JPH0464839B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a motion limit position detection device suitable for detecting the motion angle limit of a joint of an industrial robot whose motion angle range exceeds 360°. It is related to.

[Prior Art] Some joints of industrial robots, such as arc welding robots, have a range of motion of more than 360 degrees, for example, 400 degrees. In addition, in robot wrist mechanisms, power is often transmitted using bevel gears, etc., and when decelerating with this bevel gear, the rotation angle of the rotation axis for driving the wrist mechanism may be different from that of the actual wrist mechanism. It may be more than twice the output angle (operating angle) and exceed one rotation (360°).

As described above, as a means for detecting the operating angle limit when the operating angle range exceeds 360 degrees, there is conventionally a method of detecting the operating angle limit using a soft limit without providing a mechanical limit switch. This soft limit detects the operating angle limit using microcomputer-controlled software, and is quite reliable.

Further, as an operation limit position detection device that detects the operation angle limit using a limit switch, there is a device as shown in FIG. In this device, a first detection gear b is attached to the output shaft a whose operating angle limit is to be detected, and a second detection gear c engages with this gear b and reduces the rotation of the output shaft a by half. will be established. Then, attach striker d to gear c,
Limit switches e, which come into contact with the striker d to detect the end of the operating angle, are arranged near the gear c. With such a configuration, the rotation of the output shaft a is reduced to 1/2 and transmitted to the gear c via the gear b. Therefore, the rotation angle of gear c is 200 degrees with respect to the rotation angle of output shaft a of 400 degrees, and the operating angle range can be kept within one rotation, and 360 degrees can be easily achieved with striker d and limit switches e, e. It is possible to detect the limit of the operating angle that is exceeded.

[Problems to be solved by the invention] However, with the former conventional soft limit, it may malfunction due to electrical noise, etc., and there are doubts about its safety. Since the angle detection counter was not set to a normal value (the counter was reset at the zero point position), there was a problem that the soft limit function did not work properly and could not be used.

In addition, in the latter conventional operating limit position detection device,
In order to decelerate the rotation of the output shaft a, large operating angle limit detection gears b and c are required, and in some cases it may be necessary to provide a multi-stage gear train, which not only poses space problems but also reduces detection accuracy. There were problems such as the need to pay attention to the backlash of the speed reduction mechanism, which has a direct effect on the speed reduction mechanism.

The present invention is an attempt to solve the above-mentioned problems, and is a compact operation limit position detection device that can reliably and highly accurately detect the operating angle limit of a rotating shaft without providing a speed reduction mechanism or the like. The purpose is to provide equipment.

[Means for Solving the Problems] Therefore, the motion limit position detection device of the present invention moves an axially movable member having a male screw portion formed on the outer peripheral surface of the rotating shaft in the axial direction of the rotating shaft. The rotary shaft is slidably and integrally fitted onto the rotary shaft, and is screwed into the male screw portion, thereby causing the axially moving member to rotate integrally with the rotary shaft. and a detector that is activated by rotation of the coaxially moving member to detect the operating limit position of the rotary shaft when the axially moving member moves to a predetermined axial position. It is characterized by

[Operation] In the above-mentioned motion limit position detection device of the present invention, when the rotating shaft rotates, the axially moving member rotates integrally with the rotating shaft and rotates the male screw portion by the fixed guide. and is guided along the axial direction of the rotating shaft. When the axially movable member moves to a predetermined axial position, the detector is activated by the rotation of the axially movable member that rotates integrally, and the rotation corresponding to the predetermined axial position is activated. The rotation limit position of the shaft is detected. Therefore, by appropriately setting the predetermined axial position and arranging the detector, the operation limit position of any multiple rotations exceeding 360 degrees can be accurately detected.

[Embodiments of the Invention] Hereinafter, a motion limit position detection device as an embodiment of the present invention will be explained with reference to the drawings. Fig. 2 is a sectional view taken in the - arrow direction of Fig. 1, and Fig. 3 is a plan view showing the arrangement of the detector (limit switch).
FIG. 4 is a sectional view taken along the - arrow in FIG. 3.

First, with reference to FIGS. 1 and 2, the joints of an industrial robot (manipulator such as an arc welding robot) to which the apparatus of this embodiment is applied and its drive mechanism will be explained. This joint is a biaxial robot wrist portion having a bending degree of freedom α around the S1 axis and a twisting degree of freedom β around the S2 axis. In order to rotate these two axes, two drive motors 2 and 3 are installed inside the casing 1 of the robot arm.
The rotation of each drive motor 2, 3 is transmitted to rotating shafts 6, 7 via reduction gears (harmonic reduction gears) 4, 5, respectively. The rotational force transmitted to each rotating shaft 6, 7 is transmitted to the S1 shaft and S2 shaft via bevel gear mechanisms 8, 9, respectively, and each shaft is rotationally driven.

