U.S. patent application number 11/776638 was filed with the patent office on 2008-06-26 for eccentric tensioning device.
This patent application is currently assigned to SCHAEFFLER KG. Invention is credited to Roland Arneth, Rainer Baumuller, Niels Flamig.
Application Number | 20080153642 11/776638 |
Document ID | / |
Family ID | 39543662 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080153642 |
Kind Code |
A1 |
Baumuller; Rainer ; et
al. |
June 26, 2008 |
ECCENTRIC TENSIONING DEVICE
Abstract
An eccentric tensioning device for tensioning the traction means
of a traction means drive is provided. The invention provides
solutions, through which advantages are given in the installation
of tensioning devices under assembly-specific aspects. The
eccentric tensioning device for a traction means drive includes a
track roller device, which has a running disk and a rolling bearing
provided for supporting this disk, a work eccentric for supporting
the track roller device such that it can be displaced in a radial
direction relative to the rotating axis of the rolling bearing
through pivoting of the work eccentric, a torsion spring for
pretensioning the work eccentric, and a fixing device for securing
the work eccentric in a mounting position, in which the torsion
spring is located in pretensioned state. The fixing device is
constructed such that it can be brought into a released state
during attachment of the eccentric tensioning device to a flange
surface, in which the running disk is forced radially relative to
the rotating axis of the rolling bearing against the associated
traction means due to the work eccentric. Therefore, it is possible
in an advantageous way to create a tensioning device, in which
during the mounting of the traction means, the work or the
operating eccentric is fixed in an end position and an activation
of the tensioning device is guaranteed in a reliable way.
Inventors: |
Baumuller; Rainer;
(Herzogenaurach, DE) ; Arneth; Roland;
(Eggolsheim, DE) ; Flamig; Niels; (Hessdorf,
DE) |
Correspondence
Address: |
VOLPE AND KOENIG, P.C.
UNITED PLAZA, SUITE 1600, 30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103
US
|
Assignee: |
SCHAEFFLER KG
Herzogenaurach
DE
|
Family ID: |
39543662 |
Appl. No.: |
11/776638 |
Filed: |
July 12, 2007 |
Current U.S.
Class: |
474/101 ;
29/428 |
Current CPC
Class: |
F16H 7/1281 20130101;
F16H 2007/0842 20130101; F16H 2007/0844 20130101; F16H 7/1236
20130101; F16H 7/1218 20130101; F16H 2007/081 20130101; F16H
2007/0846 20130101; Y10T 29/49826 20150115; F16H 2007/0893
20130101 |
Class at
Publication: |
474/101 ;
29/428 |
International
Class: |
F16H 7/08 20060101
F16H007/08; B23P 19/04 20060101 B23P019/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 21, 2006 |
DE |
102006061793.2 |
Claims
1. Eccentric tensioning device for a traction means drive,
comprising: a track roller device, which as such comprises a
running disk and a rolling bearing provided for supporting the
running disk, a work eccentric for supporting the track roller
device, such that it can be displaced in a radial direction
relative to a rotating axis of the rolling bearing according to a
magnitude of pivoting of the work eccentric, a torsion spring for
pretensioning the work eccentric, and a fixing device for securing
the work eccentric in a mounting position, in which the torsion
spring is located in a pretensioned state, the fixing device is
positionable on a flange surface upon which the eccentric
tensioning device is mountable during attachment of the eccentric
tensioning device, in which the running disk is forced radially
relative to the rotating axis of the rolling bearing against the
associated traction means under effect of the work eccentric.
2. Eccentric tensioning device according to claim 1, wherein the
fixing device is automatically detachable through tightening of an
attachment screw with which the eccentric tensioning device is
connected to the flange surface carrying the eccentric tensioning
device.
3. Eccentric tensioning device according to claim 2, wherein a free
switching path is traversed, through an axial play being overcome,
during attachment of the eccentric tensioning device to the flange
surface using the attachment screw.
4. Eccentric tensioning device according to claim 3, wherein the
axial play (S) is overcome against an axial force applied by the
torsion spring.
5. Eccentric tensioning device according to claim 3, wherein an
engagement structure connected to the work eccentric is moved to a
released state during the course of overcoming the axial play.
6. Eccentric tensioning device according to claim 5, wherein the
engagement structure is attached to the work eccentric via an
indexer arm.
7. Eccentric tensioning device according to claim 6, wherein in the
mounting position the engagement structure engages with a holding
element that is provided by a base plate.
8. Eccentric tensioning device according to claim 7, wherein the
engagement structure is brought into a released state through axial
displacement of the engagement structure relative to the holding
element.
9. Eccentric tensioning device according to claim 7, wherein the
engagement structure is brought into a released state through
radial displacement of the engagement structure relative to the
holding element.
10. Eccentric tensioning device according to claim 9, wherein the
torsion spring is constructed as a helical spring.
11. Eccentric tensioning device according to claim 1, wherein a
damping device is provided for generating an eccentric braking
moment counteracting a radial displacement of the track roller
device.
12. Eccentric tensioning device according to claim 1, wherein the
work eccentric comprises a plastic material.
13. Eccentric tensioning device according to claim 1, wherein the
work eccentric is constructed in one piece with an inner ring of
the rolling bearing.
14. Eccentric tensioning device according to claim 1, wherein the
running disk is constructed in one piece with an outer ring of the
rolling bearing.
15. Eccentric tensioning device according to claim 1, wherein the
work eccentric is supported on an adjustment eccentric.
16. Eccentric tensioning device according to claim 15, wherein the
adjustment eccentric is axially displaceable and a released state
can be reached through axial displacement of the adjustment
eccentric by the attachment screw.
