Abstract:
A machine element is provided that includes, but is not limited to a clamping element without a slit, which is incorporated into a receiving area of the machine element. The clamping element has an opening for accommodating a shaft, and can be twisted against the machine element. A support sleeve is arranged radially outside relative to the clamping element. This makes the machine element easy to manufacture, convenient to use, and allows the absorption of high levels of force.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to German Patent Application No. 102007038971.1, filed Aug. 17, 2007, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The invention relates to a machine element for a shaft-hub connection for the torque-proof coupling of rotating or fixed machine elements with shafts by means of a lever actuated eccentric clamping sleeve, as well as a corresponding manufacturing method. 
     BACKGROUND 
     Various devices have in the past been suggested for establishing torque-proof connections between rotating or fixed machine elements, such as shafts that continuously rotate or alternatively rotate to and fro, and machine elements immovably secured thereto, such as levers, pulleys, cams, toothed wheels and the like. For example, DE 43 27 461 A1 discloses a device for the torque-proof connection of a shaft with a hexahedrally bordered machine part by means of a lever-actuated eccentric clamping sleeve. The latter includes a slit sleeve with an outer wedge profile, and the sleeve can be rotates against the outer machine element, thereby becoming jammed between the shaft and outer machine element. 
     The lengthwise slit introduced in the sleeve enables an elastic deformation of the sleeve in a radial direction. However, the truth of running is limited. Further, clamping can give rise to stresses that are so high that the machine element with the hub can be damaged, in particular at small shaft diameters. 
     In view of the foregoing, at least one object is to create a machine element that enables an easy to manufacture and convenient to use shaft-hub connection, and can absorb high levels of force, as well as to provide a method for manufacturing such a shaft-hub connection. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background. 
     SUMMARY 
     The at least one object, other objects, desirable features, and characteristics, is achieved by means of a machine element for a shaft-hub connection that includes, but is not limited to a receiving area and a clamping element without a slit incorporated in the receiving area that has an opening for accommodating a shaft and can be twisted against the machine element. The machine element also includes, but is not limited to a support sleeve arranged radially outside relative to the clamping element. 
     The at least one object, other objects, desirable features, and characteristics are also achieved by a manufacturing method. The method including, but not limited to the steps of preparing a machine element for a shaft-hub connection that includes, but is not limited to a receiving area and a clamping element without a slit incorporated in the receiving area that has an opening for accommodating a shaft and can be twisted against the machine element. The machine element also includes, but is not limited to a support sleeve arranged radially outside relative to the clamping element. The method further includes, but is not limited to machining the clamping element, in particular by drilling, turning and/or grinding, to generate the opening, insertion of a shaft into the opening and twisting the shaft and/or clamping element relative to the machine element to establish a torque-proof connection between the shaft and machine element. 
     The machine element for a shaft-hub is used for the torque-proof coupling of rotating machine elements with shafts, and the rotating machine elements include toothed wheels, pulleys, axial locking rings, parts of bearing arrangements, parts of sealing arrangements, levers and the like. The rotating motion of the respective machine element can be a continuous rotating motion with constant or alternating speed, with constant rotating direction or also a back-and-forth rotating motion with alternating rotating direction. The shaft can be a solid shaft, a hollow shaft or the like. Its exterior has a bearing surface that is preferably cylindrical. 
     The machine element has a receiving area, which incorporates a clamping element without a slit. In other words, the clamping element has no radially continuous slit in the lengthwise direction, and hence is continuously closed in the peripheral direction. It can preferably be elastically compressed in the radial direction, made possible through the selection of an appropriately low wall thickness of the clamping element, for example. The elasticity of the clamping element can be increased even further by providing it with longitudinal grooves or inclined grooves inside and/or outside. However, the latter do not penetrate through the clamping element, i.e., no slits are formed. The clamping element exhibits an opening, in particular a central borehole for accommodating the shaft, and the diameter of the opening is such that the clamping element can be slipped onto the shaft with little clearance. The elasticity of the clamping element is great enough to overcome the existing clearance during the elastic deformation of the clamping element, so as to secure the clamping element on the shaft friction-tight. The clamping element is elastically deformed through the relative twisting of the clamping element against the machine element. According to an embodiment, the machine element has a support sleeve that is arranged radially outside relative to the clamping element, and can absorb compressive forces. In particular, the clamping element is arranged inside the support sleeve, preferably in a concentric manner. It is especially preferred that the support sleeve exhibit a length in an axial direction measuring at least the axial length of the clamping element. 
