Torque Converter Evolution at Luk: Professional Article

Transcrição

Publisher: LuK GmbH & Co.
Industriestrasse 3 • D -77815 Bühl/Baden
Telephon +49 (0) 7223 / 941 - 0 • Fax +49 (0) 7223 / 2 69 50
Internet: www.LuK.de
Editorial: Ralf Stopp, Christa Siefert
Layout: Vera Westermann
Layout support: Heike Pinther
Print: Konkordia GmbH, Bühl
Das Medienunternehmen
Printed in Germany
Reprint, also in extracts, without
authorisation of the publisher forbidden.
Foreword
Innovations are shaping our
future. Experts predict that there
will be more changes in the fields
of transmission, electronics and
safety of vehicles over the next
15 years than there have been
throughout the past 50 years. This
drive for innovation is continually
providing manufacturers and suppliers with new challenges and is
set to significantly alter our world
of mobility.
LuK is embracing these challenges. With a wealth of vision and
engineering performance, our
engineers are once again proving
their innovative power.
Bühl, in April 2002
This volume comprises papers
from the 7th LuK Symposium and
illustrates our view of technical
developments.
Helmut Beier
We look forward to some interesting discussions with you.
President
of the LuK Group
Content
1
DMFW – Nothing New? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2
Torque Converter Evolution at LuK . . . . . . . . . . . . . . . . . . . . . . . 15
3
Clutch Release Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4
Internal Crankshaft Damper (ICD). . . . . . . . . . . . . . . . . . . . . . . . . 41
5
Latest Results in the CVT Development. . . . . . . . . . . . . . . . . . . . 51
6
Efficiency-Optimised CVT Clamping System . . . . . . . . . . . . . . . 61
7
500 Nm CVT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
8
The Crank-CVT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
9
Demand Based Controllable Pumps. . . . . . . . . . . . . . . . . . . . . . . 99
10
Temperature-controlled Lubricating Oil Pumps Save Fuel . . . 113
11
CO2 Compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
12
Components and Assemblies for Transmission Shift Systems 135
13
The XSG Family . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
14
New Opportunities for the Clutch? . . . . . . . . . . . . . . . . . . . . . . . 161
15
Electro-Mechanical Actuators . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
16
Think Systems - Software by LuK. . . . . . . . . . . . . . . . . . . . . . . . 185
17
The Parallel Shift Gearbox PSG . . . . . . . . . . . . . . . . . . . . . . . . . 197
18
Small Starter Generator – Big Impact . . . . . . . . . . . . . . . . . . . . . 211
19
Code Generation for Manufacturing . . . . . . . . . . . . . . . . . . . . . . 225
Lu K
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Torque Converter Evolution at
LuK
Marc McGrath
Bruno Müller
Edmund Maucher
Bhaskar Marathe
George Bailey
2
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15
2
Torque Converter Evolution at LuK
Introduction
For many years, LuK has been recognised as
a powertrain specialist with state-of-the-art
torsional vibration isolation technology. This
expertise lead LuK into the Toque Converter
Clutch and Damper powertrain arena. Following the successful completion of the first
Torque Converter Clutch projects, LuK focused energy on the entire Torque Converter
system. LuK has evolved into a premier
Torque Converter (TC) and Torque Converter
Clutch (TCC) supplier (figure 1). Today, LuK
produces
2.5 Million
TCCs
and
350 Thousand TCs, and as early as 2005 LuK
will produce over 1.5 Million TCs per year.
1983
LuK produces the first automatic
transmission damper
(customer: Ford)
1990
LuK starts developing torque converters
1997
LuK begins WT torque converter
series production
(customer: Allison Transmission)
1998
First LuK torque converter business
awarded
(customer: GM)
2002
LuK will produce 350 Thousand TCs
and 2.5 Million TCCs
2006
LuK will produce 1.5 Million TCs
Fig. 1:
To efficiently develop torque converters, LuK
realised a tool was required to link one-dimensional fluid flow, one-dimensional design, twodimensional torus generation, and three-dimensional blade architecture. This realisation
lead to the birth of LuK’s proprietary. ‘TC Design’ program. ‘TC Design’ is capable of collectively calculating torque converter performance, torus geometry, blade angles and configuration.
As with most LuK tools, ‘TC Design’ features
a parametric variation feature enabling rapid
TC analysis. To complete the development
process, ‘TC Design’ interfaces directly with
LuK's commercial 3-D CAD and analysis software. For example, the exported torus shape
is imported into blade design software, then
the 3-D blade surface is meshed to accommodate Computational Fluid Dynamic (CFD)
analysis (figure 2). To further analyse the TC
performance, CFD is used to simulate the
flows inside the torque converter, providing insight into the physics of the fluid dynamic phenomena. This insight helps to identify TC optimisation opportunities.
LuK Torque Converter Growth
Know How
LuK torque converter development is accomplished through an integrated design approach, incorporating analytical simulation,
testing, and optimisation. The TC approach
reflects LuK's traditional holistic design and
development technique, enabling problem
identification, creativity and design optimisation before prototypes are built. Commercial
tools are not always available to properly perform the necessary development tasks; in
such cases, LuK develops proprietary tools.
16
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Fig. 2:
TC CFD Analysis
2
Engine and transmission combinations possess a vibration mode where the turbine inertia, transmission inertia and transmission input shaft stiffness resonate at the engine combustion frequency. Certain vehicles exhibit
this condition at an engine speed and magnitude which prohibits TCC engagement, due to
associated noise issues, thus degrading fuel
economy. The turbine damper alters the drive
train natural frequencies, eliminating this particular vibration mode and accordingly providing fuel economy and NVH improvements.
These improvements have been recognised
by the automotive industry and the automotive
press (figure 4).
torus
characteristic
baseline
LuK
weight
15.2 kg
9.7 kg
inertia
0.21 kg · m²
0.12 kg · m²
torus oil
volume
6010 cm³
2960 cm³
K-Factor
89
89
305 mm
280 mm
size
Fig. 3:
Torque Converter Size Reduction
LuK TC development tools yield
TCs with characteristics that were
previously unthinkable. A recent
challenge was to reduce the TC size,
weight and inertia, while simultaneously flattening the K-Factor curve, and
increasing the engine torque (figure 3).
Furthermore, LuK has developed tools to
simulate the performance of the entire vehicle, to estimate changes in fuel economy,
NVH, and vehicle performance for various
TC and TCC designs. Perhaps the most famous damper solution is the Turbine Damper, which was developed utilising LuK’s TC
and TCC tools.
Fig. 4:
Turbine Damper on the Road of Success
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2
Future
powertrain arrangements and themes need to
be considered:
The key to LuK’s TC growth has been to address
today’s needs, while focusing on tomorrow’s
challenges. To continue developing innovative
TC and TCC concepts, global powertrain trends
must be considered. Future consumers will demand more of the same:

