DE102010063704A1 - Machining inner surface of cylindrical bore in workpiece e.g. cylinder crankcase using roll forming operation, by rolling a roller element of a machining tool under a contact pressure against a segment of a curved workpiece to be machined - Google Patents

Abstract

The machining method comprises rolling a roller element (180A, 180B, 180C) of a machining tool under a contact pressure against a segment (198) of a curved workpiece (200) to be machined. An outer surface of the roller element comprises a rough surface structure in a working segment intended for rolling contact with a workpiece surface (210). The contact pressure is set so that a rough roll-formed structure is generated when rolling by locally deforming a workpiece material without removing material in the area of the workpiece surface is machined. The machining method comprises rolling a roller element (180A, 180B, 180C) of a machining tool under a contact pressure against a segment (198) of a curved workpiece (200) to be machined. An outer surface of the roller element comprises a rough surface structure in a working segment intended for rolling contact with a workpiece surface (210). The contact pressure is set so that a rough roll-formed structure is generated when rolling by locally deforming a workpiece material without removing material in the area of the workpiece surface is machined. The roll forming operation at the workpiece surface of the rough roll-formed structure with an average surface roughness of 10 mu m is generated. The generated average roughness is 30-100 mu m. A coating is applied by thermal spraying after the roll forming operation on the workpiece surface, where the coating is directly applied on the rough roll-formed structure generated by the roll forming operation or the roll-formed structure is reworked after the roll forming operation using post-processing method for generating a modified roll-formed structure. The coating is subsequently applied on the modified roll-formed structure. A cleaning of the workpiece surface is performed during and/or after the roll forming operation in the form of the roll-formed structure, and is produced for removing material particles bound to the workpiece surface by the roll forming operation, where the roll-formed structure is brushed and/or pneumatically free-blown by relatively soft non-abrasive brushes. A suction of a processing residue of the roll forming operation takes place during and/or after the roll forming operation and is free-blown to the suction of the workpiece surface. One of the roll forming operations downstream in form of the roll-formed structure changes a post-processing for generating the modified roll-formed structure that comprises an elimination of tips in a range of elevations for producing a plateau with a flattened structure and lies between slots at the workpiece surface. The tips in the range of elevations are removed by a material. The roller element of the machining tool is rolled under the contact pressure against the segment of the curved workpiece to be machined, in which the machining tool is guided in a predefined distance from the workpiece surface along a predefined path. A course of the predefined path of the machining tool is dependent on a curvature of the workpiece surface as well as dependant on the contact pressure. The rolling step is effected for machining the inner surface of the cylindrical bore, in which the machining tool is used in a bore filling that is formed as a rotary tool and is rotationally driven around the tool axis. An independent claim is included for a machining tool for machining the inner surface of a bore in a workpiece cylinder crankcase or cylinder liner.

Description

The invention relates to a machining method for machining a curved workpiece surface of a workpiece, in particular for machining the inner surface of a hole in a workpiece, according to the preamble of claim 1 and a machining tool usable in carrying out the method for machining a curved workpiece surface of a workpiece according to the preamble of Claim 7. Furthermore, the invention relates to a manufactured using the machining method and / or the machining tool workpiece.

Embodiments of the invention can be used inter alia in the production of tribologically stressed, rotationally symmetric or otherwise curved sliding surfaces on workpieces for engine construction. A preferred field of application is in the production of cylinder liners in internal combustion engines, i. H. when machining inner surfaces of cylinder bores in an engine block or in a cylinder sleeve to be installed in an engine block.

Honing processes are generally used to determine the quality of finishing of cylinder surfaces, in order to meet the extremely high requirements with regard to dimensional and form tolerances as well as with regard to the desired surface structure. Honing is a machining process with geometrically indeterminate cutting, in which multi-bladed honing tools carry out a two-component cutting movement, which leads to a characteristic surface structure of the machined workpiece surface with crossed machining marks.

In some workpieces, the sliding surface is created directly on the base material of the workpiece. For example, in engine blocks (cylinder crankcases) made of gray cast iron, the cylinder surfaces are often generated directly on the gray cast iron material. If, on the other hand, the material used for the workpiece is unsuitable, due to its material properties, to serve as a tribologically stressable surface after fine machining of the workpiece surface, then the base material may be provided with a coating, the surface of which is then optionally mechanically reworked to serve as a sliding surface , For example, it is known to provide cylinder bores in motor blocks made of aluminum material by thermal spraying with a coating of an iron-containing coating material. The surface of the sprayed layer is normally post-finished mechanically after the coating process. In thermal spraying, filler materials, the so-called spray additives, are melted, fused or melted inside or outside a spray burner, accelerated in a gas flow in the form of spray particles and spun onto the surface of the workpiece to be coated. The workpiece surface is not melted in the rule and only a small thermal load. The heated spray particles strike the workpiece surface and connect to it. A layer formation takes place because the spray particles flatten more or less depending on the process and material when hitting the workpiece surface, adhere primarily by mechanical interlocking and build up in layers the coating referred to as spray coating.

The adhesive strength of the coating on the base material of the workpiece is significantly determined by the pre-processing of the workpiece surface directly before the coating process. Sufficient adhesive strength can be achieved by roughening the workpiece surface prior to coating. For this purpose, different methods have already been proposed.

The item "Process chain for the production of thermally sprayed cylinder bores" by G. Flores, A. Schwenk and C. Schnell in: VDI-Berichte Nr. 2109, 2010 describes methods for producing thermally sprayed cylinder bores. The roughening of the workpiece surface before coating is carried out by a variant of fine boring, are introduced in the profile surface intersections in the workpiece surface. As a result, the subsequently applied thermal spray coating should receive a high adhesive strength to the cylinder wall.

In the DE 196 14 328 A1 describes processes in which workpiece surfaces are patterned in a regular pattern to prepare the coating by means of laser beams.

From the EP 1 141 438 B1 It is known to roughen the cylinder bores in a cylinder crankcase before coating by corundum or sandblasting.

