Automotive Power Transmission Systems E-Book

Yi Zhang

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Serie: Automotive Series
• Sprache: Englisch

Seitenzahl: 802

Veröffentlichungsjahr: 2018

Beschreibung

Provides technical details and developments for all automotive power transmission systems

The transmission system of an automotive vehicle is the key to the dynamic performance, drivability and comfort, and fuel economy. Modern advanced transmission systems are the combination of mechanical, electrical and electronic subsystems. The development of transmission products requires the synergy of multi-disciplinary expertise in mechanical engineering, electrical engineering, and electronic and software engineering.

Automotive Power Transmission Systems comprehensively covers various types of power transmission systems of ground vehicles, including conventional automobiles driven by internal combustion engines, and electric and hybrid vehicles. The book covers the technical aspects of design, analysis and control for manual transmissions, automatic transmission, CVTs, dual clutch transmissions, electric drives, and hybrid power systems. It not only presents the technical details of key transmission components, but also covers the system integration for dynamic analysis and control.

Key features:

• Covers conventional automobiles as well as electric and hybrid vehicles.
• Covers aspects of design, analysis and control.
• Includes the most recent developments in the field of automotive power transmission systems.

The book is essential reading for researchers and practitioners in automotive, mechanical and electrical engineering.

Leseprobe

Table of Contents

Cover

Series Preface

Preface

1 Automotive Engine Matching

1.1 Introduction

1.2 Output Characteristics of Internal Combustion Engines

1.3 Road Load, Driving Force, and Acceleration

1.4 Selection of Gear Ratios

References

Problem

2 Manual Transmissions

2.1 Introduction

2.2 Powertrain Layout and Manual Transmission Structure

2.3 Power Flows and Gear Ratios

2.4 Manual Transmission Clutches

2.5 Synchronizer and Synchronization

2.6 Dynamic Modeling of Synchronization Process

2.7 Shifting Mechanisms

References

Problems

3 Transmission Gear Design

3.1 Introduction

3.2 Gear Design Fundamentals

3.3 Design of Tooth Element Proportions of Standard Gears

3.4 Design of Non‐Standard Gears

3.5 Involute Helical Gears

3.6 Gear Tooth Strength and Pitting Resistance

3.7 Design of Automotive Transmission Gears

3.8 Planetary Gear Trains

References

Problems

4 Torque Converters

4.1 Introduction

4.2 Torque Converter Structure and Functions

4.3 ATF Circulation and Torque Formulation

4.4 Torque Capacity and Input–Output Characteristics

References

Problem

5 Automatic Transmissions

5.1 Introduction

5.2 Structure of Automatic Transmissions

5.3 Ratio Analysis and Synthesis

5.4 Transmission Dynamics

5.5 Qualitative Analysis on Transmission Shifting Dynamics

5.6 General Vehicle Powertrain Dynamics

5.7 Simulation of Vehicle Powertrain Dynamics

References

Problems

6 Automatic Transmissions

6.1 Introduction

6.2 Components and Hydraulic Circuits for Transmission Control

6.3 System Circuit Configurations for Transmission Control

6.4 Transmission Control Strategy

6.5 Calibration of Transmission Control System

References

Problem

7 Continuously Variable Transmissions

7.1 Introduction

7.2 CVT Layouts and Key Components

7.3 Force Analysis for Belt CVT

7.4 CVT Control System Design and Operation Control

7.5 CVT Control Strategy and Calibration

References

Problems

8 Dual Clutch Transmissions

8.1 Introduction

8.2 DCT Layouts and Key Components

8.3 Modeling of DCT Vehicle Dynamics

8.4 DCT Clutch Control

8.5 Clutch Torque Formulation

References

Problems

9 Electric Powertrains

9.1 Basics of Electric Vehicles

9.2 Current Status and Trends for EVs

9.3 Output Characteristic of Electric Machines

9.4 DC Machines

9.5 Induction Machines

9.6 Permanent Magnet Motor Drives

9.7 Switched Reluctance Motors

9.8 EV Transmissions

9.9 Conclusions

Bibliography

10 Hybrid Powertrains

10.1 Series HEVs

10.2 Parallel HEVs

10.3 Series–Parallel HEVs

10.4 Complex HEVs

10.5 Non‐Ideal Gears in the Planetary System

10.6 Dynamics of Planetary Gear Based Transmissions

10.7 Conclusions

References

Index

End User License Agreement

List of Tables

Chapter 10

Table 10.1 Qualitative comparison of automatic and manual transmissions.

Table 10.2 Different combinations of operating modes in Tsai’s hybrid transmission.

List of Illustrations

Chapter 01

Figure 1.1 Engine output torque map.

Figure 1.2 Engine torque curves for various throttle openings.

Figure 1.3 Engine torque and power at wide open throttle.

Figure 1.4 Typical torque curve of turbo engines.

Figure 1.5 Engine specific fuel consumption map.

Figure 1.6 Free body diagram of a vehicle accelerated uphill.

Figure 1.7 Layout of RWD manual transmission powertrain.

Figure 1.8 Driving condition diagram.

Figure 1.9 Traction curve of the ideal transmission.

Figure 1.10 Power–speed chart.

Figure 1.11 Matching maximum engine power for maximum vehicle speed.

Figure 1.12 Engine RPM range.

Figure 1.13 Engine RPM vs vehicle speed for gear ratios in geometric progression.

Figure 1.14 Engine WOT output for Example 1.2.

Chapter 02

Figure 2.1 Alternative front wheel drive layouts.

Figure 2.2 Layouts for (a) RWD and (b) 4WD.

Figure 2.3 Powertrain layouts for (a) semi‐truck and (b) commercial bus.

Figure 2.4 Section view of a FWD five‐speed manual transmission.

Figure 2.5 Section view of an RWD five‐speed manual transmission.

Figure 2.6 Symbols for common powertrain components.

Figure 2.7 Stick diagrams for (a) five‐speed FWD MT and (b) five‐speed RWD MT.

Figure 2.8 Reverse idler gear.

Figure 2.9

Six

‐speed MTs for (a) FWD and (b) RWD.

Figure 2.10 Structure of coil spring clutch (a) engaged (b) disengaged.

