JPS6293623A - Sensor - Google Patents

Abstract

PURPOSE:To make it possible to detect the strength of the continuously variable force acting on an unfixed piezoelectric element, by stacking an exciting side piezoelectric element excited from the outside, an elastic member and an outlet side piezoelectric element and fixing one of both piezoelectric elements. CONSTITUTION:An exciting side piezoelectric element 1, an elastic member 6 and an outlet side piezoelectric element 7 are stacked between a changeable diaphragm 2 and a fixed rigid body 11 without forming a gap. The exciting side piezoelectric element 1 is excited at frequency f0 by an oscillator 5 and repeats minute extension and contraction in the up-and-down direction. This extension and contraction are propagated to the output side piezoelectric element 7 through the elastic member 6 to generate signal voltage V0 with the frequency f0. At this time, when force P acts on the diaphragm 2, voltage V0 becomes AC voltage corresponding to the force P and the signal corresponding to the force P is obtained from an output signal terminal 12. Therefore, even if the force P changes, the change of the force P can be continuously detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a sensor for detecting force intensity, and particularly to a sensor suitable for detecting variable force intensity or fluid pressure change fJ+.

2. Description of the Related Art A conventional sensor includes, for example, a diffused semiconductor strain gauge attached to the surface of a pressure-receiving member, and when a force is applied to the pressure-receiving member, the sensor expands and contracts together with the pressure-receiving member to detect the strength of the applied force. There has also been a sensor that uses a piezoelectric element to detect the strength of force acting on the piezoelectric element.

Problems to be Solved by the Invention The conventional sensors described above, for example, in the case of a diffused semiconductor positive gauge, have the drawbacks that temperature drift is large and the configuration of the signal amplification circuit for amplifying the output of the strain gauge is complicated. Also, a lifting platform using a piezoelectric element.

When a force acts on a piezoelectric element, it instantly outputs a voltage, so it is not suitable for detecting the strength of a continuously variable force, and has the disadvantage that it is difficult to detect, for example, pressure fluctuations in a fluid. Ta.

Therefore, an object of the present invention is to provide a sensor that eliminates the above-mentioned drawbacks.

Means and Function for Solving the Problems The present invention provides an excitation-side piezoelectric element that is externally excited and alternately deforms, and contacts one surface of an elastic member, and abuts the output-side piezoelectric element on the other side of the elastic member. It is made by contacting a piezoelectric element. The output side piezoelectric element propagates the vibration from the excitation side piezoelectric element via the elastic member, and generates an output according to the strength of the force accompanying the deformation of the elastic member. Therefore, by fixing one of the excitation-side piezoelectric element or the output-side piezoelectric element and leaving the other unfixed, an output corresponding to the strength of the force acting on the non-fixed side piezoelectric element can be obtained from the fixed side piezoelectric element. , which continuously detects the strength of the variable force without being affected by temperature.

Embodiment FIG. 1 shows a first embodiment of a sensor according to the present invention. 1st
In the figure, reference numeral 1 denotes a cylindrical excitation side piezoelectric element, which is placed on a die 17 and a flamm 2. Electrodes 1a and Ib are provided on the upper and lower surfaces of the excitation side piezoelectric cord 1, and the electric currents 111a and 1b are connected to oscillation 2! via lead wires 3 and 4, respectively. Connected to i5.

Therefore, an electric current of a constant frequency of 1'o is applied from the oscillator 5 to the electrodes 1a and lb of the excitation side piezoelectric element. Therefore, the excitation side piezoelectric element 1 has a frequency f. It is excited by

Further, an elastic member 6 is placed on the -h upper pole 1a of the excitation side piezoelectric element 1. Therefore, one electrode 1a comes into contact with the elastic member 6, and the other electrode 1b comes into contact with the diaphragm 2. The elastic member 6 is formed of a spring that expands and contracts depending on the strength of the material or number that determines elasticity, such as rubber.

