FR3132747A1 - Multi-temperature double-acting piston - Google Patents

Abstract

MULTI-TEMPERATURE DOUBLE-ACTING PISTON The multi-temperature double-acting piston (201) comprises a peripheral sealing ring (220), a lower hot cap (226) and/or an upper hot cap (232), and translates into a cold cylinder ( 204) of a thermal engine (202) which comprises a lower cylinder head (213) and an upper cylinder head (214), said piston (201) comprising a central piston pin (210) whose lower piston rod (211) passes through the lower cylinder head (213) to be connected to power transmission means (205) housed in a transmission casing (206), and the upper piston rod (212) of which passes through the upper cylinder head (214) to open into a piston cooling and lubrication chamber (217), a lubrication-cooling gallery (227) arranged in said spindle (210) communicating said chamber (217) with said housing (206) via an internal piston volume (228 ). Figure for abstract: Fig. 3

Description

Double-acting multi-temperature piston

The present invention relates to a multi-temperature double-acting piston, said piston being particularly suitable for reciprocating engines implementing the Brayton thermodynamic cycle with regeneration with pistons rather than with centrifugal compressors and turbines.

Regenerative Brayton cycle engines generally comprise separate organs dedicated to each of the phases of said cycle, said phases taking place continuously and simultaneously in said organs unlike reciprocating internal combustion engines with Beau de Rochas cycle, Miller cycle, etc. 'Atkinson or Diesel whose phases are executed successively in a single cylinder.

Consequently, regenerative Brayton cycle engines comprise at least one compressor, at least one regeneration exchanger, at least one burner operating continuously or an internal or external hot source, and at least one expander,

Entrusting each phase of a thermodynamic cycle to a dedicated body has various advantages. In particular, the temperature of the internal walls of each said organ can remain very close to that of the gases during said phase.

For example, the temperature of the internal walls of the compressor of a regenerative Brayton cycle engine can be kept as low as possible, which helps to minimize the compression work and maximize the total thermodynamic efficiency of said engine.

Conversely, the internal walls of the regulator of said engine being in contact with the hot gases coming from the burner, their temperature must be high and in all cases, maintained as close as possible to the average temperature of said gases between the start and the end. end of their relaxation.

Despite these advantages, the maximum thermodynamic efficiency of engines with centrifugal compressors and regenerative Brayton cycle turbines is in practice hardly higher than that of conventional spark ignition engines, and at best, comparable to that of fast diesel engines.

In all cases, said efficiency remains lower than that of slow two-stroke diesel engines of several tens of megawatts used for example for naval propulsion or stationary electricity production.

In addition, engines with centrifugal compressors and regenerative Brayton cycle turbines are poorly suited to low powers, and can only operate over a restricted power range outside of which their efficiency drops drastically.

This is why engines with centrifugal compressors and regenerative Brayton cycle turbines are mainly used for applications where efficiency is not the sole objective, and which require, for example, high specific and volume power, of low acoustic and vibration emissions, long life, or reduced maintenance.

This is the case, for example, of certain military ships equipped, for example, with the “Rolls-Royce WR-21” centrifugal compressor and regenerative Brayton cycle turbine engine, whose efficiency hardly exceeds forty percent, however that of the slow two-stroke diesel engines that equip some ships exceed fifty percent.

This is also the case for certain generators most often operating in cogeneration of electricity and heat such as the “T100” micro turbine from the “Turbec” company, or the “C65” micro turbine from the “Capstone” company. whose electrical efficiencies are of the order of only twenty-eight to thirty percent, but which require little maintenance while offering very long lifespans.

The advantage of these turboshaft engines is that their turbine can withstand temperatures of around one thousand three hundred degrees Celsius. However, their total thermodynamic efficiency remains limited by that of the centrifugal compressors and the turbines which constitute them, the efficiency of said compressors and said turbines hardly exceeding eighty percent over a relatively narrow operating range.

Taking into account the above, it would be particularly interesting to be able to replace the centrifugal compressors and turbines of regenerative Brayton cycle engines with positive displacement piston machines whose efficiency is significantly higher.

This is for example the subject of patent No. US4653269 of March 31, 1987, where the expansion turbine usually found on regenerative Brayton cycle turboshaft engines is replaced by a volumetric piston expansion cylinder.

However, the calculations demonstrate that if the internal walls of said volumetric expander are cooled and maintained for example around one hundred degrees Celsius like the reciprocating engines produced and marketed on a large scale, the thermodynamic efficiency of a Brayton cycle engine at regeneration cannot exceed that of an automobile Diesel engine.

For a regenerated Brayton cycle engine with a volumetric expander to deliver very high thermodynamic efficiencies, it is essential that the internal walls of its expander are maintained at a temperature close to the average temperature of the gases expanded in said expander.

For example, if the hot gases are introduced into the regulator at a temperature of one thousand three hundred degrees Celsius and are expelled from said regulator at the end of expansion at a temperature of six hundred degrees Celsius, the internal walls of said regulator must be maintained approximately at a temperature of nine hundred and fifty degrees Celsius.

The problem is that at such a temperature, it is impossible to keep a film of oil on the walls of the regulator cylinder to lubricate whatever sealing ring a regulator piston may have moving in said cylinder.

Indeed, from around one hundred and sixty degrees Celsius, the oil film on the cylinder begins to coking, then burns above two hundred and fifty degrees Celsius.

Producing a regenerative Brayton cycle engine with high thermodynamic efficiency therefore faces a double impasse.

Indeed, either said engine is made up of centrifugal compressors and turbines resistant to high temperatures, but in this case, the modest efficiency of these organs does not allow it to exceed a total efficiency equivalent to that of an automobile Diesel, or it consists of a volumetric piston expander which, to be watertight, requires a piston fitted with a segmentation sliding on an oil film formed on the surface of a cylinder, the latter having to remain at a temperature not exceeding not around one hundred and twenty degrees Celsius, which also does not allow the total efficiency of said engine to be competitive.

In this context, it would be advantageous to be able to combine the ability of turbines to operate at high temperatures with that of volumetric piston machines to expand gases at high efficiency.

It is with this objective that the heat engine with transfer-expansion and regeneration according to patent WO2016120560 published on August 4, 2016 and belonging to the applicant comprises non-contact piston sealing means consisting of a continuous perforated inflatable ring which, when 'it is subjected to a certain internal pressure, inflates and approaches a few micrometers from the regulator cylinder with which it cooperates without touching said cylinder, this while letting compressed air leak via calibrated orifices which pass through it on both sides part in its radial thickness.

The fluid cushion sealing device which has just been described was also the subject of patent No. FR 3032252 issued on May 25, 2018 and belonging to the applicant. This device makes it possible to achieve contactless sealing and therefore to no longer use oil to lubricate a segment operating by contact, and therefore to cooperate with a hot regulator cylinder, maintained at a temperature of several hundred degrees. Celsius.

In this context, it therefore effectively becomes possible to use a piston volumetric expander to produce a regenerative Brayton cycle engine, and to maximize the efficiency of said engine to largely surpass that of Diesel cycle engines.

Indeed, calculations and simulations demonstrate that the thermodynamic efficiency of a Brayton cycle engine with piston volumetric regeneration can reach or even exceed seventy percent, which in practice can lead to the production of engines whose energy efficiency to the brake exceeds sixty percent once the inevitable thermal and mechanical irreversibilities due to the very constitution of said motors are deducted.

The problem encountered with the fluid cushion sealing device of patent No. FR 3032252 is that the temperature of the cylinder still remains excessive for the available materials of which the continuous perforated ring can be made.

Indeed, for the efficiency of a Brayton cycle engine with volumetric regeneration with pistons to be significantly higher than that of existing Diesel engines, the gases must be introduced into its expander at a temperature of the order of one thousand three hundred degrees Celsius, under a pressure of around twenty bars.

As a result of these operational conditions, the temperature of the internal walls of the regulator stabilizes around nine hundred and fifty degrees Celsius.

Given that the continuous perforated ring according to patent No. FR 3032252 is close to the cylinder with which it cooperates by only a few microns, in practice, said ring adopts the temperature of approximately nine hundred and fifty degrees Celsius of said cylinder.

However, no material can both make it possible to manufacture said ring and withstand such a temperature.

Even a superalloy such as "Udimet 720", particularly used in aeronautics and the space industry and known for its resistance to extreme temperatures, cannot withstand such a temperature without being subject to creep and while being subject to the swelling stress that requires the continuous perforated ring of the fluid cushion sealing device according to patent No. FR 3032252.

It is in particular for this reason and to use more common materials than ceramics resistant to high temperatures, that the regenerative cooling system according to patent No. EP 3585993 published on April 7, 2021 and belonging to the applicant plans to lower the temperature of the internal walls of the regulator and in particular of the cylinder to practical values of the order of seven hundred degrees Celsius.

For example, the “Udimet 720” superalloy resists creep at a temperature of seven hundred degrees Celsius if it is subjected to a stress not exceeding two hundred and thirty mega Pascals.

The regenerative cooling system according to patent No. EP 3585993 provides a cooling enclosure which envelops the expander while a gas circulation space is left between said enclosure and said expander in which the gases leaving the expander itself circulate at a temperature between five hundred and six hundred degrees Celsius.

Thus, according to the regenerative cooling system according to patent No. EP 3585993, the exhaust gases from the regulator maintain the temperature of the internal walls of the regulator at a temperature of the order of seven hundred degrees Celsius while the heat exported by said gas is essentially recovered to be reintroduced into the cycle by the regeneration heat exchanger which comprises the reciprocating regenerative Brayton cycle piston engine.

In this context, the fluid cushion sealing device of patent No. FR 3032252 can be used with a continuous perforated ring, for example made of “Udimet 720” superalloy.

However, in return for this possibility, the cylinder and heads of the regenerative Brayton cycle piston reciprocating engine must be made of materials with a high nickel content such as "Niresist" cast iron which, due to the high volatility and of the high price of nickel, represents an economic disadvantage.

In all cases, we note that the temperature of the regulator remains at least six hundred degrees Celsius higher than that of the rest of the engine and in particular, of the mobile coupling and the transmission casing in which said coupling is housed.

Advantageously, the differential expansions which result from this temperature difference can in particular be managed by the double-acting expansion cylinder with adaptive support which is the subject of patent No. EP3350433 issued on August 7, 2019 and belonging to the applicant.

Said support allows an isotropic or anisotropic expansion of the expansion cylinder which is very different from that of the transmission casing on which it is fixed, this without compromising either the operation of said cylinder, nor that of the piston which evolves in said cylinder.

Said support further keeps the piston centered in the cylinder, transmits the axial forces resulting from the expansion of the gases to the transmission casing, and limits heat transfer from the expander cylinder to said casing.

On reading the above, we understand that no configuration is at this stage fully satisfactory which makes it possible to produce in the best possible conditions a reciprocating piston engine with a regenerative Brayton cycle.

