JPH0643933B2 - Load detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a load detector for detecting loads applied to various objects by separating them into forces in the axial directions orthogonal to each other and moments about those axes. .

[Conventional technology]

Detecting the load (force, moment) applied to an object is indispensable in many fields. For example, when performing assembly work, polishing work, and deburring work using a high-performance robot, it is necessary to accurately detect the force that acts on the hand of the robot, and model tests for aircraft, ships, vehicles, etc. When carrying out, detection of the load applied to each part is a major item. A load detector having excellent performance as a load detector for detecting such a load is disclosed in Japanese Patent Application No. 60-11675.
Proposed by No. 9. The schematic configuration will be described below with reference to the drawings.

FIG. 4 is a perspective view of a conventional load detector. In the figure, 1 is a hexahedral block made of a rigid body, and is A, B, C, D.
Shows its four sides. X, Y, and Z are 6 in Block 1
It is a coordinate axis assumed to be orthogonal to one plane. Reference numeral 2 denotes a rectangular through hole formed from the side surface A of the block 1 to the side surface B in the X-axis direction, and 3 denotes Y from the side surface C to the side surface D of the block 1.
It is a rectangular through hole formed so as to penetrate therethrough in the axial direction. 2f, 2
f ′ is a thin portion formed by forming the through hole 2, 3f, 3f ′
Is a thin portion formed by forming the through hole 3. The thin-walled portions 2f, 2f 'constitute a first parallel plate structure, and the thin-walled portions 3f, 2f
A second parallel plate structure is formed by 3f '.

2I, 2II and 2III are virtual lines drawn in the X-axis direction on the side surface C at the same height as the upper edge, the center line and the lower edge of the through hole 2, respectively. Further, 3I, 3II, 3III are virtual lines drawn on the side surface A of the through hole 3 similarly to the virtual line drawn on the side surface C. Virtual lines 3I, 3II, 3 on side A
A strain gauge is provided at a predetermined position on III as shown in the figure, and a strain gauge is also provided on the side surface B at a symmetrical position. Further, strain gauges are also provided at predetermined positions on the imaginary lines 2I, 2II, 2III on the side surface C, and strain gauges are also provided on the side surface D at symmetrical positions. The arrangement of these strain gauges will be described with reference to FIGS. 5 (a) and 5 (b).

5 (a) and 5 (b) are layout diagrams of the strain gauges. In each figure, 2I to 2III and 3I to 3III are the same virtual lines as shown in FIG. S _fy1 and S _fy3 are strain gauges attached to the central portion of the thin portion 2f ′ and have a force component F _{Z in the} Z-axis direction.
It is used to detect. Strain gauge for thin wall 3f '
S _fy1, S _FY3 and the gauge S _fy2 strain opposing positions, but S _FY4 is stuck not shown (hereinafter the same for each strain gauge). Each strain gauge S _fy1 , S _fy2 , S _fy3 , S
_{By forming} a Wheatstone _bridge circuit with _fy4 , an output proportional to the force component F _Y can be obtained.

S _mx1 and S _mx3 are strain gauges attached to the central portion of the thin portion 2f ′, and together with the strain gauges S _mx2 and S _mx4 attached to the opposing positions of the thin portion 2f, the moment M _X about the X axis is Used for detection. S _mz1 and S _mz3 are strain gauges attached to the ends of the thin portion 2f ′, and together with the strain gauges S _mz2 and S _mz4 attached to opposite positions of the thin portion 2f, the moment M _Z about the Z axis is Used for detection.

In exactly the same manner, strain gauges S _{fx1 to} S _fx4 for detecting a force component F _X in the X-axis direction and a strain gauge S for detecting a moment component M _Y about the Y-axis are provided in the central portion of the thin portions 3f and 3f ′.
_my1 to S _MY4, strain detecting the Z-axis direction force component F _Z gauge S _fz1 to S _Fz4 are adhered respectively.

6 (a) to 6 (d) are perspective views of one of the two parallel plate structures shown in FIG. Figure 6 (a) is thin portion 3f when force F _X is applied to the load detector shown in Figure 4, the deformation of the 3f '(where are drawn extremely exaggerated. Hereinafter the same.), The FIG. 6 (b) shows the deformation of the thin portions 3f, 3f ′ when the moment M _Z acts, and FIG. 6 (c) shows the deformation of the thin portions 3f, 3f ′ when the force F _Z acts, FIG. (d) is a figure which shows the deformation | transformation of thin-walled part 3f, 3f 'when moment M _Y acts, respectively. Further, when the force M _Y acts, the thin portions 2f and 2f ′ of the other parallel plate structure undergo the same deformation as shown in FIG. 6 (a), and when the moment M _X acts, the other parallel plate The thin portions 2f and 2f 'of the structure undergo the same deformation as that shown in FIG. 6 (d). When the force F _Z and the moment M _Z act, the thin-walled portions 2f and 2f ′ of the other parallel plate structure are also shown in FIG.
The same deformations as those shown in (c) and (b) occur.