Now, in such a joint part, the rotating shafts 6 and 7 in the casing 1 each have a sliding key 1.
0 and 11 are provided to protrude along the axial direction, and male screw members 12 and 13 as axially moving members are fitted onto the outside so as to be slidable in the axial direction. The male screw members 12, 13 are engaged with the sliding keys 10, 11, rotate integrally with the rotating shafts 6, 7 (without relative rotation), and move only in the axial direction. .

Furthermore, fixed guides 14 and 15 are attached to the casing 1 at the outer peripheral portions of the male threaded members 12 and 13 to guide the male threaded members 12 and 13, respectively. Each fixed guide 14, 15 has a male screw member 1
2, 13 corresponds to a part (rack shape) of a nut that can be screwed into the screw threads 12a, 13a on the outer periphery, and each male screw member 12, 13 is screwed and guided by the fixed guide 14, 15, respectively. As a result, it moves in the axial direction along the sliding keys 10 and 11 while rotating together with the rotating shafts 6 and 7.

In this embodiment, as shown in FIGS. 2 to 4, when the male threaded members 12 and 13 move to a predetermined axial position, each of these male threaded members 12 and 13
limit switch 1 as a detector that is activated by and detects the rotational position of the rotation shafts 6 and 7, respectively;
6a, 16b, 17a, and 17b are provided. The limit switches 16a, 16b are connected to each end surface 12b, 12c of the thread 12a of the male screw member 12.
Similarly, the limit switches 17a, 17b are operated by contacting each end face 13b, 13c of the thread 13a of the male screw member 13.
It operates by coming into contact with each.

In addition, each of the above end surfaces 12b, 12c, 13b,
13c includes limit switches 16a, 16b,
A taper is formed to protect the detection portions 17a and 17b.

In this embodiment, it is assumed that the rotating shaft 6 has an operating angle range of 420 degrees, and a male screw member 12 corresponding to a striker has three turns and a thread 12a of 120 degrees (1200 degrees), and a limit switch 16a,1
6b is 4 and a half turns (1620°) when viewed from the screw pitch.
installed at a distance. Therefore,
Limit switches 16a and 16b are 1620°-
It is possible to detect the operating angle end of the operating angle range of 1200° = 420°. The bending degree of freedom α of this robot around the S1 axis is 420° x (1/2)
=210°.

Furthermore, regarding the male threaded member 13 in this embodiment, the limit switches 17a and 17b are attached at positions separated by five and a half turns (1980°), and the male threaded member 7 corresponding to the striker has a thread of 1015°. 13a is formed. Therefore, the limit switches 17a and 17b are capable of detecting the operating angle end of the operating angle range of 1980°-1015°=965°. The twisting degree of freedom β of this robot around the S2 axis is 965° x (1/2) x (3/2)
It is ≒724°.

Furthermore, in this embodiment, as shown in FIG.
Rubber stopper members 18 and 19 are fitted onto the ends of the rotating shaft 7, respectively, at positions outside the limit switches 17a and 17b (the movement limit position of the male screw member 13). Each stopper member 18, 19
are the axial end faces 13d and 13e of the male screw member 13.
The movement of the male threaded member 13 and the rotation of the rotating shaft 7 are mechanically restricted at the movement limit position. Also, as shown in Figure 2,
Although the above-mentioned stopper member is not provided on the rotating shaft 6 side, the rotating shaft 6 is mechanically stopped by the wrist portion 20 coming into contact with the rubber stoppers 21 and 22 attached to the casing 1. are becoming regulated.

Since the operating limit position detection device as an embodiment of the present invention is configured as described above, the rotating shaft 6,
7 is rotationally driven by the drive motors 2 and 3,
Along with the rotation, the male screw members 12 and 13 move along the axial direction while rotating together with the rotating shafts 6 and 7, respectively.

And the screw thread 12 of each male screw member 12, 13
When a and 13b rotate a predetermined number of times and move to a predetermined axial position, the male screw member 12
, each end face 12b, 1 of the thread 12a
2c are limit switches 16a and 16b, respectively.
When the limit switches 16a and 16b come into contact with each other, the limit switches 16a and 16b are activated, and the operating limit position of the rotary shaft 6 (in the case of this embodiment, the operating angle limit of the operating angle range of 420 degrees) is detected. Similarly, the limit switches 17a and 17b are activated for the male threaded member 13, and the rotating shaft 7 is placed at the operating limit position (in the case of this embodiment).
The operating angle limit of the operating angle range of 965° is detected.

