JPS5977162A - Rotation decelerator for robot - Google Patents

Abstract

PURPOSE:To make a decelerator installable in the inside of a robot arm, besides excellent in rigidity as well as to aim rotation deceleration with less lost motion or backlash, by performing conversion from rotation to linear motion and further to rotation motion with a screw mechanism, while using the differential motion of a screw in combination. CONSTITUTION:Two screws 13 and 14 of an intermediate shaft 10 and a screw 15 of an output shaft 7 all are of right-handed screw in type and their leads are set down to l1, l2 and l3, and of which l1 is set to be larger than l2 in an axial distance. When the output shaft of a motor 4 rotates, the intermediate shaft 10 is shifted by l1 per rotation in the screw 13 while a column 20 is fed by l2 per rotation in the screw 14 reversely whereby its apparent move comes to a difference between leads. The output shaft 7 rotates by dint of the screw 15 screwed together with paired nuts 18A and 18B clamped to the column 20 and thereby a reduction gear ratio comes to l3/(l1-l2). Like this, with adoption of a screw mechanism, such a form as suitable for installation in the inside of a robot arm comes to fruition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a speed reducer, and particularly to a rotary speed reducer suitable for robots that require high rigidity and high precision.

[Prior art]

In industrial robots with many joints, a configuration is widely adopted in which the working arm and support arm are connected by a pivot to form a joint, and the joint is freely rotated by a combination of an electric motor and a gear train. ing.

In particular, in these drive systems, the output of the electric motor can be reduced to several tenths.
The number of gears is relatively large because the speed is reduced to about 1/100th of the original speed, which increases the amount of backlash of the gear train and reduces the rigidity of the screw system. For this reason, when moving the working arm to a predetermined position, there are problems such as increased vibration within a specific operating speed range and a relatively large positioning error.

[Purpose of the invention]

The present invention has been made based on the above-mentioned problems, and an object of the present invention is to obtain a rotary reducer that can be installed inside a robot's arm, has high rigidity, and has little play.

[Summary of the invention]

In order to achieve the above object, the present invention utilizes a screw mechanism, which is widely used as a direct-acting drive element due to its high rigidity and little backlash, to convert rotation to linear motion, and even from linear to linear motion. It is constructed so that conversion into rotational motion can be performed, and by further using differential motion of the screw, a rotational reduction mechanism is realized.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the rotary reducer for a robot according to the present invention, and is a side view of a robot joint part shown in section C. In the figure, a rotary reducer 5 for a robot according to the present invention is installed within a support arm 1. The input shaft 6 is connected to the drive shaft of the electric motor 4, and the output shaft 7 is connected to the pivot shaft 3 provided integrally with the operating arm 2 via bevel gears 8, 9.
The output of the electric motor 4 is decelerated to rotate the operating arm 2 around the drive shaft 3. Note that this rotation range is one rotation or less.

The detailed structure of the robot rotary reducer 5 described above will be explained with reference to FIG. In Fig. 2, the input shaft 6 is the intermediate shaft 1.
0 and transmits the rotation from the electric motor 4 to the intermediate shaft 1.
A hollow hole in the shape of a spline or a sliding key is provided to guide the axial movement of the 0, and the 0 is held in the frame 21 via a bearing 24. The intermediate shaft 10 is provided with splines or sliding keys 11, 12 at both ends. One end of this 10Ω intermediate shaft fits into the hollow hole of the input shaft 6 described above, and the other end is also supported by a support shaft 19 having a hollow hole similar to the input shaft 6. The intermediate shaft 10 is therefore rotatable and axially movable. Further, the intermediate shaft 10 is provided with two threaded portions 13 and 14 having different leads. A pair of nuts 16A and 16B are screwed into the first threaded portion 13, and a pair of nuts 17A is screwed into the frame 22, and a pair of nuts 17A is screwed into the second threaded portion 14.
.

17B is fixed to the column 20. The output shaft 7 has a threaded portion 15 on a part of the shaft, and the intermediate shaft 10 is also held in a V-frame 22.23 via a bearing 25.26 so as to be parallel to the shaft. Nut pair 1 screwed onto the threaded portion 15 of the output shaft 7
8A and 18B are fixed to the column 20 and are the aforementioned nut pair 17A.

17B. Note that each pair of nuts A and B in 16.17.18 is pressurized to minimize the axial clearance and to improve rigidity.

