JPH04116464A - Fluid velocity sensor - Google Patents

Abstract

PURPOSE:To obtain a fluid velocity sensor which is rigid, high in sensitivity and fast in response speed wherein an orientation of a placed apparatus need not be considered by placing a thin film temperature measuring resistor 2 at the tip of a slip plate of a heat insulating printed board. CONSTITUTION:When a fluid velocity sensor is placed in fluid to be measured, a heat dissipation amount from a first thin film temperature measuring resistor 2 which has generated heat according to the velocity changes. That is, by an increase/decrease of the fluid velocity, temperature of the resistor 2 rises or drops, while a resistance value increases/decreases according to the change in the temperature so that voltage between electrode terminals 14, 15 increases/decreases. On the other hand, an ambient temperature is detected by a second thin film temperature measuring resistor 3. Current is made flow to the resistor 2 so that a difference between temperature detected without air flow and the temperature by the resistor 2 is maintained always constant to compensate change in the ambient temperature. The voltage value of the resistor 2 thus obtained is subjected to numeric conversion whereby output voltage V which is proportional to a fourth-power root of a value of fluid velocity (v) of an equation can be obtained. The resistor 2 is placed at the tip of a strip branch part 11 to prevent a relation of the equation from largely being out by disturbance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flow rate sensor used to determine the flow rate of gas and further the flow rate of gas therefrom.

[Conventional technology]

In recent years, flow rate sensors have come into use for industrial measurement or consumer use.

There is a hot wire method to measure flow velocity. It uses the fact that the resistance value of the heating element changes depending on the gas flow rate,
This is a method of measuring flow velocity.

There are constant current type and constant temperature type of hot wire type flow rate sensors, but in both cases, the output voltage ■ or output current ■ is ■ or Icc (A0Bxv'')'' when the flow velocity is V. There is a relationship as follows.A and B are constants.

An example of a constant temperature flow rate sensor based on this principle is shown in the fourth section.
As shown in the figure.

As shown in FIG. 4(a), the sensor element 41 has a heater 4 attached to one end side on the same surface of a rectangular thin glass plate 42.
A heater temperature monitor 45 for detecting the temperature of the heater 43 is disposed at and near the heater 43, and a temperature sensor 44 is disposed at the other end. These heaters 43. Temperature sensor 44 and heater temperature monitor 4
5 are all made of thin film platinum. The sensor element 41 is held in a cantilever shape by the base 46 at the side end of the thin glass plate 42 where the temperature sensor 44 is arranged, as shown in FIG. 4(b).

This flow rate sensor is connected to a circuit that maintains a constant temperature difference detected by the heater temperature monitor 45 and the temperature sensor 44, and causes gas to flow in the direction of arrow Z shown in FIG. The flow velocity is determined from the power consumption of the heater 43 when the heater 43 is energized and the temperature difference detected by the heater temperature monitor 45 and the temperature sensor 44 is maintained constant.

[Invention or problem to be solved]

The characteristics of a flow velocity sensor are mainly evaluated by the sensitivity and response speed to the flow velocity.In the conventional flow velocity sensor described above, the sensor element 41 is substantially suspended in the air in order to increase the sensitivity and response speed. It has become. For this reason, there is a problem that the structure is unstable and the yield is very low.

An object of the present invention is to solve the above-mentioned conventional problems and provide a flow rate sensor that has excellent sensitivity and response speed, and is structurally stable.

[Means to solve the problem]

The flow rate sensor according to claim (1) comprises: a heat-insulating insulating substrate;
It includes a first thin film resistance temperature detector and a second thin film resistance temperature detector.

The heat-insulating insulating substrate has a rectangular plate portion protruding from its edge, and a first thin film resistance temperature detector is mounted on the tip of the rectangular plate portion. A second thin film resistance temperature detector is mounted on the heat-insulating insulating substrate in an area other than the strip plate portion.

The flow velocity sensor according to claim (2) is the flow velocity sensor according to claim (1), characterized in that the first thin film resistance temperature detector is formed of two thin film resistance temperature detectors. )
In the flow velocity sensor according to claim (1), a heat dissipating protruding plate is provided at the tip of the strip plate portion of the heat-insulating insulating substrate, and a first thin film resistance thermometer is disposed on the heat dissipating protruding plate. It is characterized by being equipped with.

