WO2012153356A1

WO2012153356A1 - Epicyclic gearing

Info

Publication number: WO2012153356A1
Application number: PCT/IT2011/000144
Authority: WO
Inventors: Luciano PEDERCINI
Original assignee: Crown Power Train S.R.L.
Priority date: 2011-05-10
Filing date: 2011-05-10
Publication date: 2012-11-15

Abstract

Epicycloidal reduction gear comprising three sun gears (2,6,7) with teeth number different between each other, a train holder (4) and one or more planet gears (5) characterized in that the planet gear or gears mesh with all the three sun gears at the same time. Two of said sun gears can be inner toothed crown gears (6, 7), one (6) of which can be fixed.

Description

Epicyclic gearing

The present invention relates to an epicycloidal reduction gear optimized to obtain a high reduction ratio of the angular speed between a driving shaft and a driven shaft in limited spaces.

An epicycloidal gearing is made up of a kinematic chain of gears where there are provided two gears, which are said sun gears which do not mesh with each other, and one or more gears, which are said planet gears, whose shafts are movable. The axes of the planet gears are brought by a rigid element, which is said train holder, which in turn rotates about a fixed axis coincident with the axis of the sun gears. The transmission ratio is determined by the number of the teeth of the gears (pinion, planet, crown) and by the freedom degree of each gear, and it can be calculated, the gearing geometry being known, according to formulas commonly known in the applied mechanics.

At the state of the art, there are known some embodiments of epicycloidal reduction gears which aim at obtaining high reduction ratios of the angular speed in limited spaces. Generally, such solutions comprise three-stage epicycloidal reduction gears characterized by epicycloidal gearings which are connected in series on the same great dimensioned driving shaft. In the patent application WO 2007/110169 it is described a device with epicycloidal gear apt to regulate the seat provided in the passenger compartment of an automobile. The patent application US 2010/0035719 describes another example of epicycloidal reduction gear with a system for reducing the vibrations on the shaft.

Aim of the present invention is to provide a reduction gear based on a particular epicycloidal gearing able to obtain advantageously high reduction ratios with limited dimensions.

These and other advantages will be clear in the following detailed description of the invention which refers to the drawings 1/2 and

2/2, in which an absolutely not limiting preferred embodiment of the present invention is represented. In particular:

Fig. 1 shows the side view of the reduction gear;

Fig. 2 shows an orthogonal section of the present invention;

Fig. 3 shows the kinematic scheme of the reduction gear shown in fig. 1 ;

Fig. 4 shows, for comparison aims, the kinematic scheme of the epicycloidal reduction gear known in the state of the art.

Referring to said figures, the epicycloidal reduction gear according to the invention is generally indicated with (1). It comprises a central sun pinion (2) constrained to the driving shaft (3), an epicycloidal train holder (4) to which at least a planet gear (5) is constrained, two crown gears (6, 7) with inner toothing, the one being a fixed reaction crown gear (6), the other one being an action crown gear (7) constrained to the driven shaft (8). Both the crown gears mesh with the planet gears (5) brought by the train holder (4).

As it is clear from figure 3, in an epicycloidal gearing according to the present invention there can be identified three simple epicycloidal gearings, comprising only the yet listed gears and pinions, whose geometric congruence obligations are respected at the same time. The first identifiable epicycloidal gearing is made up of the sun gear (2), the train holder (4) with the planet gears (5) and the second fixed sun gear (6); the second identifiable epicycloidal gearing is made up of the sun gear (2), the train holder (4) with the planet gears (5) and the second movable sun gear (7); the third identifiable epicycloidal gearing is made up of the two crown gears (6) and (7) and the train holder (4) with the planet gears (5).

The characterizing aspect is the particular coupling of the kinematic chains, where the planet gears (5) brought by the train holder (4) mesh with the three sun gears (2, 6 and 7) at the same time. The advantages of such an epicycloidal gearing are clear, since with a limited number of gears it allows to realize reduction ratios equivalent to the ones obtainable with more-stage epicycloidal reduction gears. As a consequence, the reduction ratio being equal, the dimension of the reduction gear is remarkably reduced, as well as the costs and the weight.

As a way of example and only to show the convenience of the present invention, it is to be observed that by realizing an epicycloidal reduction gear according to the present invention, where the sun gear (2) is provided with 19 teeth, the planet gears (5) are provided with 16 teeth, the inner toothed crown gear (6) is provided with 53 teeth and the second inner toothed crown gear (7) is provided with 50 teeth, by applying the Willis formula to two of the three previously identified kinematic chains, it is obtained a reduction ratio of -63,16. This reduction ratio is practically the same as the reduction ratio obtained by means of a three-stage epicycloidal reduction gear according to figure 4, where the inner sun gears (21) are provided with 20 teeth, the planet gears (22) are provided with 19 teeth and the outer toothed crown gear (23) is provided with 60 teeth.

The reduction in the number of gears, and as a consequence in dimensions, weight and costs, obtained by the epicycloidal reduction gear according to the present invention is clear from the highlighted comparison.

The epicicloidal reduction gear according to the present invention can be provided with a variable number of planet gears; the gears and the pinions can be realized according to geometric shapes known in the state of the art, the sole obligation to be observed being to provide radii geometrically compatible with the coupling according to what is claimed.

According to a preferred embodiment shown in figs. 2 and 3 the epicycloidal train holder (4) comprises three planet gears (5). The epicycloidal reduction gear according to the present invention can be advantageously applied to every field of mechanics which requires high values of the movement transmission ratio to be obtained.

Claims

1. Epicycloidal reduction gear comprising at least three sun gears with teeth number different between each other (2, 6, 7), a train holder (4) and at least a planet gear (5), characterized in that said planet gear meshes with all the three sun gears (2, 6, 7) at the same time.

2. Epicycloidal reduction gear according to claim 1 comprising two planet gears (5) with the same teeth number, characterized in that said planet gears mesh with all the three sun gears (2, 6, 7) at the same time.

3. Epicycloidal reduction gear according to claim 1 comprising three planet gears (5) with the same teeth number, characterized in that said planet gears mesh with all the three sun gears (2, 6, 7) at the same time.

4. Epicycloidal reduction gear according to any one of the the preceding claims, characterized in that the movement is transmitted to the reduction gear by means of a driving shaft (3) integrally connected to the sun gear (2) and is transmitted by the reduction gear to a driven shaft (8) integrally connected to the sun gear (7).