JPH102812A - Load cell - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a load cell which has improved measurement accuracy, and at the same time, has realized downsizing and space saving. SOLUTION: A load applying part 1 located at a central part is connected to a fixing part 2 by a strain generating part 4 provided with a strain gauge 3, and an installation surface 11, which is formed on the fixing part 2, to a fixing side member,
12 is located near the neutral surface of the fixed part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a load cell which can be used for weighing articles and the like and which can provide high measurement accuracy.

[0002]

2. Description of the Related Art As shown in FIG. 11, a load applying portion 1 located at a central portion and a frame-shaped fixing portion 2 surrounding the load applying portion 1 are combined with a strain generating portion 4 to which a strain gauge 3 is attached. A conventional general attachment of a load cell connected to a stationary member to a fixed side member is as follows, as shown in FIG. For example, the fixing portion 2 is brought into direct surface contact with the base floor surface 6 and the fixing portion 2 is fastened and fixed with a bolt 8 inserted through a bolt hole 7 provided therein. Each of the bottom surface 5 and the counterbore surface tightened by the head of the bolt 8 functions as an installation surface of the fixing portion 2 and thus the load cell on the fixed member.

The load cell attached in this manner mainly deforms the strain-generating portion 4 when a vertical load W is applied to the load-applying portion 1, and detects the amount of deformation by the strain gauge 3. Thus, the weight placed on the load 1 can be measured.

[0004]

However, in such a load cell, it is substantially impossible to completely concentrate all deformations on the strain generating portion 4 when the load W is applied to the load applying portion 1. Normally, as shown schematically in a cross-sectional view in FIG. 12, compressive deformation occurs on the side of the load cell where the load W is applied from the neutral surface 9, and elongation deformation occurs on the opposite side. The neutral surface 9 bends and deforms in a direction protruding downward over the entire surface.

Here, the amount of such expansion and contraction of the load cell occurs in proportion to the applied load W, and a hysteresis occurs in the amount of deformation of the load W between an increase and a decrease. If there is no bolt, there is no particular problem, but in reality, the tightening of the bolt 7 causes a large space between the fixed part bottom surface 5 and the foundation floor surface 6 and between the bolt head and the counterbore surface. Friction forces are acting, and among them, among them, the friction force between the bottom surface 5 and the floor surface 6 remarkably hinders expansion and contraction and restoration as described above.
There is a disadvantage that the performance of the load cell with respect to linearity, reproducibility, and the like, and eventually, the measurement accuracy is reduced.

Therefore, conventionally, the tightening force of the bolts 8 has been increased in order to sufficiently restrict the above-described deformation of the fixing portion 2 and the displacement caused by the deformation and to improve the measurement accuracy of the load cell. Friction force (tightening force x friction coefficient)
To deal with it.

However, according to such a conventional technique, it is necessary to accurately control the tightening force of each bolt when mounting the load cell, and in addition to increasing the rated load of the load cell, The need to increase the bolt diameter and tightening force not only hinders the downsizing and space saving of the load cell, but also limits the tightening force by itself, resulting in a constantly high measurement. There was a problem that it was impossible to provide accuracy.

The present invention provides a load cell which advantageously solves the above-mentioned problems of the prior art.

[0009]

According to a load cell of the present invention, a fixed load member located at a central portion is connected to a fixed portion by a strain generating portion provided with a strain gauge, and formed on the fixed portion. The mounting surface of the load cell is located on or near the neutral portion of the load cell, and thus the load cell.

Here, a load cell of the type in which the fixed portion is attached to the fixed member by sandwiching the fixed portion from both the upper and lower directions, for example, has two upper and lower mounting surfaces to be sandwiched. Will be located near the neutral surface and substantially parallel to that surface in relation to the mounting strength of the device.

Further, a type in which the fixing portion is pressed or pulled toward the fixed side member under the action of, for example, a screw hole provided therein and attached to the fixed side member, and a fixing portion,
A load cell of the type mounted on a fixed-side member has one mounting surface in contact with the fixed-side member, and the mounting surface is preferably located on a neutral surface.

Among the load cells of the former type, in particular, the distance between the neutral surface and one of the mounting surfaces in contact with the fixed member is far greater than that of the prior art. For example, when the lower mounting surface is in contact with the upper surface of the fixed member, when the load is applied to the load portion, the force in the extension direction acting on the mounting surface can be sufficiently reduced. Since the mounting surface can be tightened and fixed to the fixed side member with bolts or the like, a small tightening force or the like effectively opposes the above-described force in the extension direction. Therefore, it is possible to effectively restrain the expansion and contraction deformation of each installation surface and to greatly improve the measurement accuracy of the load cell without requiring a large fastening force or the like to the fixing portion.

