Cylinder head for spark-ignition engine including one spark plug

Abstract

Title: Cylinder head for spark-ignition engine comprising a spark plug. Cylinder head (3) for a spark-ignition engine (2) comprising a well (30), a spark plug (4) and a prechamber (5) disposed in the well, the cylinder head further comprising at least one channel (6) opening into the prechamber (5) and configured to permit the flow of a drain air (DA) to the intermediate volume (500), a pump (7) configured to propel the drain air (DA) and a means (8) for regulating the flow of the drain air (DA). 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 capable of evacuating residual burnt gases present in the pre-chamber at the end of previous 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, a first end of said well comprising an opening configured to open into a main combustion chamber of a cylinder. The cylinder head further comprises at least one spark plug disposed in the well and a pre-chamber comprising a body delimiting an intermediate volume and comprising at least one hole capable of allowing the passage of an air-fuel mixture between the main combustion chamber and the pre-chamber. The cylinder head also comprises at least one channel opening into the intermediate volume at at least one orifice included in a wall of the cylinder head and / or in the pre-chamber and configured to allow the circulation of a flow of drain air towards the intermediate volume.The cylinder head finally comprises a pump configured to propel the flow of drain air towards the pre-chamber via the at least one channel and at least one means for regulating the circulation of the flow of drain air. arranged on a passage of the drain air flow, in particular in the pre-chamber, so as to regulate the circulation of the drain air flow through the intermediate volume of the pre-chamber.

[0006] According to an exemplary embodiment, the cylinder head may, in addition, 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 body of the prechamber: - may include a metallic material, such as steel; and / or - can be placed in the cylinder head well by shrinking.

[0008] Optionally, the body of the pre-chamber may comprise a first cavity housing the spark plug and a second cavity housing the regulating means, the first cavity and the second cavity being in fluid connection with the opening of the pre-chamber.

[0009] According to an exemplary embodiment, the at least one means for regulating the circulation may be a non-return valve comprising at least one ball and one spring.

[0010] In particular, a second end of the well, opposite the first end, and / or the pre-chamber may comprise a sealing member.

[0011] Optionally, the cylinder head may comprise a plurality of wells each equipped with a pre-chamber, a means for regulating the circulation of the drain air flow and a spark plug, the cylinder head comprising: - a plurality of channels, each channel opening into an intermediate volume specific to one of the pre-chambers arranged in one of the wells at the level of at least one orifice; or - a single channel opening into the intermediate volumes of the different pre-chambers, each specific to one of the wells, via a plurality of orifices, each orifice opening into one of the wells and / or into one of the intermediate volumes specific to one of the pre-chambers arranged in one of the wells.

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

[0013] Optionally, the engine may comprise a pump control device and at least one pressure sensor, the control device being configured to regulate a pressure of the drain flow in the at least one channel as a function of a pressure measured at at least one point of the cylinder head.

[0014] The invention finally relates to a method of operating an ignition engine controlled according to the invention, comprising: - an intake phase comprising the injection, into the cylinder, of a flow of intake air and fuel so as to form an air-fuel mixture, the intake phase further comprising the injection of a flow of drain air drawn from the flow of intake air and propelled, by means of the pump, into the at least one channel and into the intermediate volume of the pre-chamber so as to expel residual burnt gases located in the pre-chamber; then - a compression phase comprising an increase in the pressure in the cylinder so that part of the air-fuel mixture is sent into the pre-chamber and then the ignition of said mixture in the pre-chamber; then - an expansion phase in which the air-fuel mixture in the cylinder ignites; then - an exhaust phase comprising the rise of the piston so as to move part of the residual burnt gases present in the main combustion chamber of the cylinder towards the 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 pre-chamber.

[0017] [Fig.2] is a schematic representation of a spark plug well of the cylinder head equipped with a spark plug and a 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.5] is a schematic representation of an engine and cylinder head comprising a plurality of spark plug wells and cylinders.

[0021] [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. The vehicle 1 in question may in particular be a connected and / or autonomous vehicle.

[0022] 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 can be injected an air-fuel mixture, also called a carbureted mixture.

