RU2809898C2 - Method of laser thermal hardening of working surface of internal combustion engine cylinder or air-cooled engine cylinder liner - Google Patents

Abstract

FIELD: manufacturing of machine parts.

SUBSTANCE: invention is used technological processes for the manufacture of machine parts, in particular cylinder liners of piston internal combustion engines or the cylinder of an air-cooled internal combustion engine. After machining the liner before installing it in the cylinder block or after installing it on the crankcase of an air-cooled engine, its internal working surface is thermally strengthened. To do this, on a section of its inner surface with length l≤(0.4…0.5)⋅S (S is the piston stroke) with a distance from the end surface of the sleeve of 0.1S with two relative rotations of the sleeve relative to the laser beam so that the heating zones form a grid, the lines of which are located at an angle ϕ≤(40…45°) to the longitudinal axis of the sleeve, the height of the formed edge in the heating zone h≤5 mcm, line spacing t≤2.5…3 mm. After laser hardening, the liner is installed in the cylinder block.

EFFECT: method of laser thermal hardening of an internal combustion engine cylinder is proposed.

1 cl, 4 dwg

Description

The invention relates to mechanical engineering, in particular to the cylinder-piston group of internal combustion engines (ICE), and can be used for heat treatment of a cylinder liner made of gray cast iron or a cylinder of an air-cooled internal combustion engine.

The purpose of the invention is to increase the durability of the internal combustion engine cylinder liner by creating the required roughness with flat tops and hardness on its working surface, which reduces wear of the cylinder liner.

The closest in technical essence and achieved technical result to the claimed one is the method of manufacturing a cylinder liner for an internal combustion engine (patent RU 2 084 673 C1, published 07/20/1997, IPC F02F 1/18, F16J 10/04).

However, the known method does not provide adequate wear resistance at significant costs for its implementation: heating to harden certain areas of the liner, applying a special absorbent coating, drying it, cooling the liner to a temperature of 20...30°, and then removing the coating after laser exposure. In addition, the distance between the spiral heating zones and their location relative to the longitudinal axis of the sleeve are not clearly defined. This method does not allow increasing labor productivity due to the duration of operations and the transition between them.

The technical result that the claimed method is aimed at achieving is increasing the wear resistance of the “liner-piston ring” pair in the zone of maximum lateral force loading and maximum thermal loading, which causes friction close to semi-dry.

To achieve the specified technical result in the known method of manufacturing an internal combustion engine cylinder liner, which consists in carrying out mechanical and thermal preparation of the liner, and then thermal hardening by heating the inner surface with a beam of laser radiation in the area l , from 0.1≤ l ≤(0, 4…0.6)⋅ S ( S is the piston stroke) counted from the upper end surface of the liner with two relative rotations of the latter relative to the laser beam so that the heating zones form a grid, the lines of which are located at an angle ϕ≤(40…45° ) to the longitudinal axis of the sleeve, the height of the formed ridge in the heating zone h ≤5 μm, the distance between the lines t ≤2.5...3 mm.

Since the process of laser processing of a sleeve is carried out at a laser radiation power of 0.75...1 kW, a moving speed of the laser head of 9 mm/s and lasts for 3...5 minutes, due to the short exposure time and the small amount of heat input, the deformation of the sleeve is significantly reduced and change in its shape due to thermal load.

Figure 1 shows a diagram of laser beam processing of the inner surface of an internal combustion engine cylinder liner.

Figure 2 shows a diagram of the arrangement of heating zones during laser hardening with one direction of relative rotation of the liner and the laser beam, as well as with rotation in mutually opposite directions, the thickness of the heating lines, the distance between them and the location of the heating lines relative to the longitudinal axis of the cylinder liner.

Figure 3 shows a cross-section of the cylinder liner of the TMZ-520D diesel engine produced by Tulamashzavod with an applied mesh after hardening.

