JP6842279B2 - Vibration sensor and vibration detection system - Google Patents

Description

The present invention relates to a noise reduction technique for a piezoelectric sensor that detects vibration from a vibration source or the like.

A piezoelectric sensor that converts vibration into a piezoelectric output is used to detect the vibration of a vibrating body such as a motor. The piezoelectric sensor extracts the electric charge generated in the piezoelectric body by vibration from the electrode as a piezoelectric output. Therefore, there is a tendency to receive inductive noise from the power supply on the vibrating body side. This induced noise appears on the output side together with the piezoelectric output representing vibration.
Regarding such a vibration detection sensor, it is known to install a filter circuit to remove noise (Patent Document 1). Further, it is known that the piezoelectric sensor itself has a structure for preventing the influence of voice noise (Patent Document 2).

Japanese Unexamined Patent Publication No. 5-215599 Japanese Unexamined Patent Publication No. 2001-153660

By the way, when a piezoelectric sensor is used as a vibration sensor for detecting the vibration of a vibration source such as a motor, the piezoelectric sensor is installed at the vibration detection part of the vibration source, and the piezoelectric output generated at the signal electrode and the ground electrode of the piezoelectric sensor is a signal. Taken through leads connected to poles and ground poles.

Since the power supply is connected to the motor that is the target of vibration detection, the power supply induction noise affects the detection output of the piezoelectric sensor. That is, an induced current flows from the power supply to the piezoelectric sensor and the wiring having the high impedance characteristic, and the induced noise is generated by this induced current, and this induced noise affects the detection output.
When the vibration detection output of the piezoelectric sensor is taken out by electric charge (current), if the vibration detection signal (= weak current) generated from the piezoelectric sensor is affected by the induced current, the vibration detection sensitivity of the piezoelectric sensor is lowered. It is not easy to remove the induced noise component from the weak current output, and the installation of the noise removing device has disadvantages such as high equipment cost.

Therefore, in view of the above problems, a first object of the present invention is to reduce the influence of power supply induction noise on the piezoelectric output.
A second object of the present invention is to provide a vibration detection system including a piezoelectric sensor that reduces the influence of power source induction noise.

In order to achieve the above object, according to one aspect of the vibration sensor of the present invention, it is a vibration sensor that detects vibration from a vibration source, and is connected to a piezoelectric element including a signal electrode and a ground electrode and the signal electrode. includes a second conductor connected to the ground electrode and the first conductor, said an output extraction portion for taking out the piezoelectric output generated in the piezoelectric element, before Symbol said first conductor and said second guiding piezoelectric output conductor around it Ru are individually coated by a shield conductor.
In order to achieve the above object, according to one aspect of the vibration sensor of the present invention, a piezoelectric element which is a vibration sensor that detects vibration from a vibration source and has a shield conductor layer in a laminate containing a piezoelectric body, and the above-mentioned The output take-out part for taking out the piezoelectric output generated in the piezoelectric element is provided, and the output take-out part includes a conductor for guiding the piezoelectric output and a shield conductor covering the conductor, and the electrode of the piezoelectric element and the output take-out part of the piezoelectric element. The conductor is formed of a single conductor layer, and the shield conductor and the shield conductor layer on the output extraction portion side are formed of a single conductor.

In the vibration sensor, the output extraction unit may be connected to the piezoelectric element or integrally configured with the piezoelectric element.
In the vibration sensor, the shield conductor may be connected to a reference potential.
In the vibration sensor, the piezoelectric element includes a laminate including the signal electrode and the ground electrode provided with the piezoelectric body interposed therebetween, and a shield conductor layer provided on the outside of each of the signal electrode and the ground electrode. May include.
In the vibration sensor, the shield conductor may be connected to the shield conductor layer on the piezoelectric element side to maintain the reference potential.
In the above SL vibration sensor, further comprising a shield member covering the piezoelectric element, said shield conductor of the shield member and the output extraction portion may be connected.
In the vibration sensor, the electrode includes a signal electrode and a ground electrode, and the output extraction unit includes a first conductor connected to the signal electrode, a second conductor connected to the ground electrode, and a first of these. And a shielded conductor in which the second conductor covers individually or in common.
In the vibration sensor, the output extraction unit may be a coaxial cable including the conductor and the shield conductor.
The vibration sensor may further include a holding member that detachably adheres or attracts the piezoelectric element to the vibration source to hold it.

In order to achieve the above object, according to one aspect of the vibration detection system of the present invention, a vibration source installed in an environment of an AC power source or using the AC power source as a drive source and the vibration of the vibration source are detected. A vibration sensor and a measuring means for measuring the piezoelectric output output from the output extraction unit of the vibration sensor are provided.

According to the present invention, any of the following effects can be obtained.
(1) The influence of power supply induction noise on the piezoelectric output can be reduced.
(2) Since the influence of power supply induction noise can be reduced, the detection sensitivity of vibration etc. can be improved.
(3) The influence of power supply induction noise can be reduced, and a vibration detection system with high vibration detection accuracy can be provided.
(4) Abnormal vibration of a vibration source such as a motor that uses an AC power supply as a drive source can be detected with high accuracy.

It is a figure which shows the vibration sensor which concerns on 1st Embodiment. It is a figure which shows the vibration sensor which concerns on 2nd Embodiment. It is a figure which shows the vibration sensor which concerns on 3rd Embodiment. It is a figure which shows the vibration sensor which concerns on 4th Embodiment. It is a figure which shows the vibration sensor which concerns on 5th Embodiment. It is a figure which shows the vibration detection system which concerns on 6th Embodiment. It is a figure which shows the vibration sensor which concerns on Example 1. FIG. It is a figure which shows the vibration sensor which concerns on Example 2. FIG. It is a figure which shows the vibration sensor which concerns on Example 3. FIG. A is an exploded perspective view showing the piezoelectric element according to the fourth embodiment, B is an exploded perspective view showing a vibration sensor seen from the upper surface side, and C is an exploded perspective view showing a vibration sensor seen from the back surface side. A is a diagram showing a vibration detection waveform of a motor by a conventional piezoelectric sensor, and B is a diagram showing a frequency analysis waveform thereof. A and B are diagrams showing vibration detection waveforms of a motor by a vibration sensor according to an embodiment. A and B are diagrams showing vibration detection waveforms of the motor by the vibration sensor according to the embodiment, and C is a diagram showing the frequency analysis waveforms thereof.

