JP2007170583A - Fluid control valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid control valve which achieves high durability by extending a time until an abutting part exceeds a designed limit. <P>SOLUTION: The fluid control valve controls the flow of steam by making a resin valve member 14 abut on or separate from a valve seat curved surface 16. A valve seat has the protruded valve seat curved surface 16 on the upper side. The abutting part which abuts on the valve seat curved surface 16 of a valve element has an inclined surface 14a expanding from the lower side to the upper side. As a result, the abutting part which abuts on the valve seat curved surface 16 of the valve member 14 has the inclined surface 14a. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a valve seat seal structure for a fluid control valve that controls the flow of fluid.

FIG. 7 shows an example of a seal structure of a valve seat that has been conventionally implemented in a fluid control valve for high-temperature fluid that controls high-temperature fluid such as steam. A small diameter portion 51a is formed at the lower end of a valve shaft 51 that is connected to a pilot valve (not shown) and is slidable in the vertical direction, and a screw portion 51b is formed at the tip. A support disc 52 is fitted into the small diameter portion 51a. A valve member 54 made of a fluororesin and having a flat bottom surface is fitted into the groove of the support disc 52 and is sandwiched by a pressing plate 57 and fixed by screwing the nut 56 to the screw portion 51b. The valve seat 54 is formed on the valve body 55.
Here, since the fluid is at a high temperature, the life of the rubber does not last, and the rubber cannot be used for the valve body. Therefore, a fluorine-based resin is used for the valve member 53. On the other hand, the shape of the valve seat is generally an arc shape having a certain curvature.
When the flat surface portion, which is the lower surface of the valve member 53, is brought into contact with the valve seat 54, the flow control valve is closed, and the flat surface portion, which is the lower surface of the valve member 53, is separated from the valve seat 54. As a result, the flow control valve is opened.

Another embodiment of a fluid control valve for high temperature fluid is shown in FIG. Since the schematic structure is the same as in FIG. 7, only the differences will be described. The valve member 60 made of fluororesin has an inclined surface 60a that expands upward at a portion that contacts the valve seat.
On the other hand, the valve seat 62 is configured by an inclined surface that expands upward. Therefore, the inclined surface 62a of the valve member 60 is in contact with the valve seat 62 which is an inclined surface.
FIG. 9 shows an enlarged view at the time of contact. The inclination angle of the inclined surface 60a of the valve member 60 with respect to the horizontal plane is larger than the inclination angle of the inclined surface of the valve seat 62 with respect to the horizontal plane. This is because when the angles are the same, the surfaces come into contact with each other, so that the pressing force per area decreases, the sealing force per area becomes weak, and leakage occurs.

However, the prior art has the following problems.
(1) Since a pressing force is applied to the valve member in a state where a high-temperature fluid is flowing, there has been a problem that the fluorine-based resin valve member is deformed by creep. In the valve seat seal structure shown in FIG. 7, a case where deformation due to creep occurs will be described with reference to FIG.
In FIG. 10, the left side of the center line shows the initial state. Further, the right side of the center line shows a state in which the valve member 53 is closer to the valve seat 54 by 0.5 mm due to creep. Initially, the diameter of the contact portion between the valve member 53 and the valve seat 54 was 41 mm as shown in the figure. When the valve member 53 is close to the valve seat 54 by 0.5 mm, the diameter of the contact portion between the valve member 53 and the valve seat 54 is 45 mm as shown in the drawing. Here, as the diameter of the contact portion increases, the area where the valve body comes into contact with the steam increases, so the force of the steam that presses the valve body downward increases.

In this fluid control valve, the valve body is biased downward by a spring, but the limit diameter at which the valve body comes into contact with steam, calculated from the design value of the spring force, is 42.6 mm. If this value is exceeded, the force that pushes the valve body downward will be too large than the design value, and the thrust force that pushes the valve body will increase relative to the thrust force that pushes up the piston, and the pilot pressure for opening the valve will deviate from the design value. End up.
That is, the creep causes the valve body to approach 0.5 mm from the valve seat 54, and the pressing force of the valve body becomes larger than the piston thrust force for opening the valve, resulting in poor operability. there were. Naturally, if the piston is enlarged, the thrust is increased, but it is necessary to increase the size of a pilot valve or the like that slides the valve shaft.

