Guide Stud Valve

Abstract

The valve directed by the pin (50) is housed in the stratified channel (7) and comprises a main valve body (8) exposing an axial sealing surface (10) that can rest on a channel sealing seat (11) to thermally insulate the stratified cavity (4) from the combustion chamber (5); the body (8) also has a peripheral centering surface (12), an axial opening surface (13) that can rest on a valve stopper (14) on the chamber side, and at least one guide pin (15) emerging from the axial opening surface (13), the pin (15) being able to slide in an axial guide hole (17) rigidly attached to the stratified channel (7).

Description

[Technical Field]

[0001] The present invention relates to a guide stud valve, which is an improvement on an ignition pre-chamber with a valve, the subject of French Patent No. 3,061,743 published on August 16, 2019, and assigned to the Applicant.

[0002] The guide stud valve according to the invention is compatible with the main improvements of the valve-ignited pre-chamber according to patent FR 3,061,743, said improvements being the subject of several patent applications.

[0003] Among the above improvements, the "valve magnetic return device", the subject of French patent application no. 3,085,718 published on March 13, 2020, or the "ignition insert with active prechamber", the subject of French patent application no. 1904961 filed on May 13, 2019, or the "reverse combustion direction valve ignition prechamber", the subject of French patent application no. 2001508 published on February 14, 2020, may be noted.

[0004] All these patents and patent applications have in common that they (like most prior art torch ignition devices) present an ignition pre-chamber formed by a stacked cavity located in the cylinder head of an internal combustion engine.

[0005] The strategy used by the above patents, patent applications and devices is known in particular by the Anglo-Saxon term "turbulent jet ignition".

[0006] According to the above patents and patent applications, the stack cavity is connected on the one hand to the combustion chamber of the internal combustion engine by a stack duct and, on the other hand, receives a stack injector capable of injecting into the cavity a pilot load pre-pressurized by a compression means, the load consisting of an oxidizer-fuel mixture that can be easily combusted by a spark.

[0007] The combustion chamber then receives the main load, which may be undiluted or diluted with air or recirculated exhaust gases, it being noted that dilution can particularly maximize the energy efficiency of the internal combustion engine.

[0008] The above commonly assigned patents and patent applications differ from the prior art in that the laminate duct presents a valve closure seat onto which a laminate valve can rest to close the duct, thereby isolating the laminate cavity from the combustion chamber of the internal combustion engine.

[0009] On the other hand, when the valve is moved away from the seat and placed against the chamber-side valve stop either directly or via a damping chamber, as disclosed in French Patent Application No. 3,085,718, the valve together with the stack duct forms a torch-ignited pre-combustion chamber which simultaneously communicates with the stack cavity on the one hand and with the combustion chamber via the gas discharge orifice on the other hand.

[0010] This special configuration allows for the construction of a fully combustible pilot load in the stack cavity, regardless of the nature and composition of the main load.

[0011] In fact, the composition, pressure and temperature of the pilot load may be radically different from that of the main load.

[0012] This makes it possible to avoid one of the main drawbacks of "open" torch-ignited pre-chambers, i.e., without stacked valves, which means that according to the prior art, when a gas mixture that is difficult to ignite forms the main load, the mixture also forms the pilot load in the ignition pre-chamber by partially and improperly mixing it.

[0013] Therefore, because combustion of the main load requires high ignition power, the pilot load is less able to provide high ignition power.

[0014] Conversely, if the main load is formed from a slightly diluted, highly reactive mixture, requiring low ignition power to prevent the combustion of the load from generating excessively high pressure gradients and noise in the main chamber, the pilot load will be too energetic because it is formed in part from the mixture that makes up the main load.

[0015] In other words, without a stack valve closing the stack duct, the pilot load would necessarily be formed in part from the mixture that makes up the main load. Under these conditions, the pilot load would inherit some of the ignition and combustion susceptibility of the main load, which is undesirable.

[0016] Indeed, the less reactive the main load, the more powerful the pilot load needs to be. Conversely, the easier and faster the main load can be burned, the less energetic the pilot load needs to be to avoid excessively rapid burning of the main load.

[0017] This is why the valve-fired pre-chamber of French Patent No. 3,061,743 forms an autonomous torch ignition device whose power output can be freely adjusted in order to find the best compromise between efficiency, polluting emissions and acoustic emissions of the internal combustion engine that receives it.

[0018] Thus explained, it can be seen from the figures shown in French Patent No. 3,061,743 and its various improvements that the laminated valve must be thick enough so as not to crack despite the impacts it receives when periodically coming into contact with its valve closure seat.

[0019] To prevent the valve from jamming within the laminated duct in which it is housed, the valve must either be very thick at the expense of excessive weight, or the valve must have a truncated spherical periphery rather than a cylindrical periphery, which prevents the valve from jamming within its housing regardless of its orientation relative to the laminated duct.

[0020] A disadvantage of valves with a truncated spherical profile, such as that shown in French Patent Application No. 1904961, is that when the valve opens under the influence of the pressure of the gas to open the laminated duct, it tilts relative to the laminated duct that houses it and is no longer parallel to the valve closing seat with which it cooperates.

[0021] The tilt of the laminated valve becomes even more important when the valve is returned to its valve-closed seat by a magnetic field, as disclosed in French Patent Application No. 3,085,718.

[0022] Indeed, in this particular situation, when the valve is returned by the magnetic field, the separation of the valve from its cooperating valve closure seat occurs in two steps.

[0023] In the first step, under gas pressure, the valve separates on one side, since it is simply a matter of overcoming the torque exerted on the valve by the magnetic field against the pressure. The effort required for separation is of low intensity.

[0024] In the second step, the stacked valve is already tilted, and the gas pressure must counteract the attractive closing force exerted on the valve by the magnetic field, so the valve completely separates from the valve-closing seat while assuming a more parallel position relative to the valve-closing seat. The force required for this second separation is several times greater than that required for the first separation.

[0025] As can be seen from the above, if the laminated valve is returned to its valve-closing seat by a magnetic field, as proposed in French Patent Application No. 3,085,718 (which is practically essential), and if the valve has a truncated spherical periphery to prevent it from jamming in its housing, the valve can only tilt at large angles.

[0026] The first drawback of this tilt is that it does not expose all the gas discharge orifices at the same time and in the same manner, i.e. evenly to each other.

