JPS59172950A - Motor actuator - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a motor actuator by releasing both ends of flexible spline as thin-walled cylindrical shape, forming rectangular toothform and combining it with a rotary/stationary plate to form part of a harmonic reduction gear mechanism. CONSTITUTION:Both ends of a flexible spline 49 are released as thin-walled cylindrical shape, and rectangular toothforms are formed at the both ends. Rotary discs 53, 54 on which projections of the same pitch are formed on the circumference to coincide with the rectangular toothforms are associated to form part of a harmonic reduction gear mechanism. A web generator 47 is rotated by the rotations of motors 34-34, and the rotary output decelerated at the prescribed reduction gear ratio is transmitted between a stationary base body 28 and a rotary frame 24.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor actuator for driving the joints, etc. of an articulated robot.

Structure of the conventional example and its problems The structure of the motor actuator in the conventional articulated robot includes a bracket 1, a magnet 2,
An electric motor is composed of a yoke 3, an armature 4, a motor shaft 7 with bearing devices 5 and 6 fixed on both sides, and the like.
It is fixed to the rotating frame body 8 via. here,
The armature 4 and the motor shaft 7 are fixed concentrically. 9
is a U-shaped fixed base body, cylindrical members 10.11 are provided on both sides of this fixed base body 9, and bearing devices 12.11 are provided on both sides of the fixed base body 9.
It is fitted to the rotating frame body 8 via 13. 14
16 is a harmonic reducer in which the flex spline 16 is cup-shaped, the wave generator 14 is attached to the motor shaft 7, the flex spline 16 is attached to a cylindrical member 1o, and the fixed base body 9 is connected to the fixed base body 9 via this cylindrical member 1o. Circular splines 16 are each fixed to the rotating frame body 8. A rotary encoder 17 is fixed to the fixed base body 9 via the cylindrical member 11, and the shaft of the rotary encoder 17 is fixed to the motor shaft 7. Reference numeral 18 denotes a light-shielding plate having a slit in a part of the circumference fixed to the rotating frame body 8, and 19 denotes a photocoupler that engages with this light-shielding plate, and is attached to the fixed base body 9 via the sensor mounting base 20. ing. Further, 21 and 22 are magnetic bodies fixed at 180 degree intervals on a part of the circumference of the rotating frame body 8, and 23 is a magnetic sensing element that engages with this magnetic body and is fixed via the sensor mounting base 2o. It is fixed to the base body 9.

To explain the operation of the conventional motor actuator configured as above, the wave generator rotates due to the rotation of the electric motor, and the rotational output reduced by the predetermined reduction ratio of the gnomonic reducer is transmitted to the fixed base. and is transmitted between the rotating frame bodies. If the stationary base body is fixed in this state, the rotating frame body will perform rotational movement. In this case, the rotation angle of the rotating frame body is detected by the rotary encoder, the origin position of the rotating frame body is detected by the slit signal of the light-shielding plate by the photocoupler and the origin signal from the rotary encoder, and the rotation of the rotating frame body is detected by the magnetic sensing element. By detecting the operable limit, these detection signals are received by an external control device and can be controlled.

In the conventional example described above, since one side of the cup-shaped flexspline is fixed, repetitive stress due to the deflection amplitude in the radial direction that occurs when the wave generator rotates is concentrated at the zero corner. In order to disperse and absorb this concentrated stress as much as possible, the flexspline is constructed to be long in the axial direction, so as is clear from Figure 1, the dead space inside the flexspline is large, resulting in joint damage. As the shape becomes larger, it also causes an increase in weight. In addition, since the point of application of the rotational torsional stress is a relatively long span between the external gear provided on the flexspline and the fixed part, the amount of deflection in the rotational direction is proportional to the length of the flexspline. This results in an adverse effect on positioning accuracy.

Furthermore, due to machining accuracy and assembly accuracy, misalignment between the motor axis and the center of the fixed flexspline will cause torque fluctuations in the rotation of the wave generator, resulting in vibration. It had other drawbacks.