[0023] The engine 2 also comprises a cylinder head 3. Generally, the cylinder head 3 according to the invention comprises at least one spark plug well 30 delimiting a first volume 300. 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 and a pre-chamber 5, both arranged at least partly in the at least one spark plug well 30, in particular in the first volume 300. The pre-chamber 5 comprises a body 50 delimiting an intermediate volume 500. The cylinder head 3 also comprises at least one channel 6 opening into the intermediate volume 500 of the pre-chamber 5 and configured to allow the circulation of a flow of drain air FV towards the intermediate volume 500.The cylinder head 3 also comprises a pump 7, configured to propel the flow of drain air FV towards the pre-chamber 5 via the at least one channel 6, and at least one means 8 for regulating the circulation of the flow of drain air FV.

[0024] Also, as illustrated, according to an exemplary embodiment, the cylinder head 3 comprises 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 movably and are capable of allowing or interrupting the fluid connection between the duct in which each valve considered is equipped and the main combustion chamber 23.

[0025] It is understood that the description is made with reference to a cylinder 21 considered of the engine 2 and with reference to a part of the associated cylinder head 3. It nevertheless extends to a spark-ignition engine 2 comprising a plurality of cylinders 21 each equipped with a piston 22 and, by way of extension, to a cylinder head 3 comprising a plurality of wells 30, spark plugs 4, intake valves 32 and exhaust valves 34, as further explained below.

[0026] The at least one spark plug well 30 delimits the first volume 300 in which all or part of the at least one spark plug 4 and the pre-chamber 5 are arranged. The intermediate volume 500, delimited by the pre-chamber 5, is thus included in the first volume 300. A first end of the well 30 comprises an opening 35 configured to open into the main combustion chamber 23 of the associated cylinder 21 when the engine 2 is assembled.

[0027] The spark plug 4 may be a standard spark plug. The spark plug 4 does not have an integrated pre-chamber 5. Conventionally, the spark plug 4 comprises at least one electrically insulating element 41 and an electrically insulating base 42. conductive. The electrically insulating element 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. The spark plug 4 is arranged in the well 30 of the cylinder head 3 so as to extend at least partly into the first volume 300. For example, the spark plug 4 extends along an extension direction 400.

[0028] Also, in a known manner, the spark plug 4 further comprises at least one central electrode 43 and at least one ground electrode 44. The at least one central electrode 43 and the at least one ground electrode 44 are separated from each other by an inter-electrode space, that is to say a gap separating two electrodes not being 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 43 and / or ground electrodes 44. 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 43 of the spark plug 4.

[0029] The body 50 of the pre-chamber 5 is a part arranged in the first volume 300 of the at least one well 30 of the cylinder head 3. Conventionally, the term "pre-chamber" is understood to mean a chamber separate from the main combustion chamber 23 of the at least one cylinder 21 having a limited volume, particularly a more limited volume than that of the main combustion chamber 23, at which the 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 main 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 separate from the at least one spark plug 4 and is not integrated into the base 42 and / or the electrically insulating element 41.

[0030] In a particular, preferential manner, the body 50 of the pre-chamber 5 is a part added to the well 30. In particular, according to an exemplary embodiment, the body 50 of the pre-chamber 5 is arranged in the at least one well 30 by shrink fitting. Optionally but preferentially, the body 50 of the pre-chamber 5 is made of a metallic material, in particular of a metallic material such as steel, resistant to high temperatures which may exceed 600°C.

[0031] Conventionally, the body 50 of the prechamber 5 comprises at least one hole 51 capable of allowing the passage of the air-fuel mixture between the main combustion chamber 23 and the intermediate volume 500 of the pre-chamber 5, as further described below with reference to the method according to the invention.

[0032] The pre-chamber 5 also comprises at least one wall delimiting the intermediate volume 500. For example, the pre-chamber 5 comprises a side wall 52 or a plurality of side walls 52. Also, the pre-chamber 5 comprises a lower wall 53, delimiting one side of the pre-chamber 5 arranged at the level of the opening 35 of the well 30 or at the edges of the opening 35 of the well 30, that is to say on the side of the first end of the well 30. In this case, the lower wall 53 comprises the at least one hole 51. For example, the pre-chamber 5, particularly the lower wall 53, comprises a plurality of holes 51 capable of ensuring a fluid connection between the intermediate volume 500 and the main combustion chamber 23 of the cylinder 21.

