JP2772036B2 - Valve train - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a valve operating mechanism in a reciprocating gas expander of a helium refrigerator.

(Prior Art) Generally, in reciprocating internal combustion engines, compressors, and the like,
A valve mechanism that opens and closes in response to the reciprocating motion of the piston and that supplies or discharges fluid into the cylinder is provided. There are various types of such valve operating mechanisms.

By the way, in a reciprocating gas expander of a helium refrigerator, for example, a lubricant cannot be used because the working fluid is an extremely low temperature gas. Therefore, it is necessary to adopt a mechanism having no sliding portion as a valve operating mechanism used in such a gas expander. Such a valve train is described, for example, in Japanese Patent Application No.
226289 "and" Japanese Patent Application No. 61-159178 ".

FIG. 3 shows an example of such a valve operating mechanism of a conventional gas expander. That is, 2 in the figure is a cylinder, and 1 is a piston. An intake port 11 is provided at the top of the cylinder 2, and the intake port 11 communicates with the inside of the cylinder 2 through a flow port 13. In addition, in the intake port 11, a valve body 12 that opens and closes the above-described flow port 13 to control gas supply is provided. The valve element 12 includes a valve body 14 and a prosthetic rod 16 protruding from the valve element. The valve element 12 is urged by a conical coil spring 15. The valve body 14 is pressed by the coil spring 15 against the peripheral edge of the flow port to close the flow port 13, and the push rod
16 protrudes into the cylinder 2 through the circulation port 13.

A valve opening / closing mechanism 3 for opening and closing the valve body 12 is provided at the top of the piston 1. The valve opening / closing mechanism 3 includes a pressing member 6 and a support member 5 having a dish shape. A stopper 8 protrudes from the back surface 6a of the pressing member 6, and this stopper 8 penetrates a hole formed in the center of the supporting member 5. A conical coil spring 5 is provided between the supporting member 5 and the pressing member 6, and the pressing member 6 is urged by the coil spring 4 in the projecting direction. A disc-shaped stopper head 7 is formed at the tip of the stopper 8, and the stopper head 7 comes into contact with the back surface of the upper supporting member 5, so that the maximum projecting amount of the pressing member 6 is reduced. Regulated. The support member 5 is attached to the piston 1 on the top surface. A hole 1a is formed in the center of the top of the piston 1 so that the stopper head 7 can move within the hole 1a. The spring constant of the coil spring 4 is set to be larger than the spring constant of the coil spring 15. The pressing member 6 and the valve element 12 are guided by the conical coil springs 4 and 15 for axial movement. Therefore, the stopper 8 and the supporting member 5
Gaps are formed between the holes, between the stopper head 7 and the hole 1a, between the valve body 12 and the wall of the intake port 11, etc.
These members are configured so as not to contact with each other. Therefore, the valve train has no sliding portion and is configured so that it is not necessary to use a lubricant.

In such a valve operating mechanism, when the piston 1 approaches the top dead center, the pressing member 6 abuts against and pushes the push rod 16, and the valve body 12 opens the valve against the biasing force of the coil spring 15. I do. When the piston further moves, the pressing member 6 comes into contact with the top surface of the cylinder, the coil spring 4 is compressed, and the pressing member 6 is immersed in the piston 1. Further, when the piston 1 retreats beyond the top dead center, the pressing member 6 protrudes from the piston 1, and when the stopper head 7 of the stopper 8 comes into contact with the back surface of the support member 5, the pressing member As a result, the pressing member 6 separates from the push rod 16 of the valve body 12 and the valve body 12 closes.

(Problem to be Solved by the Invention) In the valve train as described above, the coil spring 4 is
Both the urging and guidance are used. Therefore, the pressing member 6 may shift in the radial direction due to a shape error of the coil spring 4 and other causes. In such a case, especially when the pressing member 6 is inclined, the peripheral portion of the stopper head 7 may come into contact with the inner peripheral surface of the hole. In such a case, the sharp peripheral portion of the stopper head 7 and the hole
Galling occurs with the inner peripheral surface of 1a, which may cause malfunction or damage of the valve mechanism. In particular, in the case of such a gas expander of a helium refrigerator, since the lubricant cannot be used as described above, the above-described problem is likely to occur.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a reliable and highly reliable valve train.

