EP3921118B1 - Honing tool and fine machining method using the honing tool - Google Patents

Description

FIELD OF APPLICATION AND STATE OF TECHNOLOGY

The invention relates to a honing tool according to the preamble of claim 1 and a fine machining method according to the preamble of claim 13. A preferred area of application is the fine machining of cylinder running surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines.

The cylinder running surfaces in cylinder blocks (cylinder crankcases) or cylinder liners of internal combustion engines or other reciprocating piston engines are exposed to strong tribological stress during operation. Therefore, when producing cylinder blocks or cylinder liners, it is important to machine these cylinder surfaces in such a way that sufficient lubrication is later guaranteed by a lubricant film under all operating conditions and that the frictional resistance between parts moving relative to one another is kept as low as possible.

The quality-determining final processing of such tribologically stressed inner surfaces is usually carried out using suitable honing processes, which typically include several successive honing operations. Honing is a machining process with geometrically undetermined cutting edges. During a honing operation, an expandable honing tool is moved up and down or back and forth within the bore to be machined to produce a lifting movement in the axial direction of the bore and at the same time rotated to produce a rotary movement superimposed on the lifting movement. The cutting material bodies attached to the honing tool are pressed onto the inner surface to be machined via a feed system with a feed force acting radially to the tool axis. During honing, a cross-cut pattern with crossing machining marks, which are also referred to as "honing grooves", is usually created on the inner surface.

With increasing demands on the economy and environmental friendliness of engines, the optimization of the tribological system of pistons/piston rings/cylinder running surface is of particular importance in order to achieve low friction, low wear and low oil consumption. The macroscopic shape (macro shape) of the holes and the surface structure are particularly important.

In some fine machining processes, a bore shape that deviates from the circular cylindrical shape is created using fine drilling and/or honing. Such bore shapes are generally asymmetrical in the axial direction and/or in the circumferential direction because the deformations of the cylinder block are also generally not symmetrical. When in operation, the circular cylindrical shape should usually be as ideal as possible, so that the piston ring package can seal well over the entire bore circumference.

The DE 10 2013 204 714 A1 discloses honing tools that are suitable, among other things, for machining rotationally symmetrical bores that have bore sections of different diameters and/or shapes. This means that, for example, rotationally symmetrical bores with a bottle shape, a cone shape or a barrel shape can be machined and/or created. The honing tool has an annular expandable cutting group with a plurality of cutting material bodies distributed around the circumference of the tool body, the axial length of which, measured in the axial direction (parallel to the tool axis), is smaller than an effective outer diameter of the cutting group when the cutting material bodies are completely retracted. The cutting group has several radially adjustable carriers which carry cutting material bodies in the form of honing segments on their radial outer sides, each of which covers a circumferential angle range that is larger than the axial length of the cutting group.

Due to the relatively short axial length of the cutting group, such honing tools are particularly suitable for producing an axial contour and/or for tracking an already existing axial contour of the bore. In addition, short axial lengths of the cutting group can be advantageous in order to generate sufficient surface pressure for machining. Because the cutting group has a plurality of radially adjustable supports, each of which covers a circumferential angle range that is larger than the axial length of the cutting group, it can be achieved, among other things, that, for example, transverse bores in the wall of a cylinder barrel can be bridged in the circumferential direction during honing, so that despite the axially short cutting material body, there is no risk of uneven machining in the area of transverse holes. When using such honing tools, it is also possible to work with very little honing overflow at the axial ends of a bore without problems with uneven cutting body wear.

The DE 10 2014 212 941 A1 The applicant shows similar honing tools with an annular cutting group that is relatively short in the axial direction and in which a large portion of the circumference is occupied by cutting means. In addition, a guide group with adjustable guide strips is provided. The annular cutting group has relative circumferential direction wide carriers that can be delivered radially together via a delivery system. In some exemplary embodiments, the outer sides of the carriers are covered with a shell-shaped solid covering (honing segment). It can also be the case that the outer sides each carry cutting material bodies with axial longitudinal grooves, so that the radially outer cutting surfaces are interrupted several times in the circumferential direction. Variants are also described in which several relatively narrow honing stones are attached to the outside of the rigid supports, which are curved in a circular arc in the circumferential direction and are at a circumferential distance from one another, so that groove-like spaces form between the honing stones. The grooves or gaps enable efficient supply and removal of cooling lubricant and removal of abrasion.

It has been observed that in certain cases when machining non-cylindrical bores (e.g. rotationally symmetrical bores with bottle shape, cone shape or barrel shape) locally different surface structures can be created due to different cutting depths. These can cause technical disadvantages. If local roughness is undesirably too high, oil consumption and blow-by can be increased, for example. If too little material is removed locally, the risk of seizing during operation of an internal combustion engine can increase due to insufficient removal of material damage from upstream processing stages. Near the axial ends of a hole, the micrograph may differ from the micrograph in the rest of the hole.

document FR 2 977 517 A1 discloses according to the preamble of claim 1 a honing tool for machining an inner surface of a bore in a workpiece using at least one honing operation, comprising: a tool body that defines a tool axis, a first cutting group attached to the tool body with a plurality of radially adjustable first carriers, which are arranged by means of a assigned first cutting group delivery system can be delivered radially to the tool axis, and carries on the outside a single first cutting material body in the circumferential direction, which are arranged at a mutual distance from one another; and a second cutting group attached to the tool body with a plurality of radially adjustable second carriers, which can be delivered radially to the tool axis independently of the first carriers by means of an associated second cutting group delivery system, each second carrier carrying a single, narrow second cutting material body on its radial outside.

