Patent Publication Number: US-6668777-B2

Title: Arrangement for the relative angle-of-rotation adjustment of a camshaft of an internal-combustion engine with respect to a driving wheel

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     This invention relates to an arrangement for the relative angle-of-rotation adjustment of a camshaft of an internal-combustion engine with respect to a driving wheel. 
     A so-called vane cell camshaft adjuster is known from German Patent Document DE 197 45 908 A1. In this case, recesses are provided on the faces of the rotor vanes in which roll-shaped roll bodies are accommodated. These roll bodies are used for reducing the friction forces between the driving wheel and the rotor. Roller bodies are supported on one side directly in the recess and, on the other side, directly at the interior wall of the driving wheel. Furthermore, it is suggested in a modified embodiment to admit pressure oil to a duct leading to the free face of the rotor vane in order to also reduce the friction forces between the driving wheel and the rotor. 
     It is an object of the invention to improve an arrangement of the above-mentioned type for the relative angle-of-rotation adjustment of a camshaft with respect to its driving wheel such that the friction power generated between the driving wheel and the rotor is reduced further. 
     This object is achieved by the claimed invention. 
     As a result of the pressure chambers provided in the side walls of the rotor vanes, because of the thereby reduced friction surfaces, the friction resistance between the driving wheel and the rotor can be reduced considerably. As a result, a fast, low-wear and reliable adjustment of the desired inlet and outlet times for the valves of the internal-combustion engine can be achieved. 
     Further advantages and advantageous further developments of the invention are contained in dependent claims and in the description. 
     Pressure admission to the two pressure chambers provided in a side wall of the rotor vanes advantageously takes place by way of respective openings connected with the pressure spaces adjoining the blades. As a result, the feeding of pressure oil for adjusting the interior part or the rotor can simultaneously be used for the admission of pressure to the pressure chambers provided in the rotor blades. Additional pressure lines for supplying the pressure chambers are therefore not required. 
    
    
     An embodiment of the invention will be explained in detail in the description which follows and in the drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of a camshaft adjuster; 
     FIG. 2 is a sectional view along line II—II in FIG. 1; 
     FIG. 3 is an enlarged representation of a rotor vane; 
     FIG. 4 is a sectional view along line IV—IV in FIG. 3; and 
     FIG. 5 is a view of the face of a rotor vane in the assembled condition of the camshaft adjuster. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the drawings, reference number  2  indicates a schematically outlined camshaft of an internal-combustion engine at whose free end an interior part, in the following called rotor  4 , of an adjusting unit  5  is arranged. In this embodiment, the rotor  4  is equipped with five radially arranged vanes  6   a  to  6   e  which originate from a hub  8  of the rotor  4 . In the area of its vanes  6   a  to  6   e , a cell wheel  10  reaches around the rotor  4 , which cell wheel  10  is provided with five inward-projecting radial webs  12   a  to  12   e . The cell wheel  10  forming the stator of the adjusting unit  5  is closed off by a chain wheel  14  on its face facing the camshaft  2 , which chain wheel  14  is rotatably and sealingly guided on the hub  8  of the rotor  4 . The chain wheel  14  is used as a drive for the camshaft  2  which takes place, for example, by way of a drive chain connected with the crankshaft. The opposite side of the cell wheel  10  is closed by a disk  16 , the chain wheel  14  and the disk  16  being fixedly connected with the cell wheel  10  by way of fastening screws  18 . The passage bores  20  provided in the webs  12   a  to  12   e  in the cell wheel  10  are used for receiving or guiding these fastening screws  18 . By means of the webs  12   a  to  12   e  of the cell wheel  10 , five cells which are bounded by the chain wheel  14  and the disk  16  in the axial direction are constructed. The cells are divided into two pressure spaces  22   a  to  22   e  and  24   a  to  24   e  respectively by means of the vanes  6   a  to  6   e  of the rotor  4 . The rotor  4  and the cell wheel  10  rotatably guided on the latter are fastened by means of a cap screw (not shown) to the camshaft  2 . The hub  8  has a central bore  26  for receiving the cap screw. 
     By means of two dowel pins  28  and the cap screw, a signal generator disk  30  is fastened to the exterior side of the rotor  4 . By means of this signal generator disk  30 , the rotating position of the camshaft  2  with respect to the crankshaft can be detected. The five axial bores  32   a  to  32   e  arranged in the hub  8  of the rotor  4  represent a portion of the oil supply ducts for the pressure spaces  24   a  to  24   e . The pressure spaces  22   a  to  22   e  are also supplied with hydraulic oil by way of radially extending bores (not shown) arranged in the hub  8 . The hydraulic oil supply for the two pressure spaces  22   a  to  22   e  and  24   a  to  24   e  respectively takes place by way of a camshaft bearing  34  to which the corresponding control lines of the oil pressure supply of the adjusting unit  5  are connected. The manner of the oil supply to the pressure spaces  22   a  to  22   e  and  24   a  to  24   e  respectively is known, for example, from German Patent Document DE 199 30 711 C1, so that the precise construction of the oil feeding ducts to the pressure spaces does not have to be discussed in detail. 
     The side wall  36  adjoining the chain wheel  14  and the side wall  38  of the vanes  6   a  to  6   e  adjoining the disk  16  each have two recesses  40  and  42  respectively forming a pressure chamber, which recesses  40  and  42  are both separated from one another by a center web  44 . By way of a duct  46 , the pressure chambers  40  are connected with the pressure spaces  22   a  to  22   e , and by way of a duct  48 , the pressure chambers  42  are connected with the pressure spaces  24   a  to  24   e . The two chambers  40  and  42  constructed on one lateral surface of the vanes  6   a  to  6   e  respectively extend essentially along the entire lateral surface. 
     As a function of the adjusting direction, a pressure cushion is built up reciprocally in the pressure chambers  40  and  42  respectively, which pressure cushion contributes to the reduction of friction between the vanes  6   a  to  6   e  and the adjoining chain wheel  14  and the disk  16 . If the rotor  4  is to be rotated clockwise (see FIG. 1) with respect to the cell wheel  10 , hydraulic oil is admitted to the pressure spaces  22   a  to  22   e . By way of the pressure spaces  22   a  to  22   e , the hydraulic oil arrives by way of the ducts  46  in the pressure chambers  40  in which a corresponding pressure cushion is built up. If the rotor  4  is to be built up relative to the cell wheel  10  counterclockwise, analogously, hydraulic oil is admitted to the pressure spaces  24   a  to  24   e . In this case, the hydraulic oil arrives by way of the pressure spaces  24   a  to  24   e  and the ducts  48  in the pressure chambers  42 , so that a friction reducing pressure cushion is also formed in this adjusting direction in the lateral area of the vanes  6   a  to  6   e.