JPH0692850B2 - 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 Refri").
gerator ", AK Jonge, etc.).

(Problems to be Solved by the Invention) By the way, in this type of refrigerator, the displacer is set to be driven at a frequency slightly deviated from the resonance frequency determined by the mass (mass) and the spring constant of the spring. Therefore, it is impossible to operate at a drive frequency that deviates significantly from this resonance frequency. For this reason, it is difficult to freely increase and change the refrigerating capacity in accordance with the cooling down of the refrigerator or when the cooling load increases.

The present invention has been made in view of such a point, and an object thereof is to make it possible to freely adjust the refrigerating capacity of a refrigerator by making the volume of an expansion chamber in a cylinder variable, and to cool down or the like. It is to be able to deal with the demand for increased refrigeration capacity.

(Means for Solving the Problem) In order to achieve this object, in the invention described in claim (1), as shown in FIG. 1 and FIG. ) And a free displacer (18) which is reciprocally fitted in the cylinder (16) and partitions the interior 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)
And an elastic supporting means (23) for elastically supporting reciprocating motion, and the working chamber (22) is connected to a compressor (1) for generating a refrigerant gas at a predetermined cycle. Free displacer type 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 expansion chamber to expand the refrigerant gas in the expansion chamber (21). In a Stirling refrigerator, a drive means (34) is provided which moves the displacer (18) and the elastic support means (23) in the cylinder axial direction to change the dead volume of the expansion chamber (21).

Further, in the invention according to claim (2), in order to enlarge the dead space of the expansion chamber (21) and expand the refrigerating capacity adjustment range, the expansion chamber (21) is provided with a space inside the closed container (25). Use a structure that allows communication.

(Operation) With the above configuration, in the invention according to claim (1), the displacer (18) and the elastic support means (23) are moved in the cylinder axis direction by the drive means (34), and the expansion chamber (21) is wasted. When the volume is changed, the amount of the refrigerant gas flowing in and out of the expansion chamber (21) changes accordingly, and the refrigerating capacity can be changed. For example, when the refrigerating capacity of the refrigerator may be low at the time of steady operation after the cooldown, the drive means (34) reduces the dead volume of the displacer (18) and the elastic support means (23) in the expansion chamber (21). Move in the cylinder axis direction. As the dead volume of the expansion chamber (21) decreases, the amount of refrigerant gas flowing into and out of the expansion chamber (21) decreases, so that the refrigerating capacity decreases. On the other hand, when increasing the refrigerating capacity at the time of cool down or increasing the cooling load,
The displacer (18) and the elastic support means (23) are moved so that the dead volume of the expansion chamber (21) becomes large. As the dead volume of the expansion chamber (21) increases, the amount of refrigerant gas flowing into and out of the expansion chamber (21) increases, so that the refrigerating capacity increases.

Further, in the invention according to claim (2), since the space (26) separate from the expansion chamber (21) is communicated with the expansion chamber (21), the entire waste space of the expansion chamber (21) is increased, and the freezing is increased. The variable adjustment range of the ability can be expanded.

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

FIG. 2 shows the entire structure of a free displacer type Stirling refrigerator according to an embodiment of the present invention. This refrigerator is composed of a compressor (1) and an expander (13). The compressor (1) includes a hermetically sealed housing (2), a cylinder (3) fitted and fixed in the housing (2), and reciprocally fitted in the cylinder (3). The cylinder (3) is provided with a piston (5) that defines a compression chamber (4) in an internal space, and a linear motor (6) as a drive source that reciprocally drives the piston (5). 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). To 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 drive coil (10) drives the coil (10) and the movable body (9) by the action of the magnetic field passing through the gap (8). 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) 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) so that the displacer (18) allows the cavity (14) in the cylinder (16) and the housing (15) to be located at the front end side of the cylinder (16). Of the expansion chamber (21) and the working chamber (22) on the housing (15) side (base end side of the cylinder (16)). This displacer (18) has a cylindrical body (1
9) A metal regenerator material (20) (heat exchanger) is filled in the inside of the cylindrical body (19) to communicate with the working chamber (22) and the expansion chamber (21). The communication holes (19a) and (19b) are opened, and when the low-temperature refrigerant gas expanded in the expansion chamber (21) is directed to the working chamber (22), the refrigerant gas cools the regenerator material (20). Cold heat is stored in the cold storage material (20), and conversely, room temperature refrigerant gas
When going from the 2) to the expansion chamber (21), the regenerator material (20)
Is designed to cool the gas. Further, in the working chamber (22), a displacer spring (23) made of a coil spring is disposed as an elastic supporting means for elastically supporting the displacer (18) so as to be able to reciprocate. Further, the working chamber (22) is connected to the compression chamber (4) of the compressor (1) through the communication pipe (24), and the displacer (18) is driven by the refrigerant gas pressure from the compressor (1). Is reciprocated to expand the refrigerant gas in the expansion chamber (21) to generate cold in the cold head (17) at the tip of the cylinder (16).

Further, (25) is an airtight container having a space (26) therein, and the space (26) is provided in the expansion chamber (21) at the tip of the cylinder (16) of the expander (13) and the opening / closing valve (27). Are communicated with each other via a pipe (28) having.

