AC / DC ENGINE

Abstract

HOT HEAD AND COLD CYLINDER REVOLVING ENGINE The hot head and cold cylinder revolutating engine (1) comprises a cooled cylinder block (5) which receives a cold cylinder (6) coated with a lubricant film (7) and in which translates a piston (2) connected to power transmission means (3) to form a hot chamber of variable volume (11) with a hot cylinder head (10) which is held pressed but free to expand on said cylinder block (5) by cylinder head pressing means (24), while a hot cap (19) is interposed between said chamber (11) and the piston (2) and is held pressed but free to expand on said piston (2) by cap pressing means (23), the piston (2) having a cooled piston sealing ring (37) which has piston sealing means (30). Figure for the abridged version: Fig. 1

Description

Title of the invention: AC ENGINE HOT CYLINDER HEAD AND COLD CYLINDER

[0001] The present invention relates to a hot cylinder head and cold cylinder reciprocating heat engine, said engine being particularly suited to the implementation of the Brayton thermodynamic cycle with regeneration which is ordinarily carried out by means of centrifugal compressors and turbines.

[0002] Brayton cycle regenerative engines generally include separate components dedicated to each of the phases 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] Accordingly, regenerative Brayton cycle engines include at least one compressor, at least one regeneration exchanger, at least one continuously operating burner or internal or external heat source, and at least one expansion valve.

[0004] Assigning each phase of a thermodynamic cycle to a dedicated 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 said 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 motor 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 Brayton cycle turbines with regeneration 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] In addition, centrifugal compressor engines and Brayton cycle regenerative turbines are poorly suited to low power levels, and can only operate over a restricted power range outside of 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 hardly exceeds forty percent, while that of the slow two-stroke diesel engines that equip certain 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 "Turbec" company, or the "C65" micro turbine from the "Capstone" company, whose electrical efficiencies are only around twenty-eight to thirty percent, but which require little maintenance while offering very long service lives.

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

[0014] Taking into account the above, it would be particularly interesting to be able to replace the centrifugal compressors and turbines of regenerative Brayton cycle engines with positive displacement piston machines whose efficiency is notoriously higher.

[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 Brayton cycle engine with regeneration 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 expansion valve at a temperature of 1,300 degrees Celsius and are expelled from said expansion valve at the end of expansion at a at a temperature of six hundred degrees Celsius, the internal walls of said regulator must be maintained at approximately a temperature of nine hundred and fifty 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 segment 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 thermodynamically efficient 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 to within a few micrometers of the expansion cylinder with which it cooperates without touching said cylinder, while letting compressed air escape through calibrated orifices which pass through it in its radial thickness.

[0025] The fluid cushion sealing device described above is also the subject of French patent FR 3032252, issued on May 25, 2018, and belonging to the applicant. This device effectively achieves a non-contact 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 effectively possible to use a piston-type volumetric 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 engine with pistons can reach or even exceed seventy percent, which in practice can lead to the production of engines whose energy efficiency at the brake 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] It follows from these operating conditions that the temperature of the internal walls of the expansion valve stabilizes 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 make said ring possible and withstand such a temperature.

[0033] Even a superalloy such as "Udimet 720", notably used in aeronautics and in the space industry and known for its resistance to extreme temperatures, cannot withstand such a temperature without being subject to fining 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 the order of seven hundred degrees Celsius.

[0035] For example, the superalloy "Udimet 720" resists fining 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 that surrounds the expansion valve while leaving a space of gas circulation between said enclosure and said regulator in which the gases exiting the regulator itself circulate at a temperature between five hundred and six hundred degrees Celsius.

[0037] Thus, according to the regenerative cooling system according to the 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 FR 3032252 is usable 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 Brayton cycle regenerative 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 movable coupling and of 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 that is the subject of patent No. EP3350433 issued on August 7, 2019 and belonging to the applicant.

[0042] 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] Said support further 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 reading the above, it is understood that no configuration is at this stage fully satisfactory which allows to realize under the best possible conditions a regenerative Brayton cycle piston reciprocating engine.

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

[0046] This effectively reduces the final energy efficiency of said engine, and all the more so if The latter operates at low power because the amount of compressed air to be supplied to the fluid cushion sealing device is almost constant, regardless of the engine speed and load.

[0047] Furthermore, to ensure 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, said cooling system makes the path of the gases expelled from the expansion valve tortuous and induces pressure losses which reduce the total 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 dimensioning 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] In the field of application of reciprocating piston heat engines in general and heat engines in particular, the invention results in a reciprocating heat engine with a hot cylinder head and a cold cylinder: • Whose cylinder head and piston crown are kept at a high temperature so as to limit the cooling of the hot gases in contact with them; • Whose seal between the piston and the cylinder can be achieved by means of cast iron or steel piston rings such as those found in engines with conventional internal combustion 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 a regenerative cooling system such as that described in patent No. EP 3585993, and therefore does not suffer the power and efficiency losses associated with the use of a compressor supplying said sealing device, nor the additional pressure losses at the exhaust of the expansion valve linked to a more tortuous gas path, nor the heat losses due to the efficiency of the regeneration heat exchanger being less than "one", nor the specific engine power losses associated with this configuration.

[0055] Furthermore, as an alternative to materials with a high nickel content such as "Niresist" cast iron, the hot cylinder head of the hot cylinder head and cold cylinder reciprocating heat engine according to the invention can be made of silicon carbide, a material with high mechanical resistance at high temperatures, abundant and cheap, while the cylinder of said engine can be made of low-cost cast iron such as that ordinarily used to make the cylinder blocks of automotive Diesel engines.

[0056] Furthermore, the lower density of silicon carbide and the absence of a regenerative cooling system lead to a lower weight of the hot cylinder head and cold cylinder reciprocating heat engine according to the invention and to a lower total heat capacity of said engine, which promotes a rapid rise in temperature of said engine by reducing the energy required to reach its operating temperature, and which leads to lower energy consumption of said engine particularly when the latter is applied to road, rail, or maritime transport.

[0057] It is understood that the hot cylinder head and cold cylinder reciprocating heat engine according to the invention can be applied, in addition to heat engines in general, stationary or mobile and 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 engine according to the invention.

[0058] The hot-cylinder, cold-cylinder reciprocating heat engine comprising a cooled cylinder block in which is arranged at least one cold cylinder in which a piston oriented and / or located by piston guiding means can translate, 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, comprises • Lubrication methods that form a film of lubricant that interposes between the cold cylinder and the piston; • Cylinder crankcase cooling means which cool the cooled cylinder crankcase so as to maintain all or part of the internal surface of the cold cylinder at a temperature low enough to prevent the lubricant film from aging prematurely, coking, or burning; • At least one hot cylinder head whose operating temperature is significantly higher than that of the cooled cylinder block it covers to form with the piston a hot chamber of variable volume which contains a working gas, said cylinder head being on the one hand, kept pressed against the cooled cylinder block by cylinder head pressing means which leave it free to expand relative to said cylinder block, and on the other hand, located relative to said cylinder block by cylinder head centering means; • At least one piston sealing ring arranged on the periphery of the piston, said ring comprising, on the one hand, piston sealing means which form a seal between the piston and the cold cylinder, and being, on the other hand, cooled by sealing ring cooling means; • At least one hot cap which is interposed between the variable volume hot chamber and the piston and whose operating temperature is significantly higher than that of the cooled cylinder block, said cap being on the one hand kept pressed against the piston by cap pressing means which leave said cap free to expand relative to said piston, and on the other hand, located relative to said piston by cap centering means.

[0059] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes sealed thermal insulation means which are interposed between the cooled cylinder block and the hot cylinder head.

[0060] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes thermal insulation means which are interposed between the hot cylinder head and the piston.

[0061] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes sealed thermal insulation means and / or thermal insulation means which are made up of at least one insulating ring made of a material with low thermal conductivity.

[0062] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises a material with low thermal conductivity which is mainly made of zirconium oxide.

[0063] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention includes an insulating ring which forms the sealed means of thermal insulation which is directly or indirectly in contact with the cooled cylinder block and / or with the hot cylinder head via at least one low surface contact edge which prevents working gas from passing between the cooled cylinder block and the hot cylinder head.

[0064] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes an insulating ring which forms the thermal insulation means which is directly or indirectly in contact with the hot cylinder head and / or with the piston via at least one contact edge of small surface area.

[0065] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a cylinder head sealing gasket which is interposed between the insulating ring which forms the sealed means of thermal insulation and the cooled cylinder block and / or between said ring and the hot cylinder head.

[0066] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a piston seal which is interposed between the insulating ring which forms the means of thermal insulation and the hot cylinder head and / or between said ring and the piston.

[0067] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises a hot cylinder head and / or a hot cylinder cap which are wholly or partly made of a material resistant to high temperatures.

[0068] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises a high-temperature resistant material which is mainly made of silicon carbide.

[0069] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises a hot cylinder head which has a concave cylinder head surface through which said cylinder head is held pressed by cylinder head pressing means on a circular cylinder contact edge provided on the cooled cylinder block, 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 cylinder head and that of said cylinder block, the axial distance which separates the point of support of the cylinder head pressing means on the hot cylinder head from the cooled cylinder block remains approximately constant all other things being equal, while the concave cylinder head surface and the circular cylinder contact edge form the cylinder head centering means.

[0070] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a hot cap having a concave conical cap surface by means of which said cap is held pressed by cap pressing means onto a circular piston contact edge provided on the piston, 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 piston, the axial distance which separates the point of support of the cap-pressing means on the hot cap of the piston remains approximately constant all other things being equal, while the concave conical surface of cap and the circular contact edge of piston form the cap-centering means.

[0071] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises a hot cap which has an aerodynamic passivation cord at its periphery.

[0072] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises an exterior of the hot cylinder head which is covered with a thermal insulator.

[0073] The hot-cylinder head, cold-cylinder reciprocating heat engine according to the invention includes a piston sealing ring which has piston guiding means consisting of an annular sliding surface.

[0074] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a cooled cylinder block which is held clamped between a lower hot cylinder head and an upper hot cylinder head by cylinder head cladding means, while the piston is double-acting and comprises, on the one hand, a lower piston rod which connects it to the power transmission means and which passes through the lower hot cylinder head via a lower rod orifice, and on the other hand, a lower hot cap and an upper hot cap to define with the lower and upper hot cylinder heads a lower variable-volume hot chamber and an upper variable-volume hot chamber.

[0075] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises: • At least one hollow pillar which is traversed lengthwise by a rod tunnel, a first end of said pillar resting directly or indirectly on the transmission housing while a second end of said pillar supports the lower hot cylinder head, said first end being able to pivot around a ball joint and / or flex relative to said housing while said second end being able to pivot around a ball joint and / or flex relative to said lower hot cylinder head; • At least one pull rod that forms the cylinder head clamping means and that is, at least in part, housed in the rod tunnel, a first rod end of said pull rod being directly or indirectly attached to the transmission housing while a second rod end of said rod is directly or indirectly attached to the hot cylinder head. upper, said first end being able to pivot around a ball joint and / or flex relative to said casing while said second end being able to pivot around a ball joint and / or flex relative to said cylinder head; • Lower cylinder head centering means which are integral with the transmission housing and which bear directly or indirectly on the lower hot cylinder head, said means allowing said cylinder head to move freely over a short distance parallel to the longitudinal axis of the cold cylinder and relative to the transmission housing, but preventing said cylinder head from moving in the plane perpendicular to said axis relative to said housing; • Upper cylinder head centering means which are integral with a centering gantry which is rigidly fixed to the transmission housing, said means bearing directly or indirectly on the upper hot cylinder head, and said means leaving said cylinder head free to move a short distance parallel to the longitudinal axis of the cold cylinder and relative to the transmission housing, but prohibiting said cylinder head from moving in the plane perpendicular to said axis relative to said housing.

