Abstract:
A drive unit is configured for a stamping rivet setting device and has an electric direct drive which contains motor components that concentrically surround a control element which can be linearly moved in the axial direction. In order to absorb the required torques while allowing a compact construction of the device, in particular in relation to a component side, a drive housing has an asymmetrical configuration in a connecting region between a main part and a guide part in which the control element is guided, for the purpose of asymmetrical torque transmission. In addition or alternatively thereto, the highly compact construction achieves an efficient cooling by an inner cooling unit, in particular air flowing through a free inner space in which the motor components are arranged.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation, under 35 U.S.C. §120, of copending international application No. PCT/EP2016/056869, filed Mar. 30, 2016, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2015 205 995.2, filed Apr. 2, 2015; the prior applications are herewith incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a drive unit for a setting device, in particular for a rivet setting device. 
         [0003]    Such a drive unit can be found in published, non-prosecuted German patent application DE 10 2013 012 223 A1, corresponding to U.S. Pat. No. 9,339,865. The disclosed drive unit is a direct drive where motor components, namely a rotor and a stator, surround the actuator element concentrically. The motor components and the actuator element, in this case, are mounted in a common drive housing. 
         [0004]    Along with the concept of the direct drive with the motor components surrounding the actuator element in a concentric manner, solutions are also known where the electric motor is mounted laterally next to a setting unit and is coupled with the actuator element, for example by a gear drive. However, this requires a marked increased installation space at least toward one side. 
         [0005]    In the case of such a drive unit, in general the rotational movement of the electric motor is converted into a linear actuator movement of the actuator element. A punch is moved against a work-piece by use of the actuator element, in this connection the punch is pressed at a high force against the work-piece. The punch can be realized itself, in this connection, as a processing tool, such as, for example, a punching tool. Such a drive unit, however, is preferably used to press a connecting element into a component. The connecting element, in this connection, is in particular a pressing element, such as, for example, a press nut, a press bolt and in particular a rivet, preferably a self-piercing rivet. In this case, therefore, two components, in particular two metal sheets, are generally connected together using the connecting element. 
         [0006]    Such drive units are used, in particular, in the automobile industry for connecting two components together. Self-piercing rivet technology has replaced spot welding, in particular in the case of hybrid components, that is to say when connecting components (“sheets”) produced from different, also non-metal materials. The drive unit, in this connection, is fastened on a machine tool, which can also be, in particular, a robot arm of an industrial robot. High cycle rates are demanded for setting the connecting elements. In order to ensure a reliable connection, the drive unit has to exert a very high setting force which acts in the axial direction. In particular when setting self-piercing rivets, the setting force is, for example, in excess of 50 kN. This demands correspondingly large and robust dimensioning of the drive unit. 
         [0007]    At the same time, however, on account of the complex component geometry, in particular in the case of vehicle bodies, as compact a drive unit as possible is demanded which has as few interfering contours as possible in order to be able to set the rivets reliably even in tight installation areas. In addition, a low weight is striven for in order to keep the accelerating masses small when moving the machine tool, e.g. the robot arm. 
         [0008]    A typical setting operation in particular of a self-piercing rivet is subdivided, in this case, into a feed path where the self-piercing rivet is fed to the component and the subsequent actual setting operation where the setting force increases in an almost abrupt and powerful manner. 
       SUMMARY OF THE INVENTION 
       [0009]    Proceeding from here, the object underlying the invention is to provide a compact drive unit in particular for a rivet setting device. 
         [0010]    The object is achieved according to the invention by a drive unit with the features of the main claim. The drive unit includes, in this connection, an electric direct drive, in particular a servomotor, with a rotor pack and a stator pack as motor components. In addition, the drive unit includes an actuator element which is displaceable linearly in an axial direction by the direct drive, the actuator element being concentrically surrounded by the motor components for this purpose. The actuator element and the motor components are accommodated, in this case, in a free interior of a common drive housing. The drive housing contains, in this case, a front component side and a rear machine side. A front region of the drive unit, which faces the component to be processed in operation in the mounted state, is understood in this connection as the component side. Correspondingly, a rear region of the drive unit, which is situated in operation on a rear side remote from the component, is understood as the machine side. In this case, a very compact construction with a smaller radial extent is required in particular toward the component side. 
         [0011]    The terms rotor pack or stator pack are to be understood in the present case in general as the necessary electromagnetic components of the electric motor, such as, for example, a coil winding and/or permanent magnets for realizing the rotor or stator. In addition, a drive element, in particular a spindle element, especially a spindle nut, is necessary for converting the rotational movement of the rotor into the linear movement of the actuator element. The drive element is also designated in the present case as a motor component. 
