EP2650081B1 - Method and device for finishing a workpiece surface - Google Patents

Abstract

The method involves moving a workpiece surface (24) relative to an effective surface of a finish tool (26) in a rotation direction at a workpiece axis (20). A reciprocating additive movement in a direction perpendicular to the workpiece surface is superimposed to a relative movement of the workpiece surface and the effective surface, where an oscillation frequency of the additive movement is lower than 20 kHz. The workpiece surface and the effective surface are moved not relative to each other in a direction parallel to the workpiece axis. An independent claim is also included for a device for finish processing a workpiece surface by a finish tool.

Description

The invention relates to a method for finishing a workpiece surface by means of a finishing tool, wherein the workpiece surface is moved relative to an active surface of the finishing tool in a rotational direction about a workpiece axis, wherein the relative movement of workpiece surface and effective surface is superimposed on an oscillating additional movement in a direction perpendicular to the workpiece surface direction ,

The SoFi Sonic Finish Ultrasonic Assisted Superfinishing project is a hybrid technology that combines a conventional finishing process with ultrasonic machining to fine-tune a workpiece, the conventional finishing process involves rotational movement of the workpiece relative to the finish tool, and a Low-frequency, oscillating relative movement of the workpiece and the finishing tool in a direction parallel to a rotation axis of the workpiece The ultrasonic machining comprises a radial movement of the finishing tool relative to the workpiece, which oscillates at ultrasonic frequency.

It has been found that the hybrid technology described above is problematic in practice. For example, those are on the finishing tools acting loads so high that they must be replaced after a relatively short time. In addition, a high level of noise is generated, so that costly soundproofing measures are required. In addition, nebulization of coolants or lubricants may give rise to aerosols which, in the worst case, give rise to an explosion hazard. Finally, to produce a movement of the finishing tool with ultrasonic frequency, a complex drive with a sonotrode is required, which can be designed in each case only for a given ultrasonic frequency and for a certain mass of the finishing tool.

From the EP 1 447 172 A1 is a finishing device is known, with which by superimposing various movements, a zigzag structure provided workpiece surface is generated.

From the DE 10 2010 040 140 A1 is a hand tool known, with a rotating abrasive belt, which is applied in a remote from a working plane of the abrasive belt high frequency to free the abrasive belt of deposits and adhesions.

On this basis, the present invention has the object to provide an optimized method for finish machining a workpiece surface.

This object is achieved in a method of the type mentioned in the present invention, that an oscillation frequency of the additional movement is lower than 1 kHz.

In the method according to the invention, the active surface of the finishing tool is periodically in the direction of the machining workpiece surface and this opposite moves. This results in a "hammering" machining of the workpiece surface and an oscillation frequency corresponding change between a contact of the active surface and the workpiece surface with a higher pressure force and lower pressure force (which also "lifting" the effective surface of the workpiece surface is possible).

The movement of the active surface of the finishing tool takes place along an additional movement axis, which is oriented vertically relative to the workpiece surface to be machined. The oscillation frequency of the additional movement is in the low-noise range. It is lower than 1 kHz.

The "hammering" machining of the workpiece surface has the advantage that the effective components of the active surface, ie the cutting grains, penetrate deeper into the material of the workpiece than is possible with a conventional finish machining. As a result, the removal rate or the removal rate is increased compared to a conventional finish machining.

The "hammering" machining of the workpiece surface has the further advantage that the active components of the active surface, ie the cutting grains, are briefly exposed to an increased pressure load. As a result, a splinter formation can be supported, whereby a self-sharpening effect arises, which in turn contributes to an increase in the material removal rate.

The additional movement according to the invention also goes with a periodic interruption of the cut or The chip formation and thus causes an interrupted cut structure. In a classical finish machining, continuous, groove-like depressions are created, which dissipate a coolant or lubricant used during workpiece surface processing.

The interruption of the ground structure has the consequence that a larger proportion of coolant or lubricant remains on the workpiece surface to be machined. This allows a better penetration of the effective surface of the finishing tool in the workpiece surface to be machined. By periodically lifting off the finishing tool, i. By the periodic separation of the active surface of the finishing tool and the workpiece surface, cooling lubricant can better get into the contact zone and eroded material can be better flushed or removed. In addition, the kinetic energy introduced into the finishing tool as part of the additional movement promotes the cleaning of the finishing tool from abrasion embedded in or on the active surface. Overall, a significant improvement in the cutting behavior of the hot components of the finishing tool is achieved.

In addition, the periodic pressure contact of the active surface with the workpiece surface causes an increase in compressive residual stresses in near-surface portions of the workpiece, so that the fatigue strength of the workpiece (for example, a rolling bearing part or a crankshaft) can be increased.

