The Engine & ECT ECU performs the following controls.
Control of shift timing
Control of lock-up
Control of flex lock-up
The ECT vehicle can be driven smoothly and comfortable by the above controls.
Control of Shift Timing
The Engine & ECT ECU has programmed into its memory the optimal shift pattern for each shift lever position and each driving mode. Based on the shift pattern, the ECU turns the solenoid valves on or off in accordance with the vehicle speed signal from the vehicle speed sensor, with the throttle opening angle signal from the throttle position sensor and with various sensor/switch signals. In this manner, the ECU operates each solenoid valve, opening or closing the fluid passages to the clutches and brakes permits shifting up or down of the transaxle.
When a vehicle is driven, you can judge if the automatic transaxle is faulty or not by how well the shifting points conform to the automatic shift diagram.
The relationship between the vehicle speed and gear varies by the accelerator opening angle even at the same vehicle speed. When driving while normally keeping the accelerator opening constant, the vehicle speed increases and the transaxle shifts up. When the accelerator is released at point A shown in the figure at left and the accelerator opening reaches point B, the transaxle shifts up from 3rd to O/D gear. Conversely, when the accelerator is further depressed at point A and the accelerator opening reaches point C, the transmission shifts down from 3rd to 2nd gear.
When the coolant temperature is low, the transaxle does not shift up to O/D gear.
The speed at which the transaxle shifts up and the speed at which it shifts down occur with in a certain range, regardless of the gear. This range is called hysteresis. Hysteresis is a characteristic built into every automatic transaxle to prevent the transaxle from shifting up and down too frequently. The shift timing control differs depending on the driving pattern select switch mode. The ECU determines what the current mode is and controls the shift timing.
Example: For the power mode, the gear shift point and lock-up point are set to a higher engine speed than for the normal mode, which allows the driving sportier vehicle as using a higher engine speed.