Arrangement comprising a cylinder head and a spark plug for a spark-ignition engine

Abstract

Arrangement (10) comprising a cylinder head (3) equipped with a spark plug (4) comprising at least one hole (46) opening outwards into an internal volume (400) of said spark plug and at least one hole (45) providing the fluidic connection between the internal volume (400) and a combustion chamber (23), the arrangement (10) comprising a cooling air flow supply circuit (5) allowing the circulation of said flow to the internal volume (400), a pump (6) configured to propel said flow and at least one regulating means (7) for the circulation of the cooling air flow.

Description

[0001] DESCRIPTION

[0002] Arrangement comprising a cylinder head and a spark plug for a spark-ignition engine

[0003] The invention relates to an arrangement comprising a cylinder head and a spark plug for a spark-ignition engine. The invention also extends to a spark plug for an arrangement according to the invention. Lastly, the invention relates to an operating mode for the arrangement according to the invention.

[0004] In so-called “hydrogen” combustion engines, i.e. using dihydrogen as fuel, combustion can be extremely fast and generate very high gas temperatures in each of the combustion chambers of the engine. This is particularly the case when the air / fuel mixture is in stoichiometric proportions or close to stoichiometry. It is thus essential, in such engines, to limit the combustion temperature in order, on the one hand, to reduce the emissions of nitrogen oxides which form at very high temperature and, on the other hand, to avoid creating hot spots within the engine likely to initiate early combustion during the following combustion cycles, also called pre-ignition phenomenon, corresponding to an ignition of part of the air / fuel mixture by a hot spot before the spark-ignition by the spark plug. Indeed, since hydrogen has wide flammability ranges, it is sensitive to the potentially destructive phenomenon of preignition. In the event of pre-ignition, the initiation of combustion occurs early in the compression time of the engine cycle, which generates very rapid combustion causing very large increases in temperature and pressure in the cylinder, which can themselves generate new hot spots.

[0005] In order to limit the combustion temperature, it is known to increase the air / fuel ratio by means of a supercharging device in order to move away from stoichiometric conditions. Nevertheless, such a principle can be tricky to implement, particularly during transient periods of engine operating mode when the response time of the supercharging devices naturally generates a temporary enrichment of the air / fuel mixture which can then approach stoichiometric conditions.

[0006] The spark plug is naturally one of the potential hot spots of the engine that can serve as a seat for the pre-ignition phenomenon. On the one hand, it is a naturally hot part, since it is at its level that the sparks that will initiate each combustion will be triggered. In addition, conventional spark plugs comprise protruding electrodes constituting a protrusion that protrudes from the smooth surface of the combustion chamber and are consequently liable to store heat by convection during combustion times, thereby forming hot spots and damaging the spark plug.

[0007] In order to solve such a disadvantage, it is therefore known to limit the combustion temperature and prevent the pre-ignition phenomenon by limiting the formation of hot spots by cooling the cylinder head and / or the spark plug by means of a liquid cooling fluid. Such cooling may be carried out at a distance from the spark plug, by cooling the walls of the cylinder head and tend not to be sufficient. Other cooling implemented at the spark plug requires the integration of a complex, bulky liquid coolant circuit, unsuitable for an already congested environment.

[0008] The present invention falls within this context and aims to propose alternatives to the known cylinder heads and spark plugs that are suitable for a hydrogen engine and make it possible to limit, or even prevent, the formation of hot spots within the cylinder head and more particularly at the level of the spark plugs.

[0009] The invention relates to an arrangement comprising a cylinder head for a sparkignition engine, the cylinder head comprising at least one spark plug well configured to open outwards into a combustion chamber of a cylinder, the arrangement further comprising:

[0010] - at least one spark plug disposed in the well and comprising an electrically insulating body and an electrically conductive base delimiting an internal volume of said spark plug, the base comprising at least one hole opening outwards into the internal volume and at least one hole configured to provide the fluidic connection between the internal volume and the combustion chamber;

[0011] - a cooling air flow supply circuit arranged in fluid connection with the internal volume of the spark plug through the at least one hole so as to allow the flow of cooling air to the internal volume, in contact with the spark plug;

[0012] - a pump configured to propel the flow of cooling air to the internal volume via at least one supply circuit and hole;

[0013] - at least one regulating means for the flow of the cooling air arranged on a passage of the cooling air flow in the supply circuit so as to regulate the flow of said flow through the internal volume. For example, one of the regulating mechanisms for the flow is a check valve containing at least one ball and one spring.

[0014] In particular, the arrangement further comprises an intake circuit, equipped with an intake valve, and an exhaust circuit, equipped with an exhaust valve, the at least one supply circuit being connected by a fluidic connection to the intake circuit so that a cooling air flow is taken from an intake air flow circulating in the intake circuit.

[0015] For example, the cooling air flow supply circuit comprises a supply manifold, arranged upstream of the regulating means in a direction of flow of the cooling air flow, and at least one channel, arranged downstream of the regulating means.

[0016] According to an exemplary embodiment, the cylinder head comprises a plurality of spark plug wells, each equipped with a spark plug, the power circuit comprising:

[0017] - a plurality of manifolds, each manifold being configured to be in fluidic connection with the internal volume of one of the spark plugs arranged in one of the wells; or

[0018] - a single manifold being configured to be in fluidic connection with the internal volume specific to the spark plugs arranged in the plurality of wells.

[0019] In particular, the cooling air flow supply circuit comprises at least one intermediate cavity, arranged in the cylinder head so as to receive at least a part of the spark plug, the intermediate cavity housing a part of the spark plug comprising the at least one hole.

