U.S. patent application number 12/739269 was filed with the patent office on 2011-02-17 for gear stage.
Invention is credited to Bernd Bossmanns, Karsten Kalmus, Rolf Schuler.
Application Number | 20110037306 12/739269 |
Document ID | / |
Family ID | 39327413 |
Filed Date | 2011-02-17 |
United States Patent
Application |
20110037306 |
Kind Code |
A1 |
Schuler; Rolf ; et
al. |
February 17, 2011 |
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.
Inventors: |
Schuler; Rolf;
(Heiligenhaus, DE) ; Bossmanns; Bernd; (Erkrath,
DE) ; Kalmus; Karsten; (Bochum, DE) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
P.O. BOX 9227, SCARBOROUGH STATION
SCARBOROUGH
NY
10510-9227
US
|
Family ID: |
39327413 |
Appl. No.: |
12/739269 |
Filed: |
October 17, 2008 |
PCT Filed: |
October 17, 2008 |
PCT NO: |
PCT/DE2008/001765 |
371 Date: |
April 22, 2010 |
Current U.S.
Class: |
297/353 ;
475/185; 475/189 |
Current CPC
Class: |
F16H 1/32 20130101; B60N
2/2252 20130101; B60N 2/0232 20130101; B60N 2/225 20130101; F16H
13/04 20130101; F16H 13/12 20130101; B60N 2002/0236 20130101 |
Class at
Publication: |
297/353 ;
475/189; 475/185 |
International
Class: |
B60N 2/225 20060101
B60N002/225; F16H 15/48 20060101 F16H015/48 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2007 |
DE |
10 2007 051 031.6 |
Nov 16, 2007 |
DE |
10 2007 056 391.6 |
Claims
1. A gear stage of a vehicle seat, the gear stage being a friction
wheel gear stage comprising: a housing; at least a drive input; at
least one drive output spaced apart from the drive input by an
eccentricity; and at least one ball or some other rolling body for
transmitting force between the drive input and drive output, a
position of the eccentricity with respect to the housing is being
spatially fixed and the gear stage having at least two different,
direction-dependent or switchable transmission ratios.
2. The gear stage as claimed in claim 1, further comprising
bearings for the drive input and drive output arranged at spatially
fixed points in the housing.
3. The gear stage as claimed in claim 2, wherein the housing has
different bearing stiffnesses for the bearings of the drive input
and of the drive output and/or for different drive directions
and/or different spatial directions.
4. The gear stage as claimed in claim 1, wherein the ball or the
other rolling body is arranged in a wedge gap between the drive
input and the drive output.
5. The gear stage as claimed in claim 4, wherein the ball or the
other rolling body can move into and out of the wedge gap.
6. The gear stage as claimed in claim 4, further comprising a
pressure-exerting element comprising at least one of a spring fixed
to the housing and/or a magnet, which pushes or pulls the ball or
the other rolling body into a wedge gap between the drive input and
drive output.
7. The gear stage as claimed in claim 6, wherein a freewheel is
formed which opens as a result of a torque introduced at the drive
output by virtue of the ball or other rolling body moving out of a
wedge gap between the drive input and drive output.
8. The gear stage as claimed in claim 7, wherein a switchable
clutch is formed in which the ball or other rolling body is moved
out of or into a wedge gap between the drive input and drive output
electrically and/or mechanically.
9. The gear stage as claimed in claim 8, further comprising a
retaining device cooperating with the pressure-exerting element for
moving the ball or the other rolling body out of or into the wedge
gap between drive input and drive output.
10. The gear stage as claimed in claim 8, wherein, for moving the
ball or the other rolling body out of or into the wedge gap between
drive input and drive output, a control fork is provided, which can
be activated externally.
11. The gear stage as claimed in claim 8, wherein, for moving the
ball or the other rolling body out of or into the wedge gap between
drive input and drive output, a ball-guiding ring is provided,
which guides the ball or the other rolling body, and which is in
frictional contact with the drive input.
12. The gear stage as claimed in claim 4, wherein, when the
rotating movement has been finished, the drive input is rotated
back by a known angle, in order to move the ball or the other
rolling body out of the wedge gap between drive input and drive
output.
