On cars Yaris / Echo Toyota for the first time for itself massively used an interesting device – automatic clutch TFT (Toyota Free-Tronic).
The TFT drive controls the fluid pressure supplied to the clutch master cylinder, by turning the unit on and off.
Sensors mounted on the gearbox determine the current position of the gearshift lever, a speed sensor measures the speed of the gearbox input shaft. Limit switches on the lever proactively inform the unit that the driver is about to engage the gearshift lever.
The indicator warns about the presence of a malfunction in the TFT system (blinks) or that the driver is trying to make an incorrect switch (steady on).
Electric radial piston pump constantly maintains high pressure in the accumulator (diaphragm type with a cavity filled with compressed nitrogen), so that the stored volume is sufficient for several clutch disengages.
The pressure in the accumulator branch is controlled by a sensor – when the pressure drops, the unit activates the electric pump, and when the pressure reaches its nominal value again, after a few seconds the unit turns off the electric pump.
To redistribute fluid flows, a spool valve driven by an electromagnet is used. Pressure reducing valve vents if pressure is too high..
1 – reservoir of working fluid,
The spool valve operates in three modes, corresponding to a decrease, increase and retention of pressure in the MCC.
|Pressure reduction mode – the clutch engages. The degree of opening of the channel between the MCC and the drain is controlled by the amount of current supplied to the winding.||Pressure increase mode – the clutch engages. The degree of opening of the channel between the MCC and the accumulator is controlled by the amount of current supplied to the winding.|
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When engine shut off, the channel between the drain and the MCC is constantly open and the clutch remains on.
Launch. When the ignition is turned on (if the gearshift lever is in neutral), the TFT block disengages the clutch, after which the engine can be started.
Start of movement. When the lever is switched to 1st, 2nd or reverse gear, the corresponding signal is sent to the TFT control unit. When you press the accelerator pedal, the throttle position signal is also transmitted to the unit. After that, the unit puts the spool valve into pressure reduction mode, engages the clutch and the car starts to move. The position of the spool changes gradually to ensure sufficient clutch engagement. When the speed of the crankshaft and the input shaft of the gearbox are aligned, the unit completely opens the MCC channel to the drain and fully engages the clutch.
Gear shift. When moving the gearshift lever and releasing the accelerator pedal, the corresponding signals are sent to the TFT control unit, which determines the need to turn off the clutch, and connects the GCC channel to the accumulator line. After the unit determines the moment of the end of the shift (by the signal of the neutral sensor and the limit switches of the lever), the clutch is again engaged.
Stop. When the vehicle is braking, when the gearbox input shaft speed drops below the set level, the TFT control unit disengages the clutch.
At opening the driver’s door the corresponding signal enters the TFT control unit and it activates the electric pump to accumulate the pressure of the liquid in the accumulator.
If the car is in gear, then after turning on the ignition, depressing the brake pedal and moving the gearshift lever, the TFT control unit disengages the clutch, as a result, the lever can be easily turned into neutral.
Buzzer used to alert the driver in some situations:
– if the engine is running, the lever is set to a position other than neutral and the driver’s door is open;
– in case of an error during the “down” switch (for example, at a sufficiently high speed after the 5th gear, the driver tries to turn on the 2nd gear);
– if the driver tries to start the engine with the gear engaged;
– if the driver tries to move off the gear above the 3rd;
– with excessive clutch load (for example, during prolonged operation with the clutch partially engaged);
– if the brake pedal has not been pressed for a set period of time with the gear engaged.
Toyota Yaris / Echo / Yaris Verso 1999-2005
1SZ-FE (1.0) 1NZ-FE (1.5) 2NZ-FE (1.3)
Repairs. Exploitation. Maintenance.
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