Double acting multi-temperature piston

Abstract

The invention relates to a multi-temperature double-acting piston (201), which comprises a peripheral sealing ring (220), a lower hot crown (226) and / or an upper hot crown (232), and translates in a cold cylinder (204) of a heat engine (202) which has a lower yoke (213) and an upper yoke (214), said piston (201) comprising a central piston pin (210), the lower piston rod (211) of which passes through the lower yoke (213) to be connected to power transmission means (205) housed in a transmission housing (206), and the upper piston rod (212) of which passes through the upper yoke (214) in order to open into a cooling and piston lubrication chamber (217), wherein a lubrication-cooling gallery (227) arranged in said pin (210) places said chamber (217) in communication with said housing (206) via an internal piston volume (228).

Description

[0001] The present invention relates to a multi-temperature double-acting piston, said piston being particularly suited to reciprocating engines implementing the Brayton thermodynamic cycle with regeneration using pistons rather than centrifugal compressors and turbines.

[0002] Brayton cycle regenerative engines generally include separate components dedicated to each phase of said cycle, said phases taking place continuously and simultaneously in said components, unlike reciprocating internal combustion engines of Beau de Rochas, Miller, Atkinson or Diesel cycles, whose phases are executed successively in a single cylinder.

[0003] Consequently, regenerative Brayton cycle engines include at least one compressor, at least one regenerative heat exchanger, at least one continuously operating burner or internal or external heat source, and at least one expansion valve.

[0004] Dedicating each phase of a thermodynamic cycle to a specific component offers several advantages. In particular, the temperature of the internal walls of each component can remain very close to that of the gases during that phase.

[0005] 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.

[0006] Conversely, since the internal walls of the expansion valve of said engine are 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 beginning and the end of their expansion.

[0007] Despite these advantages, the maximum thermodynamic efficiency of centrifugal compressor engines and regenerative Brayton cycle turbines is in practice hardly higher than that of conventional spark-ignition engines, and at best, comparable to that of high-speed diesel engines.

[0008] 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.

[0009] Furthermore, centrifugal compressor engines and Brayton cycle regenerative turbines are poorly suited to low power outputs, and can only operate within a limited power range beyond which their efficiency drops drastically.

[0010] This is why centrifugal compressor engines and Brayton cycle regenerative turbines are mainly used in applications where efficiency is not the sole objective, and which require, for example, high power mass and volume, low acoustic and vibration emissions, long service life, or reduced maintenance.

[0011] This is the case, for example, of certain military ships equipped, for example, with the "Rolls-Royce WR-21" centrifugal compressor and Brayton cycle turbine engine with regeneration, whose efficiency barely exceeds forty percent, while that of the slow two-stroke diesel engines that equip some ships exceeds fifty percent.

[0012] This is also the case for certain generator sets operating most often in cogeneration of electricity and heat such as the "T100" micro turbine from the company "Turbec", or the "C65" micro turbine from the company "Capstone", whose electrical efficiencies are only around twenty-eight to thirty percent, but which require little maintenance while offering very long lifespans.

[0013] The advantage of these turboshaft engines is that their turbine can withstand temperatures of around 1,300 degrees Celsius. However, their overall thermodynamic efficiency remains limited by that of the centrifugal compressors and turbines that comprise them, the efficiency of said compressors and turbines barely exceeding 80 percent over a relatively narrow operating range.

[0014] In view of 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 which have a notoriously higher efficiency.

[0015] This is, for example, the subject of patent No. US4653269 of March 31, 1987, where the expansion turbine ordinarily found on regenerative Brayton cycle turboshaft engines is replaced by a volumetric piston expansion cylinder.

[0016] However, calculations show 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 regenerative Brayton cycle engine cannot exceed that of an automotive diesel engine.

[0017] 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 be maintained at a temperature close to the average temperature of the gases expanded in said expander.

[0018] For example, if hot gases are introduced into the regulator at a temperature of 1,300 degrees Celsius and are expelled from said regulator at the end of expansion at a temperature of 600 degrees Celsius, the internal walls of said regulator must be maintained at approximately a temperature of 950 degrees Celsius.

[0019] The problem is that at such a temperature, it is impossible to maintain an oil film on the walls of the regulator cylinder to lubricate any sealing ring that a regulator piston moving in said cylinder might have.

[0020] Indeed, from about one hundred and sixty degrees Celsius, the oil film on the cylinder begins to coke, then burns beyond two hundred and fifty degrees Celsius.

[0021] Producing a high-efficiency thermodynamic regenerative Brayton cycle engine therefore faces a double impasse.

[0022] Indeed, either the said engine consists of centrifugal compressors and high-temperature resistant turbines, but in this case, the modest efficiency of these components does not allow it to exceed a total efficiency equivalent to that of an automotive diesel engine, or it consists of a volumetric piston expander which, in order to be sealed, requires a piston with a ring sliding on an oil film formed on the surface of a cylinder, the latter having to remain at a temperature not exceeding about one hundred and twenty degrees Celsius, which also does not allow the total efficiency of the said engine to be competitive.

[0023] In this context, it would be advantageous to be able to combine the ability of turbines to operate at high temperature with that of positive displacement piston machines to expand gases under high efficiency.

[0024] It is with this objective in mind that the heat engine with transfer-expansion and regeneration according to patent WO2016120560 published on August 4, 2016 and belonging to the applicant includes non-contact piston sealing means consisting of a continuous perforated inflatable ring which, when subjected to a certain internal pressure, inflates and approaches within a few micrometers of the expansion cylinder with which it cooperates without touching said cylinder, while simultaneously allowing compressed air to escape through calibrated orifices which pass through it in its radial thickness.

[0025] The fluid cushion sealing device just described is also the subject of patent No. FR 3032252, issued on May 25, 2018, and belonging to the applicant. This device effectively achieves a contactless seal, thus eliminating the need for oil to lubricate a contact-operating segment and allowing it to cooperate with a hot expansion valve cylinder maintained at a temperature of several hundred degrees Celsius.

[0026] In this context, it therefore becomes possible to use a volumetric piston expansion valve to create a regenerative Brayton cycle engine, and to maximize the efficiency of said engine to far surpass that of Diesel cycle engines.

[0027] Indeed, calculations and simulations demonstrate that the thermodynamic efficiency of a volumetric regenerative Brayton cycle piston engine can reach or even exceed seventy percent, which in practice can lead to the production of engines whose energy efficiency at braking exceeds sixty percent once the inevitable thermal and mechanical irreversibilities due to the very constitution of said engines have been deducted.

[0028] The problem encountered with the fluid cushion sealing device of patent No. FR 3032252 is that the temperature of the cylinder remains excessive for the available materials which can be used to make the continuous perforated ring.

[0029] Indeed, in order for the efficiency of a volumetric regenerative Brayton cycle piston engine to be significantly higher than that of existing Diesel engines, the gases must be introduced into its expansion valve at a temperature of around 1,300 degrees Celsius, under a pressure of around 20 bars.

[0030] As a result of these operating conditions, the temperature of the internal walls of the expansion valve stabilizes at around nine hundred and fifty degrees Celsius.

[0031] Since 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 about nine hundred and fifty degrees Celsius of said cylinder.

[0032] However, no material can both be used to manufacture said ring and withstand such a temperature.

[0033] Even a superalloy such as "Udimet 720", notably 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 imposed by the continuous perforated ring of the fluid cushion sealing device according to patent No. FR 3032252.

[0034] It is in particular for this reason and to use more common materials than high temperature resistant ceramics, 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 expansion valve and in particular of the cylinder to practical values ​​of around seven hundred degrees Celsius.

[0035] For example, the superalloy "Udimet 720" resists creep at a temperature of seven hundred degrees Celsius if it is subjected to a stress not exceeding two hundred and thirty megapascals.

[0036] The regenerative cooling system according to patent No. EP 3585993 provides for a cooling chamber which surrounds the expansion valve while a gas circulation space is left between said chamber and said expansion valve in which the gases exiting the expansion valve itself circulate at a temperature between five hundred and six hundred degrees Celsius.

[0037] Thus, according to the regenerative cooling system according to patent No. EP 3585993, the exhaust gases of the expansion valve maintain the temperature of the internal walls of the expansion valve at a temperature of around seven hundred degrees Celsius, while the heat exported by said gases is essentially recovered to be reintroduced into the cycle by the regeneration heat exchanger included in the Brayton cycle regenerative piston reciprocating engine.

[0038] 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 superalloy "Udimet 720".

[0039] However, in return for this possibility, the cylinder and cylinder 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 high price of nickel, represents an economic disadvantage.

[0040] In all cases, it is noted that the temperature of the expansion valve remains at least six hundred degrees Celsius higher than that of the rest of the engine and in particular, of the moving coupling and the transmission casing in which said coupling is housed.

[0041] Advantageously, the differential expansions resulting from this temperature difference can in particular be managed by the double-acting expansion cylinder with adaptive support, the subject of patent No. EP3350433 issued on August 7, 2019 and belonging to the applicant.

[0042] The said support allows an isotropic or anisotropic expansion of the expansion cylinder which is very different from that of the transmission housing on which it is fixed, without compromising either the operation of said cylinder, or that of the piston which moves in said cylinder.

[0043] The said support also keeps the piston centered in the cylinder, transmits the axial forces resulting from the expansion of the gases to the transmission housing, and limits the heat transfers from the expansion cylinder to said housing.

