RU1792817C - Method of reconditioning crankshafts - Google Patents

Abstract

Use: in the repair of engines. SUMMARY OF THE INVENTION: a method for restoring crankshafts involves machining the necks while processing additional fillets, securing the semicircular linings to the necks. In this case, the joints of the pads are placed 2 in places farthest from the concentration zones of bending and torsional stresses, and their ends are made with a profile corresponding to the profile of the adjacent additional fillet. The parameters of each plate are those of the corresponding machined shaft journal in the following ratios: a "- (0.8-1.1) R; L I - 2 d; g (0.9 ... 1.5) R; D / d - 0.003 ... 0.05, where d is the diameter of the shaft journal; I - the length of the machined part of the neck for installing pads; R is the radius of the original fillet, g is the radius of the additional fillet; a - distance of the beginning of the additional fillet from the corresponding edge of the neck; and - lining thickness; L is the width of the lining; d is the gap between the end face of the lining and the surface of the additional fillet. 3 s.p. crystals, 3 tablets, 3 ill. ate with

Description

The invention relates to engine repair and is intended, in particular, to provide for the restoration of crankshafts worn beyond the maximum repair dimensions.

A known method of restoring worn crankshaft necks (KB), including machining the necks and fillets over the maximum repair dimensions, followed by welding steel half rings at their joints, located in the zoya of minimal wear on the necks.

However, preliminary mechanical processing of the crankshaft for setting on the chuck of the required thickness (4.,. 5 mm)

is performed by additional grinding of the necks and fillets over the maximum repair dimensions by 2.5 ... 3.5 mm in diameter, which leads to a decrease in the residual fatigue strength of the crankshaft by at least 20%, and the residual fatigue life by 5..IO times. Therefore, such a method is not effective for restoring shafts worn beyond repair dimensions. In addition, the location of the joints of the semicircles in the zone of minimal wear is not optimal, since in the general case these zones do not coincide with the zones of minimum stresses from bending and torques.

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A known method for restoring crankshafts, including machining the cylindrical surface of worn shaft necks of pre-repair sizes with simultaneous processing of a part of the fillet transition and the formation of an additional fillet, which is a continuation of the machined cylindrical surface, the beginning of the additional taltel being at a distance from the corresponding edge of the neck less than half the radius of the original fillet transition, and the radius of the additional fillet is equal to the fault of the radius of the original (main) fillet. :; /: /: -. : -:, U; ..

Thanks to the implementation of the additional fillet and preservation of the original fillet (partially), the known recovery method compared to the analogue allows saving. residual strength and residual life of the crankshaft during machining to the repair size. However, to restore the crankshaft, isio-. overshoot beyond repair dimensions by welding, for example half-rings. pads, parameters, preliminary machining of the necks indicated in the formula are not legitimate to provide the necessary durability of the crankshaft, cotton wool after restoration. These parameters, namely, the radius of the additional taltel and the distance from the edge of the neck to the beginning of the additional fillet, are valid only for shafts worn to repair sizes and require additional optimization on the basis of tests and experiments.

The closest technical solution (prototype) is the method of restoring crankshaft necks worn out beyond the limits of repair dimensions, in which the necks are machined with technological penetration into the body of the reconstructed. surfaces with simultaneous processing of additional cylindrical surfaces and, in the case of continuation of the machined cylindrical surface, fixing a compensating wear layer of the material, for example, half-ring N. ,: followed by grinding in; nominal size.

The known method of restoring crankshafts worn beyond repair dimensions involves the execution of additional fillets under the neck during the machining process on the necks — the installation and welding of wear-compensating linings, but has the following disadvantages:

1) only the general principle of the approach to the restoration of such Eals is indicated. The optimization of the ratios of the parameters of the pads and the parameters of the corresponding machined necks of the shafts was not carried out, which ultimately leads to a decrease in the durability of the restored shafts;

.2) the welding of the half rings without gluing them to the surface of the necks causes additional difficulties associated with. ensuring a tight fit of the half rings to the sheikval .-; ./-; /. ;;:. . There is a waviness of the outer surface of the half rings due to their elastic deformation under the influence of a cyclic dynamic load and the movement of the center of mass (KB, half rings, liner, connecting rod),. as a result, initiated fritting corrosion along the cylindrical part of the neck. This process leads to an increase in the probability of failure of KB according to the criteria (jamming, turning of the liners and reducing fatigue resistance..;.;;,:: In connection with the loose fit of the half rings to the necks and their elastic deformations, the so-called ; pumping effect, which is expressed in the suction of lubricant between the neck and half rings with its discharge through the gaps in the end sections, which leads to oil starvation

