Patent Description:
A micro cryocooler is mainly used to cool low-temperature optoelectronic or superconducting electronic devices to about -<NUM>, to maintain their low-temperature working environment necessary for normal operation, and thus it is an indispensable core apparatus for infrared detection systems and superconducting low-temperature electronic systems.

Currently, a mainstream technology used in the field of infrared detection is the micro linear compressor Stirling cryocooler system. In this system, one end of the compressor is connected to the expander, and they work together to achieve the compression, heat release, expansion, and heat absorption required for the refrigeration cycle. A vibration cancellation is installed at the other end of the compressor to eliminate vibrations caused by the micro linear compressor Stirling cryocooler.

However, an addition of the vibration cancellation at the end of the micro cryocooler has resulted in a larger structural size, which is not conducive to the miniaturizing the micro cryocooler. <CIT> discloses a cryocooler with a vibration absorbing unit placed in an additional reservoir which is fixedly attached to the casing of the compressor unit by a fixed shaft so as to be aligned with the vibration direction of the operating motor. The vibration is reduced by providing the vibration absorption unit with a mass body and plate springs which oppose the vibration generated by the motor in the sealed casing.

The present invention provides a cryocooler with a relatively compact structure.

The present invention provides a cryocooler as defined in claim <NUM>. It includes a shell, a compression unit, an expansion unit and a vibration damping unit, where a cavity is provided in the shell, the compression unit and the vibration damping unit are located in the cavity, the compression unit is connected to the shell, and the expansion unit is partially located in the cavity and communicates with the compression unit;
the vibration damping unit is sleeved on the compression unit, is partially located in the compression unit and is configured to reduce vibration of the cryocooler in entirety.

In one possible implementation, in the cryocooler provided in the present invention, the vibration damping unit is coaxially arranged with the compression unit, the compression unit includes a first stator and a first coil located in the first stator, the vibration damping unit includes a second coil that is located in the first stator and outside the first coil.

In one possible implementation, in the cryocooler provided in the present invention, the compression unit further includes a gas isolator, a cylinder and a first mover, the first stator is sleeved on the gas isolator, a first end of the gas isolator in an extension direction is abutted against an inner wall of a first end of the shell, and a second end of the gas isolator in the extension direction is abutted against an inner wall of a second end of the shell, so that the cavity is separated into a first cavity chamber and a second cavity chamber, and the first cavity chamber surrounds a peripheral side of the second cavity chamber.

The first stator, the first coil and the vibration damping unit are located in the first cavity chamber, the cylinder and the first mover are located in the second cavity chamber, and the first mover includes a piston and a first magnet. The piston includes a first plugging part and a connecting part connected with the first plugging part, the first plugging part is partially located in the cylinder and reciprocates along an axial direction of the cylinder. The connecting part is located outside the cylinder, and the first magnet is sleeved on the connecting part and connected with the connecting part.

In one possible implementation, in the cryocooler provided in the present invention, the compression unit further includes a second stator that is sleeved on the cylinder, and the second stator is located between the cylinder and the first magnet, and the cylinder is connected with an inner side wall of the shell.

In one possible implementation, in the cryocooler provided in the present invention, the vibration damping unit further includes a second mover including a second mover body and a second magnet, the second mover body is sleeved on the first stator, the second magnet is located in the second mover body, and both ends of the first stator are each connected with a leaf spring, and the leaf springs are connected through a first connector, and/or the leaf springs are connected with the shell through the first connector.

In one possible implementation, the cryocooler provided in the present invention further includes a circuit board that is sleeved on a first end of the gas isolator arranged between the circuit board and the expansion unit, both the compression unit and the vibration damping unit are electrically connected with the circuit board, and the circuit board is provided with an output interface that is partially located outside the shell.

In one possible implementation, in the cryocooler provided in the present invention, the vibration damping unit further includes two leaf springs and a first connector, where the two leaf springs are provided with through holes, and the first connector is connected with the leaf springs through the through holes.

