SU1754361A1 - Method of reconditioning crankshafts - Google Patents

Abstract

Usage: restoration and repair of engine crankshafts. Essence of the invention 1 measures the actual length of the crankshaft before overlaying and extends it by the value of D1f + + A 1c, where 1ph is the actual length of the crankshaft before overlaying, n is the actual length of the crankshaft after surfacing; D1f - the difference between the nominal and the actual length of the crankshaft before overlaying, А 1Н - the difference between the actual lengths of the crankshaft before and after the overlaying. The worn crank neck is then melted and polished after cooling. 5 il.

Description

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

The efficiency of the crankshaft has eaten up the wear of the necks having exhausted all repair dimensions, is violated and for its subsequent restoration the specified shaft necks are subject to metal surfacing. Metal surfacing on the necks of the crankshaft cranks is associated with high temperatures, the occurrence of thermal stresses and entails the deformation and drawing of the cheeks adjacent to the necks, which B turn causes a decrease in the length of the crankshaft (shortening) and a change in the radius of the crank.

Often the shortening of the crankshaft reaches such a value that it is impossible to put the shaft in the cylinder block of an automobile engine.

A known method of restoring the crankshaft is that metal is deposited on worn crankpins with simultaneous stretching of the crankshaft, then the necks are polished.

This method does not completely eliminate the shortening of the crankshaft, while the shaft is stretched due to deformation (distortion) in the weakest areas of the cheeks (bridges between the necks) with the appearance of dangerous plant stresses in them, which lead to a significant decrease in strength .

The purpose of the invention is to improve the quality of restoration with ensuring the nominal length of the crankshaft after overlaying.

The goal is achieved by measuring the actual length of the crankshaft and, depending on this, lengthening it by an amount

L D1f + D | n.

cl

with

N ate

s

W

about

where - the difference between the nominal (a) and the actual before welding (f) the length of the crankshaft, mm;

D IH - the difference between the actual before welding 0f) and after welding (n) the length of the crankshaft, mm, for which alternately each of the exposed surfacing connecting rod necks are mounted on supports that are located on the side of the axis of the crankshaft; The crankshaft lengths are selected depending on the indicated differences, and bend the necks in the planes of their cranks with a convexity towards the axis of the crankshaft, with each of the cranks with the neck being subjected to surfacing free divergence of cheeks in different directions by the value of L / n, where n is the number of crankpins, subjected to bending.

The amount of elongation is determined experimentally by measuring the length of a batch of crankshafts of nominal length after overlaying. It depends on the model of the crankshaft and the type of surfacing.

The pick up forces for acting on the neck can be in the range of 2 to 300 tons per mm of the length of the crankshaft, depending on its design.

When surfacing metal, the necks of the crankshaft remain bent, and the cheeks under the influence of complex redistribution of thermal stresses during the heating and cooling of the shaft deform, closer to each other, which ensures the nominal length of the crankshaft. Moreover, the preliminary bending of the crank neck before the metal welding allows to exclude the forced deformation of the cheeks adjacent to these necks and being the weakest dangerous place of the crankshaft, and to replace them with free divergence of the cheeks in different directions when they rotate along with the bend necks, elongated crankshaft. When metal is melted on the necks and the shaft is cooled, these cheeks under the influence of a complex redistribution of thermal stresses are deformed and converge, providing the nominal length of the split shaft.

Since the weakest areas of the crankshaft (cheeks) in the process of the applied restoration method are not subjected to force effects and deformation, the initial strength of the crankshaft is not reduced.

Fig. 1 shows a section of a crankshaft with a worn connecting rod neck before its metal is deposited; figure 2 - section

a crankshaft, in which the crank neck is bent by the proposed method; fig.Z - the same, after the deposition of metal on a worn pre-curved neck and thermal deformation of the cheeks; 4 is the same after grinding a metal-guided neck with a restored nominal crank length; 5 shows a four-section crankshaft of an automobile engine of nominal length (a), a change in its length after overlaying the connecting rod journals (b), a shaft received for repair with a length less than the nominal value (c) and that crankshaft extended by the proposed method to (d) and after (e) surfacing.