[First Embodiment]
FIG. 1 shows a piezoelectric sensor according to the first embodiment. The configuration shown in the figure is an example, and the present invention is not limited to such a configuration.

The vibration sensor 2 is provided with a piezoelectric element 4 and an output extraction unit 6. The piezoelectric element 4 includes a piezoelectric sheet 8 as an example of a piezoelectric body that causes a piezoelectric phenomenon, and includes a signal pole 10-1 and a grounding pole 10-2 with the piezoelectric sheet 8 interposed therebetween. The signal electrode 10-1 and the ground electrode 10-2 are examples of electrodes for extracting the piezoelectric output generated in the piezoelectric sheet 8.

One end of the connecting conductor 12-1 is connected to the signal pole 10-1 as the first conductor, and the output terminal 14-1 is connected to the other end. One end of the second connecting conductor 12-2 is connected to the grounding electrode 10-2 as the second conductor, and the output terminal 14-2 on the grounding side is connected to the other end. The output terminals 14-1 and 14-2 are provided in, for example, a single connector 14. The output terminals 14-1 and 14-2 are examples of external terminals for connecting the signal pole 10-1 and the ground pole 10-2 to an external measuring device or the like.

A shield conductor 16-1 is provided around the connecting conductor 12-1, and similarly, a shield conductor 16-2 is provided around the connecting conductor 12-2 to maintain a reference potential such as a ground potential. An insulating layer 18 insulates between the connecting conductors 12-1 and 12-2 and the shield conductors 16-1 and 16-2. The insulating layer 18 may be an air layer.

<Effect of the first embodiment>
According to the vibration sensor 2 according to the first embodiment, the following effects can be obtained.
(1) Since the connecting conductors 12-1 and 12-2 on the output take-out portion 6 side are electromagnetically shielded by the shield conductors 16-1 and 16-2, the power supply induction appearing at the output terminals 14-1 and 14-2. Noise can be reduced, and the influence of power supply induction noise can be reduced.
(2) Since the connecting conductors 12-1 and 12-2 of the signal pole 10-1 and the grounding pole 10-2 are individually electromagnetically shielded, the effect of reducing power source induction noise is enhanced.
(3) Since the shield conductors 16-1 and 16-2 for electromagnetically shielding the connection conductors 12-1 and 12-2 of the output take-out unit 6 are maintained at a common potential by grounding or the like, the influence of the potential difference can be affected. It can be avoided and the power supply induction noise can be reduced.
(4) The shield conductors 16-1 and 16-2 can be connected to the grounding point on the external device side such as the vibration detection circuit connected by the connector 14, and the potential difference between the shield conductors 16-1 and 16-2 can be increased by sharing the reference potential with the external device. The influence can be avoided and the power supply induction noise can be reduced.

[Second Embodiment]
FIG. 2 shows the piezoelectric sensor according to the second embodiment. The configuration shown in the figure is an example, and the present invention is not limited to such a configuration.

The piezoelectric element 4 of the vibration sensor 2 is provided with a laminate 20 including a piezoelectric sheet 8, a signal pole 10-1 and a grounding pole 10-2. In this embodiment, the insulating layer 22 is provided on the outside of the signal pole 10-1 and the grounding pole 10-2 of the laminated body 20, and the shield conductor layers 24-1 and 24-2 are provided on the outside of the insulating layer 22. Be prepared. That is, the vibration sensor 2 includes shield conductor layers 24-1 and 24-2, and the vibration sensor 2 side is also provided with an electromagnetic shield.

A shield conductor 16-1 is connected to the shield conductor layer 24-1, and similarly, a shield conductor 16-2 is connected to the shield conductor layer 24-2. The shield conductor layers 24-1 and 24-2 are maintained at a reference potential such as a ground potential via the shield conductors 16-1 and 16-2.

<Effect of the second embodiment>
According to the vibration sensor 2 according to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment described above.
(1) Since the electromagnetic shield on the piezoelectric element 4 side is performed in addition to the electromagnetic shield on the output take-out portion 6, the influence of electromagnetic induction noise on the piezoelectric element 4 side can be reduced.
(2) Since the piezoelectric element 4 is electromagnetically shielded by the shield conductor layers 24-1 and 24-2, the power supply induction noise appearing at the output terminals 14-1 and 14-2 can be reduced.
(3) Since the signal pole 10-1 and the ground pole 10-2 are individually electromagnetically shielded, the effect of reducing power source induction noise is enhanced.
(4) The shield conductors 16-1 and 16-2 of the output take-out unit 6 and the shield conductor layers 24-1 and 24-2 on the piezoelectric element 4 side can be maintained at a common potential by grounding or the like, and the influence of the potential difference can be avoided. , Power supply induction noise can be reduced.
(5) The shield conductors 16-1 and 16-2 and the shield conductor layers 24-1 and 24-2 can be connected to a grounding point on the external device side such as a vibration detection circuit connected by the connector 14, and have a reference potential. The influence of the potential difference between the external device and the external device can be avoided, and the power supply induction noise can be reduced.

[Third Embodiment]
FIG. 3 shows the piezoelectric sensor according to the third embodiment. The configuration shown in the figure is an example, and the present invention is not limited to such a configuration.

In this vibration sensor 2, as shown in FIG. 3, the signal pole 10-1 and the connecting conductor 12-1 on the output extraction unit 6 side are formed of a single conductor, and the output extraction unit 6 is integrated with the piezoelectric element 4. It is configured. Similarly, the grounding electrode 10-2 and the connecting conductor 12-2 on the output take-out portion 6 side are formed of a single conductor. That is, the conductor of the signal pole 10-1 may be extended to the output take-out portion 6 side to form the connecting conductor 12-1, and similarly, the ground electrode 10-2 may be extended to the output take-out portion 6 side to form the connecting conductor 12 It may be -2.

