FR3126736A1 - High pressure pump of a liquid fuel direct injection carburetion system of a bi-fuel internal combustion engine of a motor vehicle - Google Patents

Abstract

A high pressure pump (100) of a liquid fuel direct injection carburetion system of a motor vehicle dual fuel internal combustion engine configured to burn liquid fuel and 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 a valve (111, 112) for inlet and outlet 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 of the low pressure chamber (106) during operation of the engine with gaseous fuel. Figure for abstract: Fig 3

Description

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

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

More particularly, the invention relates to the cooling of a high-pressure pump.

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

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

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

Gas combustion uses positive ignition, so gasoline-based carburation will be preferred as the associated dual carburation.

A dual-carburetion gas and gasoline engine, or more generally a liquid one, is forced to comply with the same regulatory standards as a single-carburetion engine.

We are familiar with the so-called direct fuel injection technology, acronym "IDE", which allows fuel to be injected directly into the engine cylinders. Direct injection lowers fuel consumption and carbon dioxide emissions, as well as reducing pollutant emissions.

Gas carburation is therefore generally associated with gasoline direct injection carburation.

In a liquid fuel direct injection carburetion system, the injection of fuel (gasoline, gasoline and ethanol or even pure ethanol) is necessarily carried out at high pressure in order to guarantee correct atomization of the fuel in the engine cylinder while maintaining the ability to introduce a sufficient quantity of fuel into the cylinder between each combustion. The gasoline direct injection fuel system includes a high pressure fuel pump. Said pump is generally driven by an element of the internal combustion engine, in particular a camshaft and an intermediate tappet. The pump is therefore attached to the motor and heats up with it.

The fuel present inside the high pressure pump is sensitive to 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.

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

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

An existing solution consists in integrating on the engine, a coolant chamber around the high pressure pump in order to cool said pump.

Reference can be made in this respect to the document DE 10 2013 206 433 - A1 which describes cooling systems external to the high pressure pump.

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

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 zone of any mechanical element.

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

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

The pump further includes a compression chamber inlet valve and a compression chamber outlet valve.

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 engine operation with gaseous fuel.

Thus, there is no longer 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 liquid fuel direct 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.

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 liquid fuel direct injection system.

Advantageously, the high pressure pump comprises at least one downstream pressure drop member mounted between the low pressure chamber and the low pressure liquid fuel outlet. This downstream device maintains the supply pressure in the high-pressure pump.

For example, the downstream pressure drop device is configured to be open at a liquid fuel supply pressure.

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

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

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

For example, the upstream pressure drop device is a valve calibrated respectively at a low pressure of less than 1 bar.

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

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

For example, a pressure drop member is mounted at the outlet of the low pressure liquid fuel outlet.

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

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

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:

shows, very schematically, an example of the general structure of a dual-fuel internal combustion engine comprising a high-pressure pump according to the invention;

very schematically represents an example of a high pressure pump for a gasoline direct injection system of an internal combustion engine according to the prior art;

shows, very schematically, an example of a high pressure pump for a gasoline direct injection system of an internal combustion engine according to one embodiment of the invention; And

shows, very schematically, an example of a high pressure pump for a gasoline direct injection system of an internal combustion engine according to another embodiment of the invention.

On the , there is shown, schematically, 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.

This architecture is given by way of example and does not limit the invention to the sole configuration to which the high-pressure pump according to the invention can be applied.

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

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 .

In 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, in order to increase the quantity (mass flow) of air admitted into the cylinders 12 of the engine 10. The turbine 18a can be of the "variable geometry" type, that is to say that the wheel of the turbine is fitted with variable-angle fins in order to modulate the amount of energy taken from the exhaust gases, and thus the boost pressure.

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

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 Anglo-Saxon terms for Exhaust Gas Recirculation.

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

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

The engine 10 is associated with a liquid fuel direct 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 tank 40 of liquid fuel.

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

“Gas” means liquefied petroleum gas, acronym “LPG”, or compressed natural gas, acronym “CNG”.

The liquid fuel direct injection fuel system (gasoline, gasoline and ethanol or ethanol) includes a high pressure pump (not shown on the ) configured to guarantee 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.

A well-known example of a high-pressure pump is illustrated in the .

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 103A to high pressure fuel outlet 104A.

The pump 100A further comprises a low-pressure chamber 106A connected to the fuel inlet 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.

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

Low pressure chamber 106A is located axially below plunger piston 108A.

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

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

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

During the fuel suction phase in the compression chamber 105A by the plunger 108A, the uncontrolled inlet valve 111A 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. Outlet and relief valves 112A and 113A are held closed by the force of their respective (unreferenced) springs.

