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

Abstract

Title: Arrangement comprising a cylinder head and a spark plug for a spark ignition engine Arrangement (10) comprising a cylinder head (3) equipped with a spark plug (4) comprising at least one orifice (46) opening into an internal volume (400) of said spark plug and at least one hole (45) ensuring the fluid connection between the internal volume (400) and a combustion chamber (23), the arrangement (10) comprising a supply circuit (5) for a cooling air flow allowing the circulation of said flow towards the internal volume (400), a pump (6) configured to propel said flow and at least one means (7) for regulating the circulation of the cooling air flow. Abstract figure: Figure 2

Description

Title of the invention: Arrangement comprising a cylinder head and a spark plug for a spark ignition engine

[0001] 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. The invention finally relates to a method of operating the arrangement according to the invention.

[0002] In so-called "hydrogen" combustion engines, i.e. engines using dihydrogen as fuel, combustion can be extremely rapid and generate very high gas temperatures in each of the engine's combustion chambers. This is particularly the case when the air / fuel mixture is in stoichiometric or close to stoichiometric proportions. 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 are formed at very high temperatures and, on the other hand, to avoid creating hot spots within the engine which are likely to initiate early combustion during the following combustion cycles, also referred to as a pre-ignition phenomenon, corresponding to an ignition of a portion of the air / fuel mixture by a hot spot before the spark is triggered by the spark plug.Indeed, because hydrogen has wide flammability ranges, it is susceptible to the potentially destructive phenomenon of pre-ignition. In the case of pre-ignition, combustion initiation occurs early in the compression stroke of the engine cycle, which generates very rapid combustions causing very large increases in temperature and pressure in the cylinder, which can themselves generate new hot spots.

[0003] 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. However, such a principle can be difficult to implement, particularly during transient periods of engine operation during which the response time of the supercharging devices naturally generates a temporary enrichment of the air / fuel mixture which can then approach stoichiometric conditions.

[0004] The spark plug naturally constitutes one of the potential hot spots in 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 include protruding electrodes constituting a protrusion that protrudes from the smooth surface of the combustion chamber and are, consequently, likely to store heat by convection during combustion times, thus forming hot spots and damaging the spark plug.

[0005] In order to resolve such a drawback, it is therefore known to limit the combustion temperature and to prevent the pre-ignition phenomenon by limiting the formation of hot spots by cooling the cylinder head and / or the spark plug using a liquid cooling fluid. Such cooling can be carried out at a distance from the spark plug, by cooling the walls of the cylinder head and tends not to be sufficient. Other cooling implemented at the spark plug requires the integration of a complex, bulky liquid cooling fluid circuit, unsuitable for an already congested environment.

[0006] The present invention falls within this context and aims to propose alternatives to known cylinder heads and spark plugs which 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 spark plugs.

[0007] The invention relates to an arrangement comprising a cylinder head for a spark-ignition engine, the cylinder head comprising at least one spark plug well configured to open into a combustion chamber of a cylinder, the arrangement further comprising: - at least one spark plug arranged 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 orifice opening into the internal volume and at least one hole configured to ensure the fluid connection between the internal volume and the combustion chamber; - a circuit for supplying a flow of cooling air arranged in fluid connection with the internal volume of the spark plug via the at least one orifice so as to allow the circulation of a flow of cooling air towards the internal volume, in contact with the spark plug; - a pump configured to propel the cooling air flow towards the internal volume via the at least one supply circuit and the at least one orifice; - at least one means for regulating the circulation of the cooling air flow arranged on a passage of the cooling air flow in the supply circuit so as to regulate the circulation of said flow through the internal volume.

[0008] For example, the at least one means for regulating the circulation is a non-return valve comprising at least one ball and a spring.

[0009] In particular, the arrangement further comprises an intake circuit, equipped with a intake valve, and an exhaust circuit, equipped with an exhaust valve, the at least one supply circuit being connected by a fluid connection to the intake circuit so that a flow of cooling air is taken from an intake air flow circulating in the intake circuit.

[0010] For example, the cooling air flow supply circuit comprises a supply ramp, arranged upstream of the regulation means in a direction of circulation of the cooling air flow, and at least one channel, arranged downstream of the regulation means.

