JP2689615B2 - Stirling refrigerator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a split type Stirling refrigerator which is preferably used for cooling an infrared sensor or the like.

[Prior Art] FIG. 8 is a sectional view showing an outline of a conventional general split type Stirling refrigerator. As shown in the figure, this refrigerator has an expansion cylinder 1, a displacer 2 slidably fitted in the expansion cylinder 1, and an expansion / contraction mechanism between a low temperature end 2a of the displacer 2 and the expansion cylinder 1. Expansion chamber 3, a piston 4 protruding from the high temperature end 2b of the displacer 2, and a protruding end of the piston 4.
And a gas spring chamber 5 into which 4a is inserted. A regenerator (regenerator) 6 is housed in the displacer 2 for the purpose of downsizing, and the expansion chamber 3 is connected to the gas port 7 which is inverted and expanded to the high temperature end 2b side through the regenerator 6. ing. The role of the regenerator 6 is to obtain cold from the working gas sent to the expansion chamber 3 and precool the working gas newly sent to the expansion chamber 3. He is usually used as the working gas. The gas port 7 is connected to a compression chamber 9a of a compressor 9 which is separately arranged through a communication pipe 8, and the working gas is given a pressure change for operating the refrigeration cycle by the compressor 9. Further, the gas spring chamber 5 is filled with a biasing gas corresponding to an intermediate pressure between the high pressure and the low pressure of the working gas. As a result, the displacer 2 is operated by the expansion chamber 3 on the low temperature end 2a and the gas spring chamber 5
Therefore, it is driven up and down by the change in the differential pressure from the intermediate pressure acting on the protruding end 4a. 1a is a cold head.

The advantage of the split type configured in this way is that the vibration of the compressor 9 does not propagate to the expansion cylinder 1, so that a refrigerator with low vibration can be realized. Moreover, since it is only necessary to dispose the expansion cylinder 1 in a portion that requires cooling, it is convenient in that the space factor is improved. However, when the displacer 2 reaches the driving end, the low temperature end 2a or the high temperature end 2b is connected to the expansion cylinder 1
It is unavoidable that vibration occurs at this time because it is forcibly stopped by coming into contact with the corresponding inner ends of the. Moreover, since the regenerator 6 is generally made of a copper mesh having excellent thermal conductivity, the inertial mass of the displacer 2 is larger than that of the conventional one, and accordingly, the vibration when the displacer is stopped is also increased. There is. For this reason, when the purpose of use is a delicate one such as an infrared sensor, it is often the case that a sufficient vibration suppressing effect cannot be obtained only by making the refrigerator a split type.

On the other hand, as shown in Japanese Patent Laid-Open No. 64-41774 (see FIG. 9), a buffer piston is attached to the piston protruding end 4a.
10 is attached, and a pair of recessed portions 11a and 11b are provided at corresponding positions in the gas spring chamber 5 for tightly inserting the buffer piston 10 when the displacer 2 reaches both upper and lower drive ends. , The buffer piston 10 has the concave portions 11a, 1
There is also developed a device which has a buffering effect on the displacer 2 by acting a gas damping action when fitted to the 1b.

[Problems to be Solved by the Invention] However, since this type of refrigerator usually has a small displacer diameter of about 10 mm, it produces a sufficient damping action for a gas having a high diffusibility such as He. In order to make such a cushioning piston 10, the concave portions 11a, 1
For 1b, it is necessary to finish with a diameter gap of several μm, and the coaxiality of both upper and lower dampers must also be more accurate. Therefore, the above-mentioned gas damper method has a problem that processing is difficult. Further, even if such a high processing technique is adopted and proper operation is obtained, the negative pressure generated when the buffer piston 4 is separated from the recessed portions 11a and 11b acts on the displacer 2 as a braking force. On the contrary, when the displacer is reversed, it causes a malfunction. In particular, when the cold head 1a is cooled more than when the cold head 1a is close to room temperature, the expansion chamber 3
The change in the pressure of the working gas that occurs in 1) is reduced, and as a result, the differential pressure from the intermediate pressure is reduced and the driving force is reduced. Therefore, the displacer 2 may not be completely driven due to the application of the braking force.

The present invention has been made in view of these problems, and provides a Stirling refrigerator that can effectively reduce the generated vibration of a displacer without causing operational and manufacturing problems. Is intended.

[Means for Solving the Problems] The present invention employs the following means to achieve the above object.

That is, the Stirling refrigerator of the present invention has a basic structure as a split type, and has an elastic fitting that slidably fits on the outer circumference of the piston and causes friction with the piston when sliding. It is characterized in that a united body and a stopper mechanism for stopping the elastic fitting body prior to the displacer each time the displacer approaches the drive end are provided.

[Operation] With such a configuration, the elastic fitting body is stopped by the stopper mechanism prior to the displacer at the end of each stroke, whereby the relative position with respect to the piston is slidably changed and the piston is caused by friction. Apply braking force. For this reason, the displacer is gradually decelerated and quietly stopped at the drive end, and the generated vibration is reduced. And, a proper fitting state between the elastic fitting body and the piston can be relatively easily obtained,
Since it is not necessary to have a high processing accuracy as in the case of configuring the gas damper mechanism, the manufacturing becomes easy. Moreover, since the stopper mechanism does not work immediately after the displacer reverses and the elastic fitting body starts the stroke by attaching to the piston and does not generate friction, braking force is generated when it is inappropriate like the gas damper method and useful differential pressure driving force. Does not diminish.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. As is clear from FIG. 1, the basic structure of this Stirling refrigerator is almost the same as that shown in FIG. Therefore, the common parts are denoted by the same reference numerals and the description thereof is omitted. Further, the piston 4 has the same diameter and integrally protrudes from the high temperature end 2b of the displacer 2, and the conventional structure in which the high temperature end 2b contacts the inner end of the expansion cylinder 1 is abolished.

