JP2000028410A - Flow-rate sensor, temperature sensor, and flow-rate detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To speed up response and raise measurement precision while corrosion and deformation are dissolved. SOLUTION: A flow-rate sensor 1 is provided wherein a flow-rate detecting part wherein a heating element and a temperature-sensitized body are formed directly at one end part of a substrate 3 and an output terminal 4 are comprised while a part of the substrate 3 as well as that of the output terminal 4 are coated with a molded coating member 5. A temperature sensor 21 is provided wherein a temperature detecting part wherein a temperature-sensitized body is directly formed at one end part of a substrate 23 and an output terminal 24 are comprised while a part of the substrate 23 as well as that of the output terminal 24 are coated with a molded coating member 25. The flow-rate sensor 1 and the temperature sensor 21 are housed in sensor insert holes 39 and 40 opened at a easing 32, constituting a flow-rate detecting device 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate sensor, a temperature sensor, and a flow rate detection device for measuring the flow rate of a fluid such as gas or liquid flowing in a pipe.

[0002]

2. Description of the Related Art Conventionally, various types of flow sensors (or flow rate sensors) for measuring the flow rate (or flow rate) of various fluids, especially liquids, have been used, but it is easy to reduce the cost. For that reason, so-called thermal (especially indirectly heated) flow sensors are widely used.

Among them, an indirectly heated flow sensor using a thin film element disclosed in Japanese Patent Application Laid-Open No. 8-146,026 is a small and inexpensive indirectly heated flow sensor having excellent thermal response, high measurement accuracy, and low cost. Are known. As shown in FIG. 10, the flow rate sensor 101 is obtained by laminating a thin film heating element 103 and a thin film temperature sensing element 104 on a substrate 102 using a thin film technology via an insulating layer 105. As shown, it is installed at an appropriate position of the pipe 106 and used.

In the flow sensor 101, the heating element 10
By heating the temperature sensor 3, the temperature sensor 104 is heated, and a change in the electric resistance value of the temperature sensor 104 is detected. Here, since the flow rate sensor 101 is installed in the pipe 106, a part of the heat generated by the heating element 103 is released into the fluid flowing in the pipe via the substrate 102 and transmitted to the temperature sensing element 104. The calorific value is obtained by subtracting this calorific value. And
Since the amount of heat dissipated changes in accordance with the flow rate of the fluid, the flow rate of the fluid flowing through the pipe 106 can be measured by detecting a change in the electric resistance value of the temperature sensing element 104 that changes according to the supplied heat quantity. It turns out that. Further, since the amount of heat dissipated also changes depending on the temperature of the fluid, as shown in FIG.
7 is installed, and a temperature compensation circuit is added to a flow rate detection circuit for detecting a change in the electric resistance value of the temperature sensing element 104, so that an error of the flow rate measurement value due to the temperature of the fluid is reduced as much as possible. .

[0005]

However, the conventional flow sensor 101 is directly installed on the metal pipe 106, and the metal pipe 106 is exposed to the outside air. Therefore, the amount of heat held by the fluid is released to the outside air via the metal pipe 106 having high thermal conductivity, or the amount of heat is easily supplied from the outside air to the fluid.
This caused the measurement accuracy to decrease. In particular, when the flow rate of the fluid is very small, the influence on the measurement accuracy is large.When the difference between the temperature of the fluid and the temperature of the outside air is large, and when the specific heat of the fluid is small, the influence is further reduced. It was remarkable.

When the fluid is a viscous fluid having a relatively high viscosity, the flow velocity in the cross section of the pipe 106 is largely different between the vicinity of the pipe wall and the center, and the flow velocity vector has an extreme value in the center. It has a substantially parabolic shape. Therefore, as in the related art, if the substrate 102 or the casing 108 connected to the substrate 102 is installed on the pipe wall and the flow velocity only in the vicinity of the pipe wall is measured, the flow velocity in the central part is not taken into account. It had to be low. It should be noted that, even at a normal temperature, the viscosity of a fluid having a low viscosity increases as the temperature decreases, so that the above problem cannot be ignored. In particular, when the flow rate was very small, the influence of the viscosity was more remarkable.

Further, the flow rate sensor 101 is used under various different environments such as geographical conditions, indoors and outdoors, and particularly, outdoors, due to factors such as seasonal conditions, daytime and nighttime. Temperature changes must also be considered. However, since the conventional flow sensor 101 has a structure that is easily affected by such an external temperature environment, there is a large error in the measured value of the flow rate, and the flow rate can be accurately detected in a wide external temperature environment. A sensor was desired.

