JPS62119426A - Load cell - Google Patents

Abstract

PURPOSE:To prevent moisture, by providing a moisture proof cover to be bonded direct on a beam body on peripheral space portion of an insulating layer to shut out circuit parts completely from the outside air. CONSTITUTION:A moisture-proof cover 27 which comprise a first primer 23, a second primer 24, an unvulcanized paste 25 of butyl rubber and a butyl rubber sheet 26 is formed on a peripheral space 10 portion of an insulation layer 11. In such an arrangement, a butyl rubber sheet 26 is bonded direct on a body 6. So, the insulation layer is not exposed out side completely. Thus, the complete covering of highly moisture proof butyl rubber sheet 26 achieves a full moisture proofing of circuit parts.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a load cell in which a strain gauge is formed by thin film technology to form a bridge circuit and generate an electrical signal corresponding to a change in load.

Conventionally, in this type of load cell, when forming a strain gauge etc. on a beam body using thin film technology, an insulating layer is formed over the entire strain gauge forming surface of the beam body, and a layer is placed on top of this insulating layer. The strain gauge and other components are formed using thin film technology. That is,
Although only a portion is shown in the figure, as shown in FIG.
A circuit section 4 such as a strain gauge is formed on this insulating layer 3 by thin film technology, and its upper surface is covered with a moisture-proof cover 5.

Problems to be Solved by the Invention In the conventional structure shown in FIG. 8, the circuit portion 4 is not sufficiently moisture-proofed. That is, the insulating layer 3 itself has hygroscopic properties, and moisture infiltrates from the portion between the beam body 1 and the moisture-proof cover 5 that is in contact with the outside air and adversely affects the circuit portion 4. Furthermore, moisture infiltrates through the joint between the insulating layer 3 and the moisture-proof cover 5.

Means for Solving the Problems According to the present invention, an insulating layer is formed on a part of the surface of a beam body, and a moisture-proof cover is directly bonded to the beam body in a space around the insulating layer.

Function: Since the moisture-proof cover, which has no moisture-absorbing properties, is bonded directly to the beam body, moisture does not infiltrate into the circuit area through the moisture-proof cover, and moisture does not infiltrate from the bonded area between the moisture-proof cover and the beam body. circuit parts are reliably protected from moisture.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 to 7. First, in the rectangular parallelepiped beam 6, four thin-walled deformed parts 8 are formed by irregularly shaped holes 7 passing through both sides, and flat parts 9 are formed above and below the four thin-walled deformed parts 8.

In the portion of this plane portion 9 corresponding to the thin deformed portion 8,
An insulating layer 11 made of polyimide resin is formed leaving a space 10 around it. That is, this insulating layer 1
1 is partially formed so that a space 10 is formed between it and the ridgeline 12 of the beam body 6.

The insulating layer 11 is formed to be thin enough not to affect the deformation of the thin deformable portion 8, and as described above, in addition to polyimide resin, an inorganic material such as Sio is used.

As shown in FIG. 5, the flat part 9 of the beam body 6 on which the insulating layer 11 is formed has a strain gauge part,
A resistance layer 13 which is sufficiently stable in temperature and serves as a bridge balance correction section, a resistance layer 14 having a resistance temperature coefficient which serves as a temperature correction section for correcting the Young's modulus of the beam body 6 and bridge balance, and a lead wire section. The conductor layers 15 are sequentially laminated using thin film technology.

The resistive layers 13, 14 and the conductive layer 15 are selectively etched by means such as photo-etching, as shown in FIGS. 6 and 7. As a result, the strain gauge section 16, the bridge balance correction section 17. Span temperature correction section 18, bridge balance temperature correction section 19, lead section 20
A circuit portion 22 consisting of a terminal portion 21 and a terminal portion 21 is formed.

Next, a moisture-proof cover 27 made of a first primer 23, a second primer 24, an unvulcanized co-glue 25 of butyl rubber, and a butyl rubber sheet 26 is formed in the space 10 on the outer periphery of the insulating layer 11. . The first primer 23 has good adhesion to the beam body 6 made of metal, and the second primer 24 has good adhesion to butyl rubber.

Next, a lead wire 28 is connected to the terminal portion 21,
A cutout hole 29 is provided in the lead wire 28.
is formed. Butyl rubber 31, which will become a part of the moisture-proof cover 27, is attached to the upper surface of the cutout hole 29 with adhesive 30 interposed therebetween.

After doing this, the moisture-proof cover 27 is completely cured by pressure vulcanization.

In such a configuration, the butyl rubber sheet 26 is directly bonded to the beam body 6, and the insulating layer 11 is not completely exposed to the outside. Therefore, since the circuit portion 22 is completely covered with the highly moisture-proof butyl rubber sheet 26, the circuit portion 22 is completely moisture-proof.

Effects of the Invention The present invention provides a moisture-proof cover that is directly adhered to the beam body in the space around the outer periphery of the insulating layer as described above, making it possible to completely isolate the circuit portion from the outside air and make it moisture-proof. It can have a completely moisture-proof structure including the boundary layer with the body.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional side view showing the first embodiment of the present invention, and the second
The figure is a vertical cross-sectional front view with a part enlarged, Figure 3 is a perspective view of the beam body, Figure 4 is a perspective view of the beam body with an insulating layer formed thereon, and Figure 5 is a vertical cross-section of the beam body with a resistive layer etc. formed thereon. Side view, No. 6
The figure is a longitudinal sectional side view of the etched state, FIG. 7 is a plan view thereof, and FIG. 8 is a longitudinal sectional front view of a part of a conventional example. 6... Beam body, 8... Thin deformed part, 9... Plane part, 10... Space, 11... Insulating part, 12...
・Ridge line part, 22...Circuit part, 27...Moisture-proof cover Applicant: Tokyo Electric Co., Ltd...., -; Pregnancy, ;'cL' 3 A part 5 Figure 36

Claims (1)

[Scope of Claims] A rectangular parallelepiped beam body having one or four thin-walled deformed parts is provided, and an insulating layer is placed between the flat part of the beam body and the ridgeline part of the beam body with a predetermined space therebetween. A circuit part consisting of a strain gauge part and a correction part for correcting bridge balance and span is formed on the surface of this insulating layer by thin film technology, and a circuit part consisting of a strain gauge part and a correction part for correcting bridge balance and span is formed on the surface of the insulating layer, and A load cell characterized by having a moisture-proof cover that is directly bonded. 2. The load cell according to claim 1, wherein the insulating layer is made of polyimide resin. 3. The load cell according to claim 1, wherein the moisture-proof cover is made of butyl rubber.