Abstract:
A fuel feeding aggregate for supplying fuel to an internal combustion engine, the fuel feeding aggregate has a housing having a suction-side end and a pressure-side end, a check valve integrated in the pressure-side aid and provided for fuel supply to injection valves, and an additional check valve integrated in the suction-side end in the housing and maintaining a system pressure in the fuel feeding aggregate.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a fuel feeding aggregate for an internal combustion engine, such as for example electric fuel pump incorporated in a fuel supply system. 
     An electric motor is for example provided for driving fuel feeding aggregates for internal combustion engines. It is axially connected in alignment with a feed pump and arranged in a joint housing. This is disclosed for example in the German patent document DE 43 31 803 A1. The electric motor has a stator which is arranged in a housing and provided with two alternatingly current-supplied stator coils, in which a rotor non rotatably arranged on a housing-supported rotor shaft is rotatable. The rotor is composed of a support which is guided on the rotor shaft and a magnet segment arranged on the support over the peripheral surface. They are held on the rotor shaft by holding clamps in abutment with the support. The holding clamps are formed so that during the mounting of the individual components of the rotor, they provide centering of the magnet segments, and after the complete mounting all rotor components are clamped so that the magnet segments are held in abutment against the rotor. In the configuration disclosed in the prior art, a check valve is provided in the fuel feeding direction behind the fuel feeding aggregate. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a fuel feeding aggregate for internal combustion engines, which is a further improvement of the existing aggregates. 
     In accordance with the present invention a check valve is integrated a suction-side end in the housing of the fuel feeding aggregate and maintains a system pressure in the fuel feeding aggregate. 
     When the fuel feeding aggregate is designed in accordance with the present invention, it has the advantage that the check valve on the electric fuel pump maintains the feeding chamber of the fuel pump sealed relative to the tank. 
     The sealing of the feeding aggregate relative to the fuel tank acts so that even in the event of long stoppages no gradual idle running of the fuel supply system occurs and it remains filled from the electric fuel pump to the injection valve. Thereby the maintenance of the pressure in the fuel feeding system is prevented, which for example can lead to starting difficulties with the gas bubble formation in hot fuel. 
     Furthermore, with the inventive arrangement of a check valve, the pressure build up time is substantially reduced and the motor therefore can be started faster. Thereby the exhaust gas emission during the starting phase is significantly reduced. 
     In accordance with a preferable embodiment of the invention, the check valve is arranged on a rotatable feeding element, such as for example a feeding gear of the fuel feeding aggregate. It is therefore guaranteed that, for example, when the fuel feeding aggregate is formed as an electric fuel pump, its motor chamber can be substantially sealed from pressure losses. 
     In accordance with a preferable embodiment, the closing element of the check valve cooperates at the suction-side end of the fuel feeding aggregate with an abutment surface, which surrounds the feeding passage for the fuel, while the abutment surface is formed on a housing element. 
     The closing element of the check valve arranged at the suction-side end of the fuel feeding element can be formed in a manner which is advantageous for manufacture, as a semi-round head which can be guided on a shaft. In addition to the formation of the closing element as the semi-round head, it is also recommended to form the closing element as a spherical body. The spherical body can be enclosed in a spherical cage which forms a housing insert element. 
     Both the closing element formed as the semi-circular head with the guiding shaft and the ball-shaped closing body, can be formed so that a restoring force acts on them. For example a restoring spring can extend over the shaft of the semi-round head. It presses the semi-round head, with the fuel feeding aggregate stopped, against the abutment surface of the housing element and thereby closes the feeding passage. Similarly, a ball-shaped closing element in the ball cage can be subjected to the action of a spring force. The restoring spring can be supported at one side of the spherical cage, abut against a valve seat of the abutment surface, and thereby reliably close the feeding passage near the feeding element which feeds the fuel. 
