JPH11281445A - Flow rate detecting element and flow sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow rate detecting element or a flow rate sensor wherein the flowing direction of fluids is detected and quick responsiveness is provided. SOLUTION: In a flow rate detecting element or a flow rate sensor having this flow rate detecting element, an insulating supporting film 2 is formed in the surface of a silicon substrate, first and second heat resistors 4 and 5 made of thermo-sensitive resisting films are formed on the supporting film 2, and insulating protective films are formed on the heat resistors 4 and 5. The silicon substrate in the lower part of at least a portion of an area where the heat resistors 4 and 5 are formed is partially eliminated to form a diaphragm structure, the two heat resistors 4 and 5 are arranged side by side in the flowing direction of fluids to be measured on the insulating supporting film 2 and, thus, the flowing direction of the fluids is detected and quick responsiveness is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate detecting element for measuring a flow rate or a flow rate of a fluid based on a heat transfer phenomenon from a heating element or a portion heated by the heating element to the fluid, and a flow rate detecting element. The present invention relates to a flow sensor used, for example, for measuring an intake air amount of an internal combustion engine.

[0002]

2. Description of the Related Art The heat transfer amount is determined by utilizing a substantially unique functional relationship established between the flow rate or flow rate of a fluid and the heat transfer amount from a heating element disposed in the fluid to the fluid. 2. Description of the Related Art A heat-sensitive flow rate detecting element that detects a flow rate or a flow rate of a fluid based on the flow rate, or a flow rate sensor using the flow rate detecting element has been widely used for detecting an intake air amount of an internal combustion engine.

FIGS. 13 and 14 each show a conventional hot-wire probe (one type of a heat-sensitive flow rate detecting element) disclosed in, for example, Japanese Patent Publication No. 2-50406 for detecting an intake air amount of an internal combustion engine. ) And its XIV-X
FIG. 4 is a sectional view taken along line IV. 13 and FIG.
Is a heating resistor on the upstream side in the air flow direction,
2 is a heating resistor on the downstream side in the air flow direction,
Reference numeral 23 denotes a coating thin film, and reference numeral 24 denotes a cylindrical or hollow cylindrical bobbin.

In such a conventional hot wire probe, the heating current applied to the heating resistors 21 and 22 is usually higher than the air temperature detected by the temperature compensating resistor by a control circuit (not shown). The temperature is controlled to be constant. The heat generated by the heat generating resistors 21 and 22 is hardly transmitted to the temperature compensating resistor, so that the temperature of the temperature compensating resistor is substantially equal to the temperature of the air.

Thus, in this heat ray probe, when air flows in the direction of arrow A in FIG. 14, both heating resistors 21 and 22 are cooled by air, but the heating resistor 22 on the downstream side is cooled. Is the heating resistor 21 on the upstream side
Not as cool. For this reason, both heating resistors 21 and 2
The direction of the air flow can be detected based on the difference in the amount of heat dissipated between the two. In addition, by calculating the amount of heat dissipated by both the heating resistors 21 and 22, the flow velocity or the flow rate of the air can be measured. The same applies to the case where the air flows in the direction of arrow B in FIG.

[0006]

In the case of this type of hot-wire probe, when the flow rate or the flow velocity of the measurement fluid changes, the temperature change of the heating resistors 21 and 22 causes the heating resistors 21 and 22 themselves and the heating resistors 21 and 22 to change. There is a time delay determined by the thermal conductivity and heat capacity of the coating thin film 23 and the cylindrical or hollow cylindrical bobbin 24. In particular, when the bobbin 24 has a cylindrical shape, even if a ceramic having a relatively high thermal conductivity is used, the heat capacity thereof becomes considerably large, and the change in the speed or flow rate of the fluid per unit time is large. It is difficult to accurately detect the instantaneous flow rate and flow velocity. That is, there is a problem that the high-speed response required as a flow sensor cannot be satisfied. Furthermore, since the heat capacity of the entire hot wire probe is large,
There is also a problem that the power consumption increases.

