EP1815944A1 - Method and apparatus for honing bore holes. - Google Patents

Abstract

The method involves generating oscillatory movement of the cutting assembly parallel to the inner surface, which are proportional to oscillation parameter, so that portion of material removal raised through cutting assembly results from the oscillatory movement of the cutting assembly. The oscillatory movement for the generation of a material removal at the inner surface is controlled for the production of a pre determined design form of the drilling. An independent claim is also included for the honing machine.

Description

The invention relates to a method for honing the inner surface of a bore in a workpiece, in particular for honing a cylinder surface in the manufacture of engine blocks for internal combustion engines, as well as a honing machine which is particularly suitable and configured for carrying out the method.

In the production of cylinder blocks of internal combustion engines, the cylinder surfaces are usually finished by a honing process. When using the finishing process Honing considerable efforts are often made to achieve the required component shape with the lowest possible form error.

Even if there are no shape defects immediately after processing, the optimum assembly geometry is often lost after assembly or during operation of the machined workpiece due to elastic and thermal deformations. For example, it is known that the assembly of the cylinder head on a cylinder block (engine block) lead to a non-negligible deformation of the cylinder bores, especially in the area of the cylinder head bolts can. During engine operation, however, the piston rings, the cylinder bore warped by the mechanical deformation but also by thermal deformation, should be filled in such a way that a clean seal of the combustion chamber is ensured during engine operation. A complete investment of the piston rings on the cylinder bore with the most even and small clearance between the piston ring and the inner cylinder wall is facilitated if the mounted and warm engine has cylinder bores with low cylinder shape error. If the cylinder shape error is too large, the piston rings will not seal properly, engine particulate emissions will increase, efficiency will decrease, and system life may be shortened.

To avoid such problems is in the DE 28 10 322 C2 has been proposed to avoid the deterioration of the cylinder shape of the cylinder bores in the assembly of the cylinder head in that the honing machine block is deformed by means of a chip device which simulates the later deformation by the cylinder head. In the tensioned state, which corresponds to the state present later in the assembly, the honing takes place, then the tension is released again. A similar proposal is in the JP 11-267960 described.

In addition, in order to simulate the deformation by the action of temperature, it is also known to heat the workpiece by means of hot honing oil. However, these methods are complex and expensive and associated with high safety risks for the machine operator. They are therefore used only for one-off production, but not in series production.

The European patent application EP 1 321 229 A1 describes a method for producing a bore, which in the unloaded state Has starting shape and in the operating state a deviating from the initial form target shape. The method includes determining the deformation of a hole with a desired shape in the operating state. By means of the desired shape and the determined deformation, the initial shape is determined and the bore is brought by a machining process in the initial shape. The initial shape produced by the method should assume the desired desired shape in the operating state. The machining method for producing the initial shape is a honing method in which the infeed pressure of at least one honing stone attached to a honing tool is varied during the machining time.

In the dissertation " Variable Form Honing by Computer-aided Honing Process Control "by R. Zurrin, published in: wbk - Research Reports from the Institute for Machine Tools and Industrial Engineering of the University of Karlsruhe, Volume 26 (1990 ) it is proposed to solve the problems described by the manufacturing process "Formhonen". This is understood in this document to mean honing with controlled feed movement, which makes it possible to achieve different removal rates during the honing process locally (stroke and angle position-dependent) in order to produce a negative form of the deformations with a defined surface (compare in particular pages 10 to 20). Form honing is explained using the example of deformed cylinder blocks in which the cylinder bores have a four-fold symmetrical fourth-round runout, ie a bore shape with 4-fold radial symmetry relative to the bore axis. This non-circular bore shape is achieved by controlling the feed force or the contact pressure of a simply expanding honing tool on the stroke and the rotation angle.

It is an object of the invention to provide a method for honing the inner surface of a bore in a workpiece, which makes it possible to produce bores which, even in the case of large deviations from a circular cylindrical shape have a uniform surface structure. It is another object of the invention to provide a suitable for performing the method honing machine.

To solve these and other objects, the invention provides a method having the features of claim 1 and a honing machine having the features of claim 19. Advantageous developments of the invention are specified in the dependent claims. The wording of all claims is incorporated herein by reference.

In a method according to the invention for honing the inner surface of a bore in a workpiece, in particular for honing a cylinder surface in the manufacture of cylinder blocks for internal combustion engines, a honing tool is moved within the bore and at least one attached to the honing tool cutting group with at least one cutting body for material-removing machining Inner surface is pressed with a feed force to the inner surface. According to the invention, a vibration movement of the cutting group is generated substantially parallel to the inner surface in accordance with at least one vibration parameter such that a substantial proportion of a material removal caused by the cutting group results from the oscillatory movement of the cutting group. Furthermore, a control of the oscillatory movement for generating a locally varying over the inner surface material removal on the inner surface for generating a predetermined desired shape of the bore.

In most conventional honing processes, the majority of the material removal results from the continuous rotational movement of the honing tool, which often occurs at relatively high speeds. In contrast, in the case of processes according to the invention, a significant proportion of relevant for the removal of material cutting speed from the oscillatory motion of the cutting group, so that the material removal is caused to a large extent or predominantly by the oscillatory motion of the cutting group.

In some variants of the method, the oscillating movement generates at least during a certain processing time interval exclusively a directed in the circumferential direction of the bore movement component of the cutting group. For this purpose, the honing tool oscillates within the processing time interval about its tool axis, without an axial feed or an axial vibration component is present. In other variants of the method, the oscillatory motion generates at least during a processing time interval exclusively a directed in the axial direction of the bore movement component. During this processing time interval thus no rotation of the honing tool takes place about its tool axis. In many cases it may be expedient if the oscillatory movement has both a directed in the circumferential direction of the bore movement component, and a directed in the axial direction of the bore movement component, so that one can speak so far of a superposition of two oscillatory movements (axial and tangential).

As far as the oscillatory motion has a directed in the axial direction of the bore component, the axial stroke of the oscillatory motion is preferably smaller than the axial length of the bore. If the oscillatory movement has a component directed in the circumferential direction of the bore, the angular amplitude of the oscillatory movement is preferably less than 180 °.

The oscillatory motion can be generated so that it has a temporally constant oscillation amplitude. In this case, the deflection of the cutting group changes relative to the zero position of the oscillatory motion not or not essential. In other embodiments, the oscillatory motion is generated such that the oscillatory motion has a time-varying amplitude of vibration within a change time interval. Within a honing process, phases with variable oscillation amplitude and phases with constant oscillation amplitude may occur at different times.

The term "oscillation movement" here stands for a periodically changing component of movement of the cutting group, to which a vibration frequency can be assigned. In preferred embodiments, the oscillatory motion has an oscillation frequency of at least 1 Hz, the oscillation frequency preferably being between 2 Hz and 30 Hz. Frequently, oscillation frequencies between approx. 2 Hz and approx. 10 Hz to 20 Hz make sense.

The working movement of the honing tool or of the at least one cutting group attached thereto can, in some embodiments, consist exclusively of a vibratory movement or of a superimposition of several oscillatory movements. In this case, material removal takes place mainly in the area around the zero positions of the oscillatory movements defined by the oscillatory movement. This can be useful, for example, in the machining of bores whose bore length to be machined is smaller than the effective length of the honing tool or essentially corresponds to this length. This variant of the method may also be useful when e.g. only a comparatively short axial area is to be machined within an axially long bore.

In some embodiments, in addition to the at least one vibratory motion, a translational movement of the cutting group superimposed on the oscillatory motion is along the inner surface generated in accordance with at least one displacement parameter and the displacement movement is controlled so that in conjunction with the superimposed vibration movement of the locally over the inner surface varying material removal is achieved. Typically, a motion component resulting from the displacement motion is significantly slower than the motion component resulting from the vibration motion. The displacement movement is preferably aperiodic and / or the displacement movement has a very slow change in the direction of displacement and / or the speed of displacement compared to the vibration movement. However, it is also possible to work without displacement. The optional displacement movement may be particularly useful if the length of the bore to be machined is significantly greater than the effective length of a honing tool.

The displacement movement can only have a directed in the circumferential direction of the bore movement component or exclusively directed in the axial direction of the bore movement component. Overlays of these two movements are also possible, so that e.g. a resultant displacement direction may be helical within the bore.

The total movement of the oscillating cutting groups can be generated, for example, by the honing tool slowly rotating in the bore, whereas this slow displacement in the circumferential direction is superimposed by a significantly faster oscillation movement in the axial direction and / or in the circumferential direction. In this case, the zero point of the oscillation movement can slowly rotate at a uniform or variable rotation speed. It is also a relatively slow displacement movement in the axial direction with a continuous or discontinuously varying feed rate possible, the much faster oscillatory motion superimposed in the circumferential direction and / or axial direction. In some variants of the method, the honing tool does not carry out a continuous rotation, so that the oscillatory movement takes place with respect to the circumferential direction about a fixed zero position.

