JP3188597B2 - Flowmeter - Google Patents

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 use in various devices which need to accurately measure a flow rate, for example, measuring a combustion air amount of a gas-fired water heater.

[0002]

2. Description of the Related Art Conventionally, in order to measure the amount of combustion air in a gas water heater or the like, a method has been adopted in which the amount of combustion air is indirectly measured by the rotation speed of a blower or a fan motor. However, since this method simply measures the volumetric flow rate of airflow, accurate measurements cannot be made due to the effects of pressure due to altitude differences and fluctuations in external weather conditions. It is set to supply a much higher air volume. As a result, the equipment itself becomes large, and there is a problem that nitrogen oxides (NOx) are easily generated due to departure from optimal combustion conditions, and a problem such as a decrease in energy efficiency also arises.

Therefore, recently, a flow meter as shown in FIG. 3 has been developed and put to practical use. FIG. 3 is a perspective view showing a conventional flow meter. In the drawing, reference numeral 1 denotes a case provided with a flow sensor therein, and reference numeral 2 denotes a cylinder provided on a front plate 1a of the case 1. The front end opening of the cylindrical portion 2 is closed by a front surface (valve end) 3. The cylindrical portion 2 is axially partitioned by a partition plate 4 into two chambers 2a and 2b.
Two small holes 5a and 5b are provided in the vicinity of the distal end of the cylindrical portion 2, and the small hole 5a communicates the room 2a with the outside air, and the small hole 5b communicates the room 2b with the outside air.

In each of the rooms 2a and 2b, a plurality of dust collecting plates 6 are alternately arranged on the partition plate 4 from both sides.
Is provided. The front plate 1a is provided with a hole 7a communicating with the room 2a and a hole 7b communicating with the room 2b. On the front and back surfaces 4a of the partition plate 4 and the front surface 6a of each dust collecting plate 6, fine irregularities called satin are formed.

[0005] The flow rate sensor section is hardly affected by altitude differences and the outside world, and is designed to reduce the size of the entire water heater.
The chip type hot-wire flow sensor 11 shown in FIG. In this sensor 11, a diaphragm 13 having a thickness of 20 μm or less is formed at a substantially central portion of a 1.7 mm square semiconductor chip 12, and a micro flow sensor 14 including a heating resistance pattern and a temperature-sensitive resistance pattern is arranged on the diaphragm 13. Configuration.

[0006] As shown in FIG.
Is disposed in a duct 21 so as to be orthogonal to the direction in which air flows, a front plate 1 a of the case 1 is fixed to the duct 21, and a drive circuit 22 is connected to the case 1.

Next, the operation will be described. As shown in FIG. 5, when this flow meter is arranged in an air flow path such that air flows in from the lower small hole 5b, for example, the small hole 5b
The air flowing through the chamber 2 passes through the room 2b and further flows from the hole 7b through the sensor 11 in the case 1 to measure the flow rate. The air passing through the sensor 11 flows out of the hole 7a, passes through the room 2a, and flows out of the small hole 5a into the duct 21.

When the air entering the room 2b from the small hole 5b passes between the partition plate 4 and the dust collecting plate 6, dust, dirt, and the like are collected on the surface 4a of the partition plate 4 and the surface of the dust collecting plate 6. It is collected by the irregularities of 6a.

In the above description, air is taken in from the lower hole 5b and air is made to flow out from the upper small hole 5a. Conversely, air is taken in from the upper small hole 5a.
It may be used so that air flows out from the lower small hole 5b. In that case, dust and dirt in the air entering through the small holes 5a are collected by the dust collecting plate 6 in the room 2a.

[0010]

Since the conventional flow meter is constructed as described above, it has an advantage that the sensitivity is very good and accurate measurement can always be performed. There is a problem in that dew condensation easily occurs on the surfaces of the partition plate 4 and the dust collecting plate 6 due to moisture contained in the air flow while passing between the plates 6. The moisture condensed on the surfaces of the partition plate 4 and the dust collecting plate 6 enters the case 1 through the hole 7b,
Since the sensor 11 adheres to the sensor 11 to contaminate the sensor 11 and reduce the measurement accuracy, the reliability of the sensor 11 decreases, and the sensor 11 cannot withstand long-term use. In particular, in kitchens and kitchens where gas water heaters are installed, the temperature difference between when they are used and when they are not in use is large, and the relative humidity is high, so condensation is more likely to occur than other installation locations, and the reliability is significantly reduced. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can prevent the accumulation of water due to dew condensation, thereby improving the reliability and enduring long-term use. The purpose is to get.

[0012]

In the flow meter according to the present invention, a passage communicating with each room is formed in a partition plate.