TASK AND SOLUTION

It is an object of the present invention to provide a generic honing tool and a fine machining process that can be carried out with it, which allow bores of different shapes so that the machined bore surfaces have a well-defined surface structure over the entire length of the bore.

To solve this problem, the invention provides a honing tool with the features of claim 1. Furthermore, a fine machining method with the features of claim 13 is provided. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

The honing tool has a tool body that defines a tool axis. Directions parallel to the tool axis are called "axial direction" or "axial direction". Two cutting groups that can be delivered independently of one another are attached to the tool body, namely a first cutting group and a second cutting group. The first cutting group has a plurality of first carriers, which can be advanced radially to the tool axis by means of an assigned first delivery system. The first supports each cover a relatively wide circumferential angle range of at least 20° on their radial outside.

The circumferential angle range covered by a first carrier can be, for example, 25° or more or 30° or more. The circumferential angle range is preferably at most 120° or at most 90°.

The number of first carriers can vary from embodiment to embodiment, for example depending on their circumferential width. Preferably three or more first carriers are provided, for example three, four, five or six first carriers, possibly only two first carriers.

The first carriers carry on their relatively wide radial outer sides either a single first cutting material body that is relatively wide in the circumferential direction, e.g. in the manner of a shell-shaped solid covering with a continuous (uninterrupted) or interrupted by grooves cutting surface, or several narrow first cutting material bodies, which are at a mutual distance (in the circumferential direction ) are arranged to each other. Most of the first carriers have the same type of first cutting coating (full coating, possibly with grooves or a group of strips with several narrow first cutting material bodies), but this is not mandatory.

The second cutting group, which is also attached to the tool body, has a plurality of second carriers which are directed radially by means of an assigned second delivery system Tool axis can be delivered. Each of the second carriers only carries a single, narrow second cutting material body on its radial outside.

The term “cutting material body” describes the abrasive elements of the honing tools. In honing tools, a cutting material body, which can also be referred to as a cutting coating, essentially consists of irregularly shaped cutting grains of different shapes and sizes, which are bound within a bonding system. By selecting the type of cutting coating, a honing tool can be adapted particularly precisely to the desired machining task. Cutting grains can be, for example, diamond grains or cubic boron nitride (CBN) grains. Cutting grains can also be made of corundum and/or other types of ceramic materials, such as SiC. The bond can, for example, consist of a ceramic material or synthetic resin. Metallic bonding systems, e.g. galvanically produced bonds or sintered bonds, are also possible, and if necessary also soldered bonds.

The term "narrow" in connection with cutting material bodies means that the width of the (narrow) cutting material bodies in the circumferential direction is significantly smaller than a length measured in the axial direction. An aspect ratio between (axial) length and (measured in the circumferential direction) width can be, for example, in the range of 5 or more, in particular in the range of 8 to 25. Narrow cutting material bodies are often also referred to as cutting strips or honing stones. Expressed in absolute values, the narrow first cutting material bodies can, for example, have circumferential widths in the range of 1.5 mm to 5 mm, possibly also above or below.

In comparison, a first cutting material body that is relatively wide in the circumferential direction, which can be designed, for example, in the manner of a shell-shaped solid covering, preferably has a significantly smaller aspect ratio, which can be, for example, in the range of 3 or less, possibly also 1 or less, so that the width in the circumferential direction can be greater than the axial length.

The optimal dimensions of the cutting material bodies generally depend on the effective diameter of the honing tool or the diameter of the hole to be machined.

The cutting material bodies of the first cutting group and the second cutting group are arranged in an axially relatively short cutting area. The cutting area has a length, measured in the axial direction, which is significantly smaller than an effective outer diameter of the cutting groups when the cutting material bodies are completely retracted. “Much smaller” means that the axial length or extent of the cutting area is at most 80% of the effective outside diameter of the cutting groups. In other words, “significantly smaller” means: at least 20% smaller. The axial length can, for example, be less than half the effective outside diameter. The first cutting material bodies and the second cutting material bodies are therefore arranged such that they all lie completely within a relatively short cutting area when viewed in the axial direction. Due to the relatively short axial length of the cutting area, such honing tools are particularly suitable for producing bore shapes with an axial contour, i.e. different diameters in the axial direction. Alternatively or additionally, they can also be used to track such an existing axial contour of the bore.

The axial length or extent of the cutting area can, for example, be less than 40% of the effective outer diameter of the cutting groups and/or less than 20% of the bore length of the bore.

Investigations by the inventors have shown that the special distribution of cutting material bodies on the first and second carriers offers particular advantages. Each of the first carriers covers a certain, relatively wide circumferential area with the first cutting material bodies attached to it (e.g. a wide full covering or several narrow, strip-shaped cutting material bodies per carrier). It has been shown that when honing using the first cutting group, particularly good roundness values can be achieved in the hole created. In the variants with several narrow cutting material bodies per first carrier, due to the large number of first cutting material bodies, which are simultaneously in engagement with the inner wall of the bore, good service life is achieved even with a shape that removes a lot of material. In the variants with relatively wide first cutting material bodies, relatively efficient material removal with little wear is also possible.

