Double-crank piston cylinder mechanism, engine and compressor

Abstract

The utility model relates to the field of machinery, and discloses a double-crank piston air cylinder mechanism, an engine and a compressor, which can avoid lubricating oil between an air cylinder and a piston. The mechanism comprises: a cylinder; the piston reciprocates in the air cylinder, and a uniform gap is kept between the piston and the inner wall of the air cylinder; the first end of the piston rod is fixedly connected with the piston; the two motors are consistent in specification, and windings of stators of the two motors are electrically connected in series; the piston rod penetrates through the guide bearing, and the guide bearing restrains the piston rod to reciprocate along the central axis of the air cylinder; the second end of the piston rod is mechanically connected with the rotors of the two motors through the symmetrical double-crank connecting rod mechanism, and the symmetrical double-crank connecting rod mechanism is used for switching between the linear reciprocating motion of the piston rod and the rotation of the rotors of the two motors; and the oil seal is arranged between the symmetrical double-crank connecting rod mechanism and the piston, and the piston rod penetrates through the oil seal.

Description

Technical Field

[0001] This application relates to the field of machinery, and particularly to piston cylinder technology. Background Art

[0002] This section aims to provide background or context for understanding the embodiments of this application. It is for reference only and should not be considered as the applicant admitting that this section belongs to the prior art that has been made public before the filing date of this application.

[0003] The cylinder piston kinematic pair is a mechanism that realizes the motion conversion between fluid and rigid body. Through this mechanism, fluid energy and mechanical energy can be converted into each other. In order to achieve the conversion between rotational motion and the linear reciprocating motion of the piston, a crank - connecting rod mechanism (i.e., a two - link mechanism) is usually introduced. This cylinder structure with a crank - connecting rod is widely used in various fluid pumps, compressors, engines, and pneumatic - hydraulic actuators, etc.

[0004] However, the motion of the crank - connecting rod will exert a large lateral component force (perpendicular to the piston motion direction) on the piston, which needs to be resisted by the sliding friction between the piston skirt and the cylinder wall. For this reason, lubricating oil is usually used to lubricate the piston skirt to reduce friction loss and wear.

[0005] In an engine, since high temperature may damage the lubricating oil, liquid cooling or air cooling is usually adopted to reduce the cylinder temperature, but this will also bring heat dissipation energy consumption. For a compressor, the lubricating oil may contaminate the gas. Therefore, in high - requirement occasions, a cross - head structure is often adopted to offset the lateral component force, so that the piston is no longer affected by the lateral force, and thus no lubrication measures are required, and a lubricant - free piston can be realized. However, the cross - head structure is heavy, has large vibration and noise, and is prone to wear. Once wear occurs, it usually can only be replaced and cannot be repaired.

[0006] To solve the lateral force problem brought by the traditional crank - connecting rod mechanism, US Patent US8443778B2 proposed a method of implementing a double - crank. This method adopts a symmetric double - crank connecting rod mechanism, and uses the characteristic of reverse meshing of gears to keep the cranks symmetric and synchronous, so as to offset the lateral component force on the piston, reduce vibration and noise, and reduce friction energy consumption and wear. Although there are many similar symmetric double - crank connecting rod applications, they usually also use methods such as gears and chains to achieve the synchronization of the cranks. However, in the market, the actual application of the symmetric double - crank connecting rod mechanism is very rare. This is because the benefits of this mechanism have not been fully exerted, and the increase in the cost of the double - crank structure does not significantly improve its benefits. At the same time, components such as gears and chains used to synchronize the cranks are also prone to damage, which limits their wide application. The industry has been exploring how to improve the benefits of the symmetric double - crank connecting rod mechanism. Summary of the Invention

[0007] The purpose of this application is to provide a double-crank piston cylinder mechanism and its applications in engines and compressors. No lubricating oil is required between the cylinder and the piston, solving a series of problems caused by the presence of lubricating oil between the cylinder and the piston.

[0008] This application discloses a double-crank piston cylinder mechanism, comprising:

[0009] A cylinder;

[0010] A piston that reciprocates within the cylinder, with a uniform gap maintained between the piston and the inner wall of the cylinder;

[0011] A piston rod, with its first end fixedly connected to the piston;

[0012] Two motors with the same specifications, and the windings of the stators of the two motors are connected in series electrically;

[0013] A guide bearing through which the piston rod passes, and the guide bearing restricts the piston rod to reciprocate along the central axis of the cylinder;

[0014] A symmetric double-crank connecting rod mechanism that mechanically connects the second end of the piston rod and the rotors of the two motors, for converting between the linear reciprocating motion of the piston rod and the rotation of the rotors of the two motors. Among them, the rotation directions of the rotors of the two motors are opposite;

[0015] An oil seal is arranged between the symmetric double-crank connecting rod mechanism and the piston, and the piston rod passes through the oil seal, for preventing the lubricating oil on one side of the symmetric double-crank connecting rod mechanism from entering the piston side.

[0016] In a preferred example, the symmetric double-crank connecting rod mechanism comprises:

[0017] A cross connecting rod fixedly connected to the second end of the piston rod;

[0018] Two connecting rods, with the first ends of the two connecting rods respectively hinged to both ends of the cross connecting rod;

[0019] Two cranks, with the first ends of the two cranks respectively hinged to the second ends of the two connecting rods;

[0020] Among them, the rotating shafts of the rotors of the two motors are respectively fixedly connected to the second ends of the two cranks; the cross connecting rod, the two connecting rods and the two cranks are axisymmetric structures, and the axis of symmetry is parallel to the axis of the guide bearing.

[0021] In a preferred example, it further includes a crankcase, the symmetric double crank and connecting rod mechanism is arranged in the crankcase, and the crankshafts of the two cranks extend out of the crankcase and serve as dual-path transmission shafts.

[0022] In a preferred example, it further includes two inertial flywheels, which are respectively fixed on the crankshafts of the two cranks.

[0023] In a preferred example, with the axis of the guiding bearing as the axis of symmetry, the two motors are arranged in an axisymmetric manner.

[0024] This application also discloses a double crank piston cylinder mechanism, including:

[0025] A cylinder;

[0026] A piston that reciprocates in the cylinder, and a uniform gap is maintained between the piston and the inner wall of the cylinder;

[0027] A piston rod, the first end of which is fixedly connected to the piston;

[0028] A guiding bearing, the piston rod passes through the guiding bearing, and the guiding bearing restricts the piston rod to reciprocate along the central axis of the cylinder;

[0029] A planetary bevel gear differential;

[0030] A symmetric double crank and connecting rod mechanism, which includes a cross connecting rod fixedly connected to the second end of the piston rod, two symmetrically distributed connecting rods and two cranks; one ends of the two connecting rods are respectively hinged to the two ends of the cross connecting rod, and the other ends are respectively hinged to the two cranks; among the two cranks, the crankshaft of one crank is connected to one sun gear of the planetary bevel gear differential, and after the crankshaft of the other crank rotates in the reverse direction through the meshing of two gears, it is connected to the other sun gear of the planetary bevel gear differential through the hollow shaft of the sleeve shaft, and the planet carrier of the planetary bevel gear differential is connected to a single-path transmission shaft for output;

[0031] An oil seal is arranged between the symmetric double crank and connecting rod mechanism and the piston, and the piston rod passes through the oil seal to prevent the lubricating oil on one side of the symmetric double crank and connecting rod mechanism from entering the piston side.

