JP2000146655A - Flow sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow sensor capable of accurately measuring the quantity of flow of a viscous fluid in piping under a wide range of environmental and temperature conditions. SOLUTION: The flow sensor is provided with a fluid flow conduit 4 and a heat transferring fin plate 14 for detecting the quantity of flow. The fin plate 14 receives the effects of produced heat at a flow quantity detecting part in a flow quantity detecting unit 51 and is arranged so as to be extended into the fluid flow conduit 4. Temperature sensing under the effects of heat absorption by a fluid to be detected is performed via the fin plate 14 on the basis of produced heat at the flow quantity detecting part. Then the quantity of flow of the fluid to be detected in the fluid flow conduit 4 is detected on the basis of the results of the temperature detection. The fin plate 14 is exposed only in the center region within 80% of the radial distance between the center line A and wall of the conduit 4 in the conduit 4, and its base part is covered with a heat insulating member 55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid flow rate detection technique, and more particularly to a flow rate sensor for detecting a flow rate of a fluid flowing in a pipe. The present invention particularly aims at improving the measurement accuracy of the flow sensor.

[0002]

2. Description of the Related Art
Various types of flow sensors (or flow rate sensors) for measuring the flow rate (or flow rate) of various fluids, especially liquids, are used, but because of the ease of cost reduction, a so-called thermal type (or flow rate sensor) is used. In particular, indirect heat type) flow sensors are used.

In this indirectly heated flow sensor, a thin-film heating element and a thin-film temperature sensing element are laminated on a substrate using a thin-film technology via an insulating layer, and the substrate and the fluid in the pipe are thermally separated. Those that are arranged to be connected are used. By energizing the heating element, the temperature sensing element is heated to change the electrical characteristics of the temperature sensing element, for example, the value of electrical resistance. This change in the electric 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 via the substrate, and the amount of heat diffused into the fluid changes according to the flow rate (flow velocity) of the fluid. This is because the amount of heat supplied to the body changes and the electric resistance value of the thermosensitive body changes. The change in the electric resistance value of the temperature sensing element also differs depending on the temperature of the fluid. Therefore, a temperature sensing element for temperature compensation is incorporated in an electric circuit for measuring the change in the electric resistance value of the temperature sensing element. It has also been practiced to minimize the change in the flow measurement value due to the temperature of the fluid.

[0004] Such an indirectly heated flow sensor using a thin film element is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-146,026.
There is a description in the publication.

A conventional indirectly heated flow sensor is attached to a pipe so that a substrate of a flow detecting section or a casing thermally connected to the substrate is exposed to a fluid from a wall surface of the pipe. ing.

[0006] However, when the fluid is a viscous fluid, particularly a liquid, the flow velocity distribution in a cross section orthogonal to the flow of the fluid in the pipe becomes non-uniform (the flow velocity is large at the central portion and the outer peripheral portion in the cross section). different). In the case where the substrate or the casing portion connected to the substrate is simply exposed on the conventional pipe wall, the flow velocity distribution greatly affects the accuracy of flow measurement. This is because the flow rate detection does not consider the flow velocity of the fluid flowing in the central portion of the cross section of the pipe, but only considers the flow velocity of the fluid near the pipe wall of the pipe. As described above, the conventional flow sensor has a problem that it is difficult to accurately measure the flow rate of a viscous fluid. In addition, even if the fluid has a low viscosity at room temperature, the viscosity increases as the temperature decreases, so that the above-described problems related to the viscosity of the fluid occur.

[0007] The temperature environment in which the flow rate sensor is used is extremely wide depending on geographical conditions, indoors and outdoors, and seasonal conditions and day / night are added to the temperature environment. There is a need for a flow sensor that is large and that accurately detects flow under such a wide range of environmental temperature conditions.

Accordingly, an object of the present invention is to provide a flow rate sensor which can accurately measure the flow rate of a viscous fluid flowing in a pipe under a wide range of environmental temperature conditions.

