Abstract:
A camshaft adjuster ( 1 ) including a stator ( 2 ) and a rotor ( 4 ), a spring ( 6 ) tenses the rotor ( 4 ) rotationally counter to the stator ( 2 ). According to the invention, the spring is a helical spring ( 6 ), the stator ( 2 ) includes a first recess ( 8 ) of a first free end ( 10 ) of the helical spring ( 6 ) and the rotor ( 4 ) includes a second recess ( 12 ) for a second free end ( 14 ) of the helical spring ( 6 ).

Description:
[0001]    The present invention relates to a camshaft adjuster which includes a stator and a rotor, a spring rotatably bracing the rotor against the stator. 
       BACKGROUND 
       [0002]    It is generally known that camshaft adjusters are used in internal combustion engines for varying the timing of the combustion chamber valves. Adjusting the timing to the instantaneous load reduces fuel consumption and emissions. Camshaft adjusters include a stator and a rotor. The rotor is usually connected in a rotatably fixed manner to the camshaft, the rotor being situated within the stator, coaxially with respect to same. The rotor and stator include oil chambers which may be acted on by oil pressure and generate a relative movement between the stator and the rotor. 
         [0003]    To allow a torque transmission between the components of rotor and stator and also to compensate for a drive torque of the camshaft, a spring rotatably braces the rotor against the stator. This is described, for example, in German patent specification DE 103 61 509 B4 or United States patent specification U.S. Pat. No. 6,758,178 B2. In the cited publications, a coil spring is supported on each rotor by additional components or additional machining of the rotor. These additional parts or the additional machining increase not only the manufacturing costs, but also the assembly costs of a camshaft adjuster. In addition, the installation space for the coil spring is limited in the camshaft adjuster. However, since these known spring bearings require a relatively long axial installation length, installation of the coil spring in the rotor is therefore made more difficult. 
         [0004]    In addition, it is generally known and customary in the prior art for these camshaft adjusters to include a cover that is situated on both sides of the “stator-rotor assembly.” These covers may have further functions in addition to a strictly sealing function. Thus, for example, they may be designed with gear teeth or with locking elements in order to be used as a chain wheel or as a locking cover. Regardless of which specific embodiment the cover includes, it is always designed in one piece. It is also known to fasten the above-described spring to the cover in order to brace the rotor against the stator. 
         [0005]    For camshaft adjusters which provide a spring in the form of a coil spring, the coil spring is suspended in the cover and then fixed. For this purpose, a collar for spring suspension is necessary in the inner diameter of the cover. Due to the spring torque, the torsion spring in the spring suspension, which is formed as a punched or milled undercut (forming a web), is pressed against the cover collar, or axially and radially secured in a pressed-in pin. These known approaches using a cover with a drawn collar also have a number of disadvantages. 
       SUMMARY OF THE INVENTION 
       [0006]    If the installation space in the overall camshaft adjuster is very small, and the punched spring suspension has too small a cross section, during operation of a camshaft adjuster this may result in failure due to a rupture of the web. 
         [0007]    In addition, the sheet metal fibers of the cover are severed at three sides due to the punched-out or milled spring suspension. As a result, the stability of the remaining web of the spring suspension in the circumferential direction is less than in a specific embodiment which is only shaped, or punched out or bent upwardly, at fewer than three sides. 
         [0008]    It has also been shown in practice that during the punching, a cutting gap is necessary between the base of the cover and the collar. Depending on the geometric design with an excessively large material cross section on the collar, the cutting punch must also have a certain cross section in order to still allow cost-effective manufacture. For this reason, the punch generally has a square design. This means that for a radial collar thickness of 3 mm, for example, the cutting punch as well must be at least 3 mm wide. The suspended spring thus has more play on the cover than is necessary or allowed. 
         [0009]    Furthermore, a cutting force must be supported on the remaining web during the punching. The cutting force is thus determined by geometric or material limits of counterholders. For very small installation space conditions, this may be a reason for not being able to implement some spring designs. 
