Cylinder head for spark-ignition engine including a spark plug

Abstract

Title: Cylinder head for spark-ignition engine comprising a spark plug Cylinder head (3) for spark-ignition engine (2) comprising at least one spark plug well (30) below which the casting of the cylinder head delimits a first volume (300) in which a spark plug (4) and a movable pre-chamber (5) are arranged, configured to be moved in the first volume (300), relative to the spark plug (4), so as to allow the circulation of the flow of drain air in the first volume (300) and in an intermediate volume (550) of the pre-chamber (5). Abstract figure: Figure 1

Description

Title of the invention: Cylinder head for a spark-ignition engine comprising a spark plug

[0001] The invention relates to a cylinder head for a spark-ignition engine comprising a spark plug. The invention further relates to an engine equipped with said cylinder head. The invention finally relates to a method of 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 known cylinder heads, which is 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 cylinder head for a spark-ignition engine comprising at least one spark plug well and a first volume, the first volume being in particular delimited by the material of the cylinder head below said well, a first end of said first volume comprising an opening configured to open into a combustion chamber of a cylinder. The cylinder head further comprises at least one spark plug at least partly arranged in the first volume, in particular arranged in the first volume from the well, and at least one channel opening into the first volume at at least one orifice and configured to allow the circulation of a flow of drain air towards the first volume.The cylinder head also comprises a movable pre-chamber comprising at least one hole capable of allowing the passage of an air-fuel mixture between the combustion chamber and the pre-chamber, the pre-chamber being arranged in the first volume and configured to be moved in the first volume, relative to the spark plug, between a first . position, in which it extends opposite the at least one orifice so as to interrupt the circulation of the flow of drain air towards the first volume, and a second position in which it extends at a distance from the at least one orifice so as to allow the circulation of the flow of drain air in the first volume. The cylinder head also comprises a return member capable of moving the pre-chamber between the first position and the second position.

[0006] In particular, the cylinder head may further comprise an intake duct, equipped with an intake valve, and an exhaust duct, equipped with an exhaust valve, the at least one channel being connected by a fluid connection to the intake duct.

[0007] In particular, the pre-chamber: - may comprise a metallic material, such as steel; and / or - can be configured to be moved in a translational motion, along a first direction, in the first volume.

[0008] Optionally, the first volume may comprise a first cavity, comprising at least a portion of the at least one spark plug, and a second cavity, comprising the movable pre-chamber, the first cavity, the second cavity and the opening being in fluid connection.

[0009] Optionally, the return member may be a spring and / or at least one elastically deformable blade.

[0010] In particular, the pre-chamber may comprise at least one rim, the first volume further comprising at least one locking member configured to form a stop for the at least one rim so as to limit the movement of the movable pre-chamber in the first volume.

[0011] According to an exemplary embodiment, the cylinder head may comprise a lower flank comprising the opening. The movable prechamber may then comprise a lower wall comprising the at least one hole, the lower flank and the lower wall being configured to be turned towards the combustion chamber. A first face of the lower flank and a first surface of the lower wall may be flush when the movable prechamber is in the first position.

[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 at least one hole in the pre-chamber opening into the combustion chamber.

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

[0014] The invention finally relates to a method of operating an ignition engine. controlled according to the invention, comprising: - an intake phase including the intake of an intake air flow, the injection of fuel and the generation of a depression in the cylinder capable of moving the movable prechamber to the second position so as to open the at least one orifice and allow the circulation of an exhaust air flow, in particular drawn from the intake air flow, in the at least one duct, the first volume and towards the combustion chamber, said flow being capable of expelling residual burned gases located in the prechamber and / or in the first volume; then - a compression phase including an increase in pressure in the cylinder so that part of an air-fuel mixture is sent into the prechamber and further including the ignition of said mixture in the prechamber; then - an expansion phase in which the air-fuel mixture contained in the cylinder ignites; then - an exhaust phase comprising the rise of the piston so as to evacuate part of the residual burnt gases present in the combustion chamber of the cylinder towards the mobile pre-chamber.

[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 an embodiment of a vehicle equipped with a spark ignition engine comprising a cylinder head equipped with a spark plug and a movable pre-chamber.