13. The gear stage as claimed in claim 1, wherein the drive input
and/or the drive output is provided with a contour groove, within
which the ball or the other rolling body runs.
14. The gear stage as claimed in claim 1, wherein, for generating
the different transmission ratios, different effective radii of the
balls or of the other rolling bodies are used.
15. The gear stage as claimed in claim 1, wherein, for generating
the different transmission ratios, two different balls 15) and/or
contours are used at the drive input and/or the drive output.
16. The gear stage as claimed in claim 13, wherein two balls having
different sizes are provided, which run in the joint groove of the
drive input or the drive output for generating different
transmission ratios.
17. The gear stage as claimed in claim 1, wherein, for the
transmission of force between drive input and drive output,
precisely only one ball or one other rolling body is provided for
every drive direction.
18. The gear stage as claimed in claim 1, wherein, during
operation, precisely only one ball or precisely only one other
rolling body is in contact with both, drive input and drive
output.
19-24. (canceled)
25. An actuating drive comprising: a housing; a drive input; a
drive output spaced apart from the drive input by an eccentricity;
a rolling body provided for transmitting force between the drive
input and drive output to form a friction wheel first gear stage, a
position of the eccentricity with respect to the housing being
spatially fixed and the first gear stage having at least two
different, direction-dependent or switchable transmission ratios;
and a second gear stage.
26. An actuating drive as claimed in claim 25, further comprising:
a drive motor driving the first gear stage.
27. An actuating drive as claimed in claim 26, wherein the drive
motor and the first gear stage are arranged in said housing as a
common housing.
28. An actuating drive as claimed in claim 26, wherein the second
gear stage is arranged as an upstream stage in relation to the
first gear stage.
29. An actuating drive as claimed in claim 28, wherein the drive
motor, the first gear stage and the second gear stage are arranged
in said housing as a common housing.
30. An actuating drive as claimed in claim 25, further comprising:
a vehicle seat with a seat part and a backrest, the friction wheel
gear stage being connected to the vehicle seat for controlled
movement of the backrest relative to the seat part.
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. .sctn.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 output
BACKGROUND OF THE INVENTION
[0003] In electric actuating drives for seat adjusters, gear stages
are known which are designed as a rolling eccentric stage and which
are used as intermediate gear stages or drive input elements for
generating a rotating eccentricity for toothed gear stages. A known
gear stage of said type which serves as a drive input of a second
gear stage with a rotating eccentricity is illustrated in FIG.
14.
[0004] 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. The eccentricity required for precise and uniform
rolling of the toothed pinion in the ring gear, the magnitude of
which eccentricity must remain as precisely constant as possible,
arises in the known solutions from the combination of different
geometries--for example the drive balls, which push the pinion
upward in FIG. 14, a maximum limitation of said movement by the
toothing, by the drive output bolts in the pinion bores or by a
thrust bearing between the drive input and drive output, and a
minimum limitation for example by a support ball. 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.
[0005] 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.
SUMMARY OF THE INVENTION
[0006] The invention is based on the object of improving a gear
stage of the type specified in the introduction.
[0007] The drive input and drive output are rotatable about axes
which are parallel to one another and which are offset with respect
to one another by the eccentricity. The drive input and drive
output are arranged, in spatial terms, one inside the other
(nested) and act by means of the surfaces facing toward one
another. Here, the drive input may be arranged within the drive
output (the drive input then acts by means of its outer contour and
the drive output by means of its inner contour), or the situation
is exactly reversed. The ball or other rolling body is arranged in
the wedge gap formed (on account of the eccentricity) between the
drive input and drive output, and can move within the wedge gap, in
particular can move into and out of the wedge gap, with said
movement generally taking place in a plane perpendicular to the
axes of the drive input and drive output.
[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.
[0010] Although a gear stage which looks basically similar is known
from FR 601 616, the rolling bodies which are distributed over the
entire circumference are mounted as planets on a web which rotates
during operation, such that the eccentricity rotates.
