JP2022152811A - vibration sensor - Google Patents

Abstract

To provide a vibration sensor capable of detecting the vibration of a vehicle requiring no power supply and easy to miniaturize.SOLUTION: The vibration sensor is a sensor for detecting the vibration of a vehicle including a base plate and a piezoelectric cable at least one end of which is fixed to the base plate, and to which the vehicle vibration is transmitted through the base plate. The piezoelectric cable includes: an inner conductor; a piezoelectric material covering the outer circumference of the inner conductor; and an outer conductor covering the outer circumference of the piezoelectric body. The vibration sensor is configured to output a voltage that is generated between the inner conductor and the outer conductor in response to vehicle vibration transmitted to the piezoelectric cable.SELECTED DRAWING: Figure 1

Description

The present invention relates to vibration sensors.

As a technique for measuring and observing vibrations of an object, for example, Patent Document 1 discloses a technique for measuring vibrations using an acceleration sensor. Further, Patent Literature 2 discloses a technique for measuring vibration without contacting a measurement target using sound pressure from a microphone.

JP 2014-209059 A JP 2017-198525 A

A vibration sensor using an acceleration sensor requires a power supply and is not suitable for miniaturization. In addition, non-contact vibration sensors using lasers, sound waves, etc. are suitable for buildings such as bridges, that is, for non-moving objects. However, there is a problem that the device itself is vulnerable to vibration.

An object of one embodiment of the present invention is to provide a vibration sensor for detecting vibration of a vehicle that does not require a power supply and can be easily miniaturized.

A first aspect of the present invention is
A vibration sensor for detecting vibration of a vehicle,
a substrate;
a piezoelectric cable having at least one end fixed to the substrate and transmitting vibration of the vehicle through the substrate;
The piezoelectric cable has an inner conductor, a piezoelectric body covering the outer circumference of the inner conductor, and an outer conductor covering the outer circumference of the piezoelectric body,
A vibration sensor that outputs a voltage generated between the inner conductor and the outer conductor in response to vibration of the vehicle that is transmitted to the piezoelectric cable.

A second aspect of the present invention is
Having a plurality of the piezoelectric cables,
The vibration sensor according to the first aspect, wherein at least one pair of the plurality of piezoelectric cables are parallel and have the same length.

A third aspect of the present invention is
Having a plurality of the piezoelectric cables,
The vibration sensor according to the first aspect, wherein at least one pair of the plurality of piezoelectric cables are parallel and have different lengths.

A fourth aspect of the present invention is
Having a plurality of the piezoelectric cables,
The vibration sensor according to the first aspect, wherein at least one pair of the plurality of piezoelectric cables are non-parallel.

A fifth aspect of the present invention is
Having a plurality of the piezoelectric cables,
The vibration sensor according to the first aspect, wherein at least one pair of the plurality of piezoelectric cables are twisted together.

According to one embodiment of the present invention, it is possible to realize a vibration sensor that does not require a power supply and can be easily miniaturized to detect vehicle vibration.

FIG. 1 is a perspective view showing an example configuration of a vibration sensor 10 according to the first embodiment. FIG. 2 is a longitudinal sectional view of the piezoelectric cable 40 according to the first embodiment. FIG. 3 is a perspective view showing an example of the configuration of the vibration sensor 10 according to Modification 1 of the first embodiment. FIG. 4 is a perspective view showing an example of the configuration of the vibration sensor 10 according to Modification 2 of the first embodiment. FIG. 5 is a perspective view showing an example of the configuration of the vibration sensor 10 according to Modification 3 of the first embodiment. FIG. 6 is a perspective view showing an example of the configuration of the vibration sensor 10 according to Modification 4 of the first embodiment.

One embodiment of the present invention will be described below with reference to the drawings. The present invention is not limited to these exemplifications, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

<First embodiment of the present invention>
(1) Configuration of Vibration Sensor 10 First, the configuration of the vibration sensor 10 of this embodiment will be described.

