EFFICIENZA E ANALISI TERMICA - Assiot · Epicyclic gears: AGMA 6123-B06 Bevel and hyoid gears:...

EFFICIENZA E ANALISI TERMICA

Ing. Ivan SaltiniItaly Country Manager

How to get most realistic efficiency calculation for gearboxes?

Topics

Motivation / general calculation

Automotive 7-speed dual clutch transmission

Drive cycle simulations

Efficiency optimization

Conclusion

Industrial bevel-helical gearbox

Motivation industrial gearboxes

Concept and design

High demands for power loss investigations

Systematic power loss analysis and optimization process

Power Loss Thermal ratingCooler

dimensioningOperating costs

Reduction of oil temperature

Dimensioning of cooler unit

Modification of housing design


Motivation automotive applications

KISSsys-model

Efficiency investigations as contribution to reach future CO2 limits


Power loss maps

Drive cycle simulation

Improvement measures

Efficiency evaluation

Comparison of different transmission layouts

Detection of power loss drivers

Evaluation of improvement measures in NEDC

Eff

icie

ncy

Efficiency template – general handling

The thermal rating calculation is provided in a template and is added into the existing gearbox

For each machine element the power loss or efficiency calculation is added

The thermal rating is done considering the heat dissipation and cooler unit

Calculation model with added efficiency template

Efficiency template – losses calculation

o Procedure

The template checks the model for machine elements

For the gears and bearings the losses calculation are added to the shaft editor

For the input and output shaft, the sealing losses can be added if required

Modified calculation


o Gears

according to ISO/TR 14179-1/2

Epicyclic gears: AGMA 6123-B06

Bevel and hyoid gears: Niemann/Winter, Wech

o Alternative for ISO/TR 14179:

Contact analysis for meshing losses for cylindrical gears

Gear calculation

VZPVZV PPP 0


o Bearings

o 𝑃𝑉 = 𝑃𝑉𝐿0 + 𝑃𝑉𝐿𝑃

according to ISO/TR 14179-1/2

according to SKF Catalog 1994

according to SKF Catalog 2004

3210 MMMMM

dragsealslrr MMMMM

Shaft calculation


o Oil pumps, synchronizers, ..

There are a number of machine elements where no literature exists

Typical elements are oil pumps, clutches (several types), synchronizers, ..

Data maps are used to interpolate the power loss value from pre-calculated or measured data

The data map is multi dimensional, as i.e. temperature, speed difference, absolute speed, ..

Data maps

Eff

icie

ncy

Efficiency template – thermal rating

o Heat dissipation

The ISO/TR 14179-2 considers the gearbox housing design very detailed:

- housing, fins

- ventilation conditions

- input, output shafts and couplings

- foundation

o Thermal rating

The thermal rating is performed regarding:

- Calculate cooler capacity, or

- Calculate temperature

Calculation model





Conclusion


Topics


standardized gearboxes series and customized gearbox design

Helical, bevel-helical and worm-helical gearboxes

Ratio up to about 200:1

High efficiency

Calculation model

Thermal rating – testing field

o Testing of power trains

Dynamic power measurement

Reporting of temperature and efficiency

Static functional testings as i.e. total stiffness of the power train

o Single components

Gear wheels

Separate testing field for bearings and radial shaft seals

Testing field

Thermal rating – measurement of power trains

o Testing of power trains for efficiency

Measurement series with constant torque and/or constant speed

Temperature profile for ambient air and oil are recorded

Input speed, torque and output torque (controlled) are recorded

Comparisons of temperature between calculations and measurements are ok, but modifications are necessary

Measurement reports

Calculation model - experiences

o Experiences with our customers are:

detailed and fast calculation procedure according to ISO/TR 14179-2

o Next steps are:

more validation with individual test runs of machine elements

Modification of temperature calculation to get closer match

Calculation model

Topics





Conclusion


7-speed dual clutch transmission (IAV 7-DC280)

CAD design with considered power losses

Sealings

Gear meshing

Gear speed dependent losses Injection Ventilation

Bearings Load dependent Load independent

Synchronizer Drag losses

Clutches Drag losses

Oil pump 3D map interpolation

Rotary unions Sealings under

pressure

Consideration of all relevant power losses in the transmission

Calculation model

o Benefit of calculation model

Calculation model considers all kinematic and kinetic interactions (7 speeds)

For the power losses, own data maps based on measurement or calculations were imported

