High-pressure pump of a direct liquid fuel injection system of a dual-fuel internal combustion engine of a motor vehicle

Abstract

High pressure pump (100) of a direct liquid fuel injection system of a dual-fuel internal combustion engine of a motor vehicle configured to burn a liquid fuel and a gaseous fuel, said high pressure pump (100) comprising a low pressure liquid fuel inlet (102), a high pressure liquid fuel outlet (104), a compression chamber (105), a low pressure chamber (106) and a plunger (108) movable in translation in the pump, the pump (100) further comprising an inlet and outlet valve (111, 112) of the compression chamber (105). The high pressure pump (100) includes a low pressure liquid fuel outlet (120) connected to the low pressure chamber (106) and configured to create a continuous flow of liquid fuel through the inlet valve (111) and the low pressure chamber (106) during operation of the engine with the gaseous fuel.Figure for abstract: Fig 3.

Description

Title of the invention: High-pressure pump for a direct liquid fuel injection system of a dual-fuel internal combustion engine of a motor vehicle

[0001] The present invention relates to the field of internal combustion engines, and more particularly to engines comprising a dual carburetion system including at least one liquid fuel supply system comprising a high pressure pump.

[0002] More particularly, the invention relates to the cooling of a high pressure pump.

[0003] There are different types of fuels used in an internal combustion engine.

[0004] For example, gas fueling is used, for example liquefied petroleum gas, acronym "LPG", or compressed natural gas, acronym "CNG". This type of fueling makes it possible to reduce greenhouse gas emissions, in particular carbon dioxide, as well as pollutant emissions compared to fueling by injection of a liquid fuel, for example pure gasoline, or a mixture of gasoline and ethanol, or even pure ethanol.

[0005] However, gas-type fuel poses certain technical problems, such as a need to be heated for engine starting, and logistical problems since only a few supply points are available to users. Thus, it is necessary to maintain a liquid-based fuel, generally gasoline-based, in order to ensure engine starting and the vehicle autonomy required by users.

[0006] Gas combustion uses spark ignition, so gasoline-based carburation will be preferred as will the associated dual carburation.

[0007] A dual-fuel engine, gas and petrol, or more generally liquid, is required to comply with the same regulatory standards as a single-fuel engine.

[0008] We know the technology called direct gasoline injection, acronym "IDE" which allows fuel to be injected directly into the engine cylinders. Direct injection allows fuel consumption and carbon dioxide emissions to be reduced, as well as pollutant emissions to be reduced.

[0009] Gas carburation is therefore generally associated with direct gasoline injection carburation.

[0010] In a direct liquid fuel injection system, the injection of fuel (gasoline, gasoline and ethanol or even pure ethanol) is necessarily carried out at high pressure to ensure proper fuel atomization into the engine cylinder while maintaining the ability to introduce a sufficient amount of fuel into the cylinder between each combustion. The direct injection gasoline fuel system includes a high-pressure fuel pump. Said pump is generally driven by a component of the internal combustion engine, in particular a camshaft and an intermediate tappet. The pump is therefore fixed to the engine and heats up with it.

[0011] The fuel present inside the high-pressure pump is sensitive to the phenomenon of cavitation due to hydrodynamic conditions, such as the pressure drop during the suction phase in the high-pressure pump. This cavitation leads to deterioration of the high-pressure pump. It is therefore necessary to keep the temperature inside said pump below a threshold value to avoid the formation of cavitation.

[0012] In a single-fuel direct-injection gasoline engine, the direct-injection gasoline system is cooled directly by the circulation of fuel in the high-pressure pump. The flow rate consumed by the engine is in fact high enough to keep the temperature inside the pump at a low value.

[0013] However, in a dual-carburetion engine comprising a gasoline direct injection system and a gas fueling system, there is no fuel flow through the gasoline direct injection system during the gas fueling phases. The high-pressure pump then requires a dedicated cooling system.

[0014] An existing solution consists of integrating a cooling liquid chamber around the high-pressure pump into the engine in order to cool said pump.

[0015] Reference may be made in this regard to document DE 10 2013 206 433 - A1 which describes cooling systems external to the high-pressure pump.

[0016] However, such a solution imposes an additional volume on the engine in a particularly constrained environment between the different elements of the engine and the area empty of mechanical elements inside the vehicle to guarantee the safety of pedestrians in the event of impact with the vehicle.

[0017] It is therefore necessary to provide a solution without increasing the volume used by the high pressure pump, and in particular without increasing the height of the high pressure pump in order to reserve the empty area of ​​any mechanical element.