[0020] According to one exemplary embodiment, the cylinder head comprises an opening configured to open outwards into the combustion chamber, a first cavity delimiting at least a part of the spark plug well housing the spark plug and a second cavity, housing the regulating means, the first cavity and the second cavity being in a fluidic connection with the opening. Alternatively, the cylinder head includes an opening configured to open outwards into the combustion chamber, the spark plug and the regulating means being arranged in a common or distinct cavity or plurality of cavities.

[0021] In particular, the spark plug comprises a thread, arranged over at least a part of a height of the base, defined along a first direction of the spark plug, the at least one hole being arranged at the level of the thread or the at least one hole being arranged in a part of the base interposed between the thread and an end part of the spark plug comprising the at least one hole.

[0022] Also, the arrangement may comprise at least one cylinder delimiting a combustion chamber and a movable piston arranged in the at least one cylinder, the cylinder head being associated with said cylinder so as to form a spark-ignition engine, the at least one hole of the spark plug opening outwards into the combustion chamber.

[0023] Optionally, the arrangement comprises a pump control device and at least one pressure sensor, the control device being configured to regulate a pressure of the cooling flow in the supply circuit.

[0024] The invention also relates to a spark plug for an arrangement according to the invention, comprising an electrically insulating body and an electrically conductive base delimiting an internal volume of said spark plug, the spark plug comprising:

[0025] - at least one hole capable of allowing the passage of a flow of cooling air from the internal volume to a combustion chamber of a cylinder, the at least one hole being arranged at an end wall of the base configured to face said combustion chamber; and

[0026] - at least one hole, arranged in a side wall of the base, connected to the end wall, the at least one hole opening outwards into the internal volume and being configured to provide a fluidic connection between a cooling fluid supply circuit and the internal volume.

[0027] Lastly, the invention relates to an operating mode for an arrangement according to the invention, comprising:

[0028] - an intake time comprising the injection, towards the cylinder, of an intake air flow and the injection of a cooling air flow drawn from the intake air flow and propelled, via the pump, through the at least one supply circuit and the internal volume of the spark plug so as to implement a heat exchange with at least part of said spark plug, the cooling air flow being discharged towards the combustion chamber via the at least one hole of the spark plug; then

[0029] - a compression time comprising the injection, towards the cylinder, of a fuel flow so as to form an air-fuel mixture, an increase in the pressure in the cylinder and then the ignition of said mixture in the combustion chamber; then

[0030] - an expansion time wherein the air-fuel mixture contained in the cylinder ignites; then

[0031] - an exhaust time including the rise of the piston. Any further details, features and advantages shall be evident from the detailed description given below, which is illustrative and non-limiting, with reference to the various exemplary embodiments illustrated in the following figures:

[0032] Figure 1 is a schematic representation of an embodiment of a vehicle equipped with an arrangement in accordance with the invention and with a spark-ignition engine comprising a cylinder head equipped with a spark plug.

[0033] Figure 2 is a schematic representation of the arrangement comprising the cylinder head equipped with a spark plug.

[0034] Figure 3 is a schematic representation of the operating mode of the engine in the arrangement during an intake time.

[0035] Figure 4 is a schematic representation of the operating mode of the engine in the arrangement during an exhaust time.

[0036] Figure 1 schematically illustrates an exemplary embodiment of a motor vehicle 1 according to the invention. In particular, the motor vehicle 1 is equipped with a sparkignition engine 2 according to the invention. The spark-ignition engine 2 is a heat engine, particularly a hydrogen engine, i.e. a combustion engine using dihydrogen as fuel. The vehicle 1 could be of any type, for example, a passenger car, a commercial vehicle, a truck or a bus. In particular, the vehicle 1 under consideration may be a connected and / or autonomous vehicle.

[0037] The conventional spark-ignition engine 2 is equipped with a cylinder head 3 and at least one cylinder 21 , wherein a mobile piston 22 is positioned. The at least one cylinder 21 delimits a combustion chamber 23 wherein the piston 22 moves and into which air and fuel, in particular hydrogen, are introduced so as to form an air-fuel mixture, also referred to as a fuel mixture. In the example illustrated, in a non-limiting manner, the spark-ignition engine 2 comprises four cylinders 21 in line.

[0038] The vehicle particularly comprises an arrangement 10 comprising the cylinder head 3 of the engine 2, said cylinder head 3 comprising at least one spark plug well 30. In particular, the cylinder head 3 comprises a plurality of walls, all or part of said cylinder head walls 3 delimiting the at least one spark plug well 30. The cylinder head 3 also includes at least one spark plug 4 arranged at least in part in the at least one spark plug well 30. The arrangement 10 also comprises at least one circuit 5 for supplying a flow of cooling air FR configured to allow the circulation of a flow of cooling air FR capable of capturing calories from the spark plug 4 so as to allow its cooling. The arrangement 10 also comprises a pump 6, configured to propel the flow of cooling air FR towards the spark plug 4 via the supply circuit 5, and at least one means 7 for regulating the circulation of said air flow.

[0039] Optionally, the vehicle 1 , particularly the arrangement 10, further comprises an air intake circuit 31 and an exhaust circuit 33, both arranged so as to be in fluidic connection with the cylinder 21 of the engine 2. Throughout the description below, the terms “upstream” and “downstream” refer to a direction of circulation of a considered flow, shown in the figures by arrows.

[0040] Optionally but preferentially, the intake circuit 31 comprises, in particular successively in a direction of circulation of an intake air flow FA, an air filter 31 a, a flow meter 31 b capable of measuring the mass flow rate of air entering the engine 2, a turbocharger compressor 31 c capable of compressing the intake air flow FA and an intake manifold 31 d, also referred to as a distributor. In particular, the intake manifold 31 d is equipped with at least one pressure sensor 31 e, also referred to as intake pressure sensor 31 e, configured to measure the pressure of the air admitted into the cylinder or into the cylinders 21 of the engine 2. This intake pressure sensor 31 e is generally housed in the intake manifold 31 d. According to one exemplary embodiment, the intake manifold 31 d comprises a plenum and a plurality of intake ducts each serving one of the cylinders 21 of the engine 2.

