JPS60203831A - Pressure sensor - Google Patents

Abstract

PURPOSE:To prevent a diaphragm from excessive pressure and to detect the pressure highly accurately by arranging a pressure receiving plate in the front of the other side of the diaphragm mounting a piezo-electric oscillator on its one side at an interval and forming a sealed space. CONSTITUTION:The whole peripheral edge of the diaphragm 2 fixing the pressure vibrator 1 is airtightly adhered by the upper end part of a supporting member 304 and a fixing member 305 and the pressure receiving plate consisting of a metallic thin plate or the like is mounted on the upper end surface of the member 305 and tightly fixed by a fixing member 306. In the pressure receiving part 10, a pleat-like bent part (a) is formed on the peripheral part near the outer periphery and terminals 4-6 are connected to a pressure detecting circuit. Pressure from a pressure leading hole 302 is transmitted to the diaphragm 2 through the pressure receiving plate 10 and the sealed space 11 and the pressure change is transmitted to the detecting circuit. Even if the pressure medium is fluid, highly accurate detection of the pressure change can be attained without oscillation stop or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to pressure sensors. The pressure sensor according to the present invention is used for an oil pressure gauge, a water level gauge, a blood pressure gauge, or the like.

Prior Art This type of pressure sensor has a structure in which a piezoelectric vibrator is integrally bonded to one side of a diaphragm, and the open surface of the diaphragm is used as a pressure receiving surface. The applied pressure is detected as a change in oscillation frequency.

FIG. 1 shows a conventional example of this type of pressure sensor, in which a piezoelectric vibrator l is integrally bonded to one surface 201 of a diaphragm 2 formed in a disc shape, and is housed in a case 3. 3
The structure is such that the other surface 202 of the diaphragm 2 receives the pressure introduced through the pressure introduction hole 302 provided in the lid member 301 . The piezoelectric vibrator 1 includes a piezoelectric ceramic body 1 formed in a disk shape, for example, as shown in FIGS. 2 and 3.
The electrode 102 is provided on almost the entire surface of one surface of the diaphragm 01, and the electrodes 103 and 104 are coaxially formed on the other surface with a gap G1, and the electrode 102 side is fixed on one surface of the diaphragm 2. be.

The diaphragm 2 has its circumferential edge hermetically fixed onto the upper end surface of a cylindrical support 304 erected on the case bottom plate 303 . Reference numeral 305 indicates a fixing member for holding down the periphery of the diaphragm 2, and reference numerals 4 to 6 indicate terminals to which the electrodes 102, 103 and 104 of the piezoelectric vibrator I are electrically connected.

In order to detect pressure using the pressure sensor described above, an automatic oscillation type detection circuit as shown in FIG. 4 is constructed. In FIG. 4, 7 is the pressure sensor shown in FIG. 1, 8 is an amplifier,
01 to C3 are capacitors, R1-Ra is a resistor, VR is a variable resistor, Vcc is a DC power supply voltage, and 9 is an output terminal.

In this automatic oscillation circuit, the piezoelectric vibrator 1 is caused to vibrate by a voltage applied between the electrode 102 and the electrode 103 on the diaphragm 2 side that constitute the pressure sensor 7, and the resulting voltage is transmitted from the electrode 104. The automatic oscillation operation is continued by feeding it back to the input of the amplifier 8. Here, when the pressure applied to the pressure receiving surface 202 (FIG. 1) of the diaphragm 2 changes, the tension of the diaphragm 2 changes accordingly, and the resonant frequency changes. Therefore, the frequency of the feedback signal input to the amplifier 8 through the electrode 104 changes, and the oscillation frequency changes. Therefore, the pressure at that time can be detected from the oscillation frequency.

Disadvantages of the Prior Art As mentioned above, the conventional pressure sensor
Since the structure was such that diaphragm 2 is a pressure-receiving surface, when the pressure medium is a liquid such as oil, water, or blood, the pressure received by diaphragm 2 becomes too large and oscillation stops or oscillation continues. However, the problem was that it was impossible to obtain an oscillation frequency proportional to the pressure.

