Abstract:
The present disclosure relates to internal combustion engines in general. Some embodiments of the teaching may include valve units for use in a fuel tank system of an internal combustion engine having a fuel tank and a storage element for temporary storage of hydrocarbons, wherein the fuel tank and the storage element are connected together such that the hydrocarbons which gasify out of a fuel in the fuel tank are stored in the storage element. They may include a purge air pump connected to the storage element and conveying fresh air to the storage element, thereby releasing the stored hydrocarbons and supplying them to a combustion chamber of the internal combustion engine and a movable adjustment element with at least two positions. The first position may connect a pressure side of the purge air pump to a first line and a suction side of the purge air pump to a second line. The second position may connect the pressure side to the second line and the suction side to the first line.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2015/068010 filed Aug. 5, 2015, which designates the United States of America, and claims priority to DE Application No. 10 2014 216 454.0 filed Aug. 19, 2014, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to internal combustion engines in general. Some embodiments of the teaching may include valve units with a purge air pump for use in the fuel tank system of an internal combustion engine. 
       BACKGROUND 
       [0003]    To reduce pollutant emissions from motor vehicles, in recent decades numerous measures have been introduced. One of these measures is to use a fuel tank system in which a fuel tank is connected to a storage element for temporary storage of hydrocarbons. When refueling motor vehicles with hydrocarbon-based fuels, the hydrocarbons gasify out of the fuel, wherein the hydrocarbons should not enter the atmosphere. At high temperatures or when driving over uneven ground, there is increased gasification of hydrocarbons from the fuel, wherein it must be effectively ensured that these hydrocarbons do not escape to the atmosphere. In particular in hybrid vehicles, in which the internal combustion engine is completely shut down for long distances, the gasified hydrocarbons must be temporarily stored effectively in order to be burned later when the internal combustion engine restarts. 
         [0004]    For these applications, fuel tank systems have proved useful which consist of a fuel tank and a storage element for temporary storage of hydrocarbons, wherein the fuel tank and the storage element are connected together such that the hydrocarbons which gasify out of a fuel present in the fuel tank are stored in the storage element, wherein the storage element is connected to a first line through which fresh air can be conveyed to the storage element, and the storage element is connected to a second line which connects the storage element to an intake tract of the internal combustion engine and through which the fresh air enriched with hydrocarbons can be conveyed from the storage element to the intake tract. 
         [0005]    In this way, the storage element can be flushed cyclically with fresh air, and the hydrocarbons stored can be supplied to an intake tract which connects the internal combustion engine to the air filter and which supplies the internal combustion engine with air for combustion. Thus the hydrocarbons gasified out of the fuel tank can be burned in the internal combustion engine, and the escape of hydrocarbons to atmosphere is securely prevented. To convey the hydrocarbons from the storage element to the intake tract, according to the prior art a purge air pump is used, which may for example be configured as a radial pump. In order to guarantee fault-free function of the fuel tank system, it is necessary to check the tightness of the entire fuel tank system regularly. This tightness test cannot be restricted to workshop visits of the motor vehicle, but the tightness test must be carried out in the vehicle, i.e. on board, throughout the driving operation of the motor vehicle. 
       SUMMARY 
       [0006]    It is therefore an object of the present disclosure to describe an economic valve unit with a purge air pump which is configured such that the tightness of a fuel tank system can be checked regularly during driving operation of the motor vehicle. 
         [0007]    Some embodiments of the present teaching may include a valve unit ( 9 ) with a purge air pump ( 7 ) for use in the fuel tank system ( 1 ) of an internal combustion engine ( 2 ) with a fuel tank ( 16 ) and a storage element ( 19 ) for temporary storage of hydrocarbons ( 23 ), wherein the fuel tank ( 16 ) and the storage element ( 5 ) are connected together such that the hydrocarbons ( 23 ), which gasify out of a fuel ( 17 ) present in the fuel tank ( 16 ), are stored in the storage element ( 19 ), wherein the storage element ( 19 ) is connected to the purge air pump ( 7 ) which has a suction side ( 21 ) and a pressure side ( 22 ), wherein fresh air ( 24 ) can be conveyed to the storage element ( 19 ) by the purge air pump ( 7 ), whereby the hydrocarbons ( 23 ) are released from the storage element and supplied to the internal combustion engine for combustion, characterized in that the valve unit ( 9 ) has an adjustment element ( 27 ) which is mounted movably in the valve unit ( 9 ), wherein the purge air pump ( 7 ) is connected to the valve unit ( 9 ) such that in a first position of the adjustment element ( 27 ), a first adjustment element passage ( 31 ) connects the pressure side ( 22 ) of the purge air pump ( 7 ) to a first line ( 29 ) and a second adjustment element passage ( 32 ) connects the suction side ( 21 ) of the purge air pump ( 7 ) to a second line ( 30 ), and that in a second position of the adjustment element ( 27 ), a third adjustment element passage ( 33 ) connects the pressure side ( 22 ) of the purge air pump ( 7 ) to a second line ( 30 ) and a fourth adjustment element passage ( 34 ) connects the suction side ( 21 ) of the purge air pump ( 7 ) to a first line ( 29 ). 
