Abstract:
A camshaft adjuster ( 1 ) for an internal combustion engine is provided, which includes a housing ( 21 ) and in which a relative angular position between a driving gear ( 22 ′) and an output element allocated to the camshaft is adjustable. In a first connection region ( 28 ), the housing is connected in a fixed manner to a support element ( 20 ) which is connected in a fixed fashion to a plastic toothed ring ( 19 ) in a radially outward direction in a second connection region ( 29 ). The outer surface of the carrier element ( 20 ) fits an inner surface of the toothed ring ( 19 ) in the second connection region ( 29 ). The carrier element ( 20 ) makes it possible to bridge the radial gap between the toothed ring ( 19 ) and the outer surface of the housing ( 21 ), and the second connection region accurately predefines a position of the toothed ring ( 19 ).

Description:
BACKGROUND 
       [0001]    The invention relates to a camshaft adjuster for an internal combustion engine according to the preamble of Claim  1 . 
         [0002]    From DE 102 11 607 A1, a camshaft adjuster for adjusting and fixing the relative rotational angle position of a camshaft relative to the crankshaft of an internal combustion engine is known. A hydraulic adjustment device here consists of an external rotor, which is allocated to a drive wheel, and also an internal rotor, which is connected to a camshaft via a driven element. Pressure chambers are formed between the external rotor and the internal rotor. Charging these chambers hydraulically can change the angular relationship between the drive wheel and driven element. 
         [0003]    In the mentioned publication, it is proposed to produce the drive wheel and at least one of the other functional parts integrally from a high load capacity plastic. According to a first embodiment, the drive wheel and the external rotor and also two other components are produced integrally from plastic. For an alternative construction, the external rotor is produced as a separate component from plastic or from a conventional material, such as metal, and is set in a cover formed integrally with the drive wheel. 
       SUMMARY 
       [0004]    The invention is based on the objective of providing a camshaft adjuster, which is functionally ready or optimized for good production possibilities, having a small number of components, and/or low weight. 
         [0005]    According to the invention, the objective is met by the features of the independent Claim  1 . 
         [0006]    According to the invention, a housing is provided, which is optionally multifunctional:
       The housing can be used for attaching the camshaft adjuster to the internal combustion engine, for example, in the area of a cylinder head.   The housing can support internal elements of the camshaft adjuster, for example, gear elements or hydraulic components.   The housing can protect the inner components against mechanical impairments or contaminants from the outside.   The housing can be sealed tight, in order to keep lubricant or hydraulic medium arranged in the housing in the housing.   For the case that the housing includes electrically powered elements, the housing can provide electrical shielding.   The housing can also be used for supporting a control unit arranged outside of the housing, which is connected via a suitable drive shaft to gear elements of the camshaft adjuster.   The housing can have through holes, optionally sealed, for example, by a radial shaft sealing ring or the like, for passage of a shaft, for example, in connection with the camshaft or a shaft of the drive unit.       
 
         [0014]    Here, the housing can be produced with any production method, which allows for the previously mentioned functions. As possible materials for a housing, any material, especially a metal or a plastic, can be used. The possible production methods involve, for example, a casting method, an injection molding or die-casting method, and/or a shaping method. 
         [0015]    According to the invention, the housing has another function: in a first connection region, the housing is connected rigidly to a carrier element. In this way, the housing is also used for attaching the carrier element. The carrier element is connected rigidly to a toothed ring, in addition to the attachment to the housing, in a second connection region. Instead of a one-piece construction of the housing or toothed ring or an attachment of the toothed ring directly on the housing, according to the invention a carrier element is connected between the housing and toothed ring in the force flow. 
         [0016]    The invention is further based on the knowledge that the use of a toothed ring made from any plastic, especially a duroplastic, a thermoplastic, or a composite plastic, is advantageous in terms of the running properties, the operating strength, the wear, the noise development, the force transmission, the material or production costs, the installation space, and/or the weight. 
         [0017]    The housing, the carrier element, and the toothed ring can be selected from the same or different materials and can be produced with the same or different production methods, wherein the material and the production method can be selected according to the relevant requirements. For example, the toothed ring can be produced with a high precision guaranteeing good force transmission, while lower demands are possibly placed on parts of the carrier element. 
         [0018]    On the other hand, connection regions according to the invention are provided, which guarantee a selective attachment of the carrier element in one region to the housing and in another region to the toothed ring. 
