U.S. patent application number 11/995873 was filed with the patent office on 2008-09-04 for belt drive.
This patent application is currently assigned to SCHAEFFLER KG. Invention is credited to Michael Bogner, Roman Kern, Bolko Schuseil.
Application Number | 20080214341 11/995873 |
Document ID | / |
Family ID | 37070253 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080214341 |
Kind Code |
A1 |
Schuseil; Bolko ; et
al. |
September 4, 2008 |
Belt Drive
Abstract
A belt drive is provided which includes a circulating belt (8)
which is driven by at least one drive element (9) and which drives
at least one driven element (10). At least one first tensioning
device (20) acts upon the belt (8) in the slack strand and at least
one second tensioning device acts in the tightened strand. To
prevent or reduce jumps and/or transverse oscillations of the belt
(8), the second device (21) guides the belt (8) and at least one
third device (22) which is arranged radially inside the belt drive,
which is suitable, optionally, limits deviations of the belt (8).
The second device (30, 40, 50, 60, 70, 80, 90, 100) also tensions
the belt (8) in such a manner that it is subjected to a force (F1)
which is smaller than the force (F2) which is oriented counter
thereto during the operation of the belt (8) on the second
tensioning device (30, 40, 50, 60, 70, 80, 90, 100).
Inventors: |
Schuseil; Bolko; (Adelsdorf,
DE) ; Bogner; Michael; (Eckental, DE) ; Kern;
Roman; (Forchheim, 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: |
37070253 |
Appl. No.: |
11/995873 |
Filed: |
June 29, 2006 |
PCT Filed: |
June 29, 2006 |
PCT NO: |
PCT/EP2006/006295 |
371 Date: |
February 4, 2008 |
Current U.S.
Class: |
474/111 |
Current CPC
Class: |
F16H 7/18 20130101; F16H
2007/0808 20130101; F16H 7/08 20130101; F16H 2007/0874 20130101;
F16H 2007/0812 20130101; F16H 2007/081 20130101 |
Class at
Publication: |
474/111 |
International
Class: |
F16H 7/08 20060101
F16H007/08; F16H 7/18 20060101 F16H007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2005 |
DE |
102005033322.2 |
Claims
1. Belt drive, comprising a circulating belt means, which is driven
by at least one drive element and which drives at least one driven
element, at least one first tensioning device acting on the belt
means in a region of the belt drive where the belt means leaves the
drive element in its circulating direction and reaches a closest
driven element, and at least one second device in a region of the
belt drive where the belt means reaches the drive element in the
circulating direction and leaves a closest driven element the
second device is constructed for guiding the belt means and there
is at least one third device, which is arranged in a radial
direction inside the belt drive and which is also suitable for
limiting excursions of the belt means.
2. Belt drive according to claim 1, wherein the at least one third
device is provided in a region of the drive element.
3. Belt drive according to claim 2, wherein the at least one third
device is provided in the region of the drive element where the
belt means reaches the drive element in the circulating
direction.
4. Belt drive according to claim 1 or 2, wherein the at least one
third device is provided in the region of the drive element where
the belt drive leaves the drive element in the circulating
direction.
5. Belt drive according to claim 1, wherein the at least one third
device is suitable for acting both in a region of the drive element
where the belt drive reaches the drive element in the circulating
direction and also in the region of the drive element where the
belt means leaves the drive element in the circulating
direction.
6. Belt drive according to claim 1, wherein the at least one third
device is arranged at a defined distance from an inside of the belt
means.
7. Belt drive according to claim 1, wherein the at least one third
device is connected mechanically to at least one of the at least
one first devices or to the at least one second devices.
8. Belt drive according to claim 1, wherein at least one of the
first, second or third devices is provided with a surface for
reducing friction.
9. Belt drive, comprising a circulating belt means, which is driven
by at least one drive element and which drives at least one driven
element, at least one first tensioning device acting on the belt
means in a region of the belt drive where the belt means leaves the
drive element in the circulating direction and reaches the closest
driven element, and at least one second device in a region of the
belt drive where the belt means reaches the drive element in its
circulating direction and leaves a closest driven element the
second device is also constructed for tensioning the belt means,
such that the second device acts on the belt means with a force
that is less than an opposite force acting on the second tensioning
device during the operation of the belt means.
10. Belt drive according to claim 9, wherein the force acting on
the belt means is generated at least partially by a spring
force.
11. Belt drive according to claim 10, wherein the spring force is
generated by at least one of a leg, spiral, leaf, or torsion
spring.
