JP2001264190A - Seal structure of load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a seal structure which exerts no adverse influence on characteristics of an elastic body. SOLUTION: A recessed part 17 is formed in a cylindrical hole 12 of a strain inducer 11 and a strain gauge 18 and a circuit element are stuck in the recessed part 17. A thin cylindrical body 19 is inserted covering the recessed part 17 and brought into contact at the circumference of the end part of the cylindrical hole 12. Bellows 20 are formed on both the sides of the thin cylindrical body 19 except the center part and even when the point of a load on a load cell elastic body moves from the center part and a shearing force due to the torsion of the cylindrical body 19 is generated, the cylindrical body 19 has a flexible structure because of the presence of the bellows 20 to exert no influence on the elastic characteristics of the strain inducer 11, so that the measurement precision of the strain gauge 18 as a load cell will not be made worse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load cell sealing structure for improving the environmental resistance and long-term stability of a load cell.

[0002]

2. Description of the Related Art In a load cell, in order to prevent a strain gauge adhered to an elastic portion from being damaged, it is common practice to provide a protection member for protecting against physical impact and humidity. In this case, a long-term, stable and accurate load cell is manufactured unless the structure and material of the protective member are selected so that the external force applied to the elastic portion is not deteriorated to a bad characteristic such as bypass loss and hysteresis. I can't.

A protective member often used for this purpose is a thin metal plate. FIG. 8 shows a protection member for a flat portion.
The thin plate-like body 1 shown in FIG. In this case,
The strain body 2 is provided in the cylindrical portion 3, and the upper portion of the cylindrical portion 3 is covered with the thin plate-shaped body 1. Although the thin plate-like body 1 functions as a sealing material, it hardly becomes a resistance to the load F.

Further, as a sealing structure for the hole,
For example, a device according to Japanese Utility Model Laid-Open Publication No. 59-40806 is known. As shown in FIGS. 9 and 10, the sealing structure includes a thin cylindrical body 5 that also serves as a physical protector for a strain gauge provided on an elastic portion of the strain body 4 and a humidity seal.
It is inserted into the through hole 6 and fixed by welding or the like. In this case, since the cylindrical body 5 is thin and has a small degree of hindering the deformation of the strain body 4 in the cylindrical direction as shown in FIG. 11, when a load is applied to the central load point C, the characteristics of the load cell become The ratio of inhibiting the linearity and the like is relatively small.

[0005]

However, in the conventional example shown in FIGS. 9 and 10, the load point is set at the center C.
It can be understood from actual measurement that the actual load cell characteristics are significantly deteriorated when the vehicle is separated from the load cell. That is, in a one-point load cell in which a load is applied to the central portion C as shown in FIG. 9, when the load load point separates from the center C and separates in the A or B direction, torsion occurs in the through hole 6 of the strain body 4. . For example, in the case of separation in the direction B, as shown in FIG. 12, a large force acts in the shearing direction between the front half-peripheral surface of the cylindrical body 5 and the rear half-peripheral surface. Because the rigidity of the cylindrical body 5 is large, it affects the elasticity of the strain body 4 and makes it impossible to use it as a one-point load cell. May also be lost.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a load cell sealing structure that does not adversely affect the characteristics of an elastic body.

[0007]

In order to achieve the above object, a load cell sealing structure according to the present invention comprises a metal strain body block having a cylindrical hole for stress detection, and an intermediate portion of the cylindrical hole. A concave portion for accommodating a strain gauge is formed in a part of the cylindrical member, the strain gauge is attached to the concave portion, a thin cylindrical body having a bellows in a part is inserted into the cylindrical hole, and the cylindrical body is formed. The strain gauge is fixed to an end of a cylindrical hole, and the strain gauge is sealed by the cylindrical body.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a so-called S-type load cell elastic body 11 which is formed by processing a metal block. A cylindrical hole 12 having a circular cross section is formed in the center of a rectangular body in the thickness direction. Have been. Cut portions 13 and 14 cut from different directions are provided in upper and lower portions of the cylindrical hole 12, respectively, and the thickness between the cylindrical hole 12 and the cut portions 13 and 14 is extremely thin. . Reference numeral 15 denotes a screw hole provided in the strain generating element 11 for screwing a bolt for transmitting a load, and 16 denotes a lead wire introduction hole connected to a strain gauge provided inside which will be described later.

