JPH0730966B2 - Free displacer type Stirling refrigerator - Google Patents

Description

The present invention relates to a free displacer type in which a refrigerant gas is expanded in an expansion chamber in a cylinder by reciprocating movement of a displacer to generate cold in a cold head at a tip of a cylinder. Regarding Stirling refrigerator.

(Prior Art) Conventionally, this free displacer type Stirling refrigerator is known as one of small refrigerators that generate a cryogenic level of cold. This refrigerator is a combination of a compressor that compresses a refrigerant gas and an expander that expands the refrigerant gas discharged from the compressor, and the compressor has a gas pressure of, for example, a sine curve. A compressor is used which has characteristics such as the above, and is compressed so as to change with time in a predetermined cycle. On the other hand, the expander includes a cylinder whose front end is closed, a free displacer which is reciprocally fitted in the cylinder and which divides and forms the inside of the cylinder into a front end side expansion chamber and a base end side working chamber. The working chamber is connected to the compressor, and the displacer is reciprocated by the refrigerant gas pressure from the compressor to expand the refrigerant gas in the expansion chamber. It is designed to generate cold in the cold head at the tip of the cylinder.
(For example, "A Small Free-Piston Stirling Refrigerat
or ", see AK Jonge, etc.).

(Problems to be Solved by the Invention) By the way, in this type of Stirling refrigerator, the spring constant of the above-mentioned spring is such that the movable part has the maximum refrigerating capacity according to the mass (mass) of the movable part including the displacer. It is set to a constant value so as to resonate at the obtained optimum tuning frequency. However, as the cold head temperature at the tip of the cylinder decreases due to the cool-down operation, the above optimum tuning frequency changes, and the deviation of this optimum tuning frequency reduces the refrigeration capacity, resulting in a shorter cool down time. There was a limit.

Further, for the same reason, there is a limit to the improvement of the refrigerating capacity per unit electric input after the cool down.

The present invention has been made in view of such a point, and an object thereof is to provide a means for varying the optimum tuning frequency at which the maximum refrigerating capacity is obtained.
Even if the cold head temperature changes, it is possible to maintain the optimum tuning frequency accordingly, so that the cooldown of the refrigerator can be performed quickly, and at the same time, the refrigeration capacity per unit electric input is improved. .

(Means for Solving the Problem) In order to achieve this object, in the invention described in claim (1), the spring constant of the elastic supporting means for elastically supporting the displacer is made variable.

Specifically, in the present invention, as shown in FIG. 1 and FIG. 2, the base end portion is joined to the fixed body (15) as described above,
A cylinder (16) having a closed end, and the cylinder (16)
A free displacer (18) which is reciprocally fitted into the cylinder (16) to partition the inside of the cylinder (16) into an expansion chamber (21) on the distal end side and a working chamber (22) on the proximal end side, and the displacer (18) at one end. 18) while the other end is fixed (1
A spring (2) which is non-rotatably connected to the displacer (5) and elastically supports the displacer (18) so that the displacer (18) can reciprocate.
3) and the working chamber (22) is connected to a compressor (1) for compressing a refrigerant gas in a predetermined cycle, and the displacer (18) reciprocates by the refrigerant gas pressure from the compressor (1). A free displacer-type Stirling refrigerator in which cold gas is generated in the cold head (17) at the tip of the cylinder (16) by causing the refrigerant gas to expand in the expansion chamber (21) is premised.

Then, a spring constant varying means (30) for varying the spring constant of the spring (23) is provided, and the spring constant varying means (30) spirals the connecting portion of the spring (23) to the fixed body (15). Spring stopper (2 that slidably engages in the groove (28a)
8), a screw member (27) which is connected to the spring stopper (28) and is screwed by rotation to rotate the spring stopper (28), and a drive means (29) which rotates the screw member (27). By moving the screw member (27) by the drive means (29) to move the spring stopper (28) relative to the spring (23), the effective length of the spring (23) is changed. It is assumed that the spring constant is configured to be variable.

