Crank Shaft

Crankshaft introduction

The crankshaft is the most important part of the engine. It bears the force transmitted from the connecting rod and converts it into torque to output through the crankshaft and drive other accessories on the engine to work.
The crankshaft is subjected to the combined action of the centrifugal force of the rotating mass, the periodic gas inertial force and the reciprocating inertial force, so that the curved bearing is subjected to bending and torsion loads.
Therefore, the crankshaft is required to have sufficient strength and rigidity, and the surface of the journal should be wear-resistant, work uniformly, and have good balance.

Crankshaft action

It cooperates with the connecting rod to convert the gas pressure acting on the piston into rotating power, which is transmitted to the transmission mechanism of the chassis.

At the same time, it drives the air distribution mechanism and other auxiliary devices, such as fans, water pumps, and generators. When working, the curved bearing is affected by gas pressure, inertial force and moment of inertia. The force is large and complex, and it bears the impact of alternating loads.

At the same time, the crankshaft is a high-speed rotating part. Therefore, the crankshaft is required to have sufficient rigidity and strength, have a good ability to withstand impact loads, wear resistance and good lubrication.

Crankshaft parameters

Birthplace:	China	Brand:< /td>	Other
Guarantee:	3 months	Car model:	Sinotruk
Engine code:	6D14T	Product name:	Crankshaft
Application:	Diesel engine	Size:	Standard size or OEM standard
Engine type:	Diesel engine	Health/Condition:	100% new

Crankshaft inspection mainly includes crack inspection, deformation inspection and wear inspection.

(1) Inspection and repair of cracks. After cleaning the crankshaft, first check for cracks. Magnetic flaw detector or dye penetrant can be used for crack inspection. If the crankshaft is found to be cracked, it should be scrapped and replaced.
(2) Maintenance of crankshaft bending. The inspection of bending deformation should be based on the common axis of the main journal at both ends, and check the radial circle runout error of the central main journal.
When inspecting, place the main journals at both ends of the crankshaft on the V-shaped block of the inspection plate, put the dial indicator contact vertically on the middle main journal, slowly rotate the crankshaft one circle, the maximum value indicated by the dial indicator pointer Swing difference.
If the radial circle runout error value of the journal is greater than 0.15mm, the pressure should be corrected. Below this limit, it can be corrected in conjunction with grinding the main journal.

Crankshaft working principle

It bears the force transmitted from the connecting rod and converts it into torque to output through the crankshaft and drive other accessories on the engine to work. The crankshaft is subjected to the combined action of the centrifugal force of the rotating mass, the periodic gas inertial force and the reciprocating inertial force, so that the curved bearing is subjected to bending and torsion loads.

Crankshaft forging technology

Automatic lines with hot die forging presses and electro-hydraulic hammers as the main engine are the development direction of forging crankshaft production. These production lines will generally use precision shear blanking, roll forging (cross wedge rolling) billet, intermediate frequency induction heating, and finishing hydraulic press Advanced technology such as fine pressing, and auxiliary machines such as manipulators, conveyor belts, and mold changing devices with turntables are also equipped to form a flexible manufacturing system (FMS).

Through FMS, workpieces and molds can be automatically replaced, and parameters can be adjusted automatically, and continuous measurement during work. Display and record data such as forging thickness and maximum pressure and compare with the fixed value, select the best deformation to obtain high-quality products.

The entire system is monitored by the central control room to realize unmanned operation. The crankshaft forged by this forging method has the full fibrous nature of the internal metal streamline, which can increase the fatigue strength by more than 20%.

FAQ

1The clearance between the crankshaft journal and the bearing bush increases after wear:

It may be because there is too little engine oil or there are hard abrasives in the engine oil, the engine oil has deteriorated and contains acidic substances, and the matching gap between the journal and the bearing bush is too large or too small, which makes it difficult for the oil film to form and dry friction will cause early wear.
When the crankshaft rotates, under the action of centrifugal force, the mechanical impurities in the oil are biased to the side of the oil hole and become abrasive, causing uneven wear of the journal and producing taper.

2Scratches or strains on the surface of the crankshaft journal:

The lubricating oil of the oil pan was not replaced on time, so that the lubricating oil contained large metal objects and other abrasive particles mixed into the gap between the bearing bush and the journal to scratch and scratch the friction surface.
The maintenance of the air filter is not done properly, the cylinder liner, piston and piston ring wear gap increases, and the abrasives with sand, impurities, etc. are sucked into the cylinder and burned to the oil pan, circulating into the journal and bearing. Fit the gap.

3Crankshaft deformation:

The deformation of the crankshaft is usually bending deformation and torsion deformation. An excessively deformed crankshaft will cause aggravated wear of itself and its connected parts, accelerate fatigue, and cause crankshaft fracture and excessive mechanical vibration.

4Broken crankshaft:

Crankshaft fracture also represents engine damage. Generally, the common fracture locations are the crank arm where the two adjacent fillets of the journal meet, and the oil hole of the connecting rod journal.
All the causes of cracks on the surface of the crankshaft journal and the bending and twisting of the crankshaft are the causes of crankshaft fracture.