         [0012]    The drive housing additionally contains a main part and a guide part which is connected to the main part in a connecting region. The guide part, in this case, is realized in the axial direction in particular as a rear end part of the drive housing. The actuator element, in this case, is guided inside the guide part in particular so as to be slidingly displaceable. On account of the forces occurring during the setting operation, in particular when there is an abrupt increase in an axial setting force, a torque when the rotational movement is converted into the axial actuating movement also increases powerfully. In order to absorb the high torque reliably and at the same time having a compact design, the main part and the guide part—when viewed in a plane perpendicular to the axial direction—contain an asymmetric design in the connecting region in such a manner that the torque is transmitted in an asymmetric manner. An asymmetric torque transmission is to be understood, in this connection, as the torque not being transmitted from the motor components to the drive housing in a uniformly distributed manner in the axial direction and neither consequently about a rotational axis of the direct drive. The rotational forces are consequently not actually distributed uniformly about the periphery of the drive housing. Rather, the drive housing is realized in such a manner that a larger part and preferably the main part of the torque is absorbed in the rear part of the drive housing toward the component side. Torque transmitting elements, which interact together via torque surfaces to transmit the torque, are arranged, in this case, in the connecting region between the guide part and the main part. The torque transmitting elements are consequently arranged at least predominantly and preferably completely on the machine side. Transmitting a main part of the torque or the term completely is to be understood, in this connection, as at least more than 70 and in a preferred manner more than 90% of the overall torque being transmitted on the machine side and that consequently, at best, a smaller torque transmission is effected between the guide part and the main part on the component side. 
         [0013]    The measure achieves the particular advantage of the drive housing and consequently the entire drive unit being able to be realized in an extremely compact and space-saving manner toward the component side. Correspondingly, fewer interfering contours are consequently realized toward the relevant component side and the drive unit only has a small radial extent toward the component side. 
         [0014]    In a preferred design, it is provided, in this case, that the torque transmission is effected exclusively on the machine side. The torque transmitting surfaces provided for the torque transmission are consequently arranged exclusively on the machine side. 
         [0015]    With regard to as compact a configuration as possible, the main part also contain, in this case, just a thin housing wall precisely in the connecting region on the component side, whereas toward the machine side it contains a solid wall by which the torque is able to be absorbed. The housing wall toward to the component side, in this case, is simply a thin metal wall. For reasons of weight, the housing is preferably realized fundamentally from a preferably metallic, lightweight construction material, in particular aluminum. In this case, the wall thickness is preferably simply between 2 and 4 mm, and in a preferred manner is 2.5 mm. 
         [0016]    Overall, the drive housing contains an asymmetric configuration when viewed in a plane perpendicular to the axial direction. The main part is preferably realized, in this case, toward the component side as a part cylinder, in particular a half-cylinder. Consequently, when viewed in cross section, the main part—at least in the connecting region—is realized toward the component side as a part circle. Toward the machine side, the main part, in contrast to this, is preferably realized in an approximately block-shaped manner such that the main part therefore toward the machine side, when viewed in cross section, contains a polygonal, in particular approximately rectangular and preferably a trapezoidal cross-sectional area. Correspondingly, the guide part in the connection region is realized in a complementary manner to this. 
         [0017]    With regard to the design being as compact as possible in particular toward the component side, it is provided, in this case, in an expedient manner that the radial extent of the main part to the machine side is greater by at least 25% and preferably by at least 40 or 50% than its radial extent toward the component side. The maximum radial extent toward the component side, in this case, is preferably a maximum of between 60 and 70 mm and is preferably simply 65 mm. Correspondingly, the radial extent toward the machine side is clearly in excess of this and in particular is within the range of between 80 and 100 mm. 
         [0018]    With regard to a reliable transmission of the torque, the corresponding torque transmitting surfaces are realized as large as possible. In an expedient manner, in this case, the main part and the guide part interlock in a positive locking manner to realize the torque transmitting surfaces. In particular, there are consequently no connecting elements, such as screws, which are used for the torque transmission. At best small intermittent torque transmitting surfaces would be realized in the case of screws or other bolt-shaped elements that extend in the axial direction. The torque transmitting surfaces are realized, in this case, on a peripheral contour as a result of the positive-locking interlocking. With regard to the asymmetrical torque transmission, the peripheral contour, also designated as the engagement contour, is realized asymmetrically. In particular, once again a main part of the torque transmitting surfaces and preferably all the torque transmitting surfaces are realized by the engagement contour in the region toward the machine side. This allows for a corresponding thin-walled design of the drive housing in the region toward the component side. 
         [0019]    In an expedient manner, the engagement contour—when viewed in a plane perpendicular to the axial direction—has a part-circular progression toward the component side. The engagement contour consequently does not provide any contact surface for torque transmission toward the component side. 
         [0020]    In addition, the engagement contour, when viewed in cross section, is preferably realized toward the machine side in the manner of a polygon and in particular in a triangular manner. Overall, the main part consequently contains a cross sectional area that is formed by a polygon and by a part-circle that connects thereto. The part-circle is preferably at least a semi-circle. 
         [0021]    The torque transmission is preferably effected exclusively, at least 90%, by means of the engagement contour. 
