JPS6279988A - Robot wrist mechanism - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention 1] The present invention relates to a robot wrist mechanism disposed at the tip of a robot arm.

[Background of the Invention] For example, a three-degree-of-freedom robot wrist mechanism is placed at the end of a robot arm to change the posture of a workpiece. The three degrees of freedom include turning, bending, and twisting.

Generally, the center lines of rotation for turning and bending are orthogonal, and the center lines of rotation for bending and twisting are also orthogonal. Japanese Patent Publication No. 53-83265
The robot hand 6 mechanism described in the publication corrects this point and makes their mutual rotation center lines obliquely intersecting (non-orthogonal).

In this way, mutual interference between the members due to rotation is reduced.

By the way, this type of wrist mechanism, especially its internal mechanism, is mainly composed of gears. Therefore, backlash occurs due to their mutual meshing. In order to reduce such backlash, it is preferable to arrange the speed reducer as late as possible. This is because the bank crane on the preceding stage reduces the reduction according to its reduction ratio.

However, since the configuration of the above-mentioned oblique robot hand σ mechanism is unique, simply adding a reduction gear to it would make the entire system large, impairing its practicality.

[Object of the Invention] The present invention is for compactly incorporating a speed reducer into a robot wrist ALLI in which mutual rotational center lines are tilted.

[Summary of the Invention] The present invention includes a lower cover rotatably disposed at the tip of a robot arm, an upper cover rotatably disposed on the lower cover, and a tip portion rotatably disposed on the upper cover. This is a robot wrist mechanism equipped with Moreover, the rotation center line of the upper cover is inclined at an acute angle with respect to the rotation center line of the lower cover, and the rotation center line of the tip portion is inclined at an acute angle with respect to the rotation center line of the upper cover. Also, that internal space that is covered by the upper and lower covers? This rotation transmission shaft is arranged. The rotation center line of this rotation transmission shaft coincides with the rotation center line of the upper cover. An active bevel gear and a passive bevel gear are fixed to the rotation transmission shaft, and one of the active bevel gears closer to the lower cover meshes with the drive bevel gear on the robot arm side, and the other passive bevel gear closer to the upper cover is connected to the tip. It meshes with the bevel gear for rotating the tip.

In the present invention, the reducer is arranged in the internal space surrounded by the upper and lower covers, and in the space around the inclined rotation transmission shaft between the active bevel gear closer to the lower cover and the passive bevel gear closer to the upper cover. do. The rotation input bevel gear in this speed reducer meshes with another drive bevel gear on the robot arm side. Further, the reduction output shaft of the reduction gear is fixed to the upper cover so that it can be rotated.

As mentioned above, if the internal space surrounded by the upper and lower covers and around the rotation transmission axis between the active bevel gear and the passive bevel gear is effectively utilized and the reducer is placed there, the entire robot wrist mechanism will be are combined into a robot, resulting in something more practical.

[Embodiment 1 of the invention First, the robot wrist a shown in FIGS. 1 and 4 according to the present invention
The overall configuration of the robot to which ye is attached will be explained. The robot of this embodiment is of the vertically articulated type 6 shown in FIGS. 2 and 3, and is equipped with the following components indicated by component numbers in the figures.

1: Fixed base 2: Swivel base On the fixed base 1, the vertical rotation center line (not shown)
rotate around.

3: The first arm rotates with respect to the rotating base 2. Its center of rotation is the horizontal axis 21.

42 The second γ-arm rotates with respect to the first arm 3. Its center of rotation is the horizontal axis 31. Robot arm 3 along with first arm 3.
4.

5: First arm actuator electric! III machine 51 and it is driven by Ball Sufu 11
52, the whole of which is screwed onto the flange 22 of the pivot base 2. The lever 32 integrated with the first arm 3 is moved by the output of the ball screw 52.

6: Second arm actuator In FIG. 2, it is hidden behind the first arm actuator 5 and cannot be seen. This is a mechanism in which the first arm 4 is moved using a parallelogram-shaped link mechanism 34.

7.8.9: Both wrist electric motors are wrist electric motors, and these are arranged at the rear end of the first arm 4. Among these, the first wrist electric motor 817 in particular is equipped with a speed reducer including a speed reducer i7g.

