EP1475186B1 - Method and apparatus for abrasively working surfaces of revolution - Google Patents

Description

Technical area

The invention relates to a method for cylindrical grinding of a workpiece and to an apparatus for carrying out the cylindrical grinding method according to the preambles of the independent patent claims.

State of the art

For many applications, workpieces are required which are at least partially rotationally symmetrical and have a workpiece axis defining the axis of symmetry and two adjacent surfaces which are rotationally symmetrical with respect to the workpiece axis and between which a circular transitional edge is formed. Such workpieces are e.g. used as valve or nozzle needles, typically one of the two surfaces forms a sealing seat and the other of the two surfaces forms a guide surface of the valve or nozzle needle. In order for such valve or nozzle needles also for high pressure applications such. Fuel injection systems are suitable for modern gasoline or diesel engines, where partial pressures of well over 1000 bar must be mastered, high demands are to be met in terms of compliance with manufacturing tolerances. In particular, the transition edge between the seat and the guide surface must be formed as sharp as possible and burr-free.

Workpieces of the above-mentioned type are processed by application of cylindrical grinding processes, whereby so-called cylindrical grinding machines are used to carry out the cylindrical grinding process.

From the document WO 01/60565 (Robert Bosch GmbH), a cylindrical grinding process and a cylindrical grinding machine are known, which allow the production of a valve needle for a fuel injection valve by means of cylindrical grinding. The cylindrical grinding machine is provided with a grinding wheel and a deburring dome arranged in relation to the workpiece in relation to the grinding wheel. When the grinding wheel grinds an abrasive surface of the workpiece, a burr is created which projects beyond the transitional edge formed between this abrasive surface and an adjacent surface into the region of the adjacent surface. The deburring mandrel is arranged and formed in such a way that the burr is pressed back onto the grinding surface due to the rotation of the workpiece rotating about its axis from the deburring dome and ground on the next contact with the grinding wheel.

It has been found that the cylindrical grinding method and the cylindrical grinding machine according to the publication WO 01/60565 are disadvantageous for the mass production of large workpiece series. It happens over and over again that the burr formation is not reliably prevented by the deburring dome. Therefore, a costly re-inspection of the workpieces is necessary to ensure the desired manufacturing quality.

Presentation of the invention

The object of the invention is to provide a method and a device for cylindrical grinding, which allow reliable and precise machining of workpieces with a sharp and burr-free transition edge between two rotationally symmetric surfaces even in large-scale production.

The solution of the problem is defined by the features of the independent claims. According to the invention, a cylindrical grinding process is carried out for machining a workpiece having a workpiece axis. During the execution of the cylindrical grinding process, the workpiece rotates about the workpiece axis, while simultaneously a grinding wheel, which rotates about a grinding wheel axis, and the workpiece are compared against each other to grind in a grinding operation, a first workpiece surface which is rotationally symmetrical with respect to the workpiece axis. The workpiece has a second workpiece surface, which is rotationally symmetrical with respect to the workpiece axis and defined by a rectilinear generatrix. The two workpiece surfaces are arranged adjacent to each other such that a sharp, circular transition edge is formed between them. The cylindrical grinding method according to the invention is characterized in that an auxiliary abrasive tool, which rotates about an auxiliary tool axis and has a planar, perpendicular (ie normal) to the auxiliary tool axis arranged abrasive surface, is pressed against the workpiece. The auxiliary abrasive tool is pressed against the workpiece in such a way that the abrasive surface in a tangential plane to the second workpiece surface (ie in one at the second Workpiece surface adjacent tangential plane) is arranged and touches in a adjacent to the transition edge portion of the second workpiece surface, this second workpiece surface along a straight line of contact. In this case, the abrasive surface projects in the direction of the contact line away from the second workpiece surface beyond the transition edge.

The grinding method according to the invention causes a burr, which possibly arises during grinding of the first workpiece surface, to protrude beyond the transition edge into the region above the second workpiece surface, through the auxiliary abrasive tool or through its abrasive surface, so that a sharp and burr-free transition edge between the first and second burrs the second workpiece surface is formed.

The second workpiece surface is rotationally symmetrical with respect to the workpiece axis, being defined in the geometric sense by a rectilinear generatrix which is rotated about the workpiece axis. That is, the second workpiece surface has either the shape of a conical surface or a circumferential surface of a right circular cylinder. It follows that a tangential plane adjacent to the second workpiece surface (and thus also the abrasive surface of the auxiliary abrasive tool) touches the second workpiece surface not only at one point but along a straight contact line. As a result, the abrasive surface, when pressed against the second workpiece surface and rotated about the auxiliary tool axis, is not linearly but flatly worn, thereby maintaining its planar surface shape.

The first workpiece surface may also be conical or kreiszylindermantelelförmig. Alternatively, however, it may also be rotationally symmetrical with respect to the first workpiece axis in other ways, in which case it is defined by a curvilinear generator.

