tailieunhanh - Understanding Automotive Electronics P2

The transmission provides a match between engine speed and vehicle speed. within its optimal performance range regardless of the vehicle load or speed. It provides a gear ratio between the engine speed and vehicle speed such that the engine provides adequate power to drive the vehicle at any speed. To accomplish this with a manual transmission, the driver selects the correct gear ratio from a set of possible gear ratios (usually three to five for passenger cars). An automatic transmission selects this gear ratio by means of an automatic control system. Most automatic transmissions have three forward gear ratios, although a. | AUTOMOTIVE FUNDAMENTALS 1 The transmission provides a match between engine speed and vehicle speed. within its optimal performance range regardless of the vehicle load or speed. It provides a gear ratio between the engine speed and vehicle speed such that the engine provides adequate power to drive the vehicle at any speed. To accomplish this with a manual transmission the driver selects the correct gear ratio from a set of possible gear ratios usually three to five for passenger cars . An automatic transmission selects this gear ratio by means of an automatic control system. Most automatic transmissions have three forward gear ratios although a few have two and some have four. A properly used manual transmission normally has efficiency advantages over an automatic transmission but the automatic transmission is the most commonly used transmission for passenger automobiles in the United States. In the past automatic transmissions have been controlled by a hydraulic and pneumatic system but the industry is moving toward electronic controls. The control system must determine the correct gear ratio by sensing the driver-selected command accelerator pedal position and engine load. The proper gear ratio is actually computed in the electronic transmission control system. Once again as in the case of electronic engine control the electronic transmission control can optimize transmission control. However since the engine and transmission function together as a power-producing unit it is sensible to control both components in a single electronic controller. Drive Shaft The drive shaft is used on front-engine rear wheel drive vehicles to couple the transmission output shaft to the differential input shaft. Flexible couplings called universaljoints allow the rear axle housing and wheels to move up and down while the transmission remains stationary. In front wheel drive automobiles a pair of drive shafts couples the transmission to the drive wheels through flexible Joints known