JPH0676932B2 - Load detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a load detector for detecting a load (force, moment) acting on an object.

[Conventional technology]

There are various types of load detectors, and among them, the load detector using the parallel flexible beam structure proposed in Japanese Patent Laid-Open No. 61-57825 has excellent characteristics. Such a load detector will be described with reference to the drawings.

4 (a), (b) and (c) are side views of the parallel flexural beam structure. In the figure, X, Y, and Z indicate coordinate axes (Y axis is a direction perpendicular to the paper surface). Reference numerals 1 and 2 are rigid portions, and reference numerals 3 and 3 ′ are thin portions that connect the rigid portion 1 and the rigid portion 2. The thin portions 3 and 3'have a flat plate shape and are arranged in parallel with each other. The rigid body parts 1 and 2 and the thin wall parts 3 and 3'constitute a parallel flexible beam structure 4. The parallel flexible beam structure 4 is formed by forming a rectangular through hole 5 in the Y-axis direction in one rigid block. Reference numerals 6a to 6d denote strain gauges attached to the thin wall portions 3 and 3'in the vicinity of the connecting portions with the rigid body portions 1 and 2. Reference numeral 7 is a fixed portion to which the rigid body portion 1 is fixed.

The rigid part 2 of this parallel flexure beam structure 4, when the action of the Z-axis direction force F _2, parallel flexure beam structure 4 by the deformation of the thin-walled portions 3,3 ', Fig. 4 (b) It deforms as shown in. When a moment M _Y about the axis in the Y-axis direction is applied to the rigid body portion 2, the parallel flexible beam structure 4 is deformed as shown in FIG. 4 (c) due to the deformation of the thin wall portions 3 and 3 '. . Although not shown, the parallel flexible beam structure 4 is also deformed when a moment about the X-axis direction of the rigid body portion 2 is applied. The strain gauges 6a to 6d at the respective portions are expanded and contracted in accordance with these deformations, and the resistance value is changed accordingly. Therefore, if the locations where the strain gauges are attached are selected and an appropriate electric circuit is constructed by these strain gauges, the magnitude of the force or moment can be detected by the output of the electric circuit. Then, by appropriately combining such parallel flexible beam structures 4,
A load detector capable of detecting all the forces in the X, Y and Z axes and the moments around the X, Y and Z axes can be constructed.

Japanese Patent Laid-Open No. 61-57825 discloses such a load detector. This will be briefly described with reference to FIG.
FIG. 5 is a perspective view of a conventional load detector. X, Y, Z in the figure
Indicates a coordinate axis passing through the center of this load detector. Reference numeral 10 is a central rigid body portion, 11A and 11B are projecting portions that project from the central rigid body portion 10 in the Y axis direction, and 11C and 11D are projecting portions that project from the central rigid body portion 10 in the X axis direction. 12a to 12d are each overhanging part
11A and 11B show a peripheral rigid body portion which is an end portion of 11A to 11D. Each overhanging part 11
A parallel flexible beam structure 4 shown in FIG. 4 (a) is formed in A to 11D. Reference numeral 13 is a through hole formed along the Z axis at the center of the central rigid body portion 10. A rectangular through hole is formed from an intermediate portion of adjacent ones of the overhang portions 11A to 11D to the through hole 13, whereby four parallel flexible beam structures 4 are formed in the central rigid body portion 10. 14 is the peripheral rigid body part 12
Reference numeral 15 is an annular body connected to c and 12d, and 15 is an annular body connected to the peripheral rigid body portions 12a and 12b. Strain gauges 6 are attached to appropriate portions of each parallel flexible beam structure 4.

In the load detector, the parallel flexible beam structure 4 formed in each of the overhanging portions 11A to 11D detects a force along the X axis and the Y axis and a moment around the Z axis, and the central rigid body portion 10 is also detected. Flexible beam structure 4
The force along the Z-axis and the moment about the X-axis and the Y-axis are detected by. That is, the load detector can detect all forces and moments.

