JPH068707B2 - Adiabatic expansion engine - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an engine for adiabatically expanding a compressed gas in order to obtain a cryogenic temperature in a superconducting device or the like.

[Technical background of the invention] Conventionally, in order to obtain a cryogenic temperature in a superconducting device or the like, a compressed helium gas is adiabatically expanded and cooled to a required low temperature. By the way, in such an adiabatic expansion engine that adiabatically expands high-pressure helium gas, the cylinder is housed in a vacuum container, its disassembly and maintenance are troublesome, and it is cooled to an extremely low temperature, so thermal conditions are severe. ,
It should be as simple and reliable as possible.

Therefore, the conventional adiabatic expansion engine of this type has a structure as shown in FIG. That is, 1 is a cylinder, and the piston 2 is movably accommodated in this cylinder. A suction port 3 for high-pressure helium gas is formed in the cylinder 1, and the suction port 3 is opened and closed by a suction valve body 4. Further, a discharge port 5 is formed on the peripheral surface of the cylinder 1,
The discharge port 5 is configured to be opened and closed by a substantially cylindrical discharge valve body 6 slidably accommodated in the cylinder 1. The discharge valve body 6 is provided with a seal member 7 for maintaining airtightness, and when the piston 2 comes into contact with the protrusions 8 and 9, the discharge valve body 6 reciprocates a predetermined distance to open and close the discharge port 5. Is configured. Further, a slit is formed in the discharge valve body 6 along the axial direction,
It is configured so that it is brought into contact with the inner surface of the cylinder 1 by its own elastic force and is held at that position by the frictional force with the cylinder 1 when the piston 2 separates.

In the conventional apparatus as described above, when the piston 2 descends, the suction valve body 4 is pushed by the piston 2 to open the valve, and high-pressure helium gas flows into the cylinder 1. Then, the piston 2 rises and the helium gas adiabatically expands. When the piston 2 rises to the full extent, the piston 2 comes into contact with the convex portion and the discharge valve body 6 rises to open the discharge port 5. When the piston 2 descends, the adiabatically expanded helium gas is discharged from the discharge port 5. During this time, the discharge valve body 6 is held in the valve open position by the frictional force with the cylinder 1.

[Problems of the Background Art] In the above-mentioned conventional one, the seal member 7 of the discharge valve body 6 slides on the inner surface of the cylinder 1 to open and close the discharge port 5. It is necessary to increase the pressing force of. Therefore, frictional heat is generated due to the sliding resistance of the seal member 7, causing a problem that the temperature of the helium gas adiabatically expanded rises.

Further, when the seal member slides in this way, its wear or the like is great, and it is necessary to replace it relatively frequently. However, in such an adiabatic expansion engine, since the cylinder is housed in the vacuum container as described above, disassembly or the like is troublesome, and there is a problem that a lot of labor is required for maintenance of this engine.

[Object of the Invention] The present invention has been made based on the above circumstances, and an object of the present invention is to provide an adiabatic expansion engine in which the exhaust valve body generates less heat and is easy to maintain.

SUMMARY OF THE INVENTION According to the present invention, a holding body that opens a discharge port in a moving direction of a piston and that is brought into contact with the piston is provided with a frictional resistance force required to hold the holding body at a predetermined position. A holding resistance mechanism for generating is provided, and a discharge valve body is provided to this holding body via a spring. Therefore, since the discharge valve body comes into contact with and separates from the discharge port to open and close the discharge port, friction is not generated and friction heat is not generated. Further, since the discharge valve body does not slide, abrasion of the seal member and the like does not occur, and since it is not necessary to frequently replace the seal member and the like, maintenance is easy.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Reference numeral 11 in the drawing denotes a cylinder, which is housed in a vacuum container (not shown) or the like and is thermally insulated from the outside. A piston 12 is movably accommodated in the cylinder 11. A suction port 13 is formed on the bottom wall of the cylinder 11, and the suction port 13 is configured to be opened and closed by a suction valve body 14.
A discharge port 15 is formed in the peripheral portion of the bottom wall so as to open in the moving direction of the piston 12. Also,
A substantially cylindrical holder 16 is movably accommodated in the cylinder 11. A pair of convex portions 18 and 19 are formed on the inner peripheral surface of the holding body 16 so as to be separated from each other by a predetermined distance. When the piston 12 comes into contact with the convex portions 18 and 19, the holding body 16 is It is configured to reciprocate a predetermined distance. Also, this holder 1
6 is provided with a holding resistance force mechanism that generates a frictional force necessary for holding it in a predetermined position with the cylinder 11. In the case of this embodiment, the holding resistance mechanism is composed of a ring-shaped spring 17 fitted with the outer periphery of the holding body 16 and having a slit, and the elastic force of the spring 17 causes a space between the holding body and the cylinder 11. It is configured to generate a minimum frictional force necessary for holding the holding body depending on its position. A discharge valve body 20 is provided at the lower end of the holding body 16. The discharge valve body 20 has a substantially cylindrical shape, and is connected to the holding body 16 by an engaging portion 21 so as to be movable in the axial direction by a predetermined amount. The seal member 22 is provided at the lower end of the discharge valve body 29.
2 is the discharge port 1 from the moving direction of the piston 12.
5, the discharge port 15 is opened and closed. Further, a spring 23 is interposed between the discharge valve body 20 and the holding body 16, and the discharge valve body 20
Is configured to be pressed against the discharge port 15 described above.
The spring 23 is a coil spring using a wire having a rectangular cross section, and is configured to minimize an extra space formed between the wires of the spring 23.