On the other hand, since the deformation of the installation surface can be effectively restrained with a small tightening force or the like, the size of the bolts can be reduced, the thickness of the fixing portion can be reduced, and the size can be reduced. In addition, space can be saved.

Further, in the latter type of load cell, in particular, by setting the fixing portion, and eventually the load cell on the fixed side member on the installation surface existing on the neutral surface, the load on the load cell is reduced. Even if a load acts on the part, the installation surface does not undergo any expansion or contraction deformation,
The load cell does not generate a frictional force that hinders its linearity, reproducibility, etc., so that the required tightening force and the like need not be large or small.
The entire load cell can be sufficiently reduced in size and space.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of the present invention with respect to the main part. Here, the entire configuration of the load cell is the same as that described in the related art, and the same components are denoted by the same reference numerals.

Here, the load supporting portion 1 located at the center is
Is connected to the fixing portion 2 by the strain body 4, a neutral surface of the fixing portion 2, and thus a neutral surface 9 of the load cell, is provided on the fixing portion 2 at a position corresponding to the portion where the bolt hole 7 is formed. , And upper and lower mounting surfaces 11 and 12 are provided in the drawing. Here, each of these installation surfaces 11 and 12 forms a recess bottom wall which is provided by being largely recessed from the upper and lower surfaces of the fixed portion 2, and is parallel to the neutral surface 9, preferably, It is located equidistant from its neutral plane 9.

By the way, the thickness t of the thin portion between the two mounting surfaces
Are the shear forces and bending moments acting upon the application of a load to the load support 1 and the two mounting surfaces 1
It is preferable that the load cell is made as thin as possible in consideration of external forces such as bolt tightening force and the like in addition to the forces in the expansion and contraction directions acting on the load cells 1 and 12 as long as the required mounting strength of the load cell can be obtained.

Here, each mounting surface 1
The thick portion of the fixed portion 2 that surrounds the positions 1 and 12 is
It functions to sufficiently reinforce the thin portion between the installation surfaces and to provide the required strength to the entire fixing portion. Therefore, when the thin portion can provide sufficiently high strength by itself, the fixing portion 2 can be made a thin portion over the entirety.

When the load cell having such a structure is mounted on the fixed member, a projection 21 projecting upward from the mounting base 19 is integrally formed on the mounting base 19, and the height of the projection 21 is shown in FIG. As described above, the load cell is supported by bringing its top surface into contact with the lower installation surface 12 so as to protrude slightly downward from the lower recessed portion 14. Bolt 16 penetrating from above into the thin portion 15 between the respective mounting surfaces of the load cell placed on
Of the thin portion 15 by tightening the thin portion 15 into the female screw portion formed on the protrusion 21, the protrusion 21 and the bolt head 16 a
Can be carried out by clamping with a required strength.

According to such a mounting mode of the load cell, since the respective mounting surfaces 11 and 12 are located sufficiently close to the neutral surface 9, a load acts on the load supporting portion 1 as described above. In this case, the expansion and contraction deformation of the installation surfaces 11 and 12 can be effectively prevented by the small tightening force of the bolt 16, and the measurement accuracy of the load cell can be greatly improved. Therefore, here, it is possible to sufficiently cope with the increase in the rated load of the load cell without increasing the bolt diameter, the tightening force, etc., and to effectively realize the downsizing and space saving of the load cell. it can.

Here, it is preferable that the relative relationship between the contact area of the bolt head 16a on the installation surface 11 and the contact area of the hollow spacer 13 on the installation surface 12 is substantially the same. Also, it is preferable to provide a slight gap between the peripheral surface of the bolt head 16a and the respective outer peripheral surfaces of the protrusions 21 and the respective concave peripheral walls of the upper concave portion 18 and the lower concave portion 14. According to this, bolt 1
6, the bolt head 16a and the protrusion 21 come into contact with the recessed peripheral wall upon elastic deformation such as extension deformation of the protrusion 6, compression deformation of the protrusion 21 and bending deformation of the fixing portion 2, and there is no need to cause performance degradation there. The occurrence of excessive friction can be sufficiently prevented.

