JP4201861B2 - Flow sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention belongs to a fluid flow rate detection technique, and particularly relates to a flow rate sensor for detecting a flow rate of a fluid flowing in a pipe. The flow sensor of the present invention is particularly suitable for accurately measuring a fluid flow rate under a wide range of environmental temperature conditions.
[0002]
[Prior art and problems to be solved by the invention]
Conventionally, various types of flow sensors (or flow velocity sensors) for measuring the flow rate (or flow velocity) of various fluids, particularly liquids, have been used. A flow sensor of the formula (especially side heat type) is used.
[0003]
As this indirectly heated flow sensor, a thin film heating element and a thin film temperature sensing element are laminated on a substrate through an insulating layer using thin film technology, and the substrate is attached to a pipe. By energizing the heating element, the temperature sensing element is heated, and the electrical characteristics of the temperature sensing element, for example, the value of electric resistance are changed. This change in electrical resistance value (based on the temperature rise of the temperature sensing element) changes according to the flow rate (flow velocity) of the fluid flowing in the pipe. This is because a part of the calorific value of the heating element is transmitted to the fluid through the substrate, and the amount of heat diffused into the fluid changes in accordance with the flow rate (flow velocity) of the fluid, and the temperature is accordingly sensed. This is because the amount of heat supplied to the body changes and the electric resistance value of the temperature sensing body changes. The change in the electric resistance value of the temperature sensing element also varies depending on the temperature of the fluid. Therefore, a temperature sensing element for temperature compensation should be incorporated in the electric circuit for measuring the change in the electric resistance value of the temperature sensing element. The change of the flow rate measurement value due to the temperature of the fluid is also minimized.
[0004]
Such an indirectly heated flow sensor using a thin film element is described in, for example, JP-A-8-146026.
[0005]
By the way, the conventional flow rate sensor has a metal pipe line attached to a pipe portion, and fluid passes through the metal pipe line. And this metal pipe line is exposed to the open air. Metal pipes have high thermal conductivity, so if the outside air temperature changes, the effect is immediately transmitted to the fluid in the pipe (especially the part in contact with the pipe wall) and the flow measurement accuracy of the thermal flow sensor is reduced. May bring about. In particular, when the flow rate is very small, the influence on the measurement accuracy increases. Such a problem becomes conspicuous when the difference between the temperature of the fluid flowing in the pipe and the outside air temperature is large.
[0006]
In addition, when the fluid is a viscous fluid, particularly a viscous fluid having a relatively high viscosity, the flow velocity distribution in the cross section orthogonal to the flow of the fluid in the pipe becomes noticeable (the flow velocity is different between the central portion and the outer peripheral portion in the cross section. to differ greatly). In the case of a conventional tube wall in which a substrate or a casing portion connected thereto is simply exposed, the flow velocity distribution has a great influence on the accuracy of flow rate measurement. This is because, when detecting the flow rate, the flow velocity of the fluid flowing through the central portion of the cross section of the pipe is not taken into consideration, but only the flow velocity of the fluid near the pipe wall of the pipe is taken into consideration. As described above, the conventional flow rate sensor has a problem that accurate flow rate measurement is difficult in the case of a viscous fluid having a relatively high viscosity. Even if the fluid has a low viscosity at room temperature, the viscosity increases as the temperature decreases, and the above-described problems related to the viscosity of the fluid occur. In particular, when the flow rate is relatively small as compared with the case where the flow rate per unit time is large, the above problem is more remarkable.
[0007]
The temperature environment in which the flow sensor is used has a very wide range depending on geographical conditions and indoor / outdoor conditions. Furthermore, seasonal conditions and day / night conditions are added to these, and the temperature environment changes greatly. Therefore, a flow sensor that accurately detects the flow rate under such a wide range of environmental temperature conditions is desired.
[0008]
Therefore, an object of the present invention is to provide a thermal flow sensor with improved measurement accuracy by preventing adverse effects on measurement accuracy due to external environmental temperature conditions.
[0009]
Another object of the present invention is to provide a flow rate sensor that can accurately measure the flow rate of a fluid flowing in a pipe even if the fluid is a relatively high viscosity fluid.
[0010]
Furthermore, an object of the present invention is to provide a flow sensor capable of accurately measuring the flow rate of the fluid flowing in the pipe even at a relatively small flow rate.
[0011]
[Means for Solving the Problems]
According to the present invention, the object as described above is achieved.