The circuit board is provided with at least one connecting hole, and the first connector is in one-to-one correspondence with the connecting hole, and an end of the first connector towards the circuit board is provided with a threaded hole, and a second connector is connected with the threaded hole through the shell and the connecting hole in sequence.

In one possible implementation, in the cryocooler provided in the present invention, the shell includes a shell body and a shell cover covered on the shell body, the shell cover is provided with an installation hole that is in communication with the cylinder, an air flow channel is formed between the installation hole and the cylinder, and the expansion unit is installed to the installation hole and is coaxially arranged with the cylinder.

In one possible implementation, in the cryocooler provided in the present invention, the expansion unit includes an outer shell and an expeller, the outer shell is partially inserted in the installation hole, and the outer shell is internally provided with an accommodating cavity, an extension direction of the accommodating cavity is consistent with the axial direction of the cylinder, the accommodating cavity is communicated with the air flow channel, and the expeller is located in the accommodating cavity and reciprocates along the extension direction of the accommodating cavity.

In one possible implementation, in the cryocooler provided in the present invention, the outer shell includes a second plugging part, an abutting part and an extension part connected sequentially, where the accommodating cavity is sequentially extended from the second plugging part and the abutting part to the extension part, the second plugging part is plugged to the installation hole, the abutting part is abutted against an outer surface of the shell cover, and a first end of the expeller is located in the air flow channel and is connected with an end of the second plugging part through an elastic member, and a second end of the expeller is located in the accommodating cavity corresponding to the extension part.

In the cryocooler provided in the present invention, it is provided with a shell, a compression unit, an expansion unit and a vibration damping unit, where the shell internally has a cavity, the compression unit and the vibration damping unit are located in the cavity, the compression unit is connected with the shell, and the expansion unit is partially located in the cavity and is communicated with the compression unit, the vibration damping unit is sleeved on the compression unit and is partially located in the compression unit, and the vibration damping unit is used to reduce vibration of a whole cryocooler. In this way, the vibration damping unit is arranged in the shell, and the vibration damping unit and the compression unit share part of their structure and magnetic circuit, so that the cryocooler has a more compact structure, smaller size, and lighter weight, which is conducive to the miniaturization and lightweighting of the cryocooler. The vibration damping unit adopts an active damping technology, and can eliminate or reduce the high-frequency vibration generated by the compression unit and the expansion unit, and thus the cryocooler has a better vibration damping effect.

Preferred implementations of the present invention are described below with reference to the accompanying drawings. The accompanying drawings are as below.

In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be described in more detail below in combination with the accompanying drawings in the preferred embodiments of the present invention.

The same or similar signs throughout the accompanying drawings represent the same or similar parts or components with the same or similar functions. The embodiments described are some but not all of the embodiments of the present invention.

The embodiments described below by reference to the accompanying drawings are exemplary and are intended to interpret the present invention.

The embodiments of the present invention are described in detail below in combination with the accompanying drawings.

In the description of the present invention, it is to be noted that unless otherwise clearly indicated and defined, the terms "installation", "communication" and "connection" shall be understood in a broad sense, for example, they may refer to a fixed connection, or an indirect connection through an intermediate medium, or they can refer to an internal connection of two components or an interaction of two components. For those skilled in this field, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

In the description of the present invention, it should be understood that terms "up", "down", "front", "back", "vertical", "horizontal", "top", "bottom", "inside" and "outside" is based on the azimuth or position relationship of the accompanying drawings, and is only for the purpose of convenient description of the present application and simplification of description, rather than indicating or implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific direction, it cannot be understood as a restriction on the present invention.

The terms "first", "second" and "third" (if any) in the specification, claims and the above accompanying drawings of the present invention are used to distinguish similar objects and not to describe a particular order or priority. It should be understood that the data so used are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described here.

In addition, the terms "include" and "have" and any of their variations are intended to cover non-exclusive inclusions, for example, processes, methods, systems, products or displays that contain a series of steps or units need not to be limited to those clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or displays.