In order to solve such a problem in the related art, the present inventors have tried to solve the problem by using a substrate 20 as shown in FIG.
2 is a flow rate detection unit 206 in which a thin film heating element 203 and a thin film temperature sensing element 204 are laminated via an insulating layer 205, and the flow rate detection unit 206 is mounted on a horizontal plate portion 207a of a fin plate 207 bent into an L shape. Sensor 201 was developed. Then, in the casing 208, the glass 2 is placed between the vertical plate portion 207 b of the fin plate 207 and the opening of the flow pipe 209.
10, a flow rate detection device 212 is also developed in which the flow rate detection unit 206 and the entire horizontal plate portion 207a of the fin plate 207 are covered with a synthetic resin 211, sealed and fixed.

The flow rate sensor 201 and the flow rate detection device 212 greatly reduce the problem of heat radiation to or supply to the outside air, a change in flow velocity in the cross section of the pipeline, and a reduction in flow rate measurement accuracy due to the influence of the external temperature environment. Was improved.

However, in the flow rate detection device 212, the flow rate detection section 206 of the flow rate sensor 201 and the synthetic resin 211
Are in direct contact with each other, the amount of heat held by the temperature sensing element 204 is likely to flow out or flow into the synthetic resin 211. or,
The flow rate detection unit 206 uses a bonding material 213 such as a silver paste having good thermal conductivity to form the horizontal plate portion 2 of the fin plate 207.
07a, the amount of heat transmitted through the fin plate 207 easily flows out or flows into the synthetic resin 211 via the bonding material 213. Therefore, when the specific heat of the fluid is small or the flow rate is small, the sensitivity of the flow sensor 201 may be reduced.

On the other hand, the vertical plate portion 2 of the fin plate 207
Although the heat transfer is blocked by the glass 210 between the opening 07b and the opening of the flow pipe 209, the glass 210 is filled and sealed, so that the fluid flows and the fin plate 207 vibrates minutely. Then, when the sealing state is incomplete, the amount of heat transmitted through the fin plate 207 is reduced through the metal flow pipe 209 having good heat transfer to the casing 2.
08 easily flows out or in. Therefore, similarly, when the specific heat of the fluid is small or the flow rate is small, the sensitivity of the flow sensor 201 may be reduced.

Further, the flow rate sensor 201 uses the bonding material 213 to control the flow rate detecting section 206 with the fin plate 2.
07 horizontal plate portion 207a and the fin plate 20
7 between the vertical plate portion 207b and the opening of the flow pipe 209, the glass 210 is filled and sealed, and the flow rate detecting portion 206 and the entire horizontal plate portion 207a of the fin plate 207 are covered with the synthetic resin 211 and sealed. Since work is required, it is troublesome to incorporate the casing 208 into the casing 208, and the fixing state is unstable, so that there is a problem in durability.

In order to solve the above problem, the present inventors further changed the flow rate detecting unit 302 having a heating element and a temperature sensing element on a substrate, as shown in FIG. One end face is fixed via a bonding material such as silver paste, and the flow rate detecting section 302 and the output terminal 304 are connected by a bonding wire 305.
A flow sensor 3 in which a part of a fin plate 303 and a part of an output terminal 304 are covered with a molding 306
01 was developed.

A temperature detecting portion 312 having a temperature sensing element formed on a substrate is fixed to one end surface of a fin plate 313 via a bonding material such as silver paste, and the temperature detecting portion 312 and the output terminal 314 are connected by a bonding wire. Developed a temperature sensor 311 for fluid temperature compensation having the same configuration as the flow rate sensor 301, which is connected by 315, and has a temperature detecting unit 312, a part of the fin plate 313, and a part of the output terminal 314 covered with a molding 316. did. The flow sensor 301 and the temperature sensor 311
A flow rate detection device was also developed in which the fin plates 303 and 313 were suspended in a flow pipe through which the fluid to be detected flows, by inserting the fin plates 303 and 313 into a sensor insertion hole of a casing.

With the flow sensor, the temperature sensor, and the flow detection device, the amount of heat released from each part of the flow sensor and the temperature sensor to the casing and the outside can be reduced as much as possible. Even with the above, the flow rate can be measured with high accuracy. Further, the work of assembling the flow sensor and the temperature sensor into the casing was simplified, the fixed state was stabilized, and a sufficiently durable flow detection device could be realized.

