Spark-ignition engine cylinder head with spark plug and movable pre-chamber

Abstract

A cylinder head (3) for a spark-ignition engine (2) comprises at least one spark plug shaft (30), below which a cylinder head casting defines a first volume (300), and a spark plug (4) and a movable pre-chamber (5) are configured to move relative to the spark plug (4) within the first volume (300) to circulate exhaust airflow within the first volume (300) and within an intermediate volume (550) of the pre-chamber (5).

Description

Technical Field

[0001] The present invention relates to a spark ignition engine cylinder head provided with a spark plug. Furthermore, the present invention relates to an engine equipped with said cylinder head. Finally, the present invention relates to a method for operating such an engine.

Background Art

[0002] Improving the efficiency of spark ignition heat engines is one of the challenges facing the automotive industry, and increasing the compression ratio is an important area for improvement. Nevertheless, increasing the compression ratio of a heat engine involves challenges such as fuel auto-ignition, also known as knocking, which can potentially damage the engine.

[0003] A solution to these challenges is to use a spark plug with a pre-chamber, more specifically a spark plug with a passive pre-chamber, that is, a spark plug that does not have a fuel injection mechanism that operates directly into the pre-chamber. The disadvantage of such a spark plug is that residual combustion gases, i.e., GBR, gradually accumulate in the pre-chamber until they reach a high proportion, which can affect the combustion of the fuel mixture or even make such combustion inefficient.

[0004] The present invention is included in this context and aims to provide an alternative to known cylinder heads designed to discharge residual combustion gases that may remain in the pre-chamber after a combustion cycle, in order to guarantee good quality of the fuel mixture in the pre-chamber before ignition by the spark plug.

[0005] The present invention relates to a cylinder head for a spark-ignition engine comprising at least one spark plug shaft and a first volume, wherein the first volume is demarcated by cylinder head material below the shaft, and the first end of the first volume comprises an opening designed to open into a cylinder combustion chamber. Furthermore, the cylinder head comprises at least one spark plug positioned at least partially within the first volume, particularly positioned within the first volume from the shaft, and at least one channel opening into the first volume at the level of at least one orifice and configured to circulate a drain airflow toward the first volume. In addition, the cylinder head comprises a movable pre-chamber having at least one hole for passing a fuel-air mixture between the combustion chamber and the pre-chamber. The pre-chamber is positioned within a first volume and configured to move within the first volume relative to the spark plug between a first position, which extends toward at least one orifice to interrupt the circulation of drain air into the first volume, and a second position, which extends at a distance toward one or more orifices to circulate the drain airflow within the first volume. The cylinder head also includes a return member designed to move the pre-chamber between the first and second positions.

[0006] In particular, the cylinder head may further comprise an intake duct with an intake valve and an exhaust duct with an exhaust valve, with one or more channels fluidically connected to the intake duct.

[0007] In particular, the pre-chamber is -It may be made of a metal material such as steel, and / or -It may be configured to be positioned to move in translational motion along a first direction within a first volume.

[0008] Alternatively, the first volume may comprise a first chamber containing at least a portion of one or more spark plugs and a second chamber containing a movable pre-chamber, wherein the first chamber, the second chamber, and the opening are fluidically connected.

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

[0010] In particular, the pre-chamber may have at least one flange, and in addition, the first volume may have at least one block member designed to stop one or more flanges in order to restrict the movement of a movable pre-chamber within the first volume.

[0011] According to exemplary embodiments, the cylinder head may have a lower flank with an opening. The movable pre-chamber may have a lower wall containing one or more holes, and the lower flank and lower wall are positioned toward the combustion chamber. When the movable pre-chamber is in a first position, the first side of the lower flank and the first surface of the lower wall may be coplanar.

[0012] The present invention also relates to a spark-ignition engine comprising a cylinder head according to the present invention, at least one cylinder separating a combustion chamber, and a movable piston disposed in one or more cylinders, wherein the cylinder head opening and one or more pre-chamber holes open into the combustion chamber.

[0013] In particular, the engine further includes an intake valve control device for controlling the movement of the aforementioned valve, especially the movement delay.