[Problems to be Solved by the Invention]

By the way, the force F _Z , X along the Z-axis in the above load detector
Moment M _X around the _axis, and a beam structure 4 Deflection parallel to detect the moment M _Y around the Y axis are structured around the rigid portion 10 is located near the center of the load detector. Therefore, when the moments M _X and M _Y act on the load detector, the force acting on the parallel flexible beam structure 4 becomes large, and a large stress is generated in the thin portions 3, 3 ′. That is, since the moment is the product of the acting force and the distance from the point of action, the smaller the distance (the closer to the center) the greater the acting force. Therefore,
In the load detector, the thin portions 3, 3'when the moments M _X , M _Y act as compared to when the force F _Z acts.
The stress generated in the As a result, the load detector has a drawback that it is not possible to select a very large value as the rated load of the moments M _X and M _Y.

Further, the load detector is relatively complicated in shape, and there is a problem in that machining requires labor.

The object of the present invention is to solve the above-mentioned problems of the prior art, to select a large value of the rated load of the moment, and to have a simple structure and easy machining, and the forces in the three axial directions and the three axes. It is to provide a load detector that detects a moment around the load.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a plurality of parallel flexible beam structures configured by mutually thin thin parts formed by through holes penetrating a rigid part, and A load detector that includes a detection unit that detects the amount of deflection of each thin portion and that detects forces in the directions of three axes that are orthogonal to each other and a moment around the three axes, a center rigid body portion, and a center rigid body portion 90 Four rigid body overhangs are provided at intervals of 4 degrees, and the parallel flexural beam structure is installed at the end of each of these overhangs so that the surfaces of the thin-walled portions are orthogonal to each other, although they are in symmetrical positions. It is characterized by having done.

[Action]

When force or moment acts on the load detector, its X axis, Y
The thin-walled part of each parallel flexible beam structure is deformed according to the axial and Z-axis components. In this case, since each of the parallel flexural beams is located away from the center of the load detector, excessive stress generated in the thin wall portion due to the moment is suppressed. The deformation of the thin portion is taken out as a signal corresponding thereto by an appropriate means, and the load is detected based on this signal.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 is a perspective view of a load detector according to an embodiment of the present invention. In the figure, X, Y, and Z indicate coordinate axes passing through the center of the load detector. 20 is a central rigid body portion, 21A and 21B are projecting portions extending from the central rigid body portion 20 in the Y-axis direction, and 21C and 21D are central rigid body portions 20 and X.
It is an overhang portion that extends in the axial direction. Reference numerals 22a to 22d denote peripheral rigid body portions that are the end portions of the respective overhang portions 21A to 21D. Reference numeral 23 is an annular body connected to the peripheral rigid body portions 22c and 22d, and 24 is an annular body connected to the peripheral rigid body portions 22a and 22b. Each of the annular bodies 23, 24 is fixed to a predetermined position of the object whose load is to be detected.

Reference numerals 4A, 4B, 4C and 4D denote parallel flexural beam structures provided on the overhanging portions 21A, 21B, 21C and 21D, respectively, which are the same as the structure shown in FIG. 4 (a). The parallel flexible beam structure 4A has a plane (Y-Z) in which the thin portions 3, 3'are parallel to the plane formed by the Y-axis and the Z-axis.
Plane), and the parallel flexible beam structure 4D is provided so that the thin portions 3, 3'are in the XZ plane.
In the parallel flexible beam structure 4B, 4C, the thin portions 3, 3'are XY.
It is provided so as to be flat. Although strain gauges are attached to the thin portions 3 and 3 ', their illustration is omitted.

Next, a load detector using the load detector of the present embodiment shown in FIG. 1 will be described with reference to FIGS. 2 (a), (b), (c) and FIG. 2 (a), (b), and (c) are perspective views of the projecting portion in the X-axis direction. In each figure, the same parts as those shown in FIG. 1 are designated by the same reference numerals. For ease of explanation, the thin portions of the parallel flexible beam structure 4C are designated as 3c and 3c ', and the thin portions of the parallel flexible beam structure 4D are designated as 3d and 3d.
Let d ′. In the case of the structure shown in FIGS. 2 (a) to (c),
It is assumed that the peripheral rigid body portions 22c and 22d are appropriately fixed and do not deform, and the deformation of the thin wall portions 3c, 3c ', 3d and 3d' when a force or moment is applied to the central rigid body portion 20 will be considered.
This is the same state as when a force or moment is applied to the annular body 24 shown in FIG. 6e to 6l are thin-walled parts 3c and 3
It is a strain gauge attached to c ′, 3d, 3d ′.

