Force detection device and robot

Abstract

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, wherein the load variation of the second mounting surface is greater than that of the first mounting surface; and a force sensor body fixed between the first mounting portion and the second mounting portion; wherein the first mounting portion includes a first part, a second part, and a third part; the first part is a flat plate or blade-shaped part fixed to one end face of the force sensor body; the second part is columnar and one end is connected to the other side of the first part opposite to the force sensor body; the third part is disposed at the other end of the second part and fixed to the first mounting surface; an axial gap is formed between the first part and the third part; the second mounting portion is formed as a highly rigid flat plate fixed to the other end face of the force sensor body, and its rigidity is higher than that of the third part.

Description

Force detection device and robot This case concerns a force detection device and a robot. Traditionally, force detectors that are less susceptible to distortion due to mounting position variations are known to have a gap between the force sensor body and the mounting portion (see, for example, Patent Document 1). Even if the mounting surface of the force sensor is distorted, the stress acting on the mounting portion will have a longer force transmission path due to the gap, resulting in less impact on the force sensor body from stress caused by distortion or unevenness of the mounting surface. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent Application Publication No. 2021-41482 However, due to the necking of the gap between the force sensor body and the mounting part, the rigidity of this part decreases. When a heavy load is applied, the force sensor body warps in an unexpected direction, causing a decrease in detection accuracy. Therefore, it is desirable to prevent a decrease in detection accuracy caused by large fluctuations in the load on the mounting device. 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, the load variation of the second mounting surface being greater than that of the first mounting surface; and a force sensor body fixed between the first mounting portion and the second mounting portion; wherein the first mounting portion includes a first part, a second part, and a third part; the first part is a flat plate or blade-shaped part fixed to one end face of the force sensor body; the second part is columnar and one end is connected to the other side of the first part opposite to the force sensor body; the third part is disposed at the other end of the second part and fixed to the first mounting surface; an axial gap is formed between the first part and the third part; the second mounting portion is formed as a highly rigid flat plate fixed to the other end face of the force sensor body, and its rigidity is higher than that of the third part. In one embodiment, regarding a force detection device 1 and a robot 100, please refer to the drawings and the following description. As shown in FIG1, in this embodiment, the robot 100 includes a vertical six-axis multi-joint robot body 110 and a force detection device 1 fixed to the ground F (first mounting surface). The force detection device 1 includes a first mounting part 2, a second mounting part, and a force sensor body 4. The first mounting part 2 is fixed to the ground F. The second mounting part is fixed to the bottom surface (second mounting surface) B of the mounting flange 130 of the base 120 of the robot body 100. The force sensor body 4 is fixed between the first mounting part 2 and the second mounting part. The force sensor body 4 is provided with a distortion detector to detect the distortion of the force sensor body caused by external force. The distortion detector is, for example, a resistance strain gauge (illustrated but not shown). The force sensor body 4 is a six-axis sensor capable of detecting the magnitude and direction of the force applied to the force sensor body. The first mounting part 2 is manufactured by casting. The first mounting part 2 can be manufactured by cutting a metal block or by other methods. To reduce manufacturing costs, the first mounting part 2 can also be manufactured as a single component. As shown in Figure 2, the first mounting part 2 includes, from top to bottom, a first part 5, a second part 6, and a third part 7. The force sensor body 4 is fixed on top of the first part 5, and the first part 5 extends at least horizontally to form a flat plate. The second part 6 extends at least downward from below the first part 5 to form a column. The third part 7 is located below the second part 6, extends at least horizontally to form a flat plate, and is fixed to the ground F. As shown in Figure 2, a vertical gap X is formed between the first portion 5 and the third portion 7. In other words, the second portion 6 has a smaller diameter in the horizontal direction compared to the first portion 5 and the third portion 7, thus forming a constricted portion. In some embodiments, the gap X formed between the first portion 5 and the third portion 7 by the constricted portion forms the entire circumference around the central axis O. At a predetermined position around the central axis O, four through holes 9 are provided in the third part 7 of the first mounting part 2 for inserting bolts 8. On the same circumference centered on the central axis O, each through hole 9 is located outside the horizontal range of the first part 5. Each through hole 9 is located near the outer contour of the third part 7. "Near the outer contour" refers to a location further outward than the midpoint of the line connecting the central axis O and the end of the outer shape of the third part 7. As shown in Figure 2, bolts 8 inserted into the through holes 9 are screwed into screw holes 10 formed in the ground F, allowing the first mounting part 2 containing the third part 7 to be fixed to the ground F. Near the outer contour of the first part 5, a through hole 12 is provided in the first part 5 of the first mounting part 2 for fixing the first mounting part 2 and the force sensor body 4 with a plurality of bolts 11. The second mounting part is a high-rigidity, flat plate-shaped connector 3 fixed above the force sensor body 4, and its rigidity is higher than that of the third part 7. As shown in Figure 3, the connector 3, viewed from above, is a slightly square flat plate with the same outline shape as the bottom surface B of the base 120, and has screw holes 13 located at four positions on the same circumference around the central axis O and near the outer contour of the connector 3. Furthermore, the connector 3 has a plurality of through holes 14 between the central axis O and the screw holes 13, and the plurality of through holes 14 are spaced apart in the circumferential direction. Bolts 15 are inserted through each through hole 