Abstract:
A volume accumulator ( 15 ), including a guide housing ( 33 ), a separating element ( 34 ) and a spring element ( 35 ). The separating element ( 34 ) is slidably mounted on an inner lateral face of the guide housing ( 33 ) and the spring element ( 35 ) is seated against the separating element ( 34 ) on one side and on the guide housing ( 33 ) on the other side. According to the invention, at least one indentation ( 47 ) is provided on the guide housing ( 33 ), with the indentation protruding into the guide housing ( 33 ). In the direction of the spring element ( 35 ), the indentation ( 47 ) has an open end against which the spring element ( 35 ) is seated.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a volume accumulator having a guide housing, a dividing element and a spring element, wherein the dividing element is mounted in a displaceable manner on an inner lateral surface of the guide housing, and the spring element bears at one side against the dividing element and at the other side against the guide housing. 
       BACKGROUND 
       [0002]    Volume accumulators are used for example in internal combustion engines in order to assist in the supply of pressurized medium to a hydraulic consumer, for example to a camshaft adjuster or an electrohydraulic valve actuating device. Camshaft adjusters are known for example from DE 195 29 277 A1 or from EP 0 806 550 A1. 
         [0003]    A volume accumulator is disclosed for example in DE 10 2007 041 552 A1. The volume accumulator has a hollow cylindrical guide housing and has a dividing element, in the illustrated embodiment a pot-shaped piston, which is held in an axially displaceable manner in the guide housing and which divides the interior of the guide housing into a storage space and a complementary space. When the piston is acted on with pressurized medium, it is displaced counter to the force of a spring element in the direction of a stop, as a result of which the volume of the storage space increases at the expense of the volume of the complementary space. Here, the displacement travel of the piston is limited in that an open end of a skirt portion of the pot-shaped piston comes to bear against an annular stop which is formed separately from the guide housing. The annular stop bears against a radially extending wall on an axial end of the guide housing. The spring element is supported at one side on the piston and at the other side on the radially extending wall of the guide housing. 
       SUMMARY 
       [0004]    It is the object of the invention to provide a volume accumulator, the manufacturing expenditure for which should be reduced. 
         [0005]    The object is achieved according to the invention in that at least one indentation is formed on the guide housing, which indentation projects into the guide housing, wherein the indentation has, in the direction of the spring element, an open end against which the spring element bears. 
         [0006]    The volume accumulator has a dividing element, for example a piston, which is mounted in a displaceable manner within a guide housing and which divides a store space from a complementary space. When said dividing element is acted on by pressurized medium, it is displaced within the guide housing, counter to a spring element, in the direction of a stop which limits the displacement travel of the dividing element in that the latter comes to bear against the stop. Provided behind the stop in the displacement direction of the dividing element is a spring support, wherein the spring element is supported at one side against the spring support and at the other side against the dividing element. It is provided here that the spring support is formed from the material of the guide housing. For this purpose, in the guide housing, which is for example of hollow cylindrical design, a slot is provided which runs along a discontinuous line. Here, the slot runs, at least in regions, in a plane perpendicular to the displacement direction of the piston. The slot may be formed into the guide housing by punching or fine blanking, for example. Provided on the guide housing in the region of the slot is an indentation which projects into the interior of the guide housing. Here, an open end, generated by the slot, of the indentation faces the end of the spring element and serves as a spring support for the latter. Embodiments are conceivable which have one or more indentations spaced apart in the circumferential direction. The open end means the region which was connected to the guide housing before the formation of the slot into said guide housing. 
         [0007]    In this embodiment, the spring support is formed in one piece with the guide housing, such that there is no requirement for additional components which must be connected to the guide housing. The indentation can be formed in a cost-effective manner. 
         [0008]    The indentation may take on a multiplicity of forms. Embodiments are for example conceivable in which a slot is formed into the guide housing, which slot is arranged entirely in a plane perpendicular to the displacement direction of the piston. The indentation is subsequently formed into the guide housing in the region of the slot. 
