Abstract:
The invention relates to an injection valve ( 1 ), which is used in particular as an injector for fuel injection systems or exhaust gas aftertreatment systems, comprising a shock wave actuator ( 4 ), a valve closing body ( 8 ) that interacts with a valve seat surface ( 7 ) to form a sealing seat ( 9 ), and a shock wave amplification channel ( 22 ). The shock wave amplification channel ( 22 ) is used to conduct shock waves ( 27 ) generated by the shock wave actuator ( 4 ) to the sealing seat ( 9 ) and to amplify said shock waves ( 27 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to an injection valve, in particular an injector for fuel injection systems or for exhaust-gas aftertreatment systems. 
         [0002]    DE 10 2006 026 153 A1 has disclosed a spray device for fluids. The known spray device has a nozzle and an actuator for regulating the fluid flow through the nozzle outlet. Moreover, a shock-wave actuator is provided for generating shock waves in the fluid which is situated in the nozzle. Shock waves are generated in the spray device via the shock-wave actuator, which shock waves are guided onto the fluid which is situated in the nozzle. 
         [0003]    In the case of a spray device for fluids having a shock-wave actuator, the problem arises that operation has to be carried out counter to an ambient pressure which is produced, for example, by the pressure in the combustion chamber. Moreover, problems arise in the jet shaping. 
       SUMMARY OF THE INVENTION 
       [0004]    In contrast, the injection valve according to the invention has the advantage that injection behavior is improved. Specifically, defined injection jets can be realized and opening of the injection valve can be realized which is at least largely independent of the ambient pressure, in particular the combustion chamber pressure. 
         [0005]    In an advantageous way, the shock-wave actuating system generates shock waves which are guided to the sealing seat. The physical phenomenon of the shock wave is a strong pressure wave in elastic media, such as liquids, which can propagate at supersonic speed, high mechanical stresses and pressures prevailing at the shock front of the shock wave. The shock wave represents a pressure pulse, in which the pressure rises steeply within a fraction of a second and subsequently drops steeply again. The extreme pressure change which is generated by the pressure wave has its effect amplified further by the shock-wave amplifying channel. As a result, the valve closing body can be raised up from the valve seat face in an advantageous way, in order to open the sealing seat which is formed between the valve closing body and the valve seat face. As a result, very high injection pressures can be realized, in order to realize advantageous atomization even at high ambient pressures. For example, fuel can be injected into the combustion chamber of an internal combustion engine at a pressure of approximately 200 MPa (2000 bar) for direct diesel injection or of 20 MPa (200 bar) for direct gasoline injection. Here, firstly defined, individual injection jets can be realized. Secondly, opening of the injection valve can be achieved which is independent of the combustion chamber pressure or another ambient pressure. 
         [0006]    It is advantageous that a cross-sectional area of the shock-wave amplifying channel, which cross-sectional area remains free and serves to guide the shock waves, decreases at least in sections from the shock-wave actuating system toward the sealing seat. Here, the cross-sectional area which remains free preferably decreases uniformly toward the sealing seat. As a result, advantageous amplifying of the shock wave occurs, said shock wave exerting a high local pressure at the sealing seat and therefore a great opening force on the valve closing body. 
         [0007]    Furthermore, it is advantageous that an injector body is provided which has at least one internal space, that a shock-wave amplifying element is inserted into the internal space, that the shock-wave amplifying channel is configured at least in sections between an inner wall of the internal space and the shock-wave amplifying element, and that a tip of the shock-wave amplifying element is oriented in the shock-wave amplifying channel counter to a propagation direction of the shock waves which are generated. The shock wave which is generated by the shock-wave actuating system runs in the direction of the sealing seat. Here, the shock-wave front will penetrate at the tip of the shock-wave amplifying element. The shock-wave amplifying channel narrows behind the tip, with the result that the shock wave is amplified increasingly. Furthermore, it is advantageous here that, between the inner wall of the internal space and the shock-wave amplifying element, the shock-wave amplifying channel is of annular configuration at least in sections and/or is of partly annular configuration at least in sections and/or is configured at least in sections as a multiply interrupted ring. In addition or as an alternative, it is advantageous that the shock-wave amplifying element is configured at least approximately as a conical shock-wave amplifying element, and/or that the inner wall of the internal space tapers at least in sections from the shock-wave actuating system toward the sealing seat. Furthermore, it is advantageous that the inner wall of the internal space is of conical configuration at least in sections. As a result, the shock-wave amplifying channel can advantageously be configured as a narrowing annular gap which is optionally divided into sections. Here, the annular gap preferably narrows more and more in the direction of the sealing seat, with the result that the shock wave is amplified increasingly. In the region of the sealing seat, a high pressure of the shock wave, which high pressure leads to the opening of the sealing seat, then acts at least approximately uniformly in a manner distributed over the sealing seat. 
