Low-vibration active phase modulation composite pulse tube stirling refrigerator

Abstract

The application discloses a low-vibration active phase modulation composite pulse tube Stirling cryogenic refrigerator and belongs to the technical field of cryogenic refrigerators. The composite refrigerator cold finger integrates a first Stirling component as a high-temperature stage and a second pulse tube component as a low-temperature stage. The innovation is that the phase modulation unit of the second pulse tube component is composed of a second inertia tube wound and fixed in the inner circle of the gas reservoir, and the gas reservoir is integrally connected to the first cold end heat exchanger to improve the system efficiency through low-temperature arrangement. At the same time, the motion state of the compressor piston and the first displacer is monitored and cooperatively controlled in real time through the compressor displacement sensor and the cold finger displacement sensor, active and accurate phase modulation is realized, and the active vibration damper is used to perform reverse compensation according to the motion feedback of the first displacer to significantly offset the vibration output of the whole machine. The application realizes the unity of high efficiency, low vibration and high reliability, and is particularly suitable for vibration-sensitive space exploration and other application scenarios.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic refrigeration technology, specifically relating to a low-vibration active phase-modulation composite pulse tube Stirling refrigeration machine. Background Technology

[0002] Cryogenic refrigeration technology plays an irreplaceable core role in aerospace, quantum information, infrared detection, and basic scientific research. Regenerative cryogenic refrigerators, especially Stirling refrigerators and pulse tube refrigerators, are the mainstream technologies in this field. Stirling refrigerators, due to their actively moving exhaust at the cold end, can achieve highly efficient sound power recovery and phase adjustment, thus typically possessing high theoretical efficiency in the intermediate temperature range (e.g., 40K-80K). However, when extending to lower temperatures (e.g., 10K-20K), the multi-stage Stirling structure faces risks of wear and jamming due to the increased number of moving parts and extremely high precision requirements for friction pairs, severely restricting its development in space applications requiring long lifespan and high reliability.

[0003] Pulse tube refrigerators fundamentally solve reliability issues by completely eliminating moving parts at the cold end, but their intrinsic efficiency is low because acoustic power at the hot end of the pulse tube is dissipated as heat. Especially for cryogenic pulse tubes, traditional passive phase-tuning methods such as orifice-gas reservoirs or inertial tubes are difficult to establish optimal acoustic impedance matching and phase relationships in deep cryogenic regenerators. This results in the overall efficiency of multi-stage pulse tube refrigerators being significantly lower than that of Stirling refrigerators of the same class, causing disadvantages in size and weight.

[0004] To balance efficiency and reliability, hybrid refrigeration solutions (such as Stirling-pulse tube hybrids) have emerged. These solutions typically place the Stirling cycle in the high-temperature stage to leverage its efficiency advantage, while placing the pulse tube cycle in the low-temperature stage to ensure reliability in the deep cryogenic range. However, existing hybrid solutions still face two major bottlenecks: first, the insufficient phase-tuning precision and flexibility of the pulse tube in the low-temperature stage limits further improvements in overall system efficiency; second, the reciprocating motion of the Stirling ejector and compressor in the high-temperature stage generates considerable mechanical vibration, which is unacceptable for loads extremely sensitive to micro-vibrations, such as those carrying superconducting quantum interference devices (SQUIDs).

[0005] Existing technologies have attempted to provide active phasing for the cryogenic stage pulse tube using a separate phasing compressor, or to suppress vibration using an additional counter-moving balancing mass block. However, these solutions often involve complex systems, loose layouts, and difficult control coupling, and lack in-depth optimization at the system's thermodynamic cycle level. This makes it difficult to simultaneously achieve the engineering goals of high efficiency, low vibration, and high compactness within limited space and power consumption constraints. Therefore, developing a compact, precisely phasing, and significantly vibration-suppressing composite refrigerator has become a key technical problem urgently needing to be solved in this field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a low-vibration active phase-shifting composite pulse tube Stirling refrigerator. In this refrigerator, the cold finger is connected to the compressor via a connecting pipe. Oscillating helium working fluid flows sequentially from the compressor into the first-stage discharge chamber and the second-stage regenerator chamber via the connecting pipe. Cooling capacity is achieved through gas expansion within the first and second-stage cold-end heat exchanger chambers. Precise phase-shifting control is achieved by real-time monitoring and adjustment of the compressor piston and first-stage discharge chamber displacements using compressor displacement sensors and phase-shifting displacement sensors. Low-vibration output is achieved through active vibration dampers. Furthermore, by arranging the second-stage inertial tube and gas reservoir on the first-stage cold-end heat exchanger, the low temperature of the second-stage inertial tube and gas reservoir is achieved, thereby enhancing the cooling capacity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A low-vibration, actively phase-tuned composite pulse Stirling refrigerator includes a drive compressor, connecting pipes, a composite refrigerator cooling finger, and an active vibration damper.

