Force detection device and robot

Abstract

This force detection device (1)comprises: a first attachment part (2) that is fixed to a first surface to be attached (F); a second attachment part (3) that is fixed to a second surface to be attached (B), the load fluctuation of which is larger than that of the first surface to be attached (F); and a force sensor body (4) that is fixed between the first attachment part (2) and the second attachment part (3). The first attachment part (2) comprises: a planar or flange-shaped first portion (5) fixed to one end surface of the force sensor body (4); a columnar second portion (6), one end of which is connected to the first portion (5) on the opposite side from the force sensor body (4); and a third portion (7) that is provided to the other end of the second portion (6) and is fixed to the first surface to be attached (F). A gap in the axial direction of the second portion (6) is formed between the first portion (5) and the third portion (7). The second attachment part (3) is formed in a planar shape and has a higher stiffness than the third portion (7) fixed at the other end surface of the force sensor body (4).

Description

Technical Field

[0001] The present disclosure relates to a force detection device and a robot.

Background Art

[0002] Conventionally, as a force detector that is less affected by the distortion of the mounting location, a device having a gap provided between a force sensor main body and a mounting portion is known (see, for example, Patent Document 1). Even if the surface on which the force sensor is mounted is distorted and stress acts on the mounting portion mounted on that surface, the gap lengthens the force transmission path, and the stress generated by the distortion or undulation on the mounting surface can be reduced. The influence on the force sensor main body can be reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a gap is provided between the force sensor main body and the mounting portion, the rigidity of that portion is reduced due to the constriction for providing the gap. Therefore, when a large load acts, the force sensor main body is distorted in an unexpected direction, and the detection accuracy is reduced. Therefore, it is desired to prevent a decrease in detection accuracy due to large fluctuations in the load of the mounted device.

Means for Solving the Problems

[0005] A force detection device includes a first mounting portion fixed to a first mounting surface, a second mounting portion fixed to a second mounting surface with greater load fluctuation than the first mounting surface, and a force sensor body fixed between the first mounting portion and the second mounting portion. The first mounting portion includes a flat or flange-shaped first portion fixed to one end surface of the force sensor body, a columnar second portion having one end connected to the opposite side of the first portion from the force sensor body, and a third portion provided at the other end of the second portion and fixed to the first mounting surface. An axial gap of the second portion is formed between the first portion and the third portion. The second mounting portion is formed in a flat plate shape with higher rigidity than the third portion fixed to the other end surface of the force sensor body.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0007] The force detection device 1 and the robot 100 according to an embodiment of the present disclosure will be described below with reference to the drawings. As shown in FIG. 1, the robot 100 according to the present embodiment includes a vertical six-axis articulated robot body 110 and a force detection device 1 fixed to a floor surface (first mounting surface) F.

[0008] The force detection device 1 includes a first attachment portion 2 fixed to the floor surface F, a second attachment portion to which the bottom surface (second surface to be attached) B of the installation flange 130 provided on the base 120 of the robot body 110 is fixed, and a force sensor body 4 fixed between the first attachment portion 2 and the second attachment portion. The force sensor body 4 is provided with a strain detector, for example, an electric resistance strain gauge (not shown), that detects the strain of the force sensor body due to an external force. The force sensor body 4 is a six-axis sensor that detects the magnitude and direction of the force applied to the force sensor body.

[0009] The first attachment portion 2 is formed by processing a casting. The first attachment portion 2 may be formed by cutting out from a metal block, or may be formed by other methods. The first attachment portion 2 may be made as one part in order to suppress the manufacturing cost. As shown in FIG. 2, the first attachment portion 2 includes, in order from above, a first portion 5, a second portion 6, and a third portion 7.

[0010] The first portion 5 has an upper surface to which the force sensor body 4 is fixed, and is formed in a flat plate shape extending at least in the horizontal direction. The second portion 6 is formed in a columnar shape extending at least downward from the lower surface of the first portion 5. The third portion 7 is formed in a flat plate shape extending at least in the horizontal direction at the lower part of the second portion 6, and is fixed to the floor surface F.

[0011] As shown in FIG. 2, a vertical gap X is formed between the first portion 5 and the third portion 7. In other words, a constriction is formed in the second portion 6 such that the diameter is smaller along the horizontal direction compared to the first portion 5 and the third portion 7. In the present embodiment, the gap X between the first portion 5 and the third portion 7 formed by the constriction is formed over the entire circumference around the central axis О.

[0012] Four through holes 9 for inserting bolts 8 are provided at predetermined circumferential positions around the central axis О in the third portion 7 of the first attachment portion 2. Each through hole 9 is arranged horizontally outward from the first portion 5 on the same circumference centered on the central axis О.

