This application claims priority to provisional application No. 60/817,548 filed on Jun. 29, 2006, incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic pressure regulator that can be used for gaseous fuel control on internal combustion engines. More particularly, the present invention related to an electronic pressure regulator that has direct acting electromechanical operation with pressure sensor feedback. 
     2. Prior Art 
     Most of the fuel control in the world for spark ignited engines or engines in general is not electronic fuel injection. In some particular markets, mainly gaseous fuel, for example, LPG and natural gas, there are issues that make fuel injection less desirable. With LPG, it is contamination. The LPG quality in the world, especially in the United States, is not controlled very well and so you have a lot of heavy-end hydrocarbons that has equally plugged up your injectors. 
     A pressure regulator is a device that maintains a desired pressure quantity at a predetermined value or varies according to a predetermined plan. Most fuel pressure regulators for internal combustion engines are purely mechanical devices, have a fixed orifice and work off a diaphragm, piston, or other pressure balance mechanism. Mechanical regulators use a force balance to set orifice size based on spring force verses the difference in pressure between the inlet and outlet sides of the regulator. These regulators cannot make accommodations for variation in engine operating conditions in order to provide an optimum fuel to air mixture for gaseous fuel internal combustion engines. 
     Gaseous fuel means a fuel which is in the gaseous state at standard temperature and pressure. Examples of gaseous fuels used with internal combustion engines are: natural gas (derived from a liquid or compressed gas storage state), and propane/butane gas (derived from liquid petroleum gas storage). 
     Many internal combustion engine applications use direct fuel injection systems instead of pressure regulators and carburetors, but for engines using gaseous fuels there are some significant advantages to using a regulator and carburetor instead of fuel injectors. 
     Contamination. Gaseous fuels, most evident in LPG, have many contaminants that clog the small orifices in fuel injectors and cause failures, reduce component life, or increase maintenance. Regulators and carburetors do not have any small orifices that are affected by contamination from gaseous fuels. 
     Improved fuel and air mixture. Inadequate mixing of the fuel and air prior to combustion can lead to a decrease in fuel efficiency and an increase in engine emissions. In particular, gaseous fuel mixing with air is accomplished much better using a continuous flow device (regulator and carburetor) than with a discrete flow device (fuel injector). 
     In spark ignited engines, fuel can be introduced to the combustion chamber in two different states; vapor and liquid. For either of these states to be injected, the fuel must be at a higher pressure, and it must be free from contaminants that would inhibit the operation of the injector. Because of the contaminants contained in propane, injection can be problematic on propane spark ignited engines. Vapor carburetion provides a good alternative method of propane fuel introduction to the engine. 
     While the carburetor is designed to mix the fuel and air and adjust fuel to match the speed and load of the engine, it has only “ballpark” accuracy. This accuracy is not fine enough to achieve emissions targets. To achieve accurate fueling, the fuel pressure to the carburetor (in reference to the air inlet pressure to the carburetor) can be controlled. This is done in with the Electronic Pressure Regulator of this invention 
     SUMMARY OF THE INVENTION 
     The invention includes a very fast voice coil actuator, in the range of 2-5 millisecond full stroke response with high force, a circuit board located in the enclosure, a pressure sensor sensing pressure internal to the system which in the preferred embodiment is located in the actuator cap assembly but could be located in other locations, a diaphragm, a link plate, a mating ring, and a mechanical pressure regulator. An electronic pressure regulator receives pressure commands from the engine control module in a manner similar to receiving pulse width from an engine control module to an injector and calculates the required new pressure command. A novel feature of the present invention includes the Delta P control and the control of the regulator based on direct feedback of pressure. 
     An Electronic Pressure Regulator (“EPR”), serves two functions, to vaporize the liquid propane and to control the vapor pressure to a mixer, i.e., carburetor. As the propane vaporizes, the EPR monitors and controls the vapor pressure out of the EPR (and to the mixer) in reference to the inlet air pressure to the carburetor, from the engine computer that was calibrated for all speeds and loads. There is a sensor, which may be internal to the EPR, that measures the actual Delta P of the delivered fuel. The EPR will then adjust the fuel pressure to the carburetor so that the actual Delta P matches the Delta P command from the ECM. 
     A benefit of this invention is that this device can operate at lower pressures than a typical fuel injection system. Lower pressure correlates to larger metering orifices which are more tolerant to heavy-end hydrocarbons that are found many fuels. 
     Also, this device typically outputs a continuous flow of fuel to the carburetor which better matches the air flow to the engine through the carburetor. The improved match of fuel and air results in better mixing of the two resulting in a large improvement in emissions when compared to a typical pulse-width modulated fuel injection system. 