However, in the flow rate sensor 301 and the temperature sensor 311, heat is transmitted to the flow rate detecting section 302 and the temperature detecting section 312 via the fin plates 303 and 313 and a bonding material such as a silver paste. It was a bit slow. Further, heat outflow or inflow to the outside cannot be completely prevented even by the resin mold, and the layer thickness of a bonding material such as a silver paste varies from production lot to production lot, so that the measurement accuracy is slightly poor. Further, the fin plates 303 and 313
Is made of copper, copper-tungsten alloy or the like, and has a thickness of 200
Since it was a rectangular thin plate having a thickness of about 2 μm and a width of about 2 mm, it was easily corroded and deformed.

The present invention solves such a problem and further improves the flow rate sensor 301, the temperature sensor 311 and the flow rate detection device developed by the present inventors to increase the response speed of the flow rate sensor and the temperature sensor. It is another object of the present invention to provide a flow rate sensor, a temperature sensor, and a flow rate detection device which have higher accuracy in measurement and higher accuracy, and have solved the problems of corrosion and deformation of the fin plate.

[0018]

In order to achieve the above object, a flow rate sensor according to the present invention comprises a substrate on which a thin film lead wire is formed, and a flow rate detection device having a heating element and a temperature sensing element formed directly on one end of the substrate. And a protective film on the substrate so as to cover a part of the flow rate detecting part and the thin film lead wire, and a part of the substrate and a part of the output terminal are formed by molding. This is covered with a covering member.

Further, the temperature sensor of the present invention has a substrate on which a thin film lead wire is formed, a temperature detecting section having a temperature sensing element formed directly on one end of the substrate, and an output terminal. And a protective film is formed on the substrate so as to cover a part of the thin film lead wire, and a part of the substrate and a part of the output terminal are covered with a covering member by molding.

The flow rate detecting device of the present invention comprises the above flow rate sensor, a casing having a sensor insertion hole for accommodating the flow rate sensor, and a fluid to be detected having an opening formed at a position corresponding to the sensor insertion hole. And a distribution pipe for distribution. Further, if the temperature sensor and a sensor insertion hole for accommodating the temperature sensor are formed in the casing, fluid temperature compensation can be performed, which is more preferable.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a flow sensor, a temperature sensor and a flow detection device according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the flow sensor 1 comprises a flow detector 2, a substrate 3, an output terminal 4, and a covering member 5.

As shown in FIGS. 2 and 3, the flow rate detecting section 2 is provided directly on one side surface of the lower end of the substrate 3 with an insulating layer 6, a thin film heating element 7, electrode layers 8, 9, an insulating layer 10, a thin film The temperature sensing elements 11 are sequentially laminated and formed.

The heating element 7 is made of a cermet having a thickness of about 1 μm and patterned into a desired shape.
Is formed by stacking nickel having a thickness of about 0.5 μm or gold having a thickness of about 0.5 μm. The temperature sensing element 11 is made of a metal resistance film having a large temperature coefficient, such as platinum or nickel, having a film thickness of about 0.5 to 1 μm and having a desired shape, for example, a meandering pattern, such as platinum or nickel, or a manganese oxide NTC thermistor. The insulating layers 6 and 10 are made of Si having a thickness of about 1 μm.
Consists of O ₂ .

The substrate 3 is a rectangular plate made of silicon, alumina, glass or the like and having a thickness of about 600 μm and a width of about 2 mm. As shown in FIG. A lead wire 12 is formed.

Then, a protective film 13 having a water resistance, chemical resistance and insulating properties such as SiO ₂ , Al ₂ O ₂ , SiN, glass, synthetic resin or the like having a film thickness of about 1 μm is formed on the lower half of the substrate 3. , And the lower half of the thin film lead wire 12 is covered.

The upper end of the thin film lead 12 and the output terminal 4
Are connected by a bonding wire 14,
The upper half of the substrate 3 and the lower half of the output terminal 4 are covered with a covering member 5 formed by molding.

The temperature sensor 21 is, as shown in FIG.
It comprises a temperature detector 22, a substrate 23, an output terminal 24, and a covering member 25.

As shown in FIGS. 5 and 6, the temperature detecting section 22 is provided directly on one side of the lower end of the substrate 23 with an insulating layer 26,
The thin-film temperature sensing element 27 is sequentially laminated and formed. The shapes and materials of the insulating layer 26 and the temperature sensing element 27 are the same as those in the flow rate detection unit 2.

