EP1934444A1 - Device for varying compression ratio of an internal combustion engine cylinder and internal combustion engine comprising same - Google Patents

Device for varying compression ratio of an internal combustion engine cylinder and internal combustion engine comprising same

Info

Publication number
EP1934444A1
EP1934444A1 EP06808316A EP06808316A EP1934444A1 EP 1934444 A1 EP1934444 A1 EP 1934444A1 EP 06808316 A EP06808316 A EP 06808316A EP 06808316 A EP06808316 A EP 06808316A EP 1934444 A1 EP1934444 A1 EP 1934444A1
Authority
EP
European Patent Office
Prior art keywords
piston
compression ratio
cylinder
movable partition
internal combustion
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.)
Withdrawn
Application number
EP06808316A
Other languages
German (de)
French (fr)
Inventor
Grégory BLOKKEEL
Guillaume Rymer
François DABIREAU
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.)
PSA Automobiles SA
Original Assignee
Peugeot Citroen Automobiles 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
Application filed by Peugeot Citroen Automobiles SA filed Critical Peugeot Citroen Automobiles SA
Publication of EP1934444A1 publication Critical patent/EP1934444A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
    • F02B75/044—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of an adjustable piston length

Definitions

  • the invention relates to a device for varying the compression ratio of a cylinder of an internal combustion engine, and an internal combustion engine comprising such a variation device.
  • the device of the invention applies both to internal combustion engines by spark ignition compression internal combustion engines.
  • Such engines generally comprise one or more cylinders each of which comprises a piston mounted axially sliding inside the cylinder and connected to a crankshaft of the engine by means of a connecting rod.
  • One of the characteristics of these cylinders is the compression ratio which is defined as the ratio between the volume of the combustion chamber at the bottom dead center of the piston and the volume of the combustion chamber at the top dead center of the piston.
  • the compression ratio can be increased or decreased by placing the top dead center of the piston respectively closer or further from the cylinder head .
  • the compression ratio of the configuration on the left is greater than the compression ratio of the right configuration.
  • a variation of 0.5 cm from the position of the piston in top dead center results in a new compression ratio of 16. or 18 depending on the direction of movement of the top dead center.
  • the compression ratio has an influence on the temperature level and the mixture in the combustion chamber, which has a direct effect on the desired self-ignition.
  • the compression ratio is increased, this facilitates self-ignition and when it is reduced, it limits the ability of the mixture to self-ignite.
  • thermodynamic conditions in the combustion chamber tend to disadvantage self-ignition, mainly because of the low temperature; increasing the compression ratio would then make it easier to reach a temperature sufficient for safe autoignition; when the motor is heavily stressed, an increase in the compression ratio increases the efficiency of the engine; this means that, for the same power of the engine, the fuel consumption drops; when the engine is subjected to a moderate amount of pressure, a reduction in the compression ratio makes it possible to reduce the combustion temperature and thus to reduce the level of pollutants emitted, essentially the emission of nitrogen oxides; to better control combustion and to limit the emission of pollutants, including soot and nitrogen oxides, we seek to obtain the most homogeneous mixtures possible; a reduction in the compression ratio would allow an increase in the self-ignition delay and thereby an increase in the time available to effect a homogeneous mixture of fuel and air.
  • the ratchet phenomenon is a phenomenon of uncontrolled and undesired self-ignition of the fuel, leading to a high risk of engine destruction. This phenomenon is favored by high temperatures in the combustion chamber. A reduction in these temperatures could be achieved by reducing the compression ratio. On the other hand, an increase in the compression ratio would make it possible, in the limitations related to the rattling phenomenon, to optimize the efficiency of the engine over certain operating ranges thereof. - When the engine is applied in a moderate way, a reduction in the compression ratio makes it possible to limit pollutant emissions as a result of the reduction of the temperature level in the combustion chamber.
  • the object of the present invention is to provide a mechanically simpler solution and offering, if possible, the possibility of integrating this solution into existing engine designs.
  • the object of the invention is achieved with a device for varying the compression ratio of a cylinder of an internal combustion engine, the cylinder comprising a piston which is mounted axially sliding inside the cylinder and is connected to a crankshaft of the engine by means of a connecting rod.
  • the piston comprises a hollow cylindrical envelope open towards the connecting rod and comprises, inside the hollow envelope, an internal piston mounted axially sliding relative to the hollow envelope, a movable partition disposed between the internal piston and the bottom of the hollow envelope, and a grid integral with the hollow envelope and disposed between the inner piston and the movable partition, the grid dividing a constant volume delimited between the movable partition and the inner piston in two partial volumes filled with a magneto-rheological fluid to be subjected to a variable magnetic field to vary its viscosity in a controlled manner.
  • the device of the invention has the advantage of being mechanically simple, of being able to be easily implanted on existing design engines, to understand a reduced number of moving parts, to present an important flexibility of application due to a non-mechanical control of the device and the possibility of adapting the device of the invention easily to any type of engine and to different applications thereof.
  • the device of the invention may also include at least one of the following features, considered in isolation or in any technically possible combination:
  • the magnetorheological fluid has a range of viscosities between a low viscosity allowing the fluid to pass easily from one partial volume to another and a very high viscosity preventing the fluid from a partial volume to 1 'other; - the movement of the movable partition and the internal piston, movement necessarily common to ensure the constant volume delimited between the movable partition and the internal piston, is limited inside the hollow cylindrical envelope by stops;
  • the stops are made in the form of an annular abutment;
  • the device comprises springs of which one or more springs are disposed between the bottom of the hollow cylindrical envelope and the movable partition and whose other spring or springs are arranged between the inner piston and the stops; the springs are helical springs;
  • the device comprises a winding incorporated in the cylinder liner.
  • the object of the invention is also achieved with an internal combustion engine, with compression ignition or spark ignition, comprising a variation device according to the description above.
  • FIG. 1 schematically represents the influence of a modification of the relative position of the piston with respect to the connecting rod in a cylinder, on the compression ratio of the engine
  • the 2 schematically represents the device of the invention according to a preferred embodiment
  • Figure 3 shows a grid forming part of the device of the invention, respectively in a cross section ( Figure 3a) and a top view ( Figure 3b).
  • FIG. 4 shows the device of the invention when the piston is in a first top dead center
  • FIG. 5 shows the device of the invention in another configuration of the device.
  • FIG. 1 recalls the definition of the compression ratio of a combustion engine cylinder and more particularly shows the influence of the modification of the relative position of a piston by compared to the corresponding rod on the compression ratio.
  • the compression ratio is defined as the ratio between the volume of the combustion chamber when the piston is at low dead point PMB and the volume of the combustion chamber when the piston is at the top dead center TDC.
  • Figure 1 shows the elements of the definition of the compression ratio and the influence of the configuration of the cylinder / piston assembly.
  • a piston 3 In the configuration on the left, a piston 3 is disposed inside a cylinder 2 in a higher position PMH1 than in the right configuration where the position of the piston 3 is referenced PMH2.
  • the piston 3 is connected in both cases to a crankshaft with a rod 6 which has a constant length and which is mounted on the crankshaft using an axis having a fixed position on the crankshaft.
  • the upper face of the piston 3 is at a level PMH1 when the piston is at the top dead center and at one level
  • the piston 3 In the right configuration, the piston 3 is in a position PMH2 lower than that of the left configuration, when the piston 3 is in top dead center.
  • the volume of the combustion chamber is V2, which is larger than the corresponding volume Vl of the left configuration.
  • the volume of the combustion chamber corresponds to the sum of the two partial volumes V2 and V2 ', ie V2''represented by the height H2 of this volume.
  • the compression ratio is Vl '' / Vl while the compression ratio in the right configuration is V2 '' / V2.
  • Vl being smaller than V2
  • the compression ratio of the left configuration is higher than that of the right configuration.
  • FIG. 2 represents the elements of a device for varying the compression ratio of a cylinder of an internal combustion engine according to one embodiment of the invention.
  • the variation device of the invention applies to each of the cylinders 2 of an internal combustion engine 1.
  • the cylinder 2 comprises a piston 3 mounted axially sliding inside the cylinder and connected to a crankshaft of the engine by means of a connecting rod 6.
  • the various elements of the device of the invention are represented in a very simplified manner and reduced to their features. Their representation is therefore in no way a limitation to a particular embodiment of the device of the invention.
  • the piston 3 comprises a hollow cylindrical casing 31 open towards the connecting rod 6 and comprises, inside the hollow casing 31, an internal piston 5 mounted axially sliding relative to the hollow casing 31.
