JPH0481617A - Flowmeter for liquid - Google Patents

Abstract

PURPOSE:To make excellent the responsiveness to a change in the flow rate of a liquid by making the amount of movement of a free end be changed conformably when the flow rate of the liquid changes. CONSTITUTION:When the section of a pipe 3 is elliptic, the elliptic form tends to approach a true circle under the pressure of a liquid and the radius Rs of curvature changes. The effect of the pressure of the circulating liquid appears in the form that the pressure is so unbalanced as to correspond to a difference between the length of the outside circumference of the pipe 3 and that of the inside circumference thereof. According to this consideration, only a centrifugal force F can be regarded as the factor affecting the radius Rs of curvature of the pipe, and therefore the amount S of deflection of a free end is a function of the flow rate Q of the liquid circulating through the pipe 3. By measuring the amount S of deflection of the free end of the pipe 3, accordingly, the flow rate Q of the liquid can be measured.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a flowmeter that measures the flow rate of liquid.

(Prior Art) Conventionally, as a flowmeter for measuring the flow rate of a liquid, a gear type flowmeter or a Coriolis flowmeter as exemplified in Japanese Patent Application Laid-Open No. 63-54969 has been known.

(Problem to be Solved by the Invention) However, the former gear type flowmeter is difficult to use when the viscosity of the liquid to be measured changes, for example when measuring the flow rate of atomized paint used in a painting gun. The problem with this is that it is not very accurate.

In addition, gear type flowmeters also have the problem that if the object to be measured is atomized paint, it takes time to clean the flowmeter when changing colors.

On the other hand, the latter type of Coriolis flowmeter does not have the above problems, but it takes time to converge to a predetermined measurement value, so the response is not good. The constant is about 01lsec, and it is 1/1 like a painting gun attached to a painting robot.
When it is desired to change the flow rate frequently in units of 1,000 seconds, the response is not satisfactory.

Furthermore, since Coriolis flowmeters are susceptible to vibrations, there is also the problem that accuracy decreases when they are mounted on the above-mentioned painting robots.

In view of the above, an object of the present invention is to provide a flow meter that is highly responsive to changes in the flow rate of liquid.

(Means for Solving the Problems) The present invention provides that when a liquid is caused to flow from the fixed end side to the free end side of a pipe curved in a loop shape, the free end moves due to the centrifugal force of the liquid flowing inside the vibrator. This was done based on the knowledge that the amount of movement is proportional to the flow rate of the liquid, and the flow rate can be determined by measuring the amount of movement of the free end during liquid flow and converting the amount of movement into a flow rate. It is used to measure.

Specifically, the solution taken by the present invention is a loop-shaped curved structure having one end fixed as a fixed end and the other end as a free end, and allowing liquid to flow from the one end to the other end. A structure consisting of a pipe, a measuring means for measuring the amount of movement of the free end caused by the centrifugal force of the liquid flowing inside the pipe, and a converting means for converting the amount of movement measured by the measuring means into a flow rate of the liquid. That is.

(Function) With the above configuration, there is provided a pipe curved into a loop shape with one end being a fixed end and the other end being a free end, a measuring means for measuring the amount of movement of the free end of the pipe, and the amount of movement described above. Since it is equipped with a conversion means that converts the flow rate of the liquid into the flow rate of the liquid, when the flow rate of the liquid flowing in the pipe changes, the centrifugal force of the liquid changes accordingly, and the free end of the pipe moves in response. The amount changes.

Furthermore, the amount of movement of the free end of the pipe is repeatedly changed as the flow rate of the liquid changes within the elastic range of the loop-shaped vibrator.

Furthermore, since the liquid to be measured only flows through the loop-shaped pipe, it is sufficient to simply clean the inside of the pipe when replacing the liquid to be measured.

(Example) The present invention will be explained in detail below.

FIG. 1 shows a liquid flow meter according to a first embodiment of the present invention, which includes loops formed at one end 1 or a fixed end and at the other end 2 or a free end. When a liquid flows inside the shaped pipe 3 from the one end 1 side to the other end 2 side, the centrifugal force of the liquid moves the other end 2 of the pipe 3 to the outside, and the liquid flows with the amount of movement. This is based on the knowledge that there is a certain relationship between the flow rate of liquid, and a laser measurement method that measures the amount of movement at the pipe 3 having the above structure and the free end, which is the other end 2 of the pipe 3. A measuring means (not shown) consisting of a device, a strain gauge, etc., and a CP that converts the amount of movement measured by the measuring means into a liquid flow rate.
It is composed of a converting means (not shown) such as U.

The principle of the present invention will be explained below based on FIG. 1, with the following assumptions: Radius of curvature of the pipe: Rs (m) Angle between the fixed end and free end of the pipe: θ (rad) Length between free end: L (m) Inner radius of pipe: RT: (m) Pipe wall thickness: t (m) Specific gravity of liquid: γ (kg/m3) Angular velocity of liquid: ω (rad /see) Velocity of liquid: v (m/see) Cross-sectional area inside the vibrator: A (m2) Centrifugal crab applied to the pipe F (kg) Centrifugal crab per unit length of pipe f (kg/m) Centrifugal crab applied to the pipe at the free end Amount of deflection: S (m) Young's modulus of the pipe: E (kg/m2>Pipe's moment of inertia: Iz (m') Flow rate of liquid: Q (
rn”/see) respectively.