[0007] Such a hot-wire probe is usually
After the film-shaped heating resistors 21 and 22 are attached to a cylindrical or hollow cylindrical bobbin 24 made of a material such as ceramic, the outer peripheral surface is coated with a thin film 23 or the like. . In this manufacturing process, the positions where the film-shaped heat generating resistors 21 and 22 are to be attached must be positioned with high precision. When a hollow cylindrical bobbin 24 is used, it is difficult to handle the bobbin 24. Since the coating of the thin film 23 on the outer peripheral surface of the substrate must use a special coating method, the process becomes very complicated, and it is difficult to manufacture the hot wire probe at low cost.

The present invention has been made to solve the above-mentioned conventional problems, and can detect the flow direction of a fluid, has low power consumption, has high-speed response, and has a low cost. The object of the present invention is to obtain a flow rate detecting element or a flow rate sensor which can be manufactured by the method described above.

[0009]

Means for Solving the Problems A flow detecting element according to a first aspect of the present invention, which has been made to solve the above-mentioned problems, comprises: (a) a silicon substrate (a flat substrate); and (b) a silicon substrate. An insulating support film formed on the surface of (c);
A heating resistor formed of a heat-sensitive resistance film formed on the support film and supported by the support film; and (d) an insulating protective film formed on the heating resistor and protecting the heating resistor. (E) the silicon substrate is partially removed below at least a part of the region where the heating resistor is formed, and (f) heat from the portion heated by the heating resistor to the measurement fluid In a thermosensitive flow rate detecting element adapted to measure a flow rate or a flow rate of the measurement fluid based on a transmission phenomenon, (g) a heating resistor is arranged on the support film in a direction of the flow of the measurement fluid. It is characterized by having two generated heating resistors.

In the flow rate detecting element according to the first aspect, an insulating support film is formed on the surface of the silicon substrate, and a heat generating resistor portion made of a heat sensitive resistance film is formed on the support film. An insulating protective film is formed on the resistance portion, the silicon substrate under at least a part of the region where the heating resistor is formed is partially removed, and the heating resistor is formed of the supporting film. Since two heating resistors arranged in the direction of the flow of the measurement fluid are provided on the upper side, the direction of the flow of the fluid can be detected, and the heat capacity of the entire flow rate detection element becomes extremely small. For this reason, even when the speed or the flow rate of the fluid changes greatly per unit time,
Instantaneous flow rate and flow velocity can be accurately detected. That is, it is possible to obtain a flow rate detection element capable of detecting the direction of the flow of the fluid and having high-speed response. Further, since the heat capacity of the entire flow detecting element becomes extremely small, power consumption can be significantly reduced. Further, since the flow rate detecting element can be manufactured in the same manufacturing process as the semiconductor process, it can be manufactured at low cost.

[0011] The flow rate detecting element according to a second aspect of the present invention is the flow rate detecting element according to the first aspect, wherein the silicon substrate is partially formed from a surface opposite to the surface on which the support film is disposed. (A diaphragm structure). In this flow rate detection element, a diaphragm in which a silicon substrate including at least a part of a region where a heating resistor is formed is partially removed from a surface opposite to a surface on which a supporting film and a heating resistor are formed is provided. With this structure, heat release due to conduction through the silicon substrate is reduced, and the flow of fluid is not disturbed on the surface where the heating resistor is formed. Can be detected.

[0012] A flow detecting element according to a third aspect of the present invention is the flow rate detecting element according to the first aspect, wherein the two heating resistors are arranged at a distance of less than 300 μm in the flow direction of the measurement fluid. It is characterized by having. In this flow rate detecting element, the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film are arranged at a distance of less than 300 μm in the direction of the flow of the measurement fluid. It is possible to obtain a sufficient difference between the output of the heating resistor on the upstream side and the output of the heating resistor on the downstream side in the flow direction of the fluid, and accurately detect the instantaneous flow rate and the flow velocity even in a large flow rate region. Can be.

