JP2887018B2 - Fluid flow velocity and flow direction detection sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor for detecting the flow velocity and direction of a fluid (gas) flowing in a pipe or the like.

[0002]

2. Description of the Related Art As shown in FIG. 3, in a conventional sensor, a shielding plate 02 made of a flat rectangular parallelepiped is attached to the center of the upper surface of a base 01 so as to be supported by a protective cover 07, and the shielding plate 02 is sandwiched therebetween. A pair of flow rate sensors 03, 03 'are supported and fixed by two columns 04, 04', and a temperature compensating thermistor 05, 05 'is also supported and fixed by two columns 06, 06', and the flow rate of fluid and This configuration allows simultaneous measurement of the direction of flow.

[0003]

Therefore, there are the following problems.

A. Shield plate 02 and flow rate sensors 03, 0
Since the 3 'and the temperature compensating thermistors 05 and 05' are supported and fixed by two columns 04, 04 ', 06 and 06', respectively, the number of parts is large, the structure becomes complicated and the miniaturization is limited. In addition, the assembling and manufacturing are troublesome, and the price is high.

B. Since the shielding plate is a rectangular parallelepiped, turbulence easily occurs in the flow, the sensitivity of the upstream flow velocity sensor for detecting the flow velocity is reduced, and the S / N ratio and the flow direction detection performance of the flow velocity sensor are deteriorated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high-performance sensor for detecting the flow velocity and flow direction of a fluid which is small in size, low in manufacturing cost, and high in performance.

[0007]

In order to achieve the above object, the present invention employs the following structure in a sensor for detecting the flow velocity and flow direction of a fluid.

A center support is erected at the center of the base, and two temperature compensating thermistors are mounted side by side on the upper end surface of the center main support. A flow velocity and flow direction detection sensor for a fluid, wherein a side main pillar is set lower than the height, and a flow velocity sensor is attached to each upper end face of the side main pillar.

The center support and the side support may be integrally formed.

[0010]

The sensor is mounted in a pipe and its flow velocity and direction are detected based on the following measuring principle.

When a heated hot wire is placed in a stream, heat is removed and the temperature drops. This temperature change increases as the flow velocity increases. Utilizing this property, the flow rate can be known from the current value required to keep the temperature of the hot wire constant.

As the sensor, a hot thermistor (fine ceramic semiconductor) whose resistance changes greatly with temperature is used, and is incorporated on one side of the bridge. When the hot thermistor is cooled by the flow, the current necessary to maintain the initial temperature flows in the bridge circuit, and the thermistor self-heats and the temperature is kept constant at about 120 ° C. Therefore, by measuring this current, the flow velocity can be detected. Also, when the gas temperature changes, the amount of heat taken from the sensor also changes, which is compensated for by the temperature compensation thermistor.

The relationship indicating the degree of cooling by the flow is represented by King's equation shown in Equation 1.

[0014]

(Equation 1)

The amount of heat generated in the bridge is given by the following equation (2).

[0016]

(Equation 2)

Therefore, Equation 3 can be obtained from Equations 1 and 2.

[0018]

(Equation 3)

Here, a and b are constants determined by the thermal conductivity, viscosity coefficient, sensor surface area and the like of the gas.

From equation (3), the sensor output voltage is a function of the flow rate to the 1/4 power.

Next, the direction of the flow is adjusted by a differential amplifier so that the output characteristics of the two flow velocity sensors become the same, and then the magnitude of the sensor output is determined by a comparator to detect the flow direction.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes a base, 1a denotes a protective cover having an open flow direction, and a center support 2 and side supports 3, 3 'in front and behind the center support 2 in the center of the base 1. It is standing. In addition, the side support 3,
The height of 3 ′ is approximately の of the height of the center column 2.

Reference numerals 4 and 4 'denote temperature compensating thermistors mounted side by side on the upper end surface of the center column 2, and reference numerals 5 and 5' denote flow velocity sensors mounted on the upper end surfaces of the side columns 3, 3 '.

The sensor according to the embodiment is as described above.
The flow velocity is detected by the flow velocity sensors 5 and 5 ′ on the side supports 3 and 3 ′, and the temperature compensating thermistor 4 on the center support 2,
4 'detects the flow velocity and its flow direction while compensating for changes in fluid temperature.

[0025]

The sensor according to the present invention has the above-described configuration and operation, and has the following effects.

A. Since the number of pillars is reduced by half, the size can be reduced to approximately 1/4 as compared with the conventional example.

B. Since the number of parts is small and the structure is simple, manufacturing costs can be reduced.

C. Since the center support performs the function corresponding to the shielding plate, there is almost no factor that disturbs the flow and lowers the sensitivity, so that the performance of the upstream sensor in particular is improved.

FIG. 2 shows the output of the flow velocity sensor, and it can be seen that the sensitivity of the upstream sensor is improved about twice as compared with the conventional example. As a result, the detection performance is improved in both the flow velocity and the flow direction.

[Brief description of the drawings]

FIG. 1 is a perspective view of a sensor according to the present invention.

FIG. 2 is an explanatory diagram of a sensor output when the present invention is implemented.

FIG. 3 is an explanatory diagram of a conventional sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base 2 Center support 3, 3 'side support 4, 4' Temperature compensation thermistor

Claims (1)

(57) [Claims] 1. A center support is erected in the center of a base, and two temperature-compensating thermistors are mounted side by side on the upper end surface of the center main support. A sensor for detecting a flow velocity and a flow direction of a fluid, wherein a side main column is set lower than the column height, and a flow velocity sensor is attached to an upper end surface of the side main column.