SU1722765A1 - Method of crankshaft restoration - Google Patents

Abstract

The invention relates to the field of mechanical engineering, in particular, to methods for restoring and repairing engine crankshafts. The purpose of the invention is to improve the quality of repair, to increase the repair quality / 1, ensuring the restoration or preservation of the original length of the crankshaft. The crank neck 1 is flexed before the thermal action, and the bend is directed towards the axis of the crankshaft. With the atom adjacent to this neck 1, the cheeks 3 are turned in opposite directions, thereby increasing the total length of the crankshaft. After thermal exposure and cooling, the cheeks 3 are warped in the direction of their convergence. In this way, the nominal shaft length is restored. The pre-bent neck 1 is ground by the amount of the allowance of the repair size of the neck, exceeding the curvature of its axis from the bend. 4 il. (Ls

Description

YU

Yu

Xi

about ate

The invention relates to mechanical engineering and can be used in the repair of crankshafts of machines and mechanisms.

During repair, crankshafts are often subjected to thermal effects: annealing, hardening of the necks and other types of heat treatment causing thermal stresses, the redistribution of which after cooling leads to deformation of the cheeks, their convergence, which as a result causes a shortening of the crankshaft compared to the nominal length and change the radius of the crank.

After such thermal effects, it is not possible to fully restore the length of the crankshaft to the nominal ones by existing methods.

A known method of stretching the crankshaft during thermal impact on the neck consists in rigidly securing the shaft at both ends in a device that allows the shaft to lengthen freely during the thermal action, but prevents its shortening during cooling.

However, the known method does not completely eliminate the shortening of the shaft, but creates dangerous tensile stresses in the fillets, i.e. in the weakest places, webs between the necks of the shaft, which significantly reduces its strength properties. With this method of shaft extension, it is impossible to indicate which specific areas of the shaft cheeks are deformed, and therefore it is impossible to influence this process.

The purpose of the invention is to improve the quality of repair while ensuring the restoration or preservation of the original crankshaft length.

The goal is achieved by the fact that in the method in which the crankshaft crankshaft neck is subjected to thermal impact and then polished, before the thermal impact, the crankshaft neck is bent in the plane of the crank shaft, allowing the adjacent cheeks to rotate freely in different directions, and after the thermal impact and cooling the pre-bent neck is ground by the amount of the allowance of repair size of the neck, exceeding the curvature of its axis from the bend.

The crankshaft crankshaft bend is made in the plane of the crank by convexity toward the crankshaft axis. In this case, the cheeks adjacent to this neck, freely turning in different directions, increase the length of the shaft.

The neck is bent by an amount that takes into account the subsequent deformation of the cheeks as a result of the redistribution of thermal stresses after heating and cooling the shaft, providing the nominal value of the crankshaft length.

The selected forces for bending the necks of crankshaft cranks are in the range of 2-300 tons per 1 mm of the length of the crankshaft, depending on its design.

In the proposed method, the crank neck is placed on supports located along the edges of the neck and force is applied to the middle of the neck.

Figure 1 shows the crankshaft section prior to thermal exposure with nominal parameters: length, neck diameter and crank radius; figure 2 - the same in which the proposed bend

in a straight crank neck fashion and the cheeks move freely, allowing the shaft to be pre-elongated before thermal exposure; on fig.Z - the same, with a specially bent neck after

thermal effect on the neck; Fig. 4 is the same after grinding a bent neck by the amount of the oversize of the repair size exceeding the curvature of the neck and restoring the nominal length and

crank radius.

The length of the crankshaft is measured before thermal exposure and compared to the nominal value 0 (Fig. 1). Know the deviation of the measured shaft length from

nominal value, selected force bends straight neck 1 crank. For this, the crankshaft is mounted with the edges of the crank neck 1 on the two supports 2 so that the supports are with

the axis of the crankshaft (figure 2).

On the opposite side, in the middle of the neck 1, a matched force P is applied, bending it with a bulge towards the axis of the crankshaft, freely turning the cheeks 3 connected to it in opposite directions, extending the crankshaft to a value equal to AND (Fig. 2).

The values of force P and length And choose

so that with subsequent

deformation and convergence of the cheeks in the process

thermal effect and shaft cooling

its nominal length was provided.

Then, the shaft neck is subjected to thermal action, for example, nitriding, supplying the necessary amount of heat to it. In this case, the cheeks 3 in the process of heating and cooling the shaft as a result of the redistribution of thermal stresses, deform, converge, providing the nominal length of the crankshaft lo (Fig. 3).

Further, after cooling the shaft journal and warped cheeks, the curved crank neck is ground by an amount of the repair size exceeding the curvature of the axis of the neck obtained by bending it, while ensuring the nominal size of the crank radius.

After performing all the actions in sequence, the crankshaft is restored to working capacity.

Experimental studies and tests of the method of restoring crankshafts exposed to thermal effects showed that the method is efficient, simple, controllable, allows to maintain or correct crank parameters: neck diameter, crank radius, correct crank geometry, and length of the crankshaft. without reducing its strength. Furthermore, the method gives a great economic effect, preserving crankshafts, which are subject to rejection due to excessive shortening.

Claims (1)

Claims The method of restoring the crankshaft is that the crankshaft crank neck is thermally treated and then ground, characterized in that, in order to improve the quality of the repair so as to restore or maintain the original length of the crankshaft, bend before the thermal effect crankshaft neck in the plane of the crank, allowing the adjacent cheeks to rotate freely in different directions, and after thermal exposure and cooling, the preliminary a curved neck at the grind size allowance repair neck size exceeding its axis of curvature of the bend.