Abstract:
A device for independent hydraulic actuation of phase and axial positions of a camshaft of an internal combustion engine with a phase adjuster and an actuating piston arranged on a common axis for axial displacement of the camshaft. In order to reduce the space needed and construction expenditure of the device, the phase adjuster also acts as the actuating piston for the camshaft.

Description:
BACKGROUND 
     The invention concerns a device for independent actuation of the phase and axial position of a camshaft. 
     Otto motors usually operate with a load-dependent change of the fuel-air mixture. This is, as a rule, varied by a throttling device, for example by a throttle valve. This leads to throttling losses during load changes. The throttling losses can be diminished by variation of the aperture cross section of the intake valves, for example by changing its stroke. For this, for example, an axially moveable intake camshaft with a conical or three-dimensional cam contour is suitable. 
     A strong charging movement is also advantageous with a partial load as it can be triggered by a retarded beginning of suction. The high rate of combustion caused by this also brings about, even with retarded beginning of suction, a punctual end of combustion. A retarded beginning of combustion with a punctual end of combustion however brings about a low peak pressure, a slight tendency to knock and low nitrogen oxide formation without several combustion disadvantages. The shifting of opening and closing times of the intake and if need be the exhaust valves required for this can be realized by known phase adjusters arranged in the power train between crankshaft and camshaft. Variable valve cross sections and control times are accordingly advantageous for an economical and environmentally friendly operation of the Otto motor. 
     From DE 199 02 095 A, a device for independent hydraulic actuation of the phase and axial position of a camshaft is known. For reasons of construction space, the phase adjuster is arranged on the directly driven exhaust camshaft. Its output element is connected with a gear which is mounted on the exhaust camshaft and which drives the gear of the intake camshaft. The motor-attached stroke actuator is connected with this through a slide gearing. The slide gearing must be provided with minimal backlash as this is a source of disturbing noises. The same applies for the tooth wheel drive between the two camshafts. For this reason, with this solution, an expensive compensation for or restriction of the torsional backlash is provided. 
     From DE 199 03 622 A1, a device for independent hydraulic actuation of the phase and axial position of a shaft, especially the intake camshaft of an internal combustion engine, is known, with a phase adjuster constructed as rotatble piston actuator, which has a stator and a rotor, and with an actuating piston arranged in the same axis for axial movement of the intake camshaft. In addition, this device has a cylindrical housing for the actuating piston whereby the housing is connected with the stator and a drive wheel and the rotor as well as the actuating piston are in a rotationally fixed connection with the intake camshaft. 
     Since the actuators are arranged one after the other, they require a considerable construction length. Since the phase adjuster is positioned axially stationary, they require, in relation to the axially movable camshaft, a sliding gearing with the known expensive measures for avoiding gear backlash. 
     Underlying the invention is the object of creating a generic device for independent hydraulic actuation of the phase and axial position of a camshaft whereby the device is distinguished by a small space requirement and low construction expenditure. 
     SUMMARY 
     In accordance with the invention, this object is accomplished by providing a device in which the phase adjuster also forms the actuating piston for the camshaft. Since the phase adjuster is at the same time the actuating piston of the camshaft, it moves along with the axial movement of the camshaft. In this way, the necessity of a slide gearing in addition to gear backlash compensation between phase adjuster and camshaft is dispensed with, which leads to a considerable simplification of the device. Dispensing with a separate actuation piston likewise diminishes construction expense and at the same time diminishes the overall length of the device. 
     A preferred embodiment of the invention is provided in that the phase adjuster is constructed as a segment vane actuator which has a cylindrical rotor, in the peripheral area of which at least one axial, concentric hydraulic chamber in the form of a oblong hole is provided. The hydraulic chamber is subdivided by a segment into two active oil chambers A and B with sealing play and is laterally closed off by two side covers with close play. Here the side covers have apertures aligning with the cross section shape of the segment through which the same extends with sealing play. Such a segment vane actuator is described in the not previously published German patent application P 199 51 390.2. It is distinguished by a small number of structural units and its economical producibility. While the segments described in the not previously published German patent application P 199 51 390.2 are inserted between the side covers, these extend, in the construction of the invention, through the aligning apertures of the side covers. These aligning apertures permit a lengthening of the segments over the width of the rotor so that these can serve as guide rods during axial motion of the segment vane actuator. The close play between the apertures and the segments moreover serve for lateral sealing of the active oil chambers A and B. 
     An advantageous refinement of the invention is provided in that the length of the segments exceeds the greatest width of the rotor at least by the stroke dimension of the camshaft, and in that the constructed hollow segments are clamped from rotating by means of bolts that extend through the same between a bottom of the housing and a cover plate preferably constructed as a drive wheel. The length of the segments selected permits the desired axial displacement of the segment vane actuator and the intake camshaft connected with it. The driving torque of the camshaft is transferred from the drive wheel through the segments inserted between this and the housing and the pressure oil in active oil chambers A and B to the rotor and the camshaft connected with it. 
