JPH02176469A - Manufacture of flow sensor - Google Patents

Abstract

PURPOSE:To obtain easily a gas angle detector having a stable output characteristic and high sensitivity by a method wherein the opposite end parts of a gold- plated heat wire of a flow sensor are fitted to support elements by gold bonding and a laser light is applied to the heat wire in a part wherefrom the plated gold is removed by etching, so that the wire is subjected to annealing. CONSTITUTION:The main body 4 of a gas-type angular velocity sensor, which is constructed of a holder element 5, a head element 5 and a tubular body element 7, is accommodated in a casing 1 of the sensor, and a gas is sent out room a discharge port 10 into a flow channel 3 by a pumping action of a piezo plate 8 provided in a pump chamber 8 inside the holder element 5. The opposite end parts of gold-plated heat wires 21a and 21b of a flow sensor 14 provided in the fore end of a sensor chamber 13 of this sensor are fixed to gold-plated supports 20 by gold bonding. A laser light is applied to the wires 21a and 21b stretched between these supports respectively, so that the wires 21a and 21b be annealed by laser heating. Thereby the quantities of heat radiation of the wires 21a and 21b are made equal and an excellent detection characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a flow sensor in a gas type angular velocity detector that detects angular velocity acting on a detector body.

In general, gas-type angular velocity detectors are equipped with a gas-type angular velocity detector in which a gas flow is ejected from a nozzle hole toward a flow sensor within a sealed casing. , to extract an output corresponding to the difference in temperature-sensing output generated between a pair of heat wires made of tungsten or the like with a large resistance temperature coefficient in a flow sensor, and to detect the direction and magnitude of the angular velocity acting on the detector body at that time. It is possible to calculate the amount of change in the moving direction of the moving object equipped with it.

In such a gas type angular velocity detector, the thinner each heat wire in the flow sensor is, the more minute displacement of the gas flow can be sensed, and the detection sensitivity of angular velocity can be increased.

Conventionally, a heat wire is installed by being stretched between two supports, but if the material such as tungsten in the heat wire is generally left untreated, as shown in Figure 6, 1
Because the composition crystal structure is fibrous, when a heat wire is stretched between two supports and energized once to generate heat, the resistance temperature of the heat wire will increase over time due to the influence of stress. There is a problem that the characteristics change.

In addition, conventionally, in order to make it possible to attach the heat wire between the pillars using the A-wire, the heat wire was plated with gold.
Both ends of the heat wire are fixed to the book support by gold bonding, but the detection sensitivity is reduced because the heat wire is plated with gold.

Therefore, in the past, a heat wire was attached between the pillars, and a current was passed through the heat wire in a vacuum or an inert gas to prevent oxidation and resistance heating was performed.
As a result, the heat wire is recrystallized and stabilized as shown in FIG. 7, thereby suppressing secular change in resistance temperature characteristics and evaporating gold plated on one surface.

However, this type of annealing treatment using electricity is inefficient, the recrystallized area of the heat wire is small and only the central part is recrystallized, and the gold plated on the surface of the heat wire is not completely evaporated. be.

(2) The present invention has been made in consideration of the above points, and provides a method of manufacturing a flow sensor in which recrystallization of a heat wire can be performed optimally.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 3 shows an example of the configuration of a gas type angular velocity sensor according to the present invention.

In the configuration shown in the figure, one end of the casing 1 is closed,
It has a cylindrical shape with the other end open, and a flange 2 is formed on the periphery of the right end. In addition, the cross-sectional shape of the casing 1 has ridges that protrude inward at three points equally divided on the circumference, and there are gaps between these ridges and the sensor body 4 that abuts in the axial direction. flow path 3
is formed.

The sensor main body 4 housed in the casing 1 is composed of a holder part 5, a neck part 6, and a cylinder part 7, and the holder part 5 shields the gas sealed in the casing 1. ing. A pump chamber 8 is formed within the holder portion 5, and a diaphragm type pump consisting of a piezo plate 9 is provided within the pump chamber 8.

Gas is sent out from the discharge port 10 into the flow path 3 by the pump action.