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 valve 111A inlet open to inlet 102A and low pressure chamber 106A. The outlet and relief valves 112A and 113A are held closed by the force of their respective spring (not referenced) and by the fuel pressure present at the outlet 104A.

When the volume remaining in the compression chamber 105A corresponds to the quantity to be pumped, the inlet valve 111A is driven into the closed position.

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 neutral point. high.

When the engine is running on an alternative fuel, that is to say without using the gasoline direct injection system, the plunger 108A is always driven by the cam which cannot be disengaged.

Because of the fuel laminated through the inlet valve 111A by the movements of the plunger 108A, the absence of fuel renewal in the high pressure pump 100A, as well as the temperature of the environment of said pump, the fuel temperature in the 100A high pressure pump rises and reaches cavitation conditions. It is therefore necessary to cool the high-pressure pump in these phases of engine operation without using the gasoline direct injection system.

There illustrates a high pressure pump 100 according to one embodiment of the invention.

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 103 to fuel outlet 104 at high pressure.

The pump 100 further comprises a low-pressure chamber 106 connected to the fuel inlet pipe 103 by an intermediate pipe 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.

The pump 100 includes a plug 110, fixed relative to the body, in which the plunger rod 108 slides.

Low pressure chamber 106 is located axially below plunger piston 108.

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

As shown on the , the pump 100 comprises a low pressure fuel outlet 120 connected to the low pressure chamber 106.

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

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

When the engine is running on an alternative fuel, that is to say without using the gasoline direct injection system, the plunger 108 is always driven by the cam which cannot be disengaged and the low pressure pump (not shown) is configured to deliver liquid fuel (gasoline) into high pressure pump 100 through inlet 102.

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 additional injection system, in the case for example of an engine with direct and indirect injection of liquid fuel. The liquid fuel leaving outlet 120 at low pressure is thus reused.

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

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.

The embodiment of the , in which the same elements bear the same references, differs from the embodiment of the only by the fact that the high pressure pump 100 comprises one or more pressure drop devices.

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

The first pressure drop device 122 is mounted downstream of the inlet valve 111.

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

Thanks to the pressure drop devices 122, 124, the high pressure pump 100, whose plunger 108 is always driven, alone ensures the circulation of liquid fuel through the whole of the low pressure part of the fuel pump. high pressure, from the inlet 102 to the outlet 120 of low pressure fuel.

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

Energy consumption is thus reduced.

One 122 of the two pressure drop devices 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 devices is configured to be open at fuel supply pressure.

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

As a variant, provision could be made for the valve 124 calibrated at the supply pressure to be replaced by a continuously controlled solenoid valve in order to adapt the pressure in the low pressure part of the pump 100 according to the temperature in said pump 100.

The temperature can, for example, be obtained by a sensor (not shown) mounted on the low pressure fuel circuit close to the inlet 102 and/or by a model of the temperature within the low pressure part of the high pressure pump 100.

Alternatively, the high pressure pump 100 could comprise a single pressure drop device 124 mounted at the outlet of the low pressure chamber 106 and upstream of the low pressure fuel outlet 120.

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

Claims (10)

A high pressure pump (100) of a liquid fuel direct injection carburetion 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 inlet (102) pressure liquid fuel 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). pressure 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 a valve (111) inlet to the compression chamber (105) and an outlet valve (112) for the compression chamber (105), characterized in that the high-pressure pump (100) comprises an outlet (120) for liquid fuel at low pressure 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 engine operation with gaseous fuel . A high-pressure pump (100) according to claim 1, comprising at least one downstream member (124) of pressure drop mounted between the low-pressure chamber (106) and the low-pressure liquid fuel outlet (120). A high pressure pump (100) according to claim 2, wherein the downstream pressure drop member (124) is configured to be open to liquid fuel supply pressure. High-pressure pump (100) according to claim 2 or 3, in which the downstream member (124) of pressure drop is a valve calibrated at a liquid fuel supply pressure. High-pressure pump (100) according to claim 2 or 3, in which the downstream member (124) of pressure drop is a solenoid valve configured to be controlled continuously as a function of the temperature in said pump (100). 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) . High-pressure pump (100) according to Claim 6, in which the upstream member (122) for pressure drop is a valve calibrated respectively at a low pressure of less than 1 bar. 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 auxiliary injection system. 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). A motor vehicle bi-fuel internal combustion engine (10) configured to burn liquid fuel and gaseous fuel comprising a liquid fuel direct injection decarburization system comprising a high pressure pump (100) according to any preceding claim and configured to inject the liquid fuel into at least one cylinder (12) of the engine (10).