Robot arm mechanism

Abstract

The object of the present invention is to simplify the joints by making them lighter in a robot arm mechanism capable of detecting contact with a person or an object. A robot arm mechanism (1) of one embodiment of the present invention has a rotating joint (J1, J2). The rotating joint (J1) and the rotating joint (J2) are connected by a connecting rod (30). The connecting rod (30) has a plurality of connecting rod parts (31, 33, 35, 37). The connecting rod parts (31, 33) are connected via a torque sensor (61), the connecting rod parts (33, 35) are connected via a torque sensor (63), and the connecting rod parts (35, 37) are connected via a torque sensor (65).

Description

Technical Field

[0001] The invention relates to a robot arm mechanism. Background Art

[0002] As the labor force decreases, collaborative robots that can work with humans in the same space are gradually being used. For collaborative robots, it is necessary to stop safely when the robot comes into contact with a person or an object. As one of the methods for detecting the contact between a robot and a person or an object, a method using a torque sensor is disclosed (e.g., Patent Document 1). In the method using a torque sensor, for example, a torque sensor is configured at the joint of the robot. When the output value of the torque sensor exceeds a prescribed reference value, it can be judged that "the robot has come into contact with a person or an object", and based on this, measures such as stopping the robot can be taken.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-134059 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] In particular, if a torque sensor is installed at the joint part on the front end side of the robot, the weight of the front end part of the robot increases, and the weight load on the base side of the robot increases. In order to cope with the increase in weight, it is necessary to use expensive components with high rigidity. In addition, the joint part houses components such as a motor and a reducer, and these electrical components are connected to the wiring of cables, etc. Therefore, when a torque sensor is installed at the joint part, not only the joint part becomes larger, but also the structure inside the joint part becomes complicated. Therefore, in a robot arm mechanism that can detect contact with a person or an object, it is desired to simplify the structure of the joint part by reducing the weight of the joint part.

[0008] Means used to solve problems

[0009] A robot arm mechanism according to one embodiment of the present disclosure includes a rotary joint, a link connected to the rotary joint, and a plurality of torque sensors. The link includes a plurality of link parts, and the link parts are connected to each other via the torque sensors.

[0010] Effects of the Invention

[0011] According to this aspect, in a robot arm mechanism that can detect contact with a person or an object, the joint portion can be simplified (lightened). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a perspective view of a robot arm mechanism according to one embodiment.

[0013] Figure 2 yes Figure 1 Front view of the robot arm mechanism.

[0014] Figure 3 yes Figure 1 A top view of the robot arm mechanism.

[0015] Figure 4 yes Figure 1 Exploded perspective view of the connecting rod. DETAILED DESCRIPTION

[0016] Below, while referring to the attached Figure 1 In the following description, components having substantially the same function and structure are denoted by the same reference numerals, and repeated description will be given only when necessary.

[0017] Figure 1 , Figure 2 as well as Figure 3 : shows the reference posture of the robot arm mechanism 1 of this embodiment. Figure 1 , Figure 2 as well as Figure 3 As shown, the robot arm mechanism 1 of the present embodiment has a base portion 10 placed on a ground surface such as the ground. The base portion 10 is connected to the connecting rod 30 via the first rotating joint portion J1, and the first rotating joint portion J1 has a first rotating axis RA1 perpendicular to the ground surface. Specifically, the base portion 10 is connected to the fixed side of the first reducer 20 driven by the first motor not shown, and one end of the connecting rod 30 is connected to the rotating side. The first reducer 20 is driven by the first motor, so that the arm portion 50 rotates around the first rotating axis RA1 relative to the base portion 10 together with the connecting rod 30. The connecting rod 30 is connected to the arm portion 50 via the second rotating joint portion J2, and the second rotating joint portion J2 has a second rotating axis RA2 perpendicular to the first rotating axis RA1. Specifically, the other end of the connecting rod 30 is connected to the fixed side of the second reducer 40 driven by the second motor not shown, and one end of the arm portion 50 is connected to the rotating side. The second reducer 40 is driven by the second motor, so that the arm portion 50 rotates around the second rotating axis RA2 relative to the connecting rod 30.

