Abstract:
An impeller ( 15 ) of a device ( 11 ) for variable adjustment of the control times of gas exchange valves ( 9, 10 ) of an internal combustion engine ( 1 ) having a substantially cylindrical hub element ( 17 ) and at least one blade ( 18 ) which extends radially to the outside proceeding from the hub element ( 17 ), wherein at least the hub element ( 17 ) is produced from a non-metallic material.

Description:
FIELD OF THE INVENTION 
     The invention relates to an impeller of a device for variable adjustment of the control times of gas exchange valves of an internal combustion engine with an essentially cylindrical hub element and at least one vane that extends outward in the radial direction starting from the hub element, wherein at least the hub element is produced from a non-metallic material. 
     BACKGROUND 
     In modern internal combustion engines, devices for the variable adjustment of the control times of gas exchange valves are used to be able to vary the phase relation between the crankshaft and camshaft in a defined angle range between a maximum advanced position and a maximum retarded position. The device is integrated in a drive train by means of which torque is transmitted from the crankshaft to the camshaft. This drive train can be realized, for example, as a belt, chain, or gearwheel drive. In addition, the device is locked in rotation with a camshaft and has one or more pressure chambers by means of which the phase relation between the crankshaft and the camshaft can be varied selectively. 
     Such a device is known, for example, from DE 10 2007 041 552 A1. The device has a cell wheel, an impeller, and two side covers, wherein the cell wheel is in driven connection with a crankshaft and the impeller is locked in rotation on a camshaft. Here, the impeller is arranged so that it can pivot relative to the cell wheel in a defined angle interval. The side covers are arranged on the axial side surfaces of the impeller and the cell wheel and locked in rotation with the cell wheel by means of screws. The impeller includes an essentially cylindrical hub element and several separate vanes. The vanes are arranged in vane grooves that are constructed on the cylindrical outer lateral surface of the hub element and extend outward in the radial direction. In the hub element there are several hollow spaces that extend in the axial direction and are open on both axial side surfaces of the hub element. 
     The cell wheel, the impeller, and the side covers bound several pressure spaces. Each of the pressure spaces is divided by one of the vanes into pressure chambers that act against each other and form a hydraulic adjustment drive by means of which the phase position between the impeller and the cell wheel can be varied. The pressurized medium supply to and the pressurized medium discharge from the pressure chambers is realized via pressurized medium channels formed in the hub element. The pressurized medium channels communicate on one side with a central opening of the impeller and on the other side with the pressure chambers. The pressurized medium channels are constructed as boreholes that are formed in the hub element after the shaping process of the hub element. 
     Another device is known from U.S. Pat. No. 5,836,277 A. In this embodiment, pressurized medium channels are constructed as radial grooves on the axial side surfaces of the impeller. 
     Another device is known from DE 101 34 320 A1. In this embodiment, the vanes are formed integrally with the hub element. The integrally formed impeller is made from a plastic. 
     The present invention is based on the objective of specifying a cost-optimized and weight-optimized impeller of a device for the variable adjustment of the control times of gas exchange valves of an internal combustion engine. 
     SUMMARY 
     This objective is met according to the invention in that the impeller is made from at least two sub-elements that are set opposite each other in the direction of an axis of rotation of the impeller and contact each other, wherein the sub-elements are connected to each other and wherein at least one recess is formed at least on one of the contacting side surfaces of the sub-elements. 
     The impeller has an essentially cylindrical hub element and at least one vane that extends outward in the radial direction starting from an outer cylindrical lateral surface of the hub element. The vane can be constructed, for example, integrally with the hub element. Alternatively, the vane can be produced separately from the hub element and connected to this element, for example, it can be inserted into a groove formed on the hub element. At least the hub element is made from a non-metallic material, for example, a plastic, wherein the weight of the impeller is reduced in comparison with metallic impellers. In addition, the vane could also be made from a non-metallic material. The impeller includes at least two sub-elements that are set opposite each other in the direction of an axis of rotation of the impeller and contact each other. Here, the separating plane of the sub-elements can be penetrated by the axis of rotation of the impeller, for example, vertically, so that an axial side surface of one sub-element contacts an axial side surface of another sub-element. The sub-elements are connected to each other, for example, by means of an adhesive connection or a weld connection (e.g., by means of ultrasonic welding) or by means of a non-positive-fit or positive-fit connection. In addition it is provided that at least one recess is formed at least on one of the side surfaces of the sub-elements that contact each other. The recesses could have already been produced during the shaping process. For example, these could be taken into account in the mold of an injection-molding tool. Through this construction of the impeller, the recess of a sub-element is closed in the axial direction by another sub-element. The recess can be formed, for example, with a blind hole shape. In this case, an outwardly closed hollow space is realized in the impeller, so that the weight and the material requirements for producing the impeller are reduced. After assembling the device, the axial side surfaces of the impeller form a sealing contact on the side covers of the device, in order to minimize leakage from the pressure chambers inward in the radial direction. Because there are no openings on the axial side surfaces of the impeller in the area of the hollow spaces, the sealing length is made longer in this area, wherein leakage is reduced. 