[Effect]

The structure of the present invention is that the first thin film resistance temperature detector is mounted on a heat-insulating insulating substrate, so it is robust and has high sensitivity. Furthermore, since the heat capacity of the first thin film resistance thermometer is small, the temperature easily rises with a small amount of electric power. In addition, since the first thin film resistance temperature detector is mounted on the strip of the heat-insulating insulating substrate, there is little influence on changes in the flow direction of the fluid.

〔Example〕

First example A first embodiment of the invention will be described with reference to FIG.

FIG. 1 is a perspective view of a constant current type flow rate sensor according to a first embodiment of the present invention.

In FIG. 1, 1 is a heat insulating printed circuit board, and II
is a strip plate portion of the heat insulating printed circuit board 1. Reference numeral 2 denotes a first thin film resistance temperature sensor, which is arranged at the tip of the strip plate section 11, and both ends thereof are connected to the wire 6 and the lead strips 4 and 5.
are connected to electrode terminals 14.15 by. Reference numeral 3 denotes a second thin film resistance temperature detector, which is placed on the heat insulating printed circuit board 1 except for the strip plate portion 11, and its both ends are connected to electrode terminals 17.1 by wires 7 and lead strips 8.9.
8 is connected. Further, the first thin film resistance thermometer 2 has a thin plate shape with a length and width of 1 mm or less and a thickness of several tens of μm, and has an extremely small heat capacity.

The operation of the flow rate sensor of this embodiment will be explained below.

The first thin film resistance thermometer 2 generates heat when a voltage is applied between the electrode terminals 14 and 15 to energize it. Since the first thin film resistance temperature detector 2 has a small heat capacity and is arranged on the heat insulating printed circuit board 1, its temperature rises with a small amount of electric power and becomes higher than the ambient temperature. Since the resistance value of the first thin film resistance temperature sensor 2 changes in accordance with the temperature change, the voltage between the electrode terminals 14 and 15 changes accordingly.

When the flow rate sensor of this example is placed in the fluid to be measured,
The amount of heat dissipated from the first thin film resistance thermometer 2 that generates heat changes depending on the flow rate. That is, as the flow rate increases or decreases, the temperature of the first thin film resistance thermometer 2 increases or decreases. Since the resistance value of the first thin film resistance thermometer 2 increases or decreases in accordance with changes in temperature, the voltage between the electrode terminals 14 and 15 increases or decreases.

On the other hand, the ambient temperature is detected by the second thin film resistance temperature detector 3. so that the difference between the temperature detected in a windless state and the temperature detected by the first thin film resistance thermometer 2 is always kept constant.
A current is passed through the first thin film resistance temperature detector 2 to correct for changes in ambient temperature.

By performing numerical conversion, the voltage value of the first thin film resistance temperature detector 2 obtained in this way is determined by the output voltage V which is proportional to the fourth root of the value of the flow velocity is obtained.

The structure in which the first thin film resistance thermometer 2 is arranged at the tip of the strip plate part 11 is designed to minimize turbulence in the flow velocity.
This has the effect of preventing the relationship in equation (2) from being significantly deviated due to turbulence and reducing the influence of the fluid flow direction.

As described above, according to this embodiment, by arranging the first thin film resistance temperature detector 2 at the tip of the strip plate portion 11 of the heat insulating printed circuit board 1, the structure is robust, has high sensitivity, and has a fast response speed. ,
Furthermore, a flow rate sensor that does not require consideration of the direction in which the device is arranged can be obtained.

Second embodiment A second embodiment of the invention will be described based on FIG.

FIG. 2 is a plan view of a constant temperature type flow rate sensor according to a second embodiment of the present invention.

This flow rate sensor uses a first thin film resistance temperature detector 22 composed of two thin film resistance temperature detectors instead of the first thin film resistance temperature detector 2 in the first embodiment, and has both end portions has three wires 6 and a lead strip 4. 5. 10 is connected to electrode terminals 14, 15° 19. The rest of the structure is the same as that of the first embodiment, and the same reference numerals are given to the parts corresponding to those in FIG. 1.

One of the first thin film resistance thermometers 22 is connected to the lead strips 4 and 5 via the wire 6, and one of the thin film resistance thermometers 22 is connected to the lead strips 4 and 5 via the wire 6. The other thin film resistance temperature detector connected to IO is a heater temperature monitor, and the second thin film resistance temperature detector 3 is a temperature sensor that detects the ambient temperature.