Further, in order to automate the maintenance of the optimum tuning frequency, in the invention described in claim (2), the temperature detecting means (32) for detecting the temperature of the cold head (17) at the tip of the cylinder (16), and the detecting means. A control means (31) is provided which receives the output of (32) and controls the spring constant varying means (30) so that the spring constant of the spring (23) increases as the cold head temperature decreases. Further, in the invention according to claim (3), the spring (23) is provided in response to an increase in the operating time of the refrigerator, the time detecting means detecting the elapsed time from the start of operation of the refrigerator, and the output of the detecting means. )
And a control means for controlling the spring constant varying means (30) so that the spring constant of (1) becomes high.

Further, in the invention according to claim (4), as shown in FIG. 4, a power source frequency varying means (33) for varying the frequency of the driving power source of the compressor (1) and a cold end of the cylinder (16). Temperature detecting means (3 for detecting the temperature of the head (17)
2) and the output of the detection means (32), and controls the power supply frequency varying means (33) so that the power supply frequency of the compressor (1) becomes lower as the cold head temperature becomes lower. And means (31) are provided.

Further, in the invention according to claim (5), similarly to the above, the power source frequency varying means (33) for varying the frequency of the driving power source of the compressor (1) is provided, and the progress from the start of the operation of the refrigerator. A time detecting means for detecting time and an output of the detecting means, and controls the power supply frequency varying means (33) so that the power supply frequency of the compressor (1) becomes lower in accordance with the increase of the operating time of the refrigerator. And a control means.

(Operation) With the above configuration, in the invention according to claim (1), when the temperature of the cold head (17) changes, the spring constant of the spring (23) is correspondingly changed to the spring constant changing means (30).
Change by. That is, when the screw member (27) is screwed by the driving means (29), the spring stopper (28) rotates with the screwing of the screw member (27), and the spring stopper (28) and its spiral groove. The spring (23) slidably engaged with the spring (23a) moves relative to the spring (23).
Changes the effective length of and changes its spring constant. This makes it possible to maintain the optimum tuning frequency and speed up the cooldown of the refrigerator regardless of the change in the cold head temperature.

In the invention according to claim (2), the temperature of the cold head (17) is detected by the temperature detecting means (32), and the control means (31) receives the output of the detecting means (32).
The spring constant varying means (30) is controlled by this, and the spring constant of the spring (23) increases as the cold head temperature decreases. In the invention according to claim (3), the time elapsed from the start of operation of the refrigerator is detected by the time detecting means, and the spring constant varying means (30) is controlled by the control means receiving the output of this detecting means. Thus, the spring constant of the spring (23) increases as the operating time of the refrigerator increases. Therefore, in these inventions, the optimum tuning frequency can be automatically secured.

In the invention according to claim (4), the temperature detecting means (3
The power supply frequency varying means (33) is controlled by the control means (31) receiving the output of 2), and the power supply frequency of the compressor (1) is lowered in accordance with the decrease of the cold head temperature. Also,
In the invention according to claim (5), the power supply frequency of the compressor (1) decreases as the elapsed time from the start of operation of the refrigerator increases. Therefore, in these inventions, the optimum tuning frequency can be obtained by changing the power supply frequency of the compressor (1) by the power supply frequency changing means (33), and the optimum tuning frequency is always maintained regardless of the change of the cold head temperature. It is possible to maintain the maximum refrigerating capacity per unit electric input of the refrigerator and automatically secure the optimum tuning frequency.

(Example) Hereinafter, the Example of this invention is described based on drawing.

FIG. 2 shows the entire structure of the free displacer type Stirling refrigerator according to the first embodiment of the present invention. This refrigerator comprises a compressor (1) and an expander (13). The compressor (1) includes a closed housing (2), a cylinder (3) fitted and fixed in the housing (2),
A piston (5) that is reciprocally fitted in the cylinder (3) and partitions and forms a compression chamber (4) in the internal space of the cylinder (3), and a drive source that reciprocally drives the piston (5). And a linear motor (6). This linear motor (6) has an annular permanent magnet (7) arranged around the cylinder (3), and by this magnet (7), a cylindrical gap (8) concentric with the center of the cylinder (3). Generate a magnetic field. A circumferential portion of a substantially cup-shaped movable body (9) integrally fixed to the piston (5) at the central portion is reciprocally disposed in the gap (8) so that the movable body (9) can be reciprocated. A drive coil (10) is wound around the outer circumference. Also,
A piston spring composed of a coil spring for elastically supporting the piston (5) reciprocally between the outer bottom surface of the movable body (9) (opposite side of the piston (5)) and the inner bottom surface of the housing (2). The coil (10) and the movable body (9) are driven by the action of the magnetic field passing through the gap (8) by energizing the drive coil (10) with an alternating current having a predetermined frequency. By reciprocally moving the piston (5) in the cylinder (3), a gas pressure of a predetermined cycle is generated in the compression chamber (4).