In some process variants, the lifting speed is controlled as a function of the stroke position. Alternatively or additionally, the rotational speed can be controlled as a function of the rotational position or angular position. In these cases, a clear reference is made between a certain local area of the hole and the material removal to be produced in this area. As a result, shapes which deviate from a cylindrical shape can also be produced.

The oscillation movement or oscillation movement of the cutting group can be adapted to the requirements with regard to the oscillation amplitude, the oscillation frequency and / or the oscillation direction. The displacement movement may be controlled continuously or discontinuously (i.e., with pauses), with the displacement parameter and / or the displacement speed being controlled as displacement parameters in particular. The displacement movement is normally controlled so that each area of the inner surface is reached by at least one cutting material body of a cutting group and processed material removal, so that a material removal can be achieved across the board. It is also possible to process only partial areas of the inner surface by means of the method.

If the oscillatory motion is generated in such a way that its oscillation amplitude changes in a defined manner within a predefinable processing time interval, it is possible to generate specific bulges in predetermined regions of the bore or at the entire bore by locally increased removal of material continuously connect adjacent edges to adjacent bore areas without bulging. In this way, holes can be produced whose inner surfaces in the circumferential direction have selectively continuously varying radii of curvature and / or in the axial direction specifically continuously varying diameters.

Since with the aid of the method a location-dependent varying material removal on the inner surface can be achieved, the method is particularly suitable for producing noncircular cylindrical desired shapes whose shape deviations from an ideal circular cylindrical shape are clearly outside the usual tolerances in the honing methods considered here the cylindricity error, which in many cases should be less than 10 μm. In preferred variants, the shape deviations correspond to a cylindricity error of significantly more than 10 .mu.m, the cylindricity error preferably being more than 20 .mu.m, in particular between 20 .mu.m and about 60 .mu.m.

The cylindricity error is described here by the cylinder shape tolerance. The associated tolerance zone is determined by two to the bore axis and mutually coaxial, the bore inner wall inside or outside touching cylinder, wherein the radial distance between the two cylinders is a measure of the cylinder quality. For the purposes of this application, the cylindricity ΔZ is defined as ΔZ = (D _A -D _I ) / 2, where D _{A is} the diameter of the outer bore contacting cylinder and D _{I is} the diameter of the bore bore internally contacting cylinder.

One application of variable amplitude machining is the creation of oval bore bore holes, ie elliptical cross-section, in which the bore diameters deviate significantly in two mutually perpendicular directions. Such oval basic shapes of unround holes are, for example sometimes desired in connecting rods of connecting rods for internal combustion engines. Another application relates to the machining of cylinder bores of internal combustion engines, where in some cases in the vicinity of the cylinder head side entry side of the bore a non-circular cylindrical cross-sectional shape with approximately 2-fold radial symmetry and four each offset by 90 ° circumferentially bulges of the bore inner wall (roundness 4th order) may be advantageous.

However, it is also possible to compensate for cylindricity errors of bores with the aid of the method in order in this way, for example, to achieve an ideal cylindrical shape approximated cylindrical shape with a cylindricity error of 10 μm or less.

The method makes it possible to control the material removal substantially via the vibration parameter and possibly the displacement parameter, so that it is possible to dispense with a variation of the feed force or the contact pressure of the cutting group. In a preferred variant of the method, the cutting group is pressed against the inner surface with a substantially constant feed force. In this case cutting material bodies are thus pressed with a substantially constant surface pressure, so that the penetration depth of the cutting grains and thus the surface roughness generated during material removal are largely constant. With surfaces machined in this way, the surface topography which can be described by roughness parameters is thus largely independent of the macro-shape of the bore. Therefore, even with significant shape deviations from a circular cylindrical shape, a uniform roughness profile can be produced at the bore.

In other variants of the method, in addition to the oscillation movement and, if necessary, the displacement movement, it is also possible to variably change the delivery pressure in order to achieve the desired spatial distribution of the material removal and / or possibly locally different To produce surface roughness. The delivery force can do this, for example. be controlled as a function of the stroke position and / or the rotational position of the displacement movement.

In one embodiment, a vibratory motion of variable or constant amplitude of vibration is generated and the control of the displacement motion is performed in response to the desired shape. In this way, a total overflow time (total processing time or total effective time) can be set for each local area of the inner surface, which is essentially proportional to the local material removal provided for the area. Thus, by changing the feed rate locally in the bore a different material separation can be achieved. In areas with required strong material separation, the displacement speed can be reduced, with a temporary interruption of the displacement movement (speed = 0 in the direction of displacement) is possible. Areas with a required low removal of material can be overrun accordingly with a high displacement speed. In particular, in combination with a variable amplitude of vibration complex shapes of the bore inner surface are possible.

In order to achieve the required desired shape in a single stroke of the honing tool, in preferred variants, the displacement movement is controlled such that, based on the displacement movement, each area of the inner surface is processed only a maximum of once by a cutting group of the honing tool. The displacement movement may, for example, lead to a single pass through the tool through a hole from top to bottom or vice versa. In conjunction with an oscillating oscillation of the tool in the circumferential direction which takes place with a variable oscillation amplitude, a particularly fast machining process is possible. To produce larger differences in the removal at different points of the bore is also a multiple pass through possible.

The oscillatory movement of the cutting group can be generated by the fact that the cutting group is driven to oscillate relative to the tool body of the honing tool. For this purpose, an oscillating drive integrated in the honing tool can be provided. Preferred variants of the method can be carried out with conventional honing tools by the honing tool is set in the oscillatory movement and displacement movement by means of the required for the tool movement drives. The existing NC axes for stroke and / or rotation of the honing tool can be controlled so that they cause the oscillation.

In one embodiment, the honing tool for generating the oscillatory motion is set in a circumferentially oscillating motion, preferably without simultaneous axial oscillatory movement. The angular amplitudes of the oscillation movement oscillating in the circumferential direction are typically well below 180 °, in particular at less than 90 ° and / or less than 45 °. For example, they may be less than 30 degrees or less than 20 degrees. In many cases, values of 1 ° to 10 ° have been found to be practicable as the lower limit for the angle amplitude. The angular amplitudes can be controlled to vary depending on the time and / or the stroke position.

The oscillatory motion may also have an axially directed component which may be provided alone or in conjunction with a circumferentially directed component. If an axially oscillating movement is provided, its amplitude is typically in the range between about 1% and about 50% of the axial Tool length, ie the axial length, are in the cutting material body in material-removing engagement with the inner surface.

In some embodiments, the honing tool is placed in a circumferentially oscillating motion having a maximum amplitude of oscillation of at most 90 °, producing a circumferentially bore velocity component of the cutting assembly that is at least as large as a velocity component directed axially of the bore , A resulting main direction of movement of the variable amplitude oscillation cutting group is substantially in the circumferential direction under these conditions or includes with the circumferential direction only an angle of, for example, a maximum of 5 ° to 45 °. The substantial portion of the material removal is thus carried out in this process variant by the circumferential oscillatory movement, e.g. may have a variable amplitude of vibration. As a result, areas with different radii of curvature can be generated selectively in predetermined axial bore sections in order, for example, to produce a substantially oval cross-section or a cross-section with a "cloverleaf" (out-of-roundness).

If the honing tool is displaced or moved in the axial direction during the oscillation movement oscillating in the circumferential direction with variable amplitude with a time-variable lifting speed, it is possible to produce non-circular bores whose non-circular-cylindrical bore cross-sectional shape continuously varies in the axial direction of the bore. For this purpose, the lifting speed can be controlled as a function of the stroke position.

The processing with time-varying oscillation amplitude can be, for example, to produce oval bore cross-sectional shapes use. In a variant of the method, for this purpose, a honing tool with a single pair of diametrically opposed cutting groups is used and the honing tool is placed in the above-described circumferentially oscillating movement, which has a time-varying oscillation amplitude. The oscillation amplitude typically varies between a minimum value, which may be, for example, 0 ° or less than 10 °, and a maximum value which is 90 ° highest, and is normally at least twice or three times, or four times or five times or ten times larger than that minimum value. In this way, for example, an oval bore cross-sectional shape can be generated. In one embodiment, the process begins with a large vibration amplitude of about 90 °. As the process progresses over time, the vibration amplitude is continuously reduced by at least 50% or 70% or more, eg down to about 10 °.

In another variant of the method, a honing tool with four circumferentially offset by 90 ° cutting groups is used and the honing tool is set in the manner described above in a circumferentially oscillating movement with variable amplitude vibration. The maximum value of the vibration amplitude should be here at 45 ° or below. As a result, it is possible to produce targeted non-circularities of the 4th order, as are desired, for example, in the cylinder head side entry region of cylinder bores.