[0033] According to a non-limiting exemplary embodiment, the prechamber 5 comprises a cylindrical or partly cylindrical shape at least partly complementary to the shape of the well 30 in which it is arranged. For example, a base of the cylindrical shape is defined by the side wall 52 or by the plurality of side walls 52 of the prechamber 5.

[0034] Optionally but preferably, the pre-chamber 5 is shaped and dimensioned so as to receive all or part of the spark plug 4 and / or so as to receive all or part of the means 8 for regulating the flow of drain air. The pre-chamber 5 according to the invention can thus advantageously ensure the function of holding the spark plug 4 in the well 30 and of the ignition zone during the engine cycle 2, as explained above.

[0035] Figures 1 to 4 illustrate a particular example of embodiment of the pre-chamber 5, non-limiting, in which the body 50 comprises a first cavity 301 and a second cavity 302 included in the intermediate volume 500. The first cavity 301 houses the spark plug 4 while the second cavity 302 houses the regulating means 8. The first cavity 301 and the second cavity 302 are also arranged so as to be in fluid connection with each other on the one hand and with the opening 35 of the pre-chamber 5 on the other hand. For example, the first cavity 301 and the second cavity 302 open into a common intermediate cavity 303 included in the pre-chamber 5 and comprising the at least one hole 51.

[0036] In this case, the first cavity 301 extends along a primary direction 304, parallel or substantially parallel to the extension direction 400 of the spark plug 4. The common intermediate cavity 303 is interposed between the first cavity 301 and the at least one hole 51 of the prechamber 5 and / or the opening 35 of the cylinder head 3 along at least one direction. For example, the common intermediate cavity 303 is interposed between the first cavity 301 and the at least one hole 51 of the prechamber 5 and / or the opening 35 of the cylinder head 3 along a first direction 100, parallel to the extension direction 400 and / or to the primary direction 304. For example again, the first direction 100 is parallel, or substantially parallel, to a vertical direction within the engine 2. Optionally again, as illustrated in Figures 1 to 4, the first cavity 301 and the second cavity 302 may open into the intermediate cavity 303 substantially in a plane orthogonal to the first direction 100, in particular a plane parallel to the plane 200 as shown in the figures. For example, the first cavity 301 and the second cavity 302 are adjacent. In this way, the common intermediate cavity 303 is interposed between the first cavity 301 and the second cavity 302 on the one hand, and the at least one hole 51 and / or all or part of the opening 35 on the other hand along the first direction 100.

[0037] Also, optionally but preferably, the pre-chamber 5 is open on one side, in particular on a side opposite a side of the pre-chamber 5 comprising the at least one hole 51. The open side allows in particular the insertion of the spark plug 4 and / or the means 8 for regulating the flow of drain air FV. In the example illustrated, the open side is an upper side of the pre-chamber 5, along the first direction 100, corresponding to a highest side of the pre-chamber 5 within the engine 2. In a non-limiting manner, the first cavity 301 and the second cavity 302 are thus open at the open side of the pre-chamber 5.

[0038] Optionally, the cylinder head 3 and / or the pre-chamber 5 comprises at least one sealing means 45, not shown, arranged at the interface between the spark plug 4 and the cylinder head 3 and / or at the interface between the spark plug 4 and the pre-chamber 5, for example around the spark plug 4. The sealing means 45 advantageously makes it possible to limit the circulation of the flow of drain air FV and the air-fuel mixture in the first volume 300 so as to limit such circulation to all or part of the intermediate volume 500 of the pre-chamber 5. For example, the sealing means 45 prevents the circulation of the flow of drain air and the air-fuel mixture in at least part of the first volume 300 of the well 30.

[0039] Likewise, optionally, a second end of the well 30, opposite the first end, and / or the pre-chamber 5 comprises a sealing member 9. For example, the sealing member 9 is a seal, a plug or a cover. In particular, the sealing member 9 is arranged near the regulating means 8, for example so as to close the second cavity 302.

[0040] Additionally or alternatively, the second end of the well 30, not shown, is 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 the well 30.