70, 80, 90: Both rotary drive axes are rotary drive axes, and these are arranged on the inner peripheral side of the robot arm (first arm 4) so as to extend in the longitudinal direction thereof. The rotary drive shafts 70, 80, and 90 are arranged concentrically through bearings in relation to each other. The second rotary drive shaft 80 is located on the outer peripheral side of the third rotary drive shaft 90. The first rotary drive shaft 70 is connected to the first wrist electric motor 7 through a spur gear 71. The second rotary drive shaft 80 is connected to the second wrist electric motor 8 via a spur gear 81 and a timing belt 82. Third rotational drive shaft 90
is connected to the third wrist electric motor 9 through a joint 91.

1000: Robot wrist mechanism This is a device with 3 degrees of freedom placed at the end of the robot arm (first arm 4). Each rotation drive shaft 70.80.90
It operates by receiving the rotational output.

The details are as shown in FIGS. 1 to 4.

Next, the wrist mechanism 1000, which is one embodiment of the present invention, will be described with reference to FIGS. 1 and 4.

This robot arm (n81) includes the following components indicated by the part numbers in the figure. 31100. The lower cover robot arm (first arm 3) is rotatably placed on the tip of the robot arm (first arm 3) via a bearing 1102. The center line of rotation (to be more precise, the center line of rotation for the robot arm 1110) is along the longitudinal direction of the first arm 4.

The base of the lower cover 1]00 is connected to the third rotary drive shaft 7 mentioned above.
It is directly connected to 0. The lower cover 11001 years old has an open hemisphere shape.

1200: The upper cover is rotatably arranged on the lower cover 1100 via a bearing 1202. The center line of rotation is exactly 1 of the upper cover.
Rotation center of 200 with respect to lower cover 1100 +1112
04 is inclined at an acute angle with respect to the rotation center line 1104 of the lower cover 1100. The angle a in this example is 5
It is 5 degrees. Depending on how you measure the angle, it may appear as though it is tilted at an obtuse angle (180 degrees minus the acute angle). Therefore, if the rotation center lines 1]04, +204 are neither parallel nor perpendicular, one of them will inevitably be inclined at an acute angle with respect to the other. In this example, the center of rotation is lJ]104. +204 intersect at one point.

This is a preferred but not essential requirement.

The upper cover 1200 has a flange 1206 for disposing the tip. Further, like the lower cover, the upper cover 1200 is basically hemispherical with open cuts, and is arranged with respect to the lower cover + 100 so that the cuts face each other. A pair of upper and lower covers 1200.11
00, both of which together form a strong spherical cover that serves as the main outer skin of the Robonto Wrist+ (1 structure).

1: (QO: Place the bearing 1302 on the top cover 1200 of the tip so that it can rotate freely.・The center line of rotation is precisely the tip 13.
Center of rotation for the upper cover 1200 of 00! a1130
4 is inclined at an acute angle with respect to the rotation center line 1204 of the upper cover 1200. The angle in this example is also 55 degrees, which is the same as the angle a. Therefore, this rotation center line 1
304 may be aligned with the rotation center line 1104 of the lower cover 1100, as shown in FIG. The relationship between the rotation center lines 1204 and 1304 is the rotation center lines 1104 and 12
This corresponds to the above-mentioned relationship of 04. The tip 1300 serves as a seat for attaching a work tool or workpiece (not shown), but in special cases (exceptions of this embodiment), an element with one more degree of freedom may be added beyond this.

] 400: Disposed in the internal space surrounded by the upper and lower covers 1100 and 1200 of the rotation transmission shaft. The rotation center line of this rotation transmission shaft 1400 coincides with the rotation center line 1204 of the -F cover 1200. [Rotation transmission shaft] 400 transmits rotational output to the tip portion 1300
The lower cover 1100 is rotatably connected to the lower cover 1100 through a bearing 402, and the upper cover 1200 is rotatably connected to another bearing 404.

1440: Active IIi gear fixed to the end of the rotation transmission shaft 1400 closer to the lower cover 1100. This active heavy vehicle 111440 meshes with the drive bevel gear 89 on the robot arm (second arm 4) side. This Wjl parapet gear 89 is fixed to the end of the second rotary drive shaft 80 .