     The support sleeve can at least partially absorb the forces exerted on the machine element by the clamping element, so that stresses within the material of the machine element can be reduced. As a result, the machine element can also be used for shafts with relatively small diameters, making it possible to use tools with a smaller jaw spans during the assembly of the shaft-hub connection. In addition, a less expensive material can be used for the machine element, so that a machine element can be made out of plastic, in particular a duromer, without having to worry about component failure. In particular, the machine element exhibits a duroplastic material, which improves the service life and wears resistance. 
     The machine element is preferably fabricated via casting, in particular (plastic) injection molding. As a result, the support sleeve and/or clamping element can be sheathed by the machine element. This simplifies production, and yields a good connection with the material of the machine element. 
     In particular, the support sleeve has feed-through openings that in particular run in essentially a radial manner. This reduces the weight without significantly detracting from stability. In addition, the bond between the support sleeve and machine element can be improved. In particular if the support sleeve is sheathed by the machine element, the material of the machine element can penetrate into the feed-through openings and provide an additional positive fit, so that in particularly distinctly higher shearing forces can be conveyed. 
     In order to further improve the bond between the support sleeve and machine element, the contouring of the support sleeve can be coarsened. For this purpose, the support sleeve can have an average roughness R a  of about 0.1-50 μm, in particular about 1.0-50 μm, preferably about 3.0-50 μm, and especially preferred about 10.0-50 μm. Additionally or alternatively, the support sleeve can have notches, and the notches can in particular be fabricated without cutting via cold forming, rolling, embossing, sand blasting or shot preening. In particular when sheathing with the material of the machine element, the irregular surface of the support sleeve makes it possible to achieve an additional positive fit, which enables the transfer of higher forces. 
     The thickness of the support sleeve can be adjusted depending on the application. For example, the thickness of an essentially annular cylindrical support sleeve can be increased so as to enable the absorption of higher compressive forces and stresses. It is particularly preferred that the support sleeve be thick enough to provide at least one threaded borehole running in an axial direction in the support sleeve. As a result, the machine element can be connected with another component via the support sleeve, without having to provide a direct connection with the material of the machine element. This makes it possible to use a material for the machine element that might not be particularly well suited for a connection with other components, for example, owing to its brittleness. The increased flexibility in material selection permits the use of less expensive materials. 
     The clamping element can basically be incorporated into the machine element in different ways. In a first embodiment, for example, it is pressed into the machine element, so as to be held there in a press fit. The corresponding cam profile can be rough-finished in the machine element. It is also possible to design the clamping element in such a way as to itself fabricate the cam profile in a cutting process. It is radially pre-compressed by the press fit. The desired truth of running for the machine element is now established by preferably machining the borehole of the clamping element. For example, it is turned out, drilled out, ground out, etc. In addition, one or both faces of the clamping element or machine element can be end faced if they project over the machine element. Turning, milling, grinding or similar machining processes are again possible. 
     The clamping element is most preferably incorporated into the machine element already during the manufacture of the latter. For example, the machine element consists of a material that can be injection or transfer molded, such as diecast zinc, aluminum, a thermoplastic, duroplastic, duromer or another plastic, either reinforced with fiber or not. During the manufacture of the machine element, the clamping element can be introduced in the corresponding mold, and sheathed by the material of the machine element. In this state, the clamping element preferably still exhibits a wall thickness that is greater than desired and required for later use. In this molding process, the material of the machine element sheaths the clamping element, thereby adjusting to its external shape. The machine element thereby forms a receiving area for the clamping element that automatically exhibits an internal contour that fits the external contour of the clamping element. In particular, the external shape of the clamping element has at least one, but preferably two or three cam surfaces, which can be viewed as wedging surfaces, bent in the peripheral direction, and have the same direction of inclination. 
