Free-piston Stirling generator and its valve train piston coaxiality assembly method

Abstract

This invention relates to the field of generator technology, providing a free-piston Stirling generator and a method for assembling the coaxiality of its valve train piston. The free-piston Stirling generator includes a housing, a power generation mechanism, a valve train piston, an axial recovery mechanism, and an electromagnetic detection mechanism. A cylinder is disposed within the housing. The power generation mechanism includes a power piston movably disposed within the cylinder. The valve train piston is movably disposed within the cylinder and has a valve stem passing through the power piston. The axial recovery mechanism connects the valve stem and the housing. The electromagnetic detection mechanism includes a stator and an induction coil. The stator is disposed within the housing, and the induction coil is connected to the valve stem. The induction coil is located within the magnetic field formed by the stator to generate an induced electrical signal when the valve train piston oscillates. The oscillation decay state of the valve train piston is obtained through the induction coil to detect the coaxial assembly state of the valve train piston, solving the current problem of not being able to detect the coaxiality of the valve train piston after assembly.

Description

Technical Field

[0001] This invention relates to the field of generator technology, and in particular to a free piston Stirling generator and a method for assembling the valve train piston with coaxiality. Background Technology

[0002] The statements herein are provided only as background information in connection with this application and do not necessarily constitute prior art.

[0003] The free-piston Stirling generator, as an external combustion closed-cycle heat engine, converts thermal energy into electrical energy through the periodic flow of working gas between high-temperature and low-temperature regions. Due to its advantages such as wide fuel adaptability, low noise, high theoretical thermal efficiency, and high reliability, it is widely used in fields such as solar power generation, waste heat recovery, deep space exploration, and distributed energy systems.

[0004] In some free-piston Stirling generators, the valve train is connected to a valve rod, which passes through the drive piston. During generator assembly, it is necessary to ensure coaxiality not only between the drive piston and the cylinder, but also between the valve train and the cylinder, and between the valve rod and the drive piston. When coaxial misalignment exists between these components, it reduces the local clearance between the piston and cylinder, or between the valve rod and the drive piston, increasing frictional resistance and vibration damping during piston reciprocating motion, thereby affecting the stability of piston movement and the generator's operating performance.

[0005] Because the internal space of a free piston Stirling generator is relatively compact and the operating temperature near the hot end is high, it is currently impossible to test the coaxiality of the valve train piston, making it difficult to guarantee the coaxiality of the valve train piston after assembly. Summary of the Invention

[0006] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention proposes a free-piston Stirling generator that uses an induction coil to obtain the oscillation decay state of the valve train piston in order to detect the coaxial assembly state of the valve train piston, thus solving the problem that the coaxiality of the valve train piston cannot be detected after assembly.

[0007] A free-piston Stirling generator according to an embodiment of the present invention includes: The outer casing contains a cylinder. A power generation mechanism includes a power piston, which is movably disposed within the cylinder; The valve piston is movably disposed within the cylinder and has a valve rod passing through the power piston; An axial recovery mechanism is connected between the valve stem and the housing. An electromagnetic detection mechanism includes a stator and an induction coil. The stator is disposed inside the housing, and the induction coil is connected to the gas distribution rod. The induction coil is located within the magnetic field formed by the stator to generate an induced electrical signal when the gas distribution piston oscillates.

[0008] According to one embodiment of the present invention, the electromagnetic detection mechanism further includes a detection bracket, which is disposed on the gas distribution rod, and the induction coil is wound on the detection bracket.

[0009] According to one embodiment of the present invention, a detection circuit is further included, which is electrically connected to both ends of the induction coil and is used to acquire the induced electrical signal generated by the induction coil.

[0010] According to one embodiment of the present invention, the detection circuit includes a signal acquisition unit and a display, wherein the input terminal of the signal acquisition unit is electrically connected to the induction coil, and the output terminal of the signal acquisition unit is electrically connected to the display.

[0011] According to one embodiment of the present invention, the detection circuit further includes a power supply electrically connected to the induction coil for inputting an excitation current to the induction coil so that the induction coil is subjected to an electromagnetic force that drives the valve piston to move.

[0012] According to one embodiment of the present invention, the detection circuit further includes a controller connected to the power supply for controlling the power supply to input an excitation current for a preset duration to the induction coil.

[0013] According to one embodiment of the present invention, the controller is further configured to control the power supply to input a periodic current to the induction coil, and adjust the amplitude and phase angle of the periodic current so that the induction coil generates an axial electromagnetic force acting on the valve piston.

[0014] According to one embodiment of the present invention, the axial restoration mechanism includes a first permanent magnet, a second permanent magnet, and a moving permanent magnet. The moving permanent magnet is disposed on the air distribution rod. The first permanent magnet and the second permanent magnet are both fixed inside the housing and are respectively located on both sides of the moving permanent magnet along the axial direction of the air distribution rod. The moving permanent magnet has the same polarity as the opposing magnetic pole of the first permanent magnet, and the moving permanent magnet has the same polarity as the opposing magnetic pole of the second permanent magnet.

[0015] According to one embodiment of the present invention, the power generation mechanism includes a first motor, a first coil, and a coil support. The first motor is disposed inside the housing, the coil support is connected to the power piston, and the first coil is wound on the coil support and located within the magnetic field generated by the first motor.