in conjunction with a neck insert and, as follows

Stv.ie; to increase the probability of failure KB

. by the criterion of seizing and turning the liners. -.,.,; -; :: - .- - ---: ..:. -. Due to the loose fit of the half-prong to the necks, the stresses in the welds increase, with which the half rings are welded to the necks, the stresses in the welds increase, with which the half rings

cook to the necks and connect between

by myself. In this connection, cracks and fatigue occur in the heat-affected zone and along the welds, leading to the destruction of the neck-half-ring joint. . Productive

the location of the joints of the semicircular linings or in the zone of minimal wear (see analog) leads to a decrease in the fatigue life of the shafts, since in the general case the minimum stresses from the acting loads do not coincide with the zones of minimal wear.

Between the ends of the semirings and the additional fillet transition, edge effects in the form of fritting corrosion occur.

in connection with the contact and elastic micro displacements of the half rings relative to the necks of the HF. This leads to an increase in the stress concentration in the fillet transitions and to a decrease in the fatigue life and strength of the crankshaft.

The aim of the invention is to increase the durability of the crankshafts by eliminating the above disadvantages.

This goal is achieved by the fact that in the method of restoring crankshafts, worn out beyond the limits of repair dimensions, in which the necks are machined with a technical deepening into the body of the surface being restored with the simultaneous processing of additional fillets, which are a continuation of the machined cylindrical surface, fixing on processed by the necks of the compensating layer of the material, for example, half-ring pads, followed by grinding to the nominal size, on the proposal, joints the half rings are placed in the places farthest from the stress concentration zones from bending and torsion, and their ends are raised with the profile corresponding to the profile of the adjacent additional fillet, and the parameters of each plate are with the parameters of the corresponding machined shaft neck in the following ratios x:.

 a (0.8 ... 1.1); r (0.9 ... 1.5) R; d / b 0.03 ... 0.05; where d is the diameter of the corresponding shaft journal; . ...

gee

I - the length of the machined part of the neck for installing pads;

 R is the radius of the original untreated fillet;

1 g is the radius of the additional fillet after machining the neck;

1a is the distance of the beginning of the additional galdel at the initial fillet transition from the Corresponding neck neck;

b - lining thickness after final machining;

; I is the width of the outer surface of the lining;

6 - the gap between the lining and the surface of the adjacent additional fillet. ..

Moreover, on the necks, in the places of their mating with the cheeks, profiled flats are made, located perpendicular to the plane passing through the axis of symmetry of the adjacent main and connecting rod necks.

| In this case, in the case of adhesive bonding of the pads with the necks, after the adhesive has cured, the joints of the half-ring pads are mechanically cut, the wear-resistant adhesive composition is laid out, followed by its curing.

In the case of adhesive bonding of the pads, the compound is thermally tempered while the adhesive is cured at the tempering temperature equal to 5, the temperature of curing of the adhesive for 2 to 3 hours, 5 hours.

Thanks to the joints of the pads, in places farthest from the concentration zones of stresses from bending and torsion, the longevity of the elbows increases. shafts. This is illustrated in FIG. 2 and FIG. As is known, the crankshaft crank is affected by variable loads in the form of bending and torsional moments. The maximum stresses from bending loads occur in the overlap area of the connecting rod and root necks (in the flange area - Fig. 2, point a). Therefore, the joints of the semicircular overlays should be

0 are maximally removed from the zone (FIG. 3) corresponding to the location of point a in FIG. 2. On the other hand, maximum stresses from torque occur at the edges of the oil supply holes in

5 necks (Fig. 3, points b), from which also should be as far away as possible the pegs (seam line) of the overlays. Therefore, the optimal location of the joints (Fig.Z) at an equal distance from points a and b. .

0 The optimization of the ratios specified in the formula between the parameters of the plates and the parameters corresponding to the machined shaft journals allows .. on the basis of experimental results.

5 are given in table. 1-3, and also increase the durability of the crankshafts, applicable-: to the case of wear of the shafts in excess of the maximum repair dimensions.

Numerous laboratory tests. showed that to maximize the durability of KB, worn beyond the maximum repair dimensions, and restored by adhesive or glue-bonded linings, the value

5, the radius of the additional fillets must be increased in comparison with the recommended in the prototype g 0.5R to g (0.9 ... 1.5) R.

Test results are given in

0 tab. 1. .

It was also found that the optimal value of the parameter a is a: (0.80 ... 1.10) R. The test results are given in table. 2..