[Means for Solving the Problems] According to the present invention, in the above-described valve train, the peripheral surface of the stopper head of the stopper protruded from the pressing member has an axial cross-sectional shape. It is formed in a shape such as a convex curve, for example, a spherical surface.

(Operation) In the present invention, as described above, the peripheral surface of the stopper head has a shape such that the axial cross-sectional shape is a convex curve, so that the peripheral surface of the stopper head has a hole. Even if the inner peripheral surface is brought into contact with the inner peripheral surface, galling or the like does not occur between the inner peripheral surface and the valve operating mechanism with reliable operation and high reliability can be provided.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. This embodiment is a valve operating mechanism of a reciprocating gas expander of a helium refrigerator.

Reference numeral 22 in the figure denotes a cylinder of the gas expander, in which a piston 21 is accommodated in a reciprocating manner while maintaining airtightness. An intake port 31 is connected to the top of the cylinder 22. The gas compressor is further provided with an exhaust port, but this exhaust port is not shown. The intake port 31 communicates with the inside of the cylinder 22 through a flow port 33. Then, a low-temperature helium gas is supplied into the cylinder through the circulation port 33.

In the intake port 31, there is provided a valve body 32 for controlling the gas supplied by opening and closing the flow opening 33. The valve element 32 includes a valve body 34 and a push rod 36 protruding from the valve body. The valve body 34 contacts the peripheral edge of the flow port 36 to close the flow port, and the push rod 36 penetrates the flow port 33 and protrudes into the cylinder 22. Also, the above valve body
34 includes a holding portion 46 and a dish-shaped sealing member 45 held by the holding portion, such that the sealing member 45 comes into contact with the peripheral portion of the distribution port 33 to maintain airtightness. It is configured. The valve body 32 is urged in the valve closing direction by a first elastic body, that is, a conical coil spring 35. The coil spring 35 serves both to bias and support the valve element 32, and the valve element 32 is guided radially by the coil spring 35. Therefore, the valve element 32 and its push rod 16 are configured so as not to contact the inner peripheral surface of the flow port 33 and the like.

At the top of the piston 21, a valve opening / closing mechanism 23 for opening / closing the valve body 32 is provided. This valve opening and closing mechanism
23 has a pressing member 26 which can be protruded and retracted and a supporting member 25 on a plate. From the surface of this pressing member 26, a rod-shaped stopper
The stopper 28 has a disk-shaped stopper head 27 having an enlarged diameter formed at the tip of the stopper 28. The stopper 28 penetrates a hole formed in the center of the bottom wall 25a of the support member 25. A second elastic body, that is, a conical coil spring 24 is provided between the pressing member 26 and the support member 25, and is urged by the coil spring 24 in a projecting direction from the pressing member 26. .
The maximum protrusion amount of the pressing member 26 is regulated by the stopper head 27 contacting the bottom wall 25a of the support member 25.

The support member 25 is mounted in a recess formed on the top surface of the piston 21. A hole 21a is formed in the center of the top of the piston 21. The stopper 27 of the pressing member 26 is movably accommodated in the hole. In addition, the above-described coil spring 24 is
The pressing member 26 is guided in the radial direction by the coil spring 24. Therefore, the stopper 28 and the stopper head 27 of the pressing member 26 are configured so that the hole of the support member 25 and the inner peripheral surface 42 of the hole 21a do not come into contact with each other. The spring constant of the coil spring 24 is set to be larger than the spring constant of the coil spring 35.

As shown in FIG. 2, the stopper head 27 is formed such that its outer peripheral surface 41 is, for example, spherical, that is, the cross-sectional shape along the axial direction is a convex curve. I have. At least the outer peripheral surface 41 of the stopper head 27 is coated with a film made of a self-lubricating material. As the self-lubricating material, for example, a fluorine-based synthetic resin material such as Teflon (trade name) reinforced with reinforcing fibers is used. Further, such a coating may be applied to the inner peripheral surface 42 of the hole 21a.