  • the internal piston 5 is shown , in accordance with the principle of simplified representation mentioned above, only by its upper face facing the cylinder head and its anchor point P which it is connected to the connecting rod 6 pivotally.
  • the piston 3 further comprises a movable partition 4 disposed between the inner piston 5 and the bottom of the hollow envelope 31, and a grid 32 integral with the hollow envelope 31 and disposed between the inner pistons 5 and the movable partition. 4.
  • the movable partition 4 and the inner piston 5 delimit between them a constant volume which is divided by the grid 32 into two partial volumes A, B.
  • the volume delimited between the movable partition 4 and the internal piston 5 is filled with a magneto-rheological fluid intended to be subjected to a variable magnetic field generated by a coil 7 to vary the viscosity of the magnetorheological fluid in a controlled manner.
  • Figure 2 shows the device of the invention in a neutral position of the piston 3 from which the nominal compression ratio of the cylinder, and thus the nominal compression ratio of the engine, is calculated.
  • the following distances are shown in Figure 2 and similarly in Figures 4 and 5: the distance dll between the upper face of the hollow envelope 31 of the piston 3 and the anchoring point P of the connecting rod 6 on the piston 3, the distance d12 between the upper face of the inner piston 5 and the upper face of the piston 3 and the distance d13 between the movable partition 4 and the upper face of the inner piston 5.
  • the distance dl3 is representative of the constant volume delimited between the movable partition 4 and the upper surface of the piston 5.
  • the common movement of the movable partition 4 and the internal piston 5 inside the hollow cylindrical casing 31 of the piston 3 is limited by abutments 33 made, for example, in the form of an annular abutment placed in place. inside the cylindrical envelope 31 after insertion of the movable partition 4, the gate 32 and the inner piston 5.
  • the common movement of the movable partition 4 and the inner piston 5 is also subject to stresses exerted by springs 34, 35, for example coil springs, the spring 34 is disposed between the bottom of the hollow envelope 31 and the movable partition 4 and the spring 35 is disposed between the inner piston 5 and the annular abutment 33.
  • the gate 32 is integral with the hollow envelope 31 and therefore has a fixed position inside the hollow cylindrical casing 31. And the movable partition 4 and the internal piston 5 are movably mounted inside the casing hollow cylindrical 31 and subjected to the binding action of the springs 34, 35.
  • the force of the springs 34, 35 is chosen so as to ensure that the movable partition 4 and the inner piston 5 are in, or return to, a neutral position or nominal, when no effort seeking to change the compression ratio is exerted on them.
  • the neutral or nominal position of the movable partition 4 and the inner piston 5 is the one that calculates the nominal compression ratio of the cylinder and thus the engine.
  • the variation of the compression ratio of a cylinder comprising a device of the invention is obtained in the following manner.
  • the magneto-rheological fluid fills the partial volumes A and B.
  • the quantity of magnetorheological fluid occupying each of the partial volumes A and B is varied by passing a partial quantity of the fluid alternately from the volume A to the volume B or conversely, according to a force exerted by the inner piston 5, to obtain different positions of the piston 3 relative to the rod 6 shown in Figure 2.
  • the magnetorheological fluid has the particularity of a dependence of its viscosity to the magnetic field to which it is subjected. Depending on the intensity of the magnetic field generated by the winding 7, the magnetorheological fluid can become very highly viscous or even solid.
  • the fluid becomes sufficiently non-viscous or liquid to pass from one partial volume to another.
  • the variable viscosity of the magnetorheological fluid it is possible, after having varied the ratio between the partial volumes A and B, to freeze these volumes A and B by imposing a magnetic field on the magnetorheological fluid and thus to make the hollow envelope 31 integral with the inner piston 5. Indeed, under the effect of the magnetic field generated by the coil 7, the magnetorheological fluid becomes so viscous, or even solid, that it can no longer cross the gate 32 and move from one partial volume to another.
  • the magnetorheological fluid is no longer subject to the magnetic field, it becomes sufficiently non-viscous to change from partial volume A to partial volume B or vice versa, depending on the force exerted by the internal piston 5.
  • the distance d12 between the surface of the inner piston 5 and the surface of the hollow cylindrical casing 31 is variable while the distance d13 between the inner piston 5 and the movable partition 4 is constant. It is therefore possible to vary the distance d11 between the anchor point P of the connecting rod on the piston 3 and the surface of the hollow cylindrical envelope 31, representing at the same time the upper face of the piston 3. This variation in the distance d entails, in a sought-after manner, a variation in the compression ratio of the cylinder in question.
  • the magnetic field intended to exert an influence on the magnetorheological fluid, which is necessary to obtaining the desired effect according to the invention, is obtained by a winding 7 incorporated in the liner of the cylinder 2, as shown in FIGS. 2, 4 and 5.
  • the coil 7 is advantageously connected to a clean power supply cooperating with an electronic control system, preferably controlled according to the operating point of the engine. Parameters that can be recorded for this purpose are, for example, the engine speed, the load by which the motor is loaded, the position of the accelerator pedal and the engine operating phase, for example the start-up phase.
  • FIG. 3 shows in detail, respectively in FIG. 3a and in FIG.
  • the grid 32 in a cross section showing the location of four orifices 36 of a row of orifices, and in a view from above showing the
  • the number of orifices represented, in this case 16 in the form of a matrix four times four, is obviously only one of several possible arrangements.
  • the device of the invention When the compression ratio has to be increased, the device of the invention must be put in a configuration shown in FIG. 4.
  • the control means intended to obtain this effect act in the following manner.
  • compression phase that is to say when the anchor point P of the connecting rod 6 on the piston 3 rises, the connecting rod 6 exerts a force directed towards the top of the piston 3 and in particular on the internal piston 5.
  • the pressure in the cylinder 2 exerts a force in the opposite direction on the hollow cylindrical shell 31.
  • the magnetorheological fluid is not subjected to any magnetic field during this time, the fluid passes freely from the partial volume B to the partial volume A. By this movement of the magneto- rheological, the movable partition 4 is close to the surface of the hollow cylindrical casing 31.
  • the stiffness of the spring 34 imposes a force less than that provided by the magnetorheological fluid.
  • the magnetorheological fluid is again subjected to the effect of the magnetic field generated by the winding 7. This has the effect of freezing the magnetorheological fluid and thus secure the movable partition 4 and the inner piston 5 with the hollow cylindrical casing 31, as shown in FIG. 4.
  • Figure 4 shows the distance d21 between the surface of the hollow cylindrical casing 31 and the anchor point P of the rod 6 on the piston 3, the distance d22 mentioned above. before the surface of the hollow cylindrical casing 31 and the inner piston 5, and the constant distance d23 between the movable partition 4 and the inner piston 5, the distance d23 being equal to the distance d13 of the arrangement shown in FIG. 2 and also at the distance d33 indicated in FIG.
  • the variation device of the invention is activated during the expansion phase of the operation of the internal combustion engine, that is to say when the anchor point P of the connecting rod 6 goes down.
  • the connecting rod 6 exerts a force directed downwards on the internal piston 5.
  • the spring 34 exerts a force that is also directed downwards on the movable partition 4, which makes part of the magneto-rheological fluid of the partial volume A through the gate 32 to the partial volume B.
  • This passage of the magnetorheological fluid makes it possible to change the distance between the internal piston 5 and the hollow cylindrical envelope 31 and, for this purpose, the distance between the surface of the hollow cylindrical casing 31 and the anchor point P of the rod 6 on the piston 3.
  • FIG. 5 indicates, in a manner similar to the indications given in FIGS.
  • the device for varying the compression ratio of a cylinder of an internal combustion engine described above can be used in different ways.
  • a preliminary calibration is performed on the test bench of the combustion engine.
  • the imposition times of the magnetic field as a function of engine operating conditions are mapped.
  • This map directly modifies the value of the compression ratio.
  • this mapping is not dynamically adjustable.
  • the device of the invention According to a second way of using the device of the invention, there is added to the device of the invention a control device and dynamic control connected to a set of sensors and to calculate the compression ratio continuously.
  • the variation device according to the invention adapts to both the manufacturing dispersion of the internal combustion engines and to the demands of the driver as a function of the conditions of use of the vehicle propelled by the internal combustion engine provided with a device of the invention.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Output Control And Ontrol Of Special Type Engine (AREA)

Abstract

The invention concerns a device for varying compression ratio of an internal combustion engine cylinder (2), the cylinder (2) comprising a piston (3) mounted axially sliding inside the cylinder and connected to a crankshaft of the engine via a connecting rod (6). The piston (3) comprises, in a hollow cylindrical casing (31) open towards the connecting rod (6), an inner piston (5) mounted axially sliding relative to the hollow casing (31), a mobile partition (4) arranged between the inner piston (5) and the base of the hollow casing (31), and a grid (32) secured to the hollow cylindrical casing (31). The grid (32) divides a constant volume delimited between the mobile partition (4) and the inner piston (5) into two partial volumes (A, B) filled with a magnetorheological fluid designed to be subjected to a variable magnetic field (7) to vary its viscosity.

