Universal joint

Abstract

To provide a universal joint capable of freely turning like a spherical bearing, and having a large swing angle.SOLUTION: An inside surface (241S) of a second wall part (223), which is one of two wall parts of a universal joint, is formed with a recessed region (240) forming a space with a vertical surface. The recessed region (240) is formed so as to include a top part of the second wall part (223). The recessed region (240) is formed, for example, by forming a slope (241) on an inside surface (241S).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a universal joint (cardan joint).

Background Art

[0002] A universal joint is included as an essential component in the parallel links that make up a robot arm mechanism. As an example of such parallel links, there is one described in Japanese Patent Application Laid-Open No. 2014-61571 (Patent Document 1). FIG. 17 is a schematic diagram of the parallel link described in the same publication. As shown in FIG. 17, the parallel link 10 is composed of a fixed plate 12, a movable plate 13, and a plurality of arms 14 and links 17 that connect the fixed plate 12 and the movable plate 13.

[0003] A plurality of motors 15 are built into the fixed plate 12, and each of the plurality of arms 14 is driven by each of the plurality of motors 15. Each motor 15 is provided with an encoder 15a for detecting the angle of each arm 14. Each arm 14 is attached to the fixed plate 12 at one end thereof. The link 17 is connected to the other end of the arm 14 via a joint portion 11 that can freely rotate in space at one end thereof, and is connected to the movable plate 13 via two intersecting joint portions 11 at the other end thereof. These two intersecting joint portions 11 constitute the universal joint 21.

[0004] FIG. 18 is a partially enlarged view of the universal joint 21 and its surroundings. As shown in FIG. 18, a lateral through-hole is formed in one of the shafts 11a, 11b of the two intersecting joint portions 11, and the other shaft 11b is passed through this through-hole, whereby the two intersecting shafts 11a, 11b are formed. The universal joint 21 is connected to the movable plate 13 via a rotating shaft 22.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-61571 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the conventional parallel link 10 shown in Figures 17 and 18, the range of motion of the universal joint 21 is said to be wider than that of previous universal joints. Furthermore, in the conventional parallel link 10, the shape is such that each component does not interfere with one another even when the swing angle at all points is 45 degrees, and the universal joint 21 is said to be capable of achieving a swing angle of 45 degrees.

[0007] Generally speaking, in robotic arm mechanisms, the larger the overall range of motion, the more effective the operation. Therefore, a large swing angle is required for the universal joint. Here, the swing angle refers to the rotational angle when the output shaft oscillates. In robotic arm mechanisms requiring a large range of motion, a 45-degree swing angle for universal joints is insufficient; a larger swing angle is required.

[0008] This invention was made in view of the problems of conventional universal joints described above, and aims to provide a universal joint that can achieve a larger swing angle. [Means for solving the problem]

[0009] To achieve this objective, the present invention provides a universal joint for connecting a first part and a second part, the universal joint comprising: a rod end having a first part and a cylindrical second part continuous with the first part; a holder having a base part, a first wall portion upright on the base part, and a second wall portion upright on the base part parallel to the first wall portion at a position away from the first wall portion, wherein the second part of the rod end is connected to the first part so as to be rotatable about the axial center line of the second part, and the holder The base portion is connected to the second part so as to be rotatable around an axis perpendicular to the base portion, the first portion of the rod end is connected to both the first wall portion and the second wall portion so as to be rotatable around a rotation axis perpendicular to the axial centerline of the second portion, the distance between the first wall portion and the second wall portion is such that the rod end can rotate around the rotation axis, and a recessed region is formed on the inner surface of at least one of the first wall portion and the second wall portion, forming a space between it and a vertical plane, and the recessed region is formed between the first wall portion and the second wall portion at least one of the two The present invention provides a universal joint characterized by being formed to include the top portion.

[0010] The recessed region is formed, for example, by forming a bevel on the inner surface. Alternatively, the recessed region can be formed by forming an arc-shaped surface on the inner surface. Furthermore, the bevel or arc-shaped surface can be formed as a thin-walled portion with less thickness than other parts. In addition, the bevel or arc-shaped surface can be formed by bending the inner surface.