A female screw is formed on the outer peripheral wall of the hollow portion (14) of the housing (15) of the expander (13) to form a screw hole (2).
9), and a screw member (30) is screwed into the screw hole (29) so as to be movable back and forth. A spring stopper (31) for fixedly supporting the end of the displacer spring (23) is attached to the tip (end of the displacer (18)) of the screw member (30).
On the other hand, at the base end side, there is a bottomed shaft insertion hole (32) in the central portion, and a pin engaging member formed by axially notching a side wall of the shaft insertion hole (32) that is diametrically opposed. Groove (33), (3
3) and are formed. The output shaft (34) of the step motor (34) as a driving means is inserted into the shaft insertion hole (32).
a) is inserted, and pins (35) and (35) projecting radially from the tip of the output shaft (34a) are inserted into the pin engaging grooves (33) and (33).
Are slidably engaged with each other, and by moving the screw member (30) back and forth by the driving rotation of the step motor (34), the displacer (18) is moved.
And displacer spring (23) to cylinder (16)
It is configured to change the dead volume of the expansion chamber (21) by moving it back and forth in the axial direction thereof.

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 inside the displacer (18), the gas in the working chamber (22) passes through the inside of the displacer (18) to store cold in the next stage. It flows into the expansion chamber (21) while being cooled by the material (20), the pressure difference between the two chambers (21) and (22) disappears, and the displacer (18) is compressed by the contracting force of 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) It moves to the base end side (right side in Fig. 1), and the refrigerant gas in the expansion chamber (21) expands to generate cold. In the next stage, the expanded gas is discharged from the expansion chamber (21) into the displacer (1
8) The cold storage material (20) flows through the inside to flow into the working chamber (22), and the pressure difference between the two chambers (21) and (22) disappears.
The displacer (18) moves to the tip side of the cylinder (16) by the extension force of the spring (23) and returns to the original position. With the above, one cycle is completed, and by repeating the same cycle as above, the cold head (17) at the tip of the cylinder (16) is gradually cooled to the cryogenic temperature level.

During operation of the refrigerator, the screw rod (27) is screwed by the operation of the step motor (34) in the expander (13), and the displacer (18) and the displacer spring (23) are moved in the cylinder axial direction. Moving and expanding chamber (21)
The wasted volume is changed and the refrigeration capacity is adjusted. That is, when the cooling load is small, such as during normal operation of the refrigerator, the screw member (30) is positioned at the forward position (left side position in FIG. 1), the volume of the expansion chamber (21) decreases, and the expansion chamber (21) decreases. The capacity of the refrigerant gas expanding in (21) is reduced, and the refrigerating capacity is kept low.

On the other hand, at the time of cool down or when the cooling load increases, the screw member (3
0) is positioned at the retracted position (right side position in the figure), and the volume of the expansion chamber (21) increases. Because of this, the expansion chamber (21)
As a result, the capacity of the refrigerant gas that expands is increased, and the refrigerating capacity can be increased.

Further, in this case, since the space (26) separate from the expansion chamber (21) is formed in the closed container (25) and the expansion chamber (21) communicates with the space (26), the cylinder ( 16) It is possible to increase the dead space of the expansion chamber (21) without increasing the size of itself, and it is possible to expand the variable adjustment range of the refrigerating capacity.

In the above embodiment, when the cooldown operation of the refrigerator or the increase of the cooling load is detected and the step motor (34) is controlled accordingly, the variable adjustment of the refrigerating capacity is automatically performed. It is also possible to do so.

(Effect of the invention) As described above, according to the invention described in claim (1), in the free displacer type Stirling refrigerator that reciprocates the displacer in the cylinder to generate cold, the displacer and the reciprocating motion are possible. By moving the elastic support means for elastically supporting in the cylinder axial direction,
By changing the dead volume of the expansion chamber, the amount of refrigerant gas flowing in and out of the expansion chamber can be adjusted to freely change the refrigerating capacity of the refrigerator, so that it is possible to cool down or increase the cooling load. However, it is possible to increase the refrigerating capacity and take good measures against it.

Further, according to the invention as set forth in claim (2), a space separate from the expansion chamber communicates with the expansion chamber, thereby increasing the dead space of the expansion chamber and setting the variable adjustment range of the refrigerating capacity of the refrigerator. Can be expanded.

[Brief description of drawings]

The drawings show one embodiment of the present invention, FIG. 1 is an enlarged cross-sectional view of an essential part of an expander, and FIG. 2 is a cross-sectional view showing the entire structure of a refrigerator. (1) ... Compressor (13) ... Expander (16) ... Cylinder (17) ... Cold head (18) ... Displacer (21) ... Expansion chamber (22) ... Working chamber (23) ... Spring (elastic support means) (25) ... Airtight container (26) ... Space (34) ... Step motor (driving means)

Claims (2)

[Claims] 1. 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) that is partitioned and formed, and an elastic support means (23) that 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. Connected to the compressor (1)
Refrigerant gas pressure from the compressor (1) causes the displacer (18) to reciprocate to expand the refrigerant gas in the expansion chamber (21), thereby generating cold in the cold head (17) at the tip of the cylinder (16). In the Stirling refrigerator configured as described above, drive means (34) for varying the waste volume of the expansion chamber (21) by moving the displacer (18) and the elastic support means (23) in the cylinder axis direction is provided. A free displacer type Stirling refrigerator featuring. 2. The expansion chamber (21) is communicated with a space (26) in a closed container (25).
Free displacer type Stirling refrigerator described.