JPH056328U - Flowmeter - Google Patents

Abstract

(57) [Summary] [Purpose] To increase the detection output of the flow sensor. [Arrangement] By arranging the flow velocity sensor chip 42 of the flow rate sensor 4A at a portion of the pipe flow channel 2 where the flow velocity distribution is large, a large amount of gas is given to the flow velocity sensor chip 42.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a flow meter applied to measure the flow rate of gas flowing in a pipe.

[0002]

[Prior Art]

 FIG. 3 is a diagram for explaining the configuration of a conventional flow meter, FIG. 3 (a) is a sectional view of the flow meter, and FIG. 3 (b) is a flow velocity distribution in the flow meter. In the figure, 1 is a conduit through which gas flows, 2 is a flow path through which gas in the conduit 1 flows, 3 is an opening formed on the inner wall surface of the conduit 1, 4 is the flow rate in this opening 3. It is a flow sensor that is installed with the detection part protruding. Note that F is an arrow indicating the direction of gas flow.

FIG. 4 is a perspective view showing the configuration of the flow sensor 4 of FIG. In the figure, in the flow rate sensor 4, a flow rate sensor chip 42 and a through hole pad 43 are adhesively arranged on the surface of a base 41 made of, for example, ceramic, and a through hole pad 43 is provided on the back side of the base 41. An external circuit connecting pin 44 that is electrically connected to is embedded, and the flow sensor chip 42 and the through hole pad 43 are electrically connected by a wire bond 45.

FIG. 5 is a perspective view showing a configuration of the flow sensor chip 42 of FIG. In the figure, in the flow sensor chip 42, a through hole 424 that connects the left and right openings 422 and 423 is formed by anisotropic etching in the central portion of the semiconductor substrate 421 made of, for example, silicon. A flow velocity detector 425 is formed above the hole 424 so as to be spatially isolated from the semiconductor substrate 421. A thin film heater element 426 and thin film temperature measuring resistance elements 427 and 428 sandwiching the thin film heater element 426 are formed on the surface of the flow velocity detecting portion 425.

In the flow meter thus configured, as shown in FIG. 3 (a), a flow velocity distribution as shown in FIG. The flow rate sensor chip 42 of the flow rate sensor 4 installed in this flow path 2 cools the temperature measuring resistance element 427 on the upstream side by the flow of gas from the direction of the arrow F to lower the temperature. On the other hand, in the temperature-measuring resistance element 428 on the downstream side, heat conduction from the heater element 426 is promoted by using the flow of gas as a medium, and the temperature rises, resulting in a temperature difference. Therefore, by incorporating the temperature measuring resistance elements 427 and 428 into the Wheatstone bridge circuit, the temperature difference can be converted into a voltage, a voltage output according to the flow velocity can be obtained, and the flow velocity of gas can be detected.

[0006]

[Problems to be solved by the device]

However, in the conventional flow meter, as shown in FIG. 3A, the flow sensor 4 mounted on the inner wall surface of the conduit 1 has a conduit whose flow sensor chip 42 is determined from the thickness of the semiconductor substrate 421. because it was attached, et al have a height of the distance h _o from 1 inner wall surface at a flow rate v ₀ at the position a flow rate as apparent is not fast enough from the flow velocity distribution shown in FIG. 3 (b) However, there is a problem in that a large output cannot be obtained as a flow velocity sensor.

[0007]

[Means for Solving the Problems]

 In order to solve such a problem, the flowmeter according to the present invention is arranged such that the flow rate detection part of the flow rate sensor is arranged at a portion of the flow path in the conduit where the velocity distribution is large.

[0008]

[Action]

 In the flowmeter according to the present invention, since the flow velocity detecting portion of the flow rate sensor is arranged in a portion of the flow passage where the flow velocity distribution is large, a large amount of gas is applied to the flow amount detecting portion and the detection output increases. To be done.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1A and 1B are views showing the configuration of an embodiment of a flowmeter according to the present invention. FIG. 1A is a sectional view, FIG. 1B is a perspective view of a flow sensor, and FIG. 1C is a flow velocity in a flow channel. The distribution is shown, and the same parts as those in the above-mentioned figures are denoted by the same reference numerals. In FIG. 1B, the flow sensor 4A is configured such that a pedestal 46 having a certain height on the base 41 is attached and arranged, and the flow sensor chip 42 is adhesively arranged on the pedestal 46. It is being touched.

