Fuel injector assembly and fuel injection system

A fuel injector assembly is adapted to inject a compressed fuel into a combustion chamber of an internal combustion engine. The compressed fuel is stored in a fuel storage tank at a fuel storage pressure and delivered to the fuel injector assembly through a fuel supply line at a fuel supply pressure. The fuel supply pressure is lower than the fuel storage pressure. The fuel injector assembly includes a fuel injector and an adapter valve. The fuel injector injects the compressed gas fuel. The adapter valve is positioned between the fuel injector and the combustion chamber. The adapter valve allows the compressed gas fuel injected by the fuel injector to be discharged from an outlet of the adapter valve into the combustion chamber in an injection direction while preventing blowback gas entering the outlet from passing through the adapter valve in an ingress direction opposite the injection direction.

FIELD OF THE INVENTION

The present invention is directed to a fuel injection assembly configured to utilize an alternative compressed fuel in direct injection. More particularly, a fuel injector assembly configured to convert a conventional alternative compressed fuel port injector for use in direct injection.

BACKGROUND OF THE INVENTION

Recently, compressed fuels have received increased interest for development as an alternative fuel source for gasoline. One such compressed fuel is compressed natural gas which provides a stable fuel source and provides a cost-effective contribution to cleaner mobility.

Previous automotive uses for compressed natural gas, as an alternative to gasoline, in internal combustion engine have been primarily limited to indirect (port) injection fuel systems in which a port fuel injector injects the compressed natural gas into an air flow intake. In indirect injection, the injected fuel and air from the air intake is drawn into the combustion chamber due to a vacuum caused by the downward stroke of the piston when the intake valve is opened.

However, the advantages in increased fuel efficiency and higher power output of direct injection systems over port injection fuel systems have led to an increased focus on direct injection systems. As such, there has been an increased demand for the use of alternative fuels in direct injection fuel systems to combine the benefits of alternative compressed gas fuels, such as compressed natural gas, with the increased fuel efficiency and higher power output of direct injection systems. In previously known gasoline direct injection engine systems, gasoline is injected at high pressure in the range of 1,600 psi. In direct injection gasoline engines the injection timing is limited during the compression stroke of the piston.

There are disadvantages of direct fuel injection systems. One particular disadvantage of the direct injection fuel systems is the added expense due to the increase in the required resiliency of the injectors. Direct injection fuel injectors are disposed partially within the cylinder which exposes the injectors to the intense heat and pressure of combustion. As such, there is an increase in the cost of direct fuel injectors as compared with indirect fuel injectors.

A limiting factor in utilizing compressed natural gas in a direct injection fuel system is the pressure regulation of the compressed natural gas. In the fuel storage tank, the compressed natural gas is stored at a high pressure to maximize the stored volume of the compressed natural gas and the packaging requirements of the vehicle. The stored high pressure compressed natural gas is first depressurized by a regulator to <300 psi. In order to utilize direct injection, the decreased pressure of the natural gas will once again undergo an increase in pressure. This recompression of the fuel is costly in terms of recompression inefficiency due to the packaging and additional components required to recompress the fuel which can lead to a reduction in engine efficiency. Further, as low pressure compressed natural gas fuel injectors are unable to withstand blowback pressure during the combustion stroke of the engine, when located in the combustion chamber, costly direct injection compressed natural gas injectors would be required to withstand the heat and pressure of combustion.

Thus, there exists a need for a cost effective and simple conversion for utilizing low pressure compressed gas fuels in direct injection.

SUMMARY OF THE INVENTION

The present invention provides a fuel injector assembly and fuel injection system in which a conventional port compressed natural gas injector is adapted to inject compressed natural gas in a direct injection internal combustion engine.

In brief, the fuel injector assembly is adapted to inject a compressed gas fuel into a combustion chamber of an internal combustion engine. The compressed gas fuel is stored in a fuel storage tank at a fuel storage pressure and delivered to the fuel injector assembly through a fuel supply line at a fuel supply pressure. The fuel supply pressure is lower than the fuel storage pressure. The fuel injector assembly includes a fuel injector and an adapter valve.

The fuel injector is connected to the fuel supply line and is configured to inject the compressed gas fuel. The adapter valve is positioned between the fuel injector and the combustion chamber. The adapter valve has an inlet and an outlet. The inlet is adapted to receive a portion of the fuel injector. The outlet is in communication with the combustion chamber. The adapter valve allows the compressed gas fuel injected by the fuel injector to be discharged from the outlet into the combustion chamber in an injection direction while preventing blowback gas entering the outlet from passing through the adapter valve in an ingress direction opposite the injection direction.