Next, the operation of the above embodiment will be described. First, as shown in FIG. 1, when the piston 12 is rising, the convex portion 18 of the holding body 16 contacts the piston 12 and
Rises together with the piston 12, the discharge valve body 20 separates from the discharge port 15, and the discharge port 15 opens. Then, when the piston 12 descends from this state, the piston 12 separates from the convex portion 18 of the holding body 16, the holding body 16 is held in that position by the frictional force of the spring 17, and the discharge port 15 is maintained in the open state. To be done. Then, when the piston 12 descends as shown in FIG. 2, the piston 12 comes into contact with the convex portion 19 of the holding body 16 and lowers it. Then, when the holding body 16 descends, the discharge valve body 20 contacts the discharge port 15 to close it, and when the holding body 16 descends together with the piston 12, the spring 23 is compressed. Then, when the piston 12 descends to the bottom dead center, the suction valve body 14 is pressed and intervenes, and high-pressure helium gas is supplied from the suction port 13 into the cylinder 11. Then, the piston 12 rises due to the pressure of this gas, but the spring 23
Is fully extended, the discharge valve body 20 is pressed against the discharge port 15 by the elastic pressing force of the spring 23. Therefore, the helium gas is sufficiently supplied into the cylinder 11 from the suction port 13, the pressure in the cylinder 11 is sufficiently increased, and the discharge valve body 20 is pressed against the discharge port 15 by the pressure to close the cylinder 11. The discharge valve body 20 is pressed against the discharge port 15 by the urging force of the spring 23 until it is maintained. Hereinafter, the operation is repeated in the same manner.

The present invention is not limited to the above embodiment. For example, the spring 23 does not necessarily have the structure of the above-described embodiment. Further, the holding resistance mechanism is not limited to the one using the ring-shaped spring as in the above embodiment.

[Advantages of the Invention] As described above, according to the present invention, the discharge port is opened in the moving direction of the piston, and the discharge valve body is attached to the holding body which is brought into contact with the piston and is moved through the spring. The exhaust port is opened and closed by contacting and separating from the exhaust port in the moving direction of the piston. Therefore, this holding body only needs to be provided with a frictional resistance force necessary for holding its position by the holding resistance mechanism, and heat generation due to frictional heat can be minimized. Further, since the seal member of the discharge valve body does not slide, it wears little and does not require frequent maintenance. Moreover, since the above-mentioned discharge valve body is attached to the holding body through the spring,
When the suction valve body opens and high-pressure gas is supplied to the cylinder, the gas is sufficiently supplied so that the pressure in the cylinder presses the discharge valve body to the discharge port to maintain the closed state. Thus, the discharge valve body can be maintained in the closed state by the urging force of the spring until it rises, and high-pressure gas can be prevented from blowing through the discharge port.

[Brief description of drawings]

1 and 2 are vertical cross-sectional views of an embodiment of the present invention in different operating states, and FIG. 3 is a vertical cross-sectional view of a conventional engine. 11 ... Cylinder, 12 ... Piston, 15 ... Discharge port, 16
... Holder, 17 ... Spring (holding resistance mechanism), 20 ...
Discharge valve body, 23 ... Spring.

Claims (1)

[Claims] 1. A cylinder, a piston moving in the cylinder, a discharge port opened in the cylinder in the moving direction of the piston, and abutting contact with the piston movably provided in the cylinder. And a holding resistance mechanism that gives a sliding resistance necessary to hold the holding body at that position when the piston separates from the holding body and the cylinder. And a discharge valve body movably attached to the holding body via a spring and abutting on the discharge port in the moving direction of the piston to close the piston, the adiabatic expansion engine.