EP0100713B1 - Sealing element for a gas-cycle control device for a combustion chamber - Google Patents

Sealing element for a gas-cycle control device for a combustion chamber Download PDF

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Publication number
EP0100713B1
EP0100713B1 EP83401495A EP83401495A EP0100713B1 EP 0100713 B1 EP0100713 B1 EP 0100713B1 EP 83401495 A EP83401495 A EP 83401495A EP 83401495 A EP83401495 A EP 83401495A EP 0100713 B1 EP0100713 B1 EP 0100713B1
Authority
EP
European Patent Office
Prior art keywords
seal
combustion chamber
valve plug
plug
exhaust
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP83401495A
Other languages
German (de)
French (fr)
Other versions
EP0100713A1 (en
Inventor
Guy Negre
Jean-Claude Fayard
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEGRE, GUY
Elf Antar France
Original Assignee
Elf France SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FR8213071A external-priority patent/FR2531139B1/en
Priority claimed from FR8213072A external-priority patent/FR2531174A1/en
Application filed by Elf France SA filed Critical Elf France SA
Priority to AT83401495T priority Critical patent/ATE23603T1/en
Publication of EP0100713A1 publication Critical patent/EP0100713A1/en
Application granted granted Critical
Publication of EP0100713B1 publication Critical patent/EP0100713B1/en
Expired legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L7/00—Rotary or oscillatory slide valve-gear or valve arrangements
    • F01L7/16—Sealing or packing arrangements specially therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L7/00—Rotary or oscillatory slide valve-gear or valve arrangements
    • F01L7/12—Rotary or oscillatory slide valve-gear or valve arrangements specially for two-stroke engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/025—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00—Other engines
    • F02B75/02—Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/027—Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle four

Definitions

  • the present invention relates to a sealing member for a substantially cylindrical rotary plug crossed by at least one channel and to which an annular seal is applied with an axis transverse to the axis of rotation of the plug, in particular for sealing an exhaust port of a combustion chamber of an internal combustion engine and in which the annular seal is guided axially in a leaktight manner by its movable external surface in a bore and pressed against the plug by the pressure prevailing in the combustion chamber, the bore for guiding the seal having a slight taper, the point of which is directed towards the combustion chamber to permanently push the seal towards the plug and the contact zone between the plug and the seal being lubricated by a film of oil maintained despite the pressure of the gases from the combustion chamber passing through the plug.
  • Such a sealing member applies to a device for controlling a gas circuit, in particular for the evacuation of exhaust gases from a heat engine to control the exhaust of engines with rotary distribution such as internal combustion engines according to two or four stroke cycles, with spark or diesel ignition.
  • the orifice connected to the combustion chamber is arranged in a sealing ring housed in a bore and applied to the plug by the pressure prevailing in the combustion chamber and surrounded one or more sealing members such as segments, this ring being able to slide in the bore and its stroke being limited, on one side, by the rotor and, on the other side, by a retaining shoulder.
  • a metallic sealing ring of good rubbing quality makes it possible to seal the exhaust despite the high temperatures of the exhaust gases.
  • the sealing device is an integral part of the combustion chamber and is slidably mounted in a bore perpendicular to the distributor housing, thus achieving the intersection of two cylinders.
  • the seal of the device is pressed against the rotary distributor by the pressure prevailing in the chamber, which allows a clearance of operation between the rotary distributor and the annular seal.
  • the edges of the joint can form, at each end of the joint in contact with the plug, along a plane transverse to the axis of rotation of the plug, an end edge with an angle less than 90 °.
  • the end edge of the seal located on the side of the inlet in contact at the outlet of the channel formed in the plug with the annular seal, is provided with an inlet chamfer capable of forming an oil wedge which makes penetrate the oil film between the surfaces in contact with the plug and the annular seal.
  • the known devices have sealing difficulties at high operating temperatures or at cold start and high wear of the seals and the contact surfaces on the rotary distributor.
  • the annular seal has in its portion of smaller axial section an axial height close to the minimum height ensuring the pressure resistance of the combustion chamber prevailing inside the seal , so as to give it good elasticity to plating on the plug and to improve the behavior of the oil film.
  • the sealing member according to the invention for a substantially cylindrical rotary plug crossed by at least one channel and to which an annular seal is applied, with an axis transverse to the axis of rotation of the plug, in particular for sealing an exhaust port of a combustion chamber of an internal combustion engine and in which the annular seal is guided axially in a leaktight manner by its movable outer surface in a bore and pressed against the plug by the pressure prevailing in the combustion chamber, is remarkable in that the contact zone between the plug and the seal is lubricated by an oil film maintained despite the pressure of the gases (from the combustion chamber) passing through the bushel.
  • the outside diameter of the seal can be between 4/7 and 6/7 of the outside diameter of the plug to achieve a good compromise between the central passage section of the seal, the contact surface with the plug capable of improving the resistance of the film of oil and the curvature of the contact zones with the plug at the edges of the joint along a plane transverse to the axis of rotation of the plug, this curvature being able to reduce the resistance of the oil film.
  • the engine shown schematically in Figure 1 includes elements well known in engines operating according to the two-stroke cycle.
  • a crankcase 1 contains an engine cylinder 2 and is connected to a cylinder head 3, cooled by a circulation of liquid like the cylinder 2, to close a combustion chamber 4 into which opens a spark plug 5 or, in the case of diesel engines, a fuel injector.
  • the cylinder head 3 is shown in one piece with the engine crankcase 1, while in reality it is generally fixed by studs to the engine crankcase 1, while allowing the circulation of the coolant in a cooling circuit 6 common to the housing 1 and to the cylinder head 3.
  • a transfer chamber 7 which contains the crankshaft 8 of the engine connected to a connecting rod 9 and to the piston 10 movable in the cylinder 2.
  • This transfer chamber 7, of minimum volume compatible with the travel of the crankshaft 8 and of the connecting rod 9, are connected, on the one hand, to an inlet light 11 connected to a filtered air intake, direct in the case of a diesel engine and via a carburetor 12 in the case of a spark-ignition engine as shown in the figure and, on the other hand, transfer lights 13 which are more particularly visible in Figure 3 in the bottom dead center position of the piston 10.
  • the segments d seal 14 of the piston 10 reveal the openings 13 in the low position of the piston 10 to allow the admission of the carburetted gases, compressed in the transfer chamber 7, towards the combustion chamber 4.
  • a scraper and distributor segment placed on the piston of the side opposite to the piston head closing the combustion chamber 4 allows, from a relatively high position of the piston (substantially from 2/3 of the stroke of the piston towards top dead center) the gases sucked in s '' via the entry light 11 in the transfer chamber t 7 depression by the rise of the piston 10.
  • the engine exhaust circuit is controlled in the cylinder head 3 by a rotary valve 16 rotating in a chamber formed by a bore 17 with the walls of which it is not in contact although its external cylindrical surface is in the immediate vicinity of the bore wall.
  • This plug 16 is rotated by any means, such as a gear train or a chain or a toothed belt, at an angular speed half that of the crankshaft 8 of the engine and rotates around an axis 18 perpendicular to the cylinder axis 2.
  • the sealing of the ring 22 in the bore 23 is ensured by at least one segment 24 and the stroke of the ring 22 towards the combustion chamber 4 is limited by a retaining shoulder 25.
  • the sealing ring which has a front sealing surface 26 combined with that of the cylindrical surface of the plug 16, is pressed against the plug 16 by the pressure prevailing in the combustion chamber 4 and acting on its annular section against the pressure prevailing in the bore 17 and only slightly higher than atmospheric pressure.
  • the axis of the orifices 20 and 21 is placed in the figure substantially in the axis of the cylinder 2 but it can also be inclined. to provide a more advantageous arrangement of the spark plug 5 and allow the use of a combustion chamber 4 at the corner ensuring greater turbulence of the compressed gases and better propagation of the ignition flame.
  • the plug 16 which has also rotated comes to communicate its transverse channel 19, already connected to the exhaust orifice 21, with the orifice 20 which opens onto the combustion chamber 4 .
  • the movement of the piston 10 continues up to the bottom dead center shown, the pressure in the transfer chamber continues to increase while the pressure in the cylinder 2 and the combustion chamber 4 decreases very quickly through the wide passage section of the transverse channel 19 which is placed at the bottom dead center of the piston 10, exactly in the axis of the cylinder 2 and the orifice 20.
  • the cross section of the channel 19 is substantially equal to the section of the orifice 20 formed in the sealing ring 22 at contact of the external cylindrical surface of the plug 16 and the inlet and outlet edges of the channel 19 correspond thus substantially at bottom dead center of the piston 10 with the corresponding edges of the orifice 20 open on the combustion chamber.
  • the scraper segment then discovers the inlet lumen 11 which connects the carburetor 12 to the transfer chamber 7, in slight depression under the effect of the rise of the piston 10 towards the top dead center. While the piston 10 continues to climb towards top dead center, the vacuum in the transfer chamber 7 is maintained despite the supply of fresh gas and the inertia of the gas column between the carburetor 12 and the transfer chamber 7 allows the continued filling of the chamber 7 by a mechanical hysteresis effect until the moment when, after the top dead center of the piston 10 and the ignition of the compressed fuel mixture in the combustion chamber 4, the piston 10 descends again and closes again by the scraper segment the inlet 11, according to the position shown in Figure 1.
  • the exhaust control system which has just been described in combination with an internal combustion engine operating according to the two-stroke cycle could be applied to a 2- or 4-stroke engine to replace the exhaust valves and / or air intake in the cylinders and one could also use other adjustments of the position of the transverse channel 19 relative to the various positions of the piston 10.
  • This channel 19 could also consist of two openings of relatively small section opening out on a central section of larger section to produce an exhaust gas pre-expansion chamber in the plug 16.
  • the orifices 20 and 21 as well as the section of the channel 19 may have a circular shape but more advantageously the shape of a rectangle or a square (for example, with truncated angles).
  • the orifice 20 can open at any point on the wall of the combustion chamber 4 and can also constitute the admission of fresh gases into the combustion chamber 4.
  • the intake ports can be supplied by any means other than the overpressure in the transfer chamber 7 which can itself be etched with compressed air by the compressor of a turbocharger or a vane pump.
  • the sealing ring 22 is applied to the plug 16 by the only pressure prevailing in the combustion chamber 4 which, for high compression engines such as diesel engines, can, at the top dead center of the piston 10, reduce to the interior space of the ring 22, the injection of the fuel being effected by means of an injector delivering a sheet of atomized fuel substantially parallel to the upper surface of the piston 10 or to the inlet section of the ring 22 on the side of the combustion chamber 4.
  • the channel 19 could also, in certain versions, be replaced by a lateral notch formed on the side of the plug 16 and putting in communication a lateral exhaust 21 with the combustion chamber 4 and alternatively, if necessary, with the fresh gas intake.
  • the proposed sealing element is produced in such a way that its inertia at its minimum section, along the cutting plane 108 (see FIG. 3), allows it great flexibility so that, as soon as a pressure is applied. gas even weak (start of engine compression) in the combustion chamber 104, the radius of curvature OB of the element can conform to the radius of curvature OA of the distributor by the bending of element 103 even for appreciable differences between these two rays OA and OB and ensure permanent contact allowing sealing.
  • FIG. 4 represents the deformation of the annular seal 103, mainly under the effect of the heating in friction contact with the distributor 101.
  • the radius of curvature OA of the distributor is greater than the radius of curvature OB of the element d sealing. Under the effect of the application of pressure, the element 103 deforms outwards so that OA equals OB.
  • the radius of curvature of the distributor OA is smaller than the radius of curvature OB of the element 103 which is not subjected to pressure. Under the effect of the pressure of the combustion chamber 104, the sealing element 103 deforms inwards so that OA is equal to OB.
  • an initial radius of curvature OB which is smaller than the initial radius of curvature OA when machining the distributor 101, will preferably be chosen when machining the sealing element.
  • the clearance between the sealing element 103 and its bore 105 must be sufficient to accept the deformations of conformability without jamming detrimental to the proper functioning and be chosen as a function of the in-depth study of all the scenarios that may be encountered in operation. .
  • the minimum section 108 of the seal 103 is reduced to the lowest admissible height making it possible to withstand the stresses of the pressure prevailing in the passage 107a and which tends to cause the seal 103 to burst radially.
  • the thickness e of the seal 103 is between 1/10 and 1/8 of the outside diameter of the distributor 101 to achieve a good compromise between the pressure forces applied on the seal towards the plug, the section of the seal applied to the plug via the oil film and the deformation of the seal under the effect of the pressure of the gases from the combustion chamber passing through it.
  • the outside diameter of the element 103 and the bore 105 which guides it can be between 4/7 and 6/7 of the outside diameter of the plug 101 to achieve a good compromise between the central passage section of the seal, the surface contact with the valve capable of improving the resistance of the oil film and the curvature of the contact zones with the valve at the edges of the joint along a plane transverse to the axis of rotation of the valve, this curvature being capable of reducing the resistance oil film.
  • the axial clearance between the flat base 120 of the seal 103 and the bearing face 112 formed in the body 101a which contains the distributor 101 must be reduced to the minimum compatible with the expansions of this body 101a, of the seal 103 and of the distributor 101, that is to say for the current dimensions of two-stroke engines, at dimensions of the order of 5/10 of a millimeter.
  • the permanent plating of the sealing element 103 on the distributor 101 in the form of a bushel is ensured without the presence of a return spring simply because of the slight conicity of the bore 105 which tends to repel by a sort of mechano-pneumatic effect the seal 103 in the direction of the plug 101 against gravity acting on the element 103 when the sealing device is placed, according to FIG. 6, at the head of the combustion chamber.
  • the element 103 may have an outside diameter very close to that of the bore 105 so that during its diametral swelling under the action of the pressure of the combustion chamber 104, it comes to bear on the wall of this bore, which limits the risk of bursting.

