Abstract:
A filter head for a pre-filtration filter for fuel has an electric pump received in a pump channel. A connecting channel connects the pump at a suction side with a clean side of the filter. An outlet channel connects the pump at a pressure side with a main filter for the pre-filtered fuel. The pump is alternatingly operated in at least two of the following operating modes: a feed or follow-up operation in which, before switching on or after switching off an ignition of the internal combustion engine, the pump supplies fuel to the outlet channel; a venting operation in which the pump pumps air out of the filter and/or a fuel line of the filter head; and a support operation in which, with switched-on ignition, the pump supplies fuel at a pressure suitable as input pressure for a high-pressure pump arranged downstream of the main filter.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of German patent application No. 10 2013 012 440.9, filed Jul. 29, 2013, the entire contents of the aforesaid German patent application being incorporated herein by reference 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention concerns a filter head for an exchange or housing filter for pre-filtration of fuel for an internal combustion engine, a filter arrangement, a fuel system, as well as a method. 
         [0003]    For example, DE 199 17 349 A1 discloses a filter head for an exchange filter. The filter head has an integral pump that is suitable for pressurizing a fuel supply line and for removing air pockets in the fuel supply line. Here, the filter head with the exchange filter is arranged downstream of a fuel tank. Downstream, a main filter is provided and downstream thereof an injection device. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide an improved filter head for an exchange or housing filter. 
         [0005]    Accordingly, a filter head for an exchange or housing filter for filtration of fuel for an internal combustion engine comprising a pump channel, an electrically operated pump, a connecting channel, and an outlet channel is provided. The pump is at least partially received in the pump channel. The connecting channel is adapted to connect the pump at the suction side with a clean side of the exchange or housing filter. The outlet channel is adapted to connect the pump at the pressure side with a main filter for filtration of the pre-filtered fuel. The pump is adapted to be alternatingly operated in at least two of the following operating modes: a feed or follow-up operation in which, before switching on or after switching off an ignition of the internal combustion engine, it provides fuel at the outlet; a venting operation in which it pumps air out off the exchange or housing filter and/or out of a fuel line connected with the filter head; and a support operation in which, with the ignition of the internal combustion engine switched on, it supplies the fuel at a pressure that is suitable as an input pressure for a high-pressure pump downstream of the main filter. 
         [0006]    The idea upon which the present invention is based resides in that the filter head or the pump are provided with several operating modes. As described above, these are a feed or follow-up operation, a venting operation, and a support operation. The pump is adapted to alternatingly operate in at least two of these operating modes. However, the pump could also be adapted to be alternatingly operated in all three operating modes. At a defined point in time, the pump can however be operated in only one of the aforementioned operating modes. Thus, the pump can have, for example, a feed or follow-up operation as well as a venting operation. Alternatively, the pump can have a feed or follow-up operation and a support operation. Further, alternatively, the pump can have a venting operation and a support operation. Finally, the pump can have a feed or follow-up operation, a venting operation, and a support operation. The selection of the respective operating mode can be realized by means of a control device which accordingly controls the pump in the feed or follow-up operation, the venting operation, or the support operation. 
         [0007]    Since the pump can be operated in at least two different operating modes, a high flexibility results for using the filter head. The latter can be operated, as a function of the fuel system in which it is used, with a suitable operating mode without having to carry out constructive changes. 
         [0008]    The exchange filter can be in particular a spin-on filter. The exchangeable filter thus has a thread which can be screwed onto an appropriate counter thread on the filter head. When the filter medium of the exchange filter has reached the end of its service life, the exchange filter as a whole is exchanged. 
         [0009]    The housing filter comprises in particular a cup-shaped housing and a filter element which is exchangeably received therein. The housing filter is, for example, detachably screwable onto the filter head. When the filter medium of the filter housing filter has reached the end of its service life, only the filter element is exchanged. 
         [0010]    As a fuel, in particular diesel fuel or kerosene are conceivable. However, the use of the filter head for gasoline or oil is not excluded. 
         [0011]    Preferably, the exchange or housing filter is used as a pre-filter. For example, the exchange or housing filter, as a pre-filter, can separate particles with a size of, for example, &gt;10 μm and/or water contained in the fuel. 
         [0012]    The electrically operated pump comprises preferably a brushless direct current motor. The latter can be controlled flexibly and therefore realize in a simple way the various operating modes of the pump. Also, a pump wheel which is operated by the direct current motor for conveying the fuel is suitably designed for the respectively provided operating modes. 
         [0013]    The pump channel, the inlet channel, and the outlet channel can be embodied in a one-part housing. 