The micro cryocooler is mainly used to cool the cryogenic optoelectronic or superconducting electronic devices to about -<NUM> so as to maintain their low-temperature operating environment necessary for normal operation. It is an indispensable core apparatus for infrared detection system and superconducting cryogenic electronic system. The Stirling cryocooler has the advantages of high efficiency, fast refrigeration, small size, light weight, low power consumption and high reliability, so the micro Stirling cryocooler is widely used in the field of infrared detectors and cryogenic superconductors.

At present, the micro linear compressor Stirling cryocooler system is mainly used in the field of infrared detection, one end of a compressor of the micro linear compressor Stirling cryocooler is connected with an expander, so that a refrigeration cycle of compression, heat release, expansion and heat absorption is realized through a joint action of the compressor and the expander. The other end of the compressor is provided with a vibration damper to eliminate the vibration of the micro linear compressor Stirling cryocooler.

However, due to addition of the vibration damper at the end, the structure of the micro linear compressor Stirling cryocooler is large in size and weight, which is not conducive to the miniaturization and lightweighting of the micro linear compressor Stirling cryocooler. Furthermore, the damper usually uses passive damping to eliminate the vibration of the compressor, or uses flexible connection between the micro linear compressor Stirling cryocooler and the outside to block the transmission path of vibration. However, this passive vibration damping method can only eliminate low-frequency and medium-frequency vibrations of the micro linear compressor Stirling cryocooler, but not eliminate high frequency vibration of the micro linear compressor Stirling cryocooler.

Based on this, an embodiment of the present invention provides a cryocooler, which has advantages of compact structure, small size and light weight.

<FIG> is a schematic structural diagram of a cryocooler provided in an embodiment of the present invention; <FIG> is a schematic structural diagram of a rear side of the cryocooler provided in an embodiment of the present invention; <FIG> is a section view taken along A-A in <FIG>. Referring to <FIG>, the cryocooler provided by the embodiment of the present invention includes a shell <NUM>, an expansion unit <NUM>, a compression unit <NUM> and a vibration damping unit <NUM>, where the shell <NUM> is internally provided with a cavity <NUM>, and the compression unit <NUM> and the vibration damping unit <NUM> are located in the cavity <NUM>, the compression unit <NUM> is connected with the shell <NUM>, and the expansion unit <NUM> is partially located in the cavity <NUM> and is communicated with the compression unit <NUM>.

The vibration damping unit <NUM> is sleeved on the compression unit <NUM>, the vibration damping unit <NUM> is partially located in the compression unit <NUM>, and the vibration damping unit <NUM> is used to reduce the vibration of the cryocooler.

In order to make the overall appearance of the cryocooler more concise and beautiful and the structure more compact, the compression unit <NUM> and the vibration damping unit <NUM> are arranged in the shell <NUM>, and the expansion unit <NUM> is partially located in the shell <NUM>, a part of the expansion unit <NUM> outside the shell <NUM> is connected with an external apparatus to refrigerate and cool the external apparatus. The compression unit <NUM> is used to upgrade a low-pressure gas working medium to a high-pressure gas working medium, and the compression unit <NUM> drives, by rotation of a motor, a mover to compress the gas working medium, providing power for the expansion unit <NUM> and outputting the compressed gas working medium to the expansion unit <NUM>. The expansion unit <NUM> uses mechanical work outputted outwardly during expansion and depressurization of the compressed gas working medium to consume an internal energy of the gas working medium itself, so that the temperature of the gas working medium can be greatly reduced, thereby achieving the purpose of refrigerating and cooling.

The vibration damping unit <NUM> is sleeved on the compression unit <NUM>, and the vibration damping unit <NUM> and the compression unit <NUM> shares part of the structure and magnetic circuit, thereby simplifying the structure of the cryocooler, and thus the cryocooler is more compact in structure and smaller in size and weight, which is beneficial to the miniaturization and lightweighting of the cryocooler. The vibration damping unit <NUM> adopts an active vibration damping mode, and the vibration damping unit <NUM> can eliminate or reduce a high-frequency vibration generated by the compression unit <NUM> and the expansion unit <NUM>, and thus the cryocooler has better vibration damping effect.