In the EP 0 607 779 B1 ( DE 694 23 373 T2 ) it is pointed out that sandblasting is an additional step that increases coating costs. In some cases, such as in cylinder bores of internal combustion engines, there is also the risk that sand particles remain embedded in the irradiated workpiece surface and later can lead to damage to the engine to destruction.

In the DE 10 2004 038 177 A1 describe processes for preparing a cast cylinder bore for thermal coating, in which the surface of the cylinder bore is roughened by means of a jet, preferably by means of a liquid jet containing solid particles and / or a jet of water, wherein at the same time roughening material of the cylinder bore is removed in a certain thickness.

TASK AND SOLUTION

It is an object of the invention to provide a machining method for mechanically machining a curved workpiece surface of a workpiece that allows for efficient and inexpensive conditioning of curved workpiece surfaces, for example, in preparation for subsequent thermal spray coating. It is a further object of the invention to provide a processing tool suitable for carrying out the method. Furthermore, workpieces are to be provided with improved performance in the intended use.

To solve these and other objects, the invention provides a machining method having the features of claim 1. Furthermore, a machining tool having the features of claim 7 and a workpiece having the features of claim 14 are provided.

Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

The machining method is characterized by a roll embossing operation in which at least one rolling element of a machining tool is unrolled to a section of the curved workpiece surface to be machined under a prescribable contact pressure. An outer surface of the rolling element has a rough surface structure in at least one working section intended for a rolling contact with the workpiece surface. The contact pressure is adjusted so that when rolling of the rolling element on the curved workpiece surface by local forming of workpiece material in the region of the workpiece surface, a rough roll embossing structure is generated. For this purpose, the workpiece consists at least in the region of the workpiece surface to be machined of a plastically deformable workpiece material, for example of a metallic material. During the roll embossing operation, a plastic deformation of an edge layer adjoining the workpiece surface occurs. The "rough surface structure" of the working portion of the rolling element is a surface structure with elevations and with respect to the elevations deeper recesses. The spatial distribution of the elevations and depressions may be irregular, but it is also possible that the structure-forming elevations and depressions are distributed regularly on the working section. Correspondingly, the rough roll embossing structure produced by forming can also consist of elevations and depressions recessed relative to the elevations, wherein during roll embossing normally an increase in the working section of the rolling element by material displacement creates a depression in the roll embossing structure.

As a "rough surface structure" is here referred to a surface structure in which protrude and / or depressions over a mathematically smooth reference surface by several microns or recede. It is a deliberate and deliberately created roughness in contrast to unavoidable residual roughness, which can be produced, for example, on nominally smooth technical surfaces by polishing.

As a rule, the average roughness depth R _{z of} the rough surface structure in the working section is in the range of several micrometers, in particular 10 micrometers or more. In preferred embodiments, a roll embossing structure with an average roughness depth R _z of more than 10 micrometers is produced by the roll embossing operation on the workpiece surface, wherein the average roughness depth may be, for example, in the range between R _z = 30 μm and R _z = 100 μm. Average roughness depths in this area can be particularly advantageous if a subsequent coating is provided. The mean surface roughness can be greater than 100 μm after roll embossing.

In principle, roll embossing is a largely non-cutting process, since the rough roll embossing structure is essentially not produced by material removal but by material deformation or material displacement and material redistribution without significant material removal. In comparison to machining processes with material removal, generally much longer tool life results, whereby the manufacturing costs can be kept low.

In some process variants can without the support of liquid production aids, such. As coolant, to be worked, so in dry machining. This allows a particularly cost-effective surface structuring. If necessary, however, it is also possible to work wet, for example in order to reduce the adhesion between the rough tool surface and the workpiece surface.

The contact pressure may possibly be so high that it is near the surface Edge layer comes to a work hardening of the workpiece material. The term strain hardening here denotes an increase in strength of the workpiece material, which can be achieved in a largely cold state in a plastic deformation of the material. This near-surface increase in strength can be particularly favorable for relatively soft metallic materials, such as light metal based on aluminum or magnesium.

In some variants of the method, a coating is applied to the workpiece surface after the roll embossing step. The coating can be applied directly to the rough roll embossing structure produced by the roll embossing step, especially if this was produced by the dry process. It is also possible to rework this roll embossing structure after the roll embossing step with the aid of one or more reworking methods in order to produce in this way a modified rough roll embossing structure, which is then coated.

The coating is preferably applied by a thermal spraying method such as plasma spraying or high-speed flame spraying (HVOF) method. Depending on the application, the coating z. Example of a ceramic coating material, a metallic coating material or a metal matrix composite material (MMC), in particular a ceramic-metallic layer material exist.

It has proven to be advantageous if the roll embossing structure or the modified roll embossing structure before coating has an average surface roughness between R _z = 30 μm and R _z = 100 μm. If the lower limit is significantly undercut, then the adhesive strength of the coating in the critical range is not given reliably enough for some material combinations. On the other hand, if the upper limit is significantly exceeded, more coating material than is actually necessary for the coating is usually needed to fill the heavily roughened structure. The coating process can be extended unnecessarily. Average surface roughnesses in the preferred range therefore provide a good compromise between reliable bond strength and layer fabrication efficiency.

The roll embossing operation may be the last processing step on the workpiece surface. In some cases, one or more further treatment steps or processing steps may follow.

In some method variants, cleaning of the workpiece surface provided with a roll embossing structure is carried out during and / or after the roll embossing operation. The roll embossing is in principle a chipless forming process, in which a material removal is neither intended nor occurs on a larger scale. Nevertheless, it may happen with some materials that during roll embossing on the workpiece surface, material particles that are not or only weakly bonded to the material surface, for example in the form of flat leaflets or flakes, that could impair the function of the roll embossing structure. Therefore, in some process variants, the workpiece surface provided with the roll embossing structure is cleaned after the roll embossing in order to eliminate material particles which are not or only weakly bonded and which are produced by roll embossing. The cleaning can also be carried out partially or exclusively during the roll embossing operation, ie simultaneously with the roll embossing operation. The cleaning is preferably form-retaining, d. H. the shape of the roll embossed structure is practically unchanged.

