JP3258483B2 - Gas rate sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas rate sensor for detecting an angular velocity acting on a substrate.

[0002]

2. Description of the Related Art In a gas rate sensor of this type,
When the angular velocity acts on the substrate, the gas flow bends to cool one of the heat wire pairs (angular velocity detection unit) that constitutes a part of the resistance bridge circuit, and the resistance value depends on the temperature difference of the heat wire pair at this time. Changes, and the angular velocity is detected based on the voltage change caused by the change in the resistance value. Therefore, the gas ejected from the nozzle hole into the gas flow path must always generate a stable flow at a constant flow rate. There is. In other words, when the gas flow rate fluctuates, the fluctuation amount becomes a temperature-sensitive error, and the detection accuracy is reduced.

[0003] In particular, there is provided an ultra-small and very precise base body having nozzle holes, gas flow paths, etc. formed by micromachining processing by an IC manufacturing technique using a semiconductor substrate as disclosed in Japanese Patent Laid-Open No. 3-29858. In such a gas rate sensor, even a slight change in the flow rate of the gas ejected from the nozzle hole into the gas flow path causes a large detection error.

Therefore, in order to cope with such a situation, the flow rate of the gas ejected from the nozzle hole into the gas flow path via the pump is detected by a flow sensor (flow rate detecting unit) provided in the nozzle hole. There is known a method in which the drive of a pump is controlled so that the detected flow rate becomes a predetermined constant flow rate, thereby preventing fluctuation of the flow rate of gas flowing in the gas flow path and improving detection accuracy. (See Japanese Patent Application Laid-Open No. Hei 5-2026). The flow sensor is made of a heat wire similarly to the above-described angular velocity detection unit, and the resistance value changes according to a temperature difference due to a change in the gas flow rate, and the gas flow rate is determined based on a voltage change caused by the change in the resistance value. It is to detect.

However, in such a gas rate sensor, since the flow sensor is provided in the nozzle hole, the gas heated when passing through the flow sensor is cooled before reaching the angular velocity detector. Will flow inside. As a result, there is an inconvenience that an ascending air flow is generated in the gas flow path and the flow of the gas changes before reaching the angular velocity detecting unit, thereby causing an offset.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned disadvantages, and it is possible to discharge a constant flow rate of gas from a nozzle hole into a gas flow path, and to use a heat wire of an angular velocity detecting unit. It is an object of the present invention to provide a gas rate sensor that can prevent a gas flow from changing before reaching a pair and can generate a stable gas flow in a gas flow path.

Another object of the present invention is to provide a gas rate sensor which can respond to a case where the voltage applied to the heat wire of the flow rate detecting section is low.

Further, the present invention relates to an I-type semiconductor device using a semiconductor substrate.
Even with a very small and very precise substrate with nozzle holes, gas flow passages, etc. formed by micromachining processing using manufacturing technology, it is possible to prevent gas flow from changing and maintain a constant flow rate. It is an object of the present invention to provide a gas rate sensor that can cause a gas having a stable flow to be ejected from a nozzle hole into a gas flow path.

[0009]

In order to achieve the above object, the present invention provides a substrate having a gas flow path and a nozzle hole for ejecting gas into the gas flow path; Pump means for ejecting gas into the flow path to generate a gas flow in the gas flow path, and detecting a state of deflection of the gas flow when an angular velocity acts on the substrate provided in the gas flow path An angular velocity detector having a pair of heat wires, a flow detector having a heat wire for detecting a flow rate of gas ejected into the gas flow path, and a gas flow rate detected by the flow rate detector being preset. A pump drive control means for controlling the drive of the pump means so that the flow rate becomes a given flow rate, wherein the heat wire of the flow rate detection unit is located downstream of the heat wire pair of the angular velocity detection unit. It is characterized in that arranged in the scan channel.

Further, according to the present invention, the gas flow passage provided with the heat wire of the flow rate detection unit is formed to be narrower than the gas flow passage provided with the heat wire pair of the angular velocity detection unit. It is characterized by the following.

Further, the present invention relates to an I-type semiconductor device using a semiconductor substrate.
C, wherein the base is formed by micromachining using a manufacturing technique, and the angular velocity detector and the flow rate detector are formed on the base by micromachining.

Further, in the present invention, each heat wire of the angular velocity detecting section and the flow rate detecting section is formed of platinum.

[0013]

According to the present invention, since the heat wire of the flow rate detecting section is disposed in the gas flow path downstream of the pair of heat wires of the angular velocity detecting section, the heating of the gas by the heat wire of the flow rate detecting section is performed at the angular velocity. This is performed on the gas flow after the angular velocity is detected by the detection unit.

