Abstract:
A camshaft adjuster ( 1 ) including a hub ( 2 ) for securing the camshaft adjuster ( 1 ) to one end ( 3 ) of a camshaft ( 4 ) is provided. The camshaft adjuster ( 1 ) includes a drive element ( 8 ) and an output element ( 9 ). An outer cover surface ( 5 ) of one section ( 6 ) of the hub ( 2 ), which faces the camshaft, is designed as a bevel surface ( 7 ) which protrudes from the camshaft adjuster ( 1 ) and can be brought into contact with a complementary bevel surface ( 24 ) of the end of the camshaft ( 3 ).

Description:
The present invention relates to a camshaft adjuster. 
     BACKGROUND 
     Camshaft adjusters are used in internal combustion engines to vary the control times of the combustion chamber valves to be able to vary the phase relation between a crankshaft and a camshaft in a defined angle range between a maximum advance position and a maximum retard position. Adjusting the control times to the instantaneous load and rotational speed reduces consumption and emissions. For this purpose, camshaft adjusters are integrated into a drive train via which a torque is transferred from the crankshaft to the camshaft. This drive train may be designed, for example, as a belt, chain or gear drive. 
     In a hydraulic camshaft adjuster, the output element and the driving element form one or multiple pair(s) of counteracting pressure chambers to which a hydraulic medium is applied. The driving element and the output element are coaxially situated. A relative movement between the driving element and the output element is created by filling and emptying individual pressure chambers. The rotatively acting spring between the driving element and the output element pushes the driving element toward the output element in an advantageous direction. This advantageous direction may be in the same direction or in the opposite direction of the direction of rotation. 
     One design of the hydraulic camshaft adjuster is the vane-type adjuster. Vane-type adjusters include a stator, a rotor and a drive wheel which has an external toothing. The rotor as the output element is usually designed to be rotatably fixedly connectable to the camshaft. The driving element includes the stator and the drive wheel. The stator and the drive wheel are rotatably fixedly connected to each other or, alternatively, they are designed to form a single piece with each other. The rotor is situated coaxially with respect to the stator and inside the stator. Together with their radially extending vanes, the rotor and the stator form oppositely acting oil chambers to which oil pressure may be applied and which facilitate a relative rotation between the stator and the rotor. The vanes are either designed to form a single piece with the rotor or the stator or are situated as “plugged-in vanes” in grooves of the rotor or stator provided for this purpose. The vane-type adjusters furthermore have various sealing covers. The stator and the sealing covers are secured to each other with the aid of multiple screw connections. 
     Another design of the hydraulic camshaft adjuster is the axial piston adjuster. In this case, a shifting element, which creates a relative rotation between a driving element and an output element via inclined toothings, is axially shifted with the aid of oil pressure. 
     A further design of a camshaft adjuster is the electromechanical camshaft adjuster, which has a three-shaft gear set (for example, a planetary gear set). One of the shafts forms the driving element and a second shaft forms the output element. Rotation energy may be supplied to the system or removed from the system via the third shaft with the aid of an actuating device, for example an electric motor or a brake. A spring may be additionally situated, which supports or feeds back the relative rotation between the driving element and the output element. 
     The camshaft adjuster or the output element of the camshaft adjuster is rotationally fixedly fastened to the camshaft with the aid of a screw, which is coaxial to the camshaft, or a nut in such a way that a rotation of the output element is transmittable to the camshaft. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a camshaft adjuster which permits a space-saving and centering attachment of the camshaft adjuster to the camshaft. 
     The present invention provides a camshaft adjuster having a hub for attaching the camshaft adjuster to a camshaft end of a camshaft, the camshaft adjuster having a driving element and an output element, achieves the object according to the present invention in that an outer lateral surface of a camshaft-facing section of the hub is designed as a conical surface, this conical surface projecting out of the camshaft adjuster and being engageable with a complementary conical surface of the camshaft end. 
