Multi-temperature double acting piston

Abstract

The present invention relates to a multi-temperature double-acting piston (201) with a peripheral sealing ring (220), a lower hot crown (226) and / or an upper hot crown (232) translating in a cold cylinder (204) of a heat engine (202) having a lower yoke (213) and an upper yoke (214), the piston (201) having a central piston pin (210) with its lower piston rod (211) passing through the lower yoke (213) to be connected to a power transmission means (205) housed in a transmission housing (206) and its upper piston rod (212) passing through the upper yoke (214) to open into a cooled piston lubrication chamber (217), a lubrication cooling gallery (227) arranged in the pin (210) communicating the chamber (217) with the housing (206) through an internal piston volume (228).

Description

[Technical field]

[0001] The present invention relates to a multi-temperature double-acting piston that is particularly suited for reciprocating engines that implement a regenerative Brayton thermodynamic cycle using a piston rather than a centrifugal compressor and turbine. [Background technology]

[0002] Regenerative Brayton cycle engines generally have separate components dedicated to each of the cycle's stages, which occur sequentially and simultaneously within the components, as opposed to Rochas, Miller, Atkinson, or Dieselbow cycle reciprocating internal combustion engines, whose stages occur sequentially within one and the same cylinder.

[0003] Thus, a regenerative Brayton cycle engine comprises at least one compressor, at least one regenerative exchanger, at least one continuously operating burner or internal or external high temperature source, and at least one expansion valve.

[0004] Allocating each stage of the thermodynamic cycle to a dedicated component has various advantages: in particular, the temperature of the inner wall of each such component may remain very close to the temperature of the gas during that stage.

[0005] For example, the temperature of the inner walls of the compressor of a regenerative Brayton cycle engine can be kept as low as possible, thereby helping to minimize the work of compression and maximize the overall thermodynamic efficiency of the engine.

[0006] Conversely, since the inner wall of the engine's expansion valve is in contact with the hot gas coming from the burner, the temperature of the inner wall must be high and in any case must be maintained as close as possible to the average temperature of the gas between the start and end of the expansion of the inner wall.

[0007] Despite these advantages, the maximum thermodynamic efficiency of an engine with a centrifugal compressor and a regenerative Brayton cycle turbine is in fact not much higher than that of a conventional spark ignition engine, and at best is comparable to that of a high speed diesel engine.

[0008] In either case, the efficiency remains lower than that of slower two-stroke diesel engines of tens of megawatts, for example, used for ship propulsion or stationary power generation.

[0009] Furthermore, engines with centrifugal compressors and regenerative Brayton cycle turbines are not well suited for low power applications and can only operate over a limited power range, outside of which their efficiency drops significantly.

[0010] This is why engines with centrifugal compressors and regenerative Brayton cycle turbines are primarily used in applications where efficiency is not the sole objective, but rather requiring, for example, high specific and volumetric power, low sound and vibration emissions, long service life, or reduced maintenance.

[0011] This is the case, for example, in certain military vessels fitted with Rolls Royce WR-21 regenerative Brayton cycle engines with centrifugal compressors and turbines, the efficiency of which rarely exceeds 40%, whereas the efficiency of slow speed two-stroke diesel engines fitted to certain vessels exceeds 50%.

[0012] This is also the case for certain generators most often operated in combined heat and electricity generation, such as the Turbec T100 microturbine or the Capstone C65 microturbine, which have an electrical efficiency of only about 28-30%, but require little maintenance and offer a very long service life.

[0013] An advantage of these turboshaft engines is that their turbines can withstand temperatures of about 1300° C. However, the overall thermodynamic efficiency of turboshaft engines remains limited by the efficiency of their constituent centrifugal compressors and turbines, which rarely exceed 80% over a relatively narrow operating range.

[0014] In view of the above, it would be particularly advantageous to be able to replace the centrifugal compressor and turbine of a regenerative Brayton cycle engine with positive displacement piston machines, which as is well known are more efficient.

[0015] This is the subject, for example, of U.S. Pat. No. 4,653,269, issued Mar. 31, 1987, in which the expansion turbine normally found in a regenerative Brayton cycle turboshaft engine is replaced by a piston-volume expansion cylinder.

[0016] However, the calculations demonstrate that if the inner walls of the volumetric expansion valve are cooled, for example maintained at about 100° C., as is the case in large-scale produced commercial reciprocating engines, the thermodynamic efficiency of a regenerative Brayton cycle engine cannot exceed that of an automotive diesel engine.

[0017] In order for a regenerative Brayton cycle engine having a volumetric expansion valve to provide very high thermodynamic efficiency, it is essential that the inner walls of the expansion valve be maintained at a temperature close to the average temperature of the gases expanded within the expansion valve.

[0018] For example, if hot gas is introduced into an expansion valve at a temperature of 1300°C and leaves the expansion valve at the end of expansion at a temperature of 600°C, the inner walls of the expansion valve must be maintained at a temperature of approximately 950°C.

[0019] The problem is that at such temperatures it is not possible to maintain an oil film on the walls of the expansion valve cylinder to lubricate any sealing segments that the expansion valve piston may have as it moves within that cylinder.

[0020] Indeed, from about 160°C the oil film on the cylinder begins to coke and then combust above 250°C.

[0021] Thus, the production of a regenerative Brayton cycle engine having high thermodynamic efficiency faces a two-fold challenge.

[0022] In fact, the engine consists of a centrifugal compressor and a turbine that can withstand high temperatures, but in this case the moderate efficiency of these components does not allow to exceed an overall efficiency equivalent to that of an automobile diesel engine, or it consists of a piston volume expansion valve that requires a piston with sealing segments sliding on an oil film formed on the surface of the cylinder in order to be sealed, the latter having to remain at a temperature not exceeding about 120°C for this purpose, which also does not allow the overall efficiency of the engine to be competitive.

[0023] In this regard, it would be advantageous to be able to combine the ability of a turbine to operate at high temperatures with the ability of a piston volume machine to expand gases with high efficiency.

[0024] For this purpose, the heat engine with transfer expansion and regeneration according to WO2016120560, published on 4 August 2016 and belonging to the present Applicant, is equipped with non-contact piston sealing means consisting of an expandable perforated continuous ring which, when subjected to a certain internal pressure, expands and approaches to within a few micrometres of the expansion valve cylinder engaging said cylinder without contacting it, while at the same time allowing the compressed air to leak through a calibrated orifice penetrating its radial thickness.

[0025] The above mentioned fluid cushion sealing device is also the subject of French Patent No. 3032252, published May 25, 2018 and belonging to the same Applicant. This device makes it possible to provide a contactless seal, which no longer uses oil to lubricate the segments operating by contact, and thus makes it possible to engage with high-temperature expansion valve cylinders maintained at temperatures of several hundred degrees Celsius.

[0026] In this regard, it therefore becomes practically possible to use a piston volume expansion valve to produce a regenerative Brayton cycle engine and to maximize the efficiency of that engine to significantly exceed that of a Diesel cycle engine.

[0027] In fact, calculations and simulations have demonstrated that the thermodynamic efficiency of piston volume regenerative Brayton cycle engines can reach or even exceed 70%, which in reality can result in the production of engines with brake energy efficiencies in excess of 60%, once unavoidable thermal and mechanical irreversibilities due to the very construction of the engine are deducted.

[0028] The problem faced by the fluid cushion sealing device of FR 3032252 is that the temperature of the cylinder remains excessive for the available material with which the perforated continuous ring can be made.

[0029] Indeed, in order for the efficiency of a piston volume regenerative Brayton cycle engine to be significantly higher than that of existing diesel engines, gas must be introduced into its expansion valve at a temperature of about 1300° C. and under a pressure of about 20 bar.

[0030] These operating conditions result in the temperature of the inner wall of the expansion valve stabilizing at approximately 950°C.

[0031] If we assume that the continuous perforated ring according to FR 3032252 is only a few microns close to the cylinder with which it engages, then in fact it takes on a temperature of about 950° C. of the cylinder.

[0032] However, there is no material that can both manufacture the ring and withstand such temperatures.

[0033] In particular, even superalloys such as "Udimet 720", which are used in the aeronautical and space industries and are known for their resistance to extreme temperatures, are unable to withstand such temperatures without undergoing creep and whilst being subjected to the expansion stresses exerted by the continuous perforated ring of the fluid cushion sealing device according to French Patent No. 3032252.

[0034] It is for this reason in particular, and by using more conventional materials than high-temperature resistant ceramics, that the regenerative cooling system of EP Patent No. 3585993, published on April 7, 2021 and belonging to the present Applicant, makes it possible to reduce the temperature of the expansion valve, in particular the inner wall of the cylinder, to a practical value of around 700°C.

[0035] For example, the "Udimet 720" superalloy resists creep at a temperature of 700°C when subjected to stresses not exceeding 230 megapascals.

[0036] The regenerative cooling system according to EP 3585993 provides a cooling housing which surrounds the expansion valve whilst leaving a gas circulation space between the housing and the expansion valve, and gas leaving the expansion valve itself circulates at a temperature of 500-600°C.

[0037] Thus, in accordance with the regenerative cooling system of EP 3585993, the exhaust gases of the expansion valve maintain the temperature of the inner walls of the expansion valve at a temperature of about 700°C, while the heat rejected by said gases is essentially recovered for reintroduction into the cycle by a regenerative heat exchanger included in the piston regenerative Brayton cycle reciprocating engine.

[0038] In this connection, the fluid cushion sealing device of French Patent No. 3032252 can be used, for example, with a continuous perforated ring made of the "Udimet 720" superalloy.

[0039] However, instead of this possibility, the cylinders and cylinder heads of regenerative Brayton cycle reciprocating engines must be made of materials having a high nickel content, such as "Ni-resist" cast iron, which represents an economic disadvantage due to nickel's high volatility and high price.

[0040] It should be noted that in either case, the temperature of the expansion valve remains at least 600°C higher than the temperature of the rest of the engine, specifically the movable joint and the transmission casing in which it is housed.

[0041] Advantageously, the expansion differential resulting from this temperature difference can be managed by a double-acting expansion cylinder with adaptive support, which is in particular the subject of European Patent No. 3350433, published on August 7, 2019 and belonging to the present Applicant.

[0042] The support allows for isotropic or anisotropic expansion of the expansion cylinder that differs significantly from the expansion of the transmission casing to which the expansion cylinder is fixed, without impairing the operation of either the cylinder or the piston moving within the cylinder.

[0043] The support also keeps the piston centered within the cylinder, transmits axial forces resulting from gas expansion to the transmission casing, and limits heat transfer from the expansion valve cylinder to the casing.

[0044] From reading the above, it will be appreciated that the configurations which make it possible to produce piston regenerative Brayton cycle reciprocating engines under the best possible conditions are not at this stage entirely satisfactory.

[0045] In fact, the fluid cushion sealing device requires that compressed air be provided by a compressor which consumes a portion of the work available on the shaft of the piston regenerative Brayton cycle reciprocating engine, to the detriment of the overall efficiency of the latter.

[0046] This further reduces the ultimate energy efficiency of the engine, especially when the latter operates at low power, since the amount of compressed air supplied to the fluid cushion sealing device is approximately constant regardless of the engine speed and load.

[0047] Furthermore, to ensure durable operation of the fluid cushion sealing device, recourse must be had to a regenerative cooling system according to EP 3585993, which system is not energy neutral.

[0048] In effect, such cooling systems cause the gases exiting the expansion valve to follow a tortuous path, creating pressure losses that reduce the overall efficiency of the piston regenerative Brayton cycle reciprocating engine.

[0049] Furthermore, the heat extracted from the inner wall of the expansion valve by the regenerative cooling system is reintroduced into the Brayton cycle upstream of the burner or heat source by a regenerative heat exchanger, which is not 100% efficient.

