Abstract:
In a device for operating a first control element for controlling gaseous media, a transmission element is formed on a final controlling element manipulatable by an actuator, the transmission element being able to be moved, on one hand, inside a slot of a slotted lever and being, the other hand, stationary-mounted to a supporting lever, which is attached to a stationary support at a joint location. The first control element is accommodated on the slotted lever, which is manipulatable via the transmission element, the control element being movable between a closed position and an open position in response to manipulation of the final controlling element by the actuator.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an actuating element for actuating a control element for a supercharges in a combustion engine.  
       BACKGROUND INFORMATION  
       [0002]     Supercharging methods are used in combustion engines, in order to increase the engine power, which is directly proportional to the rate of air flow. In addition to the dynamic boost that utilizes the dynamics of the air drawn in, the mechanical boost is used, where the supercharging device is driven directly by the engine. In this context, the combustion engine and the supercharging device mostly have a fixed transmission ratio with respect to each other. In the scope of the mechanical supercharging, exhaust-gas turbochargers are used in which the energy of the exhaust gas is used for driving the supercharger. On one hand, the energy, which, in the case of induction engines, cannot be utilized due to the expansion ratio predetermined by the crankshaft drive, is utilized, and on the other hand, the exhaust gas is accumulated to a higher degree upon leaving the engine, in order to obtain the necessary compressor power. Supercharging controlled in two stages is used within the scope of the exhaust-gas turbochargers, where two exhaust-gas turbochargers of different sizes are connected in series.  
         [0003]     A supercharging method employing two-stage control is known from the “Automotive Handbook,” Bosch (Chief Editor Horst Bauer, 23rd updated and expanded edition, Braunschweig; Wiesbaden: Vieweg 1999, ISBN 3-528-08376-4, pages 445, 466). According to this supercharging method, which can be used in motor vehicles, the two-stage-controlled supercharging is implemented by a series connection of two differently sized exhaust-gas turbochargers, along with a bypass control unit and an intercooler.  
         [0004]     The mass flow of exhaust gas coming from the cylinders of the internal combustion engine initially flows into an exhaust-gas manifold. From here on, there is the option of either expanding the entire mass flow of exhaust gas through a high-pressure turbine or rerouting a part of the mass flow through the bypass line. The entire mass flow of exhaust gas is then utilized once more by the post-connected, low-pressure turbine. The entire mass flow of fresh air is initially precompressed by the low-pressure stage and ideally intercooled. Further compression and intercooling subsequently occurs in the high-pressure stage. Due to the precompression, the relatively small high-pressure compressor operates at a higher pressure, so that it can push through the necessary mass flow of air.  
         [0005]     In the case of lower engine speeds, i.e., when the mass flow rate of exhaust gas is small, the bypass remains completely closed, and the entire mass flow of exhaust gas expands via the high-pressure turbine. This produces a very rapid and high supercharging pressure. As the speed of the engine increases, the expansion work is continuously shifted to the low-pressure turbine by increasing the cross-sectional area of the bypass accordingly. Consequently, the two-stage-controlled supercharging of an internal combustion engine allows the side of the turbines and the compressor(s) to be continuously adjusted to the requirements of the engine operation.  
         [0006]     In order to divert the mass flow of exhaust gas in the supercharging method occurring in two stages, as outlined above, flaps suspended on one side may be used, as are known from waste-gate turbochargers.  
         [0007]     The suspended flaps allow low production costs, since the manufacturing is optimized to the greatest possible extent. In general, a suspended flap is activated by a pneumatic control capsule, which is directly coupled to a lever on the outside of the housing of the exhaust gas turbocharger. In the case of a fixed control-capsule path, the constant lever arm allows a fixed angular range to be swept over. High actuating forces may be produced upon closing the suspended flap, since the flap is moved in the opening direction by the applied exhaust-gas pressure. This means that on one hand, either large forces must be applied to the control capsule or, on the other hand, high actuating travel must be provided, in order to thus apply a large lever arm to the flap shaft. Both mean high control volumes and, consequently, limited actuating speeds and high follow-up costs from any safety reserves lying idle. In addition, the installation conditions are unfavorable in most cases, since the prevailing developmental tendency in the automotive field is for the available space in the engine compartment to become smaller and smaller.  
         [0008]     The vacuum system of a motor vehicle must also keep the necessary volumes ready, without safety-related functions, such as a power-brake unit, being affected by this.  
       SUMMARY  
       [0009]     In the present invention, the holder receiving the control capsule, and a base plate, are welded to each other and receive the control capsule. A slotted lever is mounted to the shaft actuating a control element. With the aid of a joint head, a connection to the piston rod is produced, which moves into and out of the control capsule. A guide pin moves in a slotted hole of the slotted lever and is guided by a supporting lever, whose outer support is fixed to the base plate by the support bolt. The forces are transmitted to the slotted lever via the guide sleeve, which is designed to be able to roll.  