Description

La présente invention concerne un organe d'étanchéité pour un boisseau rotatif sensiblement cylindrique traversé par au moins un canal et sur lequel vient s'appliquer un joint d'étanchéité annulaire d'axe transversal à l'axe de rotation du boisseau, en particulier pour assurer l'étanchéité d'une lumière d'échappement d'une chambre de combustion d'un moteur à combustion interne et dans lequel le joint annulaire est guidé axialement de façon étanche par sa surface extérieure mobile dans un alésage et plaqué sur le boisseau par la pression régnant dans la chambre de combustion, l'alésage de guidage du joint présentant une légère conicité dont la pointe est dirigée vers la chambre de combustion pour repousser en permanence le joint en direction du boisseau et la zone de contact entre le boisseau et le joint étant lubrifiée par un film d'huile maintenu malgré la pression des gaz de la chambre de combustion qui traversent le boisseau.The present invention relates to a sealing member for a substantially cylindrical rotary plug crossed by at least one channel and to which an annular seal is applied with an axis transverse to the axis of rotation of the plug, in particular for sealing an exhaust port of a combustion chamber of an internal combustion engine and in which the annular seal is guided axially in a leaktight manner by its movable external surface in a bore and pressed against the plug by the pressure prevailing in the combustion chamber, the bore for guiding the seal having a slight taper, the point of which is directed towards the combustion chamber to permanently push the seal towards the plug and the contact zone between the plug and the seal being lubricated by a film of oil maintained despite the pressure of the gases from the combustion chamber passing through the plug.

Un tel organe d'étanchéité s'applique à un dispositif de contrôle d'un circuit de gaz, en particulier pour l'évacuation des gaz d'échappement d'un moteur thermique pour contrôler l'échappement des moteurs à distribution rotative tels que les moteurs à combustion interne selon les cycles à deux ou quatre temps, à allumage commandé ou diésel.Such a sealing member applies to a device for controlling a gas circuit, in particular for the evacuation of exhaust gases from a heat engine to control the exhaust of engines with rotary distribution such as internal combustion engines according to two or four stroke cycles, with spark or diesel ignition.

Dans les moteurs deux temps de type connu, l'échappement des gaz brûlés s'effectue au travers d'une lumière positionnée latéralement dans le cylindre et découverte par le piston lorsqu'il arrive au point mort bas.In two-stroke engines of known type, the exhaust of the burnt gases takes place through a light positioned laterally in the cylinder and discovered by the piston when it reaches bottom dead center.

Le positionnement rigide de cette lumière détermine un angle d'avance à l'ouverture égal à l'angle de retard à la fermeture de l'échappement de part et d'autre du point mort bas, ce qui entraîne des inconvénients bien connus pour ce type de moteur :

  • - difficulté de bien vider le cylindre de ses gaz brûlés et, notamment de ceux contenus dans le haut du cylindre, la lumière d'échappement étant positionnée dans le bas de ce cylindre ;
  • - obligation de réaliser des systèmes d'échappement à contre-pression afin de ne pas évacuer trop de gaz frais à l'échappement ;
  • - impossibilité de faire fonctionner correctement le système d'alimentation en air sur une grande plage de régime, car il n'atteint son optimum qu'à une fréquence accordée sur la géométrie de l'échappement ;
  • - perte de rendement, augmentation importante de la consommation par l'évacuation de gaz frais à l'échappement ou la réaspiration des gaz brûlés, suivant les régimes ;
  • - léchage des segments de piston par les gaz chauds d'échappement qui brûlent l'huile et entraînent le gommage des segments de piston et un calaminage rapide du moteur.
The rigid positioning of this light determines an angle of advance at opening equal to the angle of delay in closing the exhaust on either side of the bottom dead center, which causes well-known drawbacks for this type of engine :
  • - difficulty in properly emptying the cylinder of its burnt gases and, in particular of those contained at the top of the cylinder, the exhaust port being positioned at the bottom of this cylinder;
  • - obligation to make exhaust systems with back pressure in order not to evacuate too much fresh gas from the exhaust;
  • - impossibility of operating the air supply system correctly over a wide speed range, because it reaches its optimum only at a frequency tuned to the geometry of the exhaust;
  • - loss of efficiency, significant increase in consumption by evacuating fresh exhaust gases or rebreathing the burnt gases, depending on the regimes;
  • - licking of the piston rings by the hot exhaust gases which burn the oil and cause the piston rings to erase and rapid scaling of the engine.