For carrying out the inventive grinding method, it is possible for the workpiece to be rotated about a workpiece axis stationary during the grinding process and the grinding wheel is delivered against the workpiece. Such grinding operations are typically carried out on cylindrical grinding machines in which an elongate workpiece is received between a workpiece spindle mounted on a headstock stationary during the grinding operation and a sleeve disposed on a tailstock stationary during the grinding operation. Alternatively, however, it is also possible for the workpiece rotating about the workpiece axis to be delivered against a grinding wheel rotating about a grinding wheel axis stationary during the grinding process. Such grinding operations are usually performed by cylindrical grinding machines, which are designed for centerless cylindrical grinding (ie for cylindrical grinding without quill). In principle, it is also possible that during the execution of the grinding process, both the grinding wheel and the workpiece axis (or a workpiece spindle defining the workpiece axis) are moved simultaneously.

Preferably, the pressing of the auxiliary abrasive tool against the workpiece and the grinding of the first workpiece surface are terminated at the same time. By performing the two abrasive operations (i.e., the grinding operation between the grinding wheel and the first workpiece surface on the one hand and the Abrasiworgang between the Hilfsabrasivwerkzeug and the second workpiece surface on the other hand) simultaneously at least at the end of the inventive method and terminated simultaneously, no burr remains at the transition edge. Simultaneity in the present context means that a possible time difference between the end of the first and the second abrasive operation is too short for burr formation even if only one of the two abrasive tools is in (sliding) contact with the workpiece during a period corresponding to that time difference.

However, the simultaneous termination of the pressing of the auxiliary abrasive tool against the workpiece and the grinding of the first workpiece surface is not mandatory for a functioning of the present invention. In particular, in the case where the auxiliary abrasive tool, while being pressed against the second workpiece surface with the abrasive surface, processes the second workpiece surface with a substantially smaller grinding power than the grinding performance with which the same Abrasive wheel machined the first workpiece surface, the pressing of the Hilfsabrasivwerkzeugs can be terminated later than the grinding, because in this case, the pressing of the Hilfsabrasivwerkzeugs virtually no burring result.

A cylindrical grinding device according to the invention, which is designed in particular for carrying out the method according to the invention, comprises a workpiece spindle rotating about a workpiece spindle axis and provided with a workpiece holder designed to receive a workpiece. The cylindrical grinding device further comprises a grinding wheel rotating about a grinding wheel axis and a first feed device. The first feed device is designed such that either the grinding wheel can be delivered against the workpiece or the workpiece together with the workpiece spindle against the grinding wheel by means of the first feed device. At the same time, however, both the grinding wheel and the workpiece, together with the workpiece spindle, can be movable with respect to a stationary base in order to deliver the grinding wheel and the workpiece against each other. The cylindrical grinding device according to the invention further comprises an auxiliary abrasion tool rotating about an auxiliary tool axis, which has a planar abrasive surface arranged at right angles to the auxiliary tool axis. Furthermore, the cylindrical grinding device according to the invention comprises a second feed device, which is designed to feed the auxiliary abrasive tool against the workpiece, and a control device for controlling the cylindrical grinding device.

The control device is designed to control the first feed device such that the grinding wheel and the workpiece are delivered against each other to process a first workpiece surface in a grinding operation. The control device is further configured to control the second feed device such that during the execution of the grinding process, the Hilfsabrasivwerkzeug is delivered by means of the second feed device against the workpiece so that it presses with its abrasive surface against a second workpiece surface. The two workpiece surfaces are rotationally symmetrical with respect to the workpiece spindle axis and the second workpiece surface is defined by a rectilinear generatrix. Furthermore, the two workpiece surfaces are arranged adjacent to one another in such a way, that between them a circular transition edge is formed. The control device and the second feed device are further configured such that when the abrasive surface presses against the second workpiece surface, the abrasive surface is disposed in a tangential plane to the second workpiece surface, the second workpiece surface contacts along a contact line and in the direction of the contact line away from the second workpiece surface the transitional edge projects out.

As the abrasive surface protrudes beyond the transition edge away from the second workpiece surface in the second workpiece surface, while simultaneously rotating the workpiece about the workpiece spindle axis and the auxiliary abrasive tool about the auxiliary tool axis, a burr arising during grinding of the first workpiece surface over the transition edge out into the region above the second workpiece surface, abraded by the Hilfsabrasivwerkzeug or by its abrasive surface, so that a sharp and burr-free transition edge between the first and the second workpiece surface is formed.

According to a preferred embodiment of the invention, at least one section of the auxiliary abrasive tool is cylindrical (also referred to as a pin-shaped design), the abrasive surface being the cylinder base surface. It may also be the entire auxiliary abrasive tool overall cylinder or pin-shaped. The pin-shaped portion of the auxiliary abrasive tool can in particular have the shape of a straight circular cylinder, with a circular surface or abrasive surface. In principle, however, other forms of auxiliary abrasive tools are possible, e.g. a hollow cylinder-shaped auxiliary abrasive tool with an annular abrasive surface, or a cuboid trained Hilfsabrasivwerkzeug with a rectangular or square Abrasivoberfläche.