[0032] This application also discloses a double crank piston cylinder mechanism, including:

[0033] A cylinder;

[0034] A piston that reciprocates in the cylinder, and a uniform gap is maintained between the piston and the inner wall of the cylinder;

[0035] A piston rod, the first end of which is fixedly connected to the piston;

[0036] A guiding bearing through which the piston rod passes, and the guiding bearing restricts the piston rod to reciprocate along the central axis of the cylinder;

[0037] A symmetric double crank and connecting rod mechanism, which includes a cross connecting rod fixedly connected to the second end of the piston rod, two connecting rods symmetrically distributed axially, and two cranks; one ends of the two connecting rods are respectively hinged to the two ends of the cross connecting rod, and the other ends are respectively hinged to the two cranks;

[0038] An oil seal is arranged between the symmetric double crank and connecting rod mechanism and the piston, and the piston rod passes through the oil seal, which is used to prevent the lubricating oil on one side of the symmetric double crank and connecting rod mechanism from entering the side of the piston;

[0039] Two propellers; the two crankshafts are respectively mechanically coupled to the two propellers to drive the two propellers to rotate.

[0040] In a preferred example, the two propellers are cross double propellers with the same torque and opposite rotation directions, and the two crankshafts are respectively mechanically coupled to the two propellers through universal couplings.

[0041] This application also discloses a two-stroke engine, which includes the above-mentioned double crank piston cylinder mechanism, wherein,

[0042] The piston of the double crank piston cylinder mechanism divides the cylinder into an upper combustion expansion chamber and a lower compression chamber;

[0043] An upper air exchange groove, a lower air exchange groove, an air inlet and an exhaust port are arranged on the side of the cylinder;

[0044] An upper sealing ring is arranged on the upper part of the piston to prevent the working medium from leaking from the combustion expansion chamber to the exhaust port through the gap on the side wall of the piston; a lower sealing ring is arranged on the lower part of the piston to prevent the working medium from leaking from the compression chamber to the air inlet through the gap on the side wall of the piston; a transfer groove is arranged on the side wall of the piston between the upper sealing ring and the lower sealing ring;

[0045] When the piston is at the bottom dead center, the upper sealing ring is at the middle position of the upper air exchange groove, and the lower sealing ring is at the middle position of the lower air exchange groove. The gas in the compression chamber can bypass the lower sealing ring through the lower air exchange groove, along the transfer groove on the side wall of the piston, and then bypass the upper sealing ring through the upper air exchange groove to reach the combustion expansion chamber. At this time, the exhaust port is above the upper sealing ring, and the working gas in the combustion expansion chamber is discharged from the exhaust port; when the piston reaches the top dead center, the lower sealing ring is above the air inlet, the compression chamber is connected to the air inlet, and the compression chamber inhales air through the air inlet.

[0046] The present application also discloses a four-stroke engine, including the double-crank piston cylinder mechanism described above. Wherein, the cylinder of the double-crank piston cylinder mechanism includes an intake valve and an exhaust valve, and there is no lubricating oil in the cylinder.

[0047] The present application also discloses a compound piston compressor, including the double-crank piston cylinder mechanism with two motors described above. Wherein, the two motors in the double-crank piston cylinder mechanism drive the piston to reciprocate in the cylinder through a symmetric double-crank connecting rod mechanism and a piston rod to achieve compression of the gas in the cylinder; the cylinder includes an intake valve, an exhaust valve, an intake port and an exhaust port; when the piston moves in a first direction driven by the two motors, the intake valve opens, the exhaust valve closes, and the gas enters the cylinder from the intake port; when the piston moves in a second direction opposite to the first direction driven by the two motors, the intake valve closes, the exhaust valve opens, and the compressed gas leaves the cylinder from the exhaust port.

[0048] In an embodiment of the present application, by adopting a symmetric double-crank connecting rod mechanism, guiding bearings to constrain the movement of the piston rod, keeping a uniform gap between the piston and the inner wall of the cylinder, connecting two motors with the same specifications in series, and the oil seal isolation design, the lateral force on the piston can be eliminated, frictionless movement can be achieved, symmetric driving force can be ensured, and lubricating oil is not required in the piston cylinder area. This design greatly reduces the manufacturing difficulty and cost, improves the operating efficiency, extends the service life, and provides a basis for lubricant-free pistons and adiabatic engines.

[0049] Furthermore, by arranging a symmetric double-crank connecting rod mechanism in the crankcase and extending the crankshaft into a two-way transmission shaft, more flexible power output can be achieved, the application range of the mechanism can be expanded, and at the same time, lubricating oil can be effectively isolated, improving the adaptability and reliability of the system.

[0050] Furthermore, by adding an inertia flywheel on the crankshaft, the stability and energy storage capacity of the system can be improved, the speed fluctuation during the movement can be reduced, the operating performance of the mechanism can be further optimized, and the overall efficiency can be improved.

[0051] Furthermore, by arranging the two motors axially symmetrically with the axis of the guiding bearing as the axis of symmetry, the balance of the overall structure can be further optimized, the smoothness of operation can be improved, which helps to reduce vibration and noise, and enhances the stability of the system.

[0052] In one embodiment, by introducing a planetary bevel gear differential and connecting the symmetric double crank-link mechanism to the differential in a specific connection manner, the reverse motion of the double crank can be converted into a single-direction output, realizing the conversion from single-channel to dual-channel transmission. This design ingeniously solves the problem of single-dual channel transmission conversion, while avoiding the overconstraint problem caused by gear meshing, and improving the reliability and lifespan of the system.

[0053] In one embodiment, by combining the symmetric double crank-link mechanism with two propellers, the reciprocating motion can be directly converted into the rotational motion of the propellers, which is particularly suitable for aviation or marine propulsion systems. This design makes full use of the symmetric characteristics of the double crank mechanism, providing a simple and efficient propulsion method, improving the propulsion efficiency, while also avoiding the overconstraint problem caused by gear meshing, and enhancing the reliability and lifespan of the system.

[0054] Furthermore, by using crossed double propellers with the same torque and opposite rotational directions and connecting them through a universal coupling, not only can the propulsion efficiency be improved, but also the counter-torque caused by rotation can be offset, enhancing the stability of the system. Compared with the existing crossed double propeller system, the easily damaged reverse gears are removed, greatly improving the reliability and safety.

[0055] In one embodiment, by applying the double crank lubrication-free piston cylinder mechanism to a two-stroke engine and designing a special scavenging structure and piston seal ring configuration, a lubrication-free two-stroke engine can be realized, overcoming the drawback of "oil burning", achieving an efficient intake and exhaust process, and improving the power output and thermal efficiency of the engine. At the same time, since no lubricating oil is required, an adiabatic design can be achieved, significantly enhancing the engine efficiency.