[0016] The valve timing piston coaxiality assembly method according to an embodiment of the present invention, applied to the aforementioned free piston Stirling generator, includes: When the power piston is in an oscillating state, the coaxiality of the power piston is adjusted according to the oscillation decay state of the power piston until the oscillation decay state of the power piston meets the first preset condition. When the valve timing piston is in an oscillating state, the induced electrical signal generated by the induction coil as the valve timing piston oscillates is acquired, and the oscillation attenuation state of the valve timing piston is determined based on the induced electrical signal. Adjust the mounting position of the axial recovery mechanism relative to the housing according to the oscillation decay state of the valve piston; Repeatedly oscillate the valve timing piston, detect the oscillation decay state of the valve timing piston, and adjust the installation position of the axial recovery mechanism until the oscillation decay state of the valve timing piston meets the second preset condition.

[0017] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: By connecting the induction coil to the valve stem and placing the induction coil within the magnetic field formed by the stator located inside the housing, the oscillation of the valve piston causes the induction coil to move relative to the stator, generating an induced electrical signal. The oscillation decay state of the valve piston can then be determined based on the change in the induced electrical signal over time, thereby determining the coaxial assembly state of the valve piston and enabling the detection of the valve piston's coaxiality.

[0018] Furthermore, the valve timing piston coaxiality assembly method provided by the present invention, since it is applied to the free piston Stirling generator as described above, also possesses the various advantages described above.

[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention and are not considered as limitations on this application. Moreover, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0021] Figure 1 This is a schematic structural diagram of the free piston Stirling generator provided by the present invention.

[0022] Figure 2This is a schematic structural diagram of the detection circuit in the free piston Stirling generator provided by the present invention.

[0023] Figure 3 This is a schematic structural diagram of the axial recovery mechanism in the free piston Stirling generator provided by the present invention.

[0024] Figure 4 This is a flowchart of the steps of the valve timing piston coaxiality assembly method provided by the present invention.

[0025] Figure label: 1. Outer shell; 2. Cylinder; 3. Generating mechanism; 31. Power piston; 32. First motor; 33. First coil; 34. Coil bracket; 35. Elastic support; 4. Gas distribution piston; 41. Gas distribution rod; 5. Axial recovery mechanism; 51. First permanent magnet; 52. Second permanent magnet; 53. Moving permanent magnet; 54. First support seat; 55. Second support seat; 6. Electromagnetic detection mechanism; 61. Stator; 62. Induction coil; 63. Detection bracket; 64. Detection circuit; 641. Power supply; 642. Controller; 7. Housing; 8. Heater; 9. Regenerator; 10. Cooler; 11. Expansion chamber; 12. Compression chamber; 13. Back pressure chamber; 14. Fixed support. Detailed Implementation

[0026] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0027] The specific terms used in this specification are for illustrative purposes only and are not intended to limit the illustrated embodiments. For example, expressions such as "same" and "identical" not only indicate a strictly identical state, but also indicate a state with tolerances or differences in the degree of functionality. For example, expressions indicating relative or absolute arrangement such as "in a certain direction," "along a certain direction," "side by side," "perpendicular," "centered on," "concentric," or "coaxial" not only strictly indicate such an arrangement, but also indicate a state of relative displacement by tolerances or angles or distances with the same degree of functionality.

[0028] The terms “center,” “longitudinal,” “lateral,” “length,” “width,” “thickness,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” “outer,” “clockwise,” “counterclockwise,” “axial,” “radial,” and “circumferential” indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0029] Furthermore, features specified as "first" or "second" may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "multiple" means two or more. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified. In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, B1 and / or B2 can represent: B1 existing alone, B1 and B2 existing simultaneously, and B2 existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] The following is combined with Figures 1 to 3 The present invention describes a free-piston Stirling generator.

[0032] A free-piston Stirling generator typically consists of a power piston and a valve train, with the valve stem of the valve train passing through the power piston. During assembly, it is crucial to ensure good coaxiality between the power piston, valve train, and cylinder; otherwise, the reciprocating motion resistance of the valve train will increase. However, since the valve train is located inside the generator, it is currently difficult to inspect its coaxial assembly.

[0033] Reference Figures 1-3In this embodiment, the free piston Stirling generator includes a housing 1, a power generation mechanism 3, a valve distribution piston 4, an axial recovery mechanism 5, and an electromagnetic detection mechanism 6. A cylinder 2 is disposed inside the housing 1. The power generation mechanism 3 includes a power piston 31, which is movably disposed inside the cylinder 2. The valve distribution piston 4 is movably disposed inside the cylinder 2 and has a valve distribution rod 41 passing through the power piston 31. The axial recovery mechanism 5 is connected between the valve distribution rod 41 and the housing 1 and is used to apply an axial recovery force to the valve distribution piston 4. The electromagnetic detection mechanism 6 includes a stator 61 and an induction coil 62. The stator 61 is disposed inside the housing 1, and the induction coil 62 is connected to the valve distribution rod 41. The induction coil 62 is located in the magnetic field formed by the stator 61 so as to generate an induced electrical signal when the valve distribution piston 4 oscillates.

[0034] By connecting the induction coil 62 to the valve stem 41 and placing the induction coil 62 within the magnetic field formed by the stator 61 located inside the housing 1, the oscillation of the valve piston 4 causes the induction coil 62 to move relative to the stator 61, generating an induced electrical signal. Therefore, the oscillation decay state of the valve piston 4 can be determined based on the change of the induced electrical signal over time, thereby determining the coaxial assembly state of the valve piston 4 and enabling the detection of the coaxiality of the valve piston 4.

