Spark plug for spark-ignition engine

Abstract

Title: Spark Plug for Spark-Ignition Engine Spark plug (4) for a spark-ignition engine (2) comprising an electrically insulating body (41), a base (42) defining a passive ignition pre-chamber (43), the spark plug (4) further comprising at least one orifice (45) disposed in the base (42) and at least one channel (46) configured to permit the flow of a drain air (DA) through at least a portion of the spark plug (4), and at least one means (47) for regulating the flow of the drain air (DA) disposed at the level of at least one orifice (45) and capable of passively controlling the flow of said DA. Figure 1

Description

Title of the invention: Spark plug for a spark-ignition engine

[0001] The invention relates to a spark plug, particularly with a passive pre-chamber, for a spark-ignition engine and to a cylinder head for a spark-ignition engine comprising such a spark plug. The invention further relates to an engine equipped with said spark plug and / or said cylinder head. The invention finally relates to a method for operating such an engine.

[0002] Improving the efficiency of spark-ignition thermal engines is one of the challenges of the development of the automobile industry and increasing the volumetric ratio constitutes an area of ​​progress in this field. Increasing the volumetric ratio of a thermal engine is nevertheless accompanied by difficulties such as fuel self-ignition phenomena, also known as knocking, which can damage the engine.

[0003] One solution to these difficulties is to use pre-chamber spark plugs, more particularly spark plugs whose pre-chamber is of the passive type, i.e. which does not include a device for injecting fuel directly into the pre-chamber. A disadvantage of such spark plugs is that residual burnt gases, or RBG, gradually accumulate in the pre-chamber to levels high enough to impact the combustion of the fuel mixture, or even make it impossible.

[0004] The invention falls within this context and aims to propose an alternative to pre-chamber spark plugs, in particular passive spark plugs, capable of evacuating residual burnt gases present in the pre-chamber at the end of combustion cycles so as to guarantee good quality of fuel mixture in the pre-chamber before ignition of the spark plug.

[0005] The invention relates to a spark plug for a spark ignition engine comprising an electrically insulating body and an electrically conductive base, said base delimiting an ignition pre-chamber comprising at least one hole capable of allowing at least the passage of a fuel mixture between a combustion chamber of a cylinder and the pre-chamber. The spark plug further comprises at least one orifice and at least one channel, the at least one orifice passing through a wall of the base and being capable of being in fluid connection with the pre-chamber via the at least one channel so as to allow the circulation of a flow of drain air at least through the pre-chamber. The spark plug also comprises at least one means for regulating the circulation of the flow of drain air arranged at the at least one orifice and capable of passively controlling the circulation of said flow.

[0006] In particular, the at least one channel may be delimited by the base and / or the electrically insulating body.

[0007] In particular, the base and / or the body may extend along a first direction, the spark plug further comprising at least one primary electrode and at least one ground electrode, the at least one orifice and the at least one regulating means being arranged so that, along the first direction, the at least one ground electrode is interposed between the at least one orifice on the one hand and the at least one hole of the pre-chamber on the other hand.

[0008] Optionally, the spark plug further comprises at least one intermediate volume interposed between the at least one orifice and all or part of the at least one channel, the intermediate volume being delimited by the base and / or the electrically insulating body and the intermediate volume being connected to the at least one channel and to the pre-chamber by a fluid connection.

[0009] 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 one spring.

[0010] The invention also relates to a cylinder head for a spark-ignition engine comprising at least one intake valve, one exhaust valve and at least one well delimiting a first volume, a first end of said well comprising an opening configured to open into a combustion chamber of a cylinder, the cylinder head further comprising at least one spark plug according to the invention arranged in the first volume at said opening so that the at least one orifice extends into the first volume and so that the pre-chamber is configured to implement a fluid connection with the combustion chamber of the cylinder.

[0011] In particular, a second end, opposite the first end, of the at least one spark plug well is at least partially open so as to allow the entry of a flow of drain air into the first volume, said second end being configured to limit, or even prevent, the entry of liquid and / or particles.

[0012] The invention also relates to a spark-ignition engine comprising a cylinder head according to the invention, at least one cylinder delimiting a combustion chamber and a movable piston arranged in the at least one cylinder, the opening of the cylinder head and the pre-chamber of the at least one spark plug opening into the combustion chamber.

