EP3964704A1 - High-pressure pump and assembly for direct and indirect injection of fuel(s) comprising a function for shutting down the high-pressure pump - Google Patents

Abstract

The subject of the present invention is an assembly for double injection, direct and indirect, of fuel comprising a high-pressure piston pump and a rotating cam (20) for actuating the high-pressure pump which acts on an axial piston (29) of the pump, characterized in that it comprises a device for controlling the actuation of the high pressure pump with a function of stopping the high pressure pump which comprises a member (24) of controlled variable axial length which is interposed axially between the drive cam (20) and the piston (29) of the high pressure pump (130) and- a control system for the element of variable axial length controlled as a function of at least one parameter of fuel injection control.

Description

Technical field of the invention

The present invention relates to a set of double injection, direct and indirect, of fuel(s) in a heat engine.

The invention relates more particularly to an assembly for the dual injection of gasoline and liquid gas in a combustion engine with positive ignition of a motor vehicle.

Technical background

To improve air quality, motor vehicles equipped with a heat or internal combustion engine must comply with so-called anti-pollution standards, and in particular with European emission standards, known as Euro standards, which are regulations of the European Union setting the maximum limits of polluting emissions for rolling vehicles.

These standards are more and more strict applying to new vehicles. Their goal is to reduce air pollution from road transport.

Thermal engines can be carburetion, petrol, diesel, gas or petrol-gas bi-fuel.

For gasoline and liquid gas dual-fuel heat engines which use a butane and propane mixture, it is known practice to use the desired fuel depending on the operating and use conditions.

Direct injection heat engines are known in which a fuel injector sprays fuel directly into a combustion chamber delimited by a cylinder hollowed out in a cylinder block of the engine, a sliding piston and a lower wall of a cylinder head mounted on the crankcases.

The injector has an injection end which opens into the combustion chamber. This type of engine requires a high power fuel injector to cope with the high pressures prevailing in the combustion chamber.

Indirect injection heat engines are known in which an injector injects fuel into the air intake circuit upstream (in the direction of air circulation) of the combustion chamber. The fuel is not injected into the cylinder but upstream in an intake channel or in an intake distributor so that the fuel and the intake air mix optimally and homogeneously. This allows for better combustion and thus reduces the formation of fine particles which constitute one of the problems of modern engines.

The fuel vaporizes under the effect of heat and burns optimally once it reaches the combustion chamber.

The invention relates in particular to a dual-fuel engine, for example based on gasoline and LPG gas.

In known manner, the gasoline fuel is injected directly into one of the combustion chambers of the engine, while the gas fuel is injected indirectly upstream (according to the direction of air circulation) of the combustion chambers of the engine, in particular in intake channels hollowed out in the cylinder head of the engine.

A dual gasoline injection system, also called "dual injection system", is a liquid fuel injection system to ensure the supply of an intake duct connected to the combustion chambers of the cylinders of a heat engine (Injection via the supply line or PFI injection), and ensure fuel injection directly into the combustion chambers (Direct injection, also called GDI for “Gasoline Direct Injection” and/or MPI for “Multi Point Injection”).

In a fuel injection system in the air intake duct, there is generally a low pressure and this is why this injection is also called "Low pressure injection".

In the case of a direct injection system, which is done at high pressure, the injection system is also called “High pressure injection”.

In such a dual fuel injection system, there is both one or more low pressure injectors indirectly injecting fuel upstream of the air intake valve, that is to say injectors for the duct intake, and also high-pressure injectors, each of which injects fuel directly into a combustion chamber. The high pressure pump is for example integrated into the cylinder head and/or the cylinder head cover of the thermal engine and a rotating cam actuates the high pressure pump by acting on an axial piston of the high pressure pump, directly or via a simple or roller mechanical pusher.

An example of design of the drive by cam(s) or eccentric(s) of the pistons of a high pressure pump is disclosed by the document US2004109775A1

The two injection modes can be combined depending on the operating conditions of the heat engine.

For bi-fuel engines, it is known practice to carry out start-up phases using gasoline fuel to ensure start-ups in all weathers, and in particular in cold weather, then to then switch to the use of gas fuel in order to reduce emissions. harmful gases and their impact on the environment.