[0018] There is a need to improve the cooling of the high pressure pump of a direct gasoline injection system without increasing the space around said pump.

[0019] The subject of the invention is a high pressure pump for a direct liquid fuel injection carburetion system of a dual-fuel internal combustion engine. of a motor vehicle configured to burn a liquid fuel and a gaseous fuel, said high-pressure pump comprising a pump body comprising a low-pressure liquid fuel inlet opening, for example, into a fuel intake duct, a high-pressure liquid fuel outlet and a compression chamber connecting the low-pressure liquid fuel inlet to the high-pressure liquid fuel outlet, the high-pressure pump further comprising a low-pressure chamber connected to the low-pressure liquid fuel inlet and a plunger movable in translation in the pump body. Said low-pressure chamber is located axially under the plunger, in particular its piston.

[0020] The pump further comprises a compression chamber inlet valve and a compression chamber outlet valve.

[0021] The high pressure pump includes a low pressure liquid fuel outlet connected to the low pressure chamber and configured to create a continuous flow of liquid fuel through the inlet valve and the low pressure chamber during operation of the engine with the gaseous fuel.

[0022] Thus, there is no longer any stagnation of the liquid fuel in the high-pressure pump. Indeed, there is a circulation of liquid fuel through the high-pressure pump of the direct liquid fuel injection system, even in the absence of flow consumed by the engine. This circulation of liquid fuel passes through the most constrained areas of the high-pressure pump in terms of pressure drop and temperature, which are the inlet valve of the compression chamber and the low-pressure chamber.

[0023] This solution makes it possible to maintain a sufficiently low temperature in the high pressure pump, of the order of 40°C to 50°C, in the absence of fuel consumption by the direct liquid fuel injection system.

[0024] Advantageously, the high pressure pump comprises at least one downstream pressure loss member mounted between the low pressure chamber and the low pressure liquid fuel outlet. This downstream member makes it possible to maintain the supply pressure in the high pressure pump.

[0025] For example, the downstream pressure drop member is configured to be open at a liquid fuel supply pressure.

[0026] According to one embodiment, the downstream pressure drop member is a valve calibrated to a liquid fuel supply pressure.

[0027] According to another embodiment, the downstream pressure drop member is a solenoid valve configured to be continuously controlled as a function of the temperature in said pump.

[0028] Advantageously, the high pressure pump comprises, in addition to the downstream pressure drop member, an upstream pressure drop member mounted upstream of the pressure drop chamber. low pressure and downstream of the inlet valve.

[0029] For example, the upstream pressure loss member is a valve calibrated respectively at a low pressure lower than Ibar.

[0030] Thanks to this combination of these two upstream and downstream members, the high-pressure pump, whose plunger is always driven, ensures by itself the circulation of liquid fuel through the entire low-pressure part of the high-pressure pump, from the inlet to the outlet of low-pressure liquid fuel. This makes it possible to deactivate the low-pressure pump from the fuel tank during the carburetion phases exclusively by a system other than the direct gasoline injection system and thus to reduce energy consumption.

[0031] The low-pressure liquid fuel outlet is, for example, connected to the liquid fuel tank or to an auxiliary injection system, for example in the case of an engine with direct and indirect liquid fuel injection. The liquid fuel leaving the low-pressure outlet is thus reused.

[0032] For example, a pressure drop device is mounted at the outlet of the low pressure liquid fuel outlet.

[0033] For example, the liquid fuel outlets, respectively high pressure and low pressure, are parallel and perpendicular to the liquid fuel inlet.

[0034] According to a second aspect, the invention relates to a dual-fuel internal combustion engine of a motor vehicle configured to burn a liquid fuel and a gaseous fuel comprising a direct liquid fuel injection carburetion system comprising a high-pressure pump as described above and configured to inject the liquid fuel into at least one cylinder of the engine.

[0035] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0036] [Fig-1] represents, in a very schematic manner, an example of general structure of a dual-fuel internal combustion engine comprising a high-pressure pump according to the invention;

[0037] [Fig.2] represents, in a very schematic manner, an example of a high pressure pump for a direct gasoline injection system of an internal combustion engine according to the prior art;

[0038] [Fig.3] represents, in a very schematic manner, an example of a high-pressure pump for a direct gasoline injection system of an internal combustion engine according to an embodiment of the invention; and

[0039] [Fig.4] represents, in a very schematic manner, an example of a high pressure pump for a direct gasoline injection system of an internal combustion engine according to another embodiment of the invention.

[0040] In [Fig.l], the general structure of a dual-fuel internal combustion engine 10, in particular of the spark-ignition type operating on gasoline and gas, of a motor vehicle is shown schematically.

