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

Abstract

The invention relates to an arrangement (20) comprising a cylinder head (3) and a spark plug (4) which comprises an opening (46) opening into an internal volume (400) of the spark plug, a hole (45) capable of opening into a combustion chamber (23), and a channel (47) capable of providing a fluid connection between the opening (46) and the hole (45), the arrangement (20) comprising a circuit (5) for supplying a flow of cooling air (FR), making it possible to circulate the flow towards the internal volume (400), a pump (6) and at least one means (7) for regulating the circulation of the flow.

Description

[0001] DESCRIPTION

[0002] TITLE: 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. The invention finally relates to a method of operating the arrangement according to the invention.

[0004] In so-called "hydrogen" internal combustion engines, i.e., spark-ignition type internal combustion 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 therefore 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 could trigger early combustion during the following combustion cycles, also known as the pre-ignition phenomenon, corresponding to an ignition of part of the air / fuel mixture by a hot spot before the spark is triggered by the spark plug. Indeed, since hydrogen has wide flammability ranges, it is sensitive to the potentially destructive pre-ignition phenomenon.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 are themselves likely to generate new hot spots. 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 when the response time of the supercharging devices naturally generates a temporary enrichment of the air / fuel mixture which can then approach stoichiometric conditions.

[0005] The spark plug is naturally 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 this level that the sparks that will initiate each combustion will be triggered. In addition, conventional spark plugs include protruding electrodes constituting a protuberance 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.

[0006] In order to eliminate 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 using a liquid coolant. Such cooling can be carried out at a distance from the spark plug, by cooling the walls of the cylinder head, but these 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.

[0007] The present invention falls within this context and aims to propose an alternative to known cylinder head and spark plug arrangements which is suitable for a hydrogen internal combustion engine and which makes it possible to limit, or even prevent, the formation of hot spots within the cylinder head and more particularly at the spark plugs.

[0008] The invention relates to an arrangement comprising a cylinder head for a spark-ignition engine comprising at least one spark plug well configured to open into a combustion chamber of a cylinder, the arrangement further comprising:

[0009] - 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 spark plug comprising at least one opening in fluid connection with the internal volume, at least one hole configured to ensure the fluid connection between the internal volume and the combustion chamber and at least one channel capable of implementing a fluid connection between the at least one opening and the at least one hole so as to allow the circulation of a flow of cooling air through the internal volume;

[0010] - at least one means for regulating the circulation of the cooling air flow arranged in the internal volume on a passage of said flow;

[0011] - a circuit for supplying a flow of cooling air connected to the at least one channel;

[0012] - a pump configured to propel the cooling airflow towards the internal volume.

[0013] 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 fluid connection to the intake circuit so that a cooling air flow is taken from an intake air flow circulating in the intake circuit.

[0014] According to exemplary embodiments, the at least one channel comprises a first part, extending through the base, and a second part, connected to the first part: - the second part of the at least one channel being delimited by the base and the electrically insulating body and / or interposed between at least one part of the base and the electrically insulating body; and / or

[0015] - the second part of the at least one channel extending through the electrically insulating body.

[0016] Optionally, the base comprises a first extreme portion, comprising at least one hole configured to ensure the fluid connection between the internal volume and the combustion chamber, a second extreme portion, opposite, and at least one side wall, connecting the first extreme portion to the second extreme portion:

[0017] - the at least one opening and / or the at least one channel extending at least partly into the second extreme portion; and / or

[0018] - the at least one opening and / or the at least one channel extending at least partly in the at least one side wall.

[0019] According to an exemplary embodiment, the at least one means for regulating the circulation of the drain air flow is a non-return valve comprising at least one ball and a spring.

[0020] In particular, the cylinder head comprises a plurality of spark plug wells, each equipped with a spark plug, the fuel circuit comprising:

[0021] - a plurality of ramps, each ramp being configured to be in fluid connection with the internal volume specific to one of the spark plugs disposed in one of the wells; or

[0022] - a single ramp configured to be in fluid connection with the internal volume specific to the spark plugs arranged in the plurality of wells.