A flow rate detection unit having a heat generation function and a temperature sensing function, and a conduit for the detected fluid formed so that heat from the flow rate detection unit is transmitted to the detected fluid and absorbed. The flow rate detection unit is a flow rate sensor that detects the flow rate of the fluid to be detected in the pipe line based on the result of the temperature detection. And
A casing in which the pipe is formed includes a metal inner portion defining the pipe and a synthetic resin outer portion covering the inner portion;
Is provided.
[0012]
In one aspect of the present invention, an element accommodating portion is formed in the outer portion, and at least a part of the flow rate detecting portion is accommodated in the element accommodating portion.
[0013]
In one aspect of the present invention, at least a part of a fluid temperature detection unit for performing fluid temperature compensation at the time of the flow rate detection is stored in the element storage unit.
[0014]
In one aspect of the present invention, the element housing portion is covered with a lid.
[0015]
In one aspect of the present invention, the flow rate detection unit is provided with a first heat transfer member extending into the pipe, and the first heat transfer member is a cross-section of the pipe. Extending at least to the vicinity of the central portion.
[0016]
In one aspect of the present invention, the fluid temperature detection unit is provided with a second heat transfer member extending into the pipe line, and the second heat transfer member is connected to the pipe line. It extends to reach at least the vicinity of the center of the cross section.
[0017]
In one aspect of the present invention, a space between the second heat transfer member and the inner portion is sealed with a second sealing material.
[0018]
In one aspect of the present invention, a gap between the first heat transfer member and the inner portion is sealed with a first sealing material.
[0019]
In one aspect of the present invention, the first sealing material is made of glass.
[0020]
In one aspect of the present invention, the second sealing material is made of glass.
[0021]
In one aspect of the present invention, the flow rate detection unit forms a thin film heating element and a thin film temperature sensing element for flow rate detection arranged on the first substrate so as to be affected by the heat generated by the thin film heating element. It becomes.
[0022]
In one aspect of the present invention, the first heat transfer member is bonded to the first substrate.
[0023]
In one aspect of the present invention, the thin film heating element and the flow rate detecting thin film temperature sensor are laminated on the first surface of the first substrate via a first insulating layer.
[0024]
In one aspect of the present invention, the first heat transfer member is bonded to the second surface of the first substrate.
[0025]
In one aspect of the present invention, the dimension of the first heat transfer member in the direction of the pipe is in a direction perpendicular to the extending direction of the first heat transfer member in the cross section of the pipe. Greater than dimensions.
[0026]
In one aspect of the present invention, the fluid temperature detection unit is formed by forming a fluid temperature detection thin film temperature sensing element on a second substrate.
[0027]
In one aspect of the present invention, the second heat transfer member is bonded to the second substrate.
[0028]
In one aspect of the present invention, the thin film temperature sensing element for detecting fluid temperature is laminated on the first surface of the second substrate via a second insulating layer.
[0029]
In one aspect of the present invention, the second heat transfer member is bonded to the second surface of the second substrate.
[0030]
In one aspect of the present invention, the dimension of the second heat transfer member in the direction of the pipe is in a direction orthogonal to the extending direction of the second heat transfer member in the cross section of the pipe. Greater than dimensions.
[0031]
In one aspect of the present invention, a wiring board is disposed in the element housing portion, and wiring of the wiring board and the flow rate detection unit are electrically connected.
[0032]
In one aspect of the present invention, the wiring of the wiring board and the fluid temperature detector are electrically connected.
[0033]
In one aspect of the present invention, the flow rate detector is sealed with a synthetic resin.
[0034]
In one aspect of the present invention, the fluid temperature detector is sealed with a synthetic resin.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0036]
FIG. 1 is a partially cutaway side view showing an embodiment of a flow sensor according to the present invention, and FIG. 2 is a sectional view thereof.
[0037]
In these drawings, reference numeral 2 denotes a casing body, and a pipe line 4 is formed through the casing body. The pipe line 4 extends to both ends of the casing body 2. Connection portions (for example, male screws) 6a and 6b for connecting to external piping are formed at both ends of the casing body 2.
[0038]
In the present embodiment, the casing body 2 includes an inner part 2-1 that defines (defines) the pipe line 4, and an outer part 2-2 that covers the inner part 2-1. The inner part 2-1 is made of metal, for example, copper, iron or stainless steel. The outer portion 2-2 is made of a synthetic resin such as a vinyl chloride resin. The connecting portions 6a and 6b may be formed on the inner portion 2-1 (that is, the connecting portions 6a and 6b may not be provided with an outer portion) or may be formed on the outer portion 2-2. Also good. An element housing portion 5 is formed above the pipe line 4 in the synthetic resin outer portion 2-2 of the casing main body portion 2, and a casing lid body portion 8 is fixed to the element housing portion 5 with screws or the like. Has been. The casing lid body portion 8 and the casing body portion 2 constitute a casing.