Pour remédier à ces inconvénients, on a aussi, notamment pour les moteurs diésel à deux temps, utilisé des soupapes d'évacuation des gaz d'échappement améliorant le remplissage des cylindres mais créant de nouveaux problèmes, tels que :

  • - laminage des gaz et pertes de charge importantes ;
  • - température élevée des soupapes due au cycle à deux temps et grandes difficultés de refroidissement ;
  • - bruit de martèlement important.
To overcome these drawbacks, use has also been made, in particular for two-stroke diesel engines, of exhaust gas discharge valves improving the filling of the cylinders but creating new problems, such as:
  • - gas rolling and significant pressure drops;
  • - high temperature of the valves due to the two-stroke cycle and great cooling difficulties;
  • - significant hammering noise.

L'un des buts de l'invention est de créer un dispositif permettant de pallier ces inconvénients, d'améliorer le rendement des moteurs deux temps de façon sensible, de diminuer la pollution qu'ils provoquent, notamment par rejet d'imbrûlés et d'huile, tout en restant simple et économique à fabriquer.One of the aims of the invention is to create a device making it possible to overcome these drawbacks, to improve the efficiency of two-stroke engines appreciably, to reduce the pollution which they cause, in particular by rejecting unburnt fuel and d oil, while remaining simple and economical to manufacture.

On a déjà proposé pour cela dans GB-A-284649 de réaliser un dispositif de contrôle de l'évacuation des gaz d'échappement d'une chambre de combustion de moteur à combustion interne, en particulier d'un moteur à cycle deux temps à piston alternatif, constitué par un boisseau ou rotor comportant un canal d'écoulement transversal, ce boisseau effectuant un mouvement tournant continu ou alternatif et synchronisé avec la rotation du moteur autour d'un axe parallèle à l'axe de rotation du moteur et débouchant au niveau du canal, d'un côté, sur un orifice relié directement à la chambre de combustion et, de l'autre côté, sur un orifice relié à l'échappement des gaz brûlés vers l'extérieur pour alternativement obturer l'orifice, puis relier la chambre de combustion à l'échappement, en synchronisme avec les phases respectives de compression, puis d'échappement de la chambre de combustion, ce boisseau étant contenu dans un alésage dans lequel débouche l'orifice relié directement à la chambre de combustion du cylindre du moteur et un orifice d'échappement vers l'extérieur.It has already been proposed for this in GB-A-284649 to produce a device for controlling the discharge of exhaust gases from a combustion chamber of an internal combustion engine, in particular of a two-stroke cycle engine with reciprocating piston, constituted by a plug or rotor comprising a transverse flow channel, this plug performing a continuous or reciprocating rotary movement and synchronized with the rotation of the engine around an axis parallel to the axis of rotation of the engine and opening at level of the channel, on one side, on an orifice connected directly to the combustion chamber and, on the other side, on an orifice connected to the exhaust of the burnt gases to the outside to alternately close the orifice, then connect the combustion chamber to the exhaust, in synchronism with the respective phases of compression, then exhaust of the combustion chamber, this plug being contained in a bore into which opens the orifice connected directly to the combustion chamber engine cylinder flow and an exhaust port to the outside.

Selon un mode de réalisation décrit dans FR-A-2123968, l'orifice relié à la chambre de combustion est aménagé dans un anneau d'étanchéité logé dans un alésage et appliqué sur le boisseau par la pression régnant dans la chambre de combustion et entouré d'un ou plusieurs organes d'étanchéité tels que des segments, cet anneau pouvant coulisser dans l'alésage et sa course étant limitée, d'un côté, par le rotor et, de l'autre côté, par un épaulement de retenue. L'utilisation d'un anneau d'étanchéité métallique et de bonne qualité frottante permet d'assurer l'étanchéité de l'échappement en dépit des températures élevées des gaz d'échappement.According to an embodiment described in FR-A-2123968, the orifice connected to the combustion chamber is arranged in a sealing ring housed in a bore and applied to the plug by the pressure prevailing in the combustion chamber and surrounded one or more sealing members such as segments, this ring being able to slide in the bore and its stroke being limited, on one side, by the rotor and, on the other side, by a retaining shoulder. The use of a metallic sealing ring of good rubbing quality makes it possible to seal the exhaust despite the high temperatures of the exhaust gases.

Néanmoins, une des principales difficultés de réalisation des moteurs à combustion interne réside dans l'étanchéité de la chambre de combustion. Lorsque, afin de contrôler le circuit d'admission pour l'échappement des gaz de la chambre de combustion, on utilise un distributeur rotatif qui vient obturer la chambre de combustion durant les phases de combustion à haute pression, il convient de réaliser un joint tournant résistant en plus à des températures élevées (600 à 900°C) et à la flamme de la combustion chimiquement agressive.However, one of the main difficulties in producing internal combustion engines lies in the sealing of the combustion chamber. When, in order to control the intake circuit for the exhaust of gases from the combustion chamber, a rotary distributor is used which closes the combustion chamber during the high pressure combustion phases, a rotary joint should be produced resistant in addition to high temperatures (600 to 900 ° C) and to the flame of chemically aggressive combustion.

De nombreux systèmes d'étanchéité ont été élaborés qui tous conduisent à des grippages ou à des défauts d'étanchéité dans le temps. Pour assurer le fonctionnement du distributeur, il est nécessaire, ainsi que décrit dans FR-A-2 239 896, de ménager un jeu de fonctionnement entre le distributeur rotatif et son logement ou alésage afin de tenir compte des dilatations. Dans FR-A-2123968 précité, le dispositif d'étanchéité fait partie intégrante de la chambre de combustion et est monté coulissant dans un alésage perpendiculaire au logement du distributeur, réalisant ainsi l'intersection de deux cylindres. Le joint du dispositif est plaqué sur le distributeur rotatif par la pression régnant dans la chambre, ce qui autorise un jeu de fonctionnement entre le distributeur rotatif et le joint annulaire.Many sealing systems have been developed, all of which lead to seizures or leaks over time. To ensure the functioning of the distributor, it is necessary, as described in FR-A-2 239 896, to provide an operating clearance between the rotary distributor and its housing or bore in order to take account of expansions. In FR-A-2123968 mentioned above, the sealing device is an integral part of the combustion chamber and is slidably mounted in a bore perpendicular to the distributor housing, thus achieving the intersection of two cylinders. The seal of the device is pressed against the rotary distributor by the pressure prevailing in the chamber, which allows a clearance of operation between the rotary distributor and the annular seal.

Les bords du joint peuvent former à chacune des extrémités du joint en contact avec le boisseau, selon un plan transversal à l'axe de rotation du boisseau, une arête d'extrémité d'angle inférieur à 90°. L'arête d'extrémité du joint, située du côté de l'entrée en contact au débouché du canal ménagé dans le boisseau avec le joint annulaire, est munie d'un chanfrein d'entrée apte à former un coin d'huile qui fait pénétrer le film d'huile entre les surfaces au contact du boisseau et du joint annulaire.The edges of the joint can form, at each end of the joint in contact with the plug, along a plane transverse to the axis of rotation of the plug, an end edge with an angle less than 90 °. The end edge of the seal, located on the side of the inlet in contact at the outlet of the channel formed in the plug with the annular seal, is provided with an inlet chamfer capable of forming an oil wedge which makes penetrate the oil film between the surfaces in contact with the plug and the annular seal.

Les dispositifs connus présentent des difficultés d'étanchéité aux températures de fonctionnement élevées ou au démarrage à froid et des usures élevées des joints d'étanchéité et des surfaces de contact sur le distributeur rotatif.The known devices have sealing difficulties at high operating temperatures or at cold start and high wear of the seals and the contact surfaces on the rotary distributor.

Afin de pallier ces difficultés dans le mode de réalisation proposé, le joint annulaire présente dans sa partie de plus faible section axiale une hauteur axiale voisine de la hauteur minimale assurant la résistance à la pression de la chambre de combustion régnant à l'intérieur du joint, de manière à lui assurer une bonne élasticité au placage sur le boisseau et à améliorer la tenue du film d'huile.In order to overcome these difficulties in the proposed embodiment, the annular seal has in its portion of smaller axial section an axial height close to the minimum height ensuring the pressure resistance of the combustion chamber prevailing inside the seal , so as to give it good elasticity to plating on the plug and to improve the behavior of the oil film.