[0011] According to an exemplary embodiment, the cylinder head comprises a plurality of spark plug wells, each equipped with a spark plug, the supply circuit comprising: - a plurality of ramps, each ramp being configured to be in fluid connection with the internal volume specific to one of the spark plugs arranged in one of the wells; or - a single ramp being configured to be in fluid connection with the internal volume specific to the spark plugs arranged in the plurality of wells.

[0012] 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 portion of the spark plug, the intermediate cavity housing a portion of the spark plug comprising the at least one orifice.

[0013] According to an exemplary embodiment, the cylinder head comprises an opening configured to open into the combustion chamber, a first cavity delimiting at least a portion 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 fluid connection with the opening. Alternatively, the cylinder head comprises an opening configured to open into the combustion chamber, the spark plug and the regulating means being arranged in a common or separate cavity or plurality of cavities.

[0014] In particular, the spark plug comprises a thread, arranged over at least a portion of a height of the base, defined along a first direction of the spark plug, the at least one orifice being arranged at the level of the thread or the at least one orifice being arranged in a portion of the base interposed between the thread and an end portion of the spark plug comprising the at least one hole.

[0015] 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 into the combustion chamber.

[0016] Optionally, the arrangement comprises a device for controlling the pump and at at least one pressure sensor, the control device being configured to regulate a pressure of the cooling flow in the supply circuit.

[0017] 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: - 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 be turned towards said combustion chamber; and - at least one orifice, arranged in a side wall of the base, connected to the end wall, the at least one orifice opening into the internal volume and being configured to provide a fluid connection between a cooling fluid supply circuit and the internal volume.

[0018] The invention finally relates to a method of operating an arrangement according to the invention, comprising: - an intake stroke 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 a portion of said spark plug, the cooling air flow being discharged towards the combustion chamber via the at least one hole in the spark plug; then - a compression stroke comprising the injection, into the cylinder, of a flow of fuel 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 - an expansion time in which the air-fuel mixture inside the cylinder ignites; then - an exhaust stroke including the piston rise.

[0019] Other details, characteristics and advantages will emerge more clearly on reading the detailed description given below, for informational and non-limiting purposes, in relation to the various exemplary embodiments illustrated in the following figures:

[0020] [Fig.l] is a schematic representation of an embodiment of a vehicle equipped with an arrangement according to the invention and a spark-ignition engine comprising a cylinder head equipped with a spark plug.

[0021] [Fig.2] is a schematic representation of the arrangement including the cylinder head equipped with a spark plug.

[0022] [Fig.3] is a schematic representation of an operation of the engine of the arrangement during an admission time.

[0023] [Fig.4] is a schematic representation of an operation of the motor of the arrangement during an exhaust stroke.

[0024] [Fig. 1] schematically illustrates an exemplary embodiment of a motor vehicle 1 according to the invention. The motor vehicle 1 is in particular equipped with a spark-ignition 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 may be of any type, for example, a private vehicle, a utility vehicle, a truck or a bus. The vehicle 1 in question may in particular be a connected and / or autonomous vehicle.

[0025] Conventionally, the spark-ignition engine 2 comprises a cylinder head 3 and at least one cylinder 21 in which a movable piston 22 is arranged. The at least one cylinder 21 delimits a combustion chamber 23 in which the piston 22 moves and in 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.

[0026] 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 comprises at least one spark plug 4 arranged at least partly in the at least one spark plug well 30. The arrangement 10 also comprises at least one supply circuit 5 for a cooling air flow FR configured to allow the circulation of a cooling air flow FR capable of capturing calories from the spark plug 4 so as to allow it to be cooled. The arrangement 10 also comprises a pump 6, configured to propel the cooling air flow 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.

[0027] 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 fluid 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 flow considered, represented in the figures by arrows.

[0028] Optionally but preferably, the intake circuit 31 comprises, in particular successively according to a direction of circulation of an intake air flow FA, an air filter 31a, a flow meter 31b capable of measuring the mass flow of air entering the engine 2, a turbocharger compressor 31c capable of compressing the flow intake air FA and an intake manifold 31d, also referred to as a distributor. In particular, the intake manifold 31d is equipped with at least one pressure sensor 31e, also referred to as an intake pressure sensor 31e, configured to measure the pressure of the air admitted into the cylinder or cylinders 21 of the engine 2. This intake pressure sensor 31e is generally housed in the intake manifold 31d. According to an exemplary embodiment, the intake manifold 31d comprises a plenum and a plurality of intake ducts each serving one of the cylinders 21 of the engine 2.