The increase in the compressive residual stress of near-surface layers of the workpiece caused by the additional machining of the workpiece surface results in a reduction in the notch effect and a reduction in the tensile stresses which occur during a Hertzian pressure occur. This also increases the life of the inventively processed workpieces.

Finally, the above-explained interruption of the ground structure has the advantage that a drainage effect can be significantly reduced in a finished workpiece. This is particularly advantageous if the workpiece is a bearing ring. A rolling of a rolling element on the bearing surface of the bearing ring then no longer causes the lubricant is displaced. Corresponding advantages arise for hydrodynamic sliding bearings, in which a better whereabouts of the lubricant (especially oil) is ensured.

It is preferred if the oscillation frequency of the additional movement is higher than approximately 50 Hz, in particular higher than approximately 100 Hz. In particular, an oscillation frequency range of between approximately 100 Hz and approximately 1 kHz is preferred, for example an oscillation frequency of 200 Hz. These are, in particular the movement frequency of the effective surface of the finishing tool along the additional movement axis. The movements in the mentioned frequency range are easy to control; at the same time, the advantages described above with reference to the "hammering" machining of the workpiece surface can be achieved.

An amplitude of the additional movement may be, for example, only 0.1 to 5 microns. However, in order to achieve a significant increase in a material removal rate, it is proposed that an amplitude of the additional movement (corresponding to half the stroke of the effective surface) is at least approximately 5 micrometers. This allows for a typical grain size of the finish material (about 10 microns) penetrate a grain with its entire extent in the material of the workpiece.

An amplitude of the additional movement may be, for example, 0.2 to several millimeters. For the best possible controllability of the finishing process, however, it is advantageous if an amplitude of the additional movement is at most approximately 200 micrometers (an advantageous amplitude value is 50 micrometers). In this way it can also be prevented that the per se advantageous effects of the method according to the invention are not accompanied by a worsening of the macrogeometry of the workpiece to be machined. An advantageous value for the amplitude of the additional movement is 100 micrometers.

In a particularly preferred embodiment of the invention, it is provided that the workpiece surface and the active surface are not moved relative to one another in a direction parallel to the workpiece axis. In this case, therefore, a relative movement used in a conventional finishing method in a direction parallel to the workpiece axis is expressly dispensed with. The relative movement of the workpiece surface and active surface is then based exclusively on the rotation of the workpiece surface about the workpiece axis and on the movement of the effective surface of the finishing tool in a direction perpendicular to the workpiece surface direction. This has the advantage that it is possible to dispense with a comparatively complex drive for the oscillatory movement of the finishing tool and / or the workpiece in a direction parallel to the workpiece axis, but nevertheless a sufficiently high material removal rate can be achieved for a large number of applications.

In an alternative embodiment of the invention it is provided that the workpiece surface and the active surface are reciprocated relative to each other in a direction parallel to the workpiece axis. Here, therefore, a conventional oscillation drive is provided. Such an oscillation drive is advantageous for the realization of particularly high material removal rates.

It is also possible to first process a workpiece surface by means of the method according to the invention (ie with rotational movement of the workpiece and with additional movement perpendicular to the workpiece surface and possibly additionally with oscillation parallel to the workpiece axis) in order to achieve a high material removal rate and with the workpiece a basic structure and to provide increased compressive residual stresses. Subsequently, the workpiece can then be further processed by means of a conventional finishing method (ie with rotational movement of the workpiece and without additional movement perpendicular to the workpiece surface and with oscillation movement parallel to the workpiece axis) in order to produce a particularly fine workpiece surface.

In the case where an above-mentioned oscillation drive is provided for generating a relative movement in a direction parallel to the workpiece axis, it is preferable that the oscillation frequency of the reciprocation in the direction parallel to the workpiece axis is at least about 1 Hz.

In the case where an above-mentioned oscillation drive is provided for generating a relative movement in a direction parallel to the workpiece axis, it is preferable that the oscillation frequency of the The reciprocating motion in the direction parallel to the workpiece axis is at most about 50 Hz.

For a finishing tool in the form of a finish band, preferred oscillation frequencies (in a direction parallel to the workpiece axis) are between 1 and 21.67 Hz, preferably 5 Hz.

For a finishing tool in the form of a finishing stone, preferred oscillation frequencies (in a direction parallel to the workpiece axis) are between 5 and 50 Hz, preferably 33.33 Hz.

Advantageously, the oscillation frequency of the additional movement by a factor of 1 to 1000, in particular by a factor of 6 to 40, higher than the oscillation frequency of the reciprocation in the direction parallel to the workpiece axis direction. These frequency ratios result in an optimum combination of a high material removal rate, an increase in the compressive residual stress of near-surface workpiece layers and a reduced drainage effect compared to a conventional cross-cut structure.

