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Alfa Romeo's new TCT transmission system |
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The new Alfa TCT transmission was designed, developed and produced by Fiat
Powertrain Technologies and is a three-shaft mechanical gearbox operated by an electrohydraulic actuation system, called CAS (Complete Actuation System) managed on its turn by the electronic control unit - TCU.
The DDCT is the pride of the development line already started in the past with the robotised transmissions MTA. What is more, as an absolute innovation, the TCT system offers the same advantages of reduced consumption of the MTA system (Fig. 2 – horizontal axis) and the same driving comfort (Fig. 2 - vertical axis) of an automatic transmission. Compared to a traditional manual gearbox, the transmission of movement from engine to transmission occurs through two clutch plates. In this way, consumption is reduced while driving comfort increases. The system basically consists of a manual transmission, with two dry clutch plates and a synchronised manual gearbox managed by an electrohydraulic robot. |
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AT |
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automatic transmission |
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ATnew |
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new generation automatic transmission |
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Wet-DCT |
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Wet Dual clutch transmission |
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MT |
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mechanical manual transmission |
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MTA Selespeed |
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robotised transmission |
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Alfa TCT |
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twin clutch dry transmission |
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ALFA TCT mechanical transmission
To transmit movement continuously, FPT engineers had to find out solutions that let the C635 mechanical transmission satisfy such requirement. The ALFA TCT main shaft is formed by two main shafts reciprocally coaxial: the outer main shaft and the inner main shaft. The junction area houses an axial bearing for the reciprocal rotation. Both shafts are made in steel, but the inner main shaft has a ribbing for keying third and fifth speed drive gears, while the outer main shaft is in a single piece. |
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LuK clutches
The clutches can be divided into odd speed gear clutch called K1, splined on the inner main shaft and housing all gears for odd speeds (first, third, fifth and reverse) and even gear clutch called K2, splined on the outer main shaft, housing all gears for even speeds (second, fourth and sixth).
The clutches are produced by LuK. The odd gear clutch K1 is normally closed and has an automatic clearance recovery mechanism. The clutch K2 is normally open and has no recovery mechanism. |
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C.A.S. (Complete Actuation System)
The CAS consists of:
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Hydraulic power unit |
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Actuation unit called CAM (Complete Actuation Module) |
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CSC, odd gear clutch K1 and CSC, even gear clutch K2 |
Hydraulic power unit.
The unit includes an electric pump, high pressure pipes connecting the CAM solenoid valve unit and a preshaped hose connecting the valve unit to the pump.
Technical specifications:
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Line pressure at room temperature between 44 and 55 bar |
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Operating temperature between -30°C and +120°C |
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Starting possible up to a temperature of -30°C |
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The pump flow rate is > 1.35 l/min |
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The accumulator volume is 480 cm3, preloaded at 30 bar at 20°C |
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Accumulator, precharged with nitrogen |
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motor |
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oil pump |
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low pressure oil pipe |
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high pressure oil pipe |
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CAM (Complete Actuation Module).
The module is formed by four proportional pressure solenoid valves PPV, a flow proportional solenoid valve QPV for CSC K1, a control pressure sensor for CSC K2, a line pressure sensor, magneto-resistive sensors controlling the shifter movement, gear engagement pistons and transmission input revolution sensors.
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The Complete Actuation Module includes: |
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Electrohydraulic kit line pressure sensor |
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Proportional pressure solenoid valve PPV K2
(for even gear clutch control) |
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Proportional pressure solenoid valve PPV-S shifter |
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Proportional pressure solenoid valve PPV1 for engagement (engagement of third - (seventh) - second - reverse speed gears) |
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Proportional flow solenoid valve QPV K1
(for odd gear clutch control) |
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Proportional pressure solenoid valve PPV2 for engagement (engagement of first-sixth-fourth-fifth speed gears) |
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Shifter selector position sensor |
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Shifter selector axis |
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CSC K2 pressure sensor |
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CSC K2 oil outlet |
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Low pressure oil outlet towards hydraulic power unit |
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CSC K1 oil outlet |
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Connection to pressure accumulator |
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High pressure oil inlet from hydraulic power unit |
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