[0013] Optionally, the engine further comprises an intake valve control device capable of controlling an opening, in particular a delay in opening, of said valve.

[0014] The invention finally relates to a method of operating an ignition engine ordered as set out above, including: - a phase of admitting an intake air flow into the cylinder comprising a step of generating a vacuum in the cylinder so as to allow the circulation of a flow of drain air from the first volume to the combustion chamber via the pre-chamber of the spark plug, the flow of drain air being capable of expelling residual burnt gases accumulated in the pre-chamber and / or in the spark plug; - a compression phase comprising an increase in the pressure in the cylinder so that a portion of a fuel mixture is sent into the pre-chamber and comprising the ignition of said mixture in the pre-chamber; then - an expansion phase in which the fuel mixture in the cylinder ignites; then - an exhaust phase comprising the raising of the piston to the high position so as to move residual burnt gases present in the combustion chamber of the cylinder at least towards the pre-chamber of the spark plug.

[0015] 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:

[0016] [Fig.l] is a schematic representation of one embodiment of a vehicle equipped with a spark-ignition engine and a pre-chamber spark plug.

[0017] [Fig.2] is a schematic representation of engine operation during an intake phase.

[0018] [Fig.3] is a schematic representation of engine operation during an exhaust phase.

[0019] [Fig.l] 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 of any type. Similarly, the vehicle 1 may be of any type, for example, a private vehicle, a utility vehicle, a truck or a bus. In particular, the vehicle 1 considered may be a connected and / or autonomous vehicle.

[0020] Conventionally, the spark-ignition engine 2 comprises 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 is moved and into which an air-fuel mixture is injected.

[0021] The engine 2 also comprises a cylinder head 3. According to an exemplary embodiment, the cylinder head 3 comprises, in a known manner, an intake duct 31 equipped with an intake valve 32 and an exhaust duct 33 equipped with an exhaust valve 34. The cylinder head 3 is mounted in the engine 2 so as to allow the implementation of a fluid connection between the intake duct 31 and the exhaust duct 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 be mobile and are capable of allowing or hindering the fluid connection between the duct in which they are equipped and the combustion chamber 23.

[0022] Also, the cylinder head 3 comprises at least one spark plug 4 according to the invention and a well 35 configured to house such a spark plug. The well 35 delimits a first volume 350 open on one side and capable of receiving all or part of the spark plug 4. In particular, a first end of the well 35 comprises an opening 36 configured to open onto the combustion chamber 23 of the at least one cylinder 21 when the cylinder head 3 is equipped in the engine 2.

[0023] A second end of the well 35, not shown, opposite the first end, is optionally but preferably at least partly closed so as to prevent the entry of liquids and particles, likely to affect the operation of the spark plug 4, into said well 35. In addition, the well 35 is configured so as to allow the entry of an air flow, called the drain air flow FV, as further detailed below in the first volume 350 of the well 35. To this end, the second end of the well 35 is at least partly open and optionally comprises at least one drain air flow passage FV adapted to allow the passage of the drain air flow FV while limiting the risk of passage of liquids and particles.

[0024] It is understood that the following description is made with reference to a spark plug 4 of the engine 2, arranged in a spark plug well 35 opposite a cylinder 21 considered. 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 35, spark plugs 4, intake valves 32 and exhaust valves 34.

[0025] Generally, the spark plug 4 according to the invention comprises at least one electrically insulating body 41 and an electrically conductive base 42 extending along a first direction 100, said base 42 delimiting an ignition pre-chamber 43. The ignition pre-chamber 43 comprises at least one hole 44 capable of allowing, on the one hand, at least the passage of an air-fuel mixture between the combustion chamber 23 of the cylinder 21 and the pre-chamber 43 and, on the other hand, the passage of the drain air flow FV towards the combustion chamber 23.

