JPH11304560A - Flow rate sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a flow rate sensor comprising thin metal film detection elements arranged on a substrate in which flow rate can be measured stably through relatively simple arrangement by averaging current velocity distribution across the entire breadthwise region of a fluid channel. SOLUTION: The flow rate sensor 1 comprises a substrate 2, and upstream and downstream thin metal film detection elements 3, 4 arranged on a substrate. The upstream detection element 3 comprises a temperature detection element 6 and the downstream detection element 4 comprises a heating element 7. The substrate 2 being arranged with the heating element 7 has thin film downstream edge 2b. In order to measure the mass flow rate of a fluid by the flow rate sensor 1, the substrate 2 is arranged in a fluid channel 5 and heat is imparted to each element 6, 7 or the fluid and thermal variation dependent on the fluid passing through each element 6, 7 is detected by each element 6, 7. The substrate 2 straddles fluid channel 5 in the breadthwise direction and the elements 6, 7 are arranged on the substrate 2 substantially over the entire region of the fluid channel 5 in the breadthwise direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow sensor suitable for measuring a mass flow rate of a fluid. More particularly, the present invention relates to a flow sensor having a thin-film metal detection element on a substrate.

[0002]

2. Description of the Related Art Conventionally, as this type of flow sensor,
The basic principle is to measure the mass flow rate of a fluid by applying heat to the detection element on the substrate or the fluid passing through the detection element and detecting the heat change that changes depending on the mass flow rate of the fluid with the detection element. And Here, in order to increase the response speed of the detection element, anisotropic etching is performed on the substrate to form a thin film on the substrate corresponding to the detection element to reduce the heat capacity. JP-A-61-88532, JP-B-3-42
No. 616 discloses an example of this type of flow sensor.

The flow sensor disclosed in Japanese Patent Application Laid-Open No. 61-88532 has a substrate having a depression, a diaphragm with a throttle substantially covering the depression, and a detection element supported on the diaphragm. . This publication discloses that the mass flow rate of a fluid is measured using a single flow sensor having the above configuration. Therefore,
By arranging this flow sensor in the fluid passage,
The flow rate of fluid in the passage can be measured using the sensor.

The flow velocity distribution in the fluid passage, for example, in the width direction in the pipe, is generally non-uniform, and varies depending on the piping condition. For example,
On the downstream side of the curved pipe portion, the flow velocity distribution in the width direction in the pipe is complicatedly disturbed. Therefore, when the above flow rate sensor is used, the flow rate is measured only for a part of the non-uniform flow velocity in the pipeline, and it is difficult to measure an accurate flow rate for the entire pipeline. is there. In order to perform accurate flow rate measurement, it is necessary to adjust the flow velocity distribution in the pipeline, and for that purpose, a separate rectifying means must be provided. For example, as the rectification means, it is necessary to provide a long straight pipe section in the pipe line on the upstream side of the flow sensor, or to separately provide a special rectification device in the pipe line. However, providing these rectifying means requires a predetermined space, and even if the rectifying means is provided with sufficient space, the occurrence of pressure loss by the rectifying means is inevitable.

Therefore, the latter Japanese Patent Publication No. 3-42616
It is conceivable to use a flow sensor (flow meter) disclosed in Japanese Patent Application Laid-Open No. H10-209,878. The flowmeter includes a substrate including an elongate channel for transporting a fluid, at least two integral members extending across at least a portion of the elongate channel and formed in the substrate, and each of the integral members. Means for forming a temperature sensor disposed on the elongate channel and a fluid disposed between the temperature sensors in the elongate channel to provide a temperature difference between the temperature sensors as the fluid is transported through the elongate channel. And means for heating. This publication discloses that a plurality of flowmeters each having the above-described configuration are arranged in a line in a width direction in a pipeline, and the mass flow rate of a fluid is measured using the plurality of flowmeters. Therefore, by obtaining the average value of the measurement results obtained from the plural sets of flow meters, it becomes possible to measure the fluid flow rate in the pipeline without providing any special rectifying means.