     In accordance with an advantageous embodiment of the present invention, in a fuel feeding aggregate with a check valve integrated at a suction-side end and a pressure-side end, at the suction-side end of the fuel aggregate a check valve is provided with a spherical closing element. In this very expensive variant of a fuel feeding aggregate it is in addition guaranteed. that a pressure reduction in the pressure conduit due to a leakage in the electric fuel pump, for example at the closure cover for the conduit to the injection valve, can be avoided. 
     The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view showing a fuel feeding aggregate with a check valve arranged at a suction-side end; 
     FIG. 2 is a view showing the check valve arranged at the suction-side end in a closed position; 
     FIG. 3 is a view showing a check valve arranged at the suction-side end, in a feeding position; and 
     FIG. 4 is a view showing a fuel feeding aggregate with a combination of a check valve in a closing cover and a check valve with a spherical closing element at a suction-side end. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A fuel feeding aggregate with a check valve arranged at a suction-side end in accordance with the present invention is shown in Figure 
     The fuel feeding aggregate  1  includes a housing  2  which has a suction-side end  3  and a pressure-side end  4 . A conduit extends from the tank to the suction-side end  3  of the fuel feeding aggregate  1 . A fuel conduit of the fuel supply system extends from the pressure-side end  4  of the fuel feeding aggregate  1  to the injection valves on the motor, which is not shown here. 
     A closing cover  5  is provided at the pressure-side end  4  of the fuel feeding aggregate  1 . It contains a pressure-side check valve  6 . It includes the closing element  7  which, for closing of the pressure-side end  4  of the fuel feeding aggregate  1  cooperates with a valve seat  8 . The closing element  7  can be spring-biased by a spring element  10  and releases the fuel supply in a fuel conduit  9 , with the fuel supplied to the individual injection valve which are not shown in the drawings. 
     A check valve  12  is provided at the suction-side end  3  of the housing  2 . Also, at the suction-side end  3  of the housing  2  of the fuel feeding aggregate, a feeding element is located. In the shown embodiment of the electric fuel pump  1  it is formed as a feeding gear or impeller. The feeding gear  11  feeds the fuel which is located at the suction-side outlet of the fuel feeding aggregate  1 , into a feeding passage  14 . The feeding passage is closeable by means of a closing element  15  of the check valve  12  and again releasable. The closing element  15  in the embodiment shown in FIG. 1 is formed as a semi-round head and fitted on a shaft  19  which extends in the longitudinal direction. A safety element  16 ,  17  for example a helical spring, extends around the shaft  17 . Thereby a restoring force is applied to the closing element  15 . The helical spring  19  is supported with its one end at a rear part of the closing element which is formed as the semi-round head. It is supported with another end against an insert piece  26  which is inserted in the housing  2 . 
     In the shown cutout of FIG.  1 ,. the semi-round head of the closing element  15  abuts against the valve seat  16  of a housing element  27  and closes the feeding passage  14  of the fuel feeding aggregate  1  at the suction-side end  3  from an undesired idle running. The surface of the valve seat  16  is adjusted to the rounding of the closing element  15  which is formed here as the semi-round head. Therefore pressure losses by leakage at the suction-side end  3  of the fuel feeding aggregate  1  are prevented. 
     FIG. 2 shows, on an enlarged scale, the inventive check valve  12  located at the suction-side end  3  in the closing position. In the condition shown in FIG. 2, the fuel feeding aggregate  1  is stopped. The semi-round head of the closing element  15  is pressed in the valve seat  16  and prevents an undesired outflow of the fuel from the feeding chamber  20  (in electric fuel pumps it is a motor chamber) through the feeding passage  14  at the suction-side end  3 . The system pressure which acts at the turning-off point of the fuel feeding aggregate  1  in the fuel supply system acts for an activation of the closing element  15 , since the pressure at the cross-sectional surface of the shaft  19  and the ring-shaped surface acts at the rear side of the closing element. The closing element  15 , being supported on an optionally provided safety element  17 , is pressed into the valve seat  16 . Thereby the fuel supply system including the feeding chamber  20  is sealed from idle running and pressure losses at the suction-side end  3  of the fuel feeding aggregate  1 . The safety element  17 , for example formed as a screw spring, in the event of a failure can act as a mechanical safety element for preventing in this situation an outflow of fuel from the feeding chamber  20 . 
