Quantcast Limit/Shutdown Pilot Valve

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control the pump pressure.
The pump pressure, as set by the accumulator,
controls the work output of the governor. Pump pressure
is also used for the auxiliary controls installed on the
governor top cover.
Increase In Speed Setting
When  the  speed  setting  shaft  is  turned
the speed setting of the governor is
increased.  The high idle screw limits the high speed
setting of the governor. As the speed setting shaft turns,
the speed setting lever pushes down on the floating lever
which is fastened to the speeder plug. The downward
pressure on the speeder plug puts the speeder spring
under compression.  The speeder spring force then
becomes greater than the centrifugal force of the
3. Base circle area. 4. Approach ramp area. 5. Cam
ballhead flyweights, and the ballhead pilot valve plunger
lift area.
is moved down.  This increases the governor speed
During the torque rise cam adjustment the set
As the pilot valve plunger is moved down,
point of the terminal shaft is positioned by the
pressure oil moves under the power piston and pushes
synchronizing pin at the full load fuel setting. The cam is
the piston up. This moves the terminal lever up and the
moved to position the cam follower on the start of the
output shafts are turned in the "increase" fuel direction to
cam lift area at a specified point that will lift the cam
follower 1.00 0.05 mm above the base circle. This
increase the engine speed.
removes the free travel (clearances) from the governor
Before the engine gets to the new set speed, the
and fuel control linkages so the torque rise will occur at
compensation system starts to move the pilot valve
the correct engine speed.
plunger back to its center position and put the governor
under stable control as follows.
Limit/Shutdown Pilot Valve
The oil above the power piston is connected to
Shutdown of the engine is done with the limit/
the upper side of the buffer piston and lower side of the
shutdown pilot valve. With the engine running on speed,
pilot valve compensation land.  As the power piston
the ballhead pilot valve is in the centered position. When
moves up the oil pressure moves the buffer piston down
the limit/shutdown pilot valve is lowered, pressure oil
and increases the compression of the lower buffer piston
above the control land of the ballhead pilot valve is
spring. The force of the spring works against the buffer
drained back to the pump area. As engine speed begins
piston movement and this results in a small increase in
to slow, ballhead flyweights move in, lowering the
oil pressure on the upper side of the buffer piston. This
ballhead pilot valve plunger. Oil under the power piston
higher pressure is directed to the lower side of the pilot
is then drained to the pump area. As the power piston
valve compensation land and makes a force to push the
moves down, the output shaft is turned in the decrease
pilot valve plunger up toward its center position. This
direction, and the engine is shut down.
stops the flow of pressure oil to the lower side of the
power piston and movement of the piston is stopped.
Make reference to the 3161 Governor Schematic
As the pilot valve plunger is returned to its center
for use with the systems operations that follow.  The
position and the power piston movement is stopped,
schematic shows the governor pilot valve in the increase
there is oil leakage through the needle valve orifice.
fuel position.
This lets the oil pressure above and below the
The 3161 Governor uses engine lubrication oil
pilot valve compensation land become equal and the
for its hydraulic system. The oil supply (under pressure)
pilot valve plunger movement is stopped and the engine
is sent to the governor through an orifice and internal
speed is returned to a stable condition. As the pressure
passages.  The oil goes from the suction side to the
above and below the compensation land become equal,
pressure side of the gerotor pump as the drive shaft is
the buffer springs return the buffer piston to its center
turned by the engine. An accumulator spring and piston
keeps the pump pressure at approximately 690 kPa (100
psi). The accumulator piston moves up in its cylinder
until the pump pressure is 690 kPa
(100 psi). At this time, ports in the piston are opened to


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