JPH08132U - Stick-on strain gauge - Google Patents

Abstract

(57) [Summary] [Purpose] Completely perform the same handling and sticking treatment as a normal stick-on type strain gauge that is generally used in load cells, and complete the treatment without any special moisture-proof treatment. (EN) Provided is a moisture-proof strain gauge having a structure capable of easily obtaining a load cell moisture-proof property. [Structure] On a strain gauge base 2 similar to a normal stick-on type strain gauge, at least on the upper surface of an insulating material layer 8 which is in contact with the strain-sensitive resistance wire portion 4 and is covered from above, a physical layer such as vacuum vapor deposition or sputtering is used. A moisture-proof structure of a strain gauge formed by forming a moisture-proof metal film layer 10 by a vapor phase growth method.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a strain gauge used to measure force, torque, weight, pressure, tension, etc., and more particularly to a stick-type unitary structure which is used by sticking to a strain body.

[0002]

[Prior art]

 For example, as shown in FIGS. 3 and 4, the stick-on type strain gauge means a strain sensitive resistance wire portion 4 made of metal foil and a lead wire connection portion integrated with this on the upper surface of a rectangular insulating substrate 2. 6 is formed, and is used, for example, in a load cell or the like by mounting the base 2 so that the base 2 is in contact with the strain generating portion of the strain generating elastic body. Conventionally, in such strain gauges, insulation between the individual wires of the strain sensitive resistance wire portion 4 and the creeping surface between the strain sensitive resistance wire portion and the strain elastic body due to humidity or contamination after being attached to the strain elastic body. In order to prevent the zero point change and span value change of the load cell due to the change of the resistance value, an organic insulating material layer 8 such as phenol resin or epoxy resin is provided on the upper surface of the base plate 2 so as to cover the strain sensitive resistance wire part 4. There was something glued.

[0003]

[Problems to be solved by the device]

 However, in the strain gauge, the insulating layer 8 has a thickness of 20 to 30 μm due to the limited capacity of the load cell constructed by sticking the strain gauge to the elastic body and the shape and size of the elastic body. A very thin thickness is required. Therefore, in the conventional strain gauge, the thickness from the upper surface of the insulating material layer 8 to the surface of the strain sensitive resistance wire portion 4 is very small, and the insulating material layer 8 has a hygroscopic phenol resin or epoxy resin. Uses organic insulating materials such as. Therefore, the insulating material layer 8 is moistened by the humidity in the atmosphere, so that the moisture is absorbed between the creeping resistance wire portion 4 and the strain sensing resistance wire portion 4 and the strain elastic body through the substrate 2. Insulation resistance may be reduced, and after attaching the strain gauge to the strain-flexing elastic body, seal the whole with flexible metal bellows including the strain-flexing elastic body, or there is a limit to the moisture resistance effect. However, there was a problem in that the insulation had to be applied again to reinforce it from the top.

[0004]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention comprises a strain gauge base formed so that it can be attached to a strain body, a strain sensitive resistance wire portion provided on the upper surface of the base, and a strain gauge resistance wire portion formed integrally with the strain gauge base wire. An insulating material layer provided on the upper surface of the substrate so as to cover the lead wire connecting portion and at least the resistance wire portion, and adhered to the upper surface of the insulating material layer by physical vapor deposition. A single stick-on type strain gauge having the moisture-proof metal layer is provided.

[0005]

[Action]

 According to this invention, since the insulating material layer covering the upper surface of the strain-sensitive resistance wire portion is covered with the two-layer structure further covered with the moisture-proof metal layer that does not permeate moisture, the moisture from the upper surface side is prevented. Penetration is blocked. The peripheral surface of the insulating material layer is exposed without being covered by the metal layer, but the thickness of the peripheral surface is extremely thin, and in comparison with this, the edge portion of the strain-sensitive resistance wire portion from the peripheral surface. Since the distance to is considerably long, water does not penetrate from the peripheral surface to the strain sensitive resistance line. Therefore, this device can prevent the permeation of water.

[0006]

【Example】

 In this embodiment, as shown in FIGS. 1 and 2, a moisture-proof metal layer 10 is deposited on the upper surface of the insulating material layer 8 of the conventional strain gauge shown in FIGS. 3 and 4. The other parts are the same as the conventional ones, and thus detailed description thereof will be omitted.

The moisture-proof metal layer 10 is formed by applying a phenol resin or an epoxy resin on the strain-sensitive resistance wire portion 4 to form the insulating material layer 8 and then applying a physical vapor deposition method such as vacuum deposition or sputtering. It is worn. The thickness of the moisture-proof metal layer 10 is 1 μm or less, which is extremely thin, while the thickness of the insulating material layer 8 is 20 to 30 μm.