[0023] In particular, the arrangement according to the invention further comprises 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, and the at least one hole of the spark plug opening into the combustion chamber. Optionally, the arrangement further comprises a pump control device and at least one pressure sensor, the control device being configured to regulate a pressure of the cooling air 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 also comprises:

[0025] - at least one hole capable of allowing the passage of a flow of cooling air through the internal volume towards a combustion chamber of a cylinder and configured to be turned towards said combustion chamber;

[0026] - at least one opening capable of being in fluid connection with the internal volume;

[0027] - at least one channel capable of implementing a fluid connection between the opening and the hole and the circulation of a cooling flow through the internal volume;

[0028] - at least one means for regulating the circulation of the cooling air flow arranged in the internal volume on a passage of said flow.

[0029] The invention finally extends to a method of operating an arrangement according to the invention, comprising:

[0030] - 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

[0031] - 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

[0032] - an expansion time in which the air-fuel mixture inside the cylinder ignites; then

[0033] - an exhaust stroke including the piston rise.

[0034] 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 examples of embodiment illustrated in the following figures:

[0035] Figure 1 is a schematic representation of an embodiment of a vehicle equipped with an arrangement according to the invention and a spark-ignition internal combustion engine comprising a cylinder head equipped with at least one spark plug.

[0036] Figure 2 is a schematic representation of the arrangement including the cylinder head equipped with at least one spark plug.

[0037] Figure 3 is a schematic representation of an engine operation of the arrangement during an intake stroke of the engine combustion cycle.

[0038] Figure 4 is a schematic representation of an engine operation of the arrangement during an exhaust stroke of the engine combustion cycle.

[0039] Figure 1 schematically illustrates an exemplary embodiment of a motor vehicle 1 according to the invention. The motor vehicle 1 is equipped with an engine 2, which is a spark-ignition internal combustion engine 2. The engine 2 is in particular a hydrogen engine, that is to say 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. Conventionally, the 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

[0040] 21 delimits a combustion chamber 23 in which the piston moves

[0041] 22 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 engine 2 comprises four cylinders 21 in line.

[0042] The vehicle 1 particularly comprises an arrangement 20 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. Generally, the cylinder head comprises one spark plug 4 per cylinder 21. In the example of FIG. 1, four spark plugs are shown, one of which is referenced.

[0043] The arrangement 20 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 its cooling. The supply circuit 5 for the cooling air flow FR is thus configured to bring the cooling air flow FR to the spark plug 4 in order to cool it. The term "cooling air flow FR" thus means an air flow capable of capturing at least a portion of the calories from the spark plug 4 accumulated during previous combustions, in particular calories accumulated at the various electrodes of the spark plug 4.The arrangement 20 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, arranged in the spark plug 4, as further detailed below. In particular, the pump 6 is an electric pump 6.

[0044] Optionally, the vehicle 1, particularly the arrangement 20, 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 considered air flow, represented in the figures by arrows. In this case, the air intake circuit 31 is arranged upstream of the at least one well 30 and the at least one combustion chamber 23 of the cylinder 21 in a direction of circulation of an air flow while the exhaust circuit 33 is arranged downstream of these.

[0045] Optionally but preferably, the intake circuit 31 comprises, in particular successively according to a direction of circulation of an intake air flow, an air filter 31 a, a flow meter 31 b capable of measuring the mass flow of air entering the engine 2, a compressor 31 c, in particular a turbocharger 31 c, capable of compressing the intake air flow 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, also referred to as an intake pressure sensor 31 e, configured to measure the pressure of the air admitted into the cylinder 21 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 an exemplary embodiment, the intake manifold 31 d comprises a plenum and a plurality of intake ducts each serving a cylinder 21 of the engine 2.Optionally, the intake circuit 31 comprises at least one intake valve or a butterfly valve, not shown, arranged downstream of the compressor 31 c and making it possible to regulate the flow rate of the intake air flow FA entering the engine 2.

[0046] Optionally, the exhaust circuit 33 comprises, according to the direction of circulation of an exhaust air flow leaving the cylinder 21, 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.