On the other hand, the expander (13) has a housing (15) as a fixed body in which a cylindrical hollow portion (14) is opened as shown in detail in FIG. A cylindrical cylinder (16) is concentrically fitted to and fixed to the hollow portion (14) of the housing (15) at the base end in a concentric manner with the hollow portion (14), and the tip of the cylinder (16) is fixed. Is closed and is said to be the cold head (17). A free displacer (18) is reciprocally fitted in the cylinder (16), and the displacer (1
8) The cavity (14) in the cylinder (16) and the housing (15) is the working chamber of the expansion chamber (21) on the tip side of the cylinder (16) and the housing (15) side (base end side of the cylinder (16)). (22) and is divided into sections. This displacer (18) has a cylindrical body (19) filled with a metal regenerator material (20) (heat exchanger), and the inside space of the cylindrical body (19) is a working chamber (22). And communication holes (19a) and (19b) for communicating with the expansion chamber (21), respectively. When the low-temperature refrigerant gas expanded in the expansion chamber (21) goes to the working chamber (22), the refrigerant gas The cold storage material (20) is cooled by the cold storage material (20) and cold heat is stored in the cold storage material (20). On the contrary, when the refrigerant gas at room temperature goes from the working chamber (22) to the expansion chamber (21), the cold storage material (20) stores the gas. It is designed to cool. Further, in the working chamber (22), a displacer spring (23) composed of a carp spring as an elastic supporting means for elastically supporting the displacer (18) in a reciprocating manner is disposed, and one end of the spring (23) is disposed. Is connected to the base end side of the displacer (18), while the other end is non-rotatably fixed to a later-described plug (25) on the housing (15) side. Further, the working chamber (22) is connected to the communication pipe (24).
Is connected to the compression chamber (4) of the compressor (1) via the compressor (1), and the displacer (18) is reciprocated by the refrigerant gas pressure from the compressor (1) to move the refrigerant gas in the expansion chamber (21). By expanding, cold is generated in the cold head (17) at the tip of the cylinder (16).

A plug (25) is airtightly fitted and fixed to the bottom of the cavity (14) of the housing (15). A screw hole (26) extending in the center line direction of the cavity (14) is formed through the center of the plug (25), and the screw pitch of the screw hole (26) is the spiral pitch of the displacer spring (23). Is almost the same as. A screw rod (27) (screw member) is screwably engaged with the screw hole (26), and a spring stopper (28) is attached to the tip (displacer (18) side end) of the screw rod (27). Are integrally formed, and a spiral groove (28a) for slidably fitting the displacer spring (23) is formed on the outer periphery of the spring stopper (28).
The spring stopper (28) is moved back and forth in the spring (23) while the spring (23) is engaged in the spiral groove (28a) by the screwing of the spring.

Further, a step motor (29) as a driving means is arranged at the bottom of the cavity (14), and the output shaft (29a) of the motor (29) is integrally rotated with the base end of the screw rod (27). And is slidably engaged with the step motor (29) by rotating the screw rod (27) to rotate the spring stopper (28) to displacer spring (23). A spring constant variable mechanism (30) is configured so as to change the effective length of the spring (23) by relative movement to make the spring constant K variable.

Then, as shown in FIG. 2, the spring constant varying mechanism (3
The operation of the step motor (29) of 0) is controlled by the control device (31). This controller (31)
The output signal of the temperature sensor (32) that detects the temperature of the cold head (17) at the tip of the cylinder (16) is input to the cold head (17) by the control device (31).
The step motor (29) is controlled so that the spring constant K of the displacer spring (23) increases as the temperature decreases.

Next, the operation of the above embodiment will be described.

