CROSS REFERENCE TO RELATED APPLICATIONS

This application is a United States National Phase Application of International Application PCT/EP2016/080540 filed Dec. 12, 2016 and claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application Serial No. DE 10 2015 226 062.3 filed Dec. 18, 2015, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a method and a tool for roughening a cylinder bore wall to be coated. The invention further relates to a component for guiding a cylinder piston.

BACKGROUND OF THE INVENTION

From EP 2 267 178 A2 (corresponding to US 2010/0326270 A1), a method for roughening a metal surface to be coated of a cylinder block is known. The metal surface bounds a cylinder bore. By means of a turning tool, a helical groove running in the peripheral direction is generated in the metal surface. Due to the helical configuration, the groove is laterally bounded by a groove web. The groove web is plastically deformed, so that it forms, in a radial direction directed toward a central longitudinal axis of the cylinder bore, undercuts. In cross section, the groove thus tapers in the radial direction due to the undercuts. As a result, a coating subsequently applied to the roughened metal surface exhibits an improved adhesion.

From DE 10 2014 209 054 A1, a method for mechanically roughening a piston running surface of a cylinder liner is known. In a first operation, a groove-forming tool is moved axially along the surface, so that axial grooves can be made in the surface. In a subsequent second operation, the groove-forming tool, in the axial position reached in the first operation, is rotated through a predefined rotation angle about the cylinder axis, whereby peripheral grooves are made in the surface, which peripheral grooves intersect the axial grooves. The axial grooves and the peripheral grooves are undercut in the shape of a dovetail.

SUMMARY OF THE INVENTION

The object of the invention is to provide a method for roughening a cylinder bore wall to be coated, which method enables in a simple manner an improved adhesion of a coating which is to be applied to the cylinder bore wall.

This object is achieved by a method for roughening a cylinder bore wall to be coated, comprising the following steps: provision of a component having a cylinder bore and a cylinder bore wall running around a central longitudinal axis, generation of at least one groove, running around the central longitudinal axis in the cylinder bore wall, and at least one associated groove web, such that the at least one groove web, in a radial direction, directed toward the central longitudinal axis, forms first undercuts for a coating which is to be applied, and generation of axial grooves, running transversely to the at least one groove in the cylinder bore wall, such that the at least one groove web, in a peripheral direction about the central longitudinal axis, forms respective second undercuts for the coating which is to be applied, and the at least one groove web beside at least one of the axial grooves, forms at least one material projection, which extends into the at least one groove and, in the peripheral direction, forms a respective further undercut for the coating which is to be applied. In the cylinder bore wall, at least one circumferential groove and at least one associated groove web are generated. The at least one groove is laterally bounded by the at least one groove web. The at least one groove and the at least one associated groove web are, in particular, of helical configuration. The generation of the at least one groove preferably comprises a machining by means of a metal-cutting machining tool and/or a plastically deforming machining by means of a shaping machining tool. The machining tool is rotated relative to the component about the central longitudinal axis and, in addition, is linearly displaced, in particular, along the central longitudinal axis. The at least one groove web is configured profiled in such a way that it forms, in a radial direction directed toward the central longitudinal axis, first undercuts for the coating which is to be applied. In the generation of the at least one groove, the groove web is configured such that it is profiled and/or profiled by a plastic deformation. For instance, the at least one groove is generated by a metal-cutting machining tool having a profiled cutting edge, so that the at least one groove, starting from a groove bottom, tapers in the radial direction, and the at least one associated groove web is profiled for the formation of the first undercut. Furthermore, the at least one groove is generated, for instance, by means of a metal-cutting machining tool of rectangular cross section, and the at least one associated groove web is subsequently plastically deformed such that it forms in the radial direction the first undercuts. As a result of the at least one groove and the at least one associated groove web, the coating which is to be applied has good adhesion in the radial direction and in an axial direction parallel to the central longitudinal axis.

