Supply assembly for a gaseous-fuel engine

Abstract

A gaseous-fuel supply system for an internal combustion engine comprises a supply rail (12) intended to receive pressurized gaseous fuel, and a plurality of fuel injectors (20) connected to the supply rail. The supply rail (12) comprises a tubular body (12.1) with a chamber (12.2) for the gaseous fuel, and a plurality of outlet connectors (14) defining an outlet passage (15) for the gaseous fuel from the fuel chamber, each injector being connected to a respective outlet connector. An oil doser is mounted on each outlet connector (14) and configured to selectively inject controlled amounts of oil into the outlet passage (15). The oil dosers (31) are supplied from a pressurized oil reservoir (70) of the membrane accumulator type.

Description

[0001] POWER ASSEMBLY FOR A GAS FUEL ENGINE

[0002] Technical field

[0003] The present invention relates to a power assembly for a gaseous fuel engine.

[0004] State of the art

[0005] For automotive applications, hydrogen engines are considered a promising alternative to gasoline or diesel engines since the emissions of a hydrogen engine consist mainly of water. However, the use of "dry" hydrogen, i.e. without additional lubricant, can create a risk of wear on engine system components. Indeed, while in liquid fuel engines, components such as pressure regulators, injectors, etc., benefit from certain lubrication and hydraulic damping effects, this is not the case with gaseous fuel engines. These components are therefore subject to increased wear, which can affect their service life and operational reliability.This lack of lubrication is even more problematic for fuel injectors fitted for direct fuel injection, as they face higher temperatures, leading to excessive wear, mainly at the needle / seat interface of the injector nozzle.

[0006] It has been proposed to integrate a lubrication system that releases a liquid lubricant into the fuel system. However, this lubricant release faces various challenges. Specifically, it is desirable to precisely control the amount of lubricant and avoid excessive lubrication of the injector, which could lead to sticking of the injector's moving components.

[0007] Subject of the invention

[0008] An object of the present invention is to provide improved means for lubricating a fuel injector for a gaseous fuel engine.

[0009] General description of the invention

[0010] The present invention relates to a gaseous fuel supply system for an internal combustion engine, the supply system comprising a fuel rail for receiving pressurized gaseous fuel and a plurality of fuel injectors connected to the fuel rail.

[0011] The fuel rail comprises a tubular body with a chamber for gaseous fuel and a plurality of outlet fittings defining an outlet passage for gaseous fuel from the fuel chamber, each injector being connected to a respective outlet fitting.

[0012] According to the invention, the system comprises a plurality of oil metering devices, one oil metering device being mounted on each outlet connection, and configured to selectively inject controlled quantities of oil into the outlet passage. The oil metering devices are supplied from a pressurized oil reservoir of the diaphragm accumulator type.

[0013] The invention thus proposes a gaseous fuel supply system with integrated lubrication. It will be appreciated that the oil metering devices are mounted directly on the rail, at the connection of each injector (i.e. in the outlet connection). It is therefore possible to introduce oil in a controlled and targeted manner at each fuel injector, into the gaseous fuel flow at the inlet of the gas injector. The lubrication is thus efficient because all the oil emitted by the metering device goes to the injector. Losses that would exist if the lubricant were introduced further upstream, for example in the chamber of the gaseous fuel supply rail, are avoided. In addition, the dose of lubricant arriving at each fuel injector is known, since it is delivered locally at the fuel injector.

[0014] The use of a diaphragm accumulator oil reservoir facilitates the implementation of the lubrication circuit, since a pressurized volume of lubricant is permanently available - without the need for a pump or hydraulic recycling circuit. Such diaphragm accumulator oil reservoirs offer several advantages, including rapid response, long service life, low maintenance and high reliability, making them an ideal component for a mobile application.

[0015] This also allows for a simplified design of the oil metering devices. Preferably, the oil metering devices incorporate an electrically controlled oil relief valve. In particular, the oil metering devices can be designed as gasoline injectors. A gasoline injector typically comprises an injection nozzle with at least one orifice controlled by a movable shutter (needle) controlled by an electromechanical actuator, e.g., solenoid-operated. A magnetic armature is mechanically coupled (e.g., by form-fitting, welding, brazing, and / or press-fitting) to the movable shutter; the latter is therefore directly controlled by the solenoid. The injection nozzle allows a controlled jet of oil to be emitted, and thus ensures selective and precise distribution of lubricant in the fuel system.