[0029] Optionally, the intake circuit 31 comprises at least one intake valve or a butterfly valve, 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.

[0030] Optionally, the exhaust circuit 33 comprises, according to 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.

[0031] As illustrated, according to an exemplary embodiment, the intake circuit 31 comprises an intake pipe 3If, formed 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, formed 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 mounted in the engine 2 so as to participate in the implementation of a fluid connection between the intake circuit 31 and the exhaust circuit 33 on the one hand, and the combustion chamber 23 of the at least one cylinder 21 on the other hand.Conventionally, the intake valve 32 and the exhaust valve 34 are mounted to move and are capable of allowing or interrupting the fluid connection between the pipe in which each valve considered is equipped and the combustion chamber 23.

[0032] It is understood that the following description is made with reference to a cylinder 21 considered of the engine 2 and with reference to a part of the cylinder head 3 associated within the arrangement 10. It nevertheless extends to a spark-ignition engine 2 comprising a plurality of cylinders 21 each equipped with a piston 22 and, by way of extension, to a cylinder head 3 comprising a plurality of wells 30, spark plugs 4 or even intake valves 32 and exhaust valves 34, as further explained below.

[0033] The at least one candle well 30 is capable of receiving all or part of the at least one spark plug 4. A first end of the well 30 comprises an opening 35 configured to open into the combustion chamber 23 of the associated cylinder 21 when the engine 2 is assembled.

[0034] The spark plug 4 is of the standard type. Here, the term “standard” means that the spark plug 4 is devoid of an integrated ignition pre-chamber, at which sparks can be generated, and, on the contrary, the spark plug 4 of the present invention is capable of generating sparks directly at the combustion chamber 23 of the engine 2, as further explained below. Conventionally, the spark plug 4 comprises 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, in particular based on alumina. The base 42 is made of an electrically conductive material, in particular a metallic material. For example, the spark plug 4 extends along a first direction 100.

[0035] The spark plug 4 comprises at least one wall, in particular a wall of the base 42. For example, the spark plug 4 comprises 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 non-limiting exemplary embodiment, the spark plug 4 comprises a cylindrical or partly 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.

[0036] The spark plug 4 comprises at least one hole 45 ensuring the fluid 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 capable of allowing the 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.

[0037] The spark plug 4 further comprises at least one orifice 46 opening into the internal volume 400 and configured to provide a fluid connection between the cooling fluid supply circuit 5 and said internal volume 400. The term “opening” means that the at least one orifice 46 extends right through within one of the walls of the spark plug 4. For example, the at least one orifice 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 orifice 46 allows the passage of the cooling air flow FR from the supply circuit 5 to the internal volume 400 so that to bring it into contact with the inside of the spark plug 4, before said flow is discharged towards the combustion chamber 23 via the hole 45.

[0038] According to a particular embodiment, illustrated in Figures 2 to 4, the spark plug 4 comprises a thread 47, arranged over at least a portion of a height of the base 42, defined along the first direction 100. The thread 47 is formed at an outer surface of the spark plug 4, in particular of the base 42, facing the walls of the cylinder head 3, in particular an outer surface of the side wall 43 or of one of the side walls of the spark plug 4. According to an example illustrated in [Fig. 2], the at least one orifice 46 is arranged in a portion of the base 42 interposed, along the first direction 100, between the thread 47 and an end portion of the spark plug 4 comprising the at least one hole 45, here the end wall 44. Alternatively, the at least one orifice 46 is arranged at the thread 47.

[0039] In a known manner, the spark plug 4 comprises at least one central electrode 48 and at least one ground 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 space, that is to say 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 comprise 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 different electrodes are shaped and arranged so as not to form protrusions or protrusions extending beyond the rest of the spark plug 4, in particular 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 flat, or substantially flat, surface arranged in the continuity of an internal surface of the cylinder head, facing the combustion chamber 23.

[0040] The vehicle 1 is, optionally, equipped with a controlled ignition system, not shown, comprising an ignition control unit and a high-voltage electrical circuit configured to supply electrical energy to the at least one central electrode 48 of the spark plug 4.

[0041] Advantageously, the arrangement 10 comprises at least one sealing means 36 arranged at the interface between the spark plug 4 and the cylinder head 3, for example 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.