[0027] As a result, on the one hand, the ignition torches consisting of hot gases are not simultaneously emitted in the main chamber through the torch-ignition pre-chamber, and on the other hand, the torches do not all have the same tendency to ignite the main load, both in terms of thermal and aerodynamic power and in terms of physico-chemical reactivity.

[0028] This dual non-uniformity of the torches relative to one another significantly impairs the homogeneity of the combustion of the main load in the main chamber.

[0029] Non-uniformity can cause knocking, i.e., abnormal combustion of the main load, which can damage the internal combustion engine. In addition, non-uniformity inevitably causes periodic variations in the rate of fast combustion of the load followed by slow combustion of the main load, and vice versa.

[0030] Periodic variations are detrimental to the energy efficiency and vibro-acoustic behavior of the engine.

[0031] The unintended tilting of the stacked valves in question occurs not only when the valves are opened, but also when the valves are closed when they are rested against their associated valve closure seats.

[0032] The temporal variation in the closure of the stacked valve is due to this tilt on the one hand and to leakage defects between the valve and the valve closure seat on the other hand, which are manifested by the undesired passage of gas from the main chamber into the stacked cavity.

[0033] Passage can result in large cycle-to-cycle variations in the initiation and progression of combustion of the pilot load in the stack cavity, since the pilot load contains some gas from the main load every cycle.

[0034] Combustion variations result in the discharge of the torch in the main chamber being earlier or later, stronger or weaker, hotter or colder, and more or less reactive from cycle to cycle, which results in cycle-to-cycle instability of the combustion of the main load, again to the detriment of the energy efficiency and the vibro-acoustic behavior of the internal combustion engine.

[0035] Another negative effect of the inconsistent behavior in the orientation and sealing of the valve is a high equilibrium temperature of the valve: in fact, the valve does not rest well on the cooperating valve closure seat, and therefore the valve also does not cool well in contact with the seat.

[0036] As a result, during operation, the laminated valve may reach excessive temperatures due to thermal expansion which may lead to clogging of the valve within the laminated duct in which it is housed.

[0037] In order to solve in particular these various operational problems of the laminated valve of the valve-ignited pre-combustion chamber according to French Patent No. 3,061,743, the guide stud valve according to the invention advantageously replaces the laminated valve described in said patent and its improvements, in that the stud valve is maintained substantially parallel to the valve closing seat with which it cooperates throughout its entire path of movement within the laminated duct.

[0038] In particular, the guide stud valve according to the invention provides: All ignition torches are emitted at approximately the same time and with the same power by the torch ignition pre-combustion chamber. Torch ignition: The power, composition, aerodynamic behavior and physicochemical reactivity of the torch released by the pre-combustion chamber into the combustion chamber of the internal combustion engine are controlled and similar for each torch. · The safety and energy efficiency of the internal combustion engine are maximized. The vibro-acoustic behavior of the engine is optimized. Proper valve cooling is ensured in all situations, including when the internal combustion engine is operating at high power. In addition, by replacing the laminated valve, the guide stud valve according to the invention advantageously increases the durability and robustness of the valve-fired pre-combustion chamber according to French Patent No. 3,061,743 as a whole by preventing the risk of mechanical jamming of the stud valve in the laminated duct that houses it, as well as by limiting wear and tear on the valve and duct.

[0039] In addition, the guided stud valve according to the invention makes better use of and optimizes the operation of the damping chamber described in French patent application no. 3,085,718.

[0040] It should be understood that the guide stud valve according to the invention can be applied not only to valve-fired pre-chambers according to French Patent No. 3,061,743, but also to any other application similar in concept and principle in which the properties and functionality of the valve can be advantageously utilized.

[0041] A valve oriented for a valve-ignited pre-chamber arranged in a cylinder head of an internal combustion engine covering a combustion chamber, the pre-chamber comprising a stack cavity in which ignition means and at least one stack injector emerge, the cavity being connected to the combustion chamber by a stack duct accommodating the valve, so that together with the stack duct it is possible to form a torch-ignited pre-chamber which positions the stack cavity relative to the combustion chamber through at least one gas discharge orifice, the valve comprising: A valve body accommodated in a laminated duct with a small amount of play; a closing axial surface disposed on the valve body, the closing axial surface being capable of resting in whole or in part on a duct closing seat of a stacked duct to close the duct and isolate the stacked cavity of the combustion chamber; at least one centering outer peripheral surface disposed on the outer periphery of the valve body, the surface being capable of contacting an inner wall of the laminated duct to center the body within the duct; an open axial surface, which is arranged on the valve body opposite the closed axial surface and which can rest on a chamber-side valve stop arranged in the stacked duct when the closed axial surface is not resting on the duct closing seat; at least one orientation stud fixedly attached to the valve body and projecting from the open axial face; at least one guide shaft orifice arranged in or near the chamber-side valve stop and into which an orientation stud is received with a small radial play, the stud being able to slide longitudinally within the orifice without completely exiting it; a valve damping chamber formed by a laminated duct, an open axial surface, and a chamber-side valve stopper, the volume of which is maximum when the closed axial surface is resting on the duct closing seat and minimum when the open axial surface is resting on the chamber-side valve stopper;

[0042] The orientation valve according to the invention comprises a guide shaft orifice passing through the laminated duct to connect the valve damping chamber with the combustion chamber, so that gas can flow between the chambers via a small radial play left between the orientation stud and the guide shaft orifice.

[0043] The directing valve according to the invention comprises at least one gas throttling orifice which connects the valve damping chamber with the combustion chamber, so that gas can flow between the chambers via the orifice.

[0044] The directing valve according to the present invention comprises a centering peripheral surface having a conical profile.

[0045] The directing valve according to the invention comprises a gas discharge orifice connected to the torch-ignited pre-chamber through at least one gas discharge slot located in the stacked duct and adjacent the duct closure seat.

[0046] The orientation valve according to the present invention comprises a valve body and / or orientation studs that are attracted towards the stack cavity by a closed magnetic field source.

[0047] The orientation valve according to the present invention comprises a closed magnetic field source consisting of at least one closed permanent magnet which generates a magnetic field, which can be cancelled or amplified by an opposite or corresponding magnetic field induced in the piloting coil core by the magnetic field piloting coil.

[0048] The orientation valve according to the present invention comprises a valve body and / or orientation stud that is attracted towards a chamber-side valve stop by an open magnetic field source.

[0049] The orientation valve according to the invention includes an orientation stud having a damping shoulder which cooperates with a damping counterbore located at the entrance of the guide shaft orifice, the counterbore emerging into the valve damping chamber.

