JP3208404B2 - Weight measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a load receiving portion to which a load of an object to be measured is applied, and a frame-like base which surrounds the entire circumference of the load receiving portion at a predetermined interval and whose lower surface is placed at a measuring place. And a beam part that connects the base and the load receiving part and floats the load receiving part in the air when the base lower surface is placed at the installation location, and a strain gauge attached to the beam part. The present invention relates to a weight measuring device for detecting, using a strain gauge, strain generated in a beam portion when a load is applied to a beam.

[0002]

2. Description of the Related Art As a conventional apparatus using a strain gauge, as shown in FIGS. 14 and 15, a load receiving portion 100 to which a load of an object to be measured is applied and a whole circumference of the load receiving portion 100 are arranged at a predetermined interval. A base 101 which is surrounded by a gap and whose lower surface is placed at a measurement location;
And a beam portion 102 for suspending the load receiving portion 100 in the air when the lower surface of the base portion 101 is placed at the measurement place by connecting
Strain gauges 103 are provided on both horizontal sides of each beam 102.
Is known. The load receiving portion 100 and the base portion 101 of this conventional device have a rectangular planar shape, and the beam portion 102 connects two short sides of both portions 100 and 101 with each other. These beam portions 102 are used as load receiving portions 10.
Distortion occurs when a load is applied to 0, and this distortion is detected by the strain gauge 103.

[0003]

In the conventional apparatus, the cross-sectional shape of the beam portion 102, which is a strain-flexing portion, is designed in relation to the load to be measured. (Vertical direction) is determined for the load to be measured. Therefore, in order to secure strength with a small number of beams 102, the height of the cross section of the beams 102 is increased, and it is difficult to reduce the thickness of the entire apparatus. Further, the beam portion 102 is strong because it has a structure in which the beam portion 102 receives a compressive and tensile force with respect to the force Fx in the x direction in FIG. 14, but the beam 102 receives a bending force with respect to the force Fy in the y direction. So weak. Therefore, the strength of the device depends on the direction of the force received,
In addition, an adverse effect on the measurement accuracy due to the force Fy in the y direction may be considered. Further, when the load point moves in the x direction (x _{1 in} FIG. 14) and when it moves in the y direction (y _{1 in} FIG. 14), the force acting on each part (100, 101, 102) is The distribution has lost symmetry, and as a result, the eccentricity error has a directivity, and the eccentricity error has increased.

[0004] Therefore, an object of the present invention is to provide a weight measuring device in which the entire device can be made thinner and measurement accuracy is improved.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a load receiving portion formed in a hexagonal shape of a square plane, and having four outer side surfaces of the load receiving portion and four inner side surfaces of the base portion. At least two beam portions are provided between the opposing side surfaces, and the beam portions between the opposing side surfaces are provided symmetrically with respect to the center line of each side formed by the inner side surface of the base.

[0006]

According to the present invention, the height of the cross section of the beam portion can be reduced by increasing the number of the beam portions, thereby making it possible to reduce the overall thickness.
Further, since each beam between the outer surface of the load receiving portion and the inner surface of the base facing each other is symmetric with respect to the center line of each side formed by the inner surface of the base, the forces Fx, It is also strong against Fy, so that the strength of the device does not vary depending on the direction of the force to be received, and the accuracy does not decrease due to this. In addition, because of the square shape, the beam portion has a 90 ° rotational symmetry with respect to the center point, and when the load point moves from the center point, that is, even when an eccentric load is applied, the distribution of the force acting on each component is symmetric. It is possible to maintain the directionality of the generation of the eccentric error and to reduce the eccentric error. Further in the base
Form a notch recessed inward in the center of each side of the side.
Depending on the location of the device when it is placed
Even if there are irregularities, the presence of these cutouts can reduce beam distortion.
No adverse effects.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

In the first embodiment shown in FIG. 1, a load receiving portion 1 to which a load of an object to be measured is applied, the entire periphery of the load receiving portion 1 is surrounded at a predetermined interval, and the lower surface is placed at a measuring place. A frame-shaped base portion 2 and a beam portion 3 connecting the base portion 2 and the load receiving portion 1 to float the load receiving portion 1 in the air when the lower surface of the base portion 2 is placed at an installation place; Strain gauges 4 are attached to both lateral sides of the beam 3. In this embodiment, the beam portions 3 are provided so as to be connected to the four sides of the base 2 two by two from the four sides of the load receiving portion 1. The planar shape of the load receiving portion 1 was square, and the base 2 was also square.
The beam portion 3 is provided between opposing side surfaces of the four outer side surfaces 1A to 1D of the load receiving portion 1 and the four inner side surfaces 2A to 2D of the base portion 2. Opposite sides (1A and 2A,
1B and 2B, 1C and 2C, and 1D and 2D) are provided so as to be symmetric with respect to the center lines 5 and 5 of the sides formed by the inner side surfaces 2A to 2D of the base 2. Further, as shown in FIG. 2, the upper surface of the load receiving portion 1 is located higher than the upper surface of the base 2.

