U.S. patent application number 10/486042 was filed with the patent office on 2005-06-16 for method and system for cooling the clutch system of a transmission.
This patent application is currently assigned to Luk Lamellen und Kupplungsbau Beteiligungs KG. Invention is credited to Ahnert, Gerd, Lang, Dietmar, Pollack, Burkhard, Schneider, Matthias.
Application Number | 20050126877 10/486042 |
Document ID | / |
Family ID | 7694565 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126877 |
Kind Code |
A1 |
Schneider, Matthias ; et
al. |
June 16, 2005 |
Method and system for cooling the clutch system of a
transmission
Abstract
A method and apparatus for reducing the thermal load on a motor
vehicle clutch system. The clutch includes at least a pressure
plate, a clutch disk, and a flywheel, by way of which a torque is
transmitted. The friction forces that exist on the respective
friction surfaces of the clutch disk are unevenly distributed. The
clutch is cooled by a flow of cooling air that is led through the
clutch bell that encloses the clutch and that defines a housing.
The cooling air is conducted from the existing ventilation air
inlets of the vehicle, and a jet pump arranged in the exhaust
system is disclosed for withdrawing the cooling air from the clutch
housing.
Inventors: |
Schneider, Matthias;
(Kilstett, FR) ; Ahnert, Gerd; (Sasbach, DE)
; Lang, Dietmar; (Hoheischweiler, DE) ; Pollack,
Burkhard; (Buhl, DE) |
Correspondence
Address: |
ALFRED J MANGELS
4729 CORNELL ROAD
CINCINNATI
OH
452412433
|
Assignee: |
Luk Lamellen und Kupplungsbau
Beteiligungs KG
Industriestrasse 3
Buhl
DE
D-77815
|
Family ID: |
7694565 |
Appl. No.: |
10/486042 |
Filed: |
May 3, 2004 |
PCT Filed: |
August 1, 2002 |
PCT NO: |
PCT/DE02/02832 |
Current U.S.
Class: |
192/113.2 ;
192/107M |
Current CPC
Class: |
F16D 13/64 20130101;
B60K 13/04 20130101; Y10T 477/677 20150115; Y10T 477/688 20150115;
Y10T 29/49826 20150115; Y10T 29/49815 20150115; Y10T 29/49822
20150115; B60K 17/02 20130101; Y10T 29/49904 20150115; F16D 13/58
20130101; F16D 2300/12 20130101; Y10T 29/4984 20150115; F16D 13/72
20130101 |
Class at
Publication: |
192/113.2 ;
192/107.00M |
International
Class: |
F16D 013/72 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2001 |
DE |
101 38 570.6 |
Claims
1. A method for reducing the thermal load in a clutch system that
includes at least a pressure plate, a clutch disk, and a flywheel,
said method comprising the steps of: transmitting a torque between
respective friction surfaces of the pressure plate, the clutch
disk, and the flywheel, and unevenly distributing frictional torque
that acts at each friction surface of the clutch disk.
2. A method in accordance with claim 1, including the step of
providing different friction linings with different coefficients of
friction on respective opposite friction surfaces of the clutch
disk.
3. A method in accordance with claim 1, including the step of
providing a lower coefficient of friction on a pressure-plate-side
friction surface of the clutch disk than on a flywheel-side
friction surface of the clutch disk, so that a smaller amount of
frictional energy is introduced into the pressure plate than into
the flywheel.
4. A method in accordance with claim 3, including the step of
providing on the flywheel-side of the clutch disk a friction lining
having a higher coefficient of friction at increasing
temperature.
5. A method in accordance with claim 1, including the step of
providing identical friction linings on respective sides of the
clutch disk, and providing different friction characteristics at a
pressure-plate to clutch disk interface and at a flywheel to clutch
disk interface for a desired frictional torque distribution.
6. A method in accordance with claim 5, wherein the friction
characteristics of at least one of the pressure plate and the
flywheel are provided by a combination of steel and aluminum
friction surfaces.
7. A method in accordance with claim 1, wherein the clutch disk has
identical friction linings on respective sides thereof and each
friction exhibits such interface has a temperature dependence in
the case of identical to provide a lower coefficient of friction
with increasing temperature, whereby a higher temperature occurs at
the pressure plate than at the flywheel, so that a desired
coefficient of friction difference is realized at the pressure
plate and the flywheel sides of the clutch disk.
8. A method in accordance with claim 1, wherein a higher
coefficient of friction exists at a friction surface on the
pressure-plate side of the clutch disk than at a friction surface
on the flywheel side when the pressure plate is cooled.
9. A method in accordance with claim 8, wherein a
temperature-resistant friction lining is utilized as the friction
lining at each friction surface.