It is further preferred that an amplitude of a reciprocating movement in a direction parallel to the workpiece axis (corresponding to half of the total stroke) is between about 0.1 mm and about 3 mm. Such an amplitude range contributes to an increased material removal rate with simultaneously high dimensional accuracy of the workpiece to be machined. A preferred amplitude for a finishing tool in the form of a finishing tape is 0.5 mm, for a finishing tool in the form of a finishing stone at least 0.5 mm, preferably 1 mm.

Advantageously, the amplitude of the additional movement by a factor of 5 to 600, in particular by a factor of 10 to 20, is smaller than the amplitude of the reciprocation in the direction parallel to the workpiece axis direction. These amplitude ratios bring about an optimal combination of a high material removal rate, an increase in the compressive residual stress of near-surface workpiece layers and a reduced drainage effect in comparison to a conventional cross-cut structure.

It may also be advantageous if the amplitude of the additional movement is smaller by a factor of 1 to 5 than the amplitude of the reciprocating movement in the direction parallel to the workpiece axis. These factors are for example particularly well suited when a laterally limited workpiece surface (for example, the connecting rod bearing of a crankshaft) is to be processed, which is only minimally wider than the finishing tool. In extreme cases, even factors from 0.5 to 1 (ratio of the amplitude of the additional movement to the amplitude of the reciprocation in the direction parallel to the workpiece axis) or even smaller factors may be suitable.

The invention further relates to a device for finish machining a workpiece surface by means of a finishing tool, with a rotary drive device for generating a rotational movement of the workpiece surface relative to an active surface of the finishing tool in a rotational direction about a workpiece axis, wherein for superimposing the relative movement of the workpiece surface and effective surface an additional drive for generating a Is provided oscillating additional movement in a direction perpendicular to the workpiece surface direction.

The invention is based on the further object of specifying an optimized device for finishing a workpiece surface.

This object is achieved in a device mentioned above according to the invention in that the auxiliary drive is designed to generate an oscillation frequency which is lower than 1 kHz.

Advantages and embodiments of the device according to the invention have in part already been explained above in connection with the advantages and embodiments of the method according to the invention. In that regard, reference is made to the above description.

Advantageously, the additional drive comprises a piezoelectric actuator. Such an actuator is particularly well suited for generating an oscillating movement of an effective surface of a finishing tool.

It is understood that instead of a piezoelectric actuator, other actuators may be used, for example, hydraulic, pneumatic or electric drives or drives based on magnetostriction.

When using a piezoelectric actuator, it is preferred for a structurally simple design, if the piezoelectric actuator is aligned along an additional movement axis, in particular along the additional movement axis stacked piezoelectric elements comprises.

Advantageously, the piezoelectric actuator and the finishing tool are coupled to each other directly in motion, so that a movement of the piezoelectric actuator along the additional movement axis is identical to a movement of the Effective surface along the additional movement axis. This means that an expansion of the piezoelectric elements in the direction parallel to the additional movement axis is converted directly into a corresponding movement of the effective surface of the finishing tool, ie a "1: 1 translation" takes place and no translation or reduction by means of a transmission.

Alternatively, it is also possible to provide transmission devices, for example levers, which translate a movement of the piezoactuator into a (preferably larger) movement of the effective surface of the finishing tool.

For a particularly simple transmission of the movement of the piezoelectric actuator on the finishing tool is proposed that a drive surface of the piezoelectric actuator and the finishing tool are rigidly connected together.

Alternatively, the piezoelectric actuator has a force transmission surface for transmitting a compressive force generated by the piezoelectric actuator to a force receiving surface of the finishing tool. This allows a "plunger-like" transmission of forces directed towards the workpiece. An oppositely directed movement of the finishing tool can be generated, for example, by an elastic re-deformation of a finishing tool holder or by additional springs.

In the context of the invention, it is possible that the finishing tool is designed in the form of a finishing stone.

In the context of the invention, it is possible that the finishing tool is designed in the form of a finishing tape. In this case, it is preferable if for pressing the Finishbands against the workpiece surface is provided a pressing shell, which has a transverse to the extending direction of the finishing strip effective pressing surface, wherein at least a part of the pressing surface is formed by a pressing portion which is movable along an additional movement axis relative to a stationary shell portion. Such a pressing shell allows a defined guidance and positioning of the finishing strip and at the same time the possibility of "hammering" a workpiece surface in the region of the pressing section.