It should be understood that the cryocooler may further includes a heat exchange unit, and the heat exchange unit is located outside the cavity <NUM> and is covered on the expansion unit <NUM>. In a specific implementation, the heat exchange unit can adopt a heat exchanger made of copper, and the heat exchange unit can increase heat capacity of the cryocooler, so that a refrigeration temperature of the cryocooler is more uniform. In a specific implementation, it can be set according to the requirements for use of the cryocooler, and is not restricted by the present embodiment.

<FIG> is a partial enlarged view of B in <FIG>. Referring to <FIG>, as an optional implementation, the vibration damping unit <NUM> is coaxially arranged with the compression unit <NUM>, the compression unit <NUM> includes a first stator <NUM> and a first coil <NUM> located within the first stator <NUM>. The vibration damping unit <NUM> includes a second coil <NUM>, and the second coil <NUM> is located in the first stator <NUM> and is located outside the first coil <NUM>.

Most of the parts in the shell <NUM>, the expansion unit <NUM>, the compression unit <NUM> and the vibration damping unit <NUM> are rotary parts, and the expansion unit <NUM>, the compression unit <NUM> and the vibration damping unit <NUM> are of a coaxial design, that is, central axes of the rotary parts in the expansion unit <NUM>, the compression unit <NUM> and the vibration damping unit <NUM> are coincident. In the description of subsequent embodiments, unless otherwise specified, a central axis refers to a central axis of the expansion unit <NUM>.

In order to fix the first coil <NUM> and the second coil <NUM>, a plurality of annular grooves <NUM> are provided in the first stator <NUM>, and the first coil <NUM> and the second coil <NUM> are sequentially arranged in different annular grooves <NUM> of the first stator <NUM>, so that the first coil <NUM> and the second coil <NUM> can share the first stator <NUM>, the vibration damping unit <NUM> does not need to set additional stator for fixing the second coil <NUM>, and the vibration damping unit <NUM> and the compression unit <NUM> can share part of the magnetic circuit, simplifying the structure of the vibration damping unit <NUM> and the compression unit <NUM>, and thereby achieving more compact structure and a lighter weight of the cryocooler.

Referring to <FIG>, in some embodiments, the compression unit <NUM> further includes a gas isolator <NUM>, a cylinder <NUM> and a first mover <NUM>, where the first stator <NUM> is sleeved on the gas isolator <NUM>, a first end of the gas isolator <NUM> in an extension direction thereof is abutted against an inner wall of a first end of the shell <NUM>, and a second end of the gas isolator <NUM> in the extension direction is abutted against an inner wall of a second end of the shell <NUM>, to separate the cavity <NUM> into a first cavity chamber <NUM> and a second cavity chamber <NUM>, and the first cavity chamber <NUM> surrounds a peripheral side of the second cavity chamber <NUM>.

The first stator <NUM>, the first coil <NUM> and the vibration damping unit <NUM> are located in the first cavity chamber <NUM>, the cylinder <NUM> and the first mover <NUM> are located in the second cavity chamber <NUM>, and the first mover <NUM> includes a piston <NUM> and a first magnet <NUM>. The piston <NUM> includes a first plugging part <NUM> and a connecting part <NUM> connected with the first plugging part <NUM>, the first plugging part <NUM> is partially located in the cylinder <NUM> and reciprocates in an axial direction of the cylinder <NUM>. The connecting part <NUM> is located outside the cylinder <NUM>, and the first magnet is sleeved on the connecting part <NUM> and connected with the connecting part <NUM>.