During indirect injection phases with interruption of direct injection, the fuel present in the high pressure pump is compressed, but it no longer circulates because there is no fuel consumption by the direct injection injectors, nor recirculation of the fuel in the petrol pumps.

Problems of coking of the ends of the injectors opening into the combustion chambers are known, in particular when the engine has switched over to the use of gas fuel and when gasoline fuel is present in the nozzle of the injector. Since the high-pressure pump is still in operation, it is capable of supplying said injectors permanently.

Different solutions to remedy this problem offer thermal protections for the ends of the injector nozzles.

The invention aims to propose another solution by allowing in particular a stoppage of the petrol fuel supply by the high-pressure pump when switching to LPG gas fuel.

Summary of the invention

• une came tournante d'actionnement de la pompe haute pression qui agit sur un piston axial de la pompe haute pression par l'intermédiaire d'un poussoir qui est interposé axialement entre la came d'entraînement et le piston de la pompe haute pression,

caractérisée en ce que :

• le poussoir est un poussoir de longueur axiale variable commandée ;
• l'ensemble comporte un système de commande de la longueur du poussoir de longueur axiale variable en fonction d'au moins un paramètre de commande de l'injection de carburant dans ladite chambre de combustion, entre un état d'actionnement de la pompe haute pression et un état d'arrêt de la pompe haute pression.

The invention proposes a high-pressure piston pump for supplying fuel to at least one direct fuel injection injector in at least one combustion chamber, in particular of a spark-ignition heat engine, and which comprises a high pressure pump actuation system comprising:

• a rotary cam for actuating the high-pressure pump which acts on an axial piston of the high-pressure pump by means of a tappet which is interposed axially between the drive cam and the piston of the high-pressure pump,

characterized in that:

• the pusher is a pusher of controlled variable axial length;
• the assembly comprises a system for controlling the length of the pusher of variable axial length as a function of at least one control parameter for the injection of fuel into said combustion chamber, between an actuation state of the high pressure pump and a high pressure pump off state.

• le poussoir de longueur axiale variable commandée est un poussoir hydraulique apte à transmettre ou non la poussée de la came au piston axial de la pompe haute pression ; et le système de commande de la longueur du poussoir hydraulique comporte un circuit de liquide sous pression qui est relié de manière commandée à une chambre de commande du poussoir hydraulique ;
• le poussoir hydraulique comporte deux pistons coaxiaux dont l'un coopère avec ladite came, et dont l'autre coopère avec le piston axial de la pompe haute pression et qui sont liés axialement entre eux par des moyens de couplage axial qui sont commandés en fonction de l'alimentation de ladite chambre de commande du poussoir hydraulique ;
• un ressort est monté comprimé axialement entre les deux pistons coaxiaux ;

According to other characteristics of the pump:

• the controlled variable axial length pusher is a hydraulic pusher able to transmit or not the thrust of the cam to the axial piston of the high pressure pump; and the system for controlling the length of the hydraulic tappet comprises a pressurized liquid circuit which is connected in a controlled manner to a control chamber of the hydraulic tappet;
• the hydraulic tappet comprises two coaxial pistons, one of which cooperates with said cam, and the other of which cooperates with the axial piston of the high-pressure pump and which are axially linked together by axial coupling means which are controlled as a function of supplying said hydraulic tappet control chamber;
• a spring is mounted compressed axially between the two coaxial pistons;

• une pompe haute pression à piston qui alimente en carburant une zone d'injection directe en amont d'au moins un injecteur d'injection directe de carburant dans ladite chambre de combustion ; et
• une came tournante d'actionnement de la pompe haute pression qui agit sur un piston axial de la pompe haute pression par l'intermédiaire d'un poussoir qui est interposé axialement entre la came d'entraînement et le piston de la pompe haute pression,

caractérisé en ce que :

• le poussoir est un poussoir de longueur axiale variable commandée ;
• l'ensemble comporte un système de commande de la longueur du poussoir de longueur axiale variable en fonction d'au moins un paramètre de commande de l'injection de carburant dans ladite chambre de combustion, entre un état d'actionnement de la pompe haute pression et un état d'arrêt de la pompe haute pression.