The gas sent into the flow path 3 is transmitted through a nozzle hole 11 formed in the center of the end surface of the cylindrical body 7 and a plurality of rectifying holes 12 formed around the nozzle hole 11 formed inside the cylindrical body 7. It is ejected into the sensor chamber 13 as a laminar flow, passes through the flow sensor 14 provided at the front of the sensor chamber 13, returns to the pump chamber 8, and is pumped again into the flow path 3 by the pumping action.
It is designed to be sent inside.

In Figure 0, in which the circuit board 16 of the amplifier circuit 15 is attached to the flange 2 portion of the casing l, 17 is a support cylinder that supports the gas rate sensor body.

As shown in FIG. 4, the flow sensor 14 includes two heat wires 21a placed on an alumina substrate 19 in which a plurality of ventilation holes 18 are formed, via a support 20.

22b are attached in parallel.

As shown in FIG. 5, the pair of heat wires 21a and 21b are arranged so as to be symmetrical with respect to the center line ○-0 of the nozzle hole 11, and are oriented laterally to the gas type angular velocity detector. When no angular velocity acts, the gas ejected from the nozzle hole 11 flows straight along its center line O-o and evenly hits each heat wire 21a, 21b, making the amount of heat radiation to each heat wire 21a, 21b equal. ing.

Furthermore, when a horizontal angular velocity ω acts on the gas type angular velocity detector, the gas flow ejected from the nozzle hole 11 is deflected as shown by the dotted line in the figure depending on the magnitude of the angular velocity ω, and the heat wires 21a and 21b are deflected. However, a deviation ε from the center line O-o occurs, so that the gas flow is directed toward one heat wire 21.
This results in a difference in the amount of heat radiated to each of the heat wires 21a and 21b. The sensor output corresponding to the difference in temperature sensing output of each heat wire 21a, 21b based on the difference in heat radiation amount is amplified by the amplifier circuit 15 and taken out to the outside, and the gas type angular velocity is The direction and magnitude of the angular velocity ω acting on the detector are detected.

In the present invention, when manufacturing the flow sensor 14 in such a gas-type angular velocity detector, both end portions of the heat wires 2La and 21b, which have been gold-plated in advance, are bonded with gold to the tip portions of the pillars 20, which are also gold-plated. each heat wire 21a,
21b is stretched between the supports 20, and then each heat wire 21a, 21b is irradiated with laser light to perform an annealing process on each heat wire 21a, 21b by laser heating.

At that time, if the heat wires 2La, 21b are still gold plated, the laser light will be reflected, so as a pretreatment for annealing by laser light irradiation, the gold plating of each heat wire 21a, 21b is chemically etched. We are trying to remove it by

Furthermore, if the beam diameter of the laser beam irradiated to each heat wire 21a, 21b is large, the light intensity differs between the outside and the center of the beam, making it difficult to uniformly heat each heat wire 21a, 21b in its length direction. Therefore, a small diameter laser beam is used to connect each heat wire 21a,
The annealing process is performed by scanning in the length direction of 21b.

Note that during the annealing process, each heat wire 21a, 21b is heated in vacuum or inert gas to prevent oxidation.
need to be irradiated with laser light.

However, according to the present invention, the annealing process is performed by irradiating the heat wires 21a and 21b from which the gold plating has been removed while scanning the laser beam with high power density at the condensing part. , each heat wire 21a, 2
It becomes possible to uniformly recrystallize 1b throughout.

Therefore, the composition of each of the heat wires 21a and 21b becomes dense, suppressing changes in resistance temperature characteristics over time, and making it possible to obtain stable output characteristics with almost no change in offset drift of the gas type angular velocity detector.

FIG. 1 shows each heat wire 21a in the flow sensor.
, 21b is irradiated with laser light while scanning to perform an annealing process.

In the configuration shown in the figure, the pulsed laser beam LB emitted from the laser oscillator 22 passes through the slit 23° reflection mirror 2.
The heat wire 2 of the flow sensor 14 is introduced into the chamber 27 from the light introduction window 26 through the light introduction window 26 through the condenser lens 25 and the heat wire 2 of the flow sensor 14 placed on the sample stage 28 in the chamber 27.
1a or 21b is irradiated.