         [0022]    The engagement contour, in this case, is expediently realized on an underside of a fastening flange. The guide part is placed with the fastening flange onto the main part of the drive housing and is connected to the same. The engagement contour consequently extends in the axial direction into the main part of the drive housing. The lateral surface of the contact contour, which realizes the torque-transmitting surfaces toward the machine side, rests, in this case, in a precise-fitting manner in a corresponding receiving contour on the main part. When viewed in a longitudinal section, an approximately step-like design is achieved as a result of realizing the engagement contour on the underside of the fastening flange. 
         [0023]    In a rear region, the guide part additionally contains a tubular part region in which the actuator element is guided in a slidingly displaceable manner. The tubular part region extends at least to the fastening flange. 
         [0024]    The tubular part region preferably projects a little into the main part and forms an abutment e.g. for a bearing arrangement of the motor component. 
         [0025]    For the non-rotatable displacement of the actuator element inside the tubular rear part region, a corresponding anti-rotation element, which is realized in particular as a polygonal sliding element, is realized on the actuator element. The sliding element is connected in a non-rotatable manner to the actuator element in the manner of a plate-shaped element in particular on the rear side of the actuator element. 
         [0026]    In operation, the actuator element is displaced in the axial direction by a defined feed stroke by the direct drive. In the case of the maximum feed stroke, the actuator element is situated, in this case, in an extended position. The drive unit is configured with regard to its dimensions preferably in such a manner that in the extended position, the anti-rotation element is positioned at the same axial height of the connecting region in which the torque transmitting surfaces are realized. The design is based on the consideration that the maximum torque typically occurs in the extended state and that as direct a transmission as possible of the torque should then be effected from the actuator element via the anti-rotation element to the drive housing without there being too large an axial distance between the torque transmitting surfaces and the anti-rotation element. The term “at the same axial height” is understood in this connection as, in the extended position, the anti-rotation element being precisely at the height of the connecting region and of the torque-transmitting surfaces or being at a spacing in the axial direction of a maximum of between 10 and 20 mm from the connecting region, that is to say from the engagement contour. 
         [0027]    For realizing the direct drive, the actuator element is realized in a rear region preferably as a spindle which is surrounded in a part region by a spindle nut. The spindle nut itself is once again non-rotatably connected to the rotor pack of the direct drive. To this end, the spindle nut is preferably fastened on the radial inside of a rotor sleeve and the rotor pack is fastened on the outside of the rotor sleeve. Correspondingly, the stator pack is then arranged radially on the outside of the rotor pack. 
         [0028]    As a result of the configuration with the rotor located in the inside, a very compact design of the entire drive unit overall is ensured. 
         [0029]    On account of the necessary high setting forces, the drive unit is realized overall in a suitable manner and is capable of generating an axial force onto the actuator element of &gt;50 kN and in particular of &gt;60 kN. On account of the special setting operation in the case of a self-piercing rivet setting operation, the force occurs as a short-term peak load. The direct drive is correspondingly configured in order to be able to generate the forces and is configured for peak current consumption of &gt;30 A and in particular of &gt;40 A up to preferably 60 A. The electric motor additionally contains overall, in this case, an electric peak performance of several kW, in particular of between 2 and 4 kW. Peak performance for a self-piercing rivet operation, in this case, is applied, for example, for a duration in each case within the range of between 100 and 150 ms. As during the peak performance at best only a small axial adjustment is still effected, an extremely high power dissipation, which is also several kW, occurs during the peak performance during the actual setting operation. The power dissipation is thus, for example, approximately 2.5 kW. On account of the high cycle rates additionally striven for, this means that the direct drive overall is also exposed to a high thermal load. 
         [0030]    In order to provide for a cooling of the drive unit, in a preferred configuration the main part of the drive housing toward the machine side and preferably exclusively toward the machine side is consequently additionally provided with a cooling rib structure. 
         [0031]    On account of the high thermal load and the extremely compact design, there is, however, the risk that even with such a cooling rib structure only deficient cooling is achieved. In principle, it is possible to provide the main part with coolant channels, through which, therefore, a cooling fluid is then run in the solid material of the main part for cooling the main part. As in the case of such electric drive units, hydraulic connections should be dispensed with as much as possible, hydraulic cooling is not desirable. 
         [0032]    Proceeding from this point, a further aspect of the invention underlying the invention is to ensure reliable cooling of such a drive unit in a reliable manner even in the case of a compact design. 
         [0033]    In order to ensure sufficient cooling, a cooling device is arranged in the main part in a preferred manner simply toward the machine side for the internal cooling of the motor components. To this end, the cooling device is realized in such a manner that a fluid can flow into the interior of the drive housing. The fluid, in this case, is in particular gas/air and not a hydraulic liquid. The use of a liquid, however, is not in principle excluded. 
