JP2000028411A - Flow sensor and flow detector - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A flow rate sensor capable of increasing response speed, improving measurement accuracy, eliminating corrosion and deformation, reducing size, and sufficiently reducing manufacturing costs. A flow detection device is provided. SOLUTION: A flow rate detecting section 2 having a heating element 9 and a temperature sensing element 13 formed directly on one end of a substrate 4, a temperature detecting section 3 having a temperature sensing element 15 formed directly on one end of the substrate 4, There is provided a flow sensor 1 having output terminals 5 and 6, wherein a part of the substrate 4 and a part of the output terminals 5 and 6 are covered with a covering member 7 formed by molding. The flow rate sensor 1 is accommodated in a sensor insertion hole 59 formed in the casing 52 to constitute the flow rate detection device 51.

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 and a flow rate detection device for measuring a 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. 11, the flow rate sensor 101 is formed by laminating a thin film heating element 103 and a thin film temperature sensing element 104 on a substrate 102 by 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 section 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.

Also, in the above-mentioned flow rate detecting device, since the installation position of the flow rate sensor and the temperature sensor is different and the temperature is measured at a position separated from the flow rate measurement position, the effect of temperature compensation is not sufficiently exhibited. However, there was a problem in terms of measurement accuracy. And since it has a flow sensor and a temperature sensor, it is necessary to drill two sensor insertion holes,
Since the assembling operation also requires much time, the flow rate detecting device cannot be reduced in size and the manufacturing cost cannot be sufficiently reduced.

The present invention solves such a problem, further improves the flow sensor 301 and the flow detection device developed by the present inventors, makes the response speed of the flow sensor faster, and increases the measurement accuracy. It is an object of the present invention to provide a flow rate sensor and a flow rate detection device that have high accuracy and that solve the problems of corrosion and deformation of the fin plate. It is another object of the present invention to provide a flow rate sensor and a flow rate detection device capable of reducing the size of the flow rate detection device and sufficiently reducing the manufacturing cost.

[0019]

In order to achieve the above object, a flow sensor according to the present invention comprises a substrate on which a thin film lead wire is formed, and a flow rate sensor having a heating element and a temperature sensing element formed directly on one end of the substrate. A detection unit, a temperature detection unit having a temperature sensing element formed directly on one end of the substrate, and an output terminal, covering the flow rate detection unit, the temperature detection unit, and a part of the thin film lead wire. In this manner, a water-resistant and insulating protective film is formed on the substrate, and a part of the substrate and a part of the output terminal are covered with a covering member formed by molding.

The flow rate detecting section and the temperature detecting section may be formed directly on both side surfaces of one end of the substrate. Further, the substrate may be one in which the substrate on which the flow rate detecting portion is formed and the substrate on which the temperature detecting portion is formed are bonded and integrated.

In order to further reduce the influence of heat generated by the heating element of the flow rate detecting section, it is preferable that the flow rate detecting section and the temperature detecting section are formed apart from each other.

[0022] The flow rate detecting section and the temperature detecting section may be formed directly on the same side surface of one end of the substrate.

Preferably, a slit is formed at one end of the substrate in order to prevent heat transfer between the flow rate detecting section and the temperature detecting section.

The flow rate detecting device according to the present invention includes a 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.

[0025]

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

FIG. 1 is a view showing an embodiment of a flow sensor according to the present invention. The flow sensor 1 comprises a flow detecting section 2, a temperature detecting section 3, a substrate 4, output terminals 5, 6, and a covering member 7. Consisting of

As shown in FIGS. 2 and 3, the flow rate detector 2 is provided directly on one side surface of the lower end of the substrate 4 with the insulating layer 8, the thin film heating element 9, the electrode layers 10, 11, the insulating layer 12, the thin film Thermosensor 1
3 are sequentially laminated and formed.

The heating element 9 is made of a cermet having a thickness of about 1 μm and patterned into a desired shape.
1 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 13 is formed of a metal resistive film having a large temperature coefficient such as platinum or nickel and a stable shape, such as platinum or nickel, having a thickness of about 0.5 to 1 μm and a manganese oxide NTC thermistor. The insulating layers 8 and 12 are made of Si having a thickness of about 1 μm.
Consists of O ₂ .

As shown in FIGS. 4 and 5, the temperature detecting section 3 is formed by sequentially laminating and forming an insulating layer 14 and a thin film thermosensitive element 15 directly on the other side of the lower end of the substrate 4. Tier 1
The shapes and materials of the temperature sensor 4 and the temperature sensing element 15 are the same as those in the flow rate detector 2.

The substrate 4 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.
The thin film lead wires 16 and 17 are formed from to the upper end.

Then, protective films 18 and 19 having a water resistance, a chemical resistance, and an insulating property such as SiO ₂ , Al ₂ O ₂ , SiN, glass, and synthetic resin having a film thickness of about 1 μm are formed on the lower half of the substrate 4.
Are formed, and the flow rate detecting part 2 and the thin film lead wire 1 are respectively formed.
6, the lower half of the temperature detecting section 3 and the thin film lead 17 are covered.