Figure 2.11 Diaphragm spring and structure of Belleville clutch (a) engaged (b) disengaged.

Figure 2.12 Distribution of clamping force on disk face.

Figure 2.13 Synchronizer assembly and gear with dog teeth.

Figure 2.14 Exploded view of a synchronizer.

Figure 2.15 Synchronization process for an upshift.

Figure 2.16 Dynamic model for synchronization process.

Figure 2.17 Example five‐speed RDW MT.

Figure 2.18 Shifting stick and shift pattern.

Figure 2.19 Internal shifting mechanism of main‐rail design.

Chapter 03

Figure 3.1 Definitions of conjugate motion.

Figure 3.2 Generation of involute curve.

Figure 3.3 Formation of involute gear teeth.

Figure 3.4 Gear generation by rack cutter.

Figure 3.5 Involute gears assembled at non‐standard center distance.

Figure 3.6 Gear tooth element proportions.

Figure 3.7 Gear mesh process and definition of contact ratio.

Figure 3.8 Determination of contact ratio.

Figure 3.9 Tooth thickness at different radius.

Figure 3.10 Standard and non‐standard cutter settings.

Figure 3.11 Undercutting of involute gears.

Figure 3.12 Undercutting avoidance for involute gears.

Figure 3.13 Operating pitch circles and operating pressure angle.

Figure 3.14 Basic geometry of involute helical gears.

Figure 3.15 Transverse and normal sections of the rack cutter for involute helical gears.

Figure 3.16 Lengthwise contact ratio for involute helical gears.

Figure 3.17 Directions of gear force components.

Figure 3.18 Determination of gear force components.

Figure 3.19 Transmission gear design examples.

Figure 3.20 Simple planetary gear train.

Figure 3.21 Dual‐planet simple planetary gear train.

Figure 3.22 Ravigneaux planetary gear train.

Figure 3.23 Internal torque directions for simple and dual‐planet PGTs.

Figure 3.24 Internal torque directions for Ravigneaux PGTs.

Chapter 04

Figure 4.1 Torque Converter Elements.

Figure 4.2 Reaction from the reactor.

Figure 4.3 Torque converter lock‐up mechanism.

Figure 4.4 Torque converter terminologies and definitions.

Figure 4.5 Mean blade curve.

Figure 4.6 AFT velocities and blade angle definition.

Figure 4.7 Velocity diagrams for impeller, turbine, and reactor.

Figure 4.8 Angular momentum change of ATF continuum over time Δ

t

.

Figure 4.9 Torque converter characteristic plot.

Figure 4.10 Joint converter–engine operation status.

Figure 4.11 Torque converter equipped powertrain system.

Figure 4.12 Engine WOT output torque and torque converter characteristic plot.

Chapter 05

Figure 5.1 Structure of an early three‐speed automatic transmission.

Figure 5.2 Structure of an early three‐speed FWD automatic transmission.

Figure 5.3 Structure of an early four‐speed FWD automatic transmission.

Figure 5.4 A Ford four‐speed RWD Ravigneaux PGT automatic transmission.

Figure 5.5 A four‐speed FWD AT with all clutch to one‐way clutch upshifts.

Figure 5.6 Structure of a five‐clutch four‐speed FWD automatic transmission.

Figure 5.7 Honda lay‐shaft four‐speed FWD automatic transmission.

Figure 5.8 Honda lay‐shaft four‐speed FWD automatic transmission without one‐way clutch.

Figure 5.9 A five‐speed RWD automatic transmission.

Figure 5.10 A Ford six‐speed FWD automatic transmission.

Figure 5.11 Ford six‐speed RWD Ravigneaux PGT automatic transmission.

Figure 5.12 Lexus eight‐speed RWD Ravigneaux PGT automatic transmission.

Figure 5.13 Hyundai eight‐speed RWD Ravigneaux PGT automatic transmission.

Figure 5.14 ZF eight‐speed RWD automatic transmission.

Figure 5.15 ZF nine‐speed FWD automatic transmission.

Figure 5.16 Direct shifts in ZF RWD eight‐speed automatic transmission.

Figure 5.17 Ratio change portion of Ford FWD six‐speed AT.

Figure 5.18 Free body diagram of the subassemblies of Ford FWD six‐speed AT.

Figure 5.19 FBD of Ford RWD six‐speed AT.

Figure 5.20 FBDs for the subassemblies of Ford RWD six‐speed AT.

Figure 5.21 FBD for ZF RWD eight‐speed AT.

Figure 5.22 FBDs for the subassemblies of ZF RWD eight‐speed AT.

Figure 5.23 Key variables in the 1–2 shift process of Ford FWD six‐speed AT.

Figure 5.24 Clutch torque profiles in the clutch to clutch 1–2 shift of Ford FWD six‐speed AT.

Figure 5.25 Clutch torque profiles and characteristics of typical downshifts.

Figure 5.26 Direct solution of state variables.

Figure 5.27 Block diagram of integrated vehicle powertrain system.

Figure 5.28 Spring–damper modeling for Input and output shafts.

Figure 5.29 EPA UDDS drive range.

Figure 5.30 Ford 10‐speed RWD AT.

Chapter 06

Figure 6.1 System ATF supply and line pressure control circuit.

Figure 6.2 Section view of a pressure control valve.

Figure 6.3 Shift solenoid and shift valve circuit.

Figure 6.4 Structure of a multiple disk clutch and apply process.

Figure 6.5 Clutch pressure control circuit with accumulator.

Figure 6.6 Clutch pressure control circuit with independent PCS.

Figure 6.7 Clutch apply pressure circuit with boost valve.

Figure 6.8 Clutch compensator feed circuit.

Figure 6.9 Torque converter clutch pressure control circuit.

Figure 6.10 Configuration of transmission control unit (TCU).

Figure 6.11 Stick diagram, clutch, and shift solenoids table for GM Hydra‐Matic 4 T80‐E.

Figure 6.12 Configuration of hydraulic circuitry for the previous generation of ATs.

Figure 6.13 Hydraulic circuitry for ATs with independent clutch pressure control.

Figure 6.14 Clutch and solenoid status table for GM Hydra‐Matic FWD six‐speed AT.

