AVTC Model Based Design Curriculum Development Project

G. Marshall Molen, Ph.D., P.E. Ergon Distinguished Professor of Electrical and Computer Engineering Leader of Vehicle Integration at CAVS Faculty Advisor to the MSU Advanced Vehicle Technology Competition

Automotive Transmission Introduction

Introduction to Automotive Transmission What is a transmission? An assembly of components that typically make use of gears that alters the speed from the engine to the wheels and the corresponding torque Floor-mounted shift lever Splined output shaft Selector fork shifts gears Reverse idler gear Splined input shaft Synchronizer collar Countershaft Source: http://www.motorera.com/cadillac/cad1900/CAD03S.HTM

Basic Concept

Powertrain Friction Clutch Fluid Coupling Gear Box Engine Transmission Differential Friction Clutch Fluid Coupling Gear Box Continuous Variable Transmission Planetary Gear Set

Main Component Gears = x Rotating components which consists of teeth that mesh with other like components in an assembly that transmits torque Gear ratio (speed ratio) is the ratio of the angular velocity of input gear to the output gear To ωi Ti ωo x = Pi = Po At Gear Interface, V = (ω r)i = (ω r)o Gear Ratio, iR = ωi/ωo = ro/ri = To/Ti

Gear Box Concept

Planetary Gear Set

Why is it used? The transmission is commonly used in motor vehicles to transform the engine speed and corresponding torque to the wheels so that the engine is operated in a desired speed range The engine operates at a high rotational speed relative to the vehicle at slower speeds that include starting and stopping thus the transmission provides more torque at the wheels Power Available at wheels In order to overcome the static friction when the vehicle is stationary, it requires high torque to be in motion. After it is in motion, high torque is no longer needed and high speed is required. With the help of transmission we can vary the torque and speed of the vehicle. We can also provide change of direction of the wheels with respect to the engine with the help of the transmission. Tractive Force Road Speed, mph Road Speed, mph Source: http://what-when-how.com/automobile/road-performance-curves-acceleration-gradability-and-drawbar-pull-automobile/

Why is it Used? (cont’d) When a vehicle is starting from rest the transmission provides higher torque to overcome losses and inertia Neutral position enables engine to operate without delivering power to the drive wheels Provides higher torque in low gear and higher speed to driving wheels with higher gear Provides reverse gear so that the vehicle can move backwards http://en.wikipedia.org/wiki/File:FIAT_500L_gear_shift.jpg

History of Transmission With the development of the steam engine the necessity arose to adapt the engine power available to intended use. The first steam powered vehicles were driven by a ratchet gear. Higher ratios were required to climb gradients than to drive on a flat surface. In 1784, James Watt patented constant 2-speed gear with a dog clutch engagement. In 1821 Griffith disclosed the 2-speed gearbox with sliding gears, which were extensively used as an inexpensive solution in the early part of the 20th century. After these two major gear configurations were produced, other basic assemblies were developed to provide even better adaptability.

Types of Transmissions Used in Automobile Applications Manual Transmission Automated Manual Transmission Automatic Transmission Continuous Variable Transmission We will discuss

Manual Transmission A driver operated clutch engages and disengages the power flow from the engine to the transmission using a foot pedal. This temporary interruption in power allows the driver to change the gear ratio by means of a hand operated lever It allows gears to be shifted when the engine is operating Source: www.wikihow.com

Automated Manual Transmission The behavior is similar to a manual transmission except the clutch is operated automatically without input from the driver http://commons.wikimedia.org/wiki/File:Red_Ferrari_F430_Spider_steering_wheel.JPG#mediaviewer/File:Red_Ferrari_F430_Spider_steering_wheel.JPG

Automatic Transmission An automatic transmission shifts automatically through forward gears without use of a lever or clutch Most automatic transmissions and transaxles have electronic control in addition to hydraulic controls Typically use a torque converter rather than a clutch Source: www.wikihow.com Fig: Automatic Transmission

Continuous Variable Transmission The relative speed between the input and output shafts is changed by variable diameter pulley that function somewhat similar to a set of gears except that infinite possible ratios can be achieved Performance is smooth as no abrupt transitions Engine is operated at optimal speed

An Alternate Solution: The Electric Motor No clutch Perhaps no gearbox Constant Torque Constant Power Power Torque Torque (Nm) Base Speed Power (kW) Speed (rpm)

Why Electric Vehicles Don’t Require a Transmission? Unlike internal combustion engines, electric motors can operate over a wide speed range There are sophisticated motor drives that provide variable frequencies which enable variations in vehicle speed Eliminating a transmission from an electric vehicle can significantly reduce the size, weight, and cost of the car http://en.wikipedia.org/wiki/File:Electric_car_charging_Amsterdam.jpg

Review & Test What is the main component(s) of an automobile transmission? Gears Powertrain Engine All the above When was the first transmission invented? 1987 1977 1784 1894 Which of the following requires a clutch for a vehicle to operate? Continuously Variable Transmission Manual Transmission Automatic Transmission Automated Manual Transmission Both b and d

References Chao-Hsu Yao. Automotive Transmissions: Efficiently Transferring Power from Engine to Wheels. ProQuest: Discovery Guides, http://www.csa.com/discoveryguides/auto/review.pdf, 2008. G. Lechner, H. Naunheimer and J. Ryborz. Automotive Transmissions: Fundamentals, Selection, Design and Application. Berlin: Springer, 1999. “Transmission in Automobile,” www.emt-india.net_process_automobile_pdf_TransmissioninAutomobile. “Transmission,” www.swe.org_regionb_b007_documents_solarmission.