[0076] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a rod cooling tube which hermetically seals around the drive rod over all or part of the length of said rod, a heat transfer fluid from a coolant source being able to circulate in a space left between the inner wall of said tube and the outer surface of said rod, while the greatest possible part of the outer surface of said tube does not touch the inner wall of the rod tunnel so as to define a gap with the latter wall.

[0077] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention comprises at least a first tube feed port which communicates with the inside of the rod cooling tube in the vicinity of the first rod end, and at least a second tube feed port which communicates with the inside of the rod cooling tube in the vicinity of the second rod end, the heat transfer fluid being able to circulate between the two said ports.

[0078] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a rod cooling tube which has a tube collar held directly or indirectly clamped by the draw rod either against a fixing lug that has the upper hot cylinder head, or against the transmission housing.

[0079] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a tube flange which is held tight by the pull rod against the mounting lug by means of a banjo fitting which has at least one radial connecting conduit which is connected to the coolant source of a on the one hand, and which communicates with the inside of the rod cooling tube on the other hand.

[0080] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a thermal insulation riser which is interposed between the tube collar and the fixing lug, said riser being traversed through and through in its length direction by a riser tunnel in which is housed the traction rod and the rod cooling tube which surrounds it in a sealed manner, while the greatest possible part of the external surface of said tube does not touch the internal wall of the riser tunnel so as to define with the latter wall a void space.

[0081] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a rod cooling tube which has at least one tube bulge consisting of an axial portion of said tube whose free diameter is substantially equivalent to or even slightly greater than that of the rod tunnel in which it is housed.

[0082] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes a rod cooling tube which has at least one tube diameter restriction consisting of an axial portion of said tube whose free diameter is substantially equivalent to or even slightly less than that of the body of the drawbar.

[0083] The hot cylinder head, cold cylinder reciprocating heat engine according to the invention comprises a drawbar which is hollow to form an internal rod cooling channel arranged along the length of said rod, said channel opening axially or radially in the vicinity of each end of said rod while a heat transfer fluid from a coolant source can circulate in said channel.

[0084] The hot cylinder head, cold cylinder reciprocating heat engine according to the invention comprises a piston cooling and lubrication chamber which is connected to a source of lubricating-cooling fluid and which is fixed to or arranged on or in the centering gantry, while an upper piston rod which extends the double-acting piston on the side of the upper variable-volume hot chamber passes through the upper hot cylinder head via an upper rod orifice arranged in said cylinder head and via an access orifice to the cooling and lubrication chamber passing through the centering gantry to open into the piston cooling and lubrication chamber so that the end of the upper piston rod which is furthest from said piston always remains immersed in said chamber regardless of the position of said piston.

[0085] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a lubricating-cooling fluid that can circulate from the piston cooling and lubrication chamber to the transmission housing, passing through successively via an internal channel of the upper piston rod arranged longitudinally in the upper piston rod, via an internal piston cavity, and via an internal channel of the lower piston rod arranged longitudinally in the lower piston rod.

[0086] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a periphery of the internal piston cavity which communicates with the external peripheral face of the piston sealing ring via at least one peripheral ring lubrication orifice which opens axially between at least two piston sealing means, said orifice constituting the lubrication means.

[0087] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention comprises a transmission casing which is capped with a centering and sealing plate pierced with an access orifice to the transmission means through which the lower piston rod passes to be connected to the power transmission means, said plate being rigidly fixed on said casing.

[0088] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes an access port to the cooling and lubrication chamber which includes rod sealing means providing a seal between said port and the upper piston rod.

[0089] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes an access port for the transmission means which includes rod sealing means providing a seal between said port and the lower piston rod.

[0090] The hot-cylinder, cold-cylinder reciprocating heat engine according to the invention includes lower cylinder head centering means and / or upper cylinder head centering means which consist of an elastic centering disc that can be pierced in its center with a disc hole through which passes respectively the lower piston rod or an upper piston rod while its periphery constitutes a disc fixing collar fixed in a sealed manner respectively on the transmission housing and / or on the centering gantry.

[0091] The hot-cylinder, cold-cylinder reciprocating internal combustion engine according to the invention comprises a centering and sealing plate which carries the lower cylinder head centering means, which consist of an elastic centering disc whose periphery forms a disc-fixing flange sealed to said plate, said disc having a hole in its center through which the lower piston rod passes without touching said disc, the edge of the disc hole having a circular contact pad which is maintained in seal-proof contact with a centering and sealing cone on the lower hot cylinder head, said cone being male or female, and the contact between said pad and said cone having effect of axially deforming the elastic centering disk from its center.

[0092] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes upper cylinder head centering means which consist of an elastic centering disc whose periphery forms a disc fixing collar fixed in a sealed manner on the centering gantry, said disc being pierced in its center with a disc hole whose edge has a circular contact pad which is kept in sealed contact with a centering and sealing cone which has the upper hot cylinder head, said cone being able to be male or female, and the contact between said pad and said cone having the effect of axially deforming the elastic centering disc from its center.

[0093] The hot cylinder head and cold cylinder reciprocating heat engine according to the invention includes an anti-rotation link which directly or indirectly connects the lower hot cylinder head and / or the upper hot cylinder head and / or the cooled cylinder block to the centering gantry.

[0094] The following description, with reference to the attached drawings given by way of non-limiting examples, will allow for a better understanding of the invention, its features, and the advantages it is likely to provide:

[0095] [Fig. 1] is a schematic cross-sectional view of the hot-head, cold-cylinder reciprocating heat engine according to the invention, of the valves which supply the variable-volume hot chamber of said engine not appearing on said cross-section.

[0096] [Fig.2] is a three-dimensional view of the hot cylinder head reciprocating heat engine and cold cylinder according to the invention whose piston is double-acting, said engine forming an expansion valve which allows, for example, the implementation of a regenerative Baryton thermodynamic cycle.

[0097] [Fig.3] is a three-dimensional cross-sectional view of the reciprocating heat engine hot cylinder head and cold cylinder according to the invention, and according to the particular configuration of said engine shown in [Fig.2], the double-acting piston defining, with a lower hot cylinder head and an upper hot cylinder head, a lower hot chamber of variable volume and an upper hot chamber of variable volume.

[0098] [Fig.4] is a cross-sectional view of the hot-cylinder head reciprocating heat engine and cold cylinder according to the invention, and according to the particular configuration of said engine shown in figures 2 and 3.

[0099] [Fig. 5] is a close-up cross-sectional view of the cylinder head reciprocating heat engine hot and cold cylinder according to the invention and according to the particular configuration of said engine shown in figures 2 to 4, said view highlighting in particular how the double-acting piston is connected to the power transmission means, and how the seal is achieved between the lower piston rod and the transmission housing.

[0100] [Fig.6] is a close-up cross-sectional view of the cylinder head reciprocating internal combustion engine hot and cold cylinder according to the invention and according to the particular configuration of said engine shown in figures 2 to 5, said view highlighting in particular how the upper piston rod of the double-acting piston opens into the piston cooling and lubrication chamber, and how the seal is achieved between said rod and a centering gantry.

[0101] [Fig.7] is an exploded three-dimensional view of the cylinder head reciprocating heat engine hot and cold cylinder according to the invention and according to the particular configuration of said engine shown in [Fig.2].

[0102] [Fig.8] is a view partly three-dimensional and partly schematic cross-section of a part of the hot cylinder head and cold cylinder reciprocating heat engine according to the invention and according to the particular configuration of said engine shown in figures 2 to 7, said view highlighting the main sections which make up the hollow pillars and the pull rods which form the cylinder head clamping means of the hot cylinder heads on the cooled cylinder block.

[0103] [Fig.9] is a close-up schematic cross-sectional view of the reciprocating heat engine with hot cylinder head and cold cylinder according to the invention and according to the particular configuration of said engine shown in figures 2 to 8, said view showing the position and dimensions of the hot crowns of the double-acting piston and of the upper hot cylinder head relative to the cooled cylinder block when said crowns and said cylinder head are cold.

[0104] [Fig. 10] is a schematic cross-sectional view similar to that shown in [Fig.9], said view showing the position and dimensions of the hot crowns of the double-acting piston and the upper hot cylinder head relative to the cooled cylinder block when said crowns and said cylinder head are hot and expanding under the effect of temperature.

[0105] DESCRIPTION OF THE INVENTION:

[0106] Figures 1 to 10 show the hot-cylinder head, cold-cylinder 1 reciprocating heat engine according to the invention, various details of its components, its variants, and its accessories.

[0107] The hot-cylinder head, cold-cylinder reciprocating heat engine 1 comprises a cooled cylinder block 5 in which is arranged at least one cold cylinder 6 in which a piston 2 oriented and / or located by piston guiding means 29 can translate.

[0108] The piston 2 is directly or indirectly connected by power transmission means 3 housed in a transmission casing 42 to at least one rotary or reciprocating power output shaft 4.

[0109] The power transmission means 3 may, for example, take the form of a connecting rod 34 articulated around a crank 48 mounted on a crankshaft 35, said connecting rod 34 can be connected to the piston 2 directly by a piston pin or indirectly by means of a cross 49.

[0110] Said means 3 may also consist of a cam, a hydraulic emitting pump, a linear or rotary electricity generator or any other transmission means known to those skilled in the art.

[0111] As can be seen in figures 1 to 10, the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention includes lubrication means 8 which form a lubricant film 7 which is interposed between the cold cylinder 6 and the piston 2, said means 8 being able to be for example made up of the bubbling of the power transmission means 3 in liquid lubricant which is contained in the transmission casing 42.

[0112] Figures 1, 3, 4, 9 and 10 clearly show that the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention also includes cylinder block cooling means 9 which are for example made up of a cooling chamber 27 which surrounds the cooled cylinder block 5 while a heat transfer fluid 32 can circulate in said chamber 27, said means 9 cooling the cooled cylinder block 5 so as to maintain all or part of the internal surface of the cold cylinder 6 at a temperature low enough so that the lubricant film 7 does not age prematurely, coke, or burn;

[0113] In figures 1 to 10, it has been shown that the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention also includes at least one hot cylinder head 10 which can include at least one intake valve 31 and at least one exhaust valve 33 which are controlled by a valve actuator 50.

[0114] The operating temperature of the hot cylinder head 10 is significantly higher than that of the cooled cylinder block 5 which it covers to form with the piston 2 a hot chamber of variable volume 11 which contains a working gas 17.

