JPS63210622A - Flow rate measurement based on liquid level difference - Google Patents

Abstract

PURPOSE:To measure the flow rate of a liquid like paint, by combining two storage pipes (measuring pipes) having liquid level detection sensors with return passages and a change-over valve and allowing the liquid to entirely flow through pipelines. CONSTITUTION:Each of the branch pipes 4, 4' of an input side three-way valve 3 communicates with the lower part of either one of storage pipes 5, 6 and simultaneously changed over to allow a liquid to continuously flow out in conjunction with an outlet side three-way valve 7. Each of the liquid level detection sensor 12 provided to the storage pipes 5, 6 is constituted by arranging an outer electrode 13 to a main pipe on one side along the longitudinal direction and providing sensor electrodes 14a, 14b to said main body on the other side thereof in adjacent relation to each other in an up-and-down direction to detect a liquid level a' as the change in capacity. A flow rate is a value calculated by multiplying the internal cross-section of a pipe by the movement of the liquid level and can be measured by calculating the ratio to a required time. As mentioned above, since the liquid flows only through a pipeline, even the liquid like paint can be measured.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a liquid level difference flow rate measurement method for stably measuring the flow rate of fluids with various physical properties such as paints, and more particularly, This relates to an indirect method of measuring flow rate when something is avoided.

<Prior art> Generally, when measuring the flow rate of a liquid such as paint,
Since various problems occur when contact with liquid occurs, measurement methods are subject to many restrictions.

For example, conventionally, a rotary positive displacement flowmeter, a Coriolis mass flowmeter, etc. have been used. All of these are complicated and expensive flowmeters, and rotary and float types are subject to problems such as sticking with paint, inability to measure due to clogging, poor quality of the measuring device due to material limitations, and limitations on the paints that can be used.

In addition, a method of measuring the flow rate over a certain period of time is also used as a simple flow rate measurement method, but it is not possible to measure the flow rate during the flow or continuously, and it is inefficient to dispose of spilled paint and clean it. It is.

<Problems to be Solved by the Invention> In view of the above-mentioned circumstances, the present invention adopts an indirect method that captures changes in capacitance outside the storage pipe, and enables measurement without being influenced by the physical properties of the liquid to be measured. The purpose of the present invention is to provide a liquid level difference flow measurement method that can be measured at low cost with a simple measuring device, has no moving parts, is free from sticking or clogging, and allows continuous measurement. This is what I did.

Means for Solving the Problems> The present invention provides two storage pipes, which serve as measurement pipes, which are attached to respective branch pipes of the return route provided to branch and join the flow path, By switching the three-way valve provided on the return path, liquid is sent into and out of the storage pipe provided on the return path, and the liquid level in the storage pipe is detected by an external electrode placed on the outside of the pipe and on the opposite side. The difference in capacitance is detected by a liquid level detection sensor formed by placing two electrodes arranged above and below, and the flow rate is measured by the liquid level detection sensor installed at two places on the top and bottom of the storage pipe. This method measures the time the liquid level changes between the liquid level detection sensors, and calculates it based on the changed capacity and time. However, this liquid level detection sensor only needs to be installed on at least one of the storage pipes to detect the flow rate during inflow (rise) and the flow rate during outflow (rise).
According to the method described above, two-way flow rate can be measured from the inlet side three-way valve installed in the pipe.
After sending the liquid into one of the branch pipes of the main return route and storing the liquid in the first storage pipe which becomes the measurement pipe of the main return route, the three-way valve on the inlet side is switched and the liquid is transferred into the second storage pipe of the other branch pipe. send in. At this time, the outlet side three-way valve is placed in a position communicating with the first storage pipe, and the stored liquid is allowed to flow out from the outlet side three-way valve.

Next, if you switch the inlet side three-way valve again to communicate with the first storage pipe side and simultaneously connect the outlet side three-way valve with the second storage pipe side, liquid will enter the first storage pipe. At the same time, the liquid in the second storage pipe is discharged through the three-way valve on the outlet side.

Therefore, the fluid is substantially continuously discharged, and each storage pipe repeatedly moves up and down due to the inflow and outflow of the liquid. The amount of liquid that flows while the liquid level moves between the upper and lower fixed points is the product of the internal cross-sectional area of the pipe and the amount of movement, and the flow rate per unit time can be measured by calculating the ratio to the required time. .

Furthermore, the liquid level is detected by determining whether the inside of the storage pipe is liquid or gas based on the difference in capacitance between the outer electrode and the sensor electrode. In other words, when the sensor electrodes are in the air layer above the liquid level, the capacitance between them is small, and when they are in the liquid layer, it is large, creating a difference in capacitance between the two sensor electrodes. It can be determined that there is a liquid level between the two. The difference in capacitance appears as a difference in pulse width or a difference in frequency, and can be detected by a comparison circuit.

<Example> Hereinafter, the method of the present invention will be described in detail based on the apparatus used for carrying out the method.