With the start of operation of the refrigerator, the linear motor (6) of the compressor (1) operates, the piston (5) reciprocates in the cylinder (3), and the reciprocating motion of the piston (5) causes the compression chamber ( A pressure wave having a predetermined period is generated in 4). Since the compression chamber (4) communicates with the working chamber (22) of the expander (13) via the communication pipe (24), the piston (5) advances and the pressure in the compression chamber (4) increases. Then, the pressurized refrigerant gas is supplied to the working chamber (22) to increase the pressure in the working chamber (22). This increase in pressure causes the working chamber (22)
Between the expansion chamber (21) and the expansion chamber (21), and this pressure difference causes the displacer (18) to displace (2).
While extending 3), move it to the tip side of the cylinder (16) (left side in Fig. 1). Since the working chamber (22) communicates with the expansion chamber (21) through the space in the displacer (18), the gas in the working chamber (22) passes through the displacer (18) to cool in the next stage. It flows into the expansion chamber (21) while being cooled by the material (20), the pressure difference between both chambers (21) and (22) disappears, and the displacer (18) is compressed by the spring (23) to the base end of the cylinder (16). Move to the side and return to the original position. Immediately thereafter, the piston (5) of the compressor (1) retracts and the pressure in the compression chamber (4) decreases. For this reason, the refrigerant gas in the working chamber (22) returns to the compression chamber (4) via the communication pipe (24), and the pressure in the working chamber (22) is increased to the expansion chamber (21).
Lower than. The pressure difference between the working chamber (22) and the expansion chamber (21) causes the displacer (18) to contract the displacer spring (23), which in turn causes the cylinder (1
6) The refrigerant gas moves to the base end side (right side in FIG. 1), and the refrigerant gas in the expansion chamber (21) adiabatically expands to generate cold. In the next stage, the expanded gas flows from the expansion chamber (21) through the displacer (18) to the working chamber (22) while applying cold heat to the regenerator material (20), and both chambers (21), (22) ), The displacer (18) moves to the tip side of the cylinder (16) by the extension force of the spring (23) and returns to its original position. With the above, one cycle is completed, and by repeating the same cycle thereafter, the cold head (17) at the tip of the cylinder (16) is gradually cooled to the cryogenic temperature level.

During operation of this refrigerator, the cold head (1
The temperature of (7) is detected by the temperature sensor (32), and based on the output signal of this sensor (32), the control device (31) controls the operation of the step motor (29) in the expander (13). The spring constant K of the displacer spring (23) is adjusted by screwing the screw rod (27) by the rotation of the output shaft (29a) of (29). That is,
Since the temperature of the cold head (17) is high near room temperature immediately after the start of operation of the refrigerator, the screw rod (27) is in the retracted position (right side position in FIG. 1). The effective length of the spring (23) is increased and the spring constant K thereof is decreased. Then, when the temperature of the cold head (17) decreases as the operation of the refrigerator continues, the screw rod (2
7) is screwed, and the spring stopper (28) at its tip moves forward while engaging the spring (23), and this forward movement causes the spring (23) between the screw stopper (28) and the displacer (18). The effective length of is shortened and its spring constant K is increased.

In this way, the spring constant K of the displacer spring (23) automatically increases in response to the temperature drop of the cold head (17), so that the displacer (18) supported by the spring constant K and the spring (23). Mass M
Vibration frequency ωd {= of the displacer (18) determined by
2π (K / M) ^1/2 } increases. On the other hand, since the vibration frequency ω of the compressor (1) is constant, the ratio ωd /
ω increases. Then, as shown in FIG. 3, the maximum value of the refrigerating capacity calculated by the P-V diagram showing the relationship between the pressure and the volume of the refrigerant gas in the expansion chamber (21) is the temperature drop of the cold head (17). Since it moves to the side where the vibration frequency ωd of the displacer (18) is higher, it is possible to automatically secure the optimum tuning frequency of the refrigerator that can obtain the maximum value of the refrigerating capacity, thus speeding up the cooldown of the refrigerator. can do.

FIG. 4 shows a second embodiment of the present invention (note that the same parts as those in FIG. 2 are designated by the same reference numerals and detailed description thereof is omitted), and the tuning frequency ω of the displacer (18) is shown.
Instead of varying the spring constant K of the spring (23) that determines d, the compressor vibration frequency ω, which is another factor that determines the maximum value of the refrigerating capacity, is variable.