A flow rate detecting element according to a fourth aspect of the present invention is the flow rate detecting element according to the first aspect, wherein each of the two heating resistors has a shape which is bilaterally symmetrical (linearly symmetric) to each other. It is characterized by having. In this flow rate detecting element, since the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film have a symmetrical shape, the difference between the resistance values of the two heating resistors is minimized. The error added to the difference between the output of the heating resistor on the upstream side and the output of the heating resistor on the downstream side resulting from the difference between the resistance values of the two heating resistors can be eliminated, and the instantaneous flow rate and the flow velocity can be more accurate. Can be detected.

[0014] A flow detecting element according to a fifth aspect of the present invention is the flow rate detecting element according to the first aspect, wherein the first end and the second end of each of the two heating resistors are provided. , Are arranged on opposite sides (opposite sides) with respect to a direction orthogonal to the flow direction of the measurement fluid. In this flow rate detecting element, with respect to the two heat generating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film, each end of the heat generation resistor is related to the direction orthogonal to the direction of the flow of the measurement fluid. Since they are arranged on opposite sides, the width of the wiring portion (lead line) can be made wider than the width of the heating resistor, and the electrode area can be made wider. For this reason, the reliability of the flow rate detecting element is improved, and further, heat generation in the wiring portion is prevented, and the influence of the heat generation can be eliminated. Thereby, the instantaneous flow rate and the flow velocity can be detected more accurately.

A flow detecting element according to a sixth aspect of the present invention is the flow rate detecting element according to the fifth aspect, wherein the first end of each of the two heating resistors is connected to an external circuit. The connection part (electrode) and the second connection part (electrode) for connecting the second end to an external circuit are arranged on the same side in a direction orthogonal to the direction of the flow of the measurement fluid. It is assumed that. In this flow rate detecting element, the respective ends of the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film are arranged on opposite sides with respect to the direction orthogonal to the flow direction of the measurement fluid. In addition, since the connection portion with the external circuit is arranged on the same side, the connection between the flow rate detecting element and the external circuit is facilitated, and the manufacturing process is simplified.

A flow rate sensor according to a seventh aspect of the present invention is adapted to measure the flow rate of a measurement fluid using the flow rate detecting element according to any one of the first to sixth aspects. It is a feature. That is, a flow rate sensor is formed using the flow rate detection element according to any one of the first to sixth aspects. According to this flow sensor, the first
The same operation as in the case of the flow rate detecting element according to the sixth to sixth aspects is obtained.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 1 and 2
It is an elevation sectional view and a plan view of the flow rate detecting element according to Embodiment 1 of the present invention, respectively. FIG. 3 is a partial plan view showing, in an enlarged manner, a heating resistor portion made of a heat-sensitive resistor film in FIG. In FIG. 1 to FIG. 3, reference numeral 1 denotes a flat substrate or silicon substrate made of, for example, silicon having a thickness of about 0.4 mm.
For example, an insulating support film 2 made of silicon nitride or the like having a thickness of 1 μm is formed using a sputtering method, a CVD method, or the like. Then, on the support film 2, a first heating resistor 4 and a second heating resistor 5 each made of a heat-sensitive resistor film of, for example, 0.2 μm thick made of platinum or the like are formed by vapor deposition or sputtering. ing. These heating resistors 4 and 5 are respectively
Patterning is performed using a photolithography method, a wet etching method, a dry etching method, or the like, thereby forming a current path. Here, the first heating resistor 4 and the second heating resistor 5 are arranged side by side in the direction indicated by the arrow Y in FIG. 2, that is, in the direction of the flow of the measurement fluid in the normal state. Then, the first heating resistor 4 and the second heating resistor 5
They are arranged at a distance of 10 μm in the flow direction of the measurement fluid (the direction of arrow Y). Further, an insulating protective film 3 made of, for example, silicon nitride having a thickness of 1 μm is formed on both the heating resistors 4 and 5 and the later-described comparative resistor 10 or the support film 2 by a sputtering method, a CVD method, or the like. ing.