Purpose of the Invention 6.-2. In view of the drawbacks of the above-mentioned conventional example, the present invention shortens the length of the flexspline in the axial direction to the minimum necessary, eliminates structural dead space, and achieves compactness and weight reduction. By making the flexspline support structure at both ends, the amount of deflection in the rotational direction due to rotational torsional stress is minimized, increasing positioning accuracy, and by creating a structure that absorbs misalignment between the motor axis and the center of the flexspline. An object of the present invention is to provide a motor actuator for driving joints of a robot, which can eliminate a source of vibration without causing rotational torque fluctuations.

Structure of the Invention The present invention comprises a rotating frame body having two bearing devices and an arm attachment portion, a U-shaped fixed base body supporting the bearing device and having an arm attachment portion, and this fixed base body. A drive electric motor, a rotary encoder, a cylindrical member, a rotating frame body, and a fixed base body are fixed to a part of the drive motor, a rotary encoder, and a rotary frame body, with both ends open and rectangular teeth machined at both ends, and an external gear in the center. It consists of a processed thin-walled cylindrical 7-rex spline, a circular spline equipped with an internal gear to mesh with the external gear of the flex spline, and a gear reduction device consisting of an elliptical wave generator. The wave generator is fixed to the shaft of the electric motor, the circular spline is fixed to the rotating frame body, and the flexspline is provided between the wave generator and the circular spline so that the internal gear of the circular spline meshes with the internal gear of the circular spline. A rotary fixing plate with an uneven outer circumference that matches the tooth profile is fitted in the axial direction to the toothed part, and this rotary fixing plate is attached to a cylindrical member provided at both ends of the rotary fixing plate, and fixed via this cylindrical member. By fixing them to the upright parts on both sides of the base body, the flexspline is fixed to the rotating fixing plate in the rotating direction, but the rotation is fixed with respect to the deflection in the radial direction due to the wave generator. Since it has a structure that allows it to slide freely between the plates, there are no stress concentration points on the 7-rex spline due to deflection, and the length in the axial direction of the reflex spline can be shortened to the minimum necessary. As a result, it is possible to eliminate structural dead space, thereby achieving a smaller size and lighter weight, and to minimize the amount of deflection in the rotational direction due to rotational torsional stress, thereby increasing positioning accuracy. Furthermore, misalignment between the motor shaft center and the center of the flexspline can be absorbed, and the source of vibration can be eliminated without causing fluctuations in rotational torque. This has a unique effect.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a partial sectional view of a motor actuator for driving robot joints in an embodiment of the present invention, and FIG.
Fig. 4 is a front view showing the fitted state between the flexspline and the rotary fixing plate, Fig. 6 is a partial sectional view along line fq, and Figs. 6 and 7 are the flexspline. FIG. 8 and FIG. 9 are operation explanatory diagrams showing the deformation of the end face of the flex spline when the wave generator is actually inserted inside, and the fitted state of the rotary fixed plate and the circular spline. This figure shows a state in which a part of the rectangular tooth section of the spline is bent inward and fitted with the rotary fixing plate.

In FIGS. 2, 3, 4, and 6, reference numeral 24 denotes a rotating frame body provided with an arm attachment portion 26, to which an arm or other joint portion is attached. 26
．． Reference numeral 27 denotes a bearing device mounted on both ends of the rotating frame body 24, and 28 denotes a U-shaped fixed base body having an arm attachment portion 29. Cylindrical members 30 and 31 are fitted and fixed concentrically to the upright portions 32 and 33 of the fixed base body 28, respectively. Furthermore, the cylindrical parts 30, 31 each support a bearing arrangement 26, 27.

In this state, the rotating frame body 24 and the fixed base body 28 are
The structure allows the two to freely rotate within a range (approximately 180 degrees) where they collide. 34 to 44 are driving electric motors, 34 is a placket, 35 is a magnet, 36 is an armature, and 37
The motor shaft is fixed concentrically to the armature 36 with bearing devices 38.degree. 3e fixed on both sides. 4o is yoke 41,
Brush 42.10: A motor case equipped with a brush spring 43 and a brush lid 44, which is fixed concentrically with the placket 34.