[0016] In this application, the term oil designates a lubricating liquid suitable for reducing friction and wear between moving parts, particularly at the fuel injectors. Any type of oil suitable for the application may be used, taking into account the type of fuel, the design of the fuel injector, and the operating conditions (in particular ambient temperature). In particular, an engine oil, for example type 5W30 or 0W30, may be used. Hereinafter, the terms oil and lubricant are used as synonyms.

[0017] Fuel injectors are adapted to inject gaseous fuel into the engine. This can be any type of injector suitable for injecting gaseous fuel. Depending on the applications, the fuel injectors can be designed for direct injection of the fuel, so that the fuel injector is adapted for direct injection of the fuel into a combustion chamber (cylinder) of the respective engine. However, the fuel injector could also be configured for indirect injection (injection into the intake manifold or intake tract). Fuel injectors for gaseous fuel, in particular for fuel comprising hydrogen and / or consisting of hydrogen, are known in the prior art and the details of the fuel injector are not essential in the context of the invention.It is understood that the number of fuel injectors in the fuel system may correspond to the number of cylinders in the engine, but there may also be a plurality of fuel injectors for a single cylinder. Preferably, all the fuel injectors are identical. In all cases, one oil metering device is provided per fuel injector.

[0018] To minimize oil loss, the fuel injectors are advantageously connected directly to the gaseous fuel rail. In other variants, they can be connected indirectly to the fuel rail by a tube.

[0019] The present invention was developed in the context of hydrogen-powered combustion engines, but also works with other gaseous fuels such as, for example, natural gas (CNG), biogas, etc.

[0020] Alternatively, the oil meters are connected to an oil supply rail, which is connected to the pressurized oil reservoir.

[0021] According to variants, the pressurized oil tank comprises a single membrane accumulator. Depending on the applications, the single membrane accumulator has a volume of the order of 0.5 to 3 L. In addition, it is advantageously designed to operate at a pressure higher than the operating pressure of the gaseous fuel rail, in particular at pressures between 45 and 250 bar.

[0022] According to variants, the oil metering device is configured to emit an oil jet in a first axial direction, the oil metering device being mounted in the outlet connection such that said first axis meets a gaseous fuel inlet opening of the injector.

[0023] The gaseous fuel injector extends in a second axial direction. Depending on the embodiment, the oil metering device may be installed such that the first axial direction is parallel to the axis of the fuel injector (second axial direction), or inclined (oblique) relative to the axis of the fuel injector.

[0024] In particular, the oil metering device may be arranged such that the first axial direction is substantially coaxial with the second axial direction.

[0025] According to variants, the oil metering device comprises an injection nozzle with at least one orifice controlled by a movable shutter controlled by an electromechanical actuator, preferably a solenoid.

[0026] According to variants, the outlet connection comprises an oil metering coupling channel opening into the outlet passage and provided with a sealing seat; and an outlet orifice at the end of the outlet passage surrounded by a sealing seat.

[0027] According to variants, the fuel injectors are directly coupled to their respective outlet connection. According to variants, the system comprises a pressure sensor and a temperature sensor arranged to measure the temperature and pressure of oil supplied to the injectors, in particular integrated in an oil supply line connecting the oil reservoir to the oil metering devices.

[0028] According to another aspect, the invention relates to an internal combustion engine comprising a gaseous fuel supply system according to the invention. In such an engine, the fuel rail is preferably supplied with pressurized gas from a gas tank by means of a gas supply line provided with a pressure regulator, the gas tank comprising one or more pressurized gas containers.

[0029] Brief description of the drawings

[0030] Other features and characteristics of the invention will emerge from the detailed description of some advantageous embodiments presented below, by way of illustration, with reference to the appended drawings. These show:

[0031] Fig. 1: is a schematic view of an embodiment of the gaseous fuel supply system according to the invention;

[0032] Fig. 2: is a partial view of the system of Fig. 1, in which the oil metering device, the rail and the feed rail are shown in section; and

[0033] Fig. 3: is a schematic diagram of the membrane accumulator.

