1.2. General requirements to car repairs
The main part of malfunctions of mechanical knots and units in operation arises owing to process of friction, deformation of elements, aging of material of details, etc. These and other processes involve wear and damage of details. Process of wear can be divided into three periods: to extra earnings, normal wear and emergency. In process extra earnings there is an intensive wear of the rubbing details, as a result of microroughness of the interfaced surfaces decrease, the area of contact grows, specific loadings decrease, the speed of wear is slowed down and turns into normal wear. The period of normal wear is characterized by rather small growth rate of a gap in interface, however on reaching a certain gap wear speed sharply increases that speaks about the beginning of emergency wear. Operation of the unit with emergency iznosa leads to breakages which complicate and raise the price of restoration. It is in use very important to subject knot to repair before emergency wear.
Before making decision on repair it is necessary to carry out diagnostics of a condition of interfaces in units. As a rule, diagnosing is conducted on indirect signs, such as: the increased noise, vibration, an oil consumption, break of crankcase gases, etc. For better diagnostics the unit needs to be disassembled, details to wash out, examine and take measurements. By results of survey and measurements the decision on continuation of operation without repair or is made on carrying out repair. At the same time it is necessary to be guided by the following reasons: if the actual sizes of details are in borders of fields of the admissions allowed by the this manual, then continuation of operation of the unit without repair is possible; if the sizes went beyond admissible fields of admissions, then repair is necessary. The expansion of fields of admissions given in the present manual should be understood as a possibility of use of a residual resource of knot without restoration of interfaces. In case of repair of the unit at restoration of interfaces expansion of fields of admissions over nominal is not allowed.
The technology of repair can be divided into four main stages of works:
1. Dismantling — a sink.
2. Control — sorting.
3. Actually repair: restoration micro and macrogeometry of surfaces and physicomechanical properties of details.
4. Assembly with preliminary control of the details arriving on assembly.
Dismantling and washing operations conduct in several stages: an external wash of the unit, subdismantling, a nodal sink, dismantling on a detail, a sink and cleaning of details. All details before control sorting should be cleared carefully of dirt and a deposit, to degrease, wash out and dry up. To clean, wash out oil channels and openings in details under pressure and to blow compressed air.
Details from aluminum and zinc alloys are not allowed to be washed out in the alkaline solutions applied to a sink of steel and pig-iron details as aluminum and zinc are dissolved in alkalis.
In the course of control of details fiascos, cracks, dents, sinks and other damages find external survey. At responsible details existence of cracks is checked by means of the defectoscope. The sizes of details need to be controlled in places of the greatest iznos. Teeths of gear wheels wear out unevenly therefore at their control it is necessary to measure not less than three teeths located approximately at an angle 120 °. In view of need to guarantee operation of tooth gearings during all between-repairs run a splitting off on teeths and vykroshivany the working surface of teeths of fatigue character is not allowed.
Assembly units — such as rod with a rod cover, the block of cylinders
with covers of radical bearings, gear wheels of the transmission and the main transfer cannot be razukomplektovyvat. Other assembly units can be razukomplektovyvat; if the decision on continuation of operation of the interfaced elements without repair is made, then them it is inexpedient to razukomplektovyvat.
In all cases of repair of details welding and a naplavka the welded seam should not have slag inclusions, not boiled thoroughly sites, undercuts and other defects.
After welding to smooth out a seam. To eliminate flows of metal that they did not prevent installation of the interfaced details.
Openings with the worn-out or damaged carving restore, cutting a carving of the increased repair size, making openings with the subsequent cutting of a carving of the nominal size, statement vvertyshy and spiral carving inserts. Application of carving inserts is more preferable for reasons of quality of restoration and decrease in labor costs.
The details given on assembly have to be pure and dry. Threaded connections have to be without damages. Disposable самоконтрящиеся carving fasteners have to be replaced with new. In case of impossibility to apply new самоконтрящиеся details, at statement old it is necessary to stop in addition them from an otvorachivaniye.
At assembly to establish new laying and epiploons. To oil the rubbing surfaces of details about assembly pure. At statement of cuffs their working surface should be greased in order to avoid damage at installation. At installation of cuffs with the metal case the nest under a cuff should be greased with a thin layer of sealant.
Assembly of knots and units needs to be carried out according to the present manual.
By means of the measuring tool to check the sizes of the details forming landings before assembly.
At assembly of the details having mobile landing in interface their free relative movement without jammings has to be provided. Plugs, rings of ball and roller bearings to establish by means of mandrels. At a press fitting of bearings the effort should not be transmitted through balls or rollers. Tools for a press fitting have to rest against the pressed ring. The direction of effort of a press fitting has to coincide with a bearing axis in order to avoid a distortion of rings.
If under the terms of assembly installation of responsible details is made by blow of the hammer, it is necessary to apply mandrels and hammers from non-ferrous metals, plastic, rubber, and also the device for a press fitting of details.
Splines have to be densely put in shponochny grooves of shaft by means of the hammer or mandrels from non-ferrous metal. The side play of splines in grooves of shaft is not allowed.
Hairpins have to be wrapped in carving openings densely without side play. Details have to be put on hairpins freely. Podgibaniye of hairpins at installation of details on them is not allowed, fastening of knot or detail several nuts or bolts has to be made evenly on perimeter — at first previously, and then is final.
In all cases provided by the Management it is necessary to apply the keys allowing to limit torque.
The moments of an inhaling of threaded connections if they are specially not stipulated in specifications, are defined depending on diameter of a carving according to tab. 1.3.
The bolt has to act from a nut (except especially stipulated cases) on two-three strings of a carving.
Forelocks should not act from cuts of nuts. The ends of forelocks have to be divorced and unbent — one on a bolt, and another on a nut.
Tubes of fuel-supply lines and the drive of brakes before assembly need to be blown compressed air.