JP3129116B2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor,
In particular, it relates to a cantilever-type acceleration sensor including a vibrator that vibrates in the length direction and has two or more node portions.

[0002]

2. Description of the Related Art FIG. 4 is a perspective view showing an example of a conventional acceleration sensor, and FIG. 5 is a side view thereof. The acceleration sensor 1 includes a vibrator 2 that vibrates in a length direction. The vibrator 2 includes, for example, a strip-shaped vibrator 3. The two main surfaces of the portion on the one end side from the center in the longitudinal direction of the vibrating body 3
The two piezoelectric elements 4a and 4b are formed so as to face each other. Similarly, two piezoelectric elements 4c and 4d are also provided on both main surfaces of a portion from the center to the other end in the longitudinal direction of the vibrating body 3.
Are formed to face each other. These piezoelectric elements 4a to
Reference numerals 4d each include a piezoelectric layer, and electrodes are respectively formed on both main surfaces of the piezoelectric layer. Then, the electrode on one main surface of the piezoelectric layer is bonded to the main surface of the vibrator. The piezoelectric layers of the piezoelectric elements 4a and 4b are respectively
It is polarized in the thickness direction from the outside to the vibrating body 3 side. Conversely, the piezoelectric layers of the piezoelectric elements 4c and 4d respectively
Polarized in the thickness direction outward from the vibrating body 3 side.

At one end of the vibrator 2 in the longitudinal direction,
Two support members 5 are formed. In this case, the two support members 5 extend in the width direction from the node portion and the end on one end side in the longitudinal direction of the vibrating body 3 and are formed integrally with the vibrating body 3. These support members 5 support one end of the vibrator 2.

[0004] At the other end in the longitudinal direction of the vibrator 2, a mounting member 7 is formed via a thin connecting member 6. In this case, the connecting member 6 and the mounting member 7 extend from the end on the other end side in the longitudinal direction of the vibrating body 3 and
And formed integrally with it. The weights 8 are attached to both main surfaces of the attachment member 7 by welding or soldering. The weight 8 is for increasing the deflection of the vibrator 2 due to acceleration.

In this acceleration sensor 1, the supporting member 5 is fixed to support one end of the vibrator 2, and when the driving signals of the same phase are applied to the four piezoelectric elements 4 a to 4 b, the vibrating body 2 becomes Vibrates in the longitudinal direction. in this case,
Since the piezoelectric elements 4a and 4b and the piezoelectric elements 4c and 4d are polarized in directions opposite to each other, they are displaced in directions opposite to each other. Therefore, when the portion on one end side from the center in the longitudinal direction of the vibrating body 3 extends, the portion on the other end side from the center in the longitudinal direction of the vibrating body 3 contracts. Conversely, when the portion on the one end side from the center in the longitudinal direction of the vibrating body 3 contracts, the portion on the other end side from the center in the longitudinal direction of the vibrating body 3 extends. Further, in this case, the amount of expansion and contraction of the portion from the center to the one end side in the longitudinal direction of the vibrating body 3 is offset from the amount of expansion and contraction of the portion from the center to the other end side in the longitudinal direction of the vibrating body 3. The distance between both ends in the longitudinal direction hardly changes. Further, in this case, the vibrating body 3
Is a central part between the piezoelectric elements 4a and 4b and the piezoelectric element 4
The center part between c and 4d vibrates as a node part. The vibrating body 3 vibrates with both ends in the longitudinal direction as antinodes.

When an acceleration is applied to the vibrating body 3 of the vibrator 2 in a direction orthogonal to the main surface, the vibrating body 3 bends together with the piezoelectric elements 4a to 4d according to the acceleration, and a voltage corresponding to the bending is generated. It occurs in the piezoelectric elements 4a to 4d. Therefore, the acceleration can be detected by measuring any of the voltages generated in the piezoelectric elements 4a to 4d.

[0007]

In the acceleration sensor 1, the connecting portion 6 between the vibrator 2 and the weight 8 is formed thin so that the vibration of the vibrator 2 is hardly hindered by the weight 8. The vibration of the child 2 is hardly transmitted to the weight 8 by being absorbed by the connecting portion 6.

However, if the connecting portion 6 is formed to be thin, the strength of the vibrator 2 supporting the weight 8 is weakened, and when acceleration is applied to the acceleration sensor 1, the displacement of the weight 8 due to the acceleration is reduced. 2, and the sensitivity of detecting acceleration is deteriorated.

[0009] Therefore, a main object of the present invention is to provide an acceleration sensor in which the vibration of the vibrator is hardly hindered by the weight and the strength of supporting the weight by the vibrator is high.

[0010]

SUMMARY OF THE INVENTION The present invention relates to an acceleration sensor having a cantilever structure including a vibrator vibrating in a longitudinal direction and having two or more node portions, wherein a weight is placed near a node portion of the vibrator. Is an acceleration sensor to which is attached.