[0042] As indicated above, the cooling air flow FR supply circuit 5 is configured to bring the cooling air flow FR to the spark plug 4 in order to cool it. Thus, the term “cooling air flow FR” means an air flow capable of capturing at least a portion of the calories of the spark plug 4 accumulated during previous combustions. Said circuit is at least partly included 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 fluid connection with the internal volume 400 of the spark plug 4 via the at least one orifice 46 so as to allow the circulation of the cooling air flow FR towards the internal volume 400 and in the internal volume 400. The cooling air flow FR then circulates in contact with at least a portion of the base 42 of the spark plug 4 and allows the latter to be cooled.Also, the cooling air flow circulates in the internal volume 400 and towards the combustion chamber 23 in order to capture calories from the at least one central electrode 48 and from the at least one ground electrode 49. It thus prevents the formation of hot spots at the base 42 and the different electrodes by lowering their temperature, in particular before the implementation of combustion.

[0043] According to a preferred embodiment illustrated by [Fig. 1], the supply circuit 5 of the cooling air flow FR is connected by a fluid 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, a portion of the intake air flow FA is taken and the latter is separated in order to form, on the one hand, the cooling air flow FR, directed towards the supply circuit 5 and towards 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.

[0044] Preferably, the supply circuit 5 is connected to the intake duct 31 downstream of the filter 31a and the flow meter 31b according to the direction of circulation of the intake air flow FA. In other words, the bifurcation point 51 is arranged downstream of the filter 31a and the flow meter 31b. In this way, the air taken to form the cooling air flow FR is free of particles, that is to say clean, and is taken into consideration in the calculation of the flow of fresh air arriving in the combustion chamber 23, conventionally determined by engine control software 2. The overall quantity of air sucked into the cylinder 21 thus corresponds to the air flow measured by the flow meter, this flow corresponding to the sum of the flow rate of the cooling air flow FR and the remaining intake air flow rate FAr.

[0045] According to an illustrated exemplary embodiment, simpler to implement, the supply circuit 5 is connected to the intake circuit 31 at a branch point 51 arranged upstream of the compressor 31c in the direction of circulation of the intake flow. Alternatively, the supply circuit 5 is connected to the intake circuit 31 at a branch point 51 arranged downstream of the compressor 31c in the direction of circulation of the intake flow. Such a principle, more complex to implement due to the size present downstream of said compressor 31c, advantageously makes it possible to take a flow of compressed cooling air FR, thereby reducing the magnitude of the effort to be provided by the pump 6.

[0046] Figures 1 to 4 illustrate an exemplary embodiment in which the supply circuit 5 generally comprises at least one supply ramp 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 ramp 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 orifice 46. The at least one ramp 52 and the at least one channel 53 are configured to be in fluid connection with each other, they are thus open at their different ends.It is thus possible to distinguish a first part 5a of the supply circuit 5, arranged upstream of the regulation means 7, in particular between the bifurcation point 51 and said regulation means 7, and a second part 5b of the supply circuit 5, arranged downstream of the regulation means 7, for example between the latter and the at least one orifice 46 of the spark plug 4.

[0047] The at least one ramp 52 is at least partly 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, a part of said ramp 52 can 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 there are spark plugs 4 and / or cylinders 21, each of said channels 53 being configured to be arranged in fluid connection with the internal volume 400 specific to one of the spark plugs 4 of the cylinder head 3 and, indirectly, in fluid connection with the combustion chamber 23 of one of the cylinders 21 of the engine 2.

[0048] [Fig.l] schematically illustrates an example of a preferred embodiment of a cylinder head 3 equipped with a plurality of spark plugs 4 and regulation means 47 associated with a supply circuit 5 comprising a single ramp 52, configured to bring the cooling air flow FR to the different spark plugs 4. The single ramp 52 is associated with a plurality of channels each bringing a portion 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 branch point 51. Each of the regulation means can be arranged within one of the channels 53 or upstream of said channels, for example in the ramp 52 or between the ramp 52 and said channels 53 as described above.

[0049] According to an alternative embodiment, not shown, the supply circuit 5 comprises a plurality of ramps 52 and channels 53, each ramp 52 being configured to bring 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.