[0044] From the above, it is clear that no configuration is currently fully satisfactory that would allow for the realization, under the best possible conditions, of a Brayton cycle regenerative piston reciprocating engine.

[0045] Indeed, the fluid cushion sealing device must be supplied with compressed air by a compressor which consumes some of the work available on the shaft of the regenerative Brayton cycle piston reciprocating engine, to the detriment of the overall efficiency of the latter.

[0046] This effectively reduces the final energy efficiency of the said engine, 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, regardless of the speed and load of the said engine.

[0047] Furthermore, to ensure the 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.

[0048] Indeed, the said cooling system makes the path of the gases expelled from the expansion valve convoluted and induces pressure losses which reduce the overall efficiency of the Brayton cycle regenerative reciprocating piston engine.

[0049] In addition, the heat extracted from the internal walls of the expansion valve by the regenerative cooling system is reintroduced into the Brayton cycle upstream of a burner or hot source by a regeneration heat exchanger whose efficiency is not one hundred percent.

[0050] A portion of the heat extracted from the internal walls of the expansion valve is therefore lost, and the power passing through the exchanger increases due to the presence of said cooling system.

[0051] Furthermore, the specific power of the Brayton cycle regenerative piston reciprocating engine is substantially reduced by the regenerative cooling system according to patent No. EP 3585993, which implies revising upwards the sizing of said engine to meet the power objectives of the application for which it is intended.

[0052] It is also noted 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 shocks and vibrations.

[0053] Therefore, without excluding any other application in any field whatsoever, the hot cylinder head and cold cylinder reciprocating heat engine according to the invention is intended, among other things, to produce Brayton cycle regenerative reciprocating piston engines in which the mainly hot expansion valve limits heat losses, while ensuring a robust and durable seal between the piston and the cylinder of said expansion valve.

[0054] Document WO 2016 / 120556 A1 shows a multi-temperature double-acting piston according to the prior art.

[0055] In the field of application of reciprocating piston machines in general and heat engines in particular, the invention results in a multi-temperature, double-acting piston: Whose piston crowns are kept at a high temperature so as to limit the cooling of the hot gases in contact with them; Whose sealing with the cylinder with which it cooperates can be achieved by means of cast iron or steel rings 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 no longer requires the engine receiving it to be equipped with the regenerative cooling system such as that described in patent No. EP 3585993, the said engine therefore no longer suffers either the power and efficiency losses linked to the use of a compressor supplying the said sealing device, or the additional pressure losses at the exhaust of the expansion valve linked to a more tortuous gas path, or the heat losses due to the efficiency of the regeneration heat exchanger being less than "one", or the losses in specific engine power associated with this configuration.

[0056] Consequently, the multi-temperature double-acting piston according to the invention makes it possible to avoid the engine which houses it being made 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 blocks of automotive Diesel engines, and said engine being able to include hot cylinder heads operating at high temperature made of silicon carbide, a material with high mechanical resistance at high temperatures, abundant and cheap.

[0057] 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 to be used to make 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.

[0058] This promotes a rapid temperature rise of said engine by reducing the energy required to reach its operating temperature, and leads to lower energy consumption of said engine particularly when the latter is applied to road, rail, or maritime transport.

[0059] It is understood that the multi-temperature double-acting piston according to the invention can be applied, in addition to thermal engines in general, stationary or mobile and with internal or external combustion, to any other application similar in its concept and principle which could advantageously take advantage of the particular characteristics and functionalities of said piston according to the invention.

[0060] 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.

[0061] The double-acting, multi-temperature piston capable of translating within a cold cylinder arranged in a cooled cylinder block comprising a heat engine, said piston being directly or indirectly connected by power transmission means housed in a transmission housing to at least one rotary or reciprocating power output shaft, while said piston forms a lower variable-volume chamber with the cold cylinder and a lower cylinder head 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 having a first end forming a lower piston rod which passes through the lower cylinder head via a lower rod orifice which cooperates with lower rod sealing means to open into the transmission housing and to be directly or indirectly connected to the power transmission means by piston fastening means, while the second end of said pin forms an upper piston rod which passes through the upper cylinder head via an 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 outer diameter is substantially smaller than the inner diameter of the cold cylinder, said ring having piston sealing means which are in contact with said cylinder to achieve a seal with the latter; A lower radial connecting disc which radially connects the central piston pin with the peripheral sealing ring on the side of the lower variable volume chamber, and an upper radial connecting disc 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 housing; At least one peripheral lubrication orifice for the ring which connects the internal volume of the piston 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 bear directly or indirectly 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 peripheral sealing ring centered in the cold cylinder;A lower hot cap interposed between the lower radial connecting disc and the lower variable volume chamber and / or an upper hot cap interposed between the upper radial connecting disc and the upper variable volume chamber; Hot cap clamping means that directly or indirectly hold the lower hot cap clamped to the peripheral sealing ring and / or to the lower radial connecting disc, and / or that directly or indirectly hold the upper hot cap clamped to said ring and / or to the upper radial connecting disc, said means leaving said hot caps free to expand relative to said ring and / or to said discs; Hot cap centering means that locate the lower hot cap and / or the upper hot cap relative to the peripheral sealing ring.

[0062] The multi-temperature double-acting piston according to the invention comprises a lower hot cap and / or an upper hot cap which are wholly or partly made of a material resistant to high temperatures.

[0063] The multi-temperature double-acting piston according to the invention comprises a high-temperature resistant material which is mainly made of silicon carbide.

[0064] The multi-temperature double-acting piston according to the invention includes 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 lower radial connecting disc, or between the upper hot cap and said ring and / or the upper radial connecting disc, or both.

[0065] The multi-temperature double-acting piston according to the invention includes 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 upper hot cap and said pin, or both.

[0066] The multi-temperature double-acting piston according to the invention includes thermal insulation means which consist of at least one insulating ring made of a material with low thermal conductivity.

[0067] The multi-temperature double-acting piston according to the invention comprises a material with low thermal conductivity which is mainly composed of zirconium oxide.

[0068] The multi-temperature double-acting piston according to the invention comprises an insulating ring which is held 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 lower radial connecting disc and / or the upper hot cap and / or the upper radial connecting disc via at least one small contact edge.

[0069] The multi-temperature double-acting piston according to the invention comprises an insulating ring which is held 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 lower radial connecting disc and / or the upper hot cap and / or the upper radial connecting disc by means of at least one insulating ring seal which is gas-tight.

[0070] The multi-temperature double-acting piston according to the invention includes cap-plating means which directly or indirectly maintain the lower hot cap plated on the peripheral sealing ring and / or on the lower radial connecting disc, which are formed of an external coaxial lower spindle tube which encloses the central piston spindle, said tube bearing on one side, on the lower hot cap in the vicinity of said spindle, and on the other side, on the power transmission means.

[0071] The multi-temperature double-acting piston according to the invention includes cap-pressing means which directly or indirectly maintain the upper hot cap pressed against the peripheral sealing ring and / or the upper radial connecting disc, which are formed of an external coaxial upper spindle tube which encloses the central piston spindle, said tube bearing on one side, on the upper hot cap in the vicinity of said spindle, and on the other side, on an upper rod stop provided directly or indirectly on the upper piston rod in the vicinity of its end which opens into the piston cooling and lubrication chamber.

[0072] 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 through which said tubes respectively bear on the lower hot cap and on the power transmission means and / or on the upper hot cap and on the upper rod stop.

[0073] The multi-temperature double-acting piston according to the invention comprises a lower hot cap and / or an upper hot cap having a concave conical cap surface through which said cap is held pressed by cap pressing means onto a peripheral circular contact edge which is directly or indirectly integral with the peripheral sealing ring and / or the periphery of the lower radial connecting disc and / or the periphery of the upper radial connecting disc, the angle of the concave cone formed by said surface 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 connecting disc, the upper radial connecting disc and the central piston pin,The axial distance separating the support point of the cap-pressing means on said cap from the peripheral sealing ring remains approximately constant, all other things being equal, while the concave conical surface of the cap and the circular peripheral contact edge form the cap-centering means.

[0074] The multi-temperature double-acting piston according to the invention includes piston fixing means which consist of a double-acting axial piston screw which includes, firstly, a piston screw body which is housed in a piston screw tunnel which passes through the central piston spindle lengthwise, said screw including, on the one hand, a piston screw head which bears against 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.

[0075] 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 volume of piston, and a second section which goes from said volume to the inside of the transmission housing.

[0076] The multi-temperature double-acting piston according to the invention includes guiding means which consist of a barrel-shaped skirt which is arranged on the outer periphery of the peripheral sealing ring and which bears against the cold cylinder.

[0077] 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 disc which is housed in said volume and, on the other hand, the upper radial connecting disc, said distribution disc being approximately parallel to said radial connecting disc and forming, on the one hand, a seal with the central piston pin, and ending, on the other hand, radially in the vicinity of the internal wall of the peripheral sealing ring, the lubricating-cooling fluid from the piston cooling and lubrication chamber being able to exit at the level of said vicinity.

[0078] The multi-temperature double-acting piston according to the invention comprises a central piston pin which includes, inside the internal volume of the piston and in the vicinity of the lower radial connecting disc, a fluid recirculation collar which, when the central piston pin 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.