CVT

increased torque/cylinder

fuel economy
durability
performance
comfort
cost
Powertrain engineers will approach the consumer’s desires quite differently this decade.
With respect to TC development, multiple new
Fig. 5:
18
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Slipping TCC Theory and Components
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6-speed stepped automatic
cylinder shut-off
starter alternator systems
diesels / direct injection gasoline engines
lower TCC lock-up speeds
TC idle disconnect
Building on these trends, LuK has numerous
creative new ideas to address the future challenges. The remainder of this paper will highlight a selection of LuK’s advanced concepts.
2
Grooved Cover
Slipping the TCC is an additional approach to
solving NVH issues. Unlike a damper approach, slipping the TCC provides vibration
isolation by absorbing or filtering the engine’s
vibrational energy before it excites the powertrain (figure 5). Although slipping implies efficiency reduction, the slipping TCC efficiency
is generally higher than the TC alone. An additional efficiency gain is achieved by operating the engine at a more favourable fuel consumption condition. The undesired energy
loss is converted to heat carried away by conduction and transmission oil convection. It is
critical to reduce the temperature so the friction material or the transmission fluid does not
deteriorate. Deteriorated material and/or oil
can lead to detrimental shudder or TCC control conditions.
Fig. 6:
Grooved Cover Cooling
Fig. 7:
Comparison of Cover and Facing
Grooves
Today, LuK has both development and production experience with two slipping TCC concepts, organic facings with cooling grooves
and carbon facings (figure 5). The grooved organic facing offers desired friction characteristics and a possible cost advantage, where as
the carbon technology offers improved durability especially for high energy applications.
As the current friction materials wear over life,
the cooling flow diminishes degrading the
cooling performance. LuK is currently developing the Grooved Cover concept. This concept maintains a constant flow over life
(figure 6). Since grooves in the cover don’t
wear, they don’t need to be as deep. Therefore, a greater number of grooves can be used
improving the friction interface flushing
(figure 7). Additionally, the sides of the
grooves in the steel add surface area for heat
transfer to the oil via convection. The result is
better cooling efficiency than a grooved paper
TCC with the same flow rate.
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2
Speed Dependent
Cooling
The cooling flow or oil transfer rate is depend-
For driving comfort, it is advantageous to engage the TCC at high differential speed and/or
torque levels, requiring the TCC to dissipate
large power amounts. For this scenario, it is
beneficial to increase the cooling flow relative
to power. Unfortunately, with today's production concepts, the flow is dependent on the required TCC torque. To fulfil this need, LuK is
developing an innovative concept (figure 8).
The concept links the cooling flow to the TCC
slip speed or relative engine/transmission
speed. The increased flow is achieved by
transferring oil from the apply pressure side to
piston chambers and then to the release pressure side.
sion). Since TCC torque capacity is defined by
ent on the relative speed between the TC cover (engine) and the TCC piston (transmisapply pressure, the amount of oil transferred
from one side to the other side is maintained
proportional to the torque. Accordingly, the
cooling flow varies relative to power levels.
Multifunction Torque
Converter
It is possible to further minimise losses associated within the torque converter. To maximise efficiency the TCC should remain engaged
as much as possible, yet, powertrain natural
frequencies often limit TCC operation to higher engine speeds. In manual transmission vehicles, this limitation is overcome with a dual
mass flywheel designed to lower these natural
frequencies, allowing lower operating speeds.
When a vehicle is stopped at traffic lights, the
torque converter is pumping fluid but no useful
work is being done. Some manufacturers shift
the transmission into neutral by opening a
clutch in the transmission. To move the vehicle, the clutch must be reengaged quickly,
which requires the freewheeling transmission
components to come to an abrupt stop
(figure 9). This must be done carefully or there
will be a bump when the clutch engages, similar to what is felt when a transmission is shifted into drive.
LuK has devised two- and three-pass MultiFunction Torque Converter (MFTC) concepts to
1. lower powertrain natural frequencies, and
Fig. 8:
20
LuK
Power Dependent Cooling TCC Concept
S YMP OS IUM 20 02
2. provide an idle disconnect function.
2
Fig. 9:
Benefit of Idle Disconnect in the TC
A cross-section of a two-pass concept is
is invisible to the operator, because only the
shown in figure 10. A second clutch, an im-
relatively small impeller inertia is accelerated
peller clutch, has been introduced between
instead of decelerating the turbine and trans-
the cover and impeller (or TC pump). The TCC
mission components.
release pressure (channel 2 in figure 10) is
fed between the input shaft and stator shaft,
To lock the TCC, apply pressure pushes be-
and the TCC apply pressure (channel 1 in
tween the impeller and cover and the impeller
figure 10) is fed between the pump hub and
