JPH07225168A - Differential type pressure sensor - Google Patents

Abstract

PURPOSE:To obtain a differential type pressure sensor which can be handled easily and is not affected by external force and noise for measurincj the pressure difference between two points and the alternate frequency. CONSTITUTION:A piezoelectric ceramic plate 19 is adhered to a diaphragm 16. The inside of a sensor case 20 where the diaphragm 16 is mounted to an opening is subdivided into two cavities 25a and 25b by the diaphragm 16 and a first screening plate 22a which is adhered to the surface inside the sensor case 20. Conduits 23 and 24 for leading the pressure at a part where a pressure difference is measured to each cavity in the sensor case 20 are mounted to the sensor case 20. The front surface of the case 20 is provided with a second screening plate 22b located on the extension of the first screening plate 22a and is covered with a cover 33 for dividing the front space of the diaphragm 16 into the cavities 25c and 25d.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The differential pressure type pressure sensor of the present invention is
It is used to measure the oscillatory changing fluid pressure difference between two parts, such as in a flow meter utilizing fluid vibration.

[0002]

2. Description of the Related Art To measure the flow rate of a fluid such as air, fuel gas, or water flowing in a pipe, a fluid oscillator is installed in the middle of the pipe to cause the fluid to vibrate, and the vibration frequency is measured to measure the flow rate. There are known ways to know.

FIG. 10 is a sectional view showing an example of a fluid oscillator called a fluidic element. This oscillator
In the case 1, the target 2, the flow guiding projections 3, 3, and the flow guiding wall 4
When the fluid is ejected from the nozzle 5 toward the target 2, the jet flow causes two flows of a white arrow a and a hatching arrow b due to the target 2, the flow guide projections 3, the flow guide wall 4, and the like. It flows out from the outlet 6 while taking alternately. The fluid thus oscillates by changing the flow path. At this time, the part c or d of the flow that is going to the side portion of the nozzle that has become a dead end generates a positive pressure at the dead end portion, and at this time, a negative pressure at the opposite part of the nozzle. By measuring the pressure change through the through holes 7 and 8 on both sides of 5, the frequency of the fluid oscillator can be known. The shape of the fluid oscillator in FIG. 10 is two-dimensional (that is, the flow path shape in the casing does not change in the direction perpendicular to the paper surface).
Then, it is known that the frequency of the fluid vibration is proportional to the flow rate.

FIG. 11 shows another example of a fluid oscillator invented in order to simplify the structure of the above-mentioned oscillator. A fluid is jetted from a nozzle 10 formed at the inlet of a case 9 toward a target 11 to produce the target 11. And the diversion walls 12, 1
3, the fluid vibration is generated, the pressure change is measured from the through holes 7 and 8, the frequency of the vibration is known, and the flow rate of the fluid is known based on this.

In these fluid oscillators, the through holes 7 and 8
In order to measure the pressure difference acting on the pipe 14, as shown in FIGS. 12 and 13, both ends of the pipe 14 are connected to the through holes 7 and 8, the pressure gradient type sensor 15 is placed in the pipe 14, and the diaphragm 16 The pressure difference is measured by deflection. Positive pressure enters through the through hole 7, and through hole 8
When the pressure becomes negative, the vibration plate 16 of the sensor bends toward the through hole 8 side as shown in FIG. 12, and when the through hole 7 side becomes negative pressure and the through hole 8 side becomes positive pressure, the vibration plate 16 becomes as shown in FIG. Since it bends toward the through hole 7 side, the magnitude of the pressure acting on both through holes and the alternating frequency can be measured.

However, at the time of the above measurement, FIG. 12 and FIG.
3, when external force F due to noise or mechanical vibration is applied from the outside in the direction perpendicular to the vibration plate 16, the operation of the sensor 15 becomes uncertain due to this, and the flow rate measurement of the flow meter becomes inaccurate. turn into.

Therefore, in order to eliminate the influence of such external force, two sensors 15a and 15b are used as shown in FIG. 14, and the straight pipe 14a and the bent pipe 14b form the through holes 7 and 8, respectively. It is considered that the pressure is communicated to different sides of the sensors 15a and 15b to cancel the influence of external vibration and the like for measurement.

As the sensors 15, 15a and 15b, as shown schematically in FIG.
Piezoelectric element 1 in which electrodes 17 and 18 of thin metal plates (for example, aluminum foil) are bonded to both surfaces of the piezoelectric ceramic plate 34
9 are adhered (the above-mentioned parts are
(Thick and separated) is used to detect the amount of bending by extracting the voltage change generated in the piezoelectric element 19 by the bending of the vibrating plate 16 through the conductors 20 and 21. In order to increase the voltage generated by the piezoelectric element, as shown in FIG.
7, 18 are electrodes 17a, 17b, 17c, 18a, 18
It is also practiced to superimpose the generated voltage of the piezoelectric element by dividing as shown in b. In FIG. 17, the number of divisions is reduced. In FIG. 18, this electrode division is performed in the half part of the diaphragm.