Figure 6.15 Hydraulic circuit for GM Hydra‐Matic FWD six‐speed AT.

Figure 6.16 Hydraulic circuit for ATs with direct clutch pressure control.

Figure 6.17 Example shift schedule for a five‐speed automatic transmission.

Figure 6.18 Shift schedules for Normal and Power modes.

Figure 6.19 Torque converter clutch lock‐up schedule optimized for fuel economy.

Figure 6.20 Torque converter clutch lock‐up schedule optimized for fuel economy.

Figure 6.21 Pressure ramping for torque converter clutch control.

Figure 6.22 Engine torque reduction by spark retarding during clutch to one‐way clutch upshifts.

Figure 6.23 Engine torque reduction by spark retarding during clutch to clutch upshifts.

Figure 6.24 Clutch pressure profiles during clutch to clutch upshifts.

Figure 6.25 Clutch piston initial stroke attributes.

Figure 6.26 Control loops for torque phase and inertia phase.

Figure 6.27 Shift control in inertia phase with feedback on engine speed.

Figure 6.28 Torque based shift control logic.

Figure 6.29 Torque based shift control logic.

Figure 6.30 Transmission control system testing set‐up.

Chapter 07

Figure 7.1 Belt or chain CVT structural layouts.

Figure 7.2 Structure of metal belt.

Figure 7.3 Input and output pulleys.

Figure 7.4 Belt central line tilt.

Figure 7.5 Belt pitch line and contact arcs.

Figure 7.6 Forces acting on a metal block.

Figure 7.7 Forces acting on a metal block and on the input pulley on the axial section.

Figure 7.8 Free body diagram of the movable sheave of the input pulley.

Figure 7.9 Ring tension and block compression forces.

Figure 7.10 Ring tension and block compression distribution when

and

.

Figure 7.11 Ring tension and block compression distribution under light load conditions.

Figure 7.12 Forces acting on the belt as a whole body.

Figure 7.13 Typical thrust ratio plotted against CVT ratio.

Figure 7.14 CVT VBS based control system design.

Figure 7.15 CVT servo mechanism control system design.

Figure 7.16 Initiation of upshifts in CVT servo mechanism control system.

Figure 7.17 Operation of servo mechanism during upshifts.

Figure 7.18 Completion of upshifts in CVT servo mechanism control system.

Figure 7.19 Initiation of downshifts in CVT servo mechanism control system.

Figure 7.20 Operation of servo mechanism during downshifts.

Figure 7.21 Completion of downshifts in CVT servo mechanism control.

Figure 7.22 Block diagram of CVT line pressure control.

Figure 7.23 Block diagram of CVT control system.

Figure 7.24 CVT steady state operation line and transient operations.

Figure 7.25 CVT‐engine joint control block diagram.

Figure 7.26 CVT stepped gear ratios and ratio variations.

Figure 7.27 Shift lines for a CVT controlled with six stepped gear ratios.

Chapter 08

Figure 8.1 Dual clutch transmission structural layout.

Figure 8.2 Section view of dry dual clutch module and clutch actuator.

Figure 8.3 Dry DCT clutch control mechanism.

Figure 8.4 Dry DCT gear shifting cams.

Figure 8.5 Pitch lines for shifting cam grooves.

Figure 8.6 Dry DCT with hydraulically actuated clutches and gear shifting.

Figure 8.7 Wet DCT layout and gear shifting pistons.

Figure 8.8 DCT dynamic model structure.

Figure 8.9 Engine torque output in terms of throttle opening and speed.

Figure 8.10 Dynamic model structure for DCTs with dual mass flywheels.

Figure 8.11 Typical DCT shift schedule.

Figure 8.12 Comparison on DCT launching variables.

Figure 8.13 Typical clutch torque profiles during upshift.

Figure 8.14 Typical clutch torque profiles during downshifts.

Figure 8.15 Engine torque reduction by spark retarding for DCT upshifts.

Figure 8.16 Simulation and test results torque and speed variables in 1–2 upshift.

Figure 8.17 Engine torque reduction by spark retard for DCT downshifts.

Figure 8.18 Simulation and test results for torque and speed variables in 5–4 downshift.

Figure 8.19 Relationship between release bearing travel and engagement load.

Figure 8.20 Engagement load before and after bearing travel.

Figure 8.21 Clutch torques plotted against roller displacements.

Figure 8.22 Clutch torque comparison during launch.

Figure 8.23 Clutch torque comparison during the 1–2 upshift.

Figure 8.24 Clutch torque comparison during operation in the fourth gear.

Chapter 09

Figure 9.1 Basic structure of an EV.

Figure 9.2 Electric system of a passenger car, which includes a PM motor, a power electronics inverter, and a gearbox.

Figure 9.3 Classification of electric machines.

Figure 9.4 Principle of DC machines (cross‐sectional view).

Figure 9.5 Equivalent circuit when stationary.

Figure 9.6 Equivalent circuit when rotating.

Figure 9.7 Torque–speed relationship of DC machines and the operating points when driving a typical vehicle.

Figure 9.8 Motor speed–torque relationship and as a function of load torque.

Figure 9.9 Power flow in a DC machine.

Figure 9.10 Excitation of DC motors: (a) parallel‐excited or shunt DC machine; (b) separately excited DC machines; (c) Series‐excited DC machines; (d) Permanent magnet DC machines.

Figure 9.11 Motor speed–torque control by adjusting terminal voltage.

Figure 9.12 Voltage control of DC motors via a buck converter.

Figure 9.13 Voltage control of DC motors via a half bridge converter.

Figure 9.14 Voltage control of DC motors via a full bridge converter.

Figure 9.15 Motor speed–torque control by adjusting magnetic flux.

Figure 9.16 Motor speed–torque control by armature resistance.

Figure 9.17 An induction motor: (a) rotor and stator assembly; (b) rotor squirrel cage; (c) cross‐sectional view of an ideal induction motor with six conductors on the stator.

Figure 9.18 Flux distributions of a four‐pole induction motor during transient finite element analysis.

Figure 9.19 Stator and rotor circuits of an induction machine.