         [0008]    In some embodiments, in a third position of the adjustment element ( 27 ), the adjustment element ( 27 ) separates the suction side ( 21 ) and the pressure side ( 22 ) of the purge air pump ( 7 ) from the first line ( 29 ) and/or from the second line ( 30 ). 
         [0009]    In some embodiments, the adjustment element ( 27 ) has a fifth adjustment element passage ( 40 ) and a sixth adjustment element passage ( 41 ), wherein the cross-sections of the fifth adjustment element passage ( 40 ) and the sixth adjustment element passage ( 41 ) are smaller than the cross-sections of the first adjustment element passage ( 31 ) and the second adjustment element passage ( 32 ). 
         [0010]    In some embodiments, in a fourth position of the adjustment element ( 27 ), the fifth adjustment element passage ( 40 ) connects the pressure side ( 22 ) of the purge air pump ( 7 ) to a first line ( 29 ), and a sixth adjustment element passage ( 41 ) connects the suction side ( 21 ) of the purge air pump ( 7 ) to a second line ( 30 ). 
         [0011]    In some embodiments, the purge air pump ( 7 ) is configured as a radial pump. 
         [0012]    In some embodiments, the storage element ( 19 ) is configured as an active charcoal filter. 
         [0013]    In some embodiments, a pressure sensor ( 8 ) is arranged in the fuel tank system ( 1 ). 
         [0014]    Because the valve unit has a valve cylinder which is mounted rotatably about its rotation axis in the valve unit, wherein the purge air pump is connected to the valve unit such that in a first position of the valve cylinder, a first valve cylinder passage connects the pressure side of the purge air pump to a first line and a second valve cylinder passage connects the suction side of the purge air pump to a second line, and that in a second position of the valve cylinder, a third valve cylinder passage connects the pressure side of the purge air pump to a second line and a fourth valve cylinder passage connects the suction side of the purge air pump to a first line, a single pump can be used both for purging the storage element in the fuel system and for testing the tightness of the fuel system. 
         [0015]    If, in a third position of the valve cylinder, the valve cylinder separates the suction side and the pressure side of the purge air pump from the first line and/or from the second line, the valve unit may, in addition to the functions described above, also be used as a shut-off valve. 
         [0016]    In the valve cylinder has a fifth valve cylinder passage and a sixth valve cylinder passage, wherein the cross-sections of the fifth valve cylinder passage and the sixth valve cylinder passage are smaller than the cross-sections of the first valve cylinder passage and the second valve cylinder passage. 
         [0017]    If, in a fourth position of the valve cylinder, the fifth valve cylinder passage connects the pressure side of the purge air pump to the first line and a sixth valve cylinder passage connects the suction side of the purge air pump to the second line, a very gentle purging of the storage element can take place. Because of the low volume flows of the fresh air which can be finely regulated with the purge air pump, the hydrocarbons can be released very evenly from the storage element, whereby it can be ensured that an optimum air/fuel mix can be set in the combustion chambers of the internal combustion engine by means of the lambda control system, although additional hydrocarbons may reach the combustion chambers from the purging of the storage element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    An advantageous embodiment of the invention is described with reference to the figures. 
           [0019]      FIG. 1  shows an internal combustion engine with a fuel tank system according to the teachings of the present disclosure, 
           [0020]      FIG. 2  shows a first position of the valve cylinder, 
           [0021]      FIG. 3  shows a second position of the valve cylinder, 
           [0022]      FIG. 4  shows a third position of the valve cylinder, 
           [0023]      FIG. 5  shows a fourth position of the valve cylinder. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    In some embodiments, the purge air pump is configured as a radial pump. A radial pump has an easily reproducible ratio between the pressure it generates and the rotation speed with which it is driven or the power which it absorbs, if the physical parameters, for example the temperature, of the conveyed air are known. Thus the positive pressure generated in the fuel tank system can easily be monitored by the control unit on the basis of the power consumption of the radial pump. 
         [0025]    In some embodiments, the storage element is configured as an active charcoal filter. Hydrocarbons can adhere well to active charcoal, in particular in granular form, and thus be temporarily stored. 