The auxiliary abrasion tool is preferably designed in such a way and, during the pressing against the second workpiece surface, arranged such that the contact line on the abrasive surface as an uninterrupted line from an outer edge of the abrasive surface along a diameter passing through the auxiliary tool axis (or through its extension) to beyond the auxiliary tool axis (or its extension) to the transition edge. In the present context, an axis is always understood to mean an axis in the geometric sense. Thus, the nip on the abrasive surface extends as an uninterrupted line from an outer edge of the abrasive surface along a diameter passing through the (mechanical) auxiliary tool axis or extension thereof beyond the (mechanical) auxiliary tool axis or its extension to the transition edge. As a result, if during the pressing of the abrasive surface against the second workpiece surface of the Hilfsabrasivwerkzeugs simultaneously rotated about the Hilfswerkzeugachse, the entire abrasive surface is worn. As a result, the abrasive surface remains substantially flat during wear, thereby avoiding undesirable rounding of the transition edge. Preferably, the abrasive surface protrudes beyond the transition edge only with a small area fraction in order to ensure the most uniform possible wear of the abrasive surface. Thus, for example, the contact line between the abrasive surface and the second workpiece surface can measure more than two thirds, preferably more than three quarters, in particular even more than four fifths of the diameter of the abrasive surface passing through the auxiliary tool axis.

According to a further advantageous embodiment of the invention, during the pressing of the auxiliary abrasive tool against the second workpiece surface, the workpiece is driven for rotation about the workpiece spindle axis and the auxiliary abrasive tool for rotation about the auxiliary tool axis such that the auxiliary abrasive tool (or the abrasive surface) in the region of the intersection of Contact line with the transition edge has a velocity component opposite to the direction of the speed of the workpiece in this area. In other words, the direction of rotation of the workpiece with respect to the workpiece spindle axis and the direction of rotation of the auxiliary abrasive tool with respect to the auxiliary tool axis are selected such that in the region of the transition edge where the abrasive surface touches the second workpiece surface, the abrasive surface has a counter to the speed of the workpiece directed velocity component. As a result, a large relative speed between the abrasive surface and the workpiece is achieved in this region, which causes an efficient removal of the burr generated by the grinding wheel and thus leads to an efficient prevention of burr formation at the transition edge of the workpiece.

The auxiliary abrasive tool of the cylindrical grinding apparatus according to the present invention may comprise a honing pin or a fine grinding stone (also called Degussit stone, superfinish stone, polishing stone, or honing stone) provided with the abrasive surface. In this case, the abrasive surface is preferably formed as an end face of the honing pin or the fine grinding stone.

The device according to the invention may further comprise a conditioning tool for conditioning (also referred to as dressing) the abrasive surface of the auxiliary abrasive tool. Such a conditioning tool may be part of a conditioning device designed specifically for conditioning the abrasive surface (ie separate). As an alternative to a specific conditioning device, however, the conditioning tool may also be merely a hard-surfaced tool which is received on the workpiece spindle in the manner of a workpiece for conditioning, whereupon the auxiliary abrasive tool rotating about the auxiliary tool axis abuts against the conditioning tool rotating about the workpiece spindle axis is delivered to effect the conditioning of the abrasive surface of the auxiliary abrasive tool. Such a conditioning tool may in particular have a shape which is identical to the shape of the device to be machined by means of the cylindrical grinding. However, as an alternative to the use of a conditioning tool, an auxiliary abrasive tool can also be used whose abrasive surface is made of a material which wears so well during operation of the cylindrical grinding device that no conditioning is required. Such a material can be, for example, a material used for the production of honing tools, in particular honing pencils.

Advantageously, the cylindrical grinding device according to the invention further comprises means for selectively adjusting the force with which the auxiliary abrasive tool presses against the second workpiece surface. This creates the possibility of adapting the pressure with which the abrasive surface presses against the second workpiece surface to the burr formation to be expected during grinding by means of the grinding wheel. Advantageously, the force or the pressure is kept as small as possible, so that while any burr arising during grinding is just barely removed, without at the same time the mass of the second workpiece surface being substantially changed by the machining by means of the auxiliary abrasive tool.

Advantageously, the cylindrical grinding device according to the invention is designed such that the auxiliary abrasive tool, while being pressed against the second workpiece surface with the abrasive surface, processes the second workpiece surface with a substantially smaller grinding power than the grinding performance with which the grinding wheel simultaneously processes the first workpiece surface. In the present context, the grinding performance is understood to be the area performance defined in general terms for the cutting workpiece machining, which has the physical unit [surface / time unit]. The ratio of the grinding power of the auxiliary abrasive tool to the grinding performance of the grinding wheel usually corresponds to the installed maximum power which the spindle drive of the auxiliary abrasive tool is capable of providing when machining the second workpiece surface to the installed maximum power which the grinding wheel spindle drive performs when grinding the first Workpiece surface can afford. Since the grinding performance of the auxiliary abrasive tool is substantially smaller than that of the grinding wheel during grinding of the first workpiece surface, the dimension of the second workpiece surface, which may have already been ground to a desired dimension with high precision in a preceding grinding operation, remains in the course of carrying out the inventive grinding process Essentially unchanged. The grinding performance of the auxiliary abrasive tool may be less than 1%, preferably less than 0.5%, in particular even less than 0.1% of the grinding power of the grinding wheel.