[0014] Furthermore, the present invention relates to an operating method for a spark ignition engine according to the present invention, and this operating method is - An intake phase comprising intake of airflow within a cylinder, fuel injection, and negative pressure generation, designed to open one or more orifices and shift a movable pre-chamber to a second position in order to circulate a drain airflow, particularly extracted from the intake airflow, toward the combustion chamber through one or more channels, a first volume, and said flow designed to discharge residual combustion gases located in the pre-chamber and / or the first volume, then, - A compression step comprising increasing the pressure in the cylinder so that a portion of the air-fuel mixture is sent to a pre-chamber, further comprising ignition of the mixture in the pre-chamber, and then, -Expansion phase, in which the air-fuel mixture in the cylinder ignites, and then, - The system comprises an exhaust stage, in which the piston is lifted to discharge residual combustion gases contained in the cylinder's combustion chamber toward a mobile pre-chamber.

[0015] Further details, features, and advantages will become apparent from the illustrative and non-limiting detailed description given below, with reference to the various exemplary embodiments illustrated in the following figures. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a schematic diagram of a vehicle equipped with a spark-ignition engine that includes a cylinder head, spark plug, and movable pre-chamber. [Figure 2] Figure 2 is a schematic diagram of a cylinder head equipped with a spark plug and a movable pre-chamber. [Figure 3] Figure 3 is a schematic diagram of engine operation during the intake phase. [Figure 4] Figure 4 is a schematic diagram of engine operation during the exhaust phase. [Modes for carrying out the invention]

[0017] Figure 1 schematically illustrates an exemplary embodiment of an automated vehicle 1 according to the present invention. In particular, the automated vehicle 1 is equipped with a spark-ignition engine 2 according to the present invention. The spark-ignition engine 2 is all types of thermal engines. Furthermore, the vehicle 1 may be any type of vehicle, such as a passenger car, commercial vehicle, truck, or bus. In particular, the vehicle 1 may be a connected vehicle and / or an autonomous vehicle.

[0018] A conventional spark-ignition engine 2 comprises at least one cylinder 21 in which a movable piston 22 is positioned. One or more cylinders 21 divide a combustion chamber 23 in which the piston 22 moves and an air-fuel mixture is injected.

[0019] Engine 2 also comprises a cylinder head 3. Generally, the cylinder head 3 according to the present invention comprises at least one shaft 30, also called a spark plug shaft, below which the casting of the cylinder head 3, or more precisely the material of the cylinder head 3, demarcates at least one first volume 300, and at least one spark plug 4 and a movable pre-chamber 5 located within one or more first volumes 300. The cylinder head 3 also comprises at least one channel 6 opening into the first volume 300, the channel 6 being designed to circulate a drain airflow FV toward the first volume 300 and then toward the interior of the pre-chamber 5 by extending toward the first volume 300, and a return member 7 being designed to shift the movable pre-chamber 5, as will be described in more detail below.

[0020] Furthermore, as illustrated, according to an exemplary embodiment, the cylinder head 3 comprises an intake duct 31 with an intake valve 32 and an exhaust duct 33 with an exhaust valve 34. The cylinder head 3 is mounted on the engine 2 to ensure fluid connection between the intake duct 31 and the exhaust duct 33 on the one hand and between the combustion chambers 23 of one or more cylinders 21 on the other hand. The intake valve 32 and the exhaust valve 34 are conventionally mounted to be movable and are designed to facilitate or hinder fluid connection between the duct in which each valve is installed and the combustion chamber 23.

[0021] The following description refers to a cylinder head 3 comprising a shaft 30, a spark plug 4, a first volume 300, and a pre-chamber 5. It is also understood that the description is provided with reference to the considered cylinder 21 of the engine 2 and the relevant portions of the cylinder head 3. Nevertheless, the disclosure extends to a spark-ignition engine 2 comprising a plurality of cylinders 21 each provided with a piston 22, and extends to a cylinder head 3 provided with a plurality of shafts 30, first volumes 300, spark plugs 4, intake valves 32, and exhaust valves 34.

[0022] The cylinder head 3 comprises a first volume 300 in which one or more spark plugs 4 and a movable pre-chamber 5 are positioned. Accordingly, the first volume 300 is a space delimited by the material of the cylinder head 3. The shaft 30 opens into the first volume 300, and the spark plug 4 is positioned so as to extend at least partially into the first volume 300. In particular, as illustrated, the spark plug 4 extends partially into the shaft 30 and into the first volume 300, specifically such that the threads of the spark plug 4 extend into the first volume 300. A first end of the first volume 300 is provided with an opening 35 designed 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 shaft 30 and is at least partially sealed, in particular by the spark plug 4, to prevent the ingress of liquids and particles that could affect the operation of the spark plug 4.

