JPS62180226A - Acceleration pickup - Google Patents

Abstract

PURPOSE:To simplify structure of the titled device and to reduce its cost by forming an envelope incorporating a vibration detection part therein of insulating material and further, forming a conductive layer to its inside and giving a proper shielding function to the device. CONSTITUTION:The vibration detection part 14 is stored in the envelope 16 for shielding. Then, the envelope 16 is formed of an insulator and the conductive layer 17 is formed to the inner surface of the envelope. Then, the conductive layer 17 is made the continuous conductive layer to envelope the detection part 14. The detection part 14 is constituted of a piezoelectric element 12 and a plumb 13 made of metallic material which is a mass body. Then, in a shear type pickup, the element 12 is made annular and the plumb 13 is made similarly annular and the element 12 is fitted and coupled on the inside peripheral surface of the plumb to make a complex and a column 15 erected on the base in the envelope 16 is pierced to the inside peripheral surface of the element 12 and fixed with a conductive adhesive, etc., and the detection part 14 is erected to the space of lumen of the envelope 16 with the column 15 as a carrier. In this way, the detection part 14 is insulated from the outside and the inflow of the electric noise, etc., is prevented and the vibration can be detected stably with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric, semiconductor, or electrodynamic acceleration pickup that extracts mechanical vibrations of an object to be measured as electrical output.

Conventional technology For example, a piezoelectric acceleration pick amplifier utilizes the mechanical-electrical conversion characteristics of a piezoelectric element such as a piezoelectric ceramic. Quantity (metal) 2
There are two types of acceleration pickups: shear type acceleration pickups that apply the gravity of a mass body in the shearing direction, and compression type acceleration pickups that apply the gravity of a mass body in the compression direction.

In both cases, in order to prevent electrical noise, the vibration detection unit 3 consisting of the piezoelectric element 1 and the mass body 2 is housed in a metal envelope 4, and is passed through the envelope 4 to the object to be measured 5. At the same time, one electrode of the piezoelectric element is connected to the core wire of the cable, and the other electrode is connected to the shield wire of the cable and grounded.

Furthermore, if the envelope 4 is attached so as to be in contact with the object to be measured, there is a risk that electrical noise may flow in from the object to be measured, resulting in a reduction in the signal-to-noise ratio during vibration measurement.

Therefore, it is necessary to electrically insulate the envelope 4 and the object to be measured 5. Conventionally, for example, in the case of a piezoelectric acceleration pickup, an insulating and mounting pedestal 6 as shown in FIG. 1 is separately prepared. do. This pedestal 6 has a composite structure consisting of a plate-shaped mounting seat 8 made of gold FA with a mounting screw 7 integrally machined on its lower surface, and a metal support seat lO with a mounting screw 9 integrally machined on its upper surface. An insulating layer 11 (a thin hardened layer of synthetic resin, which also functions as a bonding medium for both 8° and 10) is formed between the insulating and mounting pedestal 6 and the supporting seat IO. Vibration detection unit 3 with screw 9
It is configured to be attached to the bottom surface of a metal envelope 4 containing a built-in device, and to be attached to a fixed object 5 using a screw 7 of a mounting seat 8. It is conceivable that the entire pedestal 6 could be integrally molded from an insulating material such as a synthetic resin material, but fixing the acceleration pickup would require heavy screw tightening, and resin would not have sufficient strength to withstand this tightening. Therefore, the actual situation is that a composite structure of a pair of metal and resin is used as described above.

The problem to be solved by the invention is that the insulating mounting base 6 is mainly made of metal, and since the mounting base 8 and the support seat 10 are very close to each other, there is a risk of conduction due to moisture such as rainwater. However, depending on the usage conditions, accurate insulation cannot be expected.

In addition, it is not only necessary to prepare intervening parts such as the insulating mounting base 6 as a separate part in order to insulate the object to be measured 5, but also the metal cutting of the mounting seat 8 and the support seat 1O requires highly accurate processing technology. Similarly, high processing technology is required to form a thin and uniform insulating layer 11 in a small flat pedestal structure and to maintain the horizontal level of the support seat 10. Therefore, there is a drawback that the cost is very high. In addition, manufacturing the envelope requires precision cutting such as drilling, grinding, and surface treatment from a metal block, making the cost of the envelope extremely high.

Although the above-mentioned problems are different in structure, the same can be said for acceleration pickups that use electrodynamic semiconductors to extract mechanical vibrations as electrical output.

The present invention has a very simple structure that solves the above-mentioned problems in insulation performance and manufacturing technology, and also makes it possible to reduce costs and obtain an appropriate shielding effect for the vibration detection section. The purpose is to provide an acceleration pickup.