[0011] The aforementioned slope can be composed of multiple inclined surfaces with different angles of inclination relative to each other. Preferably, the inclined surface or the arc-shaped surface starts at a position between the axis of rotation and one end of the first wall portion or the second wall portion in the width direction, and ends at the other end of the first wall portion or the second wall portion in the width direction. The inclination angle of the slope is set, for example, to be within the range of 5 to 45 degrees.

[0012] It is preferable that a curved shape is formed at the corner of the slope or the arc-shaped surface. The first wall portion or the second wall portion located below the slope or the arc-shaped surface inner corner teeth curved shape to It is preferable that it is formed. The aforementioned recessed region is In the height direction of the first wall and the second wall, between the height of the rotation axis and the apex of the first wall or the second wall at The thinnest Becoming It is preferable.

[0013] Preferably, the recessed region is formed on one side of the first wall portion in the width direction with respect to the axis of rotation, and on the other side of the second wall portion in the width direction with respect to the axis of rotation. [Effects of the Invention]

[0014] In the universal joint according to the present invention, recessed regions are formed on the inner surfaces of one or both of the first and second wall portions, creating a space between them and a vertical plane. Conventional universal joints could only achieve a swing angle of approximately 45 degrees, but the universal joint according to the present invention can achieve a swing angle of approximately 90 degrees by forming the aforementioned recessed region. Universal joints, which can achieve a larger swing angle than conventional joints, are ideal for applications such as parallel links that make up robot arm mechanisms. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view of a universal joint according to the first embodiment of the present invention. [Figure 2] Figure 1 is a longitudinal cross-sectional view of the universal joint shown. [Figure 3] It is a perspective view showing only the second wall portion of the universal joint shown in FIG. 1. [Figure 4] It is a longitudinal sectional view of the second wall portion along the line A-A in FIG. 3. [Figure 5] It is a perspective view showing the operation of the universal joint according to the first embodiment of the present invention. [Figure 6] It is a perspective view showing the operation of the universal joint according to the first embodiment of the present invention. [Figure 7] It is a perspective view showing the operation of the universal joint according to the first embodiment of the present invention. [Figure 8] It is a perspective view showing the operation of the universal joint according to the first embodiment of the present invention.

[0016] [Figure 9] It is a perspective view showing the operation of the universal joint according to the first embodiment of the present invention. [Figure 10] It is a perspective view of the second wall portion of the universal joint according to the second embodiment of the present invention. [Figure 11] It is a front view of the universal joint shown in FIG. 10. [Figure 12] It is a longitudinal sectional view of the second wall portion in the universal joint according to the third embodiment of the present invention. [Figure 13] It is a longitudinal sectional view of the second wall portion in the universal joint according to the fourth embodiment of the present invention. [Figure 14] It is a longitudinal sectional view of the second wall portion in the universal joint according to the fifth embodiment of the present invention. [Figure 15] It is a perspective view showing a schematic structure of a robot arm mechanism to which the universal joints according to the first to fifth embodiments are applied. [Figure 16A] In the robot arm mechanism shown in FIG. 15, it is a perspective view showing the behavior of the robot arm mechanism when the lever ratio is changed to various values. [Figure 16B]Figure 15 is a perspective view showing the behavior of the robot arm mechanism when the lever ratio is changed to various values. [Figure 16C] Figure 15 is a perspective view showing the behavior of the robot arm mechanism when the lever ratio is changed to various values. [Figure 17] This is a schematic diagram of a conventional parallel link. [Figure 18] Figure 17 shows a partially enlarged view of the universal joint and its surroundings in a conventional parallel link. [Modes for carrying out the invention]

[0017] (First embodiment) Figure 1 is a perspective view of a universal joint 200 according to the first embodiment of the present invention. 2 This is a longitudinal cross-section of the Universal Joint 200. As shown in Figures 1 and 2, the universal joint 200 comprises a rod end 210 and a holder 220. The rod end 210 consists of a first part 211 that is roughly cylindrical in shape, and a second cylindrical part 212 that extends radially from a point on the circumference of the first part 211.