In the strain gauge according to the present invention, by providing the moisture-proof metal layer 10 that does not permeate moisture on the upper surface of the insulating material layer 8 provided on the substrate 2 so as to cover the strain sensitive resistance wire portion 4, The strain-sensitive resistance wire portion 4 is doubly covered. Therefore, it is possible to prevent the permeation of water from the upper surface of the strain sensitive resistance wire portion 4. Moreover, the thickness of the insulating material layer 8 is as thin as 20 to 30 μm, and compared with the thickness of the insulating material layer 8, the permeation distance from the exposed peripheral surface to the edge of the strain sensitive resistance wire portion 4 is equivalent to 1 mm or more. Since it is long, moisture does not penetrate from the exposed peripheral surface to the strain sensitive resistance wire portion 4.

Note that, instead of depositing the metal layer by a physical vapor deposition method such as vacuum deposition or sputtering, a thin metal foil can be attached onto the insulating material layer 8, but it is thin. In order to attach the foil so that it does not wrinkle easily, which may cause breakage holes, the foil must be handled and applied carefully, resulting in poor workability.

In the above embodiment, the insulating material layer 8 and the moisture-proof metal layer 10 are provided only on the resistance wire portion 4. However, the insulating material layer 8 and the moisture-proof metal layer 10 are also covered, that is, the insulating material is formed on the entire upper surface of the substrate 2. The layer 8 and the moisture-proof metal layer 10 may be provided. In that case, it is necessary to connect a lead wire to the lead wire connecting portion 6 before forming the insulating material layer 8. Further, an organic insulating material layer may be further provided on the upper surface of the moisture-proof metal layer 10 to prevent the thin moisture-proof metal layer from being damaged by an external force.

[0011]

[Effect of device]

 As described above, in the strain gauge according to the present invention, the moisture-proof metal layer is coated on the upper surface of the insulating material layer that covers at least the strain-sensitive resistance wire portion provided on one side of the substrate, and the double layer is formed. Since it is designed to be moisture-proof, the moisture-proof effect is perfect. Therefore, such a strain gauge does not need to be subjected to moisture-proof treatment and moisture-proof measures again after being attached to the strain-sensitive part of the strain-flexing body, and the structure of the load cell can be simplified. Manufacturing costs can also be reduced. Since the moisture-proof metal layer is deposited on the insulating material layer by a physical vapor deposition method such as vacuum deposition or sputtering, its thickness can be made extremely thin. For example, the rigidity of the moisture-proof metal layer does not affect the load characteristics of the load cell, etc., and the strain gauge installation work can be handled exactly like a normal strain gauge. This is because in manufacturing, the work becomes easier and productivity is improved.

A pattern including a plurality of strain gauges formed by etching a metal layer on the insulating material layer and lead wires for wiring these is provided on one surface of the strain body, and a pattern is formed on the pattern. It is conceivable to form the moisture-proof metal film by physical vapor deposition method after forming the insulating film.However, in this method, metal vapor deposition method is used in a fairly wide area on one side of the strain element. Since a film has to be formed, the manufacturing process thereof is troublesome, and especially in the case of a large strain element, the handling of manufacturing is troublesome. However, in the strain gauge according to this consideration, since the moisture-proof metal layer is formed by the physical vapor deposition method on the insulating material layer on each substrate of the strain gauge alone, any strain Just attach it to an elastic body, that is, a large one or a small one, in the same way as a normal strain gauge, and thereafter, without forming a metal film by physical vapor deposition. In addition, complete moisture resistance is obtained and the moisture resistant load cell can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of a strain gauge according to the present invention.

FIG. 2 is a partially cutaway plan view of the same embodiment.

FIG. 3 is a vertical sectional view of a conventional strain gauge.

FIG. 4 is a partially cutaway plan view of a conventional strain gauge.

[Explanation of symbols]

 2 substrate 4 resistance wire part 6 lead wire connection part 8 insulating material layer 10 moisture-proof metal layer

Claims (1)

[Scope of utility model registration request] 1. A base formed so that it can be attached to a strain body,
A strain sensitive resistance wire portion provided on the upper surface of the base and a lead wire connecting portion integrally formed with the strain sensitive resistance wire portion; and an insulating material layer provided on the upper surface of the base so as to cover at least the strain sensitive resistance wire portion. A stick-on strain gauge, comprising a moisture-proof metal layer deposited on the upper surface of the insulating material layer by physical vapor deposition.