FUSO 4M4 – INTAKE AND EXHAUST – STRUCTURE AND OPERATION – Exhaust Shutter

4.1 Overview
• The exhaust shutter is used for controlling the diesel particulate filter regeneration and facilitating the warming up of the exhaust brake.

4.2 Operation

• The butterfly valve operates in interlocking with the lever movement.

(1) When the butterfly valve is fully opened (exhaust shutter is not operating)
• The spring in the power chamber is acting in the direction where the butterfly valve is forced open since no negative pressure is supplied from the vacuum tank.

(2) When the butterfly valve is half closed
• The negative pressure having passed through the pressure reducing valve compresses the spring in the power chamber, which causes the butterfly valve to move in the closing direction and the piston end to be pressed against the stopper bolt. At this time, however, the butterfly valve is not brought in its fully closed position because the force of the spring attached to the lever exceeds the reduced negative pressure.

(3) When the butterfly valve is fully closed
• The negative pressure is directly applied to the power chamber and compresses the spring in the power chamber, which causes the butterfly valve to move in the closing direction and the piston end to be pressed against the stopper bolt. At this time, the negative pressure is higher and therefore compresses the spring attached to the lever farther, which allows the butterfly valve to move to the fully closed position.

4.3 Control
• The exhaust shutter opens/closes the butterfly valve by the signal from the engine electronic control unit.

(1) Operation
(1.1) When the butterfly valve is fully opened (exhaust shutter is not operating)
• As there is no signal from the engine electronic control unit, the exhaust shutter 3-way magnetic valve 1 and 2 are not activated and the butterfly valve is kept open.

(1.2) When the butterfly valve is half closed
• By the ON signal from the engine electronic control unit, the exhaust shutter 3-way magnetic valve 2 is activated.
• The negative pressure from the vacuum tank is reduced by the pressure reducing valve, and the reduced pressure is applied to the power chamber. Therefore, the butterfly valve is half closed.

(1.3) When the butterfly valve is fully closed
• By the ON signal from the engine electronic control unit, the exhaust shutter 3-way magnetic valve 1 is activated.
• The negative pressure from the vacuum tank is applied to the power chamber and the butterfly valve is fully closed.