The vibrator of the acceleration sensor according to the present invention includes, for example, a plate-shaped vibrator and piezoelectric elements formed on both main surfaces of the vibrator. Further, the acceleration sensor according to the present invention has, for example, a support member formed near the other node portion of the vibrator to support the vibrator.

[0012]

[Function] Since the weight is attached near the node part of the vibrator, even if the strength of supporting the weight with the vibrator is increased, the vibration of the vibrator is hardly transmitted to the weight and is hardly hindered by the weight. .

[0013]

According to the present invention, it is possible to obtain an acceleration sensor in which the vibration of the vibrator is hardly hindered by the weight and the strength of supporting the weight by the vibrator is high. Therefore, in the acceleration sensor according to the present invention, the displacement of the weight due to the acceleration can be easily transmitted to the vibrator, and the sensitivity of detecting the acceleration can be improved.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0015]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a side view thereof. This acceleration sensor 10
Includes a vibrator 12 that vibrates in the length direction.

The vibrator 12 is, for example, a strip-shaped vibrator 1.
4 inclusive. The vibrating body 14 is made of, for example, a constant elastic metal material such as nickel, iron, chromium, titanium, or an alloy thereof such as elinvar or an iron-nickel alloy. Note that the vibrating body 14 may be formed of a material other than a metal that generally generates mechanical vibration, such as quartz, glass, quartz, or ceramic.

Two piezoelectric elements 16a and 16b are formed on both main surfaces of a portion of the vibrating body 14 at one end from the center in the longitudinal direction so as to face each other. One piezoelectric element 1
6a includes a piezoelectric layer 18a made of, for example, ceramic, and electrodes 20a and 22a are formed on both main surfaces of the piezoelectric layer 18a, respectively. And the electrode 20a is
One main surface of the vibrating body 14 is adhered with, for example, an adhesive. Similarly, the other piezoelectric element 16b includes a piezoelectric layer 18b made of, for example, ceramic, and electrodes 20b and 22b are formed on both main surfaces of the piezoelectric layer 18b, respectively. Then, the electrode 20b is bonded to the other main surface of the vibrating body 14 with, for example, an adhesive. Also, the piezoelectric layers 18a and 18b of these piezoelectric elements 16a and 16b
Are connected to the electrodes 20a and 20b from the electrodes 22a and 22b.
b, that is, polarized in the thickness direction from the outside toward the vibrating body 14.

Further, two piezoelectric elements 16 are provided on both main surfaces of a portion from the center to the other end of the vibrating body 14 in the longitudinal direction.
c and 16d are formed to face each other. One of the piezoelectric elements 16c includes a piezoelectric layer 18c made of, for example, ceramic, and electrodes 20 are provided on both main surfaces of the piezoelectric layer 18c.
c and 22c are formed respectively. And electrode 2
Oc is bonded to one main surface of vibrating body 14 with, for example, an adhesive. Similarly, the other piezoelectric element 16d includes a piezoelectric layer 18d made of, for example, a ceramic.
Electrodes 20d and 22d are formed on both main surfaces of 8d, respectively. Then, the electrode 20d is bonded to the other main surface of the vibrating body 14 with, for example, an adhesive. Also, the piezoelectric layers 18c and 1c of these piezoelectric elements 16c and 16d are formed.
8d is polarized in the thickness direction from the electrodes 20c and 20d toward the electrodes 22c and 22d, that is, from the vibrating body 14 side to the outside.

The vibrator 12 includes piezoelectric elements 16a to 16a
When a drive signal of the same phase is applied to d, the vibration occurs in the length direction. In this case, since the piezoelectric elements 16a and 16b and the piezoelectric elements 16c and 16d are polarized in opposite directions, they are displaced in opposite directions. Therefore, as shown by a solid line arrow in FIG. 2, when a portion on one end side extends from the center in the longitudinal direction of the vibrating body 14,
The portion on the other end side from the center in the longitudinal direction is shrunk. Conversely, as shown by the one-dot chain line arrow in FIG. 2, when the portion on the one end side from the center in the longitudinal direction of the vibrating body 14 contracts, the portion on the other end side from the center in the longitudinal direction of the vibrating body 14 extends. Further, in this case, the amount of expansion and contraction of the portion from the center to the one end in the longitudinal direction of the vibrating body 14 and the amount of expansion and contraction of the portion from the center to the other end in the longitudinal direction of the vibrating body 14 cancel each other. The distance between both ends in the longitudinal direction hardly changes. Further, in this case, the vibrating body 14 vibrates with the central part between the piezoelectric elements 16a and 16b and the central part between the piezoelectric elements 16c and 16d as node parts. The vibrating body 14 vibrates with both ends in the longitudinal direction as antinodes.