In the case where the gas flow path provided with the heat wire of the flow rate detecting section is formed narrower than the gas flow path provided with the heat wire pair of the angular velocity detecting section, the narrowed gas flow path is provided. By providing the heat wire of the flow rate detection unit corresponding to the width, the resistance of the heat wire can be reduced.

Further, when each heat wire of the angular velocity detecting section and the flow rate detecting section is made of platinum, the temperature sensing characteristics of each heat wire are improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 is an overall schematic view of a gas rate sensor according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a base, FIG. 3 is a sectional view taken along line III-III of FIG. 2, and FIG.
FIG. 4 is a sectional view taken along line IV.

The overall structure will be described with reference to FIG. 1. The gas rate sensor comprises an ultra-compact base 1 formed by micromachining using a semiconductor substrate, and the base 1
An angular velocity detector 3 provided in the gas flow path 2 for detecting a state of deflection of a gas flow when an angular velocity acts on the base 1;
A flow rate detector 4 provided in the gas flow path 2 downstream of the angular velocity detector 3 to detect the flow rate of gas flowing through the gas flow path 2
And a micropump 6 connected to the nozzle hole 5 of the base 1 and ejecting a gas flow from the nozzle hole 5 into the gas flow path 2;
Pump driving control means 7 for controlling the driving of the micro pump 6 so that the flow rate of the gas detected by the flow rate detection section 4 becomes a preset flow rate.

The base 1 is formed by bonding a lower semiconductor substrate 8 and an upper semiconductor substrate 9 as shown in FIGS. Has a nozzle hole 5 for jetting out. Gas flow path 2
Is formed by abutting a concave portion 10 formed in the lower semiconductor substrate 8 and a concave portion 11 (see FIG. 3) formed in the upper semiconductor substrate 9 with each other. On the other hand, as shown in FIG.
The upper semiconductor substrate 9 is formed by aligning the bonding surface of the upper semiconductor substrate 9 with the groove 12 formed so as to communicate with the groove 12.

The angular velocity detector 3 detects the state of deflection of the gas flow when the angular velocity acts on the substrate 1, and detects the state of the heat-sensitive resistance elements symmetrically arranged with respect to the center line of the gas flow path 2. Heat wire pairs 13 and 14. The heat wire pairs 13 and 14 constitute a resistance bridge circuit with a circuit portion (not shown) separately wired outside the base 1 and extend over the concave portion 10 of the lower semiconductor substrate 8. A heat-sensitive resistance material is deposited on the upper surface of the bridge portion 15 formed in the step (1), and the pattern is formed by etching. Here, in this embodiment, platinum having excellent heat-sensitive characteristics is used as the heat-sensitive resistance material. Also, on both sides of the heat wire pairs 13 and 14, the heat wire pair 1
The electrode part 16 connected to the heat wire pair 13
The pattern is formed in the same manner as 14.

The flow rate detecting section 4 detects the flow rate of the gas flowing through the gas flow path 2.
A heat wire 17 composed of a heat-sensitive resistance element is provided so as to linearly cross the gas flow path 2 downstream of 14. The heat wire 17 is formed into a pattern by depositing a heat-sensitive resistance material on the upper surface of the bridge portion 18 formed so as to straddle the concave portion 10 on the downstream side of the bridge portion 15 and then performing etching. As a thermal resistance material,
Like the heat wire pairs 13 and 14, platinum having excellent heat sensitivity is used. On both sides of the heat wire 17, electrode portions 18 a are pattern-formed in the same manner as the heat wire 17.

The micropump 6 is driven in a gas atmosphere such as helium so as to jet a gas flow from the nozzle hole 5 into the gas flow path 2. In the present embodiment, the micropump 6 is driven by a pulse signal. A diaphragm type is used.

The pump drive control means 7 controls the drive of the micropump 6 so that the flow rate of the gas detected by the flow rate detection section 4 becomes a predetermined flow rate. As shown in FIG. Control unit 19, power detection unit 20,
The microcomputer comprises a microcomputer having a pulse signal generating section 21 and a waveform shaping section 22.

