JPH11271120A - Heat-sensitive flow velocity sensor and heat-sensitive flow velocity detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a heat-sensitive flow velocity sensor to measure the flow rate and flow velocity of a fluid over a wide range and, particularly, to make the sensitivity of the sensor changeable regardless of its driving current by using two heating element type detecting elements in which a pair of heating elements are faced oppositely to each other in the flowing direction of the fluid. SOLUTION: A fluid flow passage 3 through which a fluid is made to flow and a bridge 4a are formed on a substrate 1 and a plurality of sets of detecting elements 5a and 5b are arranged on the bridge 4a in such a way that the upstream-and downstream-side heating elements 51a and 52a of another set of detecting element 5a are positioned between the paired upstream-and downstream-side heating elements 51b and 52b of a certain set of detecting element 5b. Therefore, the measuring region of a heat-sensitive flow velocity sensor can be increased by switching a plurality of detecting elements 5a and 5b having different sensitivity and formed on one substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a detection element in which heating elements are arranged on the upstream and downstream sides in the flow direction of a fluid, and the difference in cooling amount between the heating element on the upstream side and the heating element on the downstream side. The present invention relates to a heat-sensitive flow rate sensor and a heat-sensitive flow rate detecting device for detecting the flow rate and flow rate of a fluid by calculating the flow rate as a difference between electric signals.

[0002]

2. Description of the Related Art First, a schematic structure of a general thermal flow sensor A will be described with reference to FIGS. 8 is a plan view, and FIG. 9 is a vertical sectional front view taken on line XX in FIG. In the figure, reference numeral 1 denotes a substrate formed of a material such as silicon. The surface of the substrate 1 is covered with an insulating film 2, and a moat 3 as a fluid flow passage for flowing a fluid such as gas from the direction of the arrow is formed in the center by etching or the like. Further, a bridge 4a is formed on the substrate 1 so as to cross a part of the moat 3 orthogonally to the flow direction of the fluid. On the surface of the bridge 4a, a detection element 5a is formed by a metal thin film. The detection element 5a is formed by two heating elements (heating resistor films) 51a and 52a arranged on the upstream side and the downstream side in the fluid flow direction.

Further, a heating element 51 is provided on the surface of the substrate 1.
a, bonding pads 53a, 5a connected to 52a
4a, a slit 6 for thermally disconnecting the heating elements 51a and 52a from the substrate 1, a temperature measuring element 7, and a bonding pad 8 connected to the temperature measuring element (heating resistance film) 7. Is formed. The detection element 5a and the temperature sensor 7 are covered with an insulating protective film.

[0004] Such a thermal flow sensor A is shown in FIG.
The pipe main body 9 shown in FIG. FIG. 10A is a plan view showing the pipe main body 9 in a state where the pipe 10 is opened. 10B is a vertical sectional side view taken on line YY in FIG. 10A, and FIG. 10C is XX in FIG. 10A.
FIG. 4 is a vertical cross-sectional front view taken along a line, showing a state in which the conduit main body 9 is closed by a lid 11. A rectifier 19 having a honeycomb structure or a thick mesh structure is arranged on the upstream side of the pipe 10. Thermal flow sensor A is line 1
0. As a result, a fluid such as a gas flows through the pipeline 10 as shown by the arrow, passes through the rectifier 19, and at this time, the flow velocity or flow rate of the fluid is detected.

Referring now to FIG. 8, the operation of the heat-sensitive flow rate sensor A for detecting the flow rate of a fluid will be schematically described. When the flow velocity of the fluid such as gas is zero, the heating elements 51a, 52
Although the resistance values of a and a are equal, when the fluid flows in the direction of the arrow, the upstream heating element 51a is cooled first by the fluid, and the downstream heating element 52a is exposed to the fluid that has taken heat from the upstream heating element 51a. Therefore, the outputs of the heating elements 51a and 52a are different. Therefore, the flow velocity of the fluid can be obtained from the output difference. The flow velocity is determined by the flow rate per unit time and the cross-sectional area of the flow path of the pipeline 10 shown in FIG.

FIG. 11 shows an example of a drive circuit of the thermal type flow sensor A. In this example, the heating elements 51a and 52a and the constant current power supply 12 are connected in series. When a constant current flows, a voltage Vu is generated at both ends of the heating element 51a,
A voltage Vd is generated at both ends of 2a. Heating elements 51a, 5
2a, the voltage drops Vhu and Vhd are detected, and Vdu (Vhd−Vh) is determined as a quantity related to the flow rate (or flow rate).
u), and the flow rate per unit time can be obtained from this value and a predetermined relational expression.

The driving method of the heat-sensitive flow velocity sensor A includes a constant voltage driving method and a constant temperature driving method in addition to the above constant current driving method, and all of them take the difference between the outputs of the heating elements 51a and 52a. The same is true.