[0023] A conventional spark plug 4 comprises at least one electrical insulator 41 and a conductive base 42 extending along an extension direction 400. The body 41 is made of an electrically insulating material such as ceramic, particularly an alumina-based material. The base 42 is made of a conductive material, particularly metal. The spark plug 4 is fixed in the cylinder head 3 and is positioned so as to extend partially into the spark plug shaft 30 of the cylinder head 3 in order to extend at least partially into the first volume 300. According to an optional but preferred exemplary embodiment, the spark plug 4 is positioned within the first chamber 301 of one or more first volumes 300. Alternatively, the cylinder head 3 comprises at least one sealing member 35a positioned at the interface between the spark plug 4 and the cylinder head 3, for example positioned around the spark plug 4. In particular, this may be a spark plug joint.

[0024] In addition, the spark plug 4 also comprises at least one center electrode 43 and at least one ground electrode 44 separated by an inter-electrode gap, that is, a gap separating two non-contacting electrodes intended to support a spark between the respective electrodes. It is understood that the spark plug 4 may comprise a plurality of ground electrodes 44. Alternatively, the vehicle 1 is equipped with a spark ignition system comprising a high-voltage electrical circuit and a spark control unit designed to supply electrical energy to one or more center electrodes 43 of the spark plug 4. Accordingly, the one or more spark plugs 4 are standard and do not have an integrated pre-chamber.

[0025] One or more channels 6 are positioned to supply a drain airflow FV to a first volume 300 by extending an intermediate volume 550 that is separated by a mobile pre-chamber 5 and at least partially contained within the first volume 300. The term “drain airflow FV” refers to the airflow that circulates through all or part of the first volume 300, particularly through one or more channels 6 and the mobile pre-chamber 5, to discharge any residual combustion gases that may have accumulated there toward the combustion chamber 23. As will be described in more detail below, the drain airflow FV allows for the cleaning of the pre-chamber 5.

[0026] One or more channels 6 open into the first volume 300 through at least one orifice 61. According to an exemplary preferred embodiment, one or more channels 6 are fluidly connected to the inlet duct 31 at a branching point 62. Thus, one or more channels 6 extend between the inlet duct 31 and the first volume 300. This extracts a portion of the intake airflow FA that flows through the intake duct 31 toward the combustion chamber 23 and directs it toward the first volume 300 and the movable pre-chamber 5. The extracted portion of the intake airflow FA forms the drain airflow FV as described above.

[0027] Alternatively, the engine intake system (not shown) that supplies the intake airflow FA to the intake duct 31 may be equipped with at least one filter and a flow meter. One or more channels 6 are preferably connected to the intake duct 31 downstream of the filter and / or the measuring device in the direction of the intake airflow (FA). According to various exemplary embodiments, one or more channels 6 form passages in the casting material of the cylinder head 3, or tubes connecting various points on the cylinder head 3, namely branching points 62 and one or more orifices 61 to each other.

[0028] The movable pre-chamber 5 is an insert positioned within a first volume 300 in the material of the cylinder head 3. The term “pre-chamber 5” has conventionally been interpreted to refer to a chamber separated from the combustion chamber 23 of one or more cylinders 21, having a limited volume, particularly a volume more limited than the volume of the combustion chamber 23, into which a fuel mixture, also known as an air-fuel mixture, is injected and then spark-ignited. A high-temperature jet of combustion gases is then generated and delivered to the external environment of the cylinder head 3, i.e., the combustion chamber 23 of the cylinder 21. In particular, according to the present invention, the pre-chamber 5 is a passive chamber, i.e., a pre-chamber 5 without a fuel supply system or injector, which is conventionally used to inject fuel directly into the pre-chamber 5. According to the present invention, the pre-chamber 5 is also separated from one or more spark plugs 4.

[0029] The mobile pre-chamber 5 includes at least one opening 51 designed to facilitate the passage of the air-fuel mixture between the combustion chamber 23 and the pre-chamber 5, as will be described in more detail below with reference to the process according to the present invention. The mobile pre-chamber 5 also includes at least one wall that partitions the intermediate volume 550 of the pre-chamber 5.

[0030] According to non-limiting exemplary embodiments, the movable pre-chamber 5 has a cylindrical shape that is at least partially complementary to the first volume 300 in which the movable pre-chamber 5 is positioned, or a partially cylindrical shape. For example, the pre-chamber 5 is centered on a main axis 500 and extends along the axis. In particular, the pre-chamber 5 has one or more side walls 52 that define the cylindrical shape of the base. The pre-chamber 5 also has a base wall 53 that separates one side of the pre-chamber 5 from the spark plug 4. In this case, the base wall 53 has at least one hole 51. For example, the movable pre-chamber 5, in particular the base wall 53, has an intermediate volume 550 and a plurality of holes 51 designed for fluid connection between it and the combustion chamber 23 of the cylinder 21 by extending the first volume 300 containing the spark plug 4.

