Abstract:
A camshaft adjuster has multiple locking guide slots and multiple locking pins spring-loaded in the direction of engagement with the locking guide slots and which, by varying assignment to the rotor and to the stator, are arranged relative to one another such that the rotor can, under the action of fluctuating torques, be automatically locked into the predetermined center position relative to the stator proceeding from a first early or late stop position by a successive engagement of the locking pins into the locking guide slots. The locking pins and the locking guide slots are arranged so that, in the event of a rotation of the rotor in the direction of the center locking position proceeding from the respective other second early or late stop position, the locking pins lock into the locking guide slots in the reverse sequence from different directions.

Description:
The present invention relates to a camshaft adjuster. 
     BACKGROUND 
     Camshaft adjusters are generally used in valve train assemblies of internal combustion engines to vary the valve opening and closing times, whereby the consumption values of the internal combustion engine and the operating behavior in general may be improved. 
     One specific embodiment of the camshaft adjuster, which has been proven and tested in practice, includes a vane adjuster having a stator and a rotor, which delimit an annular space, which is divided into multiple working chambers by projections and vanes. A pressure medium may be optionally applied to the working chambers, which is supplied to the working chambers on one side of the vanes of the rotor from a pressure medium reservoir in a pressure medium circuit via a pressure medium pump, and which is fed back into the pressure medium reservoir from the working chambers on the particular other side of the vanes. The control of the pressure medium flow, and thus the adjusting movement of the camshaft adjusting device, takes place, e.g., with the aid of a central valve having an complex structure of flow-through openings and control edges, and a valve body, which is movable within the central valve and which closes or unblocks the flow-through openings as a function of its position. 
     One problem with camshaft adjusters of this type is that the camshaft adjuster is not yet completely filled with pressure medium in a start phase or may even have been emptied, so that, due to the alternating torques applied by the camshaft, the rotor may execute uncontrolled movements relative to the stator, which may result in increased wear and an undesirable noise development. To avoid this problem, it is known to provide a locking device between the rotor and the stator, which locks the rotor in a rotation angle position with respect to the stator which is favorable for startup when the internal combustion engine is turned off. In exceptional cases, for example if the internal combustion engine stalls, it is possible, however, that the locking device does not properly lock the rotor, and the camshaft adjuster must be operated with an unlocked rotor in the subsequent start phase. However, since some internal combustion engines have a very poor start behavior if the rotor is not locked in the central position, the rotor must then be automatically rotated into the central locking position and locked in the start phase. 
     Such an automatic rotation and locking of the rotor with respect to the stator are known, for example, from DE 10 2008 011 915 A1 and from DE 10 2005 011 916 A1. Both locking devices described therein include a plurality of spring-loaded locking pins, which successively lock into locking gates provided on the sealing cover of the stator when the rotor rotates and which each permit a rotation of the rotor in the direction of the central locking position before reaching the central locking position while blocking a rotation of the rotor in the opposite direction. After the internal combustion engine has warmed up and/or the camshaft adjuster has been completely filled with pressure medium, the locking pins are forced out of the locking gates, actuated by the pressure medium, so that the rotor is subsequently able to properly rotate with respect to the stator to adjust the rotation angle position of the camshaft. 
     One disadvantage of the approach described therein is that the automatic locking is always active only during a rotation of the rotor in one direction, i.e., the rotor is automatically locked only during a rotation from an “advance” or “retard” stop position in the direction of the central locking position. An automatic locking of the rotor from both “advance” and “retard” stop positions in the direction of the central locking position is not possible using the locking devices described therein. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a camshaft adjuster having an automatic locking device, which automatically locks the rotor in the central locking position during a rotation from both “advance” and “retard” stop positions. 
     The present invention provides that the locking pins and the locking gates are situated with respect to each other in such a way that the locking pins lock in the locking gates in reverse order from different directions during a rotation of the rotor from the particular other second “advance” or “retard” stop position in the direction of the central locking position. Due to the proposed approach, the same pair of locking gates and locking pins may be used for locking the rotor from both “advance” and “retard” stop positions. The approach according to the present invention is based on the fact that the locking gates and the locking pins only have to be shaped and situated with respect to each other in such a way that the locking pins lock into the locking gates from different directions during a rotation in both directions, so that the present invention may be implemented without additional costs compared to the prior art. 