The heat-sensitive flow rate sensor has high sensitivity and low power consumption, and its application to a gas meter or the like is being studied. When the flow rate of the gas for maintaining the ignition of the water heater in an igniting state is 3 liters per hour, when the cross-sectional area of the flow path is about 1 cm ² , the flow velocity is very low at several mm to ² cm per second. As an application for detecting a region, a thermal flow sensor exhibits excellent characteristics. However, the flow rate of the gas meter is 3000 l / h or more at maximum, and the flow rate is 10
It is necessary to detect a three-digit or more wide area exceeding the meter. On the other hand, with a single thermal flow sensor, there is a problem that the sensitivity in the high speed region is reduced even if the sensitivity in the low speed region is good, and the dynamic range that can be detected by one thermal flow sensor is limited to about two digits. is there.

In order to increase the measurement area, it is necessary to use a plurality of thermal flow sensors having different sensitivities in some way.
FIG. 12 shows the characteristics of the detection element in the case of using heat-sensitive flow velocity sensors having different sensitivities. The graph on the left shows the characteristics of a high-sensitivity thermo-sensitive flow rate sensor. At 300 liters / hour of city gas, saturation of sensitivity starts. On the other hand, a heat-sensitive flow rate sensor for high flow rate (high flow rate) reaches practical accuracy from about 100 liters / hour and can be used for measurement at 3000 liters / hour or more. As described above, the thermal type flow rate sensors having different characteristics can be combined and the thermal type flow rate sensor can be switched according to the measurement area, but the apparatus becomes large.

A description will be given of a conventional example in which a single heat-sensitive flow velocity sensor can measure a wide area. First, Japanese Patent Laid-Open No. 6-1
The proposal described in Japanese Patent No. 1374 will be described. This is a configuration in which four thin-film heat sensing elements (heating elements) formed on a bridge portion (bridge) formed on a substrate are assembled in a Wheatstone bridge circuit.

Second, the proposal described in Japanese Patent Application Laid-Open No. HEI 8-29226 makes it possible to measure a wide area by switching the output of a plurality of detection portions (detection elements) having different sensitivities according to the region to be measured. Is to try. In this case, the plurality of detection portions have different sensitivities by changing the heat capacity.

Thirdly, the proposal described in Japanese Patent Application Laid-Open No. 4-343024 discloses a method of measuring a flow rate accurately regardless of the flow rate to be measured, with a pair of resistance temperature sensors each having a heating section in between. It has a large flow measurement unit and a small flow measurement unit whose parts are arranged opposite to each other.

[0013]

Problems to be Solved by the Invention
The proposal described in Japanese Patent Application Laid-Open Publication No. H10-123840 aims to expand the measurement area by improving the sensitivity or improving the nonlinearity of the output characteristics. However, taking gas flow measurement as an example, a region of 300 liters / hour or less,
It is unlikely that the non-linearity of the output characteristics can be improved to satisfy the measurement of a wide area including the area of 100 to 3000 liters / hour.

The proposal described in Japanese Patent Application Laid-Open No. HEI 8-29226 can measure a wide area by switching a detection part, but is used for a heat-sensitive flow velocity sensor used in a gas meter or the like which requires low power consumption. In this case, if the heat capacity of the detection portion is increased, the response time during pulse driving becomes longer. In addition, there is a problem that power consumption increases to drive a detection portion having a large heat capacity.

In the proposal described in Japanese Patent Application Laid-Open No. 4-343024, a resistance temperature sensor section is disposed so as to sandwich a heating section to form a flow rate measuring section. The sensitivity in the low-amount region is lower than that of the configuration in which the components are opposed to each other.

The present invention makes it possible to measure the flow rate and the flow velocity in a wide area, and in particular, to use a two-heating element type detection element in which a pair of heating elements are arranged opposite to each other in the flow direction of the fluid, and to increase the sensitivity regardless of the drive current. The aim is to be able to change.

[0017]

According to the first aspect of the present invention,
A fluid flow passage for flowing a fluid and a bridge that bridges a part of the fluid flow passage are formed on a substrate, and a detection device includes a pair of heating elements disposed on an upstream side and a downstream side in a fluid flow direction. In a heat-sensitive flow rate sensor in which an element is formed on the bridge, a plurality of sets of the detection elements are provided, and the upstream-side heating element and the downstream-side heating element forming a pair of the one set of the detection elements are provided. In the meantime, a plurality of sets of the detection elements are arranged on the bridge with an arrangement relation in which the heating elements on the upstream side and the heating elements on the downstream side of another set of the detection elements are located.

Therefore, it is possible to form a plurality of detection elements having different sensitivities on one substrate.
This makes it possible to increase the measurement area by switching the detection element to be used according to the flow velocity and the flow rate of the fluid.

According to a second aspect of the present invention, in the first aspect of the present invention, the plurality of sets of detecting elements are disposed on the bridge at different positions near the center of the fluid flow passage and near the side wall of the fluid flow passage. Have been.