         [0019]    In the second connection region between the toothed ring and carrier element, the carrier element has an outer casing surface, which is formed corresponding to an inner casing surface of the toothed ring. In connection with this, a corresponding construction is understood to be any positive-fit or non-positive fit surface shape, at least in one spatial direction:
       In particular, the casing surfaces involve cylindrical surfaces, which are supported against each other. Here, the inner casing surface of the toothed ring and the outer casing surface of the carrier element can be formed as a press fit, transition fit, or small clearance fit. In such a case, the second connection region must automatically ensure that the alignment of the toothed ring, which is important for good running of a drive belt or a drive chain, is guaranteed as a result of the corresponding casing surfaces. On the other hand, the inner casing surface of the toothed ring can be supported possibly over a large surface when the camshaft adjuster is operating over the outer casing surface of the carrier element, so that a rigid support is given while maintaining the necessary orientation of the toothed ring. Here, the mentioned casing surfaces can satisfy the mentioned support or centering effect only during an assembly of the camshaft adjuster, while after the assembly, a non-positive fit or else additional attachment elements support the connection between the carrier element and toothed ring.   Alternatively or additionally, the carrier element and toothed ring can engage each other with a positive fit, for example, by means of radial projections or shoulders allocated to one of the components named above, which engage in radial recesses or grooves of the other component in the peripheral direction and/or in the longitudinal direction. In this case, the use of elastic materials, for example, a plastic for the toothed ring, can be advantageous for the assembly and disassembly of the positive-fit connection, because these can be deformed elastically in the radial direction for producing and detaching the positive-fit connection. It is especially advantageous when the material that is used, especially a composite material, has anisotropic elasticity properties with a given elasticity in the radial direction for allowing the assembly or disassembly and a reduced elasticity in the longitudinal direction and/or peripheral direction, so that good force transfer is guaranteed between the toothed ring and carrier element. Also conceivable is that the positive fit is produced under the use of thermal deformation in the radial direction.       
 
         [0022]    According to the invention, the radius of the first connection region is smaller than the radius of the second connection region. Thus, the carrier element covers the region between the radius of the first connection region and the radius of the second connection region. Such bridging of this region by the carrier element can be implemented possibly with a carrier element with small extent in the direction of the longitudinal axis of the camshaft adjuster. Alternatively or additionally, a body closed in the peripheral direction and running around the longitudinal axis of the camshaft adjuster does not absolutely have to be provided for the carrier element, but instead only individual carrier arms or a circular ring surface with suitable recesses can possibly be used, whereby a reduction in the weight and a reduction in the mass moment of inertia can be achieved, while bodies running typically in the peripheral direction are required for the housing and the toothed ring. 
         [0023]    The surfaces of the housing, carrier element, and toothed ring involved in the connection regions can be produced directly according to requirements or can be brought to a desired dimension in a later processing step. 
         [0024]    A carrier element that is particularly easy to produce for a camshaft adjuster according to the invention is produced when the carrier element is rotationally symmetric to a longitudinal axis of the camshaft adjuster. Such a carrier element can be produced, for example, in an injection molding process or in a molding process. Another advantage of a rotationally symmetric construction of the carrier element is that such a carrier element does not present an unbalanced mass for the camshaft adjuster, which has advantages for an operation of the camshaft adjuster, especially at high rotational speeds. In this way, the requirement of possible compensation masses for compensating for an unbalanced mass can be met. 
         [0025]    According to one improvement of the invention, the carrier element is formed with a hollow cylindrical contact connecting piece, whose inner casing surface is part of the first connection region. This inner casing surface can contact the housing over a large surface during the assembly or operation of the camshaft adjuster, whereby the orientation of the carrier element relative to the housing is set by the inner casing surface. 
         [0026]    Alternatively or additionally, the carrier element has a hollow cylindrical outer body, with whose outer casing surface the second connection region is formed. On this outer casing surface, the toothed ring can contact a corresponding, especially cylindrical, inner surface with an exact fit, whereby a position and orientation of the toothed ring relative to the carrier element (and possibly relative to the housing) is given. Also conceivable is a positive fit between the casing surface and the inner surface. 
         [0027]    According to one special construction of the camshaft adjuster according to the invention, the outer body and the contact connecting piece are connected to each other via a circular ring-shaped carrier body. Such a circular ring-shaped carrier body provides, for low material use and low extent in the direction of the longitudinal axis of the camshaft adjuster, a bridge from the radius of the first connection region from the housing to the radius of the second connection region of the toothed ring. 