[0050] Thus, part of the heat extracted from the inner wall of the expansion valve is lost and the power passing through the exchanger is increased due to the presence of the cooling system.

[0051] In addition, the specific power of a piston regenerative Brayton cycle reciprocating engine is substantially reduced by the regenerative cooling system according to EP 3585993, which entails upward sizing of the engine to meet the power targets of the intended application.

[0052] It is also noted that the development of the fluid cushion sealing device of FR 3032252 remains complex, in particular to ensure its correct operation within non-stationary applications subject to shocks and vibrations. Summary of the Invention

[0053] Thus, without excluding other applications in any field, the hot cylinder head and cold cylinder reciprocating heat engine according to the invention is provided inter alia for making a piston regenerative Brayton cycle reciprocating engine, in which the hot expansion valve primarily limits heat losses and at the same time ensures a robust and durable seal between the piston and cylinder of said expansion valve.

[0054] In the field of application of piston reciprocating heat machines in general, and heat engines in particular, the result of the present invention is a multi-temperature double-acting engine. · The piston crown in a multi-temperature double-acting engine is maintained at a high temperature to limit the cooling of the hot gases in contact with it. Sealing of a multi-temperature double acting engine with the cylinder it engages can be achieved by segments made of cast iron or steel such as those contained in conventional spark ignition or diesel cycle internal combustion engines. The multi-temperature double-acting engine no longer uses the fluid cushion sealing device that is the subject of FR Patent No. 3 032 252 and therefore it is no longer necessary for an engine receiving a multi-temperature double-acting engine to be equipped with a regenerative cooling system as described in EP Patent No. 3 585 993 and therefore said engine no longer suffers the power and efficiency losses associated with the use of a compressor to supply said sealing device, the additional pressure losses at the outlet of the expansion valve associated with a more tortuous path for the gases, the heat losses due to a regenerative heat exchanger efficiency less than "1", and the specific engine power losses associated with this configuration.

[0055] As a result, the multi-temperature double-acting piston according to the invention allows the engine which houses it to avoid being manufactured from a material having a high nickel content, such as "Ni-resist" cast iron, allowing the cylinders of the engine to be made from low-cost cast iron, such as that typically used to make cylinder casings for automotive diesel engines, and the engine can operate at high temperatures and have high-temperature cylinder heads made from silicon carbide, a material which has high mechanical strength at high temperatures and is abundant and inexpensive.

[0056] The advantages offered by the multi-temperature double-acting piston according to the invention are, on the one hand, the lower density of silicon carbide, which allows it to be used to produce the high-temperature cylinder head of the engine which houses it, and, on the other hand, the absence of a regenerative cooling system, which results in a lower weight and a lower total heat capacity of the engine.

[0057] This facilitates a quicker increase in temperature of the engine by reducing the energy required to reach its operating temperature, resulting in a reduction in the engine's energy consumption, especially when the latter is applied in road, rail or maritime transport.

[0058] It will be understood that the multi-temperature double-acting piston according to the invention can be applied in addition to heat engines, generally stationary or mobile, and having internal or external combustion, in any other application similar in design and principle and which can advantageously take advantage of the specific features and functions of said piston according to the invention.

[0059] Other features of the invention are set forth in the description and in the secondary claims which depend directly or indirectly from the specification and the main claims.

[0060] A multi-temperature double-acting piston capable of translational movement in a cold cylinder arranged in a cooled cylinder casing comprising a heat engine, said piston being directly or indirectly connected to at least one rotary or reciprocating power output shaft by a power transmission means housed in a transmission casing, while said piston forms a lower variable volume chamber together with the cold cylinder and a lower cylinder head positioned between said piston and the transmission casing, said piston simultaneously forms an upper variable volume chamber together with said cylinder and an upper cylinder head, said chamber containing a working gas, said multi-temperature double-acting piston: a central piston pin, substantially coaxial with the cold cylinder, a first end of the central piston pin forming a lower piston rod passing through the lower cylinder head via a lower rod orifice engaging with the lower rod seal means so as to open into the transmission casing and to be connected directly or indirectly to the power transmission means via the piston fixing means, while a second end of the central piston pin forming an upper piston rod passing through the upper cylinder head via an upper rod orifice engaging with the upper rod seal means so as to open into a piston cooling lubrication chamber connected to a source of lubricating cooling fluid, the second end introducing the lubricating cooling fluid into said chamber; a peripheral seal ring, the outer diameter of which is substantially smaller than the inner diameter of the cryogenic cylinder, said ring comprising piston seal means in contact with said cylinder to provide a seal therewith; a lower radial connecting disk radially connecting the central piston pin to the peripheral seal ring on the lower variable volume chamber side, and an upper radial connecting disk radially connecting the central piston pin to the peripheral seal ring on the upper variable volume chamber side, the space left between the disk, the peripheral seal ring and the central piston pin forming an internal piston volume; a lubrication cooling gallery arranged mainly axially in the central piston pin and in one or more sections, which gallery on the one hand connects the piston cooling lubrication chamber with the internal piston volume and on the other hand connects said volume with the inside of the transmission casing; at least one peripheral ring lubrication orifice communicating the internal piston volume with an outer peripheral surface of a peripheral seal ring, said orifice opening axially from said surface between at least two piston seal means; Guide means for supporting directly or indirectly against or in the vicinity of the power transmission means and / or the cold cylinder and / or the lower cylinder head and / or the upper cylinder head, said guide means holding directly or indirectly a peripheral seal ring located in the center of the cold cylinder; a lower high temperature crown interposed between the lower radial connecting disc and the lower variable volume chamber, and / or an upper high temperature crown interposed between the upper radial connecting disc and the upper variable volume chamber; a crown application means for directly or indirectly holding a lower high temperature crown applied to a peripheral seal ring and / or a lower radial connecting disk and / or for directly or indirectly holding an upper high temperature crown applied to said ring and / or to said upper radial connecting disk, said means allowing said crown to expand freely relative to said ring and / or said disk; and crown centering means for locating the lower high temperature crown and / or the upper high temperature crown relative to a peripheral seal ring.

[0061] A multi-temperature double-acting piston according to the present invention includes a lower high temperature crown and / or an upper high temperature crown that are made, in whole or in part, of a high temperature resistant material.

[0062] A multi-temperature double-acting piston according to the present invention comprises a material that is resistant to high temperatures and is comprised primarily of silicon carbide.

[0063] The multi-temperature double-acting piston according to the present invention comprises thermal insulation means and / or crown seal means interposed either between the lower high temperature crown and the peripheral seal ring and / or lower radial connecting disk, or between the upper high temperature crown and said ring and / or upper radial connecting disk, or both.

[0064] The multi-temperature double-acting piston according to the present invention includes thermal insulation means and / or crown seal means interposed between either the lower high temperature crown and the central piston pin, or between the upper high temperature crown and the pin, or both.

[0065] The multi-temperature double-acting piston according to the invention comprises thermal insulation means consisting of at least one insulating ring made of a material with low thermal conductivity.

[0066] The multi-temperature double-acting piston according to the present invention comprises a low thermal conductivity material consisting essentially of zirconium oxide.

[0067] The multi-temperature double-acting piston according to the present invention comprises an insulating ring held in direct or indirect contact with a central piston pin and / or a peripheral sealing ring and / or a lower high temperature crown and / or a lower radial connecting disk and / or an upper high temperature crown and / or an upper radial connecting disk by at least one small surface area contact edge.

[0068] The multi-temperature double-acting piston according to the present invention comprises an insulating ring held in direct or indirect contact with the central piston pin and / or the peripheral sealing ring and / or the lower high temperature crown and / or the lower radial connecting disk and / or the upper high temperature crown and / or the upper radial connecting disk by at least one insulating ring sealing gasket sealed against the working gas.

[0069] The multi-temperature double-acting piston according to the invention comprises a crown application means for directly or indirectly holding a lower high temperature crown applied to the peripheral sealing ring and / or to the lower radial connecting disk, the crown application means being formed by an outer coaxial lower pin tube surrounding a central piston pin, said tube bearing on the lower high temperature crown in the vicinity of said pin, on the one hand, and on the power transmission means, on the other hand.

[0070] The multi-temperature double-acting piston according to the invention comprises crown application means for holding an upper high temperature crown applied directly or indirectly to the peripheral sealing ring and / or to the upper radial connecting disk, the crown application means being formed by an upper outer coaxial pin tube surrounding a central piston pin, said tube bearing on the one hand against the upper high temperature crown in the vicinity of said pin and on the other hand against an upper rod abutment formed directly or indirectly on the upper piston rod in the vicinity of its end opening into the piston cooling lubrication chamber.

[0071] The multi-temperature double-acting piston according to the present invention comprises some or all of the ends of the lower outer coaxial pin tube and / or the upper outer coaxial pin tube which receive tube springs which support the tubes against the lower high temperature crown and against the power transmission means and / or against the upper high temperature crown and against the upper rod abutment, respectively.

[0072] The multi-temperature double-acting piston according to the invention comprises a lower high temperature crown and / or an upper high temperature crown having a crown concave conical surface by which said crown is held applied by a crown application means against a circular peripheral contact edge fixed directly or indirectly to the peripheral part of the peripheral sealing ring and / or the lower radial connecting disk and / or the peripheral part of the upper radial connecting disk, the angle of the concave cone formed by said surface being such that when said surface slides over said edge due to the difference between the thermal expansion of said crown and the thermal expansion of the assembly formed by the peripheral sealing ring, the lower radial connecting disk, the upper radial connecting disk and the central piston pin, the axial distance separating the bearing points of the crown application means on said crown of the peripheral sealing ring remains approximately constant, all else being equal, while the crown concave conical surface and the circular peripheral contact edge form a crown centering means.

[0073] The multi-temperature double-acting piston according to the invention comprises, on the one hand, piston fixing means consisting of an axial double-acting piston screw with a piston screw body accommodated in a piston screw tunnel passing through the central piston pin in its longitudinal direction, said screw comprising, on the one hand, a piston screw head bearing against the end of the upper piston rod opening into the piston cooling and lubrication chamber, and, on the other hand, a piston thread screwed into the power transmission means.

[0074] A multi-temperature double-acting piston according to the present invention comprises a piston thread tunnel forming at least a part of a lubrication cooling gallery, wherein a lubrication cooling fluid can circulate between the piston thread body and an inner wall of the tunnel, the inner wall forming together with the body a first section extending from the piston cooling lubrication chamber to an internal piston volume, and a second section extending from said volume within the transmission casing.

[0075] The multi-temperature double-acting piston according to the present invention includes guide means comprising a barrel skirt disposed on the outer periphery of the peripheral seal ring and bearing against the cold cylinder.

[0076] The multi-temperature double-acting piston according to the invention comprises a lubrication cooling gallery which opens into the internal piston volume through a small axial gap left between, on the one hand, the fluid distribution disc received in said volume and, on the other hand, the upper radial connecting disc, which is approximately parallel to said radial connecting disc and which, on the one hand, forms a seal with the central piston pin and, on the other hand, terminates radially in the vicinity of the inner wall of the peripheral sealing ring, in said vicinity, where the lubrication cooling fluid coming from the piston cooling lubrication chamber can exit.

[0077] The multi-temperature double-acting piston according to the present invention comprises a central piston pin having a fluid recirculation collar within the internal volume and adjacent the lower radial connecting disk, which displaces lubricating cooling fluid accumulated within the volume and on the surface of the disk radially and towards the inner wall of the peripheral seal ring as the central piston pin moves towards the lower cylinder head.

[0078] The multi-temperature double-acting piston according to the invention comprises a lower radial connecting disc having a hollow profile at its connection with the central piston pin, said profile constituting an overflow reservoir in which lubrication cooling fluid can be stored, while at least one overflow orifice communicating with the inside of the transmission casing via a lubrication cooling gallery sets the maximum liquid level of said reservoir.