         [0010]    In particular, the grindability of such drawn covers is limited or is not economically viable. Due to the large differences in surface area between the cover area and the narrow collar area, grinding removal with high asymmetry is to be expected. In addition, an option for turning the cover area is not always the best choice from a cost-effectiveness and qualitative standpoint, for example due to chatter marks from interrupted cuts, insufficiently large clamping surfaces for tools, or too precise requirements for squareness. 
         [0011]    It is an object of the present invention to refine a camshaft adjuster in such a way that it compensates for a drive torque of the camshaft in a cost-effective and space-saving way, and during operation meets technical and mechanical requirements in a functionally reliable way. 
         [0012]    The camshaft adjuster according to the present invention is made up of a stator and a rotor. A spring rotatably braces the rotor against the stator, so that during operation of the camshaft adjuster a drive torque of the camshaft may be at least partially compensated for. 
         [0013]    According to the present invention, the spring is a coil spring, for which the stator has a first recess for a first free end of the coil spring, and the rotor has a second recess for a second free end of the coil spring. 
         [0014]    In a first specific embodiment of the camshaft adjuster according to the present invention, a polygon, for example a square, forms the second recess at an inner wall of the rotor, with which a correspondingly shaped spring winding of the second free end of the coil spring cooperates in a form-fit manner. In particular, a last spring winding of the coil spring is appropriately shaped to ensure the required form fit. If the coil spring is thus inserted into the base, i.e., into the inner wall, of the rotor, a rotatably fixed connection is established between the second free end of the coil spring and the rotor. 
         [0015]    Another specific embodiment provides that a width across flats of the polygon in the rotor is designed to be small enough that the polygon is situated beneath a screw head of a screw which fastens at least one cover to the stator. The second free end of the coil spring is axially held in position in this way. 
         [0016]    In a second specific embodiment of the present invention, a borehole is provided in the rotor. The borehole is situated at an angle less than or equal to 90° with respect to the pulling direction of the coil spring in the rotor, and represents the second recess into which the second free end of the coil spring is inserted. This specific embodiment generates an axial force in a self-acting manner which automatically forces the second free end of the coil spring into the installation position. 
         [0017]    In particular, the camshaft adjuster provides at least one cover in order to prevent oil within the camshaft adjuster from escaping. The at least one cover is mounted on the stator via at least one screw. 
         [0018]    One specific embodiment of the present invention provides that a metal sheet is mounted on the stator via the at least one screw, and which has formed an axial bulge which forms the first recess, and in which the first free end of the coil spring rests. To prevent the first free end of the coil spring from falling out of the axial bulge, a partially cut-out element, such as a window, is additionally provided on the metal sheet or cover. This specific embodiment functions as a bayonet lock for the second free end of the coil spring. In particular, another specific embodiment may be provided here, in which the metal sheet is designed in such a way that in addition to this axial fixing of the first free end of the coil spring, further spring windings of the coil spring may be axially held in position. The coil spring is thus prevented from falling out. 
         [0019]    In another specific embodiment of the camshaft adjuster according to the present invention, the at least one screw forms an extended screw head or screw shank for the first recess, in which the first free end of the coil spring is suspended. 
         [0020]    Another specific embodiment provides that the at least one cover forms an axial extension element for the first recess, in which the first free end of the coil spring is suspended. In this specific embodiment, for example a press-in part, which is necessary on the inner side of the cover for mechanical locking of the camshaft adjuster, is appropriately modified on the outer side to form an axial extension element. 
         [0021]    In another preferred specific embodiment, the at least one cover is made up of an inner cover and an outer cover. The inner cover is a sealing cover for preventing oil within the camshaft adjuster from escaping. The outer cover forms a spring recess cover for the first recess, in which the first free end of the coil spring is suspended. In the present invention, instead of a cover with a drawn collar, two covers are thus used as a “package” in this specific embodiment, in contrast to the prior art. The strength or rigidity of the spring recess cover is thus advantageously increased, which as a whole ensures the functioning of the overall camshaft adjuster under all operating conditions. The sealing cover preferably includes at least one ground sealing surface as a contact surface for the “stator-rotor assembly.” The coil spring suspension is introduced into the spring recess cover as an axially punched or shaped spring suspension. This spring recess cover may provide various specific embodiments for the first recess of the first free end of the coil spring, such as a cutout, an elevated element, an upwardly bent element, a free punched out portion, or a combination thereof. 
