Abstract:
A camshaft adjuster for motor vehicles has a stator and a rotor rotatable relative thereto between which pressure chambers are provided. Pressure medium is supplied in a controlled way via a valve to the pressure chambers in order to rotate the rotor relative to the stator. Mounting of the valve in the internal combustion engine of the motor vehicle is often difficult when mounting conditions are tight, sometimes even impossible. In order for the camshaft adjuster to be usable even in tight spatial conditions, the valve is arranged on the side facing away from the camshaft connection. The valve can therefore be arranged stationarily axially outside of the engine of the motor vehicle. The camshaft adjuster requires thus only little mounting space.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a camshaft adjuster for internal combustion engines of motor vehicles comprising a stator and a rotor rotatable relative to the stator, between which pressure chambers are provided that are connected by lines with at least one valve via which pressure medium is supplied to the pressure chambers, respectively. 
     By means of camshaft adjusters, the timing of opening of intake and exhaust valves of internal combustion engines is controlled as a function of the output required at the moment. Often it is difficult to mount the valve in the internal combustion engine of the motor vehicle because there is not enough space. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to configure the camshaft adjuster of the aforementioned kind such that it can be used even in tight space conditions in the motor vehicle. 
     This object is solved according to the invention for the camshaft adjuster of the aforementioned kind in that the valve is arranged on the side of the camshaft adjuster facing away from the camshaft connection. 
     In the camshaft adjuster of the present invention the valve is arranged on the side facing away from the camshaft connection. For this reason, the valve can be arranged stationarily axially outside of the motor. The camshaft adjuster according to the invention requires thus only little mounting space. Moreover, the camshaft adjuster according to the invention can also be retrofitted. 
     According to another embodiment, the valve is arranged at least partially within the camshaft adjuster. In this way, no additional mounting space for the valve in the internal combustion engine is required. 
     Further features of the invention can be taken from the further claims, the description, and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail by means of one embodiment illustrated in the drawings. It is shown in: 
         FIG. 1  in axial section a camshaft adjuster according to the invention (A and B bores); 
         FIG. 2  in another axial section the camshaft adjuster according to the invention according to  FIG. 1  (T bore); 
         FIG. 3  a section along the line III—III in  FIG. 2 ; 
         FIG. 4  a section along the line IV—IV of  FIG. 2 ; 
         FIG. 5  on an enlarged scale and in axial section a valve of the camshaft adjuster according to the invention (A and B bores); 
         FIG. 6  in a representation corresponding to  FIG. 5  another axial section of the valve of the camshaft adjuster according to the invention (T bore). 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The camshaft adjuster according to  FIGS. 1 through 4  serves for adjusting the timing of opening of the intake and exhaust valves of an internal combustion engine of a motor vehicle in accordance with the output requirement of the engine. Such camshaft adjusters are known and will therefore be explained only briefly. 
     The camshaft adjuster has a rotor  1  which is connected fixedly to the camshaft  2 . The rotor  1  is surrounded by a stator  3 . It has a cylindrical jacket  4  provided on its inner wall with radially inwardly projecting stays  5  that are uniformly spaced from one another. They are identical and rest with their end faces  6  areally against an outer cylindrical peripheral surface  7  of a base member  8  of the rotor  1 . Radially outwardly projecting stays  9  that are uniformly spaced project from the rotor and rest with their end faces areally and sealingly against an inner cylindrical peripheral surface  11  of the jacket  4  of the stator  3 . The stays  5 ,  9  of the stator  3  and of the rotor  1  are configured as unitary parts of the jacket  4  and the base member  8 , respectively. 
     Neighboring stays  5  of the stator delimit pressure chambers  12  which are divided by the rotor stays  9  into two pressure chambers  13  and  14 , respectively; they are sealed relative to one another by the rotor stays  9 . In the end position illustrated in  FIGS. 3 and 4 , the radially extending lateral surfaces  15  of the rotor stays  9  rests areally against the radially extending sidewall  16  of the stator stays  5 . From this first end position, the rotor  1  can be rotated in a counterclockwise direction relative to the stator  3  by introduction of a pressure medium into the pressure chambers  14  to such an extent that the rotors stays  9  with their oppositely positioned sidewalls  17  rest against the neighboring sidewalls  18  of the stator stays  5 . Between these two end positions, the rotor  1  can be rotated by a corresponding pressure loading of the sidewalls  15 ,  17  of the rotor stays  9  into any intermediate position relative to the stator  3 . 