17. Eccentric tensioning device according to claim 1, further
comprising a base plate having an annular disk section for clamping
onto the flange surface, and the annular disk section is coupled
locked in rotation with a carrier body in an area of an inner
peripheral edge, and a holding element is formed on the base plate
in an outer edge region of the base plate.
18. Eccentric tensioning device according to claim 17, wherein a
projection is formed on the base plate for rotationally locked
anchoring of the base plate on the flange surface.
19. Eccentric tensioning device according to claim 18, wherein the
projection is constructed so that the rotationally locked anchoring
of the base plate on the flange surface is achieved before an axial
release path is overcome.
20. Eccentric tensioning device according to claim 19, wherein the
released state is attained by pivoting the work eccentric back
against a pivoting direction caused by the torsion spring.
21. Eccentric tensioning device according to claim 20, wherein the
released state is attained by an overload moment also introduced
into the work eccentric and acting in a direction of the tensioning
moment generated by the torsion spring.
22. Eccentric tensioning device according to claim 1, wherein
securing means are provided, which prevent re-engagement of the
fixing device.
23. Method for integrating an eccentric tensioning device into a
traction means drive of an internal combustion engine, comprising:
within the scope of a preparation mounting step, partially
attaching an eccentric tensioning device located in a pretensioned
state to a flange surface, such that the eccentric tensioning
device remains in the pretensioned state, wherein in the
pretensioned state, the eccentric tensioning device is configured
such that a track roller of the device has a large distance from a
traction means running path, and bringing the eccentric tensioning
device into a released state through tightening of an attachment
screw used for fastening the eccentric tensioning device in
position, releasing the pretensioned state and moving the track
roller onto an associated traction means of the traction means
drive.
Description
BACKGROUND
[0001] The present invention relates to an eccentric tensioning
device for tensioning a traction means constructed, for example, as
a flat belt or toothed belt, in a traction means drive. In
particular, the invention here relates to an eccentric tensioning
device, which is provided for integration into a traction means
drive of an internal combustion engine, which automatically
guarantees a required pretensioning of the traction means through
an adjustment moment generated on the side of a spring device.
[0002] Such a tensioning device is known, for example, from DE 40
33 777 A1. This conventional tensioning device, also designated as
a double eccentric tensioning device, comprises an adjustment
eccentric, which makes available a bore arranged eccentrically for
receiving an attachment screw. By means of the attachment screw,
the tensioning device is mounted on a housing, especially a housing
of the internal combustion engine, wherein the adjustment eccentric
is supported by means of a base plate on the housing. Placed on
this adjustment eccentric is a working or operating eccentric, with
there being a plain or slide bearing in an annular gap between a
casing surface of the adjustment eccentric and an inner wall of the
operating eccentric. On the outside, a rolling bearing surrounds
the operating eccentric, whose outer ring provides the function of
a running disk, which in the installed state presses against the
traction means of the traction means drive and applies a force to
this with a transverse force extending perpendicular to the running
direction. For achieving a firm contact of the running disk on the
traction means, between the base plate and the operating eccentric
there is a torsion spring, which forces the operating eccentric and
the running disk connected to this operating eccentric continuously
into a position loading and thus tensioning the traction means.
SUMMARY
[0003] The invention is based on the objective of creating
solutions, through which advantages are produced under
assembly-specific aspects in the installation of tensioning devices
of the type noted above.
[0004] This task is achieved according to the invention by an
eccentric tensioning device for a traction means drive, with:
[0005] a track roller device, which as such comprises a running
disk and a rolling bearing provided for supporting the running
disk,
[0006] a work eccentric for supporting the track roller device such
that it can be displaced in a radial direction relative to the
rotating axis of the rolling bearing through pivoting of the work
eccentric,
[0007] a torsion spring for pretensioning the work eccentric,
and
[0008] a fixing device for securing the work eccentric in a
mounting position, in which the torsion spring is located in
pretensioned state,
[0009] wherein the fixing device is constructed such that it is led
into a released state, in which the running disk is forced under
the effect of the work eccentric radially relative to the rotating
axis of the rolling bearing against the associated traction means,
within the scope of attaching the eccentric tensioning device to a
flange surface carrying this device.
[0010] Therefore, in an advantageous way it becomes possible to
create a tensioning device, in which during the mounting of the
traction means, the work or operating eccentric is fixed in an end
position under pretensioning of the torsion spring, wherein this
secured state can be released by the installation of the tensioning
device. The work eccentric is preferably fixed in each mounting
position so that relative movements between the work eccentric and
the base plate and/or the adjustment eccentric are prevented.
[0011] According to an especially preferred embodiment of the
invention, the fixing device is constructed such that this
automatically detaches in the course of tightening an attachment
screw, through which as such the eccentric tensioning device, in
particular the adjustment eccentric of this device, is screwed onto
a flange surface carrying the tensioning device. This automatic
detachment or release process of the fixing device can be
initiated, in particular, in that a free switching path is
traversed or an axial play provided in the tensioning device is
overcome within the scope of attaching the eccentric tensioning
device to the flange surface of components of the tensioning device
under the effect of the axial force applied by the attachment
screw. In the course of overcoming this axial play, especially
against an axial force applied by the torsion spring or by
secondary support structures, an engagement structure of the fixing
device can be brought into a released state.
[0012] The engagement structure is preferably coupled rigidly with
the work eccentric. In particular, it is possible to shape the
engagement structure so that this is connected to the work
eccentric via an indexer arm.
[0013] The fixing device according to the invention is preferably
shaped so that in the mounting position, the engagement structure
is engaged with a holding element, which is provided by the base
plate. The engagement structure is brought into the released state
preferably through axial displacement of the engagement structure
relative to the holding element.