[0009]

According to the present invention, a flow detecting section having a heat generating function and a temperature sensing function, and a fluid flow pipe for flowing a fluid to be detected are provided. And a flow rate detecting heat transfer member arranged to be affected by heat generation in the flow rate detecting section and extend into the fluid flow conduit, and the flow rate detecting section detects the flow rate based on heat generation in the flow rate detecting section. A temperature sensing effected by the heat absorption by the fluid to be detected is performed via the heat transfer member for detection, and the flow rate at which the flow rate of the fluid to be detected in the fluid flow conduit is detected based on the result of the temperature sensing A sensor, wherein the heat transfer member for detecting flow rate is located within a center area within 80% of a radial distance from a pipe center line to a pipe wall in the fluid flow pipe in a radial direction of the fluid flow pipe. Only be exposed Flow sensor, wherein, is provided.

[0010] In one aspect of the present invention, the heat transfer member for detecting flow rate extends into the fluid flow conduit in a radial direction of the fluid flow conduit. The distal end of the extension portion is located in the central region, and the base of the extension portion located outside the central region is covered with a heat insulation member related to flow rate detection.

In one embodiment of the present invention, a portion of the flow rate detecting portion and the flow rate detecting heat transfer member which is thermally connected to the flow rate detecting portion is accommodated in a flow rate detecting base having thermal insulation. The flow rate detection related heat insulating member is formed by a part of the flow rate detection base.

In one embodiment of the present invention, the base body for flow rate detection and the heat insulating member related to flow rate detection are made of synthetic resin.

In one embodiment of the present invention, the flow rate detecting section is affected by a thin film heating element formed on the flow rate detecting heat transfer member outside the fluid flow conduit and heat generated by the thin film heating element. And a thin film temperature sensing element for flow rate detection arranged as described above.

In one embodiment of the present invention, the heat transfer member for detecting a flow rate has a flat plate shape and is arranged in the fluid flow channel along the direction of the channel.

In one embodiment of the present invention, a fluid temperature detecting portion for compensating for the temperature at the time of the flow rate detection is included, and the fluid temperature detecting portion and the fluid temperature detecting portion extend into the fluid flow pipe. The arranged temperature detecting heat transfer member is thermally connected.

In one aspect of the present invention, the heat transfer member for temperature detection is exposed only in the central region in the fluid flow conduit.

In one embodiment of the present invention, the temperature detecting heat transfer member extends radially into the fluid flow channel and into the fluid flow channel. The tip of the extension portion is located within the central region, and the base of the extension portion located outside the central region is covered with a temperature detection-related heat insulating member.

In one embodiment of the present invention, a portion of the temperature detecting portion and the temperature detecting heat transfer member that is thermally connected to the temperature detecting portion is housed in a temperature detecting base having thermal insulation. The temperature detecting related heat insulating member is formed by a part of the temperature detecting base.

In one embodiment of the present invention, the heat transfer member for detecting temperature is formed in a flat plate shape and is arranged in the fluid passage along the direction of the passage.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are cross-sectional views showing one embodiment of a flow sensor according to the present invention. FIG. 1 shows a cross section along a fluid circulation pipe through which a fluid to be detected flows, and FIG. 2 shows a cross section orthogonal to the pipeline.

In these figures, reference numeral 2 denotes a casing main body, and a fluid circulation pipe 4 for circulating the fluid to be detected is formed through the casing main body. The pipe 4 extends to both ends of the casing body 2. A indicates the center line of the pipeline 4. At both ends of the casing body 2, connecting portions (for example, a quick coupling structure not shown in detail) 6a, 6 for connecting to an external pipe.
b is formed. The casing body 2 is made of synthetic resin such as vinyl chloride resin or glass fiber reinforced polyphenylene sulfide (PP) having high chemical resistance and oil resistance.
S) or polybutylene terephthalate (PBT). The casing main body 2 has an element accommodating portion 5 formed above the conduit 4, and a casing lid 8 is fixed to the element accommodating portion 5 by screws or fitting. The casing lid 8 and the casing body 2
These form a casing.

In the present embodiment, two element unit holding portions 50 and 60 are formed adjacent to the pipe 4 inside the element accommodating section 5 of the casing main body 2 (that is, on the pipe 4 side). Each of these element unit holding portions 50 and 60 has a two-stage cylindrical inner surface centered on the radial direction of the pipeline 4. The first element unit holding unit 50 allows the flow rate detection unit 5
1 is held, and the fluid temperature detection unit 61 is held by the second element unit holding portion 60.