The invention also proposes an assembly for double injection, direct and indirect, of fuel(s) into at least one combustion chamber of a cylinder of a spark-ignition heat engine comprising:

• a high-pressure piston pump which supplies fuel to a direct injection zone upstream of at least one direct fuel injection injector in said combustion chamber; and
• a rotary cam for actuating the high-pressure pump which acts on an axial piston of the high-pressure pump by means of a tappet which is interposed axially between the drive cam and the piston of the high-pressure pump,

characterized in that:

• the pusher is a pusher of controlled variable axial length;
• the assembly comprises a system for controlling the length of the pusher of variable axial length as a function of at least one control parameter for the injection of fuel into said combustion chamber, between an actuation state of the high pressure pump and a high pressure pump off state.

• le poussoir de longueur axiale variable commandée est un poussoir hydraulique apte à transmettre ou non la poussée de la came au piston axial de la pompe haute pression ; et le système de commande de la longueur du poussoir hydraulique comporte un circuit de liquide sous pression qui est relié de manière commandée à une chambre de commande du poussoir hydraulique ;
• le poussoir hydraulique comporte deux pistons coaxiaux dont l'un coopère avec ladite came, et dont l'autre coopère avec le piston axial de la pompe haute pression et qui sont liés axialement entre eux par des moyens de couplage axial qui sont commandés en fonction de l'alimentation de ladite chambre de commande du poussoir hydraulique ;
• le ressort est monté comprimé axialement entre les deux pistons coaxiaux.

According to other features of the set:

• the controlled variable axial length pusher is a hydraulic pusher able to transmit or not the thrust of the cam to the axial piston of the high pressure pump; and the system for controlling the length of the hydraulic tappet comprises a pressurized liquid circuit which is connected in a controlled manner to a control chamber of the hydraulic tappet;
• the hydraulic tappet comprises two coaxial pistons, one of which cooperates with said cam, and the other of which cooperates with the axial piston of the high-pressure pump and which are axially linked together by axial coupling means which are controlled as a function of supplying said hydraulic tappet control chamber;
• the spring is mounted compressed axially between the two coaxial pistons.

The invention also proposes a heat engine, characterized in that it comprises a high pressure pump according to the invention.

The invention finally proposes a heat engine, characterized in that it comprises a set of double injection, direct and indirect, of fuel(s) according to any one of the invention.

Brief descriptions of figures

• [Fig.1] - la figure 1 est une représentation schématique d'un ensemble de double injection, directe et indirecte, de carburants dans trois cylindres d'un moteur à combustion à essence et à gaz GPL ;
• [Fig.2] - la figure 2 est une vue en perspective d'une culasse de moteur à combustion à essence à trois cylindres avec son couvre-culasse intégrant une pompe d'injection à haute pression commandée selon l'invention ;
• [Fig.3] - la figure 3 est une vue en coupe par un plan radial passant par l'axe du piston de la pompe haute pression de la figure2 ;
• [Fig.4] - la figure 4 est une vue en coupe par un plan axial d'un exemple de réalisation d'un poussoir hydraulique commandé associé à la commande de la pompe d'injection à haute pression ;
• [Fig.5] - la figure 5 est une vue en coupe axiale selon un autre plan du poussoir de la figure 5.

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

• [ Fig.1 ] - the figure 1 is a schematic representation of a set of double injection, direct and indirect, of fuels in three cylinders of a gasoline and LPG gas combustion engine;
• [ Fig.2 ] - the figure 2 is a perspective view of a cylinder head of a three-cylinder gasoline combustion engine with its cylinder head cover incorporating a high-pressure injection pump controlled according to the invention;
• [ Fig.3 ] - the picture 3 is a sectional view through a radial plane passing through the axis of the piston of the high pressure pump of the picture2 ;
• [ Fig.4 ] - the figure 4 is a view in section through an axial plane of an embodiment of a controlled hydraulic tappet associated with the control of the high-pressure injection pump;
• [ Fig.5 ] - the figure 5 is an axial sectional view according to another plane of the pusher of the figure 5 .

Detailed description of the invention

Schematically represented in figure 1 a system 110 of double injection according to the state of the art.

In the system 110, gasoline is transferred from a tank 112 by a low pressure pump 114 which is for example an electric pump capable of compressing the fuel for example at a pressure of approximately 5 bars.

The low pressure pump 114 sends the fuel into a line 116 which is a supply line for a low pressure zone 118.