         [0034]    A decisive consideration in this connection is that the free interior in which the motor components are arranged is traversed directly by the fluid. Contrary to, for example, in the case of simply hydraulic housing cooling systems where a corresponding fluid simply flows through the solid wall of the main part or of a cooling body, as a result of the internal cooling proposed here, the cooling fluid is therefore guided directly through the interior in which the components are stored. This results therefore in the heat being output directly from the motor components to the fluid such that direct, immediate and consequently efficient cooling is affected. Sufficient cooling is also ensured consequently, in particular, when using air as fluid as a result of the direct cooling. Therefore, any hydraulic components for the cooling and in particular also for the entire drive unit are preferably dispensed with. 
         [0035]    To realize the cooling device, cooling channels, which open out from an outside into the free interior of the drive housing, are realized, in this case, inside the main part. In an expedient manner, the cooling channels are realized, in this case, as bores. In a preferred manner, in this case, realized on the inflow side is an in particular single feed channel which then opens out into a free annular chamber, which is therefore realized as a quasi-distributing chamber such that the inflowing fluid is distributed on the periphery as uniformly as possible. 
         [0036]    At a spacing in the axial direction from this, realized in an expedient manner on an outflow side is also a free annular chamber which serves as a collecting chamber and extends from the at least one outlet channel in the radial direction to an outside of the main part. The corresponding connections for the fluid are arranged in a preferred manner on an outside of the main part on the machine side such that no connections are present on the component side. The two annular chambers on the inflow side and outflow side are realized, in this case, in each case on the end of the motor components. In operation, the fluid consequently flows via the feed channel into the distributor annular chamber on the inflow side, then flows in the axial direction past the motor components distributed over the entire periphery and reaches the collecting chamber on the outflow side and leaves the collecting chamber via corresponding outlet channels. 
         [0037]    Flow channels which are realized as grooves for the fluid are realized in an expedient manner for cooling along the motor components. The grooves extend, in this case, in particular directly along at least one of the motor components. The grooves, in this case, are preferably distributed about the periphery and are realized, in particular, distributed in an equal manner. For example, more than five and preferably more than eight, for example between eight and 15 flow channels are realized. As a result of additionally providing such flow grooves, a large cross-sectional flow area is provided overall such that, overall, only a small amount of dynamic pressure is created and consequently a sufficient cooling current and consequently sufficient cooling is ensured. 
         [0038]    Grooves are to be understood in general as groove-like channels which extend from the inflow side to the outflow side. They run, for example, in a straight line as longitudinal grooves. They can, in principle, however, also assume a meander-shaped progression. 
         [0039]    The motor components, especially the rotor pack or the stator pack are usually fastened, in this case, on a carrier. In a preferred manner, the carrier preferably contains the grooves for realizing the flow channels. Efficient direct cooling of the at least one motor component is achieved as a result of the measure. The motor component is, in particular, the rotor pack which is fastened on the already mentioned rotor sleeve. The grooves are worked into the outside of the rotor sleeve, on which the rotor pack is also fastened. 
         [0040]    In an expedient design, the grooves are arranged on a side of the carrier located opposite the motor components (rotor pack or stator pack). They do not necessarily have to be incorporated in the carrier in this case. The consideration underlying said design is that a high packing density of the individual magnets, for example of the rotor pack, is frequently necessary for electrical reasons such that on the side of the carrier facing the magnets, no sufficient space is made possible for providing grooves as flow channels. 
         [0041]    In the case of the design preferred here, the carrier is realized as a rotor sleeve which is connected to a drive element especially of the spindle drive and in particular to the spindle nut for transmitting the rotational movement. In a preferred manner, the grooves are then provided in the outer casing of the spindle nut to which the rotor sleeve is non-rotatably connected. The rotor sleeve, in this case, surrounds the spindle nut in a typically concentric manner and in a preferred manner abuts—up to the grooves—over the entire surface against the outer casing of the spindle nut. 
         [0042]    In order to ensure sufficient cooling and in particular in addition to the grooves, spaces or gaps inside the motor components, in particular between the individual magnets, are utilized as further flow channels, i.e. they are incorporated in the cooling path from the inlet side to the outlet side. 
         [0043]    In an expedient manner, the entire cross-sectional area of the flow channels is generally equal to or greater than a cross sectional area of a feed channel, via which the fluid is supplied. The dynamic pressure is kept low as a result. If just grooves are used as flow channels, they form the overall cross-sectional area exclusively. If the gaps are additionally used as flow channels, they contribute to the overall cross-sectional area. 
         [0044]    A pump element, which is directly incorporated in a preferred manner into a channel portion in particular of the feed channel, is additionally arranged with regard to the necessary traversing of the main part by the fluid. When using air as fluid, the pump element is realized, in this case, especially as a fan or blower. In an expedient manner, air is sucked-in out of the surrounding area by the pump element such that a connection to a cooling circuit is therefore not necessary. 
         [0045]    In an expedient manner, the blower is realized, in this case, for an air flow of several 10 l/min and preferably of in excess of 100 l/min. It is especially realized for an output of between 120 and 150 l/min. 