Figure 9.20 Modified equivalent circuit of an induction machine: (a) neglecting iron loss; (b) considering iron loss.

Figure 9.21 Torque–speed characteristics of an induction motor for a constant frequency and constant voltage supply.

Figure 9.22 Adjusting the speed of an induction motor by varying the terminal voltage.

Figure 9.23 Adjusting induction motor speed using variable frequency supply. In this example, the rated speed is 6000 RPM, and the maximum speed is 12,000 RPM. The adjustable speed range

X

 = 2.

Figure 9.24 Losses in an induction motor.

Figure 9.25 Stator and rotor current in

α

,

β

coordinates.

Figure 9.26 Stator current in

d

,

q

and

α

,

β

coordinates.

Figure 9.27 Block diagram of the rotor flux observer.

Figure 9.28 Field‐oriented control of an induction machine.

Figure 9.29 Flowchart of the closed‐loop control of an induction machine.

Figure 9.30 Surface‐mounted magnets and interior magnets: left, SPM motor; right, IPM motor. 1 – magnet; 2 – iron core; 3 – shaft; 4 – non‐magnetic material; 5 – non‐magnetic material.

Figure 9.31 Four commonly used IPM rotor configurations: (a) circumferential‐type magnets suitable for brushless DC or synchronous motor; (b) circumferential‐type magnets for the line‐start synchronous motor; (c) rectangular slots IPM motor; (d) V‐type slots IPM motor.

Figure 9.32 Exploded view of a PM motor for EV powertrain applications.

Figure 9.33 Magnetic field distribution of PM machines at no‐load conditions (the stator current is zero): (a) a four‐pole SPM motor; (b) an eight‐pole symmetrical IPM motor; (c) a four‐pole unsymmetrical IPM configuration.

Figure 9.34 Operation of a PM synchronous machine: (a) no load; (b) operating as generator; (c) operating as motor.

Figure 9.35 Phasor diagram of PM synchronous motors: (a) SPM; (b) IPM; (c) flux weakening mode of IPM.

Figure 9.36 Power of IPM motor as a function of inner power angle.

Figure 9.37 Torque–speed characteristics of a typical PM motor.

Figure 9.38 Losses in PM motor.

Figure 9.39 Efficiency map of a typical EV motor.

Figure 9.40 synchronous reluctance motor.

Figure 9.41 Cross‐section of a 6/8‐pole switched reluctance motor (top) and its control circuit (bottom).

Figure 9.42 A multi‐stage gear based single‐speed transmission for EVs.

Figure 9.43 A planetary gear based single‐speed transmission for EVs.

Figure 9.44 Single‐ratio speed reduction gearbox for EV applications.

Figure 9.45 Structure of a two‐speed EV transmission based on automatic gearbox.

Figure 9.46 Structure of a two‐speed EV transmission based on planet‐gear.

Chapter 10

Figure 10.1 Architecture of a series HEV.

Figure 10.2 Hub motor configuration of a series HEV.

Figure 10.3 Architecture of a parallel HEV.

Figure 10.4 The powertrain layout of the Honda Civic hybrid.

Figure 10.5 Architectures of a series–parallel HEV.

Figure 10.6 Toyota Prius (2010 model).

Figure 10.7 Powertrain layout of the Toyota Prius (PM – permanent magnet; EM – electric machine).

Figure 10.8 Ford Escape hybrid SUV.

Figure 10.9 Toyota Prius Transmission.

Figure 10.10 The electrical four‐wheel drive system using a complex architecture.

Figure 10.11 The Chrysler Aspen Two‐Mode Hybrid.

Figure 10.12 GM two‐mode hybrid transmission.

Figure 10.13 Power flow during launch and backup.

Figure 10.14 Low Range.

Figure 10.15 High range.

Figure 10.16 Power flow in regenerative braking.

Figure 10.17 Speed relationships of the two‐mode transmission in example 1.

Figure 10.18 Speed relationships of the two‐mode transmission in example 2.

Figure 10.19 Dual clutch transmission. (Note: the reverse gear is omitted from the diagram).

Figure 10.20 Gear shift schedule.

Figure 10.21 Hybrid powertrain based on dual clutch transmissions. Reverse gear is not needed because the motors can be used to back up the vehicle.

Figure 10.22 Power flow in the combined mode.

Figure 10.23 Hybrid transmission proposed by Zhang,

et al

.

Figure 10.24 Renault two‐mode transmission.

Figure 10.25 Timken two‐mode transmission.

Figure 10.26 Low speed mode of the Timken two‐mode transmission.

Figure 10.27 High‐speed mode of the Timken two‐mode transmission.

Figure 10.28 Series operating mode of the Timken two‐mode transmission.

Figure 10.29 Multimode hybrid transmission proposed by Tsai,

et al

.

Figure 10.30 Hybrid transmission proposed in [11].

Figure 10.31 Schematics of electric four‐wheel drive hybrid system.

Figure 10.32 Hybrid powertrain with separate driving axles.

Figure 10.33 Toyota Camry hybrid transmission.

Figure 10.34 The Chevy Volt transmission.

Guide

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Automotive Series

Series Editor: Thomas Kurfess

Automotive Power Transmission Systems

Zhang and Mi

September 2018

Hybrid Electric Vehicles: Principles and

Mi and Masrur

October 2017

Applications with Practical Perspectives, 2nd Edition

Hybrid Electric Vehicle System Modeling and Control, 2nd Edition

Liu

April 2017

Thermal Management of Electric Vehicle Battery Systems

Dincer, Hamut and Javani

March 2017

Automotive Aerodynamics

Katz

April 2016

The Global Automotive Industry

Nieuwenhuis and Wells

September 2015

Vehicle Dynamics

Meywerk

May 2015

Vehicle Gearbox Noise and Vibration: Measurement, Signal Analysis, Signal Processing and Noise Reduction Measures

Tůma

April 2014

Modeling and Control of Engines and Drivelines

Eriksson and Nielsen

April 2014

Modelling, Simulation and Control of Two‐Wheeled Vehicles

Tanelli, Corno and Savaresi

March 2014

Advanced Composite Materials for

Elmarakbi

December 2013

Automotive Applications: Structural Integrity and Crashworthiness

Guide to Load Analysis for Durability in Vehicle Engineering

Johannesson and Speckert

November 2013

Automotive Power Transmission Systems

Yi Zhang

University of Michigan‐DearbornUSA

Chris Mi

San Diego State UniversityUSA

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Library of Congress Cataloging-in-Publication Data