     After molding the machine element, the clamping element is preferably centrally machined. This can be done by turning, drilling, grinding or another type of machining process. For example, the machine element is accommodated by the clamping system of a machining device (e.g., the chuck of a lathe), after which the central borehole is turned to size. This automatically produces the desired dimensional correlation between a reference surface of the machine element and the central receiving borehole. Also achieved is the desired thinness of the clamping element walls, and hence its radial elasticity. For example, if the machine element is a pulley, the latter can be held on its outer periphery or some other reference surface, so as to achieve the desired centering of the borehole of the clamping element. 
     One or more mold clamping profiles are preferably provided on the clamping element and at a suitable location of the machine element, so as to hold tools for applying a relative clamping moment. For example, these profiles include an outer hub profile and inner clamping element profile (e.g., a bihexagonal Allen wrench or a claw coupling profile on the face). 
     The embodiment further relates to a shaft-hub connection with which rotating machine elements can be coupled in a torque-proof manner to shafts. The shaft-hub connection exhibits a shaft with a bearing surface and a machine element, and the machine element can be designed and further developed as described above. The bearing surface of the shaft is connected with the machine element via the clamping element. The shaft-hub connection is easy to fabricate, effective in use, and permits the absorption of high forces. 
     The embodiment further relates to a method for manufacturing a shaft-hub connection that involves first providing a machine element that can be designed and further developed as described above. The clamping element is then machined, in particular through drilling, turning and/or grinding, to create the opening. Subsequently, a shaft is inserted into the opening. Finally, the shaft and/or clamping element are twisted relative to the machine element to achieve a torque-proof connection between the shaft and machine element. 
     In particular, the machine element and clamping element are snapped onto the shaft to fabricate the shaft-hub connection between the machine element and shaft. This takes place after correspondingly establishing the interior dimensions of the clamping element and exterior dimensions of the shaft with a low clearance, and can hence be easily accomplished by hand. Corresponding handling systems or lever apparatuses, such as wrenches, are now positioned on the machine element and clamping element and a relative rotation is executed. As a rule, there is a weak material connection between the clamping element and the material of the machine element, which can be overcome with a slight torque if the outer surface of the clamping element is correspondingly smooth. The clamping element is broken off in the process. Once this has occurred, turning the clamping element generates a radial force that secures the machine element and clamping element to the shaft friction-tight. 
     It has been shown that the shaft-hub connections manufactured in this way are indeed durable and capable of bearing. They have a high truth of running at the lowest manufacturing costs. The type of connection can be used in a variety of ways. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and 
         FIG. 1  shows a vertical sectional view of a shaft-hub connection with the machine element according to an embodiment; 
         FIG. 2  shows a vertically cut view a hub of the machine element for attachment to a shaft prior to hollowing process; 
         FIG. 3  shows a front view of the hub according to  FIG. 2 ; 
         FIG. 4  shows a front view of the clamping element of the hub according to  FIG. 3 ; 
         FIG. 5  shows a side view of the clamping element according to  FIG. 4 ; 
         FIG. 6  shows a lengthwise cut view of the clamping element according to  FIG. 5  prior to hollowing process; 
         FIG. 7  shows a partial lengthwise cut view of a shaft with an axial locking ring with wedge clamping device according to an embodiment; and 
         FIG. 8  shows a cut along the VIII-VIII line of the shaft and axial locking ring according to  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding summary and background or the following detailed description. 
       FIG. 1  shows a shaft-hub connection  1  between a machine element  2  in the form of a pulley  3  and a shaft  4  or a shaft end. The shaft  4  is used to drive an aggregate  5  in a motor vehicle (not shown in any greater detail). However, the shaft-hub connection can be used elsewhere for connecting other machine elements and shafts. 