         [0046]    The pump unit, in this case, is additionally preferably a control and/or regulatable pump element, the delivery capacity of which is controlled or regulated in dependence on a current cooling requirement. 
         [0047]    On account of the displaceable bearing arrangement of the actuator element inside the drive housing, the actuator element is usually guided in a slidingly displaceable manner by lubricant such as, for example, oil or grease. In an expedient further development, a flow chamber for the fluid, which is sealed toward the actuator element, is now realized inside the drive housing. The seal consequently ensures that the fluid does not come into contact with such lubricants such as oil, bearing grease etc. Such contact would result, on the one hand, in stress and contamination of the interference components for the fluid, especially also for the blower. On the other hand, there would also be lubricant consumption as a result which would lead either to increased maintenance expenditure or to a shortened service life. This is consequently avoided in an advantageous manner by the sealed flow chamber. 
         [0048]    For sealing the flow chamber, the fluid consequently flows simply between two sealing regions which are axially spaced apart from one another. The sealing regions are obtained in particular by sealed bearings by way of which the rotor sleeve is mounted. In particular, when a flow is guided along the longitudinal grooves on the outside of the rotor sleeve, flow guiding is consequently ensured in an (annular) chamber outside of the actuator element in combination with the sealed bearings and consequently contact with the lubricant is avoided. 
         [0049]    With regard to a desired compact design, the drive unit has an overall length which is composed of twice the actuating stroke plus a constant which is simply within the range of between 70 and 100 mm. The actuating stroke in the case of such drive units is typically within the range of between 120 and 200 mm and is preferably, for example, within the range of 160 mm. The overall length, in particular, on account of the previously described concepts and of the fundamental design as a direct drive is consequently simply approximately between 390 and 420 mm in the case of an actuating stroke of 160 mm. 
         [0050]    The constant corresponds, in this case, in particular to a length of the spindle nut. 
         [0051]    In order to achieve as compact a design as possible overall, especially a short installation length, a drive unit is provided. In the case of conventional drive units, the actuator element is realized in multiple parts, the rear part being realized by a spindle element, conventionally the spindle and a front plunger. The spindle, in this case, is provided with a spindle thread and is conventionally realized as a separate construction unit. The separate construction unit is connected to the plunger in a connecting region. 
         [0052]    In order to achieve as compact and short a design as possible, it is now provided according to the invention that the spindle element and the plunger are realized as a one-piece part without mechanical connecting elements. In particular, the two parts are realized from a common workpiece, no connecting parts are therefore present between the two parts, neither as a result of mechanical nor other connections. In the case of conventional designs, a connection, which can accept high forces, is necessary between the two separate parts on account of the high torque occurring. In a corresponding manner, the connecting region is also configured in a comparatively large manner. As a result of one-piece design, a clearly shorter design can now be achieved. A further advantage of the one-piece design can be seen in the improved rigidity of the entire actuator element. 
         [0053]    The design is advantageous in particular in the case of drive units where the plunger is realized as a tube in which further components are received. Thus, it is necessary, for example, in the case of many setting operations for a hold-down device, for example for pressing the components, to be provided. Especially in the case of such designs with an integrated hold-down device, the hold-down device is guided on the plunger, in particular inside the plunger tube, so as to be slidingly displaceable against the spring force of a spring element. 
         [0054]    As a result of the measures described here, an extremely compact drive unit overall is achieved in particular for a rivet setting device which contains simply a short overall length with at the same time a small radial extent at least toward the component side. Such a drive unit is conventionally fastened on a holder of a machine. The holder is preferably a C frame. The drive unit is held expediently in the C frame by way of a front part region of the drive housing. In addition, the actuator element conventionally contains the plunger on its front end. The actuator element is consequently realized overall as a spindle in its rear part region and as a plunger in its front region, for example as a plunger rod or also as a plunger tube. The plunger moves, in this case, in the axial direction to exert the feed stroke at the front out of the front end of the drive housing. In addition, a punch and additionally a hold-down device and/or an automatic feed unit for fastening elements, in particular rivets, is conventionally realized on the plunger. The rivets are fed in this connection, in particular, by a feed hose. 
         [0055]    The drive unit described here is not limited to use with self-piercing rivet devices, but is generally useable for applications where high axial linear forces are necessary in the case of compact installation space, in particular for applications in the field of mechanical joining technology. In a preferred manner, the drive unit is used with joining or setting units by way of which joining or connecting elements are inserted, in particular pressed, into a component. The connecting elements are, for example, automatic punching elements such as, for example, self-piercing rivets or piercing nuts or also other pressing elements, such as nuts or bolts, for pressing into a pre-punched (metal) component. 