[0079] The multi-temperature double-acting piston according to the invention comprises a lower radial connecting disc which has a hollow shape at the point of its connection with the central piston pin, said shape constituting an overflow reservoir which can store lubricating-cooling fluid, while at least one overflow orifice which communicates with the interior of the transmission housing via the lubrication-cooling gallery fixes the maximum level of said reservoir.

[0080] The multi-temperature double-acting piston according to the invention includes 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.

[0081] 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-cooling gallery via at least one radial reservoir-gallery connecting conduit.

[0082] The multi-temperature double-acting piston according to the invention includes a screw check 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 to the lubrication-cooling gallery, but not the other way around.

[0083] 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 inlet check valve which allows fluid-forced air to enter said chamber without allowing it to exit, while said chamber is connected to an air tank by a pressure-limiting valve which allows fluid-forced air to flow from said chamber to said tank when the pressure of said air in said chamber reaches a certain value.

[0084] The multi-temperature double-acting piston according to the invention comprises a reflective screen which is interposed between the lower hot cap and the lower radial connecting disc to which a part of the peripheral sealing ring may be added and / or, between the upper hot cap and the upper radial connecting disc to which a part of said ring may be added.

[0085] The multi-temperature double-acting piston according to the invention includes thermal insulation means which are made of a cellular or fibrous insulating material which occupies all or part of the space between the lower hot cap and the lower radial connecting disc and / or between the upper hot cap and the upper radial connecting disc.

[0086] The multi-temperature double-acting piston according to the invention comprises at least a first radial space left between the outer coaxial upper spindle tube and the central piston spindle, at least a second radial space left between the outer coaxial lower spindle tube and the central piston spindle, and one or more radial spaces left between the piston screw body and the inner wall of the piston screw tunnel which form at least a part of the lubrication-cooling gallery, the lubricating-cooling fluid being able to circulate successively in said spaces to go from the piston cooling and lubrication chamber to the internal piston volume, and then from said volume to the inside of the transmission housing.

[0087] The multi-temperature double-acting piston according to the invention includes lower rod sealing means and / or upper rod sealing means which consist of a continuous extensible ring which is directly or indirectly attached to the cooled cylinder housing, and whose inner diameter is substantially smaller than the outer diameter of the lower piston rod or the upper piston rod which it encloses.

[0088] The multi-temperature double-acting piston according to the invention comprises a continuous extensible ring which is connected to a ring plate by a ring tube of low radial thickness, said ring, said plate and said ring being made from a single piece of material.

[0089] The multi-temperature double-acting piston according to the invention comprises a continuous extensible ring which is axially clamped between two ring rings by an axial ring compression spring.

[0090] The following description, with reference to the attached drawings given as non-limiting examples, will allow for a better understanding of the invention, its characteristics, and the advantages it is likely to provide: [ Fig. 1 ] is a three-dimensional view of a heat engine as it can be designed to receive the multi-temperature double-acting piston according to the invention, said engine forming an expansion valve which allows, for example, the implementation of a regenerative Baryton thermodynamic cycle. Fig. 2 ] is a three-dimensional cross-sectional view of the multi-temperature, double-acting piston according to the invention, housed in the heat engine shown in figure 1 said engine is also shown in three-dimensional cross-section. Fig. 3 ] is a cross-sectional view of the multi-temperature, double-acting piston according to the invention, housed in the heat engine shown in figure 1said engine is also shown in cross-section. Fig. 4 ] is a three-dimensional cross-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 double-acting piston screw, while the crown-pressing means consist in particular of an external coaxial lower spindle tube and an external coaxial upper spindle tube. Fig. 5 ] is an exploded three-dimensional view of the multi-temperature double-acting piston according to the invention and in its particular configuration shown in figures 2 to 5 . [ Fig. 6 ] is a close-up cross-sectional view of the multi-temperature, double-acting piston according to the invention, placed in the context of the engine shown in figure 1said view showing in particular how said piston is connected to the power transmission means, and how the lower hot cap is held pressed against the peripheral sealing ring by an external coaxial lower spindle tube via insulating rings. Fig. 7 ] is a close-up cross-sectional view of the multi-temperature, double-acting piston according to the invention, placed in the context of the engine shown in figure 1 said view notably highlighting how the upper piston rod opens into the piston cooling and lubrication chamber, and how the upper hot cap is held pressed against the peripheral sealing ring by an external coaxial upper spindle tube via insulating rings. Fig. 8 ] is a cross-sectional view of the multi-temperature, double-acting piston according to the invention as shown in figures 2 to 7said view showing how a lubricating-cooling fluid can circulate from an axial screw reservoir into the transmission housing to successively cool the upper radial connecting disc, the peripheral sealing ring, and the lower radial connecting disc, while simultaneously cooling and lubricating the piston sealing means and the barrel-shaped skirt of said ring, said means and said skirt being maintained in contact with the cold cylinder. Fig. 9 ] is a cross-sectional view of the multi-temperature, double-acting piston according to the invention as shown in figure 8said view showing in particular how the lubricating-cooling fluid can recirculate within the internal volume of the piston to complete the cooling of the welded assembly formed by the peripheral sealing ring, the lower radial connecting disc, the upper radial connecting disc and the central piston pin, and to supply peripheral ring lubrication ports present in the peripheral sealing ring. Fig. 10 ] is a close-up schematic cross-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 welded assembly and the insulating ring when said caps are cold. Fig. 11] is a close-up schematic cross-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 welded assembly and the insulating ring when said caps are hot. Fig. 12 ] 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, both of which are connected inside the transmission housing, which here acts as an air source and air reservoir. Fig. 13] is a cross-sectional view of a variant of the multi-temperature double-acting piston according to the invention, in which part of the lubrication-cooling gallery is formed by a radial space left between, on the one hand, the outer coaxial upper spindle tube and the outer coaxial lower spindle tube, and on the other hand, the central piston spindle, while a reflective screen and a cellular or fibrous insulating material are interposed between the lower and upper hot caps and the lower and upper radial connecting discs to which said caps face. Fig. 14 ] is a close-up cross-sectional view of the upper rod sealing means of the multi-temperature double-acting piston according to the invention, said means consisting of a continuous extensible ring connected to a ring plate by a ring tube of low radial thickness. Fig. 15] is a close-up cross-sectional view of the upper rod sealing means of the multi-temperature double-acting piston according to the invention, said means being made up of a continuous axially extensible ring clamped between two ring rings by an axial ring compression spring. DESCRIPTION OF THE INVENTION :

[0091] We showed 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.

[0092] As shown by 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 casing 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.

[0093] As can clearly be seen in figure 7 , 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 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.

[0094] As illustrated in figures 2 to 5 and in figures 8 And 9The 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 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 housing 206 and to be directly or indirectly connected to the power transmission means 205 by means of piston fixing means 231.

[0095] The second end of said pin 210 forms an upper piston rod 212 which passes 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.

[0096] It is noted that the lower rod sealing means 280 and the upper rod sealing means 281 can be in contact with the lower piston rod 211 and the upper piston rod 212 respectively, either directly or indirectly via an external coaxial lower spindle tube 243 and an external coaxial upper spindle tube 248 respectively, as illustrated by the figures 2 , 3 , 6 , 7 ,14 And 15 .

[0097] We notice in figures 2 to 11 that the multi-temperature double-acting piston 201 according to the invention comprises a peripheral sealing ring 220 whose outer diameter is substantially smaller than the inner diameter of the cold cylinder 204.

[0098] It is noted in the said figures that the peripheral sealing ring 220 includes piston sealing means 221 for example consisting of compression rings 222 made of cast iron or steel such as those ordinarily found on the pistons of conventional automobile engines, the said means 221 being in contact with the said cylinder 204 to achieve a seal with the latter.

[0099] We can see very clearly in figure 4that the multi-temperature double-acting piston 201 according to the invention also comprises a lower radial connecting disc 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 connecting disc 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.

[0100] It should be noted that the lower radial connecting disk 224 and / or the upper radial connecting disk 225 can be a simple metal disk, a cone, a dome or a truncated sphere, or be of any geometry, whether non-ribbed or ribbed, to give the said disks 224, 225 great rigidity.

[0101] It is also noted that, as an alternative embodiment of the multi-temperature double-acting piston 201 according to the invention, the lower radial connecting disc 224 can be connected inside the internal volume of the piston 228 to the upper radial connecting disc 225 by struts, spokes, fins or by any other mechanical connection which joins said discs 224, 225 so that they form a rigid assembly.

[0102] It should also be noted that the lower radial connecting disc 224 and / or the upper radial connecting disc 225 can preferably be made integral with the central piston pin 210 and / or the peripheral sealing ring 220 by friction welding, electron beam welding or arc welding, or by any type of welding or assembly known to those skilled in the art.

[0103] We notice in figures 8 And 9that 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 spindle 210 and in one or more sections, said gallery 227 communicating on the one hand, the piston cooling and lubrication chamber 217 with the internal volume of piston 228, and on the other hand, said volume 228 with the interior of the transmission housing 206.

[0104] 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 lubrication orifice of ring 229 which connects the internal volume of piston 228 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.

[0105] The multi-temperature double-acting piston 201 according to the invention also includes guiding means 230 particularly visible in figure 4 , said means 230 taking direct or indirect support 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.