[0050] 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 a portion 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 outer 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 portion of the base of the spark plug 4. Such a principle advantageously allows the cooling of a portion of the outer surface of the spark plug 4.The intermediate cavity 50 houses a portion of the spark plug 4, in particular the base 42, comprising the at least one orifice 46 so as to ensure the fluid connection between the rest of the supply circuit 5 and the at least one orifice 46. Optionally, the spark plug 4, in particular the base 42, comprises a plurality of orifices 46 distributed over the circumference of the spark plug, the intermediate cavity 50 being shaped and dimensioned to receive the portion of the spark plug 4 housing said orifices. In this way, the cooling air flow FR enters the internal volume 400 via the various orifices 46, the intermediate cavity 50 allowing the distribution of the cooling air flow FR in the various orifices 46.

[0051] As indicated above, the pump 6 is configured to take a portion of the intake air flow FA in order to form the cooling air flow FR. It also makes it possible to propel said cooling air flow FR towards the internal volume 400 of the spark plug 4 via the supply circuit 5 and the at least one orifice 46. In particular, the pump 6 is an electric pump 6. The pump 6 advantageously makes it possible to circulate the cooling air flow FR to 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 stroke during which the intake valve 32 of the engine 2 is open, and in particular measured by the intake pressure sensor 31e.

[0052] 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 31e, the pressure losses between the pressure measurement point and the combustion chamber 23 being negligible.

[0053] Optionally but preferably, the vehicle 1 and / or the arrangement 10 comprises a control device 61 for the pump 6 and at least one pressure sensor 54 for 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 needed based on a pressure measured at at least one point of the cylinder head 3 and / or the intake circuit 31. For example, as illustrated in [Fig.l], the vehicle 1 comprises the intake pressure sensor 31e, capable of measuring the pressure of the remaining intake air flow FAr in the intake duct, for example arranged at the intake manifold 31d, and / or a pressure sensor 54 arranged at the supply circuit 5, configured to measure the pressure of the cooling air flow FR.

[0054] 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. By "regulating" is meant the possibility of allowing or interrupting the circulation of the cooling flow in at least a portion of the supply circuit 5 and through the spark plug 4. Consequently, such regulation also consists of allowing or interrupting the fluid connection between at least a portion 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. By "passive" control is meant that the regulating means 7 itself is not directly actuated in a motorized manner or that it does not require a power supply, for example electrical.

[0055] According to a preferred embodiment, the at least one regulating means 7 is a non-return 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 maintain the spring 72. Optionally, the regulating means 7 further comprises a member 74 for holding the ball 71. The holding member 74 comprises a tube arranged in the continuity of the passage, or the trajectory, of the cooling air flow FR so as to allow the circulation of said flow. The holding member 74 also comprises a recess, arranged opposite the tubing and configured to receive the ball 71.

[0056] The regulating means 7 allows the circulation of the cooling air flow FR towards 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 higher than the pressure prevailing in the combustion chamber 23 of the engine 2, that is to say the intake pressure prevailing in the intake manifold 31d as explained above. Furthermore, the regulating means 7 prevents the reverse circulation of an air-fuel mixture flow from the internal volume 400 towards the entire supply circuit 5 when the pressure in the internal volume 400 and / or the combustion chamber 23 is higher than the pressure of the supply circuit 5, in particular of the first part 5a of the supply circuit 5 arranged upstream of the regulating means 7.

[0057] 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 member 74. As a result, the ball 71 blocks the circulation of the cooling air flow FR towards 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 member 74 and through the latter. In the "open" configuration, the cooling air flow 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 member 74. The ball 71 then exerts a force on the spring 72 and compresses it.The movement of the ball 71 then allows the passage of the cooling air flow FR 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 their cooling. The air flow is then evacuated towards the combustion chamber 23 through the at least one hole 45.

[0058] Also, the ball 71 prevents the passage of the air-fuel mixture towards the entire supply circuit 5, particularly the rise of the air-fuel mixture towards 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 movement of the ball 71.

[0059] For example, the spring 72 is pre-calibrated in order to actuate the re regulation 7 from a predefined threshold pressure of the cooling air flow FR at the time of an intake stroke of the engine cycle 2 and / or from a predefined threshold of pressure differential 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.

[0060] 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 shrink fitting, for example made of a metallic material such as steel, resistant to high temperatures which can exceed 600°C. The support 75 thus carries the regulating means 7 and comprises cutouts making it possible to ensure the circulation of the cooling air flow FR, particularly its entry and its exit within the support 75.In this case and in a non-limiting manner, a first cutout is arranged upstream of the regulation means 7 and is configured to ensure the fluid connection with the first part 5a of the supply circuit 5, here formed by the ramp 52 in particular, while a second cutout is arranged downstream of the regulation means 7 and is configured to ensure the fluid connection with the second part 5b of the supply circuit 5, here formed by the channel or one of the channels 53.