[0056] In one embodiment, by applying the double crank lubrication-free piston cylinder mechanism to a four-stroke engine and having no lubricating oil in the cylinder, the problem of "oil burning" can be completely eliminated, a higher working temperature can be adopted, an adiabatic design can be realized, and the thermal efficiency can be significantly improved. In addition, the piston and the cylinder do not directly contact each other, greatly reducing the manufacturing difficulty and cost of the piston and extending the lifespan of the engine.

[0057] In one embodiment, by applying the double crank lubrication-free piston cylinder mechanism to a reciprocating piston compressor, the lateral force in the traditional compressor can be eliminated, and there is no need to use a heavy crosshead assembly, greatly reducing the mechanical loss. At the same time, since the piston and the cylinder do not directly contact each other, a non-contact seal can be adopted to avoid particulate contamination of the compressed gas caused by friction, which is particularly suitable for high-end precision compressors. This design also reduces the manufacturing difficulty and cost, improves the compression efficiency, and extends the equipment lifespan.

[0058] Each of the technical features disclosed in the above-mentioned invention content, each of the technical features disclosed in the following embodiments, and each of the technical features disclosed in the drawings can be freely combined with each other to form various new technical solutions (all of these technical solutions should be regarded as having been recorded in this specification), unless the combination of such technical features is technically infeasible. For example, in one embodiment, features A + B + C are disclosed, in another embodiment, features A + B + D + E are disclosed, and features C and D are equivalent technical means that perform the same function. Technically, only one of them can be selected and it is impossible to use both at the same time. Feature E can be combined with feature C technically. Then, the solution of A + B + C + D should not be regarded as having been recorded because it is technically infeasible, while the solution of A + B + C + E should be regarded as having been recorded. Description of the Drawings

[0059] Figure 1 is a schematic diagram of the basic structure of a double-crank piston cylinder mechanism according to an embodiment of the present application;

[0060] Figure 2 is a schematic diagram of the structure of a symmetric series motor according to an embodiment of the present application;

[0061] Figure 3 is a schematic diagram of the arrangement of motors according to an embodiment of the present application;

[0062] Figure 4 is a schematic diagram of a double-crank piston cylinder mechanism employing a planetary bevel gear differential according to an embodiment of the present application;

[0063] Figure 5 is a schematic diagram of a double-crank piston cylinder mechanism cooperating with a double propeller according to an embodiment of the present application;

[0064] Figure 6 is a schematic diagram of a double-crank piston cylinder mechanism cooperating with a crossed double propeller according to an embodiment of the present application;

[0065] Figure 7 is a schematic diagram of the structure of a reciprocating piston compressor according to an embodiment of the present application;

[0066] Figure 8 is a schematic diagram of the structure of a four-stroke adiabatic engine according to an embodiment of the present application;

[0067] Figure 9 is a schematic diagram of the structure of a two-stroke adiabatic engine according to an embodiment of the present application;

[0068] Figure 10 is Figure 9 a schematic diagram of four typical states of the two-stroke adiabatic engine shown.

[0069] The reference numerals used in the drawings are as follows:

[0070] 1: Cylinder; 2: Piston; 3: Piston rod

[0071] 4: Oil seal; 5: Guide bearing; 6: Crankcase

[0072] 7: Cross connecting rod; 8: Crank; 9: Crankshaft

[0073] 10: Flywheel; 11: Dynamic seal; 12: Clearance

[0074] 13: Motor; 14: Sun gear; 15: Planet carrier

[0075] 16: Transmission shaft; 17: Gear; 18: Differential

[0076] 19: Propeller; 20: Bevel gear; 21: Bevel gear

[0077] 22: Universal coupling; 23: Intake port; 24: Exhaust port

[0078] 25: Top dead center; 26: Intake valve; 27: Exhaust valve

[0079] 28: Bottom dead center; 29: Connecting rod; 30: Intake door

[0080] 31: Exhaust door; 32: Spark plug; 33: Compression ring

[0081] 34: Oil scraping ring; 35: Fuel injector; 36: Combustion chamber

[0082] 37: Combustion ring; 38: Upper scavenging groove; 39: Transfer groove

[0083] 40: Lower scavenging groove; 41: Compression ring; 42: Compression chamber

[0084] 43: Sealing ring Detailed implementation manners

[0085] In the following description, many technical details are provided to help the reader better understand the present application. However, those of ordinary skill in the art can understand that the technical solutions claimed in the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0086] To make the objectives, technical solutions, and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the drawings.

[0087] The embodiment of the present application discloses a double-crank piston cylinder mechanism. By adding a guiding bearing between the piston body and the cross connecting rod to constrain the symmetric synchronization of the double cranks, not only the lateral force is eliminated, but also a stable gap is ensured between the piston body and the inner wall of the cylinder, avoiding frictional contact. Thus, a lubricant-free cylinder piston moving pair is successfully realized, and the friction components such as the piston skirt and the crosshead are removed. In the application of an engine, this lubricant-free piston design makes it no longer necessary to set up a cylinder cooling device to prevent lubricating oil from burning out, thereby realizing an adiabatic engine. For a common engine, the heat dissipation loss usually exceeds 20% of the energy. However, after using the double-crank piston cylinder mechanism of the embodiment of the present application, the cooling requirement of the cylinder is cancelled, which will greatly reduce the heat dissipation energy consumption and thus significantly improve the efficiency of the internal combustion engine.

[0088] First, the basic symmetric double-crank connecting rod lubricant-free cylinder piston mechanism will be described. As Figure 1 shown, the cylinder 1, the piston 2, and the piston rod 3 form a lubricant-free piston 2 cylinder 1 moving pair. The center of the piston rod 3 coincides with the central axis of the cylinder 1. The other end of the piston rod 3 is fixedly connected to the center point of the cross connecting rod 7. The two ends of the cross connecting rod 7 are respectively hinged to two sets of crank connecting rod mechanisms. These two sets of crank connecting rod mechanisms have the same crank radius and connecting rod length, and they are axisymmetric with the central axis of the cylinder 1 as the axis of symmetry. Together with the cross connecting rod 7, they form a symmetric double-crank connecting rod mechanism (or a symmetric five-link mechanism). This symmetric double-crank connecting rod mechanism is placed in the crankcase 6. A guiding bearing 5 and a oil seal 4 are fixed on the crankcase 6, and the piston rod 3 passes through them. The central axis of the guiding bearing coincides with the central axis of the cylinder 1. Constrained by the guiding bearing 5, the piston rod 3 can only move up and down along the central axis of the cylinder 1. A uniform gap 12 is maintained between the side wall of the piston 2 and the inner wall of the cylinder 1, and the piston 2 and the cylinder 1 do not come into direct contact. The oil seal 4 isolates the lubricating oil in the crankcase 6, making the upper cylinder 1 piston 2 pair operate without lubricating oil. A dynamic seal 11 is provided between the side wall of the piston 2 and the inner wall of the cylinder 1. The dynamic seal 11 can be a contact sealing measure such as a piston ring, or a non-contact sealing measure such as a labyrinth seal.

