JP2000329611A - Load-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin measuring apparatus having a high measurement accuracy, by setting a strain-detecting means for detecting a strain in a longitudinal direction of a load cell and a frame body having a projecting part for supporting the strain-generating body from the opposite side to a load stage, and constituting a supporting member of an elastic body. SOLUTION: A load cell 3 has uniaxial type strain gages 4 attached to the center in a longitudinal direction of an upper and a lower faces of a long body. A reference line of the strain gages 4 agrees with the longitudinal direction of the load cell 3. When a distributed load by an object to be measured acts to a top plate 1, the load is transmitted from two load points 2 to the load cell 3. The load points 2 are constituted of an elastic body. The load cell 3 and top plate 1 are freely supported via the elastic bodies. A size of a moment acting to the load cell 3 becomes a constant value determined by a load irrespective of a contact area of a load face where the object is placed. A stable load output can be obtained by placing the object so that the center of gravity is positioned to the center of the top plate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an object to be measured, such as a truck or a gas cylinder on which a load is loaded, is mounted on the load table from an end of the load table, and the object is measured using a strain gauge. The present invention relates to a load measuring device for measuring the weight of a load.

[0002]

2. Description of the Related Art FIG. 14 is a schematic view showing the structure of a load measuring device 20 using a conventional one-point support load cell. The load measuring device 20 has a frame-shaped strain body 21A having four thin portions 21k. Load cell 21 composed of
A strain gauge 21 attached to the upper surface and the lower surface of the thin portion 21k for detecting the bending of the strain body 21A in the longitudinal direction.
s and a mounting portion 2 for fixing one end of the load cell 21
2 and a plate-shaped load table 25 connected to the other end of the load cell 21 at the joint 24 and for mounting an object to be measured. The weight of an object to be measured, such as a trolley or a gas cylinder, is measured. The load cell 21 has a cantilever structure,
The strain gauge 21s detects the amount of strain of the strain body 21A that bends and deforms due to the load placed on the tower 5 by using the strain gauge 21s.
From the amount of strain and the size and Young's modulus of the strain body 21A,
The load on the object to be measured can be obtained by calculating the moment acting on the strain generating body 21A from the object to be measured mounted on the load table 25.

[0003]

However, in the above-described conventional load measuring device, the load cell 21 is configured such that the strain body 21A is formed so as to increase the amount of strain while maintaining strength.
Has a problem that the thickness of the load measuring device is increased because the cross section of the frame has a frame structure. Further, when the object to be measured is mounted on the load table 25, even if the center of gravity of the object to be measured is concentrated on one end of the load table 25 and a large moment acts, the load table 25 and the load cell 21 only withstand it. Since the thickness of the load table 25 and the strain body 21A is increased so as to have the strength described above, there is a problem that the apparatus is further increased in size.

The present invention has been made in view of the conventional problems, and an object of the present invention is to provide a load measuring apparatus which is thin and has high measuring accuracy.

[0005]

According to a first aspect of the present invention, there is provided a load measuring device which is joined to the load table via a load table on which an object to be measured is mounted and a support member serving as a load point of the load table. Elongate flexure element, strain detection means for detecting longitudinal strain of the flexure element, a frame for accommodating the flexure element and the flexure element from the side opposite to the load table. A frame having a supporting projection, and the supporting member is formed of an elastic body, and the amount of distortion of the strain-generating body caused by the load of the object to be measured is detected by the distortion detecting means, and the object to be measured is detected. Is to measure the load.

According to a second aspect of the present invention, in the load measuring device, the protrusion is formed of an elastic body.

According to a third aspect of the present invention, the load measuring device comprises the frame portion made of an elastic body.

According to a fourth aspect of the present invention, the external dimensions of the load table are made larger than the internal dimensions of the frame.

According to a fifth aspect of the present invention, the elasticity of the supporting member has a hardness of 50 or more.

According to a sixth aspect of the present invention, at least one of the frame portions is provided with a tapered portion.

