JPH08146026A - Thermistor flow velocity sensor and flow rate sensor for liquid - Google Patents

Abstract

PURPOSE: To provide a flow rate sensor for fluids which is superior in thermal responsivity, compact and highly accurate, by installing a heat-generating body and a thermistor and forming the body and thermistor into a plane shape. CONSTITUTION: The thermistor flow velocity sensor 72 is arranged in a flow passage of a piping 70 or the like in a manner not to disturb the flow of a fluid. The sensor 72 has a sensor part 73 at a face on the inner wall of a container where the flow of the fluid is detected. The sensor part 73 is connected to a connection terminal 74 set at an outer face of the container via a lead wire 75. The sensor part 73 has a heat-generating body 11 on one face of a flat substrate 10 of alumina or the like, electrodes 12, 17 at both ends, an insulating body 13 formed to cover the upper surface of the heat-generating body 11 and a thermistor 14 on the upper surface of the insulating body 13. The thermistor 14 is equipped with upper and lower electrodes 16, 15 and is of a size not to come outside the heat-generating body 11. Since the sensor part 73 is formed into a plane, the sensor 72 itself is made compact and superior in thermal responsivity, achieving highly accurate measurements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor flow velocity sensor and a liquid flow sensor for measuring and measuring the flow rate and fluid velocity of a fluid such as gas or liquid.

[0002]

2. Description of the Related Art Conventionally, sensors used to measure the flow rate of liquids are mainly electromagnetic flowmeters, ultrasonic flowmeters, vortex flowmeters and Coriolis mass flowmeters. Etc. Each of them can be used according to its purpose and accuracy, but it has the drawback that the price is generally high.
On the other hand, there is a thermal type flow meter as a method for measuring the flow velocity and flow rate of a fluid. This thermal type flow meter is provided with a heating unit heated to a constant temperature higher than the fluid temperature, and a temperature detecting unit in which the current value flowing according to the temperature changes, and by being cooled by the fluid flowing around the heating unit, Detects that the current flowing through the temperature detector changes. The higher the flow velocity of the fluid, the greater the degree of cooling. Therefore, the flow velocity of the fluid can be known by detecting the current flowing through the temperature detection unit.

As shown in FIG. 13, the thermal type flow meter has a pipe 80.
Compensation thermometer 81 for measuring the fluid temperature in the flow path such as
A flow velocity sensor 82 including a heating unit and a temperature detection unit is arranged, and a signal from the compensating thermometer 81 and a signal from the flow velocity sensor 82 are guided to the measurement circuit 83 and converted into a flow velocity.

Conventionally, a thermistor has been used in the temperature detecting section, and there are a self-heating type and an indirectly heating type in the flow velocity sensor using the thermistor. In the self-heating type, the temperature detecting section also serves as the heating section. In the indirectly heated type, the temperature detecting part and the heating part are separately provided.

In the self-heating type thermistor flow velocity sensor,
Since the thermistor having a negative characteristic is used in a self-heating region, an overcurrent is caused to flow in the thermistor, which causes deterioration, which significantly changes with time and cannot be used for a long time.

On the other hand, the indirectly heated thermistor flow velocity sensor is
For example, the one shown in FIG. 14 is known. In this flow velocity sensor, the thermistor 87 having a positive characteristic is surrounded by a heater 86 as a heating element, and they are put in a container 85 such as glass, and nitrogen gas or the like is enclosed in the container 85, and the thermistor 87 and the heating element 86 are sealed. The lead wire is taken out of the container.

Since this indirectly heated thermistor flow velocity sensor uses a region having a positive characteristic of the thermistor, the current flowing through the thermistor may be small (up to several hundreds μA at maximum), so that it hardly deteriorates, and it does not occur for a long time. It can be used, but due to its structure, the flow velocity sensor becomes large, it cannot be attached to thin pipes, it disturbs the flow of fluid, and accurate flow velocity cannot be measured. Also, because of the large size, the heat capacity increases,
Responsiveness is significantly slowed down, it is not possible to properly measure the flow velocity of the fluid that changes from moment to moment.Furthermore, it is used when the fluid has a small heat capacity such as a gas body or the difference between the fluid temperature and the heating element temperature is small. Can not. Moreover, the thermistor and the heating element are put in a container such as glass and a special facility for enclosing nitrogen gas is required, which significantly increases the manufacturing cost. Incidentally, it took 10 seconds or more for the thermal response of the indirectly heated thermistor flow velocity sensor shown in FIG. 14 to stabilize in temperature.

