Based on the hydraulic pressure created by the oil pump, the hydraulic control system governs the hydraulic pressure acting on the torque converter, clutches, and brakes in accordance with the vehicle condition.
There are five solenoid valves on the valve body.
| • | The S1 and S2 solenoid valves are turned on and off by the TCM to operate the shift valves, which change the gear positions. |
| • | Neutral control is operated by switching on the SN solenoid. |
| • | The SLT solenoid valve is operated by signals from the TCM to the hydraulic pressure for the clutches and brakes to reduce shock. |
| • | The SLU solenoid valve modulates lock up on and off pressure in the torque converter by control signals from the TCM. The SLU also controls active pressure to the lock up clutch and creates perfect up shift feel. |
Control Functions of the TCM
Shift Control and Lock Up Control
Using the vehicle speed and the position of the throttle the TCM operates the automatic shifting control by switching the 2-3 Shift Solenoid Valve Assembly S1 (313), the 1-2/3-4 Shift Solenoid Valve Assembly S2 (316) on and off for each transmission gear. The lock up control solenoid SLU (310) is also switch on and off according to operate the lock up control.
Gear | S1 | S2 |
|---|---|---|
1st | Off | On |
2nd | On | On |
3rd | On | Off |
4th | Off | Off |
The AF 17 has the capability to change some of the running modes automatically when a certain specific condition is satisfied. The AF 17 is always in the "Economy mode". The "Winter mode" is operated by a switch on the shifter control panel.
| • | Driver's adaptive shift control (Economy mode, Power mode) |
| Economy mode is used for normal driving condition after the ignition is ON. The driver's driving habits are detected by the using fuzzy logics from the accelerator pedal operation. This control changes shift points to Economy mode (low speed) and Power mode (high speed) according to the drivers driving habits. |
| • | Winter Mode |
| The mode is used to start moving the vehicle on slippery roads by activating the winter mode switch. The transmission will be in 3rd gear. |
Throttle Pressure Control
In accordance with the throttle position and the selected gear position the throttle position is controlled by the TCM.
Line Pressure Control
| • | Engagement pressure control when shifting |
| TCM controls the energizing current of the line pressure control solenoid valve assembly SLT (312) to reduce the shift shock and the output of the throttle position for each shift. |
| • | Increase line pressure with low temperature |
| When the transmission oil temperature is below 10 degree C (50 degree F) and the vehicle speed is below 5 km/h (3 mph), the TCM sends signal to the line pressure control solenoid valve assembly SLT (312) to increase the pressure to reduce the shift times. N to D and N to R |
Lock Up Slip Control
A slight slipping in the lock up clutch in the disengagement range of the lock up clutch permits the lock up clutch engagement range to expand to the low vehicle speed, and controls the increase of engine RPMs. The acceleration slip control is for "improved transmission efficiency from low vehicle speed". The deceleration slip control can achieve the excellent mileage by "the expansion of the fuel efficiency range".
Neutral Control
When a vehicle is stopped in "D" and the brakes applied, the AF 17 will go to the neutral condition releasing the forward clutch (C1) will engage, the transmission will be in 1st gear and creep force will occur again.
If the vehicle is stopped on an upslope, creep force does not operate because of neutral condition by the Neutral control. Therefore the TCM operates the 2nd and 4th clutch brake (B1) and keeps the equivalent force to creeping force. This is called the "Hill Hold" function.
If the TCM detects steep upslope by decreasing of acceleration, Neutral control does not operate.
The TCM directly controls the forward clutch (C1) by the linear solenoid function of the Line Pressure Control Solenoid Valve Assembly (SLT).
When vehicle is operated in the Winter mode, the TCM implements Neutral control by keeping the AF 17 in 3rd gear, engages the over drive clutch (C0) and operates the Hill Hold function.
Neutral control does the following 3 processes:
- C1 release control
- C1 neutral control (keep in neutral)
- C1 apply control
| • | C1 release control |
| The TCM detects a stopped vehicle due to RPM change in the C1. Oil pressure is released and the C1 clutch disengages smoothly. |
| The TCM operates the Hill Hold function after sends signal to turn ON the 1-2/3-4 Shift Solenoid Valve Assembly S2 (316), and engages the 2nd and 4th clutch brake ((B1). The releasing time of the C1 is learned by varying the C1 piston stroke. |
| • | C1 in neutral control |
| This control applies the C1 clutch with the Line Pressure Control Solenoid Valve Assembly (SLT) by switching on the neutral switching solenoid SN (301) and keeps neutral control moderately during neutral. This control decreases the load of the C1 clutch and prevents delay in re-engagement. |
| • | C1 apply control |
| This control applies C1 pressure smoothly and C1 clutch is engaged moderately when brake pedal is release. It releases the B1 and cancels the Hill Hold function. The control then switches off the S2 and SN to be able to start driving in 1st gear. |
| • | Self Diagnosis |
| The TCM constantly monitors the sensors, solenoid valves and the other electrical parts to detect malfunctions. If a malfunction occurs in the system, the TCM turns on the SES light and sets a DTC. |
| • | Backup Program |
| When the TCM detects that a malfuntion has occurred, all five solenoids will be turned off. The vehicle can then be driven to the nearest service facility by manual shifting the gears. |
Hydraulic Control System
Bases on the hydraulic pressure created by the oil pump, the hydraulic control system governs the hydraulic pressure acting on the torque converter, clutches, and brakes in accordance with the vehicle condition.
There are five solenoid valves on the valve body.
| • | The S1 and S2 solenoid valves are turned on and off by the TCM to operate the shift valves, which change the gear positions. |
| • | Neutral control is operated by switching on the SN solenoid. |
| • | The SLT solenoid valve is operated by signals from the TCM to the hydraulic pressure for the clutches and brakes to reduce shock. |
| • | The SLU solenoid valve modulates lock up on and off pressure in the torque converter by control signals from the TCM. The SLU also controls active pressure to the lock up clutch and creates perfect up shift feel. |
Operation of Clutches and Brakes
Clutch and Brake | Operation | |||||
|---|---|---|---|---|---|---|
1 | C1-Forward Clutch |
| ||||
2 | C3-Coast Clutch | Connects input shaft and rear planetary ring gear when C1 operates | ||||
3 | C0-Overdrive Clutch | Connects input shaft and front planetary ring gear when C1 operates | ||||
4 | B2-1st and Reverse Brake | Locks rotation of front planetary ring gear | ||||
5 | C2-Reverse Clutch | Connects input shaft and planetary sun gear | ||||
6 | B1-2nd and 4th Brake | Locks rotation of planetary sun gear | ||||
7 | F0-Overrun Oneway Clutch | When C1 operates and the transission is being driven by the engine, this clutch connects input shaft and rear planetary ring gear | ||||
8 | F1-Coast Oneway Clutch | Locks counterclockwise rotation of front planetary ring gear | ||||