L'organe d'étanchéité selon l'invention pour un boisseau rotatif sensiblement cylindrique traversé par au moins un canal et sur lequel vient s'appliquer un joint d'étanchéité annulaire d'axe transversal à l'axe de rotation du boisseau, en particulier pour assurer l'étanchéité d'une lumière d'échappement d'une chambre de combustion d'un moteur à combustion interne et dans lequel le joint annulaire est guidé axialement de façon étanche par sa surface extérieure mobile dans un alésage et plaqué sur le boisseau par la pression régnant dans la chambre de combustion, est remarquable en ce que la zone de contact entre le boisseau et le joint est lubrifiée par un film d'huile maintenu en dépit de la pression des gaz (de la chambre de combustion) traversant le boisseau.The sealing member according to the invention for a substantially cylindrical rotary plug crossed by at least one channel and to which an annular seal is applied, with an axis transverse to the axis of rotation of the plug, in particular for sealing an exhaust port of a combustion chamber of an internal combustion engine and in which the annular seal is guided axially in a leaktight manner by its movable outer surface in a bore and pressed against the plug by the pressure prevailing in the combustion chamber, is remarkable in that the contact zone between the plug and the seal is lubricated by an oil film maintained despite the pressure of the gases (from the combustion chamber) passing through the bushel.

Le joint annulaire présente dans le sens axial une épaisseur de paroi variable dont l'inertie à la section. minimale est déterminée pour permettre la déformation du joint et son placage sur le boisseau pour de faibles surpressions de l'ordre de 0,1 à 1 bar tout en assurant la résistance du joint à l'éclatement sous l'effet de la pression de la chambre de combustion et le maintien du film d'huile entre le joint et la surface du boisseau.The annular seal has a variable wall thickness in the axial direction, the inertia of which in section. minimum is determined to allow the deformation of the seal and its plating on the plug for low overpressures of the order of 0.1 to 1 bar while ensuring the resistance of the seal to bursting under the effect of the pressure of the combustion chamber and maintaining the oil film between the seal and the surface of the plug.

Le diamètre extérieur du joint peut être compris entre 4/7 et 6/7 du diamètre extérieur du boisseau pour réaliser un bon compromis entre la section de passage central du joint, la surface de contact avec le boisseau apte à améliorer la tenue du film d'huile et la courbure des zones de contact avec le boisseau aux bords du joint selon un plan transversal à l'axe de rotation du boisseau, cette courbure étant propre à diminuer la tenue du film d'huile.The outside diameter of the seal can be between 4/7 and 6/7 of the outside diameter of the plug to achieve a good compromise between the central passage section of the seal, the contact surface with the plug capable of improving the resistance of the film of oil and the curvature of the contact zones with the plug at the edges of the joint along a plane transverse to the axis of rotation of the plug, this curvature being able to reduce the resistance of the oil film.

D'autres buts, avantages et caractéristiques de l'invention apparaîtront à la lecture de la description d'un moteur de réalisation de l'élément d'étanchéité, faite à titre non limitatif et en regard du dessin annexé où :

  • la figure 1 représente schématiquement une vue en coupe transversale d'un moteur à deux temps monocylindrique, équipé du dispositif de contrôle d'échappement selon l'invention, et dans lequel le piston est représenté en position de début de compression de l'air carburé aspiré dans le carter de vilebrequin ;
  • la figure 2 représente une vue en coupe transversale d'un distributeur rotatif équipé de l'élément ou organe d'étanchéité selon l'invention ;
  • la figure 3 représente une vue en coupe transversale de l'élément d'étanchéité montrant sa section minimale ;
  • la figure 4 représente, de façon exagérée dans un but d'illustration et à grande échelle, une vue en coupe transversale de l'élément d'étanchéité lorsqu'il est déformé par un échauffement de friction et/ou une usure du contact avec la surface du boisseau ;
  • la figure 5 représente, également à grande échelle, une vue en coupe transversale de l'élément d'étanchéité lorsqu'il est déformé exagérément par des gaz d'échappement.
Other objects, advantages and characteristics of the invention will appear on reading the description of an engine for producing the sealing element, given without limitation and with reference to the appended drawing in which:
  • FIG. 1 schematically represents a cross-sectional view of a single-cylinder two-stroke engine, equipped with the exhaust control device according to the invention, and in which the piston is shown in the position of start of compression of the fuel air sucked into the crankcase;
  • 2 shows a cross-sectional view of a rotary distributor equipped with the sealing element or member according to the invention;
  • Figure 3 shows a cross-sectional view of the sealing element showing its minimum section;
  • 4 shows, exaggeratedly for illustrative purposes and on a large scale, a cross-sectional view of the sealing element when it is deformed by friction heating and / or wear of contact with the bushel area;
  • Figure 5 shows, also on a large scale, a cross-sectional view of the sealing element when it is excessively deformed by exhaust gases.

Le moteur représenté schématiquement sur la figure 1 comporte des éléments bien connus dans les moteurs fonctionnant selon le cycle à deux temps. Un carter moteur 1 contient un cylindre moteur 2 et est relié à une culasse 3, refroidie par une circulation de liquide comme le cylindre 2, pour fermer une chambre de combustion 4 dans laquelle débouche une bougie d'allumage 5 ou, dans le cas des moteurs diésel, un injecteur de carburant. La culasse 3 est représentée d'une pièce avec le carter moteur 1, alors que dans la réalité, elle est généralement fixée par des goujons au carter moteur 1, tout en permettant la circulation du liquide de refroidissement dans un circuit de refroidissement 6 commun au carter 1 et à la culasse 3.The engine shown schematically in Figure 1 includes elements well known in engines operating according to the two-stroke cycle. A crankcase 1 contains an engine cylinder 2 and is connected to a cylinder head 3, cooled by a circulation of liquid like the cylinder 2, to close a combustion chamber 4 into which opens a spark plug 5 or, in the case of diesel engines, a fuel injector. The cylinder head 3 is shown in one piece with the engine crankcase 1, while in reality it is generally fixed by studs to the engine crankcase 1, while allowing the circulation of the coolant in a cooling circuit 6 common to the housing 1 and to the cylinder head 3.

A la partie inférieure du carter 1, est aménagée une chambre de transfert 7 qui contient le vilebrequin 8 du moteur relié à une bielle 9 et au piston 10 mobile dans le cylindre 2. Cette chambre de transfert 7, de volume minimal compatible avec le débattement du vilebrequin 8 et de la bielle 9, est reliés, d'une part, à une lumière d'entrée 11 reliée à une admission d'air filtré, directe dans le cas d'un moteur diésel et via un carburateur 12 dans le cas d'un moteur à allumage commandé par bougie comme représenté sur la figure et, d'autre part, à des lumières de transfert 13 qui sont plus spécialement visibles sur la figure 3 en position de point mort bas du piston 10. Les segments d'étanchéité 14 du piston 10 découvrent les lumières 13 en position basse du piston 10 pour autoriser l'admission des gaz carburés, comprimés dans la chambre de transfert 7, vers la chambre de combustion 4. Un segment racleur et distributeur placé sur le piston du côté opposé à la tête de piston fermant la chambre de combustion 4, autorise, à partir d'une position relativement haute du piston (sensiblement à partir des 2/3 de la course du piston vers le point mort haut) les gaz aspirés à s'écouler via la lumière d'entrée 11 dans la chambre de transfert 7 mise en dépression par la montée du piston 10.At the lower part of the casing 1, there is a transfer chamber 7 which contains the crankshaft 8 of the engine connected to a connecting rod 9 and to the piston 10 movable in the cylinder 2. This transfer chamber 7, of minimum volume compatible with the travel of the crankshaft 8 and of the connecting rod 9, are connected, on the one hand, to an inlet light 11 connected to a filtered air intake, direct in the case of a diesel engine and via a carburetor 12 in the case of a spark-ignition engine as shown in the figure and, on the other hand, transfer lights 13 which are more particularly visible in Figure 3 in the bottom dead center position of the piston 10. The segments d seal 14 of the piston 10 reveal the openings 13 in the low position of the piston 10 to allow the admission of the carburetted gases, compressed in the transfer chamber 7, towards the combustion chamber 4. A scraper and distributor segment placed on the piston of the side opposite to the piston head closing the combustion chamber 4, allows, from a relatively high position of the piston (substantially from 2/3 of the stroke of the piston towards top dead center) the gases sucked in s '' via the entry light 11 in the transfer chamber t 7 depression by the rise of the piston 10.

