JPH10196756A - Straight line actuator using roller screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate back-lash occurs in the straight line actuator, and enhance accuracy in position for suspending an output shaft. SOLUTION: A straight line actuator 10 is equipped with a motor M which is fixed to a housing H, and can be rotated normally and reversely, and with a roller screw shaft 12 which is deceleratingly driven by the motor M through a gear G. Paired front and rear roller nuts 14 and 14 are disposed thereto in such a way that the roller screw shaft 12 is thereby enclosed. A plurality of planetary rollers 16 are disposed in a gap between the roller screw shaft 12 and each roller nut 14 so as to be meshed with male screws and female screws, and a roller screw is formed out of the roller screw shaft 12, the roller nuts 14, and of a plurality of planetary rollers. Each roller nut 14 is inserted an elastic ring made of resin so as to be held, and is divided before and after. The paired roller nuts 14 are inwardly fitted into a sleeve shaped adapter 22. A preload adjusting nut 30 is threadedly engaged with the inner circumference at the other end of the adapter 22, and the elastic ring is deformed so as to allow the paired roller nuts 14 to be displaced to the approaching direction by fastening the aforesaid preload adjusting nut 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator for converting the rotational driving force of a forward / reverse rotating motor into a linear operating force of an output shaft and reciprocating an article connected to the output shaft.

[0002]

2. Description of the Related Art A linear actuator is disclosed in Japanese Unexamined Patent Publication No. 7-332454.
As described in Japanese Patent Application Laid-Open Publication No. H10-209, the rotational driving force of a forward / reverse rotating motor is converted into a linear operating force of an output shaft. In order to convert the rotational driving force of a motor into a linear operating force at the time of output, a linear actuator of this type includes a ball screw shaft connected to a motor rotating shaft via a gear, and a ball connected to the ball screw shaft via a ball. A ball nut to be screwed together and an output shaft fixed to the ball nut. An article such as a door is connected to the tip of the output shaft. Therefore, when the motor rotates forward and backward,
The output shaft reciprocates according to the rotation speed, and stops the article at a predetermined position.

[0003]

However, in the conventional linear actuator, the rotary driving force of the motor is converted into the linear operating force of the output shaft by using the ball screw composed of the ball screw shaft, the ball and the ball nut. doing. Ball screw is
Due to its structure, the ball rolling grooves of the ball screw and the ball nut are arc-shaped in cross section. Therefore, in addition to when a high load is applied to the output shaft, when the output shaft moves forward / backward, or when acceleration is applied to the output shaft, such as when the motor starts / stops, the ball moves in the ball rolling groove. And move in the axial direction, inevitably causing backlash.

[0004] When such backlash exists,
Since the output shaft cannot be stopped with high accuracy and the stop position of the output shaft cannot be maintained, it is extremely difficult to position the article with high accuracy. On the other hand, when the output shaft moves forward and backward, the output shaft response to the rotation of the motor becomes poor due to the presence of backlash, and even if the motor performance is improved, the operating characteristics of the linear actuator can be reduced. There is a limit to improvement.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a linear actuator for converting the rotational driving force of a forward-reverse rotating motor into a linear operating force of an output shaft and reciprocating an article connected to the output shaft. A roller screw shaft rotatably supported by the motor and rotatably driven by the motor; a pair of front and rear roller nuts surrounding the roller screw shaft; a roller screw shaft and the pair of roller nuts; A plurality of planetary rollers inserted into an annular gap and meshing with a male screw formed on a roller screw shaft and a female screw formed on a pair of roller nuts, and an elastic ring inserted between opposing surfaces of the pair of roller nuts And displacing the pair of roller nuts in the proximity direction to generate a preload between the roller nut and the planetary roller and between the planetary roller and the roller screw shaft, respectively, By concatenating the output shaft to the nut, it has solved the problems by a linear actuating machine using the roller screw.

[0006]

[Function] The output shaft is connected with articles such as a door.
The roller nut connected to the output shaft is restrained from rotating. When the motor that rotates in the normal and reverse directions is started in this state, the roller screw shaft is rotationally driven, the planet roller revolves, and the roller nut reciprocates in the axial direction. In the present invention, the roller is arranged between the screw shaft and the nut, not the ball,
Even if a load in the pushing / pulling direction is applied to the output shaft, the roller is less likely to be displaced in the axial direction.Furthermore, the pair of roller nuts integrally held by the elastic ring are displaced in the proximity direction, and the roller nut and planet Since preload is generated between the roller and between the planet roller and the roller screw shaft, there is no backlash between them. Therefore, even when a high load is applied to the output shaft, the axial displacement of the output shaft at the stop position can be made extremely small. Also, since there is no backlash, the output shaft responds accurately to the rotation of the motor even when a large acceleration acts on the output shaft, such as when the motor reverses or starts and stops. , The stop position, stroke, and linear operating speed of the output shaft can be controlled with high accuracy.

[0007]

1 is a sectional view of a linear actuator according to the present invention, and FIG. 2 is a sectional view of a main part thereof. The linear actuator 10 is
It has a motor M fixed to the housing H, which rotates in the forward and reverse directions, and a roller screw shaft 12, which is decelerated from a rotating shaft of the motor M via a gear G. One end of the roller screw shaft 12 is rotatably supported by the housing H, and the other end is a free end.