[0079] A multi-temperature double-acting piston according to the present invention includes a fluid nozzle supplied by a lubricating cooling fluid source, the fluid nozzle opening into the piston cooling lubrication chamber for ejecting a fluid jet into the piston cooling lubrication chamber.

[0080] The multi-temperature double-acting piston according to the present invention is provided with a fluid nozzle which injects a jet of lubricating cooling fluid into an axial screw reservoir arranged axially in the piston screw head, said reservoir communicating with a lubricating cooling gallery via at least one radial reservoir-gallery connecting duct.

[0081] The multi-temperature double-acting piston according to the present invention includes a threaded check valve housed within the axial thread of the double-acting piston, which allows the passage of lubrication cooling fluid from the axial thread reservoir to the lubrication cooling gallery, but not vice versa.

[0082] The multi-temperature double-acting piston according to the present invention comprises a piston cooling and lubricating chamber, which is connected to an air source by an intake check valve that allows the forced air fluid to flow into the chamber without flowing out of the chamber, and at the same time, the chamber is connected to an air waterproof sheet by a pressure limiting valve that allows the forced air fluid to flow from the chamber to the waterproof sheet when the pressure of the air in the chamber reaches a certain value.

[0083] The multi-temperature double-acting piston according to the present invention includes a reflective screen, which is interposed between the lower high temperature crown and the lower radial connecting disc and a portion of a peripheral seal ring can be added to the lower radial connecting disc, and / or which is interposed between the upper high temperature crown and the upper radial connecting disc and a portion of the ring can be added to the upper radial connecting disc.

[0084] The multi-temperature double-acting piston according to the present invention comprises thermal insulation means consisting of a honeycomb or fibrous insulating material occupying all or part of the space located between the lower high temperature crown and the lower radial connecting disc and / or between the upper high temperature crown and the upper radial connecting disc.

[0085] The multi-temperature double-acting piston according to the present invention comprises at least one first radial space left between the outer coaxial upper pin tube and the central piston pin, at least one second radial space left between the lower outer coaxial pin tube and the central piston pin, and a plurality of radial spaces left between the piston screw body and the inner wall of the piston screw tunnel, which spaces form at least a part of a lubrication cooling gallery, in which a lubrication cooling fluid can be continuously circulated to move from the piston cooling lubrication chamber to the internal piston volume and then out of said volume in the transmission casing.

[0086] The multi-temperature double-acting piston according to the present invention comprises a lower rod seal means and / or an upper rod seal means consisting of an expandable continuous ring fixed directly or indirectly to a cooled cylinder casing, the inner diameter of the continuous ring being substantially smaller than the outer diameter of the lower piston rod or upper piston rod it clamps.

[0087] The multi-temperature double-acting piston according to the present invention comprises an extensible continuous ring connected to a ring plate by a ring tube of small radial thickness, the ring, the plate and the ring being made from a single and same piece of material.

[0088] A multi-temperature double-acting piston according to the present invention includes an expandable continuous ring that is axially sandwiched between two ring bushings by a ring axial compression spring. [Brief description of the drawings]

[0089] The following description, given by way of non-limiting example and with reference to the accompanying drawings, enables the invention to be better understood and the characteristics it presents and the advantages it is likely to offer. [Figure 1] FIG. 2 is a three-dimensional view of a heat engine as may be provided to receive a multi-temperature double-acting piston according to the invention, said engine forming, for example, an expansion valve making it possible to implement a regenerative Brayton thermodynamic cycle. [Diagram 2]FIG. 2 is a three-dimensional cross-sectional view of a multi-temperature double-acting piston according to the present invention housed in the heat engine shown in FIG. 1, the engine also being shown in three-dimensional cross-section. [Diagram 3] 2 is a cross-sectional view of a multi-temperature double-acting piston according to the invention housed in the heat engine shown in FIG. 1, the engine also being shown in cross-section. [Figure 4] FIG. 2 is a three-dimensional cross-sectional view of a multi-temperature double-acting piston according to the present invention, said piston being connected to a power transmission means by an axial double-acting piston screw, while the crown application means specifically consists of a lower outer coaxial pin tube and an upper outer coaxial pin tube. [Diagram 5] FIG. 6 is an exploded three-dimensional view of a multi-temperature double-acting piston according to the present invention and its specific configuration shown in FIGS. 2-5. [Figure 6] FIG. 2 is an enlarged cross-sectional view of a multi-temperature double-acting piston according to the present invention associated with the engine shown in FIG. 1, specifically showing how the piston is connected to a power transmission means and how the lower high temperature crown is applied and held against the peripheral seal ring by the lower outer coaxial pin tube by the insulating ring. [Figure 7] FIG. 2 is an enlarged cross-sectional view of a multi-temperature double-acting piston according to the present invention associated with the engine shown in FIG. 1 , specifically showing how the upper piston rod opens into the piston cooling lubrication chamber and how the upper high temperature crown is applied and held against the peripheral seal ring by the upper outer coaxial pin tube with the insulating ring. [Figure 8] 8 is a cross-sectional view of the multi-temperature double-acting piston according to the present invention shown in FIG. 2 to FIG. 7, which shows how the lubricating cooling fluid can be circulated from the axial screw reservoir to the inside of the transmission casing to continuously cool the upper radial connecting disc, the peripheral sealing ring and the lower radial connecting disc, while cooling and lubricating the piston sealing means and the barrel skirt which it has, said means and said skirt being maintained in contact with the cold cylinder. [Figure 9]FIG. 9 is a cross-sectional view of the double-acting multi-temperature piston according to the present invention shown in FIG. 8, specifically showing how lubricating cooling fluid can be recirculated within the internal piston volume to complete the cooling of the mechanically welded assembly formed by the peripheral seal ring, the lower radial connecting disc, the upper radial connecting disc and the central piston pin, and to supply the peripheral ring lubrication orifices contained in the peripheral seal ring. [Figure 10] FIG. 10 is an enlarged schematic cross-sectional view of a multi-temperature double-acting piston according to the present invention and the particular configuration of the piston shown in FIGS. 2-9, showing the location and dimensions of the lower and upper high temperature crowns relative to the welded mechanical assembly and insulating ring when the crowns are cold. [Figure 11] FIG. 10 is an enlarged schematic cross-sectional view of a multi-temperature double-acting piston according to the present invention and the particular configuration of the piston shown in FIGS. 2-9, showing the location and dimensions of the lower and upper high temperature crowns relative to the welded mechanical assembly and insulating ring when the crowns are hot. [Figure 12] FIG. 2 is a three-dimensional view aligned with the piston cooling lubrication chamber of a multi-temperature double-acting piston according to the present invention, specifically showing the intake check valve and the pressure limiting valve, both of which are connected inside the transmission casing, which in this case acts as the air source and air waterproofing. [Figure 13] FIG. 2 is a cross-sectional view of a variant of a multi-temperature double-acting piston according to the invention, according to which part of the lubrication cooling gallery is formed by the radial space left between the upper and lower outer coaxial pin tubes, on the one hand, and the central pin of the piston, on the other hand, while a reflective screen and a honeycomb or fibrous insulating material are interposed between the lower and upper high temperature crowns and the lower and upper radial connecting disks facing them. [Figure 14]FIG. 2 is an enlarged cross-sectional view of an upper rod seal means of a multi-temperature double-acting piston according to the present invention, said means consisting of an expandable continuous ring connected to a ring plate by a ring tube having a small radial thickness. [Figure 15] FIG. 2 is an enlarged cross-sectional view of the upper rod seal means of the multi-temperature double-acting piston according to the present invention, said means consisting of a continuous axially extensible ring sandwiched between two ring bushings by an axial compression spring for the ring. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0090] 1-12 show a multi-temperature double-acting piston 201 according to the present invention, various details of its components, its variants and its accessories.

[0091] As shown in Figures 2, 3, 6 and 7, a multi-temperature double-acting piston 201 is capable of translational movement in a cold cylinder 204 formed in a cooled cylinder casing 203 of a heat engine 202, and the piston 201 is directly or indirectly connected to at least one rotary or reciprocating power output shaft 207 by a power transmission means 205 housed in a transmission casing 206.

[0092] As can be clearly seen in FIG. 7, the piston 201 forms a lower variable volume chamber 208 having a low temperature cylinder 204 and a lower cylinder head 213 positioned between the piston 201 and the transmission casing 206, and the piston 201 simultaneously forms an upper variable volume chamber 209 having the cylinder 204 and an upper cylinder head 214, the chambers 208, 209 containing a working gas 240.

[0093] As illustrated in Figures 2 to 5 and 8 and 9, the multi-temperature double-acting piston 201 according to the present invention comprises a central piston pin 210 that is substantially coaxial with the low-temperature cylinder 204, a first end of which forms a lower piston rod 211 that penetrates the lower cylinder head 213 via a lower rod orifice 215 that is engaged with a lower rod seal means 280 so as to open into the transmission casing 206 and to be directly or indirectly connected to the power transmission means 205 by a piston fixing means 231.

[0094] The second end of the pin 210 forms an upper piston rod 212 which passes through the upper cylinder head 214 via an upper rod orifice 216 which engages with an upper rod seal means 281 to open into a piston cooling lubrication chamber 217 connected to a lubrication cooling fluid source 218, the second end introducing lubrication cooling fluid 257 into the chamber 217.

[0095] It should be noted that as illustrated in Figures 2, 3, 6, 7, 14 and 15, the lower rod seal means 280 and the upper rod seal means 281 can contact the lower piston rod 211 and the upper piston rod 212, respectively, directly or indirectly via the lower outer coaxial pin tube 243 and the upper outer coaxial pin tube 248, respectively.

[0096] 2-11, it should be noted that the multi-temperature double-acting piston 201 according to the present invention has a peripheral seal ring 220 having an outer diameter substantially smaller than the inner diameter of the cold cylinder 204.

[0097] It will be noted in this figure that the peripheral sealing ring 220 comprises a piston sealing means 221 consisting of a compression segment 222 of, for example, cast iron or steel, such as is commonly found in conventional automobile engine pistons, which contacts and provides a seal with the cylinder 204.

[0098] It can be seen very clearly in FIG. 4 that the multi-temperature double-acting piston 201 according to the invention also comprises a lower radial connecting disc 224 radially connecting the central piston pin 210 to the peripheral sealing ring 220 on the side of the lower variable volume chamber 208 and an upper radial connecting disc 225 radially connecting the central piston pin 210 to the peripheral sealing ring 220 on the side of the upper variable volume chamber 209, the space left between said discs 224, 225, the peripheral sealing ring 220 and the central piston pin 210 forming an internal piston volume 228.

[0099] It should be noted that the lower radial connecting disk 224 and / or the upper radial connecting disk 225 may be a simple metal disk, a cone, a dome, or a truncosphere, or may be of any geometric shape, with or without ribs, to provide increased stiffness to the disks 224, 225.

[0100] It should also be noted that, as a variant of the embodiment of the multi-temperature double-acting piston 201 according to the present invention, the lower radial connecting disc 224 can be connected to the upper radial connecting disc 225 within the internal piston volume 228 by struts, spokes, fins or any other mechanical connection that secures the discs 224, 225 together to form a rigid assembly.

[0101] It should also be noted that the lower radial connecting disk 224 and / or the upper radial connecting disk 225 may be fixed to the central piston pin 210 and / or the peripheral seal ring 220 preferably by friction welding, electron beam welding or arc welding, or by any type of welding or assembly known to those skilled in the art.

[0102] It can be seen in Figures 8 and 9 that the multi-temperature double-acting piston 201 according to the invention is provided with a lubrication cooling gallery 227 arranged mainly axially in the central piston pin 210 and in one or more sections, said gallery 227 connecting the piston cooling lubrication chamber 217, on the one hand, with the internal piston volume 228 and, on the other hand, with said volume 228 in the transmission casing 206.