[0089] Figure 1 The cross connecting rod 7, the two connecting rods 29, and the two cranks 8 in form a symmetric double-crank connecting rod mechanism. Specifically, the middle part of the cross connecting rod 7 is fixedly connected to the lower end of the piston rod 3. The first ends of the two connecting rods 29 are respectively hinged to the two ends of the cross connecting rod 7. The first ends of the two cranks 8 are respectively hinged to the second ends of the two connecting rods 29. The second ends of the two cranks 8 are crank shafts 9. The cross connecting rod 7, the two connecting rods 29, and the two cranks 8 are axisymmetric structures, and the axis of symmetry is the axis of the guiding bearing 5. The symmetric double-crank connecting rod mechanism is arranged in the crankcase 6, and the crank shafts 9 of the two cranks 8 extend out of the crankcase 6 and serve as double-channel transmission shafts.

[0090] Optionally, the two crankshafts 9 can also be respectively connected to two inertial flywheels 10. The flywheel can improve the stability of the system and the energy storage capacity, reduce the speed fluctuation during the movement, further optimize the operating performance of the mechanism, and improve the overall efficiency.

[0091] The guide bearing 5 can be one or more. Multiple guide bearings 5 can better restrain the piston rod 3.

[0092] Generally, one piston 2 is only connected to one piston rod 3. In some embodiments with special requirements, one piston 2 can also be connected to the same cross-link 7 through multiple parallel piston rods 3. Correspondingly, there are also multiple oil seals 4 and guide bearings 5, and each piston rod 3 passes through the corresponding oil seal 4 and guide bearing 5 respectively.

[0093] Next, Figure 1 the principle of the mechanism will be described.

[0094] Figure 1 The shown symmetric double-crank connecting rod mechanism is composed of two sets of crank connecting rod mechanisms hinged to the cross-link 7. Taking the central vertical line of the cross-link 7 as the axis of symmetry, the two sets of crank connecting rods are symmetrically arranged, and the connecting rods 29 are of equal length and the crank 8 has the same radius. The difference between this embodiment and the prior art is that in the prior art, the two crank connecting rods are directly hinged on the piston body, that is, the piston body acts as the cross-link, while in this embodiment, the cross-link 7 is separated from the piston 2 body, connected through the piston rod 3, and guide bearings 5 and oil seals 4 are arranged on the piston rod 3. This design cleverly places the entire symmetric double-crank connecting rod mechanism, including the cross-link 3, completely in the crankcase 6, so that the piston-cylinder pair is completely separated from the crankcase 6, thereby realizing the isolation of lubricating oil through the oil seal 4, ensuring that the lubricating oil is limited to the crankcase 6 and there is no lubricating oil in the piston cylinder.

[0095] This symmetric double-crank connecting rod mechanism can only cancel the lateral force when the two cranks run symmetrically, so an additional structure is needed to ensure the symmetry of the two cranks. The prior art usually uses the reverse meshing characteristic of gears to restrain the symmetric operation of the cranks. However, due to the certain clearance in gear meshing and the inconsistent pitch caused by machining and wear, it is difficult for the existing methods to achieve strict synchronization of the double cranks, and thus it is impossible to ensure that there is no friction between the piston and the cylinder. Therefore, a piston skirt still needs to be set and lubricated. This embodiment uses the guide bearing 5 to restrain the piston rod 3, so that the connected cross-link 7 runs along the central axis of the cylinder 1, and further restrains the two crank connecting rods 29 hinged thereto to maintain symmetric synchronization. The matching accuracy of the guide bearing is significantly higher than that of gear meshing, which is sufficient to ensure the frictionless and smooth operation of the piston.

[0096] In the method of using gear meshing to constrain the synchronous rotation of a double crank in the prior art, it is not feasible to additionally add a piston rod and a guide bearing. The reason is that this would constitute overconstraint, which would cause the meshing position of the gears to deviate from the theoretical optimal position, and the resulting stress fluctuations and collisions would cause the gears to quickly wear out and fail. Therefore, the method of using a piston rod and a guide bearing to constrain the synchronous rotation of a double crank in this embodiment is unique. Once other methods are adopted, the opportunity to use this method is lost.

[0097] Due to the different methods of constraining the symmetric synchronization of the crank, there are also significant differences in the actual benefits. The double crank piston of the prior art can only eliminate the lateral force, while in this embodiment, the piston skirt and the crosshead assembly are removed, realizing a lubricant-free piston, providing a simple and stable support platform for high-value applications such as labyrinth compressors and adiabatic engines.

[0098] In summary, in the double crank piston, adding the piston rod 3 and the guide bearing 5 is a clever idea that kills three birds with one stone. This seemingly simple means simultaneously achieves three purposes: precisely constraining the piston 2, completely separating the piston 2 from the crankcase 6, and synchronously constraining the double crank.

[0099] It should be noted that the external application system connected to this embodiment requires a special transmission method to cooperate with it. Since this embodiment has precisely constrained the rotation phase of the double crank using the piston rod and the guide bearing, if there is an additional rigid constraint on the rotation phase of the two crankshafts in the external system, it will constitute overconstraint and greatly reduce the service life of the entire system. Therefore, the external system needs to meet the following conditions: provide two symmetric transmission fits, and their transmission torques need to satisfy equal magnitudes and opposite rotation directions; the external system cannot impose a rigid constraint on the rotation phase of these two transmission shafts. To meet the above transmission requirements, the following provides an example of a transmission fit solution that can meet most cases.

[0100] In one embodiment, Figure 1 The basic structure can cooperate with a symmetric series motor. By cooperating with the motor, it can meet various application scenarios such as compressors, fuel generators (including range-extended engines), etc., and has wide applicability. This embodiment uses two motors of the same model (or specification) to meet the requirement that the transmission torques of the two motor drive shafts are equal and opposite. And the series connection method is used, and the windings of the two motors are connected end to end according to the axisymmetric principle, so that the windings are respectively connected in series to form a logically single motor. At the same time, during installation, the polar directions of the two motor rotors should be in an axisymmetric position. That is, in the perspective view looking along the axis of the crankshaft, the two motors are arranged axially symmetrically with the axis of the guide bearing as the axis of symmetry.

[0101] Figure 2This is the wiring diagram of a symmetrical series motor. Figure 2 The stator windings UA, VA, and WA of motor A on the left are connected end-to-end with the stator windings UB, VB, and WB of motor B on the right, forming a series connection, logically forming windings U, V, and W. Specifically, the tail terminal UA2 of the UA winding is connected to the head terminal UB1 of the UB winding, forming a logical single winding U. The head terminal UA1 of the original UA winding becomes the head terminal U1 of the logical winding U, while the tail terminal UB2 of the original UB winding becomes the tail terminal U2 of the logical winding U. The same applies to the other windings, thus combining the two motors in series into a logical single motor. This connection ensures equal torque transmission to both crankshafts, as the current in the series circuit is equal, and the torque of the motor is primarily determined by the current. If the two motors are not connected in series, even if they use the same model or specifications, if the loads on the two motors are different, the currents drawn by the two motors may differ, resulting in different torques and, in turn, a lateral force on the piston rod.