[0106] Particularly in figure 7 , it is noted that the multi-temperature double-acting piston 201 according to the invention comprises a lower hot cap 226 interposed between the lower radial connecting disc 224 and the lower variable volume chamber 208 and / or an upper hot cap 232 interposed between the upper radial connecting disc 225 and the upper variable volume chamber 209;

[0107] The multi-temperature, double-acting piston 201 according to the invention also includes cap-pressing 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 the lower radial connecting disc 224, and / or which directly or indirectly maintain the upper hot cap 232 pressed against said ring 220 and / or the upper radial connecting disc 225, said means 234 leaving said caps 226, 232 free to expand with respect to said ring 220 and / or said discs 224, 225.

[0108] Finally, the multi-temperature double-acting piston 201 according to the invention includes crown centering means 235 - for example shown in figure 7- which locate the lower hot cap 226 and / or the upper hot cap 232 in relation to the peripheral sealing ring 220.

[0109] It should be noted that according to one 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 made in whole or in part of a high-temperature resistant material 275 such as silicon carbide 276 and its various variants, alloyed or not with other materials.

[0110] As another variant shown in figures 2 to 11, thermal insulation means 233 and / or dome sealing means 239 may be interposed either, between the lower hot dome 226 and the peripheral sealing ring 220 and / or the lower radial connecting disc 224, or, between the upper hot dome 232 and said ring 220 and / or the upper radial connecting disc 225, or both, said means 233, 239 being able to form an integral part of said dome 226, 232 and / or said discs 224, 225.

[0111] 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 be an integral part of said caps 226, 232 and / or of said pin 210.

[0112] Wherever they are located, the thermal insulation means 233 may consist of at least one insulating ring 236 made of a material with low thermal conductivity 237 such as zirconium oxide 238 and its various variants, alloyed or not with other materials, or such as quartz.

[0113] As a non-limiting alternative, the insulating ring 236 can also be made of quartz, which also has low thermal conductivity and a low modulus of elasticity that gives it a great ability to adapt to the geometry of the components with which it is in contact and cooperates.

[0114] It should be noted that the insulating ring 236 can be 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 connecting disc 224 and / or the upper hot cap 232 and / or the upper radial connecting disc 225 via at least one small contact edge 241.

[0115] We will notice in Figures 10 And 11 advantageously, the insulating ring 236 may include a de-rigidifying groove 291 which gives it more flexibility and ensures a 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.

[0116] 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 lower hot cap 226 and / or the lower radial connecting disc 224 and / or the upper hot cap 232 and / or the upper radial connecting disc 225 by means of at least one insulating ring seal 242 which is tight against the working gas 240.

[0117] It is noted that the 242 insulating ring seal can, for example, include several metal sheets like the cylinder head gaskets found in modern automotive internal combustion engines, or be made of high-temperature resistant materials like "Therma-pur" developed by the "Garlock" company.

[0118] As can be seen in figures 2 to 9, the cap-pressing means 234 which directly or indirectly maintain the lower hot cap 226 pressed against the peripheral sealing ring 220 and / or the lower radial connecting disc 224, may be formed of an external coaxial lower spindle tube 243 which encloses the central piston spindle 210, said tube 243 bearing on one side, on the lower hot cap 226 in the vicinity of said spindle 210, and on the other side, on the power transmission means 205 which may for example consist of a cross 244 which translates in a cross cylinder 293, said cross 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.

[0119] We also observe in figures 2 to 5 and in figures 7 to 9that the cap-pressing means 234 which directly or indirectly maintain the upper hot cap 232 pressed against the peripheral sealing ring 220 and / or the upper radial connecting disc 225, may be formed of an external coaxial upper spindle tube 248 which encloses the central piston spindle 210, said tube 248 bearing on one side, on the upper hot cap 232 in the vicinity of said spindle 210, and on the other side, 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.

[0120] As can clearly be seen in figure 4, some or all of the ends of the external coaxial lower spindle tube 243 and / or the external coaxial upper spindle tube 248 may 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, the tube spring 250 being advantageously able to consist of a stack of "Belleville" washers known per se.

[0121] THE Figures 10 And 11illustrate 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 may advantageously have a concave conical cap surface 251 through which said cap 226, 232 is held pressed by cap pressing means 234 on a circular peripheral contact edge 252 which is directly or indirectly integral with the peripheral sealing ring 220 and / or the periphery of the lower radial connecting disc 224 and / or the periphery of the upper radial connecting disc 225.

[0122] 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 connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210, the axial distance which separates the point of support of the cap 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 centering means of the cap 235.

[0123] It is noted that this particular configuration of the multi-temperature double-acting piston 201 according to the invention allows the force to which the cap clamping means 234 are subjected - which are outside the image in Figures 10 And 11 but actually present - remains approximately constant regardless of the difference between the thermal expansion of said cap 226, 232 and that of the welded assembly 289 formed by the peripheral sealing ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210.

[0124] Furthermore, said configuration makes it possible to limit the variation of the volumetric ratio of the internal combustion engine 202 according to its temperature, particularly during the cold start phases of said engine 202.

[0125] It is noted that advantageously and as an unrepresented variant, the circular edge of peripheral contact 252 could advantageously present a spherical contact to the concave conical surface of cap 251.

[0126] 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 includes, firstly, a piston screw body 255 which is housed in a piston screw tunnel 256 which passes through the central piston spindle 210 in its length direction, said screw 219 comprising, firstly, a piston screw head 253 which bears against the end of the upper piston rod 212 which opens into the piston cooling and lubrication chamber 217, and secondly, a piston screw thread 254 which is screwed into the power transmission means 205.

[0127] According to one 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 fastener which will be obvious to those skilled in the art.

[0128] As can clearly be seen in figures 8 And 9, the piston screw tunnel 256 may advantageously form at least a part of the lubrication-cooling gallery 227, the lubricating-cooling fluid 257 being able to circulate between the piston screw body 255 and the inner 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 to the inside of the transmission housing 206, the piston screw body 255 being able to include screw sealing bulges 258 to separate the piston screw tunnel 256 into sections, said bulges 258 being able for these purposes to have a bulge sealing seal 259.

[0129] As clearly illustrated by the figure 4, the guiding means 230 can consist of a barrel-shaped skirt 260 which is arranged on the outer periphery of the peripheral sealing ring 220 and which bears on the cold cylinder 204, said skirt 260 having a convergent shape which promotes the establishment of a hydrodynamic lubrication regime between itself and the cold cylinder 204 with which it cooperates.

[0130] It is clearly noticeable in Figures 10 And 11 that the barrel-shaped skirt 260 can advantageously be positioned between two compression segments 222 and adjoin an oil scraper segment 278.

[0131] There figure 8illustrates that the lubrication-cooling gallery 227 can open into the internal volume of piston 228 via a small axial clearance left between, on the one hand, a fluid distribution disc 261 which is housed in said volume 228 and, on the other hand, the upper radial connecting disc 225, said distribution disc 261 being approximately parallel to said radial connecting disc 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 the level of said vicinity for example via distribution weirs 290, orifices or slots of any kind provided in the periphery of the fluid distribution disc 261.

[0132] As clearly illustrated by the figure 9According to a particular variant of the multi-temperature double-acting piston 201 according to the invention, the central piston pin 210 may include, within the internal piston volume 228 and in the vicinity of the lower radial connecting disc 224, a fluid recirculation collar 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 has accumulated in said volume 228 and on the surface of said disc 224, said collar 262 being able to include collar grooves 263 which form radial jets of lubricating-cooling fluid 257 which are uniformly distributed over three hundred and sixty degrees.

[0133] Particularly in figure 8, it is noted that the lower radial connecting 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-cooling fluid 257, while at least one overflow orifice 265 which communicates with the interior of the transmission housing 206 via the lubrication-cooling gallery 227 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 the lubricating-cooling fluid 257 which contains said reservoir 264 does not exceed that of the overflow orifice 265, said excess fluid 257 being expelled into the transmission housing 206.

[0134] In figure 7It is noted that a fluid nozzle 266, supplied by the lubricating-cooling fluid source 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 .

[0135] Still in figures 8 And 9 , it is observed 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 reservoir-gallery connecting conduit 268.

[0136] THE figures 8 And 9also clearly show that a screw check valve 269 can be housed in the axial screw of the double-acting piston 219, said valve 269 allowing the lubricating-cooling fluid 257 to go from the axial screw reservoir 267 to the lubrication-cooling gallery 227, but not the other way around, 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 contained in 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.

[0137] As a variant of the multi-temperature double-acting piston 201 according to the invention, it has been shown in figure 12that the piston cooling and lubrication chamber 217 can be connected to an air source 270 or to any gas source of any kind by an air inlet check valve 271 which allows fluid force air 272 to enter said chamber 217 without allowing it to exit, while said chamber 217 is connected to an air tank 273 by a pressure limiting valve 274 which allows fluid force air 272 to flow from said chamber 217 to said tank 273 when the pressure of said air 272 in said chamber 217 reaches a certain value.

[0138] 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.

[0139] We also notice in figure 12that 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.

[0140] As has been shown in figure 13 , a reflective screen 295 may be interposed between the lower hot cap 226 and the lower radial connecting disc 224 to which a part of the peripheral sealing ring 220 may be added and / or, between the upper hot cap 232 and the upper radial connecting disc 225 to which a part of said ring 220 may be added, said reflective screen 295 returning to the lower hot cap 226 and / or to the upper hot cap 232 the heat emitted, in particular in the form of infrared radiation, by said cap 226, 232.

