Abstract:
A bi-fuel and dual-fuel engine variable pressure fuel system is presented facilitating individual or simultaneous use of liquid and gaseous fuels including natural gas and gasoline, through employment of a variable output pressure gaseous fuel regulator incorporating an attached hydraulic amplifying structure communicating with a relatively low pressure hydraulic servo circuit that may in turn communicate with a variable pressure automotive liquid fuel system to facilitate relatively high pressure gaseous fuel injection.

Description:
TECHNICAL FIELD AND BACKGROUND 
     This invention is applicable to bi-fuel and dual-fuel internal combustion engines that utilize gaseous and liquid fuels either simultaneously or individually. It is aimed at dealing with the limited response characteristics of high pressure solenoid type gaseous fuel injectors when activated by present 12 volt petrol (gasoline) engine control units (ECU&#39;s,) where the injectors are synchronized to the speed, or RPM of the engine. To compensate for the larger volumes of gaseous fuel required to deliver the equivalent energy of gasoline, gaseous (gas) injectors operate under higher pressures, with larger, heavier moving valve components as compared to petrol type injectors. This can result in minimum open/close cycle periods twice as long as those of their petrol counterparts. At low speed idle power with a static, high fuel rail pressure necessary for maximum power, the gas injector can fail to fully open in response to short ECU commanded voltage pulse widths. Minimum open cycle periods for solenoid gas injectors are typically around 4 milliseconds. At idle with a static gas fuel rail pressure that can meet the engines full operating power range, the ECU may command an injector open pulse width far less than 4 milliseconds. The injector may thus fail to respond fast enough to these short open signals, resulting in inconsistent fuel delivery, roughness and excessive emissions. 
     Where fuel injectors are typically synchronized by the ECU to cycle with engine RPM, low engine speeds allow more time for the injector to more accurately meter fuel. By lowering fuel supply pressure at idle speeds the injector can remain open longer, allowing more accurate response to the ECU. However when fuel demand increases with speed and the available injector cycle time decreases, a variably higher pressure fuel rail supply then becomes necessary to avoid fuel starvation. 
     SUMMARY 
     The operating limitations of solenoid actuated gas injector valves are overcome here by proportionately raising and lowering fuel injector rail pressure with engine speed and load. Longer “open” voltage pulse width commands at low speeds are made possible with lower fuel supply pressures, allowing the injector to deliver small gas quantities per cycle with greater accuracy, while high fuel rail supply pressures are available at maximum speed and load. A means of controlling fuel flow through statically open gaseous injectors is also made possible through a precisely controlled variable pressure injector rail supply responsive to engine speed and load. 
     The present invention eliminates the typical load spring that acts upon the pressure sensing element (usually a piston or flexible diaphragm attached to a flow control valve,) within a gas regulator to control output pressure, and replaces it with a variable hydraulic pressure amplifying actuator attached to the regulator body, henceforth referred to here as a “hydraulic amp.” The regulator represented here is of the piston sensing type, similar to the CNG (compressed natural gas) regulators presently made by Tescom, of Elk River, Minn. 
