Automotive Transmissions

Frontmatter

1. Introduction

Abstract

All vehicles, aircraft and watercraft included, require transmissions in order to convert torque and engine speed. Transmissions are distinguished in accordance with their function and purpose – e.g. selector gearboxes, steering boxes and power take-offs. This book deals exclusively with transmissions for road vehicles as well as for vehicles designed for both on-road and off-road use (Figure 1.1).

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

2. Overview of the Traffic – Vehicle – Transmission System

Abstract

The interrelations between traffic and traffic engineering and the economy as a whole are as close as they are fundamental. Transport processes have a basic economic function similar to that of money, without which a modern economy, based on the division of labour and with complex system processes, cannot function. As an example of this interrelation, Figure 2.1 shows a constant increase in goods traffic performance, both universally and with reference to the population of Germany. The lion’s share of this goods traffic takes place on the road.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

3. Mediating the Power Flow

Abstract

Vehicle transmissions mediate between the engine and the drive wheels. The transmission adapts the power output to the power requirement by converting torque and rotational speed. The power requirement at the drive wheels is determined by the driving resistance [3.9].

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

4. Power Conversion: Selecting the Ratios

Abstract

Chapter 3 dealt with the relationship between the power available from the engine and the power requirement arising from driving resistance. The torque/speed profile of the internal combustion engine is not suited to use in motor vehicles (see also Section 2.3.2 “Why do Vehicles Need Gearboxes?”).

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

5. Matching Engine and Transmission

Abstract

Chapter 3 dealt with the available and the required power. Chapter 4 then elaborated the principles for selecting overall gear ratios. The purpose of this chapter is now to consider matching the transmission to the engine and the vehicle. This is a task in the field of vehicle longitudinal dynamics. The powertrain and its components are optimised by means of computer driving simulation and road and bench tests. The powertrain components - engine, moving-off element, selector gearbox, final drive etc. - must be “harmoniously” combined. This matching process is called “powertrain matching”

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

6. Vehicle Transmission Systems: Basic Design Principles

Abstract

This chapter presents a systematic exposition of basic design concepts for vehicle transmissions. These principles are related to specific examples in Chapter 12 “Typical Designs of Vehicle Transmissions”.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

7. Design of Gearwheel Transmissions for Vehicles

Abstract

The declared aim of this book is to present a complete picture of the development process for vehicle transmissions. Chapters 3 to 5 showed how the ratios are selected-the fundamental design decision. In Chapter 6 some basic design concepts were introduced. Chapters 7 to 11 consider the layout and design of important components.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

8. Specification and Design of Shafts

Abstract

The specification and design of transmission shafts is of special significance in the layout of vehicle transmissions. Shaft diameters are a key factor in determining the centre distance of a gearbox, and thus its size. Strength andresistance to deformation must therefore be carefully considered during the design process.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

9. Gearshifting Mechanisms

Abstract

Vehicle transmissions require devices to match the ratio, and thus the power available, to the prevailing driving conditions. “Power matching” is one of the four main functions of a vehicle transmission. In manual gearboxes, changing gear is controlled and carried out by the driver. Depending on the amount of automation, in all other gearboxes electronics and actuator systems take over this function partially or completely. Certain transmission functions, such as Neutral, Reverse, and Park are however still controlled by the driver using a shifting device.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

10. Moving-Off Elements

Abstract

The internal combustion engine has a minimum speed (idle speed). To move-off from vehicle standstill, the speed gap between the lowest engine operating speed and the stationary transmission input shaft must be closed by means of a speed converter (see also Section 4.1 “Powertrain”).

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

11. Design and Configuration of Further Design Elements

Abstract

This chapter deals with the theory, design and configuration of vehicle transmission bearings, lubrication, oil supply, oil pumps, housings, seals and continuous service brakes. The aim is to give guidance for tackling these design elements. Sophisticated modern quantitative techniques, such as the Finite Element Method (FEM) for calculating housings or designing bearings for operational fatigue strength, are not examined in fine detail. Further literature references are given where appropriate.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

12. Typical Designs of Vehicle Transmissions

Abstract

This chapter examines some particular transmission designs, and considers their structural design. With regard to the gearwheel configurations in the transmissions examined, you may refer to the gearbox diagrams in Sections 6.6 “Passenger Car Transmissions”, 6.7 “Commercial Vehicle Transmissions”, 6.8 “Final Drives” and 6.9 “Power Take-Offs”.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

13. Electronic Transmission Control

Abstract

Innovations in the area of transmissions have been primarily made by means of the integration of electrics, electronics, hydraulics, actuators and sensors. A great amount of transmission functionality is realised by software. Electronic and software functions do not only complement mechanics, they also open up further possibilities. The aim is to create superordinate functions in the vehicle by means of information networking. In this way, functions can be obtained of which one system alone could never have been capable [13.2].

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

14. Computer-Aided Transmission Development

Abstract

Increasing time and cost pressure in automotive transmission development demands the systematic use of CAE methods (Computer-Aided Engineering, Figure 14.1). Early computer testing and optimising of as many properties of the individual components and of the entire ransmission system as possible do indeed raise expenditures in the early phase of development. However, conserving developmental loops results in the end in obvious advantages in time, cost and quality.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

15. The Automotive Transmission Development Process

Abstract

The purpose of this book is to present the development process for automotive transmissions in its totality. A product is only successful if people buy it!

A healthy product range (Section 15.1) requires product planning oriented to strategic goals (Section 15.2). The product development process (Figure 15.1) starts with product planning, taking into account the main boundary conditions of the product environment. Next follows the conceptual design phase, which is based on formulating the requirements list (specification); in this phase, solution variants are proposed and evaluated and the most suitable solution selected. This solution concept is then realised by general and detailed form design of all partial solutions. The new product finally is released for series production when all the documentation has been completed and tests have been successfully concluded.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

16. Transmission Manufacturing Technology

Abstract

Automotive transmissions, like any other product, are in a constant state of competition,both between different transmission manufacturers and between different transmission designs. The product “transmission” must therefore not only satisfy its function but must also be economically producible and reach the desired level of quality. Basic requirements of product development are therefore knowledge of the manufacturing process and consideration of this even in the design phase.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

17. Reliability and Testing of Automotive Transmissions

Abstract

Legislation (e.g. that relating to product liability and environment protection), higher product complexity, shorter innovation cycles and increased customer expectations require more and more efforts to produce reliable, safe products. To achieve this, certain basic rules need to be observed, even during the development of the product.

Harald Naunheimer, Bernd Bertsche, Joachim Ryborz, Wolfgang Novak

Backmatter