Through the generation of axial grooves running transversely to the at least one groove in the cylinder bore wall, the at least one groove web additionally forms, in a peripheral direction about the central longitudinal axis, respective second undercuts for the coating which is to be applied. The transversely running axial grooves run, in particular, perpendicularly or at an angle, deviating from 90°, to the at least one groove, so that the axial grooves intersect the at least one groove. The axial grooves interrupt the at least one groove web at least partially, wherein, in the region of the interruption, the respective second undercuts are formed. As a result of the axial grooves, there are thus generated in the peripheral direction undercuts or interruptions, which improve the adhesion of the coating in the peripheral direction. This is in particular advantageous if the component is made of a light metal, for instance of aluminum, and the component and the coating material which is to be applied have markedly different coefficients of thermal expansion. This is the case, for instance, if the component is made of a light metal and the coating material contains iron. Because the component heats up strongly in the course of the thermal coating, mechanical stresses are generated during the coating and the following cooling. As a result of the second undercuts and the improved adhesion of the coating to the cylinder bore wall in the peripheral direction, these stresses do not lead to stress cracks, running parallel to the central longitudinal axis, in the coating, or detachments of the coating from the component. The component is, in particular, a cylinder crankcase or a cylinder liner. Both cylinder liners and cylinder crankcases heat up strongly in the course of the thermal coating owing to the low mass. The strong heating relates, in particular, also to cylinder crankcases, since these, as a result of the so-called downsizing and as a result of the sought-after weight reduction, have a comparatively low mass.

Because the at least one groove web beside at least one of the axial grooves, preferably beside a plurality of axial grooves, forms at least one material projection, for the coating which is to be applied an enlarged adhesion area is provided. In particular, the at least one groove web beside all axial grooves forms a respective material projection. If the axial grooves are generated by a plastic deformation of the at least one groove web, then the associated material projections are formed by material displacement together with the axial grooves. The respective material projection forms for the coating which is to be applied further undercuts, so that the adhesion is additionally improved.

Firstly, the at least one groove running in the cylinder bore wall is generated, so that subsequently the axial grooves have to be generated only in the at least one groove web. The axial grooves are generated, for instance, by plastic deformation, by machining, such as, for instance, milling, slotting, broaching or honing, and/or by energy irradiation, for instance by laser irradiation. The axial grooves are preferably generated such that these are distributed over the whole of the periphery of the cylinder bore wall.

After the generation of the undercuts, the cylinder bore wall is thermally coated. In the thermal coating is applied a coating material, which, after the cooling, forms the coating. As a result of the undercuts, the coating exhibits an improved adhesion in three directions, namely in the radial direction directed toward the central longitudinal axis, in the axial direction parallel to the central longitudinal axis, and in the peripheral direction about the central longitudinal axis. During and after the coating, in particular in motor-powered operation, stress cracks in the coating and flaking of the coating are hereby avoided. Moreover, the adhesion of the coating, in the region of the at least one incoming and outgoing groove, to the top chamfer and/or bottom chamfer of the cylinder bore wall is improved.

A method according to which the at least one groove has a groove depth TNand the axial grooves have a groove depth TA, wherein: 0.05≤TA/TN≤2, in particular 0.1≤TA/TN≤1, and in particular 0.2≤TA/TN≤0.9, ensures in a simple manner an improved adhesion of the coating which is to be applied. The groove depth TNis defined starting from a groove bottom of the at least one groove up to the cylinder bore wall. Correspondingly, the groove depth TAis defined from a groove bottom of the respective axial groove up to the cylinder bore wall. As a result of the ratio TA/TN, on the one hand a sufficiently high adhesion of the coating in the peripheral direction, and on the other hand a simple generation of the axial grooves, is ensured.

A method according to which the at least one groove web has a groove web width and the axial grooves extend over the whole of the groove web width ensures in a simple manner an improved adhesion. Because the axial grooves extend respectively over the whole of the groove web width, the second undercuts have a largest possible extent and thus provide to the coating which is to be applied a large adhesion area. Moreover, the generation of the axial grooves is easily possible.

A method according to which the at least one groove has a groove width BNand the axial grooves have a groove width BA, wherein: 0.05≤BA/BN≤2, in particular 0.2≤BA/BN≤1.5, and in particular 0.4≤BA/BN≤1, ensures in a simple manner an improved adhesion. The at least one groove defines a maximum groove width BN. Correspondingly, the axial grooves define a maximum groove width BA. By the ratio BA/BN, it is on the one hand ensured that the coating which is to be applied, in the region of the axial grooves, has sufficient material thickness, and thus sufficient strength, so that an improved adhesion in the peripheral direction is obtainable. On the other hand, by the ratio BA/BN, a simple generation of the axial grooves is ensured.