[0034] Description of a favorite performance

[0035] A gaseous fuel supply system 10 for an internal combustion engine 60 (of the spark-ignition type) is shown schematically in FIG. 1. The supply system 10 is adapted to supply a gaseous fuel, in this case hydrogen, to the engine 60 operating with this gaseous fuel. Hereinafter the gaseous fuel is simply referred to as "gas". The engine 60 comprises a plurality of cylinders (not shown) with which respective gaseous fuel injectors 20 are associated. In the variant, the engine has four cylinders, and there are therefore four injectors. The injectors 20 may be conventional gaseous fuel injectors, for example of the type described in WO 2023 / 052263. The design being known, it will be described briefly. Typically, the injector 20 comprises a body 20.1 of elongated shape (along a Y axis), generally symmetrical and cylindrical, defining an internal passage for the gas which flows from a proximal end P to a distal end D. A nozzle 20.2 is arranged at the distal end of the body 20.1 and is configured to inject / discharge the gas into the combustion chamber. For this purpose, a gas outlet orifice is surrounded by a sealing seat, which is controlled by an axially movable needle, controlled by an actuator. In this type of injector, the needle typically opens outwards, when the actuator is activated. The actuator can be of the electromechanical type (solenoid, or others). In the case of a solenoid actuator, the latter cooperates with a magnetic armature fixed to the movable needle. When the solenoid is energized, the armature is attracted in the opening direction, driving the needle which clears the outlet orifice, allowing gas discharge through nozzle 20.2.When the magnetic field is switched off, the needle is returned to the closed position by a spring. The sign 23 indicates the gas inlet port of the injector 20.

[0036] Each gas injector 20 is connected to a supply rail 12, itself supplied with pressurized gas from a gas tank 40 via a gas supply line 42. The tank 40 generally comprises one or more containers (not shown) containing the gaseous fuel, with filling pressures which may be of the order of 350 to 700 bar. The tank 40 may also comprise a mechanical pressure regulator (not shown), in order to deliver gas into the line 42 at a predetermined pressure, e.g. of the order of 50 bar, and a shut-off valve (not shown) to isolate the tank 40 from the rest of the supply system 10. The reference signs 44 and 46 designate respectively, mounted in series in the line 42, a shut-off valve and an electronic pressure regulator.The electronic pressure regulator 46 makes it possible to regulate the downstream gas pressure (therefore in the rail 12) within a predetermined pressure range, for example between 5 and 40 bar. The shut-off valve 44 and the electronic pressure regulator 46 can be incorporated in the same housing 48 called HRM (for Hydrogen Regulation Module). Other components may be provided on the line 42, for example a filter, a purge valve, and / or a relief valve, possibly incorporated in the housing 48. Said fuel rail 12 comprises, in a conventional manner, a tubular body 12.1, for example made of steel / stainless steel, forming a chamber 12.2 for the gaseous fuel extending along the longitudinal axis 12.3 of the body 12.1, as well as a plurality of outlet fittings 14. Each outlet fitting 14 defines an outlet passage 15 for the gas from the chamber 12.2, which terminates in an outlet orifice 17 (see Fig. 2).The outlet passage 15 therefore comprises a portion transverse to the chamber 12.2. The outlet connections 14 are integral with the supply ramp 12. They may be integral with the ramp 12, or they may be added parts which are fixed in a sealed manner to the ramp 12, for example by welding or brazing.

[0037] It will be noted that the outlet fittings 14 are here configured for direct coupling to the gas injectors 20. That is to say that each outlet fitting 14 comprises, at the end of the outlet passage, a coupling section 18 configured to receive an inlet portion of the gas injector. The coupling section 18 terminates in the outlet orifice 17. This is visible in Fig. 2. The coupling section 18 may have a cylindrical and / or conical section, in order to define an annular sealing surface upstream of the outlet orifice 17, which cooperates with a sealing means of the injector, for example an O-ring 9. In the variant, the outlet passage 15 extends radially relative to the chamber 12.1 and the coupling section 18 of the outlet passage 15 extends transversely to this radial direction.

[0038] Furthermore, the supply system 10 comprises an oil metering device 31 mounted on each outlet connection 14, and configured to selectively inject controlled quantities of oil into the outlet passage 15. The oil metering devices 31 are supplied from a pressurized oil reservoir 70 of the membrane accumulator type. There is therefore one oil metering device per gas injector 20 (here 4 in number), allowing targeted (selective and individualized) metering of lubricant into the gas injectors 20.