[0115] As can easily be seen in figures 9 and 10, the hot cylinder head 10 is, on the one hand, held pressed against the cooled cylinder block 5 by cylinder head pressing means 24 which allow it to expand freely with respect to said cylinder block 5, and on the other hand, located with respect to said cylinder block 5 by cylinder head centering means 39 which could, for example, consist of a centering pin or a support collar.

[0116] Furthermore, and as shown in [Fig. 1] and Figures 3 to 10, the hot-cylinder, cold-cylinder reciprocating heat engine 1 comprises at least one piston sealing ring 37 arranged on the periphery of the piston 2, said ring 37 comprising, on the one hand, piston sealing means 30, for example, consisting of compression rings 44 made of cast iron or steel such as those ordinarily found on the pistons of conventional automobile engines, said means 30 forming a sealing between the piston 2 and the cold cylinder 6, and being on the other hand, cooled by sealing ring cooling means 38.

[0117] As shown in [Fig. 1] and Figures 3 to 10, the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention also includes at least one hot cap 19 which is interposed between the variable volume hot chamber 11 and the piston 2 and whose operating temperature is significantly higher than that of the cooled cylinder block 5.

[0118] As clearly illustrated in Figures 9 and 10, said cap 19 is, on the one hand, held pressed against the piston 2 by cap pressing means 23 which leave said cap 19 free to expand relative to said piston 2, and on the other hand, located relative to said piston 2 by cap centering means 40 which could, for example, consist of a centering pin or a support collar.

[0119] In [Fig. 1], in figures 2 to 7, and in figures 9 and 10, it can be seen that the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention can include sealed thermal insulation means 12 which are interposed between the cooled cylinder block 5 and the hot cylinder head 10, said means 12 being able moreover - according to a particular embodiment - to be an integral part of the cooled cylinder block 5 and / or of the hot cylinder head 10.

[0120] Similarly, and as particularly visible in figures 9 and 10, thermal insulation means 22 can be interposed between the hot cap 19 and the piston 2, said means 22 being able to be an integral part of the hot cap 19 and / or the piston 2.

[0121] It is also noted in [Fig.1] as well as in figures 3 to 7 and in figures 9 and 10 that the watertight thermal insulation means 12 and / or the thermal insulation means 22 can consist of at least one insulating ring 13 made of a material with low thermal conductivity 14, said material 14 being mainly composed of zirconium oxide 15.

[0122] As particularly shown in Figures 1, 9 and 10, the insulating ring 13 which forms the sealed thermal insulation means 12 can be directly or indirectly in contact with the cooled cylinder block 5 and / or with the hot cylinder head 10 by way of at least one contact edge of small surface 16 which prevents the working gas 17 from passing between the cooled cylinder block 5 and the hot cylinder head 10.

[0123] As another variant of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention, particularly visible in figures 1, 9 and 10, the insulating ring 13 which forms the thermal insulation means 22 can also be directly or indirectly in contact with the hot cap 19 and / or with the piston 2 by means of at least one contact edge of small surface area 16, this to prevent the working gas 17 from passing between the hot cap 19 and the piston 2.

[0124] It is also noted in figures 1, 9 and 10 that a cylinder head sealing gasket 18 can be interposed between the insulating ring 13 which forms the sealing means of thermal insulation 12 and the cooled cylinder block 5 and / or between said ring 13 and the hot cylinder head 10.

[0125] Similarly, a piston seal 36 can be interposed between the insulating ring 13 which forms the thermal insulation means 22 and the hot cap 19 and / or between said ring 13 and the piston 2.

[0126] It is noted that the cylinder head gasket 18 and / or the piston gasket 36 may, for example, comprise several metal sheets like the cylinder head gaskets found in modern automotive internal combustion engines, or be made of materials resistant to high temperatures such as "Therma-pur" developed by the "Garlock" company.

[0127] It should also be noted that the hot cylinder head 10 and / or the hot cap 19 may be made in whole or in part of a high-temperature resistant material 20, the latter being mainly made of silicon carbide 21.

[0128] According to a variant of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, particularly visible in figures 9 and 10, the hot cylinder head 10 may have a concave conical cylinder head surface 25 through which said cylinder head 10 is held pressed by the cylinder head pressing means 24 on a circular cylinder contact edge 51 arranged on the cooled cylinder block 5.

[0129] In this case, the angle of the concave cone formed by said surface 25 is such that when said surface 25 slides on said edge 51 due to the difference between the thermal expansion of said cylinder head 10 and that of said cylinder block 5, the axial distance which separates the point of support of the cylinder head clamping means 24 on the hot cylinder head 10 from the cooled cylinder block 5 remains approximately constant all other things being equal, while the concave conical surface of cylinder head 25 and the circular contact edge of cylinder 51 form the cylinder head centering means 39.

[0130] It will be noted that this particular configuration of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention allows the force to which the cylinder head shoring means 24 are subjected to remain approximately constant regardless of the difference between the thermal expansion of the hot cylinder head 10 and that of the cooled cylinder block 5, said difference resulting from both a temperature and a coefficient of thermal expansion possibly different between those of the hot cylinder head 10 and those of the cooled cylinder block 5.

[0131] Furthermore, said configuration makes it possible to limit the variation in the compression ratio of the hot-cylinder, cold-cylinder reciprocating heat engine 1 according to the invention as a function of its temperature, particularly during the cold start phases of said engine. engine 1.

[0132] It is noted that advantageously, the circular contact edge of cylinder 51 can present a spherical contact to the concave conical surface of cylinder head 25.

[0133] As another variant of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, particularly visible in figures 9 and 10, the hot cap 19 may also have a concave conical cap surface 26 through which said cap 19 is held pressed by cap pressing means 23 on a circular piston contact edge 52 provided on the piston 2.

[0134] In this case, the angle of the concave cone formed by said surface 26 is such that when said surface 26 slides on said edge 52 due to the difference between the thermal expansion of said cap 19 and that of the piston 2, the axial distance which separates the point of support of the cap 23 on the hot cap 19 of the piston 2 remains approximately constant all other things being equal, while the concave conical surface of cap 26 and the circular contact edge of piston 52 form the centering means of cap 40.

[0135] It is noted that this particular configuration of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention allows the force to which the cap 23 slap means are subjected to remain approximately constant regardless of the difference between the thermal expansion of the hot cap 19 and that of the piston 2.

[0136] In addition, said configuration makes it possible to limit the variation of the volumetric ratio of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention as a function of its temperature, particularly during the cold start phases of said engine 1.

[0137] It is noted that advantageously, the circular contact edge of piston 52 can present a spherical contact to the concave conical surface of cap 26.

[0138] As shown in [Fig.1], as an alternative embodiment of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, the hot cap 19 may have at its periphery an aerodynamic passivation cord 53 which limits the turbulence of the working gas 17 in the vicinity of the cold cylinder 6 and which, as a result, limits the convective forcing which increases the loss of part of the heat of said gas 17 by transfer of said heat to said cold cylinder 6.

[0139] Fig. 1 also illustrates that the outside of the hot cylinder head 10 can be covered with a thermal insulator 41 which prevents the heat of said cylinder head 10 from dissipating into the environment of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention.

[0140] Said thermal insulation 41 may, for example, consist of several layers of thin metal sheets having studs which leave between each said sheet an air gap, or be any other thermal insulator 41 known to the person skilled in the art.

[0141] It is noted in [Fig.1], in figures 2 to 7, and in figures 9 and 10, that the piston sealing ring 37 may have piston guiding means 29 consisting of an annular sliding surface 43 which has a barrel shape in contact with the cold cylinder 6, said shape being able to be positioned between two compression rings 44 and adjoin an oil scraper ring 45.

[0142] According to a particular configuration of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention shown in figures 2 to 10, the cooled cylinder block 5 can be held clamped between a lower hot cylinder head 10 and an upper hot cylinder head 10 by the cylinder head clamping means 24 while the piston 2 is double-acting and comprises on the one hand, a lower piston rod 46 which connects it to the power transmission means 3 and which passes through the lower hot cylinder head 10 via a lower rod orifice 47, and on the other hand, a lower hot cap 19 and an upper hot cap 19 to define with the lower and upper hot cylinder heads 10 a lower variable volume hot chamber 11 and an upper variable volume hot chamber 11.

[0143] Still according to this particular configuration, the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention comprises at least one hollow pillar 101 which can be either totally closed or openwork, said pillar 101 being traversed through and through in the direction of its length by a rod tunnel 102.

[0144] In this case, a first end of pillar 103 of the hollowed pillar 101 rests directly or indirectly on the transmission housing 42 while a second end of pillar 104 of said pillar 101 supports the lower hot cylinder head 10, said first end 101 being able to pivot about a ball joint 105 and / or flex relative to said housing 42 while said second end 104 is able to pivot about a ball joint 105 and / or flex relative to said lower hot cylinder head 10.

[0145] It will be noted that the pivoting of said ends 103, 104 can be carried out either by means of a mechanical link of the pivot or cardan type or a ball joint 105, or by the bending of all or part of the hollow pillar 101, or by both.

[0146] According to a particular embodiment of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention, the hollow pillar 101 can be made of zirconium dioxide, known as "zirconia", this ceramic offering good mechanical resistance at high temperature, low thermal conductivity, and a coefficient of expansion close to that of steel.

[0147] In this case, at least one traction rod 106 forms the cylinder head clamping means 24, said rod 106 being, at least in part, housed in the rod tunnel 102, a first end of rod 107 of said rod 106 being directly or indirectly attached to the transmission housing 42 while a second end of rod 108 of said rod 106 is directly or indirectly attached to the upper hot cylinder head 10, said first end 107 being able to pivot about a ball joint 105 and / or flex relative to said housing 42 while said second end 108 is able to pivot about a ball joint 105 and / or flex relative to said cylinder head 10, the pivoting of said ends 107, 108 being able to be carried out either by means of a mechanical link of the pivot or cardan type or a ball joint 105, or by the flexing of all or part of the traction rod 106, or by both.

[0148] As shown in [Fig.8], it is noted that in order to be attached to the upper hot breech 10, the second end of rod 19 can pass through an ear orifice 144 which includes a fixing ear 117 which is present in said breech 10, while either a rod head 145 or a rod nut 147 screwed onto a rod thread 146 provided on the draw rod 106 bears against said ear 117.

[0149] It is also noted in [Fig.8] that the first end of rod 107 can be attached to the transmission housing 42 also by means of a rod head 145, or of a rod nut 147 screwed onto a rod thread 146.

[0150] Alternatively, said thread of rod 146 can be screwed into a tapped hole directly or indirectly made in the transmission housing 42.

[0151] According to a particular embodiment of the double-acting expansion cylinder 1 according to the invention, a compression spring 148 can be interposed either between the rod head 145 or the rod nut 147 and the fixing lug 117, or between said head 145 or any other threaded part into which the rod thread 146 is screwed, and any other support part.

[0152] As illustrated in [Fig.8], said spring 148 may consist of one or more “Belleville” washers.

[0153] Such a spring 148 can in particular limit the tension to which the traction rod 106 is subjected when the various parts which it holds together expand under the effect of their temperature rise.