Dry or wet cleaning procedures are possible. In some process variants, the roll embossing structure is cleaned using relatively soft, possibly rotating brushes. The bristles of the brushes are non-abrasive and so soft that the shape of the roll embossed structure remains unchanged. Alternatively or additionally, the workpiece surface provided with a roll embossing structure can be pneumatically cleaned by means of compressed air or another compressed gas. The compressed gas can be passed externally and / or by means of suitable compressed gas channels through the machining tool and out of outlet openings on the roll embossing structure. Alternatively or additionally, during and / or after the roll embossing operation, an extraction of shavings and other processing residues of the roll embossing operation may be provided, wherein preferably in addition to the suction, the workpiece surface is blown free.

Even a wet cleaning with the help of a cleaning liquid is possible. When preparing for a subsequent coating, for example, a grease-dissolving cleaning liquid (alcohol, acetone or the like) can be used. Also a cleaning with water is possible.

In some variants of the method, the surface of the workpiece provided with a roll embossing structure is still slightly changed in its shape in order to create a modified roll embossing structure by post-processing. For this purpose, some method variants envisage elimination of tips in the region of elevations of the roll embossing structure in order to produce a plateau structure with flattened elevations and intervening depressions on the workpiece surface.

In some process variants, the tips in the area of elevations are removed by a material-removing fine machining. For this purpose, a honing operation is normally performed with relatively fine-grained cutting means to provide a plateau honing type of modified roll embossing structure having flattened elevations with plateau-like flat surfaces having a fine ridged structure. In between are the depressions generated by the roll embossing operation. In such process variants, the roll embossing can replace the conventional base honing (honing with a comparatively coarse cutting agent). In contrast to conventional workpiece surfaces, which are first processed in a multi-stage machining process with a basic and then with a Plateauhonung, a method with roll embossing step and subsequent plateau honing has the advantage, inter alia, that the near-surface region in the roll embossing step can be additionally strengthened by work hardening increased strength , It is true that cold hardening can also occur in base clay. The zone of work hardening, however, is lower in roll embossing than in base clay, as in the case of base clay a possible work hardening layer is for the most part immediately removed again.

The material-removing elimination of tips may be the last processing step of a multi-stage machining of the workpiece surface, so that the workpiece surface is made then manufactured for the intended use. However, further processing steps may follow.

In another variant of the method, the tips are removed in the region of elevations of the roll embossing structure by forming, for example by rolling elements with a smooth outer surface are rolled under suitable contact pressure on the Rollprägestruktur. As a result, the tips could be flattened without material removal. In this material-forming reworking laterally projecting material noses may arise on the sides of the resulting plateaus. Such structures with an undercut are particularly suitable for a subsequent coating, since the coating material reaching into the depressions can interlock positively with the workpiece surface in the region of the lateral noses, whereby a particularly good layer adhesion to the workpiece surface can be achieved.

The invention also relates to a machining tool suitable for carrying out the method for machining a curved workpiece surface of a workpiece. The machining tool is designed as a rotary tool and has a tool body that defines a tool axis. When used as intended the machining tool is rotationally driven so that it rotates about the tool axis. The machining tool has at least one rolling element supported by the tool body, which is rotatable about a Wälzelementachse lying outside the tool axis and has an outer surface. The rolling element can rotate during machining about its Wälzelementachse and thereby rotates as a whole about the tool axis of the machining tool. The outer surface of the rolling element has a rough surface structure in at least one working section intended for a rolling contact with the workpiece surface. This normally has the above-mentioned elevations and depressions in order to produce the rough roll embossing structure on the machined workpiece surface by roll embossing.

A rolling element usually has a rotatably mounted rolling element body, which may for example consist of a metallic material of suitable hardness, of a ceramic material or of a metal-ceramic composite material. The rough surface structure can be introduced directly into a rotationally symmetrical outer surface of the rolling element body. The rough surface structure can be produced for example by laser processing or by an etching process. For example, the outer surface of a metallic roll may be etched chemically or electrochemically or mechanically (eg, by sandblasting) to create depressions and projecting protuberances therebetween. On the rough surface produced thereby can be used to improve the wear resistance, a thin layer of hard material z. Example by means of a PVD (physical vapor deposition) method or a CVD (chemical vapor deposition) method can be applied.

The rolling element body may also be made entirely of a hard material with bonded hard grains in the manner of a grindstone to form a rough outer surface.

In preferred embodiments, the rolling element has a rolling element body which carries a coating with a rough surface structure in the working section. This construction is u. a. by ease of manufacture and great flexibility in the design of the geometry and other embossing properties of the rough surface structure. The rolling element body can be a simple turned part made of a metallic material, while the hardness of the rough surface structure required for the roll embossing step and its geometry can be determined by the coating.

The coating, in some embodiments, has a plurality of in a bond bonded hard grains, which protrude on the outside of the bond and thereby form the elevations of the rough surface structure. The average grain size of the hard material grains is preferably at least 15 microns. In particular, the average particle size may be in the range of about 30 microns to about 250 microns. As a result, for example, in the machining of workpieces made of aluminum or an aluminum alloy on the workpiece surface average roughness depths between about 10 microns and about 100 microns can be generated. Embossed structures with these roughness characteristics are in many cases particularly suitable for a subsequent coating.

The hard material grains may consist, for example, of diamond, corundum, cubic boron nitride or other hard materials whose hardness is preferably significantly greater than the hardness of steel. The bond is preferably applied galvanically in order to achieve a good adhesion to a metallic rolling element body and at the same time a high wear resistance against breaking off of hard material grains from the bond.