A pair of front and rear roller nuts 14 and 14 are arranged so as to surround the roller screw shaft 12. The roller screw shaft 12 has a male screw formed on its outer peripheral surface, and the roller nut 14 has a female screw formed on its inner peripheral surface. A plurality of planetary rollers 16 are arranged in the gap between the roller screw shaft 12 and the roller nut 14 and mesh with the male screw and the female screw. The roller screw shaft 12, the roller nut 14 and the plurality of planetary rollers 16 form a roller screw. ing. The planetary rollers 16 are equally spaced in the circumferential direction by guide rings 18 that are fitted in both ends of the roller nut 14.
A dust seal may be provided outside the guide ring 18. As described above, the use of the roller screw improves the rigidity of the linear actuator against a load, and reduces the axial displacement of the output shaft at the stop position even when a high load or impact occurs on the output shaft. .

The roller nut 14 of the roller screw is divided into front and rear portions with a resin elastic ring 20 interposed therebetween. The elastic rings 20 are respectively fixed to the opposing surfaces of the roller nuts 14 and hold the pair of roller nuts 14 integrally. The pair of roller nuts 14 are fitted inside a sleeve-shaped adapter 22 and are fixed to a flange 24 formed at one end of the adapter 22. 26 is a keyway, 28
Is a key for preventing relative rotation between the pair of roller nuts 14, 14 and the adapter 22. Adapter 2
A preload adjusting nut 30 is screwed into the inner circumference of the other end of 2.
By tightening the preload adjusting nut 30, the elastic ring 20 is deformed and the pair of roller nuts 14 is displaced in the approaching direction. And the planetary roller 16 is the roller screw shaft 1
2 and is elastically deformed by being pressed against the female screw formed on the roller nut 14, and a preload is generated between the roller screw shaft 12, the planetary roller 16 and the pair of roller nuts 14. By generating the preload, the space between the roller screw shaft 12 and the planetary roller 16 and between the planetary roller 16
Backlash between the roller nut 14 and the roller nut 14 is eliminated.

An output shaft 32 surrounding the roller screw shaft 12 is fixed to the flange portion 24 of the adapter 22.
An article such as an opening / closing door is connected to the tip thereof. The output shaft 32 may have an enlarged diameter end on the roller nut side, and a plurality of tightening bolts may be passed through the roller nut and the enlarged diameter end. These fastening bolts fix the output shaft and the roller nut in a non-rotatable manner, and displace the pair of roller nuts in the approaching direction. An outer cylinder 34 surrounding the roller screw shaft 12 and the output shaft 32 is provided in the housing H.
Is fixed. The outer cylinder 34 guides the outer peripheral surface of the adapter 22 and the outer peripheral surface of the output shaft 32. As described above, when the adapter is not provided, the outer cylinder guides the outer peripheral surface of the roller nut and the outer peripheral surface of the output shaft.

As described above, in the linear actuator according to the present invention,
By displacing the pair of roller nuts 14 in the approaching direction, the output shaft 32 outputs due to inertia of the output shaft 32 and articles connected thereto when the forward and backward movements are reversed or when the motor M is started and stopped. Even if a sudden acceleration occurs on the shaft 32, the axial displacement of the output shaft 32 with respect to the roller screw shaft 12 is extremely small. by this,
The responsiveness of the output shaft 32 to the motor M is improved, and by controlling the motor M electrically, the stroke, the stop position,
And by controlling the speed and acceleration of the output shaft very precisely,
Articles can be operated linearly.

[0012]

According to the present invention, the rotational driving force of the motor is converted into the linear operating force of the output shaft by using a roller screw comprising a roller screw shaft, a roller nut and a planetary roller, and the article connected to the output shaft is converted. Because of reciprocating motion, it has excellent rigidity and impact resistance, and can realize a linear actuator with a smaller diameter, higher load and longer life than before, and even when a high load acts on the output shaft, a planetary roller. It is less likely to be displaced in the axial direction within the male screw and the female screw, and the article can be positioned with high accuracy. Further, since the pair of roller nuts are displaced in the proximity direction to apply a preload to the roller screw, there is no backlash between the roller screw shaft and the planetary roller, and between the planetary roller and the pair of roller nuts. Even when the output shaft is suddenly accelerated such as when the motor is reversed or when the motor is started or stopped, the responsiveness of the output shaft to the rotation of the motor is improved, and the stop position, stroke and linear operation of the output shaft are improved. Speed can be controlled with high precision.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a linear actuator according to the present invention.

FIG. 2 is an enlarged sectional view of a roller screw used in the linear actuator of FIG.

[Explanation of symbols]

 H Housing G Gear M Motor 10 Linear actuator 12 Roller screw shaft 14 Roller nut 16 Planetary roller 18 Guide ring 20 Resin elastic ring 22 Adapter 30 Preload adjusting nut 32 Output shaft 34 Outer cylinder

Claims (1)

[Claims] 1. A linear actuator for converting a rotational driving force of a forward-reverse rotating motor into a linear operating force of an output shaft and reciprocating an article connected to the output shaft, wherein the linear actuator is
A roller screw shaft rotatably supported and driven by the motor, a pair of front and rear roller nuts surrounding the roller screw shaft, and an annular gap between the roller screw shaft and the pair of roller nuts. A plurality of planetary rollers meshing with each of a male screw formed on a roller screw shaft and a female screw formed on a pair of roller nuts, and an elastic ring inserted between opposing surfaces of the pair of roller nuts, A roller screw in which a pair of roller nuts are displaced in the proximity direction to generate preloads between the roller nut and the planetary roller and between the planetary roller and the roller screw shaft, respectively, and the output shaft is connected to the roller nut. Linear actuator using.