According to a further preferred variant of the invention, the auxiliary abrasive tool is arranged on a so-called measuring device platform, which can be moved relative to the workpiece spindle and which is equipped with at least one measuring device. The second feed device, which serves to feed the auxiliary abrasive tool against the workpiece, can then be formed by the movement device for moving or moving the measuring device platform. By using only a single movement device for advancing or moving the auxiliary abrasive tool on the one hand and for moving or moving the measuring device platform on the other hand, a simple and inexpensive construction of the cylindrical grinding device results. As an alternative to the arrangement on a measuring device platform, the auxiliary abrasion tool can also be arranged on another part of the cylindrical grinding device which can be moved relative to a stationary machine frame, e.g. on a tailstock quill. As a further alternative, the second feed device can also be designed as a separate movement device, which exclusively serves to feed the auxiliary abrasive tool against the workpiece.

According to a further advantageous aspect of the invention, the auxiliary abrasion tool is arranged during the pressing against the second workpiece surface on a side facing away from the grinding wheel side of the workpiece. The abrasive surface of the auxiliary abrasive tool and the grinding wheel then simultaneously press against the workpiece from opposite sides in opposite directions. This results in an additional stabilization of the workpiece during the grinding process, which can contribute to increasing the precision during grinding.

From the following detailed description and the totality of the claims, further advantageous embodiments and feature combinations of the invention result.

Brief description of the drawings

Fig. 1

in einer vereinfachten Teilansicht von schräg oben eine Rundschleifvorrichtung gemäss einer ersten bevorzugten Ausführungsart der Erfindung, in einer ersten Arbeitsstellung;

Fig. 2

die Rundschleifvorrichtung aus Fig. 1 in einer zweiten Arbeitsstellung, in einer in einer vereinfachten Teilansicht von schräg oben;

Fig. 3

in einer vereinfachten, schematischen Teilansicht von oben eine Rundschleifvorrichtung gemäss einer ersten bevorzugten Ausführungsart der Erfindung;

Fig. 4

die Rundschleifvorrichtung aus Fig. 1 in einer vereinfachten, schematischen Teilansicht von vorne.

The drawings used to explain the embodiments show:

Fig. 1

in a simplified partial view obliquely from above a cylindrical grinding device according to a first preferred embodiment of the invention, in a first working position;

Fig. 2

the cylindrical grinding apparatus of Figure 1 in a second working position, in a simplified partial view obliquely from above ..;

Fig. 3

in a simplified, schematic partial view from above a cylindrical grinding device according to a first preferred embodiment of the invention;

Fig. 4

the cylindrical grinding apparatus of Fig. 1 in a simplified, schematic partial view from the front.

Basically, the same parts are provided with the same reference numerals in the figures.

Ways to carry out the invention

In Figures 1 and 2, an external cylindrical grinding machine 10 is shown, which has a stable stationary machine bed (not shown). On the machine bed, a straight linear guide (not shown) is arranged, which is referred to below as the first linear guide. A carriage 11, hereinafter referred to as the first carriage 11, is linearly movable on the first linear guide, as indicated in FIG. 1 by the double arrow 62.

On the first carriage 11, a workpiece headstock 13 is fixed, in which a workpiece spindle 12 is rotatably mounted about a substantially horizontal workpiece spindle axis (not shown), wherein the workpiece spindle axis parallel to the direction of movement of the first carriage 11 on the first linear guide (ie parallel to first linear guide). At a flying end of the workpiece spindle 12, a workpiece clamping device 16 is arranged, in which a longitudinal end of an elongate workpiece 18 is clamped. The workpiece spindle 12 is driven by a motor (not shown) such that it rotates about the workpiece spindle axis during grinding with a number of revolutions of approximately 800 rpm, as indicated by the arrow 15 in FIG.

On the machine bed, another straight linear guide (not shown) is arranged, which is referred to below as the second linear guide. A carriage (not shown), hereinafter referred to as a second carriage, can be moved substantially horizontally along the second linear guide obliquely to the workpiece spindle axis. The second carriage carries the wheelhead (not shown) of the external cylindrical grinding machine 10, wherein in the wheelhead a grinding wheel 20 about a substantially horizontal grinding wheel axis (not shown) is rotatably mounted. The second carriage and the second linear guide are part of a first feed device, which serves to deliver the grinding wheel 20 against the workpiece 18 and to drive away from it again, as indicated in Fig. 1 by the double arrow 22.

