JPH0599384A - Bellows for fluid passage - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a bellows for a fluid passage, and an object thereof is to reduce pressure loss due to the bellows and to allow a fluid or the like to pass through without being accumulated inside the bellows. [Structure] The mass flowmeter 1 includes a pair of sensor tubes 7 and 8.
Vibrate in the Y direction by the shaker 13, and the pickup 1
4 and 15 output a signal of a phase difference proportional to the flow rate to measure the flow rate. A bellows 4 having a bellows shape in which a small-diameter valley portion and a large-diameter peak portion are alternately formed is interposed between the inflow pipe 5 and the inflow-side manifold 6, and the axial direction of the sensor tubes 7 and 8 due to the temperature rise Absorb thermal expansion. An elastic filler 16 is filled in the bellows 4, and a smooth passage 17 formed by the filler 16 extends in the flow direction in the bellows 4 to reduce pressure loss and reduce the passage 17
It is possible to prevent the fluid flowing therethrough from adhering and accumulating inside the bellows 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid passage bellows, and more particularly to a fluid passage bellows configured to reduce pressure loss due to the bellows and preferably to prevent fluid from accumulating in the passage inside the bellows.

[0002]

2. Description of the Related Art Conventionally, there is a mass flowmeter having a straight sensor tube as an example in which a bellows for a fluid passage is used.

In this type of mass flow meter, a straight sensor tube is vibrated, and the displacement of the sensor tube due to the Coriolis force generated when a fluid flows in the sensor tube is detected to measure the flow rate. There is.

As described above, when the sensor tube is formed in a straight tube, there is an advantage that the resistance when the fluid passes through is small, but on the other hand, when the sensor tube is thermally expanded in the axial direction when measuring the high temperature fluid, the sensor tube is expanded. Since both ends are fixed, compressive stress due to thermal expansion acts on the sensor tube, and accurate flow rate measurement cannot be performed.

Therefore, conventionally, a bellows-like bellows, in which a large-diameter peak portion and a small-diameter valley portion are alternately formed continuously in the middle of the pipeline, is provided, and the thermal expansion of the sensor tube is absorbed by the bellows, and a compressive stress is applied to the sensor tube. I was trying not to work.

[0006]

However, in the above-mentioned fluid passage bellows, since the peaks and the troughs are alternately formed continuously, there is a problem that the flow is disturbed and the pressure loss becomes large. Further, when the bellows is provided in the fluid passage as described above, since the inner wall of the passage inside the bellows is not smooth, the fluid easily accumulates in the concave portion formed by the inner wall of the large-diameter mountain portion, and the inner wall of the mountain portion gradually becomes smaller. There is a problem that a solid fluid film is deposited. In particular, when the fluid is food or the like, the fluid for food accumulated in the bellows deteriorates, which causes a problem that it is not hygienic. Further, when measuring a fluid such as a chemical agent, the bellows may be corroded by the chemical agent accumulated in the bellows, and the accumulated chemical agent causes liquid leakage. Therefore, an object of the present invention is to provide a bellows for a fluid passage, which solves the above problems.

[0007]

According to a first aspect of the present invention, there is provided a fluid passage bellows which is provided in the middle of a pipeline through which a fluid flows and in which large-diameter peaks and small-diameter valleys are alternately formed continuously. The recess formed by the inner wall of the mountain portion is filled with an elastic filler to form a smooth passage inside the bellows.

According to a second aspect of the present invention, there is provided a fluid passage bellows, which is provided in the middle of a pipeline through which a fluid flows and in which large-diameter peaks and small-diameter valleys are alternately formed continuously. The tube is inserted through the inner peripheral side, and the upstream side portion or the downstream side portion of the tube is fixed to the inner wall of the bellows.

[0009]

According to the first aspect of the present invention, by filling the recess formed inside the bellows with the elastic filler, the inside of the bellows becomes a smooth passage to reduce the pressure loss, and the fluid The filler is elastically deformed so as not to accumulate inside the bellows and to prevent the bellows from expanding and contracting.