[0011] The load measuring device according to claim 7 is 100
A load measuring device capable of measuring a load up to kg, wherein a thickness from the bottom of the frame to the upper surface of the load table is 25 mm or less.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing a configuration of a load measuring device 10 according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. The load measuring device 10
A flat load table (hereinafter referred to as a top plate) 1 on which an object to be measured, such as a trolley or a gas cylinder on which luggage is mounted, is mounted.
On the lower surface side of the top plate 1, load points 2 and 2 made of a pair of block-shaped elastic bodies
Two elongate flexure elements 3, 3 which are freely supported by the top plate 1 and are installed at predetermined intervals in parallel with each other, and upper and lower surfaces of each of the flexure elements 3, 3 A strain gauge 4 which is a strain detecting means for detecting a strain in the longitudinal direction of the strain body and a convex portion 5 made of a block-shaped elastic body which supports both ends of the strain body 3. And a frame 6 provided. Note that neoprene rubber having a hardness of JIS Shore A65 is used as the elastic body constituting the load points 2 and 2.
Reference numeral 7 denotes a connection board for relaying the lead wire 4s of the strain gauge 4 and a measurement cable 7s from a strain detection circuit (not shown). Reference numeral 8 denotes a cable fitting provided on the frame 6 for holding the measurement cable 7s. is there.

FIG. 3 is a view showing the structure of the frame body 6 (a).
The drawing is a plan view, and the drawing (b) is a sectional view taken along the line AA of the drawing (a). The frame body 6 is provided with a bottom plate 6a in which four block-shaped convex portions 5 for supporting the strain body 3 respectively are provided symmetrically, and is provided around the bottom plate 6a. A frame main body 6A including a frame portion 6b for housing a body, and a frame-shaped outer peripheral portion 6B formed integrally with the frame main body 6A on the outer periphery of the frame main body 6A and having a height slightly lower than the frame main body 6A. ,
A climbing portion 6C is provided on one of the lengths of the flexure elements 3 and 3 of the outer peripheral portion 6B and has a slope portion 6k for guiding an object to be measured to the top plate 1. The cable fitting 8 is attached to a surface of the frame body 6A perpendicular to the riding portion 6C. As shown in FIG. 3B, nuts 5n for connecting both ends of the flexure element 3 and the protrusions 5 are embedded in the block-like protrusions 5, and the nuts 5n of the bottom plate 6a are embedded therein. A recess 6p for inserting a bolt is provided in a portion corresponding to the screw hole. In the present embodiment, the frame body 6A,
The outer peripheral portion 6B and the riding portion 6C are integrally formed of neoprene rubber having a hardness of JIS Shore A80-90. A seal member 6D for preventing water or dust from entering the frame portion 6b is inserted into a step between the outer peripheral portion 6B and the frame body 6A.

As shown in FIGS. 4 (a) and 4 (b), the flexure element 3 is provided at the longitudinal center of the upper surface 3a and the lower surface 3b for measuring the amount of distortion of the flexure element 3 in the longitudinal direction. It is a long flat plate to which uniaxial (bending) type strain gauges 4 and 4 are adhered, and the strain gauges 4 are adhered so that the adhesion axis Z thereof coincides with the longitudinal direction of the strain generating element 3. . At both ends of the flexure element 3, through holes 3p for inserting bolts 5m screwed into nuts 5n embedded in the block-shaped protrusions 5 are provided.
Is provided, and the strain body 3 and the frame 6 are joined by the bolt 5m and the nut 5n (see FIG. 2). Further, a pair of block-shaped load points 2 are provided at a predetermined distance inside the through-hole 3p, and the load points 2 are used to connect the strain generating element 3 and the top plate 1. Of the nut 2n at the load point 2 is provided with a hole 2p below the screw hole.

The top plate 1 is shown in FIGS.
As shown in the figure, a flat plate having a countersunk hole 1p for inserting a countersunk screw provided at a position corresponding to the nut 2n of the load point 2, the top plate 1, the strain bodies 3, 3 As shown in FIG. 2, as shown in FIG. 2, the lower surface is joined by a countersunk screw 2 m and a nut 2 n so that the lower surface is higher than the upper surface of the frame body 6 </ b> A by a predetermined interval. The outer dimensions of the top plate 1 are designed to be larger than the outer dimensions of the frame body 6A of the frame body 6 and slightly smaller than the outer dimensions of the outer peripheral portion 6B.