The upper shield conductor 16-11 on the output take-out portion 6 side is extended to the piezoelectric element 4 side to form the shield conductor layer 24-1. Similarly, the lower shield conductor 16-21 on the output take-out portion 6 side is extended to the piezoelectric element 4 side to form the shield conductor layer 24-2. In this case, the insulating layers 18 and 22 may be formed of a common insulating material.

A shield conductor 16-12 is installed below the connecting conductor 12-1 of the output take-out portion 6 via an insulating layer 18, and a shield conductor 16-22 is installed above the connecting conductor 12-2 via an insulating layer 18. ing. These shield conductors 16-12 and 16-22 are installed only on the output take-out portion 6 side, and may be formed of a common conductor. The insulating layer 18 may use the same insulating material as the insulating layer 22 on the piezoelectric element 4 side. Such a configuration of the output extraction unit 6 may be realized by a hybrid IC (Integrated Circuit) technology.

<Effect of the third embodiment>
According to the vibration sensor 2 according to the third embodiment, the following effects can be obtained in addition to the effects of the first and second embodiments described above.
(1) The piezoelectric element 4 and the output take-out unit 6 can be integrated, the configuration of the vibration sensor 2 can be simplified, and the piezoelectric output with reduced electromagnetic induction noise can be taken out.
(2) It is not necessary to separately manufacture and connect the piezoelectric element 4 and the output take-out unit 6, and it is not necessary to take measures against electromagnetic shielding at the connection point.
(3) Compared with the case where the piezoelectric element 4 and the output take-out unit 6 are manufactured individually, they can be manufactured by a common manufacturing process, and the manufacturing cost can be reduced.

[Fourth Embodiment]
FIG. 4 shows the vibration sensor 2 according to the fourth embodiment. In this embodiment, the piezoelectric element 4 is covered with an insulating layer 26 on the piezoelectric element 4 side, and the shield case 28 is installed on the outside of the insulating layer 26. For the shield case 28, for example, a copper foil tape may be used as the conductor. The shield case 28 is an example of a shield member. The shield case 28 and the shield conductors 16-1 and 16-2 are connected and maintained at a reference potential such as a ground potential.

<Effect of the fourth embodiment>
According to the vibration sensor 2 according to the fourth embodiment, the following effects can be obtained in addition to the effects of the first to third embodiments described above.
(1) After the piezoelectric element 4 is manufactured, the shield case 28 can be installed to provide the piezoelectric element 4 with an electromagnetic shield.
(2) Since the insulating layer 26 and the shield case 28 may be installed as needed, an electromagnetic shield suitable for the installation environment can be realized.

[Fifth Embodiment]
FIG. 5 shows the vibration sensor 2 according to the fifth embodiment. In the first to fourth embodiments, the output extraction unit 6 is provided with a connecting conductor 12-1 for the signal pole 10-1 of the vibration sensor 2 and a connecting conductor 12-2 for the grounding pole 10-2. However, in this embodiment, the connecting conductor 12 is provided for the signal pole 10-1, and the shield conductor 16 is provided for the grounding pole 10-2. The shield conductor 16 is a shield member that covers the periphery of the connecting conductor 12. A connecting conductor 12 is connected to the signal pole 10-1, a shield conductor 16 is connected to the grounding electrode 10-2, and a reference potential such as a grounding potential is maintained. Similarly, the connector 14 is connected to the end of the connecting conductor 12 and the shield conductor 16.
In the vibration sensor 2 of the fifth embodiment, the connecting conductor 12 is a common conductor with the signal pole 10-1, and the shield conductor 16 is common with the grounding pole 10-2, as in the third embodiment. It may be formed of a conductor.

<Effect of the fifth embodiment>
According to the fifth embodiment, in addition to obtaining the same effects as those of the first to fourth embodiments, the following effects can be obtained.
(1) The connecting conductor 12 and the shield conductor 16 can be simplified, and the material cost can be reduced.
(2) The connection process can be simplified, and the manufacturing cost and connection work cost can be reduced.
(3) The weight of the output take-out unit 6 can be reduced, and the wiring cost can be reduced, for example, a coaxial cable can be used.

[Sixth Embodiment]
FIG. 6 shows a vibration detection system according to a sixth embodiment. The vibration detection system 30 is a system in which a vibration sensor 2 is provided in a vibration source 32 which is a vibration detection target such as a motor M, and the vibration of the vibration source 32 is detected by the vibration sensor 2.
The vibration source 32 may be, for example, a device such as a motor driven by an AC power source. As the vibration sensor 2, the vibration sensor 2 shown in FIG. 5 is used as an example, but the vibration sensor 2 including the shield conductor layer and the shield case may be used. The output extraction unit 6 has the same configuration as that of the fifth embodiment (FIG. 5) as an example, but may be either the first embodiment or the fourth embodiment (FIGS. 1 to 4).
A measuring device 33 for measuring the vibration detection output is connected to the connector 14 provided in the output extraction unit 6. The measuring device 33 includes a voltmeter, an oscilloscope, a frequency analysis device, and the like.

<Effect of the sixth embodiment>
According to the sixth embodiment, the following effects can be obtained.
(1) By using the vibration sensor 2 according to the first to fifth embodiments, even if inductive noise such as alternating current is received from the vibration source 32, the inductive noise can be reduced from the output extraction unit 6 side, and the vibration sensor 2 can be used. Piezoelectric output can be taken out.
(2) Since the influence of the induced noise can be suppressed, the detection sensitivity of vibration detection can be enhanced without impairing the detection sensitivity of the vibration sensor 2.

FIG. 7 shows the piezoelectric sensor according to the first embodiment. In FIG. 7, the same parts as those in FIG. 1 are designated by the same reference numerals. In this vibration sensor 2, the configuration on the piezoelectric element 4 side is the same as that of the first embodiment (FIG. 1), so the same reference numerals are given and the description thereof will be omitted.

