JPH0454358A - Planetary roller speed reducer - Google Patents

Abstract

PURPOSE:To detect a position of an output shaft without any affect caused by slide of a transmitting mechanism by making planetary rollers rotate and revolve, connecting them to an output shaft via an output flange, and detecting a rotating angle formed between a base table and the output shaft by means of a rotating angle detector. CONSTITUTION:A sun roller 3 is rotated together with rotation of a motor 1, and planetary rollers 4 are rotated accordingly. Because an outer ring 22 is fixed, it cannot be rotated. The planetary rollers 4 revolves around the sun roller while rotating. An output shaft 10 is connected to an output flange 9 and is rotatably secured to the outer ring 22 via a bearing 11 so that a decelerated output is transmitted to the output shaft 10 to drive, for example, a robot arm. Meanwhile, a hollow shaft type encoder 7, which is driven via an encoder fixing flange 7a connected to the lower end 5a of a shaft 5, detects a rotating angle formed between a base table and the output shaft 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a planetary roller speed reducer used in devices where rotation and stopping accuracy are important, such as robot arms.

[Conventional technology]

Conventionally, this type of planetary roller reducer was disclosed in Japanese Patent Application Laid-open No. 58-39.
It is disclosed in Publication No. 873 and the like.

FIG. 5, FIG. 6, and FIG. 7 are configuration diagrams showing conventional examples, respectively.

In the one shown in FIG. 5, the angle detection encoder is not attached to the output side of the planetary roller reducer, but the angle is detected by an encoder 44 directly connected to the motor 41, and the motor 41 is controlled by the control device 42 based on this detected value. positioning control.

In the one shown in FIG. 6, the output shaft of the planetary roller speed reducer and the encoder shaft are connected by a transmission mechanism 43 such as a timing belt or gears to detect the position.

In the one in Figure 7, the outer ring is the output shaft, and the rotation of the robot arm attached to the output shaft can be directly detected, but the planetary rollers are fixed to the base or base, and the planetary roller reducer has the largest The planetary rollers, which are a distinctive feature, cannot revolve around the planet while rotating.

[Problem to be solved by the invention]

Among the conventional examples described above, the one shown in Fig. 5 has a problem in that the position of the output side is distorted when slipping occurs in the roller part, whereas the one shown in Fig. 6 eliminates the worry of positional deviation due to roller slipping. However, play in the transmission mechanism not only prevents accurate position detection, but also poses control problems and concerns about wear of gears, etc.

Also, if the outer ring is fixed and the planetary rollers are rotated and revolved, the reduction ratio will be increased by 1 compared to when the outer ring rotates, but in the case of the one in Figure 7, the planetary rollers are not revolved and the outer ring is rotated. The reduction ratio becomes smaller. Furthermore, the outer ring, which has a large inertia, must be rotated.

In view of the above problems, an object of the present invention is to provide a planetary roller speed reducer that rotates and revolves a planetary roller and directly detects the rotation angle of the revolving planetary roller with respect to a base.

[Means to solve the problem]

The planetary roller speed reducer of the present invention includes a sun roller rotatably attached to a base and driven by a motor, and a plurality of planetary rollers circumscribing the sun roller, driven by the sun roller, and rotating around the sun roller. a flange connecting one end of the rotating shaft of each planetary roller so that the planetary rollers rotate while maintaining a constant positional relationship with each other; and a flange inscribed with the planetary roller and attached to the base. Preferably, the planetary roller reducer has a fixed outer ring and an output shaft connected to the flange, further comprising rotation angle detection means for directly detecting a rotation angle between the base and the output shaft. The rotation angle detecting means is a hollow shaft encoder fixed to a base, and a sun roller is loosely fitted into the hollow part of the hollow shaft of the hollow shaft encoder, and the sun roller is inserted outward from one end of the hollow shaft. The other ends of the rotating shafts of the planetary rollers are respectively attached to the encoder flanges extending in the shape of a horizontal plate, and more preferably, the position detection value of the output shaft detected by the rotation angle detection means is used as position information to be transmitted to the control device. It has a feedback control system that inputs the encoder output directly connected to the sun roller drive motor into the F/V converter and feeds back the converted output value as speed information to the control device.