The fuel injection system may also include a crank angle sensor that detects a crank angle of a crank shaft of the internal combustion engine. Additionally, an injection timing control unit may be provided. The injection timing unit is programmed to compare the crank angle detected by the crank angle sensor to determine the current stroke of the cylinder in the internal combustion engine. The injection timing control unit is also programmed to control a fuel injector to initiate injection at a beginning of an intake stroke and to inhibit injection after the completion of the intake stroke.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention has utility as a fuel injector assembly operable to convert a conventional low pressure compressed gas fuel injector, designed for indirect injection, for use in a direct fuel injection system. The direct fuel injector assembly includes a fuel injector and an adapter valve configured to adapt the indirect fuel injector for use in the direct injection system.

The adapter valve is positioned between the combustion chamber of the internal combustion chamber and the fuel injector. The adapter valve allows for the fuel injected by the fuel injector to be discharged into the combustion chamber and prevents blowback gas, from the combustion of the injected fuel, from reaching and damaging the fuel injector.

The fuel injection system utilizes the fuel injector and the adapter valve with a crank angle sensor and an injection timing control unit. The injection timing control unit controls the fuel injector to extend the injection period beyond the intake stroke, as the fuel is injected at a low pressure, compared to typical gasoline direct injections systems.

With reference toFIG. 1, a direct fuel injection system using an alternative compressed fuel for an internal combustion engine is generally illustrated at10. The system includes a storage tank12in which the alternative compressed fuel is stored in a compressed state. In the remaining description the alternative compressed fuel will be described as a Compressed Natural Gas (CNG); however, the alternative compressed fuel is not limited only to CNG and illustratively includes Liquefied Natural Gas (LNG), Liquid Petroleum Gas (LPG), Hydrogen (H2), Liquefied Hydrogen gas (LH2) or any other compressed fuel known to those skilled in the art and suggested by this disclosure.

In the illustrated embodiment, the storage tank12stores the CNG at a CNG storage pressure. The CNG storage pressure is within a range of 3,000 psi to 5,000 psi, preferably at 3,600 psi. Although not shown, the storage tank12is provided with a fueling port allowing the storage tank12to be refilled with the CNG.

The direct fuel injection system10includes an internal combustion engine14having a plurality of cylinders each of which includes a direct fuel injector assembly18. The fuel injector assemblies18are attached to fuel rails20and connected to the storage tank12through a fuel supply line22.

A regulator24is provided on the fuel supply line22and disposed between the storage tank12and the fuel rails20. The regulator24regulates the CNG from the high CNG storage pressure to a lower fuel supply pressure. The fuel supply pressure of the CNG after the regulator24is typically less than 500 psi preferably less than 300 psi. The CNG at the fuel supply pressure is supplied to the fuel rails20and direct injected into the internal combustion engine14by the fuel injector assemblies18, which will be described in greater detail below.

As will be described in greater detail below, the direct fuel injection system10includes an electronic control unit (ECU)30which controls the injection timing and amount of the fuel injector assemblies18based on signals from various sensors. The ECU30is connected to the regulator24to control the dispersion of the CNG from the storage tank12. Although not shown, the ECU30is optionally connected to a CNG pump which is provided either upstream or downstream from the regulator24to ensure proper movement and pressure of the CNG along the fuel supply line22.

FIG. 2illustrates a schematic structure of the direct fuel injection system10in which the direct fuel injector assembly18has been applied to the internal combustion engine14. The internal combustion engine14is a four-cycle spark-ignition multiple cylinder (six cylinder) engine; however, the internal combustion engine14is not limited to such a configuration. Only a single cross section of one of the plurality of cylinders has been illustrated as the remaining cylinders have the same structure as the illustrated cylinder.

The internal combustion engine14includes a cylinder block portion40, a cylinder head portion50that is fixed to an upper portion of the cylinder block portion40, an intake system60for introducing gas that is a mixture of air and fuel (i.e., an air-fuel mixture) into the cylinder block portion40, an exhaust system70for discharging gas (i.e., exhaust gas) from the cylinder block portion40to outside of the internal combustion engine14, an accelerator pedal26, and various sensors81to87connected to the electronic control unit (ECU)30.

The cylinder block portion40includes a cylinder41, a piston42, a connecting rod43, and a crankshaft44. The piston42moves in a reciprocating manner inside the cylinder41. The reciprocating movement of the piston42is transmitted to the crankshaft44via the connecting rod43, causing the crankshaft44to rotate. A combustion chamber45is defined by an inner peripheral surface of the cylinder41, an upper surface of the piston42, and a lower surface of the cylinder head portion50. As will be described in greater detail below, the fuel injector assembly18injects the compressed fuel (CNG) into the combustion chamber45.