[0041] The at least one channel 6 opens into the intermediate volume 500 of the prechamber 5 at the level of at least one orifice 61. The at least one orifice 61 is included in one of the walls of the cylinder head 3 and / or in one of the walls of the pre-chamber 5. For example, one of the walls of the cylinder head 3 comprises a first orifice 61a while the body 50 of the pre-chamber 5, in particular the side wall 52 or one of the side walls 52 of the pre-chamber 5, comprises a second orifice 61b. The second orifice 61b is then arranged opposite the first orifice 61a so as to ensure the fluid connection between the at least one channel 6 and the intermediate volume 500 of the pre-chamber 5.

[0042] The at least one channel 6 is configured to allow the circulation of a flow of drain air FV towards the intermediate volume 500. In other words, the at least one channel 6 is configured to supply the intermediate volume 500 with a flow of drain air FV. The term “flow of drain air” means a flow of air circulating through all or part of the intermediate volume 500 of the pre-chamber 5 in order to evacuate residual burnt gases likely to have accumulated there during previous combustions towards the main combustion chamber 23. The flow of drain air FV thus allows, as further explained below, the cleaning of at least the pre-chamber 5.

[0043] According to a preferred embodiment illustrated by [Fig. 5], the at least one channel 6 is connected by a fluid connection to the intake duct 31 at a bifurcation point 62. The at least one channel 6 thus extends between the intake duct 31 and the well 30, particularly the intermediate volume 500 of the pre-chamber 5. It makes it possible to extract a portion of an intake air flow FA, circulating in the intake duct 31 in the direction of the main combustion chamber 23, in order to direct it towards the intermediate volume 500 of the pre-chamber 5. The extracted portion of the intake air flow FA thus forms the drain air flow FV as explained above. According to distinct embodiments, the at least one channel 6 is a passage machined in the material of the cylinder head 3 or a tube connecting different points of the cylinder head 3 to each other, namely here said bifurcation point 62 and the at least one orifice 61.

[0044] Optionally, the intake duct 31 is equipped with at least one filter and / or a flow rate measuring device, or flow meter. The at least one channel 6 is then, preferably, connected to the intake duct 31 downstream of said filter and / or said measuring device according to a direction of circulation of the intake air flow FA.

[0045] The cylinder head 3 according to the invention particularly comprises a pump 7, in particular an electric pump 7. The pump 7 is configured to take a portion of the intake air flow FA, thus forming the drain air flow FV that said pump 7 is then able to propel towards the intermediate volume 500 of the prechamber 5 via the at least one channel 6. The pump 7 thus allows the active blowing of the drain air flow FV through the at least one channel 6, that is to say a blowing carried out by a motorized device. In particular, the pump 7 advantageously allows the projection of the drain air flow at a desired defined pressure. For example, optionally, the cylinder head 3 comprises a control device 71 of the pump 7 and at least one pressure sensor 72. For example, as illustrated in [Fig. 5], the cylinder head 3 comprises an intake pressure sensor 72a, capable of measuring the pressure of the intake air flow FA and / or a pressure sensor 72b arranged at the at least one channel 6, configured to measure the pressure of the drain air flow FV. The control device 71 is configured to control the operation of the pump 7 so as to adapt the pressure of the drain air flow FV in the at least one channel 6 as needed based on a pressure measured at at least one point of the cylinder head 3.For example, the pressure of the drain air flow FV is defined as a function of the pressure of the intake air flow FA, measured by the at least one pressure sensor 72, in particular the intake pressure sensor 72a, in the intake duct 31.

[0046] The regulating means 8 is configured to regulate the circulation of the drain air flow FV through the intermediate volume 500 of the pre-chamber 5. In particular, the regulating means 8 is configured to regulate, or control the circulation of said flow. By "regulate" or "control" is meant the possibility of interrupting the circulation of said flow and, consequently, the fluid connection between the at least one channel 6 and the entire intermediate volume 500. In particular, the regulating means 8 is of the passive type. By "passive" control is meant that the regulating means 8 is not directly actuated in a motorized manner or that it does not require a power supply, for example electrical.