It is understandable that a direction of the expansion unit <NUM> away from the shell <NUM> is a front end of the cryocooler, and correspondingly, an opposite direction is a tail end of the cryocooler. The gas isolator <NUM> is a cylindrical part with an opening at one end, a direction of the opening of the gas isolator <NUM> is the same direction as that of the front end of the cryocooler, and there is an extension edge at the opening of the gas isolator <NUM>, and the extension edge of the gas isolator <NUM> is abutted against the inner wall of the shell <NUM> at the front end of the cryocooler, the other end of the gas isolator <NUM> is abutted against the inner wall of the shell <NUM> at the tail end of the cryocooler. In this way, the gas isolator <NUM> can divide the cavity <NUM> of the shell <NUM> into two parts, namely, the second cavity chamber <NUM>, which is a cavity chamber in the gas isolator <NUM>; and the first cavity chamber <NUM>, i.e., a part enclosed between the outer side wall of the gas isolator <NUM> and the inner side wall of the shell <NUM>, which is isolated from the second cavity chamber <NUM>. The first stator <NUM>, the first coil <NUM> and the vibration damping unit <NUM> are located in the first cavity chamber <NUM>, and the cylinder <NUM> and the first mover <NUM> are located in the second cavity chamber <NUM>. In this way, the gas isolator <NUM> can set the first coil <NUM> and the first stator <NUM> on the outside of the compression unit <NUM> to achieve the purpose that the compression unit <NUM> and the vibration damping unit <NUM> share the first stator <NUM>, thereby making the cryocooler have a more compact structure and a lighter weight.

The connecting part <NUM> is provided with an annular groove, the first magnet <NUM> is arranged in the annular groove, and there is a gap between the first magnet <NUM> and the inner wall of the gas isolator. The cylinder <NUM> is fixed to the shell <NUM>, and there is a gap between the first plugging part <NUM> and the inner wall of the cylinder <NUM>. When the cryocooler is working, an alternating current is passed through the first coil <NUM>, thereby generating an alternating magnetic field. The alternating magnetic field drives the first magnet <NUM> to reciprocate along the central axis. The piston <NUM>, under the drive of the first magnet <NUM>, can reciprocate relative to the cylinder <NUM> along the central axis, and the gas working medium in the cylinder <NUM> reciprocates under the drive of the piston <NUM>. An alternating pressure fluctuation is produced in the compression cavity enclosed by the first plugging part <NUM>, the inner wall of the cylinder <NUM> and the shell <NUM>, and the gas working medium is compressed and releases heat in the compression unit <NUM> and expands and absorbs heat in the expansion unit <NUM>, thereby realizing a refrigeration cycle of compression, heat release, expansion and heat absorption. The gas working medium may be helium or other refrigerating gases, and the present embodiment does not limit this.

Referring to <FIG>, as an optional embodiment, the compression unit <NUM> further includes a second stator <NUM>, the second stator <NUM> is sleeved on the cylinder <NUM> and located between the cylinder <NUM> and the first magnet <NUM>, and the cylinder <NUM> is connected to the inner side wall of the shell <NUM>.

Specifically, the second stator <NUM> is located in the second cavity chamber <NUM>, and the second stator <NUM> is located between the cylinder <NUM> and the connecting part <NUM>. There is a gap between the connecting part <NUM> and the second stator <NUM>, and there is a gap between the connecting part <NUM> and the inner wall of the gas isolator <NUM>, so that the piston <NUM> may reciprocate along the central axis relative to the second stator <NUM> and the cylinder <NUM>. The second stator <NUM> is located on a side of the first magnet <NUM> near the central axis, and the first stator <NUM> is located on a side of the first magnet <NUM> away from the central axis. When the cryocooler is working, an alternating current is passed through the first coil <NUM>, and an alternating magnetic field is generated in the first stator <NUM>, the second stator <NUM> and the first magnet <NUM> to drive the first magnet <NUM> to reciprocate along the central axis, thereby driving the piston <NUM> to reciprocate along the central axis so as to compress the gas working medium. A side of the cylinder <NUM> near the front end of the cryocooler is abutted against the inner side wall of the shell <NUM>, and the second stator <NUM> is abutted against a side of the cylinder <NUM> near the tail end of the cryocooler, thereby fixing the cylinder <NUM> and the second stator <NUM> to the shell <NUM>. Where the first magnet <NUM> may be a permanent magnet.

Referring to <FIG>, as an optional implementation, the vibration damping unit <NUM> further includes a second mover <NUM>, the second mover <NUM> includes a second mover body <NUM> and a second magnet <NUM>, where the second mover body <NUM> is sleeved on the first stator <NUM>, the second magnet <NUM> is located in the second mover body <NUM>, both ends of the first stator <NUM> are each connected with a leaf spring <NUM>, and the leaf springs <NUM> are connected by a first connector <NUM> and/or the leaf springs <NUM> are connected with the shell <NUM> through the first connector <NUM>.

