JPH0633995A - Planetary reduction gear - Google Patents

Abstract

PURPOSE:To provide a reduction gear which is small, low-costed and of low noise even with a high reduction gear ratio available. CONSTITUTION:A planetary reduction gear set has an input shaft 11; an eccentric shaft 12 secured to the input shaft 11; a planetary gear 13a freely rotatably supported to and concentric with the eccentric shaft 12; a fixed internal gear 14 constantly meshing at part with the planetary gear 13a and differing in the number of teeth with the planetary gear 13a; and an output shaft 16a. A steel ball 15 is assembled between an end face of the boss 13b of the planetary gear 13a and a circular recessed portion in an end face of the output shaft so as to take out only an output of decelerated rotation of the planetary gear 13a on its axis without preventing the planetary gear 13a from rotating around the shaft 12.

Description

Description: [0001] The present invention relates to a planetary gear reducer. The present invention can be applied to mechanical devices in various industrial fields such as robots, automobiles, machine tools, and power tools. [0002] [Prior Art] Conventionally used reduction gears having a high reduction ratio include a harmonic drive system and a Ferguson gear system. As shown in Fig. 1, the harmonic drive system rotates the elliptical wave generator to engage the elastic gears by sequentially pushing them against the internal gear, and the elastic gears are moved in opposite directions by the difference in the number of teeth of the internal gear. It is a device that can be rotated to obtain deceleration output. Further, in the Ferguson gear system, as shown in FIGS. 2 and 3, when the sun gear is rotated and the planetary gear is revolved while revolving, the movable internal gear has a difference in the number of teeth from the fixed internal gear. This is a device that rotates and takes out deceleration output. [0003] [Problems to be solved by the invention] However, since the conventional harmonic drive system includes a special mechanism such as a wave generator and elastic gears, a high manufacturing technique is required, and the manufacturing cost is high. There is.
Further, in the conventional Ferguson gear system, since the sun gear and the planetary gear are meshed with each other by the external gears, there is a problem that the meshing ratio is low and the noise is high. Therefore, an object of the present invention is to provide a reduction gear that is small in size, low in cost, and low in noise while obtaining a high reduction gear ratio. [Means for Solving the Problems] Means for achieving the above object will be described below with reference to FIGS. 4 and 5 corresponding to the embodiments. The speed reducer of the present invention includes an input shaft 11, an eccentric shaft 12 fixed to the input shaft 11, a planetary gear 13a rotatably supported by the eccentric shaft 12, and revolved by the rotation of the input shaft 11. A fixed internal gear 14 arranged concentrically with the input shaft 11 so that the number of teeth is slightly different from that of the planetary gear 13a and always partially meshes with the planetary gear 13a, and an end face of the boss 13b of the planetary gear 13a. An output shaft 16a which has an end face facing with and which is concentric with the input shaft,
It consists of a plurality of steel balls 15. Boss 13b of planet gear 13a
A plurality of circularly shaped steel balls 15 are incorporated in the end face of each of the steel balls 15, and each of the steel balls 15 is in contact with the bottom of a circular recess 16b on the end face of the output shaft. The diameter of the circular recess 16b is a value obtained by adding the diameter of the steel ball to twice the eccentric radius due to the revolution of the planetary gear. The bottom of the circular recess 16b is cylindrical or has a pot-like shape having the same curved surface as the radius of the steel ball 15, and a gap is provided so that the facing end faces do not come into contact with each other. [Operation] When the input shaft 11 is rotated with this structure, the planetary gear 13a revolves around the inner circumference of the fixed internal gear 14 while revolving by the number of teeth difference from the fixed internal gear 14. Rotate in the opposite direction. Boss 13b of planet gear 13a
A plurality of steel balls 15 are installed in a circular shape on the end surface of the steel ball 1.
Reference numeral 5 denotes a circular recess 16b on the end face of the output shaft 16a facing each other.
Since it is in contact with the bottom of the steel ball 15, the steel ball 15 rolls while sliding along the R surface of the bottom, and makes a circular motion having a radius of the eccentric distance by the revolution. Circular recess 16 on the end surface of the output shaft 16a
Since the diameter of b is a value obtained by adding the diameter of the steel ball to twice the eccentric radius due to the revolution of the planet gear 13a, there is no backlash between the planet gear and the output shaft 16a without hindering the revolution of the planet gear. . Further, since there is little friction, it is quiet, smooth and efficient, and only the decelerated rotation due to the rotation of the planetary gear 13a is transmitted to the output shaft 16a, and only the decelerated output can be taken out. In this configuration, the same result can be obtained even when the side where the steel ball 15 is incorporated is on the end face side of the output shaft 16a.