[0047] The at least one means 8 for regulating the circulation of the drain air flow FV is arranged on a passage of the drain air flow FV, corresponding to a trajectory of the drain air flow in the cylinder head 3. According to a preferred embodiment, the at least one regulating means 8 is arranged in the pre-chamber 5 so as to regulate the circulation of the drain air flow FV through the intermediate volume 500 of the pre-chamber 5. For example, the at least one regulating means 8 is arranged near the at least one orifice 61 and / or the at least one channel 6 so as to minimize the circulation of the drain air flow in the intermediate volume 500 of the pre-chamber 5. For example, as described above in a non-limiting manner, the regulating means 8 is arranged in the second cavity 302.According to a preferred embodiment, illustrated, the regulation means 8 is arranged on the path or passage of the drain air flow FV, in particular between the at least one orifice 61 and the at least one hole 51 of the pre-chamber 5 in a direction of circulation of the drain air flow FV through the well 30. According to an alternative embodiment, not shown, the at least one regulation means 8 is configured to cooperate with the at least one orifice 61, for example so as to close the at least one orifice 61 and thus interrupt the circulation of the drain air flow FV through the pre-chamber 5.

[0048] According to a preferred embodiment, the at least one regulating means 8 is a non-return valve comprising at least one ball 81 and a spring 82. The spring 82 is in particular arranged to bear on an intermediate surface 83, formed by a part of the pre-chamber 5 in order to maintain the spring 82. For example, the intermediate surface 83 is included in the second cavity 302 and / or in the intermediate cavity 303. Optionally, the regulating means 8 further comprises a holding member 84 for the ball 81. The holding member 84 comprises a tube arranged in the continuity of the passage, or of the trajectory, of the drain air flow FV so as to allow the circulation of said flow. The holding member 84 also comprises a recess, arranged opposite the tube and configured to receive the ball 81.

[0049] The regulating means 8 thus allows, in particular, the circulation of the drain flow FV from the channel 6 to the pre-chamber 5 when the pressure in the channel 6 is higher than the pressure in the pre-chamber 5, to which it is appropriate in particular to add the calibration of the spring 82, and prevents the reverse circulation of a flow of fuel mixture or residual burnt gases from the pre-chamber 5 to the channel 6 when the pressure in the pre-chamber 5 becomes higher than the pressure in the channel 6. More particularly, the ball 81 is configured to be moved between a “closed” configuration and an “open” configuration. In the “closed” configuration, the spring 82 is in the nominal position, the ball 81 is arranged in support of the spring 82, in particular the ball 81 extends into the recess of the holding member 84.It blocks the circulation of the drain air flow FV in at least a portion of the prechamber 5, here by preventing the passage of the drain air flow FV beyond the holding member 84 and, conversely, prevents the passage of residual burnt gases towards the at least one channel 6. Such a configuration can be observed when no drain air flow FV is projected into the at least one channel 6 or when the pressure of said drain air flow FV is insufficient to allow the actuation of the regulating means 8, in this case the movement of the ball 81. In the “open” configuration, the drain air flow FV is projected into the at least one channel 6 with sufficient pressure to move the ball 81. The latter is in particular moved out of the recess of the holding member 84. The ball 81 then exerts a force on the spring 82 and compresses it.The movement of the ball 81 then allows the passage of the flow of drain air FV into the pre-chamber 5 and through the at least one hole 51, towards the main combustion chamber 23, here by releasing the tubing from the holding member 84.

[0050] As further explained below, with reference to the method according to the invention, the regulation means 8 is thus actuated passively, here by displacement of the ball 81 due to the flow of drain air FV propelled by the pump 7. For example, the spring 82 is previously calibrated in order to actuate the regulation means 8 from a predefined drain air flow pressure threshold at the time of an intake phase of engine cycle 2 and / or from a predefined pressure differential threshold between the drain air flow pressure FV and the pressure in the pre-chamber 5.

[0051] [Fig. 5] schematically illustrates an exemplary embodiment in which the cylinder head 3 comprises a plurality of wells 30 each equipped with a pre-chamber 5, a means 8 for regulating the circulation of the drain air flow FV and a spark plug 4 as explained above. Also 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 are associated with each well 30.