[0031] In addition, the movable pre-chamber 5 is preferably open on one side, in particular the side facing the spark plug 4 within the first volume 300 and / or the side opposite to the side having at least the hole 51. In the illustrated example, the open side is the upper side of the movable pre-chamber 5, which corresponds to the uppermost part of the pre-chamber 5 in the engine 2, in order to facilitate the inflow of drain flow and the diffusion of flame.

[0032] Alternatively, but preferably, the pre-chamber 5 is made of a metallic material such as steel, particularly a metallic material that can withstand temperatures of about 600°C.

[0033] According to the illustrated exemplary embodiment, the spark plug 4 is positioned within the first chamber 301 as described above, the first volume 300 further comprises a second chamber 302, and the movable pre-chamber 5 is positioned and movable. The first cavity 301, the second cavity 302, and the opening 35 of the cylinder head 3 are fluidly connected. Alternatively, the spark plug 4 and the movable pre-chamber 5 may be positioned within the same cavity of the first volume 300, with the spark plug 4 being held in a fixed position to at least partially extend into this cavity, while the pre-chamber 5 is movable within this cavity.

[0034] The movable pre-chamber 5 is positioned within a first volume 300 and is designed to move within the said volume. As a result, the movable pre-chamber 5 is positioned to be displaced relative to the spark plug 4, which remains in a fixed position within the first volume 300, separated by the material of the cylinder head 3 below the spark plug well 30.

[0035] The movable pre-chamber 5 is specifically designed to move between a first position and a second position. The first position is a “closed” configuration, in which the movable pre-chamber 5 closes by blocking one or more orifices 61 to block the drain airflow FV flowing through one or more channels 6 into the first volume 300. For example, one or more pre-chamber walls seal at least one orifice 61. In this case, one or more walls can be considered to be one of the side walls 52 or side walls. The term “closed” referring to one or more orifices 61 indicates that at least a portion of the movable pre-chamber 5 is positioned opposite at least one orifice 61, in particular in contact with a flank that demarcates the first volume 300 containing the orifice 61, in order to block the fluid connection between one or more channels and the first volume 300. For example, the flank under consideration is a side flank of the first volume 300. On the other hand, the second position represents an "open" configuration, in which the movable pre-chamber 5 extends at a non-zero distance from one or more orifices 61 to re-establish the fluid connection between one or more channels 6 and the first volume 300 and to circulate the drain airflow FV within the first volume 300 and intermediate volume 550 of the pre-chamber 5. One or more orifices 61 are not completely or partially obstructed.

[0036] According to preferred but optional exemplary embodiments, the movable pre-chamber 5 is configured to move in a translational motion T1 along a first direction 100 within a first volume. For example, the first direction 100 is parallel or substantially parallel to the extension direction of the spark plug 4 and / or 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.

[0037] Alternatively, but preferably, the movable pre-chamber 5 is provided with at least one flange 54 to restrict its movement. The first volume 300 is provided with at least one block member 36 configured to stop one or more flanges 54 in order to restrict the movement of the movable pre-chamber 5 within the first volume 300, in particular within the second cavity 302.

[0038] For example, one or more walls, in particular one or more side walls 52, are provided with flanges 54. One or more flanges extend from all or part of the outer surface of one or more walls facing one or more sides of the first volume 300. According to the illustrated exemplary embodiment, one or more flanges 54 extend along a second direction 200 that is transverse to the main axis 500 and / or a first direction 100 of the pre-chamber, in particular a second direction that is orthogonal. Preferably, one or more flanges 54 are located in the upper half of the pre-chamber 5. One or more flanges 54 extend around all or part of the cylindrical shape of the movable pre-chamber 5. For example, one or more flanges 54 are designed to surround all or part of the outer surface of the pre-chamber 5.

[0039] The movable pre-chamber 5 is sized to be displaceable within the first volume 300. Here, the first dimension of the pre-chamber 5, defined along the main axis 500, is strictly smaller than the first dimension of the first volume 300 and / or the first dimension of the second cavity 302 along these same directions. The second dimension of the pre-chamber 5, measured along the second direction 200, is strictly smaller than the second dimension of the first volume 300. The second dimension of the pre-chamber 5 corresponds, for example, to the diameter or diagonal of a cylindrical base. Alternatively, one or more flanges can at least partially contact one or more flanks of the first volume 300, particularly the lateral flanks, by, for example, limiting the displacement of the pre-chamber 5 along the second direction 200.