[0102] Figure 3 This is the arrangement diagram of the two motors ( Figure 1 The piston, cylinder, and connecting rod are omitted in all subsequent diagrams. The two motors can be arranged on the same side of the crankcase (i.e., at the X and Y positions) or on opposite sides of the crankcase (i.e., at the X and Z positions). When viewed from the crankshaft axis, the two motors are arranged in an axisymmetric arrangement, with the guide shaft axis as the axis of symmetry.

[0103] It can be understood that because the stator and rotor of the motor interact through electromagnetic force, there is no direct contact between them. Furthermore, the torque of the motor is mainly controlled by the current, and the slight phase difference between the rotor and the stator does not affect the torque of the motor. In other words, the motor does not constrain the phase of rotation while transmitting torque. This embodiment cleverly utilizes this physical law. Through the symmetrical motors connected in series, a stable transmission match is provided for the two crankshafts, and the separation of torque transmission and phase constraint is achieved, thereby avoiding the over-constraint introduced by the transmission mechanism. The solution of this embodiment can be used as an engine or as a compressor. If used as an engine, the motor operates in generator mode. If used as an actuator such as a compressor, the motor operates in motor mode.

[0104] In one embodiment, Figure 1 The basic structure can be matched with the planetary bevel gear differential. Figure 1 When the basic structure is combined with a system that can only provide a single-way transmission, a single-to-two-way transmission conversion mechanism is required. As previously discussed, directly using gear meshing is impractical, as it introduces overconstraint and causes rapid gear wear and failure. This embodiment utilizes a planetary bevel gear differential to address this problem.

[0105] As shown Figure 4 in the figure, in this embodiment, a planetary bevel gear differential and a pair of gears with equal number of teeth are adopted to realize the conversion from single-path to dual-path transmission. Figure 1 One crankshaft 9 of the symmetric double crank and connecting rod mechanism shown is directly connected to one sun gear 14 of the differential 18 through the center shaft of the sleeve shaft; the other crankshaft 9 is reversely rotated through the meshing of two gears 17 and then connected to the other sun gear 14 of the differential 18 through the hollow shaft of the sleeve of the sleeve shaft, while the planet carrier 15 of the differential 18 is directly connected to the single-path transmission shaft 16 used as the output. In this way, the characteristic that the differential 18 only transmits torque without restricting the synchronization of the two sun gears 14 is skillfully utilized to solve the problem of single-dual path transmission conversion. Obviously, this embodiment can cover most application scenarios requiring single-path output.

[0106] In one embodiment, Figure 1 the basic structure can cooperate with a twin propeller. There is no rigid mutual constraint between the twin propellers, and it will not cause Figure 1 the basic structure to form overconstraint. As shown Figure 5 in the figure, when Figure 1 the solution is used in an aero engine or a marine engine, the twin propeller method can be adopted to solve the dual-path transmission problem. The direction and arrangement position of the propeller can be flexibly changed by adding a steering gear. Specifically, Figure 1 the two crankshafts 9 of the symmetric double crank and connecting rod mechanism shown are respectively mechanically coupled to the two propellers 19 to drive the two propellers 19 to rotate. There are various ways of mechanical coupling, such as gear meshing connection, shaft connection, belt connection, etc. Considering that the directions of the propellers and the crankshafts of the double crank piston cylinder mechanism may not be the same, a steering gear (such as bevel gears 20 and 21) can be used to realize the change of the direction of the rotational power.

[0107] In one embodiment, the two propellers can be cross twin propellers, see Figure 6 . The cross twin propeller is a relatively special arrangement of the propellers of a rotary-wing helicopter. The cross twin propeller not only cancels the counter torque on the cabin by the opposite rotation directions of the twin propellers to prevent the cabin from spinning, but also does not occupy a large space like a common dual rotor. And the two transmission shafts of this embodiment just meet the characteristics of the same torque and opposite rotation directions. Therefore, after the directions are appropriately adjusted by the universal coupling 22 respectively, they can be connected to the cross propeller to form a stable and reliable transmission connection. Compared with the existing cross twin propeller system, this embodiment removes the relatively easily damaged reverse gear, greatly enhances the reliability, and further greatly improves the safety of the aircraft.

[0108] In one embodiment, Figure 1The basic structure and the scheme cooperating with the aforementioned dual-route motor can be used in a reciprocating piston compressor. As Figure 7 shown, the main body of this embodiment is the aforementioned symmetrical double-crank non-lubricating cylinder piston driven by a series-connected dual motor 13. On this basis, like other compressors, an air inlet 23 and an air inlet valve 26, an air outlet 24 and an air outlet valve 27 are provided in the cylinder 1; the piston 2 is constrained by a guide bearing 5 to move along the central axis of the cylinder 1, so that a uniform gap 12 is maintained between the side wall of the piston 2 and the inner wall of the cylinder 1; contact sealing measures such as piston rings are provided between the piston 2 and the cylinder 1, or non-contact sealing measures such as labyrinth seals. In particular, since non-contact seals have no friction and completely avoid particulate contamination of the compressed gas caused by friction, the labyrinth seal method can be used for high-end precision compressors.

[0109] Those skilled in the art know that traditional reciprocating piston compressors all use heavy crosshead assemblies, and the huge lateral force generated by the single-crank connecting rod mechanism is offset by the friction sliding of the crosshead skate in the guide plate. Although this lateral force is offset in the crosshead assembly, it also causes huge internal stresses in the entire mechanical support structure and causes the body to shake and vibrate, affecting the operation of moving parts and increasing the wear of moving parts. Especially for precision labyrinth seal compressors, due to extremely high requirements for the gap between the piston and the cylinder, in order to overcome the adverse effects brought by the shaking of the base, it is necessary to design complex and strong guide bearings, piston rods and piston cylinder bodies, so the manufacturing is extremely difficult and the manufacturing cost is extremely high.

[0110] After adopting the scheme of this embodiment, the lateral force is successfully offset, the body will no longer shake and vibrate due to the deformation caused by the lateral force, the operating conditions of the piston are greatly improved, the manufacturing difficulty of components such as guide bearings, piston rods and piston cylinder bodies is greatly reduced, the manufacturing cost is reduced, and the service life is extended. At the same time, the favorable conditions of eliminating shaking can be utilized to further reduce the sealing gap and reduce the leakage amount.

[0111] It should be noted that although an additional motor is added in this embodiment, the cost of the motor is mainly determined by the power. Since the friction loss is removed in this embodiment and the operating efficiency is improved, the total power of the two motors is smaller than the power of the motor with a single crank, and the two motors are connected in series to become a logically single motor, and only one set of motor control systems is required. Therefore, this change will not increase the cost and thus has good economic benefits.