The cylinder head portion50includes an intake port51, an intake valve52, an intake camshaft53, an exhaust port55that is communicated with the combustion chamber45, an exhaust valve56, an exhaust camshaft57, a spark plug58, and an igniter59. The intake port51is in communication with the combustion chamber45and the intake valve52opens and closes the intake port51. The intake camshaft53drives the intake valve52. The exhaust port55is in communication with the combustion chamber45and the exhaust valve56opens and closes the exhaust port55. The exhaust camshaft57drives the exhaust valve56. The igniter59includes an ignition coil that generates high voltage that is applied to the spark plug58.

The intake system60includes an intake manifold61, an intake pipe62, an air cleaner63, an intake throttle valve64, and a throttle valve actuator64a. The intake manifold61is in communication with each cylinder41via the intake port51described above. The intake pipe62is connected to a uniting portion upstream of the intake manifold61. The air cleaner63is provided on an end portion of the intake pipe62. The intake throttle valve64is capable of changing the opening sectional area of the intake pipe62, and the throttle valve actuator64arotatably drives the intake throttle valve64according to a command signal from the ECU30. The intake port51, the intake manifold61, and the intake pipe62together form an intake passage.

The exhaust system70includes an exhaust manifold71, an exhaust pipe72, and an exhaust gas catalyst73. The exhaust manifold71is in communication with each of the cylinders41via the exhaust port55described above. The exhaust pipe72is connected to a uniting portion downstream of the exhaust manifold71. The exhaust gas catalyst73is provided in the exhaust pipe72. The exhaust port55, the exhaust manifold71, and the exhaust pipe72together form an exhaust passage.

The accelerator pedal26is operated by a driver of a vehicle provided with the internal combustion engine14. The accelerator pedal26inputs an acceleration request and the required torque to the internal combustion engine14.

The direct fuel injection system10is provided with various sensors81to87to maintain control over operation of the internal combustion engine14, such as an intake air amount sensor81, a throttle valve opening amount sensor82, a crank position sensor83, a coolant temperature sensor84, air-fuel ratio sensors85and86, and an accelerator operation amount sensor87.

The crank position sensor83is provided near the crankshaft44. The crank position sensor83is configured to output a first signal indicative of the operation condition of the piston42cycle such as which stroke the cylinder41is currently undergoing. The crankshaft44rotates through two rotations as the cylinder41undergoes the intake, compression, combustion and exhaust strokes. As described in greater detail below, the current stroke of the cylinder41is able to be determined based on the output of the crank position sensor83.

The ECU30includes a CPU31, ROM32in which programs to be executed by the CPU31, as well as constants and tables (maps), have been stored in advance, RAM33in which data is temporarily stored as necessary by the CPU31, back-up RAM34that stores data when a power supply is on and retains the stored data while the power supply is off, and an interface35that includes an AD converter. The CPU31, the ROM32, the RAM33, the back-up RAM34, and the interface35are all connected together by a bus.

The interface35is connected to the various sensors81to87and is configured to transmit the signals output from these sensors to the CPU31. In addition, the interface35is connected to the fuel injector assembly18, the igniter59, and the throttle valve actuator64aand the like. The CPU31is configured to send command signals to the fuel injector assembly18, the igniter59, and the throttle valve actuator64ato control injection timing and ignition of the internal combustion engine14based on the output of the various sensors81to87.

With reference toFIG. 3, the fuel injector assembly18includes a compressed natural gas fuel injector (CNG injector)90and an adaptor valve100. It is appreciated, of course, that CNG injector90and the adaptor valve100are separate elements for connect to form the fuel injector assembly18. As separate elements, the adaptor valve100is optionally utilized with a variety of different CNG injectors90, and allows for quick and easy installation. It is appreciated, of course, that fuel injector assembly18is optionally a one piece unit in which the CNG injector90and the adaptor valve100are formed as a monolithic structure.

The CNG injector90is optionally a conventional low pressure compressed natural gas injector such as a low pressure CNG injector sold under the brand name Delphi Multec® used for indirect injection fuel systems in which the CNG is injected into the intake pipe62upstream of the intake port51. As the CNG injector90is designed for intake (port) injection, injection pressure is within the range of 75 to 150 psi, preferably at 120 psi.

The CNG injector90includes a fuel inlet92that is in communication with the fuel supply line22through the fuel rail20. It is appreciated, of course, that the fuel inlet92of the CNG injector90is directly connected to the fuel supply line22. The CNG injector90further includes an electrical connector94which allows the CNG injector90to be in electrical communication with the ECU30through the interface35. The CNG injector90includes an injector nozzle96through which the CNG injector90discharges the CNG upon control from the ECU30. A seal98is provided around the injector nozzle96. The seal98is optionally a deformable resilient member that, upon insertion into an aperture of corresponding size, provides a secure frictional engagement between the CNG injector90and the aperture.