In the first embodiment constructed as described above, even when the load point moves to the position of x ₂ or y ₂ as shown in FIG. Since it is 90 ° rotationally symmetric, the distribution of the force acting on each component is kept symmetric, the directionality of the occurrence of the eccentric error is eliminated, and the eccentric error can be reduced.

In the second embodiment shown in FIG. 4, a notch 6 depressed inward is formed at the center of each side of the inner side surfaces 2A to 2D of the base 2. By forming such a notch 6, deformation of the surrounding portion can be concentrated on the notch 6. Thus, when the peripheral portion of the base 2 is placed at the measurement location, even if the surface of the measurement location has irregularities and the like, and the peripheral portion is deformed by the influence of the irregularities due to the load, The deformation can be concentrated on the notch 6 so that the deformation of the portion without the notch 6 to which the beam 3 is connected can be reduced. Therefore, the beam 3 is the base 2
Only the deformation due to the load without being affected by the deformation. Accordingly, it is possible to reduce the influence of the output characteristics on the load of the weighing device due to the unevenness of the installation surface.

In a third embodiment shown in FIG. 5, an arc-shaped portion 7 which is depressed inward is formed on the side surface of the beam portion 3. The formation of the arc-shaped portion 7 in the horizontal direction of the beam portion 3 is performed by using a machining tool 8
Can be formed. At this time, assuming that the distance between the outer surfaces 1A to 1D of the load receiving portion 1 and the inner surfaces 2A to 2D of the base 2 is 1 (ell), if the radius of the arc-shaped portion 7 is R, R = 1/2. 1 (L), and it is possible to process the gap between the beam portions 3 and simultaneously process the arc-shaped portion 7. Moreover, the gap between the beam portions 3 and the arc-shaped portion 7 can be simultaneously processed by one-time unidirectional feed, so that the processing time and cost can be reduced.

As shown in FIGS. 6 and 7, when a load is applied to the central portion of the load receiving portion 1, the bending stress acting on the upper and lower surfaces of the beam portion 3 is such that one load of the beam portion 3 is F. Then, at the point x,

[0013]

(Equation 1)

## EQU1 ## That is, since the bending stress increases in proportion to the distance x from the center of the beam 3, the maximum stress occurs at both ends 31 of the beam 3. Therefore, if a semicircular side surface shape as indicated by reference numeral 7 'is formed, the width w of the beam portion 3 becomes larger as approaching both end portions 31, which is advantageous in strength. Naturally, it is effective to add an R to the upper and lower surfaces of the beam portion 3 as indicated by reference numeral 7 ", but if a large R is added, the height of the beam portion 3 increases, leading to an increase in the thickness of the entire weighing device. Therefore, the size is designed in relation to the overall thickness.

FIGS. 8 and 9 show a semi-circular side surface as shown in FIGS. 6 and 7, in which strain gauges 4 are attached to both lateral sides of the beam 3 in the horizontal direction. The strain gauge 4 has resistance lines in the direction of 45 ° on both sides with respect to the center line. The strain gauge 4 detects a shear strain that is proportional to the shear stress generated in the beam 3 and converts it electrically to measure the weight.

One way to increase the strain detection accuracy of the strain gauge 4 is to generate as large a strain as possible, and this strain is proportional to the stress. The shear stress τ can be expressed by the following equation.

[0017]

(Equation 2)

The shear stress becomes maximum at the center of the beam 3 which is the minimum section. Therefore, by attaching the strain gauge 4 to the center of the beam 3, a larger strain can be detected, and the detection power increases. Although the bending moment increases as the distance from the center of the beam 3 increases, in the embodiments shown in FIGS. 8 and 9, the cross section increases as the distance from the center increases, and the strength can be maintained.

The fourth embodiment shown in FIG. 10 shows an example in which both the cutout 6 of the second embodiment and the arc-shaped portion 7 of the third embodiment are formed. It is suitable for measuring the weight, and four sides of the load receiving portion 1 extend outward to form an overhang portion 11. The overhang portion 11 has a structure that covers the upper surface of the base 2,
Due to the presence of the overhang portion 11, the area of the load receiving portion 1 is increased, and the weight of the wheel can be easily mounted especially when the wheel of the vehicle is mounted at the time of weight measurement. Also, there is no need to attach a protective cover or the like for the beam portion 3.

