JPH0222516A - Flow sensor - Google Patents

Abstract

PURPOSE:To hold the temperature in an element constant and to eliminate variance in output characteristics due to resistance adjustment by providing a resistance adjustment zone in the center of the heating part of a resistance body. CONSTITUTION:A flow sensor element 3 is arranged in a flow passage tube and the resistance body 2 is applied with a voltage so that a flow velocity detection part is a constant temperature higher than the temperature of fluid. Then the flow velocity of the fluid is found from heating value absorbed by the passage of the fluid in the flow passage tube. At this time, the resistance adjustment zone in the flow sensor element 3 is arranged in the center of the heating part 5 of the resistance body 2, so the temperature distribution in the element becomes constant without reference to whether or not the resistance adjustment is made and the variance in output characteristics due to the resistance adjustment can be eliminated. Further, variance among elements is eliminated and the flow velocity can be detected symmetrically about the flow direction without reference to whether the fluid flows to the element from the right or left.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermal flow sensor in which a resistance adjustment band is provided on a resistor formed on an insulating substrate.

<Prior Art> There are the following types of thermal flow sensors that have been commonly used.

The first is to install a bypass channel pipe in the main channel pipe, connect a heater to this channel pipe, and heat the channel pipe to generate a temperature in the flow direction of the channel pipe due to the flow. This is a flowmeter that uses a method to detect flow rate from distribution. This flowmeter has good accuracy and is widely used as a flow rate controller for semiconductor gas, etc., but its structure makes it unsuitable for miniaturization and mass production, and it is expensive, so its uses are limited.

The second is a flow sensor that uses a method in which a heating element is installed in the fluid, and the change in the amount of heat transferred from the heating element to the surrounding fluid is detected, and the driftwood is measured from the detected value. There is. Flow sensors using this method include:
2. Description of the Related Art Conventionally, there is a flow sensor constructed using a transistor formed on a silicon chip. This flow sensor uses silicon process technology and is therefore highly suitable for mass production. However, on the other hand, it has drawbacks such as large variations in temperature characteristics between elements and difficulty in using it at high temperatures.
have.

Furthermore, some of the above methods use resistance wires made of high-melting point metals such as platinum or tungsten for the heating elements, but these have small resistance values and large variations between elements, making it difficult to control the heating temperature and to measure the temperature. Accuracy is poor. Furthermore, since thin wires are used, there are drawbacks such as difficulty in processing and lack of mass production.

Furthermore, a thermal film flow sensor that uses a thin resistor on an insulating substrate instead of a resistance wire can be made smaller and can be manufactured by arranging a large number of elements on a single substrate. , it is also excellent in mass production. In addition, in this structure, variations in resistance value between elements occur due to variations in film thickness during thin film fabrication, but by providing a resistance adjustment band and adjusting the resistance value with a laser cutter etc., variation in resistance value between elements is suppressed. was.

FIGS. 6(a) and 6(b) show an example of a heat generating element (flow sensor element) in which a resistance adjusting band is provided on the resistor, and the resistance adjusting band is arranged at the end of the heat generating portion of the resistor.

6(a) is a cross-sectional plan view when the resistance adjustment band is not adjusted in resistance, and FIG. 6(b) is a cross-sectional plan view when the resistance adjustment band is adjusted to the maximum.

In addition, a heating resistor and a heating temperature resistance thermometer that applies a voltage to the heating resistor while detecting the heating temperature of the heating resistor are formed on the substrate, and the heating resistor and the heating temperature resistance thermometer are formed on the substrate. Figure 7 shows an example of a heat generating element (flow sensor element) in which a resistor adjustment band is arranged at the end of each heat generating part.
) (b). FIG. 7(a) is a cross-sectional plan view when the resistance adjustment band is not adjusted in resistance, and FIG. 7(b) is a cross-sectional plan view when the resistance adjustment band is adjusted to the maximum.

As shown in the figure, a first resistance adjustment band 4a is placed at the end of the heat generating portion 5a of the heat generating resistor 2a, and a second resistance adjusting band 4b is placed at the end of the heat generating portion 5b of the heat generating temperature sensing resistor 2b. are provided at both ends of the substrate 1 so as to face each other.

