770G and 772G Off-Highway Truck Hydraulic and Braking System: Brake Accumulator, Brake Valve (Parking) & Brake Valve (Front Service Brake)

1.-Brake Accumulator

Left side view of truck (1) Brake Accumulator (Parking)(2) Brake Accumulator (Service)

The brake charging section of Gear Pump (Brake, Brake Cooling, Hoist) supplies Brake Accumulator (Parking) (1) and Brake Accumulator (Service) (2). The accumulators supply the required oil flow in order to engage the front and rear service brakes. The accumulators supply oil in order to disengage the rear parking brakes. The service brake system is applied by oil pressure and released by springs. The parking brake system is applied by springs and released by oil pressure. The brake accumulators are located on the left side of the machine near the entrance to the cab.

The accumulator relief valves in the Control Manifold (Brake Accumulator Charge) control the amount of pressure in the brake accumulators.

The braking system uses a check valve between Brake Accumulator (Parking) (1) and Brake Accumulator (Service) (2). The check valve only allows Brake Accumulator (Parking) (1) to be filled by the parking brake release section of Pump and Motor (Parking Brake Release, Secondary Steering). Filling Brake Accumulator (Parking) (1) allows the parking brake to be released.

Note: The pressure in the brake system is fully released through the brake accumulators approximately 45 seconds after the engine is shut down with the key in the cab. If the engine is shut down with the engine shutdown switch that is located on the left side stairs, the accumulators will remain charged indefinitely.

2.-Brake Valve (Parking)

Brake Valve (Parking) (1) Parking brake solenoid valve (2) Purge solenoid valve (3) Port for pressure switch (4) Port for parking brake oil (5) Inlet for pressurized oil from brake accumulator(6) Outlet to hydraulic tank

The Brake Valve (Parking) is located inside the left frame rail immediately forward of the middle crossmember.

Pressurized oil flows from the parking brake accumulator to port (5) on the Brake Valve (Parking). When parking brake solenoid valve (1) is energized, brake oil moves a valve that allows pressurized brake oil to flow through port (4). The pressurized brake oil flows through port (4) to the front parking brakes and the rear parking brakes.

When the machine is shut down, purge solenoid valve (2) is energized which drains the brake accumulators to the hydraulic tank through port (6) .

The parking brake pressure switch that is in port (3) monitors the pressure at the parking brakes.

3.-Brake Valve (Front Service Brake)

Brake Valve (Front Service Brake) (1) Front service brake solenoid(2) Front service brake manifold

View of the underside of the cab on the left upper frame (1) Front service brake solenoid (2) Front service brake manifold (3) Foot Brake Control (Service) (4) Position Sensor (Foot Brake Control)(5) Service Brake Valve (Foot Control)

The Brake Valve (Front Service Brake) is mounted below the cab on the left upper frame. The Brake Valve (Front Service Brake) consists of front service brake manifold (2) and front service brake solenoid (1). Front service brake solenoid (1) controls oil flow to the front service brakes. The amount of oil flow to the front service brakes is determined by the Brake ECM based on a signal from Position Sensor (Foot Brake Control) (4). The Brake ECM allows some oil from the service brake accumulator to flow to the front service brakes. The Brake ECM regulates the oil flow by controlling the position of front service brake solenoid (1) .

The Brake ECM also uses Position Sensor (Foot Brake Control) (4) in order to energize the brake light relay (located in cab). Energizing the brake light relay turns on the brake lights.

Service Brake Valve (Foot Control) (5) is mounted below the floor of the cab. When Foot Brake Control (Service) (5) is depressed, an internal spool directs oil flow from the service brake accumulator to the Brake Valve (Rear Service Brake, Retarder Control, Traction Control). Oil then flows to the rear service brakes.

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770G and 772G Off-Highway Truck Hydraulic and Braking System: Brake Accumulator, Brake Valve (Parking) & Brake Valve (Front Service Brake) 2012-12-26T20:12:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown