JPH0524024Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a piezoelectric vibration detector, and in particular,
This piezoelectric vibration detector has an explosion-proof structure for detecting vibrations of compressors, rotating machines, etc., and has an impedance conversion circuit and a high voltage protection circuit housed in the same metal case as the vibration-to-electricity conversion section.

[Prior Art] Conventionally, waterproof insulated vibration detectors are a type of so-called equipment diagnosis vibration detectors that measure vibrations of rotating machines, etc. online or offline, and are intended for the maintenance of the machines. Its structure has a double or triple metal shield structure and a waterproof structure because it is installed in areas where noise is likely to occur, such as the motor of a machine, or where oil and water are likely to splash. Furthermore, vibration detectors used in hazardous locations such as explosive gas environments must have an explosion-proof structure as specified in JIS C 0903, and the explosion-proof structure specified here includes flameproof, oil-filled, and explosion-proof structures. There are explosion-proof, internal pressure explosion-proof, increased safety explosion-proof, and intrinsically safe explosion-proof structures. This invention belongs to an intrinsically safe explosion-proof structure.

Figure 6 shows a piezoelectric vibration detector with a conventional explosion-proof structure described in Japanese Utility Model Application No. 61-102829.
A connecting tube 22 is connected to the upper end of a cylindrical metal case 21 having a mounting screw 21a at the lower end, and a vibration-electrical converter 25 is fixed to a base 23 provided at the bottom of the case 21 with bolts 24. has been done. The vibration-electricity converter 25 includes a pair of piezoelectric elements 27 and a weight 28 with an electrode plate 26 in between, and the outer periphery of the piezoelectric element 27 is surrounded by an insulating member 29. A high voltage protection circuit 30 is provided on the upper surface of the insulating member 29.
is arranged, and an impedance conversion circuit 32 attached to a circuit board 31 is arranged above it. The detection signal output to the electrode plate 26 is input to the impedance conversion circuit 32 through the lead wire 33a, the high voltage protection circuit 30, and further through the lead wire 33b. The output of the impedance conversion circuit 32 is led out to a connecting terminal bar 35 provided in the connecting tube 22 via an insulating member 34. Further, a metal tube 36 for shielding is provided on the outer periphery of the circuit board 31 from the vibration-electric conversion section 25 .

With the above configuration, the device is fixed to the object to be measured using the mounting screw 21a, and vibrations are detected. That is, the weight 28 responds to the vibration of the object to be measured, and the piezoelectric element 27 receives a compressive force, and a signal corresponding to the electromotive force generated is extracted from the connecting terminal bar 35, thereby detecting the vibration.

[Problem to be solved by the invention] In conventional piezoelectric vibration detectors as described above, the impedance conversion circuit 32 does not have a completely shielded structure, so it is susceptible to external noise. In order to prevent this, it is necessary to provide metal shielding for each of these circuits and the vibration-electricity conversion section, which not only complicates the structure but also increases the assembly labor.

Not limited to the one shown in Figure 6, conventional piezoelectric vibration detectors with explosion-proof construction use various parts due to the above-mentioned structural requirements, and are inevitably large and heavy. Ta. In particular, those with built-in high voltage protection circuits and impedance conversion circuits have fairly complex structures including the circuits, leading to problems such as high cost, lack of installation space due to large size, and deterioration of frequency characteristics. Ta.

This idea is an attempt to solve the above problem, and by arranging the electric circuit in a completely shielded structure, it is not affected by disturbance noise, is small, inexpensive, and has excellent frequency characteristics. The purpose is to obtain.

[Means for Solving the Problems] The piezoelectric vibration detector according to this invention has a flat plate part and a convex protrusion with a flat top surface provided at the center of the flat plate part. a unit base; a vibration-electrical converter having a piezoelectric element secured to a center bolt erected on the upper surface of the protrusion and sandwiched between a pair of terminal plates; an inner cover fixed to the outer periphery of the base; provided in a space around the protrusion formed by the protrusion, the inner cover, and the flat plate part;
3, each serving as a high voltage protection circuit, an impedance conversion circuit and a connection to the output lead.
An electric circuit mold consisting of two parts, a base fixed to the lower side of the unit base, and an outer cover surrounding the unit base and the inner cover and fixed to the outer periphery of the base. be.

[Function] In this invention, the electric circuit mold is placed in the outer peripheral space of the protrusion of the unit base.