[0052] According to the illustrated embodiment, the cylinder head 3 comprises a single channel 6 opening into the intermediate volumes 500 of the different pre-chambers 5 arranged in the different wells 30 via a plurality of orifices 61. Each orifice 61 thus opens into the first volume 300 of one of the wells 30 and by extension into the intermediate volume 500 of the pre-chamber 5 equipped in said well 30. The channel 6 thus forms a distribution ramp for the drain air flow FV. The channel 6 opens, for example, into the intake duct 31 at a single bifurcation point 62 as explained above. According to an alternative embodiment, not shown, the cylinder head 3 comprises a plurality of channels 6, each channel 6 opening into one of the wells 30 at at least one orifice 61.In particular, each of the channels 6 is connected, by a fluid connection, to the intake duct 31 by a bifurcation point 62 which is specific to it or, alternatively, by a common bifurcation point 62. Regardless of whether the cylinder head 3 comprises a single channel 6 or a plurality of channels 6, the pump 7 allows the propulsion of the flow of drain air towards the different wells 30 and the intermediate volume 500 of the pre-chambers 5 which they comprise.

[0053] 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.

[0054] As illustrated in [Fig. 3], during the intake phase, in a conventional manner, the intake valve 32 is open, an intake air flow FA circulates in the intake duct 31 and is sent to the main combustion chamber 23 of the at least one cylinder 21. In parallel, 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 main combustion chamber 23.

[0055] The method then comprises, in parallel with the admission of the intake air flow FA, the injection of a flow of drain air FV taken from the flow of intake air FA into the at least one channel 6 and into the intermediate volume 500 of the pre-chamber 5. The flow of drain air FV is extracted via the pump 7 and propelled by the latter through the at least one channel 6, into the volume of the pre-chamber 5, then through the at least one hole 51 in order to reach the main combustion chamber 23 so as to expel residual burnt gases located in the pre-chamber 5. All or part of the residual burnt gases present in the intermediate volume 500 delimited by the body 50 of the pre-chamber 5, accumulated during a previous combustion of a previous engine cycle 2, are then propelled towards the cylinder 21. This allows the cleaning, also called “draining”, at least partial of the pre-chamber 5 by active blowing of the residual burnt gases.

[0056] As indicated above, according to a preferred embodiment, the at least one channel 6 is connected to the intake duct 31, as illustrated in FIGS. 1 to 5, the drain air flow FV is then a portion of the intake air flow FA extracted by the pump 7 and diverted from its conventional trajectory, namely from the intake duct 31, and redirected towards the intermediate volume 500 of the pre-chamber 5 via the at least one channel 6. Advantageously, the sampling of a portion of the intake air flow FA allows the implementation of a draining of the pre-chamber 5 without it being necessary to integrate an air reservoir in the cylinder head 3.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, since this air flow has been previously filtered by the filter. It also makes it possible to ensure that the overall quantity of air sucked into the cylinder 21 corresponds to the air flow measured by the air flow meter mounted downstream of the filter, this flow rate corresponding to the sum of the flow rate of the drain air flow FV and the flow rate of the intake air flow remaining after sampling the drain air flow.

[0057] The drain air flow is propelled under pressure into the pre-chamber 5 by the electric pump 7 controlled by the control device 71 of the pump 7. For example, the control device 71 is an injection computer. The pressure of the drain air flow FV is particularly regulated so as to allow the actuation of the at least one regulation means 8. In particular, the pressure of the drain air flow FV, measured in the at least one channel 6, is strictly greater than the pressure measured in the main combustion chamber 23 and / or in the intake duct 31 in order to allow the opening of the at least one regulation means 8 and the circulation of the drain air flow in the pre-chamber 5 as previously explained. In particular, the pressure of the drain air flow measured in the at least one channel 6 is strictly greater than the sum of the pressure measured in the main combustion chamber 23 and the force of the spring 82 of the at least one regulating means 8. As indicated above, for example, the spring 82 is previously calibrated in order to actuate the regulating means 8 from a predefined threshold of pressure differential between the pressure of the drain air flow FV and the pressure in the pre-chamber 5, which, during the intake phase, is in particular close to the pressure of the intake flow FA. When such a threshold is reached, or exceeded, in the example illustrated, the ball 81 is moved and exerts a force on the spring 82.It frees the passage of the drain air flow FV, here by being moved out of the recess and by releasing the tubing of the holding member 84, so as to allow the circulation of the drain air flow FV through the pre-chamber 5 and towards the main combustion chamber 23. The at least one regulation means 8 also advantageously makes it possible to avoid the reflux of the drain air flow FV, also called "back flow" in English.