[0011] The gear stage according to the invention is preferably used
in an actuating drive for a vehicle seat, for example a backrest
inclination adjuster, a height adjuster or an inclination adjuster.
The actuating drive comprises a drive motor and the gear stage
according to the invention, and drives for example a load-absorbing
gearing as disclosed in DE 10 2004 019 466 B4 which forms a
constituent part of the inherently movable seat structure. The
actuating drive may if appropriate also have a second gear stage or
further gear stages which are positioned downstream of the first
gear stage according to the invention and upstream of the
load-absorbing gearing. The load-absorbing gearing may perform a
rotational movement or a linear movement or a superposition of both
movements. The actuating drive may also be designed as or drive an
actuator, for example rotate a cable drum which winds up a cable
for unlocking Applications outside a vehicle seat are also
conceivable, for example in window lifters and adjustable
mirrors.
[0012] Below, the invention is explained in more detail on the
basis of an exemplary embodiment illustrated in the drawing, with
additions and modifications. The various features of novelty which
characterize the invention are pointed out with particularity in
the claims annexed to and forming a part of this disclosure. For a
better understanding of the invention, its operating advantages and
specific objects attained by its uses, reference is made to the
accompanying drawings and descriptive matter in which preferred
embodiments of the invention are illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] In the drawings:
[0014] FIG. 1 is a cross sectional view through the first gear
stage, with only one ball and, at the outer right-hand side, the
radial load diagram thereof, being shown for the purpose of
clarity;
[0015] FIG. 2 is a longitudinal sectional view through an actuating
drive with a drive motor, first gear stage and second gear
stage;
[0016] FIG. 3 is a longitudinal sectional view through a sleeve
which serves as a drive output of the first gear stage and as a
drive input shaft of the second gear stage;
[0017] FIG. 4 is a cross sectional view through the first gear
stage with a spiral compression spring as a pressure-exerting
element;
[0018] FIG. 5 is a cross sectional view through the first gear
stage with a leaf spring as a pressure-exerting element;
[0019] FIG. 6 is a cross sectional view through the first gear
stage with magnets as pressure-exerting elements;
[0020] FIG. 7 is a schematic side view of a vehicle seat in a rear
seat row;
[0021] FIG. 8 is a cross sectional view through the first gear
stage with a damping and overrunning function;
[0022] FIG. 9 is a cross sectional view through the first gear
stage with an electric clutch function;
[0023] FIG. 10 is a cross sectional view through the first gear
stage with a mechanical clutch function by means of a shift
fork;
[0024] FIG. 11 is a cross sectional view through the first gear
stage with a mechanical clutch function by means of frictional
contact;
[0025] FIG. 12 is a cross sectional view through the first gear
stage with a housing with different bearing stiffnesses;
[0026] FIG. 13 is a cross sectional view through the first gear
stage with different transmission ratios and two longitudinal
sections in the region of the two balls; and
[0027] FIG. 14 is a cross sectional view through a gear stage
according to the prior art.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] Referring to the drawings in particular, An actuating drive
1 for a vehicle seat 3 has a housing 5 and a drive motor 7 arranged
in the housing 5. The housing 5 is generally of multi-part design,
but formed with as few parts as possible. The drive motor 7, which
is formed in the present case as an EC inner-rotor-type motor,
comprises a rotor 8 which is mounted in the housing 5 so as to be
rotatable about a first axis A and which bears permanent magnets,
and an electronically commutated stator 9. The rotor 8 is mounted
in the housing 5 by means of two rotor bearings 8a which are
designed as rolling bearings.