First, based on the above conditions, the centrifugal force of the liquid flowing inside the vibrator 3 at a flow rate ■ is applied to the pipe 3 between the other end 2 (fixed end) and one end 1 (free end) (length: L). Find the uniformly distributed load F (-centrifugal force applied to the pipe).

The minute volume dV of the minute length dl of the pipe 3 is dV-A-
dl...■ (However, A-π・RT2) The minute type fi d m with the same minute length dl is dm-γ・dV...■ The minute centrifugal force df that the pipe 3 receives is d□f- It becomes R8・ω2・dm.

Here, since vwR6・ω, it becomes ω−v / R6, and from the above ■ and formula 0, df−R5・(v/Rs)・γ・(πRr2)・d
ll konari, d 1-RS fist dθ, so df-
Rs ・(v/Rs) ・γ・(πRT2)・RSφ
dθ, and further becomes df−π・γ・RT2 φV2・dθ...■.

Therefore, the total F of the uniformly distributed load applied between the fixed end and the free end of the pipe 3 is: F,, t: ・df −π・γ・RT2・v2・f; dθ −πφγ・θ・RT2・v2 ... becomes ■.

Also, the uniformly distributed load f applied per unit length is f−F
/L −(π・γ・θ・RT2・■2)/(R8・θ)−(π
・γ・RT2 ・v)/Rs...■.

When a uniformly distributed load F due to centrifugal force is applied to the pipe 3, the radius of curvature R6 of the pipe 3 increases, the free end of the pipe 3 bends and moves, and the amount of bending of this free end is S.

Next, the amount of deflection S of the free end is determined.

However, since finding this solution is quite complicated, the following conditions are set. That is: a) The length L between the fixed end and the free end of the vibrator is sufficiently larger than the amount of deflection S. Therefore, the amount of deflection in the circumferential direction when the free end is deflected can be ignored.

b) When the pipe bends and the radius of curvature Rs increases, the uniformly distributed weight F due to centrifugal force also changes, or according to the condition of a) above,
The amount of change is sufficiently small and can be ignored.

By setting these conditions, the deflection 2S becomes
It can be considered as a cantilever beam receiving a simple uniformly distributed load as shown in the figure, and the amount of deflection S at the free end of the pipe 3 is S=(f-L')/(8EIz)-=■.

In case 2, the cross-sectional moment of inertia Iz of the pipe 3 is expressed by the following formula. That is, Iz = (π/64.) X ((2(RT + t
) l 4('2R d)4) 1π1(Rv+t) -R7'l/4...■Next,
Substituting ■, ■ and L into equation 0, S= (f-L')
/ (8EIz) = f (π・7 ・RT2− v2/Rs)X
(Rs・θ)'l/(8E[π((RT+t)'RT'
l /4]) −(γ・θ' ・R72*R,53ev2)/ [2・
Et(RT+t) -RT'))...■The amount of deflection S at the free end of the pipe has been found above, but in order to make it easier to calculate the formula, the flow rate of the liquid is replaced by the flow rate: Q
It is expressed as (rn”/see).

Since there is a relationship of Q-A-v, V-Q/A-Q/ (π・RT 2)=−■ Substituting this into formula ■, we get S=(γ・θ4・R83・Q2)/[2π2・E・RT
2 f(RT+t)'-Rv'l)... [phase] Next,
Consideration will be given to the influence of the pressure of the liquid inside the vibrator 3 on the radius of curvature RS of the vibrator.

In addition to the centrifugal force F mentioned above, there is a concern that the radius of curvature R6 of the pipe will increase due to the pressure of the liquid flowing inside the pipe 3. This can be solved by keeping the pressure of the flowing liquid as low as possible. That is, when the cross section of the pipe 3 is elliptical, the radius of curvature RS changes as the ellipse approaches a perfect circle due to the pressure of the liquid, or the cross section of the pipe 3 approaches a perfect circle as described above. In this case, the influence of the pressure of the flowing liquid appears in the form that the pressure balance is disturbed by an amount corresponding to the difference between the outer circumference length and the inner circumference length of the pipe 3. Regarding this,
This problem can be solved by increasing the radius of curvature RS of the pipe 3 to some extent.

From the above considerations, the centrifugal crab F can be considered as the only factor that affects the radius of curvature of the pipe: R8, so the deflection of the free end ffi:S is the flow rate of the liquid flowing inside the pipe 3,
It becomes a function of Q. Therefore, by measuring the deflection amount S of the free end of the pipe 3, the liquid flow rate Q can be measured. However, from the [phase] formula, the amount of deflection: S is Q
2, the conversion from the amount of deflection (S) to the flow rate (Q) is a little complicated.