[0018] In the following, the axis parallel to the first rotation axis RA1 of the robot arm mechanism 1 is referred to as the Z axis, the axis parallel to the second rotation axis RA2 of the robot arm mechanism 1 in the reference posture is referred to as the X axis, and the axis orthogonal to the first rotation axis RA1 and the second rotation axis RA2 is referred to as the Y axis for appropriate description.

[0019] In the robot arm mechanism 1 of the present embodiment, a plurality of torque sensors are provided on the link 30 between the first rotation joint J1 closest to the base 10 and the second rotation joint J2 adjacent to the first rotation joint J1. The link 30 has four link parts 31, 33, 35, 37, and three torque sensors 61, 63, 65 are dispersedly provided on the link 30. The four link parts 31, 33, 35, 37 are referred to as the first link part 31, the second link part 33, the third link part 35, and the fourth link part 37, respectively, from the side away from the base 10, that is, from the side close to the front end of the robot arm mechanism 1. The three torque sensors 61, 63, 65 are referred to as the first torque sensor 61, the second torque sensor 63, and the third torque sensor 65, respectively, from the side away from the base 10.

[0020] In addition, the torque sensor used here is a sensor having a thin cylindrical shape and used to detect torque around the central axis of its cylinder (hereinafter referred to as the detection axis). The torque sensor cannot detect force components that cross the detection axis perpendicularly and force components along the detection axis. The torque sensor is arranged between two components and outputs a torque value corresponding to the angle at which one component is twisted relative to the other component around the detection axis. By comparing the torque value with a specified threshold value, the torsion can be detected. As a method of detecting torque, known methods such as capacitive type and strain gauge type can be used.

[0021] A feature of the robot arm mechanism 1 of the present embodiment is that torque sensors 61, 63, and 65 are provided on the connecting rod 30 between the first rotating joint part J1 and the second rotating joint part J2. Compared with the case where the torque sensor is accommodated in the second rotating joint part J2, the configuration freedom of the components accommodated inside the second rotating joint part J2, such as the motor and reducer driving the second rotating joint part J2, can be improved, and it can be expected that the cost of components will be reduced, the manufacturing cost will be reduced, and wiring defects will be reduced due to easier wiring. In addition, since it is not necessary to accommodate the torque sensor in the second rotating joint part J2, the second rotating joint part J2 itself can be made small and lightweight, and it can be expected that the components closer to the base part side than the second rotating joint part J2 will be replaced with components with lower rigidity.

[0022] In addition, by providing torque sensors 61, 63, and 65 in the connecting rod 30, even when the first rotating joint portion J1 and the second rotating joint portion J2 are driven, since the connecting rod 30 itself does not move, the torque sensor can be sealed with a simple structure compared to the case where the torque sensor is accommodated in the second rotating joint portion J2, etc., which helps to improve the sealing performance and reduce costs.

[0023] Furthermore, by providing the torque sensors 61, 63, 65 on the link 30 connected to the first rotation joint J1 closest to the base 10, the distance from the tip of the arm 50, which is the part with high frequency of contact with people or objects, to the torque detection source, namely the torque sensors 61, 63, 65, can be lengthened. Thus, even if the external force applied to the tip of the arm 50 is small, the moment of the force applied to the torque sensors 61, 63, 65 can be increased because the distance from the tip of the arm 50 to the torque sensors 61, 63, 65 is long. That is, the sensitivity of the torque sensors 61, 63, 65 can be improved, and slight contact such as slightly touching the tip of the arm 50 can be detected by the torque sensors 61, 63, 65, which helps to improve safety.

[0024] The effects described above are independent of the number of torque sensors provided on the connecting rod. The number of torque sensors provided on the connecting rod may be one or more than three, and the same effects can be achieved.

[0025] In addition, in the present embodiment, the robot arm mechanism 1 having two rotating joints is described as an example, and when the present embodiment is applied to a robot arm mechanism having 4 axes, 5 axes, 6 axes, etc., the effect is better. For example, in a robot arm mechanism having 6 joints, the torque sensor is mounted on a connecting rod between the first joint closest to the base and the second joint adjacent to the first joint among the multiple connecting rods. By arranging the torque sensor on the connecting rod between the first joint and the second joint on the side close to the base 10, the second joint, the third joint, the fourth joint, the fifth joint, and the sixth joint, which are closer to the front end of the robot arm mechanism than the connecting rod, can be made small and lightweight. By making the joint on the front end of the robot arm mechanism lightweight, the rigidity required for each component such as the connecting rod can also be reduced, and the cost of the components can be suppressed. Of course, as described above, by configuring the torque sensor, the distance from the front end of the arm to the torque sensor can be lengthened, and the sensitivity of detecting contact with the arm can be improved. Furthermore, in a robot arm mechanism having six joints, the torque sensor may be mounted on a link between the base and a first joint closest to the base.