Indeed, the fluid cushion sealing device must be supplied with compressed air by a compressor which consumes part of the work available on the shaft of the regenerative Brayton cycle piston engine, to the detriment of the total efficiency of this last.

This in fact reduces the final energy efficiency of said motor, and all the more so if the latter operates at low power because the quantity of compressed air to be supplied to the fluid cushion sealing device is almost constant, whatever the speed and load of said engine.

Furthermore, to guarantee long-term operation of the fluid cushion sealing device, it is necessary to use the regenerative cooling system according to patent No. EP 3585993, however, said system is not energy neutral.

In fact, said cooling system makes the path of the gases expelled from the expander tortuous and induces pressure losses which reduce the total efficiency of the regenerative Brayton cycle piston engine.

In addition, the heat extracted from the internal walls of the expander by the regenerative cooling system is reintroduced into the Brayton cycle upstream of a burner or a hot source by a regeneration heat exchanger whose efficiency is not one hundred percent.

Part of the heat extracted from the internal walls of the expander is therefore lost, and the power passing through the exchanger increases due to the presence of said cooling system.

In addition, the specific power of the regenerative Brayton cycle piston engine is significantly reduced by the regenerative cooling system according to patent No. EP 3585993, which involves revising upwards the dimensioning of said engine to meet the objectives. power of the application for which it is intended.

We also note that the development of the fluid cushion sealing device of patent No. FR 3032252 remains complex, particularly to ensure its proper functioning in the context of non-stationary applications subject to shock and vibration.

This is why, without excluding any other application in any field whatsoever, the reciprocating thermal engine with hot cylinder head and cold cylinder according to the invention is, among other things, intended to produce reciprocating Brayton cycle piston engines with regeneration whose mainly hot regulator limits thermal losses, while ensuring a robust and durable seal between the piston and the cylinder of said regulator.

• Dont les calottes de piston sont maintenues à haute température de sorte à limiter le refroidissement des gaz chauds à leur contact ;
• Dont l’étanchéité avec le cylindre avec lequel il coopère peut être réalisée au moyen de segments en fonte ou en acier tels que ceux que comprennent les moteurs à combustion interne conventionnels à allumage commandé ou à cycle de Diesel ;
• Qui ne recourt plus au dispositif d’étanchéité à coussin de fluide objet du brevet N° FR 3032252 et donc, qui ne requiert plus que le moteur qui le reçoit soit doté du système de refroidissement régénératif tel que celui que décrit le brevet N° EP 3585993, ledit moteur ne subissant donc plus ni les pertes de puissance et de rendement liées à l’emploi d’un compresseur d’alimentation dudit dispositif d’étanchéité, ni les pertes de charges additionnelles à l’échappement du détendeur liées à un parcours des gaz plus tortueux, ni les pertes de chaleur dues au rendement inférieur à « un » de l’échangeur thermique de régénération, ni les pertes en puissance spécifique du moteur associées à cette configuration.

In the field of application of reciprocating piston thermal machines in general and thermal engines in particular, the invention results in a multi-temperature double-acting piston:

• Whose piston caps are maintained at a high temperature so as to limit the cooling of the hot gases in contact with them;
• Whose seal with the cylinder with which it cooperates can be achieved by means of cast iron or steel segments such as those included in conventional internal combustion engines with spark ignition or Diesel cycle;
• Which no longer uses the fluid cushion sealing device covered by patent No. FR 3032252 and therefore, which no longer requires the engine which receives it to be equipped with a regenerative cooling system such as that described in patent No. EP 3585993, said engine therefore no longer suffering either the power and efficiency losses linked to the use of a supply compressor of said sealing device, nor the additional pressure losses at the exhaust of the regulator linked to a path more tortuous gases, nor the heat losses due to the efficiency less than “one” of the regeneration heat exchanger, nor the specific power losses of the engine associated with this configuration.

Consequently, the multi-temperature double-acting piston according to the invention makes it possible to prevent the engine which houses it from being manufactured with materials with a high nickel content such as “Niresist” cast iron, the cylinder of said engine being able to be made of low-cost cast iron such as that ordinarily used to make the cylinder casings of automobile Diesel engines, and said engine may include hot cylinder heads operating at high temperatures made of silicon carbide, a material with high mechanical resistance at high temperatures, abundant and cheap.

As an advantage induced by the multi-temperature double-acting piston according to the invention, the lower density of the silicon carbide which it allows the use to produce the hot cylinder heads of the engine which houses it on the one hand, and the absence of a regenerative cooling system on the other hand, lead to a lower weight and a lower total heat capacity of said engine.

This promotes a rapid rise in temperature of said engine by reducing the energy necessary to reach its operating temperature, and leads to lower energy consumption of said engine particularly when the latter applies to road, rail, or maritime.

It is understood that the multi-temperature double-acting piston according to the invention can be applied, in addition to generally stationary or mobile heat engines and internal or external combustion, to any other application similar in its concept and in its principle which could advantageously take advantage of the particular characteristics and functionalities of said piston according to the invention.

The other features of the present invention have been described in the description and in the secondary claims directly or indirectly dependent on the main claim.

• Une broche centrale de piston approximativement coaxiale au cylindre froid et dont une première extrémité forme une tige inférieure de piston qui traverse de part en part la culasse inférieure via un orifice de tige inférieure qui coopère avec des moyens d’étanchéité de tige inférieure pour déboucher dans le carter de transmission et pour être directement ou indirectement reliée aux moyens de transmission de puissance par des moyens de fixation de piston, tandis que la deuxième extrémité de ladite broche forme une tige supérieure de piston qui traverse de part en part la culasse supérieure via un orifice de tige supérieure qui coopère avec des moyens d’étanchéité de tige supérieure pour déboucher dans une chambre de refroidissement et de lubrification de piston reliée à une source de fluide lubrifiant-refroidissant, cette dernière introduisant un fluide lubrifiant-refroidissant dans ladite chambre ;
• Un anneau périphérique d’étanchéité dont le diamètre extérieur est sensiblement inférieur au diamètre intérieur du cylindre froid, ledit anneau comportant des moyens d’étanchéité de piston qui sont en contact avec ledit cylindre pour réaliser avec ce dernier une étanchéité ;
• Un disque de liaison radiale inférieure qui relie radialement la broche centrale de piston avec l’anneau périphérique d’étanchéité du côté de la chambre de volume variable inférieure, et un disque de liaison radiale supérieure qui relie radialement la broche centrale de piston avec l’anneau périphérique d’étanchéité du côté de la chambre de volume variable supérieure, l’espace laissé entre lesdits disques,, l’anneau périphérique d’étanchéité et la broche centrale de piston formant un volume interne de piston ;
• Une galerie de lubrification-refroidissement aménagée principalement axialement dans la broche centrale de piston et en une ou plusieurs sections, ladite galerie mettant en communication d’une part, la chambre de refroidissement et de lubrification de piston avec le volume interne de piston, et d’autre part, ledit volume avec l’intérieur du carter de transmission ;
• Au moins un orifice périphérique de lubrification d’anneau qui met en communication le volume interne de piston avec la face périphérique externe de l’anneau périphérique d’étanchéité, ledit orifice débouchant axialement de ladite face entre au moins deux moyens d’étanchéité de piston ;
• Des moyens de guidage qui prennent directement ou indirectement appui sur ou à proximité des moyens de transmission de puissance et/ou du cylindre froid et/ou de la culasse inférieure et/ou de la culasse supérieure, lesdits moyens conservant directement ou indirectement l’anneau périphérique d’étanchéité centré dans le cylindre froid ;
• Une calotte chaude inférieure interposée entre le disque de liaison radiale inférieure et la chambre de volume variable inférieure et/ou une calotte chaude supérieure interposée entre le disque de liaison radiale supérieure et la chambre de volume variable supérieure ;
• Des moyens de plaquage de calotte qui maintiennent directement ou indirectement la calotte chaude inférieure plaquée sur l’anneau périphérique d’étanchéité et/ou sur le disque de liaison radiale inférieure, et/ou qui maintiennent directement ou indirectement la calotte chaude supérieure plaquée sur ledit anneau et/ou sur le disque de liaison radiale supérieure, lesdits moyens laissant lesdites calottes, libres de se dilater par rapport audit anneau et/ou auxdits disques ;
• Des moyens de centrage de calotte qui localisent la calotte chaude inférieure et/ou la calotte chaude supérieure par rapport à l’anneau périphérique d’étanchéité.

The multi-temperature double-acting piston can translate in a cold cylinder arranged in a cooled cylinder block which comprises a heat engine, said piston being directly or indirectly connected by power transmission means housed in a transmission casing to at least one shaft rotary or reciprocating power output while said piston forms a lower variable volume chamber with the cold cylinder and a lower cylinder head which is positioned between said piston and the transmission housing, said piston simultaneously forming an upper variable volume chamber with said cylinder and an upper cylinder head, said chambers, containing a working gas, comprises

• A central piston pin approximately coaxial with the cold cylinder and a first end of which forms a lower piston rod which passes right through the lower cylinder head via a lower rod orifice which cooperates with lower rod sealing means to open into the transmission casing and to be directly or indirectly connected to the power transmission means by piston fixing means, while the second end of said pin forms an upper piston rod which passes right through the upper cylinder head via a upper rod orifice which cooperates with upper rod sealing means to open into a piston cooling and lubrication chamber connected to a source of lubricating-cooling fluid, the latter introducing a lubricating-cooling fluid into said chamber;
• A peripheral sealing ring whose external diameter is substantially less than the internal diameter of the cold cylinder, said ring comprising piston sealing means which are in contact with said cylinder to achieve sealing with the latter;
• A lower radial connection disk which radially connects the central piston pin with the peripheral sealing ring on the lower variable volume chamber side, and an upper radial connection disk which radially connects the central piston pin with the peripheral sealing ring on the side of the upper variable volume chamber, the space left between said discs, the peripheral sealing ring and the central piston pin forming an internal piston volume;
• A lubrication-cooling gallery arranged mainly axially in the central piston pin and in one or more sections, said gallery connecting on the one hand, the piston cooling and lubrication chamber with the internal volume of the piston, and on the other hand, said volume with the interior of the transmission casing;
• At least one peripheral ring lubrication orifice which places the internal volume of the piston in communication with the external peripheral face of the peripheral sealing ring, said orifice opening axially from said face between at least two piston sealing means ;
• Guiding means which directly or indirectly bear on or near the power transmission means and/or the cold cylinder and/or the lower cylinder head and/or the upper cylinder head, said means directly or indirectly retaining the ring sealing device centered in the cold cylinder;
• A lower hot cap interposed between the lower radial connection disc and the lower variable volume chamber and/or an upper hot cap interposed between the upper radial connection disc and the upper variable volume chamber;
• Cap plating means which directly or indirectly maintain the lower hot cap pressed on the peripheral sealing ring and/or on the lower radial connection disc, and/or which directly or indirectly maintain the upper hot cap pressed on said ring and/or on the upper radial connection disc, said means leaving said caps free to expand relative to said ring and/or said discs;
• Cap centering means which locate the lower hot cap and/or the upper hot cap relative to the peripheral sealing ring.

