Patent Publication Number: US-2020278706-A1

Title: Metering valve and jet pump unit for controlling a gaseous medium

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a metering valve and jet pump unit for controlling a gaseous medium, in particular hydrogen, for example for use in vehicles with a fuel cell drive. 
     DE 10 2010 043 618 A1 describes a metering valve and jet pump unit for controlling a gaseous medium, in particular hydrogen, wherein the metering valve comprises a valve housing, an ejector unit, an actuator, and a closing element. A through opening, which can be released from or sealed against a valve seat by the closing element, is formed in the valve housing. The ejector unit comprises an inflow region to which a first pressurized gaseous medium is fed, an intake region at which a second medium is present, and a mixing tube region from which a mixture of the first and second gaseous medium emerges. The through opening is arranged between the inflow region and the intake region of the ejector unit. 
     Purging actions in an anode path of a fuel cell arrangement can be optimized by a combination of a metering valve and a jet pump. This can, however, result in a reduction in the sealing action of the metering valve and in leakage from the components involved. 
     SUMMARY OF THE INVENTION 
     A reduction in sealing and leakage and hence optimal functioning of the metering valve and the jet pump in the fuel cell arrangement can be achieved by an improved design of the combination of metering valve and jet pump. 
     The metering valve according to the invention and the jet pump unit for controlling a gaseous medium, in particular hydrogen, has the advantage that, owing to the optimized integration of a metering valve into a jet pump unit, the tolerances at the valve seat are improved and consequently the sealing action inside the metering valve increased. 
     For this purpose, the metering valve for controlling a gaseous medium, in particular hydrogen, has a valve housing in which an interior space is formed. A closing element which can be moved along a longitudinal axis of the metering valve and interacts with a valve seat in order to open or close an opening cross-section of an inflow region into a passage duct is arranged in the interior space. The metering valve furthermore has a nozzle in which the passage duct is formed, wherein at least one sealing element is arranged on the outer side of the nozzle and is designed for the purpose of sealing a gap in an opening which receives the nozzle. 
     The jet pump unit furthermore comprises the metering valve according to the invention, a jet pump housing, a mixing tube region, an intake duct, and an outflow region. The jet pump housing here comprises the valve housing of the metering valve and a pump housing. The longitudinal axis of the metering valve is identical to a longitudinal axis of the jet pump unit. 
     The pump housing advantageously has a through bore which has a stepped design at least in some portions, wherein the nozzle of the metering valve is arranged on a first step formed on the pump housing, coaxially inside the pump housing upstream from the mixing tube region, and is received in an opening of the pump housing, wherein the at least one sealing element seals a gap between the nozzle and the pump housing. The through bore furthermore advantageously has a conical design at least in some portions, wherein an outflow duct of the jet pump unit is formed radially with respect to the longitudinal axis of the jet pump unit in the pump housing in the conical region of the through bore. The inflow duct of the metering valve is advantageously formed radially with respect to the longitudinal axis of the jet pump unit at least partially in the pump housing, wherein the valve housing is arranged with a step on the pump housing and is rigidly connected thereto, preferably by means of a screw element. The inflow region of the metering valve is advantageously arranged in the through bore. 
     Owing to the integration of the nozzle into the metering valve, it is possible to guide the flow of the gaseous medium downstream from the valve seat directly into the jet pump unit. An optimized design of the metering valve and the pump housing of the jet pump unit can be obtained as a result. The connection point between the metering valve and the nozzle is furthermore arranged in the pump housing of the jet pump unit, wherein the nozzle is integrated into the pump housing at the first step of the pump housing and is sealed with respect to the pump housing by the sealing element such that leakage in the direction of the intake region is minimized at the connection point between the metering valve and the nozzle. 