Description

"Dispositif de variation du taux de compression d'un cylindre d'un moteur à combustion interne et moteur à combustion interne comprenant un tel dispositif" "Device for varying the compression ratio of a cylinder of an internal combustion engine and an internal combustion engine comprising such a device"
La présente invention revendique la priorité de la demande française 0509336 déposée le 13/09/2005 dont le contenu (description, revendications et dessins) est incorporé ici par référence.The present invention claims the priority of the French application 0509336 filed on 13/09/2005 whose content (description, claims and drawings) is incorporated herein by reference.
L'invention concerne un dispositif de variation du taux de compression d'un cylindre d'un moteur à combustion interne, ainsi qu'un moteur à combustion interne comprenant un tel dispositif de variation.The invention relates to a device for varying the compression ratio of a cylinder of an internal combustion engine, and an internal combustion engine comprising such a variation device.
Le dispositif de l'invention s'applique aussi bien à des moteurs à combustion interne par allumage commandé qu'à des moteurs à combustion interne par compression. De tels moteurs comprennent généralement un ou plusieurs cylindres dont chacun comporte un piston monté axialement coulissant à l'intérieur du cylindre et relié à un vilebrequin du moteur au moyen d'une bielle. Une des caractéristiques de ces cylindres est le taux de compression qui est défini comme le rapport entre le volume de la chambre de combustion au point mort bas du piston et le volume de la chambre de combustion au point mort haut du piston. Dans un même cylindre et pour une course constante entre le point mort haut et le point mort bas du piston, le taux de compression peut être augmenté ou diminué en plaçant le point mort haut du piston respectivement plus proche ou plus loin de la tête de cylindre. La figure 1 annexée représente cela schématiquement de la manière suivante : pour un même niveau du point mort bas de la bielle, le taux de compression de la configuration de gauche est plus important que le taux de compression de la configuration de droite. A titre d'exemple, pour un moteur de 2000 cm3 de cylindre ayant un taux de compression nominal de 17, une variation de 0,5 cm de la position du piston en point mort haut résulte en un nouveau taux de compression de 16 ou de 18 selon l'orientation du déplacement du point mort haut .The device of the invention applies both to internal combustion engines by spark ignition compression internal combustion engines. Such engines generally comprise one or more cylinders each of which comprises a piston mounted axially sliding inside the cylinder and connected to a crankshaft of the engine by means of a connecting rod. One of the characteristics of these cylinders is the compression ratio which is defined as the ratio between the volume of the combustion chamber at the bottom dead center of the piston and the volume of the combustion chamber at the top dead center of the piston. In the same cylinder and for a constant stroke between the top dead center and the bottom dead center of the piston, the compression ratio can be increased or decreased by placing the top dead center of the piston respectively closer or further from the cylinder head . The appended FIG. 1 shows this schematically in the following manner: for the same level of the bottom dead point of the connecting rod, the compression ratio of the configuration on the left is greater than the compression ratio of the right configuration. By way of example, for a 2000 cm 3 cylinder engine having a nominal compression ratio of 17, a variation of 0.5 cm from the position of the piston in top dead center results in a new compression ratio of 16. or 18 depending on the direction of movement of the top dead center.
Indépendamment des différences conceptionnelles entre un moteur à allumage par compression et un moteur à allumage commandé, selon lesquelles les moteurs mentionnés en premier ont un taux de compression plus élevé que les moteurs mentionnés en second, il a été constaté que des variations du taux de compression apportent pour chacun des deux types de moteur à combustion interne un certain nombre d'avantages dont voici les principaux.Regardless of the conceptual differences between a compression ignition engine and a positive-ignition engine, in which the engines mentioned first have a higher compression ratio than the engines mentioned second, it has been found that variations in the compression ratio provide for each of the two types of internal combustion engine a number of advantages, here the main ones.
Dans un moteur à allumage par compression, le taux de compression exerce une influence sur le niveau de température et sur le mélange dans la chambre de combustion, ce qui a un effet direct sur 1 ' auto- inflammation recherchée. Lorsque l'on augmente le taux de compression, ceci facilite l' auto- inflammation et lorsque l'on le réduit, cela limite la capacité du mélange à s' auto-inflammer . Sur le plan pratique, lors d'un démarrage à froid, les conditions thermodynamiques dans la chambre de combustion ont tendance à défavoriser l' auto-inflammation, principalement en raison de la faible température ; augmenter le taux de compression permettrait alors d'atteindre plus facilement une température suffisante pour une auto-inflammation sûre ; lorsque le moteur est fortement sollicité, une augmentation du taux de compression permet d'augmenter le rendement du moteur ; cela signifie notamment que, pour une même puissance du moteur, la consommation de carburant baisse ; lorsque le moteur est sollicité de manière modérée, une diminution du taux de compression permet de diminuer la température de combustion et de diminuer ainsi le niveau des polluants émis, essentiellement l'émission des oxydes d'azote ; pour mieux maîtriser la combustion et pour limiter l'émission de polluants, notamment de suies et d'oxydes d'azote, on recherche à obtenir des mélanges les plus homogènes possible ; une réduction du taux de compression permettrait une augmentation du délai d'auto- inflammation et par cela une augmentation du temps disponible pour effectuer un mélange homogène de carburant et air.In a compression ignition engine, the compression ratio has an influence on the temperature level and the mixture in the combustion chamber, which has a direct effect on the desired self-ignition. When the compression ratio is increased, this facilitates self-ignition and when it is reduced, it limits the ability of the mixture to self-ignite. In practical terms, during a cold start, the thermodynamic conditions in the combustion chamber tend to disadvantage self-ignition, mainly because of the low temperature; increasing the compression ratio would then make it easier to reach a temperature sufficient for safe autoignition; when the motor is heavily stressed, an increase in the compression ratio increases the efficiency of the engine; this means that, for the same power of the engine, the fuel consumption drops; when the engine is subjected to a moderate amount of pressure, a reduction in the compression ratio makes it possible to reduce the combustion temperature and thus to reduce the level of pollutants emitted, essentially the emission of nitrogen oxides; to better control combustion and to limit the emission of pollutants, including soot and nitrogen oxides, we seek to obtain the most homogeneous mixtures possible; a reduction in the compression ratio would allow an increase in the self-ignition delay and thereby an increase in the time available to effect a homogeneous mixture of fuel and air.
Au vu des quelques avantages énoncés ci-avant d'une variation du taux de compression d'un moteur à allumage par compression, on constate qu'il pourrait être bien pratique de concevoir un moteur à combustion interne dont le taux de compression est variable en fonction des conditions de fonctionnement du moteur. Une telle possibilité semble particulièrement intéressante pour pouvoir respecter certaines normes de pollution déjà en vigueur et d'autres à venir.In view of the few advantages mentioned above of a variation in the compression ratio of a compression ignition engine, it is found that it could be very practical to design an internal combustion engine whose compression ratio is variable in depending on the operating conditions of the motor. Such a possibility seems particularly interesting to be able to respect certain pollution standards already in force and others to come.
Dans un moteur à allumage commandé, une variation du taux de compression selon des situations de fonctionnement du moteur permettrait d'optimiser son utilisation, par exemple, des deux manières suivantes :In a spark ignition engine, a variation of the compression ratio according to engine operating situations would make it possible to optimize its use, for example, in the following two ways:
Lorsque le moteur est fortement chargé, une réduction du taux de compression est favorable à une limitation du phénomène de cliquetis. Le phénomène de cliquet est un phénomène d' auto- inflammation non contrôlée et non désirée du carburant, entraînant un risque fort de destruction du moteur. Ce phénomène est favorisé par des températures élevées dans la chambre de combustion. Une réduction de ces températures pourrait être obtenue en réduisant le taux de compression. Par contre, une augmentation du taux de compression permettrait, dans les limitations liées au phénomène de cliquetis, d'optimiser le rendement du moteur sur certaines plages de fonctionnement de celui-ci. - Lorsque le moteur est sollicité de manière modérée, une diminution du taux de compression permet de limiter les émissions polluantes par suite de la réduction du niveau de température dans la chambre de combustion.When the engine is heavily loaded, a reduction in the compression ratio is favorable to a limitation of the knocking phenomenon. The ratchet phenomenon is a phenomenon of uncontrolled and undesired self-ignition of the fuel, leading to a high risk of engine destruction. This phenomenon is favored by high temperatures in the combustion chamber. A reduction in these temperatures could be achieved by reducing the compression ratio. On the other hand, an increase in the compression ratio would make it possible, in the limitations related to the rattling phenomenon, to optimize the efficiency of the engine over certain operating ranges thereof. - When the engine is applied in a moderate way, a reduction in the compression ratio makes it possible to limit pollutant emissions as a result of the reduction of the temperature level in the combustion chamber.