Names: Zhang, Yi, 1962 September 1- author. | Mi, Chris, author.Title: Automotive power transmission systems / by Yi Zhang, Chris Mi.Description: Hoboken, NJ : John Wiley & Sons, 2018. | Includes bibliographical references and index. |Identifiers: LCCN 2018013178 (print) | LCCN 2018028719 (ebook) | ISBN 9781118964910 (pdf) | ISBN 9781118964903 (epub) | ISBN 9781118964811 (cloth)Subjects: LCSH: Automobiles‒Transmission devices.Classification: LCC TL262 (ebook) | LCC TL262 .Z43 2018 (print) | DDC 629.2/44‒dc23LC record available at https://lccn.loc.gov/2018013178

Cover design by WileyCover images: Background: © solarseven/Shutterstock; Left: Courtesy of Yi Zhang and Chris Mi; Middle: © Dong liu/Shutterstock; Right: © Scharfsinn86/Getty Images

Series Preface

Automotive power transmission systems are critical elements of any automobile. The ability to transmit power from the engine of a vehicle to the rest of the drive train is of primary importance. Furthermore, the design of power transmission systems is of critical importance to the overall vehicle system performance, as it affects not only performance characteristics such as torque and acceleration, but it also directly affects fuel efficiency and emissions. The power transmission system also presents one of the most complex design tasks in the overall automotive systems design and integration because it must interface with a variety of power plants such as internal combustion, electric, and hybrid plants. This is further complicated by the fact that engineers must consider a variety of transmission designs such as manual, automatic, and continuously variable systems. Furthermore, all of these elements must be condensed into the smallest, lightest package possible while functioning under significant loads over long periods of time.

Automotive Power Transmission Systems presents a thorough discussion of the various concepts that must be considered when designing a power transmission system. The book begins with an excellent discussion of how a transmission is designed by matching the engine output and the vehicle performance via proper transmission ratio selection. It then proceeds to discuss the basics of manual transmission and the analysis and design of essential transmission subsystems and components such as the gears, torque converter, and clutches. The authors then discuss more advanced transmission types such as dual clutch transmissions, continuously variable transmissions and automatic transmissions. In the final chapters, advanced control concepts for transmissions are presented, leading to the final chapters on electric and hybrid powertrains. This powerful combination of concepts results in a text that has both breadth and depth that will be valued as both a classroom text and a reference book.

The authors of Automotive Power Transmission Systems have done an excellent job in providing a thorough technical foundation for vehicle power transmission analysis and control. The text includes a number of clearly presented examples that are of significant use to the practicing engineer, resulting in a book that is an excellent blend of practical applications and fundamental concepts. The strength of this text is that it links a number of fundamental concepts to very pragmatic examples, providing the reader with significant insights into modern automotive power transmission technology. The authors have done a wonderful job in clearly and concisely bringing together the significant breadth of technologies necessary to successfully implement a modern power transmission system, providing a fundamentally grounded book that thoroughly explains power transmissions. It is well written, and is authored by recognized experts in a field that is critical to the automotive sector. It provides an excellent set of pragmatic and fundamental perspectives to the reader and is an excellent addition to the Automotive series.

Thomas KurfessJanuary 2018

Preface

Automotive power transmission systems deliver output from the power source, which can be an internal combustion engine or an electric motor or a combination of them, to the driving wheels. There are many valuable books and monographs published for internal combustion engines (ICE), but only a few can be found in the public domain, as referenced in this book, that are specifically written for automotive transmissions. Technical publications by the Society of Automotive Engineers (SAE) in transmissions are mostly for conventional ICE vehicles and are basically collections of research papers that are aimed at readers with high expertise in transmission sub‐areas. The purpose of this book is to offer interested readers, including undergraduate or graduate students and practicing engineers in the related disciplines, a systematic coverage of the design, analysis, and control of various types of automotive transmissions for conventional ICE vehicles, pure electric vehicles, and hybrid vehicles. The aim is that this book can be used either as a textbook for students in the field of vehicular engineering or as a reference book for engineers working in the automotive industry.

The authors have taught a series of courses on powertrain systems for both ICE and electric‐hybrid vehicles over many years in the graduate programs of mechanical engineering, electrical engineering, and automotive systems engineering at the University of Michigan‐Dearborn. The lecture notes of these courses form the framework for the book chapters, the main topics of which are highlighted below.

The book starts with automotive engine matching in Chapter 1, which covers the following technical topics: output characteristics of internal combustion engines, vehicle road loads and acceleration, driving force (or traction) and power requirements, vehicle performance dynamics and fuel economy, and transmission ratio selection for fuel economy and performance. The formulation and related analysis in Chapter 1 on road loads, performance dynamics, and powertrain kinematics are applicable to all vehicles driven by wheels and will be used throughout the book.

Chapter 2 covers manual transmissions, focusing on gear layouts, clutch design, synchronizer design, and synchronization analysis. Detailed analysis is provided on the operation principles of synchronizers and on the synchronization process during gear shifts. Example production transmissions are used as case studies to demonstrate principles and approaches that are then generally applicable.

For readers’ convenience, Chapter 3 provides the basics of the theory of gearing and gear design with specific application to manual transmissions (MT). With example transmissions, the chapter details geometry design, gear load calculation, and gear strength and power ratings for standard and non‐standard gears using existing equations or formulae from AGMA standards. The chapter also includes a separate section on the kinematics of planetary gear trains which are widely applied in automatic transmissions (AT). Readers are strongly recommended to read this section before reading Chapters 5 and 6.

Chapter 4 covers the structure, design, and characteristics of torque converters, focusing on torque converter operation principles, functionalities, and input–output characteristics. Methods for the determination of engine–converter joint operation states are presented in detail. The chapter also deals with the modeling of the combined operation of the entire vehicle system that consists of the engine, torque converter, automatic transmission, and the vehicle itself.