As shown in FIGS. 2 and 3, a concave portion 17 is provided in the cylindrical hole 12, and a strain gauge 18 and a circuit element are attached to the concave portion 17. A thin cylindrical body 19 made of, for example, metal as shown in FIG. 4 is inserted into the cylindrical hole 12 so as to cover the concave portion 17, and is closely attached to a peripheral portion of an end of the cylindrical hole 12 by welding or the like. The center of the thin-walled cylindrical body 19 is slightly smaller in diameter than both ends, and on both sides of the center, the peaks face inward, and the number of peaks is 1 each.
A plurality of bellows 20 are formed.

Thus, even if the load point on the load cell elastic body moves from the center and generates a shearing force due to torsion in the cylindrical body 19, the bellows 20
The cylindrical body 19 has a flexible structure deformed from the state shown in FIG. 5 to the state shown in FIG. 6 due to the presence of the strain gauge 18, without affecting the elasticity of the strain body 11. Does not worsen.

As described above, by forming a part of the cylindrical body 19 as a parallel cylindrical pipe and the remaining part as a combined pipe with the bellows 20, even if both ends of the cylindrical body 19 are fixed to the strain body 11, The presence of the bellows 20 facilitates movement in the free direction, and softens the apparent rigidity in the shear direction. The cylindrical body 19 has a small spring constant with respect to the movement in all directions, easily follows the movement of the cylindrical hole, and does not impair the elastic characteristics of the load cell elastic body. In addition, cylindrical body 1
By making the diameters of the parallel cylindrical portion and the bellows provided in the middle of 9 smaller than the cylindrical diameters at both ends, the concave portion 1 for attaching the strain gauge 18 can be formed shallowly. A load cell with a small load can be manufactured without impairing the elastic properties of the elastic body.

The cylindrical body 19 may have a shape in which a bellows 20 is provided at the center as shown in FIG. Note that the present invention is not limited to the above-described embodiment,
Various modifications are possible within the scope of the claims.

[0013]

As described above, in the load cell sealing structure according to the present invention, a part of a thin-walled cylindrical tube for sealing a strain gauge provided in a concave portion provided in a cylindrical hole is formed into a parallel cylindrical tube, and the remaining portion is formed in a bellows shape. By tightly contacting the cylindrical hole as a combined pipe, the elastic characteristics of the load cell elastic body are not impaired, and the role of the seal due to destruction is not lost.

[Brief description of the drawings]

FIG. 1 is a perspective view of a flexure element.

FIG. 2 is a cross-sectional view as viewed from the side.

FIG. 3 is a cross-sectional view as viewed from the front with a part cut away.

FIG. 4 is a perspective view of a thin cylinder.

FIG. 5 is an explanatory diagram of an operation of a thin cylindrical body.

FIG. 6 is an operation explanatory view of a thin cylindrical body.

FIG. 7 is a cross-sectional view of another example of a thin cylindrical body.

FIG. 8 is a sectional view of a conventional example.

FIG. 9 is a sectional view of a conventional example.

FIG. 10 is a front view of a conventional example.

FIG. 11 is an operation explanatory view of a conventional example.

FIG. 12 is an operation explanatory view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Strain generating body 12 Cylindrical hole 13, 14 Notch 17 Depression 18 Strain gauge 19 Thin cylinder 20 Bellows

Claims (3)

[Claims] 1. A stress-sensing cylindrical hole is formed in a metal strain generating element block, a concave portion for accommodating a strain gauge is formed in a part of an intermediate portion of the cylindrical hole, and the strain gauge is formed. A thin cylindrical body having a bellows in part is fitted into the cylindrical hole, the cylindrical body is fixed to an end of the cylindrical hole, and the strain gauge is sealed by the cylindrical body. Characteristic load cell seal structure. 2. The load cell sealing structure according to claim 1, wherein said thin cylindrical body is welded to circumferential portions at both ends of said cylindrical hole. 3. The seal structure for a load cell according to claim 1, wherein the cylindrical body is made of metal.