[0026] The spark plug is arranged in the well 35 of the cylinder head 3 so as to extend at least partly into the first volume 350. In particular, the spark plug is arranged at the opening 36 in such a way that, within the engine 2, the pre-chamber 43 is in fluid connection with the combustion chamber 23 of the cylinder 21 via the at least one hole 44. Optionally but preferably, the cylinder head 3 comprises at least one sealing member 37, arranged at the interface between the spark plug 4 and the cylinder head 3, for example around the spark plug 4 and / or at the opening 36, so as to prevent the circulation of a flow of combustion gas from the combustion chamber 23 to the well 35 of the spark plug 4, or in other words the first volume 350, during the compression, expansion and exhaust phases, in which the pressure in the cylinder is higher than atmospheric pressure, and conversely, the circulation of a flow of fresh air circulating from the well 35, or first volume 350, to the combustion chamber 23 during a phase of the engine cycle in which the cylinder 21 may be under vacuum, for example during the phase admission.

[0027] The body 41 has an elongated shape extending along the first direction 100. When the spark plug 4 is arranged in the cylinder head 3 and the engine 2, the body 41 comprises, for example, an upper end at which the electrical connection of the spark plug 4 can be made and an opposite lower end. The body 41 is made of an electrically insulating material, such as ceramic, in particular based on alumina.

[0028] The base 42 is made of an electrically conductive material, in particular a metallic material. The base 42 comprises a wall or several walls forming an at least partly hollow shape configured to surround all or part of the body 4L. For example, the base 42 has an at least partly cylindrical, or substantially cylindrical, shape. The base 42 and the body 41 extend for example along the same direction, here the first direction, and are for example concentric.

[0029] The base 42 delimits in particular an internal volume 400 of the spark plug 4 comprising in particular the pre-chamber 43 for ignition of the spark plug. Conventionally, the term "pre-chamber" is understood to mean a chamber included in the spark plug 4 at the level of which a fuel mixture, also called an air-fuel mixture, is introduced via the at least one hole 44 and then ignited using a spark. A jet of hot combustion gases is then produced and is then delivered to an external environment, namely here the combustion chamber 23 of the cylinder 21, via the at least one hole 44. In particular, according to the invention, the pre-chamber 43 is a passive chamber, that is to say a pre-chamber 43 without a fuel supply device, or injector, making it possible to inject the fuel directly into the pre-chamber 43.

[0030] The spark plug 4 further comprises at least one orifice 45 and at least one channel 46 fluidly connected to each other and to the pre-chamber 43. In other words, the at least one orifice passes right through a wall of the base 42 and is capable of being in fluid connection with the pre-chamber 43 via the at least one channel 46. The at least one orifice 45 and the at least one channel 46 are configured to allow the circulation of the drain air flow FV through the internal volume 400 of the spark plug, particularly through the pre-chamber 43 and the at least one hole 44. The term "drain air flow" refers to the air flow from the first volume 350 circulating through the spark plug 4, particularly through the pre-chamber 43, in order to evacuate to the combustion chamber 23 any residual burnt gases likely to be accumulated in the spark plug 4, particularly in the pre-chamber 43. The drain air flow FV thus circulates from the first volume 350 of the spark plug well 35 to the combustion chamber 23 via the internal volume 400 of the spark plug 4, and not in the environment external to it, so as to allow the cleaning of the pre-chamber 43.The at least one channel 46 thus allows the circulation of the drain flow FV from the well 35 of the spark plug 4 towards the combustion chamber 23 by sweeping burnt gases accumulated in the pre-chamber 43 during a previous combustion towards the combustion chamber 23.

[0031] In particular, the at least one orifice 45 is arranged in one of the walls of the base 42 so that, when the spark plug 4 is equipped in the vehicle 1, the at least one orifice 45 extends into the first volume 350 of the at least one well 35 of the cylinder head 3.

[0032] According to a particular embodiment, the at least one channel 46 is delimited by the base 42 and / or the electrically insulating body 41. For example, the at least one channel 46 extends partly along the first direction 100. The at least one channel 46 and the at least one orifice 45 are directly or indirectly connected and are configured to implement a fluid connection between the first volume 350 and the pre-chamber 43 so as to allow the passage of the drain air flow FV. Consequently, the at least one orifice 45 and the at least one channel 46 are capable of providing the fluid connection between the first volume 350 of the cylinder head 3 and the combustion chamber 23 of the at least one cylinder 21.

[0033] As illustrated, the spark plug 4 optionally comprises a plurality of orifices 45 and channels 46 as described above. According to a non-limiting exemplary embodiment, the spark plug 4 comprises two orifices 45 and two channels 46. The orifices 45 are, for example, distributed over a periphery of the base 42.