According to the inventors' findings, the second cutting group with individual, relatively narrow cutting material bodies offers other advantages. It was found that individual second cutting material bodies, which can be delivered individually in different radial directions, tend to rest more firmly (better, more uniform surface contact) on an existing surface than first cutting material bodies, which only rest together or in groups per second carrier in a common radial direction on the inner wall of the bore can be pressed. This makes it possible to achieve particularly high surface qualities.

The total cutting area of the second cutting group can be less than the total cutting area of the first cutting group. This can be particularly beneficial if... With the second cutting group, only relatively little substantial material removal is to be achieved, for example when plateau honing or when smoothing a surface that has previously been machined with a coarser cutting material.

The first and second cutting groups can be adapted to each other and to the honing process with regard to the type and dimensions of the cutting material bodies in such a way that they wear more or less equally or at the same rate during the intended honing process. This is, among other things, favorable for economical new equipment.

In many embodiments, the number of second cutting material bodies is greater than the number of first cutting material bodies, among other things in order to obtain comparable service lives and overlaps.

In the variants with several narrow cutting material bodies per first carrier, more than two first cutting material bodies are preferably attached to the radial outside of a first carrier, for example three, four, five, six, seven or more first cutting material bodies. Experience has shown that between three and seven first cutting material bodies per carrier are often advantageous.

In some embodiments of these variants, the mutual distance between immediately adjacent first cutting material bodies is in the order of magnitude of the circumferential width of the cutting material bodies or less. If the mutual distance is smaller than the circumferential width of the first cutting material bodies, a relatively high surface area of the abrasive material of the first cutting material bodies can be ensured when viewed in the circumferential direction, so that high material removal is possible with at the same time low wear. Removed material chips can be easily removed by means of cooling lubricant through the channels located between the first cutting material bodies, so that the risk of clogging of the abrasive outer surfaces of the cutting material bodies can be kept low.

Preferably, the first cutting material bodies carried by a first carrier with their external cutting surfaces cover a total circumferential angle range which corresponds to at least 30% or at least 50% of the circumferential width of the carrier, so that a relatively large total cutting surface is used in the first cutting group when viewed in the circumferential direction and thus, if necessary, a relatively high removal rate can be achieved with a long service life.

It may be sufficient if the second cutting group has relatively few narrow second cutting material bodies that can be delivered in different radial directions, for example four, six, eight or ten second cutting material bodies. The second cutting material bodies can be distributed symmetrically or asymmetrically over the circumference of the honing tool.

In some embodiments, first carriers and second carriers and the associated cutting material bodies are arranged alternately in the circumferential direction on the tool body. The distribution in the circumferential direction can vary. Preferably, at least one second carrier is arranged between first carriers that are adjacent in the circumferential direction. It may be that exactly one second carrier with an associated second cutting material body is arranged between a pair of immediately adjacent first carriers. Elsewhere on the circumference and/or in another embodiment, it may be the case that two or more second carriers are arranged between immediately adjacent first carriers, so that there are second carriers that are immediately adjacent in the circumferential direction. In this way, the density of the second carriers and/or the second cutting material bodies carried by them, viewed in the circumferential direction, can be optimized for each application.

A uniform distribution of first and second supports, viewed in the circumferential direction, is possible. In many embodiments, however, the first carriers and the second carriers are arranged unevenly distributed in the circumferential direction, in particular in such a way that intermediate circumferential angles vary.

Preferably, the arrangement is such that pairs of similar carriers and cutting material bodies are arranged at diametrically opposite positions on the circumference, so that during delivery, due to this symmetry, there are no design-related resulting transverse forces that lead to an unwanted deflection of the honing tool during machining can.

The first cutting material bodies and the second cutting material bodies can have the same length in the axial direction. Furthermore, if all are arranged in the same axial section, the axial length of the cutting area results from the axial length of the first and second cutting material bodies. The first and second cutting material bodies can also be axially slightly offset from one another, so that the axial length of the cutting area can become slightly larger than the axial length of the longest of the cutting material bodies.

In one embodiment, the first cutting material bodies are shorter in the axial direction than the second cutting material bodies. The axial length of the first cutting material bodies can be, for example, less than 80% or less than 70% of the axial length of the second cutting material bodies, but generally not less than 50% of this length. With that you can What can be achieved is that the first cutting group in the advanced state, i.e. when machining the inner surface of the bore, acts in an effective first cutting area that is shorter than the cutting area of the honing tool. This means that, for example, bore sections with larger diameter changes in the axial direction (small radii) can be machined particularly well. It is also possible for second cutting material bodies to be shorter in the axial direction than first cutting material bodies.

In some embodiments, the second cutting material bodies are mounted in an elastically flexible manner with respect to the tool body. The elastically flexible mounting can improve the ability of the second cutting material bodies to follow contours without contact pressure peaks, which can have a positive effect on the quality of the surfaces that can be achieved. Elastic compliance can be achieved in different ways. For example, it is possible to work within the second delivery system up to the carrier without design-related flexibility and to provide elastic flexibility between the carrier and the cutting material body being carried. This can be achieved, for example, by arranging an elastically flexible intermediate layer in an intermediate space between a cutting material body and the carrier carrying the cutting material body, which can be formed, for example, by a layer made of an elastomer. The intermediate layer can completely fill the gap to avoid the penetration of cutting agent residues or abrasion. With regard to this aspect, reference is made to: DE 10 2017 202 573 A1 referred to the applicant, which describes the implementation options for this.