[0040] One or more block members 36 are positioned within the first volume 300 to prevent, for example, the movable pre-chamber 5 from moving further than the first and / or second positions. In this case, the first volume 300 comprises a plurality of block members 36. The first block member 36a comprises an intermediate flank 37 of the first volume 300 configured to stop the pre-chamber 5 moving along the first direction 100. The second block member 36b comprises a lower flank 38 of the first volume 300 configured to stop one or more flanges 54 along the first direction 100 and along a second direction opposite to the first direction. In this case, non-limitingly, the intermediate flank 37 serves to separate the first cavity 301 and the second cavity 302. Similarly, for example, the lower flank 38 comprises an opening 35 of the first volume 300, and the second block member 36 comprises, in particular, the edge of the opening 35.

[0041] The return member 7 can move the pre-chamber 5 between a first position and a second position, and thus indirectly control the drain airflow FV. In particular, as described below, the return member 7 can move the movable pre-chamber 5 from the second position to the first position. Therefore, it operates together with the movable pre-chamber 5 during the engine cycle 2. The return member 7 indirectly controls the drain airflow FV according to the position of the movable pre-chamber 5 as described above. The term “control” is used herein to describe the interruption of the fluid connection between one or more channels 6 and the combustion chamber 23 in such a manner as to interrupt the circulation of the flow, or the activation of such a fluid connection.

[0042] Therefore, the return member 7 is a passive, non-engine driven member. The term "passive" refers to a control that does not require direct engine-driven operation. 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 pre-chamber 5. The return member 7 extends into the space between the movable pre-chamber 5 and one or more side walls of the first volume 300. In particular, the return member 7 is positioned in contact with the surface of the first volume 300, for example, the lower side wall 38. According to the illustrated exemplary non-limiting embodiment, the return member 7 is positioned in contact with one or more block members 36, in particular the second block member 36b. The return member 7 is also positioned in contact with the movable pre-chamber 5. For example, the return member 7 is positioned in contact with one or more flanges 54. In particular, the return member 7 is interposed between at least a portion of the pre-chamber 5 and at least a portion of the first volume 300 along the first direction 100 and / or the main axis 500. In this case, the return member 7 is interposed between at least one flange 54 of the pre-chamber 5 and the lower flank 38 of the first volume 300.

[0043] When the pre-chamber is in the first position, in the "open" configuration, the return member is in particular in the initial or nominal configuration. As will be described in more detail below with reference to the process according to the present invention, the return member 7 is actuated passively, in this case by moving the movable pre-chamber 5. The movement of the movable pre-chamber 5 is first performed in accordance with the differential pressure defined between the pressure measured in the first volume 300 and the pressure measured in the combustion chamber 23.

[0044] The movable pre-chamber 5 shifts to a second position when negative pressure is generated in the combustion chamber 23 during the intake phase of the engine cycle 2. In particular, the movable pre-chamber 5 is drawn in at the second position and therefore moved toward the cylinder 21 and the combustion chamber 23. The term "negative pressure" is used herein to refer to a pressure drop in the combustion chamber 23 to a value strictly below atmospheric pressure. Once moved to the second position, the pre-chamber 5 exerts force on the return member 7. In particular, the return member 7 is pre-adjusted to exhibit resistance adapted to such movement of the pre-chamber, depending on a predetermined negative pressure level. As a result of the movement of the pre-chamber 5, one or more orifices 61 are exposed, and the drain airflow FV circulates through one or more channels 6, within the first volume 300, particularly through the pre-chamber 5, and then through one or more holes 51 to the combustion chamber 23 of the cylinder 21. Therefore, the drain airflow FV discharges all or part of the residual combustion gas accumulation contained in the first volume 300, particularly the intermediate volume 550 of the pre-chamber 5, toward the combustion chamber 23.

[0045] Subsequently, as the pressure difference decreases, the mobile pre-chamber 5 passively moves to the first position. Next, the return force exerted by the return member 7 passively returns the return member 7 to its initial configuration, thereby pushing the pre-chamber 5 toward the first position in the contact zone between the pre-chamber 5 and the return member 7. The pre-chamber 5, positioned in the first position, again closes one or more orifices 61, preventing the circulation of the drain airflow FV within the first volume 300. This principle can be observed, for example, when the differential pressure decreases to a point where it is insufficient to hold the pre-chamber 5 in the second position, particularly when the return member 7 is adjusted.