     It is advantageous if the rotor has, on both sides, coaxial, cylindrical recesses for the side covers and that the side covers are axially fixed though retaining rings. Since the side covers, in the construction of the segment vane actuator of the invention, cannot be braced on one another, their close play in relation to the rotor is guaranteed through the exact axial position of the retaining rings sitting in the grooves of the same. The side walls moreover serve exclusively for lateral sealing of active oil chambers A and B and not for transfer of the driving torque of the segments. 
     An appropriate construction of the invention is provided in that on the periphery of the rotor, at least sealing element is arranged though which the cylindrical housing is subdivided into first and second operating chambers. Since the rotor is radially guided by the segments, it must have radial play in relation to the cylindrical housing which is bridged by the sealing element. The sealing element can be constructed as a sealing ring, sealing strip or piston guide way. 
     Due to the fact that first and second 4/3 way proportional valve are provided for independent hydraulic control of active oil chambers A and B and the first and second chambers, a motor-optimal control of the camshafts is made possible. 
     It is advantageous that a preferably decentralized control apparatus is provided for the proportional valves which receives signals on phase and stroke position of the camshaft from a camshaft sensor and such on, for example, motor speed, motor load and motor temperature from a central control apparatus of the internal combustion engine. The central control apparatus makes possible a flexible supplementation of the motor control apparatus which is not affected by possible changes of the camshaft. 
     Preferably a seal ring carrier of a rotary oil through passage device is located between rotor and intake camshaft, which has oil sealing rings for mutual and outward acting sealing of the radial grooves of oil supply channels. In this way, oil leakage losses of the rotary oil through passage with a relatively long overall length are minimized. 
     An advantageous refinement of the invention is provided in that the radial forces of the drive wheel are transmissible over the segments and the rotor or directly to the sealing ring carrier and the camshaft. The mounting of the drive wheel over the segments on the walls of the hydraulic chambers (the so-called internal mounting) offers the advantage of the smallest play possible between active oil chambers A and B with correspondingly low leakage. A precondition for this is a correspondingly wear and tear resistant surface of the walls of the hydraulic chambers. In contrast, with direct mounting of the driving wheel on the seal ring carrier (or so-called external mounting), owing to the bearing play there, a corresponding enlargement of the close play of the segments in the hydraulic chambers is necessary, which has increased oil leakage losses or the installation of additional sealing elements as a consequence. For this, the walls of the hydraulic chambers in this case require no protection against wear and tear, so that the rotor can be formed of light metal, for example, of aluminum, and be manufactured by the extrusion or cold forging method. 
     Due to the fact that the rotor has a locking element, preferably an axial fixing pin which is latchable in a blind aperture of one of the side covers, the starting position of the rotor is assured which among other things is important for a good motor start. Of course, the use of a radial fixation pin or a wedge locking device or the like is also conceivable. 
     Further features of the invention are provided in the patent claims, the following description and the drawings in which an embodiment of the invention is schematically represented. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention is explained in detail in connection with the drawings. In the drawings: 
     FIG. 1 is a longitudinal section view through the segment vane actuator along section plane A—A of FIG. 2; 
     FIG. 2 is a cross sectional view through the rotor of the segment vane actuator along section plane B—B of FIG. 1; 
     FIG. 3 is a cross sectional view through an operating chamber of the segment wing vane along section plane C—C of FIG. 1; 
     FIG. 4 is an elevational view of the housing in direction Z of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The segment vane actuator  1  represented in FIG. 1 has a cylindrical housing  2  which is also constructed as an operating hydraulic cylinder for a cylindrical rotor  3  of the segment vane actuator. This serves as a phase adjuster for a camshaft  4  and at the same time as an actuating piston for axial displacement of the camshaft  4 . 
     One end of the housing  2  is provided with a bottom  5 , and a flange  6  is provided on its other end. Both are connected in one piece with the cylindrical part of the housing  2 . The bottom  5  has a central assembly aperture with a screw cap  7 . The flange  6  is joined rotatably fast by flange screws  8  with a cover plate constructed as drive wheel  9 . The drive wheel  9  is driven through a chain (not shown) by a crankshaft (not shown). 
     The housing  2  is axially fixed on the camshaft side though the face  43  of a bearing bushing  44  affixed to the motor against which the outer surface  45  of the drive wheel  9  runs. On the opposite side, the housing  2  is axially fixed by a control space cover (not represented) affixed to the motor and a bearing pin  46  which engages in the hexagon  47  of the screw cap  7 . 
     In the interior of the housing  2 , five hollow constructed segments  10  are arranged. These are connected by through bolts  11  which extend through aligned holes in the drive wheel  9 , the segments  10  and the bottom  5  in order to brace the segments  10  with the bottom  5  and the drive wheel  9  and in this way provide a positive force connection. The housing  2  with the drive wheel  9 , the segments  10  and the side covers  12 ,  12 ′, as will be explained in detail below, together form the stator of the segment vane actuator  1 . 