In some embodiments, the elastic compliance is achieved in that the second carrier has an elastically flexible section with (support material-free) recesses and spring elements formed in one piece with the carrier close to or adjacent to a second cutting material body. In comparison to possible designs with separate springs within the delivery system, such variants with monolithically integrated spring elements are characterized, among other things, by the fact that the spring force can be specified with high precision during the production of the carrier. This solution is also extremely robust and durable.

In variants with separate springs for flexible mounting of the second cutting material bodies and in variants with recesses in the carrier material, it can happen that abrasion gets into the spring area and impairs function. In some embodiments, this is prevented by filling the area between spring coils or in the recesses that is free of spring material with an elastically flexible elastomeric material or another elastically flexible filling material.

This means that the spring effect is retained in the long term. By selecting suitable elastically flexible filling materials, the spring characteristics, e.g. the “hardness” of the suspension, can be precisely adjusted. Some of the free spaces in the spring area may be filled. Regardless of the other features of the invention, these measures can also be used for honing tools not according to the invention with elastic flexibility in the honing tool

In some embodiments, the honing tool has a guide group with a plurality of guide strips distributed around the circumference of the tool body. These can be firmly attached to the tool body. Individual, several or all guide strips can extend at least partially into axial areas outside the cutting area. In some embodiments, the guide strips are arranged exclusively within the cutting area. This can ensure that even in bore sections with axially highly varying diameters, the guide strips do not come into unwanted contact with the inner surface of the bore. One, several or all guide bars can be arranged directly next to a second carrier, so that the adjacent second carriers are protected by the immediately adjacent guide bar.

In some embodiments, a further contribution to achieving high surface quality is achieved in that the honing tool has an integrated multi-axis joint for limitedly movable coupling of the tool body to a connecting piece. It is preferably provided that an axial distance between the joint and the cutting area designed with cutting material bodies is smaller than the effective outer diameter of the cutting groups when the cutting material bodies are completely retracted. This results in an axially compact design. In addition, any tilting moments when the tool axis is tilted relative to the rotation axis of the drive spindle can be kept low, which, according to the inventors' experience, can have a positive effect on the surface quality of the honed inner bore surface. In the context of this application, the axial distance is measured between the plane of the hinge point and the axial end of the cutting area.

The invention also relates to a fine machining method for machining the inner surface of a bore in a workpiece, in particular for fine machining of cylinder running surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines. The fine machining process includes at least one honing operation in which an expandable honing tool is placed within the bore to generate a lifting movement in the axial direction Bore is moved back and forth and at the same time rotated to generate a rotary movement superimposed on the lifting movement, a honing tool according to the claimed invention being used during the honing operation.

According to a further development, a honing operation is carried out as a multi-stage honing operation, wherein in a first honing stage the first cutting group is pressed against the inner surface of the bore and a bore shape which deviates from the circular cylindrical shape, preferably rotationally symmetrical, is produced by means of the first cutting group by means of axially uneven material removal starting from an initial shape, and wherein the second cutting group is then advanced in a second honing stage and a desired surface structure is produced on the inner surface of the bore by means of the second cutting group, essentially without changing the macro shape of the bore. The honing tool can therefore be used here, without an intermediate tool change, to change the shape of the bore by means of axially uneven material removal (first honing stage) and then, with the first cutting group retracted and the second cutting group advanced, to improve the surface structure of the inner surface of the bore, essentially without further material removal or . with at most very little material removal.

Since there is no need to change tools between the two honing stages, the cycle time can be significantly reduced compared to processes with tool changes. Inaccuracies that can be caused by a tool change can also be avoided.

In the first honing stage, a path control is preferably used in order to achieve the desired bore shape with high accuracy. In the second honing stage, honing is preferably force-controlled. In some variants, honing is carried out over the entire length of the bore with essentially constant contact pressure in order to achieve a largely uniform surface structure over the entire length.

In other variants, the bore is divided in terms of control technology into at least two adjacent axial bore sections (a first bore section and at least one second bore section) and the control is carried out in such a way that the honing parameters in the bore sections differ, for example in one of the bore sections being honed with greater pressing force than in another borehole section. The surfaces in the bore sections can thereby be optimized with regard to different conditions during intended use (e.g. piston speed in reciprocating piston engines).

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1

zeigt eine schrägperspektivische schematische Ansicht einer Ausführungsform eines Honwerkzeugs gemäß der beanspruchten Erfindung;

Fig. 2

zeigt eine Ansicht des Honwerkzeugs aus Fig. 1 in Axialrichtung auf das spindelferne Ende;

Fig. 3

zeigt eine Seitenansicht des Honwerkzeugs aus Fig. 1;

Fig. 4

zeigt einen Schnitt in einer die Werkzugachse enthaltende Radialebene durch einzeln zustellbare zweite Schneidstoffkörper gemäß Linie IV-IV in Fig. 2;

Fig. 5

zeigt einen Schnitt in einer die Werkzugachse enthaltende Radialebene durch erste Träger gemäß Linie V-V in Fig. 2;

Fig. 6

zeigt einen Schnitt in einer die Werkzugachse enthaltende Radialebene durch erste Träger einer anderen Ausführungsform;

Fig. 7 bis 10

zeigen verschiedene Varianten von leistenförmigen zweiten Trägern, die im Bereich nahe der Außenfläche zur Befestigung eines Schneidstoffkörpers durch ein Muster von Ausnehmungen und integrale Federelemente elastisch nachgiebig ausgestaltet sind.