[0014] The spring device provided for generating the torsion moment
pivoting the work eccentric is preferably constructed as a helical
spring. This helical spring can be embodied so that it has several
spring windings. The helical spring can be constructed as a
leg-less helical spring, so that the forces generated by this
helical spring are introduced via the ends of the spring ends and
optionally via a peripheral section offset from these ends by an
angle of typically 90.degree. into the appropriate components
loaded by the spring. The spring can also be provided in the area
of the spring ends with engagement structures, especially in the
form of hook sections formed by radially inwards or outwards bent
wire ends. The spring device can be shaped in terms of the cross
section of the spring wire so that this has a polygonal, in
particular a square or flat cross section. Furthermore, the spring
device is preferably shaped so that in the installed state, this is
also at least slightly flattened, e.g., to 30% of its length in the
axially unloaded state.
[0015] The tensioning device according to the invention preferably
comprises a damping or braking device, which as such is used for
generating an eccentric braking moment, through which the pivoting
of the work eccentric is braked. This damping or braking device can
be formed by an axially loaded disk structure, by a radially loaded
bushing structure, or also by a cone structure. Preferably, at
least one part of the loading force acting on this damping or
braking device is generated or transmitted by the torsion
spring.
[0016] The work eccentric can be made from a plastic material.
Furthermore, it is also possible to construct the work eccentric in
one piece with the inner ring of the rolling bearing. Furthermore,
it is also possible to construct the running disk in one piece with
the outer ring of the rolling bearing.
[0017] According to an especially preferred embodiment of the
invention, the work eccentric is supported on an adjustment
eccentric. Through the fixing device according to the invention,
preferably the position of the work eccentric is also fixed
relative to the adjustment eccentric. It is possible to shape the
tensioning device structurally so that the adjustment eccentric can
be displaced by a small distance axially relative to the work
eccentric or a base plate, wherein the released state of the fixing
device can be generated in the course of the axial displacement of
the adjustment eccentric, especially under the action of the
attachment screw.
[0018] The base plate is preferably shaped such that this comprises
an annular disk section provided for mounting on the flange
surface. This annular disk section can be shaped so that this is
coupled locked in rotation with a bearing bushing in the area of an
inner peripheral edge.
[0019] On the base plate, a projection or some other engagement
structure can be formed, which as such is used for rotationally
locked anchoring of the base plate on the flange surface.
Preferably, the projection is shaped so that the rotationally
locked anchoring of the base plate on the flange surface is reached
before the axial release path has been overcome.
[0020] As an alternative to the previously described measures, it
is also possible to shape the tensioning device according to the
invention so that the creation of the released state is not
realized through axial loading of the tension roller device, but
instead, for example, by pivoting the work eccentric back against
the pivoting direction caused by the torsion spring. In this
pivoted back even farther state, a spring elastic locking element
preloaded, for example, in a released position, can be unlocked and
here can release the work eccentric, so that this is pivoted
towards the traction means running path under the effect of the
torsion spring and thus the running disk can be lowered onto the
traction means.
[0021] It is also possible to shape the tensioning device so that
the generation of the released state is realized by an overload
moment also introduced into the work eccentric and acting in the
direction of the tensioning moment generated by the torsion
spring.
[0022] Preferably securing means are provided, through which
re-engagement of the fixing device is prevented. In this way it
becomes possible to guarantee that no inadvertent relocking of the
fixing device is performed during the operation of the tensioning
device.
[0023] The invention includes, in particular, the following
variants:
[0024] Variant 1
[0025] Before the mounting of the tensioning device, this is
pretensioned into the delivery state. A radially directed indexer
connected to the operating eccentric is supported with a firm fit
and/or a positive fit on a holding element of the base plate or the
adjustment eccentric. Here, the work eccentric and thus the indexer
connected to it are pressed and thus fixed in position on the
holding element of the base plate due to the force of the torsion
spring with a rotationally non-positive fit. The indexer assumes
this position through a limited axial displacement of the work
eccentric relative to the adjustment eccentric, wherein this
displacement acts against an axial force component of the torsion
spring. From this starting position, the tensioning device is
positioned loosely, i.e., without rigid attachment, to the internal
combustion engine, with the help of the attachment screw. By means
of the base plate in connection with an axially extending
projection, which engages in a corresponding bore or receptacle of
the internal combustion engine in the area of the flange surface,
an aligned installation position of the tensioning device is set.
In the mounting position, the operating eccentric is fixed at an
end stop, which is also designated as a hot stop, whereby the
traction means, in particular a belt, can be mounted easily, i.e.,
can be placed on all of the running disks of the traction means
drive. After successful mounting of the traction means, with the
help of the attachment screw, the tensioning device is fixed
rigidly to the housing of the internal combustion engine. In sync
with the tightening of the attachment screw, the adjustment
eccentric and the base plate connected to this eccentric are
displaced axially in the direction of the internal combustion
engine, whereby the indexer connected in one piece with the base
plate detaches from the holding element and the torsion spring
turns the operating eccentric into a position pretensioning the
traction means. The release of the indexer and thus the work
eccentric from the locking during the mounting position is then
reached as soon as an axial play "S" between the work eccentric and
the base plate or the adjustment eccentric is equalized or reduced
by tightening the tensioning device.
[0026] Variant 2
[0027] For achieving effective transport locking, which prevents
relative movement between the work eccentric and the base plate in
the mounting position, an indexer connected to the work eccentric
or a similarly formed object is actively connected to a stop of the
base plate. The locking can be realized through suitable shaping of
the base plate alone or with the help of additional elements, e.g.,
splints or a plate, which are removed after the traction means are
placed, in order to tension the traction means.