[0041] This architecture is given as an example and does not limit the invention to the sole configuration to which the high pressure pump according to the invention can be applied.

[0042] In the illustrated example, the internal combustion engine 10 comprises, in a non-limiting manner, four cylinders 12 in line, a fresh air intake manifold 14, an exhaust manifold 16 and a turbo-compression system 18.

[0043] The cylinders 12 are supplied with air via the intake manifold 14, or intake distributor, itself supplied by a pipe 20 provided with an air filter 22 and the compressor 18b of the turbocharger 18 of the engine 10.

[0044] In a known manner, the turbocharger 18 essentially comprises a turbine 18a driven by the exhaust gases and a compressor 18b mounted on the same axis or shaft as the turbine 18a and providing compression of the air distributed by the air filter 22, with the aim of increasing the quantity (mass flow rate) of air admitted into the cylinders 12 of the engine 10. The turbine 18a may be of the “variable geometry” type, that is to say that the turbine wheel is equipped with blades with variable inclination in order to modulate the quantity of energy taken from the exhaust gases, and thus the boost pressure.

[0045] As regards the exhaust manifold 16, the latter recovers the exhaust gases resulting from the combustion and evacuates them to the outside, via a gas exhaust duct 24 opening onto the turbine 18a of the turbocharger 18 and via an exhaust line 26 mounted downstream of said turbine 18a.

[0046] In a non-limiting manner, the engine 10 comprises a partial recirculation circuit 28 of the exhaust gases at the intake, also called “EGR” gases, according to the acronym in English terms for Exhaust Gas Recirculation.

[0047] The high-pressure exhaust gas recirculation circuit 28, also called the “HP EGR” circuit, originates at a point on the exhaust line 26, upstream of said turbine 18a, and returns the exhaust gases upstream of the intake manifold 14.

[0048] By way of non-limiting example, the engine 10 comprises a system 30 for depolluting the combustion gases of the engine. The depollution system 30 will not be described further.

[0049] The engine 10 is associated with a direct liquid fuel injection carburetion system comprising, for example, fuel injectors (not referenced) injecting a liquid fuel, such as for example pure gasoline, or a mixture of gasoline and ethanol, directly into each cylinder 12 from a reservoir 40 of liquid fuel.

[0050] The engine 10 is associated with a second carburetion system (not shown) by injection of gas into the cylinders 12 from a tank 50 of gaseous fuel.

[0051] By “gas” we mean liquefied petroleum gas, acronym “LPG”, or compressed natural gas, acronym “CNG”.

[0052] The direct injection liquid fuel (gasoline, gasoline and ethanol or ethanol) carburetion system comprises a high pressure pump (not shown in [Fig.l]) configured to ensure correct spraying of the liquid fuel into the cylinder 12 of the engine 10 while retaining the ability to introduce a sufficient quantity of liquid fuel into the cylinder between each combustion. Said high pressure pump is driven by an element of the internal combustion engine, in particular a camshaft and an intermediate tappet. The pump is therefore fixed to the cylinder head or any other part of the engine.

[0053] A known example of a high pressure pump is illustrated in [Fig.2].

[0054] The pump 100A comprises a substantially cylindrical pump body 101A comprising a low pressure fuel inlet 102A opening into a fuel inlet duct 103A, a high pressure fuel outlet 104A and a compression chamber 105A connecting the fuel inlet duct 103A to the high pressure fuel outlet 104A.

[0055] The pump 100A further comprises a low-pressure chamber 106A connected to the fuel intake duct 103A by an intermediate duct 107A and a plunger 108A movable in translation in the pump body 101A. The plunger 108A comprises a piston movable in translation in a cylindrical housing 109A of the body 101A opening into the compression chamber 105A and an end rod extending axially from the piston towards the outside of the body 100A.

[0056] The pump 100A comprises a plug 110A, fixed relative to the body, in which the rod of the plunger 108A slides.

[0057] The low pressure chamber 106A is located axially below the plunger piston 108A.

[0058] As illustrated, the pump 100A comprises an inlet valve 11 IA of the compression chamber 105A, an outlet valve 112A of the compression chamber 105A and a discharge valve 113A of the high pressure circuit mounted in a conduit 114A connecting the high pressure chamber 105A and the fuel outlet 104A.

[0059] In normal operation of the direct gasoline injection system, the plunger 108A is driven by a cam (not shown) and via a pusher (not shown), generally at the rate of one pumping cycle per combustion cycle of the engine.

[0060] Fuel is pushed into the high pressure pump 100A at a pressure supply of the order of 3 bars to 6 bars by a low pressure pump (not shown) through the fuel inlet 102A.

