JP3136816B2 - Robot arm with torque sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology relating to an arm or hand of an industrial robot.

[0002]

2. Description of the Related Art In the case of an articulated robot, a second arm is pivotally movable by a first joint with respect to a first arm, and a third arm is pivotally mounted by a second joint with respect to the second arm. Structure is generally taken. Hands that can detect the torque acting on each arm have also been developed. An example of such a robot hand is disclosed in
No. 3-28580 or a magazine entitled "Yaskawa Electric", Vol. 55 (Vol. 211), No. 2, 1991, pp. 86-93. In the latter technical report, the torque sensor shown in FIG. 4B, that is, if the magnetostrictive films 104a, 104b... Note that the magnetic permeability changes due to distortion of 104a, 104b,...
2 shows a technique for detecting the value of.

[0003]

As illustrated in FIG. 5, the third member E is connected to the rotation axis (longitudinal direction) of the first member B at the distal end of the first member (or the first arm) B. If it is attempted to make a large turn around the axis D1 perpendicular to B1, especially indefinitely (ie 360 ° or more),
The rotation axis B1 of the first member B and the rotation axis E1 of the third member E
Can not be placed in a cross. That is, illustrated B
The axes shown at 1, D1 and E1 cannot cross at one point. This is because the first member B prevents the third member E from turning around the axis D1.

[0004] Therefore, as shown in FIG.
It is conceivable to dispose the second member D with the member E offset from the first member B. In this way, the third member E can turn without being restricted by the first member B.

At this time, in order to detect the state of the torque acting on the arm or the hand of the robot, the torque acting around the axis D1 of the second member D must also be detected. Here, it is conceivable to use the torque sensor shown in FIG. 4B. However, according to the conventional torque sensor, a long axial distance is required, and the third member E is connected to the first member.
The member B has to be largely offset. However, at the time of actual work of the robot, the smaller the offset amount between the first member B and the third member E, the easier the work is, and it is also preferable in terms of miniaturization of the hand.

Accordingly, in the present invention, the second member D is offset between the first member B and the third member E to secure a wide turning range of the third member E,
The offset amount between the first member B and the third member E is reduced as much as possible by shortening the axial length of the torque sensor for detecting the torque value acting on the member D.

[0007] In addition to the torque sensor shown in FIG. 4 (b), as shown in FIG.
There is a type in which a strain gauge 110 is attached to the shaft 8 or a method of detecting a relative amount of twist between a pair of flanges 114 and 116 formed on a shaft 112. However, even if such a type of torque sensor is used, it becomes longer in the axial direction, and the offset amount between the first member B and the third member E cannot be sufficiently reduced.

[0008]

Accordingly, in the present invention, FIG.
The robot hand with the torque sensor shown schematically in Fig. 2 was created. In other words, the robot hand is rotatable about an axis D1 orthogonal to the longitudinal direction B1 of the first member B with respect to the first member B, and is attached to a position offset from the first member B. 2 members D,
A second member actuator A attached to the base of the first member B for rotating the second member rotator C;
An outer ring F fixed to one of the second member D and the second member rotating body C, an inner ring J fixed to the other, and a plurality of beams G holding the outer ring F and the inner ring J coaxially. And a displacement sensor H for detecting an amount of displacement generated between the outer ring F and the outer ring end of the inner ring extension piece I projecting from the inner ring J to the outer ring F side. Features.

[0009]

According to the robot hand having this configuration, since the third member E is offset from the first member B by the second member D, the turning of the third member E is performed by the first member.
There is no restriction by member B. Also, the second member rotating body C and the second member D are connected to the outer race F and the inner race J by the beam G
Are connected by a torque transmission member G connected by Here, if the second member D is attached to the outer ring F, the rotating member C for the second member is attached to the inner ring J. On the contrary, the rotating member C for the second member is attached to the outer ring F, and the second member D is attached to the inner ring J. 2
Member D may be attached. Either way, beam G
, The torque is transmitted between the second member rotating body C and the second member D.

Now, the external force acting on the second member D is large,
When the second member actuator A opposes the external force with a large torque, the beam G is largely bent. On the other hand, if the torque value of the actuator A is small, the deflection of the beam G is also small. That is, the torque value corresponds to the magnitude of the deflection of the beam G. In the present invention, since the magnitude of the deflection of the beam G is detected by the displacement sensor H, the torque value acting on the second member D is detected. In this case, the inner ring J
And the outer ring F can be arranged to overlap in the axial direction, so that the distance between the second member rotating body C and the second member D,
That is, the offset amount between the first member B and the third member E can be made sufficiently small.