5 Experimental studies have shown that the optimum ratio of the thickness of the patch to the diameter of the corresponding shaft journal is in the range of b / a (0.03-0.05).

The experimental results are given in table. 3.

The execution of the end face in the overlays adjacent to the additional fillets with a profile corresponding to the profile of the adjacent fillet, providing the necessary optimal gap between them equal to ensure the maximum possible increase in the length of the overlays while excluding the friction of the ends of the overlays with the surface of the adjacent fillets.

The implementation of paragraph 2 of the proposed formula allows to increase the reliability of the crankshaft by reducing the peak voltage in the dangerous sections of the shaft on the necks in the places of their contact with the cheeks.

It should be added that effects in the form of fretting corrosion in dangerous sections are excluded due to the exclusion of elastic micromotion of the half rings relative to the necks. This reduces the stress concentration in the fillet transitions and increases the fatigue life of the shaft as a whole. Moreover, as tests have shown, the maximum width of the flat is at least the radius of the original fillet. Its depth for cast iron (non-hardened shafts) should be at least 1 / 3R, and for steel shafts (hardened) no more than 0.10 ... 0.20 mm. Only to exclude fretting corrosion in the joint between the ends of the half rings and the fillet transitions of the necks.

Thermal tempering of the welded joint of the pads simultaneously with the curing of the adhesive at a tempering temperature equal to the curing temperature of the adhesive for 2.5 .., 3.5 hours not only improves the reliability of the connection, but also the productivity of the restoration process as a whole

The use of a glue-welded joint of overlays, in contrast to the prototype where only welding is used, ensures that the overlays are tight against the surface of the cylindrical part of the necks and at the fillet transitions, which eliminates all of the above-mentioned disadvantages associated with the loose fit of the overlays in the joints.

In FIG. 1 shows a neck of a shaft restored by glue-welded (glue) connection of half-ring overlays, general view; in FIG. 2 is a section AA in FIG. 1; FIG. 3 is a section BB in FIG. 1.

The method is carried out as follows.

Grinding the shaft necks 1 to create a technological recess for installing the pads is offset from the cheeks 2 (Fig. 1) by a value (0.8 ... 1.1) R. This preserves the initial geometry of the fillet in the zone of maximum stress concentration, where the nucleation is also fatigue failure, without introducing additional concentrators from machining and without excluding the surface cleanliness. Deepening is carried out with the formation of an additional fillet with a radius r (0.9-1.5) R to a depth along the neck diameter b (0.03 ... 0.05) R, counting from the nominal diameter size

necks of a shaft.

If the shaft has already undergone resurfacing and regrinding to repair dimensions, then the design geometry, i.e. provided for by the drawing, of the fillet transition is restored, then the necks are deepened technologically.

Next, profiled flats are applied in dangerous sections of the shaft, located perpendicular to the plane passing

through the axis of symmetry of the adjacent main and connecting rods. - The main sizes of the flats in relation to cast iron (non-hardened) shafts are: Ch S: R; e 1 / 3R. Applicable to steel (hardened) shafts

sizes of flats are: hl S R, e (0.03 ... 0.04) R. In this case, it is necessary to ensure smooth transitions from the cheek to the flat, This completes the preparation of the shaft necks for the installation of overlays.

Semi-ring pads 3 are made of sheet material

B b + d

where A is the machining allowance. They are made by stamping, followed by drilling oil-supplying holes, boring along the inner surface with smooth curvature of the ends from the inner surface, providing the necessary width of the half rings and hardening in order to ensure optimal hardness on the outer surface. The length of the lining on the outer surface L I is 2 d, where d is the gap between the ends of the lining and the surface of the adjacent additional fillets (d 0.2, „0.3 mm).

Next, the half rings 3 along the inner surface and the shaft journal are cleaned and degreased. An adhesive layer 4 is applied to the prepared surfaces and joints are assembled using special clamps. After that, if necessary, the plates are welded with longitudinal seams 5 to the necks and between each other.

I

I The curing of adhesive 4 is carried out in a furnace with simultaneous tempering at a temperature of 250 ... 300 ° C equal to the temperature of the adhesive curing (the adhesive is taken from the class of hot adhesives; curing).

 Example. Restoration of the crankpins of the crankshaft of the ZMZ-53 engine from ductile iron VCh-50 (d 60 mm - diameter of the shaft journal, R 2 mm (radius of the original fillet).

1 The grinding of the neck of the shaft to create a technological deepening is offset from the cheeks by a value of 1.6 mm, which is 0.8 R.