Two support members 24 are formed at one end of the vibrator 12 in the longitudinal direction. In this case, 2
The two support members 24 extend in the width direction from a node portion and an end on one end side in the longitudinal direction of the vibrating body 14 and are formed integrally with the vibrating body 14. These support members 24
This is for supporting a portion on one end side of the vibrator 12.

Further, at the other end of the vibrator 12 in the longitudinal direction, for example, two projecting piece-shaped mounting members 26 are formed. In this case, the mounting member 26 extends in the width direction from a node portion on the other end side in the longitudinal direction of the vibrating body 14 and is formed integrally with the vibrating body 14. Then, weights 28 are respectively attached to both main surfaces of these attachment members 26 by welding or soldering. These weights 28 are for increasing the deflection of the vibrating body 14 due to acceleration.

In this acceleration sensor 10, one end of the vibrator 12 is supported by fixing two support members 24, and a driving signal having the same phase is applied to the four piezoelectric elements 16a to 16d. Numeral 12 vibrates in the length direction as indicated by the solid line arrow and the dashed line arrow in FIG.

When acceleration is applied to the vibrating body 14 of the vibrator 12 in a direction perpendicular to the main surface, the vibrating body 14 bends together with the piezoelectric elements 16a to 16d in accordance with the acceleration, and a voltage corresponding to the bending is generated. It occurs in the piezoelectric elements 16a to 16d. Therefore, the acceleration can be detected by measuring any of the voltages generated in the piezoelectric elements 16a to 16d.

Further, in the acceleration sensor 10, since the weight 28 is mounted on the mounting member 26 near the node portion of the vibrator 12, even if the strength of supporting the weight 28 by the vibrator 12 is increased, the vibration The vibration of the child 12 is hardly transmitted to the weight 28 and is hardly hindered by the weight 28. Therefore, in the acceleration sensor 10, the weight 28
Can be easily transmitted to the vibrator 12, and the sensitivity for detecting acceleration can be improved.

FIG. 3 is a perspective view showing another embodiment of the present invention. In the embodiment shown in FIG. 3, the attachment member 26 is formed in a rod shape, and a weight 28 is attached around the tip of the attachment member 26, as compared with the embodiment shown in FIGS.

In the embodiment shown in FIG. 3, as in the embodiment shown in FIGS. 1 and 2, the weight 28 is mounted on the mounting member 26 near the node portion of the vibrator 12, so that the vibrator 12 Even if the strength for supporting the weight 28 is increased, the vibration of the vibrator 12 is hardly transmitted to the weight 28 and the weight 28
It is hard to be disturbed. Therefore, even in the acceleration sensor 10 shown in FIG. 3, the displacement of the weight 28 due to the acceleration can be easily transmitted to the vibrator 12, and the sensitivity of detecting the acceleration can be improved.

In each of the above embodiments, the vibrator has two node portions, a weight is attached near one node portion, and the vicinity of the other node portion is supported by a support member. According to the present invention, the vibrator may have three or more node portions, a weight may be attached near one of the node portions, and the vicinity of the other node portion may be supported by the support member.

In each of the above embodiments, the piezoelectric element 16
The acceleration can also be detected by detecting the difference between the voltages generated at a and 16b and the difference between the voltages generated at the piezoelectric elements 16c and 16d.

Further, in each of the above embodiments, the polarization directions of the piezoelectric layers of the one or more piezoelectric elements are reversed.
The phase of the drive signal applied to the piezoelectric element whose polarization direction is reversed may be reversed.

In each of the above-described embodiments, the reason that the vibrator is vibrated in the length direction is that the vibrator is vibrated in the length direction when the acceleration is applied to the vibrator. Is greatly bent, and the sensitivity for detecting the acceleration is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a side view of the embodiment shown in FIG.

FIG. 3 is a perspective view showing another embodiment of the present invention.

FIG. 4 is a perspective view showing an example of a conventional acceleration sensor.

FIG. 5 is a side view of the acceleration sensor shown in FIG.

[Explanation of symbols]

 Reference Signs List 10 acceleration sensor 12 vibrator 14 vibrator 16a to 16d piezoelectric element 18a to 18d piezoelectric layer 20a to 20d, 22a to 22d electrode 24 support member 26 mounting member 28 weight

Claims (3)

(57) [Claims] An acceleration sensor having a cantilever structure including a vibrator having two or more node portions vibrating in a longitudinal direction, wherein a weight is attached near a node portion of the vibrator. . 2. The acceleration sensor according to claim 1, wherein the vibrator includes a plate-shaped vibrator and piezoelectric elements formed on both main surfaces of the vibrator. 3. The acceleration sensor according to claim 1, further comprising a support member formed near another node portion of the vibrator and supporting the vibrator.