Further, according to the second aspect of the present invention, the tube is inserted into the inner peripheral side of the bellows to cut off the peaks and valleys of the bellows from the flow passage, thereby reducing the pressure loss.

[0011]

1 and 2 show a mass flowmeter to which a first embodiment of a fluid passage bellows according to the present invention is applied.

In both figures, a mass flowmeter 1 is provided with a pipe 3 and a pipe 3 through which a fluid to be measured passes in a closed box-shaped casing 2.
And a bellows 4 which holds the shaft so as to be displaceable in the axial direction. The pipe line 3 is formed of an inflow pipe 5 having an inflow port 5a, an inflow side manifold 6, a pair of sensor tubes 7 and 8, an outflow side manifold 9, and an outflow pipe 10 having an outflow port 10a.

The inflow pipe 5 has a flange 5b connected to an upstream pipe (not shown) at the inflow end, and the other end of the inflow pipe 5 penetrates the side wall 2a of the casing 2 to enter the inside of the casing 2. It extends into the formed chamber 2b.

The inflow side manifold 6 includes an upstream side connection port 6a to which the bellows 4 is connected and fixed, a sensor tube 7,
8 is a downstream connection port 6b, 6 to which the upstream end of 8 is connected and fixed.
with c and. The upstream side connection port 6a and the downstream side connection port 6b,
6c is communicated with each other via branch channels 6d and 6e.

The outflow side manifold 9 has a pair of connection ports 9 to which the downstream ends of the sensor tubes 7 and 8 are connected and fixed.
It has a and 9b, and a connection port 9c to which the upstream end of the outflow pipe 10 is connected. Further, in the outflow-side manifold 9, a flow path 9 that communicates the pair of connection ports 9a and 9b with the connection port 9c.
d and 9e are provided.

The pair of sensor tubes 7 and 8 are straight tubes extending linearly in the fluid flow direction (X direction), and are provided in parallel between the inflow side manifold 6 and the outflow side manifold 9. There is. The sensor tubes 7 and 8 made of straight pipes are easy to manufacture because they have little pressure loss when the fluid to be measured passes and need not be processed into a complicated shape.

The upstream end of the outflow pipe 10 is connected and fixed to the connection port 9c of the outflow manifold 9, and the downstream end thereof penetrates the side wall 2c of the casing 2 and projects downstream (in the X direction). The outlet 10 is provided at the downstream end of the outflow pipe 10.
A is opened, and a flange 10b connected to a downstream pipe (not shown) is provided on the outer periphery thereof.

The bellows 4 is provided in the middle of the pipe line 3 so as to be interposed between the inflow pipe 5 and the inflow side manifold 6. That is, as shown in FIG. 2, the upstream end 1 of the bellows 4 is
1 is fixed to the mounting portion 5c of the inflow pipe 5 by welding or the like, and the downstream end 12 is fixed to the connection port 6a of the inflow manifold 6 by welding or the like.

The bellows 4 is, for example, a stainless steel pipe formed in a bellows shape, and has a plurality of arcuate valley portions 4a.
(4a ₁ ... 4a _n ) and mountain portions 4b (4b ₁ ... 4b _n ) are alternately and continuously formed. The valley portion 4a and the mountain portion 4b
For example, when an axial force due to thermal expansion of the sensor tubes 7 and 8 acts, the sensor tubes 7 expand and contract in the axial direction to absorb the stress due to the thermal expansion, and also absorb the axial pipe vibration when it is transmitted.

As will be described later, the bellows 4 is formed with valleys 4a and peaks 4b so that the effective cross-sectional area of the effective diameter D _a is larger than the total cross-sectional area of the inner diameters of the sensor tubes 7 and 8.

An elastic filler 16 is injected into the bellows 4. The filler 16 is coated on the inner wall of the bellows 4 so as to fill the recess 4c formed by the inner wall of the crest 4b between the troughs 4a. Therefore, the filler 16 is provided inside the bellows 4 so that the passage 1 is smooth and has no unevenness.
7 are formed.