         [0009]    Likewise conceivable are embodiments in which the indentation is formed as a lug. Here, a slot which deviates from a straight line is formed into the guide housing, which slot forms a lug which is connected to the guide housing. Said lug may for example be triangular or tetragonal and may if appropriate be bulged corresponding to the shape of the guide housing, and projects into the guide housing. 
         [0010]    The dividing element may for example be designed as a pot-shaped piston with a base and an adjoining skirt portion, wherein the spring element bears against the base. The guide housing and the piston are advantageously produced by non-cutting processes from in each case one sheet-metal blank, for example by means of a deep-drawing process. The base of the piston serves as a pressure surface, which is acted on with a force by the pressurized medium flowing in, as a result of which the piston is displaced. The lateral surface serves for mounting the piston in the guide housing, wherein the open end of the skirt portion comes to bear against the stop when the volume accumulator is completely full. Furthermore, the sealing of the storage space with respect to the complementary space is realized by means of close-tolerance play between the skirt portion and the inner lateral surface of the guide housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    Further features of the invention will emerge from the following description and from the drawings, in which exemplary embodiments of the invention are illustrated in simplified form. In the drawings: 
           [0012]      FIG. 1  shows an internal combustion engine merely in highly schematic form, 
           [0013]      FIG. 2  shows a longitudinal section through a camshaft adjuster which is fastened to a camshaft in which a first embodiment of a volume accumulator is arranged, 
           [0014]      FIG. 3  shows a cross section through the camshaft adjuster from  FIG. 2  along the line wherein the central screw is not illustrated, 
           [0015]      FIG. 4  shows the detail X from  FIG. 2  without a camshaft, 
           [0016]      FIG. 5  shows a cross section through the volume accumulator along the line V-V in  FIG. 4 , 
           [0017]      FIG. 6  shows a perspective view of the first embodiment of a volume accumulator, 
           [0018]      FIG. 7  shows a perspective view of a second embodiment of a volume accumulator. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]      FIG. 1  depicts an internal combustion engine  1 , wherein a piston  3  is shown which is seated on a crankshaft  2  and which is arranged in a cylinder  4 . In the embodiment illustrated, the crankshaft  2  is connected via in each case one traction mechanism drive  5  to an intake camshaft  6  and an exhaust camshaft  7 , wherein a first and a second camshaft adjuster  11  can effect a relative rotation between the crankshaft  2  and the camshafts  6 ,  7 . Cams  8  of the camshafts  6 ,  7  actuate one or more intake gas exchange valves  9  or one or more exhaust gas exchange valves  10 . Provision may also be made for only one of the camshafts  6 ,  7  to be equipped with a camshaft adjuster  11 , or for only one camshaft  6 ,  7  to be provided, which is provided with a camshaft adjuster  11 . 
         [0020]      FIGS. 2 and 3  show a camshaft adjuster  11  in longitudinal section and cross section. Furthermore,  FIG. 2  shows a volume accumulator  15  which is arranged in a camshaft  6 ,  7  which is connected in a rotationally conjoint manner to the camshaft adjuster  11 . 
         [0021]    The camshaft adjuster  11  comprises a drive input element  14 , a drive output element  16  and two side covers  17 ,  18  which are arranged on the axial side surfaces of the drive input element  14 . The drive output element  16  is designed in the form of a vane wheel and has a hub element  19  which is of substantially cylindrical design and from the external cylindrical lateral surface of which, in the embodiment illustrated, five vanes  20  extend outward in the radial direction. 
         [0022]    Five pressure spaces  22  are provided within the camshaft adjuster  11 , wherein a vane  20  projects into each pressure space  22 . Here, the vanes  20  are designed so as to bear both against the side covers  17 ,  18  and also against the circumferential wall  21 . Each vane  20  thereby divides the respective pressure space  22  into two oppositely-acting pressure chambers  23 ,  24 . 
         [0023]    Formed on an external lateral surface of the drive input element  14  is a sprocket  12  via which torque can be transmitted from the crankshaft  2  to the drive input element  14  by means of a chain drive (not illustrated). The drive output element  16  is connected in a rotationally conjoint manner to the camshaft  6 ,  7  by means of a central screw  13 . 