     The shaft end  4  is essentially cylindrical. It has a face  6  that is preferably essentially flat, and sits inside an opening in the form of a borehole  7  of a clamping element  8  incorporated in a hub  9  of the pulley  3 . The clamping element  8 , and hence the borehole  7 , are concentrically oriented relative to a rotational axis  10  that coincides with the rotational axis of the shaft  4 . 
     The pulley  3  has a support sleeve  26 , which can be used to absorb forces and stresses arising in the pulley  3 , so that the pulley  3  can tolerate distinctly higher forces emanating from the clamping element than without a support sleeve  26 . The support sleeve  26  is arranged concentrically relative to the clamping element  8 , and radially outside relative to the clamping element  8 . In the exemplary embodiment shown, the support sleeve  26  and clamping element  8  have essentially the same axial length. The support sleeve  26  exhibits several feed-through openings  27 , so that the bond between the support sleeve  26  and pulley  3  can be improved in particular if the support sleeve  26  is sheathed by the pulley  3 . In this case, the material of the pulley  3  can flow into the feed-through openings  27  and penetrate through the support sleeve  26 . In the exemplary embodiment shown, the support sleeve further exhibits schematically depicted threaded boreholes  28 , so that further components (not shown) can be easily connected with the pulley  3  via the support sleeve  26 . 
     The pulley  3  is not limited in shape. It can be set up for narrow belts as shown in the top half of  FIG. 1 , or for wide belts as shown in the bottom half of  FIG. 1 . The outer portion of the pulley  3  is connected with the hub  9  via a narrow, disk-shaped section  11 . As shown, the outside of the hub  9  can be conical, or alternatively be cylindrical or some other shape (e.g., as a crown gear, toothed wheel, flat pulley, frictional wheel, cam or the like). In addition, the outer edge of the pulley  3  can have essentially cylindrical annular surfaces  12 ,  13 , which are provided on either side of the disk-shaped sections  11 . 
     The pulley  3  can be formed of a plastic, for example a duroplastic material, a thermoplastic material, or a metal that is not too solid, such as diecast zinc, aluminum, an aluminum alloy, magnesium, a magnesium alloy or the like. The pulley  3  is preferably manufactured in an injection or transfer molding process. The latter, in particular, is preferably used when using fiber-reinforced plastics with a high content of fiber. 
     As evident from  FIG. 2  along with  FIG. 4 to 6 , the clamping element  8  is essentially sleeve-shaped in design. It has a relatively thin wall  14 , which centrally envelops the borehole  7 . For example, the wall  14  consists of a metal, such as steel. The clamping element  8  is slightly flexible in the radial direction. In this case, its wall  14  is closed over its entire periphery, i.e., no slits are provided. The elasticity is created by predetermined bending points or breaking points, or by the thinness of the clamping element wall. 
     The outside of the clamping element  8  has at least one, and preferably two, essentially cylindrical jacket surface sections  15 ,  16 , between which a clamping section  17  is arranged. The clamping section  17  exhibits a profile that is not circular. One such example is illustrated on  FIG. 4 . In the present case, it consists of two cylindrically bent cam surfaces  18 ,  19 , the radii R of which relate to midpoints M 1 , M 2 , which each are spaced apart from the rotational axis  10 . 
     The cylindrical section of the borehole  7  is followed by an Allen wrench segment  20  bordered hexagonally or on multiple surfaces. The mold clamping profile can also be a front claw profile. The latter is used for placing an Allen wrench in order to twist the clamping element  8  against the machine element  2 . 
     The hub  9  is correspondingly provided with a mold clamping profile  21 , for example in the form of a toothed profile or notched profile, which is also suitable for the placement of a torque-generating tool, such as a clamping system or the like. The Allen wrench section  20  and mold clamping profile  21  are separately displayed on  FIG. 3 . This figure illustrates the hub  9  and a portion of the disk-shaped section  11  enveloping it. 