Preferred embodiments are characterized by a rolling element delivery system for variably controllable delivery of the rolling element in a direction of feed extending radially to the tool axis. This makes it possible to continuously vary the effective diameter of the tool over a predetermined range, so that, for example, a machining tool can first be introduced with retracted rolling elements in a bore before the rolling elements are then delivered to achieve the contact with the bore inner surface to the outside and the processing begins. By a variably controllable delivery and the contact pressure is precisely adjustable and can optionally be changed during processing.

A machining tool may have a single rolling element. A rolling element may be integrally or segmented into a plurality of independently rotatable, coaxial Wälzelementsegmente. In general, a plurality of evenly or non-uniformly distributed around the circumference rolling elements are arranged on the tool body. One embodiment has three evenly distributed around the circumference rolling elements. It has been found that, as a result, the machining tool can optimally follow the bore shape resulting from upstream processing stages, so that substantially the same contact pressures are set on all rolling elements without pressure peaks and a uniformly structured surface results. If a plurality of rolling elements are provided, they are preferably deliverable together via a common rolling element delivery system. Separate delivery independently is also possible.

A rolling element can be mounted directly on the tool body or in a bearing mounted on the tool body. Preferably, however, at least one relative to the tool body radially to the tool axis movable support member is arranged on the tool body and the rolling element is rotatably mounted on the support member. Machining tools for machining the inner surface of holes can be constructed so far similar honing tools for Innenrundhonen, but u. a. one or more non-abrasive rolling elements are provided instead of the abrasive honing stones required for honing.

In order to allow the radial delivery of rolling elements, in some embodiments in the tool body a movable parallel to the tool axis feed element is arranged with at least one wedge portion, which may for example have the shape of a cone or truncated cone. Whose inclined surfaces can cooperate with inclined surfaces on the inside of support elements for the rolling elements in the manner of a wedge drive, so that an axial movement of the Zustellelementes leads to a radial movement of support elements and the rolling elements attached thereto.

In some embodiments, the outer surface of the rolling element in the working portion forming the rough surface structure carries a thin non-stick coating which reduces the adhesion between the rough outer surface of the working portion and the machined workpiece surface to an outer surface without the non-stick coating. The non-stick coating can z. Example, a TiN coating or a DLC (diamond like carbon) coating be. If the adhesion is reduced, the rough surface structure of the outer area during unwinding after penetration into the workpiece material is more easily detached from the subsequently patterned workpiece material without tearing out small adhering material particles from the structured surface, which may then impair subsequent downstream processing steps. As a result, the use of liquid production auxiliaries, such as, for example, cooling lubricant or the like, can be dispensed with during the roll embossing process, so that the roll embossing operation can be carried out as a dry processing step. As a result, manufacturing costs can be saved to a considerable extent. In addition, dry produced roll embossing structures are usually suitable immediately without further processing for a coating.

The invention also relates to a workpiece produced using the machining method and / or using the machining tool. The workpiece may in particular be a cylinder crankcase made of a light metal material or a cylinder sleeve to be installed in a cylinder bore. It may also be a connecting rod, in which at least one connecting rod bore has been machined with the aid of a roll embossing operation, possibly with a downstream coating. The workpiece may also be an extruded tube with internal coating.

These and other features, in addition to the claims, will be apparent from the description and drawings, in which the individual features may be implemented alone or in combination in the form of sub-combinations in one embodiment of the invention and in other fields, and advantageous embodiments that are capable of protection can represent. Embodiments are illustrated in the drawings and are explained in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

1 shows an axial longitudinal section through an embodiment of an easily expandable machining tool for roll embossing of bore inner surfaces;

2 shows a side view in partial section of the machining tool 1 ;

3 shows an axial section through an embodiment of a machining tool with double widening;

4 shows in 4A an oblique perspective view of a support element for a rolling element, which is resiliently mounted on the support element and in 4B and 4C Examples of the use of springs in the elastically flexible storage of rolling elements;

5 schematically shows the flow of a roll embossing step in the processing of a concave cylindrical curved bore inner surface by means of a rolling element, which has a rough surface structure with statistically distributed elevations and depressions;

6 schematically shows the flow of a Rollprägeschrittes in the processing of a concave cylindrical curved bore inner surface by means of a rolling element, which has evenly distributed elevations on its circumference;

7 schematically shows the roll embossing on a convexly curved workpiece outer surface;

8th shows a schematic section through a workpiece surface, which was first roughened by roll embossing and then coated by thermal spraying;

9 shows a schematic section through the region of the workpiece surface in another workpiece, in which between the roll embossing and a subsequent coating nor a forming machining was interposed for flattening tips of the roll embossing structure; and

10 shows a schematic oblique perspective view of the area of a workpiece surface, which was first structured by roll embossing and then finished by Plateauhonen.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In 1 is a schematic axial section through a first embodiment of a machining tool 100 shown for roll embossing. The machining tool (roller embossing tool) is designed for the machining of largely circular cylindrical inner surfaces of holes, in particular for the production of cylinder surfaces for an internal combustion engine. The machining tool has a steel-made, largely rotationally symmetrical tool body 110 whose central axis is the tool axis 112 Are defined. The spindle-facing end of the tool body is characterized by a tapered coupling portion 114 formed with cylindrical outer contour, at the diametrically opposite positions radially projecting driving pins 116 are attached. With the help of these coupling devices, the machining tool to the provided with angled receiving slots for the driving pins free end of the drive rod 150 be coupled to a honing machine. The coupled machining tool is not rigidly connected to the driven honing spindle of the honing machine, but with respect to this limited mobility, which can be achieved for example by a gimbal coupling or a coupling in the manner of a floating head or by a flexible elastic drive rod.

From the end facing away from the spindle of the tool body performs a central cylindrical receiving bore 118 with a flat end surface 120 into the tool body, so that this section is tubular. In the tube wall formed thereby are three evenly distributed around the circumference, radially from inside to outside continuous, substantially rectangular passage slots 122 for receiving later explained in more detail support elements for Rolling elements. From the spindle-facing end of the coupling section 114 leads another cylindrical receiving bore 124 with a flat base in the coupling section inside. Between the mounting holes 124 and 118 there is a cylindrical through hole 126 with even smaller diameter.