[0041] Also optionally, the intake circuit 31 comprises at least one intake valve or throttle box, not shown, arranged downstream of the compressor 31c and making it possible to regulate the flow rate of the intake air flow FA entering the engine 2.

[0042] Optionally, the exhaust circuit 33 comprises, depending on the direction of circulation of an exhaust air flow leaving the cylinder, an exhaust manifold 33a, a turbine 33b of the turbocharger 31c, for example mounted on a common shaft with the compressor 31c, and at least one pollution control device 33c.

[0043] As illustrated, according to an exemplary embodiment, the intake circuit 31 comprises an intake pipe 31 f, provided in the material of the cylinder head 3, equipped with an intake valve 32 and configured to be connected to the intake duct, or to one of the intake ducts, of the intake circuit 31 . Similarly, the exhaust circuit 33 may comprise an exhaust pipe 33d, provided in the material of the cylinder head 3, equipped with an exhaust valve 34 and capable of being connected to the exhaust duct, or to one of the exhaust ducts, of the exhaust circuit 33. The cylinder head 3 is installed in the engine 2 so as to participate in the implementation of a fluidic connection between the intake circuit 31 and the exhaust circuit 33 on the one hand, and the combustion chamber 23 of one or more cylinders 21 , on other side. The inlet valve 32 and the exhaust valve 34 are conventionally mounted mobile and designed to facilitate or hinder the fluidic connection between the pipe wherein each valve is installed and the combustion chamber 23.

[0044] It is understood that the following description is made with reference to a considered cylinder 21 of the engine 2 and with reference to a part of the cylinder head 3 associated with the arrangement 10. Nevertheless, it extends to a spark-ignition engine 2 with a plurality of cylinders 21 each equipped with a piston 22 and, alternatively, the cylinder head 3 with a plurality of shafts 30, spark plugs 4 or else intake valves 32 and exhaust valves 34, as further explained below.

[0045] The at least one spark plug well 30 is adapted to receive all or part of the at least one spark plug 4. A first end of the well 30 comprises an opening 35 designed to open into the combustion chamber 23 of the associated cylinder 21 when the engine 2 is assembled.

[0046] The spark plug 4 is of the standard type. Here “standard” means that the spark plug 4 has no built-in ignition prechamber, at which sparks can be generated, and, on the contrary, the spark plug 4 of the present invention is able to generates further explained below, sparks directly at the level of the combustion chamber 23 of the engine 2, as further explained below. The conventional spark plug 4 has at least one electrically insulating body 41 and an electrically conductive base 42 together delimiting an internal volume 400 of said spark plug. The electrically insulating body 41 is made of an electrically insulating material such as ceramic, especially aluminabased. The base 42 is made of an electrically conductive material, particularly metal. For example, the spark plug 4 extends along a first direction 100.

[0047] The spark plug 4 comprises at least one wall, in particular a wall of the base 42. For example, the spark plug 4 includes a side wall 43 or a plurality of side walls 43 connected to an end wall 44, facing the combustion chamber 23. According to a nonlimiting exemplary embodiment, the spark plug 4 comprises a cylindrical shape or part of a cylindrical shape. In this case, and in a non-limiting manner, the base 42 comprises a single side wall 43 and the end wall 44, which are inscribed in a cylindrical or substantially cylindrical shape.

[0048] The spark plug 4 comprises at least one hole 45 providing the fluidic connection between the internal volume 400 of the spark plug 4 and the combustion chamber 23 of the cylinder 21 . In particular, the at least one hole 45 is able to allow passage of the cooling air flow FR from the internal volume 400 to the combustion chamber 23 of the cylinder 21 , as further described below with reference to the method according to the invention. In this case, the at least one hole 45 is arranged in the end wall 44.

[0049] The spark plug 4 further comprises at least one hole 46 opening outwards into the internal volume 400 and configured to provide a fluidic connection between the cooling fluid supply circuit 5 and said internal volume 400. The term “opening outwards” means that the at least one hole 46 extends right through within one of the walls of the spark plug 4. For example, the at least one hole 46 is arranged in the side wall 43 or in one of the side walls of the spark plug 4, in particular of the base 42. The at least one hole 46 allows the flow of cooling air FR to pass from the supply circuit 5 to the internal volume 400 so as to bring it into contact with the inside of the spark plug 4, before said flow is discharged to the combustion chamber 23 via the hole 45.

[0050] According to a particular exemplary embodiment, illustrated in Figures 2 to 4, the spark plug 4 comprises a thread 47, arranged over at least part of a height of the base 42, defined along the first direction 100. The thread 47 is formed at the level of an external surface of the spark plug 4, in particular the base 42, facing the walls of the cylinder head 3, in particular an external surface of the side wall 43 or one of the side walls of the spark plug 4. According to an exemplary illustrated in Figure 2, the at least one hole 46 is arranged in a part of the base 42 interposed, along the first direction 100, between the thread 47 and an end part of the spark plug 4 comprising the at least one hole 45, here the end wall 44. Alternatively, the at least one hole 46 is arranged at the level of the thread 47.