The multi-temperature double-acting piston according to the invention comprises a lower hot cap and/or an upper hot cap which are entirely or partly made of a material resistant to high temperatures.

The multi-temperature double-acting piston according to the invention comprises a material resistant to high temperatures which is mainly made of silicon carbide.

The multi-temperature double-acting piston according to the invention comprises thermal insulation means and/or cap sealing means which are interposed either between the lower hot cap and the peripheral sealing ring and/or the disc lower radial connection, either, between the upper hot cap and said ring and/or the upper radial connection disc, or both.

The multi-temperature double-acting piston according to the invention comprises thermal insulation means and/or cap sealing means which are interposed either between the lower hot cap and the central piston pin, or between the hot cap upper and said pin, or both.

The multi-temperature double-acting piston according to the invention comprises thermal insulation means which consist of at least one insulating ring made of a material with low thermal conductivity.

The multi-temperature double-acting piston according to the invention comprises a material with low thermal conductivity which consists mainly of zirconium oxide.

The multi-temperature double-acting piston according to the invention comprises an insulating ring which is kept directly or indirectly in contact with the central piston pin and/or the peripheral sealing ring and/or the lower hot cap and/or the disc lower radial connection and/or the upper hot cap and/or the upper radial connection disk via at least one contact edge of small surface area.

The multi-temperature double-acting piston according to the invention comprises an insulating ring which is kept directly or indirectly in contact with the central piston pin and/or the peripheral sealing ring and/or the lower hot cap and/or the disc lower radial connection and/or the upper hot cap and/or the upper radial connection disc via at least one insulating ring seal which is tight to the working gas.

The multi-temperature double-acting piston according to the invention comprises cap-plating means which directly or indirectly maintain the lower hot cap pressed on the peripheral sealing ring and/or on the lower radial connection disc, which are formed of an external coaxial lower spindle tube which envelops the central piston spindle, said tube bearing on the one hand, on the lower hot cap in the vicinity of said spindle, and on the other hand, on the power transmission means.

The multi-temperature double-acting piston according to the invention comprises cap-plating means which directly or indirectly maintain the upper hot cap pressed on the peripheral sealing ring and/or on the upper radial connection disc, which are formed of 'an upper external coaxial spindle tube which envelops the central piston spindle, said tube bearing on the one hand, on the upper hot cap in the vicinity of said spindle, and on the other hand, on an upper rod stop arranged directly or indirectly on the upper piston rod near its end which opens into the piston cooling and lubrication chamber.

The multi-temperature double-acting piston according to the invention comprises some or all of the ends of an external coaxial lower spindle tube and/or an external coaxial upper spindle tube which receive a tube spring via which said tubes respectively support on the lower hot cap and on the power transmission means and/or on the upper hot cap and on the upper rod stop.

The multi-temperature double-acting piston according to the invention comprises a lower hot cap and/or an upper hot cap which has a concave conical cap surface via which said cap is kept pressed by the cap plating means on a circular edge of peripheral contact which is directly or indirectly secured to the peripheral sealing ring and/or to the periphery of the lower radial connection disc and/or to the periphery of the upper radial connection disc, the angle of the concave cone that said surface forms being such that when said surface slides on said edge due to the difference between the thermal expansion of said cap and that of the assembly formed by the peripheral sealing ring, the lower radial connection disc, the upper radial connection disc and the central piston pin, the axial distance which separates the point of support of the cap plating means on said cap from the peripheral sealing ring remains approximately constant all other things being equal, however that the concave conical surface of the cap and the circular peripheral contact edge form the cap centering means.

The multi-temperature double-acting piston according to the invention comprises piston fixing means which consist of an axial double-acting piston screw which firstly comprises a piston screw body which is housed in a screw tunnel piston which passes right through the central piston pin in the direction of its length, said screw comprising on the one hand, a piston screw head which bears on the end of the upper piston rod which opens into the piston cooling and lubrication chamber, and on the other hand, a piston screw thread which is screwed into the power transmission means.

The multi-temperature double-acting piston according to the invention comprises a piston screw tunnel which forms at least part of the lubrication-cooling gallery, the lubricating-cooling fluid being able to circulate between the piston screw body and the internal wall of said tunnel, the latter forming with said body a first section which goes from the piston cooling and lubrication chamber to the internal piston volume, and a second section which goes from said volume to the interior of the transmission casing.

The multi-temperature double-acting piston according to the invention comprises guide means which consist of a barrel skirt which is arranged on the external periphery of the peripheral sealing ring and which is supported on the cold cylinder.

The multi-temperature double-acting piston according to the invention comprises a lubrication-cooling gallery which opens into the internal volume of the piston via a small axial clearance left between, on the one hand, a fluid distribution disk which is housed in said volume and on the other hand, the upper radial connection disk, said distribution disk being approximately parallel to said radial connection disk and forming on the one hand, a seal with the central piston pin, and on the other hand ending, radially in the vicinity of the internal wall of the peripheral sealing ring, the lubricating-cooling fluid coming from the piston cooling and lubrication chamber being able to exit at said vicinity.

The multi-temperature double-acting piston according to the invention comprises a central piston pin which comprises, inside the internal volume of the piston and in the vicinity of the lower radial connection disc, a fluid recirculation flange which, when the central pin piston moves towards the lower cylinder head, rejects radially and towards the internal wall of the peripheral sealing ring the lubricating-cooling fluid which has accumulated in said volume and on the surface of said disc.

The multi-temperature double-acting piston according to the invention comprises a lower radial connection disk which has a hollow shape at the level of its connection with the central piston pin, said shape constituting an overflow reservoir which can store lubricating fluid -cooling, while at least one overflow port which communicates with the interior of the transmission casing via the lubrication-cooling gallery sets the maximum level of said tank.

The multi-temperature double-acting piston according to the invention comprises a fluid nozzle supplied by the source of lubricating-cooling fluid which opens into the piston cooling and lubrication chamber to inject a jet of fluid there.

The multi-temperature double-acting piston according to the invention comprises a fluid nozzle which injects a jet of lubricating-cooling fluid into an axial screw reservoir which is arranged axially in the piston screw head, said reservoir communicating with the lubrication gallery -cooling via at least one radial tank-gallery connection conduit.

The double-acting multi-temperature piston according to the invention comprises a screw non-return valve which is housed in the axial screw of the double-acting piston, said valve allowing the lubricating-cooling fluid to go from the axial screw reservoir towards the gallery of lubrication-cooling, but not vice versa.

The multi-temperature double-acting piston according to the invention comprises a piston cooling and lubrication chamber which is connected to an air source by an air intake check valve which lets in fluid forcing air in said chamber without letting it come out, while said chamber is connected to an air tank by a pressure relief valve which lets the fluid forcing air go from said chamber to said tank when the pressure of said air in said chamber reaches a certain value.

The description which follows with reference to the appended drawings and given as non-limiting examples will allow a better understanding of the invention, the characteristics it presents, and the advantages it is likely to provide:

is a three-dimensional view of a heat engine such as it can be designed to receive the multi-temperature double-acting piston according to the invention, said engine forming a regulator which allows, for example, to implement a thermodynamic cycle from Baritone to regeneration.

is a three-dimensional sectional view of the multi-temperature double-acting piston according to the invention, housed in the heat engine shown in , said engine also being represented in three-dimensional section.

is a sectional view of the multi-temperature double-acting piston according to the invention, housed in the heat engine shown in , said engine also being shown in section.

is a three-dimensional sectional view of the multi-temperature double-acting piston according to the invention, said piston being connected to the power transmission means by an axial screw of the double-acting piston while the cap-plating means are in particular made up of a outer coaxial lower pin tube and an outer coaxial upper pin tube.

is an exploded three-dimensional view of the multi-temperature double-acting piston according to the invention and according to its particular configuration shown in Figures 2 to 5.

is a close-up sectional view of the multi-temperature double-acting piston according to the invention placed in the context of the engine shown in , said view notably highlighting how said piston is connected to the power transmission means, and how the lower hot cap is kept pressed against the peripheral sealing ring by an external coaxial lower spindle tube via insulating rings.

is a close-up sectional view of the multi-temperature double-acting piston according to the invention placed in the context of the engine shown in , said view showing in particular how the upper piston rod opens into the piston cooling and lubrication chamber, and how the upper hot cap is kept pressed against the peripheral sealing ring by an upper external coaxial spindle tube via insulating rings.

is a sectional view of the multi-temperature double-acting piston according to the invention as shown in Figures 2 to 7, said view showing how a lubricating-cooling fluid can circulate from an axial screw reservoir to the interior of the housing. transmission to successively cool the upper radial connection disk, the peripheral sealing ring and the lower radial connection disk, this while cooling and lubricating the piston sealing means and the barrel skirt presented by said ring, said means and said skirt being maintained in contact with the cold cylinder.

is a sectional view of the multi-temperature double-acting piston according to the invention as shown in , said view showing in particular how the lubricating-cooling fluid can recirculate inside the internal volume of the piston to complete the cooling of the mechanically welded assembly formed by the peripheral sealing ring, the lower radial connection disk, the upper radial connection disc and the central piston pin, and to supply peripheral ring lubrication orifices that the peripheral sealing ring has.

is a close schematic sectional view of the multi-temperature double-acting piston according to the invention and according to the particular configuration of said piston as shown in Figures 2 to 9, said view showing the position and dimensions of the lower and upper hot caps relative to the mechanically welded assembly and the insulating ring when said caps are cold.

is a close schematic sectional view of the multi-temperature double-acting piston according to the invention and according to the particular configuration of said piston as shown in Figures 2 to 9, said view showing the position and dimensions of the lower and upper hot caps relative to the mechanically welded assembly and the insulating ring when said caps are hot.

is a three-dimensional view framed on the piston cooling and lubrication chamber of the multi-temperature double-acting piston according to the invention, said view showing in particular the air intake non-return valve and the pressure limiting valve which are all two connected inside the transmission case which here acts as an air source and air cover.

DESCRIPTION OF THE INVENTION:

We have shown in Figures 1 to 12 the multi-temperature double-acting piston 201 according to the invention, various details of its components, its variants, and its accessories.

As shown in Figures 2, 3, 6 and 7, the multi-temperature double-acting piston 201 can translate in a cold cylinder 204 arranged in a cooled cylinder block 203 which comprises a heat engine 202, said piston 201 being directly or indirectly connected by power transmission means 205 housed in a transmission casing 206 to at least one rotary or reciprocating power output shaft 207.

As can be clearly seen in , said piston 201 forms a lower variable volume chamber 208 with the cold cylinder 204 and a lower cylinder head 213 which is positioned between said piston 201 and the transmission casing 206, said piston 201 simultaneously forming an upper variable volume chamber 209 with said cylinder 204 and an upper cylinder head 214, said chambers 208, 209 containing a working gas 240.