[0006]

However, in the latter flow meter, it is necessary to average the measurement results of a plurality of sets of flow meters, and a special arithmetic circuit is required for the processing. Further, it is necessary to provide wiring on the substrate corresponding to each of a plurality of sets of flow meters, and there is a problem that the structure of the entire flow meter becomes extremely complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a flow sensor having a thin-film metal detecting element on a substrate, and a flow velocity distribution across the width of a fluid passage. An object of the present invention is to provide a flow sensor which can stably measure a fluid flow rate with a relatively simple configuration by averaging the values.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a detecting element made of a thin-film metal provided on a substrate and a detecting element on the substrate provided with the detecting element. Forming at least a part of a thin film, in order to measure a mass flow rate of the fluid, disposing a substrate in the fluid passage and applying heat to the sensing element or the fluid, and heat dependent on the fluid passing through the sensing element. In the flow sensor in which the change is detected by the detection element, the substrate is provided so as to span the width direction of the fluid passage, and the detection element is provided over substantially the entire area in the width direction of the fluid passage.

According to the configuration of the present invention, since the detecting element is provided over substantially the entire width direction of the fluid passage, the fluid flowing through the passage passes through the detecting element over substantially the entire flow width thereof. In addition, since at least a part of the portion of the substrate where the detection element is provided has a thin film shape, the heat capacity at that portion is small. Therefore, even if the flow velocity distribution of the fluid in the width direction of the fluid passage is non-uniform, the fluid-dependent heat change is detected by the detecting element with good responsiveness in a manner encompassing the non-uniform flow, and the mass of the fluid Used for flow rate measurement.

In order to achieve the above object, according to a second aspect of the present invention, in the configuration of the first aspect, the detecting element comprises an upstream detecting element positioned upstream with respect to the flow of the fluid; It is intended to include a downstream detection element located on the downstream side, the upstream detection element being a temperature detection element for detecting the temperature of the fluid, and the downstream detection element being a heating element for self-heating.

[0011] According to the above arrangement, the fluid-dependent heat change is detected with good responsiveness by the temperature detecting element and the heating element, and is used for measuring the mass flow rate of the fluid. Here, by causing the heating element located on the downstream side to generate heat by itself, a heat change depending on the fluid passing through the element is used for measuring the mass flow rate of the fluid. The temperature detected by the temperature detecting element located on the upstream side can be used for correcting the measured mass flow rate.

According to a third aspect of the present invention, in order to achieve the above object, in the configuration of the first aspect of the present invention, both the upstream detecting element and the downstream detecting element are different from the second aspect of the present invention. Is a heating element for causing self-heating.

According to the above configuration, the heat change depending on the fluid is detected by the two heating elements with good response, and is used for measuring the mass flow rate of the fluid. Here, it is assumed that both heating elements generate self-heating with the same amount of heat, and a fluid passing through each heating element causes a heat change in each heating element. At this time, the temperature of the heating element located on the upstream side decreases, but the temperature of the heating element located on the downstream side hardly decreases due to heat from the upstream side. Therefore, it is possible to measure the mass flow rate of the fluid based on the difference between these temperature drops, that is, the difference between the thermal changes.

According to a fourth aspect of the present invention, there is provided an upstream detecting element and a downstream side detecting element which are different from the second or third aspect of the present invention. It is intended that both of the detection elements are temperature detection elements.

According to the above configuration, even if the flow velocity distribution of the fluid in the width direction of the fluid passage is non-uniform, the fluid-dependent heat change includes both of the temperature detecting elements in a manner encompassing the non-uniform flow. Thus, it is detected with good responsiveness, and is used for measuring the mass flow rate of the fluid. Here, between the temperature detected by the temperature detection element located on the upstream side and the temperature detected by the temperature detection element located on the downstream side,
Some temperature difference occurs. Therefore, it becomes possible to measure the mass flow rate of the fluid based on these temperature differences.

According to a fifth aspect of the present invention, in order to achieve the above object, a substrate is provided between a heating element located on the upstream side and a heating element located on the downstream side. The purpose is to provide a slit in

According to the configuration of the present invention, since the heating element located on the upstream side and the heating element located on the downstream side are separated by the slit, the difference in heat change between the two heating elements is reduced. Amplified.

In order to achieve the above object, the present invention according to claim 6 is the invention according to claim 4 in which the temperature detecting element located between the upstream side and the temperature detecting element located downstream is provided. , A slit is provided in the substrate.

According to the configuration of the present invention, since the temperature detecting element located on the upstream side and the temperature detecting element located on the downstream side are separated by the slit, the temperature is detected by the two temperature detecting elements. The temperature difference is amplified.

