Volvo EC330B Excavator Parking Brake Operation
Procedures:
The slew brake is spring applied and hydraulically released. Friction plates are splined to cylinder block and rotate with cylinder block. Mating plates are splined to motor casing.Volvo Techtoo diagnostic software
1. When there is no SH signal, parking brake will be engaged by spring force.
2. When there is SH signal, primary pilot pressure(40bar) goes to brake piston through PG and push the brake piston against spring.
3. When there is no SH signal, Pilot pressure can not go to the brake chamber and oil in side of that chamber shoud be drained. But there is only small hole for drain near to time delay valve. In the beginning, oil pass through the orifice and go to tank, but pressure will be built up in front of the orifice and push the valve. Now the valve blocks tank line. There is no flow to tank. That means there is no pressure difference between front and rear side of valve. But the valve has return-spring at the rear side.
So the valve can return to initial position and open tank passage again. The oil from brake chamber can go to tank again.
Open-close-open movement can delay the parking brake engaging time for 6.5 seconds.
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