CN105814375A - Cold Heads for Refrigerators - Google Patents

Abstract

A cold head for a refrigeration refrigerator includes a displacer (72, 76) mounted in a working chamber (38, 40, 46) of a housing (34, 36). The cold head also has a high pressure connection (64) for supplying highly compressed refrigerant and a low pressure connection (60) for discharging expanded refrigerant. Control valve means (58) for controlling the supply and discharge of refrigerant are also provided. According to the invention there is also a bypass channel (80) connecting the high voltage connection to the low pressure connection.

Description

Cold Heads for Refrigerators

technical field

The present invention relates to cold heads for refrigeration refrigerators.

Background technique

WO 94/29653 describes a cold head for a refrigeration refrigerator operating with helium as working gas and connected to high and low pressure sources. The cold head comprises a multi-channel control valve which controls the respective connection of the high pressure inlet and the low pressure inlet to the piston cylinder unit and the working chamber of the cold finger on the warm side. At one of its ends, the displacer, which may include a regenerator, defines a warm-side working chamber, and at the opposite end, it defines a cold-side working chamber. Although the regenerator is periodically reciprocated by the piston-cylinder unit, heat is continuously obtained from the coldhead's housing. Using a cold head with a single stage displacer, temperatures down to about 30K can be generated. Using a two- or three-stage displacer, temperatures below 1K can be generated. A thermodynamic cycle process (Stirling process or Gifford-McMahon process) is performed in the cold head using a process gas (usually helium) which is directed in a closed loop. As a result, heat is obtained from one end region of the casing surrounding the displacer.

The cold head is connected to the compressor. Since the circuit is a closed circuit, both the high pressure and low pressure connections of the cold head are connected to the compressor. Such compressors usually include a relief valve. The overflow valve is arranged in a return conduit arranged between the high-pressure side and the low-pressure side. Typically, the overflow valve is a spring-loaded check valve, which is usually designed for the pressure difference between the high and low pressures of eg 18 bar compressors. When a cold head with a high resistance is connected to the compressor, the working pressure on the high pressure side at the compressor increases excessively. In order to discharge this excess energy, the overflow valve is opened so that the refrigerant, specifically helium, flows to the low pressure side of the compressor via the return conduit. A pulsed gas supply from the compressor to the cold head is achieved due to the cyclic handling of the cold head. Here, gas oscillations may occur. Especially over longer periods of time, this can lead to frequent opening and closing of the overflow valve. As a result, the relief valve will experience significant overload. This can lead to damage to or even damage to the valve seat of the overflow valve. Further, this results in significant noise and loss of performance. When the overflow valve is damaged, it may happen that oil enters the refrigeration circuit. Another disadvantage is that a performance loss occurs due to the existing hysteresis of the relief valve between the opening pressure and the closing pressure.

Contents of the invention

The object of the invention is to reduce the load on the overflow valve.

According to the invention, this object is solved with a cold head as defined in claim 1 .

The cold head used in the refrigeration refrigerator of the present invention has a working chamber in a housing (possibly a multi-part housing). Single-stage or multi-stage displacers are arranged in the working chamber. The coldhead further comprises a high pressure connection for supplying highly compressed refrigerant to the working chamber and a low pressure connection for discharging expanded or low pressure refrigerant. Further, a control valve device is provided. The control valve arrangement serves to control the supply and discharge of refrigerant to and from the working chamber. Here, the control device may comprise a plurality of valves, for example an inlet valve and an outlet valve. It is preferred that the control valve arrangement has a multi-channel control valve which controls the connection between the high-pressure connection, the low-pressure connection and the working chamber. According to the invention, the cold head has a bypass channel which is arranged between the high-voltage connection and the low-pressure connection and connects these two connections. If desired, excess refrigerant can flow directly from the high pressure connection through the passage to the low pressure connection without passing through the cold head. Such occurring excess energy can thus be discharged via a bypass. As a result, the overflow valve integrated in the compressor is relieved. Possibly, the overflow valve could be omitted from the compressor entirely, or it could be provided only as a safety device. As a result, at least significantly lower cost relief valves can be used.

In a particularly preferred development of the invention, the throughflow regulating device is arranged in the bypass channel. It can be, for example, a nozzle and/or a valve. The throughflow regulating device may be adjustable. In this context, a fixed setting can be made prior to operation so that the valve opens eg when the differential pressure is exceeded. Furthermore, it is possible to allow an adjustment of the throughflow adjustment device from the outside, for example from outside the cold head. This allows corresponding adjustments to be made during operation as well.

Due to the bypass provided by the present invention in the cold head which preferably includes pressure regulating means, a significant cost reduction can be achieved for the compressors used. Further, operation safety of the compressor can be enhanced and compressor performance can be increased. The risk of oil breakthrough caused by a broken relief valve in the compressor is also reduced. Further, the service life is extended and constant noise characteristics can be achieved.