[0009]

Conventionally, as shown in FIG. 14, two sensors and two pipes or a sound guide passage acting similarly are used to eliminate the influence of noise and vibration from the outside. Therefore, the device for detecting the fluid vibration is complicated. The present invention is intended to obtain a differential pressure type pressure sensor for detecting a differential pressure between two points without using two separate sensors or a complicated sound guiding tube system.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a diaphragm bonded to a piezoelectric element and a sensor case are provided in the sensor so as to divide the diaphragm into two parts. It is divided into two sets that operate, and the front surface of the sensor case is covered with a cover having a cavity that covers each of the divided diaphragm parts independently, and both sets of piezoelectric elements are connected so as to output the difference in their outputs. In this case, two conventional sensors are integrally formed by individually introducing pressure into the divided cases.

[0011]

In the case divided into two parts, the pressure at two points to be measured is introduced by one simple tube. As a result, when the diaphragm vibrates, the two sets of piezoelectric elements bonded to the diaphragm generate outputs, and the pressure difference between the two points and the frequency of fluid vibration can be known from the outputs. Even if the case vibrates in a straight line direction due to an external force or external noise is generated, it does not affect the measurement by acting on the diaphragm.

[0012]

1 to 3 show a first embodiment of such a differential pressure type pressure sensor, FIG. 1 is an external perspective view, and FIG. 2 is A of FIG.
-A sectional view, FIG. 3 is a BB sectional view of FIG. The edge of the diaphragm 16 is supported by the crimped edge of the bottomed cylindrical sensor case 20, the cover 33, and the spacers 21a and 21b, and the electrodes 17 and 18 are bonded to the edge of the piezoelectric element 1.
9 is glued. The first partition plate 22a and the first partition plate 22a that come into contact with one diameter of the diaphragm 16 and come into contact with the bottom of the sensor case 20 and the inner surface of the spacer 21a to divide the inside of the case into two cavities 25a and 25b. Cavities 25c, 2 are provided between the diaphragm 16 and the cover 33 on the extension of the partition plate 22a.
A second partition plate 22b that is divided into 5d is bonded to the diaphragm 16, the sensor case 20, the spacers 21a and 21b, and the cover 33. The conduits 23 and 24 are connected to the cavities 25a and 25b in the case, which are divided into two parts by the first partition plate 22a. FETs 26a and 26b attached to a part of the diaphragm are connected to the circuits of the piezoelectric element that are driven by the respective divided portions of the diaphragm and act individually.

Due to this structure, the conduits 23, 2
4 to the through holes 7 and 8 of the fluid oscillator (FIGS. 10 and 11) described above.
, The pressure applied to the through holes 7 and 8 is introduced into the cavities 25a and 25b in the case to vibrate the vibration plate 16 and generate a voltage in the piezoelectric element bonded to the vibration plate.
The piezoelectric element is divided into two parts 19a and 19b, which act on each side by divided polar plates on both sides of the partition plate, which are connected as shown in FIG. 4 or FIG. 27,
27a and 27b are gate resistances, 28 is a power supply, 29 and 29
Reference symbol a is a balance adjustment resistor, and 30a and 30b are output terminals. The circuit 31 is provided in the sensor case, and the circuit 32 is an external circuit.

In principle, this circuit is as shown in FIG. That is, when a strong and weak fluid pressure is introduced from the through holes 7 and 8, the piezoelectric elements 19a and 19b generate voltages of e-Δe and e + Δe, which are the voltage difference ± 2Δ due to the circuits A and B. e is output from the output terminals 30a and 30b. Therefore, by measuring the outputs of the terminals 30a and 30b, it is possible to know the difference between the fluid pressures acting on the through holes 7 and 8 and the alternating frequency thereof.

FIG. 7 shows a second embodiment in which piezoelectric elements 19c and 19d are independently adhered to the middle portion of the diaphragm 16 which is divided into two parts by the diaphragms 22a and 22b and has a large amplitude. In the first embodiment described above, since the partition plates 22a and 22b are adhered to the central position portion of the piezoelectric element, the deflection of a part of the piezoelectric element is limited, but in the second embodiment, the deflection of the piezoelectric element is suppressed. Can be larger.