10. A method in accordance with claim 1, including the step of
introducing a cooling airflow into a housing that surrounds the
clutch.
11. A method in accordance with claim 10, including the step of
utilizing at least one existing air inlet for the ventilation of
the interior of a motor vehicle as an inlet for the cooling
airflow, and conducting the cooling airflow through the clutch
housing.
12. A method in accordance with claim 10, wherein cooling airflow
is withdrawn from the housing to the environment through an
existing exhaust system of the vehicle.
13. A method in accordance with e claim 10, wherein the cooling
airflow is provided by a pump means positioned in the exhaust gas
flow of the exhaust system.
14. A method in accordance with claim 13, wherein the pump means is
a jet pump.
15. A method in accordance with claim 10, including the step of
Periodically interrupting the cooling airflow by a blocking means
to allow a stationary exhaust gas measurement
16. A method in accordance with claim 15, wherein the blocking
means is a shutter.
17. A method in accordance with claim 10, wherein the clutch is
included in a power train that includes one of a load-shift
transmission and a double-clutch transmission.
18. A system for cooling a clutch in a motor vehicle power train,
said system comprising: a flywheel, a clutch disk, and a pressure
plate, wherein the flywheel and the pressure plate frictionally
engage respective opposed surfaces of the clutch disk, a clutch
bell that surrounds at least the clutch disk and the pressure plate
as a clutch housing, and means for introducing a cooling airflow
into the clutch housing.
19. A system in accordance with claim 18, wherein the means for
introducing cooling airflow includes as an air inlet at least one
existing air inlet for the ventilation of the interior of the motor
vehicle.
20. A system in accordance with claim 18, wherein an existing
exhaust system of the motor vehicle is in communication with the
clutch housing for withdrawal of cooling airflow from the clutch
housing.
21. A system in accordance with one claim 20, including pump device
is means in the exhaust gas flow of the exhaust system for
producing the cooling airflow.
22. A system in accordance with claim 21, wherein the pump means
includes at least one jet pump.
23. A system in accordance with claim 20, including blocking is
means provided in the exhaust system for blocking flow into an
exhaust gas stream of cooling airflow from the clutch housing.
24. A system in accordance with claim 23, wherein the blocking
means is a shutter.
25. A system in accordance with claim 18, wherein the system is
incorporated into a motor vehicle power train that includes a
high-performance clutches clutch and at least one of a load-shift
transmission and a double-clutch transmission.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for the reduction
of thermal loads and a method for cooling clutch systems, as well
as a system therefor.
[0003] 2. Description of the Related Art
[0004] It has been shown that the thermal economy in clutch
systems, such as, for example, a dry friction clutch, is
problematic, especially at high power input. A thermal overload is
especially to be suspected in a load-shift clutch of an
uninterruptible transmission (USG).
[0005] The components of the clutch, especially the friction
lining, have a limited temperature resistance, and the energy input
is very high in relation to the available space, whereby the heat
transfer to the environment is too low.
[0006] In addition, the pressure plate, for example, has a smaller
heat capacity in contrast to the flywheel of the clutch.
Furthermore, the heat flow to the surrounding parts is relatively
low and the heat transfer to the surrounding air within the clutch
bell housing is also low. Thus, there is a limit relative to the
operation of the clutch system as a result of the expected
temperature rise in known clutch systems, especially of the
pressure plate.
[0007] Therefore, especially in load-shift transmissions, it is a
necessity that the temperature load on the clutch be lowered by
cooling measures. In the case of a so-called inline transmission,
for example for a rear drive motor vehicle, an open type of
construction, which of a certain size makes cooling possible
(tunnel assembly, water spray, near the exhaust system), can only
be realized with limitations.
[0008] The object of the present invention is directed to a method
and a system of the above-described type that makes possible the
optimal cooling of a clutch system of a power train, so that the
operating conditions of the clutch system in particular are
improved.
SUMMARY OF THE INVENTION
[0009] The object of the invention is particularly achieved by
providing a method for the reduction of the thermal load on a
clutch system with which torque is transmitted. The clutch system
includes at least a pressure plate, a clutch disk, and a flywheel,
whereby the frictional torque that exists at the time on the
friction surfaces of the clutch disk is unevenly distributed.
[0010] The frictional load generated in the clutch system is
determined by the frictional torque that acts and the relative
speed. In known clutch systems an identical speed condition at both
friction surfaces of the clutch disk is preferred. A solution can
consequently lie in producing uneven frictional torques on the
respective friction surfaces. In that way, the pressure plate, for
example, can be supplied with a smaller portion of the frictional
energy that occurs, so that the thermal load is reduced.