         [0028]    According to one preferred construction of the camshaft adjuster, non-positive fit connections between the carrier element and the housing or the toothed ring are provided in the first connection region and/or second connection region. According to this construction, the mounting positions are given by the corresponding casing surfaces of the carrier element, the toothed ring, and/or the housing. Final fixing of the components named above is performed by producing the non-positive fit connection, which guarantees an especially reliable connection when the camshaft adjuster is operating. 
         [0029]    Alternatively or additionally, in the second connection region the toothed ring can be connected to the carrier element with a friction fit or positive fit. For example, the toothed ring can be shrunk onto the carrier element or a transmission of the drive forces of a drive wheel can be realized with a positive fit by means of radial projections and/or recesses in the carrier element and also the toothed ring. 
         [0030]    Preferably, the toothed ring has a shoulder in the longitudinal direction. Such a shoulder can be used as a stop during assembly, so that the shoulder sets the maximum mounting position of the toothed ring relative to the carrier element. Accordingly, the shoulder is used for setting an end position of the toothed ring relative to the carrier element in a direction of the longitudinal axis of the camshaft adjuster. Alternatively or additionally, the shoulder can also set an angular position of the toothed ring, for example, about an axis that is oriented perpendicular to the longitudinal axis of the camshaft adjuster. Here, the shoulder noted above contacts a corresponding counter surface or end face of the carrier element. 
         [0031]    An outer body of the carrier element can also have a radially outwardly oriented shoulder or projection. At least for mounting, the toothed ring can contact this shoulder or projection for setting the relative position between the carrier element and toothed ring. Alternatively or additionally, such a shoulder can be used for guiding a drive means, such as a toothed belt or a toothed chain. 
         [0032]    Furthermore, it is allowed according to the invention that the toothed ring has a radially inwardly directed projection extending at least partially in the peripheral direction. This is then advantageous when the toothed ring is not to contact the carrier element over its entire axial width. The circular projection then has, e.g., a radial inner casing surface, with which the second connection region is formed, optionally under the intermediate connection of non-positive fit material. Here, it is also possible that the projection is first produced with an over-measure, which is still too small for mounting due to the inner diameter of the inner casing surface, and in a subsequent production step the projection is brought to a dimension allowing the mounting and attachment to the toothed ring. 
         [0033]    A good attachment of the toothed ring to the carrier element is further produced when the toothed ring has at least one radially inwardly oriented projection, which is held with a positive fit in a suitable recess or groove of an outer body of the carrier element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Additional features of the invention emerge from the following description and the associated drawings, in which embodiments of the invention are presented schematically. Shown are: 
           [0035]      FIG. 1  a cross-sectional view of a part of a camshaft adjuster with an outer rotor and a carrier body made from plastic with a non-positive fit connected insert body and also an inner rotor supported rotatably in the outer rotor; 
           [0036]      FIG. 2  a longitudinal cross-sectional half view of a camshaft adjuster in which the drive wheel made from plastic or an attachment element is attached to a flange; 
           [0037]      FIG. 3  a view of a drive wheel made from plastic with radially inwardly pointing brackets for receiving attachment elements; 
           [0038]      FIG. 4  a longitudinal cross-sectional half view of a drive wheel with a connecting piece or a bracket and inserts inserted into the connecting piece or bracket; 
           [0039]      FIG. 5  a partial cross-sectional view of a drive gearwheel with radially inwards pointing brackets and inserts arranged in these brackets; 
           [0040]      FIG. 6  a cross-sectional view of a camshaft adjuster, wherein attachment elements are drawn radially inwardly, so that their spacing from the longitudinal axis of the camshaft adjuster is smaller than the outer diameter of the pressure chambers, and 
           [0041]      FIG. 7  a view of a drive gearwheel made from plastic, which is attached to a housing of the camshaft adjuster via a carrier element. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    The invention relates to a hydraulic camshaft adjuster  1  of a known construction. The camshaft adjuster has a drive wheel  2 , which is formed as a pulley in the shown embodiments. An outer rotor  3 , which is arranged, in particular, radially inwardly from the drive wheel  2 , is connected rigidly to the drive wheel  2 . The outer rotor  3  is formed with bearing surfaces  4 , which correspond to segments of a casing surface of a cylinder, and also radial bulges for pressure chambers  5 . According to the embodiment shown in  FIG. 1 , four bearing surfaces  4  and also four pressure chambers  5  are provided, which are distributed uniformly about the periphery. An inner rotor  6 , which can be locked or is locked in rotation with the camshaft, is arranged in the outer rotor  3  so that it can rotate relative to this outer rotor about a longitudinal axis of the camshaft adjuster  1 . The inner rotor  6  has bearing surfaces  7  formed corresponding to the bearing surfaces  4  of the outer rotor  3  and also has vane-like radial projections  8 , wherein four bearing surfaces  7  and four projections  8  are provided, which are distributed uniformly around the periphery of the inner rotor, according to the embodiment shown in  FIG. 1 . The bearing surfaces  4  and  7  form a seal in the peripheral direction and the end faces of the projections  8  contact the associated pressure chambers  5  forming a seal radially on the outside, so that in the peripheral direction pressure spaces  9 ,  10  are formed on both sides of the projections. Through suitable charging of the pressure spaces  9 ,  10 , the relative angular position between the outer rotor  3  and the inner rotor  6  can be changed, whereby the angular relationship between the drive wheel  2  and a camshaft can be changed for adjusting the opening times of valves. 