         [0010]     The lever arm is lengthened or shortened with respect to the flap-shaped control element, by sliding the guide bolt on the slotted lever. Consequently, it is possible to transmit different torques to the control element as a function of position. In a first position, the opening movement of the control element is inhibited by the lateral forces absorbed by the supporting lever. The opening movement may be unintentionally caused by disruptive forces acting upon the control element. In the event of high pressures applied to the closed control element, the design approach of the present invention already prevents it from opening unintentionally by producing low actuating forces.  
         [0011]     In a further position, a large adjustment angle may be produced via a small lever arm on the flap shaft. This allows a large opening angle of the control element to be attained in ranges where only small changes in the flow resistance occur with respect to the flap angle.  
         [0012]     Because of the low friction that occurs in the rolling movement of the provided design approach, the hysteresis of the provided system is extremely small.  
         [0013]     The considerably reduced actuating forces provided by the design approach of the present invention allow a pneumatic control capsule, as is presently used, to be replaced by an alternative actuator, such as an electric actuator. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  shows a partially sectioned view of an exhaust-gas turbocharger having a turbine part and a compressor part.  
         [0015]      FIG. 2  shows the kinematics of the activation of a control element, the control element being adjusted into a closed position.  
         [0016]      FIG. 3  shows the kinematics described in  FIG. 2 , in an open position of the control element.  
         [0017]      FIG. 4  shows, in a front view, the kinematics for actuating the control element according to  FIGS. 2 and 3 . 
     
    
     DETAILED DESCRIPTION  
       [0018]     A partially sectioned view of an exhaust-gas turbocharger is shown in  FIG. 1 .  
         [0019]     Exhaust gas turbocharger  1  represented in  FIG. 1  includes a turbine part  2  and a compressor part  3 . Exhaust-gas turbocharger  1  represented in  FIG. 1  may be used, for example, in internal combustion engines of automobiles and commercial vehicles, or in other combustion engines. A turbine wheel  6  is acted upon by exhaust gas via an exhaust-gas inlet  5 , and is set into rotation by the exhaust gas. Turbine wheel  6  is seated in a rotatably fixed manner on an exhaust-gas turbocharger shaft  4 , on which a compressor impeller is accommodated. Turbine wheel  6  is accommodated by a turbine housing  7 , in which a bypass line  20  is formed. Bypass line  20  may be unblocked or closed by a control element  19 , which is formed in the shape of a flap in the representation of  FIG. 1 . When a combustion engine is supercharged in multiple stages, a partial stream of the exhaust gas may be fed via bypass line  20  to a further exhaust-gas turbocharger, which is not shown in the representation according to  FIG. 1 . In order to control the partial exhaust-gas stream fed to the additional exhaust-gas turbocharger, control element  19  is actuated with the aid of a control capsule  13  positioned on exhaust-gas turbocharger  1 .  
         [0020]     Turbine housing  7  of exhaust-gas turbocharger  1  is connected to a compressor housing  10 . Exhaust-gas turbocharger shaft  4 , which is assigned a lubricant supply  8  in order to ensure low-friction running of exhaust-gas turbocharger shaft  4  during operation of exhaust-gas turbocharger  1 , extends through the two housings  7  and  10 . Shaft bearings  9 , which are preferably friction bearings, are provided with lubricant by lubricant supply  8 , so that a lubricant film forms on shaft bearings  9 , between the surface of exhaust-gas turbocharger shaft  4  and the bearings. Air is compressed and fed to a charge-air outlet  11  by the compressor impeller, which is positioned on exhaust-gas turbocharger shaft  4  and is set into rotation by the impingement of the exhaust gas upon turbine wheel  6 . The precompressed charge air is fed to the induction tract of a combustion engine, not shown here, to improve the cylinder charging.  
         [0021]     A branch  12  is provided at compressor housing  10  of exhaust-gas turbocharger  1 . Pressure above atmospheric may be applied to control capsule  13  shown in  FIG. 1 , via branch  12 , which means that control element  19  may be actuated via a control capsule  13 , to which pressure above atmospheric has been applied. In addition, control capsule  13  shown in  FIG. 1  may also be actuated via application of negative pressure, which is provided, for example, in motor vehicles having self-igniting combustion engines.  
         [0022]     Compressor housing  10  of exhaust-gas turbocharger  1  communicates with control capsule  13  via branch  12 , the control capsule being flange-mounted to the exhaust-gas turbocharger branch. Control capsule  13  is attached to compressor housing  10  via a flange  15 . A spring element  17 , which takes the form of a helical spring in the representation of  FIG. 1 , is situated inside the housing of control capsule  13 . A piston rod  16  is moved in a straight line by applying positive/negative pressure to control capsule  13 .  