[0011] Within the scope of the invention a further embodiment can
be provided in which different friction linings with different
coefficients of friction can be utilized at the two friction
surfaces of the clutch disk. The frictional load that is produced
is thereby introduced unequally to the two friction surfaces by
providing different friction parameters at both frictional sides of
the clutch disk.
[0012] The frictional torque that is generated depends on the
effective friction radius, the contact pressure of the pressure
plate, and the coefficient of friction of the respective friction
surfaces. Influencing the clutch system coefficient of friction
conditions provides the possibility to suitably distribute the
thermal load. It is also conceivable that the other influence
values could be changed.
[0013] In the method in accordance with the invention several
possibilities are provided for influencing the coefficient of
friction conditions in the clutch system, which are described
below.
[0014] For example, a lower coefficient of friction can be utilized
on the pressure-plate-side friction surface of the clutch disk than
on the flywheel-side friction surface, so that a lesser amount of
frictional energy is introduced on the pressure plate than on the
flywheel. In that way, a desired distribution of the frictional
load can be realized. Thereby, in an advantageous way, lower
thermal loads arise on the pressure plate.
[0015] In accordance with the invention, by the use of different
friction linings on the clutch disk it can be provided that the
respective friction partners on the flywheel-side are selected in
such a way that a higher coefficient of friction arises when the
temperature increases. For example, the clutch disk can have
different friction linings on its two friction surfaces. The
friction partners on the flywheel-side have such a type of
temperature dependence that a higher coefficient of friction arises
with increasing temperature. If, as expected, a higher temperature
arises at the friction point during the operation of the clutch,
the coefficient of friction on the pressure plate side decreases,
so that the desired coefficient of friction difference is
adjusted.
[0016] In addition, in accordance with the invention it can be
provided that in the case of identical friction linings on the
clutch disk two friction partners with different characteristics
are utilized, so that the desired coefficient of friction
difference or frictional torque distribution results. For example,
the pressure plate and the flywheel can be made from combinations
of the materials steel and aluminum.
[0017] Furthermore, in the case of identical friction linings on
the clutch disk, it can be provided that the respective friction
partners have such a temperature dependence that a lower
coefficient of friction arises with increasing temperature, whereby
a higher temperature exists on the pressure plate than on the
flywheel, so that the desired coefficient of friction difference is
realized.
[0018] The previously-described possibilities can also be
arbitrarily combined in order to further improve the proposed
method.
[0019] Alternatively, in the method in accordance with the
invention it can also be provided that a higher coefficient of
friction is utilized on the pressure-plate-side friction surface of
the clutch disk, for example, than on the flywheel-side friction
surface if the pressure plate is suitably cooled. In that way,
under certain circumstances, namely when cooling measures are
carried out at the pressure plate, a reverse friction load
distribution is also conceivable. Thereby, a higher temperature of
the pressure plate, for example, can lead to an altogether better
heat elimination at the clutch system by reason of a higher
temperature differential. At the same time, it must be noted,
however, that a temperature-resistant friction lining must be
utilized at each friction surface as the friction lining.
[0020] Furthermore, the underlying object of the invention is also
especially achieved in that a method is proposed for cooling the
clutch in a power train of a motor vehicle, in which a flow of
cooling air for the clutch is utilized. Furthermore, particularly
for carrying out the method, a system for cooling the clutch of a
power train of a motor vehicle is proposed, wherein a flow of
cooling air is provided that can be conducted through the clutch
bell surrounding the clutch as a housing.
[0021] Advantages and additional embodiments of the system and the
method in accordance with the invention for cooling the clutch of a
power train are described in greater detail below.
[0022] In accordance with an advantageous further development of
the invention, the already-existing air inlets of the motor
vehicle, for example for the ventilation of the interior, can be
utilized as a cooling airflow to cool the clutch. Preferably, the
flow of cooling air can be guided through the clutch bell that
surrounds the clutch as a housing.
[0023] For that purpose, the inlets, for example, could be designed
and dimensioned accordingly. All together, the advantage of using
already-existing air inlets is that, for example, filters, dirt
pans, water drains, and the like, only have to be provided once in
a motor vehicle because of their dual usage. In addition, by means
of the air passages provided, acoustic advantages can be realized
in contrast with open clutches.
[0024] Within the scope of an arrangement of the invention, the
exiting cool air flow can be carried off to the environment using
the existing exhaust gas system of the motor vehicle. The cool air
flow can thus be carried off through the exhaust gas system
together with the exhaust gas. Especially in motor vehicles with
rear drive, the exhaust system is located near the transmission. In
accordance with that arrangement there results the advantage that
in that way clutch noises are not considered to be disturbing in
the surrounding area because of the muffler.