The output extraction unit 6 of the vibration sensor 2 is provided with coaxial cables 34-1 and 34-2. A conductor 36 is provided at the center of each of the coaxial cables 34-1 and 34-2, and a shield conductor 40 is provided around the conductor 36 via an insulating layer 38. The conductor 36 is covered and shielded by the shield conductor 40. The conductor 36 is an example of the connecting conductors 12-1 and 12-2, the insulating layer 38 is an example of the insulating layer 18, and the shield conductor 40 is an example of the shield conductors 16-1 and 16-2.
The signal pole 10-1 of the vibration sensor 2 is connected to the conductor 36 of the coaxial cable 34-1, and the grounding pole 10-2 is connected to the conductor 36 of the coaxial cable 34-2. The shield conductors 40 of the coaxial cables 34-1 and 34-2 are connected in common and are maintained at the reference potential by grounding or the like.

The conductor 36 of the coaxial cable 34-1 is connected to the output terminal 14-1 of the connector 14, and the conductor 36 of the coaxial cable 34-2 is connected to the output terminal 14-2. Therefore, the piezoelectric output of the vibration sensor 2 can be taken out from the connector 14 via the coaxial cables 34-1 and 34-2.

<Effect of Example 1>
According to the first embodiment, the same effect as that of the first embodiment can be obtained. Further, since the coaxial cables 34-1 and 34-2 are used, the wiring structure of the output take-out unit 6 can be simplified.

FIG. 8 shows the piezoelectric sensor according to the second embodiment. In FIG. 8, the same parts as those in FIG. 7 are designated by the same reference numerals. In this vibration sensor 2, the configuration on the piezoelectric element 4 side is the same as that of the fourth embodiment, so the same reference numerals are given and the description thereof will be omitted.

A shield cover 42 is placed on the piezoelectric element 4 with an insulating layer 44 interposed therebetween, and the piezoelectric element 4 is shielded by the shield cover 42. The shield cover 42 is formed of a shield conductor such as a conductor foil, and for example, a copper foil tape having an adhesive layer is used. The insulating layer 44 is an example of an insulating means for electrically insulating the shield cover 42, which is a conductor, with the piezoelectric sheet 8 of the piezoelectric element 4, the signal pole 10-1 or the grounding pole 10-2.
The shield cover 42 is commonly connected to the shield conductor 40 of each of the coaxial cables 34-1 and 34-2 and is grounded.

<Effect of Example 2>
According to the second embodiment, the same effect as that of the first embodiment or the first embodiment can be obtained, and the shield cover 42 is provided on the piezoelectric element 4 side as in the fourth embodiment. The shielding effect of the piezoelectric element 4 itself can be obtained. As a result, the piezoelectric output with reduced inductive noise can be taken out from the connector 14.

FIG. 9 shows the vibration sensor 2 according to the third embodiment. In FIG. 9, the same parts as those in FIG. 8 are designated by the same reference numerals. In this vibration sensor 2, the configuration on the piezoelectric element 4 side is the same as that of the fourth embodiment, so the same reference numerals are given and the description thereof will be omitted.

In the third embodiment, a single coaxial cable 34 is used instead of the coaxial cables 34-1 and 34-2 described above. The signal pole 10-1 of the piezoelectric element 4 is connected to the conductor 36 of the coaxial cable 34, and the grounding electrode 10-2 and the shield cover 42 are connected to the shield conductor 40 to be grounded. The output terminal 14-1 of the connector 14 is connected to the conductor 36, and the output terminal 14-2 is connected to the shield conductor 40.

<Effect of Example 3>
According to the third embodiment, the same effect as that of the second embodiment can be obtained, and the wiring form can be simplified by the single coaxial cable 34.

<Vibration sensor 2>
FIG. 10A shows the disassembled state of the piezoelectric element 4 according to the fourth embodiment. On the piezoelectric element 4, a signal pole 10-1, a shield conductor layer 42-1 and a surface protection layer 46-1 are laminated on the upper surface side of the piezoelectric sheet 8, and a grounding electrode 10-2, on the lower surface side of the piezoelectric sheet 8. The shield conductor layer 42-2 and the surface protection layer 46-2 are laminated. The signal electrode 10-1 and the ground electrode 10-2 are, for example, patterned electrodes with a Kapton film, and the shield conductor layers 42-1 and 42-2 are, for example, copper foil tape. The surface protective layers 46-1 and 46-2 are, for example, Kapton with a single-sided adhesive.
The conductor 36 of the coaxial cable 34 is directly attached to the signal pole 10-1 by a connecting means such as solder, and the shield conductor 40 of the coaxial cable 34 is attached to the grounding electrode 10-2 and the shield conductor layers 42-1 and 42-2. Similarly, it is directly attached by a connecting means such as solder.
Magnet sheets 48-1 and 48-2 are installed on the exposed surface side of the surface protective layer 46-2 on the lower surface side as an example of the holding member.

In the vibration sensor 2, as shown in FIG. 10B, the piezoelectric element 4 has a signal pole 10-1, a shield conductor layer 42-1 and a surface protection layer 46-1 laminated on the upper surface side of the piezoelectric sheet 8. A single laminate is formed in which a grounding electrode 10-2, a shield conductor layer 42-2, and a surface protection layer 46-2 are laminated on the lower surface side of the piezoelectric sheet 8.
In the coaxial cable 34 which is the output take-out portion 6, the conductor 36 is directly attached to the signal pole 10-1, and the shield conductor 40 is directly attached to the grounding electrode 10-2 and the shield conductor layers 42-1 and 42-2. As a result, it is pulled out from one side of the piezoelectric element 4. A connector 14 is provided at the end of the coaxial cable 34, a conductor 36 is connected to the output terminal 14-1, and a shield conductor 40 is connected to the output terminal 14-2.

As shown in FIG. 10C, the piezoelectric element 4 is provided with magnet sheets 48-1 and 48-2 on the back surface side thereof, and can be attached to the vibration source 32. The magnet sheets 48-1 and 48-2 may be double-sided adhesives.

