JPH05215191A - Planetary gear device without backlash - Google Patents

Abstract

PURPOSE:To provide a planetary gear device in which respective gears mesh with one another substantially with no backlash. CONSTITUTION:The planetary gear 3 of a planetary gear device 1 can be radially elastically displaced. A planetary gear bearing 5 is bent to an elliptical form by a planetary gear shaft 6 of an elliptical shape in section. Thus, between the planetary gear and the planetary gear bearing, a clearance 7 is formed. Since the planetary gear can be elastically displaced in the direction of a minor axis L1 of an ellipse, the respective gears mesh with one another substantially with no backlash.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planetary gear device, and more particularly to a backlashless planetary gear device capable of engaging a planetary gear with a sun gear and an internal gear without backlash.

[0002]

2. Description of the Related Art As is well known, a planetary gear device comprises a sun gear and an internal gear that are coaxially arranged, and one or a plurality of planet gears that mesh with both of them. .. A certain amount of backlash is formed between the tooth flanks in mesh between the gears to ensure smooth rotation of the gears. However, this backlash uses, for example, a planetary gear device as a reduction mechanism,
This may be an obstacle to realizing high-speed precision control in various machine tools. Therefore, it is necessary to assemble a backlash removing mechanism of any type to the planetary gear device.

[0003]

SUMMARY OF THE INVENTION In view of this point, an object of the present invention is to realize a planetary gear device incorporating a backlash removing mechanism having a new structure.

[0004]

In order to solve the above problems, in the planetary gear device of the present invention, the structure of each part is as follows. First, it is assumed that each planetary gear can be elastically displaced in the radial direction. Further, the planetary gear shaft is an elliptical shaft or a shaft having a cross-sectional shape similar thereto. Further, in order to rotatably attach the planetary gear to the planetary gear shaft, the planetary bearing mounted between them is also provided with an outer ring and an inner ring that are elastically displaceable in the radial direction. In addition to this, the circumference of the inner peripheral surface of the planetary gear is set to be slightly longer than the circumference of the outer peripheral surface of the outer ring of the planetary bearing, and the planetary gears and the planetary gears corresponding to the meshing positions of the respective gears are set. A gap can be formed between the bearings.

[0005]

When the planetary gear shaft has, for example, an elliptical cross section, the outer peripheral surface of the outer ring of the planetary bearing mounted therein also has an elliptical contour. In addition, due to the difference in circumferential length between the outer peripheral surface of the outer ring of the planetary bearing and the inner peripheral surface of the planetary gear, there is a predetermined amount of clearance in the minor axis direction of the ellipse (that is, at the position corresponding to the meshing position of each gear) Is formed.
The elastic radial displacement of the planet gears eliminates the backlash between the planet gears and the sun gear and between the planet gears and the internal gear. Also, thermal expansion,
The influence on the meshing hardness due to the manufacturing and assembling errors of the gear is absorbed by the gap formed between the planetary gear and the outer peripheral surface of the outer ring of the planetary bearing.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the invention will be described below with reference to FIG.

As shown in FIG. 1, the planetary gear device 1 of the present example.
The basic structure of is the same as a general planetary gear unit,
For example, three planetary gears 3 are arranged on the outer periphery of the sun gear 2 located at the center, and an internal gear 4 is arranged outside the planetary gears 3 in a concentric state with the sun gear 2. Each planetary gear 3 is rotatably supported by a planetary gear shaft 6 via a planetary gear bearing 5.

The planetary gear 3 is formed by carving teeth on the outer circumference of a thin-walled cylindrical elastic member, and is elastically displaceable in the radial direction. The planetary gear bearing 5 is a ball bearing including an outer ring 51 and an inner ring 52 made of a thin annular elastic member, and a plurality of balls 53 inserted between them. The planetary gear shaft 6 mounted inside the bearing 5 is formed of a rigid body having an elliptical cross section. The elliptical cross section of the planetary gear shaft is set so that its short axis L1 is oriented in the direction of the meshing position of each gear (that is, the radial direction of the planetary gear device 1). The elliptical cross-sectional shape of the planetary gear shaft has a minor axis L1 slightly longer than the major axis L2.
The length of the long axis L2 is shorter than that of the planetary gear, and is set so as to fit exactly into the inner peripheral surface 3a of the planetary gear having the cylindrical shape via the planetary gear bearing 5.

The circumference of the inner peripheral surface 3a of the planetary gear 3 is set to be slightly longer than the circumference of the outer peripheral surface 51a of the outer ring 51 of the planetary gear bearing 5. Therefore, in the assembled state, the inner peripheral surface 3 of the cylindrical planetary gear is
a and an outer peripheral surface 51a of the elliptical planetary gear bearing
A pair of gaps 7 are formed between and, which are maximum at both ends of the elliptical short axis L1 and zero at both ends of the long axis L2.

The planetary gear device 1 of the present embodiment configured as described above
In the above, if the respective gears are set in advance so that a slightly overlapping meshing state is formed, a gap 7 exists at both end positions of the ellipse-shaped short axis L1. It is slightly elastically displaced inward in the radial direction, thereby forming a backlash-free mesh between the gears. Also, the gap 7
Therefore, even if an error in manufacturing or assembling the gear, thermal expansion, or the like occurs, the planetary gear 3 can be slightly displaced in the radial direction, so that the meshing engagement is not affected.

[0011]

As described above, in the planetary gear device of the present invention, the planetary gears are assumed to be elastically displaceable in the radial direction, and between the planetary gears and the planetary gear bearings corresponding to the meshing positions of the respective gears. A slight gap is formed at the position. Therefore, according to the present invention, the existence of the gap allows the planetary gears to be elastically displaced in the radial direction, whereby the gears can be meshed with each other in a substantially backlash-free state. Further, even if an error in manufacturing or assembling gears, thermal expansion, or the like occurs, the planetary gear device can be elastically displaced, so that it is possible to avoid affecting the meshing engagement of each gear.

[Brief description of drawings]

FIG. 1 is a partial configuration diagram showing a main part of a planetary gear device according to an embodiment of the present invention.

[Explanation of symbols]

 1 ... Planetary gear device 2 ... Sun gear 3 ... Planetary gear 3a ... Inner peripheral surface of planetary gear 4 ... Internal gear 5 ... Planetary gear bearing 51 ... Outer ring 51a ...・ Outer ring outer peripheral surface 52 ・ ・ ・ Inner ring 53 ・ ・ ・ Ball 6 ・ ・ ・ Planet gear shaft 7 ・ ・ ・ Gap

Claims (1)

[Claims] 1. A planetary gear that is elastically displaceable in a radial direction, and a planetary gear shaft that is a rotation shaft of this planetary gear is an elliptical shaft or a cross-sectional shape similar thereto, and the planetary gear and the planetary gear shaft. Between the planet bearings mounted between
An outer ring and an inner ring that are elastically displaceable in the radial direction are provided, and the circumference of the inner peripheral surface of the planetary gear is set to be slightly longer than the circumference of the outer peripheral surface of the outer ring of the planetary bearing. A backlash-less planetary gear device characterized in that a gap is formed between the planetary gear and the planetary gear bearing corresponding to the meshing position of each gear.