     Alternatively or additionally, the recess could be constructed as a groove that extends outward in the radial direction starting from a central opening of the impeller and opens into an area, for example, a pressure chamber, adjacent to the vanes in the peripheral direction. In this case, the grooves are covered, in turn, by another sub-element in the axial direction. The grooves could thus be used as pressurized medium channels for feeding pressurized medium to or for discharging pressurized medium from the pressure chambers. Through this construction of the pressurized medium channels, these are arranged within the impeller, without cost-intensive post processing steps, for example, drilling the pressurized medium channels, being necessary. Because pressurized medium is led in this embodiment within the impeller to the pressure chambers and does not come in contact with one of the side covers, no transverse forces act on the impeller, wherein these forces would press the impeller against one of the side covers and thus would increase the wear at this point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional features of the invention can be found in the following description and from the drawings in which an embodiment of the invention is shown in simplified form. Shown are: 
         FIG. 1  only very schematically, an internal combustion engine, 
         FIG. 2  a device for the variable adjustment of the control times of gas exchange valves of an internal combustion engine in a top view along the axis of rotation of the device with an impeller according to the invention, 
         FIG. 3  a perspective view of the impeller from  FIG. 2 , 
         FIG. 4  a sub-element of the impeller from  FIG. 3  in a top view, and 
         FIG. 5  a perspective diagram of the sub-element from  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , an internal combustion engine  1  is shown schematically, wherein a piston  3  sitting on a crankshaft  2  is indicated in a cylinder  4 . The crankshaft  2  connects to an intake camshaft  6  or an exhaust camshaft  7  in the illustrated embodiment by means of a traction mechanism drive  5 , wherein a first and a second device  11  for the variable adjustment of the control times of gas exchange valves  9 ,  10  can provide for a relative rotation between the crankshaft  2  and the camshafts  6 ,  7 . The cams  8  of the camshafts  6 ,  7  actuate one or more intake gas exchange valves  9  and one or more exhaust gas exchange valves  10 , respectively. 
       FIG. 2  shows a device  11  according to the invention in a top view along an axis of rotation  33  of the device  11 . The device  11  has a cell wheel  14 , an impeller  15 , and two side covers  16 . The side covers are arranged on axial side surfaces of the cell wheel  14  and attached to this by means of screws  12 . In  FIG. 2 , only the rear side cover  16  is shown. The impeller  15  is made from a suitable plastic and has an essentially cylindrical hub element  17  from whose outer cylindrical lateral surface five vanes  18  extend outward in the radial direction. In the illustrated embodiment, the vanes  18  are formed integrally with the hub element  17 . Also conceivable are embodiments in which the vanes  18  are formed separately from the hub element  17  and are arranged in vane grooves that are formed on the cylindrical lateral surface of the hub element  17 . In this case, the vanes  18  can also be produced from plastic. Also conceivable are vanes  18  made from a metallic material, for example, from steel. 
     Starting from an outer peripheral wall  19  of the cell wheel  14 , five projections  20  extend inward in the radial direction. In the illustrated embodiment, the projections  20  are formed integrally with the peripheral wall  19 . The cell wheel  14  is supported on the impeller so that it can rotate relative to this impeller  15  by means of radially inner peripheral walls of the projections  20 . 
     On the not-shown side cover, a similarly not-shown chain wheel is formed by means of which torque can be transmitted from the crankshaft  2  to the cell wheel  14  by means of the traction mechanism drive  5 . The impeller  15  is locked in rotation with the camshaft  6 ,  7  in the assembled state. For this purpose, the impeller  15  has a central opening  13  that is penetrated by a not-shown central screw that is screwed to the camshaft  6 ,  7 . 
     Within the device  11 , a pressure space  21  is formed between every two projections  20  adjacent in the peripheral direction. Each of the pressure spaces  21  is bounded in the peripheral direction by adjacent projections  20 , in the axial direction by the side covers  16 , inward in the radial direction by the hub element  17 , and outward in the radial direction by the peripheral wall  19 . In each of the pressure spaces  21 , a vane  18  projects, wherein the vanes  18  contact both the side covers  16  and also the peripheral wall  19 . Each vane  18  thus divides the respective pressure space  21  into two counteracting pressure chambers  22 ,  23 . 