[0034] The spark plug 4 according to the invention further comprises at least one means 47 for regulating the circulation of the drain air flow FV. The regulating means 47 is arranged on the passage of the drain air flow FV, within the spark plug 4, in particular the internal volume 400 of the spark plug 4, so as to passively control the circulation of said flow. Here, the term “control” means the possibility of hindering the circulation of said flow so as to interrupt the fluid connection between the first volume 350 and the combustion chamber 23 or the possibility of allowing the circulation of said flow from the first volume 350 to the combustion chamber 23. By “passive” control is meant that it does not require motorized actuation.

[0035] The at least one regulating means 47 is in particular arranged at the level of the at least one orifice 45, for example opposite and / or in the vicinity thereof. For example, the at least one regulating means 47 is configured to close the at least one orifice 45 so as to interrupt the circulation of the flow of drain air FV. The at least one regulating means 47 is then in contact with the edges of the at least one orifice 45. Also, preferably, the spark plug 4 comprises as many regulating means 47 as there are orifices 45, each of said regulating means 47 being arranged at one of the orifices 45.

[0036] According to a preferred embodiment, illustrated, the at least one regulating means 47 is a non-return valve comprising at least one ball 47a and a spring 47b. The spring 47b is in particular arranged to bear on an intermediate surface 47c, formed by a wall of the base 42 and / or by the body 41, in order to maintain the spring 47b. The ball 47a is on the one hand arranged to bear on the edges of the at least one orifice 45 and, on the other hand, to bear on the spring 47b so as to maintain the ball 47a in the internal volume 400 of the spark plug 4.The ball 47a is thus configured to be moved between a “closed” configuration, in which the ball 47a bears against the edges of the at least one orifice 45 in order to close the latter and interrupt the circulation of the drain air flow FV in the internal volume 400, and an “open” configuration, in which the ball 47a exerts a force against the spring 47b and extends at a non-zero distance from the at least one orifice 45 so as to allow the passage of the drain air flow FV into the internal volume 400.

[0037] As further explained below, with reference to the method according to the invention, the regulating means 47 is actuated passively, here by displacement of the ball 47a, as a function of a differential pressure defined between a pressure measured in the first volume 350 and a pressure measured in the combustion chamber 23. For example, the spring 47b is previously calibrated in order to allow the regulating means 47 to be actuated when a depression is generated in the combustion chamber 23, and by extension in the internal volume 400 and the pre-chamber 43 of the spark plug 4, at the time of an intake phase of the engine cycle 2. Here, the term “depression” is understood to mean the lowering of the pressure to a value strictly lower than atmospheric pressure. Thus, the spring 47b is very weakly calibrated and serves to hold the ball 47a in place within the spark plug 4.The ball 47a is subjected to atmospheric pressure on the side of the well 35, or first volume 350, and to the pressure of the cylinder 21 on the side of the pre-chamber 43. In this way, as soon as the pressure in the cylinder 21 becomes lower than atmospheric pressure, the ball 47a is sucked towards. the latter and releases the passage to the flow of drain air FV. In particular, when a depression is generated in the combustion chamber 23, the ball 47a is sucked towards the combustion chamber 23 via the passages existing in the internal volume 400 of the spark plug 4, namely in particular via the at least one channel 46 and the pre-chamber 43. The ball 47a is then moved against the spring 47b and compresses the latter against the intermediate surface 47c.

[0038] It should 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. It is then necessary, as further explained below, to delay the opening of the intake valve 32 to generate a suitable pressure, in the cylinder 21, which is lower than atmospheric pressure due to the descent of the piston 22.

[0039] Conventionally, the spark plug 4 further comprises at least one primary electrode 5 and at least one ground electrode 51. The primary electrode 5 extends, for example, through the body 4L. The at least one ground electrode 51 is included in the base 42 and defines, relative to the at least one primary electrode 5, a primary inter-electrode space, that is to say a gap, or space, separating two electrodes not in contact intended to be the seat of sparks between said electrodes. For example, the at least one ground electrode 51 comes from an internal surface of the base 42, facing the internal volume 400, and extends into said volume. It is understood that the spark plug 4 may comprise a plurality of primary electrodes 5 and / or ground electrodes 51.

[0040] The vehicle 1 is, optionally, equipped with a controlled ignition system comprising an ignition control unit and a high-voltage electrical circuit configured to supply electrical energy to the at least one primary electrode 5 of the spark plug 4.