[0013] Each through-hole 9 is provided near the outer contour of the third part 7. "Near the outer contour" means outside the midpoint of the straight line connecting the central axis О and the end of the outer shape in the third part 7. As shown in FIG. 2, by fastening the bolt 8 inserted into the through-hole 9 to the screw hole 10 formed in the floor surface F, the first mounting portion 2 including the third part 7 can be fixed to the floor surface F.

[0014] In the first part 5 of the first mounting portion 2, through-holes 12 are provided for fixing the first mounting portion 2 and the force sensor body 4 near the outer contour near the outer periphery in the first part 5 by a plurality of bolts 11.

[0015] The second mounting portion is a flat plate-shaped adapter 3 that is more rigid than the third part 7 fixed to the upper surface of the force sensor body 4. As shown in FIG. 3, the adapter 3 is formed in a flat plate shape that is substantially square in plan view, has an outer shape equivalent to the contour shape of the bottom surface B of the base 120, and has four screw holes 13 near the outer contour of the adapter 3 on the same circumference around the central axis О. Further, the adapter 3 is provided with a plurality of through-holes 14 formed at intervals in the circumferential direction at positions between the central axis О and the screw holes 13, and is fixed to the upper surface of the force sensor body 4 by bolts 15 that penetrate through the respective through-holes 14.

[0016] In the robot 100 according to the present embodiment, the base 120 of the robot body 110 has a form in which the inside is hollow and the bottom surface B is open, and installation flanges 130 for fixing to the adapter 3 are provided at its four corners. The installation flanges 130 are provided with four through-holes 16 arranged at positions corresponding to the four screw holes 13 of the adapter 3, which is the second mounting portion, in a state where the bottom surface B of the installation flange 130 provided on the base 120 is in close contact with the upper surface of the adapter 3.

[0017] By fastening bolts 17 that penetrate through the respective through-holes 16 to the screw holes 13 of the adapter 3, the robot body 110 is fixed to the force detection device 1. In this case, in the robot 100 according to the present embodiment, the ratio α of the sum of the thickness dimension t1 of the adapter 3, which is the second attachment portion, to the size A of the installation flange 130 and the thickness dimension t2 of the installation flange 130, α = (t1 + t2) / A ≥ Th is formed in a shape such that it is equal to or greater than a predetermined threshold Th. Also, the thickness dimension t1 of the adapter 3 is a thickness dimension larger than the thickness dimension t2 of the installation flange 130.

[0018] FIG. 4 shows a graph obtained by analyzing and calculating the error amount of the force detection device 1 when the thickness dimension t1 of the adapter 3 is changed. According to this figure, it can be seen that if the thickness dimension t1 of the adapter 3 becomes larger than a predetermined size, the error amount of the force detection device 1 decreases significantly. Also, even if the thickness of the adapter 3 is thin, if the thickness dimension t2 of the installation flange 130 of the robot body 110 fixed to the adapter 3 is large, it is considered that the same effect can be obtained.

[0019] Therefore, by forming the ratio α of the sum of the thickness dimension t1 of the adapter 3 to the size A of the installation flange 130 and the thickness dimension t2 of the installation flange 130 to be equal to or greater than a predetermined threshold Th, the error amount of the force detection device 1 can be significantly reduced. That is, the larger the thickness dimension t2 of the installation flange 130 of the robot body 110, the larger the thickness dimension t1 of the adapter 3 is set, or the smaller the size A of the installation flange 130 is set, the higher the error reduction effect.

[0020] Here, when the size A of the installation flange 130 is, for example, the perimeter of a quadrilateral (shown by a dashed line in FIG. 3) connecting the centers of the four bolts 17 that fix the installation flange 130 and the adapter 3, the predetermined threshold Th is 4%. FIG. 5 shows the relationship between various robots R1 to R8, the ratio α, and the thickness dimension t1 of the adapter 3.

[0021] According to this, it has been found that in many robots 100, by configuring to satisfy the above relationship, the error amount of the force detection device 1 can be reduced. Also, for the robot 100 in which the ratio α is 4% or less, by adjusting the thickness dimension t1 of the adapter 3 so that the ratio becomes 4% or more, the error amount of the force detection device 1 could be reduced.

[0022] According to the force detection device 1 and the robot 100 according to this embodiment configured as described above, a vertical gap (axial gap of the second portion 6) X is formed between the third portion 7 fixed to the floor surface F and the first portion 5 fixed to the force sensor main body 4. As a result, the force transmission path from the outer periphery of the third portion 7 to the first portion 5 becomes longer by the amount of the gap X.

[0023] That is, according to this embodiment, when the bolt 8 that penetrates the through hole 9 provided in the third portion 7 and is fastened to the screw hole 10 provided in the floor surface F is fastened, the stress generated in the third portion 7 due to the distortion of the floor surface F or the undulation of the surface can be reduced from affecting the force sensor main body 4. Thereby, even if there are distortions or undulations on the floor surface F, the detection accuracy of the force acting on the robot main body 110 can be improved.