On the other hand, among the thermal type flow meters, a flow rate sensor as shown in FIG. 17 is used because it is relatively inexpensive and measures the flow rate of gas. This sensor is a resistance thermometer 101 arranged in a fluid flowing in the direction of the arrow in the figure.
And 102, heat is applied to the fluid by the hot wire 103, and the flow rate of the fluid is measured by obtaining the temperature difference measured by the resistance thermometers 101 and 102. However, according to this, it is necessary that the specific heat of the fluid to be measured is sufficiently small, and it is not suitable for measuring the flow rate of liquid, especially water.

Therefore, the object of the present invention is to provide excellent thermal response,
An object of the present invention is to provide a small thermistor flow velocity sensor with high measurement accuracy, which is small in size and inexpensive. Another object of the present invention is to provide a liquid flow sensor suitable for measuring the flow rate of a liquid having a large specific heat, especially water.

[0010]

In order to achieve the above object, the present invention provides a thermistor flow velocity sensor comprising a heating element and a thermistor for detecting the temperature of the heating element, the heating element and the thermistor. And are made to be planar.

The heating element is made of a nichrome alloy or a cermet material, and the thermistor is made of a spinel type transition metal oxide or an NTC material such as silicon carbide or silicon.

Further, the heating element and the thermistor are formed by a film forming method such as sputtering or CVD.

Furthermore, the heating element and the thermistor are characterized in that a paste containing the respective components is formed by a thick film process such as printing.

Furthermore, this heating element and the thermistor 1
It is characterized by being arranged on one substrate.

In addition, the heating element and the thermistor are arranged on one surface of one substrate.

Further, a heating element is arranged on one surface of the substrate, and the thermistor is laminated on the heating element via an insulating layer.

In addition, the thermistor flow velocity sensor is formed by laminating the thermistor on one surface of the heating element with an insulating layer interposed therebetween.

The electrode connected to the heating element and the thermistor is formed by a film forming method or a thick film process.

Further, the heating element and the thermistor are enclosed in a container which is hermetically sealed, and a connecting terminal for wiring is provided on the outer surface of the container.

Further, it is characterized in that connection terminals respectively connected to the heating element and the thermistor are connected by an FPC.

Furthermore, the substrate or the heating element is fixed to the inner wall surface of the container (cap).

Further, it is characterized in that the substrate or the heating element is fixed to the inner wall surface of the container (cap) via the solder layer.

On the other hand, for the purpose of providing a liquid flow rate sensor particularly suitable for measuring the flow rate of water or the like having a large specific heat, the present invention provides a heating element and a temperature measuring device arranged in the vicinity of the heating element. In an indirectly heated flow sensor for liquids, which includes an element and a cover that covers the elements, a substrate having high thermal conductivity and electrical insulation is provided, and the heating element and the temperature measuring element are formed on this substrate. The cover is adhered to the surface of the substrate opposite to the side where the covers are formed, and is in contact with the liquid whose flow rate is to be measured outside the adhered portion.

Here, the cover is made of a metal having a high thermal conductivity and a high corrosion resistance against a liquid whose flow rate is measured, and the shape and size of the cover are the same as those of the heating element. Is preferably approximately equal to. Further, it is preferable to have a heat insulating material covering the side opposite to the side in contact with the liquid.

According to this, since the temperature in the vicinity of the heating element when the heat is effectively taken away by the liquid through the substrate and the cover is measured by the temperature measuring element, the fluid is heated by the heater and the temperature is controlled. Compared with the thermal type flow meter as shown in FIG. 17, which measures, the flow rate of a liquid having a large specific heat, such as water, can be measured accurately with good response, and the liquid and the sensor are separated by the cover. The stability against corrosion is also improved.

