2.2 Torque Converter (TC). The primary functions of the torque converter (TC) include torque multiplication to provide sufficient torque during vehicle launch and fluid damping to smooth torque fluctuations in the powertrain. A fluid-filled three-element TC has two phases: torque multiplication phase and fluid coupling phase. The TC impeller (also referred to as the TC pump) is driven by the engine and the turbine is attached to the transmission input shaft. The turbine and the stator that are connected to the TC housing via a one-way clutch are initially at rest during vehicle launch. The turbine speed begins to increase under the angular momentum of the impeller that is transmitted through circulating fluid inside the TC.When the ratio of the turbine speed to the pump speed is low, the stator remains at rest and it redirects the fluid flow in the same direction as the pump torque such that the resulting output torque of the TC is amplified.This is called the torque multiplication or torque amplification phase. At higher turbine speed, the stator rotates freely in the same direction of the pump and it is considered to consume no torque. Therefore, the turbine torque in this torque coupling phase is the same as the pump torque [4].
TC act as hydraulic dampers to interrupt vibration propagation originated from either engines or road bumps and to provide torque multiplication during vehicle launch [5]. Since TC is essentially a damper, losses are not negligible.
However, these losses can be reduced by employing a TC bypass clutch, which mechanically connects the TC pump
and the turbine when the clutch is engaged. This connection improves TC efficiency at the price of losing the capability to absorb oscillations in the powertrain. A compromising solution is proposed by Kazemi et al., allowing 1 to 2% of clutch slip to achieve similar results as the TC is working as a damper [4]. Obviously, people desire to minimize this slip for efficiency consideration. This type of bypass clutch is a socalled minimal slip-type TC clutch.
2.2 Torque Converter (TC). The primary functions of the torque converter (TC) include torque multiplication to provide sufficient torque during vehicle launch and fluid damping to smooth torque fluctuations in the powertrain. A fluid-filled three-element TC has two phases: torque multiplication phase and fluid coupling phase. The TC impeller (also referred to as the TC pump) is driven by the engine and the turbine is attached to the transmission input shaft. The turbine and the stator that are connected to the TC housing via a one-way clutch are initially at rest during vehicle launch. The turbine speed begins to increase under the angular momentum of the impeller that is transmitted through circulating fluid inside the TC.When the ratio of the turbine speed to the pump speed is low, the stator remains at rest and it redirects the fluid flow in the same direction as the pump torque such that the resulting output torque of the TC is amplified.This is called the torque multiplication or torque amplification phase. At higher turbine speed, the stator rotates freely in the same direction of the pump and it is considered to consume no torque. Therefore, the turbine torque in this torque coupling phase is the same as the pump torque [4].TC act as hydraulic dampers to interrupt vibration propagation originated from either engines or road bumps and to provide torque multiplication during vehicle launch [5]. Since TC is essentially a damper, losses are not negligible.However, these losses can be reduced by employing a TC bypass clutch, which mechanically connects the TC pump
and the turbine when the clutch is engaged. This connection improves TC efficiency at the price of losing the capability to absorb oscillations in the powertrain. A compromising solution is proposed by Kazemi et al., allowing 1 to 2% of clutch slip to achieve similar results as the TC is working as a damper [4]. Obviously, people desire to minimize this slip for efficiency consideration. This type of bypass clutch is a socalled minimal slip-type TC clutch.
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