(2) On the other hand, in the valve seat seal structure illustrated in FIG. 8, one end portion of the valve seat 62 is initially in contact with the inclined surface 60 a of the valve member 60. When creep occurs, one end portion of the valve seat 62 is in a state of biting into the inclined surface 60a of the valve member 60, as shown in FIG. Here, a portion 60d indicated by a dotted line in the figure is a plastic deformation portion due to creep, and the sealing force is almost lost. The portion 60c is an elastically deforming portion, and is a portion that bears the sealing force. However, the portion 60c has an inclination angle at which the inclined surface 60a and the valve seat 62 are slightly different, so the width of the portion 60c increases. , 60c will contact and seal as a flat surface. For this reason, the surface pressure is lowered, the stability of the seal is lacking, and leakage may occur.

  Accordingly, the present invention has been made to solve such a problem, and an object thereof is to provide a highly durable fluid control valve.

In order to achieve the above object, the fluid control valve of the present invention has the following characteristics.
(1) A fluid control valve that controls the flow of fluid by bringing a resinous valve body into contact with or away from the valve seat, wherein the valve seat forms a curved surface that is convex upward, and the valve of the valve body The contact portion that contacts the seat curved surface has an inclined surface that expands from the lower side toward the upper side.
(2) In the fluid control valve described in (1), an inclination angle between the inclined surface and a horizontal plane is approximately 30 degrees.

The operation and effect of the fluid control valve having the above configuration will be described.
Since the contact portion that contacts the valve seat curved surface of the valve body has an inclined surface, it is the inclined surface that contacts the arcuate valve seat curved surface of the valve seat. Initially, the circumferential surface of the inclined surface is in contact with the curved surface of the valve seat.
As the time elapses, the resin valve body is pressed in a high temperature state by a high temperature fluid such as steam, and plastic deformation due to creep occurs. The deformation due to creep is plastic deformation, and the plastically deformed portion can no longer function as a seal. However, on the inclined surface of the valve body, there is newly formed a part that comes into contact with the curved surface of the valve seat on the outside subjected to plastic deformation. Since that portion is elastically deformed and is in contact with the valve seat, it performs a sufficient sealing function.

As the creep progresses, the seal portion gradually moves to the upper side of the inclined surface. As a result, the diameter of the seal portion increases. However, since it has an inclination of, for example, 30 degrees, since the diameter is only moved by the sin of the moving distance in the inclined portion, the moving distance as the diameter can be reduced.
Thereby, the time until the contact portion exceeds the design limit can be extended, and a high-temperature flow control valve with high durability can be provided.

A fluid control valve according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of the fluid control valve 10. FIG. 1 shows a case where the fluid control valve 10 is in a valve closed state, and FIG. 2 shows a case where the fluid control valve 10 is in a valve open state.
An input port 23 and an output port 24 are formed in the metal valve body main body 17. The input port 23 and the output port 24 communicate with each other through a valve hole in which the valve seat curved surface 16 is formed. A hollow cylinder 20 is attached to the valve body main body 17 via a pair of valve shaft brackets 25 and 26 that hold the valve shaft 11 slidably in the vertical direction. A piston 18 is held in the hollow portion of the cylinder 20 so as to be slidable in the vertical direction.

A valve shaft 11 is attached to the center of the piston 18 downward. The valve shaft 11 is held by a pair of valve shaft brackets 25 and 26 via a seal member.
Of the hollow portion of the cylinder 20, the lower hollow portion 20 a divided by the piston 18 communicates with the air port 22. Of the hollow portion of the cylinder 20, the upper hollow portion 20 b divided by the piston 18 communicates with the air vent port 21. A biasing spring 19 for biasing the piston 18 downward is attached to the upper hollow portion 20b.

As shown in FIG. 3 as an enlarged view, a small diameter portion 11a is formed at the lower end of the valve shaft 11, and a screw portion 11b is formed at the tip thereof. A support disk 12 is fitted to the small diameter portion 11a. A valve member 14 made of a resin such as fluororesin is fitted in the groove 12a of the support disc 12, and is fixed by being clamped by a pressing plate 15 and screwed onto the screw portion 11b. As a material of the valve member 14, a PPS resin, a PEEK resin, or the like may be used in addition to the fluororesin.
On the lower surface of the valve member 14, an inclined surface 14 a having a horizontal plane and an inclination angle of 30 degrees is formed. As shown in FIG. 1, the inclined surface 14 a comes into contact with the valve seat curved surface 16 to block the fluid flow. The valve member 14, the support disk 12, and the pressing plate 15 constitute a valve body.
Here, since the fluid is at a high temperature, the life of the rubber does not last and the rubber cannot be used for the valve body. Therefore, the fluorine resin is used for the valve member 14. On the other hand, the shape of the valve seat curved surface 16 is an upwardly convex arc shape having a certain curvature.