FIG. 1 is a perspective view showing an example of the configuration of the vibration sensor 10. As shown in FIG. As shown in FIG. 1, the vibration sensor 10 has, for example, a housing 20, a substrate 30, a piezoelectric cable 40, and a cable displacement limiter 50. As shown in FIG. The vibration sensor 10 is configured, for example, to detect vibrations of the vehicle, particularly abnormal vibrations of the vehicle. In this specification, the abnormal vibration of a vehicle means, for example, vibration that differs in magnitude, vibration frequency, vibration direction, etc., from vibration when the vehicle is operating normally. In FIG. 1, the x direction is the direction in which the vehicle travels, the y direction is the wheel rotation axis direction, and the z direction is the vertical direction.

The housing 20 is, for example, a molding made of resin or metal, and is configured to accommodate the substrate 30 and the like. The housing 20 is provided with a flange 21 that allows the vibration sensor 10 to be attached to a predetermined position on the vehicle. Specifically, the vibration sensor 10 is preferably installed at a position below the suspension of the vehicle (so-called unsprung position). This is because parts to be mounted under the springs of a vehicle are particularly required to be compact, lightweight, and do not require a power source. In addition, since there are many rotating parts such as tires and hubs under the springs of a vehicle, the vibration sensor 10 having a wide detectable vibration frequency band can be particularly preferably used.

The board 30 is, for example, a resin circuit board provided in the housing 20 and having a predetermined circuit pattern printed thereon. The substrate 30 is arranged, for example, so that its main surface is parallel to the xy plane. A piezoelectric cable 40 is arranged on the substrate 30 . A sensor other than the vibration sensor 10 (for example, an anti-lock braking system (ABS) sensor), an IC chip, or the like may be mounted on the substrate 30 .

FIG. 2 is a longitudinal sectional view of the piezoelectric cable 40. As shown in FIG. As shown in FIG. 2, the piezoelectric cable 40 includes, for example, an inner conductor 41, a piezoelectric body 42 that covers the outer circumference of the inner conductor 41, an outer conductor 43 that covers the outer circumference of the piezoelectric body 42, and an outer conductor 43 that covers the outer circumference. a coaxial cable having an insulator 44; Piezoelectric cable 40 is configured to generate a voltage between inner conductor 41 and outer conductor 43 when stress is applied to piezoelectric body 42 . As the piezoelectric cable 40, for example, a known cable disclosed in Japanese Unexamined Patent Application Publication No. 2005-351664 can be used.

At least one end of the piezoelectric cable 40 is fixed to the substrate 30 by soldering, for example. Therefore, vehicle vibrations are transmitted to the piezoelectric cable 40 via the substrate 30 . When the vibration of the vehicle is transmitted to the piezoelectric cable 40 , stress is applied to the piezoelectric body 42 , so that a voltage corresponding to the vibration is generated between the inner conductor 41 and the outer conductor 43 . A voltage generated between the inner conductor 41 and the outer conductor 43 is transmitted through the substrate 30 to a relay cable (not shown) and output. Thus, the vibration sensor 10 of this embodiment is configured to output the voltage generated between the inner conductor 41 and the outer conductor 43 according to the vehicle vibration transmitted to the piezoelectric cable 40 .

The piezoelectric cable 40 is preferably fixed to the substrate 30 at the end closer to the flange 21 (that is, the connection with the vehicle). In this case, the end closer to the connecting portion with the vehicle is the fixed end, and the end farther from the connecting portion with the vehicle is the free end. As a result, the vibration of the vehicle can be easily transmitted to the piezoelectric cable 40, and the sensitivity of the vibration sensor 10 can be improved.