     In a first advantageous development of the invention it is provided that the nozzle comprises a pot-shaped region, wherein the at least one sealing element is arranged in the pot-shaped region. The pot-shaped region furthermore has a pot base on which the valve seat is formed. The valve housing advantageously has a protuberant end by means of which the valve housing is accommodated in the pot-shaped region of the nozzle, wherein the protuberant end in the inflow region has a surface which bears against a complementary surface formed on the nozzle. The nozzle can thus be connected to the valve housing in a structurally simple fashion, wherein it is not necessary for a seal to be guaranteed because the metering valve is sealed with respect to the pump housing by means of the sealing element. 
     In a further embodiment of the invention, it is advantageously provided that an adjusting element is arranged between the valve housing and the nozzle. Variable adjustment of the axial stroke of the closing element is thus achieved. 
     In an advantageous development it is provided that the valve seat is designed as a flat seat and an elastic sealing element is arranged between the valve seat and the closing element. By virtue of the use of a flat valve seat in combination with an elastic sealing element for sealing on the valve seat, the sealing of the metering valve can be ensured simply and without any large structural changes such that, for example, no hydrogen can escape from the metering valve. 
     In a further embodiment of the invention, it is advantageously provided that the metering valve comprises an electromagnet with an internal pole, wherein the internal pole and the valve housing are actively connected to each other via a magnetic throttle point. Owing to the one-part design of the internal pole and the valve housing and in combination with the connection point between the valve housing and the nozzle, the tolerances at the valve seat can be minimized and overall the sealing action of the metering valve improved. 
     In an advantageous development, the closing element is actively connected to a solenoid armature device, wherein the internal pole has a first guide section and a second guide section and wherein second bearing bushes are arranged on the second guide section, on which second bearing bushes the solenoid armature device is guided with a piston-shaped section. The piston-shaped section is advantageously manufactured from a material with a high mechanical strength. Radial tilting of the solenoid armature device is consequently minimized and the wear on the solenoid armature is also reduced when guided on the piston-shaped section. The latter can furthermore then be adapted to the mechanical circumstances such as, for example, the choice of a material with a high mechanical strength. 
     The jet pump unit described is preferably suited in a fuel cell arrangement for controlling the supply of hydrogen to an anode region of a fuel cell. Advantages are the low pressure fluctuations in the anode path and quiet operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of a metering valve according to the invention and a jet pump unit for controlling the supply of gas, in particular hydrogen, to a fuel cell are shown in the drawings, in which: 
         FIG. 1  shows an exemplary embodiment of a metering valve according to the invention with a nozzle in a longitudinal cross-section, 
         FIG. 2  shows an exemplary embodiment of a jet pump unit according to the invention with the metering valve shown in  FIG. 1  in a longitudinal cross-section. 
     
    
    
     Components with the same function have been designated with the same reference numerals. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a first exemplary embodiment of a metering valve  1  according to the invention in a longitudinal cross-section. The metering valve  1  has a valve housing  2  with an internal space  3 . An electromagnet  26 , which comprises a solenoid  12 , an internal pole  14 , and an external pole  13 , is arranged in the internal space  3 . 
     A solenoid armature device  25  which can move with a stroke movement is furthermore arranged in the internal space  3 . The solenoid armature device  25  comprises a solenoid armature  8  and a connection element  9  which is accommodated in a recess  22  of the solenoid armature  8  and is hence rigidly connected to the solenoid armature  8 , for example by a weld seam or by crimping. The solenoid armature  8  takes the form of a plunger and is accommodated in the internal pole  14 . The internal pole  14  has a recess  21  with a recess edge  24  into which the solenoid armature  8  is inserted during its stroke movement. 
     First bearing bushes  60 , in which the connection element  9  is accommodated and guided on a first guide section  6  of the internal pole  14 , are arranged on the internal pole  14 . Second bearing bushes  70 , in which a piston-shaped section  23  of the connection element  9  is accommodated and guided in a second guide section  7 , are furthermore arranged on the valve housing  2 . The piston-shaped section  23  of the connection element  9  is here manufactured from a material with a high mechanical strength. 