[0025] Preferably, the cool air flow can be provided by a pump
device provided in the exhaust gas flow of the exhaust gas system.
The cool airflow can thereby be drawn off through the clutch bell.
The pump device can especially be a jet pump, or the like, which is
preferably provided in the exhaust gas stream. In that way, other
necessary (active) cooling measures can be avoided.
[0026] It is also possible that the cool airflow is interrupted at
least periodically through a shutter device in the exhaust system,
so that an independent stationary exhaust gas measurement is made
possible. Preferably, at least a flap, or the like, can be utilized
as a shutter device.
[0027] Preferably, the proposed system and method can be utilized
in high performance clutches, especially in a load-shift
transmission (USG) and/or a double-clutch transmission (DKG).
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Additional advantages and embodiments follow from the
dependent claims and the following description and drawings in
which:
[0029] FIG. 1 is a schematic view of a system for cooling a clutch
with a jet pump; and
[0030] FIG. 2 is a graph with the results of a simulation
calculation for a method for reducing the thermal load of a
clutch.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] There is shown in FIG. 1 one possible embodiment of a system
in accordance with the invention to cool a clutch, whereby an
engine 101 with a connected exhaust gas system 102, and a
transmission 103 with a clutch bell 104, as well as a drive shaft
105, are shown in schematically. In addition, there is shown in
FIG. 1 an exemplary existing air inlet 107, for example for the
windshield for ventilating the motor vehicle interior, which is
utilized additionally for the cooling airflow in accordance with
the invention. Other air inlets can also be provided for the
cooling airflow.
[0032] The cooling airflow can be withdrawn from the clutch bell
104 by means of at least one air outlet 108 through a jet pump 106.
The jet pump 106 is located in the exhaust system 102, and which is
shown larger in the FIG. 1 enlargement portion.
[0033] The system in accordance with the invention, by
interconnection with the existing air inlet system and exhaust gas
system provided in the motor vehicle, can enable the supply and
withdrawal of the cooling airflow in accordance with the invention
for the cooling of the clutch.
[0034] The system can especially be utilized in connection with a
load-shift transmission (USG), a double-clutch transmission (DKG),
and all types of high-performance clutches that require (air)
cooling.
[0035] In FIG. 2 there is shown the result of a simulation
calculation for a method for reducing the thermal load on a clutch.
There are shown therein different temperature trends over time.
[0036] The simulation model was prepared for a load-shift clutch of
a USG system. In that way, the effect of the changed coefficients
of friction can be shown.
[0037] Moreover, the coefficients of friction of the respective
friction surfaces are assumed, one time with a constant ratio (1:1)
and one time with a ratio of 0.7:1. A plurality of maximum
accelerations of the motor vehicle to a speed of 100 km/h were
assumed as the loading. The upper curve of the pressure plate
temperature TDP signifies the coefficient of friction ratio of 1:1,
while the lower curve shows the pressure plate temperature T.sub.DP
at the coefficient of friction ratio of 0.7:1.
[0038] One can clearly appreciate that the pressure plate
temperature is lower at a coefficient of friction ratio of 0.7:1.
The temperatures of the flywheel T.sub.SR by comparison increased
only slightly. That is perceptible in the curve for T.sub.SR.
[0039] The patent claims included in the application are
illustrative and are without prejudice to acquiring wider patent
protection. The applicants reserve the right to claim additional
combinations of features disclosed in the specification and/or
drawings.
[0040] The references contained in the dependent claims point to
further developments of the object of the main claim by means of
the features of the particular claim; they are not to be construed
as renunciation to independent, objective protection for the
combinations of features of the related dependent claims.
[0041] Although the subject matter of the dependent claims can
constitute separate and independent inventions in the light of the
state of the art on the priority date, the applicants reserve the
right to make them the subject of independent claims or separate
statements. They can, moreover, also embody independent inventions
that can be produced from the independent developments of the
subject matter of the included dependent claims.
[0042] The exemplary embodiments are not to be considered to be
limitations of the invention. On the contrary, many changes and
variations are possible within the scope of the invention in the
existing disclosure, in particular such variants, elements, and
combinations and/or materials which, for example, are inventive by
combining or modifying single features that are in combination and
are described individually in relation to the general specification
and embodiments as well as the claims and shown in the drawings, as
well as elements or method steps that can be derived by a person
skilled in the art in the light of the disclosed solutions of the
problem, and which by means of combined features lead to a new
object or new method steps or sequences of method steps, as well as
manufacturing, testing, and operational procedures.
* * * * *