[0141] It was also shown in figure 13that the thermal insulation means 233 may consist of a cellular or fibrous insulating material 296 which occupies all or part of the space between the lower hot cap 226 and the lower radial connecting disc 224 and / or between the upper hot cap 232 and the upper radial connecting disc 225.

[0142] There figure 13also illustrates that at least a first radial space left between the outer coaxial upper spindle tube 248 and the central piston spindle 210, at least a second radial space left between the outer coaxial lower spindle tube 243 and the central piston spindle 210, and one or more radial spaces left between the piston screw body 255 and the inner wall of the piston screw tunnel 256 can form at least a part of the lubrication-cooling gallery 227, the lubricating-cooling fluid 257 being able to flow successively in said spaces to go from the piston cooling and lubrication chamber 217 to the internal piston volume 228, and then from said volume 228 into the transmission housing 206.

[0143] According to this particular configuration of the multi-temperature double-acting piston according to the invention, the outer wall of the outer coaxial upper spindle tube 248 and the outer wall of the outer coaxial lower spindle tube 243 are always kept at a low temperature, so that a lubricating oil film which coats the outer wall of said tubes 248, 243 is preserved from any coking or spontaneous combustion by excess temperature, including when the heat engine 202 is stopped after having operated at high temperature, and particularly insofar as an electric pump is provided which forces lubricating-cooling fluid 257 to circulate in the lubrication-cooling gallery 227 after the stopping of said engine 202.

[0144] We showed in Figures 14 And 15that the lower rod sealing means 280 and / or the upper rod sealing means 281 can consist of a continuous expandable ring 297 which is directly or indirectly integral with the cooled cylinder housing 203, and whose inner diameter is substantially smaller than the outer diameter of the lower piston rod 211 or the upper piston rod 212 which it encloses.

[0145] It is noted that in this case, the radial thickness and axial thickness of the continuous extensible ring 297 are advantageously low to limit the energy losses produced by the friction of said ring 297 on the lower piston rod 211 and / or the upper piston rod 212.

[0146] There figure 14illustrates that the continuous extensible ring 297 can be connected to a ring plate 298 by a ring tube 299 of low radial thickness, said ring 297, said plate 298 and said ring 297 being made from a single piece of material.

[0147] It is noted that in this case and advantageously, the ring plate 298 can move directly or indirectly radially and in a sealed manner in the cooled cylinder housing 203, and include at least one radial ring stop 303 which limits its eccentricity relative to the lower piston rod 211 or relative to the upper piston rod 212.

[0148] Another variant illustrated in figure 15provides that the continuous extensible ring 297 can be axially clamped between two ring rings 300 by an axial compression ring spring 301 which can cooperate with a sealing ring 302, the two ring rings 300 being able to expose to the lower piston rod 211 or the upper piston rod 212 a radial ring stop 303 which can come into contact with said rod 211, 212. HOW THE INVENTION WORKS :

[0149] The operation of the multi-temperature double-acting piston 201 according to the invention is easily understood from the following: figures 1 to 15 .

[0150] The said piston 201 can be applied to any heat engine 202 performing a Beau de Rochas, Miller, Atkinson, Diesel, or any other thermodynamic cycle known to those skilled in the art.

[0151] In figures 1 to 15, we have shown the multi-temperature double-acting piston 201 according to the invention and as it can be implemented in a heat engine 202 performing a regenerative Brayton cycle which is identical to that performed by the heat engine with transfer-expansion and regeneration according to patent No. WO2016120560.

[0152] In this particular context, the said piston 201 applies only to the expansion valve 279 of the said engine 202, therefore, the other components of the latter such as one or more compressors, a burner or a regeneration exchanger necessary for the implementation of the regenerative Brayton cycle, are not represented.

[0153] 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 regenerative Brayton 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 used in mass-produced automotive internal combustion engines, said rings 222 cooperating with an oil scraper ring 278.

[0154] Achieving this objective implies, in particular, that the largest possible proportion of the external wall surface of the 201 multi-temperature double-acting piston is maintained at a high temperature.

[0155] 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, by means of lower rod sealing means 280 and upper rod sealing means 281, said means 280, 281 being formed either of metallic cut segments 282 known per se, or of a continuous expandable ring 297 which is directly or indirectly integral with the cooled cylinder block 203 as shown in the Figures 14 And 15 .

[0156] In order for the said objective to be fully achieved, the multi-temperature double-acting piston 201 according to the invention is advantageously applied to a heat engine 202 based on the same said objective and which, as such, limits to the maximum the heat losses of the working gas 240 by having the largest possible part of its internal walls brought to high temperature.

[0157] That is why in figures 1 to 3 We have shown a heat engine 202 in which the expansion valve 279 receives the multi-temperature double-acting piston 201, said expansion valve 279 comprising a lower cylinder head 213 and an upper cylinder head 214 whose operating temperature is high - on 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 on the order of fourteen hundred degrees Celsius, and which can be used in an oxidizing environment at these high temperatures.

[0158] Only the internal surfaces of said regulator 279 which are in contact with both the working gas 240 and the piston sealing means 221 are maintained at a temperature of only one hundred degrees Celsius, said temperature remaining compatible with a lubricating-cooling fluid 257 such as lubricating and cooling oil 283, and preventing the latter - in this case engine oil known per se - from coking, burning, or degrading prematurely.

[0159] As we can see in figures 2 And 3, said surfaces are, in addition to the cold cylinder 204 arranged in a cooled cylinder casing 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 components 220, 204, 211, 212 totaling a surface in contact with the working gas 240 much smaller 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.

[0160] 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 here intended to transform the back-and-forth movements of said piston 201 in the cold cylinder 204 into continuous rotational movement of a crankshaft 247, have been shown.

[0161] According to this non-limiting embodiment example, 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.

[0162] We notice 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 by means of a cross 244, said connecting rod 34 being articulated around a crank 246 fitted on the crankshaft 247, the latter forming a power output shaft 207.

[0163] As can clearly be seen in figures 2 to 5 and in figures 8 , 9 And 13The welded assembly 289, which consists of the peripheral sealing ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210, is fixed to the stock 244 by a double-acting axial piston screw 219, the body of which is housed in a piston screw tunnel 256 which passes through the central piston pin 210 lengthwise.

[0164] The piston screw tunnel 256 here forms a lubrication-cooling gallery 227, the lubrication and cooling oil 283 being able in particular 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 volume of piston 228, and a second section of said gallery 227 which goes from said volume 228 to the inside of the transmission housing 206.

[0165] Advantageously, the piston screw body 255 has screw sealing bulges 258 which hermetically separate the piston screw tunnel 256 into two sections by means of bulge sealing gaskets 259.

[0166] As clearly shown by figures 2 to 5 and the figures 8 , 9 And 13The double-acting axial piston screw 219 also includes a piston screw head 253 which bears against 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.

[0167] We will assume here that the working gas 240 is introduced into the regulator 279 via an intake valve 284 at a temperature of 1,300 degrees Celsius, while the operational equilibrium temperature of the lower cylinder head 213 and the upper cylinder head 214 which enclose 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 950 degrees Celsius.

[0168] It is noted that advantageously and as illustrated by the Figures 1 And 2 and the figures 6 And 7 , the inlet valve 284 and an exhaust valve 285 through which the working gas 240 is expelled from the regulator 279 after being expanded there are autoclaves, and can each be piloted by a hydraulic regenerating valve actuator as described in patent No. 3071896 dated October 11, 2019 and belonging to the applicant.

[0169] Unlike the heat engine with transfer-expansion and regeneration according to patent WO2016120560, in which all the internal walls of the expansion valve 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 expansion valve 279 of the heat engine 202 is here maintained by cylinder-case cooling means 286 at the relatively low temperature of one hundred degrees Celsius, this temperature being given only as an example.

[0170] In figures 2 And 3It has been shown that the means of cooling the crankcase-cylinder 286 can consist of a cooling chamber 287 which envelops the external surface of the cold cylinder 204, a heat transfer fluid 288, in this case water, circulating in said chamber 287.

[0171] Thus, and as clearly shown by figures 2 And 3 , practically all the internal walls of the expansion valve 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.

[0172] The remaining hot surfaces are sufficient to obtain from the regenerative Brayton cycle a significantly higher thermodynamic efficiency in practice than that obtained from the Otto and Diesel cycles.

[0173] We 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 around 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.

[0174] It is therefore understood that, unlike the heat engine with transfer-expansion and regeneration according to patent WO2016120560, the piston sealing means 221 are no longer here made up of a fluid cushion sealing device according to patent FR 3032252, but rather of a segmentation comparable to that of conventional automotive internal combustion engines, the said means 221 being cooled and lubricated in the same way.

[0175] This similarity allows the 201 multi-temperature double-acting piston according to the invention to benefit from more than a century of know-how in the field of piston segmentation for internal combustion engines.