The external cylindrical grinding machine 10 shown in FIGS. 1 and 2 is provided with a machine control which is designed to control all components of the external cylindrical grinding machine 10 and in particular also to control the first feed device and the second feed device described below.

Further, a tailstock 30 is fixedly mounted on the first carriage relative to the workpiece headstock 13. At the end of the tailstock 30 facing the workpiece headstock 13, a sleeve 32 projecting in the direction of the workpiece headstock 13 is arranged, this sleeve 32 being movable parallel to the workpiece spindle axis with respect to the tailstock 30 by means of a hydraulic drive (not shown).

The workpiece spindle 12 and the sleeve 32 are arranged such that the workpiece 18 clamped at one longitudinal end in the workpiece clamping device 16 is in the middle the workpiece spindle 12 and the sleeve 32 is received, being stabilized during its rotation about the workpiece spindle axis at the other longitudinal end of the Pinolenspitze. In addition, the tailstock 30, the workpiece headstock 13 and the movable on the second linear guide grinding spindle are arranged relative to each other such that the grinding wheel 20 can be fed by means of the first feed device between the workpiece spindle 12 and the Pinolenspitze against the workpiece 18.

The grinding wheel 20 is designed for grinding a conical outer surface of the workpiece 18, which is rotationally symmetrical with respect to the workpiece spindle axis. The workpiece 18 further has a circular cylindrical outer surface, which is also formed rotationally symmetrical with respect to the workpiece spindle axis. The two workpiece surfaces are arranged adjacent to each other such that a circular transition edge is formed between them, wherein the workpiece in the region of the cylindrical outer surface (and thus in the region of the transition edge) has a diameter of about 4 mm. The grinding wheel 20 has a pulley diameter of about 500 mm and is driven by a motor (not shown) to rotate about the wheel axis during grinding at a speed of about 1750 rpm. In this case, the direction of rotation of the grinding wheel 20 - as indicated in Fig. 1 by the arrow 21 - chosen such that the speed of the grinding wheel 20 in the area where the grinding wheel 20 touches the workpiece 18, the speed of the workpiece 18 according to its rotation around the Workpiece spindle axis is directed in this area opposite.

On the first carriage 11, a measuring platform base 42 is further fixed in the area between the workpiece headstock 13 and the tailstock 30. On the measuring platform base 42, a third carriage 50 is arranged, which is movable along a third linear guide perpendicular to the workpiece spindle axis and substantially horizontally with respect to the measuring platform base 42, as indicated in Fig. 1 by the double arrow 52. The third carriage 50 serves as a measuring platform 50, which carries a measuring device which is used to measure inter alia the diameter of the with Grinding wheel 20 machined workpiece 18 is formed to perform a measuring controlled grinding process can.

The measuring platform base 42 and the third carriage 50 as well as the third linear guide are part of a measuring platform positioning device, which serves to move the measuring platform 50 against the workpiece 18 and away from it. In this case, the measuring platform positioning device is designed and arranged such that the third carriage 50 or the measuring platform 50 is arranged on the opposite side of the workpiece 18 with respect to the workpiece 18 of the grinding wheel 20.

On the third carriage 50 and the measuring platform 50, an auxiliary spindle 56 is further arranged, which is rotatably mounted with respect to the third carriage 50 about an axis arranged at right angles to the workpiece spindle and obliquely downwardly inclined auxiliary spindle axis. At a flying end of the auxiliary spindle 56, a honing pin tensioning device is arranged, in which a longitudinal end of an elongated honing pin 54 is clamped, which has substantially the shape of a right circular cylinder, wherein the cylinder axis of the honing pin 54 is arranged coaxially to the auxiliary spindle axis. The cylinder base surface of the cylindrical honing pin 54 removed from the auxiliary spindle forms the abrasive surface or honing surface of the honing pin 54.

The auxiliary spindle 56 is linearly movable together with the honing pin 54 by means of a pneumatic drive with respect to the third carriage 50 in the direction of the auxiliary spindle axis, as indicated by the double arrow 44 in FIG. This pneumatic drive and the measuring platform positioning device formed from the measuring platform base 42 and the third carriage 50 are part of a second feed device, which serves to deliver the honing pin 54 against the workpiece 18 such that its honing surface presses against the cylindrical outer surface of the workpiece 18. In the case of the external cylindrical grinding machine 10 illustrated in FIGS. 1 and 2, the second feed device is designed and arranged such that the honing pin 54 presses against the cylindrical outer surface of the workpiece from the side of the workpiece 18 opposite the workpiece 18 of the grinding wheel 20 while at the same time the grinding wheel from the first feed device is delivered substantially horizontally against the workpiece 18 to grind the conical outer surface of the workpiece 18. Further, the pneumatic drive for moving the auxiliary spindle 56 of the machine control is so actuated that this drive presses the honing pin on the auxiliary spindle 56 with an application-specific set force against the workpiece 18. This application-specific force can be set manually by a surgeon at a suitable setting device in the course of setting the external cylindrical grinding machine 10 for a series of grinding processes (ie for an application).