     Within the hydraulic amp of the present invention is a hydraulic pressure sensing piston and contiguous pushrod structure referred to henceforth as a “piston-pushrod.” This spool-like structure has a relatively large pressure sensing piston crown surface at the “piston” end, and a smaller surface at the opposite “pushrod” end that abuts the gas regulator&#39;s pressure sensing element on a seating area normally acted upon by the load spring. This piston-pushrod structure reciprocates within the hydraulic amp in response to pressure exerted on its&#39; piston crown by a variable pressure hydraulic servo circuit, which in the illustrated embodiment is comprised of a communicating gasoline or diesel liquid fuel supply system having an electric or engine driven fuel or “lift” pump. Alternately, other sources of hydraulic servo pressure may be derived from vehicle systems such as a windshield washer fluid system that uses a methanol/water solution. One or more variable flow controlling devices within the hydraulic servo circuit may include a variable flow control valve and a typical fuel pressure regulator, in order to variably restrict flow and create variable backpressure that is sensed by the communicating hydraulic amp. An engine control unit (ECU) or separate computers may control servo pressure by sending variable voltages to the fuel pump and variable flow servo control devices in response to engine fuel demand parameters related to speed and load such as manifold absolute pressure (MAP), RPM, and operator power demand. Variable backpressure in the present embodiment caused by a fuel pump working against the servo flow control devices results in a variable servo pressure of approximately 12 to 40 psig. Servo pressure acting within the hydraulic amp acting upon the piston-pushrod transmits an amplified control force to the contacting pressure sensing element (piston) within the gas regulator. The flow control valve within the gas regulator attached to the sensing piston variably reciprocates upon a closeable orifice positioned between the regulator&#39;s gas inflow and outflow conduits and meters outflowing gas pressure in response to control pressure exerted by the piston-pushrod. The high pressure gaseous fuel supply is thereby reduced to a variably lower injector rail pressure. Gas regulator outflow pressure is multiplied over that of the servo pressure by a factor determined by the difference in diameters between the hydraulic pressure sensing crown of the piston-pushrod within the amp, and the smaller abutting gas pressure sensing piston within the regulator. 
     Throttle by Wire 
     Because typical air inlet throttle mechanisms respond to transient power commands faster than can variable output pressure gas regulators due to gas compressibility, air inlet throttle mechanisms can thus track and respond to servo commanded gas regulator output pressure changes faster than can variable output pressure gas regulators track and respond to commanded air throttle induced MAP pressure changes. In one embodiment of the present invention especially applicable to engines operating within narrow air/fuel ratio limits, a “throttle by wire” system having an intake throttle valve operable in response to variable gas injector rail pressure may be employed to counter compressibility induced rail pressure lag during rapid power changes. 
     More precise air/fuel ratio control may therefore be obtained in the present embodiment through employment of a pneumatic or electrically actuated throttle mechanism that responds to operator commanded variable pressure within the gas injector rail. Power output in the present invention thus may be controlled by a “gas pedal” that actuates the variable hydraulic flow and pressure controlling components within the servo circuit such as a variable flow hydraulic valve, that in turn control amplified gas regulator output and injector rail pressure. Variable gas rail pressure can then operate a pneumatically actuated throttle valve, or be sensed by a throttle controlling ECU which may then in turn proportionately actuate a motorized throttle valve. 
     Injector/Cylinder Deactivation 
     In multi injector configurations of the present invention, transient fuel rail pressure imbalances resulting from rapid power changes may be countered by employing a ECU injector or injector/cylinder cut off circuit. This circuit may contain a map that defines an injector operating envelope determined by RPM, fuel rail pressure and minimum pulse width. When fuel rail pressures exceed the injector&#39;s minimum pulse width, such as may occur when the operator rapidly lifts off of a fully depressed gas pedal with maximum fuel rail pressure, the ECU may deactivate one or more injectors (and cylinders,) causing the remaining injectors to operate at higher loads with longer pulse widths. When engine load and intake air flow increase, or fuel rail pressure decreases to points within the injector operating envelope, the idle injectors may then be progressively reactivated allowing continuously optimal injector operation and precise air/fuel ratio control. 
     Advantages 
     Droop and Supply Pressure Effect 
     By eliminating the “load spring” in a typical gas pressure regulator, the present hydraulic amp embodiment serves to eliminate output pressure drop or “droop” that occurs when the pressure exerted by the spring on the sensing element decays as the attached pressure sensing piston opens the flow control valve. Output pressure thus declines as gas flow demand increases with a typical gas regulator governed by a load control spring. 