[0176] The particular configuration of said piston 201 and of the regulator 279 of which said piston 201 is a part is justified in that, under the temperature conditions which have just been described, the heat given to the cold cylinder 204 by the working gas 240 forms an energy loss comparable to or even less than that induced on the one hand, by the fluid cushion sealing device which is the subject of patent FR 3032252 due to the means of compression necessary for its supply of compressed air, and on the other hand, by the regenerative cooling system according to patent No. EP 3585993 because of the additional exhaust pressure losses which it generates, and the reintroduction into the thermodynamic cycle of the heat extracted from the internal walls of the regulator via a regeneration heat exchanger whose efficiency is less than one.

[0177] As proof of the validity of the multi-temperature double-acting piston 201 according to the invention, it is noted 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 lower hot cap 226 and the upper hot cap 232 - were maintained at only one hundred degrees Celsius like the internal walls of mass-produced automotive internal combustion engines, the average specific surface heat power - for example expressed in kilowatts per square meter - given by the working gas 240 to the cold cylinder 204, would be much less than that given by said gas 240 to said cylinder heads 213, 214 and said caps 226, 232.

[0178] Indeed, the surface area that the cold cylinder 204 exposes to the working gas 240 is small at the beginning of the expansion of said gas 240, then increases as said gas 240 expands and, in parallel, its temperature decreases, unlike the lower cylinder head 213, the upper cylinder head 214, the lower hot cap 226 and the upper hot cap 232, whose surface area exposed to the working gas 240 remains constant.

[0179] Thus, assuming that said cylinder heads 213, 214 and said cylinder caps 226, 232 are deliberately maintained at one hundred degrees Celsius during expansion, the specific surface cooling power would be much lower at the internal walls of the cold cylinder 204 than at those of said cylinder heads 213, 214 and said cylinder caps 226, 232.

[0180] Furthermore, the multi-temperature double-acting piston 201, as its name indicates, is double-acting, so the surface area of ​​the cold cylinder 204 relative to that of said cylinder heads 213, 214 and said caps 226, 232 is greatly reduced compared to what said surface area would be if said piston 201 were single-acting.

[0181] Indeed, since the cold cylinder 204 is common to the lower variable volume chamber 208 and the upper variable volume chamber 209, its surface area is, in this case and according to the example 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 is brought into contact with the working gas 240.

[0182] It is also observed that at the same maximum power, the internal combustion engine 202, equipped with the multi-temperature double-acting piston 201 and performing a regenerative Brayton cycle, has an internal surface area of ​​its cold cylinder 204 that is smaller in absolute terms than the internal surface area of ​​the cylinder of an Otto cycle or conventionally designed Diesel engine.

[0183] This reduces the relative heat losses attributable to said cold cylinder 204.

[0184] Furthermore, the maximum temperature reached by the gases in the cylinder of a conventional Otto cycle or Diesel engine is on the order of 2,500 degrees Celsius, compared to only about 1,300 degrees Celsius for the internal combustion engine 202 running a Brayton cycle with regeneration shown in figures 1 to 3 .

[0185] All other things being equal, this lower temperature further reduces the heat losses of the working gas 240 in contact with the cold cylinder 204.

[0186] 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 being equipped with the multi-temperature double-acting piston 201 according to the invention, its cold cylinder 204 is located in a low turbulence zone of the working gas 240 when said gas 240 is introduced into the lower variable volume chamber 208 or the upper variable volume chamber 209 via the corresponding intake valve 284, or when said gas 240 is expelled from said chambers 208, 209 via their exhaust valve 285.

[0187] This low intensity turbulence limits the convective forcing and the transfer of heat by the working gas 240 to the cold cylinder 204.

[0188] It should also be noted that, unlike conventional Otto or Diesel cycle engines, the turbulence of the gases introduced into the expansion valve 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.

[0189] Indeed, insofar as the heat engine 202 equipped with the multi-temperature double-acting piston 201 according to the invention performs a regenerative Brayton cycle - which is its primary purpose - the combustion or heating of the working gas 240 is 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 concentrator.

[0190] The lack of need to create deliberate turbulence to promote combustion further reduces the heat losses of the heat engine 202 equipped with the multi-temperature double-acting piston 201 according to the invention performing a regenerative Brayton cycle compared to those of a conventional Otto cycle or Diesel engine, due to less convective forcing between the working gas 240 and the inner wall of the cold cylinder 204.

[0191] Having stated this, in order to benefit from the advantages of the multi-temperature double-acting piston 201 according to the invention, it is understood that said piston 201 involves making hot parts and cold parts, separated from each other by only a few millimeters, cooperate.

[0192] To demonstrate how the multi-temperature double-acting piston 201 according to the invention allows this cooperation of hot and cold parts very close to each other, we will assume here that the central piston pin 210, the lower radial connecting disc 224, the upper radial connecting 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 high mechanical strength steel, while the lower hot cap 226 and the upper hot cap 232 are made of silicon carbide 276.

[0193] 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.

[0194] We will also assume here that the internal diameter of the cold cylinder 204 is two hundred and forty millimeters.

[0195] 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 challenge related to differential expansions and the limitation of heat transfers from the said hot parts 226, 232, to the said cold parts 210, 224, 225, 220, 203, 204.

[0196] 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, in its particular configuration shown in figures 2 to 4 , in figures 6 to 11 , and in figure 13 the operation of the upper hot cap 232 being identical.

[0197] The said cap 226 and the welded assembly 289 which forms the peripheral sealing ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210 with which the said cap 226 cooperates, are both manufactured at a temperature of around twenty degrees Celsius.

[0198] In operation, the temperature of the welded assembly 289 stabilizes at approximately one hundred degrees Celsius, while that of the lower hot cap 226 stabilizes at nine hundred and fifty degrees Celsius.

[0199] Taking into account the coefficients of expansion of the constituent materials of the lower hot cap 226 and of the 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.

[0200] Similarly, under the effect of temperature, the total axial length of the lower hot cap 226 also increases by about one millimeter, such a variation in said length being difficult to absorb by the cap plating means 234 which must also take back the axial forces generated by the inertia of said cap 226 during the accelerations of the multi-temperature double-acting piston 201 according to the invention.

[0201] Furthermore, the close proximity between the lower hot cap 226 and the 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 Brayton cycle regenerative heat engine 202.

[0202] The multi-temperature double-acting piston 201 according to the invention meets this dual need, on the one hand, to absorb significant differences in expansion between various parts held in contact with each other and operating at very different temperatures, and on the other hand, to limit heat exchange between said parts.

[0203] Indeed, as we can see for example in figure 5 , said piston 201 comprises on the one hand, an insulating ring 236 of zirconium oxide 238 or of quartz - materials known for their good temperature resistance and their very low thermal conductivity - which is interposed between the lower hot cap 226 and the peripheral 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.

[0204] As we can see in figure 6Advantageously, the external coaxial lower tube of the spindle 243 which forms the cap plating means 234 rests on the insulating ring 236 which is radially close to the central piston spindle 210.

[0205] We also note in figure 6 the tube spring 250 which rests on the stock 244 and which consists of a stack of "Belleville" elastic washers.

[0206] It is also noted that in order to limit the heat losses which are detrimental to the efficiency of the Brayton cycle regenerative 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 by means of a small surface contact edge 241 which reduces the cross-section left to the passage of heat.

[0207] As can be seen in Figures 10 And11 , thanks to the particular configuration of the double-acting multi-temperature piston 201 according to the invention, the thermal expansion of the lower hot cap 226 has little or no effect on the total length of the assembly which constitutes said cap 226 with the peripheral sealing ring 220, so that the cap plating means 234 which plate said cap 226 on said ring 220 are not over-stressed by said expansion.

[0208] Indeed, we notice in Figures 10 And 11 that the lower hot cap 226 has a concave conical cap surface 251 through which said cap 226 is held pressed by cap pressing means 234 on a circular peripheral contact edge 252 which has the insulating ring 236 which is integral with the peripheral sealing ring 220, said edge 252 acting as a low surface contact edge 241.

[0209] 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 peripheral contact edge 252 due to the difference between the thermal expansion of the lower hot cap 226 and that of the welded assembly 289, the axial distance which separates the support point of the external coaxial lower spindle tube 243 on said cap 226 from the peripheral sealing ring 220 remains approximately constant all other things being equal.

[0210] 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 centering means of the cap 235.

[0211] According to said configuration, the axial force to which the external coaxial lower tube of spindle 243 is subjected remains approximately constant regardless of the difference between the thermal expansion of the lower hot cap 226 and that of the welded assembly 289, while said cap 226 remains radially centered with respect to the peripheral sealing ring 220.

[0212] It should also be noted that this configuration also makes it possible to limit the variation in the volumetric ratio of the internal combustion engine 202 according to its temperature, particularly during the cold start phases of said engine 202.

[0213] We will notice, for example, in figure 6 , that the insulating ring 236 which is interposed between the lower hot cap 226 and the lower external coaxial spindle tube 243 does not properly have a low surface contact edge 241, the radial thickness of said tube 243 constituting in itself said edge 241.

[0214] As clearly shown by figures 4 And 5 and the figures 8 , 11 And 13 , a barrel-shaped skirt 260 is therefore well arranged on the external periphery of the peripheral sealing ring 220 so as to bear against 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.

[0215] In the vicinity of the two axial ends of the peripheral sealing ring 220, one notices, particularly clearly in Figures 10 And 11 , the two compression segments 222 which form the piston sealing means 221 and which prevent the working gas 240 from passing from the lower variable volume chamber 208 to the upper variable volume chamber 209, and vice versa.