Purpose of the Invention Therefore, the present invention eliminates the above-mentioned conventional drawbacks and provides a pressure sensor that is capable of obtaining an oscillation output proportional to the pressure without causing oscillation stoppage, etc. even when the pressure medium is a liquid. The purpose is to provide.

Structure of the present invention In order to achieve the above object, a pressure sensor according to the present invention includes:
The present invention is characterized in that a pressure receiving plate is arranged at a distance in front of the other side of the diaphragm on which the piezoelectric vibrator is mounted.

Example FIG. 5 is a partial sectional view of a pressure sensor according to the present invention.

In the figure, the same reference numerals as in FIG. 1 indicate the same components. In this embodiment, the entire periphery of the diaphragm 2 to which the piezoelectric vibrator l is fixed is connected to the upper end surface of a cylindrical support member 304 attached to a case bottom plate 303, and to a cylindrical fixing member 305 coupled thereon. At the same time, a pressure receiving plate 10 made of a thin metal plate, a polymer film, etc. is placed on the upper end surface of the fixing member 305, and this pressure receiving plate 1
The entire periphery of the fixing member 305 is tightly fixed between the end face of the fixing member 305 and the end face of the fixing member 30B fitted on the outer circumference of the fixing member 305. Therefore, a sealed space 11 is formed between the surface 202 of the diaphragm 2 and the pressure receiving plate 10. In this embodiment, the pressure receiving plate lO is shown in FIGS. 6 and 7.
As shown in the figure, a fold-shaped bent part (A) is used in the peripheral part near the outer periphery. When such a bent portion (a) exists, the amount of deflection of the pressure receiving plate 10 increases with respect to the same pressure.

The pressure sensor according to the present invention has the above-described structure,
The pressure introduced into the case 3 through the pressure introduction hole 302 is first received by the pressure receiving plate 10.
causes a deflection proportional to the pressure. Then, due to the deflection of the pressure receiving plate lO, the pressure in the closed space 11 is changed in proportion to the amount of deflection, and the change in the pressure in the closed space 11 is caused by the diaphragm 2.
Receive pressure at Therefore, even if the pressure medium is a liquid such as oil or water, excessive pressure will not be applied to the diaphragm 2. Therefore, a pressure detection circuit as shown in Fig. 4 is configured to detect pressure. When this is done, it becomes possible to change the oscillation frequency in proportion to the pressure without causing oscillation to stop or the like.

FIG. 8 is a pressure-frequency characteristic diagram when the pressure detection circuit shown in FIG. 4 is constructed using the pressure sensor according to the present invention. The pressure range can be designed to be used over the widest range.

In addition, in this embodiment, since the pressure receiving plate 10 is provided with a bent portion (A) around its periphery, the amount of deflection of the pressure receiving plate 10 is increased, and the oscillation frequency change range in response to pressure changes is increased, allowing for highly accurate pressure detection. becomes possible.

Effects of the present invention As described above, the pressure sensor according to the present invention has a pressure receiving plate arranged at intervals in front of the other side of the diaphragm on which the piezoelectric vibrator is mounted on the negative side. Because of this feature, even if the pressure medium is liquid, it will not cause one oscillation stop, etc.
A pressure sensor capable of obtaining an oscillation output proportional to pressure can be provided.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view of a conventional pressure sensor, Fig. 2 is a plan view of a piezoelectric vibrator, Fig. 3 is a sectional view thereof, Fig. 4 is an electric circuit diagram of a pressure detection circuit, and Fig. 5 is a main 6 is a plan view of the pressure receiving plate, FIG. 7 is a sectional view of the same, and FIG. 8 is a partial front sectional view of the pressure sensor according to the invention, and FIG. It is a pressure-oscillation output frequency characteristic diagram when a pressure detection circuit is configured. l--Piezoelectric vibrator 2--Vibration plate 3--Case 10--Pressure plate 11...Closed space Fig. 1 Fig. 2 Fig. 5 Fig. 6 0

Claims (2)

[Claims] (1) A pressure sensor characterized in that a pressure receiving plate is arranged at a distance in front of the other side of a diaphragm on which a piezoelectric vibrator is mounted. (2) The pressure sensor according to claim 1, wherein the pressure receiving plate has a bent portion at a peripheral portion.