Problems to be Solved by the Invention 〉 However, when an element is installed in a flow pipe, fluid is caused to flow from one direction, and the flow velocity and power consumption are measured, the conventional flow shown in Fig. 6 (a) and (b) is In the sensor element 3, if the resistance adjustment band 4 is adjusted, the temperature distribution inside the element 3 will be different, so as shown in Figure 8, the output characteristic A when the resistance adjustment is not performed and the resistance adjustment is maximized. An error can be seen in the output characteristic B when the

Similarly, in the conventional flow sensor element 3 shown in FIGS. 7(a) and 7(b), errors are observed in the output characteristics as shown in FIG. 8.

Furthermore, when the element is installed in a flow pipe and the output characteristics of the element are measured with respect to the fluid flow direction, in the conventional flow sensor element 3 shown in FIG. 6(b), the temperature distribution inside the element 3 changes. As shown in FIG. 9, the output characteristics R when fluid flows from the left side (resistance adjustment band 4 side) of element 3 and the output characteristics R when fluid flows from the right side (opposite side to resistance adjustment band 4)
Errors can be seen.

Similarly, in the conventional flow sensor element 3 shown in FIG. 7(b), as shown in FIG.
An error can be seen in the output characteristic R when flowing from the first resistance adjustment band 4a side) and the output characteristic R when flowing from the right side (second resistance adjustment band 4b side).

Therefore, in a hot film flow sensor that uses a thin resistor on an insulating substrate instead of a conventional resistance wire, if the resistance adjustment band is poorly placed, the temperature distribution inside the element will vary when the resistance is adjusted. As a result, the amount of heat transferred from the resistor to the fluid changes, causing variations in output characteristics.

Furthermore, there is a drawback that a significant error occurs in the output characteristics between when fluid flows from one side of the element and when fluid flows from the pond side.

In view of the above-mentioned problems, the present invention has been developed so that when a large number of flow sensor elements are arranged and manufactured on one substrate, the temperature distribution within the element remains constant even if the resistance is adjusted in the resistance adjustment band. The purpose of the present invention is to provide a flow sensor that can suppress variations in output characteristics between elements, and that can be easily installed in piping, etc., without directional dependence in the output characteristics of the elements even when placed in a flow pipe. That is.

<Means for solving the problems> The means for solving the problems according to the present invention are as shown in FIGS. 1(a) and (b),
As shown in FIGS. 2(a) and (b), the insulating substrate 1 and the insulating substrate 1
A flow sensor element 3 having a resistor 2 formed on the top of the flow sensor element 2 whose resistance value changes with respect to temperature changes, and causing the resistor 2 in the flow sensor element 3 to generate heat to change the amount of heat removed by passage of the fluid. In the flow sensor that determines the flow velocity of the fluid based on the above, the resistor 2 is provided with a resistance adjustment band 4, and the resistance adjustment band 4 is disposed at the center of the heat generating portion 5 of the resistor 2.

<Operation> In the above-mentioned means for solving the problem, the flow sensor element 3 is placed in the flow pipe, and a voltage is applied to the resistor 2 so that the flow rate detection portion becomes a certain temperature higher than the fluid temperature. and,
Based on the amount of heat removed by the passage of fluid in the flow pipe,
The flow velocity of the fluid is determined.

At this time, since the resistance adjustment band 4 in the flow sensor element 3 is placed in the center of the heat generating part 5 of the resistor 2, the temperature distribution within the element is constant regardless of whether resistance adjustment is performed, and the output due to resistance adjustment is It is possible to eliminate variations in characteristics. Further, there is no variation between elements, and the flow velocity can be detected symmetrically regardless of whether the fluid flows from the left or right side of the element.

<Examples> Examples of the present invention will be described below with reference to the drawings. Fig. 1 (6) is a cross-sectional plan view when no resistance adjustment is made to the resistance adjustment band of the flow sensor element in the first embodiment of the present invention, and Fig. 1 (b) is a cross-sectional plan view when the resistance adjustment band is adjusted to the maximum. FIG.

As shown in the figure, the present invention includes a flow sensor element 3 having an insulating substrate 1 and a resistor 2 formed on the insulating substrate 1 and having a resistance value that changes with temperature changes. In a thermal flow sensor that generates heat in a resistor 2 and determines the flow velocity of the fluid based on a change in the amount of heat removed by the passage of the fluid, the resistor 2 is provided with a resistance adjustment band 4, and the resistance adjustment band 4 is It is arranged at the center of the heat generating part 5 of the resistor 2.

As shown in FIGS. 1(a) and 1(b), the insulating substrate 1 is formed into a rectangular shape using a thermally insulating material with low thermal conductivity such as glass as the substrate material.