[0051] As is known, the spark plug 4 comprises at least one central electrode 48 and at least one mass electrode 49. The at least one central electrode 48 and the at least one ground electrode 49 are separated from each other by an inter-electrode gap, i.e. a gap separating two electrodes not in contact intended to be the seat of sparks between said electrodes. It is understood that the spark plug 4 may have a plurality of central electrodes 48 and / or ground electrodes 49. The at least one central electrode 48 extends into the internal volume 400 of the spark plug 4 while the at least one ground electrode 49 is included and arranged in the base 42 so as to participate in delimiting said internal volume 400. For example, the at least one ground electrode 49 is included in the end wall 44. Also, the various electrodes are shaped and arranged so as not to form protuberances or protrusions projecting from the rest of the spark plug 4, in particular from the walls of the spark plug 4. Such a principle advantageously makes it possible to limit, or even prevent, the formation of hot spots at the electrodes. In particular, the end wall 44 of the spark plug and the at least one central electrode 49 are inscribed in a plane, or substantially plane, surface arranged in the continuity of an internal surface of the cylinder head, facing the combustion chamber 23.

[0052] Alternatively, the vehicle 1 is equipped with a spark ignition system, not shown, including a spark control unit and a high-voltage electrical circuit designed to supply electrical energy to one or more central electrodes 48 of the spark plug 4.

[0053] Advantageously, the arrangement 10 comprises at least one means for sealing 36 arranged at the interface between the spark plug 4 and the cylinder head 3, for example positioned around the spark plug 4. The sealing means 36 advantageously makes it possible to limit the circulation of the cooling air flow FR in the spark plug well 30.

[0054] As indicated above, the cooling air flow FR supply circuit 5 is configured to supply the cooling air flow FR to the spark plug 4 in order to cool the latter. "Cooling air flow FR" is thus understood to mean an air flow capable of capturing at least part of the calories of the spark plug 4 accumulated during previous combustion. Said circuit is at least partly comprised in the cylinder head 3, for example in at least one of the walls of the cylinder head 3. The supply circuit 5 is arranged in fluidic connection with the internal volume 400 of the spark plug 4 via the at least one hole 46 so as to allow the flow of cooling air FR to the internal volume 400 and into the internal volume 400. The cooling air flow FR then circulates in contact with at least part of the base 42 of the spark plug 4 and allows the latter to cool. Also, the flow of cooling air circulates in the internal volume 400 and to the combustion chamber 23 in order to capture calories from the at least one central electrode 48 and the at least one ground electrode 49. It thus prevents the formation of hot spots at the base 42 and the various electrodes by lowering their temperature, in particular before the implementation of combustion.

[0055] According to a preferred exemplary embodiment illustrated by Figure 1 , the supply circuit 5 of the cooling air flow FR is connected by a fluidic connection to the intake circuit 31 at a bifurcation point 51 so that the cooling air flow FR is taken from an intake air flow FA circulating in the intake circuit 31 . Thus, at the bifurcation point 51 , part of the intake air flow FA is taken and separated in order to form, on the one hand, the cooling air flow FR, directed to the supply circuit 5 and to the internal volume 400 of the spark plug 4 before being returned to the combustion chamber 23, and, on the other hand, a remaining intake air flow FAr sent to the combustion chamber 23 of the cylinder 21 for combustion without passing through the internal volume 400 of the spark plug 4.

[0056] Preferably, the supply circuit 5 is connected to the intake duct 31 downstream of the filter 31 a and the flowmeter 31 b according to the direction of flow of the intake air flow FA. In other words, the bifurcation point 51 is arranged downstream of the filter 31 a and the flowmeter 31 b. In this way, the air taken off to form the cooling air flow FR is free of particles, i.e. clean, and is taken into consideration in the calculation of the flow of fresh air arriving in the combustion chamber 23, conventionally determined by an engine control software 2. The overall amount of air sucked in the cylinder 21 thus corresponds to the air flow measured by the flowmeter, this flow corresponding to the sum of the flow rate of the cooling air flow FR and the flow rate of the remaining intake air flow FAr.

[0057] According to an illustrated exemplary embodiment, simpler to implement, the supply circuit 5 is connected to the intake circuit 31 at a bifurcation point 51 arranged upstream of the compressor 31 c according to the direction of flow of the intake flow. Alternatively, the supply circuit 5 is connected to the intake circuit 31 at a bifurcation point 51 arranged downstream of the compressor 31c according to the direction of flow of the intake flow. Such a principle, which is more complex to implement because of the bulk present downstream of said compressor 31 c, advantageously makes it possible to sample a flow of compressed cooling air FR, thereby reducing the magnitude of the force to be provided by the pump 6. Figures 1 to 4 illustrate an exemplary embodiment wherein the power supply circuit 5 generally comprises at least one power supply manifold 52 and at least one channel 53. The regulating means 7 is arranged on the passage of the cooling air flow FR in the supply circuit 5, corresponding to a trajectory of the cooling air flow FR. In particular, the at least one manifold 52 is arranged upstream of the regulating means 7 in the direction of circulation of the cooling air flow FR while the at least one channel 53 is arranged downstream of the regulating means 7, in particular so as to extend between the at least one regulating means 7 and the at least one hole 46. The at least one manifold 52 and the at least one channel 53 are configured to be in fluidic connection with each other, thus being open at their different ends. It is thus possible to distinguish a first part 5a of the supply circuit 5, arranged upstream of the regulating means 7, in particular between the bifurcation point 51 and said regulating means 7, and a second part 5b of the supply circuit 5, arranged downstream of the regulating means 7, for example between the latter and the at least one hole 46 of the spark plug 4.

[0058] The at least one manifold 52 is at least partially machined in the material of the cylinder head 3, at the level of at least one of the walls of the cylinder head 3. Also, for example, part of said manifold 52 may be formed by at least one pipe connecting the bifurcation point 51 to one of the walls of the cylinder head 3. Similarly, the at least one channel 53 is machined in the material of the cylinder head 3. The arrangement 10 preferably comprises at least as many channels 53 as spark plugs 4 and / or cylinders 21 , each of said channels 53 being configured to be arranged in fluidic connection with the internal volume 400 specific to one of the spark plugs 4 of the cylinder head 3 and, indirectly, in fluidic connection with the combustion chamber 23 of one of the cylinders 21 of the engine 2.