+46 Q: Passive bevel gear Fixed to the end of the rotation transmission shaft 1400 near the upper cover 1200. This passive bevel gear 1460 has a tip rotation command l#Jtf1306 that rotates the tip 300.
meshes with

1500・Reducer for upper cover This is for decelerating and rotating the upper cover 1200. Such a speed reducer 1500 is required unless the handheld full-speed motor is for low-speed, high-torque applications. Deceleration [1500] is an internal space surrounded by upper and lower covers 1100 and 1200, and includes an active bevel gear 1440 near the lower cover ttoo and a passive heavy vehicle RL1 near the upper cover 1200.
460 in a space around the rotation transmission shaft 1400 that is inclined.

In this embodiment, the reducer 1500 has upper and lower covers 1200
．． 1] Heal the cut at 00 and place it so as to partition its internal space. This reduction p + 5000') 4Its wheel 1510 for the N transfer force is also an active bevel gear 1440. 1ζ is arranged between the passive bevel gear 146o and the robot arm (
It meshes with the drive bevel gear 99 of the second arm 4) l17ff. The drive bevel gear 99 is different from the above-mentioned 89, and is fixed to the end of the above-mentioned third rotary drive shaft 9o. Also, the deceleration output shaft 1590 of this deceleration @1500
is fixed to the upper cover 1200. This is upper cover 12
00 and to hold the deceleration output shaft 1590 itself.

A speed reducer for the 1600i tip section This is for slowing down and rotating the tip section 1300. In this embodiment, which includes a reducer 1600 for the tip, the bevel gear 1306 for rotating the tip is connected to the reducer 1600.
It becomes the bevel gear for rotation input in 00. Further, the deceleration output shaft 1690 is fixed to the tip portion 1300 so as to rotate it.

The speed reducer 1500 in this embodiment is of a harmonic type. This will be explained in more detail below with reference to the principle diagram shown in FIG. This reduction gear 4J1500 is equipped with the following components, which are indicated by component numbers in FIGS. 1 and 4.

1520: Weave Generator The weave generator 1520 is mainly composed of an elliptical rotating body 1522. Further, it includes a bearing 1526 arranged on the outer peripheral side of the elliptical rotating body 1522. The inner ring 1524 of this bearing 1526 is an elliptical rotating body 1522
rotates with Outer ring of bearing 1526 l528
is an elliptical body of revolution 1522. It deforms according to the rotational difference between it and the inner ring 1524. The elliptical rotating body 1522 is coupled to the shaft 1512 of the rotation input bevel gear 1510. Further, the elliptical rotating body 1522 is arranged to be freely rotatable around the rotation transmission shaft 1400 via the shaft 1512 and the bearing 1514. The load of the entire weave generator 1520 including the elliptical rotating body 1522 is mainly borne by the rotation transmission shaft 400.

1530: Flex spline This is a metal elastic body arranged on the outer peripheral side of the outer ring 1528. According to the deformation of the outer ring 1528, it deforms along with it. External teeth 15 are provided on the outer peripheral side of the flex spline 1530.
32 is engraved on it.

1540; First circular spline - ring-shaped internal ma-roll body of W. The number of internal teeth 1542 is two more than the number of external teeth 1532 of flexspline 1530.

The internal teeth 1542 partially mesh with a pair of opposing external teeth 1532 that are swollen in an elliptical shape.

The first circular spline 1540 is the lower part 110
Fixed to 0. This first circular spline 154
0 itself is supported by the lower cover 1100.

1590: i1g speed output shaft This deceleration output shaft 1590 described above corresponds to a second circular spline. This is similar to the first circular spline 1540. However, the number of inner teeth tM (not shown) on this deceleration output shaft 1590 is the same as the number of outer teeth 1532 of the flex spline 1530, and the number of teeth [1542
2 more than that! Few.

Therefore, as the deformation phase of the flexspline 1530 progresses, a rotational phase shift occurs between the pair of internal teeth that mesh with the external tooth 1532, and the first circular spline 1540 The second circular spline, that is, the deceleration output shaft 1590 rotates slowly. The reduction ratio of the reduction output shaft 1590 shown in comparison with the rotation input bevel gear 1510 is about 100/1.

In addition to the reducer 1500 for the upper cover, the robot wrist machine yI4000 also incorporates a reducer 600 for the tip. This is also a harmonic form, and basically matches the one in Figure 4. However, as can be seen from Figure 1, the reducer 1600 for the tip is small.
'lJ and speed machine 1500 for the upper cover are large. The reason why the reducer 1i11500 for the upper cover becomes larger is because
This is because high torque is required, and this is because the negative radius (work tool or workpiece attached to the tip 300) is placed far away from the rotation center line 1204 of the upper cover 1200. be. For this reason,
The problem is how to incorporate this large-sized reduction gear 811500 for high torque, and the structure for incorporating it.