[0018] The holder 220 consists of a base portion 221, a first wall portion 222 that stands upright on the base portion 221, and a second wall portion 223 that stands upright on the base portion 221 parallel to the first wall portion 222 at a position away from the first wall portion 222 and has the same height as the first wall portion 222. The second portion 212 of the rod end 210 is connected to the first part 231 via a bearing 230A so that it can rotate around the axial centerline Y1 of the second portion 212. Although not shown, a base 110 is connected to the first part 231.

[0019] The base portion 221 of the holder 220 is connected to the second part 232 via a bearing 230B so as to be rotatable around an axis Y2 parallel to the height direction of the first wall portion 222 and the second wall portion 223, that is, an axis Y2 perpendicular to the rotation axis X of the first part 211, which will be described later. The first connecting member 140 or the second connecting member 150 is connected to the second part 232. The first portion 211 of the rod end 210 is connected to both the first wall portion 222 and the second wall portion 223 via a cylindrical shaft 224 so as to be rotatable around a rotation axis X (see Figure 1; in Figure 2, the axis perpendicular to the plane of the paper in Figure 2) that is perpendicular to the plane defined by the first wall portion 222 and the second wall portion 223.

[0020] The distance between the first wall portion 222 and the second wall portion 223 is set such that the second portion 212 of the rod end 210 does not interfere with the rod end 210 when the rod end 210 rotates around the rotation axis X. Figure 3 is a perspective view showing only the second wall portion 223, and Figure 4 shows the second wall portion 223 along line AA in Figure 3. beside This is a cross-section. As shown in Figure 3, the inner surface (the surface facing the first wall portion 222) 241S of the second wall portion 223 is provided with a recessed region 240 (see Figure 4) that forms a space (gap) between it and the vertical plane including the inner surface 241S of the second wall portion 223.

[0021] As shown in Figures 3 and 4, the recessed region 240 is formed as a thin-walled portion with a smaller wall thickness than the other parts. Specifically, the recessed region 240 is formed by providing a slope 241 on the inner surface 241S of the second wall portion 223. As shown in Figure 4, the inclined surface 241 is formed by linearly reducing the thickness of the second wall portion 223 from end 223A to end 223B in the width direction H, with starting point 241A being on the inner surface 241S between one end 223A and the rotation axis X of the shaft 224, and ending point 241B being on the surface of the other end 223B in the width direction H.

[0022] The starting point 241A of the inclined surface 241 is set between the end 223A of the second wall portion 223 and the rotation axis X of the shaft 224 in order to set a large contact range for the second portion 212 of the rod end 210 with respect to the inclined surface 241, and to ensure that the second portion 212 of the rod end 210 makes contact with the second wall portion 223. The recessed region 240 is formed to include the top of the second wall 223. That is, the recessed region 240 or slope 241 has a height from the top of the second wall 223 to the axis of rotation X of the shaft 224 in the height direction of the second wall 223.

[0023] By forming the recessed region 240 to include the top of the second wall portion 223, the second portion 212 of the rod end 210 can come into contact with the recessed region 240. Figure 4 shows an example of the dimensions of the second wall section 223. Width of the second wall section 223 (length of horizontal direction H) = 40 mm The thickness of the second wall portion 223 (length in the direction perpendicular to the horizontal direction H) = 9 mm Diameter of the hole into which shaft 224 is fitted = 10 mm Distance between the axis of rotation X and the starting point 241A of the inclined plane 241 = 7 mm The distance between the inner surface 241S and the endpoint 241B of the inclined surface 241 = 4.5 mm

[0024] The inclination angle of the slope 241 of the second wall portion 223 shown in Figures 3 and 4 is approximately 10 degrees. The inclination angle of the slope 241 can be set within the range of 5 to 45 degrees. However, when increasing the inclination angle, it is necessary to increase the thickness of the second wall portion 223 in proportion to the inclination angle. Figures 5 to 9 are perspective views showing the operation of the universal joint 200 according to this embodiment. The movement of the universal joint 200 will be described below with reference to Figures 5 to 9.