Chapters 5 and 6 can be considered as the core of the book, as these two chapters present the design, analysis, and control of conventional automatic transmissions (AT) which are typically designed with planetary gear trains. Chapter 5 focuses on how multiple gear ratios are achieved by different combinations of clutches and planetary gear trains. A systematic method will be presented in this chapter for the design and analysis on the gear ratios and clutch torques of automatic transmissions. The chapter also gives an in‐depth analysis of the dynamics of automatic transmissions during gear shifts and the general vehicle powertrain dynamics in a systematic approach, using an eight‐speed production automatic transmission as the example in the case study.

Chapter 6 concentrates on hardware and software technologies of both component and system levels which are applied in the control systems for the implementation of transmission functionalities. The chapter begins with the functional descriptions of the hardware components, including hydraulic components, electronic sensors, and solenoids. The chapter then presents transmission control system configurations and the related design guidelines. Examples based on the production transmissions of previous and current generations are used to demonstrate the operation logic and functions of the control systems. A specific section is devoted to present concurrent transmission control technologies commonly applied in the automotive industry. This focuses on the accurate clutch torque control during gearshifts and torque converter clutch actuation. The chapter ends with the identification of control variables and control system calibration.

Chapter 7 mainly presents the design and control of belt type continuously variable transmissions (CVT), starting with the structural layouts of CVT systems and key components, including the basic CVT kinematics and operation principles. Topics are concentrated on force analysis during the CVT’s operations, and the mechanisms for torque transmission and ratio changes. The chapter provides details of control system design and the analysis of the control of ratio changing processes. CVT system control strategies, including continuous ratio control, stepped ratio control, and system pressure control are also presented.

The design and control of dual clutch transmissions (DCT) are covered in Chapter 8. The chapter concentrates on the dynamic modeling and analysis of DCT operations, including DCT vehicle launch and shifts. DCT control system design, and shift and launch control processes are included here, and the chapter also dedicates a specific section to DCT clutch torque formulation during launch and shifts, using an electrically actuated dry DCT as the example in the case study.

Chapter 9 covers power train systems for pure electric vehicles (EV). It includes several key technical topics: design optimization and control of electric machines for EV applications, power electronics for electric power transmission and inverter design, and system control under various operation modes. The chapter also includes a section on mechanical transmissions with a fixed ratio or two ratios which are specifically designed for pure electric vehicles. Two‐speed or multi‐speed automated gear boxes enable EV driving motors to operate within the speed range for optimized efficiency and performance.

Finally, hybrid powertrain systems are discussed in Chapter 10, which presents various hybrid powertrain configurations including series, parallel, and complex architectures. It provides detailed analysis of the operation modes and operation control for hybrid vehicle powertrain systems. Production hybrid vehicles are used as case studies in mode analysis and operation control.

As highlighted above, each chapter of the book is dedicated to a specific transmission, and readers may choose the chapter of interest to read. If the book is used as a textbook, the course syllabus can follow the order of the chapters. If the book is used as a reference, readers with transmission expertise may just choose the chapter of interest, and those readers without broad expertise may wish to first read Chapters 1 and 4 and then read the chapter of interest.

The authors would like to express their hearty thanks for the help received from friends and colleagues in preparing the manuscript. We would like to thank especially Prof. Qiu Zhihui of Xian Jiaotong University and Prof. He Songping of Huazhong University of Science and Technology for their help in drawing the pictures for this book. We also want to thank the publisher, John Wiley & Sons, for giving us the opportunity to publish this book, and we dedicate our deep appreciation to Ms Ashmita Rajaprathapan for her invaluable contributions in editing and finalizing the book. Lastly and most importantly, the authors would like to express their thanks to engineers, scholars, and researchers who have contributed to the technologies of vehicular power transmission systems and whose work may or may not have been specifically acknowledged in the reference lists.

Yi Zhang and Chris Mi

1Automotive Engine Matching

1.1 Introduction

Internal combustion engines have been the primary power source for automotive vehicles since the beginning of the automotive industry. Although automobiles powered by electric motors have entered the automotive market and are likely to grow in market share, the vast majority of vehicles will still be powered by internal combustion engines in the foreseeable future. This is partly due to the bottleneck in the development of key technologies for electric vehicles, such as battery energy density, durability and charging time, and the lack of infrastructure and facilities necessary for the daily use of electric vehicles. On the other hand, proven crude oil reserves can still fuel internal combustion engines for decades to come.

Modern internal combustion engines are sophisticated systems that integrate synergistically mechanical, electrical, and electronic subsystems. Engine technologies are subjects of study in great breadth and depth in the areas of combustion, heat transfer, mechanical design and manufacturing, material engineering, and electronic control [1,2,3,4]. However, this book does not cover engines themselves and is concerned only with how the engine outputs are transmitted to the driving wheels. Readers interested in engine topics are directed to the books referenced here or other related books. The engine outputs, in terms of power and torque, fuel economy, and emissions, are considered as given throughout the text of this chapter and indeed the whole book. Note that engine mapping data are highly proprietary and is usually not available in the public domain. Figures and plots pertaining to engine data in this book are mainly for illustration purposes and may not show the precise data of production engines.

The main topic of this chapter is the matching between the engine outputs and vehicle performance through the selection of transmission ratios. The chapter specifically covers: output characteristics of internal combustion engines; vehicle road loads and acceleration; driving force (or traction) and power requirements; vehicle performance dynamics and fuel economy; and transmission ratio selection. These topics are interconnected and are described in sequential order.

Although the chapter concerns automotive engine matching, as the title indicates, the formulation and related analysis of road loads, performance dynamics, and powertrain kinematics are applicable for all ground vehicles driven by wheels. The equations derived in this chapter will be referenced throughout the book wherever needed by the text.

1.2 Output Characteristics of Internal Combustion Engines

The output of an internal combustion engine depends on its design, control, and calibration. Although computer simulation can be used to analyse engine output, engine mapping is the only experimental approach to obtain reliable engine output data. For a given production engine, its output data are provided in terms of power and torque, as well as specific fuel consumption and emissions.