[0009] The drive compressor is connected to the gas chamber of the composite refrigeration unit via a connecting pipe in a sealed manner, so as to transmit the pressure wave generated by compression to the composite refrigeration unit.

[0010] The composite refrigeration unit includes a first-stage Stirling assembly and a second-stage pulse tube assembly integrated on the same axis. The second-stage pulse tube assembly includes a second-stage inertial tube and a gas reservoir, which serve as a phase-adjusting unit. The gas reservoir and the second-stage inertial tube are integrated into a single structure and directly fixed to the first-stage cold-end heat exchanger of the first-stage Stirling assembly, so that the phase-adjusting unit is in a low-temperature environment provided by the first-stage cold-end heat exchanger during operation.

[0011] The active vibration damper is rigidly connected to the cooling finger of the composite refrigeration unit.

[0012] Furthermore, the compressor piston assembly that drives the compressor is elastically supported inside the compressor housing by the compressor leaf spring assembly, and the compressor motor assembly is fixed to the compressor housing and is driven by the compressor piston assembly to drive its reciprocating motion. The compressor piston assembly, compressor leaf spring assembly and compressor motor assembly are all arranged opposite each other, and the compressor displacement sensor is arranged at the tail end of the piston assembly to detect its displacement.

[0013] Furthermore, the first stage exhaust of the first stage Stirling assembly is elastically supported within the housing of the first stage exhaust via a cold finger leaf spring assembly. The moving part of the cold finger phase-shifting motor is connected to the first stage exhaust via a drive connection, and a cold finger displacement sensor is arranged at the tail end of the first stage exhaust to detect its displacement.

[0014] Furthermore, the secondary pulse tube assembly adopts a coaxial structure, with its annular secondary accumulator surrounding and sleeved on the outside of the tubular secondary pulse tube, and the low-temperature end of the secondary accumulator is connected to the secondary cold-end heat exchanger.

[0015] Furthermore, the secondary inertial tube is tightly coiled in a spiral shape within the internal cavity of the gas reservoir, and the secondary inertial tube and the gas reservoir are fixed together as an integral structure by welding or bonding with a high thermal conductivity adhesive.

[0016] Furthermore, the balance mass block of the active damper is elastically supported inside the damper housing by the damper leaf spring assembly, the moving part of the damping motor is connected to the balance mass block for transmission, and the self-sensing displacement sensor is arranged at the tail end of the first-stage discharger to detect its motion state.

[0017] Furthermore, it also includes a control system, in which the signals of the compressor displacement sensor, the cold finger displacement sensor, and the self-inductive displacement sensor are all connected. The control system controls the driving voltage of the compressor motor assembly and the cold finger phase-adjusting motor respectively according to the detection signals of the compressor displacement sensor and the cold finger displacement sensor, and controls the vibration damping motor to drive the balance mass block to generate a compensating motion opposite to the motion of the first-stage discharger according to the detection signal of the self-inductive displacement sensor.

[0018] Furthermore, the outer wall of the gas storage is entirely covered with an insulation layer composed of multiple layers of highly reflective thin films.

[0019] Furthermore, the control system integrates a unified control unit, which synchronously processes the signals from the compressor displacement sensor, the cold finger displacement sensor, and the self-inductance displacement sensor, and collaboratively outputs drive commands to the compressor motor assembly, the cold finger phase-adjusting motor, and the vibration damping motor.

[0020] The beneficial effects of this invention are as follows:

[0021] Significantly improved efficiency: By integrating the inertial tube used for phase adjustment in the secondary pulse tube with the gas reservoir and directly fixing it to the primary cold-end heat exchanger, the phase adjustment unit achieves low-temperature operation. This structure significantly reduces energy loss caused by environmental heat leakage from the inertial tube and gas reservoir, making their acoustic characteristics more suitable for deep cryogenic conditions. This optimizes the phase distribution within the cryogenic stage regenerator at the system level, effectively improving the overall refrigeration efficiency and cooling capacity.