[0028] Variant 3
[0029] Another variant for positioning the operating or work
eccentric in a mounting position provides for the shaping of the
locking device for maintaining the pretensioned torsion spring, so
that this does not exceed the radial outer contours of the
tensioning unit. Suitable for this purpose is, for example, a
groove or recess formed on the end towards the flange surface of
the internal combustion engine in the work eccentric or in the base
plate, in which a locking device is engaged through a positive fit,
force-generated fit, or through a combination of these two fits, in
order to prevent rotational movement of the work eccentric relative
to the base plate or the adjustment eccentric in the mounting
position. The object interacting with the groove or the recess,
which is located according to the arrangement of the connecting rod
either on the base plate or the work eccentric, can be constructed
as a bent part, cast part, or as an add-on part (e.g., as a dowel
pin). The projection of the object out of the groove or the recess
in the direction of the beginning of the groove is prevented by the
clamping of the work eccentric and the associated limiting of the
axial play of the tensioning unit. According to another embodiment,
the object encompasses the work eccentric. In the mounting
position, in particular a molded part connected to the base plate
engages in a groove or recess of the work eccentric. Due to the
axial force of the torsion spring, in the mounting position there
is effective locking between the base plate and the work
eccentric.
[0030] The invention is directed, in particular, to tensioning
devices, which guarantee a nearly constant pretensioning force of
the traction means under all operating conditions and with which a
long service life can be achieved. The measures according to the
invention allow a semi-automated setting of the desired traction
means force for the first assembly and for service work for
equalizing: [0031] diameter and positional tolerances of the
individual disks of the traction means drive; [0032] length
tolerances of the traction means, especially toothed belts; [0033]
belt wear; [0034] temperature differences; [0035] and effects due
to the dynamic behavior of the internal combustion engine.
[0036] The invention is further directed also to a method for
integrating an eccentric tensioning device in a traction means
drive of an internal combustion engine, in which an eccentric
tensioning device located in a pretensioned state is partially
attached to a flange surface within the scope of a prepared
assembly step, such that the eccentric tensioning device remains in
a pretensioned state, wherein in this pretensioned state the
eccentric tensioning device is configured and oriented such that
the running roller of this device has a large distance from the
traction means running path, and wherein the eccentric tensioning
device is brought into a released state through tightening of an
attachment screw used for the fastening, in which the pretensioned
state is released and the running roller is lowered onto the
associated traction means of the traction means drive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] Additional details and features of the invention emerge from
the following description in connection with the drawing. Shown
are:
[0038] FIG. 1 an axial section view for illustrating the
construction of a double eccentric tensioning device according to
the invention,
[0039] FIG. 2 a perspective view of the base plate of the eccentric
tensioning device according to FIG. 1,
[0040] FIG. 3 a perspective view of the work eccentric of the
tensioning device according to FIG. 1,
[0041] FIG. 4 a detail view for illustrating the construction of
the fixing device of the eccentric tensioning device according to
FIG. 1,
[0042] FIG. 5 another axial section view for illustrating the
eccentric tensioning device according to the invention, here in a
state axially inserted and thus brought into a released
position,
[0043] FIG. 6 a perspective view of the work eccentric of an
eccentric tensioning device according to the invention according to
a second embodiment of the invention,
[0044] FIG. 7 a perspective view of a base plate structure, which
as such interacts with the work eccentric according to FIG. 6,
[0045] FIG. 8 a perspective view of a tensioning device formed with
the inclusion of the work eccentric and the base plate according to
FIGS. 6 and 7,
[0046] FIG. 9 a perspective exploded view for illustrating the
construction of the eccentric tensioning device according to FIG.
8,
[0047] FIG. 10 another perspective view for illustrating the double
eccentric tensioning device according to FIG. 8 in unlocked
state,
[0048] FIG. 11 a perspective detailed view for illustrating the
engagement state of the fixing device in a double eccentric
tensioning device according to FIG. 8,
[0049] FIG. 12 a perspective view of a double eccentric tensioning
device according to a third embodiment of the invention,
[0050] FIG. 13 a perspective view of a double eccentric tensioning
device according to the invention according to a fourth embodiment
of the invention with an indexer device blocked by a stop,
[0051] FIG. 14 a side view for illustrating additional details of
the double eccentric tensioning device according to FIG. 12,
[0052] FIG. 15 a perspective view of a fifth embodiment of a double
eccentric tensioning device according to the invention with a
securing pin lying outside of the periphery of the tension roller
device,
[0053] FIG. 16 a perspective view of the base plate of the double
eccentric tensioning device according to FIG. 15,
[0054] FIG. 17a a perspective view of the base plate for a double
eccentric tensioning device according to a fifth embodiment of the
invention,
[0055] FIG. 17b a sketch for illustrating the function of the
fixing device formed in interaction with the base plate according
to FIG. 17a,
[0056] FIG. 18 another sketch for illustrating the construction of
a base plate for realizing a fixing device according to the
invention,
[0057] FIG. 19 a view for illustrating the individual phases of the
mounting process for connecting the tensioning device according to
the invention to an internal combustion engine,
[0058] FIG. 20 a basic sketch for illustrating another mechanism
for automatically releasing a tensioning device according to the
invention,
[0059] FIG. 21 a basic sketch for illustrating another variant of
an automatically releasable fixing device,
[0060] FIG. 22 another sketch for illustrating a fixing device
according to the invention with a spring elastic securing arm
pretensioned into a released position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0061] FIG. 1 shows a tensioning device according to the invention
in the form of an axial section view. The tensioning device 1
comprises an adjustment eccentric 2, which is inserted into a
carrier body 3 constructed as a cylindrical bushing, by means of
which the tensioning device 1 in connection with an attachment
screw not shown in FIG. 1 can be connected to a flange surface F,
especially an end of an internal combustion engine.