FIG. 3 is a sectional view of the flow rate detection unit 51. As shown in FIG.
Reference numeral 1 denotes a flow rate detecting unit 12, a fin plate 14 as a heat transfer member joined to the flow rate detecting unit 12 by a bonding material 16 having good thermal conductivity, an electrode terminal 52, and an electrode of the flow rate detecting unit 12. It has a bonding wire 28 electrically connected to the corresponding electrode terminal 52 and a base 53 made of synthetic resin. The base portion 53 has low heat transfer (that is, has thermal insulation) and high chemical resistance and oil resistance, and is made of, for example, PPS or PBT. The base portion 53 has a two-stage cylindrical outer peripheral surface corresponding to the inner peripheral surface of the element unit holding portion 50. From the base portion 53, a part of the fin plate 14 extends toward the conduit 4 and a part of the electrode terminal 52 extends on the side (outside) opposite to the conduit 4. That is, the flow rate detector 12, the bonding material 16, a part of the fin plate 14, a part of the electrode terminal 52, and the bonding wire 28 are sealed by the base 53.

As shown in FIG. 4, the flow rate detector 12 includes an insulating layer 12-2 on the upper surface (first surface) of the substrate 12-1.
Is formed thereon, and a thin film heating element 12-3 is formed thereon, and a pair of electrode layers 12-4, 12 for the thin film heating element is further formed thereon.
-5, an insulating layer 12-6 is formed thereon, a thin film temperature sensing element 12-7 for flow rate detection is formed thereon, and an insulating layer 12-8 is formed thereon. Consists of 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 having a thickness of about 1 μm and patterned into a desired shape, and the electrode layers 12-4 and 12-5 have a thickness of about 1 μm. A layer made of nickel of about 0.5 μm or a layer of gold having a thickness of about 0.1 μm can be used, and the insulating layers 12-2, 12-6, and 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, since the thin-film heating element 12-3 and the thin-film thermosensitive element 12-7 are disposed very close to each other with the thin-film insulating layer 12-6 interposed therebetween, the thin-film thermosensitive element 12-7 is thin-film. Heating element 12-
3 will be immediately affected.

As shown in FIG. 3, the flow rate detector 1
2, a flat fin plate 14 as a heat transfer member is provided on one surface of the substrate 2, ie, the second surface of the substrate 12-1.
It is joined by. The fin plate 14 may be a flat plate made of, for example, copper, duralumin, or a copper-tungsten alloy, and the joining material 16 may be, for example, a silver paste.

As shown in FIGS. 1 and 2, between the outer peripheral surface of (the base portion 53 of) the flow rate detecting unit 51 and the inner peripheral surface of the element unit holding portion 50, a seal for the pipe line 4 is provided. An O-ring 54 as a member is interposed.

The fin plate 14 has an upper part joined to the flow rate detecting part 12 and a lower part extending into the pipeline 4. The fin plate 14 extends across the line 4 from the top to the bottom through the center in the cross section of the line 4 having a substantially circular cross section. However, pipeline 4
Does not necessarily have to have a circular cross section, but can have an appropriate cross section. In the pipeline 4, the width (dimension in the pipeline direction) of the fin plate 14 is
Bigger than the thickness of For this reason, the fin plate 14
The heat transfer between the flow rate detecting unit 12 and the fluid can be favorably performed without greatly affecting the flow of the fluid in the pipeline 4.

An element unit holding section 60 is disposed in the casing main body 2 at a position separated from the element unit holding section 50 along the pipeline 4. The fluid temperature detection unit 61 is held by the element unit holding section 60.

The fluid temperature detecting unit 61 is basically different from the flow rate detecting unit 51 in that a fluid temperature detecting unit is used instead of the flow rate detecting unit 12. That is, the fluid temperature detection unit 61 corresponds to the fin plate 14 ′ as a heat transfer member joined to the fluid temperature detection unit by a bonding material having good heat conductivity, the electrode terminal 62, and the electrode of the fluid temperature detection unit. And a bonding wire electrically connected to the electrode terminal 62 to be formed, and a base made of synthetic resin. From the base portion, a part of the fin plate 14 ′ extends to the side of the conduit 4, and a part of the electrode terminal 62 extends to the side (outside) opposite to the conduit 4.