As illustrated in Figures 2 to 5 and in Figures 8 and 9, the multi-temperature double-acting piston 201 according to the invention comprises a central piston pin 210 approximately coaxial with the cold cylinder 204 and a first end of which forms a lower piston rod 211 which passes right through the lower cylinder head 213 via a lower rod orifice 215 which cooperates with lower rod sealing means 280 to open into the transmission casing 206 and to be directly or indirectly connected to the power transmission means 205 by piston fixing means 231.

The second end of said pin 210 forms an upper piston rod 212 which passes right through the upper cylinder head 214 via an upper rod orifice 216 which cooperates with upper rod sealing means 281 to open into a piston cooling and lubrication chamber 217 connected to a source of lubricating-cooling fluid 218, the latter introducing a lubricating-cooling fluid 257 into said chamber 217.

We note in Figures 2 to 11 that the multi-temperature double-acting piston 201 according to the invention comprises a peripheral sealing ring 220 whose external diameter is substantially less than the internal diameter of the cold cylinder 204.

It can be seen in said figures that the peripheral sealing ring 220 comprises piston sealing means 221, for example consisting of compression segments 222 made of cast iron or steel such as those ordinarily found on the pistons of conventional automobile engines, said means 221 being in contact with said cylinder 204 to achieve sealing with the latter.

We see very clearly in that the multi-temperature double-acting piston 201 according to the invention also comprises a lower radial connection disk 224 which radially connects the central piston pin 210 with the peripheral sealing ring 220 on the side of the lower variable volume chamber 208, and an upper radial connection disk 225 which radially connects the central piston pin 210 with the peripheral sealing ring 220 on the side of the upper variable volume chamber 209, the space left between said disks 224, 225, the peripheral sealing ring 220 and the central piston pin 210 forming an internal piston volume 228.

It will be noted that the lower radial connection disk 224 and/or the upper radial connection disk 225 can be a simple metal disk, a cone, a dome or a truncosphere, or be of any geometry whether non-ribbed or ribbed for give said discs 224, 225 great rigidity.

Note also that as an alternative embodiment of the multi-temperature double-acting piston 201 according to the invention, the lower radial connection disk 224 can be connected inside the internal piston volume 228 to the upper radial connection disk 225 by props, spokes, fins or any other mechanical connection which secures said discs 224, 225 so that they constitute a rigid assembly.

It will also be noted that the lower radial connection disk 224 and/or the upper radial connection disk 225 can be preferably made integral with the central piston pin 210 and/or the peripheral sealing ring 220 by friction welding, by electron beam or by arc welding, or not any type of welding or assembly known to those skilled in the art.

We note in Figures 8 and 9 that the multi-temperature double-acting piston 201 according to the invention comprises a lubrication-cooling gallery 227 which is arranged mainly axially in the central piston pin 210 and in one or more sections, said gallery 227 putting in communication on the one hand, the piston cooling and lubrication chamber 217 with the internal piston volume 228, and on the other hand, said volume 228 with the interior of the transmission casing 206.

In Figures 10 and 11, it can be seen very clearly that the multi-temperature double-acting piston 201 according to the invention comprises at least one peripheral ring lubrication orifice 229 which places the internal volume of the piston 228 in communication with the external peripheral face. of the peripheral sealing ring 220, said orifice 229 opening axially from said face between at least two piston sealing means 221.

The multi-temperature double-acting piston 201 according to the invention also comprises guide means 230 which are particularly visible in , said means 230 directly or indirectly bearing on or near the power transmission means 205 and/or the cold cylinder 204 and/or the lower cylinder head 213 and/or the upper cylinder head 214, said means 230 retaining directly or indirectly the peripheral sealing ring 220 centered in the cold cylinder 204.

Particularly in , we note that the multi-temperature double-acting piston 201 according to the invention comprises a lower hot cap 226 interposed between the lower radial connection disc 224 and the lower variable volume chamber 208 and/or an upper hot cap 232 interposed between the disc upper radial connection 225 and the upper variable volume chamber 209;

The multi-temperature double-acting piston 201 according to the invention also comprises cap-plating means 234, all of which appear in Figures 2 to 5 and in Figures 8 and 9, and which directly or indirectly maintain the lower hot cap 226 pressed against the peripheral sealing ring 220 and/or on the lower radial connection disk 224, and/or which directly or indirectly maintain the upper hot cap 232 pressed on said ring 220 and/or on the upper radial connection disk 225, said means 234 leaving said caps 226, 232 free to expand relative to said ring 220 and/or said discs 224, 225.

Finally, the multi-temperature double-acting piston 201 according to the invention comprises cap centering means 235 – for example shown in - which locate the lower hot cap 226 and/or the upper hot cap 232 relative to the peripheral sealing ring 220.

It will be noted that according to an alternative embodiment of the multi-temperature double-acting piston 201 according to the invention, the lower hot cap 226 and/or the upper hot cap 232 can be entirely or partly made up of a material resistant to high temperatures 275 such as silicon carbide 276 and its different variants, alloyed or not with other materials.

As another variant shown in Figures 2 to 11, thermal insulation means 233 and/or cap sealing means 239 can be interposed either, between the lower hot cap 226 and the peripheral sealing ring 220 and/or the lower radial connection disc 224, or between the upper hot cap 232 and said ring 220 and/or the upper radial connection disc 225, or both, said means 233, 239 being able to form an integral part of said caps 226, 232 and/or said disks 224, 225.

In Figures 4 to 9, it has also been shown that thermal insulation means 233 and/or cap sealing means 239 can be interposed either between the lower hot cap 226 and the central piston pin 210, or, between the upper hot cap 232 and said pin 210, or both, said means 233, 239 being able to form an integral part of said caps 226, 232 and/or said pin 210.

Wherever they are located, the thermal insulation means 233 can consist of at least one insulating ring 236 made of a material with low thermal conductivity 237 such as zirconium oxide 238 and its different variants, alloyed or no to other materials.

It will be noted that the insulating ring 236 can be kept directly or indirectly in contact with the central piston pin 210 and/or the peripheral sealing ring 220 and/or the lower hot cap 226 and/or the radial connection disk lower 224 and/or the upper hot cap 232 and/or the upper radial connection disk 225 via at least one small surface contact edge 241.

It will be noted in Figures 10 and 11 that advantageously, the insulating ring 236 can include a de-rigidification groove 291 which gives it more flexibility and which ensures more homogeneous and better distributed contact between said ring 236 and the part 210, 220, 226, 224, 232, 225 with which said ring 236 cooperates.

According to a particular configuration of the multi-temperature double-acting piston 201, the insulating ring 236 can also be kept directly or indirectly in contact with the central piston pin 210 and/or the peripheral sealing ring 220 and/or the hot cap lower 226 and/or the lower radial connection disk 224 and/or the upper hot cap 232 and/or the upper radial connection disk 225 via at least one insulating ring seal 242 which is working gas tight 240.

Note that the insulating ring seal 242 can for example comprise several metal sheets like the cylinder head gaskets included in modern automobile internal combustion engines, or be made of materials resistant to high temperatures such as “Therma-pur” developed by the company “Garlock”.

As can be seen in Figures 2 to 9, the cap plating means 234 which directly or indirectly maintain the lower hot cap 226 pressed on the peripheral sealing ring 220 and/or on the lower radial connection disc 224, can be formed of an external coaxial lower tube of spindle 243 which envelops the central piston spindle 210, said tube 243 bearing on the one hand, on the lower hot cap 226 in the vicinity of said spindle 210, and on the other hand, on the power transmission means 205 which can for example consist of a stick 244 which translates in a stick cylinder 293, said stick 244 being articulated around the foot of a connecting rod 245 which is itself articulated around a crank 246 arranged on a crankshaft 247, the latter forming the power output shaft 207.

We also see in Figures 2 to 5 and in Figures 7 to 9 that the cap plating means 234 which directly or indirectly maintain the upper hot cap 232 pressed on the peripheral sealing ring 220 and/or on the connecting disc upper radial tube 225, can be formed of an outer coaxial upper tube of spindle 248 which envelops the central piston pin 210, said tube 248 bearing on the one hand, on the upper hot cap 232 in the vicinity of said spindle 210, and on the other hand, on an upper rod stop 249 arranged directly or indirectly on the upper piston rod 212 in the vicinity of its end which opens into the piston cooling and lubrication chamber 217.

As can be clearly seen in , some or all the ends of the lower external coaxial spindle tube 243 and/or the upper external coaxial spindle tube 248 can receive a tube spring 250 by means of which said tubes 243, 248 respectively bear on the lower hot cap 226 and on the power transmission means 205 and/or on the upper hot cap 232 and on the upper rod stop 249, the tube spring 250 can advantageously consist of a stack of “Belleville” washers known per se.

Figures 10 and 11 illustrate that according to a particular configuration of the multi-temperature double-acting piston 201 according to the invention, the lower hot cap 226 and/or the upper hot cap 232 can advantageously present a concave conical surface of cap 251 via of which said cap 226, 232 is held pressed by the cap plating means 234 on a circular edge of peripheral contact 252 which is directly or indirectly secured to the peripheral sealing ring 220 and/or to the periphery of the disk of lower radial connection 224 and/or the periphery of the upper radial connection disc 225.

According to said configuration, the angle of the concave cone formed by the concave conical surface of the cap 251 is such that when said surface 251 slides on said edge 252 due to the difference between the thermal expansion of said cap 226, 232 and that of the assembly formed by the peripheral sealing ring 220, the lower radial connection disk 224, the upper radial connection disk 225 and the central piston pin 210, the axial distance which separates the point of support from the means of plating of cap 234 on said cap 226, 232 of the peripheral sealing ring 220 remains approximately constant all other things being equal, while the concave conical surface of cap 251 and the circular edge of peripheral contact 252 form the means of centering of cap 235.

We note that this particular configuration of the multi-temperature double-acting piston 201 according to the invention allows the force to which the cap-plating means 234 are subjected - which are outside the image in Figures 10 and 11 but present in reality - remains approximately constant whatever the difference between the thermal expansion of said cap 226, 232 and that of the mechanically welded assembly 289 which forms the peripheral sealing ring 220, the lower radial connection disk 224, the disk upper radial connection 225 and the central piston pin 210.

Furthermore, said configuration makes it possible to limit the variation in volumetric ratio of the thermal engine 202 as a function of its temperature, particularly during the cold start phases of said engine 202.

Note that advantageously and as a variant not shown, the circular peripheral contact edge 252 could advantageously present a spherical contact with the concave conical surface of the cap 251.

In Figures 2 to 9, it has been shown that the piston fixing means 231 can consist of a double-acting axial piston screw 219 which firstly comprises a piston screw body 255 which is housed in a tunnel of piston screw 256 which passes right through the central piston pin 210 in the direction of its length, said screw 219 comprising on the one hand, a piston screw head 253 which bears on the end of the rod upper piston 212 which opens into the cooling and lubrication chamber of piston 217, and on the other hand, a piston screw thread 254 which is screwed into the power transmission means 205.

