Electronic control of automatic transmission

It gives the complete description and working of Electronic control of automatic transmission

1. BY ARAVINDKUMAR B ELECTRONIC CONTROL OF AUTOMATIC TRANSMISSION

2. I N T R O D U C T IO N The modern automatic transmission is by far, the most complicated mechanical component in today’s automobile. Automatic transmissions contain Mechanical systems, Hydraulic systems, Electrical systems and Computer controls , all working together in perfect harmony which goes virtually unnoticed until there is a problem.

3. WHAT IS TRANSMISSION ? The transmission is a device that is connected to the back of the engine and sends the power from the engine to the drive wheels Purpose of the transmission is to provide high torque at the time of starting the engine, hill climbing , accelerating and pulling a road.

4. TYPES OF AUTOMATIC T R A N S M I SS ION Rear wheel drive Front wheel drive

5. REAR WHEEL DRIVE The transmission is usually mounted to the back of the engine. Power flow on this system is simple and straight forward going from the engine, through the torque converter, then through the transmission and drive shaft until it reaches the final drive where it is split and sent to the two rear wheels. Example of rear wheel – Alpha Romeo Alfeta in early 70’s

6. REAR WHEEL DRIVE

7. FRONT WHEEL DRIVE On a front wheel drive car, the transmission is usually combined with the final drive to form what is called a transaxle. Transaxle is a device set up in the transmission gear box, clutch, final drive, combined into a single unit. . Front-wheel-drive layouts are those in which the front wheels of the vehicle are driven. The most popular layout used in cars today is the front-engine, front-wheel drive, with the engine in front of the front axle, driving the front wheels. This layout is typically chosen for its compact packaging. Front axles are connected directly to the transaxle and provide power to the front wheels.

8. FRONT WHEEL DRIVE

9. To improve conventional automatic transmission in the following ways. Gear changes should be smoother and quieter. Improved performance. Reduced fuel consumption. Reduction of characteristic changes over system life. Increased reliability. Electronic control of automatic Transmission

10. Engine Drive Transmission Systems The engine drive train system of the automobile consists of the engine, transmission, drive shaft, differential, and driven wheels . The transmission is a gear system that adjusts the ratio of engine speed to wheel speed. It enables the engine to operate 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.

11. To accomplish this with a manual transmission, the driver selects the correct gear ratio from a set of possible gear ratios . An automatic transmission selects this gear ratio by means of an automatic control system . Properly used manual transmission has efficiency advantages over an automatic transmission, but the automatic transmission is the most commonly used transmission for passenger automobiles Engine Drive Transmission Systems

12. Automatic Transmission Automatic transmissions is 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. 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.

13. Electronic control of automatic Transmission

14. TRANSMISSION COMPONENTS Planetary Gear Sets Hydraulic System Oil Pump Valve Body Clutches Band Seals and Gaskets Torque Converter Governor Computer Controls

15. PLANETARY GEAR SETS A gear set in which all of the gears are in one plane, grouped around each other like the planets around the sun. The central gear is called the "sun gear". In mesh with it is a circular grouping of gears, called "planet gears", mounted on a rotating carrier. The planet gears also engage teeth on the inner periphery of the "ring gear". By holding any one of the three gear elements motionless, different ratios can be produced between the other two. Planetary gear sets are common in automatic transmissions.

16. SIDE VIEW

17. CLUTCH PACKS A clutch is a mechanical device which provides for the transmission of power (and therefore usually motion) from one component (the driving member) to another (the driven member). the simplest application clutches are employed in devices which have two rotating shafts.

18. B A N D S A band is a steel strap with friction material bonded to the inside surface. One end of the band is anchored against the transmission case while the other end is connected to a servo. A flexible metal ring fits around the outside of the clutch housing. It tightens to engage the gears, and loosens to release them.

19. TORQUE CONVERTER A torque converter is a fluid coupling that is used to transfer rotating power from a prime mover , such as an internal combustion en or electric motor , to a rotating driven load.

20. HYDRAULIC SYSTEM The Hydraulic system is a complex maze of passages and tubes that sends transmission fluid under pressure to all parts of the transmission and torque converter It works with some components. Oil Pump Valve Body

21. COMPUTER CONTROLS The computer uses sensors on the engine and transmission to detect such things as throttle position, vehicle speed, engine speed, engine load, brake pedal position, etc. to control exact shift points as well as how soft or firm the shift should be. Once the computer receives this information, it then sends signals to a solenoid pack inside the transmission

22. NON-COMPUTERIZED TRANSMISSIONS Governor Vacuum Modulator Throttle Cable Seals and Gaskets

23. SPOTTING PROBLEMS BEFORE THEY GET WORSE Watch for leaks or stains under the car. Check fluid for color and odor. Be sensitive to new noises, vibrations and shift behavior.

24. TRANSMISSION REPAIRS Adjustments and In-Car Repairs Reseal job Replace accessible parts Complete Overhaul Replacement unit vs. overhaul existing unit