Reference numerals 6a to 6f denote electrodes (connecting portions) for electrically connecting the respective portions of the flow rate detecting element to an external circuit or the like. In these portions, protective films are provided for making electrical connection. 3 have been removed. Here, the first heating resistor 4 is electrically connected to the electrode 6d via a relatively wide wiring portion 4a (lead line), while being electrically connected to the electrode 6d via a relatively wide wiring portion 4b (lead line). Is electrically connected to the electrode 6c. The second heating resistor 5 is electrically connected to the electrode 6a via a relatively wide wiring portion 5a (lead line), while being electrically connected to the electrode 6a via a relatively wide wiring portion 5b (lead line). It is electrically connected to the electrode 6b.

Further, an etching hole 8 is formed on the back surface protective film 7 formed on the surface (back surface) of the silicon substrate 1 opposite to the surface on which the support film 2 is formed by using a photolithography method or the like. After the formation, a portion of the silicon substrate 1 is removed by performing, for example, alkali etching or the like, thereby forming the diaphragm 9 (diaphragm portion).

In this flow rate detecting element, both the heating resistors 4 and 5 are controlled by a control circuit (not shown) so as to have a predetermined average temperature (constant temperature). The average temperature is, for example, two times lower than the ambient temperature measured by the comparative resistance 10 provided on the upstream side in the fluid flow direction outside the region where the diaphragm 9 is formed.
The temperature is set higher by 00 ° C. The first heating resistor 4 is arranged on the upstream side in the flow direction of the fluid, and the second heating resistor 5 is arranged on the downstream side. Here, when the flow of the fluid occurs, both the heating resistors 4 and 5 decrease in temperature in accordance with the flow rate of the fluid, but the average temperature of the first heating resistor 4 on the upstream side decreases on the downstream side. Is lower than the average temperature of the second heating resistor 5. This is because the fluid heated when passing through the first heating resistor 4 on the upstream side reaches the first heating resistor 5 on the downstream side. Therefore, a predetermined voltage is applied to each of the first heating resistor 4 and the second heating resistor 5 by a circuit (not shown).
5 is detected, or the first heating resistor 4 and the second
A terminal current is detected by applying a constant current to each of the heating resistors 5 or the first heating resistor 4 and the second heating resistor 5 are detected.
The flow rate or flow velocity of the fluid can be accurately measured by measuring and comparing the amounts of the temperatures of the first heating resistor 4 and the second heating resistor 5 by, for example, detecting the power consumption of the fluid. .

In the first embodiment, since the silicon substrate 1 is used as the flat base material, the thickness of the base material can be set (selected) very thin. Furthermore, since a semiconductor process, particularly a precise etching technique, can be applied to the manufacture of the flow rate detecting element, the productivity can be increased, and the cost of the flow rate detecting element can be reduced. Further, since the supporting film 2 and the protective film 3 are formed of an insulating thin film made of silicon nitride or the like so that the total thickness thereof is 2 μm, the film thickness becomes extremely small and the heat is reduced. Good insulation properties. For this reason, the heat loss of the heating resistors 4 and 5 in the diaphragm 9 becomes extremely small, and most of the heat generated in the heating resistors 4 and 5 is transmitted to the fluid (air) flowing on the surface of the flow rate detecting element. It can respond very quickly to changes in fluid flow. Therefore, the heat generation is used only for measuring the flow rate or the flow rate of the fluid, and the instantaneous flow rate or the flow rate can be accurately detected. That is,
The high-speed response required as a flow sensor can be satisfied. Further, since the heat capacity of the entire flow detecting element is small, the power consumption thereof can be reduced. In addition,
In all of the embodiments described below, including the first embodiment, a diaphragm type flow detecting element is described as an example, but it goes without saying that the same effect can be obtained in the case of a bridge type flow detecting element. No.

Embodiment 2 FIG. FIG. 4 is a plan view of a heating resistor portion of the flow rate detecting element according to Embodiment 2 of the present invention. In the flow detecting element according to the second embodiment, the first heating resistor 4 and the second heating resistor 5 arranged in the flow direction of the measurement fluid are arranged at a distance of 100 μm in the flow direction of the measurement fluid. Have been. Other configurations are the same as those of the flow rate detecting element according to the first embodiment.