         [0014]    In embodiments, the outlet channel can be configured to connect the pump at the pressure side directly with an injection device, without intermediate positioning of a main filter or a high-pressure pump. 
         [0015]    In the feed or follow-up operation, the fuel that is provided at the outlet channel can be used for cooling components of the internal combustion engine and/or of the injection device. 
         [0016]    In the venting operation, in particular air or air pockets contained in the exchange or housing filter are removed. Such air pockets result regularly after an exchange of the exchange filter or of the filter element of the housing filter. In general, air can be removed from the fuel system by means of the venting operation. 
         [0017]    In the support operation, it is possible to eliminate a presupply pump because the pump supplies the fuel at a pressure which is suitable as an input pressure for the high-pressure pump. This can contribute to simplifying assembly as well as to lowering costs. In the support operation, the pump continuously supplies fuel to the high-pressure pump. 
         [0018]    The ignition being switched on means that a combustion process is taking place in the internal combustion engine for which purpose fuel is supplied by means of the filter head or the fuel system to an injection device of the internal combustion engine. 
         [0019]    According to an embodiment, a first bypass valve is provided which connects the pump at the pressure side with a raw or clean side of the exchange or housing filter when the pressure at the pressure side of the pump surpasses a predetermined pressure. 
         [0020]    When, for example, the main filter is clogged or a valve in the injection device is closed accidentally, there is the risk that the pump will be destroyed as a result of current strengths that are too high. The first bypass valve remedies this in that it returns the pre-filtered fuel downstream of the pump to the raw side of the exchange or housing filter. This takes place when the pressure at the pressure side of the pump surpasses a predetermined pressure. This pressure can be, for example, between 2.5 bar and 7.5 bar, preferably between 4.5 bar and 5.5 bar. 
         [0021]    According to an embodiment, the first bypass valve is a check valve biased by a spring. Such a check valve can be produced easily. 
         [0022]    According to a further embodiment, a second bypass valve is provided which connects the clean side of the exchange or housing filter with the outlet channel when, with the pump switched off, the pressure in the outlet drops below a predetermined pressure. 
         [0023]    When the ignition of the internal combustion engine is switched on and the pump is switched off, a pre-supply and/or high-pressure pump arranged downstream of the filter head or the main filter can suck in the fuel directly out of the exchange or housing filter. The second bypass valve can be provided without the first bypass valve being provided. 
         [0024]    According to an embodiment, the second bypass valve is a gravity-loaded check valve. The gravity-loaded check valve can have, for example, a valve member which, in the closed state of the check valve, seals relative to a valve seat wherein the sealing forces are generated by the gravity acting on the valve member. In the open position of the check valve, the fuel forces the valve member from below in upward direction and can thus flow between valve seat and valve member into the outlet channel. A gravity-loaded check valve is particularly inexpensive with regard to manufacture. 
         [0025]    According to a further embodiment, the second bypass valve has a spherical valve member. The latter is associated advantageously with only minimal pressure loss. 
         [0026]    According to a further embodiment, the pump is connectable in the pump channel alternatingly to one or the other of the ends of the pump channel. 
         [0027]    In other words, the pump, for example, as a function of the spatial conditions, can be installed from different ends into the pump channel. This facilitates in particular supply of current to the pump. 
         [0028]    According to a further embodiment, a heating element is receivable at least partially in an inlet channel of the filter head and is alternatingly connectable to one or the other of the ends of the inlet channel. 
         [0029]    The heating element can be configured, for example, as a heating rod. Since the heating element can be installed from different ends into the inlet channel, for example, as a function of the spatial conditions, a current supply to the heating element can be guided beneficially. 
         [0030]    According to an embodiment, the pump channel, the inlet channel, and/or the outlet channel are arranged parallel to each other. 
         [0031]    A housing provided with the channels can be, for example, produced of metal, in particular by a diecasting method, and/or of plastic material, in particular by an injection molding process. The channels can be formed each within a tubular body. Closure elements can close off an end of a corresponding channel, respectively. 
         [0032]    According to a further embodiment, a connecting socket, with which the clean-side opening of the exchange or housing filter is connectable, is provided with the connecting channel which opens radially into the pump channel. 
         [0033]    In particular, the connecting socket can be oriented vertically, like the exchange or housing filter. 
         [0034]    According to a further embodiment, a branch channel connects the pump channel with the outlet channel. The branch channel can be arranged, for example, at a slant relative to a center axis of the pump channel or of the outlet channel in order to be able to produce it in a simple way. 
         [0035]    According to a further embodiment, a bypass channel connects the connecting channel with the outlet channel wherein the second bypass valve has a valve seat which connects a vertical section of the bypass channel with the outlet channel. 
