Abstract:
A camshaft phaser for an internal combustion engine having—a stator ( 1 ) driven by a crankshaft of the internal combustion engine; a rotor ( 3 ) connected to the camshaft ( 24 ) for co-rotation therewith; and working chambers, which are configured between the stator ( 1 ) and the rotor ( 3 ) and which are subdivided into pressure chambers (A, B) by vanes ( 18 ) that are associated with the rotor ( 3 ); and - a pressure medium circuit having a plurality of pressure medium channels (A 1,  B 1,  C 1,  E 1 ) that fulfill different functions, at least two of the pressure medium channels (A 1,  B 1,  C 1,  D 1 ) merging into one another in one section ( 14 ); and one of the pressure medium channels (A 1,  B 1,  C 1,  D 1 ) being separated in a pressure medium-tight manner from the other pressure medium channel (A 1,  B 1,  C 1,  D 1 ) by a guide sleeve ( 13 ) that is inserted into the section ( 14 ).

Description:
[0001]    The present invention relates to a camshaft phaser for an internal combustion engine. 
       BACKGROUND 
       [0002]    Camshaft phasers are used in modern internal combustion engines to optimize fuel-economy figures and performance data. They serve to variably adjust the opening and closing times of the gas-exchange valves. For that purpose, the camshaft phaser has a stator driven by the crankshaft and a rotor connected to the camshaft for co-rotation therewith. Between the rotor and the stator, working chambers are provided that are able to be acted upon by a pressure medium and that are subdivided by vanes associated with the rotor into reciprocally acting pressure chambers. During operation of the internal combustion engine, both pressure chambers are permanently filled with pressure medium, so that the rotor and the stator are interconnected relatively stiffly. The timing of the gas-exchange valves is then thereby varied by increasing the pressure prevailing in one of the pressure chambers, while decreasing the pressure in the respective other pressure chamber. This requires supplying the pressure medium to the one pressure chamber and conducting it away from the other pressure chamber. To ensure that the system is not set into vibration, the inflow of the pressure medium must generally be controlled by the outflow thereof. 
         [0003]    During engine start, the situation can occur where both pressure chambers are only partially filled with pressure medium since the camshaft phaser can drain itself independently via leakage sites. During this time period, the rotor is not hydraulically clamped in the camshaft phaser, so that it can vibrate uncontrollably. To avoid this effect, camshaft phasers are already equipped with a mechanical locking system that couples the rotor to the stator via a fixed mechanical connection. To ensure that the rotor is reliably locked, the locking position corresponds to the limit stop of the rotor relative to the stator either in the timing advance or the timing retard direction. 
         [0004]    The German Patent Application DE 10 2008 052 275 A1 describes a camshaft phaser having two hydraulically actuatable locking devices, where the rotor can be locked in a middle position relative to the stator. This requires providing additional pressure medium channels in the camshaft phaser. 
         [0005]    In the case of such a camshaft phaser, the relatively costly pressure medium circuit thereof presents a problem that is to be generally resolved. The pressure medium channels must essentially extend over a certain extent in order to form suitable control edges and convey the pressure medium, whereby an installation space problem can arise, in particular at constrictions, since, in any case, the pressure medium channels must be separate from one another to prevent any short-circuiting. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the present invention to provide a camshaft phaser that will allow the pressure medium channels to be configured even under very restricted installation-space conditions, without any risk of the pressure medium flows short-circuiting. 
         [0007]    The present invention provides a camshaft phaser for an internal combustion engine, having
       a stator driven by a crankshaft of the internal combustion engine;   a rotor connected to the camshaft for co-rotation therewith; and
 
working chambers, which are configured between the stator and the rotor and are subdivided into pressure chambers by vanes associated with the rotor; and
   a pressure medium circuit having a plurality of pressure medium channels that fulfill different functions; the basic idea of the present invention being that   at least two of the pressure medium channels merge into one another in one section and that one of the pressure medium channels be separated in a pressure medium-tight manner from the other pressure medium channel by a guide sleeve that is inserted into the section.       