[0035] Both the power piston 31 and the valve timing piston 4 can reciprocate along the axial direction of the cylinder 2. A through hole is provided through the power piston 31, located in the middle of the power piston 31. The valve timing rod 41 of the valve timing piston 4 passes through the through hole, and there is a fitting clearance between the valve timing rod 41 and the through hole to allow the valve timing rod 41 to reciprocate. Thus, when the valve timing piston 4 moves, the valve timing rod 41 can reciprocate relative to the power piston 31.

[0036] The axial recovery mechanism 5 is disposed between the valve stem 41 and the housing 1. The axial recovery mechanism 5 is used to support the valve stem 41 and the valve piston 4, and can apply a restoring force to the valve piston 4 when the position of the valve piston 4 deviates.

[0037] The free-piston Stirling generator also includes a fixed support 14 fixed relative to the outer casing 1. The axial recovery mechanism 5 may include a leaf spring or a diaphragm spring; in this embodiment, the axial recovery mechanism 5 uses a leaf spring. The middle part of the leaf spring is connected to the valve stem 41, and the outer periphery of the leaf spring is connected to the fixed support 14. This allows for axial support of the valve stem 41 while simultaneously limiting its radial displacement and allowing the valve stem 41 to reciprocate axially along the power piston 31. It should be noted that the number, thickness, outer diameter, and specific connection method of the leaf springs can be adjusted according to the required support stiffness and oscillation frequency of the valve stem 4; this embodiment does not impose specific limitations in this regard.

[0038] The stator 61 is fixed relative to the outer casing 1 and forms a magnetic field at the location of the induction coil 62. The induction coil 62 is connected to the gas distribution rod 41 and can reciprocate relative to the stator 61 along with the gas distribution piston 4 and the gas distribution rod 41.

[0039] The free-piston Stirling generator may also include a second motor, where the stator 61 is a fixed portion of the second motor relative to the housing 1, used to generate a magnetic field in the region where the induction coil 62 is located. The specific magnetic circuit structure of the second motor can be set according to the required magnetic field strength and range of motion of the induction coil 62, and this embodiment does not impose specific limitations on this.

[0040] In some embodiments, the induction coil 62 can be directly connected to the air distribution rod 41. Alternatively, the electromagnetic detection mechanism 6 may also include a detection bracket 63, which is mounted on the air distribution rod 41, and the induction coil 62 is wound around the detection bracket 63. The detection bracket 63 facilitates the arrangement and fixation of the induction coil 62, enabling it to move synchronously with the air distribution rod 41, thereby stably generating an induced electrical signal during the oscillation of the air distribution piston 4.

[0041] Optionally, the detection bracket 63 can adopt a cylindrical, annular, or U-shaped structure. In addition, the specific shape and size of the detection bracket 63 can be adapted according to the number of turns of the induction coil 62 and the structure of the air distribution rod 41.

[0042] In some embodiments, the power generation mechanism 3 includes a first motor 32, a first coil 33, and a coil support 34. The first motor 32 is disposed inside the housing 1 and is mounted on the fixed support 14 and fixedly disposed relative to the housing 1. The coil support 34 is connected to the power piston 31. The first coil 33 is wound on the coil support 34 and located within the magnetic field generated by the first motor 32. When the power piston 31 reciprocates, it can drive the first coil 33 to move relative to the first motor 32 through the coil support 34, causing the first coil 33 to cut the magnetic field generated by the first motor 32 and generate induced electrical energy, thereby converting the reciprocating motion of the power piston 31 into electrical energy.

[0043] An output circuit is connected to the power generation mechanism 3, allowing the electrical energy generated by the power generation mechanism 3 to be output through the output circuit. The output circuit includes a capacitor and a load, which are connected to the first coil 33 to form an electrical energy output circuit. When the power piston 31 drives the first coil 33 to reciprocate within the magnetic field formed by the first motor 32, the first coil 33 generates an induced current, which supplies power to the load through the electrical energy output circuit.

[0044] Optionally, the power generation mechanism 3 further includes an elastic support 35, which is supported on the fixed support portion 14 and used to support the coil bracket 34. It also provides elastic restoring force to the power piston 31 during its reciprocating motion. The elastic support 35 may include a leaf spring or a diaphragm spring. In this embodiment, a leaf spring is used as the elastic support 35, which can improve the stability of the power piston 31 during its movement.

[0045] In some embodiments, the free-piston Stirling generator further includes a housing 7, on which a heater 8, a regenerator 9, and a cooler 10 are sequentially disposed. The housing 7 is filled with an inert high-pressure gas as the working fluid for the Stirling cycle. First, the heater 8 is assembled into the housing 7 to form a hot end, absorbing heat from the outside. Then, the regenerator 9 is filled with heat storage material, and the cooler 10 is assembled into the housing 7 to form a cold end, releasing heat to the outside, thus creating a cold and hot end with a temperature difference within the housing 7. When the working fluid flows from the heater 8 to the cooler 10 inside the housing 7, the working fluid releases heat to the heat storage material; when the working fluid flows from the cooler 10 to the heater 8, the heat storage material releases heat to the working fluid. During the reciprocating flow of the working fluid, heat exchange occurs between the working fluid and the heat storage material, resulting in energy release and absorption.