[For production]

The rotation angle detection means directly detects the revolution angle of the planetary roller connected to the output shaft with respect to the base, that is, the position on the output shaft side.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of a planetary roller speed reducer according to the present invention, and FIG. 2 is a sectional view showing a hollow shaft encoder of the embodiment shown in FIG.

A motor mounting flange 2 is mounted on the reducer fixing base 20 which is a base.
1 and an outer ring 22 are attached. The drive motor 1 (hereinafter referred to as motor 1) is attached to the motor mounting flange 21.
The rotational speed of the motor 1 is detected and output by an encoder 14 directly connected to the motor.

The sun roller 3 has a cylindrical shape with a smooth surface, and is coupled to the output shaft 1a of the motor 1 by a coupling 2, and is attached to a motor mounting flange 21 which is a part of the casing.
The sun roller 3 is rotatably supported via a set of bearings 13, and a plurality of planetary rollers (described later) are circumscribed on the outer periphery of its free end to prevent the sun roller 3 from swinging around. The rotational force of the sun roller 3 is applied to a plurality of planetary rollers 4 having the same diameter and arranged circumscribed around the sun roller 3.
It is transmitted by the frictional force of The plurality of planetary rollers 4 are each rotatably supported by a shaft 5 fixed to an output flange 9 via a pair of bearings 12 . Each shaft 5 extends also to the output axis la side of the sun roller 3, and its lower end 5a is connected to an encoder mounting flange 7a, respectively. Each planetary roller 4 has a cylindrical shape with a smooth surface, and each planetary roller 4 has an outer ring 22 inside the casing.
is inscribed in

The reduction ratio of the planetary roller speed reducer of this embodiment is expressed by equation (1) in which the sun roller diameter is dl and the outer ring inner diameter is d2.

In other words, when the motor 1 rotates, the sun roller 3 rotates,
Accordingly, each planetary roller 4 rotates.

However, since the outer ring 22 is fixed, it cannot rotate, and each planetary roller 4 rotates on its own axis and revolves around the sun roller. This phenomenon is unique to planetary roller speed reducers, and the speed reduction ratio can be increased by +1 compared to when the speed is simply reduced by the sun roller and the outer ring.

The output shaft 10 is connected to the output flange 9, and is rotatably attached to the outer ring 22 together with the output flange 9 via a bearing 11. Therefore, the decelerated output is transmitted to the output shaft 10, and the
For example, the robot arm 15 (see FIG. 3) is driven. On the other hand, the rotation angle between the base and the output shaft 10 is determined by a hollow shaft encoder 7 which is a rotation angle detection means and is driven via an encoder mounting flange 7a connected to the lower end 5a of the shaft 5. detected. As shown in FIG. 2, the hollow shaft encoder 7 includes a fixed part 7f, a slit plate 7b, an optical system device 7c, a hollow shaft 7d, an encoder mounting flange 7a integrated with the hollow shaft 7d, and a bearing 7.
e, a bearing housing 7g forming part of the fixed part 7f, a cover 7h, etc. The fixed portion 7f is fixed to the motor mounting flange 21, and the optical system device 7C is further fixed to the fixed portion 7f. On the other hand, the hollow shaft 7d is integrated with the encoder mounting flange 7a, and the bearing housing 7 is a part of the fixed part 7f to which the cover 7h and the optical system device 7C are attached.
g via a pair of hair rings 7e so as to be rotatable. The slit plate 7b is fixed to the hollow shaft 7d,
It is arranged between the optical system device 7C and the fixed part 7f. Therefore, when the encoder mounting flange 7a is rotated by the planetary roller 4, the rotation becomes the rotation of the slit plate 7b via the hollow shaft 7d, which is detected and output by the optical system device 7C.

Although the hollow shaft encoder 7 can be installed between the output shaft 10 and the outer ring 22, the hollow shaft of the hollow shaft encoder 7
Since the diameter of d is approximately φ30 to φ50, when the purpose is to drive the robot arm 15 as shown in FIG. 3, the output shaft that transmits large torque must be approximately φ30 to φ50. Therefore, the problem arises that the material strength of the output shaft is insufficient (this is not a problem if a small torque is to be transmitted). Since the sun roller 3 is a shaft connected to the motor 1 without a speed reduction mechanism, the transmitted torque is small and the diameter may be about φ20 to φ30. Therefore, the hollow shaft encoder 7 is attached to the drive motor output shaft connection side of the sun roller. In addition, motor 1, motor direct-coupled encoder 1
4. The hollow shaft encoder 7 is connected to and controlled by the control device 23.