         [0008]    Furthermore, it is advantageous that the valve closing body is formed on the shock-wave amplifying element. Here, the shock-wave amplifying element can be configured in one part or multiple parts. In the case of a multiple part configuration, the individual parts are connected to one another in a suitable way. Here, it is also advantageous that at least one guide element is provided for the shock-wave amplifying element, which guide element is arranged in the internal space of the injector body. As a result, guidance of the guide element is ensured, for example, along a longitudinal axis of the injection valve. 
         [0009]    Furthermore, it is advantageous that a spring element is provided which loads the valve closing body against the sealing seat. Here, the opening force on the valve closing body, which opening force is induced by the shock wave on account of the high local pressure at the sealing seat, acts counter to a prestress of the spring element. As a result, tuning of the injection valve can be performed. 
         [0010]    It is also advantageous that the valve closing body has at least one pressure equalization channel. As a result, hydraulic damping of the valve closing body is avoided during an opening movement. 
         [0011]    It is advantageous that the shock-wave actuating system has an electrically conductive, elastic diaphragm and at least one field coil, and that the field coil is assigned to the diaphragm in order to generate an induction current in the diaphragm. Via the field coil, an induction current can be generated in the diaphragm. The interaction of the magnetic field of the field coil and the induced magnetic field which is generated by the induction current in the diaphragm leads to a force on the diaphragm. As a result, bending of the diaphragm occurs. As a result of the bending of the diaphragm, a shock wave is generated in the medium which adjoins the diaphragm. Said shock wave then runs from the diaphragm through the shock-wave amplifying channel to the sealing seat. 
         [0012]    It is advantageous that the diaphragm is configured as an at least approximately circular diaphragm, and that the field coil is arranged in the region of a side of the diaphragm, which side faces away from the shock-wave amplifying channel. Upon the actuation of the shock-wave actuating system, a repulsion force is generated on the basis of the magnetic field of the coil and the induced magnetic field in the diaphragm. Here, an induction current (eddy current) occurs in the diaphragm, which induction current is oriented such that it opposes the current through the field coil. 
         [0013]    However, it is also advantageous that the diaphragm is configured as a tubular and/or conical diaphragm, that an inner side of the diaphragm delimits the shock-wave amplifying channel, and that the field coil is arranged in the region of an outer side of the diaphragm. As a result, the area of the diaphragm which serves to generate the shock wave can be increased in relation to an available installation space. 
         [0014]    The diaphragm is preferably configured as a metal diaphragm. In particular, the metal diaphragm can be formed at least substantially from copper. A diaphragm can also be formed from at least two components which serve to seal and to make the excitation possible. For example, the diaphragm can be formed from at least one precious metal, in particular platinum, and copper. The diaphragm can also be formed from a ferromagnetic steel sheet. In order to improve the conductivity of the diaphragm, a ferromagnetic steel sheet which is coated with copper or the like toward the field coil can also be used as diaphragm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    Preferred exemplary embodiments of the invention are explained in greater detail in the following description with reference to the appended drawings, in which corresponding elements are provided with coinciding designations and in which: 
           [0016]      FIG. 1  shows a first exemplary embodiment of an injection valve of the invention in a partial, diagrammatic sectional illustration, and 
           [0017]      FIG. 2  shows a second exemplary embodiment of an injection valve of the invention in a partial, diagrammatic sectional illustration. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a first exemplary embodiment of an injection valve  1  in a partial, diagrammatic sectional illustration. The injection valve  1  can serve, in particular, as an injector  1  for fuel injection systems. An injector  1  of this type can be used for air-compressing, compression-ignition internal combustion engines or for mixture-compressing, spark-ignition internal combustion engines. Specifically, the injection valve  1  can serve for the injection of diesel fuel or of gasoline into a combustion chamber of an internal combustion engine. However, the injection valve  1  can also be used for an exhaust-gas aftertreatment system, for example for the injection for DeNOx systems. However, the injection valve  1  according to the invention is also suitable for other applications. 