In a preferred development of the invention, the cold head has a movement device for moving the displacer. The moving means may be a motor. The displacer may be moved using a slotted guide by a motor, which may be, for example, an electric motor. This can be achieved, for example, by means of an eccentric, so that a rotational movement of the motor can be easily converted into a longitudinal movement of the displacer. Alternatively, a piston/cylinder unit may be provided for moving the displacer. The piston-cylinder unit may eg be driven via a separate hydraulic system. However, for moving purposes it is preferred to connect the piston-cylinder unit to the high pressure and low pressure connections. In a preferred embodiment, the braking of the piston-cylinder unit and thus the movement of the displacer takes place via refrigerant.

It is further preferred that the cold head has a distributor body ("distributor body") in which at least the first connecting channel is provided. The first connecting channel serves to connect the high voltage connection to the working chamber. Preferably, the connection is made via the control valve arrangement, so that the first connecting channel is arranged between the control valve arrangement and the working chamber. Preferably, the distribution body additionally has a second connecting channel, which is arranged between the control valve arrangement and the low-pressure connection.

In a particularly preferred embodiment, the valve body is designed such that it also includes the control channel. The control channel serves the supply and discharge of the control medium to the mobile device, ie in particular the piston-cylinder unit. The control medium is preferably a refrigerant.

The present invention will be explained in detail below with reference to preferred embodiments and with reference to the accompanying drawings.

Description of drawings

Fig. 1 is a schematic diagram of a refrigeration refrigerator of the prior art,

Fig. 2 is a schematic diagram of a refrigeration refrigerator of the present invention,

Figure 3 is a schematic cross-sectional view of an embodiment of a coldhead according to the invention.

detailed description

A prior art refrigerated refrigerator (FIG. 1) includes a compressor 10 that compresses a refrigerant, such as helium. On the high pressure side, the compressor 10 is connected via a conduit 12 to a high pressure connection 14 of a cold head 16 . The low pressure connection 18 of the cold head 16 is connected to the low pressure side of the compressor 10 via a conduit 20 . In order to avoid overloading on the compressor 10 , a check valve 24 is arranged in the return line 22 which connects the high-pressure side of the compressor 10 to the low-pressure side of the compressor 10 .

A working chamber 26 is provided within the cold head 16 , in which a displacer piston, not shown in FIG. 1 , is arranged. An inlet valve 28 is connected to the high pressure connection 14 such that compressed refrigerant flows into the working chamber 26 when the inlet valve 28 is open. The expanded refrigerant may be directed to the low pressure connection 18 via a discharge valve 30 .

In the basic configuration of the system of the present invention shown in Fig. 2, similar and identical components are identified by the same reference numerals.

According to the schematically illustrated invention, a bypass channel 32 is provided between the inlet valve 28 of the cold head 16 and the outlet valve 30 of the cold head 16 , in which bypass channel 32 a throughflow regulating device can be arranged. As shown in phantom in FIG. 2 , the provision of the bypass channel 32 of the present invention makes it possible to omit the return conduit 22 and the overflow valve 24 .

A preferred embodiment of the cold head 16 is shown in the schematic sectional view in FIG. 3 .

The cold head 16 has a housing formed by two housing parts 34 and 36 . In housing part 34 two cylindrical cold side working chambers 38 and 40 are provided for two displacer stages 42 and 44 .

The upper displacer stage 42 delimits a warm-side working chamber 46 and is provided with a drive piston 48 arranged in a cylinder 50 of a distributor body 52 . Thus, the displacers 42 and 44 are arranged in the working chambers 38, 40, 46 formed by a plurality of partial chambers.

The distribution body 52 delimits a warm-side working space 46 provided with bore holes forming a control channel 54 , a first connecting channel 56 and a second connecting channel 57 . The first connecting channel 56 leads to the working chamber 46 and serves to supply this chamber with working gas. All three channels are controlled by control valve 58 . A first connecting passage 56 connects the control valve 58 to the warm side working chamber 46 , a control passage 54 connects the control valve 58 to the cylinder 50 , and a second connecting passage 57 connects the control valve 58 to the low pressure connection 60 . The control valve 58 is further connected to a chamber 62 which communicates with a high pressure connection 64 . High pressure connection 64 supplies helium at a pressure of about 20 bar, while helium at a pressure of about 5 bar is prevalent at low pressure connection 18 . The two pressures are supplied to corresponding connections (not shown) of the control valve 58 via the chamber 62 and the second connecting channel 57 , respectively. All conduits lead into the upper side of the distribution body 52 and from there to the valve 58 .

Housing portion 36 houses a motor 66 that drives control valve 58 via a shaft 68 . The valve is acted upon by compressing the spring 70 .

In the illustrated embodiment, the process gas subjected to the thermodynamic cycle process is the same as the drive gas for the piston cylinder units 48 , 50 . Suitable for use with helium. A gas different from the process gas may be used as the driving gas.

Instead of providing a piston-cylinder unit 48 , 50 for moving the displacers 72 , 76 in the illustrated embodiment, the displacers 72 , 76 may also be moved by a motor, for example using an electric motor. For this purpose, the motor can be provided with an eccentric and a slotted guide, whereby the rotation of the eccentric is converted into a linear motion.