[0058] Optionally but preferably, the pressure of the drain air flow FV and / or the defined pressure differential threshold is adjusted by the control device 71 of the pump 7 as a function of the pressure measured by the at least one pressure sensor 72, in particular the intake pressure sensor 72a arranged at the intake duct 31. Note that, when the intake valve 32 opens and the piston 22 descends, the pressure in the cylinder 21 and the main combustion chamber 23 tends to approach the pressure measured in the intake duct 31. This pressure of the intake flow FA is much lower than atmospheric pressure when the engine 2 operates at low load and can, on the other hand, be much higher than atmospheric pressure at high load when the engine 2 is supercharged.

[0059] It should be noted that, preferably, the method according to the invention can be configured to be executed only during defined periods or cycles of operation of the engine 2. The method according to the invention can then be inactive and no emptying of the pre-chamber 5 is carried out.

[0060] In a known manner, the engine cycle 2 continues with the compression phase. The intake valve 32 and the exhaust valve 34 are closed. The fuel injection continues and the fuel mixture is homogenized due to the turbulence which prevails in the main combustion chamber 23 of the cylinder 21. The piston 22 rises in the cylinder 21, thereby increasing the pressure in the main combustion chamber 23. A portion of the fuel mixture is then sent into the pre-chamber 5 via the at least one hole 51. The active blowing of the flow of drain air by the pump 7 is interrupted. The regulating means 8 is in the “closed” configuration and the circulation of the drain air flow is interrupted in the pre-chamber 5. The fluid connection between the intermediate volume 500 of the pre-chamber 5 and the at least one channel 6 is then interrupted.

[0061] 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. Due to the combustion, the pressure rises in the pre-chamber 5 and expels the ignited gases towards the main combustion chamber 23 in the form of jets of fire.

[0062] Then, during the expansion phase of the engine cycle 2, the flame front propagates in the main combustion chamber 23 in the form of jets of fire which constitute a multitude of ignition points, making it possible to initiate combustion very quickly in the main combustion chamber 23 and thus to optimize the timing of the heat release law and the combustion efficiency. The intake valve 32, the exhaust valve 34 and the regulating means 8 are then always closed.

[0063] Finally, during the exhaust phase, illustrated in [Fig. 4], the exhaust valve 34 opens. The piston 22 rises and simultaneously displaces residual burnt gases present in the main combustion chamber 23 of the cylinder 21 towards the exhaust duct 33 and towards the 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 500 of the pre-chamber 5. The residual burnt gases thus accumulated in the pre-chamber 5 can be evacuated during the execution of the intake phase of a subsequent engine cycle 2, as described above.The pressure measured in the main combustion chamber 23 drops but remains strictly higher than the pressure measured in the at least one channel 6 and / or in the intake duct 31, so that the regulation means 8 remains in the “closed” configuration as indicated above and the fluid connection between the intermediate volume 500 of the pre-chamber 5 and the at least one channel 6 remains interrupted.

[0064] The cylinder head and the method according to the invention thus allow the implementation of an active emptying of the pre-chamber, thus limiting an accumulation of residual burnt gases in the vicinity of the spark plug to a concentration that is too high and 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 during the intake phase, thus allows the pre-chamber to be cleaned before it is refilled with a fuel mixture.

[0065] The invention thus proposes an alternative to cylinder heads equipped with spark plugs, in particular pre-chamber spark plugs, for example passive. The invention is capable of preventing the accumulation of residual burnt gases around said spark plug. The proposed solution is advantageously suitable for receiving standard spark plugs, without a pre-chamber. The integration of a pre-chamber in the well advantageously makes it possible to optimize the volume of said pre-chamber for combustion while allowing the regulation of a flow of drain air capable of evacuating residual burnt gases. The invention thus makes it possible to optimize the operation of the pre-chamber over a wide operating range, which makes it possible to optimize the efficiency of the engine by phasing the combustion in an optimal manner. The cylinder head according to the invention also advantageously allows an implementation that does not require the integration of an air reservoir specifically dedicated to draining the pre-chamber, thus making it possible to limit the size and costs generated.