The resistor 2 is formed by depositing a metal thin film having a large resistance temperature coefficient, such as platinum, on the insulating substrate 1 by vacuum evaporation, sputtering, plasma CVD, or the like, and then patterning the film by etching. There is.

The resistance pattern of the resistor 2 is provided symmetrically with respect to the resistance adjustment band 4 . Above the resistance pattern, the heat generating portion 5 is provided which is patterned in a rectangular pulse shape in the fluid flow direction. Furthermore, pads 6 are provided at both ends of the resistor pattern for adjusting the body shape of the resistor pattern.

In the resistance adjustment band 4, the resistance value is adjusted using a laser cutter or the like in order to suppress variations in resistance value between the elements 3.

The flow sensor element 3 constructed as described above is obtained by depositing a resistor 2 on an insulating substrate 1 by depositing a metal thin film such as platinum having a large resistance temperature coefficient by vacuum evaporation, sputtering, plasma CVD, etc. , is formed by patterning using etching technology. As shown in FIG. 3, this flow sensor element 3 is placed in a flow path pipe 8, and a voltage is applied to the resistor 2 so that the flow rate detection portion becomes a certain temperature higher than the fluid temperature. Then, the flow velocity of the fluid is determined based on the amount of heat taken away by the passage of the fluid in the flow path pipe 8. At this time, the voltage V applied to the flow sensor element 3 and the resistor 2
The relationship between the consumption voltage P of the resistor 2 and the flow velocity V, which is determined from out, is as follows: P = Vout''/Rh = (A + Bf) 'Δ
'F. Note that Rh is the resistance value of resistor 2,
A and B are constants, and ΔT is the difference between the heat generation temperature of the flow sensor element 3 and the fluid temperature. Here, if △T is constant,
Since the power P dissipated by the resistor 2 is proportional to the square root 6 of the flow velocity, the flow velocity can be determined from the voltage VouL or the power consumption P.

Therefore, as shown in Fig. 3, the flow sensor element of the present invention is installed in the flow path pipe 8, and the flow rate and power consumption are measured by flowing fluid from one direction, and the conventional flow sensor element is installed similarly. A comparison of the flow velocity and power consumption measured by flowing fluid from one direction is as follows.

In the conventional flow sensor element 3 shown in FIGS. 6(a) and 6(b) in which the resistance adjustment band 4 is arranged at the end of the heat generating part 5 of the resistor 2, when the resistance adjustment band 4 is adjusted, the inside of the element 3 is temperature distribution is different. For this reason, as shown in FIG. 8, there is an error between the output characteristic A when no resistance adjustment is made and the output characteristic B when resistance adjustment is made to the maximum.

On the other hand, in the flow sensor element 3 of the present invention shown in FIG. Also, the temperature distribution within the element 3 becomes constant. Therefore, no error is observed between the output characteristic A when the resistance is adjusted as shown in FIG. 4 and the output characteristic B when the resistance is adjusted to the maximum.

Further, as shown in FIG. 3, the output characteristics of the flow sensor element of the present invention and the output characteristics of the conventional flow sensor element are compared with respect to the fluid flow direction when the flow sensor element 3 is arranged in the flow path pipe 8. Then it becomes as follows.

In the conventional flow sensor element 3 shown in FIG. 6(b), since the temperature distribution inside the element 3 changes, the fluid flows to the left side (resistance adjustment band 4 side) with respect to the flow sensor element 3, as shown in FIG.
There is an error in the output characteristic R when the flow is from the right side (opposite side to the resistance adjustment band 4).

On the other hand, the flow sensor element 3 of the present invention shown in FIG. 1(b)
Since the temperature distribution inside the element 3 is constant, the output characteristics R when the fluid flows from the left side of the flow sensor element 3 and the output characteristics R when the fluid flows from the right side as shown in Fig. 5.
No errors can be seen.

That is, when the resistance adjustment band 4 in the flow sensor element 3 is arranged in the center of the heat generating part 5 of the resistor 2 as in the flow sensor of the present invention, the temperature distribution in the element becomes constant regardless of whether resistance adjustment is performed or not. It is possible to eliminate variations in output characteristics due to resistance adjustment.

In addition, there is no variation between elements, and the flow velocity can be detected symmetrically no matter which side the fluid flows from the left or right side of the element.