[0046] After the heater 8, regenerator 9, and cooler 10 are assembled into the housing 7, the fixed support 14 is fixed to the housing 7. A cylinder 2 is installed inside the housing 7, with one part of the cylinder 2 located within the housing 7 and the other part protruding from the housing 7. Both the power piston 31 and the distribution piston 4 are reciprocatingly installed in the cylinder 2. An expansion chamber 11 is formed on the side of the distribution piston 4 away from the power piston 31, and a compression chamber 12 is formed between the distribution piston 4 and the power piston 31. The elastic support 35 and the first motor 32 are both installed on the fixed support 14. Then, the electromagnetic detection mechanism 6 is installed on the fixed support 14. After the coaxiality of the distribution piston 4 and the power piston 31 is adjusted, the outer shell 1 is assembled onto the housing 7 and onto the cooler 10. The side of the elastic support 35 away from the power piston 31 forms a back pressure chamber 13 between itself and the outer shell 1.

[0047] The periodic absorption and release of heat by the working fluid creates periodically changing pressure in the expansion chamber 11 and compression chamber 12. This pressure acts on the power piston 31, causing it to reciprocate along the axis of the cylinder 2. When the power piston 31 moves, it drives the first coil 33 in the power generation mechanism 3 to move relative to the first motor 32, causing the first coil 33 to cut the magnetic field formed by the first motor 32 and generate induced electrical energy.

[0048] The valve stem 41 passes through the power piston 31. Therefore, the coaxial assembly state between the valve stem 4, the power piston 31, and the cylinder 2 will affect the motion resistance of the valve stem 4 and the power piston 31. When the coaxial deviation of the valve stem 4 after assembly is large, the gap between the valve stem 41 and the power piston 31 or between the valve stem 4 and the cylinder 2 will decrease, increasing the frictional resistance during the movement of the valve stem 4.

[0049] In some embodiments, the free-piston Stirling generator further includes a detection circuit 64 electrically connected to both ends of the induction coil 62, used to acquire the induced electrical signal generated by the induction coil 62. When the valve timing piston 4 oscillates, the induction coil 62 reciprocates within the magnetic field formed by the stator 61 along with the valve timing rod 41, generating an induced electrical signal that changes with the oscillation state of the valve timing piston 4. By being electrically connected to both ends of the induction coil 62, the detection circuit 64 can acquire the induced voltage or induced current during the oscillation process of the valve timing piston 4, thereby determining the oscillation decay state of the valve timing piston 4.

[0050] In some embodiments, the detection circuit 64 includes a signal acquisition unit and a display. The input terminal of the signal acquisition unit is electrically connected to the induction coil 62, and the output terminal of the signal acquisition unit is electrically connected to the display. The signal acquisition unit is used to acquire the induced electrical signal generated by the oscillation of the induction coil 62 with the valve timing piston 4, and transmits the acquired induced electrical signal to the display. The display is used to display the waveform of the induced electrical signal changing over time. Thus, the operator can judge the oscillation attenuation state of the valve timing piston 4 by observing the content displayed on the display, and thus determine the coaxiality assembly of the valve timing piston 4. When the oscillation attenuation state of the valve timing piston 4 does not meet the requirements, the installation position of the elastic support 35 in the direction perpendicular to the axis of the valve timing rod 41 can be adjusted to adjust the coaxiality of the valve timing piston 4. After the oscillation attenuation state of the valve timing piston 4 meets the requirements, the elastic support 35 is fixed to the fixed support part 14, that is, fixed relative to the outer casing 1.

[0051] Optionally, the damping parameters of the valve timing piston 4 can be calculated based on the waveform of the induced electrical signal changing over time, such as the damping coefficient, amplitude attenuation rate, adjacent peak ratio, or oscillation duration. Alternatively, instead of calculating specific damping parameters, the coaxial assembly state of the valve timing piston 4 can be determined by comparing the attenuation rate and duration of the induced electrical signal at different assembly positions. The faster the induced electrical signal attenuates, the greater the motion resistance experienced by the valve timing piston 4; the slower the induced electrical signal attenuates and the longer its duration, the smaller the motion resistance experienced by the valve timing piston 4.

[0052] Optionally, the detection circuit 64 may also include a signal amplifier connected between the induction coil 62 and the signal acquisition unit to amplify the induced electrical signal generated by the induction coil 62. When the vibration amplitude of the valve piston 4 is small or the induced electrical signal output by the induction coil 62 is weak, the signal amplifier can improve the identification of the induced electrical signal and facilitate the determination of its attenuation over time.

[0053] In some embodiments, the detection circuit 64 further includes a power supply 641, which is electrically connected to the induction coil 62 and is used to input an excitation current into the induction coil 62 so that the induction coil 62 is subjected to an electromagnetic force that drives the valve piston 4 to move. Optionally, the power supply 641 is a frequency converter. After the excitation current is applied to the induction coil 62, the magnetic field formed by the induction coil 62 and the stator 61 interacts, causing the induction coil 62 to drive the valve piston 4 to move through the valve rod 41. After the excitation current is stopped, the valve piston 4 oscillates back and forth under the restoring force of the axial recovery mechanism 5, and the induction coil 62 oscillates back and forth in the magnetic field with the valve piston 4 and generates an induced electrical signal. Thus, the induction coil 62 can serve as an excitation component for the valve piston 4 when energized, and as a detection component for the oscillation state of the valve piston 4 after the excitation current is stopped, reducing the influence of the assembly of additional excitation components on the assembly state of the valve piston 4. Furthermore, by inputting excitation current to the induction coil 62 through the power supply 641, relatively consistent initial excitation conditions can be provided for oscillation detection at different assembly positions, thereby improving the reliability of oscillation decay state comparison.