     By pressurizing a group of pressure chambers  22 ,  23  and depressurizing the other group, the phase position of the impeller  15  to the cell wheel  14  and thus the phase position of the camshaft  6 ,  7  to the crankshaft  2  can be varied. By pressurizing both groups of pressure chambers  22 ,  23 , the phase position can be kept constant. 
     The impeller  15  has a blind-hole-like receptacle  31  that is formed open on an axial side surface of the impeller. A locking pin  32  that can move in the axial direction is held in the receptacle  31 , wherein a force is applied to this locking pin by a spring in the direction of the not-shown side cover. The not-shown side cover has a slot in which the locking pin  32  can engage when this is opposite the slot in the axial direction. Thus, a mechanical coupling between the impeller  15  and the cell wheel  14  can be produced and can be disconnected by feeding pressurized medium to the slot. 
     The impeller  15  is formed of two sub-elements  24  ( FIG. 3 ) that are set opposite each other and contact each other along a separating plane running in the illustrated embodiment perpendicular to the axis of rotation  33  of the device  11  or the impeller  15 . The two sub-elements  24  are attached to each other by means of an adhesive connection. 
     The side surfaces  25  of the sub-elements  24  contacting each other have several recesses  26  ( FIGS. 4 and 5 ). First recesses  26  are constructed as radial grooves  27 . The grooves  27  extend up to an opening on the outer cylindrical lateral surface of the hub element  17  starting from a ring channel  28  formed in the central opening  13 . Here, the grooves  27  simultaneously extend into the area of the vanes  18 . The grooves  27  thus communicate with an area of the pressure chambers  22 ,  23 , adjacent to the vanes  18  in the peripheral direction. Both sub-elements  24  have identical forms with respect to the grooves  27 , so that after their assembly, the grooves  27  of one sub-element  24  are closed in the axial direction by an area of the side surface  25  of the other sub-element  24 . Thus, the grooves  27  are used as pressurized medium channels by means of which pressurized medium can be fed from the ring channels  28  to the pressure chambers  22 ,  23  or pressurized medium can be discharged from the pressure chambers  22 ,  23  to the ring channels  28 . Through the construction of the pressurized medium channels as grooves  27  in the sub-elements  24 , it is achieved that the pressurized medium channels are not constructed on an axial side surface of the impeller  15 . Thus, no axial forces act on the impeller  15  when the grooves  27  are pressurized, wherein the frictional forces between the side covers  16  and the side surfaces of the impeller  15  are minimized. In addition, the grooves  27  are formed without added costs during the shaping process of the sub-elements  24 , for example, during an injection molding process. Thus, no additional metal-cutting post processing steps, for example, drilling of the pressurized medium channels, are necessary. 
     In addition to the grooves  27 , second recesses  26  that are constructed as blind holes  29  are provided on the side surfaces  25  of the sub-elements contacting each other. The only opening of the blind holes  29  is in the joint plane of the two sub-elements  24 . Thus, the axial side surfaces of the impeller  15  are formed without recesses. The blind holes  29  can also be formed during the shaping process of the sub-elements  24 . Thus, the material costs and the weight of the impeller  15  are reduced. Simultaneously, the sealing effect between the side covers  16  and the hub element  17  is increased due to the smooth side surfaces of the impeller  15 , so that leakage from the pressure chambers  22 ,  23  to the central opening  13  is reduced. 
     Each of the sub-elements  24  has, in addition to the described structures, positive-fit elements  30  that are formed in the vanes  18 . Here, a peg is formed on each of two vanes  18  and an opening adapted to the peg is formed on each of two additional vanes  18 . When the sub-elements  24  are joined, the pegs engage in the corresponding openings, so that the sub-elements  24  are automatically positioned relative to each other. 
     The two sub-elements  24  have identical constructions, so that only one injection-molding mold is required for their production. 
     Reference Symbols 
     
         
           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  Device 
           12  Screw 
           13  Central opening 
           14  Cell wheel 
           15  Impeller 
           16  Side cover 
           17  Hub element 
           18  Vane 
           19  Peripheral wall 
           20  Projection 
           21  Pressure space 
           22  First pressure chamber 
           23  Second pressure chamber 
           24  Sub-element 
           25  Side surface 
           26  Recess 
           27  Groove 
           28  Ring channel 
           29  Blind hole 
           30  Positive-fit element 
           31  Receptacle 
           32  Locking pin 
           33  Axis of rotation