JPH0328612B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a differential gear mechanism, and more particularly, to a differential gear mechanism that eliminates backlash.

[Prior Art] As shown in Fig. 3, a differential gear mechanism composed of three bevel gears is used as a joint drive mechanism in a multi-jointed arm, and two of the bevel gears are connected by wires. If the arm is configured to be driven by, for example, it is effective in that the weight of the joint can be reduced and that an actuator for driving the joint can be provided on the base side of the arm.

To briefly explain the drive mechanism of each joint 1 to 3 in the above-mentioned multi-jointed arm, each joint 1 to 3 connects the distal arm member to the proximal arm member in a rotatable and bendable manner. The differential gear mechanism adopted for each joint 1 to 3 to enable rotation and bending is a joint cover 5 fixed to the arm member 4 on the proximal end side, and a pair of drive umbrellas inside the cover 5. The gears 6 and 7 are opposed to each other, and the wires 9 and 10 introduced through the arm member 4 on the proximal end side are wound around the gears 6 and 7 so as to be rotatably supported, and both of the bevel gears 6 and 7 are A driven bevel gear 8 is engaged with the driven bevel gear 8, and the driven bevel gear 8 is fixed to the arm member 11 on the distal end side.

Therefore, the bevel gears 6, 7 are connected by the wires 9, 10.
By rotating in the same direction, the arm member 11 on the distal side can be bent with respect to the arm member 4 on the proximal side, and by rotating the bevel gears 6 and 7 in the opposite direction, the arm member 11 on the distal side can be bent with respect to the arm member 4 on the proximal side. The arm member 11 can be rotated.

The problem when performing joint drive using a differential gear mechanism with such a configuration is that since the drive bevel gears 6, 7 and the driven bevel gear 8 are in mesh with each other, due to the backlash between them, the driven bevel gear 8. That is, the rotation and bending of the arm member 11 on the distal end side cannot be precisely controlled.

Note that the differential gear mechanism described above is used not only for joint drive but also for various drive mechanisms, and even in these cases, it is necessary or often desirable to avoid backlash.

[Problems to be Solved by the Invention] The present invention provides a differential gear mechanism configured with three bevel gears, in which backlash occurs between a pair of driving bevel gears and a driven bevel gear that meshes with the pair of driving bevel gears. The technical challenge is to prevent it from existing.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the differential gear mechanism of the present invention has a pair of drive bevel gears that are rotatably supported in an opposing state, and are driven in opposite directions by respective drive devices. It is constructed by nesting two inner and outer bevel gears that can be rotationally driven, and each bevel gear in the pair of drive bevel gears is meshed with one driven bevel gear, and the pair of drive bevel gears is formed by meshing with one driven bevel gear. A technical means is adopted in which the inner and outer bevel gears are biased in opposite directions to each other by a rotational force for removing bumps that causes the tooth surfaces of these bevel gears and the tooth surfaces of the driven bevel gear to constantly come into contact with each other. ing.

[Operations and Effects] In the differential gear mechanism having the above configuration, the two inner and outer bevel gears constituting both drive bevel gears are urged to rotate in opposite directions with the rotational force for removing backlash. The tooth surfaces of the two inner and outer bevel gears are always in contact with the opposing tooth surfaces of the driven bevel gear. Therefore, when rotating any one of the drive bevel gears, the two bevel gears constituting the drive bevel gear By rotating the bevel gear in which the gear on the rotation direction side is in contact with the tooth surface of the driven bevel gear, the driven bevel gear accurately follows the movement of the driving bevel gear without bumping, and is driven with high precision. Ru.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an example in which the differential gear mechanism according to the present invention is applied to the multi-joint arm shown in FIG. This joint is a side arm member, and this joint connects the arm member 23 on the distal side to the arm member 21 on the proximal side so as to be rotatable and bendable.

