JPH05322624A - Flow meter - Google Patents

Abstract

PURPOSE:To stabilize the accuracy of heat-wire type mass flow rate sensor for a long term by blocking intrusion of dust into the heat-wire type mass flow rate sensor located at a part of gas passage of a gas introduction pipe to be measured. CONSTITUTION:The flow meter comprises a pipe 1 for introducing gas to be measured, a heat-wire type mass flow sensor located at a part of gas passage of the introduction pipe 1, and at least one dust trapping wall 2, 4-8 formed on the inner wall of the introduction pipe on the upstream side of the heat-wire mass flow sensor so that dust in the introduced gas adheres to the dust trapping wall upon collision of the introduced gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter suitable for long-term and accurate measurement of combustion air amount in a water heater or the like installed in a kitchen where the dust is floating or the temperature difference is large or the temperature difference is large.

[0002]

2. Description of the Related Art Conventionally, the amount of combustion air in a gas water heater or the like has been measured by the number of rotations of a block or a fan motor. However, the rotation speed of the fan motor is only measuring the volume flow rate, and the influence of pressure due to the altitude difference,
Since it is not possible to make accurate measurements due to the weather conditions in the outside world, the safety side normally supplies more air than required. As a result, it was large even instrument itself, there are problems such as generation of NO _X, it can not be optimal combustion.

Therefore, in order to prevent this problem, as shown in FIG. 10, two cylinders 101 and 102 are arranged side by side in a duct 103 so as to be orthogonal to the direction of air flow, and project outside the duct 103. The end of the cylindrical body is connected to the through hole 105 of the sensor body 104 by the tubes 106 and 107, and the heat wire type mass flow sensor 108 is provided in the through hole 105.

The hot-wire type mass flow sensor 108 is required to be small in order to make it difficult to be affected by the difference in altitude and the external environment and to downsize the entire shape of the gas water heater or the like. Therefore, a diaphragm 112 having a thickness of 20 μm or less is provided on a 1.7 mm square semiconductor chip 111 as shown in FIG. 11, and a heating resistance pattern 113 and temperature sensitive resistance patterns 114 and 115 are provided on the diaphragm 112. I am configuring.

With the above structure, the hole 1 is formed in the one cylinder 101.
The air flowing in from 01a is supplied to the tube 106 and the through hole 1
05, through the tube 107 through the hole 102a of the cylindrical body 102, the output of the hot wire type mass flow sensor 108 based on the flowing air amount can be supplied to the drive circuit 109 to accurately measure the combustion air amount. Has been done.

[0006]

Since the conventional flowmeter is constructed as described above, the hot-wire mass flow sensor is very small, for example, 1.7 mm square, and has very good sensitivity.
While accurate measurement is always possible, it is unreliable with respect to dust in the air and dew condensation water and cannot withstand long-term use. In particular, there is a problem that a kitchen or a kitchen in which a gas water heater is installed has a large temperature difference between when it is used and when it is not used. Further, the hot-wire type mass flowmeter has a problem that when it gets wet with dew condensation water, the resistance value of the resistance pattern changes remarkably and accurate flow rate measurement cannot be performed.

The present invention has been made in order to solve the above problems, prevents dust from entering the hot-wire mass flow sensor, and stabilizes the accuracy of the hot-wire mass flow sensor for a long period of time. In addition, it is an object of the present invention to obtain a flow meter which can realize dust removal at a lower cost.

[0008]

A flowmeter according to the present invention collides the introduced gas with a hot wire type mass flow sensor provided in a part of a gas flow path of an introduction pipe for introducing a gas to be measured. It is provided with at least one dust capturing wall formed on the inner wall of the introduction pipe upstream from the heat ray type mass flow sensor so that the dust in the colliding gas is attached.

[0009]

The dust trapping wall according to the present invention adheres dust contained in the colliding gas to prevent the dust from entering the heat ray type mass flow sensor on the downstream side. As a result, the hot wire mass flow sensor can maintain stable accuracy for a long period of time.

[0010]

【Example】

First Embodiment FIG. 1 is a structural sectional view showing the structure of a dust trap wall in a first embodiment of the flowmeter according to the present invention. In this figure, 1 is a conduit. The gas flows in the conduit 1 from the left to the right. The flow rate measuring unit (not shown) is arranged to the right of the conduit 1. 2 is a first dust capturing wall. A nozzle portion 3 is formed below the dust capturing wall 2. The dust trapping wall 2 is vertically provided on the inner wall surface of the conduit 1 so as to close the circular cross section of the conduit 1. Reference numeral 4 denotes a second dust trapping wall, which is vertically provided on the inner surface of the conduit 1 so as to face the nozzle portion 3 at a predetermined distance, and the upper portion of the second dust trapping wall 4 is gas. It becomes a flow path. The first dust trapping wall 2 and the second dust trapping wall 4 constitute one dust trapping wall 5. The dust trapping wall 6 and the dust trapping wall 7 have the same configuration as the dust trapping wall 2 and the dust trapping wall 4, and the dust trapping wall 6 and the dust trapping wall 7 constitute one dust trapping section 8. There is. Therefore, the dust traps 5 and 8 are arranged in series in the conduit 1.

In this embodiment, the dust in the gas flowing in the conduit 1 first collides with the wall surface 2a of the dust capturing wall 2 and adheres to the wall surface 2a to be captured. Further, since the opening area of the nozzle portion 3 formed on the dust capturing wall 2 is configured to be smaller than the cross-sectional area of the conduit 1, the flow velocity of the gas flowing through the nozzle portion 3 becomes high, and the velocity of the dust in the gas also increases. growing.
In the dust catching section 5, the gas bypasses the dust catching wall 4 and flows, while the dust in the gas collides with the wall surface 4a of the dust catching wall 4 due to its inertia due to its mass. Also in the dust capturing part 8, the wall surfaces 6a and 7a are the same as above.
Dust in the gas is captured by.

