JP2734495B2 - 6-axis load cell - 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 cell capable of simultaneously measuring six-axis loads, for use in a vibration test apparatus, a simulator for testing mobility, and the like.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view of a conventional vibration test apparatus. In the figure, reference numeral 7 denotes a vibration table, 8 denotes a cylinder, and 9 denotes a hydraulic piston mounted in the cylinder. The cylinder 8 and the hydraulic piston 9 support the shaking table 7 and
A vibration device for applying a vibration force to the vibration table is configured. 1
Reference numeral 2 denotes a test specimen, reference numeral 20 denotes a load cell supporting the test specimen on the vibrating table 7, and reference numerals 21 and 21 'denote resistance wire strain gauges attached to the side surfaces of the load cell 20.

This apparatus applies a vibrating force to a specimen 12 to measure a reaction force thereof, or uses a vibrating machine such as a rotary machine as a specimen to measure a force or a vibrating force generated by the machine. The vibration and the vibrating force are detected by the load cell 20. Normally, a conventional load cell can only measure loads in two axial directions, that is, the axial direction and the torsional direction.

[0004] By attaching a plurality of resistance wire type strain gauges 21 and 21 'to the cylindrical portion of the load cell, it is possible to measure the axial eccentric load and determine the triaxial or quadriaxial load. However, there is a great influence on accuracy due to gauge pitch errors and the like.

[0005] In any case, conventionally, forces Fx, Fy, and Fz in three orthogonal X, Y, and Z directions are obtained by one load cell.
Torsional moments Mx, My, Mz around these axes
It was not possible to measure the 6-axis load at the same time. Actually, the 6-axis load was measured by combining a plurality of load cells or measuring twice in two times using two types of load cells. Was.

[0006]

SUMMARY OF THE INVENTION The present invention relates to forces and moments about six axes, that is, forces Fx, Fy, Fz in three orthogonal X, Y, and Z directions, and torsional moments Mx, My, Mz around those axes. Is to provide a six-axis load cell capable of simultaneously measuring with high accuracy.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and relates to a six-axis load cell having the following features. (1) A pair of discs placed parallel to each other, both ends of which are connected to each other in the vicinity of the outer periphery of the pair of discs via a connecting member, and adjacent ones are inclined to opposite sides. 6
Book rod, means for detecting the strain of the rod provided on each of the rods, and a constant matrix determined from the geometric shape, dimensions, and material properties of the structure comprising the disk, the connecting member, and the rod Means for calculating forces and moments in three orthogonal axes directions from the detected strain values using (2) In the six-axis load cell according to the above (1),
Attach each end of two rods to one support member.

[0008]

[Action]

(1) Since the directions of the six-axis loads are all different from each other, the six-axis loads, that is, the forces Fx, Fy, and Fz in the three orthogonal X, Y, and Z directions are calculated from the forces applied to the six rods. Can be obtained through a 6-by-6 constant matrix. This matrix is determined by the geometric shape and dimensions of a structure including a disk, a support member, a rod, and the like, and this constant is obtained in advance by calculation or actual measurement. This calculation is performed using a computer. In the processing by the computer, a six-axis load is calculated from the strain of the rod. (2) The load cell can be made compact by attaching each end of the two rods to one support member.

[0009]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. In the drawing, 1 is an upper disk, 5 is a lower disk, 2 is a support member provided on the upper disk and the lower disk, and 3 is an upper disk and a lower disk connected by the same support member. Rods 4 and 4 are nuts for fixing the rod. Numeral 11 denotes a strain gauge attached to each rod. A 6-axis load cell is constituted by the parts denoted by the reference numerals 1 to 5 and 11. The other parts are the same as in the prior art.

In this load cell, three support members 2 each having a hemispherical shape and having screw holes for connecting rods 3 at two positions are attached to the upper disk 1, and three support members 2 are similarly attached to the lower disk 5. Is mounted. The support member 2 is arranged in a staggered manner with the upper disc 1 and the lower disc 5, and both ends of the rod 3 are simultaneously screwed into holes provided in the support member 2 in the vertical direction. The screwing of the support member 2 and the rod 3 can be simultaneously performed by reversing the screw directions of the screws to the right and left. After screwing, it is fixed firmly by nut 4. A strain gauge 11 is attached to each rod.