[0154] Still in the case shown in Figures 2 to 10 where the cooled cylinder block 5 is held clamped between a lower hot cylinder head 10 and an upper hot cylinder head 10, while the piston 2 is double-acting, the hot-cylinder, cold-cylinder reciprocating heat engine 1 according to the invention comprises lower cylinder head centering means 109 which are integral with the transmission housing 42 and which bear directly or indirectly on the lower hot cylinder head 10, said means 109 leaving said cylinder head 10 free to move a short distance parallel to the longitudinal axis of the cold cylinder 6 and relative to the transmission housing 42, but preventing said cylinder head 10 from moving in the plane per- pendicular audit axis relative to audit casing 42.

[0155] Similarly, upper cylinder head centering means 110 attached to a centering gantry 127 which is rigidly fixed to the transmission housing 42 bear directly or indirectly on the upper hot cylinder head 10, said means 109 leaving said cylinder head 10 free to move a short distance parallel to the longitudinal axis of the cold cylinder 6 and relative to the transmission housing 42, but preventing said cylinder head 10 from moving in the plane perpendicular to said axis relative to said housing 42.

[0156] In this case, as can be seen in figures 2, 3, 7 and 8, a rod cooling tube 111 can tightly enclose the traction rod 106 over all or part of the length of said rod 106, a heat transfer fluid 32 from a coolant source 113 being able to circulate in a space left between the inner wall of said tube 111 and the outer surface of said rod 106, while the greatest possible part of the outer surface of said tube 111 does not touch the inner wall of the rod tunnel 102 so as to define with this latter wall a space empty or filled with atmospheric air, or filled with a gas of any kind.

[0157] Thus, the heat transfer fluid 32 can cool the traction rod 106 and maintain it at a sufficiently low temperature so that the material constituting said rod 106 retains its highest mechanical characteristics, while the empty space left between the external surface of the rod cooling tube 111 and the internal wall of the rod tunnel 102 limits the cooling of the hollow pillar 101.

[0158] It is noted that according to a particular embodiment of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention, only a rod head 145 which may have the traction rod 106 could be cooled, said head 145 being directly or indirectly in contact with the upper hot cylinder head 10.

[0159] As clearly shown in [Fig.8], at least one first tube feed orifice 114 can communicate with the interior of the rod cooling tube 111 in the vicinity of the first rod end 107, and at least one second tube feed orifice 115 can communicate with the interior of the rod cooling tube 111 in the vicinity of the second rod end 108, the heat transfer fluid 32 being able to circulate between the two said orifices 114, 115 however said fluid 32 is colder when it enters the rod cooling tube 111 than when it exits it.

[0160] It is noted that a fluid pump can be provided to force the heat transfer fluid 32 to circulate in the cooling tube of rod 111, said pump being able to continue to operate for some time after the stopping of the heat engine to which the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention applies.

[0161] This last arrangement allows, for example, the heat that the hot cylinder heads 10 lower and upper are likely to continue to transmit, during their cooling, to the pull rod 106 to be evacuated.

[0162] It is noted that once out of the rod cooling tube 111, the heat transfer fluid 32 can be cooled by a heat exchanger before being reintroduced into said tube 111, or renewed.

[0163] In [Fig.8], it is noted that the rod cooling tube 111 may include a tube collar 116 which is held directly or indirectly clamped by the pull rod 106 either against a fixing lug 117 which has the upper hot cylinder head 10, or against the transmission housing 42.

[0164] In this context, the tube collar 116 can be held tight by the pull rod 106 against the fixing lug 117 by means of a Banjo fitting 118 which has at least one radial connecting conduit 119 which is connected to the coolant source 113 on one side, and which communicates with the inside of the rod cooling tube 111 on the other.

[0165] It is noted that the radial connecting conduit 119 can be connected to the coolant source 113 or to other radial connecting conduits 119 that comprise the Banjo fitting 118 of other stem cooling tubes 111 by means of a flexible or deformable conduit that can accommodate the variations in distance induced by the thermal expansion of the various components that constitute the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention.

[0166] Still in this context and as shown in [Fig.8], a thermal insulation riser 120 can be interposed between the tube collar 116 and the fixing lug 117, said riser 120 being traversed through and through in its length direction by a riser tunnel 121 in which is housed the traction rod 106 and the rod cooling tube 111 which envelops it in a sealed manner, while the greatest possible part of the external surface of said tube 111 does not touch the internal wall of the riser tunnel 121 so as to define with this last wall a space empty or filled with atmospheric air, or filled with a gas of any kind.

[0167] It is noted that the thermal insulation extension 120 can advantageously be made of a material resistant to high temperatures and offering low thermal conductivity such as zirconium dioxide.

[0168] Figure 8 also shows that, according to an alternative embodiment of the hot-cylinder, cold-cylinder reciprocating heat engine 1 according to the invention, the rod cooling tube 111 may include at least one tube bulge 122 consisting of an axial portion of said tube 111 whose free diameter is substantially equivalent to, or even slightly greater than, that of the rod tunnel 102 in which it is housed, which makes it possible to center said tube 111 in said tunnel 102 or even to achieve to create a seal between said tube 111 and said tunnel 102.

[0169] Conversely, the rod cooling tube 111 may include at least one tube diameter restriction 123 consisting of an axial portion of said tube 111 whose free diameter is substantially equivalent to or even slightly less than that of the body of the traction rod 106, which allows said tube 111 to be centered around said rod 106 or even to achieve a local seal between said tube 111 and said rod 106.

[0170] It is noted that, as an alternative or in addition and as clearly shown in [Fig.8], the rod cooling tube 111 can receive at least one tube seal 157 made of elastomer or plastic to perfect the seal formed between said tube 111 and the rod tunnel 102.

[0171] As an alternative not shown, the traction rod 106 could be hollow to form an internal rod cooling channel arranged in the length of said rod 106, said channel opening axially or radially in the vicinity of each end of said rod 106 while a heat transfer fluid 32 from a coolant source 113 could circulate in said channel and this, to cool the traction rod 106 and maintain it at a temperature low enough so that the material constituting said rod 106 retains its highest mechanical characteristics.

[0172] As illustrated in Figures 4, 6 and 7, a piston cooling and lubrication chamber 125 connected to a source of lubricating-cooling fluid 126 can be fixed to the centering gantry 127 or provided on or in the latter, while an upper piston rod 128 which extends the double-acting piston 2 on the side of the upper variable-volume hot chamber 11 passes through the upper hot cylinder head 10 via an upper rod orifice 129 provided in said cylinder head 10 and via an access orifice to the cooling and lubrication chamber 130 passing through the centering gantry 127 to open into the piston cooling and lubrication chamber 125 so that the end of the upper piston rod 128 which is furthest from said piston 2 always remains immersed in said chamber 128 regardless of the position of said piston 2.

[0173] In this case, a lubricating-cooling fluid 139 can advantageously circulate from the piston cooling and lubrication chamber 125 to the transmission housing 42 by passing successively through an internal channel of the upper piston rod 140 arranged longitudinally in the upper piston rod 128, through an internal piston cavity 141, and through an internal channel of the lower piston rod 142 arranged longitudinally in the lower piston rod 46.

[0174] As can be seen in Figures 3, 9 and 10, the periphery of the internal piston cavity 141 can communicate with the external peripheral face of the piston sealing ring 37 via at least one peripheral ring lubrication orifice 143 which opens axially between at least two piston sealing means 30, said orifice 143 constituting the lubrication means 8 and the cooling means of the sealing ring 38.

[0175] Fig. 5 shows that the transmission housing 42 can be fitted with a centering and sealing plate 131 pierced with an access hole to the transmission means 132 through which the lower piston rod 46 passes to be connected to the power transmission means 3, said plate 131 being rigidly fixed on said housing 42 by screws or by any other means known to those skilled in the art.

[0176] Alternatively, said plate 131 may be an integral part of said housing 42.

[0177] As shown in [Fig. 6], the access port to the cooling chamber and lubrication 130 may include rod sealing means 133 providing a seal between said orifice 130 and the upper piston rod 128.

[0178] Fig. 5 shows that the access port to the transmission means 132 can include rod sealing means 133 providing a seal between said port 132 and the lower piston rod 46.

[0179] In figures 5 and 6, it can be noted that the lower cylinder head centering means 109 and / or the upper cylinder head centering means 110 can consist of an elastic centering disc 134 which can be pierced in its center with a disc hole 135 through which passes respectively the lower piston rod 46 or an upper piston rod 128 while its periphery constitutes a disc fixing collar 136 fixed in a sealed manner respectively on the transmission housing 42 and / or on the centering gantry 127.

[0180] It is noted in [Fig.5] that the centering and sealing plate 131 can carry the lower cylinder head centering means 109 which consist of an elastic centering disc 134 whose periphery forms a disc fixing collar 136 fixed in a sealed manner on said plate 131, said disc 134 being pierced in its center with a disc hole 135 through which the lower piston rod 46 passes without touching said disc 134, the edge of the disc hole 135 having a circular contact pad 137 which is maintained in sealed contact with a centering and sealing cone 138 which is present on the lower hot cylinder head 10, said cone 138 being able to be male or female, and the contact between said pad 137 and said cone 138 having the effect of axially deforming from its center the elastic centering disc 134.

[0181] It is noted that the disc fixing collar 136 can be fixed to the centering and sealing plate 131 by means of at least one screw, a clip, or any other fixing means known to those skilled in the art.

[0182] It is noted that advantageously, the elastic centering disc 134 can be made of a material resistant to high temperatures and offering low thermal conductivity such as zirconium dioxide.

[0183] As illustrated in [Fig.6], the upper cylinder head centering means 110 can consist of an elastic centering disc 134 whose periphery forms a disc fixing collar 136 fixed in a sealed manner on the centering gantry 127, said disc 134 being pierced in its center with a disc hole 135 whose edge has a circular contact pad 137 which is maintained in sealed contact with a centering and sealing cone 138 which has the hot upper cylinder head 10, said cone 138 being able to be male or female, and the contact between said pad 137 and said cone 138 having the effect of axially deforming the elastic centering disc 134 from its center.

[0184] It is noted that the disc fixing collar 136 can be fixed to the centering gantry 127 by means of at least one screw, a clip, or any other fixing means known to those skilled in the art.

[0185] It is noted that if the double-acting piston 2 is extended by an upper piston rod 128, the latter passes through the hole in the disc 135 without touching the elastic centering disc 134.

[0186] It is further noted that advantageously, the elastic centering disc 134 can be made of a material resistant to high temperatures and offering low thermal conductivity such as zirconium dioxide.

[0187] It can also be noted that, as an alternative to what has just been described, and whether it concerns the lower cylinder head centering means 109 or the upper cylinder head centering means 110, a contact pad similar to that which is present in the hole in the disc 135 can be provided respectively either on the lower hot cylinder head 10 or on the upper hot cylinder head 10, while a centering and sealing cone similar to that which is present in said cylinder heads 10 is provided on or in the elastic centering disc 134.

[0188] It is noted that the centering and sealing function provided by the elastic centering disc 134 can be entrusted, for example, to a split or unsplit torus made of steel or a superalloy, to an expanding washer made or not of multiple radially stacked plies made of the same piece of metal or ceramic, to at least three spring-driven pins distributed every one hundred and twenty degrees and cooperating with a sealing segment, and in general, to any solution capable of ensuring centering and sealing under the desired functional conditions while limiting heat loss from any hot part to any cold part.

