JP2532214Y2 - Gas rate sensor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat wire comprising a pair of heat-sensitive resistance elements, which detects 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 that occurs in a gas rate sensor.

[0002]

[Prior art]

Recently, a semiconductor type gas rate formed by micromachining a semiconductor substrate using an IC manufacturing technique has been used to form a sensor body comprising a nozzle hole, a gas flow path and a heat wire pair provided in the gas flow path. Sensors have been developed (see JP-A-3-29858).

FIGS. 5 to 7 show the main body of the sensor.
As shown in FIG. 5, the lower semiconductor substrate 1 and the upper semiconductor substrate 2 in which the semi-holes 31 forming the nozzle holes 3 and the semi-grooves 41 forming the gas flow paths 4 connected thereto are formed in the semiconductor substrate by etching, respectively. The nozzle hole 3 and the gas flow path 4 are formed by overlapping the respective half holes 31 and the half grooves 41 so as to abut each other and bonding them.

The lower semiconductor substrate 1 is provided with a bridge 6 extending over the gas flow path 4, and a pair of heat wires 51 and 52 are formed on the upper surface of the bridge 6 by patterning.

In the figure, reference numeral 7 denotes a pair of heat wires 51,5.
2 are electrode portions pattern-formed on the lower semiconductor substrate 1 on both sides.

In such a gas rate sensor, by driving a micropump in a gas atmosphere, gas is ejected from the nozzle hole 3 of the sensor body into the gas flow path 4 to form a pair of heat wires 51, 52. The gas flow is generated in advance, and the deflection of the gas flow when the angular velocity acts on the sensor body is taken as a change in each resistance value generated in each of the heat wires 51 and 52, as shown in FIG. Each of the heat wires 51 and 52 and the reference resistance Rs1,
Rs2 uses a resistance bridge circuit provided in each branch, and obtains the angular velocity from the output of the bridge circuit.

In such a gas rate sensor, conventionally, as shown in FIG. 3, a pair of heat wires 51 and 52 arranged in parallel in a gas flow path 4 are connected by an external wiring 9. I have to.

That is, inside the gas flow path 4, one heat wire 51 is connected between the electrode portions 711 and 721, and the other heat wire 52 is connected between the electrode portions 712 and 722. , 722 are connected by the external wiring 9.

Here, reference numerals 711 and 712 denote electrode portions to which a bias voltage Vcc is applied in the resistance bridge circuit. Numerals 721 and 722 denote electrode portions of neutral points a and b in the resistance bridge circuit.
The output Vout of the resistance bridge circuit is taken out from between 722.

FIG. 4 shows the patterns of the heat wires 51 and 52 formed on the upper surface of the conventional bridge portion 6 and the internal wirings thereof.

However, the length of the wiring connecting the heat wires 51 and 52 becomes long, and the resistance cannot be ignored. A current flows between the heat wires 51 and 52 through the wiring, and the voltage drop in the wiring is reduced. Becomes a problem,
Also, the portion of the external wiring 9 and each of the heat wires 51, 5
A temperature drift or the like due to a difference in temperature environment between the two causes a problem, and the bridge condition in the resistance bridge circuit changes, which causes fluctuation in detection sensitivity and causes a detection error.

[0013]

The problem to be solved is that, when a pair of heat wires arranged in a gas flow path are connected by an external wire, a current is supplied to each heat wire through the external wire. Flows, the voltage drop generated in the relatively long wiring portion becomes a problem, and the temperature drift due to the difference in the temperature environment between the external wiring and each of the heat wires 51 and 52 becomes a problem. Is changed.

[0014]

According to the present invention, a pair of heat wires arranged in parallel in a gas flow path are connected in series in the gas flow path, and the connection point is used as a neutral point of a resistance bridge circuit. I am trying to pull it out.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas rate sensor according to the present invention is, for example,
In the above-described semiconductor type, as shown in FIG. 1, a pair of heat wires 51 and 52 provided on the upper surface of the bridge portion 6 of the lower semiconductor substrate 1 are connected in series in the gas flow path 4, The connection point m is taken out to the outside by the internal wiring 8 as a neutral point of the resistance bridge circuit shown in FIG.