[0061] Optionally but preferably, the cylinder head 3 comprises a first cavity 301 and a second cavity 302 both in fluid connection with the opening 35 configured to open 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.

[0062] The invention also relates to a method for operating the arrangement 10 comprising a spark-ignition engine 2 according to the invention. Said method is implemented during an engine cycle 2 comprising, in a conventional manner, intake, compression, expansion and exhaust strokes.

[0063] As illustrated in [Fig.3], during the intake stroke, in a conventional manner, the intake valve 32 is open, the piston descends towards the bottom dead center, the intake air flow FA circulates in the intake circuit 31 towards the combustion chamber 23.

[0064] The method then comprises, in parallel with the admission of the intake air flow FA, the circulation of the cooling air flow FR in the supply circuit 5. The cooling air flow 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 cooling air flow FR captures calories from the heated spark plug 4 and allows it to cool before implementing a new combustion. The cooling air flow FR thus heated is then discharged to the combustion chamber via the at least one hole 51.

[0065] 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 portion of the intake air flow FA extracted by the pump 6 and diverted from its conventional path, 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 towards the combustion chamber 23. Advantageously, the taking of a portion of the intake air flow FA allows the implementation of the cooling of the spark plug without it being necessary to integrate an air reservoir in the cylinder head 3.

[0066] 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 greater than the pressure measured in the combustion chamber 23, and measured during the intake stroke by the intake pressure sensor 31 housed in the intake manifold 31d, in order to allow the opening of the at least one regulating means 7. As indicated previously, 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 cooling air flow FR, here by being moved out of the recess and by releasing the tubing of the holding member 74, so as to allow the circulation of the cooling air flow towards the internal volume 400 of the spark plug 4. The at least one regulation means 7 also advantageously makes it possible to avoid the reflux of the cooling air flow, also called “back flow” in English.

[0067] Optionally but preferably, the pressure of the cooling air flow FR can be adjusted by the control device 71 of the pump 6 as a function of the measured pressure of the remaining intake air flow FAr, in particular as a function of the pressure prevailing in the intake manifold 31d as it is measured by the intake pressure sensor 31e. Note 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 is caused to vary according to the operation of the engine. The same applies to the pressure of the remaining intake air flow Far.

[0068] In particular, at low load, the pressure of the remaining intake flow FAr, for example measured at the intake manifold 31d, is significantly lower than 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 the combustion temperatures of the fuel are lower at low load, heating of the spark plug 4 will be less significant and will be less likely to generate hot spots. The flow rate of the cooling air flow FR can thus be lower than in a supercharging situation while still ensuring suitable cooling of the spark plug 4.

[0069] Conversely, when the engine 2 is supercharged, that is to say when it operates at high load, the pressure of the intake flow FA, particularly of the remaining intake air flow FAr, is significantly higher than atmospheric pressure. It will therefore be necessary to propel the cooling air flow FR at 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 greater in order to prevent the formation of hot spots at the spark plug 4.

[0070] In a known manner, the engine cycle 2 continues with the compression stroke. The intake valve 32 and the exhaust valve 34 are closed. The injection of fuel, here dihydrogen in particular, is initiated. The atomized fuel is mixed with the moving intake air flow FA in order to form a fuel mixture, also called an air-fuel mixture, in the combustion chamber 23.

[0071] It will be noted that, in the case of hydrogen, the fuel is injected during the compression stroke, with the valves 32, 34 closed, rather than during the intake stroke as is the case with conventional fuels such as gasoline, in order to avoid a backflow, also called "backflow", of the fuel mixture into the intake manifold 31d. Indeed, the flammability limits of hydrogen are very wide, and a hot spot would be enough to ignite the mixture in the intake circuit 31. The resulting explosion could damage said circuit.

[0072] The fuel mixture is homogenized due to the turbulence which prevails in the combustion chamber 23 of the cylinder 21. The piston 22 rises in the cylinder 21 towards its top dead center, thereby increasing the pressure in the combustion chamber 23. The regulating means 7 is in the “closed” configuration and the circulation of the cooling air flow FR is interrupted in the internal volume 400. The fluid connection between the internal volume 400 and the entire supply circuit is thus interrupted. In particular, the fluid connection between the first part 5a of the supply circuit 5 and the internal volume 400 is interrupted.