[0189] As shown in Figures 2 and 7, an anti-rotation link 149 can directly or indirectly connect the lower hot cylinder head 10 and / or the upper hot cylinder head 10 and / or the cooled cylinder block 5 to the centering gantry 127, said link 149 being, for example, a pin or a connecting rod, and preventing the assembly formed by said cylinder heads 10 and the cooled cylinder block 5 to rotate around the longitudinal axis of the cold cylinder 6.

[0190] OPERATION OF THE INVENTION:

[0191] The operation of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention can be easily understood from the view of figures 1 to 10.

[0192] Said engine 1 may include a single-acting piston 2 as shown in [Fig. 1] or a double-acting piston 2 as illustrated in Figures 2 to 10. Said engine 1 may perform a Beau de Rochas, Miller, Atkinson, Diesel, or any other thermodynamic cycle known to those skilled in the art.

[0193] According to the particular embodiment of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention shown in figures 2 to 10, the piston 2 is double-acting while said engine 1 performs a Brayton cycle with regeneration which is identical to that performed by the heat engine with transfer-expansion and regeneration according to patent No. WO2016120560.

[0194] In this particular context, the invention applies only to the expansion valve 28 of said engine 1, 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.

[0195] The objective of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention is to limit as much as possible the heat losses of the working gas 17 by bringing as much of the internal wall surface of the regulator 28 as possible to a high temperature, while allowing the piston 2 to achieve a seal with the cold cylinder 6 by using conventional piston sealing means 30, in this case compression rings 44 and an oil scraper ring 45 similar to those used in mass-produced automotive internal combustion engines.

[0196] It is noted, particularly in figures 1, 3 and 4, that according to the particular embodiment of the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention shown therein, the power transmission means 3 which are housed in the transmission casing 42 are provided to transform the reciprocating movements made by a double-acting piston 2 in the cold cylinder 6, into a continuous rotational movement of a crankshaft 35.

[0197] According to this non-limiting example of a particular embodiment of said engine 1 according to the invention, the transmission casing 42 and the power transmission means 3 are maintained at a temperature close to one hundred degrees Celsius.

[0198] In Figures 3 and 4, and by way of example of an embodiment of the hot-cylinder, cold-cylinder reciprocating heat engine 1 according to the invention, it can be seen that the power transmission means 3 advantageously consist of a connecting rod 34 which is connected to the double-acting piston 2 by a crossmember 49 itself connected to said piston 2 by a lower piston rod 46, said connecting rod 34 being articulated around a crank 48 fitted on the crankshaft 35 the latter forming a power output shaft 4.

[0199] As can be clearly seen in figures 3 and 4, the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention presented here has for the same cold cylinder 6 a lower hot cylinder head 10 which forms with the double-acting piston 2 a lower hot chamber of variable volume 11, and an upper hot cylinder head 10 which forms with said piston 2 an upper hot chamber of variable volume 11.

[0200] As can be understood from figures 3 and 4, the cooled cylinder block 5 is held axially clamped between the lower and upper hot cylinder heads 10, while the double-acting piston 2 receives a hot cap 19 on each of its lower and upper axial faces, said caps 19 interposing themselves between said piston 2 and the variable volume hot chamber 11 with which they cooperate.

[0201] We will assume here that the working gas 17 is introduced into the regulator 28 via an inlet valve 31 at a temperature of 1,300 degrees Celsius, while the operational equilibrium temperature of the hot cylinder heads 10 and the hot cylinder caps 19 is 950 degrees Celsius.

[0202] It is noted advantageously that the inlet valve 31 and an exhaust valve 33 through which the working gas 17 is expelled from the regulator 28 after being expanded there can each be autoclaved, and controlled by a hydraulic regenerative valve actuator 50 as described in patent No. 3071896 dated October 11, 2019 belonging to the applicant.

[0203] 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 6 of the expansion valve 28 of the heat engine 1 according to the invention is maintained by the cylinder-case cooling means 9 at a relatively low temperature of only one hundred degrees Celsius, this temperature being given only as an example.

[0204] In figures 1, 3, 4, 9 and 10, it has been shown that the means for cooling the crankcase-cylinder 9 can consist of a cooling chamber 27 which envelops the external surface of the cold cylinder 6, a heat transfer fluid 32 - in this case water - circulating in said chamber 27.

[0205] Thus, and as clearly shown in Figures 3, 6, 9 and 10, practically all the internal walls of the expansion valve 28 of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention remain hot like those of the heat engine with transfer-expansion and regeneration according to patent WO2016120560, with the exception of the cold cylinder 6.

[0206] It should also be noted in this regard that in order to avoid any loss of heat, the expansion valve 28 shown in figures 2, 3, 4 and 7 includes an articulated inlet plenum 159 and an articulated exhaust plenum 159 made of silicon carbide 21, said plenums 159 being arranged according to the principle of patent No. FR 3094416 published on March 5, 2021 and belonging to the applicant.

[0207] In this respect, figures 2 to 4 clearly show that said plenums 159 are held pressed, on the one hand, against the hot cylinder heads 10 lower or upper as the case may be, and on the other hand, against a gas manifold by elastic plenum flanges 158 held clamped by screws and elastic plenum flange springs 56.

[0208] This particular arrangement allows said plenums 159, which provide the hot cylinder heads 10 and the manifolds with a spherical bearing surface, to articulate freely around said cylinder heads 10 and said manifolds to allow the constituent parts of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention to expand.

[0209] Similarly, it is noted in Figures 2, 3, 4 and 7 that the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention and following a non-limiting embodiment, the valve actuators 50 are held pressed against the articulated plenum 159 with which they cooperate by an elastic flange of actuators 54 and by elastic flange springs of actuators 55 with regard to said actuators 50 which control the intake valve 31 and the exhaust valve 33 of the upper variable volume hot chamber 11, and by an elastic actuator pushrod 160 with regard to said actuators 50 which control the intake valve 31 and the exhaust valve 33 of the lower variable volume hot chamber 11.

[0210] It is also noted that the elastic actuator pushers 160 are telescopic and are put under pressure by a nut which presses "Belleville" washers.

[0211] If, as previously stated, practically all the internal walls of the expansion valve 28 remain hot except for the cold cylinder 6, the remaining hot surfaces are sufficient to obtain from the regenerative Brayton cycle a significantly higher thermodynamic efficiency in practice than that of the Otto and Diesel cycles.

[0212] It is noted in figures 3, 4, 9 and 10 that the piston guiding means 29 and the piston sealing means 30 of the piston 2 are also maintained at a temperature of around one hundred degrees Celsius, close to that of the cold cylinder 6, in particular to preserve the integrity of the lubricant film 7 which covers the internal wall of said cylinder 6.

[0213] It is therefore understood that, unlike the heat engine with transfer-expansion and regeneration according to patent WO2016120560, the piston sealing means 30 no longer consist of a fluid cushion sealing device according to patent FR 3032252, but with a segmentation comparable to that of conventional automotive internal combustion engines, the said means 30 being cooled and lubricated in the same way.

[0214] This similarity allows the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention to benefit from more than a century of know-how in the field of piston segmentation for internal combustion engines.

[0215] The particular configuration of said engine 1 is justified in that, under the temperature conditions just described, the heat given to the cold cylinder 6 by the working gas 17 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 because of the compression means 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 expansion valve via a regeneration heat exchanger whose efficiency is less than one.

[0216] As proof of the validity of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, it is noted that if all the internal walls of the expansion valve 28 shown in figures 3 to 7 and in figures 9 and 10 - including the lower and upper hot cylinder heads 10 and the hot cylinder caps 19 - were kept at only one hundred degrees Celsius like the internal walls of mass-produced automotive internal combustion engines, the average specific heat power at the surface - for example expressed in kilowatts per square meter - given by the working gas 17 to the cold cylinder 6, would be much lower than that given by said gas 17 to said hot cylinder heads 10 and said hot cylinder caps 19.

[0217] Indeed, the surface area that the cold cylinder 6 exposes to the working gas 17 is small at the beginning of the expansion of said gas 17, then increases as said gas 17 expands and, in parallel, its temperature decreases, unlike the hot cylinder heads 10 and the hot cylinder caps 19 whose surface area exposed to the working gas 17 remains constant.

[0218] Thus, assuming that said cylinder heads 10 and said cylinder caps 19 are deliberately maintained at one hundred degrees Celsius during expansion, the specific cooling power at the surface would be much lower at the internal walls of the cold cylinder 6 than at those of said hot cylinder heads 10 and said hot cylinder caps 19.

[0219] Furthermore, according to the particular configuration of the hot-cylinder-cold-cylinder reciprocating heat engine 1 shown in Figures 2 to 10, the piston 2 is double-acting and not single-acting, which minimizes the surface area of ​​the cold cylinder 6 relative to the combined surface area of ​​hot cylinder heads 10 and hot cylinder caps 19.

[0220] Indeed, since the cold cylinder 6 is common to the lower and upper hot chambers of variable volume 11, its surface area here is less than thirty percent of the total internal surface area of ​​the expansion valve 28 which comes into contact with the working gas 17.

[0221] It is also observed that, at identical maximum power, the hot-cylinder head, cold-cylinder reciprocating heat engine 1 according to the invention, having a double-acting piston 2 as shown in Figures 2 to 7 and in Figures 9 and 10, and performing a regenerative Brayton cycle, has a smaller internal surface area than the internal surface area of ​​the cylinder of a conventional Otto cycle or Diesel engine.

[0222] This reduces the relative heat losses attributable to said cold cylinder 6.

[0223] Moreover, the maximum temperature reached by the gases in the cylinder of a conventional Otto cycle or Diesel engine is on the order of two thousand five hundred degrees Celsius compared to only about one thousand three hundred degrees Celsius for the hot cylinder head and cold cylinder reciprocating heat engine 1 performing a regenerative Brayton cycle.

[0224] All other things being equal, this lower temperature further reduces the heat losses of the working gas 17 in contact with the cold cylinder 6.

[0225] In addition, it will be noted that unlike the hot cylinder heads 10 and the hot cylinder caps 19, the cold cylinder 6 of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention is located in a low turbulence zone of the working gas 17 when said gas 17 is introduced into one or the other hot chamber of variable volume 11 via the corresponding intake valve 31, or when said gas 17 is expelled from said chamber 11 via the exhaust valve 33.

[0226] This low intensity turbulence limits the convective forcing and the transfer of heat by the working gas 17 to the cold cylinder 6.

[0227] It will also be noted that, unlike conventional Otto or Diesel cycle engines, the turbulence of the gases introduced into the expansion valve 28 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.

[0228] Indeed, insofar as the hot cylinder head and cold cylinder reciprocating heat engine 1 according to the invention performs a regenerative Brayton cycle - which is its primary purpose - the combustion or heating of the working gas 17 is carried out by means of a hot source located upstream of the regulator 28 and not in said regulator 28, said source being able to consist of a burner, a heat exchanger or, by way of non-limiting example, a solar radiation concentrator.

[0229] The lack of need to create deliberate turbulence to promote combustion further reduces the heat losses of the hot-head, cold-cylinder reciprocating heat engine 1 according to the invention performing a regenerative Brayton cycle compared to those of a conventional Otto or Diesel cycle engine, due to less convective forcing between the working gas 17 and the inner wall of the cold cylinder 6.