         [0036]    A valve member, for example, in the form of a ball, can be seated in the valve seat. The second bypass valve, in particular the valve member, can be accessible by an oppositely provided maintenance opening in the tubular body which is forming the outlet channel. The maintenance opening can be formed in a vertical channel which is provided with a venting opening in its wall. Additionally or alternatively, the vertical channel can serve as a connector for a fuel line which connects the outlet channel with a main filter. 
         [0037]    Moreover, a filter arrangement for an internal combustion engine with a filter head, as described above, and an exchange or housing filter is proposed. 
         [0038]    Furthermore, a fuel system for an internal combustion engine with a filter head or a filter arrangement, as described above, and a control device is provided. The control device is adapted to control the pump alternatingly in at least two of the operating modes. 
         [0039]    Moreover, a method for operating the afore described filter head, the afore described filter arrangement or the afore described fuel system is provided, wherein initially one of at least two of the operating modes of the pump is selected and the pump thereafter is operated in the selected operating mode. 
         [0040]    The features described in connection with the filter head apply likewise to the filter arrangement, the fuel system, and the method, and vice versa. 
         [0041]    In the present application, “a” does not preclude a multitude. 
         [0042]    Further possible implementations of the invention comprise also combinations, not explicitly mentioned, of features explained above or in the following with regard to the embodiments. A person of skill in the art will also add or modify individual aspects as improvements or supplements to the respective basic form of the invention. 
         [0043]    Further advantageous configurations and aspects of the invention are subject matter of the dependent claims as well as of the embodiments of the invention described in the following. In the following, the invention will be explained in more detail with the aid of embodiments with reference to the attached figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  is a perspective view a filter head with a screwed-on exchange filter according to an embodiment. 
           [0045]      FIG. 2  shows the components of  FIG. 1  in an exploded view. 
           [0046]      FIG. 3  shows the filter head of  FIG. 1  in enlarged illustration. 
           [0047]      FIG. 4  shows the filter head of  FIG. 3  in an exploded view as well as in mirror-symmetrical assembly arrangement. 
           [0048]      FIG. 5  is a section V-V as indicated in  FIG. 1 . 
           [0049]      FIG. 6  is a section VI-VI as indicated in  FIG. 1 . 
           [0050]      FIG. 7  is a section VII-VII as indicated in  FIG. 1 . 
           [0051]      FIG. 8  is a section VIII-VIII as indicated in  FIG. 1 . 
           [0052]      FIG. 9  is a section IX-IX as indicated in  FIG. 1 . 
           [0053]      FIG. 10  shows a fuel system with the arrangement of  FIG. 1  in a first operating state. 
           [0054]      FIG. 11  shows the fuel system of  FIG. 10  in a second operating state. 
           [0055]      FIG. 12  shows the fuel system of  FIG. 10  in a third operating state. 
           [0056]      FIG. 13  is an exploded view of a filter head with a housing filter according to an embodiment. 
           [0057]      FIG. 14  is a section XIV-XIV as indicated in  FIG. 13 . 
       
    
    
       [0058]    In the Figures, same reference characters identify same, or functionally the same, components inasmuch as nothing to the contrary is indicated. 
       DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0059]      FIG. 1  shows a filter arrangement  1  with a filter head  2  and an exchange filter  3 , also referred to as spin-on filter, screwed onto the filter head  2 . 
         [0060]    The filter head  2  comprises a base plate  4  with bores  5  for attachment of the filter head  2  on a vehicle frame or an engine block. 
         [0061]    As can be seen in  FIG. 4 , the filter head  2  comprises three parallel channels  6 ,  7 ,  8 , wherein  6  indicates an inlet channel,  7  indicates a pump channel, and  8  indicates an outlet channel. The channels  6 ,  7 ,  8  can be formed each in a tubular body  9 ,  10 ,  11  which are connected to each other by a web  12  and connected with the base plate  4 . In downward direction, the filter head  2  comprises a connecting socket  13  that can be seen in  FIGS. 3 and 6  and has at its lower end an outer thread  14 . An inner thread  15  of the exchange filter  3 , indicated in  FIG. 2 , can be screwed onto the outer thread  14 . The inner thread  15  delimits a clean-side outlet opening  16  of the exchange filter  3 . 
         [0062]    Returning to  FIG. 6 , there can be seen that the filter head  2  has an annular flange  18 . In the screwed-on state, the circular ring-shaped flange  18  seals relative to a circular ring-shaped seal  19  of the exchange filter  2  that is illustrated in  FIG. 2 . Raw-side inlet openings  21  ( FIG. 2 ) of the exchange filter  3  open into the thus formed chamber  20  (see  FIG. 5 ). The inlet openings  21  are, for example, arranged on a circular line about the outlet opening  16 . 
