Patent Document

The present invention relates to a hydraulic camshaft adjuster having stator and a rotor situated so that it is rotatable in relation thereto, the stator being connected to at least one separate cover, which seals a cavity situated between the rotor and the stator. 
     BACKGROUND 
     Camshaft adjusters, in particular hydraulic camshaft adjusters, are already known from the prior art from U.S. Pat. No. 6,276,321 B1, for example. 
     Such devices for variable adjustment of the control times of gas exchange valves are used in modern internal combustion engines to be able to variably set the phase ratio between the crankshaft and the camshaft in a defined angle range between a maximum “advance” position and a maximum “retard” position. For this purpose, the camshaft adjuster is integrated into a drive train, via which the torque is transferred from the crankshaft to the camshaft. This drive train may include a traction means such as a belt drive or a chain drive. A gear drive may also be used in this regard. 
     Details of how camshafts are modified in comparison with a crankshaft of an internal combustion engine are to be found in the publications DE 10 2010 012 482 A1 and DE 2011 003 556 A1, for example. A device for controlling and/or influencing valve control times of an internal combustion engine is also known from DE 10 2010 024 596 A1 and DE 10 2009 037 976 A1. 
     The details described in these publications also form the basis for the refinement presented here and will not be discussed further here but should be considered as integrated therein. 
     Previously, the cavity between the rotor and the stator, which is to be filled with a hydraulic fluid, such as a liquid, namely oil, has been sealed by at least one cover with respect to the outside. A screw connection is usually used here. 
     However, such a screw connection approach has the disadvantage that it requires many individual parts. This makes the assembly difficult. Furthermore, the possibility of leakage cannot always be ruled out reliably. Furthermore, such a screw connection approach is relatively heavy, so that heavy camshaft adjusters must be used. This is disadvantageous for the consumption of the motor vehicles, which use such camshaft adjusters on internal combustion engines. The precision of the adjustment angle between the rotor and the stator is also not adequately high in some application cases. Unfortunately, ease of dismantling and/or misuse cannot be ruled out in all application cases. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to eliminate these disadvantages, to omit screw connections and nevertheless make available a long-lived as well as a permanently well-functioning assembly subunit. 
     The present invention provides that in the case of a generic hydraulic camshaft adjuster, the material of the stator, encompassing the cover at least partially, is formed without machining in the area of the cover. 
     Thus a secure connection is created which is designed to withstand higher pressure loads at minimized costs nevertheless. A simple design of the camshaft adjuster is just as possible as the provision of a larger adjustment angle. Misuse is ensured due to the secure connection making dismantling difficult. Leakage may also be reduced substantially. External leakage is even completely ruled out. Fewer individual parts must be used and screws and nuts may be omitted in particular. 
     It is advantageous if there is a force-locked and/or form-fitting connection between the stator and the cover. This makes it possible to simplify production and ensure a fail-safe cooperation of the individual parts. 
     It is also advantageous if the connection forms an undercut in which the cover is retained with a seal. This makes it possible to withstand particularly high pressures. 
     It has been found to be almost optimal if the cover is secured on the stator by a rolled connection. 
     It is advantageous here if the rolled connection is formed over the entire circumference of the cover or if it is formed on only some sections. If a flow of material is induced over 360°, then the seal is formed over the entire circumference and is particularly resilient. 
     If the material of the stator is forced and/or flows into a cavity, the cavity being between the stator and a chamfer situated on the side of the cover facing away from the cavity and extending preferably over the circumference, then a particularly efficient connection of the two components is ensured. It is advantageous here if the cavity is completely filled by the material of the stator. 
     An advantageous exemplary embodiment is also characterized in that the cover is mounted on at least one axial end of the cavity accommodating a hydraulic fluid such as oil, preferably on the face side of the stator, and the other axial end of the cavity is situated above an integral bottom of the stator, which is then designed in the form of a cup. Furthermore, another exemplary embodiment is characterized in that a first cover, which is separate from the stator, is attached to at least one first axial end of the cavity, preferably to a first face side of the stator, which is then in the form of a bushing or sleeve, and a second cover is attached to a second axial end of the cavity, preferably the second face side of the stator. The two covers may be connected to the stator via exterior rolled connections. In the first of the aforementioned two exemplary embodiments, the same parts may be increasingly resorted to, while the number of individual parts may be reduced in the second of the aforementioned two exemplary embodiments. 
     It is also particularly effective if the cover is designed as a sealing cover and/or as a locking cover having a locking contour. The cover may then be connected to the stator via a rolled connection in a form-fitting manner after insertion of the interior structure of the adjuster, with the stator in a predefined location, thereby causing a flow of material over the cover by 360°. 
     It is also advantageous if the first cover is designed as a sealing cover and the second cover, which is preferably situated on the side of a gearwheel engaging on the stator, is designed as a locking cover, which seals the cavity. This results in a particularly secure connection having good force distribution properties. 
     It is also advantageous if the stator and/or the cover is/are made of metal such as sintered metal because then a particularly stable approach is achievable. 