<Manufacturing process>
As an example, the manufacturing method of the vibration sensor 2 includes (a) a manufacturing process of the piezoelectric element 4, (b) a connecting step of the coaxial cable 34, and (c) a connecting step of the connector 14.
(A) Manufacturing process of the piezoelectric element 4 For example, when assembling from the upper surface side of the piezoelectric element 4, the shield conductor layer 42-1 is adhered to the insulating sheet constituting the surface protection layer 46-1, and the shield conductor layer 42 The signal pole 10-1 is attached on the signal pole 10-1 via an insulating layer, and the piezoelectric sheet 8 is installed and fixed on the signal pole 10-1.
A grounding electrode 10-2 is mounted on the piezoelectric sheet 8, a shielded conductor layer 42-2 is mounted on the grounding electrode 10-2 via an insulating layer, and a surface protection is provided on the shielded conductor layer 42-2. The insulating sheet constituting the layer 46-2 is adhered.
As a result, the piezoelectric element 4 which is a single laminated body is formed. The magnet sheets 48-1 and 48-2 are mounted on the surface protective layer 46-2.
(B) Connection Step of Coaxial Cable 34 Before shifting to the manufacturing process or manufacturing process of the piezoelectric element 4, the conductor 36 of the coaxial cable 34 is connected to the signal pole 10-1.
The shield conductor 40 of the coaxial cable 34 is connected to the ground electrode 10-2 and the shield conductor layers 42-1 and 42-2.
(C) Connection step of connector 14 The connector 14 is attached to the end of the coaxial cable 34, and the output terminal 14-1 is formed on the conductor 36 and the output terminal 14-2 is formed on the shield conductor 40.

<Material of piezoelectric element 4 etc.>
The piezoelectric element 4 may be a piezoelectric functional layer of a single member or a laminate of a plurality of members. The piezoelectric sheet 8 is an example of a piezoelectric layer, and a double-sided smoothing layer, a protective layer, an insulating layer, and the like may be laminated, or may be a monomorph, a bimorph, or a laminated type. The piezoelectric layer may be an organic piezoelectric layer such as a sheet made of a piezoelectric resin or a porous resin sheet, or an inorganic piezoelectric material layer such as quartz, barium titanate, or lead zirconate titanate.
The shape and size of the piezoelectric layer may be any shape as long as the vibration of the vibration source 32 can be detected, and includes a shape parallel to the surface of the vibration source 32.
In order to achieve a better vibration detection function in the vibration detection in the thickness direction of the piezoelectric element 4, for example, the piezoelectric constant d33 is preferably 20 × 10 ^-12 [C / N] or more, more preferably 100 × 10 ^{−. A piezoelectric material of 12} [C / N] or higher may be used.
For example, a porous resin sheet may be used for the piezoelectric element 4. This porous resin sheet has the following features.

a) It has high charge responsiveness to minute vibrations and vibration detection function, and can retain charge in a high temperature environment. An excellent vibration detection function can be obtained, and it is possible to reduce the weight as well as high wrestling resistance and impact resistance.
b) It is possible to obtain a shape followability to an arbitrary shape or curved surface shape such as a thin film of the vibration sensor 2 or a large area, and a detection surface shape of the vibration source 32, and the degree of freedom of the detection surface is expanded.
c) If the porous resin sheet is used, any fixed form such as winding or sticking to the vibration source 32 can be selected. Therefore, the polarization axis of the piezoelectric layer can be aligned with the normal of the surface of the vibration source 32, and the sensitivity of vibration detection can be increased.

The porous resin sheet is preferably a sheet made of, for example, an organic material that can retain an electric charge. The porous resin sheet includes a non-woven fabric or woven fabric made of fibers, a sheet-like foam made of an organic polymer, a stretched porous film made of an organic polymer, a matrix resin and hollow particles (at least one of the surfaces of the hollow particles). A porous resin sheet containing (a conductive substance may be attached to the portion) and a phase separating agent dispersed in the organic polymer are removed using an extractant such as supercritical carbon dioxide to open pores. Sheets and the like formed by the forming method are included. From the viewpoint of maintaining durability and deformation performance, a non-woven fabric or woven fabric using polymer fibers is preferable.
The porous resin sheet may contain one kind or two or more kinds of inorganic fillers. As a result, the amount of charge retained is high and excellent piezoelectric characteristics can be obtained. If an inorganic filler is used, a sheet having a high piezoelectricity can be obtained. The inorganic filler preferably has a higher dielectric constant than the polymer, and may have a relative permittivity of ε = 10 to 10,000. Inorganic fillers include titanium oxide, aluminum oxide, barium titanate, lead zirconate titanate, zirconium oxide, cerium oxide, nickel oxide, tin oxide and the like.
The thickness of the porous resin sheet may be, for example, 10 [μm] to 1 [mm], more preferably 50 [μm] to 500 [μm]. In order to obtain high charge retention, the porosity may be preferably 60 [%] or more, more preferably 75 [%] or more, still more preferably 80 to 99 [%]. This vacancy rate is
(True Density of Resin-Apparent Density of Porous Resin Sheet) x 100 / True Density of Resin
・ ・ ・ (1)
Demanded by. For the apparent density, a value calculated by using the weight of the porous resin sheet and the apparent volume may be used.
The polymer for forming the fiber should have a volume resistance of 1.0 × 10 ¹³ [Ω · cm] or more, for example, a polyamide resin (6-nylon, 6,6-nylon, etc.), an aromatic polyamide. Based resins (aramid, etc.), polyolefin resins (polyethylene, polypropylene, etc.), polyester resins (polyethylene terephthalate, etc.), polyacrylonitrile, phenolic resins, fluororesins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), imide Any of the based resins (polymeric, polyamideimide, bismaleimide, etc.) may be used.

From the viewpoint of excellent heat resistance and weather resistance, a polymer having no dipole due to its molecular and crystal structures is preferable. For example, polyolefin resins (polyethylene, polypropylene, ethylene propylene resin, etc.), polyester resins (polyethylene elephthalate, etc.), polyurethane resins, polystyrene resins, non-fluorine resins such as silicon resins, and polytetrafluoroethylene (PTFE). , Fluorine-based resins such as tetrafluoroethylene-perfluoroalkylpinyl ether copolymer (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP) may be used.