Further advantages and aspects of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are explained below with reference to the figures.

Fig. 1

shows an oblique perspective schematic view of an embodiment of a honing tool according to the claimed invention;

Fig. 2

shows a view of the honing tool Fig. 1 in the axial direction to the end remote from the spindle;

Fig. 3

shows a side view of the honing tool Fig. 1 ;

Fig. 4

shows a section in a radial plane containing the tool axis through individually adjustable second cutting material bodies according to line IV-IV in Fig. 2 ;

Fig. 5

shows a section in a radial plane containing the tool axis through the first carrier according to line VV in Fig. 2 ;

Fig. 6

shows a section in a radial plane containing the tool axis through first carriers of another embodiment;

Fig. 7 to 10

show various variants of strip-shaped second carriers, which are designed to be elastically flexible in the area near the outer surface for fastening a cutting material body through a pattern of recesses and integral spring elements.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows an oblique perspective view of a honing tool 100 according to an embodiment of the invention. The honing tool is used to process an inner surface of a bore in a workpiece by means of honing and, in the example, is designed to hone cylinder running surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines. The honing tool is particularly suitable for machining rotationally symmetrical bores that have bore sections of different diameters and/or different shapes, for example bottle-shaped Bores, barrel-shaped bores and/or bores that have at least one conical bore section with an axially continuously variable diameter. However, the honing tool can also be used to machine circular cylindrical bores, i.e. rotationally symmetrical bores without an axial contour.

The honing tool has a material body 110 made of a steel material, which defines a tool axis 112, which is also the axis of rotation of the honing tool during honing. At the spindle-side end of the honing tool there is a coupling structure 120 for coupling the honing tool to a drive rod or a work spindle of a honing machine or another processing machine, which has a work spindle that is both rotatable about the spindle axis and can be moved back and forth in an oscillating manner parallel to the spindle axis . In Fig. 1 the coupling structure 120 is designed as a functional part of a bayonet connection. In exemplary embodiments for use on the work spindle of a machining center, for example, a coupling structure in the manner of a hollow shaft cone or another cone can be provided.

In the end section of the tool body facing away from the coupling structure 120 or the work spindle (not shown) there is the cutting area 130 of the honing tool, in which all abrasive cutting material bodies (general reference number 140) are attached. Within the cutting area 130, many cutting material bodies are arranged, distributed around the circumference of the tool body, which have an axial length LS in an axial direction running parallel to the tool axis, which is several times smaller than a minimum effective outer diameter AD of the honing tool in the cutting area 130 equipped with cutting material bodies .

In the exemplary embodiment, all cutting material bodies are designed as cutting material strips that are narrow in the circumferential direction, the width BS of which, measured in the circumferential direction, is small compared to the axial length LS. An aspect ratio between length LS and width BS can be in the range from 4:1 to 25:1, for example.

The honing tool has only a single cutting area 130. This is arranged more or less flush with the end of the tool body remote from the spindle in the end section of the tool body facing away from the spindle, so that blind holes can also be machined down to the bottom of the hole if necessary.

With the honing tool 100 in Fig. 1 It is a honing tool with double expansion, which is characterized in that a first cutting group 160-1 and a second cutting group 160-2 that can be delivered independently of it are arranged on the tool body. The first cutting group 160-1 has several (in the example, exactly four) first carriers 150-1, which can be delivered radially to the tool axis 112 in associated radial directions by means of an assigned first delivery system 170-1. The second cutting group 160-2 has several (in the example a total of eight) second carriers 150-2, which can be delivered independently of the first carriers 150-1 in associated radial directions radially to the tool axis 112, for which purpose a second delivery system 170-2 is provided .

The carriers 150-1, 150-2, which carry the respective cutting material bodies 140-1 and 140-2, are each one-piece components made of steel material, which are essentially rigid in themselves. Each of the first carriers 150-1 has a relatively wide carrier section 152-1 in the circumferential direction with a generally cylindrically curved outer side 154-1 and a substantially flat inner side facing the tool body, on which a plate-shaped feed section 156-1 protrudes inwards. On the inside of the feed section facing away from the outside 154-1 there are inclined surfaces which cooperate with a corresponding inclined surface of an axially displaceable first feed cone in the manner of a wedge drive, so that an axial movement of the feed cone inside the tool body leads to a radial movement of the carrier. The delivery section 156-1 of the carrier 150-1 sits in a radially movable manner in a substantially rectangular recess in the tool body, so that a radial movement (radial to the tool axis 112) is possible, but tilting movements in the transverse direction are largely avoided. The carriers are preloaded into the inwardly retracted position using several circumferential coil springs, so that the radial outward advance occurs against the force of these return springs.

The outer carrier sections 152-1 are so wide in the circumferential direction that the first carriers each cover a circumferential section of more than 20° circumferential width, in the example it is more than 30°, namely approximately 35° circumferential width. When advancing in the radial direction to the workpiece axis, only the central region of this carrier section viewed in the circumferential direction is advanced exactly radially to the tool axis. The areas further out are delivered parallel to this central radial direction, so that there is a small angular deviation between the local radial direction and the actual delivery device. Therefore, in many embodiments, the circumferential width is no greater than 45°, or no greater than 60°, or no greater than 90°.

