Thermal Analysis of a Park Lock System in a DCT Transmission

69 Pages·2017·7.09 MB·English

Master's Degree Thesis
ISRN: BTH-AMT-EX--2017/D11--SE
Thermal Analysis of a Park Lock
System in a DCT Transmission
Arjun Valishetty
Venkata Sai Krishna Varma
Rudraraju
Department of Mechanical Engineering
Blekinge Institute of Technology
Karlskrona, Sweden
2017
Supervisors: Robert Johansson, #
Ansel Berghuvud, BTH
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Thermal analysis of a park lock
system in a DCT transmission
Arjun Valishetty
Venkata Sai Krishna Varma Rudraraju
Department of Mechanical Engineering
Blekinge Institute of Technology
Karlskrona, Sweden.
2017
Thesis submitted for completion of Master of Science in Mechanical
Engineering with emphasis on Structural Mechanics at the Department of
Mechanical Engineering, Blekinge Institute of Technology, Karlskrona,
Sweden.
Abstract:
A park lock is a mechanism used to prevent unintentional movement of
the vehicle. A failure in the proper function of this mechanism can lead
to the safety concerns of an automobile. The main focus of this thesis is
to understand the reason behind the failure of the park lock mechanism
by FEM analysis in ANSA. For this, temperature build up during the
park lock engagement has been studied in a dynamic explicit analysis.
The FE results are compared to results from experiments on park lock.
The modelling has been done in ANSA, ABAQUS was used as a solver
for simulation and the results have been studied in META. The results
indicate that there is a rise in the temperature. This is due to the friction
between the contact surfaces and the oscillations generated in the
vehicle. Based on the observations, discussions and conclusions are
formulated and the research questions are answered.

Keywords:
ABAQUS, Dynamic Explicit Analysis, FEM Analysis, Thermal
Analysis, Park Lock Mechanism.
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Acknowledgements

This work was carried out at the Department of Mechanical
Engineering, Blekinge Institute of Technology, Karlskrona, Sweden, and a
large automobile company from February 2017 to October 2017 under the
supervision of Dr. Ansel Berguvud and Dr. Robert Johansson.
We wish to express our sincere appreciation to Dr. Robert Johansson,
for his guidance and professional engagement throughout the work. We are
thankful to our academic supervisor Dr. Ansel Berguvud, BTH, Sweden for
his valuable information and insightful remarks. We wish to thank Marcin
Serafin and Martin Nyman for their valuable support and advice.
We would also like to express our deepest gratitude to the staff, at the
company subjected to this study, in particular Alejandro Martinez, for their
timely help, support and everlasting patience. We are thankful to this
company to provide the required equipment and software to carry out the
project.
Finally, we are very thankful to our parents for their constant support,
love and care.

Karlskrona, October 2017
Arjun Valishetty
Venkata Sai Krishna Varma Rudraraju

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CONTENTS
List of Figures 7
List of Tables 9
1. Notation 10
1.1 Indices 11
1.2 Abbreviations 12
1.3 Definitions 13
2. Introduction 14
2.1 Background 14
2.2 Problem Description 18
2.3 Aim and Objectives 18
2.4 Research Questions 19
2.5 Disposition 20
3. Literature review 21
3.1 Analysis on the Park Lock Mechanism 21
3.2 Fretting in Non-Lubricated Systems 22
3.3 Fretting in Lubricated Systems 23
4. Studied system 25
5. Method overview 26
6. Finite element analysis 28
6.1 Model Description 28
6.2 Meshing of the Model 29
6.3 Material Data 32
6.4 Problem Setup 34
6.4.1 Function 34
6.4.2 Couplings 36
6.4.3 Rigid body 37
6.4.4 Joints 37
6.4.5 Displacements 38
6.4.6 Rotations 39
6.4.7 Loads 39
6.4.8 Contacts 39
6.4.9 Springs 40
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6.4.10 Mass Elements 41
6.4.11 Moment of Inertia 42
6.4.12 Initial condition 42
6.5 Results of the Finite Element Analysis 43
6.5.1 Temperature at the contact surface of pawl and ratchet. 43
6.5.2 Temperature at the contact surface of cone and pawl. 45
6.5.3 Temperature at the contact surface of cone and block. 46
6.5.4 Temperature at the contact surface of cone and actuating rod. 48
7. Experimental Testing 51
7.1 Experimental setup 51
7.2 Test procedure 53
7.3 Test Results 54
7.4 Test results discussion 55
8. Validation 57
9. Discussion 59
10.Answering the research Questions / Conclusion 63
10.1 Is there a temperature build up in the areas of contact of pawl-
ratchet and pawl-cone? 63
10.2 How is the friction affected by temperature? 63
10.3 How is the contact affected by lubrication? 63
10.4 How can the design be improved to be more robust? 64
10.5 Relevance of the Test Procedure 64
11.Future works 65
References 66