That is, in this embodiment, the power source of the compressor (1) is provided with the inverter (33) as a power source frequency varying means for varying the frequency of the power source. Further, the inverter (33) is configured to be controlled based on the output signal of the control device (31 ′), and the power supply frequency ω of the compressor (1) decreases as the cold head temperature decreases. Controlled as.

Therefore, in this embodiment, when the temperature of the cold head (17) drops, the power supply frequency ω of the compressor (1) is correspondingly lowered by the inverter (33),
The ratio ωd / ω between the vibration frequency ωd of the displacer (18) and the compressor power supply frequency ω is increased, and the optimum tuning frequency of the refrigerator can be automatically obtained. Therefore, the same operation as that of the first embodiment described above is performed. The effect can be obtained.

In addition, in this embodiment, the power supply frequency ω of the compressor (1) can be lowered by setting the optimum tuning frequency even during steady operation after cooldown, so that the input power in the steady operation state can be reduced. There is an advantage that it can be kept low.

In each of the above-mentioned embodiments, instead of the cold head temperature, the elapsed time from the start of operation of the refrigerator (at the time when the compressor (1) is turned on) is detected by a timer (time detection means), and the refrigerator operation is performed. The spring constant variable mechanism (30) is controlled so that the spring constant K of the displacer spring (23) becomes higher according to the increase in time, or the inverter (33) is controlled so that the power supply frequency of the compressor (1) becomes lower. You may do it.

(Effect of the invention) As described above, according to the invention described in claim (1), in a free displacer type Stirling refrigerator in which a displacer is reciprocated in a cylinder to generate cold, the displacer is elastically movable. By changing the effective length of the spring and changing its spring constant by the relative movement of the supporting spring and its spring stopper, the tuning frequency of the refrigerator can always be maintained at the optimum tuning frequency. You can speed up the cooldown of the machine.

Further, in the invention described in claim (2), the temperature of the cold head at the tip of the cylinder is detected, and the spring constant of the spring is changed to a higher value as the temperature decreases. Further, in the invention according to claim (3), the elapsed time from the start of operation of the refrigerator is detected, and the spring constant of the spring is changed to be higher as the elapsed time becomes longer. Therefore, according to these inventions, the optimum tuning frequency can be automatically secured.

In the invention described in claim (4), in the above free displacer type Stirling refrigerator, the power supply frequency of the compressor is made variable, the temperature of the cold head at the tip of the cylinder is detected, and the compression is performed as the temperature becomes lower. The power supply frequency of the machine was changed low. Also, claim (5)
In the invention described above, the elapsed operating time of the refrigerator is detected, and the power supply frequency of the compressor is changed to a lower value as the elapsed time becomes longer. Therefore, according to these inventions, the tuning frequency of the refrigerator is always maintained at the optimum tuning frequency, the refrigerating capacity per unit electric input of the refrigerator can be kept to the maximum, and the optimum tuning frequency is automatically secured. be able to.

[Brief description of drawings]

1 to 3 show a first embodiment of the present invention, FIG. 1 is an enlarged cross-sectional view of an essential part of an expander, FIG. 2 is a cross-sectional view showing the entire structure of a refrigerator, and FIG. 3 is a displacer. FIG. 4 is a characteristic diagram showing characteristics of a change in refrigerating capacity with respect to a ratio between the vibration frequency of ∘ and the power frequency of the compressor. FIG. 4 is a sectional view showing the overall structure of the refrigerator in the second embodiment. (1) ...... Compressor (13) ...... Expander (15) ...... Housing (fixed body) (16) ...... Cylinder (17) ...... Cold head (18) ...... Displacer (21) ...... Expansion chamber (22) ...... Working chamber (23) ...... Spring (elastic support means) (27) ...... Screw rod (screw member) (29) ...... Step motor (drive means) (30) ...... Spring constant variable mechanism ( 31), (31 ') …… Control device (control means) (32) …… Temperature sensor (temperature detection means) (33) …… Inverter (power supply frequency varying means)

Claims (5)