The second carriers 150-2 are significantly narrower in the area of their radial outer sides 154-2 than the wide carrier sections 152-1. In the example case, they each cover a circumferential angle range of less than 10°, with the circumferential angle range being approximately 5° to 7° in the example case. In absolute terms, the widths can be in the range from 1.5 mm to 4.0 mm, for example. Like the first carriers, the second carriers have a plate-shaped delivery section which projects inwards and has inclined surfaces on its tapered inside for cooperation with an axially displaceable delivery cone of a second delivery system 170-2. Here too, the feed sections are located in a rectangular recess in the tool body, which can be moved radially but are essentially immovable in the transverse direction, so that radial displacement is possible and displacements transverse to it are prevented.

On their radial outer sides, the first carriers 150-1 each carry six relatively narrow first cutting material bodies 140-1 in the form of cutting strips, which are attached to the outside of the carrier section at a mutual circumferential distance, for example by gluing, soldering, screwing or the like. are attached. Between the cutting material bodies there are groove-like, axially parallel spaces, the circumferential width of which is smaller than the circumferential width of the adjacent cutting material bodies. With their outer cutting surfaces, the cutting material bodies cover a total circumferential angle range of approximately half or slightly more of the circumferential width of the carrier section, so that there is a relatively high surface density of abrasive cutting surfaces in the circumferential direction, but interrupted by longitudinal gaps that allow the supply and removal of Cooling lubricant and, if necessary, promote abrasion.

In contrast, each of the second carriers 150-2 carries on its outside only a single, relatively narrow cutting material body 140-2, the axial length of which determines the axial length of the cutting area. The circumferential width is only approximately 20% of the length, but in the example it is larger than the circumferential width of the many narrower first cutting material bodies of the first cutting group.

The first cutting material bodies 140-1 are in the example of Fig. 1 only about half as long as the second cutting material bodies (approximately between 40% and 70% of this length) and end on the side facing away from the spindle at the same height as the second cutting material bodies 140-2. The first cutting material bodies thereby define an effective first cutting area which is only approximately half as long as the cutting area 130, the length of which is defined by the length of the second cutting material bodies.

In other embodiments, the shorter first cutting material bodies can also be arranged approximately in the middle of the cutting area or at the upper end of the cutting area facing the coupling section.

The first cutting material bodies are very wear-resistant and preferably have diamond cutting grains in a metallic bond. The second cutting material bodies can be constructed differently, for example with a ceramic bond or plastic bond.

The honing tool also has a guide group with several non-cutting guide strips 180 distributed around the circumference of the tool body, each of which is firmly attached to the tool body at predetermined positions, i.e. cannot be adjusted. The guide strips, which are aligned parallel to the tool axis, have an axial length that approximately corresponds to the length of the cutting area and are arranged exclusively within the cutting area 130. The guide strips, for example made of hard metal, are axially no longer than the cutting material bodies, so that the guidance in the axial direction is limited to the area in which material removal can also take place. There are no guide strips arranged outside the cutting area 130. The guide group has six guide strips which are evenly distributed over the circumference of the tool body 110 at 60° intervals. The arrangement is such that each of the guide strips 180 is arranged directly next to an individual second cutting material body 140-2, i.e. an individually adjustable cutting material body of the second cutting group. The distance in the circumferential direction is smaller than the guide width of the respective guide strips measured in the circumferential direction.

Two diametrically opposite guide strips 180-M are designed as measuring strips. In their middle, i.e. halfway up the cutting area, they have measuring nozzles 185 of a pneumatic diameter measuring system. Depending on the application, these can also be above or below the middle.

Some special features of the honing tool that cannot be seen from the outside are shown in the sectional views Figs. 4 and 5 recognizable. This shows Fig. 4 a cut through a radial plane that passes through the carrier and cutting strips of the second cutting group (with individual strips), while Fig. 5 shows a section through first carrier 150-1 and first cutting strips 140-1 of the first cutting group.

The first delivery system 170-1 has a first delivery element 172-1 in the form of a tube which is axially displaceably mounted in the tool body and which has two axially at the end facing away from the spindle has conical sections arranged offset from one another. The first carriers 150-1 of the first cutting group, which are operatively connected to one another, have two inclined surfaces which are axially offset from one another and which interact with the conical sections in the manner of a wedge drive. As a result, each first carrier is supported on the associated feed element in two areas that are axially spaced apart from one another, so that tilting of the first carrier is reliably avoided.

The infeed for the second cutting group is solved similarly. The second delivery system has a second delivery element 172-2 in the form of a rod which is guided in the interior of the tube (first delivery element) so that it can move axially relative thereto. At the end of the rod there are two conical sections at an axial distance from one another. Correspondingly, the second carriers 150-2 have two axially offset inclined surfaces on their radial inside, which cooperate with the corresponding conical surfaces. This also reliably prevents the second carrier from tipping during delivery.

As in Fig. 6 shown, alternative solutions are also possible in which, for example, the first carriers only have a single inclined surface on their radial inner sides, which interacts with a cone attached to the feed element. The same is also possible for the second carriers.