[0039] The oil tank contains a volume of liquid oil under pressure, ready to be dispensed. Although the oil is referred to as "liquid", in the present context, it is not excluded that it may include small quantities of solid particles, either as additives or as (undesirable) impurities.

[0040] Advantageously, an oil supply rail 30 is provided between the oil reservoir and the oil metering devices 31. The rail 30 comprises a tubular body 30.1 defining a longitudinally extending chamber 30.2 and a plurality of connectors 30.3 in communication with the rail chamber, is configured to be coupled to the oil metering devices (here direct coupling). In operation, the rail 30 is therefore supplied by the pressurized oil reservoir 70, via a pipe 79, and contains a volume of pressurized oil (at the pressure of the reservoir 70) available for the metering devices 31. Preferably, pressure 84 and temperature 85 sensors are provided to determine the temperature and pressure of the oil, in particular for the purpose of controlling the oil injection. These sensors are here mounted on the pipe 79, but could be installed elsewhere, e.g. on the rail 30.

[0041] The oil dispensers 31 are advantageously configured to emit an oil jet 8 in a predetermined axial direction X, corresponding here to the longitudinal axis of the oil dispenser. The oil jet emitted by the injector generally contains oil droplets, the dimensions of which depend on the design of the dispenser (in particular the nozzle).

[0042] The mounting of the oil metering devices 31 on the fuel rail 12 will be better seen in Fig. 2. Each oil metering device 31 is mounted in the outlet connection 14 so that the X-axis of the metering device 31 meets the inlet opening 23 of the injector 20. As seen, the end of the oil metering device 31 is mounted in a coupling channel 14.1 through the wall of the connection 14, which opens into the outlet passage 15. The mounting is sealed, for example by means of an annular seal (not shown) or other sealing solution on the metering device 31, which cooperates with an annular sealing surface of the channel 14.1. More particularly, the channel 14.1 is aligned with the coupling section 18, so that the X-axis meets the inlet opening 23 of the injector. In the illustrated variant, the X axis is substantially coaxial with the Y axis of the gas injector.

[0043] In other words, channel 14.1 is positioned so as to be "opposite" the inlet opening 23 of the fuel injector 20.

[0044] This configuration advantageously makes it possible to inject directly into the inlet opening 23 the quantity of oil necessary for the lubrication of the gaseous fuel supply system, thus limiting potential oil losses in the outlet passage 15.

[0045] It will be appreciated that the present system can be implemented with conventional and inexpensive components. For example, the oil metering device 31 may typically have an electrically controlled valve design. In the present variant, the oil metering device 31 has the configuration of a gasoline injector. It comprises a tubular body 32 extending along the axis and which defines a passage between an inlet orifice 33 and one (or more) outlet orifices 34 at the opposite end. The end of the body with the outlet orifice is implemented as a nozzle 35. A needle 36, axially movable in the body 32, controls the passage of oil towards the outlet orifice 34. The needle is controlled by an electric actuator, here a solenoid 37.When the solenoid is powered, it generates an electric field which attracts a magnetic armature 38 mechanically coupled to the needle 36: the needle rises from its sealing seat, freeing the passage for the pressurized oil through the outlet orifice(s) 34. When the power is cut off, the magnetic field disappears and the needle 36 is returned to its sealing seat by a spring 39: the metering device is closed.

[0046] Furthermore, the pressurized oil reservoir 70 may be a conventional diaphragm accumulator. One embodiment of the accumulator 70 is shown schematically in FIG. 3. The accumulator typically comprises a body 72, generally made of steel, defining a sealed interior chamber. This chamber is divided by a flexible and resistant elastomeric diaphragm 74, often made of synthetic rubber. The lower portion 76 typically contains the oil intended to lubricate the injectors 20. Above the diaphragm, in the upper portion 77, there is a gas which may be nitrogen or air, and which constantly exerts pressure on the diaphragm and the oil below. This compressed gas pressure (changing according to consumption) keeps the oil under pressure and ready to be quickly released when necessary, via an outlet 78.A tap 80 is arranged in the lower part to close the orifice 78 of the lower chamber; this tap is open when the accumulator 70 is connected to the pipe 79 in the configuration of Fig. 2. A tap 82 is arranged in the upper part, which controls a filling orifice of the upper chamber.