[0103] In Figures 10 and 11 it can be seen very clearly that the multi-temperature double-acting piston 201 according to the invention comprises at least one peripheral ring lubrication orifice 229 which communicates the inner piston volume 228 with the outer peripheral surface of the peripheral sealing ring 220, said orifice 229 opening axially from said surface between at least two piston sealing means 221.

[0104] The multi-temperature double-acting piston 201 according to the invention also comprises guide means 230, particularly visible in FIG. 4, which directly or indirectly bear against or in the vicinity of the power transmission means 205 and / or the low-temperature cylinder 204 and / or the lower cylinder head 213 and / or the upper cylinder head 214, and which directly or indirectly retain the peripheral sealing ring 220 located in the center of the low-temperature cylinder 204.

[0105] Specifically, in FIG. 7 , it is noted that the multi-temperature double-acting piston 201 according to the present invention comprises a lower high temperature crown 226 interposed between the lower radial connecting disc 224 and the lower variable volume chamber 208, and / or an upper high temperature crown 232 interposed between the upper radial connecting disc 225 and the upper variable volume chamber 209.

[0106] The multi-temperature double-acting piston 201 according to the present invention also comprises a crown application means 234, all of which are shown in Figures 2 to 5 and 8 and 9, for directly or indirectly holding a lower high temperature crown 226 applied against the peripheral sealing ring 220 and / or the lower radial connecting disc 224, and / or for directly or indirectly holding an upper high temperature crown 232 applied against said ring 220 and / or the upper radial connecting disc 224, said means 234 allowing said crowns 226, 232 to freely expand against said ring 220 and / or said discs 225, 225.

[0107] Finally, the multi-temperature double-acting piston 201 according to the present invention includes a crown centering means 235, shown for example in FIG. 7, which positions the lower high temperature crown 226 and / or the upper high temperature crown 232 relative to the peripheral seal ring 220.

[0108] It should be noted that according to variations in the embodiment of the multi-temperature double-acting piston 201 according to the present invention, the lower high temperature crown 226 and / or the upper high temperature crown 232 may be made in whole or in part of a high temperature resistant material 275, such as silicon carbide 276 and its various variations, whether or not alloyed with other materials.

[0109] As another variation shown in Figures 2 to 11, thermal insulation means 233 and / or crown sealing means 239 can be interposed either between the lower high temperature crown 226 and the peripheral sealing ring 220 and / or the lower radial connecting disc 224, or between the upper high temperature crown 232 and said ring 220 and / or upper radial connecting disc 225, or both, said means 233, 239 possibly forming an integral part of said crowns 226, 232 and / or said discs 224, 225.

[0110] 4-9 it is also shown that thermal insulation means 233 and / or crown sealing means 239 may be interposed either between the lower high temperature crown 226 and the central piston pin 210, or between the upper high temperature crown 232 and said pin 210, or both, and said means 233, 239 may form an integral part of said crowns 226, 232 and / or said pin 210.

[0111] Wherever they are located, the thermal insulation means 233 may consist of at least one insulating ring 236 made of a material having a low thermal conductivity 237, such as zirconium oxide 238 and its various variations, or quartz, whether or not alloyed with other materials.

[0112] As a non-limiting alternative, the insulating ring 236 can be made of quartz, which also has a low thermal conductivity and whose low modulus of elasticity gives it a large ability to accommodate the geometry of the components it contacts and engages.

[0113] It should be noted that the insulating ring 236 may be held in direct or indirect contact with the central piston pin 210 and / or the peripheral seal ring 220 and / or the lower high temperature crown 226 and / or the lower radial connecting disk 224 and / or the upper high temperature crown 232 and / or the upper radial connecting disk 225 by at least one small surface area contact edge 241.

[0114] 10 and 11, it is noted that advantageously, the insulating ring 236 can be provided with non-rigidifying grooves 291 which provide more flexibility and ensure more uniform and better distributed contact between the ring 236 and the components 210, 220, 226, 224, 232, 225 with which it engages.

[0115] Depending on the particular configuration of the multi-temperature double-acting piston 201, the insulating ring 236 may also be held in direct or indirect contact with the central piston pin 210 and / or the peripheral seal ring 220 and / or the lower high temperature crown 226 and / or the lower radial connecting disk 224 and / or the upper high temperature crown 232 and / or the upper radial connecting disk 225 by at least one insulating ring seal gasket 242 that is sealed against the working gas 240.

[0116] It should be noted that the insulating ring seal gasket 242 may comprise multiple metal sheets, as is the case for example with cylinder head gaskets in modern automotive internal combustion engines, or may be made of a material that can withstand high temperatures, such as the "Therma-pur" material developed by "Garlock".

[0117] As can be seen in Figures 2 to 9, the crown application means 234, which holds the lower high temperature crown 226 applied directly or indirectly to the peripheral sealing ring 220 and / or applied to the lower radial connecting disc 224, can be formed by a lower outer coaxial pin tube 243 surrounding the central piston pin 210, which tube 243 bears, on the one hand, against the lower high temperature crown 226 in the vicinity of said pin 210 and, on the other hand, against the power transmission means 205, which can consist, for example, of a crosshead 244 translating in a crosshead cylinder 293, which is hinged around the foot of a connecting rod 245 which is itself hinged around a crank 246 provided on a crankshaft 247, the latter forming the power output shaft 207.

[0118] It can also be seen in Figures 2 to 5 and 7 to 9 that the crown application means 234 holding the upper high temperature crown 232 applied directly or indirectly to the peripheral sealing ring 220 and / or the upper radial connecting disk 225 can consist of an upper outer coaxial pin tube 248 surrounding the central piston pin 210, said tube 248 bearing, on the one hand, against the upper high temperature crown 232 in the vicinity of said pin 210 and, on the other hand, against an upper rod abutment 249 provided directly or indirectly on the upper piston rod 212 in the vicinity of the end opening into the piston cooling lubrication chamber 217.

[0119] As can be clearly seen in FIG. 4 , some or all of the ends of the lower outer coaxial pin tube 243 and / or the upper outer coaxial pin tube 248 can receive a tube spring 250, whereby said tubes 243, 248 respectively bear against the lower hot crown 226 and the power transmission means 205 and / or on the upper hot crown 232 and the upper rod abutment 249; advantageously, the tube spring 250 can be formed by a stack of “Belleville” washers, which are known per se.

[0120] 10 and 11 illustrate that according to a particular configuration of the multi-temperature double-acting piston 201 according to the present invention, the lower high temperature crown 226 and / or the upper high temperature crown 232 can advantageously have a crown concave conical surface 251, whereby said crowns 226, 232 are applied and held by a crown application means 234 against a circular peripheral contact edge 252 which is directly or indirectly fixed to the peripheral sealing ring 220 and / or the peripheral portion of the lower radial connecting disc 224 and / or the peripheral portion of the upper radial connecting disc 225.

[0121] According to this configuration, the angle of the concave cone formed by the crown concave conical surface 251 is such that, due to the difference between the thermal expansion of the crowns 226, 232 and the thermal expansion of the assembly formed by the peripheral seal ring 220, the lower radial connecting disk 224, the upper radial connecting disk 225 and the central piston pin 210, when the surface 251 slides over the edge 252, the axial distance separating the bearing point of the crown application means 234 on the crowns 226, 232 from the peripheral seal ring 220 remains approximately constant, all else being equal, while the concave conical surface of the crown 251 and the circular peripheral contact edge 252 form the crown centering means 235.

[0122] It should be noted that this particular configuration of the multi-temperature double-acting piston 201 according to the present invention allows the force experienced by the crown application means 234, which is outside the images of Figures 10 and 11 but is actually present, to remain approximately constant regardless of the difference between the thermal expansion of said crowns 226, 232 and the thermal expansion of the mechanically welded assembly 289 formed by the peripheral sealing ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210.

[0123] Moreover, the configuration makes it possible to limit the variation of the volume ratio of the heat engine 202 as a function of its temperature, in particular during the cold start phase of said engine 202 .

[0124] It should be noted that advantageously, and as a variant not shown, the peripheral circular contact edge 252 may advantageously present a spherical contact with the crown concave conical surface 251 .

[0125] In Figures 2 to 9 it is shown that the piston fixing means 231 can consist of an axial double-acting piston screw 219, which firstly has a piston screw body 255 housed in a piston screw tunnel 256 passing through the central piston pin 210 in its longitudinal direction, said screw 219 having, on the one hand, a piston screw head 253 bearing against the end of the upper piston rod 212 opening into the piston cooling and lubrication chamber 217, and on the other hand a piston thread 254 screwed into the power transmission means 205.

[0126] According to a variation of the embodiment of the multi-temperature double-acting piston 201 according to the present invention, a screw-nut assembly can replace the piston screw head 253, and furthermore, as will be apparent to those skilled in the art, can be replaced by any other type of fastener.

[0127] As can be clearly seen in Figures 8 and 9, the piston thread tunnel 256 can advantageously form at least a part of the lubrication cooling gallery 227, a lubrication cooling fluid 257 can circulate between the piston thread body 255 and the inner wall of said tunnel 256, the latter forming together with said body 255 a first section from the piston cooling lubrication chamber 217 towards the internal piston volume 228 and a second section from said volume 228 towards the inside of the transmission casing 206, the piston thread body 255 being provided with a thread seal bulge 258 for separating the piston thread tunnel 256 into sections, the bulge 258 being able to have a bulge seal gasket 259 for such purpose.

[0128] As clearly illustrated in FIG. 4, the guide means 230 may consist of a barrel skirt 260 disposed on the outer periphery of the peripheral seal ring 220 and bearing against the cold cylinder 204, said skirt 260 having a converging shape that promotes the establishment of a hydrodynamic lubrication regime between itself and the cold cylinder 204 it engages.

[0129] 10 and 11, it can be clearly seen that the barrel skirt 260 can advantageously be positioned between the two compression segments 222 and adjacent to the oil scraper segment 278.

[0130] FIG. 8 illustrates that the lubrication cooling gallery 227 can open into the internal piston volume 228 through a small axial gap left between, on the one hand, the fluid distribution disc 261 contained in said volume 228 and, on the other hand, the upper radial connecting disc 225, which distribution disc 261 is approximately parallel to said radial connecting disc 225 and, on the one hand, forms a seal with the central piston pin 210 and, on the other hand, terminates in the radial vicinity of the inner wall of the peripheral seal ring 220, in which vicinity the lubrication cooling fluid 257 coming from the piston cooling lubrication chamber 217 can exit, for example, through any kind of distribution weir 290, orifice or gap that can be arranged around the periphery of the fluid distribution disc 261.

[0131] As best illustrated in FIG. 9, according to a particular variant of the multi-temperature double-acting piston 201 according to the invention, the central piston pin 210 may be provided with a fluid recirculation collar 262 in the internal piston volume 228 and in the vicinity of the lower radial connecting disk 224, which displaces the lubricating cooling fluid 257 accumulated in said volume 228 and on the surface of said disk 224 radially towards the inner wall of the peripheral sealing ring 220 when the central piston pin 210 moves towards the lower cylinder head 213, and said collar 262 may be provided with a collar groove 263 forming a radial jet of the lubricating cooling fluid 257 evenly distributed over 360 degrees.

[0132] It should be noted in particular in FIG. 8 that the lower radial connecting disc 224 can advantageously have a hollow shape 294 at the connection with the central piston pin 210, said shape 294 constituting an overflow reservoir 264 capable of storing the lubrication cooling fluid 257, while at least one overflow orifice 265 communicating with the inside of the transmission casing 206 via the lubrication cooling gallery 227 sets a maximum level of said reservoir 264 so that at each acceleration of the multi-temperature double-acting piston 201 according to the invention towards the upper cylinder head 214, the level of the lubrication cooling fluid 257 contained in said reservoir 264 does not exceed the level of the overflow orifice 265, said excess fluid 257 being discharged into the transmission casing 206.