[0026] Reference Figure 4 , the configuration structure of the three torque sensors 61, 63, 65 provided on the connecting rod 30 is described. Figure 4 As shown, the end of the fourth link part 37 corresponding to one end of the link 30 is connected to the rotating part of the first rotation joint part J1 (first reducer 20), and the end of the first link part 31 corresponding to the other end of the link 30 is connected to the fixed part of the second rotation joint part J2 (second reducer 40).

[0027] The first link portion 31 and the second link portion 33 are connected via the first torque sensor 61. The first torque sensor 61 is arranged so that the first detection axis DA1 is parallel to the second rotation axis RA2. The first torque sensor 61 outputs a torque value corresponding to the angle at which the first link portion 31 is twisted relative to the second link portion 33 about the first detection axis DA1.

[0028] The second link portion 33 and the third link portion 35 are connected via the second torque sensor 63. The second torque sensor 63 is arranged so that the second detection axis DA2 is parallel to the first rotation axis RA1. The second torque sensor 63 outputs a torque value corresponding to the angle at which the second link portion 33 is twisted relative to the third link portion 35 about the second detection axis DA2.

[0029] The third link portion 35 and the fourth link portion 37 are connected via the third torque sensor 65. The third torque sensor 65 is configured so that its third detection axis DA3 is parallel to the plane (XY plane) perpendicular to the first rotation axis RA1 and is inclined at an angle less than 90 degrees relative to the second rotation axis RA2. If the positional relationship between the detection axes is described, the third torque sensor 65 is configured so that its third detection axis DA3 is perpendicular to the second detection axis DA2 and is inclined at an angle less than 90 degrees relative to the first detection axis DA1. The third torque sensor 65 outputs a torque value corresponding to the angle at which the third link portion 35 is twisted around the third detection axis DA3 relative to the fourth link portion 37.

[0030] By configuring the torque sensors 61, 63, and 65 so that each detection axis is in the above-mentioned positional relationship, the first detection axis DA1 and the second detection axis DA2 can be made parallel to two axes (X axis and Z axis) of the three orthogonal axes, respectively, and the third detection axis DA3 can be tilted at an angle less than 90 degrees in the direction of the third detection axis DA3 relative to the remaining one axis (Y axis) of the three orthogonal axes. In this way, the first torque sensor 61, the second torque sensor 63, and the third torque sensor 65 are configured so that the first detection axis DA1, the second detection axis DA2, and the third detection axis DA3 are not parallel to each other, that is, they are in a twisted or crossed positional relationship, thereby, the first torque sensor 61, the second torque sensor 63, and the third torque sensor 65 can detect torques around different axes, and can expand the range and direction of the robot arm mechanism 1, especially the contact of the arm 50 with a person or an object that can be detected.

[0031] In addition, by configuring the first torque sensor 61 and the second torque sensor 63 to have a positional relationship in which the first detection axis DA1 is perpendicular to the second detection axis DA2, the direction of the torque detectable by the first torque sensor 61 can be orthogonal to the direction of the torque detectable by the second torque sensor 63. Thus, the range and direction of the contact with the arm 50 etc. that can be detected can be expanded, and the safety of the robot arm mechanism 1 can be improved.

[0032] Compared with when the robot arm mechanism 1 is stationary, when the robot arm mechanism 1 is in motion, the possibility of a person or an object accidentally contacting the arm 50 or the like is high. As in the present embodiment, by configuring the first torque sensor 61 so that the first detection axis DA1 is parallel to the second rotation axis RA2 of the second rotation joint J2, the first torque sensor 61 can detect contact with the arm 50 or the like during the rotational motion around the second rotation axis RA2 with high sensitivity. Similarly, by configuring the second torque sensor 63 so that the second detection axis DA2 is parallel to the first rotation axis RA1 of the first rotation joint J1, the second torque sensor 63 can detect contact with the arm 50 or the like during the rotational motion around the first rotation axis RA1 with high sensitivity. These contribute to improving the safety of the robot arm mechanism 1.