Therefore, a plurality of detection elements having different sensitivities can be formed on one bridge.

According to a third aspect of the present invention, in the second aspect of the present invention, the arrangement pattern of the heating element on the upstream side and the heating element on the downstream side of the detecting element is arranged so that the center line in the fluid stream direction is an axis. They are arranged symmetrically.

Therefore, it is possible to smoothly change the output voltage of the detection element disposed near the side wall of the fluid flow passage with respect to the flow rate.

According to a fourth aspect of the present invention, a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage are formed on the substrate, and the upstream and downstream sides in the fluid flow direction are formed. In the thermosensitive flow rate sensor formed by forming a detection element consisting of a pair of heating elements arranged in the bridge, a plurality of the bridges are formed from the upstream side to the downstream side in the flow direction of the fluid, and each of the bridges is formed. The detection element is formed at the bottom.

Therefore, it is possible to form a plurality of detection elements having different sensitivities on one substrate.
This makes it possible to increase the measurement area by switching the detection element to be used according to the flow velocity and the flow rate of the fluid. By providing a plurality of bridges in accordance with the number of detection elements, it is possible to increase the degree of freedom in arranging the detection elements on the bridge. Further, it is possible to prevent thermal interference between the plurality of detection elements.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the pattern width of the heating element in the direction of fluid flow is changed for each of the plurality of detection elements.

Therefore, even when the width of the fluid flow passage is constant and the length of the bridge is constant, a plurality of detection elements having a large sensitivity difference are utilized by utilizing the difference in the pattern width of the heating element (corresponding to the bridge width). Can be formed.

According to a sixth aspect of the present invention, in the fifth aspect, the resistance value of the heating element is changed for each of the plurality of detection elements.

Therefore, it is possible to further increase the difference in the sensitivity of the detection element due to the difference in the resistance value of the heating element.

According to a seventh aspect of the present invention, in the fifth aspect of the invention, the resistance value of the heating element of the detection element having the larger pattern width is smaller than the resistance value of the heating element of the detection element having the smaller pattern width. It is set to a large value.

Therefore, it is possible to easily obtain the difference in the sensitivity of the detection element without largely changing the pattern width of the detection element (corresponding to the width of the bridge). In particular, by selecting the parameters of the resistance value of the detection element and the driving method, it is possible to easily obtain the difference in the sensitivity of the detection element.

According to an eighth aspect of the present invention, in the sixth aspect of the present invention, the plurality of bridges are formed with different lengths in a direction orthogonal to the flow direction of the fluid, and a detection element is formed in each of the bridges. Have been.

Therefore, it is possible to increase the difference in the sensitivity of the detection element by using the difference in the length of the bridge.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, the resistance value of the detection element formed on each of the plurality of bridges formed with different lengths in the direction orthogonal to the flow direction of the fluid. Is set to a higher value as the length of the heating element in the direction orthogonal to the flow direction of the fluid is longer.

Therefore, even if the pattern width of the detecting element in the flow direction of the fluid is constant, the resistance value of the heating element is set to a different value by utilizing the difference in the length of the bridge, thereby increasing the difference in sensitivity of the detecting element. It becomes possible.

According to a tenth aspect of the present invention, a fluid flow passage for flowing a fluid and a bridge for bridging a part of the fluid flow passage are formed on the substrate, and the upstream and downstream sides in the flow direction of the fluid are formed on the substrate. A plurality of heat-sensitive flow velocity sensors are formed by forming a detection element composed of a pair of heating elements disposed on the bridge, and the cross-sectional area of the flow path on the upstream side in the flow direction of the fluid is calculated from the cross-sectional area of the downstream side. Provide a pipeline set to a large value,
The heat-sensitive flow rate sensors were disposed at a plurality of positions where the cross-sectional area of the flow path of this conduit was different.

Therefore, since the plurality of thermal flow sensors have different sensitivities due to differences in the cross-sectional area of the flow path (difference in flow velocity of fluid), a wide range of measurement can be performed by switching the thermal flow sensors to be used. Becomes In addition, since the flow path cross-sectional area of the pipeline is set to a large value on the upstream side and a small value on the downstream side, when the flow of the fluid is rectified by the rectifier to reduce pressure loss, the flow path on the upstream side By arranging the rectifier at a position where the cross-sectional area is large, the flow path cross-sectional area can be reduced toward the downstream side where the heat-sensitive flow velocity sensor is disposed, thereby making it possible to reduce the size of the flow path.

According to an eleventh aspect of the present invention, in the invention according to the tenth aspect, a thermosensitive flow rate sensor having low sensitivity is disposed at an upstream position where the cross-sectional area of the flow path is large in the pipeline, and the cross-sectional area of the flow path is reduced. A highly sensitive thermo-sensitive flow rate sensor was installed at a small downstream position.