[0047] As illustrated, according to an exemplary embodiment, the intake circuit 31 comprises an intake pipe 31 f, formed in the material of the cylinder head 3, equipped with an intake valve 32 and configured to be connected to an intake duct, or to intake ducts, included in the intake circuit 31. Similarly, the exhaust circuit 33 may comprise an exhaust pipe 33 d, formed in the material of the cylinder head 3, equipped with an exhaust valve 34 and capable of being connected to an exhaust duct, or to exhaust ducts, of the exhaust circuit 33.

[0048] The cylinder head 3 is thus 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 movably 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.

[0049] 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 20. 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 spark plug wells 30 or even intake valves and exhaust valves, as further explained below.

[0050] The at least one spark plug well 30 is capable of receiving all or part of the at least one spark plug 4. A first end 30a of the well 30 comprises an orifice 35 configured to open into the combustion chamber 23 of the cylinder 21 associated with said well 30 when the engine 2 is assembled. A second end 30b of the well 30, not detailed, opposite the first end 30a, is optionally but preferably at least partially closed so as to prevent the entry of liquids and particles, likely to affect the operation of the spark plug 4, into said well 30.

[0051] The spark plug 4 is of the standard type. By "standard" is meant here 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.

[0052] 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.

[0053] In particular, the spark plug 4 comprises at least a first end portion 40a, configured to be turned towards the combustion chamber 23, and a second end portion 40b, opposite. For example, the first end portion 40a comprises at least a first end wall while the second end portion 40b comprises at least a second end wall. The spark plug 4 also comprises at least one side wall 43, or a plurality of side walls 43, in particular a wall of the base 42, here connecting the first end wall to the second end wall. 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 at least partly inscribed in a cylindrical or substantially cylindrical shape.

[0054] 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 first end wall.Also, the various electrodes are shaped and arranged so as not to form protrusions or protrusions extending beyond the rest of the spark plug 4 into the environment outside the spark plug. Such a principle advantageously makes it possible to limit, or even prevent, the formation of hot spots at the electrodes.

[0055] Also, 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. In general, the spark plug 4 comprises at least one hole 45 configured to ensure 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 first end wall of the first end portion 40a.

[0056] The spark plug 4 further comprises at least one opening 46 configured to provide a fluid connection between the cooling fluid supply circuit 5 and said internal volume 400. The at least one opening 46 allows the passage of the cooling air flow FR from the supply circuit 5 to the internal volume 400 so as to cause it to circulate in contact with at least a portion of the interior of the spark plug 4, in particular in contact with the different electrodes, before said flow is discharged to the combustion chamber 23 via the hole 45. For example, the at least one opening 46 is arranged in the first end wall.

[0057] Also, the spark plug 4 comprises at least one channel 47 capable of at least implementing a fluid connection between the opening 46 and the at least one hole 45 so as to allow the circulation of the cooling air flow FR through the internal volume 400, and in particular at the level of the different electrodes. The cooling air flow FR thus circulates through all or part of the internal volume 400 and the at least one channel 47 ensures the fluid connection between the supply circuit 5 and the combustion chamber 23 by passing through the internal volume 400 of the spark plug 4.

[0058] As illustrated, the spark plug 4 optionally but preferably comprises a plurality of openings 46 and channels 47 as described above, each opening 46 being associated with at least one of the channels 47. In particular, the spark plug 4 comprises as many openings 46 as channels 47. According to a non-limiting exemplary embodiment, the spark plug 4 comprises two openings 46 and two channels 47.

[0059] According to a particular preferred embodiment, illustrated in Figures 2 to 4, the at least one opening 46 and / or the at least one channel 47 extend at least partly in the second end portion 40b. In particular, the at least one opening 46 is arranged at the first end wall so as to maximize contact between the base 42, in particular the side wall 43 of the spark plug 4, and the structure of the cylinder head 3. Such a principle makes it possible to optimize the heat exchange conventionally implemented between the structure of the cylinder head 3 and the spark plug 4 so as to allow the latter to cool.

[0060] According to an alternative not shown, the at least one opening 46 and / or the at least one channel 47 extend at least partly into the at least one intermediate side wall 43.

