Brake Assisted Differential Locking System

Brake Assisted Differential Locking System

Abstract

Some of the biggest advances in the field of automotive technology in the past 10 years have come in the area of safety. Spurred by the improvements in the microprocessor speed, miniaturization, and software development, the automobile continues to evolve. In this paper, we are going to see an electronic and a pneumatic circuit to automatically control the traction of the vehicle.

During ordinary conditions, when the vehicle is driven down a straight road, or if the difference between speeds of the two (rear) wheels is below a specified limit, no signal will be generated by the electronic circuit. This helps the vehicle negotiate the turns with better traction control as differential action is unaltered. But if the difference between speeds is beyond a specified limit, the signal will be generated by the electronic circuit which will actuate the pneumatic circuit. This causes gradual braking on the faster wheel until it gains traction. Hence, the wheels will never lose traction.

This system reduce more than 50% in the capital investment as compared to the already existing systems can tilt the scales in the favour of the manufacturing company and eventually the cost conscious consumer.

INTRODUCTION

In dry conditions, when there is plenty of traction, the amount of torque applied to the wheels is limited by the engine and gearing; in a low traction situation, such as when driving on ice, the amount of torque is limited to the greatest amount that will not cause a wheel to slip under those conditions. So, even though a car may be able to produce more torque, there needs to be enough traction to transmit that torque to the ground .As long as the tyre grips the road, providing a resistance to turning, the drive train forces the vehicle forward. Driveline torque is evenly distributed between the two rear drive axle shafts by the differential. When one tyre encounters a slippery spot on the road, it looses traction, resistance to rotation drops, and the wheel begins to spin. Because the resistance has dropped, the torque delivered to both the wheels

changes. The wheel with good traction is no longer driven. If the vehicle is stationary in this condition, only the wheel over the slippery spot rotates. Hence the vehicle does not move.

This situation places stress on differential gears. As the traction fewer wheels rotates at a very high speed, amount of heat generated increases rapidly, lubricating film breaks down, metal to metal contact occurs, and the parts are damaged. Now if the spinning wheel suddenly has traction, then the shock of the sudden traction can cause severe damage to the drive axle assembly.

To overcome these problems, differential manufacturers have developed the –Limited Slip Differential. In automotive applications, a limited slip differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In an automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity. The main advantage of a limited slip differential is found by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate at twice its intended velocity – the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential sufficient. For more demanding use however, such as driving off-road, or for high performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some friction available on at least one of the wheels. The clutch type LSD responds to drive shaft torque. The more drive shaft input torque present, the harder the clutches are pressed together and thus the more closely the drive wheels are coupled to each other.

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