JPH0242153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a control valve that can prevent cavitation from occurring in a valve portion.

[Prior art]

Cavitation, which occurs in the valve portion of a control valve, occurs when a separation phenomenon occurs in the flowing water due to a sudden change in the flow velocity and condition of the flowing water, and is a cause of noise generation and erosion of the flow channel wall surface.

Therefore, various proposals have been made to prevent the occurrence of cavitation.
Among them, examples of control valves equipped with piston-type valve plugs include the Japanese Patent Publication No. 52-2728
The valve shown in the publication is known. This is designed to suppress and prevent cavitation by providing a pressure reducing chamber on the downstream side of the valve part with a water flow area that is smaller than the opening area of the valve and providing resistance to the flowing water, thereby lowering the flow velocity in the valve part. It is.

However, in such valves, in order to protect the valve seat, it is necessary to set the flow area of the outlet of the decompression chamber so that it does not exceed the opening area of the valve, so it is difficult to obtain flow characteristics with a high degree of freedom. However, there were other inconveniences such as the maximum flow rate when the valve was fully open was significantly restricted.

[Summary of the invention]

The present invention has been made in view of the above-mentioned points, and includes a valve seat ring having a first enlarged diameter portion following the valve seat and a diameter slightly larger than the first enlarged diameter portion and a circumferential wall for obtaining a predetermined flow rate characteristic. a second enlarged diameter portion in which a porous hole is formed; the valve plug includes a seat portion that seats on the valve seat; and an intermediate step portion and a thick body portion corresponding to the first and second enlarged diameter portions, respectively; However, by axially moving the valve plug using pneumatic pressure, cavitation between the valve seat and the seating area is prevented, improving reliability and durability. The present invention provides a control valve with a

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of the control valve according to the present invention in a fully open state, FIG. 2 is a sectional view showing the valve in a fully closed state, and FIG. 3 is an enlarged sectional view of the main parts of the valve. be. In these figures, reference numeral 1 denotes a cylindrical valve seat ring, and an inner hole 2 of the valve seat ring 1 has an inflow hole 3 that opens at the lower end surface of the valve seat ring 1 and communicates with an upstream passage. an annular valve seat 4 made of an inclined surface formed at the inner end of the inflow hole 3; a first enlarged diameter portion 5 following the valve seat 4 and having a larger diameter than the inflow hole 3;
Continuing from the first enlarged diameter section 5, there is a second enlarged diameter section 6 that opens at the upper end of the valve seat ring 1 and communicates with the flow path on the downstream side. The second enlarged diameter part 6 is formed coaxially with the first enlarged diameter part 5, and the second enlarged diameter part 6 is formed coaxially with the first enlarged diameter part 5.
A number of holes (porous holes) 7 having a slightly larger diameter and opening in the outer peripheral surface of the valve seat ring 1 and communicating with the downstream flow path are provided in the middle of the peripheral wall thereof. This porous hole 7 is composed of a plurality of small holes (for example, 12) arranged in parallel in the circumferential direction of the valve seat ring 1 in a staggered manner in several steps in the axial direction, and the number of holes is determined by the flow rate of the control valve. It is set arbitrarily according to the characteristics. In other words, the flow rate characteristics of the control valve can be arbitrarily set depending on the number of holes 7.

Reference numeral 10 denotes a valve plug which is screwed onto the valve shaft 9 or is provided integrally with the valve seat ring 1 and is slidably fitted into the valve seat ring 1, and includes a seat portion 11 that seats on the valve seat 4; The first enlarged diameter portion 5 is provided subsequent to the first enlarged diameter portion 5.
It is composed of an intermediate step portion 12 that is slidably fitted into the middle step portion 12, and a thick body portion 13 that is provided following the middle step portion 12 and is slidably fitted into the second enlarged diameter portion 6. For example, two annular grooves 14 are provided on the outer peripheral surface of the intermediate step portion 12, thereby applying resistance to the fluid and reducing the pressure of the fluid. In this case, the annular groove 14 is not limited to the intermediate step portion 12 but may be provided on the peripheral wall of the first enlarged diameter portion 5 or both of these portions.

In the control valve configured as described above, when the valve shaft 9 moves up and down by the operation of the drive section by the automatic control device, the valve plug 10 moves together with it. Therefore, when the seating part 11 separates from the valve seat 4 as the valve plug 10 rises, the fluid flowing into the inflow hole 3 from the side flow path passes through the valve seat 4 and the first enlarged diameter part 5 and flows into the second valve seat 4. It flows into the enlarged diameter portion 6 and flows out through the porous holes 7 to the downstream flow path.

