JP2001147165A - Load cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strain gauge type load cell having a plurality of sensitive parts improved in strength to other shafts and heightened in the degree of freedom in the mechanical connection of the sensitive parts while reducing the flexure quantity of the sensitive parts of low capacity and high sensitivity. SOLUTION: Sensitive part structure is formed as a parallel plate system to heighten mechanical rigidity to multiple shafts, and a plurality of sensitive parts are connected by a combination of fitting and fastening with screws, or fixing with screws to heighten the degree of freedom in mechanical connection. Notching or boring is applied to the sensitive parts of low capacity and high sensitivity to concentrate stress thereon. Specified output can thereby be obtained, and the quantity of flexure can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance strain cage type load cell for measuring a load by utilizing a change in electric resistance. More specifically, the present invention relates to a structure of a sensing portion of a strain gauge type load cell having a plurality of detection elements and enabling an arbitrary combination.

[0002]

2. Description of the Related Art A resistance wire strain gauge as a force sensor using an analog output signal according to the strength of a force is formed by attaching a sensing part of a mechanism for receiving a force at one point and attaching the gauge to the sensing part. It is used as a load cell with a built-in bridge circuit.

In a strain gauge type load cell, a Wheatstone bridge is constituted by a strain gauge, and its resistance change is detected as a bridge unbalanced output voltage. The unbalanced output voltage is determined in proportion to the Wheatstone bridge applied voltage, the cage ratio of the strain cage, and the amount of strain in the load cell sensing portion.

In a load cell having a multiaxial sensing portion having an Fx detecting element receiving a force in the X direction and an Fz detecting element receiving a force in the Z direction in the same case of the load cell, the load cell is resistant to a force from the other axis. A protective material such as a diaphragm is employed as a strength measure.

In addition, Fx and Fz of the load cell sensing section
In many cases, the connection method for mechanically connecting the detection elements is of an integral structure or a screw fixing method.

Furthermore, in the case of a low-capacity, high-sensitivity sensing portion, the amount of deflection is generally large.

[0007]

When a diaphragm is used as a measure against the strength of the load cell sensing part from the other axis, the lateral load resistance is about 10% of the rated capacity, which is not sufficient. . Further, in the case where the mechanical connection of the plurality of sensing units is an integral structure or a screw fixing method, the combination of the Fx and Fz detection elements has no flexibility. Furthermore, a low-capacity, high-sensitivity load cell sensing part generally has a large amount of bending, and depending on the object to be measured (in the case of low bending), it is difficult to measure accurately.

[0008]

In view of this situation, the present inventors have made intensive studies and, as a result, have solved the above-mentioned problems relating to the conventional strain gauge type load cell.

The sensing part of the load cell has a parallel plate structure by wire cutting, electric discharge machining or cutting and welding, and it is possible to improve lateral load resistance by enhancing mechanical rigidity from the other axis. . Further, by adopting the parallel plate structure, the structure can be simplified, and the cost of manufacturing the load cell can be reduced.

The plurality of sensing parts of the load cell having the Fx and Fz detecting elements can be arbitrarily selected by adopting an integrated structure or a screw fixing method, a combination method of fitting and screw connection, or a fixing method using screws. Can be taken, and the degree of freedom of the combination of the Fx and Fz detecting elements used in the sensing unit is increased.

In order to prevent the deformation of the low-capacity sensing part during machining, the deformation of the processing part is kept within a negligible range, and the resulting decrease in output is cut out or perforated in the sensing part. The stress is compensated by concentrating the stress on the site. This makes it possible to reduce the amount of deflection.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the following embodiments, but the present invention is not limited thereto.

FIG. 1 shows an outline of a combination of an Fz detecting element and a load cell in which the Fz detecting element is combined. FIG. 1A is an outline of the Fx detecting element, and FIG.
FIG. 1D schematically shows the structure of the Fz detecting element. FIG. 1 (b) shows a case of two parallel plate beam bending.
FIG. 1 (c) shows the case of four beam shearing, and FIG. 1 (d) shows the case of eight parallel plate bending. The Fx detection element and the Fz detection element are connected by fitting and screw fixing, or screw fixing. In any case, the structure is not a load-bearing structure using a diaphragm, but a structure that receives a force by a parallel plate.

FIG. 2 is a schematic diagram showing a method of mechanically connecting the Fx sensor detecting element (1) and the Fz sensor detecting element (2). FIG. 2A shows a case where the connection is made by fitting and fixing with a screw, and FIG. 2B shows a case where the connection is made by fixing with a screw. In these connection methods, there is a greater degree of freedom in the combination of the detection elements as compared to a sensing section in which the Fx sensor sensing element (1) and the Fz sensor sensing element (2) are integrated or a screw-fixed sensing section. .

FIG. 3 is a schematic view showing portions (3, 4) where notches or perforations are made in the low-volume sensing portion. Since the stress received by the sensing part concentrates on the notch (3) or the perforated part (4), it is possible to minimize the measures for preventing deformation of the sensing part when machining the sensing part. ,Also,
This has the effect of suppressing an increase in the amount of bending.

[0016]

The present invention is effective in simplifying the structure of the load cell sensing portion, improving the lateral load resistance, and increasing the degree of freedom in combining a plurality of sensing portion elements.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an outline of an Fx detection element and an Fz detection element and a combination thereof.

FIG. 2 is a schematic diagram illustrating a method of mechanically connecting an Fx detection element and an Fz detection element.

FIG. 3 is a schematic view showing a notch or a hole to be drilled on an Fz detecting element to concentrate stress.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fx detection element 2 Fz detection element 3 Notch part 4 Perforation part

Claims (3)

[Claims] 1. A load cell of a resistance strain gauge type load cell, wherein the structure of the load cell sensing part is a plurality of parallel plate type. 2. A load cell of a resistance strain gauge type load cell, wherein a method of connecting and connecting the load cell sensing portion comprises an arbitrary combination of fitting and screw connection. 3. A load cell of a resistance wire strain gauge type wherein cutouts or perforations are applied to a load cell sensing portion, and stress is concentrated on the processed portion to achieve an increase in output and low deflection. And the load cell.