     The rotor  3  is connected in a non-rotatable manner, with the aid of a central clamping screw  13  through a seal ring carrier  14  with camshaft  4 . The rotor  3  has in its peripheral area five hydraulic chambers  15 , as shown in FIG. 2, constructed as axially extending, concentric oblong holes with curved walls  16 ,  16 ′ separated from one another by radially extending bars  17 ,  17 ′. The hydraulic chambers  15  are penetrated by the segments  10  and subdivided sealingly into two active oil chambers A and B in each case. 
     The segments  10  have an approximately trapezoidal outer contour with two sides adapted to the shape of the radially standing bars  17 ,  17 ′ and two sides adapted to the curved walls  16 ,  16 ′. Due to the enlarged seal length of the segments against the circular cross section, leakage between active oil chambers A and B is diminished. 
     The hydraulic chambers  15  are sealed off laterally by the side covers  12 ,  12 ′ mentioned above with seal play. These are installed in coaxial, cylindrical recesses  18  on both sides of the rotor  3 . The axial position of the side covers  12 ,  12 ′, and in this way their close play in relation to the rotor  3 , are fixed through retaining rings  19  which are arranged in the cylindrical part of the recesses  18  in grooves. The side covers  12 ,  12 ′ have aligned apertures  20  with the cross section shape of the segments  10  through which these extend with close play. As parts of the stator, the side covers  12 ,  12 ′ are non-rotatable in relation to the segments  10  and are rotatable in relation to the rotor  3 . 
     The length of the segments  10  exceeds the greatest width of the rotor  3  by more than the stroke length of the camshaft  4  in order to guarantee the same free space necessary for axial actuation. The extended segments  10  serve the rotor  3  during axial displacement as guide rods on which this glides with the small radial play of the segments  10  in their hydraulic chambers  15 . In order to avoid a redundant determination of the mounting of the drive wheel  9 , the radial play between the drive wheel  9  and the seal ring carrier  14  as well as between the cylindrical housing  2  and the rotor must be greater than the radial play between segments  10  and the curved walls  16 ,  16 ′ of the hydraulic chambers  15 . Radial forces of the drive wheel  9  are consequently not directly transmitted over the segments  10  and the rotor  3  to the sealing ring bearer  14 . On the periphery of the rotor  3 , for bridging the radial play in relation to the cylindrical housing  2 , a sealing ring  21  is arranged, through which the same is subdivided into a first and second operating chamber  22 ,  23 . For damping the striking noise of the rotor  3  on the bottom  5 , an elastic buffer  33  is arranged on the latter. 
     The pressurized oil supply to the operating chambers  22 ,  23  takes place through a first 4/3 way proportional valve  24 . This takes place through a from connection with a first and a fourth radial groove  25 ,  26  of the sealing ring carrier  14 . The first radial groove  25  is connected via four axial bore holes  27  evenly distributed through the sealing ring carrier  14  with the first operating ring chamber  22 . The fourth radial groove  26  is connected via a central bore hole  28  in the clamping screw  13  with the second operating chamber  23 . 
     The pressurized oil supply to the active oil chambers A and B takes place through a second 4/3 way proportional valve  29 . This takes place through a flow connection with second and third radial grooves  30 ,  31  of the seal ring carrier  14 . The second radial groove  30  is connected through an outer annular space  32  between a central recess of the seal ring carrier  14  and a sheath  34  as well as over (not represented) radial bore holes in rotor  3  with the active oil chambers A. The third radial groove  31  is connected via an inner annular space  35  between the sheath  34  and the clamping screw  13  and through radial bore holes  36  in the rotor with the active oil chambers B. 
     The proportional valves  24 ,  29  are controlled by a decentralized control apparatus  37 . This receives signals from a camshaft sensor  38  on the phase and stroke position of the camshaft  4 , and from a central control apparatus  39 , which signals on motor speed, load and temperature. The two control apparatuses  37 ,  39  are connected with each other through a data bus. Since the proportional valves  24 , 29  are activatable independently of each other, phase and stroke relationship of the camshafts  4  can be varied independently of each other. 
     Between radial grooves  25 ,  26 ,  30 ,  31  of the seal ring carrier  14  and outside of the same, oil sealing rings  40  are provided which bring about a short overall length and low leakage for this rotary transmission through passage. 
     For locking of the rotor  3  on starting, an axial fixing pin  41  is provided which is latchable into a blind aperture  42  of the side cover  12 ′ with spring force when the internal combustion engine is coasting, and can snap out again when a minimum oil pressure is exceeded in active oil chambers A and B. 
     In FIG. 3, the segments  10  operating in the region of the section plane C—C as guide rods are represented. Likewise, the retaining ring  19  for the side cover  12 ′ is shown. Also the clamping screw  13  with its central bore hole  28 , the sheath  34  with the outer and inner annular space  32 ,  35  and the sealing ring carrier  14  with the four axial bore holes  27  are represented. 
     FIG. 4 shows the drive wheel  9  with the flange screws  8  and the bottom  5  with the through bolts  11  as well as the screw cap  7  with the hexagon  47  and the bearing pin  46 . 
     The actuating device of the invention can obviously not only be used in connection with intake valves but also in connection with outlet valves or in connection with both camshafts at the same time. It is also conceivable that the actuating device is bringable into a base position by suitable springs in the emptied state. 
     