In the present embodiment, this load cell is
, And the specimen is mounted above it. Shaking table 7
Is vibrated by the hydraulic piston 9 and the cylinder 8. The reaction force of the specimen 12 attached to the load cell upper disk 1 at the time of excitation is transmitted to the rod 3 via the load cell upper disk 1 and the support member 2. From the forces acting on each rod measured by the strain gauges 11 attached to the six rods, a six-axis load is calculated. The calculation method is as follows.

Since the directions of the six-axis loads are all different, the six-axis loads can be obtained from the forces applied to the six rods. That is, the forces in the orthogonal X, Y, and Z axis directions are Fx, Fy, and Fz, the moments around the respective axes are Mx, My, and Mz, and the forces received by the six rods are represented by R _{1 to} R ₆ . And the 6-axis load is expressed by the following equation.

[0013]

(Equation 1)

In the above equation, {a} is a 6 × 6 constant matrix determined by the geometric shape and size of the load cell.
By calculating these constants in advance or as calibration data by actual measurement, by measuring R _{1 to} R ₆ , the load Fx, F of six axes is assisted by a computer.
y, Fz, Mx, My, and Mz can be obtained simultaneously.

FIG. 3 is a flow chart of a six-axis load calculation using a computer in the above embodiment. In the figure, S _{1 to} S ₆ are detection signals output from each strain gauge. In recent computers, there are cases in which the computer obtains the A / D conversion, the multiplexer, the operation, the display, and even the control output signal in some cases. FIG. 3 is a somewhat simplified representation, but in actuality, many signals are recorded and processed in addition to S _{1 to} S ₆ .

FIG. 4 is a longitudinal sectional view of a load cell according to another embodiment of the present invention, and FIG. 5 is a transverse sectional view of the same embodiment. This embodiment consists of a large diameter upper disc 1A and a lower disc 5A.
And a support member 2A.
Are arranged on the upper disk 1A and the lower disk 5A, respectively. By doing so, the upper disk 1
A and even if the diameter of the lower disk 5A is large, the rod 3A
Does not become long, so that the buckling strength when compressive load is applied is not reduced. Therefore, even when the strain gauge 11 is attached and the load applied thereto is measured using the stress, the accuracy does not decrease. Also, it is possible to prevent the rigidity of the entire six-axis load cell from being significantly reduced. Since the procedure and effects of calculating the six-axis load in the present embodiment are the same as those in the first embodiment, the description is omitted.

[0017]

According to the six-axis load cell of the present invention, a pair of disks placed in parallel with each other, and both ends of which are connected to each other in the vicinity of the outer periphery of the pair of disks via a connecting member and are adjacent to each other. Six rods which are inclined to the opposite sides to each other, means for detecting the strain of the rod provided on each of the rods, and the geometrical shape of the structure comprising the disk, the connecting member and the rods , Dimensions, and means for calculating the forces and moments in the three orthogonal directions from the detected strain values using a constant matrix determined from the material characteristics of each part. The load can be measured with high accuracy at the same time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a flowchart of a six-axis load calculation using a computer in the embodiment.

FIG. 4 is a longitudinal sectional view of another embodiment of the present invention.

FIG. 5 is a transverse sectional view of the embodiment.

FIG. 6 is a longitudinal sectional view of a conventional vibration test apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper disk 2 Support member 3 Rod 4 Nut 5 Lower disk 7 Shaking table 8 Cylinder 9 Hydraulic cylinder 11 Strain gauge 12 Specimen

Claims (2)

(57) [Claims] 1. A pair of discs placed in parallel with each other, both ends of which are connected to each other in the vicinity of the outer periphery of the pair of discs via connecting members, and adjacent ones are inclined to opposite sides. Six rods, means for detecting the strain of the rod provided on each of the rods, and the geometrical shape, dimensions, and material properties of each part comprising the disk, the connecting member, and the rod. A six-axis load cell comprising means for calculating forces and moments in three orthogonal directions from the detected strain values using a constant matrix obtained. 2. The six-axis load cell according to claim 1, wherein each end of two rods is attached to one support member.