12. Belt drive according to claim 9, wherein at least one of the
tensioning devices is provided with a surface for reducing
friction.
13. Belt drive according to claim 9, wherein the at least one
second tensioning device has a guide body, which is acted upon with
a force by at least one spring in a direction toward the belt means
as well as with an opposite force during operation of the belt
means.
14. Belt drive according to claim 1, wherein the at least one
second tensioning device has a deformable guide body or a guide
body with a deformable surface.
15. Belt drive according to claim 14, wherein the at least one
second tensioning device has a guide body having a sliding coating
constructed to be spring-elastic in a direction toward the belt
means or the at least one second tensioning device has a guide body
having a sliding coating that is pressed by a spring against the
belt means, with the spring being arranged between the guide body
and the sliding coating.
16. Belt drive according to claim 9, wherein the at least one
second tensioning device has a multiple-part guide body, whose
individual parts are connected to each other in an articulated
manner on facing ends thereof at a hinge point and wherein, at the
hinge point, a spring attaches, such that a force is generated in a
direction toward the belt means.
17. Belt drive according to claim 9, wherein the at least one first
tensioning device is activated by pressurized medium and is also
acted upon with a spring force, which acts constantly on the belt
means in the tensioning direction.
18. Belt drive according to claim 17, wherein the at least one
first tensioning device and the at least one second tensioning
devices are connected to each other elastically by a spring,
wherein the spring generates a spring force acting constantly on
the belt means in a tensioning direction.
19. Belt drive according to claim 17 wherein the at least one first
tensioning device and the at least one second tensioning device are
connected to each other by a hinge mechanism, wherein the hinge
mechanism is connected to a spring, which generates a force acting
constantly on the belt means in the tensioning direction via the
hinge mechanism.
20. Belt drive according to claim 19, wherein the guide body of the
at least first and second tensioning devices are each supported so
that they can pivot in separate attachment points, the guide bodies
are each connected in an articulated way at attachment points with
a lever-like connection element, the connection elements are
connected to each other so that they can pivot at a connection
point, and the spring engages at the connection point, such that a
basic contact force of the guide bodies acts on the belt means via
the connection elements.
21. Belt drive according to claim 20, wherein the connection
elements and the spring are arranged in a radial direction inside
the belt drive.
Description
BACKGROUND
[0001] The invention relates to a belt drive comprising a
circulating belt means, which is driven by at least one drive
element and which drives at least one driven element, as well as at
least one first tensioning device acting on the belt means in a
region of the belt drive, in which this belt means leaves the drive
element in the circulating direction and reaches the closest driven
element, and at least one second device in a region of the belt
drive, in which the belt means reaches the drive element in its
circulating direction and leaves the closest driven element.
[0002] Such belt drives are used, for example, for timing and/or
accessory drives in internal combustion engines. The traction
means, for example, the timing belt, is here driven by a driving
gear mounted on a crankshaft of the engine and drives driven gears,
which are connected to timing shafts or camshafts of the engine.
For limiting transverse vibrations in the timing belt, this belt is
led over a guide on its tensioned side running into the driving
gear and a force tensioning the belt is applied by a tensioning
device to the slack side of the belt running out from the driving
gear.
[0003] EP 1 262 685 also shows a belt drive according to the class,
in which for limiting transverse vibrations of a timing belt, a
force is applied to this belt both on its tensioned side running
into the driving gear and also on its slack side running out from
the driving gear. The forces are set here by a rotating, adjustable
ring body, to which guide rails are attached that act on the timing
belt. The tensioning force acting on the timing belt increases or
decreases with the degree of rotation of the ring body. The
rotation of the ring body itself is generated by a combination of
oil pressure and spring force.
[0004] DE 196 16 081 C1 shows a belt drive comprised of belt disks
and an endless belt with a device for steadying belt vibrations, in
which a guide plate is arranged fixed at a close distance to the
belt for reducing belt vibrations in a corresponding critical
region.
[0005] Limiting transverse vibrations in belt drives is of great
importance with respect to their functionality, service life, and
noise output. This applies independent of how many driving and
driven gears are actually used for a belt drive. The belt means can
involve, for example, a chain or a toothed belt of a timing drive,
which synchronizes crankshafts and camshafts with each other, or,
for example, also a driving belt, which connects a belt disk of a
drive shaft to the belt disk of a driven shaft for some assembly in
a driving manner.