By adopting the structure of this embodiment, the rotation center of the output shaft 10 and the rotation center of the hollow shaft encoder 7 for detecting the rotation angle can be made coaxial, and the rotation of the output shaft can be directly detected. It is possible to configure a feedback control system with (:1 osed loop).

FIG. 4 shows an example of this feedback control system.

The control device 23 includes a speed control section 23a1 and a position control section 23b.
, memory 23c, operation section 23d, I10 control circuit 23e
, an F/V converter 23f and a CPU 23g, and a command is output to the motor 1 to control the output shaft 10 of the planetary roller reducer connected to the robot arm 15, and the output shaft 10 is driven by the motor 1 according to the command. be done. Speed data is fed back from the motor 1 to the speed control unit 23a via the motor direct-coupled encoder 14 and the F/V converter 23f, and position data is fed back from the output shaft 10 side to the position control unit 23b via the hollow shaft encoder 12. will be given feedback. Therefore, this control system is a completely closed loop, and in the driving force transmission path from the motor 1 to the output shaft 10,
Even if slippage occurs, the position of the output shaft 100 rotations can be accurately controlled without being affected by the slippage at all. Note that the position control of the output shaft 10 can be controlled without problems by using a known numerical control means, and in order to increase the accuracy, the only thing that can be done is to increase the precision of the hollow shaft encoder 7, and the robot arm 15 etc. It is possible to rotate the coupled output shaft 10 with high precision.

(Effects of the Invention) As explained above, the present invention rotates and revolves the planetary roller, connects it to the output shaft via the output flange, and detects the rotation angle between the base and the output shaft using the rotation angle detection means. This has the effect of being able to detect the position of the output shaft without being affected by slippage in the transmission mechanism, and unlike reduction gears that use gears, there is no bala crash, so the control system can form a completely closed loop feedback system. This has the effect of improving absolute positioning accuracy, and also has the effect of making the entire system more compact by detecting the rotation angle using a hollow shaft encoder.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the planetary roller reducer of the present invention, FIG. 2 is a sectional view showing a hollow encoder of the embodiment of FIG. 1, and FIG. 3 is a sectional view of the embodiment of FIG. 1. Fig. 4 is a block diagram showing details of the control device of the embodiment shown in Fig. 1, and Figs. 5, 6, and 7 are conventional examples. FIG. ! ... Drive motor, 2... Coupling,
3... Sun roller, 4... Planetary roller, 5
...Shaft, 7...Hollow encoder,
7a... Encoder mounting flange, 9... Output flange, 10-... Output shaft, 11.
12.13...Bearing, 14--Motor direct-coupled encoder, 15--Robot arm, 20--Reduction gear fixing base, 21--Motor mounting flange, 22--Outer ring.゛Engineer 8-Coffee Lagoon Frashia Figure 2 Patent Applicant: Canon Co., Ltd.

Claims (3)

[Claims] (1) A sun roller rotatably attached to a base and driven by a motor; a plurality of planetary rollers that circumscribe the sun roller and are driven by the sun roller and rotate around the sun roller; and each of the planetary rollers. a flange connecting one end of the rotating shaft of each planetary roller so that the planetary rollers rotate while maintaining a constant positional relationship with each other; an outer ring that is inscribed with the planetary roller and fixed to the base; A planetary roller speed reducer having an output shaft connected to the flange, further comprising a rotation angle detection means for directly detecting a rotation angle between the base and the output shaft. (2) The rotation angle detection means is a hollow shaft type encoder fixed to a base, and a sun roller is loosely fitted into the hollow part of the hollow shaft of the hollow shaft encoder, and the sun roller is loosely fitted into the hollow part of the hollow shaft of the hollow shaft. 2. The planetary roller speed reducer according to claim 1, wherein the other end of the rotating shaft of the planetary roller is attached to each of the encoder flanges extending in the shape of a horizontal plate. (3) The position detection value of the output shaft detected by the rotation angle detection means is fed back to the control device as position information, the encoder output directly connected to the sun roller drive motor is input to the F/V converter, and the converted output value is 3. The planetary roller deceleration device according to claim 1, further comprising a feedback control system that feeds back the speed information to the control device as speed information.