JP2599319B2 - 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 heating device comprising a pair of heat-sensitive resistance elements, which determines the deflection state of a gas flow ejected from a nozzle hole of a sensor body into a gas flow path when an angular velocity acts on the sensor body. The present invention relates to a gas rate sensor that detects a change in each resistance value generated in a wire.

[0002]

[Prior art]

In this type of gas rate sensor, the deflection state of the gas flow when the angular velocity acts on the sensor body is detected as a change in the gas flow by a pair of heat wires. It is necessary to eject a gas at a constant flow rate from the gas flow to generate a stable gas flow in the gas flow path.

Therefore, conventionally, a pump is stably driven at a predetermined cycle by using a drive circuit which is stable against fluctuations in power supply voltage and temperature drift.

[0005] However, when such a means is employed, the flow rate of the gas actually flowing in the gas flow path of the gas rate sensor cannot be known. When the flow rate of the gas to be ejected fluctuates, the fluctuation results in a detection error, and the sensor accuracy is reduced.

[0006] Recently, a gas rate sensor in which a sensor main body comprising a nozzle hole, a gas flow path and a heat wire pair provided in the gas flow path is formed by micromachining using an IC manufacturing technique using a semiconductor substrate. (See Japanese Patent Application Laid-Open No. 3-29858), however, when such a sensor body is of a very small size, the flow rate of gas ejected from the nozzle hole into the gas flow path is particularly small. Even a large change causes a large detection error.

[0007]

The problem to be solved is that when the flow rate of the gas ejected from the nozzle hole into the gas flow path by the driving of the pump fluctuates, the fluctuation in the gas flow rate becomes a detection error. The sensor accuracy is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a gas rate sensor, and more particularly, to means for detecting the flow rate of gas injected into a gas flow path by a flow sensor provided on a sensor body, and detecting the flow rate. Means for controlling the driving of the pump so that the flow rate of the supplied gas becomes a preset flow rate.

In this case, the sensor body is formed by micromachining using an IC manufacturing technique using a semiconductor substrate, and the flow sensor is formed on the sensor body by micromachining.

[0010]

1 to 4 show a sensor body 8 in a gas rate sensor formed by micromachining using a semiconductor substrate.

In this case, when the gas is ejected from the nozzle hole 3 of the sensor main body 8 by driving the pump to generate a gas flow in the gas flow path 4, the pulsation of the gas flow caused by the driving of the pump is buffered. In this way, the gas reservoir 9 for generating a stable gas flow in the sensor body 8 is formed integrally with the sensor body 8.

The sensor body 8 and the gas reservoir 9 have a half hole 31 for forming the nozzle hole 3, a half groove 41 for forming the gas flow path 4, and the gas reservoir 9 on the nozzle hole 3 side. The lower semiconductor substrate 1 and the upper semiconductor substrate 2 in which a half groove 91 for forming the gas inlet hole 10 and a half hole 101 for forming the gas inflow hole 10 are formed by etching, respectively, are connected to the respective half holes 31, half grooves 41, and half. The groove 91 and the half hole 101 are overlapped so as to abut each other, and the two are bonded to each other.

A gas passage 4 is formed in the lower semiconductor substrate 1.
Is formed, and a heat wire material such as platinum is vapor-deposited on the upper surface of the bridge portion 6 and is etched to form a pair of heat wires 51,
52 is pattern-formed, and electrode portions 7 are similarly pattern-formed on both sides thereof.

In the case where the sensor body 8 and the gas reservoir 9 are integrally formed as described above, as shown in FIG. Is connected, and the micropump 11 is driven in an atmosphere of a gas such as helium, so that the gas reservoir 9 is
The gas is sent into the inside, the pulsating portion of the gas sent by the pump is effectively removed, and then the gas flow is ejected from the nozzle hole 3 in the sensor body 8 into the gas flow path 4.

At this time, in the present invention, a flow sensor 12 composed of a heat-sensitive resistance element for detecting a gas flow rate is provided in the nozzle hole 3 of the sensor body 8, and the flow sensor 12 is ejected from the nozzle hole 3 into the gas flow path 4. The pump drive control circuit 15 reads a detection signal of the flow sensor 12 according to the flow rate of the gas to be supplied, and controls the drive of the micro pump 11 so that the detected gas flow rate always becomes a specified flow rate. It is characterized by:

The flow sensor 12 is shown in FIGS.
As shown in FIG. 5, a bridge portion 13 is formed by etching in a portion of the half hole 31 forming the nozzle hole 3 in the lower semiconductor substrate 1, and a heat-sensitive resistance material such as platinum is deposited on the upper surface of the bridge portion 13, It is patterned by etching it.