1.2.1 Engine Output Power and Torque

The operation status of an internal combustion engine is defined by its crankshaft rotational speed and the output torque from its crankshaft. The output torque and power depend on the throttle opening and the engine speed, i.e. the crankshaft rotational speed in RPM. It should be noted that the output torque and output power are not independent since power is the product of torque and angular velocity. The torque map of a typical IC engine is shown in Figure 1.1, where the two horizontal axes are respectively the throttle opening as a percentage of the wide open throttle (WOT) or as a degree of throttle angle and the engine speed in RPM. The vertical axis shows the engine output torque in foot pounds in the imperial standard or in newton‐meters in the international standard (SI). Without considering the engine transient behavior, the engine static output torque can be found from Figure 1.1, usually by numerical interpolation, for a given set of engine speed and throttle opening. This is the torque as a load at which the engine reaches dynamic equilibrium at the specified engine speed and the throttle opening.

Figure 1.1 Engine output torque map.

In practice, the engine output torque is often plotted as a curve against the engine speed for specific throttle openings as shown in Figure 1.2, where the throttle opening for each torque curve is represented as a percentage of the wide open throttle angle. Clearly, the engine output torque is a function of engine RPM for a given throttle opening and there is a torque vs RPM curve for each throttle opening. Figures 1.1 and 1.2 provide the same output torque data and are just drawn for convenience of reference.

Figure 1.2 Engine torque curves for various throttle openings.

Apparently, the engine capacity torque output or the power output is achieved at the wide open throttle (WOT), as shown in Figure 1.3. It should be noted that the maximum engine torque and the maximum engine power occur only at two separate RPM values on the WOT torque and power curves. The two popularly referred engine performance specifications, engine power and engine torque, are actually the peak values for the power and torque on the WOT output plot. As can be observed in Figure 1.3, internal combustion engines provide stable power output within a range of engine rotational speed, defined by the so‐called idle RPM and redline RPM. Below the idle, the engine does not run stably but stalls, without being able to provide any usable output. On the other side, running the engine beyond the redline speed may cause excessive damage to the engine.

Figure 1.3 Engine torque and power at wide open throttle.

The shape of the torque curve in the operation range defined by the idle and redline is characteristic of the IC engine, depending on its design, fuel injection method, control, and calibration. As an example, the torque curve in Figure 1.3 has a local peak at around 2500 RPM and the maximum engine torque occurs around 4800 RPM. The engine power increases from the idle point almost linearly up to a peak at around 6100 RPM.

In general, the torque curves for naturally aspirated engines can be categorized as rising and buffalo shaped [5], while for turbo‐charged engines, the torque curves are flat from a certain low RPM up to a relatively high RPM, as shown in Figure 1.4. Using turbo technology, the maximum output torque can be increased by more than 50% for the same engine displacement. To make things better, this maximum torque becomes available at a much lower RPM in comparison to naturally aspirated engines and stays flat up to a high RPM. This provides the vehicle with much better acceleration performance, especially at low vehicle speed. Turbo engines with small displacements provide outputs in torque and power equivalent to those of naturally aspirated engines of much larger displacements but consumes less fuel. Because of these advantages, vehicles powered by turbo engines are increasingly popular and represent the trend in the automotive industry.

Figure 1.4 Typical torque curve of turbo engines.

1.2.2 Engine Fuel Map

Engine fuel efficiency is a top performance specification in today’s automotive industry. The fuel consumption data of internal combustion engines are indispensable for the design, operation and control of vehicle powertrain systems. These data are experimentally obtained by intensive engine mapping and are usually provided for a production engine as a fuel map, which indicates in contour plots the specific fuel consumption of the engine at a given operation status, as shown in Figure 1.5. The specific fuel consumption is the amount of fuel that the engine needs to burn in order to do one horsepower hour of work, either in litres, grams, or pounds of weight.

Figure 1.5 Engine specific fuel consumption map.

The horizontal and vertical axes in Figure 1.5 are respectively the engine RPM and the engine output torque that define the engine operation status. The numbers by the contours are the specific fuel consumption in gram per kilowatt‐hour (grams of fuel the engine consumes for it to do one kilowatt‐hour of work). For example, if the engine runs stably at 4000 RPM with an output torque of 94 Nm, the specific fuel consumption is 275 gr/kW.hr. At the operation status defined by the RPM and the torque, the engine power is 39.37 kW. If the engine runs at the status continuously for one hour, the fuel consumed by the engine will then be 10.82 kg. The engine fuel consumption along a contour is the same even though the operation status is different, so the hourly fuel consumption of the engine is also 10.82 kg if it runs stably at 4740 RPM with an output torque of 125 Nm. Apparently, the engine will be more fuel efficient if it runs along the contour with 250 gr/kW.hr. It can also be observed that the most fuel efficient operation status is near the point with 2500 RPM and 125 Nm. When a vehicle is driven on a road at constant speed, the engine operation status depends on the road load, the vehicle speed, and the transmission gear ratio, the last determining the engine RPM and torque at a given vehicle speed and thus largely affects the vehicle fuel economy.

1.2.3 Engine Emission Map

When internal combustion engines generate power to propel ground vehicles, unwanted pollutants, harmful to the environment and to human health, are emitted in the process of combustion. These pollutants include CO, CO2, NOX, and other harmful gasses or particulate matter. The standard on emission control is increasingly stringent in the automotive industry due to environmental and human health concerns. Engine technologies, especially the technologies for combustion control and after‐combustion treatment, are the key to minimizing the emission of pollutants. Transmissions also contribute to lowering vehicle emission levels by keeping the engine running in more efficient and less polluting operating ranges.

Engine emission maps are even more difficult to obtain than fuel maps because the quantity of a pollutant under various operation conditions is hard to measure. Computer simulation can be used to analyse engine emissions, but reliable emission data can only be obtained experimentally through extensive tests. Engine emission maps are provided for a given engine in formats similar to engine fuel maps. The specific quantity of a particular pollutant emitted by the engine is interpolated from the emission contour for a given engine operation status. Using the emission maps of the engine, the amount of emission of a pollutant can be simulated for a specified drive range.