[0025] Firstly, as shown in Figures 5 and 6, the rod end 210 (and the first component 231) rotates within the space between the first wall portion 222 and the second wall portion 223 about the rotation axis X of the shaft 224. Specifically, it rotates within a range of approximately 180 degrees between the first limit position shown in Figure 5 (where the second portion 212 of the rod end 210 contacts the base portion 221) and the second limit position shown in Figure 6 (the position opposite to the first limit position).

[0026] During the transition from the state shown in Figure 5 to the state shown in Figure 6, the first part 231 continues to rotate around the axial centerline Y1 relative to the rod end 210, and the second part 232 continues to rotate around axis Y2 relative to the rod end 210, but the second part 212 of the rod end 210 does not rotate around the axial centerline Y1. In other words, the swing angle is 0 degrees. Secondly, as shown in Figures 7 to 9, the rod end 210 rotates around the axial centerline Y1 while twisting. That is, it performs motion with an angle of swing.

[0027] First, as shown in Figure 7, the first component 231 rotates around the axial center line Y1 relative to the rod end 210, and the second component 232 rotates around the axis Y2 relative to the rod end 210, causing the rod end 210 to move in the direction of arrow R, that is, to tilt toward the second wall portion 223, and the second portion 212 of the rod end 210 comes into contact with the inclined surface 241 formed on the inner surface 241S of the second wall portion 223. As shown in Figure 8, while the first part 231 and the second part 232 continue to rotate, the rod end 210 slides along the inclined plane 241 from the starting point 241A toward the ending point 241B.

[0028] Next, as the rod end 210 passes the end point 241B of the slope 241, it falls into the space between the first wall 222 and the second wall 223, as shown in Figure 9. This state is the same as the state shown in Figure 5, but in the operation shown in Figure 5, the rod end 210 is tilted down while the swing angle remains at 0 degrees. In contrast, in the operations shown in Figures 7 to 9, the rod end 210 is tilted down while having achieved a swing angle of approximately 90 degrees.

[0029] Thus, while conventional universal joints could only achieve a swing angle of approximately 45 degrees, the universal joint 200 according to this embodiment can achieve a swing angle of approximately 90 degrees. The inclination angle of the slope 241 in this embodiment is approximately 10 degrees, and by setting the inclination angle of the slope 241 to be even larger, it is possible to further increase the swing angle.

[0030] (Second Embodiment) Figure 10 is a perspective view of the second wall portion 223 of the universal joint 300 according to the second embodiment of the present invention, and Figure 11 is a front view of the universal joint 300. As shown in Figure 10, in this embodiment, the corners (peripheral edges) of the slope 241 and the corners of the inner surface 241S of the second wall 223 located below the slope 241 are all formed in a curved shape.

[0031] By making at least the corners of the slope 241 curved in this way, the rod end 210 can slide more smoothly along the slope 241, thereby increasing the speed and efficiency of the universal joint 300's operation. Furthermore, by forming the corner portion of the inner surface 241S of the second wall portion 223 located below the slope 241 into a curved shape, the tilting motion of the rod end 210 shown in Figure 9 can be made smoother.

[0032] Furthermore, as shown in Figures 10 and 11, a portion 223C with the smallest wall thickness is formed in the height direction of the second wall portion 223 between the height of the rotation axis X and the apex of the second wall portion 223, and the corner portion of this portion 223C can also be formed into a curved shape. By forming part 223C, the swing angle of the rod end 210 can be further increased, and by forming the corner of part 223C into a curved shape, the movement of the rod end 210 can be made smoother. The structures of the universal joints 200 and 300 according to the first and second embodiments are not limited to the above-described structures, and various modifications are possible.