[Example] An example of this invention will be described below with reference to FIGS. 1 to 5. 1 and 2, on the top surface of a metal base 1 provided with three mounting holes 1a,
A metal unit base 2 whose contact surfaces are coated with an insulating layer 2a by thermal spraying of alumina is connected by insulating screws 3. A receptacle 4 for holding a coaxial double-shielded cable 4a is provided on the side of the base 1. A center bolt 5 is erected on the upper surface of the unit base 2, and a piezoelectric element 6 and a weight 7, which are sandwiched between terminal plates 9a and 9e, are fixed to the center bolt 5 with a nut 8, and vibration-
An electrical conversion section A is formed. unit base 2
An electric circuit mold 9 is placed on the side of the holder. An outer cover 1b, a lid 1c, and an inner cover 2b made of metal are bonded to the base 1 and unit base 2 via an adhesive layer 20, respectively. 10
is a low-noise coaxial double-shielded cable, which connects the cable 4a and the electric circuit mold 9.
The shaded area is filled with epoxy resin.

Next, the structure of the electric circuit mold 9 will be explained in detail. First of all, Unit Base 2 is
As shown in FIG. 3, there is a circular flat plate part 2c with an alumina sprayed insulating layer 2a on the lower surface, and a square protrusion part 2d with a flat upper surface and a convex shape integrally formed on the upper surface of this flat plate part 2c. It is made up of. The vibration-electric converter A is then fixed on the upper surface of the protrusion 2d, and the electric circuit mold 9 is placed in the space around the protrusion 2d. The screw hole 2e is for the center bolt 5, and the screw hole 2f is for screwing the lug plate to which the outer shield lead wire of the double shielded cable 10 is soldered to the unit base 2.

The electric circuit mold 9, as shown in FIG.
Two terminal plates 9a and 9e that should sandwich the piezoelectric element 6
A circuit portion 9b consisting of an IC and a resistor, a connection portion 9c to the low-noise coaxial double-shielded cable 10 serving as an output lead, and a circuit portion 9d consisting only of an IC are mounted and arranged on the outer periphery of the epoxy resin molded structure. ing. The IC includes a Zener diode for impedance conversion and high voltage protection.

The circuit portions 9b and 9d configured as described above function as a high voltage protection circuit and an impedance conversion circuit, and can be compactly housed around the protrusion 2d of the unit base 2 together with the connection portion 9c.

FIG. 5 shows the electric circuit E of the above embodiment, in which the piezoelectric element 6 and circuit portions 9b and 9d are connected to each other by a tinned copper wire at a connecting portion 9c, and further connected to a cable 4a via a low-noise coaxial cable 10. ing.

To assemble the above configuration, an electric circuit mold 9 and a piezoelectric element 6, which form the connection part between the impedance conversion circuit, the high voltage protection circuit, and the output lead, must be assembled.
This is completed into a single component by gluing and fixing this onto the unit base 2, assembled together with the weight 7, and press-fitting the inner cover 2b.
The electrical conversion part can be assembled compactly.

[Effects of the invention] As is clear from the above explanation, this invention has the following effects:
The unit base that fixes the vibration-electrical converter is
The circular flat plate part and the rectangular protruding part are integrated, and the impedance conversion circuit and high voltage protection circuit are placed in the outer space of the protruding part as an electric circuit mold structure, making it compact and inexpensive to manufacture. Since it has a heavy shield structure, it is not affected by disturbance noise and has the effect of obtaining excellent frequency characteristics.

[Brief explanation of drawings]

Figures 1 to 5 show an embodiment of this invention,
Fig. 1 is a longitudinal sectional view, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a plan view of the unit base and a sectional view of b, and Fig. 4 is a cross-sectional view of the electric circuit mold. Lines B-B and C in the plan view and this figure a, respectively.
- Cross-sectional views b, c on the plane along line C and line D-D,
d, FIG. 5 is a circuit diagram. FIG. 6 is a longitudinal sectional view of a conventional piezoelectric vibration detector. 2...Unit base, 2b...Inner cover, 2
c...Flat plate part, 2d...Protrusion part, 6...Piezoelectric element, 7...Weight, 9b, 9c, 9d...Three parts of electric circuit mold 9, 9a, 9e...Terminal board, 5... ...Center bolt, 1b...Outer cover.

Claims (1)

[Claims for Utility Model Registration] A unit base in which a flat plate part and a convex protrusion with a flat top surface provided at the center of the flat plate part are integrated; a vibration-to-electrical converter having a piezoelectric element fixed to a center bolt and sandwiched between a pair of terminal plates; an inner cover surrounding the vibration-to-electric converter and fixed to the outer periphery of the unit base; provided in a space around the protrusion formed by the protrusion, the inner cover, and the flat plate part;
3, each serving as a high voltage protection circuit, an impedance conversion circuit and a connection to the output lead.
A piezoelectric device comprising: an electric circuit mold consisting of two parts; a base fixed to the lower side of the unit base; and an outer cover surrounding the unit base and the inner cover and fixed to the outer periphery of the base. shaped vibration detector.