[0066] 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. Cylinder head (3) for a spark-ignition engine (2) comprising at least one spark plug well (30), a first end of said well (30) comprising an opening (35) configured to open into a main combustion chamber (23) of a cylinder (21), the cylinder head (3) further comprising: - at least one spark plug (4) arranged in the well (30); - a pre-chamber (5) comprising a body (50) delimiting an intermediate volume (500) and comprising at least one hole (51) capable of allowing the passage of an air-fuel mixture between the main combustion chamber (23) and the pre-chamber (5); - at least one channel (6) opening into the intermediate volume (500) at the level of at least one orifice (61) included in a wall of the cylinder head (3) and / or in the pre-chamber (5) and configured to allow the circulation of a flow of drain air (FV) towards the intermediate volume (500);- a pump (7) configured to propel the flow of drain air (FV) towards the pre-chamber (5) via the at least one channel (6); - at least one means (8) for regulating the circulation of the flow of drain air (FV) arranged on a passage of the flow of drain air (FV), in particular in the pre-chamber (5), so as to regulate the circulation of the flow of drain air through the intermediate volume (500) of the pre-chamber (5).;

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 body (50) of the pre-chamber (5): - comprises a metallic material, such as steel; and / or - is arranged in the well (30) of the cylinder head (3) by shrink fitting.

4. Cylinder head (3) according to one of the preceding claims, in which the body (50) of the pre-chamber (5) comprises a first cavity (301) housing the spark plug (4) and a second cavity (302) housing the regulating means (8), the first cavity (301) and the second cavity (302) being in fluid connection with the opening (35) of the pre-chamber (5).

5. Cylinder head (3) according to one of the preceding claims, in which the at least one means (8) for regulating the circulation is a non-return valve comprising at least one ball (81) and a spring (82).

6. Cylinder head (3) according to one of the preceding claims, in which a second end of the well (30), opposite the first end, and / or the pre-chamber (5) comprises a sealing member (9).

7. Cylinder head (3) according to one of the preceding claims comprising a plurality of wells (30) each equipped with a pre-chamber (5), a means (8) for regulating the circulation of the drain air flow (FV) and a spark plug (4), the cylinder head (3) comprising: - a plurality of channels (6), each channel (6) opening into an intermediate volume (500) specific to one of the pre-chambers (5) arranged in one of the wells (30) at the level of at least one orifice (61); or - a single channel (6) opening into the intermediate volumes (500) of the different pre-chambers (5) each specific to one of the wells (30) via a plurality of orifices (61), each orifice (61) opening into one of the wells (30) and / or into one of the intermediate volumes (500) specific to one of the pre-chambers (5) arranged in one of the wells (30).

8. Spark-ignition engine (2) comprising a cylinder head (3) according to one of the preceding claims, at least one cylinder (21) delimiting a main 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 main combustion chamber (23).

9. Spark-ignition engine (2) according to the preceding claim, comprising a control device (71) for the pump (7) and at least one pressure sensor (72), the control device (71) being configured to regulate a pressure of the drain flow in the at least one channel (6) as a function of a pressure measured at at least one point of the cylinder head (3).

10. Method of operating a spark-ignition engine (2) according to claim 8 or 9, comprising: - an intake phase comprising the injection, into the cylinder (21), of a flow of intake air and fuel so as to form an air-fuel mixture, the intake phase further comprising the injection of a flow of drain air (FV) taken from the flow of intake air and propelled, by means of the pump (7), into the at least one channel (6) and into the intermediate volume (500) of the pre-chamber (5) so as to expel residual burnt gases located in the pre-chamber (5); then - a compression phase comprising an increase in the pressure in the cylinder (21) so that a portion of the air-fuel mixture is sent into the pre-chamber (5) then 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 move part of the residual burnt gases present in the main combustion chamber (23) of the cylinder (21) towards the pre-chamber (5).

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