Means for Solving the Problems The present invention solves the above problems by forming an envelope in which the vibration detecting section is built in from an insulating material, particularly a ceramic such as steatite or aluminium-based ceramic, While achieving complete insulation from objects and external objects, a conductive layer is formed on the inner surface of the insulating material envelope by plating, baking, etc., and the conductive layer is used as a continuous conductive layer surrounding the vibration detection section to provide an appropriate shield. Also includes functions! The configuration is such that the

Embodiments of the Invention Below, embodiments of the present invention will be described in detail with reference to FIGS. 2 to 7, using a piezoelectric acceleration pickup as a representative example.

12 is a piezoelectric element such as piezoelectric ceramic, 13 is quality; I:2
The body is a weight made of a metal material, and together they constitute the vibration detection section 14. Reference numeral 16 denotes a shielding envelope that houses the vibration detection section 14.

In the cross-section type acceleration pickup (see the JSZ diagram), the piezoelectric element 12 is formed into a ring shape, a pair of electrodes 12a and 12b are formed on the inner and outer peripheral surfaces of the piezoelectric element 12, and the weight 13 is formed into a ring shape. The piezoelectric element 12 is mounted on the inner peripheral surface of the composite body to form a composite body, and the piezoelectric element 12 is
A pillar 15 erected on the inner bottom surface of the envelope is inserted through the inner peripheral surface of the housing and fixed with a conductive adhesive or the like, and the vibration detecting section 14 is inserted into the inner cavity of the envelope using the pillar 15 as a carrier.

As described above, the electrode L2a on the inner peripheral surface of the piezoelectric element 12 is connected to the metal support 15, and the electrode 12b on the outer peripheral surface is connected to the weight 13.

In addition, in the compression type acceleration pickup (see Fig. 7), the piezoelectric element 12 and the weight 13 are inserted into the support 15 set on the inner bottom of the envelope 14 and screwed into the support 15 with a nut. The piezoelectric element 12 is tightened so that the compressive load of the weight 13 is applied to the piezoelectric element 12.

In this case, the piezoelectric element 12d and the center poles 12a and 12b are formed on the mating surface of the piezoelectric element 12 and the weight 13, and the electrodes on the uppermost surface and the lowermost surface of the similar mating surface are i'l'[13
and the support column 15, and the electrodes on the overlapping surfaces of the piezoelectric elements 12 are in contact with each other.

Accordingly, in the present invention, the envelope 16 is formed of an insulating material. Ceramics, particularly aluminum oxide ceramics, steatite, etc. are suitable as the insulating material. In addition to ceramic, synthetic resin, glass, etc. can be used.

Steatite is 5i02. The main component is MgO, with a trace amount of Al201. It is made of a composite component containing 20, etc., and in addition to being extremely hard, it also has watertightness, heat resistance,
It is a suitable material with excellent chemical resistance, mechanical strength, and insulating properties.Also, like aluminum oxide ceramics, it can be easily formed into the cylindrical, cup, etc. shapes required for this product by press molding. Can be processed freely.

A conductive layer I7 is formed on the inner surface of the envelope 16 made of an insulating material.
form. The conductive layer 17 is a continuous conductive layer surrounding the vibration detecting section 14 . A band-shaped continuous conductive layer is proposed as the form of the continuous conductive layer 17.

As a suitable example, as shown in FIG. 4, an example is proposed in which substantially the entire inner peripheral surface of the envelope 16 is made of a conductive layer 17. The insulating material envelope 16 has a divided structure in order to accommodate the vibration detecting section 14 and to enable the formation of the conductive layer 17, and becomes a hollow body when closed. In order to facilitate the formation of the conductive layer 17 and the accommodation of the vibration detection unit 14, the envelope 16 is closed with an insulating material lid 16b in an insulating material bottomed cylinder 16a as shown in FIGS. 2 to 4. The structure is as follows. In this case, the conductive layers are formed on the joint surfaces of the bottomed cylindrical body 16a and the four bodies 16b, as shown in FIG. Make it.

Reference numeral 17a indicates an end portion of the conductive layer that matches the type. The cylindrical body 16a and the lid body 16b are joined together using a conductive adhesive, screws, or the like.

A mounting hole 18 is formed in the center of the inner bottom wall of the insulating material envelope 16, and a column 15 that supports the vibration detecting section 14 is provided upright in the mounting hole 18. As a suitable example, a female thread is formed in the attachment hole 18, a screw 19 is formed at the lower end of the metal support 15, and the support 15 is screwed into the attachment hole 18 and tightened. In this case post 15
A seating portion 2O is formed and pressed against the continuous conductive layer 17 to bring it into contact. As a result, one pole 12a of the piezoelectric element 12, the pillar 15, and the conductive layer 17 are brought into electrical continuity yp.