     Based on the example of the pulley  3 , the machine element  2  is manufactured as follows: The pulley  3  is manufactured using an injection molding tool with a central receptacle for the clamping element  8 . The latter is already provided with its Allen wrench profile or other profile. It can also exhibit the completely machined borehole  7 . However, it most preferably has a greater wall thickness, (i.e., the borehole  7  is undersized). The clamping element  8  is positioned in the injection molding tool in such a way that the outer cylindrical surface sections  15 ,  16  are arranged largely coaxial to the later desired rotational axis. The precision requirements are here not all that stringent. The hub  9 , section  11  and outer part of the pulley  3  are then fabricated in the injection molding process, wherein the here liquid or plastic material envelops the clamping element  8 . As a result, in particular the clamping section  17  projecting radially outward over the surface sections  15 ,  16  are overlapped on both sides by the material of the hub  9 . The material of the hub  9  seamlessly abuts the preferably very smooth surface of the clamping element  8 . If necessary, a liquid or powder release agent can be applied to prevent too intimate a bond between the material of the hub  9  and the outer surface of the clamping element  8 . 
     After the pulley  3  has been molded, the borehole  7  is formed centrally relative to the rotational axis  10 , and the wall thickness of the clamping element  8  is reduced. For example, this can be accomplished by drilling or, as preferred, hollowing out. To this end, the pulley  3  is accommodated by a clamping system on a suitable surface, for example the annular surface  12  or  13 , or on its outer edge  22 . It is then concentrically turned relative to the rotational axis  10 , and the inner surface of the borehole  7  is machined to size with a hollowing tool. This size (i.e., the inner diameter established in this way) is large enough so that the pulley  3  with the borehole  7  can be easily slipped onto the shaft  4  by hand, without generating too great a resistance or too much clearance. 
     The clamping element  8  is twisted slightly against the hub  9  to manufacture the shaft-hub connection  1 . To this end, a clamping system or tool is placed in the Allen wrench section  20 , and a corresponding gripper is placed on the clamp molding profile  21 . Twisting the clamping element  8  against the hub  9  by several (few) degrees first loosens a potentially adhesive bond between the clamping element  8  and pulley (i.e., the clamping element  8  is broken off). This is followed on  FIG. 4  by a clockwise rotation (i.e., in such a way that the cam surfaces of the counter-surfaces  23 ,  24  formed in the hub  9  during the injection molding process are forced radially inward). As a result, the centering of the sleeve formed by the clamping element  8  is retained owing to the centering of the surface sections  15 ,  16 . The clamping element  8  deforms elastically, wherein the inner wall of the borehole  7  presses rigidly against the shaft  4 , in particular in the area of the clamping section  17 , creating a torque-proof connection. This yields a precisely true running, easily manufactured shaft-hub connection that can be detached again if needed. 
       FIG. 7  depicts a modified application. The shaft-hub connection serves for axially securing a locking ring  23 , illustrated in the top half of  FIG. 7  and bottom half of  FIG. 7  in different variants. For example, it differs in terms of axial length. The face of the axial locking ring  23  can exhibit teeth  24  used to secure a tool. The locking ring  23  can consist of plastic, steel or another material. The clamping element  8  is once more pressed into a central opening of the machine element  2  here designed as the locking ring  23 , and can be rotated against the locking ring  23 , so as to elastically deform radially inward in the process. The face of the clamping element  8  can have teeth, so as to be twisted against the locking ring  24 . 
     During manufacture, the clamping element  8  is again pressed into the locking ring  23 , after which the central borehole  7  and possibly yet another axial face of the clamping element  8  and/or a face  25  of the locking ring  23  are finish-machined. The subsequent machining of the unit comprised of the machine element  2  and clamping element  8  results in a precise true running and, in the case of the locking ring  23 , avoids any wobbling impact of the face  25 . 
     The shaft-hub connection according to the embodiment encompasses a machine element  2  with a clamping element  8 , which forms a structural unit with the machine element  2 . The clamping element  8  has a central, preferably cylindrical borehole  7  for accommodating a shaft, and is thin-walled enough so that it can be defined radially inward. Its inner cylindrical bearing surface is preferably generated only once a molded blank provided to form the clamping element  8  has been securely placed in the machine element  2 . The machine element  2  provided with the clamping element  8  has a high clamping accuracy, and is easy and efficiently to manufacture. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.