Kubota D1803-CR-E4, Workshop Manual

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2.14.3 Function of rocker arm
When one end of a rocker arm is pushed up by a push
rod, the rocker arm rotates centered on the rocker arm
shaft and the other end pushes open a valve.
2.15 Camshaft
2.15.1 Outline of camshaft
The camshaft determines the intake and exhaust valve
timing.
2.15.2 Structure of camshaft
The camshaft is made up of a camshaft and cam gear.
(1) Cam gear
(2) Camshaft stopper
(3) Cam journal (4) Intake valve cam
(5) Exhaust valve cam
2.15.3 Function of camshaft
The camshaft determines the intake and exhaust valve
timing.
Intake cams and exhaust cams are integrated onto the
camshaft for each cylinder.
The rotation of the gear at the end of the crankshaft is
transferred to the cam gear and the camshaft rotates
synchronized with the crankshaft.
The camshaft rotates once for every two rotations of
the crankshaft.
2.15.4 Specification of camshaft
Intake valve
timing
Open angle 0.20 rad (9°) before T.D.C.
Close angle 0.68 rad (39°) after B.D.C.
Exhaust valve
timing
Open angle 0.72 rad (41°) before B.D.C.
Close angle 0.20 rad (9°) after T.D.C.
2.16 Valve
2.16.1 Outline of valve
Valves open and close passages (ports) that conducted
to the combustion chamber.
2.16.2 Structure of valve
Intake and exhaust valves are mounted to the cylinder
head via valve springs, valve retainers, and collets.
(1) Exhaust valve
(2) Intake valve
(3) Valve stem (4) Valve face
(5) Valve head
2.16.3 Function of valve
In general, intake valve diameters are designed larger
than exhaust valve diameters.
Have a function of making the combustion chamber
airtight while the intake and exhaust valves are closed.
Intake valve
• Intake valves are valves through which intake air
flows into the combustion chamber.
• Open and close timing is determined by the intake
cams.
Exhaust valve
• Exhaust valves are valves that eject exhaust gases
after combustion.
• Open and close timing is determined by the
exhaust cams.
2.16.4 Specification of valve
Intake valve head diameter
37.5 mm
1.48 in.
Exhaust valve head diameter
32.0 mm
1.26 in.
Valve clearance
0.18 to 0.22 mm
0.0071 to 0.0086 in.
4. ENGINE
MECHANISM
2. Engine body
4-10
D1803-CR-E4,D1803-CR-TE4,D1803-CR-TIE4,V2403-CR-E4,V2403-CR-TE4,V2403-CR-TE4BG,V2403-CR-TIE4
KiSC issued 12, 2018 A