         [0024]    The drive output element  16  is arranged so as to be rotatable relative to the drive input element  14  over a defined angle range. By supplying pressurized medium to one group of pressure chambers  23 ,  24  and discharging pressurized medium from the other group, the phase position of the drive input element  14  with respect to the drive output element  16  (and therefore the phase position of the camshafts  6 ,  7  with respect to the crankshaft  2 ) can be varied. By supplying pressurized medium to both groups of pressure chambers  23 ,  24 , the phase position can be held constant. 
         [0025]    The camshaft  6 ,  7  has, in the region of a camshaft bearing  32 , a plurality of openings  28  via which pressurized medium delivered by a pressurized medium pump  37  passes into the interior of said camshaft. Formed within the camshaft  6 ,  7  is a pressurized medium path  29  which communicates at one side with the openings  28  and at the other side with a control valve  27  which serves for the supply of pressurized medium to the camshaft adjuster  11 . The control valve  27  is arranged in the interior of the central screw  13 . Through use of the control valve  27 , pressurized medium can be selectively conchanneled to the first or second pressure chambers  23 ,  24  and discharged from the other pressure chambers  23 ,  24  in each case. 
         [0026]    Provided in the interior of the central screw  13  is a pressurized medium channel  30  which communicates at one side with the pressurized medium path  29  and at the other side with a cavity  31  of the hollow camshaft  6 ,  7 . The pressurized medium channel  30  is formed as an axial bore which extends through the threaded portion of the central screw  13 . 
         [0027]    The volume accumulator  15  is arranged in the cavity  31 . The volume accumulator  15  comprises a guide housing  33 , a dividing element  34  and a force store which, in the embodiment illustrated, is designed as a spring element  35  in the form of a helical compression spring. The guide housing  33  is connected in a non-positively locking manner to a wall  36  of the cavity  31 . Embodiments are also conceivable in which the guide housing  33  is connected in a cohesive or positively locking manner to the wall  36 . 
         [0028]    The dividing element  34  is arranged in an axially displaceable manner in the interior of the guide housing  33 , wherein, in the embodiment illustrated, said dividing element is formed as a pot-shaped piston with a base  25  and a skirt portion  26 . The dividing element  34  is mounted by means of the skirt portion  26  in an axially displaceable manner in the guide housing  33 . The outer lateral surface of the dividing element  34  is matched to the inner lateral surface of the guide housing  33  in such a way that the guide housing  33  is separated in a pressure-medium-tight manner into a store space  45  axially in front of and a complementary space  46  behind the base  25  of the dividing element  34 . 
         [0029]    The spring element  35  is supported at one side on a spring support  39  ( FIG. 4 ), which is formed on that end of the guide housing  33  which faces away from the camshaft adjuster  11 , and at the other side on the base  25  of the dividing element  34 . The spring element  35  therefore loads the dividing element  34  with a force in the direction of the pressurized medium channel  30 . The spring support  39  is formed by three radial indentations  47  of the guide housing  33 , which indentations project into said guide housing. For this purpose, the cylindrical guide housing  33  has formed into it three first slots  40  which run in the circumferential direction of the guide housing  33  and which are spaced apart in the circumferential direction. The guide housing  33  is subsequently deformed radially inward in the regions between the first slots  40  and the end facing away from the camshaft. The depth of the indentations  47  is selected such that the spring element  35  bears, even at maximum spring eccentricity, against the open ends, which have been separated from the guide housing  33  by the first slots  40 , of the indentations  47 . The spring support  39  is thus formed in one piece with the guide housing  33 , as a result of which production costs and production outlay are reduced. 
