Abstract:
A device ( 11 ) for variably adjusting the control times of gas exchange valves ( 9, 10 ) of an internal combustion engine ( 1 ), including a drive element ( 13 ) that can be brought into driven connection with a crankshaft ( 2 ) of the internal combustion engine ( 1 ), an output element ( 14 ) which can be brought into driving connection with a camshaft ( 6, 7 ) of the internal combustion engine ( 1 ) and which is arranged in a pivotable manner with respect to the drive element ( 13 ), and at least one lateral cover ( 15 ) which lies on an axial lateral surface of the output element ( 14 ) or of the drive element ( 13 ), which is connected to the drive element ( 13 ) or to the output element ( 14 ) in a rotationally fixed manner and which has a disk-shaped portion ( 33 ). The disk-shaped portion ( 33 ) has a sliding guide depression ( 36   c ) which is open to the drive or output element ( 13, 14 ), said sliding guide depression being equipped with a stop element ( 40 ), and the sliding guide depression ( 36   c ) and the stop element ( 40 ) form a sliding guide into which a locking element ( 38 ) can engage.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to a device for variably adjusting the control times of gas exchange valves of an internal combustion engine, comprising a drive element which can be placed in a driven connection with a crankshaft of the internal combustion engine, an output element which can be placed in a driving connection with a camshaft of the internal combustion engine and is arranged pivotably with respect to the drive element, and comprising at least one side cover which is arranged on an axial side face of the output element or of the drive element and is connected in a rotationally fixed fashion to the drive element or the output element and has a disk-shaped section, wherein the disk-shaped section has a sliding guide depression which is open to the drive element or the output element and in which a stop element is arranged, and wherein the sliding guide depression and the stop element form a sliding guide in which a locking element can engage. 
       BACKGROUND 
       [0002]    In modern internal combustion engines, devices for variably adjusting the control times of gas exchange valves are used to be able to variably adjust the phase relation between a crankshaft and a camshaft in a defined angular range, between a maximum advanced position and a maximum retarded position. The device is integrated into a drive train by means of which torque is transmitted from the crankshaft to the camshaft. This drive train may be implemented, for example, as a belt drive, chain drive or gearwheel drive. Furthermore, the device is connected in a rotationally fixed fashion to a camshaft and can have, for example, one or more pressure chambers by means of which the phase relation between the crankshaft and the camshaft can be varied selectively by applying a pressure medium. 
         [0003]    A device of this type is known, for example, from DE 10 2006 020 314 A1. The device has a drive element, an output element and two side covers, wherein the drive element has a driven connection from a crankshaft, and the output element is attached in a rotationally fixed fashion to a camshaft. The output element is arranged so as to be pivotable with respect to the drive element in a predefined angular interval. The drive element, the output element and the side covers bound a plurality of pressure spaces which are divided by vanes into pressure chambers which act against one another. The pressure chambers form a hydraulic actuator drive by means of which the phase angle between the output element and the drive element can be adjusted in a variable fashion. The side covers are arranged on the axial side faces of the output element and of the drive element and are connected in a rotationally fixed fashion to the drive element by means of screws. In order to apply pressure medium to the pressure chambers, drilled holes are provided in the output element, said drilled holes starting from a central opening in the output element, running in the radial direction and opening into the pressure chambers. 
         [0004]    The device has a locking mechanism which comprises a sliding guide and a spring-loaded locking element. The sliding guide is formed by a depression in the side cover which is embodied as a solid cast part and a hardened insertion element which is arranged in the depression. In order to ensure a flush termination between the axial side face of the side cover and the insertion element, the depression must be worked in a metal-cutting manner. The locking element is arranged in an axially displaceable fashion inside a receptacle which is formed inside the output element. If the sliding guide and the locking element are located axially opposite one another, the locking element can engage in the sliding guide and couple the output element mechanically to the drive element. In order to release the locked connection, the sliding guide is provided with pressure medium which forces the locking element back into the receptacle. The insertion element makes available a stop face for the locking element, with the result that only the insertion element has to have a high degree of strength and the side cover can be fabricated from more cost-effective materials. The application of force by the insertion element to the side cover is done via contact over a surface, with the result that the load at this point is smaller than in the case of the linear contact between the locking element and the insertion element. 
       SUMMARY 
       [0005]    The present invention is based on the object of proposing a cost-effective device which is optimized in terms of weight. 
         [0006]    The object is achieved according to the invention in that a base of the sliding guide depression has a planar stop face against which the stop element bears, wherein the stop face is arranged spaced apart from an edge of the sliding guide depression, and the depth of the stop face is made to be less than a maximum depth of the sliding guide depression. 
