JP7022646B2 - Heat ray type flow meter - Google Patents

Description

The present invention relates to a heat ray type flow meter that measures the flow rate of the fluid to be measured.

Conventionally, various techniques related to a flow meter for measuring the flow rate of the fluid to be measured have been proposed.

For example, in the flow rate measuring device described in Patent Document 1 below, a bypass flow path member is provided in the fluid flow path, and the upstream flow path of the bypass flow path provided in the bypass flow path member is divided into two by a partition wall. By partitioning the branch flow path, mounting a thermal flow sensor on one surface of the partition wall, and forming a convex portion on the inner wall of the upstream flow path, even when pulsation occurs in the fluid flow, the entire device The fluid flow rate is measured with high accuracy without changing the size and shape.

Similar to the flow rate measuring device, the flow rate of the fluid to be measured is measured, but since the measuring method is different from that of the flow rate measuring device, a heat ray type flow meter having a different configuration has been conventionally known. There is.

FIG. 3 shows an example of such a conventional heat ray type flow meter. The heat ray type flow meter 1000 shown in the figure is composed of a heat ray type flow rate sensor 100 and a flow path 120 through which a fluid to be measured flows. The heat ray type flow sensor 100 is composed of a heater 101, two first and second heat sensing elements 102 and 103, and two first and second fluid temperature measuring elements 104 and 105, and the heater 101. , 1st and 2nd heat sensing elements 102, 103, and 1st and 2nd fluid temperature measuring elements 104, 105 are formed on the silicon substrate 110.

The silicon substrate 110 is inserted into the flow path 120 through a hole (not shown) formed in the side wall of the flow path 120, and the heat ray type flow sensor 100 is inserted into the flow path 120 through the silicon substrate 110. It is installed horizontally to the flow in the center where the flow velocity changes greatly. Then, the flow rate of the fluid to be measured is measured by the heat ray type flow rate sensor 100 in the state where the fluid to be measured is flowing in the flow path 120 as follows.

That is, first, the temperature of the fluid to be measured is measured by using the first or second fluid temperature measuring elements 104 and 105, and the electric power corresponding to the temperature is applied to the heater 101 to heat the heater 101. Next, according to the flow of the fluid to be measured, the amount of heat taken from the heater 101 or the electrical change according to the heat distribution formed by the heater 101 using the first and second heat sensing elements 102 and 103 is performed. measure. Then, the flow velocity of the fluid to be measured is calculated from the measured electrical change, and the flow velocity of the fluid to be measured is calculated from the flow velocity.

In FIG. 3, since the fluid to be measured flows in the direction of the arrow Ar1, the heat ray type flow rate sensor 100 measures the flow rate of the fluid to be measured flowing in the direction, but the heat ray type flow rate sensor 100 , It is configured to be able to measure the flow rate of the fluid to be measured flowing in the opposite direction. That is, the heat ray type flow rate sensor 100 can measure the fluid to be measured flowing in both forward and reverse directions with one sensor device. Therefore, the first heat sensing element 102 and the second heat sensing element 103 are formed on the silicon substrate 110 at symmetrical positions on both sides of the heater 101, and the first fluid temperature measuring element 104 and the second. The fluid temperature measuring element 105 is formed outside the first heat sensing element 102 and the second heat sensing element 103, respectively, on the silicon substrate 110 at positions symmetrical about the heater 101 on both sides thereof. There is.

Japanese Patent Application Laid-Open No. 2002-54962

However, in the conventional heat ray type flow meter 1000, when the flow velocity of the fluid to be measured becomes a predetermined flow velocity value or more, the silicon substrate 110 affects the flow of the fluid to be measured, and the fluid to be measured is the heat ray type flow sensor 100. The flow rate of the fluid to be measured increases because it stops flowing along the surface of the heater 101, that is, the formed surfaces of the heater 101, the first and second heat sensing elements 102, 103, and the first and second fluid temperature measuring elements 104, 105. On the other hand, a phenomenon occurred in which the output of the heat ray type flow meter 1000 did not increase monotonically.

In FIG. 5, graph g10 shows an example of the output of the heat ray type flow meter 1000 when this phenomenon occurs. In the figure, the horizontal axis shows the flow rate of the fluid to be measured, and the vertical axis shows the output of the heat ray type flow meter 1000.