[0006] For transverse vibrations that become too large, adjacent
components can be damaged, if a toothed belt or a chain temporarily
loses positive-fit contact with a driving or also driven element
due to transverse vibrations that are too large. Furthermore,
unsuitably high mechanical loads for the belt means itself can
occur due to excessive transverse vibrations, which lead to a
shortened service life of the belt means. In addition, excessive
transverse vibrations cause a comparatively high noise
generation.
[0007] Finally, synchronization errors between at least two
camshafts and/or between these and the crankshaft of an internal
combustion engine can occur, when the belt drive is lengthened due
to wear and a tensioning device on a belt means strand compensates
this by an increased tensioning path. Because this single
tensioning device is typically activated by an actuator acted upon
by the oil pressure of the internal combustion engine, in
particular, at the start of the internal combustion engine,
insufficient oil pressure is present in the actuator, so that
disadvantageously, tooth jumping is hard to prevent in known belt
drives.
[0008] To be noted is also the increasing complexity of accessories
for usually only limited space relationships in the region of the
belt drive, as well as the necessary flexibility of the belt drive
due to the increasing number of different accessories with respect
to adaptability to different operating conditions.
SUMMARY
[0009] The invention is based on the objective of creating a belt
drive, in which tooth jumping caused by wear-related lengthening of
the belt means between the belt means and the driving element or
driven element can be prevented reliably and also at least the
amplitude of transverse vibrations of the belt means can be
reduced.
[0010] The invention is based on the knowledge that through
selective improvement of the belt drive layout or belt drive
construction, transverse vibrations of the belt means can be
reduced and also tooth jumping can be prevented. Here, the
important feature is that a special means is provided and arranged
on the belt drive for preventing loosening of the belt means due to
decreasing force application by the actuator-controlled tensioning
device, which would hold back the belt means before the drive
element of the belt drive and would lift the belt means from this
drive.
[0011] The invention starts from a belt drive, comprising a
circulating belt means, which is driven by at least one drive
element and which drives at least one driven element, as well as at
least one first tensioning device acting on the belt means in a
region of the belt drive, in which the belt means leaves the drive
element in its circulating direction and reaches the closest driven
element, and at least one second device in a region of the belt
drive, in which the belt means reaches the drive element in its
circulating direction and leaves the closes driven element.
[0012] In this belt drive, according to the invention it is also
provided that the second device provided at least once in this
drive is constructed for guiding the belt means and at least one
third device arranged in the radial direction within the belt drive
is provided, which is also suitable for limiting excursions of the
belt means.
[0013] Such a belt drive can be a timing drive of an internal
combustion engine in the form of a toothed-belt drive or a chain
drive, but it can also be constructed as a toothed-belt drive or
chain drive for driving auxiliary accessories.
[0014] Through this construction, it is advantageously achieved
that a belt means lengthened due to wear past its original
installed dimensions cannot lift from the drive element of the belt
drive so that it jumps out of the teeth or it cannot be held back
in front of this drive element, when the contact force of an
allocated tensioning device that can be activated by a pressurized
medium is not yet or no longer present due to operation. In
addition, with a belt or chain drive built structurally according
to the invention, the likelihood and the extent of the appearance
of transverse vibrations of the belt means can be reduced.
[0015] The third device arranged in the radial direction within the
belt drive is suitable for this purpose and also provided to
produce a steering effect on the inside of the belt means not
reached by the other devices and, if necessary, is arranged where
this appears most relevant to someone skilled in the art for
fulfilling this purpose.
[0016] Preferably, it is provided that the third device provided at
least once in the belt drive is arranged in the region of the drive
element, for example, a crankshaft drive wheel, by means of which,
in this usually critical region, an additional avoidance or
prevention of undesired vibrations and tooth jumping is
advantageously enabled.
[0017] If the third device present at least once in the belt drive
is arranged in the region of the drive element, in which the belt
means has reached the drive element in its circulating direction or
is arranged in the region of the drive element, in which the belt
means leaves the drive element in its circulating direction, then a
positive effect on the vibrating behavior of the belt means, as
well as a given run-in and run-out angle and a given advantageous
contact length of the belt means on the drive element, can be
realized on these sections of the belt means located in the direct
area of the drive element,
[0018] In this connection, it is especially useful if, in the
construction of the invention, the third device present at least
once in the belt drive is suitable for acting both in the region of
the drive element, in which the belt means reaches the drive
element in its circulating direction and also in the region of the
drive element, in which the belt means leaves the drive element in
its circulating direction.