         [0022]    In particular, in one specific embodiment the spring recess cover may be designed in the form of a stamped closed ring; in another specific embodiment it is likewise conceivable for the spring recess cover to be at least a partial segment of a ring. 
         [0023]    In addition, it is noted here that the inner diameter of the spring recess cover may be designed as described below. On the one hand, the inner diameter may be smaller than an outer diameter of the coil spring, thus achieving additional axial spring lock. On the other hand, the inner diameter may be greater than or equal to the outer diameter of the coil spring. This larger area may then be used as an additional spring work area. However, guiding of the coil spring is not possible then. 
         [0024]    All of the above-described specific embodiments of the coil spring on the rotor and/or on the stator or on the at least one cover may be arbitrarily combined with one another, provided that the coil spring rotatably braces the rotor against the stator. It is likewise conceivable for spring suspensions on the rotor or on the stator, already known from the prior art, to be combinable with the above specific embodiments of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Exemplary embodiments of the present invention and their advantages are explained in greater detail below with reference to the appended figures. For the sake of clarity, the shapes in the figures are simplified and are not always illustrated true to scale. 
           [0026]      FIGS. 1A and 1B  show a perspective view and a sectional view of a first specific embodiment of the camshaft adjuster according to the present invention, in which a second free end of a coil spring cooperates with a second recess on the rotor; 
           [0027]      FIG. 1C  shows a sectional view of one refinement of the specific embodiment from  FIGS. 1A and 1B ; 
           [0028]      FIG. 2  shows a sectional view of a second specific embodiment of the present invention, in which the second free end of the coil spring is introduced into the second recess on the rotor; 
           [0029]      FIGS. 3A and 3B  show a perspective view and a sectional view of a first specific embodiment of the present invention, in which a first free end of the coil spring rests in a first recess on the stator; 
           [0030]      FIG. 4  shows a perspective view of one refinement of the specific embodiment from  FIGS. 3A and 3B ; 
           [0031]      FIGS. 5A and 5B  show a perspective view and a sectional view of another specific embodiment of the present invention, in which the first free end of the coil spring is suspended in the first recess on the stator; 
           [0032]      FIGS. 6A and 6B  show another perspective view and a sectional view of another specific embodiment of the present invention, in which the first free end of the coil spring is suspended in the first recess on the stator; 
           [0033]      FIG. 7  shows a sectional view of a cover of the camshaft adjuster according to the present invention, which is made up of an inner cover and an outer cover; 
           [0034]      FIGS. 8A, 8B, and 8C  each show a side view and a top view of known coil springs that are used in the present invention for subsequent  FIGS. 9A through 9F ; and 
           [0035]      FIGS. 9A through 9F  each show a top view and a side view of specific embodiments of the cover according to  FIG. 7 , in which the outer cover is a spring recess cover, and the first free end of the coil spring cooperates with same. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Identical reference numerals are used for similar or functionally equivalent elements of the present invention. In addition, for the sake of clarity, only reference numerals are illustrated in the individual figures that are necessary for describing the particular figure. The illustrated specific embodiments are used only to illustrate the camshaft adjuster according to the present invention by way of example, but are not to be construed as limiting the present invention. 
         [0037]      FIG. 1A  shows a perspective view and  FIG. 1B  shows a sectional view of a first specific embodiment of camshaft adjuster  1  according to the present invention, which is made up of a stator  2  and a rotor  4 . A spring in the form of a coil spring  6  rotatably braces rotor  4  against stator  2 , so that a drive torque of a camshaft, not illustrated here, may be compensated for during operation of camshaft adjuster  1 . According to the present invention, stator  2  includes a first recess  8  for a first free end  10  of coil spring  6 , and rotor  4  includes a second recess  12  for a second free end  14  of coil spring  6 . 