     The metering valve  1  furthermore comprises a nozzle  15  which has a pot-shaped region  151  with a pot base  1510  and a protuberance  152 . The valve housing  2  is accommodated, with a protuberant end  38  remote from the electromagnet  26 , in the pot-shaped region  151  of the nozzle  15 , wherein the valve housing  2  bears with a surface  381  against a complementary surface  153  of the nozzle  15 . An adjusting element  36  is arranged between the protuberant end  38  of the valve housing  2  and the nozzle  15 . Furthermore, sealing elements  54  are arranged on an outer side  90  of the nozzle  15 , and sealing elements  53  are arranged on the valve housing  2 . 
     The connection element  9  is rigidly connected at one end to a closing element  10 . The closing element  10  has an elastic sealing element  11  at its end remote from the connection element  9 . The elastic sealing element  11  interacts with a valve seat  19  formed on the pot base  1510  of the nozzle  15  such that, when the elastic sealing element  11  bears against the valve seat  19 , a passage duct  18  formed in the nozzle  15  is closed. The valve seat  19  is formed here as a flat seat. 
     In the internal pole  14 , a spring space  30  is formed which forms a part of the internal space  3 . In the spring space  30 , a closing spring  4  is arranged which is supported between the internal pole  14  and a plate-shaped end  5  of the connection element  9 . The closing spring  4  stresses the solenoid armature device  25  with a force in the direction of the valve seat  19 . 
     The internal space  3  furthermore comprises a solenoid armature space  300  in which the solenoid armature  8  is arranged. The solenoid armature space  300  is connected to the spring space  30  via a connection duct  16 . At its end facing the closing element  10 , the solenoid armature  8  adjoins an inflow region  28  which can be filled with a gaseous medium, for example hydrogen, via an inflow duct  17  which is arranged radially with respect to a longitudinal axis  40  of the metering valve  1  and formed in the valve housing  2 . 
     The valve housing  2  and the internal pole  14  are connected to each other magnetically and mechanically via a magnetic throttle point  20 . They can advantageously be formed as a single piece. The magnetic throttle point  20  comprises a thin-walled cylindrical web  201  and a conical region  202 , as a result of which an annular groove is formed in the solenoid armature space  300 . 
     Functioning of the Metering Valve  1   
     When there is no current applied to the solenoid  12 , the closing element  10  is pressed onto the valve seat  19  via the closing spring  4  such that the connection between the inflow region  28  and the passage duct  18  is interrupted and there is no flow of gas. 
     When current is applied to the solenoid  12 , a magnetic force is generated on the solenoid  8  which acts counter to the closing force of the closing spring  4 . This magnetic force is transmitted to the closing element  10  via the connection element  9  such that the closing force of the closing spring  4  is overcompensated and the closing element  10  lifts off from the valve seat  19  with the elastic sealing element  11 . The flow of gas through the metering valve  1  is released. 
     The stroke of the closing element  10  can be adjusted via the magnitude of the current strength at the solenoid  12 . The greater the current strength at the solenoid  12 , the greater the stroke of the closing element  10  and the greater too the flow of gas in the metering valve  1  because the force of the closing spring  4  is dependent on the stroke. If the current strength at the solenoid  12  is reduced, the stroke of the closing element  10  is reduced too and the flow of gas is thus throttled. 
     If the supply of current to the solenoid  12  is interrupted, the magnetic force on the solenoid armature  8  is decreased such that the force on the closing element  10  by means of the connection element  9  is reduced. The closing element  10  moves in the direction of the passage duct  18  and forms a seal on the valve seat  19  by means of the elastic sealing element  11 . The flow of gas in the metering valve  1  is interrupted. 
     The metering valve  1  according to the invention can be used, for example, in a fuel cell arrangement. Hydrogen can be fed from a tank by means of the metering valve  1  to an anode region of the fuel cell. Depending on the magnitude of the current strength at the solenoid  12  of the metering valve  1  by means of which the stroke of the closing element  10  is triggered, a flow cross-section at the passage duct  18  is thereby modified in such a way that appropriate adjustment of the gas flow fed to the fuel cell takes place continuously. 