Deepening is carried out with the formation of an additional fillet with a radius of r 2 mm (R g), to a depth of b 2 mm in diameter of the journal of the shaft, counting from the nominal size, which is: at d 60 mm; b / d 0.033. Profiled flats are made with a cylindrical profile cutter with a flat radius of 3 mm; and the depth of the hole is I 1 mm, which is I 1/2 R. Semi-ring pads are made by stamping from sheet material with a thickness of bo 2.2 mm with a finishing allowance A of 0.2 mm. Then, oil-supplying holes are drilled, half-ring overlays are bored1 in a special chuck along the inner side of the surface to a thickness of b 2 mm, the ends of the overlays adjacent to the additional fillets are smoothly curved, with a profile corresponding to the profile of the additional fillet, keeping the width of the outer surface of the half ring equal to L .1 - 2 d. For the particular

case L 26.2 ± 0.1 mm. This provides an average clearance of 6 0.2 mm between the end face of the patch and the surface of the fillet transition. After appropriate

the preparation of the plates makes them glued to the necks. Further, the overlays are additionally attached to the sheigmm and between the owl along the longitudinal welded willows along the joints to preserve the limit joints in the zone

the required level of wear resistance close to the level of wear resistance of the surface of the pads.

When refusing to use welding, compounds were tested whose ha after

the curing of the glue, the joints were cleared from the glue gaps (mechanical cutting) with the subsequent introduction of an antifriction wear-resistant composition into the joint zone, for example, based on anaerobic

materials (glues), etc., with fillers in the form of copper, iron and aluminum powders.

Curing of the glue is carried out in a furnace with simultaneous tempering at a temperature

250 .., 300 ° С, equal to the temperature of curing the adhesive. The adhesive is selected from the class of hot cured adhesives. After the adhesive has cured, the necks are final machined to a nominal size.

The restoration of the crankshaft main journals is similar.

The crankshafts restored by the proposed method have two

times fatigue durability in comparison with cranked i-lami, restored by the method prot prototype.

Claims (4)

Formula and Notices 1. A method for restoring crankshafts worn beyond the maximum repair dimensions, in which the necks are machined with technological penetration into the body of the surface being restored with the simultaneous processing of additional fillets, which are a continuation of the machined cylindrical surface, for - fastening on machined necks of semicircular linings, with subsequent grinding to a nominal size, with a lt; and so on, so that, in order to increase the durability of the crankshaft shafts restored by gluing or gluing the semicircular overlays, the joints of the latter are placed at the locations of the most distant stress concentration zones from bending and torsion, and the ends of the overlays are made with a profile corresponding to the profile of the adjacent additional fillet, and the parameters of each overlay are with the parameters corresponding to the machined shaft journal in the following ratios: a (0.0-1.1) R, r "(0.9-1.5) R; b / d 0.03-0.05, where d is the diameter of the corresponding shaft journal; I is the length of the machined part of the neck for the installation of pads; R is the radius of the original untreated fillet ;. . r-radius of the additional fillet after machining the neck; a - distance of the beginning of the additional fillet at the initial fillet transition from the corresponding edge of the neck; b is the thickness of the lining after the final machining; I is the width of the outer surface of the lining; ...- .. ...; 6 - the gap between the end face of the lining and the surface of the adjacent additional fillet. 2. The method according to claim 1, characterized in that on the necks in the places of their mating with the cheeks, profiled Fatigue strength compared to the original, accepted for 100% 10-25% lower 100% saved 15% increase NOTE Tests were carried out at 9R; 6 - 0.4 d. Note. Tested at 04d 0 5 flats located perpendicular to the plane passing through the axis of symmetry of the adjacent main and connecting rod necks. 3. The method according to claim 1, wherein the adhesive in the joint is cured, the joints of the semicircular overlays are mechanically cut, the wear-resistant composition is added to the cut, followed by curing. 4. The method according to claim 1, with the exception that in the case of adhesive bonding of the pads, the compound is thermally tempered while the adhesive is cured at a tempering temperature equal to: adhesive curing temperature for 2.5-3 5 hours Table 1 Grip strength Enough There is a decrease table 2 Indicators of wear resistance, scoring resistance and fatigue strength of the joint , 03d , 03d, 04d, 05d, 05d Residual stresses arise in the plates, leading to an increase in the waviness of the outer surface and, as a result, to a decrease in wear resistance and scoring resistance. All indicators satisfy the requirements Fatigue strength is reduced. Note I and e. Tests carried out at, 30R, Tabl. 3 Fatigue strength is reduced.