JP3616189B2 - Piezoelectric load sensor and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric load sensor.
[0002]
[Prior art]
Normally, a piezoelectric element that generates electric charge when pressure is applied, a pressure receiving plate made of a conductive material that transmits pressure, an electrode plate that extracts electric charge generated from the piezoelectric element, lead wires connected to the electrode plate, and components A piezoelectric load sensor that consists of a holding outer frame and detects a dynamic load is used to detect the dynamic load of equipment that has a drive source, such as flying water, lubricating oil, moisture or oil content due to condensation, etc. It may be used even in a usage environment where a conductive material such as droplets adheres and a short circuit is likely to occur. For this reason, conventionally, a waterproof process for protecting the entire sensor from intrusion of water or the like has been performed, and this waterproof process has a problem that the manufacturing is troublesome and the manufacturing cost is increased.
[0003]
[Problems to be solved by the invention]
However, in recent years, there has been a demand for using a piezoelectric load sensor in a waterproof environment such as in a housing of a device that has been waterproofed, or in an incomplete but waterproof environment.
An object of the present invention is to provide a simple piezoelectric load sensor having a structure capable of reducing the manufacturing cost while omitting the waterproof property of the piezoelectric load sensor itself.
[0005]
[Means for Solving the Problems]
The piezoelectric load sensor according to claim 1 is configured such that a plate-shaped insulating plate, an electrode plate, and a piezoelectric element each having a center hole are coaxially sandwiched between plate-shaped pressure receiving plates having a center hole. The laminate is fixed by a fixing means that passes through each of the center holes. The adhering means is a rivet, and a recess for receiving the head of the rivet is provided on the outer surface of each pressure receiving plate. In this configuration, the solid because securing the stack with rivets as Chakushudan, assembling productivity is high and to automate processes.
[0006]
In the structure of Claim 2 , the outer peripheral surface of the said laminated body is a cylindrical surface, and this outer peripheral surface is enclosed with the resin-made frame or the rubber-made frame. In this configuration, in the case of a resin frame, there is an advantage that the laminated body can be fixed at both the center and the outer periphery, and in the case of a rubber frame, it is possible to provide a sealing property using elasticity.
[0007]
In the configuration according to claim 3 , a lead portion extends on the outer periphery of the electrode plate, and an end portion of a lead wire is connected to the lead portion, and the resin frame or the rubber frame is connected to the lead plate. Is characterized in that a lead wire connecting portion surrounding the lead portion and the end portion of the lead wire is integrally formed , thereby improving productivity and reducing manufacturing cost .
[0008]
In the configuration according to claim 4, a disc-shaped insulating plate having a center hole, an electrode plate, and a piezoelectric element are stacked and coaxially stacked between the disc-shaped pressure receiving plates having the center hole . the laminate is formed, the said laminate is fixed by inserting a rivet into each central hole, Ri Na to form a resin frame by injection molding on the outer periphery of the laminate, the productivity while reducing manufacturing costs To improve .
[0009]
[Operation and effect of the invention]
According to the present invention, the piezoelectric load sensor can be assembled by simply fixing the pair of pressure receiving plates. This fixing method may be a rivet or an elastic frame made of resin or rubber, and any of them can be mass-produced with a simple automatic assembling apparatus. When the resin frame is injection-molded, the productivity can be further improved and the manufacturing cost can be reduced by integrally forming the lead wire holding portion.
In addition, the use of an elastic frame makes it possible to obtain waterproofness or moistureproofness of the pressure-receiving element portion of the load sensor.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a piezoelectric load sensor A according to a first embodiment of the present invention. This piezoelectric load sensor A has a disk-shaped pressure-receiving plate 1, 1 having a center hole 11 facing back, and a disk-shaped insulating plate 2 having a center hole 21 between the pressure-receiving plates 1, 1. The disc-shaped electrode plate 3 having the central hole 31 and the piezoelectric element 4 having the central hole 41 are stacked and coaxially sandwiched to form a laminated body 10, and the laminated body 10 is the central holes 11, 21, 31, It is fixed with a rivet 5 inserted through 41, and the outer periphery of the laminate 10 is fixed with a resin frame 6.
[0011]
In this embodiment, only one piezoelectric element 4 having piezoelectricity such as lead titanate (PT) or lead zirconate titanate (PZT) is used, the pressure receiving plate 1 is a positive electrode, and the electrode plate 3 is Although it has a negative polarity, the electrode plate 3 and the piezoelectric element 4 may be overlapped on both sides of the insulating plate 2, respectively, and the electrode plate 3 and the insulating plate 2 are stacked on both sides of the piezoelectric element 4. There may be.
The polarities of the pressure receiving plate 1 and the electrode plate 3 may be reversed.
[0012]
The pressure receiving plate 1 is made of an iron-Ni alloy (Fe-42Ni), and the outer side surface 12 is provided with a recess 13 for accommodating the head 51 of the rivet 5 around the center hole 11, and the outer peripheral edge 14. Is thin and serves as a clamping surface by the resin frame 6. A space between the recess 13 and the outer peripheral edge 14 is smoothly formed, preferably formed in a mirror surface, and forms an annular pressure receiving surface 15. Further, the inner side surface 16 is formed smoothly and is preferably formed as a mirror surface.
[0013]