The honing pin 54 has a diameter between about 1 and 2 mm. The auxiliary spindle 56 (and with it the honing pin 54) is driven by a motor (not shown) such that it rotates about the auxiliary spindle axis during honing with a number of turns between approximately 50 and 100 rpm. The direction of rotation of the auxiliary spindle 56 - as indicated in Fig. 1 by the arrow 55 - selected such that when the honing surface touches the workpiece 18 in the region formed between the conical and the Lindrischen workpiece surfaces transition edge, the honing pin (or Honing surface) in the region of the intersection of the contact line with the transition edge has a speed component opposite to the direction of the speed of the workpiece 18 (according to the rotation of the workpiece 18 about the workpiece spindle axis) in this area.

In Fig. 1, the external cylindrical grinding machine 10 is shown in a working position in which both the grinding wheel 20 and the Honsitft 54 are delivered against the workpiece 18 and the workpiece 18 is simultaneously processed by both the grinding wheel 20 and the honing pin 54. In Fig. 2, the external cylindrical grinding machine 10 is shown in a working position in which the honing pin 54 is moved away from the workpiece 18. In addition, the grinding wheel 20 is not shown in FIG. 2 for the sake of clarity.

In order to grind the workpiece 18 by means of the external cylindrical grinding machine 10 shown in FIGS. 1 and 2 such that a sharp, burr-free, circular transitional edge exists between its cylindrical outer surface and its conical outer surface is first formed, the workpiece 18 is clamped in the workpiece clamping device 16 of the external cylindrical grinding machine 10 shown in Figures 1 and 2 and driven by the workpiece spindle 12 for rotation about the workpiece spindle axis. In a first grinding operation, the grinding wheel 20 rotating about the grinding wheel axis is then controlled against the workpiece 18 by the first feed device, controlled by the machine control, so that the cylindrical outer surface of the workpiece 18 is ground with high precision by means of a first profile section of the grinding wheel 20.

Subsequently, controlled by the machine control, the grinding wheel 20 rotating about the grinding wheel axis is delivered against the workpiece 18 by means of the first feed device such that the grinding wheel 20 grinds the conical outer surface of the workpiece 18 by means of a second profile section of the grinding wheel 20. Simultaneously with the grinding of the conical workpiece surface, actuated by the machine control, the honing pin 54 rotating about the auxiliary spindle axis is delivered against the workpiece 18 by means of the second feed device such that the honing surface of the honing pin 54 is pressed against the cylindrical outer surface of the workpiece 18. The pneumatic drive for moving the auxiliary spindle 56 has previously been adjusted in the course of setting the external cylindrical grinding machine 10 by an operator such that this drive presses the honing pin 54 against the workpiece 18 with a force of approximately 0.5 to 1 Newton via the auxiliary spindle 56. The honing pin 54 is pressed by means of the second feed device against the workpiece 18 in such a way that the honing surface 54 of the honing pin 54 arranged at right angles to the auxiliary spindle axis is arranged in a tangential plane to the cylindrical workpiece surface and touches it along a straight contact line in a section of the cylindrical workpiece surface adjoining the transition edge , The contact line extends on the honing surface as an uninterrupted line from an outer edge of the honing surface along a diameter passing through the cylinder axis of the honing pin 54 beyond the cylinder axis to the transition edge. In this case, the honing surface of the honing pin 54 protrudes in the direction of the contact line away from the cylindrical workpiece surface by approximately 0.2 to 0.3 mm beyond the transition edge. As a result, when grinding the conical workpiece surface By means of the grinding wheel 20 any resulting burr that protrudes beyond the transition edge into the area above the cylindrical workpiece surface is immediately removed by the honing pin 54 or by its Honoberfläche, so that a sharp and burr-free transition edge between the cylindrical and the conical outer surface of the Workpiece 18 is formed. However, machining by means of the honing pin 54 does not substantially change the mass of the cylindrical outer surface of the workpiece 18, which has previously been ground to a high precision, because the grinding performance provided by the honing pin 54 when machining or honing the cylindrical outer surface of the workpiece 18 is less than approximately 0.5%. the grinding performance provided by the grinding wheel 20 during grinding of the conical outer surface of the workpiece 18.

Controlled by the machine control, simultaneously with the completion of the grinding operation for grinding the conical outer surface of the workpiece 18 by means of the grinding wheel 20, the honing process for honing the cylindrical outer surface of the workpiece 18 by means of the honing pin 54 is completed. This ensures that no burr remains on the transition edge formed between the conical and the cylindrical outer surface of the workpiece 18.

The external cylindrical grinding machine 10 shown in FIGS. 1 and 2 is further provided with an end position monitoring device for the honing pin, which comprises two end position sensors. The one end position sensor detects the end position of the honing pin 54 shown in FIG. 1 (honing pin 54 delivered to the workpiece 18). The other end position sensor detects the end position of the honing pin 54 shown in FIG. 2 (honing pin 54 moved away from the workpiece 18). By means of the end position monitoring device can be prevented in an automatic or semi-automatic operation of the rotary grinding machine 10 a workpiece change when the honing pin 54 is delivered against the workpiece 18. In addition, the Endlagenüberwachungseinrichtung also allows the detection of a fracture of the honing pin 54 and / or wear of the honing pin 54 such that it must be replaced.

