Kubota D650-B Handbuch Seite 66

[A) Delivery Valve
(4)
(5)
(6)
OOlIF042
[8] Pump Element
~-(10)
(8)
(9)
----(12)
OOlIF043
• Delivery Valve
The delivery valve is composed of the valve and the valve
seat. It performs two functions:
(1) Reverse flow prevention
If the circuit between the delivery chamber and the nozzle
is always closed, a time lag will occur between pressure ­
feed start of valve element and start of nozzle injection.
This, in turn, will prevent injection from stopping
properly until after completion of pressurefeed.
To eliminate this time lag, the valve lowers on completion
of pressure-feed and the relief valve contacts the valve
seat, and breaks the circuit between the injection pipe and
plunger.
(2)
Fuel dribbling prevention
After the relief valve contacts delivery valve seat, this
valve lowers a little. Since the relief valve breaks the
circuit, pressure in the injection pipe is reduced as the
valve lowers. preventing fuel dribbling from the nozzle.
• Pump Element
The pump element is composed of a cylinder and a plunger.
Their contact surfaces are precision finished to provide a high
injection pressure even at low speeds. The cylindrical surface
of the plunger has slanted grooves, which are called control
grooves, and a connecting hole for plunger head.
• Control Rack
This is connected directly to the governor fork in the engine
body. It is connected with the plunger by pinion to change
injection volume.
• Tappet
The tappet converts rotating movement of the camshaft into
a reciprocating movement to drive plunger. A roller is used
where it contacts the cam to reduce friction.
(1)
Relief valve
(2) Seat
(3)
Delivery valve seat
(4) Pressure decrease because of increase in this volume
(51 End of pressure-feed and start of sucking back
(61 End of sucking back
(7)
Pump element
(10) Feed hole
(81
Cylinder
(11)
Control groove
(9) Plunger
t12)
Driving face
70