Gear stage

Abstract

A gear stage (10), in particular of a vehicle seat (3), is embodied as a friction wheel gear stage. The gear stage (10) includes a housing (5), a drive (12), an output (14) that is set off from the drive (12) by an excentricity (e) and at least one sphere or another rolling body (15) for the transmission of force between the drive (12) and t he output (14). According to the invention, the position of the excentricity (e) relative to the housing (5) is arranged in a spatially fixed manner and the gear stage has at least two different direction-dependent and / or shiftable gear ratios.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a United States National Phase application of International Application PCT / DE2008 / 001765 and claims the benefit of priority under 35 U.S.C. §119 of each of German Patent Application DE 10 2007 051 031.6 filed Oct. 23, 2007 and German Patent Application 10 2007 056 391.6 filed Nov. 16, 2007, the entire contents of each of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention relates to a gear stage, in particular of a vehicle seat, that is designed as a friction wheel gear stage having a housing, at least a drive input, at least one drive output which is spaced apart from the drive input by an eccentricity, and at least one ball or some other rolling body (a rolling body) which is provided for transmitting force between the drive input and drive outputBACKGROUND OF THE INVENTION[0003]In electric actuating drives for seat adjusters, gear stages are known which are designed as a rolling ecc...

AI Technical Summary

Benefits of technology

[0008]By virtue of the position of the eccentricity with respect to the housing in said gear stage, which is significant in terms of the generation of noise, being spatially fixed, which is preferably achieved by means of a fixed, that is to say spatially fixed mounting of the drive input and drive output in a common housing, the points of force engagement are fixed in space. With this extremely precise definition of the magnitude and direction of the eccentricity, the degree of eccentricity is positively adhered to precisely during the rotation, as a result of which periodic changes in the load conditions, and a generation of noise and vibrations, are prevented on account of the stable overall running properties. With this fixed position of the eccentricity between the drive input and drive output with respect to one another, a precise, freely-moving mounting of said components relative to one another and the use of a ball (or some other rolling body) in the wedge gap, firstly a high transmission ratio is obtained with a high level of efficiency, and secondly a radial force which is proportional to the respective torque is exerted as a preload on the rotor, which minimizes noises during operation.

[0009]The gear stage according to the invention is based on the same basic principle as the known gear stage. The transmission ratio can thus be set by means of contours on the drive input and / or drive output, for example by means of a groove within which the ball runs. The gear stage according to the invention, however, improves the properties with regard to transmission ratio, efficiency and lack of noise and, as is desired, preloads the rotor at all times, thereby eliminating the described disadvantages, in particular the generation of noise in EC drives with rotors of low mass and the low efficiencies of single-stage differential gears with a large step-down ratio. Besides the basic principle, numerous possible secondary functions and secondary properties are obtained, in particular various possibilities for changing and controlling the transmission ratio and simple solutions for clutch functions which, in the overall context of seat drive technology, can bring about numerous advantages. In one desired drive device, provision is made of preferably precisely one rolling body, for example one roller, but preferably one ball, in order to avoid overdetermination. If only one drive device is required, then also only a single ball or a single other rolling body is required.

Problems solved by technology

Although the expected properties of such rolling eccentric stages, specifically a transmission ratio in the range from 1.5 to 7 with a high efficiency and a low noise level, have indeed been realized in practice, said concept nevertheless has disadvantages which can be compensated only with a comparatively high level of expenditure.

Overall, the relatively large number of components which form the eccentricity result in a system which, as a result of tolerances, load-dependent deformations and internal stresses, is extremely sensitive and susceptible to failure and which, under mass production conditions, can presumably be brought up to a good quality level only with a high level of expenditure.

As a further basic disadvantage, it should be stated that a rolling eccentric of said type can be formed effectively and simply as a drive input element which operates in one plane and with a single pinion (as illustrated in FIG. 14), but the radial bearing forces, proportional to the overall drive output torque, must be absorbed directly and entirely by the rotor bearing rotating at high rotational speed, and there, with increasing loading, lead to increasing power losses and therefore falling efficiency under relatively high operating load.

In contrast, if two or ideally three pinions are arranged in planes one above the other in a known way, then the radial forces can support one another—but with the illustrated design, this is not possible by means of a simple arrangement of identical stages one above the other, because even minimal geometric differences of the components involved lead to fundamentally different transmission ratios, and therefore, during extended periods of operation, to a phase offset of the gear stages to one another and / or to stresses in the case of forced synchronicity, and therefore to losses.

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