[0062] The tensioning device 1 further comprises a work or
operating eccentric 5, which is arranged rotatably on the carrier
body 3 by means of a plain or slide bearing 4. On the outside, the
work eccentric 5 is surrounded by a rolling bearing 6, on which in
turn a running disk 7 is positioned, which makes firm contact with
a traction means with in the installed state.
[0063] For pretensioning and rotating the work eccentric 5 into a
position pretensioning the traction means, a torsion spring 9 is
provided, which is supported with a first spring end on the work
eccentric 5 and with the other spring end on a base plate 8. This
base plate 8 is connected locked in rotation with the carrier body
3 in this embodiment.
[0064] The adjustment eccentric 2 can pivot about a pivoting axis
E2 defined by the attachment screw. The work eccentric 5 can pivot
about an eccentric axis E defined by the outer peripheral surface
of the carrier body. This eccentric axis E is radially offset
relative to a rotating axis X of the rolling bearing 6. For
integrating a traction means into the corresponding traction means
drive, the work eccentric 5 and the adjustment eccentric 2 are each
arranged in a pivoted position, in which the greatest possible
distance of the traction means running surface of the running disk
7 from the traction means running path is produced.
[0065] For guaranteeing the installation of the tensioning device
in a required installation orientation, i.e., for guaranteeing an
aligned installation position of the tensioning device, the base
plate 8 is provided with an axially extending projection 10, which
engages in a corresponding receptacle of the internal combustion
engine (indicated here as a bore) provided in the area of the
flange surface.
[0066] An indexer 11 arranged locally on the work eccentric 5
illustrates the pivoted position of the work eccentric 5 in the
installed state of the tensioning device 1. The tensioning device 1
is constructed such that an axial play "S" initially remaining
between an end face of the work eccentric 5 and the base plate 8 is
eliminated within the scope of the mounting of the tensioning
device, especially tightening the attachment screw (as has already
happened here).
[0067] The tensioning device according to the invention comprises a
locking device 12, which automatically detaches within the scope of
the advancing attachment of the tensioning device to the internal
combustion engine and after placement of a traction means in the
traction means drive due to a completed mounting step.
[0068] The following description relates in particular to the
locking device 12 according to the invention and active here
between the base plate 8 and the work eccentric. The mounting step
provided for releasing this locking device includes completing the
tightening of the attachment screw not shown here in more detail.
During this tightening, the axial play S mentioned above is
overcome and the work eccentric 5 unlocked in this way pivots
automatically into a position pretensioning the traction means
under the effect of the torsion spring 9.
[0069] The construction and the function of the locking device 12
between the base plate 8 and the work eccentric 5 is further
illustrated in FIGS. 4 and 5. FIGS. 2 and 3 also belonging to this
first embodiment show structural details of the locking device 12
with reference to detailed drawings.
[0070] Here, FIG. 3 shows in the form of a perspective view how the
work eccentric 5 is used in the tensioning device according to FIG.
1. The work eccentric 5 comprises an axially projecting section 13,
in which a recess or groove 14 and an engagement recess 16 is
formed.
[0071] For locking the tensioning device 1 in a pretensioned
mounting state, a radial cam 15 constructed in one piece with the
base plate 8 shown in FIG. 2 locks in the engagement recess 16. A
block can prevent the cam 15 from leaving the groove 14 in the
direction of a beginning of the groove 16.
[0072] As an alternative to the previously described locking device
12, it is also possible to arrange this so that the engagement
recess 16 or the groove 14 is allocated to the base plate 8 and the
cam 15 is allocated to the work eccentric 5.
[0073] Automatic detachment of the locking device 12 is realized
through tightening of the attachment screw, in which the axial play
"S" (FIG. 1) between the end face of the work eccentric 5 and the
base plate 8 is simultaneously reduced, whereby the cam 15 detaches
from the engagement recess 16 and is inserted into the groove 14.
In this way, a released state is reached, in which the work
eccentric 5 automatically pivots into a position pretensioning the
traction means.
[0074] FIG. 4 shows in the form of an enlarged view the detail
designated by the reference symbol Z in FIG. 1. In the released
state shown here, the cam 15 connected to the base plate 8 is
inserted into the groove 14.
[0075] FIG. 5 shows the tensioning device 1 in a view, from which
the construction of the locking device 12 becomes clearer. The
tensioning device is located in the state shown here in a released
position, in which pivoting of the work eccentric 5 is allowed.
[0076] In FIGS. 6 to 11, a second embodiment of a tensioning device
according to the invention is shown, which differs from the first
embodiment especially in terms of the shape of the fixing device or
locking device 17.
[0077] For realizing the locking device 17, the base plate 8 is
provided locally with an axially extending projection 18. A
radially inwardly directed projection 19 is formed on the end on
this projection 18. According to the shape of the projection 19,
the work eccentric 5 has a corresponding recess 21 or groove 22, in
which the projection 19 locks with a positive fit in the mounting
position, i.e., in the pretensioned state.
[0078] As FIG. 8 shows, the projection 18 of the base plate 8
surrounds the outer contours of the work eccentric 5 in the region
of the groove 22 or recess 21, wherein the radial outer contours of
the running disk 7 are not exceeded.
[0079] Furthermore, according to FIG. 8 the tensioning device 1 is
provided with a rotation limiter 23 for the work eccentric 5. For
this purpose, the base plate 8 has a locally bent rim 24, which
engages with a positive fit in a recess 25 of the work eccentric 5,
wherein the extent of the recess 25 determines the maximum rotation
of the work eccentric 5 relative to the base plate 8.