1.3 Road Load, Driving Force, and Acceleration

Various forces are applied to a vehicle when it travels on a road surface. These forces include gravity, wheel–road contacting forces, road load, and driving force, which is also termed traction. Road load is against the motion of the vehicle, while traction force, or driving force, propels the motion of the vehicle. The driving force of a vehicle originates from the engine via the transmission and is fundamentally limited by the road traction limit. The total road load is the resultant of three separate road loads: rolling resistance, grade load, and air resistance. Figure 1.6 is the free body diagram of a vehicle of weight W that is being accelerated uphill.

Figure 1.6 Free body diagram of a vehicle accelerated uphill.

In the free body diagram, v and a are the vehicle speed and acceleration respectively. RA is the air drag or air resistance. The air drag is a distributed load, but for simplicity, it is assumed to be a point load acting at height hA. RF and RR are the rolling resistance from the front and rear wheels respectively. PF and PR are the driving force from the front and rear wheels respectively. WF and WR are the axle loads, which are respectively the contact force between the front wheels and the road surface and between the rear wheels and the road surface. A and B denote the points of contact between the wheels and the road surface. θ is the grade angle of the slope and r is the rolling radius of the tire. The height of the center of gravity and the height of the air resistance are respectively denoted as h and hA. For passenger cars, these two heights are assumed to be the same. The vehicle wheelbase is L and the longitudinal position of the gravity center is determined by b and c, which is the distance from the gravity center to the front axle and rear axle respectively. Unless otherwise stated, the US customary unit system will be used in the equations, where forces are in pounds, linear dimensions are in feet, speed is in ft/s, and acceleration is in ft/s2. It should be noted that the inertia force in the free body diagram is in the opposite direction to the acceleration, based on the D’Alembert’s principle. γ is the equivalent mass factor that is introduced to account for the mass moments of inertia of all rotational components in the powertrain, including transmission input and output shafts, gears in the power flow path, drive shaft, differential, wheels, etc. The value of γ can be accurately determined based on the total vehicle equivalent kinetic energy as follows,

(1.1)

In the equation above, Ji is the mass moment of inertia of each rotational component and n is the total number of rotational components in the powertrain. The equivalent mass factor is then determined as,

(1.2)

For a given vehicle, the ratio is a constant for each rotational component that depends on the transmission gear ratios. Empirical formula and tables are available for the approximation of the equivalent mass factor [6]. For passenger cars, the value of γ is small and can be considered to be equal to one for vehicle acceleration analysis and transmission ratio selections.

1.3.1 Axle Loads

The forces in the free body diagram (Figure 1.6) form a system of equilibrium, and three scalar equations can be written based on the condition of equilibrium. As shown below, the first two equations are based on the conditions that the sum of moments made by all forces about point A and point B must be equal to zero. The third equation is that the sum of all forces, including the inertia force, must be equal to zero in the direction of vehicle motion.

(1.3)

These equations can be arranged to express the axle loads and the inertia force as follows:

(1.4)

(1.5)

(1.6)

The first two equations determine the dynamic axle weights for the vehicle. During acceleration, there is a weight transfer equal to the magnitude of the inertia force from the front axle to the rear axle, as shown in Eqs (1.4) and (1.5). The static axle weights on level ground are obtained from the equations by making the slope angle θ, the air drag RA, and the acceleration a equal to zero. It should be noted that tractions are available from both front and rear wheels only for a four wheel drive vehicle. PR is zero for front wheel drive and PF is equal to zero for rear wheel drive. Total driving force and rolling resistance from both front wheels and rear wheels are:

(1.7)

The rolling resistance depends on many factors, such as tire material, texture, tread, inflation, speed, etc. Accurate calculation of the rolling resistance is very difficult, indeed impractical. For simplicity, it is common practice in the automotive industry to calculate the rolling resistance by:

(1.8)

where f is the rolling resistance coefficient and is approximately equal to 0.02. By rearranging Eqs (1.4–1.7) with the assumption that , the axle loads can be solved in the following form:

(1.9)

(1.10)

(1.11)

where and are the weight distribution factors. The term is the dynamic weight transfer. Eqs (1.10) and (1.11) represent the dynamic axle weights in terms of the static axle weights and the weight transfer. The dynamic axle weight on the driving axle determines the maximum traction available for the vehicle under a given road condition.

1.3.2 Road Loads

There are three kinds of road loads that are against vehicle motion when the vehicle travels on a road surface: rolling resistance, air drag, and grade load, as shown in Figure 1.6. The rolling resistance is calculated by Eq. (1.8). The grade load is the component of gravity on the slope direction and is equal to W sin θ. At level ground, only rolling resistance and air drag exist. At high vehicle speed, the air drag becomes more significant than the rolling resistance.

There are two causes for the generation of air resistance: friction between the air and the vehicle body surface; and air turbulence formed around the vehicle body [6]. The latter is the main cause of air drag for ground vehicles. Factors affecting the magnitude of the air drag include the shape and finish of vehicle body, the vehicle frontal projected area, air density and atmospheric condition, and most importantly, the vehicle’s speed. It is very challenging to exactly determine the air drag by analytical means. In the standard of the Society of Automotive Engineers (SAE), the air resistance or air drag is calculated by the following formulation [6]:

(1.12)

where CD is the unit less air drag coefficient that mainly depends on vehicle body shape and body surface smoothness. The air drag coefficient can be determined with high accuracy by wind tunnel testing. Modern passenger cars with streamlined body can have an air drag coefficient as low as 0.26. A is the vehicle frontal projected area in ft2 that mainly depends on the vehicle size. This is the area of the vehicle body that confronts the air flow in the direction perpendicular to vehicle motion. To determine this area, a flat board can be held perpendicular to the road surface behind the parked vehicle and a flashlight is then used to beam the vehicle body horizontally in front of the vehicle. The area of the shadow casted on the board is the frontal projected area. As shown in the formulation, the air drag is proportional to the square of the vehicle speed v relative to the wind. With the speed v in mph, the formulation determines the air drag as a force in pounds. For the analysis and calculations of vehicle dynamics, the vehicle speed and acceleration are often in ft/s and ft/s2, then the formulation for air drag will be used in the following form:

(1.13)

The equation above is directly transformed from Eq. (1.12)