         [0026]    In some embodiments, a pressure sensor is arranged in the fuel tank system. The pressure sensor allows simple testing of the tightness of the fuel tank system. 
         [0027]      FIG. 1  shows an internal combustion engine  2  with a fuel tank system  1  according to the teachings of the present disclosure. The internal combustion engine  2  has an exhaust tract  3  and an intake tract  4 . To recover the kinetic energy contained in the exhaust gas, the exhaust tract is equipped with a turbocharger which can compress the intake air in the intake tract  4 . The internal combustion engine  2  is supplied with fresh air  24  via the intake tract  4 . Starting from the fresh air side, fresh air  24  is guided via an air filter  6  into the intake tract  4  and may be compressed using the exhaust turbocharger  5  or a compressor and then supplied to the combustion chambers of the internal combustion engine  2 . In addition, fuel  17  is supplied to the internal combustion engine  1  from the fuel tank  16  via a fuel line  37 . 
         [0028]      FIG. 1  furthermore shows the fuel tank system  1  with the fuel tank  16  and a storage element  19  for temporary storage of hydrocarbons  23 . The fuel tank  16  and the storage element  19  are connected together such that the hydrocarbons  23 , which gasify out of the fuel  17  in the fuel tank  16 , can be stored in the storage element  19 . 
         [0029]    The storage element  19  may for example be configured as an active charcoal store. An active charcoal store is a closed canister in which normally granular carbon is arranged, so that the hydrocarbons  23  to be stored are deposited onto the carbon. The storage element  19  however only has a limited storage capacity, so the storage element  19  must be evacuated regularly in that fresh air  24  is drawn in, e.g., via a purge air filter  20 , and aspirated or pressed into the storage element  19  via a line by means of the purge air pump  7 . The fresh air  24  flows through the active charcoal in the storage element  19  and collects the hydrocarbons  23 , whereupon the fresh air  20  enriched with hydrocarbons  23  is conveyed along further lines to the intake tract  4 . 
         [0030]    In the intake tract  4 , the fresh air  24  enriched with hydrocarbons  23  mixes with the fresh air  24  which is drawn in via the air filter  6 . Thus the hydrocarbons  23  can be supplied to the internal combustion engine  2 , where the hydrocarbons  23  are burned in the combustion chambers of the internal combustion engine  2 . Since the fuel tank system  1  contains highly volatile hydrocarbons  24 , it is necessary to test the tightness of the entire fuel tank system  1  regularly. 
         [0031]    An essential part of the fuel tank system  1  shown in  FIG. 1  is a valve unit  9 . In this example, the valve unit  9  consists of a first valve  11 , a second valve  12 , a third valve  13 , a fourth valve  14  and a fifth valve  15 . The fifth valve  15  together with the purge air valve  10  serves for the complete sealing of the fuel tank system  1 . Thus if the fifth valve  15  and the purge valve  10  are closed, and there are no leaks in the fuel tank system, the pressure present in the fuel tank system  1  on closure of the fifth valve  15  and purge air valve  10  will be maintained constantly until one of these valves is opened again. This constant pressure can be detected by the pressure sensor  8  and monitored by the control unit  25 . 
         [0032]    The first valve  11 , the second valve  12 , the third valve  13  and the fourth valve  14 —which are part of the valve unit  9 —serve to reverse the direction of flow of the fresh air  24 , whereby firstly fresh air  24  can be conveyed by the purge air pump  7  in the direction of the internal combustion engine  2 , and secondly fresh air  24  can be conveyed by the purge air pump  7  into the fuel tank  16 . To purge the storage element  19 , the purge air valve  10  is opened and in the valve unit  9 , the second valve  12 , the fourth valve  14  and the fifth valve  15  are opened. The first valve  11  in the valve unit  9  and the third valve  13  in the valve unit  9  are closed. 
         [0033]    If the purge air pump  7 —which is configured as a radial pump and hence can convey the medium to be pumped only from the suction side  21  to the pressure side  22 —is now operated, fresh air is supplied from the purge air filter  20  via the purge air valve  10 , through the storage element  19 , to the intake tract  4  of the internal combustion engine  2 . In this configuration therefore the storage element  19 , which may be configured as an active charcoal filter, is flushed with fresh air  24 , wherein the hydrocarbons  23  deposited in the storage element  19  are flushed out and supplied to the internal combustion engine  2 . If the storage element  19  need not be purged, because for example it only has a low charge of hydrocarbons  23 , the purge air valve  10  can be closed. 