The piezoelectric cable 40 is preferably stripped in steps (three-step stripping) in the vicinity of the end (fixed end) on the side fixed to the substrate 30 . More specifically, the coating near the fixed end is step-stripped so that the exposed portion of the internal conductor 41 and the exposed portion of the external conductor 43 are in contact with the substrate 30 respectively. is preferred. This makes it easier to electrically connect the inner conductor 41 and the outer conductor 43 to the substrate 30 . In addition, since the center of gravity is shifted toward the end (free end) on the side not fixed to the substrate 30, the piezoelectric cable 40 can be easily vibrated. As a result, the sensitivity of the vibration sensor 10 can be improved.

The length of the piezoelectric cable 40 is preferably 5 mm or more and 20 mm or less, for example. If the length of the piezoelectric cable 40 is less than 5 mm, the piezoelectric cable 40 will be difficult to vibrate, and the sensitivity of the vibration sensor 10 may decrease. On the other hand, the sensitivity of the vibration sensor 10 can be improved by setting the length of the piezoelectric cable 40 to 5 mm or more. On the other hand, if the length of the piezoelectric cable 40 exceeds 20 mm, miniaturization of the vibration sensor 10 may be hindered. On the other hand, by setting the length of the piezoelectric cable 40 to 20 mm or less, the size of the vibration sensor 10 can be easily reduced. Although the diameter of the piezoelectric cable 40 is not particularly limited, it is, for example, 0.3 mm or more and 1 mm or less.

Moreover, since the natural frequency of the piezoelectric cable 40 changes by changing the length of the piezoelectric cable 40, the vibration frequency band detectable by the vibration sensor 10 can be adjusted. Therefore, the vibration sensor 10 of the present embodiment can easily handle various vibration frequencies, and can be suitably used, for example, for detecting abnormal vibration of a vehicle.

In FIG. 1, the piezoelectric cable 40 is arranged so that the arrangement direction (longitudinal direction of the piezoelectric cable 40 when arranged on the substrate 30) is the y direction. In this case, since the piezoelectric cable 40 is likely to vibrate in the x-direction and z-direction, the vibration in the x-direction and z-direction can be detected with high accuracy. Note that the piezoelectric cable 40 may be arranged in a direction other than the y direction. By changing the arrangement direction of the piezoelectric cable 40, the direction in which the piezoelectric cable 40 is likely to vibrate can be changed. Therefore, the vibration sensor 10 of the present embodiment can easily cope with vibrations in various directions, and can be suitably used, for example, for detecting abnormal vibrations of a vehicle.

The cable displacement limiting part 50 is, for example, a molded body made of resin provided inside the housing 20 and has a groove formed along the arrangement direction of the piezoelectric cable 40 . The cable displacement limiter 50 is configured to limit displacement of the piezoelectric cable 40 within a predetermined range. When the vibration of the vehicle is transmitted to the piezoelectric cable 40 and the piezoelectric cable 40 is largely displaced, a load may be applied to the fixed portion between the piezoelectric cable 40 and the substrate 30 . Since the groove is formed along the arrangement direction of the piezoelectric cable 40, the displacement of the piezoelectric cable 40 is physically limited within a predetermined range. can be reduced. The direction of displacement limited by the cable displacement limiter 50 is not particularly limited. Also, the cable displacement limiter 50 can be omitted.

Vibration of the vehicle can be detected by using the vibration sensor 10 having the configuration described above. Since the vibration sensor 10 of this embodiment does not require a power supply, it can detect vehicle vibrations at low cost. Moreover, since the piezoelectric cable 40 is short (for example, 5 mm or more and 20 mm or less), miniaturization is easy.

(2) Modifications of First Embodiment The above-described embodiment can be modified as in the following modifications, if necessary. Hereinafter, only elements different from the above-described embodiment will be described, and elements that are substantially the same as those described in the above-described embodiment will be given the same reference numerals, and descriptions thereof will be omitted.