         [0023]     A baffle  18  is actuated by piston rod  16 . Baffle  18  includes a compound-lever system, which is described in detail in  FIGS. 2, 3 , and  4 , and with the aid of which control element  19 , which may be formed in the shape of a flap, may be adjusted into an open position or a closed position or an operationally dependent, intermediate position.  
         [0024]     Control element  19  according to the representation in  FIG. 1  takes the form of an axially symmetric, circular flap and, in the closed state, rests against a contact surface  21  on the end face of bypass line  20 , in turbine part  2  of exhaust-gas turbocharger  1 . In the closed position, bypass line  20  for admitting exhaust gas of the combustion engine into a further exhaust-gas turbocharger, is closed. Flap surface  22  of control element  19  formed in the shape of a flap is dimensioned in such a manner that bypass line  20  is completely closed with respect to a further exhaust-gas turbocharger when control element  19  rests against contact surface  21 . On the basis of the volumetric flow rate of exhaust gas prevailing in bypass duct  20  of exhaust-gas turbocharger  1 , the closed position of control element  19  formable in the shape of a flap is implemented by the spring force of spring  17  accommodated in control capsule  13 , in order to prevent a partial exhaust-gas stream from unintentionally overflowing through bypass channel  20  into the further exhaust-gas turbocharger not shown in  FIG. 1 . According to the view shown in  FIG. 1 , piston rod  16  extends from control capsule  13 , which is accommodated on compressor part  3  of exhaust-gas turbocharger  1 , in parallel to exhaust-gas turbocharger shaft  4 , to turbine part  2  of exhaust-gas turbocharger  1 .  
         [0025]     Shown in  FIG. 2  is the actuating device for the control element, in a first actuating position.  
         [0026]     Control capsule  13 , by which piston rod  16  is manipulated, is not shown in further detail in the representation according  FIG. 2 . Piston rod  16  reaches through an opening in a base plate  31  and has a joint head  32  on its end pointing towards control element  19 . Joint head  32  may be screwed, for example, onto a threaded segment of piston rod  16 . A base plate  30  is welded to control-capsule holder  31  or  15 . Base plate  30  includes a first joint  38 , to which a supporting lever  36  is linked. For this purpose, a support bolt  35  is provided at first joint  38 , the support bolt allowing supporting lever  36  to swivel relative to base plate  30 .  
         [0027]     A guide pin  34  is supported on supporting lever  36 , at the end opposite to first joint  38 . On one hand, guide pin  34  is accommodated on joint head  32 , and on the other hand, it passes through a slot  39  in slotted lever  33 , the slot preferably taking the form of a slotted hole. Guide pin  34  includes a guide sleeve  37 , which is received at guide pin  34  so as to be able to rotate. Guide sleeve  37  roles at its circumferential surface on the inside of slot  39  in slotted lever  33 . Situated at one end of slotted lever  33  is a flap bearing  40 , to which control element  19  taking the form of, e.g., a circular control flap is attached. Also accommodated on slotted lever  33  is a path limiter  41 , which, in the position of slotted lever  33  according to the representation in  FIG. 2 , is run over joint head  32 . Slotted lever  33  partially passes through the wall of bypass line  20 . With the aid of guide sleeve  37 , which is supported on guide pin  34  and positioned so as to be able to rotate, the actuating forces of piston rod  16  are transmitted to slotted lever  33  and therefore to control element  19 , for opening and closing bypass line  20  in turbine part  2  of exhaust-gas turbocharger  1  according to the representation in  FIG. 1 .  
         [0028]     In the view according to  FIG. 2 , supporting lever  36  is parallel to control-capsule holder  31 . The guide pin  34  movable in slot  39 , together with guide sleeve  37 , is adjusted up with respect to the longitudinal extension of slot  39 , whereby control element  19  rests against contact service  21  of bypass line  20  in turbine part  2  of exhaust-gas turbocharger  1  and consequently closes bypass line  20 .  
         [0029]     The kinematics of the actuating device can be gathered from the representation according to  FIG. 3 , the control element actuated by the actuating device being moved into its open position.  