Next, the steady operation of the load measuring device 10 having the above configuration will be described. Assuming that a distributed load due to the object to be measured acts on the top plate 1, as shown in FIG.
The above load is applied to the flexure element 3 from the two load points 2 and 2.
When the object X is placed substantially at the center of the top plate 1, the force P transmitted to the strain body 3 is independent of the width w of the distributed load of the object X. , 2 above
The load points 2 and 2 have the same size. Here, in the case of the fixed support in which the load points 2 and 2 are made of a rigid body such as a metal, the moment M acting on the strain element 3
Depends on the width w of the distributed load. That is, when the width w of the distributed load is small, as shown in FIG. 7 (a), a large moment M _1, the width w of the distributed load
When it is large, as shown in FIG. 7 (b), a moment M ₂ decreases. On the other hand, in the load measuring device 10 of the present embodiment, the load points 2 and 2 are formed of an elastic body, and the strain generating body 3 and the top plate 1 are configured to freely support each other via the elastic body. Therefore, the moment M ₃ when the width w of the distributed load is small as shown in FIG.
The magnitude of the moment M ₄ when the width w of the distributed load is large as shown in FIG.

That is, when the strain body 3 and the top plate 1 are fixedly supported, even if the object to be measured is placed at the center of the scale (the center of the top plate 1), the width w of the distributed load, In other words, when the contact area of the tower mounting surface of the object to be measured is different, the magnitude of the moment M acting on the flexure element 3 changes, so that the magnitude of the strain generated in the flexure element 3 changes. Therefore, the value of the load output detected by the strain gauge 4 also changes, and the load on the object to be measured cannot be measured stably. On the other hand, when the load points 2 and 2 are made of an elastic body and the flexure element 3 and the top plate 1 are freely supported, the magnitude of the moment M acting on the flexure element 3 is measured. Regardless of the contact area of the object on the tower mounting surface, it is almost constant value determined by the load,
A stable load output can be obtained. That is, if the object to be measured is mounted so that the center of gravity is located at the center of the top plate 1, the tower of the object to be measured can be used even if the simple strain-generating body 3 made of a long plate as described above is used. Regardless of the mounting surface contact area,
The load on the object to be measured can be measured stably and accurately.

It should be noted that the strain amount ε = Δl / l of the flexure element 3 is:
The measurement is performed by a known bridge circuit as shown in FIG.
That is, the upper surface 3a and the lower surface 3b of one strain body 3 having one side
Strain gauges 4 with resistance values of R ₁₁ and R ₁₂
a, 4b, and the other side is adhered to the upper surface 3a and the lower surface 3b of the other flexure element 3, respectively, and the resistance value is R ₂₁ , R
_A bridge circuit composed of a series circuit of ₂₂ strain gauges 4c and 4d is formed. The voltage applied to both ends A and B of the bridge circuit is V ₀ , the length of the strain body 3 is 1 and the amount of elongation is Δl. Then, the strain gauges 4a and 4b and the strain gauge 4
The output difference V between the connection points C and D of c and 4d is V = (ΔR /
R) V ₀ = 2εV ₀ Therefore, a moment M acting on the strain element 3 is calculated based on the strain amount ε and the size and Young's modulus of the strain element 3, and the moment M
From this, the load of the object to be measured can be obtained.

As shown in FIG. 10 (a), the object to be measured X such as a trolley or a gas cylinder loaded with luggage is mounted on the top plate 1 from the slope 6k provided on the climbing portion 6C of the frame 6 as shown in FIG. It rests on the edge and then moves to the center of the top plate 1. When the object to be measured X is placed on the top plate 1, a load acts on the end of the top plate 1, so that the top plate 1 bends. However, the load measuring device 10 according to the present embodiment uses the top plate 1. Is larger than the outer dimension of the frame portion 6b of the frame body 6A, and when the top plate 1 is bent downward, as shown in FIG. The outer peripheral portion 6B of the frame body 6A is brought into contact with the outer peripheral portion 6B. That is, since the outer peripheral portion 6B side of the frame main body 6A is configured to function as a stopper against bending (displacement downward) of the top plate 1, when the object X is placed on the top plate 1, , Top plate 1 and strain body 3
Can be limited. At this time, the sealing member 6D is
And the frame body 6 </ b> A is not crushed by the bending of the top plate 1.