         [0056]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0057]    Although the invention is illustrated and described herein as embodied in a drive unit for a setting device, in particular a rivet setting device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0058]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0059]      FIG. 1  is a diagrammaticm, side view of a setting device, in particular a rivet setting device, with a holder in the shape of an arched C, on which a drive unit is fastened according to the invention; 
           [0060]      FIG. 2  is a side view of the drive unit shown in  FIG. 1 ; 
           [0061]      FIG. 3  is a side view of the drive unit shown in  FIG. 1 ; 
           [0062]      FIG. 4  is a longitudinal sectional view through the drive unit according to  FIG. 2 , 
           [0063]      FIG. 5  is a perspective view of the drive unit, a guide part of the drive housing, among other things, being blanked out; 
           [0064]      FIG. 6  is a perspective view of the drive unit where, among other things, a main part of the drive housing is blanked out; and 
           [0065]      FIG. 7  is a sectional view taken along the cutting line VI-VI in  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0066]    Identically acting parts are provided with the identical references in the figures. 
         [0067]    Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a setting device  2  which includes a drive unit  4  which is fastened on a holder  6  which is realized in particular as a C-frame. The drive unit  4 , in this case, is fixedly gripped in a front part region by an upper arm of the holder  6 . The setting device  2  is a punching device for inserting self-piercing rivets (not shown in any detail here) into components to connect two components. In this connection, the components are moved into the C-frame, then a self-piercing rivet is moved by the drive unit  4  against the components to be connected and the components to be connected are connected by the self-piercing rivet. The lower frame arm, in this case, forms an abutment. Such a setting device  2  is used in particular for connecting components in the case of motor vehicles. The holder  6 , in this connection, is fastened in particular on a movable machine part, for example on a robot. As an alternative to this, the components to be joined or even an entire automobile body can be moved correspondingly into the opening of the holder  6 . 
         [0068]    The drive unit  4  extends overall from a rear end in an axial direction  8  to a front end. It contains a drive housing  10  which has a front side which is designated as a component side  12  and a rear side which is designated as the machine side  14 . The sides are, with reference to the axial direction  8 , oppositely located outsides of the drive unit  4 , specifically the side which is oriented to the holder  6  in the mounted state (machine side  14 ) or is oriented directed away from the holder  6  (component side  12 ). 
         [0069]    The basic geometry of the drive unit  4  and in particular also of the drive housing  10  can be found in  FIGS. 2 and 3 . The drive housing includes a central main part  16 , a rear guide part  18  and a front, further guide part  20 . While the guide parts  18 ,  20  are realized in a manner substantially rotationally symmetrical to the axial direction  8  with cylindrical lateral surfaces—in the event of the rear guide part  18  up to a connecting region  21  to the main part  16 —the main part  16  is realized asymmetrically with reference to the axial direction  8  and not rotationally symmetrically. It is certainly realized toward the component side  12  in the manner of a part cylinder and toward the machine side  14  as a substantially block-shaped element. As can additionally be found in  FIGS. 2 and 3 , the main part  16  contains exclusively, and additionally exclusively toward the machine side  14 , a cooling structure formed by cooling ribs  22 . The drive housing  10  consists overall preferably of a metallic light construction material with good thermal conductivity, in particular aluminum. 
         [0070]    On the machine side  14  in the block-shaped part of the drive housing  10 , inlet openings of cooling channels can be seen, namely of one (single) feed channel  24   a  and multiple outlet channels  24   b . Electric connector plugs  26  for a power supply and also for data connection of control lines can additionally be seen on the machine side  14 . A blower  28  can also be seen inside the feed channel  24   a . In operation, where necessary, a cooling fluid, in particular ambient air, is sucked-in b the blower  28  and by the cooling channels  24   a ,  24   b  and conducted through the interior of the drive housing  10  and output again via the outlet channels  24   b.    
         [0071]    The design of the drive unit  4  is produced in particular from the sectioned representation in  FIG. 4  and additionally also from the perspective representations in  FIGS. 5 and 6 . 
         [0072]    The three housing parts—rear guide part  18 , main part  16  and front further guide part  20 —can be seen in the sectioned drawing. The rear guide part  18 , in this case, contains a tubular, rear part region  30  which reaches up to a fastening flange  32  and which is closed by a cover  33  at the oppositely situated end. A support part  34  of the part region  30  projects into the main part  16 . The fastening flange  32  contains, in this case, the identical asymmetric cross-sectional contour as the main part  16 , as is shown in particular by a comparison of  FIGS. 5 and 6 . 
         [0073]    The main part  16  contains toward the component side  12  simply one thin housing wall  36 . The thickness of the wall, in this case, is within the range of a few millimeters between 2 and 4 mm. The comb-like structure for the realization of the cooling ribs  22  can be found on the machine side  14 . The further front guide part  20  connects to the main part  16  in the axial direction  8 . The further front guide part is also realized in a tubular manner. It is realized in a stepped manner in this connection and is tapered toward the front. A front bearing  38  is arranged in the rear widened part region, in particular two roller bearing rings being arranged for this purpose in the exemplary embodiment. 
