JPH0726672Y2 - Load detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a load detector for detecting a load (force, moment) acting on an object.

[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 to perform model tests on 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 JP-A-61-2756.
Proposed by No. 31. The schematic configuration will be described below with reference to the drawings.

FIG. 4 is a partially cutaway perspective view of the entire structure of the load detector, and FIG.
FIG. 5A is a perspective view of the load detection unit shown in FIG. 4, and FIG. 5A is a perspective view of the load detection unit shown in FIG. In FIG. 4, reference numeral 1 is a load detection unit, the structure of which will be described later. E and F are flanges that are integrally formed with the load detection unit 1 above and below the load detection unit 1 in the figure. For example, when the load detector is applied to a robot, the flange E is connected to the robot hand and the flange F is connected to the robot arm. G is a case of the load detector, which is fixed to the flange F. H is a pin provided between the case G and the flange E, and has a stopper function of preventing the load detector from being broken when an excessive load acts on the load detector. 1 is a bolt hole for mounting provided on the flange E, and J is a flange F
3 shows a bolt hole for mounting provided on the.

Next, the structure of the load detector 1 will be described. FIG. 5 (a),
In (b), X, Y, and Z indicate coordinate axes, and A, B, C, and D indicate each surface of the cubic load detecting unit 1. Reference numeral 2 is a through hole formed in the X-axis direction, 3 is a through hole formed in the Y-axis direction, and by forming these through holes 2 and 3, thin-walled portions 2f and 2f 'are formed at both ends of the through holes 2 and 3. , 3f, 3f ′ are formed and each through hole
Rigid body portions 10, 20, 30 are formed on both sides of 2, 3, respectively. Rigid body part 10,
The thin wall portions 3f, 3f 'and the rigid body portion 20 constitute one parallel plate structure, and the rigid body portion 20, the thin wall portions 2f, 2f' and the rigid body portion 3 are formed.
0 constitutes another parallel plate structure. Each thin part 2f, 2f ′, 3
A large number of strain gauges S are attached to predetermined positions on the outer surface of f, 3f '. Each of these strain gauges S is for detecting a predetermined load, and these loads are attached as a subscript to the symbol S representing the strain gauge. That is, the subscript f indicates a force component, m indicates a moment component, and X, Y, and Z coordinate axes. The numbers in the subscripts indicate the strain gauge numbers for detecting the same load. For example, strain gauge S
_fx1l is the 11th strain gauge that detects the force component in the X-axis direction.

FIGS. 6A to 6D 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) shows thin parts 3f and 3f 'when moment M _Y acts.
It is a figure which each shows the deformation | transformation. Also, when force F _Y is applied, the thin-walled portions 2f and 2f 'of the other parallel plate structure are shown in FIG. 6 (a).
When the moment M _X acts, the same deformation as that shown in FIG. 6 (d) occurs in the thin portions 2f and 2f 'of the other parallel plate structure. When a force F _Z and a moment M _Z are applied, the thin-walled part of the parallel plate structure
The same deformations as those shown in FIGS. 6 (c) and 6 (b) also occur in 2f and 2f '.

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

Here, refer to the deformation state diagram shown in FIG. 7 for the reason that the strain gauges for detecting the force component F _Z and the moment components M _X and M _Y are attached to the end portions of the thin-walled portions instead of the central portion. While explaining. Now, as shown in FIG.
Consider the case where an axial force F _Z acts. The force F _Z is the rigid body
10, thin parts 3f, 3f ', rigid part 20, thin parts 2f, 2f', rigid part
30 through which each thin section 2
f, 2f ′, 3f, 3f ′ are deformed. By the way, it has been considered that the deformation of the thin portion is the same in all the thin portions, for example, 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. 7.
It appears in a variant of 2f '(indicated by the dashed line). That is, when the force F _Z is applied, both ends of the thin wall portion 2f ′ are compressed and deformed more 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.

It should be noted that 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 conventional load detector, in consideration of the result of the above analysis, the strain gauges for detecting the force component F _Z and the moment components M _X , M _Y are thin-walled parts as shown in FIGS. 5 (a) and 5 (b). It is configured to be attached to the end portion of. This gives the same force component
Larger strain will be generated for each strain gauge for the F _Z and moment components M _X , M _Y than if they are attached to the central portion, and eventually the detection sensitivity will be improved without any reduction in overall rigidity. Can be made. On the contrary, if the detection sensitivity is the same as the conventional one, the rigidity can be improved.

[Problems to be solved by the device]

As shown in FIG. 4, in the conventional load detector, the diameter of the flange F for mounting the case G is increased,
Further, the diameter of the flange E becomes smaller. Further, it is desired to make the dimension of the mounting length direction (Z-axis direction) as small as possible. However, since the stopper structure needs to be configured by the pin H, the thickness of the flange E must be increased, and this Therefore, the flange F has a smaller thickness. By the way, in general, the load detector is adjusted to 0 point before it is attached to a structure such as a robot, but in the above-mentioned conventional load detector, it is adjusted to 0 point by the flanges E and F. When attached to an external structure, the output of the Wheatstone Bridge circuit that detects the force component in the Z-axis direction is 0
There was a situation where the points shifted, that is, drift occurred.

The object of the present invention is to solve the above-mentioned problems in the conventional technology,
An object is to provide a load detector that does not cause drift.