     It is furthermore proposed that the locking gates are situated and shaped in such a way that the locking gate in which the first locking pin first locks or is locked during a rotation from a first “advance” or “retard” stop position is simultaneously the locking gate in which the last locking pin locks during a rotation of the rotor from the second “advance” or “retard” stop position into the central locking position. As a result, all locking gates used for locking the rotor from one “advance” or “retard” stop position are also used when locking the rotor from the other stop position, so that the number of necessary locking gates may be kept as small as possible with a predetermined number of locking steps. 
     It is furthermore proposed that the locking gate in which the first locking pin locks or is locked during a rotation of the rotor from the first or the second “advance” or “retard” stop position is shaped in such a way that the first locking pin locked therein comes to stop against the edge of the locking gate when the central locking position is reached and prevents the rotor from continuing to rotate in the same direction. The locking gate in which the first locking pin is locked thereby forms a stop surface and defines the predetermined central locking position in one direction due to the position of the edge side. 
     In this case, it is furthermore proposed that the locking gate in which the last locking pin locks during a rotation of the rotor from the first or second “advance” or “retard” stop position is situated and shaped in such a way that the locking pin locked therein blocks a rotation of the rotor counter to the preceding rotary motion. Due to the proposed refinement, the rotor is additionally blocked in the other direction of rotation after the last locking pin is locked, so that the rotor is unable to rotate from the central locking position in either the direction of the stop position “advance” or in the direction of the stop position “retard.” 
     It is furthermore proposed that at least three pairs of locking gates and locking pins are provided, and the locking gates are formed by curved, ring segment-shaped recesses or indentations, and the distances between the two locking gates in which the first and the second locking pins lock during a rotation of the rotor from one of the “advance” or “retard” stop positions and the distances between the locking pins locking therein are identical in the circumferential direction. Due to the proposed shaping and arrangement of the locking gates and the locking pins, identical locking paths of the rotor result during the rotary motion from the two stop positions. This also results in the possibility of situating the rotor in two different positions in the stator, if permitted by the pressure medium lines and the vanes of the rotor. 
     It is furthermore proposed that the two locking gates in which the first and second locking pins lock during a rotation of the rotor from the “advance” or “retard” stop position are situated axisymmetrically to a middle axis. Due to the axisymmetrical arrangement of the locking gates and the locking pins, the locking action may be implemented from the two stop positions particularly easily and using identical rotation angles. 
     It is furthermore proposed that the base surface of the locking gates has at least one step in at least one edge section. Due to the steps, multiple stop surfaces may be created in one locking gate, against which the locking pins are stopped in a blocking manner in the direction of the central locking position in the locking steps following the first locking of the locking pin. 
     In this case, the width of the step in the circumferential direction should correspond to the rotation angle of the rotor, around which the latter is rotated with respect to the stator until the next locking pin locks into the adjacent locking gate. Due to the proposed dimensioning of the width of the step, the locking pin engaging with the locking gate may be used to block the rotor against reverse rotation also in the additional locking steps after the first locking action, in that the locking pin then rests against the shoulder created by the step. 
     The locking gates in which one of the locking pins first locks or is locked during a rotation of the rotor from the “advance” or “retard” stop position may have one or multiple steps only on the edge section of the base surface, against which the locking pin rests in the “advance” or “retard” stop position, and the locking gates in which the engaging locking pins lock after the locking action of the first locking pin have at least one step on both edge sections of the base surface facing the adjacent locking gates. Due to the proposed arrangement of the steps, the circumstance may be taken into account that the first engaging locking pins always approach the locking gate only from one edge side and are finally inserted, while the second and third locking pins, provided that a total of four pairs of locking pins and locking gates are used, also approach the locking gates from different directions and are finally inserted therein as a function of the stop position from which the rotor is rotated in the direction of the central locking position. 
     It is furthermore proposed that the locking gates in which the first locking pin is locked in the “advance” or “retard” stop position are shaped in the manner of a circular arc section, and the length of the circular arc of the locking gates is dimensioned in such a way that the locking pins guided therein are movable from the “advance” or “retard” stop position into the central locking position. The locking pins which already engage with the first locking gate in the stop position are thereby guided into the locking gate until reaching the central locking position. The length of the circular arc is the length of the indentation or recess in the circumferential direction, minus the diameter of the locking pin, and corresponds to the length of the arc around which the locking pin is moved relative to the locking gate when the rotor moves with respect to the stator from the “advance” or “retard” stop position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is explained in greater detail below on the basis of one preferred exemplary embodiment. Specifically: 
         FIGS. 1, 2 and 3  show a camshaft adjuster, including a rotor in different locking positions, starting from the “retard” stop position in the direction of rotation toward the central locking position; 
         FIGS. 4, 5 and 6  show a camshaft adjuster, including a rotor in different locking positions, starting from the “advance” stop position in the direction of rotation toward the central locking position; 
         FIG. 7  shows a camshaft adjuster, including a rotor which is locked in the central locking position; and 
         FIG. 8  shows a sealing cover or the base surface of the stator, including multiple locking gates, and a sectional representation of a locking gate. 
