JPH11304606A - Load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a load cell of low profile in which the effect of tension onto a strain gauge is eliminated while facilitating machining. SOLUTION: A strain generating body 11 is cut from an integral metal block. An annular frame part 13 is disposed around a columnar load receiving part 12 and three prism beam parts 14, for example, are stretched radially between the load receiving part 12 and the frame part 13. The beam part 14 is coupled directly, at one end thereof, with the load receiving part 12 and coupled with the frame part 13 through a wall part 15 provided thereat. The wall part 15 is provided on the frame part 13 orthogonally to the beam part 14 and has a central part connected with the other end of the beam part 14 and the opposite lower end parts integrated with the frame part 13. An oval hole 16 is made in the beam part 14 in the horizontal direction orthogonal to the longitudinal direction and strain gauges 17 are pasted to two flexure parts above and below the hole 16. A lead wire is laid along the strain generating body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-profile, low-profile, easy-to-process and high-accuracy load cell.

[0002]

2. Description of the Related Art For example, Japanese Patent Publication No. 2515645 has a load receiving portion 1 at a central portion as shown in FIG. And a roberval mechanism is formed in the beam 3 through the hole 4.
A low and thin load cell to which the flexure strain gauge 5 is attached is disclosed.

[0003]

However, when a force F is applied to the load receiving portion 1 as shown in FIG. 6, the load cell flexes a flexure portion formed on the beam portion 3 so that a roberval mechanism portion is formed. In addition to the bending strain generated in proportion to the force F, the influence of hysteresis due to the tension is added to the output of the strain gauge 5 to cause an error, in addition to the bending strain generated in proportion to the force F.

Further, the load cell of this conventional example is complicated in processing, and in particular, the hole 4 is formed by drilling a hole 8 in the frame 2 by a drill as shown in FIG. Hole 4 must be formed, and the processing is extremely difficult.

An object of the present invention is to solve the above-mentioned problems,
The height is low and the strain gauge is not affected by tension.
Another object is to provide a load cell that can be easily processed.

[0006]

A load cell according to the present invention for achieving the above object is a load cell formed by processing an integral metal block, wherein a load receiving portion provided at a central portion and an outer annular ring are provided. A plurality of prism-shaped beam portions are formed in the horizontal direction between the frame portions, and one ends of these beam portions are connected to the frame portion via a bending portion provided on the frame portion,
A hole is provided in the beam portion in a horizontal direction orthogonal to the longitudinal direction to constitute a roberval mechanism, and a strain gauge is attached to a flexure portion formed by the hole portion.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment.

FIG. 1 is a perspective view, and the strain body 11 is formed by cutting an integral metal block of steel, aluminum or the like with a lathe, a milling machine or the like. An annular frame portion 13 is arranged around the columnar load receiving portion 12, and a rectangular column-shaped, for example, 3
The beam portions 14 are radially bridged. Each beam 14
Is directly connected to the load receiving portion 12, but is connected to the frame 13 via a flexible portion provided on the frame 13. The flexible portion is disposed on the frame portion 13 so as to be orthogonal to the beam portion 14, and a lower portion at both ends thereof is formed as a wall portion 15 integrated with the frame portion 13.
The other end of the beam portion 14 is connected to the center of 5.

An elliptical hole 16 is formed in the beam portion 14 in a horizontal direction orthogonal to the longitudinal direction thereof, thereby forming a Roberval mechanism. In addition, even if the hole 16 is a single hole,
It is also known from the results of stress analysis that two upper and lower flexure portions are formed there. And the hole 16
A strain gauge 17 is attached to each of the two upper and lower flexure portions, and a lead wire (not shown) is laid along the flexure element 1, but the lower strain gauge 17 is not shown. ing. The load receiving portion 12 is provided with a screw hole 18 for coupling to a load, and the frame portion 13 is provided with a plurality of screw holes 19 for fixing the strain body 11 to another member. Is formed.

When a load is applied to the load receiving portion 12, the load is divided into three equal parts, and the load can be measured by the strain gauges 17 at each beam portion 14. Therefore, the output of each strain gauge 17 may be added. In this case, as shown in an exaggerated manner in FIG. 2, when a load F is applied to the load receiving portion 12 as shown by an arrow, each wall portion 15 bends, and the tension affecting the measured value is applied to the wall portion 1.
5, the applied load can be accurately measured by the output of the strain gauge 17.

Processing of the strain body 11 is extremely easy. For example, since the beam portion 14 is located above the frame portion 13, the hole portion 16 can be cut without being disturbed by the frame portion 13. It becomes possible. In addition, the cutting out of the load receiving portion 12, the frame portion 13, the beam portion 14, and the wall portion 15 can be performed without interference with other portions.