[0019] The third device present at least once in the belt drive
here does not necessarily have to be constructed as guide means for
the belt means. That is, it does not have to be in constant contact
with the belt means, but instead it is absolutely advantageous when
this is arranged at a defined distance from the inside of the belt
means. In this way, this occurs only for actually appearing
undesired transverse vibrations and/or holding back of the belt
means in the slack belt strand, which leads, as a whole, to a
reduction in friction on this third device.
[0020] In addition, it can be advantageously provided that the
third device present at least once in the belt drive is connected
mechanically to the first tensioning device present at least once
in the belt drive and/or to the second guide device present at
least once in the belt drive. In this way, the devices connected to
each other can be aligned in common and adjusted easily.
[0021] If at least one of the mentioned devices is advantageously
provided with a surface reducing the friction with the belt means,
this can lead to further friction reduction and thus an increase in
the service life of the belt means.
[0022] Alternatively, according to the invention a belt drive can
be created, comprising a circulating belt means, which is driven by
at least one drive element and which drives at least one driven
element, as well as at least one first tensioning device acting on
the belt means in a region of the belt drive, in which the belt
means leaves the drive element in its circulating direction and
reaches the closest driven element, and at least one second device
in a region of the belt drive, in which the belt means reaches the
drive element in its circulating direction and leaves the closest
driven element.
[0023] According to the invention, it is also provided that the
second device present at least once in the belt drive is also
constructed for tensioning the belt means, such that this means
acts on the belt means with such a force F1 that is smaller than an
opposite force F2 acting on the second tensioning device in the
operation of the belt means. This opposite force F2 acting on the
second tensioning device is applied by the belt means tensioned by
the first tensioning device.
[0024] Through this construction, it is achieved that, especially
in a standstill phase, in which the first tensioning device
operated by pressurized medium does not exert a force tensioning
the belt means on the belt means due to the lack of pressure in the
pressurized medium, a wear-dependent lengthening of the belt means
is compensated in the belt drive, in which this second tensioning
device exerts an appropriate tensioning force on the belt
means.
[0025] Therefore, tooth jumping as well as associated rotational
angle errors or synchronous running errors, for example, on a
crankshaft disk or on the camshaft disks of an internal combustion
engine, can be reliably prevented. In addition, the appearance
likelihood and also the amplitude of transverse vibrations of the
belt means are further reduced or even completely avoided.
[0026] In addition, the second tensioning device can have a more
compact construction in its structural design than the first
tensioning device that can be activated by pressurized medium and
is also suitable for guiding the belt means during its operation
along its optimum belt path. Because the force F1 of the second
tensioning device acting on the belt means is less than the
opposite force F2 acting on the second tensioning device in the
operation of the belt means, the force F1 of the second tensioning
device has no noticeable effect for the operation of the belt
means. However, for the lack of pressurized medium supply to the
actuator of the first tensioning device, it is in the position to
strongly tension the belt means, so that lengthening of the belt
means, for example, caused by wear or by counter rotation of the
drive element, is compensated, especially when the belt drive is
turned off or after the belt drive has been turned off.
[0027] In addition, it can be provided that the force of the second
tensioning device acting on the belt means is generated at least
partially by a spring force, which allows a structurally simple
construction of the device for high reliability. If the spring
force is generated by at least one spiral, leaf, or torsion spring,
costs can be saved tracing back to common structural elements.
[0028] It is absolutely advantageous for the service life of the
belt means if the second tensioning device, which is present at
least once in the belt drive and which is acted upon by a spring
force or which itself has a spring-elastic construction, is
provided with a surface reducing the friction. In this way, the
size of the spring can be kept smaller and thus space can be saved
or the spring possibly could be completely eliminated.
[0029] The second tensioning device present at least once in the
belt drive can have, in an advantageous refinement of the concept
of the invention, a guide body that can move in a direction toward
the slack belt strand of the belt means or can have a guide body
with a deformable construction. By moving the guide body, a very
precise adjustment of this body on the belt drive is possible. The
use of a deformable guide body leads to an additional force and
supports the spring force of the second tensioning device acting on
the belt means, by which a spring provided in the structure can be
kept smaller.
[0030] In an especially advantageous construction of the invention,
it is provided that the first tensioning device present at least
once in the belt drive can also be acted upon with a spring force
acting on the belt means. In this way, a certain basic tensioning
of the belt means on both sides of the drive element is guaranteed,
independent of the operating situation of a tensioner of the first
tensioning device that can be activated by pressurized medium.