゛Next, the operation of one embodiment of the above-mentioned rotary reducer for a robot according to the present invention will be explained. Two screws 13 of intermediate shaft 10
．． 14 and the screw 15 of the output shaft 7 are all right-handed screws, and their respective leads are tt + 12 + t3. Sara K
It is assumed that tl is slightly larger than t2. Now, when the output shaft of the electric motor 4 rotates clockwise (as seen from the output shaft), the intermediate shaft 1
Rotation is transmitted to 0. This rotation causes the intermediate shaft 10
Since the pair of nuts 16A and 16B screwed together by the threaded portion 13 is fixed to the frame 22, it is sent in the right direction of the axis. The amount of movement for this movement to the right is 401 rotations of the electric motor (#)l-1
It is. Furthermore, Natsuto vs. 17A.

The column 20 that fixes the shaft 17B will be moved one rotation bt2 to the left by the rotation of the screw 14, but since the entire intermediate shaft 10 moves to the right as described above, the appearance of the column 20 will be The movement appears as the difference. In other words, the amount of movement per revolution of the electric motor is equal to the lead difference between the two screws 13 and 14 by 1. -12, the direction is to the right of the axis since tl is larger than t2. Furthermore, as the nut pair 18A, 18B fixed to the column 20 moves to the right, the output shaft 7
rotates clockwise (viewed from the output side). Note that the reduction ratio i of the output shaft 7 to the human power shaft 6 in this example is expressed by the following equation.

Therefore, for example, the lead difference between the two screws 13° 14 of the intermediate shaft 1o is 1. -12 is 0.1 cylinder, and the lead t3 of the screw 15 of the output shaft 7 is 1orftIn, the reduction ratio is 1/100.
becomes. Note that in order to widen the operating angle range of the output shaft 7, it is necessary to lengthen the threaded portions 13 and 14, which lengthens the entire reducer, but the operating angle is relatively small in robots, and generally 1. It can be easily mounted inside the arm because it rotates less than 30 minutes, and the arm is relatively long so that a sufficient installation space can be secured. Further, according to this embodiment, the two nuts are pressurized and screwed together with the screw, which has the effect of reducing backlash and improving rigidity.

FIG. 3 shows another embodiment of the rotary reducer for a robot according to the present invention, and in this figure, the same reference numerals as in FIG. 2 are the same or corresponding parts.

In this embodiment, the intermediate shaft 10 in FIG.
It is divided into 0A1 second intermediate shaft 10B and the length in the axial direction of the reducer is shortened. a first intermediate shaft i0A, a second intermediate shaft,
tOB and the output shaft 7 are installed parallel to the axes, and the rotation of the input shaft 6 by the electric motor 4 is transmitted to the first intermediate shaft 10A and also to the second intermediate shaft 10B via gears 29, 30, 31. Ru. Further, a connecting frame 32 is provided between the first intermediate shaft 10A and the second intermediate shaft 10B.

The connecting frame 32 rotatably holds the intermediate shafts 10A and IOB through bearings 33 and 34, and the nut pair 16A,
The LMIOB is installed to transmit the axial displacement of the first intermediate shaft 10A sent by the LMIOB 16B to the second intermediate LMIOB. Therefore, the column 2o differentially moves due to the rotation input manually applied through the gear 29.3031 and the axial displacement caused by the connecting frame 32, and similarly to the embodiment shown in FIG. 2, the column 2o decelerates the input from the electric motor 4. and transmits the signal to the output shaft 7. Therefore, this practical example not only has the same effect as the example shown in FIG. 2, but also has the effect of reducing the size of the reducer in the axial direction.

〔Effect of the invention〕

As described in detail above, according to the present invention, since a screw mechanism is employed, rigidity is high, there is little backlash, and the backlash adjustment is easy. Furthermore, it has advantages such as a shape suitable for being mounted inside a robot's arm.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of a joint drive system including an example of the rotary reducer for a robot according to the present invention, FIG. 2 is a cross-sectional view showing an example of the rotary reducer for a robot according to the present invention, and FIG. FIG. 2 is a diagram showing another embodiment of the rotary reducer for a robot according to the present invention. 6...Input 1 song, 7...Output shaft, 1o river axis, 1
1゜12...Spline, 13,14.15...Thread part, 16.17.18 River nut, 2o...Column,
28...Base.

Claims (1)

[Claims] An input shaft is rotatably held in a base via a bearing and has a hollow hole in the shape of a spline or a sliding key, and a second threaded portion with one end fitted into the hollow hole of the input shaft and having two threaded portions with different leads. The threaded part 1 has an intermediate shaft held on the base through a nut screwed onto the threaded part, and a threaded part on a part of the shaft that is parallel to the intermediate shaft and rotatably held from the base via a bearing. a column connecting the nut screwed to the second threaded portion of the intermediate shaft and the nut screwed to the threaded portion of the output shaft; The column is moved in the axial direction by the differential action of two screws provided on the intermediate shaft, and then rotated again by a nut screwed into the threaded part on the output shaft connected to the column. A rotary reducer for robots that is characterized by obtaining rotational output through conversion.