[0047] For application in a 4-cylinder hydrogen engine of a passenger car, the accumulator 70 can be configured to initially contain a volume of 0.25 and 1 L. For more powerful engines equipping medium utility vehicles, an accumulator with a volume of 0.5 to 1.5 L can be fitted. For larger engines (trucks) an accumulator of 1.5 to 3 L (or more) can be provided.

[0048] The gas pressure in the accumulator 70 is intended to be higher than the pressure in the gaseous fuel rail during the operating period. Depending on the applications, the initial pressure in the accumulator 70 may be between 45 and 250 bar.

[0049] The quantity of oil to be introduced per injector is very small. It is estimated that the on-board volume is sufficient to allow nominal lubrication between two service periods while maintaining the appropriate pressure in the oil rail.

[0050] The gasoline injector type design, chosen for the metering device 31, is suitable for injecting this type of quantity. The metering devices 31 are advantageously controlled by a control unit associated with a controller which applies the control signal (current) to the metering device coil to carry out an oil injection event. The control unit, which may be the engine control unit (ECU), preferably uses a correspondence (e.g. table / map) which links the quantity of oil to be injected to the injector actuation time (opening time, called 'pulse width' in gasoline injectors), to the oil pressure and to the oil temperature (determined by the sensors 84, 85).

Claims

Claims 1. A gaseous fuel supply system for an internal combustion engine, the supply system comprising a fuel rail (12) for receiving pressurized gaseous fuel and a plurality of fuel injectors (20) connected to the fuel rail, wherein: the fuel rail (12) comprises a tubular body (21.1) with a chamber (12.2) for the gaseous fuel and a plurality of outlet fittings (14) defining an outlet passage (15) for the gaseous fuel from the fuel chamber, each injector being connected to a respective outlet fitting; characterized by a plurality of oil metering devices (31), one oil metering device being mounted on each outlet fitting (14), and configured to selectively inject controlled amounts of oil into the outlet passage (15); the oil metering devices (31) being supplied from a pressurized oil reservoir (70) of the membrane accumulator type.

2. A supply system according to claim 1, wherein the oil metering devices (31) are connected to an oil supply rail (30), which is connected to the pressurized oil reservoir (70).

3. A fuel system according to claim 1 or 2, wherein the pressurized oil reservoir (70) comprises a single membrane accumulator.

4. A power supply system according to claim 3, wherein the single membrane accumulator has a volume of the order of 0.5 to 3 L.

5. A fuel system according to claim 3 or 4, wherein the single membrane accumulator is designed to operate at a pressure higher than the operating pressure of the gaseous fuel rail (12), in particular at pressures between 45 and 250 bar.

6. A feed system according to any one of the preceding claims, wherein the oil metering device (31) is configured to emit an oil jet in a first axial direction (X), the oil metering device being mounted in the outlet connection (14) such that said first axis meets a gaseous fuel inlet opening (23) of the fuel injector (20).

7. A fuel system according to claim 5, wherein the gaseous fuel injector (20) extends in a second axial direction (Y); and the oil meter (31) is installed such that the first axial direction (X) is parallel to the second axial direction (Y), or inclined relative to the second axial direction.

8. A fuel system according to claim 5, wherein the gaseous fuel injector (20) extends in a second axial direction (Y); and the oil metering device (31) is arranged so that the first axial direction (X) is substantially coaxial with the second axial direction (Y).

9. A feed system according to any one of the preceding claims, wherein the oil metering device (31) comprises an injection nozzle with at least one orifice controlled by a movable shutter controlled by an electromechanical actuator, preferably a solenoid.

10. A feed system according to any preceding claim, wherein the outlet fitting (14) comprises an oil metering coupling channel (14.1) opening into the outlet passage and provided with a sealing seat; and an outlet orifice (17) at the end of the outlet passage surrounded by a sealing seat.

11. A fuel system according to any preceding claim, wherein the fuel injectors are directly coupled to their respective outlet connection.

12. A supply system according to any preceding claim, comprising a pressure sensor and a temperature sensor arranged to measure the temperature and pressure of oil supplied to the injectors, in particular integrated in an oil supply line connecting the oil reservoir to the oil metering devices.

13. Internal combustion engine comprising a gaseous fuel supply system according to one of the preceding claims.

Images