Changes in length in the belt means, for example, due to wear or
due to counter rotation of the drive element, which can appear,
e.g., when a motor is turned off or after the motor has been turned
off, can be advantageously compensated.
[0031] It is further advantageous when the first tensioning device
that can be activated by pressurized medium and that is present at
least once in the belt drive and the second tensioning device
present at least once are connected to each other elastically by at
least one spring. In this way, this spring generates a force acting
on the belt means both on the tightened strand and also on the
slack strand, so that too much slack in the belt drive is overcome
when the drive machine is turned off or when the pressure supply is
stopped for the tensioner of the first tensioning device that can
be activated by pressurized medium.
[0032] Similarly, however, it also offers advantages when the first
tensioning device that can be activated by pressurized medium and
that is present at least once in the belt drive and the second
tensioning device present at least once in the belt drive are
connected to each other by a linkage mechanism, wherein the linkage
mechanism is connected to at least one spring, which generates a
force acting constantly on the belt means.
[0033] In a preferred embodiment, it is provided that the guide
body of the two tensioning devices are each supported at separate
attachment points so that they can pivot, that these guide bodies
are connected in articulated ways at other attachment points to a
lever-like connection element, that these connection elements are
connected to each other so that they can pivot at a connection
point, and that at this connection point a spring attaches, such
that a basic contact force acts on the belt means through the
connection elements and the noted guide bodies.
[0034] In addition, it has been judged to be advantageous when the
connection elements and the spring of this belt drive are arranged
in the radial direction inside of this drive.
[0035] Through the above structural features, an equal distribution
or different distribution of the basic contact force F1 acting on
the belt 8 due to different lever-arm lengths of the connection
elements can be achieved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The invention will be explained in more detail below with
reference to the enclosed drawing using a few embodiments. Shown
therein are
[0037] FIG. 1 a block diagram of a belt drive according to a first
solution according to the invention and
[0038] FIGS. 2 to 9 different schematic diagrams for embodiments of
a belt drive according to a second solution according to the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] The belt drive shown schematically in FIG. 1 can be used in
a motor-vehicle engine and features at the bottom a belt disk 9,
which is connected to a not-shown crankshaft and which drives a
circulating belt 8 in the counterclockwise direction. The belt 8
also drives two belt disks 10, which are arranged at the top and
which are connected to not-shown camshafts.
[0040] The region of the belt drive, in which the belt 8 leaves the
driving belt disk 9 in its circulating direction and reaches the
closest belt disk 10, it designated in general as the slack strand.
The region of the belt drive, in which the belt 8 reaches the
driving belt disk 9 in its circulating direction and leaves the
closest belt disk 10, is designated in general as the tightened
strand.
[0041] As FIG. 1 shows, in the slack strand a first tensioning
device 20 is provided, which is comprised of a tensioner 1 that can
be activated by pressurized medium in the form of a piston-cylinder
arrangement, a guide body 2 hinged to an attachment point 4 so that
it can pivot, and a friction-reducing sliding coating 3 deposited
on the guide body 2 on the belt side. The tensioner 1 applies a
force on the guide body 2 of the first tensioning device 20 with a
force that presses and thus tensions the belt 8 running over the
sliding coating 3 in this diagram to the right in the radial
direction approximately in the direction of the center of the belt
drive.
[0042] In the tightened strand, an additional device 21 is provided
for guiding the traction means, which is constructed as a belt 8,
and which has a guide body 5 that is mounted at two attachment
points 4 and a friction-reducing sliding coating 7 is deposited on
this guide body on the belt side. Furthermore, below in the direct
area of the belt disk 9, a guide device 22, which is suitable for
guiding the belt 8, is provided in the radial direction within the
belt drive and above the belt disk 9.
[0043] This guide device 22 has a guide body 13, which carries two
guide rails that are each provided, in turn, with a sliding coating
14. Of the two guide rails, one guide rail faces the inside of the
slack strand and the other guide rail faces the inside of the belt
8 located in the tightened strand.
[0044] The guide rails are arranged with their sliding coating 14
at a slight distance from the belt 8, such that an approximately
funnel-shaped guide channel 23, 24 for the belt 8 is formed between
the sliding coating 7 of the guide body 5 of the additional device
21 and the sliding coating 14 of the guide body 13 or between the
sliding coating 3 of the guide body 2 of the first tensioning
device 20 and the sliding coating 14 of the guide body 13.