 
         [0012]    The design approach of the present invention makes it possible to substantially simplify the pressure medium circuit, even in a restricted installation space, since the pressure medium channels are thereby able to merge into one another, at least in sections, thus be able to be formed by a common pressure medium channel, the separation of the pressure medium flows then being realized by the inserted guide sleeve. The inserted guide sleeve may then be virtually considered to be a continuation of one of the pressure medium channels in the common section, so that the pressure medium flows are again separated from one another in a pressure medium-tight manner even in the common section of the pressure medium channels. The guide sleeve may be formed as a simple separating wall. It is merely important that inserting the guide sleeve again divides the common section of the pressure medium channels into two sections that are separated from one another in a pressure medium-tight manner. 
         [0013]    A hydraulically actuatable locking device is provided in accordance with the present invention that is able to be acted upon by a pressure medium in a pressure medium channel extending in one section through the rotor, the pressure medium channel associated with the locking device merging transitionally in one section into the pressure medium channel associated with one of the pressure chambers and being sealed in a pressure medium-tight manner in the section by the guide sleeve. The inventive approach is particularly advantageous since, in terms of fluid mechanics, it is especially difficult to connect the hydraulic locking device, which is able to be acted upon by a pressure medium via a pressure medium channel configured in the rotor, to the pressure medium circuit. This is because the pressure medium channel in the rotor is preferably connected to the pressure medium circuit in a radially inner section due to the rotational mobility of the rotor. Also, the pressure medium channels of the pressure chambers extend toward the pressure chambers, likewise starting out from the radially inner side of the rotor. Thus, together with the adjoining components, the radially inner side of the rotor forms an extremely restricted installation space within which the pressure medium channels must be configured. Especially problematic in terms of fluid mechanics is connecting the pressure medium channel of the locking device, that extends through the rotor, past the pressure medium channels of the pressure chambers. 
         [0014]    The present invention also provides that the pressure medium channel associated with the locking device be formed in a first section by an end-face bore in the camshaft, and, in a second section, by a pressure medium channel in the rotor, and, in terms of fluid mechanics, that the first and the second section be interconnected by the guide sleeve. Thus, the guide sleeve forms a pressure medium-tight connection of the two sections of the pressure medium channels, so that it is continued by the actually common section of the pressure medium channels and is separated in a pressure tight-manner from the other pressure medium channel. 
         [0015]    Another preferred specific embodiment of the present invention provides that the guide sleeve extend into the pressure medium channel of the rotor and couple the rotor to the camshaft by positive engagement and for co-rotation therewith. Thus, the guide sleeve may be simultaneously used as an element that fixes the rotor in co-rotation with the camshaft. In the related art, this is also referred to as “timing spin,” and it is required by various vehicle manufacturers. 
         [0016]    It is also provided that that section, in which the pressure medium channels merge into one another, be larger than the guide sleeve, and that a free space be provided laterally of the guide sleeve through which the pressure medium of the respective other pressure medium channel flows past along the guide sleeve. Thus, the guide sleeve does not completely fill the common section in the cross section of the flow direction, so that a cross-sectional area remains free for the pressure medium flow of the other pressure medium channel. 
         [0017]    It is also provided that the guide sleeve rest laterally against a wall in that section in which the pressure medium channels merge into one another. Thus, the guide sleeve is laterally supported in the common section of the pressure medium channels, so that it, itself, is loaded to a lesser degree should a transversal loading occur. 
         [0018]    It is also provided that the guide sleeve be formed by a tube. It is advantageous to use a tube as a guide sleeve since the tube itself is already a part that is radially outwardly pressure medium-tight and that only needs to be connected by the open ends thereof to the respective sections of the pressure medium channels. 
         [0019]    It is also provided in this case that the tube be configured in parallel to the longitudinal axis of the camshaft. The guide sleeve may thereby be preferably located in a wall of the camshaft in parallel to the longitudinal axis thereof. This is particularly advantageous since, in this section, the camshaft is designed to be tubular and to include a central bolt that engages into the camshaft, and, for that reason, the wall constitutes a smaller cross-sectional area for configuring the guide sleeve in which the guide sleeve may be mounted in an installation space-saving manner due to the configuration provided. 