The mounting of the load cell having such a structure to the fixed side member is performed, for example, by placing the load cell on the base floor 6 and lowering the top surface of the hollow spacer 13 constituting a part of the fixed side member. In a state in which the load cell is lifted and supported by the hollow spacer 13 having a height higher than the depth of the lower recessed portion 14, and is passed through the thin portion 15 and the hollow spacer 13 between the respective mounting surfaces. The thin bolt 15 is screwed into a female screw member 17 or the like provided on the foundation floor, so that the thin portion 15 has a required strength between the hollow spacer 13 and the bolt head 16a that has entered the upper concave portion 18. It can be performed by pinching.

FIG. 2 is a cross-sectional view showing another mounting mode of the load cell. The mode shown in FIG.
The top surface of the hollow spacer 13, which is placed on the base floor surface 6 and forms a part of the fixed side member, is brought into contact with the lower mounting surface 12, and the hollow spacer 13 is higher than the depth of the lower recess 14. While the load cell is lifted and supported by the spacer 13, the thin portion 15 and the hollow spacer 1 between the respective mounting surfaces are provided.
3 is screwed into a female screw member 17 or the like provided on the foundation floor, and the thin portion 15 is screwed into the hollow spacer 13 and the bolt head 16 that has entered the upper recess 18.
a with the required strength.

In the embodiment shown in FIG. 2 (b), a bolt 16 penetrating the mounting base 19 from below is inserted into each of the hollow spacer 13 and the thin-walled bolt hole. By screwing the nut 20 to the tip of the
And the hollow spacer 13 with a required strength.

According to the above-described mounting mode,
Since the two mounting surfaces 11 and 12 are located close to the neutral surface 9, the same operation and effect as described with reference to FIG. 1 can be obtained.

In these mounting modes, since the hollow spacer 13 is separate from the base floor 6 or the mounting base 19, the lower surface of the spacer 13 and the base floor 6
Alternatively, there may be concerns about the occurrence of problems related to frictional force between the mounting base and the surface, as described in the prior art, but according to the results of actual tests, linearity, reproducibility, etc. Could provide much better performance than the prior art.

That is, the hollow spacer 13 has physical properties that make it easier to compress and deform as compared with the fixing portion 2, the foundation floor 6, and the like. The spacer 13 is not displaced with respect to the floor 6 or the like,
It is considered that the energy caused by the bending deformation was absorbed by its own elastic deformation.

By the way, as shown in FIG. 3, the configuration of the load cell is such that the planar shape of the load applying portion 1 is circular and the planar shape of the fixing portion 2 is an annular shape surrounding the load applying portion 1. Further, a bolt hole 7 may be provided in the annular fixing portion 2 on an extension of the center axis of the strain body 4, and as shown in FIG. 4, the inside of the fixing portion 2 having a substantially rectangular frame shape. In addition, the strain applying portion 4 extending in the diagonal direction of the fixing portion 2 enables the load applying portion 1 also having a rectangular shape.
Can be connected in a posture displaced by 90 ° with respect to the fixing portion 2 and a bolt hole 7 can be provided at a corner of the fixing portion 2. Further, as shown in FIG. 3, a load applying portion 1 and a fixed portion 2 similar to those shown in FIG. 3 are connected by a thin annular strain-generating portion 4, and a plurality of strain gauges 3 are provided on the upper and lower surfaces of the strain-generating portion 4. In any of these, by forming the mounting surfaces 11 and 12 as described above, the same operation and effect as described above can be obtained.

In these load cells, the planar contours of the load applying portion 1 and the fixing portion 2, the position and number of strain generating portions 4, the mounting position and the number of strain gauges 3, and the like are appropriately changed as required. be able to.

FIGS. 6 to 8 are views each showing another form of load cell on the beam as a whole. The load cell shown in FIG. 6 is a load load section having a centrally located upward projection 22. 1 is a strain-generating portion 4 located on both sides thereof.
In addition to being integrally connected to each fixing portion 2, each fixing portion 2 is provided with a bolt hole 7 located on the center axis in the width direction of the fixing portion 2, and at a position corresponding to a portion where the bolt hole 7 is formed, The same mounting surface 11, as in the above case,
12 are provided. Here, the strain gauge 3 of the strain-generating portion 4 is attached to the wall surface of a through-hole 4a provided in the strain-generating portion 4 in the vertical direction by sticking or the like.

Such a load cell is mounted under the action of the respective mounting surfaces 11, 12 located sufficiently close to the neutral surface 9, for example, by attaching it to the base floor 6 as described with reference to FIG. The same operation and effect as described above can be obtained.

