JL481Q connecting-rod journal is 48mm. All the cranks circle around the central main bearing journal to form mirror
symmetry. One-reciprocating inertia is mutually balanced with one-inertia torque. And two-reciprocating inertia and torque
are very small, which are generally omitted. Because all the cranks are symmetrically arranged with 180°, rotary inertia and
rotary inertia torque are balanced as a whole. But the bending torque inside the crankshaft is so large that all the cranks
are locally affected by bending. In order to relieve the bending torque between the crankshaft and the cylinder block, a
group ignition sequence of 1.4-2.3 is adopted, and meanwhile, there are 8 counterweights made at the opposite directions
of 8 cranks (Fig. 187). The centrifugal forces F1 and F4 at the two connecting-rod journals of No. 1 and No. 4 are equiva-
lent to the centrifugal forces F2 and F3 at the two connecting-rod journals, in opposite directions. F1 and F2 form moment
of couple M1-2 and F3. F4 forms moment of couple M3, also mutually balanced. But the two moments of couple have
provided bending load to the crankshaft while load on the main bearing shell is also increased so that main bearing journal
and main bearing shell are abraded slantingly. After counterweights are added, the load on main bearing shell is reduced
while the running stability of engine is improved.
In order to lubricate the connecting-rod journal, there is an oil hole with diameter of 5mm drilled from main bearing journal
to connecting-rod journal. The first main bearing journal oil hole is drilled through the first connecting-rod journal, the
second journal oil hole through the second connecting-rod journal; the fourth main bearing journal through the third
connecting-rod journal. The fifth journal oil hole is drilled through the fourth connecting-rod journal; the third main bearing
journal is without oil hole. The oil hole on the crank pin is provided at the area 220 in front of rotating crank plane, and at
the hole opening area is the low load area as far as the transition round angle of two journals. The oil hole of main bearing
journal is arrayed at the low load area. All the hole openings are polished and chamfered.
MR479Q Crankshaft stack-up degree ∆ = 9.5mm. Thickness of crank arm = 16.75mm. Width of crank arm =70mm.
MR479QA/MR481QA Crankshaft stack-up degree ∆ = 5.5mm. Thickness of crank arm = 16.75mm. Width of crank arm
=76mm. JL481Q Crankshaft stack-up degree ∆ = 5.25mm. Thickness of crank arm = 16.75mm. Width of crank arm
=76.5mm. Crank is good in rigidity and strength. The crank arm takes the shape of ellipse so that the stress is evenly
distributed, resulting in a good bending strength and torsion rigidity. Meanwhile, thickness of crank arm is transited through
the shoulder. In order to relieve the crankshaft’s weight and reduce the unbalanced properties of crankshaft rotating, the
shoulder of crankshaft adopts a big angle. In order to reduce the stress centralization between cranks and main bearing
journal and between crank and connecting-rod journal, R2 bevel is used for transition at the connecting area and roll-press
polishing treatment is provided. Crankshaft is nitridation treated in order to increase its abrasive resistance. In order to
avoid axial crankshaft displacement, two crankshaft thrust washers are placed on either side of the central main bearing.
Engine has a key slot in the front of crankshaft, through which peripheral locating and transmitting of the torque can be
carried out for crankshaft timing gear and crankshaft belt. In the forefront of crankshaft there is a hole of M12x1.25-6H and
32 in depth. Using the bolt, it can tighten the crankshaft pulley. The bearing shoulder on the side and in front of the first
main bearing journal is milled with 4 planes. The ridge among the planes can directly drive the oil pump. On the back end
of crankshaft there is a flange with diameter of 70. The end face is provided with 6 drilling holes of M10x1.25-6H, in which
the locating hole with diameter of 13 is used as a mounting mark for alignment with the locating hole on the flywheel.
For easier selection of bearing shell for assy., there are three groups separately arranged in terms of diameters of main
bearing journal and connecting-rod journal. Each group is separately marked with red, yellow and green. The mark of
crank pin is at the big chamfer of cranks, and the diameter mark for main bearing journal is at the w-type counterweight.
II. Main Bearing
Main bearing of engine includes upper bearing harf and lower bearing harf. In order to achieve a reasonable oil clearance,
there are 5 groups in terms of the total thickness of bearing center.
Upper bearing half and lower bearing half are of the steel-backed—wear-reducing layer structure. The steel-backed mate-
rial is 08F, wear-reducing layer is aluminum base alloy. The total central The steel-backed material is 08F, wear-reducing
layer is aluminum base alloy. The total central thickness is 2 ,in which aluminum base alloy is 0.3±0.1 in thickness
and bearing 20mm in width. Upper bearing has a filler hole of 6mm in diameter, and an oil reservoir of 4mm in width and
1mm in depth in the middle so that it is easy for the lubricant to enter the oil hole of main bearing journal. On the back of
upper bearing and lower bearing there is a locating recess punched. To avoid bearing bulging due to inner shrinkage during
assembly, there is a thinning area prepared on the inner sides of two ends of bearing.
+0.017
+0.002
77
Содержание JL481Q
Страница 1: ......
Страница 9: ...5 Fig 3 Components Assembly Drawing of MR479Q MR479QA Engine ...
Страница 10: ...6 Fig 4 MR479Q MR479QA Engine and Its Power System ...
Страница 11: ...7 Fig 5 Assembly Drawing of Engine and Its Auxiliaries MR479Q MR479QA ...
Страница 12: ...8 Fig 6 Electronic Control Fuel Injection System in Engine MR479Q MR479QA ...
Страница 13: ...9 Fig 7 Front view of Engine JL481Q MR481QA ...
Страница 14: ...10 Fig 8 Sectional elevation of Engine JL481Q MR481QA ...
Страница 15: ...11 Fig 9 Electronic Control Fuel Injection System in Engine JL481Q MR481QA ...
Страница 21: ...17 Fig 13 Exterior Feature of JL481Q Engine Power Me N m Torque Pe Kw ge g kwh Fuel Consumption Ratio ...