[0112] In one embodiment, the Figures 1-6 corresponding scheme can be applied to a four-stroke adiabatic engine. Figures 1-6The corresponding solution solves the problems of lateral force and lubricating oil existing in the traditional crank - connecting rod mechanism and can be directly applied to various piston - cylinder kinematic pairs. For an internal combustion engine that uses the friction of the piston skirt to offset the lateral force, with the embodiments, a lubricant - free cylinder can be achieved. The piston no longer contacts and rubs against the cylinder, and only contacts and seals with the cylinder through the piston rings. Those skilled in the art know that a common four - stroke internal combustion engine piston usually has three piston rings: two compression rings and one oil - scraping ring. The oil - scraping ring is responsible for isolating the lubricating oil to prevent the lubricating oil from contacting the high - temperature gas and causing "oil burning". This embodiment is equivalent to moving the oil - scraping ring to the crankcase. There is no lubricating oil in the cylinder at all, thus completely eliminating the hidden danger of "oil burning". At the same time, since there is no lubricating oil, there is no need to worry about "oil burning", and the cylinder temperature can be higher, that is, the cylinder heat dissipation measures are cancelled to achieve an "adiabatic engine", thereby reducing the energy loss caused by cylinder heat dissipation and greatly improving the efficiency of the engine.

[0113] Figure 8 An example of a four - stroke internal combustion engine is shown. It can be noted that the piston 2 has no skirt and does not directly contact the cylinder 1. It only contacts the cylinder 1 through the compression ring 33 to maintain the seal. The oil - scraping ring 34 is arranged in the crankcase 6 to isolate the lubricating oil so that there is no lubricating oil in the cylinder 1. To further reduce the volume, an inverted layout of the crankshaft 9 is adopted, that is, the crankshaft 9 is above and the cross - connecting rod 7 is below, and two upper and lower guide bearings 5 are provided to ensure that the piston rod 3 moves along the symmetry axis. The working process of this example is exactly the same as that of a common four - stroke engine and will not be elaborated here.

[0114] Those skilled in the art can know that for the existing four-stroke engines, the manufacture of pistons is very difficult. The pistons of existing engines operate under high temperature, high pressure and high speed conditions. They have to bear the lateral force from the crank and the high-speed friction with the cylinder, and also overcome the thermal expansion deformation caused by high temperature. Therefore, the requirement for the clearance between the piston and the cylinder is extremely high, and the shape of the piston is usually not a simple cylinder. In order to offset the deformation caused by the lateral force, the cross-section of the piston is often made elliptical. Since the temperature distribution on the piston is higher at the top and lower at the bottom, the amount of thermal expansion deformation is also larger at the top and smaller at the bottom. Therefore, the longitudinal section of the piston is often made conical with a smaller top and a larger bottom. All these make the manufacture of pistons very difficult. After adopting this embodiment, the lateral force no longer exists. Under the constraint of the guiding bearing, the piston and the cylinder are completely non-contact, and enough clearance can be left between the piston and the cylinder, far exceeding the deformation of thermal expansion. The side wall of the piston does not need to be very smooth. Therefore, the manufacturing difficulty and cost of the piston are greatly reduced. During operation, the piston has no wear, and there will be no jamming, impact and other situations, greatly improving the service life. On the other hand, since the piston skirt is removed, the weight of the piston is greatly reduced. The piston operates in a simple harmonic vibration mode. As an oscillator, when the weight of the piston is reduced, the vibration restoring force that the piston has to bear is reduced, which also reduces the manufacturing difficulty of the piston from another angle. At the same time, a lighter piston is beneficial to increasing the engine speed and improving the engine power.

[0115] In one embodiment, Figures 1-6 the corresponding solution can be applied to a two-stroke adiabatic engine. A two-stroke adiabatic internal combustion engine has the advantages of simple structure and high power density. However, in order to solve the lubrication of the piston skirt, lubricating oil must be added to the fuel, so there is the drawback of "burning oil". By using the new two-stroke adiabatic internal combustion engine of this embodiment, the advantages of the existing two-stroke internal combustion engine in the prior art can be inherited, and at the same time, the drawback of "burning oil" can be completely eliminated.

[0116] In Figures 1-6 the corresponding symmetric double crank connecting rod piston cylinder without lubricating oil, after the lower end of the cylinder is hermetically connected to the upper part of the crankcase, a double-acting piston cylinder pair is formed. As Figure 9 shown, the space above the piston 2 in the cylinder 1 forms a combustion expansion chamber 36, and the space below the piston 2 constitutes a compression chamber 42. Different from ordinary two-strokes, the compression chamber 42 and the crankcase 6 are separated, and they are sealed by a sealing ring 43, so that the lubricating oil in the crankcase 6 cannot reach the compression chamber 42, and at the same time, the pressure gas in the compression chamber 42 is prevented from entering the crankcase 6.

[0117] The working principle of this example is basically the same as that of a common two-stroke engine. The difference is that since the lateral force is eliminated in this embodiment, the piston 2 no longer contacts the cylinder 1, and there is a certain gap between the piston 2 and the cylinder 1. Therefore, it is impossible to rely on the piston wall to block the intake port and the exhaust port on the cylinder 1 as in a common two-stroke engine. To solve this problem, Figure 9 the following improvements are made to the scheme: An upper sealing ring 37 (which can be called the "expansion ring") is provided on the upper part of the piston 2 wall, and a lower sealing ring 41 (which can be called the "compression ring") is provided on the lower part of the piston 2 wall. A transfer groove 39 is provided on the side wall of the piston 2, and an upper ventilation groove 38 and a lower ventilation groove 40 are provided on the cylinder 1.

[0118] Figure 10 shows Figure 9 four typical states of the engine.

[0119] In Figure 10 state A, when the piston 2 reaches the top dead center 25, the compression ring 41 is above the intake port 23, and the compression chamber 42 is connected to the intake port 23 to achieve air intake. Since the side wall of the piston 2 does not contact the cylinder 1, a compression ring 41 is provided at the lower part of the piston 2 to prevent the working medium from leaking from the compression chamber 42 through the gap between the side wall of the piston 2 to the intake port 23.

[0120] In Figure 10 state B, the gas in the combustion expansion chamber 36 is ignited and expanded, and the piston 2 moves from the top dead center 25 to the bottom dead center 28, and the gas in the compression chamber 42 is compressed.

[0121] In Figure 10 state C, when the piston 2 reaches the bottom dead center 28, the combustion expansion ring 37 is exactly at the middle position of the upper ventilation groove 38, while the compression ring 41 is at the middle position of the lower ventilation groove 40. At this time, the gas in the compression chamber 42 can pass through the lower ventilation groove 40, bypass the compression ring 41, along the transfer groove 39 on the side wall of the piston 2, and then through the upper ventilation groove 38, bypass the combustion expansion ring 37, and enter the combustion expansion chamber 36 to achieve scavenging and ventilation. In other words, the upper and lower ventilation grooves 40 and the transfer groove 39 form a channel connecting the compression chamber 42 and the combustion expansion chamber 36. At the same time, the combustion expansion ring 37 on the piston 2 is below the exhaust port 24, and the fresh air in the compression chamber 42 quickly enters the combustion expansion chamber 36 to complete scavenging and ventilation, while the exhaust gas is discharged from the exhaust port 24.