Therefore, the sensitivity of the heat-sensitive flow velocity sensor disposed on the upstream side is further reduced because it is exposed to the fluid at the position where the flow velocity is low, and the heat-sensitive flow velocity sensor disposed on the downstream side is exposed to the fluid at the position where the flow velocity is high. Therefore, the sensitivity is further increased. This makes it possible to increase the difference between the sensitivities of the plurality of thermal flow sensors.

[0039]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG. In the present embodiment, FIG.
The same parts as those described in FIG. 9 are described using the same reference numerals. As shown in FIG. 1, a substrate 1 formed of a material such as silicon has a surface covered with an insulating film 2, and a moat 3 serving as a fluid flow passage for flowing a fluid such as a gas from the direction of an arrow is etched in the center. And the like. Further, a bridge 4a is formed on the substrate 1 so as to cross a part of the moat 3 orthogonally to the flow direction of the fluid. On the surface of the bridge 4a, two detection elements 5a and 5b are formed by a metal thin film. One of the detection elements 5a is composed of two heating elements (heating resistor films) 51a and 51a arranged upstream and downstream in the flow direction of the fluid.
The other detection element 5b is formed by two heating elements (heating resistor films) 51b and 52b arranged on the upstream side and the downstream side in the flow direction of the fluid.

Further, a heating element 51 is provided on the surface of the substrate 1.
a, 51b, 52a, 52b, bonding pads 53a, 53b, 54a, 54b;
And a bonding pad 8 connected to the temperature measuring element (heating resistor film) 7. Detection element 5
a and the temperature measuring element 7 are covered with an insulating protective film.

FIG. 2 is an explanatory diagram symbolically showing the patterns of the two detection elements 5a and 5b. As is clear from this figure, the heating elements 51a and 52a of one of the detection elements 5a are arranged on the bridge 4a in a central portion of the moat 3 so as to be arranged symmetrically with respect to the center line in the fluid stream direction. And the heating element 51 of the other detection element 5b.
The bridges 4b and 52b are arranged near the side wall 13 of the moat 3 so as to be symmetrical with respect to the center line in the streamline direction of the fluid.
Is formed on. That is, the detection elements 5a,
5b is provided at a position where thermal interference does not occur.

Between the upstream heating element 51b and the downstream heating element 52b, which form a pair of the detection elements 5b, the upstream heating element 51a and the downstream heating element of the other detection element 5a are arranged. A plurality of sets of detection elements 5a and 5b are arranged on the bridge 4a with an arrangement relationship where the body 52a is located.

FIG. 3 shows bridge 4a and moat 3 (see FIG. 1).
Of the bridge 4a divided into four by a straight line 14 passing through the center of the bridge 4a and a straight line 15 passing through the center of the bridge 4a. A slit 6 is formed to avoid interference. Although not shown in FIG. 3, the heating elements 52a, 52
A slit 6 is also formed in a portion close to b in order to further avoid thermal interference.

In such a thermosensitive flow velocity sensor B, when the flow velocity of a fluid such as gas is zero, the resistance values of the heating elements 51a and 52a of the detection element 5a are made equal, and
It is desirable that the resistance values of the heating elements 51b and 52b of the detection element 5b be equal. Now, assuming that the fluid flows in the direction of the arrow, the upstream heating elements 51a, 51b are cooled first by the fluid, and the downstream heating elements 52a, 52b take the heat from the upstream heating elements 51a, 51b. To the output of the heating elements 51a and 52a,
The outputs of b and 52b are different. Therefore, the flow velocity and flow rate of the fluid can be obtained from the output difference.

In this case, between the upstream-side heating element 51b and the downstream-side heating element 52b that form a pair of the detection element 5b, the upstream-side heating element 51a and the downstream-side heating element 51a of the other set of detection elements 5a are located. A plurality of sets of detecting elements 5a and 5b are connected to the bridge 4 in a positional relationship where the heating element 52a on the side is positioned.
a, a plurality of detection elements 5a, 5 having different sensitivities on one substrate 1 are arranged.
b can be formed. Therefore, by switching the detection elements 5a and 5b to be used according to the flow velocity and the flow rate of the fluid, it is possible to increase the measurement area.

Further, a plurality of sets of detection elements 5a, 5
b is disposed on the bridge 4a at different positions in the center of the moat 3 and near the side wall 13 of the moat 3 (corresponding to claim 2).
Therefore, a plurality of detection elements 5a and 5b having different sensitivities can be formed on one bridge 4a.

Here, the heating elements 51b and 52b of the one detecting element 5b are located near the side wall 13 of the moat 3 (bridge 4a).
(In the vicinity of the base), but when not arranged symmetrically about the center line in the fluid stream direction, the output characteristics of the detection element 5b are as shown in FIG. 4A shows the output of the heating element 51b on the upstream side and the output of the heating element 52b on the downstream side, and FIG.
This indicates the sum of the outputs b and 52b. The curve indicating the sum bends twice at the points A and B, and is unlikely to be a smooth curve.

