JPH041397Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to joint mechanisms of robots, etc., and effectively prevents the occurrence of backlash due to the meshing of the gears of a gear reducer and improves the drive accuracy of the arm. At the same time, it realizes a small and simple joint mechanism.

[Problems to be solved by conventional technology and invention]

In robot joint mechanisms, the rotational angular velocity is relatively small but large torque is required.
Conventionally, reduction gears using multi-stage gears have been used.

However, when a gear reducer is used, the occurrence of backlash is unavoidable, which causes a decrease in the driving accuracy of the arm. Furthermore, in the case of multi-jointed robots, transmission mechanisms such as chains and links are often used to drive the joints at the tip, but these mechanisms have drawbacks such as being complex and inefficient.

On the other hand, JP-A-51-94062 and JP-A-Sho
The harmonic type reducer described in Publication No. 50-89756 etc. uses the difference between the number of teeth of the internal gear and the number of teeth of the external gear that meshes with it to obtain a relatively large reduction ratio. Therefore, it is suitable for joint mechanisms.

However, the harmonic reducer has rotation angle-torque characteristics as shown in FIG. a-b
This is due to the backlash caused by the meshing of the gears, which takes about 3 minutes at the minimum. Assuming this for an arm with a total length of 1m, the tip would be equivalent to 0.9mm. Parts b-c and a-e are unique to harmonic drive type reducers, and are bumps in areas with low rigidity due to uneven tooth meshing, and the drive side gear changes from 0 to c. , or 0
→ Uniform rigidity of parts c-d and parts e-f can be obtained only after rotation to e.

The technical problem of this invention is to solve such problems in a joint mechanism with a large reduction ratio using a harmonic drive type reducer, and to solve not only the problems caused by the meshing of gears but also the problems inherent in a harmonic drive type reducer. The purpose of this invention is to make it possible to put a harmonic drive type reducer with a large reduction ratio into practical use as a joint mechanism, and to downsize the joint mechanism by also eliminating bumps in the low-rigidity parts of the joint mechanism.

[Means to solve the problem]

As shown in FIG. 4, both ends of the drive shaft 4' are rotatably supported by the first arm 21 at the joint between the first arm 21 and the second arm 22. As shown in FIG.

The inner side of the motor M is fixed to the drive shaft 4' between the supporting parts on both sides,
The outer side is fixed to the second arm 22. Moreover, two sets of harmonic drive type reducers A and B, which utilize the difference in the number of teeth between an internal gear and a flexible external gear, are arranged at approximately symmetrical positions on both sides of the motor M, respectively. , flexible external gears 10a and 10b of harmonic drive type reducers A and B are attached to a drive shaft 4'.

The harmonic drive type reducers A and B have fixed internal gears 11a and 11b and output internal gears 12a and 12 for one flexible external gear 10a and 10b, respectively.
The two internal gears b are meshed. and,
Fixed internal gear 11 of both harmonic drive type reducers A and B
a, 11b are each attached to the first arm 21, and output internal gears 12a, 12b are each attached to the second arm 22.

At this time, the flexible external gear 10a of one harmonic drive type reducer A and the flexible external gear 10b of the other harmonic drive type reducer B have their contact surfaces with the internal gears in opposite directions. Output internal gear 12a [or fixed internal gear 11a] of harmonic drive type reducer A so that
The output internal gear 12b (or fixed internal gear 11b) of the harmonic drive type reducer B is shifted in the rotational direction and fixed at an angle of deviation.

〔Example〕

Next, an embodiment of the joint mechanism according to the present invention will be described based on the drawings. FIG. 3 is a side view of the multi-joint arm type robot, and FIG. 4 is an enlarged sectional view taken along the line -' of FIG. In the figure, 1 is a base, and 21 to 25 are arms. The arms 21 to 25 have joints 3,
3' is connected in a bendable or rotatable manner.

FIG. 4 is an enlarged sectional view of the first bending joint 3, in which both ends of the rotating shaft 4 are rotatably supported by the first arm 21, and between these support parts, the rotating shaft 4 is The rotor 5 of motor M is in the middle part of
is fixed, and a pair of harmonic drive type reducers A and B are arranged with the rotor 5 in between.

The stator 6 outside the rotor 5 is connected to the second arm 2
The rotating shaft 4 serves as a driving shaft 4'. Input shafts 8a and 8b of harmonic drive type reducers A and B are fixed to the drive shaft 4'.

FIG. 5 is a left side view of the harmonic drive type reducer A, and in order from the inside, an elliptical input shaft 8a, a bearing 9a, . . . , an external gear 10 made of a flexible material.
a, a fixed internal gear 11a that meshes with the external gear 10a at two points on its circumference and has fewer teeth than the external gear 10a, and a fixed internal gear 1
1a and an output internal gear 12a disposed on the back side. The other harmonic drive type reducer B
Similarly, it is composed of an input shaft 8b, a bearing 9b, an external gear 10b, a fixed internal gear 11b, and an output internal gear 12b.