[0026]

【Example】

[Embodiment 1] Flow velocity measurement using the thermistor flow velocity sensor according to the present invention will be described with reference to FIG. As shown in FIG. 1, a compensating thermometer 76 and a thermistor flow velocity sensor 72 are arranged in a flow path such as a pipe 70. At this time, the arrangement positions of the compensating thermometer 76 and the flow velocity sensor 72 are determined so that the flow of the fluid 71 in contact with the thermistor flow velocity sensor 72 is not disturbed.

In the thermistor flow velocity sensor 72, a sensor portion 73 is arranged on the surface of the inner wall surface of the container for detecting the flow of fluid, a connecting terminal 74 is provided on the outer surface of the container, and they are connected by a lead wire 75. Further, the compensating thermometer 76 is provided with a temperature detector 77, and takes out a signal from its output line 78,
Measure the temperature.

The container of the thermistor flow velocity sensor 72 has a hermetically sealed structure so that the fluid flowing outside the container does not enter the container.

The sensor section 73 will be described with reference to FIG. In the figure, 10 is a flat plate-shaped substrate such as alumina or SiO ₂ , 11 is a heating element, and electrodes 12 and 1 are provided at both ends.
7 and is formed on one surface of the substrate 10.

Numeral 13 is an insulator, which is formed on the heating element 11 so as to cover the entire surface. Reference numeral 14 denotes a thermistor, which is formed on the upper surface of the insulator 13. The thermistor 14 includes electrodes 15 and 16 on the upper and lower sides, and the heating element 1
It is formed in a size that does not protrude beyond 1.

Next, the heating element 11 is made of nichrome, (Ni-
Cr) alloy or cermet material (Ta-SiO ₂ , Cr
It is formed by a film forming method such as sputtering or CVD using a material such as —SiO ₂ ). Insulator 13 is heating element 1
A material having heat resistance equal to or higher than the exothermic temperature of 1 and excellent in thermal conductivity is preferable, but an adhesive material such as epoxy resin, furan resin, or polyimide resin, or an insulating material such as SiO ₂ may be used. The thermistor 14 selects a material having a small heat capacity and a heat resistance characteristic, in particular, a resistance value that changes around the temperature corresponding to the temperature change of the heating element 11. For example, a spinel type transition metal oxide, SiC (silicon carbide), Si, or the like is used. It is formed by a film forming method such as sputtering or CVD using an NTC material. The electrodes 12, 15, 16, 17 are made of Ni, C
A material such as r / Pd or Cr / Ag is used and is formed by lift-off or etching.

According to the above materials and manufacturing method, for example, the substrate 10 has a thickness of 0.5 mm and the heating element has a thickness of 0.3 μm.
The insulator is 0.3 μm thick and the thermistor is 0.6
The thickness is about μm. The size of this board is 5 x 5
mm size is sufficient.

In the above description, the thin film method such as sputtering, CVD, lift-off and etching is used, but it may be formed by a thick film process such as printing using a paste having each component.

When this thick film process is used, the thickness of each of the heating element 11, the insulator 13, the thermistor 14, and the electrode is about 0.5 to 100 μm.

[Second Embodiment] A second embodiment will be described with reference to FIG. 3, in which the sensor section is another embodiment. In the figure, the thermistor flow velocity sensor 61 is viewed from above. In the figure, 62 is a substrate made of alumina or the like which is an insulator, 63 is a heating element, 64 is a thermistor, 65 is one electrode of the heating element, 66 is one electrode of the thermistor, 6
Reference numeral 7 is the other common electrode of the heating element and the thermistor.

The heating element 63 is formed in a U shape on one surface of the substrate 62, and the thermistor 64 is formed inside the U shape of the heating element 63 with a space from the heating element 63. The electrode 65 is formed on one end of the heating element 63 in a U-shape, the electrode 66 is formed on one end of the thermistor 64, and the common electrode 67 is formed on the other end of the U-shape of the heating element. It is formed so as to be connected to the other end of the thermistor 64.