In a particularly preferred embodiment of the invention it is provided that the pressing portion and the stationary shell portion are formed integrally with each other and connected to each other via a connecting portion, wherein the connecting portion is formed such that driving forces of the auxiliary drive cause movement of the pressing portion along the additional movement axis. In this way, the surfaces of the pressing portion and the stationary shell portion facing the workpiece can be produced in one operation and thus produced geometrically exactly matched to one another. At the same time, it is possible to position the pressing portion and the stationary shell portion with high accuracy relative to each other, since a relative movement between these sections takes place only by a (elastic) deformation of the connecting portion, starting from an undeformed starting position.

In one embodiment of the invention, an oscillating drive is provided for producing a relative reciprocating movement of the workpiece surface and the effective surface in a direction parallel to the workpiece axis.

In an alternative embodiment of the invention, an oscillation drive for generating a relative reciprocating movement of the workpiece surface and the effective surface in a direction parallel to the workpiece axis direction is expressly not provided.

Further features and advantages of the invention are the subject of the following description and the drawings of preferred embodiments.

Figur 1

eine Seitenansicht einer Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 2

einen in Figur 1 mit II bezeichneten Ausschnitt in vergrößerter Darstellung;

Figur 3

eine Vorderansicht des Ausschnitts gemäß Figur 2;

Figur 4

ein der Figur 2 entsprechender Ausschnitt einer weiteren Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 5

eine der Figur 3 entsprechende Ansicht des Ausschnitts gemäß Figur 4;

Figur 6

eine schematische Ansicht einer mittels eines herkömmlichen Finishprozesses hergestellten Werkstückoberfläche;

Figur 7

eine schematische Ansicht einer mittels eines erfindungsgemäßen Verfahrens hergestellten Werkstückoberfläche;

Figur 8

eine perspektivische Ansicht einer weiteren Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 9

eine perspektivische Ansicht einer weiteren Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 10

eine Seitenansicht eines in Figuren 8 und 9 mit VI, VII bezeichneten Teils der Vorrichtung;

Figur 11

einen in Figur 10 mit XI bezeichneten Ausschnitt in vergrößerter Darstellung;

Figuren 12 bis 16

Seitenansichten von Ausführungsformen von Andrückschalen zur Verwendung bei Vorrichtungen gemäß Figuren 8 bis 11;

Figur 17

eine Seitenansicht einer Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 18

eine Draufsicht einer weiteren Ausführungsform einer Vorrichtung zur Finishbearbeitung einer Werkstückoberfläche;

Figur 19

eine Seitenansicht der Vorrichtung gemäß Figur 18; und

Figur 20

eine schematische Ansicht einer mittels den Vorrichtungen gemäß Figuren 17 bis 19 hergestellten Werkstückoberfläche.

In the drawings show:

FIG. 1

a side view of an embodiment of a device for finish machining a workpiece surface;

FIG. 2

one in FIG. 1 with II designated section in an enlarged view;

FIG. 3

a front view of the cutout according to FIG. 2 ;

FIG. 4

one of the FIG. 2 corresponding section of another embodiment of a device for finish machining a workpiece surface;

FIG. 5

one of the FIG. 3 corresponding view of the section according to FIG. 4 ;

FIG. 6

a schematic view of a workpiece surface produced by a conventional finishing process;

FIG. 7

a schematic view of a workpiece surface produced by a method according to the invention;

FIG. 8

a perspective view of another embodiment of a device for finish machining a workpiece surface;

FIG. 9

a perspective view of another embodiment of a device for finish machining a workpiece surface;

FIG. 10

a side view of a FIGS. 8 and 9 part of the device labeled VI, VII;

FIG. 11

one in FIG. 10 with XI designated section in an enlarged view;

FIGS. 12 to 16

Side views of embodiments of Andrückschalen for use in devices according to FIGS. 8 to 11 ;

FIG. 17

a side view of an embodiment of a device for finish machining a workpiece surface;

FIG. 18

a top view of another embodiment of a device for finishing a workpiece surface;

FIG. 19

a side view of the device according to FIG. 18 ; and

FIG. 20

a schematic view of one of the devices according to FIGS. 17 to 19 produced workpiece surface.

In FIG. 1 is a device for finishing a workpiece surface in total with the reference numeral 10th designated. The device 10 comprises a machine frame 12 for setting up the device 10 on a footprint 14. On the frame, a workpiece holder 16 is provided for receiving a finish-machined workpiece 18.

The workpiece 18 has a central workpiece axis 20. The workpiece 18 is, for example, a bearing ring.

The device 10 comprises a rotary drive device 22 for rotationally driving the workpiece 18 held on the workpiece holder 16 about the workpiece axis 20. The workpiece axis 20 extends coaxially to the axis of rotation of the rotary drive device 22.

The workpiece 18 has a workpiece surface 24 extending in particular concentrically to the workpiece axis 20, which is machined finish with a finish tool 26 described below.