       
         
               
             
               
               
               
               
             
           
               
                   
               
               
                 Reference Number List 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Segment vane 
                 24 
                 First 4/3 way proportional valve 
               
               
                   
                 actuator 
               
               
                 2 
                 Housing 
                 25 
                 First radial groove 
               
               
                 3 
                 Rotor 
                 26 
                 Fourth radial groove 
               
               
                 4 
                 Camshaft 
                 27 
                 Axial bore hole 
               
               
                 5 
                 Bottom 
                 28 
                 Central bore hole 
               
               
                 6 
                 Flange 
                 29 
                 Second 4/3 way proportional valve 
               
               
                 7 
                 Screw cap 
                 30 
                 Second radial groove 
               
               
                 8 
                 Flange screw 
                 31 
                 Third radial groove 
               
               
                 9 
                 Drive wheel 
                 32 
                 Outer annular space 
               
               
                 10 
                 Segment 
                 33 
                 Buffer 
               
               
                 11 
                 Through bolt 
                 34 
                 Sheath 
               
               
                 12, 12′ 
                 Side cover 
                 35 
                 Inner annular space 
               
               
                 13 
                 Clamping screw 
                 36 
                 Radial bore hole 
               
               
                 14 
                 Seal ring carrier 
                 37 
                 Decentralized control apparatus 
               
               
                 15 
                 Hydraulic chamber 
                 38 
                 Camshaft sensor 
               
               
                 16, 16′ 
                 Curved wall 
                 39 
                 Central control apparatus 
               
               
                 17, 17′ 
                 Bar 
                 40 
                 Oil sealing ring 
               
               
                 18 
                 Recess 
                 41 
                 Axial fixation pin 
               
               
                 19 
                 Retaining ring 
                 42 
                 Blind aperture 
               
               
                 20 
                 Aperture 
                 43 
                 Face 
               
               
                 21 
                 Sealing ring 
                 44 
                 Bearing bushing 
               
               
                 22 
                 First operating 
                 45 
                 Outer surface 
               
               
                   
                 chamber 
               
               
                 23 
                 Second operating 
                 46 
                 Bearing pin 
               
               
                   
                 chamber 
                 47 
                 Hexagon