(Modification 1)
FIG. 3 is a perspective view showing an example of the configuration of the vibration sensor 10 of this modified example. As shown in FIG. 3 , the vibration sensor 10 of this modified example has a plurality of piezoelectric cables 40 . FIG. 3 shows the case where the vibration sensor 10 has two piezoelectric cables 40, but the number of the piezoelectric cables 40 is not particularly limited. good too. Note that FIG. 3 shows a case where the cable displacement limiter 50 is omitted.

In this modification, as shown in FIG. 3, the plurality of piezoelectric cables 40 are arranged in parallel and have the same length. In this case, since the vibration of the vehicle is transmitted to the plurality of piezoelectric cables 40 in the same manner, the voltage generated between the inner conductor 41 and the outer conductor 43 of the plurality of piezoelectric cables 40 is separately output to achieve redundancy. can ensure the integrity of the In this specification, the phrase "the plurality of piezoelectric cables 40 have the same length" includes not only completely the same length but also a case with an error of about ±0.1 mm. Further, it is not always necessary that all of the plurality of piezoelectric cables 40 of the vibration sensor 10 are arranged in parallel and have the same length. They should be parallel and of equal length.

(Modification 2)
FIG. 4 is a perspective view showing an example of the configuration of the vibration sensor 10 of this modified example. As shown in FIG. 4, the vibration sensor 10 of this modified example has a plurality of piezoelectric cables 40 as in the first modified example. FIG. 4 shows the case where the vibration sensor 10 has two piezoelectric cables 40, but the number of the piezoelectric cables 40 is not particularly limited. good too. Note that FIG. 4 shows a case where the cable displacement limiter 50 is omitted.

In this modification, as shown in FIG. 4, the plurality of piezoelectric cables 40 are arranged in parallel and have different lengths. As described above, by changing the length of the piezoelectric cable 40, the vibration frequency band detectable by the vibration sensor 10 can be adjusted. Therefore, the vibration sensor 10 of this modified example can widen the detectable vibration frequency band. It should be noted that it is not always necessary that all of the plurality of piezoelectric cables 40 of the vibration sensor 10 are arranged in parallel and have different lengths. and have different lengths.

(Modification 3)
FIG. 5 is a perspective view showing an example of the configuration of the vibration sensor 10 of this modified example. As shown in FIG. 5, the vibration sensor 10 of this modified example has a plurality of piezoelectric cables 40, like the first and second modified examples described above. FIG. 5 shows the case where the vibration sensor 10 has two piezoelectric cables 40, but the number of the piezoelectric cables 40 is not particularly limited. good too. Note that FIG. 5 shows a case where the cable displacement limiter 50 is omitted.

In this modification, as shown in FIG. 5, the plurality of piezoelectric cables 40 are arranged in non-parallel (preferably orthogonal) directions. As described above, by changing the arrangement direction of the piezoelectric cable 40, the direction in which the piezoelectric cable 40 is likely to vibrate can be changed. Therefore, the vibration sensor 10 of this modified example can simultaneously detect vibrations in various directions. It should be noted that it is not always necessary that all of the piezoelectric cables 40 of the vibration sensor 10 are arranged in non-parallel directions. good.

In this modification, the lengths of the plurality of piezoelectric cables 40 may be equal as in modification 1, or may be different as in modification 2. FIG.

(Modification 4)
FIG. 6 is a perspective view showing an example of the configuration of the vibration sensor 10 of this modified example. As shown in FIG. 6, in the vibration sensor 10 of this modified example, two piezoelectric cables 40 are twisted together (twisted pair). As a result, the influence of external noise can be reduced. The number of twisted piezoelectric cables 40 is not particularly limited as long as at least a pair of piezoelectric cables 40 are twisted together. Note that FIG. 6 shows a case in which the cable displacement limiter 50 is omitted.