According to a variant embodiment of the multi-temperature double-acting piston 201 according to the invention, a screw-nut assembly can replace the piston screw head 253 which can also be replaced by any other type of fixing which will appear evidently from the man of the art.

As can be clearly seen in Figures 8 and 9, the piston screw tunnel 256 can advantageously form at least part of the lubrication-cooling gallery 227, the lubricating-cooling fluid 257 being able to circulate between the piston screw body 255 and the internal wall of said tunnel 256, the latter forming with said body 255 a first section which goes from the piston cooling and lubrication chamber 217 to the internal piston volume 228, and a second section which goes from said volume 228 to the interior of the transmission housing 206, the piston screw body 255 may include screw sealing bulges 258 for separating the piston screw tunnel 256 into sections, said bulges 258 may for these purposes have a seal of bulge 259.

As clearly illustrated by , the guide means 230 can consist of a barrel skirt 260 which is arranged on the external periphery of the peripheral sealing ring 220 and which bears on the cold cylinder 204, said skirt 260 having a convergent shape which favors establishing a hydrodynamic lubrication regime between itself and the cold cylinder 204 with which it cooperates.

It is evident in Figures 10 and 11 that the barrel skirt 260 can advantageously be positioned between two compression segments 222 and adjoin an oil scraper segment 278.

There illustrates that the lubrication-cooling gallery 227 can open into the internal piston volume 228 via a small axial clearance left between, on the one hand, a fluid distribution disk 261 which is housed in said volume 228 and on the other hand, the upper radial connection disk 225, said distribution disk 261 being approximately parallel to said radial connection disk 225 and forming on the one hand, a seal with the central piston pin 210, and ending on the other hand, radially in the vicinity of the internal wall of the peripheral sealing ring 220, the lubricating-cooling fluid 257 coming from the piston cooling and lubrication chamber 217 being able to exit at said vicinity for example via distribution overflows 290, orifices or slots of any nature whatsoever arranged around the periphery of the fluid distribution disk 261.

As well illustrated by the , according to a particular variant of the multi-temperature double-acting piston 201 according to the invention, the central piston pin 210 may comprise, inside the internal piston volume 228 and in the vicinity of the lower radial connection disk 224, a flange of fluid recirculation 262 which, when the central piston pin 210 moves towards the lower cylinder head 213, rejects radially and towards the internal wall of the peripheral sealing ring 220 the lubricating-cooling fluid 257 which is accumulated in said volume 228 and on the surface of said disk 224, said flange 262 may include flange channels 263 which form radial jets of lubricating-cooling fluid 257 which are uniformly distributed over three hundred and sixty degrees.

Particularly in , we note that the lower radial connection disc 224 can advantageously have a hollow shape 294 at the level of its connection with the central piston pin 210, said shape 294 constituting an overflow reservoir 264 which can store lubricating fluid- cooling 257, while at least one overflow orifice 265 which communicates with the interior of the transmission casing 206 via the lubrication-cooling gallery 227 fixes the maximum level of said reservoir 264 so that at each acceleration in the direction of the upper cylinder head 214 of the multi-temperature double-acting piston 201 according to the invention, the level of the lubricating-cooling fluid 257 contained in said reservoir 264 does not exceed that of the overflow orifice 265, said excess fluid 257 being expelled inside the transmission housing 206.

In , we note that a fluid nozzle 266 supplied by the source of lubricating-cooling fluid 218 can open into the piston cooling and lubrication chamber 217 to inject a jet of fluid 267 which is shown in Figures 8 and 9.

Still in Figures 8 and 9, we see that the fluid nozzle 266 can inject a jet of lubricating-cooling fluid 257 into an axial screw reservoir 267 which is arranged axially in the piston screw head 253, said reservoir 267 communicating with the lubrication-cooling gallery 227 via at least one radial tank-gallery connection conduit 268.

Figures 8 and 9 also clearly show that a screw check valve 269 can be housed in the axial screw of double-acting piston 219, said valve 269 allowing the lubricating-cooling fluid 257 to go from the axial reservoir of screw 267 towards the lubrication-cooling gallery 227, but not vice versa, so that at each acceleration towards the upper cylinder head 214 of the multi-temperature double-acting piston 201 according to the invention, the lubricating-cooling fluid 257 that contains said reservoir 267 is forced to enter the lubrication-cooling gallery 227 while when said piston 201 accelerates towards the lower cylinder head 213, said fluid 257 contained in said gallery 227 does not return to said reservoir 267.

As a variant of the multi-temperature double-acting piston 201 according to the invention, we have shown in that the piston cooling and lubrication chamber 217 can be connected to an air source 270 or to any gas source of any nature whatsoever by an air intake check valve 271 which lets in a fluid forcing air 272 in said chamber 217 without letting it come out, while said chamber 217 is connected to an air tank 273 by a pressure limiting valve 274 which lets the fluid forcing air 272 go from said chamber 217 to said tarpaulin 273 when the pressure of said air 272 in said chamber 217 reaches a certain value.

According to this particular configuration of the multi-temperature double-acting piston 201 according to the invention, the pressure which supplies the fluid nozzle 266 with lubricating-cooling fluid 257 is advantageously greater than the opening pressure of the pressure limiting valve 274.

We also notice in that the altitude of the conduit which connects the piston cooling and lubrication chamber 217 to the pressure relief valve 274 can determine the maximum level of the lubricating-cooling fluid 267 in said chamber 217, said conduit acting as an overflow.

OPERATION OF THE INVENTION:

The operation of the multi-temperature double-acting piston 201 according to the invention is easily understood in view of Figures 1 to 12.

Said piston 201 can be applied to any heat engine 202 executing a Beau de Rochas, Miller, Atkinson, Diesel cycle, or any other thermodynamic cycle known to those skilled in the art.

In Figures 1 to 12, the multi-temperature double-acting piston 201 according to the invention is shown and such that it can be implemented in a heat engine 202 executing a regenerative Brayton cycle which is identical to that which executes the heat engine with transfer-expansion and regeneration according to patent No. WO2016120560.

In this particular context, said piston 201 only applies to the regulator 279 of said engine 202, also, the other members of the latter such as one or more compressors, a burner or a regeneration exchanger necessary for the implementation of the Brayton cycle with regeneration, are not shown.

The objective of the multi-temperature double-acting piston 201 according to the invention is to limit as much as possible the heat losses of the working gas 240 during the expansion phase of said gas 240 carried out during the Brayton regeneration cycle, while ensuring that said piston 201 achieves a good seal with the cold cylinder 204 by using only conventional piston sealing means 221, in this case compression rings 222 similar to those which equip the automobile internal combustion engines produced in large series, said segments 222 cooperating with an oil scraper segment 278.

Achieving this objective implies in particular that as much of the external wall surface as possible of the multi-temperature double-acting piston 201 is maintained at high temperature.

Achieving this objective also requires that the multi-temperature double-acting piston 201 according to the invention achieves a good seal with the lower cylinder head 213 and with the upper cylinder head 214, respectively thanks to lower rod sealing means 280 and means of sealing. sealing of upper rod 281, said means 280, 281 being formed of metallic cutting segments 282 known per se.

In order for said objective to be fully achieved, the multi-temperature double-acting piston 201 according to the invention advantageously applies to a heat engine 202 based on the same said objective and which, as such, limits the heat losses of the gas as much as possible. working 240 by having the greatest possible part of its internal walls brought to high temperature.

This is why in Figures 1 to 3 we have shown a heat engine 202 whose regulator 279 receives the multi-temperature double-acting piston 201, said regulator 279 comprising a lower cylinder head 213 and an upper cylinder head 214 whose operating temperature is high - of the order of nine hundred and fifty degrees Celsius - said cylinder heads 213, 214 being made of silicon carbide 276, a material which retains its mechanical characteristics up to temperatures of the order of one thousand four hundred degrees Celsius, and which can be used in an oxidizing environment at these high temperatures.

Only the internal surfaces of said regulator 279 which are in contact with both the working gas 240 and with the piston sealing means 221 are maintained at a temperature of only one hundred degrees Celsius, said temperature remaining compatible with a lubricating fluid- cooling 257 such as lubricating and cooling oil 283, and preventing the latter - in this case engine oil known per se - from coking, burning, or deteriorating prematurely.

As seen in Figures 2 and 3, said surfaces are, in addition to the cold cylinder 204 arranged in a cooled cylinder block 203, a part of the peripheral sealing ring 220, a part of the lower piston rod 211 and a part of the upper piston rod 212, these members 220, 204, 211, 212 totaling a surface in contact with the working gas 240 much less than that totaled by the lower cylinder head 213, the upper cylinder head 214, the lower hot cap 226, and the upper hot cap 232.

In Figures 2 and 3, as an example of a particular implementation of the multi-temperature double-acting piston 201 according to the invention, the power transmission means 205 which are housed in the transmission casing 206 and which are provided here are shown. to transform the back and forth movements of said piston 201 in the cold cylinder 204 into continuous rotational movement of a crankshaft 247.

Still according to this non-limiting exemplary embodiment, the transmission casing 206 and the power transmission means 205 are advantageously maintained at a temperature close to one hundred degrees Celsius, compatible with the lubricating and cooling oil 283.

We note in Figures 2 and 3 that the power transmission means 205 are for example made up of a connecting rod 245 which is connected to the lower piston rod 211 via a crosshead 244, said connecting rod 34 being articulated around a crank 246 arranged on the crankshaft 247, the latter forming a power output shaft 207.

As can be clearly seen in Figures 2 to 5 and in Figures 8 and 9, the mechanically welded assembly 289 which forms the peripheral sealing ring 220, the lower radial connection disk 224, the upper radial connection disk 225 and the central piston pin 210 are fixed on the stock 244 by a double-acting axial piston screw 219, the piston screw body 255 of which is housed in a piston screw tunnel 256 which passes right through the central piston pin. piston 210 in the direction of its length.

The piston screw tunnel 256 here forms a lubrication-cooling gallery 227, the lubricating and cooling oil 283 being able to circulate between the piston screw body 255 and the internal wall of said tunnel 256, the latter forming with said body 255 a first section of lubrication-cooling gallery 227 which goes from the piston cooling and lubrication chamber 217 to the internal piston volume 228, and a second section of said gallery 227 which goes from said volume 228 to the interior of the casing transmission 206.

Advantageously, the piston screw body 255 has screw sealing bulges 258 which sealingly separate the piston screw tunnel 256 into two sections by means of bulging seals 259.

As clearly shown in Figures 2 to 5 and Figures 8 and 9, the double-acting piston axial screw 219 also includes a piston screw head 253 which bears on the end of the upper piston rod 212 which is oriented towards the piston cooling and lubrication chamber 217, and a piston screw thread 254 which is screwed into the stock 244.