The armature 36 is mounted on a bearing device 38 fixed to the motor shaft 37.
It is supported concentrically by the motor case 4o and the placket 34 via the motor case 4o. 45 is a rotary encoder whose rotating shaft is fixed to the motor shaft 37 and the fixing bracket 34. Note that this motor shaft 37 is supported by a bearing device 46 mounted on the cylindrical member 3o. 47 to 49 are gear reduction devices,
In this embodiment, a harmonic speed reduction mechanism is used.

Reference numeral 47 denotes an elliptical wave generator fixed concentrically to the motor shaft 37. Reference numeral 48 is a circular spline equipped with internal gears and is fixed to the rotating frame body 24. 49 is a thin-walled cylindrical flex spline, which has external teeth 60 with the same pitch as the internal teeth of the circular spline 48 but two fewer teeth, and is installed between the wave generator 47 and the circular spline 48. , the inner teeth of the circular spline 48 and the outer teeth 60 of the flex spline 49 mesh with each other on the long axis side of the wave generator 47 deformed into an elliptical shape.

Also, both ends of this flex spline 49 are shown in FIG.

As shown in Fig. 6, a thin cylindrical shape 11 is open, and rectangular teeth 51 and 52 are formed around the entire circumference. Also 5
3 and 54 are rotary fixed plates fixed to the cylindrical members 30 and 31, respectively, and the rectangular teeth 51.
52, and has convex external teeth 55 and 56 on its outer periphery to match the grooves of the teeth 61 and 52, and can be fitted and twisted in the axial direction so that it can be thrust with ease. The structure is perfect. In other words, in this state, the flexspline 490 is fixed in the rotational direction via the rotational fixing plates 53 and 54 on the fixed base body 2. However, regarding the deflection in the radial direction due to the wave generator 47, the external teeth 5 of the rotating fixed plates 53 and 54
6.56 and the rectangular tooth 51.5 of the flexspline 49
It has a structure that allows it to slide freely at the engagement part with 2. 57 is a light-shielding plate having a slit 58 on a part of the circumference fixed to the rotating frame body 24, and 59 is a photocoupler that engages with this light-shielding plate 57 and is connected to the sensor mounting base 6o.
It is fixed to the fixed base body 28 via. Also 61.6
2 is a magnetic body fixed on the circumference of the rotating frame body 24 at approximately 1800 intervals, and 63 is a magnetic sensing element that engages with the magnetic bodies 61 and 62, and is attached to the fixed base body 2 via the sensor mounting base 6o.
It is fixed at 8.

The operation of the robot joint drive motor actuator configured as described above will be described below.

The wave generator rotates due to the rotation of the electric motor, and a rotational output reduced by a predetermined reduction ratio is transmitted between the fixed base body and the rotating frame body.

If the stationary base body is fixed in this state, the rotating frame body will perform rotational movement. This is bent into an elliptical shape by the wave generator as shown in FIG. 6, and the meshing portion m of the flex spline and circular spline is created at the extension of one part on the long axis side. When the wave generator rotates in this state, the long axis side l moves as shown in FIG. 7, and the tooth meshing part m moves. At this time, Figure 6,
As is clear from Figure 7, the flexspline has an A structure that allows it to slide in the radial direction at the part where the teeth engage with the rotating fixed plate, so it can flex freely according to the shape of the wave generator. I can't stand it. However, since the rotational direction is fixed, the circular spline is decelerated by (difference in the number of teeth between the circular spline and flexspline/number of teeth of the circular spline) and is transmitted as an output. With twisted flex splines, there are no stress concentration points due to deflection, and the stress is distributed throughout the body, so the length in the axial direction can be shortened to the minimum necessary, eliminating dead space in the structure and making it smaller and lighter. Since the rotational torsional stress can be divided into both ends, and the point of application of the torsional stress can be made extremely short, the amount of deflection can be kept to a minimum and the positioning accuracy can be improved. Furthermore, since the axial center of the flexspline always naturally aligns with the axial center of the wave generator, the rotation of the wave generator is 14.