[0050] The directing valve according to the invention comprises a damping counterbore connected directly or indirectly to the combustion chamber by at least one pressure reducing duct.

[0051] The directing valve according to the present invention comprises a laminated duct including a directly mounted non-magnetic sleeve on which a duct closure seat is disposed.

[0052] The following description of the accompanying drawings, given as non-exhaustive examples, will provide a better understanding of the invention, its features and the potential advantages it may offer. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 is an enlarged schematic cross-sectional view of a guide stud valve according to the present invention, in which the valve is in an "open" position within a laminated duct, so that the open axial surface rests on the chamber-side valve stop, and the valve, together with the laminated duct, forms a torch-ignited pre-combustion chamber that positions the laminated cavity relative to the combustion chamber via a gas discharge orifice. [Figure 2]2 is an enlarged schematic cross-sectional view of a guide stud valve according to the present invention, according to the variant shown in FIG. 1, with the valve in a "closed" position within the laminated duct, so that the valve's closing axial face rests on the duct closing seat and the laminated cavity is no longer in communication with the combustion chamber. [Figure 3] 1 is a schematic cross-sectional view of a cylinder head of an internal combustion engine that can be designed to receive a guide stud valve according to the invention, with an ignition insert having an active pre-chamber as described in French patent application no. 1904961, the valve being returned to closure by a valve magnetic return device, the subject of French patent application no. 3,085,718, and a stacked injector emerging in a stack of cavities that is part of a cam hydraulic injection system, the subject of French patent application no. 1913528 of November 29, 2019, the stacked cavity receiving an inverter housing as shown in French patent application no. 2001508 entitled "Reverse combustion direction valve ignition prechamber"; [Figure 4] 4 is a three-dimensional cross-sectional view of a guide stud valve according to the present invention in the variant and environment shown in FIG. 3, but without the internal combustion engine cylinder head. [Figure 5] 4 is an exploded three-dimensional view of a guide stud valve according to the present invention, according to the variant and environment shown in FIG. 3, but without the internal combustion engine cylinder head. [Figure 6] 1 is a schematic cross-sectional view of a cylinder head of an internal combustion engine that may be designed to receive a guide stud valve according to the present invention, with an ignition insert having an active pre-chamber as described in French Patent Application No. 1904961, the valve being returned to closure by a magnetic field generated by a closing permanent magnet, which may be counteracted or amplified by a respective opposite or corresponding magnetic field induced in the pilot coil core by a field pilot coil; [Figure 7]FIG. 1 is an enlarged schematic cross-sectional view of a modified guide stud valve according to the present invention, whereby the valve receives a damping shoulder that cooperates with a damping counterbore located at the inlet of the guide shaft orifice, the valve body being attracted toward the chamber-side valve stop by an annular open permanent magnet integral with the non-magnetic pre-chamber nose, and the valve being in the "open" position to form a torch-ignited pre-chamber together with the stacked duct. [Figure 8] 8 is an enlarged schematic cross-sectional view of a guide stud valve according to the present invention, according to the variation shown in FIG. 7, with the valve in a "closed" position within the laminated duct, so that the valve's closure axial face rests on the duct closure seat and the laminated cavity is no longer in communication with the combustion chamber. DETAILED DESCRIPTION OF THE INVENTION

[0054] Various details of a guide stud valve 50 according to the present invention, its components, variations, and accessories are shown in FIGS.

[0055] As shown in Figures 3 to 6, the stud directional valve 50 is primarily provided for a valve-fired pre-chamber 1 that may be located in a cylinder head 2 of an internal combustion engine, the cylinder head capping a combustion chamber 3.

[0056] It should be noted in Figures 1 to 4 and 6 to 8 that, as shown in Figures 3 to 6, the valve-fired pre-chamber 1 comprises a stack cavity 4 from which emerges ignition means 5 and at least one stack injector 6.

[0057] As can be seen in Figures 1-4 and 6-8, the laminate cavity 4 is connected to the combustion chamber 3 by a laminate duct 7 which houses a guide stud valve 50 according to the present invention so as to form a torch-ignited pre-combustion chamber 9 when the valve 50 is in the "open" position, as clearly shown in Figures 1 and 7.

[0058] 1 and 7 show that in fact a torch-ignited pre-chamber 9 connects the stack cavity 6 to the combustion chamber 5 through at least one gas discharge orifice 16 .

[0059] 1 to 8, it can be seen that the guide stud valve 50 according to the invention comprises a valve body 8 which is accommodated with a small amount of play in a laminated duct 7.

[0060] In a variant, not shown, of a guide stud valve 50 according to the invention, the valve body 8 may be provided with an indexing stud that prevents it from rotating about its longitudinal axis.

[0061] Such studs may be provided in particular when openings (not shown) are provided on the outer periphery of the valve 50, each of which opens a gas outlet 16 when the closing axial surface 10 of the valve 50 moves away from the duct closing seat 11 of the stacked duct 7.

[0062] 1, 2, 7 and 8, it can be seen that the guide stud valve 50 according to the invention has, according to a not shown embodiment of the guide stud valve 50 according to the invention, a closing axial surface 10 arranged on the valve body 8, on the surface of which can receive at least one flow passage for passing gas to the gas discharge orifice 16.

[0063] As shown in Figures 2 and 8, the closure axial surface may rest in whole or in part on the duct closure seat 11 of the stack duct 7, thereby sealing the duct 7 and isolating the stack cavity 4 from the combustion chamber 5.

[0064] According to a variant not shown, the closing axial surface 10 may advantageously have an aerodynamic dome that promotes the flow of gas 19 between the stacked duct 7 and the torch-ignited pre-combustion chamber 9; it should be noted that such a dome is similar to that shown in French Patent No. 3,061,743 belonging to the Applicant.

[0065] 1-8 show that the guide stud valve 50 according to the present invention includes at least one centering outer peripheral surface 12 disposed on the outer periphery of the valve body 8, the surface 12 being capable of contacting the inner wall of the laminated duct 7 to center the body 8 within the duct 7.

[0066] It should be noted that the centering outer peripheral surface 12 may advantageously be connected to the closed axial surface 10 and / or the open axial surface 13 by chamfers, strips or spokes, this being provided to avoid excessive contact pressure between the valve body 8 and the laminated duct 7 containing it.