According to a seventh aspect of the present invention, there is provided an image forming apparatus according to the sixth aspect of the present invention, wherein the temperature detecting element is located between the temperature detecting element located on the upstream side and the slit and on the downstream side. It is intended that a heater for heating each temperature detecting element is provided between each of the temperature detecting element and the slit.

According to the configuration of the present invention, since both the temperature detecting elements are heated, the sensitivity for detecting the temperature is enhanced. Here, the temperature detecting element located on the upstream side is strongly cooled by the fluid, and the temperature detecting element located on the downstream side is weakly cooled by receiving heat from the upstream side. Therefore, the temperature difference detected by the two temperature detecting elements is further amplified.

In order to achieve the above-mentioned object, the invention according to claim 8 is an embodiment of the invention according to one of claims 1 to 7 in which the reinforcing member is used to reinforce the thin film portion of the substrate. The purpose of the present invention is to provide a thin-film metal for use on a substrate along a detection element.

According to the above construction, in addition to the function of one of the first to seventh aspects of the present invention, the thin-film metal for reinforcement is provided along the detection element on the thin-film portion of the substrate, so that the detection can be performed. The vicinity of the element is reinforced without increasing the heat capacity, and the mechanical strength is increased.

According to a ninth aspect of the present invention, there is provided a method for manufacturing a flow sensor according to the first aspect of the present invention, wherein a first surface film is formed on both surfaces of a substrate. A second step of forming a detection element on the surface film, a third step of forming a protective film on the detection element and the surface film, and an anisotropic etching of the protection film and the surface film. A fourth step of opening the window; and a fifth step of engraving the substrate in a wedge shape corresponding to the window to form a V notch by performing anisotropic etching on the window.
The purpose is to manufacture a plurality of flow sensors divided from each other by dividing the substrate at the notch.

According to the above configuration, in the final step of manufacturing, since a plurality of flow sensors can be obtained by dividing the substrate at the V notch, it is necessary to use a dicing saw to divide each flow sensor. There is no possibility that the substrate is broken by the dicing saw.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] Hereinafter, a first embodiment of a flow sensor according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a flow sensor 1 according to this embodiment.
2 is a cross-sectional view taken along line AA of FIG. 1, and FIG. 3 is a cross-sectional view taken along line BB of FIG.
The flow sensor 1 is used in a semiconductor manufacturing apparatus or the like to measure a flow rate of, for example, a process gas or a purge gas. The flow sensor 1 includes a long silicon substrate 2 and detection elements 3 and 4 provided on the substrate 2 and made of thin-film metal. Flow sensor 1
Arranges the substrate 2 in a fluid passage 5 such as a process gas or the like, applies heat to each of the detection elements 3 and 4 or the fluid, and passes through the detection elements 3 and 4 to measure the mass flow rate of the fluid. The thermal change depending on the fluid is detected by the detecting elements 3 and 4.

The flow sensor 1 has a substrate 2 whose fluid path 5
In the width direction. Here, each detection element includes an upstream detection element 3 provided at the upstream edge 2a of the substrate 2 in the flow direction of the fluid, and a downstream detection element 4 provided at the downstream edge 2b. In this embodiment, the upstream detection element 3 is constituted by a temperature detection element 6 for detecting the temperature of the fluid, and the downstream detection element 4 is constituted by a heating element 7 for self-heating. As shown in FIGS. 1 to 3, the portion where the heating element 7 is provided on the downstream side edge 2 b of the substrate 2 forms a thin film portion 8 formed in a thin film shape.

As shown in FIG. 1, each of the elements 6 and 7 has a substantially uniform rectangular wave shape over substantially the entire width of the fluid passage 5 in the width direction of the fluid passage 5 on the substrate 2. It is provided on the substrate 2 in a pattern. Each element 6, 7 has electrode portions 6a, 7a at both ends thereof.
Respectively. In each of the elements 6 and 7, the rectangular wave-shaped detection portion exposed to the fluid passage 5 is formed of a thin line, and the electrode portions 6a and 7 are formed.
a forms a wide band. Each of the elements 6, 7 is formed of nickel or platinum. The thin film portion 8 of the substrate 2 is provided with a reinforcing rib 8a having a thickness equivalent to that of a portion other than the thin film portion 8 at an intermediate portion in the longitudinal direction. The heat generating element 7 is formed by dividing a rectangular wave-shaped pattern into two parts at a portion corresponding to the rib 8a and connecting them by a wide band-shaped pattern.