The temperature detecting section is formed in a chip shape in which a similar thin-film thermosensitive element (a thin-film thermosensitive element for fluid temperature compensation) is formed on the same substrate as the flow rate detecting section 12. That is, the temperature detecting section can be configured in the same manner as in FIG. 4 except that the thin film heating element 12-3, the pair of electrode layers 12-4 and 12-5, and the insulating layer 12-6 are removed. Further, the fin plate 14 ′ is joined to the temperature detecting section by a joining material in the same manner as the flow rate detecting section 12.

As shown in FIG. 1, between the outer peripheral surface of the fluid temperature detecting unit 61 and the inner peripheral surface of the element unit holding portion 60, an O-
A ring 64 is interposed.

The fluid temperature detecting unit 61 is preferably arranged on the downstream side of the flow rate detecting unit 51 in the fluid flow direction in the pipe 4.

A holding plate 32 for the flow rate detecting unit 51 and the fluid temperature detecting unit 61 is arranged in the element housing portion 5 of the casing main body 2, and the wiring board 26 is fixedly arranged thereon. I have. Some of the electrodes of the wiring board 26 are electrically connected to the electrode terminals 52 of the flow rate detection unit 51 by wire bonding or the like (not shown). 62 are electrically connected by wire bonding or the like (not shown). Some of the other electrodes of the wiring board 26 are connected to external leads 30, which extend outside the casing. The external lead wire 30 is previously arranged integrally at a predetermined position of the casing main body 2, and when the wiring board 26 is attached to the casing main body 2,
Electrical connection with the electrode 6 can be made.

FIG. 5 is a circuit diagram of the flow sensor according to the present embodiment. The power supply is, for example, + 15V (± 10%)
And is supplied to the constant voltage circuit 102. The constant voltage circuit 102 has an output of 0.1 W at +6 V (± 3%), for example, and the output is supplied to a bridge circuit 104. The bridge circuit 104 includes a thin film temperature sensing element for flow rate detection 104-1 (12-7), a thin film temperature sensing element for temperature compensation 104-2, and variable resistors 104-3 and 104-4.

The voltages at points a and b of the bridge circuit 104 are input to the differential amplifier circuit 106. The differential amplifier circuit 106
Is made variable by a variable resistor 106a. The output of the differential amplification circuit 106 is input to the integration circuit 108. The variable amplification factor differential amplifier circuit 106 and the integration circuit 108 function as responsiveness setting means as described later.

On the other hand, the power supply is connected to the collector of the NPN transistor 110, and the emitter of the transistor 110 is connected to the heating element 112. The output of the integration circuit 108 is input to the base of the transistor 110. That is, the power supply is through the transistor 110 and the thin film heating element 112 (the above-described 12
-3), and the voltage applied to the heating element 112 is controlled by the voltage division of the transistor 110. The voltage division of the transistor 110 is controlled by the output current of the integration circuit 108 input to the base via the resistor, and the transistor 110 functions as a variable resistor, and controls the heat generation of the heating element 112. Functions as a means.

That is, in the flow rate detecting section 12, the thin film heating element 1-3 is affected by the heat absorption of the fluid to be detected through the fin plate 14 based on the heat generated by the thin film heating element 12-3.
The temperature sensing according to 2-7 is executed. As a result of the temperature sensing, a difference between the voltages Va and Vb at points a and b of the bridge circuit 104 shown in FIG. 5 is obtained.

The value of (Va-Vb) changes when the temperature of the thin film temperature sensing element 104-1 for flow rate detection changes according to the flow rate of the fluid. Variable resistors 104-3, 104-4 in advance
By appropriately setting the resistance value, the value of (Va-Vb) can be made zero in the case of a desired fluid flow rate serving as a reference. At this reference flow rate, the output of the differential amplifier circuit 106 is zero, the output of the integration circuit 108 is constant, and the resistance value of the transistor 110 is also constant. In this case, the partial pressure applied to the heating element 112 is also constant, and the flow rate output at this time indicates the reference flow rate.