Strain occurs in each strain gauge according to these deformations,
This strain changes the resistance value of the strain gauge, and an output proportional to the load acting from the corresponding Wheatstone bridge is generated, and each load can be detected.

[Problems to be solved by the invention]

The conventional load detector shown in FIG. 4 has already been put to practical use, and its excellent performance is recognized. By the way, of the loads acting on the load detector, the forces F _X and F _Y are forces in the reference axis direction, and the deformation of each thin portion is large and can be detected with sufficient sensitivity. This load detector shows relatively high rigidity for loads other than F _X and F _Y.
It is difficult to detect with high sensitivity. However,
In actual use, greater sensitivity to the detection of these other loads has been demanded.

It is possible to meet such a demand by making each thin portion thinner, but if so, the rigidity of the entire load detector is unnecessarily lowered, and various inconveniences occur during use. For example, when F _X and F _Y act, there is a problem that the deformation of the thin-walled portion becomes too large and stress becomes unreasonable.

An object of the present invention is to provide a load detector which solves the above-mentioned problems of the prior art and can improve the detection sensitivity without lowering the rigidity.

[Means for solving problems]

In order to achieve the above object, the present invention provides a load detector in which a first parallel plate structure and a second parallel plate structure are stacked orthogonally to each other, and is parallel to any of the parallel plates of each of the parallel plate structures. A detection element group for detecting a force component along the first axis, a detection element group for detecting a moment component around a second axis in a direction orthogonal to the parallel plate of the first parallel plate structure, and a first Each detection element of at least one detection element group of the detection element group for detecting a moment component around a third axis orthogonal to the axis and the second axis is provided near a predetermined end of the parallel plate. It is characterized by

[Action]

When a force component along the first axis, a moment component about the second axis, and a moment component about the third axis act on the load detector, these loads act on the parallel plates of the first parallel plate structure Transmission is performed via a rigid body portion existing between the flat plate and the parallel flat plate of the second parallel flat plate structure, and the parallel flat plate of the second parallel flat plate structure. At this time, at least one of these loads is detected by the detection element provided near the end of the parallel plate.

〔Example〕

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

FIG. 1 (a) is a perspective view of a load detector according to an embodiment of the present invention, and FIG. 1 (b) shows the load detector shown in FIG.
It is the perspective view seen from the direction. In each figure, the same parts as those shown in FIG. 10,2
0 and 30 indicate a rigid body part. S _{fz11 to} S _fz18 are strain gauges for detecting the force component F _Z in the Z-axis direction, and S _{mx11 to} S _mx14 are X.
Strain gauges for detecting the moment component M _X around the axis, S _{my11 to} S _my14 are the moment components M around the Y axis.
It is a strain gauge for detecting _Y. X-axis direction force component F _X, Y-axis direction force component F _Y, and strain detecting a moment component M _Z around the Z axis, respectively gauge Fig. 4 and FIG. 5 (a), shown in (b) Although it is attached at the same position as the position, their illustration is omitted in FIGS. 1 (a) and (b).

In this embodiment, the strain gauges S _fz13 , S _fz14 , S _fz17 , S
_{The fz18} is different from the conventional load detectors in which the strain gauges S _{fz1 to} S _fz4 are attached to the central part of the thin wall part.
It is attached to the ends of f and 2f '. Similarly, strain gauge, S
_{mx11 to} S _mx14 , S _{my11 to} S _my14 also have strain gauges S _{mx1 to} S _mx4 and S _{my1 to} S _{my4 of} the conventional load detector, which are different from the _ones attached to the central part of the thin part 3f. , 3f ′, 2f, 2f ′
Affixed to the edge of

Here, the reason why the strain gauges for detecting the force component F _Z and the moment components M _X and M _Y are attached not to the central portion of the thin-walled portion but to the end portion is referred to the deformation state diagram shown in FIG. While explaining. Now, in Block 1, as shown in Fig. 2, Z
Consider the case where an axial force F _Z acts. The force F _Z is transmitted through the rigid body portion 10, the thin-walled portions 3f and 3f ′, the rigid body portion 20, the thin-walled portions 2f and 2f ′, and the rigid body portion 30, and during the transmission process, each thin-walled portion is transmitted.
2f, 2f 'and 3f, 3f' are deformed. By the way, it has been considered that the deformation of the thin portion is the same in one thin portion, for example, in the thin portion 2f. However,
When the present inventors analyzed the deformation of the thin portion in detail by the finite element method analysis (FEM analysis), it was found that the deformation was not uniform over the entire thin portion. The state of this deformation is shown in FIG. 2, and the characteristic of the deformation is particularly shown in the deformation of the thin portion 2f '(shown by the broken line). That is, when the force F _Z is applied, both ends of the thin wall portion 2f 'are largely compressed and deformed than the central portion thereof. Such deformation similarly occurs in the other thin-walled portions 2f, 3f, 3f '. It is considered that such non-uniform deformation occurs because the rigid body portions 10, 20, 30 are not completely rigid bodies, and some deformation occurs when the force F _Z acts.