         [0019]    The injection valve  1  has an injector body  2 , an injector sleeve  3  which is connected to the injector body  2 , and a shock-wave actuating system  4 . Here, the shock-wave actuating system  4  is arranged in the injector body  2 . Moreover, the injector body  2  has an internal space  5 . Here, the internal space  5  is delimited by an inner wall  6  of the injector body  2 . 
         [0020]    A valve seat face  7  is formed on the injector body  2 . Moreover, a valve closing body  8  which is assigned to the valve seat face  7  is provided, which valve closing body  8  interacts with the valve seat face  7  to form a sealing seat  9 . Furthermore, a shock-wave amplifying element  10  is provided which is arranged at least partially in the internal space  5  of the injector body  2 . Here, a plurality of guide elements  11 ,  12 ,  13  are provided which hold the shock-wave amplifying element  10 . Here, the guide elements  11 ,  12 ,  13  are connected to the injector body  2 . 
         [0021]    In this exemplary embodiment, the valve closing body  8  is formed on the shock-wave amplifying element  10 . Here, a single part or multiple part embodiment of the shock-wave amplifying element  10  with the valve closing body  8  is possible. In this case, the guide elements  11 ,  12 ,  13  make an adjustment of the shock-wave amplifying element  10  and therefore also of the valve closing body  8  possible from the starting position (shown in  FIG. 1 ) in an opening direction  14  along an axis  15  of the injection valve  1 . Here, moreover, the valve closing body  8  and therefore also the shock-wave amplifying element  10  are guided on a guide hole  16  of the injector sleeve  3 . 
         [0022]    The shock-wave actuating system  4  comprises an electrically conductive, elastic diaphragm  17  or a piston. Here, the diaphragm  17  can be configured as a metal diaphragm  17 . The metal diaphragm  17  can be formed from a metal or else from a plurality of metals. For example, the metal diaphragm  17  can be formed from a steel foil with a copper coating. The shock-wave actuating system also comprises a field coil  18 . The field coil  18  is assigned to the diaphragm  17  and is arranged on a side  19  of the diaphragm  19  which is of circular configuration in this exemplary embodiment. If the metal diaphragm  17  has a copper coating, said copper coating preferably faces the field coil  18  and is therefore provided on the side  19 . Moreover, the diaphragm  17  has a further side  20  which faces away from the side  19 . 
         [0023]    The side  20  of the diaphragm  17 , the inner wall  6  of the internal space  5  and an outer side  21  of the shock-wave amplifying channel  10  delimit a shock-wave amplifying channel  22 . The shock-wave channel  22  extends from the diaphragm  17  of the shock-wave actuating system  4  as far as the sealing seat  9 . The shock-wave amplifying channel  22  has a cross-sectional area  23  which remains free, serves to guide shock waves and is oriented perpendicularly with respect to the axis  15 . In the region of the shock-wave amplifying element  10 , the cross-sectional area  23  which remains free is configured to be annular or as a multiply interrupted ring, as is the case in the region of the guide elements  11 ,  12 ,  13 . 
         [0024]    Upon actuation of the diaphragm  17  by means of the field coil  18 , the diaphragm  17  arches into the internal space  5 , as is illustrated by a broken line  24 . The injector body  2  has an inflow channel  25  and an outflow channel  26 . A medium, in particular fuel, is guided into the internal space  5  via the inflow channel  25 . The medium can be guided out of the internal space  5  via the outflow channel  26 . As a result, bubbles which are produced or the like can also be guided out of the internal space  5 . During operation of the injection valve  1 , the shock-wave amplifying channel  22  is filled completely with the medium. Upon actuation of the diaphragm  17 , a shock wave  27  is generated in the medium, which shock wave  27  is of approximately planar configuration in this exemplary embodiment. The shock wave  27  propagates in a direction  28  in the medium and therefore runs from the diaphragm  17  through the shock-wave amplifying channel  22  to the sealing seat  9 . 