As shown in the graph g10, the output of the heat ray type flow meter 1000 increases monotonically up to the flow rate F11, but starts to decrease from the flow rate F11 to the flow rate F12, and further increases again when the flow rate F12 is exceeded.

Therefore, when the heat ray type flow rate sensor 100 is installed in the horizontal direction with respect to the flow of the fluid to be measured, the flow rate range before the output starts to decrease, that is, in the above graph g10, the range from 0 to F11. Only the flow rate can be measured.

In order to deal with this, it is conceivable to incline and install the heat ray type flow rate sensor 100. FIG. 4 shows an example in which the heat ray type flow rate sensor 100 is installed by tilting it counterclockwise by a predetermined angle so as to follow the flow of the fluid to be measured flowing in the direction of the arrow Ar1.

The graph g20 in FIG. 5 shows an example of the output of the heat ray type flow meter 1000 when the heat ray type flow rate sensor 100 is installed at an angle in this way. As can be seen from the graph g20, even when the flow rate of the fluid to be measured is between F11 and F12, the output of the heat ray type flow meter 1000 maintains a monotonous increase without turning to a decrease.

However, when the flow of the fluid to be measured is changed in the direction of the arrow Ar2 opposite to the direction of the arrow Ar1 and the flow rate is measured, the heat ray type flow meter 1000 installed with the heat ray type flow rate sensor 100 tilted as described above Then, accurate measurement is not possible.

Therefore, in order to deal with the above, the present invention can accurately measure the flow rate of the fluid to be measured regardless of the flow rate, regardless of whether the fluid to be measured flows in either the forward or reverse direction. It is an object of the present invention to provide a heat ray type flow meter.

The invention according to claim 1 made to solve this problem has a tubular flow path through which the fluid to be measured flows and a heat ray type flow rate sensor arranged in the flow path, and has a heat ray type flow rate sensor. Is a substrate, a heater formed on the substrate, two heat sensing elements formed on the substrate symmetrically on both sides of the heater as a center, and each heat sensing element on the substrate. It is equipped with two fluid temperature measuring elements symmetrically arranged around the heater on the outside, the flow path is provided with a squeeze wall that protrudes from the inner wall and squeezes the flow path, and the squeeze wall has a gable roof shape. The large building is formed so as to be positioned perpendicular to the flow direction of the fluid to be measured, and further includes the large building and is plane-symmetrical with respect to the plane perpendicular to the flow direction of the fluid to be measured. The heat ray type flow sensor is formed so as to be measured at a position between the large ridge of the drawing wall and the inner wall of the flow path facing the large ridge, where the vertical plane intersects the heater. It is characterized in that the fluid is installed in a direction in which the fluid temperature measuring element, the heat sensing element, the heater, the heat sensing element, and the fluid temperature measuring element come into contact with each other in this order according to the flow.

The invention according to claim 2 is the heat ray type flow meter according to claim 1, wherein the large ridge portion of the throttle wall has a rounded shape.

The invention according to claim 3 is the heat ray type flow meter according to claim 2, and when the height of the flow path is d, the large building portion of the drawing wall is 1/10 or more of the height d. It is characterized by having a radius of curvature of.

The invention according to claim 4 is the heat ray type flow meter according to any one of claims 1 to 3, wherein each roof surface included in the drawing wall includes a large ridge portion and is a fluid to be measured. It is characterized in that the elevation angle is inclined in the range of 10 ° to 30 ° with respect to the horizontal plane with respect to the flow direction of.

The invention according to claim 5 is the heat ray type flow meter according to any one of claims 1 to 4, wherein the distance between the large building of the drawing wall and the surface of the heat ray type flow sensor is a distance b. Assuming that the distance between the back surface of the heat ray type flow sensor and the inner wall of the flow path facing the back surface is the distance c and the height of the flow path is the height d, the distance b + the distance c: the height d is 1: It is characterized in that it is in the range of 1.5 to 1: 4.