When the flow rate of the fluid increases or decreases from the reference flow rate, the output of the differential amplifier circuit 106 varies depending on the polarity (Va-Vb) depending on the polarity of the resistance (temperature-sensing element 104-1 for flow rate detection). ) And the magnitude changes, and the output of the integration circuit 108 changes accordingly. The rate of change of the output of the integrating circuit 108 is determined by the variable resistor 106a of the differential amplifier 106.
Can be adjusted by setting the amplification factor. The response characteristics of the control system are set by the integrating circuit 108 and the differential amplifier circuit 106.

When the flow rate of the fluid increases, the temperature of the temperature sensing element 104-1 decreases, so that the amount of heat generated by the heating element 112 is increased (that is, the amount of current is increased).
From the integration circuit 108, a control input is made to the base of the transistor 110 so as to reduce the resistance of the transistor 110.

On the other hand, when the flow rate of the fluid decreases, the temperature of the flow rate detecting temperature sensing element 104-1 increases.
12 to reduce the amount of heat generation (that is, reduce the amount of current)
As described above, a control input for increasing the resistance of the transistor 110 is made from the integration circuit 108 to the base of the transistor 110.

As described above, the heat generation of the heating element 112 is feedback-controlled so that the temperature detected by the flow rate detecting temperature sensor 104-1 always becomes the target value regardless of the change in the fluid flow rate. (If necessary, the polarity of the output of the differential amplifier circuit 106 is appropriately inverted according to the positive / negative of the resistance-temperature characteristic of the temperature sensing element 104-1 for flow rate detection). Since the voltage applied to the heating element 112 at this time corresponds to the fluid flow rate, this is taken out as a flow rate output.

According to this, regardless of the flow rate of the fluid to be detected, the flow rate detecting temperature sensing element 10 around the heating element 112 can be used.
Since the temperature of 4-1 is maintained substantially constant, the deterioration of the flow rate sensor with time is small, and the occurrence of an ignition explosion of the flammable fluid to be detected can be prevented. The heating element 11
2 does not require a constant voltage circuit.
There is an advantage that a low-output constant voltage circuit 102 for P.4 may be used. For this reason, the calorific value of the constant voltage circuit can be reduced, and the flow rate detection accuracy can be maintained well even if the flow rate sensor is downsized.

In the present embodiment, as shown in FIGS. 1 to 3 and particularly in FIG.
The lower part of 3 protrudes into the pipeline 4, and a heat insulating member 55 is formed by this protruding part. Similarly, a lower portion of the base portion of the temperature detecting unit 61 projects into the duct 4, and the projecting portion forms a heat insulating member 65. These heat insulating members 55 and 65 prevent the bases of the extending portions of the fin plates 14 and 14 ′ from being exposed into the conduit 4.

FIG. 6 shows a pipeline 4 and a fin plate 14 extending therethrough in a cross section orthogonal to the pipeline center line A.
FIG. 4 is a schematic diagram showing a heat insulating member 55. Thermal insulation member 5
Numeral 5 covers the base of the extended portion of the fin plate 14. That is, the fin plate 14 is
A portion extending from the pipeline center line A to the base side (upper side) up to a distance r1 and a portion extending from the pipeline center line A to the distal side (downward) up to a distance r2 (up to the distal end) are exposed. The exposed portion of the fin plate 14 is located in the central region X from the pipeline center line A to the radius Ra, and is not exposed in the outer peripheral region Y around the central region X. Here, when the radius of the pipeline 4 is R, Ra = 0.8R. r1 and r2 are preferably set so that the sum (r1 + r2) of them becomes 0.7R or more. This is r1 + r
This is because the amount of heat transmitted between the fin plate 14 and the fluid tends to decrease and the flow rate detection efficiency tends to decrease as 2 becomes smaller.