[0033] In Figures 3 and 10, the slope 241 is formed only on one side of the second wall 223 (one side of the second wall 223 centered on the axis of rotation X in the width direction, which is to the left of the axis of rotation X in Figures 3 and 10). However, it is also possible to form a slope similar to the slope 241 on the first wall 222. When forming a slope similar to the slope 241 on the first wall 222, the slope of the first wall 222 is formed diagonally opposite the slope 241 of the second wall 223. That is, if the slope 241 of the second wall 223 is formed to the left of the axis of rotation X as shown in Figures 3 and 10, the slope of the first wall 222 is formed to the right of the axis of rotation X. By arranging the first wall portion 222 and the second wall portion 223 to face each other at an angle in this way, and forming inclined surfaces, the range in which the rod end 210 can rotate around the rotation axis X with a large swing angle can be maximized.

[0034] (Third embodiment) In the first embodiment described above, the recessed region 240 or the slope 241 is formed by linearly reducing the thickness of the second wall portion 223, but the method of forming the recessed region 240 or the slope 241 is not limited thereto. Figure 12 shows the second wall portion 223 in the universal joint according to the third embodiment. beside This is a cross-section.

[0035] As shown in Figure 12, instead of linearly reducing the thickness of the second wall portion 223, it is also possible to form a slope 241 by bending the second wall portion 223, which has a constant thickness, and inclining the inner surface 241S of the second wall portion 223 with respect to the vertical plane. According to the universal joint of the third embodiment, it is possible to obtain the same effects as the universal joint 200 of the first embodiment, and it is also possible to apply the curved shape of the universal joint 300 of the second embodiment to this embodiment.

[0036] (Fourth embodiment) The formation of the recessed region 240 is not limited to the formation of the slope 241. Figure 13 shows the second wall portion 223 in the universal joint according to the fourth embodiment. beside This is a cross-section. As shown in Figure 13, instead of the single slope 241, a slope consisting of multiple (three in Figure 13) inclined surfaces 241A, 241B, and 241C with different angles of inclination can also be used.

[0037] The inclined surfaces 241A, 241B, and 241C are formed in that order from the rotation axis X toward the end 223B of the second wall portion 223. The length components of the three inclined surfaces 241A, 241B, and 241C in the horizontal direction H are the same, but their inclination angles with respect to the horizontal direction H are different. The inclination angle G1 of inclined surface 241A is smaller than the inclination angle G2 of inclined surface 241B, and the inclination angle G2 of inclined surface 241B is smaller than the inclination angle G3 of inclined surface 241C. G1 <G2<G3

[0038] In this way, by providing multiple inclined surfaces 241A, 241B, and 241C, it is possible to provide many variations in the operation of the rod end 210. The universal joint according to this embodiment can also achieve the same effects as the universal joints according to the first and third embodiments, and the curved shape of the universal joint 300 according to the second embodiment can also be applied to this embodiment.

[0039] (Fifth embodiment) Figure 14 shows the second wall portion 223 in the universal joint according to the fifth embodiment. beside This is a cross-section. As shown in Figure 14, it is also possible to form an arc-shaped surface 242 instead of the slope 241. By forming an arc-shaped surface 242, the same effect as when forming an inclined surface 241 can be obtained.

[0040] Figure 14 shows an arc-shaped surface 242 that is concave toward the first wall portion 222, but it is also possible to form an arc-shaped surface that is convex toward the first wall portion 222. The universal joint according to this embodiment can also achieve the same effects as the universal joints according to the first, third, and fourth embodiments, and the curved shape of the universal joint 300 according to the second embodiment can also be applied to this embodiment.

[0041] The universal joints according to the first to fifth embodiments described above can be applied in various fields as devices that rotatably connect two members to each other. Below, as an example of an application, a robot arm mechanism to which the universal joints according to the first to fifth embodiments are applied will be described. Figure 15 is a perspective view showing the schematic structure of a robot arm mechanism 100 to which a universal joint according to the first to fifth embodiments is applied.

