MMD Equipment 185S-6C2 - Manual (Page 31)

4.Operation
4-12
4.5 Capacity Control Device
Step Response
Start
When starting operation, purge solenoid valve SV1 opens.
And compressed air is sent to unloader chamber A and speed regulator
chamber B . The pressure in chamber A rises soon, and unloader
valve fully closes due to low pressure. Thus the load required for starting
is reduced.
Load operation
After the unit starts, it automatically performs unloaded operation and
then solenoid valve SV1 closes. As discharge pressure increases and
decreases, air flow from pressure regulator to the chamber A and
B increases and decreases. Thus, unloader valve position and engine
speed changes, and accordingly it regulates delivery air steplessly from
0 to 100 %
Suction port closing
unload operation
When air consumption is reduced, and the pressure exceeds the rated
one, speed regulator functions to lower the engine speed in proportion to
the pressure rise and, at the same time, to close unloader valve.
Under unloaded operation, the interior of compressor air-end becomes
vacuum and vacuum noise is caused. In order to prevent occurrence of
vacuum noise, it functions to open the vacuum relief valve, detecting the
secondary pressure of pressure regulator and thus it prevents high
vacuum state inside the compressor air end from being caused.
A100449E