[0061] Optionally, according to an example illustrated in Figure 2, the at least one channel 47 is at least partly delimited by the base 42 and / or the electrically insulating body 41. The at least one channel 47 thus extends between the base 42 and the electrically insulating body 41 so as to be delimited by them. In this case, in the illustrated example, the at least one channel 47 comprises a first part 47a, extending through at least a part of the base 42, and a second part 47b, connected to the first part 47a. For example, the first part 47a comprises a cannula connected to the at least one opening 46 or extending through the at least one opening 46 so as to be directly connected to the supply circuit 5.

[0062] The second part 47b of the at least one channel 47 is here arranged between the base 42 and the electrically insulating body 41 so that it is interposed between them in a localized manner when moving along a radial direction originating from the first direction 100 of extension of the spark plug 4. The first part 47a, in particular the cannula, thus opens into a space arranged between the base 42 and the electrically insulating body 41, for example partly hollowed out in the electrically insulating body 41.

[0063] When the spark plug 4 comprises a plurality of channels 47, all or part of said channels 47 are arranged between a part of the base 42 and a part of the electrically insulating body 41. For example, in a non-limiting manner, the different channels 47 are diametrically opposed within the spark plug 4.

[0064] Alternatively or additionally, at least a portion of the at least one channel 47 extends through the electrically insulating body 41. Such a principle makes it possible to maximize the heat exchange implemented between the electrically insulating body 41 and the base 42. Indeed, the contact between the electrically insulating body 41 and the base 42 makes it possible to evacuate calories from the electrically insulating body 41 to the base 42 and then to the structure of the yoke 3 by contact. For example, the second portion 47b of the at least one channel 47 extends through the electrically insulating body 41. The first portion 47a may then comprise a cannula as described above, opening onto the second portion of the at least one channel 47 hollowed out or machined within the electrically insulating body 41.

[0065] The at least one means 7 for regulating the circulation of the cooling air flow FR is arranged in the internal volume 400 of the spark plug 4, in particular on a passage of said flow. Such a principle makes it possible to integrate the spark plug 4 into different types of cylinder heads 3 or to connect it to different types of supply circuits 5. The at least one regulating means 7 is configured to be moved between different configurations so as to regulate the circulation of said flow. Here, the term "regulate" means the possibility of hindering, that is to say interrupting, the circulation of the cooling air flow FR so as to interrupt the fluid connection between the supply circuit 5 and the combustion chamber 23 or the possibility of allowing the circulation of said flow from the supply circuit 5 to the combustion chamber 23. 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 does not require a power supply, for example electrical.

[0066] The regulating means 7 in particular 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 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 31 d. Furthermore, the regulating means 7 prevents the reverse circulation of a flow of air-fuel mixture from the internal volume 400 towards the 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.

[0067] The at least one regulating means 7 is in particular arranged in the at least one channel 47. For example, the at least one regulating means 7 is arranged in the first part 47a of the at least one channel 47. Alternatively, the at least one regulating means 7 is arranged at the interface between the first part 47a and the second part 47b. Also, preferably, the spark plug 4 comprises as many regulating means as there are channels 47, each of said regulating means 7 being arranged in one of the channels 47, on the passage of the cooling air flow FR in the internal volume 400.

[0068] According to a preferred embodiment, illustrated, the at least one regulating means 7 is a non-return valve comprising at least one ball 71 and a spring 72 and arranged at a constriction 73 or a narrowing of a width or a diameter of the at least one channel 47. The spring 72 is in particular arranged to bear on an intermediate surface, included in the at least one channel 47 in order to maintain the spring 72. The ball 71 is arranged to bear on the spring 72 and 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 and the ball 71 bears on the spring 72 and on the edges of the constriction 73 or the narrowing in order to close the latter and interrupt the circulation of the cooling air flow FR in the internal volume 400.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 at a non-zero distance from the constriction 73 or the narrowing so as to allow the passage of the cooling air flow FR into the internal volume 400. The ball 71 exerts a force against the spring 72 which is compressed.