In some applications, it is desired that a bore in a defined limited axial region have an enlarged bore cross section with respect to the adjacent axial regions, which in the axial section of the bore represents an axially extending bulge. For example, in engine operation, particularly thin cross-sections, eg, the lands between the cylinders, tend to heat more than other areas of the engine block. These thinner ones Areas then expand, which narrows the hole in the area of the lands, causing more wear at that location. By targeted local generation of bulges, these deformations can be kept, so that the wear in these areas is reduced. Such deviations from an ideal circular-cylindrical bore geometry can be generated according to a variant of the method in that the honing tool is displaced within a predefinable machining time interval into a vibrational movement with a variable oscillation amplitude that oscillates in the axial direction over a short-stroke to a predefinable axial position. The stroke of the oscillatory motion, which is twice the maximum amplitude of vibration, is typically small relative to the axial bore length and may, for example, be less than 50% or less than 30% of the bore length. The generation of local bulges described here preferably takes place as the last material-removing processing step, so that the bulging is not reduced or eliminated again by subsequent material-removing processing steps.

In all variants of the method with variable oscillation amplitude, it may be advantageous if the oscillation amplitude is reduced continuously or stepwise within a change time interval from a maximum oscillation amplitude to a minimum oscillation amplitude, preferably without a subsequent increase in oscillation amplitude. If, in a certain processing range, the process is first started with the maximum oscillation amplitude and the amplitude of oscillation is then reduced stepwise or continuously with the progress of the processing, a particularly uniform surface pressure can be realized, since it is ensured that the cutting group never enters a diameter smaller area enters.

As mentioned, in some machining tasks it is desirable to produce circular bore shapes with complex deviations from an exact circular shape by honing. This can be provided by the aforementioned "shaping honing" of cylinder treads in the manufacture of engine blocks for internal combustion engines to produce in the unstressed workpiece (cylinder block) a negative form of Cylindrizitätfehlers, which is caused by the deformations generated during assembly and during operation to obtain an optimal cylindrical bore geometry during operation In order to achieve a particularly high degree of flexibility with regard to the achievable desired shape, in a preferred embodiment, a substantially rigid guidance of the axial movement of the honing tool for generating an axial movement of the honing tool substantially parallel to the bore axis of the bore and, if necessary temporally asymmetric, controlling the vibration movement and / or the displacement movement of a one side of the tool axis attached to the honing tool cutting group provided in dependence on the stroke position and / or the angular position of the honing tool.

Through this process management can be achieved that this cutting group causes in their Eingriffswinkeibereich a material removal, without necessarily leading to a comparable material removal on the diametrically opposite side of the bore inner surface. The contact pressure of the cutting group counteracting opposing force is not applied by material-removing cutting material on the diametrically opposite side, but by the substantially rigid guidance of the axial movement of the honing tool, which prevents dodging of the honing tool transverse to the tool axis in one-sided pressing the cutting material body to the bore inner surface.

In this way, the method can be carried out in particular such that the bore receives a non-circular-cylindrical bore shape, at least in an axial bore section, which deviates significantly from a two-fold radially symmetrical shape with respect to the bore axis.

In a further development of the method, the honing tool is supported for substantially rigid guidance of the axial movement within the bore in an axially slidable manner and substantially immovably transversely to the tool axis. This makes it possible to dispense with outside of the workpiece to be arranged guide devices.

In a further development, a honing tool is used for this purpose, which comprises a set of distributed around the circumference of the honing tool guide rails for axial guidance of the honing tool in the bore, which are preferably fed independently of the cutting group in the direction of the inner surface of the bore, wherein the substantially rigid guidance of the axial movement is achieved in that the guide rails are pressed during the movement of the honing tool in the bore to the inner surface of the bore.

In this process variant, the guide rails center the honing tool within the bore. The guide rails are preferably designed so that they generate little or no material removal, which is referred to herein as "substantially non-cutting guide rails". The guide rails can at least in the coming into contact with the inner surface of the bore areas of a plastic, rubber, an elastomer of suitable hardness (eg Vulkollan®), a metal, a hard metal or a ceramic or it can be honing stones with a act high proportion of cutting material.

It is also possible for the substantially rigid guidance of the axial movement of the honing tool to be attained in that the honing tool is guided axially immovably outside the bore of the workpiece and substantially immovably transversely to the tool axis. Depending on the type of bore can this purpose a one-sided guide exclusively on the inlet side of the bore, a one-sided guide only on the inlet side opposite exit side of the bore (for through holes), or provided a two-sided guide both on the inlet side, as well as on the gegenübliegenden outlet side be. A rigidly against transverse load coupling of the honing tool to a rigidly guided against transverse load honing spindle may possibly also be sufficient to ensure the rigid guidance of the axial movement of the honing tool. Then possibly can be completely dispensed with guide elements in the field of honing tool. The exclusively external guidance of the axial movement of the honing tool requires the highest accuracy in the relative positioning between the workpiece and the honing tool.

In order to obtain the most flexible possible control of the shape of the bore cross section in the machining area, it is provided in a variant that a honing tool is used which has a single separately deliverable cutting group, which preferably has a pressure angle of less than 90 °. The term "pressure angle" here describes the angular range along the circumference of the honing tool, are in the cutting material body of the cutting group in engagement with the bore wall. Often it is advantageous if the pressure angle between about 1 ° and about 70 °, it may for example be between 5 ° and 60 ° and / or between 20 ° and 45 °. The smaller the pressure angle, the more accurate is a complex shape of the contour of the inner surface to be achieved by controlling the feed force in dependence on the angular position of the honing tool. It can also be honing tools be used with several independently deliverable cutting groups.

The cutting material bodies can also be distributed symmetrically or almost symmetrically over the circumference of the honing tool. In this case, desired shapes with two-fold or multiple radial symmetry can be generated, since a vibratory movement and displacement movement of the honing tool can equally affect all cutting material bodies. In the substantially rigid guidance of the axial movement of the honing tool can be dispensed with in these cases.

The honing process may be carried out in accordance with processing parameters determined before the honing process, which may include in particular the at least one vibration parameter, the at least one displacement parameter, at least one parameter for the delivery force or its temporal change, and further parameters. The vibration parameters may include an amplitude change parameter defining the temporal change of the vibration amplitude. In one variant of the method, a measurement of the diameter of the bore during machining takes place at at least two measuring positions offset in the circumferential direction and / or in the axial direction for generating a first and at least one second diameter measuring signal. The diameter measurement signals allow conclusions to be drawn about the current shape of the hole being processed. Since the diameter is measured simultaneously at at least two mutually offset locations and / or in at least two different directions, even complex bore geometries can be detected in a spatially resolving manner, which, for example, have a defined deviation from an ideal circular-cylindrical shape. Such a measurement can thus be independent of the other features of Invention be particularly useful in all process variants of Formhonen.

In preferred embodiments, a control of honing processing is performed in accordance with the at least two diameter measurement signals. By measuring value feedback in the control unit and possibly based thereon change the machining parameters during processing, a regulation of the machining process is possible. As a result, holes with even less deviation from a desired target geometry can be generated at optimized processing times. In the context of such a regulation, for example, the oscillation amplitude and / or the change of the oscillation amplitude and / or the frequency of the oscillation and / or at least one displacement parameter and / or the surface pressure can be regulated as a variable.

The invention also relates to a honing machine having a motion control device for controlling the movement of at least one attached to a honing tool cutting group in response to the stroke position and / or the angular position of the honing tool in a bore, wherein the motion control means for generating a vibrational movement of the Cutting group is configured substantially parallel to an inner surface of the variable amplitude bore bore in accordance with at least one vibration parameter, and preferably for generating a displacement movement of the cutting group along the inner surface of the bore in accordance with at least one displacement parameter superimposed on the oscillation movement.

For example, the motion control device of a conventional honing machine may be modified so that the known long-stroke lifting movement and the circumferential movement of the honing tool an oscillation in the lifting and / or circumferential direction can be superimposed with a significantly shorter stroke. In one embodiment, to set a locally different material separation, both the lifting and / or circumferential speed of the long-stroke movements, and the lifting and / or peripheral speed of the relatively short-stroke oscillatory motion in each case depending on the lifting and angular position of the honing tool separately adjustable , Supporting can also be provided an adjustment to change the contact pressure of the cutting material body in dependence on the lifting and angular position.

The motion controller may be configured to include adjustment for suitable amplitude change parameters, in particular for the maximum and minimum vibration amplitude, and a desired time history of the vibration amplitude change during a change time interval.

In some embodiments, the honing machine has a measuring system for measuring the diameter of the bore during machining at at least two measuring positions offset in the circumferential direction and / or in the axial direction of the bore for producing a first and at least one second diameter measuring signal. This allows the monitoring of the processing progress during the machining process in order to make any corrections to the machining parameters. Preferably, the motion control device is configured as a control device that allows to control the honing processing in accordance with the at least two diameter measurement signals. In this way, without any intervention by an operator, the processing parameters of the honing process can be automatically optimized during processing as needed.