The high pressure zone 120 is connected to a pipe 128 equipped with a high pressure piston pump 130 whose function is to increase the low pressure of approximately 5 bars prevailing in the supply pipe 116 up to a high pressure for example equal to about 100 bar.

The fuel is then injected directly into each of the cylinders of the combustion engine, not shown, by three high pressure injectors 132 providing direct injection from the high pressure zone 120.

The low pressure pump 114 also sends the fuel into a line 128 which is a supply line to a high pressure zone 120 of the fuel injection system 110.

Supply line 116 is equipped with a pressure regulator 122 which maintains the pressure in supply line 116 at a substantially constant value.

The low pressure zone 118 comprises a pipe 124 which is directly connected to a tank 113 of LPG gas.

The low pressure zone 118 is here in the form of a low pressure tubular ramp, which is connected to three low pressure injectors 126 which inject gas fuel into the intake duct, not shown, of the combustion engine.

As a variant, the low pressure zone may comprise only a single low pressure injector which injects fuel into the intake duct.

The intake duct is connected to the various combustion chambers, not shown, of the cylinders of the combustion engine.

We represented at the figure 2 a cylinder head 10 of a three-cylinder heat engine which is associated with a cylinder head cover 12 which is fixed to it along a parting plane 14.

These two components are for example made by molding in light alloy.

The cylinder head cover 14 comprises a tubular body 16 which extends along an axis A orthogonal to an axis X which is here the axis of rotation of a camshaft 22.

As can be seen in section at picture 3 , the axis A of the tubular body 16 intersects with the axis X of the camshaft 22 which carries and drives in rotation a cam 20 with three lobes for actuating the high pressure pump 130.

The cam 20 acts on a piston, not shown, of the high pressure pump 130.

The tubular body 16 is in the form of a stepped cylinder whose end section 15 of larger diameter houses the body of the high-pressure pump 130 which is fixed by means of screws 26 to the tubular body.

The high-pressure pump 130 is shown in section in the form of a cylindrical block and the reference 29 has designated a radial end face which is an end face of a sliding axial piston of the pump.

In known manner, the three-lobed cam acts cyclically on the end 29 of the sliding piston of the high-pressure pump 130.

To this end, a sliding mechanical pusher of constant axial length for actuating the high pressure pump is interposed axially between the cam and the axial end 29 of the piston of the high pressure pump 130 In accordance with the teachings of the invention, a pusher 24 of controlled variable axial length is interposed axially along the axis A between the drive cam 20 and the end face 29 of the piston of the high pressure pump 130, and the assembly comprises a system for controlling the length of the pusher of variable axial length as a function of at least one fuel injection control parameter in the combustion chamber, between a state of actuation of the high pressure pump and a disengaged state with stoppage of the high pressure pump.

By way of non-limiting example, the pusher 24 of controlled variable axial length is here a hydraulic pusher of controlled axial length which is mounted in the inner section 17 of smaller diameter of the tubular body 16.

We also represented at the picture 3 a section 18 of the oil supply rail under pressure of the hydraulic tappet 24.

The invention thus consists in replacing a sliding mechanical pusher of constant axial length for actuating the high-pressure pump by a hydraulic pusher of controlled variable length.

More precisely, the axial length of the hydraulic tappet varies between a maximum value corresponding to the actuation state of the high pressure pump and a minimum value corresponding to the stop state of the high pressure pump.

Hydraulic tappets are a known technology used for controlling the actuation of combustion engine valves in order, for example, to deactivate an engine cylinder. You can either use a classic friction tappet or derive a version with a roller to reduce friction between the cam and the tappet.

A design of a hydraulic tappet 24 is for example similar to that of the hydraulic valve tappet described and shown in the documents DE9306685U1 and DE19728100A1 (INA-Schaeffler) whose content can be referred to.

An example of such a hydraulic tappet is shown in figure 4 and 5 .

The figure 4 represents a hydraulic tappet 24 in axial section.

By way of example, the pusher 24 consists of a radially outer tubular piston 202 which includes a hollow tubular cylindrical jacket 203.

Via this sleeve 203, the pusher 24 is received in an axially sliding manner in the section 17 of the body 16.

The upper part 203a of the radially outer piston 202 is capable of being actuated by one or two cams, not shown in figure 4 and 5 , say big race.