[0133] It should be noted in FIG. 7 that a fluid nozzle 266 supplied by the lubricating cooling fluid source 218 can open into the piston cooling lubrication chamber 217 for spraying therein a fluid jet 267 shown in FIGS. 8 and 9.

[0134] It can further be seen in Figures 8 and 9 that the fluid nozzle 266 is capable of injecting a jet of lubrication cooling fluid 257 into an axial thread reservoir 267 arranged axially in the piston screw head 253, said reservoir 267 being in communication with the lubrication cooling gallery 227 via at least one radial reservoir gallery connecting duct 268.

[0135] 8 and 9 also clearly show that a screw-on check valve 269 can be accommodated in the double-acting piston axial screw 219, said valve 269 allowing the lubrication cooling fluid 257 to flow from the axial screw reservoir 267 to the lubrication cooling gallery 227, but not in the opposite direction, so that at each acceleration of the multi-temperature double-acting piston 201 according to the invention towards the upper cylinder head 214, the lubrication cooling fluid 257 contained in said reservoir 267 is forced into the lubrication cooling gallery 227, while, when the piston 201 accelerates towards the lower cylinder head 213, said fluid 257 contained in said gallery 227 does not return to said reservoir 267.

[0136] As a variant of the multi-temperature double-acting piston 201 according to the invention, FIG. 12 shows that the piston cooling and lubrication chamber 217 can be connected to an air source 270 or any type of gas source by an intake check valve 271 that allows the fluid forced air 272 to enter the chamber 217 without leaving the chamber 217, while the chamber 217 is connected to the waterproof sheet by a pressure limiting valve 274 that allows the air 272 to pass from the chamber 273 to the waterproof sheet 273 when the pressure of the fluid forced air 272 in the chamber 217 reaches a certain value.

[0137] With this particular configuration of the multi-temperature double-acting piston 201 according to the invention, the pressure supplying the lubricating cooling fluid 257 to the fluid nozzle 266 is advantageously greater than the opening pressure of the pressure limiting valve 274 .

[0138] Also note in FIG. 12 that the height of the duct connecting the piston cooling lubrication chamber 217 to the pressure limiting valve 274 can determine the maximum level of the lubrication cooling fluid 267 in said chamber 217, said duct acting as an overflow.

[0139] As shown in FIG. 13, a reflective screen 295 may be interposed between the lower high temperature crown 226 and the lower radial connecting disk 224, to which a portion of the peripheral seal ring 220 may be added, and / or between the upper high temperature crown 232 and the upper radial connecting disk 225, to which a portion of the ring 220 may be added, the reflective screen 295 returning heat emitted by the crowns 226, 232, specifically in the form of infrared radiation, to the lower high temperature crown 226 and / or the upper high temperature crown 232.

[0140] FIG. 13 also shows that the thermal insulation means 233 can consist of a honeycomb or fibrous insulating material 296 occupying all or a portion of the space located between the lower high temperature crown 226 and the lower radial connecting disk 224 and / or between the upper high temperature crown 232 and the upper radial connecting disk 225.

[0141] FIG. 13 also illustrates that at least one first radial space left between the upper outer coaxial pin tube 248 and the central piston pin 210, at least one second radial space left between the lower outer coaxial pin tube 243 and the central piston pin 210, and a plurality of radial spaces left between the piston screw body 255 and the inner wall of the piston screw tunnel 256 can form at least a portion of a lubrication cooling gallery 227, and a lubrication cooling fluid 257 can be continuously circulated within said spaces from the piston cooling lubrication chamber 217 to the internal piston volume 228 and then from said volume 228 within the transmission casing 206.

[0142] With this particular configuration of the multi-temperature double-acting piston according to the present invention, the outer wall of the upper outer coaxial pin tube 248 and the outer wall of the lower outer coaxial pin tube 243 are always maintained at a low temperature, so that the film of lubricating oil covering the outer walls of said tubes 248, 243 is protected from any coking or spontaneous ignition due to excessive temperatures, including when the heat engine 202 is stopped after operating at a high temperature, and in particular, after the engine 202 is stopped, so long as an electric pump is provided to circulate the lubrication cooling fluid 257 in the lubrication cooling gallery 227.

[0143] In Figures 14 and 15 it is shown that the lower rod sealing means 280 and / or the upper rod sealing means 281 can consist of an expandable continuous ring 297 fixed directly or indirectly to the cooled cylinder casing 203, the inner diameter of the continuous ring 297 being substantially smaller than the outer diameter of the lower piston rod 211 or upper piston rod 212 it clamps.

[0144] It should be noted that in this case, the radial and axial thicknesses of the extensible continuous ring 297 are advantageously small in order to limit energy losses caused by friction of said ring 297 on the lower piston rod 211 and / or the upper piston rod 212.

[0145] FIG. 14 illustrates that an expandable continuous ring 297 can be connected to a ring plate 298 by a ring tube 299 of small radial thickness, with the ring 297, the plate 298, and the ring 297 being made from a single piece of material.

[0146] It should be noted that in this case, advantageously, the ring plate 298 can be provided with at least one radial ring stop 303 which can move radially and sealingly, directly or indirectly, within the cooled cylinder casing 203 and which limits its eccentricity relative to the lower piston rod 211 or relative to the upper piston rod 212.

[0147] Another variation illustrated in FIG. 15 proposes that the continuously extensible ring 297 can be axially sandwiched between two ring bushings 302 by an axial ring compression spring 301 that can engage with a sealed ring bushing 300, and the two ring bushings 300 can expose a radial ring stop 303 that can contact the lower piston rod 211 or the upper piston rod 212.

[0148] Operation of the invention The operation of the multi-temperature double-acting piston 201 according to the present invention can be readily understood with reference to FIGS.

[0149] The piston 201 may be applied to any heat engine 202 running the Beau de Rochas, Miller, Atkinson, Diesel cycle, or any other thermodynamic cycle known to those skilled in the art.

[0150] 1-15 show a multi-temperature double-acting piston 201 according to the present invention that can be used in a heat engine 202 performing a regenerative Brayton cycle, which is identical to the cycle performed by the transfer expansion and regenerative heat engine of WO2016120560.

[0151] In this particular situation, the piston 201 applies only to the expansion valve 279 of the engine 202; other components of the latter, such as one or more compressors, burners, or regenerative exchangers, required to implement a regenerative Brayton cycle, are not shown.

[0152] The purpose of the multi-temperature double-acting piston 201 according to the invention is to limit as much as possible the heat loss of the working gas 240 during the expansion phase of said gas 240 carried out during the regenerative Brayton cycle, while ensuring that said piston 201 achieves a good seal with the cold cylinder 204 by using only conventional piston sealing means 221, in this case a compression segment 222 similar to those equipping mass-produced automotive internal combustion engines, said segment 222 being engaged with an oil scraper segment 278.

[0153] Specifically, maintaining this objective means that as much of the exterior wall surface of multi-temperature double-acting piston 201 as possible is maintained at an elevated temperature.

[0154] To achieve this purpose, the multi-temperature double-acting piston 201 according to the invention must also provide good sealing with the lower cylinder head 213 and the upper cylinder head 214, respectively, by lower rod sealing means 280 and upper rod sealing means 281, said means 280, 281 being formed by metal cut segments 282, known per se, or by an expandable continuous ring 297 fixed directly or indirectly to the cooled cylinder casing 203, as shown in Figures 14 and 15.

[0155] To fully achieve said objective, the multi-temperature double-acting piston 201 according to the invention is advantageously applied to a heat engine 202 based on the same objective, thus minimizing heat loss from the working gas 240 by raising the largest possible portion of its inner walls to high temperatures.

[0156] For this purpose, Figures 1 to 3 show a heat engine 202, the expansion valve 279 of which receives a multi-temperature double-acting piston 201, which comprises a lower cylinder head 213 and an upper cylinder head 214, the operating temperature of which is high (around 950°C), the cylinder heads 213, 214 being made of silicon carbide 276, i.e. a material that maintains its mechanical characteristics up to temperatures of around 1400°C and that can be used in an oxidizing medium at these high temperatures.

[0157] Only the internal surfaces of the expansion valve 279, which are in contact with both the working gas 240 and the piston sealing means 221, are maintained at a temperature of only 100°C, which remains compatible with the lubrication cooling fluid 257, such as the lubrication cooling oil 283, preventing the latter (in this case engine oil, as known per se) from prematurely coking, burning or deteriorating.

[0158] As can be seen in Figures 2 and 3, the surface in question is the low temperature cylinder 204 disposed within the cooled cylinder casing 203, as well as part of the peripheral seal ring 220, part of the lower piston rod 211, and part of the upper piston rod 212, and the combined surface of these members 220, 204, 211, 212 in contact with the working gas 240 is much smaller than the combined surface of the lower cylinder head 213, the upper cylinder head 214, the lower hot crown 226, and the upper hot crown 232.

[0159] In Figures 2 and 3, a power transmission means 205 housed in a transmission casing 206 and provided to convert the reciprocating motion of said piston 201 in the cold cylinder 204 into the continuous rotational motion of a crankshaft 247 is shown as an example of a particular embodiment of a multi-temperature double-acting piston 201 according to the invention.

[0160] Further, according to this non-limiting embodiment, the transmission casing 206 and power transmitting means 205 are advantageously maintained at a temperature close to 100° C. which is compatible with the lubricating cooling oil 283 .

[0161] It should be noted that in Figures 2 and 3 the power transmission means 205 consists, by way of example, of a connecting rod 245 connected by a crosshead 244 to the lower piston rod 211, said connecting rod 245 being hinged around a crank 246 provided on a crankshaft 247, the latter forming the power output shaft 207.

[0162] As can be clearly seen in Figures 2 to 5 and Figures 8, 9 and 13, the mechanically welded assembly 289 formed by the peripheral sealing ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225 and the central piston pin 210 is fixed to the crosshead 244 by an axial double-acting piston screw 219, the piston screw body 255 of which is received in a piston screw tunnel 256 that passes longitudinally through the central piston pin 210.

[0163] The piston thread tunnel 256 in this case forms a lubrication cooling gallery 227, and the lubrication cooling oil 283 can flow in particular between the piston thread body 255 and the inner wall of the tunnel 256, the latter forming together with the body 255 a first section of the lubrication cooling gallery 227 extending from the piston cooling lubrication chamber 217 to the internal piston volume 228, and a second section of the gallery 227 extending from the volume 228 in the transmission casing 206.

[0164] Advantageously, the piston screw body 255 includes a thread seal bulge 258 that sealingly separates the piston screw tunnel 256 into two sections by a bulge seal 259 .

[0165] As is clearly shown in Figures 2 to 5 and also in Figures 8, 9 and 13, the axial double-acting piston screw 219 also comprises a piston screw head 253 which bears against the end of the upper piston rod 212 facing the piston cooling lubrication chamber 217, and a piston thread 254 which screws into the crosshead 244.

[0166] In this case, the working gas 240 is introduced into the expansion valve 279 through the intake valve 284 at a temperature of 1300°C, and at the same time, the operating equilibrium temperatures of the lower cylinder head 213 and the upper cylinder head 214 sandwiching the cooled cylinder casing 203, on the one hand, and the lower high temperature crown 226 and the upper high temperature crown 232 covering the multi-temperature double-acting piston 201, on the other hand, are assumed to be 950°C.

[0167] Advantageously, as illustrated in Figures 1 and 2 and Figures 6 and 7, it should be noted that the intake valve 284 and the exhaust valve 285 from which the working gas 240 is discharged after expanding in the expansion valve 279 can be autoclaved and controlled by a regenerative valve hydraulic actuator as described in Patent No. 3,071,896, dated October 11, 2019, belonging to the present applicant.

