JPH0318602A - Valve system - Google Patents

Abstract

PURPOSE:To secure positive operation of a valve system, and to improve its reliability by forming an outer surface of a stopper head projecting from a push member, so that its axial profile is a convex curve. CONSTITUTION:A valve system 23 of a valve 32 for supplying gas into a cylinder 22 is composed of a push member 26 and a coil spring 24. The maximum projecting length of the push member 26 from a piston 21 is limited by a stopper head 27. An outer surface 41 of the stopper head 27 is formed so that a profile of its axial section is a convex curve such as a spherical surface. In this way, scuffing or the like is prevented because of smooth contact of the outer surface 41 with the inner surface 42 even if the stopper head 27 is brought into contact with the inner surface 42 of a hollow part 21a in such a state that the push member 26 is offset or inclined owing to an error of the coil spring 24 or some other reasons.

Description

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

(Prior Art) Generally, reciprocating internal combustion engines, compressors, and the like are provided with a valve mechanism that opens and closes in response to the reciprocating motion of a piston to supply or discharge fluid into a cylinder. Conventionally, there are various types of such valve operating mechanisms.

By the way, in a reciprocating type gas expander such as a helium refrigerator, for example, a lubricant cannot be used because the working fluid is a cryogenic gas. Therefore, the valve operating mechanism used in such a gas expander needs to have no sliding parts. Such a valve mechanism is known, for example, from the ``Japanese Patent Application 1986
-226289”, “Patent Application No. 159178/1983”
has been disclosed.

An example of such a conventional valve mechanism for a gas expander is shown in FIG. That is, 2 in the figure is a cylinder, and 1 is a piston. An intake boat 11 is provided at the top of the cylinder 2, and the intake boat 11 communicates with the inside of the cylinder 2 through a flow port 13. Also, this intake port 1
A valve body 12 is provided within the gas flow chamber 1 for controlling gas supply by opening and closing the above-mentioned flow port 13. The valve body 12 includes a valve body 14 and a push rod 16 protruding from the valve body.
It is composed of. Further, this valve body 12 is biased by a conical coil spring 15. The valve body 14 is pressed by the coil spring 15 against the periphery of the communication port 13 to close the communication port 13.
Further, the push rod 16 passes through the flow port 13 and projects into the cylinder 2.

Furthermore, a valve opening/closing mechanism 3 for opening and closing the valve body 12 is provided at the top of the piston 1 .

This valve opening/closing mechanism 3 includes a pressing member 6 and a support member 5 having a plate shape. A stopper 8 protrudes from the back surface 6a of the pressing member 6, and this stopper 8 passes through a hole formed in the center of the support member 5 shown in FIG. Further, a conical coil spring 5 is provided between the supporting member 5 and the suppressing member 6, and the pressing member 6 is biased in the projecting direction by the coil spring 4. Further, a disc-shaped stopper head 7 is formed at the tip of the stopper 8, and the stopper head 7 abuts against the back surface of the support member 5, thereby regulating the maximum amount of protrusion of the pressing member 6. has been done. This support member 5 is attached to the top surface of the piston 1 described above. Further, a six part 1a is formed at the center of the top of the piston 1, and the above-mentioned stopper head 7 is configured to be movable within this hole part la. Also,
The spring constant of the coil spring 4 is set larger than that of the coil spring 15. Note that this pressing member 6
The axial movement of the valve body 12 and the valve body 12 is guided by a conical coil spring 4.15. Therefore, gaps are formed between the stopper 8 and the hole in the support member 5, between the stopper head 7 and the six part 1a, between the valve body 12 and the wall of the intake boat 11, etc. It is constructed in such a way that it cannot be touched. Therefore, this valve operating mechanism is constructed so that the sliding parts do not require the use of lubricant.

In such a valve mechanism, when the piston 1 approaches the top dead center, the pressing member 6 contacts and presses the push rod 16, and the valve body 12 resists the biasing force of the coil spring 15 to open the valve. Cheating. When the piston moves further, the pressing member 6 comes into contact with the top of the cylinder, the coil spring 4 is compressed, and the pressing member 6 is retracted into 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, this pressing member It no longer stands out,
This pressing member 6 separates from the push rod 16 of the valve body 12, and this valve body 12 closes.