We will assume here that the working gas 240 is introduced into the expander 279 via an inlet valve 284 at a temperature of one thousand three hundred degrees Celsius, while the operational equilibrium temperature of the lower cylinder head 213 and the cylinder head upper 214 which surround the cooled cylinder block 203 on the one hand, and that of the lower hot cap 226 and the upper hot cap 232 which cover the multi-temperature double-acting piston 201 on the other hand, is nine hundred and fifty degrees Celsius.

Note that advantageously and as illustrated in Figures 1 and 2 and Figures 6 and 7, the inlet valve 284 and an exhaust valve 285 by which the working gas 240 is expelled from the regulator 279 after having been relaxed are autoclaves, and can each be controlled by a hydraulic regenerative valve actuator as described in patent No. 3071896 dated October 11, 2019 and belonging to the applicant.

Differently from the heat engine with transfer-expansion and regeneration according to patent WO2016120560 of which all the internal walls of the expander are maintained at a high temperature of for example nine hundred and fifty degrees Celsius, the internal wall of the cold cylinder 204 of the expander 279 of the engine thermal 202 is here maintained by cylinder crankcase cooling means 286 at the relatively low temperature of one hundred degrees Celsius, this temperature being given only by way of example.

In Figures 2 and 3, it has been shown that the cylinder crankcase cooling means 286 can consist of a cooling chamber 287 which envelops the external surface of the cold cylinder 204, a heat transfer liquid 288, in this case water, circulating in said chamber 287.

Thus and as clearly shown in Figures 2 and 3, practically all the internal walls of the expander 279 of the heat engine 202 remain hot like those of the heat engine with transfer-expansion and regeneration according to patent WO2016120560, with the exception of the cold cylinder 204.

The remaining hot surfaces are sufficient to obtain from the regenerative Brayton cycle a thermodynamic efficiency significantly higher in practice than that obtained from the Otto and Diesel cycles.

Note, which is clearly shown in Figures 10 and 11, that the peripheral sealing ring 220 has a barrel skirt 260, two compression segments 222 and an oil scraper segment 278, these components 260, 222, 278 also being maintained at a temperature of the order of one hundred degrees Celsius, close to that of the cold cylinder 204 with which they cooperate, this in particular to preserve the integrity of the lubricating and cooling oil 283 which forms a film on the internal wall of said cylinder 204.

We therefore understand that, unlike the heat engine with transfer-expansion and regeneration according to patent WO2016120560, the piston sealing means 221 are no longer made up here of a fluid cushion sealing device according to patent FR 3032252, but of a segmentation comparable to that of conventional automobile internal combustion engines, said means 221 being cooled and lubricated in the same way.

This similarity allows the multi-temperature double-acting piston 201 according to the invention to benefit from more than a century-old know-how in the field of segmentation of internal combustion engine pistons.

The particular configuration of said piston 201 and of the regulator 279 of which said piston 201 is part is justified in that, under the temperature conditions which have just been described, the heat transferred to the cold cylinder 204 by the working gas 240 forms a loss energy comparable or even lower than that induced on the one hand, by the fluid cushion sealing device subject to patent FR 3032252 due to the compression means necessary for its compressed air supply, and on the other hand, by the system regenerative cooling according to patent No. EP 3585993 because of the additional exhaust pressure losses that it generates, and the reintroduction into the thermodynamic cycle of the heat extracted from the internal walls of the expander via a regeneration heat exchanger including the yield is less than one.

As proof of the validity of the multi-temperature double-acting piston 201 according to the invention, we note that if all the internal walls of the regulator 279 shown in Figures 2 and 3 - including the lower cylinder head 213, the upper cylinder head 214, the cap lower hot 226 and the upper hot cap 232 - were maintained at only one hundred degrees Celsius like the internal walls of mass-produced automobile internal combustion engines, the average specific heat output at the surface - for example expressed in kilowatts per square meter - transferred by the working gas 240 to the cold cylinder 204, would be much lower than that transferred by said gas 240 to said cylinder heads 213, 214 and to said caps 226, 232.

Indeed, the surface that the cold cylinder 204 exposes to the working gas 240 is small at the start of expansion of said gas 240, then increases as said gas 240 expands and at the same time, its temperature drops, unlike the lower yoke 213, the upper yoke 214, the lower hot cap 226 and the upper hot cap 232, the surface of which exposed to the working gas 240 remains constant.

Thus, assuming that said cylinder heads 213, 214 and said caps 226, 232 are voluntarily maintained at one hundred degrees Celsius during expansion, the specific cooling power at the surface would be much lower at the level of the internal walls of the cold cylinder 204 than at the level of those of said cylinder heads 213, 214 and said caps 226, 232.

Furthermore, the multi-temperature double-acting piston 201 being, as its name indicates, double-acting, the surface of the cold cylinder 204 relative to that of said cylinder heads 213, 214 and said caps 226, 232 is found to be greatly reduced compared to what would be said surface if said piston 201 was single-acting.

Indeed, the cold cylinder 204 being common to the lower variable volume chamber 208 and to the upper variable volume chamber 209, its surface is valid here and according to the example of embodiment of the multi-temperature double-acting piston 201 according to the invention shown in Figures 2 and 3, less than thirty percent of the total internal surface of the regulator 279 which is brought into contact with the working gas 240.

It is also observed that at identical maximum power, the thermal engine 202 being equipped with the multi-temperature double-acting piston 201 and executing a regenerative Brayton cycle, the internal surface of its cold cylinder 204 is smaller in absolute terms than the internal surface of the cylinder of an Otto cycle or Diesel engine of conventional architecture.

This reduces the relative thermal losses attributable to said cold cylinder 204.

In addition, the maximum temperature reached by the gases in the cylinder of an Otto cycle or conventional Diesel engine is of the order of two thousand five hundred degrees Celsius compared to only around one thousand three hundred degrees Celsius when it comes to of the heat engine 202 executing a regenerative Brayton cycle shown in Figures 1 to 3.

All things being equal, this lower temperature further reduces the heat losses of the working gas 240 in contact with the cold cylinder 204.

Furthermore, it will be noted that unlike the lower cylinder head 213, the upper cylinder head 214, the lower hot cap 226 and the upper hot cap 232, the heat engine 202 is equipped with the multi-temperature double-acting piston 201 according to the invention. , its cold cylinder 204 is located in a zone of low turbulence of the working gas 240 during the introduction of said gas 240 into the lower variable volume chamber 208 or the upper variable volume chamber 209 via the corresponding inlet valve 284 , or during the expulsion of said gas 240 from said chambers 208, 209 via their exhaust valve 285.

This low intensity turbulence limits the convective forcing and the transfer of heat by the working gas 240 to the cold cylinder 204.

It will also be noted that, unlike conventional Otto or Diesel cycle engines, the turbulence of the gases introduced into the regulator 279 does not need to be forced by movements known to those skilled in the art. under the Anglo-Saxon terms of “tumble”, “swirl” or “squish”, to promote any combustion whatsoever.

Indeed, to the extent that the heat engine 202 equipped with the multi-temperature double-acting piston 201 according to the invention executes a regenerative Brayton cycle - which is its primary purpose - the combustion or reheating of the working gas 240 occurs. carried out by means of a hot source located upstream of the regulator 279 and not in said regulator 279, said source being able to consist of a burner, a heat exchanger or even and by way of non-limiting example, a solar radiation concentration sensor.

The non-need to create voluntary turbulence to promote combustion therefore further reduces the thermal losses of the heat engine 202 equipped with the multi-temperature double-acting piston 201 according to the invention executing a regenerative Brayton cycle compared to those of an engine conventional with an Otto or Diesel cycle, and this, due to less convective forcing between the working gas 240 and the internal wall of the cold cylinder 204.

That being said, to benefit from the advantages of the multi-temperature double-acting piston 201 according to the invention, we understand that said piston 201 involves making hot parts and cold parts distant from each other only a few millimeters cooperate.

To demonstrate how the multi-temperature double-acting piston 201 according to the invention allows this cooperation of hot parts and cold parts very close to each other, we will assume here that the central piston pin 210, the lower radial connection disk 224, the upper radial connection disc 225, the peripheral sealing ring 220 as well as the lower external coaxial spindle tube 243 and the upper external coaxial spindle tube 248 are made of steel with high mechanical characteristics, while the lower hot cap 226 and the upper hot cap 232 are made of silicon carbide 276.

The cooled cylinder block 203 and the cold cylinder 204 are made of cast iron, while the lower cylinder head 213 and the upper cylinder head 214 are also made of silicon carbide 276.

We will also assume here that the internal diameter of the cold cylinder 204 is two hundred and forty millimeters.

The close proximity between the cold parts 210, 224, 225, 220 in steel or those in cast iron 203, 204, and the hot parts 226, 232, reveals a double issue linked to differential expansions and the limitation of heat transfers from said hot parts 226, 232, towards said cold parts 210, 224, 225, 220, 203, 204.

Let us take for example the case of the lower hot cap 226 of the multi-temperature double-acting piston 201 according to the invention, according to its particular configuration shown in Figures 2 to 4 and in Figures 6 to 11, the operation of the upper hot cap 232 being identical .

Said cap 226 and the mechanically welded assembly 289 which forms the peripheral sealing ring 220, the lower radial connection disc 224, the upper radial connection disc 225 and the central piston pin 210 with which said cap 226 cooperates, are both manufactured at a temperature of around twenty degrees Celsius.

However, in operation, the temperature of the mechanically welded assembly 289 stabilizes at one hundred degrees Celsius while that of the lower hot cap 226 stabilizes at nine hundred and fifty degrees Celsius.

Taking into account the expansion coefficients of the materials constituting the lower hot cap 226 and the mechanically welded assembly 289, these temperatures lead to differences in hot diameter between that of said cap 226 and that of said assembly 289 of nearly one millimeter.

Likewise, under the effect of the temperature, the total axial length of the lower hot cap 226 also increases by around one millimeter, such a variation in said length being difficult to absorb by the plating means of cap 234 which must also take up the axial forces generated by the inertia of said cap 226 during accelerations of the multi-temperature double-acting piston 201 according to the invention.

Furthermore, the close proximity between the lower hot cap 226 and the mechanically welded assembly 289 is likely to promote heat transfers from said cap 226 to said assembly 289, said transfers being detrimental to the thermodynamic efficiency of the cycle heat engine 202. of Brayton to regeneration.

The multi-temperature double-acting piston 201 according to the invention meets this double need on the one hand, to absorb significant differences in expansion between various parts kept in contact with each other and operating at very different temperatures , and on the other hand, to limit the heat exchanges between said parts.

Indeed, as we see for example in , said piston 201 comprises on the one hand, an insulating ring 236 made of zirconium oxide 238 - a material renowned for its good temperature resistance and its very low thermal conductivity - which is interposed between the lower hot cap 226 and the peripheral ring sealing ring 220 and on the other hand, an insulating ring 236 made of the same material which is interposed between said cap 226 and the central piston pin 210.

As we see in , advantageously, the lower external coaxial pin tube 243 which forms the cap plating means 234 rests on the insulating ring 236 which is radially close to the central piston pin 210.