Le circuit d'échappement du moteur est contrôlé dans la culasse 3 par un boisseau rotatif 16 tournant dans une chambre constituée par un alésage 17 avec les parois duquel il n'est pas en contact bien que sa surface cylindrique extérieure soit au voisinage immédiat de la paroi de l'alésage. Ce boisseau 16 est entraîné en rotation par tous moyens, tels qu'un train d'engrenage ou une chaîne ou une courroie crantée, à une vitesse angulaire moitié de celle du vilebrequin 8 du moteur et tourne autour d'un axe 18 perpendiculaire à l'axe du cylindre 2. Le boisseau 16 comporte un canal transversal 19 qui, au cours de la rotation du boisseau, vient alternativement s'ouvrir, d'un côté, sur un orifice 20 relié à la chambre de combustion 4 et, de l'autre côté, sur un orifice 21 relié à l'échappement des gaz brûlés vers l'extérieur par tout moyen adéquat tel qu'un pot d'échappement. L'étanchéité du boisseau 16 en direction de la chambre de combustion où règnent des pressions très élevées après l'allumage du mélange carburé (50 à 60 bars pour un moteur deux temps à carburateur mais jusqu'à 160 bars pour certains moteurs diésel suralimentés) est assurée par un anneau d'étanchéité métallique 22 mobile dans un alésage 23 ouvert sur la chambre de combustion 4. L'étanchéité de l'anneau 22 dans l'alésage 23 est assurée par au moins un segment 24 et la course de l'anneau 22 vers la chambre de combustion 4 est limitée par un épaulement de retenue 25. En fait, l'anneau d'étanchéité qui présente une surface d'étanchéité frontale 26 conjuguée de celle de la surface cylindrique du boisseau 16, est plaqué sur le boisseau 16 par la pression régnant dans la chambre de combustion 4 et agissant sur sa section annulaire à l'encontre de la pression régnant dans l'alésage 17 et seulement légèrement supérieure à la pression atmosphérique.The engine exhaust circuit is controlled in the cylinder head 3 by a rotary valve 16 rotating in a chamber formed by a bore 17 with the walls of which it is not in contact although its external cylindrical surface is in the immediate vicinity of the bore wall. This plug 16 is rotated by any means, such as a gear train or a chain or a toothed belt, at an angular speed half that of the crankshaft 8 of the engine and rotates around an axis 18 perpendicular to the cylinder axis 2. The plug 16 has a transverse channel 19 which, during the rotation of the plug, alternately opens, on one side, on an orifice 20 connected to the combustion chamber 4 and, from the 'other side, on an orifice 21 connected to the exhaust of the burnt gases to the outside by any suitable means such as an exhaust. The tightness of the plug 16 in the direction of the combustion chamber where very high pressures prevail after the ignition of the fuel mixture (50 to 60 bars for a two-stroke engine with carburetor but up to 160 bars for certain supercharged diesel engines) is ensured by a metal sealing ring 22 movable in a bore 23 open on the combustion chamber 4. The sealing of the ring 22 in the bore 23 is ensured by at least one segment 24 and the stroke of the ring 22 towards the combustion chamber 4 is limited by a retaining shoulder 25. In fact, the sealing ring which has a front sealing surface 26 combined with that of the cylindrical surface of the plug 16, is pressed against the plug 16 by the pressure prevailing in the combustion chamber 4 and acting on its annular section against the pressure prevailing in the bore 17 and only slightly higher than atmospheric pressure.

L'axe des orifices 20 et 21 est placé sur la figure sensiblement dans l'axe du cylindre 2 mais il peut aussi être incliné. pour ménager une disposition plus avantageuse de la bougie d'allumage 5 et permettre d'utiliser une chambre de combustion 4 en coin assurant une plus grande turbulence des gaz comprimés et une meilleure propagation de la flamme d'allumage.The axis of the orifices 20 and 21 is placed in the figure substantially in the axis of the cylinder 2 but it can also be inclined. to provide a more advantageous arrangement of the spark plug 5 and allow the use of a combustion chamber 4 at the corner ensuring greater turbulence of the compressed gases and better propagation of the ignition flame.

L'alésage 23 de guidage de l'anneau d'étanchéité présente généralement une section supérieure à celle de l'orifice d'échappement 21 pour assurer une section minimale à l'orifice 20 relié à la chambre de combustion 4 et pour assurer un graissage suffisant au contact de l'anneau 22 et du boisseau 16. Le graissage du contact entre l'anneau 22 et le boisseau rotatif 16 ne peut être maintenu qu'en refroidissant énergiquement le boisseau 16 par une circulation de liquide de refroidissement traversant des évidements 27 du boisseau et reliés à la culasse 3 par des joints appropriés et adaptés à la position des paliers de guidage du boisseau 16 dans la culasse 3.The bore 23 for guiding the sealing ring generally has a cross section greater than that of the exhaust orifice 21 to ensure a minimum cross section of the orifice 20 connected to the combustion chamber 4 and to provide lubrication sufficient in contact with the ring 22 and the plug 16. The lubrication of the contact between the ring 22 and the rotary plug 16 can only be maintained by vigorously cooling the plug 16 by a circulation of coolant passing through recesses 27 of the plug and connected to the cylinder head 3 by suitable seals adapted to the position of the guide bearings of the valve 16 in the cylinder head 3.

Le fonctionnement du dispositif de contrôle de l'évacuation des gaz d'échappement va maintenant être explicité en regard de la figure 1. Si l'on se reporte à la figure 1 et au sens de rotation du vilebrequin 8 représenté par la flèche parallèle au contrepoids de ce vilebrequin, on voit que le piston 10 au cours de sa descente va obturer par son segment racleur la lumière d'entrée 11 pour comprimer les gaz carburés frais dans la chambre de transfert 7. Poursuivant sa course vers le bas, le piston 10 découvre par le segment de coup de feu, les lumières de transfert 13 qui permettent aux gaz frais légèrement comprimés dans la chambre de transfert 7 de se décharger dans la chambre de combustion 4.The operation of the device for controlling the exhaust gas discharge will now be explained with reference to FIG. 1. If we refer to FIG. 1 and to the direction of rotation of the crankshaft 8 represented by the arrow parallel to the counterweight of this crankshaft, we see that the piston 10 during its descent will close by its scraper segment the inlet light 11 to compress the fresh carburetted gases in the transfer chamber 7. Continuing its downward movement, the piston 10 discovers by the gunshot segment, the transfer lights 13 which allow the fresh gases slightly compressed in the transfer chamber 7 to be discharged in the combustion chamber 4.

Juste avant que les lumières 13 ne soient découvertes, le boisseau 16 qui a tourné également vient mettre en communication son canal transversal 19, déjà relié à l'orifice d'échappement 21, avec l'orifice 20 qui débouche sur la chambre de combustion 4.Just before the lights 13 are discovered, the plug 16 which has also rotated comes to communicate its transverse channel 19, already connected to the exhaust orifice 21, with the orifice 20 which opens onto the combustion chamber 4 .

A l'instant où les lumières 13 sont ouvertes de façon significative, sous l'effet de la pression relativement élevée régnant dans la chambre de combustion 4 (de l'ordre de 10 bars pour un moteur deux temps à pleine admission) à l'ouverture de l'orifice 20 sur le canal 19, une partie importante des gaz brûlés est déjà déchargée à l'échappement. La surpression régnant encore dans la chambre de combustion 4 refoule éventuellement par les lumières 13 une partie des gaz frais dans le canal de transfert existant entre la chambre de transfert principale 7 contenant le vilebrequin 8 et les lumières 13. Le mouvement du piston 10 se poursuivant jusqu'au point mort bas représenté, la pression dans la chambre de transfert continue à augmenter tandis que la pression dans le cylindre 2 et la chambre de combustion 4 diminue très rapidement à travers la large section de passage du canal transversal 19 qui vient se placer au point mort bas du piston 10, exactement dans l'axe du cylindre 2 et de l'orifice 20. La section transversale du canal 19 est sensiblement égale à la section de l'orifice 20 ménagée dans l'anneau d'étanchéité 22 au contact de la surface cylindrique extérieure du boisseau 16 et les arêtes d'entrée et de sortie du canal 19 correspondent ainsi sensiblement au point mort bas du piston 10 avec les arêtes correspondantes de l'orifice 20 ouvert sur la chambre de combustion.At the moment when the lights 13 are open significantly, under the effect of the relatively high pressure prevailing in the combustion chamber 4 (of the order of 10 bars for a two-stroke engine at full intake) at the opening of the orifice 20 on the channel 19, a large part of the burnt gases is already discharged to the exhaust. The overpressure still prevailing in the combustion chamber 4 eventually discharges through the ports 13 a portion of the fresh gases into the transfer channel existing between the main transfer chamber 7 containing the crankshaft 8 and the ports 13. The movement of the piston 10 continues up to the bottom dead center shown, the pressure in the transfer chamber continues to increase while the pressure in the cylinder 2 and the combustion chamber 4 decreases very quickly through the wide passage section of the transverse channel 19 which is placed at the bottom dead center of the piston 10, exactly in the axis of the cylinder 2 and the orifice 20. The cross section of the channel 19 is substantially equal to the section of the orifice 20 formed in the sealing ring 22 at contact of the external cylindrical surface of the plug 16 and the inlet and outlet edges of the channel 19 correspond thus substantially at bottom dead center of the piston 10 with the corresponding edges of the orifice 20 open on the combustion chamber.