[0046] To optimize the positioning of the movable pre-chamber 5 within the cylinder head 3 and minimize its influence on the volume of the combustion chamber 23, the movable pre-chamber 5 is dimensioned and positioned such that when the pre-chamber 5 is positioned in a first position, the first surface 531 of the lower wall 53 within the pre-chamber 5 and the first surface 381 of the lower flank 38 within a first volume 300 configured to face the combustion chamber 23 in the engine 2 are aligned at the same level. Thus, the first surface 531 and the first surface 381 are perfectly coplanar. Alternatively, when the pre-chamber 5 is positioned in a first position, the first surface 531 of the lower wall 53 within the pre-chamber 5 is higher than the position of the first surface 381 of the lower side wall 38 within the first volume 300, and as a result, the first surface 381 is interposed between the combustion chamber 23 and the first surface 531 within the pre-chamber 5 along the first direction 100 and / or the main axis 500. The mobile pre-chamber 5 does not affect the volume of the combustion chamber 23 or the engine 2 during operation.

[0047] The present invention also relates to a method of operation for a spark-ignition engine 2 according to the present invention. This process is carried out during an engine cycle 2, which typically comprises intake, compression, expansion, and exhaust stages.

[0048] As illustrated in Figure 3, during the intake phase, the intake airflow FA into one or more cylinders 21 also comprises the generation of a negative pressure within the cylinders 21, particularly within the combustion chamber 23, which can shift the mobile pre-chamber 5 to a second position. As mentioned above, the negative pressure here consists of a pressure drop within the combustion chamber 23 to a value strictly below atmospheric pressure. The generated negative pressure drives the pre-chamber 5 toward the second position, i.e., toward the combustion chamber 23, such that the mobile pre-chamber 5 extends at a non-zero distance from one or more orifices 61. Thus, the mobile pre-chamber 5 is in an open configuration, with at least one orifice 61 open, and at least one channel 6 fluidly connects with the combustion chamber 23 by extending and fluidizing with the first volume 300. The drain airflow FV then circulates through one or more channels 6 into the first volume 300, particularly into the intermediate volume 550 of the mobile pre-chamber 5, and then toward the combustion chamber 23 through one or more holes 51.

[0049] According to a preferred exemplary implementation of the process of the present invention, a negative pressure is generated in the combustion chamber 23 by an implementation of delayed intake opening or ROA, which consists of maintaining the intake valve 32 in a closed state when the piston 22 begins to descend. For example, intake opening delay is performed by a control device (not shown) for the intake valve 32, which can trigger a shift in the opening row 35 of the valve in the engine cycle 2. Thus, the pressure in one or more cylinders 21 is mechanically reduced to a value strictly below atmospheric pressure and strictly below the pressure in the intake duct 31. As described above, if the negative pressure generated in the combustion chamber 23 is sufficient, the movable pre-chamber 5 is drawn toward the combustion chamber 23. It then shifts to a second position, passively opening one or more orifices 61. Thus, the movable pre-chamber 5 is in an "open" configuration, and the drain airflow FV circulates through one or more channels 6, enters the first volume 300, and passes through the pre-chamber 5 and one or more holes 51 before being drawn into the combustion chamber 23 as a result of the negative pressure. All or part of the residual combustion gases accumulated during the previous combustion in the previous engine cycle 2, remaining in the first volume 300 and the intermediate volume 550, particularly in the mobile pre-chamber 5, are then drawn toward the cylinder 21. Thus, the mobile pre-chamber 5 can be cleaned, also known as a "drain," by passively discharging the residual combustion gases, without requiring a tank or electric system for discharging the drain airflow. At the same time, the mobile pre-chamber 5 exerts force on the return member 7, particularly via the flange 54 as described above. For example, it is lowered so as to extend at least partially into the combustion chamber 23 of the cylinder 21.

[0050] As described above, when one or more channels 6 are connected to the intake duct 31, as shown in Figures 1 to 4, the drain airflow FV is a portion of the intake airflow FA that is diverted from its conventional trajectory, i.e., from the intake duct 31, and redirected through one or more channels 6 to the first volume 300. A preferred branching point 62, for example, a tapping point for one or more channels 6 on the intake duct 31, is positioned downstream of the filter and / or the device for measuring the intake airflow FA, depending on the circulation of the intake airflow FA to the intake duct 31. This principle advantageously ensures that the drain airflow FV extracted from the intake airflow FA does not contain particles, and / or that the amount of air injected into the cylinder 21, corresponding to the combination of the remaining intake airflow and the drain airflow FV, is known.