A method according to which the axial grooves form with the central longitudinal axis an angle α, wherein: −60°≤α≤60°, in particular −20°≤α≤20°, and in particular −10°≤α≤10°, ensures in a simple manner an improved adhesion. By a small angle ≤, it is on the one hand ensured that the axial grooves run substantially perpendicular to the peripheral direction. On the other hand, the angle a ensures a quick and simple generation of the axial grooves, for instance by an axial movement and a, where necessary, superimposed rotational movement of a tool relative to the component.

A method according to which the generation of the at least one groove comprises a machining, and/or the at least one groove has a spiral angle ß, wherein: 0°<ß≤4°, in particular 0.1°≤ß≤3°, and in particular 0.2°≤ß≤2°, ensures a simple generation of the at least one groove and of the at least one associated groove web. The at least one groove is generated by a combined linear and rotational movement of a metal-cutting machining tool. The formation of the first undercut is realized by a profiled cutting edge of the metal-cutting machining tool and/or by a plastic deformation by means of a shaping machining tool.

A method according to which in the peripheral direction, adjacent axial grooves have an angular spacing Δφ, wherein: 0.5°≤Δφ24°, in particular 0.5°≤Δφ15°, and in particular 0.5°≤Δφ≤2°, ensures in a simple manner an improved adhesion. The angular spacing corresponds to the number of axial grooves. The smaller is the angular spacing, the larger is the number of axial grooves. The angular spacing is chosen such that, on the one hand, sufficiently many axial grooves are distributed over the whole of the periphery of the cylinder bore wall. On the other hand, the angular spacing is chosen such that the at least one groove web between two adjacent axial grooves has sufficient material thickness, and thus sufficient strength. As a result of the angular spacing, an improved adhesion for the coating which is to be applied is ensured in the peripheral direction.

A method according to which the axial grooves have a tapered cross section, which, in particular, is of wedge-shaped configuration, ensures in a simple manner an improved adhesion. The axial grooves have a cross section which tapers, starting from the at least one groove web, in the direction of the groove bottom of the respective axial groove. It is hereby ensured that the coating material to be applied can penetrate into the respective axial groove as far as the groove bottom. Furthermore, axial grooves of tapered cross section can be easily generated, for instance by a plastic deformation of the at least one groove web.

A method according to which the at least one groove web has a plurality of groove web windings extending in the peripheral direction over 360°, and the axial grooves configured in the groove web windings are oriented along straight lines ensures in a simple manner an improved adhesion. The at least one groove web is of helical or circumferential configuration and has a plurality of groove web windings extending in the peripheral direction over 360°. The axial grooves oriented in the groove web windings along a straight line are generated in a simple manner by a linear movement of a tool along the central longitudinal axis.

A method according to which for the generation of the axial grooves, a tool having at least one deformation roller is moved along the central longitudinal axis, and the at least one deformation roller rotates about a rotational axis, running transversely to the central longitudinal axis, in such a way on the cylinder bore wall that the at least one deformation roller plastically deforms the cylinder bore wall, in particular the at least one groove web, for the formation of the axial grooves, ensures in a simple manner the generation of the axial grooves. The axial grooves are generated by a plastic deformation of the at least one groove web, in that a tool having at least one deformation roller is moved relative to the component along the central longitudinal axis. The at least one deformation roller bears against the cylinder bore wall and rotates, due to the linear movement of the tool, about the rotational axis running transversely, in particular perpendicular, to the central longitudinal axis, so that, due to a contact pressure, a plastic deformation of the cylinder bore wall, in particular of the at least one groove web, is realized.

A method according to which the at least one deformation roller is rotatably mounted on a tool main body and is radially displaceable relative to the tool main body ensures in a simple manner an improved adhesion. As a result of the at least one deformation roller, which is displaceable radially to the tool main body, the contact pressure of the at least one deformation roller, with which this bears against the cylinder bore wall, is adjusted in a simple manner. As a result, the axial grooves can be generated with an adjustable groove depth.