Après le passage au point mort bas, le piston 10 remonte en position de compression et les segments 14 obturent les lumières de transfert 13, tandis que la rotation du boisseau 16 a obturé les orifices 20 et 21 isolant la chambre de combustion de l'échappement.After shifting to bottom dead center, the piston 10 rises to the compression position and the segments 14 block the transfer ports 13, while the rotation of the plug 16 has closed the orifices 20 and 21 isolating the combustion chamber from the exhaust. .

Les orifices d'échappement 20, 19, 21 sont disposés dans le cylindre 2 à l'opposé des lumières d'admission 13 et les gaz frais déversés à travers les lumières 13 en légère surpression peuvent repousser les gaz brûlés devant eux en direction de l'échappement. Cet effet de refoulement « sans mélange des gaz d'échappement est d'ailleurs renforcé par l'effet de dépression sur les gaz d'échappement que provoquent certains circuits d'échappement à fréquence propre accordée sur la fréquence de rotation du moteur.The exhaust ports 20, 19, 21 are arranged in the cylinder 2 opposite the intake ports 13 and the fresh gases discharged through the ports 13 at slight overpressure can push the burnt gases in front of them towards the 'exhaust. This discharge effect "without mixing of the exhaust gases is further reinforced by the vacuum effect on the exhaust gases which certain exhaust circuits cause with their own frequency tuned to the frequency of rotation of the engine.

Le segment racleur découvre ensuite la lumière d'entrée 11 qui relie le carburateur 12 à la chambre de transfert 7, en légère dépression sous l'effet de la montée du piston 10 vers le point mort haut. Pendant que la montée du piston 10 se poursuit vers le point mort haut, la dépression dans la chambre de transfert 7 se maintient malgré l'apport de gaz frais et l'inertie de la colonne de gaz entre le carburateur 12 et la chambre de transfert 7 permet la poursuite du remplissage de la chambre 7 par un effet d'hystérésis mécanique jusqu'à l'instant où, après le point mort haut du piston 10 et l'allumage du mélange carburé comprimé dans la chambre de combustion 4, le piston 10 redescend et vient à nouveau obturer par le segment racleur l'orifice d'entrée 11, selon la position représentée à la figure 1. Pendant le déplacement du piston 10, la liaison mécanique entre le vilebrequin 8 et le boisseau 16 continue à entraîner celui-ci en rotation pour lui faire exécuter un demi-tour pendant un cycle de rotation du moteur et l'autre débouché du canal 19 remplit à son tour les fonctions d'ouvertures et d'obturation en coopération avec l'anneau d'étanchéité 22.The scraper segment then discovers the inlet lumen 11 which connects the carburetor 12 to the transfer chamber 7, in slight depression under the effect of the rise of the piston 10 towards the top dead center. While the piston 10 continues to climb towards top dead center, the vacuum in the transfer chamber 7 is maintained despite the supply of fresh gas and the inertia of the gas column between the carburetor 12 and the transfer chamber 7 allows the continued filling of the chamber 7 by a mechanical hysteresis effect until the moment when, after the top dead center of the piston 10 and the ignition of the compressed fuel mixture in the combustion chamber 4, the piston 10 descends again and closes again by the scraper segment the inlet 11, according to the position shown in Figure 1. During the displacement of the piston 10, the mechanical connection between the crankshaft 8 and the plug 16 continues to cause that -this in rotation to make it perform a half-turn during a motor rotation cycle and the other outlet of the channel 19 in turn fulfills the functions of openings and shutters in cooperation with the sealing ring 22 .

La section longitudinale du canal 19, le cas échéant couplée avec l'alésage interne de l'anneau 22, et la section de l'échappement 21, peuvent présenter la forme générale ,d'un venturi en convergent-divergent dont le col est situé sensiblement au centre de ce canal 19, mais peut se trouver au voisinage des bords de sortie de ce canal si la section du circuit d'échappement le permet. Pour des pressions de gaz d'échappement suffisantes, l'écoulement dans la partie divergente peut atteindre des vitesses supersoniques et le bruit d'échappement, les transferts thermiques et les pertes de charge sont notablement réduits quelle que soit la pression d'échappement.The longitudinal section of the channel 19, if necessary coupled with the internal bore of the ring 22, and the section of the exhaust 21, may have the general shape of a convergent-divergent venturi whose neck is located substantially in the center of this channel 19, but may be in the vicinity of the outlet edges of this channel if the section of the exhaust circuit allows it. For sufficient exhaust gas pressures, the flow in the diverging part can reach supersonic speeds and the exhaust noise, heat transfers and pressure drops are significantly reduced whatever the exhaust pressure.

Le système de contrôle de l'échappement qui vient d'être décrit en combinaison avec un moteur à combustion interne fonctionnant selon le cycle à deux temps pourrait s'appliquer à un moteur à 2 ou 4 temps pour remplacer les soupapes d'échappement et/ou d'admission d'air dans les cylindres et on pourrait également utiliser d'autres réglages de la position du canal transversal 19 par rapport aux diverses positions du piston 10. Ce canal 19 pourrait également être constitué de deux ouvertures de section relativement réduite débouchant sur une partie centrale de section plus importante pour réaliser une chambre de prédétente des gaz d'échappement dans le boisseau 16. Les orifices 20 et 21 ainsi que la section du canal 19 peuvent présenter une forme circulaire mais plus avantageusement la forme d'un rectangle ou d'un carré (à angles tronqués, par exemple).The exhaust control system which has just been described in combination with an internal combustion engine operating according to the two-stroke cycle could be applied to a 2- or 4-stroke engine to replace the exhaust valves and / or air intake in the cylinders and one could also use other adjustments of the position of the transverse channel 19 relative to the various positions of the piston 10. This channel 19 could also consist of two openings of relatively small section opening out on a central section of larger section to produce an exhaust gas pre-expansion chamber in the plug 16. The orifices 20 and 21 as well as the section of the channel 19 may have a circular shape but more advantageously the shape of a rectangle or a square (for example, with truncated angles).

L'orifice 20 peut déboucher en un point quelconque de la paroi de la chambre de combustion 4 et peut constituer également l'admission des gaz frais dans la chambre de combustion 4. De même, on doit comprendre que les lumières d'admission peuvent être alimentées par tous moyens autres que la surpression dans la chambre de transfert 7 qui peut, elle, être gravée en air comprimé par le compresseur d'un turbocompresseur ou une pompe à palettes. L'anneau d'étanchéité 22 est appliqué sur le boisseau 16 par la seule pression régnant dans la chambre de combustion 4 qui, pour des moteurs à forte compression tels que des moteurs diésel, peut, au point mort haut du piston 10, se réduire à l'espace intérieur de l'anneau 22, l'injection du carburant s'effectuant à l'aide d'un injecteur délivrant une nappe de combustible pulvérisé sensiblement parallèle à la surface supérieure du piston 10 ou à la section d'entrée de l'anneau 22 du côté de la chambre de combustion 4.The orifice 20 can open at any point on the wall of the combustion chamber 4 and can also constitute the admission of fresh gases into the combustion chamber 4. Likewise, it should be understood that the intake ports can be supplied by any means other than the overpressure in the transfer chamber 7 which can itself be etched with compressed air by the compressor of a turbocharger or a vane pump. The sealing ring 22 is applied to the plug 16 by the only pressure prevailing in the combustion chamber 4 which, for high compression engines such as diesel engines, can, at the top dead center of the piston 10, reduce to the interior space of the ring 22, the injection of the fuel being effected by means of an injector delivering a sheet of atomized fuel substantially parallel to the upper surface of the piston 10 or to the inlet section of the ring 22 on the side of the combustion chamber 4.

En variante, le canal 19 pourrait aussi, dans certaines versions, être remplacé par une entaille latérale ménagée sur le côté du boisseau 16 et mettant en communication un échappement latéral 21 avec la chambre de combustion 4 et alternativement, le cas échéant, avec l'admission de gaz frais.As a variant, the channel 19 could also, in certain versions, be replaced by a lateral notch formed on the side of the plug 16 and putting in communication a lateral exhaust 21 with the combustion chamber 4 and alternatively, if necessary, with the fresh gas intake.

Si l'on se reporte aux figures 2 à 5, on voit que le distributeur rotatif 101 en forme de boisseau (figure 2) est supporté par des roulements ou paliers lisses et tourne à l'intérieur de l'alésage 102 d'un logement ou stator 101a avec un jeu de fonctionnement empêchant tout contact avec les parois de l'alésage malgré les dilatations différentielles que le passage des gaz chauds peut engendrer. Le sens de rotation du rotor est indiqué par une flèche au voisinage de la périphérie du distributeur 101.If we refer to Figures 2 to 5, we see that the rotary distributor 101 in the form of a plug (Figure 2) is supported by bearings or plain bearings and rotates inside the bore 102 of a housing or stator 101a with an operating clearance preventing any contact with the walls of the bore despite the differential expansions that the passage of hot gases can cause. The direction of rotation of the rotor is indicated by an arrow in the vicinity of the periphery of the distributor 101.