[0051] It should be noted that the process according to the present invention can preferably be implemented to run only during a defined operating period of the engine 2. For example, the process can be run when the engine 2 is operating at a low load. The process according to the present invention is inactive when the engine 2 is operating at an overload, and no discharge of the pre-chamber 5 occurs.

[0052] Conventionally, the intake valve 32 is then opened, the intake airflow FA from the intake duct 31 fills the cylinder 21, and fuel injection is started. The atomized fuel is mixed with the moving intake airflow FA to form a fuel-air mixture in the combustion chamber 23.

[0053] It should be noted that when the inlet valve 32 opens, the pressure in the combustion chamber 23 converges toward the pressure spreading into the inlet duct 31. This reduces or interrupts the initially generated negative pressure. For example, in the case of a heavily loaded supercharged engine 2, the pressure measured in the intake duct 31 is strictly higher than atmospheric pressure. During this part of the intake flow FA stage, the pre-chamber 5 can be moved to a first position or held in a second position according to 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. The movable pre-chamber 5 can be raised to the first position or to an intermediate position between the first and second positions under the control of the return member 7.

[0054] As you know, engine cycle 2 continues the compression phase. The intake valve 32 and exhaust valve 34 are closed. Under the control of the return member 7, the pre-chamber 5 is displaced to a first position corresponding to its nominal position if such movement had not occurred during the intake phase. The movable pre-chamber 5 then enters a "closed" configuration, blocking one or more orifices 61, thereby severing the fluid connection between the first volume 300 and one or more channels 6.

[0055] Fuel injection continues, and the fuel mixture is homogenized by turbulence within the combustion chamber 23 of the cylinder 21. The piston 22 retracts into the cylinder 21, increasing the pressure in the combustion chamber 23 and the first volume 300. The pressure in the combustion chamber 23 rises. A portion of the fuel mixture is then sent to the pre-chamber 5 through one or more holes 51. At the end of the compression phase, the spark ignition system ignites a spark at the spark plug 4, causing the compressed fuel mixture to burn in the pre-chamber 5 and a portion of the intermediate volume 550. As combustion continues, the pressure in the mobile pre-chamber 5 rises, and the flame jet releases the burning gases into the combustion chamber 23.

[0056] Subsequently, during the expansion phase of the engine cycle, the flame front expands within the combustion chamber 23 to form a flame jet that constitutes multiple ignition points, thereby optimizing the timing and combustion efficiency of the heat release mechanism. The inlet valve 32, exhaust valve 34, and one or more orifices 61 are always closed.

[0057] Finally, during the exhaust phase as illustrated in Figure 4, the exhaust valve 34 opens. The piston 22 retracts, simultaneously moving the residual combustion gases remaining in the combustion chamber 23 of the cylinder 21 toward the exhaust duct 33 and the movable pre-chamber 5. In particular, most of the residual combustion gases are discharged into the exhaust duct 33, and some are directed toward the movable pre-chamber 5. Thus, some of the residual combustion gases are discharged from the engine 2 through the exhaust duct 33, and some are collected in the intermediate volume 550 and the pre-chamber 5. Therefore, residual combustion gases collected in the intermediate volume 550 adjacent to one or more spark plugs 4 can be discharged during the intake phase of the subsequent engine cycle 2, as described above.

[0058] Therefore, the cylinder head 3 and process according to the present invention facilitate the passive discharge of the movable pre-chamber 5 located within the first volume 300, thereby limiting the residual combustion gases that would otherwise be collected around the spark plug 4 by excessive concentration, which can prevent the fuel mixture from starting to burn. By discharging the residual combustion gases collected during the previous combustion and discharged into the cylinder 21 during the intake phase, the pre-chamber 5 can be independently cleaned before being refilled with the fuel mixture.

[0059] Accordingly, the present invention provides an alternative to a cylinder head equipped with a spark plug, particularly a pre-chamber spark plug, such as a passive spark plug. The present invention is designed to prevent residual combustion gases from accumulating around the spark plug. The proposed solution is advantageously designed to accommodate a standard spark plug without a pre-chamber 5. The integration of the movable pre-chamber 5 advantageously optimizes the volume of the pre-chamber 5 for combustion, while facilitating the passive discharge of residual combustion gases without requiring direct engine-driven intervention into the pre-chamber.