         [0043]    According to  FIG. 1 , both the pressure chambers  5  and also the bearing surfaces  4  are both formed with a metallic insert body  11 , which extends in the peripheral direction and which has an approximately constant wall thickness. The insert body  11  is held with a non-positive fit in a carrier body  12 , which according to the embodiment shown in  FIG. 1  is formed integrally with the drive wheel  2  or is formed as a separate component, which can be connected rigidly to the drive wheel  2 . 
         [0044]      FIG. 2  shows a camshaft adjuster  1 ′ in longitudinal section. For this camshaft adjuster, the drive wheel  2 ′ is formed integrally with inwardly projecting brackets  13 , which are arranged approximately in the middle in the axial direction, which extend in the direction of a longitudinal axis X-X of the camshaft adjuster  1 ′ over one third to one fourth of the width of the running gearing of the drive wheel  2 ′, and which are distributed uniformly over the periphery, cf.  FIG. 3 . A flange  14 , which is formed integrally with the outer rotor  3 ′, contacts an end of the brackets  13 . The brackets  13  and the flange  14  are connected to each other with a friction, positive, and/or firmly bonded fit and/or via attachment elements  15 , which are formed as screws according to  FIG. 2 . Here, the brackets  13  and also the flange  14  have suitable bores  16  with or without threading. The bores  16  with or without threading can here be formed directly in the material forming the drive wheel or are prepared according to  FIG. 4  by reinforcement intermediate layers  17 , especially inserts, for example, made from metal, which are attached preferably with a firmly bonded fit to the other integral elements of the drive wheel  2 . 
         [0045]    In terms of the drive wheel  2 , the outer rotor  3 , the bearing surface  4 , the inner rotor  6 , the bearing surface  7 , the projections  8 , the insert body  11 , the carrier body  12 , the brackets  13 , and/or the flange  14 , there are the following shaping possibilities:
       The components named above can be made from any plastic or from a fiber composite material. In particular, a thermoplastic or a duroplastic of any composition can be used.   Furthermore, any composite material can be provided, for example, a plastic with an iron metal or a non-iron metal. In terms of the thermal expansion coefficients, these can be adapted to each other mutually, so that, for example, plastic, fiber composite materials, or composite materials have equal thermal expansion coefficients, such as adjacent components made from different materials. In particular, components arranged on the driven side, that is, components connected rigidly to the camshaft, can have a greater thermal expansion coefficient than components arranged on the drive side.   The components named above can be joined to form units in one or more pieces. For example, the drive wheel  2 , the outer rotor  3 , the bearing surface  4  with insert body  11 , bracket  13 , and carrier body  12 , as well as flange  14  are formed as an integral, installation space-optimized component made from one or more materials or composite materials.   For weight reduction and for improving the mounting possibilities, pockets can be provided in the components named above.   The drive wheel  2  and insert body  11  can be connected to each other optionally under the intermediate connection of additional (sub) bodies with a positive fit, for example, by screws, with a form fit, for example, by rivets, or with a non-positive fit, for example, by adhesive, injection molding, or integral production, wherein combinations of the connection possibilities named above are conceivable.   Non-plastic elements can be used as aids for the screw connection, for example, based on a “mold-in” or “after-molding” technology. A “mold-in” technology involves, for example, a metal bushing with threading, which is injection molded in a die, while as an example for an “after-mold” technique, a metal bushing with threading is conceivable, which is inserted in a plastic part after the injection-molding process.   Metallic elements or sub-bodies can be formed as reinforcement material in other materials, for example, for homogenizing the expansion and/or for bracing, for forming support material, and for increasing the component stiffness.   A selection of materials and their orientation can be used as thermal construction parameters, in which the expansion coefficient can be set to a desired target according to the element and its volume percentage.   The use of reinforcement intermediate layers or inserts can be used, in particular, for minimizing setting force losses and for permitting direct screw connections.   According to  FIG. 1 , the outer rotor can be embedded directly into a plastic material. Assembling this plastic material with the outer rotor can be realized directly, for example, in an injection molding process or else by means of a later assembly.       