If the formation of the macro-shape of the hole substantially without a variation of the contact pressure of the cutting group, the generated bore inner surface is characterized by a very small variation of the roughness. This reduces the material removal required in the subsequent surface-forming machining operations, so that these processes can be carried out in shorter processing times. For example, it is possible to produce a workpiece having at least one bore having a honed inner surface, wherein the bore has a non-circular cylindrical bore shape in at least one axial bore portion such that the bore has a cylindricity error greater than 20 microns, with a Fluctuation range for the arithmetic mean roughness R _a over the circumference of the hole is less than 30%. After the shaping machining described here, the machining tracks of the short-stroke machining produced by the oscillatory movement of the cutting group on the inner surface are usually recognizable. As a rule, however, it is the case that these machining tracks are removed again in subsequent machining operations which essentially change only the surface topography.

• Fig. 1 zeigt eine schematische Gesamtansicht einer Honmaschine, die zur Durchführung einer Ausführungsform eines erfindungsgemäßen Honverfahrens konfiguriert ist;
• Fig. 2 zeigt eine schematische Perspektivansicht eines 4-Zylinder-Motorblockes bei der Bearbeitung mit einer Ausführungsform eines erfindungsgemäßen Honverfahrens;
• Fig. 3 zeigt eine schematische Darstellung von Geschwindigkeitskomponenten der Schwingungsbewegung und der Verschiebungsbewegung einer Schneidgruppe bei der Bearbeitung einer Bohrungsinnenfläche; und
• Fig. 4 zeigt eine schematische Darstellung des Einflusses der Verschiebungsgeschwindigkeit v₃ auf die Abtragsrate A einer konstant schwingend angetriebenen Schneidgruppe, jeweils in Abhängigkeit von der Zeit t;
• Fig. 5 zeigt schematische Messdiagramme einer Zylinderbohrung mit großem Zylindrizitätsfehler und signifikanter Abweichung von einer 2-zähligen Radialsymmetrie;
• Fig. 6 zeigt schematische Diagramme zur Erläuterung des Zusammenhanges zwischen der Geometrie einer Bohrung mit großem Zylindrizitätsfehler und der zur Erzeugung der unrunden Bohrungsform erforderlichen Variation der Verschiebungsgeschwindigkeit über die Winkelposition einer einseitig an einem Honwerkzeug angebrachten, oszillierenden Schneidgruppe;
• Fig. 7 bis 9 zeigen schematisch unterschiedliche Honwerkzeuge, die bei Ausführungsformen erfindungsgemäßer Verfahren eingesetzt werden können;
• Fig. 10 zeigt eine schematische Darstellung einer Zylinderbohrung, die mit Hilfe eines mit vier Honleisten ausgestatteten Honwerkzeuges bearbeitet wird, das in eine in Umfangsrichtung verlaufende Schwingungsbewegung mit veränderlicher Schwingungsamplitude versetzt wird;
• Fig. 11 zeigt ein schematisches Diagramm für die Wirkzeit t_W (wirksame Bearbeitungszeit) und die Axialgeschwindigkeit v_AX des Honwerkzeuges in Abhängigkeit von der Axialposition des Honwerkzeuges in der Bohrung gemäß Fig. 10;
• Fig. 12 zeigt ein schematisches Diagramm der Veränderung der Schwingungsamplitude über die Zeit gemäß verschiedener Varianten von Bearbeitungsverfahren; und
• Fig. 13 zeigt ein schematisches Diagramm einer Bohrung mit einer lokal begrenzten Durchmessererweiterung in einem Axialabschnitt sowie ein zugehöriges Diagramm für die Axialgeschwindigkeit v_AX eines zur Bearbeitung der Bohrung genutzten Honwerkzeuges.

The foregoing and other features will become apparent from the claims and from the description and drawings. In this case, the individual features may be implemented individually or in the form of subcombinations in one embodiment of the invention and in other fields, and may represent advantageous and protectable embodiments. Preferred embodiments will be explained with reference to the accompanying drawings.

• Fig. 1 shows a schematic overall view of a honing machine, which is configured to carry out an embodiment of a honing method according to the invention;
• Fig. 2 shows a schematic perspective view of a 4-cylinder engine block during machining with an embodiment of a honing method according to the invention;
• 3 shows a schematic representation of velocity components of the oscillatory motion and the displacement movement of a cutting group when machining a bore inner surface; and
• 4 shows a schematic representation of the influence of the displacement speed v ₃ on the removal rate A of a constantly oscillatingly driven cutting group, in each case as a function of the time t;
• 5 shows schematic measurement diagrams of a cylinder bore with a large cylindricity error and a significant deviation from a 2-fold radial symmetry;
• Fig. 6 shows schematic diagrams for explaining the relationship between the geometry of a bore with a large cylindricity error and the variation of the displacement speed required for producing the non-circular bore shape over the angular position of an oscillating cutting group mounted on one side on a honing tool;
• FIGS. 7 to 9 schematically show different honing tools which can be used in embodiments of methods according to the invention;
• Fig. 10 shows a schematic representation of a cylinder bore, which is processed by means of a honing tool equipped with four honing stones which is put in a circumferentially oscillating motion with variable amplitude vibration;
• 11 shows a schematic diagram for the effective time t _W (effective machining time) and the axial speed v _{AX of} the honing tool as a function of the axial position of the honing tool in the bore according to FIG. 10;
• FIG. 12 is a schematic diagram showing the variation in oscillation amplitude over time according to various variants of machining methods; FIG. and
• 13 shows a schematic diagram of a bore with a locally limited diameter extension in an axial section and a corresponding diagram for the axial velocity v _{AX of} a honing tool used for machining the bore.

FIG. 1 schematically shows the front view of a honing machine 100 that can be used in various embodiments of methods according to the invention for machining inner surfaces of bores in workpieces in order to carry out one or more honing operations on the workpiece. On the machine bed 102 of the honing machine a clamping plate 104 is fixed, which carries a workpiece 106 clamped thereon, which in the example is an engine block of a multi-cylinder internal combustion engine. In the engine block several cylinder bores are formed with a generally vertical orientation of their cylinder axes. The cylinder surfaces formed by the inner surfaces of the cylinder bores are subjected to a quality-determining finishing on the honing machine, in which both the macro-shape of the cylinder surfaces, as well as their surface topography is produced by suitable honing processes.

In the two-spindle honing machine 100, two essentially identical honing units 110, 112 are mounted on a portal-like support structure 108 and can be used alternately or simultaneously during workpiece machining. Their structure is explained in more detail with reference to the honing unit 110. The honing unit comprises a spindle box 114 mounted on the support structure and guiding the honing spindle 120. The honing spindle can be rotated around its longitudinal axis by means of a spindle motor 118 attached to the spindle box. The lower end of the honing spindle is formed by a joint rod, at the lower, free end of which the honing tool 150 serving as a machining tool is mechanically coupled in a limited manner. A linear actuator 124 mounted on the headstock 114 effects vertical movement of the honing spindle upon insertion of the tool into the workpiece or withdrawal from the workpiece and is controlled during the honing process so that the honing tool makes vertical reciprocation within the bore of the workpiece , The spindle motor 118 and the linear actuator 124 are driven by a motion controller 180, which forms a subsystem of the overall control of the honing machine.

In this embodiment, the motion controller 180 controls all honing axes of the honing machine. This control system is used to create the added compared to conventional Honsystemen vibrational movement of the cutting group and to superimpose the displacement movement. For this purpose, a suitable work program of the computer numerical control can be provided. In order to set a locally different material separation, the following parameters can be set in the controller as a function of the stroke and angular position of the honing tool: (1) stroke and / or peripheral speed of the long-stroke displacement movements; (2) Lifting and / or peripheral speed of the shorter-stroke oscillatory movements. There is also an adjustment option with which the contact pressure of the cutting group is variable in dependence on the stroke and angular position.

The honing machine is equipped with a feed system 140 which comprises two independently operable feeders associated with different sets of elements on the honing tool.

Fig. 2 shows a schematic oblique perspective view of a cylinder block (engine block) 200 for a 4-cylinder internal combustion engine. In the cylinder block consisting of a cast material or a light metal material, four axially parallel cylinder bores 201, 202, 203, 204 are arranged at equal distances in series next to one another in such a way that their central bore axes lie in a common plane (cylinder plane 212). From the upper side of the cylinder block are provided with internal thread holes 215 axially parallel to the cylinder bores so introduced that four of these holes are evenly distributed around the circumference of a cylinder bore. The holes 215 serve to receive cylinder head bolts, with the help of which, after completion of the processing of the cylinder block, the associated cylinder head is screwed onto the cylinder block 200 with the interposition of a cylinder head gasket.