The coaxial bores 118 . 126 and 124 serve to accommodate the tool-internal elements of a rolling element delivery system. This includes a double conical expansion cone 142 , the axially displaceable and free of play in the spindle-facing receiving opening 118 sitting. At the spindle-facing end face of the Aufweitkonus a central blind hole is provided with internal thread, in which during assembly of the machining tool a threaded outer threaded portion of a push rod 144 is screwed, from the spindle-facing side into the receiving opening 124 the coupling portion is used. The push rod has a widened cylindrical head section 146 , which essentially free from side play, but axially movable in the receiving bore 124 fits. During assembly, the push rod passes through a into the receiving bore 124 introduced helical compression spring 148 , after screwing the push rod with the Aufweitkonus on the one hand on the widened head section 146 and on the other hand on the flat bottom of the receiving bore 124 supported. This ensures that in the absence of external forces, the push rod and the screwed-on Aufweitkonus their in 1 shown upper stop position, in which the spindle-side end face of the Aufweitkonus on the flat bore bottom of the receiving bore 118 strikes.

In the hollow drive rod 150 is located with the aid of a feed drive the honing machine axially displaceable feed rod 152 whose free end face with coupled machining tools on the spindle-side end face of the push rod 144 acts.

In each of the circumferentially offset by 120 °, radially continuous through slots 122 sits a strip-shaped carrier element 160 , which fits radially movable and axially and in the circumferential direction largely free of play in the passage slot. Each carrier element has on its inside two axially superimposed inclined surfaces, which in the assembled tool with the axially superimposed conical surfaces of the expansion cone 142 cooperate in the manner of a wedge drive such that an axial displacement of the expansion cone causes a radial displacement of the carrier element.

Each support element has an inner base section 162 , on which the inner inclined surfaces are mounted, and on the narrow end sides in each case outwardly projecting bearing sections 164A . 164B , Each support element carries a rolling element 180A . 180B . 180C , which is rotatably mounted on the bearing portions of the support element such that as rolling element axis 182 Designated axis of rotation of the rolling element at a distance outside the tool axis 112 runs parallel to this.

Falling out of the support elements with fully assembled machining tool is by rotating return springs 170A . 170B prevented, are held in the outer grooves in the bearing sections and exert a restoring force on the support elements in the direction of the tool axis. In the absence of pressure on the upper end face of the push rod 144 The carrier elements are in their maximum retracted position, which corresponds to the minimum effective diameter of the machining tool. The effective diameter can be increased by the feed rod 152 in the direction of the machining tool is advanced so far that the push rod is pressed in the direction of the distal end of the spindle. As a result, the Aufweitkonus also moves to the spindle distal end, so that the inclined surfaces in the region of the cone sections slide together and the support bars to increase the distance between the tool axis and Wälzelementachse against the force of the compression spring 148 and the return springs 170A . 170B be pushed outward. To retract only needs the Zustellstange 152 be withdrawn, the restoring force is then from the spring elements.

Each rolling element has a rotationally symmetrical, substantially cylindrical rolling element body 184 made of tool steel, at the opposite ends blind holes are introduced.

In each of the holes sits an outer ring of a sealed needle bearing 186 , The inner element of a needle bearing is formed by a cylindrical bolt which is fastened during assembly in the bearing portion of the support element. The running with low rolling resistance and against radial forces very stable needle bearing is encapsulated outward against ingress of contaminants, such as tinsel-like material particles to allow during processing a trouble-free rotation of the rolling element relative to the support element.

In the enlarged detail in 1 is particularly good to recognize that the outer surface of the rolling element 180A in a working section intended for a rolling contact with the workpiece surface 190 a rough surface texture having. For this purpose, the rolling element body has a cylindrical annular collar whose outer diameter is slightly larger than the outer diameter of the axially adjoining outer sections. The outer surface of this collar bears a coating 192 with relatively coarse diamond grains 194 , which in a galvanically applied to the rolling element body metallic bond 196 firmly adherent. The grain portions projecting outwardly from the bonding material form elevations projecting outwardly in relation to intermediate regions of the bond which appear as depressions relative to the elevations. The mean grain size of the diamond grains is between about 30 μm and about 100 μm.

The width of the working section measured parallel to the tool axis or to the rolling element axis 190A is only about one third of the axial length of the Wälzelementkörpers. As in 2 can be clearly seen, the other two have attached to the circumference of the machining tool rolling elements 180B . 180C basically a similar structure. However, the working portions of the rolling elements are axially offset from each other such that a total when turning the machining tool a machining width 198 is covered, which corresponds to about three times the width of a single work section. Each of the relatively narrow work sections thus processed when turning a relatively narrow strip of the concave cylindrical workpiece surface 210 of the workpiece 200 , In this strip sufficient for the roll embossing pressure can be adjusted and maintained relatively uniform throughout the work area. The axially offset working sections of the other rolling elements work directly adjacent and slightly overlapping neighboring strips, so that overall results in an efficient processing of a relatively wide processing section of the inner surface.

For machining the inner surface of a bore, the machining tool is first retracted into the bore so far that the combined machining region of the individual rolling elements covers the beginning of a section to be machined. This introduction takes place with retracted rolling elements. Thereafter, the rolling elements with the help of the rolling element delivery system are delivered to the outside until the rolling elements bear against the inner surface under suitable contact pressure. Before this radial infeed, after this radial infeed or during the radial infeed, the tool is set in rotation about the tool axis via the rotary drive of the honing spindle. In this case, the working areas of the rolling elements are pressed against the inner surface in such a way that their rough surface structure is impressed into the workpiece surface and essentially produces a complementary roll embossing structure with adjacent elevations and depressions. After one or more rotations, the roll embossing operation is completed for the corresponding axial portion of the bore and the support members are returned to the inside so that the contact between the rolling elements and the bore inner surface is canceled.

