Subject: Automobile Engineering

Topic: Suspension, Wheels & Tires

Difficulty: Medium

i) Fluid flywheel & Torque converter:

Fluid flywheel:- The fluid flywheel is mostly known as hydraulic coupling. It a hydrodynamic device used to transmit isolating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch & in cars having automatic transmission. It also has application in marine & industrial machine devices, where variable speed operation & controlled start-up without shock loading of power transmission system is essential.
The fluid coupling consists of three components :
i) The housing, also known as the shell, has an oil-tight seal around the drive shafts.
ii) Two turbines (fan like components)
• One connected to input shaft, known as pump or impellor.
• Other connected to output shaft, known as turbine or runnner.

The driving turbine, known as pump, is rotated by prime rover. The two turbines are mounted very close, with their open ends facing each other,so that they can be turned independently without touching. Housing surround both units to make a closed assembly. About 80% of interior of assembly is filled with oil.

Working:
• When the engine is started, the driving member starts move inside the housing containing oil.
• As the impeller is desgined such that the splashed oil will the vanes of driven member.
• The impeller is designed such that the splashed oil will the vanes of driven member.
• Hence, the runner is forced to move in the same direction tends to rotate at the same speed.

The working & application of Torque Converter
The construction of torque converter is similar to that of fluid flywheel; the only difference being that it has an additional stationary members called the stator or the reacton member & all the members have blade or vane of specific shape.

The operation of the two however is not similar, whereas the fluid flywheel transmits the same torque as, given to it by the engine shaft. The torque converter increases the Torque in a ratio of about 2:1 to 3:1. Thus, it serves the same purpose as that of a gearbox & that too in a better Way, whereas in the gearbox the torque variation is only in finite no of steps, in the case of torque converter torque output variation is continuous. However, the efficiency of a torque converter is high only with narrow limits of speeds

ii) Explain working of freewheel unit: Freewheel unit (Freewheel clutch) is provided just after gearbox. Fig 17:2 shows the construction of this unit. It is very similar in action to the bicycle free freewheel. The inner driving member is connected to the gearbox shaft & the outer one to the propeller shaft. The driving member has three steps as shown in fg 17. 2. In each step, thero are three spring mounted rollers of different sizes. When the driving members is rotating in the direction shown in the figure 17.2, the driven member will also be rotating in the same direction. But when the driven member becomes the driving member.