It can be seen that the cylinder block 200 is a structurally non-uniform workpiece, in which in particular each of the cylinder bores 201-204 has a different workpiece environment, in particular with regard to the wall thickness in the region of the cylinder bores and also by different connections to the coolant channels of the engine block internal cooling system. For example, the inboard cylinder bores 202 and 203 of the second and third cylinders each have two adjacent cylinder bores in the cylinder plane, while the outboard cylinder bores (Cylinders 1 and 4) only have a respective inner adjacent cylinder bore and border on the opposite side to thicker wall sections of the workpiece.

At the lower end of the honing spindle 220, an embodiment of a honing tool 250 according to the invention is coupled, in which it is a gimbal-mounted honing tool with double widening. The honing tool has a tool body 255 which carries on one side of its circumference a cutting group 260 formed by a single honing stone, which can be delivered or withdrawn in the radial direction to the bore inner wall by means of a not-shown cutting group delivery system. The cutting group 260 is attached on one side to the honing tool. This means, in particular, that all of the cutting material bodies standing in honing processing in material-removing engagement with the bore inner wall are located on the same side of a tool-dividing tool plane, which contains the tool axis and is perpendicular to the bisector of the cutting group. Furthermore, a set of non-uniformly distributed around the circumference of the honing tool guide rails 270 is provided on the tool body, which can be delivered independently of the cutting group 260 in the direction of the inner surface of the bore by means of a guide rail delivery system. When the substantially non-cutting guide rails abut against the inner surface of the bore, substantially rigid guidance of the axial movement of the honing tool within the bore parallel to the bore axis 213 results, so that the guide rails form an axial guide device for the honing tool.

The feed movement of both the guide rails and the cutting group and the respectively applied feed force are controlled independently by means of a feed force control device 290 of the honing machine. The movements of the Honing tools within the bore are controlled by the motion controller 280.

It will now be explained with reference to FIGS. 3 and 4 how, in a preferred embodiment of the machining method, by means of suitable control of the oscillation movement and the displacement movement of a cutting group of the honing tool at different locations on the inner surface of a bore, different degrees of material removal can be achieved in order to form a non-circular-cylindrical bore shape to create. 3 schematically shows an axial section through a cylinder bore 303 of an engine block 300. Introduced into the cylinder bore is a honing tool, of which only one honing blade 360 is shown, which forms the only cutting group of the honing tool and which is in cutting engagement with the inner surface 330 the hole is.

In the motion control device of the honing machine, a work program is active, which controls a vibratory movement and a displacement movement of the honing tool and the cutting group superimposed on the oscillating motion. The oscillatory motion is composed of a circumferentially directed component (direction of the vector V ₂ ) and an axially directed component (direction of the vector V ₁ ), wherein both the vibration amplitude and the vibration frequency can be set as vibration parameters on the motion control device , In the exemplary variant, the oscillation amplitude in the axial direction (vector V ₁ ) is set to the value 0, so that there is only an oscillatory movement in the circumferential direction (vector V ₂ ), in which the cutting group 360 is oscillating in the circumferential direction with an angle amplitude of approximately 4 ° and a frequency of about 2 Hz is reciprocated. This oscillatory machining movement, in conjunction with that provided by the feed force controller constant predetermined contact pressure at the site of the cutting group a material removal, the amount of which is substantially proportional to the present at each location processing time (or iw inversely proportional to the local displacement speed).

The oscillation movement is superimposed on a displacement movement of the cutting group in the direction of the displacement vector V ₃ , whereby both the direction and the speed of this displacement movement (speed v ₃ ) can be predetermined as displacement parameters on the motion control device. The direction of the displacement movement is variable and ensures that the cutting group reaches all areas of the bore inner surface. In the embodiment shown, the displacement movement is parameterized in such a way that the honing bar 360 generates a rotational movement (in the circumferential direction), which is applied to the classical honing, in conjunction with an alternating stroke movement in the axial direction (see dashed arrow). Along the displacement path, ie when sweeping the inner surface of the bore, the velocity v _{3 of} the displacement movement is varied. The control of the displacement speed v ₃ takes place as a function of the required desired shape of the bore. The change in the displacement speed results in locally different processing times, so that different degrees of material separations are achieved locally in the bore. This is shown schematically in FIG. With constant oscillation movement (ie constant oscillation amplitude, frequency and direction), an approximate proportionality between material removal A and displacement velocity v ₃ results since in regions of higher displacement speed the local processing time and thus the locally achieved material removal is lower than in regions of lower displacement speed. Accordingly, the controller is programmed so that in areas with required strong material separation, the displacement speed v ₃ low or for a fixed Time interval is also zero, while for areas with required lower material separation, a higher displacement speed is provided.

Since in this process variant only the time or the displacement speed is used as the control parameter, while the contact force of the cutting group remains constant during the entire processing time, the generated roughness of the machined inner surface is independent of the generated shape. Typical average roughness depths R _Z lie over the entire machined inner surface in the range R _Z = 4 μm to 6 μm.

The components of the oscillatory motion in the circumferential direction and in the axial direction may have constant or variable amplitudes and / or frequencies. The change in amplitude and / or frequency can be used to support the control of the removal. For example, for local areas with required high material removal, the oscillation frequency can be increased in order to achieve an increased removal rate for the same residence time of the cutting group on the bore inner surface.

It is also possible that the surface pressure is controlled as a variable, that is, that the contact pressure of the cutting group is varied depending on the stroke position and / or the angular position of the honing tool or cutting group. In any case, the control curve of the responsible for the material removal parameter depends on the desired shape of the hole.

A typical hole geometry which can be produced on an unstrained workpiece with the aid of the method and which can be produced when machining cylinder running surfaces of a cylinder block is explained with reference to FIG.

For characterizing the macro-shape of a cylinder surface, Fig. 5 (a) shows a schematic circumferential plot and Fig. 5 (b) a schematic longitudinal plot of the dimensions of a cylinder surface. For circumferential writing, radial distances of the bore inner wall from the bore axis BA are shown as a function of the circumferential position along the bore inner surface, wherein the zero point of the circumferential direction and the 180 ° position in the cylinder plane 212 defined by the bore axes of the cylinders (see FIG. and the 90 ° and 270 ° positions represent the perpendicular areas near the front and rear broad sides of the cylinder head. The curves R _O , R _M and R _U represent the radius in the vicinity of the upper inlet opening of the cylinder bore (R _O ), in the axial center region of the cylinder bore (R _M ) and in the vicinity of the lower end of the cylinder bore (R _U ). In the manner known to the person skilled in the art, the circulating measuring curves of the peripheral document are each related to a zero line lying concentrically to the bore axis, which in the representation in FIG. 6 (a) is shown in dashed lines. The same radial scale in the radial direction serves for all measuring curves. The longitudinal letters in FIG. 5 (b) each show the course of the surface lines (parallel to the bore axis) in the selected circumferential regions at 0 °, 90 °, 180 ° and 270 °.

The measurement results represent the marginal fourth cylinder bore 204 in FIG. 1. It can be seen that the bore near the cylinder head side entry side (represented by the curve R _O ) has approximately 2-fold radial symmetry about the bore axis BA at which the largest diameter obliquely to the cylinder plane in the range of the circumferential angle 135 ° or 315 ° results, while perpendicular thereto (corresponding to angular positions 45 ° and 225 °) also form local maxima of the radius, but which lie at smaller absolute radius values. The approximately 2-fold symmetrical basic shape superimposed smaller radius variations, for example in the range of 180 °.

In the axial center region of the bore (curve R _M ) results in a much more complex relationship between circumferential position and bore radius or bore diameter. In the example shown, approximately eight local maxima of the inner radius, which are separated by local minimums of the inner radius, result in the circumferential direction. The largest radii tend to remain inclined to the cylinder plane.

In the cylinder head end region facing away from the end of the cylinder bore, represented by the curve R _U , the bore cross section is also asymmetrical, but the 2-fold radial symmetry still indicated at the cylinder head end no longer dominates and dominates an almost completely irregular bore cross-sectional shape.

In the axial direction of the bore inner wall also result in significant variations in the bore radius. While along the surface line at 0 °, the radius decreases to the lower end of the bore, the bore wall on the opposite side (at 180 °) is significantly distorted in the axial direction, so that a strong minimum radius results near the entrance opening and in the lower third, while in the middle region the radius becomes maximum. If, on the other hand, a section perpendicular to the cylinder plane (at 90 ° and 270 °) results in minimal radii near the upper inlet opening, while in the lower third the bore radius assumes a local maximum.

In this example, the asymmetrically warped hole shape that can be characterized in this way corresponds to a cylindricity ΔZ of between 30 μm and 40 μm. This complex and asymmetrically deformed bore geometry becomes when mounting and screwing a cylinder head and heating of the resulting hull motor deform into the range of operating temperatures again to a largely cylindrical bore shape. It thus forms approximately a negative form of the deformations in the operating state.

