JPH02187808A - Reducing valve - Google Patents

Abstract

PURPOSE:To eliminate chattering by checking the frequency characteristic of input/output pressure in which secondary side pressure is set as input and pressure at the lower plane area of a diaphragm as output, and arranging plural orifices whose diameters can be set so as to go less than the frequency to generate the chattering by a break frequency at that time in series. CONSTITUTION:The orifices 72 and 74 are arranged at a secondary pressure detecting path 34 passing the main body 10 of a pressure reducing valve and a pilot body 70. The orifices 72 and 74 are provided with certain volumes in the inside, and holes with the same diameter are formed, respectively. A gain curve C is set by checking the frequency characteristic of the input/output pressure in which the secondary side pressure of the pressure reducing valve is set as the input and the pressure at the lower plane area of the diaphragm 28 as the output. And the orifices 72 and 74 whose diameters are decided so as to go less than the frequency to generate the chattering by the break frequency at that time are connected in series, and thereby, the chattering can be prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a pressure reducing valve that is attached to a piping system for steam, compressed air, etc. to reduce the fluid pressure on the secondary side and maintain it at a constant set pressure.

BACKGROUND ART A conventional pressure reducing valve is as shown in FIG. 4, and is composed of a pressure reducing valve section 1, a steam/water separator section 2, and a drain valve section 3.

The main body 10 has an entrance 12. Valve port 14. An outlet 16 is formed.

The inlet is connected to a high-pressure fluid source on the primary side, and the outlet is connected to a low-pressure region on the secondary side. The main valve 1B is disposed at the inlet side end of the valve port 14 while being elastically biased by a coil spring.

The piston 2Q is slidably inserted into the cylinder 22, and the piston rod 20b is brought into contact with the central projection rod 18a of the main valve 18 through the valve port 14. The lower surface of the piston 20 and the piston rod 20b are connected by a substantially hemispherical surface. A pilot valve 26 is disposed in a primary pressure passage 24 communicating between the inlet 12 and the upper space of the piston 20, that is, the screw 20a.A diaphragm 28 is attached with its outer peripheral edge sandwiched between seven flanges 30 and 32. The space below the diaphragm 28 communicates with the outlet 16 through a secondary pressure detection passage 34 .

The head end surface of the valve stem 36 of the pilot valve 26 abuts against the central lower surface of the diaphragm 28 .

A pressure setting coil spring 40 is brought into contact with the upper surface of the diaphragm 28 via a spring seat 38. The adjustment screw 44 is screwed and attached to the spring case 66.

By turning the adjustment screw 44 left and right, the elastic force of the pressure setting spring 40 that pushes down the diaphragm 28 changes.

Using the elastic force of the pressure setting spring 40 as a reference value, the diaphragm 28 curves in response to the secondary pressure acting on its lower surface, displacing the valve rod 36 and opening and closing the pilot valve 26. As a result, the -next side fluid pressure increases to the piston chamber 20.
a, the piston 20 is driven to displace the main valve 18, and the fluid flows through the valve port 14 to the outlet 16. This automatically operates so that the valve port 14 opens when the fluid pressure on the secondary side decreases and closes when it increases.

A cylindrical partition member 46 is attached below the valve port 14,
An annular space 48 is formed between the main body 10 surrounding it, and the upper part of the annular space 48 is passed through a cone-shaped screen 50.
The lower part communicates with the upper part of the drain valve chamber 52. Further, the upper part of the drain valve chamber 52 communicates with the valve port 14 through the central opening of the partition member 46. In the annular space 48, a swirl vane 54 consisting of an inclined wall is arranged.

Therefore, when the valve port 14 opens and the fluid passes through the annular space 48, its direction is bent by the swirling vanes 54 and the fluid is swirled. The liquid is shaken out to the outside, hits the surrounding inner wall of the main body, and flows down into the drain valve chamber 52, while the light gas swirls in the center and flows from the central opening of the partition member 46 to the valve port 1.
4, through which it flows away to exit 16.

A drain valve port 58 communicating with the drain port 56 is formed at the bottom of the drain valve chamber 52 . Covered with a float cover 62, a spherical valve float 60 is movably accommodated. A ventilation hole 64 is opened in the upper part of the float cover 62.

Therefore, the valve float 60 floats up and down with the water level in the drain valve chamber 52 to open and close the drain valve port 58, and automatically removes water accumulated in the drain valve chamber 52.