     In the inner peripheral surface  11  of the statorjacket  4  in a transitional area into the lateral surfaces  16 ,  18  of the stator stays  5 , dirt collecting grooves  19  are provided where, during operation of the camshaft adjuster, dirt that is contained in the pressure medium is displaced as a result of centrifugal forces radially outwardly and will collect in the dirt collecting grooves  19 . In this way, it is ensured that the rotor stays  9  in the respective end position rest properly against the sidewalls  16 ,  18  of the stator stays  5  and that no dirt particles are positioned between them. In this way, at any time a precise relative position between stator  3  and rotor  1  in the end position is ensured. The dirt collecting grooves  19  extend across the axial width of the stator  3 . In deviation from the illustrated embodiment, the dirt collecting grooves  19  can be arranged, for example, also along the inner peripheral surface  11  of the stator jacket  4 . It is also possible to provide the dirt collecting grooves  19  in the sidewalls  16 ,  18  of the stator stays  5  and/or in the sidewalls  15 ,  17  of the rotor stays  9 . The bottom of the dirt collecting grooves  19  is curved in radial section according to  FIGS. 3 and 4  so as to have a part-circular shape. 
     The stator  3  is closed at one side by a drive wheel  20  which can be a chain wheel or a pulley. It is screwed onto the stator  3 . On the opposite side, the stator  3  is closed by a cover plate  21 . It has the same outer diameter as the stator  3  and rests with its radial inner end on an annular shoulder surface  22  of the rotor  1 . Advantageously, the drive wheel  20  and the cover plate  21  are connected by screwing relative to one another by screws  23  ( FIGS. 3 and 4 ) penetrating the stator stays  5 . By means of these screws  23  the drive wheel  20  and the cover plate  21  are forced axially tightly against the end faces of the stator  3 . Also, the drive wheel  20  rests against an annular shoulder surface  24  on the rotor  1 . The drive wheel  20  has a greater outer diameter than the stator  3 . 
     The camshaft adjuster is covered by a hood-shaped covering cap  25  that has a radial bottom  26  penetrated centrally by a valve housing  27 . It has a radially outwardly oriented flange  28  with which the valve housing  27  rests against the underside of the bottom  26  of the covering cap  25  and is fastened thereon, for example, by screws. The cylindrical jacket  29  of the covering cap  25  projects axially past the drive wheel  20  and surrounds it at a radial spacing. 
     The rotor  1  is provided at its end facing away from the bottom  26  of the covering cap  25  with a central recess  30  into which the camshaft  2  projects with its axial projection  31 . The recess  30  of the rotor  1  is separated by a radially inwardly oriented flange  33  from a receptacle  32  for receiving the valve housing  27 ; the flange  33  axially delimits the recess  30 . A central screw  35  projects through a central opening  34  in the flange  33  and is screwed into an axially and centrally arranged threaded bore  36  of the camshaft  2  in order to connect the camshaft adjuster to the camshaft  2 . The head  37  of the screw  35  is supported on the flange  33  of the base member  8  of the rotor  1  in the axial direction. By means of the central screw  35 , the rotor  1  is connected fixedly to the camshaft  2 . 
     The valve housing  27  is a component of a hydraulic valve  38  via which the hydraulic medium is supplied to the pressure chambers  13  and  14  of the camshaft adjuster in a way to be described in the following. The valve housing  27  is provided on its exterior with annular grooves  39  for receiving annular seals  40  by means of which the valve housing  27  is mounted in a seal-tight way in the receptacle  32  of the rotor  1 . As illustrated in  FIGS. 1 and 2 , the valve housing  27  extends into close proximity of the screw head  37 . 
     A hollow piston  41  is mounted axially slidably within the valve housing  27  and is closed at the end facing away from the screw  35  by a bottom  42 . At the other end, the hollow piston  41  is open. At this end, the hollow piston  41  has a widened inner diameter. At least one pressure spring  43  projects into this end and loads the hollow piston  41  in the direction of a lid  44  that rests against the flange  28  of the valve housing  27  and is fastened thereto. The lid  44  has a central recess  45  into which the hollow piston  41  projects with its bottom  42 . The pressure spring  43  is supported with one end on the radial inner shoulder surface  46  within the hollow piston  41 . The other end of the pressure spring  43  rests against the end face of a bushing  47  which is received in a cup-shaped housing  48  that is screwed into the end of the valve housing  27  facing away from the lid  44 . The bushing  47  is supported on the bottom  49  of the housing  48 . It has at least one opening  50  via which the hydraulic medium can be supplied. The hydraulic medium is supplied centrally to the camshaft adjuster via the camshaft  2  and an axial through bore  51  in the screw  35 . 