Inside the joint cover 22, a pair of drive bevel gears 24 and 25 constituting a differential gear mechanism are supported so as to face each other and to be rotatable. Both drive bevel gears 24, 25 are inner bevel gears 26, 2.
8 are inserted into outer bevel gears 27 and 29 in a nested manner so that they can rotate with each other, and those bevel gears 2
Pulleys 26a to 29a are provided on the shaft portions 6 to 29,
Wires 30 to 33 for power transmission are wound around these pulleys 26a to 29a. Drive bevel gear 24
Wires 30 and 31 wound around pulleys 26a and 27a in , and wires 32 and 33 wound around pulleys 28a and 29a in drive bevel gear 25 are as follows:
The winding directions are opposite to each other.

One driven bevel gear 35 is meshed with each of the inner and outer bevel gears of the pair of driving bevel gears 24 and 25, thereby forming a differential gear mechanism. The arm member 23 of is fixed.

Furthermore, the other end side of each of the wires 30 to 33 is
The drive device is connected to a drive device (not shown) such as a motor, but this drive device always pulls the wires 30 to 33 with a constant tension to take up the slack in the wires, and when driving, the inner or outer bevel gear It is configured to transmit enough tension to the wire to rotate together with the driven bevel gear.

That is, the drive device has one drive bevel gear 24.
The wires 30 and 31 wound around the inner and outer bevel gears 26 and 27 are
7 in a direction that rotates them in opposite directions, applying opposite rotational forces to each of the inner and outer bevel gears 26 and 27 to remove backlash, as shown in FIG. Gears 26b, 27b of the inner and outer bevel gears 26, 27
are always brought into contact with the gears 35a and 35b facing in opposite directions in the driven bevel gear 35, and a predetermined preload is applied between these gears, and each wire 30,
31 to the inner or outer bevel gears 26, 2.
7 is rotated together with the driven bevel gear 35,
It is configured to rotate in that direction while maintaining the state in which the preload force is applied.

In addition, the inner and outer bevel gears 28,
29 is also configured to operate in the same manner as above.

In a joint having such a configuration, in order to rotate the distal arm member 23 (driven bevel gear 35) with respect to the proximal arm member 21, the pair of drive bevel gears 24 and 25 must rotate in opposite directions. In addition, in order to bend the arm member 23 on the distal end side with respect to the arm member 21 on the proximal end side, a pair of drive bevel gears 24, 2
5 should be rotated in the same direction and at the same speed.

Therefore, in order to rotate the drive bevel gears 24 and 25, the inner or outer bevel gears 26 to 2 are rotated.
By wires 30 to 33 wound around pulley 9,
It is sufficient to transmit the rotational driving force to these bevel gears with the preload applied thereto, and the driven bevel gear 35 is rotated by this rotational force. Since the tooth surfaces are in contact with each other without any gap, the driven bevel gear 35
is driven with high precision without backlash. Further, when the driven bevel gear 35 rotates in this manner, the driven bevel gear 35 causes the drive bevel gear 2 to rotate.
Among the inner and outer bevel gears 26 to 29 in 4 and 25, the bevel gears that are not rotationally driven are pressed and rotated by the driven bevel gear 35, and the tooth surfaces of the inner and outer bevel gears 26 to 29 and the driven bevel gear 35 are always pressed by the preload. are maintained in contact with each other with a constant force.

It goes without saying that the bevel gear mechanism described above can also be used in parts that transmit force other than the above-mentioned joints.

[Brief explanation of the drawing]

Fig. 1 is a partial sectional view showing the main part of an embodiment of the present invention, Fig. 2 is a partial explanatory view showing the meshing state of the driving bevel gear and the driven bevel gear, and Fig. 3 is the overall configuration of the multi-jointed arm. FIG. 24, 25... Drive bevel gear, 26, 28... Inner bevel gear, 27, 29... Outer bevel gear, 35...
Driven bevel gear.

Claims (1)

[Claims] 1. A pair of drive bevel gears that are rotatably supported in an opposing state are constructed by nesting together two inner and outer bevel gears that can be rotated in opposite directions by respective drive devices, and the above-mentioned Each bevel gear in the pair of driving bevel gears is meshed with one driven bevel gear, and the inner and outer bevel gears in the pair of driving bevel gears are connected to each other by connecting the tooth surfaces of those bevel gears and the tooth surfaces of the driven bevel gear. A differential gear mechanism characterized in that the gears are always in contact with each other and biased in opposite directions by rotational force for removing bumps.