[0067] 1 to 8, it should be noted that the guide stud valve 50 according to the present invention has an open axial surface 13 that is disposed on the valve body 8 opposite the closed axial surface 10 and that can rest on a chamber-side valve stop 14 disposed within the laminated duct 7 when the closed axial surface 10 is not resting on the duct closing seat 11.

[0068] 1-8 clearly show that the guided stud valve 50 according to the present invention has at least one orientation stud 15 rigidly attached to the valve body 8 and projecting from the open axial face 13.

[0069] 1, 2, 5, 7 and 8, it can be clearly seen that the guide stud valve 50 according to the present invention is arranged in or near the chamber-side stop valve 14 and has at least one guide shaft orifice 17 in which the aligning stud 15 is accommodated with a small radial play, and the stud 15 can slide longitudinally within the orifice 17 without coming out completely.

[0070] Advantageously, the guide stud valve 50 according to the present invention may be wholly or partially coated with a material having a low coefficient of friction and resistant to abrasion, such as a "diamond-like coating" or physical vapor deposition such as "Ionbond 90", and it should be noted that the inner surface of the laminated duct 7 in contact with the valve 50 may be wholly or partially coated with, for example, chemical nickel.

[0071] In the guide stud valve 50 according to the present invention, the laminated duct 7, the open axial surface 13 and the chamber-side valve stop 14 form a valve damping chamber 18, the volume of which is maximum when the closed axial surface 10 rests on the duct closing seat 11 and minimum when the open axial surface 13 rests on the chamber-side valve stop 14, as particularly shown in Figures 2 and 7.

[0072] It should be noted that according to a particular embodiment, not shown, of the guide stud valve 50 according to the present invention, a pocket may be arranged on the surface of the chamber-side valve stop 14 so that the residual volume of the valve damping chamber 18 is increased when the open axial face 13 rests on the stop 14.

[0073] As shown in Figures 1 to 8, the guide shaft orifice 17 may advantageously pass completely through the stacked duct 7 to connect the valve damping chamber 18 with the combustion chamber 3, so that gas 19 can circulate between the chamber 18 and the chamber 3 via a small radial play left between the orientation stud 15 and the guide shaft orifice 17.

[0074] 1-5 show that at least one gas throttling orifice 20 may connect the valve damping chamber 18 and the combustion chamber 3, allowing gas 19 to flow between the chamber 18 and the chamber 3 through the orifice 20.

[0075] 1 and 2, it is shown that the centering outer peripheral surface 12 of the guide stud valve 50 according to the present invention may have a conical profile 21 so as to orient the valve body 8 substantially relative to the laminated duct 7, which is provided to ensure that the closure axis surface 10 can lie flat on the cooperating duct closure seat 11.

[0076] As clearly shown in FIG. 5, the gas discharge orifice 16 may be connected to the torch-ignited pre-combustion chamber 9 through at least one gas discharge slot 22 located in the stacked duct 7 near the duct closure seat 11.

[0077] Advantageously, the slots 22 allow the hot gases 19 coming from the stack cavity 4 through the stack duct 7 to pass in such a way that, on the one hand, they are cooled as little as possible, especially in contact with the duct 7, before being discharged into the combustion chamber 3 through the gas discharge orifices 16, and, on the other hand, the flow of the gases 19 is promoted.

[0078] 3 to 5 show that the valve body 8 and / or the orientation stud 15 of the guide stud valve 50 according to the invention can be attracted towards the stack cavity 4 by a closing magnetic field source 23, which may be a closing permanent magnet 24 or a coil of conductive wire, following the example provided by the valve magnetic return device that is the subject of French Patent Application No. 3,085,718 published on March 13, 2020.

[0079] In this case, the valve body 8 should preferably be made mainly of a magnetic material such as steel or stainless steel, but this is not necessarily the case.

[0080] In Figures 3 to 6 it is clearly shown that the closed magnetic field source 23 may consist of at least one closed permanent magnet 24 which generates a magnetic field.

[0081] However, FIG. 6 shows that the magnetic field generated by the permanent magnet 24 can be canceled or amplified by an opposing or corresponding magnetic field induced in the piloting coil core 37 by the field piloting coil 38, the current flowing through the coil 38 being controllable by a calculator 39.

[0082] With this particular configuration of the guide stud valve 50 according to the present invention, the magnetic field piloting coil 38, depending on the strength and direction of the current flowing through it, can cancel or enhance the magnetic return of the guide stud valve 50 on the duct closure seat 11 generated by the closing permanent magnet 24, or can vary the strength of the magnetic return over time scales ranging from a few degrees of rotation of the internal combustion engine crankshaft to several seconds or minutes.

[0083] As shown in FIG. 6, the piloting coil core 37 may have at least one cooling ring 40 around its periphery that forms a thermal bridge between the core 37 and the portion in which the core 37 is housed, to contribute to proper cooling of the core 37.

[0084] As shown in FIG. 6, the piloting coil core 37 may be provided with magnetic support means 41 located directly on the active pre-chamber ignition insert 42, and for this purpose passes through insert clamping means 43 which hold the insert 42 in the internal combustion engine cylinder head 2.

[0085] 7 and 8 show that the valve body 8 and / or the orientation stud 15 can be attracted toward the chamber-side valve stop 14 by an open magnetic field source 44, which may be an annular open permanent magnet 45 integral with the non-magnetic pre-chamber nose 34.

[0086] The magnet 45 may be made from AlNiCo, a material known per se to be resistant to high temperatures, impacts and corrosion.

[0087] This particular configuration of the guide stud valve 50 according to the present invention can be advantageously combined with that shown in FIG. 6, in which case the closing permanent magnet 24 attracts the valve body 8 and / or the orienting stud 15 towards the stack cavity 4, the magnetic field of the permanent magnet 24 may be controlled or amplified by a respective opposite or corresponding magnetic field induced in the piloting coil core 37 by the magnetic field piloting coil 38, and the current passing through the coil 38 may be controlled by a calculator 39.

[0088] This combination of means makes it possible to dynamically open or close the guide stud valve 50, depending in particular on whether the magnetic fields generated by the closing permanent magnet 24, the opening permanent magnet 45 and the magnetic field piloting coil 38, respectively, at the level of the guide stud valve 50, result in a magnetic field that tends to press the valve 50 against the valve seat 11 or against the chamber-side valve stop 14.