[0017] [Fig.2] is a schematic representation of the cylinder head equipped with a spark plug and a movable pre-chamber.

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

[0019] [Fig.4] is a schematic representation of engine operation during an exhaust phase.

[0020] [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 thermal 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. The vehicle 1 in question may in particular be a connected and / or autonomous vehicle.

[0021] 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 in which an air-fuel mixture is injected.

[0022] The engine 2 also comprises a cylinder head 3. Generally, the cylinder head 3 according to the invention comprises at least one well 30, also referred to as a spark plug well, below which a casting of the cylinder head 3, or more precisely the material of the cylinder head 3, delimits at least a first volume 300, as well as at least one spark plug 4 and a movable pre-chamber 5, arranged in the at least one first volume 300. The cylinder head 3 also comprises at least one channel 6 opening into said first volume 300, configured to allow the circulation of a flow of drain air FV towards the first volume 300 then by extension towards the interior of the pre-chamber 5, and a return member 7 capable of moving the movable pre-chamber 5, as further explained below.

[0023] Also, as illustrated, according to an embodiment, the cylinder head 3 includes 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 enable 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 movably and are adapted to allow or interrupt the fluid connection between the duct in which each considered valve is equipped and the combustion chamber 23.

[0024] The following description is made with reference to a cylinder head 3 including a bore 30, a spark plug 4, a first volume 300, and a prechamber 5. It is also understood that the description is made with reference to a cylinder 21 of the engine 2 and to an associated part of the cylinder head 3. Nevertheless, it extends to a spark-ignition engine 2 including a plurality of cylinders 21 each equipped with a piston 22 and, by extension, to a cylinder head 3 including a plurality of bores 30, first volumes 300, spark plugs 4, intake valves 32, and exhaust valves 34.

[0025] The cylinder head 3 comprises the first volume 300 in which the at least one spark plug 4 and the movable pre-chamber 5 are arranged. The first volume 300 is thus a space delimited by the material of the cylinder head 3. The well 30 is open onto the first volume 300 and the spark plug 4 is arranged so as to extend at least partly into the first volume 300. In particular, as illustrated, the spark plug 4 extends partly into the well 30 and into the first volume 300, in particular so that a thread of said spark plug 4 extends into the first volume 300. A first end of said first volume 300 comprises an opening 35 configured to open into the combustion chamber 23 of the associated cylinder 21 when the engine 2 is assembled. A second end of the first volume 300, opposite the first end, is connected to the well 30 and is at least partly closed, in particular by the spark plug 4, so as to prevent the entry of liquids and particles, likely to affect the operation of the spark plug 4.

[0026] Conventionally, the ignition plug 4 includes at least one electrically insulating body 41 and an electrically conductive base 42 extending along an extension direction 400. The body 41 is made of an electrically insulating material such as ceramic, in particular alumina-based. The base 42 is made of an electrically conductive material, in particular a metallic material. The ignition plug 4 is arranged so as to extend partly into the spark plug well 30 of the cylinder head 3, so as to be fixed in the cylinder head 3 and so as to extend at least partly into the first volume 300. According to an exemplary embodiment, optional but preferred, the ignition plug 4 is arranged at a first cavity 301 of the at least one first volume 300. Optionally, the cylinder head 3 includes at least one sealing member 35a arranged at the interface between the ignition plug 4 and the cylinder head 3, for example around the ignition plug 4.This could include a spark plug gasket.

[0027] Also, in a known manner, the spark plug 4 further comprises at least one central electrode 43 and at least one ground electrode 44 separated by an 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. It is understood that the spark plug 4 may comprise a plurality of ground electrodes 44. 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 central electrode 43 of the spark plug 4. The at least one spark plug 4 is thus of the standard type and is devoid of an integrated pre-chamber.

[0028] The at least one channel 6 is configured to supply the first volume 300, and by extension an intermediate volume 550 delimited by the movable pre-chamber 5 and at least partly included in the first volume 300, with a flow of drain air FV. The term “flow of drain air FV” means a flow of air circulating through all or part of the first volume 300, particularly through the at least one channel 6 and the movable pre-chamber 5, in order to evacuate towards the combustion chamber 23 residual burnt gases likely to be accumulated there. The flow of drain air FV thus allows, as further explained below, the cleaning of the pre-chamber 5.

