JPS6113050A - Articulation mechanism - Google Patents

Abstract

PURPOSE:To improve the accuracy of position nearly in the stop state by connecting one edge of an elastic member onto the output side of a harmonic drive type reduction gear and the other edge to a member for fixing a driving source. CONSTITUTION:One edge of a spiral spring 7 is connected to the output side of a harmonic drive type reduction gear 3, and the other edge is connected to a member 5 for fixing a servomotor 1. Therefore, since even if the input shaft 2 of the harmonic drive type reduction gear 3 is in stop, a load torque is always applied onto an output shaft 4, the torsional state of said output shaft 4 is brought outside a backlash range, and the torsional rigidity inreases, and the accuracy of the stop position of an articulation, namely of the stop position of revolution angle can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a joint mechanism that is used in a joint of a machine such as a robot and has a harmonic drive type reduction gear.

[Background of the invention]

Conventionally, robot joints require a relatively small angular velocity but a large torque, so a joint mechanism with a reducer has been used, which consists of an internal gear, a flexible external gear that meshes with the internal gear, and a flexible external gear that meshes with the internal gear. A so-called harmonic gear is a type of differential gear that can obtain a relatively large reduction ratio by utilizing the difference in the number of teeth between Drive-type reducers are often used. The harmonic drive type speed reducer has rotation angle-torque characteristics as shown in FIG.

That is, in the region a-b where the torque is relatively small,
Because the meshing of the teeth between the internal gear and the external gear is uneven, there is backlash that occurs as the number of meshing teeth increases as the torque increases, and the drive side gear changes from 0 to aI2. , or only after rotation from 0 to bQ can uniform torsional rigidity similar to that in the a-c and b-d sections be obtained. Due to the weight of the driven member being applied to the indirect mechanism, the first
If a load torque exceeding a or b□ in the figure is applied, the torsional state of the output shaft of the harmonic drive type reduction gear during stopping is outside the backlash range. However, in the case of a horizontal pivot joint around a vertical axis, the weight of the driven member does not act as a load torque, so the torsional state of the output shaft is within the backlash region, and the torsional rigidity in the stopped state is reduced. When the value of torsional rigidity is small, it is strongly influenced by residual vibration after positioning and the position repeatability of rotation angle is low. There was a problem in that the positional accuracy was lower compared to joints that

[Purpose of the invention]

An object of the present invention is to provide a joint mechanism using a harmonic drive reducer for improving positional accuracy near a stopped state.

[Summary of the Invention] The joint mechanism of the present invention has one end of the elastic member connected to the output side connected to the driven member of the harmonic drive type reducer, and the other end of the elastic member connected to the member fixing the drive source. Each of them is fixed.

According to the above configuration, the elastic material always applies a moderate load torque to the output shaft, and the torsional state of the output shaft of the harmonic drive type reducer is out of the backlash region, resulting in high torsional rigidity and constant accuracy. It can be stopped at a suitable position,
Stop position accuracy can be increased.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on FIG. 2.6 A harmonic drive type reducer 3 is attached to a vertical or nearly vertical input shaft 2 that is rotationally driven by a servo motor 1 that is a drive source. .

The speed reducer 3 consists of an elliptical cam 3a having a ball bearing on its outer periphery, an elastically deformable external gear 3b, and an internal gear 3c.The cam 3a is fixed to the input shaft 2, and the external gear 3b is fixed to the input shaft 2. An internal gear 30 is fixed to a member 5 that is fixed to the output shaft 4 and to which the servo motor 1 is fixed. A driven member 6 is fixed to the output shaft 4 . One inner end of the spiral spring 7, which is an elastic member, is fixed to the output shaft 4, and the other outer end is fixed to the member 5. Note that one inner end of the spiral spring 7 may be fixed to the driven member 6.

Next, the operation of one embodiment of the present invention will be explained.

The cam 3a is rotationally driven by the servo motor 1 via the input shaft 2, and as the cam 3a rotates, the meshing position between the external gear 3b and the internal gear 3c moves. When the input shaft 2 rotates once, the external gear 3b rotates both gears 3 in a direction opposite to the rotational direction of the input shaft 2 with respect to the internal gear 3c fixed to the member 5.
The output shaft 4 rotates by the difference in the number of teeth between b and 3c and is fixed to the number of external teeth 3b, and the driven member 6 fixed to the output shaft 4
Rotate. At this time, a spiral spring 7 is wound around the output shaft 4, and tension is applied to the output shaft 4, so that torque is constantly applied to the output shaft 4. Therefore, even when the servo motor is stopped, the torsional state of the output shaft 4 is kept out of the backlash region. This increases the torsional rigidity and increases the repeatability of the stop position.

Furthermore, another embodiment of the present invention will be described based on FIG.

The same reference numerals as in FIG. 2 indicate the same parts, and in this embodiment, the elastic member is a coil spring 8. .

82, one end of each of the coil springs 81 and 82 is fixed to the output shaft 4 by an engaging means such as a pin 9, and the other end of each is fixed to the member 5. In addition, coil spring 8.
．． 8. Of course, one end of each may be fixed to the driven member 6. Coil spring 8. ．． 8. is fixed in a stretched state at both ends so that tension is constantly applied within the range of motion of this joint, and this configuration also has the same effect as the previous embodiment.

〔Effect of the invention〕

As described above, according to the present invention, load torque is constantly applied to the output shaft even when the input shaft of the harmonic drive type reducer is stopped, so the torsional state of the output shaft is outside the backlash region, and the torsional rigidity is improved. is increased, and the accuracy of the stopping position of the joint, that is, the stopping position of the rotation angle can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a rotational angle-torque characteristic diagram of a harmonic drive type speed reducer, and FIGS. 2 and 3 are longitudinal sectional views of joints showing different embodiments of the present invention. l...Servo motor, 2...Input shaft, 3...Harmonic drive type reducer, 4...Output shaft, 5--Member for fixing the servo motor, 6--Driven member, 7 Spiral spring, 81.8°...Coil spring.

Claims (1)

[Claims] 1. A harmonic drive type reducer is attached to a drive shaft rotated by a drive source, and in a joint where a driven member is connected to the output shaft of the reducer, one end is connected to the output side of the reducer. , an elastic member having the other end fixed to a member fixing the drive source, respectively. 2. The joint mechanism according to claim 1, characterized in that a spiral spring is used as the elastic member. 3. The joint mechanism according to claim 1, wherein a coil spring is used as the elastic member.