         [0025]    The shock-wave amplifying element  10  is of conical configuration. The shock-wave amplifying element  10  can also be configured such that it is exponentially shaped. Here, a tip  29  of the shock-wave amplifying element  10  is directed at the center of the diaphragm  17 . The shock-wave amplifying element  10  is of symmetrical configuration with regard to the axis  15 . In the region of the shock-wave amplifying element  10 , a width  30  of the annular cross-sectional area  23  which remains free decreases in the direction  28  as far as the sealing seat  9 . Furthermore, the cross-sectional area  23  which remains free also decreases between the diaphragm  17  and the tip  29 . The cross-sectional area  23  is of circular configuration between the diaphragm  17  and the tip  29 . 
         [0026]    After the deflection of the diaphragm  17  in order to generate the shock wave  27  with the aid of the shock-wave actuating system  4 , the shock wave  27  runs in the direction  28  to the shock-wave amplifying element  10 . The conical shock-wave amplifying element  10  penetrates the planar shock wave front of the shock wave  27  with its tip  29 . Here, the shock-wave amplifying element  10  is configured in such a way that only a minimum part of the shock wave  27  is reflected at the tip  29 . Correspondingly, the guide elements  11 ,  12   13  are also configured in such a way that reflections are avoided as far as possible. Since the cross-sectional area  23  which remains free, in particular the width  30  of the annular cross-sectional area  23 , and therefore the area of the shock wave front  27  decrease in the direction  28 , the shock wave  27  is amplified in the narrowing shock-wave amplifying channel  22 . 
         [0027]    When the amplified shock wave reaches the sealing seat  9 , a force is exerted on the valve closing body  8  in the opening direction  14  on account of the high local pressure. The magnitude of the force can be set via the given area ratios and angles of the level of the valve closing body  8  and the area in the region of the sealing seat  9 . 
         [0028]    A spring element  36  in the form of a disk spring assembly and a setting means  37  in the form of adjustment disks are arranged in an internal space  35  of the injector sleeve  3 . The spring element  36  is prestressed, with the result that the valve closing body  8  is pressed, counter to the opening direction  14 , with a prestress against the valve seat face  7 . If the opening force which acts on the valve closing body  8  as a result of the amplified shock wave  27  exceeds the closing force of the spring element  36 , the valve closing body  8  is adjusted in the opening direction  14 . As a result, opening of the sealing seat  9  and therefore the discharge of the medium out of the internal space  5  via spray holes  38 ,  39  occur. Here, as a result of the shock wave, atomization of the medium into the surrounding space, in particular a combustion chamber of an internal combustion engine, can be achieved. 
         [0029]    The valve closing body  8  has a pressure equalization channel  40 , with the result that hydraulic damping of the valve closing body  8  is avoided during the opening movement. 
         [0030]    After the amplified shock wave has left the pressure-active regions of the valve closing body  8  at the sealing seat  9 , the closing force of the spring element  36  predominates again, with the result that the valve closing body  8  is adjusted counter to the opening direction  14  and the sealing seat  9  is closed again by placing the valve closing body  8  on the valve seat face  7 . The medium which is discharged via the spray holes  38 ,  39  during the injection operation is replaced via the inflow channel  25 . Here, a continuous flow of the medium to be injected via the inflow channel  25  and the outflow channel  26  can be achieved, gas bubbles which are possibly formed being conveyed out of the internal space  5 . The injection valve  1  is therefore prepared for the next injection. 
         [0031]    In this exemplary embodiment, a sealing ring  41  which seals the internal space  35  of the injector sleeve  3  is provided on the guide hole  16 . The sealing ring  41  is formed from a temperature-resistant material which is resistant, for example, up to a maximum combustion chamber temperature. The pressure of the medium in the internal space  4  can lie, for example, in a range between 100 kPa (1 bar) and 500 kPa (5 bar). 
         [0032]    The injection valve  1  can therefore generate individual injection jets in a defined manner. Specifically, a sufficient pressure is generated in a reliable way, in order to generate, for example, a reliable injection against a great combustion chamber pressure. 