[0168] Unlike the heat engine with transfer expansion and regeneration according to WO2016120560, in which all inner walls of its expansion valves are maintained at a high temperature of, for example, 950°C, the inner walls of the low-temperature cylinder 204 of the expansion valve 279 of the heat engine 202 are in this case maintained by the casing cylinder cooling means 286 at a relatively low temperature of 100°C, this temperature being given by way of example only.

[0169] 2 and 3 show that the casing cylinder cooling means 286 may consist of a cooling chamber 287 surrounding the outer surface of the low temperature cylinder 204, within which a heat transfer liquid 288, in this case water, circulates.

[0170] As a result, as clearly shown in Figures 2 and 3, substantially all of the inner walls of the expansion valve 279 of the heat engine 202 remain hot, except for the cold cylinder 204, similar to the inner walls of a transfer expansion and regenerative heat engine according to WO2016120560.

[0171] The remaining hot surface is sufficient to obtain thermodynamic efficiencies from the regenerative Brayton cycle that are in fact significantly higher than those obtainable from the Otto and Diesel cycles.

[0172] As clearly shown in Figures 10 and 11, the peripheral seal ring 220 comprises a barrel skirt 260, two compression segments 222, and an oil scraper segment 278, and it should be noted that these components 260, 222, 278 are also maintained at a temperature of approximately 100°C, close to the temperature of the cold cylinder 204 they engage, specifically to preserve the integrity of the lubricating cooling oil 283 that forms a film on the inner wall of that cylinder 204.

[0173] It will therefore be understood that, unlike the transfer expansion and regenerative heat engine of WO 2016120560, the piston sealing means 221 are in this case no longer constituted by the fluid cushion sealing device of FR 3032252, but rather by sealing segments comparable to those of conventional automotive internal combustion engines, said means 221 being cooled and lubricated in the same way.

[0174] This similarity allows the multi-temperature double-acting piston 201 according to the present invention to benefit from over 100 years of knowledge in the field of segmenting pistons in internal combustion engines.

[0175] The particular configuration of said piston 201 and of the expansion valve 279 of which it forms part is justified in that, under the abovementioned temperature conditions, the heat given to the cold cylinder 204 by the working gas 240 forms an energy loss comparable to or less than that caused by the regenerative cooling system according to EP patent No. 3585993, on the one hand, due to the compression means necessary to supply compressed air, by the fluid cushion sealing device which is the subject of French patent No. 3032252, and on the other hand, due to the additional pressure loss in the exhaust gas which it generates, and due to the reintroduction into the thermodynamic cycle of the heat extracted from the inner wall of the expansion valve via a regenerative heat exchanger, the efficiency of which is less than 1.

[0176] As proof of the effectiveness of the multi-temperature double-acting piston 201 according to the present invention, it should be noted that if all of the interior walls of the expansion valve 279 shown in Figures 2 and 3 (including the lower cylinder head 213, the upper cylinder head 214, the lower high temperature crown 226, and the upper high temperature crown 232) were maintained at only 100°C, like the interior walls of a mass-produced automotive internal combustion engine, the average surface specific heat power (e.g., expressed in kilowatts per square meter) delivered by the working gas 240 to the low temperature cylinder 204 would be much lower than the average surface specific heat power delivered by the gas 240 to the cylinder heads 213, 214 and the crowns 226, 232.

[0177] In fact, the surface area of ​​the cold cylinder 204 exposed to the working gas 240 is small at the beginning of the expansion of the gas 240 and then increases as the gas 240 expands and its temperature decreases, in contrast to the lower cylinder head 213, the upper cylinder head 214, the lower hot crown 226, and the upper hot crown 232, whose surfaces exposed to the working gas 240 remain constant.

[0178] As a result, assuming that the cylinder heads 213, 214 and the crowns 226, 232 are spontaneously maintained at 100° C. during expansion, the specific cooling power at the surface will be much lower on the inner walls of the cold cylinder 204 than on the inner walls of the cylinder heads 213, 214 and the crowns 226, 232.

[0179] Furthermore, because the multi-temperature double-acting piston 201 is, as the name suggests, double-acting, the surface area of ​​the cold cylinder 204 relative to the surface area of ​​the cylinder heads 213, 214 and the crowns 226, 232 is significantly reduced as compared to the surface area if the piston 201 were single-acting.

[0180] In fact, since the low-temperature cylinder 204 is common to the lower variable volume chamber 208 and the upper variable volume chamber 209, its surface area in this case and in the embodiment of the multi-temperature double-acting piston 201 according to the invention shown in Figures 2 and 3 is less than 30% of the total internal surface area of ​​the expansion valve 279 in contact with the working gas 240.

[0181] It is also observed that at the same maximum power, the heat engine 202 is equipped with a multi-temperature double-acting piston 201 and runs a regenerative Brayton cycle, the internal surface of its low-temperature cylinder 204 being absolutely smaller than the internal surface of the cylinder of an Otto cycle engine or a Diesel cycle engine of conventional architecture.

[0182] This reduces the relative heat loss due to the cold cylinder 204 .

[0183] In addition, the maximum temperature reached by the gases in the cylinder of a conventional Otto cycle or Diesel cycle engine is about 2500°C, compared to only about 1300°C for the heat engine 202 implementing the regenerative Brayton cycle shown in Figures 1-3.

[0184] All other things being equal, this lower temperature further reduces heat loss to the working gas 240 in contact with the cold cylinder 204 .

[0185] It is further noted that unlike the lower cylinder head 213, the upper cylinder head 214, the lower hot crown 226 and the upper hot crown 232, the heat engine 202 is provided with a multi-temperature double-acting piston 201 according to the present invention, and its cold cylinder 204 is located in a low turbulence zone of the working gas 240 during introduction of the working gas 240 into the lower variable volume chamber 208 or the upper variable volume chamber 209 via the corresponding intake valve 284, or during exhaust of the working gas 240 from said chambers 208, 209 via the exhaust valve 285.

[0186] This low intensity turbulence limits the convective forces and heat transfer from the working gas 240 to the cold cylinder 204 .

[0187] Also, note that unlike conventional Otto cycle or Diesel cycle engines, the turbulent flow of gases entering the expansion valve 279 does not need to be forced by motions known to those skilled in the art as "tumble," "swirl," or "squish" in order to promote any combustion.

[0188] Indeed, insofar as the heat engine 202 equipped with the multi-temperature double-acting piston 201 according to the present invention performs its primary purpose, the regenerative Brayton cycle, the combustion or heating of the working gas 240 is not performed within the expansion valve 279, but by a heat source located upstream of the expansion valve 279, which may consist of a burner, a heat exchanger, or, as a non-limiting example, a solar radiation concentration sensor.

[0189] Therefore, the lack of need to generate spontaneous turbulence to promote combustion further reduces the heat loss of the heat engine 202 provided with the multi-temperature double-acting piston 201 according to the present invention performing a regenerative Brayton cycle compared to the heat loss of a conventional Otto cycle or Diesel cycle engine due to less convective forces between the working gas 240 and the inner wall of the cold cylinder 204.

[0190] It will be appreciated that this is described in order to benefit from the advantages of the multi-temperature double-acting piston 201 according to the present invention, which includes engaging hot and cold components separated by only a few millimeters.

[0191] To demonstrate how the multi-temperature double-acting piston 201 according to the present invention allows for high temperature components to be engaged with low temperature components in close proximity to each other, in this case it is assumed that the central piston pin 210, the lower radial connecting disk 224, the upper radial connecting disk 225, the peripheral seal ring 220, and the lower outer coaxial pin tube 243 and the upper outer coaxial pin tube 248 are made of steel having high mechanical characteristics, while the lower high temperature crown 226 and the upper high temperature crown 232 are made of silicon carbide 276.

[0192] The cooled cylinder casing 203 and the cold cylinder 204 are made of cast iron, while the lower cylinder head 213 and upper cylinder head 214 are also made of silicon carbide 276 .

[0193] Also in this case, the inner diameter of the cryogenic cylinder 204 is assumed to be equal to 240 millimeters.

[0194] The close proximity between the cold components 210, 224, 225, 220 made of steel or the cold components 203, 204 made of cast iron and the hot components 226, 232 presents a dual challenge of differential expansion and limited heat transfer from the hot components 226, 232 to the cold components 210, 224, 225, 220, 203, 204.

[0195] For example, considering the case of the lower high temperature crown 226 of the multi-temperature double acting piston 201 according to the present invention with its specific configuration shown in Figures 2-4, 6-11, and 13, the operation of the upper high temperature crown 232 is the same.

[0196] The crown 226 and the mechanically welded assembly 289 formed by the peripheral seal ring 220, the lower radial connecting disc 224, the upper radial connecting disc 225, and the central piston pin 210 with which the crown 226 engages are both manufactured at a temperature of approximately 20°C.

[0197] However, during operation, the temperature of the mechanically welded assembly 289 stabilizes at approximately 100°C, while the temperature of the lower hot crown 226 stabilizes at 950°C.

[0198] Considering the expansion coefficients of the constituent materials of the lower high temperature crown 226 and the mechanically welded assembly 289, these temperatures result in a difference between the high temperature diameter of the crown 226 and the high temperature diameter of the assembly 289 of approximately one millimeter.

[0199] Similarly, under the influence of temperature, the total axial length of the lower high-temperature crown 226 also increases by about 1 millimeter, and such a variation in length is difficult to absorb by the crown application means 234, which must also absorb the axial forces generated by the inertia of the crown 226 during acceleration of the multi-temperature double-acting piston 201 according to the present invention.

[0200] Furthermore, the close proximity between the lower high temperature crown 226 and the mechanically welded assembly 289 is such as to promote heat transfer from the crown 226 to the assembly 289, which is detrimental to the thermodynamic efficiency of the regenerative Brayton cycle heat engine 202.

[0201] The multi-temperature double-acting piston 201 according to the invention serves, on the one hand, to absorb the large differences in expansion between the various parts held in contact with each other and operating at very different temperatures, and, on the other hand, to limit the heat exchange between said parts.

[0202] For example, as can be seen in FIG. 5 , the piston 201 in fact comprises, on the one hand, an insulating ring 236 made of zirconium oxide 238 or quartz (materials known to withstand temperatures well and have very low thermal conductivity) between the lower high-temperature crown 226 and the peripheral seal ring 220, and, on the other hand, an insulating ring 236 made of the same material interposed between the crown 226 and the central piston pin 210.

[0203] As can be seen in FIG. 6, advantageously, the lower outer coaxial tube of the pin 243 forming the crown application means 234 rests on an insulating ring 236 radially close to the central piston pin 210 .

[0204] FIG. 6 also shows a tube spring 250 which bears against the crosshead 244 and is made up of a stack of "Belleville" spring washers.

[0205] Also, in order to limit heat losses detrimental to the efficiency of the regenerative Brayton cycle heat engine 202 receiving the multi-temperature double-acting piston 201 according to the present invention, it should be noted that the insulating ring 236 interposed between the lower high temperature crown 226 and the peripheral seal ring 220 is applied and held against said crown 226 by a small surface area contact edge 241, thereby reducing the cross section left for the passage of heat.

[0206] As can be seen in Figures 10 and 11, due to the particular configuration of the multi-temperature double-acting piston 201 according to the present invention, the thermal expansion of the lower high temperature crown 226 has little or no effect on the overall length of the assembly formed by said crown 226 and the peripheral seal ring 220, so that the crown application means 234 which applies said crown 226 to said ring 220 is not overstressed by said expansion.

[0207] In fact, in Figures 10 and 11 it can be seen that the lower high temperature crown 226 has a concave conical crown surface 251 whereby said crown 226 is applied and held by crown application means 234 against a circular peripheral contact edge 252 of an insulating ring 236 which is fixed to the peripheral seal ring 220, said edge 252 acting as a low surface area contact edge 241.