Parts of a grinding wheel 120, a circular cylindrical honing pin 154 and a workpiece 118 are shown in FIGS. 3 and 4, respectively. The grinding wheel 120 and the honing pin 154 are components of an external cylindrical grinding machine 110 constructed according to a second preferred embodiment of the invention. The remaining components of the external cylindrical grinding machine 110 are not shown in FIGS. 3 and 4 for the sake of clarity.

The workpiece 118 illustrated in FIGS. 3 and 4 is identical to the workpiece 18 formed in FIGS. 1 and 2. It is rotationally symmetrical with respect to a workpiece axis 114 and has a circular-cylindrical outer surface 113 and a conical outer surface 117, which are arranged adjacent to one another such that a circular transition edge 119 is formed between them.

In FIGS. 3 and 4, the external cylindrical grinding machine 110 is shown in a working position. In this working position, the workpiece 118 rotates about a workpiece spindle axis arranged coaxially with respect to the workpiece axis 114, as indicated by the arrow 115 in FIGS. 3 and 4. In addition, the grinding wheel 120 is delivered against the conical outer surface 117 of the workpiece 118, wherein the grinding wheel 120 about a grinding wheel axis (not shown) rotates, as indicated in Figures 3 and 4 by the arrow 121. Further, in this working position, the honing pin 154 is also delivered with its honing surface against the cylindrical outer surface 113 of the workpiece 118, wherein the honing pin 154 rotates about an auxiliary spindle axis 153 coaxial with the cylinder axis of the honing pin 154, as indicated by the arrow 155 in FIGS is. In this case, the honing surface of the honing pin 154 projects in the direction of the contact line 109 formed between the honing surface and the cylindrical workpiece surface 113 away from the cylindrical workpiece surface by 10% of the length of the contact line beyond the transition edge 119.

Thus, in the operative position of the grinding machine 110 illustrated in FIGS. 3 and 4, the workpiece 118 is simultaneously machined by both the grinding wheel 120 and the honing pin 154. The direction of rotation 115 of the workpiece 118 and the direction of rotation 121 of the grinding wheel 120 is set such that the speed of the grinding wheel 120 in the area where the grinding wheel 120 contacts the workpiece 118 is directed counter to the speed of the workpiece 118 due to its rotation about the workpiece spindle axis in that area. Further, the rotational direction 155 of the honing pin 154 is set such that the honing pin (or the honing surface) in the region of the intersection of the contact line 109 formed between the honing surface and the cylindrical workpiece surface 113 with the transition edge 119 has a velocity component counter to the direction of the velocity of the workpiece 118 in this area has.

The external cylindrical grinding machine 110 shown in FIGS. 3 and 4 essentially differs from the external cylindrical grinding machine 10 illustrated in FIGS. 1 and 2 only in that the honing pin 154 is not delivered obliquely from above, but essentially horizontally against the workpiece 118, so that the face of the honing pin 154 presses against the cylindrical outer surface 119 of the workpiece 118 substantially from a side facing away from the grinding wheel 120 against the feed direction in which the grinding wheel 120 is delivered against the conical outer surface 117 of the workpiece 118. This results in a good stabilization of the workpiece 118 during the grinding process, which can contribute to increasing the precision in grinding.

In a further, not shown in the figures, external cylindrical grinding machine according to an advantageous variant of the invention, the entire second feed device together with the measuring platform base, the pneumatic drive, the third carriage, the auxiliary spindle and the honing pin on a fourth carriage is arranged along a fourth straight linear guide parallel to Workpiece spindle axis (and thus parallel to the first linear guide) with respect to the first carriage movable. The mobility of the fourth carriage offers the possibility of carrying out a plurality of inventive methods in series succession during a single workpiece clamping in order to machine a plurality of sharp, burr-free transition edges between in each case two adjacent rotationally symmetrical surfaces of the workpiece.

In summary, it should be noted that a method and a device for cylindrical grinding are specified by the invention, which allow a reliable and precise cylindrical grinding of workpieces with a sharp and burr-free transition edge between two rotationally symmetric surfaces in large-scale production.