As the filler 16, for example, a synthetic resin material having elasticity such as synthetic rubber, silicone rubber, polypropylene, or tetrafluoroethylene resin is used. Therefore, even if the filling material 16 is filled in the concave portion 4c of the inner wall of the bellows 4, the expansion and contraction operation of the bellows 4 is not hindered by the filling material 16.

A passage 17 formed by the filling material 16 is also provided.
The inner diameter D ₁ of the cross-sectional area is substantially equal to the sum of the cross-sectional areas of the sensor tubes 7 and 8. Therefore, the flow rate of the fluid is not restricted by the passage 17 of the filling material 16.

In this way, the filler 1 is placed inside the bellows 4.
Since 6 is filled, the inner peripheral side of the bellows 4 is smoothed, pressure loss is reduced, and the fluid is less likely to accumulate in the passage 17, and even if a fluid consisting of food flows in the passage 17, it is hygienic. Further, even when the flow rate of the chemical is measured, the chemical is prevented from directly contacting the bellows 4 because the inner wall of the bellows 4 is covered with the filler 16. Thereby, the corrosion resistance and the durability of the mass flowmeter 1 are improved.

Reference numeral 13 denotes a vibration exciter, which has a structure substantially similar to that of an electromagnetic solenoid, and is provided between the pair of sensor tubes 7 and 8 at a substantially middle portion.

Reference numeral 14 denotes an upstream pickup, which is a vibrator 1
It is provided between the sensor tubes 7 and 8 on the upstream side of 3.

Reference numeral 15 denotes a pickup on the downstream side, which is a vibrator 1
The pickup is located on the downstream side of 3, and is provided between the sensor tubes 7 and 8 on the downstream side of the vibrator 13. The pickups 14 and 15 have the same structure as the electromagnetic solenoids, and the sensor tubes 7 and 8 vibrated by the vibration exciter 13 are used.
Detects the displacement of.

When measuring the flow rate, a pair of sensor tubes 7, 8
Is oscillated by the vibration exciter 13 in the direction of approaching and separating (Y direction). The fluid to be measured supplied from the upstream pipe (not shown) flows into the bellows 4 through the inflow port 5a, and the filler 16
To the manifold 6 through the passage 17 formed in
Further, it passes through the flow paths 6d and 6e of the manifold 6 and flows into the vibrating sensor tubes 7 and 8. Then, the fluid that has passed through the sensor tubes 7 and 8 passes through the flow passages 9a and 9b of the manifold 9 and flows out from the outlet 10a to a downstream side pipe (not shown).

In this way, the vibrating sensor tube 7,
When the fluid flows in 8, Coriolis force corresponding to the flow rate is generated. Therefore, an operation delay occurs between the inflow side and the outflow side of the straight tubular sensor tubes 7 and 8, which causes a phase difference in the output signals of the pickups 14 and 15. Since this phase difference is proportional to the flow rate, the pickups 14 and 15
The flow rate is obtained based on the phase difference of the output signals from the.

Here, the operation for measuring the flow rate of the high temperature fluid will be described. Inlet 5 as in the above flow rate measurement
When the high temperature fluid is supplied from a, thermal expansion occurs due to the sensor tubes 7 and 8 extending in the X direction. Since the upper and lower flanges 5b and 10b are respectively connected and fixed to the upper and lower pipes, axial strain stress due to thermal expansion of the sensor tubes 7 and 8 is absorbed by expansion and contraction of the bellows 4.

As a result, fluctuations in the instrumental difference level due to thermal expansion of the sensor tubes 7 and 8 are prevented, and accurate flow rate measurement can be performed.

Next, the operation when the fluid pressure fluctuates during flow rate measurement will be described.

First, consider the operation in a state where the inner wall of the bellows 4 is not filled with the filler 16.