[0029] The actuating drive 1 also has a first gear stage 10 which
comprises a drive input 12 rotatable about the first axis A and a
drive output 14 rotatable about a second axis B which is parallel
thereto, which drive input 12 and drive output 14 are each mounted
in the housing 5. The drive input 12, which in the present case is
of annular design, is preferably formed in one piece with the rotor
8 of the drive motor 7 and thereby rolling-bearing-mounted in the
housing 5 by means of the rotor bearing 8a. It is however also
possible for the rotor 8 and drive input 12 to be provided
separately with suitable coupling and separate mounting in the
housing 5. The drive output 14, which in the present case is
likewise of annular design, is mounted in the housing 5 by means of
a drive output bearing 14a which is likewise designed as a rolling
bearing. Here, the first axis A and the second axis B are spaced
apart from one another by an eccentricity e by virtue of the rotor
bearing 8a and the drive output bearing 14a being arranged fixedly
with respect to one another in the housing 5. In the illustration
of FIG. 1, the second axis B is offset in the upward direction in
relation to the first axis A. The position of the eccentricity e is
therefore spatially fixed in relation to the housing 5.
[0030] In relation to a cylindrical coordinate system defined by
the second axis B, the drive input 12, which has a relatively small
diameter, is arranged radially at the inside and the drive output
14, which has a relatively large diameter, is arranged radially at
the outside. In the present design as a friction wheel gear stage,
the transmission of force between the drive input 12 and the drive
output 14 takes place by means of at least one ball 15 (or some
other rolling body) which is arranged between the drive input 12
and drive output 14, where a curved, wedge-shaped free space,
referred to for short as the wedge gap, is formed between the drive
input 12 and drive output 14. When the drive input 12 rotates, the
ball 15 is automatically clamped in the direction of said wedge gap
(clockwise in the illustration of FIG. 1), then rotates about its
own axis and thereby drives the drive output 14. In the present
case, precisely one ball 15 (or some other rolling body) is
provided between the drive input 12 and drive output 14 for each
drive direction, which balls or other rolling bodies act in the
same way (with the exception of the rotational direction).
[0031] With regard to the transmission ratio of said first gear
stage 10, in which now all the components involved rotate only
about their own axes, the known ratios apply, specifically firstly
the ratio of the circumferences or radii of the drive input 12 to
drive output 14, and secondly, multiplicatively, the transmission
ratio of the balls 15 themselves. By means of contours on the drive
input 12 and/or drive output 14, the contact points with respect to
the ball 15 can be shifted out of the plane which is perpendicular
to the axes A and B and which serves as the plane of the drawing in
FIG. 1. Other effective radii of the balls 15, that is to say drive
input radius and drive output radius, then emerge as a projection
in said plane, as a result of which the transmission ratio of the
ball 15 changes. The drive output 14 is preferably provided on
the--radially inwardly pointing--active surface with a contour, for
example a channel or a V-shaped groove or the like within which the
ball 15 runs and, in so doing, rolls on oblique walls. In this way,
the drive output radius of the ball 15 can be reduced, even set to
be smaller than the drive input radius, and the transmission ratio
thereby manipulated. For example, a step-up transmission ratio can
be generated by using a V-shaped groove on the drive input and a
cylindrical surface on the drive output. This is the
advantage--aside from the direct transmission of the radial
forces--of a friction wheel gear stage over a gearwheel gear
stage.
[0032] If the drive input torque is regarded as a constant, the
eccentricity e results in an angle between the lines of force
action of the forces acting on the ball 15 and a radial force which
is proportional to the tangent of said angle, the magnitude and
direction of which radial force is plotted in FIG. 1 as a radial
load diagram on the outer side of the drive output 14. Viewed
across all possible ball positions, the magnitude of said radial
force twice assumes a (theoretically infinite) maximum value and a
minimum value. If, for example, the ball 15 in FIG. 1 is situated
in the vicinity of the 12 o'clock or 6 o'clock positions, that is
to say in a prohibited angle range R>, then the wedge angle is
minimal, and the smallest tangential drive forces of the drive
input 14 lead to exorbitant radial forces and therefore to extreme
deformations in real components with limited strengths. Conversely,
for the mounting of the drive input 12 and drive output 14, this
relationship means that, for real bearings with maximum permissible
bearing forces, at a given maximum torque of the drive 12, the ball
15 may be operated only in a precisely definable permitted angle
range R<(approximately between 1 o'clock and half past 4 in the
radial load illustration of FIG. 1). The same naturally applies for
the loading of the ball 15 itself.