The adapter valve100includes a housing102, a plug or bullet104, a biasing member106, and an insert108. The housing102is formed as a tiered cylindrical shape having a gas path extending from an inlet110and an outlet112. The housing102includes a nozzle portion114formed as a hollow shaft having the outlet112at a distal end thereof. The nozzle portion114includes a nozzle passage116that extends from the outlet112to a nozzle inlet118, as seen inFIG. 5A-5B.

The nozzle portion114includes a sealing portion in which a seal member120is positioned between two recessed portions122. The seal member120and the recessed portions122are positioned on the nozzle portion114upstream of the outlet112. The seal member120allows for the housing102, specifically the nozzle portion114, to be secured to within an injector aperture that is formed within the cylinder41and extends, at least partially, into the combustion chamber45. The seal member120provides a seal which prevents the ejection of the housing102, and consequently the fuel injector assembly18, from its engagement with the combustion chamber45, specifically, the injector aperture.

The nozzle portion114is provided with a tiered portion including a first tapered portion124that extends the outer diameter of the nozzle portion114to an outer diameter of a second shaft portion126. The outer diameter of the second shaft portion126is larger than the diameter of the nozzle portion114; however, the inner diameter of the nozzle portion114is constant from the outlet112to the nozzle inlet118along the entire nozzle passage116. The second shaft portion126further includes a second tapered portion128in a stepwise manner. The tiered portion of the nozzle portion114allows for the nozzle portion114to fit various configurations of injector apertures of combustion chambers45having various sizes.

The housing102further includes a chamber portion132that defines a hollow chamber that extends from the nozzle inlet118to the inlet110of the housing102. The chamber portion132is formed of a bullet chamber134, an insert chamber136and an injector chamber138. The insert chamber136is positioned between the bullet chamber134and the injector chamber138. The bullet chamber134is positioned between the nozzle inlet118and the insert chamber136and the injector chamber138is positioned between the insert chamber136and the inlet110of the housing102. The injector chamber138, the inset chamber136, the bullet chamber134, and the nozzle passage116provide a pathway from the inlet110to the outlet112.

The bullet chamber134is formed having a generally hollow cylindrical shape. The bullet chamber134is formed having an inner diameter that is the same or less than the inner diameter of the insert chamber136and the inner diameter of the injector chamber138. The bullet chamber134is sized so as to receive the bullet104in a sliding relationship, as will be described in greater detail below.

The insert chamber136is formed having an inner diameter that is the same or greater than the inner diameter of the bullet chamber134. The insert chamber136is provided with internal threads140. The insert chamber136is configured to receive the insert108. The insert108is formed generally as a ring-shaped member.

The insert108includes external threads142that are configured to engage the internal threads140of the insert chamber136to secure the insert108therein. The insert108includes a downstream (bullet) side144, an upstream (injector) side146, and a bore148that extend from the downstream side144to the upstream side146. The bore148is optionally provided having a hexagonal cross-sectional shape, so as to facilitate the engagement of the external threads142of the insert108with the internal threads140of the insert chamber136.

The downstream side144of the insert108is provided with a seat portion150that bounds the bore148to increase the diameter of the bore148adjacent the downstream side144of the insert108. The seat portion150is provided at an angle of generally 45 degrees with the downstream side144of the insert108, as seen inFIG. 4B. It is appreciated, of course, that various angles can be incorporated without deviation from the scope of the invention as will be described in greater below.

The injector chamber138of the chamber portion132is configured to receive at least a portion of the injector nozzle96. The CNG injector90is partially received within the injector chamber138, specifically, the injector nozzle96portion is received within the bore148adjacent the upstream side146of the insert108and the seal98provides a frictional engagement between the inner surface of the injector chamber138and the CNG injector90to retain the CNG injector90within the housing102. It is appreciated, of course, that the engagement of the CNG injector90and the injector chamber138is not limited to the frictional engagement due to the seal98.

The bullet104is formed as a generally cylindrical member having a first end152and an opposite second end154. As will be described in greater detail below, the bullet104is positioned within the bullet chamber134such that the first end152is positioned adjacent the insert108and the second end154is positioned adjacent the nozzle inlet118of the nozzle portion114.

The bullet104is slidably received within the bullet chamber134between an injection position, as seen inFIG. 5B, and a closed position, as seen inFIG. 5A. In order to facilitate the sliding of the bullet104within the bullet chamber134, the bullet is optionally covered in a lubricating film, such as a dry molybdenum disulfide lubricant, to reduce wear and tear on the components of the fuel injector assembly18. However, the lubricant is not limited to such a film and optionally includes a liquid lubricant, oil based lubricant, other dry lubricants, or any other lubricant known to those skilled in the art to reduce friction under the conditions of the fuel injector assembly18. The lubricant further helps to prevent carbon from adhering to the bullet104, and prevents oils and aerosols from clogging the passageways of the bullet104, the inlet110, and the nozzle inlet118of the nozzle portion114.

