Browse Publications Technical Papers 2019-28-0029
2019-10-11

Fuel efficiency improvement in automatic Transmissions by Lock-up clutch slip control methodology. 2019-28-0029

Introduction :- Nowdays, Automatic transmissions (AT) have taken over more in the automotive market. Because of traffic, frequently clutch pedal pressing and shift lever operation becomes annoyance in manual transmission.Automatic Transmissions (AT) has better driving comfort, simple operation, but a lower transmission efficiency, higher fuel consumption, can't be competed with manual transmissions. Fuel economy of Automatic Transmissions is poor especially in city drive (Because of driving @ low engine speeds where Torque Converter(TC) is opened). Objective :- The objective of this paper is to present a methodology for torque converter clutches (TCC) to enable clutch slip control at low engine speeds in torque converter without adversely affecting noise and vibration (N&V) performance and increasing fuel economy. The effect of gear state, torque converter slip and power delivered to the driveline on fuel economy are to be discussed. Lock-Up Slip Schedule Determination:- A reasonable slip control area is choosen for achieving increase in transmission efficiency, fuel economy and isolation of torsional vibration. 1. Running in first gear, the torque converter clutch must be unlocked to obtain greater torque for starting, climbing and high power allowing low engine speed to use pure hydraulic mode to separate engine torsion vibration. 2. Running in third gear, the clutch will be locked to make the vehicle get higher speed and larger utilization of power the engine torsion vibration is low and transmission efficiency is high. With mentioned above two conditions,where lock-up clutch slipping is not initiated. 3. Running in second gear, the clutch slipping is initiated and determined by throttle angle and Turbine speed. Lockup Slip Criteria/conditions :- 1. Slipping the clutch to the point where the speed ratio approaches to coupling point (e=> 0.9) to have maximum transmission efficiency. 2. Ensuring minimum amount of slip is controlled so as not to lose the slip speed especially during Tip in/out by driver The objective is proposed to achieve by applying lockup-slip in AT vehicle and the experimental results will be compared in all basis for the beneficial of fuel economy.

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