     The bushing  47  receives a support body  57  having at the end face facing the bottom  49  of the housing  48  a central recess  52  for receiving a pressure spring  53 . By means of the pressure spring, the valve disk  54  of a check valve  59  is forced against a radial shoulder surface  55  of the bushing  47 . The valve disk  54  is arranged within the bushing  47  and closes a central opening  56  of the bushing  47 . 
     The support member  57  has a smaller outer diameter than the bushing  47 . The bushing  47  is provided with a filter  58  at the side facing away from the pressure spring  53  through which the hydraulic medium will flow before entering the hollow piston  41 . Contaminants in the hydraulic medium are retained in the filter  58 . 
     The hydraulic valve  38  has two working connectors A and B, a tank connector T as well as a pressure connector P. Via the working connectors A and B, the hydraulic medium is supplied, depending on the position of the hollow piston  41 , to the pressure chamber  13  or  14  of the camshaft adjuster. Via the tank connector T the hydraulic medium is returned from the pressureless pressure chambers  13  or  14  into the tank. 
     A check valve  59  is arranged upstream of the hydraulic valve  38  and ensures that the hydraulic medium cannot flow from the hollow piston  41  back into the camshaft  2 . The force exerted by the pressure spring  53  of the check valve  59  onto the valve disk  54  is smaller than the force of the pressure spring  43  for loading the hollow piston  41 . 
     Since the hydraulic valve  38  is provided centrally on the camshaft adjuster and is aligned with the camshaft  2 , the camshaft adjuster requires only little mounting space. Therefore, the camshaft adjuster can be retrofitted in a motor vehicle. The valve housing  27  of the hydraulic valve  38  can be simply inserted from an end face of the camshaft adjuster into the receptacle  32  of the base member  8  of the rotor  1 . The mounting position of the hydraulic valve  38  can be determined simply in that the flange  28  of the valve housing  27  will come to rest against the bottom  26  of the covering cap  25 . The hollow piston  41  in the illustrated embodiment is slidably guided in the valve bushing  60  which is arranged in a seal-tight way in the valve housing  27 . The valve bushing  60  has at its end facing the lid  44  a radially outwardly oriented flange  61  with which it rests against the bottom of a recess  62  provided at an end face of the valve housing  27 . In this way, the axial mounting position of the valve bushing  60  can be simply determined. By means of the lid  44 , the valve bushing  60  is secured in its position in that the lid  44  rests against the flange  61  of the valve bushing  60 . 
       FIGS. 3 and 4  show that bores  63 ,  64 , extending from the hydraulic valve  38  and penetrating radially the base member  8  of the rotor  1 , open into the pressure chambers  13 ,  14  of the camshaft adjuster, respectively. In  FIGS. 3 and 4 , the pressure chambers  13  are pressurized by means of the hydraulic medium. Accordingly, the hydraulic medium is supplied via the camshaft  2 , the through bore  51  of the screw  35 , the check valve  59 , the work connector A and the bores  63  to the pressure chambers  13 . The pressure chambers  14 , separated by the rotor stays  5  from the pressure chambers  13 , are relieved of pressure. The hydraulic medium contained therein is displaced via the bores  64 , the work connector B of the hydraulic valve  38 , and the tank connector T to the tank. The hollow piston  41  of the hydraulic valve  38  is adjusted such that the hydraulic medium under pressure is supplied via the working connector A to the pressure chambers  13  and the hydraulic medium is returned from the pressure chambers  14  via the working connector B and the tank connector T to the tank. When it is desired to rotate the rotor  1  from the position according to  FIGS. 3 and 4  in a counterclockwise direction relative to the stator  3 , the hydraulic valve  38  is switched such that the pressure connector P is connected to the working connector B and the working connector A is connected to the tank connector T. The hydraulic medium under pressure is therefore supplied via the camshaft  2 , the screw  35 , the check valve  59 , the working connector B, and the bores  64  to the pressure chambers  14 . The hydraulic medium contained in the pressure chambers  13  is accordingly displaced via the bores  63  and the working connector A to the tank connector T. 