Here, when the valve plug 10 rises slightly from the fully closed state shown in FIG. 2 and the seating part 11 separates from the valve seat 4 as shown in FIG. 3, at that moment the fluid flows into the first enlarged diameter part 5. Therefore, the pressure inside the first enlarged diameter portion 5 increases rapidly, and the force pushing up the valve plug 10 becomes stronger than when the valve is closed by the increase in the area of action of the primary pressure on the valve plug 10.

At this time, in the present invention, which utilizes air pressure such as a pneumatic piston cylinder device (not shown) as a drive unit for axially moving the valve plug, the above-mentioned valve plug pushing force generated on the controlled fluid side drives the valve by air pressure. Exceed the force momentarily and press the valve plug 10.
jumps up and stops at the position where it balances with the drive section pressure. The position is approximately the position shown in FIG. 3 where the shoulder of the valve plug thick body 13 approaches the porous hole 7, that is, the position where the internal pressure of the first enlarged diameter portion 5 easily escapes from the porous hole 7 via the second enlarged diameter portion 6. be. When the valve plug 10 springs up, the seat 11 quickly separates from the valve seat 4, creating a sufficient gap between the seat 11 and the valve seat 4.
The space between the shoulder portion A and the upper end edge of the first enlarged diameter portion 5 is narrowest. As a result, cavitation occurs only between the back portion A of the seating portion 11 and the first enlarged diameter portion 5, and does not occur between the seating portion 11 and the valve seat 4. Therefore, cavitation occurs between the seating portion 11 and the valve seat. 4 from cavitation, and can prevent erosion caused by cavitation.

Note that the annular groove 14 produces fluid resistance due to the labyrinth effect, and is highly effective in suppressing the occurrence of cavitation in the vicinity of the valve seat 4.

Next, when the valve is closed from the fully open state shown in FIG.
When inserted into the enlarged diameter portion 5, the differential pressure before and after the valve seat 4 is small and the valve seat is quickly seated. Therefore, cavitation does not occur between the valve seat 4 and the seating portion 11 even during the valve closing operation, and the valve seat 4 and the seating portion 11 are not eroded by cavitation.

〔Effect of the invention〕

As explained above, the control valve according to the present invention has a first enlarged diameter part next to the valve seat of the valve seat ring, which has a slightly larger diameter, and has porous holes in the peripheral wall to obtain predetermined flow characteristics. The second enlarged diameter part is provided, and the valve plug is composed of a seated part, an intermediate stage part and a thick body part that fit into the first and second enlarged diameter parts, respectively, so that the seat part closes when the valve opens and closes. It is possible to quickly separate from the seat and come into close contact with each other to prevent cavitation between these two parts. Therefore, the valve seat and the seating portion are not eroded at all, and leakage of the controlled fluid when the valve is closed can be reliably prevented. Also,
If there is less leakage from the controlled object, more precise fluid control can be performed, and if there is less erosion, the durability of the control valve itself can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of the control valve according to the present invention in a fully open state, FIG. 2 is a sectional view of the same valve in a fully closed state, and FIG. 3 is an enlarged sectional view of the main parts of the valve. . 1...Valve seat ring, 3...Inflow hole, 4...Valve seat, 5
...First enlarged diameter part, 6... Second enlarged diameter part, 7... Porous, 10... Valve plug, 11... Seating part, 12...
...middle step part, 13... thick body part, 14... annular groove.

Claims (1)

[Scope of Claims] 1. A valve seat provided in the inflow hole, a second enlarged diameter part that is provided following the first enlarged diameter part adjacent to the valve seat and has a larger diameter than the first enlarged diameter part, and this enlarged diameter part. A porous hole provided in the middle of the circumferential wall of the second enlarged diameter part is provided in the valve seat ring, a seating part that can be brought into close contact with the valve seat, and an intermediate stage whose circumferential surface corresponds to the first and second enlarged diameter parts, respectively. and a thick body part are provided on the valve plug, and the valve plug is moved axially within the valve seat ring by adjusting the pressure balance with the controlled fluid pressure using a driving part that uses air pressure. A control valve characterized by: 2. The control valve according to claim 1, wherein the first enlarged diameter portion has an annular groove in its peripheral wall. 3. The control valve according to claim 1 or 2, wherein the intermediate member has an annular groove on its circumferential surface.