[0042] The robot arm mechanism 100 consists of a base 110, a first plate 120, a second plate 130, three first connecting members 140, three second connecting members 150, a bar 160, and a joint member 170. The base 110 and the first plate 120 are each circular, flat members, and the second plate 130 is a ring-shaped member with a circular opening in the center. The base 110 and the first plate 120 are connected via three first connecting members 140.

[0043] The three first connecting members 140 are positioned on the circumferences of the base 110 and the first plate 120 at equicircular angles (i.e., at positions where the inscribed angle is 120 degrees). Each of the three first connecting members 140 consists of two bars 141a and 141b, and a linear actuator 142 that connects these two bars 141a and 141b.

[0044] Generally, a linear actuator 142 comprises an electric motor, a ball screw, and a reduction mechanism. The ball screw converts the rotational motion of the electric motor into linear motion, and the reduction mechanism reduces the speed of the linear motion to an appropriate speed before outputting it. By controlling the rotation direction and rotation speed of the electric motor, the direction and speed of the linear motion can be adjusted.

[0045] In this way, by controlling the operation of the linear actuator 142, one of the two bars 141a and 141b can be displaced linearly in the longitudinal direction relative to the other. Displacing one of the two bars 141a and 141b away from the other increases the overall length of each first connecting member 140, and displacing one of the two bars 141a and 141b closer to the other decreases the overall length of each first connecting member 140. In other words, the linear actuator 142 makes it possible to extend or retract each of the first connecting members 140 to a desired length, and consequently, the distance between the base 110 and the first plate 120 can be adjusted to a desired value, and furthermore, the posture determined by the inclination angle of the first plate 120 relative to the base 110 can be adjusted to a desired posture.

[0046] The second plate 130 is positioned on the same side as the first plate 120 relative to the base 110, and furthermore, the second plate 130 is positioned further away from the base 110 than the first plate 120. The base 110 and the second plate 130 are connected via three second connecting members 150.

[0047] The three second connecting members 150 are positioned on the circumferences of the base 110 and the second plate 130 at equicircular angles (i.e., at positions where the inscribed angle is 120 degrees). Each of the three second connecting members 150, like the first connecting member 140, consists of two bars 151a and 151b and a linear actuator 152 connecting these two bars 151a and 151b. Similar to the first connecting member 140, each of the second connecting members 150 can be extended or retracted to a desired length by controlling the operation of the linear actuator 152, thereby adjusting the distance between the base 110 and the second plate 130 to a desired value, and further adjusting the posture determined by the inclination angle of the second plate 130 relative to the base 110 to a desired posture.

[0048] The bar 160 is connected to the first plate 120 at one end (the upper end in Figure 15) via a universal joint 122. Therefore, the first plate 120 and the bar 160 can each rotate relative to each other in any direction. The other end of bar 160 (the lower end in Figure 15) constitutes the end effector 161.

[0049] Furthermore, the bar 160 is connected to the second plate 130 at a point between its ends via a joint member 170. The joint member 170 allows the bar 160 to rotate and slide relative to the second plate 130, and by being connected to the second plate 130 via the joint member 170, the bar 160 is rotatable relative to the second plate 130 in any direction within the range of motion of the joint member 170, and is also slidable relative to the second plate 130 in the longitudinal direction of the bar 160.

[0050] In the robot arm mechanism 100, the base 110, the first plate 120, and three first connecting members 140 constitute the first parallel manipulator, and furthermore, the base 110, the second plate 130, and three second connecting members 150 constitute the second parallel manipulator. The robot arm mechanism 100 is formed by combining a first parallel manipulator (parallel link) and a second parallel manipulator, which share the base 110, and further combining them with a bar 160 and a joint member 170.

[0051] Thus, the robot arm mechanism 100 includes two parallel manipulators and has a composite structure in which the first parallel manipulator and the second parallel manipulator are in a serial positional relationship. Thus, in the robot arm mechanism 100 composed of two parallel manipulators, once the lengths of the first connecting member 140 and the second connecting member 150 are determined, the positions and orientations of the base 110, the first plate 120, and the second plate 130 are uniquely determined. Furthermore, if the lengths of the first connecting member 140 and the second connecting member 150 are kept constant, the positions and orientations of the base 110, the first plate 120, and the second plate 130 are fixed.