     The total force required to open a closed, unbalanced gas regulator flow control valve must exceed the force exerted upon the valve head by the upstream tank supply pressure plus the force that the out flowing gas pressure exerts upon the pressure sensing piston. When pressure on the inlet (tank) side of the valve falls with fuel consumption, the total force holding the valve closed decreases. Thus, the total force required to open the valve is reduced as the upstream supply tank pressure falls as fuel is consumed. For a conventional gas regulator with a fixed output controlling load spring, the output pressure to the fuel rail will increase as supply tank pressure decreases. To maintain a constant regulator outflow pressure, the controlling pressure exerted on the load or control side of the regulator sensing piston must be reduced as supply tank pressure decreases. By replacing the common regulator load spring with the present servo pressure actuated hydraulic amp controlled by an ECU having input from an upstream pressure sensor such as a fuel tank quantity gauge, the present invention can maintain consistent outflow pressures independent of falling tank pressure, and eliminate droop associated with a regulator load spring. 
     Expanded Range, Fewer Components, Safety 
     The wide range of controllable gas regulator output pressures (approximately 30 to over 95 psig in this iteration) made possible by the present servo controlled hydraulic amp expands the limited operating bandwidth of solenoid gas injectors. By lowering rail pressure at reduced engine speeds and loads, more accurate metering, lower injector noise and reduced power consumption is attained. Conversely, as RPM increases and the available injector open time per cycle decreases, the present invention increases injector rail pressure with increasing engine speed and fuel demand, increasing fuel flow through injectors that eventually may remain statically open at maximum engine speeds. Employed in a throttle body injection (TBI) configuration, the present variable gas rail pressure invention facilitates the utilization of fewer gas injectors, verses employing a plurality of injectors staged to operate over a wide load and speed range with a constant rail pressure 
     By replacing the regulator load spring in a gas regulator with the present hydraulic servo pressure controlled amp, when the engine and hydraulic servo pump stop, servo pressure bleeds down and residual gas rail pressure acts unopposed against the regulator&#39;s sensing piston to close the regulator flow control valve. Gas flow to the injectors is then blocked, reducing potential gas leakage through the injectors and the need for a shut off valve typically placed in the conduit running between the regulator and the injector rail. 
     A safety advantage over common dome loaded regulators that have a load or servo control fluid applied directly to the regulator pressure sensing element occurs whereby the servo fluid and communicating vehicle fuel system of the present invention are protected from high pressure gas incursion from a damaged gas regulator sensing element by the present hydraulic amp. 
     RELATED PRIOR ART 
     A variable pressure gas rail injector pressure means is described by Willi in U.S. Pat. No. 5,771,857, as applied to direct injection, glow ignited natural gas engines. Here variable gas rail pressure is generated by an electronically modulated diesel injection pump that applies high pressure diesel fuel to the control side of a dome loaded regulator to produce correspondingly high, unamplified variable gas injection near TDC to optimize variable pressure direct injection. 
     Laing and Prichard in Canadian patent CA1203132 describe a duel fuel diesel engine, utilizing variably reduced hydraulic pressure in a servo circuit bled from the diesel injection pump and controlled by a centrifugal governor which variably pressurizes the control or load chamber of a gas regulator with diesel fuel in typical dome load fashion, to provide variable gas fuel pressure to a diesel engine air intake. 
     Bickley in U.S. Pat. No. 7,178,335 describes a spool valve hydraulic pressure regulator with variable output pressure controlled by a hydraulic load chamber augmented by an internal load spring whose compressive force is varied by an abutting moveable piston adjustable by means of a separate hydraulic actuating chamber contiguous with the end of the piston opposite the spring. 
     McMahon and O&#39;Halloran in U.S. Pat. No. 7,922,833 describe an invention utilizing a hydraulic cylinder attached to a gas regulator that contains a piston displaceable against a point on a flexible regulator pressure sensing diaphragm for the purpose of varying the tension within the diaphragm in order to vary the pressure of the outflowing gas flowing into a deburring thermal energy machine (TEM.) Variable regulator outflow pressure is here determined by varying the tension of the flexible diaphragm, as opposed to the present invention, where variable hydraulic servo pressure acting through an amplifying piston-pushrod structure upon a regulator pressure sensing piston is the regulator load controlling element as opposed to variable tension within a regulator sensing diaphragm. 