FIG. 12 shows a strain gauge. The strain gauge 4 has two resistance wires 41 and 42 at 45 ° on both sides with respect to the center line. All strain gauges 4
The resistance wires 41 and 42 are arranged such that the bridge becomes non-parallel due to a change in the resistance value of the resistance wires 41 and 42 when a load is applied, for example, as shown in FIG. A voltage is applied to the wires wired in this manner by the low voltage generator 9, and the potential difference due to the bridge non-parallelism caused by the change in the resistance value of the resistance wires 41 and 42 of the strain gauge 4 due to the load is amplified by the amplifier 10. It is converted into a load value through the digital converter 12 and the computer 13 and output to a display unit or the like (see FIG. 13). Here, the portion where the cross-sectional area of the base portion 2 becomes small, that is, the location of the notch portion 6 is set such that its width w ₁ is ｗ w
By setting it to ₂ , the cross-sectional area is halved. Further, the two beam portions 3 arranged on each side surface are symmetrical with respect to the center line at an interval of 3 / 4S ₂ with respect to the length S of the central portion side surface. It is preferable that the load receiving portion 1 is made of an aluminum alloy to reduce the weight. In the embodiment shown in FIG. 10, in order to measure the wheel weight of a large aircraft, the size of one wheel of the large aircraft, ie, L in FIG. 10, was set to 650 mm, and a maximum measured load of 30 tons was realized. The thickness of such an apparatus, that is, h in FIG. 11, could be reduced to 90 mm.

The results of the load test of the weight measuring apparatus of the embodiment shown in FIGS. 10 to 13 are shown in the following table.

[0022]

[Table 1]

〜 In the table are values when a load is applied to the positions 〜 in FIG. 10 respectively. In the table, “go” means increasing the load, and “return” means decreasing the load. The error is hysteresis. Although this device is thin and portable, it has a non-linearity of 0.02
% FS and hysteresis of 0.05% FS, and high accuracy of 0.15% in eccentricity error.
“FS” is the ratio to full scale.

[0024]

As described above, according to the present invention, the load receiving portion is formed in a hexagonal shape of a plane square, and the four outer surfaces of the load receiving portion and the four inner surfaces of the base oppose each other. Since at least two beam portions are provided between the side surfaces, the number of the beam portions is increased, and the height of the cross section of the beam portion can be reduced, and the whole can be thinned. In addition, since each beam between the outer surface of the load receiving portion and the inner surface of the base facing each other is symmetrical with respect to the center line of each side formed by the inner surface of the base, the lateral force is reduced. The strength of the device no longer varies depending on the direction of the force received,
The accuracy as a measuring device is also improved. In addition, the beam portion is 90 ° rotationally symmetric with respect to the center point of the load receiving portion, and even when the load point moves from the center point, symmetry is maintained in the distribution of the force acting on each component, and the eccentric error The directionality of occurrence is eliminated, and the eccentricity error can be reduced. In general, the entire device can be made thinner, and the measurement accuracy can be greatly improved.

Further, in the case of forming a cutout recessed inward at the center of each side of the inner surface of the base, even if the installation place has irregularities when the apparatus is set up, the cutout The presence of the portion does not adversely affect the distortion of the beam portion. Further, in the case where the arc-shaped portion which is depressed inward is formed on the side surface of the beam portion, the beam portion can maintain strength against a bending moment.

[Brief description of the drawings]

FIG. 1 is a plan view showing a first embodiment.

FIG. 2 is a front view of FIG. 1;

FIG. 3 is a plan view illustrating an unbalanced load according to the first embodiment.

FIG. 4 is a plan view showing a second embodiment.

FIG. 5 is a plan view showing a third embodiment.

FIG. 6 is a plan view of a beam.

FIG. 7 is a front view of a beam.

FIG. 8 is a plan view showing an example in which arcuate portions are formed on both side surfaces in the horizontal direction of a beam portion.

FIG. 9 is a front view of the beam shown in FIG. 8;

FIG. 10 is a plan view showing a fourth embodiment.

FIG. 11 is a front view of a half section of FIG. 10;

FIG. 12 is a resistance wiring diagram of a strain gauge.

FIG. 13 is a signal conversion block diagram of the device.

FIG. 14 is a plan view showing a conventional example.

FIG. 15 is a front view of FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Load receiving part 2 Base 3 Beam part 4 Strain gauge 1A-1D Outer side 2A-2D Inner side

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-315056 (JP, A) JP-A-1-21333 (JP, A) JP-A-2-52134 (JP, U) (58) Survey Field (Int.Cl. ⁷ , DB name) G01G 21 / 23,21 / 28 G01G 3 / 12,3 / 14 G01G 1/22

Claims (2)

(57) [Claims] A load receiving portion to which a load of an object to be measured is applied;
Surround the entire circumference of this load receiver at a predetermined interval and
A frame-shaped base on which the surface is placed at the measurement location, and the base and load
When the bottom of the base is connected to the
The beam part that makes the heavy receiving part float in the air, and the beam part
When a load is applied to the load receiving part
Measurement using a strain gauge to detect the strain generated in the beam part
In the device, the load receiving portion is formed in a flat square hexahedron, and the four external surfaces of the load receiving portion and the four internal surfaces of the base portion are connected to each other.
At least two beam portions are provided between the opposing side surfaces, and each side of the base portion forming the beam portion between the opposing side surfaces.
Provided symmetrically with respect to the center line of, In addition, a notch recessed inward at the center of each side of the base inside surface
Formed A weight measuring device characterized by the above-mentioned. 2. The weight measuring device according to claim 1, wherein an arc-shaped portion depressed inward is formed on a side surface of the beam portion.