The invention according to claim 6 is the heat ray type flow meter according to any one of claims 1 to 5, wherein the distance between the large building of the drawing wall and the surface of the heat ray type flow sensor is a distance b. Assuming that the distance between the back surface of the heat ray type flow sensor and the inner wall of the flow path facing the back surface is the distance c, the distance b: the distance c is in the range of 1: 1 to 2: 1. do.

According to the heat ray type flow meter according to claim 1, since the flow path is narrowed by the drawing wall, even if the flow rate of the fluid to be measured increases and the flow velocity becomes high, the surface of the heat ray type flow rate sensor is measured. The flow of fluid will follow. As a result, the range in which the output of the heat ray type flow meter increases monotonically with the increase in the flow rate of the fluid to be measured expands, and measurement in a wide flow rate range becomes possible.

Further, in the heat ray type flow meter according to claim 1, the drawing wall includes the large building of the drawing wall and is formed so as to be plane-symmetrical with respect to the plane perpendicular to the flow direction of the fluid to be measured. Since the heat ray type flow sensor is also arranged so as to be plane-symmetric with respect to the vertical plane, the flow of the fluid to be measured to the surface of the heat ray type flow sensor becomes the same in both forward and reverse directions, and the flow rate can be measured from either direction. Can now be done.

According to the heat ray type flow meter according to claim 2, since the large ridge portion of the drawing wall has a rounded shape, it is possible to suppress the occurrence of peeling of the fluid to be measured in the large ridge portion.

According to the heat ray type flow meter according to claim 3, since the large ridge portion of the drawing wall has a radius of curvature of 1/10 or more of the height d of the flow path, the fluid to be measured is peeled off in the large ridge portion. Can be further suppressed.

According to the heat ray type flow meter according to claim 4, each roof surface included in the throttle wall includes the large ridge portion, and the elevation angle is from 10 ° to 30 ° with respect to the horizontal plane with respect to the flow direction of the fluid to be measured. Since the slope is in the range of, it is possible to obtain the effect of suppressing the turbulence of the flow of the fluid to be measured due to the formation of the throttle wall.

According to the heat ray type flow meter according to claim 5, since the distance b + the distance c: the height d is set in the range of 1: 1.5 to 1: 4, the height d of the flow path 120 is set. Assuming that the range is 3 to 20 mm and the flow rate range is 300 ml / min or less, the average flow velocity of the fluid to be measured is about 1.0 m / s or less, and the sensitivity of the heat ray type flow rate sensor can be kept good. ..

According to the heat ray type flow meter according to claim 6, since the distance b: distance c is set in the range of 1: 1 to 2: 1, the flow velocity at which the fluid to be measured flows on the surface of the heat ray type flow sensor. Is limited to a predetermined range, and the measurable flow rate range can be expanded as much as possible while maintaining the sensitivity of the heat ray type flow rate sensor.

It is sectional drawing which shows the schematic structure of the heat ray type flow meter which concerns on one Embodiment of this invention. It is a figure which shows the output characteristic of the heat ray type flow meter of FIG. 1 and the output characteristic of the conventional heat ray type flow meter. It is sectional drawing which shows the state when the heat ray type flow rate sensor included in the conventional heat ray type flow meter is installed in the flow path in the horizontal direction with respect to the flow of the fluid to be measured. It is sectional drawing which shows the state when the hot wire type flow rate sensor included in the conventional hot wire type flow meter is installed at an angle different from the horizontal direction of FIG. It is a figure which shows an example of the output characteristic of the conventional heat ray type flow meter for each installation direction of FIG. 3 and FIG.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

The heat ray type flow meter according to the embodiment of the present invention is a heat ray type MEMS (Micro Electro Mechanical Systems) flow meter, and the heat ray type flow rate sensor included in the heat ray type flow meter is a flow path through which the fluid to be measured flows. It is installed inside and measures the flow rate of the fluid to be measured. Possible uses include flow control of medical chemicals and control of reagents and culture solutions for biochemical tests.

As shown in FIG. 1, the heat ray type flow meter 10 of the present embodiment has the same configuration as that of the heat ray type flow meter 1000 described above in the [Background Art] column, and the description of the configuration is described. Omit.

