BENDIX M-21-M-22 ANTILOCK MOD ASSY Manual de servicio descargar pdf (Pagina 7)

Governor

The governor (D2) is mounted on the compressor. It operates in conjunction with the

compressor unloading mechanism and maintains reservoir air pressure between a pre-

determined maximum and minimum pressure.

Reservoir air pressure enters the governor at its reservoir connect port and acts on the

piston and inlet/exhaust valve. As the air pressure builds up, the piston and valve

move together against the resistance of the pressure setting spring. When the reser-

voir air pressure reaches the cut-out setting of the governor, the exhaust stem seats

on the inlet/exhaust valve, closing the exhaust passage and then opening the inlet

passage. Reservoir air pressure then flows around the inlet valve, through the passage

in the piston and out the unloader port to the compressor unloading mechanism. Air

also flows around the piston, which is slightly larger at the upper end. The added force

resulting from this larger area assures a positive action and fully opens the inlet valve.

As the system reservoir air pressure drops to the cut-in setting of the governor, the

force exerted by the air pressure on the piston will be reduced so that the pressure

setting spring will move the piston down. The inlet valve will close and the exhaust will

open. With the exhaust open, the air in the unloader line will escape back through the

piston, through the exhaust stem and out the exhaust port.

Air Dryer (optional)

Reservoirs

A reservoir is a storage tank. Its function is to provide a volume of compressed air for

the braking that will be adequate in relation to the volume used by the brake cham-

bers and auxiliary devices. It also provides a location in the brake system where the

air, heated by compression, may be cooled and the water vapor condensed. Oil,

passed by the air compressor, collects along with the water condenses as an emul-

sion, and should be drained regularly.

The Ottawa dual brake system utilizes three reservoirs. The first one in the circuit,

starting from the compressor, is the primary reservoir. The outlet of this reservoir is

connected through one-way check valves to the inlets of the rear brake reservoir and

the front brake reservoir. The check valves isolate each brake reservoir from each

other. If air is lost in one, the other is still available for braking in its split circuit.

Low Pressure Indicator

The low pressure indicator is a safety device designed to give an automatic warning to

the driver whenever air pressure in the air brake system is below the safe minimum for

normal vehicle operation. It is used to operate an electrical buzzer and warning light,

which are audible and visible to the driver.

The electrical contacts of the indicator switch remain closed by spring force until the

air brake system pressure below the diaphragm is above the setting (force) of the low-

pressure indicator spring.

Air Brake System

Revised 11/15/99

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BENDIX M-21-M-22 ANTILOCK MOD ASSY Manual de servicio Pagina 7