[0060] Nevertheless, the present invention is not limited to the methods and configurations described and illustrated herein, but extends to any equivalent methods or configurations, and any technically effective combination of such methods, as long as they ultimately satisfy the functionality described and illustrated herein.

Claims

1. A cylinder head (3) for a spark-ignition engine (2) comprising at least one spark plug shaft (30) and a first volume (300), wherein the first volume (300) is separated in particular by the material of the cylinder head (3) below the shaft (30), and the first end of the first volume (300) comprises an opening (35) configured to open into a combustion chamber (23) of a cylinder (21), and the cylinder head (3) also, - At least one spark plug (4) positioned at least partially within the first volume (300), particularly positioned within the first volume from the shaft (30), - At least one channel (6) is configured to open to the first volume (300) at the level of at least one orifice (61) and to allow circulation of a drain airflow (FV) toward the first volume (300), - A movable pre-chamber (5) having at least one hole (51) designed to allow a fuel-air mixture to pass between the combustion chamber (23) and the pre-chamber (5), the pre-chamber (5) being positioned within the first volume (300) and configured to move within the first volume (300) relative to the spark plug (4) between a first position extending opposite the at least one orifice (61) to interrupt the circulation of drain air (FV) into the first volume (300) and a second position extending at a distance from one or more orifices (61) to circulate the drain airflow (FV) within the first volume (300), - A cylinder head (3) comprising a return member (7) designed to move the pre-chamber (5) between the first position and the second position.

2. The cylinder head (3) according to claim 1, further comprising an intake duct (31) equipped with an intake valve (32) and an exhaust duct (33) equipped with an exhaust valve (34), wherein at least one channel (6) is connected to the intake duct (31) by a fluid connection.

3. The aforementioned pre-chamber (5) is - Equipped with a metal material such as steel, and / or - The cylinder head (3) according to claim 1 or 2, configured to be positioned to move in translational motion along a first direction (100) within the first volume (300).

4. The cylinder head (3) according to any one of claims 1 to 3, wherein the first volume (300) comprises a first cavity (301) having at least a portion of one or more spark plugs (4) and a second cavity (302) having the movable pre-chamber (5), and the first cavity (301), the second cavity (302), and the opening (35) are fluidly connected.

5. The cylinder head (3) according to any one of claims 1 to 4, wherein the return member (7) is a spring and / or at least one elastically deformable blade.

6. The cylinder head (3) according to any one of claims 1 to 5, wherein the pre-chamber (5) comprises at least one flange (54), and the first volume (300) also comprises at least one block member (36) configured to form a stop for one or more flanges (54) in order to restrict the movement of the pre-chamber (5) that is movable within the first volume (300).

7. A cylinder head (3) according to any one of claims 1 to 6, comprising a lower flank (38) having the opening (35), the movable pre-chamber (5) comprising a lower wall (53) having one or more holes (51), the lower flank (38) and the lower wall (53) being configured to face the combustion chamber (23), and when the movable pre-chamber (5) is in a first position, the first surface (381) of the lower flank (38) and the first surface (531) of the lower wall (53) are on the same plane.

8. A spark-ignition engine (2) comprising a cylinder head (3) according to any one of claims 1 to 7, at least one cylinder (21) separating a combustion chamber (23), and a movable piston (22) disposed within the at least one cylinder (21), wherein the opening (35) of the cylinder head (3) and one or more holes (51) of the pre-chamber (5) open into the combustion chamber (23).

9. The spark ignition engine (2) according to claim 8, also comprising a device for controlling an intake valve (32) designed to control the movement of the valve, particularly the delay of its movement.

10. - An intake phase comprising intake of airflow in the cylinder (21), fuel injection, and negative pressure generation of airflow in the cylinder (21) designed to open one or more orifices (61) and circulate a drain airflow (FV), particularly extracted from the intake airflow, toward the combustion chamber (23) in at least one channel (6), a first volume (300), and the flow is used to discharge combustion gases into the combustion chamber (23), the flow is designed to discharge residual combustion gases located in the pre-chamber (5) and / or the first volume (300), and then, - A compression step comprising increasing the pressure in the cylinder so that a portion of the air-fuel mixture is sent to the pre-chamber (5), and also comprising ignition of the mixture in the pre-chamber (5), and then, - Expansion stage, in which the air-fuel mixture in the cylinder (21) is ignited, and then, A method of operation for a spark-ignition engine (2) according to claim 8 or 9, comprising: an exhaust stage in which a piston (22) is lifted to discharge a portion of the residual combustion gas contained in the combustion chamber (23) of the cylinder (21) toward the movable pre-chamber (5).

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