The upper end of the thin film lead 16 and the output terminal 5,
The upper end of the thin film lead 17 and the output terminal 6 are connected by bonding wires 20 and 21, and the upper half of the substrate 4 and the lower half of the output terminals 5 and 6 are covered with a covering member 7 by molding. It is.

The flow rate sensor 1 of the present invention comprises a flow rate detector 2
Further, since the temperature detecting section 3 is formed directly on both side surfaces of the lower end of the substrate 4, a bonding material such as a fin plate and a silver paste is not required, and the flow detecting section 2 is immediately passed from the fluid to be detected via the protective films 18 and 19. Since the heat is transmitted to the temperature detecting unit 3, the response speed becomes extremely high.

Further, the flow rate detecting section 2 and the temperature detecting section 3 are located in the fluid to be detected, heat does not flow out or inflow from the covering member 7 to the outside, and a bonding material such as silver paste is unnecessary. Since there is no variation between production lots, the measurement accuracy is extremely high.

Furthermore, since a fin plate is not required, it is not necessary to consider this corrosion and deformation.

Further, since the flow rate detecting section 2 and the temperature detecting section 3 are formed directly on both side surfaces of the lower end of the substrate 4, the flow rate measurement and the temperature measurement can be performed at substantially the same position, and the effect of temperature compensation can be obtained. Is sufficiently exhibited, and the measurement accuracy is further improved.

FIG. 6 is a view showing another embodiment of the flow sensor according to the present invention. The flow sensor 31 also includes a flow detector 2, a temperature detector 3, substrates 32 and 33, output terminals 5 and 6, and a cover. It is composed of the member 7. The difference between the flow sensor 31 and the flow sensor 1 is that the substrate 32 on which the flow detection unit 2 is formed
And the substrate 33 on which the temperature detecting section 3 is formed by bonding with an adhesive material 34 to be integrated.

In the flow sensors 1, 31, the substrates 4, 3
Materials with low thermal conductivity are used as 2,33,
In order to further reduce the influence of heat generated by the heat generating element 7 of the flow rate detection unit 2, it is preferable that the flow rate detection unit 2 and the temperature detection unit 3 are formed apart from each other as shown in FIGS.

FIG. 7 is a view showing another embodiment of the flow sensor according to the present invention. The flow sensor 41 also includes a flow detecting section 2, a temperature detecting section 3, a substrate 42, output terminals 43 and 44, and a covering member 7. Consisting of The flow sensor 41 differs from the flow sensor 1 in that the flow detection unit 2 and the temperature detection unit 3 are formed on the same side surface of the lower end of the substrate 42 and are integrated.

In the flow rate sensor 41, a slit 45 is formed at the lower end of the substrate 42 as shown in FIG. The transfer of heat to and from the detection unit 3 is prevented.
The slit 45 can be formed by grinding with a dicing saw, or by etching when the substrate 42 is made of silicon.

Then, thin film leads 46 and 47 are formed from the flow rate detecting section 2 and the temperature detecting section 3 to the upper end, and
A protective film 48 having water resistance, chemical resistance, and insulation properties is formed on the lower half of the lower layer 2 to cover the flow rate detector 2, the temperature detector 3, and the lower halves of the thin film leads 46 and 47.

The upper end of the thin film lead 46 and the output terminal 4
3. The upper end of the thin film lead wire 47 and the output terminal 44 are connected by bonding wires 49 and 50, and the upper half of the substrate 42 and the lower half of the output terminals 43 and 44 are covered by the covering member 7 by molding. Coated.

Next, the case where the flow rate sensor 1 is mounted on the flow rate detecting device of the present invention will be described. 8 and 9
As shown in FIG. 10, the flow detection device 51 includes a casing 52, a flow pipe 53, a flow sensor 1, a flow detection circuit board 54, and the like.

The casing 52 is made of a synthetic resin such as a vinyl chloride resin, polybutylene terephthalate (PBT), or polyphenylene sulfide (PPS). Both ends are connection portions 57 for connecting to an external pipe, and a flow pipe 53 is penetrated in the main body portion 55. A sensor insertion space 58 is defined in the upper part of the main body 55, and a sensor insertion hole 59 is formed from the sensor insertion space 58 toward the circulation pipe 53.

The flow pipe 53 is a circular pipe made of a metal such as copper, iron, and stainless steel, and has an opening 60 at a position corresponding to the sensor insertion hole 59.

The flow sensor 1 is inserted into the sensor insertion hole 59 from the sensor insertion space 58 of the casing 52,
The lower half of the substrate 4 is located in the flow tube 53 through the opening 60 of the flow tube 53, and the lower end of the substrate 4 reaches below the axis of the flow tube 53 when fitted. is there.
Note that there is no O between the flow sensor 1 and the sensor insertion hole 59.
The ring 61 is interposed to prevent the fluid from leaking from these gaps.

After the flow sensor 1 is inserted, the sensor pressing plate 62 is inserted into the sensor insertion space 58 to press the upper surface of the covering member 7 of the flow sensor 1, and the flow detection circuit board 54 is further mounted.