Fig. 6 shows by way of example for two axial positions of the cylinder (represented by the curves R _O and R _M ) in Fig. 6 (a) the stroke and rotation angle-dependent radius of the bore and in Fig. 6 (b) the associated curve of the reciprocal 1N the displacement speed V of a short-stroke oscillating in the circumferential direction cutting group on the rotation angle φ, respectively in the corresponding axial heights. The cutting group is pressed against the inner surface with a constant contact pressure (F = const). Large values of the reciprocal value correspond to a slow shift and thus to a larger material removal. In Fig. 6 (b), the broken line V _{O represents} that variation of the reciprocal of the displacement speed over the rotation angle which would be required when a honing tool whose oscillating cutting group is circumferentially displaced in the upper end portion of the cylinder bore processes the inner surface. The solid line V _M corresponds to the temporal variation or angle variation that would be required in the middle region of the bore (R _M ). While the approximate but not exactly 2-fold radially symmetric bore cross-sectional shape at the top can be achieved essentially by varying the rate of displacement with two local minima and intermediate local maxima (as well as a momentary slowdown at 180 °), shaping honing in the center region of the bore requires (Curve R _M ) in a single revolution of the honing tool a multiple, rapid change between increase and decrease of the displacement speed, which leads to the formation of six to eight local Abmax maxima and local removal minima in one full revolution. If, during honing, the honing tool is moved axially with long strokes and at the same time rotated about its tool axis, this results in the actual time Course of the effective at a cutting group displacement speed (or Abtragsleistungen) from a superposition of the explained here for simplicity gradients, with the strong variation in the axial direction (Fig. 5 (b)) in a contribution to the variation of the displacement speed.

After performing the mold honing, the cylinder bore can be measured by means of a shape measuring system. Any existing, measured difference between the actual shape and the desired shape can be used to correct the machining parameters as a function of stroke position and angle of rotation. In particular, during and / or after a shape-generating honing operation, a measurement of the bore shape for determining actual shape values can thus be carried out, and a difference between the shape Is values and the desired shape can be processed to correct the control of the material-removing machining. By this control loop improved accuracy of the Formhonprozesses can be achieved.

Numerous variants of the machining method are possible, wherein different types of honing tools and / or differently constructed and / or controlled honing machines can be used. In a variant of the honing machine shown in Fig. 1 additional assemblies are inserted into the structure to produce the displacement movement superimposed oscillatory movement of cutting groups. For example, within the spindle 120, a vibrator may be installed which decouples the part of the spindle carrying the honing tool 150 from a drive-side part of the spindle and permits relative movement of the honing-tool-carrying section with respect to the drive-side section in the axial direction and / or in the circumferential direction, around the oscillation movement to realize the cutting group. It is also possible to mount a vibrator within the honing tool, which oscillates the cutting material body of the cutting group relative to the tool body. In both cases, less mass must be moved to generate the oscillatory motion than in the embodiment described above, so that larger vibration frequencies are possible with the same force introduced.

In addition, it is possible to use other types of honing tools instead of the honing tool 250 shown in FIG. For this purpose, FIG. 7 shows, by way of example, a honing tool 700 with four homogeneous honing stones 760 distributed symmetrically around the circumference, which are actuated together via a single, common feed system 770. There are no expandable or non-expandable guide rails. Such simply constructed honing tools can be used in particular if substantially rotationally symmetrical bore shapes are to be produced, if necessary with a diameter which varies greatly in the axial direction, and / or bore shapes with a 4-fold radial symmetry.

The honing tool 800 in FIG. 8 is a double widening system, ie with two independently operable infeed systems. In this case, four uniformly distributed around the circumference first honing stones 860 are adjusted together via a first feed system 870. A honing blade 810 arranged symmetrically in the circumferential direction between two honing stones 860 is actuated via a separate second delivery system 820. By means of the four similar cutting material bodies 860, for example, a dominant 4-fold rotational symmetry of the bore shape can be generated with suitable control of the movement speed of the honing tool. By activating the second expansion system, the individual honing stone 810 is simultaneously delivered, which then generates a targeted local removal of material in order to produce, for example, a bore shape with a geometry deviating from a 2-fold radial symmetry (cf. 5). Both Zustellsysteme are independently controllable as a function of stroke position and angular position of the honing tool.

In another embodiment, another honing stone is provided on the opposite side of the honing stone 810, which can be actuated by the second delivery system 820. By common delivery of the diametrically opposed second honing stones as a function of stroke position and angular position of the honing tool, for example, an ovality can be generated, which can be superimposed on a fourfold symmetrical shape.

Figure 9 shows schematically a honing tool 900, which is designed as a Mehrleistenhonwerkzeug. On one side of the honing tool, a single material-removing honing stone 960 is arranged. At the side diametrically opposite to the tool axis, two guide belts 970 which can also be delivered, but which do not cut, are arranged, which with respect to their construction can substantially correspond to the guide rails 270 in FIG. 2. The single honing stone 960 and the non-cutting guide rails 970 are delivered via a common infeed device 980. During machining, the guide rails 970 absorb the counterforce of the machining force generated by the honing stone 960. It is also possible to use a honing tool with a unidirectional honing stone, which is also supported by guide rails, which are located on the opposite side (similar to Fig. 9), but not extended (delivered).

A not shown variant of a double widening honing tool has a first cutting group effective in a first axial portion of the honing tool and at least one second separately deliverable cutting group axially offset from the first cutting group, for example above the first cutting group or below the cutting group (seen in the axial direction). It is possible to control such a honing tool so that the different, axially offset cutting regions are acted upon by different Aufweitkräften, thereby to achieve different ablations in different axial heights of the bore.

A further, not shown variant of a honing tool with double widening has a first cutting group, which is effective in a first circumferential angular range of the honing tool, and at least a second, separately deliverable cutting group, which is effective in a circumferentially offset to the first circumferential angular range lying second circumferential angular range of the honing tool , The cutting bars, which are controlled by these two widening (or delivery systems) are thus at different angular positions. The feed force is controlled separately for both expansions depending on the angular position and the stroke position.

Unless otherwise stated, the process variants described above can be carried out optionally with a constant oscillation amplitude or with a time-varying oscillation amplitude. Further variants of the method will be described with reference to FIGS. 10 to 13, in which the oscillation amplitude of the oscillation movement of at least one cutting group varies within a processing time interval between a maximum value φ _MAX and a minimum value φ _MIN . The term "oscillation amplitude" here describes the respective deflection of the movement of the periodically oscillating cutting group from a reference position, which represents the zero position of the oscillatory movement.

In analogy to FIG. 2, a cylinder bore 1003 is shown, which extends from an upper, cylinder-head-side inlet opening O over an axial middle region M to the lower end region U. The cross-sectional shape of the bore in these areas is strong in FIG. 10 exaggerated by a solid line for the upper region O, and dashed lines for the middle and lower regions (see also Fig. 5 (a)). This desired desired shape is generated in the illustrated method, starting from a substantially circular-cylindrical initial shape in the manner described below.

In the honing process, a honing tool is used which has four cutting groups circumferentially offset by 90 ° in each case, which are represented in FIG. 10 by individual honing stones 1060. The width of the honing stones in the circumferential direction can be very small and produce, for example, an engagement width of 6 mm or less. There is provided a common feed device for all honing stones, in other embodiments, there are two separate feed devices for each pair of diametrically opposed honing stones.

The motion control device of the honing machine is configured so that the honing spindle that drives the honing tool performs an angularly limited oscillating rotational movement about its spindle axis, so that the honing tool is set in a circumferentially oscillating motion. The oscillation amplitude φ of the rotational movement is limited to a maximum of 45 °, so that each honing stone only processes a circumferential angular range of a maximum of 90 °. Typical vibration frequencies may be in the range between 1 Hz and 30 Hz, for example. In contrast to classical honing, no rotational movement of the honing spindle is thus produced with continuous, if necessary multiple, rotation about its axis. The zero position of the oscillatory motion in the azimuthal direction remains unchanged (no rotation of the honing spindle). The cutting groups are pressed against the bore inner surface 1030 with a constant contact pressure (F = const).

The axial feed of the honing spindle is controlled in some embodiments in such a way that the circumferential speed component of the cutting groups is many times greater than the speed component directed in the axial direction (parallel to the bore axis BA). The resulting machining marks on the bore inner wall thus include very large angles with the axial direction, typically between 70 ° and 90 °. These values correspond to very small honing angles in the range of a maximum of 40 °. In other embodiments, the ratio of velocity components in the circumferential direction and in the axial direction may be different, for example up to an axial feed whose axial velocity component is about the same size as the circumferential velocity component. In this case, for example, honing angles up to 90 ° can be generated. It is also possible that the axial velocity component is greater than the tangential (circumferentially directed) velocity component.