The first end152of the bullet104is formed having a generally flattened circular shape. It is appreciated, of course, that the first end152is not limited to such a shape and optionally is provided with a bulbous or semi-spherical shape. The first end152has a diameter smaller than the diameter of the seat portion150at the downstream side144of the insert108and larger than the opening formed by the bore148of the insert108.

An engagement portion156surrounds the first end152. The engagement portion156extends radially from the first end152and expands along the diameter bullet104moving from the first end152towards the second end154. The engagement portion156is provided to have a corresponding angle to the seat portion150of the insert108.

A generally cylindrical shoulder158extends between the engagement portion156and a tapered portion160. The shoulder158has a diameter that is larger than the first end152but smaller than the tapered portion160as seen inFIG. 4A. A plurality of passages162extend from the shoulder158, specifically, a junction of the shoulder158and the tapered portion160.

As seen inFIGS. 5A-5B, the second end154of the bullet104is formed as a generally hollow member defining a first cavity164. Specifically, the second end154is formed by an annular wall166to define the first cavity164. A second cavity168is formed adjacent the first cavity164, the second cavity168having a diameter that is smaller than the diameter of the first cavity164. The second cavity168being bound by an annular inner wall170and an end wall172. A stepped wall174bounds the opening of the second cavity168and extends between the annular inner wall170and the annular wall166in between the openings of the plurality of passages162.

The plurality of passages162extend between the exterior of the bullet104and the second cavity168which is in communication with the first cavity164that is open to the second end154. Specifically, the plurality of passages162extend from the junction of the shoulder158and the tapered portion160, to the annular inner wall170to open to the second cavity168. As the second cavity168is open to the first cavity164, which includes the open second end, a bullet bypass path is formed from the plurality of passages162, the first cavity164, the second cavity168, and the second end154. The bullet bypass path allows gas to bypass the bullet104in the direction of arrow F2 inFIG. 5B.

The bullet104is optionally formed with a total of six passages162are formed equally spaced around the first end152, as shown inFIG. 4A; however, the bullet104is not limited to six passages and optionally includes more or less than six passages total. The plurality of passages162are disposed to extend at a predetermined angle α with a longitudinal axis (or an axis perpendicular to the longitudinal axis) of the bullet104. The predetermined angle α extends obliquely with the longitudinal axis of the bullet104, preferably the predetermined angle α extends at a 45° angle to the longitudinal axis of the bullet104; however, various other angles are within the scope of the disclosure.

The biasing member106includes a bullet end176and an opposite housing end178. The bullet end176of the biasing member106is received within the first cavity164and abuts the stepped wall174to bias the bullet104towards the closed position, as best shown inFIG. 5B. The housing end178of the biasing member106abuts an end wall180of the bullet chamber134. The end wall180bounds the nozzle inlet118. As such, the first cavity164is formed to have a diameter larger than the diameter of the biasing member106, so as to receive the biasing member106therein, and the nozzle inlet118is formed to have a diameter that is less than the diameter of the biasing member106to prevent the biasing member106from entering the nozzle path116.

The biasing member106is optionally formed as a coil spring having a generally open interior that allows for the compressed gas fuel, such as CNG, to be passed there-through as will be described in greater detail below.

In order to facilitate a better understanding of the fuel injector assembly18, the operation of the fuel injection assembly18will now be discussed. During engine operation, the ECU30controls the injection timing and injection amount based on the output signals from the various sensors81to87, such as an intake air amount sensor81, a throttle valve opening amount sensor82, a crank position sensor83, a coolant temperature sensor84, air-fuel ratio sensors85and86, and an accelerator operation amount sensor87.

With reference toFIG. 5A, the housing adapter valve100is shown in the closed state prior to injection. The bullet104is in slidable relation within the interior of the bullet chamber134. The insert108is received within the insert chamber136and secured by the engagement of the internal threads140of the insert chamber136and the external threads142of the insert108. The CNG injector90is retained within the injector chamber138due to the engagement of the seal98with the interior walls of the injector chamber138, such that the injector nozzle96is engaged with the bore148of the insert108.