     Multiple variable pressure regulator control means including pneumatic, hydraulic, mechanical, electric and electro-hydraulic are cited in the ECU controlled variable gas pressure system of King in U.S. Pat. No. 5,367,999. A detailed description is provided describing a variable pressure pneumatic regulator actuator embodiment in this specification, but only general reference is made to other variable hydraulic pressure regulator biasing means in the claims, with no details provided in the specification. 
     Douville, Noble, Baker, Tran and Touchette describe a dual fuel diesel direct injection system in U.S. Pat. No. 6,298,833 having one injector that injects both a gaseous main charge and a diesel fuel pilot ignition charge into the engine cylinder, and where a dome loaded regulator directly senses diesel pilot injector fuel pressure, and regulates the main gaseous fuel charge at an equal or slightly lower output pressure, to maintain a positive seal between the gas and liquid fuels within the injector. 
     Post and Brook in Pub. No. US2006/0213488 A1 describe a variable pressure direct gas injection system that includes a hydraulic dome loaded regulator that contains a spring biased flow control valve where the hydraulic load fluid acts against the bias spring to vary gas injector fuel pressure (in a manner similar to McMahon and O&#39;Halloran.) The hydraulic load fluid may consist of diesel pilot fuel and here is always approximately equal to or higher than the regulator outflow gas pressure to avoid gas leakage into the diesel load control fluid. 
     Ancimer, Batenburg and Thompson in U.S. Pat. No. 7,463,967 present a variable pressure, direct supersonic gas injection control system utilizing a single injector for both the diesel pilot and the main gaseous fuels. This also includes a dome loaded regulator that maintains almost equal pressure within the gas and the liquid portions of the injector to insure an effective seal between the two fluids. 
     Palma in U.S. Pat. No. 6,626,150 and Dokas, Pyle and Yu in U.S. Pat. No. 7,624,720 describe electromagnetically controlled gasoline type regulators. 
     Hashemi in U.S. Pat. No. 7,140,354 reveals a means for depressurizing a gaseous fuel injector supply rail with a pump that pumps excess gas from the fuel rail back upstream into either the gas supply tank or to a point upstream of one of the pressure reducing regulators that feed the fuel rail. This pumping means is controlled by an ECU for the purpose of maintaining rail pressures compatible with the operating characteristics of gaseous fuel injectors. 
     My invention, can be differentiated from prior art by its&#39; ability to safely utilize low pressure, volatile spark ignitable fuels as a hydraulic regulator servo pressure fluid to produce an amplified, high pressure fuel supply from a gas regulator. The present servo amplifying means differs from conventional dome loaded regulators in that the pressurized servo fluid is mechanically isolated and amplified by means of the piston-pushrod structure, which moves to block orifices in the present hydraulic amp communicating with the vehicle fuel system in response to a high pressure leak from the gas regulator. 
     The presently described electronic cylinder cutoff and fuel pressure sensing throttle control means obviate the need for the pump dependent, high pressure fuel rail de-pressurizing means described in Hashemi. 
    
    
     
       DRAWINGS 
         FIG. 1  is a detailed schematic of the present invention employed in a bi or dual-fuel throttle body injector fuel induction system. 
         FIG. 1   a  is a voice coil actuated iteration of the electromagnetic liquid fuel pressure regulator  56  shown in  FIG. 1   
         FIG. 2  is a detailed cross sectional representation of the hydraulic amp of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cross sectional representation of the present invention where gaseous and liquid fuels may be injected into the air inlet of an engine at throttle body  24 . 
     Gaseous fuel tank  2  may hold fuels such as natural gas and hydrogen at pressures currently averaging 3600 psig or higher. Liquid tank  4  may hold fuels such as gasoline, alcohol or diesel. Tank  4  supplies variable output fuel pump  7 , which may be electrically or engine driven. Pump  7  supplies petrol injectors  28  within throttle body  24  through fuel line  5  and fuel rail  30 . Throttle body  24  is represented here with two throttle bores  26  having typical shaft mounted throttle valves  29 . Gaseous injectors  22  are mounted opposite liquid injectors  28  in throttle body  24 . Either a gaseous or a liquid fuel can alternately be injected at throttle body  24  through either gas injectors  22  or liquid (“petrol”) injectors  28  in a “bi-fuel” application of the embodiment. In a “dual-fuel” mode, gaseous and liquid fuels may be injected simultaneously by gas injectors  22  and liquid injectors  28 , such as where alcohol or an alcohol solution may be selectively injected with methane or hydrogen in a supercharged application to avoid detonation or knock. 