     Additional benefits are that it is less expensive of a system than standard fuel injection. Better fuel economy is another benefit. And, the benefit of being able to use standard fuel that is contaminated and have the system actually last a long time, unlike most standard fuel injection systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a fuel control system with an electronic pressure regulator of the current invention. 
         FIG. 2  is another illustration of the electronic pressure regulator according to the exemplary embodiment. 
         FIG. 3  is a cutaway view of the electronic pressure regulator according to the exemplary embodiment. 
         FIG. 4  is an exploded view of the exemplary embodiment 
         FIG. 5  is another exploded view of the exemplary embodiment. 
         FIG. 6  is a longitudinal, assembled view of the exemplary embodiment taken along line x,x′ of  FIG. 3 . 
         FIG. 7  is a diagram of the operation and control of the electronic pressure regulator according to the exemplary embodiment. 
         FIG. 8  is an illustration of a flexure element located in the electronic pressure regulator of the exemplary embodiment. 
         FIG. 9  is a block diagram of the operation of the electronics according to the exemplary embodiment of the invention. 
         FIG. 10  is a software flow diagram for the operation of the microcontroller of the exemplary embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the present invention, an operation diagram of the operation and control of the electronic pressure regulator is set forth in  FIG. 7  illustrating how all of the regulation and vaporization of the fuel is done in one unit with a very fast actuator. A single pressure sensor monitors the unit&#39;s performance by measuring difference between the pressure P Out  at the fuel outlet and the pressure P Air  at the air inlet. 
     In the preferred embodiment, real time pressure control is achieved through the use of a Comparator and Pressure Control Algorithm. The desired pressure P Setpoint  is compared to the actual pressure P Actual  in Comparator. The output of Comparator, P Error  is input into the Pressure Control Algorithm the output of which is Actuator Command . 
     The Pressure Control Algorithm could include any common or advanced control loop transfer function including, but not limited to, series, parallel, ideal, interacting, noninteracting, analog, classical, and Laplace types. The Pressure Control Algorithm utilizes a simple proportional-integral-derivative (PID) algorithm of the following type (exemplified by the following transfer function):
 
Actuator Command   =K   p   P   Error   +∫K   i   P   Error   dt+K   d ( d/dt ) P   Error  
 
Where K p , K d , and K i  are, respectively, the appropriate proportional, derivative, and integral gains.
 
     The pressure sensor senses pressure going to the carburetor. In the present invention, a venture carburetor or variable venturi carburetor can be used. As shown in  FIG. 1  the terms mixer and carburetor can be used interchangeably. 
     The pressure P Actual  being measured by the pressure sensor is the differential between P Out  and the P Air . Although the preferred embodiment utilizes a single differential pressure sensor, an additional embodiment could use two separate pressure sensors and an additional comparator to result in a similar P Actual  output. 
     An additional embodiment utilizes a single pressure sensor that only measures P Out  and not P Air . 
     A linear actuator (for example a connecting rod) responsive to a valve control signal (actuator command) output from the pressure control algorithm is linked to the diaphragm of the regulator. The linear actuator is a voice coil armature capable of operation at frequencies up to 1000 Hz. The position of the diaphragm regulates fuel pressure leaving the electronic pressure regulator and entering the engine. 
     The pressure regulator diaphragm position is controlled by a combination of two factors: 
     (1) Standard mechanical operation force balance: The diaphragm, piston, etc. moves to a force balanced position based on the delta pressure on the two sides of the diaphragm verses the spring force. 
     (2) Additional force (pushing or pulling) on the diaphragm created by the linear voice coil actuator. The additional force provided by the linear actuator is enough force to completely override the standard mechanical force balance, thus giving the EPR full control over fuel pressure leaving the actuator. 
     As shown in  FIG. 7 , an electronic control mechanism can provide the actuator command signal to the linear actuator in accordance with a pressure control algorithm. The direction and magnitude of the force created by the actuator on the diaphragm is determined based on the desired delta pressure between the engine inlet air pressure and the regulator outlet fuel pressure. The desired delta pressure at a given engine operating point is determined by engine development testing and live feedback from sensors monitoring engine performance. Both the air inlet pressure from the mixer and regulator outlet pressure to the fuel line are available for measurement at the EPR which contains an integrated delta pressure sensor. 
     The combination of a rapid response force solenoid (voice coil) and a high bandwidth control signal (delta pressure sensor) allows the EPR to achieve unprecedented response time to engine operating conditions. 
       FIGS. 3 ,  4 ,  5 , and  6  illustrate various views of the electronic pressure regulator (EPR  100 ). EPR  100  is seen to be comprised of three sub-assemblies, actuator cap assembly ( 40 ), voice coil actuator ( 50 ), and mechanical pressure regulator ( 60 ). 