[0061] During the fuel suction phase into the compression chamber 105A by the plunger 108A, the non-piloted inlet valve 11 IA is open and the fuel arrives from the fuel inlet 102A and the low pressure chamber 106A while the plunger 108A descends from its top dead center to its bottom dead center. The outlet and discharge valves 112A and 113A are kept closed by the force of their respective springs (not referenced).

[0062] During the phase of controlling the quantity of fuel pumped, that is to say when the plunger 108A begins to rise from its bottom dead center, a volume of fuel is expelled from the compression chamber 105A through the open inlet valve 111A towards the inlet 102A and the low pressure chamber 106A. The outlet and discharge valves 112A and 113A are kept closed by the force of their respective springs (not referenced) and by the fuel pressure present at the outlet 104A.

[0063] When the volume remaining in the compression chamber 105A corresponds to the quantity to be pumped, the inlet valve 11 IA is controlled in the closed position.

[0064] During the fuel compression phase in the compression chamber 105A and in the outlet 104A, the fuel is expelled from the compression chamber 105A by the outlet valve 112A while the plunger 108A continues its rise to its top dead center.

[0065] When operating the engine on an alternative fuel, i.e. without using the direct gasoline injection system, the plunger 108A is always driven by the cam which is not disengageable.

[0066] Due to the fuel being rolled through the inlet valve 111A by the movements of the plunger 108A, the lack of fuel renewal in the high pressure pump 100A, as well as the temperature of the environment of said pump, the temperature of the fuel in the high pressure pump 100A increases and reaches cavitation conditions. It is thus necessary to cool the high pressure pump in these phases of engine operation without use of the direct gasoline injection system.

[0067] [Fig. 3] illustrates a high pressure pump 100 according to one embodiment of the invention.

[0068] The pump 100 comprises a substantially cylindrical pump body 101 comprising a low-pressure fuel inlet 102 opening into a fuel inlet duct 103, a high-pressure fuel outlet 104 and a compression chamber 105 connecting the fuel inlet duct 103 to the high-pressure fuel outlet 104.

[0069] The pump 100 further comprises a low pressure chamber 106 connected to the conduit fuel intake 103 via an intermediate conduit 107 and a plunger 108 movable in translation in the pump body 101. The plunger 108 comprises a piston movable in translation in a cylindrical housing 109 of the body 101 opening into the compression chamber 105 and an end rod extending axially from the piston towards the outside of the body 101.

[0070] The pump 100 comprises a plug 110, fixed relative to the body, in which the rod of the plunger 108 slides.

[0071] The low pressure chamber 106 is located axially below the plunger piston 108.

[0072] As illustrated, the pump 100 comprises an inlet valve 111 for the compression chamber 105, an outlet valve 112 for the compression chamber 105 and a discharge valve 113 for the high pressure circuit mounted in a conduit 114 connecting the high pressure chamber 105 and the fuel outlet 104.

[0073] As illustrated in [Fig.3], the pump 100 includes a low pressure fuel outlet 120 connected to the low pressure chamber 106.

[0074] The fuel outlets 104, 120, respectively high pressure and low pressure, are, here, parallel and perpendicular to the fuel inlet 102.

[0075] The normal operation of the direct gasoline injection system is identical to that of the state of the art described with reference to [Fig.2] and will not be described further here.

[0076] When operating the engine on an alternative fuel, i.e. without using the direct gasoline injection system, the plunger 108 is always driven by the cam which is not disengageable and the low pressure pump (not shown) is configured to convey the liquid fuel (gasoline) into the high pressure pump 100 through the inlet 102.

[0077] The low-pressure fuel outlet 120 is configured to create a continuous flow of liquid fuel through the inlet valve 111 and the low-pressure chamber 106. Thus, there is no longer any stagnation of the liquid fuel in the high-pressure pump 100. The low-pressure fuel outlet 120 can be connected to the fuel tank or to an auxiliary injection system, for example in the case of an engine with direct and indirect injection of liquid fuel. The liquid fuel leaving the low-pressure outlet 120 is thus reused.

[0078] In order to maintain a supply pressure in the high pressure pump 100, a pressure drop member (not shown) can advantageously be mounted at the outlet of the low pressure outlet 120.

[0079] However, such a solution requires activating the low pressure pump to maintain a flow of liquid fuel in the high pressure pump 100. This generates excess energy consumption.

[0080] The embodiment of [Fig.4], in which the same elements bear the same references, differs from the embodiment of [Fig.3] only in that the high pressure pump 100 comprises one or more pressure loss members.