The internal wiring 8 includes heat wires 51,
The pattern is formed on the upper surface of the bridge portion 6 together with 52.

FIG. 2 shows an example of a pattern of the heat wires 51 and 52 and the internal wiring 8 formed on the upper surface of the bridge portion 6.

At this time, for example, a predetermined pattern is formed by depositing a metal such as platinum on the upper surface of the bridge portion 6 and then etching the metal.

In FIG. 1, reference numerals 711 and 712 denote electrode portions to which a bias voltage Vcc is applied in a resistance bridge circuit. Numerals 721 and 722 denote electrode portions of neutral points a and b in the resistance bridge circuit.
The output Vout of the resistor bridge circuit is taken out from between 722

Although not particularly shown, a reference resistor Rs1 is connected between the electrode portion 711 and the electrode portion 721 and a reference resistor Rs2 is connected between the electrode portion 712 and the electrode portion 722 outside the sensor body. As a result, a resistance bridge circuit is formed.

According to the present invention, since the heat wires 51 and 52 are connected in series in the gas flow path 4,
The connection between the heat wires 51 and 52 becomes the shortest, and a voltage drop at the connection portion when a bias voltage is applied between the electrode portions 711 and 712 and a current flows through the heat wires 51 and 52 is ignored. It does not matter at all that it causes a detection error.

According to the present invention, each heat wire 5
Since the connection points m of 1, 52 are drawn out to the outside as neutral points of the resistance bridge circuit, each heat wire 5
The internal wiring 8 for drawing out the connection points m of 1, 52 to the outside includes:
This becomes the neutral line of the resistance bridge circuit, so that no current flows when the bridge is balanced, and the voltage drop in the internal wiring 8 does not matter at all.

Further, according to the present invention, the main wiring portion in the resistance bridge circuit for detecting a change in the resistance value of each of the heat wires 51 and 52 due to the deflection of the gas flow is located in the gas flow path. Wiring part and each heat wire 5
The problem of the temperature drift due to the difference in the temperature environment between the first and second temperature environments is eliminated, and the bridge condition is stabilized.

[0024]

As described above, in the gas rate sensor according to the present invention, a pair of heat wires arranged in parallel in the gas flow path are connected in series in the gas flow path, and the connection point is connected to the resistance bridge circuit. It is designed to be pulled out to the outside as a neutral point, so that each heat wire can be connected as short as possible in the gas flow path under the same temperature environment so that there is no problem of temperature drift or voltage drop. In addition, since the current flowing through the wiring part that draws out the connection point of each heat wire to the outside does not flow when the bridge is balanced because it becomes the neutral wire of the resistance bridge circuit, there is no problem with the voltage drop in that wiring part. This has the advantage that the angular velocity acting on the sensor body can be detected accurately with stable sensitivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a connection state of a heat wire pair in a gas rate sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a pattern of a heat wire pair and its internal wiring in the embodiment.

FIG. 3 is a diagram showing a connection state of a heat wire pair in a conventional gas rate sensor.

FIG. 4 is a diagram showing a pattern of a heat wire pair and its internal wiring in a conventional gas rate sensor.

FIG. 5 is a perspective view of a sensor body of the semiconductor type gas rate sensor.

FIG. 6 is a plan view of a lower semiconductor substrate in a sensor body of the semiconductor type gas rate sensor.

FIG. 7 is a front sectional view of a sensor main body in the semiconductor type gas rate sensor.

FIG. 8 is an electric circuit diagram showing a resistance bridge circuit in the gas rate sensor.

[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

Claims (1)

(57) [Scope of request for utility model registration] 1. A pair of heat-sensing devices arranged in a gas flow path based on deflection of a gas flow ejected into a gas flow path from a nozzle hole in the sensor main body when an angular velocity acts on the sensor main body. In a gas rate sensor for detecting an angular velocity by detecting a change in each resistance value generated in a heat wire composed of a resistance element by a resistance bridge circuit provided in each branch and each heat wire, a reference is made to each heat wire by a gas. A gas rate sensor, wherein the gas rate sensor is connected in series in a flow path, and the connection point is drawn out to the outside as a neutral point of a resistance bridge circuit.