In the closed position, the biasing force of the biasing member106biases the bullet104against the insert108in the direction of arrow F1. Specifically, the engagement portion156of the bullet104engages with the seat portion150of the insert108to form a mechanical seal such that the first end152of the bullet104blocks/closes the bore148of the insert108, thereby, closing off the pathway from the inlet110to the outlet112. As will be described later in greater detail, the engagement of the engagement portion156and the seat portion150allows the first end152to block the bore148to prevent blowback gas resulting from the ignition of the CNG within the combustion chamber45from flowing in an ingress direction of arrows A up the outlet112entering the bore148of insert108. As such, the CNG injector90is prevented from being ejected from the injector chamber138.

At the appropriate timing, the ECU30, based on the output of the various signals, sends a control signal to the CNG injector90to initiate the injection of CNG. Upon injection of the CNG from the CNG injector90, the adapter valve100moves from the closed position (FIG. 5A) to the injection position (FIG. 5B). During injection, the CNG injected by the CNG injector90flows through the bore148in an injection direction of arrow B. As the first end152is blocking the downstream side144of the bore148due to the engagement of the engagement portion156and the seat portion150, the injected CNG, flowing in the direction of arrow B, pushes against the first end152. As the first end152is generally flattened, the force applied by the injected CNG overcomes the biasing force of the biasing member106and the bullet104is moved from the closed position towards the injection position in the direction of arrow F2. The movement of the bullet104in the direction of arrow F2 from the closed position towards the injection position disengages the mechanical seal formed by the engagement of the seat portion150and the engagement portion156. The compressive force needed to overcome the biasing force of the biasing member106is selected so as to be overcome by the force applied by the injected compresses fuel.

The continued force of the injected CNG will force the second end154of the bullet104to abut the end wall180of the bullet chamber134. As the bore148is now unblocked due to the movement of the bullet104in the direction of F2, the injected CNG flows in the injection direction F2, as seen by arrows B, to bypass the first end154and passes through the plurality of passages162to bypass the bullet104. The injected CNG flows through the second cavity168and the first cavity164to enter the nozzle passage116through the nozzle inlet118and exits the outlet112into the combustion chamber45in the injection direction of F2.

Upon competition of injection event, the injected CNG is no longer able to overcome the biasing force of the biasing member106and the biasing member106biases the bullet104from the injection position (FIG. 5B) to the closed position (FIG. 5A).

Concurrently with or subsequent to the injection event, the ECU30controls the igniter59of the spark plug58to ignite the CNG injected in the combustion chamber45. Upon ignition of the injected CNG, the combustion of the CNG causes blowback gas arrows A to enter the outlet112of the housing102. As the blowback gas arrows A flows in the ingress direction of arrow F1 the blowback gas passes through the nozzle path116and enters the bullet chamber134through the nozzle inlet118. However, as the injection has ceased, the bullet104has moved from the injection position to the closed position and the blowback gas arrows A is prevented from entering the bore148due to the engagement of the engagement portion156and the seat portion150that blocks the path from the outlet112to the inlet110. Specifically, although the blowback gas is able to enter the bullet chamber134and pass through the first cavity164and second cavity168of the bullet104to enter the plurality passages162to enter the portion of the bullet chamber134upstream of the bullet104, the biasing force of the biasing member106prevents the blowback gas arrows A from disengaging the bullet104from the insert108.

Specifically, the flattened shape of the first end152that is received within the seat portion150, and the engagement of the engagement portion156with the seat portion150, provides a mechanical seal between the bullet104and the insert108. As such, during combustion stroke of the combustion chamber piston42, blowback gas arrows A which enters through the outlet112is prevented from being applied to the CNG injector90. Specifically, the mechanical seal between the bullet104and the seat portion150prevents blowback gas arrows A from the combustion from damaging the CNG injector90.

Accordingly, the adapter valve100provides a one way gas passage valve which allows injected CNG arrows B to be diffused through the bullet104in an injection direction arrow F1 and enter the combustion chamber45through the outlet112while preventing the blowback gas arrows A due to the combustion from flowing, in an ingress direction arrow F1, to damage the CNG injector90.

As discussed above, an advantage of the fuel injector assembly18and the fuel injection system10, is the ability to use conventional CNG injectors that are typically utilized for intake injection rather than direct injection. As such, the CNG injectors90inject the CNG at an injection pressure that is lower than the fuel supply pressure and the fuel storage pressure.

Injecting the CNG at the fuel injection pressure that is lower than the fuel supply pressure, avoids the necessity to include additional components such as a high pressure pump to re-pressurizing the CNG which has previously been regulated from the CNG storage pressure within the range of 5,000 psi to 3,000 psi down to the supply pressure of less than 500 psi, and then up to a pressure similar to the gasoline injection pressure 1600 psi.

The housing102is formed of a metallic material that is capable of withstanding the heat and pressure of combustion within the combustion chamber45. The bullet104, biasing member106, and insert108are also formed of a suitable material, such as a metallic material, to be able to withstand frequent use, and the contact of the blowback gases arrows A.