         [0034]    In addition, the second valve  12  and the fourth valve  14  in the valve unit  9  can also be closed. Initially the fifth valve  15  remains open. If the purge air pump  7  is now operated, fresh air  24  is drawn in via the air filter  6  and pressed in the direction of the storage element  19  and the fuel tank  17 . Thus a controlled pressure rise occurs in the fuel tank system  1 . The pressure rise in the fuel tank system  1  may be monitored via the pressure sensor  8  and/or the rotation speed or power consumption of the purge air pump  7 . For this, both the pressure sensor  8  and the purge air pump  7  are connected to an electronic control unit  25 . All said valves  10 ,  11 ,  12 ,  13 ,  14 ,  15  can also be controlled by the control unit  25 . 
         [0035]    Also, at least one temperature sensor  39  may be connected to the control unit. If now the fuel tank system is pressurized to a predefined pressure, the fifth valve  15  may be shut off, whereby the pressure built up in the fuel tank system  1  remains constant as long as there are no leaks in the fuel tank system  1 . Using the fuel tank system  1  described here, during normal operation of a motor vehicle, the tightness of the fuel tank system  1  can be checked regularly, which is an important requirement arising from the regulations for protection of the environment and atmosphere. 
         [0036]    Because of the valve unit  9 , the radial pump  7 —which, because of its construction, can only convey the medium to be conveyed in one direction, namely from the suction side  21  to the pressure side  22 —can be used both for purging the storage element  19  and for pressurizing the fuel tank system  1 . The very simple, durable and economic radial pump  7  used as a purge air pump, in cooperation with the valve unit  9 , can fulfil a double function, so the entire fuel tank system becomes both economic and efficient. 
         [0037]    By means of the temperature sensors  39  which may be arranged at various positions on the fuel tank system  1 , a correlation can be created between the pressure generated by the radial pump  7  and the rotation speed with which it is driven or the power which it consumes. Thus the positive pressure generated in the fuel tank system  1  can easily be monitored by the control unit  25  on the basis of the power consumption of the radial pump  7 . 
         [0038]    One configuration of the valve unit  9  is described in  FIGS. 2 to 4 . The valve unit  9  has an adjustment element  27  and a first to a sixth adjustment element passage ( 31 ,  32 ,  33 ,  34 ,  40 ,  41 ). The adjustment element  27  may be configured for example as a linear slider which is mounted movably in the valve unit  9 , wherein the linear slider has six bores forming the first to sixth adjustment element passages ( 31 ,  32 ,  33 ,  34 ,  40 ,  41 ). In the example below, the invention is explained with reference to a valve unit  27  in which the adjustment element  27  is configured as a valve cylinder, wherein the first to sixth adjustment element passages ( 31 ,  32 ,  33 ,  34 ,  40 ,  41 ) are configured as first to sixth valve cylinder passages. 
         [0039]      FIG. 2  shows the purge air pump  7  which is connected to the valve unit  9  on its suction side  21  and its pressure side  22 . In this figure and the following figures, the purge air pump  7  and the valve unit  9 —as already shown in  FIG. 1 —may be connected electrically to a control unit  25 . The control unit  25  may for example move the valve cylinder  27  into various positions. In  FIG. 2 , the valve cylinder  27  is in a first position and is provided with a first valve cylinder passage  31  and a second valve cylinder passage  32 . The first to sixth valve cylinder passages are intended to conduct air or an air-hydrocarbon mixture through the valve cylinder  27 . 
         [0040]    Using the valve drive  26 , the valve cylinder  27  may be rotated about a rotation axis  38  into the first position. The first position of the valve cylinder  27 , in which the first valve cylinder passage  31  connects the pressure side  22  of the purge air pump  7  to the first line  29  leading to the internal combustion engine  2 , is marked with cylinder position marking  28 . In this first position, the suction side  21  is also connected by means of the second valve cylinder passage  32  to the second line  30 , which leads via the storage element  19  to the fuel tank  16 . In this first position of the valve cylinder  27 , the storage element  19  can be purged since fresh air  24  is aspirated via the second line  30 , wherein it passes through the storage element  19  and is conveyed via the suction side  21  to the pressure side  22  by the purge air pump  7 , and is then conducted via the first valve cylinder passage  31  and the first line  29  to the intake tract  4  of the internal combustion engine  2 . 
         [0041]    The valve unit  9  has a valve housing  35  in which the valve cylinder is mounted. The valve cylinder  27  can be rotated about a rotation axis  38  via a valve drive  26 . When the valve cylinder  27  is rotated about the rotation axis  38  by means of the valve drive  26 , which may be configured as an electric motor, the valve unit  9  can reverse the direction of flow of the fresh air  24 , whereby the fresh air  24  is no longer conveyed by the purge air pump  7  towards the internal combustion engine  2 , but fresh air  24  is conveyed by the purge air pump  7  to the fuel tank. This situation is shown in  FIG. 3 . 