[0054] In addition, the valve piston 4 can be made to oscillate by pushing the valve rod 41 or striking the axial recovery mechanism 5, and then oscillate freely after the external force stops.

[0055] In some embodiments, the detection circuit 64 further includes a controller 642 connected to a power supply 641. The controller 642 controls the power supply 641 to input an excitation current for a preset duration to the induction coil 62, and then controls the power supply 641 to stop inputting the excitation current. During the oscillation attenuation detection of the valve timing piston 4, the controller 642 controls the power supply 641 to input an instantaneous excitation current to the induction coil 62, causing the induction coil 62 to experience electromagnetic force within the magnetic field formed by the stator 61, and driving the valve timing piston 4 to generate initial movement via the valve timing rod 41. Subsequently, the controller 642 controls the power supply 641 to stop inputting the excitation current, allowing the valve timing piston 4 to enter a free oscillation state. This allows control over the energizing excitation phase of the induction coil 62 and the free oscillation phase of the valve timing piston 4, enabling the valve timing piston 4 in different assembly positions to be oscillated under relatively consistent excitation conditions, improving the comparability between different oscillation attenuation results, and reducing the impact of excessively long excitation time on the free oscillation process of the valve timing piston 4.

[0056] The preset duration can be set according to the initial motion state required by the valve piston 4. Optionally, the excitation current is a pulse current with a short duration.

[0057] It should be noted that stopping the input of excitation current to the induction coil 62 means stopping the supply of external excitation current from the power supply 641 to the induction coil 62, and does not mean that the electrical connection between the induction coil 62 and the detection circuit 64 is broken. During the free oscillation of the valve piston 4, the induction coil 62 remains connected to the detection circuit 64, so that the induced voltage or induced current generated by the reciprocating motion of the induction coil 62 with the valve piston 4 in the magnetic field can be transmitted to the detection circuit 64.

[0058] In some embodiments, the controller 642 is further configured to control the power supply 641 to input a periodic current to the induction coil 62, and adjust the amplitude and phase angle of the periodic current so that the induction coil 62 is subjected to an electromagnetic force acting along the axial direction of the valve distribution rod 41 within the magnetic field formed by the stator 61. After the periodic current is applied to the induction coil 62, the induction coil 62 interacts with the magnetic field formed by the stator 61, and is subjected to an electromagnetic force that varies along the axial direction of the valve distribution rod 41, which then acts on the valve distribution piston 4 through the valve distribution rod 41. By adjusting the amplitude of the periodic current, the magnitude of the axial electromagnetic force can be adjusted; by adjusting the phase angle of the periodic current, the timing of the axial electromagnetic force relative to the reciprocating motion of the valve distribution piston 4 can be adjusted, so that the axial electromagnetic force is adapted to the motion state of the valve distribution piston 4.

[0059] Optionally, the frequency of the periodic current can be the same as or adapted to the operating frequency of the free piston Stirling generator, so that the axial electromagnetic force changes according to the movement cycle of the valve timing piston 4. When the valve timing piston 4 moves, by adjusting the phase angle of the periodic current, the axial electromagnetic force can drive the valve timing piston 4 to move towards the equilibrium position, thereby forming an adjustable electromagnetic axial support.

[0060] During the assembly and testing phase, the induction coil 62 oscillates with the valve train piston 4 and generates an induced electrical signal. During generator operation, it generates an axial electromagnetic force under the action of a periodic current. This allows the electromagnetic detection mechanism 6 to both detect the oscillation state of the valve train piston 4 and support it. Furthermore, by adjusting the amplitude and phase angle of the periodic current, the electromagnetic support effect can be adjusted according to the operating state of the valve train piston 4, reducing the axial support force required by the axial recovery mechanism 5.

[0061] In other words, when using a leaf spring to provide axial support for the valve timing piston 4, the leaf spring can be designed according to the axial stiffness required for the reciprocating motion of the valve timing piston 4, and after assembly, it is used to provide elastic restoring force for the valve timing piston 4. After the coaxiality of the valve timing piston 4 is detected and adjusted, the connection between the induction coil 62 and the detection circuit 64 can be disconnected, so that the circuit where the induction coil 62 is located is in an open circuit state. The valve timing piston 4 is supported by the leaf spring and reciprocates under the action of the elastic restoring force provided by the leaf spring.

[0062] In addition, leaf springs with low axial stiffness can be used to support and position the valve stem 41, thereby limiting the radial offset of the valve piston 4 and maintaining the valve piston 4 in reciprocating motion in a predetermined direction. After the assembly and coaxiality adjustment of the valve piston 4 are completed, the power supply 641 inputs a periodic current to the induction coil 62, causing the induction coil 62 to generate an electromagnetic force acting along the axis of the valve stem 41 within the magnetic field formed by the stator 61. Combined with the elastic restoring force provided by the leaf spring, this forms a reliable support for the reciprocating motion of the valve piston 4.

[0063] In some embodiments, the axial recovery mechanism 5 includes a first permanent magnet 51, a second permanent magnet 52, and a moving permanent magnet 53. The moving permanent magnet 53 is disposed on the air distribution rod 41. The first permanent magnet 51 and the second permanent magnet 52 are both fixedly disposed relative to the outer shell 1 and are respectively located on both sides of the moving permanent magnet 53 along the axial direction of the air distribution rod 41. The moving permanent magnet 53 and the first permanent magnet 51 have the same polarity in opposite directions, and the moving permanent magnet 53 and the second permanent magnet 52 have the same polarity in opposite directions, so that the moving permanent magnet 53 is subjected to repulsive forces applied by the first permanent magnet 51 and the second permanent magnet 52 respectively.