The sectional views of the Fig. 4 to 6 also reveal another special feature. The honing tool 100 has an integrated joint 190, with the help of which the tool body 110 is coupled to the connecting piece with limited mobility, which serves to connect to the work spindle of the processing machine. In the example, the joint 190 is designed as a ball joint, in which the joint ball 192 is formed at the lower end of the connecting piece, while the corresponding bearing elements with concave spherical bearing surfaces are attached within the tool body 110. This allows limited mobility of the tool body relative to the connecting piece in an infinite number of directions running transversely to the tool axis, whereby the honing tool can follow the surfaces particularly well, particularly when reworking the inner surfaces of bores to improve the surface quality. The axial distance AB between the articulation point (in the center of the joint ball) or the plane defined thereby orthogonal to the tool axis and the end of the cutting area 130, which is remote from the spindle and equipped with cutting material bodies, is smaller than the effective outer diameter AD of the cutting groups when the cutting material bodies are completely retracted. This can potentially cause an offset between the spindle axis and bore axis tilting moments can be reduced compared to conventional designs with a larger distance, which has a positive effect on the machining quality.

The second carriers 150-2, which carry the individual cutting material bodies of the second cutting group, can be manufactured completely as rigid components made of solid material, for example steel. Particularly for the tracking of non-circular cylindrical bore inner surfaces when improving the surface quality using the second cutting group, it can be advantageous to incorporate a certain flexibility in the force flow when pressing the second cutting material bodies, so that pressing force peaks can be avoided.

In the exemplary embodiments based on the Fig. 7 to 10 are shown, this is solved in each case in that the plate-shaped, narrow strip-shaped second carriers have an elastically flexible section 150-2E near or on the radial outside, which is intended to support a narrow cutting material body. The elastic compliance is achieved in these embodiments by creating recesses A of suitable shape, size and distribution in the initially monolithic support by means of spark erosion or other means in such a way that the material adjacent to the recess is under external load in the manner of a spring acts elastically, so that the outer section 150-2E becomes elastically flexible overall in the radial direction of the carrier. This solution with integrally formed FE spring elements has proven to be particularly robust and durable. The spring force can be adjusted by appropriately dimensioning the recesses or remaining spring elements.

A variant of these designs is shown Fig. 8 explained. In this exemplary embodiment, the carrier material-free recesses A are not empty, but are completely filled with an elastically flexible elastomer material EL. This can prevent material abrasion from penetrating the recesses. In addition, the spring characteristics can be precisely adjusted through a suitable choice of elastic filling material (elastomeric material EL) and any vibrations can be dampened. As shown, all recesses or only some of the recesses can be filled.

The honing tool can be used for a variety of fine machining processes to machine the inner surface of a hole with a workpiece. In one variant of the method it is intended to use the honing tool for fine machining of cylinder running surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines, in which starting from a bore with a For example, a circular cylindrical initial shape is intended to produce a preferably rotationally symmetrical bore with an axial contour, i.e. a bore that has different diameters in different axial sections, which merge more or less continuously into one another. It can be, for example, a conical bore shape or a bottle-shaped bore shape or a barrel-shaped bore shape.

For this purpose, the honing tool is coupled to the work spindle of a processing machine. In the example, the initial shape is circular cylindrical and can be produced by honing or by fine machining with a defined cutting edge, for example fine turning. In a first honing stage, the first cutting group is used. After inserting the honing tool into the hole, this is pressed onto the inner surface of the hole using the first feed system. Using the first cutting group, a rotationally symmetrical bore shape that deviates from the circular cylindrical shape is then created, starting from the initial shape, by axially uneven material removal. For this purpose, for example, the pressing force can be varied as a function of the stroke position of the honing tool in the bore using the control so that more material is removed in areas with higher pressing force, so that larger inner diameters are created than in other areas. Alternatively or additionally, an axially uneven material removal can be generated by varying the stroke length of the processing strokes, for example by reducing the axial height of the upper reversal point of the stroke movement while maintaining the same lower reversal point.

When the desired rotationally symmetrical bore shape is achieved within the scope of the specification intended for this first honing stage (can be determined, for example, by means of pneumatic diameter measurement), the first cutting group is withdrawn and the second cutting group is advanced. In the second honing stage that follows, with the help of the individual strips of the second cutting group, which are advanced in different radial directions, only a small amount of material is removed or almost no material is removed, so that the macro shape of the hole does not change or does not change significantly, but only the desired surface structure is created.

In many cases, the fine machining process is used to create a rotationally symmetrical bore shape with an axial contour, i.e. axially different diameters, and to generate the appropriate surface structure or surface structure distribution without having to change tools in the meantime. In principle, it is also possible to use the honing tool to create and/or machine bore shapes that have at least one bore section that deviates from the circular shape Have cross-sectional shape. A bore can, for example, have an oval bore shape or a cloverleaf shape in at least one section. Honing tool embodiments suitable for this purpose preferably have in the first cutting group, i.e. in the one with the first carriers that are relatively wide in the circumferential direction, only a single pair of diametrically opposed first carriers with corresponding first cutting material bodies (for example full coating or several individual strips at a distance from one another). The circumferential width is preferably less than 90 or less than 60°. When producing this bore shape, for example, the pressing force can be varied depending on the rotational position of the honing tool in order to produce areas with a larger diameter by gradually increasing the contact pressure and areas with a smaller diameter by reducing the contact pressure. If necessary, procedures can also be carried out in accordance with EP 1 815 943 A1 using oscillatory movements.