[0013]

In the flow meter according to the present invention, the passage formed in the partition plate allows moisture condensed on the partition plate and the dust collecting plate to pass through the passage and to be discharged to the outside of the cylindrical portion from the small hole below. Water does not stay on the plate and the dust collecting plate, and there is no possibility that the flow sensor will be stained by the water. This makes it possible to maintain the long-term stability of the sensor characteristics of the flow sensor unit, improve the reliability of the flow meter, and enable long-term use.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 31 denotes a passage formed at the end of the partition plate 4 and communicating the rooms 2a and 2b. The passage 31 is formed so as to be shifted horizontally so that the position of the lower opening and the position of the upper opening do not overlap on the same axis.

Next, the operation will be described. In this flow meter, the air flowing from the lower small hole 5b or the upper small hole 5a passes through the room 2b or 2a, enters the case 1 from the hole 7b or 7a, and the flow rate is measured by the sensor 11. The air that has passed through the sensor 11 is the room 2a or 2
b and is discharged from the upper small hole 5a. During this time, when dew condensation occurs on the surfaces of the partition plate 4 and the dust collecting plate 6 of the room 2a, the dew water is discharged to the outside through the small hole 5b through the passage 31. As a result, the condensed water flows through the passage 31 and the small hole 5.
b, it is quickly discharged, and does not stay on the partition plate 4 or the dust collecting plate 6.

On the other hand, the output of the sensor 11 gradually becomes saturated as the flow rate of air increases. For example, FIG.
As shown in (2), the output sharply changes in a region where the flow rate is small, but hardly changes in a region where the flow rate is equal to or higher than a certain value, and the sensitivity sharply decreases. In this flow meter,
Since the passage 31 plays the role of a bypass, the small holes 5b
From the room 2b according to the magnitude of the flow rate
And the air passing through the passage 31 are branched off, and the flow rate of the air passing through the sensor 11 is relatively reduced, so that the detection sensitivity can be maintained. Therefore, the range of the flow rate that can be measured by the sensor 11 is widened, and the characteristics are improved.

According to the flow meter of this embodiment, since the partition plate 4 is formed with the passage 31 communicating the respective rooms 2a and 2b,
The moisture condensed on the partition plate 4 and the dust collecting plate 6 can be quickly discharged to the outside, and the contamination of the sensor 11 by the moisture can be prevented. Therefore, the sensor 11
Characteristics can be maintained for a long time, the reliability as a flowmeter can be improved, and long-term use can be achieved. Further, since the passage 31 is formed as a branch of the inflowing air, the flow rate of the air passing through the sensor 11 can be relatively reduced, and the measurement range can be expanded while maintaining the detection sensitivity of the sensor 11.

In this embodiment, the passage 31 is provided at the front end of the partition plate 4. However, the passage 31 may be formed at a plurality of places depending on the condition of dew condensation. Further, the shape of the passage 31 is not limited to the above embodiment, and various shapes can be implemented.

[0019]

As described above, according to the present invention, since a passage communicating with each room is formed in the partition plate, moisture condensed on the partition plate and the dust collecting plate is quickly discharged outward. It can be discharged, and the flow sensor can be prevented from being contaminated by the dew condensation water. Therefore, long-term stability of the characteristics of the flow sensor unit can be maintained, and the reliability of the flow meter can be improved and long-term use can be achieved. Further, since the passage serves as a branch of the inflowing air, the flow rate of the air passing through the flow rate sensor unit can be relatively reduced, and the measurement range of the flow rate can be expanded while maintaining the detection sensitivity of the flow meter. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a main part of a flow meter according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a sensor output and an air flow rate.

FIG. 3 is a perspective view showing a conventional flow meter.

FIG. 4 is a perspective view showing a chip type thermal flow sensor.

FIG. 5 is a cross-sectional view showing a state where a conventional flow meter is provided in a duct.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 1a Front plate 2 Cylindrical part 2a, 2b Room 3 Front (valve end) 4 Partition plate 5a, 5b Small hole 6 Dust collecting plate 7a, 7b Hole 31 Passage

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Seki 1-12-2 Kawana, Fujisawa-shi, Kanagawa Yamatake-Honeywell Co., Ltd. Fujisawa Plant (56) References JP-A-5-288581 (JP, A) ( 58) Field surveyed (Int. Cl. ⁷ , DB name) G01F 1/684 G01F 1/00 G01F 15/12

Claims (1)

(57) [Claims] 1. A case in which a flow sensor is provided inside and a front plate is provided with a hole for introducing a fluid into the flow sensor, and a case is provided in the front plate, and the valve end of the cylinder body is closed and the inside is closed. A cylinder which is divided into two chambers in the axial direction by a partition plate, and a pair of small holes are formed in the cylinder main body to communicate the respective rooms and the outside, and further, dust collecting plates are formed on both sides of the partition plate. A flow path comprising: a passage communicating with each of the chambers in the partition plate.