[0064] When the moving permanent magnet 53 is in the equilibrium position between the first permanent magnet 51 and the second permanent magnet 52, the repulsive forces on both sides of the moving permanent magnet 53 are balanced. When the valve piston 4 drives the valve rod 41 and the moving permanent magnet 53 to move towards the side where the first permanent magnet 51 is located, the distance between the moving permanent magnet 53 and the first permanent magnet 51 decreases, and the repulsive force between them increases. At the same time, the distance between the moving permanent magnet 53 and the second permanent magnet 52 increases, and the repulsive force between them decreases. This results in the moving permanent magnet 53 receiving a resultant force towards the side where the second permanent magnet 52 is located. Correspondingly, when the moving permanent magnet 53 moves towards the side where the second permanent magnet 52 is located, the moving permanent magnet 53 receives a resultant force towards the side where the first permanent magnet 51 is located. This causes the moving permanent magnet 53 to tend to move towards the equilibrium position and provides an axial restoring force to the valve piston 4 through the valve rod 41.

[0065] Specifically, the fixed support part 14 is provided with a first support seat 54 and a second support seat 55. The second support seat 55 is located on the side of the first support seat 54 away from the power piston 31. The first permanent magnet 51 is fixedly installed on the first support seat 54, and the second permanent magnet 52 is fixedly installed on the second support seat 55.

[0066] In this embodiment, the free-piston Stirling generator is assembled by first assembling the heater 8, regenerator 9, and cooler 10 into the housing 7, and then fixing the fixed support 14 to the housing 7. The first motor 32 is installed on the side of the cooler 10 away from the regenerator 9 and fixed to the fixed support 14. The valve piston 4 is installed into the cylinder 2, and the power piston 31, the first coil 33, and the coil support 34 are assembled. The coil support 34 is connected to the power piston 31, the first coil 33 is wound around the coil support 34, and the coil support 34 is supported on the housing 7 by the elastic support 35 and the fixed support 14.

[0067] After the power piston 31 is assembled, it is made to oscillate, and the oscillation attenuation state of the power piston 31 is determined according to the induced electrical signal generated by the first coil 33. Then, the installation position of the power piston 31 relative to the cylinder 2 is adjusted to complete the coaxiality adjustment of the power piston 31.

[0068] Both the stator 61 and the axial recovery mechanism 5 are fixed to the fixed support 14, and the stator 61 and the axial recovery mechanism 5 are spaced apart to avoid collision between the stator 61 and the axial recovery mechanism 5 during the operation of the free piston Stirling generator. The induction coil 62 is wound around the detection bracket 63, and the axial recovery mechanism 5 and the detection bracket 63 are connected to the distribution rod 41 of the distribution piston 4, so that the induction coil 62 can reciprocate with the distribution piston 4. The axial recovery mechanism 5 is first pre-fixed to the fixed support 14. At this time, the side of the distribution piston 4 away from the power piston 31 forms an expansion chamber 11, and the distribution piston 4 and the power piston 31 form a compression chamber 12. Then, the two ends of the induction coil 62 are connected to the detection circuit 64 to obtain the induced electrical signal generated by the induction coil 62. The controller 642 provides an instantaneous excitation current to drive the valve piston 4 to move. After the excitation current is disconnected, the valve piston 4 oscillates back and forth under the action of the axial restoring force provided by the axial return mechanism 5, and gradually decays under the action of motion resistance. The detection circuit 64 collects the induced electromotive force generated by the induction coil 62, and determines the oscillation decay state of the valve piston 4 according to the change of the induced electromotive force over time, and then adjusts the coaxiality of the valve piston 4.

[0069] Furthermore, when the oscillation attenuation state of the valve train 4 does not meet the requirements, the mounting position of the axial recovery mechanism 5 relative to the fixed support 14 can be adjusted to adjust the support position of the valve train 41 and the axis of motion of the valve train 4. Specifically, the axial recovery mechanism 5 can be moved slightly relative to the housing 1 in different directions perpendicular to the axis of the valve train 41, and the valve train 4 can be oscillated again after each adjustment to compare the oscillation attenuation state before and after the adjustment. By repeatedly adjusting the position and detecting the oscillation in different circumferential directions of the valve train 41, the coaxial deviation between the valve train 4 and the cylinder 2, and between the valve train 41 and the power piston 31, can be gradually reduced.

[0070] Optionally, the outer periphery of the axial recovery mechanism 5 is disposed on the fixed support portion 14. The outer periphery of the axial recovery mechanism 5 has multiple mounting holes spaced apart circumferentially. Fasteners pass through these mounting holes and connect to the fixed support portion 14 to fix the axial recovery mechanism 5 to the fixed support portion 14. The fasteners include screws or bolts. During the coaxiality adjustment of the valve timing piston 4, the fasteners are not fully tightened, allowing the axial recovery mechanism 5 to move slightly relative to the fixed support portion 14 in a direction perpendicular to the axis of the valve timing rod 41. After the oscillation attenuation state of the valve timing piston 4 meets the requirements, the fasteners are tightened to fix the axial recovery mechanism 5 in the adjusted position.