[0033] The described radial forces, which reach a minimum at
precisely one point, must be absorbed in the bearing arrangements
and in the ball contact point, and inevitably lead to losses there.
A preferred embodiment with maximum efficiency is consequently the
variant in which the ball position is arranged precisely in the
region of the minimum radial forces, which is dependent not only on
the magnitude of the eccentricity e but also on the diameter
ratios.
[0034] The described first gear stage 10 with fixed-position
eccentricity may fundamentally be used in any desired combinations
with other gear stages. In the present case, the actuating drive 1
has a second gear stage 20. The first gear stage 10 serves as an
upstream stage for the second gear stage 20 arranged at the drive
output side.
[0035] In the present case, the second gear stage 20 is designed as
a toothed eccentric epicyclic gear. A drive input shaft 21 which is
rotatable about the second axis B serves by means of its first
eccentric section 21a, and a second eccentric section 21b offset
axially along the second axis B, to mount two pinions 22a and 22b
which are preferably offset by 180.degree. with respect to one
another and which are arranged in two planes. Both the first pinion
22a and also the second pinion 22b, which are preferably of
identical design, are externally toothed and mesh with an internal
toothing of the housing 5 which has a number of teeth greater than
that of the pinions 22a and 22b by at least one. During the
rotation of the drive input shaft 21 which is connected centrally
and fixedly to the drive output 14, the pinions 22a and 22b perform
a rolling movement on the housing 5. The pinions 22a and 22b act by
means of bolts and bores on a common drive output shaft 24 which is
designed as a hollow shaft and which then likewise rotates. In the
present case, the drive input shaft 21 and also the drive output
shaft 23 are concentric with respect to the second axis B, such
that the drive motor 7 is ultimately arranged offset with respect
to the two-stage gearing assembly, composed of first gear stage 10
and second gear stage 20, overall by the eccentricity E which is
fixed in terms of position and magnitude by the common housing 5.
The extremely high number of rolling bearings in FIG. 2 serves to
increase the overall efficiency. In modified embodiments, however,
it is also possible for plain bearings to be used.
[0036] As a design detail solution, it is preferably provided that
the annular drive output 14 of the first gear stage 10 and the
drive input shaft 21, which is connected thereto and designed as a
double eccentric shaft, of the second gear stage 20 are formed in
one piece as a sleeve with all the required ball running channels,
and that preferably said sleeve is produced by non-cutting shaping
and calibration processes. This is shown by FIG. 3.
[0037] On account of the position of the eccentricity e, and
therefore also of the balls 15, now being spatially fixed relative
to the housing 5, under operating conditions, a multiplicity of new
solution possibilities arises both with regard to structural design
and also with regard to overall functionality. Some advantageous
aspects are explained below.
[0038] In the known rotating rolling eccentric designs, the balls
15 rotate in space and the pressure-exerting element 31 for
generating an ever-present low pressure force for the balls 15 must
inevitably likewise co-rotate. A simple and frequently used
solution here is spiral compression springs as illustrated in FIG.
4. However, the spiral compression springs tend toward natural
vibrations and are in forced, loss-afflicted contact both with the
balls 15 and also with the drive output 14. On account of the
position now being fixed with respect to the housing 5, it is
possible to realize considerably more advantageous designs for the
pressure-exerting element 31, such as for example the use of a
metal or plastic leaf spring, which is fixed to the housing, with a
minimal ball contact surface, as illustrated in FIG. 5.
[0039] As a possibly economically worse but technically more
elegant, virtually loss-free and noise-free design, it is
expedient, when using balls 15 composed of steel, for magnets as
pressure-exerting elements 31 for generating a contact-free
pressure force to be positioned fixedly with respect to the
housing, as illustrated in FIG. 6.
[0040] In all cases, the balls 15 are pushed or pulled into the
wedge gap by the pressure-exerting element or elements 31, and are
thereby simultaneously pressed against the drive input 12 and drive
output 14. Viewed from a design systematic aspect, the balls 15
with their forces acting at an angle to one another ultimately
simultaneously constitute a clamping roller or, in this case,
clamping ball freewheel. The freewheel constitutes a self-switching
clutch. In operation, that is to say during the drive movement,
therefore, only the ball 15 which is moved further into the wedge
gap by the drive input 12 will remain in contact both with the
drive input 12 and also with the drive output 14. The opposite ball
15 for the opposite drive direction is, despite the
pressure-exerting element 31, moved out of the wedge gap which is
assigned thereto and then loses the double contact.