[0029] The at least one channel 6 opens into the first volume 300 at the level of at least one orifice 61. According to a preferred embodiment, the at least one channel 6 is connected, by a fluid connection, to the intake duct 31 at the level of a point of divergence 62. The at least one channel 6 thus extends between the intake duct 31 and the first volume 300. It makes it possible to extract a portion of an intake air flow FA, circulating in the intake duct 31 towards the combustion chamber 23, in order to direct it towards the first volume 300 and the movable pre-chamber 5. The extracted portion of the intake air flow FA thus forms the drain air flow FV as explained above.

[0030] Optionally, an engine intake system (not shown) that supplies the intake duct 31 with intake air flow FA is equipped with at least one filter and a flow measuring device, or flowmeter. The at least one passage 6 is then preferably connected to the intake duct 31 downstream of said filter and / or said measuring device in the direction of flow of the intake air flow FA. According to distinct embodiments, the at least one passage 6 is a passage formed in the material, also referred to as a "casting", of the cylinder head 3 or a tube connecting different points of the cylinder head 3 to each other, namely here the bifurcation point 62 and the at least one orifice 61.

[0031] The movable pre-chamber 5 is an added part arranged in the first volume 300 formed in the material of the cylinder head 3. Conventionally, the term "pre-chamber 5" means a chamber separate from the combustion chamber 23 of the at least one cylinder 21 having a limited volume, particularly a more limited volume than that of the combustion chamber 23, at which a fuel mixture, also referred to as an air-fuel mixture, is introduced and then ignited using a spark. A jet of hot combustion gases is then produced and is then delivered to an environment outside the cylinder head 3, namely here to the combustion chamber 23 of the cylinder 21. In particular, according to the invention, the pre-chamber 5 is a passive chamber, i.e. a pre-chamber 5 without a fuel supply device, or injector, conventionally making it possible to inject the fuel directly into the pre-chamber 5.Also according to the invention, the pre-chamber 5 is distinct and separated from the at least one spark plug 4.

[0032] Conventionally, the movable pre-chamber 5 comprises at least one hole 51 capable of allowing the passage of an air-fuel mixture between the combustion chamber 23 and the pre-chamber 5, as further described below with reference to the method according to the invention. The movable pre-chamber 5 also comprises at least one wall delimiting the intermediate volume 550 of the pre-chamber 5.

[0033] According to a non-limiting exemplary embodiment, the movable prechamber 5 comprises a cylindrical or partly cylindrical shape at least partly complementary in shape to the first volume 300 in which it is arranged. For example, the prechamber 5 is centered on a main axis 500 and extends along said axis. The prechamber 5 comprises in particular a side wall 52 or a plurality of walls lateral 52 defining the cylindrical base. Also, the prechamber 5 comprises a lower wall 53, delimiting a side of the prechamber 5 furthest from the spark plug 4. In this case, the lower wall 53 comprises at least one hole 51. For example, the movable prechamber 5, particularly the lower wall 53, comprises a plurality of holes 51 capable of ensuring a fluid connection between the intermediate volume 550, and by extension the first volume 300 comprising the spark plug 4, and the combustion chamber 23 of the cylinder 21.

[0034] Also, preferably, the movable pre-chamber 5 is open on one side, in particular on a side facing the spark plug 4 within the first volume 300 and / or a side opposite that comprising the at least one hole 51. In the example illustrated, the open side is an upper side of the movable pre-chamber 5, corresponding to a highest side of the pre-chamber 5 within the engine 2, so as to allow the entry of the drain flow and the propagation of flames.

[0035] Optionally but preferably, the pre-chamber 5 is made of a metallic material such as steel, in particular of a metallic material resistant to temperatures of the order of 600°C.

[0036] According to the exemplary embodiment shown, the spark plug 4 is arranged in the first cavity 301 as described above, and the first volume 300 further comprises a second cavity 302, in which the movable pre-chamber 5 is arranged and can be moved. The first cavity 301, the second cavity 302 and the opening 35 of the cylinder head 3 are then in fluid connection. Alternatively, the spark plug 4 and the movable pre-chamber 5 could be arranged in the same cavity of the first volume 300, the spark plug 4 being kept fixed so as to extend at least partly in such a cavity while the pre-chamber 5 would be able to be moved in said cavity.