[0045] The guide channel 23 prevents, for example, on the slack
strand side that a lengthened belt 8 caused by wear can lift so far
from the belt disk 9 that the belt jumps from the teeth when
tension on the belt 8 falls due to decreasing application of force
by the first tensioning device 20. The other guide channel 24
generates the same effect on the tightened strand side of the
driving belt disk 9, where tooth jumping caused by the belt 8 being
held back is prevented. In addition, in this way the production of
transverse vibrations in the belt 8 is advantageously prevented or
at least advantageously reduced.
[0046] However, the guide rails of the guide device 22 can also be
arranged with the sliding coatings 14 such that they are located in
constant contact with the belt 8. It is also possible that the
additional guide device 22 located in the radial direction inside
the belt drive is arranged at a different position in the radial
direction inside of the belt drive, or other guide devices are
provided in the radial direction inside the belt drive.
[0047] It is also possible that only one guide device 22 or several
guide devices each with only one guiding surface allocated to the
belt 8 are arranged in the radial direction inside the belt
drive.
[0048] The guide body 13 of the guide device 22 can be connected
mechanically in another variation to one of the two other guide
bodies 2 or 5 or also to both guide bodies 2 and 5 in a suitable
way.
[0049] FIG. 2 likewise shows a belt drive of an internal combustion
engine with a circulating traction means constructed as a belt 8
and connecting a driven wheel and at least one drive wheel. In the
present case, the drive of the belt disk 9 is transmitted by the
belt 8 to the two belt disks 10. In the slack strand, in turn, a
first tensioning device 20 composed of a tensioner 1 that can be
activated by pressurized medium and a guide body 2 with a sliding
coating 3 is arranged.
[0050] On the tightened strand, there is a second tensioning device
30 with a guide body 35 featuring a sliding coating 7. The guide
body 35 is acted upon by a spring 6 with a force, wherein the
spring attachment 11 can be realized on a stationary part, for
example, on the housing of the internal combustion engine. In
addition, a piston-cylinder arrangement 31 is connected to the
guide body 35 and to the housing of the internal combustion engine,
such that the guide body 35 of this second tensioning device 30 can
be moved away from the belt 8 against the contact force of the
spring 6.
[0051] To enable the movement of the guide body 35 of this second
tensioning device 30, this also features two elongated recesses 51
and 52, which are aligned in the direction toward the tightened
strand of the belt 8 and which are intersected by two attachment
points 4 constructed as stay bolts, so that the guide body 35 is
arranged so that it can move in the direction toward the belt
8.
[0052] During operation of the internal combustion engine, a
sufficiently large pressurized medium pressure is generated, which
is led to the tensioner 1 of the first tensioning device 20 and to
the piston-cylinder arrangement 31 of the second tensioning device
30. Therefore, the first tensioning device 20 presses against the
belt 8 in order to tension the belt, while the piston-cylinder
arrangement 31 of the second tensioning device 30 is acted upon
with oil pressure 12, such that the guide body 35 lifts from the
belt 8 in a friction-reducing way against the force of the spring 6
or contacts the belt 8 at least with low force in a guiding manner
on this belt strand.
[0053] If the internal combustion engine is turned off and thus
there is no more pressurized medium available for the tensioner 1
or for the piston-cylinder arrangement 31, then the tensioner 1 of
the first tensioning device 20 also cannot tension the belt 8. Now
if the belt 8 becomes longer than its installed dimension due to
wear, this leads to a belt 8 suspended in the belt drive that is
overall only relatively looser without additional means. Now if the
internal combustion engine is started again, undesired tooth
jumping can occur on the drive disk 9 and/or on the driven disks
10, which would lead to phase or rotational angle errors of the
shafts in this belt drive.
[0054] Because the piston-cylinder arrangement 31 of the second
tensioning device 30 for a deactivated drive motor or for no or
insufficient pressurized medium pressure does not generate a
counter force overcoming the force of the spring 6, the spring 6
presses the guide body 35 against the belt 8 just with this spring
force F1, so that the belt is also tensioned in this operating
position and tooth jumping is reliably prevented.
[0055] In contrast, for an activated drive motor, that is, during
operation of the belt 8, sufficient oil pressure 12 for the
tensioner 1 that can be activated by pressurized medium is
generated, which acts against the spring force F1 of the spring 6
with a force F2 on the belt 8 or the second tensioning device 30
arranged in the slack strand, which is greater than the spring
force F1. Therefore, the guide body 35 is pressed outward until, as
FIG. 2 shows, the attachment points 4 constructed as stay bolts are
located at the left stop of the recesses 51, 52 in the guide body
35 of the second tensioning device 30.