Reference numeral 7 denotes an output side piezoelectric element, which is placed on the upper surface of the elastic member 6. Further, electrodes 7a are provided on the upper and lower surfaces of the output side piezoelectric element.
7b71/1 installed. Electrode 7a.

7b are each connected to an amplifier 10 via a lead wire 8.9. One electrode 7b of the output side piezoelectric element 7 is in contact with the upper surface of the elastic member 6, and the other upper electrode 7a is in contact with the fixed rigid body 11. Therefore, the excitation side piezoelectric cord 1
2 elastic member 6. The output piezoelectric element 7 is stacked seamlessly between the displaceable diaphragm 2 and the fixed rigid body 11.

Therefore, the vibration of the excitation side pressure Xtffi element 1 caused by the oscillator 5 is elastically absorbed by the elastic member 6. However, when the force P acts on the diaphragm 2, the excitation side piezoelectric cord 1 is pressurized via the diaphragm 2.

Therefore, the excitation side piezoelectric cord 1 compresses the elastic member 6, and the output side piezoelectric element 7 is further pressed against the rigid body 11.

In this state, when the excitation side piezoelectric element 1 is excited by the oscillator 5, it repeatedly expands and contracts minutely in the vertical direction. That is,
When the excitation side piezoelectric element 1 expands, the force P pressing the elastic member 6 increases, and when the excitation side pressure 'ifX element 1 contracts, it is equivalent to a decrease in the force P by -ΔF. Therefore, when a force P acts on the diaphragm 2, a force of ±ΔF has a frequency f.

act alternately on the lower surface of the elastic member 6. This P±ΔF
A portion of the force is absorbed by the elastic member 6, but the remaining force P'±ΔF' is transmitted to the output side piezoelectric element 7. Furthermore, since the force of ±ΔF' changes at the frequency fo in the j side pressure type element 7, a signal voltage Vo at the frequency fo is generated. This signal voltage Vo is amplified by an amplifier 10 and output to an output signal terminal 12. Further, the elastic member 6 is compressed according to the strength of the force P, and the rate at which the force ΔF from the excitation side piezoelectric element 1 is absorbed by the elastic member 6 changes depending on the compression surface of the elastic member 6. That is, when the elastic member 6 is compressed, a part of the component force ΔF is not absorbed and the output side piezoelectric element 1
is propagated to.

Therefore, the voltage V generated by the output side piezoelectric element 7.

is proportional to the force ΔF', and the force transmission efficiency by the elastic member 6 is ? of the force P? The voltage Vo is an alternating voltage that depends on the force P since it changes depending on the force P. When a force P is applied to the diaphragm 2, a signal corresponding to the force P is obtained from the output No. 3 terminal 12. Therefore, even if the force P fluctuates, changes in the force P can be continuously detected. In addition, piezoelectric element 1
, 7 have a high Curie temperature, so the detection characteristics do not change due to temperature increase yt, and the force P can be detected even at high temperatures. Since a voltage of frequency fo is applied from the output side piezoelectric element 7, an AC amplifier can be used as the amplifier 10. Also, the frequency ro
By selecting , a selective amplifier can be used, and even when the output voltage vO of the output signal terminal 12 is small, Vo can be amplified to a sufficient level.

Next, a case will be described in which the sensor 13 having the above configuration is used as a pressure saw sensor. In FIG. 2, a flow path 15a of a pipe 15 for feeding fluid has an orifice 16 in the middle thereof. The piping 15 on the upstream and downstream sides of the orifice 16 has four parts 15b and 1 for housing the sensor 13 shown in FIG.
5G is installed.

A pair of sensors 13 and 13 are respectively connected to the NF of the output side piezoelectric element 7.
The output side piezoelectric element 7 is fixed to the pipe 15 with the i 7 a in contact with the upper surfaces of the recesses 15b and 15c. The excitation side piezoelectric element 1 has an opening 15d that opens into the flow path 15a,
It is in contact with a diaphragm 2 provided so as to close 15e.