Specifically, the first coil <NUM> and the second coil <NUM> are sequentially set in the annular groove <NUM> of the first stator <NUM>, the second mover body <NUM> is sleeved on the first stator <NUM>, and the second magnet <NUM> is located in the second rotor body <NUM> on a side near the central axis, and the first coil <NUM> is located on a side of the first stator <NUM> near the central axis, and the second mover <NUM> is located on a side of the first stator <NUM> away from the central axis. When the cryocooler is working, an alternating current is passed through the second coil <NUM>, thereby generating an alternating magnetic field, the alternating magnetic field drives the second magnet <NUM> to reciprocate along the central axis, thereby driving the second mover body <NUM> to reciprocate along the central axis, and a direction of motion of the second mover <NUM> is opposite to that of the first mover <NUM>, so as to eliminate or reduce the vibration of the compression unit <NUM>, so as to achieve the purpose of reducing vibration of the cryocooler. Both ends of the first stator <NUM> are each connected with a leaf spring <NUM>, and the first stator <NUM>, the first coil <NUM>, the second coil <NUM> and the second mover <NUM> form a mass block, and the leaf spring <NUM> is a spring. As such, the mass block and the spring form a vibration damping system to eliminate or reduce the vibration of the compression unit <NUM> and the expansion unit <NUM>. In a specific implementation, a resonant frequency of the leaf spring <NUM> is designed to be consistent with or close to the resonant frequency of the compression unit <NUM> according to different powers of the cryocooler, which can reduce the energy consumed by the vibration damping unit <NUM> due to actively eliminating or reducing the vibration of the cryocooler. As a result, the cryocooler is more energy efficient. Where the second magnet <NUM> may be a permanent magnet.

The leaf spring <NUM> includes a first leaf spring <NUM> and a second leaf spring <NUM>, and both the first leaf spring <NUM> and the second leaf spring <NUM> are provided with through holes, and the first connector <NUM> passes through the through holes of the first leaf spring <NUM> and the second leaf spring <NUM> so as to connect the first leaf spring <NUM> and the second leaf spring <NUM>. A diameter of a side of the first connector <NUM> near the tail end of the cryocooler is larger than inner diameters of the through holes, and the first connector <NUM> runs through the through hole of the first leaf spring <NUM> so that the first leaf spring <NUM> abuts against the first connector <NUM>. A side of the first connector <NUM> near the front end of the cryocooler is provided with an external thread, and the first connector <NUM> runs through the through hole of the second leaf spring <NUM>, and the first leaf spring <NUM> and the second leaf spring <NUM> are fixedly connected to the first connector <NUM> by fitting the external thread with a nut <NUM>. The side of the first connector <NUM> near the tail end of the cryocooler is threaded with the shell <NUM> to fix the leaf spring <NUM> to the shell <NUM>.

The leaf spring <NUM> may be an annular leaf spring, and the first connector <NUM> may be a stud, bolt or other fastening connector, the present embodiment has no limitation on this.

Referring to <FIG>, in some implementations, the cryocooler further includes a circuit board <NUM>. The circuit board <NUM> is sleeved on the first end of the gas isolator <NUM>, the gas isolator <NUM> is located between the circuit board <NUM> and the expansion unit <NUM>. Both the compression unit <NUM> and the vibration damping unit <NUM> are electrically connected to the circuit board <NUM>, i.e., the circuit board <NUM> shared by the compression unit <NUM> and the vibration damping unit <NUM>, and the circuit board <NUM> is provided with an output interface <NUM>, and the output interface <NUM> is partially located outside the shell <NUM>.