As shown in FIG. 4 on an enlarged scale, at the downstream edge 2b of the substrate 2, a reinforcing pattern 9 as a thin metal film for reinforcing is used to reinforce the thin film portion 8 thereof. Along the substrate 2. This reinforcing pattern 9 is formed of the same material as the heating element 7.

FIGS. 5 to 9 show a method of manufacturing the flow sensor 1. This manufacturing method is for manufacturing a plurality of flow sensors 1 at the same time. First, in a first step shown in FIG. 5, a surface film 10 made of silicon oxide or silicon nitride is formed on both surfaces of a silicon substrate 2. Here, the substrate 2 has a thickness of “0.4 mm”,
0 has a thickness of “0.5 to 1.0 μm”.

Next, in a second step shown in FIG. 6, nickel or platinum is deposited on the surface film 10 to form the elements 6, 7 and the reinforcing pattern 9. Here, each element 6, 7 and the reinforcing pattern 9 are formed by the number of the plurality of flow sensors 1. Each element 6,7
The reinforcing pattern 9 has a thickness of “0.3 to 1.0 μm”.

Next, in a third step shown in FIG. 7, a protective film 11 made of silicon oxide or silicon nitride is formed on each of the elements 6, 7 and the reinforcing pattern 9. This protective film 11 has the same thickness as the surface film 10.

Next, in a fourth step shown in FIG. 8, a window 12 for anisotropic etching is formed on the surface film 10 and the protective film 11.
Open. These windows 12 are for separating the individual flow sensors 1 from each other.

Then, in a fifth step shown in FIG.
Each window 12 is subjected to anisotropic etching. The etching solution used here can change the etching speed depending on the difference in silicon crystallinity of the substrate 2. As a result, the substrate 2 is engraved in a wedge shape corresponding to each window 12 as shown in the figure, and a V notch 13 for dividing each flow sensor 1 is formed. Then, V notch 1
By dividing the substrate 2 at the boundary 3, a plurality of flow sensors 1 divided from each other are obtained.

FIG. 10 shows an electrical configuration of the flow sensor 1. The temperature detecting element 6 and the heating element 7 are respectively connected in parallel to a power supply via a predetermined resistor 20, and supplied with a power supply voltage Vcc. Output terminals of the elements 6 and 7 are connected via an amplifier (AMP) 14. The amplifier 14 is connected to the arithmetic circuit 15. Then, a change in voltage (current) in each of the elements 6 and 7 is output as a detection signal, amplified by the amplifier 14, processed by the arithmetic circuit 15, and output. This output signal indicates the mass flow rate of the fluid.

FIG. 11 shows a flow rate-output characteristic of the flow sensor 1. From this graph, it can be seen that the rate of change of the sensor output of the flow rate sensor 1 is large with respect to the change of the gas flow rate in the small flow rate range, and the rate of change of the sensor output is small with respect to the change of the gas flow rate of the medium and large flow rate ranges.

As described above, according to the configuration of the flow sensor 1 of this embodiment, each element 6, 7 is connected to the fluid passage 5
Is provided on the substrate 2 with a uniform pattern over substantially the entire area in the width direction. Therefore, the fluid flowing through the fluid passage 5 passes through the elements 6 and 7 over substantially the entire flow width thereof. Moreover, in the substrate 2, in particular, the heating element 7
Is a thin film portion 8, the heat capacity of the thin film portion 8 is smaller than that of the other portions.

Therefore, even if the flow velocity distribution of the fluid in the width direction of the fluid passage 5 is non-uniform, the fluid-dependent heat change can be performed with good responsiveness in a manner encompassing the non-uniform flow. And the heating element 7 to detect the mass flow rate of the fluid. Here, by causing the heating element 7 located at the downstream side edge portion 2b to self-heat, a heat change depending on the fluid passing through the element 7 is used for measuring the mass flow rate of the fluid. In particular, since the heat capacity of the thin film portion 8 corresponding to the heating element 7 is small, the response speed of the flow rate measurement by the element 7 can be increased. On the other hand, the temperature of the fluid detected by the temperature detection element 6 located at the upstream side edge 2a is used for correcting the measured mass flow rate. As a result, according to the flow rate sensor 1, the mass flow rate of the fluid can be stably measured with a relatively simple configuration by averaging the flow velocity distribution in the entire width direction of the fluid passage 5. Become. Moreover, by correcting the mass flow rate based on the fluid temperature detected by the temperature detection element 6, the measurement accuracy of the mass flow rate can be improved.