         [0063]    As shown in  FIG. 5 , the chamber  20  is connected by a channel  22 , extending radially to the inlet channel  6 , to the inlet channel  6 . Also,  FIG. 5  shows a heating device  24  for heating fuel which is flowing into the inlet channel  6 . The heat prevents gelling (waxing) of the fuel. The heating device  24  can be an electrical attachment module  25  and can comprise a heating rod  26 . The heating rod  26  extends in the mounted state from one end  23  of the inlet channel  6  into the inlet channel  6 . The attachment module  25  is flange-connected to the tubular body  9  by means of screws  27  (see  FIG. 4 ) and seals the end  23  of the inlet channel  6 . At the other end  35  of the inlet channel  6 , an adapter  28  can be flange-connected by means of screws  29 . By means of the adapter  28 , the inlet channel  6  can be connected with a fuel line  30  which is shown in  FIG. 10 . The fuel line  30  opens upstream into a tank  31 . 
         [0064]    With the aid of  FIGS. 2 and 4  it can be seen that the heating device  24  can be installed from both ends  23 ,  35  into the inlet channel  6 . In this way, it is possible to simply accommodate spatial conditions, in particular with regard to guiding a current connector  32  of the heating device  24 . 
         [0065]    Returning to  FIG. 5 , it is shown therein that the fuel  33 , after having entered the inlet channel  6 , flows through the heating rod  26  and then through the channel  22  into the chamber  20 . From here, the fuel  33  flows through the inlet openings  21  (see  FIG. 2 ) and then through a filter medium, not shown, of the exchange filter  3 . 
         [0066]    By means of the filter medium, for example, particles with a grain size &gt;10 μm are separated from the fuel  33 . Alternatively or additionally, by means of the filter medium water can be separated in the exchange filter  3 . When the exchange filter  3  is spent, it can be separated from the filter head  2  by unscrewing it and can be exchanged. 
         [0067]    After having passed through the filter medium, the pre-filtered fuel  33  passes from the outlet opening  16  (see  FIG. 2 ) into a connecting channel  34  which is formed in the connecting socket  13 , as shown in  FIG. 6 . It is, for example, vertically oriented and opens perpendicularly into the pump channel  7 . 
         [0068]    A pump  36  is arranged in the pump channel  7 . The pump  36  comprises a brushless direct current motor  37  which drives a pump wheel, not illustrated. Moreover, the pump  36  comprises an electrical connecting module  38 . The connecting module  38  is seal-tightly attached by means of a securing ring  39  at an end  40  of the pump channel  7 , as shown in  FIG. 6 . The other end  41  of the pump channel  7  is seal-tightly closed off by a cap  42  which is secured in its position by a securing ring  43 . 
         [0069]    With the aid of  FIGS. 2 and 4 , it can be seen that also the pump  36  can be installed from both ends  40 ,  41  into the pump channel  7  so that also in this regard spatial considerations can be accommodated. 
         [0070]    Starting from the connecting channel  34 , the fuel  33  flows, as shown in  FIG. 6 , radially into the pump channel  7 , thereafter along the pump channel  7 , then through the pump  36  in reverse direction and by means of a radial outlet opening  45  out of it back into the pump channel  7  and from there through a branch channel  46 , shown in  FIG. 7 , into the outlet channel  8 . The branch channel  46  is slanted, i.e., is arranged at an angle different from 90° degrees relative to the outlet channel  8 . 
         [0071]    The outlet channel  8  is closed off seal-tightly at its end  49  by a screwed-in cap  50 . The other end  51  of the outlet channel  8  is connected by means of a fuel line  52  illustrated in  FIG. 10  with a main filter  53 . The main filter  53  is connected in turn to a high pressure pump  54 . The high-pressure pump  54  supplies the fuel to an injection device, not illustrated, of an internal combustion engine  55 . 
         [0072]    Returning to  FIG. 7 , a first bypass valve  56  and a second bypass valve  57  are shown therein. The bypass valves  56 ,  57  can also be seen in  FIG. 8 . 
         [0073]    The first bypass valve  56  comprises a branch channel  58  which connects the outlet channel  8  with the chamber  20 . In the branch channel  58  a valve seat  59  is formed against which, in the closed state of the first bypass valve  56  shown in  FIG. 8 , a spherical valve member  60  is resting seal-tightly. The valve member  60  is biased by means of a spiral spring  61  arranged in the branch channel  58  against the valve seat  59 . The first bypass valve  56  opens only at the time when the pressure in the outlet channel  8  has surpassed a predetermined pressure, for example, 5 bar. This is typically the case when the main filter  53  (see  FIG. 10 ) is clogged. Here, the branch channel  58  forms a bypass channel. The return flow through the first bypass valve  56  is illustrated in  FIG. 12 . 