         [0020]    It is also provided that the guide sleeve be joined in a press-fit connection to the camshaft and/or the rotor. The connection provided is an especially cost-effective type of connection that is suited for high-volume production and that fully suffices here for the acting forces. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0021]    The present invention is clarified in the following with reference to the figures, in each of which are readily apparent in detail: 
           [0022]      FIG. 1 : a camshaft phaser with a view of the rotor and the stator; 
           [0023]      FIG. 2 : a camshaft phaser including a center locking device; 
           [0024]      FIG. 3 : a central valve having a central bolt and a camshaft; and 
           [0025]      FIG. 4 : a camshaft having a guide sleeve in a sectional representation and oblique view. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The camshaft phaser according to the present invention having a symbolically illustrated control unit  20  is discernible in  FIG. 1 . The camshaft adjusting device has a basic design that is known in the related art and includes a crankshaft-driven stator  1  and a rotor  3  that is connected to a camshaft for co-rotation therewith. On the outside thereof, stator  1  has a toothing  2  into which engages a drive chain that transmits the rotary motion of the crankshaft in direction of rotation “D.” Stator  1  is provided with radially inwardly directed projections that subdivide the hollow space between stator  1  and rotor  3  into working chambers. In addition, the working chambers are divided by vanes  18  configured on rotor  3  into pressure chambers A and B, vanes  18  being braced by the radial outer side thereof via seals  8  against stator  1 . In rotor  3 , pressure medium channels A 1  and B 1  are provided that, in response to control unit  20 , are acted upon by a pressure medium from an oil pump “I” via a central valve  21  that is discernible in  FIG. 3 , respectively that conduct the pressure medium away into a tank “II.” Pressure medium channels A 1  and B 1  lead into pressure chambers A and B; in response to oil pump “I” acting on one of the pressure chambers A or B, the pressure medium being conducted away from respective pressure chamber A or B, which is not acted upon by the pressure medium, into tank “II.” 
         [0027]    Discernible in  FIG. 2  is the camshaft phaser having an intermediate cover  15  which is configured on front sealing cover  16  and in which locking devices V 1  and V 2  are located. Each locking device V 1  and V 2  is composed of a locking element  4 ,  5 , an arresting device  9 ,  10 , and a pressure chamber C and E. Arresting devices  9  and  10  are formed by longitudinally displaceably guided pistons and are spring-loaded by springs  11  and  12  into the locking position illustrated in  FIG. 2 . Pressure medium channels C 1  and E 1  discharge into pressure chambers C and E to unlock locking devices V 1  and V 2 ; pressure medium channel E 1  not being discernible due to the perspective representation. As a general principle, pressure medium channels C 1  and E 1  may be connected by a common control line to a control valve and a common discharge line to tank “II,” since the pressure medium always acts only jointly on pressure chambers C and E of adjusting devices V 1  and V 2 . 
         [0028]    The camshaft phaser including rotor  3 , which is rotatably mounted in stator  1 , front sealing cover  16 , intermediate cover  15 , a front cover and rear sealing cover (not shown) is entirely assembled using five bolts  6 , which are distributed over the periphery, and two centering pins  7 . In the basic design thereof, the described camshaft phaser corresponds to that described in the German Patent Application DE 10 2008 052 275 A1 which is to be expressly added to the disclosure of this invention for the understanding thereof 
         [0029]    Discernible in  FIG. 3  is camshaft  24  including rotor  3  and central bolt  25 . At least in the illustrated end portion, camshaft  24  has a tubular form, including a first annular section  22  and a second annular section  23  and an internal thread into which central bolt  25  is screwed. Central bolt  25  has a bolt head  19  and penetrates a middle opening in rotor  3 , thereby clamping rotor  3  between bolt head  19  and the end face of camshaft  24 . 