[0080] In FIG. 9, in the form of a perspective exploded view a
tensioner optimized with respect to carrying out a mounting process
is shown for a traction means drive. This tensioner corresponds
essentially to the tensioner described previously in connection
with FIGS. 6 to 8. The statements regarding these figures apply
analogously in this respect. As can be seen from this illustration,
the mounting-optimized tensioning device comprises a rolling
bearing 6, which is constructed as a sealed, double-row ball
bearing and which comprises its own inner ring 6a, an outer ring
6b, and a bearing seal 6c. This rolling bearing 6 sits on an outer
peripheral surface 6a of the work eccentric 5 over the cylindrical
inner surface formed by the inner ring 6a. The work eccentric 5 is
constructed such that an eccentric axis E defined by its inner bore
5b is radially offset relative to a rolling bearing rotating axis X
defined by the inner ring 6a. This degree of offset corresponds to
half the maximum necessary radial adjustment tensioning lift of the
work eccentric in the operating state of this eccentric. The
coupling of an adjustment tensioning torque pivoting the work
eccentric 5 is performed under the effect of the torsion spring 9
shown here and constructed as a helical spring. This torsion spring
9 is supported on an inner region that cannot be seen here in more
detail in a bell-shaped section 5c of the work eccentric 5. In the
embodiment shown here, the rotationally locked anchoring of the
torsion spring 9 on the work eccentric 5 is realized by a radially
outwardly bent engagement end 9a of the torsion spring 9.
Preferably, the attachment of the torsion spring 9 on the work
eccentric 5 is implemented such that a sufficiently more reliable
engagement is also guaranteed under unfavorable operating or
mounting conditions. It is possible to provide retaining elements,
through which an especially reliable coupling state between the
torsion spring 9 and the work eccentric 5 is guaranteed on the work
eccentric 5, on the torsion spring 9, or also via additional
securing structures. In the embodiment shown here, the torsion
spring 9 is supported with its second end section 9b on the base
plate 8. The base plate 8 forms a structural component, which can
be flanged at the projection 10 already discussed above so that it
is locked from rotation to a flange surface provided for receiving
the tensioning device, especially an end face of an engine block or
cylinder head. In the embodiment shown here, the base plate 8
further forms a structural component, through which the work
eccentric 5 can be locked in a pivoted position, in which the
torsion spring 9 arranged kinematically between the base plate 8
and the work eccentric 5 is tensioned. This locked position can
correspond especially to the position, in which the rolling bearing
6 has been lifted farther from the running path of the associated
traction means of a traction means drive. As an alternative to this
extreme position, however, it is also possible to shape the locking
device, so that the work eccentric 5 is anchored in intermediate
positions, in which, for example, only a 90 degree pivoting of the
work eccentric 5 takes place. In the embodiment shown here, the
locking mechanism comprises a projection 18, which is formed on the
base plate 8 and which as such carries a catch structure that is
constructed as a projection 19 and that can engage in a counter
structure or groove 22 provided on the side of the work eccentric
5, especially the bell section 5c of this eccentric, as can be seen
better from the other views.
[0081] In the embodiment shown here, an engagement state set
between the base plate 8 and the work eccentric 5 is released, in
that the work eccentric 5 is pushed in a direction of its eccentric
axis E towards the base plate 8, so that the projection 19 moves
axially out of the groove 22 and thus unlocks the work eccentric 5
in the peripheral direction and thus allows pivoting of this
eccentric under the effect of the pivoting moment applied by the
torsion spring 9. The pivoting coupling of the work eccentric 5
with the base plate 8 is implemented in this embodiment by a
carrier body 3 constructed as a bushing, which here is coupled
preferably locked in rotation with an inner peripheral region 8a of
the base plate 8. This coupling can be realized, in particular, by
pressing a foot region 3a of the carrier body 3 into the base plate
8.
[0082] Preferably, the work eccentric 5 does not sit directly on an
outer peripheral surface 3b provided by the carrier body 3, but
instead sits on the carrier body 3 under inclusion of a bushing
constructed as a slide bearing, as shown here. The slide bearing 4
can be constructed, so that a certain friction moment is generated
by this bearing, through which the pivoting motion of the work
eccentric 5 is braked or damped on the carrier body 3.
[0083] It is possible to shape the slide bearing 4 so that
different braking moments for moving the work eccentric 5 in the
adjustment tensioning direction and also in the counter direction
are generated by this bearing. For this purpose, it is possible, in
particular, to construct the slide bearing bushing 4 as a slotted
structure, so that especially when the work eccentric 5 pivots
against the adjustment tensioning direction, a greater friction
moment is produced than when the work eccentric 5 pivots in the
adjustment tensioning direction. For this purpose, it is possible
to anchor the slide bearing bushing 4 locked in rotation either on
the work eccentric 5 or on the carrier body 3, as shown here.
[0084] The mounting-optimized tensioning device according to the
invention can also be shaped in some other way in terms of the
torsion spring device and also especially in terms of the damping
device. In particular, it is also possible to provide friction disk
structures, through which the pivoting motion of the work eccentric
5 is also braked or damped in a defined way relative to the base
plate 8.
[0085] The attachment of the mounting-optimized tensioning device
shown here can be performed by an attachment screw, which as such
is passed through the inner bore 3c provided by the carrier body 3.
This inner bore 3c is shaped so that this has a considerably larger
diameter than the attachment screw required for sufficient
attachment of the tensioning device. The intermediate space
remaining between the outer region of the shaft of the
corresponding attachment screw and the inner peripheral wall 3c can
be filled by an eccentric body formed as an adjustment eccentric,
so that in addition to the radial displacement of the rolling
bearing 6 achieved by the work eccentric 5, the entire tensioning
device can also still be fixed through corresponding pivoting of
the adjustment eccentric inserted into the inner bore 3c.