slides toward the turbine (figure 12). The
stator shaft. At stops both pressures are kept
torque now flows from the cover, through the
high, therefore no torque is transmitted to the
damper, through the TCC, and to the input
impeller and the converter drag is eliminated.
shaft. The cover inertia is fixed to the engine,
and the impeller and turbine are fixed to the
When the driver releases the brake, the TCC
input shaft, moving the impeller inertia from
apply side is open and the release pressure
the engine into the powertrain thereby lower-
applies the impeller clutch, which is designed
ing its natural frequency. Idle resonance and
for adequate torque capacity while maintain-
start-up/shut-off noise issues are completely
ing cooling flow (figure 11). The engagement
avoided with this concept.
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2
Fig. 10: Multi-Function Torque Converter (Idle Disconnect Mode)
Fig. 11: Multi-Function Torque Converter (Torque Converter Mode)
Fig. 12: Multi-Function Torque Converter (TCC Lock-up Mode)
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Torque Reverse
Converter
To provide reverse motion, a continuous variable transmission (CVT) requires a planetary
gear set with two clutch packs. Vehicle launch
is achieved via a start up element. This can
be a fluid coupling or a torque converter. Both
the start up element and the reverse gear arrangement are only employed during limited
vehicle operations, launch and backing. Unfortunately, a considerable portion of the CVT
cost is consumed by the planetary gear set
and the start up element. To reduce the cost,
LuK’s idea is to combine the two auxiliary functions into one structural element.
Connecting the stator to the transmission
input shaft would propel the vehicle backward.
To achieve the required reverse torque, torque
multiplication can be regained by connecting
the turbine to the transmission case.
Creative
connections within
the torque
converter interchanging the transmission
input shaft and transmission case connections will provide both forward and reverse
vehicle operations.
A four-element torque converter is utilised to
independently control forward and reverse
characteristics. Three elements of the torque
converter are active in forward mode
(figure 13). In the reverse mode, all four ele-
In the forward operation, the TC stator redirects the turbine exiting fluid into the impeller,
enabling torque multiplication. The redirection
attempts to rotate the stator in the opposing
direction as compared to the turbine and impeller. The stator counter rotation is restricted
via its connection to the transmission case.
ments are active (figure 14).
Fig. 13: Torque Reverse Converter
(Forward Operation)
Fig. 14: Torque Reverse Converter
(Reverse Operation)
LuK’s Torque Reverse Converter (TRC) concept realises the required start-up and reverse
function in a single unit. This configuration not
only reduces cost, it saves crucial space as
well.
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2
Starter Alternator
Torque Converter
LuK has been involved with the development
of starter alternator systems since the early
1980s. The advantages of starter alternator
Systems are increased electrical power and
reduced fuel consumption, providing both
comfort and economy.
Combining a starter alternator with a TC
equipped drive train places new demands on
the torque converter design, and offers the
ability to disconnect the engine from the TC
and starter alternator while maintaining continuous transmission pump operation. These
demands are required to foster inertia starts
and brake regeneration.
LuK is focusing on TC solutions that meet the
previously mentioned demands. LuK is developing several torque converter starter alternator arrangements in conjunction with
various starter alternator suppliers
(figure 15).
LuK’s future advanced development efforts
are concentrating on possible configurations
with the multifunction-torque-converter where
the demands can be fulfilled without requiring
extra parts (figure 16).
Fig. 15: Starter Alternator Solutions
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Fig. 16: MFTC Starter Alternator Concept
2
Summary
tion, reverse gear, and starter-alternator
torque converters, become apparent.
At LuK, the design and development of torque
converters is achieved through an integrated
design approach, incorporating analytical
simulation, testing, and optimisation. This approach is a systematic design and development process that uses several analytical
tools. Where commercial software was not
available to perform the necessary tasks, programs were developed internally. This process was intended to optimise and improve designs, but it also allows for identification of
problem areas before prototypes are built.
This results in high-efficiency optimum torque
converter designs.
LuK is presently working on the following innovative torque converter concepts:
The torque converter clutch (TCC) and damper are integral parts of the torque converter,
and LuK has similar analytical tools to design
these components and predict their performance. LuK’s 20 years of experience results in
a perfect marriage between the TCC and
torque converter performance. Tools have
been developed to predict powertrain torsional vibrations, so that damper characteristics
can be optimised. TCC thermal models are
built so that cooling concepts can be designed
which allow continuous slipping of the clutch
to isolate vibrations.