         [0007]    The device has a drive element and an output element, wherein the drive element is driven by a crankshaft of the internal combustion engine, and the output element drives a camshaft of the internal combustion engine. The drive element can have a driven connection to the crankshaft by means of, for example, a flexible drive or gearwheel drive. The output element can, for example, be connected in a rotationally fixed fashion to the camshaft. 
         [0008]    The output element is pivotable with respect to the drive element in a predefined angular interval. For this purpose, the device can, for example, have a hydraulic actuator drive with at least one pressure space. 
         [0009]    A side cover is provided on an axial side face of the drive element or of the output element and is connected in a rotationally fixed fashion to one of these components. In this context, the side cover has a disk-shaped section, if appropriate with a central opening, which section seals, for example, the pressure spaces in the axial direction. The disk-shaped section has a sliding guide depression in which a separately fabricated stop element is secured. The sliding guide depression and the stop element form a sliding guide into which a locking element can engage, which locking element is arranged in a component of the device which can pivot with respect to the side cover. If the locking element engages in the sliding guide, the output element is mechanically coupled to the drive element. In this context, the drive torque of the crankshaft is transmitted via the locking element and the stop element from the drive element to the output element. The force is applied, on the one hand, between the locking element and the stop element, generally via a linear contact, and the stop element and an axially extending boundary wall of the sliding guide depression via contact over a surface. In this way, only the locking element and the stop element have to be hardened, and the side cover can be fabricated from more cost-effective materials since the loading due to the contact over a surface between the stop element and the side cover is less. 
         [0010]    The base of the sliding guide depression has a planar stop face against which the stop element bears. The stop face is arranged spaced apart from an edge of the sliding guide depression, wherein the depth of the stop face is made less than a maximum depth of the sliding guide depression. In this context it is possible to provide that the depth of the stop face is embodied so as to be less than a depth in the edge region of the sliding guide depression. The edge of the sliding guide depression is to be understood as being the region of the sliding guide depression adjoining the axially extending boundary walls of the sliding guide depression. The depth is understood to be the axial distance between the side face of the disk-shaped section which faces the output element and/or the drive element and the respective point on the base of the sliding guide depression. 
         [0011]    The stop face which projects out of the base of the sliding guide depression in a plateau-like fashion ensures that the stop element terminates flush with the side face of the disk-shaped section. The stop face can be embodied with a high level of dimensional accuracy in the manufacturing process of the disk-shaped section. For example it is possible to provide for the disk-shaped section to be manufactured by means of a deep drawing method by means of which at the same time the sliding guide depression and the stop face are formed. Alternatively, the disk-shaped section can be manufactured by means of a deep drawing method by means of which at the same time the sliding guide depression is formed, and the stop face can be subsequently formed by means of a stamping method. The dimensions can be implemented reliably in terms of processing during the manufacturing process so that costly metal-cutting working steps for the sliding guide depression can be eliminated and the stop element nevertheless terminates flush with the side face of the first side cover. The stop face which is spaced apart from the edge of the sliding guide depression and protrudes from the base thereof ensures that during the mounting of the stop element it does not dip into the region of a radius which is formed in the junction region between the base and the axially extending boundary wall of the sliding guide depression. In this way, precise positioning of the stop element in the sliding guide depression is possible, while avoiding damage to the walls. At the same time, a frictionally locking connection can be produced between the axially extending boundary wall and the stop element. Materially joined or positively locking connections are also conceivable. In contrast to cast side covers which are of solid design, in this way it is possible to use a thin-walled sheet-metal cover or a plastic cover, which reduces the weight and the manufacturing costs. 
         [0012]    In one advantageous development of the invention it is possible to provide that the sliding guide depression forms a bulge on the side of the disk-shaped section facing away from the drive element. The raising of the outer face improves the cooling of the side cover and therefore lowers the thermal loading. 
         [0013]    The stop element advantageously projects beyond the support face in the direction of the sliding guide. The stop element is positioned by bearing against the support face, wherein the support face does not extend into the contact region between the stop element and the locking element. This ensures that the locking element comes to bear exclusively against the stop element, and the force is not transmitted directly between the side cover and the locking element. 