Thus, this one uses a brake shoe 21 in which a rubber 21b is attached to the inner circumference of a ring-shaped housing 21a as an elastic fitting body, which is fitted to the outer circumference of the piston 4.
The coefficient of friction between the brake shoe 21 and the piston 4 can be adjusted by changing the tightening force of the housing 21a.

The brake shoe 21 is provided with a pair of contact surfaces 22a and 22b on the inner wall of the gas spring chamber 5 for restricting the movable range of the brake shoe 21 to form a stopper mechanism 22. The contact surfaces 22a and 22b of
When the displacer 2 approaches the drive upper end or the drive lower end, the brake shoe 21 can be stopped prior to the displacer 2 (see FIGS. 2 and 5). That is, FIG. 2 shows a state in which the brake shoe 21 contacts the upper contact surface 22a and is stopped during the upward movement of the displacer 2. From this point onward, only the piston 4 moves upward, While the brake shoe 21 slides and changes the relative position with respect to the piston 4, the braking force F ₁ as shown in the figure is applied. For this reason,
The displacer 2 is gradually decelerated and, as a result, is quietly stopped at the upper end of the drive shown in FIG. Next, when the displacer 2 is driven in reverse from this state, as shown in FIG.
It is separated from the upper contact surface 22a in the state of being attached to and goes toward the drive lower end. Then, in FIG. 5, when the brake shoe 21 comes into contact with the lower contact surface 22b and is stopped, only the piston 4 moves downward from this point onward, so that the brake shoe 21 is positioned relative to the piston 4. The braking force F ₂ as shown in the figure is applied while slidingly changing in the direction opposite to the above. Therefore, the displacer 2 is gradually decelerated, and as a result, the displacer 2 is quietly stopped at the driving lower end shown in FIG. Further, when the displacer 2 is reversely driven from this state, as shown in FIG. 7, the brake shoe 21, while being attached to the piston 4, separates from the lower contact surface 22b and moves toward the upper end of the drive again. . The operation timing of the brake shoe 21 can be accelerated by providing a short distance between the contact surfaces 22a and 22b, and delayed by providing a long distance.

Therefore, according to the illustrated Stirling refrigerator, the generated vibration at the drive end can be effectively reduced as compared with the conventional structure in which the displacer 2 is forcibly stopped. Moreover, according to this structure, since the braking force is not generated immediately after the displacer 2 is reversed, it does not cause a malfunction as in the gas damper system. Further, if the tightening force of the housing 21a is provided so that it can be adjusted with a screw or the like, the braking effect can be easily set, and high processing accuracy as when configuring the gas damper mechanism is not required. Therefore, it is easy to manufacture.

Although the embodiment of the present invention has been described above, the elastic body is not limited to the rubber shape as shown in the drawing, and may be a metal spring or the like having a coating on the sliding surface. Further, it is also possible to adopt a structure in which a sliding portion made of resin or the like is pressed by a metal spring.

[Effect of the Invention] In the Stirling refrigerator of the present invention, the stopper mechanism works before the displacer reaches the drive end, and the elastic fitting body is stopped before the displacer.
A braking force due to friction acts on the displacer from the elastic fitting body, so that the displacer is quietly stopped at the drive end, which effectively reduces the vibration generated at the drive end. The setting of the braking force by the elastic fitting body is relatively easy, and stable performance can be exhibited without high processing accuracy, which is advantageous in manufacturing and cost. Further, since the braking force does not act when the displacer reverses from the driving end, it does not affect the differential pressure driving force, and secure operation is ensured even when the cold head temperature is low.

[Brief description of the drawings]

1 to 7 show an embodiment of the present invention, FIG. 1 is a schematic sectional view, and FIGS. 2 to 7 are partially enlarged sectional views for explaining the operation. FIG. 8 is a sectional view corresponding to FIG. 1 showing a conventional example, and FIG. 9 is a sectional view showing another conventional example.
9 is a sectional view corresponding to FIG. 8 and FIG. 8. 1 ... Expansion cylinder, 2 ... Displacer 2a ... Low temperature end, 2b ... High temperature end 3 ... Expansion chamber, 4 ... Piston 4a ... Projection end, 5 ... Gas spring chamber 21 ... Elastic fitting ( Brake shoe) 22 …… Stopper mechanism

Claims (1)

(57) [Claims] 1. An expansion cylinder, a displacer slidably fitted in the expansion cylinder, an expansion chamber expanded and contracted between a low temperature end of the displacer and the expansion cylinder, and a high temperature end of the displacer. It has a projecting piston and a gas spring chamber into which the projecting end of this piston is inserted, and by the differential pressure between the working pressure acting from the expansion chamber to the low temperature end and the intermediate pressure acting from the gas spring chamber to the projecting end. The displacer is configured to be vertically driven, and an elastic fitting body that slidably fits on an outer circumference of the piston and generates friction between the displacer and the piston at the time of sliding, and the displacer has a driving end. And a stopper mechanism for stopping the elastic fitting body prior to the displacer each time it approaches the Stirling refrigerator.