[0086] In the embodiment shown here, the axial displacement of the
work eccentric 5 towards the base plate takes place within the
scope of tightening the attachment screw provided for attaching the
tensioning device to an internal combustion engine. In a first
mounting step, the attachment screw is tightened only slightly, so
that the tensioning device is definitely already sufficiently
secured on the internal combustion engine, but the fixing device
realized between the base plate 8 and the work eccentric 5 still
remains in a secured state. Only after a traction means has been
placed in the traction means drive, after the adjustment eccentric
is pivoted into a position that is closest to the rolling bearing
axis X on the running path of the traction means, is the attachment
screw tightened further and thus the fixing device is brought into
a released state. As soon as this fixing device is led into the
released state, the work eccentric 5 snaps into a tensioned
position under the effect of the torsion spring 9 and thus exerts a
pressure force on the traction means defined by the tensioning
moment generating the torsion moment of the torsion spring 9.
[0087] In FIG. 10, in the form of a perspective detailed view, the
fixing device provided in the tensioning device according to FIG. 9
is shown in an engaged state. As can be seen in this view, the work
eccentric 5 is coupled locked in rotation with the base plate 8.
This rotationally locked coupling is constructed by the engagement
of the engagement structure constructed as projection 19 with the
counter structure provided as engagement groove 22 and provided on
the side of the work eccentric 5. By displacing the work eccentric
5 in the direction of the arrow symbol P1 shown here, the
projection 19 can move out of the groove 22 into the area of the
recess 21 and thus frees the work eccentric 5 relative to the base
plate 8. The displacement of the work eccentric 5 is the direction
of arrow P1 is realized in this embodiment against an axial force
generated by the torsion spring 9. On the work eccentric 5 an
indexer 26 is formed, by means of which the pivoted state of the
work eccentric 5 can be better seen from the outside. In the
embodiment shown here, the fixing device is shaped such that the
locking structure engaged with the work eccentric 5 engages
radially from the outside into a counter structure provided by the
work eccentric 5. However, it is also possible to shape this fixing
device, as described in more detail in the following embodiment,
such that this engages from the inside into a corresponding counter
structure of the work eccentric 5.
[0088] In FIG. 11, the mounting-optimized tensioning device
according to the invention from FIGS. 8 to 10 described above is
shown in a state, in which the previously described fixing device
is located in a detached position, in which the work eccentric 5
can be pivoted freely relative to the base plate 8. As can be seen,
the engagement structure constructed as a projection 19 is located
in the area of the recess 21 and in this position can no longer
engage with the engagement structure constructed as groove 22
provided by the work eccentric 5.
[0089] FIGS. 12 to 18 show additional constructions of locking
devices according to the invention for the work eccentric 5
relative to the base plate 8.
[0090] To prevent relative motion between the work eccentric 5 and
the base plate 8 in the mounting position, according to FIG. 12 an
indexer 26 connected in one piece with the work eccentric 5 is
secured on the base plate 8. The locking device 27 can be realized
through suitable shaping of the base plate 8 itself or with the
help of additional elements, such as a sheet or a splint, wherein
these elements must be removed for releasing the work eccentric 5.
According to FIG. 12, the locking device 27 comprises a sheet or a
sheet clip 28 connected to the base plate 8 with an elongated hole
or an inverted U-shaped bend open on one side. In the mounting
position of the tensioning device 1, the indexer 26 is supported
for forming the locking device 27 with a firm contact fit on the
sheet clip 28.
[0091] From FIG. 15 the tensioning device 1 is seen in connection
with a locking device 29, in which the base plate 8 encloses a
guide 30, in which the indexer 31 of the work eccentric 5 is
guided. On one end, the guide 30 forms a receptacle 32, which is
designed for a pin 33 and with which an end position of the indexer
31 connected in one piece with the work eccentric 5 can be
reached.
[0092] FIG. 16 shows the base plate 8 used in the tensioning device
according to FIG. 15 in connection with the guide 30 as an
individual part in perspective.
[0093] In FIG. 17a, in the form of a perspective view, another
embodiment for the shaping of a base plate 8 of a
mounting-optimized tensioning device according to the invention is
shown. This base plate 8 is constructed as a sheet metal drawn part
similar to embodiments described above. The base plate forms
several pivoting claws 34, which are pivoted radially outwards
within the scope of tensioning the base plate 8 on a flange surface
carrying the tensioning device. For pivoting the pivoting claws 34,
on each of these a pivot wing 35 is formed, which initially
contacts the flange surface when the base plate 8 is set and which
pivots the entire pivoting claw structure 34 about pivoting
sections 36, 37 in the course of further pressing the base plate 8
onto the flange surface. In the embodiment shown here, the pivot
sections 36, 37 are shaped so that a slight, plastic deformation of
the pivoting claws takes place within the scope the pivoting these
pivoting claws 34 outwardly, so that the pivoting claws 34 no
longer pivot back into the radially inwards pivoted position not
shown here even after subsequent lifting. In this way the pivoting
claws 34 are prevented from pivoting back inwards and thus cause an
engaged state due to loosening of the tensioning of the base plate
on the associated flange surface. Through the structure shown here,
it becomes possible to bring the pivoting claws 34, as shown in
FIG. 17b, in engagement with a groove 22 constructed on the outer
periphery of the work eccentric 5 or with some other engagement
structure.
[0094] However, it is also possible, as is visible from FIG. 18, to
shape the pivoting claws 34 so that these are pivoted inwardly
within the scope of placing the base plate 8 on a flange surface
not shown here in more detail and thus project out of corresponding
catch geometries provided on the side of the work eccentric 5 and
thus cause a release of the work eccentric 5 relative to the base
plate 8.