As described above, the envelope 16 is completely electrically insulated from the outside world such as rainwater, and has a shield structure with the continuous conductive layer 17 that is electrically conductive at the inner peripheral surface and surrounds the vibration detection section. is formed. The insulating material envelope 16 can be directly attached to the object 21 to be measured. As a means for attaching to the object to be measured 21, the drawing shows a case where a mounting hole 22 is provided in the envelope and is attached to the object to be measured 2 with a screw 23.The mounting hole 22 is, for example, as shown in FIG. Either a protruding portion 24 is formed at the bottom of the insulating envelope 16 using an integral material, or a mounting hole 2 is provided through which the joint surface of the lid 16b and the cylindrical body 16a passes through S' as shown in FIG.
2 is provided, and a screw 23 is attached to the object to be measured 21.

As described above, the insulating material envelope 16 is directly attached to the object to be measured 21 without using any inclusions harmful to vibration propagation.

As mentioned above, the envelope 16 is made of an insulating material and has a continuous conductive layer 17 on the inner surface.
When the coaxial cable 25 has a single core structure, the core wire 25a is connected to one electrode 12b of the piezoelectric element 12, and the shield wire 25c is connected to the continuous conductive layer 17, as shown in FIG. Connect to. The core wire 25a is connected to the electrode 12b via the weight 13.

If the coaxial cable 25 has two cores, as shown in FIG. The shield wire 25c is connected to the conductive layer 17 on the inner surface of the insulating material outer envelope 'Jj16. In this case, the conductive layer 17
5 (other parts are continuous), and are insulated from the pillar 15.

26 indicates a portion where the conductive layer is missing.

Although not shown, if the coaxial cable 25 has a single core and an internally shielded wire and an externally shielded wire, the connection of the core wire 25b shown in FIG. 6 is used as the internally shielded wire, and the shielded wire 25c
Consider replacing the connection with an external shield wire.

Although not shown, the vibration detection section 14 may be assembled on an insulating material base corresponding to the bottom wall of the envelope, and a cylindrical insulating material case may be fitted onto this to form the above-mentioned envelope 16.

Effect of shell according to the present invention, in an acceleration pickup that extracts mechanical vibration as electrical output, the insulating material envelope completely insulates the vibration detection part from the outside world, thereby preventing the inflow of electrically induced noise, etc. This enables highly accurate and stable vibration detection by reliably preventing vibrations. In addition, the envelope can be directly attached to the object to be measured, and even if it is directly attached, the disturbance caused by the electrical noise from the object to be measured can be effectively prevented, and in addition, intervening parts such as the insulating mounting base can be This eliminates the need for highly difficult pedestal processing. Therefore, by making the structure simple and inexpensive, it is expected that performance will be improved by removing inclusions.

Further, according to the present invention, while obtaining the above-mentioned good electrical insulation effect, an appropriate shielding effect can be exhibited by the continuous conductive layer formed on the inner surface of the insulating material, and there is an advantage that the form of the conductive layer can be freely changed.

Furthermore, according to the present invention, the required shape can be easily formed by press forming without incurring the processing time and cost required when drilling or shaping a metal lump, and the cost is also reduced. It will be cheaper.

[Brief explanation of drawings]

FIG. 1 is a sectional view illustrating a conventional piezoelectric acceleration pickup, FIG. 2 is a sectional view of a shear type acceleration pickup illustrating an embodiment of the present invention, FIG. 3 is a sectional view of the same envelope, and FIG.
Does the figure constitute the same envelope? , a partially cutaway view of the two bodies, Figures 5 and 6 are cross-sectional views illustrating the connection state of the coaxial cable and the acceleration pickup, and Figure 7 is a compressed acceleration diagram showing the other side. FIG. 3 is a cross-sectional view of the pickup. 12... Piezoelectric element, 12a, 12b... Electrode, 13
... Weight, 14 ... Vibration detection section, 15 ... Support column, 16 ... Envelope made of insulating material, 17 ... Continuous conductive layer, 21 ... Measured object. Figure 1 Figure 2 Figure 3! ! I! 7 19 old 4th s.

Claims (2)

[Claims] (1) In an acceleration pickup in which a vibration detection section is housed in a shielding envelope, the envelope is formed of an insulating material, a conductive layer is formed on the inner surface of the insulating material, and the conductive layer is An acceleration pickup characterized in that the vibration detection section is surrounded by a continuous conductive layer. (2) The acceleration pickup according to claim 1, wherein the insulating material envelope is made of ceramic.