As described above, in the present embodiment, the heat transfer between the fluid to be detected and the fin plate 14 in the pipeline 4 is performed in the outer peripheral region Y where the flow velocity of the fluid to be detected is small and the sensitivity is low in terms of flow rate detection. Is performed substantially only at the fin plate exposed portion in the central region X where the flow rate is relatively large and the flow rate can be efficiently detected.

Further, the shear stress generated in the fluid to be detected based on the contact friction with the pipe wall when the fluid to be detected flows is large in the outer peripheral region Y, and the surface roughness of the pipe wall is generally not zero. Therefore, small eddies are randomly generated in the outer peripheral region Y during the flow of the fluid. For this reason, in the outer peripheral region Y, the flow of the detected fluid becomes unstable. Therefore, by performing heat transfer for flow rate detection only in the central area X avoiding the outer peripheral area Y, a stable flow rate output can be obtained.

The structure related to the flow rate detection in which the base of the fin plate 14 extending into the conduit 4 is covered by the heat insulating member 55 has been described above.
The same structure can be applied to the temperature detection-related structure in which the base of the portion of 4 'extending into the conduit 4 is covered by the heat insulating member 65. This makes it possible to accurately detect the temperature of the fluid in the central region X through which the main portion of the fluid to be detected passes, and as described above, between the fin plate 14 and the fluid to be detected in the central region X. Temperature compensation of the fluid to be detected for flow rate detection performed based on heat transfer can be accurately performed.

FIG. 7 shows the flow rate sensor of the present embodiment as described above.
11 is a graph showing a result of measuring a change in output voltage when the flow rate after the change is maintained immediately after the flow rate is changed to n. Here, kerosene was used as the fluid to be detected, the pipe diameter (2R) was 4 mmφ, and r1 = r2 = 0.5R. On the other hand, FIG. 8 does not use the heat insulating member 55 (ie,
8 is a graph showing the results of similar flow measurement performed using the same flow sensor as obtained in FIG. 7 except that r1 = R and r2 = 0.5R). The amplitude of the flow rate output voltage is smaller in the case of FIG. 7 than in the case of FIG.
3) It can be seen that the measurement error is small.

Thus, in the present embodiment, the pipe 4
It is possible to accurately and stably detect the flow rate of the fluid to be detected in the inside.

[0052]

As described above, according to the flow rate sensor of the present invention, the heat transfer member for detecting the flow rate is set at 80 mm in the radial distance from the pipe center line to the pipe wall in the fluid flow pipe.
%, The flow rate is relatively large, the flow rate can be detected efficiently, and the flow rate of the detected fluid and the flow rate of the fluid to be detected is relatively high in the central area of the pipeline where the flow of the detected fluid is relatively stable. Heat transfer between the heat transfer member and the heat transfer member. This makes it possible to accurately and stably detect the flow rate of the fluid to be detected in the pipeline under a wide range of environmental temperature conditions.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view taken along a fluid flow conduit showing one embodiment of a flow sensor according to the present invention.

FIG. 2 is a cross-sectional view of a flow sensor according to an embodiment of the present invention, which is orthogonal to a fluid flow conduit.

FIG. 3 is a cross-sectional view of a flow detection unit of one embodiment of the flow sensor according to the present invention.

FIG. 4 is an exploded perspective view of a flow rate detector of one embodiment of the flow rate sensor according to the present invention.

FIG. 5 is a circuit configuration diagram of one embodiment of a flow sensor according to the present invention.

FIG. 6 is a schematic view showing a conduit of a flow sensor according to an embodiment of the present invention, a fin plate extending therefrom, and a heat insulating member.

FIG. 7 is a graph showing a result of measuring a change in an output voltage in one embodiment of the flow sensor according to the present invention.

FIG. 8 is a graph showing a result of measuring a change in output voltage in a flow sensor for comparison with the present invention.