In particular, in the above-mentioned conventional flow meter,
In order to average the measurement results of multiple sets of flow meters,
A special arithmetic circuit was required. On the other hand, in the flow sensor 1 of the present embodiment, there is no need to provide an arithmetic circuit for averaging the detection results of the elements 6 and 7. Further, in the conventional flowmeter, it is necessary to provide wiring on the substrate corresponding to each of the plural sets of flowmeters, and the structure of the entire flowmeter becomes extremely complicated. On the other hand, in the flow sensor 1, wiring may be simply provided on the substrate 2 corresponding to the two elements 6 and 7, and the structure and manufacturing including the wiring are extremely simple. In addition, stable measurement of the mass flow rate of the fluid can be realized regardless of the difference in the flow velocity distribution of the fluid.

In this embodiment, a reinforcing pattern 9 made of a thin film metal is provided on the thin film portion 8 of the substrate 2 along the heating element 7. Therefore, the portion near the heating element 7 is reinforced by the reinforcing pattern 9 without increasing the heat capacity,
The mechanical strength is increased. As a result, the durability of the detection unit can be increased without impairing the responsiveness of the flow measurement at all.

According to the method of manufacturing the flow sensor 1 of this embodiment, in the final step, a plurality of flow sensors 1 are obtained by dividing the substrate 2 with the V notch 13 as a boundary. Therefore, it is not necessary to use a dicing saw to divide the individual flow rate sensors 1, and there is no possibility that the substrate 2 is broken by the dicing saw.
In particular, in the substrate 2 of this embodiment, the thin film portion 8
By dividing the notch 13 at the boundary, division can be performed easily and safely.

[Second Embodiment] Next, a second embodiment of the flow sensor according to the present invention will be described with reference to the drawings. In the following embodiments including this embodiment, the same members as those of the flow sensor 1 according to the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. Shall be explained.

FIG. 12 is a plan view of the flow sensor 20 according to this embodiment, and FIG. 13 is a cross-sectional view taken along line AA of FIG. In this embodiment, the temperature detecting element 6
The second embodiment differs from the first embodiment in that a thin film portion 8 including a rib 8a and a reinforcing pattern 9 are provided for both the heating element 7 and the heating element 7.

Accordingly, the flow rate sensor 20 of this embodiment
Accordingly, the same operation and effect as those of the first embodiment can be obtained. In addition, in this embodiment, also in the temperature detecting element 6, since the heat capacity of the thin film portion 8 becomes small, the response speed of temperature measurement by the element 6 can be increased. Similarly, since the thin film portion 8 corresponding to the temperature detecting element 6 is reinforced by the reinforcing pattern 9 and the mechanical strength is enhanced, the durability of the detecting portion can be improved without impairing the responsiveness for temperature measurement. Can be enhanced.

[Third Embodiment] Next, a third embodiment of a flow sensor according to the present invention will be described with reference to the drawings.

FIG. 14 is a plan view of a flow sensor 30 according to this embodiment, and FIG. 15 is a cross-sectional view taken along line AA of FIG. In this embodiment, both the upstream and downstream detection elements are formed by the heating elements 7 having the same pattern.
These are arranged near the center of the substrate 2, and a slit 16 is provided in the substrate 2 between the heating element 7 located on the upstream side and the heating element 7 located on the downstream side. The second embodiment differs from the first and second embodiments in that a reinforcing pattern 9 is provided between the first and second embodiments.