FIG. 1 shows a schematic diagram of the apparatus, in which liquid a fed from a pump 1 flows from an inlet pipe 2 through a three-way valve 3 on the inlet side to a branch pipe 4.4' which is a return path branching into two directions. One branch pipe 4 is provided with a first storage pipe 5 serving as a measurement pipe, and the other branch 4' is provided with a second storage pipe, and each branch pipe 4.4' is connected again at the outlet side three-way valve 7. and outflow pipe 1
0 and is sent from the pressure reducing valve 8 to the gun 9.

In this case, each of the storage pipes 5.6 communicates at its lower part with the incoming branch pipe 4.4', and its upper part communicates with each other via a connecting pipe 11. Further, the three-way valves 3 each communicate with the lower part of one of the storage pipes 5.6, and are configured to be switched at the same time.

In addition, the liquid level detection sensor 12 provided on the storage pipe 5 or the storage pipero has an outer electrode 13 (minus) arranged along the elongated direction on one side of the pipe body, and an opposing electrode 14 (plus) on the opposite side. provided, and the sensor electrode 14a1.
14b II are provided vertically adjacent to each other, and constitute one liquid level detection sensor 12 as a whole. When the liquid level a' comes between these two sensor electrodes 14a and 14b, the liquid a and A difference occurs, and the liquid level can be detected (see Figure 2).

The liquid level detection sensor 12 is housed in a Teflon tube to prevent damage and malfunction due to contact with liquid. Sensor operation is always performed using the two sensor electrodes 14a and 14b.
Detection accuracy is high and stable as it operates between
Furthermore, since both electrodes are affected by the influence of the surrounding environment, there is little variation. Further, the liquid level detection sensor 12 may be disposed on either one of the storage pipes 5.6, and may be disposed at two locations with a predetermined interval. Since the amount and time during which the liquid level a' rises or falls depends on the thickness of the storage pipe and the interval (length) of the detection sensors, the appropriate size should be selected depending on the flow rate (if the interval of measurement time is If it is too long, it is impossible to measure the flow rate between them, and if it is too short, frequent switching will occur, which poses a problem in terms of the durability of the three-way valve.

Further, a similar operation can be obtained by using a four-way switching valve 15 as shown in FIG. 4 instead of the two three-way valves 3.7. Also, instead of providing the liquid level detection sensors 12 above and below one of the storage pipes 5, which serve as measurement pipes, one liquid level detection sensor 12 is provided above or below each storage pipe 5.6. You can also do that. For example, as shown in FIG.
b is provided to detect when the liquid a has flowed up to the sensor 12a, and to switch the flow path as shown by the dotted line in the figure. Thereafter, when the liquid (paint) in the storage pipe 5 is discharged and the liquid that has flowed into the storage pipe reaches the sensor 12b, the flow path is simultaneously switched as shown by the solid line, and the same process is repeated thereafter.

<Effects of the Invention> As described above, the liquid level difference flow rate measurement method of the present invention combines two storage pipes (measuring pipes) in which liquid level detection sensors are arranged, a return path, and a switching valve, so that all liquid flows through the pipes. Since it only flows and there is no wetted part in the detection part, it is extremely effective for pumping liquids with various physical properties, such as paint. In addition, since there are no moving parts in the measurement unit, liquid problems and
Highly reliable and stable measurement is possible without worrying about wear and the like.

[Brief explanation of the drawing]

The drawings show an apparatus for carrying out the present invention, in which Fig. 1 is a schematic diagram, Fig. 2 is an explanatory diagram of a part of the liquid level detection sensor, and Fig. 3 is an explanation of pulse length comparison and frequency comparison between two electrodes. Figure, 4th
The figure is a sectional view showing an embodiment other than the switching valve, and FIG. 5 is an explanatory view of another mounting state of the liquid level detection sensor. ■３０． Pump 281. Inflow pipe 308. Inlet side three-way valve 4.4911 Branch pipe 50. , first storage pipeline 09. Second storage pipe 700. Outlet side three-way valve 12, ..., liquid level detection sensor 13, ..., outer electrodes 14a, 14b, ..., sensor electrode patent applicant Iwata Painting Machine Co., Ltd. Fig. 1 4' Fig. 2 Fig. 3 Kay 1 Fig. 4 Comparison of ethnic groups Figure 5

Claims (1)

[Claims] 1. When liquid is alternately fed into each of two storage pipes set up in a flow path, and the upper parts of the storage pipes are communicated with each other, and the liquid is flowing into one of the storage pipes, Drain the liquid from the other storage pipe and repeat this process alternately,
A liquid level difference flow rate measurement method characterized in that a liquid level movement time in the storage pipe is measured by a liquid level detection sensor arranged on the outer surface of the storage pipe, and the flow rate is measured from the liquid movement volume and time. 2. The liquid level difference flow rate measuring method according to claim 1, wherein the liquid level detection sensor is a sensor that detects the liquid level by detecting a difference in capacitance due to a difference in dielectric constant between air and liquid. 3. The liquid level difference flow rate measuring method according to claim 1, wherein liquid inflow and outflow of the storage pipe is performed by a valve operated by a liquid level detection signal from a liquid level detection sensor.