[0037] The movable pre-chamber 5 is arranged in the first volume 300 and is configured to be moved in said volume. Consequently, the movable pre-chamber 5 is configured to be moved relative to the spark plug 4 which has a fixed position within the first volume 300 delimited by the material of the cylinder head 3 below the spark plug well 30.

[0038] The movable pre-chamber 5 is particularly configured to be moved between a first position and a second position. The first position corresponds to a “closed” configuration in which the movable pre-chamber 5 obstructs and closes the at least one orifice 61 so as to interrupt the circulation of the flow of drain air FV passing through the at least one channel 6 towards the first volume 300. For example, the at least one wall of the pre-chamber closes the at least one orifice 61. In this case, the at least one wall considered is the side wall 52 or one of the side walls. By “closing” the at least one orifice 61 is meant that at least a part of the movable pre-chamber 5 is arranged opposite the at least one orifice 61, in particular in contact with a flank delimiting the first volume 300 comprising said orifice 61, in order to interrupt the fluid connection between the at least one channel 6 and the first volume 300. For example, the flank considered is a lateral flank of the first volume 300. Conversely, the second position corresponds to an “open” configuration in which the movable pre-chamber 5 extends at a non-zero distance from the at least one orifice 61 so as to re-establish the fluid connection between the at least one channel 6 and the first volume 300 and allow the circulation of the drain air flow FV in the first volume 300 and the intermediate volume 550 of the pre-chamber 5. The at least one orifice 61 is then cleared in whole or in part.

[0039] According to an optional but preferred embodiment, the movable pre-chamber 5 is configured to be moved according to a translation movement T1, along a first direction 100, in the first volume 300. For example, the first direction 100 is parallel, or substantially parallel, to the direction of extension of the spark plug 4 and / or to the main axis 500 of the pre-chamber 5. In particular, the movement of the movable pre-chamber 5 is limited to the second cavity 302.

[0040] Optionally but preferably, in order to limit the travel of the movable pre-chamber 5, the latter comprises at least one rim 54. The first volume 300 then comprises at least one blocking member 36 configured to form a stop for the at least one rim 54 so as to limit the movement of the movable pre-chamber 5 in the first volume 300, in particular in the second cavity 302.

[0041] For example, the at least one wall, in particular the at least one side wall 52, comprises a rim 54. The at least one rim extends projecting from all or part of an outer surface, facing the at least one side of the first volume 300, of the at least one wall. According to the illustrated embodiment, the at least one rim 54 extends along a second direction 200, transverse, particularly orthogonal, to the main axis 500 of the pre-chamber and / or to the first direction 100. Preferably, the at least one rim 54 is arranged in an upper half of the pre-chamber 5. The at least one rim 54 extends over all or part of a circumference of the cylindrical shape of the movable pre-chamber 5. For example, the at least one rim 54 forms a collar surrounding all or part of the outer surface of the prechamber 5.

[0042] The movable pre-chamber 5 is dimensioned so as to allow its movement in the first volume 300. Also, a first dimension of the pre-chamber 5, here defined along the main axis 500, is strictly less than a first dimension of the first volume 300 and / or a first dimension of the second cavity 302 along these same directions. A second dimension of the pre-chamber 5, measured along the second direction 200, is strictly less than a second dimension of the first volume 300. The second dimension of the pre-chamber 5 corresponding, for example, to a diameter or a diagonal of the base of the cylindrical shape. Optionally, the at least one rim is at least partly in contact with the at least one flank, in particular lateral, of the first volume 300, for example so as to limit the movement of the pre-chamber 5 along the second direction 200.

[0043] The at least one blocking member 36 is arranged in the first volume 300 and makes it possible, for example, to prevent the movement of the movable prechamber 5 beyond the first position and / or the second position. In this case, the first volume 300 comprises a plurality of blocking members 36. A first blocking member 36a comprises an intermediate flank 37 of the first volume 300 configured to form a stop for the movable prechamber 5 along a first direction of the first direction 100. A second blocking member 36b comprises a lower flank 38 of the first volume 300 configured to form a stop for the at least one rim 54 along a second direction, opposite the first direction along the first direction 100. In this case, in a non-limiting manner, the intermediate flank 37 participates in delimiting the first cavity 301 and the second cavity 302.Likewise, the lower flank 38 comprises, for example, the opening 35 of the first volume 300, the second blocking member 36 comprising in particular a border of the opening 35.