<Problems to be Solved by the Invention> In all existing pressure reducing valves, including the conventional pressure reducing valve having the above-mentioned configuration, a chattering phenomenon that generates significant vibration and noise is a phenomenon that cannot be eliminated. This may occur when the pressure is set at an appropriate flow rate and the operation is normal, but when the load on the secondary side decreases and the flow rate decreases, or the set pressure (secondary pressure ) is small, that is, when the decompression ratio is large.

The pressure reduction ratio is, for example, - outlet pressure 10KH/aa to outlet pressure 2! This is a case where the pressure is reduced to about j/ci or less,
Movable parts such as the main valve 18 and the piston 20 move, causing a chattering phenomenon. This is because when the secondary pressure decreases and the pressure change is transmitted through the secondary pressure detection passage 34 and the pilot valve 26 opens, the valve opens by more than the pressure drop and then returns to the valve closing direction. One cause is thought to be the vibration of the pilot valve 26, which repeatedly exhibits a vibrating state, causing rapid pressure fluctuations in the piston chamber 20a in the upper space of the piston 20, and causing the main valve 18 to also exhibit a vibrating state. As the main valve 18 opens and closes, the secondary pressure pulsates, and this sensing acts again on the lower surface of the diaphragm via the secondary pressure detection passage 34, causing the pilot valve 26 to open and close. This process occurs at an accelerated rate, creating a state of large vibration.

In addition, the vibration is caused by the sudden opening of the main valve 18, which causes a jet of steam heading toward the secondary side to act on the lower surface of the piston 20, rapidly pushing up the piston 20 and colliding with its upper wall, resulting in the rise of the piston 20. This is considered to be because the main valve 18 cannot follow the piston 20 and collides with the piston 20 when it descends again. Re-contact is shocking, and such movement of the main valve 18 and piston 20 poses problems such as damage to the shaft portion 20b of the piston 20 and damage to the valve seat of the main valve 18. Damage to these members may make it impossible to set the secondary pressure or shorten the life of the pressure reducing valve.

Therefore, the technical problem of the present invention is to provide a pressure reducing valve that does not cause the chattering phenomenon.

Technical Means for Solving the Problems In order to solve the above problems, one idea is to provide an orifice in the secondary pressure detection passage 34 to reduce the response and prevent chattering. However, depending on the diameter of the orifice, there is a problem in that the response to normal setting changes is also poor.

Therefore, by inputting the pressure on the secondary side of the pressure reducing valve, the diaphragm 2
If the frequency characteristics of the input and output pressures are examined and plotted on a Bode diagram using the pressure in the downward region of 8 as the output, the gain curve shown in FIG. 2 is obtained.

When the input frequency is changed, the chattering phenomenon that causes significant imaging and noise from the large pulsation that is the pre-chattering stage occurs from about 30 to 2001 fZ, and the corner frequency is -2 around 300 to 40 Otfz.
It was found that the same wave number response includes a first-order lag element that attenuates at 0 dB/dec. In other words, even in the 3011z6A case where chattering begins to occur, the gain is transmitted without attenuation, so the secondary side pressure is directly transmitted to the lower surface of the diaphragm and induces chattering.

It is also understood that if an orifice is provided in the secondary pressure detection passage 34, the frequency response will further include a first-order lag element, and if the diameter of the orifice is further changed, the corner frequency will shift.
I understood that

Therefore, it would be better to provide an orifice with a certain diameter in the secondary pressure detection passage, bring the corner frequency before the region where chattering begins, and attenuate the gain in the region where chattering occurs. In order to reduce the gain sufficiently in the region where chattering occurs as shown in gain curve B, the attenuation rate in this area must be -20 dB/d.
ec, the corner frequency must be set well before the chattering occurrence region. In other words, the gain is attenuated even in the frequency range where chattering does not occur,
Responsiveness deteriorates.

The technical means of the present invention taken to solve the problem in consideration of the above results is to apply the elastic force of a pressure setting spring to the upper surface of the diaphragm, and apply secondary pressure to the lower surface of the diaphragm. By controlling the flow rate by opening and closing the valve port between the inlet connected to the primary side and the outlet connected to the secondary side using a double-sided balance, the secondary side pressure is brought to the set pressure. In a pressure reducing valve with a structure that maintains the pressure, the secondary pressure is input to the secondary pressure detection passage that introduces the secondary pressure to the lower surface of the diaphragm, and the frequency of the input and output pressure is A plurality of orifices are arranged in series, whose diameters are determined by examining the characteristics and determining the corner frequency to be below the frequency range where chattering occurs.