Therefore, the flow rate sensor 30 of this embodiment
Accordingly, the same operation and effect as those of the first embodiment can be obtained. In particular, according to the configuration of this embodiment, the heat change depending on the fluid is detected with high responsiveness by the two heating elements 7 on the upstream side and the downstream side, and is used for measuring the mass flow rate of the fluid. . Here, it is assumed that the two heating elements 7 self-heat with the same amount of heat, and the fluid passing through each heating element 7 causes a heat change in each heating element 7. At this time, the temperature of the heating element 7 on the upstream side decreases, but the temperature of the heating element 7 on the downstream side hardly decreases due to heat from the upstream side. Therefore,
It is possible to measure the mass flow rate of the fluid based on the difference between these temperature drops, that is, the difference between the thermal changes. Specifically, for example, an electric circuit according to FIG. 10 is applied to the flow rate sensor 30, and a bridge circuit is provided in the arithmetic circuit. Then, a difference between signal values output from the respective heating elements 7 is processed by a bridge circuit,
It is possible to measure the mass flow rate of the fluid.

In particular, in this embodiment, the gap between the heating element 7 on the upstream side and the heating element 7 on the downstream side is divided by the slit 16. For this reason, a difference in heat change generated between the two heating elements 7 is amplified. As a result, the measurement accuracy of the mass flow rate performed based on the difference in the thermal change can be improved.

[Fourth Embodiment] Next, a fourth embodiment of a flow sensor according to the present invention will be described with reference to the drawings.

FIG. 16 is a plan view of a flow sensor 40 according to this embodiment, and FIG. 17 is a sectional view taken along line AA of FIG. In this embodiment, both the upstream and downstream detection elements are temperature detection elements 6 made of the same pattern, and between the upstream temperature detection element 6 and the slit 16 and the downstream temperature detection element 6. The third embodiment is different from the third embodiment in that an electric heater 17 for heating each temperature detecting element 6 is provided between each of the first and second slits 16. In this embodiment, each temperature detecting element 6 is heated to 100 to 150 ° C. by the electric heater 17. In addition, in the electric circuit of this embodiment, FIG.
As shown in FIG. 8, a constant current is supplied to an electric heater 17 provided corresponding to each temperature detecting element 6.
The configuration is different from that of the electric circuit of FIG.

Therefore, the flow rate sensor 40 of this embodiment
Accordingly, the same operation and effect as those of the third embodiment can be obtained. In particular, according to the configuration of this embodiment, the fluid-dependent heat change is detected with good responsiveness by the two temperature detection elements 6 on the upstream side and the downstream side, and is used for measuring the mass flow rate of the fluid. Become. Here, a slight temperature difference occurs between the temperatures detected by the two temperature detecting elements 6. Therefore, it becomes possible to measure the mass flow rate of the fluid based on these temperature differences.

Also in this embodiment, since the space between the two temperature detecting elements 6 is divided by the slit 16, the third
Similarly to the embodiment, the difference between the temperatures detected by the respective temperature detecting elements 6 is amplified, whereby the accuracy of measuring the mass flow rate of the fluid can be improved. In particular, in this embodiment, since each of the temperature detecting elements 6 is heated by the electric heater 17, the sensitivity for temperature detection by each of the temperature detecting elements 6 is increased. Here, the heated temperature detecting element 6 on the upstream side is strongly cooled by the fluid, and the heated temperature detecting element 6 on the downstream side is weakly cooled by receiving heat from the upstream side. Therefore, the temperature difference detected by the two temperature detecting elements 6 is further amplified by the cooperation of the slit 16 and the electric heater 17, and as a result, the measurement accuracy of the mass flow rate of the fluid is further improved. Will be able to do it.

The present invention is not limited to the above embodiments, but can be implemented as follows without departing from the spirit of the invention. In each of the following embodiments, the same basic functions and effects as those of the above embodiments can be obtained.

(1) In each of the above embodiments, the detection elements are configured as a set of the upstream and downstream detection elements 3 and 4 provided on the substrate 2. It may be provided.

(2) In the first and second embodiments, the reinforcing pattern 9 is provided on the substrate 2 respectively, but this may be omitted.

(3) In the third embodiment, the substrate 2
Although the reinforcing pattern 9 and the slit 16 are provided in the first embodiment, at least one of the reinforcing pattern 9 and the slit 16 may be omitted.

(4) In the fourth embodiment, the substrate 2
Although the reinforcing pattern 9, the slit 16 and the electric heater 17 are provided in the first embodiment, at least one of the reinforcing pattern 9, the slit 16 and the electric heater 17 may be omitted.