[0044] The return member 7 is capable of moving the pre-chamber 5 between the first position and the second position, thus indirectly allowing the flow of drain air FV to be controlled. In particular, as further explained below, the return member 7 is configured to move the movable pre-chamber 5 from the second position to the first position. It thus cooperates with the movable pre-chamber 5 during the engine cycle 2. The return member 7 indirectly allows the circulation of the flow of drain air FV to be controlled as a function of the position of the movable pre-chamber 5 as explained above. Here, the term "control" is understood to mean the possibility of interrupting the fluid connection between the at least one channel 6 and the combustion chamber 23 so as to interrupt the circulation of said flow or the possibility of allowing such a fluid connection.

[0045] The return member 7 is thus a passive, non-motorized member. By “passive” control is meant that it does not require direct motorized actuation. For example, the return member 7 is a spring and / or at least one elastically deformable blade. According to an exemplary embodiment, the return member 7 surrounds at least a portion of the movable prechamber 5. The return member 7 extends into a space between the movable prechamber 5 and the at least one lateral flank of the first volume 300. The return member 7 is in particular arranged to bear against a surface of the first volume 300, for example the lower flank 38. According to the illustrated, non-limiting exemplary embodiment, the return member 7 is arranged to bear against the at least one locking member 36, in particular the second locking member 36b. The return member 7 is also arranged in contact with the movable prechamber 5. For example, the recall member 7 is arranged in contact with the at least one edge 54. Notably, the recall member 7 is interposed, along the first direction 100 and / or the main axis 500, between at least a part of the prechamber 5 and at least a part of the first volume 300. In the present case, the recall member 7 is interposed between the at least one edge 54 of the prechamber 5 and the lower flank 38 of the first volume 300.

[0046] When the pre-chamber is in the first position, in the “open” configuration, the return member is in particular in an initial, or nominal, configuration. As further explained below, with reference to the method according to the invention, the return member 7 is actuated passively, here by displacement of the movable pre-chamber 5. The displacement of the movable pre-chamber 5 is done initially as a function of a differential pressure defined between a pressure measured in the first volume 300 and a pressure measured in the combustion chamber 23.

[0047] The movable pre-chamber 5 is moved to the second position when a depression is generated in the combustion chamber 23 at the time of an intake phase of the engine cycle 2. In particular, in the second position, the movable pre-chamber 5 is sucked in and thus moved towards the cylinder 21 and the combustion chamber 23. Here, the term "depression" means the lowering of the pressure in the combustion chamber 23 to a value strictly lower than atmospheric pressure. When it is moved to the second position, the pre-chamber 5 exerts a force on the return member 7. In particular, the return member 7 is previously calibrated in order to present a resistance adapted to allow such a movement of the pre-chamber according to a predefined depression level.Due to the movement of the pre-chamber 5, the at least one orifice 61 is uncovered and the flow of drain air FV circulates in the at least one channel 6, in the first volume 300, in particular through the pre-chamber 5, then is sent to the combustion chamber 23 of the cylinder 21 via the at least one hole 51. The flow of drain air FV thus makes it possible to evacuate all or part of an accumulation of residual burnt gases located in the first volume 300, in particular in the intermediate volume 550 of the pre-chamber 5, towards the combustion chamber 23.

[0048] Then, when the differential pressure decreases, the movable pre-chamber 5 is moved to the first position passively. Subsequently, thanks to the return force exerted by the return member 7, the return member 7 passively returns to its initial configuration, and, consequently, pushes the pre-chamber 5 to the first position at the contact zones between the pre-chamber 5 and the return member 7. The pre-chamber 5 arranged in the first position again obstructs the at least one orifice 61 and prevents the circulation of the flow of drain air FV in the first volume 300. Such a principle can be observed, for example, when the differential pressure decreases to the point of being insufficient to maintain the pre-chamber 5 in the second position, in particular depending on the setting of the return member 7.

