GILLIG LOW FLOOR, Руководство по обслуживанию

Страница: 194 / 506

94
Air System
Operation
The compressor is driven by the engine and its crankshaft turns continuously while the engine is run-
ning. Compression of air is controlled by the governor and by the compressor’s unloading mechanism.
The governor maintains the brake system air pressure at preset maximum and minimum levels.
The governor is mounted apart from the compressor, either horizontally or vertically. The governor port
is located on the crankcase of the compressor (Figure 6-7).
The unloader mechanism controls the air compression cycle; an air compression cycle has three phases:
1. Induction: Air flows from the engine to the compressor, opening an inlet valve in the cylinder
head of the compressor.
2. Compression: Air pressure is increased, caus-
ing the compressor’s discharge valve to open.
3. Unloading: Air passes from the cylinder to
the inlet chamber of the cylinder head via a
port controlled by a sliding leaf valve. When
system cut-in pressure (110 psi) is reached, air
is exhausted from the unloader port.
After unloading, the unloader piston returns
the sliding leaf valve to the loaded position.
This seals the unloader ports and compression
resumes (Figure 6-8).
CyLINDER HEAD
2 CRANKCASE (CyLINDER BLOCK)
NON-THROUGH DRIVE THROUGH DRIVE
2
2
Figure 6-6, Compressor Subassemblies
GOVERNOR PORT
Figure 6-7, Governor Port
SLIDING LEAF VALVE
Figure 6-8, Sliding Leaf Valve