In this modification, voltages generated between the inner conductors 41 and the outer conductors 43 of the two piezoelectric cables 40 may be output separately. In this case, redundancy can be ensured as in the first modification. Also, the voltages generated between the inner conductors 41 and the outer conductors 43 of the two piezoelectric cables 40 may be synthesized on the substrate 30 and output. In this case, compared with the case of using one piezoelectric cable 40, the voltage can be doubled and output. As a result, the sensitivity of the vibration sensor 10 can be improved. Moreover, the cost can be reduced as compared with the case where the voltages are output separately.

In this modification, as shown in FIG. 6, a weight 60 such as solder is provided at one end (free end) of the piezoelectric cable 40 . It is preferable that the weight 60 is provided at the far end from the flange 21 (that is, the connecting portion with the vehicle). Since the weight 60 is fixed to the free end of the piezoelectric cable 40 and not fixed to the substrate 30, the piezoelectric cable 40 vibrates more easily than when the weight 60 is not provided. As a result, the sensitivity of the vibration sensor 10 can be improved. Moreover, when a plurality of piezoelectric cables 40 are twisted together as in this modified example, the piezoelectric cables 40 are less likely to vibrate, so providing the weight 60 is particularly effective.

(3) Effects According to the Present Embodiment According to the present embodiment, one or more of the following effects can be obtained.

(a) Since the vibration sensor 10 according to the present embodiment does not require a power supply, it can detect vehicle vibrations at low cost. Moreover, since the piezoelectric cable 40 is short (for example, 5 mm or more and 20 mm or less), miniaturization is easy.

(b) In the vibration sensor 10 according to the present embodiment, changing the length of the piezoelectric cable 40 changes the natural frequency of the piezoelectric cable 40, so that the vibration frequency band detectable by the vibration sensor 10 is adjusted. can be done. Therefore, the vibration sensor 10 of the present embodiment can easily handle various vibration frequencies, and can be suitably used, for example, for detecting abnormal vibration of a vehicle.

(c) In the vibration sensor 10 according to the present embodiment, by changing the arrangement direction of the piezoelectric cable 40, the direction in which the piezoelectric cable 40 tends to vibrate can be changed. Therefore, the vibration sensor 10 of the present embodiment can easily cope with vibrations in various directions, and can be suitably used, for example, for detecting abnormal vibrations of a vehicle.

(d) The vibration sensor 10 according to Modification 1 of the present embodiment has a plurality of piezoelectric cables 40, and at least one pair of the plurality of piezoelectric cables 40 are parallel and equal in length. This makes it possible to ensure redundancy.

(e) The vibration sensor 10 according to Modification 2 of the present embodiment has a plurality of piezoelectric cables 40, and at least one pair of the plurality of piezoelectric cables 40 are parallel and have different lengths. This makes it possible to widen the detectable vibration frequency band.

(f) The vibration sensor 10 according to Modification 3 of the present embodiment has a plurality of piezoelectric cables 40, and at least one pair of the plurality of piezoelectric cables 40 are non-parallel. Thereby, vibrations in various directions can be detected simultaneously.

(g) The vibration sensor 10 according to Modification 4 of the present embodiment has a plurality of piezoelectric cables 40, and at least one pair of the plurality of piezoelectric cables 40 are twisted together. As a result, the influence of external noise can be reduced. Further, since the weight 60 is provided at one end of the piezoelectric cable 40, the piezoelectric cable 40 is easily vibrated. As a result, the sensitivity of the vibration sensor 10 can be improved.

<Other embodiments of the present invention>
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, in the above embodiment, one end of the piezoelectric cable 40 is fixed to the substrate 30 , but both ends of the piezoelectric cable 40 may be fixed to the substrate 30 . In this case, the vibration frequency band detectable by the vibration sensor 10 can be shifted to the high frequency side.

<Preferred embodiment of the present invention>
Preferred embodiments of the present invention are described below.