[0230] That being said, in order to benefit from the advantages of the hot cylinder head and cold cylinder 1 reciprocating heat engine, it is understood that said engine 1 requires hot parts and cold parts separated from each other by only a few millimeters to cooperate.

[0231] To demonstrate how the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention allows this cooperation of hot and cold parts very close to each other, we will assume here that the cooled cylinder block 5 is made of cast iron, while the hot cylinder heads 10 and the hot caps 19 are made of silicon carbide 21, the piston body 2 being made of high mechanical characteristics steel.

[0232] It should be noted that silicon carbide retains its mechanical characteristics up to temperatures of around 1,400 degrees Celsius, and can be used in oxidizing environments up to these high temperatures.

[0233] We will also assume here that the internal diameter of the cold cylinder 6 is two hundred and forty millimeters.

[0234] The proximity of hot and cold rooms reveals a dual challenge related to differential expansion and the limitation of heat losses.

[0235] Let us take for example the case of the upper hot cylinder head 10 of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, according to its particular configuration shown in figures 2 to 10.

[0236] Said hot cylinder head 10 and the cold cylinder 6 with which it cooperates are both manufactured at a temperature of around twenty degrees Celsius.

[0237] However, in operation, the temperature of the cold cylinder 6 stabilizes at one hundred degrees Celsius while that of the hot cylinder head 10 stabilizes at nine hundred and fifty degrees Celsius.

[0238] Taking into account the coefficients of expansion of the constituent materials of the hot cylinder head 10 of the cold cylinder 6, these temperatures lead to differences in diameter when hot between that of the hot cylinder head 10 and that of the cold cylinder 6 of nearly one millimeter.

[0239] Similarly, under the effect of temperature, the total height of the hot cylinder heads 10 lower and upper also increases by about one millimeter, such a variation in height being difficult to absorb by the plating means of cylinder head 24 which must also take up the axial forces generated by the pressure of the working gas 17 in the hot chambers of variable volume 11 lower and upper.

[0240] Furthermore, the close proximity between the lower and upper hot cylinder heads 10 and the cold cylinder 6 is likely to promote heat transfers from said cylinder heads 10 to said cylinder 6, said transfers being detrimental to the thermodynamic efficiency of the regenerative Brayton cycle.

[0241] The hot cylinder head and cold cylinder 1 reciprocating heat engine 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.

[0242] Indeed, as can be seen in Figures 2 to 4 and in Figures 7 and 8, said engine 1 includes hollow pillars 101 for example made of stainless steel, which are traversed through and through in the direction of their length by a rod tunnel 102, a first end of pillar 103 of said pillar 101 resting on the transmission housing 42 by means of a ball joint 105 while a second end of pillar 104 of said pillar 101 supports the lower hot cylinder head 10, also by means of a ball joint 105.

[0243] The hollow pillars 101 being of great length, they form a thermal barrier and limit the transfer of heat by the hot cylinder head 10 lower than the transmission housing 42.

[0244] In figures 1, 2, 7 and 8, the traction rods 106 which form the cylinder head clamping means 24 are noted, said rods 106 each being partly housed in the rod tunnel 102 of the hollow pillar 101 with which they cooperate, a first rod end 107 of each said traction rod 106 being attached to the transmission housing 42 by means of a rod thread 146 and a rod nut 147, and by means of a compression spring 148 here consisting of a stack of “Belleville” washers.

[0245] It is noted that a rod cooling tube 111 tightly encloses each traction rod 106 over most of its length, a heat transfer fluid 32 supplied by a coolant source 113 at a temperature close to one hundred degrees Celsius circulating in a space left between the inner wall of said tube 111 and the outer surface of said rod 106, while most of the outer surface of said tube 111 does not touch the inner wall of the rod tunnel 102 so as to define a gap with the latter wall.

[0246] As seen in [Fig. 8], a first tube feed port 114 communicates with the interior of the rod cooling tube 111 in the vicinity of the first rod end 107, while a second tube feed port 115 communicates with the interior of the rod cooling tube 111 in the vicinity of the second end of rod 108, the heat transfer fluid 32 being able to circulate between the two said orifices 114, 115.

[0247] In [Fig.8], it has been shown that according to the variant embodiment of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention described herein, the cooling tube of rod 111 may advantageously comprise a tube collar 116 held tight by the draw rod 106 and by means of a thermal insulation riser 120 against a fixing lug 117 which is present in the upper hot cylinder head 10.

[0248] As shown in [Fig.8], the tube collar 116 is here held tightly by the pull rod 106 against the fixing lug 117 by means of a Banjo fitting 118 which has a radial connecting conduit 119 which is connected to the coolant source 113 on one side, and which communicates with the inside of the rod cooling tube 111 on the other.

[0249] It is noted in [Fig.8] that the rod cooling tube 111 has several tube bulges 122 consisting of an axial portion of said tube 111 whose free diameter is slightly greater than that of the rod tunnel 102 in which it is housed, which allows said tube 111 to be centered in said tunnel 102.

[0250] It is noted in area "D" of [Fig.8] that the rod cooling tube 111 has a first tube supply orifice 114 located between two tube bulges 122, said first orifice 114 communicating with the interior of the rod cooling tube 111 in the vicinity of the first rod end 107 on the one hand, and being connected to a coolant source 113 like that shown in [Fig.1], by channels provided in the transmission housing 42 on the other hand.

[0251] On the side of the first end of rod 107, it is noted that the rod cooling tube 111 has, on the contrary, a restriction of tube diameter 123 consisting of an axial portion of said tube 111 whose free diameter is slightly less than that of the body of the traction rod 106, which makes it possible to center said tube 111 around said rod 106 and to achieve locally a seal between said tube 111 and said rod 106.

[0252] Advantageously, said tube diameter restriction 123 can be supplemented with or replaced by an elastomer tube seal 157 in order to ensure a perfect seal between the pull rod 106 and the rod cooling tube 111.

[0253] Thus constituted, the traction rod 106 can operate at a temperature close to one hundred degrees Celsius regardless of the temperature of the hot cylinder heads 10 lower and upper, and can be made of a steel with high mechanical characteristics, without risk of hardening said steel.

[0254] In any event, this particular configuration which allows the traction rod 106 to be cooled may prove unnecessary if the latter is made of a material resistant to high temperatures such as “zirconia”, silicon carbide, alumina or any superalloy specifically developed for this type of use.

[0255] Advantageously, the ball joints 105 which are in contact with the hot cylinder heads 10 lower and upper can be made of a material with very low thermal conductivity such as Zirconium oxide, this to limit the passage of heat from the hot cylinder heads 10 lower and upper to the hollow pillars 101 and the traction rods 106.

[0256] As can be seen in Figures 1, 2, 7 and 8, thermal insulation risers 120 can indeed be interposed between the pull rods 106 and the upper hot cylinder head 10, in order to reduce the heat flow from said cylinder head 10 to the pull rods 106, the latter being in this case housed in a riser tunnel 121 which passes through said risers 120 in the direction of their length.

[0257] This particular configuration is specified in [Fig.8], on which we see that each hollow pillar 101 actually has two ball joints 105 around which it articulates.

[0258] It is noted in zone "D" of said [Fig.8] that between the first end of pillar 103 of said pillar 101 and the transmission housing 42 there is a first ball joint 105 while zone "C" of the same [Fig.8] shows that between the second end of pillar 104 of said pillar 101 and the lower hot cylinder head 10 there is a second ball joint 105.

[0259] Fig. 8 also shows that each hollow pillar 101 is effectively traversed through and through along its length by a rod tunnel 102 in which a traction rod 106 is housed.

[0260] As illustrated in area “D” of said [Fig.8], the first end of the rod 18 of the traction rod 107 is attached to the transmission housing 42 by means of a first ball joint 105.

[0261] Zone “A” of [Fig.8] recalls that the second end of rod 108 is indeed indirectly attached to the upper hot cylinder head 10 by means of a rod head 145, a ball joint 105, and a thermal insulation riser 120.

[0262] The rod head 145 keeps the lower hot cylinder head 10 and the upper hot cylinder head 10 pressed against the cooled cylinder block 5, the latter being sandwiched between the two said cylinder heads 10.

[0263] This is made possible in particular by means of mounting lugs 117 which are provided in said cylinder heads 10, said lugs 117 having an ear opening 144 traversed by the traction rod 106.

[0264] Areas “B” and “C” of [Fig.8] illustrate this arrangement in a particularly obvious way.

[0265] Thus, the various ball joints 105 around which the four hollow pillars 101 and the traction rod 106 with which they cooperate are articulated allow the hot cylinder heads 10 lower and upper to expand freely, in particular in relation to the transmission housing 42.

[0266] This can occur however that the hollowed pillars 101 transmit tensile and compressive forces to said housing 42, said forces arising from the pressure exerted by the working gas 17 alternately on the lower hot cylinder head 10, and on the upper hot cylinder head 10.

[0267] As can be seen in figures 9 and 10, the expansion of the hot cylinder heads 10 lower and upper has little or no effect on the total length of the assembly formed together by said cylinder heads 10 and the cooled cylinder block 5.

[0268] This results from the fact that said cylinder heads 10 each have a concave conical cylinder head surface 25 through which said cylinder heads 10 are held pressed by the traction rods 106 on a circular cylinder contact edge 51 arranged on the cooled cylinder block 5.

[0269] The angle of the concave cone formed by said surface 25 has been previously calculated so that when said surface 25 slides on said edge 51 due to the difference between the thermal expansion of one or the other cylinder head 10 and that of said cylinder block 5, the distance which separates the rod head 145 from the cooled cylinder block 5 remains approximately constant all other things being equal.

[0270] Regardless of the differential expansion between that of said lower and upper cylinder heads 10 and that of the cooled cylinder block 5, the circular contact edge of cylinder 51 and the respective concave conical surfaces of cylinder head 25 of said cylinder heads 10 ensure that the latter always remain centered on the cooled cylinder block 5.

[0271] In this respect, the concave conical surface of the cylinder head 25 and the circular contact edge of the cylinder 51 form the cylinder head centering means 39 of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention.

[0272] As clearly shown in Figures 9 and 10, the cylinder head centering means 39 and the insulating ring 13 which forms the sealing means of thermal insulation 12 can be one, the circular cylinder contact edge 51 being an integral part of said ring 13, the latter constituting a thermal barrier which drastically limits heat transfers from the hot cylinder heads 10 to the cooled cylinder block 5.

[0273] It should be noted that the advantageous provisions just described cannot function correctly only with the lower cylinder head centering means 109 attached to the transmission housing 42 which are particularly visible in [Fig.5], and with the upper cylinder head centering means 110 as shown in [Fig.6] which are also attached to said housing 42 via a centering gantry 127 rigidly fixed to said housing 42.

[0274] Said means 109, 110 ensure the centering and parallelism with respect to the transmission housing 42 of the assembly formed by the lower and upper hot cylinder heads 10 and the cooled cylinder housing 5.

[0275] Said means 109, 110 each consist of an elastic centering disc 134 pierced in its center with a disc hole 135 through which passes, without touching said disc 134, the lower piston rod 46 on the side of the lower hot cylinder head 10, and an upper piston rod 128 on the side of the upper hot cylinder head 10.

