JPH0618244Y2 - Fluid vibration type flow meter - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention is a fluid vibration type flow meter (fluidic flow meter).
It is about.

[Prior art and its problems] In the case of a fluid vibration type flow meter, it is necessary to reduce the cross-sectional area of its throttle portion in order to measure a small flow rate. However, if the cross-sectional area is reduced in this way, pressure loss increases. Become. As a result, there is a practical problem in applying it to the measurement of a fluid having a large fluctuation range of flow rate, such as a gas appliance pilot fire 3 / h to a gas instantaneous water heater 3,000 / h, such as city gas.

FIG. 5 shows a known example proposed to remedy such drawbacks.

In this known example, a large fluid vibration type flow meter 02 for measuring a flow rate above a certain flow rate is installed on the upstream side of the flow path 01, and a small fluid vibration type flow meter for measuring a flow rate smaller than the flow meter 02 on the downstream side. 03, the bypass valve 05 is opened by the flow path switching mechanism 04 to measure on the flow meter 02 side when the flow rate is equal to or higher than a certain flow rate, and closed in the following cases.
It is possible to measure in the small flow range by measuring on the side.

However, in this known example, if the shutoff property of the flow path switching mechanism 04 is poor, a measurement error occurs, and the switching timing of the flowmeters 02 and 03 is difficult, which results in a measurement error, which is within the so-called allowable instrumental error. Difficult to fit. Further, there is a problem that since the two flowmeters and the switching mechanism are incorporated, the flowmeter becomes complicated and large, and the cost also increases.

[Object of the Invention] The object of the present invention is to expand the measurement range in a small flow rate range by a simple means in a fluid vibration type flowmeter.

[Structure and Operation of the Present Invention] The present invention proposes a fluid vibration type flow meter having the following structure as a technical means for achieving the above object.

A fluid vibration type flow meter in which a flow velocity detecting means is attached to a throttle portion of a fluid vibration element, and a flow rate is calculated from the flow velocity detected by the flow velocity detecting means to improve a measurement range in a low flow rate region.

In the above flow meter, for example, a thermal type flow sensor is attached to the throttle section (nozzle section) as a flow rate detecting means, and the flow rate at a small flow rate is measured by this sensor so that the flow rate vibration is less likely to occur. It is something that is calculated.

[Examples and Operations] FIG. 1 shows a fluid vibration type flow meter according to the present invention.

Reference numeral 1 is a vibrating element, 2 is a throttle portion, 3 is a thermal type flow sensor incorporated in the throttle portion 2, the flow velocity of the fluid to be measured is measured by this sensor 3, and calculation is performed based on this value. The flow rate value is calculated by calculating the following equation in the container 4.

Q = Sv, where Q: flow rate v: flow velocity S: cross-sectional area of throttle portion 5 is vibration (pressure) arranged on the downstream side of the target 11.
The fluid ejected from the throttle unit 2 in the detection unit becomes a flow along the side wall 6 due to the Coanda effect, and when the flow reaches the inlet of the feedback flow passage 8, this pressure propagates through the feedback flow passage 8 to cause the flow. It is pushed toward the side wall 6 ', and the flow is switched to the side wall 6'. When this flow reaches the inlet of the feedback channel 8 ', this pressure propagates through the feedback channel 8'and pushes the flow again toward the side wall 6 side. This repetition is fluid vibration, and this fluid vibration is proportional to the flow rate. Therefore, this fluid vibration is captured by the detection holes 9 and 9'of the detection unit 5, and the fluid vibration detection sensor 12 is passed through the pressure guiding tubes 10 and 10 '.
And the flow rate value is obtained by measuring the fluctuation frequency of the differential pressure between the detection holes 9 and 9 '.

In the figure, 13 is a signal line.

In the above flow meter, the flow rate measurement by the fluid vibration and the flow rate measurement using the thermal type flow sensor 3 are simultaneously performed, and which of them is displayed or the average value of the both is displayed freely.

However, in the case of the embodiment, when the flow rate is 150 / h or more, the flow rate measurement value detected on the vibration element 1 side is given priority.

FIG. 2 shows the relationship between the oscillation frequency of the fluid vibration element and the flow rate (the frequency is proportional to the flow rate as described above), and FIG. 3 shows the relationship between the output voltage and the flow rate when the thermal flow sensor 3 is used. (Voltage is proportional to flow rate) and FIG. 4 shows the overall characteristics of the fluid vibration type flow meter embodying the present invention.

[Effects of the Invention] As described above, the invention calculates the flow rate from the flow velocity detected by the flow velocity detecting means for a small flow rate, and therefore, as shown in FIG. Can also be measured.

Next, in the case of the thermal type flow sensor, since there is no large protrusion in the throttle portion, the pressure loss due to this is small and there is no practical problem.

Next, by incorporating the flow velocity detecting means, the outer shape hardly becomes large, and since the structure is simple, there is no fear of failure and the cost is low.

Next, since there is no movable part such as the switching mechanism as seen in the conventional example, there is no occurrence of a measurement error due to such a movable part.

Therefore, the fluid vibration type flow meter according to the present invention is particularly practical and effective as a meter for city gas or propane gas in general households.

[Brief description of drawings]

FIG. 1 is a perspective view of a fluid vibration type flow meter according to the present invention, and FIG.
Fig. 4 is a graph showing the relationship between the oscillation frequency of the fluid vibration element and the flow rate, Fig. 3 is a graph showing the relationship between the output and flow rate of the thermal flow sensor, and Fig. 4 is a graph showing the overall characteristics of the flowmeter according to the present invention. 5 is an explanatory view of a conventional fluid vibration type flow meter. 1 ... Fluid vibration element, 2 ... Throttle section 3 ... Thermal flow sensor, 4 ... Calculator 5 ... Detection end 12 ... Fluid vibration detection sensor

Claims (2)

[Scope of utility model registration request] 1. A fluid vibration type flow meter comprising a flow velocity detecting means attached to a narrowed portion of a fluid vibration element, and calculating a flow rate from the detected flow velocity to improve a measurement range in a low flow rate region. 2. A fluid vibration type flowmeter according to claim 1, wherein the flow velocity detecting means comprises a thermal type flow sensor.