The flow rate detection circuit board 54 includes the flow rate sensor 1
(Not shown), and as a whole, constitutes a flow rate detection circuit as shown in FIG. The voltage supplied from the DC power supply 63 is applied to the heating element 9 and the bridge circuit 64 connected in parallel,
As an output of the differential amplifier 65 disposed in the bridge circuit 64, an output indicating a flow rate is obtained.
That is, in the flow rate detecting unit 2, the thermosensitive element 13 detects the amount of heat released to the fluid via the protective film 18 by subtracting the amount of heat from the heat generating element 9. The temperature sensing element 15 detects the amount of heat held by the fluid via the protective film 19, and the fluid temperature is compensated, so that the flow rate of the fluid is accurately detected.

Since the flow rate detecting device 51 of the present invention has the flow rate sensor 1 in which the flow rate detecting section 2 and the temperature detecting section 3 are integrated, it is not necessary to form two sensor insertion holes and it is necessary for the assembling work. The time can be shortened, and the flow rate detection device 51
Can be made more compact, and the manufacturing cost can be sufficiently reduced.

[0050]

As described above, according to the flow rate sensor of the present invention, since 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, the response speed is extremely high. Becomes

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.

Further, the flow rate sensor of the present invention can
Since there is no need to worry about deformation, the components are simply integrated by the covering member and inserted into the sensor insertion holes, the incorporation into the casing is extremely simple, the fixed state is stable, and the durability is high.

Further, since the flow rate detecting device of the present invention has a flow rate sensor in which the flow rate detecting section and the temperature detecting section are integrated, the time required for assembling work can be shortened, the flow rate detecting apparatus can be made smaller, and the manufacturing cost can be reduced. Can also be reduced sufficiently.

[Brief description of the drawings]

FIG. 1A is a front sectional view and FIG. 1B is a side sectional view of one embodiment of a flow sensor according to the present invention.

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

FIG. 5 is a longitudinal sectional view of a temperature detecting section of the flow sensor according to the present invention.

6A is a front sectional view and FIG. 6B is a side sectional view of another embodiment of the flow sensor according to the present invention.

7A is a front sectional view and FIG. 7B is a side sectional view of another embodiment of the flow sensor of the present invention.

FIG. 8 is a front sectional view of the flow rate detecting device of the present invention.

FIG. 9 is a side sectional view of the flow rate detection device of the present invention.

FIG. 10 is a flow detection circuit diagram of the flow detection device of the present invention.

FIG. 11A is a perspective view and FIG. 11B is a cross-sectional view of a flow detection unit of a conventional flow sensor.

FIG. 12 is a cross-sectional view showing a state where a conventional flow sensor is installed in a pipe.

FIG. 13 is a schematic explanatory view of a flow sensor developed by the present inventors and having a flow detecting unit mounted on a fin plate and a flow detecting device provided with the flow sensor.

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

FIG. 15 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]

 1, 31, 41 Flow rate sensor 2 Flow rate detector 3 Temperature detector 4, 32, 33, 42 Substrate 5, 6, 43, 44 Output terminal 7 Coating member 9 Heating body 13, 15 Thermosensitive body 16, 17, 46, 47 Thin film lead wire 18, 19, 48 Protective film 34 Adhesive material 45 Slit 51 Flow rate detecting device 52 Casing 53 Flow pipe 59 Sensor insertion hole 60 Opening

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Kawanishi 1333-2, Hara-shi, Ageo-shi, Saitama Prefecture Mitsui Kinzoku Mining Co., Ltd. (72) Inventor Kiyoshi Yamagishi 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Kinzoku Mining Co., Ltd. F-term in the Research Institute (reference) 2F035 EA05 EA08

Claims (7)

[Claims] 1. A substrate on which a thin-film lead wire is formed, a flow rate detecting unit on which a heating element and a temperature sensing element are formed directly on one end of the substrate, and a temperature sensing element is formed directly on one end of the substrate. A temperature detection unit, having an output terminal, forming a protective film having water resistance and insulation on the substrate so as to cover the flow rate detection unit, the temperature detection unit and a part of the thin film lead wire. A flow sensor, wherein a part of the substrate and a part of the output terminal are covered with a covering member formed by molding. 2. The flow rate sensor according to claim 1, wherein the flow rate detection section and the temperature detection section are formed directly on both side surfaces of one end of the substrate. 3. The substrate according to claim 1, wherein the substrate on which the flow rate detection unit is formed and the substrate on which the temperature detection unit is formed are bonded and integrated. Flow sensor. 4. The flow sensor according to claim 1, wherein the flow detection unit and the temperature detection unit are formed apart from each other. 5. The flow sensor according to claim 1, wherein the flow detection unit and the temperature detection unit are formed directly on the same side surface of one end of the substrate. 6. A slit is formed at one end of the substrate,
6. The flow sensor according to claim 5, wherein heat transfer between the flow detection unit and the temperature detection unit is prevented. 7. A flow rate sensor according to claim 1, 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 flow pipe through which the fluid flows.