The heat ray type flow rate sensor 100 included in the heat ray type flow meter 10 of the present embodiment is installed horizontally in the flow path 120 in the direction in which the fluid to be measured flows. The heat ray type flow meter 10 of the present embodiment can accurately measure the flow rate of the fluid to be measured regardless of whether the fluid to be measured is flown in the direction of the arrow Ar1 or the direction of the arrow Ar2 opposite to the direction of the arrow Ar1. I am doing it.

In order to realize this, the heat ray type flow meter 10 of the present embodiment has the following features. That is,
(1) The throttle wall 121a is formed on the inner wall of the inner wall 121 of the flow path 120 and facing the surface of the heat ray type flow sensor 100. (2) The optimum shape of the throttle wall 121a is set. (3) The optimum position for installing the heat ray type flow rate sensor 100 is set.

The surface of the heat ray type flow sensor 100 is the surface of the silicon substrate 110, that is, the heater 101, the first and second heat sensing elements 102, 103, and the first and second fluid temperature measuring elements 104, 105 are formed. The back surface of the heat ray type flow sensor 100 refers to the back surface of the silicon substrate 110, that is, the heater 101, the first and second heat sensing elements 102, 103, and the first and second fluid temperature measuring elements 104, 105. I will refer to the surface opposite to the forming surface of.

As shown in FIG. 1, the throttle wall 121a is formed on a part of the inner wall 121 of the flow path 120, that is, on the portion facing the surface of the heat ray type flow rate sensor 100 when the heat ray type flow rate sensor 100 is installed. Has been done. The squeezing wall 121a protrudes from the inner wall 121 into the flow path 120 to squeeze the flow path 120. By providing such a throttle wall 121a, it is experimental that the flow of the fluid to be measured follows the surface of the heat ray type flow sensor 100 even if the flow rate of the portion increases and the flow velocity increases. Has been verified.

The squeezed wall 121a has a gable roof shape and protrudes from the inner wall 121 into the flow path 120. The portion of the gable roof corresponding to the large ridge (hereinafter referred to as "large ridge portion") extends in the width direction of the inner wall 121 of the flow path 120. That is, the diaphragm wall 121a is formed in the flow path 120 without a gap in the width direction. The width direction of the flow path 120 means the direction from the front surface to the back surface on the paper surface of FIG. 1.

Further, the drawing wall 121a is formed so that the large ridge portion is located perpendicular to the flow direction of the fluid to be measured.

FIG. 1 is a cross-sectional view when the flow path 120 is cut in the lateral direction, that is, in the cut surface in the flow direction of the fluid to be measured. Shows the cut surface of. The cross section of the diaphragm wall 121a shown in FIG. 1 has an isosceles triangle shape. That is, the throttle wall 121a includes the large ridge portion and is formed so as to be plane-symmetrical with respect to the plane perpendicular to the flow direction of the fluid to be measured. This is to ensure that the flow of the fluid to be measured flows in the same direction in both the forward direction and the reverse direction.

The heat ray type flow sensor 100 is installed in the flow path 120 so that the center of the heater 101 comes to the position of the apex e of the isosceles right triangle in FIG. 1, that is, the position extending vertically downward from the main building. The reason why the heat ray type flow rate sensor 100 is installed in this way is that the fluid to be measured flows in the same manner along the heat ray type flow rate sensor 100 regardless of whether the flow of the fluid to be measured is in the forward direction or the reverse direction.

Then, in order to determine the optimum shape of the diaphragm wall 121a and the optimum position of the heat ray type flow sensor 100, a range of various values including the apex e, specifically, an angle a and a distance shown in FIG. Each range of b, distance c and height d is set. Here, the angle a indicates the angle of the base angle of the isosceles triangle which is the shape of the cross section of the drawing wall 121a, and the distance b indicates the distance between the surface of the heat ray type flow sensor 100 and the apex e. c indicates the distance between the back surface of the heat ray type flow sensor 100 and the inner wall 121 facing the back surface, and the height d indicates the height of the flow path 120 (strictly speaking, the inner wall 121). Further, "optimal" means that the fluid to be measured flows along the surface of the heat ray type flow sensor 100 even if the flow velocity of the fluid to be measured becomes high.

Hereinafter, the setting range of various values and the reason for the setting will be described.