For example, when the fluid pressure rises during flow rate measurement, the pressure of the high-pressure fluid acts on the inner wall of the bellows 4.

When the internal pressure acts on the inner wall of the bellows 4, the peak portion 4b of the bellows 4 slightly bulges, and a force corresponding to the pressure receiving area is generated in the axial direction. This pressure receiving area is the effective cross-sectional area of the bellows 4.

Now, the effective area A _a of the bellows 4 will be described.

As shown in FIG. 3, the effective diameter D _{a of the} bellows 4 is
In the axially projected cross-section on the inner surface side of the bellows 4, the axially projected area of the portion from the mountain portion to the valley portion on the inner surface side of the bellows 4 (hatched portion in FIG. 3) is the valley side ( The boundary where the area of the inner shaded portion I) in FIG. 3 and the mountain side (the outer shaded portion II in FIG. 3) are equal is called the effective diameter D _{a of the} bellows.

As described above, since the shaded areas I and II in FIG. 3 have the same area, the effective radius γ _a of the bellows 4 is obtained by the following equation (1).

[0039]

[Equation 1]

Here, r _{0 is} the radius from the mountain portion on the inner surface side of the bellows, and r _i is the radius from the valley portion on the inner surface side of the bellows.

Therefore, the effective area A _a of the bellows 4 is expressed by the following equation (2).

[0042]

[Equation 2]

Next, the principle of operation according to the size of the effective area A _a of the bellows 4 will be described.

First, the principle of operation when the filler 16 is not filled in the bellows 4 will be described with reference to FIG. FIG. 4 shows that the effective area A _a of the bellows 4 arranged on the upstream side of the sensor tubes 7 and 8 is the sensor tubes 7 and 8.
FIG. 6 is a principle diagram in the case of being larger than the total cross-sectional area of the inner diameter of (a total area when there are two or more sensor tubes). In FIG. 4, the axial force generated by the internal pressure is indicated by arrows ~
Shown in. Both ends of the flow meter are fixed by casings 12. When the internal pressure acts, a force is generated in the bellows 4 portion. However, the force of occurs in close proximity to the fixed casing 12 and is counteracted by the reaction force of the fixed casing 12.

Further, when internal pressure acts on the manifolds 6 and 9, forces of and are generated, but these forces cancel each other out because they have the same magnitude and opposite directions. Further, since the manifold 6 is usually much higher in rigidity than the bellows 4 and the sensor tubes 7 and 8, and the axial length is extremely shorter than the sensor tubes 7 and 8,
It is not necessary to consider that the manifolds 6 and 9 extend in the axial direction by the forces of ,, and.

The force generated on the bellows 4 pushes the sensor tubes 7 and 8. That is, when the effective cross-sectional area A _a of the bellows 4 is not equal to the total inner cross-sectional area of the sensor tubes 7 and 8, the sensor tubes 7 and 8 are affected by the internal pressure on the difference of the cross-sectional areas. A tensile or compressive stress acts on them.

That is, in the case shown in FIG. 4, since the effective cross-sectional area A _a of the bellows 4 is larger than the total cross-sectional area of the inner diameters of the sensor tubes 7 and 8, the sensor tubes 7 and 8 are the above-mentioned bellows 4.
It will be compressed by the force of the internal pressure.

Since the amplitudes of the detection positions of the two pickups 14 and 15 theoretically have the same phase change,
If there are two sensor tubes 7 and 8, the phase change will be canceled out and the sensing should not be affected, but in reality, there are slight differences in welding conditions and mounting positions of various parts. When the sensor tubes 7 and 8 are subjected to stress due to the influence of the slightest deviation, etc., the amount of change in the phase is different between the two pickups 14 and 15. That is, the stress acting on the sensor tubes 7 and 8 causes a phase difference between the pickups 14 and 15.
As a result, the Coriolis force causes the same phenomenon in the sensor tubes 7 and 8 as the phase difference between the signals of the sensor tubes 7 and 8 to occur in the two pickups 14 and 15, and the accurate flow rate cannot be measured. ..