[Explanation of symbols]

 Reference Signs List 2 Casing main body 4 Fluid flow pipe 5 Element housing 6a, 6b Connection 8 Casing lid 12 Flow rate detector 12-1 Substrate 12-2 Insulating layer 12-3 Thin film heating element 12-4, 12-5 Electrode Layer 12-6 Insulating layer 12-7 Thin film temperature sensing element for flow rate detection 12-8 Insulating layer 14, 14 'Fin plate 16 Bonding material 22 Fluid temperature detecting unit 26 Wiring board 28 Bonding wire 30 External lead wire 32 Holding plate 40 DC Power supply 42 Bridge circuit 44 Differential amplifier 50 Element unit holding part 51 Flow rate detecting unit 52 Electrode terminal 53 Base part 54 O-ring 55 Flow rate detection related heat insulating member 60 Element unit holding part 61 Fluid temperature detecting unit 62 Electrode terminal 63 Base part 64 O-ring 65 Thermal insulation member related to temperature detection 104-1 Thin film temperature sensing element for flow rate detection 10 -2 temperature compensating film temperature sensitive body 112 film heating element A pipe center line X pipe center region Y pipe outer peripheral region

Continuation of the front page (72) Inventor Takayuki Takahata 1333-2, Hara-shi, Ageo-shi, Saitama F-term (reference) 2F035 EA04 EA08

Claims (11)

[Claims] 1. A flow rate detecting section having a heat generating function and a temperature sensing function, a fluid flow path for flowing a fluid to be detected, and a flow path affected by heat generated in the flow rate detecting section and located in the fluid flow path. And a heat transfer member for flow rate detection arranged so as to extend therefrom, wherein the flow rate detection section is influenced by heat absorption by the detected fluid via the heat transfer member for flow rate detection based on heat generation in the flow rate detection section. A flow rate sensor for detecting a flow rate of the fluid to be detected in the fluid flow path based on a result of the temperature sensing, wherein the heat transfer member for flow rate detection is located in the fluid flow path. A flow sensor characterized in that it is exposed only in a central region within 80% of a radial distance from a pipe center line to a pipe wall in a radial direction of the fluid flow pipe. 2. The heat transfer member for flow rate detection extends radially into the fluid flow channel into the fluid flow channel, and a tip of a portion extending into the fluid flow channel is The flow sensor according to claim 1, wherein the base of the extension portion located in the center region and located outside the center region is covered with a flow rate detection-related heat insulating member. 3. The flow rate detecting portion and a portion of the flow rate detecting heat transfer member that is thermally connected to the flow rate detecting portion are housed in a flow rate detecting base portion having thermal insulation. The flow rate sensor according to claim 2, wherein the flow rate detection-related heat insulating member is formed by a part of the base body. 4. The flow rate detecting base and the flow rate detecting related heat insulating member are made of synthetic resin.
The flow sensor according to claim 3. 5. The thin film heating element formed on the flow rate detecting heat transfer member outside the fluid flow conduit and a flow rate arranged so as to be affected by heat generated by the thin film heating element. The flow sensor according to any one of claims 1 to 4, further comprising a thin-film thermosensitive element for detection. 6. The heat transfer member for flow rate detection is formed in a flat plate shape, and is arranged in the fluid flow channel along the direction of the channel. The flow sensor according to any one of claims 1 to 5. 7. A fluid temperature detecting unit for performing temperature compensation for detecting the flow rate, the fluid temperature detecting unit and a temperature detecting unit arranged so as to extend into the fluid flow pipe. The flow sensor according to any one of claims 1 to 6, wherein the flow sensor is thermally connected to the heat transfer member. 8. The flow sensor according to claim 7, wherein the temperature detecting heat transfer member is exposed only in the central region in the fluid flow conduit. 9. The heat transfer member for temperature detection extends radially into the fluid flow channel into the fluid flow channel, and a tip of an extending portion into the fluid flow channel is 9. The base according to claim 7, wherein the base of the extension portion located in the central region and located outside the central region is covered with a temperature detection-related heat insulating member. 10. Flow sensor as described. 10. A portion of the temperature detecting portion and the temperature detecting heat transfer member that is thermally connected to the temperature detecting portion is housed in a temperature detecting base portion having thermal insulation.
The flow sensor according to claim 9, wherein the temperature detection-related heat insulating member is formed by a part of the temperature detection base part. 11. The heat transfer member for temperature detection has a flat plate shape, and is arranged along the direction of the fluid passage in the fluid passage. The flow sensor according to any one of claims 10 to 10.