The outer tubular piston 202 houses a radially inner coaxial tubular piston 204.

The upper part 205 of the internal piston 204 is adapted to be actuated by a cam, not shown, called a short stroke cam.

A helical compression spring 201 is mounted compressed axially between the two external coaxial pistons 202, 204 so as to permanently urge the external piston axially upwards (considering the figure 4 and 5 ) away from the internal coaxial piston 204.

The lower axial end of the spring 201 rests on a flange 200 which is integral with the internal piston 204

A controlled hydraulic compensation element 206 is arranged inside the internal piston 204.

A controlled mechanism for coupling the two pistons 202 and 204 is arranged at the upper part and it comprises in particular a radial coupling piston 209.

Movement of the coupling radial piston 209 towards a stopper 210 causes the hydraulic tappet 24 to be coupled to the stroke of the long stroke cams.

In the coupling position shown in figure 4 , the hydraulic tappet 24 only follows the stroke of the cam associated with the radially internal piston 204.

Opposed radial housings 207 and 208 for coupling piston 209 extend into sections 211, 212 which extend from portions 203a, 205.

In the circumferential direction, the sections 211 of the tubular piston 202 delimit two approximately semi-circular storage chambers 213, 214 (First chambers 213 and second storage chambers 214) for the hydraulic fluid.

The figure 5 shows that two separate passages 215, 216 (First passage 215 and second passage 216) are arranged in the jacket 203.

These passages 215, 216 serve for the separate supply of hydraulic fluid to the coupling means 209 on the one hand and to the hydraulic compensation element 206 on the other hand.

Inside the tubular piston 202, as those skilled in the art can also see at figure 4 , only a thin-walled tubular part 217, for example manufactured by stamping, is arranged. This tubular part 217 is applied in the direction of the cam against the sections 211 of the tubular piston 202. In the direction of the gas exchange valve and radially to the outside, the tubular part 217 merges into a sleeve 218. The sleeve 218 is generally liquid-tight along the inner sleeve 219 of the sleeve 203. The tubular part 217 thus delimits the first and second storage chambers 213, 214 below the sleeve 203 in the direction away from the cam.

From the first pass 215 (see figure 5 ), a first channel 220 is formed in the sleeve 218 of the tubular part 217 in the axial direction. This channel 220 opens into the first storage chamber 213 on the cam side. From this first storage chamber 213, a passage 221 (see figure 4 ) for the hydraulic fluid in front of the coupling means 209 (Which is not shown in more detail) is realized. Diametrically opposite the first passage 215, the second passage 216 is located in the sleeve 203, axially in the direction of the cam with respect to the first passage 215. This second passage 216 opens here in the second storage chamber 214. From the second storage chamber 214, a hydraulic fluid connection (Not shown in more detail) to the hydraulic compensation element 206 is made.

A dual-flow feed is achieved by which the hydraulic compensation element 206 and the coupling means 209 can be actuated separately. An excellent tight hydraulic separation of the storage chambers 213 and 214 is achieved, so that the hydraulic fluid therein cannot escape undesirably, nor pass into the other storage chamber 214, 213 respectively.

For the operation and control of this type of hydraulic tappet, reference may be made, for example, to the document entitled "INA - Valve Train Components - Technology and Failure Diagnosis - (Pages 17 to 20) - © Schaeffler Automotive Aftermarket GmbH &Co.KG"

One can add to such a system, a control law of the system because it is necessary to maintain the rail and injector pressure for their tightness. The closing of the injector being dependent on the pressure in the rail. A minimum pressure in continuous operation is ensured.

The pressurized oil from the internal combustion engine is used to control the hydraulic tappet.

In the implementation according to the invention, and as can be seen in picture 3 , the free lower axial end of the internal coaxial piston 204 of the hydraulic tappet 204 is in contact and in permanent axial support against the radial end face 29 of the piston of the high pressure pump 130, while the free external face of the part upper 203a of the outer coaxial piston 202 is in contact and in permanent axial support with the cam 20.