If the inner portion of the bore to be machined is longer than the working width of the combined work areas, then the machining tool is then advanced in the axial direction so far that the tool is at the height of the next section of the bore to be machined. Then the sequence of operations with radial outward delivery, onset of rotation, roll embossing and subsequent retraction is repeated.

During roll embossing, d. H. During the machining engagement of the rolling elements on the bore inner surface, no axial feed of the working spindle or the machining tool takes place.

The decisive for the material deformation during roll embossing contact pressure can be set variable in time with the help of the rolling element delivery system. It is thus possible, for example, to produce two or more differently machined sections on one and the same inner surface of the bore by roll embossing, during the machining of which the rolling elements have been pressed with different contact pressure. It is also possible to leave unembossed sections next to roll embossed sections. For example, the roll embossing may be limited to the upper and / or lower gusset portion of a cylinder bore.

That in the 1 and 2 shown machining tool 100 is designed as a pure roll embossing tool. It is also possible to carry out the roll embossing with the aid of a combination tool, which makes it possible to perform at least one further machining operation on the workpiece surface in addition to the roll embossing (or alternatively thereto) without tool change. 3 shows an example of a longitudinal section through a machining tool 300 in addition to a plurality of evenly distributed around the circumference rolling elements (a rolling element 380 is shown) a set of several, also uniform around the circumference of the machining tool distributed honing stones, which are independent of the rolling elements radially to the tool axis 312 are deliverable. The honing stones are exemplary for further processing elements, which are designed for a different processing method, in the example for a material-removing cutting method with indefinite cutting.

In other variants of combination tools, in addition to one or more rolling elements with a rough surface (for roll embossing), still deliverable smooth rolling elements (eg smooth rolls) or non-rolling smoothing bars with a hard, smooth working surface are provided for work hardening without substantial material removal.

The substantially tubular tool body 310 has six evenly distributed around the circumference, axially elongated and relatively narrow in the circumferential direction, radially through through holes for receiving support elements for the processing elements. In three by 120 ° circumferentially offset passage openings sit support elements 360 for the rotatably mounted therein rolling elements 380 , Their structure and arrangement can be substantially as in connection with the 1 to 2 Therefore, reference is made to the description there. Each in the circumferential direction centered between these support elements are honing stones 390 arranged in the through holes. A honing stone has a radially displaceable guided in the through hole of the tool body support bar 392 , which on its radial outside a cutting surface 394 with cutting grains of diamond or another hard, z. B. carries nitride or carbide material in a metallic or ceramic bond. On the inside of the support bar in each case inclined surfaces are mounted in the upper and lower regions, with tapered sections at the lower end of a central Zustellstange 340 cooperate such that an axial displacement of the Zustellstange causes a radial displacement of the honing stones. The axial movement of the feed rod 340 is generated by a not shown feed motor of the honing machine. The infeed bar is part of a second infeed system acting on the honing stones (honing stone infeed system).

The supporting elements 360 for the rolling element axes 312 rotatable rolling elements have on their inner sides inclined surfaces, with conical inclined surfaces on the outside of a tubular Zustellstange 350 interact, which the inner Zustellstange 340 surrounds. The rolling element delivery system operates independently of the delivery system for the honing stones, so that in particular optionally only the rolling elements or only the honing stones can be brought into machining engagement with the bore inner surface to be machined. If the machining tool z. B. is to be used exclusively for roll stamping, the inner Zustellstange 340 remain retracted so that the honing stones are permanently out of engagement with the workpiece surface.

The machining tool can be used in particular in machining methods in which first a Honbearbeitung the bore inner surface and then a roll embossing operation is to be generated on the honed surface. It is also possible to use the honing tool in methods in which the bore inner surface is first prepared by other methods and in which thereafter with the aid of the combination tool first a roll embossing operation and then a honing operation is performed. It would also be possible, with the aid of the machining tool, to first lift an inner surface with the aid of the honing stones, then to subject the honed workpiece surface to a roll embossing operation and then to rework the resulting roll embossing structures again with the same honing stones but less material removal. In the second honing operation, it is preferable to operate with a reduced contact pressure compared to the first honing operation in order to produce a finer surface structure on plateau surfaces.

Due to the limited mobility of the coupling between the machining tool and this driving honing spindle, the machining tool is able to run to some extent in the roll embossing operations of the bore shape, so that no unacceptable constraining forces occur even with minor deviations of the bore shape of an ideal circular cylindrical shape.

A further improvement and equalization of the machining quality during roll embossing is achieved in some embodiments by the fact that the bearing of the rolling elements has a certain elastic compliance, in order to be able to retreat, for example when rolling over surface elevations and / or compensate for irregularities in the bore shape by slight inclination of the rolling element axis. 4 shows exemplary embodiments of support elements, which allow an elastically resilient mounting of the rolling elements.

The support element 460 in 4A has an elongated base section 462 , which softens the inclined surfaces on its rear side for interaction with an expansion cone. On the opposite side are at the ends of the two bearing sections 464A . 464b attached, which serve for the storage of the rolling element. In contrast to the embodiment in 1 the bearing portions are not integrally formed with the base portion, but realized as separate components thereof, which are fixed to the base portion with the interposition of resilient connecting structures to allow limited mobility of the bearing portions relative to the base portion. In the variant in 4A is located between the base section and the Storage sections one layer each 465 from a relatively hard, but elastically yielding elastomeric material. As in 4B . 4C shown, the compliance of the storage can also be achieved by that between the base section 462 and a storage section 464A or 464b a small distance remains, which is bridged by means of an elastically yielding connection device. This contains in the example of 4B Plate spring elements and in the case of 4C Helical compression spring elements.

