JPH07103838A - Micromanometer - Google Patents

Abstract

PURPOSE:To provide a micromanometer for detecting the leakage of gasoline vapor from a gasoline tank accurately with high S/N. CONSTITUTION:A crystal speaker 10 and a crystal receiver 15 are disposed oppositely through a space. Sound pressure generated from the crystal speaker 10 is transmitted to the crystal receiver 15 in proportion to the pressure of gas in the space which is then detected based on the sound pressure thus detected. This constitution allows highly accurate detection of micropressure in the order of 50mmHg full-scale with high S/N ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro pressure sensor for detecting leak of gasoline vapor from a gasoline tank.

[0002]

2. Description of the Related Art Conventionally, a semiconductor pressure sensor has been used as a low pressure sensor for detecting gasoline vapor leaking from a gasoline tank of a vehicle for environmental purification, and the pressure sensor is a silicon diaphragm. The strain when pressure is applied is detected by a strain gauge with four bridges formed in silicon, and the voltage obtained from the bridge is converted into pressure in response to this strain.

3 to 5 show the structure of a conventional low pressure sensor. 3 and 4, a diaphragm body 2 made of silicon is formed with a diaphragm portion 2 which responds to a leak pressure of gasoline vapor by etching or the like. The diaphragm portion 2 has four semiconductor strain gauges 3a to 3a. 3d is fixed. Further, the semiconductor strain gauges 3a to 3d are connected to a bridge as shown in FIG.

Next, the operation of the above conventional example will be described.
When pressure is applied, the diaphragm portion 2 is bent. For example, when pressure is applied from the upper surface of FIG. 4, the resistance values of the semiconductor strain gauges 3a and 3d are increased, and the resistance values of the semiconductor strain gauges 3b and 3c are increased. Becomes smaller. Along with this, a voltage appears at the output terminal Vout of the bridge shown in FIG.
By amplifying this, a voltage proportional to the pressure can be obtained from the sensor.

As described above, the above-mentioned conventional low pressure sensor can obtain a voltage proportional to the pressure.

[0006]

However, in the above-mentioned conventional low pressure sensor, when it is attempted to detect a low pressure of about 50 mmHg of full scale, the thickness of the diaphragm is made considerably thin and the amplification factor of the amplifier circuit is increased. Inevitably,
There is a problem that the S / N is good and it is impossible to detect the minute pressure with high accuracy.

An object of the present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide a fine pressure sensor having a good S / N and capable of detecting a fine pressure with high accuracy.

[0008]

In order to achieve the above-mentioned object, the present invention provides a cabinet, a crystal speaker having a diaphragm provided in the cabinet and a piezoelectric element attached to the diaphragm, and a predetermined frequency for the diaphragm and the piezoelectric element. And an oscillating means for generating a sound pressure from the crystal speaker by applying a signal from the crystal speaker to the crystal speaker, the sound being propagated from the crystal speaker in proportion to the pressure of the gas in the space. A structure is provided that includes a diaphragm that receives pressure, a case that supports the diaphragm, and a crystal receiver that is attached to the diaphragm and that has a piezoelectric element that generates a voltage proportional to the sound pressure.

Further, according to the present invention, the frequency is set so as to maximize the sensitivity of the crystal speaker or the crystal receiver.

[0010]

Therefore, according to the present invention, the sound pressure generated from the crystal speaker is propagated to the crystal receiver in proportion to the atmospheric pressure. Therefore, by receiving this sound pressure at the crystal receiver, the pressure of gas from the crystal receiver is increased. A voltage proportional to can be detected. Also,
By setting the frequency at which the sensitivity of the crystal speaker or crystal receiver is maximized, it is possible to obtain pressure information with a good S / N.

[0011]

【Example】

(Embodiment 1) FIG. 1 is a block diagram of a micro pressure sensor showing a first embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a crystal speaker. This crystal speaker 10 has a cylindrical speaker cabinet 11 with one end closed, and a conductive diaphragm 1 provided in an opening of the speaker cabinet 11.
2, and a disk-shaped piezoelectric element 13 made of ceramic or the like attached to the center of the outer surface of the diaphragm 12.

Further, between the piezoelectric element 13 and the diaphragm 12, the oscillator 1 for vibrating the diaphragm 12 by the distortion due to the piezo effect of the piezoelectric element 13 to generate a sound pressure.
4 is connected.