     Functionally, cap assembly ( 40 ) will receive and/or process signals from the ECM, (which may be separate or internal with cap assembly  40 ) and generate a signal to the voice coil actuator ( 50 ), which signal is a actuator command signal, a function of pressure error as measured between the set point pressure generated by the fuel control algorithm and the actual pressure sensed in the P out line. The cap assembly ( 40 ) will generate a signal to the voice coil of voice coil actuator ( 50 ), the signal being responsive to the difference between pressure set point and actual pressure, which signal will control the connecting rod ( 7 ). Connecting rod ( 7 ) is operatively coupled to a diaphragm ( 26 ). Movement of the diaphragm responsive to the voice coil, which is driving connecting rod ( 7 ), will move lever ( 25 ) operating the seat/jet/port assembly ( 103 ) to regulate output pressure, which feeds fuel to the carburetor. 
     The function of mechanical pressure regulator ( 60 ) is to provide fuel at a variable pressure to the outlet port ( 34 ). Outlet port ( 34 ) is operatively connected to the line ( 72 ) feeding fuel to the carburetor ( 200 ) in  FIG. 7 . 
     The function of pressure regulator ( 60 ) is to receive fuel such as LPG from a fuel tank and provide a regulator chamber for that fuel. Turning now to  FIGS. 4 ,  5 , and  6 , it is seen that LPG is received at inlet port ( 32 ) and is controlled through primary diaphragm spring and lever assembly ( 101 ) to provide constant pressure in chambers A and B as seen in  FIG. 6 . As is also seen in  FIG. 6 , regulating gas pressure in Chamber B is controlled through a secondary stage regulator assembly, including lever ( 25 ) and diaphragm ( 26 ). More particularly, the secondary stage assembly controls the seat jet and port assembly between chambers B and C. Chamber C is a regulator chamber regulated by seat jet port assembly ( 103 ) and is in gaseous communication with outlet ( 34 ) which will carry the vaporized fuel through line ( 72 ) to carburetor ( 74 ) (see operation schematic  FIG. 7 ). 
     It is further seen with reference to  FIGS. 3 ,  4 , and  5  that the diaphragm ( 26 ) between chambers C and D is operatively engaged with connecting rod ( 7 ) which, in turn, is controlled by signals received in the voice coil ( 8 ). Moreover, chamber D receives an air pressure from the carburetor ( 200 ), P-Air, as seen in  FIG. 1  and  FIG. 6 . 
     The P-Air from the carburetor found in cavity D and without any activation of the voice activated coil ( 8 ), unit ( 100 ) acts as a standard mechanical pressure regulator controlling the pressure to gas at port ( 34 ). 
     Turning now to a car at idle, it can be seen with reference to the figures that depressing the accelerator will open the throttle control valve, for example, a butterfly valve (BV), located below the carburetor as illustrated in  FIGS. 1 ,  3 ,  4 ,  5  and  7 . When this occurs, a drop in pressure will occur in fuel outlet line ( 72 ) which is connected to outlet port  34  (seed  FIG. 4 ) and, therefore, in chamber C. A drop in pressure in chamber C will allow the seat jet port assembly ( 103 ) to open allowing gas to flow into chamber C and out to the carburetor. 
     Explained in the paragraph above is the mechanical aspects of Applicant&#39;s invention. However, Applicant provides for pressure sensing in the fuel outlet line, preferably said pressure is measured against a pressure set point defined by the fuel control algorithm, which is in turn a function of, in part, throttle position. If there is an error between the pressure sensed in the fuel outline line and the pressure set point, from that error an electronic signal is sent to the voice coil which, operating on the actuator rod can move the diaphragm between chambers C and D. Such movement, responsive to the error “corrects” the pressure in chamber C. Of course, the pressure in chamber C is the pressure of the fuel in the fuel outlet line. Thus, Applicant has provided the ability to fine tune pressure in the EPR fuel outlet line as a function of not only a mechanical pressure differential but an electronic measured preferred pressure set point, which pressure set point is a preferred pressure in the fuel outlet line defined by a number of conditions set forth in the ECM and fuel control algorithm. 
     In a preferred embodiment, pressure sensor ( 66 ) can receive pressure from both the fuel outlet line designated P-Out ( 72 ) in the operation schematic and P-Air ( 68 ). The use of P-Air ( 68 ) provides compensation, for example, for altitude changes in various configurations for changing the configurations of the air inlet (for example, a clogged air cleaner.) 
     Turning out the details of EPR ( 100 ), mechanical pressure regulator (MPR) ( 60 ) is engaged, in ways known to the trade to actuator housing through the use of adapter ( 28 ). As stated above, MPR ( 60 ) is an “off the shelf” mechanical pressure regulator, for example IMPCO “Cobra”. It is adapted through the use of adapter  28  which also acts as a clamp to seal diaphragm ( 28 ) to actuator chamber housing ( 2 ) which defines a chamber. Received inside the chamber is pot core ( 4 ) which is one component of a magnetic structure for actuator. 