[0056] In contrast to FIG. 2, FIG. 3 shows a belt drive, in which
the guide body 45 of a second tensioning device 40 provided in the
slack strand has a deformable construction. For this purpose, in
this embodiment the guide body 45 has a two-part construction,
wherein this is fixed so that it can pivot on attachment points 4
at the ends of its longitudinal extent. The two individual parts 41
and 42 of the multiple-part guide body 45 are connected to each
other so that they can pivot in a middle region of this body at an
attachment point 4'. A spring 6, which is fixed in position on the
motor housing, for example, with its other end, also engages to
this attachment point 4'. For this embodiment, the spring force F1
generated by the spring 6 and acting in the direction toward the
belt 8 is also smaller than the force F2 generated by the first
tensioning device 20 and acting on the guide body 45 via the belt 8
in the activated drive motor.
[0057] The belt drive shown in FIG. 4 has, in contrast to the
variant according to FIG. 2, in the tightened strand a second
tensioning device 50, in which the one-part guide body 55 is fixed
to two end-side attachment points 4 and in which a spring 6' is
arranged between the sliding coating 7 and the guide body 55. The
term sliding coating is understood in this connection not as a
coating of a body but instead the body itself, which is in contact
with the belt 8 in a spring-loaded manner.
[0058] However, this so-called sliding coating 7 itself (as shown
in FIG. 5) can also have a spring-elastic, for example, leaf
spring-shaped construction, which is supported on the end on a
guide body 65 according to the second tensioning device 60 shown
there. This guide body 65 is here fixed to the housing also at two
attachment points 4. For the belt drives shown in FIG. 4 or FIG. 5,
the spring force F1 generated by the spring 6' or the
spring-elastic sliding coating 7 itself in the direction toward the
belt 8 is also smaller than the force F2 generated by the tensioner
1 of the first tensioning device 20 that can be activated by
pressurized medium and guided by the belt 8 to the guide body 55 or
65.
[0059] In contrast to the embodiment according to FIG. 2, FIG. 6
shows a belt drive with a second tensioning device 70, in which a
guide body 75 of this second tensioning device 70 provided on the
tightened strand is hinged so that it can pivot via an attachment
point 4 only in a lower region pointing toward the drive element 9.
In addition, the two tensioning devices 20, 70 arranged in the
slack strand and tightened strand, respectively, are connected
elastically to each other via a spring 6. Therefore, it is achieved
that the belt 8 is acted upon with a basic tension that overcomes
belt slack that is too much independent of the pressure supply for
the tensioner 1 that can be activated by pressurized medium both in
the slack strand and also in the tightened strand.
[0060] For an internal combustion engine during operation,
pressurized medium under sufficient operating pressure is generated
for the tensioner 1, so that this tensions a belt 8 compensating
for belt slack caused by wear. The spring 6 between the first
tensioning device 20 and the second tensioning device 70 also
generates in this operating phase a contact force, with which the
guide body 75 is pressed against the belt 8.
[0061] If the pressure supply for the tensioner 1 that can be
activated by pressurized medium is interrupted, this definitely
leads to a restoring motion of the guide body 2 of the first
tensioning device 20 away from the belt 8, because the spring 6 is
pulled along for this restoring movement but with its end fixed to
this guide body 2, the force at least of the guide body 75 of the
second tensioning device 70 on the belt 8 remains at least the same
size. An undesired large belt slack, as well as tooth jumping in
the belt drive, is reliably prevented.
[0062] In FIG. 7, in a modification to the embodiment according to
FIG. 6, a belt drive is shown, in which a lever-like connection
element 15 or 16 is hinged to a corresponding attachment point 4''
on the guide bodies 2 and 85 of the two tensioning devices 20 and
80 arranged on the slack strand or tightened strand in their region
pointing away from the drive element 9. These connection elements
15 or 16 are connected to each other in an articulated manner with
their other end at a connection point 48. In turn, a spring 6,
whose spring force acts on the guide body 2 or 5 through the use of
the lever-like connection elements 15 or 16 for approximately the
same parts, engages at this connection point 48. This happens in
that the belt 8 is acted upon with a basic tensioning force that
tensions a slack belt 8 for no compressed-means supply for the
tensioner 1 independent of the tensioner 1 that can be activated by
pressurized medium both in the slack strand and also in the
tightened strand. In the operating behavior, that is, for an
activated or deactivated pressure supply for the tensioner 1, these
two tensioning devices 20 and 80 according to FIG. 7 act like the
two tensioning devices 20 and 70 according to FIG. 6.