Effect> The diameter of the orifice is determined so that the gain is attenuated in the frequency range where chattering occurs, so even if the secondary pressure oscillates at high frequencies, the pressure is attenuated and transmitted to the diaphragm, preventing chattering. be done.

Also, as mentioned above, one orifice produces the response of a first-order lag element, and if multiple orifices are arranged in series, the overall response becomes the sum of the first-order lag elements of one orifice and the number of orifices. . Therefore, if we set the attenuation rate at a certain value and compare it with the case of one orifice, we get
Since the attenuation rate is larger with multiple pieces, it is possible to bring the corner frequency closer to the frequency range where chattering occurs.
It is possible to have a wide band in which the gain does not attenuate in a region where chattering does not occur.

<Example> An example showing a specific example of the above technical means will be described. (
(See Figures 1 and 3) The following embodiment is an improvement of the secondary pressure detection passage of a conventional pressure reducing valve, and the parts corresponding to those in Figure 4 are given the same reference numerals and can be used as pressure reducing valves. A detailed explanation will be omitted.

Orifices 72,74 are arranged in the secondary pressure detection passage 34 passing through the main body 10 and the pylon 1 to the body 70.

The orifices 72, 74 have internal volumes and each define holes of the same diameter.

When the frequency characteristics of the input and output pressures of this pressure reducing valve are examined, with the secondary side pressure as input and the pressure in the lower surface area of the diaphragm as output, a gain curve C shown in FIG. 3 is obtained. Since there are two orifices, the frequency response includes a second-order lag element that reduces the gain by 14 QdB/dec in the frequency region where chattering occurs. In this case, the corner frequency is determined while changing the diameter of the orifice so that the attenuation rate becomes a suitable value in the frequency range where chattering occurs.

Therefore, if the slope of the attenuating portion of the gain curve is increased, that is, if the number of orifices is increased, the corner frequency will move to the right in the drawing, and if the slope is decreased, it will move to the left. When determining this corner frequency, it is necessary to set it to a level that does not affect normal setting changes.

The gain display above is in dB, so a 40 dB decrease in gain means 1/100 in amplification.
This corresponds to a very large effect of 17.

And if there are 3 orifices, -60dB/dec
It is attenuated by

Therefore, according to the above-mentioned pressure reducing valve, the secondary side pressure is attenuated and transmitted to the lower surface of the diaphragm 28 from the frequency range where chattering occurs, so the pilot valve 26 also changes smaller than before, and the piston 20 is no longer stimulated suddenly. chattering will no longer occur.

<Effects of the Invention> As described above, according to the present application, the structure is extremely simplified and chattering is eliminated. Therefore, there is no photographing, and each member is not damaged, and the pressure reducing valve can continue to maintain the set pressure in a stable state.

It also has the advantage that the frequency characteristics can be easily changed due to its simple structure.

Furthermore, by eliminating chattering, it becomes possible to set pressures in a low pressure range, which could not be set conventionally, and the range of use as a pressure reducing valve becomes wider.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing frequency characteristics of input and output pressures of a pressure reducing valve, and FIG. 4 is a sectional view of a conventional pressure reducing valve. Pressure reducing valve part Drain valve part Inlet outlet Pilot valve Secondary pressure detection passage 72° Steam water separator part Main body valve port Piston diaphragm 74 Niorifice

Claims (1)

[Claims] 1. The elastic force of the pressure setting spring is applied to the upper surface of the diaphragm, and the secondary pressure is applied to the lower surface of the diaphragm, and the balance between the two blades creates a gap between the inlet connected to the primary side and the outlet connected to the secondary side. In a pressure reducing valve that maintains the secondary pressure at a set pressure by opening and closing a valve port provided in the diaphragm to control the flow rate, the secondary pressure is introduced into the lower surface of the diaphragm. Check the frequency characteristics of the input and output pressures in the pressure detection passage, with the secondary side pressure as input and the pressure in the lower surface area of the diaphragm as output, and select the diameter so that the corner frequency at that time is below the frequency range where chattering occurs. A pressure reducing valve characterized by having a plurality of determined orifices arranged in series.