The circuit board <NUM> is sleeved on the side of the gas isolator <NUM> near the tail end of the cryocooler, and the circuit board <NUM> is abutted against the inner wall of the shell <NUM> near the tail end of the cryocooler. In this way, the structure of the cryocooler is more compact and the weight of the cryocooler is lighter, and the external electromagnetic radiation of the motor driving pulse is reduced at the same time. The circuit board <NUM> has an output interface <NUM> reserved outside the shell, and a flexible printed circuit <NUM> is electrically connected with the circuit board <NUM> through the output interface <NUM>, so as to realize the drive and control of the compression unit <NUM> and the vibration damping unit <NUM>.

Referring to <FIG>, as an optional implementation, the circuit board <NUM> is provided with at least one connecting hole <NUM>, and the first connector <NUM> is arranged in one-to-one correspondence with the connecting hole <NUM>. An end of the first connector <NUM> towards the circuit board <NUM> is provided with a threaded hole <NUM>, and the second connector <NUM> is connected with the threaded hole <NUM> through the shell <NUM> and the connecting hole <NUM> in sequence.

In order to fix the circuit board <NUM> to the shell <NUM>, the circuit board <NUM> is provided with at least one connecting hole <NUM>, and the first connector <NUM> is fixedly connected with the circuit board <NUM> and the shell <NUM> through the second connector <NUM>. In a specific implementation, a different number of connecting holes <NUM> can be arranged on the circuit board <NUM> according to different requirements of the cryocooler, and correspondingly, the number of the first connector <NUM> is consistent with the number of connecting hole <NUM>, so that the circuit board <NUM> can be stably and reliably fixed to the shell <NUM>. The first connector <NUM> further includes a threaded hole <NUM>, the side of the first connector <NUM> near the tail end of the cryocooler is provided with the threaded hole <NUM>, and the second connector <NUM> is connected with the threaded hole <NUM> through the shell <NUM> and the connecting hole <NUM> in sequence so as to fix the circuit board <NUM> and the leaf spring <NUM> to the shell <NUM>. The second connector may be a bolt, stud or screw, which is not limited in the present embodiment.

Referring to <FIG>, in some embodiments, the shell <NUM> includes a shell body <NUM> and a shell cover <NUM> covered on the shell body <NUM>, where the shell cover <NUM> is provided with an installation hole <NUM>, the installation hole <NUM> is communicated with the cylinder <NUM>. An air flow channel is formed between the installation hole <NUM> and the cylinder <NUM>, the expansion unit <NUM> is installed to the installation hole <NUM>, and the expansion unit <NUM> is coaxially arranged with the cylinder <NUM>.

Specifically, the shell body <NUM> and the shell cover <NUM> covered on the shell body <NUM> are enclosed together to form the cavity <NUM> to accommodate the compression unit <NUM> and the vibration damping unit <NUM>. The shell cover <NUM> may be a rotary part with a through hole at the center thereof, that is, the installation hole <NUM> is provided at the center of the shell cover <NUM>, and the installation hole <NUM> is communicated with the cylinder <NUM> so as to form an air flow channel between the installation hole <NUM> and the inner wall of the cylinder <NUM>, to provide the gas working medium with an air flow channel from the compression unit <NUM> to the expansion unit <NUM>. And the installation hole <NUM>, the inner wall of the cylinder <NUM>, the piston <NUM> and the expansion unit <NUM> are enclosed to form a compression cavity. The expansion unit <NUM> is communicated with the compression cavity, the piston <NUM> reciprocates along the central axis to produce an alternating pressure, and the gas working medium is compressed and releases heat in the compression cavity under the action of the alternating pressure. The expansion unit <NUM> and the cylinder <NUM> have one and same central axis, and the expansion unit <NUM> reciprocates along the central axis under the drive of the cylinder <NUM>, so that the gas working medium expands and absorbs heat in the expansion unit <NUM>, thereby realizing the refrigeration cycle, and thereby, the compression unit <NUM> can provide power for the expansion and heat absorption of the expansion unit <NUM>.

