JPH0454182B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to gas rate sensors, and more particularly to novel improvements for eliminating zero-point voltage fluctuations caused by hot wire resistance temperature coefficient imbalances.

b. Prior Art Various configurations have been adopted for this type of gas rate sensor that have been used in the past, but the most general configurations are shown in Figures 3 to 5. It is as expected.

In the figure, the casing designated by reference numeral 1 is approximately cylindrical in shape and has both ends open. Each end of the casing is connected to a pump holder 2 and a relay terminal plate 3. Each is closed, and the inside of the casing 1 is cut off from the outside.

This pump holder 2 is provided with a diaphragm 4a made of an electrostrictive ceramic disk, and its peripheral edge is integrally fixed to the pump holder 2, so that the electrostrictive oscillating pump 4 (gas pump) is formed.

Further, an electrode holder 5 is arranged inside the casing 1 at a position spaced apart from the diaphragm 4a by a predetermined distance, and the electrode holder 5 is constructed as shown in FIG. 4.

That is, four gas guide holes 5a to 5d are formed in the electrode holder 5, and four electrodes 6 are formed in the electrode holder 5.
a to 6d are arranged symmetrically with respect to the central axis. Among these electrodes 6a to 6d, electrode 6a
and 6b and between 6c and 6d, hot wires 7a and 7b are connected by welding.

Furthermore, a nozzle plate 10 having a nozzle hole 8 and an auxiliary hole 9 is provided in the vicinity of the relay terminal plate 3 in the casing 1, and between the relay terminal plate 3 and the nozzle plate 10, A dust plate 11 is provided at a substantially intermediate position.

A pump chamber 12 is formed between the diaphragm 4a of the electrostrictive vibration pump 4 (gas pump) and the pump holder 2, and the gas sent out by the electrostrictive vibration pump 4 is Guide holes 5a-5
It is sent to the gas flow path 13 via d.

A signal processing circuit section 14 consisting of an IC is provided at a position outside the relay terminal plate 3 of the casing 1,
This signal processing circuit section 14 receives power from the outside and is connected to the relay terminal 1 of the relay terminal board 3 for taking out the output signals of the hot wires 7a and 7b to the outside.
5.

Further, the relay terminal 3 is provided with a lead pin 16, and this lead pin 16 is connected to the outer casing 1.
It is connected to an external terminal 18 provided at 7.

The external terminal 18 transmits the electric power required for operating the electrostrictive vibration pump 4 and the electric power required for heating the hot wires 7a and 7b through the signal processing circuit section 14 and the lead pin 16, and also in the axial direction inside the casing 1. It has the function of appropriately supplying the liquid via a plurality of lead wires 19 arranged in the .
Further, this external terminal 18 has the function of outputting the output signals of the hot wires 7a and 7b after passing through the signal processing circuit section 14 to the outside.

The conventional gas rate sensor is configured as described above, and its operation will be explained below.

First, when the electrostrictive vibration pump 4 (gas pump) is energized, the diaphragm 4a vibrates, compressing the gas in the pump chamber 12, and this compressed gas is transferred to the diaphragm 4a.
It flows into the flow path 13 through the discharge port 4b of the electrode holder 5 and the discharge port 5e of the electrode holder 5, is guided into the space formed between the nozzle plate 10 and the dust plate 11, and connects the nozzle hole 8 and the auxiliary port 9. Then, each electrode 6a moves inside the space 1b in the hollow cylindrical part 1a in the casing 1.
It is ejected towards ~6d.

The compressed gas mentioned above uniformly cools each hot wire 7a and 7b welded to each electrode 6a to 6d, and then is discharged toward the diaphragm 4a through the gas guide holes 5a to 5d, and this discharged gas is returned to the electrodes 6a to 6d. By the action of the strain vibration pump 4 (gas pump), the flow path 13
The liquid then returns to the nozzle plate 10 and circulates within the casing 1 in the direction of the arrow.