Calculation model

Power loss maps instead of equations

Exemplary power losses of gear 7 at 60°C oil temperature

Data maps calculated for gear, bearing and sealing losses according to literature

Data maps calculated for other elements according to measurements or literature

0.0

0.5

1.0

1.5

2.0

2.5

3.0

50

0

15

00

25

00

35

00

45

00

55

00

Po

we

r lo

ss [

kW

]

Speed [rpm]

Power loss bearings

0.0

0.5

1.0

1.5

2.0

2.5

3.0

50

0

15

00

25

00

35

00

45

00

55

00

Po

we

r lo

ss [

kW

]

Speed [rpm]

Power loss gear meshing

0.0

0.1

0.1

0.2

0.2

0.3

0.3

0.4

50

0

15

00

25

00

35

00

45

00

55

00

Po

we

r lo

ss [

kW

]

Speed [rpm]

Power loss injection

Power loss maps

0

2

4

6

8

10

12

14

50

0

15

00

25

00

35

00

45

00

55

00

Po

we

r lo

ss [

kW

]

Speed [rpm]

Overall power loss

80%

85%

90%

95%

50

0

15

00

25

00

35

00

45

00

55

00

Speed [rpm]

Overall efficiency

Exemplary power losses of gear 7 at 60°C oil temperature

Topics





Conclusion


Drive cycle simulationso Simulation target

Evaluate the overall power loss distribution in the consumption relevant NEDC

Identification of power loss drivers and evaluate improvement measures directly on the basis of CO2 reduction predictions

o NEDC simulation environment

Mid size car with gasoline engine

Boundary conditions

0 500 1 103

0

1

2

3

Absoluter Verbrauch

2 103

4 103

6 103

8 103

100

0

100

200

Drehzahl [1/min]

Vol

llast

dreh

mom

ent [

Nm

]

Speed [rpm]

2000 4000

Torq

ue [N

m]

0

100

200

-1006000

300

Drive cycle NEDC

Vehicle medium-class

Drive train front transverse

Mass 1650 kg

Combustion engine gasoline

Power 140 kW

Torque 265 Nm

Operating points in engine map

time

ve

locity NEDC

Result of drive cycle simulation

Bearings19.0%

Gear meshing18.1%

Injection4.1%

Clutches1.3%Synchronizers

10.7%

Sealings4.6%

Rotary unions6.4%

Oil pump35.7%

Gear 14%

Gear 27%

Gear 33%

Gear 43%

Gear 514%

Gear 610%

Gear 759%

Energy losses over components Energy losses over speeds

Highest optimization potential in hydraulic actuation, bearings, tooth system and synchronizers

Evaluation of energy losses in 7th gear corresponding to the high time share of 41.6% in the NEDC

Topics





Conclusion



o Tooth system

Basic design exhibits a distribution between contact and overlap ratio of εα = 2 and εβ = 1

New design of macro geometry with decrease of profile contact ratio εα = 1.5 and increase of overlap contact ratio εβ = 1.5

o Bearings

Substitution of tapered roller bearing at differential with fixed/free bearing solution

Optimization measures regarding efficiency improvement


Angle of rotation

Specifi

c s

lidin

g

Slid

e s

peed Gear A – Specific sliding

Gear B – Specific sliding

Slide speed

Pow

er

loss

No modification

Optimized

Norm

al f

orc

e (

line load)

Angle of rotation Angle of rotation

Efficiency optimization of gear micro geometry

Micro geometry (tip relief, crowning,…) gives further reduction of losses

Exemplary efficiency increase of the final drive from 99.06% without modifications up to 99.6% by low load conditions


Efficiency Transmission error

10 % load

100 % load

Efficiency optimization using contact analysis

Automatic variation of modifications and load inside to obtain best variant

Assessment based on tooth contact analysis

Topics





Conclusion


How to get most realistic efficiency calculation:

The ISO/TR 14179 provides a good basis for calculation of power losses and thermal rating

However, for the power losses, meanwhile newer and more detailed literature are available, and also needed (i.e. for churning losses, etc.)

Instead of analytical approach, also contact analyses or data maps can be applied

The thermal rating is quite detailed, but requires some adjustment work for the individual gearbox

Energy losses over components

THANK YOU

FOR YOUR ATTENTION!

EFFICIENZA E ANALISI TERMICA - Assiot · Epicyclic gears: AGMA 6123-B06 Bevel and hyoid gears:...

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