As the laser oscillator 22, for example, Y is used as a laser source.
AG is used and the pulse width is 1. On+S, voltage 230V
, a laser beam with an average power of 7 W and a beam diameter of 1.5 mm is emitted.

Further, the reflection mirror 24 is installed on the X-direction moving stage 29 and the rotation stage 30, and the condenser lens 25 is
The chamber 27 is installed on the Z-direction moving stage 31, and the chamber 27 is installed on the X-Y direction moving stage 32 to position the heat wire 21a or 21b for laser beam irradiation.

It is now possible to

Here, after determining the irradiation position of the laser beam LB on the heat wire 21a or 21b, the irradiation position is fixed and the stage 29 or 32 is moved in the X direction, or the stage 30 of the reflection mirror 24 is rotated. I'm trying to make it scan by letting it scan.

When the flow sensor 14 placed on the sample stage 28 is viewed from the side, as shown in FIG. 2, the flow sensor 14 is tilted and each heat wire 21a is bent.

21b is irradiated with laser light LB.

A beam damper 33 is provided at the bottom of the chamber 27, and by circulating cooling water W, the optical energy of the laser beam irradiated onto the damper portion is absorbed.

Further, after the inside of the chamber 27 is evacuated by the turbo pump 34 and the rotary pump 35, the nitrogen gas in the gas cylinder 36 is sent into the chamber 27 through the adjustment valve 37, and the inside of the chamber 27 is filled with nitrogen gas. It looks like this.

In the figure, 38 indicates a pressure gauge, and 39 indicates a valve. Further, 540 is a heat wire 21a.

21b shows a monitoring device for each resistance value.

When the heat wires 21a and 21b in the flow sensor were annealed using this laser annealing device, more than 90% of the tungsten heat wires with a diameter of 5 μm and a length of 2 mm could be recrystallized.

As described above, in the method for manufacturing a flow sensor according to the present invention, the gold-plated P1 to both ends of the wire are attached to the support part by gold bonding, and then the gold plating of the heat wire is removed by etching. The wire from which the gold plating has been removed is irradiated with laser light to perform annealing treatment, which allows optimal recrystallization of the heat wire, resulting in a highly sensitive wire with stable output characteristics. It has the excellent advantage that a gas type angular velocity detector can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a configuration example of a laser annealing device for carrying out the present invention, FIG. 2 is a side view of a flow sensor portion in the same configuration example, and FIG. 3 is a diagram showing a gas type angular velocity detector according to the present invention. Fig. 4 is a perspective view of the flow sensor; Fig. 5 is a diagram showing the deflection state of the gas flow when angular velocity is applied to the gas type angular velocity detector; Fig. 6 is the wire drawing process. Figure 7 showing the composition of the heat wire formed by
The figure shows the composition of a recrystallized heat wire. Fig. 3/7 14...Flow sensor 21a, 21b...Heat wire 22...Laser oscillator 24...Reflection mirror 26...Light introduction window 27...Chamber 28...
・Sample stand 29, 30, 31. 32... Stage 33... Beam damper 34... Turbo pump 3
5... Rotary pump 36... Gas cylinder 37
...Adjustment valve 40...Resistance monitor device Fig. 4

Claims (1)

[Claims] 1. Temperature sensing generated in the heat wire pair in the flow sensor based on the deflection of the gas flow that occurs when angular velocity acts on the gas flow ejected from the nozzle hole toward the flow sensor. In a gas type angular velocity detector that generates an output according to the difference in output, both ends of a gold-plated heat wire are attached to the support part by gold bonding.
The method for manufacturing a flow sensor includes removing the gold plating on the heat wire by etching, and then irradiating the heat wire with the gold plating removed with a laser beam to perform an annealing process. 2. The method for manufacturing a flow sensor according to item 1 above, characterized in that the laser beam is scanned in the length direction of the heat wire.