[0059] Figure 1 schematically illustrates an preferred exemplary embodiment of a cylinder head 3 equipped with a plurality of spark plugs 4 and regulating means 47 associated with a supply circuit 5 comprising a single manifold 52, configured to bring the flow of cooling air FR to the different spark plugs 4. The single manifold 52 is associated with a plurality of channels each leading a part of the cooling air flow FR to one of the spark plugs 4. The supply circuit 5 is then advantageously connected to the supply circuit 5 by a single bifurcation point 51 . Each of the regulating means may be arranged within one of the channels 53 or upstream of said channels, for example in the manifold 52 or between the manifold 52 and said channels 53 as described above.

[0060] According to an alternative embodiment, not shown, the supply circuit 5 comprises a plurality of manifolds 52 and channels 53, each manifold 52 being configured to supply a flow of cooling air FR to at least one of the channels 53 and to one of the spark plugs 4. The arrangement 10 then comprises a plurality of bifurcation points 51 , in particular connected to the intake circuit 31 .

[0061] Optionally, the supply circuit 5 of the cooling air flow FR comprises at least one intermediate cavity 50, arranged in at least one wall of the cylinder head 3 so as to surround and / or receive at least part of the spark plug 4. In particular, the intermediate cavity 50 forms a recess in the cylinder head 3 surrounding the spark plug 4 over the entire circumference of the external surface of the spark plug 4. The intermediate cavity 50 is machined in the cylinder head 3 and defines a cylindrical shape allowing the circulation of the cooling air flow FR in contact with a part of the base of the spark plug 4. Such a principle advantageously allows the cooling of part of external surface of the spark plug 4. The intermediate cavity 50 houses a part of the spark plug 4, in particular the base 42, comprising the at least one hole 46 so as to ensure the fluidic connection between the rest of the supply circuit 5 and the at least one hole 46. Optionally, the spark plug 4, in particular the base 42, comprises a plurality of holes 46 distributed around the circumference of the spark plug, the intermediate cavity 50 being shaped and dimensioned to receive the part of the spark plug 4 housing said holes. In this way, the cooling air flow FR enters the internal volume 400 via the various holes 46, the intermediate cavity 50 allowing the cooling air flow FR to be distributed in the various holes 46.

[0062] As indicated above, the pump 6 is configured to take part of the intake air flow FA in order to form the cooling air flow FR. It also makes it possible to propel said flow of cooling air FR towards the internal volume 400 of the spark plug 4 via the supply circuit 5 and the at least one hole 46. In particular, the pump 6 is an electric pump 6. The pump 6 advantageously allows the circulation of the cooling air flow FR at a desired defined pressure, particularly at a pressure higher than the pressure prevailing in the combustion chamber 23 of the engine 2, corresponding in particular substantially to the pressure prevailing in the exhaust manifold 33a during the intake time when the intake valve 32 of the engine 2 is open, and in particular measured by the intake pressure sensor 31 e.

[0063] It should also be noted that, during the intake time, when the intake valve 32 of the engine 2 is open, or the intake valves 32, it can be considered that the pressure in the cylinder 21 , more precisely in the combustion chamber 23, is substantially equal to the supercharging pressure measured by the supply pressure sensor 31 e, the load losses between the pressure measurement point and the combustion chamber 23 being negligible.

[0064] Optionally but preferably, the vehicle 1 and / or the arrangement 10 comprises a control device 61 of the pump 6 and at least one pressure sensor 54 of the cooling air flow FR, the control device 61 being configured to control the operation of the pump 6 so as to adapt the pressure of the cooling air flow FR as required according to a pressure measured at, at least, one point of the cylinder head 3 and / or of the intake circuit 31 . For example, as illustrated in Figure 1 , the vehicle 1 comprises the intake pressure sensor 31 e, capable of measuring the pressure of the intake air flow remaining FAr in the intake duct, for example arranged at the intake manifold 31 d, and / or a pressure sensor 54 arranged at the level of the supply circuit 5, configured to measure the pressure of the cooling air flow FR.

[0065] The regulating means 7 is configured to regulate the circulation of the cooling air flow FR through the supply circuit 5 and towards the internal volume 400 of the spark plug 4. The term “regulating” is understood to mean the possibility of allowing or interrupting the circulation of the cooling flow in at least one part of the supply circuit 5 and through the spark plug 4. Consequently, such regulating also consists in allowing or interrupting the fluidic connection between at least part of the supply circuit 5 and the internal volume 400 of the spark plug 4. In particular, the regulating means 7 is of the passive type. A "passive" control means that the regulating means 7 itself is not directly actuated in a motorised manner or that it does not require an energy supply, for example electrical.

[0066] According to an exemplary preferred embodiment, one or more regulating mechanisms 7 is a check valve comprising at least one ball 71 and a spring 72. The spring 72 is in particular arranged to bear on an intermediate surface making it possible to hold the spring 72. Optionally, the regulating means 7 further comprises a device 74 for holding the ball 71 . The holding device 74 comprises a tubing arranged in the continuity of the passage, or of the trajectory, of the flow of cooling air FR so as to allow the circulation of said flow. The holding device 74 also comprises a recess, arranged with reference to the tubing and configured to receive the ball 71 .