[0049] In order to optimize the positioning of the movable pre-chamber 5 in the cylinder head 3, and so as to minimize its impact on the volume of the combustion chamber 23, the movable pre-chamber 5 is dimensioned and arranged so that a first surface 531 of the lower wall 53 of the pre-chamber 5 and a first face 381 of the lower flank 38 of the first volume 300, configured to be turned towards the combustion chamber 23 within the engine 2, are inscribed in the same plane when the pre-chamber 5 is arranged in the first position. The first surface 531 and the first face 381 are thus flush.Alternatively, when the pre-chamber 5 is arranged in the first position, the first surface 531 of the lower wall 53 of the pre-chamber 5 has a position greater than a position of the first face 381 of the lower flank 38 of the first volume 300 so that the first face 381 is interposed between the first surface 531 of the pre-chamber 5 and the combustion chamber 23 along the first direction 100 and / or the main axis 500. The movable pre-chamber 5 thus does not affect the volume of the combustion chamber 23 or the operation of the engine 2 during its operation.

[0050] 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.

[0051] During the admission phase, as illustrated in [Fig. 3], of an intake air flow FA into the at least one cylinder 21, the method comprises generating a depression in the cylinder 21, particularly in the combustion chamber 23, capable of moving the movable pre-chamber 5 into the second position. As indicated above, the depression here consists of lowering the pressure in the combustion chamber 23 to a value strictly lower than atmospheric pressure. The generated depression allows the pre-chamber 5 to move towards the second position, i.e. towards the combustion chamber 23, so that the movable pre-chamber 5 then extends at a non-zero distance from the at least one orifice 61. The movable pre-chamber 5 is then in the open configuration, the at least one orifice 61 is clear and the at least one channel 6 is in fluid connection with the first volume 300 and, by extension, with the combustion chamber 23.The flow of drain air FV then circulates through the at least one channel 6, in the first volume 300, particularly in the intermediate volume 550 of the movable pre-chamber 5, then through the at least one hole 51 in order to reach the combustion chamber 23.

[0052] According to a preferred example of execution of the method according to the invention, a de pressure is generated in the combustion chamber 23 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 of an opening law 35 of said valve in the engine cycle 2. The pressure in the at least one cylinder 21 is thus mechanically lowered to a value strictly lower than a value of atmospheric pressure and strictly lower than a value of the pressure in the intake duct 31. As indicated above, when the depression generated in the combustion chamber 23 is sufficient, the movable pre-chamber 5 is sucked towards the combustion chamber 23. It then moves towards the second position and passively releases the at least one orifice 61.The movable pre-chamber 5 is then in the “open” configuration, the flow of drain air FV circulates through the at least one channel 6, enters the first volume 300 and passes through the pre-chamber 5 and the at least one hole 51 before being sucked into the combustion chamber 23 due to the depression. All or part of the residual burnt gases present in the first volume 300 and the intermediate volume 550, in particular in the movable pre-chamber 5, accumulated during a previous combustion of a previous engine cycle 2 are then sucked towards the cylinder 21. This allows the cleaning, also called “draining”, of the movable pre-chamber 5 by passive blowing of the residual burnt gases without it being necessary to integrate a tank or a motorized system for blowing the drain air flow. At the same time, the movable pre-chamber 5 exerts a force on the return member 7, in particular via the rim 54 as described above.It is lowered, for example so as to extend at least partly into the combustion chamber 23 of the cylinder 21.

[0053] As indicated above, when the at least one channel 6 is connected to the intake duct 31, as illustrated in FIGS. 1 to 4, the drain air flow FV is a portion of the intake air flow FA diverted from its conventional trajectory, namely the intake duct 31, and redirected towards the first volume 300 via the at least one channel 6. Preferably, the bifurcation point 62, corresponding for example to a tapping point of the at least one channel 6 on the intake duct 31, is produced downstream of the filter and / or the device for measuring the flow rate of the intake air flow FA according to the direction of circulation of the intake air flow FA in the intake duct 31.Such a principle advantageously makes it possible to ensure that the drain air flow FV extracted from the intake air flow FA is free of particles and / or to ensure that the quantity of air injected into the cylinder 21, corresponding to a combination of the remaining intake air flow and the drain air flow FV, is known.