The heating element 63, the thermistor 64, the electrode 6
The manufacturing methods and materials of 5 to 67 are the same as the manufacturing methods and materials of the first embodiment.

[Third Embodiment] A second embodiment will be described with reference to FIG. 4, in which the sensor section is another embodiment. In FIG. 4, 1 is a heating element, 2 and 9 are electrodes of the heating element 1, 3
Is an insulator, 4 is a thermistor, and 7 and 8 are electrodes connected to the thermistor.

The heating element 1 is, for example, a quadrangular plate,
It is a carbon solid resistor or a resistor formed by mixing ceramic and carbon or metals and solidifying. Thickness is 0.1
The size is, for example, 2 × 4 (m
m). The thermistor 4 is formed on one surface of the heating element 1 with the insulator 3 interposed therebetween. The size of the thermistor 4 is smaller than the size of the heating element 1 and does not contact the electrodes 2 and 9 of the heating element 1. It is preferable that the insulator 3 has heat resistance equal to or higher than the heat generation temperature of the heating element 1 and has excellent thermal conductivity, and is, for example, an insulating layer of epoxy resin, furan resin, polyimide resin, or the like. The thermistor 4 is formed by the material and manufacturing method described in the first embodiment. The electrodes 2 and 9 are provided at both ends of the heating element 1, and the electrodes 7 and 8 are provided at both ends of the thermistor 4. The material and manufacturing method of the electrodes 2, 9, 7, and 8 are
This is the same as that shown in the first embodiment.

The thermistor flow velocity sensor described in Embodiments 1 to 3 can measure the flow velocity by the measuring circuit shown in FIG. In the figure, a thermistor flow velocity sensor 21 including a heating element 19 and a thermistor 20 and a compensating thermometer 22 are provided in contact with a fluid, and a connector 24 for leading out those electrodes, a power supply 25 of, for example, about 5V, a thermistor for detection. It is composed of a voltage dividing resistor 26 with respect to 20, a voltage dividing resistor 27 with respect to the compensating thermometer 22, and terminals 28 and 29 for outputting the terminal voltage of the thermistor and the compensating thermometer.

The measuring circuit of the thermistor flow velocity sensor detects the temperature of the fluid by the compensating thermometer 22. In this case, the temperature of the fluid itself can be measured simply by checking the voltage at the terminal 28. If the temperature of the fluid rises, the temperature of the compensating thermistor rises, and if the temperature of the thermistor rises, the resistance value of the NTC type is lowered and the terminal 28
Voltage drops. If the voltage and the actual temperature are calibrated in advance, the temperature of the fluid can be easily known.

In the thermistor flow velocity sensor 21, a DC power supply 25 is connected between the common electrode terminal 24 ₁ of the connector 24 and the heating element electrode 24 ₂ to heat the heating element 19 so that the thermistor 20 as a whole is more fluid than the fluid. Exothermic at high temperature. The heating amount of the heating element can be easily changed through the resistance from the power source. Here, the heat of the heating element 19 or the alumina substrates 10 and 62 is taken according to the flow velocity of the fluid, the temperature of the heating element 19 and the like is lowered, and if the thermistor is an NTC type, the resistance value of the thermistor increases. The voltage of the voltage dividing terminal 29 will increase. At this time, when the flow of the fluid is fast, the heat of the heating element or the alumina substrate having a temperature higher than that of the fluid is absorbed according to the speed, so that the temperature is lowered and the temperature is lowered.

As described above, in the measuring circuit using the thermistor flow velocity sensor, as described below in particular,
Since the sensitivity can be adjusted, the thermal response is good, and there are few variations in manufacturing, it is easy to use in control circuits using computers in recent years. In this case, the temperature control of the thermistor is performed by converting an analog signal into a digital signal and introducing it into a computer.