[0052] To achieve this, the first connecting member 140 and the second connecting member 150 must be connected to the base 110 so as to be rotatable in all directions, and each must be connected to the first plate 120 and the second plate 130 with one degree of freedom. To satisfy this condition, in the robot arm mechanism 100, the first connecting member 140 and the second connecting member 150 are connected to the base 110 via universal joints 111 and 112, respectively, and to the first plate 120 and the second plate 130 via hinge joints 121 and 131, respectively.

[0053] In the robot arm mechanism 100 having the structure described above, any of the universal joints according to the first to fifth embodiments can be used as the universal joints 111, 112, and 122. The robot arm mechanism 100 can be configured as a mechanism that performs the function of a lever. Specifically, the universal joint 122 connecting the bar 160 and the first plate 120 functions as the point of force application, the joint member 170 connecting the bar 160 and the second plate 130 functions as the fulcrum, and the end effector 161 at the tip of the bar 160 functions as the point of application.

[0054] Here, we define the leverage ratio as follows: Lever ratio R = D1 / D2 D1 = Distance between joint member 170 (fulcrum) and end effector 161 (point of application) D2 = Distance between joint member 170 (fulcrum) and universal joint 122 (point of effort).

[0055] For example, if the end effector 161 at the tip of the bar 160 is grounded, and the end effector 161 is fixed as the point of application, then when the length of each second connecting member 150 is extended or retracted, the joint member 170, which functions as a fulcrum, moves up and down together with the second plate 130. That is, the distances D1 and D2 change, and consequently, the lever ratio R changes. Furthermore, by simultaneously extending or retracting the length of each first connecting member 140, the distances D1 and D2 change in two ways, allowing the leverage ratio R to be changed over a wider range.

[0056] Thus, in the robot arm mechanism 100, by changing the length of either or both of the first connecting member 140 and the second connecting member 150 via the linear actuators 142 and 152, the joint member 170 slides along the bar 160, and the lever ratio R changes accordingly. This change in the lever ratio R can be applied to mechanisms for various purposes. For example, it can be applied to walking assistance mechanisms that support human walking. Figures 16A, 16B, and 16C are perspective views showing the behavior of the robot arm mechanism 100 when the lever ratio R is changed to various values.

[0057] In the state shown in Figure 16A, the joint member (fulcrum) 170 is closer to the universal joint (point of force application) 122 than to the end effector (point of application) 161. That is, distance D1 is relatively large, and distance D2 is relatively small. In the state shown in Figure 16B, the joint member (fulcrum) 170 is located approximately midway between the end effector (point of application) 161 and the universal joint (point of force application) 122, so distance D1 is smaller than distance D1 in Figure 16A, and distance D2 is larger than distance D2 in Figure 16A. In the state shown in Figure 16C, the joint member (fulcrum) 170 is closer to the end effector (point of application) 161 than to the universal joint (point of force application) 122. That is, distance D1 is smaller than distance D1 in Figure 16B, and distance D2 is larger than distance D2 in Figure 16B.

[0058] Therefore, if we denote the lever ratios in Figures 16A, 16B, and 16C as R1, R2, and R3, respectively, the relative magnitudes of R1, R2, and R3 are as follows. R1>R2>R3 The magnitude of the lever ratio R directly correlates to the magnitude of the swing arc. Swing refers to the arc motion that the bar 160 performs around the joint member (fulcrum) 170 in response to the expansion and contraction of the first connecting member 140 and the second connecting member 150, assuming that the universal joint (point of force application) 122 is a fixed point, or assuming that the movement of the universal joint (point of force application) 122 is the same. When the bar 160 performs an arc motion, the end effector (point of application) 161 also performs an arc motion in the same way. The swing width refers to the horizontal component of the displacement of the end effector (point of application) 161 when the end effector (point of application) 161 performs an arc motion.