The angle a indicates the angle formed by the surface of the single roof of the aperture wall 121a and the surface of the inner wall 121. In the present embodiment, since the pipe having a rectangular cross section is used as the flow path 120, the surface of the inner wall 121 on which the drawing wall 121a is formed is a flat surface. Therefore, the angle a can be defined.

However, when a pipe having a circular cross section is used as the flow path 120, the angle a cannot be defined. In that case, the large ridge of the drawing wall 121a is included and the flow direction of the fluid to be measured is relative to the flow direction. The elevation angle with respect to the horizontal plane (the plane shown by the alternate long and short dash line in FIG. 1) may be defined. Since the elevation angle in this case is the same as the above angle a, the following description is similarly established for the elevation angle a by reading the angle a as the elevation angle a.

The angle a is set from 10 ° to 30 °. FIG. 2 is a diagram showing the output characteristics of the heat ray type flow meter 10 of the present embodiment and the output characteristics of the conventional heat ray type flow meter. In the figure, graph g0 is a conventional heat ray type flow meter, that is, a diaphragm. An example of the output characteristics of the heat ray type flow meter without the wall 121a is shown, and graphs g1 to g3 show an example of the output characteristics of the heat ray type flow meter 10 of the present embodiment. The graphs g1 to g3 show the output characteristics of the heat ray type flow meter 10 when the angles a are set to 10 °, 20 °, and 30 °, respectively.

As can be seen from FIG. 2, in the graph g0, although the flow rate of the fluid to be measured increases monotonically up to F1, it starts to decrease from the flow rate F1 to the flow rate F2, and further increases again when the flow rate exceeds F2. On the other hand, in the graphs g1 to g3, the output of the heat ray type flow meter 10 maintains a monotonous increase without turning to decrease even when the flow rate of the fluid to be measured is between F1 and F2.

As described above, as is clear from the experimental results, at least when the angle a is in the range of 10 ° to 30 °, the effect of suppressing the turbulence of the flow of the fluid to be measured due to the formation of the throttle wall 121a is obtained. Has been obtained.

The ratio of the distance b to the distance c, b: c, is set in the range of 1: 1 to 2: 1. The reason for this is that, first, when b: c = 1: 1, that is, the heat ray type flow rate sensor 100 is installed in the center between the large ridge of the throttle wall 121a and the inner wall 121 of the flow path 120 facing the ridge. In this case, since the change in the flow velocity at the center is large, the change in the output of the heat ray type flow rate sensor 100 can also be large.

However, in the heat ray type flow rate sensor 100, when the flow velocity of the fluid to be measured becomes high, the sensitivity (change in output with respect to the change in flow rate) decreases and the measurement becomes impossible (the relationship between the change in flow rate and the change in output does not become a simple increase or decrease).

On the other hand, the flow velocity of the fluid to be measured becomes slower as it approaches the inner wall 121 of the flow path 120. Therefore, when the heat ray type flow rate sensor 100 is brought closer to the inner wall 121, the flow velocity of the fluid to be measured measured by the heat ray type flow rate sensor 100 becomes slower, and the flow rate range can be widened.

However, if the heat ray type flow rate sensor 100 is brought too close to the inner wall 121, the heat ray type flow rate sensor 100 is affected by the temperature due to the structure of the flow path 120. Further, when bubbles are attached between the back surface of the heat ray type flow sensor 100 and the inner wall 121, the flow velocity between the back surface of the heat ray type flow sensor 100 and the inner wall 121 is slow, so that the bubbles are difficult to be removed and the heat ray type. It may affect the output of the flow meter 10.

Therefore, in the range where the height d of the flow path 120 is in the range of 3 to 20 mm, b: c is set only to 2: 1.

Next, the ratio of the sum of the distance b and the distance c to the height d, b + c: d, is set in the range of 1: 1.5 to 1: 4.

When the flow path 120 is throttled at an angle, the flow of the fluid to be measured follows the surface of the heat ray type flow sensor 100, and the measurable flow rate range is widened. The flow velocity in the above becomes faster, and the sensitivity (change in output with respect to the change in flow rate) decreases, so that the flow rate range becomes narrower. Good sensitivity can be obtained by suppressing the average flow velocity near the heat ray type flow sensor 100 to about 1.0 m / s or less.