Fixed internal gear 11 of each harmonic drive type reducer A, B
a, 11b are first arms 21 serving as primary side members;
is fixed to the output internal gears 12a, 12b.
is fixed to the second arm 22, which serves as a secondary side member. At least one of the fixed internal gears 11a and 11b and the output internal gears 12a and 12b, for example, the output internal gears 12a and 12b is the sixth internal gear.
As shown in the figure, they are fixed to the second arm 22 in a state where the biases α are applied by shifting them in different rotational directions.

Next, the operation of the joint mechanism in this configuration will be explained. In FIG. 5, when the drive shaft 4' is driven by the rotor 5 and rotates counterclockwise, the oval input shafts 8a and 8b rotate in the same direction. Input shaft 8
When a and 8b rotate counterclockwise, external gear 1
Since 0a and 10b are made of flexible material, they deform as the input shafts 8a and 8b rotate, and while meshing with the fixed internal gears 11a and 11b, the input shafts 8
Each time a and 8b rotate once, they rotate clockwise by the difference in the number of teeth, rotate the output internal gears 12a and 12b clockwise by the difference in the number of teeth, and bend the second arm 22.

Next, after stopping, when the drive shaft 4' rotates in the opposite direction, the flexible external gears 10a and 10b rotate in the opposite direction, causing the second arm 22 to extend. At this time, since an argument α is given between the output internal gears 12a and 12b, as shown in FIG. The contact surfaces are reversed. That is, the tooth surface 13a of the external gear 10a and the tooth surface 14a of the output internal gear 12a are brought into contact with each other in the counterclockwise direction as shown in FIG.
tooth surface 13b of the output internal gear 12b and tooth surface 14b of the output internal gear 12b.
has its tooth surfaces in contact with each other in a clockwise direction.
Therefore, when the drive shaft 4' rotates, the counterclockwise rotation of the flexible external gear requires the left harmonic drive type reducer A.
When the external gear rotates in the clockwise direction, the harmonic drive type reducer B on the right prevents the backlash from occurring.In the end, no matter which direction the drive shaft 4' rotates, backlash always occurs. do not.

The conventional backlash removal mechanism was developed in 1973.
As described in Publication No. 30782 and Japanese Utility Model Application Publication No. 55-120849, a special spring is provided to shift the two gears and apply contact pressure to the common mating gear, so the drive The rigidity of the system depends on the rigidity of the spring, so it is not suitable for robot joint mechanisms that require high rigidity. In contrast, the present invention has two independent flexible external gears 10.
a, 10b, for example, output internal gears 12a,
12b is shifted in the opposite direction and is fixed in meshing contact. Therefore, the rigidity of the flexible external gears 10a and 10b is much greater than that of the spring, and the shafts of the two sets of harmonic drive type reducers A and B are integrated with the motor shaft, resulting in a compact structure.

The harmonic drive type reducer has an input shaft 8 as shown in Fig. 5.
A bearing 9 is provided between the flexible external gear 10a and the flexible external gear 10a.
As shown in Fig. 1, the rigidity The lower part of 0-a, 0-
b is unavoidable and is considered to be a problem unique to harmonic drive type reducers.

However, as mentioned above, the harmonic drive type reducer A
A deflection angle α is given between Since the meshing contact pressure is always maintained due to the elasticity caused by the flexibility, the low rigidity parts inherent to the harmonic drive type reducer are also removed, and high rigidity and uniform characteristics as shown in FIG. 2 are obtained. Moreover, the force transmission system of the first arm and the second arm is changed from the first arm to the fixed internal gear 11a to the flexible external gear 10a to the output internal gear 1.
By creating a closed loop with the route 2a → second arm → output internal gear 12b → flexible external gear 10b → fixed internal gear 11b → first arm,
It is possible to reliably eliminate the backlash and low rigidity parts inherent in harmonic drive type reducers with a simple configuration without adding springs or the like.

Further, as shown in FIG. 7, the output internal gear 12
By shifting a and 12b in opposite directions and reversing the contact surfaces of the two independent flexible external gears 10a and 10b, the overall rigidity of the joint mechanism itself as seen from the output side is doubled. . That is, the torque in the contact direction shown in FIG. 7A becomes contact pressure plus rotational force, whereas the torque in the contact direction shown in FIG. 7B becomes contact pressure minus rotational force. If this is shown in a rotation angle-torque characteristic diagram, the curves will be as shown in FIG. 8a and b. Therefore, when viewed from the output side, as shown in FIG. 8c, the characteristic is the difference between the curves a and b in FIG. 8, and the rigidity is approximately doubled. Therefore, the natural frequency of the joint mechanism becomes high, and high-speed positioning becomes possible.