[0095] As shown in FIG. 19, the attachment of the eccentric
tensioning device 1 on the flange surface F only indicated here for
an internal combustion engine BK takes place by means of an
attachment screw 40 in three steps. Within the scope of step A, the
tensioning device is set without special pressing force on the
flange surface F, so that the projection 10 of the base plate 8 is
inserted into the indexing recess U provided on the side of the
internal combustion engine. In this way, the peripheral position of
the base plate 8 is fixed. Within the scope of step A, the
attachment screw 40 is inserted into the adjustment eccentric
2.
[0096] Within the scope of the subsequent mounting step B, the
attachment screw 40 is tightened until the screw head of the
attachment screw 40 is seated lightly and without special axial
force on the end of the adjustment eccentric 2. Within the scope of
the attachment step B, the torsion spring 9 has not yet been loaded
axially and thus the fixing device 12 has not yet been brought into
a released position. After the attachment performed in this way for
the tensioning device, the corresponding traction means can be
inserted into the traction means drive of the internal combustion
engine without using force.
[0097] After completion of the placement process of the traction
means in the traction means drive, the final tightening of the
tensioning device 1 on the flange surface F is performed. For this
purpose, the attachment screw 40 is charged with an increased
tightening moment within the scope of the attachment step C. Here,
the work eccentric 5 is forced together with the adjustment
eccentric 2 axially towards the base plate 8 until the base surface
of the adjustment eccentric 2 sits on the flange surface F. During
this phase C, the engagement element 15 formed on the base plate 8
emerges from a locking groove, as can be seen in this view, and
thus releases the work eccentric 5. The work eccentric 5 now snaps
into the tensioned position under the effect of the tensioning
moment generated by the torsion spring 9 and in this way generates
a transverse force applied to the traction means via the running
disk 7.
[0098] In FIG. 20, another variant of a fixing mechanism
automatically guided into a released state within the scope of the
mounting process of the tensioning device is shown. In this
concept, the generation of the released state is realized through
axial displacement of the slide bearing bushing 4. The slide
bearing bushing 4 is here provided with a conical section 4a, which
forces engagement claws 34 radially outwards for axial displacement
indicated by the arrow symbol P2 and brings these out of the
engagement position shown here with corresponding counter
structures of the work eccentric 5. The displacement of the slide
bearing bushing 4 in the way shown here can be realized especially
in that this is pushed axially under the effect of the rim 20 of
the adjustment eccentric 2.
[0099] In FIG. 21, another variant of an automatically releasable
fixing mechanism is shown. In this embodiment, the indexer 26
attached to the work eccentric is secured by a holding arm 41. This
holding arm 41 is constructed in one piece with the base plate 8.
When clamping the base plate 8 onto the flange surface F of the
internal combustion engine, a projecting length 42 of the holding
arm 41 is charged with a pressure force, so that the entire arm 41,
as indicated by the arrow symbol P3, pivots upwards and thus
releases the indexer 26.
[0100] In FIG. 22, another variant of a fixing device is shown. The
indexer 26 of the work eccentric 5 (not shown) is here secured by a
hook section 43 of a spring elastic spring arm 44 pretensioned
downwards. The release of the fixing mechanism shown in this way
can be realized in that the work eccentric 5 is pivoted by a small
angular amount against its pretensioning direction, so that the
hook structure shown here comes free from the indexer 26 and the
entire spring arm 44 can tilt downwards. It is also possible to
provide structures, through which the spring arm 44 can be forced
downwards and in this way comes free from the indexer section 26
within the scope of the last tightening phase of an attachment
screw.
[0101] The rolling bearing of the tensioning device is preferably
constructed as a radial rolling bearing, which is comprised of an
inner bearing ring and an outer bearing ring, as well as a
plurality of cylinder bodies rolling between the bearing rings in
groove-shaped raceways and held relative to each other by a bearing
cage at a constant distance and which has axially on both sides of
its cylinder bodies a seal, with which the intermediate space
constructed as a grease storage area between the bearing rings is
sealed, wherein this rolling bearing is distinguished in that this
is constructed as a ball roller bearing, whose cylinder bodies are
each constructed with two parallel side surfaces symmetrically
flattened from a basic ball shape. Relative to a comparable ball
bearing, this ball rolling bearing offers an increased bearing
capacity due to the higher number of cylinder bodies that can be
mounted and due to the reduced installation space of the cylinder
bodies together with an enlarged grease storage area. The cylinder
bodies constructed as ball rollers are preferably shaped so that
these preferably have a width between their side surfaces of
approximately 70% of the diameter of their basic ball shape and can
be inserted at first axially "flat" into the radial rolling bearing
through a distance between the concentric bearing rings having a
height of approximately 80% of the diameter of the basic ball shape
of the cylinder body and can each be pivoted through a
corresponding rotation by about 90.degree. in the raceways of the
bearing rings. The outer bearing ring here can form the running
disk directly. The inner bearing ring can be formed directly by the
work eccentric.
LIST OF REFERENCE NUMBERS
[0102] 1 Tensioning device [0103] 2 Adjustment eccentric [0104] 3
Carrier body [0105] 4 Slide bearing [0106] 5 Work eccentric [0107]
6 Rolling bearing [0108] 7 Running disk [0109] 8 Base plate [0110]
9 Torsion spring [0111] 10 Projection [0112] 11 Indexer [0113] 12
Locking device [0114] 13 Section [0115] 14 Groove [0116] 15 Cam
[0117] 16 Beginning of groove [0118] 17 Locking device [0119] 18
Projection [0120] 19 Projection [0121] 20 Inclined section [0122]
21 Recess [0123] 22 Groove [0124] 23 Rotating limiter [0125] 24 Rim
[0126] 25 Recess [0127] 26 Indexer [0128] 27 Locking device [0129]
28 Sheet bracket [0130] 29 Locking device [0131] 30 Guide [0132] 31
Indexer [0133] 32 Receptacle [0134] 33 Pin
* * * * *