The finishing tool 26 is, for example, a finishing stone 28. The finishing tool 26 is mounted on a finishing tool holder 30 and along an additional movement axis 32 (see FIG FIG. 2 ) is oscillatory drivable relative to the finishing tool holder 30. As a result, an active surface 34 of the finishing tool 26 facing the workpiece surface 24 is moved in the direction of the workpiece surface 24 and opposite thereto.

To generate the movement of the finishing tool 26, the device 10 comprises an auxiliary drive 36, in particular in the form of a piezoelectric actuator 38. The auxiliary drive 36 generates an oscillating movement of the active surface 34 along the additional movement axis 32.

For coupling the movement of the auxiliary drive 36 and the finishing tool 26, for example, a transmission element 40 is provided, which is connected to a clamping device 42.

The clamping device 42 includes, for example, a sleeve 44, which is subjected to a movement by the auxiliary drive 36 by means of the transmission element 40. The sleeve 44 is slidably received along the additional movement axis 32 in a housing 46 of the finish tool holder 30.

The clamping device 42 further comprises a clamping element 48, which is connected by means of a screw connection with the sleeve 44, so that the finishing stone 28 can be clamped by means of clamping element 48 and sleeve 44.

The finishing tool holder 30 can be positioned relative to the frame 12 by means of a positioning device 50 along a positioning axis 52 (cf. FIG. 1 ). The positioning axis 52 runs parallel to the workpiece axis 20. The positioning device 50 comprises a holder 54 which can be moved on the frame 12 along an infeed axis 53 and on which a carriage 56 which is movably driven along the positioning axis 52 is mounted.

The carriage 56 and the finish tool holder 30 are connected to each other such that the finish tool holder 30 is positionable relative to the carriage 56 in a direction perpendicular to the workpiece axis 20. For this purpose, a finishing tool guide 57 is provided, by means of which the finishing tool holder 30 can be positioned parallel to a feed axis 59. This allows wear compensation of the finishing tool 26 and a easy handling of the finishing tool 26 during assembly or tool changing operations.

The carriage 56 and the finish tool holder 30 may be connected to each other such that the finish tool holder 30 is not movable relative to the carriage 56 in the direction parallel to the workpiece axis 20.

Alternatively, the apparatus 10 comprises an oscillation drive 58 for generating a reciprocating movement of the tool holder 30 in a direction parallel to the workpiece axis 20.

The oscillation drive 58 has, for example, a known per se and therefore not explained in more detail eccentric 60, which is rotatably driven about an eccentric axis 62 and generates a double arrow 64 designated oscillatory motion of an output element 66. The output member 66 is fixedly connected to the finish tool holder 30, so that an oscillating movement of the output member 66 is transmitted to the finish tool holder 30 and thus also to the finishing tool 26.

Alternatively to a in FIGS. 2 and 3 shown (hydrodynamic or hydrostatic) sliding bearing sleeve 44 in the housing 46, the clamping device 42 may be mounted by means of at least one linear roller guide in the housing 46.

Another possibility is to mount the clamping device 42 movably relative to the housing 46 of the finishing tool holder 30 by means of at least one membrane element 68 (see FIG FIGS. 4 and 5 ). The membrane element 68 preferably extends in a direction perpendicular to the additional movement axis 32 Direction. Preferably, the membrane element 68 is designed in the form of an annular disc, which is connected radially on the outside to the housing 46 and radially inward to the sleeve 44.

Preferably, two membrane elements 68 are provided, which are arranged with respect to the additional movement axis 32 on opposite sides of the sleeve 44.

If the workpiece 18 is processed by means of a conventional finishing process, there is no movement of the active surface 34 along the additional movement axis 32. In this conventional process, a relative movement between the workpiece surface 24 and active surface 34 consists of a rotational movement of the workpiece surface 24 about the workpiece axis 20 and one to the Workpiece axis 20 parallel oscillatory movement 64 of the active surface 34 together. In this way, a characteristic for a conventional finishing process cross-cut structure 70, which in FIG. 6 is shown schematically. The cross-cut structure 70 comprises a plurality of, in each case at least partially mutually substantially parallel, each continuous grooves 72 and hereby intersecting, also continuous grooves 74. The patency of the grooves 72 and 74 causes the grooves 72 and 74 fluidly connected at intersection points 76 are. This results in a conventional finishing process, an increased drainage effect, in which coolant or lubricant is dissipated prematurely and therefore must be continuously provided in relatively large quantities again.

If the above with reference to FIG. 6 described relative movement between the workpiece 18 and finishing tool 26 from a further movement, namely the additional movement of the finishing tool 26 along the Additional motion axis 32, is superimposed, creates an in FIG. 7 illustrated surface structure 78.

