  and the coupler  200  to provide the desired co-rotation. As described above, the coupler  200  may be formed from an at least somewhat flexible material to, for example, damp impulse forces and vibrations, and is also resilient so that the desired or commanded rotation of the valve shaft  56  ultimately occurs. 
     The coupler  200  may include a cavity  207  in which the magnet  192  is received, and the magnet  192  and cavity  207  may have complementary anti-rotation features  209 ,  211  that inhibit or prevent rotation of the magnet  192  relative to the coupler  200 . The anti-rotation features  209 ,  211  may include engaged flat surfaces (e.g. a surface that defines the cavity and an exterior surface of the magnet) or other complementary non-circular geometric features, and/or an adhesive or other connector may be used between the magnet  192  and coupler  200 . Thus, the rotational position of the magnet  192  can more accurately represent the rotational position of the coupler  200  and valve shaft  56 . To facilitate proper assembly and/or calibration of the sensor assembly, or for other reasons, a marking  213  or some indicia may be provided on the magnet  192  to indicate a polarity of that portion of the magnet. In the example shown, the magnet  192  can be received in the cavity  207  in two different orientations (e.g. it may be flipped over) and the indicia may help to ensure that the magnet  192  is installed in the desired orientation. 
     In at least some implementations, as shown in  FIG.  7   , one of the drive shaft  186  or valve shaft  56  extends through a void  208  in the circuit board  166 . This enables the sensor element  192  to be located close to the sensor  194  (e.g. less than 8 mm away) to improve position sensing. In the example shown, a motor  210  of the actuator  60  is on a first side of the circuit board  166  and the coupler  200  is on the opposite, second side of the circuit board  166 , and the drive shaft  186  extends through the void  208  in the circuit board, and an aligned void/boss  212  in the sub-housing  164  which may support and guide rotation of the drive shaft  186 . The valve shaft  56  could instead extend through the void  208  in the circuit board  166 , and the coupler  200  and drive shaft  186  could be located on the first side of the circuit board  166 , which is the side opposite to the throttle bores  20 . 
     In the throttle body shown in  FIG.  10   , a passage  220  is provided that communicates at a first end  222  with a throttle bore  20 . The passage also communicates with a pressure sensor  224 , which is shown as being mounted to the circuit board  166 . Thus, the passage  220  in this implementation extends through the sub-housing  164  to a second end that is open to an area in which the pressure sensor  224  is located. The pressure in the throttle bore  20  in the area of the first end  222  of the passage  220  is communicated with the pressure sensor  224  which provides an output signal that corresponds to the sensed pressure. 
     In at least some implementations, the first end  222  of the passage  220  is arranged near an area in which fuel is injected into the throttle bore  20 . The throttle bore has an axis  226 . IN at least some implementations, an imaginary plane  228  that is perpendicular to the axis  226 , and which extends through the center of the injection port  230  through which fuel enters the throttle bore  20 , intersects or is within 1-inch of the first end  222  of the passage  220 . In the example shown, fuel enters the throttle bore  20  through a port  230  that is formed in a boost venturi  36  located within the throttle bore  20 , as described above, with reference to, for example,  FIG.  4   . Of course, other arrangements may be used. Thus, the output from the pressure sensor  224  is indicative of the pressure in the area of the fuel injection port  230  and is thus indicative of the pressure that acts on fuel at the injection port  230 . In at least some implementations, the timing of the fuel injection may be coordinated or chosen as a function of this sensed pressure, to control fuel flow into the throttle bore  20 . Also, upon energization of the controller  162 , which may occur before the engine is started, the controller  162  can interrogate or receive a signal from the pressure sensor  224  for a reference value of barometric pressure, which may be used to determine an initial ignition timing and/or fuel/air mixture calibration or for other engine control purposes. 
     In the graph shown in  FIG.  11   , a first waveform  240  relates to a voltage induced in a coil of an engine ignition system, such as by a magnet mounted to an engine flywheel. A second waveform  242  relates to a fuel metering valve or fuel injector control signal, that is, the waveform shows when a voltage is applied to open the fuel injector(s) as described above. And a third waveform  244  shows the pressure sensed by the sensor  224 . A little more than one engine revolution is shown in this graph, as can be seen by the two instances in the ignition coil/sensor waveform  240  wherein a flywheel magnet induced voltage in the ignition system coil. Within this engine revolution, the pressure at sensor  224  decreased between points  246  and  248  as an engine intake valve opened and a downward-travelling piston creates a negative relative pressure in the engine intake. There generally is no negative or positive relative pressure signal when the intake valve is closed. The time when the negative pressure occurs at the injection location, which may or may not occur within the throttle body (that is the injector could be located outside of the throttle body and the pressure may be taken in the area of the injector outlet, as noted above), is the optimum time for a low-pressure injection system to open the injector and control the injection of fuel as a greater flow rate of fuel may be achieved with this negative engine pressure signal which aids fuel flow from the port  230 . 
     In general, the greater the magnitude of the negative relative pressure, the more fuel will flow from the injector for a given amount of time in which the injector is open and permits fuel flow. Thus, the start of the negative pressure, generally indicated at  246 , to the end of the negative pressure, generally indicated at  248 , may be the optimum time period within which to inject fuel, at least where the pressure is measured at or very near the location of injection. Of course, in at least some situations, fuel may be provided only during a portion of the negative pressure signal, and improved control of the fuel injection event may be enabled by timing the injection event to a desired portion of the negative pressure signal which does not necessarily include the maximum relative pressure. 
     Thus, the injection timing can be controlled as a function of the instantaneous pressure at or near the injection outlet or port. The pressure may be continuously measured or sensed, or sampled at fixed rate, as desired. Further, the injection event may be tied to one or more pressure thresholds so that a known flow rate of fuel can be achieved and the efficiency of the fuel injection events can be improved. In the example shown in  FIG.  11   , a signal indicated at  250  is provided from a controller to the fuel injector (or fuel metering valve which may considered to be a fuel injector) to open a valve of the fuel injector and cause fuel to flow when the pressure signal exceeds a threshold relative pressure. Thus, until the pressure signal exceeds the threshold, the injector valve is closed and fuel is not delivered from the injector. The injection strategies described herein may improve fuel injection efficiency, in, but not limited to, situations in which a sensed or calculated crankshaft angular position may not be as accurate as desired, such as during engine acceleration or deceleration. Additionally, any changes in the pressure signal due to degradation of the engine system (pumping efficiency due to wear, air filter being plugged, etc) can be compensated for to continue to inject fuel at optimum relative negative pressure, despite the change in shape, magnitude, or timing of the relative negative pressure pulse (which calibration based on engine crankshaft angular displacement/position cannot instantaneously compensate for). 
     The forms of the invention herein disclosed constitute presently preferred embodiments and many other forms and embodiments are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention. 
     As used in this specification and claims, the terms “for example,” “for instance,” “e.g.,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.