The control unit 19 reads a detection signal based on a voltage change of the heat wire 17 when the flow rate of the gas passing through the heat wire 17 of the flow rate detection unit 4 changes, amplifies the signal, and detects the gas flow rate. A value is calculated, and the detected value is compared with a specified value determined based on a specified flow rate in advance, and a specified power value for the micro pump 6 such that the detected value matches the specified value is indicated. The power detection unit 20 detects the actual power consumption of the micropump 6 and outputs a frequency control signal such that the detected power consumption value matches the specified power value specified by the control unit 19. Pulse signal generator 21
Generates a pulse signal corresponding to the frequency control signal provided from the power detection unit 20. The waveform shaping unit 22 shapes the waveform of the pulse signal provided from the pulse signal generation unit 21 and provides a driving pulse to the micro pump 6. Thereby, the drive control of the micro pump 6 is performed so that the flow rate of the gas detected by the flow rate detection unit 4 becomes the specified flow rate.

When the lateral angular velocity does not act on the substrate 1 at all, the gas ejected from the nozzle hole 5 into the gas flow path 2 by the driving of the micropump 6 moves along the center line of the gas flow path 2. When the angular velocity acts on the base 1, the gas flow is shifted from the center line of the gas flow path 2, and the heat wire pairs 13 and 14 are uniformly cooled.
3 and 14 to one side. At this time, one heat wire pair
The resistance value changes due to a temperature difference between 3, and 14, and the angular velocity is detected based on the voltage change due to the change in the resistance value.

The gas that has passed through the heat wire pairs 13 and 14 strikes the heat wire 17 of the flow rate detector 4 and cools the heat wire 17. At this time, if the flow rate of the gas flowing through the gas flow path 2 fluctuates from the specified flow rate for some reason, a temperature difference occurs in the heat wire 17 and the resistance value changes, and the voltage change due to the change in the resistance value occurs. The gas flow rate changed based on the above is detected and output to the control unit 19 of the pump drive control means 7.

When a detection signal is output from the heat wire 17 to the control unit 19, the control unit 19 amplifies the signal and calculates a detected value of the gas flow rate. The detected value is determined in advance based on the specified flow rate. A specified power value for the micropump 6 such that the detected value matches the specified value as compared with the specified value is instructed to the power detection unit 20. When the specified power value is indicated,
The power detection unit 20 compares the specified power value with the actually detected power consumption value of the micropump 6 and sends a frequency control signal to the pulse signal generation unit 21 such that the detected power consumption value matches the specified power value. Output. The pulse signal generating section 21 outputs a pulse signal corresponding to the frequency control signal to the waveform shaping section 22, and the waveform shaping section 22 shapes the pulse signal to give a driving pulse to the micropump 6, and The drive control of the pump 6 is performed, and the flow rate of the changed gas is corrected to the specified flow rate.

In the gas rate sensor having the above configuration,
Since the heat wire 17 of the flow rate detection unit 4 is provided in the gas flow path 2 downstream of the pair of heat wires 13 and 14 of the angular velocity detection unit 3 to detect the gas flow rate, the gas generated by the heat wire 17 of the flow rate detection unit 4 Is heated by a heat wire pair 13,
This is performed on the gas flow after the angular velocity is detected by 14. Therefore, unlike the related art, an ascending airflow does not occur in the gas flow path 2 before reaching the heat wire pairs 13 and 14 of the angular velocity detector 3. Therefore, even in a very small and very precise gas rate sensor formed by subjecting a semiconductor substrate to micromachining as in the present embodiment, a constant flow rate of gas can be jetted into the gas flow path 2. In addition, it is possible to prevent the gas flow from changing before reaching the heat wire pairs 13 and 14 of the angular velocity detecting unit 3, and to generate a stable gas flow. For this reason, the detection accuracy of the angular velocity can be improved, and the offset due to the heating of the gas by the heat wire 17 can be favorably avoided, and the reliability of the angular velocity detection can be improved.

Further, the heat wire 17 conventionally provided in the nozzle hole is replaced with the heat wire pair 1 of the angular velocity detector 3.
Since it is only necessary to dispose the gas rate sensor in the gas flow path 2 on the downstream side of the gas flow rates 3 and 14, no new parts are required as compared with the conventional gas flow path, and a gas rate sensor having a simple structure and low cost can be provided.

Further, the angular velocity detector 3 and the flow rate detector 4
Since each of the heat wires 13, 14, and 17 is formed of platinum having excellent temperature-sensitive characteristics, the accuracy of detecting the angular velocity and the gas flow rate can be further improved.

The present invention is not limited to the above embodiment, but can be appropriately modified without departing from the gist of the present invention. For example, in the above embodiment, the heat wire 17 of the flow rate detection unit 4 and the heat wire pairs 13 and 14 of the angular velocity detection unit 3 are provided in the gas flow path 2 having the same width in accordance with the width. Instead, as shown in FIG. 5, the gas flow path 2 a provided with the heat wire 17 a of the flow rate detection unit 4 is connected to the heat wire pair 13 of the angular velocity detection unit 3.
It may be formed narrower than the gas flow path 2b provided with. In this way, the resistance of the heat wire 17a can be reduced by providing the short heat wire 17a corresponding to the narrowed width of the gas flow path 2a. Even if it is used, the flow rate of gas can be accurately detected.