[0041] The action as a clamping roller or clamping body freewheel
may, in some cases of drive technology, by all means be co-utilized
in an expedient combination. FIG. 7 shows the rear region of a
motor vehicle with an electrically unlockable backrest lock 33 at
the upper edge of the backrest 35 of the vehicle seat 3. To enable
the vehicle interior space to be changed in a comfortable and fast
manner, arrangements are known in which the backrest 35 is
installed so as to be spring-loaded in the forward direction and is
releasably locked. Therefore, when the backrest lock 33 is
electrically released, the backrest 35 pivots forward
automatically. To re-assume the illustrated position, the backrest
35 must be pivoted up again manually.
[0042] A further increase in comfort of said function can be
obtained firstly by means of possibly controlled damping of the
spring-induced forward pivoting function and secondly by means of
an electric pivoting-up facility. Both may be achieved by means of
a variant of the actuating drive 1 with a design according to the
invention of the first gear stage 10 with fixed-position
eccentricity and in a friction wheel embodiment if the downstream
gear stages are not self-locking, which is entirely expedient in
the described application.
[0043] FIG. 8 shows a gearing variant which operates with only one,
in this case magnetically pre-loaded ball 15. The actuating drive 1
with said first gear stage 10 is integrated into a fitting which
serves as a backrest inclination adjuster. If, in the position
shown in FIG. 7, the backrest 35 is electrically unlocked at its
upper edge and then pivots forward, that is to say counterclockwise
in FIG. 7, then the drive output 14 in FIG. 8 likewise rotates
counterclockwise, maintains contact with the drive output 12 and
therefore drives the rotor 8. In the present case of an EC motor,
the rotor 8 may be acted on either without a braking moment or with
a precisely controlled braking moment, for example in order to
define a maximum pivoting speed or brake the movement shortly
before the end of the possible movement angle. If the backrest 35
is later to be pivoted back up again electrically, the rotor 8 is
in the present case operated counterclockwise and the drive output
14 and the backrest 35 rotate clockwise in FIGS. 7 and 8. It is
also a peculiarity that said motor-driven movement of the backrest
35 can be manually overrun ("overrun function"). In the event of a
torque being introduced at the drive output 14, that is to say an
acceleration of the drive output 14 imparted externally, the
clamping ball freewheel specifically opens automatically, that is
to say the ball 15 moves out of the wedge gap, the drive input 12
runs freely and the backrest 35 can be pivoted up manually. This
allows the backrest 35 to be pivoted up purely manually even for
example in the event of an electrical failure or in emergency
situations.
[0044] On account of the physical conditions at the ball 15, which
in the case just described lead to an automatic decoupling of the
first gear stage 10, said first gear stage 10 can in an extremely
simple manner be expanded to encompass a further function often
required in drive technology, specifically that of a switched
clutch function, which may if required even be direction-dependent.
FIG. 9 shows an arrangement in which the two balls 15 can be
switched in each case into a passive and an active position
independently of one another. For both balls 15, a retaining device
37 (in the present case a simple geometry with a very weak magnet)
is provided in the upper region of the free space between the drive
input 12 and drive output 14. The retaining device 37 positions the
ball 15 in the rest position such that the latter is not in contact
at least with the drive input 12 and/or drive output 14 (that is to
say at least with one or possibly both components), as a result of
which, in the rest position, the drive input 12 and drive output 14
are fully decoupled from one another. In the lower region of the
free space, two separate and separately switchable electromagnets
are provided as pressure-exerting elements 31 which, when
activated, attract the respectively associated ball 15 and thereby
close the frictional connection for said respective movement
direction. Since the ball pressure forces required at relatively
high torques are automatically adjusted in operation on account of
the wedging action, said clutch can be switched with minimal
energy, which need merely ensure "loose" contact at the start of
movement. The electromagnets which are used as pressure-exerting
elements 31 may consequently be switched into the currentless state
in operation.