[0054] It should be noted that, preferably, the method according to the invention can be configured to be executed only during defined periods of operation of the engine 2. For example, the method can be executed when the engine 2 is operating at low load. The method according to the invention can then be inactive and no emptying of the pre-chamber 5 is performed, when the engine 2 is operating at overload.

[0055] Then, in a conventional manner, the intake valve 32 is opened, the cylinder 21 is filled with an intake air flow FA, coming from the intake duct 31, and the fuel injection 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.

[0056] Note that, when the intake valve 32 opens, the pressure in the combustion chamber 23 converges towards the pressure prevailing in the intake duct 31. This therefore results in the initially generated depression being reduced, or even interrupted. For example, in the case of a supercharged engine 2 at high load, the pressure measured in the intake duct 31 is strictly higher than atmospheric pressure. During this part of the intake phase of the intake air flow FA, the pre-chamber 5 can, depending on the operation of the engine 2, the pressure measured in the cylinder 21, the pressure measured in the intake duct 31 and the setting of the return member 7, be moved towards the first position or be maintained in the second position.The movable pre-chamber 5 can rise until it is arranged in the first position or in an intermediate position, between the first position and the second position, under the effect of the return member 7.

[0057] In a known manner, the engine cycle 2 continues with the compression phase. The intake valve 32 and the exhaust valve 34 are closed. Under the effect of the return member 7, the pre-chamber 5 is moved into the first position, corresponding to its nominal position, if such a movement has not taken place during the intake phase. The movable pre-chamber 5 is then in the “closed” configuration and obstructs the at least one orifice 61, thereby interrupting the fluid connection between the first volume 300 and the at least one channel 6.

[0058] 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, thereby increasing the pressure in the combustion chamber 23 and in the first volume 300. The pressure of the combustion chamber 23 increases. A portion of the fuel mixture is then sent into the pre-chamber 5 via the at least one hole 51. 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 5 and in a portion of the intermediate volume 550. Due to the combustion, the pressure rises in the movable pre-chamber 5 and expels the ignited gases towards the combustion chamber 23 in the form of jets of fire.

[0059] Then, during the expansion phase of the engine cycle, the flame front propagates in 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 the at least one orifice 61 are then always closed.

[0060] Finally, during the exhaust phase, illustrated in [Fig.4], the exhaust valve 34 opens. The piston 22 rises and simultaneously moves residual burnt gases present in the combustion chamber 23 of the cylinder 21 towards the exhaust duct 33 and towards the movable pre-chamber 5. In particular, a majority of the residual burnt gases is evacuated towards the exhaust duct 33 while a portion is sent towards the movable pre-chamber 5. A portion of the residual burnt gases is thus evacuated from the engine 2 via the exhaust duct 33, while a portion accumulates in the intermediate volume 550 and in the pre-chamber 5. The residual burnt gases thus accumulated in the intermediate volume 550, in the vicinity of the at least one spark plug 4, may be evacuated during the execution of the intake phase of a subsequent engine cycle 2, as described above.

[0061] The cylinder head 3 and the method according to the invention thus allow the implementation of a passive emptying of the movable pre-chamber 5 arranged in the first volume 300, thus limiting an accumulation of residual burnt gases in the vicinity of the spark plug 4 to an excessively high concentration likely to prevent the initiation of combustion of the fuel mixture. The emptying of the residual burnt gases accumulated during previous combustions, evacuated towards the cylinder 21 during the intake phase, thus allows autonomous cleaning of the pre-chamber 5 before it is refilled with a fuel mixture.

[0062] The invention thus proposes an alternative to cylinder heads equipped with spark plugs, in particular spark plugs with a pre-chamber, for example passive. The invention is capable of preventing the accumulation of residual burnt gases around said spark plug. The proposed solution is advantageously adapted to receive standard spark plugs, without a pre-chamber 5. The integration of a mobile pre-chamber 5 advantageously makes it possible to optimize the volume of said pre-chamber 5 for combustion while allowing the implementation of a passive emptying of the residual burnt gases not requiring motorized intervention directly on said pre-chamber.