[0089] Alternatively, the guide stud valve 50 may itself be permanently magnetized so as to be attracted or repelled by the magnetic field generated by the closing permanent magnet 24 and / or the field piloting coil 38.

[0090] To this end, the valve 50 may incorporate a permanent magnet attached to any surface of the valve 50 or incorporated wholly or partially within it.

[0091] According to a particular variant of the guide stud valve 50 according to the invention, shown in FIGS. 6 to 8, the aligning stud 15 may have a damping shoulder 46 which cooperates with a damping counterbore 47 arranged at the inlet of the guide shaft orifice 17, the counterbore 47 emerging into the valve damping chamber 18, the relative position of the shoulder 46 and the counterbore 47 being such that when the guide stud valve 50 has moved a certain distance in its movement from the duct closing seat 11 to the chamber-side valve stop 14, the damping shoulder 46 reaches the level of the damping counterbore 47, thereby restricting the passage left for the gases contained in the valve damping chamber 18 to pass to the combustion chamber 3 via the radial play left between the aligning stud 15 and the guide shaft orifice 17.

[0092] It should be noted that the damping counterbore 47 may be confused with the chamber-side valve stop 14 or may be replaced by a protrusion.

[0093] 6 to 8 show that the damping counterbore 47 can be directly or indirectly connected to the combustion chamber 3 by at least one pressure reducing duct 48 through which the gas contained in the valve damping chamber 18 can move freely towards the combustion chamber 3, as long as the damping shoulder 46 has not yet reached the level of the damping counterbore 47 while the guide stud valve 50 moves from the duct closing seat 11 towards the chamber side valve stop 14.

[0094] 6 to 8 show that the laminated duct 7 may include a directly mounted non-magnetic sleeve 26 on which the duct closure seat 11 is located, and the sleeve 26 may be fretting mounted around the gas exhaust pipe 25 formed by the laminated duct 7.

[0095] In this case, the directly mounted non-magnetic sleeve 26 may advantageously be made of "Inconel", a material with high mechanical properties at high temperatures.

[0096] It should be noted in Figures 7 and 8 that a slight axial offset may be provided between the duct closure seat 11, located on the directly mounted non-magnetic sleeve 26, and the end of the gas discharge pipe 25, which offset allows pressure to come between the pipe 25 and the closure axial surface 10, facilitating the opening of the guide stud valve 50 by the pressure of the gas contained in the stack cavity 4.

[0097] Operation of the invention The operation of the guide stud valve 50 according to the present invention can be easily understood from the diagrams of FIGS.

[0098] It should be noted that in Figures 1 and 2 and 7 and 8, the stacked duct 7 is made up of at least three separate parts, by way of non-limiting example.

[0099] First, the duct 7 comprises a gas discharge pipe 25 made from a magnetic material, in this case stainless steel, which has high magnetic permeability and low magnetic remanence, the pipe 25 receiving the duct closure seat 11 in Figures 1 to 5.

[0100] Secondly, the laminated duct 7 comprises a directly mounted non-magnetic sleeve 26, for example made from copper or from "Inconel", which is fretting mounted on the gas discharge pipe 25. According to the variant shown in Figures 6 to 8, the directly mounted non-magnetic sleeve 26 receives the duct closure seat 11 instead of the gas discharge pipe 25, thus being the opposite to what is shown in Figures 1 to 5.

[0101] Thirdly, the laminated duct 7 includes a non-magnetic pre-chamber nose 34 made of copper or stainless steel, which may or may not be coated with a highly wear-resistant anti-friction material. The nose 34 is fretting mounted across the gas discharge pipe 25 and the directly mounted non-magnetic sleeve 26. Additionally, the nose 34 accommodates the guide stud valve 50 with a small amount of play and receives the chamber-side valve stop 14.

[0102] As shown in particular in Figures 2, 7 and 8, the non-magnetic pre-chamber nose 34, together with the guide stud valve 50, forms the valve damping chamber 18, which is connected to the combustion chamber 3 only in the configuration shown in Figures 1 to 5, on the one hand, through the gap formed by the small radial play left between the orientation stud 15 and the guide shaft orifice 17, and on the other hand, through the gas throttling orifice 20.

[0103] As is clear from Figures 1, 2, 7 and 8, the orientation stud 15 can slide longitudinally in the guide shaft orifice 17 without exiting completely.

[0104] The play left between the orientation stud 15 and the guide shaft orifice 17 is calculated to allow the guide stud valve 50 to tilt sufficiently to compensate for any non-perpendicularity between the gas discharge pipe 25 and the duct closure seat 11, i.e. to ensure that the closure shaft surface 10 can make full contact with the seat 11 over its entire surface.

[0105] The slight tilting of the guide stud valve 50 is possible because only a very short axial length of the peripheral contact line on the centering peripheral surface 12, located near the closing axial surface 10, actually contacts the inner wall of the stacked duct 7, which in this case is the inner wall of the non-magnetic pre-combustion chamber nose 34.

[0106] 1 and 2, as an example of the design of the guide stud valve 50 according to the present invention, it should be noted that the centering outer peripheral surface 12 arranged on the outer periphery of the valve body 8 has a conical profile 21, which allows the body 8 to be substantially oriented relative to the stacked duct 7, but the conical profile 21 does not come into contact with the inner wall of the non-magnetic pre-chamber nose 34 over its entire height.

[0107] Thus, only the upper portion, i.e., the largest diameter, of the conical profile 21 of the centering outer surface 12 can contact the inner wall of the non-magnetic pre-chamber nose 34, with the remaining surface of the profile 21 merely being somewhat close to the wall without contacting it.

[0108] 7 and 8 then show that the centering peripheral surface 12 has a truncated spherical profile at its peripheral contact line, the remaining part of the centering peripheral surface 12 being purely cylindrical.

[0109] In Figures 1 and 7, the guide stud valve 50 is shown in the "open" position, with the closing axial surface 10 located on the valve body 8 spaced apart from the duct closing seat 11 with which it cooperates, while the opening axial surface 13 rests on or is very close to the chamber-side valve stop 14 located within the stacked duct 7, or more precisely, within the non-magnetic pre-chamber nose 34 that partially forms the duct 7.

[0110] It should be noted that when in the "open" position, the guide stud valve 50 together with the stack duct 7 forms an annular torch-ignited pre-combustion chamber 9 which communicates with the stack cavity 4 on the one hand and with the combustion chamber 3 on the other hand via the gas discharge orifice 16.