         [0014]    The stop element can have, on the side face bearing against the stop face, at least one groove for conducting pressure medium, with the result that, for example, the sliding guide or a pressure medium line leading to one of the pressure spaces can be supplied with pressure medium. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Further features of the invention emerge from the following description and from the drawings in which an exemplary embodiment of the invention is illustrated in simplified form. In the drawings: 
           [0016]      FIG. 1  shows an internal combustion engine in only very schematic form, 
           [0017]      FIG. 2  shows a longitudinal section through a device according to the invention for variably adjusting the control times of gas exchange valves of an internal combustion engine, 
           [0018]      FIG. 3  shows a cross section through the device according to the invention along the line III-III in  FIG. 2 , 
           [0019]      FIG. 4  shows a plan view of a side face of the side cover bearing against the drive element, 
           [0020]      FIG. 5  shows a perspective view of the outside of the side cover from  FIG. 4 , 
           [0021]      FIG. 6  shows a longitudinal section through the side cover along the line VI-VI in  FIG. 4 , and 
           [0022]      FIG. 7  shows a view of the side cover according to  FIG. 4  without a stop element. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  is a schematic diagram of an internal combustion engine  1 , wherein a piston  3  which is seated on a crankshaft  2  is indicated in the cylinder  4 . In the illustrated embodiment, the crankshaft  2  is connected to an intake camshaft  6  or an exhaust camshaft  7  via a flexible drive  5  in each case, wherein a first and a second device  11  for variably adjusting the control times of gas exchange valves  9 , can ensure that there is a relative rotation between the crankshaft  2  and the camshafts  6 ,  7 . Cams  8  of the camshafts  6 ,  7  activate one or more intake gas exchange valves  9  and/or one or more exhaust gas exchange valves  10 . 
         [0024]      FIGS. 2 and 3  show a device  11  according to the invention in a longitudinal section and cross section, respectively. The device  11  has a drive element  13 , an output element  14  and two side covers  15 ,  16  which are arranged on axial side faces of the drive element  13  and are attached thereto by means of screws  12 . The output element  14  is embodied in the form of an impeller wheel and has an essentially cylindrically embodied hub element  17 , from whose outer cylindrical lateral surface vanes  18  extend outward in the radial direction. 
         [0025]    Projections  20  extend radially inward starting from an outer circumferential wall  19  of the drive element  13 . The drive element  13  is mounted on the output element  14  in such a way that it is rotatable in relation to said drive element  14  by means of radially inner circumferential walls of the projections  20 . 
         [0026]    The drive element  13  is provided with a belt pulley  21 , via which torque can be transmitted from the crankshaft  2  to the drive element  13  by means of a belt drive (not illustrated). The output element  14  is connected in a rotationally fixed fashion to the camshaft  6 ,  7  by means of a central screw  22 . 
         [0027]    Pressure spaces  23  are formed within the device  11 , between in each case two projections  20  which are adjacent in the circumferential direction. Each of the pressure spaces  23  is bounded by adjacent projections  20  in the circumferential direction, by the side covers  15 ,  16  in the axial direction, radially toward the inside by the hub element  17 , and radially toward the outside by the circumferential wall  19 . A vane  18  projects into each of the pressure spaces  23 , wherein the vanes  18  bear both against the side covers  15 ,  16  and against the circumferential wall  19 . Each vane  18  therefore divides the respective pressure space  23  into two pressure chambers  24 ,  25  which act against one another. 
         [0028]    The output element  14  is arranged so as to be rotatable with respect to the drive element  13  in a defined angular range. The angular range is bounded in one rotational direction of the output element  14  by virtue of the fact that each of the vanes  18  comes to bear against an advanced stop  26 . In an analogous fashion, the angular range is bounded in the other rotational direction by virtue of the fact that each of the vanes  18  comes to bear against a retarded stop  27 . 
         [0029]    By applying pressure medium to a group of pressure chambers  24 ,  25  and relieving the other group of pressure medium, the phase angle of the drive element  13  can be varied with respect to the output element  14  (and therefore the phase angle of the camshaft  6 ,  7  with respect to the crankshaft  2 ). By applying pressure medium to both groups of pressure chambers  24 ,  25 , the phase angle can be kept constant. 
         [0030]    The camshaft  6 ,  7  has a central pressure medium line  28  and a plurality of coaxial pressure medium lines  29  which extend in the axial direction. The pressure medium lines  28 ,  29  communicate with a control valve (not illustrated) via annular grooves  30   a,b  which are formed on an outer lateral face of the camshaft  6 , 7 . The coaxial pressure medium lines  29  communicate with a first group of pressure chambers  24  via radial holes  39 . 
         [0031]    The central pressure medium line  28  extends through the central screw  22  to the side of the output element  14  facing away from the camshaft  6 ,  7 , and opens into a closed-off space  31  which is sealed off by a closure stopper  32 . 