Aussi bien pour les moteurs à allumage par compression que pour les moteurs à allumage commandé, une variation du taux de compression semble permettre d'optimiser l'utilisation du moteur suivant les différentes situations de fonctionnement de celui-ci, par exemple une adaptation à des conditions particulières d'une phase de démarrage ou à des conditions de fonctionnement particulières dans une phase d' accélération.For compression-ignition engines as well as for spark-ignition engines, a variation in the compression ratio seems to make it possible to optimize the use of the engine according to the various operating situations thereof, for example an adaptation to particular conditions of a starting phase or at particular operating conditions in an acceleration phase.
Certains avantages d'une variation du taux de compression au cours du fonctionnement d'un moteur à combustion interne ont déjà été reconnus avant la présente invention.Some advantages of varying the compression ratio during the operation of an internal combustion engine have already been recognized before the present invention.
Un moteur à combustion interne pourvu d'un système permettant de varier le taux de compression à l'aide d'un fluide magnéto-rhéologique est décrit dans le document US-6, 394, 048. Dans ce moteur, les fixations des bielles sur le vilebrequin sont conformées de manière à obtenir une variation de la longueur effective des bielles par des moyens mécaniques et des moyens électromagnétiques agissant sur le fluide magnéto-rhéologique. La variation de la longueur des bielles correspondant à un déplacement du point mort haut et du point mort bas des pistons dans les cylindres, une telle variation entraîne, comme cela est expliqué plus haut, une variation du taux de compression du moteur.An internal combustion engine provided with a system for varying the compression ratio using a magneto-rheological fluid is described in US-6, 394, 048. In this engine, the fasteners of the rods on the crankshaft are shaped so as to obtain a variation of the effective length of the connecting rods by mechanical means and electromagnetic means acting on the magnetorheological fluid. The variation of the length of the connecting rods corresponding to a displacement of the top dead center and the bottom dead point of the pistons in the cylinders, such a variation causes, as explained above, a variation of the compression ratio of the engine.
Le but de la présente invention est de proposer une solution mécaniquement plus simple et offrant, si possible, la possibilité d'intégrer cette solution dans des conceptions existantes de moteurs.The object of the present invention is to provide a mechanically simpler solution and offering, if possible, the possibility of integrating this solution into existing engine designs.
Le but de l'invention est atteint avec un dispositif de variation du taux de compression d'un cylindre d'un moteur à combustion interne, le cylindre comportant un piston qui est monté axialement coulissant à l'intérieur du cylindre et est relié à un vilebrequin du moteur au moyen d'une bielle.The object of the invention is achieved with a device for varying the compression ratio of a cylinder of an internal combustion engine, the cylinder comprising a piston which is mounted axially sliding inside the cylinder and is connected to a crankshaft of the engine by means of a connecting rod.
Conformément à l'invention, le piston comprend une enveloppe cylindrique creuse ouverte vers la bielle et comporte, à l'intérieur de l'enveloppe creuse, un piston interne monté axialement coulissant par rapport à l'enveloppe creuse, une cloison mobile disposée entre le piston interne et le fond de l'enveloppe creuse, ainsi qu'une grille solidaire de l'enveloppe creuse et disposée entre le piston interne et la cloison mobile, la grille divisant un volume constant délimité entre la cloison mobile et le piston interne en deux volumes partiels remplis d'un fluide magnéto-rhéologique destiné à être soumis à un champ magnétique variable pour faire varier sa viscosité de manière contrôlée.According to the invention, the piston comprises a hollow cylindrical envelope open towards the connecting rod and comprises, inside the hollow envelope, an internal piston mounted axially sliding relative to the hollow envelope, a movable partition disposed between the internal piston and the bottom of the hollow envelope, and a grid integral with the hollow envelope and disposed between the inner piston and the movable partition, the grid dividing a constant volume delimited between the movable partition and the inner piston in two partial volumes filled with a magneto-rheological fluid to be subjected to a variable magnetic field to vary its viscosity in a controlled manner.
Le dispositif de l'invention présente l'avantage d'être mécaniquement simple, de pouvoir être implanté facilement sur des moteurs de conception existante, de comprendre un nombre de pièces mobiles réduit, de présenter une flexibilité d'application importante du fait d'une commande non mécanique du dispositif et de la possibilité d'adapter le dispositif de l'invention facilement à tout type de moteur et à différentes applications de celui-ci. Le dispositif de l'invention est susceptible de comprendre également l'une au moins des caractéristiques ci-après, considérées isolément ou selon toute combinaison techniquement possible :The device of the invention has the advantage of being mechanically simple, of being able to be easily implanted on existing design engines, to understand a reduced number of moving parts, to present an important flexibility of application due to a non-mechanical control of the device and the possibility of adapting the device of the invention easily to any type of engine and to different applications thereof. The device of the invention may also include at least one of the following features, considered in isolation or in any technically possible combination:
- le fluide magnéto-rhéologique présente une gamme de viscosités comprise entre une faible viscosité permettant au fluide de passer sans difficulté d'un volume partiel à l'autre et une très forte viscosité empêchant le fluide de passer d'un volume partiel à 1 ' autre ; - le mouvement de la cloison mobile et du piston interne, mouvement nécessairement commun pour assurer le volume constant délimité entre la cloison mobile et le piston interne, est limité à l'intérieur de l'enveloppe cylindrique creuse par des butées ;- The magnetorheological fluid has a range of viscosities between a low viscosity allowing the fluid to pass easily from one partial volume to another and a very high viscosity preventing the fluid from a partial volume to 1 'other; - the movement of the movable partition and the internal piston, movement necessarily common to ensure the constant volume delimited between the movable partition and the internal piston, is limited inside the hollow cylindrical envelope by stops;
- les butées sont réalisées sous la forme d'une butée annulaire ; - le dispositif comprend des ressorts dont un ou plusieurs ressorts sont disposés entre le fond de l'enveloppe cylindrique creuse et la cloison mobile et dont le ou les autres ressorts sont disposés entre le piston interne et les butées ; - les ressorts sont des ressorts hélicoïdaux ;the stops are made in the form of an annular abutment; - The device comprises springs of which one or more springs are disposed between the bottom of the hollow cylindrical envelope and the movable partition and whose other spring or springs are arranged between the inner piston and the stops; the springs are helical springs;
- le dispositif comprend un bobinage incorporé dans la chemise du cylindre.the device comprises a winding incorporated in the cylinder liner.
Le but de l'invention est également atteint avec un moteur à combustion interne, à allumage par compression ou à allumage commandé, comprenant un dispositif de variation selon la description ci-avant.The object of the invention is also achieved with an internal combustion engine, with compression ignition or spark ignition, comprising a variation device according to the description above.
La description de l'invention sera poursuivie en référence aux dessins dans lesquels la figure 1 représente schématiquement l'influence d'une modification de la position relative du piston par rapport à la bielle dans un cylindre, sur le taux de compression du moteur, la figure 2 représente schématiquement le dispositif de l'invention selon un mode de réalisation préféré, la figure 3 montre une grille faisant partie du dispositif de l'invention, respectivement en une coupe transversale (figure 3a) et en une vue de dessus (figure 3b) , - la figure 4 montre le dispositif de l'invention lorsque le piston est en un premier point mort haut, et la figure 5 montre le dispositif de l'invention dans une autre configuration du dispositif.The description of the invention will be continued with reference to the drawings in which FIG. 1 schematically represents the influence of a modification of the relative position of the piston with respect to the connecting rod in a cylinder, on the compression ratio of the engine, the 2 schematically represents the device of the invention according to a preferred embodiment, Figure 3 shows a grid forming part of the device of the invention, respectively in a cross section (Figure 3a) and a top view (Figure 3b). FIG. 4 shows the device of the invention when the piston is in a first top dead center, and FIG. 5 shows the device of the invention in another configuration of the device.
La figure 1 rappelle la définition du taux de compression d'un cylindre de moteur à combustion et montre plus particulièrement l'influence de la modification de la position relative d'un piston par rapport à la bielle correspondante sur le taux de compression.FIG. 1 recalls the definition of the compression ratio of a combustion engine cylinder and more particularly shows the influence of the modification of the relative position of a piston by compared to the corresponding rod on the compression ratio.
