1. Lock-up relay valve and Lock-up signal valve
These valves switch the lock-up. The lock-up relay valve reverses the fluid flow through the converter (lockup clutch) in accordance with a signal pressure from the lock-up signal valve. When signal pressure is applied on the bottom of the lock-up relay valve, the lock-up relay valve is pushed up. This opens up the fluid passage to the rear of the lock-up clutch, causing it to engage. If signal pressure is cut off, the lockup relay valve is forced downward by the line pressure and spring force applied on the top of the relay valve. This opens up the passage to the front of the lock-up clutch, causing it to disengage.
2. Secondary regulator valve
This valve regulates the converter pressure and lubrication pressure. The balance of these two forces regulates the converter fluid pressure and lubrication pressure. The converter pressure is supplied from the primary regulator valve and sent out to the lock-up relay valve.
3. Cut-back valve
This valve regulates the cut-back pressure applied on the throttle valve, and is actuated by line pressure and throttle pressure. Applying cut-back pressure to the throttle valve in this manner lowers the throttle pressure to prevent unnecessary power loss from the oil pump.
4. Throttle modulator valve
This valve products throttle modulator pressure. The throttle modulator pressure is slightly lower than the throttle pressure when the throttle valve is wide open. This causes throttle modulator pressure to be applied on the primary regulator valve so that changes in line pressure are more nearly in accordance with engine output.
The accumulator acts to cushion shifting shock. There is a difference in the surface area of the operating side and the back pressure side of the accumulator piston. When the line pressure from the manual valve is applied on the operating side, the piston slowly rises and the line pressure sent to the clutches and brakes is gradually raised. Some models control the hydraulic pressure applied on the accumulator with the linear solenoid valve for even smoother shifting.
In full hydraulically-controlled automatic transaxles, a governor valve is used to detect the vehicle speed. The governor valve generates the governor pressure according to the rotation speed of the output shaft. The vehicle speed required for gear shift is detected from the level of the governor pressure.