[0069] As further explained below, with reference to the method according to the invention, the regulating means 7 is actuated passively, here by displacement of the ball 71, as a function of a differential pressure defined between a pressure measured in the supply circuit 5 and a pressure measured in the combustion chamber 23 or between a pressure measured in the first part 47a of the at least one channel 47 and the pressure measured in the combustion chamber 23. The pump 6 advantageously makes it possible to vary the pressure and / or the flow rate of the cooling air flow FR circulating in the supply circuit 5 and towards the internal volume 400 so as to actuate the regulating means 7.Thus, as soon as the pressure of the cooling air flow FR, that is to say the pressure measured in the supply circuit 5 in particular, becomes greater than the pressure measured in the combustion chamber 23, the ball 71 is moved and releases the passage to the cooling air flow FR within the at least one channel 47 and the internal volume 400, in particular at the level of the constriction 73 or the narrowing.

[0070] For example, the spring 72 is pre-calibrated in order to actuate the regulating means 7 from a predefined pressure threshold of the cooling air flow FR at the time of 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 31.

[0071] It will be noted that, in the case of a supercharged engine 2, the intake is at a pressure which may be higher than atmospheric pressure depending on the operating conditions, i.e. depending on the engine speed-load operating point. The pump 6 thus makes it possible to generate a pressure adapted as required to enable the actuation of the regulating means 7.

[0072] Optionally, the arrangement 20 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.

[0073] The supply circuit 5 is arranged in fluid connection with the internal volume 400 of the spark plug 4 of the at least one opening 46 and the at least one channel 47 so as to allow the circulation of the cooling air flow FR in the internal volume 400. The cooling air flow FR then circulates at least in contact with the different electrodes so as to allow their cooling. Optionally, depending on the position of the at least one channel 47, the cooling air flow FR is able to capture calories from the base 42 and / or the electrically insulating body 41. It thus prevents the formation of hot spots within the spark plug 4 by lowering its temperature, in particular before the implementation of combustion.

[0074] 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, in particular by means of the pump 6, and this 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. ignition 4.

[0075] Preferably, the supply circuit 5 is connected to the intake duct downstream of the filter 31 a and the flow meter 31 b according to the direction of circulation of the intake air flow FA. In other words, the bifurcation point

[0076] 51 is arranged downstream of the filter 31 a and the flow meter 31 b. 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 31 b, 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.

[0077] According to an illustrated embodiment, the supply circuit 5 is connected to the intake circuit 31 at a branch point 51 arranged upstream of the compressor 31 c 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 31 c in the direction of circulation of the intake flow. Such a principle advantageously makes it possible to take a flow of compressed cooling air FR, thereby reducing the amount of effort required by the pump 6.

[0078] Figure 1 illustrates an exemplary embodiment in which the supply circuit 5 generally comprises at least one supply ramp 52 configured to be in fluid connection with the at least one channel 47 specific to the at least one spark plug 4. The at least one ramp

[0079] 52 comprises at least one conduit capable of distributing the cooling air flow FR to the at least one spark plug 4 or, advantageously, to a plurality of spark plugs 4. The at least one conduit extends, for example, between the bifurcation point 51 and the at least one spark plug 4, in particular the at least one channel 47.

[0080] Figure 1 schematically illustrates a preferred embodiment of a cylinder head 3 equipped with a plurality of spark plugs 4 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, in particular to the at least one channel 47 specific to each of said spark plugs 4. The supply circuit 5 is then advantageously connected to the supply circuit 5 by a single branch point 51.

[0081] According to an alternative embodiment, not shown, the supply circuit 5 comprises a plurality of ramps 52, each ramp 52 being configured to bring a flow of cooling air FR to at least one of the channels 47 and to one of the spark plugs 4. The arrangement 20 then comprises a plurality of branch points 51, in particular connected to the intake circuit 31.