     The metering valve  1  for controlling a gaseous medium thus has the advantage that the feed of the first gaseous medium and the metered addition of hydrogen to the anode region of the fuel cell by means of electronically controlled adaptation of the flow cross-section of the passage duct  18  with simultaneous regulation of the anode pressure can take place in a significantly more precise fashion. As a result, the operational safety and durability of the connected fuel cell are considerably improved because hydrogen is at all times fed in a superstoichiometric proportion. Related damage such as, for example, damage to a catalytic convertor arranged downstream, can additionally be prevented. 
       FIG. 2  shows a jet pump unit  46  with the metering valve  1  according to the invention in a longitudinal cross-section. The jet pump unit  46  has a jet pump housing  41  which comprises the valve housing  2  of the metering valve  1  and a pump housing  49 . The jet pump unit  46  has a longitudinal axis  40 ′ which is identical to the longitudinal axis  40  of the metering valve  1 . 
     In the pump housing  49 , a through bore  42  which has a partially stepped design and a partially conical design is formed axially with respect to the longitudinal axis  40 ′, and an intake duct  43  and the inflow duct  17  of the metering valve  1  are formed radially with respect to the longitudinal axis  40 ′. An intake region  44 , a mixing tube region  52 , and an outflow region  45  are formed in the through bore  42 . Portions of the metering valve  1  are accommodated coaxially in the pump housing  49 . The valve housing  2  is here arranged with a step  37  on the pump housing  49  and is rigidly connected to the latter via a screw element  35 . The valve housing  2  and the pump housing  49  are sealed with respect to each other by the sealing elements  53  of the valve housing  2  and the sealing elements  54  of the nozzle  15 . 
     Furthermore, the nozzle  15  of the metering valve  1  bears against a step  39  formed on the pump housing  49  and is accommodated in an opening  55  of the pump housing  49 . The nozzle  15  is sealed with respect to the first step  39  of the pump housing  49  by the sealing elements  54  on the nozzle  15  such that a gap  56  between the nozzle  15  and the pump housing  49  is sealed and no gaseous medium can pass via this gap  56  in the direction of the intake region  44 . Gaseous medium from the inflow duct  17  thus passes only via the passage duct  18  in the direction of the intake region  44 . 
     The pump housing  49  furthermore has a step  57  by means of which the nozzle  15  is centered radially in the pump housing  49  and is thus arranged coaxially in the pump housing  49  upstream from the mixing tube region  52 . The positional tolerances of the metering valve  1 , especially the nozzle  15 , with respect to the pump housing  49  in conjunction with the step  39  can thus be minimized. 
     An outflow duct  48  is formed on that end region of the pump housing  49  remote from the metering valve  1 , radially with respect to the longitudinal axis  40 ′ in the pump housing  49 , wherein the through bore  42  is sealed by a cover  50  on that end region of the pump housing  49  remote from the metering valve  1 . 
     Functioning of the Jet Pump Unit  46   
     When the valve seat  19  of the metering valve  1  is open or partially open, gaseous medium, in this case hydrogen, flows from the tank into the passage duct  18  in the nozzle  15  via the valve seat  19  out of the inflow duct  17  of the metering valve  1 . After it emerges from the nozzle  15  and enters the through bore  42 , in the intake region  44  this hydrogen meets a gaseous medium which has already been conveyed to the fuel cell but has not been consumed and has been returned to the jet pump unit  46  via the intake duct  43 . The returned gaseous medium mainly comprises hydrogen but also steam and nitrogen. In the mixing tube region  52 , a mass flow is drawn from the intake region  44  owing to momentum exchange of the gaseous medium and is conveyed in the direction of the outflow region  45  and hence in the direction of the anode region of the fuel cell. Depending on the geometry of the through bore  42  and the angle of insertion of the metering valve  1  and hence the nozzle  15 , the gas flow conveyed to the fuel cell can be adjusted as required.