• soit les deux pistons coaxiaux 202 et 204 sont solidaires axialement et la came 20 agit « normalement » sur le piston de la pompe à haute pression par l'intermédiaire du poussoir hydraulique 24 qui est de longueur constante ;
• soit les deux pistons coaxiaux 202 et 204 ne sont pas solidaires axialement l'un de l'autre et la came 20 - qui agit sur le piston externe 202 - ne provoque aucun déplacement axial du piston interne 204, la longueur axiale du poussoir hydraulique 24 variant cycliquement et librement en fonction de la position angulaire de la came 20.

Depending on the controlled position of the coupling radial piston 209:

• either the two coaxial pistons 202 and 204 are axially integral and the cam 20 acts “normally” on the piston of the high-pressure pump via the hydraulic tappet 24 which is of constant length;
• either the two coaxial pistons 202 and 204 are not axially integral with each other and the cam 20 - which acts on the outer piston 202 - does not cause any axial displacement of the inner piston 204, the axial length of the hydraulic tappet 24 varying cyclically and freely depending on the angular position of the cam 20.

Claims (10)

High-pressure piston pump (130) for supplying fuel to at least one injector (132) for direct fuel injection into at least one combustion chamber, in particular of a spark-ignition heat engine, and which comprises a system for actuating the high pressure pump comprising: - a rotating cam (20) for actuating the high pressure pump which acts on an axial piston (29) of the high pressure pump (130) by means of a tappet (24) which is interposed axially between the cam (20) and the piston (29) of the high pressure pump (130), characterized in that : - the pusher (24) is a pusher of controlled variable axial length; - the assembly comprises a system for controlling the length of the pusher of variable axial length as a function of at least one control parameter for the injection of fuel into said combustion chamber, between a state of actuation of the high pump pressure and a stop state of the high pressure pump. Pump according to Claim 1, characterized in that : - the pusher (24) of controlled variable axial length is a hydraulic pusher able to transmit or not the thrust of the cam (20) to the axial piston (29) of the high pressure pump (130); and - the control system for the length of the hydraulic tappet (24) comprises a pressurized liquid circuit which is connected (221) in a controlled manner to a control chamber of the hydraulic tappet (24). Pump according to Claim 2, characterized in that the hydraulic pusher (24) comprises two coaxial pistons (202, 204), one of which (202) cooperates with the said cam (20), and the other (204) of which cooperates with the axial piston of the high pressure pump and which are axially linked together by axial coupling means (209) which are controlled according to the supply to said control chamber of the hydraulic tappet. Pump according to Claim 3, characterized in that a spring (201) is mounted compressed axially between the two coaxial pistons (202, 204). Assembly for double injection, direct and indirect, of fuel(s) into at least one combustion chamber of a cylinder of a spark-ignition heat engine comprising: - a high-pressure piston pump (130) which supplies fuel to a direct injection zone (120) upstream of at least one injector (132) for direct fuel injection into said combustion chamber; and - a rotating cam (20) for actuating the high pressure pump which acts on an axial piston (29) of the high pressure pump (130) by means of a tappet (24) which is interposed axially between the cam (20) drive and the piston (29) of the high pressure pump (130) characterized in that : - the pusher (24) is a pusher of controlled variable axial length; - the assembly comprises a system for controlling the length of the pusher of variable axial length as a function of at least one control parameter for the injection of fuel into said combustion chamber, between a state of actuation of the high pump pressure and a stop state of the high pressure pump. Assembly according to the preceding claim, characterized in that : - the pusher (24) of controlled variable axial length is a hydraulic pusher able to transmit or not the thrust of the cam (20) to the axial piston (29) of the high pressure pump (130); and - the control system for the length of the hydraulic tappet (24) comprises a pressurized liquid circuit which is connected (221) in a controlled manner to a control chamber of the hydraulic tappet (24). Assembly according to the preceding claim, characterized in that the hydraulic tappet (24) comprises two coaxial pistons (202, 204), one of which (202) cooperates with the said cam (20), and the other (204) of which cooperates with the axial piston of the high-pressure pump and which are axially linked to one another by axial coupling means (209) which are controlled according to the supply to said control chamber of the hydraulic tappet. Assembly according to Claim 3, characterized in that a spring (201) is mounted compressed axially between the two coaxial pistons (202, 204). Heat engine, characterized in that it comprises a high-pressure pump according to any one of Claims 1 to 4. Heat engine, characterized in that it comprises a set of double injection, direct and indirect, of fuel(s) according to any one of Claims 5 to 8.

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