A dual cold head linear cryogenic refrigerator with a high power-to-weight ratio

Abstract

The present invention discloses a dual cold head linear cryogenic refrigerator with a high power-to-weight ratio, which comprises a linear compressor, two cold fingers and two connecting pipes; wherein, the linear compressor has two axially symmetrically arranged air outlets, and the two air outlets are respectively connected to the air inlets of the two cold fingers through the connecting pipes. The present invention solves the problem of piston offset of the linear compressor, improves the overall efficiency of the machine, enables two sets of detector chip systems to work independently and with high reliability, and has a small size, light weight and high power-to-weight ratio.

Description

Technical Field

[0001] The present invention relates to the field of linear cryogenic refrigerators, including linear Stirling refrigerators and linear pulse tube refrigerators, and particularly relates to a dual-cooling-head linear cryogenic mechanical refrigerator with a high power-to-weight ratio. Background Art

[0002] Infrared detectors are the core components of infrared detection, infrared night vision, and infrared guidance devices. Stirling refrigerators and pulse tube refrigerators are widely used in military and civilian scenarios such as space and ground infrared detection, infrared night vision, and infrared guidance. Cryogenic mechanical refrigerators provide a low-temperature environment for detector chips, which can reduce noise and improve imaging quality, and are the core components of infrared detectors.

[0003] Aviation, aerospace, and weapon-class infrared detectors require refrigerators to comply with the SWaP principle, that is, small size (Size), light weight (Weight), and high performance (Performance), which requires the refrigerator to have a high power-to-weight ratio (the ratio of input power to weight).

[0004] Infrared detectors that can simultaneously identify multiple bands such as short-wave, medium-wave, and long-wave can meet the detection requirements in complex environments and are becoming a research and application hotspot. Multi-cooling-head cryogenic refrigerators are an important technical route to realize multi-band infrared detectors. Summary of the Invention

[0005] The object of the present invention is to provide a dual-cooling-head linear cryogenic mechanical refrigerator with a high power-to-weight ratio, which solves the problem of piston offset of the linear compressor, improves the overall efficiency of the machine, can realize the independent and highly reliable operation of two sets of detector chip systems, and has a small size, light weight, and high power-to-weight ratio.

[0006] To achieve these objects and other advantages of the present invention, a dual-cooling-head linear cryogenic mechanical refrigerator is provided, including a linear compressor, two cold fingers, and two connecting pipes; wherein,

[0007] The linear compressor has two axially symmetrically arranged air outlets, and each of the two air outlets is connected to the air inlet of one of the two cold fingers through a connecting pipe.

[0008] According to a preferred embodiment of the present invention, the linear compressor includes a compressor housing, a linear motor, and two sets of support compression systems arranged in reverse axial symmetry; the linear motor and the support compression systems are both arranged in the compressor housing;

[0009] The support compression system includes a cylinder and a piston sliding in the cylinder, and the cylinders of the two sets of support compression systems are respectively communicated with the two air outlets; the linear motor is arranged to drive the pistons of the two sets of support compression systems to move.

[0010] According to a preferred embodiment of the present invention, the linear motor includes an outer yoke, a coil, a permanent magnet, an inner yoke, and a mover skeleton;

[0011] Both ends of the permanent magnet are axially symmetrically connected to a pair of mover skeletons. An inner yoke is disposed at intervals inside the permanent magnet, and an outer yoke is disposed at intervals outside the permanent magnet. The coil is embedded in the outer yoke, and the mover skeleton is connected to the piston of the support compression system.

[0012] According to a preferred embodiment of the present invention, the support compression system further includes a leaf spring; the piston is disposed in the compressor through the leaf spring.

[0013] According to a preferred embodiment of the present invention, the leaf spring realizes the clearance seal between the piston and the cylinder.

[0014] According to a preferred embodiment of the present invention, a plurality of leaf springs are provided on each piston, and the number of leaf springs on the pistons at both ends is the same.

[0015] According to a preferred embodiment of the present invention, the cold finger is a Stirling type cold finger or a pulse tube type cold finger.