[0067] The regulating means 7 allows the flow of cooling air FR to the internal volume 400 of the spark plug 4 when the pressure in the supply circuit 5, in particular in the first part 5a of the supply circuit 5, is greater than the pressure prevailing in the combustion chamber 23 of the engine 2, i.e. the intake pressure prevailing in the intake manifold 31 d as explained above. Furthermore, the regulating means 7 prevents the reverse circulation of a flow of air-fuel mixture from the internal volume 400 to the entire supply circuit 5 when the pressure in the internal volume 400 and / or the combustion chamber 23 is greater than the pressure of the supply circuit 5, in particular of the first part 5 a of the supply circuit 5 arranged upstream of the regulating means 7.

[0068] More particularly, the ball 71 is configured to be moved between a “closed” configuration and an “open” configuration. In the "closed" configuration, the spring 72 is in the nominal position, the ball 71 is arranged in support of the spring 72, in particular the ball 71 extends into the recess of the holding device 74. As a result, the ball 71 blocks the flow of the cooling air flow FR to the internal volume 400 of the spark plug 4, here by preventing the passage of the cooling air flow FR through the tubing of the holding device 74 and through the latter. In the "open" configuration, the flow of cooling air FR is propelled into the supply circuit 5 with sufficient pressure to move the ball 71 so that it is moved out of the recess of the holding device 74. The ball 71 then exerts a force on the spring 72 and compresses it. The movement of the ball 71 then allows the flow of cooling air FR to pass through the holding means 74, towards the internal volume 400 where it captures the calories from a part of the base 42 and the different electrodes, thus allowing them to cool. The air flow is then discharged to the combustion chamber 23 through the at least one hole 45.

[0069] Also, the ball 71 prevents the passage of the air-fuel mixture to the entire supply circuit 5, particularly the rise of the air-fuel mixture to the first part 5a of the supply circuit 5. Such a configuration can be observed when no flow of cooling air FR is projected into the supply circuit 5 or when the pressure of said flow of cooling air FR is insufficient to allow the actuation of the regulating means 7, in this case the displacement of the ball 71. For example, the spring 72 is previously calibrated in order to actuate the regulating means 7 from a predefined pressure threshold of the cooling air flow FR during an intake time of the engine cycle 2 and / or from a predefined pressure differential threshold between the pressure of the cooling air flow FR and the pressure in the combustion chamber 23 and / or in the second part of the intake circuit 5b.

[0070] For example, the at least one regulating means 7 is arranged in a support 75 delimiting an intermediate passage within the supply circuit 5. In particular, the support 75 is a part arranged in the cylinder head 3 by hooping, for example made of a metallic material such as steel, resistant to high temperatures that can exceed 600°C. The support 75 thus carries the regulating means 7 and comprises cut-outs making it possible to ensure the circulation of the cooling air flow FR, particularly its inlet and outlet within the support 75. Specifically and in a non-limiting manner, a first cutout is arranged upstream of the regulating means 7 and is configured to ensure the fluidic connection with the first part 5a of the supply circuit 5, here formed by the manifold 52 in particular, while a second cutout is arranged downstream of the regulating means 7 and is configured to ensure the fluidic connection with the second part 5b of the supply circuit 5, here formed by the channel or one of the channels 53.

[0071] Optionally but preferentially, the cylinder head 3 comprises a first cavity 301 and a second cavity 302 both in fluidic connection with the opening 35 configured to open outwards into the combustion chamber 23. The first cavity 301 forms the spark plug well 30 housing the spark plug 4 while the second cavity 302 houses the regulating means 7, in particular the assembly formed by the support 75 and the regulating means 7. For example, the first cavity 301 and the second cavity extend along the first direction 100, parallel or substantially parallel to each other. In particular, the first cavity 301 and the second cavity 302 are adjacent to each other and separated by at least one intermediate wall of the cylinder head 3.

[0072] The invention also relates to an operating mode for the arrangement 10 comprising an engine 2 with spark-ignition according to the invention. This process is implemented during an engine cycle 2, which typically comprises intake, compression, expansion and exhaust times. As illustrated in Figure 3, during the intake time, in a conventional manner, the intake valve 32 is open, the piston descends to the bottom dead centre, the intake air flow FA circulates in the intake circuit 31 in the direction of the combustion chamber 23.

[0073] The method then comprises, in parallel with the intake of the intake air flow FA, the circulation of the cooling air flow FR in the supply circuit 5. The flow of cooling air FR is propelled by the pump 6 through the supply circuit 5 to the internal volume 400 of the spark plug 4. In contact with the spark plug 4, in particular the base 42 and the various electrodes, the flow of cooling air FR captures calories from the heated spark plug 4 and allows it to cool before the implementation of a new combustion. The flow of cooling air FR thus heated is then discharged to the combustion chamber through the at least one hole 51.

[0074] As indicated above, according to a preferred embodiment, the cooling air flow FR is drawn from the intake air flow FA, in particular taken from the intake circuit 31 upstream or downstream of the compressor 31c. The cooling air flow FR is then a part of the intake air flow FA extracted by the pump 6 and diverted from its conventional trajectory, namely from the intake circuit 31 , and redirected to the internal volume 400 of the spark plug 4 via the supply circuit 5 while the remaining intake air flow FAr continues in the intake circuit 31 to the combustion chamber 23. Advantageously, the extraction of part of the intake air flow FA allows the spark plug to be cooled without the need for a built-in air reservoir in the cylinder head 3.