However, in the present invention, the above-mentioned filling material 16 is filled in the concave portion 4c inside the bellows 4,
As described above, since the cross-sectional area of the inner diameter D ₁ of the bellows 4 and the total cross-sectional area of the sensor tubes 7 and 8 are substantially equal, the stress due to the difference does not act on the sensor tubes 7 and 8. .. Furthermore, the pressure loss of the fluid passing through the bellows 4 can be reduced.

It should be noted that the filling material 16 may be filled so as to cover not only the concave portion 4c inside the bellows 4 but also the entire inner wall of the valley portion 4a as shown in FIG. In that case, it is desirable that the cross-sectional area of the inner diameter D ₂ of the passage 17 formed in the filling material 16 is substantially equal to the sum of the cross-sectional areas of the sensor tubes 7 and 8.

Further, by filling the concave portion 4c inside the bellows 4 with the filling material 16, the pressure receiving area in the axial direction of the bellows 4 becomes zero, and the bellows is not expanded directly by the fluid pressure, but its expansion. The force can be relieved, and even if the bellows 4 has a large diameter, the sensor tubes 7, 8
It becomes difficult for the stress due to the internal pressure to act on.

FIG. 6 and FIG. 7 show an enlarged main part of the second embodiment of the present invention.

In both figures, a tube 18 for guiding the fluid to the inflow side manifold 6 is inserted in the inner circumference of the bellows 4. The tube 18 is formed of, for example, a stainless steel pipe in the form of a serpentine film, and the ridges 4b _{1 to} 4b of the bellows 4
It is installed so as to cover the concave portion 4c with a dimension longer than the total length of n.

The upstream end 18a of the tube 18 is welded to the inner wall of the inflow port 4d of the bellows 4. Further, the downstream end 18b of the tube 18 is a free end without being welded to the outflow port 4e of the bellows 4.

Further, the outer diameter of the tube 18 is the bellows 4
The diameter is slightly smaller than the inner diameter of the valley portion 4a, and the tube 18 is inserted so as not to contact the valley portion 4a.

Further, four through holes 18c are formed at 90 degree intervals on the outer periphery of the tube 18 near the upstream end 18a. The through hole 18c is formed by the bellows 4 and the tube 18.
It is provided to supply a part of the fluid to the outer peripheral side of the tube 18 so that the fluid does not easily stay between

Therefore, the inlet 4 of the bellows 4 at the time of flow rate measurement
Most of the fluid flowing into d reaches the outlet 4e through the inside of the tube 18 and flows into the inflow side manifold 6. Therefore, the pressure loss due to the valleys 4a and the peaks 4b of the bellows 4 can be reduced, and the fluid can be prevented from staying in the recesses 4c.

When measuring the high temperature fluid, the bellows 4 expands and contracts to absorb the amount of thermal expansion even if the sensor tubes 6 and 7 expand in the longitudinal direction. At this time, the tube 18 is configured such that the expansion / contraction operation of the bellows 4 is not hindered because only the upstream end 18a is fixed to the inner wall of the bellows 4.

FIG. 8 shows a third embodiment of the present invention.

In the figure, the tube 19 inserted into the bellows 4 has a downstream end 19a inserted from the inflow port 4d of the bellows 4 into the outflow port 4e, and an upstream end 19b of the inflow pipe 5 attached to the attachment part 5c. It is welded. Further, the end of the inlet 4d of the bellows 4 is welded to the outer circumference 19c on the upstream side of the tube 19, and the downstream end 19a is not fixed to the bellows 4 and is a free end.

The tube 19 is formed by cutting a stainless steel pipe longer than the entire length of the bellows 4, and its outer diameter is smaller than the inner diameter of the trough so that it does not come into contact with the trough 4a.