     The filter  58  upstream of the hydraulic valve  38  contributes to the robustness of the camshaft adjuster and of the entire system. The check valve  59  arranged upstream of the hydraulic valve  38  optimizes the entire performance of the system. 
       FIG. 5  shows in an enlarged illustration the hydraulic valve of the camshaft adjuster.  FIG. 5  illustrates the situation that the hydraulic medium supplied via the axial pressure connector P from the camshaft  2  flows via the check valve  59  into the hollow piston  41 . It is in such a position that the working connector A of the hydraulic valve  38  is connected to the tank connector T while the working connector B is connected to the axial pressure connector P. The hydraulic medium under pressure flows via radial openings  65  out of the hollow piston  41  into the working connector B. From here the hydraulic medium flows into axially extending bores  66  arranged within the valve housing  27  and configured as blind bores closed at their end facing the camshaft  2  by a closure part  67 . Bores  68  open into the bores  66  that are provided at the bottom of an annular groove  69  in the outer peripheral surface  70  of the valve housing  27 . The bores  63  open into the annular groove  69  provided within the base member  8  of the rotor. 
     In the peripheral surface  70  of the valve housing  27  an additional annular groove  71  is provided, and bores  72  open into the bottom of this groove and are distributed circumferentially; they connect the annular groove  71  with axial bores  73  in the valve housing  27 . As illustrated in  FIG. 5 , the bores  73  are shorter than the bores  66 . The bores  73  open into the end face of the valve housing  27  facing the camshaft  2  and are closed by a closure part  74 . Radial bores  64  in the base member  8  of the rotor open into the annular groove  71 , positioned at an axial spacing from the annular groove  69 . Radial bores  75  that are distributed about the circumference open into the axial blind bores  73  and are provided near the inner end of the blind bores  73  for connecting them to bores  76  radially penetrating the hollow piston  41 . Via these bores, the hydraulic medium can be supplied to the tank connector T.  FIG. 6  shows that in the valve housing  27  of the hydraulic valve  38  at least one axially extending tank bore  77  is provided and opens also at the end face of the valve housing  27  facing the camshaft  2  where it is closed by a closure part  78 . On the end facing away from the closure part  78 , the tank bore  77  is connected to an annular groove  79  provided in the valve housing  27 ; radial bores  80  that are distributed uniformly about the circumference open into the annular groove and penetrate the valve bushing  60 . By means of these radial bores  80 , the annular groove  79  is connected with an additional annular groove  81  provided at the inner side of the valve bushing  60  and opens into the radial bores  82  penetrating the hollow piston  41  in direct vicinity of its bottom  42 . 
     An elastically deformable annular band  83  rests against the bottom of the annular groove  81  with elastic pretension and is axially secured. It closes the radial bores  80  of the valve bushing  60  relative to the hollow piston  41 . The annular band  83  forms thus a check valve which prevents that the hydraulic medium under pressure can reach the tank bore  77  via the inner chamber of the hollow piston  41  and its radial bores  82 . 
     In the position of the hollow piston  41  illustrated in  FIG. 6 , the hydraulic medium supplied axially from the camshaft  2  to the hydraulic valve  38  flows via the pressure connector P into the hollow piston  41 . From here, the hydraulic medium flows via the radial bores  65  ( FIG. 5 ) penetrating it and the axial bores  66  to the working connector B. From here, the pressure medium flows into the corresponding pressure chambers of the camshaft adjuster. The hydraulic medium displaced from the other pressure chamber, respectively, flows according to  FIG. 6  via the working connector A and the bores  75 ,  76  into the tank bore  77 . From here, the hydraulic medium flows via the annular groove  79  and the radial bores  80  to the annular band  83 . It is bent elastically inwardly under the pressure of the medium so that the radial bores  80  in the valve bushing  60  are released. The hydraulic medium can therefore flow via the annular groove  81  and the radial bores  82  into the hollow piston  41 . This displaced medium mixes with the pressurized hydraulic medium that is supplied via the pressure connector P and is supplied via the working connector B to the pressure chambers of the camshaft adjuster, respectively. The ring band  83  serving as a check valve prevents that the pressurized hydraulic medium can reach the tank bore  77 . 
     In deviation from the illustrated embodiment, it is also possible to supply the hydraulic medium outside of the camshaft  2  radially to the hydraulic valve  38 .