[0111] The “open” position of the guide stud valve 50 occurs when the gas pressure prevailing in the stack cavity 4 is greater than the pressure prevailing in the combustion chamber 3 .

[0112] This situation is mainly due to the ignition by means 5 of a pilot load 31 previously introduced into the stack cavity 4 by the stack injector 6, the pilot load 31 consisting of a highly combustible air-fuel mixture AF previously pressurized by compression means 30, here formed by some type of stack compressor 32, as shown in Figures 3 and 6.

[0113] It should be noted that in Figures 3 to 6 the ignition means 5 is nothing other than a spark plug 33 known per se.

[0114] 2 and 8 show the guide stud valve 50 in the "closed" position, with the closing axial surface 10 located on the valve body 8 in contact with its associated duct closing seat 11, while the opening axial surface 13 is spaced from the chamber-side valve stop 14.

[0115] As can be easily inferred from Figures 1 and 2 and Figures 7 and 8, in order to move from the "open" position to the "closed" position, the guide stud valve 50 was forced by the orienting stud 15 to remain approximately perpendicular to the axis of the stacked duct 7.

[0116] It should be noted that if the conical profile 21 shown in Figures 1 and 2, or the purely cylindrical portion of the centering outer peripheral surface 12 shown in Figures 7 and 8, means that the outer peripheral surface 12 does not come into contact with the inner wall of the non-magnetic pre-chamber nose 34 only on the outer peripheral contact line at a low axial height, which is located near the closing axial surface 10, the orientation stud 15 for that portion will only come into contact with the guide axial orifice 17 at the outlet to the combustion chamber 3.

[0117] Thus, a maximum axial distance is left between the two contact points of the guide stud valve 50 with the laminated duct 7, which avoids the risk of the valve 50 becoming stuck in the duct 7 due to the bracing.

[0118] To enhance the angular stability of the guide stud valve 50, it is advantageously shown in FIG. 5 that the damping chamber of the valve 18 is connected to the combustion chamber 3 by three gas throttling orifices 20 distributed on the surface of the chamber-side valve stop 14.

[0119] This particular configuration causes the opening shaft surface 13 to assume an orientation as parallel as possible to the stop 14, particularly when the surface 13 reaches only a few hundredths of a millimeter from the stop 14 when the guide stud valve 50 is opened.

[0120] From the above, it can be seen that, unlike the laminated valves which it replaces, the stud valve guide 50 will not get stuck in the laminated duct 7 with which it cooperates by means of a brace, as described in French Patent No. 3,061,743 for a "valve ignition prechamber" and its various improvements.

[0121] In addition, the stud valve 50 is no longer oriented in an uncontrolled manner, unlike the laminated valves described in French Patent Application No. 1904961 for "Ignition insert with active prechamber", the outer periphery of which is truncated and spherical to avoid clogging within its housing.

[0122] As a result of the particular configuration of the guide stud valve 50 according to the invention, the valve 50 translates between the duct closure seat 11 and the chamber-side valve stop 14 with which it cooperates so as to remain approximately perpendicular to the axis of the laminated duct 7 during its entire stroke, or at least be able to tilt by a maximum of 1 degree, for example, according to the selected initial play and the relative temperatures of the various parts involved.

[0123] As a result of the above, hot gas torches are actually simultaneously discharged into the combustion chamber 3 by the torch ignition pre-chamber 9, the torches being of identical composition, temperature, geometry and power.

[0124] This homogeneity of the ignition torch emitted into the combustion chamber 3 of an internal combustion engine receiving a valve-ignition pre-chamber 1 equipped with a guide stud valve 50 according to the present invention ensures high energy efficiency, excellent stability and optimal safety, especially with regard to motor knocking.

[0125] Whether the guide stud valve 50 moves toward the duct closure seat 11 or toward the room-side valve stop 14, the stability of the orientation of the valve 50 along two axes perpendicular to the axis of the laminated duct 7 makes it possible to ensure optimal closure of the laminated duct 7 by the valve 50.

[0126] The term "optimal closure" means that a clear contact is quickly established between the closure axial surface 10 and the duct closure seat 11, which prevents gases 19 contained in the combustion chamber 3 from entering the stack cavity 4 through the stack duct 7.

[0127] In fact, the directional guidance exerted on the guide stud valve 50 by the directional stud 15 as a whole prevents the guide stud valve 50 from opening and closing in two stages as explained at the beginning.

[0128] As a result, only the separation force exerted on the guide stud valve 50 by the magnetic field generated by the closing magnetic field source 23 shown in Figures 3 to 5, which in this case is the closing permanent magnet 24, determines the force for bringing the valve 50 into firm contact with the duct closing seat 11 and for separating the valve from this seat.

[0129] Due to the particular configuration of the guide stud valve 50 according to the present invention, the torque exerted on the valve 50 no longer intervenes or substantially does not intervene, either during firm contact on the seat or during separation, which is advantageous since the force counteracting the torque is of very low magnitude compared to the force required to counteract the magnetic force for firm contact on the seat.

[0130] However, prohibiting the gases 19 contained in the combustion chamber 3 from entering the stack cavity 4 makes it possible to keep the pilot load 31 contained in the stack cavity 4 intact by preventing mixing of the load 31 with the main load 27 contained in the combustion chamber 3, the latter load 27 being likely to be significantly diluted with air or recirculated exhaust gases.

[0131] Maintaining the integrity of the pilot load 31 ensures good combustion stability of the pilot load 31, especially in the stack cavity 4, and therefore good stability of the internal combustion engine, which is an important condition for the best possible efficiency of the internal combustion engine.

[0132] The brief closure of the guide stud valve 50 also allows valve cooling to be optimized on the duct closure seat 11, and the gas blade 19 left between the valve 50 and the seat 11 is likely to reduce the amount of heat transferred by the valve 50 to the seat 11.

[0133] This brief closure is also not the only factor in optimizing the cooling of the guide stud valve 50 according to the present invention.

[0134] In fact, the conical profile 21, or in some cases purely cylindrical, of the centering outer surface 12 leaves a small average play between the surface 12 and the inner wall of the non-magnetic pre-chamber nose 34, and in particular a larger surface area than that left by a truncated spherical laminate valve such as that described in French Patent Application No. 1904961.

[0135] In addition to a better sealing of the guide stud valve 50, which is favorable for the proper functioning of the valve damping chamber 18, this good radial proximity and the large surface area left between the conical profile 21 and the non-magnetic pre-chamber nose 34 promote heat transfer by the valve 50 to the nose 34, which is cooler than the valve 50.