Next, FIG. 6 shows the relationship between the flow velocity sensor and the flow velocity. This graph shows the case where the compensating thermometer and the flow velocity sensor are inserted into the pipe that flows water, using water as the fluid, and the horizontal axis shows the amount of water in the water and the vertical axis shows the water temperature and the flow velocity sensor that are the detection temperatures of the compensating thermometer. FIG. 5 is a diagram showing a difference in indicated temperature of the thermistor. When the water temperature is 5 ° C and 60 ° C, the temperature of the compensating thermometer 22 indicates 5 ° C and 60 ° C, respectively, and the temperature of the thermistor is 60 ° C when there is no fluid flow.
Set higher than. From the results of this graph, it can be seen that when there is almost no water speed, there is a considerable temperature difference between the high temperature flow sensor and the temperature of the fluid, but there is almost no temperature difference when the water flow becomes faster. In this way, it is demonstrated that the present thermistor flow velocity sensor functions as a flow velocity sensor with excellent sensitivity.

By utilizing this result and adjusting the heat generation amount of the heating element, it can be used in a region where the temperature difference with respect to the flow rate is large, and the flow rate sensitivity can be adjusted. From this, it can be said that it can be used in a region where performance is highly sensitive to temperature changes.

The response characteristics of this embodiment will be described with reference to FIGS. 7 and 8. FIG. 7 shows that the temperature measured by the thermistor with respect to the electric power supplied to the heating element is 63% of the saturation temperature by using three types of thermistor flow velocity sensors.
It is a comparison graph which showed the relationship of the time used as (1 / e). Here, the □ mark indicates the thermistor flow velocity sensor according to the first embodiment in the stacked film formation, the ○ mark indicates the thermistor flow velocity sensor using the plate-shaped heating element and the plate-like thermistor according to the third embodiment, and the ● mark indicates the second embodiment. A thermistor flow velocity sensor in which a heating element and a thermistor are arranged parallel to each other on a single alumina substrate. Each of these three types has merits and demerits depending on the usage mode and manufacturing mode, but the heat response characteristics are shown in Example 1
It can be seen that Mark's thermistor flow velocity sensor responds instantly to changes in the temperature of the heating element. In addition, in FIG.
In the case shown in (1), it took 10 seconds or more as the heat response characteristic.

Further, FIG. 8 is a comparative diagram showing the relationship between the electric power supplied to the heating element and the temperature difference with the fluid (water in the figure) detected by the thermistor, similarly using three types of thermistor flow velocity sensors. Each mark is the same as in FIG. From this result, it can be seen that the larger the inclination according to the electric power applied to the heating element, the better the thermal sensitivity. Therefore, the laminated film formation in which the heating element, the insulator, and the thermistor have a three-layer structure has a small heat capacity and the fluid, It can be demonstrated that it is effective as a means for measuring the flow velocity and flow rate of gas.

As another embodiment, the invention shown in FIG. 9 will be described. In FIG. 9A, reference numeral 32 is a substrate made of alumina, ceramics or the like, and a solder layer 31 is added to one surface thereof. The heating element 3 is provided on the other surface of the substrate 32.
3, the insulator 34, and the thermistor 35 are formed in a laminated form to form a laminated type thermistor flow velocity sensor. 36,
Reference numerals 37, 39 and 40 denote terminals taken out from the respective electrodes.

FIG. 9B shows a diagram in which the sensor portion of the laminated thermistor is mounted. Solder is attached to the inner wall of the inside of the container 30, and the solder layer 31 of the laminated thermistor is bonded with the solder. In this case, since the fluid flows on the back surface of the surface of the container to which the solder is attached, the temperature drop of the container 30 due to the flow velocity of the fluid immediately leads to the temperature drop of the heating element 33 via the solder layer 31 having a high thermal conductivity. The thermistor 35 can detect this falling temperature and can perceive an increase in the resistance value as an electric signal.