Referring to <FIG>, as an optional implementation, the expansion unit <NUM> includes an outer shell <NUM> and an expeller <NUM>, where the outer shell <NUM> is partially inserted in the installation hole <NUM>, and an accommodating cavity <NUM> is provided in the outer shell <NUM>, an extension direction of the accommodating cavity <NUM> is consistent with the axial direction of the cylinder <NUM>, and the accommodating cavity <NUM> is communicated with the air flow channel, and the expeller <NUM> is located in the accommodating cavity <NUM> and reciprocates along the extension direction of the accommodating cavity <NUM>.

A cavity chamber formed by enclosure of the accommodating cavity <NUM> and a side of the expeller <NUM> near the front end of the cryocooler is an expansion cavity, and the heat transfer unit is covered on a side of the outer shell <NUM> near the front end of the cryocooler, and the gas working medium expands and absorbs heat in the expansion cavity to generate cooling power. The cryocooler transfers the cooling power to an external apparatus through a heat exchange unit to cool the external apparatus. Furthermore, there is a gap between the expeller <NUM> and the outer shell <NUM>, and the expeller <NUM> reciprocates along the central axis in the accommodating cavity <NUM>.

When the cryocooler is working, an alternating current is enabled to pass through the first coil <NUM>, thereby generating an alternating magnetic field, the alternating magnetic field drives the first magnet <NUM> to reciprocate along the central axis, and the piston <NUM> reciprocates along the central axis under the drive of the first magnet <NUM>. The gas working medium is compressed and releases heat in the compression cavity, producing an alternating pressure fluctuation in the compression cavity, thereby driving the expeller <NUM> to reciprocate in a direction of the central axis, and the gas working medium expands and absorbs heat in the expansion cavity. As such, the cryocooler completes a refrigeration cycle of compression, heat release, expansion and heat absorption.

Continuing to refer to <FIG>, in some embodiments, the outer shell <NUM> includes a second plugging part <NUM>, an abutting part <NUM> and an extension part <NUM> connected sequentially, and the accommodating cavity <NUM> extends sequentially from the second plugging part <NUM> and the abutting part <NUM> to the extension part <NUM>. The second plugging part <NUM> is plugged to the installation hole <NUM>, the abutting part <NUM> is abutted against an outer surface of the shell cover <NUM>, and a first end of the expeller <NUM> is located in the air flow channel, and the first end of the expeller <NUM> is connected with an end of the second plugging part <NUM> through an elastic member <NUM>, and a second end of the expeller <NUM> is located in the accommodating cavity <NUM> corresponding to the extension part <NUM>.

In order to form a closed cavity chamber, the second plugging part <NUM> is plugged to the installation hole <NUM>, and the abutting part <NUM> is abutted against the outer surface of the shell cover <NUM>, and the gas working medium is not easily leaked from the shell cover <NUM> and the outer shell <NUM>. Thus, the gas isolator <NUM>, the shell cover <NUM> and the outer shell <NUM> are enclosed together to form a closed cavity chamber so as to provide a closed space for compression and expansion of the gas working medium.

In order to limit a displacement of the expeller <NUM> when reciprocating along the central axis, the elastic member <NUM> is arranged at the end of the second plugging part <NUM>, and the side of the expeller <NUM> near the tail end of the cryocooler is connected with the second plugging part <NUM> through the elastic member <NUM>. As a result, when the expeller <NUM> moves along the central axis to the tail end of the cryocooler, displacement of the expeller <NUM> along the central axis to the tail end of the cryocooler is limited due to that the expeller <NUM> is pulled by the elastic member <NUM>.

Claim 1:
A cryocooler, comprising a shell (<NUM>), a compression unit (<NUM>), an expansion unit (<NUM>) and a vibration damping unit (<NUM>), wherein a cavity (<NUM>) is provided in the shell (<NUM>), the compression unit (<NUM>) and the vibration damping unit (<NUM>) are located in the cavity (<NUM>), the compression unit (<NUM>) is connected to the shell (<NUM>), and the expansion unit (<NUM>) is partially located in the cavity (<NUM>) and communicates with the compression unit (<NUM>);
the vibration damping unit (<NUM>) is sleeved on the compression unit (<NUM>), is partially located in the compression unit (<NUM>) and is configured to reduce vibration of the compression unit (<NUM>).