[0136] It should be noted, particularly in FIG. 5, that the gas discharge orifice 16 is advantageously connected to the torch-ignited pre-combustion chamber 9 via a gas discharge slot 22 located adjacent the duct closure seat 11 in a directly mounted non-magnetic sleeve 26 that forms the stacked duct 7.

[0137] In addition to the advantage that passing the hot gas 19 from the stack cavity 4 through the stack duct 7 encourages its flow without the gas 19 coming into contact with the duct 7 and being cooled as little as possible, the slot 22 also creates a large cold surface facing the face 10, close to the closure axial face 10.

[0138] Therefore, this adjacent cool surface also aids in cooling the guide stud valve 50 according to the present invention.

[0139] As shown in Figures 3-5, the spark plug 33 includes an inverter housing 28 that is integral with the spark plug 12, as described in French Patent Application No. 2001508, entitled "Valve ignition prechamber with reversed direction of combustion," and the housing 28 receives a priming load.

[0140] It should be noted in Figures 3 and 4 that the ground electrode 35, which is integral with the inverter housing 28, consists of a protruding iridium pad 29 facing the center electrode 36 of the spark plug 33, which center electrode 36 is also made from iridium.

[0141] In this case, three further main exhaust nozzles, strongly offset towards the outer periphery of the inverter housing 28, connect the inverter housing 28 with the interior of the stack cavity 4, the three nozzles being barely visible in the drawing due to their small size.

[0142] A variant of the guide stud valve 50 according to the invention is shown in FIG. 6, whereby the source 23 of the closed magnetic field is a closed permanent magnet 24 which generates a magnetic field which can be cancelled or amplified by an opposite or corresponding magnetic field induced in the piloting coil core 37 by passing a current through the field piloting coil 38 whose strength is controlled by a calculator 39.

[0143] Advantageously, the piloting coil core 37 may be made from a material with high magnetic permeability and low magnetic remanence.

[0144] With this particular configuration of the guide stud valve 50 according to the present invention, the magnetic field piloting coil 38, depending on the strength and direction of the current passing through it, can either eliminate the magnetic return of the guide stud valve 50 on the duct closure seat 11 generated by the closing permanent magnet 24, strengthen the magnetic return, or vary the power of the return over some long time scale, which can range from a few degrees of rotation of the crankshaft of the internal combustion engine to several seconds or minutes.

[0145] The dynamic piloting of the magnetic return of the guide stud valve 50 according to the present invention makes it possible to avoid residual bracing of the valve 50, particularly during the opening of the valve 50 following the firing of the pilot load 31 contained within the stack cavity 4.

[0146] In fact, if the orientation stud 15 opposes tilt of the guide stud valve 50, the tilt is due to the torque exerted on the valve 50 by the magnetic field, and the elimination of the magnetic field by the magnetic field piloting coil 38 cancels the very cause of the tilt.

[0147] This allows the calculator 39 to suppress the magnetic return of the guide stud valve 50 under the influence of the combustion of the pilot load 31 several hundred microseconds before the valve 50 opens.

[0148] When the ignition torch is released by the torch ignition pre-combustion chamber 9 in the combustion chamber 3, the calculator 39 can restore the magnetic return of the guide stud valve 50 so as to bring the guide stud valve 50 back into contact with the duct closing seat 11 with less impact.

[0149] This strategy for piloting the magnetic field for the return of the guide stud valve 50 according to the present invention makes it possible to significantly reduce wear and tear on the valve 50 and on the laminated duct 7 in which the valve 50 is housed with little play.

[0150] In addition, piloting the magnetic field for the return of the guide stud valve 50 makes it possible to ensure cold starting of the internal combustion engine at low temperatures by allowing the stack cavity 4 to no longer be filled with the oxidizer-fuel mixture AF via the stack injector 6 but rather via the gas discharge orifice 16.

[0151] In this case, the guide stud valve 50 is held open during engine compression to fill the stack cavity 4 .

[0152] During such compression, when the pressure within the stack cavity 4 reaches the recondensation limit of the oxidizer-fuel mixture AF contained therein, the guide stud valve 50 is closed by the calculator 39, which ensures complete combustion of the mixture and provides an efficient solution to the difficulty or even impossibility of starting engines with ignition pre-chambers at very low temperatures.

[0153] The piloting of the magnetic field for the return of the guide stud valve 50 additionally makes it possible to optimize the emptying of the stack cavity 4 between two fillings, minimizing the amount of residual exhaust gas from the previous cycle and improving the combustion of the pilot load 31 in the cavity 4.

[0154] In fact, when the ignition torch is discharged into the combustion chamber 3 through the gas discharge orifice 16, forcing the guide stud valve 50 to close when the pressure in the stack cavity 4 is at its lowest makes it possible to achieve the expected result.

[0155] 7 and 8 show an open permanent magnet 45 that may be provided in accordance with the present invention to attract the guide stud valve 50 toward the chamber-side valve stop 14.

[0156] The magnet 45 cooperates with the closing permanent magnet 24 and the field piloting coil 38. The magnet 45 allows the guide stud valve 50 to be forced closed against the duct closing seat 11 as appropriate, but also allows the valve 50 to be forced open toward the chamber side valve stop 14 as appropriate.

[0157] The calculator 39 is thus able to neutralize the magnetic field of the closing permanent magnet 24 , generated by the closing permanent magnet 24 at the level of the guide stud valve 50 , via the field piloting coil 38 .

[0158] In this case, only the magnetic field generated by the open permanent magnet 45 remains on the guide stud valve 50 , and the guide stud valve 50 is attracted toward the chamber-side valve stop 14 .

[0159] Conversely, the calculator 39 can enable or strengthen the magnetic field generated by the closing permanent magnet 24 at the level of the guide stud valve 50, depending on the strength and direction of the current circulating in the magnetic field piloting coil 38.

[0160] The magnetic field generated by the closing permanent magnet 24 is naturally stronger at the level of the guide stud valve 50 than the magnetic field generated by the opening permanent magnet 45, so that when no current is circulating in the magnetic field piloting coil 38, the valve 50 is attracted towards the duct closing seat 11.

[0161] It will be readily appreciated that the calculator 39 can advantageously give dominance to one or the other of the opposing magnetic fields of the closing permanent magnet 24 or the opening permanent magnet 45 via the magnetic field piloting coil 38, which is provided to force the guide stud valve 50 towards the duct closing seat 11 or towards the chamber side valve stop 14 as required.