[0063] The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any means or configuration equivalents and any technically effective combination of such means to the extent that they ultimately fulfill the functionalities described and illustrated in this document.

Claims

Claims

1. Cylinder head (3) for a spark-ignition engine (2) comprising at least one spark plug well (30) and a first volume (300), the first volume (300) being in particular delimited by the material of the cylinder head (3) below said well (30), a first end of said first volume (300) comprising an opening (35) configured to open into a combustion chamber (23) of a cylinder (21), the cylinder head (3) further comprising: - at least one spark plug (4) at least partly arranged in the first volume (300), in particular arranged in the first volume from the well (30); - at least one channel (6) opening into the first volume (300) at at least one orifice (61) and configured to allow the circulation of a flow of drain air (FV) towards the first volume (300);- a movable pre-chamber (5) comprising at least one hole (51) capable of allowing the passage of an air-fuel mixture between the combustion chamber (23) and the pre-chamber (5), the pre-chamber (5) being arranged in the first volume (300) and configured to be moved in the first volume (300), relative to the spark plug (4), between a first position, in which it extends opposite the at least one orifice (61) so as to interrupt the circulation of the flow of drain air (FV) towards the first volume (300), and a second position in which it extends away from the at least one orifice (61) so as to allow the circulation of the flow of drain air (FV) in the first volume (300); - a return member (7) capable of moving the pre-chamber (5) between the first position and the second position.;

2. Cylinder head (3) according to the preceding claim, further comprising an intake duct (31), equipped with an intake valve (32), and an exhaust duct (33), equipped with an exhaust valve (34), the at least one channel (6) being connected by a fluid connection to the intake duct (31).

3. Cylinder head (3) according to one of the preceding claims, in which the pre-chamber (5): - comprises a metallic material, such as steel; and / or - is configured to be moved in a translational movement, along a first direction (100), in the first volume (300).

4. Cylinder head (3) according to one of the preceding claims, in which the first volume (300) comprises a first cavity (301), comprising at least a part of the at least one spark plug (4), and a second cavity (302), comprising the movable pre-chamber (5), the first cavity (301), the second cavity (302) and the opening (35) being in fluid connection.

5. Cylinder head (3) according to one of the preceding claims, in which the return member (7) is a spring and / or at least one elastically deformable blade.

6. Cylinder head (3) according to one of the preceding claims, in which the pre-chamber (5) comprises at least one rim (54), the first volume (300) further comprising at least one locking member (36) configured to form a stop for the at least one rim (54) so ​​as to limit the movement of the movable pre-chamber (5) in the first volume (300).

7. Cylinder head (3) according to one of the preceding claims, comprising a lower flank (38) comprising the opening (35) and in which the movable pre-chamber (5) comprises a lower wall (53) comprising the at least one hole (51), the lower flank (38) and the lower wall (53) being configured to be turned towards the combustion chamber (23), a first face (381) of the lower flank (38) and a first surface (531) of the lower wall (53) being flush when the movable pre-chamber (5) is in the first position.

8. A spark-ignition engine (2) comprising a cylinder head (3) according to one of the preceding claims, 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 (35) of the cylinder head (3) and the at least one hole (51) of the pre-chamber (5) 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 a movement, in particular a movement delay, of said valve.

10. Method of operating a spark-ignition engine (2) according to claim 8 or 9, comprising: - an intake phase comprising the admission of an intake air flow, the injection of fuel and the generation of a depression in the cylinder (21) capable of moving the movable pre-chamber (5) in the second position so as to open the at least one orifice (61) and allow the circulation of a flow of drain air (FV), in particular drawn from the flow of intake air, in the at least one channel (6), the first volume (300) and towards the combustion chamber (23), said flow being capable of expelling residual burnt gases located in the pre-chamber (5) and / or in the first volume (300); then - a compression phase comprising an increase in the pressure in the cylinder so that a portion of an air-fuel mixture is sent into the pre-chamber (5) and further comprising the ignition of said mixture in the pre-chamber (5); then - an expansion phase in which the air-fuel mixture contained in the cylinder (21) ignites; then - an exhaust phase comprising the rise of the piston (22) so as to evacuate part of the residual burnt gases present in the combustion chamber (23) of the cylinder (21) towards the movable pre-chamber (5).

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