Embodiment 3 FIG. FIG. 5 is a plan view of a heating resistor portion of the flow rate detecting element according to Embodiment 3 of the present invention. In the flow rate detecting element according to the third embodiment, the first heating resistor 4 and the second heating resistor 5 arranged in the direction of the flow of the measurement fluid are arranged at a distance of 200 μm in the direction of the flow of the measurement fluid. Have been. Other configurations are the same as those of the flow rate detecting element according to the first embodiment.

Embodiment 4 FIG. 6 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 4 of the present invention. In the flow rate detecting element according to the fourth embodiment, the first heating resistor 4 and the second heating resistor 5 arranged in the flow direction of the measurement fluid are arranged at a distance of 300 μm in the flow direction of the measurement fluid. Have been. Other configurations are the same as those of the flow rate detecting element according to the first embodiment.

FIG. 7 shows the flow rate detection characteristics of the flow rate detection elements according to the first to fourth embodiments, that is, the flow rate (g / g) of the measurement fluid.
It is a figure showing an example of the voltage output characteristic to s). FIG.
In the case, the flow rate of 0 means that the flow of the measurement fluid is not generated, and the flow rate of which is a negative value means that the measurement fluid is flowing backward. As is clear from FIG. 7, any of the flow rate detection elements can detect the backflow of the measurement fluid. It should be noted here that when the flow rate is a positive value, the output of any of the flow rate detection elements monotonously increases up to a flow rate of about 150 g / s, but the two heating resistors 4
5 is arranged at a distance of 300 μm in the direction of the flow of the measurement fluid,
That is, the output is saturated at a flow rate around 150 g / s.

This is because the first heating resistor 4 and the second heating resistor 5
Is too far away, the fluid heated by the first heating resistor 4 on the upstream side hardly affects the second heating resistor 5 on the downstream side in a large flow rate region, and the two heating resistors 4 and 5 are the same. It is thought that this is because the behavior is exhibited. Therefore, in the flow rate detecting element for performing the flow rate measurement in the large flow rate range where the flow rate is 150 g / s or more, the two heat generating resistors 4 and 5 arranged in the direction of the flow of the measurement fluid are smaller than 300 μm in the flow direction of the measurement fluid. Must be arranged at a distance from each other. Of course, it is possible to improve the output characteristics of the flow rate detecting element by increasing the initial set temperature of the heating resistor. However, if this set temperature is increased, the power consumption is increased and the flow rate detecting element is increased. This causes a problem that the reliability of the device is reduced.

Embodiment 5 FIG. FIG. 8 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 5 of the present invention. In the flow detecting element according to the fifth embodiment, a wiring portion 5a for electrically connecting the second heating resistor 5 and the electrode 6a is provided.
In the portion indicated by P, the first heating resistor 4
It is thinner (narrower) than the wiring portion 4a that electrically connects the electrode 6d to the wiring portion 4a. Other configurations are the same as those of the flow rate detecting element according to the first embodiment.

With respect to the flow rate detecting element according to the fifth embodiment, the time from when power was supplied for flow rate detection to when flow rate detection became possible was measured. It turned out that there was a difference in time. This is because the first heating resistor 4 and the second heating resistor 5
It is considered that the difference between the resistance values is due to the difference in the time required to reach a certain temperature. That is, in this flow rate detecting element, thermal imbalance occurs until both the heating resistors 4 and 5 reach the set temperature, and an error occurs in the flow rate measurement. In the flow rate detecting element according to the first embodiment, the first heating resistor 4 and the second heating resistor 5 are connected to the wiring section 4.
a, 4b, 5a, and 5b have the same pattern shape, and have the same thermal behavior including the time from when the power is turned on until the temperature reaches the set temperature. It turned out to be detectable. Therefore,
In the flow rate detecting element capable of detecting the flow rate immediately after the power is turned on, both the heating resistors 4 and 5 including the wiring portions 4a, 4b, 5a and 5b need to have the same pattern shape.