[0276] As can be seen in figures 5 and 6, the periphery of the elastic centering discs 134 forms a disc fixing collar 136 which is fixed in a sealed manner either on the transmission housing 42 or on the centering gantry 127 as the case may be.

[0277] Figures 5 and 6 show that the edge of the disc hole 135 has a male circular contact pad 137 which is kept in tight contact with a female centering and sealing cone 138 which are present in the lower and upper hot cylinder heads 10, the contact between said pad 137 and said cone 138 having the effect of slightly axially deforming the elastic centering disc 134 from its center and within its elastic range, and of preventing the working gas 17 contained in the lower and upper variable volume hot chambers 11 from escaping from said chambers 11.

[0278] In figures 5 and 6, we will have noticed the relatively large radial length left on the elastic centering disc 134 between its disc fixing collar 136 and its contact pad 137.

[0279] This length is necessary so that said disc 134 can deform axially from its center without damage, and is also useful to limit as much as possible the heat transfer from the centering and sealing cone 138 to said collar 136.

[0280] As such, the body of the elastic centering disc 134 is preferably of small thickness, and can be made of zirconium oxide known for its low thermal conductivity.

[0281] It should also be noted that the narrow linear contact made between the centering and sealing cone 138 and the contact pad 137 also constitutes in itself an effective thermal barrier.

[0282] According to this particular configuration of the hot cylinder head reciprocating heat engine and cold cylinder 1 according to the invention, the assembly formed by the lower and upper hot cylinder heads 10 and the cooled cylinder block 5 can substantially expand longitudinally or move relative to the transmission block 42 over a very short distance parallel to the longitudinal axis of the cold cylinder 6, but said assembly cannot in any case move in the plane perpendicular to said axis relative to said block 42.

[0283] Figures 2 and 7 also show the anti-rotation link 149 which connects the cooled cylinder housing 5 to the centering gantry 127, this to prevent said assembly from rotating around the longitudinal axis of the cold cylinder 6.

[0284] As seen in [Fig.5], the elastic centering disc 134 of the lower hot cylinder head 10 cooperates with a centering and sealing plate 131 rigidly fixed on the transmission housing 42, said plate 131 being pierced with an access orifice to the transmission means 132 through which the lower piston rod 46 passes to be connected to the power transmission means 3.

[0285] It is noted that the access port to the transmission means 132 includes rod sealing means 133 which here take the form of two segment cut 150 which are held pressed against each other by a segment pressing spring 156 and whose cuts are offset, said segments 150 making a seal between said port 132 and the lower piston rod 46.

[0286] As seen in [Fig.6], the elastic centering disc 134 of the upper hot cylinder head 10 is fixed to the centering gantry 127 which has an access orifice to the cooling and lubrication chamber 130 through which the upper piston rod 128 passes to open into a piston cooling and lubrication chamber 125 connected to a source of lubricating-cooling fluid 126.

[0287] On [Fig.6], it is noted that the access port to the cooling and lubrication chamber 130 also has rod sealing means 133 which also take the form of two segmented sections 150 whose sections are offset, said segments 150 also being held pressed against each other by a segment pressing spring 156.

[0288] As can be easily understood from the view of figures 5 and 6, the lower piston rod 46 and the upper piston rod 128 are respectively lubricated, sealed and cooled by lubricant which resides and / or circulates in the transmission housing 42 and in the piston cooling and lubrication chamber 125.

[0289] As shown in Figures 9 and 10, the principles which prevail at the level of the lower and upper cylinder heads 10 and at the level of the cooled cylinder block 5 are also found at the level of the double-acting piston 2.

[0290] It can be seen in the said figures that the piston sealing ring 37 which is arranged around the periphery of the piston 2 includes piston sealing means 30 here formed of piston rings 151 similar to those found in conventional internal combustion engines with spark ignition or compression ignition.

[0291] The piston sealing ring 37 is maintained at a temperature close to one hundred degrees Celsius by a lubricating-cooling fluid 139 - in this case oil - which circulates from the piston cooling and lubrication chamber 125 to the transmission housing 42 passing respectively through an internal channel of the upper piston rod 140 arranged longitudinally in the upper piston rod 128, through an internal cavity of the piston 141, and through an internal channel of the lower piston rod 142 arranged longitudinally in the lower piston rod 46.

[0292] It should be noted that when the hot cylinder head and cold cylinder reciprocating heat engine 1 as described herein by way of example stops, the source of lubricating-cooling fluid 126 which ensures the circulation of the lubricating-cooling fluid 139 from the piston cooling and lubrication chamber 125 to the transmission housing 42 via the internal piston cavity 141, can continue to circulate said fluid 139 to cool the constituent elements of the double-acting piston 2 and this, as long as the hot cylinder heads 10 and the hot lower and upper caps 19 continue to transmit heat to said elements and risk raising the lubricating-cooling fluid 139 contained in said elements to coking or even combustion temperature.

[0293] It is noted, particularly in figures 9 and 10, that the periphery of the internal cavity of piston 141 communicates with the external peripheral face of the piston sealing ring 37 via peripheral ring lubrication orifices 143 which open axially between two piston segments 151, while said orifices 143 constitute both the lubrication means 8 and at least part of the sealing ring cooling means 38.

[0294] It is noted that the piston sealing ring 37 has - between the two piston rings 151 - piston guiding means 29 which guide the piston 2 in the cold cylinder 6, said means 29 here being made up of an annular sliding surface 43 in the shape of a barrel which promotes the hydrodynamic lift of the lubricant film 7 interposed between said surface 43 and said cylinder 6.

[0295] It is also noted - as easily seen in figures 5, 6, 9 and 10 - that an oil scraper ring 152 can advantageously be interposed between the annular sliding surface 43 and the piston ring 151 which is placed on the side of the lower variable volume hot chamber 11, the peripheral lubrication orifices of ring 143 opening between two lips that present said scraper ring 152.

[0296] The oil scraper segment 152 has the dual function of spreading the lubricating-cooling fluid 139 on the inner wall of the cold cylinder 6, while also recovering said fluid 139 present in excess on said wall.

[0297] As can be seen in figures 9 and 10, the lower and upper hot caps 19 have a concave conical cap surface 26 through which they are each held pressed by the cap pressing means 23 on a circular piston contact edge 52 arranged on the piston 2.

[0298] It can be seen in figures 3, 7, 9, and 10 that the means for clamping the cap 23 are here constituted by an axial double-acting piston screw 153 which, on the one hand, fixes the double-acting piston 2 on the stock 49, and on the other hand, clamps the lower and upper hot caps 19 on the piston sealing ring 37 by means of cap clamping tubes 154 and cap clamping springs 155, said springs 155 being in this case made up of a stack of "Belleville" washers.

[0299] Figures 9 and 10 show that, whether it is the lower or upper hot cap 19, the angle of the concave cone formed by the concave conical surface of cap 26 has been previously calculated so that when said surface 26 slides on the circular contact edge of piston 52 with which it cooperates, due to the difference between the thermal expansion of said cap 19 and that of the piston 2, the distance which separates the head of the axial screw of the double-acting piston 153 from the point of support of the cap clamping means 23 on the hot cap 19 remains approximately constant all other things being equal, so that the cap clamping springs 155 are neither more compressed nor more relaxed.

[0300] Thus, all other things being equal, the tensile force to which the axial screw of the double-acting piston 153 is subjected remains about constant regardless of the difference in thermal expansion between that of the lower and upper hot caps 19 and that of the piston 2.

[0301] According to this particular configuration of the hot cylinder head and cold cylinder 1 reciprocating heat engine according to the invention, the concave conical surface of the crown 26 and the circular contact edge of the piston 52 form the crown centering means 40.

[0302] The possibilities of the hot cylinder head and cold cylinder 1 reciprocating heat engine 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

Demands

1. A hot-cylinder, cold-cylinder reciprocating heat engine (1) comprising a cooled cylinder block (5) in which is arranged at least one cold cylinder (6) in which a piston (2) oriented and / or located by piston guiding means (29) can translate, said piston (2) being directly or indirectly connected by power transmission means (3) housed in a transmission housing (42) to at least one rotary or reciprocating power output shaft (4), characterized in that it comprises: • Lubrication means (8) which form a film of lubricant (7) which is interposed between the cold cylinder (6) and the piston (2); • Cylinder crankcase cooling means (9) which cool the cooled cylinder crankcase (5) so as to maintain all or part of the internal surface of the cold cylinder (6) at a temperature low enough that the lubricant film (7) does not age prematurely, coke, or burn; • At least one hot cylinder head (10) whose operating temperature is significantly higher than that of the cooled cylinder block (5) which it covers to form with the piston (2) a hot chamber of variable volume (11) which contains a working gas (17), said cylinder head (10) being on the one hand, kept pressed against the cooled cylinder block (5) by cylinder head pressing means (24) which leave it free to expand relative to said cylinder block (5), and on the other hand, located relative to said cylinder block (5) by cylinder head centering means (39); • At least one piston sealing ring (37) arranged on the periphery of the piston (2), said ring (37) comprising, on the one hand, piston sealing means (30) which form a seal between the piston (2) and the cold cylinder (6), and being, on the other hand, cooled by sealing ring cooling means (38); • At least one hot cap (19) which is interposed between the hot chamber of variable volume (11) and the piston (2) and whose operating temperature is significantly higher than that of the cooled cylinder block (5), said cap (19) being on the one hand, kept pressed against the piston (2) by cap pressing means (23) which leave said cap (19) free to expand relative to said piston (2), and on the other hand, located relative to said piston (2) by cap centering means (40).

2. Reciprocating heat engine according to claim 1, characterized in that sealed thermal insulation means (12) are interposed between the cooled cylinder block (5) and the hot cylinder head (10).

3. Reciprocating heat engine according to claim 1, characterized in that thermal insulation means (22) are interposed between the hot cap (19) and the piston (2)).

4. Reciprocating heat engine according to claim 2 or 3, characterized in that the sealed thermal insulation means (12) and / or the thermal insulation means (22) are made of at least one insulating ring (13) made of a material with low thermal conductivity (14).

5. Reciprocating heat engine according to claim 4, characterized in that the material with low thermal conductivity (14) is mainly made of zirconium oxide (15).

6. Reciprocating heat engine according to claim 4, characterized in that the insulating ring (13) which forms the sealed thermal insulation means (12) is directly or indirectly in contact with the cooled cylinder block (5) and / or with the hot cylinder head (10) by means of at least one contact edge of small surface area (16) which prevents the working gas (17) from passing between the cooled cylinder block (5) and the hot cylinder head (10).

7. Reciprocating heat engine according to claim 4, characterized in that the insulating ring (13) which forms the thermal insulation means (22) is directly or indirectly in contact with the hot cap (19) and / or with the piston (2) via at least one small surface contact edge (16).

8. A reciprocating heat engine according to claim 4, characterized in that a cylinder head gasket (18) is interposed between the insulating ring (13) which forms the sealed thermal insulation means (12) and the cooled cylinder block (5) and / or between said ring (13) and the hot cylinder head (10).