[0045] In addition to the electric actuation of the clutch function
just described, a mechanical solution can also be realized. In the
exemplary embodiment according to FIG. 10, for example, use is made
of control forks 41, of which only one is illustrated. A control
fork 41 of said type can be activated externally. The activated
control forks 41 move the balls 15 in each case into active (into
the wedge gap) or passive (out of the wedge gap) positions and
thereby enable the drive motor 7 to be decoupled, for example in
order to enable a manual quick adjustment or, again, an emergency
actuation as described above in conjunction with FIGS. 7 and 8.
[0046] A further advantageous embodiment of a clutch function is
illustrated in FIG. 11, which shows a ball-guiding ring 43 which
surrounds the drive input 12 and which is in light frictional
contact with the latter at three points and which guides the ball
15. The ball-guiding ring 43 will as a tendency, on account of the
weak frictional contact with the drive input 12, seek to always
move the ball 15 within the free space in the drive direction of
the rotor 8 (that is to say into the wedge gap) and consequently,
in the coupled state, maintain its own angle position and also that
of the ball 15. In contrast, in the event of a rotational direction
reversal, the ball 15 will--having been released from its previous
contact--be pivoted onto the opposite side. The resulting saving of
a second ball 15 is of less significance here than the fact that,
with said arrangement, it is possible without further active
actuating elements or magnets for the gearing to be fully decoupled
by virtue of the rotor 8 (and therefore the drive input 12) being
rotated back by a known angle (approximately 80.degree.
counterclockwise in the illustration of FIG. 11) after the end of
the drive movement. This makes it possible for stresses in the
entire actuating drive 1 to be relieved in a controlled fashion,
and for example allows the drive input or drive output bearing
arrangements to be encased with an elastomer ring for the purpose
of reducing body-borne noise transmission or also for the purpose
of targetedly controlling the elastic displacements of the gearing
elements in operation under load. A side-effect to be noted here is
that such a design also permits the use of non-magnetic ball
materials such as for example ceramic or plastic.
[0047] FIG. 12 shows a conceivable design with a housing 5 which is
intentionally provided with different bearing stiffnesses. With
said different bearing stiffnesses--which are dependent on the
spatial directions--it is for example possible for the radial
forces to be reduced. This is a modification of the embodiment of
FIG. 11. In particular when thermoplastics are used as a housing
material, it is recommendable for the first gear stage 10 to be
decoupled in order to minimize material creep over relatively long
standstill periods at high temperatures.
[0048] With the described possibilities of the coupling and
decoupling of balls 15, it is obtained as a consequence that the
first gear stage 10 may also be formed as a gearing with different,
direction-dependent or switchable transmission ratios. FIG. 13
shows, by way of example, a stepped inner contour of the drive
output 14. In combination with the spacing, which differs on
account of the eccentricity e, to the drive output 12, balls 15 of
different size are in contact with said inner contour. Said
transmission ratios can therefore be switched by decoupling the one
ball 15 and coupling the other ball 15. In the field of said
drives, movement-direction-dependent power and torque requirements
are common. With said switching facility, it is possible for
different load situations (seat height adjuster upwards--high
torque, seat height adjuster downwards--low torque) for a suitable
transmission ratio for each rotational direction to be installed
from the start. It is also possible for more than two transmission
ratios to be installed according to the same principle.
[0049] Alternatively to the design shown in FIG. 13 with two balls
15 of different transmission ratio in a single drive output 14, it
is of course also possible for the contact geometries of the drive
input 12 to be defined in the same way, or one or more drive
outputs 14 (or drive inputs 12) may be arranged axially one above
the other, or two different contours may be provided on the drive
output 14 (or drive input 12). It is also possible for other
rolling bodies to be provided instead of the balls 15.
[0050] While specific embodiments of the invention have been
described in detail to illustrate the application of the principles
of the invention, it will be understood that the invention may be
embodied otherwise without departing from such principles.
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