[0022] Extremely low vibration output: By installing an independent displacement sensor on the first-stage discharger side and linking it with the active vibration damper to form a closed-loop control, the system can accurately monitor and feedback the discharger's motion status in real time. This drives the vibration damper to generate a counterforce of equal amplitude but opposite phase, thereby actively counteracting most of the reciprocating inertial forces and vibrations generated by the main drive compressor and the first-stage discharger. This enables the entire unit to achieve the low vibration level required for applications such as superconducting devices and precision optical systems that are extremely sensitive to micro-vibrations.

[0023] Precise control and high reliability: High-precision displacement sensors are installed on both the compressor side and the first-stage discharger side, enabling independent real-time monitoring and coordinated phase-adjustment control of the motion status of the pressure wave source (compressor piston) and the core moving component of the high-temperature stage (discharger). This not only facilitates rapid optimization under varying operating conditions and achieves optimal allocation of primary and secondary cooling capacity, but also gives the system a stronger adaptive compensation capability for load changes and long-term performance degradation, improving operational stability and reliability.

[0024] Compact structure and high integration: The aforementioned cryogenic phasing unit and active vibration damping mechanism both adopt a highly integrated coaxial or tightly coupled design and are integrated with the composite cold finger body. This avoids the volume and weight burden caused by multiple compressors, long connecting pipes, and loose balancing mass blocks in traditional solutions, making the overall structure more compact and easier to integrate and install with spacecraft payloads or experimental platforms. Attached Figure Description

[0025] Figure 1 This is a structural diagram of a low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to the present invention.

[0026] Figure label:

[0027] 1. Drive compressor; 1.1 Compressor piston assembly; 1.2 Compressor leaf spring assembly; 1.3 Compressor displacement sensor; 1.4 Compressor motor assembly; 1.5 Compressor housing;

[0028] Connecting pipe 2;

[0029] The composite refrigeration unit includes: 3. Cold finger (cold finger), 3.1. Cold finger leaf spring assembly, 3.2. Cold finger phase-adjusting motor, 3.3. Cold finger displacement sensor, 3.4. First-stage discharge device, 3.5. First-stage discharge device housing, 3.6. First-stage cold-end heat exchanger, 3.7. Second-stage pulse tube, 3.8. Second-stage cold accumulator, 3.9. Second-stage cold accumulator housing, 3.10. Second-stage inertial tube, 3.11. Gas storage tank;

[0030] Active vibration damper 4, vibration damping motor 4.1, vibration damper housing 4.2, vibration damper leaf spring assembly 4.3, self-sensing displacement sensor 4.4. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] like Figure 1 As shown, this embodiment of the invention provides a low-vibration active phase-modulation composite pulse Stirling refrigerator. It includes a drive compressor 1, connecting pipes 2, a composite refrigerator cooling finger 3, and an active vibration damper 4. The drive compressor 1 is sealed to one end of the connecting pipe 2 via a flange at its output end, while the other end of the connecting pipe 2 is sealed to the flange of the hot end (i.e., the high-temperature end of the first-stage Stirling component) of the composite refrigerator cooling finger 3. Thus, the drive compressor 1, connecting pipes 2, and composite refrigerator cooling finger 3 are connected in series to form a rigid gas power transmission and refrigeration execution body. The housing of the active vibration damper 4 (damper housing 4.2) is directly and rigidly fixed to the housing of the composite refrigerator cooling finger 3 by bolts or welding, so that the active vibration damper 4 and the refrigeration body physically form an integrated vibration control unit. Their axes are typically coaxial or parallel to optimize the force transmission path and vibration reduction effect.

[0033] The driving compressor 1 is a linear compressor. Inside its compressor housing 1.5, the compressor piston assembly 1.1 is supported by the elastic restoring force provided by the compressor leaf spring assembly 1.2 and driven by the compressor motor assembly 1.4 (e.g., a moving magnet linear motor) to perform precise axial reciprocating motion. This motion periodically compresses the helium working fluid in the piston compression chamber, thereby generating pressure waves with the frequency and amplitude required for the cooling index 3 of the composite refrigeration machine. The compressor motor assembly 1.4 can be a moving magnet motor, a moving coil motor, a moving ferromagnetic motor, etc. To precisely control this process, a compressor displacement sensor 1.3 is fixedly connected to the end of the compressor piston assembly 1.1. The compressor displacement sensor 1.3 is a non-contact displacement sensor, which can be a self-inductance coil type or a mutual inductance coil type displacement sensor. It can monitor and provide feedback on the motion state of the compressor piston assembly 1.1 in real time, thereby achieving precise control of the motion amplitude and phase of the compressor piston assembly 1.1.

[0034] The pressure wave is transmitted to the cooling index 3 of the composite refrigeration unit through the connecting pipe 2.