As seen inFIGS. 6A and 6B, the outlet112of the nozzle portion114of the housing102at least partially extends into the interior of the combustion chamber45such that the outlet112is disposed within the combustion chamber45. As the CNG injector90is a conventional intake injector which is limited to an injection timing to the intake stroke of the piston, as the opening of the intake valve52in conjunction with the intake stroke of the piston41creates a vacuum that sucks the air from the intake port51in which the CNG was injected into, the duration of the indirect intake injection is limited to the intake stroke. However, as the fuel injector assembly18and the fuel injection system10, is utilizes direct injection, the injection timing can be extended beyond the intake stroke.

The CNG injector90is controlled by the ECU30to inject the compressed natural gas in a wider time period than a normal intake injected system. Specifically, as the fuel injection assembly18is not limited to the intake stroke, the fuel injection assembly18has a wider window to inject the CNG into the combustion chamber45. The injection window includes the intake stroke and the compression stroke.

As shown inFIGS. 6A and 6B, the internal combustion engine14is a four stoke cycle engine that operates in an intake, compression, ignition and exhaust strokes. As the crank shaft extends through two rotations during each complete four stroke cycle, each stoke is divided into 180° segments. At the start of each new cycle the intake stroke begins at 0° and progress to 180° which then begins the compression stroke as the piston42has moved from top dead center to bottom dead center. Upon completion of the intake stroke at the compression stroke starts at 180° at bottom dead center and progress to 270° at top dead center. It is appreciated, of course, that the above description is variable based upon particular engines and engine operating conditions.

As stated above, the indirect intake injection systems are limited to an injection time equal to the intake stroke as that is the only time that the intake valve51is open to allow the fuel injected into the air intake to enter the combustion chamber45.

In the intake stroke, as shown inFIG. 6A, the intake valve51is open and the piston42is moving from a top dead center position towards bottom dead center in the direction of arrow C1. Upon competition of the intake stroke, the piston42moves from the bottom dead center towards the top dead center in the direction of arrow C2, as shown inFIG. 6B.

In order to accurately control the injection timing of the CNG injector, the fuel injection system10is provided with an injection timing control unit36, as seen inFIG. 7. The injection timing control unit36includes a stroke determination unit37and an injection actuation unit38. It is appreciated, of course, that the injection timing control unit36, the stroke determination unit37and the injection actuation unit38are portions of the ECU30and are programmed to operate in the identified manner.

The stroke determination unit37is connected to the crank angle sensor83and receives the output from the crank angle sensor83to determine the current stroke of the cylinders41. The identification of the current stroke of the cylinders41is provided to the injection actuation unit38which outputs an injection signal to the CNG injector90based on the current stroke of the cylinders41. As described in greater detail below, the stroke determination unit37includes a prestored first threshold and a prestored second threshold. The first threshold is a crank angle that corresponds to the initiation of the intake stroke and the second threshold is a crank angle within the compression stroke. As an illustrative example, the first threshold is set at a crank angle of 0° and the second threshold is set within the range of 180° to 360° preferably within the range of 240° to 300°. It is appreciated, of course, that the thresholds are not limited to the examples provided herein.

FIG. 8is a flowchart showing an example of an injection timing control method executed by the ECU30, specifically, the injection timing control unit36.

In step S1, it is determined whether predetermined conditions have been satisfied. The predetermined conditions, relate to the operational state of the engine such as engine speed. When it is determined that the predetermined conditions have not been satisfied (NO in S1), the process proceeds to step S8and the process is terminated.

On the other hand, when it is determined that the predetermined conditions have been satisfied, the process proceeds to step S2. In step S2, the crank angle θ is measured by the crank angle sensor83. The process proceeds to step S3.

In step S3, the crank angle θ as determined by the crank angle sensor83is compared to a first threshold by the stroke determination unit37. The stroke determination unit37includes a prestored first threshold and compares the crank angle θ to the first threshold to determine the current stroke of the cylinder41. Specifically, the first threshold is set such that when the crank angle θ is not equal to the first threshold, the cylinder has not begun the intake stroke for the current cycle or has already performed the intake stroke for the current cycle. When the crank angle θ is equal to the first threshold, the stroke determination unit37determines that the cylinder41is starting the injection stroke.

When it is determined that the crank angle θ is not equal to the first threshold (NO in step S3) the process repeats the determination of step S2and step S3. On the other hand, when it is determined that the crank angle θ is equal to the first threshold (YES in step S3) the process proceeds to step S4.

