FI81510B - FOERFARANDE FOER AOTERSTAELLANDE AV KAMAXLAR. - Google Patents

Description

1 81510

Method of restoring camshafts

TECHNICAL FIELD The present invention relates to the repair of machines, and more particularly to methods of restoring camshafts.

Industry background

Wear on some machine parts is limited to the surfaces to which the load is applied during use. Thus, for example, the camshafts of automotive valve devices wear out 10 locally at the cams, but hardly at all at the hubs.

One method of restoring worn camshafts is known in the art, in which material is ground as much as the cams are worn, circumferential strips are placed on the soot, and these are ground (see JP Patent No. 5,247,094; Series 4/1; Bulletin 77/383; 1977).

Although this method requires a lot of work, it does not ensure good reliability of the repaired parts. It also cannot be used to build camshaft hubs and bad-worn cams.

In addition, a method of restoring the valve devices of internal combustion engines is known, in which the worn surfaces of the camshaft are machined to a repair size and the inserts are mounted in the bores of the camshaft bearings (see "Remont 25 dvigatelei avtmobilei GAZ", Shneider G.K. Gorky Publishers, 1955, 1955).

However, this method is also not suitable for repairing badly worn beakers. It also does not guarantee the reliability of the restored cams, as they lose the non-wearing layer, which is sanded off during machining. The manufacture and installation of the insides requires a lot of work.

In addition, a method of restoring camshafts using flame spraying is known (see "Gazo-termicheskoe napylenie iznoshennykh detalei mekhanizma 35 gazoraspredelenia dvigatelei avtomobilei VAZ", B.I.

2,81510

Maximovich et al., "Avtomobilnaya promyshlennost", No. 7, 1983).

Here, the worn nozzles are turned to a certain diameter and a 2.5 to 3.0 mm layer of self-melting alloy powder is melted in the molten state by means of a spray gun. The second and fourth bearing centers are constructed in the same manner with a layer having a thickness of only 0.3 or 0.4 mm. 120-150 g of material is needed to build eight cams and two bearing centers and the work takes 10-15 minutes. 10 When construction is complete and the camshafts have cooled to room temperature, they are straightened in the implement using the center bearing center as a check surface. The built-in cams and bearing centers are ground in a replicator or rotary grinder.

15 Such repair of camshafts is expensive. This requires a lot of expensive alloy powder. Surface treatment, construction of bearing centers and grinding require a lot of work due to the difficulties encountered in the processing of the alloy powder. Additional round-20 grinders are required for the job. The method cannot be used to build the first, third, and fifth bearing centers.

One method of constructing worn surfaces of steel camshafts is known in the art. followed by hardening and grinding 25 (see "Remont traktorov", Pogorely I.P. et al., Government Publication OTIZ Selkhos, 1960, pp. 154-155). The beak is roughened before construction. To prevent deformation of the camshaft caused by hardening, the centers are ground to the repair size. At the same time, the hubs are refurbished, but in this case, additional parts must be made. Therefore, the method requires both a lot of work and substance.

A method for restoring metal parts by powder arc welding and a steel electrode is also known in the art (see V.A. Nalivkin, "Tsentralizovannoe vosstanovlenie 35 detalei avtomaticheskoi naplavkoi i svarkoi", Privolshskoe, Saratov, 1965, pp. 106-107).

3 81510 This method is performed as follows.

Once the impurities left in use have been removed from the surface, the parts are inspected for defects (cracks, holes, cracks, signs of wear) that affect the size, shape and mechanical properties of the parts 5.

The following surface treatment includes the performance and refurbishment of the base surfaces to be treated and the equipping of each part with equipment to facilitate construction.

Worn surfaces are then constructed either "cold" 10 or after heating.

The first heat treatment after this is intended to remove the stresses arising during construction. K. O. treatment is either emission or annealing in air.

Next is machining, which involves rough and fine turning, milling, planing, and drilling of the formed layers. Sometimes it is necessary to perform straightening either after construction or more usually after heat treatment.

Machining is followed by a second heat treatment consisting of quenching with subsequent emissions and annealing in air.

Finally, it is the turn of rough and precise grinding, precise drilling, and so on. Various miniature finishes, such as honing and rubbing, may also be done.

25 The above measures are commonly used in the refurbishment of steel parts, mainly rotating parts.

Any surface that has been worn any amount can be constructed by powder arc welding. When wear is low, a small amount of metal must be removed from the worn surface to form a reconstituted metal layer of the required thickness. The heat treatment commonly used for reinforcement is induction hardening. Steel alloy electrodes are used to provide the desired strength of the metal layer.

4 81510 However, the cost of the material used is high, the machining required requires a lot of work and the wear resistance of the formed surfaces is low.

DISCLOSURE OF THE INVENTION The main object of the invention is to develop a method for restoring camshafts, which ensures that the quality of the restored product is the same as due to the use of a new, modified method.