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LIST OF FIGURES

Figure 2.1 Park lock mechanism, (1) ratchet wheel, (2) pawl, (3) shaft, (4)
guide block, (5) cone, (6) actuator spring, (7) actuator rod, (8) fork,
(9) return spring, (10) bracket. ........................................................ 15
Figure 2.2 Position of the Pawl when the gear shift lever is not in Park
Mode. .............................................................................................. 16
Figure 2.3 Position of the Pawl when the gear shift lever is in Park Mode.17
Figure 2.4 Coordinated Approach. ............................................................. 19
Figure 4.1 Studied CAD model .................................................................. 25
Figure 5.1. Method overview. .................................................................... 27
Figure 6.1 Studied CAD model. ................................................................. 29
Figure 6.2 Block. ........................................................................................ 30
Figure 6.3 Cone. .......................................................................................... 30
Figure 6.4 Area on the pawl that is contact with the cone. ......................... 31
Figure 6.5 Area on the pawl that is contact with the ratchet. ..................... 31
Figure 6.6 Area on the ratchet that is in contact with the Pawl. ................. 32
Figure 6.7 Material input data. .................................................................... 34
Figure 6.8 Material input data. .................................................................... 34
Figure 6.9 List of function. ......................................................................... 35
Figure 6.10 Coupling joints. ....................................................................... 37
Figure 6.11 Hinge. ...................................................................................... 38
Figure 6.12 Friction input. .......................................................................... 40
Figure 6.13 Actuating Spring. ..................................................................... 41
Figure 6.14 Inertia input. ............................................................................ 42
Figure 6.15 Initial conditions. ..................................................................... 43
Figure 6.16 Temperature of the Pawl. ........................................................ 44
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Figure 6.17 Temperature of the Ratchet...................................................... 44
Figure 6.18 Temperature on the cone.......................................................... 45
Figure 6.19 Temperature of the Pawl. ......................................................... 46
Figure 6.20 Temperature of the Cone. ........................................................ 47
Figure 6.21 Temperature of the Block. ....................................................... 47
Figure 6.22 Temperature of the Cone. ........................................................ 48
Figure 6.23 Temperature of the Actuating rod. ........................................... 49
Figure 6.24 Misalignment of the Cone........................................................ 50
Figure 6.25 Misalignment of the Cone........................................................ 50
Figure 7.1 Holes drilled in the pawl and cone to insert the thermocouples 51
Figure 7.2 Cone with an actuating rod fixed with a M2 screw. .................. 52
Figure 7.3 Position of pawl in the gearbox. ................................................ 52
Figure 7.4 Position of Pawl in the gearbox when it is engaged. ................. 53
Figure 9.1 Relationship between the steady state COF and temperature. ... 60
Figure 9.2 Development of the COF with cycle count during fretting as a
function of temperature. .................................................................. 61

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LIST OF TABLES

Table 6.1 Thermal Expansion of the material. ............................................ 32
Table 6.2 Actuating spring input values. .................................................... 40
Table 7.1 Test Results. ................................................................................ 53
Table 8.1 Comparison between simulation and experimental results. ....... 56

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1 NOTATION

A Area
c Specific heat
E Young’s modulus
F Force
Fe O Ferric Oxide
2 3
Fe O Ferro ferric oxide
3 4
g Acceleration due to gravity
I Moment of inertia
k Conductivity
L Angular momentum vector
m Mass of the vehicle
v
N Reference node
n Number of teeth on ratchet wheel
ratchet
r Radius
r Radius on wheel
w
R Gear ratio
t Time
α Angular acceleration
μ Coefficient of friction
ν Poisson’s ratio
ρ Density
τ Torque
ω Angular velocity
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