Therefore, the pressures P+ and P2 of the fluid flowing in the flow path 15a act on the diaphragms 2, 2. The pressures P+ and P2 are applied to the output side piezoelectric elements 7 and 1 by pressing the excitation side piezoelectric element 1.1 via the diaphragms 2, 2.
It is detected as the output of 7.

Therefore, the pressure fluctuation of the fluid flowing inside the pipe 15 is detected by the sensor
j13.13 can be used for continuous detection.

Moreover, the sensors 13 and 13 are located above the orifice 16.

It is also possible to easily detect the differential pressure between the pressures P+ and P2 on the downstream side, and it can also be applied to a gas leak detection device, etc.

Next, a case where the sensor 13 is applied to a load cell will be explained. In Fig. 3, the sensor 13 is the load cell body 1
-0. In this case, the excitation side piezoelectric element 1
is fixed to the load cell body 17. In addition, a load receiving member 18 is provided in the upper opening 17a of the load cell body 17.
-1 It is installed so that it can be moved freely. The load receiver is covered with one pressure transmitting body interposed between the member 18 and the output side piezoelectric element 7. Therefore, in the load receiver, when an object is placed on the member 18 and a load W acts downwardly, the elastic member 6 is compressed according to the magnitude of the load W. Furthermore, the force acts on the output side piezoelectric element 7 of the sensor 13.

Therefore, the elastic member 6 is compressed by the pressing force of the output side piezoelectric element 7. However, since the excitation side piezoelectric element 1 fixed to the load cell body 17 is excited by the oscillator 5 at the frequency fo, the output side piezoelectric element 7 is pressed from above by the load W and is crossed by the force ΔF from below. There is widespread pressure. Therefore, the output side piezoelectric element 7 has a frequency f depending on the magnitude of the load ff1W. outputs the voltage Vo.

Effects of the Invention As described above, the sensor according to the present invention can obtain an output from the output side piezoelectric element according to the strength of the force acting on the non-fixed side piezoelectric element, and furthermore, the The force fluctuations can be continuously detected in an analog manner by the output of the expansion/contraction frequency, and therefore the output from the output side piezoelectric element can be amplified in an alternating current manner, and the S/N ratio is also good. In addition, the piezoelectric element Curi f! Because the temperature is relatively high, it is possible to perform stable pressure detection even at high temperatures compared to, for example, diffusion semiconductor strain gauges.In particular, it is also possible to detect pressure fluctuations in fluid flowing in piping channels, for example, to detect differential pressure in piping. It has features such as being able to measure continuously, being able to be applied to a load cell that visually measures the ΦG of an object, and being able to detect all kinds of forces using piezoelectric elements.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the sensor according to the present invention;
FIG. 2 is a schematic configuration diagram when the sensor shown in FIG. 1 is used as a pressure sensor, and FIG. 3 is a schematic configuration diagram when the sensor shown in FIG. 1 is applied to a load cell. 1... Excitation side piezoelectric element, 2... Diaphragm, 5...
... Oscillator, 6... Bone member, 7... Output side piezoelectric element, 10... Amplifier, 11... Rigid body, 13... Sensor.

Claims (1)

[Claims] an excitation-side piezoelectric element that is excited from the outside and deforms alternately;
an elastic member having one surface in contact with one surface of the excitation-side piezoelectric element; and one surface in contact with the other surface of the elastic member to transmit vibrations from the excitation-side piezoelectric element through the elastic member. and an output-side piezoelectric element that generates an output according to the strength of the force that is propagated by the elastic member, and the other surface of the excitation-side piezoelectric element or the output-side piezoelectric element is fixed and the output-side piezoelectric element is A sensor characterized in that the sensor is configured to obtain an output corresponding to the strength of a force acting on the other surface of the output-side piezoelectric element or the excitation-side piezoelectric element on the non-fixed side of the element.