14 to fix the connector 3 above the force sensor body 4. In this embodiment, the base 120 of the robot body 110 is hollow inside, and its bottom surface B is an open, inverted cup shape. Mounting flanges 130 for fixing to the connecting member 3 are provided at the four corners of the base 120. With the bottom surface B of the mounting flanges 130 on the base 120 in close contact with the connecting member 3, four through holes 16 are provided on the mounting flanges 130 at positions corresponding to the four screw holes 13 of the connecting member 3, which serves as the second mounting part. The robot body 110 is fixed to the force detection device 1 by bolts 17 passing through each through hole 16 and screwed into the screw hole 13 of the connector 3. In this case, the robot 100 of this embodiment is formed such that the sum of the thickness value t1 of the connector 3 (which serves as the second mounting part) and the thickness value t2 of the mounting flange 130, relative to the size A of the mounting flange 130, has a ratio α greater than a preset threshold Th, where α = (t1 + t2) / A ≥ Th. Furthermore, the thickness value t1 of the connector 3 is higher than the thickness value t2 of the mounting flange 130. Figure 4 is a graph showing the error of the force detection device 1 as the thickness value t1 of the connecting part 3 changes during analysis. As can be seen from the graph, when the thickness value t1 of the connecting part 3 is greater than a preset value, the error of the force detection device 1 decreases significantly. Furthermore, even if the thickness of the connecting part 3 is very thin, if the thickness value t2 of the mounting flange 130 of the robot body 110 fixed to the connecting part 3 is larger, the same effect should be achieved. Therefore, by forming a shape where the sum of the thickness t1 of the connecting member 3 (which serves as the second mounting part) and the thickness t2 of the mounting flange 130 is greater than a preset threshold Th relative to the size A of the mounting flange 130, the error of the force detection device 1 can be significantly reduced. In other words, the larger the thickness t2 of the mounting flange 130 of the robot body 110 is set, the larger the thickness t1 of the connecting member 3 is set, or the smaller the size A of the mounting flange 130 is set, the better the effect of reducing the error. Here, the size A of the mounting flange 130 is used, for example, when the perimeter of the quadrilateral formed by the center line connecting the four bolts 17 of the fixed mounting flange 130 and the connector 3 (as shown in Figure 3) is used, the preset threshold Th is 4%. Figure 5 shows the relationship between different robot types R1~R8, ratio α and the thickness value t1 of the connector 3. Therefore, it can be seen that various robots 100 that satisfy the above relationship can reduce the error of the force detection device 1. Furthermore, even for robots 100 with a ratio α of 4% or less, by adjusting the thickness value t1 of the connecting member 3 to satisfy the ratio of 4% or more, the error of the force detection device 1 can also be reduced. In this embodiment, the force detection device 1 and robot 100 constructed therethere form a vertical gap X (the axial gap of the second part 6) between the third part 7 fixed to the ground F and the first part 5 fixed to the force sensor body 4. Therefore, the amount of gap X makes the force transmission path from the outer periphery of the third part 7 to the first part 5 longer. In other words, according to the configuration of this embodiment, when the bolt 8 passes through the through hole 9 of the third part 7 and is screwed into the screw hole 10 provided on the ground F, the influence of the stress on the force sensor body 4 caused by the distortion or surface undulation of the ground F can be reduced. Therefore, even if the ground F is distorted or surface undulation, the accuracy of detecting the force acting on the robot body 110 can still be improved. Furthermore, in the robot 100 according to this embodiment, the connecting member 3 of the mounting flange 130 fixed to the base 120 of the robot body 110 is formed into a fairly thick flat plate. Therefore, compared to the first mounting part 2, which reduces the distortion effect of the ground F due to the gap X, the connecting member 3 has considerable rigidity. As a result, even if the movement of the robot body 110 causes large load variations acting on the connecting member 3, which serves as the second mounting part, it is possible to prevent the force sensor body 4 from distorting in a direction other than a predetermined one. In other words, even though the base 120 of the robot body 110 is a cup-shaped structure with an opening at the bottom surface B of the mounting flange 130, resulting in relatively low structural rigidity, the deformation of the base 120 due to large load variations can be suppressed by fixing it to the connecting member 3, which has a larger thickness, through the mounting flange 130. Therefore, it has the advantage of preventing a decrease in the force detection accuracy of the force sensor body 4. Furthermore, in this embodiment, the mounting flange 130 and connecting member 3, which are used to implement the base 120 of the robot body 110 connected by four bolts 17, are used as the size A of the quadrilateral connected by the centers of the four bolts 17. The size A of the mounting flange 130 can also be replaced by the diagonal length of the quadrilateral. Furthermore, when fixed with three bolts 17, the perimeter of the triangle formed by connecting the centers of the three bolts 17 can be used as the size A of the mounting flange 130. Alternatively, the circumference or diameter of the circle passing through the centers of the three bolts 17 can be set as the size A of the mounting flange 130. 1: Force detection device; 2: First mounting part; 3: Connector; 4: Force sensor body; 5: First part; 6: Second part; 7: Third part; 8: Bolt; 9: Through hole; 10: Screw hole; 11: Bolt; 12: Through hole; 13: Screw hole; 14: Through hole; 15: Bolt; 16: Through hole; 100: Robot; 110: Robot body; 120: Base; 130: Flange; B: Bottom surface; F: Ground surface; X: Clearance; O: Central axis [Figure 1] A side view of a robot with a force detection device in one embodiment. [Figure 2] A partial side view of the robot's base and the force detection device in Figure 1. [Figure 3] A top view of the connector mounted on the robot in Figure 1. [Figure 4] A graph showing the relationship between the thickness of the connector and the error of the force detection device. [Figure 5] A chart showing the relationship between various robot types, ratio α, and the thickness t1 of the connector. 1: Force detection device 2: First Installation Section 3: Connectors 4: Force sensor body 5: Part One 6: Part Two 7: Part Three 100: Robot 110: Robot Body 120: Base 130: Install flange B: Bottom surface F: Ground