The surface structure 78 also includes grooves 80 and 82 that run at an angle to one another. However, the grooves 80 and 82 are not continuous, but have interruptions 84, so that separate groove sections 86 are formed. The groove portions 86 serve as storage space for coolant and lubricant, which in contrast to the cross-cut structure 70 according to FIG. 6 not discharged prematurely. As a result, not only an improvement in the cooling and lubrication of the finishing tool 26 can be achieved, but in particular a reduction of the drainage effect of the workpiece surface 24 in use of the workpiece 18th

In the FIGS. 8 to 11 Further embodiments of devices 10 for finishing a workpiece surface 24 are shown. These devices 10 comprise a finishing tool 26 in the form of a finishing belt 88 (see FIG FIG. 10 ).

The device 10 according to FIG. 8 The frame 12 serves to arrange an oscillation drive, indicated overall by the reference numeral 58, by means of which an oscillation movement of a workpiece holder 16 and a workpiece 18, indicated by a double arrow 64, can be generated. This oscillatory movement is aligned parallel to a workpiece axis 20 of the workpiece 18.

The workpiece holder 16 is part of the rotary drive device 22, by means of which the workpiece 18 is rotatably driven about the workpiece axis 20. The rotary drive device 22 comprises a headstock 90 and a tailstock 92. At the in FIG. 8 illustrated embodiment of the headstock 90 of the tailstock 92 are mounted on an output member 66 of the oscillation drive 58.

At the in FIG. 9 illustrated device 10 is no oscillation drive 58 is provided. The headstock 90 and the tailstock 92 are mounted directly on the frame 12 of the device 10.

With the exception of the difference described above (oscillatory drive 58 present or absent), the devices 10 according to FIG FIGS. 8 and 9 an identical structure. Therefore, the following description concerns both the device 10 according to FIG FIG. 8 as well as the device 10 according to FIG. 9 ,

The workpiece surface 24 of the workpiece 18 to be machined is, for example, a connecting rod bearing surface of a crankshaft which is radially offset from the workpiece axis 20. As a result, such a workpiece surface 24 moves in a circular manner about the workpiece axis 20. It is therefore necessary that the finishing tool 26 can also follow this movement of the workpiece surface 24.

Therefore, for supporting the finishing tool 26, a bearing device 94 is provided for mounting on the frame 12, which has two degrees of freedom and which allows movement of the finishing tool 26 within a plane perpendicular to the workpiece axis 20.

The bearing device 94 comprises a pivoting part 96, which by means of a pivot bearing 98 about a pivot axis 100 pivotally mounted on a frame part 102 of the frame 12th is held. The pivot axis 100 extends parallel to the workpiece axis 20.

The pivoting part 96 serves to arrange at least one linear guide 104 (cf. FIG. 10 ), by means of which a bearing part 106 along a guide axis 108 of the linear guide 104 is slidably mounted relative to the pivot member 96.

The bearing part 106 extends substantially within a plane perpendicular to the workpiece axis 20 extending plane.

The bearing part 106 has an opening 108 which is penetrated by the pivot bearing 98.

The bearing part 106 has a bearing part end 110 facing the workpiece 18 for the arrangement of a pressing device 112.

The pressing device 112 includes at least two forceps arms 114. The forceps arms 114 are relative to the bearing portion 106 about Zangenarmschwenkachsen 116 (see FIG. 10 ) pivotable. The Zangenarmschwenkachsen 116 parallel to the pivot axis 100 of the pivoting part 96th

The pliers arms 114 have, at their end facing the workpiece 18, a unit 118 which will be described below with reference to FIG FIG. 11 will be explained in more detail.

To generate a pressing force is a known per se and therefore not further explained Andrückantrieb 119 is provided, which the units 118 of the gun arms 114th acted upon in the direction of the workpiece 18 forces 120 acting.

The units 118 have a holder 122 which is fixedly connected to the tong arms 114 and which serves to provide a clamping device for the finishing belt 88.

The device 10 includes an auxiliary drive 36 in the form of a piezoelectric actuator 38. The piezoelectric actuator 38 has a plurality of piezo elements stacked on top of the additional movement axis 32 ("stack").

The auxiliary drive 36 is connected to a drive housing 126 fixed to the gun arm 114. On a front side 128 of the piezoelectric actuator 38 is connected to a power transmission element 130. This has a force transmission surface 132, which transmits a pressure force generated by means of the piezoelectric actuator 38 to a force receiving surface 134 of an output element 136. The force transmission surface 132 and the force receiving surface 134 may also be firmly connected to each other, so that tensile forces of the piezoelectric actuator 38 to the output member 136 are transferable.

For pressing the finishing strip 88 against the workpiece surface 24, the units 118 each comprise a pressing shell 138, which each have a curved pressing surface 140.