[0208] The angle of the concave cone formed by the concave conical crown surface 251 is calculated so that the axial distance separating the bearing point of the lower outer coaxial pin tube 243 on the crown 226 from the peripheral seal ring 220 remains approximately constant as the surface 251 slides over the circular peripheral contact edge 252 due to the difference between the thermal expansion of the lower high temperature crown 226 and the thermal expansion of the mechanically welded assembly 289, all else being equal.

[0209] According to this particular configuration of the multi-temperature double-acting piston 201 according to the present invention, the concave conical crown surface 251 and the circular peripheral contact edge 252 of the insulating ring 236, which is fixedly mounted to the peripheral seal ring 220, form the crown centering means 235.

[0210] With this configuration, the axial force experienced by the lower outer coaxial pin tube 243 remains approximately constant regardless of the difference between the thermal expansion of the lower high temperature crown 226 and the thermal expansion of the mechanically welded assembly 289, while the crown 226 always remains radially centered relative to the peripheral seal ring 220.

[0211] It should be noted that the configuration also makes it possible to limit the variation of the volume ratio of the heat engine 202 as a function of its temperature, in particular during the cold start phase of said engine 202 .

[0212] For example, in FIG. 6 , note that the insulating ring 236 interposed between the lower hot crown 226 and the lower outer coaxial pin tube 243 does not strictly speaking have a low surface area contact edge 241; rather, the radial thickness of that tube 243 itself constitutes that edge 241.

[0213] As clearly shown in Figures 4 and 5, as well as Figures 8, 11 and 13, the barrel skirt 260 is therefore well positioned on the outer periphery of the peripheral seal ring 220 to bear on the low-temperature cylinder 204, the skirt 260 having a converging shape that promotes the establishment of a hydrodynamic lubrication regime between itself and the cylinder 204.

[0214] Near the two axial ends of the peripheral seal ring 220, two compression segment rings 222 which form piston seal means 221 and prevent the working gas 240 from passing from the lower variable volume chamber 208 to the upper variable volume chamber 209 and vice versa are particularly clearly visible in Figures 10 and 11.

[0215] 10 and 11, below the barrel skirt 260 is an oil scraper segment 278 and a peripheral ring lubrication orifice 229 opening at the rear of the segment 278.

[0216] This arrangement makes it possible, on the one hand, to supply lubricating cooling oil 283 to lubricate the barrel skirt 260 and the compression segment 222, and, on the other hand, to return any excess of said oil 283 to the internal piston volume 228.

[0217] 8 and 9 show the path of the lubricating / cooling oil 283 through the mechanically welded assembly 289.

[0218] In fact, said oil 283 coming from the lubricating cooling fluid source 218 is in this case sprayed into the piston cooling lubrication chamber 217 by a fluid nozzle 266, the latter spraying a jet of lubricating cooling oil 283 into an axial screw reservoir 267 arranged axially in the piston screw head 253.

[0219] The axially threaded reservoir 267 allows for storing lubricating cooling oil 283 regardless of the direction of movement of the multi-temperature double-acting piston 201 according to the present invention, as well as maximizing the portion of said oil 283 that passes through the internal piston volume 228 before being discharged into the transmission casing 206.

[0220] In fact, a relatively small amount of the oil 283 is used, on the one hand, to lubricate the cut segments 282 or the expandable continuous ring 297 that form the seal between the upper outer coaxial pin tube 248 and the upper cylinder head 214, and, on the other hand, to cool the tube 248.

[0221] In this regard, FIG. 12 shows a pressure limiting valve 274 acting as an overflow for the piston cooling lubrication chamber 217 and engaging an intake check valve 271 connected to an air source 270 to allow forced air 272 to enter the chamber 217 and slightly pressurize the chamber 217 while limiting the level of the lubrication cooling oil 283 contained within the chamber 271.

[0222] Indeed, below a certain pressure prevailing in the piston cooling and lubrication chamber 217, the intake check valve 271 allows the forced air fluid 272 from the air source 270 into said chamber 217, while above that certain pressure the pressure limiting valve 274 expels the forced air fluid 272 into the air waterproof sheet 273.

[0223] Advantageously, the inside of the transmission casing 206 can form both the air source 270 and the air tarpaulin 273, as can be seen in FIG.

[0224] A slight pressurization of the piston cooling lubrication chamber 217 by the fluid forced air 272 allows the lubrication cooling oil 283 to be forced into the lubrication cooling gallery 227 arranged in the central piston pin 210 when the heat engine 202 is operating at low speed and the acceleration of the multi-temperature double-acting piston 201 according to the present invention is low intensity.

[0225] Furthermore, for the purpose of maximizing the portion of the lubrication cooling oil 283 passing through the internal piston volume 228, Figures 7, 8, 9 and 13 in this case show a screwed check valve 269 positioned at the bottom of the reservoir 267 so that at each acceleration of the multi-temperature double-acting piston 201 according to the invention towards the upper cylinder head 214, the lubrication cooling oil 283 stored in the axially threaded reservoir 267 is forced to enter the lubrication cooling gallery 227 via the radial reservoir-gallery connecting duct 268, while when the piston 201 accelerates towards the lower cylinder head 213, the oil 283 stored in the gallery 267 does not return to the reservoir 267.

[0226] All of these arrangements in the piston cooling lubrication chamber 217 and the piston screw head 253 ensure that the barrel skirt 260 and segment rings 222, 278 are suitably lubricated while ensuring the circulation of lubricating cooling oil 283 within the mechanically welded assembly 289 to maintain the temperature of the latter at approximately 100°C.

[0227] As can be seen in Figures 8, 9 and 13, the first section of the lubrication cooling gallery 227 conveys the lubrication cooling oil 283 from the piston cooling lubrication chamber 217 to the inner piston volume 228, passing first through the axially threaded reservoir 267, the threaded check valve 269 and the radial reservoir gallery connecting duct 268.

[0228] In Figures 8 and 9 it is shown that the lubricating cooling oil 283 opens into the internal piston volume 228 through a small axial gap left between the fluid distribution disc 261 and the upper radial connecting disc 225, which is mainly parallel to said radial connecting disc 225, on the one hand forming a seal with the central piston pin 210 and on the other hand terminating radially in the vicinity of the inner wall of the peripheral sealing ring 220, in which vicinity the lubricating cooling oil 283 coming from the piston cooling lubrication chamber 217 can exit via a distribution weir 290.

[0229] The axial proximity between the fluid distribution disc 261 and the upper radial connecting disc 225 is such that the lubricating cooling oil 283 is forced to lick the entire inner surface of the upper radial connecting disc 225 before exiting through the distribution weir 290.

[0230] This particular configuration of the multi-temperature double-acting piston 201 according to the invention makes it possible to maintain the temperature of the upper radial connecting disc 225 close to 100° C. regardless of the power delivered by the heat engine 202 .

[0231] It should further be noted that in FIG. 13, in order to limit the heat received by the lower radial connecting disk 224 and the upper radial connecting disk 225, a reflective screen 295 may advantageously be interposed between the lower hot crown 226 and the lower radial connecting disk 224 and between the upper hot crown 232 and the upper radial connecting disk 225, said reflective screen 295 specifically returning the heat emitting from said crowns 226, 232 in the form of infrared radiation back to the lower hot crown 226 and / or the upper hot crown 232.

[0232] FIG. 13 illustrates that in addition to the reflective screen 295, a honeycomb or fibrous insulating material 296 can occupy all or a portion of the space between the lower hot crown 226 and the lower radial connecting disk 224, and between the upper hot crown 232 and the upper radial connecting disk 225.

[0233] As can be seen in FIG. 8 , a part of the lubricating cooling oil 283 exiting the distribution weir 290 cools the peripheral seal ring 220 from the inside and is fed to the peripheral ring lubrication orifice 229, so that a small amount of the oil 283 exits between the two lips of the oil scraper segment 278, and the latter forms a lubricating cooling oil film 283 on the surface of the low-temperature cylinder 204 following the reciprocating motion made by the multi-temperature double-acting piston 201 in the low-temperature cylinder 204, and at the same time collects the excess oil 283 present on the surface.

[0234] 8 and 9, it should be noted that acceleration forces are used by the multi-temperature double-acting piston 201 according to the present invention to displace the lubricating cooling oil 283 so that all surfaces of the internal piston volume 228 are uniformly cooled.

[0235] In this regard, FIGS. 8 and 9 show the fluid recirculation collar 262 of the central piston pin 210 within the inner piston volume 228 and adjacent the lower radial connecting disc 224.

[0236] During each acceleration of the multi-temperature double-acting piston 201 according to the present invention towards the lower cylinder head 213, as illustrated in FIG. 9, the collar 262 expels the lubricating cooling oil 283 accumulated in the hollow overflow reservoir 264 at the connection part of the lower radial connecting disc 224 with the central piston pin 210 in the radial direction and towards the inner wall of the peripheral sealing ring 220.

[0237] As shown in Figures 4-11, the fluid recirculation collar 262 may advantageously include collar channels 263 that form radial jets of lubricating cooling fluid 257 to ensure that the lubricating cooling oil 283 is evenly distributed over 360 degrees.

[0238] 8 and 9 show an overflow orifice 265 opening from the outer wall of the central piston pin 210 and communicating with the inside of the transmission casing 206 via the lubrication cooling gallery 227.

[0239] The axial position of the orifice 265 sets the maximum level of the reservoir 264 so that during each acceleration of the multi-temperature double-acting piston 201 according to the present invention towards the upper cylinder head 214, the level of the lubricating / cooling oil 283 contained in the reservoir 264 does not exceed the level of the overflow orifice 265, and the excess oil 283 is discharged towards the inside of the transmission casing 206.

[0240] It should be understood that the possibilities of the multi-temperature double-acting piston 1 according to the invention are not limited to the applications described herein, and furthermore, that the above description is given merely as an example and does not limit the field of the invention, from which it would not be possible to deviate by replacing the details of implementation described by any other equivalent ones.

Claims

1. A multi-temperature double-acting piston (201) capable of translational movement in a cold cylinder (204) arranged in a cooled cylinder casing (203) comprising a heat engine (202), said piston (201) being directly or indirectly connected to at least one rotary or reciprocating power output shaft (207) by a power transmission means (205) housed in a transmission casing (206), while said piston (201) forms a lower variable volume chamber (208) together with said cold cylinder (204) and a lower cylinder head (213) positioned between said piston (201) and said transmission housing (206), said piston (201) simultaneously forms an upper variable volume chamber (209) together with said cylinder (204) and an upper cylinder head (214), said chambers (208, 209) containing a working gas (240), said multi-temperature double-acting piston (201) being a central piston pin (210) substantially coaxial with said low-temperature cylinder (204) and having a first end forming a lower piston rod (211) passing through said lower cylinder head (213) via a lower rod orifice (215) engaging with a lower rod seal means (280) so as to open into said transmission casing (206) and to be connected directly or indirectly to said power transmission means (205) by a piston fixing means (231), while a second end of said pin (210) forms an upper piston rod (212) passing through said upper cylinder head (214) via an upper rod orifice (216) engaging with an upper rod seal means (281) so as to open into a piston cooling lubrication chamber (217) connected to a lubrication cooling fluid source (218), said second end introducing a lubrication cooling fluid (257) into said chamber (217); a peripheral sealing ring (220), the outer diameter of said peripheral sealing ring (220) being substantially smaller than the inner diameter of said cold cylinder (204), said ring (220) comprising piston seal means (221) in contact with said cylinder (204) to provide a seal therewith; a lower radial connecting disk (224) radially connecting the central piston pin (210) to the peripheral sealing ring (220) on the lower variable volume chamber (208) side, and an upper radial connecting disk (225) radially connecting the central piston pin (210) to the peripheral sealing ring (220) on the upper variable volume chamber (209) side, the space left between the disks (224, 225), the peripheral sealing ring (220) and the central piston pin (210) forming an internal piston volume (228); a lubrication cooling gallery (227) arranged mainly axially in the central piston pin (210) and in one or more sections, said gallery (227) communicating, on the one hand, the piston cooling lubrication chamber (217) with the internal piston volume (228) and, on the other hand, said volume (228) with the inside of the transmission casing (206); at least one peripheral ring lubrication orifice (229) communicating said internal piston volume (228) with an outer peripheral surface of said peripheral sealing ring (220), said orifice (229) opening axially from said surface between at least two piston sealing means (221); - guide means (230) bearing directly or indirectly on or near said power transmission means (205) and / or said low temperature cylinder (204) and / or said lower cylinder head (213) and / or said upper cylinder head (214), said means (230) directly or indirectly maintaining said peripheral sealing ring (220) located in the center of said low temperature cylinder (204); a lower hot crown (226) interposed between the lower radial connecting disc (224) and the lower variable volume chamber (208) and / or an upper hot crown (232) interposed between the upper radial connecting disc (225) and the upper variable volume chamber (209); a crown application means (234) for directly or indirectly holding the lower high temperature crown (226) applied against the peripheral sealing ring (220) and / or the lower radial connecting disk (224) and / or for directly or indirectly holding the upper high temperature crown (232) applied against the ring (220) and / or the upper radial connecting disk (225), said means (234) keeping the crowns (226, 232) freely expanding against the ring (220) and / or the disks (224, 225); a crown centering means (235) for locating said lower high temperature crown (226) and / or said upper high temperature crown (232) relative to said peripheral seal ring (220).