[0059]

According to the first aspect of the present invention, there is provided a flow sensor having a thin-film metal detecting element on a substrate.
The substrate is provided so as to span the width direction of the fluid passage, and the detection element is provided over substantially the entire area in the width direction of the fluid passage. Therefore, even if the flow velocity distribution of the fluid in the width direction of the fluid passage is non-uniform, the fluid-dependent heat change is detected by the detecting element with good responsiveness in a manner encompassing the non-uniform flow, and the fluid mass Used for flow rate measurement.
As a result, it is possible to stably measure the fluid flow rate with a relatively simple configuration by averaging the flow velocity distribution over the entire width direction of the fluid passage.

According to the invention described in claim 2, according to claim 1
In the configuration of the present invention, the upstream detection element is a temperature detection element, and the downstream detection element is a heating element. Therefore,
Fluid-dependent heat change is detected with good response by the temperature detection element and the heating element, and is used for measuring the mass flow rate of the fluid.The temperature detected by the temperature detection element is corrected for the mass flow rate measured by the heating element. It becomes possible to offer.
As a result, in addition to the effect of the first aspect, the measurement accuracy of the mass flow rate can be improved.

According to the invention described in claim 3, according to claim 1
In the configuration of the present invention, both the upstream and downstream detection elements are heat generating elements. Therefore, a difference in temperature drop (difference in heat change) occurs between the upstream and downstream heating elements, and it is possible to measure the mass flow rate of the fluid based on the difference. As a result, an effect equivalent to that of the first aspect can be obtained.

According to the invention set forth in claim 4, according to claim 1,
In the above configuration, both the upstream and downstream detection elements are temperature detection elements. Therefore, a difference in temperature drop occurs between the temperatures detected by the upstream and downstream temperature detection elements, and it is possible to measure the mass flow rate of the fluid based on the difference. As a result, an effect equivalent to that of the first aspect can be obtained.

According to the invention described in claim 5, according to claim 3
In the configuration of the invention, a slit is provided in the substrate between the heating element on the upstream side and the heating element on the downstream side. Therefore,
Since both heating elements are separated by slits,
The difference in thermal change between the two heating elements is amplified. As a result,
In addition to the effect of the third aspect of the present invention, it is possible to improve the measurement accuracy of the mass flow rate performed based on the difference in thermal change.

According to the invention set forth in claim 6, according to claim 4,
In the configuration of the invention, a slit is provided in the substrate between the upstream and downstream temperature detecting elements. Therefore, since the gap between the two temperature detecting elements is divided by the slit, the difference between the temperatures detected by the two temperature detecting elements is amplified. As a result, in addition to the effect of the invention of claim 4, the accuracy of the measurement of the mass flow rate performed based on the detected temperature difference can be improved.

According to the invention of claim 7, according to claim 6,
In the configuration of the invention, heaters for heating the respective temperature detecting elements are provided between the temperature detecting element on the upstream side and the slit and between the temperature detecting element on the downstream side and the slit, respectively. Therefore, since both the temperature detecting elements are heated, the sensitivity for detecting the temperature is increased, and the difference between the temperatures detected by the two temperature detecting elements is further amplified. As a result, the measurement accuracy of the mass flow rate can be further improved with respect to the effect of the sixth aspect.

According to the invention of claim 8, according to claim 1,
In one embodiment of the present invention, a thin metal film for reinforcement is provided along a detecting element in a thin film portion of the substrate. Therefore, since the thin-film metal for reinforcement is provided on the thin-film portion of the substrate, the portion near the detection element is reinforced without increasing the heat capacity, and the mechanical strength is increased. As a result, in addition to the effects of one of the first to seventh aspects of the present invention, the durability of the detection element portion for detecting the flow rate can be increased.

According to the ninth aspect of the present invention, the first aspect is provided.
The protective film is formed on the detection element and the surface film on the substrate, a window is opened in the protective film and the surface film, and the window is anisotropically etched. By applying, a V-notch is formed on the substrate corresponding to the window, and the substrate is split at the V-notch, whereby a plurality of flow sensors divided from each other are manufactured. Therefore, there is no need to use a dicing saw to divide the individual flow sensors in the final step of manufacturing, and there is no risk of breaking the substrate. As a result, there is an effect that the substrate can be easily and safely divided to obtain a plurality of flow sensors.

[Brief description of the drawings]

FIG. 1 is a plan view showing a flow sensor according to a first embodiment.

FIG. 2 is a sectional view taken along the line AA in FIG.