Assuming that the distance between the load point 2 and the load load point K is L and the force exerted on the top plate 1 of the object to be measured is P, M = P near the load point of the top plate 1.
・ Because the moment of L is generated, it has strength to withstand it, that is, a thick top plate was required,
By setting the gap t between the top plate 1 and the frame body 6A to an appropriate value, the load load point K can be adjusted to the top plate 1
Moment M at the end of the top plate 1
In this case, the end of the top plate 1 contacts the seal member 6D of the outer peripheral portion 6B and no further force is applied. Therefore, it is not necessary to increase the thickness of the top plate 1 and the strain body 3 to increase the strength. The top plate 1 and the strain body 3 can be made thin, and the load measuring device 10 can be made thin.
The weight can be reduced. For example, when a load measuring device capable of measuring a load of up to 100 kg is constituted by a conventional load cell type, the thickness of the measuring section (height to the top plate upper surface) is about 50 mm or more in order to secure strength. In contrast, the load measuring device 10 of the present embodiment can reduce the thickness to about 25 mm or less. Also, by making the load measuring device 10 thin, the slope portion 6k
Since the height of the climbing portion 6C having the slope can be reduced and the gradient of the slope portion 6k can be reduced, the object to be measured can be more easily mounted on the top plate. The deformation of the top plate 1 can be limited by the frame body 6A without the outer peripheral portion 6B and the sealing member 6D. However, by providing the outer peripheral portion 6B and the sealing member 6D, the top plate 1 and the Since contact with the frame 6b of the main body 6A is avoided, the durability of the frame main body 6A is improved.

Further, the load measuring device 10 of the present embodiment
Since the entire frame 6 is made of an elastic body, as shown in FIG. 11, even if there is some unevenness or undulation on the surface Y on which the load measuring device 10 is installed, the elastic body is deformed. Since the influence of the irregularities and undulations is absorbed, the flexure element 3
Unnecessary deformation can be prevented, and stable load measurement can be performed.

As described above, in the present embodiment, the load measuring device 10 includes the top plate 1 on which the object to be measured is mounted,
Strain-generating body 3 composed of a long flat plate to which a strain gauge 4 is attached
Are connected by the load points 2 and 2 made of an elastic body, and the strain generating element 3 is freely supported by the top plate 1. Therefore, the magnitude of the moment M acting on the strain generating element 3 is It can be a constant value regardless of the contact area of the measured object on the tower mounting surface. Therefore, it is possible to measure the load of the object to be measured stably and accurately.

In the above embodiment, both ends of the flexure element 3 are supported by the block-shaped projections 5, and inside the flexure element 3, are freely supported by the load points 2 and 2 made of an elastic body. The deformable body 3 is configured to be deformed so as to protrude downward. However, as shown in FIG. 12, both ends of the deformable body 3 are supported by the load points 2 and 2, and a block shape is formed on the inner side. The flexure element 3 may be supported by the convex portion 5 of the above, and may be configured to deform so that the flexure element 3 becomes convex upward during measurement.

In the above example, neoprene rubber having a hardness of JIS Shore A65 is used for the load points 2 and 2;
The frame 6 was formed of neoprene rubber having a hardness of JIS Shore A 80 to 90, and the hardness at the load point 2 was J.
If the IS Shore A is 50 or more, the flexure element 3 and the top plate 1 can be sufficiently freely supported. If the hardness of the frame 6 is also JIS Shore A50 or more, it is possible to absorb the influence of unevenness and undulation while maintaining the strength of the frame 6. Further, in the above example, the entire frame 6 is made of an elastic body,
Although the influence of the unevenness and undulation on the installation surface is absorbed, the effect of the unevenness and undulation can be absorbed even if only the block-shaped convex portion 5 is formed of an elastic body.

Further, in the above example, the strain gauge 4 is stuck to the center of the strain body 3, but as shown in FIG. Between the portion corresponding to the block-shaped convex portion 5 excluding the section C (section A in the same figure) and the position corresponding to the block-shaped convex portion 5 outside (section a in the figure). Any position may be used as long as it is located, and any portion may be provided between the block-shaped convex portions 5 (section B in the drawing) on the lower surface of the flexure element 3.