Next, the operation of the robot according to the embodiment shown in FIGS. 1 to 4, particularly the robot wrist 81 and skin 1000, will be explained.

The rotational output of the first wrist electric motor 7 is transmitted to the lower cover 1100 via the following transmission path.

(]) First wrist electric motor 7 - spur tooth IIt71 - first rotational drive shaft 70 - lower cover 1100 The rotational output of the second wrist electric motor 8 is transmitted to the upper cover 1200 via the following transmission path. reactor.

(2) Second wrist electric motor 8 - Spur gear 8 - Timing belt 82 - Second rotary drive lh shaft 8o - Drive bevel gear 89
-Bevel gear for rotation input of reducer 1500]5]〇-Axle 15
12-Elliptical rotating body 15 of weave generator 1520
22-Bearing 1524-Flerus spline 153
0-M output shaft 159〇-upper cover 1200 The rotational output of the third wrist electric motor 9 is transmitted as follows! ! is transmitted to the distal end portion 1300 via the channel.

(3) Third wrist electric motor 819 - Joint 91 - Third rotation drive shaft 90 - Drive bevel gear 89 - Active bevel gear 144〇 - Rotation transmission f + 400 - Passive bevel gear 146〇 - Tip rotation bevel Gear 1306-Deceleration ml60〇-Deceleration output shaft】69
〇 - Lower cover 110 with the tip part 1300 or more
0, a rotational movement about the rotational center line 1104 occurs at the top cover 1200, a rotational movement about the rotational center line 1204 occurs at the top cover 1200, and a rotational movement about the rotational center line 1304 occurs at the tip 1300. These rotational movements are combined, and the robot wrist mechanism 1000 allows its tip 300 to move in three degrees of freedom (wrist degrees of freedom). Robot wrist i#R1ooo
The robot arm itself allows three degrees of freedom, so there are six degrees of freedom in total.

The transmission path of the above (21 (31) includes a plurality of gears, and a considerable amount of backlash occurs due to gear meshing. This parafresh is harmful in that it impairs the positioning accuracy of the robot. However, Therefore, in this embodiment, the reducer 1500 or 1600 is arranged at the final stage of the transmission path.
Backlash is reduced according to the reduction ratio.

Now, let's consider the overall configuration of the robot wrist 811I#11000 again. Lower cover] Wrist 2 due to rotational movement of 000 and rotational movement of upper cover 1200
As the degree of freedom moves, the tip 13θO moves along the surface of a virtual sphere (virtual sphere). In this embodiment, the rotation center point of the wrist 2 of the wrist 2 is the intersection of the rotation center lines 1104 and 1204. Upper and lower covers 1100.120
The reason why 0 is made into a hemispherical shape is in response to the above-mentioned virtual sphere, and also because its mechanical strength is high. By the way, for miniaturization, the robot wrist mechanism 10
It is desirable to fit the main tIi components of 00 into the inner range of the spherical cover 1100.1200 that corresponds to the virtual sphere. For this purpose, it is necessary to effectively utilize the internal space of the sphere (11θ0.1200). In the internal space of this sphere! Various bevel gears 89 (99
1,1440, 1306, and 1460 are arranged almost radially, but the bevel gear 89 (81#I11 parts such as gears are interrupted between 991 and 1460, and 1440.13061Ql facing there across the center of the sphere) But it is still interrupted. Deceleration for upper cover 1111500+
Arrange yourself so as to connect comrades where others have broken off.1. As can be seen from FIG. 1, this arrangement increases the density of the arrangement of the 81 components within the sphere, making the entire structure 1ζ compact without increasing its size. The m-speed machine 1500 is a large-diameter type with high torque as mentioned above, but this is arranged along the maximum diameter of the ball, and the cover 1100°1200 as a ball that encloses it is also relatively small. Become something. From the opposite point of view, it becomes possible to incorporate a high-torque type reduction gear [1500] necessary for the rotation of the upper cover 1200. Of course, the upper and lower covers 1100 and 1200 do not have to be properly spherical, but the entire mechanical parts inside them should be arranged as one radial unit, and the reducer included therein should be along the direction of the large diameter of the cover. This arrangement is necessary for downsizing.