However, in the present embodiment, the heating element 51b on the upstream side of the detection element 5b and the heating element 52b on the downstream side
Is arranged symmetrically with respect to the center line of the fluid in the streamline direction as an axis (corresponding to claim 3), the output pattern of the detection element 5b disposed near the side wall 13 of the moat 3 corresponds to the flow rate of the output voltage. Changes can be smoothed.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment and other embodiments that follow, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

Thermal type flow sensor C in this embodiment
Forms a plurality of bridges 4a, 4b from the upstream side to the downstream side in the flow direction of the fluid indicated by arrows, and each of these bridges 4a, 4b has a detection element 5a, 5b.
Is formed (corresponding to claim 4).

Therefore, similarly to the first embodiment, a plurality of detection elements 5a, 5a having different sensitivities are formed on one substrate 1.
5b can be formed. Thereby, the detection elements 5a, 5b used in accordance with the flow velocity and the flow rate of the fluid
By switching between, the measurement area can be increased. Further, by forming only one detection element 5a or 5b in each of the bridges 4a and 4b, the detection elements 5a and 5b are different from those of the first embodiment.
The degree of freedom in the arrangement of b can be increased. Further, since the bridges 4a and 4b are separated from each other and the moat 3 is formed between them, it is possible to more effectively prevent the thermal interference of the plurality of detection elements 5a and 5b.

Further, as shown in FIG. 5, the heating elements 51a and 52a and the heating elements 51b and 51b in the direction of the fluid flow.
By making the pattern width (width in the direction of fluid flow) 52b different for each of the plurality of detection elements 5a and 5b (corresponding to claim 5), the width of the moat 3 is constant and the length of the bridges 4a and 4b is longer. It is possible to form a plurality of detection elements 5a and 5b having different sensitivities even when the distance is constant. In this example, the width of the upstream bridge 4b and the pattern width of the detection element 5b disposed thereon are increased.

Further, the heating element 51 of the detection element 5a
a, 52a and the heating element 5 of the detection element 5b.
Configuration in which resistance values of 1b and 52b are changed (corresponding to claim 6)
By doing so, it is possible to further increase the difference in sensitivity between the detection elements 5a and 5b. Thereby, the area to be measured can be further widened.

Further, the resistance values of the heating elements 51b and 52b of the detection element 5b having the larger pattern width are changed by the heating elements 51a and 52b of the detection element 5a having the smaller pattern width.
A configuration set to a value larger than the resistance value of 52a.
Response), the sensitivity of the detection element 5b having the wider pattern width is further increased without greatly changing the pattern width of the detection elements 5a and 5b, and the sensitivity of the two detection elements 5a and 5b greatly differs. Can be further increased. In this case, the heating element 51
By selecting and combining the resistance values of a, 52a, 51b, and 52b and the parameters of the driving method, it is possible to further easily obtain the difference in sensitivity between the detection elements 5a and 5b. Tables 1 and 2
3 will be described.

[0055]

[Table 1]

In the case of the constant current driving method, as shown in Table 1, the resistance of the heating element of the detection element having high sensitivity has a high resistance value, and the heating element size (bridge size) of the detection element has a small value. I do. Therefore, the temperature of the heating element is set high by driving. Of course, the drive current is
The higher the sensitivity, the higher the sensitivity.

[0057]

[Table 2]

In the case of the constant voltage driving method, as shown in Table 2, when the resistance value of the heating element is increased, the power consumption decreases as the current value decreases. Therefore, the sensitivity also decreases. Of course, the higher the voltage, the higher the sensitivity.

[0059]

[Table 3]

In the case of the constant temperature driving method, as shown in Table 3, the resistance value of the heating element does not affect the power consumption, and the resistance of the heating element increases due to an increase in the voltage larger than the decrease in the driving current. Sensitivity is higher. The size of the heating element (the size of the bridge) is substantially proportional to the increase in power consumption, and the sensitivity increases accordingly. The higher the driving temperature, the higher the sensitivity.

FIG. 6 shows a third embodiment of the present invention.
It will be described based on. In the present embodiment, a plurality of bridges 4a and 4b are formed with different lengths in a direction orthogonal to the flow direction of the fluid indicated by arrows, and detection elements 5a and 5b are formed on the bridges 4a and 4b, respectively. Configuration (claim 8). In this example, the length of the upstream bridge 4b is set longer.

Therefore, it is possible to increase the length of the detection element 5a of the longer bridge 4b to increase the resistance value, thereby increasing the sensitivity. This makes it possible to increase the difference in sensitivity between the two detection sensors 5a and 5b.