[0041] According to the preferred embodiment illustrated, the at least one orifice 45 and the at least one regulating means 47 are arranged so that, along the first direction 100, the at least one ground electrode 51 is interposed between the at least one orifice 45 on the one hand and the at least one hole 44 of the pre-chamber 43 on the other hand. In particular, the at least one orifice 45 and the at least one regulating means 47 extend at a non-zero distance from the pre-chamber 43 of the spark plug 4. For example, the at least one orifice 45 is arranged in an upper portion, for example in an upper half, of the spark plug 4, configured to be arranged in the at least one well 35 of the cylinder head 3.

[0042] Optionally, the spark plug 4 further comprises at least one intermediate volume 48 interposed between the at least one orifice 45 and all or part of the at least one channel 46. The intermediate volume 48 is included in the internal volume 400 of the spark plug 4 and distinct from a volume of the pre-chamber 43. The intermediate volume 48 is also fluidically connected to the at least one orifice 45, to the at least one channel 46 and to the pre-chamber 43. The intermediate volume 48 is delimited by the base 42 and / or the electrically insulating body 41. It is, for example, in an annular shape at least partially surrounding the body 4L. The intermediate volume 48 makes it possible to ensure the fluidic connection between the at least one orifice and the at least one channel 46, or between different channels 46. It is understood that the shapes of the intermediate volume 48 and of the at least one channel 46 illustrated are in no way limiting and that other variants may be envisaged.

[0043] The invention also relates to a method for operating the 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 phases.

[0044] During the admission phase, as illustrated in [Fig. 2], of an intake air flow FA into the at least one cylinder 21, the method comprises a step of generating a vacuum in the cylinder 21, particularly in the combustion chamber 23. As indicated above, the vacuum here consists of lowering the pressure in the cylinder, and consequently in the internal volume 400 and the pre-chamber 43 of the spark plug 4, to a value strictly lower than atmospheric pressure. The vacuum generated allows the activation of the at least one regulation means 47, for example here the movement of the ball in the “open” configuration, so as to allow the circulation of the drain air flow FV from the first volume 350 to the combustion chamber 23 via the internal volume 400 of the spark plug.

[0045] The vacuum can be obtained in different ways depending on the mode and time of operation of the engine 2. A first strategy for obtaining the vacuum in the at least one cylinder 21 can be implemented when the engine is operating at low load. The pressure in the intake duct 31, and more generally in the intake manifold, of the engine 2 then drops below atmospheric pressure. The engine 2 operates in an atmospheric zone and a vacuum is naturally generated at the level of the at least one cylinder 21 and the intake duct 31. The conditions observed in the engine 2 are then favorable to the actuation of the regulating means 47 without any mechanical intervention being required. The regulating means 47, for example here the spring 47b of the non-return valve, is previously calibrated in order to allow the actuation of the regulating means 47 passively when such a vacuum is naturally generated.

[0046] Conversely, the engine 2 can operate at high load, i.e. overloaded or supercharged. The pressure in the intake duct 31, and by extension in the intake manifold, of the engine 2 is then higher than atmospheric pressure at the start of the intake phase. The pressure in the at least one cylinder 21 and in the intake duct 31 being higher than atmospheric pressure, the vacuum must be mechanically generated. In this case, the vacuum is generated by implementing an intake opening delay, or ROA, consisting of keeping the intake valve 32 closed while the descent of the piston 22 is initiated. The intake opening delay is, for example, implemented by a control device, not shown, of the intake valve 32, capable of triggering a shift in an opening law of said valve in the engine cycle.Such a delay generates, similarly to what was indicated above, a depression in the cylinder 21, particularly in the combustion chamber 23, and in the internal volume 400 of the spark plug, particularly in the pre-chamber 43, sufficient to cause the passive opening 36 of the at least one regulation means 47. When the regulation means 47 comprises a non-return valve, the spring 47b of the valves is advantageously calibrated beforehand in order to allow the opening 36 of the valve due to the depression which then prevails in the cylinder 21.