[0216] Still in Figures 10 And 11, below the barrel-shaped skirt 260, we can distinguish the oil scraper segment 278 and the peripheral ring lubrication orifices 229 which open at the rear of said segment 278.

[0217] This arrangement allows, on the one hand, the supply of lubricating and cooling oil 283 to lubricate the barrel skirt 260 and the compression rings 222, and on the other hand, the return of any excess of said oil 283 into the internal volume of piston 228.

[0218] THE figures 8 And 9 show the path of the lubricating and cooling oil 283 through the welded assembly 289.

[0219] Indeed, the oil 283 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 and cooling oil 283 into an axial screw reservoir 267 which is arranged axially in the piston screw head 253.

[0220] The axial screw reservoir 267 allows the lubricating and cooling oil 283 to be stored regardless of the direction of movement of the multi-temperature double-acting piston 201 according to the invention, and maximizes the proportion of said oil 283 which passes through the internal volume of piston 228 before being expelled into the transmission housing 206.

[0221] Indeed, a relatively small part of said oil 283 is used on the one hand, to lubricate the cutting segments 282 or the continuous expandable ring 297 which form a seal between the external coaxial upper spindle tube 248 and the upper cylinder head 214 and on the other hand, to cool said tube 248.

[0222] In this respect, we note in figure 12 the pressure limiting valve 274 which acts as an overflow for the piston cooling and lubrication chamber 217 and which allows, in cooperation with an air intake non-return valve 271 connected to an air source 270 said valve 271 allowing fluid force air 272 to enter said chamber 217, to slightly pressurize the latter while limiting the level of lubrication and cooling oil 283 contained in said chamber 217.

[0223] Indeed, below a certain pressure prevailing in the piston cooling and lubrication chamber 217, the air intake check valve 271 allows fluid force air 272 from the air source 270 into said chamber 217, while above a certain said pressure, the pressure limiting valve 274 expels fluid force air 272 into an air tank 273.

[0224] As we can see in figure 12 Advantageously, the interior of the transmission casing 206 can form both the air source 270 and the air reservoir 273.

[0225] The slight pressurization of the piston cooling and lubrication chamber 217 by means of a fluid-forced air 272 allows, when the heat engine 202 is running at low speed and the accelerations of the multi-temperature double-acting piston 201 according to the invention are of low intensity, to force the lubricating and cooling oil 283 to enter the lubrication-cooling gallery 227 which is provided in the central piston spindle 210.

[0226] Still with the aim of maximizing the proportion of lubricating and cooling oil 283 that passes through the internal volume of the piston 228, it is noted that figures 7 , 8 , 9 And 13the screw check valve 269 which is here positioned at the bottom of the axial screw reservoir 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 which is contained in said reservoir 267 is forced to enter the lubrication-cooling gallery 227 via radial connecting conduits reservoir-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 reservoir 267.

[0227] 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 a circulation of lubricating and cooling oil 283 inside the welded assembly 289 to maintain the temperature of the latter at around one hundred degrees Celsius, while ensuring appropriate lubrication of the barrel skirt 260 and the rings 222, 278.

[0228] As we can see in figures 8 , 9 And 13 , a first section of the lubrication-cooling gallery 227 carries the lubrication and cooling oil 283 from the piston cooling and lubrication chamber 217 to the internal piston volume 228, passing first through the axial screw reservoir 267, the screw check valve 269 and the radial reservoir-gallery connecting conduits 268.

[0229] In figures 8 And9 It has been shown that the lubricating and cooling oil 283 flows into the internal volume of the piston 228 via a small axial clearance left between a fluid distribution disc 261 and the upper radial connecting disc 225, said distribution disc 261 being mainly parallel to said radial connecting disc 225 and forming on one side, a seal with the central piston pin 210, and ending on the other side, radially in the vicinity of the inner wall of the peripheral sealing ring 220, the lubricating and cooling oil 283 from the piston cooling and lubrication chamber 217 being able to exit at said proximity via distribution weirs 290.

[0230] The axial proximity between the fluid distribution disc 261 and the upper radial connecting disc 225 is such that the lubricating and cooling oil 283 is forced to lick the entire internal surface of the upper radial connecting disc 225 before exiting through the distribution weirs 290.

[0231] 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 link disc 225 close to one hundred degrees Celsius, regardless of the power delivered by the heat engine 202.

[0232] Moreover, it is noticeable in figure 13 that in order to limit the heat received by the lower radial connecting disk 224 and by the upper radial connecting disk 225, a reflective screen 295 can advantageously be interposed between the lower hot cap 226 and the lower radial connecting disk 224 and between the upper hot cap 232 and the upper radial connecting disk 225, said reflective screen 295 returning to the lower hot cap 226 and / or the upper hot cap 232 the heat emitted, in particular in the form of infrared radiation, by said cap 226, 232.

[0233] There figure 13 illustrates that in addition to the reflective screen 295, a cellular or fibrous insulating material 296 can occupy all or part of the space between the lower hot cap 226 and the lower radial bonding disc 224 and between the upper hot cap 232 and the upper radial bonding disc 225.

[0234] As we can see in figure 8 , part of the lubricating and cooling oil 283 exiting the distribution weirs 290 cools the peripheral sealing ring 220 from the inside and supplies the peripheral ring lubrication orifices 229, so that some of said oil 283 comes out between the two lips of the oil scraper ring 278, the latter forming, following the back and forth movements of the multi-temperature double-acting piston 201 in the cold cylinder 204, a film of lubricating and cooling oil 283 on the surface of said cylinder 204, while recovering said oil 283 present in excess on said surface.

[0235] We notice in figures 8 And 9that the acceleration efforts 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 surfaces of the internal volume of piston 228 are uniformly cooled.

[0236] In this respect, we note in figures 8 And 9 the fluid recirculation collar 262 which comprises the central piston pin 210, inside the internal piston volume 228 and in the vicinity of the lower radial connecting disc 224.

[0237] With each acceleration towards the lower cylinder head 213 of the multi-temperature double-acting piston 201 according to the invention and as illustrated in the figure 9 , said collar 262 radially discharges towards the inner wall of the peripheral sealing ring 220 the lubricating and cooling oil 283 which has accumulated in an overflow reservoir 264 consisting of a hollow shape which is present in the lower radial connecting disc 224 at the level of its connection with the central piston pin 210.

[0238] As shown in figures 4 à 11 , the fluid recirculation collar 262 may advantageously include collar grooves 263 which form radial jets of lubricating-cooling fluid 257 so as to ensure that the lubricating and cooling oil 283 is uniformly distributed over three hundred and sixty degrees.

[0239] We notice in figures 8 And 9the overflow ports 265 which open from the outer wall of the central piston pin 210 and which communicate with the inside of the transmission housing 206 via the lubrication-cooling gallery 227.

[0240] 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 double-acting multi-temperature 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 housing 206.

[0241] The possibilities of the multi-temperature double-acting piston 1 according to the invention are not limited to the applications just described and it must also be understood that the preceding description has been given only by way of example and that it does not in any way limit the scope of the said invention, which would not be exceeded by replacing the execution details described with any other equivalent.

Claims

1. A multi-temperature double-acting piston (201) being able to move in translation in a cold cylinder (204) arranged in a cooled cylinder crankcase (203) that comprise 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) while 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 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), characterised in that the multi-temperature double-acting piston comprises: • a central piston pin (210) that is approximately coaxial with the cold cylinder (204) and that has a first end that forms a lower piston rod (211) that passes right through the lower cylinder head (213) by means of a lower rod orifice (215) that co-operates with lower rod sealing means (280) so as to open out into the transmission casing (206) and so as to be connected directly or indirectly to the power transmission means (205) by means of piston fixing means (231), while the second end of said pin (210) forms a upper piston rod (212) that passes right through the upper cylinder head (214) by means of an upper rod orifice (216) that co-operates with upper rod sealing means (281) so as to open out into a piston cooling and lubricating 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) the outside diameter of which is substantially smaller than the inside diameter of the cold cylinder (204), said ring (220) including piston sealing means (221) that are in contact with said cylinder (204) to provide sealing therewith; • a lower radial connecting disk (224) that radially connects the central piston pin (210) with the peripheral sealing ring (220) on the lower variable volume chamber (208) side, and an upper radial connecting disk (225) that radially connects the central piston pin (210) with the peripheral sealing ring (220) on the upper variable volume chamber (209) side, 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); • a lubricating-cooling gallery (227) arranged mainly axially in the central piston pin (210) and in one or more sections, said gallery (227) putting the piston cooling and lubricating chamber (217) in communication with the internal piston volume (228) and said volume (228) in communication with the inside of the transmission casing (206); • at least one peripheral ring lubricating orifice (229) that puts the internal piston volume (228) into 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); • guide means (230) which directly or indirectly bear on or in the vicinity of 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) centred in the cold cylinder (204); • a lower hot crown (226) interposed between the lower radial connecting disc (224) and the lower variable volume chamber (208) and / or an upper hot crown (232) interposed between the upper radial connecting disc (225) and the upper variable volume chamber (209); • crown applying means (234) which directly or indirectly hold the lower hot crown (226) applied onto the peripheral sealing ring (220) and / or onto the lower radial connecting disk (224), and / or which directly or indirectly hold the upper hot crown (232) applied onto said ring (220) and / or onto the upper radial connecting disk (225), said means (234) leaving said crowns (226, 232) free to expand relative to said ring (220) and / or to said disks (224, 225); • crown centring means (235) which locate the lower hot crown (226) and / or the upper hot crown (232) with respect to the peripheral sealing ring (220).