         [0032]      FIGS. 4 to 6  show the first side cover  15  in various views. The first side cover  15  has a disk-shaped section  33  with a central opening  34  and is comprised of sheet steel. A plurality of bulges  35   a - c  are formed on the disk-shaped section  33 , on the side face facing away from the output element  14  ( FIG. 5 ). A first bulge  35   a  extends in an annular shape around the central opening  34 . Furthermore, five second bulges  35   b  are provided which are embodied in the form of ribs and extend radially outward from the first bulge  35   a . A third bulge  35   c  adjoins the first bulge  35   a  in the region of one of the second bulges  35   b  and covers a part of the disk-shaped section  33  between two of the second bulges  35   b . The surface of the first side cover  15  is enlarged by the bulges  35   a - c , with the result that the cooling of the device  11  is improved. Furthermore, during the operation of the internal combustion engine  1 , the bulges  35   a - c  generate air turbulence in the region of the first side cover  15 , as a result of which the cooling thereof is improved further. Overall, this leads to lower thermal loading of the first side cover  15  and to more effective cooling of the pressure medium present in the device  11 , which is generally engine oil of the internal combustion engine  1 . 
         [0033]    At the same time, the bulges  35   a - c  increase the rigidity of the first side cover  15 , as a result of which the sealing of the pressure chambers  24 ,  25  can be improved or the first side cover  15  can be constructed with thinner walls. 
         [0034]    Corresponding first depressions  36   a , corresponding second depressions  36   b  and a sliding guide depression  36   c  are formed in the region of the bulges  35   a - c , on the side face of the disk-shaped section  33  facing the output element  14  ( FIG. 4 ). The first depression  36   a  is embodied in the form of an annular duct and communicates with the central pressure medium line  28  via the space  31 . The second depressions  36   b  are embodied in the form of radially extending grooves which open into the first depression  36   a  and communicate with a second group of pressure chambers  25 . 
         [0035]    During the operation of the internal combustion engine  1 , pressure medium is fed to the control valve (not illustrated) by means of a pressure medium pump (not illustrated). If a phase adjustment in the direction of advanced control times is requested by the engine controller, pressure medium passes from the control valve (not illustrated) to the first pressure chambers  24  via the annular groove  30   a , the coaxial pressure medium lines  29  and the radial drilled holes  39 . At the same time, pressure medium is carried away from the second pressure chambers  25  to the control valve via the second depressions  36   b , the first depression  36   a , the space  31 , the central pressure medium line  28  and the annular groove  30   b , and is discharged from said control valve into a tank of the internal combustion engine  1 . As a result, the vanes  18  are forced in the direction of the advanced stops  26 , and the control times are adjusted in the advanced direction. 
         [0036]    If the engine controller requests a phase adjustment in the direction of retarded control times, pressure medium passes from the control valve (not illustrated) into the second pressure chambers  25  via the annular groove  30   b , the central pressure medium line  28 , the space  31 , the first depression  36   a  and the second depressions  36   b . At the same time, pressure medium is carried away from the first pressure chambers  24  to the control valve via the radial drilled holes  39 , the coaxial pressure medium lines  29  and the annular groove  30   a , and is discharged from said control valve into a tank of the internal combustion engine  1 . As a result, the vanes  18  are forced in the direction of the retarded stops  27 , and the control times are adjusted in the retarded direction. 
         [0037]    The supply of pressure medium to the second pressure chambers  25 , and the carrying away of pressure medium therefrom therefore occurs via the first and second depressions  36   a,b , which are embodied on the disk-shaped section  33  of the first side cover  15 . The otherwise customary radial drilled holes within the output element  14 , which have to be formed in a blank by means of metal-cutting working steps, can be dispensed with, which significantly reduces the expenditure involved in manufacturing said output element  14 . 
         [0038]    The device  11  furthermore has a locking mechanism by means of which a detachable mechanical connection can be produced between the output element  14  and the drive element  13 . For this purpose, the output element  14  has a receptacle  37  in which an axially displaceable locking element  38  is accommodated. A force is applied to the locking element  38  in the direction of the disk-shaped section  33  by means of a compression spring. 
         [0039]    The sliding guide depression  36   c  is fabricated with excess dimensions with respect to the locking element  38  and accommodates a stop element  40 . The stop element  40  and the sliding guide depression  36   c  bound a sliding guide in which the locking element  38  can engage when the latter is located opposite the sliding guide in the axial direction. The mechanical coupling between the output element  14  and the drive element  13  is produced in this way. If the coupling is to be disconnected, pressure medium is fed to the sliding guide, said pressure medium forcing the locking element  38  back into the receptacle  37 . 