[Means for Solving the Problems]

As a result of various studies conducted by the present inventors to achieve the above object, the drift is caused by mounting the flange F to an external structure by bolting. That is, for example, in FIG. 4, the bolt holes J on both sides of the end of the thin portion 2f,
When bolted with J, the flange F is thin, so the flange F deforms and pushes up the end of the thin portion 2f in the stacking direction of the parallel plate structure to deform it, and this deformation causes the thin portion 2f, It is thought that it occurs at each end of 2f '.

For this reason, the present invention comprises a load detecting part composed of two parallel flat plate structures which are stacked orthogonally to each other, and two flanges which are integrally formed with the load detecting part and are provided on both sides of the parallel plate structure in the stacking direction. In the load detector configured, the detection element group for detecting a force component along the stacking direction is arranged in a parallel plate structure on the flange side of the flanges, which has a larger dimension in the stacking direction. To do.

[Action]

When the load detector is attached to the external structure by each flange, even if the flange with a small dimension in the stacking direction of the parallel plate structure is deformed, the force in the stacking direction is applied to the parallel plate structure on the side adjacent to the flange. Since there is no detection element group for detecting the component, there is no influence on the detection of the force component.

〔Example〕

 Hereinafter, the present invention will be described with reference to the illustrated embodiments.

FIG. 1 (a) is a perspective view of a load detector of a load detector according to an embodiment of the present invention, and FIG. 1 (b) is an arrow 1b in FIG. 1 (a).
It is a perspective view of a direction. In the figure, the same parts as those shown in FIGS. 5 (a) and 5 (b) are designated by the same reference numerals, and the description thereof will be omitted. Further, as for each strain gauge, only the strain gauges shown in FIGS. 5 (a) and 5 (b) in which the bonding positions are changed are shown, and the strain gauges whose bonding positions are not changed are not shown. In the present embodiment and the conventional one, the strain gauge for detecting the force component in the Z-axis direction is arranged in the parallel plate structure in which all the through holes 2 exist, in contrast to the conventional one. Are arranged in a parallel plate structure in which all the through holes 3 are present, that is, a parallel plate structure connected to the flange E having a large dimension in the Z-axis direction, and with this arrangement, FIG. The difference is that the strain gauges S _mxl1 and S _mxl3 for detecting the moment around the X-axis are displaced inward as shown in FIG. 4), and the other configurations are the same. In FIGS. 1A and 1B, strain gauges for detecting a force component in the Z-axis direction are indicated by _reference numerals S _{fz21 to} S _fz28 with new numbers.

As described above, in this embodiment, since all the strain gauges for detecting the force component in the axial direction are arranged in the parallel plate structure on the flange E side, the load detector is attached to the external structure by bolting the flanges E and F together. When this is done, there is no effect on these strain gauges, and there is no deviation at the adjusted zero point of the force component detection mechanism in the Z-axis direction.

FIG. 2 is a side view of the load detector when the force component F _{Z in the} Z-axis direction acts. In the figure, the same parts as those shown in FIG. 1 are designated by the same reference numerals. The figure is a side view different from that of FIG. 7, but the reason why such deformation occurs is already explained. However, as a result of further FEM analysis,
It was found that a slight amount of elongation deformation occurred near the center of the thin portions 3f and 3f '.

FIG. 3 is a circuit diagram of a Wheatstone bridge circuit for detecting a force component in the Z-axis direction. In the figure, S _{fz21 to} S _fz28 are the first
Strain gauges the same as those shown in FIGS. (A) and (b), E is a power supply, and V _fz is an output voltage. When the force F _Z shown in FIG. 2 acts, the output voltage V _fz becomes a value according to the force F _z .

[Effect of device]

As described above, in the present invention, the detection element group for detecting the force component in the stacking direction of the two parallel plate structures is arranged in the parallel plate structure on the flange side having the larger size in the stacking direction. It is possible to prevent the occurrence of drift at the time of fastening.

[Brief description of drawings]

1 (a) and 1 (b) are perspective views of a detecting portion of a load detector according to an embodiment of the present invention, FIG. 2 is a side view of the detecting portion shown in FIG. 1, and FIG. 3 is a Wheatstone bridge. Circuit schematic,
FIG. 4 is a partially broken perspective view of the load detector, FIG. 5 (a),
FIG. 6B is a perspective view of a conventional detector, FIG.
(B), (c), (d) is a perspective view showing the deformation of the detection unit,
FIG. 7 is a side view of the detector. 1 ... Load detection part, 2f, 2f ', 3f, 3f' ... Thin-walled part, E, F ...
… Flange, G… Case, I, J… Bolt hole, S _fz21 ～
S _fz28 , S _mxl1 , S _mxl3 …… Strain gauge

Continuation of the front page (56) Reference JP-A-1-318934 (JP, A) JP-A 64-35235 (JP, A) JP-A 61-275631 (JP, A) JP-A 64-10137 (JP , A)

Claims (1)

[Scope of utility model registration request] 1. A load detecting section composed of two parallel flat plate structures that are laminated orthogonally to each other, and two flanges integrally formed with the load detecting section and provided on both sides of the parallel flat plate structure in the stacking direction. In the load detector according to claim 1, a detection element group for detecting a force component along the stacking direction is arranged in a parallel plate structure on the flange side of the flanges having a larger dimension in the stacking direction. Detector