(Appendix 1)
According to one aspect of the invention,
A vibration sensor for detecting vibration of a vehicle,
a substrate;
a piezoelectric cable having at least one end fixed to the substrate and transmitting vibration of the vehicle through the substrate;
The piezoelectric cable has an inner conductor, a piezoelectric body covering the outer circumference of the inner conductor, and an outer conductor covering the outer circumference of the piezoelectric body,
A vibration sensor is provided that outputs a voltage developed between the inner conductor and the outer conductor in response to vibrations of the vehicle transmitted to the piezoelectric cable.
Preferably, the piezoelectric cable has a length of 5 mm or more and 20 mm or less.
Preferably, the piezoelectric cable is fixed to the substrate at an end portion closer to a connection portion with the vehicle.
Preferably, it further has a cable displacement limiter for limiting displacement of the piezoelectric cable within a predetermined range.

(Appendix 2)
The vibration sensor according to Appendix 1,
Having a plurality of the piezoelectric cables,
At least one pair of the plurality of piezoelectric cables are parallel and of equal length.

(Appendix 3)
The vibration sensor according to Appendix 1,
Having a plurality of the piezoelectric cables,
At least one pair of the plurality of piezoelectric cables are parallel and have different lengths.

(Appendix 4)
The vibration sensor according to Appendix 1,
Having a plurality of the piezoelectric cables,
At least one pair of the plurality of piezoelectric cables are non-parallel.

(Appendix 5)
The vibration sensor according to Appendix 1,
Having a plurality of the piezoelectric cables,
At least one pair of the plurality of piezoelectric cables are twisted together.

(Appendix 6)
The vibration sensor according to any one of appendices 1 to 5,
A weight is provided at one end of the piezoelectric cable.
Preferably, the weight is provided at the end farther from the connecting portion with the vehicle.

(Appendix 7)
The vibration sensor according to any one of appendices 1 to 5,
Both ends of the piezoelectric cable are fixed to the substrate.

(Appendix 8)
According to another aspect of the invention,
A vibration sensor for detecting vibration of a vehicle,
a substrate;
a piezoelectric cable having one end fixed to the substrate and transmitting vibration of the vehicle through the substrate;
The piezoelectric cable is arranged such that an end portion closer to the connection portion with the vehicle is a fixed end and an end portion farther from the connection portion with the vehicle is a free end,
The piezoelectric cable has an inner conductor, a piezoelectric body covering the outer circumference of the inner conductor, and an outer conductor covering the outer circumference of the piezoelectric body,
A vibration sensor is provided that outputs a voltage developed between the inner conductor and the outer conductor in response to vibrations of the vehicle transmitted to the piezoelectric cable.

10 Vibration sensor 20 Housing 21 Flange 30 Substrate 40 Piezoelectric cable 41 Inner conductor 42 Piezoelectric body 43 Outer conductor 44 Insulator 50 Cable displacement limiter 60 Weight

Claims (5)

A vibration sensor for detecting vibration of a vehicle,
a substrate;
a piezoelectric cable having at least one end fixed to the substrate and transmitting vibration of the vehicle through the substrate;
The piezoelectric cable has an inner conductor, a piezoelectric body covering the outer circumference of the inner conductor, and an outer conductor covering the outer circumference of the piezoelectric body,
A vibration sensor that outputs a voltage generated between the inner conductor and the outer conductor in response to vibration of the vehicle that is transmitted to the piezoelectric cable. Having a plurality of the piezoelectric cables,
2. The vibration sensor of claim 1, wherein at least one pair of the plurality of piezoelectric cables are parallel and of equal length. Having a plurality of the piezoelectric cables,
2. The vibration sensor of claim 1, wherein at least one pair of the plurality of piezoelectric cables are parallel and of different lengths. Having a plurality of the piezoelectric cables,
2. The vibration sensor of claim 1, wherein at least one pair of the plurality of piezoelectric cables are non-parallel. Having a plurality of the piezoelectric cables,
2. The vibration sensor of claim 1, wherein at least one pair of the plurality of piezoelectric cables are twisted together.

Images