[0039]
Thus, by forming the element accommodating portion 5 in the synthetic resin outer portion 2-2 of the casing main body portion 2, the element accommodating portion 5 and the casing main body portion 2 can be easily formed integrally.
[0040]
A flow rate detector 12 is disposed in the element housing 5 of the casing. As shown in FIG. 3, the flow rate detector 12 forms an insulating layer 12-2 on the upper surface (first surface) of the substrate 12-1, and forms a thin film heating element 12-3 thereon. Then, a pair of electrode layers 12-4 and 12-5 for the thin film heating element is formed thereon, an insulating layer 12-6 is formed thereon, and a thin film temperature sensing element for flow rate detection is formed thereon. 12-7 is formed and it consists of a chip | tip thing which formed the insulating layer 12-8 on it. As the substrate 12-1, for example, a substrate made of silicon or alumina having a thickness of about 0.5 mm and a size of about 2 to 3 mm square can be used (when an insulating substrate such as alumina is used, the insulating layer 12- 2 can be omitted), the thin film heating element 12-3 can be made of a cermet patterned to a desired shape with a film thickness of about 1 μm, and the electrode layers 12-4 and 12-5 can have a film thickness. A layer made of nickel having a thickness of about 0.5 μm or a layer in which gold having a thickness of about 0.1 μm is stacked thereon can be used. The insulating layers 12-2, 12-6, 12-8 have a thickness of about 1 μm. can be used made of SiO _2, the temperature coefficient such as platinum or nickel which is patterned into a desired shape for example meandering film thickness of about 0.5~1μm is a thin film temperature sensitive body 12-7 It can be used stable metal resistive film listening (or may be used made of NTC thermistor of manganese oxide based). As described above, the thin film heating element 12-3 and the thin film temperature sensing element 12-7 are arranged in close proximity via the thin film insulating layer 12-6, so that the thin film temperature sensing element 12-7 is a thin film. Immediately affected by the heat generated by the heating element 12-3.
[0041]
As shown in FIGS. 1 and 2, a fin plate 14 as a heat transfer member is bonded to the lower surface of the flow rate detection unit 12, that is, the lower surface (second surface) of the substrate 12-1, with good thermal conductivity. Bonded by the material 16. The fin plate 14 can be made of, for example, copper, duralumin, or a copper-tungsten alloy, and the bonding material 16 can be made of, for example, silver paste. The casing body 2 is formed with an opening through which the fin plate 14 passes at the position where the flow rate detecting unit 12 is disposed, and for sealing with the fin plate 14 inserted into the opening. The glass seal 18 is formed. The glass seal 18 is interposed between the fin plate 14 and the casing body inner portion 2-1. As described above, the glass seal 18 is interposed between the fin plate 14 and the metal inner portion 2-1, so that the glass seal 18 is interposed between the fin plate 14 and the synthetic resin outer portion 2-2. In addition, it is possible to suppress the occurrence of damage such as cracks in the seal portion due to the difference in thermal expansion coefficient with the glass seal 18 due to the thermal expansion and contraction caused by the temperature change.
[0042]
The fin plate 14 is bent at a substantially right angle at the center, the upper horizontal portion is joined to the flow rate detection unit 12, and the lower vertical portion extends into the pipe 4. The fin plate 14 extends across the pipe line 4 from the upper part to the lower part through the center in the pipe line 4 having a substantially circular cross section. However, the pipe 4 does not necessarily have a circular cross section, and can have an appropriate cross sectional shape. In the pipe 4, the dimension L ₁ of the fin plate 14 in the pipe direction is sufficiently larger than the thickness L ₂ of the fin plate 14. For this reason, the fin plate 14 can satisfactorily transfer heat between the flow rate detection unit 12 and the fluid without greatly affecting the fluid flow in the pipe 4.
[0043]
In the element housing part 5 of the casing, a fluid temperature detection part 22 is arranged at a position separated from the flow rate detection part 12 along the pipeline 4. The temperature detector 22 is formed of a chip-like member in which a similar thin film temperature sensor (fluid temperature compensating thin film temperature sensor) is formed on the same substrate as the flow rate detector 12. That is, the temperature detection unit 22 can be configured in the same manner as that obtained by removing the thin film heating element 12-3, the pair of electrode layers 12-4 and 12-5, and the insulating layer 12-6 in FIG.