When it is attached to the tip end 1300, the surface that becomes the seat is somewhat ubiquitous from the surface of the sphere formed by the upper and lower covers 1100 and 1200), which may hinder work with a working tool (not shown) fixed thereto.

The reducer 1600 for the tip portion is incorporated by utilizing the space for speeding up the work tool as described above.

Next +c, the embodiment shown in FIG. 5 will be explained. Since this robot wrist 819791002 is similar to the one in FIG. 1, the parts numbers will be quoted as is, and redundant explanation will be omitted. Bevel gear 1 for rotation input of the upper cover reducer 1500 in the robot wrist mechanism 1002 in FIG.
510a meshes with the drive bevel gear 99a. In addition, the active bevel gear 1440a of the rotation transmission shaft 1400 is the drive bevel gear 89.
meshes with a. A rotary drive shaft 80a to which a drive bevel gear 89a is fixed is for rotating the tip portion 1300.

Also, a rotational drive shaft 90a to which a drive bevel gear 99a is fixed.
This is for rotating the upper cover 1200. In this embodiment, a rotary drive shaft 80a for the tip portion is disposed on the inner peripheral side of a rotary drive shaft 90a for the upper cover. Accordingly, the drive bevel gear 89a is configured to protrude beyond the station umbrella 1199n.

Next, the embodiment shown in FIG. 6 will be explained. The parts numbers in FIG. 1 will be quoted as is. In the robot wrist machine 1Jj10041 of this embodiment, the shaft 1512b of the upper cover 3ffli+soo is lengthened (extended), and the bevel gear 15 for rotational input fixed thereto]01+
is arranged so that it is very close to the active bevel gear +4401ζ. The rotation input bevel gear 1510b meshes with the driving bevel gear 99, but the meshing is on the right side of the driving bevel gear 99 (
It is taken from the right side in FIG. 6, which is the side opposite to the reducer 1500. For this reason, deceleration [15
The configuration between 00 and the drive bevel gear 89, 99 is simplified by 0 because the rotation input bevel gear +510b is not interposed.

Next, the embodiment shown in FIG. 7 will be described. Here too, the first
Please quote the part numbers in the diagram as much as possible. The side 1006 of the robot wrist 81 in this embodiment involves a configuration change on the robot arm side. The rotational output of the second hand office electric ghffll'l placed on the robot throat arm is the spur gear 8.
1C, spur gear 82C1 and spur gear 83c, and is transmitted to the second rotational drive shaft 80C.

The spur gear 82c is disposed on the outer circumferential side of the third rotational drive shaft 90c and is concentric with it, and this @5 rotational drive shaft 90c is arranged on the outside of the second rotational drive shaft 80c in parallel with this. It is arranged so that The second and third rotary drive shafts 80c and 90cl are arranged on the inner peripheral side of the first rotary drive shaft 70, and one of them (in this embodiment, the third rotary drive shaft 90C) is the third rotary drive shaft 90c. It is arranged concentrically with one rotary drive shaft 70. It is also possible to partially modify this embodiment of the seventh TXi and mesh the rotation input bevel gear 1510 with the drive bevel gear 99 so as to approach it from the right side (right pi in the drawing).

[Effects of the Invention] As described above, the present invention provides an upper and lower internal space around an inclined rotation transmission axis between an active bevel gear closer to the lower cover and a passive bevel gear closer to the upper blade l<-. (A reduction gear for the upper cover is arranged. According to this, the reduction gear 131 with the required high torque can be incorporated into the Conopact, and a more practical robot hand σ81#R can be obtained. .

[Brief explanation of drawings]

FIG. 2 is a side view of the entire robot to which the robot wrist 81 structure according to the present invention is attached, FIG. 3 is an explanatory diagram showing the wrist power transmission path within the robot arm, and FIG. 1 is the robot according to the present invention. 4 is a principle diagram showing a harmonic type reduction mechanism therein, FIG. 5 is a sectional view of a robot wrist mechanism showing another embodiment of the present invention, and FIG. 6 is a further sectional view showing another embodiment of the robot wrist mechanism. FIG. 7 is a sectional view of a robot wrist mechanism showing an embodiment of 1. t is a sectional view of a robot wrist machine or a robot arm showing another embodiment. Main parts numbers in the figure 1100 - Lower cover 1200 = Upper force bar 1300 =
Tip part 1400 = Rotation transmission shaft 1306 - Bevel gear for tip rotation 1440 - Active bevel gear 1460 = Passive bevel gear 150Q
=Deceleration 8J 1600-Reduction gear 15]〇One-rotation input bevel gear 159〇-Deceleration output path 1104.1204.1304=Rotation center line 3.4-Robot arm 70.80.9〇One-rotation drive shaft 89. 99 = Drive bevel gear