[0162] This "pull-push" function of the guide stud valve 50, managed by the calculator 39, makes it possible, in particular, to unlock the valve 50 in case of blockage, to force it open when gravity does not help, especially on flat piston engines, or to optimize the filling and emptying of the stack cavity 4 under all circumstances.

[0163] 7 and 8, it will be noted that the orientation stud 15 is provided with a damping shoulder 46 which cooperates with a damping counterbore 47 located at the entrance of the guide shaft orifice 17, the counterbore 47 opening into the valve damping chamber 18.

[0164] This particular configuration of the guide stud valve 50 according to the present invention allows the guide stud valve 50 to move through the initial portion of its stroke toward the chamber-side valve stop 14 while being damped as little as possible by the valve damping chamber 18.

[0165] In fact, as long as the damping shoulder 46 does not reach the level of the damping counterbore 47, the gases contained in the valve damping chamber 18 can leave the valve damping chamber 18 very freely in the direction of the combustion chamber 3, via the play left between the shoulder 46 and the counterbore 47, and then via the pressure reduction duct 48, as shown in Figures 7 and 8.

[0166] When the damping shoulder 46 reaches the level of the damping counterbore 47, the gas is strongly stacked by the passage restriction thus formed, as a result of which the guide stud valve 50 is braked during the second part of the stroke towards the chamber-side valve stop 14, which accordingly reduces the force of impact that may occur between the open shaft face 13 and the chamber-side valve stop 14.

[0167] Therefore, this particular configuration of the guide stud valve 50 according to the present invention provides the guide stud valve 50 with a longer service life.

[0168] It should be noted that the exemplary embodiment of the guide stud valve 50 according to the present invention described herein is not intended to be limiting.

[0169] In fact, the guide stud valve 50 according to the present invention may be applied in areas other than internal combustion engines. For example, the valve 50 may be applied to a gas nail gun, a firearm, or any device that requires a pilot load to fire a main load with the highest possible efficiency.

[0170] It should be understood that the possibilities of the guide stud valve 50 according to the present invention are not limited to the applications described herein, and that the above description is given merely as an example and does not in any way limit the field of the invention, from which it would not be liable to depart from the invention by substituting the details of implementation described by other equivalent ones.

Claims

1. A directional valve (50) for a valve-ignited pre-combustion chamber (1) arranged in an internal combustion engine cylinder head (2) covering a combustion chamber (3), said pre-combustion chamber (1) comprising a stack cavity (4) in which ignition means (5) and at least one stack injector (6) emerge, said cavity (4) being connected to said combustion chamber (3) by a stack duct (7) accommodating said valve (50), so that together with said stack duct (7) a torch-ignited pre-combustion chamber (9) can be formed which connects said stack cavity (6) with said combustion chamber (5) by at least one gas discharge orifice (16), said directional valve comprising: a valve body (8) accommodated with a small amount of play in the laminated duct (7); a closing axial surface (10) arranged on the valve body (8), which can rest wholly or partly on a duct closing seat (11) presented by the stack duct (7) in order to close the duct (7) and isolate the stack cavity (4) from the combustion chamber (5); at least one centering outer peripheral surface (12) located on the outer periphery of the valve body (8), said surface (12) being capable of contacting the inner wall of the stacked duct (7) in order to center the body (8) within the duct (7); an open axial surface (13) arranged on the valve body (8) opposite the closed axial surface (10), which can rest on a chamber-side valve stop (14) arranged in the stacked duct (7) when the closed axial surface (10) is not resting on the duct closing seat (11); at least one orientation stud (15) fixedly attached to said valve body (8) and projecting from said open axial face (13); at least one guide shaft orifice (17) arranged in or near the chamber-side valve stop (14) and in which the orientation stud (15) is received with a small radial play, the stud (15) being able to slide longitudinally within the orifice (17) without completely exiting; a valve damping chamber (18) formed by the laminated duct (7), the open axial surface (13) and the chamber-side valve stop (14), wherein the volume of the valve damping chamber (18) is maximum when the closing axial surface (10) rests on the duct closing seat (11) and is minimum when the open axial surface (13) rests on the chamber-side valve stop (14).

2. 2. Directional valve according to claim 1, characterized in that the guide shaft orifice (17) passes completely through the stacked duct (7) to connect the valve damping chamber (18) and the combustion chamber (3), so that gas (19) can circulate between the chambers (18, 3) via a small radial play left between the orienting stud (15) and the guide shaft orifice (17).

3. 2. A directional valve according to claim 1, characterized in that at least one gas throttling orifice (20) connects the valve damping chamber (18) and the combustion chamber (3), so that gas (19) can flow between the chambers (18, 3) via the orifice (20).

4. 2. Directional valve according to claim 1, characterized in that the centering peripheral surface (12) has a conical profile (21).

5. 2. The directional valve according to claim 1, characterized in that the gas discharge orifice (16) is connected to the torch-ignited pre-combustion chamber (9) by at least one gas discharge slot (22) arranged in the stacked duct (7) and in the vicinity of the duct closing seat (11).

6. 2. Directional valve according to claim 1, characterized in that the valve body (8) and / or the orientation stud (15) are attracted towards the stack cavity (4) by a closed magnetic field source (23).

7. 7. The directional valve according to claim 6, characterized in that the closed magnetic field source (23) consists of at least one closed permanent magnet (24) generating a magnetic field, which can be cancelled or amplified by a respective opposite or corresponding magnetic field induced in a piloting coil core (37) by a field piloting coil (38).

8. 2. The directional valve according to claim 1, characterized in that the valve body (8) and / or the orientation stud (15) are attracted towards the chamber-side valve stop (14) by an open magnetic field source (44).

9. 3. A directional valve according to claim 2, characterized in that the orienting stud (15) comprises a damping shoulder (46) cooperating with a damping counterbore (47) arranged at the inlet of the guide shaft orifice (17), the counterbore (47) opening into the valve damping chamber (18).

10. Directional valve according to claim 9, characterized in that the damping counterbore (47) is connected directly or indirectly to the combustion chamber (3) by at least one pressure reduction duct (48).

11. 2. Directional valve according to claim 1, characterized in that the laminated duct (7) comprises a directly mounted non-magnetic sleeve (26) on which the duct closing seat (11) is located.

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