Claims (12)

1. Method for the circular grinding of a workpiece (18, 118) which has a workpiece axis (114) and, while the method is being carried out, rotates about the workpiece axis (114), whilst at the same time a grinding wheel (20, 120) rotating about a grinding-wheel axis and the workpiece (18, 118) are advanced towards one another, in order to grind a first workpiece face (117) which is designed to be rotationally symmetrical with respect to the workpiece axis (114), the workpiece further having a second workpiece face (113) which is designed to be rotationally symmetrical with respect to the workpiece axis (114) and which is defined by a rectilinear generatrix, and the two workpiece faces (117, 113) being arranged adjacently to one another in such a way that a circular transition edge (119) is formed between them, characterized in that, during grinding, an auxiliary abrasive tool (54, 154), which rotates about an auxiliary-tool axis (153) and has a plane abrasive surface arranged at right angles to the auxiliary-tool axis (153), is pressed against the workpiece (18, 118) in such a way that the abrasive surface is arranged in a tangential plane to the second workpiece face (113) and touches the second workpiece face (113) along a contact line (109), the abrasive surface projecting in the direction of the contact line (109) away from the second workpiece face (113) beyond the transition edge (119).
2. Method according to Claim 1, characterized in that the pressing of the auxiliary abrasive tool (54, 154) against the workpiece (18, 118) and the grinding of the first workpiece face (117) are terminated at the same time.
3. Apparatus for the circular grinding, in particular according to Claim 1 or 2, of a workpiece (18, 118), with a workpiece spindle (12) which rotates about a workpiece-spindle axis and which is provided with a workpiece holder (16) designed for receiving the workpiece (18, 118), with a grinding wheel (20, 120) rotating about a grinding-wheel axis, and with a first advancing device in order to advance the grinding wheel (20, 120) and the workpiece (18, 118) towards one another, characterized in that the apparatus further comprises an auxiliary abrasive tool (54, 154) which rotates about an auxiliary-tool axis (153) and which has a plane abrasive surface arranged at right angles to the auxiliary-tool axis (153), a second advancing device for advancing the auxiliary abrasive tool (54, 154) towards the workpiece (18, 118), and a control device for controlling the apparatus in such a way that, by means of the first advancing device, the grinding wheel (20, 120) and the workpiece (18, 118) are advanced towards one another, in order to grind a first workpiece face (117) in one grinding operation, and in that, during the grinding operation, the auxiliary abrasive tool (54, 154) is advanced towards the workpiece (18, 118) by means of the second advancing device in such a way that the auxiliary abrasive tool (54, 154) presses with its abrasive surface against a second workpiece face (113), the two workpiece faces (117, 113) being designed to be rotationally symmetrical with respect to the workpiece-spindle axis, and the second workpiece face (113) being defined by a rectilinear generatrix, and the two workpiece faces (117, 113) being arranged adjacently to one another in such a way that a circular transition edge (119) is formed between them, and the abrasive surface being arranged in a tangential plane to the second workpiece face (113) and touching the second workpiece face (113) along a contact line (109), and the abrasive surface projecting in the direction of the contact line (109) away from the second workpiece face (113) beyond the transition edge (119).
4. Apparatus according to Claim 3, characterized in that a portion of the auxiliary abrasive tool (54, 154) is of cylindrical design, the abrasive surface being the cylinder base area.
5. Apparatus according to Claim 3 or 4, characterized in that the auxiliary abrasive tool (54, 154) is designed in such a way and, while being pressed against the second workpiece face (113), is arranged in such a way that the contact line (109) on the abrasive surface extends as an uninterrupted line from an outer margin of the abrasive surface, along a diameter leading through the auxiliary-tool axis (153), beyond the auxiliary-tool axis (153) as far as the transition edge (119).
6. Apparatus according to Claim 5, characterized in that, while the auxiliary abrasive tool (54, 154) is being pressed against the second workpiece face (113), the workpiece (18, 118) is made to rotate about the workpiece-spindle axis in such a way and the auxiliary abrasive tool (54, 154) is made to rotate about the auxiliary-tool axis (153) in such a way that the auxiliary abrasive tool (54, 154) has, in the region of the intersection point of the contact line (109) with the transition edge (119), a speed component opposite to the direction of the speed of the workpiece (18, 118) in this region.
7. Apparatus according to one of Claims 3 to 6, characterized in that the auxiliary abrasive tool (54, 154) comprises a honing pin (54, 154) or a precision-grinding stone.
8. Apparatus according to one of Claims 3 to 7, characterized in that it further comprises a conditioning tool for the conditioning of the abrasive surface.
9. Apparatus according to one of Claims 3 to 8, characterized in that it further comprises means for the selective setting of the force with which the auxiliary abrasive tool (54, 154) presses against the second workpiece face (113).
10. Apparatus according to one of Claims 3 to 9, characterized in that the auxiliary abrasive tool (54, 154), while being pressed with the abrasive surface against the second workpiece face (113), machines the second workpiece face (113) with a substantially lower grinding power than the grinding power with which the grinding wheel (20, 120) at the same time machines the first workpiece face (117).
11. Apparatus according to one of Claims 3 to 10, characterized in that the auxiliary abrasive tool (54, 154) is arranged on a platform (50) which is movable with respect to the workpiece spindle (12) and which is equipped with at least one measuring instrument.
12. Apparatus according to one of Claims 3 to 11, characterized in that the auxiliary abrasive tool (54, 154), while being pressed against the second workpiece face (113), is arranged on a side of the workpiece (18, 118) which faces away from the grinding wheel (20, 120).

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