Alternatively, a wire made of platinum or the like may be formed in the half hole 31 for forming the nozzle hole 3 without providing the bridge portion 13.
May be bonded to the lower semiconductor substrate 1 so as to straddle.

Similarly, on both sides of the flow sensor 12, electrode portions 14 are formed by patterning.

The pump drive control circuit 15 includes:
Specifically, as shown in FIG. 5, a bias voltage is applied to the flow sensor 12 provided in the nozzle hole 3 portion of the sensor body 8 so that the flow when the gas flow rate passing through the nozzle hole 3 changes. A sensor signal based on a change in the resistance value of the sensor 12 is read, and a detected value of a gas flow rate obtained by amplifying the signal in a predetermined manner is compared with a preset reference value, and power control is performed so that the two become equal. The control unit 151 that outputs the signal WS and the actual power consumption of the micro pump 11 are detected, and the detected power consumption signal is compared with the power control signal WS transmitted from the control unit 151, A power detection unit 152 for outputting a pump drive frequency control signal FS such that both are equal, and a pulse signal generation unit for generating a pulse signal with a predetermined frequency in accordance with the frequency control signal FS 53, the pulse signal waveform shaping is constituted by a waveform shaping section 154 applying a driving pulse to the micro pump 11.

Here, a micropump driven by a diaphragm type pulse signal is used as the micropump 11.

In the embodiment described above, the flow sensor 12 is provided inside the nozzle hole 3 in order to accurately detect the flow rate of the gas ejected into the gas flow path 4.
The flow sensor 12 may be provided near the inlet side or the outlet side of the nozzle hole 3. Alternatively, the flow sensor 12 may be provided on the downstream side in the gas flow path 4 although the detection accuracy is slightly lowered.

[0022]

As described above, in the gas rate sensor according to the present invention, the flow sensor is provided at or near the nozzle hole and the flow rate of the gas ejected from the nozzle hole into the gas flow path is actually detected. The drive control of the pump is performed so that the flow rate of the detected gas becomes a preset flow rate, and the flow rate of the gas flowing in the gas flow path is always kept constant without fluctuation. The state in which the gas flow is deflected by the angular velocity acting on the sensor body can be accurately detected by the heat wire pair. In particular, the sensor body is formed by micromachining processing using IC manufacturing technology using a semiconductor substrate. This is advantageous in a very small gas rate sensor.

[Brief description of the drawings]

FIG. 1 is a perspective view of a sensor main body integrally provided with a gas reservoir formed by micromachining using an IC manufacturing technique using a semiconductor substrate.

FIG. 2 is a plan view of a lower semiconductor substrate in the sensor body.

FIG. 3 is a front sectional view taken along line AA of FIG. 1;

FIG. 4 is a front sectional view taken along the line BB of FIG. 1;

FIG. 5 is a block diagram showing a simplified configuration of a gas rate sensor according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower semiconductor substrate 2 Upper semiconductor substrate 3 Nozzle hole 4 Gas flow path 51 Heat wire 52 Heat wire 8 Sensor main body 9 Gas reservoir 11 Micro pump 12 Flow sensor 15 Pump drive control circuit

Claims (3)

(57) [Claims] A gas is ejected from a nozzle hole in a sensor main body by driving a pump to generate a gas flow in a gas flow path, and a state of deflection of the gas flow when an angular velocity acts on the sensor main body. In a gas rate sensor that detects a change in each resistance value generated in a heat wire composed of a pair of heat-sensitive resistance elements juxtaposed in the gas flow path, the gas is ejected into the gas flow path by a flow sensor provided in the sensor body. A gas rate sensor comprising: means for detecting a flow rate of a gas to be detected; and means for controlling driving of a pump so that the flow rate of the detected gas becomes a preset flow rate. 2. A sensor body consisting of a nozzle hole, a gas flow path and a heat wire pair provided in the gas flow path is formed by micro-machining processing by an IC manufacturing technique using a semiconductor substrate. 2. The gas rate sensor according to claim 1, wherein the flow sensor is formed by machining. 3. The method according to claim 1, wherein the flow sensor is provided at or near a nozzle hole in the sensor body.
Gas rate sensor according to the description of the section.