Embodiment 6 FIG. FIG. 9 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 6 of the present invention. In the flow detecting element according to the sixth embodiment, the ends of the two heating resistors 4 and 5 are all arranged on the same side in the direction orthogonal to the direction of the flow of the measurement fluid, and the wiring portions 4a, 4b and 5a are provided. , 5b are all arranged on the same side. In addition, in this flow detecting element, the wiring of the heating resistors 4 and 5 is provided to secure a necessary area of the electrodes 6a to 6d which are arranged on the wiring portion and electrically connect the flow detecting element to an external circuit or the like. The widths of the portions 4a, 4b, 5a, and 5b are the same as those of the flow rate detecting element according to the first embodiment. For this reason, in the flow rate detecting element according to the sixth embodiment, the two heating resistors 4 and 5 arranged in the direction of the flow of the measurement fluid.
Is 300 μm (or 4 μm) in the direction of the flow of the measurement fluid.
00 μm).

Therefore, in the flow rate detecting element according to the sixth embodiment, the output is saturated at a flow rate near 150 g / s as described above. In the flow rate detecting element according to the sixth embodiment, if the distance between the heating resistors 4 and 5 in the direction of the flow of the measurement fluid is set to less than 300 μm, the wiring portions 4a, 4b, 5a and 5b are made thin (width). It is necessary to make the wiring portion 4 narrow.
Heat generation at a, 4b, 5a, and 5b causes an increase in power consumption and a decrease in the electrode area, thereby lowering the reliability of the connection portion.

Therefore, the flow rate detecting elements for measuring the flow rate in the large flow rate range where the flow rate is 150 g / s or more are arranged in the flow direction of the measurement fluid, like the flow rate detecting element according to the first embodiment. After arranging the respective ends of the two heat generating resistors 4 and 5 on opposite sides with respect to a direction orthogonal to the flow direction of the measurement fluid, the wiring portions 4a, 4b, 5a and 5b are formed as shown in FIG. Must be formed. By doing so, the width of the wiring portions 4a, 4b, 5a, 5b can be made sufficiently larger than the width of the heating resistors 4, 5, and the wiring portions 4a,
4b, 5a, and 5b can be prevented from generating heat, the influence of heat generated in the wiring portions 4a, 4b, 5a, and 5b can be eliminated, and the required area of the electrodes 6a to 6d can be secured. The reliability of the flow rate detecting element can be further improved.

Embodiment 7 Like the flow rate detecting element according to the first embodiment, each end of the two heating resistors 4 and 5 arranged in the direction of the flow of the measurement fluid is set in the direction orthogonal to the direction of the flow of the measurement fluid. With respect to the flow rate detecting element in which the wiring sections 4a, 4b, 5a, and 5b are connected to the ends after being disposed on the opposite side with respect to the electrodes 6a to 6c for electrically connecting the flow rate detecting element to an external circuit or the like. 6d is preferably located on the same side. Since these electrodes 6a to 6d are electrodes for connection to a control circuit for controlling the flow rate detection element, when they are arranged on the same side, connection between the flow rate detection element and the control circuit or the like is easy. Therefore, the manufacturing process of the flow rate detecting element is simplified.

FIG. 10 shows, as a seventh embodiment of the present invention, electrodes 6a to 6c for making electrical connection with an external circuit or the like.
Reference numeral 6d denotes a flow rate detecting element arranged on the opposite side of each of the heating resistors 4 and 5, respectively. As is clear from FIG. 10, in the flow rate detecting element according to the seventh embodiment, the connection with the control circuit is complicated. Therefore, in order to realize a low-cost flow rate detecting element, the ends of the two heating resistors 4 and 5 arranged in the direction of the flow of the measurement fluid on the insulating support film 2 are connected to the flow direction of the measurement fluid. It is desirable to arrange the electrodes 6a to 6d, which are the connection portions with the external circuit, on the same side after being arranged on the opposite side with respect to the direction orthogonal to.