In FIG. 1, reference numeral 15 denotes a crystal receiver that is arranged to face the crystal speaker 10 with a predetermined gap therebetween. The crystal receiver 15 has a cylindrical receiver case 16 with one end closed, and the receiver case 16. A conductive diaphragm 17 provided in the opening,
A disk-shaped piezoelectric element 18 made of ceramic or the like is attached to the center of the outer surface of the diaphragm 17.

Further, between the piezoelectric element 18 and the diaphragm 17, a measuring instrument 19 for measuring an electric signal generated by the piezoelectric effect in the piezoelectric element 18 when the sound pressure from the crystal speaker 10 is received is connected.

Next, the operation of the first embodiment will be described. The low pressure sensor having the above-described configuration is installed in a pressure atmosphere such as in a gasoline tank, and the gap between the crystal speaker 10 and the crystal receiver 15 is filled with the pressure gas to be measured.

In such a state, an oscillator 14 is provided between the piezoelectric element 13 and the diaphragm 12 of the crystal speaker 10.
When a voltage of a predetermined frequency is applied from the above, the diaphragm 12 vibrates due to the piezoelectric effect of the piezoelectric element 13, and sound pressure is generated from the crystal speaker 10. This sound pressure becomes a sound pressure proportional to the pressure of the gas in the gap and is propagated to the crystal receiver 15.

In the crystal receiver 15, when the sound pressure acts on the diaphragm 17 and the piezoelectric element 18, a voltage proportional to the sound pressure is generated in the piezoelectric element 18 by the piezoelectric effect of the piezoelectric element 18, and this voltage is supplied to the measuring instrument 19. To be done.
Therefore, the pressure of the gas can be detected from the display value of the measuring device 19.

In the first embodiment as described above,
Since the pressure is converted into an electric signal through sound, there is an effect that the sensitivity of the crystal speaker 10 and the crystal receiver 15 can be set independently of the pressure, and the frequency at which the sensitivity of the crystal speaker 10 and the crystal receiver 15 is maximized. If the sound pressure is transmitted and received, the S / N is improved, and there is an effect that the minute pressure information can be converted into an electric signal with high accuracy.

As the conditions for maximizing the sensitivity of the crystal speaker and the crystal receiver, it is desirable that they have the same method (ceramic) and the same structure, and that they have the same frequency.

(Embodiment 2) A second embodiment is a constitutional view showing a second embodiment of the micro pressure sensor of the present invention.

In the second embodiment, the crystal speaker 10 has a speaker cabinet 11, a diaphragm 12 and a piezoelectric element 13 as in the case of FIG. 1, but the piezoelectric element 13 is different from the first embodiment. Is attached to the inner surface of the diaphragm 12.

The crystal receiver 15 is composed of a receiver case 16, a diaphragm 17 and a piezoelectric element 13 as in the case of FIG. 1. However, the point different from the first embodiment is that the piezoelectric element 18 is replaced by the diaphragm 17.
It is attached to the center of the inner surface of the.

Also in the second embodiment as described above, the same effect as that of the first embodiment can be obtained.

[0025]

As is apparent from the above-described embodiment, the present invention converts pressure into voltage through sound, so that a speaker,
By setting the receiver to the method, structure, and frequency that maximize the sensitivity, the S / N is good and the pressure can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a low pressure sensor showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a low pressure sensor showing a second embodiment of the present invention.

FIG. 3 is a plan view of a conventional low pressure sensor.

FIG. 4 is a front view of a conventional low pressure sensor.

FIG. 5 is a circuit diagram of a semiconductor strain gauge in a conventional low pressure sensor.

[Explanation of symbols]

 10 Crystal Speaker 11 Speaker Cabinet 12 Diaphragm 13 Piezoelectric Element 14 Oscillator 15 Crystal Receiver 16 Receiver Case 17 Diaphragm 18 Piezoelectric Element 19 Measuring Instrument

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G01N 7/00 A 6928-2J H04R 17/00 330 K

Claims (1)

[Claims] 1. A crystal speaker having a cabinet, a diaphragm provided in the cabinet, and a piezoelectric element attached to the diaphragm, and sound pressure is generated from the crystal speaker by applying a signal of a predetermined frequency to the diaphragm and the piezoelectric element. The oscillating means, the diaphragm disposed opposite to the crystal speaker via a space, and receiving a sound pressure propagated from the crystal speaker in proportion to the pressure of the gas in the space, a case supporting the diaphragm, and the diaphragm. A minute pressure sensor, comprising: a crystal receiver attached to which a piezoelectric element that generates a voltage proportional to the sound pressure is provided. 2. The micro pressure sensor according to claim 1, wherein the crystal speaker or the crystal receiver is set to a frequency at which the sensitivity is maximized.