L'élément d'étanchéité 103 est destiné à assurer l'étanchéité d'une chambre de combustion 104 d'un moteur à combustion interne. Cet élément est monté libre et coulissant avec un jeu fonctionnel important dans un alésage 105 perpendiculaire à l'alésage 102 du logement ou stator et qui présente une faible conicité dont la pointe est dirigée vers la chambre de combustion 104. L'étanchéité périphérique de l'élément 103 constituant une bague annulaire est assurée par un ou plusieurs segments 106. Le passage des gaz d'échappement de la chambre de combustion 104 vers l'échappement s'effectue via un passage transversal 107 ménagé dans le distributeur et l'orifice central 107a de la bague annulaire 103. Au cours du fonctionnement du moteur thermique, le distributeur rotatif 101 et son élément d'étanchéité 103 sont soumis à diverses contraintes mécaniques et thermiques provoquées par :

  • - la différence de température moyenne entre le distributeur 101 et l'élément d'étanchéité 103 qui reçoit le « coup de feu des gaz d'échappement et évacue une grande partie de la chaleur reçue par sa surface en contact avec le distributeur 101 ;
  • - le fait que les matériaux dans lesquels sont réalisés le distributeur 101 et l'élément d'étanchéité 103 sont différents. Pour conserver de bonnes qualités frottantes et thermiques, l'élément d'étanchéité est généralement réalisé en fonte possédant un coefficient de dilatation sensiblement moitié de celui de l'alliage d'aluminium dans lequel est réalisé le distributeur 101 et son logement 101a ;
  • - les déformations géométriques du distributeur dues à sa forme, aux dilatations, aux contraintes mécaniques engendrées par sa rotation et à la force centrifuge.
The sealing element 103 is intended to seal a combustion chamber 104 of an internal combustion engine. This element is mounted free and sliding with a large functional clearance in a bore 105 perpendicular to the bore 102 of the housing or stator and which has a low taper whose tip is directed towards the combustion chamber 104. The peripheral sealing of the element 103 constituting an annular ring is provided by one or more segments 106. The passage of the exhaust gases from the combustion chamber 104 to the exhaust takes place via a passage transverse 107 formed in the distributor and the central orifice 107a of the annular ring 103. During the operation of the heat engine, the rotary distributor 101 and its sealing element 103 are subjected to various mechanical and thermal stresses caused by:
  • - The average temperature difference between the distributor 101 and the sealing element 103 which receives the “shot of the exhaust gases and dissipates a large part of the heat received by its surface in contact with the distributor 101;
  • - The fact that the materials in which the distributor 101 and the sealing element 103 are made are different. To maintain good rubbing and thermal qualities, the sealing element is generally made of cast iron having a coefficient of expansion substantially half that of the aluminum alloy in which the distributor 101 and its housing 101a are produced;
  • - the geometric deformations of the dispenser due to its shape, expansions, mechanical stresses caused by its rotation and to the centrifugal force.

Les paramètres ci-dessus ont pour résultat que le rayon de courbure OA du distributeur et le rayon de courbure OB de la surface frottante de l'élément d'étanchéité 103, qui devraient être continuellement confondus, se déforment, principalement sous l'effet du choc thermique des bouffées alternées de gaz d'échappement du moteur.The above parameters result in the radius of curvature OA of the distributor and the radius of curvature OB of the friction surface of the sealing element 103, which should be continually merged, being deformed, mainly under the effect of the thermal shock from alternating puffs of engine exhaust.

L'élément d'étanchéité proposé est réalisé de telle sorte que son inertie à sa section minimale, suivant le plan de coupe 108 (voir la figure 3), lui permette une grande souplesse afin que, dès l'application d'une pression de gaz même faible (début de compression moteur) dans la chambre de combustion 104, le rayon de courbure OB de l'élément puisse se conformer sur le rayon de courbure OA du distributeur par la flexion de l'élément 103 même pour des différences sensibles entre ces deux rayons OA et OB et assurer le contact permanent permettant l'étanchéité.The proposed sealing element is produced in such a way that its inertia at its minimum section, along the cutting plane 108 (see FIG. 3), allows it great flexibility so that, as soon as a pressure is applied. gas even weak (start of engine compression) in the combustion chamber 104, the radius of curvature OB of the element can conform to the radius of curvature OA of the distributor by the bending of element 103 even for appreciable differences between these two rays OA and OB and ensure permanent contact allowing sealing.

La figure 4 représente la déformation du joint annulaire 103, principalement sous l'effet de l'échauffement au contact de friction avec le distributeur 101. Le rayon de courbure OA du distributeur est plus grand que le rayon de courbure OB de l'élément d'étanchéité. Sous l'effet de l'application de la pression, l'élément 103 se déforme vers l'extérieur pour que OA égale OB. Sur la figure 5, le rayon de courbure du distributeur OA est plus petit que le rayon de courbure OB de l'élément 103 non soumis à la pression. Sous l'effet de la pression de la chambre de combustion 104, l'élément d'étanchéité 103 se déforme vers l'intérieur pour que OA soit égale à OB.FIG. 4 represents the deformation of the annular seal 103, mainly under the effect of the heating in friction contact with the distributor 101. The radius of curvature OA of the distributor is greater than the radius of curvature OB of the element d sealing. Under the effect of the application of pressure, the element 103 deforms outwards so that OA equals OB. In FIG. 5, the radius of curvature of the distributor OA is smaller than the radius of curvature OB of the element 103 which is not subjected to pressure. Under the effect of the pressure of the combustion chamber 104, the sealing element 103 deforms inwards so that OA is equal to OB.

On doit noter que l'application de la pression à l'intérieur de l'orifice de passage 107a de l'élément d'étanchéité 103 tend à provoquer l'éclatement dudit élément en créant une contrainte maximale dans sa section minimale, suivant le plan de coupe 108 (figure 3) qui doit être suffisante pour que la contrainte en ce point de résistance minimale soit compatible avec les caractéristiques mécaniques et de résistance du matériau utilisé pour l'élément d'étanchéité annulaire 103.It should be noted that the application of pressure inside the passage opening 107a of the sealing element 103 tends to cause the bursting of said element by creating a maximum stress in its minimum section, along the plane. of cutting 108 (FIG. 3) which must be sufficient for the stress at this point of minimum resistance to be compatible with the mechanical and resistance characteristics of the material used for the annular sealing element 103.

Il apparaît dès lors évident que les meilleurs résultats seront obtenus avec des matériaux ayant de faibles modules d'élasticité et de bonnes caractéristiques en traction et en flexion et tels que l'acier ou la fonte pour segments.It therefore appears obvious that the best results will be obtained with materials having low moduli of elasticity and good characteristics in tension and in bending and such as steel or cast iron for segments.

Pour favoriser les démarrages à froid, on choisira de préférence à l'usinage de l'élément d'étanchéité, un rayon de courbure initial OB, qui soit plus petit que le rayon de courbure initial OA à l'usinage du distributeur 101.To favor cold starts, an initial radius of curvature OB, which is smaller than the initial radius of curvature OA when machining the distributor 101, will preferably be chosen when machining the sealing element.

Le jeu entre l'élément d'étanchéité 103 et son alésage 105 doit être suffisant pour accepter les déformations de conformabilité sans coincement néfaste au bon fonctionnement et être choisi en fonction de l'étude approfondie de tous les cas de figure pouvant être rencontrés en fonctionnement.The clearance between the sealing element 103 and its bore 105 must be sufficient to accept the deformations of conformability without jamming detrimental to the proper functioning and be chosen as a function of the in-depth study of all the scenarios that may be encountered in operation. .

Selon l'invention, diverses mesures sont appliquées au joint annulaire 103 afin de maintenir un film d'huile continu sous la surface de contact entre la surface cylindrique extérieur 115 du distributeur 101 et la surface conjuguée 116 ménagée sur le joint annulaire (figures 3 à 5).According to the invention, various measures are applied to the annular seal 103 in order to maintain a continuous oil film under the contact surface between the external cylindrical surface 115 of the distributor 101 and the mating surface 116 formed on the annular seal (FIGS. 3 to 5).

Parmi ces mesures, on peut prévoir sur l'arête d'extrémité 117 du joint (voir la figure 4) située du côté de l'entrée en contact du débouché du canal 107 (repère 114 sur la figure 2) avec le joint annulaire, un chanfrein d'entrée 118 qui vient former un coin d'huile à l'entrée des surfaces d'étanchéité en contact. Une source de pression d'huile, ou simplement pour les moteurs à deux temps la condensation de l'huile transportée par les gaz d'échappement, vient alimenter une zone reliée en permanence à un conduit d'échappement vers l'extérieur 119. L'huile déchargée dans cette zone délimitée par le ou les segments d'étanchéité 106 du joint 103 dans l'alésage 105, est entraînée dans l'espace annulaire 113 compris entre la surface de l'alésage 102 et la surface extérieure 115 du distributeur 101 et vient s'accumuler dans le coin d'huile formé par le chanfrein 118.Among these measures, provision can be made on the end edge 117 of the seal (see FIG. 4) located on the side of the entry into contact of the outlet of the channel 107 (reference 114 in FIG. 2) with the annular seal, an inlet chamfer 118 which forms an oil wedge at the inlet of the sealing surfaces in contact. A source of oil pressure, or simply for two-stroke engines, the condensation of the oil transported by the exhaust gases, supplies a zone permanently connected to an exhaust duct to the outside 119. L the oil discharged into this zone delimited by the sealing segment or segments 106 of the seal 103 in the bore 105, is entrained in the annular space 113 comprised between the surface of the bore 102 and the external surface 115 of the distributor 101 and accumulates in the corner of oil formed by the chamfer 118.