         [0033]    A very rapid, explosive discharge of the stored energy quantity is required for the shock-wave generation by way of the shock-wave amplifying element  10 . Here, an energy quantity of approximately 20 J can be discharged in a time of a few microseconds, which corresponds to a power output of a few MW. In the case of ferromagnetic or piezoelectric actuators, the power densities are limited on account of the saturation effects of the ferromagnetism and the ferroelectric. Secondly, relatively great volumetric displacements are required, in order to convey and therefore inject a sufficient quantity of medium through the shock-wave amplifying channel  22 . 
         [0034]    The metal diaphragm  17  is therefore actuated inductively in this exemplary embodiment. Here, a brief current pulse is generated in the field coil  18  which is configured as a helical air-core coil. Said current pulse generates a magnetic field which induces an induction current in the conductive metal diaphragm  17  in the form of an eddy current which is directed counter to the coil current through the field coil  18 . Here, the force which acts on the metal diaphragm  17  in accordance with the law of induction is greater, the shorter the spacing of the field coil  18  from the metal diaphragm  17 . The field coil  18  is therefore arranged as near as possible to and preferably directly on the side  19  of the metal diaphragm  17 . At a current rating of 1000 A, a force in the range of a few kN, for example, can act on the metal diaphragm  17 . Relatively great deflections, in particular deflections of more than 1 mm, of the metal diaphragm  17  can be achieved by way of forces of this type, as is illustrated, for example, by the broken line  24 . 
         [0035]    The field coil  18  can also be attached to a cylindrical or conical circumferential face of a cylinder or cone, in order to increase the amplitude of the shock wave  27  by way of suitable wave concentrators. 
         [0036]    The degree of efficiency for the purely magnetic coupling is approximately 75%. Part of the energy is converted into heat in the metal diaphragm  17  and is output to the medium in the region of the side  20 . As a result of heating, an expansion of the medium occurs on the side  20  of the diaphragm  17 , which leads as it were to a thermal wave which assists the generation process of the shock wave  27 . 
         [0037]    Moreover, the shock-wave actuating system  4  can realize a pump function. The metal diaphragm  17  or the piston is preferably formed from a ferromagnetic steel sheet which is coated with copper or the like toward the field coil  18  in order to improve the conductivity. After the quantity which is determined by the pulse of the current through the field coil  18  has been injected by actuation of the diaphragm  17 , the diaphragm  17  can be pulled into the original position (shown in  FIG. 1 ) by means of a direct current which is routed through the field coil  18  or by means of a low-frequency current at a frequency of less than 1 kHz. As a result, a vacuum which leads to the medium being sucked out of the inflow channel  25  is generated on the side  20  of the diaphragm  17 . 
         [0038]    In addition or as an alternative, the restoring function can also be realized by a restoring spring which acts on the diaphragm  17 . 
         [0039]    Fuels, in particular gasoline or diesel, urea for exhaust gas improvement or other media can therefore be ejected in a reliable way from the injection valve  1  via the spray holes  38 ,  39 . 
         [0040]      FIG. 2  shows an injection valve  1  in a partial, diagrammatic sectional illustration in accordance with a second exemplary embodiment. In this exemplary embodiment, the diaphragm  17  is configured as a tubular and conical diaphragm  17 . Here, an inner side  20 ′ of the diaphragm  17  delimits the shock-wave amplifying channel  22 . Furthermore, the field coil  18  is arranged in the region of an outer side  19 ′ of the diaphragm  17 . In order to actuate the shock-wave actuating system, a current is routed through the field coil  18 , which current generates an induction current (eddy current) in the diaphragm  17  and therefore leads to a repelling force on the diaphragm  17 . As a result, the diaphragm  17  arches circumferentially in the direction of the axis  15 . The generation of a shock wave  27  therefore occurs, which shock wave  27  propagates through the shock-wave amplifying channel  22  in the direction  28 . The shock wave  27  is amplified in the shock-wave amplifying channel  22 . The amplified shock wave runs as far as the sealing seat  9 , as a result of which the ejection of the medium via the spray holes  38 ,  39  occurs. 
         [0041]    In this embodiment, the amplitude of the shock wave  27  can be increased by way of suitable wave concentrators. 
         [0042]    The inflow channel  25  can open into the internal space  5  at one end  42  of the internal space  5 . 
         [0043]    The invention is not restricted to the exemplary embodiments which have been described.