         [0040]    The base of the pot-shaped sliding guide depression  36   c  has a planar support face  43  ( FIG. 7 ). The support face  43  is embodied spaced apart from the edge of the sliding guide depression  36   c , i.e. from the axially extending boundary walls of the sliding guide depression  36 . In this context, the depth of the support face  43 , i.e. the axial distance from the side face of the disk-shaped section  33  facing the output element  14  is made smaller than the depth of the sliding guide depression  36   c  in the adjacent edge regions, with the result that a groove-shaped cavity which runs around the support face  43  is formed. The stop element  43  is connected in a frictionally locking fashion to the sliding guide depression  36   c , wherein an axial side face of the stop element  40  bears against the support face  43 . The plateau-shaped support face  43  ensures that the stop element  40  does not engage in the edge region of the sliding guide depression  36   c , which edge region typically has a radius. In this context, the support face  43  advantageously projects beyond the radius region, with the result that the stop element  40  can be joined in a flush fashion to the side face of the disk-shaped section  33 , without damaging the sliding guide depression  36 , wherein a frictionally locking connection can be produced between the stop element  40  and the axially extending walls of the sliding guide depression  36   c.    
         [0041]    The stop element  40  projects beyond the support face  43  in the direction of the sliding guide, with the result that the locking element  38  can come to bear merely against the stop element  40  and not against the support face  43 . If the locking element  38  engages in the sliding guide, the force is generally applied via linear contact. In the illustrated embodiment, this linear contact is produced between the locking element  38  and the stop element  40 , which has a higher degree of strength than the disk-shaped section  33 . The application of force to the disk-shaped section  33  by the stop element  40  occurs by means of contact over a surface, with the result that the load at this point is smaller. The disk-shaped section  33  can therefore be produced from a more cost-effective material, and only the stop element  40  has to be provided with relatively high strength. Since the stop element  40  projects beyond the support face  43  in the direction of the sliding guide, it is ensured that the force from the locking element  38  is transmitted exclusively to the stop element  40 . 
         [0042]    The stop element  40  has, on a side face facing the support face  43 , two grooves  41 ,  42 . The first groove  41  connects the first depression  36   a  to the second depression  36   b , which adjoins the sliding guide depression  36   c ,  40 , with the result that the pressure medium is supplied to this second depression  36   b , and therefore to the corresponding pressure chamber  25 , via the first groove  41 . The second groove  42  connects the first groove  41  to the sliding guide and therefore ensures the supply of pressure medium thereto, in order to disconnect the mechanical connection between the drive element  13  and the output element  14 . The grooves  41 ,  42  can alternative or additionally be formed in the sliding guide depression  36   c  in the region of the stop element  40 . 
         [0043]    If the first side cover  15  is produced by means of a non-metal-cutting shaping method or a metal casting method or injection molding method, the bulges  35   a - c  and the corresponding depressions  36   a - c  can be fabricated in a cost-neutral fashion. The first side cover  15  can be manufactured, for example, from a sheet-metal blank by means of a deep drawing method, wherein at the same time the sliding guide depression  36   c  and the support face  43  can be formed with this method. Alternatively, the first side cover  15  together with the sliding guide depression  36   c  can be produced by means of a deep drawing process, and the support face  43  can be formed by stamping in a further working step. 
       REFERENCE NUMBERS 
       [0000]    
       
           1  Internal combustion engine 
           2  Crankshaft 
           3  Piston 
           4  Cylinder 
           5  Flexible drive 
           6  Intake camshaft 
           7  Exhaust camshaft 
           8  Cam 
           9  Intake gas exchange valve 
           10  Exhaust gas exchange valve 
           11  Device 
           12  Screw 
           13  Drive element 
           14  Output element 
           15  Side cover 
           16  Side cover 
           17  Hub element 
           18  Vane 
           19  Circumferential wall 
           20  Projection 
           21  Belt pulley 
           22  Central screw 
           23  Pressure space 
           24  First pressure chamber 
           25  Second pressure chamber 
           26  Advanced stop 
           27  Retarded stop 
           28  Central pressure medium line 
           29  Coaxial pressure medium line 
           30   ab  Annular groove 
           31  Space 
           32  Closure stopper 
           33  Disk-shaped section 
           34  Opening 
           35   abc  Bulges 
           36   ab  Depression 
           36   c  Sliding guide depression 
           37  Receptacle 
           38  Locking element 
           39  Radial drilled hole 
           40  Stop element 
           41  First groove 
           42  Second groove 
           43  Stop face