     Pot core, Magnet and front plate  4 ,  5 , and  6  provide the magnetic structure, which is provided to interact with voice coil  8 , which comprised wire windings which receive the actuator command current to provide an actuator force. 
     Moveable elements are connecting rod ( 7 ), Coil ( 8 ), and Coil cap ( 9 ) and are engaged together and through a pair of flexure elements ( 3 ). The flexure elements ( 3 ) are in turn is fixedly secured to the housing of the chamber. The moveable elements are suspended substantially within the pot core (a ferrous substance), and the magnetic field generated by changes in the current in the coil respond to the magnetic field of the fixed magnet. The moveable elements are suspended and free to move as set forth below, and this movement responsive to the current changes in the voice coil ( 8 ). 
     Flexures  3  typically a pair serve a number of functions. They are engaged at the perimeter thereof to actuator housing ( 3 ). However, their novel shape allows it to engage the connecting rod, engaging the connecting rod at the center ( 88 ) of the flexures  3  and held at along the longitudinal axis of the diaphragm ( 26 ) while being allowed to move longitudinally freely, responsive to the current and the voice coil. The connecting rod  7  engages the diaphragm at upper link  1 . Upper link  1  is engaged with fasteners through diaphragm  6  to lower link plate  27 . 
     The actuator rod  7  can be suspended along the launch to the axis of the voice coil and be maintained along the longitudinal axis of the voice coil at either end thereof. Connector rod  7  is maintained along this axis, but allowed to flex along that axis responsive to changes of current in the voice coil. Thus the use of flexures provides for an accurate longitude in the location of a connecting rod within the voice coil, and with the end of the voice coil. 
     In about the two flexures, the structure of which may be appreciated with respect to  FIG. 8 , provide rigidity in maintaining the connector rod longitudinally, while allowing the rod, whose nose is engaged with upper link plate  1  to move axially (left and right,  FIG. 4 ), and thus diaphragm  26 . Flexures also provide infinite life of linear actuator cycling due to zero contact or friction between the moving and stationary portions of the actuator. The absence of friction in the suspension element(s) provides for extremely accurate behavior and control of the linear actuator. Another benefit to the use of a flexure(s) is that it provides a means for linear travel with minimal space requirements 
     The operation of the circuit board will now be described with reference to  FIG. 9 . Upon initialization, the ECM  906  sends a signal P-setpoint to the microcontroller  904 . Microcontroller  904 , which can be any commercially available microcontroller with a memory that is capable of receiving machine readable code, i.e. software. Microcontroller  904  provides the “brains” of the invention, and receives pressure signal S from pressure sensor  902 , and outputs as an actuator signal to drive circuit  910 . Drive circuit  910  can be any commercially available driver, e.g. a Motorola H-bridge drive circuit, and provides a signal to the coil  8  of voice coil actuator assembly  50 . While the above description is a generalization of the operation of the circuitry of Applicant&#39;s invention, one skilled in the art will appreciate the different electronic components that may be added to the above without departing from the spirit and scope of the invention 
     The operation of the microcontroller  904  will now be describe with reference to  FIG. 9  and  FIG. 10 . When the regulator of the instant embodiment is powered on, the microcontroller  904  goes into standby, i.e., waits pressure sensors  902  to send a signal indicative of the differential between P-air and P-out, delta-p[step  1008 ]. It should be noted that at this point the electronic pressure regulator of the instant embodiment is functioning as a mechanical regulator. When microcontroller  904  receives the delta-p signal from pressure sensors  902 , microcontroller  904  adds or subtracts from the pressure signal [P-actual], the desired pressure from the ECM, or the P setpoint [step  1006 ]. The result of this calculation is the pressure error, or P-error. Using a PID or similar in step  1004 , he pressure error P error is converted to a value the actuator must move to adjust the pressure P actual to equal the P-setpoint Once this value is calculated, the microcontroller  904  sends an actuator signal to the drive circuit  910 , so that the drive circuit can cause the actuator to move, thereby adjusting P output. 
     While certain features and embodiments of the invention have been described in detail herein, it will be readily understood that the invention encompasses all modifications and enhancements within the scope and spirit of the following claims.
The invention includes a very fast voice coil actuator, in the range of 2-5 millisecond full stroke response with high force, a circuit board located in the enclosure, a pressure sensor sensing pressure internal to the system which in the preferred embodiment is located in the actuator cap assembly but could be located in other locations, a diaphragm, a link plate, a mating ring, and a mechanical pressure regulator. An electronic pressure regulator receives pressure commands from the engine control module in a manner similar to receiving pulse width from an engine control module to an injector and calculates the required new pressure command. A novel feature of the present invention includes the Delta P control and the control of the regulator based on direct feedback of pressure.