Embodiment 8 FIG. FIG. 11 and FIG. 12 are a front view and a side sectional view, respectively, showing an embodiment of the flow sensor using the flow detecting elements according to the first to seventh embodiments. 11 and 12, reference numeral 11 denotes a flow detecting element, 12 denotes a detection pipe, 13 denotes a main passage which is a fluid passage, 14 denotes a grid-shaped rectifier,
Reference numeral 5 denotes a case in which a control circuit is housed, and reference numeral 16 denotes a connector for supplying power to the flow rate sensor and extracting output. As described above, by incorporating the flow rate detecting elements according to the first to seventh embodiments, a flow rate sensor having the same operation and effect as those of the flow rate detecting elements according to the respective embodiments can be obtained.

In the above embodiment, the case where the flow of the measurement fluid is in the direction indicated by arrow Y (see FIGS. 2 and 12) has been described. Even in the case where the measurement fluid flows (moves) in the direction opposite to the direction Y, in principle, the backflow can be detected by the flow rate detection elements and the flow rate sensors according to all the above-described embodiments.

[0036]

According to the present invention, the following remarkable effects can be obtained. That is, according to the flow rate detecting element according to the first aspect of the present invention, an insulating support film is formed on the surface of the silicon substrate, and a heat generating resistance portion made of a heat sensitive resistance film is formed on the support film. An insulating protective film is formed on the heating resistor portion, and the silicon substrate is partially removed under at least a part of the region where the heating resistor portion is formed. Since the two heat generating resistors arranged in the direction of the flow of the measurement fluid are arranged in the sensor, it is possible to detect the direction of the flow of the fluid, and the heat capacity of the entire flow rate detecting element becomes extremely small. Therefore, even when the velocity of the fluid changes greatly per unit time, the instantaneous flow rate and the flow velocity can be accurately detected. That is, it is possible to obtain a flow rate detecting element capable of detecting the direction of the flow of the fluid and having high-speed response. Further, since the heat capacity of the entire flow rate detecting element becomes extremely small, power consumption can be reduced. Further, since the flow rate detecting element can be manufactured in the same manufacturing process as the semiconductor process, it can be manufactured at low cost.

According to the flow rate detecting element according to the second aspect of the present invention, the silicon substrate including at least a part of the region where the heating resistor is formed is opposite to the surface on which the support film is formed. Since the diaphragm structure is partially removed from the side surface, heat release due to conduction through the silicon substrate is reduced, and fluid flow is disturbed on the surface where the heating resistance is formed And the instantaneous flow rate and flow velocity can be detected more accurately.

According to the flow rate detecting element of the third aspect of the present invention, the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film have a thickness of 300 μm in the flow direction.
It is possible to obtain a sufficient difference between the output of the heating resistor on the upstream side and the output of the heating resistor on the downstream side. Can be detected.

According to the flow rate detecting element according to the fourth aspect of the present invention, the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film have a symmetrical shape. As a result, the difference between the resistance values of the two heating resistors can be minimized, and the output of the upstream heating resistor and the output of the downstream heating resistor resulting from the difference in the resistance values of the two heating resistors can be reduced. Can be eliminated, and the instantaneous flow rate and the flow velocity can be detected more accurately.

According to the flow rate detecting element according to the fifth aspect of the present invention, the two heating resistors arranged in the direction of the flow of the measurement fluid on the insulating support film have the ends of the respective heating resistors. Are arranged on the opposite side with respect to the direction orthogonal to the flow direction of the measurement fluid, so that the width of the wiring portion can be made wider than the width of the heat generating resistor. Therefore, the electrode area can be increased, and the reliability of the flow rate detecting element is improved.
Further, heat generation in the wiring portion is prevented, the influence of the heat generation can be eliminated, and the instantaneous flow rate and flow velocity can be detected more accurately.