         [0074]    A direct drive  40 , which is realized as a servomotor, is realized in the main part  16 . The direct drive includes a stator located on the outside which is formed by a corresponding stator pack  42  as well as an inside rotor which is formed by a rotor pack  44  and a rotor sleeve  46 . The rotor rotates in operation about a rotational axis shown by the broken line in  FIG. 4 . The rotor pack  44 , in this case, is fastened on the outside of the rotor sleeve  46 . The rotor sleeve  46  is tapered in a step-like manner and contains a front bearing region which is mounted in the front bearing  38  toward the outer wall of the further guide part  20 . In the rear part, the rotor sleeve  46  is mounted on the inside by a rear bearing  48 , the rear bearing  48  being arranged between the support part  34  and the rotor sleeve  46 . As can easily be seen, the front bearing  38  is clearly larger than the rear bearing  48  as considerably larger forces have to be absorbed in the region of the front bearing  38 . The design and arrangement of the rear bearing as an inner bearing between the rotor sleeve  46  and the support part  34  are worth pointing out. As a result, a very compact design can be achieved with only a small radial extent R 1  toward the component side  12 . 
         [0075]    On account of the asymmetric design of the main part  16 , the radial extent R 2  toward the machine side  14  is clearly larger. 
         [0076]    The rotor sleeve  46  is fixedly connected on the inside to a spindle nut  50  such that, in operation, a rotational movement of the rotor is transmitted to the spindle nut. A spindle  52 , which is mounted so as to be slidingly displaceable inside the tubular part region  30 , is received by the spindle nut  50 . 
         [0077]      FIG. 4  shows a situation with the spindle  52  retracted fully into the rear position. The spindle can be displaced forward by a feed stroke H in the axial direction  8 . 
         [0078]    At the maximum feed stroke H, the rear end of the spindle  52  is situated at the height of the fastening flange  32  or somewhat above the rear bearing  48 . 
         [0079]    The spindle  52  is guided non-rotatably inside the guide part  18 . To this end, an anti-rotation element in the form of a somewhat block-shaped plate  54  is fastened on the rear end of the spindle  52 . The anti-rotation element contains beveled corner regions. On account of the polygonal design and complementary guiding inside the guide part  18 , the spindle  52  is consequently guided in a non-rotatable manner. 
         [0080]    A plunger  56 , which is preferably realized as a tube and in which two spring elements  58  with different spring hardnesses are arranged in the exemplary embodiment, connects to the spindle  52  in the front part region. The spring elements  58 , in this case, are each realized as compression springs (helical springs). A hold-down device  59 , which emerges out of the front of the plunger  56 , is guided so as to be slidingly displaceable inside the plunger  56 . The hold-down device  59 , in this case, is resiliently mounted in opposition to the spring force of one of the two spring elements  58 . In addition, a punch  60  is mounted so as to be sliding displaceable inside the hold-down device  59 . In the exemplary embodiment, another compression rod  61  is fastened in particular on the end of the punch  60  so as to be exchangeable. The compression rod  61  is connected to the spindle  52  in this connection just as the plunger  56 . The three components  52 ,  56 ,  61  together form, in this case, an actuator element  62 . If the spindle  52  is displaced forward by the feed stroke H, the plunger  56  moves, and with it the compression rod  61 , out of the front further guide part  20 . 
         [0081]    Overall, the drive unit  4  contains an overall length L which is defined by the distance between the rear end of the guide part  18  and the front end of the further guide part  20 . On the front end of the further guide part  20 , the drive unit  4  is held on the holder  6  ( FIG. 1 ) overall by, for example, a holding element  64  in the manner of a clip. 
         [0082]    A feed unit, which is not shown here in any more detail and by which the individual connecting elements, in particular self-piercing rivets, are fed in singles and then are set by the punch  60 , additionally connects at the front in the axial direction  8 . 
         [0083]    The realization variant shown here with the plunger tube  56  and the hold-down device  56  is realized for a special self-piercing rivet application. In the case of other designs, the hold-down device  56 , for example, is not integrated into the drive unit  4 . 
         [0084]    On account of the high setting forces occurring during operation, in particular in the case of an abrupt increase during the punching operation when inserting a punching element, for example a self-piercing rivet, into a component, the transmission of a high torque between the spindle  52  and the drive housing  10  is necessary. 
         [0085]    In order to obtain a compact design, in particular as small an extent as possible in the radial direction R 1 , the drive housing  10  is realized for asymmetrical torque absorption in a connecting region  21 , that is to say in the region of the fastening flange  32 . To this end, it is provided, in particular, that the fastening flange  32  contains on its underside an asymmetrical engagement contour  68  which corresponds in a corresponding manner to a receiving contour  70  of the main part  16 . The engagement contour  68  is formed, in this case, by an approximately plate-shaped shoulder on the underside of the fastening flange  32 , the plate containing a peripheral contour which is realized toward the component side  12  as a part circle and toward the machine side  14  as a polygon and is realized in particular in the manner of a triangle. The lateral surfaces of the plate of the engagement contour  68  define, in this case, torque transmitting elements and in particular torque transmitting surfaces  72 . The receiving contour  70  of the main part is realized in a precisely complementary manner to the engagement contour  68 . The two parts are consequently inserted into one another in a play-free manner. On account of the part-circular design toward the machine side  14 , torque transmission is effected exclusively on the machine side  14 . 