[0044]
Further, similarly to the flow rate detector 12, the temperature detector 22 is joined with a fin plate 14 'by a joining material 16', and the fin plate 14 'and the metal inner portion 2-1 are interposed. Is interposed by a glass seal 18 '. As these fin plate 14 ′, bonding material 16 ′, and glass seal 18 ′, those similar to the fin plate 14, bonding material 16, and glass seal 18 can be used, respectively.
[0045]
The fluid temperature detector 22 is preferably arranged on the upstream side of the flow rate detector 12 with respect to the fluid flow direction in the pipe 4.
[0046]
The flow rate detection unit 12 and the temperature detection unit 22 are sealed with synthetic resin coatings 20 and 24, respectively. These synthetic resin coatings 20 and 24 also have functions of fixing and maintaining the positions of the fin plates 14 and 14 ′ joined to the flow rate detection unit 12 and the temperature detection unit 22.
[0047]
In the element housing part 5 of the casing, a wiring board 26 is fixedly arranged in a part other than the flow rate detection part 12 and the temperature detection part 22. Some of the electrodes of the wiring board 26 are electrically connected to the electrodes of the flow rate detection unit 12 by bonding wires 28. Similarly, the electrodes of the temperature detection unit 22 and the bonding wires 29 are electrically connected. It is connected. These bonding wires 28 are sealed with the synthetic resin coatings 20 and 24. Some other electrodes of the wiring board 26 are connected to the external lead wire 30, and the external lead wire 30 extends out of the casing.
[0048]
FIG. 4 is a circuit configuration diagram of the flow sensor of the present embodiment. As shown in the figure, the voltage of the DC power supply 40 is applied to the thin film heating element 12-3 and the bridge circuit 42. As the output of the differential amplifier 44 in the bridge circuit 42, an output indicating the flow rate is obtained. That is, in the flow rate detection unit 12, based on the heat generated by the thin film heating element 12-3, the temperature sensing by the thin film temperature sensing element 12-7 is performed under the influence of heat absorption by the fluid to be detected via the fin plate 14. Based on the temperature sensing result, the temperature detection unit 22 further compensates the detected fluid temperature detected via the fin plate 14 ′, and the flow rate of the detected fluid in the pipe 4 is detected.
[0049]
According to the above embodiment, the metal inner part 2-1 that defines the pipe line 4 of the casing body 2 is covered with the synthetic resin outer part 2-2 having low thermal conductivity. Even if the conditions change, the influence does not immediately affect the fluid to be detected in the pipe 4 and adversely affect the flow rate measurement. Since the metal inner part 2-1 is used, the mechanical strength is good.
[0050]
Further, since the fin plates 14 and 14 'are used, even if the fluid to be detected is a viscous fluid having a relatively high viscosity, what is the radial flow rate distribution in the cross section of the pipeline 4? However, accurate flow rate detection that sufficiently reflects the flow rate distribution is possible.
[0051]
Accordingly, it is possible to accurately measure the flow rate of the fluid flowing in the pipe even under a relatively small flow rate or under a wide range of environmental temperature conditions.
[0052]
In the above embodiment, the fin plates 14 and 14 ′ pass from the upper part to the lower part through the central part of the pipe cross section, but the fin plates 14 and 14 ′ are arranged from the upper part to the central part of the pipe cross section. It can be extended to the vicinity. Thereby, whatever the radial flow distribution in the cross section of the pipe line 4 is, it is possible to accurately detect the flow rate reflecting the flow distribution well.
[0053]
【The invention's effect】
As described above, according to the flow rate sensor of the present invention, it is possible to perform accurate flow rate measurement that is not easily affected by fluctuations in the outside air temperature. Further, according to the flow rate sensor of the present invention, the flow rate of the fluid flowing in the pipe can be accurately measured even for a viscous fluid having a relatively high viscosity. Furthermore, according to the present invention, the flow rate of the fluid flowing in the pipe can be accurately measured even at a relatively small flow rate.
[Brief description of the drawings]
FIG. 1 is a partially cutaway side view showing an embodiment of a flow sensor according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a flow sensor according to the present invention.
FIG. 3 is an exploded perspective view of a flow rate detection unit of an embodiment of a flow rate sensor according to the present invention.
FIG. 4 is a circuit configuration diagram of a flow sensor of one embodiment of the flow sensor according to the present invention.