Pour maintenir le film d'huile interposé entre le distributeur 101 et le joint annulaire métallique 103, lorsque la température des gaz d'échappement déforme les pièces en contact, il est nécessaire de prévoir une grande élasticité entre ces pièces pour que la pression régnant dans la chambre de combustion 104 plaque bien le joint 103 sur le distributeur.To keep the oil film interposed between the distributor 101 and the metallic annular seal 103, when the temperature of the exhaust gases deforms the parts in contact, it is necessary to provide a high elasticity between these parts so that the pressure prevailing in the combustion chamber 104 properly seals the seal 103 on the distributor.

Dans ce but, la section minimale 108 du joint 103 est réduite à la plus faible hauteur admissible permettant de résister aux efforts de la pression régnant dans le passage 107a et qui tend à faire éclater radialement le joint 103. De même l'épaisseur e du joint 103 est comprise entre 1/10 et 1/8 du diamètre extérieur du distributeur 101 pour réaliser un bon compromis entre les efforts de pression appliqués sur le joint en direction du boisseau, la section du joint appliquée sur le boisseau par l'intermédiaire du film d'huile et la déformation du joint sous l'effet de la pression des gaz de la chambre de combustion qui le traversent.For this purpose, the minimum section 108 of the seal 103 is reduced to the lowest admissible height making it possible to withstand the stresses of the pressure prevailing in the passage 107a and which tends to cause the seal 103 to burst radially. Similarly, the thickness e of the seal 103 is between 1/10 and 1/8 of the outside diameter of the distributor 101 to achieve a good compromise between the pressure forces applied on the seal towards the plug, the section of the seal applied to the plug via the oil film and the deformation of the seal under the effect of the pressure of the gases from the combustion chamber passing through it.

Le diamètre extérieur de l'élément 103 et de l'alésage 105 qui le guide peut être compris entre 4/7 et 6/7 du diamètre extérieur du boisseau 101 pour réaliser un bon compromis entre la section de passage centrale du joint, la surface de contact avec le boisseau apte à améliorer la tenue du film d'huile et la courbure des zones de contact avec le boisseau aux bords du joint selon un plan transversal à l'axe de rotation du boisseau, cette courbure étant propre à diminuer la tenue du film d'huile.The outside diameter of the element 103 and the bore 105 which guides it can be between 4/7 and 6/7 of the outside diameter of the plug 101 to achieve a good compromise between the central passage section of the seal, the surface contact with the valve capable of improving the resistance of the oil film and the curvature of the contact zones with the valve at the edges of the joint along a plane transverse to the axis of rotation of the valve, this curvature being capable of reducing the resistance oil film.

Le jeu axial entre la base plane 120 du joint 103 et la face d'appui 112 ménagée dans le corps 101a qui contient le distributeur 101 doit être réduit au minimum compatible avec les dilatations de ce corps 101a, du joint 103 et du distributeur 101, c'est-à-dire pour les dimensions courantes des moteurs deux temps, à des dimensions de l'ordre de 5/10 de millimètre.The axial clearance between the flat base 120 of the seal 103 and the bearing face 112 formed in the body 101a which contains the distributor 101 must be reduced to the minimum compatible with the expansions of this body 101a, of the seal 103 and of the distributor 101, that is to say for the current dimensions of two-stroke engines, at dimensions of the order of 5/10 of a millimeter.

Le placage permanent de l'élément d'étanchéité 103 sur le distributeur 101 en forme de boisseau est assuré sans la présence d'un ressort de rappel du simple fait de la légère conicité de l'alésage 105 qui tend à repousser par une sorte d'effet mécano-pneumatique le joint 103 en direction du boisseau 101 à l'encontre de la pesanteur agissant sur l'élément 103 lorsque le dispositif d'étanchéité est placé, selon la figure 6, en tête de la chambre de combustion.The permanent plating of the sealing element 103 on the distributor 101 in the form of a bushel is ensured without the presence of a return spring simply because of the slight conicity of the bore 105 which tends to repel by a sort of mechano-pneumatic effect the seal 103 in the direction of the plug 101 against gravity acting on the element 103 when the sealing device is placed, according to FIG. 6, at the head of the combustion chamber.

De plus, l'élément 103 peut présenter un diamètre extérieur très voisin de celui de l'alésage 105 de façon qu'au cours de son gonflement diamétral sous l'action de la pression de la chambre de combustion 104, il vienne en appui sur la paroi de cet alésage, ce qui permet de limiter les risques d'éclatement.In addition, the element 103 may have an outside diameter very close to that of the bore 105 so that during its diametral swelling under the action of the pressure of the combustion chamber 104, it comes to bear on the wall of this bore, which limits the risk of bursting.

Claims (2)

1. Sealing element for a rotative valve plug (16, 101) of substantially cylindrical shape, which is provided with at least one passage (19, 107) and against which an annular seal (22, 103) having an axis transversally oriented with respect to the axis of rotation of said valve plug (16, 101) is applied, particularly with a view to ensuring the tightness of an exhaust opening of a combustion chamber (4, 104) of an internal combustion motor, and wherein said annular seal (22, 103) is axially guided in a tight manner by its outer surface which is displaceable in a bore (23; 105) and pressed against the valve plug (16, 102) by the pressure prevailing in said combustion chamber (4, 104), the bore (23, 105) guiding said seal (22, 103) having a slightly conical shape tapering toward said combustion chamber (4,104) so as to bias said seal (23, 103) permanently in the direction of said valve plug (16, 101), and the zone of contact between the valve plug (16, 101) and the seal (22,103) being lubricated by an oil film which is maintained in spite of the pressure generated by the gases of-said combustion chamber (4,104) which flow through said valve plug (16, 101), characterized in that in its portion having the smallest axial cross-section said annular seal (103) has an axial height substantially corresponding to the minimum height which ensures resistance to the pressure of the combustion chamber (104) prevailing within said seal, so as to confer thereon satisfactory elasticity when applied against said valve plug (101), and as to improve the resistance of said oil film, and in that the outer diameter of the annular seal (103) is comprised between 4/7 and 6/7 of the outer diameter of said valve plug (101), thereby achieving a satisfactory compromise between the central passage section (107a) of the seal, the surface area of contact with the valve plug (101) which is adapted to improve the resistance of the oil film, and the curvature of the zones of contact with the valve plug at the edges of said seal (103) in a plane oriented transversely with respect to the axis of rotation of the valve plug (101), which curvature might tend to decrease the resistance of the oil film.
2. Element according to claim 1, characterized in that said annular seal (103) has, in the axial direction, a variable wall thickness the inertia modulus of which, in the smallest section (108) is determined so as to allow the deformation of said seal (103) and its application against the valve plug (101) under a slight overpressure of about 0.1 to 1 bar, while ensuring the blow-off resistance of said seal (103) under the action of the pressure of said combustion chamber (104), as well as the maintaining of the oil film between said seal (103) and the surface of said valve plug (101).
EP83401495A 1982-07-27 1983-07-20 Sealing element for a gas-cycle control device for a combustion chamber Expired EP0100713B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83401495T ATE23603T1 (en) 1982-07-27 1983-07-20 SEALING ELEMENT FOR A GAS CYCLE CONTROL DEVICE OF A COMBUSTOR.

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
FR8213071A FR2531139B1 (en) 1982-07-27 1982-07-27 DEVICE FOR CONTROLLING A GAS CIRCUIT OF A COMBUSTION CHAMBER
FR8213071 1982-07-27
FR8213072A FR2531174A1 (en) 1982-07-27 1982-07-27 Sealing element for a rotary ball-cock.
FR8213072 1982-07-27

Publications (2)

Publication Number Publication Date
EP0100713A1 EP0100713A1 (en) 1984-02-15
EP0100713B1 true EP0100713B1 (en) 1986-11-12

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US (1) US4506636A (en)
EP (1) EP0100713B1 (en)
BE (1) BE897345A (en)
DE (1) DE3367651D1 (en)

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Also Published As

Publication number Publication date
EP0100713A1 (en) 1984-02-15
US4506636A (en) 1985-03-26
DE3367651D1 (en) 1987-01-02
BE897345A (en) 1984-01-20

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