Such non-uniform deformation also occurs when the force F _Z acts in the opposite direction (in this case, the end portion causes a larger tensile deformation than the central portion), and the moments M _X and M _Y act. The same happens when you do.

In the present embodiment, in consideration of the result of the above analysis, the force component F attached to the central portion of the thin portion in the conventional load detector.
_As shown in FIGS. 1 (a) and 1 (b), the strain gauges for detecting _Z and moment components M _X and M _Y are attached to the ends of the thin portion. As a result, a larger strain is generated for the same force component F _Z and moment components M _X , M _Y than when the strain gauges are attached to the central portion, and eventually the overall rigidity is reduced. It is possible to improve the detection sensitivity without doing so. On the contrary, if the detection sensitivity is the same as the conventional one, the rigidity can be improved.

3 (a) to (c) are force component F _Z and moment components M _X , M _Y.
3 is a circuit diagram of the detection circuit of FIG. Each detection circuit is composed of a Wheatstone bridge circuit, and E indicates its power source. or,
Each strain gauge has the same reference numeral as that shown in FIGS. 1 (a) and 1 (b). FIG. 3 (a) is a moment M _X detection circuit, FIG. 3 (b) is a moment M _Y detection circuit, and FIG. 3 (c).
Is a detection circuit for the force F _Z , and outputs electric signals V _mx , V _my , and V _{fz, which} are proportional to the applied moment and force, respectively.

Each of these detection circuits outputs an electric signal only when a corresponding load acts, and does not output any signal for other loads, because the reason is clear from the characteristics of the Wheatstone Bridge circuit. , The description is omitted. Strain gauge in the detection circuit of force F _Z
S _fz11 , S _fz12 , S _fz15 , S _fz16 are dummy gauges. The reason for using such a dummy gauge is as follows.
That is, deformation utilized for the detection of the force F _Z is dependent on when the direction of the force F _Z is positive in only compressive deformation of the thin portion, if the direction opposite to the force F _Z is negative tension of the thin portion deformed Because it depends only on. However, when the eight strain gauges are used as described above, the applied voltage can be increased, so that the force F _Z can be detected with higher sensitivity.

In the description of the above embodiment, the load detector for detecting the forces F _X , F _Y , F _Z and the moments M _X , M _Y , M _Z has been described, but at least the forces F _Z , moments _X , M _Y are detected. It may be one that detects one.

〔The invention's effect〕

As described above, in the present invention, the force F _Z , the moment _X ,
Since the detection element for detecting at least one of M _Y is provided near the end of the parallel plate, the load detection sensitivity can be improved without lowering the rigidity.

[Brief description of drawings]

1 (a) and 1 (b) are perspective views of a load detector according to an embodiment of the present invention, and FIG. 2 is a deformation state diagram of the load detector shown in FIGS. 1 (a) and 1 (b), 3 (a), (b), and (c) are circuit diagrams of the detection circuit,
The figure is a perspective view of a conventional load detector, Figures 5 (a) and (b) are layout diagrams of strain gauges, and Figures 6 (a), (b), (c), and (d) are Figures 4 and 5. FIG. 5 is a deformation state diagram of the parallel plate structure shown in FIG. 1 ... Block, 2, 3 ... Through hole, 2f, 2f ', 3f, 3f'
...... Thin section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 59-204732 (JP, A) JP 61-83929 (JP, A) JP 61-275631 (JP, A) JP 63- 113327 (JP, A) JP-A-1-10137 (JP, A)

Claims (1)

[Claims] 1. A load detector in which a first parallel plate structure and a second parallel plate structure are stacked orthogonally to each other, along a first axis parallel to each parallel plate of each parallel plate structure. A group of detecting elements for detecting a force component, a group of detecting elements for detecting a moment component around a second axis in a direction orthogonal to the parallel plate of the first parallel plate structure, and a first axis and a second axis. Load detecting means, wherein each detecting element of at least one detecting element group of the detecting element group for detecting a moment component around a third axis orthogonal to the axis is provided near an end of a predetermined parallel plate. vessel