The pressing shells 138 comprise a stationary shell section 142, which is firmly connected to the tong arm 114, for example by means of a screw connection 144. The stationary shell portion 142 serves to arrange a pressing portion 146 which is movable relative to the stationary shell portion 142, along the additional movement axis 32.

The pressing portion 146 has a curved surface 148, which forms part of the pressing surface 140 (the other part of the pressing surface 140 is formed by the stationary shell portion 142). The pressing portion 146 is integrally formed with the stationary shell portion 142 and connected thereto via at least one connecting portion 150.

For example, the connecting portion 150 is formed in the form of a thin web 152, which extends transversely, in particular perpendicularly, to the additional movement axis 32. The pressing portion 146 is fixedly connected to the output element 136, so that an expansion of the piezoelectric actuator 38 acts on the force receiving surface 134 via the force transmission surface 132 and is transmitted by the output element 136 directly into a movement of the Andrückabschnitts 146 and thus the curved surface 148.

With reference to FIGS. 12 to 16 Hereinafter, various embodiments of pressing cups 138 will be described. In the pressing shell 138 according to FIG. 11 For example, the curved surface 148 formed by the pressing portion 146 is comparatively short in the extending direction of the finishing tape 88, so that the curved surface 148 is smaller than half of the entire pressing surface 140.

At the in FIG. 12 In the illustrated embodiment of a pressing shell 138, the pressing portion 146 is enlarged so that the curved surface 148 formed by the pressing portion 146 is larger than half of the secured pressing surface 140.

The peculiarity of in FIG. 13 shown Andrückschale 138 is that the Connecting portion 150 in the form of a thin-walled web with a surface 154 also forms part of the pressing surface 140. The pressing surface 140 is thus composed of a curved surface 148, which is formed by the connecting portion 146, at least one partial surface 154, which is formed by one or more of the connecting portions 152 and optionally from an additional partial surface 156, which of the stationary shell portion 142nd is formed.

In extreme cases, the entire pressing surface 140 may be formed by the pressing portion 146; this is in FIG. 14 shown.

At the in FIGS. 15 and 16 illustrated embodiments of Andrückschalen 138, the pressing surface 140 is also completely formed by the curved surface 148 of the Andrückabschnitts 146. In addition, the stationary shell section 142 has arms 158, which are provided at their free end with pressure elements 160, for example in the form of pressure rollers. The pressing elements 160 serve to support the workpiece 18, so that the workpiece surface 24 to be machined can be positioned exactly relative to the pressing surface 140.

When the forces 120 are introduced into the workpiece 18 via the pressing elements 160, an area of the workpiece surface 24 to be machined remains unaffected by the forces 120. The forces 120 generated by the Andrückantriebs 119 and the surface machining forces generated by the piezoelectric actuator 38 can thus be set independently.

It is possible that the pressing elements 160 substantially in the direction of the forces 120 (see FIG FIG. 10 ) parallel direction, as in the FIG. 15 illustrated embodiment is the case.

But it is also possible that the pressing elements 160 substantially transverse to the direction of the forces 120 (see FIG. 10 ) act as in the embodiment according to FIG. 16 the case is.

In the FIGS. 17 to 19 Embodiments of devices 10 for finishing a workpiece surface 24 are shown in which an additional movement axis 32 is not perpendicular to a workpiece surface to be machined 24, but parallel thereto (see FIG. 17 ) or tangentially thereto (cf. FIG. 18 ).

In the device 10 according to FIG. 17 a rotational movement of a workpiece 18 about the workpiece axis 20 is superimposed on an additional movement of the active surface 34 of the finishing tool 26 in parallel to the workpiece axis 20, as shown in FIG FIG. 17 is indicated with a small double arrow 162. The additional movement 162 is generated, for example, by a piezoelectric actuator 38, which displaces a finishing stone holder 30 and thus a finishing stone 28 into the oscillating additional movement 162.

The additional movement 162 can also be superimposed on a conventional oscillatory movement, which is generated by means of a conventional oscillation drive (in FIG FIG. 17 indicated by a larger double arrow 64).

At the in FIGS. 18 and 19 illustrated device 10 is the rotational movement of the workpiece surface 24 relative to the active surface 34 of the finishing tool 26 superimposed on the workpiece surface 24 tangential additional movement 162 of the active surface 34. For this purpose, an additional drive 36 may be provided in the form of a piezoelectric actuator, which drives a finish stone holder 30 with a movement along the additional movement axis 32 movement. Again, optionally, a conventional oscillating movement may be provided parallel to the workpiece axis 20 (see double arrow 64 in FIG FIG. 19 ).