[Explanation of symbols]
2 Casing body part 2-1 Casing body part inner part 2-2 Casing body part outer part 4 Pipe line 5 Element accommodating part 6a, 6b Connection part 8 Casing cover part 12 Flow rate detection part 12-1 Board | substrate 12-2 Insulation layer 12-3 Thin Film Heating Element 12-4, 12-5 Electrode Layer 12-6 Insulating Layer 12-7 Thin Film Temperature Sensing Body 12-8 for Flow Rate Detection Insulating Layer 14, 14 ′ Fin Plate 16, 16 ′ Bonding Materials 18, 18 'Glass seal 20 Resin coating 22 Fluid temperature detector 24 Resin coating 26 Wiring boards 28, 29 Bonding wire 30 External lead wire 40 DC power supply 42 Bridge circuit 44 Differential amplifier

Claims (21)

A flow rate detection unit having a heat generation function and a temperature sensing function, and a conduit for the detected fluid formed so that heat from the flow rate detection unit is transmitted to the detected fluid and absorbed. The flow rate detection unit is a flow rate sensor that detects the flow rate of the fluid to be detected in the pipe line based on the result of the temperature detection. And
The casing in which the conduit is formed includes an inner portion made of metal that defines the conduit, and an outer portion made of synthetic resin covering the inner portion ,
An element accommodating portion is formed in the outer portion, and the flow rate detecting portion is accommodated in the element accommodating portion,
The flow rate detection unit is provided with a first heat transfer member extending into the pipe, and the first heat transfer member reaches at least the vicinity of the center of the cross section of the pipe. A flow sensor characterized by extending in the manner described above . A dimension of the first heat transfer member in the direction of the pipe line is larger than a dimension in a direction orthogonal to the extending direction of the first heat transfer member in a cross section of the pipe line. The flow sensor according to claim 1 . 3. The flow sensor according to claim 1 , wherein a gap between the first heat transfer member and the inner portion is sealed with a first sealing material. 4. The flow sensor according to claim 3 , wherein the first sealing material is made of glass. The flow rate detection unit is characterized in that a thin film heating element and a thin film temperature sensing element for flow rate detection arranged so as to be affected by the heat generation of the thin film heating element are formed on a first substrate. The flow sensor according to claim 1 . 6. The flow sensor according to claim 5 , wherein the first heat transfer member is bonded to the first substrate. Wherein the thin film heating element and said flow rate detecting thin-film temperature sensing element are laminated through a first insulating layer at the first surface of the first substrate, according to claim 5 Flow sensor. The flow sensor according to claim 7 , wherein the first heat transfer member is bonded to the second surface of the first substrate. The flow rate sensor according to claim 1 , wherein the flow rate detection unit is sealed with a synthetic resin. The wiring board is arrange | positioned in the said element accommodating part, The wiring of this wiring board and the said flow volume detection part are electrically connected, The Claim 1 characterized by the above-mentioned. Flow sensor. The flow sensor according to claim 1 , wherein the element housing portion is covered with a lid. The element accommodating portion accommodates a fluid temperature detecting portion for performing fluid temperature compensation when detecting the flow rate of the detected fluid, and the fluid temperature detecting portion extends into the pipe line. The second heat transfer member is attached, and the second heat transfer member extends so as to reach at least the vicinity of the center of the cross section of the pipe . The flow sensor according to any one of 11 . The dimension of the direction of the pipe line of the second heat transfer member is larger than the dimension in a direction orthogonal to the extending direction of the second heat transfer member in the cross section of the pipe line. The flow sensor according to claim 12 . The flow sensor according to any one of claims 12 to 13, wherein a space between the second heat transfer member and the inner portion is sealed with a second sealing material. The flow sensor according to claim 14 , wherein the second sealing material is made of glass. The flow rate sensor according to any one of claims 12 to 15, wherein the fluid temperature detection unit is formed by forming a thin film temperature sensing element for fluid temperature detection on a second substrate.   The flow rate sensor according to claim 16, wherein the second heat transfer member is bonded to the second substrate.   The flow rate sensor according to claim 16, wherein the fluid temperature sensing thin film temperature sensor is laminated on the first surface of the second substrate via a second insulating layer.   The flow sensor according to claim 18, wherein the second heat transfer member is bonded to the second surface of the second substrate. The flow rate sensor according to claim 12 , wherein the fluid temperature detection unit is sealed with a synthetic resin. Wherein the element receiving portion is disposed a wiring substrate, characterized in that the line and the fluid temperature detecting portion of the wiring board are electrically connected, according to any one of claims 12 to 20 Flow sensor.

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