In the above-mentioned state, when no angular velocity is applied to the casing 1, each hot wire 7a and 7b is cooled uniformly, but when an angular velocity is applied from the outside, the gas flow is deviated within the casing, Non-uniform cooling occurs between the hot wires 7a and 7b, which causes a slight voltage difference between the hot wires 7a and 7b, and by measuring this voltage difference, the angular velocity applied to the casing is detected. be able to.

c Problems to be Solved by the Invention Since the conventional gas rate sensor was configured as described above, it had various problems as described below.

(1) The material of each hot wire 7a and 7b has a high temperature coefficient of resistance.
When welding to the wires, slight variations occur, which affects the heat transfer to the electrodes when a voltage is supplied to each hot wire 7a and 7b to generate heat, resulting in uneven heat transfer. Therefore, a temperature difference occurred between each hot wire, and as a result, the potential at the junction point 14a fluctuated.

(2) Furthermore, due to the problem mentioned in item 1 above, the detection accuracy became unstable and the reliability became extremely low.

The present invention has been made to solve the above-mentioned problems, and in particular, it is an object of the present invention to provide a gas rate sensor that does not have zero-point voltage fluctuations caused by imbalance in temperature coefficient of resistance of hot wires.

d Means for Solving the Problems The gas rate sensor according to the present invention includes a gas pump provided in a casing, an electrode holder provided adjacent to the gas pump, and an electrode holder provided opposite to the electrode holder. , a nozzle plate having a nozzle, at least four power supply electrodes provided on the electrode holder, a hot wire connected to each of the power supply electrodes, and each of the power supply electrodes. This configuration includes at least four output signal electrodes disposed inside the output signal electrodes.

e Function In the gas rate sensor according to the present invention, the electrode of the electrode holder is composed of a power supply electrode and an output signal electrode, and hot wires are connected to each power supply electrode, and the signal processing circuit is connected to the output signal Since the power supply electrode is connected to the power supply electrode, the current circuit flowing through the hot wire and the output signal circuit are separated, and even if an imbalance in temperature coefficient of resistance and heat generation occurs due to variations in welding of each power supply electrode connected to the hot wire, , the signal output is guided regardless of the source, and a stable output signal can be obtained.

f Embodiments Hereinafter, preferred embodiments of the gas rate sensor according to the present invention will be described in detail with reference to the drawings.

Regarding the overall structure of the gas rate sensor,
Since it is exactly the same as the configuration explanation shown in Figure 3,
To avoid redundant explanation, only the electrode holder and the signal processing circuit section, which are different from the conventional structure, will be explained with reference to FIGS. 1 and 2.

Further, the same or equivalent parts as in the conventional example will be described using the same reference numerals.

In FIGS. 1 and 2, the reference numeral 5 indicates an electrode holder, in which four gas guide holes 5a to 5d are formed, and four power supply holes are formed in the electrode holder 5. Electrodes 6a to 6d are formed, and output signal electrodes 20a to 20d are arranged inside each of these power supply electrodes 6a to 6d.

Each of the aforementioned electrodes is a power supply electrode 6a and 6b.
The output signal electrodes 20a and 20b are arranged in series on the same straight line, and the hot wire 7a is connected to each electrode 6a and 6b and the output signal electrode 20a and 20b by welding.

Further, the power supply electrodes 6c and 6d and the output signal electrodes 20c and 20d are arranged in series on the same straight line, and the hot wire 7b is connected to each electrode 6c and 6d.
d and the output signal electrodes 20c and 20d by welding.

The aforementioned hot wires 7a and 7b are connected in series with each other to supply a power source, as shown in FIG.
PS, the power supply PS is connected to the power supply electrodes 6a and 6d, and the power supply electrodes 6b and 6c are connected to each other in series.