[0082] 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 allows the propulsion of said cooling air flow FR towards the internal volume 400 of the spark plug 4 via the supply circuit 5 at a desired defined pressure, particularly at a pressure higher than the pressure prevailing in the combustion chamber 23 of the engine 2. In particular, the pressure prevailing in the combustion chamber 23 of the engine 2 corresponds substantially to the pressure prevailing in the exhaust manifold 33a during the intake time during which the intake valve 32 of the engine 2 is open.Optionally but preferably, the vehicle 1 and / or the arrangement 20 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. 1, the vehicle 1 comprises the intake pressure sensor 31 e, capable of measuring the pressure of the remaining intake air flow FAr in the intake duct and / or a pressure sensor 54 arranged at the supply circuit 5, configured to measure the pressure of the cooling air flow FR.

[0083] The invention also relates to a method for operating the arrangement 20 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.

[0084] As illustrated in Figure 3, during the intake stroke the intake valve 32 is open, the piston 22 descends towards the bottom dead center, the intake air flow FA circulates in the intake circuit 31 towards the combustion chamber 23.

[0085] 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 towards the internal volume 400 of the spark plug 4.

[0086] More particularly, the use of pump 6 is always necessary when the engine speed-load operating point is in the supercharged range, in which the pressure in the combustion chambers 23 is higher than atmospheric pressure, that is to say there is no depression, and it can also be necessary in the atmospheric range if the depression created by the descent of the piston is too weak to suck in the air.

[0087] It should be noted that at certain operating points of the atmospheric domain, the depression created by the descent of the piston may be sufficient to suck in air without the assistance of pump 6.

[0088] In contact with the spark plug 4, in particular the various electrodes, the cooling air flow FR captures calories from the heated spark plug 4 and allows it to cool before a new combustion is carried out. The cooling air flow FR thus heated is then discharged to the combustion chamber 23 via the at least one hole 45.

[0089] 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 31 c. The cooling air flow FR is then a portion of the intake air flow FA extracted by the pump 6, diverted from its conventional trajectory, namely from the intake circuit 31 , and redirected towards 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 4 without it being necessary to integrate an air reservoir in the cylinder head 3.

[0090] The cooling air flow FR is then propelled under pressure by the electric pump 6 controlled by the control device 61 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 regulation means 7. In particular, the pressure of the cooling air flow FR, measured in the supply circuit 5 and sent to the internal volume 400, is strictly greater than the pressure measured in the combustion chamber 23, measured during the intake stroke by the intake pressure sensor 31 e housed in the intake manifold 31 d, in order to allow the opening 46 of the at least one regulation means 7.

[0091] As indicated previously, due to such a pressure differential, the ball 71 is displaced and exerts a force on the spring 72. It frees the passage of the cooling air flow FR, here by being displaced away from the constriction 73 or the narrowing, so as to allow the circulation of the cooling air flow FR through the entire at least one channel 47 towards the volume of the combustion chamber 23. The at least one regulation means 7 also advantageously makes it possible to avoid the reflux of the cooling air flow FR, also called "back flow" in English.

[0092] Optionally but preferably, the pressure of the cooling air flow FR can be adjusted by the control device 61 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 31 d as measured by the intake pressure sensor 31 e.

[0093] It should be noted that, during the intake time, when the intake valve 32 of the engine 2 is open, or the intake valves, it can be considered that the pressure in the cylinder 21 is substantially equal to the boost pressure measured by the intake pressure sensor 31 e in the intake circuit 31 , the pressure losses between the pressure measurement point and the combustion chamber 23 being negligible. The pressure of the intake flow is nevertheless caused to vary according to the operation of the engine 2. The same applies to the pressure of the remaining intake air flow FAr.

[0094] In particular, at low load, the pressure of the remaining intake air flow FAr, measured at the intake manifold 31 d, is significantly lower than atmospheric pressure. The pressure of the cooling air flow FR circulating in the supply circuit 5 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.

[0095] Conversely, when engine 2 is supercharged, i.e. operating at high load, the pressure 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.

[0096] 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. It will be noted that, in the case of hydrogen, the fuel is injected during the compression stroke, with the valves 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 a "backflow", of the fuel mixture into the intake manifold 31 d. 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.The fuel mixture is homogenized due to the turbulence that 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 5 is thus interrupted. In particular, the fluid connection between the first part of the supply circuit 5 and the internal volume 400 is interrupted.