Furthermore, FIG. 10 will be described as another embodiment. In FIG. 10 (A), a sensor 42 is the thermistor flow velocity sensor shown in Embodiments 1 and 3, and is fixed to the inner wall of the container 41 with an adhesive or the solder layer, and the container 41 has a velocity of gas or liquid. Cause mechanical vibration, and also to prevent disconnection and non-contact of the connection line between the sensor and the terminal due to deterioration of the electrode part due to vibration during handling during installation, shock, etc. An FPC (flexible printed circuit) 43 is used to connect to the terminals 44 to 46. Further, as shown in FIG. 10B, the FPC 43 and the sensor unit 42
May be connected using the anisotropic conductive film 49, and the sensor unit 42 fixed to the container 41 and the FPC 43 may be adhered to each other to prevent connection failure.

In addition to this, as another embodiment, FIG.
Will be described. This embodiment is an application example of the thermistor flow velocity sensor according to the first and third embodiments. In FIG. 11A, a temperature measuring thermistor 50 for measuring the temperature of the fluid itself, a substrate 51 such as alumina, and a heating element as a heating element. 52 and a thermistor 53 which faces the heat generating element 52 via an insulating layer and measures the temperature of the heat generating element. FIG. 11 (B)
Is a diagram showing the state of the container and the outlet. By sealing the inside of the container and applying a vacuum or filling it with a heat insulating resin, the life of the sensor unit is lengthened and the temperature of the heating element is adjusted. It is arranged so that it can be detected promptly and accurately. By including the temperature measuring thermistor in one container, the size of the indirectly heated thermistor can be reduced.

Still another embodiment will be described with reference to FIG. This embodiment is also an application example of the thermistor flow velocity sensor of Embodiments 1 and 3, and the substrate 56 in FIG.
Temperature measuring thermistor 55, heating element 57 and thermistor 5
And 8 are arranged. On the same substrate, the temperature measuring thermistor 55 of the reference compensating thermometer measures the temperature of the fluid, and the heating element 57 facing the substrate generates heat, and the heat generation temperature is detected by the thermistor film. FIG. 12B is a diagram in which this flow velocity sensor is mounted. Also in this case, the entire flow meter can be downsized.

FIG. 19 is a sectional view of a liquid flow sensor according to the present invention, which is particularly preferable for measuring the flow rate of a liquid having a large specific heat such as water. This sensor includes a heating element 111 and a thermistor film 11 for temperature measurement arranged on the heating element 111.
2 and an indirectly heated type flow sensor for liquids having a cover 105 covering them, a substrate 109 having high thermal conductivity and high electric insulation, and a heating element 111 and a thermistor film 112 formed on the substrate 109. Was done,
The cover 105 is the substrate 1 on the side opposite to the side where these are formed.
It is adhered to the 09 surface and is in contact with the liquid whose flow rate is to be measured outside the adhered portion. The heating element 111 and the thermistor film 112 have an electrode 110 connected to the outside.

The cover 105 is a cap having an inner diameter of 13.3 mmφ, has a good thermal conductivity, and has a good corrosion resistance to a liquid whose flow rate is measured, for example, stainless SUS3.
The cover 105 has a shape and size substantially equal to the shape and size of the heating element 111. Further, although not shown in the drawing, the cover 10
In FIG. 5, the heating element 111, the thermistor film 112, and the upper surface of the substrate 109 are covered with a heat insulating substance, for example, a filling material such as urethane foam, polyethylene, or silicon resin. The substrate 109 is similar to the type of FIG. 2, but has a thermal conductivity of 156 W / Km and a size of 5 × 3 m.
It is made of silicon and has a thickness of 0.53 mm and has an oxide film with a thickness of 1 μm on both sides. The size of the heating element 111 is 3.5 × 1.8 mm.

A sensor of this embodiment having this structure and a sensor for comparison having only the structure of the substrate different from that of this embodiment were manufactured by using the sputtering and lift-off methods and subjected to a comparison test. The results shown in are obtained. However, the substrate of the comparative sensor is made of borosilicate glass having a thermal conductivity of 1.1 W / Km and a thickness of 0.5 mm, and as shown in FIG. The power is supplied to 111, the resistance of the thermistor film 112 is measured by the thermistor resistance measuring unit 107, and the result is processed by the CPU 108 to obtain the result.