Furthermore, the output signal electrodes 20a to 20d
are connected to the first operational amplifier Q ₁ and the second operational amplifier Q ₂ of the signal processing circuit section 14, respectively, and the outputs of the operational amplifiers Q ₁ and Q ₂ are connected to the third operational amplifier Q ₃ .

These first and second operational amplifiers Q ₁ and Q ₂ are
In particular, the one with high input impedance and the third operational amplifier _Q3 are constructed of low-drift type components, and the current circuit flowing through each hot wire 7a and 7b and the output signal processing circuit 14 are separated from each other. They are structured so that they are not influenced by each other.

Note that this electrode holder 5 and signal processing circuit section 14
For configurations other than the configuration, as mentioned above,
The configuration is exactly the same as that of the conventional example shown in FIG.

The gas rate sensor according to the present invention is constructed as described above, and its operation will be described below.

In the connection state shown in FIG. 2, a constant current is supplied from the power source PS to the hot wires 7a and 7b. In this state, each power supply electrode 6a~
The voltage drop due to the welding variation in 6d occurs in the same manner as in the conventional case, but since each output signal electrode 20a to 20d is connected to each high impedance type operational amplifier _Q1 and _Q2 , the flowing current is Each output signal electrode 20
It is not affected by the welding in a to 20d.

Furthermore, even if an imbalance in the temperature coefficient of resistance and heat generation occurs due to variations in welding of the power supply electrodes 6a to 6d, each power supply electrode 6a to 6, which is the source of the imbalance,
Since the output signal is derived from each of the output signal electrodes 20a to 20d and the power source PS is a constant current type, the hot wires 7a and 7 are connected to the pure frame.
Since the temperature b is output as a voltage, a stable and accurate output signal can be obtained without being affected by zero point fluctuations caused by variations due to welding of the hot wires 7a and 7b.

g Effects of the Invention Since the gas rate sensor according to the invention is configured as described above, the following effects can be obtained.

(1) Each output signal electrode is separated from each power supply electrode, and the power supply is a constant current type, so
Each output signal electrode allows the temperature of the hot wire to be extracted purely as a voltage, making it possible to obtain extremely accurate detection.

(2) Since each output signal electrode is connected to a high-impedance operational amplifier, the amount of power flowing through it is very small, and stable output signals can be obtained without being affected by welding of each power supply electrode. It can be carried out.

[Brief explanation of the drawing]

1 and 2 are for showing the main parts of the gas rate sensor according to the present invention. FIG. 1 is a side view showing an electrode holder, and FIG. 2 is an electrical connection configuration including a signal processing circuit section. Figures 3 to 5 are a circuit diagram showing the conventional configuration, Figure 3 is a cross-sectional view showing the overall structure, and Figure 4 is a view of the electrode holder in Figure 3 taken from line A-A'. The side view shown in FIG. 5 is a circuit diagram showing the electrical connection configuration. 1 is a casing, 4 is an electrostrictive vibration pump (gas pump), 5 is an electrode holder, 6a to 6d are power supply electrodes, 7a and 7d are hot wires, 8 is a nozzle, 10 is a nozzle plate, 14 is a signal processing circuit section ,
Q ₁ and Q ₂ are operational amplifiers, and 20a to 20d are output signal electrodes.

Claims (1)

[Claims] 1 Gas pump 4 provided in casing 1
In the gas rate sensor, the electrode holder 5 is provided adjacent to the gas pump 4, and the nozzle plate 10 is provided opposite to the electrode holder 5 and has a nozzle 8. At least four power supply electrodes 6a~
6d, hot wires 7a and 7b connected to each of the power supply electrodes 6a to 6d, and at least four output signal electrodes disposed inside each of the power supply electrodes 6a to 6d. 20a~
20d, each of the output signal electrodes 20a to 20d.
A gas rate sensor characterized in that a signal processing circuit section 14 having a pair of high impedance operational amplifiers _Q1 to _Q2 is connected to 20d.