[0026]

As described above, according to the first aspect of the present invention, the load table on which the object to be measured is mounted and the load table via the support member serving as a load point of the load table are connected. Along with a long strain body that is joined and provided with a strain detection means, the support member is configured by an elastic body,
Since the flexure element is freely supported, the magnitude of the moment acting on the flexure element can be kept constant regardless of the contact area of the tower mounting surface of the measurement object, and the load of the measurement object can be increased. Can be measured stably and accurately.

According to the second aspect of the present invention, since the projection is made of an elastic body, even if the installation surface has some irregularities or undulations, the elastic body is deformed due to the irregularities or undulations. Since the influence is absorbed, unnecessary deformation of the flexure element can be prevented, and stable load measurement can be performed.

According to the third aspect of the present invention, since the frame portion is made of an elastic body, it is possible to more reliably absorb the influence of unevenness or undulation on the installation surface.

According to the fourth aspect of the present invention, the outer dimensions of the load table are larger than the inner dimensions of the frame.
If the load table is deformed downward when the object to be measured is placed on the load table, the frame section serves as a stopper, and the magnitude of the force and moment acting on the load table and the strain element may be limited. As a result, the thickness of the load table and the flexure element can be reduced.

According to the fifth aspect of the present invention, the elastic body constituting the support member has a hardness of 50 or more. Can be freely supported.

According to the sixth aspect of the present invention, since at least one of the frame portions is provided with the tapered portion, the object to be measured can be easily mounted on the top plate.

[0032] According to the invention of claim 7, according to claim 1 of the present invention.
According to the configuration, a load of up to 100 kg can be measured, and the thickness from the bottom of the frame to the upper surface of the load table can be set to 25 mm or less, so that a high-performance and compact load measuring device can be obtained. Can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing a load measuring device according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a load measuring device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a frame according to the present embodiment.

FIG. 4 is a diagram showing a configuration of a strain body according to the present embodiment.

FIG. 5 is a diagram showing a configuration of a top plate according to the present embodiment.

FIG. 6 is a view for explaining deformation of a flexure element.

FIG. 7 is a diagram illustrating a relationship between a distributed load and a moment at a fixed support.

FIG. 8 is a diagram showing a relationship between a distributed load and a moment in free support.

FIG. 9 is a diagram illustrating a method for measuring a distortion amount.

FIG. 10 is a diagram showing a state of the top plate when the object to be mounted is placed on an end of the top plate.

FIG. 11 is a diagram showing a relationship between a frame of the load measuring device and an installation surface.

FIG. 12 is a view showing another example of the load measuring device of the present invention.

FIG. 13 is a view showing a position where a strain gauge is attached.

FIG. 14 is a diagram showing a configuration of a conventional load measuring device.

[Explanation of symbols]

1 top plate, 2 load points, 3 strain body,
4a, 4b strain gauge, 5 block-shaped projection, 6
Frame, 6A Frame main body, 6a Bottom plate, 6b Frame, 6B
Outer peripheral part, 6C riding part, 6k slope part, 6D seal member, 10 load measuring device.

Claims (7)

[Claims] 1. A load table on which an object to be measured is mounted, an elongated strain body joined to the load table via a support member serving as a load point of the load table, A strain detecting means for detecting a strain in the longitudinal direction, a frame having a frame for accommodating the strain generating body and a projection having a projection for supporting the strain generating body from the side opposite to the load table, A load measuring device, wherein the support member is formed of an elastic body. 2. The load measuring device according to claim 1, wherein said projection is made of an elastic body. 3. The load measuring device according to claim 1, wherein said frame portion is made of an elastic body. 4. The external dimensions of the load table are made larger than the dimensions inside the frame portion.
The load measuring device as described. 5. The load measuring device according to claim 1, wherein the hardness of the elastic body constituting the supporting member is 50 or more. 6. The load measuring device according to claim 1, wherein at least one of the frame portions is provided with a tapered portion. 7. A load measuring apparatus capable of measuring a load up to 100 kg, wherein the thickness from the bottom of the frame to the upper surface of the load table is 25 mm or less. measuring device.