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

3. 3. The multi-temperature double-acting piston of claim 2, wherein said high temperature resistant material (275) consists essentially of silicon carbide (276).

4. 2. The multi-temperature double-acting piston according to claim 1, characterized in that thermal insulation means (233) and / or crown seal means (239) are interposed either between said lower high temperature crown (226) and said peripheral sealing ring (220) and / or said lower radial connecting disc (224), or between said upper high temperature crown (232) and said ring (220) and / or said upper radial connecting disc (225), or both.

5. 2. The multi-temperature double-acting piston of claim 1, characterized in that thermal insulation means (233) and / or crown seal means (239) are interposed either between said lower high temperature crown (226) and said central piston pin (210), or between said upper high temperature crown (232) and said pin (210), or both.

6. A multi-temperature double-acting piston according to claims 4 and 5, characterized in that said thermal insulation means (233) consist of at least one insulating ring (236) made of a material with low thermal conductivity (237).

7. 7. The multi-temperature double-acting piston of claim 6, wherein said low thermal conductivity material (237) consists essentially of zirconium oxide (238).

8. 7. A multi-temperature double-acting piston according to claim 6, characterized in that the insulating ring (236) is held in direct or indirect contact with the central piston pin (210) and / or the peripheral sealing ring (220) and / or the lower high temperature crown (226) and / or the lower radial connecting disk (224) and / or the upper high temperature crown (232) and / or the upper radial connecting disk (225) by at least one small surface area contact edge (241).

9. 7. The multi-temperature double-acting piston according to claim 6, characterized in that the insulating ring (236) is held in direct or indirect contact with the central piston pin (210) and / or the peripheral sealing ring (220) and / or the lower high temperature crown (226) and / or the lower radial connecting disk (224) and / or the upper high temperature crown (232) and / or the upper radial connecting disk (225) by at least one insulating sealing gasket (242) sealed against the working gas (240).

10. 2. A multi-temperature double-acting piston according to claim 1, characterized in that the crown application means (234), which directly or indirectly holds the lower high temperature crown (226) applied against the peripheral sealing ring (220) and / or the lower radial connecting disk (224), are formed by a lower outer coaxial pin tube (243) surrounding the central piston pin (210), said tube (243) bearing on the one hand against the lower high temperature crown (226) in the vicinity of said pin (210) and on the other hand against the power transmission means (205).

11. 2. A multi-temperature double-acting piston according to claim 1, characterized in that the crown application means (234), which directly or indirectly holds the upper high temperature crown (232) applied against the peripheral sealing ring (220) and / or the upper radial connecting disk (225), consist of an upper outer coaxial pin tube (248) surrounding the central piston pin (210), said tube (248) bearing on the one hand against the upper high temperature crown (232) in the vicinity of said pin (210) and on the other hand against an upper rod abutment (249) provided directly or indirectly on the upper piston rod (212) in the vicinity of its end opening into the piston cooling lubrication chamber (217).

12. 12. A multi-temperature double-acting piston according to claims 10 and 11, characterized in that some or all of the ends of the lower outer coaxial pin tube (243) and / or the upper outer coaxial pin tube (248) receive tube springs (250) which support the tubes (243, 248) against the lower hot crown (226) and against the power transmission means (205) and / or against the upper hot crown (232) and against the upper rod abutment (249), respectively.

13. The lower hot crown (226) and / or the upper hot crown (232) have a concave conical crown surface (251) by which the crowns (226, 232) are held applied by the crown application means (234) against a circular peripheral contact edge (252) that is fixed directly or indirectly to the periphery of the peripheral sealing ring (220) and / or the periphery of the lower radial connecting disk (224) and / or the periphery of the upper radial connecting disk (225), and the angle of the concave cone formed by the surface (251) is adjusted to a desired value based on the thermal expansion of the crowns (226, 232) and the thermal expansion of the peripheral sealing ring (220).

2. A multi-temperature double-acting piston according to claim 1, characterized in that an axial distance separating the bearing points of said crown application means (234) on said crown (226, 232) of said peripheral sealing ring (220) when said surface (251) slides over said edge (252) due to differences between the thermal expansion of an assembly formed by said lower radial connecting disk (224), said upper radial connecting disk (225) and said central piston pin (210) remains approximately constant, all else being equal, while said crown concave conical surface (251) and said circular peripheral contact edge (252) are at an angle such that they form said crown centering means (235).

14. 2. A multi-temperature double-acting piston according to claim 1, characterized in that the piston fixing means (231) consist of a double-acting axial piston screw (219) with a piston screw body (255) accommodated in a piston screw tunnel (256) passing through the central piston pin (210) in its longitudinal direction, the screw (219) comprising, on the one hand, a piston screw head (253) bearing against the end of the upper piston rod (212) opening into the piston cooling lubrication chamber (217) and, on the other hand, a piston thread (254) screwed into the power transmission means (205).

15. 15. The multi-temperature double-acting piston of claim 14, wherein the piston thread tunnel (256) forms at least a part of the lubrication cooling gallery (227), and the lubrication cooling fluid (257) can circulate between the piston thread body (255) and an inner wall of the tunnel (256), the inner wall forming with the body (255) a first section extending from the piston cooling lubrication chamber (217) to the internal piston volume (228) and a second section extending from the volume (228) within the transmission casing (206).

16. 2. The multi-temperature double-acting piston of claim 1, wherein said guide means (230) comprises a barrel skirt (260) disposed on an outer periphery of said peripheral seal ring (220) and bearing against said cold cylinder (204).

17. 2. A multi-temperature double-acting piston according to claim 1, characterized in that the lubrication cooling gallery (227) opens into the internal piston volume (228) through a small axial gap left between, on the one hand, a fluid distribution disc (261) accommodated in the volume (228) and, on the other hand, the upper radial connecting disc (225), the distribution disc (261) being approximately parallel to the radial connecting disc (225) and, on the one hand, forming a seal with the central piston pin (210) and, on the other hand, terminating radially in the vicinity of the inner wall of the peripheral sealing ring (220), in which the lubrication cooling fluid (257) coming from the piston cooling lubrication chamber (217) can exit.

18. 2. The multi-temperature double-acting piston according to claim 1, characterized in that the central piston pin (210) comprises a fluid recirculation collar (262) in the internal piston volume (228) and in the vicinity of the lower radial connecting disc (224), the fluid recirculation collar (262) displacing the lubricating cooling fluid (257) accumulated in the volume (228) and on the surface of the disc (224) in a radial direction and towards the inner wall of the peripheral seal ring (220) as the central piston pin (210) moves towards the lower cylinder head (213).

19. 2. A multi-temperature double-acting piston according to claim 1, characterized in that the lower radial connecting disc (224) has a hollow profile (294) at its connection with the central piston pin (210), the profile (294) constituting an overflow reservoir (264) capable of storing a lubricant-oil cooling fluid (257), while at least one overflow orifice (265) communicating with the inside of the transmission housing (206) via the lubricant-oil cooling gallery (227) sets a maximum level of the reservoir (264).

20. 2. The multi-temperature double-acting piston of claim 1, wherein a fluid nozzle (266) fed by said lubrication cooling fluid source (218) opens into said piston cooling lubrication chamber (217) for injecting a fluid jet (267) therein.

21. 21. A multi-temperature double-acting piston according to claims 14 and 20, characterized in that the fluid nozzle (266) injects a jet of lubrication cooling fluid (257) into an axial thread reservoir (267) arranged axially in the piston screw head (253), the reservoir (267) communicating with the lubrication cooling gallery (227) through at least one radial reservoir-gallery connecting duct (268).

22. 22. The multi-temperature double-acting piston of claim 21, wherein a threaded check valve (269) is housed in the double-acting piston axial screw (219), the valve (269) allowing the lubrication cooling fluid (257) to pass from the axial screw reservoir (267) to the lubrication cooling gallery (227) but not vice versa.

23. 2. The multi-temperature double-acting piston according to claim 1, characterized in that the piston cooling and lubrication chamber (217) is connected to an air source (270) by an intake check valve (271) which allows the fluid forced air (272) to flow into the chamber (217) without flowing out of the chamber (217), and at the same time, the chamber (217) is connected to an air waterproof sheet (273) by a pressure limiting valve (274), which allows the fluid forced air (272) to flow from the chamber (217) to the waterproof sheet (273) when the pressure of the air (272) in the chamber (217) reaches a certain value.

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

25. 5. The multi-temperature double-acting piston according to claim 4, characterized in that said thermal insulation means (233) consists of a honeycomb or fibrous insulating material (296) occupying all or part of the space between said lower hot crown (226) and said lower radial connecting disc (224) and / or between said upper hot crown (232) and said upper radial connecting disc (225).

26. 15. The multi-temperature double-acting piston of claims 10, 11 and 14, characterized in that at least a first radial space left between the upper outer coaxial pin tube (248) and the central piston pin (210), at least a second radial space left between the outer coaxial lower pin tube (243) and the central piston pin (210), and a plurality of radial spaces left between the piston thread body (255) and the inner wall of the piston thread tunnel (256) form at least a portion of the lubrication cooling gallery (227), and the lubrication cooling fluid (257) can be continuously circulated within said spaces from the piston cooling lubrication chamber (217) to the internal piston volume (228) and then from the volume (228) into the transmission casing (206).

27. 2. The multi-temperature double-acting piston according to claim 1, characterized in that the lower rod seal means (280) and / or the upper rod seal means (281) consist of an expandable continuous ring (297) fixed directly or indirectly to the cooled cylinder casing (203), the inner diameter of the continuous ring (297) being substantially smaller than the outer diameter of the lower piston rod (211) or the upper piston rod (212) it clamps.

28. 28. A multi-temperature double-acting piston according to claim 27, characterized in that the extendable continuous ring (297) is connected to a ring plate (298) by a ring tube (299) of small radial thickness, and the ring (297), the plate (298) and the ring (297) are made from a single piece of material.

29. 28. The multi-temperature double-acting piston according to claim 27, characterized in that the continuously extendable ring (297) is axially sandwiched between two ring bushings (300) by a ring axial compression spring (301).

Images