A method according to which the generation of the axial grooves comprises the following steps: movement of a tool, having at least one deformation roller, along the central longitudinal axis, such that the at least one deformation roller plastically deforms the cylinder bore wall, in particular the at least one groove web, for the formation of a first part of the axial grooves, pivoting of the tool, if the at least one deformation roller is disengaged from the cylinder bore wall, and movement of the tool along the central longitudinal axis such that the at least one deformation roller plastically deforms the cylinder bore wall, in particular the at least one groove web, for the formation of a second part of the axial grooves ensures a quick and simple generation of the axial grooves for improvement of the adhesion. As a result of a first linear movement of the tool relative to the component, firstly a first part of the axial grooves is generated by plastic deformation of the cylinder bore wall, in particular of the at least one groove web. If the at least one deformation roller is disengaged from the cylinder bore wall, the tool is pivoted through a pivot angle. After this, by a second linear movement, a second part of the axial grooves is generated. The pivoting and subsequent generation of the axial grooves is repeated, in particular until the axial grooves have been generated along the whole of the periphery of the cylinder bore wall. The linear movements can by superimposed by a rotational movement, so that the axial grooves form with the central longitudinal axis an angle α. Successive linear movements have, in particular, an opposite direction.

A further object of the invention is to provide a component for guiding a cylinder piston, which component enables in a simple manner an improved adhesion of a coating which is to be applied to the cylinder bore wall.

This object is achieved by a component for guiding a cylinder piston, in particular of an internal combustion engine, having a main body, at least one cylinder bore configured in the main body, a cylinder bore wall, running around a central longitudinal axis of the at least one cylinder bore, and at least one groove, running around the central longitudinal axis in the cylinder bore wall, and at least one associated groove web, which, in a radial direction directed toward the central longitudinal axis, forms first undercuts for a coating which is to be applied, wherein in the at least one groove web are configured a plurality of axial grooves, which run transversely to the at least one groove, and the at least one groove web, in a peripheral direction about the central longitudinal axis, due to the axial grooves, forms respective second undercuts for the coating which is to be applied, wherein the at least one groove web beside at least one of the axial grooves forms at least one material projection, which extends into the at least one groove and in the peripheral direction forms a respective further undercut for the coating which is to be applied. The advantages of the component according to the invention correspond to the already described advantages of the method according to the invention. The component according to the invention can be refined, in particular, also with the features of the method according to the invention. The component is, for instance, a cylinder crankcase or a cylinder liner.

A further object of the invention is to provide a tool for roughening a cylinder bore wall to be coated, which tool enables in a simple manner an improved adhesion of a coating which is to be applied to the cylinder bore wall.

This object is achieved by a tool for roughening a cylinder bore wall to be coated, having a tool main body for clamping in a tool spindle, at least one deformation roller rotatably mounted on the tool main body, wherein the at least one deformation roller is arranged peripherally on the tool main body, a rotational axis of the at least one deformation roller runs perpendicular to a main body central longitudinal axis, and the at least one deformation roller, in particular, is displaceable radially to the main body central longitudinal axis. By means of the tool according to the invention, axial grooves can be generated in a simple manner in the cylinder bore wall. The generated axial grooves enable an improved adhesion of the coating which is to be applied to the cylinder bore wall, in the peripheral direction, about a central longitudinal axis of the cylinder bore. The tool is preferably inserted into the cylinder bore in such a way that the central longitudinal axis of the main body runs parallel, in particular concentrically, to the central longitudinal axis of the cylinder bore. In the inserted state, the at least one deformation roller bears against the cylinder bore wall. As a result of a linear movement of the tool in the direction of the central longitudinal axis, by means of the at least one deformation roller the axial grooves are generated by plastic deformation of the cylinder bore wall. The at least one deformation roller herein bears with a contact pressure against the cylinder bore wall and, owing to the linear movement, rotates about an associated rotational axis running transversely to the central longitudinal axis of the main body. Because the at least one deformation roller is preferably displaceable radially to the central longitudinal axis of the main body, the contact pressure is adjustable, so that the groove depth of the respective axial groove is adjustable. Preferably, the tool has a plurality of deformation rollers, which are arranged distributed over the periphery of the tool main body, rotatably thereon. The tool according to the invention enables a simple generation of the axial grooves in the cylinder bore wall by plastic deformation.

The present invention is described in detail below with reference to the attached figures. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.