Le taux de compression est défini comme le rapport entre le volume de la chambre de combustion lorsque le piston est au point mort bas PMB et le volume de la chambre de combustion lorsque le piston est au point mort haut PMH. La figure 1 représente les éléments de la définition du taux de compression et l'influence de la configuration de l'ensemble cylindre/piston. Dans la configuration de gauche, un piston 3 est disposé à l'intérieur d'un cylindre 2 dans une position PMHl plus haute que dans la configuration de droite où la position du piston 3 est référencée PMH2. Le piston 3 est relié dans les deux cas à un vilebrequin à l'aide d'une bielle 6 qui a une longueur constante et qui est monté sur le vilebrequin à l'aide d'un axe ayant une position fixe sur le vilebrequin.The compression ratio is defined as the ratio between the volume of the combustion chamber when the piston is at low dead point PMB and the volume of the combustion chamber when the piston is at the top dead center TDC. Figure 1 shows the elements of the definition of the compression ratio and the influence of the configuration of the cylinder / piston assembly. In the configuration on the left, a piston 3 is disposed inside a cylinder 2 in a higher position PMH1 than in the right configuration where the position of the piston 3 is referenced PMH2. The piston 3 is connected in both cases to a crankshaft with a rod 6 which has a constant length and which is mounted on the crankshaft using an axis having a fixed position on the crankshaft.
Selon la configuration de gauche, la face supérieure du piston 3 se trouve à un niveau PMHl lorsque le piston se trouve au point mort haut et à un niveauAccording to the configuration on the left, the upper face of the piston 3 is at a level PMH1 when the piston is at the top dead center and at one level
PMBl lorsque le piston se trouve au point mort bas. La coïncidence du niveau PMBl avec la position de l'articulation reliant la bielle 6 au piston 3, lorsque le piston est en position PMHl, est arbitraire et est ainsi sans influence sur la présente explication. La course du piston 3 dans la configuration de gauche est indiquée par la flèche double tête HO. Lorsque le piston 3 est en point mort haut PMHl, le volume de la chambre de combustion est Vl. Et lorsque le piston 3 est en point mort bas PMBl, le volume de la chambre de combustion correspond à la somme des deux volumes partiels Vl et Vl', soit Vl'' représenté par la hauteur Hl de ce volume.PMBl when the piston is in the bottom dead center. The coincidence of the PMBl level with the position of the joint connecting the connecting rod 6 to the piston 3, when the piston is in position PMH1, is arbitrary and is thus without influence on the present explanation. The stroke of the piston 3 in the configuration on the left is indicated by the double headed arrow HO. When the piston 3 is in top dead center PMH1, the volume of the combustion chamber is V1. And when the piston 3 is in low dead point PMB1, the volume of the combustion chamber corresponds to the sum of the two partial volumes V1 and V1. Vl ', ie Vl' 'represented by the height H1 of this volume.
Dans la configuration de droite, le piston 3 se trouve dans une position PMH2 plus basse que celle de la configuration de gauche, lorsque le piston 3 est en point mort haut. Lorsque, dans la configuration de droite, le piston 3 est au point mort haut PMH2 , le volume de la chambre de combustion est V2 , qui est plus grand que le volume correspondant Vl de la configuration de gauche. Lorsque, dans la configuration de droite, le piston est au point mort bas PMB2, le volume de la chambre de combustion correspond à la somme des deux volumes partiels V2 et V2 ' , soit V2 ' ' représenté par la hauteur H2 de ce volume .In the right configuration, the piston 3 is in a position PMH2 lower than that of the left configuration, when the piston 3 is in top dead center. When, in the right configuration, the piston 3 is at the top dead center PMH2, the volume of the combustion chamber is V2, which is larger than the corresponding volume Vl of the left configuration. When, in the configuration on the right, the piston is at low dead point PMB2, the volume of the combustion chamber corresponds to the sum of the two partial volumes V2 and V2 ', ie V2''represented by the height H2 of this volume.
Dans la configuration de gauche, le taux de compression est Vl''/ Vl alors que le taux de compression dans la configuration de droite est V2 ' ' / V2. Vl étant plus petit que V2 , le taux de compression de la configuration de gauche est plus élevé que celui de la configuration de droite. En effet, si on note CRl le taux de compression dans la configuration de gauche et CR2 celui dans la configuration de droite, on peut écrire :In the left configuration, the compression ratio is Vl '' / Vl while the compression ratio in the right configuration is V2 '' / V2. Vl being smaller than V2, the compression ratio of the left configuration is higher than that of the right configuration. Indeed, if we note CRl the compression ratio in the configuration of left and CR2 that in the configuration of right, one can write:
ou encore or
1 11 1
CRl = et CRl- donc si H2 >H1 ,CRl = and CRl- so if H2> H1,
1 H0 1 H0 H1 H2 inf érieur à CRl . 1 H 0 1 H 0 H 1 H 2 inferior to CRl.
La figure 2 représente les éléments d'un dispositif de variation du taux de compression d'un cylindre d'un moteur à combustion interne selon un mode de réalisation de l'invention. Le dispositif de variation de l'invention s'applique à chacun des cylindres 2 d'un moteur à combustion interne 1.FIG. 2 represents the elements of a device for varying the compression ratio of a cylinder of an internal combustion engine according to one embodiment of the invention. The variation device of the invention applies to each of the cylinders 2 of an internal combustion engine 1.
Le cylindre 2 comporte un piston 3 monté axialement coulissant à l'intérieur du cylindre et relié à un vilebrequin du moteur au moyen d'une bielle 6. Les différents éléments du dispositif de l'invention sont représentés de manière très simplifiée et réduite à leurs fonctionnalités. Leur représentation ne constitue donc en aucun cas une limitation à un mode de réalisation particulier du dispositif de l'invention. Le piston 3 comprend une enveloppe cylindrique creuse 31 ouverte vers la bielle 6 et comporte, à l'intérieur de l'enveloppe creuse 31, un piston interne 5 monté axialement coulissant par rapport à l'enveloppe creuse 31. Le piston interne 5 est représenté, conformément au principe de la représentation simplifiée évoqué ci-avant, uniquement par sa face supérieure orientée vers la tête du cylindre et par son point d'ancrage P auquel il est relié à la bielle 6 de manière pivotante.The cylinder 2 comprises a piston 3 mounted axially sliding inside the cylinder and connected to a crankshaft of the engine by means of a connecting rod 6. The various elements of the device of the invention are represented in a very simplified manner and reduced to their features. Their representation is therefore in no way a limitation to a particular embodiment of the device of the invention. The piston 3 comprises a hollow cylindrical casing 31 open towards the connecting rod 6 and comprises, inside the hollow casing 31, an internal piston 5 mounted axially sliding relative to the hollow casing 31. The internal piston 5 is shown , in accordance with the principle of simplified representation mentioned above, only by its upper face facing the cylinder head and its anchor point P which it is connected to the connecting rod 6 pivotally.
Le piston 3 comprend par ailleurs une cloison mobile 4 disposée entre le piston interne 5 et le fond de l'enveloppe creuse 31, ainsi qu'une grille 32 solidaire de l'enveloppe creuse 31 et disposée entre les pistons internes 5 et la cloison mobile 4. La cloison mobile 4 et le piston interne 5 délimitent entre eux un volume constant qui est divisé par la grille 32 en deux volumes partiels A, B. Le volume délimité entre la cloison mobile 4 et le piston interne 5 est rempli d'un fluide magnéto-rhéologique destiné à être soumis à un champ magnétique variable engendré par un bobinage 7 pour faire varier la viscosité du fluide magnéto-rhéologique de manière contrôlée.The piston 3 further comprises a movable partition 4 disposed between the inner piston 5 and the bottom of the hollow envelope 31, and a grid 32 integral with the hollow envelope 31 and disposed between the inner pistons 5 and the movable partition. 4. The movable partition 4 and the inner piston 5 delimit between them a constant volume which is divided by the grid 32 into two partial volumes A, B. The volume delimited between the movable partition 4 and the internal piston 5 is filled with a magneto-rheological fluid intended to be subjected to a variable magnetic field generated by a coil 7 to vary the viscosity of the magnetorheological fluid in a controlled manner.
La figure 2 représente le dispositif de l'invention dans une position neutre du piston 3 à partir de laquelle le taux de compression nominal du cylindre, et ainsi le taux de compression nominal du moteur, est calculé. Pour faciliter la comparaison de la configuration représentée sur la figure 2 avec celles représentées sur les figures 4 et 5 , les distances suivantes sont indiquées sur la figure 2 et de manière analogue sur les figures 4 et 5 : la distance dll entre la face supérieure de l'enveloppe creuse 31 du piston 3 et le point d'ancrage P de la bielle 6 sur le piston 3, la distance dl2 entre la face supérieure du piston interne 5 et la face supérieure du piston 3 et la distance dl3 entre la cloison mobile 4 et la face supérieure du piston interne 5. La distance dl3 est représentative du volume constant délimité entre la cloison mobile 4 et la surface supérieure du piston 5.Figure 2 shows the device of the invention in a neutral position of the piston 3 from which the nominal compression ratio of the cylinder, and thus the nominal compression ratio of the engine, is calculated. To facilitate comparison of the configuration shown in Figure 2 with those shown in Figures 4 and 5, the following distances are shown in Figure 2 and similarly in Figures 4 and 5: the distance dll between the upper face of the hollow envelope 31 of the piston 3 and the anchoring point P of the connecting rod 6 on the piston 3, the distance d12 between the upper face of the inner piston 5 and the upper face of the piston 3 and the distance d13 between the movable partition 4 and the upper face of the inner piston 5. The distance dl3 is representative of the constant volume delimited between the movable partition 4 and the upper surface of the piston 5.