Now, when a force F _Z in the Z-axis direction is applied to the central rigid body portion 20,
Shear deformation in the direction perpendicular to the Y axis and tensile and compressive deformation in the X axis direction occur in the thin portions 3c and 3c ', and the thin portions 3c and 3c' are deformed as shown in FIG. 2 (b). At this time, strain gauge
6e and 6g expand, and strain gauges 6f and 6h contract. Therefore, it is possible to detect the force F _Z By configuring the Buritsuji circuit respective strain gauges 6E～6h. This bridge circuit is shown in FIG.

FIG. 3 is a circuit diagram of a bridge circuit for detecting the force F _Z. In the figure, 6e to 6h are strain gauges shown in FIGS. 2A to 2C, Ein is a DC power supply, and Eout is an output signal of the bridge circuit. Strain gauges that are in the relationship of causing opposite deformations (elongation and contraction) are connected symmetrically. By the deformation of the strain gauges 6e to 6h, the resistance value changes correspondingly, and the output signal Eout also changes accordingly. Eventually, the output signal Eout since a value proportional to the force F _Z, thereby to detect the force F _Z.

Then, when an acting moment M _Y around the Y axis in the center the rigid portion 20, as shown in FIG. 2 (b), the thin portion
A deformation similar to that when a force F _Z is applied is generated in 3c and 3c '. However, since the positive and negative signs of the shear deformation are opposite, the two deformations are not exactly the same. Where the moment M _Y
If the strain gauges for detecting the strain gauges are attached at the positions on the thin portion 3c 'corresponding to the attachment positions of the strain gauges 6e to 6h of the thin portion 3c, as shown in FIG. The moment M _Y can be detected by configuring a similar bridge circuit.

Furthermore, if an acting moment M _X around the X axis in the center the rigid portion 20, a deformation entire central rigid portion 20 is rotated around the X axis. In this case, the thin portions 3c, 3c ', 3d, 3d' are deformed as shown in FIG. 2 (c). Due to this deformation, the strain gauges 6i and 6l expand and the strain gauges 6j and 6k contract. By configuring the Buritsuji circuit as shown in parentheses in Fig. 3 these strain gauges 6I～6l, its output signal Eout is proportional to the moment M _X, thereby to detect the moment M _X.

When a force F _Y in the Y-axis direction is applied to the central rigid body portion 20, the thin-walled portions 3d and 3d ′ are thin-walled portions 3c and 3d shown in FIG. 2 (b).
It is modified in the same manner as the modification of c '. It is clear from the above description that the force F _Y can be detected by taking out this deformation with, for example, four strain gauges attached to the thin portion 3d ′ and constructing a bridge circuit with these strain gauges. Is.

The detection of the force and the moment by the overhanging portions 21C and 21D has been described above, but the detection of the force and the moment by the overhanging portions 21A and 21B is performed in exactly the same manner. After all, the first
With the load detector shown in the figure, force components in the X-axis, Y-axis, and Z-axis directions,
It is possible to detect the moment component around the X axis, the Y axis, and the Z axis.

Here, the mode of deformation of the thin portion of each parallel flexible beam structure when forces F _X , F _Y , F _Z and moments M _X , M _Y , M _Z are applied to the load detector shown in FIG. The thin parts used for detection are summarized in the following table.

In addition, in the above table, the deformation of FIG. 2 (b) means FIG. 2 (b).
A modified mode similar to the thin portions 3c and 3c 'shown in FIG.
The deformation of FIG. 2C is the thin portion 3d, 3 shown in FIG. 2C.
This is a modification similar to d '.

By the way, the deformation such as the thin portions 3c and 3c 'shown in FIG. 3 (b) is caused by a force or a moment. That is, for example, in order to detect the force F _X , the deformation of the thin portion of the parallel flexible beam structure 4A is used from the above table. On the other hand, in order to detect the moment M _Z , it is possible to use the deformation of the thin wall portion of the parallel flexible beam structure 4A or the thin wall portion of the parallel flexible beam structure 4D from the above table, which is the moment M _Z acted. At this time, it means that the thin portion of the parallel flexible beam structure 4A is deformed accordingly. Looking at this from the thin-walled portion of the parallel flexural beam structure 4A, an output signal corresponding to the force F _X and the moment M _Z from the bridge circuit formed by the strain gauge attached to the bridge circuit Eout will be output. Therefore, it is impossible to distinguish whether the output signal Eout is due to the action of the force F _{X or} the action of the moment M _Z only by looking at the output signal Eout. In order to solve this problem and distinguish the applied load, the following means may be used. Hereinafter, this means will be described.

