Yanmar YM276 Service Manual page 500

Fuel System
GOVERNOR (Continued)
-
HOW THE GOVERNOR WORKS
Two major forces affect governor operation - ( 1 ) centrifugal
force and, ( 2 ) Regulator spring. Centrifugal force acts upon the
governor flyweights and thrust sleeve. Counteracting centrifugal
force i s the force exerted by the regulator spring.
A third force, torque spring, works t o oppose regulator spring force
when the engine speed drop below the rated speed
(a
condition
of low centrifugal force).
Essentially for a constant speed, the centrifugal force and regulator
spring force must be balanced. When either one of the two forces
exceeds the other, a change in fuel delivery will take place as long
a s thedeffteRdwewsk+e
.
.
e e ~ t i o n a l limits.
Let's take a look a t two different operating conditions and see
how the governor responds t o them:
(1
)
Engine load increased,
and (21 Engine load decreased.
Engine Load Increased
Referring t o the illustration, notice how the governor responds to
an increased load on the engine. The regulator lever (I) had
previously been set for the desired engine speed. This tensions the
regulator spring
( G ) .
1. As the load on the engine is increased, engine speed
i s
reduced
(needs more fuel). The centrifugal force, therefore, i s reduced.
2.
A decrease in the centrifugal force causes the governor fly-
weighs (A) t o come closer together. This in turn, moves the
-
governor thrust sleeve
(B)
t o the left, toward the crankshaft
gear
(J).
3.
The 1st governor lever
(C)
moves t o the left, following the
thrust sleeve, because o f tension on the regulator spring through
pin
(K)
on control lever (HI.
4.
I f the increased load o n the engine does not produce an over.
load condition, governor lever will move against fuel limiter
spring (Dl, but not compress
it
(this is the rated, or full load
speed position).
5.
If an overload condition exists, the 1st governor lever will
move t o the left, and 2nd governor lever will move t o the right
t o increase fuel injection volume.
6.
When moving the 2nd governor lever r o the right, the control
lever (H) also moves t o right by regulator spring force, until
the pin
(KI
hit. against the 2nd governor lever, compressing
limiter spring
(D).
7.
As the load on engine stabilizes or
i s decreased, the centrifugal
force becomes balanced with the governor spring force, and
the arnwnt of fuel delivered t o the engine will be lessened
t o produce a constant speed.
Should an overload condition still exist, the injection pump
will deliver fuel at is maximum rate until either the overload
condition is removed, or the tractor stalls.
A
-
F l p e b h ~
G
-
Rwlamr
Spring
B
-
ThntR S l w a H
-
Contml Lava.
- .
C
-
I s l Gowarnor
Lsvar
I
-
Rqul.tor Lwer
0
-
Fuel Limiter snd
Spring J
-
Cnnkhaft Gear
E
-
2nd Governor Lwer K -Pin
F
-
Contml R r k
SMEZ76OIl
JB3M YMZ76and 2760
I(;amota.
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