     If, in addition to the rolled connection, form-fitting elements take effect such as protrusions engaging in recesses, then a twist-proof security is achievable in a particularly effective manner and microgliding may also be prevented. The form-fitting elements may be aligned in the axial direction and/or in the radial direction just like additional force-locking elements. Such force-locking elements may be formed by roughened areas, application of adhesive or addition of solder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is also explained in greater detail below with the aid of drawings in which two exemplary embodiments are shown. 
         FIG. 1  shows a longitudinal sectional diagram through a first specific embodiment of a hydraulic camshaft adjuster according to the present invention having only one cover, 
         FIG. 2  shows an enlargement of the connecting area between the cover and the stator from  FIG. 1 , 
         FIG. 3  shows a view from the front of the camshaft adjuster from  FIG. 1 , 
         FIG. 4  shows a longitudinal section through a second specific embodiment of a hydraulic camshaft adjuster having two covers, each being connected to the stator via one rolled connection, 
         FIG. 5  shows an enlargement of the connecting area between a cover at a distance from the gearwheel and the stator on the camshaft adjuster from  FIG. 4 , and 
         FIG. 6  shows a side view of the hydraulic camshaft adjuster from  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     These figures are only of a schematic nature and only promote an understanding of the present invention. The same elements are provided with the same reference numerals. 
       FIG. 1  shows a first specific embodiment of a hydraulic camshaft adjuster  1  according to the present invention. The hydraulic camshaft adjuster has a stator  2 , which is designed in the form of a cup in the exemplary embodiment shown here. 
     A rotor  3  is accommodated in the interior of stator  2 . Rotor  3  is rotatably mounted in relation to stator  2  about a common longitudinal axis  4 , which functions as the axis of rotation. Stator  2  has a bottom  5  and a longitudinal wall  6  which extends completely around longitudinal axis  4  and is closed on the circumference. Bottom  5  is an integral part of longitudinal wall  6 . A cover  7  is provided on the side opposite bottom  5 . 
     An integral gearwheel  8  is also formed on stator  2  on the side of bottom  5 . Gearwheel  8  is designed for coming into force-transferring contact with a traction means, such as a chain or a belt for transferring force from a crankshaft to stator  2 . 
     Rotor  3  has an insert area  9  for insertion of a central valve. Two fluid lines  10  are recognizable in the sectional view in  FIG. 1 , although multiple fluid lines  10  are used. Different cells of a cavity  11  situated between stator  2  and rotor  3  may be supplied with hydraulic fluid (hydraulic oil) in a targeted or directed manner. 
     A connection  12  is formed between stator  2  and cover  7  on the side of cover  7  facing away from bottom  5 . This connection  12  is discernible in a particularly clear manner in  FIG. 2 . Connection  12  is created by a rolling operation in which material of stator  2  has been formed/compressed around an edge of cover  7 . In the corresponding formation without machining, the material flows pressure-induced behind cover  7 . 
     Cover  7  is inserted fittingly or with an excess of fit into the cavity between a chamfer  13  and an inner wall  14  of stator  2 . Cover  7  acts as a sealing cover. 
     The material of stator  2  situated adjacent to cover  7 , in particular adjacent to chamfer  13  of cover  7  and on the end of stator  2  remote from the bottom in longitudinal wall  6  of stator  2 , has been forced into the aforementioned cavity between cover  7  and stator  2  by a rolling operation/formation without machining. The material of stator  2  has flowed into this cavity and completely fills the cavity. 
     The end of stator  2  remote from bottom  5  protrudes beyond cover  7  (protruding axially). A recess  15  is formed there and may also be referred to as a groove or channel. 
       FIG. 3  shows the hydraulic camshaft adjuster  1  having a central valve which is not yet inserted into insert area  9 . 
       FIGS. 4 through 6  illustrate an exemplary embodiment, which has been modified in comparison with  FIGS. 1 through 3 . Whereas stator  2  is designed in the form of a cup in the exemplary embodiment illustrated in  FIGS. 1 through 3 , stator  2  in the second exemplary embodiment is designed in the form of a sleeve or bushing. It is designed in the manner of a hollow cylinder having a circular interior and exterior contour, circumferential grooves or channels for accommodating cover  7  being provided on the inner circumference at the ends. 
     Stator  2  thus has no bottom  5  but instead also has a cover  7  in this location but it is inserted into stator  2  as a locking cover having a locking contour, thereby forming a seal. As is also the case with cover  7  (sealing cover), which (only) forms a seal at a distance from the gearwheel, this second cover  7  (locking cover) is also in contact with a shoulder  16  of stator  2 , the shoulder being formed by the corresponding groove or channel. 
     Just as left cover  7  is attached to stator  2  via a rolled connection, right cover  7  is also attached to stator  2  via a rolled connection. The corresponding rolled connections extend around longitudinal axis  4  by 360°. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  hydraulic camshaft adjuster 
           2  stator 
           3  rotor 
           4  longitudinal axis 
           5  bottom 
           6  longitudinal wall 
           7  cover 
           8  gearwheel 
           9  insert area 
           10  fluid line 
           11  cavity 
           12  connection 
           13  chamfer 
           14  interior wall 
           15  recess 
           16  shoulder

Technology Category: 2