This object is achieved in that in a method of restoring camshafts 10, which comprises constructing worn surfaces of steel, removing the heat treatment of the camshaft, straightening the heat treatment to strengthen it and grinding, the construction according to the invention is limited to the worn surfaces of the cams. out of the allowable limit and formed to form layers slightly larger than the size after restoration, and the constructed cams and intact cams are ground after heat treatment and straightening to remove any stress on the repair size, and then the 20 camshafts are nitrided to further strengthen them; and it is straightened once more.

It is suitable to use steel electrodes to build the local parts of the cast iron camshafts.

It is also suitable that the stress-relieving heat treatment of the cast iron camshafts 25 be performed at 600-610 ° C.

at a temperature of 3 to 3.5 hours.

The described method of restoring the camshafts results in low material consumption and durable joints between the cast iron and steel surfaces of the cams.

30 Nitriding evens out the strength properties of cast iron and steel surfaces. It also builds bearings while strengthening them.

The described method of restoring camshafts requires half the workload required to manufacture new camshafts.

Il 5 81510

The described method also utilizes a secondary metal.

Brief description of the drawings

A preferred embodiment 5 of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a camshaft to be restored; Figure 2 shows a cam restored in accordance with the invention; Fig. 3 shows a cam ground in accordance with the invention; and Fig. 4 shows a contact zone between the formed steel surface and the cast iron surface of the cam and a carbon nitride layer according to the invention.

15 Best Mode for Carrying Out the Invention

Consider, for example, the manner in which the cast-iron camshaft is restored (Fig. 1).

After the operating time, the five cams 2 have worn out beyond the permissible limit by an amount of - C2 / 20 2 where C. j is the diameter of the base circle of the new cam and C2 is the diameter of the base circle of the repair-sized cam.

The wear of each hub 4 (Fig. 1) is uniform and does not exceed 0.01 mm due to the operating conditions of the camshaft. The maximum wear of the hubs 4 does not exceed 0.03 mm on such camshafts.

After camshaft washing, centering bevels 5 and 6 are restored on lathes (not shown).

Five cams 2 are then constructed with a wear area si-30 reservoir that exceeds - C2 (Fig. 2), i. between points 2 7 and 8, using a steel electrode (not shown) under a gas arc formed by a semi-automatic building device. The fact that only wear areas 35 in the cam 2 are built reduces the need for alloy additions, 81510 6. In addition, the heat used is small in this case, so it does not affect the malleability of the cast iron camshaft 1 (Fig. 1). Only a little worn cam 3 is not restored at all. This further saves the alloy-5 in the sheds.

In order to remove the stresses formed inside the camshaft during manufacture (these can be, for example, induction hardening stresses), to remove the fatigue stresses and the stresses caused by the construction of the cams 2, the camshafts are heat treated in a shaft furnace shielding gas at 600 ° C for 3-3.5 hours. and cooled. These stress relief conditions prevent cracking in the dividing surface between the steel and cast iron parts of the cams 2 and keep the extensibility of the camshaft 1 constant-15 Mana, so that it can be straightened to precise dimensions.

Deformations are removed in a straightening press.

After straightening, the cams 2 and 3 are ground to repair size (Figs. 2, 3) in a semi-automatic, copier-20 grinder. During grinding, care must be taken to ensure that the protrusion H (Fig. 3) in the soot, which is the correction size chosen taking into account the design of the valve devices, so that the engine power is not impaired and no additional valve components have to be made, is equal to the original value.

The straightened camshaft is nitrided in a mixture of ammonia gas and exo gas using a shaft furnace.

The carbon nitride layer 9 (Fig. 4) formed on the surface of the cams 2 (Fig. 2) in nitriding provides 30 the same strength properties to the cast iron surfaces 10 and the steel spokes 11.

The radial formation of nitrided surfaces resulting from the use of carbon and nitrogen allows the centers to be restored to the dimensions shown in the drawing.

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The deformation of the camshaft 1 during nitriding (Fig. 1) is removed in a straightening press.

The camshafts restored in accordance with the present invention fully meet the requirements for new camshafts and have a service life of at least 125,000 km.

Restoring the camshafts by the described method requires half the work required to manufacture new camshafts with similar equipment.

Applicability in Industry 10 The invention is applicable to the restoration of steel and cast iron camshafts for spark ignition and diesel engines.

Claims (3)

81510 A method of restoring camshafts, comprising rebuilding worn surfaces from steel, removing stresses from the heat treatment of the camshaft (1), straightening the heat treatment to strengthen it, and grinding, characterized in that the construction is limited to those surfaces of the cams (2) have worn out beyond the permissible limit and are carried out 10 to form layers slightly larger than the size after restoration, and the rebuilt cams (2, 3) and intact cams are ground after all stress-relieving heat treatment and the camshaft (1) after straightening and then the camshaft (1) 15 is nitrided to further strengthen it and straightened again. Camshaft restoration method according to Claim 1, characterized in that steel electrodes are used for rebuilding the cast iron camshafts (1) in areas which have worn away locally above the permissible limit. Method for restoring camshafts according to Claim 1, characterized in that the stress-relieving heat treatment of the cast iron camshafts (1) is carried out at a temperature of 600 to 610 ° C for 3 to 3.5 hours. li 81 510