     A fastening device for connecting the camshaft adjuster to the camshaft thus includes the camshaft adjuster-side camshaft end of the camshaft and the hub of the camshaft adjuster, the outer lateral surface of the camshaft-facing section of the hub being designed as a conical surface, this conical surface projecting out of the camshaft adjuster in the axial direction and engaging with the complementary conical surface of the camshaft end. The hub of the camshaft adjuster is also surrounded by the camshaft end, so that both conical surfaces contact each other. 
     The hub of the camshaft adjuster is rotatably fixedly connected to the output element. The hub may be designed as a single piece or separately from the output element. The hub, in particular its conical surface, advantageously projects beyond a front-side delimiting plane of the camshaft adjuster to be able to be surrounded by the camshaft end. 
     The camshaft adjuster-side camshaft end of the camshaft is the end piece of the camshaft to which the camshaft adjuster will be or is attached. The end piece may be designed to form a single piece with the camshaft or to be separate from the camshaft. 
     Due to the camshaft adjuster according to the present invention, a space-saving and reliable attachment of the camshaft adjuster to the camshaft on the camshaft-facing side of the camshaft adjuster is facilitated. 
     In one embodiment of the present invention, the conical surface of the hub tapers in the axial direction toward the camshaft. The axial direction in this case is oriented along the rotation axis of the camshaft adjuster or the camshaft. Due to the tapering, the camshaft adjuster may be easily mounted on the camshaft, a centering being simultaneously provided by the conical surface pairing. A permanent securing of the conical surface pairing may take place or have taken place with the aid of an integral fit, such as welding, gluing, soldering, etc. 
     Another embodiment of the present invention provides that the hub is designed as a separate component from the output element. The hub is advantageously designed as a tube or a sleeve. It may be thermally treated differently from the output element and/or be made of a different material than the output element. The rotatably fixed connection between the output element and the hub is provided by a force fit, form fit and/or integral fit. 
     In one advantageous embodiment of the present invention, the hub is designed as a sheet metal sleeve. The sheet metal sleeve may either have a central through-opening or be provided with a base. The conical surface of the sheet metal sleeve may advantageously be provided by forming, whereby the material in the area of the conical surface is compressed, and an improved surface quality is achieved, preferably without subsequent machining steps. 
     In one embodiment of the present invention, the hub has a contact surface for a fastening nut or a fastening screw. This contact surface may be provided by a shoulder, a collar or a front-side delimiting surface of the hub. This contact surface is advantageously provided by the hub on the side of the camshaft adjuster facing the camshaft. 
     In another embodiment of the present invention, the camshaft adjuster includes a fastening nut, both the contact surface and the fastening nut itself being provided on the side of the camshaft adjuster facing the camshaft. The installation space on the side of the camshaft adjuster facing the camshaft is advantageously reduced thereby. The camshaft adjuster may be supplied as a structural unit with the fastening nut, which is captively situated between the contact surface and the camshaft adjuster, due to the axial delimitation on both sides. 
     In another embodiment of the present invention, the camshaft adjuster includes a fastening screw, both the contact surface and the fastening screw itself being provided on the side of the camshaft adjuster facing the camshaft. The fastening screw advantageously does not fully penetrate the hub of the camshaft adjuster in the axial direction, so that the screw head of the fastening screw is also situated on the side of the camshaft adjuster facing the camshaft. Axially adjacent to the screw head and radially surrounded by the output element of the camshaft adjuster, the installation space inside the hub may be used for a central valve. Radial installation space is advantageously saved, since the fastening screw no longer surrounds the central valve. It is furthermore advantageous that the axial installation space on the side of the camshaft adjuster facing away from the camshaft is no longer blocked by the screw head. The sequence of the arrangement in the axial direction, starting from the side of the camshaft adjuster facing away from the camshaft, may begin with the central valve, followed by the fastening screw in the axial direction of the camshaft, which is finally embedded in the camshaft end of the camshaft to the greatest possible extent. 