Considering heat resistance and weather resistance, it is preferable that the continuous usable temperature is high and the glass transition point is not provided in the working temperature range. For example, according to the continuous use temperature test of UL746B (UL standard), the continuous use temperature of the polymer is preferably 50 [° C.] or higher, more preferably 100 [° C.] or higher, and further preferably 200 [° C.]. ℃] or higher. Considering moisture resistance, those exhibiting water repellency are preferable.
For the polymer having these characteristics, for example, a polyolefin resin or a fluorine resin may be used. If a polyolefin-based resin or a fluorine-based resin is used, vibration detection can be performed without deteriorating the piezoelectric characteristics even in vibration detection at a temperature of 100 [° C.] or a high temperature exceeding 100 [° C.]. PTFE is preferable as the fluororesin.
In PTFE, it is possible to realize a vibration sensor 2 that is excellent in heat resistance, vibration detection ability and durability, and can detect vibration of a high temperature vibration source 32, and can maintain vibration detection performance and structure in high temperature and high pressure environments. Is.

For the fibers, the average fiber diameter may be preferably 0.05 to 50 [μm], more preferably 0.1 to 20 [μm], and even more preferably 0.3 to 5 [μm]. When the average fiber diameter is within this range, a non-woven fabric or woven fabric showing high flexibility can be obtained. When the surface area of the fiber is large, a space sufficient to retain the electric charge can be formed, and the distribution uniformity of the fiber can be improved even when the non-woven fabric or the woven fabric is thinly formed.
The average fiber diameter of the fiber can be adjusted by selecting the fiber forming conditions. For example, according to the electric field spinning method, the average fiber diameter of the obtained fiber is reduced by lowering the humidity, reducing the nozzle diameter, increasing the applied voltage, or increasing the voltage density during electric field spinning. Tend.
Here, the average fiber diameter is a plurality of, for example, 20 at random from the SEM image obtained by observing the fiber (group) to be measured with a scanning electron microscope (SEM) and observing at a magnification of 10,000 times. It is an average value based on the measurement results of these fiber diameters (major diameters) after selecting fibers.
The coefficient of variation of the fiber diameter of the fiber is preferably 0.7 or less, more preferably 0.01 to 0.5, from the value calculated by the following formula. When this coefficient of variation of fiber diameter is within a predetermined range, the fiber diameter of the fiber becomes uniform, and the non-woven fabric or woven fabric obtained from this fiber has a higher porosity and a porous resin sheet having high charge retention. It is also preferable from the viewpoint of obtaining.

Fiber diameter coefficient of variation = standard deviation / average fiber diameter ・ ・ ・ (2)
The "standard deviation" is the standard deviation of the fiber diameters of the 20 fibers described above.
The fiber length of the fiber is preferably 0.1 to 1000 [mm], more preferably 0.5 to 100 [mm], and even more preferably 1 to 50 [mm].
The fiber may be produced by, for example, an electric field spinning method, a melt spinning method, a molten electric field spinning method, a spunbond method (melt blow method), a wet method, or a spunlace method. The fiber obtained by the electrospinning method has a small fiber diameter. In a non-woven fabric or woven fabric using this fiber, a porous resin sheet having a high porosity, a high specific surface area, and high piezoelectricity can be obtained.
In the electrospinning method, a spinning solution containing a polymer and, if necessary, a solvent is used. The polymer may be used alone or in combination of two or more. The proportion of the polymer contained in the spinning solution may be, for example, 5 to 100 [% by weight], preferably 5 to 80 [% by weight], and more preferably 10 to 70 [% by weight].
The solvent is not limited as long as it can dissolve or disperse the polymer. Solvents include, for example, water, dimethylacetamide, dimethylformamide, tetrahydrofuran, methylpyrrolidone, xylene, acetone, chloroform, ethylbenzene, cyclohexane, benzene, sulfolane, methanol, ethanol, phenol, pyridine, propylene carbonate, acetonitrile, trichloroethane, hexafluoroisopropanol, It may be any of diethyl ether. These solvents may be used alone or in combination of two or more. The solvent contained in the spinning solution may be, for example, 0 to 90 [% by weight], preferably 10 to 90 [% by weight], and more preferably 20 to 80 [% by weight].

The spinning solution may contain additives other than polymers such as inorganic fillers, surfactants, dispersants, charge modifiers, functional particles, adhesives, viscosity modifiers, fiber-forming agents and the like. The additive may be used alone or in combination of two or more. In a spinning solution, if the polymer has low solubility in a solvent, for example if the polymer is PTFE and the solvent is water, one or more fiber-forming agents to keep the polymer in fiber shape during spinning. Is preferably included.
The fiber-forming agent is preferably a polymer having high solubility in a solvent. Examples of the fiber forming agent include polyethylene oxide, polyethylene glycol, dextran, alginic acid, chitosan, starch, polyvinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, cellulose and polyvinyl alcohol. The amount of the fiber forming agent used may be, for example, 0.1 to 15 [% by weight], preferably 1 to 10 [% by weight] in the spinning solution, although it depends on the viscosity of the solvent and the solubility in the solvent.
The spinning solution may be produced by mixing a polymer, a solvent and, if necessary, additives by a known method. If the polymer is PTFE, the spinning solution contains 30 to 70 [% by weight], preferably 35 to 60 [% by weight] of PTFE and 0.1 to 10 [% by weight] of the fiber forming agent, preferably 1 to 1. A spinning solution containing 7% by weight and a total of 100 [% by weight] of solvent is preferable.
The applied voltage during electrospinning may be preferably 1 to 100 [kV], more preferably 5 to 50 [kV], and even more preferably 10 to 40 [kV].
The tip diameter (outer diameter) of the spinning nozzle used for electric field spinning is preferably 0.1 to 2.0 [mm], more preferably 0.2 to 1.6 [mm].
For example, when a spinning solution is used, the applied voltage is preferably 10 to 50 [kV], more preferably 10 to 40 [kV]. The tip diameter (outer diameter) of the spinning nozzle is preferably 0.3 to 1.6 [mm].

To form a non-woven fabric with fibers, for example, a step of manufacturing the fibers by using an electrospinning method and a step of accumulating the fibers in a sheet to form a non-woven fabric may be performed at the same time, or a step of manufacturing the fibers. After that, a step of accumulating the fibers in a sheet shape to form a non-woven fabric may be performed by a wet method.