First, strain gauges are adhered to the thin-walled portions of each parallel flexural beam structure in the structure shown in FIG. 1 according to the above table. Then, each load to be detected F _X , F _Y , F _Z , M _X , M _Y , M _Z
A bridging circuit is constructed by these strain gauges every time. After constructing the load detector in this way, known loads are sequentially applied to the load detector, and the calibration work of measuring the outputs of the six bridge circuits is repeated for each case. As a result, the following equation can be obtained.

Here, when the outputs of the respective bridge circuits calibrated for the respective loads F _X , F _Y , F _Z , M _X , M _Y , M _Z are represented by E _{1 to} E ₆ , As shown in equation (4), Are weights, outputs, and transformation matrices. The proofreading work is a work for obtaining this conversion matrix. This work will be specifically described based on the above equations.

For example, when only the known force F _X is applied to the load detector, the equation (1) is expressed as follows.

In (5), F _X is known, because E ₁ to E ₆ is a value obtained by measurement, it is possible to determine the C ₁₁ -C ₆₁ (5) below. Similarly, the forces F _Y , F _Z and the moments M _X , M _Y , M _Z
If the load detector is operated individually, the conversion matrix Can be completed.

Here, the conversion matrix on both sides of equation (1) Inverse matrix of The following equation can be obtained by multiplying by.

After all, the component of the load acting on the load detector on each axis can be known based on the equation (6). That is, when an unknown load acts on the load detector, the output of 66 bridge circuits Is measured and the calculation of formula (6) (compensation calculation) is executed,
The unknown load can be determined separately for each axis component.

In this embodiment, since the structure shown in FIG. 1 is adopted, all the parallel flexible beam structures involved in load detection are arranged at positions apart from the central portion of the load detector, which is a conventional load detector. , It is possible to solve the problem that excessive stress occurs in the thin wall part of the parallel flexible beam structure near the center part, and when the load detector of the same size as the conventional one is configured, the rated load of that moment is It can be set to a large value.

In addition, the overhang portion has a simple cross shape, and the number of through holes for forming the thin wall portion is four. Therefore, the entire structure is simpler than the conventional load detector, and the processing is easy. Can be manufactured at low cost.

[Effects of the Invention] As described above, in the present invention, parallel flexural beam structures are provided at the ends of the four overhanging parts, and the surfaces of the thin-walled parts of the parallel flexural beam structures at symmetrical positions are orthogonal to each other. Since it is configured as described above, not only can all three orthogonal axial forces and moments about the three axes be detected, but each of these parallel flexible beam structures can be placed at a location away from the central portion. It is possible to prevent excessive stress from being generated in the thin portion of the parallel flexural beam structure, and if a load detector of the same size as the conventional one is configured, set the rated load of that moment to a larger value. Can be selected. Furthermore, since the entire structure is simple, processing is easy and the cost can be reduced.

[Brief description of drawings]

1 is a perspective view of a load detector according to an embodiment of the present invention, and FIGS. 2 (a), (b), and (c) are perspective views of a projecting portion in the X-axis direction shown in FIG. 1, and FIG. The figure is a circuit diagram of the bridge circuit of the strain gauge shown in Fig. 2 (a), Fig. 4 (a),
(B) and (c) are side views of the parallel flexural beam structure, and FIG. 5 is a perspective view of a conventional load detector. 4A, 4B, 4C, 4D …… Parallel flexible beam structure, 20 …… Center rigid body part, 21A, 21B, 21C, 21D …… Overhang part.

Claims (1)

[Claims] 1. A plurality of parallel flexible beam structures constituted by mutually parallel thin-walled portions formed by through holes penetrating a rigid body portion, and a detection means for detecting a bending amount of each thin-walled portion, Forces in three axial directions orthogonal to each other and the three
In the load detector that detects the moment around the axis,
A central rigid body part and four rigid body projecting parts projecting from the central rigid body part at intervals of 90 degrees are provided, and the parallel flexible beam structure is provided at the symmetrical position at the end of each projecting part. A load detector characterized by being installed such that the surfaces of the thin portions are orthogonal to each other.