Therefore, when manufacturing a large number of flow sensor elements side by side on one board, the temperature distribution within the element does not change even if the resistance adjustment band is adjusted, so it is possible to suppress variations in output characteristics between elements. . Moreover, since the output characteristics of the element do not have directional dependence even when placed in a flow pipe, installation in a pipe or the like becomes easy.

Next, a second embodiment of the present invention will be described with reference to the drawings. Figure 2 (,) is a cross-sectional plan view of the case where no resistance adjustment is made to the resistance adjustment band of the flow sensor element in the second embodiment of the present invention, and Figure 2 (b) is a cross-sectional view when the resistance adjustment band is adjusted to the maximum. FIG.

As shown in the figure, in the flow sensor of the second embodiment of the present invention, a heat generating resistor 2a is used as the resistor 2, and a heat generating temperature measuring resistor which applies a voltage to the heat generating resistor 2a while detecting the heat generating temperature of the heat generating resistor 2a. 2b are formed on the insulating substrate 1. The heat generating temperature measuring resistor 2b is provided in a patterned manner inside the heat generating resistor 2a.

A first resistance adjustment band 4a is arranged at the center of the heat generating part 5a of the heat generating resistor 2a, and a second resistance adjustment band 4 is arranged at the center of the heat generating part 5b of the heat generating temperature measuring resistor 2b.
b. The configuration of the pond is the same as that of the first embodiment.

In the flow sensor element 3 configured as described above, the heat generating resistor 2a and the heat generating temperature measuring resistor 2b are made of a metal thin film such as platinum having a large resistance temperature coefficient on the insulating substrate 1, as in the first embodiment. Vacuum evaporation method, sputtering method, or plasma C
After being deposited by a VD method or the like, it is patterned by an etching I technique. This flow sensor element 3
is placed in the flow pipe 8 as shown in FIG.
Apply voltage to a. Then, the flow velocity of the fluid is determined based on the amount of heat taken away by the passage of the fluid in the flow path pipe 8.

At this time, the relationship between the power consumption P of the heating resistor 2a and the flow velocity V, which is determined from the voltage Vout applied to the heating resistor, is expressed as P:=Vout2/Rh=(A+BC)−△T, as in the first embodiment. be done. Note that Rh is the resistance value of the heating resistor 2a, A and B are constants, and ΔT is the difference between the heating temperature of the flow sensor element 3 and the fluid temperature. Here, if ΔT is constant, the power consumption P of the heating resistor 2a is proportional to the square root F of the flow velocity, so the flow velocity can be determined from the voltage Vout or the power consumption P2.Therefore, similarly to the first embodiment, The flow sensor element of the present invention and the conventional flow sensor element are installed in the flow path pipe 8 shown in FIG. 3, and a fluid is flowed from one direction, and the flow velocity and power consumption are measured and compared.

FIGS. 7(a) and 7(b) show that the first resistance adjustment band 4a and the second resistance adjustment band 4b are arranged at both ends of the substrate 1 so as to face each other.
In the conventional flow sensor element 3 shown in FIG. 3, the temperature distribution within the three elements differs when resistance is adjusted.

For this reason, as shown in FIG. 8, there is an error between the output characteristic A when no resistance adjustment is made and the output characteristic B when resistance adjustment is made to the maximum.

On the other hand, the first resistance adjustment band 4a is connected to the heat generating portion 5 of the heat generating resistor 2a.
Fig. 2(a) in which the second resistance adjustment band 4b is arranged in the center of the heat generating part 5b of the heat generating temperature measuring resistor 2b.
In the flow sensor element 3 of the present invention shown in b), the temperature distribution within the element 3 remains constant even when the resistance is adjusted. Therefore, as shown in FIG. 4, no error is observed between the output characteristic A when the resistance is adjusted and the output characteristic B when the resistance is adjusted to the maximum.

Further, as in the first embodiment, the flow sensor element 3 is installed in the flow path pipe 8 as shown in FIG. 3, and the output characteristics of the flow sensor element of the present invention and the conventional flow sensor element with respect to the fluid flow direction are A comparison with the output characteristics of No. 3 is as follows.

In the conventional flow sensor element 3 shown in FIG. 7(b), since the temperature distribution inside the element 3 changes, the fluid flows from the left side (first resistance adjustment zone 4a) with respect to the element 3, as shown in FIG. An error can be seen between the output characteristic R when the current flows and the output characteristic R when the current flows from the right side (second resistance adjustment band 4b).