     Petrol pressure in rail  30  may be controlled by a typical spring loaded bypass regulator communicating with fuel rail  30 , or by the variable pressure electromagnetic bypass regulator shown here at  56 , connected to rail  30  through pipe  57 . Fuel bypassed through regulator  56  returns to tank  4  from output pipe  59  through contiguous fuel return line  54 . Regulator  56  may be electronically controlled to maintain petrol pressure in rail  30  in a typical throttle body or port fuel injector pressure range of approximately 15 to 75 psig. 
     Fuel tank  2  supplies high pressure gaseous fuel, typically stored at pressures ranging from 200 to over 3600 psig, to piston type gas regulator  10 , through pipe  6 . Pipe  6  contains an electromagnetic shut off valve  8 , and a temperature and pressure sensor  23 . Gas regulator  10  variably reduces storage tank pressure to a range of approximately 40 to 95 psig in the present embodiment to feed gaseous injectors  22  through pipe  18  and rail  20 . Variable output pressure from regulator  10  is produced by means of attached hydraulic amp assembly  32  that controls regulator pressure output in place of an output governing load spring. Amp  32  is variably pressurized by liquid fuel from pump  7  communicating with internal amp pressure sensing chamber  40  through fuel lines  5  and  9 . Amp  32  may have orifice  48  located near the periphery of sensing chamber  40  to allow communication between it and weep line  49 , and may then be rotated to locate orifice  48  uppermost so as to allow trapped air to rise and pass out of chamber  40  through weep line  49 , and into return line  54  and tank  4 . Tank  4  may then be vented in a typical fashion. Line  49  is of a sufficiently small diameter so as to allow variable servo pressure to be maintained in chamber  40 , while still allowing a small venting flow of fluid into return line  54 . 
     Referencing  FIG. 1  and  FIG. 2 , hydraulic fluid pressure transmitted through lines  5  and  9  through orifice  52  to chamber  40  is sensed through diaphragm  42  (here composed of 1/32 inch thick fluorosilicone rubber.) Diaphragm  42  acts to seal pressurized servo fluid within chamber  40  and transmit variable servo pressure to the piston crown  35  of piston-pushrod  34 . Pressure acting upon crown  35  exerts an amplified force through piston-pushrod  34  upon the load sensing surface  61  of regulator pressure sensing piston  16 . An alternative means of sealing chamber may consist of an O-ring (not shown) placed circumferentially between crown  35  of piston-pushrod  34  and the inner adjacent surface of hydraulic amp  32 . Gaseous regulator sensing piston  16  is attached to flow control valve  14 , which is variably closeable upon valve seat  15 . Valve  14  reciprocates upon seat  15  to control the flow of gas from inlet pipe  6  through orifice  21 , into gaseous pressure sensing chamber  19  and out pipe  18 . Variable output pressure from regulator  10  is determined by the reciprocation of valve  14  upon seat  15  in response to the opposing forces acting on attached regulator sensing piston  16  by the outflowing gas pressure in chamber  19  acting on piston surface  60 , and the servo pressure in amp chamber  40  acting through structure  34  upon piston surface  61 . Upstream supply pressure within valve head chamber  27  may act variably against valve  14  when valve  14  is on or near seat  15 , and can thus add a variable closing force to that of the pressure within chamber  19 . The approximate amplification factor of gas regulator output pressure to liquid servo circuit pressure is determined by the ratio of the surface area of crown  35  of structure  34  to the smaller surface area  60  of regulator piston  16 . Hydraulic servo circuit pressure in the present iteration ranges from approximately 12 to 35 psig, resulting in a gas rail pressure of about 40 to 95 psig. 
