4.3.14. Check of a condition of inserts of radical and conrod bearings of a bent shaft
Typical examples of wear of inserts of bearings of a bent shaft
And — Are scratched by foreign debris - the particles which plunged into a working layer of an insert are visible
In — the Lack of oil - the top layer is erased
With — Inserts are incorrectly located at installation - there are brilliant (polished) sites
D — the Neck is cramped on a cone - is skimmed all surface
Е — Wear of edge of an insert
F — Malfunction of "fatigue" - were formed craters or pockets
Despite obligation of replacement of inserts of radical and conrod bearings in the course of performance of capital repairs of the engine, the condition of old inserts needs to be subjected to attentive studying as on it it is possible to gather a lot of useful information about the general condition of the engine. Inserts of bearings are graduated on thickness and accessory to their this or that dimensional class is determined by color marking.
Exit of bearings out of operation can result from a lack of lubricant, hit of dirt or foreign particles, overloads of the engine, development of corrosion and other adverse effects. Examples of the most characteristic defects of inserts of bearings of sliding are given on an illustration Typical examples of wear of inserts of bearings of a bent shaft. Regardless of the defect nature, the reason of its emergence has to be established and eliminated prior to assembly of the engine in order to avoid a recurrence.
For survey take inserts from the beds in the block engine cylinders/case, radical and conrod covers and the lower heads of rods. Spread out the removed inserts on a pure plain working surface as an arrangement on the engine that it was possible to correlate their state to a condition of the corresponding necks of a bent shaft. Try not to touch working surfaces of inserts with hands in order to avoid casual damage of soft material.
Dirt and foreign particles get to the engine in various ways. They can be left inside after completion of capital repairs, get via filters or system of ventilation of a case. Often dirt gets at first to motive oil and already together with it gets into bearings. It is worth to remember that in the course of normal wear of the engine metal sawdust is inevitably formed. If after performance of recovery work due attention is not paid to the procedure of cleaning of the engine, in it by all means there will be abrasive particles. Regardless of a way of penetration into the engine, all foreign particles are introduced in a soft surface of inserts of bearings of sliding sooner or later and are easily distinguished at visual survey of the last. The largest particles usually do not get stuck tightly in inserts, but deep furrows and teases leave on their working surfaces and the surfaces of the corresponding necks of a shaft. The best protection against emergence of such defects is the conscientious attitude to performance of cleaning of the engine after completion of capital repairs and installation in the course of assembly of only absolutely pure components. Also it is worth to remember need of performance of regular and frequent change of motive oil.
Oil starvation can be also caused by several reasons which often are closely interconnected with each other. Treat those: the engine overheat (leading to oil fluidifying), overloads (as a result of which oil is forced out from bearings), the oil leak (connected with the excessive size of a working gap in bearings, wear of the oil pump, or excessive increase in turns of the engine), etc. The violation of passability of maslotok most often connected with negligence of installation of components at the assembly conducting to a rassovmeshcheniye of oil openings also causes reduction of supply of oil in bearings and, finally, to an exit of inserts out of operation. A characteristic sign of oil starvation is the wipe and replacement of a soft working layer of inserts from their steel substrate. Sometimes temperature increases to such an extent that on a steel substrate as a result of an overheat violet spots are formed.
It is necessary to remember that the driving manner has significant effect on service life of bearings. Increase in load of the engine is promoted by frequent full opening of a butterfly valve, the movement on small turns, etc. Replacement of an oil film from a working gap of bearings results that conducts to a softening of inserts of the last and education on their working surface of small cracks (fatigue deformation). Finally there is a peeling of separate fragments of material of a working layer and a vyryvaniye them from a substrate.
The driving manner also considerably affects service life of bearings. The movement with completely open butterfly valve, the movement on a low gear is conducted to strong overloads of bearings and squeezing from working gaps of an oil film. At the same time material of inserts is softened, and the working layer cracks. Such modification of bearing surfaces is called fatigue deformation. As a result over time the working layer begins to separate fragments from a substrate and bearings become useless.
Operation of the car in a city cycle is often connected with commission of a set of short trips that leads to development of corrosion of bearings as insufficient warming up of the engine promotes loss in it of condensate and formation of caustic gases. Aggressive products accumulate in motive oil, forming slime and acid and as oil continuously comes to bearings, finally, influence material of inserts of the last, causing its oxidation and destruction.
The wrong installation of inserts at assembly of the engine also leads to their bystry destruction. At too dense landing the size of a working gap is inadmissibly reduced that is the reason of oil starvation of bearings. Hit between backs of inserts and beds of bearings of foreign particles leads to formation of sites of an eminence of a working surface and destruction of the last in the course of normal operation of the engine.
As it was already mentioned above in this section, replacement of inserts at capital repairs of the engine has to be made without fail, regardless of their state (see Installation of a bent shaft and check of working gaps of radical bearings) - the attempt to ignore this requirement is capable to lead only to the seeming economy.