     The semi-round head  15  which moves in its longitudinal direction, mechanically separates the feeding channel  14  from the feeding chamber  20  which partially extends in the hollow space of the insert member  26 . Therefore, an idle running of the feeding chamber  20  is suppressed. 
     FIG. 3 shows a fuel feeding aggregate  1  with the check valve  12  located at the suction-side end  3 , and shown in a feeding position. After turning on of the fuel feeding aggregate  1 , the feeding gear  11  feeds fuel into the feeding channel  14  at the suction-side end  3  of the housing  2 . The built-up hydrostatic pressure moves the closing element  15 , and the above described semi-round head or a spherical element  23  against the oppositely provided spring force, so that the system pressure is built up in the feeding chamber  20  of the fuel feeding aggregate  1 . The fuel feeding is performed, and fuel acts through the passage  14  first on the hollow chamber which surrounds the shaft  19  and is formed in the insert member  26 , before it enters the feeding chamber  20 . Since the closing element  15  formed as the semi-round head is moved back from its valve seat  16 , the fuel is supplied in the feeding direction  22  into the hollow chamber of the insert member  26  of the feeding chamber  20  arranged after it, or in other words the motor chamber of the electric fuel pump. A housing element  27  in the housing  2  is adjusted to the contour of the gear wheel  11 , contains the feeding chamber  14 , and operates as an abutment surface. The valve seat  16  is provided on it and its contour corresponds to the contour of the closing element  15 . 
     Fuel is continuously supplied into the feeding chamber  20  in the feeding position  21  shown in FIG.  3 . The check valve  12  at the suction-side end  3  and the check valve  6  provided at the pressure-side end  4  in the closure cover  5  are inactive. The check valves are introduced into the action during turning-off of the electric fuel pump, to maintain the system pressure in the fuel supply system and in particular to prevent an idle running of the feeding chamber  20  of the fuel feeding aggregate  1 . 
     FIG. 4 shows a fuel feeding aggregate with a combination of the check valve in the closing cover and a check valve with a spherical closing element. In this expensive embodiment, the closure element  15  of the check valve  12  is formed at the suction-side end  3  of the housing  2  by a spherical body. The spherical body  23  is surrounded by a spherical cage  24  which is formed in the insert member  26  located under the housing wall  13 . In the closing position  18  shown here, the spherical body  23  abuts against an abutment surface  16  of the insert member  26  and surrounds the feeding passage  14 . The system pressure in the feeding chamber  20  of the fuel feeding aggregate is sufficient to press the ball  23  against the valve seat  16 . The ball  23  can be pressed against the valve seat  16  by a spring which produces a restoring force. The spring in turn can be supported on a surface, preferably on a surface of the spherical cage  24  which surrounds for example the opening  25 . 
     The combination of FIG. 4 can be used advantageously for preventing in the pressure conduit a pressure reduction due leakages on the pressure limiting valve of the electric fuel pump. For this purpose a check valve  6  can be used on the closing cover  5  in combination with a check valve  12  which has a sphere  23  as a closing element. After turning off of the electric fuel pump, the feeding passage  14  closed by the spherical body  23  prevents an idle running of the fuel aggregate  1 . In addition to the above mentioned advantage, such as the shortening of the pressure build up time in the fuel supply system and the reduced emissions, the maintenance of the system pressure in the fuel supply system leads to a faster possible start of the motor with a reduced battery power since the preliminary time for building up of the system pressure is substantially shorter. 
     It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above. 
     While the invention has been illustrated and described as embodied in fuel feeding aggregate for an internal combustion engine, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.