The shape and material of the substrate 23 are the same as those of the flow sensor 1.
As shown in FIG. 4, the thin film lead wires 28 are also provided on the substrate 23 from the temperature detecting section 22 to the upper end.
Is formed. A protective film 29 is also formed on the lower half of the substrate 23 in the same manner as in the flow sensor 1, and covers the lower half of the temperature detector 22 and the thin film lead 28.

The upper end of the thin film lead 28 and the output terminal 24
Are also connected by bonding wires 29, and the upper half of the substrate 23 and the lower half of the output terminal 24 are
It is covered with a covering member 25 by molding.

The flow rate sensor 1 and the temperature sensor 21 of the present invention include the flow rate detection unit 2 and the temperature detection
Since it is formed directly on one side of the lower end portion of the bottom surface, a bonding material such as a fin plate and a silver paste is not required, and heat is immediately transmitted from the fluid to be detected to the flow rate detecting section 2 and the temperature detecting section 22 via the protective films 13 and 29. Since it is transmitted, the response speed becomes extremely high.

Further, the flow rate detecting section 2 and the temperature detecting section 22 are located in the fluid to be detected, so that heat does not flow out or inflow from the covering members 5 and 25 to the outside, and a joining material such as silver paste is unnecessary. Since there is no variation between manufacturing lots, the measurement accuracy is extremely high.

Further, since the fin plate is unnecessary, it is not necessary to consider the corrosion and the deformation.

The flow detecting device 31 is shown in FIGS.
As shown in the figure, the casing 32, the flow pipe 33, the flow sensor 1, the temperature sensor 21, and the flow detection circuit board 3
Consists of 4 mag.

The casing 22 is made of a synthetic resin such as vinyl chloride resin, polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), etc., and comprises a main body 35 and a lid 36 detachable from the main body. Both ends are connecting portions 37 for connecting to an external pipe, and a flow pipe 33 is penetrated in the main body 35. A sensor insertion space 38 is defined in an upper portion of the main body 35, and sensor insertion holes 39 and 40 are formed from the sensor insertion space 38 toward the circulation pipe 33.

The flow pipe 33 is a circular pipe made of a metal such as copper, iron, and stainless steel.
The openings 41 and 42 are formed at the positions corresponding to.

The flow rate sensor 1 and the temperature sensor 21 are inserted into the sensor insertion holes 39 and 40 from the sensor insertion space 38 of the casing 32, and the lower halves of the substrates 3 and 23 are provided with openings 41 and 42 of the flow pipe 33. Are inserted into the flow pipe 33, and the lower ends of the substrates 3 and 23 are
To reach below the axis. The flow sensor 1, the temperature sensor 21 and the sensor insertion hole 39,
O-rings 43 and 44 are interposed between the O-rings 40 and 40 to prevent fluid leakage from these gaps.

After the flow sensor 1 and the temperature sensor 21 have been fitted, the sensor pressing plate 45 is inserted into the sensor insertion space 38 to press the upper surfaces of the covering members 5 and 25 of the flow sensor 1 and the temperature sensor 21. The flow path detection board 34 is mounted.

The flow rate detection circuit board 34 includes the flow rate sensor 1
Are electrically connected to the output terminals 4 and 24 of the temperature sensor 21 (not shown), and a flow rate detection circuit as shown in FIG. 9 is configured as a whole. The voltage supplied from the DC power supply 46 is applied to the heating element 7 and the bridge circuit 47 connected in parallel, and an output indicating the flow rate is obtained as an output of the differential amplifier 48 disposed in the bridge circuit 47. Has become. That is, in the flow sensor 1, the heat sensing element 11 detects a heat quantity obtained by subtracting the heat quantity released to the fluid via the protective film 13 from the heat generation quantity of the heating element 7,
On the other hand, in the temperature sensor 21, the heat sensing element 27 detects the amount of heat held by the fluid via the protective film 29, the fluid temperature is compensated, and the flow rate of the fluid is accurately detected.

Further, the flow rate sensor 1 and the temperature sensor 21 of the present invention comprise a flow rate detecting section 2, a temperature detecting section 22, an upper half of the substrates 3 and 23 and a lower half of the output terminals 4 and 24 which are covered by molding. 5 and 25, and are simply inserted into the sensor insertion holes 39 and 40 formed in the casing 32.
It is very easy to assemble it, and has a stable fixed state and high durability.

