System Description

SYSTEM DIAGRAM 

Courtesy of NISSAN NORTH AMERICA, INC.

SYSTEM DESCRIPTION 

The exhaust valve timing intermediate lock control improves the cleaning ability of exhaust gas at cold starting by fixing at the intermediate position using two lock pins.

Courtesy of NISSAN NORTH AMERICA, INC.

EXHAUST VALVE TIMING INTERMEDIATE LOCK CONTROL SOLENOID VALVE CONTROL 

Cam phase is fixed at the intermediate phase by two lock keys in the camshaft sprocket (EXT).

Lock pin 1 controls retard position and lock pin 2 controls advance position. ECM controls the intermediate phase lock by opening/closing the exhaust valve timing intermediate lock control solenoid valve to control oil pressure acting on the lock pin and locking/unlocking the lock pin.

Lock/Unlock Activation 

When ECM activates the exhaust valve timing intermediate lock control solenoid valve, oil pressure generated in the oil pump is drained through the oil pressure path in the control valve. Since oil pressure is not acted on the lock pin, the lock pin position is fixed by the spring tension and the cam phase is fixed at the intermediate phase. When ECM deactivates the exhaust valve timing intermediate lock control solenoid valve, unlocking oil pressure acts on each lock pin. Lock pin 1 is not released because it is under load due to sprocket rotational force. For this reason, lock pin 2 is released first by being pushed up by unlocking oil pressure. When lock pin 2 is released, some clearance is formed between lock pin 1 and the rotor due to sprocket rotational force and return spring force. Accordingly, lock pin 1 is pushed up by unlocking oil pressure and the intermediated phase lock is released.

Courtesy of NISSAN NORTH AMERICA, INC.

When stopping the engine 

When the ignition switch is turned from idle state to OFF, ECM receives an ignition switch signal from BCM via CAN communication and activates the exhaust valve timing intermediate lock control solenoid valve and drains oil pressure acting on the lock pin before activating the exhaust valve timing control solenoid valve and operating the cam phase toward the advance position. The cam phase is fixed by the lock pin when shifting to the intermediated phase and ECM performs Lock judgment to stop the engine. The cam phase is fixed by the lock pin when shifting to the intermediated phase and ECM performs Lock judgment to stop the engine.

When starting the engine 

When starting the engine by cold start, ECM judges the locked/unlocked state when ignition switch is turned ON. When judged as locked state (fixed at the intermediate phase), the exhaust valve timing intermediate lock control solenoid valve is activated. Since oil pressure does not act on the lock pin even when the engine is started, the cam phase is fixed at the intermediate phase and the exhaust valve timing control is not performed. When the engine stops without locking the cam phase at the intermediate phase due to an engine stall and the state is not judged as locked, the exhaust valve timing intermediate lock control solenoid valve and the exhaust valve timing control solenoid valve are activated and the cam phase shifts to the advanced position to be locked at the intermediate phase. Even when not locked in the intermediate lock phase due to no oil pressure or low oil pressure, a ratchet structure of the camshaft sprocket (EXT) rotor allows the conversion to the intermediate phase in stages by engine vibration. When engine coolant temperature is more than 60 °C, the exhaust valve timing is controlled by deactivating the exhaust valve timing intermediate lock control solenoid valve and releasing the intermediate phase lock. When the engine is started after warming up, ECM releases the intermediate phase lock immediately after the engine start and controls the exhaust valve timing.