(Problems to be Solved by the Invention) In the above-described valve operating mechanism, the coil spring 4 serves both to bias and guide the pressing member 6. Therefore, due to the shape error of this coil spring 4 and other causes, this pressing member 6
may shift in the radial direction.

In such a case, especially if the pressing member 6 is tilted, the peripheral edge of the stopper head 7 may come into contact with the inner peripheral surface of the hole. In such a case, galling may occur between the sharp peripheral edge of the stopper head 7 and the inner circumferential surface of the hole 1a, resulting in malfunction or damage to the valve mechanism. Particularly, in the case of a gas expander of such a helium refrigerator, a lubricant cannot be used as described above, so the above-mentioned problems are likely to occur.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a valve train mechanism with reliable operation and high reliability.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a valve mechanism as described above, in which the peripheral surface of the stopper head of the stopper protruding from the pressing member has an axial cross-sectional shape. It is formed into a convex curved shape, for example, a spherical surface.

(Function) As described above, the circumferential surface of the stopper head is shaped so that its axial cross-sectional shape is a convex curve. It is possible to provide a valve train mechanism that does not cause galling or the like even when it comes into contact with the inner circumferential surface, and has reliable operation and high reliability.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. This embodiment is a valve mechanism for a reciprocating type gas expander of a helium refrigerator.

22 in the figure is a cylinder of this gas expander, and a piston 21 is housed in the cylinder 22 so as to be airtight and movable back and forth. An intake boat 31 is connected to the top of the cylinder 22. Note that this gas compressor is provided with other exhaust ports, but this exhaust port is omitted from illustration. This intake boat 31 communicates with the inside of the cylinder 22 through a flow port 33. Then, low-temperature helium gas is supplied into the cylinder through this flow port 33.

A valve body 32 is provided within the intake port 31 to open and close the flow port 33 to control the gas supplied.

The valve body 32 is composed of a valve zero body 34 and a push rod 36 protruding from the valve body. The valve body 34 contacts the peripheral edge of the communication port 36 to close the communication port, and the push rod 36 penetrates the communication port 33 and projects into the cylinder 22. Further, the valve body 34 includes a holding portion 46 and a dish-shaped sealing member 45 held by the holding portion.
This sealing member 45 is configured to abut against the peripheral edge of the above-described flow port 33 to maintain airtightness. Further, the valve body 32 is biased 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 body 32, and the valve body 32 is guided in the radial direction by the coil spring 35. Therefore, this valve body 32
The push rod 16 is configured so as not to come into contact with the inner circumferential surface of the flow port 33 or the like.

Furthermore, a valve opening/closing mechanism 23 is provided at the top of the piston 21 to open and close the valve body 32 . This valve opening/closing mechanism 23 includes a suppressing member 26 and a dish-shaped support member 25 that can be freely extended and retracted. A rod-shaped stopper 28 is protruded from the surface of the suppressing member 26, and this stopper 28
A disk-shaped stopper head 27 with an enlarged diameter is formed at the tip. Further, this stopper 28 passes through a hole formed in the center of the bottom wall portion 25a of the support member 25. Further, a second elastic body, that is, a conical coil spring 24 is provided between the pressing member 26 and the support member 25, and the pressing member 26 is biased in the projecting direction by the coil spring 24. . Furthermore, the stopper head 27 comes into contact with the bottom wall portion 25a of the support member 25, so that the maximum amount of protrusion of the pressing member 26 is regulated.

