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Drag Torque and Synchronization Modelling in a Dual Clutch Transmission

Lund, Mikael LU (2018) MMEM01 20181
Machine Elements
Abstract
Noise, vibration and harshness (NVH) is a big consideration in the automotive industry. In order
to create an as pleasant driving experience as possible for the driver, NVH should be minimized.
One of the sources of NVH comes from the transmission due to the synchronization process. When
shifting between gears, the speeds of the target gear and the output shaft it is supported by, have to
be synchronized. This is achieved through synchronization rings that, through friction, synchronize
the speeds of the components before engaging them to each other. However, there is a torque, the
gearbox’s drag torque, that can interfere with this process by slowing down the input shaft. This drag
torque therefore aids the synchronization process... (More)
Noise, vibration and harshness (NVH) is a big consideration in the automotive industry. In order
to create an as pleasant driving experience as possible for the driver, NVH should be minimized.
One of the sources of NVH comes from the transmission due to the synchronization process. When
shifting between gears, the speeds of the target gear and the output shaft it is supported by, have to
be synchronized. This is achieved through synchronization rings that, through friction, synchronize
the speeds of the components before engaging them to each other. However, there is a torque, the
gearbox’s drag torque, that can interfere with this process by slowing down the input shaft. This drag
torque therefore aids the synchronization process during an up-shift and resists it during a down-shift.
Today’s automotive industry lacks a definite method to calculate this drag torque and as a result,
values are assumed to simplify the problem.
This thesis has provided a model that calculates the drag torque at different operating conditions
depending on input speed, input torque, temperature and other variables. The drag torque comes
from several different sources in a transmission and can be separated into load dependent and speed
dependent drag torque. The sources include viscous shear in the clutch, gears churning in an oil bath,
gear windage in an air-oil mist, bearing rolling elements churning in oil, friction in bearings, friction
in gear meshes, pocketing (also called squeezing) of oil between surfaces in gear meshes and viscous
shear between concentric shafts. The load dependent are those which are generated through friction,
i.e. the friction in bearings and gear meshes. Speed dependent are those generated through resistance
from a surrounding medium.
This thesis has developed multiple models within each source of drag torque and summed them up for a
total drag torque. The results have been compared to test data to verify which combination of models
from each source of drag torque sums up to a reliable result. The thesis also shows big differences
between different models, but manages to acquire a combination of models that lies relatively close to
the test results.
The thesis has further used the new drag torque model to evaluate the friction lining on the existing
synchronizer rings of a particular transmission to see if the design is appropriate. It also analyzes how a
different inertia in the gearbox influences the maximum speed the synchronizers are able to synchronize.
Here, it is found that only frictional work and the slip time are influenced of the investigated parameters;
specific frictional work, slip time, pressure, slip speed and specific frictional power. (Less)
Popular Abstract
This paper develops a model for the drag torque in dual clutch transmission and includes it in a synchronization model. This is done in order to evaluate synchronizer ring designs and how the transmission behaves with a varied inertia.
Please use this url to cite or link to this publication:
author
Lund, Mikael LU
supervisor
organization
alternative title
Modellering av motstånd och synkronisering i en dubbelkopplad växellåda
course
MMEM01 20181
year
type
H2 - Master's Degree (Two Years)
subject
keywords
drag torque, synchronization, dual clutch transmission
language
English
id
8948437
date added to LUP
2018-06-12 12:26:07
date last changed
2018-06-12 12:26:07
@misc{8948437,
  abstract     = {Noise, vibration and harshness (NVH) is a big consideration in the automotive industry. In order
to create an as pleasant driving experience as possible for the driver, NVH should be minimized.
One of the sources of NVH comes from the transmission due to the synchronization process. When
shifting between gears, the speeds of the target gear and the output shaft it is supported by, have to
be synchronized. This is achieved through synchronization rings that, through friction, synchronize
the speeds of the components before engaging them to each other. However, there is a torque, the
gearbox’s drag torque, that can interfere with this process by slowing down the input shaft. This drag
torque therefore aids the synchronization process during an up-shift and resists it during a down-shift.
Today’s automotive industry lacks a definite method to calculate this drag torque and as a result,
values are assumed to simplify the problem.
This thesis has provided a model that calculates the drag torque at different operating conditions
depending on input speed, input torque, temperature and other variables. The drag torque comes
from several different sources in a transmission and can be separated into load dependent and speed
dependent drag torque. The sources include viscous shear in the clutch, gears churning in an oil bath,
gear windage in an air-oil mist, bearing rolling elements churning in oil, friction in bearings, friction
in gear meshes, pocketing (also called squeezing) of oil between surfaces in gear meshes and viscous
shear between concentric shafts. The load dependent are those which are generated through friction,
i.e. the friction in bearings and gear meshes. Speed dependent are those generated through resistance
from a surrounding medium.
This thesis has developed multiple models within each source of drag torque and summed them up for a
total drag torque. The results have been compared to test data to verify which combination of models
from each source of drag torque sums up to a reliable result. The thesis also shows big differences
between different models, but manages to acquire a combination of models that lies relatively close to
the test results.
The thesis has further used the new drag torque model to evaluate the friction lining on the existing
synchronizer rings of a particular transmission to see if the design is appropriate. It also analyzes how a
different inertia in the gearbox influences the maximum speed the synchronizers are able to synchronize.
Here, it is found that only frictional work and the slip time are influenced of the investigated parameters;
specific frictional work, slip time, pressure, slip speed and specific frictional power.},
  author       = {Lund, Mikael},
  keyword      = {drag torque,synchronization,dual clutch transmission},
  language     = {eng},
  note         = {Student Paper},
  title        = {Drag Torque and Synchronization Modelling in a Dual Clutch Transmission},
  year         = {2018},
}