Further, the resistance values of the long heating elements 51b and 52b of the detection element 5b on the longer bridge 4b are
By setting the resistance value of the short heating elements 51a and 52a of the detection element 5b on the shorter bridge 4a to be higher than the resistance value (claim 9), the pattern width of the detection elements 5a and 5b in the flow direction of the fluid is constant. However, by using the length of the bridge 4b, the resistance values of the heating elements 51b and 52b are set to a high value, whereby the detection element 5b
And the difference between the sensitivities of the two detection elements 5a and 5b can be increased.

Next, a fourth embodiment of the present invention will be described with reference to FIG. First, the present embodiment (Claim 10)
Is an example of a heat-sensitive flow velocity detecting device in which a plurality of heat-sensitive flow velocity sensors are attached to a pipe main body. First, FIG.
6 shows the configuration of FIG. FIG. 7A is a plan view showing the pipe main body 16 with the pipe 17 opened. FIG. 7B shows FIG.
7A is a vertical sectional side view taken on line YY, FIG. 7C is a vertical sectional front view taken on line XX in FIG. 7A, and FIG. 16 shows a state where 16 is closed by a lid 18. The conduit 17 has three portions 17a, 17b, and 17a, 17b,.
17c.

The portion 17 having the largest flow path cross-sectional area
A and rectifiers 19a and 19b for linearizing the flow of the fluid are provided in a and the next largest portion 17b. For example, these rectifiers 19a and 19b have a honeycomb structure in which a space is finely divided by a large number of partition walls and both ends on an upstream side and a downstream side are open, or a mesh structure having a large thickness. . In the following portions 17b and 17c of the pipeline 17, for example, a thermal flow sensor A as described with reference to FIGS. A sensor may be used.

The principle of measuring the flow velocity and the flow rate of the fluid by the thermal type flow rate sensors A is as described above. Even if the two thermal type flow rate sensors A have the same sensitivity, these thermal type flow rate sensors A A has a different sensitivity due to a difference in the cross-sectional area of the flow path (difference in the flow velocity of the fluid). Therefore, by switching the heat-sensitive flow velocity sensor A to be used, a wide range of measurement is possible.

Further, since the flow path cross-sectional area of the pipeline is set to a large value on the upstream side and a small value on the downstream side, when the flow of fluid is rectified by the rectifier 19 to reduce pressure loss, The rectifier is arranged at a position where the flow path cross-sectional area on the side is large, and the flow path cross-sectional area can be reduced toward the downstream side where the heat-sensitive flow rate sensor A is disposed, thereby reducing the size of the flow path. Becomes possible.

Further, if the sensitivity is the same, the sensitivity of the heat-sensitive flow rate sensor A disposed in the portion 17a having a small cross-sectional area of the flow channel where the flow velocity of the fluid is small is higher than that of the portion 17b having a larger cross-sectional area of the flow channel. Since the sensitivity is higher than that of the thermal type flow sensor A disposed in the upstream, the thermal type flow rate sensor A having low sensitivity is disposed in the upstream portion 17b having a large flow path cross-sectional area in the pipeline 17, and the flow path cross-sectional area is provided. Downstream portion 17 where
Since the thermal flow sensor A having a high sensitivity is disposed in c (claim 11), the thermal flow sensor A disposed in the upstream portion 17b is exposed to the fluid at a position where the flow velocity is low, so the sensitivity is high. Is further reduced, and the sensitivity of the thermal flow sensor A disposed in the downstream portion 17c is further increased because the flow sensor is exposed to the fluid at a position where the flow velocity is high. Thereby, the difference in sensitivity between the plurality of thermal flow sensors A is further increased, and measurement over a wider area becomes possible.

[0069]

According to the first aspect of the present invention, a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage are formed in the substrate, and the upstream side and the downstream side in the flow direction of the fluid are formed. A plurality of pairs of the detection elements are provided on the bridge, and a plurality of the detection elements are provided, and a pair of the detection elements is provided on the upstream side. Between the heating element and the heating element on the downstream side, a plurality of sets of the detection elements having an arrangement relationship in which the heating element on the upstream side and the heating element on the downstream side of the other set of the detection elements are located. Since the detection elements are arranged on the bridge, a plurality of detection elements having different sensitivities can be formed on one substrate.
Thus, the measurement area can be increased by switching the detection element to be used according to the flow velocity and the flow rate of the fluid.

According to a second aspect of the present invention, in the first aspect of the present invention, the plurality of sets of detecting elements are disposed on the bridge at different positions near the center of the fluid passage and near the side wall of the fluid passage. Thus, a plurality of detection elements having different sensitivities can be formed on one bridge.

According to a third aspect of the present invention, in the second aspect of the present invention, the arrangement pattern of the heating element on the upstream side and the heating element on the downstream side of the detection element is lined with the center line in the fluid stream direction as an axis. Since they are arranged symmetrically, it is possible to smoothly change the output voltage of the detection element arranged near the side wall of the fluid flow passage with respect to the flow rate.