In the heat ray type flow meter 10 of the present embodiment, assuming that the height d of the flow path 120 is in the range of 3 to 20 mm and the flow rate range is 300 ml / min or less, the average flow velocity of the fluid to be measured is about 1. B + c: d is set in the range of 1: 1.5 to 1: 4 so as to be 0 m / s or less.

Next, when the apex e has an acute angle, the fluid to be measured is peeled off at the large ridge, so that the apex e needs to have a rounded shape. Specifically, the radius of curvature of the large ridge is set to 1/10 or more of the height d.

As described above, the heat ray type flow meter 10 of the present embodiment is provided with a tubular flow path 120 through which the fluid to be measured flows and a heat ray type flow sensor 100 arranged in the flow path 120. ..

The heat ray type flow sensor 100 is formed on a silicon substrate 110, a heater 101 formed on the silicon substrate 110, and two firsts symmetrically arranged on both sides of the heater 101 on the silicon substrate 110. And the second heat sensing elements 102 and 103, and the two first and second fluid temperature measuring elements 104 and 105 formed symmetrically with respect to the heater on the substrate and outside each heat sensing element. It is equipped with.

The flow path 120 includes a narrowing wall 121a that protrudes from the inner wall thereof and narrows the flow path. The squeezed wall 121a has a gable roof shape, and its large ridge is formed so as to be positioned perpendicular to the flow direction of the fluid to be measured, and further includes the large ridge of the fluid to be measured. It is formed so as to be plane-symmetric with respect to a plane perpendicular to the flow direction.

The heat ray type flow sensor 100 is located between the large ridge of the drawing wall 121a and the inner wall 121 of the flow path 120 facing the large ridge, at a position where the vertical surface intersects the heater 101, and is covered. The measuring fluid follows the flow in the order of the first fluid temperature measuring element 104, the first heat sensing element 102, the heater 101, the second heat sensing element 103 and the second fluid temperature measuring element 105, or the second fluid temperature measuring element 105. , The second heat sensing element 103, the heater 101, the first heat sensing element 102, and the first fluid temperature measuring element 104 are installed in such a direction that they come into contact with each other in this order.

According to the heat ray type flow meter 10 of the present embodiment, since the flow path 120 is throttled by the drawing wall 121a, the surface of the heat ray type flow rate sensor 100 is formed even if the flow rate of the fluid to be measured increases and the flow velocity increases. The flow of the fluid to be measured will follow. As a result, the range in which the output of the heat ray type flow meter 10 of the present embodiment monotonically increases with respect to the increase in the flow rate of the fluid to be measured is expanded, and measurement in a wide flow rate range becomes possible.

Further, in the heat ray type flow meter 10 of the present embodiment, the drawing wall 121a includes the large building portion of the drawing wall 121a and is formed so as to be plane-symmetrical with respect to the plane perpendicular to the flow direction of the fluid to be measured. Further, since the heat ray type flow rate sensor 100 is also arranged so as to be plane-symmetric with respect to the vertical plane, the flow of the fluid to be measured with respect to the surface of the heat ray type flow rate sensor 100 becomes the same in both forward and reverse directions, and the flow rate is from either direction. It became possible to make measurements.

Further, in the heat ray type flow meter 10 of the present embodiment, since the large ridge portion of the drawing wall 121a has a rounded shape, it is possible to suppress the occurrence of peeling of the fluid to be measured in the large ridge portion. ..

Further, in the heat ray type flow meter 10 of the present embodiment, since the large ridge portion of the drawing wall 121a has a radius of curvature of 1/10 or more of the height d of the flow path 120, the measurement is performed in the large ridge portion. The occurrence of fluid separation can be further suppressed.

Further, in the heat ray type flow meter 10 of the present embodiment, each roof surface included in the drawing wall 121a includes the large ridge portion, and the elevation angle is 10 ° to 30 ° with respect to the horizontal plane with respect to the flow direction of the fluid to be measured. Since the inclination is in the range up to, it is possible to obtain the effect of suppressing the turbulence of the flow of the fluid to be measured due to the formation of the drawing wall 121a.