         [0030]     In contrast to the representation according  FIG. 2 , piston rod  16  is moved out of control capsule  13  which is not shown in  FIG. 3  (cf. representation according  FIG. 1 ). Therefore, joint head  32 , which is connected to piston rod  16 , is extended out in the direction of bypass line  20 . While piston rod  16  is moved out of control capsule  13 , the coupling of guide pin  34  to joint head  32  causes guide sleeve  37  accommodated on guide pin  34 , together with guide pin  34 , to be moved inside of slot  39  of slotted lever  33 . Since guide pin  34  is also mounted on supporting lever  36 , the extension movement of piston rod  16  out of control capsule  13  in the vertical direction of bypass channel  20  impresses a clockwise swiveling motion in slotted lever  33 . As shown in  FIG. 3 , the swivel motion of slotted lever  33  is limited by the contact of path limiter  41  with a lateral surface of supporting lever  36 . During the clockwise swiveling movement of slotted lever  33 , control element  19  taking the form of a control flap is also rotated clockwise about guide pin  34  and assumes its open position represented in  FIG. 3 . In the position of circularly formable control element  19  shown in  FIG. 3 , the outlet cross section of bypass line  20  is unblocked by control element  19 . A partial exhaust-gas stream or another gaseous medium is now able to flow through uncovered bypass duct  20  and, e.g., to flow into a further exhaust-gas turbocharger downstream from the one in  FIG. 1 . In the open position of control element  19  formed in the shape of a circle, it follows from the representation of  FIG. 3  that slot  39  assumes a nearly horizontal position. At first joint  38 , supporting lever  36  is inclined about supporting bolt  35 , out of its position parallel to control-capsule holder  31 .  
         [0031]     The positioning travel with respect to the swiveling path of control element  19  formed in the shape of a circle may be influenced, for example, by adjusting joint head  32  on the end segment of piston rod  16  that moves out of control capsule  13 . This allows the open and closed positions of circular control element  19  to be adjusted, and allows the positioning path traveled by circularly formable control element  19  from its closed position (cf. view according to  FIG. 2 ) to its open position (cf. view according to  FIG. 3 ) to be finely adjusted.  
         [0032]     It can be deduced from the view according to  FIG. 4  that joint head  32  has a shell-shaped bearing body for receiving guide pin  34 . In the region of slot  39 , guide sleeve  37  is accommodated on guide pin  34  so as to be rotatable. Guide pin  34  also passes through supporting lever  36  and may be fastened to it, for example, by a threaded member or the like. At its circumferential surface, guide sleeve  37  rotatably accommodated on guide pin  34  rolls on the inside of slot  39  and forces slotted lever  33 , for its part, to swivel clockwise from the closed position of control element  19  according to the view in  FIG. 2 , into its open position (cf. view according to  FIG. 3 ). Supporting lever  36  is also mounted on base plate  30  via supporting bolt  35 , it being ensured that supporting lever  36  can swivel relative to supporting bolt  35  of first joint  38 , by inserting a bearing shell. For the sake of completeness, it should be mentioned that the support for control element  19  is attached to the lower end of slotted lever  33  (cf. reference numeral  40 ).  
         [0033]     Using actuating device  18  described in detail in connection with  FIGS. 2, 3 , and  4 , the lever arm with respect to control element  19  may be lengthened or shortened by moving guide pin  34  inside slot  39  of slotted lever  33 . This allows different torques to be transmitted to control element  19  as a function of the position of slotted lever  33 . In the position shown in  FIG. 2 , the absorption of lateral forces by supporting lever  36  inhibits the opening movement of control element  19 , which may be designed, for example, as a circular flap; the opening movement being able to be caused unintentionally by disruptive forces on control element  19 . When the occurring pressure of the gaseous medium to be controlled is high, e.g., in the case of pressure fluctuations that can bring about the opening of control element  19  in its closed state, this situation may be counteracted by relatively small actuating forces.  
         [0034]     In the case of the position of control element  19  shown in  FIG. 3 , a large adjusting angle of control element  19  is achieved by a small lever arm with respect to flap shaft  40 . This allows large opening angles of control element  19  formed in the shape of a flap to be attained in ranges, in which only small changes in the flow resistance occur in relation to the opening angle of control element  19 . Due to the low friction during the rolling movement of guide sleeve  37  inside slot  39  formed within slotted lever  33 , the hysteresis of the actuating device provided by the present invention is very small. Due to the relatively small actuating forces for actuating baffle  18 , a pneumatic control capsule  13 , e.g., one operated by the action of negative pressure, may also be replaced by an alternative actuator, such as an electric actuator. This eliminates the need for a negative-pressure consumer, which means that all of the negative pressure is available to a safety-related system in the motor vehicle, such as the power-break unit, and that no negative pressure would have to be diverted for operating control capsule  13  of an exhaust-gas turbocharger  1 .  
         [0035]     The very compact baffle  18  according to the representation in  FIGS. 2, 3 , and  4  eliminates long actuating paths, which take up space and negatively affect the actuating speeds. The design of baffle  18  provided by the present invention allows high forces to be applied, which reliably hold the control element  19  able to take the form of, e.g., a flap, in its closed position, i.e., resting against contact surface  21  of bypass line  20 , which means that control element  19  formed in the shape of a flap is reliably prevented from opening unintentionally.