The operation of the flow rate sensor of this embodiment will be explained below.

The operation of this flow velocity sensor is similar to that of the conventional flow velocity sensor, and one first thin film resistance temperature detector 22 is detected by the other first thin film resistance temperature detector 22 (heater temperature monitor). (heater) and the temperature detected by the second thin film resistance thermometer 3 (temperature sensor) is always kept constant. When the temperature difference detected by the other first thin film resistance thermometer 22 (heater temperature monitor) and the second thin film resistance thermometer 3 (temperature sensor) is held constant, One of the first
The flow velocity can be determined from the power consumption of the thin film resistance thermometer 22 (heater).

Note that either of the two thin film resistance temperature detectors of the first thin film resistance temperature detector 22 may be used as a heater or a heater temperature monitor.

According to this embodiment, like the first embodiment, it is robust and
A flow rate sensor with high sensitivity, no need to consider the direction in which the device is placed, and faster response speed than the first embodiment can be obtained.

Third embodiment A third embodiment of the invention will be described based on FIG.

FIG. 3(a) is a plan view of a constant current type flow rate sensor according to a third embodiment of the present invention, and FIG. 3(b) is a sectional view taken along the X-Y line in FIG. 3(a). be.

This flow rate sensor consists of a strip plate portion 1 of a heat insulating printed circuit board 1.
A heat dissipating protruding plate 31 made of metal is provided on the tip side of the heat dissipating protruding plate 31, and the first thin film resistance thermometer 2 is disposed on the heat dissipating protruding plate 31. The other configurations are the same as the first embodiment, and the first
Components corresponding to those in the figures are given the same reference numerals.

The operation of the flow velocity sensor of this embodiment is the same as that of the first embodiment, but the heat generated in the first thin film resistance temperature detector 2 is quickly transferred to the heat dissipating protruding plate 31, and this portion Dissipation of heat occurs. Therefore, the influence of changes in the fluid flow direction is further reduced compared to the first embodiment.

In this embodiment, metal is used for the heat dissipating protrusion plate 31, but any material with good thermal conductivity may be used.

Also, 1st. The heat insulating printed circuit board 1 in the second and third embodiments may be any heat insulating board.

〔Effect of the invention〕

The flow velocity sensor of the present invention is robust and has high sensitivity because the first thin film resistance temperature detector is mounted on a heat-insulating insulating substrate. Furthermore, since the heat capacity of the first thin film resistance thermometer is small, the temperature can be easily increased with a small amount of electric power, and the response speed is fast. Furthermore, since the first thin film resistance temperature detector is mounted on the strip of the heat-insulating insulating substrate, there is little influence on changes in the flow direction of the fluid, and there is no need to consider the direction in which the device is arranged. In this way, the flow velocity can be detected efficiently.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a flow velocity sensor according to a first embodiment of the present invention, FIG. 2 is a plan view of a flow velocity sensor according to a second embodiment of this invention, and FIG. A plan view of the flow velocity sensor of Example 3, FIG. 3(b) is the X in FIG. 3(a).
- A cross-sectional view taken along the Y line, FIG. 4 (aj is a plan view of an element in a conventional flow velocity sensor, and FIG. 4(b) is a perspective view of a conventional flow velocity sensor. 1. A heat-insulating printed circuit board; 2, 22...First thin film resistance temperature detector, 3...Second thin film resistance temperature detector, 11 Strip plate portion, 31...Heat dissipating protruding plate (b)

Claims (3)

[Claims] (1) A heat insulating insulating substrate with a strip plate protruding from its edge, a first thin film resistance temperature detector mounted on the tip of the strip plate on the heat insulating insulating substrate, and the heat insulating insulating and a second thin film resistance temperature detector mounted on an area other than the strip plate portion on the substrate. (2) The flow velocity sensor according to claim (1), wherein the first thin film resistance temperature detector is formed of two thin film resistance temperature detectors. (3) A heat dissipating protruding plate is provided at the tip of the strip plate portion of the heat insulating insulating substrate, and the first thin film resistance temperature detector is mounted on the heat dissipating protruding plate. flow rate sensor.