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.