[0081] As illustrated, the high pressure pump 100 comprises a first or upstream pressure loss member 122 mounted upstream of the low pressure chamber 106 and a second or downstream pressure loss member 124 mounted downstream of the low pressure chamber 106.

[0082] The first pressure drop member 122 is mounted downstream of the inlet valve 111.

[0083] The second pressure drop member 124 is mounted upstream of the outlet 120 of the low pressure liquid fuel.

[0084] Thanks to the pressure drop members 122, 124, the high pressure pump 100, whose plunger 108 is always driven, ensures by itself the circulation of liquid fuel through the entire low pressure part of the high pressure pump, from the inlet 102 to the low pressure fuel outlet 120.

[0085] This makes it possible to deactivate the low pressure pump of the fuel tank during the carburetion phases exclusively by a system other than the direct gasoline injection system.

[0086] Energy consumption is thus reduced.

[0087] One 122 of the two pressure drop members is configured to be open at a low pressure value, for example less than 1 bar of differential pressure and the other 124 of the two pressure drop members is configured to be open at a fuel supply pressure.

[0088] As illustrated, the pressure drop members 122, 124 are valves calibrated respectively at a low pressure and at a fuel supply pressure.

[0089] Alternatively, it could be provided that the valve 124 calibrated to the supply pressure is replaced by a continuously controlled solenoid valve in order to adapt the pressure in the low pressure part of the pump 100 as a function of the temperature in said pump 100.

[0090] The temperature may, for example, be obtained by a sensor (not shown) mounted on the low pressure fuel circuit near the inlet 102 and / or by a model of the temperature within the low pressure portion of the high pressure pump 100.

[0091] Alternatively, the high pressure pump 100 could comprise only one pressure drop member 124 mounted at the outlet of the low pressure chamber 106 and upstream of the low pressure fuel outlet 120.

[0092] Thanks to the invention, it is possible to cool a high-pressure pump of a direct gasoline injection system of a dual-fuel engine without increasing the clutter around said pump.

Claims

Claims

1. High pressure pump (100) of a direct liquid fuel injection system of a dual-fuel internal combustion engine (10) of a motor vehicle configured to burn a liquid fuel and a gaseous fuel, said high pressure pump (100) comprising a pump body (101) comprising a low pressure liquid fuel inlet (102), a high pressure liquid fuel outlet (104) and a compression chamber (105) connecting the low pressure liquid fuel inlet (102) to the high pressure liquid fuel outlet (104), the high pressure pump (100) further comprising a low pressure chamber (106) connected to the low pressure liquid fuel inlet (102) and a plunger (108) movable in translation in the pump body (101), said low pressure chamber (106) being located axially under the plunger (108),the pump (100) further comprising an inlet valve (111) for the compression chamber (105) and an outlet valve (112) for the compression chamber (105), the high-pressure pump (100) comprising a low-pressure liquid fuel outlet (120) connected to the low-pressure chamber (106) and configured to create a continuous flow of liquid fuel through the inlet valve (111) and the low-pressure chamber (106) during operation of the engine with the gaseous fuel, characterized in that it comprises at least one downstream pressure drop member (124) mounted between the low-pressure chamber (106) and the low-pressure liquid fuel outlet (120).,

2. The high pressure pump (100) of claim 1, wherein the downstream pressure drop member (124) is configured to be open at a liquid fuel supply pressure.

3. High pressure pump (100) according to claim 1 or 2, in which the downstream pressure drop member (124) is a valve calibrated to a liquid fuel supply pressure.

4. High pressure pump (100) according to claim 1 or 2, in which the downstream pressure drop member (124) is a solenoid valve configured to be continuously controlled as a function of the temperature in said pump (100).

5. A high pressure pump (100) according to any preceding claim, comprising an upstream pressure drop member (122) mounted upstream of the low pressure chamber (106) and downstream of the inlet valve (111).

6. High pressure pump (100) according to claim 5, in which the upstream pressure loss member (122) is a valve calibrated respectively at a low pressure lower than Ibar.

7. A high pressure pump (100) according to any preceding claim, wherein the low pressure liquid fuel outlet (120) is connected to the liquid fuel tank or to an ancillary injection system.

8. A high pressure pump (100) according to any preceding claim, wherein a pressure drop member is mounted at the outlet of the low pressure liquid fuel outlet (120).

9. A dual-fuel internal combustion engine (10) of a motor vehicle configured to burn a liquid fuel and a gaseous fuel comprising a direct liquid fuel injection fuel system comprising a high-pressure pump (100) according to any one of the preceding claims and configured to inject the liquid fuel into at least one cylinder (12) of the engine (10).

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