     Hydraulic Servo Circuit 
     Referencing  FIG. 1 , variable pressure within amp chamber  40  is determined by a hydraulic servo pressure control circuit comprised here of the following communicating fuel lines and variably restrictive components: Fuel pump  7  which feeds fuel line  5  and branching line  9 ; line  43  branching off of line  9  beneath solenoid valve  11  communicating with variable flow control valve  45 ; line  63  fluidly connecting valve  45  with bypass regulator  47 ; and line  53  fluidly connecting regulator  47  to fuel tank return line  54 . Pressure within chamber  40  can be modulated through variable activation of pump  7  and valve  45 , as well as by electromagnetic regulator  56  communicating with fuel lines  5  and  9  through pipe  57  and liquid fuel injector rail  30 . Bypass regulator  47  is located downstream of valve  45  in order to facilitate stable pressure within the servo circuit at minimal fluid flow, and is set to maintain a minimum servo circuit pressure of 12 psig in this embodiment. Variable flow valve  45  may be comprised of a housing containing an orifice variably closeable by a threaded needle or spool valve reciprocating within a threaded bore, or of a rotating barrel valve, all of which may be actuated by an electronic stepper motor. Valve  45  if of a reciprocating spool or needle configuration, may alternately be actuated by a linear motor. 
     Electromagnetic petrol regulator  56  communicating through pipe  57 , rail  30  and fuel lines  5  and  9 , may control hydraulic fuel pressure to both injectors  28 , and selectively to upstream hydraulic amp chamber  40  through solenoid valve  11 . Regulator at  56  variably reciprocates valve head  72  by means of an attached armature  62  actuated by a surrounding coil as depicted, or may alternately actuate valve  72  by means of an attached voice coil moveable within a magnetic field as seen in  FIG. 1   a . A single variable pressure regulator of sufficient dynamic range at  56  can thus obviate the requirement for separate parallel servo circuit components  45  and  47 . 
     Restating the basic control principal of the invention, variable servo pressure within amp pressure chamber  40  may be regulated by varying the speed and output of pump  7  through electric or engine driven means, and/or by varying the flow capacity of variable valve  45 , and/or by electrically modulating the movement of valve  72  within electromagnetic regulator  56 . Backpressure generated by these components is sensed within amp pressure chamber  40  and amplified by virtue of the relatively large diameter of crown  35  of piston-pushrod structure  34 , versus the smaller diameter of regulator sensing piston  16 . Regulator piston  16 , sensing the amplified force of pressure chamber  40  acting through structure  34 , and the opposing force from regulator output chamber  19 , variably reciprocates connected flow control valve  14  upon orifice seat  15  to deliver a servo controlled variable gas pressure supply to injector rail  20 . 
     Bi-Fuel and Dual-Fuel Modes 
     Referencing  FIG. 1 , in petrol fuel only mode solenoid valve  11  within pipe  9  is closed, allowing hydraulic pressure within amp pressure chamber  40  to bleed down through weep line  49  and/or through the communicating, downstream parallel servo circuit components communicating with pipe  43 . Depressurized chamber  40  then allows gas pressure within regulator pressure sensing chamber  19  to move regulator sensing piston  16  and connected flow control valve  14  upward against valve seat  15 , closing off orifice  21  blocking gas flow from pipe  6  through pipe  18  to downstream gas injectors  22 . Injectors  22  may be deactivated by ECU  31 . Petrol injectors  28  then operate with fuel supplied by fuel pump  7  through fuel line  5  and rail  30 , controlled by pressure regulator  56 . 