Claims (1)

[Claims] 1. A lower cover rotatably disposed at the tip of the robot arm, an upper cover rotatably disposed on the lower cover, and a tip rotatably disposed on the upper cover. The center line of rotation of the upper cover is inclined at an acute angle with respect to the center line of rotation of the lower cover, the center line of rotation of the tip is inclined at an acute angle with respect to the center line of rotation of the upper cover, and the A rotation transmission shaft is arranged in the internal space surrounded by the upper and lower covers, the rotation center line of this rotation transmission shaft coincides with the rotation center line of the upper cover, and an active bevel gear and a passive bevel gear are arranged on the rotation transmission shaft. One of the active bevel gears near the lower cover meshes with a driving bevel gear on the robot arm side, and the other passive bevel gear near the top cover meshes with a tip rotation bevel gear that rotates the tip. , a reduction gear is installed in an internal space surrounded by the upper and lower covers, around the inclined rotation transmission shaft between the active bevel gear closer to the lower cover and the passive bevel gear closer to the upper cover. Place the
A robot wrist mechanism characterized in that a rotation input bevel gear in this reducer meshes with another drive bevel gear on the robot arm side, and a reduction output shaft of the reducer is fixed to the upper cover so as to rotate it. 2. The robot wrist mechanism according to claim 1, wherein the reducer is of a harmonic type, and a weave generator including an elliptical rotating body is arranged around the rotation transmission axis via a bearing. 3. The robot wrist mechanism according to claim 1, wherein the rotation input bevel gear in the reduction gear is disposed between the active bevel gear and the passive bevel gear. 4. Make each of the upper and lower covers hemispherical with open cuts, arrange these pairs of covers so that their respective cuts face each other, and extend the internal space covered by these covers along the cuts. The robot wrist mechanism according to claim 1, wherein the reducer is arranged so as to partition the robot wrist mechanism. 5. A rotation drive shaft for rotating the lower cover, a rotation drive shaft for rotating the drive bevel gear that meshes with the rotation input bevel gear in the reduction gear, and a rotation drive shaft for rotating the drive bevel gear that meshes with the active bevel gear on the rotation transmission shaft. 2. The robot wrist mechanism according to claim 1, wherein the rotational drive shafts of the robot arms are arranged inside the robot arms along the longitudinal direction thereof. 6. The robot wrist mechanism according to claim 5, wherein the rotational drive shafts are arranged concentrically. 7. A patent in which a rotary drive shaft for rotating a drive bevel gear that meshes with an active bevel gear on a rotation transmission shaft is arranged on the outer circumferential side of a rotary drive shaft for rotating a drive bevel gear that meshes with a rotation input bevel gear on a rotation transmission shaft. A robot wrist mechanism according to claim 6. 8. A rotary drive shaft for rotating the drive bevel gear that meshes with the active bevel gear on the rotation transmission shaft is arranged on the inner circumferential side of the rotary drive shaft that rotates the drive bevel gear that meshes with the rotation input bevel gear on the speed reducer. A robot wrist mechanism according to claim 6. 9. A rotary drive for rotating the drive bevel gear that meshes with the active bevel gear on the rotation transmission shaft, on the outside of and parallel to the rotation drive shaft for turning the drive bevel gear that meshes with the rotation input bevel gear in the reduction gear. The robot wrist mechanism according to claim 5, in which a shaft is arranged. 10. A rotary drive shaft for rotating the drive bevel gear that meshes with the rotation input bevel gear in the reducer, and a drive bevel that meshes with the active bevel gear on the rotation transmission shaft, on the inner peripheral side of the rotation drive shaft for rotating the lower cover. 10. The robot wrist mechanism according to claim 9, wherein a rotational drive shaft for rotating a gear is disposed, and one of the rotational drive shafts is concentric with the rotational drive shaft for rotating the lower cover.