[0011]

According to the present invention, the second member which offsets the third member from the first member so that the third member can turn without being hindered by the first member is connected to the inner ring and the outer ring by a beam. The first member and the third member are connected to the rotating member for the second member by the torque transmitting member.
The torque acting on the second member can be detected in a state where the offset amount between the members is small, so that the robot hand can be downsized and various operations can be performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIG. In FIG. 2, reference numeral 50 denotes a base of the robot hand, in which the first member servomotor 1 and the second
Servo motor 2 for member, servo motor 3 for third member
Has been fixed. The first member 10 is attached to the base 50 by a bearing 52 so as to be rotatable about its longitudinal axis 10a. 1st member 1
The second member 20 is rotatably mounted around the axis 20a with respect to the shaft 20 by a bearing 54. Further, the bearings 56, 58, 60
Thereby, the third member 30 is rotatably mounted around the axis 30a. Rotation axis 20 of second member 20
a is orthogonal to the rotation axis (longitudinal direction of the first member 10) 10a of the first member 10, and is the rotation axis 30 of the third member 30.
a is orthogonal to the rotation axis 20 a of the second member 20.

The rotation of the first member servomotor 1 is reduced by a reduction mechanism 11 to rotate the shaft 12 and the gear 13. The gear 13 meshes with a gear 14 arranged coaxially with the first member 10, and the gear 14 is fixed to the inner ring 15. An outer ring 17 is arranged outside the inner ring 15 at the same height position in the axial direction, and the inner ring 15 and the outer ring 17 are connected by a plurality of beams 16. And the outer ring 17
The member 10 is fixed. The inner ring 15 and the outer ring 17
Since the structure of the torque transmitting member formed by the beam 16 is the same as that for the second member 20,
This will be described in detail when describing the torque transmitting member for the second member 20 with reference to FIGS.

When the first member servomotor 1 is rotated, the inner ring 15 is rotated, and the inner ring 15 rotates the outer ring 17 via the beam 16, so that the first member 10 fixed to the outer ring 17 is rotated. You. As a result, the second member 20
Is turned around the axis 10a.

The rotation of the second member servomotor 2 is reduced by a reduction mechanism 21 to rotate the shaft 22 and the gear 23. The gear 23 meshes with a gear 24a coaxially arranged with the first member 10, and the gear 24a is
4b and rotates together. A bevel gear 24c is fixed to the lower end of the tube 24b, and the bevel gear 24c is in mesh with one bevel gear 25a. Bevel gear 2
5a is integrated with the cylinder 25b, and the cylinder 25b is
6 fixed.

As shown in FIG. 3, six beams 27 are fixed radially outward on the inner ring 26, and the outer ring 28 is held coaxially with the inner ring 26 by the six beams. You. From the inner ring 26, a pair of overhang pieces 29a, 2
9b is projected over the diameter, and the outer ends of the projecting pieces 29a, 29b are formed with a pair of recesses 28 formed in the outer race 28.
a, 28b with a gap therebetween. Outer ring 2
8, a pair of gap sensors 90a and 90b
The sensors 90a, 90b are fixed so as to face the outer ends of 9a, 29b, respectively, and detect the gap between the sensors 90a, 90b and the overhanging pieces 29a, 29b.

For example, when a clockwise torque Tr acts on the outer ring 28 and a counterclockwise torque Tr acts on the inner ring 26, as shown in FIG. 1, the outer ring moves clockwise with respect to the inner ring as shown in FIG. , The gap between the overhanging piece 29a and the sensor 90a increases, and conversely, the gap between the overhanging piece 29b and the sensor 90b decreases. That is, the gap amount corresponds to the relative displacement between the inner ring and the outer ring. The sensor 90a,
90b detects this gap amount, that is, the relative displacement amount of the outer ring to the inner ring.

According to the above configuration, the gap sensor for detecting the gap between the outer end of the projecting piece radially projecting from the inner ring side into the recess formed in the outer ring is fixed to the outer ring. In addition, the clearance between the overhanging piece and the gap sensor generated by the shaft torque acting on the inner and outer rings can be increased without increasing the outer diameter of the outer ring, and the torque detection accuracy can be improved. Further, since the outer diameter of the outer ring can be reduced as much as possible within the required torque detection accuracy, the torque sensor itself can be made compact.

For example, when an external force for moving the outer ring 28 upward acts on the outer ring 28 and the inner ring 26 resists this force, the gap amount decreases on both the sensor 90a side and the 90b side. Therefore, if the output difference between the two sensors 90a and 90b is calculated, the influence of the external force other than the torque is canceled. Similarly, outer ring 2
Even if an external force is applied to move the sensor 90 downward, the sensor 90
It does not affect the output difference between a and 90b. In addition, the external torque in the axial direction of the inner and outer rings does not change the amount of clearance in both sensors 90a and 90b, so that the detected torque value is not affected. In this embodiment, a pair of overhanging pieces 29a, 29b arranged on the diameter and a pair of sensors 90a,
The torque is accurately detected by devising the difference between the output of the sensor 90b and the sensor output. That is, even if an external force in the vertical direction and an external force in the horizontal direction act on the paper surface of FIG. 3, the gap amount does not change, and the output difference between the sensors 90a and 90b does not change even in the vertical external force.
That is, the output difference depends only on the torque. Outer ring 28
Is attached to the first member 10 via the bearing 54, so that an external force hardly acts on the structure.