In the formation of the non-woven fabric by the wet method, for example, a method of using an aqueous dispersion containing fibers and depositing (accumulating) the fibers on the mesh to form a sheet (papermaking) may be used.
The amount of fiber used in this wet method may be preferably 0.1 to 10 [% by weight], more preferably 0.1 to 5 [% by weight], based on the total amount of the aqueous dispersion. If fibers are used within this range, water can be efficiently used in the process of depositing the fibers, and the fibers are well dispersed, and a uniform wet non-woven fabric can be obtained.
In the aqueous dispersion, one each is a dispersant or oil agent composed of cationic, anion-based, nonionic-based surfactants, etc., and a defoaming agent that suppresses the generation of bubbles in order to improve the dispersed state. Seeds or two or more may be added.
The method for producing a woven fabric using fibers may include a fiber manufacturing step and a woven fabric forming step in which the fibers obtained in this step are woven into a sheet. As a method for weaving fibers into a sheet, a known weaving method may be used. Examples of this weaving method include a water jet room, an air jet room, and a rapier room.
If the polymer is PTFE, it is preferable to perform heat treatment after forming the non-woven fabric or woven fabric. In this heat treatment, the non-woven fabric or woven fabric may be heat-treated under the conditions of usually 200 to 390 [° C.] and 30 to 300 [minutes]. By performing this heat treatment, the solvent, fiber forming agent, etc. remaining on the non-woven fabric or woven fabric can be removed.

As an example of the method for producing a non-woven fabric, a case including a process for producing a fiber made of PTFE by an electric field spinning method will be illustrated. A known production method can be adopted as a method for producing a non-woven fabric made of PTFE fiber, and examples thereof include the methods described in JP-A-2012-515850. This production method includes a step of providing a spinning solution containing PTFE, a fiber forming agent and a solvent and having a viscosity of at least 50,000 [cP], and the spinning solution is spun from a nozzle and fiberized by electrostatic traction. A non-woven fabric consisting of PTFE fibers is formed by collecting the fibers on a collector (eg, a take-up spool) and forming a precursor, and calcining the precursor to remove a solvent and a fiber forming agent. Includes steps to do.

The basis weight of the non-woven fabric and the woven fabric is preferably 100 [g / m ² ] or less, more preferably ^{0.1 to 50 [g / m 2} ], and further preferably 0.1 to 20 [g / m ² ]. .. The basis weight tends to increase by lengthening the spinning time and increasing the number of spinning nozzles.
Nonwoven fabrics and woven fabrics are made by accumulating or weaving fibers in a sheet form. Such non-woven fabrics and woven fabrics may be composed of a single layer or two or more layers having different materials and fiber diameters.
The porous resin sheet is preferably polarized. If the polarization treatment is performed, an electric charge can be injected into the sheet, and the electric charge is concentrated in the pores in the porous resin sheet to induce polarization. In the internally polarized sheet, the electric charge can be taken out from the front and back surfaces of the sheet by the compressive load applied in the thickness direction of the sheet. That is, such charges cause charge transfer to an external load (electric circuit), and an electromotive force is obtained. This causes a potential difference, that is, a voltage.

As a method of polarization treatment, a known method may be used. For example, a corona discharge treatment may be used in addition to a DC voltage or AC voltage application treatment.
In the corona discharge treatment, a high voltage power supply and an electrode device may be used. The discharge conditions are appropriately selected according to the material and thickness of the porous resin sheet. For example, in the case of a porous resin sheet made of PTFE, the voltage is −0.1 to -100 [kV] as a preferable treatment condition. , More preferably -1 to -20 [kV], current 0.1 to 100 [mA], more preferably 1 to 80 [mA], and more preferably 0.1 to 100 [cm] distance between electrodes. The applied voltage may be 1 to 10 [cm], the applied voltage may be 0.01 to 10.0 [MV / m], and more preferably 0.5 to 2.0 [MV / m].
Regarding the polarization treatment, the porous resin sheet alone may be subjected to the polarization treatment, but if a laminate of, for example, the porous resin sheet and the insulating layer is formed as the piezoelectric layer, the laminate is formed. After that, it is preferable to carry out a polarization treatment after laminating the insulating layer. The layer laminated on the porous resin sheet plays a role of preventing the electric charge held in the porous resin sheet by the polarization treatment from being electrically connected to the external environment and being attenuated. This contributes to increasing the sensitivity of vibration detection. Further, there is a tendency that a new interface capable of retaining an electric charge can be formed between the porous resin sheet and the layer laminated on the porous resin sheet. It is considered that this improves the piezoelectricity of the porous resin sheet.

<Vibration source 32>
The vibration source 32, which is the vibration detection target of the vibration sensor 2, is not limited to the motor described above. For example, machines, grounds, buildings, vehicles, ships, aircraft, etc. including piping, rotating parts, etc. installed in an environment of an AC power source, which are affected by power source induction noise such as an AC power source, may be included. The piping may include, for example, water supply piping, gas piping, petrochemical plant piping, heat exchanger piping, fuel piping, hydraulic / pneumatic piping, chemical solution piping, food plant piping, and the like. Rotating components may include pumps, compressors, engines, bearings, turbines, wheels, and other parts that generate vibration due to rotational movement.
For example, if the vibration sensor 2 is applied to detect the vibration of the pipe, it is possible to detect the abnormal vibration due to the leakage of the fluid in the pipe. If the vibration sensor 2 is applied to detect the rotational vibration of the rotating system component, the rotation abnormality can be detected from the vibration.
The surface material of the vibration source 32 may be any metal material such as metal, ceramics, rubber or resin, an inorganic material, or a polymer material. The surface state of the vibration source 32 may be a flat surface, a curved surface such as a cylinder or a sphere, or an uneven surface.

Regarding the vibration detection system 30 (FIG. 6), an AC motor was used as the vibration source 32 to reduce power source induction noise and detect motor vibration. The vibration sensor 2 was fixed to the motor with double-sided adhesive tape. The motor was not grounded. An oscilloscope was used as an example of waveform observation equipment for waveform observation.
A conventional piezoelectric sensor in which the output extraction unit 6 is not shielded is used as a comparative example.