We also note in the tube spring 250 which rests on the stock 244 and which is made up of a stack of “Belleville” washers.

We also note that to limit heat losses detrimental to the efficiency of the regenerative Brayton cycle heat engine 202 which receives the multi-temperature double-acting piston 201 according to the invention, the insulating ring 236 interposed between the lower hot cap 226 and the peripheral sealing ring 220 is kept pressed against said cap 226 via a small surface contact edge 241 which reduces the section left for the passage of heat.

As can be seen in Figures 10 and 11, thanks to the particular configuration of the multi-temperature double-acting piston 201 according to the invention, the thermal expansion of the lower hot cap 226 has little or no influence on the total length of the assembly which constitutes said cap 226 with the peripheral sealing ring 220, so that the cap pressing means 234 which press said cap 226 onto said ring 220 are not over-constrained by said expansion.

Indeed, we note in Figures 10 and 11 that the lower hot cap 226 has a concave conical surface of cap 251 by means of which said cap 226 is kept pressed by the cap plating means 234 on a circular contact edge peripheral 252 presented by the insulating ring 236 which is integral with the peripheral sealing ring 220, said edge 252 acting as a small surface contact edge 241.

The angle of the concave cone formed by the concave conical surface of the cap 251 is calculated so that when said surface 251 slides on the circular edge of peripheral contact 252 due to the difference between the thermal expansion of the lower hot cap 226 and that of the entire mechanically welded assembly 289, the axial distance which separates the point of support of the lower external coaxial tube of spindle 243 on said cap 226 from the peripheral sealing ring 220 remains approximately constant, all other things being equal.

According to this particular configuration of the multi-temperature double-acting piston 201 according to the invention, the concave conical surface of the cap 251 and the circular peripheral contact edge 252 presented by the insulating ring 236 which is integral with the peripheral sealing ring 220, form the cap centering means 235.

According to said configuration, the axial force to which the lower external coaxial spindle tube 243 is subjected remains approximately constant whatever the difference between the thermal expansion of the lower hot cap 226 and that of the mechanically welded assembly 289, while said cap 226 remains radially always centered in relation to the peripheral sealing ring 220.

Note also that said configuration also makes it possible to limit the variation in volumetric ratio of the thermal engine 202 as a function of its temperature, particularly during the cold start phases of said engine 202.

We will notice, for example in , that the insulating ring 236 which is interposed between the lower hot cap 226 and the lower external coaxial spindle tube 243 does not strictly speaking have a small surface contact edge 241, the radial thickness of said tube 243 constituting in itself said edge 241.

As clearly shown in Figures 4 and 5 and Figures 8 to 11, a barrel skirt 260 is therefore well arranged on the external periphery of the peripheral sealing ring 220 so as to bear on the cold cylinder 204, said skirt 260 having a convergent shape which promotes the establishment of a hydrodynamic lubrication regime between itself and said cylinder 204.

In the vicinity of the two axial ends of the peripheral sealing ring 220, we notice, particularly clearly in Figures 10 and 11, the two compression segments 222 which form the piston sealing means 221 and which prevent the gas working 240 to pass from the lower variable volume chamber 208 to the upper variable volume chamber 209, and vice versa.

Still in Figures 10 and 11, below the barrel skirt 260, we can see the oil scraper segment 278 and the peripheral ring lubrication orifices 229 which open at the rear of said segment 278.

This arrangement allows, on the one hand, to bring lubricating and cooling oil 283 to lubricate the barrel skirt 260 and the compression segments 222, and on the other hand, to return any excess of said oil 283 into the internal volume of piston 228.

Figures 8 and 9 show the path of the lubricating and cooling oil 283 through the mechanically welded assembly 289.

Indeed, said oil 283 coming from a source of lubricating-cooling fluid 218 is here injected into the piston cooling and lubrication chamber 217 by a fluid nozzle 266, the latter projecting a jet of lubricating oil and cooling 283 in an axial screw reservoir 267 which is arranged axially in the piston screw head 253.

The axial screw reservoir 267 makes it possible to store lubricating and cooling oil 283 whatever the direction of movement of the multi-temperature double-acting piston 201 according to the invention, and to maximize the portion of said oil 283 which passes through the internal volume of piston 228 before being expelled into the transmission casing 206.

Indeed, a relatively small part of said oil 283 is used on the one hand, to lubricate the cut segments 282 which form a seal between the upper external coaxial spindle tube 248 and the upper cylinder head 214 and on the other hand, to cool said tube 248.

In this respect, we note in the pressure relief valve 274 which acts as an overflow of the cooling and piston lubrication chamber 217 and which allows, in cooperation with an air intake check valve 271 connected to an air source 270 said valve 271 letting a fluid forcing air 272 enter said chamber 217, to slightly pressurize the latter while limiting the level of lubricating and cooling oil 283 contained in said chamber 217.

Indeed, below a certain pressure prevailing in the piston cooling and lubrication chamber 217, the air intake non-return valve 271 lets in fluid forcing air 272 coming from the air source 270 in said chamber 217, while above a certain said pressure, the pressure limiting valve 274 expels fluid forcing air 272 into an air tank 273.

As we see in , advantageously, the interior of the transmission casing 206 can form both the air source 270 and the air cover 273.

The slight pressurization of the piston cooling and lubrication chamber 217 by means of a fluid forcing air 272 allows, when the heat engine 202 is rotating at low speed and the accelerations of the multi-temperature double-acting piston 201 following the invention are of low intensity, to force the lubricating and cooling oil 283 to enter the lubrication-cooling gallery 227 which is arranged in the central piston pin 210.

Still in order to maximize the portion of lubricating and cooling oil 283 which passes through the internal volume of piston 228, we note in Figures 8 and 9 the screw non-return valve 269 which is here positioned at the bottom of the axial reservoir of screw 267 so that at each acceleration towards the upper cylinder head 214 of the multi-temperature double-acting piston 201 according to the invention, the lubricating and cooling oil 283 contained in said reservoir 267 is forced to penetrate into the lubrication gallery -cooling 227 via radial conduits connecting the tank-gallery 268, while when said piston 201 accelerates towards the lower cylinder head 213, said oil 283 contained in said gallery 227 does not return to said tank 267.

All of these arrangements made at the level of the piston cooling and lubrication chamber 217 and at the level of the piston screw head 253 ensure circulation of lubricating and cooling oil 283 inside the mechanically welded assembly 289 to maintain the temperature of the latter at around one hundred degrees Celsius, while ensuring that the barrel skirt 260 and the segments 222, 278 have appropriate lubrication.

As seen in Figures 8 and 9, a first section of the lubrication-cooling gallery 227 routes the lubricating and cooling oil 283 from the piston cooling and lubrication chamber 217 to the piston internal volume 228 , this by first passing through the axial screw reservoir 267, the screw non-return valve 269 and the radial reservoir-gallery connection conduits 268.

In Figures 8 and 9, it has been shown that the lubricating and cooling oil 283 opens into the internal volume of piston 228 via a small axial clearance left between a fluid distribution disk 261 and the upper radial connection disk 225, said distribution disk 261 being mainly parallel to said radial connection disk 225 and forming on the one hand, a seal with the central piston pin 210, and ending on the other hand, radially in the vicinity of the internal wall of the peripheral ring seal 220, the lubricating and cooling oil 283 coming from the piston cooling and lubricating chamber 217 being able to exit at said vicinity via distribution overflows 290.

The axial proximity between the fluid distribution disk 261 and the upper radial connection disk 225 is such that the lubricating and cooling oil 283 is forced to lick the entire internal surface of the upper radial connection disk 225 before exiting through the distribution spillways 290.

This particular configuration of the multi-temperature double-acting piston 201 according to the invention makes it possible to maintain the temperature of the upper radial connection disk 225 close to one hundred degrees Celsius, whatever the power delivered by the heat engine 202.

As we see in , part of the lubricating and cooling oil 283 leaving the distribution weirs 290 cools the peripheral sealing ring 220 from the inside and supplies the peripheral ring lubrication orifices 229, so that a little of said oil 283 springs between the two lips of the oil scraper ring 278, the latter forming, consecutively to the back and forth movements carried out by the multi-temperature double-acting piston 201 in the cold cylinder 204, a film of lubricating oil and cooling 283 on the surface of said cylinder 204, this while recovering said oil 283 present in excess on said surface.

We note in Figures 8 and 9 that the acceleration forces are used by the multi-temperature double-acting piston 201 according to the invention to force the path of the lubricating and cooling oil 283 so that all the surfaces of the internal volume of piston 228 are uniformly cooled.

In this respect, we note in Figures 8 and 9 the fluid recirculation flange 262 which the central piston pin 210 comprises, inside the internal volume of piston 228 and in the vicinity of the lower radial connection disk 224.

At each acceleration towards the lower cylinder head 213 of the multi-temperature double-acting piston 201 according to the invention and as illustrated in , said flange 262 rejects radially and in the direction of the internal wall of the peripheral sealing ring 220 of the lubricating and cooling oil 283 which has accumulated in an overflow tank 264 consisting of a form hollow that the lower radial connection disc 224 presents at the level of its connection with the central piston pin 210.

As shown in Figures 4 to 11, the fluid recirculation flange 262 can advantageously comprise flange channels 263 which form radial jets of lubricating-cooling fluid 257 so as to guarantee that the lubricating and cooling oil 283 is uniformly distributed over three hundred and sixty degrees.

We note in Figures 8 and 9 the overflow orifices 265 which open from the external wall of the central piston pin 210 and which communicate with the interior of the transmission casing 206 via the lubrication-cooling gallery 227.

The axial position of said orifices 265 fixes the maximum level of said reservoir 264 so that at each acceleration towards the upper cylinder head 214 of the multi-temperature double-acting piston 201 according to the invention, the level of lubricating and cooling oil 283 contained in said reservoir 264 does not exceed that of said overflow orifices 265, said excess oil 283 being expelled towards the interior of the transmission casing 206.

The possibilities of the multi-temperature double-acting piston 1 according to the invention are not limited to the applications which have just been described and it must also be understood that the preceding description has only been given as a guide. example and that it in no way limits the field of said invention from which we would not escape by replacing the details of execution described by any other equivalent.