Further, in the present invention, since it is composed only of the external gear, the internal gear and the steel ball 15, and no special component such as a wave generator or elastic gear is used, it is easy to manufacture and low in cost. Can be manufactured at cost. Further, the meshing of the planetary gear 13a and the fixed internal gear 14 is high because of the meshing of the external gear and the internal gear, resulting in a low noise. [Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 4 shows the internal structure of a planetary gear reducer to which the present invention is applied. Further, FIG. 5 is a view seen from a direction corresponding to the AA ′ cross section in FIG. 4. In the figure, 11 is an input shaft, 12 is a cylindrical eccentric shaft fixed to the input shaft 11, and its axis is eccentric with respect to the axis of the input shaft 11. Reference numeral 13a is a planetary gear having external teeth, which is arranged concentrically with the eccentric shaft 12 via a bearing 20 and is provided with a boss 13b in which a steel shaft 15 is incorporated. 14 is a planetary gear 13
It is a fixed internal gear that has one more tooth than a. It is concentric with the input shaft 11 and always meshes partially with the planetary gear 13a. 16
Reference numeral a denotes an output shaft, which has a circular recessed portion 16b having an R-shaped bottom and an end face. 17 is a bracket, 18 is a casing, 2
2, 23 and 24 are bearings, and 19 is a screw for fixing the bracket 17 and the casing 18. Therefore, the input shaft 11
When the eccentric shaft 12 is rotated, the eccentric shaft 12 fixed to the input shaft 11 rotates, but the planet gear 13a concentric with the eccentric shaft 12 does not rotate together with the eccentric shaft 12 because of the bearing 21. Revolve while meshing. And planetary gear 13
When "a" revolves for one revolution, the planetary gear 13a has one tooth less than that of the fixed internal gear, so that the planetary gear 13a rotates by one sheet in the direction opposite to the revolving direction. Output shaft 1
The end face of 6 has a circular concave portion 16b whose bottom is the same radius as the radius of the steel ball 15, and the steel ball 15 incorporated in the end face of the boss 13b of the planet gear 21 is the planet gear 1
Only the rotational output decelerated by the rotation of the planetary gear 13a is transmitted to the output shaft 16a with the same radius as the revolution of 3a, rolling while sliding on the bottom of the recess 16b, performing circular motion. The reduction ratio at this time can be represented by (number of teeth of fixed internal gear-number of teeth of planet gear) / (number of teeth of planet gear). For example, when the number of teeth of the fixed internal gear 14 is 101 and the number of teeth of the planetary gear is 100, the reduction ratio is 1/100. [Advantage] According to the present invention, only two gears, an external gear and an internal gear, are required, and a large reduction ratio can be obtained with these two gears, and transmission of deceleration output is possible. Since the sliding and rolling of the steel balls 15 are utilized, the loss due to friction is small and the transmission efficiency is good. In addition, since the gear meshes with the internal gear and the external gear, the meshing ratio is high and the noise is low. Moreover, since the number of parts is small and the processing is easy, there is an advantage that it can be easily downsized and can be manufactured at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS [FIG. 1] FIG. 1 is an explanatory view of harmonic drive systems. [FIG. 2] FIG. 2 is a block diagram of a Ferguson gear system. [FIG. 3] FIG. 3 is a schematic front view of a Ferguson gear system. FIG. 4 is a sectional view showing an embodiment of the present invention. [FIG. 5] FIG. 5 is an explanatory view of FIG. 4 viewed from AA. [FIG. 6] FIG. 6 is an explanatory diagram when a steel ball is used to transmit the deceleration output of the planetary gears. [Explanation of Codes] 1 Internal gear 2 Elastic gear 3 Wave generator 5 Sun gear 6, 13a Planet gears 7, 14 Fixed internal gear 8 Movable internal gear 11 Input shaft 12 Eccentric shaft 13b Planet gear boss 15 Steel ball 16a Output shaft 16b Circular recess 17 on output shaft end face Bracket 18 Casing 19 Screws 20, 21, 22, 23, 24 Bearing

Claims (1)

Claims: 1. An input shaft, an eccentric shaft coupled to the input shaft, a planet gear rotatably supported by the eccentric shaft, and revolved by the rotation of the input shaft, and the planet. In a speed reducer having a fixed internal gear that is slightly different from the gear in the number of teeth and is concentric with the input shaft, and is arranged so that the planetary gears mesh with each other, and an output shaft that is concentric with the fixed internal gear. ,
A planetary gear speed reducer characterized in that a plurality of circular recesses are provided in the end face of the planetary gear and the end face of the output shaft, and steel balls are arranged between the recesses. [Claim 2] The planetary gear reducer according to claim 1, wherein the shape of the bottom corner of the circular recess is a curved surface having the same radius as the steel ball.