Next, the operation of the fluid control valve 10 having the above configuration will be described. Pilot air is not supplied to the air port 22 when the steam that is the control target fluid is shut off. At this time, the piston 18 is urged downward by the urging spring 19. The inclined surface 14 a of the valve member 14 is pressed against the valve seat curved surface 16 by the force of the biasing spring 19 through the valve shaft 11 and the support disk 12.
On the other hand, when steam flows to the output port 24, pilot air is supplied to the air port 22 by a solenoid valve (not shown). The piston 18 moves upward by the force of the pilot air, and the state shown in FIG. 2 is obtained. That is, the valve member 14 is moved upward via the valve shaft 11 and the holding plate 15, the inclined surface 14 a of the valve member 14 is separated from the valve seat curved surface 16, and the steam is transferred to the input port 23 or the output port 24. Flowing.

Next, creep that occurs when the fluid control valve 10 is used for a long period of time will be described. Since a pressing force is repeatedly applied in a high temperature state, creep occurs on the inclined surface 14a of the valve member 14 that is in contact with the valve seat curved surface 16. FIG. 4 shows a state in which creep has occurred due to use for a predetermined period, and the valve body has approached the valve seat curved surface by 0.5 mm.
In FIG. 4, the left side of the center line shows the initial state. Further, the right side of the center line shows a state in which the valve member 14 has approached the valve seat curved surface 16 by 0.5 mm due to creep. Initially, the diameter of the contact portion between the valve member 14 and the valve seat curved surface 16 was 40 mm as shown in the figure. When the valve member 14 was close to the valve seat curved surface 16 by 0.5 mm, the diameter of the contact portion between the valve member 14 and the valve seat curved surface 16 was 41.9 mm as shown in the figure. Here, by increasing the diameter of the contact portion,
Since the area where the valve body comes into contact with the steam increases, the force of the steam that pushes the valve body downward increases.

In the fluid control valve 10, the valve member 14 is urged downward by the urging spring 19, but the limit diameter with which the valve member 14 comes into contact with steam, calculated from the design value of the spring force, is 42.6 mm. . If this value is exceeded, the force that pushes the valve element downward will be too large compared to the design value, and the thrust force that pushes the valve element will increase relative to the thrust force that pushes the piston, and the pilot pressure for opening the valve will deviate from the design value. End up.
In the conventional fluid control valve shown in FIG. 10, the valve body is only 0.5 mm closer to the valve seat curved surface 54 due to creep and exceeds the limit diameter of 42.6 mm. Since the piston thrust is larger than that for opening the cylinder, and the operability is deteriorated, there is a problem of lack of durability. Naturally, if the piston is enlarged, the thrust is increased, but it is necessary to increase the size of a pilot valve or the like that slides the valve shaft.
On the other hand, in the fluid control valve 10 of the present invention, even when approaching 0.5 mm, the diameter with which the valve member 14 comes into contact with the steam is 41.9 mm and is within the limit diameter of 42.6 mm. Since the pressing force of the valve body does not become larger than the piston thrust for opening the valve and the operability is not deteriorated, sufficient durability is provided.

Next, a mechanism for improving durability by the fluid control valve 10 will be described.
The case of the conventional fluid control valve seal structure shown in FIG. 10 will be described with reference to FIG. FIG. 5 shows, as a dot mesh portion 53b, a portion plastically deformed by creep when creep occurs and the valve member 53 moves 0.5 mm in the vertical direction with respect to the valve seat curved surface 54. Of the valve seat curved surface 54, a point that is initially in contact with the valve member 53 is indicated by 54 a. Since the point mesh portion 53b is plastically deformed by creep, the amount of elastic deformation is small and does not function as a seal. The portion 53a in contact with the right end of the point mesh portion 53b functions as a seal. Since both sides of the point mesh portion 53b have not yet been plastically deformed, it can be elastically deformed. However, since the portion 53a receives the force of the urging spring more strongly than the left portion in the figure, the sealing force is strong. The portion 53a performs the sealing function.
Therefore, it has moved outward by W1 = 2.0 mm from the initial seal portion.