The tube 19 inserted in the bellows 4
A through hole 19d is formed in the outer periphery of the through hole, and a part of the fluid flows between the tube 19 and the bellows 4 through the through hole 19d to make it hard for the fluid to stay in the recess 4c.

When measuring the flow rate, most of the fluid flows through the tube 19 and reaches the inflow side manifold 6. Therefore, the tube 19 reduces the pressure loss in the bellows 4 and does not hinder the expansion and contraction operation of the bellows 4 when measuring the high temperature fluid. Further, in the case of the present embodiment, the tube 19 is welded to the bellows 4 at the outer periphery 19c, so that there is an advantage that the welding operation can be easily performed.

In the above second and third embodiments, the left side of FIGS. 6 and 8 has been described as the upstream side, but the downstream side of the tubes 18 and 19 is the bellows 4 with this side as the downstream side.
It may be fixed to the inner wall of the. Also, tube 1
Although the outer circumferences of 8 and 19 are not in contact with the valley portion 4a of the bellows 4, the outer circumferences of the tubes 18 and 19 are opposite.
Bellows 4 by positively contacting the inner circumference of the valley 4a
It may be used as a guide when expanding and contracting.

Furthermore, in each of the above-mentioned embodiments, the bellows applied to the mass flowmeter has been described as an example, but the present invention is not limited to this, and the density is changed according to the natural frequency of the sensor tube through which the fluid flows. Of course, it can be applied to a bellows provided in the middle of a pipe such as a density meter for measurement.

[0066]

As described above, according to the first aspect of the present invention, by filling the concave portion formed inside the bellows with the elastic filler, the inside of the bellows becomes a smooth passage, and due to the unevenness of the bellows. It is possible to reduce the turbulence of the generated flow and reduce the pressure loss generated in the bellows. Moreover, it is possible to prevent the fluid from accumulating inside the bellows, which makes the inside of the bellows hygienic and prevents the corrosion due to the deposits.

According to the second aspect of the present invention, the turbulence of the flow generated in the bellows is reduced by inserting the tube into the bellows and fixing the upstream end or the downstream end of the tube. Therefore, the pressure loss can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a mass flowmeter to which an embodiment of a fluid passage bellows according to the present invention is applied.

FIG. 2 is a cross-sectional view showing an enlarged main part of the present invention.

FIG. 3 is a diagram for explaining an effective sectional area of a bellows.

FIG. 4 is a principle diagram for explaining a stress acting on a conduit of a mass flowmeter.

FIG. 5 is a sectional view showing a modified example of the present invention.

FIG. 6 is an enlarged vertical sectional view showing a main part of a second embodiment of the present invention.

FIG. 7 is a perspective view of a tube.

FIG. 8 is a longitudinal sectional view showing an enlarged main part of a third embodiment of the present invention.

[Explanation of symbols]

 1 Mass flowmeter 2 Casing 3 Pipe line 7,8 Sensor tube 13 Exciter 14,15 Pickup 16 Filler 17 Passage 18,19 Tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Shigeru Nishiyama 1-6-3 Fujimi, Kawasaki-ku, Kawasaki-shi, Kanagawa Tokiko Co., Ltd. (72) Mikihiro Hori 1-6-3 Fujimi, Kawasaki-ku, Kawasaki-shi, Kanagawa Issue Tokiko Co., Ltd.

Claims (2)

[Claims] 1. A bellows for a fluid passage, which is provided in the middle of a pipeline through which a fluid flows, and in which large-diameter crests and small-diameter troughs are alternately formed continuously, in a recess formed by an inner wall of the crests. A bellows for a fluid passage, characterized by being filled with an elastic filler and forming a smooth passage inside the bellows. 2. A bellows for a fluid passage, which is provided in the middle of a pipeline through which a fluid flows and in which large-diameter peaks and small-diameter valleys are alternately formed continuously, wherein a tube is inserted into an inner peripheral side of the bellows. A bellows for a fluid passage, characterized in that an upstream side portion or a downstream side portion of the tube is fixed to the inner wall of the bellows.