     
    
    
     DETAILED DESCRIPTION 
     A camshaft adjuster of an internal combustion engine according to the present invention, including a stator  1  and a rotor  2 , is apparent in  FIG. 1 . Stator  1  has a cup-shaped design and is provided with a toothing  3  on its outside for the purpose of being driven by a crankshaft via a chain or toothed belt. Rotor  2  is connectable to a camshaft in the known manner, e.g., via a central screw, and is driven to a rotary motion with the aid of stator  1 . Stator  1  furthermore includes a plurality of stator webs  20 ,  21 ,  22 , and  23 , including threaded bores  4  situated therein, which divide an annular space provided between stator  1  and rotor  2  into multiple pressure chambers I. Rotor  2  includes a plurality of vanes  14 ,  15 ,  16  and  17 , which extend radially outwardly to the inner wall of stator  1  and divide each pressure chamber I into two working chambers A and B. A translucently represented sealing cover  5  is furthermore provided, which is screwed into threaded bores  4  of stator  1  with the aid of fastening screws and which includes four locking gates  6 ,  7 ,  8  and  9 . Four locking pins  10 ,  11 ,  12 ,  13  are also provided in rotor  2 , which are spring-loaded in the engagement direction of locking gates  6 ,  7 ,  8  and  9  and to which pressure medium may be applied via a common pressure medium channel  26  for the purpose of unlocking from locking gates  6 ,  7 ,  8  and  9 . During operation of the internal combustion engine, pressure chambers I are filled with pressure medium at least after a certain start phase, whereby the rotary motion of stator  1  is transmitted to rotor  2 . 
     Locking gates  6 ,  7 ,  8  and  9  are ring segment-like or circular arc-shaped recesses or indentations in sealing cover  5 , which are oriented and dimensioned in such a way that their center lines run on a common diameter. 
     Upper left vane  14  in the illustration is designed to be wider than remaining vanes  15 ,  16  and  17  and is used as a stop for rotor  2  for the purpose of limiting the rotary motion of rotor  2  with respect to stator  1  in the “advance” and “retard” stop positions. In order for rotor  2  to rotate into the provided stop positions in a preferably controlled manner without it being blocked in its rotary motion, e.g., by existing production radii, recesses  18  and  19  are provided on vane  14  on its outer edge sides extending into the illustration plane. For the same reasons, recesses  24  and  25  are provided on the two stator webs  20  and  21 , which delimit pressure chamber I in which vane  14  is situated, on the radially inner edge sides extending into the illustration plane. 
     In the illustration in  FIG. 1 , rotor  2  is in the “retard” stop position, i.e., rotor  2  rests with vane  14  against the right side of stator web  20  delimiting pressure chamber I. In this position of rotor  2 , working chamber A has the smallest volume and working chamber B to the right of vane  14  has the largest volume. In the event that the internal combustion engine is suddenly turned off in this position of rotor  2  or, e.g., if it suddenly shuts down due to stalling, problems may arise when the internal combustion engine is restarted, which are to be eliminated by the automatic reverse rotation of rotor  2 , which is described below, into central locking position MVP apparent in  FIG. 7 . The alternating torques which act upon the camshaft when the camshaft adjuster is not yet completely filled with pressure medium, in connection with the design of locking gates  6 ,  7 ,  8  and  9 , locking pins  10 ,  11 ,  12  and  13  proposed according to the present invention, are used for the automatic reverse rotation of rotor  2  into central locking position MVP as described below. 
