The crankshaft acts to convert the linear motion of the pistons into revolving motion. In order to be able to receive great force and revolve at high speed, it needs enough strength and rigidity, along with durability to wear, and to be statically and dynamically balanced to rotate smoothly. The crank pin and the crank journal are attached by a hardening process in order to make it enduring and durable against wear. The balance weight is installed to balance with the crankshaft rotation. The crank pin and the crank journal have an oil hole. The oil travels from the cylinder block, enters into the oil hole of the journal and goes through to the crank pin.
Offsetting the crankshaft center and the cylinder bore center serves to raise engine efficiency
The maximum amount of combustion pressure that the pistons receive can be efficiently transferred to thecrankshaft.
By reducing the amount of force in the thrust direction of the piston, friction loss is reduced.
ExampleAmount of crankshaft offset
1NZ-FE and 2NZ-FE engines12 mm (0.472 in.)
1SZ-FE and 2SZ-FE engines8 mm (0.315 in.)
The numbers for the journal installation
position and installation orientation are
inscribed on the crankshaft bearing cap.
ExampleZZ engine series.
Some bearing caps are single unit with
ladder-frame construction, which consists
of the bottom of the cylinder block.