The output waveform shown in FIG. 11A was observed with the piezoelectric sensor not provided with the shielding measures. In FIG. 11A, the vertical axis represents the vibration level and the horizontal axis represents the time t. In this output waveform, superposition of high-frequency components is observed for sinusoidal periodic fluctuations.
When frequency analysis (FFT) was performed on this output waveform, the frequency component shown in B of FIG. 11 was observed. In FIG. 11B, the vertical axis represents the frequency distribution level and the horizontal axis represents the frequency f. However, as a result of the power supply induction noise component being included in this frequency analysis output, it is not possible to discriminate the waveform peculiar to the motor vibration from this frequency analysis output.

On the other hand, in the vibration sensor 2 provided with the shield conductor layers 42-1 and 42-2 on the piezoelectric element 4 side, the output waveform shown in A of FIG. 12 was observed. Although this output waveform includes a sinusoidal periodic fluctuation, it can be seen that its vibration level is significantly reduced with respect to the output waveform shown in FIG. 11A.

Further, the output waveform shown in FIG. 12B was observed in the vibration sensor 2 provided with the shield conductor layers 42-1 and 42-2 on the piezoelectric element 4 side and the output extraction unit 6 provided with the shield countermeasure. In B of FIG. 12, the vertical axis represents the vibration level and the horizontal axis represents the time t. In this output waveform, no sinusoidal periodic fluctuation is observed, and it can be seen that there is no power supply induction noise.
When the 1-scale range on the vertical axis of this output waveform was changed from, for example, 1 [V] to 20 [mv], a vibration component signal peculiar to the motor was observed as shown in A of FIG.
When FFT was performed on this output waveform, the frequency component shown in B in FIG. 13 was observed. In this frequency analysis output, vibration frequencies of commercial AC frequency f0 = 60 [Hz], motor-specific frequencies f1 = 30 [Hz], and f1 = 125 [Hz] were confirmed.

As is clear from this embodiment, the shield measures described above in the output extraction unit 6 can reduce the power supply induction noise, and the natural vibration generated by the vibration source 32 such as the motor is affected by the power supply induction noise by the vibration sensor 2. It was confirmed that it was detected with high accuracy without receiving it.

[Other Embodiments]
A noise canceling means for canceling the noise transmitted to the connecting conductor may be provided.

As described above, the most preferable embodiments of the vibration sensor and the vibration detection system have been described. The present invention is not limited to the above description. Various modifications and modifications can be made by those skilled in the art based on the gist of the invention described in the claims or disclosed in the form for carrying out the invention. Needless to say, such modifications and modifications are included in the scope of the present invention.

In the present invention, the output extraction part of the vibration sensor that detects vibration from the vibration source or the piezoelectric element is shielded, the influence of power supply induction noise can be removed from the piezoelectric output that represents vibration, and the output with high detection accuracy is extracted. It is possible to detect abnormal vibration of a vibration source such as a motor that uses an AC power source as a drive source.

2 Vibration sensor 4 Piezoelectric element 6 Output take-out part 8 Piezoelectric sheet 10-1 Signal pole 10-2 Grounding pole 12, 12-1, 12-2 Connecting conductor 14 Connector 14-1, 14-2 Output terminal 16, 16-1 , 16-11, 16-12, 16-2, 16-21, 16-22 Shield conductor 18 Insulation layer 20 Laminated body 22 Insulation layer 24-1, 24-2 Shield conductor layer 26 Insulation layer 28 Shield case 30 Vibration detection System 32 Vibration source 33 Measuring equipment 34, 34-1, 34-2 Coaxial cable 36 Conductor 38 Insulation layer 40 Shield conductor 42 Shield cover 42-1, 42-2 Shield conductor layer 44 Insulation layer 46-1, 46-2 Surface Protective layer 48-1, 48-2 Magnet sheet

Claims (10)

A vibration sensor that detects vibration from a vibration source.
Piezoelectric elements including signal poles and ground poles,
An output take-out unit that includes a first conductor connected to the signal electrode and a second conductor connected to the ground electrode and takes out the piezoelectric output generated in the piezoelectric element.
With
Wherein the first conductor second conductors, vibration sensor, characterized in that its periphery is covered separately by shield conductor directing pre Symbol piezoelectric output. The vibration sensor according to claim 1, wherein the output extraction unit is connected to the piezoelectric element or integrally configured with the piezoelectric element. The vibration sensor according to claim 1 or 2, wherein the shield conductor is connected to a reference potential. The piezoelectric element is characterized by including a laminate including the signal electrode and the ground electrode provided with the piezoelectric body interposed therebetween, and a shield conductor layer provided on the outside of each of the signal electrode and the ground electrode. The vibration sensor according to claim 1 to 3. The vibration sensor according to claim 1, 3, or 4 , wherein the shield conductor is connected to the shield conductor layer on the piezoelectric element side and maintained at a reference potential. A vibration sensor that detects vibration from a vibration source.
A piezoelectric element having a shield conductor layer in a laminate containing a piezoelectric material,
An output take-out unit that takes out the piezoelectric output generated in the piezoelectric element,
With
The output extraction unit includes a conductor that guides the piezoelectric output, a shield conductor that covers the conductor, and the like.
Comprising a, in that the said conductor electrode and the output extracting portions of the piezoelectric element is formed of a single conductive layer, and the shield conductor layer and the shield conductor of the output extraction portion side is formed by a single conductor vibration sensors that characterized. Further, any one of claims 1 to 3 and 5, wherein a shield member covering the piezoelectric element is provided, and the shield member is connected to the shield conductor of the output extraction unit. The vibration sensor described in the section. The vibration sensor according to any one of claims 1 to 7, wherein the output extraction unit is a coaxial cable including the conductor and the shield conductor. The vibration sensor according to any one of claims 1 to 8, further comprising a holding member that detachably adheres or attracts and holds the piezoelectric element to the vibration source. A vibration source installed in an AC power supply environment or using the AC power supply as a drive source,
The vibration sensor according to any one of claims 1 to 9, which detects the vibration of the vibration source, and the vibration sensor.
A measuring means for measuring the piezoelectric output output from the output extraction unit of the vibration sensor, and
A vibration detection system characterized by being equipped with.

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