The crankshaft, which had the original crank parameters: length 0, crank radius r0 and diameter of the necks do, which lost its operation due to wear of the necks beyond the limits of the repair dimensions, and received diameter of the necks cN, is restored as follows.

Before overlaying metal on worn straight crankpins, 1 measure the actual length (φ) of the crankshaft (Figures 1 and 5 c) and compare it with the nominal length (1a). Depending on the actual shaft length, extend it by L D | f + D1N, where - the difference between the nominal (a) and actual (f) lengths of the crankshaft before overlaying; D n - the difference between the actual before the overlaying (f) and after the overlaying (1c) crankshaft lengths. To extend the shaft, alternately each of the connecting rod journals 1 being exposed to surfacing is set with edges 2 on the supports 2, so that the supports 2 are located on the side of the shaft axis ( 2 and 5d). On the opposite side of each neck, efforts P are applied depending on the differences in the lengths of the crankshaft (D1F and D1H) and bend the necks in the planes of their cranks with a bulge toward the axis of the crankshaft. Each of the cranks with the deposited neck 1 is lengthened due to the free divergence of its cheeks in different directions by the value L / n, where n is the number of connecting rod necks 1 subjected to bending. Thus, the length of the crankshaft is increased to the value of L, i.e. to a value that ensures the restoration of the length of the crankshaft during the deposition and cooling of the necks, taking into account its shortening from deformation of the cheeks.

If one or several necks are to be deposited (not all), then only they affect the change in the total length of the crankshaft, since only as a result of their surfacing the cheeks adjacent to them will deform. Therefore, only these crankpins must be bent in order to restore the nominal length of the crankshaft,

Then, metal is deposited on pre-curved worn crankshaft necks, in which the cheeks associated with them, under the influence of complex redistribution of thermal stresses, are deformed and converge, providing the nominal length of the crankshaft (Fig. 3 and 5). .

Then, the pre-curved necks 1 are polished to a diameter do, while maintaining the radius of the cranks equal to the initial value (figure 4). The presence of a grinding allowance makes it possible to restore the nominal value of the diameter of the necks.

After performing in the sequence of actions described, the crankshaft is restored to operability.

The proposed method of restoring the crankshaft is highly efficient, since it provides full recoverability of the nominal length of the crankshaft during surfacing of worn-out necks. This method is simple, does not require large expenses, and provides special technological equipment because it allows the elongation of the crankshaft in a cold state with the possibility direct control over the results of the process, while eliminating the force on the most dangerous weak elements of the crankshaft - cheeks, which contributes to maintaining its strength and allows the use of this method for restoring crankshafts of brittle materials - cast iron.

The proposed method makes it possible to have a large economic effect in restoring the chamfered shafts by welding metal to the necks, saving about 30% of the crankshafts, which are rejected as the final scrap as a result of excessive shortening. The method allows to maintain the repair stock, save spare parts and metal for the manufacture of these spare parts.

Claims (1)

Invention Formula A crankshaft restoration method, in which metal is deposited on worn crankshafts and, after cooling, the welds are grinded, characterized in that, in order to improve the quality of recovery by ensuring the nominal length of the crankshaft after surfacing, the actual crankshaft length and elongation are measured before the weld they are his value L D1f + D1n, where A 1f is the difference between the nominal and actual lengths of the crankshaft before overlaying, mm; A 1c - the difference between the actual lengths of the crankshaft before and after overlaying, mm, for which each of the crank pins of the restored crank is alternately mounted on supports that are positioned on the axis of the crankshaft, force is applied from the opposite side of the neck and the curvature is curved toward the axis the crankshaft, wherein each of the cranks with the neck being subjected to surfacing is lengthened by L / n, where n is the number of crank journals subjected to welding. fS / Fs / fid H Fg //: 2 Q uh FIG. five