Le mouvement commun de la cloison mobile 4 et du piston interne 5 à l'intérieur de l'enveloppe cylindrique creuse 31 du piston 3 est limité par des butées 33 réalisées, par exemple, sous la forme d'une butée annulaire mise en place à l'intérieur de l'enveloppe cylindrique 31 après insertion de la cloison mobile 4, de la grille 32 et du piston interne 5. Le mouvement commun de la cloison mobile 4 et du piston interne 5 est par ailleurs soumis à des contraintes exercées par des ressorts 34, 35, par exemple des ressorts hélicoïdaux, le ressort 34 est disposé entre le fond de l'enveloppe creuse 31 et la cloison mobile 4 et le ressort 35 est disposé entre le piston interne 5 et la butée annulaire 33.The common movement of the movable partition 4 and the internal piston 5 inside the hollow cylindrical casing 31 of the piston 3 is limited by abutments 33 made, for example, in the form of an annular abutment placed in place. inside the cylindrical envelope 31 after insertion of the movable partition 4, the gate 32 and the inner piston 5. The common movement of the movable partition 4 and the inner piston 5 is also subject to stresses exerted by springs 34, 35, for example coil springs, the spring 34 is disposed between the bottom of the hollow envelope 31 and the movable partition 4 and the spring 35 is disposed between the inner piston 5 and the annular abutment 33.
La grille 32 est solidaire de l'enveloppe creuse 31 et a donc une position fixe à l'intérieur de l'enveloppe cylindrique creuse 31. Et la cloison mobile 4 et le piston interne 5 sont montés mobiles à l'intérieur de l'enveloppe cylindrique creuse 31 et soumis à l'action contraignante des ressorts 34, 35. La force des ressorts 34, 35 est choisie de manière à assurer que la cloison mobile 4 et le piston interne 5 se trouvent dans, ou retournent à, une position neutre ou nominale, lorsque aucun effort cherchant à modifier le taux de compression n'est exercé sur eux. La position neutre ou nominale de la cloison mobile 4 et du piston interne 5 est celle qui permet de calculer le taux de compression nominal du cylindre et ainsi du moteur.The gate 32 is integral with the hollow envelope 31 and therefore has a fixed position inside the hollow cylindrical casing 31. And the movable partition 4 and the internal piston 5 are movably mounted inside the casing hollow cylindrical 31 and subjected to the binding action of the springs 34, 35. The force of the springs 34, 35 is chosen so as to ensure that the movable partition 4 and the inner piston 5 are in, or return to, a neutral position or nominal, when no effort seeking to change the compression ratio is exerted on them. The neutral or nominal position of the movable partition 4 and the inner piston 5 is the one that calculates the nominal compression ratio of the cylinder and thus the engine.
La variation du taux de compression d'un cylindre comportant un dispositif de l'invention est obtenue de la manière suivante. Le fluide magnéto-rhéologique remplit les volumes partiels A et B. La quantité de fluide magnéto-rhéologique occupant chacun des volumes partiels A et B est variée en faisant passer une quantité partielle du fluide alternativement du volume A vers le volume B ou inversement, suivant un effort exercé par le piston interne 5, pour obtenir des positions différentes du piston 3 par rapport à la bielle 6 représentée sur la figure 2. Le fluide magnéto-rhéologique présente la particularité d'une dépendance de sa viscosité au champ magnétique auquel il est soumis. Suivant l'intensité du champ magnétique engendré par le bobinage 7, le fluide magnéto-rhéologique peut devenir très fortement visqueux, voire solide. Lorsque aucun champ magnétique n'est appliqué, le fluide devient suffisamment non visqueux ou liquide pour passer d'un volume partiel à l'autre. Grâce à la viscosité variable du fluide magnéto-rhéologique, il est donc possible, après avoir varié le rapport entre les volumes partiels A et B, de figer ces volumes A et B en imposant un champ magnétique au fluide magnéto- rhéologique et de rendre ainsi l'enveloppe creuse 31 solidaire du piston interne 5. En effet, sous l'effet du champ magnétique engendré par le bobinage 7, le fluide magnéto-rhéologique devient si visqueux, voire même solide, qu'il ne peut plus traverser la grille 32 et passer d'un volume partiel à l'autre. Lorsque le fluide magnéto-rhéologique n'est plus soumis au champ magnétique, il redevient suffisamment non visqueux pour passer du volume partiel A au volume partiel B ou vice- versa, selon l'effort exercé par le piston interne 5.The variation of the compression ratio of a cylinder comprising a device of the invention is obtained in the following manner. The magneto-rheological fluid fills the partial volumes A and B. The quantity of magnetorheological fluid occupying each of the partial volumes A and B is varied by passing a partial quantity of the fluid alternately from the volume A to the volume B or conversely, according to a force exerted by the inner piston 5, to obtain different positions of the piston 3 relative to the rod 6 shown in Figure 2. The magnetorheological fluid has the particularity of a dependence of its viscosity to the magnetic field to which it is subjected. Depending on the intensity of the magnetic field generated by the winding 7, the magnetorheological fluid can become very highly viscous or even solid. When no magnetic field is applied, the fluid becomes sufficiently non-viscous or liquid to pass from one partial volume to another. Thanks to the variable viscosity of the magnetorheological fluid, it is possible, after having varied the ratio between the partial volumes A and B, to freeze these volumes A and B by imposing a magnetic field on the magnetorheological fluid and thus to make the hollow envelope 31 integral with the inner piston 5. Indeed, under the effect of the magnetic field generated by the coil 7, the magnetorheological fluid becomes so viscous, or even solid, that it can no longer cross the gate 32 and move from one partial volume to another. When the magnetorheological fluid is no longer subject to the magnetic field, it becomes sufficiently non-viscous to change from partial volume A to partial volume B or vice versa, depending on the force exerted by the internal piston 5.
La distance dl2 entre la surface du piston interne 5 et la surface de l'enveloppe cylindrique creuse 31 est variable tandis que la distance dl3 entre le piston interne 5 et la cloison mobile 4 est constante. On peut donc faire varier la distance dll entre le point d'ancrage P de la bielle sur le piston 3 et la surface de l'enveloppe cylindrique creuse 31, représentant en même temps la face supérieure du piston 3. Cette variation de la distance dll entraîne, de manière recherchée, une variation du taux de compression du cylindre considéré.The distance d12 between the surface of the inner piston 5 and the surface of the hollow cylindrical casing 31 is variable while the distance d13 between the inner piston 5 and the movable partition 4 is constant. It is therefore possible to vary the distance d11 between the anchor point P of the connecting rod on the piston 3 and the surface of the hollow cylindrical envelope 31, representing at the same time the upper face of the piston 3. This variation in the distance d entails, in a sought-after manner, a variation in the compression ratio of the cylinder in question.
Le champ magnétique destiné à exercer une influence sur le fluide magnéto-rhéologique, qui est nécessaire à l'obtention de l'effet recherché selon l'invention, est obtenu par un bobinage 7 incorporé dans la chemise du cylindre 2, comme cela est représenté sur les figures 2, 4 et 5. Lorsque le dispositif de l'invention est mis en place dans un moteur à combustion interne, le bobinage 7 est avantageusement relié à une alimentation électrique propre coopérant avec un système électronique de commande, avantageusement asservie en fonction du point de fonctionnement du moteur. Des paramètres pouvant être relevés à cet effet sont, par exemple, le régime du moteur, la charge par laquelle le moteur est sollicité, la position de la pédale de l'accélérateur et la phase de fonctionnement du moteur, par exemple la phase de démarrage . La figure 3 représente en détail, respectivement sur la figure 3a et sur la figure 3b, la grille 32 en une coupe transversale montrant l'emplacement de quatre orifices 36 d'une rangée d'orifices, et en une vue du dessus montrant l'ensemble des orifices 36 de la grille 32. La quantité d'orifices représentés, en l'occurrence 16 sous forme d'une matrice quatre fois quatre, n'est évidemment qu'une disposition parmi plusieurs dispositions possibles.The magnetic field intended to exert an influence on the magnetorheological fluid, which is necessary to obtaining the desired effect according to the invention, is obtained by a winding 7 incorporated in the liner of the cylinder 2, as shown in FIGS. 2, 4 and 5. When the device of the invention is put into placed in an internal combustion engine, the coil 7 is advantageously connected to a clean power supply cooperating with an electronic control system, preferably controlled according to the operating point of the engine. Parameters that can be recorded for this purpose are, for example, the engine speed, the load by which the motor is loaded, the position of the accelerator pedal and the engine operating phase, for example the start-up phase. . FIG. 3 shows in detail, respectively in FIG. 3a and in FIG. 3b, the grid 32 in a cross section showing the location of four orifices 36 of a row of orifices, and in a view from above showing the The number of orifices represented, in this case 16 in the form of a matrix four times four, is obviously only one of several possible arrangements.