In this way, each limit switch 16a,
When 16b, 17a, 17b is activated, normally,
The operation of the motor 2 or 3 is stopped, the rotation of the rotating shafts 6 and 7 is also stopped, and the rotation of the wrist portion 20 around the S1 axis or the S2 axis is stopped at a predetermined position.

In the event that the limit switches 16a, 16b, 17a, 17b do not operate due to an electrical failure or the like, in this embodiment, the rotating shaft 7 is
comes into contact with the stopper member 18 or 19, thereby absorbing the impact force and restricting the movement of the male threaded member 13.
The rotation of the rotating shaft 7, which is integral with the rotating shaft 7, is restricted. Regarding the rotation shaft 6, the rotation of the rotation shaft 6 is regulated by the end surface of the wrist portion 20 coming into contact with a stopper 21 or 22 provided at an appropriate position, and the rotation of the wrist portion 20 around the S1 axis is restricted. , is mechanically regulated at a predetermined limit position.

As described above, according to this embodiment, in principle, the limit switches 16a, 16b, 17a, 17b
By arranging the limit switches 16a, 16b, 17a,
The detection error caused by the rotational shaft 17b is almost exclusively an error in the rotational direction, and is not affected by backlash or the like due to the meshing of the screw structures, so that the operating angle limit of the rotating shafts 6 and 7 can be detected extremely reliably and with high precision.

In addition, there is no need to provide a speed reduction mechanism (see Figure 5) as used in conventional devices, and it is only necessary to provide male screw members 12, 13 that move along the rotating shafts 6, 7, a limit switch, etc. , the device can be made into a compact structure, and an optimal device can be obtained for detecting the rotation limit position in the wrist portion of an industrial robot as shown in this embodiment.

Furthermore, since the wear of the threaded surfaces (threads 12a, 13a) hardly affects the outer diameters of the male screw members 12, 13, there is an advantage that the detection of the operation limit position is not easily affected by the wear.

In the above embodiment, the sliding keys 10 and 11 are protruded from the rotating shafts 6 and 7, respectively, but a ball spline may also be used. This is effective when the rotation speed is high and there is a risk of keyway wear.

Further, in the above embodiment, a limit switch is used as the detector, but a proximity switch, a Hall element, etc. may also be used.

[Effects of the Invention] As detailed above, according to the motion limit position detection device of the present invention, the axially moving member that moves in the axial direction and integrally rotates as the rotating shaft rotates, and the A detector activated by the rotation of the movable member is provided, and the rotational position of the rotating shaft is detected by detecting the movement of the axially movable member with the detector. By arranging it in the position, the operating limit position (operating angle limit of the operating angle range) in the case of arbitrary multiple rotations can be detected easily and with extremely high accuracy, and there is no need to provide a deceleration mechanism, making the device It has a compact structure, and has the effect of providing an optimal device for detecting the operating limit position in a narrow space such as the wrist of an industrial robot.

[Brief explanation of the drawing]

1 to 4 show an operating limit position detection device as an embodiment of the present invention, and FIG. 1 is a cross-sectional view of a joint of a robot to which the device of this embodiment is applied (- Fig. 2 is a sectional view taken in the - arrow direction of Fig. 1, Fig. 3 is a plan view showing the arrangement of the detector (limit switch), and Fig. 4 is a sectional view taken in the - arrow direction of Fig. 3. FIG. 5 is a schematic diagram showing a conventional motion limit position detection device. In the figure, 6, 7...Rotating shaft, 12, 13... Male screw member as an axially moving member, 12a, 13
a...Screw thread, 12b, 12c, 13b, 13c...
End face of screw thread, 14, 15...Fixed guide, 16
a, 16b, 17a, 17b...Limit switches as detectors.

Claims (1)

[Scope of Claims] 1. An axially movable member having a male thread formed on the outer peripheral surface of the rotating shaft is slidable in the axial direction of the rotating shaft and rotatable integrally with the rotating shaft. A fixed guide is provided that is fitted externally and screws into the male threaded portion to move the axially moving member in the axial direction of the rotating shaft while rotating integrally with the rotating shaft, and An operation limit position detection device comprising: a detector that is activated by rotation of the coaxially moving member to detect the operation limit position of the rotary shaft when the moving member moves to a predetermined axial position. 2. The operating limit position detection device according to claim 1, wherein the detector operates by detecting the end of the male threaded portion in its rotational direction. 3. Claims 1 or 2, characterized in that the rotation axis is a joint rotation axis of a manipulator, and the axially moving member and the detector are installed within a casing of the manipulator. The operating limit position detection device described in . 4. The operating limit position detection device according to claim 3, wherein the manipulator is an arc welding robot.