[0122] In Figure 10 state D, the piston 2 moves from the bottom dead center 28 to the top dead center 25, and the gas in the combustion expansion chamber 36 is gradually compressed. This state is basically the same as that of the existing two-stroke engine.

[0123] The two-stroke adiabatic internal combustion engine of this embodiment fully inherits the advantages of high power density, simple structure, and no need for a valve mechanism, while eliminating the defect that oil must be added to the fuel. The innovative design enables this two-stroke engine to not require oil, and the piston is completely oil-free. In addition, the compression chamber and the crankcase have been completely separated, significantly reducing the clearance volume of the cylinder, improving the intake effect and the compression air pressure, and ensuring the thoroughness of scavenging and gas exchange.

[0124] The two-stroke adiabatic engine of this embodiment also eliminates the cooling device, eliminating the cooling energy consumption, thus significantly improving the efficiency, reducing the volume, and lightening the weight. Since the number of combustion and work cycles of the two-stroke is twice that of the four-stroke, the power density is further improved. This engine has the advantages of simple production, low cost, high power density, small vibration, and low noise.

[0125] In this embodiment, the piston does not contact the cylinder, and the side wall of the piston does not need to be particularly smooth, thus reducing the requirement for the machining dimensional accuracy, reducing the production difficulty and cost, and significantly extending the service life. This engine has a simple structure and reliable operation. Combined with the design of matching with the propeller, it is very suitable for use as an aeroengine.

[0126] The symmetric double crank connecting rod lubrication-free piston disclosed in the embodiment of this application simultaneously achieves the effects of offsetting the side force, precisely restricting the piston to run along the central axis of the cylinder, and no friction and no lubrication between the piston and the cylinder, completely changing the limitation that the existing double crank technology only improves the friction loss and noise between the piston and the cylinder. The solution of this application can be widely applied to various cylinder piston mechanisms, bringing significant benefits in aspects such as production manufacturing, stable operation, quality improvement, energy conservation, and consumption reduction. Specifically, there are the following aspects:

[0127] 1. Reduce the production difficulty and production cost.

[0128] The embodiment of this application eliminates friction components such as the crosshead assembly and the piston skirt, directly saving the production cost of these components. At the same time, due to the elimination of friction, the production difficulty of the lubrication system is also greatly reduced, and the production cost is reduced.

[0129] For the application of compressors, after using the solution of this application to replace the heavy crosshead assembly, the deformation and shaking of the fuselage caused by the side force of the single crank are eliminated, providing a stable support platform for the piston operation, greatly reducing the production difficulty of the piston, piston rod, guide bearing, and sealing structure, and significantly reducing the production cost. For high-precision labyrinth compressors, this stable fuselage platform can be further utilized to significantly reduce the sealing gap and significantly improve the leakage of compressed gas.

[0130] When the solution of this application is used in an internal combustion engine, the piston no longer contacts and rubs against the cylinder, leaving enough clearance between them. This not only eliminates friction components such as the piston skirt, but also completely changes the problems of high precision requirements and great manufacturing difficulty of the piston. After adopting the innovative method, the requirements for the machining precision and surface finish of the piston side wall are greatly reduced, and the manufacturing difficulty and cost are reduced accordingly.

[0131] 2 The operating level is greatly improved

[0132] After adopting the solution of this application, not only the jitter and vibration are eliminated, but also the easily worn friction components such as the crosshead and piston skirt are eliminated, greatly reducing various types of wear during operation, reducing potential fault hazards, and extending the service life. After eliminating the friction components, the demand for lubrication guarantee during operation is also greatly reduced. For the engine, the piston does not contact the cylinder, completely eliminating the hidden danger of cylinder scoring; there is no lubricating oil in the piston, completely eliminating the hidden danger of burning lubricating oil.

[0133] 3 Improve the product performance and quality, improve energy efficiency, and save energy and reduce consumption

[0134] After adopting the solution of this application, the compressor benefits from a significant reduction in internal stress and the removal of the heavy crosshead assembly, resulting in a significant reduction in the volume and weight of the fuselage; the weight of the moving parts is also significantly reduced, which is beneficial to increasing the rotational speed and reducing the energy consumption generated by overcoming the inertia of reciprocating motion; after eliminating friction, the energy consumption caused by friction is also eliminated; after reducing the shaking and vibration of the fuselage, the sealing conditions can be improved, reducing the leakage of compressed gas and the resulting energy consumption and losses.

[0135] For the engine, after realizing the piston without lubricating oil, the cylinder cooling device set to prevent burning lubricating oil is also eliminated, thus realizing an adiabatic engine. For a common engine, heat dissipation will result in a loss of more than 20% of the energy. Using the double-crank piston without lubricating oil of this application, the cooling of the cylinder is eliminated, which can greatly reduce the heat dissipation energy consumption, thereby greatly improving the efficiency of the internal combustion engine. After removing the piston skirt, the weight of the piston is reduced, which is beneficial to increasing the rotational speed and thus increasing the power.

[0136] It should be noted that in this application, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one" does not exclude the presence of additional identical elements in the process, method, article or device comprising the element. In this application, if it is mentioned that an act is performed according to a certain element, it means that the act is performed at least according to that element, including two cases: the act is performed only according to that element, and the act is performed according to that element and other elements. Expressions such as "multiple", "many times", "multiple types", etc. include 2, 2 times, 2 types, as well as more than 2, more than 2 times, more than 2 types.

[0137] The terms "upper", "lower", etc. in this application are relative concepts used for convenience of description and are relative to the orientation in the drawings, not absolute orientations. For example, in one drawing, a cylinder includes an upper air exchange groove and a lower air exchange groove, which only means that in this drawing, the upper air exchange groove is above the lower air exchange groove. In some application scenarios, if the cylinder is inverted or placed horizontally, the upper air exchange groove is not above the lower air exchange groove in the absolute sense, but the relative positional relationship between the upper air exchange groove and the lower air exchange groove remains unchanged.

[0138] This specification includes combinations of various embodiments described herein. Separate references to embodiments (such as "one embodiment" or "some embodiments" or "preferred embodiments") do not necessarily refer to the same embodiment; however, unless indicated to be mutually exclusive or clearly understood by those skilled in the art to be mutually exclusive, these embodiments are not mutually exclusive. It should be noted that, unless the context clearly indicates or requires otherwise, the word "or" is used in a non-exclusive sense in this specification.

[0139] All documents mentioned in this application are considered to be integrally included in the disclosure of this application so that they can be used as a basis for modification if necessary. In addition, it should be understood that after reading the content of this application, those skilled in the art can make various changes or modifications to this application, and these equivalent forms also fall within the scope claimed by this application.