[0073] Note that, during the compression stroke, 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 via the pump 6 as a function of the intake pressure so that the regulating means 7 remains closed. The pump 6 is then active throughout 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 non-return 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 ramp 52.

[0074] Towards the end of the compression stroke, the controlled ignition system triggers a spark at the spark plug 4, which causes the combustion of the compressed fuel mixture in the combustion chamber 23. It should be noted that, due to the architecture of the spark plug 4 according to the invention, which has no pre-chamber, the ignition takes place essentially outside the spark plug 4 and the internal volume 400, at the combustion chamber 23.

[0075] Then, during the expansion time of the engine cycle 2, the flame front propagates in the combustion chamber 23. The intake valve 32 and the exhaust valve 34 are then closed. The piston is moved towards the bottom dead center 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.

[0076] Finally, during the exhaust stroke, illustrated in [Fig. 4], the exhaust valve 34 opens. The piston 22 rises and discharges residual burnt gases present in the combustion chamber 23 towards the exhaust circuit 33. The pressure prevailing in the combustion chamber 23 drops but remains strictly higher than the pressure prevailing 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 fluid connection between the internal volume 400 of the spark plug 4 and the entire supply circuit 5 remains interrupted.

[0077] The arrangement and the method according to the invention thus make it possible to resolve one of the problems faced by internal combustion engines fueled 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.

[0078] The present invention advantageously makes it possible to ensure cooling of 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 pre-ignition of the air-fuel mixture. The circulation of the cooling air flow directly in contact with the spark plug makes it possible to optimize the cooling implemented and the integration of such cooling in the cylinder head and the engine described above makes it possible to avoid the need to integrate a specific cooling fluid and any associated storage tank, thus making it possible to limit the size and costs generated.

[0079] The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means or configuration and to any technically operative combination of such means insofar as they ultimately fulfill the functionalities described and illustrated in the present document.

Claims

Claims

1. 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 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 orifice (46) opening into the internal volume (400) and at least one hole (45) configured to ensure the fluid connection between the internal volume (400) and the combustion chamber (23);- a supply circuit (5) for supplying a cooling air flow (FR) arranged in fluid connection with the internal volume (400) of the spark plug (4) via the at least one orifice (46) so as to allow the circulation of a cooling air flow (FR) towards the internal volume (400), in contact with the spark plug (4); - a pump (6) configured to propel the cooling air flow (FR) towards the internal volume (400) via the at least one supply circuit (5) and the at least one orifice (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 fluid 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 one of the preceding claims, in which the cylinder head (3) comprises a plurality of spark plug wells (30), each equipped with a spark plug (4), the supply circuit (5) comprising: - a plurality of ramps (52), each ramp (52) being configured to be in fluid connection with the internal volume (400) specific to one of the spark plugs (4) arranged in one of the wells (30); or - a single ramp (52) being configured to be in fluid connection with the internal volume (400) specific to the spark plugs (4) arranged in the plurality of wells (30).

4. Arrangement (10) according to one of the preceding claims, in which the supply circuit (5) of the cooling air flow (FR) 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 orifice (46).

5. Arrangement (10) according to one of the preceding claims, in which 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 fluid connection with the opening (35).

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

7. Arrangement (10) according to one 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 said cylinder so as to form a spark ignition engine (2), the at least one hole (45) of the spark plug (4) opening into the combustion chamber (23).

8. Arrangement (10) according to the preceding claim, comprising a control device (61) for the pump (6) and at least one pressure sensor (31e), 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 one 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 cooling air flow (FR) from the internal volume (400) towards 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 be turned towards said combustion chamber (23); and - at least one orifice (46), arranged in a side wall (43) of the base (42), connected to the end wall (44), the at least one orifice (46) opening into the internal volume (400) and being configured to ensure a fluid connection between a cooling fluid supply circuit (5) and the internal volume (400).

10. A method of operating an arrangement according to claim 7 or 8, comprising: - an intake stroke 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 a portion 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 stroke comprising the injection, towards the cylinder (21), of a flow of fuel so as to form an air-fuel mixture, an increase in the pressure in the cylinder (21) then the ignition of said mixture in the combustion chamber (23); then - an expansion time in which the air-fuel mixture contained in the cylinder (21) ignites; then - an exhaust stroke including the rise of the piston (22).

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