[0016] According to a preferred embodiment of the present invention, the cold finger is a Stirling type cold finger, which includes: a cold finger cavity, a displacer piston, a regenerator, a spring, and a cold finger back pressure cavity;

[0017] The regenerator divides the cold finger cavity into an expansion cavity and a room temperature cavity. One end of the displacer piston is connected to the regenerator, and the other end of the displacer piston penetrates from the room temperature cavity into the cold finger back pressure cavity and is connected to the spring. The spring is fixed to the bottom of the cold finger back pressure cavity.

[0018] According to a preferred embodiment of the present invention, the communication channel between the cold finger back pressure cavity and the greenhouse cavity is in clearance fit with the displacer piston.

[0019] The present invention has at least the following beneficial effects:

[0020] 1) Small size, light weight, and high power-to-weight ratio

[0021] The new high power-to-weight ratio double piston linear compressor adopts a structural form of a single motor driving two sets of axially symmetric pistons in opposite directions, and couples two sets of cold fingers, which has one less set of motor systems than a conventional double cold finger refrigerator, significantly reducing the size of the refrigerator, reducing the weight, and increasing the power-to-weight ratio.

[0022] 2) Solve the problem of piston offset of the linear compressor and improve the overall efficiency of the machine

[0023] Two sets of reverse and identical piston-cylinder systems balance the resultant force on the compressor mover, eliminating axial offset static force, thus fundamentally solving the piston offset problem. The absence of piston offset allows the compressor to operate at full stroke, increasing the input power, power-to-weight ratio, motor efficiency, and overall efficiency of the machine.

[0024] 3) Two sets of detector chip systems can operate independently and with high reliability

[0025] Adopting an air-circuit independent dual cold finger structure, there is no problem of uneven gas distribution between the two cold fingers, enabling the two infrared detectors to operate independently, and improving the stability and reliability of the detectors.

[0026] Other advantages, objectives, and features of the present invention will be partially reflected by the following description, and partially will also be understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a dual cold-head high power-to-weight ratio linear cryogenic mechanical refrigerator in an embodiment of the present invention.

[0028] Figure 2 It is a schematic structural diagram of a linear compressor in another embodiment of the present invention.

[0029] Figure 3 It is a schematic structural diagram of a Stirling-type cold finger in another embodiment of the present invention.

[0030] Description of the reference numerals: 1 left cold finger, 2 right cold finger, 3 connecting pipe, 4 infrared chip, 5 air outlet, 6 compressor housing, 7 left piston, 8 right piston, 9 outer magnetic yoke, 10 coil, 11 permanent magnet, 12 inner magnetic yoke, 13 mover skeleton, 14 cylinder, 15 leaf spring, 16 push piston, 17 regenerator, 18 spring, 19 cold finger back pressure chamber, 20 room temperature chamber, 21 expansion chamber, 22 air inlet. DETAILED DESCRIPTION OF THE INVENTION

[0031] The following further elaborates on the present invention in conjunction with the drawings, enabling those skilled in the art to implement it with reference to the written description.

[0032] The following description is used to disclose the present invention so that those skilled in the art can implement it. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles defined in the following description can be applied to other embodiments, variations, improvements, equivalent solutions, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0033] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationship indicated by terms such as "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0034] It can be understood that the term "one" should be understood as "at least one" or "one or more". That is, in one embodiment, the number of an element can be one, while in other embodiments, the number of the element can be multiple. The term "one" should not be construed as a limitation on the quantity.

[0035] Considering that the conventional linear compressor adopts a single linear motor and single piston structure, and the form of placing two compressors axially symmetrically, there are problems such as large volume, heavy mass, small power-to-weight ratio, piston offset, low efficiency, etc., and it cannot well meet the requirements of lightweight and high power-to-weight ratio of the detector.