[0075] The cooling air flow FR is propelled under pressure by the electric pump 6 controlled by the control device 71 of the pump 6. The pressure of the cooling air flow FR is particularly regulated so as to allow the actuation of the at least one regulating means 6. In particular, the pressure of the cooling air flow FR, measured in the supply circuit 5, is strictly higher than the pressure measured in the combustion chamber 23, and measured during the intake time by the intake pressure sensor 31 e housed in the intake manifold 31 d, in order to allow the opening of at least one regulating means 7. As previously indicated, due to such a pressure differential, the ball 71 is moved and exerts a force on the spring 72. It frees the passage of the flow of cooling air FR, here by being moved out of the recess and releasing the tubing of the holding device 74, so as to allow the circulation of the flow of cooling air towards the internal volume 400 of the spark plug 4. The at least one regulating means 7 furthermore advantageously makes it possible to avoid back flow of the cooling air flow. Optionally but preferably, the pressure of the cooling air flow FR can be adjusted by the control device 71 of the pump 6 according to the measured pressure of the remaining intake air flow FAr, in particular according to the pressure prevailing in the intake manifold 31 d as measured by the intake pressure sensor 31 e. It should be noted that, when the intake valve 32 opens and the piston 22 descends, the pressure in the cylinder 21 and the combustion chamber 23 tends to approach the pressure measured in the intake circuit 31 . The pressure of the intake flow FA varies according to the operating mode of the engine. The same applies to the pressure of the remaining intake air flow far.

[0076] In particular, at low load, the remaining intake flow pressure FAr, for example measured at the level of intake manifold 31 d, is well below atmospheric pressure. The pressure of the cooling air flow FR circulating in the supply circuit can then be low as long as it remains strictly higher than the pressure of the remaining intake air flow far or the pressure of the combustion chamber 23. Since fuel combustion temperatures are lower at low load, the spark plug 4 will be less heated and less likely to generate hot spots. The flow rate of the cooling air flow FR can thus be lower than in supercharging conditions, while making it possible to ensure appropriate cooling of the spark plug 4.

[0077] Conversely, when the engine 2 is supercharged, i.e. operating at a high load, the pressure of the intake flow FA, particularly the remaining intake air flow FAr is much higher than atmospheric pressure. It will therefore be necessary to propel the flow of cooling air FR to a pressure higher than that implemented in a low load situation. Also, the combustion temperatures then tend to be higher than in a low load situation and the flow rate of the cooling air flow FR must be higher in order to prevent the formation of hot spots at the spark plug 4.

[0078] As it is known, the engine cycle 2 continues with the compression time. The inlet valve 32 and the exhaust valve 34 are closed. Fuel injection, in this case dihydrogen in particular, is initiated. The atomized fuel is mixed with the moving intake air flow FA to form a fuel-air mixture in the combustion chamber 23.

[0079] It will be noted that, in the case of hydrogen, the fuel is injected during the compression time, valves 32, 34 closed, rather than during the intake time as is the case with conventional fuels such as petrol, in order to avoid a back flow of fuel mixture into the intake manifold 31 d. Indeed, the flammability limits of hydrogen are very extensive, and a hot spot would be enough to ignite the mixture in the intake circuit 31 . The resulting explosion could damage said circuit.

[0080] The fuel mixture is homogenised by the turbulence in the combustion chamber 23 of cylinder 21 . The piston 22 rises in the cylinder 21 towards its top dead point, thereby increasing the pressure in the combustion chamber 23. The regulating means 7 is in a “closed” configuration and the circulation of the cooling air flow FR is interrupted in the internal volume 400. The fluidic connection between the internal volume 400 and the entire supply circuit is thus interrupted. In particular, the fluidic connection between the first part 5a of the supply circuit 5 and the internal volume 400 is interrupted.

[0081] It should be noted that, during the compression time, and by extension during the rest of the engine cycle 2, the blowing of the cooling air flow FR can be maintained in other words it is not interrupted and is permanent. On the other hand, the pressure of said flow is modified by means of the pump 6 as a function of the intake pressure so that the regulating means 7 remains closed. The pump 6 is then active all the time of the engine cycle 2. In particular, the intake pressure, and by extension the pressure in the cylinder 21 is then strictly greater than the pressure of the cooling air flow FR. The regulating means 7, for example the check valve, then closes as soon as the pressure prevailing in the cylinder 21 is strictly greater than the pressure measured in the first part 5a of the supply circuit 5, in particular in the manifold 52.

[0082] Towards the end of the compression time, the spark ignition system triggers a sparkle at spark plug 4, which causes the compressed fuel mixture to burn in the combustion chamber 23. It should be noted that, due to the architecture of the spark plug 4 according to the invention, without a prechamber, ignition takes place essentially outside the spark plug 4 and the internal volume 400, at the level of the combustion chamber 23.

[0083] Then, during the expansion time of the engine cycle 2, the flame front propagates into the combustion chamber 23. The inlet valve 32 and the exhaust valve 34 are then closed. The piston is moved towards the bottom dead point and, due to the high pressure prevailing in the combustion chamber 23, the regulating means 7 is closed, preventing any circulation between the combustion chamber and the entire supply circuit and vice versa.

[0084] Lastly, during the exhaust time, illustrated in Figure 4, the exhaust valve 34 opens. The piston 22 moves upwards and expels the residual burnt gases remaining in the combustion chamber 23 into the exhaust circuit 33. The pressure in the combustion chamber 23 drops but remains strictly higher than the pressure in the supply circuit 5, in particular in the first part 5a of the supply circuit 5, so that the regulating means 7 remains in the "closed" configuration as indicated above and the fluidic connection between the internal volume 400 of the spark plug 4 and the entire supply circuit 5 remains interrupted.

[0085] The arrangement and method according to the invention thus make it possible to solve one of the problems faced by internal combustion engines supplied with dihydrogen, namely the generation of hot spots at the spark plug resulting from the high temperatures to which the spark plug may be subjected due to the high combustion temperatures.

[0086] The present invention advantageously makes it possible to cool the spark plug, in particular before each combustion, so as to ensure its reliability over time, its durability, and so as to prevent it from becoming a hot spot likely to cause the preignition of the air-fuel mixture. The circulation of the cooling air flow directly in contact with the spark plug makes it possible to optimise the cooling implemented and the integration of such cooling in the cylinder head and the engine described above makes it possible to overcome the need to integrate a specific cooling fluid and any associated storage tank, thus making it possible to limit the space required and the costs generated.

