RU2063324C1 - Method for hardening crankshaft and device for its implementation - Google Patents

Abstract

FIELD: plastic metal working. SUBSTANCE: method is meant for surface hardening of crankshaft s to enhance their wear resistance. Crankshaft neck is installed between indenters of bearing and pressing units. Static load is applied to it simultaneously and plastic deformation of neck is conducted in cold state by reduction with indenters arranged opposite to each other. While hardening neck loads are successively applied along and over perimeter of neck embracing the whole of its working surface. Pressing and bearing units of device for implementation of method are manufactured for paired change of distance between indenter along shaft axis and for movement of indenters in plane perpendicular to shaft axis. Indenters are separable. EFFECT: enhanced wear resistance of shaft neck. 6 dwg

Description

 The invention relates to the processing of metals by pressure, in particular, to hardening associated with increased wear resistance of the service surfaces of the journal journals, for example, cast iron crankshafts.

 Known conventional methods for increasing the wear resistance of the necks of the crankshafts by increasing their surface hardness using surface hardening or chemical-thermal treatment (1).

 However, in known methods of increasing the surface hardness is achieved by heating the part, followed by rapid cooling (usually TB4) or saturation of its surface, for example, nitrogen with prolonged high heating. This is accompanied by structural changes, often causing cracks, as well as significant radial (runout) and axial (shortening) deformations of the shafts and, in particular, crankshafts of engines, reaching large values, sometimes measured in millimeters.

 The appearance of these defects often leads to the rejection of parts or to the use of additional corrective technological methods, such as additional hot dressing and others that are not capable of high-quality manufacturing or restoration of parts due to additional thermal deformations, as well as an increase in the cost of parts and, above all cast iron crankshafts.

 The possibility of increasing the neck hardness for some types of crankshafts and, in particular, cast-iron shafts of automobile engines, acquires special significance also because there are certain difficulties in introducing conventional methods for increasing hardness. Because of this, the crankshafts of many automobile engines are operated with "raw", unhardened necks, having increased wear.

 The problem solved by the invention is the ability to increase the wear resistance of the neck of the shaft by increasing their hardness by plastic deformation by successively compressing the surfaces of the necks of the indenters in the cold state.

 It was established, in particular, that when compressing the neck of a cast-iron crankshaft by indenters, the hardness on its surface increases significantly. The obtained dependence of the change in hardness under the indenter at the neck of the cast-iron crankshaft is shown in FIG. 1.

 Closest to the technical nature of the proposed technical solution is a method of hardening the crankshaft, carried out to increase its fatigue strength (2), in which the neck of the shaft is installed between the support and pressure blocks and a static load is applied to it at the same time.

 A known device for implementing this method, i.e. to increase the fatigue strength of the shaft, it contains identical push and support blocks with indenters mounted one against the other and having a constant defined distance between the indenters.

 In this case, the press force is transmitted to the neck of the crankshaft at the same time from the side of the pressure and support blocks only in the sections of the interface between the neck of the crankshaft and dumbbells.

 In order to increase the wear resistance in the described method of hardening the crankshaft, in which the neck is installed between the support and pressure blocks and simultaneously applied to it by the static load from the side of the pressure and support blocks, according to the invention, hardening is carried out by plastic deformation of the neck in the cold state of compression by indenters gradually mating in pairs along and around the periphery with the neck, covering its entire working surface.

 In the hardening device, which contains identical pressure and support blocks with indenters between which the shaft is located, the pressure and support blocks have indenters located along the shaft neck, the distance between which varies along the length of the neck and which are moved forward, rotated or displaced in pairs to transfer the load neck, gradually along and around the periphery, covering its working surface.

 In FIG. Figure 1 shows the dependence of the change in the hardness of the neck of the crankshaft from ductile iron on the load applied to the indenters.

 In FIG. 2 shows a flow chart of a method of hardening the neck of a cast iron crankshaft to increase hardness (wear resistance).

 In FIG. 3, 4, 5 and 6 indicate the design options of devices using rotation (Fig. 3), extension by wedges (Fig. 4) and cams (Fig. 5), as well as a change (Fig. 6) of indenters for hardening the working surface of the shaft necks .

The method is as follows. The neck of the shaft 4 (figure 2), starting from the middle part (possibly otherwise) is installed on the indenters 3 of the support block 2, having a shape along the periphery similar to the neck of the shaft. On the opposite side, on the hardenable part of the neck opposite the support block 2, a pressure block 1 with similar indenters 3 is installed in the shape and size of the support block 2. Press forces (not shown) are applied to the pressure block 1, corresponding to obtaining the necessary surface hardness of the neck to increase its wear resistance ( 2.300 t). The strictly opposite arrangement of the indenters 3 of the support and pressure blocks located at the same distance along the neck from its middle creates conditions when the reactions in the support block are equal and oppositely directed to the applied forces, and therefore, approximately the same hardness is obtained from opposite sides of the neck . After removing the load, the neck of the shaft 4 is rotated to the required angle, for example, 90 ^o and perform similar actions. Thus, the required hardness is obtained in the hardened area along the entire periphery of the neck.