2. The multi-temperature double-acting piston according to claim 1, wherein the lower hot crown (226) and / or the upper hot crown (232) are entirely or partly made of a high-temperature-resistant material (275).

3. The multi-temperature double acting piston according to claim 2, wherein the high-temperature resistant material (275) is consisting of silicon carbide (276).

4. The multi-temperature double-acting piston according to Claim 1, wherein thermal insulation means (233) and / or crown sealing means (239) are interposed either between the lower hot crown (226) and the peripheral sealing ring (220) and / or the lower radial connection disc (224), or between the upper hot crown (232) and the said ring (220) and / or the upper radial connection disc (225), or both.

5. The multi-temperature double-acting piston according to claim 1, wherein thermal insulation means (233) and / or crown sealing means (239) are interposed either between the lower hot crown (226) and the central piston pin (210), or between the upper hot crown (232) and said pin (210), or both.

6. The multi-temperature double-acting piston as claimed in claims 4 and 5, wherein the thermal insulation means (233) consist of at least one insulating ring (236) made of a low thermal conductivity material (237).

7. The multi-temperature double-acting piston according to claim 6, wherein the low thermal conductivity material (237) mainly consist of zirconium oxide (238).

8. The multi-temperature double-acting piston according to Claim 6, wherein 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 crown (226) and / or the lower radial connecting disc (224) and / or the upper hot crown (232) and / or the upper radial connecting disc (225) by means of at least one small-surface area contact edge (241).

9. The multi-temperature double-acting piston according to Claim 6, wherein 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 crown (226) and / or the lower radial connecting disc (224) and / or the upper hot crown (232) and / or the upper radial connecting disc (225) by means of at least one insulating sealing gasket (242) which is sealed against the working gas (240).

10. The multi-temperature double-acting piston as claimed in claim 1, wherein the crown applying means (234) which directly or indirectly hold the lower hot crown (226) applied against the peripheral sealing ring (220) and / or the lower radial connecting disk (224) are formed by an lower outer coaxial pin tube (243) which envelops the central piston pin (210), said tube (243) bearing, on the one hand, against the lower hot crown (226) in the vicinity of said pin (210), and, on the other hand, against the power transmission means (205).

11. The multi-temperature double-acting piston according to claim 1, wherein the crown applying means (234) that directly or indirectly hold the upper hot crown (232) applied against the peripheral sealing ring (220) and / or the upper radial connecting disk (225) consist of an upper outer coaxial pin tube (248) that envelops the central piston pin (210), said tube (248) bearing, on the one hand, against the upper hot crown (232) in the vicinity of said pin (210) and, on the other hand, against an upper rod abutment (249) that is provided directly or indirectly against the upper piston rod (212) in the vicinity of its end that opens out into the piston cooling and lubricating chamber (217).

12. The multi-temperature double-acting piston according to claims 10 and 11, wherein some or all of the ends of the lower outer coaxial pin tube (243) and / or of the upper outer coaxial pin tube (248) receive a tube spring (250) by means of which said tubes (243, 248) bear respectively against the lower hot crown (226) and against the power transmission means (205) and / or against the upper hot crown (232) and against the upper rod abutment (249).

13. The multi-temperature double-acting piston according to claim 1, wherein the lower hot crown (226) and / or the upper hot crown (232) has a concave conical crown surface (251) by means of which said crown (226, 232) is held applied by the crown applying means (234) against 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 connecting disk (224) and / or the periphery of the upper radial connecting 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) because of the difference between the thermal expansion of said crown (226, 232) and that of the assembly formed by the peripheral sealing ring (220), the lower radial connecting disk (224), the upper radial connecting disk (225) and the central piston pin (210), the axial distance which separates the bearing point of the crown applying means (234) on said crown (226, 232) of the peripheral sealing ring (220) remains approximately constant, all else being equal, while the crown concave conical surface (251) and the circular peripheral contact edge (252) form the crown centring means (235).

14. The multi-temperature double-acting piston according to claim 1, wherein the piston fixing means (231) consist of a double-acting axial piston screw (219) that comprises, on the one hand, a piston screw body (255) that is housed in a piston screw tunnel (256) that passes right through the central piston pin (210) in the longitudinal direction thereof, said screw (219) comprising, on the one hand, a piston screw head (253) that bears against the end of the upper piston rod (212) that opens out into the piston cooling and lubricating chamber (217) and, on the other hand, a piston screw thread (254) that is screwed into the power transmission means (205).

15. The multi-temperature double-acting piston according to claim 14, wherein the piston screw tunnel (256) forms at least a part of the lubricating-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 extends from the piston cooling and lubricating chamber (217) to the internal piston volume (228), and a second section which extends from said volume (228) inside the transmission casing (206).

16. The multi-temperature double-acting piston according to claim 1, wherein the guide means (230) consist of a barrel skirt (260) that is arranged on the outside periphery of the peripheral sealing ring (220) and that bears against the cold cylinder (204).

17. The multi-temperature double-acting piston according to claim 1, wherein the lubricating-cooling gallery (227) opens out into the internal piston volume (228) via a small axial clearance left between, on the one hand, a fluid distribution disk (261) that is housed in said volume (228) and, on the other hand, the upper radial connecting disk (225), said distribution disk (261) being approximately parallel to said radial connecting disk (225) and forming, on the one hand, a sealing with the central piston pin (210) and, on the other hand, terminating 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 lubricating chamber (217) being able to leave in said vicinity.

18. The multi-temperature double-acting piston according to claim 1, wherein the central piston pin (210) includes, inside the internal piston volume (228) and in the vicinity of the lower radial connecting disk (224), a fluid recirculation collar (262) which, when the central piston pin (210) moves towards the lower cylinder head (213), rejects the lubricant-cooling fluid (257) that has accumulated in said volume (228) and at the surface of said disk (224) radially and towards the inside wall of the peripheral sealing ring (220).

19. The multi-temperature double-acting piston according to claim 1, wherein the lower radial connecting disc (224) has a recessed shape (294) at its connection with the central piston pin (210), said shape (294) constituting an overflow reservoir (264) which can store lubricant-cooling fluid (257), while at least one overflow orifice (265) which communicates with the interior of the transmission housing (206) via the lubricant-cooling gallery (227) sets the maximum level of said reservoir (264).

20. The multi-temperature double-acting piston according to Claim 1, wherein a fluid nozzle (266) fed by the lubricating-cooling fluid source (218) opens into the piston cooling and lubricating chamber (217) for injecting a fluid jet (267) therein.

21. The multi-temperature double-acting piston according to claims 14 and 20, wherein 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 reservoir (267) communicating with the lubricating-cooling gallery (227) via at least one radial reservoir-gallery connection duct (268).

22. The multi-temperature double-acting piston according to claim 1, wherein 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) to the lubricating-cooling gallery (227), but not vice versa.

23. The multi-temperature double-acting piston according to claim 1, wherein the piston cooling and lubricating chamber (217) is connected to an air source (270) by an air intake check valve (271) that lets fluid forcing air (272) into said chamber (217) without letting it leave, while said chamber (217) is connected to an air tank (273) by a pressure-limiting valve (274) which lets 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.

24. The multi-temperature double-acting piston according to claim 1, wherein a reflective shield (295) is interposed between the lower hot crown (226) and the lower radial connecting disk (224) to which a portion of the peripheral sealing ring (220) may be added and / or between the upper hot crown (232) and the upper radial connecting disk (225) to which a portion of said ring (220) may be added.

25. The multi-temperature double-acting piston according to Claim 1, wherein the thermal insulation means (233) consist of an honeycomb or fibrous insulating material (296) that occupies all or part of the space between the lower hot crown (226) and the lower radial connecting disc (224) and / or between the upper hot crown (232) and the upper radial connecting disc (225).

26. The multi-temperature double-acting piston according to claims 10, 11 and 14, wherein at least a first radial space left between the upper outer coaxial pin tube (248) and the central piston pin (210), at least a second radial space left between the outer coaxial lower pin tube (243) and the central piston pin (210), and a plurality of radial spaces left between the piston screw body (255) and the inner wall of the piston screw tunnel (256) form at least a part of the lubricating-cooling gallery (227), the lubricating-cooling fluid (257) being able to circulate successively in said spaces from the piston cooling and lubricating chamber (217) to the internal piston volume (228), then from said volume (228) inside the transmission casing (206).

27. The multi-temperature double-acting piston according to claim 1, wherein the lower rod sealing means (280) and / or the upper rod sealing means (281) consist of an expandable continuous ring (297) which is directly or indirectly secured to the cooled cylinder housing (203), and the inner diameter of which is substantially smaller than the outer diameter of the lower piston rod (211) or the upper piston rod (212) that it clamps.

28. The multi-temperature double-acting piston according to claim 27, wherein the extensible continuous ring (297) is connected to a ring plate (298) by a ring tube (299) of small radial thickness, said ring (297), said plate (298) and said ring (297) being made of a single piece of material.

29. The multi-temperature double-acting piston according to Claim 27, wherein the continuously extensible ring (297) is axially clamped between two ring bushings (300) by a ring axial compression spring (301).

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