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K. Rehak et al.
demands on transmitted torque, higher rotational speed, smaller build-in dimension
and reduction of used material because of efficiency [1].
Commonly, the transmissions are designed for the purpose of transfer the rotation
speed and power from input, where source can be engine or electric motor, to the
defined rotation and torque on the output. For that purpose, it is necessary to design
gears, shafts, bearings, housing for given operation conditions. In case of single stage
gearbox, the input shaft is connected to the input gear, which is in contact with the
output gear. The torque is transferred from one gear to second gear trough teeth in
contact, which is changing in dependence on the type and dimensions of gears and
number of teeth. The dependency between input and output rotation and torque is
not constant, but it is dependent on the stiffness of teeth variability. The changes of
gear mesh stiffness can be evaluated by using static transmission error (TE) [2, 3]. In
this parameter there is included also the stiffness of the shafts, bearings and gearbox
housing. The TE can be measured from experiment or calculated by computational
modeling. The gear mesh stiffness, which corresponds the TE, can be calculated by
using Finite element method (FEM) [4].
The excitation of whole gearbox can occur due to several causes, but the main
source of gearbox excitation is the variability of gears contact [5, 6]. The amplitude
of force excitation is changing based on the type and geometry of the gears. The
shape of the gears included macro and micro geometry is designed to minimalist
it, but the frequency is still dependent on the rotation speed and number of teeth.
The excitation force at given frequency is transferred through shafts and bearings
(transfer path) to the gearbox housing. The gearbox housing is the biggest component
with large areas, where the excitation can cause high level of vibration and noise.
The housing is designed to determine the bearing position, thus shaft axis. In the
most cases, the stiffness in this direction is higher than in rest of housing, where
the purpose of housing is dominantly to cover the gears, protect parts and to allow
using of oil. To decrease the total weight, this part of housing is subject of design
optimization. On the other side significant reducing of stiffness can affect the modal
properties, vibration and emitted noise.
2 Methods
There are several approaches to determine the dynamic behavior of gearboxes, which
can be divided into three different levels based on the complexity. The first one is the
modal analysis, which is very often used at designing phase to find, if the operation
conditions across eigen frequencies of designed structure [7]. In case of gearbox it
is necessary to take into account all components, which are closely connected, thus
they can affect each other.
The second level is harmonic analysis, which is also solved in frequency domain.
The excitation of structure is necessary to know.
K. Rehak et al.
demands on transmitted torque, higher rotational speed, smaller build-in dimension
and reduction of used material because of efficiency [1].
Commonly, the transmissions are designed for the purpose of transfer the rotation
speed and power from input, where source can be engine or electric motor, to the
defined rotation and torque on the output. For that purpose, it is necessary to design
gears, shafts, bearings, housing for given operation conditions. In case of single stage
gearbox, the input shaft is connected to the input gear, which is in contact with the
output gear. The torque is transferred from one gear to second gear trough teeth in
contact, which is changing in dependence on the type and dimensions of gears and
number of teeth. The dependency between input and output rotation and torque is
not constant, but it is dependent on the stiffness of teeth variability. The changes of
gear mesh stiffness can be evaluated by using static transmission error (TE) [2, 3]. In
this parameter there is included also the stiffness of the shafts, bearings and gearbox
housing. The TE can be measured from experiment or calculated by computational
modeling. The gear mesh stiffness, which corresponds the TE, can be calculated by
using Finite element method (FEM) [4].
The excitation of whole gearbox can occur due to several causes, but the main
source of gearbox excitation is the variability of gears contact [5, 6]. The amplitude
of force excitation is changing based on the type and geometry of the gears. The
shape of the gears included macro and micro geometry is designed to minimalist
it, but the frequency is still dependent on the rotation speed and number of teeth.
The excitation force at given frequency is transferred through shafts and bearings
(transfer path) to the gearbox housing. The gearbox housing is the biggest component
with large areas, where the excitation can cause high level of vibration and noise.
The housing is designed to determine the bearing position, thus shaft axis. In the
most cases, the stiffness in this direction is higher than in rest of housing, where
the purpose of housing is dominantly to cover the gears, protect parts and to allow
using of oil. To decrease the total weight, this part of housing is subject of design
optimization. On the other side significant reducing of stiffness can affect the modal
properties, vibration and emitted noise.
2 Methods
There are several approaches to determine the dynamic behavior of gearboxes, which
can be divided into three different levels based on the complexity. The first one is the
modal analysis, which is very often used at designing phase to find, if the operation
conditions across eigen frequencies of designed structure [7]. In case of gearbox it
is necessary to take into account all components, which are closely connected, thus
they can affect each other.
The second level is harmonic analysis, which is also solved in frequency domain.
The excitation of structure is necessary to know.