Crankshaft; Pistons And Piston Rings - Kubota D650-B Handbuch

Crankslultt
(8)
0076F007
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1-3 CRANKSHAFT
The crankshaft is driven by the pistons and connecting rods,
and translates its reciprocating movement into a circular
movement. It also drives the oil pump, camshaft and fuel
camshaft. Six counterweights are integrated into one unit to
minimize bearing wear and lubricating oil temperature rise.
Crankshaft journals, crankpins and oil seal sliding section
are induction-hardened to raise wear resistance quality.
Crankshaft journals are supported by the main bearing cases
in which bearing is used.
Crankshaft bearing 1 at the front end is a wind type bushing
and the three bearings 2 behind are split type bushings.
Side bearings 1, 2 of split type are mounted on both sides of
the main bearing case 1 at the flywheel side.
Crankshaft bearings and side bearings are plated with special
alloy to raise wear resistance quality.
(11 Crankshaft
(5) Crankshaft bearing 1
(2) Piston
(6)
Crankshaft bearing
2
(3) Connecting rod
(7) Side bearing
(4) Oil passage
(8) Counterweight
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[AJ Pistons and piston rings
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1-4 PISTON AND PISTON RINGS
Piston circumference has a special elliptic shape in considera­
tion of expansion due to explosion heat. Piston head is flat­
formed. Furthermore, ribs are provided between the piston
head and top ring to reduce distortion and to help heat
radiation (only 0850-B, OH850-B, 0950-B).
Piston is made of special aluminum alloy of low thermal
expansion and high temperature resistance.
Top ring is of key stone type which can stand against heavy
load, and the sliding surface to the cylinder wall is shaped
into barrel face which is well fitted to the wall and plated
with hard chrome.
Second ring is of under-cut type which is effective to prevent
oil rising.
Oil ring is effective to scrape oil because it is closely fitted to
the cylinder wall by coil expander and the upper and lower
ends of its sliding surface are cut diagonally to raise fare
pressure to the cylinder walls.
A part of scraped oil is forced into the inside of piston
through oil escape holes of rings and piston. The oil ring is
plated with hard chrome to increase wear resistance quality.
(11 Rib (4)
Herd chrome plating
(2) Top ring
(5) Second ring
(3) Berrel fece
(6) Coil expander ring
42