         [0030]    The displacement travel of the dividing element  34  is limited in the direction of the pressurized medium channel  30  by an annular, radially inwardly running portion of the guide housing  33 , which portion engages around a housing opening  38  through which pressurized medium can be supplied to the volume accumulator  15 . The displacement travel of the dividing element  34  is limited in the direction of the spring support  39  by a stop. The stop is designed, between the axial ends of the guide housing  33 , in the form of three indentations  41  which are formed in one piece with and project into the guide housing  33  ( FIGS. 4-6 ). Embodiments are likewise conceivable which have more or fewer indentations. Each indentation  41  has an open end on the side facing toward the dividing element  34 , wherein the open end has a surface perpendicular to the direction of movement of the dividing element  34 . The production of the indentations  41  takes place in two stages. Firstly, there is formed into the guide housing  33  a second slot  42  which runs in the circumferential direction of the guide housing  33 . Subsequently, the material of the guide housing  33  in the region of the second slot  42  is plastically deformed into the guide housing, thus forming the indentation  41 . 
         [0031]    Each indentation  41  projects into the guide housing  33  such that the open end of said indentation faces the open end of the skirt portion  26  of the dividing element  34  in the displacement direction of the latter. These open ends of the indentations  41  therefore serve as a stop for the dividing element  34 . 
         [0032]    Furthermore, each indentation  41  has a guide portion  43  which extends in the axial direction and runs parallel to the axis of the spring element  35 . Here, the diameter of the spring element  35  is selected such that said spring element bears against the guide portions  43  when it is in the compressed state. The spring element  35  is therefore mounted via the guide portions  43 , whereby the radial position of the spring element  35  is defined. The length L of the guide portion  43  is greater than the spacing between two spring windings in the relaxed state. It is thereby ensured that, due to the mounting of the spring element  35  on the guide portions  43 , the spring element  35  does not become misaligned or jammed against the stop of the indentation  41 . 
         [0033]    In the embodiment illustrated, the guide housing  33  and the dividing element  34  are formed as sheet-metal parts produced for example by means of a non-cutting production process, for example a deep-drawing process. Aside from low production costs, this has the advantage that, by means of said shaping process, the bearing surfaces of the skirt portion  26  and of the guide housing  33  can be produced with such precision that they do not require any reworking. 
         [0034]    In an alternative embodiment of a volume accumulator  15 , the first slot  40  describes a curved line with two ends, such that a lug  44  is formed which projects into the guide housing  33 . A volume accumulator  15  of this type is illustrated in  FIG. 7  in a perspective view. In this embodiment, a rectangular lug  44  which projects into the guide housing  33  is formed by means of an L-shaped second slot  42 . Here, one portion of the L-shaped slot  40  runs in the circumferential direction of the guide housing  33 , such that the open end thereby formed serves as a spring support  39 . The second portion of the L-shaped slot  40  extends to the end of the guide housing  33 . Aside from the embodiment illustrated in  FIG. 7 , in which the lug  44  is connected to the guide housing  33  in the circumferential direction, embodiments are also conceivable in which the lug  44  merges into the guide housing  33  in the axial direction. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           1  Internal combustion engine 
           2  Crankshaft 
           3  Piston 
           4  Cylinder 
           5  Traction mechanism drive 
           6  Intake camshaft 
           7  Exhaust camshaft 
           8  Cam 
           9  Intake gas exchange valve 
           10  Exhaust gas exchange valve 
           11  Camshaft adjuster 
           12  Sprocket 
           13  Central screw 
           14  Drive input element 
           15  Volume accumulator 
           16  Drive output element 
           17  Side cover 
           18  Side cover 
           19  Hub element 
           20  Vane 
           21  Circumferential wall 
           22  Pressure space 
           23  First pressure chamber 
           24  Second pressure chamber 
           25  Base 
           26  Skirt portion 
           27  Control valve 
           28  Openings 
           29  Pressurized medium path 
           30  Pressurized medium channel 
           31  Cavity 
           32  Camshaft bearing 
           33  Guide housing 
           34  Dividing element 
           35  Spring element 
           36  Wall 
           37  Pressurized medium pump 
           38  Housing opening 
           39  Spring support 
           40  First slot 
           41  Indentation 
           42  Second slot 
           43  Guide portion 
           44  Lug 
           45  Store space 
           46  Complementary space 
           47  Indentation 
         L Length