[0024] Also, according to the robot 100 according to this embodiment, the adapter 3 that fixes the installation flange 130 of the base 120 of the robot main body 110 is formed in a sufficiently thick flat plate shape. As a result, the rigidity of the adapter 3 can be made sufficiently large compared to the first attachment portion 2 in which the influence of the distortion of the floor surface F is reduced by the gap X.

[0025] As a result, even if a large load fluctuation acts on the adapter 3, which is the second attachment part, due to the operation of the robot body 110, it is possible to prevent the force sensor body 4 from being distorted in an unexpected direction. That is, even if the base 120 of the robot body 110 has a cup-shaped structure with relatively low rigidity having an opening in the bottom surface B of the installation flange 130, by fixing the installation flange 130 to the adapter 3 having a large thickness dimension, deformation of the base 120 due to a large load fluctuation can be suppressed. Thereby, there is an advantage that it is possible to prevent a decrease in the detection accuracy of the force by the force sensor body 4.

[0026] In addition, in the present embodiment, the connection between the installation flange 130 of the base 120 of the robot body 110 and the adapter 3 is carried out by four bolts 17, and as the size of the installation flange 130, the perimeter of the quadrilateral connecting the centers of the four bolts 17 is adopted. Instead of this, the length of the diagonal of the quadrilateral may be adopted as the size A of the installation flange 130.

[0027] Further, when fixing with three bolts 17, the perimeter of the triangle connecting the centers of the three bolts 17 may be adopted as the size A of the installation flange 130. Also, the perimeter or the diameter dimension of the circle passing through the centers of the three bolts 17 may be set as the size A of the installation flange 130.

Explanation of Signs

[0028] 1 Force detection device 2 First attachment part 3 Adapter (second attachment part) 4 Force sensor body 5 First part 6 Second part 7 Third part 100 Robot 110 Robot body 120 Base 130 Installation flange B Bottom surface (second surface to be attached) F Floor surface (first surface to be attached) X Gap

Claims

1. a first mounting portion fixed to the first mounting surface; a second mounting portion fixed to a second mounting surface having a larger load fluctuation than the first mounting surface; a force sensor body fixed between the first mounting portion and the second mounting portion, wherein the first mounting portion includes a flat or flange-shaped first portion fixed to one end surface of the force sensor body, a columnar second portion having one end connected to the opposite side of the first portion from the force sensor body, and a third portion provided at the other end of the second portion and fixed to the first mounting surface; a gap in the axial direction of the second portion is formed between the first portion and the third portion; a force detection device, wherein the second mounting portion is formed in a flat plate shape having higher rigidity than the third portion fixed to the other end surface of the force sensor body.

2. the second mounting surface is provided on an installation flange fixed to the second mounting portion in a state of being in close contact with the surface of the second mounting portion, the force detection device according to claim 1, wherein the second mounting portion has a thickness dimension larger than that of the installation flange.

3. a ratio of the sum of the thickness dimension of the installation flange and the thickness dimension of the second mounting portion to the size of the installation flange is equal to or greater than a predetermined threshold value, the force detection device according to claim 2, wherein the size of the installation flange is a perimeter of a quadrilateral connecting centers of four bolts for fixing the installation flange and the second mounting portion.

4. the first mounting surface is a floor surface, the force detection device according to claim 2 or claim 3, wherein the second mounting surface is a bottom surface of the installation flange provided on the base of the robot body.

5. the force detection device according to claim 4, wherein the second mounting portion has an outer shape equivalent to a contour shape of the bottom surface.

6. a force detection device according to claim 4 or claim 5, a robot including the force detection device and a robot body having the bottom surface fixed to the second mounting portion of the force detection device.

7. a force detection device, a robot body having an installation flange of a bottom surface fixed to the force detection device, wherein the force detection device includes a first mounting portion fixed to a floor surface, a second mounting portion fixed to the installation flange, and a force sensor body fixed between the first mounting portion and the second mounting portion, a ratio of the sum of the thickness dimension of the installation flange and the thickness dimension of the second mounting portion to the size of the installation flange is 4% or more, a robot, wherein the size of the installation flange is a perimeter of a quadrilateral connecting centers of four bolts for fixing the installation flange and the second mounting portion.

8. The first attachment portion includes a flat plate-shaped or flange-shaped first portion fixed to one end surface of the force sensor body, a columnar second portion having one end connected to the opposite side of the first portion from the force sensor body, and a third portion provided at the other end of the second portion and fixed to the floor surface. The robot according to claim 7, wherein an axial gap of the second portion is formed between the first portion and the third portion.

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