Yanmar 4TNV98, Service Manual

Page: 174 / 246

4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System 172
Overview
Pump
Figure 7-4
The drive shaft directly receives the engine
revolution via the timing belt (or gear) and transfers
it to the cam disc via the cross coupling. Since the
dowel pin of the cam disc is integrated with the
plunger and fixed in the groove in the plunger collar,
the plunger operates at the same speed as the cam
disc.
The cam disc has a face cam and conducts
reciprocating operations by the specified cam lift on
the roller in the roller holder assembly.
On the outside of the plunger are two plunger
springs having the settling force to return the
plunger lifted by the cam disc during the lowering
process. Thus, the plunger revolves by means of
the drive shaft and the reciprocates by means of
the cam disc. When the fuel fed under high
pressure by the plunger reaches the outlet port, the
delivery valve opens to inject it into the engine
combustion chamber via the nozzle and nozzle
holder.
Governor
Figure 7-5
The governor is located above the inspection pump
chamber and mainly consists of a flyweight holder
and governor lever assembly. The flyweight holder
holds four flyweights and governor sleeves, and is
supported by the governor shaft.
The drive gear engages with the flyweight holder
gear to increase the revolutions of the drive shaft
and to turn the flyweight holder assembly. The
governor lever assembly is secured by the pivot
bolt of the pump housing and the ball pin at the
bottom of the assembly is inserted into the control
sleeve which slides on the outer periphery of the
plunger. The governor spring at the top of the
assembly is connected to the tension lever by the
retaining pin. The end of the governor spring is
connected to the control lever via the control lever
shaft. The control lever is linked to the acceleration
pedal via the link to change the set force of the
governor spring according to the inclined angle.
The difference between the governor spring set
force and the flyweight centrifugal force determines
the moving distance of the control sleeve, thereby
increasing or decreasing the fuel injection volume.