According to the flow rate detecting element of the sixth aspect of the present invention, the ends of the two heating resistors arranged on the insulating support film in the direction of the flow of the measurement fluid are connected to the flow of the measurement fluid. Since it is arranged on the opposite side with respect to the direction orthogonal to the direction and the connection part with the external circuit is arranged on the same side, the connection between the flow detection element and the external circuit becomes easy, and the production of the flow detection element The process becomes simple.

According to the flow rate sensor according to the seventh aspect of the present invention, since the flow rate detecting elements according to the first to sixth aspects are used, the same effects as in the case of these flow rate detecting elements can be obtained.

[Brief description of the drawings]

FIG. 1 is an elevational sectional view of a thermosensitive flow rate detecting element according to Embodiment 1 of the present invention.

FIG. 2 is a plan view of the flow rate detecting element shown in FIG.

FIG. 3 is a partial plan view showing, on an enlarged scale, a heating resistor portion of the flow rate detection element shown in FIG. 2;

FIG. 4 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 2 of the present invention.

FIG. 5 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 3 of the present invention.

FIG. 6 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 4 of the present invention.

FIG. 7 is a diagram showing a flow rate detection characteristic of the flow rate detection element according to the first to fourth embodiments of the present invention.

FIG. 8 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 5 of the present invention.

FIG. 9 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 6 of the present invention.

FIG. 10 is a plan view of a heating resistor portion of a flow rate detecting element according to Embodiment 7 of the present invention.

FIG. 11 is a front view of a flow sensor according to Embodiment 8 of the present invention.

FIG. 12 is a side sectional view of the flow sensor shown in FIG. 11;

FIG. 13 is a perspective view of a conventional hot-wire probe.

FIG. 14 shows the XIV of the conventional hot-wire probe shown in FIG.
FIG. 14 is a sectional view taken along line XIV.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Silicon substrate (plate-shaped base material), 2 support film, 3 protective film, 4 1st heating resistance, 4a wiring section, 4b wiring section, 5 2nd heating resistance, 5a wiring section, 5b wiring section,
6a electrode, 6b electrode, 6c electrode, 6d electrode, 6
e electrode, 6f electrode, 7 back surface protective film, 8 etching hole, 9 diaphragm, 10 comparative resistance, 11 flow detection element, 12 detection conduit, 13 main passage, 14 rectifier, 15 case, 16 connector, 21 heating resistor, 22 Heating resistor, 23 Coating thin film, 24
A cylindrical or hollow cylindrical bobbin.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yukihisa Yoshida 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation

Claims (7)

[Claims] A silicon substrate; an insulating support film formed on the surface of the silicon substrate; and a heating resistor portion formed on the support film and supported by the support film, the heating resistor portion comprising a heat-sensitive resistor film. An insulating protective film formed on the heating resistor portion to protect the heating resistor portion, wherein at least a part of a region where the heating resistor portion is formed, the silicon substrate is A heat-sensitive flow rate detecting element configured to measure a flow rate or a flow rate of the measurement fluid based on a heat transfer phenomenon from a portion heated by the heating resistance portion to the measurement fluid; The flow rate detecting element, wherein the resistance portion includes two heat generating resistors arranged on the support film in a direction of the flow of the measurement fluid. 2. The flow detecting element according to claim 1, wherein the silicon substrate is partially removed from a surface opposite to a surface on which the support film is disposed. 3. The flow rate detecting element according to claim 1, wherein the two heating resistors are arranged at a distance of less than 300 μm in a flow direction of the measurement fluid. 4. The flow rate detecting element according to claim 1, wherein each of the two heat generating resistors has a shape which is symmetrical to each other. 5. A first end and a second end of each of the two heating resistors are arranged on opposite sides in a direction orthogonal to a flow direction of the measurement fluid. The flow rate detecting element according to claim 1, wherein: 6. A first connection for connecting the first end to an external circuit and a second connection for connecting the second end to an external circuit in each of the two heating resistors. The flow rate detecting element according to claim 5, wherein the part is arranged on the same side in a direction orthogonal to the direction of the flow of the measurement fluid. 7. A flow rate sensor, wherein the flow rate of a measurement fluid is measured using the flow rate detection element according to claim 1.