As can be seen from FIG. 15, in the case of the comparative sensor using the glass substrate (in the figure, the measured value is indicated by "●"), the sensor of this embodiment (the measured value in the figure is "■"
It is understood that the temperature difference from the water temperature with respect to the change in the flow rate is significantly smaller than that of the above), and the sensitivity with respect to the change in the flow rate is extremely poor. Therefore, it is understood that the glass substrate is not suitable as the substrate, and the silicon substrate having good thermal conductivity is preferable. In addition, in the above-mentioned comparative sensor, when the measurement is performed by directly inserting into the running water without the cap, the result shown by “◯” in FIG. 15 is obtained, which is different from the case of the comparative sensor in that the cap is attached. It can be seen that this significantly affects the measurement sensitivity. It should be noted that if the sensor is placed in water without a cover, moisture will enter from the wiring portion of the sensor within a few hours and the sensor will be damaged, so the cover is necessary.

When the cap has an inner diameter of 7.7 mm and a heat insulating filler, the inner diameter of the cap is 13.3.
The same measurement was carried out for each of the case where the heat insulating filler was used in mmφ and the case where the inner diameter of the cap was 7.7 mmφ and the heat insulating filler was not used.
The results shown in 6 are obtained. As a result, it can be seen that the cover should be as close as possible to the size of the sensor and that it should be covered with the filler having poor thermal conductivity.

[0058]

As described above in detail, according to the present invention, since the flow velocity sensor has a planar shape or a film shape,
The thermistor flow velocity sensor itself is small and has thermal response
The heat followability and heat sensitivity are excellent, and the measurement accuracy is high and the cost is low.

Further, the thermistor may be applied with a maximum current of about several hundred μA, and it can be used for a long time without deterioration.

Further, according to the present invention, the flow velocity sensor has good thermal sensitivity and thermal responsiveness, and is suitable for flow rate measurement of a fluid having a small heat capacity such as gas.

Further, according to the present invention, since the heating element and the thermistor are planar, the thickness is reduced.

Further, the heating element and the thermistor are sealed in a container, and a connecting terminal for wiring is provided on the outer surface of the container. Since the heating element and the thermistor are connected to the connecting terminal by FPC or the like, Excellent vibration resistance and shock resistance.

Further, a substrate having high thermal conductivity and electrical insulation is provided, the heating element and the temperature measuring element are formed on this substrate, and the cover is bonded to the substrate surface opposite to the side where these are formed. Since the bonded portion is in contact with the liquid whose flow rate is to be measured, the flow rate of a liquid having a large specific heat such as water can be accurately measured with good responsiveness, and the liquid and the sensor body are covered by the cover. The isolation also improves stability against corrosion.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a flow meter using a flow velocity sensor according to an embodiment of the present invention.

FIG. 2 is an external view and a configuration diagram showing a sensor unit of a flow velocity sensor according to an embodiment of the present invention.

FIG. 3 is a structural diagram of a sensor unit of a flow velocity sensor according to an exemplary embodiment of the present invention.

FIG. 4 is a structural diagram of a sensor unit of a flow velocity sensor according to an exemplary embodiment of the present invention.

FIG. 5 is a circuit diagram showing an application of one embodiment of the present invention.

FIG. 6 is a graph showing characteristics according to an embodiment of the present invention.

FIG. 7 is a graph showing characteristics according to an embodiment of the present invention.

FIG. 8 is a graph showing characteristics according to an embodiment of the present invention.

FIG. 9 is a structural diagram of a flow velocity sensor according to another embodiment of the present invention.

FIG. 10 is a structural diagram of a flow velocity sensor according to another embodiment of the present invention.

FIG. 11 is a structural diagram of a flow meter according to another embodiment of the present invention.

FIG. 12 is a structural diagram of a flow meter according to another embodiment of the present invention.

FIG. 13 is a structural diagram of a flow meter using a conventional flow velocity sensor.

FIG. 14 is an external view of a conventional flow velocity sensor.

FIG. 15 is a graph showing the results of a comparison test performed on the sensor of FIG.

16 is a graph showing the results of another comparison test performed on the sensor of FIG.