[0097] 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, that is to say not interrupted. 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 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 then closes as soon as the pressure prevailing in the cylinder 21 is strictly greater than the pressure measured in the supply circuit 5.

[0098] Towards the end of the compression stroke, the controlled ignition system triggers a spark at the spark plug 4, which causes the compressed fuel mixture to combust in the combustion chamber 23. Due to the architecture of the spark plug 4, which has no pre-chamber, ignition takes place essentially outside the spark plug 4 and the internal volume 400, at the combustion chamber 23.

[0099] 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 22 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 23 and the entire supply circuit 5.

[0100] Finally, during the exhaust stroke, illustrated in Figure 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 so that the regulating means 7 remains in the “closed” configuration and the fluid connection between the internal volume 400 of the spark plug 4 and the entire supply circuit 5 remains interrupted.

[0101] The arrangement and method according to the invention thus make it possible to resolve one of the problems faced by internal combustion engines fueled by 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.

[0102] 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.

[0103] 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 (20) comprising a cylinder head (3) for a spark-ignition engine (2) comprising at least one spark plug well (30) configured to open into a combustion chamber (23) of a cylinder (21), the arrangement (20) 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 spark plug (4) comprising at least one opening (46) in fluid connection with the internal volume (400), at least one hole (45) configured to ensure the fluid connection between the internal volume (400) and the combustion chamber (23) and at least one channel (47) capable of implementing a fluid connection between the at least one opening (46) and the at least one hole (45) so as to allow the circulation of a cooling air flow (FR) through the internal volume (400); - at least one means (7) for regulating the circulation of the cooling air flow (FR) arranged in the internal volume (400) on a passage of said flow; - a supply circuit (5) for a cooling air flow (FR) connected to the at least one channel (47); - a pump (6) configured to propel the cooling air flow (FR) towards the internal volume (400).

2. Arrangement (20) 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 (20) according to one of the preceding claims, in which the at least one channel (47) comprises a first part (47a), extending through the base (42), and a second part (47b), connected to the first part (47a): - the second part (47b) of the at least one channel (47) being delimited by the base (42) and the electrically insulating body (41) and / or interposed between at least one part of the base (42) and the electrically insulating body (41); and / or - the second part (47b) of the at least one channel (47) extending through the electrically insulating body (41).

4. Arrangement (20) according to one of the preceding claims, in which the base (42) comprises a first end portion (40a), comprising at least one hole (45) configured to ensure the fluidic connection between the internal volume (400) and the combustion chamber (23), a second end portion (40b), opposite, and at least one side wall (43), connecting the first end portion (40a) to the second end portion (40b): - the at least one opening (46) and / or the at least one channel (47) extending at least partly in the second extreme portion (40b); and / or - the at least one opening (46) and / or the at least one channel (47) extending at least partly in the at least one side wall (43).

5. Arrangement (20) according to one of the preceding claims, in which the at least one means (7) for regulating the circulation of the flow of drain air is a non-return valve comprising at least one ball (71) and a spring (72).

6. Arrangement (20) 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) configured to be in fluid connection with the internal volume (400) specific to the spark plugs (52) arranged in the plurality of wells (30).

7. Arrangement (20) 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 (21) 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 (20) according to the preceding claim, comprising a control device (61) for the pump (6) and at least one pressure sensor, the control device (61) being configured to regulate a pressure of the cooling air flow (FR) in the supply circuit (5).

9. Spark plug (4) for an arrangement (20) 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) through the internal volume (400) towards a combustion chamber (23) of a cylinder (21) and configured to be turned towards said combustion chamber (23); - at least one opening (46) capable of being in fluid connection with the internal volume (400); - at least one channel (47) capable of implementing a fluid connection between the opening (46) and the hole (45) and the circulation of a flow cooling (FR) through the internal volume (400); - at least one means (7) for regulating the circulation of the cooling air flow (FR) arranged in the internal volume (400) on a passage of said flow.

10. Method of operating an arrangement (20) according to one of claims 1 to 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 piston rise.

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