JPH053983Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a piezoelectric acceleration pickup.
More specifically, the present invention relates to means for coupling and fixing piezoelectric elements of shear type acceleration pickups using annular piezoelectric elements.

[Conventional technology and problems]

In a piezoelectric shear type acceleration pick-up, when the base vibrates, a shear stress corresponding to the vibration is applied to the shear type piezoelectric element connected and fixed between the base and the mass body, and at this time, surface sliding occurs in the shear type piezoelectric element. It utilizes piezoelectric output caused by strain. Therefore, the means for connecting and fixing the shear type piezoelectric element is very important as it affects the performance of the acceleration pickup.

Below, the structure of a conventional acceleration pickup will be explained according to the drawings. In Fig. 2, numeral 1 is a ring-shaped shear type piezoelectric element, and after polarization treatment (the arrows indicate the polarization direction) electrodes are placed on the inner and outer circumferential surfaces, respectively. 2
A and 2B are provided.

In FIG. 3, reference numeral 3 denotes a disc-shaped base, and a cylindrical support part 8 protrudes from the center of the base 3.
The piezoelectric element 1 is fitted into the support part 8, and the inner peripheral surface of the piezoelectric element 1 is attached to the support part 8 using an epoxy adhesive.
is fixedly supported at an appropriate position. A cylindrical mass body 4 is fitted and fixed to the outer peripheral surface of the piezoelectric element 1 using an epoxy adhesive.
9A and 9B are the adhesive layers.

Next, to describe the action of the acceleration pick-up shown in Fig. 3, when the vibration is transmitted to the base 3 fixed to the object to be detected, the support part 8 also vibrates together, and the mass body 4 is the pendulum. In order to perform its function, a sliding stress acts on the piezoelectric element 1, and a piezoelectric output proportional to this stress and therefore to the acceleration is generated. This output is led to an external device via a conductor (not shown) and is used for vibration evaluation.

By the way, in the above-mentioned acceleration pickup, since adhesive is used as a means for connecting and fixing the piezoelectric element, the support part, and the mass body, the mechanical strength is insufficient and it is easy to break. Moreover, the adhesive layer softens at high temperatures, causing damage to each part. It cannot be used in high-temperature environments because the bond cannot be maintained. Generally speaking, the maximum operating temperature for a device with such a configuration is said to be 160°C. Furthermore, when used for many years, the adhesive layer peels off due to aging, resulting in a decrease in bonding strength. Furthermore, during assembly, it takes time for the adhesive to dry, and the bonding work requires skill.

[Purpose of invention]

The present invention aims to solve the above-mentioned problems and provide a means for mechanically coupling and fixing shear type piezoelectric elements without using adhesive.

[Means for solving problems]

In order to achieve the above object, the present invention provides a piezoelectric acceleration pickup comprising an annular shear type piezoelectric element, a protruding cylindrical support part at the center of the base, and a cylindrical mass body. A stepped portion is formed on the outer circumferential surface and the inner circumferential surface of the mass body, and the shear type piezoelectric element is held between the supporting portion and the mass body by abutting on the stepped portions of both, and the upper end of the supporting portion is A preload is applied to the mass body by a tightening nut connected to the part, thereby coupling and fixing the piezoelectric element, the support part, and the mass body.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a side sectional view showing an embodiment of the acceleration pickup according to the present invention. Note that the same reference numerals as in FIG. 2 indicate equivalent parts.

1 is an annular shear type piezoelectric element. 3 is a disc-shaped base with a cylindrical support part 8 in the center thereof.
This support portion 8 is composed of a large diameter portion 8A and a small diameter portion 8B, and a fine stepped portion 8C is formed at the boundary between the two. The diameter of the small diameter portion 8B is slightly smaller than the inner diameter of the piezoelectric element 1 to which it is fitted, and the piezoelectric element 1 is locked at the step portion 8C. Further, a threaded portion 8D is formed at the upper end portion of the small diameter portion 8B. Reference numeral 4 denotes a cylindrical mass body, the hole diameter of which is slightly larger than the outer diameter of the piezoelectric element 1, and a minute step 4A is formed on its inner circumferential surface, and this step 4A and the piezoelectric element 1 is in contact with the upper edge of the outer periphery. At this time, the mass body 4 is hooked to the piezoelectric element 1 at the step portion 4A. Reference numeral 5 denotes a tightening nut made of an elastic body, and a screw hole 5A is formed in the center thereof, and the outer end thereof serves as a pressing portion 5B for pressing the mass body 4 downward. Reference numeral 7 denotes an insulating plate interposed between the pressing portion 5B and the mass body 4 to electrically insulate them.

Describing the assembly procedure of the above-mentioned acceleration pickup, the small diameter portion 8B of the support portion 8 integrated with the base 3
The piezoelectric element 1 is fitted into the step portion 8C and brought into contact with the stepped portion 8C. Next, the mass body 4 is fitted on the outside of the piezoelectric element 1, and the stepped portion 4A inside the mass body 4 and the piezoelectric element 1 are brought into contact. After that, an insulating plate 7 is placed on the upper surface of the mass body 4, and the screw hole 5A of the tightening nut 5 is inserted.
is screwed onto the threaded portion 8D at the upper end of the small diameter portion, and after the edge 5B of the tightening nut 5 is brought into contact with the insulating plate 7, further screw tightening is performed. In this way, the elasticity of the tightening nut 5 applies preload to each member, thereby coupling and fixing each part. Note that this preload does not hinder the operation of the acceleration pickup in any way, and when measuring vibrations, the mass body 4 acts as a pendulum in accordance with the amount of vibration, similar to the conventional acceleration pickup.

As mentioned above, this embodiment is assembled without using adhesive, but the operation of this acceleration pickup is exactly the same as that shown in FIG.

[Effect of idea]

As described above, according to the present invention, in a piezoelectric acceleration pick-up, the use of adhesive is eliminated and a stepped portion is formed on the outer peripheral surface of the support portion and the inner surface of the mass body, and the step portion is formed between the support portion and the mass body. The shear type piezoelectric element is sandwiched between the step portions, and a preload is applied to the mass body by a tightening nut connected to the upper end of the support portion, so that the piezoelectric element, the support portion, and the mass body are connected to each other. This piezoelectric acceleration pick-up has excellent mechanical strength and can be used in high-temperature environments of, for example, 260°C, and its bonding strength will not deteriorate due to aging even after long-term use.Furthermore, it is easy to assemble. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a piezoelectric acceleration pickup according to an embodiment of the present invention, FIG. 2 is an external perspective view of a shear type piezoelectric element, and FIG. 3 is a side sectional view showing a conventional acceleration pickup. DESCRIPTION OF SYMBOLS 1...Piezoelectric element, 3...Base, 4...Mass body, 4A...Step part, 5...Tightening nut, 8...
...Support part, 8C...Step part.

Claims (1)

[Claims for Utility Model Registration] A piezoelectric acceleration pickup comprising an annular shear type piezoelectric element, a protruding cylindrical support portion at the center of the base, and a cylindrical mass body, comprising: an outer circumferential surface of the support portion; A stepped portion is formed on the circumferential surface of the mass body, and the shear type piezoelectric element is held between the supporting portion and the mass body by coming into contact with the stepped portions of both, and is coupled to an upper end portion of the supporting portion. A piezoelectric acceleration pickup characterized in that a preload is applied to the mass body by a tightening nut, and the piezoelectric element, the support portion, and the mass body are coupled and fixed.