According to a fourth aspect of the present invention, a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage are formed in the substrate, and the upstream and downstream sides in the flow direction of the fluid are formed on the substrate. In the thermosensitive flow rate sensor formed by forming a detection element consisting of a pair of heating elements arranged in the bridge, a plurality of the bridges are formed from the upstream side to the downstream side in the flow direction of the fluid, and each of the bridges is formed. Since the detection elements are formed on a single substrate, a plurality of detection elements having different sensitivities can be formed on one substrate. Thus, the measurement area can be increased by switching the detection element to be used according to the flow velocity and the flow rate of the fluid. Further, by providing a plurality of bridges according to the number of detection elements, the degree of freedom in arranging the detection elements on the bridges can be increased. Further, the plurality of detection elements can be separated from each other to prevent thermal interference between them.

According to a fifth aspect of the present invention, in the invention of the fourth aspect, since the pattern width of the heating element in the direction of fluid flow is changed for each of the plurality of detection elements, the width of the fluid flow passage is constant. Even when the length of the bridge is constant, a plurality of detection elements having a large difference in sensitivity can be formed by utilizing the difference in the pattern width of the heating element (corresponding to the bridge width). Thereby, the measurement range can be further widened.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the resistance of the heating element is changed for each of the plurality of detection elements. Can be further increased.

According to a seventh aspect of the present invention, in the fifth aspect of the invention, the resistance value of the heating element of the detection element having the larger pattern width is larger than the resistance value of the heating element of the detection element having the smaller pattern width. Since the value is set to a large value, it is possible to easily obtain the difference in the sensitivity of the detection element without largely changing the pattern width of the detection element (corresponding to the width of the bridge). In particular, by selecting and combining parameters of the resistance value of the detection element and the driving method, it is possible to easily obtain a difference in sensitivity of the detection element.

According to an eighth aspect of the present invention, in the sixth aspect, the plurality of bridges are formed so as to have different lengths in a direction orthogonal to the flow direction of the fluid, and a detection element is formed in each of the bridges. Therefore, the difference in the sensitivity of the detection element can be increased by using the difference in the length of the bridge.

According to a ninth aspect of the present invention, in accordance with the eighth aspect of the present invention, the resistance value of the detecting element formed on each of the plurality of bridges formed with different lengths in the direction orthogonal to the flow direction of the fluid. Is set to a higher value as the length of the heating element in the direction perpendicular to the fluid flow direction is longer, so even if the pattern width of the detection element in the fluid flow direction is constant, use the difference in bridge length Thus, the resistance value of the heating element can be set to a different value, and the difference in the sensitivity of the detection element can be increased.

According to a tenth aspect of the present invention, a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage are formed on the substrate, and the upstream and downstream sides in the fluid flow direction are formed. A plurality of heat-sensitive flow velocity sensors are formed by forming a detection element composed of a pair of heating elements disposed on the bridge, and the cross-sectional area of the flow path on the upstream side in the flow direction of the fluid is calculated from the cross-sectional area of the downstream side. Provide a pipeline set to a large value,
Since the thermosensitive flow rate sensors are disposed at each of a plurality of positions where the flow passage cross-sectional areas of the conduits are different, the plurality of heat-sensitive flow velocity sensors are arranged due to a difference in flow passage cross-sectional area (difference in fluid flow velocity). Since the sensitivities are different, wide-area measurement can be performed by switching the thermal flow sensor used.
In addition, since the flow path cross-sectional area of the pipeline is set to a large value on the upstream side and a small value on the downstream side, when the flow of the fluid is rectified by the rectifier to reduce pressure loss, the flow path on the upstream side By arranging the rectifier at a position where the cross-sectional area is large, the flow path cross-sectional area can be reduced toward the downstream side where the heat-sensitive flow velocity sensor is disposed, whereby the flow path can be downsized.

According to an eleventh aspect of the present invention, there is provided the pipe line invention according to the tenth aspect, wherein a thermosensitive flow rate sensor having low sensitivity is disposed at an upstream position where the flow path cross-sectional area of the pipe is large.
Since a high-sensitivity thermo-sensitive flow rate sensor is arranged at the downstream position where the flow path cross-sectional area is small, the sensitivity is further reduced because the thermo-sensitive flow rate sensor arranged at the upstream side is exposed to the fluid at a position where the flow velocity is slow, The sensitivity of the heat-sensitive flow velocity sensor arranged downstream is further increased because the flow velocity sensor is exposed to the fluid at a position where the flow velocity is high. As a result, the difference between the sensitivities of the plurality of thermal flow sensors can be increased, and the measurement range can be further widened.

[Brief description of the drawings]

FIG. 1 is a plan view of a thermal flow sensor according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing detection elements symbolically.

FIG. 3 is a plan view showing a part of a bridge and a detection element.