[0063] In contrast to the embodiment according to FIG. 6, in the
belt drive shown in FIG. 8, the guide body 2, 95 of the two
tensioning devices 20 and 90 are each acted upon by a spring 6 with
a spring force. In this way, it is also achieved that the belt 8 is
acted upon with a spring-generated basic tensioning force
independent of an activation force of the tensioner 1 that can be
activated by pressurized medium both in the slack strand and also
in the tightened strand. Here, for a stopped pressurized medium
supply for the tensioner 1, the guide bodies 2 and 95 each press
onto the belt 8 via an associated spring 6, so that tooth jumping
of the belt means 8 is prevented, compensating for too much
undesired belt slack.
[0064] Deviating from the embodiment according to FIG. 6, in the
belt drive shown in FIG. 9, the guide bodies 2 and 105 supported so
that they can pivot on one side at the attachment points 4 in the
two tensioning devices 20 and 100 each act with a spring force on
their lower end close to the drive wheel through torsion springs 6'
constructed as leg springs. The torsion springs 6' are here
supported against stationary spring attachment points 11'. In this
way, it is also achieved that the belt 8 is acted upon with a basic
tensioning force independent of the tensioner 1 that can be
activated by pressurized medium both in the slack strand and also
in the tightened strand. Belt lengthening caused by wear is
compensated in this way and also, finally, rotational angle errors
between the shafts rotating in the belt drive are prevented.
[0065] As the embodiments according to FIGS. 6 to 9 make clear,
also for these embodiments, during operation of the belt means or
when pressure is applied to the tensioner 1 that can be activated
by pressurized medium, a force F1 acts via the second tensioning
device 30, 40, 50, 60, 70, 80, 90, 100 on the belt means 8, with
this force being smaller than the force F2 that the belt means 8
itself exerts during operation on these second tensioning devices
30, 40, 50, 60, 70, 80, 90, 100.
[0066] The second tensioning devices 40, 50, 60, 70, 80, 90, and
100 according to FIGS. 3 to 9 can also be equipped with a
piston-cylinder arrangement 31 according to FIG. 2, which presses
such a second tensioning device away from the belt 8, reducing
friction, when during operation of the drive motor, a sufficiently
high pressurized medium pressure is provided for the tensioner 1
that can be activated by pressurized medium in the first tensioning
device 20, so that this can reliably tension a non-tensioned belt
means 8 that becomes too loose in the belt drive (not shown).
LIST OF REFERENCE SYMBOLS
[0067] 1 Tensioner that can be activated by pressurized medium
[0068] 2 Guide body of slack strand [0069] 3 Sliding coating of
guide of slack strand [0070] 4 Attachment point [0071] 4'
Attachment point, hinge point [0072] 4'' Attachment point [0073] 5
Guide body on guide body [0074] 6 Spring [0075] 6' Torsion spring
[0076] 7 Sliding coating or surface of guide body [0077] 8 Belt,
belt means [0078] 9 Drive element, belt disk on crankshaft [0079]
10 Drive element, belt disk on camshaft [0080] 11 Spring attachment
[0081] 11' Spring attachment [0082] 12 Oil pressure [0083] 13 Guide
body of inner guide device [0084] 14 Sliding coating of guide of
inner guide device [0085] 15 Connection element [0086] 16
Connection element [0087] 20 First tensioning device [0088] 21
Second device, second tensioning device [0089] 22 Guide device
[0090] 23 Guide channel [0091] 24 Guide channel [0092] 30 Second
tensioning device [0093] 31 Piston-cylinder arrangement [0094] 35
Guide body [0095] 40 Second tensioning device [0096] 41 Individual
part of guide body 40 [0097] 42 Individual part of guide body 40
[0098] 45 Guide body [0099] 48 Connection point [0100] 50 Second
tensioning device [0101] 51 Recess of guide body [0102] 52 Recess
of guide body [0103] 55 Guide body [0104] 60 Second tensioning
device [0105] 65 Guide body [0106] 70 Second tensioning device
[0107] 75 Guide body [0108] 80 Second tensioning device [0109] 85
Guide body [0110] 90 Second tensioning device [0111] 95 Guide body
[0112] 100 Second tensioning device [0113] 105 Guide body [0114] F1
Force of second tensioning device on belt means [0115] F2 Force of
belt means during its operation on second tensioning device
* * * * *