[0035] The composite refrigerator's cold finger 3 coaxially integrates a high-temperature stage Stirling assembly and a low-temperature stage pulse tube assembly. The first-stage Stirling assembly, located near the active damper 4, includes a cold finger leaf spring assembly 3.1, a cold finger phase-adjusting motor 3.2, a cold finger displacement sensor 3.3, a first-stage discharger 3.4, a first-stage discharger housing 3.5, and a first-stage cold-end heat exchanger 3.6. The first-stage discharger 3.4 is installed inside the first-stage discharger housing 3.5, with one end rigidly connected to the mover portion of the cold finger phase-adjusting motor 3.2 and the cold finger leaf spring assembly 3.1 via a connecting rod. At the end of its stroke (i.e., the other end of the first-stage discharger 3.4), the first-stage cold-end heat exchanger 3.6 is located. Driven by the pressure wave transmitted from the connecting pipe 2, the first-stage discharger 3.4 reciprocates, thereby completing the expansion process of the helium working fluid at the first-stage cold-end heat exchanger 3.6, achieving the cooling effect. In order to accurately sense and control the motion state of the first-stage discharger 3.4, a cold finger displacement sensor 3.3 (which can be a self-inductance coil type or a mutual inductance coil type displacement sensor) is fixedly installed at the end of the first-stage discharger 3.4 to monitor and provide feedback on the motion state of the first-stage discharger 3.4 in real time, thereby realizing the precise motion amplitude and phase control of the first-stage discharger 3.4 through the cold finger phase-adjusting motor 3.2.

[0036] The secondary pulse tube assembly, employing a highly compact coaxial structure and connected in series after the primary Stirling assembly, is the key innovation in improving efficiency. It mainly comprises a secondary pulse tube 3.7, a secondary accumulator 3.8, a secondary accumulator shell 3.9, a secondary cold-end heat exchanger 3.10, a secondary inertial tube 3.11, and a gas reservoir 3.12. The annular secondary accumulator 3.8 is housed inside the secondary accumulator shell 3.9. The tubular secondary pulse tube 3.7 is coaxially arranged on the central axis of this annular accumulator. The secondary cold-end heat exchanger 3.10 is located at the end (low-temperature end) of the secondary accumulator 3.8. The working fluid from the primary Stirling assembly is pre-cooled by flowing through the annular secondary accumulator 3.8, then expands and cools at the secondary cold-end heat exchanger 3.10, achieving optimal phase matching at the secondary cold-end heat exchanger 3.10 through the low-temperature secondary inertial tube 3.11 and gas reservoir 3.12.

[0037] The cylindrical gas reservoir 3.12 and the tightly coiled secondary inertial tube 3.11 within its internal cavity constitute a phase-tuning unit, which is integrated into a compact module by welding or bonding with high thermal conductivity adhesive. This module is not placed in a normal temperature environment, but rather securely mounted to the outer wall or end face of the primary cold-end heat exchanger 3.6 via bolts or welding through the base of its gas reservoir 3.12, ensuring extremely low thermal resistance between them. This "low-temperature" installation method ensures that the secondary inertial tube 3.11 and gas reservoir 3.12 operate in a low-temperature environment (e.g., 80K) provided by the primary cold-end heat exchanger 3.6, optimizing the acoustic impedance characteristics of the working fluid at low temperatures, improving phase-tuning capability, and thus significantly enhancing the cooling efficiency of the secondary pulse tube assembly. To reduce heat leakage, the outer wall of the gas reservoir 3.12 is covered with a high-reflectivity insulation layer composed of multiple layers of aluminized polyester film and other materials.

[0038] The active vibration damper 4 is a key component for achieving low vibration output of the entire unit. Inside the damper housing 4.2, the moving part of the damping motor 4.1 reciprocates. The probe of the self-sensing displacement sensor 4.4 is arranged at the end of the first-stage discharge unit 3.4 to continuously and in real-time collect the motion signal of the first-stage discharge unit 3.4. This motion signal is sent to an integrated control system. Based on this motion signal, the control system calculates in real-time the amount of compensation required to counteract the inertial force generated by the motion of the first-stage discharge unit 3.4, and drives the damping motor 4.1 to generate a reverse motion of the internal balancing mass block, which is opposite to the motion direction of the first-stage discharge unit 3.4 and has an amplitude in precise proportion to it. Through this active force cancellation mechanism, the vibration transmitted to the housing of the composite refrigeration unit's cooling finger 3 and the entire refrigeration unit's mounting foundation can be effectively neutralized.