The lifting movement of the honing spindle generates an axial velocity or stroke velocity v _{AX of} the cutting groups, which changes over time in the course of a stroke, from a relatively low axial velocity in the region of the upper inlet opening continuously to a significantly higher axial velocity in the vicinity of the lower end U. This is illustrated by the dashed line in the diagram of FIG. 11 as well as on the left side of the bore shown in FIG. Since the bore inner surface is subjected to a machining engagement by the honing stones for a relatively short time in the region of relatively high axial velocity, the varying stroke velocity produces a variation of the respective contact time t _{W of} the honing stones in the different axial regions such that the exposure time in regions of relatively high stroke speed in the lower end region of the bore is relatively low while being continuous to the upper end region O. increases. This is schematically illustrated by the dashed curve t _W in FIG. 11 and at the left edge of the bore in FIG.

The axial feed of the honing spindle with variable stroke speed is superimposed by the movement oscillating in the circumferential direction, for the course of time different variants are possible. Various variants are shown with reference to FIG. 12. According to variant I, the oscillation amplitude decreases continuously over time Δ within a change time interval Δt from a maximum value φ _MAX to a minimum value φ _MIN > 0 or φ _MIN = 0. According to variant II, the oscillation amplitude changes periodically between oscillations with a relatively large amplitude (at or near φ _MAX ) and oscillations with a relatively small oscillation amplitude (at or near 0 °) within a change time interval Δt. Other courses, such as a zigzag-shaped time course of the oscillation amplitude, or a continuous or discrete increase in the oscillation amplitude are possible. Within a change time interval .DELTA.t, a one-time continuous or discontinuous decrease or increase in the oscillation amplitude is just as possible as a single or multiple change between decreasing and increasing oscillation amplitude.

By suitable adaptation of the duration of the change time interval Δt of the oscillation amplitude change to the axial feed speed v _{AX of} the honing tool, different possibilities are now given for honing holes with a defined non-circular bore cross section. These variants can be set by a suitable ratio between the stroke duration t _H for a single stroke and the change time interval Δt for the change in the vibration amplitude.

In a variant of the method, the change time interval Δt, within which the oscillation amplitude is continuous (as in variant I) or gradually decreases (or increases) from a maximum value to a minimum value, significantly greater than the stroke duration t _H required for a single axial stroke. In this case, for example, one to two or more strokes may first be performed with relatively large vibration amplitudes near or at the maximum vibration amplitude before the vibration amplitude is further reduced continuously or in discrete steps. In this way, first removed at the maximum circumferential width of for example 60 ° to 90 ° with one or more strokes over the full length of the bore, but the lifting speed in the upper region of the bore is slower than in the lower region. This results in the upper area already a greater removal. By discrete or continuous reduction of the oscillation amplitude, the engagement width of the honing beads oscillating in the circumferential direction is gradually reduced, so that only the further inner regions of a bulge are successively processed. Again, in combination with the varying in the axial direction of stroke speed in the upper part of the bore a greater material removal than in the lower part of the bore. Starting from a substantially ideal circular cylindrical bore, the bore geometry shown schematically in FIG. 10 can result in this way, which is characterized in that the bore cross section is still circular cylindrical in the lower region of the bore, where overall only relatively short overall processing times of the honing stones , while towards the upper end of the bore towards a more pronounced out-roundness fourth order with four by 90 ° circumferentially offset "bulges" results.

In another variant of the method, the oscillation amplitude varies once or several times between maximum and minimum oscillation amplitude during a single axial stroke. In this case, therefore, the change time interval .DELTA.t is in the order of the stroke duration t _H or smaller than the stroke duration. For example, the oscillation amplitude according to variant II in FIG. 12, several times vary between the maximum value and the minimum value, while the honing tool moves only very slowly in the axial direction. In this way, in the upper inlet region of the bore at a slow axial feed speed (or temporarily interrupted axial feed), the non-circular bore shape desired in this region can be produced with pronounced bulges. With unchanged change of the vibration amplitudes, the speed of the axial feed can then increase gradually, so that fewer and fewer periods of the oscillation amplitude change occur at a predetermined axial position of the bore. Accordingly, the strength of the expression of the Asubeulungen from the upper opening O to the lower end U of the hole is successively lower. In the region of the lower end, the axial feed can be so high, for example, with a suitable overflow of the honing tool, that the varying oscillation amplitude does not lead to a noticeable deviation from the circular shape.

It is possible to configure the movement control device so that the honing tool executes oscillating oscillation in the axial direction, the oscillation amplitude of which is variable. In such a case, thus, the axial stroke of the honing tool varies during the machining of the bore. This can for example be used in the production of a non-circular bore, as shown schematically in FIG. 10, in that the lower region U of the bore is achieved by no or only a few axial strokes of the honing tool, while the number of successive machining operations of the honing tool to the closer to the upper opening O axial areas increases more and more. The variable amplitude axial swing motion may be performed at varying lift speed or at continuous lift speed.

In the method variant explained with reference to FIG. 13, a diameter enlargement 1305 in the form of a bulge is produced on the cylinder bore 1303 in an intermediate region located between the upper inlet opening and the lower end of the cylinder bore, which results in the diameter of the bulge in the central axial region of the bulge Bore 1303 is maximum and drops continuously in both directions to the ends of the bore to the diameter present in the end regions. To generate this bulge, the honing tool is placed in an axial movement with temporally varying Hubgeschwindikgeit v _AX , which has a minimum in the central region of the bulge. In this way, the local processing time in the area of the bulge becomes particularly large in comparison to adjacent axial areas, so that an increased material removal results, which leads to the generation of the bulge. The oscillatory motion can be exclusively or predominantly in the circumferential direction. The bulge may also be generated with a vibrational motion having motion components in both directions (axially and circumferentially). Regardless of the type of vibration movement, it is expedient if the oscillation movement begins in each case with the maximum amplitude and is reduced stepwise or continuously to smaller oscillation amplitudes.

The mold honing which can be carried out with the aid of these or other variants of the method can be carried out in accordance with control parameters established before the honing process. In an embodiment explained with reference to FIG. 10, however, an in-process control of the honing process is provided in accordance with a plurality of diametrically measured values recorded simultaneously during honing. For this purpose, the honing machine has a schematically shown, pneumatic measuring system 1070 for determining the bore diameter during machining in two measuring directions circumferentially offset by 45 °. The pneumatic measuring system (air measuring system) comprises a first pair of measuring nozzles 1071A, 1071B, which are arranged on the honing tool diametrically opposite between the circumferentially offset honing stones 1060. The metering nozzles 1072A, 1072B of a second pair of metering nozzles are circumferentially offset by 45 ° from the first metering nozzles. Each pair of measuring nozzles is connected via a pressure line to a pneumatic / electrical transducer, which provides electrical signals from which the diameter in the respective measuring direction can be derived. The pairs of measuring nozzles are connected to separate transducers, so that the diameters can be detected independently of each other in the first measuring direction M1 defined by the first pair of measuring nozzles and in the measuring direction M2 defined by the second pair of measuring nozzles. In the orientation of the honing tool shown, a larger diameter is accordingly displayed in the first measuring direction M1 than in the second measuring direction offset in azimuth. The diameter measured values are processed in an evaluation device 1075 belonging to the control device of the honing machine and compared with nominal values for the corresponding diameters. As soon as there is a deviation above a tolerance threshold from a desired measured value, at least one honing parameter is changed in order to optimize the honing process in the sequence so that the desired finished dimension is achieved within the permissible tolerances. Thus, a controlled honing process is possible during shaping.

In principle, the measurement of the diameter can be carried out in at least two measuring directions offset in the circumferential direction and / or at at least two measuring positions offset in the axial direction to produce a first and at least one second diameter signal during processing, after processing or both during and after processing.

In some embodiments, it is possible, starting from a hole with ideal circular cylindrical shape within less than 60 seconds to produce a desired target shape with the schematically illustrated with reference to FIG. 10 roundness fourth order, the extent of the cylinder head side opening side to the bottom decreases continuously and gives a total cylindricity of more than 10μm.

In general, the material-removing processing steps for generating the possibly complex, non-round and possibly asymmetrical bore shapes are produced with the aid of a honing tool (or with the aid of a plurality of honing tools used in succession), the cutting group of these honing tools being designed for a substantial removal of material, the macro-form to produce the bore in the desired manner. As a result, the microstructure of the machined inner bore surface may not meet the operational requirements for surface roughness and / or surface texture. Therefore, in preferred processes, after the forming processing steps, at least one substantially shape-neutral, i. the macro-shape of the bore is performed essentially non-altering machining operation. In this case, honing tools can be used with correspondingly adapted to the surface requirements grain of cutting material body and / or brushing or Plateauhonwerkzeuge and / or other surface structure changing processing tools, such as non-contact tools, such as laser and / or water jet generator, the surface structure of the bore inner surface without significant influence can change the macro shape.