         [0042]    In  FIG. 3 , the valve cylinder  27  is rotated through 180 degrees about the rotation axis  38  into its second position, which can be identified by the cylinder position marking  28 . Now neither the first valve cylinder passage  31  nor the second valve cylinder passage  32  is connected to the suction side  21  or pressure side  22  of the purge air pump  7 . However, a third valve cylinder passage  33  and a fourth valve cylinder passage  34  are connected to the suction side  21  and pressure side  22  respectively. If now the purge air pump  7  is set in operation, fresh air  24  is drawn in via the air filter  6  and conveyed to the suction side  21  of the purge air pump  7  via the first line  29  which is connected to the fourth valve cylinder passage  34 . 
         [0043]    The purge air pump  7  then presses this fresh air  24  via the pressure side  22  and the third valve cylinder passage  33  towards the second line  30 , whereby a pressure is built up in the fuel tank system  1 , i.e. in the fuel tank  16  itself, and in the storage element  19  and in the connected lines. For this, evidently the purge air valve  10  must be closed. When a sufficient pressure has been built up in the fuel tank system  1  by the purge air pump  7 , the valve cylinder  27  can be rotated for example by a further 90 degrees about the rotation axis  38  by the valve drive  26 , whereby neither the first valve cylinder passage  31  nor the second valve cylinder passage  32 , nor the third valve cylinder passage  33  nor the fourth valve cylinder passage  34 , is connected to the suction side  21  or pressure side  22 , or to the first line  29  or second line  30  respectively. In this position of the valve cylinder  27 , the entire fuel tank system  1  is closed pressure-tightly as long as there are no leaks in the fuel tank system  1 . 
         [0044]    The third position of the valve cylinder  27  shown in  FIG. 4  constitutes a possible embodiment of the closed fifth valve  15  from  FIG. 1 . If the entire fuel tank system  1  is pressurized and closed pressure-tightly by the position of the valve cylinder  27  shown in  FIG. 4  and a closed purge air valve  10 , by means of the pressure sensor  8  it can be checked whether the pressure present in the fuel tank system  1  is falling, which would indicate a leak in the fuel tank system  1 . This is an important monitoring function for modern fuel tank systems  1  in order to prevent the uncontrolled escape of hydrocarbons  23  from the fuel tank system  1 . 
         [0045]    The purge air pump  7  and the valve unit  9  may be formed in a common housing  36 , whereby the system of purge air pump  7  and valve unit  9  can easily be hermetically sealed. In this way, an escape of hydrocarbons  23  from the system of purge air pump  7  and valve unit  9  can be effectively prevented. 
         [0046]      FIG. 5  shows a fourth position of the valve cylinder  27 . The fourth position of the valve cylinder  27  can be identified from the orientation of the cylinder position marking  28 . The valve cylinder  27 , as well as the first valve cylinder passage  31 , second valve cylinder passage  32 , third valve cylinder passage  33  and fourth valve cylinder passage  34 , has a fifth valve cylinder passage  40  and a sixth valve cylinder passage  41 . The flow cross-sections of the fifth valve cylinder passage  40  and the sixth valve cylinder passage  41  are smaller than the flow cross-sections of the first valve cylinder passage  31  and the second valve cylinder passage  32 , which is clearly shown in  FIG. 5 . 
         [0047]    In the fourth position of the valve cylinder  27 , the fifth valve cylinder passage  40  connects the pressure side  22  of the purge air pump  7  to the first line  29 . Furthermore, the sixth valve cylinder passage  41  connects the suction side  21  of the purge air pump  7  to a second line  30 ; if the purge air pump  7  is now driven, fresh air  24  can be drawn in through the storage element  19  and conveyed via the second line and the sixth valve cylinder passage  41  to the purge air pump  7 . Hydrocarbons  23  are now released from the storage element  19  and conveyed by the purge air pump  7  via the pressure side  22  and the fifth valve cylinder passage  40  to the first line  29 , which in turn is connected to the intake tract  4  of the internal combustion engine  2 . Due to the smaller flow cross-section of the fifth valve cylinder passage  40  and sixth valve cylinder passage  41 , the storage element  19  can be purged with a very low purge rate. Because of the smaller flow cross-section in the fifth valve cylinder passage  40  and sixth valve cylinder passage  41 , the purge air pump  7  can be regulated very finely with low purge rates, whereby very small volume flows can be produced, which leads to a highly efficient purging of the storage element  19 .