9. Reciprocating heat engine according to claim 4, characterized in that a piston seal (36) is interposed between the insulating ring (13) which forms the thermal insulation means (22) and the hot cap (19) and / or between said ring (13) and the piston (2).

10. Reciprocating heat engine according to claim 1, characterized in that the hot cylinder head (10) and / or the hot cap (19) are wholly or partly made of a high-temperature resistant material (20).

11. Reciprocating heat engine according to claim 10, characterized in that the high-temperature resistant material (20) is mainly made of silicon carbide (21).

12. A reciprocating heat engine according to claim 1, characterized in that the hot cylinder head (10) has a concave cylinder head surface (25) by means of which said cylinder head (10) is held pressed by cylinder head pressing means (24) against a circular cylinder contact edge (51) formed on the cooled cylinder block (5), the angle of the concave cone formed by said surface (25) being such that when said surface (25) slides on said edge (51) due to the difference between the thermal expansion of said cylinder head (10) and that of said cylinder block (5), the axial distance separating the point of contact of the cylinder head pressing means (24) on the hot cylinder head (10) from the cooled cylinder block (5) remains approximately constant, all other things being equal, while the concave cylinder head surface (25) and the circular edge cylinder contact (51) form the cylinder head centering means (39).

13. A reciprocating heat engine according to claim 1, characterized in that the hot cap (19) has a concave conical cap surface (26) by means of which said cap (19) is held pressed by cap pressing means (23) against a circular piston contact edge (52) formed on the piston (2), the angle of the concave cone formed by said surface (26) being such that when said surface (26) slides on said edge (52) due to the difference between the thermal expansion of said cap (19) and that of the piston (2), the axial distance separating the point of contact of the cap pressing means (23) on the hot cap (19) from the piston (2) remains approximately constant, all other things being equal, while the concave conical cap surface (26) and the circular contact edge piston (52) form the means for centering cap (40).

14. Reciprocating heat engine according to claim 1, characterized in that the hot cap (19) has on its periphery an aerodynamic passivation cord (53).

15. Reciprocating heat engine according to claim 1, characterized in that the outside of the hot cylinder head (10) is covered with a thermal insulator (41).

16. Reciprocating heat engine according to claim 1, characterized in that the piston sealing ring (37) has piston guiding means (29) consisting of an annular sliding surface (43).

17. A reciprocating heat engine according to claim 1, characterized in that the cooled cylinder block (5) is held clamped between a lower hot cylinder head (10) and an upper hot cylinder head (10) by the cylinder head clamping means (24) while the piston (2) is double-acting and comprises, on the one hand, a lower piston rod (46) which connects it to the power transmission means (3) and which passes through the lower hot cylinder head (10) via a lower rod orifice (47), and on the other hand, a lower hot cap (19) and an upper hot cap (19) to define with the lower and upper hot cylinder heads (10) a lower variable volume hot chamber (11) and an upper variable volume hot chamber (11).

18. A reciprocating heat engine according to claim 17, characterized in that it comprises: • At least one hollow pillar (101) traversed lengthwise by a rod tunnel (102), a first pillar end (103) of said pillar (101) resting directly or indirectly on the transmission housing (42) while a second pillar end (104) of said pillar (101) supports the lower hot cylinder head (10), said first end (101) being able to pivot about a ball joint (105) and / or flex relative to said housing (42) while said second end (104) is able to pivot about a ball joint (105) and / or flex relative to said lower hot cylinder head (10); • At least one drawbar (106) which forms the means of cylinder head plate (24) and which is, at least in part, housed in the rod tunnel (102), a first rod end (107) of said traction rod (106) being directly or indirectly attached to the transmission housing (42) while a second rod end (108) of said rod (106) is directly or indirectly attached to the upper hot cylinder head (10), said first end (107) being able to pivot about a ball joint (105) and / or flex relative to said housing (42) while said second end (108) is able to pivot about a ball joint (105) and / or flex relative to said cylinder head (10); • Lower cylinder head centering means (109) attached to the transmission housing (42) and which bear directly or indirectly on the lower hot cylinder head (10), said means (109) leaving said cylinder head (10) free to move a short distance parallel to the longitudinal axis of the cold cylinder (6) and relative to the transmission housing (42), but preventing said cylinder head (10) from moving in the plane perpendicular to said axis relative to said housing (42); • Upper cylinder head centering means (110) attached to a centering gantry (127) which is rigidly fixed to the transmission housing (42), said means (110) bearing directly or indirectly on the upper hot cylinder head (10), and said means (109) leaving said cylinder head (10) free to move a short distance parallel to the longitudinal axis of the cold cylinder (6) and relative to the transmission housing (42), but prohibiting said cylinder head (10) from moving in the plane perpendicular to said axis relative to said housing (42).

19. A reciprocating heat engine according to claim 18, characterized in that a rod cooling tube (111) hermetically seals around the drive rod (106) along all or part of the length of said rod (106), a heat transfer fluid (32) from a coolant source (113) being able to circulate in a space left between the inner wall of said tube (111) and the outer surface of said rod (106) however the greatest possible part of the external surface of said tube (111) does not touch the internal wall of the rod tunnel (102) so as to define with the latter wall an empty space.

20. Reciprocating heat engine according to claim 19, characterized in that at least a first tube feed orifice (114) communicates with the inside of the rod cooling tube (111) in the vicinity of the first rod end (107), and at least a second tube feed orifice (115) communicates with the inside of the rod cooling tube (111) in the vicinity of the second rod end (108), the heat transfer fluid (32) being able to circulate between the two said orifices (114, 115).

21. Reciprocating heat engine according to claim 19, characterized in that the rod cooling tube (111) has a tube collar (116) held directly or indirectly clamped by the draw rod (106) either against a fixing lug (117) which has the upper hot cylinder head (10), or against the transmission housing (42).

22. Reciprocating heat engine according to claim 21, characterized in that the tube collar (116) is held tight by the draw rod (106) against the fixing lug (117) by means of a Banjo fitting (118) which includes at least one radial connecting conduit (119) which is connected to the coolant source (113) on one side, and which communicates with the inside of the rod cooling tube (111) on the other.

23. A reciprocating heat engine according to claim 21, characterized in that a thermal insulation riser (120) is interposed between the tube collar (116) and the fixing lug (117), said riser (120) being traversed through and through in its length direction by a riser tunnel (121) in which is housed the traction rod (106) and the rod cooling tube (111) which hermetically encloses it, while the greatest possible part of the external surface of said tube (111) does not touch the internal wall of the riser tunnel (121) so as to define with the latter wall a void space.

24. Reciprocating heat engine according to claim 19, characterized in that the rod cooling tube (111) has at least one tube bulge (122) consisting of an axial portion of said tube (111) whose free diameter is substantially equivalent to or even slightly greater than that of the rod tunnel (102) in which it is housed.

25. Reciprocating heat engine according to claim 19, characterized in that the rod cooling tube (111) has at least one tube diameter restriction (123) consisting of an axial portion of said tube (111) whose free diameter is substantially equivalent to or even slightly less than that of the body of the traction rod (106).

26. Reciprocating heat engine according to claim 18, characterized in that the drive rod (106) is hollow to form an internal rod cooling channel arranged in the length of said rod (106), said channel opening axially or radially in the vicinity of each end of said rod (106) while a heat transfer fluid (32) from a coolant source (113) can circulate in said channel.

27. ​​A reciprocating heat engine according to claim 18, characterized in that a piston cooling and lubrication chamber (125) connected to a source of lubricating-cooling fluid (126) is fixed to, or arranged on, or within the centering gantry (127), while an upper piston rod (128) extending from the double-acting piston (2) on the side of the upper variable-volume hot chamber (11) passes through the upper hot cylinder head (10) via an upper rod orifice (129) arranged in said cylinder head (10) and via an access orifice to the cooling and lubrication chamber (130) passing through the centering gantry (127) to open into the piston cooling and lubrication chamber (125), such that the end of the upper piston rod (128) furthest from said piston (2) remains always immersed in said chamber (128) regardless of the position of said piston (2). piston (2).

28. Reciprocating heat engine according to claim 27, characterized in that a lubricating-cooling fluid (139) can circulate from the piston cooling and lubrication chamber (125) to the transmission housing (42) by passing successively through an internal channel of the upper piston rod (140) arranged longitudinally in the upper piston rod (128), through an internal piston cavity (141), and through an internal channel of the lower piston rod (142) arranged longitudinally in the lower piston rod (46).

29. A reciprocating heat engine according to claim 28, characterized in that the periphery of the internal piston cavity (141) communicates with the external peripheral face of the piston sealing ring (37) via at least one peripheral ring lubrication orifice (143) which opens axially between at least two piston sealing means (30), said orifice (143) constituting the lubrication means (8).

30. Reciprocating heat engine according to claim 18, characterized in that the transmission casing (42) is capped with a centering and sealing plate (131) pierced with an access orifice to the transmission means (132) through which the lower piston rod (46) passes to be connected to the power transmission means (3), said plate (131) being rigidly fixed on said casing (42).

31. Reciprocating heat engine according to claim 27, characterized in that the access port to the cooling and lubrication chamber (130) includes rod sealing means (133) providing a seal between said port (130) and the upper piston rod (128).

32. Reciprocating heat engine according to claim 30, characterized in that the access port to the transmission means (132) includes rod sealing means (133) providing a seal between said port (132) and the lower piston rod (46).

33. Reciprocating heat engine according to claim 18, characterized in that the lower cylinder head centering means (109) and / or the upper cylinder head centering means (110) are made up of an elastic centering disc (134) which can be pierced in its center with a disc hole (135) through which passes respectively the lower piston rod (46) or an upper piston rod (128) while its periphery constitutes a disc fixing collar (136) fixed in a sealed manner respectively on the transmission housing (42) and / or on the centering gantry (127).

34. A reciprocating heat engine according to claim 30, characterized in that the centering and sealing plate (131) carries the lower cylinder head centering means (109), which consist of a flexible centering disc (134) whose periphery forms a disc mounting flange (136) fixed in a sealed manner to said plate (131), said disc (134) having a disc hole (135) in its center through which the lower piston rod (46) passes without touching said disc (134), the edge of the disc hole (135) having a circular contact pad (137) which is maintained in sealed contact with a centering and sealing cone (138) present in the lower hot cylinder head (10), said cone (138) being able to be male or female, and the contact between said pad (137) and said cone (138) having the effect of axially deforming from its center the elastic centering disk (134).

35. Reciprocating heat engine according to claim 18, characterized in that the upper cylinder head centering means (110) consist of an elastic centering disc (134) the periphery of which forms a disc fixing collar (136) fixed in a sealed manner on the centering gantry (127), said disc (134) being pierced in its center by a disc hole (135) the edge of which has a circular contact pad (137) which is kept in sealed contact with a centering and sealing cone (138) which has the upper hot cylinder head (10), said cone (138) being able to be male or female, and the contact between said pad (137) and said cone (138) having the effect of axially deforming from its center the elastic centering disc (134).

36. Reciprocating heat engine according to claim 18, characterized in that an anti-rotation link (149) directly or indirectly connects the lower hot cylinder head (10) and / or the upper hot cylinder head (10) and / or the cooled cylinder block (5) to the centering gantry (127).

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