[0033] In the present embodiment, the following is also a feature, that is, the first torque sensor 61 and the second torque sensor 63 are configured so that the first detection axis DA1 and the second detection axis DA2 are parallel to two axes (X axis and Z axis) of the three orthogonal axes, respectively, and the third torque sensor 65 is configured so that the third detection axis DA3 is not parallel to the remaining one axis (Y axis) of the three orthogonal axes. As in the present embodiment, the third torque sensor 65 is configured so that the third detection axis DA3 is perpendicular to the second detection axis DA2 and is inclined at an angle less than 90 degrees relative to the first detection axis DA1, thereby, the third torque sensor 65 can detect the torque around the Y axis that cannot be detected by the first torque sensor 61 and the second torque sensor 63, and can also detect the torque around the X axis. That is, the torque around each axis of the three orthogonal axes can be detected by the three torque sensors 61, 63, and 65, and the torque around the X axis can be detected by both the first torque sensor 61 and the third torque sensor 65. Instead of configuring the three torque sensors so that the detection axes are parallel to the three orthogonal axes, one of the torque sensors is configured so that the detection axis is tilted at an angle less than 90 degrees relative to the other detection axes, thereby enabling the torque around each of the three orthogonal axes to be detected while the two torque sensors detect the torque around a specific axis. For example, by setting the axial direction of the torque detected by the two torque sensors to the axial direction of the torque with a high detection frequency of the torque, i.e., the contact frequency, the contact detection accuracy can be improved.

[0034] In addition, the above description does not deny that the three torque sensors 61, 63, and 65 are arranged so that each detection axis is parallel to each axis of the three orthogonal axes. In addition, if two torque sensors are provided instead of three, the detection axes of the two torque sensors are not parallel to each other, for example, they can be arranged in a mutually orthogonal manner. If there are four or more torque sensors, the detection axes of three torque sensors are arranged so that each detection axis is parallel to each axis of the three orthogonal axes, and the detection axis of the remaining torque sensor is not parallel to the other three detection axes.

[0035] Several embodiments of the present invention are described, and these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without exceeding the scope of the subject matter of the invention. These embodiments or their variations are included in the invention described in the claims and in the scope equivalent thereto, as well as being included in the scope and subject matter of the invention.

[0036] Description of Reference Numerals

[0037] 1…robot arm mechanism, 10…base, 20…first reducer, 30…connecting rod, 31…first connecting rod portion, 33…second connecting rod portion, 35…third connecting rod portion, 37…fourth connecting rod portion, 40…second reducer, 50…arm portion, RA1…first rotating axis, RA2…second rotating axis, DA1…first detection axis, DA2…second detection axis, DA3…third detection axis.

Claims

1. A robot arm mechanism, wherein: have: Base part, a plurality of connecting rods arranged on the base portion, a plurality of rotating joints connecting the plurality of connecting rods, and Multiple torque sensors; The plurality of torque sensors are concentratedly provided on a link closest to the base portion among the plurality of links.

2. The robot arm mechanism according to claim 1, wherein: The plurality of torque sensors are arranged in a positional relationship in which the plurality of detection axes are twisted or crossed.

3. The robot arm mechanism according to claim 2, wherein: Among the plurality of torque sensors, a first torque sensor is arranged in a positional relationship in which a detection axis of the first torque sensor is perpendicular to a detection axis of a second torque sensor.

4. The robot arm mechanism according to claim 3, wherein: Among the plurality of torque sensors, a third torque sensor is arranged in a positional relationship in which a detection axis of the third torque sensor is inclined at an angle smaller than 90 degrees with respect to a detection axis of the first torque sensor.

5. The robot arm mechanism according to claim 4, wherein: The third torque sensor is arranged in a positional relationship in which a detection axis of the third torque sensor is perpendicular to a detection axis of the second torque sensor.

6. The robot arm mechanism according to any one of claims 3 to 5, wherein: The first torque sensor and the second torque sensor are configured such that detection axes of the first torque sensor and the second torque sensor are respectively parallel to rotation axes of two rotation joints connected to both sides of at least one of the connecting rods.

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