     In one advantageous embodiment of the present invention, the fastening screw is situated inside the hub, only the thread of the fastening screw projecting out of the hub. Here, the contact surface for the fastening screw is situated in the axial area of the output element, the fastening screw not projecting out of the side of the camshaft adjuster facing away from the camshaft in the axial direction but being embedded within the hub. A fastening screw of this type may advantageously have a longer screw shaft, which has the necessary elongation length with regard to the required pretensioning force. 
     In another embodiment of the present invention, a fastening device for connecting the camshaft adjuster to the camshaft includes the camshaft adjuster-side camshaft end of the camshaft and the hub of the camshaft adjuster, the outer lateral surface of the camshaft-facing section of the hub being designed as a conical surface, this conical surface projecting out of the camshaft adjuster in the axial direction and engaging with the complementary conical surface of the camshaft end. The hub of the camshaft adjuster is also surrounded by the camshaft end, so that both conical surfaces contact each other. 
     In one favored embodiment of the fastening device, the camshaft has an external thread, which is in engagement with the fastening nut and which clamps the camshaft adjuster or its hub with the camshaft end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention are illustrated in the figures. 
         FIG. 1  shows a fastening device according to the present invention, including a fastening nut; and 
         FIG. 2  shows a fastening device according to the present invention, including a fastening screw. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a fastening device  10  according to the present invention, including a fastening nut  13 . 
     Fastening device  10  includes a camshaft adjuster  1 , a camshaft adjuster-side camshaft end  3  of a camshaft  4 , a fastening nut  13  and a hub  2  of camshaft adjuster  1 . All aforementioned components are situated coaxially to each other and to rotation axis  17  of fastening device  10 . 
     Camshaft adjuster  1  has a driving element  8 , an output element  9  and a hub  2 . Hub  2  is rotatably fixedly connected to output element  9  and is designed as tube  18 . Tube  18  has a largely uniform wall thickness as well as a central through-opening  19 , which is situated coaxially to rotation axis  17 . Section  6  of hub  2  projects out of camshaft adjuster  1  and has a conical surface  7  on its outer lateral surface  5 . Conical surface  7  tapers in axial direction  11  toward camshaft  4 . Hub  2  furthermore has a contact surface  12 , which is provided by a folded collar  20 . Folded collar  20  extends in radial direction  21  and is adjacent to section  6  with conical surface  7 . Contact surface  12  is oriented toward output element  9  of camshaft adjuster  1  and is designed to have a circular ring shape. Collar  20  abuts a cylindrical section  22  in axial direction  11 , which accommodates output element  9  and, in this exemplary embodiment, penetrates output element  9 . Through-opening  19  may accommodate a central valve in the area of cylindrical section  22 . 
     Camshaft end  3  of camshaft  4  has a conical surface  24  on its inner lateral surface  23 , which is widened in axial direction  11  of its camshaft adjuster-facing front side  25 . The cone angle of conical surface  24  is designed to be complementary to the cone angle of conical surface  7  and ideally has approximately the same size. Camshaft end  3  furthermore has an external thread  16  for fastening nut  13 . 
     Fastening nut  13  of fastening device  10  rotatably fixedly clamps hub  2  to camshaft end  3 . For this purpose, fastening nut  13  with its internal thread  32  is in engagement with external thread  16  of camshaft end  3 . In addition, fastening nut  13  includes a collar  26 , which is directed radially to the inside and which contacts contact surface  12  of hub  2  with its camshaft-facing front side  27 , ideally over a wide area. A mounting tool may engage with outer lateral surface  28  of fastening nut  13 , which may be designed, for example, as a hexagon, and screw fastening nut  13  to camshaft  4 . Collar  20  is clamped thereby in axial direction  11  of camshaft  4 , conical surface pairs  7 ,  24  being pressed against each other. Due to a remaining gap between front side  25  and collar  20  and due to the folded design of collar  20  from a hub  2  as tube  18 , this screw connection has sufficient flexibility, which reliably counteracts the setting behavior of the screw connection over the service life. Sufficient pretensioning force is also provided for the rotatably fixed connection between hub  2  and camshaft  4  to be reliably maintained over the service life. 