In addition, due to the above characteristics, the amount of change in the amount of deflection: S differs between regions where the flow rate: Q is small and large, so in reality, there are restrictions such as resolution when detecting the amount of deflection: S. , flow rate: The measurement range of Q is somewhat restricted. Even in this case, when the flow meter is applied to a painting gun, the flow rate Q is about 100 to 900 c, c, /win, so it can be covered with a digital resolution of 12 bits.

FIG. 3 shows a liquid flowmeter according to a second embodiment of the present invention, and in the second embodiment, the free end, which is the other end 2 of the pipe 3, is formed into a folded structure.

(Hereinafter, blank space) Table 1 shows the relationship between the flow rate: Q and the amount of deflection: S when the flowmeter of the second embodiment is used to measure the flow rate of paint. Flow rate: Q is 0
(c, c, /win) to 1000 (c, c,
/min) or 1.667X10-”(m3/se
e) in steps of 50 (c, c, /rAin), and the amount of deflection: S and pressure loss: dP corresponding to the flow ffi:Q are calculated. In this case, pipe 3
and paint were set as follows. That is,
For pipe 3, the material is stainless steel (SUS304), Young's modulus E: approximately 2. I x 1010 (kg/m
2) Radius of curvature Rs: 50. 0 (mu) Angle θ between fixed end and free end: 5. 326 (rad)-3
00,0 (deg) Length L: 261.8 (+n mark) Inner radius RT: 2. 00 (mm) wall thickness t: 0°10 (mm), and for the paint, the color specific gravity of the general topcoat solid γ21. 00 (g/c, c,) Viscosity (Ford
cup #4): 25. 0 (see) Viscosity (poise conversion): Each was set at 0.747 (g*/cm·S).

Table 1 also shows the calculation results of the pressure loss that occurs when the paint passes through the pipe 3, which is one of the items that must be taken into consideration when using the above flowmeter as a paint flowmeter. ing.

From the calculation results in Table 1, when actually measuring the deflections x and S, the lower limit of the measurement range for flow rate: Q is 100 (c, c,
/min), the upper limit is 900 (c, c, /min
), the difference in change in deflection amount: S is 3.651769
36079mm (~3.69741647780-0
．． 04564711701), this is measured in units of 0.001 mm with a digital resolution of 12 bits (4096). In this case, the amount of movement of the object is 0.001 mm.
Sensors that can measure in units include laser measuring instruments and strain cages.

In addition, the pressure loss of the paint caused by the above flowmeter is
Flow rate: Q or 900 (c, c, /min) pipe 3
It is 0.573 kg/cm2 (7) twice per side of C1, which results in a slight pressure loss, but it is within the allowable range.

Furthermore, in order to make it difficult for the flowmeter to be affected by temperature changes in the external environment, it is preferable to eliminate linear expansion of the pipe 3 and drift of the measuring instruments as much as possible due to heat.

In this case, the thermal linear expansion coefficient of stainless steel is approximately 0.000011, so even if the temperature changes by 10 degrees, the linear expansion of the pipe 3 due to heat will be 261
．． 8mm, the amount of expansion and contraction due to heat is 261.8XO,
0OOIIXIO=0.0295mm. The difference in expansion and contraction of pipe curvature radius: R8 due to this amount of expansion and contraction is 0
．． 010mm, and the pipe deflection change due to the centrifugal crab F is small: Q = 100 (c, c, /
min), an error of 0.2% will occur in the measured value. However, this error is due to the flow rate, Q or 0.
This can be reduced to the extent that it can be achieved by automatically performing zero point correction at the appropriate time.

Table 1 shows the range of paint flow rate and Q from 100 to 90.
0 (c, c, /l1lin), but the flow rate range can be changed as necessary.

(Effects of the Invention) As explained above, according to the liquid flowmeter according to the present invention, there is a pipe that is curved in a loop shape with one end being a fixed end and the other end being a free end, and the pipe is free. It consists of a measuring means for measuring the amount of movement of the end, and a conversion means for converting the amount of movement into the flow rate of the liquid.When the liquid flow rate changes, the amount of movement of the free end changes immediately in response to the change in the liquid flow rate. The response to changes in flow rate is extremely good.

Furthermore, when the liquid flowmeter of the present invention is used to measure the flow rate of atomized paint, when changing the color or cleaning the paint, it is only necessary to flow the cleaning liquid through the loop-shaped pipe. and extremely easy to clean.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid flow meter according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of the principle of the liquid flow meter, and FIG. 3 is a cross-sectional view of a liquid flow meter according to a second embodiment of the present invention. FIG. 1... One end (fixed end) 2... Other end (free end) 3... Pipe

Claims (1)

[Claims] (1) A loop-shaped pipe that is curved into a loop shape with one end fixed and the other end free, allowing liquid to flow from the one end to the other end; A liquid flowmeter comprising: a measuring means for measuring the amount of movement of the free end caused by centrifugal force of the liquid; and a converting means for converting the amount of movement measured by the measuring means into a flow rate of the liquid.