         [0074]    The second bypass valve  57  comprises a valve seat  62  which is closed off by a spherical valve member  63 . Here, the closure force is generated by gravity that is acting on the valve member  63 . The valve seat  62  is formed at the end of a vertical section  64  of a bypass channel  65  and opens into the outlet channel  8 . The bypass channel  65  has moreover a horizontal section  66  which, as shown in  FIG. 9 , connects the vertical section  64  with the connecting channel  34  that is correlated with the clean side of the exchange filter  3 . 
         [0075]    Furthermore, in  FIG. 9  in combination with  FIG. 8 , a cap  67  is to be seen which is screwed into a maintenance opening  68  opposite the valve member  63 . The maintenance opening  68  is formed in a maintenance channel  44  which is oriented perpendicular to the outlet channel  8  and upward. A venting opening  47  can be formed below the cap  67  in the wall of the maintenance channel  44 . 
         [0076]    In an embodiment, the fuel line  52  can be connected also to the maintenance channel  44 . 
         [0077]    In  FIG. 9 , a cap  69  is moreover illustrated which is screwed seal-tightly into the horizontal section  66  of the bypass passage  65 . 
         [0078]    When the high-pressure pump  54  is sucking, with the pump  63  switched off, it generates underpressure in the outlet channel  8 . When this underpressure drops below a predetermined value, for example,  30  mbar, the valve member  63  moves upwardly so that the second bypass valve  57  opens. Accordingly, fuel  33  can flow directly, bypassing the pump  36 , from the clean side of the exchange filter  3  through the connecting channel  34  illustrated in  FIG. 9  and the bypass channel  65  to the outlet channel  8 , as illustrated in  FIG. 11 . 
         [0079]    In addition to the already disclosed components, the fuel system  70  shown in  FIG. 10  comprises a control device  71  which is adapted to control the pump  36 , in particular the direct current motor  37 , in three different operating modes. The first operating mode is a feed or follow-up operation in which the pump  36 , before switching on or after switching off an ignition of the internal combustion engine  55 , supplies the fuel to the outlet of the outlet channel  8 . The second operating mode is a venting operation in which the pump  36  pumps air out of the exchange filter  3  as well as out of the fuel lines  30 ,  52 . The control device  71  switches the pump  36  in particular automatically into the venting operation when the control device  71  determines that the exchange filter  3  has been exchanged. Alternatively, the control device  71  can be switched to venting operation by means of a user input, for example, by pressing on a button. The third operating mode is a support operation in which the pump  36 , with switched-on ignition of the internal combustion engine  55 , supplies the fuel for the high-pressure pump  54  at a pressure that is suitable as an input pressure. 
         [0080]      FIGS. 13 and 14  show a filter head  2  with a housing filter  80  according to an embodiment. 
         [0081]    The housing filter  80  comprises a cup-shaped housing  81  with a filter element  82  that is exchangeably provided therein. The filter element  82  has, for example, a filter medium  84  which is arranged between two end disks  83 . The filter medium  84  has in particular a cylindrical configuration with a circular ring-shaped base surface. A support tube  85  extends centrally through an interior  87  of the filter medium  84 . The filter element  82 , in particular the upper end disk  83 , has an outlet  86  which seal-tightly projects into the connecting channel  34  of the connecting socket  13  of the filter head  2 . The outlet  86  is connected with the interior  87  and forms the clean side of the filter element  82 . A space  88  which surrounds the filter medium  84  is in communication with the inlet channel  6  by means of the channel  22  illustrated in  FIG. 5  and forms therefore the raw side of the filter element  82 . 
         [0082]    The housing  81  has at the upper end an outer thread  89  by means of which it is seal-tightly screwed into an inner thread  90  at the annular flange  18  of the filter head  2 . The housing  81  and the flange  18  delimit the space  88  in outward direction. In the unscrewed state of the housing  81 , the filter element  84  can be exchanged. By screwing the housing  81  into the filter head  2 , the outlet  86  is pushed seal-tightly into the connecting socket  13 . Accordingly, the thread  14  shown in  FIG. 6  is not needed. 
         [0083]    In other respects, the configuration and function correspond to the embodiment according to  FIGS. 1 through 12 . 
         [0084]    Even though the present invention has been explained with the aid of various embodiments, it is not limited thereto but can be modified in many ways.