In a conventional, known from the prior art finishing process generates an effective part of the active surface 34 of a finishing tool 26, so for example, a grain, around the workpiece axis 20 on the workpiece surface 24 encircling, sinusoidal action line 164, cf. FIG. 20 , By means of in FIGS. 18 and 19 shown device 10 may be generated by this line of action 164 deviating an overall sinusoidal, but on a smaller scale wavy line of action 166. The line of action 166 consists essentially of wave sections oriented along the course of the action line 164.

When using a device 10 according to FIG. 17 In deviation from the line of action 164, a line of action 168 can be generated, which in its coarse course likewise orients itself on the line of action 164, but has shaft sections extending substantially perpendicular to the line of action 164.

Claims (17)

1. A method for finish machining a workpiece surface (24) by means of a finishing tool (26), wherein the workpiece surface (24) is moved relative to an effective area (34) of the finishing tool (26) in a direction of rotation about a workpiece axis (20), and wherein an additional oscillating movement is superimposed on the relative movement of the workpiece surface (24) and effective area (34) in a direction perpendicular to the workpiece surface (24), characterised in that an oscillation frequency of the additional movement is lower than 1 kHz.
2. The method according to any one of the preceding claims, characterised in that the oscillation frequency of the additional movement is higher than 50 Hz, in particular higher than 100 Hz.
3. The method according to any one of the preceding claims, characterised in that an amplitude of the additional movement is at least approximately 5 micrometers.
4. The method according to any one of the preceding claims, characterised in that an amplitude of the additional movement is a maximum of approximately 200 micrometers.
5. The method according to any one of the preceding claims, characterised in that the workpiece surface (24) and the effective area (34) are not moved relative to each other in a direction parallel with the workpiece axis (20).
6. The method according to any one of Claims 1 to 4, characterised in that the workpiece surface (24) and the active area (34) are moved backward and forward relative to each other in a direction parallel with the workpiece axis (20).
7. The method according to Claim 6, characterised in that the oscillation frequency of the backward and forward movement is at least approximately 1 Hz in the direction parallel with the workpiece axis (20).
8. The method according to Claim 6 or 7, characterised in that the oscillation frequency of the backward and forward movement is a maximum of approximately 50 Hz in the direction parallel with the workpiece axis (20).
9. The method according to any one of Claims 6 to 8, characterised in that the oscillation frequency of the additional movement is higher by a factor of 1 to 1000, in particular by a factor of 6 to 40, than the oscillation frequency of the backward and forward movement in the direction parallel with the workpiece axis (20).
10. The method according to any one of Claims 6 to 9, characterised in that an amplitude of the backward and forward movement is between approximately 0.1 mm and approximately 3 mm in the direction parallel with the workpiece axis (20).
11. The method according to any one of Claims 6 to 10, characterised in that an amplitude of the additional movement is smaller by a factor of 5 to 600, in particular by a factor of 10 to 20, than the amplitude of the backward and forward movement in the direction parallel with the workpiece axis (20).
12. A device (10) for finish machining a workpiece surface (24) by means of a finishing tool (26), with a rotary drive device (22) for generating a rotary movement of the workpiece surface (24) relative to an active area of the finishing tool (26) in a direction of rotation about a workpiece axis (20), wherein an additional drive (36) is provided for overlapping the relative movement of the workpiece surface (24) and the active area (34) in order to generate an oscillating additional movement in a direction perpendicular to the workpiece surface (24), characterised in that the additional drive (36) is designed to generate an oscillation frequency, which frequency is lower than 1 kHz.
13. The device (10) according to Claim 12, characterised in that the additional drive (36) comprises a piezoelectric actuator (38).
14. The device (10) according to Claim 13, characterised in that the piezoelectric actuator (38) is aligned along an additional axis of movement (32), in particular along the additional axis of movement (32) of stacked piezoelectric elements.
15. The device (10) according to any one of Claims 12 to 14, characterised in that the finishing tool (26) is designed in the form of a finishing stone (28).
16. The device (10) according to any one of Claims 12 to 14, characterised in that the finishing tool (26) is designed in the form of a finishing belt (88), and in that a pressing bowl (138) is provided for pressing the finishing belt (88) against the workpiece surface (24), which bowl has a pressing surface (140) that acts transversely to the direction of running of the finishing belt (88), wherein at least a part of the pressing surface (140) is formed by a pressing section (146) which is moveable along an additional axis of movement (32) relative to a stationary bowl section (142).
17. The device (10) according to Claim 16, characterised in that the pressing section (146) and the stationary bowl section (142) are designed so that they are integral with each other and are connected to each other by a connecting section (150), and wherein the connecting section (150) is designed in such a manner that driving forces of the additional drive (36) give rise to a movement of the pressing section (146) along the additional axis of movement (32).

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