[0036] As Figures 1 to 3 shown, the embodiment of the present invention provides a dual-cooling-head high power-to-weight ratio linear cryogenic mechanical refrigerator, which includes a linear compressor, two cold fingers (as Figure 1 shown, which are the left cold finger 1 and the right cold finger 2 respectively) and two connecting pipes 3. In this embodiment, the two infrared chips 4 symmetrically arranged thereon are cooled by the dual-cooling-head high power-to-weight ratio linear cryogenic mechanical refrigerator. Among them, the linear compressor has two axially symmetrically arranged air outlets 5, and each of the two air outlets 5 is connected to the air inlets 22 of the two cold fingers through a connecting pipe 3 respectively. The linear compressor includes a compressor housing 6, a linear motor, and two sets of support compression systems arranged axially symmetrically in the reverse direction; the linear motor and the support compression system are both arranged in the compressor housing 6; the support compression system includes a cylinder 14 and a piston sliding in the cylinder, and the cylinders of the two sets of support compression systems are respectively communicated with the two air outlets 5; the linear motor is arranged to drive the pistons of the two sets of support compression systems to move.

[0037] In the above implementation, the dual-cooling-head high power-to-weight ratio linear cryogenic mechanical refrigerator adopts a structure form of a single linear motor driving two sets of pistons axially symmetrically in the reverse direction, and couples two sets of cold fingers. The linear motor powered by sinusoidal alternating current drives the left piston 7 and the right piston 8 to reciprocate with a phase difference of 180°. The working medium gas is compressed and expanded in the two sets of cylinders 14 respectively, providing a periodic pressure wave for the cold fingers. It has one less set of motor systems than the conventional dual-cooling-finger refrigerator, bringing advantages such as smaller overall size, lighter weight, lower cost, and higher power-to-weight ratio.

[0038] In this embodiment, two sets of reverse and identical support compression systems balance the resultant force on the compressor mover skeleton 13, eliminating the axial offset static force. Thus, the problem of piston axial offset is fundamentally solved. The piston's lack of offset allows the linear compressor to operate at full stroke, improving the input power, work-to-weight ratio, motor efficiency, and overall efficiency of the machine.

[0039] Moreover, a pair of cold fingers in this application are connected to a single linear compressor, changing the way that a single cryocooler cold head cools a single multi-band infrared chip in a multi-band infrared detector. This reduces the high development difficulty of the infrared chip and the detection system and also reduces the overall cost.

[0040] Conventional dual cold finger cryogenic mechanical refrigerators use a Y-shaped structure, that is, a single gas path of a conventional linear compressor is divided into two paths to drive two sets of cold fingers respectively, which has problems such as uneven gas path distribution between the two cold fingers, mutual influence, and low reliability. In some embodiments of the present invention, the structure of the linear motor is improved:

[0041] The linear motor includes an outer yoke 9, a coil 10, a magnet 11, an inner yoke 12, and a mover skeleton 13; both ends of the magnet 11 are axially symmetrically connected to a pair of mover skeletons 13. An inner yoke 12 is arranged at intervals inside the magnet 11, and an outer yoke 9 is arranged at intervals outside the magnet 11. The coil 10 is embedded in the outer yoke 9, and the mover skeleton 13 is connected to the piston of the support compression system. When a sinusoidal alternating current is passed through the coil 10, an alternating magnetic field is formed in the air gap between the outer yoke 9 and the inner yoke 12. The radially magnetized magnet 11 makes a linear reciprocating motion in the alternating magnetic field. The piston and the magnet 11 adopt a rigid connection structure form and are connected through the mover skeleton 13. Driven by the magnet 11, the piston also makes a linear reciprocating motion. At the same time, the gas at the front end of the piston is successively compressed and discharged and expanded and inhaled, and so on in a cycle.

[0042] In some embodiments of the present invention, the support compression system further includes a leaf spring 15; the piston is arranged in the compressor through the leaf spring 15, as Figure 1 shown, the pistons of the two sets of support compression systems are the left piston 7 and the right piston 8 respectively. The leaf spring 15 has a large radial stiffness, supports the entire moving part, and ensures that the piston does not contact the cylinder 14, thus realizing characteristics such as oil-free operation, low friction, and long life.