The inner race 26 extends outwardly below the beam 27 toward the outer race 28 (see 26a), and two pairs of blocks 26b, 26b are fixed thereto.
The blocks 26b, 26b are arranged so as to sandwich the beam 27 with a certain gap therebetween, and prevent further deformation of the beam 27 before the deformation of the beam 27 becomes so large that the beam 27 may be damaged. Act like so.
For this reason, even if the torque becomes large, the torque transmission member will not be damaged.

The above structure is the same for the inner ring 15, the beam 16 and the outer ring 17 of the first member. The same applies to the overhanging piece and the gap sensor, and the torque value acting on the first member 10 can also be detected.

As shown in FIG. 2, the second member 20 is fixed to the outer race 28. Therefore, when the second member servomotor 2 rotates, this rotation is performed by the bevel gear 24.
The rotation of the inner ring 26 is transmitted to the outer ring 28 via the beam 27, and the outer ring 28 causes the second member 20 to rotate. As a result, the second member 20 is rotated around the axis 20a, and the third member 3 is rotated.
0 will be turned in the vertical plane.

The part for rotating the last third member 30 around the axis 30a will be described. When the third member servomotor 3 rotates, the shaft 32 rotates via the speed reduction mechanism 31 and the bevel gear 33 rotates. Therefore, the other bevel gear 34 is rotated, and the shaft 35 is rotated. Bevel gear 3 by shaft 35
6 is rotated, which causes the bevel gear 37 to rotate. As a result, the third member 30 is rotated around the axis 30a. Note that a plate 38 is attached to the third member 30, and the plate 38 is rotated together with the third member 30. A member that finally works on the work, such as a screw bit, is attached to the plate 38.

Since the third member 30 has a certain length in the axial direction, a torque sensor 39 of the type shown in FIG. 4B is mounted thereon. This torque sensor 39
Is a non-contact type, and allows the third member 30 to rotate infinitely. The torque acting on the third member 30 is also detected by the torque sensor 39.

According to this embodiment, the rotating member 25b rotated by the second member servomotor 2 is fixed to the inner race 26, while the second member 20 is fixed to the outer race 28. The inner ring 26 and the outer ring 28 overlap at the same position in the axial direction. For this reason, the rotating member 25b for the second member
The distance between the first rotating member 20 and the second rotating member 20 is extremely short, and the offset amount between the first member 10 and the third member 30 is kept small. In spite of this small offset amount, the second member 20 is deflected from the amount of deflection generated in the beam 27.
It is possible to detect the torque value acting on the motor. In this embodiment, the second member 20 is the first member 1
The third member 30 can be oriented in any direction in a vertical plane by being rotatable 360 ° around the axis 20a with respect to zero. The third member 30 is rotatable indefinitely, and can perform a screw tightening operation or the like. For this reason, according to the present invention, screws in any direction can be tightened.

Further, in the robot hand according to the present embodiment, since the offset amount between the third member 30 and the first member 20 is small, the size is small, and it is possible to work by entering a narrow space. In this embodiment, the second member is fixed to the outer ring. Alternatively, the second member may be fixed to the inner ring, and the rotating member for the second member may be fixed to the outer ring. In this embodiment, the inner ring overhanging piece 29a,
29b, the relative displacement between the inner race 26 and the outer race 28 is detected in an expanded state. For this reason, the torque detection accuracy is high.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the concept of the present invention.

FIG. 2 is a sectional view of one embodiment.

FIG. 3 is a detailed view of a torque transmission member and a displacement sensor according to one embodiment.

FIG. 4 is a diagram showing a conventional torque sensor.

FIG. 5 is a diagram schematically showing a conventional technique.

[Explanation of symbols]

 A Actuator for second member B First member C Rotating body for second member D Second member E Third member F Outer ring G Beam I Inner ring overhanging piece J Inner ring H Displacement sensor

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Minoru Tanaka 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. No. 41, Yokomichi Inside Toyota Central Research Laboratory Co., Ltd. (56) References JP-A-4-360788 (JP, A) JP-A-4-152234 (JP, A) 58) Field surveyed (Int. Cl. ⁷ , DB name) B25J 17/02 B25J 19/00 G01L 3/14

Claims (1)

(57) [Claims] 1. An axis perpendicular to a longitudinal direction of a first member.
Instead, the first member is rotatable with respect to the first member.
Member mounted at a position offset from
And a circuit for the second member attached to the base of the first member.
A second member actuator for rotating the rolling element, and fixed to one of the second member and the second member rotating body.
The outer ring, the inner ring fixed to the other, the outer ring and the inner ring.
With multiple beams held coaxially, the diameter increases from the inner ring to the outer ring.
Having a pair of inner ring overhanging pieces arranged so as to overhang
Between the outer ring and the outer ring of the pair of inner ring overhangs
And a pair of displacement sensors for detecting the direction, and the detection directions of the pair of displacement sensors are reversed.
Robot arm with torque sensor.