In a cylindrical working chamber 46 the displacer stage 42 has a tubular displacer 72 filled with a thermal regenerator 74 permeable to gas. The regenerator 74 serves to store cold air and emit the stored cold air to the incoming warm air.

Similarly, displacer stage 44, which has a smaller diameter than displacer stage 42, includes a tubular displacer 76 offset axially within cylindrical working chamber 40, which is connected to displacer 72 and also Regenerator 78 filled with permeable gas.

In operation of the cold finger, the working chamber 46 on the warm side is firstly connected to the high-pressure connection 64 via the first connecting channel 56 and the control valve 58 . Simultaneously, high pressure is introduced into the cylinder 50 through the control passage 54 . Displacers 72 and 76 are offset (downward) to the cold side. Gas at high pressure also flows to the cold side through regenerators 74 and 78 . In doing so, it expands while cooling, with further expansion achieved by heat exchange with the regenerator.

In the second phase, the control channel 54 is connected to the low voltage connection. Under the effect of the high pressure, the displacers 72 and 76 are displaced towards the warm side, so that the working chamber 46 on the warm side becomes smaller and gas flows through the regenerators 74 and 78 into the working chamber 40 on the cold side .

In the third phase, the control valve 58 causes the working chamber 40 to be connected to the low pressure connection 60 via the conduit 56 . Thus, while cooling, the gas in all working chambers of the cold head expands.

Thereafter the displacers 72 and 76 are moved towards the cold side, whereby the volume of the cold side working chamber 40 contracts, ready for the next cycle. During this phase, cold air flows from the working chamber 40 into the regenerators 74 and 78 and is further cooled by them.

The frequency of the duty cycle is approximately 2 Hz.

Further, in the illustrated embodiment, a bypass channel 80 according to the invention is provided in the distribution body 52 . A bypass channel 80 connects the second control channel 57 to the chamber 62 . The bypass channel 80 thus connects the high-voltage connection 64 to the low-voltage connection 60 . As shown schematically, a throughflow regulating device, for example a valve 82 , is arranged in the bypass channel 80 . If an undesired high pressure builds up in the chamber 62 , a part of the refrigerant thus flows directly back into the channel 57 connected to the low-pressure connection 60 via the bypass channel 80 .

Claims (13)

1. for a cold head for freezing refrigeration machine, including:

Displacer (72,76), it is disposed in the work chamber (38,40,46) of housing (34,36)；

High pressure connects (64), and it for supplying the cold-producing medium of high compression to described work chamber (38,40,46)；

Low pressure connects (60), its cold-producing medium for expanding from described work chamber (38,40,46) discharge；And

Control valve gear (28,30；58), it commutes the supply of cold-producing medium and the discharge of described work chamber (38,40,46) for control,

It is characterized in that,

Bypass channel (80), described high pressure is connected (64) and is connected to described low pressure connection (60) by it.

2. the cold head for freezing refrigeration machine according to claim 1, it is characterised in that arrange through-flow adjusting apparatus (82) in described bypass channel (80).

3. the cold head for freezing refrigeration machine according to claim 2, it is characterised in that described logical flow modulation device (82) is specifically adjustable during operation.

4. the cold head for freezing refrigeration machine according to any one of claim 1-3, it is characterised in that be used for moving the mobile device (48,50) of described displacer (72,76).

5. the cold head for freezing refrigeration machine according to claim 4, it is characterized in that described mobile device is configured to piston cylinder unit (48,50), and in order to brake, described piston cylinder unit is connected to described high pressure and connects (64) and described low pressure connection (60).

6. the cold head for freezing refrigeration machine according to claim 4, it is characterised in that described mobile device has motor, is specially motor.

7. the cold head for freezing refrigeration machine according to claim 6, wherein said motor drives eccentric, and described eccentric acts on grooved guider to cause the linear mobile of described displacer (72,76).

8. according to the cold head for freezing refrigeration machine one of claim 1-7 Suo Shu, it is characterised in that described control valve gear (28,30；58) having the Multi-way control valve (58) cyclically operated, it controls work chamber (38,40,46) and connects (64) to high pressure and connect the connection of (60) to low pressure.

9. the cold head for freezing refrigeration machine according to claim 8, it is characterised in that described control valve (58) controls the connection of described piston cylinder unit (48,50).

10. according to the cold head for freezing refrigeration machine one of claim 1-9 Suo Shu, it is characterized in that dispensing body (52), at least a part of which the first interface channel (56) is provided for and described high pressure connection (64) is connected to described work chamber (38,40,46).

11. the cold head for freezing refrigeration machine according to claim 10, it is characterised in that described first interface channel (56) is arranged between described control valve (58) and described work chamber (38,40,46).

12. the cold head for freezing refrigeration machine according to claim 8 or claim 9, it is characterised in that described dispensing body (52) has described control valve (58) and described low pressure connects the second interface channel (57) between (60).

13. according to the cold head for freezing refrigeration machine one of claim 10-12 Suo Shu, it is characterized in that described dispensing body (52) has go to for supply and/or discharge and/or come from described piston cylinder unit (48,50) the control passage (54) controlling medium, described control medium is specially cold-producing medium.