[0043] In some embodiments of the present invention, the leaf spring realizes gap sealing between the piston and the cylinder, and the air outlet 5 is axially symmetrically arranged on the compressor housing 6; the cylinder 14 is arranged at the air outlet 5 of the housing. Driven by the mover skeleton 13, the piston makes a reciprocating motion in the cylinder 14, and the pressurized working medium gas is sent into the cold finger through the air outlet 5 and the connecting pipe 3 for endothermic expansion.

[0044] In some embodiments of the present invention, a plurality of leaf springs 15 are provided on each piston, and the number of leaf springs 15 on the pistons at both ends is the same. The axial stiffness of the leaf spring 15 provides axial freedom for the linear movement of the piston, and its maximum axial stroke is limited by the fatigue limit of the material of the leaf spring 15.

[0045] In some embodiments of the present invention, the cold finger is a Stirling type cold finger or a pulse tube type cold finger. The difference between the two is that the Stirling type cold finger has moving parts, namely a displacer piston. The overall efficiency of a refrigerator equipped with a Stirling type cold finger is usually higher than that of a refrigerator equipped with a pulse tube type cold finger; while the pulse tube type cold finger has no moving parts, so the reliability of a refrigerator equipped with a pulse tube type cold finger is usually higher than that of a refrigerator equipped with a Stirling type cold finger.

[0046] In some embodiments of the present invention, the cold finger is a Stirling type cold finger, which includes: a cold finger cavity, a displacer piston 16, a regenerator 17, a spring 18, and a cold finger back pressure cavity 19; the regenerator 17 divides the cold finger cavity into an expansion cavity 21 and a room temperature cavity 20. The room temperature cavity 20 is connected to the connecting pipe 3. One end of the displacer piston 16 is connected to the regenerator 17, and the other end of the displacer piston 16 penetrates from the room temperature cavity 20 into the cold finger back pressure cavity 19 and is connected to the spring 18. The spring 18 is fixed to the bottom of the cold finger back pressure cavity 19. The communication channel between the cold finger back pressure cavity 19 and the greenhouse cavity is in clearance fit with the displacer piston 16. The pressurized working medium gas enters the room temperature cavity 20 through the connecting pipe 3 for expansion and heat absorption. Adopting an air path independent double cold finger structure, there is no problem of uneven gas distribution between the two cold fingers, and the two sets of infrared detectors can work independently, improving the stability and reliability of the detectors.

[0047] The working process of the double cold head high power-to-weight ratio linear cryogenic mechanical refrigerator: The linear compressor is supplied with sinusoidal alternating current. The working medium gas (such as helium) is compressed and pressurized in the two sets of support compression systems of the linear compressor. The pressurized working medium gas enters the left cold finger 1 and the right cold finger 2 respectively through the connecting pipe for expansion and heat absorption. The infrared chip 4 located at the cold head of the cold finger is cooled. The gas expanded in the cold finger is sucked into the connecting pipe and then enters the compressor, and the whole cycle is completed in a form combining pneumatic and electric drive. Specifically, when the compressor mover moves to the left under the action of the electromagnetic force of the motor, such as Figure 1As shown in the figure, the left piston 7 moves leftward to compress the gas. The pressurized gas enters the left cold finger 1 through the left connecting pipe 3. The gas pressure in the left room temperature chamber 20 of the left cold finger 1 is greater than the gas pressure in the left cold finger back pressure chamber 19. The left push piston 16 moves toward the spring 18 under the action of the gas force. The gas is cooled after passing through the left regenerator 17 and then enters the left expansion chamber 21. At the same time, the right piston 8 moves leftward to inhale the gas. The gas pressure in the right room temperature chamber 20 decreases. The gas pressure in the right cold finger back pressure chamber 19 is greater than the gas pressure in the right room temperature chamber 20. The right push piston 16 moves toward the right expansion chamber 21 under the action of the gas force. The gas in the right expansion chamber 21 is heated after passing through the right regenerator 17 and then enters the right room temperature chamber 20, and then is inhaled into the right cylinder 14 through the right connecting pipe 3. When the compressor mover moves rightward under the action of the motor electromagnetic force, the left piston 7 moves rightward to inhale the gas. The gas pressure in the left room temperature chamber 20 decreases. The gas pressure in the left cold finger back pressure chamber 19 is greater than the gas pressure in the left room temperature chamber 20. The left push piston 16 moves toward the left expansion chamber 21 under the action of the gas force. The gas in the left expansion chamber 21 is heated after passing through the left regenerator 17 and then enters the left room temperature chamber 20, and then is inhaled into the left cylinder 14 through the left connecting pipe 3. At the same time, the right piston 8 moves rightward to compress the gas. The pressurized gas enters the right cold finger 2 through the right connecting pipe 3. The gas pressure in the right room temperature chamber 20 of the right cold finger 2 is greater than the gas pressure in the right cold finger back pressure chamber 19. The right push piston 16 moves toward the spring 18 under the action of the gas force. The gas is cooled after passing through the right regenerator 17 and then enters the right expansion chamber 21, completing the entire working cycle.