FIG. 4A is a characteristic diagram showing an output of a heating element on an upstream side and an output of a heating element on a downstream side, and FIG. 4B is a characteristic diagram showing a sum of outputs of heating elements on an upstream side and a downstream side; It is.

FIG. 5 is a plan view of a thermosensitive flow rate sensor according to a second embodiment of the present invention.

FIG. 6 is a plan view of a thermal flow sensor according to a third embodiment of the present invention.

FIG. 7A is a plan view showing a pipe main body of a heat-sensitive flow velocity detecting device according to a fourth embodiment of the present invention, and FIG. 7B is a longitudinal side view taken along a line YY in FIG. FIG. 1C is a vertical sectional front view taken on line XX in FIG.

FIG. 8 is a plan view showing a schematic configuration of a general thermal flow sensor.

9 is a longitudinal sectional front view taken on line XX in FIG. 8;

10A is a plan view showing a pipe main body of a conventional thermosensitive flow velocity detecting device, FIG. 10B is a vertical sectional side view taken on line YY in FIG. 10A, and FIG. X- in a)
It is the longitudinal front view made into the cross section on X-ray.

FIG. 11 is a circuit diagram showing an example of a drive circuit for a thermal flow sensor.

FIG. 12 is a characteristic diagram showing an output of a detection element when using thermal flow sensors having different sensitivities.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 3 Fluid flow path 4a, 4b Bridge 5a, 5b Detection element 51a, 52b, 51a, 52b Heating element 13 Side wall of fluid flow path 17 Pipe

Claims (11)

[Claims] A substrate having a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage;
In a thermosensitive flow rate sensor in which a detection element composed of a pair of heating elements arranged on the upstream side and the downstream side in the flow direction of the fluid is formed in the bridge, a plurality of the detection elements are provided, and one set of the detection elements is provided. An arrangement in which the upstream heating element and the downstream heating element of another set of the detection elements are located between the upstream heating element and the downstream heating element forming a pair of the detection elements. A heat-sensitive flow velocity detection sensor, wherein a plurality of sets of the detection elements are arranged on the bridge in a relation. 2. The heat-sensitive flow velocity sensor according to claim 1, wherein the plurality of sets of detection elements are disposed on the bridge at different positions near the center of the fluid flow passage and near the side wall of the fluid flow passage. 3. The heat-sensitive flow velocity according to claim 2, wherein the arrangement pattern of the heating element on the upstream side and the heating element on the downstream side of the detection element is arranged symmetrically with respect to the center line in the streamline direction of the fluid. Sensor. 4. A substrate having a fluid flow passage for flowing a fluid and a bridge bridging a part of the fluid flow passage,
In a heat-sensitive flow rate sensor in which a detection element composed of a pair of heating elements disposed on an upstream side and a downstream side in a flow direction of a fluid is formed in the bridge, the bridge is arranged from an upstream side to a downstream side in a flow direction of the fluid. Wherein the detection element is formed in each of the bridges. 5. The pattern width of the heating element in the direction of fluid flow is varied for each of the plurality of detection elements.
A thermal flow sensor as described. 6. The heat-sensitive flow velocity sensor according to claim 5, wherein the resistance value of the heating element is changed for each of the plurality of detection elements. 7. The heat-sensitive type according to claim 5, wherein the resistance value of the heating element of the detection element having the larger pattern width is set to be larger than the resistance value of the heating element of the detection element having the smaller pattern width. Flow rate sensor. 8. The heat-sensitive flow velocity detection sensor according to claim 6, wherein the plurality of bridges are formed so as to have different lengths in a direction orthogonal to the flow direction of the fluid, and each of the bridges has a detection element. 9. A resistance value of a detection element formed in each of a plurality of bridges formed with different lengths in a direction orthogonal to a fluid flow direction is equal to a resistance value of a heating element in a direction orthogonal to a fluid flow direction. The thermal flow sensor according to claim 8, wherein the longer the length, the higher the value. 10. A fluid flow passage for flowing a fluid, and a bridge bridging a part of the fluid flow passage are formed in the substrate, and a pair of a pair of the fluid flow passage are arranged on an upstream side and a downstream side in a fluid flow direction. A pipe in which a plurality of heat-sensitive flow velocity sensors each having a detection element formed of a heating element formed on the bridge are provided, and the cross-sectional area of the upstream flow path in the flow direction of the fluid is set to a value larger than the cross-sectional area of the downstream flow path. A heat-sensitive flow velocity sensor, wherein the heat-sensitive flow velocity sensor is disposed at each of a plurality of positions where the flow passage cross-sectional areas of the conduits are different. 11. A thermosensitive flow rate sensor having a low sensitivity is disposed at an upstream position where a cross-sectional area of a flow path is large in a pipeline, and a thermosensitive flow rate sensor having a high sensitivity is disposed at a downstream position where a cross-sectional area of a flow path is small. The thermosensitive flow velocity detecting device according to claim 10, which is provided.