     In a gaseous fuel only mode, petrol injectors  28  are deactivated by ECU  31  while solenoid valve  11  is energized, opening conduit  9  to allow variable hydraulic pressure to communicate with amp chamber  40  Pressure regulated gas from chamber  19  then flows through pipe  18  and rail  20  to gas injectors  22 , activated by ECU  31 . In a supercharged “dual-fuel” application, gas and liquid fuels may be injected simultaneously within throttle body  24 , as where a heat absorbing fuel such as methanol may be variably utilized with a gaseous fuel to cool the inlet fuel-air mix in order to reduce detonation and add power. This may be accomplished by selectively activating liquid injectors  28  in response to boosted air charge pressures, while gas injectors  22  and solenoid valve  11  remain continuously operative to supply the main gaseous fuel charge. Diesel dual-fuel operation employing a diesel fuel pilot charge injected into the cylinders as an ignition source, with the main gaseous fuel injected into the inlet air at throttle body  24 , can be accomplished by utilizing pump  7  as a lift pump to feed a high pressure diesel fuel injection pump and injectors (not shown) through fuel line  5 , while simultaneously utilizing all of the variable hydraulic servo components of the present embodiment to deliver a variable pressure fuel supply to gas injectors  22 . 
     Throttle by Wire 
     ECU  31  may receive fuel demand signals from sensors (not shown) that measure engine speed, and from sensors within throttle body  24  that measure manifold pressure, inlet air mass flow and temperature. Fuel tank quantity may be determined by ECU  31  from signals received from pressure/temperature sensor  23  within gas pipe  6 . Sensor  23  output can also be used for feed-forward circuitry to compensate for increased regulator output pressure that can occur with declining tank pressure. Sensor  25  located on gas rail  20 , supplies ECU  31  with pressure and temperature signals to control injector operating pulse widths, and to calculate variable supply voltages for pump  7 , valve  45  and electric regulator  56  in order to maintain variable gas pressure in rail  20  for optimal injector performance. 
     ECU  31 , receiving power demand input from an operator controlled “gas pedal” may control engine output by variably controlling gas injector rail pressure through modulation of hydraulic servo components pump  7 , valve  45  and/or electromagnetic regulator  56 . Variable servo pressure thereby produced variably actuates hydraulic amp  32  to produce in an amplified variable gas injector rail pressure from regulator  10 . Pneumatic actuator  33  or a throttle motor powered by ECU  31  then regulates inlet air flow via throttle valves  29  in response to variable fuel pressure to produce an optimum air/fuel ratio. 
     Safety 
     Referencing  FIG. 1  and  FIG. 2 , diaphragm  42  is clamped between the upper  1  and lower  3  halves of hydraulic amp  32 , and primarily serves to seal hydraulic servo pressure within chamber  40 . Annular space  44  surrounding piston-pushrod  34  is vented to a suitable place outside of the vehicle through communicating vent conduit  17 . Vent  17  with appropriate connected piping, serves to direct fuel to a safe area should diaphragm  42  or pressure sensing piston  16  within gas regulator  10  leak. In  FIG. 1 , diaphragm  42  is held against the periphery of piston crown  35  of piston-pushrod  34  by attached retaining ring  41 , represented here in cross section. Should high pressure gas from regulator  10  leak past regulator piston  16  and structure  34  into annular space  44 , excess pressure in space  44  will force structure  34  upward with diaphragm  42  and ring  41  to block orifices  52  and  48 , preventing the ingress of gas into chamber  40  and the communicating vehicle fuel system. This possibility is reduced by the venting function of conduit  17 . 
     Referencing  FIG. 2 , the function of retaining ring  41  may be supplanted by plate  64  which secures diaphragm  42  to crown  35  of piston-pushrod  34  with bolt  68 . Air pockets within chamber  40  can rise and exit through orifice  52 , eliminating the need for orifice  48  and weep line  49  shown in  FIG. 1 . A high pressure leak from regulator  10  into to space  44  will force piston-pushrod  34  upward with diaphragm  42 , causing the top surface  70  of bolt  68  to contact seating surface  50  surrounding orifice  52 , blocking the ingress of high pressure gas into chamber  40  and the communicating vehicle fuel system. In  FIG. 2 , sealing diaphragm  42  and diaphragm retaining plate  64  may be replaced with an O-ring contacting the inner wall of amp  32  positioned within an annular groove machined into the side of crown  35  (not shown), in order to seal hydraulic servo pressure within chamber  40 . Bolt  68  or a convex valve head means (not shown) formed at the apex of crown  35  may block orifice  52  in the event that a high pressure gas leak from regulator  10  forces structure  34  upward against orifice  52 .