8 and 9 show a third embodiment of the present invention, FIG. 8 is an external perspective view, and FIG. 9 is a sectional view taken along line CC of FIG. The sensor case 20a formed of metal or resin has independent bottomed cavities 25a and 25b, and the cover 3 having the second partition plate 22b formed at the open end of the case.
The diaphragms 16a and 16b are attached while being suppressed by 3a. The diaphragm and the cover may be attached by screwing the cover 33a to the case 20a so as to sandwich the diaphragm between the two as shown in the figure, or may be attached by an adhesive. The conduits 23 and 24 leading to the cavities 25a and 25b are attached to the case 20a. The operation of this sensor is similar to that of the second embodiment.

As can be seen from the above embodiments, in the differential pressure type pressure sensor of the present invention, the conduits 23 and 24 are provided in the portions such as the through holes 7 and 8 in FIGS. 10 and 11 where the pressure difference is to be measured. If connected, the differential pressure and alternating frequency of both parts can be measured, and even if an external force in a linear direction is applied, the diaphragm will move in the same direction, so there will be no effect of external vibration, and Since the diaphragm is covered with the case and the cover even when noise is coming from the outside, it is not moved by the noise, and it is not necessary to form a complicated conduit as shown in FIG.

[0018]

【The invention's effect】

(1) A single sensor for measuring two pressures is formed, and a single sensor can measure a pressure difference between two parts and an alternating frequency. Therefore, the handling of the sensor is easy.

(2) The pressure difference measurement only needs to connect the conduits 23 and 24 to the part to be measured and does not need to form a complicated conduit.

(3) If the sensor case is used so as not to rotate, the measurement will not be hindered by external vibration or noise.

[Brief description of drawings]

FIG. 1 is an external perspective view of a pressure sensor showing a first embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

3 is a sectional view taken along line BB of FIG.

FIG. 4 is a circuit diagram showing a first example of a circuit incorporating the sensor of the first embodiment.

FIG. 5 is a circuit diagram showing a second example of a circuit incorporating the sensor of the first embodiment.

FIG. 6 is an operation principle diagram of the above.

FIG. 7 is an external perspective view of the second embodiment.

FIG. 8 is an external perspective view of the third embodiment.

9 is a sectional view taken along line CC of FIG.

FIG. 10 is a sectional view of a first example of a conventional fluid oscillator.

FIG. 11 is a sectional view of a second example of a conventional fluid oscillator.

FIG. 12 is a schematic diagram showing sensor connections for differential pressure measurement in these fluid oscillators.

FIG. 13 is a similar schematic diagram showing a case where the positive and negative pressures in FIG. 12 are reversed.

FIG. 14 is a schematic diagram showing a conventional sensor and a conduit for eliminating the influence of external force.

FIG. 15 is a sectional view schematically showing the configuration of a piezoelectric element.

FIG. 16 is a schematic view showing a first example of piezoelectric element division.

FIG. 17 is a schematic view showing a second example of piezoelectric element division.

FIG. 18 is a schematic view showing a third example of piezoelectric element division.

[Explanation of symbols]

1 Case 2 Target 3 Flow Protrusion 4 Flow Wall 5 Nozzle 6 Outlet 7, 8 Through Hole 9 Case 10 Nozzle 11 Target 12, 13 Flow Wall 14, 14a, 14b Pipe 15, 15a, 15b Sensor 16, 16a, 16b Diaphragm 17, 17a, 17b, 17c, 18, 18a, 18b
Electrode 19, 19a, 19b, 19c, 19d Piezoelectric element 20, 20a Sensor case 21a, 21b Spacer 22a, 22b Separator 23, 24 Conduit 25a, 25b, 25c, 25d Cavity 26a, 26b FET 27, 27a, 27b Gate Resistance 28 Power supply 29, 29a Balance adjustment resistance 30a, 30b Output terminal 31, 32 Circuit 33, 33a Cover 34 Piezoelectric ceramic plate

Claims (3)

[Claims] 1. A diaphragm to which a piezoelectric element is bonded is attached to an open end of a sensor case, and the inside of this case is divided into two parts by a first partition plate bonded to the diaphragm. Is divided into two parts that act independently of each other, conduits that respectively communicate with the divided compartments in the case are attached to the sensor case, and the front surface of the case is separated from the second partition located on the extension of the first partition plate. A differential pressure type pressure sensor comprising a plate and a cover that divides the front space of the diaphragm into two parts. 2. The differential pressure type pressure sensor according to claim 1, wherein two separate piezoelectric elements are bonded to a large amplitude portion of the diaphragm divided by the first partition plate. 3. A diaphragm having a piezoelectric element bonded to one end of each cavity of a sensor case in which two separate cavities are formed, conduits leading to the respective cavities are attached to the case, and a front surface of each diaphragm is attached. , A differential pressure type pressure sensor comprising a cover having cavities independently located in front of the two cavities.