Yanmar 4LHA-DTP, Operation Manual

Page: 372 / 670

Chapter 3 Fuel Injection Equipment
5. Injection Pump Construction and Operation
Delivery valve holder
Damping valve
spring
Orifice
Damping valve
Delivery valve
spring
Delivery valve
n
fa
i 4LHA Series
The damping valve is a component of the deliv-
ery valve and its construction is shown in Fig.
17.
The damping valve compresses the damping
valve spring and opens almost simultaneously
with the opening of the delivery valve. Fuel oil
delivered by the plunger through the injection
pipe is then delivered to the nozzle holder and
the nozzle. After the end-of-injection the damp-
ing valve is closed more quickly (seated) than
the delivery valve by the set force of the damp-
ing valve spring.
Following this, because only the retracted fuel
oil is returned through the small orifice in the
centre of the damping valve up until the time
that the delivery valve is seated, a sudden re-
duction in the injection pipe's in-line pressure
can be prevented.
A sudden reduction in pressure may some-
times result in negative pressure, thereby
causing cavitation. This may result in corrosion
of the injection pipes and finally the danger of
pipe breakage.
The damping valve is installed to prevent the
above problems.
:
i g . 17 Damping valve operation
v
3-1-15