Claims

1. A force detection device, comprising: A first mounting portion is fixed to a first mounting surface; a second mounting portion is fixed to a second mounting surface, the load variation of the second mounting surface being greater than that of the first mounting surface; and a force sensor body is fixed between the first mounting portion and the second mounting portion; wherein, the first mounting portion includes a first part, a second part, and a third part, the first part being a flat plate or blade-shaped part fixed to one end face of the force sensor body; the second part being columnar and having one end connected to the other side of the first part opposite to the force sensor body; the third part being disposed at the other end of the second part and fixed to the first mounting surface; an axial gap is formed between the first part and the third part; the second mounting portion is formed as a highly rigid flat plate fixed to the other end face of the force sensor body, and its rigidity is higher than that of the third part.

2. The force detection device as claimed in claim 1, wherein the second mounting surface is in close contact with the surface of the second mounting portion, and the second mounting surface is provided with a mounting flange fixed to the second mounting portion, wherein the thickness of the second mounting portion is greater than the thickness of the mounting flange.

3. The force detection device as claimed in claim 2, wherein the sum of the thickness values ​​of the mounting flange and the second mounting portion, relative to the size of the mounting flange, has a ratio greater than a preset threshold; wherein the size of the mounting flange is the perimeter of the quadrilateral formed by the centers of the four bolts fixing the mounting flange and the second mounting portion.

4. The force detection device as described in claim 2 or 3, wherein the first mounting surface is the ground and the second mounting surface is the bottom surface of the mounting flange disposed on a base of a robot body.

5. The force detection device as claimed in claim 4, wherein the second mounting portion has the same shape as the outline of the bottom surface.

6. A robot, comprising: Such as the force detection device described in claim 4 or claim 5; And a robot body, the bottom surface of which is fixed to the second mounting part of the force detection device.

7. A robot, comprising: Force detection device; The system includes a robot body and a mounting flange on its bottom surface fixed to a force detection device. The force detection device has a first mounting part, a second mounting part, and a force sensor body. The first mounting part is fixed to the ground, the second mounting part is fixed to the mounting flange, and the force sensor body is disposed between the first mounting part and the second mounting part. The sum of the thickness values ​​of the mounting flange and the second mounting part, relative to the size of the mounting flange, has a ratio greater than 4%. The size of the mounting flange is the perimeter of the quadrilateral formed by the centers of the four bolts fixing the mounting flange and the second mounting part.

8. The robot as claimed in claim 7, wherein the first mounting portion has a first part, a second part and a third part, the first part being a flat plate or blade-shaped part fixed to one end face of the force sensor body; the second part being columnar and having one end connected to the other side of the first part opposite to the force sensor body; the third part being disposed at the other end of the second part and fixed to the ground; and a gap in the axial direction of the second part being formed between the first part and the third part.

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