Claims (23)

Multi-temperature double-acting piston (201) capable of translating in a cold cylinder (204) arranged in a cooled cylinder crankcase (203) which comprises a heat engine (202), said piston (201) being directly or indirectly connected by means of power transmission (205) housed in a transmission housing (206) to at least one rotary or reciprocating power output shaft (207) while said piston (201) forms a lower variable volume chamber (208) with the cylinder cold (204) and a lower cylinder head (213) which is positioned between said piston (201) and the transmission housing (206), said piston (201) simultaneously forming an upper variable volume chamber (209) with said cylinder (204 ) and an upper cylinder head (214), said chambers (208, 209) containing a working gas (240),characterized in thatHe understands

• A central piston pin (210) approximately coaxial with the cold cylinder (204) and of which a first end forms a lower piston rod (211) which passes right through the lower cylinder head (213) via a lower rod orifice (215 ) which cooperates with lower rod sealing means (280) to open into the transmission casing (206) and to be directly or indirectly connected to the power transmission means (205) by piston fixing means (231 ), while the second end of said pin (210) forms an upper piston rod (212) which passes right through the upper cylinder head (214) via an upper rod orifice (216) which cooperates with means of upper rod seal (281) to open into a piston cooling and lubrication chamber (217) connected to a source of lubricating-cooling fluid (218), the latter introducing a lubricating-cooling fluid (257) into said chamber ( 217);
• A peripheral sealing ring (220) whose external diameter is substantially less than the internal diameter of the cold cylinder (204), said ring (220) comprising piston sealing means (221) which are in contact with said cylinder ( 204) to achieve sealing with the latter;
• A lower radial connection disk (224) which radially connects the central piston pin (210) with the peripheral sealing ring (220) on the lower variable volume chamber side (208), and a radial connection disk upper (225) which radially connects the central piston pin (210) with the peripheral sealing ring (220) on the side of the upper variable volume chamber (209), the space left between said discs (224, 225 ), the peripheral sealing ring (220) and the central piston pin (210) forming an internal piston volume (228);
• A lubrication-cooling gallery (227) arranged mainly axially in the central piston pin (210) and in one or more sections, said gallery (227) connecting on the one hand, the piston cooling and lubrication chamber (217) with the internal piston volume (228), and on the other hand, said volume (228) with the interior of the transmission casing (206);
• At least one peripheral ring lubrication orifice (229) which places the internal piston volume (228) in communication with the external peripheral face of the peripheral sealing ring (220), said orifice (229) opening axially from said face between at least two piston sealing means (221);
• Guiding means (230) which directly or indirectly bear on or near the power transmission means (205) and/or the cold cylinder (204) and/or the lower cylinder head (213) and/or the upper cylinder head (214), said means (230) directly or indirectly retaining the peripheral sealing ring (220) centered in the cold cylinder (204);
• A lower hot cap (226) interposed between the lower radial connection disc (224) and the lower variable volume chamber (208) and/or an upper hot cap (232) interposed between the upper radial connection disc (225) and the upper variable volume chamber (209);
• Cap plating means (234) which directly or indirectly maintain the lower hot cap (226) pressed onto the peripheral sealing ring (220) and/or onto the lower radial connection disc (224), and/or which directly or indirectly maintain the upper hot cap (232) pressed on said ring (220) and/or on the upper radial connection disc (225), said means (234) leaving said caps (226, 232) free to expand relative to said ring (220) and/or said discs (224, 225);
• Cap centering means (235) which locate the lower hot cap (226) and/or the upper hot cap (232) relative to the peripheral sealing ring (220).

Multi-temperature double-acting piston according to claim 1, characterized in that the lower hot cap (226) and/or the upper hot cap (232) are entirely or partly made of a material resistant to high temperatures (275). Multi-temperature double-acting piston according to claim 2, characterized in that the high temperature resistant material (275) consists mainly of silicon carbide (276). Multi-temperature double-acting piston according to claim 1,characterized in thatthermal insulation means (233) and/or cap sealing means (239) are interposed either between the lower hot cap (226) and the peripheral sealing ring (220) and/or the disc lower radial connection (224), either, between the upper hot cap (232) and said ring (220) and/or the upper radial connection disc (225), or both. Multi-temperature double-acting piston according to claim 1, characterized in that thermal insulation means (233) and/or cap sealing means (239) are interposed either, between the lower hot cap (226) and the central piston pin (210), either between the upper hot cap (232) and said pin (210), or both. Multi-temperature double-acting piston according to claims 4 and 5, characterized in that the thermal insulation means (233) consist of at least one insulating ring (236) made of a material with low thermal conductivity (237). Multi-temperature double-acting piston according to claim 6, characterized in that the low thermal conductivity material (237) consists mainly of zirconium oxide (238). Multi-temperature double-acting piston according to Claim 6, characterized in that the insulating ring (236) is held directly or indirectly in contact with the central piston pin (210) and/or the peripheral sealing ring (220). and/or the lower hot cap (226) and/or the lower radial connection disc (224) and/or the upper hot cap (232) and/or the upper radial connection disc (225) via at least one contact edge of small surface area (241). Multi-temperature double-acting piston according to Claim 6, characterized in that the insulating ring (236) is held directly or indirectly in contact with the central piston pin (210) and/or the peripheral sealing ring (220). and/or the lower hot cap (226) and/or the lower radial connection disc (224) and/or the upper hot cap (232) and/or the upper radial connection disc (225) via at least one insulating ring seal (242) which is tight to the working gas (240). Multi-temperature double-acting piston according to claim 1, characterized in that the cap-plating means (234) which directly or indirectly maintain the lower hot cap (226) pressed against the peripheral sealing ring (220) and/or on the lower radial connection disk (224), are formed of an external coaxial lower spindle tube (243) which envelops the central piston spindle (210), said tube (243) bearing on the one hand, on the lower hot cap (226) in the vicinity of said spindle (210), and on the other hand, on the power transmission means (205). Multi-temperature double-acting piston according to claim 1, characterized in that the cap-plating means (234) which directly or indirectly maintain the upper hot cap (232) pressed against the peripheral sealing ring (220) and/or on the upper radial connection disk (225), are formed of an upper outer coaxial spindle tube (248) which envelops the central piston spindle (210), said tube (248) bearing on the one hand, on the upper hot cap (232) in the vicinity of said pin (210), and on the other hand, on an upper rod stop (249) arranged directly or indirectly on the upper piston rod (212) in the vicinity of its end which opens in the piston cooling and lubrication chamber (217). Multi-temperature double-acting piston according to claims 10 and 11, characterized in that some or all of the ends of the lower coaxial outer spindle tube (243) and/or the upper coaxial outer spindle tube (248) receive a tube spring ( 250) through which said tubes (243, 248) respectively bear on the lower hot cap (226) and on the power transmission means (205) and/or on the upper hot cap (232) and on the upper rod stop (249). Multi-temperature double-acting piston according to claim 1, characterized in that the lower hot cap (226) and/or the upper hot cap (232) has a concave conical cap surface (251) via which said cap ( 226, 232) is held pressed by the cap plating means (234) on a circular peripheral contact edge (252) which is directly or indirectly secured to the peripheral sealing ring (220) and/or the periphery of the lower radial connection disk (224) and/or of the periphery of the upper radial connection disk (225), the angle of the concave cone formed by said surface (251) being such that when said surface (251) slides on said edge (252) due to the difference between the thermal expansion of said cap (226, 232) and that of the assembly formed by the peripheral sealing ring (220), the lower radial connection disc (224) , the upper radial connection disk (225) and the central piston pin (210), the axial distance which separates the point of support of the cap plating means (234) on said cap (226, 232) from the peripheral sealing ring (220) remains approximately constant all other things being equal, while the concave conical surface of the cap (251) and the circular peripheral contact edge (252) form the cap centering means (235). Multi-temperature double-acting piston according to claim 1, characterized in that the piston fixing means (231) consist of a double-acting piston axial screw (219) which firstly comprises a piston screw body (255) which is housed in a piston screw tunnel (256) which passes right through the central piston pin (210) in the direction of its length, said screw (219) comprising on the one hand, a head of piston screw (253) which bears on the end of the upper piston rod (212) which opens into the piston cooling and lubrication chamber (217), and on the other hand, a screw thread of piston (254) which is screwed into the power transmission means (205). Multi-temperature double-acting piston according to claim 14, characterized in that the piston screw tunnel (256) forms at least part of the lubrication-cooling gallery (227), the lubricating-cooling fluid (257) being able to circulate between the piston screw body (255) and the internal wall of said tunnel (256), the latter forming with said body (255) a first section which goes from the piston cooling and lubrication chamber (217) to the internal volume of piston (228), and a second section which goes from said volume (228) inside the transmission housing (206). Multi-temperature double-acting piston according to claim 1, characterized in that the guide means (230) consist of a barrel skirt (260) which is arranged on the external periphery of the peripheral sealing ring (220) and which is supported on the cold cylinder (204). Multi-temperature double-acting piston according to claim 1, characterized in that the lubrication-cooling gallery (227) opens into the internal volume of the piston (228) via a small axial clearance left between, on the one hand, a pressure distribution disk. fluid (261) which is housed in said volume (228) and on the other hand, the upper radial connection disk (225), said distribution disk (261) being approximately parallel to said radial connection disk (225) and forming 'on the one hand, a seal with the central piston pin (210), and finishing on the other hand, radially in the vicinity of the internal wall of the peripheral sealing ring (220), the lubricating-cooling fluid (257) coming from the piston cooling and lubrication chamber (217) which can exit at said vicinity. Multi-temperature double-acting piston according to claim 1, characterized in that the central piston pin (210) comprises, inside the internal piston volume (228) and in the vicinity of the lower radial connection disc (224), a fluid recirculation flange (262) which, when the central piston pin (210) moves towards the lower cylinder head (213), rejects radially and towards the inner wall of the peripheral seal ring (220 ) the lubricating-cooling fluid (257) which has accumulated in said volume (228) and on the surface of said disk (224). Multi-temperature double-acting piston according to claim 1, characterized in that the lower radial connection disc (224) has a hollow shape (294) at the level of its connection with the central piston pin (210), said shape (294 ) constituting an overflow tank (264) which can store lubricating-cooling fluid (257), while at least one overflow port (265) which communicates with the interior of the transmission housing (206) via the lubrication-cooling gallery (227) sets the maximum level of said tank (264). Multi-temperature double-acting piston according to claim 1, characterized in that a fluid nozzle (266) supplied by the source of lubricating-cooling fluid (218) opens into the piston cooling and lubrication chamber (217) to inject a jet of fluid (267). Multi-temperature double-acting piston according to claims 14 and 20, characterized in that the fluid nozzle (266) injects a jet of lubricating-cooling fluid (257) into an axial screw reservoir (267) which is arranged axially in the piston screw head (253), said tank (267) communicating with the lubrication-cooling gallery (227) via at least one radial tank-gallery connection conduit (268). Multi-temperature double-acting piston according to claim 21, characterized in that a screw check valve (269) is housed in the double-acting piston axial screw (219), said valve (269) allowing the lubricating-cooling fluid (257) to go from the axial screw reservoir (267) towards the lubrication-cooling gallery (227), but not the reverse. Multi-temperature double-acting piston according to claim 1, characterized in that the piston cooling and lubrication chamber (217) is connected to an air source (270) by an air intake check valve ( 271) which allows fluid forcing air (272) to enter said chamber (217) without letting it exit, while said chamber (217) is connected to an air tank (273) by a pressure limiting valve ( 274) which lets the fluid forcing air (272) go from said chamber (217) to said tank (273) when the pressure of said air (272) in said chamber (217) reaches a certain value.