On the other hand, the flow sensor element 3 of the present invention shown in FIG. 2(b)
Since the temperature distribution inside the element 3 is constant, the output characteristics R when the fluid flows from the left side of the flow sensor element 3 and the output characteristics R when the fluid flows from the right side as shown in Fig. 5.
No errors can be seen.

Therefore, even if the first resistance adjustment band 4a is arranged in the center of the heat generating part 5a of the heat generating resistor 2a and the second resistance adjusting band 4b is arranged in the center of the heat generating part 5b of the heat generating temperature measuring resistor 2b, the Effects similar to those of the embodiment can be obtained.

FIGS. 6(a) and 7(b) and FIGS. 7(a) and 7(b) showing conventional flow sensors are given the same numbers as in the embodiment.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

For example, although platinum is used as the material for the resistor in the examples, platinum alloys with a large resistance coefficient, platinum alloys other than platinum,
Nickel, nickel alloy, thermistor, etc. may also be used.

<Effects of the Invention> As is clear from the above description, according to the present invention, the flow sensor element includes an insulating substrate and a resistor formed on the insulating substrate and whose resistance value changes with respect to temperature changes. In a flow sensor that generates heat in a resistor in a flow sensor element and determines the flow velocity of the fluid based on a change in the amount of heat removed by passage of the fluid, the resistor is provided with a resistance adjustment band, and the resistance adjustment band is connected to the resistance Since it is placed in the center of the heat generating part of the body, the temperature distribution within the element is constant regardless of whether resistance adjustment is performed, and variations in output characteristics due to resistance adjustment can be eliminated. In addition, there is no variation between elements, and the flow velocity can be detected symmetrically regardless of whether the fluid flows from either the left or right side of the element.

Therefore, when manufacturing a large number of flow sensor elements side by side on a single board, the temperature distribution within the element does not change even if the resistance adjustment band is adjusted, making it possible to suppress variations in output characteristics between elements. There are excellent effects that can be achieved. Furthermore, even when placed in a flow pipe, the output characteristics of the device do not have directional dependence, which provides an excellent effect of simplifying installation in piping and the like.

[Brief explanation of the drawing]

Figure 1 (, ) is a cross-sectional plan view of the flow sensor element according to the first embodiment of the present invention without resistance adjustment;
) is a cross-sectional plan view when the resistance is adjusted to the maximum,
Fig. 2(a) is a cross-sectional plan view of the flow sensor element according to the second embodiment of the present invention without resistance adjustment; Fig. 2(b)
) is a cross-sectional plan view when the resistance is adjusted to the maximum,
Fig. 3 shows the state in which the flow sensor element is arranged in the flow path pipe, and Fig. 4 shows Fig. 1(,)(b), Fig. 5(a)(
Figure 5 shows the directional dependence of the output characteristics of the flow sensor element of the present invention shown in Figures 1 (b) and 2 (b). The figure shown,
Figure 6(,) is a cross-sectional plan view of a flow sensor element equipped with a conventional resistor without resistance adjustment;
b) is a cross-sectional plan view when the resistance adjustment band is also maximized, and Fig. 7 (,) is a flow sensor element equipped with a conventional heat generating resistor and a heat generating temperature measuring resistor with resistance adjusted. Figure 8 is a cross-sectional plane view when the resistance is adjusted to the maximum, Figure 8 is a cross-sectional plane view when the resistance is not adjusted to the maximum, and Figure 7 (a). (b) is a diagram showing the output characteristics of the conventional flow sensor element, and Figure 9 is similar to Figure 6 (
b) is a diagram showing the directional dependence of the output characteristics of the conventional flow sensor element shown in FIG. 7(b). 1: Insulating substrate, 2: Resistor, 2a: Heat generating resistor, 2b:
Heat generating temperature resistance thermometer, 3 near 0-sensor element, 4: resistance adjustment band, 4a: first resistance adjustment band, 4b: second resistance adjustment band, 5: heat generating section. Applicant: Sharp Corporation

Claims (1)

[Claims] A flow sensor element includes an insulating substrate and a resistor formed on the insulating substrate and whose resistance value changes with temperature changes. In the flow sensor that determines the flow velocity of the fluid based on a change in the amount of heat generated, the flow sensor is characterized in that the resistor is provided with a resistance adjustment band, and the resistance adjustment band is disposed at the center of the heat generating part of the resistor. sensor.