FIG. 17 is a block diagram showing a conventional thermal type flow meter.

18 is a diagram showing how the temperature difference from the water temperature is measured using the sensor of FIG.

FIG. 19 is a cross-sectional view of a liquid flow sensor according to a preferred embodiment of the present invention for measuring the flow rate of a liquid having a large specific heat such as water.

[Explanation of symbols]

1, 11, 63, 111: heating element, 2: electrode, 3: insulator, 4, 14, 64: thermistor, 5: electrode, 10, 1
09: substrate, 13: insulator, 105: cover, 107:
Thermistor resistance measuring unit, 108: CPU, 110: electrode, 112: thermistor film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoyo Kobayashi 1-17-17 Numakage, Urawa-shi, Saitama Mitsui Mining & Smelting Co., Ltd. -2 Mitsui Mining & Smelting Co., Ltd. in the Research Center of the Formula Company (72) Inventor Motohiro Yabuzaki 1333-2 Hara, Ageo-shi, Saitama Prefecture -In the Research & Research Center of the Mitsui Mining Co., Ltd. (72) Inoue Shinichi 1333-2 Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd.

Claims (16)

[Claims] A thermistor flow velocity sensor comprising a heating element and a thermistor for detecting the temperature of the heating element, wherein the heating element and the thermistor are planar. 2. The thermistor flow velocity sensor according to claim 1, wherein the heating element is made of a nichrome alloy or a cermet material, and the thermistor is made of a spinel type transition metal oxide or an NTC material such as silicon carbide or silicon. sensor. The thermistor flow velocity sensor according to claim 1 or 2, wherein the heating element and the thermistor are formed by a film forming method such as sputtering or CVD. The thermistor flow sensor according to claim 1 or 2, wherein the heating element and the thermistor are formed by a thick film process such as printing a paste containing respective components. 5. The thermistor flow velocity sensor according to claim 1, wherein the heating element and the thermistor are arranged on one substrate. 6. The thermistor flow velocity sensor according to claim 5, wherein the heating element and the thermistor are arranged on one surface of one substrate. 7. The thermistor flow velocity sensor according to claim 5, wherein the heating element is disposed on one surface of the substrate,
A thermistor flow velocity sensor, wherein the thermistor is laminated on the heating element via an insulating layer. 8. The thermistor flow velocity sensor according to claim 1, wherein the thermistor is laminated on one surface of the heating element with an insulating layer interposed therebetween. 9. The thermistor flow velocity sensor according to claim 3, wherein an electrode connected to the heating element and the thermistor is formed by the film forming method or the thick film process. 10. The thermistor flow velocity sensor according to claim 1, wherein the heating element and the thermistor are sealed in a container, and a connection terminal for wiring is provided on an outer surface of the container. Is a thermistor flow velocity sensor. 11. The thermistor flow velocity sensor according to claim 10, wherein the heating element and the thermistor are connected to the connection terminal by an FPC. 12. The thermistor flow velocity sensor according to claim 10, wherein the substrate or the heating element is fixed to an inner wall surface of the container. 13. The thermistor flow velocity sensor according to claim 12, wherein the substrate or the heating element is fixed to the inner wall surface of the container via a solder layer. 14. A heating element, a temperature measuring element arranged in the vicinity of the heating element, and an indirectly heated flow sensor for liquid, which includes a cover for covering the heating element, and a substrate having high thermal conductivity and electrical insulation. However, the heating element and the temperature measuring element are formed on this substrate, and the cover is adhered to the surface of the substrate opposite to the side on which these are formed, and the flow rate is measured outside this adhered part. A flow sensor for liquid, which is in contact with a liquid. 15. The cover is made of a metal having good thermal conductivity and good corrosion resistance to a liquid whose flow rate is measured, and the shape and size of the cover are the same as those of the heating element. 15. The liquid flow sensor according to claim 14, wherein the flow sensors are substantially equal to each other. 16. The liquid flow sensor according to claim 14, further comprising a heat insulating material covering a side opposite to the side in contact with the liquid.