[0039] This integrated control system simultaneously receives signals from the compressor displacement sensor 1.3 and the cold finger displacement sensor 3.3. Through a built-in control algorithm, the system can independently and collaboratively adjust the drive voltage of the compressor motor assembly 1.4 and the cold finger phase-adjusting motor 3.2, thereby achieving dynamic and precise control of the compressor piston's motion amplitude and frequency, as well as the relative phase between the compressor piston and the first-stage discharger. This dual closed-loop control strategy enables the refrigeration unit to quickly adjust to its optimal or near-optimal operating point under varying loads and conditions, achieving optimal distribution of primary and secondary cooling capacity and maintaining long-term operational stability.

[0040] In summary, this invention, through its innovative "low-temperature integrated phase modulation unit" mechanical structure, deeply integrates with the "active vibration reduction and coordinated phase modulation" closed-loop control strategy based on multi-sensor feedback, simultaneously overcoming multiple technical challenges such as efficiency, vibration, and control accuracy on a highly compact mechanical platform.

[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator, characterized in that, This includes the drive compressor, connecting pipes, cooling index of the combined refrigeration unit, and active vibration dampers. The drive compressor is connected to the gas chamber of the composite refrigeration unit via a connecting pipe in a sealed manner, so as to transmit the pressure wave generated by compression to the composite refrigeration unit. The composite refrigeration unit includes a primary Stirling assembly and a secondary pulse tube assembly integrated on the same axis. The secondary pulse tube assembly includes a secondary inertial tube and a gas reservoir, which serve as a phase-adjusting unit. The gas reservoir and the secondary inertial tube are integrated into a single structure and directly fixed to the primary cold-end heat exchanger of the primary Stirling assembly. This allows the secondary inertial tube and the gas reservoir to be cooled directly by the primary cold-end heat exchanger during operation, thus maintaining a low-temperature environment. The secondary inertial tube is tightly coiled in a spiral shape within the internal cavity of the gas reservoir, and the secondary inertial tube and the gas reservoir are fixed into a single structure by welding or bonding with a high thermal conductivity adhesive. The active vibration damper is rigidly connected to the cooling finger of the composite refrigeration unit.

2. The low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 1, characterized in that, The compressor piston assembly that drives the compressor is elastically supported inside the compressor housing by the compressor leaf spring assembly. The compressor motor assembly is fixed to the compressor housing and is driven by the compressor piston assembly to drive its reciprocating motion. The compressor piston assembly, compressor leaf spring assembly and compressor motor assembly are all arranged opposite each other. The compressor displacement sensor is arranged at the tail end of the piston assembly to detect its displacement.

3. The low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 1, characterized in that, The first stage Stirling assembly's first stage ejector is elastically supported within the first stage ejector housing by a cold finger leaf spring assembly. The moving part of the cold finger phase-shifting motor is connected to the first stage ejector via a transmission connection. A cold finger displacement sensor is arranged at the tail end of the first stage ejector to detect its displacement.

4. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 1, characterized in that, The secondary pulse tube assembly adopts a coaxial structure, with its annular secondary accumulator surrounding and sleeved on the outside of the tubular secondary pulse tube. The low-temperature end of the secondary accumulator is connected to the secondary cold-end heat exchanger.

5. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 1, characterized in that, The balance mass block of the active damper is elastically supported inside the damper housing by the damper leaf spring assembly. The moving part of the damping motor is connected to the balance mass block for transmission. The self-sensing displacement sensor is arranged at the tail end of the first-stage discharger to detect its motion state.

6. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 2, characterized in that, It also includes a control system, and the signals from the compressor displacement sensor, the cold finger displacement sensor, and the self-induction displacement sensor are all connected to the control system.

7. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 6, characterized in that, The control system controls the driving voltage of the compressor motor assembly and the cold finger phase-adjusting motor respectively according to the detection signals of the compressor displacement sensor and the cold finger displacement sensor, and controls the vibration damping motor to drive the balance mass block to generate a compensating motion opposite to the motion of the first-stage discharger according to the detection signal of the self-induction displacement sensor.

8. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 1, characterized in that, The outer wall of the gas storage facility is entirely covered with an insulation layer composed of multiple layers of highly reflective thin films.

9. A low-vibration active phase-modulation composite pulse tube Stirling refrigerator according to claim 6, characterized in that, The control system integrates a unified control unit, which synchronously processes the signals from the compressor displacement sensor, cold finger displacement sensor, and self-induction displacement sensor, and collaboratively outputs drive commands for the compressor motor assembly, cold finger phase-adjusting motor, and vibration damping motor.

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