The seal structure of the fluid control valve 10 of the present invention shown in FIG. 4 will be described based on FIG. FIG. 6 shows a dot mesh portion 14d where a creep occurs and the valve member 14 is plastically deformed by creep when the valve member 14 moves 0.5 mm in the vertical direction with respect to the valve seat curved surface 16. Of the valve seat curved surface 16, the point 16 a is initially in contact with the inclined surface 14 a of the valve member 14. Since the point mesh portion 14d is plastically deformed by creep, the amount of elastic deformation is small and does not function as a seal. The portion 14c in contact with the right end of the point mesh portion 14d functions as a seal. Since both sides of the point mesh portion 14d have not yet been plastically deformed, they can be elastically deformed, but the portion 14c is more strongly subjected to the force of the biasing spring 19 than the left portion in the figure, so the sealing force is strong, It is the portion 14c that actually performs the sealing function.
Therefore, it has moved outward by W2 = 0.95 mm from the initial seal portion.
In this way, the inclined surface 14a abuts the valve seat curved surface 16 when the moving distance of the portion 14b exhibiting the sealing function is less than half compared to the case of FIG. This is because, since the seal is formed, the moving distance on the horizontal plane is shorter than the moving distance on the inclined surface.

  As described above in detail, according to the fluid control valve 10 of the present embodiment, it is a fluid control valve that controls the flow of steam by bringing the resin valve member 14 into contact with or away from the valve seat curved surface 16. The valve seat has a valve seat curved surface 16 that is convex upward, and the contact portion that contacts the valve seat curved surface 16 of the valve body has an inclined surface 14a that expands from the lower side toward the upper side. Therefore, since the contact portion that contacts the valve seat curved surface 16 of the valve member 14 has the inclined surface 14a, it is the inclined surface 14a that contacts the circular valve seat curved surface 16 of the valve seat. Initially, the circumferential surface of the inclined surface is in contact with the curved surface of the valve seat. As the time elapses, the resin valve member 14 is pressed by the steam in a high temperature state, so that plastic deformation occurs due to creep. The deformation due to creep is plastic deformation, and the plastically deformed portion can no longer function as a seal. However, on the inclined surface 14a of the valve body, there is newly formed a part in contact with the valve seat curved surface 16 on the outside subjected to plastic deformation. Since that portion is elastically deformed and is in contact with the valve seat, it performs a sufficient sealing function.

Furthermore, since the inclination angle of the inclined surface with respect to the horizontal plane is approximately 30 degrees, when the seal portion gradually moves to the upper side of the inclined surface due to the progress of creep, the diameter of the seal portion is accordingly increased. Although the diameter increases, since the diameter only moves by the sign of the moving distance at the inclined portion, the moving distance as the diameter can be reduced.
Thereby, the time until the contact portion exceeds the design limit can be extended, and a highly durable flow control valve can be provided.

Although the embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments, and various applications are possible.
For example, in the embodiment, the angle of the inclined surface with respect to the horizontal is 30 degrees, but may be 15 degrees or more and 45 degrees or less.

It is sectional drawing which shows the structure of the flow control valve 10 which is one embodiment of this invention. 3 is a cross-sectional view showing a valve open state of the flow control valve 10. FIG. 3 is an enlarged view of the vicinity of a valve seat curved surface 16 of the flow control valve 10. FIG. It is a figure which shows the change by the flow control valve 10 creep. It is a figure which shows the positional relationship of the valve seat and valve member of the conventional flow control valve. 3 is a view showing a positional relationship between a valve seat curved surface 16 of the flow control valve 10 and a valve member 14. FIG. It is sectional drawing of the valve seat vicinity of the flow control valve of a prior art. It is sectional drawing of the valve seat vicinity of the flow control valve of another prior art. FIG. 9 is an enlarged view of the vicinity of the valve seat of FIG. It is a figure which shows the change by creep of the flow control valve shown in FIG. It is a figure which shows the change by creep of the conventional flow control valve shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flow control valve 11 Valve shaft 12 Support disk 14 Valve member 14a Inclined surface 16 Valve seat curved surface 19 Energizing spring

Claims (2)

In a fluid control valve that controls the flow of fluid by abutting or separating a resin valve body from a valve seat,
The valve seat is formed as a curved surface that is convex upward,
The fluid control valve according to claim 1, wherein the contact portion of the valve body that contacts the curved surface of the valve seat has an inclined surface that expands from the lower side toward the upper side. The fluid control valve according to claim 1,
The fluid control valve according to claim 1, wherein an inclination angle of the inclined surface with respect to a horizontal plane is approximately 30 degrees.

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