       FIG. 2  shows a fastening device  10  according to the present invention, including a fastening screw  14 . 
     Fastening device  10  includes a camshaft adjuster  1 , a camshaft adjuster-side camshaft end  3  of a camshaft  4 , a fastening screw  14  and a hub  2  of camshaft adjuster  1 . All aforementioned components are situated coaxially to each other and to rotation axis  17  of fastening device  10 . 
     Camshaft adjuster  1  has a driving element  8 , an output element  9  and a hub  2 . Hub  2  is rotatably fixedly connected to output element  9  and designed as tube  18 . Tube  18  has a largely uniform wall thickness as well as a central through-opening  19 , which is situated coaxially to rotation axis  17 . Section  6  of hub  2  projects out of camshaft adjuster  1  and has a conical surface  7  on its outer lateral surface  5 . Conical surface  7  tapers in axial direction  11  toward camshaft  4 . Through-opening  19  of hub  2  furthermore has a shoulder  29  which includes a contact surface  12 , which is provided for contacting with a front side  27  of fastening screw  14 . Shoulder  29  is situated in the area of conical surface  7  in axial direction  11 . Contact surface  12  is oriented toward output element  9  of camshaft adjuster  1  and is designed to have a circular ring shape. Tube  18  furthermore has a cylindrical section  22  adjacent to shoulder  29 , which accommodates output element  9  and, in this exemplary embodiment, penetrates output element  9 . Through-opening  19  may accommodate a central valve in the area of cylindrical section  22 . 
     Camshaft end  3  of camshaft  4  has a conical surface  24  on its inner lateral surface  23 , which is widened in axial direction  11  of its camshaft adjuster-facing front side  25 . The cone angle of conical surface  24  is designed to be complementary to the cone angle of conical surface  7  and ideally have approximately the same size. Camshaft end  3  furthermore has an internal thread  31  for fastening screw  14 . Front side  25  may be in contact with output element  9 . 
     Fastening screw  14  of fastening device  10  rotatably fixedly clamps hub  2  to camshaft end  3 . For this purpose, fastening screw  14  is in engagement with internal thread  31  of camshaft end  3 . In addition, fastening screw  14  includes a collar  26 , which is directed radially to the outside and which contacts contact surface  12  of shoulder  9  of hub  2  with its camshaft-facing front side  27 , ideally over a wide area. Collar  26  of fastening screw  14  is part of its screw head. A mounting tool may engage with inner lateral surface  30  of fastening screw  14 , which may be designed, for example, as a hexagon, and screw fastening screw  14  to camshaft  4 . Fastening screw  14  is elongated thereby in axial direction  11  toward camshaft  4 , conical surface pairs  7 ,  24  being pressed against each other. Due to the axial length of fastening screw  14 , this screw connection has a sufficient flexibility, which reliably counteracts the setting behavior of the screw connection over the service life. Sufficient pretensioning force is also provided for the rotatably fixed connection between hub  2  and camshaft  4  to be reliably maintained over the service life. 
     LIST OF REFERENCE NUMERALS 
     
         
           1 ) Camshaft adjuster 
           2 ) Hub 
           3 ) Camshaft end 
           4 ) Camshaft 
           5 ) Outer lateral surface 
           6 ) Section 
           7 ) Conical surface 
           8 ) Driving element 
           9 ) Output element 
           10 ) Fastening device 
           11 ) Axial direction 
           12 ) Contact surface 
           13 ) Fastening nut 
           14 ) Fastening screw 
           15 ) Thread 
           16 ) External thread 
           17 ) Rotation axis 
           18 ) Tube 
           19 ) Through-opening 
           20 ) Collar 
           21 ) Radial direction 
           22 ) Cylindrical section 
           23 ) Inner lateral surface 
           24 ) Conical surface 
           25 ) Front side 
           26 ) Collar 
           27 ) Front side 
           28 ) Outer lateral surface 
           29 ) Shoulder 
           30 ) Inner lateral surface 
           31 ) Internal thread 
           32 ) Internal thread