The support member 25 described above is installed in a recess formed in the front surface of the piston 21. Further, a hole 21a is formed in the center of the top of the piston 21. and,
The stopper head 27 of the pressing member 26 is movably accommodated in this hole. In addition, the above coil spring 2
Reference numeral 4 serves to urge and support the pressing member 26, and the suppressing member 26 is guided in the radial direction by the coil spring 24. Therefore, the stopper 28, stopper head 27, etc. of this pressing member 26 are configured so as not to contact the hole of the support member 25 or the inner circumferential surface 42 of the hole portion 21a. Further, 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 has an outer circumferential surface 41 formed in a spherical shape, that is, a cross-sectional shape along the axial direction is a convex curve. There is. Further, at least the outer circumferential surface 41 of the stopper head 27 is coated with a coating made of a self-lubricating material. As this self-lubricating material, for example, a fluorine-based synthetic resin material such as Teflon (trade name) reinforced with reinforcing fibers is used. In addition, the hole 21
The tl coating may also be applied to the inner circumferential surface 42 of a.

Next, the operation of such an embodiment will be explained. When the piston 21 moves to the right in the figure and approaches its top dead center,
The pressing member 26 of the valve opening/closing mechanism 23 provided at 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 that urges this pressing member 26 is larger than the spring constant of the coil spring 35 that presses the valve body 32, when the piston 21 moves further, this coil spring 53 is compressed. Valve body 32
is moved to open the valve, and gas is supplied into this cylinder 22 through the flow port 33. And this piston 21
When the press member 26 moves further, the pressing member 26 presses against the cylinder 22.
The coil spring 24 is compressed and the pressing member 26 is retracted into the piston 21. Next, as this piston 21 moves beyond the top dead center toward the side in the figure, this pressing member 26 protrudes from this piston 21. Then, the stopper head 27 is attached to the support member 25.
When it comes into contact with the bottom wall of the valve body 32, the pressing member 26 no longer protrudes, and the pressing member 26 separates from the top surface of the cylinder 22 and then from the push rod 36 of the valve body 32. In this state, the valve body 32 is moved forward by the coil spring 35, closes the flow port 33, and gas supply is stopped. By appropriately setting the stroke of the pressing member 26, the amount of protrusion of the push rod 36, etc., the timing of supplying the gas is controlled.

The above-mentioned pressing member 26 is a coil spring 24 as described above.
This coil spring 24
This pressing member 26 may be displaced or tilted due to errors 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 circumferential surface of the stopper head 27 is formed into a spherical surface, that is, its cross-sectional shape in the axial direction is a convex curve, the circumferential surface of the stopper head 27 smoothly moves inside the hole. It hits the peripheral surface and does not cause galling or the like between them. In addition, in this embodiment, a membrane made of a self-lubricating material is attached around the stopper head, so that the resistance when the stopper head comes into contact with the inner peripheral surface of the hole is extremely small. This further improves reliability.

It should be noted that the present invention is not limited to the above-described embodiment, but can also be applied to valve train mechanisms 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 mechanism can be provided.

[Brief explanation of the drawing]

FIGS. 1 and 2 show an embodiment of the present invention, with FIG. 1 being a longitudinal cross-sectional view of the entire device, and FIG. 2 being a longitudinal cross-sectional view showing an enlarged portion of the stopper head and hole portion. Moreover, FIG. 3 is a longitudinal cross-sectional view showing a conventional valve operating mechanism.

Claims (3)

[Claims] (1) A cylinder, a piston provided in the cylinder so as to be able to reciprocate, a communication port that communicates with the top of the cylinder through which fluid flows, and a valve body that opens and closes the communication port;
a first elastic body that biases the valve body in the valve-closing direction; a pressing member provided on the top of the piston so as to be protrusive and retractable; and a second elastic body that biases the pressing member in the protruding direction. , a hole formed at the top of the piston, a stopper protruding from the pressing member and inserted into the hole, and a stopper head formed at the tip of the stopper for regulating the maximum amount of protrusion of the pressing member. and configured such that when the piston moves to the top of the cylinder, the pressing member comes into contact with the valve body to open the valve body, wherein the circumferential surface of the stopper head is A valve mechanism characterized in that its axial cross-sectional shape is formed into a convex curve. (2) The valve train mechanism according to claim 1, wherein a coating made of a self-lubricating material is applied to the circumferential surface of the stopper head. (3) The valve operating mechanism according to claim 1, wherein the valve body includes a seal member that abuts against a peripheral edge of the flow port to maintain sealing performance.