         [0038]    In  FIGS. 1A and 1B , only the specific embodiment is described in which second free end  14  of coil spring  6  cooperates with second recess  12  of rotor  4 . The description for  FIGS. 3A and 3B  is to be used for the specific embodiment of first recess  8  of first free end  10  of coil spring  6  on stator  2 . 
         [0039]    A square  16  at an inner wall  18  of rotor  4  forms second recess  12 , with which a correspondingly shaped spring winding  20  of second free end  14  of coil spring  6  cooperates in a form-fit manner. In particular, a last spring winding  20  of coil spring  6  has a corresponding angular or right-angled shape. When coil spring  6  is thus inserted into inner wall  18  of rotor  4 , a rotatably fixed connection is established between second free end  14  of coil spring  6  and rotor  4 . According to one specific embodiment of the present invention, a form-fit and rotatably fixed connection is established between coil spring  6  and rotor  4 . 
         [0040]      FIG. 1C  shows a sectional view of one refinement of the first specific embodiment from  FIGS. 1A and 1B , in which a width across flats of square  16  is designed to be small enough that square  16  is situated beneath a screw head of a screw  24  which fastens a cover  26  to stator  2 . Second free end  14  of coil spring  6  is axially held in position in this way. 
         [0041]      FIG. 2  shows a sectional view of a second specific embodiment of the present invention. A borehole  22  forms second recess  12  at an angle α less than 90° with respect to pulling direction R of coil spring  6  in rotor  4 , into which second free end  14  of coil spring  6  is introduced. This specific embodiment generates an axial force in a self-acting manner which automatically forces second free end  14  of coil spring  6  into the installation position. 
         [0042]      FIG. 3A  shows a perspective view and  FIG. 3B  shows a sectional view of a first specific embodiment of the present invention, in which a first free end  10  of coil spring  6  rests in a first recess  8  in stator  2 . For this purpose, camshaft adjuster  1  provides an additional metal sheet  28  which is mounted on stator  2  via at least two screws  24 , and which has formed an axial bulge  30  which forms first recess  8 , and in which first free end  10  of coil spring  6  rests. A partially cut-out element  52  is additionally provided on stator  2  to facilitate insertion of first free end  10  of coil spring  6  into axial bulge  30 . 
         [0043]      FIG. 4  shows a perspective view of one refinement of the specific embodiment from  FIGS. 3A and 3B . Here, metal sheet  28  is designed in such a way that in addition to this axial fixing of first free end  10  of coil spring  6 , further spring windings  20  of coil spring  6  are axially held in position. Coil spring  6  is thus prevented from falling out. 
         [0044]      FIG. 5A  shows a perspective view and  FIG. 5B  shows a sectional view of another specific embodiment of the present invention, in which first free end  10  of coil spring  6  is suspended in first recess  8  in stator  2 , in particular in such a way that at least one screw  24  forms an extended screw head  32  for first recess  8 . 
         [0045]      FIG. 6A  shows a perspective view and  FIG. 6B  shows a sectional view of another specific embodiment of the present invention, in which cover  26  forms an axial extension element  34  for first recess  8 , in which first free end  10  of coil spring  6  is suspended. Axial extension element  34  has a T-shaped design. 
         [0046]      FIG. 7  shows a sectional view of a cover  26  of camshaft adjuster  1  according to the present invention, which is made up of an inner cover  36  and an outer cover  38 . The inner cover is a sealing cover  36 , and the outer cover forms a spring recess cover  38  for first recess  8 , in which first free end  10  of coil spring  6  is suspended. This illustration of the screwing direction shows the screwing direction from the side of sealing cover  36  and of spring recess cover  38 . Alternatively, a screwing direction is also possible in which the thread in spring recess cover  38  is implemented in the form of cut threads or via press-in nuts. 
         [0047]    Detailed specific embodiments of the design of spring recess cover  38  are apparent from  FIGS. 9A through 9F  and are described with reference to same. 
         [0048]      FIGS. 8A, 8B, and 8C  each show a side view and a top view of known coil springs  6  used in the present invention for subsequent  FIGS. 9A through 9F . 