For example, a "plateau honing" can be performed in order to cut the tips of the roughness profile still present after the shaping honing process and thereby the carrying component to increase the surface. In the substantially shape-neutral machining operation, the inner surface of the bore can be machined, for example, with a plurality of relatively movable, elastically mounted cutting bodies, which have a maximum extension of less than 10% of the length of the cutting area of the honing tool in the axial direction of the honing tool. Such a highly segmented plateau honing tool is able to process the corrugated surface of a well-machined hole with a cylindricity error of substantially more than 10 μm substantially evenly. It may have cutting material bodies formed by honing stone segments, which are applied to an inherently elastic basic body, for example a plate made of a rubber-like material. This inherently elastic body is applied to the actual base material of the honing stone, for example a support made of steel, copper or the like by gluing or otherwise. For example, the honing stone segments may have an extension of 10mm x 10mm. Thus, a flat contact of the segments is secured to the formgehonte hole in the Plateauhonbearbeitung because the cutting material body can adapt to the wavy course of the bore inner surface under local elastic deformation of the elastic body. A rounding of hard edges that would create a jump in the second derivative in the form letter, at the transition of the molding area to the cylindrical area may even be desirable here.

Since the pre-machined inner surface can have a very uniform roughness distribution even with strongly asymmetrically deformed, non-circular-cylindrical bore shapes, a uniform surface structure is ensured even after the last processing step.

Claims (23)

A method for honing the inner surface of a bore in a workpiece, in particular for honing a cylinder surface in the manufacture of cylinder blocks for internal combustion engines, in which a honing tool is moved within the bore and at least one mounted on the honing tool cutting group with at least one cutting body for material-removing machining of the inner surface is pressed against the inner surface with a feed force, characterized by the following steps: Generating a vibration movement of the cutting group substantially parallel to the inner surface in accordance with at least one vibration parameter such that a substantial portion of a material removal caused by the cutting group results from the oscillatory movement of the cutting group; Controlling the oscillation movement for generating a locally over the inner surface varying material Abtrag on the inner surface for generating a predetermined desired shape of the bore. The method of claim 1, wherein said oscillatory motion has an oscillation frequency of at least 1 Hz, said oscillation frequency being preferably between 2 Hz and 10 Hz. The method of claim 1 or 2, wherein the oscillatory motion is generated such that the oscillatory motion within the change time interval has a time-varying amplitude of oscillation, wherein the amplitude of oscillation is preferably continuously or stepwise reduced within a change time interval from a maximum amplitude of oscillation to a minimum amplitude of oscillation, in particular without subsequent ones Increase in vibration amplitude. Method according to one of the preceding claims, wherein in addition to the at least one oscillatory motion, a displacement movement of the cutting group superimposed on the inner surface is generated along the inner surface in accordance with at least one displacement parameter and the displacement movement is controlled so that in conjunction with the superimposed oscillatory motion the locally varying over the inner surface Material removal is achieved, wherein the displacement movement is preferably aperiodic and / or compared to the oscillatory motion very slow change of the displacement direction and / or the displacement speed. Method according to one of the preceding claims, wherein a lifting speed of the honing tool as a function of the stroke position and / or a rotational speed of the honing tool as a function of the rotational position is controlled. A method according to any one of the preceding claims, wherein the honing tool is set in a circumferentially oscillating oscillatory motion of variable amplitude having a maximum amplitude of oscillation of at most 90 °, and a circumferentially bored velocity component of the cutting group being at least as large such as a velocity component directed in the axial direction of the bore, wherein preferably the honing tool is displaced in the axial direction during the oscillatory movement in the circumferential direction with variable oscillation amplitude with a time-variable lifting speed. A method according to any one of claims 4 to 6, wherein the translational movement results in a single pass of the tool through the bore in the axial direction and the displacement movement a vibration movement with variable vibration amplitude of the tool is superimposed in the circumferential direction. Method according to one of the preceding claims, wherein the honing tool does not carry out a continuous rotation, so that the oscillatory movement relative to the circumferential direction takes place about a fixed zero position. Method according to one of the preceding claims, wherein a honing tool is used with a single pair of diametrically opposed cutting groups and the honing tool is set in a vibration oscillation oscillating in the circumferential direction of the bore, preferably having a maximum oscillation amplitude of at most 90 °, preferably a bore is produced with an oval bore shape. Method according to one of claims 1 to 8, wherein a honing tool is used with four circumferentially offset by 90 ° cutting groups and the honing tool is placed in a circumferentially of the bore oscillating oscillatory motion with variable amplitude vibration, which preferably has a maximum Schwingungsampliude of at most 45 °, wherein preferably in a bore portion of the bore a non-circular cylindrical cross-sectional shape with approximately 2-fold radial symmetry and four circumferentially offset by 90 ° offset bulges of the bore inner wall is generated. Method according to one of the preceding claims, wherein the honing tool within a predeterminable processing time interval in a vibratory movement oscillating in the axial direction with a short-stroke about a predeterminable axial position with a variable oscillation amplitude is offset, which preferably has a maximum axial amplitude of between 1% and 50% of the tool length. Method according to one of the preceding claims, characterized by a substantially rigid guide of the axial movement of the honing tool for generating an axial movement of the honing tool substantially parallel to the bore axis of the bore and a control of the oscillatory motion and the displacement movement of a cutting group mounted on one side of the honing tool in dependence on the Hublage and / or the angular position of the honing tool. A method according to claim 12, wherein a honing tool is used which comprises a set of guide rails distributed around the circumference of the honing tool for axially guiding the honing tool in the bore, which are preferably deliverable independently of the cutting group towards the inner surface of the bore; substantially rigid guidance of the axial movement is achieved by pressing the guide rails against the inner surface of the bore during the movement of the honing tool in the bore. A method according to any one of claims 1 to 11, wherein a honing tool is used which has a first cutting group operative in a first circumferential angular range of the honing tool and at least one second, separately deliverable cutting group disposed in a circumferential circumferential offset from the first circumferential angular range second circumferential angular range of the honing tool is effective, the feed force for both cutting groups is controlled separately as a function of angular position and stroke position of the honing tool. Method according to one of the preceding claims, wherein the cutting group is pressed against the inner surface with a substantially constant feed force. Method according to one of the preceding claims, wherein form deviations are produced at the bore, which correspond to a cylindricity ΔZ of more than 10 μm, wherein the cylindricity ΔZ is preferably more than 20 μm, in particular between 20 μm and about 60 μm, wherein the Cylindricity error is defined as ΔZ = (D _A -D _I ) / 2, where D _{A is} the diameter of a cylinder contacting the inner surface of the bore externally and D _{I is} the diameter of a cylinder contacting the inner surface of the bore internally. Method according to one of the preceding claims, characterized by a measurement of the diameter of the bore during machining in at least two circumferentially offset measuring directions and / or at least two offset in the axial direction measuring positions for generating a first and at least one second diameter measuring signal. A method according to claim 17, characterized by a control of honing processing in accordance with the at least two diameter measuring signals, wherein preferably the oscillation amplitude and / or the change of the oscillation amplitude and / or the frequency of the oscillation and / or at least one displacement parameter and / or the surface pressure as a variable during the editing is changed. Honing machine, in particular for carrying out the method according to one of claims 1 to 18, which comprises a movement control device for controlling the movement of at least one attached to a honing tool cutting group in dependence from the stroke position and / or the angular position of the honing tool in a bore, wherein the motion control means is configured to generate oscillatory motion of the cutting group substantially parallel to an inner surface of the bore in accordance with at least one vibration parameter, the vibration motion having an oscillation frequency of at least one Hz has. Honing machine according to claim 18, wherein the oscillation frequency is between 2 Hz and 30 Hz. A honing machine according to claim 19 or 20, wherein the motion control means is further configured to include an amplitude amplitude parameter adjustment possibility of the vibration amplitude, in particular the maximum and minimum vibration amplitude and a time course of change of the vibration amplitude during a change time interval. A honing machine according to any one of claims 19 to 21, wherein motion control means is further configured to generate a displacement movement of the cutting assembly over the inner surface of the bore superimposed on the inner surface of the bore in accordance with at least one displacement parameter, preferably for adjusting a locally different material separation both the lifting and / or or circumferential speed of long-stroke displacement movements, as well as the lifting and / or peripheral speed of comparison in comparison kurzhubigeren vibration movement in each case depending on the lifting and angular position of the honing tool are separately adjustable. Honing machine according to one of claims 19 to 22, characterized by a measuring system for measuring the diameter of the bore during machining in at least two offset in the circumferential direction Measuring directions and / or at least two axially offset measuring positions for generating a first and at least one second diameter measuring signal, wherein the motion control device is preferably configured as a control device to control the honing processing in accordance with the at least two diameter measuring signals.

Images