     In the “retard” stop position illustrated in  FIG. 1 , first locking pin  10  already engages with locking gate  6 , while the other locking pins  11 ,  12  and  13  still rest against the side wall of sealing cover  5  outside locking gates  7 ,  8  and  9 . It is important that first locking pin  10  engages with locking gate  6  in such a way that rotor  2  is able to rotate relative to stator  1  at least clockwise in the direction of central locking position MVP. In the event that a torque acts upon rotor  2  in the clockwise direction in this position of rotor  2 , rotor  2  is rotated clockwise with respect to stator  1  into the position in  FIG. 2 , in which second locking pin  13  locks into adjacent locking gate  9 . If a subsequent torque occurs in the opposite direction, rotor  2  can no longer rotate back into the “retard” stop position. The next time a torque oriented in the clockwise direction acts upon the camshaft and thus on rotor  2 , the latter continues to be rotated in the clockwise direction into the position illustrated in  FIG. 3 , in which second locking pin  13  locks into locking gate  9 . Locking pin  10  is also moved into locking gate  6 , so that it no longer rests against the radially oriented edge section of locking gate  6 . The reverse rotation of rotor  2  back to the “retard” stop position is blocked in this position of rotor  2  by locking pin  13 , which rests against the radial edge section of locking gate  9 . During another rotation of rotor  2 , locking pin  12  finally locks into locking gate  8  (see  FIG. 3 ) in a next step, and last locking pin  11  finally locks into locking gate  7  in the central locking position MVP illustrated in  FIG. 7 . 
     In central locking position MVP illustrated in  FIG. 7 , locking pins  10  and  11  rest against the radial edge sections of locking gates  6  and  7 , so that rotor  2  is locked with respect to stator  1  in both directions of rotation. 
     The same camshaft adjuster having rotor  2  situated in the “advance” stop position is apparent in  FIG. 4 , in which rotor  2  rests with vane  14  against stator web  21 , which delimits pressure chamber I on the other side. Locking pin  11  is already locked into locking gate  7 . If the internal combustion engine is started with the aid of a rotor  2  in this position, rotor  2  is gradually rotated counterclockwise into the position shown in  FIG. 5  and  FIG. 6 , based on the same principle of the active alternating torques, locking pins  12  and  13  consecutively locking until last locking pin  10  finally locks into locking gate  6 , and rotor  2  is blocked with respect to stator  1  in central locking position MVP illustrated in  FIG. 7 . The automatic reverse rotation of rotor  2  from the “advance” and “retard” stop positions is based on the same principle, with the difference that, during a rotation of rotor  2  from the “advance” stop position, locking pins  10 ,  11 ,  12  and  13  lock into locking gates  6 ,  7 ,  8  and  9  in the reverse order and from different directions than during a reverse rotation of rotor  2  from the “retard” stop position. The automatic reverse rotation of rotor  2  is thus implemented using the same locking pins  10 ,  11 ,  12 ,  13  and locking gates  6 ,  7 ,  8  and  9 , so that no additional costs arise compared to the approach known from the prior art. 
       FIG. 8  shows two locking gates  6 ,  7 ,  8 ,  9  in which the first and second locking pins  10 ,  11 ,  12 ,  13  lock during a rotation of the rotor  2  from the “advance” or “retard” stop position are situated axisymmetrically to a middle axis X. 
     Sealing cover  5 , including locking gates  6 ,  7 ,  8  and  9 , is apparent in  FIG. 8 . A sectional representation along section line F-F of locking gate  8  is shown in the illustration on the right. Locking gates  8  and  9 , in which second or third locking pin  12  or  13  locks during a rotation of rotor  2  from the “advance” and “retard” stop positions, are each provided with steps  27  on their edge sections of the base surface oriented in the circumferential direction, while locking gates  6  and  7 , into which first or last locking pin  10  or  11  locks, are provided with steps  27  only on their edge sections of the base surfaces facing each other. This is due to the fact that locking pins  10  and  11  always lock into locking gates  6  and  7  only from one side during the automatic reverse rotary motion, since one of locking pins  10  and  11  already engages with locking gate  6  or  7  in the “advance” and “retard” stop positions. 
     Steps  27  each form stop surfaces in the manner of a grid pattern, against which locking pins  10 ,  11 ,  12  and  13  rest in the circumferential direction in the intermediate positions between the “advance” and “retard” stop positions and central locking position MVP. As a result, the reverse rotation of rotor  2  is blocked in the direction of the “advance” and “retard” stop positions, and a continued rotation of rotor  2  in the direction of central locking position MVP is simultaneously facilitated. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  stator 
           2  rotor 
           3  toothing 
           4  threaded bore 
           5  sealing cover 
           6  locking gate 
           7  locking gate 
           8  locking gate 
           9  locking gate 
           10  locking pin 
           11  locking pin 
           12  locking pin 
           13  locking pin 
           14  vane 
           15  vane 
           16  vane 
           17  vane 
           18  recess 
           19  recess 
           20  stator web 
           21  stator web 
           22  stator web 
           23  stator web 
           24  recess 
           25  recess 
           26  pressure medium channel 
           27  step