Lorsque le taux de compression doit être augmenté, le dispositif de l'invention doit être mis dans une configuration représentée sur la figure 4. Les moyens de contrôle destinés à obtenir cet effet agissent de la manière suivante. En phase de compression, c'est-à-dire lorsque le point d'ancrage P de la bielle 6 sur le piston 3 remonte, la bielle 6 exerce un effort dirigé vers le haut du piston 3 et notamment sur le piston interne 5. En même temps, la pression dans le cylindre 2 exerce un effort dans la direction opposée sur l'enveloppe cylindrique creuse 31. Le fluide magnéto-rhéologique n'étant soumis à aucun champ magnétique pendant ce temps, le fluide passe librement du volume partiel B au volume partiel A. Par ce mouvement du fluide magnéto- rhéologique, la cloison mobile 4 se rapproche de la surface de l'enveloppe cylindrique creuse 31. La raideur du ressort 34 impose un effort inférieur à celui fourni par le fluide magnéto-rhéologique. Lorsque la distance d22 entre l'enveloppe cylindrique creuse 31 et le piston intérieur 5 atteint la valeur souhaitée pour l'obtention du taux de compression désiré, le fluide magnéto- rhéologique est à nouveau soumis à l'effet du champ magnétique engendré par le bobinage 7. Ceci a pour effet de figer le fluide magnéto-rhéologique et de solidariser ainsi la cloison mobile 4 et le piston interne 5 avec l'enveloppe cylindrique creuse 31, comme cela est représenté sur la figure 4.When the compression ratio has to be increased, the device of the invention must be put in a configuration shown in FIG. 4. The control means intended to obtain this effect act in the following manner. In compression phase, that is to say when the anchor point P of the connecting rod 6 on the piston 3 rises, the connecting rod 6 exerts a force directed towards the top of the piston 3 and in particular on the internal piston 5. At the same time, the pressure in the cylinder 2 exerts a force in the opposite direction on the hollow cylindrical shell 31. The magnetorheological fluid is not subjected to any magnetic field during this time, the fluid passes freely from the partial volume B to the partial volume A. By this movement of the magneto- rheological, the movable partition 4 is close to the surface of the hollow cylindrical casing 31. The stiffness of the spring 34 imposes a force less than that provided by the magnetorheological fluid. When the distance d22 between the hollow cylindrical shell 31 and the inner piston 5 reaches the desired value for obtaining the desired compression ratio, the magnetorheological fluid is again subjected to the effect of the magnetic field generated by the winding 7. This has the effect of freezing the magnetorheological fluid and thus secure the movable partition 4 and the inner piston 5 with the hollow cylindrical casing 31, as shown in FIG. 4.
De manière analogue à la représentation de la figure 2, la figure 4 indique la distance d21 entre la surface de l'enveloppe cylindrique creuse 31 et le point d'ancrage P de la bielle 6 sur le piston 3, la distance d22 évoquée ci-avant entre la surface de l'enveloppe cylindrique creuse 31 et le piston interne 5, ainsi que la distance constante d23 entre la cloison mobile 4 et le piston interne 5, la distance d23 étant égale à la distance dl3 de la disposition représentée sur la figure 2 et aussi à la distance d33 indiquée sur la figure 5.In a similar manner to the representation of Figure 2, Figure 4 shows the distance d21 between the surface of the hollow cylindrical casing 31 and the anchor point P of the rod 6 on the piston 3, the distance d22 mentioned above. before the surface of the hollow cylindrical casing 31 and the inner piston 5, and the constant distance d23 between the movable partition 4 and the inner piston 5, the distance d23 being equal to the distance d13 of the arrangement shown in FIG. 2 and also at the distance d33 indicated in FIG.
Lorsque l'on souhaite diminuer le taux de compression, le dispositif de variation de l'invention est activé en phase de détente du fonctionnement du moteur à combustion interne, c'est-à-dire lorsque le point d'ancrage P de la bielle 6 descend. Pendant cette phase de détente, la bielle 6 exerce un effort dirigé vers le bas sur le piston interne 5. En même temps, le ressort 34 exerce un effort également dirigé vers le bas sur la cloison mobile 4, ce qui fait passer une partie du fluide magnéto-rhéologique du volume partiel A à travers la grille 32 vers le volume partiel B. Ce passage du fluide magnéto-rhéologique permet de faire changer la distance entre le piston interne 5 et l'enveloppe cylindrique creuse 31 et, pour cela, la distance entre la surface de l'enveloppe cylindrique creuse 31 et le point d'ancrage P de la bielle 6 sur le piston 3. A noter que dans tous les cas, la distance entre la culasse C et le point P est constante. Lorsque la distance entre l'enveloppe cylindrique creuse 31 et le piston interne 5 atteint la valeur souhaitée pour obtenir le taux de compression désiré, le fluide magnéto-rhéologique est à nouveau soumis au champ magnétique engendré par le bobinage 7. Le fluide magnéto- rhéologique est alors figé, ce qui solidarise la cloison mobile 4 et le piston interne 5 à l'enveloppe cylindrique creuse 31. Cette nouvelle configuration des moyens du dispositif de l'invention à l'intérieur du piston 3 est représentée sur la figure 5. La figure 5 indique, de manière analogue aux indications données dans les figures 2 et 4 , une distance d31 ente la surface de l'enveloppe cylindrique creuse 31 et le point d'ancrage P de la bielle 6 sur le piston 3, une distance d32 entre la surface de l'enveloppe cylindrique creuse 31 et la surface du piston interne 5, ainsi que la distance constante d33 entre la cloison mobile 4 et le piston interne 5.When it is desired to reduce the compression ratio, the variation device of the invention is activated during the expansion phase of the operation of the internal combustion engine, that is to say when the anchor point P of the connecting rod 6 goes down. During this expansion phase, the connecting rod 6 exerts a force directed downwards on the internal piston 5. At the same time, the spring 34 exerts a force that is also directed downwards on the movable partition 4, which makes part of the magneto-rheological fluid of the partial volume A through the gate 32 to the partial volume B. This passage of the magnetorheological fluid makes it possible to change the distance between the internal piston 5 and the hollow cylindrical envelope 31 and, for this purpose, the distance between the surface of the hollow cylindrical casing 31 and the anchor point P of the rod 6 on the piston 3. Note that in all cases, the distance between the cylinder head C and the point P is constant. When the distance between the hollow cylindrical shell 31 and the inner piston 5 reaches the desired value to obtain the desired compression ratio, the magnetorheological fluid is again subjected to the magnetic field generated by the coil 7. The magnetorheological fluid is then fixed, which secures the movable partition 4 and the inner piston 5 to the hollow cylindrical casing 31. This new configuration of the means of the device of the invention inside the piston 3 is shown in FIG. FIG. 5 indicates, in a manner similar to the indications given in FIGS. 2 and 4, a distance d 31 between the surface of the hollow cylindrical envelope 31 and the anchoring point P of the connecting rod 6 on the piston 3, a distance d32 between the surface of the hollow cylindrical casing 31 and the surface of the inner piston 5, as well as the constant distance d33 between the movable partition 4 and the internal piston 5.
Le dispositif de variation du taux de compression d'un cylindre d'un moteur à combustion interne décrit ci-avant peut être utilisé de différentes manières. Selon une première manière, une calibration préalable est effectuée au banc de test du moteur à combustion. Selon cette utilisation, les temps d'imposition du champ magnétique en fonction de conditions de fonctionnement du moteur sont cartographiés . Cette cartographie modifie directement la valeur du taux de compression. Toutefois, cette cartographie n'est pas ajustable dynamiquement. Ainsi, on ne peut pas palier des problèmes de dispersion de taux nominaux habituellement constatés sur des moteurs produits en grande série. En effet, la cartographie enregistrée sur le banc de test du moteur ne permet pas d'obtenir des taux de compression précis, mais est conçue plutôt pour obtenir des variations du taux de compression préalablement déterminées.The device for varying the compression ratio of a cylinder of an internal combustion engine described above can be used in different ways. In a first way, a preliminary calibration is performed on the test bench of the combustion engine. According to this use, the imposition times of the magnetic field as a function of engine operating conditions are mapped. This map directly modifies the value of the compression ratio. However, this mapping is not dynamically adjustable. Thus, we can not solve the problems of dispersion of nominal rates usually found on engines mass produced. Indeed, the mapping recorded on the test bench of the engine does not allow to obtain precise compression rates, but is designed rather to obtain compression rate variations previously determined.
Selon une seconde manière d'utiliser le dispositif de l'invention, on ajoute au dispositif de l'invention un dispositif d'asservissement et de contrôle dynamique relié à un ensemble de capteurs et permettant de calculer le taux de compression en continu. Le dispositif de variation selon l'invention s'adapte à la fois à la dispersion de fabrication des moteurs à combustion interne et aux sollicitations du conducteur en fonction des conditions d'utilisation du véhicule propulsé par le moteur à combustion interne pourvu d'un dispositif de 1 ' invention. According to a second way of using the device of the invention, there is added to the device of the invention a control device and dynamic control connected to a set of sensors and to calculate the compression ratio continuously. The variation device according to the invention adapts to both the manufacturing dispersion of the internal combustion engines and to the demands of the driver as a function of the conditions of use of the vehicle propelled by the internal combustion engine provided with a device of the invention.