[0071] After the coaxiality of the valve train piston 4 is adjusted, the oscillation attenuation state of the power piston 31 can be checked again. If the oscillation attenuation state of the power piston 31 changes, the power piston 31 is fine-tuned, and the oscillation attenuation state of the valve train piston 4 is checked again. After the oscillation attenuation states of both the power piston 31 and the valve train piston 4 meet the corresponding requirements, the axial recovery mechanism 5 is fastened to the fixed support part 14, and finally the outer shell 1 is fixed to the housing 7, and the fixed support part 14 is fixedly connected to the outer shell 1, thereby completing the assembly of the free piston Stirling generator.

[0072] The following is combined with Figures 1 to 4 The present invention describes a method for assembling the valve train piston with coaxiality, used in the aforementioned free-piston Stirling generator, comprising: S100: When the power piston 31 is in an oscillating state, the coaxiality of the power piston 31 is adjusted according to the oscillation attenuation state of the power piston 31 until the oscillation attenuation state of the power piston 31 meets the first preset condition. S200: When the valve timing piston 4 is in an oscillating state, acquire the induced electrical signal generated by the induction coil 62 as the valve timing piston 4 oscillates, and determine the oscillation attenuation state of the valve timing piston 4 based on the induced electrical signal. S300: Adjust the mounting position of the axial recovery mechanism 5 relative to the housing 1 according to the oscillation attenuation state of the gas distribution piston 4; S400: Repeatedly oscillate the valve timing piston 4, detect the oscillation attenuation state of the valve timing piston 4, and adjust the installation position of the axial recovery mechanism 5 until the oscillation attenuation state of the valve timing piston 4 meets the second preset condition.

[0073] Specifically, before assembling the valve piston 4, the assembly and coaxiality adjustment of the power piston 31 are completed first. The power piston 31 is connected to the first coil 33 in the power generation mechanism 3, and the first coil 33 is located within the magnetic field formed by the first motor 32. This allows the power piston 31 to move and oscillate back and forth under the elastic restoring force of the corresponding elastic support 35. When the power piston 31 oscillates, it drives the first coil 33 to reciprocate within the magnetic field formed by the first motor 32, causing the first coil 33 to generate a corresponding induced electrical signal. Based on the change of the induced electrical signal generated by the first coil 33 over time, the oscillation decay state of the power piston 31 can be determined.

[0074] When the oscillation decay rate of the power piston 31 is relatively fast, it indicates that the power piston 31 is experiencing greater motion resistance. The installation position of the power piston 31 and its elastic support 35 relative to the cylinder 2 can be adjusted, and the power piston 31 can be made to oscillate again after adjustment. This process of adjusting the position of the power piston 31 and detecting the oscillation decay state is repeated until the oscillation decay state of the power piston 31 meets the first preset condition. The first preset condition can be determined based on the damping coefficient and amplitude decay rate of the power piston 31.

[0075] After the coaxiality of the power piston 31 is adjusted, the valve timing piston 4 is installed into the cylinder 2, so that the valve timing rod 41 of the valve timing piston 4 passes through the through hole on the power piston 31. The axial recovery mechanism 5 is connected between the valve timing rod 41 and the fixed support part 14. The fixed support part 14 is fixedly set relative to the housing 7. The housing 1 is fixedly assembled onto the housing 7 after the coaxiality of the valve timing piston 4 and the power piston 31 is adjusted. During the coaxiality adjustment of the valve timing piston 4, the axial recovery mechanism 5 and the fixed support part 14 maintain a connection that allows for position adjustment, so that the support position of the valve timing rod 41 can be adjusted according to the test results.

[0076] The oscillation of the valve timing piston 4 can be achieved by inputting an instantaneous excitation current into the induction coil 62, pushing the valve timing rod 41, or striking the axial recovery mechanism 5. When electromagnetic excitation is used, the power supply 641 inputs an excitation current into the induction coil 62, causing the induction coil 62 to experience an electromagnetic force within the magnetic field formed by the stator 61, which in turn drives the valve timing piston 4 to produce initial motion via the valve timing rod 41. After the input excitation current stops, the valve timing piston 4 oscillates reciprocally under the elastic restoring force of the axial recovery mechanism 5.

[0077] When the valve timing piston 4 oscillates, the induction coil 62 reciprocates within the magnetic field formed by the stator 61 along with the valve timing rod 41, generating an induced electrical signal. Based on the change of the induced electrical signal over time, the oscillation decay state of the valve timing piston 4 can be determined. Specifically, the oscillation decay state of the valve timing piston 4 can be judged based on the amplitude decay rate and damping coefficient of the induced electrical signal to determine whether the second preset condition is met.

[0078] When the oscillation decay state of the valve timing piston 4 does not meet the second preset condition, the mounting position of the axial recovery mechanism 5 relative to the fixed support 14 is adjusted to change the support position of the valve timing rod 41 and the axis of motion of the valve timing piston 4. For example, the axial recovery mechanism 5 can be slightly moved relative to the housing 1 in a direction perpendicular to the axis of the valve timing rod 41. After adjustment, the valve timing piston 4 is oscillated again, and the oscillation decay state before and after adjustment is compared. If the decay rate of the induced electrical signal decreases or the oscillation duration increases after adjustment, it indicates that the motion resistance of the valve timing piston 4 has decreased, and slight adjustments can continue in the corresponding direction; if the decay rate of the induced electrical signal increases after adjustment, the adjustment direction of the axial recovery mechanism 5 can be changed.