 Further, for plastic deformation of subsequent, more distant sections from the middle of the neck along the shaft, the shaft neck is mated outside the already hardened section with newly extended or rotated indenters spaced at the same distance and perform the described actions.

 A device for hardening (increasing hardness) of the surface of the necks of crankshafts, increasing their wear resistance, contains a pressure unit with indenters 3, mating their working surfaces with a shaft 4 and a support block 2 with indenters 3 identical to the pressure unit. The indenters 3 of the push and support blocks are installed in pairs with an offset along the axis of the shaft (Fig. 3) or have the possibility of adjustable extension, movement along the axis of the shaft, changing the distance equally (Fig. 4, 5, 6).

 On the side of the support and pressure blocks, two indenters are in contact with the shaft at the same time, which are initially installed next to each other.

 After the application of press forces and hardening of opposing surfaces, the shaft is rotated by a certain angle and the indicated indenters 3 strengthen the surfaces of the shaft neck around the entire perimeter.

 To harden the working surface of the neck of the shaft along the axis located behind the already hardened section, it is necessary to equally change the distance between the indenters of the pressure and support blocks by the value of their width and carry out the above steps in the specified sequence.

A variant of the device in which the indenters of both the support and the pressure blocks are mounted in pairs from different sides and with different distances between themselves, covering the entire working surface along the length and periphery of the neck, is shown in FIG. 3. It is necessary to turn the push and support blocks of the device and the shaft neck will mate with the indenters having the desired distance. After turning the device and pairing the neck with the indenters 3, 3a, 3b and 3c and applying the press forces, the necessary working surface of the shaft neck will be hardened
A device with indenters of the pressure and support blocks arranged in a row and covering the entire length of the neck is shown in Fig. 4. The indenters contact in pairs, starting from the middle of the neck, by extending the indenters perpendicular to the axis of the shaft neck with wedges of bars 5, placed under the desired pair of indenters 3 of push 1 and support 2 units of the device, before applying the load. After the creation of efforts by the press in each of the provisions I, II, III and IV, the neck is hardened.

 The design of the device with indenters-cams at the pressure and support blocks mounted on separate shaft-bushings, with the ability to rotate, is given in FIG. 5. Rotating the shafts 5, 6, 7 and 8 behind the squares with a key, indentors are put forward in pairs with different distances and pair the required pair of indenter cams with a hardened neck, covering its entire surface.

 A variant of the device is also proposed (Fig. 6), in which the push and support blocks are equipped with replaceable indenters, each pair having different distances between each other (or having the ability to adjust this distance), allowing to cover and strengthen the entire working surface of the neck.

The device operates as follows. The neck of the shaft 4 is installed with the middle part on the shifted indenters 3 of the support block 2 (or on a pair of permanently mounted indenters, the support block 2 of the device, Fig. 3), they are mated with similarly assembled indenters 3 of the pressure block 1 and press forces are applied. Plastic deformation of the middle portion of the working surface and the neck (top and bottom) occurs, turning which, after removing the load at the required angle, for example 90 ^o , produce similar actions.

 After hardening the middle part of the neck of the shaft, its surface is mated with indenters and pressure blocks of the device having a distance greater than the width of the indenter by turning the blocks (Fig. 3), extending (Figs. 4, 5) or changing the indenters (Fig. 6).

 Hardening of the subsequent section of the neck along its axis outside the middle hardened section, performing the above steps.

 Thus, the entire working surface of the neck is hardened.

 During the operation of the engines, there are seizures of individual necks of the crankshafts, when their hardness is lost as a result of heating. The proposed method and device allows quite easily and cheaply without heating to restore the wear resistance, and therefore the performance of both individual necks and shafts as a whole, which were previously rejected into scrap metal. YYY2 YYY4

Claims (2)

 1. A method of hardening the crankshaft, in which the neck is installed between the indenters of the support and pressure blocks, simultaneously applying a static load to it from the side of the pressure and support blocks and plastic deformation of the neck is carried out by cold pressing by indenters in pairs located opposite each other, characterized in that when hardening the neck, the load is applied sequentially along and along the perimeter of the neck and cover its entire working surface.  2. A device for hardening the crankshaft, comprising a pressure and support blocks with indenters located along the axis of the shaft and having identical structural design, with a distance between the indenters of the pressure block equal to the distance between the indenters of the support block, characterized in that the pressure and support blocks for the sequential load transfer during hardening and coverage of the entire hardened surface of the shaft journal is made with the possibility of pairwise changing the distance between indenters along the axis of the shaft and with the possibility of placement of indenters in a plane perpendicular to the axis of the shaft, as well as with the possibility of changing indenters.

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