This has the effect of increasing lifespan by eliminating torque fluctuations and eliminating the source of vibration.

- The rotation angle of the rotating frame obtained in this way is detected by a rotary encoder, and the origin position of the rotating frame is detected by the slit signal of the light-shielding plate by the photocoupler and the origin signal from the rotary encoder. By detecting the rotatable range IJ of the rotary frame body using a magnetic element, a control device provided externally receives these detection signals and can perform normal control.

The above explanation is based on the case where the teeth at both ends of the flexspline are cut into a rectangular shape while remaining on a thin cylinder. The same effect can be obtained when a rectangular tooth is formed by bending a portion of the teeth at both ends in order to increase the strength of the meshing portion.

Effects of the Invention As described above, the present invention has a flexspline which has both ends left open in a thin cylindrical shape and has rectangular tooth profile processing applied to both ends, and a flexspline which is the same on the circumference and which matches the rectangular teeth. The flexspline is fixed in the rotational direction by combining it with a rotary fixing plate provided with a pinch convex part to form a part of the harmonic deceleration mechanism, but the deflection amplitude in the radial direction is not fixed, and the wave generator The length of the flexspline in the axial direction, which can be bent over the entire elliptical shape, can be shortened to the minimum necessary, eliminating dead space in the structure, making it possible to reduce the size and weight. Stress can be divided, and the amount of deflection in the rotational direction can be minimized, increasing positioning accuracy. In addition, since the axis of the flexspline naturally aligns with the axis of the wave generator, it has the effect of eliminating sources of vibration without causing rotational torque fluctuations, and its practical effects are second to none. There is something.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a conventional motor actuator, FIG. 2 is a partially sectional view of a motor actuator for driving a joint according to an embodiment of the present invention, and FIG. 3 is a partially sectional front view of a conventional motor actuator.
4 is a front view of the flexspline and rotation fixing plate; FIG. 6 is a partial sectional view taken along line fq in FIG. 4; FIGS. 6 and 7. 8 is a front view of the flexspline and the rotary fixing plate, and FIGS. 8 and 9 are a front view and a partially broken sectional view of the flexspline with some of the rectangular teeth bent inward. 24... Rotating frame body, 28... Fixed base body, 47... Wave generator,
48...Circular spline, 49...
... Flex spline, 53.54 ... Rotating fixed plate, 30, 31 ... Cylindrical member. Name of agent: Patent attorney Toshio Nakao and 1 other person @1
Figure 2 Figure 3 Figure 2, 9 Figure 4 Figure 5 n Figure 6 Figure 7 Figure 8 Figure 8-1 Figure 9

Claims (2)

[Claims] (1) a rotating frame body having two bearing devices and an arm attachment portion at both ends of its outer surface; a fixed base body having an approximately U-shape that supports the bearing device and having an arm attachment portion;
A driving electric motor fixed to a part of this fixed base body,
Between the rotary encoder and the cylindrical member, the rotary frame body and the fixed base body, there is a thin cylindrical flexible body with both ends open and with rectangular tooth profile machining on both ends and an external gear machining in the center. It consists of a spline, a circular spline equipped with an internal gear to mesh with the external gear of the flexspline, and a gear reduction device consisting of an elliptical wave generator, and the wave generator is connected to the shaft of the electric motor. , the circular spline is disposed on the rotating frame body, the flexspline is provided between the wave generator and the circular spline so that an internal gear of the circular spline meshes with the circular spline, and rectangular tooth profiles are provided at both ends. A rotary fixing plate having irregularities on the outer periphery to match the tooth profile is fitted in the axial direction, and this rotary fixing plate is attached to a cylindrical member provided at both ends of the rotary fixing plate, and the fixing plate is attached to the cylindrical member via the cylindrical member. A motor actuator configured by being fixed to the upright parts on both sides of the base body. (2) The motor actuator according to claim 1, wherein a part of the rectangular tooth profile provided at both ends of the flexspline is bent.