Next, the operation of such an embodiment will be described. When the above piston 21 moves rightward in the figure and approaches its top dead center,
The pressing member 26 of the valve opening / closing mechanism 23 provided on the top of the piston 21 comes into contact with the tip of the push rod 36 of the valve body 32.
Since the spring constant of the coil spring 24 urging the pressing member 26 is larger than the spring constant of the coil spring 35 pressing the valve body 32, when the piston 21 further moves, the coil spring 53 is compressed. , The valve body 32 is moved to open the valve,
Gas is supplied into the cylinder 22 via 33. When the piston 21 further moves, the pressing member
26 comes into contact with the top surface of the cylinder 22, the coil spring 24 is compressed, and the pressing member 26 is immersed in the piston 21. Next, when the piston 21 moves to the left in the drawing beyond the top dead center, the pressing member 26 protrudes from the piston 21. Then, the stopper head 27 is
When pressed against the bottom wall, the pressing member 26 no longer protrudes, and the pressing member 26 separates from the top surface of the cylinder 22 and then separates from the push rod 36 of the valve body 32. In such a state, the valve element 32 is advanced by the coil spring 35, closes the circulation port 33, and the supply of gas stops. By appropriately setting the stroke of the pressing member 26, the projecting amount of the push rod 36, and the like, the supply timing of the gas is controlled.

Since the pressing member 26 is guided only by the coil spring 24 as described above, the pressing member 26 may shift or tilt due to an error of the coil spring 24 or other reasons. In such a case, the stopper head 27 of the pressing member 26 may come into contact with the inner peripheral surface 42 of the hole 21a. However, since the peripheral surface of the stopper head 27 is formed into a spherical surface, that is, a shape in which the cross-sectional shape in the axial direction is a convex curve, the peripheral surface of the stopper head is smoothly formed in the hole. There is no galling between them due to the contact with the peripheral surface. Further, in this embodiment, since a coating made of a self-lubricating material is applied to the peripheral surface of the stopper head, the resistance when the stopper head contacts the inner peripheral surface of the hole becomes extremely small. , Reliability is further improved.

It should be noted that the present invention is not limited to the above embodiment, but can be applied to a valve operating mechanism other than this embodiment.

[Effects of the Invention] As described above, according to the present invention, galling between the stopper head and the hole can be reliably prevented, and a highly reliable valve train can be provided.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is an overall longitudinal sectional view, and FIG. 2 is an enlarged longitudinal sectional view showing a stopper head and a hole. FIG. 3 is a longitudinal sectional view showing a conventional valve train. 21 ... Piston, 22 ... Cylinder, 25 ... Support member, 26
…… Pressing member, 27 …… Stopper head, 32 …… Valve, 45…
... Seal member

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hitoshi Hattori 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Research Institute, Inc. (72) Inventor Katsumasa Araoka 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Address Toshiba Research Institute, Inc. (58) Fields investigated (Int. Cl. ⁶ , DB name) F01L 21/00 F25B 9/06

Claims (3)

(57) [Claims] 1. A cylinder, a piston provided reciprocally in the cylinder, a flow port communicating with a fluid in a top portion of the cylinder, and a valve body for opening and closing the flow port. A first elastic body for urging the valve body in a valve closing direction;
A pressing member provided at the top of the piston so as to be able to protrude and retract, a second elastic body for urging the pressing member in the protruding direction, a hole formed at the top of the piston, A stopper installed and inserted into the hole,
A stopper head formed at the tip of the stopper to regulate the maximum projecting amount of the pressing member, wherein when the piston moves to the top of the cylinder, the pressing member comes into contact with the valve body and the valve body Wherein the peripheral surface of the stopper head is formed in such a shape that its axial cross-section has a convex curve. 2. The valve mechanism according to claim 1, wherein a coating made of a self-lubricating material is applied to a peripheral surface of the stopper head. 3. The valve mechanism according to claim 1, wherein the valve body includes a seal member that abuts on a peripheral portion of the flow opening to maintain a sealing property.