         [0086]    As can be seen in particular from  FIG. 6 , fastening elements  74  (screws), which serve for the axial securement of the rear guide part  18  on the main part  16 , are arranged on the machine side  16 . The fastening elements, however, do not absorb any torque forces. 
         [0087]    A further aspect, independent of the special design of the torque entrainment, is internal cooling in the region of the motor components, that is to say in the region of the stator pack  42  and of the rotor pack  44 . A free interior  76 , in which the individual motor components are arranged, is defined inside the main part  16 . The internal cooling is now characterized in that cooling air, which flows along the motor components in the axial direction  8  through the main part  16  and then leaves the main part again by the outlet channels  24   b , is introduced into the free interior by means of the feed channel  24   a . The flow configuration of the cooling air can also be seen in particular in  FIGS. 5 to 7 . 
         [0088]    First flow channels, which are realized as grooves  78 A and extend in the axial direction  8 , are provided in order to enable the flow configuration of the cooling air. Spaces and gaps  78 B inside the rotor pack  44 , that is to say in particular spaces between the individual magnets  79 , are preferably additionally utilized as second flow channels and are traversed in operation by cooling air (variant according to  FIG. 7 ). 
         [0089]    The flow channels (grooves  78 A or gaps  78 B), in this case, connect a rear annular chamber  80  on the inflow side to a front annular chamber  80  on an outflow side (cf.  FIG. 4 ). The fed air is distributed over the periphery of the rear annular chamber  80  and flows forward via the flow channels such that uniform cooling is achieved about the entire periphery. The flow channels are preferably arranged equally distributed about the periphery. 
         [0090]    According to a first variant shown in  FIGS. 5 and 6 , the grooves  78 A are realized on the outside of the rotor sleeve  46 . The grooves  78 A consequently extend directly beneath the rotor pack  44 . 
         [0091]    The grooves  78 A, however,—as shown in  FIG. 7 —are preferably arranged on the side of the rotor sleeve  46  located opposite the rotor pack  44 . They can be realized in an inner lateral surface of the rotor sleeve  46 . In the exemplary embodiment, they are mounted in an outside lateral surface of the spindle nut  50 . As a result of the arrangement, the electro-mechanical design of the motor components remains uninfluenced by the grooves  78 A. Immediate, direct cooling of the rotor components is achieved at the same time. 
         [0092]    It can be seen in general from  FIG. 7  that the spindle  52  is surrounded concentrically by the spindle nut  50 , to which, once again, the rotor sleeve  46  is fastened in a directly abutting and non-rotatable manner. The rotor pack  44  is provided with a plurality of magnets  79  on the outside of the rotor sleeve  46 . The gaps  78 B are realized in each case between adjacent magnets  79 . Leaving a small motor gap, the rotor pack  44  is surrounded by the stator pack  42  which is ultimately surrounded by the housing of the main part  16 . It is easy to see the trapezoidal cross-sectional area with the solid cooling ribs  22  on the machine side  14  and on the component side  12  the at least semi-circular design which merges into the trapezoidal machine side  14  in a preferably aligning and shoulder-free manner. 
         [0093]    The (flow) cross sectional area formed by the sum of the grooves  78 A, in this case, is preferably larger than the (flow) cross sectional area formed by the sum of the gaps  78 B. It is preferably more than 50% larger and in particular approximately twice the size. The sum of the grooves  78 A and of the gaps  78 B define an overall cross-sectional area. This is equal to or larger than a cross sectional area of the feed channel  24   a . In a preferred manner, in addition, the cross-sectional area of the feed channel  24   a  is equal to the sum of the cross-sectional areas of the outlet channels  24   b  (cf.  FIG. 3 ). 
         [0094]    The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:
     2  Setting device     4  Drive unit     6  Holder     8  Axial direction     10  Drive housing     12  Component side     14  Machine side     16  Main part     18  Guide part     20  Further guide part     21  Connecting region     22  Cooling ribs     24   a  Feed channel     24   b  Outlet channel     26  Connector     28  Blower     30  Tubular part region     32  Fastening flange     33  Cover     34  Support part     36  Housing wall     38  Front bearing     40  Direct drive     42  Stator pack     44  Rotor pack     46  Rotor sleeve     48  Rear bearing     50  Spindle nut     52  Spindle     54  Anti-rotation element     56  Plunger     58  Spring element     59  Hold-down device     60  Punch     61  Compression rod     62  Actuator element     64  Holding element     68  Engagement contour     70  Receiving contour     72  Torque transmitting surface     74  Fastening element     76  Free interior     78 A Groove     78 B Gap     79  Magnet     80  Annular chamber   R 1 , R 2  Radial extent   H Feed stroke   L Overall length