[0047] The method according to the invention thus advantageously proposes different strategies for generating a vacuum within the at least one cylinder 21, adapted to different operating points of the engine 2. It should be noted that, preferably, the method according to the invention can be configured to be executed only during operation of the engine at low load so as to drain the spark plug 4 without intervening in the operation of the engine cycle. The method according to the invention can then be inactive and no draining is performed, when the engine 2 is operating under overload.

[0048] Due to the depression, natural or generated, present in the cylinder 21 and in the pre-chamber 43, the fresh air contained in the first volume 350 of the spark plug well 35 is sucked into the internal volume 400 and towards the combustion chamber 23 of the cylinder 21, the flow of drain air FV thus passing through the pre-chamber 43 then through the at least one hole 44. For example, the flow of drain air FV passes successively through the at least one orifice 45, the intermediate volume 48, the at least one channel 46 then the pre-chamber 43, which makes it possible to sweep away all residual burnt gases accumulated during a previous combustion of a previous engine cycle 2. The circulation of the drain air flow FV through the internal volume 400 of the spark plug 4 allows passive blowing capable of expelling residual burnt gases located in the internal volume 400 of the spark plug 4 following a previous engine cycle.For example, the drain air flow FV expels residual burnt gases located in the pre-chamber 43, the at least one channel 46 and / or the intermediate volume 48.

[0049] Then, in a conventional manner, the intake valve 32 is opened, the cylinder 21 is filled with an intake air flow FA, from the intake duct 33, and fuel injection is initiated. The atomized fuel is mixed with the moving intake air flow FA to form a fuel mixture, also referred to as an air-fuel mixture, in the combustion chamber 23.

[0050] Also, in a known manner, the engine cycle 2 continues with the compression phase. The fuel injection continues and 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 and the intake valve 32 is closed, thereby increasing the pressure in the combustion chamber 23 and in the internal volume 400 of the spark plug, particularly in the pre-chamber 43. The pressure in the combustion chamber 23, and by extension in the internal volume 400 of the spark plug, is then greater than or equal to the pressure in the first volume 350 and all the regulating means 47 are closed, hindering the circulation of the flow of drain air FV.A portion of the fuel mixture is then sent into the pre-chamber 43 and, at the end of the compression phase, the controlled ignition system triggers a spark at the spark plug 4, which causes the combustion of the compressed fuel mixture in the pre-chamber 43.

[0051] Then, the engine cycle 2 includes the expansion phase. The flame front propagates in the pre-chamber 43. The pressure rises in the pre-chamber 43, the ignited gases enter the combustion chamber 23 in the form of jets of fire which constitute a multitude of ignition points thus making it possible to optimize the timing of the heat release law and the combustion efficiency. The intake valve 32, the exhaust valve 34 and all the regulating means 47 are then closed and the seal is ensured between the combustion chamber 23 and the first volume 350 of the well 35 of the spark plug 4.

[0052] Finally, during the exhaust phase, illustrated in [Fig. 3], the exhaust valve 34 opens. The rise of the piston 22 simultaneously displaces residual burnt gases present in the combustion chamber 23 of the cylinder 21 towards the exhaust duct 33 and towards the internal volume 400 of the spark plug 4, in particular at least towards the pre-chamber 43. For example, a portion of the residual burnt gases are sent towards the at least one channel 46 and throughout the ignition pre-chamber 43, in particular into the intermediate volume 48. In parallel, a portion of the residual exhaust gases is discharged from the engine 2 via the exhaust duct 33. The residual burnt gases accumulated in the internal volume 400 may be discharged from the spark plug 4 during the execution of the intake phase of a subsequent engine cycle 2, as described above.

[0053] The spark plug 4 and the method according to the invention thus allow the implementation of passive draining of the spark plug 4 limiting an accumulation of residual burnt gases in the pre-chamber 43 at too high a concentration likely to prevent the initiation of combustion of the fuel mixture. The emptying of the residual burnt gases generated during previous combustions, evacuated towards the cylinder 21 during the intake phase, thus allows the pre-chamber 43 to be cleaned before it is refilled with a fuel mixture.

[0054] The invention thus proposes an alternative to pre-chamber spark plugs capable of preventing the accumulation of residual burnt gases in the spark plug. The proposed solution is advantageously simple to implement and inexpensive since it is directly integrated into the spark plug and can be applied to various cylinder heads and thermal engines. Furthermore, the invention does not affect the architecture or operation of the pre-chamber.

