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Can you provide more detailed comparisons (pros/cons) between hydro-mech and electro-mech
activated DCT?
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Basically, from a fuel efficiency benefit viewpoint, both systems are close. Hydro-mechanical
has the benefit of packaging and clutch response over electro-mechanical. The choice
for the most part is determined by customer requirements and preferences.
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When BW has dry clutch DCT, what torque range do you expected?
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The dry clutch torque range will be up to 300 Nm, but an additional range will be
required for the transmission. This additional range will need to act like a creeper
gear. This gear is required for reasonable thermal performance of the clutch. Wet
clutch technology is better suited for large thermal energies.
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The dry clutch torque range will be up to 300 Nm, but an additional range will be
required for the transmission. This additional range will need to act like a creeper
gear. This gear is required for reasonable thermal performance of the clutch. Wet
clutch technology is better suited for large thermal energies.
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Analysis shows pressures higher than 100 Bar will begin to degrade system performance
and efficiency.
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Does a BorgWarner "moist clutch" DCT have different fluid requirements than a typical
wet clutch DCT?
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Moist clutch is a system optimization between clutch friction and oil characteristics.
BW has been active in the development of both and isworking with fluid technology
companies such as Lubrizol.
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Are there any basic patents in force that would generally restrict widespread use
of DCTs?
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The basic layout for DCT is unrestricted. BorgWarner's New High Efficiency configuration
layout is covered by BW patents.
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How much of a wet DCT clutch duty cycle needs to be operated in "dry" mode in order
to be competitive with a dry DCT in terms of parasitic loss?
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The primary benefit of the dry clutch is low or no drag at idle conditions. While
the vehicle is in motion dry clutch has no benefit. The prevalence of start/stop
will eliminate this efficiency benefit for dry clutch.
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Will a DCT require a clutch change during life circle? And is it relatively easy
to change?
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No clutch change will be required for normal operation. BorgWarner Wet Clutch is
designed for the life of the vehicle.
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Why is slipping performance an important characteristic in DCT?
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Clutch slipping or micro slip performance is very important for vehicle creep. The
micro slip has additional benefit that allows for the clutches to be very responsive
for clutch-to-clutch shifting. One last item is that micro slip allows for better
NVH performance of the system.
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What percentage of the hybrid market do you believe DCT will support in the future?
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DCTs have the best architecture for conversion into hybrids. This is due to the
many hybrid types that can be created using the DCT as the base architecture.
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Does BorgWarner offer individual DCT components for small companies working on
DCT design and manufacture?
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Yes. BW is working to offer standard modules that can be incorporated in customer
transmissions. Customization is also possible.
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What driving cycle was used to get the 15% improvement in fuel consumption and what
transmission were you comparing the DCT to?
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15% is the top range for improvement; for some application, this will be less. The
base system used for comparison is a planetary automatic with torque converter.
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Does DCT use pressure sensors to control clutch pressures via closed loop? How important
is it to control DCT clutch pressure accurately?
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Controlling clutch pressure accurately allows for better micro slip of the clutches.
Operating the system at the micro slip level allows the overall system pressure
to be lowered. This lowering of the system pressure then improves fuel economy.
BorgWarner is actively improving the accuracy of our solenoids.
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What is the expected mileage replacement interval for the clutch friction material
in high performance applications?
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If the proper oil characteristics are maintained, the clutch material does not have
to be changed. The clutch friction plates would only have to be changed due to some
system failure.
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