Based on 5 to 10 For example, some machining methods will be described in which a roll embossing operation is performed on a curved workpiece surface. 5 shows, for example, a section of a workpiece 500 in the area of a cylindrical bore, whose inner surface 510 forms the workpiece surface to be machined by roll embossing. For example, it can be the edge region of a cylinder bore in a cylinder crankcase made of an aluminum material. To prepare the roll embossing operation, the cylinder bore is brought into the desired macro-shape by a multi-stage material-removing machining process (eg, fine boring and honing or only power honing). By an immediately preceding honing operation, the workpiece surface is processed so finely that there is a surface structure with crossed machining marks and an average roughness depth of less than 5 μm (see enlarged detail). Thereafter, a set up for roll embossing machining tool, such as the machining tool 1 or 3 , retracted into the bore and the rolling elements 580 are delivered in the direction of the bore inner wall, until they rest with a contact pressure. As the machining tool rotates, the rolling elements roll off the inner wall of the bore. The coarse diamond-grained diamond coating forms a rough surface structure, with the portions of the diamond grains projecting from the bond forming raised portions between which recessed depressions are interposed. The raised portions are irregularly distributed over the surface of the work area. When rolling the rolling element on the surface and a contact pressure set by the Wälzelement-delivery system, the irregular structures of the work area in the near-surface edge region of the relatively soft material, so that a Rollprägstruktur 558 with irregularly distributed elevations and depressions, which is not dissimilar when viewed superficially on a sandblasted surface. However, the effort to provide and dispose of radiation material can be saved. In addition, dangers are avoided, which can be caused by unresolved particles of the blasting material. In addition, during roll embossing, a work hardening of near-surface edge layers of the workpiece can be produced by the contact pressure acting between the rolling element and the workpiece surface, which leads to an increase in the strength of the workpiece material in the immediate vicinity of the workpiece surface. In 5 this is symbolized schematically by the high dislocation density in the immediate vicinity of the roll embossing structure.

In the process variant of 6 become rolling elements 680 used, on an otherwise relatively smooth, circular cylindrical outer surface in the work area evenly distributed, elongated hard protrusions 682 can be applied, for example, by welding, soldering or by a lithographic process on the rolling element body. Is a surface provided by honing or otherwise with a certain basic roughness 610 a workpiece 600 machined with the help of these rolling elements, a smoothing of the surface can be achieved by the smooth peripheral portions between the projections. The projections, on the other hand, dig into the workpiece surface with material displacement, so that a roll embossing structure 658 with a regular pattern of relatively narrow pockets of finite length and closed perimeter edge. These can serve as a lubricant reservoir when the machined workpiece surface is used as intended.

Based on 7 a variant of the method is explained, in which with the aid of a roller embossing tool rotating about its tool axis, the convex cylindrical outer surface 710 a workpiece 700 is edited to a Rollprägestruktur 758 to create. The machining tool may be constructed similar to a Außenhonwerkzeug, but with the radially inwardly deliverable honing stones are replaced by support members, each one or more rolling elements 780 with a rough working section.

In 8th is a schematic section through a workpiece 800 from an aluminum material in the area of a curved workpiece surface 810 shown. The workpiece 800 in the example is a cylinder sleeve made of an aluminum alloy, whose inner surface is to serve as the cylinder surface of an internal combustion engine after completion of the processing. The manufacturing method comprises a multi-stage pre-processing of the inner surface of the cylinder sleeve including a final Honbearbeitungsschritt, through which the bore inner surface receives the right macro-shape and dimension to a slight excess. Similar to from 5 described, the honed starting structure is then by roll embossing in a rough roll embossed structure 858 transformed, which in the example a mean surface roughness between 30 microns and about 100 microns. The roll embossing operation is carried out without the aid of cooling lubricant or the like, ie in a dry process.

Immediately after the roll embossing, the roll embossing structure is ready for subsequent coating by thermal spraying without further treatment. In the example, an iron-containing coating is produced by means of a flame spraying process 860 directly on the roll embossing structure 858 applied. Due to the roughness of the roll embossing structure, the coating material interlocks well with the metallic base material of the workpiece, so that a firm adhesion between the workpiece and coating is formed. The relatively rough surface of the coating after the thermal spraying can then be subjected to a mechanical post-processing, for example by honing, in order to produce the desired final roughness of the surface and the desired final size.

In 9 is a schematic section through a cylinder sleeve 900 in the area of its inner surface 910 shown after it has been made with a variant of the method described above. As in the example of 8th After a pre-processing, a roll embossing operation was carried out first. This created the in 8th schematically shown irregular Rollprägestruktur with statistically distributed elevations and depressions. Thereafter, in another dry machining operation, the tips of the ridges were flattened by means of a rolling element having a smooth outer surface to produce a plateau structure at the ridges by material deformation. During material reshaping, so much material was forced sideways in some of the elevations that laterally protruding noses protrude laterally from the elevations 959 arise. Will now be the modified Rollprägestruktur created thereby 958 coated by thermal spraying, so the reaching into the wells layer material can formschüssig in the region of the lateral noses 959 hooked with the roll embossed structure, whereby an improved layer adhesion can be achieved. Similar to the example of 8th can the surface of the coating 850 be post-finished mechanically after completion of the coating process to z. B. by honing a finished surface with the desired degree and the desired surface structure to obtain. If necessary, the roll embossing operation and the subsequent non-abrasive smoothing operation can be carried out with the same processing tool (with double feed). This can be similar to in 3 be constructed, but instead of the honing stones non-abrasive smoothing elements are provided in the form of smooth rolls or smoothing with smooth hard outer surface.

In the case of 10 explained processing method is first, similar to the method of 8th or 9 , on the curved workpiece surface 1010 of the workpiece 1000 produces a roll embossing structure with statistically distributed depressions and elevations. Immediately thereafter, the resulting roll embossing structure is plateau honed with the aid of relatively fine-grained honing stones. In this processing stage, the outermost tips of the roll embossing structure are removed, leaving plateaus between the depressions 1051 with a textured by honing relatively flat surface with fine Honriefen 1052 result. Surfaces treated in this way have an increased bearing component compared to pure roll embossing structures and can serve directly as a sliding partner for piston rings.