TCCs with grooved covers instead of
grooved facings to increase interface cooling in slipping systems

Slip dependent cooling to increase the volume of cooling flow as the power generated
by the slipping TCC increases

Multi-Function Torque Converter as a combination of a dual-mass flywheel and a
torque converter

Torque converter incorporating reverse gear

Torque converters for starter alternator systems
References
[1]
Middlemann, V.;
Wagner, U:
The
Torque Converter as a System, 6th LuK
Symposium 1998.
[2]
Jürgens, G.: Transmission Systems: A
Comparitive View, 5th LuK Symposium
1994.
[3]
Middlemann, V.;
Gundlapalli, R.;
Halene, C.; Marathe, B.: Development
of Axially-Squashed Torque Converters
for Newer Automatic Transmissions,
2000 ASME International Fluids Engineering Division Annual Summer Meeting, June 11-15, 2000, Boston, MA,
FEDSM2000-11326.
[4]
Kozarekar, S.;
Maucher, E.;
Marathe, B.: Analysis of 3-Element
Torque Converter as Reverse Gear,
2000 ASME International Fluids Engineering Division Annual Summer Meeting, June 11-15, 2000, Boston, MA,
FEDSM2000-11327.
In addition, LuK has developed inhouse software to simulate the performance of the entire
vehicle. Changes in fuel economy and vehicle
performance for various torque converter designs can be predicted before a prototype vehicle is even made.
Another benefit of this integrated design and
development approach is that innovative solutions that may otherwise be overlooked,
such as improved TCC cooling for slipping applications, unique TCC damper configurations, and TC systems such as the multifunc-
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