The insulating plate 2 is made of an insulating material such as alumina or mullite, and the electrode plate 3 is preferably made of iron-Ni alloy (Fe-42Ni) because it has a thermal expansion coefficient close to that of the PZT piezoelectric element. As long as the material has a similar thermal expansion coefficient, it may be made of SUS material or SKD material. Both of these and the central hole 41 of the piezoelectric element 4 have an inner diameter somewhat larger than the central hole 11 of the pressure receiving plate 1, and the central hole 41 of the piezoelectric element 4 has each of the pressure receiving plate 1, the insulating plate 2, and the electrode plate 3. It may be the same as or somewhat larger than the diameter of the center holes 11, 21, 31. Further, these outer diameters are formed substantially the same as the outer diameter of the pressure receiving plate 1. A lead portion 32 extends from the outer periphery of the electrode plate 3, and a core wire 71 exposed from the end of the lead wire 7 is inserted into a cylindrical portion 33 provided at the tip of the lead portion 32 and is connected by caulking or soldering. Has been.
The cylindrical portion 33 may be formed integrally with the electrode plate 3, but the electrode plate 3 and the cylindrical portion 33 may be separately manufactured and joined together by welding, brazing, or caulking.
[0014]
The resin frame 6 is injection-molded so as to sandwich the pressure receiving plates 1 and 1 from the outer periphery with the outer peripheral edges 14 and 14 therebetween, and has a thickness that is somewhat smaller than the thickness between the pressure receiving surfaces 15 and 15. From the outer periphery of the resin frame 6, a lead wire enclosing portion 61 that surrounds the end portion of the lead wire 7 projects from a cylindrical portion 33 provided at the tip of the lead portion 32.
[0015]
The rivet 5 is advantageously made of aluminum from the viewpoint of cost reduction, but other soft metals such as copper and soft iron can also be used. In this piezoelectric load sensor A, the laminated body 10 is fixed with a rivet 5 in order to reduce the manufacturing cost. However, the piezoelectric load sensor A is fastened with bolts and nuts, Other fixing means such as fastening with a screw inserted from the other can be adopted.
[0016]
The resin frame 6 is preferably PBT (polybutyl terephthalate), nylon, polyphenyl sulfide (PPS), ethylene propylene rubber (EPDM), silicone rubber, or fluorine rubber. In addition, fixing the laminated body 10 at the center with fixing means such as the rivet 5 and fixing it from the outer periphery with the resin frame 6 is effective in that the structural strength of the piezoelectric load sensor A can be increased. Either one can be used as the piezoelectric load sensor A. In addition, a resin rivet may be used when electrical conduction is separately established between the pressure receiving plates 1 and 1 or when electrical conduction between the pressure receiving plates 1 and 1 is not required. The fixing means such as the rivet 5 is effective as a holding means for the laminate 10 during the injection molding of the resin frame 6.
The shape of each of the recess 13, the rivet 5 and the resin frame 6 provided in the pressure receiving plate 1 is such that the pressure receiving surfaces 15 and 15 are at the outermost side in a direction perpendicular to the pressure receiving surfaces 15 and 15. Shape.
[0017]
In the piezoelectric load sensor A, since the pressure receiving surfaces 15 and 15 are on the outermost side in a direction perpendicular to the pressure receiving surfaces 15 and 15, as shown in FIG. 1, for example, the lower surface 1A of the fixed leg of the motor housing in a waterproof environment And pressure receiving surfaces 15 and 15 are mounted between the motor fastening seat surface 1B and used for measuring a dynamic load applied to the motor housing.
[0018]
FIG. 3 shows a second embodiment. In this embodiment, the center of the laminate 10 is fixed by a fixing means such as a rivet 5 and the outer periphery is surrounded by a rubber frame 8 made of silicone rubber. On the upper and lower surfaces of the rubber frame 8, annular ridges 81, 81 having a semicircular cross section are provided. However, the annular projections 81, 81 are projected from the pressure receiving surfaces 15, 15 to the outside in a direction perpendicular to the pressure receiving surfaces 15, 15. The annular protrusions 81 and 81 are compressed at the measurement surfaces 1C and 1D or the bottom surfaces of the seal grooves 1e and 1f provided on the measurement surfaces 1C and 1D so that the compression portion has a sealing property.
In this embodiment, when set between parallel dynamic load measuring surfaces 1C and 1D, the annular protrusions 81 and 81 act as a seal ring, and there is an advantage of having a certain degree of waterproofness or moistureproofness.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a piezoelectric load sensor according to a first embodiment.
FIG. 2 is a perspective view of FIG.
FIG. 3 is a cross-sectional view of a piezoelectric load sensor according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pressure receiving plate 2 Insulating plate 3 Electrode plate 4 Piezoelectric element 5 Rivet 6 Resin frame 7 Lead wire 8 Rubber frame 10 Laminated bodies 11, 21, 31, 41 Center hole

Claims (4)

Adhering a laminated body in which a plate-like insulating plate, electrode plate, and piezoelectric element each having a central hole are overlapped and coaxially sandwiched between plate-shaped pressure receiving plates having a central hole are inserted through the central holes. In a piezoelectric load sensor fixed by means,
It said fixing means is a rivet, a piezoelectric load sensor above the outer surface of the pressure receiving plate, characterized in that the recess to accommodate the head of the rivet is provided. 2. The piezoelectric load sensor according to claim 1 , wherein the outer peripheral surface of the laminate is a cylindrical surface, and the outer peripheral surface is surrounded by a resin frame or a rubber frame. According to claim 2, together with the lead portions on the outer periphery in the electrode plate is extended, the said lead portion is connected to an end of the lead wire, the resin frame and the rubber frame, the A piezoelectric load sensor, wherein a lead wire and a lead wire connecting portion surrounding an end portion of the lead wire are integrally formed. Between each disk-shaped pressure receiving plate having a center hole, a disk-shaped insulating plate having a center hole, an electrode plate, and a piezoelectric element are stacked to form a laminated body , the laminate was fixed by inserting a rivet into the hole, the method of manufacturing a piezoelectric load sensor obtained by forming a resin frame by injection molding on the outer periphery of the laminate.

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