[0042]

As described above, according to the flow rate sensor and the temperature sensor of the present invention, the heat is immediately transmitted from the fluid to be detected to the flow rate detection section and the temperature detection section via the protective film, so that the response speed is improved. Is extremely fast.

Further, since the flow rate detecting section and the temperature detecting section are located in the fluid to be detected, heat does not flow out or in from the covering member to the outside, and there is no variation between manufacturing lots.
The measurement accuracy is also extremely high.

Furthermore, since the flow rate sensor and the temperature sensor of the present invention need not consider corrosion and deformation, they are integrated with the covering member and simply inserted into the sensor insertion hole, so that they can be incorporated into the casing very easily. The fixing state is stable and the durability is high.

[Brief description of the drawings]

FIG. 1A is a front sectional view of a flow sensor of the present invention,
(B) is a side sectional view.

FIG. 2 is an exploded perspective view of a flow detection unit of the flow sensor according to the present invention.

FIG. 3 is a longitudinal sectional view of a flow detecting unit of the flow sensor according to the present invention.

FIG. 4A is a front sectional view of the temperature sensor of the present invention,
(B) is a side sectional view.

FIG. 5 is an exploded perspective view of a temperature detector of the temperature sensor according to the present invention.

FIG. 6 is a longitudinal sectional view of a temperature detecting section of the temperature sensor of the present invention.

FIG. 7 is a front sectional view of the flow detecting device of the present invention.

FIG. 8 is a side sectional view of the flow detection device of the present invention.

FIG. 9 is a flow detection circuit diagram of the flow detection device of the present invention.

FIG. 10A is a perspective view and FIG. 10B is a cross-sectional view of a flow detection unit of a conventional flow sensor.

FIG. 11 is a cross-sectional view showing a state where a conventional flow sensor is installed in a pipe.

FIG. 12 is a schematic explanatory view of a flow sensor developed by the present inventors and mounted on a fin plate and a flow detection device provided with the flow sensor.

FIG. 13 shows a flow sensor (A) developed by the present inventors.
Is a front sectional view, and (B) is a side sectional view.

FIG. 14 shows a temperature sensor (A) developed by the present inventors.
Is a front sectional view, and (B) is a side sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow rate sensor 2 Flow rate detection part 3 Substrate 4 Output terminal 5 Covering member 7 Heating element 11 Thermosensitive body 12 Thin film lead wire 13 Protective film 21 Temperature sensor 22 Temperature detecting part 23 Substrate 24 Output terminal 25 Covering member 27 Thermosensitive body 28 Thin film Lead wire 29 Protective film 31 Flow rate detection device 32 Casing 33 Flow pipe 39 Sensor insertion hole 40 Sensor insertion hole 41 Opening 42 Opening

Continued on the front page (72) Inventor Toshiaki Kawanishi 1333-2, Hara-shi, Ageo-shi, Saitama Prefecture Mitsui Mining & Smelting Co., Ltd. (72) Inventor Kenji Tomonari 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. In-house F-term (reference) 2F035 EA04 EA05 EA08

Claims (4)

[Claims] 1. A substrate having a thin film lead formed thereon, a flow detector directly formed at one end of the substrate with a heating element and a temperature sensing element, and an output terminal, wherein the flow detector and the thin film lead are provided. A flow rate sensor, wherein a protective film is formed on the substrate so as to cover a part of the substrate, and a part of the substrate and a part of the output terminal are covered with a covering member formed by molding. 2. A semiconductor device comprising: a substrate on which a thin film lead is formed; a temperature detector on which a temperature sensing element is directly formed at one end of the substrate; and an output terminal, wherein the temperature detector and a part of the thin film lead are provided. A protective film is formed on the substrate so as to cover
A temperature sensor, wherein a part of the substrate and a part of the output terminal are covered with a covering member formed by molding. 3. The flow sensor according to claim 1, a casing having a sensor insertion hole for accommodating the flow sensor, and a fluid to be detected having an opening formed at a position corresponding to the sensor insertion hole. And a flow detecting device. 4. A casing having a flow sensor according to claim 1, a temperature sensor according to claim 2, a sensor insertion hole for accommodating the flow sensor and the temperature sensor, and a casing corresponding to the sensor insertion hole. And a flow pipe for flowing a fluid to be detected having an opening formed at a position where the flow rate is to be detected.