 
         [0056]      FIG. 6  shows a partial cross section allocated to the embodiment according to  FIG. 2 . From here it is visible that the flange  14  does not have circular outer contours, but instead projects radially outwards in the connection region to the brackets  13 . Furthermore, it can be seen that the outer rotor  3  has sub-regions with the pressure chambers  5 , which project radially outwards and the attachment elements  15  are connected to the outer rotor  3  in the region of recesses  18  or radially inwards oriented pockets. In this way, the attachment elements  15  can be “pulled down” to small radii, so that the attachment elements  15  act at a radius that lies in a region of the outer diameter of the pressure chamber  5  or that is smaller than this. Here, the attachment elements  15 , the brackets  13 , and an optional flange  14  are provided axially between the end faces of the drive wheel  2 ′, so that a small axial installation size is produced. 
         [0057]      FIG. 7  shows an example construction for a drive wheel  2 ″ with allocated components, here a toothed ring  19 , a carrier element  20 , and a housing  21 . 
         [0058]    The housing  21  is formed especially as a sheet-metal part with an approximately cylindrical casing surface  22  and includes additional components of the camshaft adjuster  1 ″. The carrier element  20  is supported rigidly on the casing surface  22 , especially by a firmly bonded connection. Here, the carrier element  20  has a hollow cylindrical contact connecting piece  23 , which contact the casing surface  22  radially at the inside and is connected to the housing  21  with a firmly bonded fit on at least one axial end face. The contact connecting piece  23  transitions, especially under the intermediate connection of a transition radius, into a circular disk-shaped carrier body  24 , which is oriented coaxial to the longitudinal axis X-X and which, in turn, transitions in a hollow cylindrical outer body  25  with a surrounding shoulder  26  or collar in the end region opposite the carrier body  24 . 
         [0059]    The toothed ring  19  contacts the shoulder  26  in the region of an axial end face, while the opposite end of the toothed ring  19  has a radially inwardly projecting radial projection  27 , which contacts the carrier body  24  or the transition region between the carrier body  24  and outer body  25 . The toothed ring  19  has radially on the inside, especially approximately in the middle, a surrounding projection or connection region  29  provided across partial-peripheries, which extends approximately over half the width of the toothed ring  19 . The connection region  29  is connected to the outer casing surface of the outer body  25  with a firmly bonded fit. 
         [0060]    For the toothed ring  19 , the carrier element  20 , and the housing  21 , all of the previously mentioned materials or material combinations can be used. As an example embodiment, a production of the toothed ring  19  from plastic, especially a duroplastic, is conceivable, while the carrier element  20  and the housing  21  are produced from a metal. 
         [0061]    The shoulder  26  can be used alternatively or additionally for simplifying the mounting of a guide of a drive element like a toothed belt or a control chain in the direction of the longitudinal axis X-X. 
         [0062]    The outer body  25  has on its outer casing surface preferably recesses  31  or depressions or grooves, which can be formed as pockets in the outer body or can pass through this body. For the shown embodiment, the recesses  31  are formed with an approximately rectangular cross section. Radially inwardly oriented projections  32  or a surrounding collar extend radially inwards from the toothed ring  19 , especially form the projection  30 . These projections are held with a positive fit at least in the longitudinal direction X-X and/or in the peripheral direction in the recess  31 , depression, or groove. In the radial direction, the toothed ring  19  can be guided opposite the carrier element  20  through the projection  30  and/or projection  32 . 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           1  Camshaft adjuster 
           2  Drive wheel 
           3  Outer rotor 
           4  Bearing surface of outer rotor 
           5  Pressure chamber 
           6  Inner rotor 
           7  Bearing surface of inner rotor 
           8  Projections 
           9  Pressure space 
           10  Pressure space 
           11  Insert body 
           12  Carrier body 
           13  Bracket 
           14  Flange 
           15  Attachment element 
           16  Bore 
           17  Reinforcement insert 
           18  Recess 
           19  Toothed ring 
           20  Carrier element 
           21  Housing 
           22  Casing surface 
           23  Contact connecting piece 
           24  Carrier body 
           25  Outer body 
           26  Shoulder 
           27  Projection 
           28  First connection region 
           29  Second connection region 
           30  Projection 
           31  Recess 
           32  Projection