[0048] Although the embodiments of the present invention have been disclosed as above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the illustrated and described examples here.

Claims

1. A linear low-temperature mechanical refrigerator with two cold heads and a high power-to-weight ratio, characterized in that, It includes a linear compressor, two cold fingers and two connecting pipes; wherein, the linear compressor has two axially symmetrically arranged air outlets, and each of the two air outlets is connected to the air inlets of the two cold fingers through a connecting pipe respectively, forming an air path independent dual cold finger structure; the cold finger is a Stirling type cold finger; The linear compressor includes a compressor housing, a linear motor and two sets of support compression systems arranged in reverse axial symmetry; the linear motor and the support compression systems are both arranged in the compressor housing; the support compression system includes a cylinder and a piston sliding in the cylinder, and the cylinders of the two sets of support compression systems are respectively communicated with the two air outlets; the linear motor is arranged to drive the pistons of the two sets of support compression systems to move.

2. The dual-cooling-head high power-to-weight ratio linear cryogenic mechanical refrigerator according to claim 1, wherein The linear motor includes an outer yoke, a coil, a magnet, an inner yoke and a mover skeleton; both ends of the magnet are axially symmetrically connected with a pair of mover skeletons, an inner yoke is arranged at intervals in the inner circle of the magnet, an outer yoke is arranged at intervals in the outer circle of the magnet, the coil is embedded in the outer yoke, and the mover skeleton is connected to the piston of the support compression system.

3. A dual cold head high power-to-weight ratio linear cryogenic mechanical refrigerator according to claim 1, characterized in that, The support compression system further includes a leaf spring; the piston is arranged in the compressor through the leaf spring.

4. A dual cold head high power-to-weight ratio linear cryogenic mechanical refrigerator according to claim 3, characterized in that, The leaf spring realizes the clearance seal between the piston and the cylinder.

5. A dual cold head high power-to-weight ratio linear low temperature mechanical refrigerator according to claim 3, characterized in that A plurality of leaf springs are arranged on each piston, and the number of leaf springs on the pistons at both ends is the same.

6. The linear low-temperature mechanical refrigerator with a high power-to-weight ratio and two cold heads according to claim 1, wherein, The cold finger includes: a cold finger cavity, a push piston, a regenerator, a spring and a cold finger back pressure cavity; the regenerator divides the cold finger cavity into an expansion cavity and a room temperature cavity, one end of the push piston is connected to the regenerator, the other end of the push piston penetrates from the room temperature cavity into the cold finger back pressure cavity and is connected to the spring, and the spring is fixed to the bottom of the cold finger back pressure cavity.

7. A dual cold head high power-to-weight ratio linear cryogenic mechanical refrigerator according to claim 6, characterized in that, The communication channel between the cold finger back pressure cavity and the room temperature cavity is in clearance fit with the push piston.

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