         [0030]    In the illustrated detail, pressure medium channels A and B extend in various through holes of central valve  21  and of central bolt  25  and into an annular space on the inner side of rotor  3  and into an annular space  29  formed by second annular section  23  having a smaller wall thickness than first annular section  22 . Second annular section  23  has an outside diameter that is identical to second annular section  22 , but a smaller inner diameter, whereby radially inner annular space  29  is formed. Pressure medium channel C 1 , which, in this section, is identical to pressure medium channel E 1 , is formed in a first section by a bore  26  in annular sections  22  and  23  that is oriented in parallel to the longitudinal axis of camshaft  24  and, in a second section, is formed as an L-shaped bore  28  in rotor  3 . Bore  26  leads into annular space  29 , so that pressure medium channels C 1  and B 1  merge into one another in a common section  14  that is constituted of a partial section of annular space  29 . To ensure that pressure medium channels B 1  and C 1  and the pressure medium flows contained therein are nevertheless separate from one another, a guide sleeve  13  is provided that is pressed into bore  26  and is dimensioned in length in a way that allows it to project beyond the end face of camshaft  24 , as is also discernible in  FIG. 4 , and project into L-shaped bore  28 . 
         [0031]    During assembly, rotor  3  is fitted via the opening of L-shaped bore  28  onto the protruding end of guide sleeve  13 , whereby rotor  3  is simultaneously fixed in a predefined orientation relative to camshaft  24  for co-rotation therewith. Thus, guide sleeve  13  simultaneously forms the rotationally fixed connection of camshaft  24  to rotor  3  required by various vehicle manufacturers that is also referred to as “timing spin.” Guide sleeve  13  bridges section  14  and thereby virtually forms a pressure medium-tight continuation of pressure medium channel C 1 , starting from bore  26 , continuing through annular space  29  and to bore  28 , making it possible to separate pressure medium channels C 1  and B 1  from one another in a pressure medium-tight manner in section  14  of annular space  29  and prevent any short-circuiting of pressure medium flows. 
         [0032]    Discernible in  FIG. 4  is the end of camshaft  24  including the two annular sections  22  and  23 . Discernible in first annular section  22  is bore  26  which continues as a groove on a wall  27  of second annular section  23 . Guide sleeve  13  is pressed into bore  26  and rests laterally on wall  27  in the groove. In the assembled state, guide sleeve  13  is unsupported radially inwardly toward annular space  29 . 
         [0033]    Since it is essential that second annular section  23  have a thinner wall thickness than first annular section  22  in order to form annular space  29  of pressure medium channel B 1 , the available wall thickness of second annular section  23  no longer suffices for continuing bore  26  in a pressure tight-manner in second annular section  23  as well. This disadvantage is overcome by the present invention in that guide sleeve  13  is inserted in a subsequent process, and in that pressure medium channel C 1  is closed by guide sleeve  13  from bore  26  toward bore  28 , again in a pressure medium-tight manner. 
         [0034]    In spite of the small installation space, pressure medium channels B 1  and C 1  may be separated from one another in a pressure medium-tight manner by guide sleeve  13  that is provided. This makes it possible to considerably simplify the design of the pressure medium circuit, which is particularly advantageous here with regard to intersecting pressure medium channels B 1  and C 1 . Guide sleeve  13  is configured here as a short tubular section. However, it would also be conceivable to only configure guide sleeve  13  as a separating wall, provided that this suffices for a pressure medium-tight separation of pressure medium channels B 1  and C 1 . 
       LIST OF REFERENCE NUMERALS 
       [0035]      1  stator 
         [0036]      2  toothing 
         [0037]      3  rotor 
         [0038]      4  locking device 
         [0039]      5  locking device 
         [0040]      6  bolts 
         [0041]      7  centering pins 
         [0042]      8  seals 
         [0043]      9  arresting device 
         [0044]      10  arresting device 
         [0045]      11  spring 
         [0046]      12  spring 
         [0047]      13  guide sleeve 
         [0048]      14  section 
         [0049]      15  intermediate cover 
         [0050]      16  sealing cover 
         [0051]      17  front cover 
         [0052]      18  vane 
         [0053]      19  guide contour 
         [0054]      20  control unit 
         [0055]      21  central valve 
         [0056]      22  first annular section 
         [0057]      23  second annular section 
         [0058]      24  camshaft 
         [0059]      25  central bolt 
         [0060]      26  bore 
         [0061]      27  wall 
         [0062]      28  bore 
         [0063]      29  annular space 
         [0064]    A 1 , B 1 , C 2 , E 2  pressure medium channels 
         [0065]    A, B, E, C pressure chambers 
         [0066]    V 1 , V 2  locking devices