If necessary, the relevant operations for the final surface structure (roll embossing operations and subsequent plateau hovering operation) can be generated using the same machining tool, which, for example, is the same as the machining tool of 3 can be constructed. The workpiece may for example consist of gray cast iron material or a light metal material, such as an aluminum base material.

Some embodiments of machining processes with a roll embossing operation have been explained using the example of the machining of curved workpiece surfaces in the area of cylinder bores in order to obtain tribologically high-strain cylinder running surfaces. However, the methods can also be used with other workpieces. For example, the internal machining of holes in the small or large connecting rod eye using Rollprägeoperationen is possible. For example, the small connecting rod eye can first be processed by roll embossing and then the inner surface provided with roll embossing structure can be covered with a coating of a bearing material. Alternatively, the rough roll embossing structure can serve as an anti-rotation device for an inserted bearing shell, the outer surface of which may possibly also be roughened by means of roll embossing.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19614328 A1 [0007]
• EP 1141438 B1 [0008]
• EP 0607779 B1 [0009]
• DE 69423373 T2 [0009]
• DE 102004038177 A1 [0010]

Cited non-patent literature

• "Process chain for the production of thermally sprayed cylinder bores" by G. Flores, A. Schwenk and C. Schnell in: VDI reports No. 2109, 2010 [0006]

Claims (14)

A machining method for machining a curved workpiece surface of a workpiece, in particular for machining the inner surface of a bore in a workpiece, characterized by a roll embossing operation in which at least one rolling element of a machining tool is unrolled on a portion of the curved workpiece surface to be machined under a contact pressure, wherein an outer surface of the Rolling element in at least one intended for a rolling contact with the workpiece surface working section has a rough surface structure and wherein the contact pressure is adjusted so that when rolling by local forming of workpiece material in the region of the workpiece surface, a rough Rollprägestruktur is generated. Processing method according to claim 1, wherein a roll embossing structure with an average roughness depth Rz of more than 10 μm is generated by the roll embossing operation on the workpiece surface, wherein the mean roughness depth generated is in particular in the range between Rz = 30 μm and Rz = 100 μm. A processing method according to claim 1 or 2, wherein a coating, preferably by thermal spraying, is applied to the workpiece surface after the roll embossing operation, wherein the coating is applied directly to the rough roll embossing structure produced by the roll embossing operation, or wherein the roll embossing structure after the roll embossing operation by means of one or more of several post-processing method for producing a modified roll embossed structure is post-processed and the coating is then applied to the modified roll embossing structure. Machining method according to one of the preceding claims, wherein during and / or after the roll embossing operation, a preferably non-changing cleaning of the workpiece surface is performed, in particular for eliminating generated by the roll embossing, not or only weakly bonded to the workpiece surface material particles, wherein the Roll embossed structure preferably cleaned dry during cleaning, brushed in particular by means of relatively soft non-abrasive brushes and / or pneumatically blown free. Processing method according to one of the preceding claims, wherein during and / or after the roll embossing operation, an extraction of processing residues of the roll embossing operation takes place, wherein preferably in addition to the suction, the workpiece surface is blown free. Machining method according to one of the preceding claims, characterized by a post-processing which modifies the roll embossing structure following the roll embossing operation to produce a modified roll embossing structure, wherein the reworking preferably preferably eliminates peaks in the region of elevations of the roll embossing structure to produce a flattened land plateau structure and intermediate therebetween Recesses on the workpiece surface comprises, wherein the tips are preferably removed in the region of elevations by a material-removing fine machining or by forming. Machining tool for machining a curved workpiece surface of a workpiece, in particular for machining the inner surface of a hole in a workpiece, comprising: a tool body ( 110 . 310 ), which has a tool axis ( 112 . 312 ) and at least one rolling element carried by the tool body ( 180 . 380 ), which is about a Wälzelementachse lying outside the tool axis ( 112 . 312 ) is rotatable and has an outer surface, characterized in that the outer surface in at least one intended for a rolling contact with the workpiece surface working section ( 190 ) has a rough surface texture. Machining tool according to claim 7, wherein the rolling element comprises a rolling element body ( 184 ), which in the working section has a coating ( 192 ) having a rough surface structure, wherein the coating ( 192 ) preferably a plurality of in a bond ( 196 ) bound hard material grains ( 194 ), wherein preferably a mean grain size of the hard grains is at least 15 microns, wherein the average grain size is in particular in the range of 30 microns to 250 microns. Machining tool according to one of claims 7 or 8, wherein on the tool body at least one relative to the tool body radially to the tool axis movable support member ( 160 . 460 ) is arranged and the rolling element is mounted on the carrier element, wherein the rolling element is preferably mounted elastically yielding on the carrier element. Machining tool according to one of claims 7 to 9, wherein on the tool body ( 110 ) several, in particular three, distributed around the circumference rolling elements ( 180A . 180B . 180C ) are arranged. Machining tool according to one of claims 7 to 10, characterized by a rolling element delivery system for variably controllable Infeed of the rolling element in a radial direction to the tool axis ( 112 . 312 ) extending delivery direction. Machining tool according to one of claims 7 to 11, wherein the machining tool ( 300 ) in addition to a plurality of rolling elements distributed around the circumference of the machining tool ( 380 ) has a set of a plurality of further processing elements distributed around the circumference of the processing tool, which are radially deliverable independently of the rolling elements, wherein the further processing elements preferably have honing bars ( 390 ) or smoothing elements are. Machining tool according to one of claims 7 to 12, wherein the tool body a coupling structure for coupling the machining tool to a work spindle ( 150 ) has a honing machine. Workpiece, in particular cylinder crankcase or cylinder sleeve, produced using the machining method according to one of claims 1 to 6 and / or using the machining tool according to one of claims 7 to 13

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