Claims

1. A double crank piston cylinder mechanism, characterized in that, Comprising: Cylinder; Piston, reciprocating within the cylinder, with a uniform gap maintained between the piston and the inner wall of the cylinder; Piston rod, with its first end fixedly connected to the piston; Two motors with the same specifications, and the windings of the stators of the two motors are connected in series electrically; Guide bearing, through which the piston rod passes, and the guide bearing restricts the piston rod to reciprocate along the central axis of the cylinder; Symmetrical double crank - connecting rod mechanism, which mechanically connects the second end of the piston rod and the rotors of the two motors, for converting between the linear reciprocating motion of the piston rod and the rotation of the rotors of the two motors, wherein the rotation directions of the rotors of the two motors are opposite; Oil seal, arranged between the symmetrical double crank - connecting rod mechanism and the piston, through which the piston rod passes, for preventing the lubricating oil on one side of the symmetrical double crank - connecting rod mechanism from entering the piston side.

2. The double-crank piston cylinder mechanism according to claim 1, wherein The symmetrical double crank - connecting rod mechanism includes: Cross - connecting rod, fixedly connected to the second end of the piston rod; Two connecting rods, with the first ends of the two connecting rods respectively hinged to the two ends of the cross - connecting rod; Two cranks, with the first ends of the two cranks respectively hinged to the second ends of the two connecting rods; Wherein, the rotating shafts of the rotors of the two motors are respectively fixedly connected to the second ends of the two cranks; the cross - connecting rod, the two connecting rods and the two cranks are axisymmetric structures, and the axis of symmetry is parallel to the axis of the guide bearing.

3. The double crank piston cylinder mechanism according to claim 2, wherein: It further includes two inertia flywheels, respectively fixed on the crankshafts of the two cranks.

4. The double crank piston cylinder mechanism according to claim 1, wherein Taking the axis of the guide bearing as the axis of symmetry, the two motors are arranged in an axisymmetric manner.

5. A double crank piston cylinder mechanism, characterized in that, Comprising: Cylinder; Piston, reciprocating within the cylinder, with a uniform gap maintained between the piston and the inner wall of the cylinder; Piston rod, with its first end fixedly connected to the piston; Guide bearing, through which the piston rod passes, and the guide bearing restricts the piston rod to reciprocate along the central axis of the cylinder; Planetary bevel gear differential; Symmetrical double crank - connecting rod mechanism, which includes a cross - connecting rod fixedly connected to the second end of the piston rod, two axially symmetrically distributed connecting rods and two cranks; one end of each of the two connecting rods is respectively hinged to the two ends of the cross - connecting rod, and the other end is respectively hinged to the two cranks; among the two cranks, the crankshaft of one crank is connected to one sun gear of the planetary bevel gear differential, and after the crankshaft of the other crank rotates in the reverse direction through the meshing of two gears, it is connected to the other sun gear of the planetary bevel gear differential through the hollow shaft of the sleeve shaft, and the planet carrier of the planetary bevel gear differential is connected to a single - path transmission shaft for output; Oil seal, arranged between the symmetrical double crank - connecting rod mechanism and the piston, through which the piston rod passes, for preventing the lubricating oil on one side of the symmetrical double crank - connecting rod mechanism from entering the piston side.

6. A double crank piston cylinder mechanism, characterized in that, Comprising: Cylinder; Piston, reciprocating within the cylinder, with a uniform gap maintained between the piston and the inner wall of the cylinder; Piston rod, with its first end fixedly connected to the piston; A guiding bearing through which the piston rod passes, and the guiding bearing restricts the piston rod to reciprocate along the central axis of the cylinder; A symmetric double-crank linkage mechanism, which includes a cross-link rod fixedly connected to the second end of the piston rod, two link rods symmetrically axially distributed, and two cranks; one ends of the two link rods are respectively hinged to the two ends of the cross-link rod, and the other ends are respectively hinged to the two cranks; An oil seal is arranged between the symmetric double-crank linkage mechanism and the piston, and the piston rod passes through the oil seal to prevent the lubricating oil on one side of the symmetric double-crank linkage mechanism from entering the piston side; Two propellers; the two crankshafts are respectively mechanically coupled to the two propellers to drive the two propellers to rotate.

7. The double crank piston cylinder mechanism according to claim 6, characterized in that: The two propellers are cross double propellers with the same torque and opposite rotation directions, and the two crankshafts are respectively mechanically coupled to the two propellers through universal couplings.

8. A two-stroke engine, characterized in that: Comprising the double-crank piston cylinder mechanism according to any one of claims 1-7, wherein, The piston of the double-crank piston cylinder mechanism divides the cylinder into an upper combustion expansion chamber and a lower air compression chamber; Upper air exchange grooves, lower air exchange grooves, an air inlet and an exhaust port are arranged on the side surface of the cylinder; An upper sealing ring is arranged on the upper part of the piston to prevent the working medium from leaking from the combustion expansion chamber to the exhaust port through the gaps on the side wall of the piston; a lower sealing ring is arranged on the lower part of the piston to prevent the working medium from leaking from the air compression chamber to the air inlet through the gaps on the side wall of the piston; a transmission groove is arranged on the side wall of the piston between the upper sealing ring and the lower sealing ring; When the piston is at the bottom dead center, the upper sealing ring is at the middle position of the upper air exchange groove, and the lower sealing ring is at the middle position of the lower air exchange groove. The gas in the air compression chamber can bypass the lower sealing ring through the lower air exchange groove, along the transmission groove on the side wall of the piston, and then bypass the upper sealing ring through the upper air exchange groove to reach the combustion expansion chamber. At this time, the exhaust port is located above the upper sealing ring, and the working gas in the combustion expansion chamber is discharged from the exhaust port; when the piston reaches the top dead center, the lower sealing ring is above the air inlet, the air compression chamber is communicated with the air inlet, and the air compression chamber inhales air through the air inlet.

9. A four-stroke engine, characterized in that, Comprising the double-crank piston cylinder mechanism according to any one of claims 1-7, wherein, The cylinder of the double-crank piston cylinder mechanism includes an intake valve and an exhaust valve, and there is no lubricating oil in the cylinder.

10. A reciprocating piston compressor, characterized in that: Comprising the double-crank piston cylinder mechanism according to any one of claims 1-4, wherein the two motors in the double-crank piston cylinder mechanism drive the piston to reciprocate in the cylinder through the symmetric double-crank linkage mechanism and the piston rod to realize the compression of the gas in the cylinder; The cylinder includes an intake valve, an exhaust valve, an intake port, and an exhaust port; when the piston moves in a first direction driven by the two motors, the intake valve opens, the exhaust valve closes, and gas enters the cylinder from the intake port; when the piston moves in a second direction opposite to the first direction driven by the two motors, the intake valve closes, the exhaust valve opens, and the compressed gas leaves the cylinder from the exhaust port.

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