Figure 4 shows a section of the working surface of the cylinder liner of an air-cooled diesel engine TMZ-520D of the Tulamashzavod Production Association with measured roughness before and after laser hardening.

Figure 1 shows a laser radiation source 1 that creates a beam 2 of laser radiation directed at the inner surface of the liner 3 at an angle of 45...60° to the forming wall of the cylinder liner or cylinder of an air-cooled internal combustion engine.

Figure 2 shows the spiral heating zones of the sleeve 8 (or an air-cooled internal combustion engine cylinder) when rotating it in direction 4 and moving the laser head in direction 5 (see Fig. 1), as well as the heating zones of the sleeve 9 when rotating it in the direction 6 and moving the laser head in direction 7 (see Fig. 1). The thickness of heating zones 8 and 9 is 2.5...3 mm, they are mutually perpendicular and located at an angle ϕ≤(40...45°) to the longitudinal axis of the cylinder liner.

After laser treatment, hardening structures of martensite, troostite and retained austenite are formed in the heating zones, providing high wear resistance in these areas. In addition, these hardening structures form ridges and change the roughness of the working surface of the cylinder liner in such a way that between the hardening lines 8 and 9, depressions 10 appear on the surface (see Fig. 2), in which oil is stored. This improves the operating conditions of the piston rings and reduces wear on the inner surface of the cylinder liner.

All this affects the lubrication of those areas along which the rings and piston slide. The surface tension of the oil film forces it to be drawn into the too wide recesses 10, and then the rings rub against the hardening lines 8 and 9 almost without lubrication. If the recesses are narrow, the oil is easily squeezed out of them, and another problem arises - excessive losses due to waste. The recess should be about 5 microns, and the angle ϕ at which they intersect with the longitudinal axis of the sleeve should not be more than 60°. Too sharp an angle (relative to the vertical axis of the liner) means that excessively wide recesses will appear at the intersections of the marks - and the quality of the lubricant next to them will deteriorate. The optimal angle is 40…45° (Fig. 2). If it is too large, waste losses again increase (an extreme case is longitudinal recesses in the cylinder).

To implement the method, a mesh is applied to the inner surface of a fully machined sleeve by laser heating in accordance with FIG. 2. The liner does not require additional processing after this and can be installed on the engine.

An example of a specific implementation of the method.

To implement the method of laser hardening of a cylinder liner or cylinder of an air-cooled engine TMZ-520D of the Tulamashzavod Production Association, heating is carried out on the inner working surface of the liner with a beam of laser radiation with a power of 0.55 and 0.75 kW and a moving speed of the laser head of 9 mm/s in such a way that that when the cylinder liner rotated in mutually perpendicular directions, the heating zones formed a grid with cell sizes of 2.5...3 mm. The heating lines form an angle ϕ≤40…45° with the longitudinal axis of the cylinder.

The section of the hardening line on the inner surface of the liner is located at a distance of 30 mm with a distance of 10 mm from the upper end. As dynamic calculations have shown, with a piston stroke of 40 mm from top dead center, the lateral force (from gas forces and inertia forces) decreases, which reduces the friction force.

After measuring the cross-sectional roughness, it was determined that the height of the scallop along the heating line is h = 0.5 mm, and the hardness is 68 HRC.

Claims (1)

A method of laser thermal hardening of the working surface of a cylinder liner of an internal combustion engine or an air-cooled engine cylinder, consisting in the preliminary mechanical and thermal preparation of the liner or cylinder, characterized in that thermal hardening is carried out by heating the inner surface at an angle to the generatrix of the liner with a laser beam 45…55° in the section, from 0.1≤l≤(0.4…0.6)⋅S (S is the piston stroke) counted from the upper end surface of the sleeve with two relative rotations of the latter relative to the laser beam in such a way that the heating zones formed a grid, the lines of which were located at an angle ϕ°≤(40...45°) to the longitudinal axis of the liner, the height of the formed scallop in the heating zone was h≤5 µm, the distance between the lines was t≤2.5...3 mm.