The flow rate sensor 4A thus configured is mounted in the opening 3 on the inner wall surface of the conduit 1 as shown in FIG. Therefore, the flow rate sensor chip 42 is installed so as to project into the flow path 2 in the conduit 1.

According to such a configuration, in the flow rate sensor 4A, since the flow rate sensor chip 42 is arranged at the portion having the largest flow velocity distribution in the flow path 2 as shown in FIG. Since the gas flow rate is given, the conversion output of the flow rate sensor chip 42 increases, and the flow velocity sensor 4 can obtain a large detection output.

Specifically, according to the experiments conducted by the inventors, in a flow path having a rectangular cross section with a short side b = 3.0 mm and a long side a = 33 mm, a gas flow with a flow velocity v = 8.4 mm / s. On the other hand, the detection output of the flow rate sensor 4A in which the height h ₁ of the flow rate sensor chip 42 is 1.2 mm should be increased by about 13% compared with the flow rate sensor 4 having the conventional height h ₀ = 0.4 mm. I was able to.

FIG. 2 is a view showing another embodiment of the flow meter according to the present invention, FIG. 2 (a) is a sectional view, and FIG. 2 (b) is a perspective view of the flow sensor, which are the same as the above-mentioned views. The parts are given the same reference numerals. 1 is different from that of FIG. 1 in that the flow rate sensor 4B has a flange portion 471 on _one end side and a protrusion portion 47 of a shape and a height substantially the same as the flow rate sensor chip 42 on the other end side. _The flow sensor chip 42 is adhesively arranged on a can package 47 in which ₂ is integrally formed, and this can package 47 projects the side of the protrusion 47 ₂ having the flow sensor chip 42 mounted therein into the conduit 1. Have been installed.

According to such a configuration, the can package 47, since the projecting portion 47 ₂ is formed to a size increasing only the thickness of the flow cell Nsachippu 42, gas flow in the flow channel 2 It will no longer block. In other words, there is almost no pressure loss in the flow rate at this part.

Specifically, according to the experiments conducted by the inventors, when the flow sensor chip 42 has a square shape with one side of 1.7 mm, it has a rectangular cross section with a short side b = 3.0 mm and a long side a = 33 mm. Then, in the flow path of length L = 18 mm, the pressure at the height h ₁ = 1.2 mm against the pressure loss at the height h ₀ = 0.4 mm with respect to the gas flow having the flow velocity v = 14 m / s. The increase in force loss was less than 0.1 mm water column.

[0016]

[Effect of the device]

 As described above, according to the present invention, since the flow rate detection part of the flow rate sensor is arranged at the portion of the flow path in the conduit where the flow velocity distribution is large, the detection output of the flow rate sensor is increased more than before. I was able to do it. In addition, since the detection output of the flow sensor is increased, the amplification factor of the signal processing circuit can be lowered, which reduces the influence of the offset voltage, makes it possible to use an inexpensive operational amplifier, and improve the frequency characteristic. The effect of deterioration of the flow rate detector of the flow rate sensor on the detection output is relatively small, and long-term reliability can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a flow meter according to the present invention.

FIG. 2 is a view showing the configuration of another embodiment of the flow meter according to the present invention.

FIG. 3 is a diagram showing a configuration of a conventional flow meter.

FIG. 4 is a diagram showing a configuration of a flow rate sensor.

FIG. 5 is a diagram showing a configuration of a flow sensor chip.

[Explanation of symbols]

 1 Pipeline 2 Flowpath 3 Opening 4A Flow Rate Sensor 4B Flow Rate Sensor 42 Flow Rate Sensor Chip 46 Stand 47 Can Package

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazuo Seki, 12-12 Kawana, Fujisawa, Kanagawa Yamatake Honeywell Co., Ltd. Fujisawa Factory

Claims (1)

[Claims for utility model registration] Claims: 1. A pipe through which a gas flows, and a flow rate detection part consisting of a heat generating part or a heat generating part and a temperature measuring resistance part on the chip, and A flow meter, comprising: a flow rate sensor for measuring a flow rate, wherein the flow rate detection unit of the flow rate sensor is arranged in a portion of the conduit having a large flow velocity distribution.