Further, in this embodiment, even if a small amount of liquid W such as water enters from the gas inflow side of the conduit 1, the dust capturing walls 4 and 7 become fluid blocking walls, and as shown in FIG. It is possible to prevent the liquid W from entering the mass flow sensor.

A filter generally used in the past may be provided between the hot-wire type mass flow sensor and the dust capturing section, in which case the frequency of filter replacement can be reduced.

Second Embodiment FIG. 3 is a structural sectional view showing the structure of the second embodiment, showing a case where the dust trapping wall is formed inside the Pitot tube. In this figure, 9 is a Pitot tube, 10 is a nozzle section, 11,
12 is a dust capturing wall.

Since the total pressure holes of the pitot tube 9 are open toward the gas inflow side, most of the dust flying to the front of the opening of the pitot tube enters the inside of the pitot tube due to its large inertia. .. In this embodiment, the total pressure holes of the Pitot tube 9 are used as the nozzle portion. Then, the dust capturing wall 1 is provided at a portion of the bent portion 13 of the pitot tube where the inflowing gas changes its inflowing direction.
1 and 12 are configured. The inflowing gas changes its direction and flows toward the hot-wire mass flow sensor, whereas the dust in the gas is trapped on the wall surface of the dust trapping wall.

Third Embodiment FIG. 4 is a structural cross-sectional view showing the structure of the third embodiment when a dust trapping wall is provided in an improved pitot tube in which total pressure holes are formed on the wall surface of a gas flow path. is there. In this embodiment, a dust capturing part constituted by the dust capturing walls 14, 15, 16 and 17 is formed on the inner surface of the pitot tube 18.

FIG. 5 is a sectional view of the flow pickup section 19 in the flow pickup type flowmeter. In this flow pickup type flow meter, gas is taken in through the hole 22 and discharged through the hole 21 by a negative pressure method to prevent dust. In this flow meter, strict accuracy is required for the opening positions of the holes 21, 22 formed in the pipe 20 in the gas flow path 35. Also, the negative pressure generated is small.

Fourth Embodiment FIG. 6 is a structural sectional view showing the structure of the fourth embodiment. In this embodiment, the dust trap walls 23, 24, 25 and 26 are provided in one gas inflow passage of the flow pickup section 19 in the flow pickup type flowmeter shown in FIG. As a result, the hole 21 of the flow rate pickup unit 19 is
It can be formed in the direction of gas inflow, has a dust trapping function, and since it is not a negative pressure system, it can improve sensitivity, and it does not require positional accuracy when forming holes, so it can be manufactured. It will be easy.

Further, as shown in FIG. 7, in addition to the dust capturing walls 27, 28, 29, 30 provided on the gas inflow passage side, the dust capturing walls 31, 32, 33,
With the configuration of 34, even if the gas flowing through the flow rate pickup unit 19 flows back and dust enters from the hole 22, it is possible to prevent the dust from entering the hot-wire mass flow sensor.

Further, the flow rate pickup unit 1 in the negative pressure type flow pickup type flowmeter described in FIG.
As shown in FIG. 8, the dust trap walls 27 to 34 may be formed inside 9.

Fifth Embodiment FIG. 9 is a perspective view showing the structure of the fifth embodiment. This embodiment is a flow pickup type anemometer in which a dust capturing portion is constituted by an internal structure 35 in which a dust capturing wall is formed and a pipe-shaped external structure 36 externally fitted to the internal structure 35. Both the internal structure 35 and the external structure 36 can be mass-produced, and the assembly work is easy.
The cost can be reduced. Reference numeral 37 is a substrate on which the hot-wire type mass flow sensor 108 shown in FIG. 11 is attached in the center.

[0022]

According to the flowmeter of the present invention, since the dust trapping wall is provided in the gas introducing pipe, it is possible to reliably prevent the intrusion of dust into the hot wire type mass flow sensor, and the hot wire type The accuracy of the mass flow sensor shall be stable over a long period of time.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view showing a structure of a dust trap wall in a first embodiment of a flowmeter according to the present invention.

FIG. 2 is a structural cross-sectional view that prevents liquid from entering a flow rate detection unit.

FIG. 3 is a structural cross-sectional view showing the configuration of a second embodiment of the flowmeter according to the present invention.

FIG. 4 is a structural cross-sectional view showing the configuration of a third embodiment when a dust trapping wall is provided on the improved Pitot tube.

FIG. 5 is a cross-sectional view of a flow rate pickup unit.

FIG. 6 is a structural cross-sectional view showing the configuration of a fourth embodiment of the flowmeter according to the present invention.

FIG. 7 is a cross-sectional view of a flow rate pickup unit when dust capturing walls are formed on the gas inflow side and the gas outflow side.

FIG. 8 is a perspective cross-sectional view of a negative pressure type flow pickup type velocity meter when a dust capturing wall is formed inside the flow rate pickup portion 19;

FIG. 9 is a perspective view showing the configuration of a fifth embodiment of the flowmeter according to the present invention.

FIG. 10 is a front view of a conventional flow meter.

FIG. 11 is a perspective view showing a hot-wire type mass flow sensor.

[Explanation of reference symbols] 1 conduit 4 to 8 dust trap wall 108 hot wire type mass flow sensor 2 dust trap wall

Claims (1)

[Claims] 1. An introduction pipe for introducing a gas to be measured, a hot-wire mass flow sensor provided in a part of a gas flow path of the introduction pipe, and the introduced gas to collide with each other. A flowmeter comprising: a dust trapping wall formed on at least one inner wall of an inlet pipe upstream of the heat-ray type mass flow sensor so as to adhere dust.