[0059] When the point of force application is displaced, the point of application is displaced around the fulcrum in proportion to the amount of displacement. In this case, the larger the lever ratio R, the greater the amount of displacement at the point of application. Therefore, as shown in Figures 16A, 16B, and 16C, if the swing ranges when the lever ratio R is R1, R2, and R3 are S1, S2, and S3, respectively, then the relative magnitudes of S1, S2, and S3 are as follows. S1 > S2 > S3

[0060] Thus, in the robot arm mechanism 100, by controlling the extension and retraction of the first connecting member 140 and the second connecting member 150, the joint member (fulcrum) 170 can be slid along the bar 160, and the lever ratio R can be changed to various values. For this reason, the robot arm mechanism 100 can be applied as a lever mechanism to various other mechanisms. The universal joints according to the first to fifth embodiments, used as universal joints 111, 112, and 122, improve the reliability of the operation of the robot arm mechanism 100 described above. [Explanation of symbols]

[0061] 200 Universal Joint 210 Rod End 220 holder 240 recessed area 241 Slope 300 Universal Joint (Variation) 100 Robot Arm Mechanisms 110 base 120 First Plate 130 Second Plate 140 First connecting member 150 Second connecting member 160 bar 170 Joint Members

Claims

1. A universal joint connecting the first part and the second part, The aforementioned universal joint is A rod end comprising a first part and a cylindrical second part continuous with the first part, A holder comprising a base portion, a first wall portion standing upright on the base portion, and a second wall portion standing upright on the base portion parallel to the first wall portion at a position away from the first wall portion, Equipped with, The second portion of the rod end is connected to the first component so as to be rotatable around the axial centerline of the second portion. The base portion of the holder is connected to the second component so as to be rotatable around an axis perpendicular to the base portion, The first portion of the rod end is connected to both the first wall portion and the second wall portion so as to be rotatable around a rotation axis perpendicular to the axial center line of the second portion. The distance between the first wall portion and the second wall portion is such that the rod end can rotate around the rotation axis. A recessed region is formed on the inner surface of at least one of the first wall portion and the second wall portion, which forms a space between it and the vertical plane. A universal joint characterized in that the recessed region is formed to include the top of at least one of the first wall portion and the second wall portion.

2. The universal joint according to claim 1, characterized in that the recessed region is formed by forming a slope on the inner surface.

3. The universal joint according to claim 1, characterized in that the recessed region is formed by forming an arc-shaped surface on the inner surface.

4. The universal joint according to claim 2 or 3, characterized in that the inclined surface or the arc-shaped surface is formed as a thin-walled portion with a smaller wall thickness than other parts.

5. The universal joint according to claim 2 or 3, characterized in that the inclined surface or the arc-shaped surface is formed by the curvature of the inner surface.

6. The universal joint according to claim 2, 4, or 5, characterized in that the aforementioned slope is composed of a plurality of inclined surfaces with mutually different inclination angles.

7. The universal joint according to any one of claims 2 to 6, characterized in that the inclined surface or the arc-shaped surface starts at a position between the axis of rotation and one end of the first wall portion or the second wall portion in the width direction, and ends at the other end of the first wall portion or the second wall portion in the width direction.

8. The universal joint according to any one of claims 2 and 4 to 7, characterized in that the inclination angle of the slope is within the range of 5 to 45 degrees.

9. The universal joint according to any one of claims 2 to 8, characterized in that a curved shape is formed at the corner of the inclined surface or the arc-shaped surface.

10. The universal joint according to any one of claims 2 to 9, characterized in that the corner portion of the inner surface of the first wall portion or the second wall portion located below the inclined surface or the arc-shaped surface is formed in a curved shape.

11. The universal joint according to any one of claims 1 to 10, characterized in that the thickness of the recessed region is smallest between the height of the rotation axis and the apex of the first wall or the second wall in the height direction of the first wall and the second wall.

12. The universal joint according to any one of claims 1 to 11, characterized in that the recessed region is formed on one side of the first wall portion in the width direction with respect to the axis of rotation, and on the other side of the second wall portion in the width direction with respect to the axis of rotation.

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