Claims (15)

1. Honing tool (100) for machining an inner face of a bore in a workpiece with the aid of at least one honing operation, in particular for honing cylinder surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines, comprising:

   a tool body (110) that defines a tool axis (112);

   a first cutting group (160-1), attached to the tool body, having a plurality of radially feedable first carriers (150-1) that are feedable radially with respect to the tool axis (112) by means of an associated first cutting group feeding system (170-1), and

   a second cutting group (160-2), attached to the tool body, having a plurality of radially feedable second carriers (150-2) that are feedable radially with respect to the tool axis (112, 412), independently of the first carriers (150-1), by means of an associated second cutting group feeding system (170-2), wherein each second carrier carries, on its radial outer side (154, 454), a single narrow second cutting material body (140-2),

   characterized in that

   each first carrier covers, on its radial outer side, a circumferential angle range of at least 20° and carries, on the outer side (154, 454), a single first cutting material body that is wide in the circumferential direction or a plurality of narrow first cutting material bodies (140-1) that are arranged in a manner spaced apart from one another; and

   all the cutting material bodies (140-1, 140-2) of the first and the second cutting group are arranged in an axially short cutting region (130) that has a length, measured in the axial direction, which is much less than an effective outside diameter (AD) of the cutting groups with the cutting material bodies fully retracted.
2. Honing tool according to Claim 1, characterized in that, in the case of a first cutting material body that is wide in the circumferential direction, an aspect ratio between the axial length and the width measured in the circumferential direction is 3 or less, in particular less than 1, and/or in that, in the case of a narrow first cutting material body (140-1) and/or in the case of a narrow second cutting material body (140-2), an aspect ratio between the axial length and the width measured in the circumferential direction is 5 or more, in particular in the range from 8 to 25.
3. Honing tool according to Claim 1 or 2, characterized in that the first cutting material bodies (140-1) attached to a first carrier (150-1) cover, with their external cutting faces, a total circumferential angle range that corresponds to at least 30% or at least 50% of the circumferential width of the outer side (154-1) of the first carrier.
4. Honing tool according to one of the preceding claims, characterized in that each first carrier (150-1) carries more than two first cutting material bodies (140-1) on its radial outer side, preferably three, four, five, six or seven first cutting material bodies (140-1), and/or in that a mutual spacing between immediately adjacent first cutting material bodies (140-1) lies in the order of the circumferential width of the first cutting material bodies or less.
5. Honing tool according to one of the preceding claims, characterized in that at least one second carrier (150-2) is arranged between first carriers (150-1) that are adjacent in the circumferential direction.
6. Honing tool according to one of the preceding claims, characterized in that the first carriers (150-1) and the second carriers (150-2) are arranged in a manner distributed irregularly in the circumferential direction.
7. Honing tool according to one of the preceding claims, characterized in that the first cutting material bodies (140-1) are shorter in the axial direction than the second cutting material bodies (140-2), wherein preferably an axial length of the first cutting material bodies is less than 80% and/or more than 50% of the axial length of the second cutting material bodies.
8. Honing tool according to one of the preceding claims, characterized in that the honing tool has an integrated joint (190) for coupling the tool body (110), with limited movability, to a connection piece, wherein preferably an axial spacing (AB) between an articulation point of the joint (190) and a spindle-remote end of the cutting region (130) is smaller than the effective outside diameter (AD) of the cutting groups with the cutting material bodies fully retracted.
9. Honing tool according to one of the preceding claims, characterized in that the second cutting material bodies (140-2) are mounted in an elastically resilient manner with regard to the tool body (110), wherein preferably the second carriers (150-2) have, close to or next to a second cutting material body, an elastic portion (150-2E) with cutouts (A) and spring elements (FE) formed integrally with the carrier.
10. Honing tool according to one of the preceding claims, characterized by a guide group having a plurality of guide strips (180) distributed around the circumference of the tool body, wherein preferably the guide strips (180) are arranged only within the cutting region (130).
11. Honing tool according to Claim 10, characterized in that one, a plurality or all of the guide strips (180) are arranged immediately next to a second carrier (150-2), wherein preferably a circumferential spacing between a second carrier (150-2) and the guide strip (180) is less than the width of the guide strip in the circumferential direction.
12. Honing tool according to one of the preceding claims, characterized in that the first cutting group feeding system (170-1) and/or the second cutting group feeding system (170-2) has an axially displaceable feeding element, which has a first conical portion and a second conical portion axially offset therefrom, wherein the first carriers (150-1) and/or the second carriers (150-2) have, on their radial inner side, two axially offset inclined faces that are configured to cooperate with the first and the second conical portion.
13. Fine machining method for machining the inner face of a bore in a workpiece, in particular for fine machining cylinder surfaces in the production of cylinder blocks or cylinder liners for reciprocating piston engines,

    wherein the fine machining method comprises at least one honing operation, in which an expandable honing tool (100) is moved back and forth within the bore in order to create a reciprocating movement in the axial direction of the bore and at the same time is rotated in order to create a rotary movement superimposed on the reciprocating movement,

    characterized in that,

    during the honing operation, a honing tool (100) having the features of one of the preceding claims is used.
14. Fine machining method according to Claim 13, characterized in that a honing operation is carried out as a multistage honing operation, wherein, in a first honing stage, a first cutting group is pressed against the bore inner face and a bore shape that differs from a circular-cylindrical shape and is preferably rotationally symmetric is created by means of the first cutting group, by means of axially irregular material removal, starting from an initial shape, and in that subsequently, in a second honing stage, a second cutting group is fed and, by means of the second cutting group, a desired surface structure is created on the bore inner face substantially without changing the macro shape of the bore.
15. Fine machining method according to Claim 14, characterized in that honing is carried out with path control in the first honing stage and/or is carried out with force control in the second honing stage.

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