In step S4, the CNG injector90is controlled to start injection, or continue injection if injection is current being performed, by the injection actuation unit38, as the stroke determination unit37determined that the cylinder41has begun the intake stroke.

The process proceeds to step S5where the current crank angle θ is measured by the crank angle sensor83. The process proceeds to step S6.

In step S6, the crank angle θ as determined by the crank angle sensor83is compared to a second threshold by the stroke determination unit37. The stroke determination unit37includes a prestored second threshold and compares the crank angle θ to the second threshold to determine the current stroke of the cylinder41. Specifically, the second threshold is set such that when the crank angle θ is less than the second threshold, the cylinder41is undergoing the compression stroke for the current cycle. The exact second threshold is set such that once the crank angle θ is greater than the second threshold, the CNG injector90would be incapable of injecting further CNG into the combustion chamber45due to the compression therein.

When it is determined that the crank angle θ is not greater than the second threshold (NO in step S6) the process repeats the determination of step S4and step S5. On the other hand, when it is determined that the crank angle θ is greater than the second threshold (YES in step S6) the process proceeds to step S7.

In step S7, the CNG injector90is controlled to stop injection by the injection actuation unit38, as the stroke determination unit37determined that the cylinder41has finished or almost finished the compression stroke.

The process proceeds to step S8and terminates. It is appreciated, of course, that the above described process is executed for each cylinder41of the internal combustion engine14, or is executed for a single cylinder that is used as a datum for the reaming cylinders, as the time differential between the datum cylinder and the remaining cylinders is known.

Accordingly, the fuel injector assembly18provides a system in which CNG at an injection pressure of less than 300 psi, preferably between the range of 75 to 150 psi, and more preferably at 120 psi can be used effectively in a direct injection of the combustion chamber45.

Specifically, the fuel injection system10and the fuel injector18can be controlled by the ECU30to inject the CNG during the intake stroke and partially through the compression stroke so as to receive additional amounts of CNG within the combustion chamber45. The system would allow for an increase in the injection timing to include the intake stroke and at least a portion of the compression stroke. Therefore, an increased amount of CNG can be injected by a conventional indirect intake CNG injector through application in a direct injection system.

A particular advantage of fuel injector assembly18and the fuel injection system10, is the use of a conventional CNG injector to be used in a direct injection. Accordingly, the conversion of a gasoline direct injection fuel system to a compressed natural gas direct inject fuel injection system can be easily provided with the avoidance of the increased undue number of specific parts. Rather, the fuel injection system10and the fuel injector assembly18can be provided in a simple and cost-reductive manner.

Using low pressure gas and having a mechanism to use this in the combustion chamber of a direct injection engine, will reduce cost and complexity of converting a direct injection engine to a compressed gas fuel. This can be accomplished by blocking the blowback gas from the combustion chamber from reaching the CNG injector, when using low pressure CNG intake injector which injects CNG at an injection pressure between 75 and 150 psi.

Moreover, by providing the insert108and housing102so as to be releasably attachable by corresponding internal threads140and external threads142, respectively, the fuel injector assembly18allows for easy serviceability in which wear on the bullet104and biasing member106can be monitored and easily replaced.

The housing102is formed of a suitable material, such as a metallic material, that is capable of withstanding the heat and pressure of combustion within the combustion chamber.

It is appreciated, of course, that the location of the fuel injector assembly18is not limited to the illustrated embodiment. An alternative example includes the configuration that the fuel injector assembly18includes a one piece unit in which the fuel injector and the adaptor valve are united.

In a further alternative embodiment, the adaptor valve is integrated into the fuel injector such that an outlet of the united fuel injector assembly includes a cap that provides the mechanical seal to prevent the blowback gas from entering the outlet. The cap is provided in a fitting engagement with the outlet in the closed position. An internal valve operates to move the cap from a closed position to an injection position. A shaft is optionally attached to the internal valve and extends through the nozzle portion of the united fuel injector assembly and an opposite end of the shaft is connected to the cap. Movement of the valve by the compressed gas operates to move the shaft to articulate the cap between the closed and injection positions. Upon injection of the compressed fuel, the cap is moved into the injection position in a first direction. In the injection direction the cap is spaced apart from the outlet to allow the compressed gas to be injected into the combustion chamber. Upon completion of the injection process, the cap is moved back into the closed position to prevent blowback gas from the combustion of the injected gas to enter into the outlet of the united fuel injector assembly.

Although the discussion of the present invention has been made in relation to a compressed natural gas, the present invention is not limited to such fuel source. Specifically, the present invention is operable with a plurality of alternative compressed fuels provided in a compressed gaseous or liquid nature.

Having described my invention, other and additional preferred embodiments will become apparent to those of ordinary skill in the art to which it pertains, and without deviation from the scope of the disclosure.