[0079] By repeatedly adjusting the installation position of the axial recovery mechanism 5 relative to the fixed support 14 in different directions along the circumference of the valve stem 41, and re-detecting the oscillation attenuation state of the valve piston 4 after each adjustment, the coaxial deviation between the valve piston 4 and the cylinder 2, and between the valve stem 41 and the power piston 31, can be gradually reduced. When the oscillation attenuation state of the valve piston 4 meets the second preset condition, it indicates that the motion resistance of the valve piston 4 has reached the preset requirement.

[0080] After the oscillation attenuation state of the valve timing piston 4 meets the second preset condition, the power piston 31 can be oscillated again to verify its oscillation attenuation state. If the verified oscillation attenuation state of the power piston 31 does not meet the first preset condition, the installation position of the power piston 31 can be fine-tuned, and the oscillation attenuation state of the valve timing piston 4 can be detected again after the adjustment. The detection and adjustment of the power piston 31 and the valve timing piston 4 are repeated until the oscillation attenuation state of the power piston 31 meets the first preset condition and the oscillation attenuation state of the valve timing piston 4 meets the second preset condition. The axial recovery mechanism 5 is then fastened to the housing 1 to complete the coaxiality assembly of the valve timing piston 4.

[0081] The first and second preset conditions can be determined based on the damping coefficient, amplitude decay rate, or oscillation duration corresponding to the coaxial assembly state of the power piston 31 and the valve timing piston 4. The first and second preset conditions can be the same, or they can be set separately according to the structure and motion parameters of the power piston 31 and the valve timing piston 4.

[0082] Finally, it should be noted that the above embodiments are only for illustrating the present invention and not for limiting the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that various combinations, modifications, or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention and should be covered within the protection scope of the present invention.

Claims

1. A free-piston Stirling generator, characterized in that, include: The outer casing contains a cylinder. A power generation mechanism includes a power piston, which is movably disposed within the cylinder; The valve piston is movably disposed within the cylinder and has a valve rod passing through the power piston; An axial recovery mechanism is connected between the valve stem and the housing. An electromagnetic detection mechanism includes a stator and an induction coil. The stator is disposed inside the housing, and the induction coil is connected to the gas distribution rod. The induction coil is located within the magnetic field formed by the stator to generate an induced electrical signal when the gas distribution piston oscillates.

2. The free-piston Stirling generator according to claim 1, characterized in that, The electromagnetic detection mechanism also includes a detection bracket, which is mounted on the gas distribution rod, and the induction coil is wound around the detection bracket.

3. The free-piston Stirling generator according to claim 1, characterized in that, It also includes a detection circuit, which is electrically connected to both ends of the induction coil and is used to acquire the induced electrical signal generated by the induction coil.

4. The free-piston Stirling generator according to claim 3, characterized in that, The detection circuit includes a signal acquisition unit and a display. The input terminal of the signal acquisition unit is electrically connected to the induction coil, and the output terminal of the signal acquisition unit is electrically connected to the display.

5. The free-piston Stirling generator according to claim 4, characterized in that, The detection circuit also includes a power supply, which is electrically connected to the induction coil and is used to input an excitation current to the induction coil so that the induction coil is subjected to an electromagnetic force that drives the valve piston to move.

6. The free-piston Stirling generator according to claim 5, characterized in that, The detection circuit also includes a controller connected to the power supply, which controls the power supply to input an excitation current for a preset duration to the induction coil.

7. The free-piston Stirling generator according to claim 6, characterized in that, The controller is also used to control the power supply to input a periodic current to the induction coil, and to adjust the amplitude and phase angle of the periodic current so that the induction coil generates an axial electromagnetic force acting on the valve piston.

8. The free-piston Stirling generator according to any one of claims 1-7, characterized in that, The axial recovery mechanism includes a first permanent magnet, a second permanent magnet, and a moving permanent magnet. The moving permanent magnet is disposed on the air distribution rod. The first permanent magnet and the second permanent magnet are both fixed inside the outer shell and are respectively located on both sides of the moving permanent magnet along the axial direction of the air distribution rod. The moving permanent magnet has the same polarity as the opposing magnetic pole of the first permanent magnet, and the moving permanent magnet has the same polarity as the opposing magnetic pole of the second permanent magnet.

9. The free-piston Stirling generator according to any one of claims 1-7, characterized in that, The power generation mechanism includes a first motor, a first coil, and a coil support. The first motor is disposed inside the housing, the coil support is connected to the power piston, and the first coil is wound on the coil support and located within the magnetic field generated by the first motor.

10. A method for assembling a valve train piston to ensure coaxiality, characterized in that, For use in any one of claims 1-9, comprising: When the power piston is in an oscillating state, the coaxiality of the power piston is adjusted according to the oscillation decay state of the power piston until the oscillation decay state of the power piston meets the first preset condition. When the valve timing piston is in an oscillating state, the induced electrical signal generated by the induction coil as the valve timing piston oscillates is acquired, and the oscillation decay state of the valve timing piston is determined based on the induced electrical signal. Adjust the mounting position of the axial recovery mechanism relative to the housing according to the oscillation decay state of the valve piston; Repeatedly oscillate the valve timing piston, detect the oscillation decay state of the valve timing piston, and adjust the installation position of the axial recovery mechanism until the oscillation decay state of the valve timing piston meets the second preset condition.

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