Claims

REVEND ICATIONS
1. Dispositif de variation du taux de compression d'un cylindre (2) d'un moteur à combustion interne (1) , le cylindre (2) comportant un piston (3) qui est monté axialement coulissant à l'intérieur du cylindre et est relié à un vilebrequin du moteur au moyen d'une bielle (6), caractérisé en ce que le piston (3) comprend une enveloppe cylindrique creuse (31) ouverte vers la bielle (6) et comporte, à l'intérieur de l'enveloppe creuseA device for varying the compression ratio of a cylinder (2) of an internal combustion engine (1), the cylinder (2) having a piston (3) which is axially slidably mounted inside the cylinder and is connected to a crankshaft of the engine by means of a connecting rod (6), characterized in that the piston (3) comprises a hollow cylindrical envelope (31) open towards the rod (6) and comprises, inside the hollow envelope
(31) , un piston interne (5) monté axialement coulissant par rapport à l'enveloppe creuse (31), une cloison mobile(31), an inner piston (5) axially slidably mounted relative to the hollow envelope (31), a movable partition
(4) disposée entre le piston interne (5) et le fond de l'enveloppe creuse (31), ainsi qu'une grille (32) solidaire de l'enveloppe cylindrique creuse (31) et disposée entre le piston interne (5) et la cloison mobile (4) , la grille (32) divisant un volume constant délimité entre la cloison mobile (4) et le piston interne (5) en deux volumes partiels (A, B) remplis d'un fluide magnéto- rhéologique destiné à être soumis à un champ magnétique (7) variable pour faire varier sa viscosité de manière contrôlée .(4) disposed between the inner piston (5) and the bottom of the hollow envelope (31), and a grid (32) integral with the hollow cylindrical envelope (31) and disposed between the inner piston (5) and the movable partition (4), the grid (32) dividing a constant volume delimited between the movable partition (4) and the internal piston (5) in two partial volumes (A, B) filled with a magnetorheological fluid for to be subjected to a variable magnetic field (7) to vary its viscosity in a controlled manner.
2. Dispositif de variation selon la revendication 1, caractérisé en ce que le fluide magnéto-rhéologique présente une gamme de viscosités comprise entre une faible viscosité permettant au fluide de passer sans difficulté d'un volume partiel (A ou B) à l'autre (B ou A) et une très forte viscosité empêchant le fluide de passer d'un volume partiel (A ou B) à l'autre (B ou A) . 2. Variation device according to claim 1, characterized in that the magneto-rheological fluid has a range of viscosities between a low viscosity allowing the fluid to pass without difficulty from a partial volume (A or B) to the other (B or A) and a very high viscosity preventing the fluid from passing from one partial volume (A or B) to the other (B or A).
3. Dispositif de variation selon la revendication 1 ou 2, caractérisé en ce que le mouvement de la cloison mobile (4) et du piston interne (5), mouvement nécessairement commun pour assurer le volume constant délimité entre la cloison mobile (4) et le piston interne (5), est limité à l'intérieur de l'enveloppe cylindrique creuse (31) par des butées (33) . 3. Variation device according to claim 1 or 2, characterized in that the movement of the movable partition (4) and the inner piston (5), movement necessarily common to ensure the constant volume delimited between the movable partition (4) and the internal piston (5) is limited inside the hollow cylindrical casing (31) by abutments (33).
4. Dispositif de variation selon la revendication 3, caractérisé en ce que les butées (33) sont réalisées sous la forme d'une butée annulaire.4. Variation device according to claim 3, characterized in that the stops (33) are formed in the form of an annular abutment.
5. Dispositif de variation selon la revendication 3 ou 4, caractérisé en ce qu'il comprend des ressorts (34,5. Variation device according to claim 3 or 4, characterized in that it comprises springs (34,
35) dont un ou plusieurs ressorts (34) sont disposés entre le fond de l'enveloppe cylindrique creuse (31) et la cloison mobile (4) et dont le ou les autres ressorts (35) sont disposés entre le piston interne (5) et les butées (33) .35) of which one or more springs (34) are arranged between the bottom of the hollow cylindrical casing (31) and the movable partition (4) and whose other spring or springs (35) are arranged between the internal piston (5) and the stops (33).
6. Dispositif de variation selon la revendication 5, caractérisé en ce que les ressorts (34, 35) sont des ressorts hélicoïdaux.6. Variation device according to claim 5, characterized in that the springs (34, 35) are helical springs.
7. Dispositif de variation selon l'une quelconque des revendications 1 à 6, caractérisé en ce qu'il comprend un bobinage (7) incorporé dans la chemise du cylindre (2) .7. Variation device according to any one of claims 1 to 6, characterized in that it comprises a coil (7) incorporated in the cylinder liner (2).
8. Moteur à combustion interne, caractérisé en ce qu'il comprend un dispositif de variation selon l'une quelconque des revendications 1 à 7. 8. Internal combustion engine, characterized in that it comprises a variation device according to any one of claims 1 to 7.
EP06808316A 2005-09-13 2006-09-12 Device for varying compression ratio of an internal combustion engine cylinder and internal combustion engine comprising same Withdrawn EP1934444A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0509336A FR2890693B1 (en) 2005-09-13 2005-09-13 DEVICE FOR VARYING THE COMPRESSION RATE OF A CYLINDER OF AN INTERNAL COMBUSTION ENGINE AND INTERNAL COMBUSTION ENGINE COMPRISING SUCH A DEVICE
PCT/FR2006/050878 WO2007031686A1 (en) 2005-09-13 2006-09-12 Device for varying compression ratio of an internal combustion engine cylinder and internal combustion engine comprising same

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EP1934444A1 true EP1934444A1 (en) 2008-06-25

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DE102007040699A1 (en) * 2007-08-29 2009-03-05 Robert Bosch Gmbh Reciprocating-piston internal combustion engine e.g. petrol engine, for use in e.g. passenger car, has magnetic field generating device generating variable magnetic field which appears at actuator so that compression ratio is adjusted
FR3044043A1 (en) * 2015-11-25 2017-05-26 Valeo Systemes De Controle Moteur COMPRESSION RATE CONTROL SYSTEM FOR A COMBUSTION ENGINE

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FR1217378A (en) * 1959-02-19 1960-05-03 Elastic piston for internal combustion engine or other
DE19858245A1 (en) * 1998-12-17 2000-06-21 Bayerische Motoren Werke Ag Piston with variable compression magnitude for piston machine, especially IC engine, has rheological fluid of constant amount supplied in communicating chamber system provided in piston, system comprising control and storage chambers
US6394048B1 (en) * 2001-01-16 2002-05-28 Ford Global Technologies, Inc. Variable compression ratio internal combustion engine using field-sensitive fluid

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