[0055] 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. Spark plug (4) for a spark-ignition engine (2) comprising an electrically insulating body (41) and an electrically conductive base (42), said base (42) delimiting an ignition pre-chamber (43) comprising at least one hole (44) capable of allowing at least the passage of a fuel mixture between a combustion chamber (23) of a cylinder (21) and the pre-chamber (43), the spark plug (4) further comprising: - at least one orifice (45) and at least one channel (46), the at least one orifice (45) passing through a wall of the base (42) and being capable of being in fluid connection with the pre-chamber (43) via the at least one channel (46) so as to allow the circulation of a flow of drain air (FV) at least through the pre-chamber (43); - at least one means (47) for regulating the circulation of the flow of drain air (FV) arranged at the level of the at least one orifice (45) and capable of passively controlling the circulation of said flow.

2. Spark plug (4) according to the preceding claim, in which the at least one channel (46) is delimited by the base (42) and / or the electrically insulating body (41).

3. Spark plug (4) according to one of the preceding claims, wherein the base (42) and / or the body (41) extend along a first direction (100), the spark plug (4) further comprising at least one primary electrode (5) and at least one ground electrode (51), the at least one orifice (45) and the at least one regulating means (47) being arranged such that, along the first direction (100), the at least one ground electrode (51) is interposed between the at least one orifice (45) on the one hand and the at least one hole (44) of the pre-chamber (43) on the other hand.

4. Spark plug (4) according to one of the preceding claims, further comprising at least one intermediate volume (48) interposed between the at least one orifice (45) and all or part of the at least one channel (46), the intermediate volume (48) being delimited by the base (42) and / or the electrically insulating body (41) and the intermediate volume (48) being connected to the at least one channel (46) and to the pre-chamber (43) by a fluid connection.

5. Spark plug (4) according to one of the preceding claims, in which the at least one means (47) for regulating the flow circulation drain air (FV) is a check valve comprising at least one ball (47a) and a spring (47b).

6. Cylinder head (3) for a spark-ignition engine (2) comprising at least one intake valve (32), one exhaust valve (34) and at least one well (35) delimiting a first volume (350), a first end of said well (35) comprising an opening (36) configured to open into a combustion chamber (23) of a cylinder (21), the cylinder head (3) further comprising at least one spark plug (4) according to one of the preceding claims arranged in the first volume (350) at said opening (36) so that the at least one orifice (45) extends into the first volume (350) and so that the pre-chamber (43) is configured to implement a fluid connection with the combustion chamber (23) of the cylinder (21).

7. Cylinder head (3) according to the preceding claim, in which a second end, opposite the first end, of the at least one spark plug well (35) is at least partially open so as to allow the entry of a flow of drain air (FV) into the first volume (350), said second end being configured to limit, or even prevent, the entry of liquid and / or particles.

8. Spark-ignition engine (2) comprising a cylinder head (3) according to claim 6 or 7, at least one cylinder (21) delimiting a combustion chamber (23) and a movable piston (22) arranged in the at least one cylinder (21), the opening (36) of the cylinder head (3) and the pre-chamber (43) of the at least one spark plug (4) opening into the combustion chamber (23).

9. Spark-ignition engine (2) according to the preceding claim, further comprising a device for controlling the intake valve (32), capable of controlling an opening, in particular a delay in opening, of said valve.

10. Method for operating a spark-ignition engine (2) according to claim 8 or 9, comprising: - a phase of admitting an intake air flow (FA) into the cylinder (21) comprising a step of generating a vacuum in the cylinder (21) so as to allow the circulation of a drain air flow (FV) from the first volume (350) to the combustion chamber (23) via the pre-chamber (43) of the spark plug (4), the drain air flow (FV) being capable of expelling residual burnt gases accumulated in the pre-chamber (43) and / or in the spark plug (4); - a compression phase comprising an increase in the pressure in the cylinder so that a portion of a fuel mixture is sent into the pre-chamber (43) and comprising the ignition of said mixture in the pre-chamber (43); then - an expansion phase in which the fuel mixture contained in the cylinder (21) ignites; then - an exhaust phase comprising the raising of the piston (22) to the high position so as to move residual burnt gases present in the combustion chamber (23) of the cylinder (21) at least towards the pre-chamber (43) of the spark plug (4).

Images