Furthermore, by arranging the harmonic drive type reducers A and B symmetrically on both sides of the drive motor M, the motor M
The characteristics seen from the front are uniform in forward and reverse rotations, improving controllability. That is, as a method for eliminating backlash, it is a well-known matter to arrange a plurality of gears with deviations. However, when multiple gears are attached to a rotating shaft with some deviation, in order to achieve smooth rotation (power transmission), it is necessary to make the rotating shaft easy to twist, but from the point of view of power transmission. , the response frequency becomes low. Therefore, British patent no.
Applying the description in the specification of No. 1270266, if two harmonic drive type reducers are placed on one side of the motor, the power transmission of the gear farther from the motor will be delayed.
However, in the configuration of the present invention, the response to acceleration and deceleration in both left and right directions is symmetrical, and the critical speeds for both can be made the same, making it suitable for use in robot joints. This has the effect of making control extremely easy. In addition, since the motor M that drives the harmonic drive type reducers A and B is disposed at a substantially intermediate position between the two, the limit speed for normal operation of the joint mechanism can be increased.

Although the embodiment has been explained using the bending joint 3, it goes without saying that the present invention can also be applied to the rotary joint 3'.

[Effect of idea]

As described above, according to the present invention, internal gears shifted in opposite directions mesh with separate pairs of flexible external gears, and a closed loop is established between the first arm and the second arm. By fixing it with
It is possible to reliably eliminate the backlash and low rigidity parts inherent in harmonic drive type reducers with a simple configuration without adding springs or the like.

Furthermore, by applying meshing contact pressure to the output side to provide a deflection angle, the rigidity of the joint mechanism itself as viewed from the output side can be approximately doubled.

By symmetrically arranging the harmonic drive type reducers A and B on both sides of the motor M, the characteristics seen from the motor M become uniform in normal rotation and reverse rotation. the result,
The response to acceleration and deceleration in both left and right directions is symmetrical, allowing the limit speeds of both to be the same.
Control becomes extremely easy, and the critical speed for normal operation of the joint mechanism can be increased.

As shown in the figure, both ends of the drive shaft 4' are supported by the first arm, and a drive motor M and two sets of harmonic drive type reducers A and B are built in between the supports, thereby achieving the above-mentioned A mechanism that provides the effects unique to the present invention can be realized in an extremely small size and with a simple structure.

[Brief explanation of the drawing]

Fig. 1 is a rotation angle-torque characteristic diagram of a single conventional harmonic drive type reducer, Fig. 2 is a rotation angle-torque characteristic diagram with the backlash removed, and Figs. 3 to 6 show examples of the present invention. , Fig. 3 is a side view of the multi-joint arm type robot, Fig. 4 is an enlarged sectional view at -' of Fig. 3, Fig. 5 is a left side view of harmonic drive type reducer A, and Fig. 6 is an internal gear. FIG. 7 is a partial side view showing the meshing state of two sets of internal gears and external gears, and FIG. 8 is a rotation angle diagram illustrating the effect of improving the rigidity of the joint mechanism of the present invention. This is a torque characteristic diagram. In the figure, 21 is a first arm, 22 is a second arm, 4 is a rotating shaft, 4' is a drive shaft, A, B are harmonic drive type reducers, 10a, 10b are flexible external gears, 11a, 11b is a fixed internal gear, 12a, 1
2b is an output internal gear, and M is a motor.

Claims (1)

[Claims for Utility Model Registration] In the joint movement section between the first arm 21 and the second arm 22, both ends of the drive shaft 4' are rotatably supported by the first arm 21, and both ends of the drive shaft 4' are rotatably supported by the first arm 21. The inner side of the motor M is fixed to the drive shaft 4' and the outer side is fixed to the second arm 22 between the supporting parts, and the number of teeth of the internal gear and the flexible external gear is Two sets of harmonic drive type reducers A and B that utilize the difference are arranged at substantially symmetrical positions on both sides of the motor M, respectively, and the flexible external gears 10a of the harmonic drive type reducers A and B are arranged. ，
10b is attached to the drive shaft 4', and each of the harmonic drive type reducers A and B has two internal gears, a fixed internal gear and an output internal gear, for one flexible external gear. The fixed internal gears 11 of both harmonic drive type reducers A and B must be meshed.
a, 11b are each attached to the first arm 21, output internal gears 12a, 12b are each attached to the second arm 22, and one flexible external gear of the harmonic drive type reducer A. 1
0a and the flexible external gear 10b of the other harmonic drive type reducer B, the output internal gear 12a of the harmonic drive type reducer A [ or the fixed internal gear 11a] and the output internal gear 12b of the harmonic drive type reducer B [or the fixed internal gear 11b] are fixed in a state where they are shifted in the rotational direction to give an yaw angle. joint mechanism.