The load cell shown in FIG.
In the strain-generating portion 4, horizontal gouges 4b are formed on both side surfaces thereof, and a strain gauge 3 is attached to a remaining gouge end wall 4c located in the center in the width direction. The configuration is the same as that shown in FIG.

Further, in the load cell shown in FIG. 8, the protruding portion 22 is omitted from the load applying portion 1, and the strain generating portion 4 has a substantially H-shaped profile penetrating from one side surface to the other side surface thereof. And a strain gauge 3 is attached to the upper and lower outer surfaces of the strain-generating portion 4. Here, the strain gauge 3 can be attached to the upper and lower inner wall surfaces of the horizontal hole 4d. In any of these load cells, the required functions and effects can be sufficiently exhibited based on the functions of the respective mounting surfaces 11 and 12.

FIG. 9 is a vertical sectional view of a main part showing another configuration of the installation surface.
At a required fixing point of the fixing portion 2 connected by the fixing portion 2, a recess portion 23 which is recessed from the lower surface side of the fixing portion 2 is provided, and an installation surface 24 forming a bottom wall of the recess portion 23 is attached to the neutral surface 9. It is located above.

The mounting of such a load cell is performed, for example, as shown in FIG.
Under the support, the distal end portion of the bolt 16 inserted into each of the mounting base 19 and the hollow spacer 13 from below is screwed into the female screw portion formed in the fixing portion 2, whereby the mounting surface 24 is This can be performed by pulling and fixing to the hollow spacer 13 with a required force. According to this, the load cell is attached to the fixed member on its neutral surface.

Accordingly, in this case, when the load is applied to the load applying portion 1, any deformation of the installation surface 24 does not occur in any of the expansion and contraction. For this reason, the load cell is attached to the fixed member with a small tightening force. Generation of unnecessary frictional force can be sufficiently prevented, and the measurement accuracy of the load cell can be greatly improved.

As shown in the figure, the hollow spacer 13 can be formed integrally with the mounting base 19, and in this case, a more excellent effect can be obtained.

FIG. 10 is a partial cross-sectional side view showing another form of the load cell, which is provided on the base floor surface 6 by a protruding support member 25 as a part of a fixed side member. This supports the installation surface 26 located on the upright surface 9, and according to this, the fixed portion 2 can be installed on the fixed side member by a bolt or the like without being fixedly fastened to the fixed side member. Also, the same operation and effect as those shown in FIG. 9 can be obtained.

FIG. 10 (b) shows a structure in which a climbing platform 27 is integrally formed on the projecting support member 25 in order to make it easier for a vehicle or the like to climb on the load cell.

[0040]

Thus, according to the present invention, in particular, the mounting surface for the fixed side member, which is provided on the fixed portion of the load cell, is positioned on the fixed portion, and thus on or near the neutral surface of the load cell. By doing so, the measurement accuracy of the load cell can be greatly improved, and at the same time, downsizing of the load cell and the accompanying space saving can be effectively realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing one embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing another mounting mode.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing another embodiment of the present invention.

FIG. 5 is a view showing still another embodiment of the present invention.

FIG. 6 illustrates another type of load cell embodiment.

FIG. 7 is a diagram showing another embodiment.

FIG. 8 is a diagram showing still another embodiment.

FIG. 9 is a cross-sectional view of a main part showing another configuration of the installation surface.

FIG. 10 is a partial sectional side view showing still another embodiment.

FIG. 11 is a diagram showing a conventional structure.

FIG. 12 is a cross-sectional view illustrating a deformed state of the load cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Load application part 2 Fixed part 3 Strain gauge 4 Strain generating part 4a Through hole 4b Horizontal gouge part 4c Uncut end wall 4d Horizontal hole 6 Foundation floor surface 7 Bolt hole 9 Neutral surface 11, 12, 24, 26 Installation surface 13 Hollow spacers 14, 18, 23 Depressed portion 15 Thin portion 16 Bolt 16a Bolt head 17 Female screw member 19 Mounting base 20 Nut 21,22 Projection 25 Projection support member 27 Riding ramp 27 Thickness of thin portion

Claims (1)

[Claims] 1. A load-bearing portion located at a central portion is connected to a fixed portion by a strain-causing portion provided with a strain cage, and an installation surface for a fixed-side member formed on the fixed portion is provided inside the fixed portion. A load cell located on or near an elevation.