Further, in the above embodiment, a gas rate sensor provided with an ultra-small base 1 formed by micromachining using a semiconductor substrate is taken as an example, but the present invention is not necessarily limited to this. Of course, the present invention can be applied to a general gas rate sensor having a base formed by cutting a metal such as aluminum.

[0032]

As is clear from the above description, according to the present invention, the gas flow after the angular velocity is detected by the angular velocity detector is heated by the heat wire of the flow rate detector. Conventionally, ascending airflow that has conventionally been generated on the upstream side of the heat wire pair of the angular velocity detector can be prevented well, so that the gas flow rate injected into the gas flow path from the nozzle hole toward the heat wire pair reaches the specified flow rate. Of course, it is possible to improve the accuracy of detecting the angular velocity by maintaining the flow rate, and it is possible to stabilize the gas flow in the gas flow path from the nozzle hole to the pair of heat wires, and to reduce the heat of the flow rate detection unit. Offset due to gas heating when passing through the wire can be favorably avoided.

Further, since the heat wire conventionally provided in the nozzle hole only needs to be disposed in the gas flow path on the downstream side of the heat wire pair of the angular velocity detector, the structure can be simplified. It is possible to provide a gas rate sensor which is excellent in cost without increasing the number of parts and the like.

Further, when the gas flow path provided with the heat wire of the flow rate detecting section is formed to be narrower than the gas flow path provided with the heat wire pair of the angular velocity detecting section, the heat wire of the flow rate detecting section is reduced. Since the resistance can be reduced, a low-voltage power supply such as an automobile battery can be used, and therefore, it is possible to accurately detect the gas flow rate even in a place where a high-voltage power supply cannot be obtained. it can.

Further, when a base is formed by micromachining by an IC manufacturing technique using a semiconductor substrate, and an angular velocity detecting section and a flow rate detecting section are formed on the base by micromachining, a delicate gas flow rate may be reduced. Even in a gas rate sensor with a very small and very precise substrate that is affected by fluctuations, the gas flow can be prevented from changing before reaching the heat wire pair of the angular velocity detector, and a constant flow rate can be obtained. Thus, a stable gas flow can be generated, the detection accuracy of the angular velocity can be improved, and the offset caused by gas heating by the heat wire can be avoided.

Further, when each heat wire of the angular velocity detecting section and the flow rate detecting section is made of platinum, the temperature sensitivity characteristics of each heat wire can be improved, so that the angular velocity and the gas flow rate can be adjusted with high precision. And the reliability can be further improved.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of a gas rate sensor according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a base.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a plan view showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base, 2 ... Gas flow path, 3 ... Angular velocity detection part, 4 ... Flow rate detection part, 5 ... Nozzle hole, 6 ... Micropump, 7 ... Pump drive control means, 13, 14 ... Heat wire pair, 17 ...
Heat wire

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-2026 (JP, A) JP-A-5-52862 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 9/00 G01C 19/00

Claims (4)

(57) [Claims] A substrate having a gas flow path and a nozzle hole for jetting a gas into the gas flow path; and a gas being jetted from the nozzle hole into the gas flow path to form a gas into the gas flow path. A pump means for generating a flow, an angular velocity detecting unit provided in the gas flow path and comprising a pair of heat wires for detecting a state of deflection of the gas flow when the angular velocity acts on the base, the gas flow path A flow rate detector provided with a heat wire for detecting a flow rate of gas ejected to the pump; and a pump for controlling the driving of the pump means so that the flow rate of the gas detected by the flow rate detector becomes a preset flow rate. A gas rate sensor comprising: a drive control unit; wherein the heat wire of the flow rate detection unit is disposed in the gas flow path downstream of the pair of heat wires of the angular velocity detection unit. 2. The gas flow path provided with the heat wire of the flow rate detection section is formed to be narrower than the gas flow path provided with the heat wire pair of the angular velocity detection section. The gas rate sensor according to claim 1. 3. The method according to claim 1, wherein the base is formed by micromachining by an IC manufacturing technique using a semiconductor substrate, and the angular velocity detecting section and the flow rate detecting section are formed on the base by micromachining. Item 1. Gas rate sensor according to item 1 or 2. 4. The gas rate sensor according to claim 1, wherein each of the heat wires of the angular velocity detector and the flow rate detector is formed of platinum.