In this embodiment, since the thickness of the flexure can be measured with a macrometer, the accuracy is improved by about one digit as compared with the conventional measurement using a vernier caliper, and the thickness of the flexure can be accurately adjusted.

Further, since the attachment location of the strain gauge 17 is exposed in the vertical direction, the attachment of the strain gauge 17 can be performed easily and accurately, and the attachment state can be confirmed by a microscope or the like.

Further, since a substrate provided with an electric circuit can be accommodated in the space on the side of the beam portion 14, electric processing such as amplification can be performed in the vicinity of the strain gauge 17, and electrical stability can be improved. Is improved.

The beam portion 14 can be bridged not only in three directions but also in four directions in a cross shape or in other directions.
The shape of the hole 16 is not limited to the elliptical shape as in the embodiment, but may be a round hole 16 'shown in FIG. 3 or a spectacle-shaped hole 16 "shown in FIG. The shape is not limited to the wall 15 of the embodiment.

Further, the strain gauge 17 can be protected from moisture or the like by sealingly attaching the cover to the strain body 11. In this case, the strain body 11 is fixed on, for example, a base plate, and the strain body 11 is covered with a cover fixed on the base plate, and a force from the cover is applied between the cover and the load receiving portion 12. Can be transmitted through the bellows so that the power is not transmitted to the load receiving portion 12.

The holes 16, 16 ′, and 16 ″ may not penetrate, but may have a dead end in the middle part, and the dead end may be used as a flexure.

[0018]

As described above, the load cell according to the present invention has a bending portion between a beam portion and a frame body portion.
Eliminates the effect of the tension of the conventional load cell, can perform accurate measurement, and without disturbing the frame by arranging the beam on the frame,
It is easy to process a hole having an arbitrary shape and size.

[Brief description of the drawings]

FIG. 1 is a perspective view of a strain generating section.

FIG. 2 is an explanatory diagram of deformation of a wall when a load is applied.

FIG. 3 is a perspective view of a first modified example of a hole.

FIG. 4 is a perspective view of a second modification of the hole.

FIG. 5 is a perspective view of a conventional roberval mechanism.

FIG. 6 is an explanatory diagram of a state where a load is applied to a conventional example.

FIG. 7 is a plan view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Flexure element 12 Load receiving part 13 Frame part 14 Beam part 15 Wall part 16 Hole part 17 Strain gauge

[Procedure amendment]

[Submission date] March 19, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

A load cell according to the present invention for achieving the above object is a load cell formed by processing an integral metal block, wherein a load receiving portion provided at a central portion and an outer annular ring are provided. A plurality of prismatic beam portions are formed between the frame portions in a horizontal direction at different height positions from the frame portion, and one ends of these beam portions are attached to the frame portion. Combined via the bending portion provided on the upper side, the beam portion is oriented in a horizontal direction orthogonal to the longitudinal direction and on an extension of the beam portion.
It is characterized in that a roberval mechanism is formed by providing a hole in which the frame body does not exist, and a strain gauge is attached to the flexure formed by the hole. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 15, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claim 1

[Correction method] Change

[Correction contents]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

A load cell according to the present invention for achieving the above object has a flexure element formed by processing an integral metal block, and the flexure element is provided at a central portion. A load receiving portion, an annular frame portion is formed on the outside, and a plurality of prismatic beam portions are provided horizontally and radially outward from the load receiving portion, and the beam portion is provided above the frame portion. Combine the end of the beam to a flexure provided in a direction perpendicular to the longitudinal direction,
A hole is provided in the beam portion in a horizontal direction orthogonal to the longitudinal direction to constitute a roberval mechanism, and a strain gauge is attached to a flexure portion formed by the hole portion.

Claims (5)

[Claims] In a load cell formed by processing an integral metal block, a plurality of prismatic beams are horizontally arranged between a load receiving portion provided at a central portion and an outer annular frame portion. Formed, and one end of each of these beam portions is connected to the frame portion via a flexible portion provided on the frame portion, and a hole is provided in the beam portion in a horizontal direction orthogonal to a longitudinal direction thereof. A load cell comprising a roberval mechanism, wherein a strain gauge is attached to a flexure portion formed by the hole. 2. The load cell according to claim 1, wherein the number of the beam portions is three, and the beam portions are radially arranged from the load receiving portion toward the frame body portion. 3. The bending portion is arranged perpendicular to the longitudinal direction of the beam portion, and lower portions at both ends are formed as wall portions attached to the frame portion, and the beam portion is connected to the center of the wall portion. The load cell according to claim 1. 4. The load cell according to claim 1, wherein the frame portion is surrounded by a base plate and a cover. 5. The load cell according to claim 4, wherein the space between the cover and the load receiving portion is hermetically joined with a bellows.