[0087] Nevertheless, this invention is not limited to the methods and configurations described and illustrated herein, and it also extends to any equivalent methods or configurations, and any technically effective combination of such methods, insofar as they eventually fulfil the functionalities described and illustrated herein.

Claims

CLAIMS1 . Arrangement (10) comprising a cylinder head (3) for a spark-ignition engine (2), the cylinder head (3) comprising at least one spark plug well (30) configured to open outwards into a combustion chamber (23) of a cylinder (21 ), the arrangement (10) further comprising:- at least one spark plug (4) arranged in the well (30) and comprising an electrically insulating body (41 ) and an electrically conductive base (42) delimiting an internal volume (400) of said spark plug, the base (42) comprising at least one hole (46) opening outwards into the internal volume (400) and at least one hole (45) configured to provide the fluidic connection between the internal volume (400) and the combustion chamber (23);- a cooling air flow (FR) supply circuit (5) arranged in fluidic connection with the internal volume (400) of the spark plug (4) through the at least one hole (46) so as to allow the flow of cooling air (FR) to the internal volume (400), in contact with the spark plug (4);- a pump (6) configured to propel the flow of cooling air (FR) to the internal volume (400) via the at least one supply circuit (5) and at least one hole (46);- at least one means (7) for regulating the circulation of the cooling air flow (FR) arranged on a passage of the cooling air flow (FR) in the supply circuit (5) so as to regulate the circulation of said flow through the internal volume (400).

2. Arrangement (10) according to the preceding claim, further comprising an intake circuit (31 ), equipped with an intake valve (32), and an exhaust circuit (33), equipped with an exhaust valve (34), the at least one supply circuit (5) being connected by a fluidic connection to the intake circuit (31 ) so that a cooling air flow (FR) is taken from an intake air flow (FA) circulating in the intake circuit (31 ).

3. Arrangement (10) according to any of the preceding claims, wherein the cylinder head (3) comprises a plurality of spark plug wells (30), each equipped with a spark plug (4), the power circuit (5) comprising:- a plurality of manifolds (52), each manifold (52) configured to be in a fluidic connection with the internal volume (400) of one of the spark plugs (4) arranged in one of the wells (30); or- a single manifold (52) being configured to be in a fluidic connection with the internal volume (400) of the spark plugs (4) arranged in the plurality of wells (30).

4. Arrangement (10) according to any of the preceding claims, wherein the cooling air flow (FR) supply circuit (5) comprises at least one intermediate cavity (50), arranged in the cylinder head (3) so as to receive at least a part of the spark plug (4), the intermediate cavity (50) housing a part of the spark plug (4) comprising the at least one hole (46).

5. Arrangement (10) according to any of the preceding claims, wherein the cylinder head (3) comprises an opening (35), configured to open into the combustion chamber (23), a first cavity (301 ) delimiting at least a part of the spark plug well (30) housing the spark plug (4) and a second cavity (302), housing the regulating means (7), the first cavity (301 ) and the second cavity (302) being in fluidic connection with the opening (35).

6. Arrangement (10) according to any of the preceding claims, wherein the spark plug (4) comprises a thread (47), arranged over at least a part of a height of the base (42), defined along a first direction (100) of the spark plug (4), the at least one hole (46) being arranged at the level of the thread (47) or the at least one hole (46) being arranged in a part of the base (42) interposed between the thread (47) and an end part of the spark plug (4) comprising the at least one hole (45).

7. Arrangement (10) according to any of the preceding claims, comprising at least one cylinder (21 ) delimiting a combustion chamber (23) and a movable piston (22) arranged in the at least one cylinder (21 ), the cylinder head (3) being associated with the said cylinder so as to form a spark-ignition engine (2), the at least one hole (45) of the spark plug (4) opening outwards into the combustion chamber (23).

8. Arrangement (10) according to the preceding claim, comprising a control device (61 ) of the pump (6) and at least one pressure sensor (31 e), the control device (61 ) being configured to regulate a pressure of the cooling flow (FR) in the supply circuit (5).

9. Spark plug (4) for an arrangement (10) according to any of the preceding claims, comprising an electrically insulating body (41 ) and an electrically conductive base (42) delimiting an internal volume (400) of said spark plug, the spark plug (4) comprising:- at least one hole (45) capable of allowing the passage of a flow of cooling air (FR) from the internal volume (400) to a combustion chamber (23) of a cylinder (21), the at least one hole (45) being arranged at an end wall (44) of the base (42) configured to face said combustion chamber (23); and- at least one hole (46), arranged in a side wall (43) of the base (42), connected to the end wall (44), the at least one hole (46) opening outwards into the internal volume (400) and being configured to provide a fluidic connection between a cooling fluid supply circuit (5) and the internal volume (400).

10. Operating method for an arrangement according to claim 7 or 8, comprising:- an intake time comprising the injection, towards the cylinder (21), of an intake air flow (FA) and the injection of a cooling air flow (FR) drawn from the intake air flow (FA) and propelled, via the pump (6), through the at least one supply circuit (5) and the internal volume (400) of the spark plug (4) so as to implement a heat exchange with at least part of said spark plug, the cooling air flow (FR) being discharged towards the combustion chamber (23) via the at least one hole (45) of the spark plug (4); then- a compression time comprising the injection, towards the cylinder (21), of a fuel flow so as to form an air-fuel mixture, an increase in the pressure in the cylinder (21) and then the ignition of said mixture in the combustion chamber(23); then- an expansion time wherein the air-fuel mixture contained in the cylinder (21) ignites; then- an exhaust time including the rise of the piston (22).

Images