FIG. 3 is a cross-sectional view along the line BB of FIG. 1;

FIG. 4 is an enlarged plan view showing a main part of the flow sensor.

FIG. 5 is also a flow sensor manufacturing method (first step).
FIG.

FIG. 6 is also a flow sensor manufacturing method (second step).
FIG.

FIG. 7 is also a flow sensor manufacturing method (third step)
FIG.

FIG. 8 is also a flow sensor manufacturing method (fourth step).
FIG.

FIG. 9 is also a flow sensor manufacturing method (fifth step).
FIG.

FIG. 10 is a circuit diagram showing an electrical configuration according to the flow sensor.

FIG. 11 is a graph showing a flow rate-output characteristic of the flow rate sensor.

FIG. 12 is a plan view showing a flow sensor according to the second embodiment.

FIG. 13 is a cross-sectional view along the line AA in FIG.

FIG. 14 is a plan view showing a flow sensor according to the third embodiment.

FIG. 15 is a cross-sectional view along the line AA in FIG.

FIG. 16 is a plan view showing a flow sensor according to a fourth embodiment.

FIG. 17 is a sectional view taken along the line AA of FIG. 16;

FIG. 18 is a circuit diagram showing an electrical configuration of the flow sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flow rate sensor 2 Substrate 3 Upstream side detection element 4 Downstream side detection element 5 Fluid passage 6 Temperature detection element 7 Heating element 8 Thin film part 9 Reinforcement pattern 16 Slit 17 Electric heater 20 Flow rate sensor 30 Flow rate sensor 40 Flow rate sensor

Claims (9)

[Claims] 1. A method for measuring a mass flow rate of a fluid, comprising: a detecting element made of a thin film metal provided on a substrate; and forming at least a part of a portion of the substrate on which the detecting element is provided in a thin film form. For this, in the flow sensor wherein the substrate is disposed in a fluid passage, heat is applied to the detection element or the fluid, and a heat change depending on the fluid passing through the detection element is detected by the detection element. A flow sensor, wherein a substrate is provided to extend in the width direction of the fluid passage, and the detection element is provided over substantially the entire area in the width direction of the fluid passage. 2. The flow sensor according to claim 1, wherein the detection element includes an upstream detection element positioned upstream and a downstream detection element positioned downstream with respect to the flow of the fluid, A flow sensor, wherein the upstream detection element is a temperature detection element for detecting the temperature of the fluid, and the downstream detection element is a heating element for self-heating. 3. The flow sensor according to claim 1, wherein the detection element includes an upstream detection element positioned upstream with respect to the flow of the fluid and a downstream detection element positioned downstream with respect to the flow of the fluid. Both the upstream detection element and the downstream detection element,
A flow sensor comprising a heating element for self-heating. 4. The flow sensor according to claim 1, wherein the detection element includes an upstream detection element positioned upstream with respect to the flow of the fluid and a downstream detection element positioned downstream with respect to the flow of the fluid. A flow sensor, wherein both the upstream detection element and the downstream detection element are temperature detection elements. 5. The flow rate sensor according to claim 3, wherein a slit is provided in the substrate between the heating element located on the upstream side and the heating element located on the downstream side. . 6. The flow sensor according to claim 4, wherein a slit is provided in the substrate between the temperature detection element located on the upstream side and the temperature detection element located on the downstream side. Flow sensor. 7. The flow rate sensor according to claim 6, wherein the flow rate sensor is provided between the temperature detection element located on the upstream side and the slit, and between the temperature detection element located on the downstream side and the slit. And a heater for heating each of the temperature detecting elements. 8. The flow sensor according to claim 1, wherein a reinforcing thin film metal is provided along the detection element to reinforce a thin film portion of the substrate. A flow sensor characterized in that the flow sensor is provided in. 9. The manufacturing method for a flow sensor according to claim 1, wherein: a first step of forming a surface film on both surfaces of the substrate; and forming the detection element on the surface film. A second step, a third step of forming a protective film on the detection element and the surface film, a fourth step of opening a window for anisotropic etching in the protective film and the surface film, A fifth step of engraving the substrate in a wedge shape corresponding to the window to form a V notch by performing anisotropic etching on the window, wherein the V notch is formed as a boundary. A method for manufacturing a flow sensor, comprising manufacturing a plurality of flow sensors divided from each other by breaking a substrate.