         [0049]    In  FIG. 8A , coil spring  6  is designed in such a way that it includes an axial leg  54 . Coil spring  6  in  FIG. 8B  is designed in such a way that it has formed a radial leg  54 . In contrast, in  FIG. 8C , coil spring  6  is formed from a combination from  FIGS. 8A and 8B ; i.e., coil spring  6  includes a leg  54  which is both axial and radial. 
         [0050]      FIGS. 9A through 9F  each show a top view and a side view of specific embodiments of cover  26  according to  FIG. 7 , in which the outer cover is a spring recess cover  36 , and first free end  10  of coil spring  6  is suspended therein. The leadthroughs or threads for fastening are not illustrated for the sake of simplicity. 
         [0051]    In  FIG. 9A , spring recess cover  36  for first recess  8  of first free end  10  of coil spring  6  has a cutout  40  in the form of a hole. The inner diameter of spring recess cover  36  here is preferably smaller than an outer diameter of coil spring  6 , so that an additional axial spring lock is achieved. In addition, in this specific embodiment a coil spring  6  which includes an axial leg  54  according to  FIG. 8A  is preferably used. 
         [0052]    Spring recess cover  36  in  FIG. 9B  has formed an elevated element  42 , i.e., an elevated slot, in which first free end  10  of coil spring  6  is suspended. The inner diameter of axial spring retainer and the selection of coil spring  6  correspond to  FIG. 9A . 
         [0053]    In  FIG. 9C , spring recess cover  36  for first recess  8  of first free end  10  of coil spring  6  includes an upwardly bent element  44 , such as an upwardly bent tab shown here. A coil spring  6  which includes a radial leg  54  according to  FIG. 8 b    is preferably used in this specific embodiment. The axial spring lock is preferably achieved here only via upwardly bent element  44 . However, it is also conceivable to reinforce the axial spring lock by using a coil spring  6  which includes an axial and radial leg  54  according to  FIG. 8C . 
         [0054]    Spring recess cover  36  in  FIG. 9D  has a free punched out portion  46  for first recess  8  of first free end  10  of coil spring  6  (not illustrated here). In this specific embodiment, coil spring  6  once again is a coil spring  6  which includes a radial leg  54  according to  FIG. 8 b   . An axial spring lock is not necessary in this specific embodiment. 
         [0055]    In  FIG. 9E , spring recess cover  36  for first recess  8  of first free end  10  of coil spring  6  (not illustrated here) includes, in addition to a free punched out 
         [0056]    portion  46  already described with reference to  FIG. 9D , an upwardly bent element  44  according to  FIG. 9C . Other combinations of the above-described specific embodiments of spring recess cover  36  for first recess  8  of first free end  10  of coil spring  6  are also conceivable. 
         [0057]    In  FIGS. 9A through 9E , spring recess cover  36  is a stamped closed ring  48 . However, as shown in  FIG. 9F , it is also conceivable for spring recess cover  36  to merely be at least a partial segment  50  of a ring  48  (see  FIGS. 9A through 9E ), which likewise has a cutout  40  for first recess  8  of first free end  10  of coil spring  6 . However, it is also conceivable for partial segment  50  to include an elevated element  42 , an upwardly bent element  44 , a free punched out portion  46 , or a combination thereof. 
       LIST OR REFERENCE NUMERALS 
       [0000]    
       
           1  camshaft adjuster 
           2  stator 
           4  rotor 
           6  spring, coil spring 
           8  first recess 
           10  first free end 
           12  second recess 
           14  second free end 
           16  polygon 
           18  inner wall 
           20  spring winding 
           22  borehole 
           24  screw 
           26  cover 
           28  metal sheet 
           30  axial bulge 
           32  screw head or screw shank 
           34  axial extension element 
           36  inner cover, sealing cover 
           38  outer cover, spring recess cover 
           40  cutout 
           42  elevated element 
           44  upwardly bent element 
           46  free punched out portion 
           48  ring 
           50  partial segment 
           52  cut-out element 
           54  leg 
         R pulling direction 
         α angle