[Claims] 1. A cylinder (16) having a base end coupled to a fixed body (15) and a closed front end, and a cylinder (16) fitted in the cylinder (16) so as to be reciprocally movable therein. A free displacer (18), which is partitioned into an expansion chamber (21) on the tip side and a working chamber (22) on the base end side, is connected to the displacer (18) at one end, while the other end is fixed (15). ) Non-rotatably connected with the displacer (18) to the fixed body (1
5) is provided with a spring (23) elastically supported so as to be able to reciprocate, and the working chamber (22) is connected to a compressor (1) that compresses a refrigerant gas at a predetermined cycle. Stirling refrigerator in which cold is generated in the cold head (17) at the tip of the cylinder (16) by causing the displacer (18) to reciprocate by the refrigerant gas pressure in the room to expand the refrigerant gas in the expansion chamber (21). In the above, spring constant varying means (30) for varying the spring constant of the spring (23) is provided, and the spring constant varying means (30) is provided.
Is a spring stopper (28) that slidably engages a connecting portion of the spring (23) with the fixed body (15) in a spiral groove (28a).
And a screw member (27) connected to the spring stopper (28) and screwed by rotation to rotate the spring stopper (28), and a drive means (29) for rotating the screw member (27). The driving means (29) causes the screw member (27) to be screwed to move the spring stopper (28) relative to the spring (23), thereby changing the effective length of the spring (23). A free displacer type Stirling refrigerator, which is configured to change a constant. 2. A cold head (1) at the tip of a cylinder (16).
The temperature detecting means (32) for detecting the temperature of 7) and the spring constant so that the spring constant of the spring (23) increases as the cold head temperature decreases by receiving the output of the detecting means (32). The free displacer type Stirling refrigerator according to claim 1, further comprising a control means (31) for controlling the variable means (30). 3. A time detecting means for detecting an elapsed time from the start of operation of the refrigerator, and an output of the detecting means, and a spring constant of a spring (23) increases as the operating time of the refrigerator increases. The free displacer type Stirling refrigerator according to claim 1, further comprising a control means for controlling the spring constant varying means (30). 4. A cylinder (16) having a closed end, and a cylinder (1) fitted in the cylinder (16) so as to be reciprocally movable.
6) Inside the expansion chamber (21) on the distal side and the working chamber (2 on the proximal side)
2) is provided with a free displacer (18) which is partitioned and formed, and an elastic support means (23) which elastically supports the displacer (18) so that the displacer (18) can reciprocate, and the working chamber (22) compresses the refrigerant gas at a predetermined cycle. The compressor (1) is connected to the compressor (1), and the refrigerant gas pressure from the compressor (1) causes the displacer (18) to reciprocate to expand the refrigerant gas in the expansion chamber (21), thereby the cylinder (16). A Stirling refrigerator in which cold is generated in the cold head (17) at the tip, a power frequency changing means (33) for varying the frequency of the driving power of the compressor (1), and the tip of the cylinder (16). The temperature detection means (32) for detecting the temperature of the cold head (17) and the output of the temperature detection means (32) receive the power supply frequency of the compressor (1) as the cold head temperature decreases. Low Free displacer type Stirling refrigerating machine, characterized in that a control means (31) for controlling the power supply frequency varying means (33) so. 5. A cylinder (16) having a closed end, and a cylinder (1) fitted in the cylinder (16) so as to be reciprocally movable.
6) Inside the expansion chamber (21) on the distal side and the working chamber (2 on the proximal side)
2) is provided with a free displacer (18) which is partitioned and formed, and an elastic support means (23) which elastically supports the displacer (18) so as to be capable of reciprocating, and the working chamber (22) compresses the refrigerant gas at a predetermined cycle The compressor (1) is connected to the compressor (1), and the refrigerant gas pressure from the compressor (1) causes the displacer (18) to reciprocate to expand the refrigerant gas in the expansion chamber (21), thereby the cylinder (16). In a Stirling refrigerator in which cold is generated in the cold head (17) at the tip, a power source frequency varying means (33) for varying the frequency of the drive power source of the compressor (1), and from the start of operation of the refrigerator. Of the power source frequency varying means (33) so that the power source frequency of the compressor (1) decreases as the operating time of the refrigerator increases in response to the output of the time detecting means for detecting the elapsed time. ) Free displacer type Stirling refrigerating machine, characterized in that a and Gosuru control means.