Further, in the heat ray type flow meter 10 of the present embodiment, the distance b + the distance c: the height d is set in the range of 1: 1.5 to 1: 4, so that the height of the flow path 120 is high. Assuming that d is in the range of 3 to 20 mm and the flow rate range is 300 ml / min or less, the average flow velocity of the fluid to be measured is about 1.0 m / s or less, and the sensitivity of the heat ray type flow rate sensor 100 is good. Can be kept.

Further, in the heat ray type flow meter 10 of the present embodiment, since the distance b: the distance c is set in the range of 1: 1 to 2: 1, the fluid to be measured is the surface of the heat ray type flow sensor 100. The measurable flow rate range can be expanded as much as possible while maintaining the sensitivity of the heat ray type flow rate sensor 100 by limiting the flow velocity flowing through the device to a predetermined range.

By the way, in this embodiment, the silicon substrate 110 is an example of a "substrate".

The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

(1) In the present embodiment, the silicon substrate 110 is used, but the substrate is not limited to this, and the substrate may be formed of a semiconductor material other than silicon or may be formed of a material other than the semiconductor material.

(2) In the present embodiment, one heat sensing element is formed on each side of the heater 101, but the number thereof is not limited to one and may be two or more. However, in the present invention, the number of heat sensing elements formed on one side and the number of heat sensing elements formed on the other side must be the same, and each heat sensing element on each side must be the same. Needs to be formed at symmetrical positions about the heater 101.

10 Heat ray type flow meter 100 Heat ray type flow sensor 101 Heater 102 First heat sensing element 103 Second heat sensing element 110 Silicon substrate 120 Flow path 121 Inner wall 121a Aperture wall

Claims (6)

A tubular flow path through which the fluid to be measured flows, and
A heat ray type flow sensor arranged in the flow path and
Have,
The heat ray type flow sensor includes a substrate, a heater formed on the substrate, two heat sensing elements symmetrically arranged on both sides of the heater centered on the substrate, and the substrate. Two fluid temperature measuring elements formed symmetrically with respect to the heater are provided on the outside of each heat sensing element.
The flow path is provided with a squeezing wall that protrudes from its inner wall and narrows the flow path.
The squeezed wall has a gable roof shape, and its large ridge is formed so as to be positioned perpendicular to the flow direction of the fluid to be measured, and further includes the large ridge and the flow direction of the fluid to be measured. Formed to be plane symmetric with respect to the plane perpendicular to
The heat ray type flow sensor is measured at a position between the large building portion of the drawing wall and the inner wall of the flow path facing the large building portion, at a position where the vertical surface intersects with the heater. A heat ray type flow meter characterized in that the fluid is installed in a direction in which the fluid temperature measuring element, the heat sensing element, the heater, the heat sensing element, and the fluid temperature measuring element come into contact with each other in this order according to the flow. The heat ray type flow meter according to claim 1, wherein the large ridge portion of the throttle wall has a rounded shape. Assuming that the height of the flow path is height d,
The heat ray type flow meter according to claim 2, wherein the large ridge portion of the throttle wall has a radius of curvature of 1/10 or more of the height d. Each roof surface included in the throttle wall includes the large ridge portion, and is characterized in that the elevation angle is inclined in the range of 10 ° to 30 ° with respect to the horizontal plane with respect to the flow direction of the fluid to be measured. The heat ray type flow meter according to any one of claims 1 to 3. The distance between the large ridge of the throttle wall and the surface of the heat ray type flow sensor is defined as a distance b.
The distance between the back surface of the heat ray type flow sensor and the inner wall of the flow path facing the back surface is defined as the distance c.
Assuming that the height of the flow path is height d,
The heat ray type flow meter according to any one of claims 1 to 4, wherein the distance b + the distance c: the height d is in the range of 1: 1.5 to 1: 4. The distance between the large ridge of the throttle wall and the surface of the heat ray type flow sensor is defined as a distance b.
Let the distance c be the distance between the back surface of the heat ray type flow sensor and the inner wall of the flow path facing the back surface.
Distance b: The heat ray type flow meter according to any one of claims 1 to 5, wherein the distance c is in the range of 1: 1 to 2: 1.

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