The invention is related to a fuel pump.

In brushless fuel pumps known from the state of the art, the rotor is surrounded by the stator and an impeller is connected to an axial end of the rotor. Thereby, a rotation of the rotor causes a rotation of the impeller which conveys the fuel. This layout leads to a big height of the fuel pump.

It is an object of the present invention to provide a fuel pump with a reduced height.

This object is achieved by the features of claim 1 of the invention.

The inventive fuel pump comprises a housing having a drive axis. This drive axis can be a virtual drive axis. The fuel pump further comprises an electric motor arranged in the housing and comprising a rotor for rotation about the drive axis. The fuel pump further comprises a stator, interacting with the rotor so as to cause a rotation of the rotor. A rotating fuel conveying element is arranged inside the rotor when seen in a radial direction, the rotating fuel conveying element at least partially overlapping with the rotor in an axial direction and being connected to the rotor in a non rotatable manner such that the rotation of the rotor causes a rotation of the fuel conveying element.

Since the rotor and the rotating fuel conveying element overlap in an axial direction, the inventive fuel pump has a reduced height. Further, it is possible to arrange a plurality of magnets at the periphery of the rotor which will have an increased diameter compared to the rotor of previous known fuel pumps. This is due to the reason that the fuel conveying element is arranged inside the rotor when seen in a radial direction. The increased diameter of the rotor makes it possible to use more magnets at its periphery. In addition, these magnets are arranged further away from the drive axis, thereby having a longer lever. Therefore, startup variations of the fuel pump can be reduced when compared to prior art pumps. Such startup variations can damage the connection of the fuel conveying element and the rotor (shaft cap joint).

In a preferred embodiment, the rotating fuel conveying element is an impeller.

In another preferred embodiment which may be an independent invention, the rotating fuel conveying element comprises at least one and in particular a plurality of rotating fuel conveying screws. Each screw rotates about its own longitudinal axis. For example, three rotating screws can be used. In this embodiment, the inventive fuel pump uses the principle of a screw pump. The rotating fuel conveying element further comprises a carrying element, carrying each screw in a longitudinal bore. Each bore is equidistantly spaced from the drive axis. Each screw intermeshes with a non rotating screw being arranged at the position of the virtual drive axis.

The non rotating screw can be connected in a non rotatable manner with the housing or a part connected to the housing.

The carrying element is connected with the rotor in a non rotatable manner so as to rotate with the rotor about the drive axis. The carrying element preferable has a circular cylindrical shape. This rotation of the carrying element causes a rotation of the fuel conveying screws about the drive axis. The intermeshing of the fuel conveying screws with the fixed screw at the position of the drive axis causes a rotation of each fuel conveying screw about its own longitudinal axis. This rotation causes the conveying of the fuel.

It is preferred that the electric motor is a brushless motor.

It is further preferred that the housing comprises an upper cap and a lower cap which together form a bearing for the fuel conveying element in a radial and/or axial direction.

It is further preferred that the fuel conveying element serves as a radial bearing for the rotor.

It is further preferred that the rotor is guided in an axial direction by a magnetic bearing.

In a further embodiment, the rotor can be surrounded in a radial direction by the stator, the rotor comprising magnets being arranged at its periphery.

In the following, preferred embodiments of the invention are described in the context of the figures.

Figures la and lb show a first embodiment of the fuel pump, Figures 2a - 2b show a second embodiment of a fuel pump,

Figure 3 shows a third embodiment of the fuel pump,

Figures 4 - 7 show the assembly process of the embodiment according to figure 3. Figure la which is an intersected view of figure lb shows a fuel pump 10 having a housing 12 which comprises an upper cap 32 and a lower cap 34. These serve as an axial and radial bearing for the impeller 22. Rotation of the impeller 22 takes place about the drive axis 14. The basic function of the impeller in order to cause a conveying of the fuel is known from the state of the art and is therefore not described in more detail.

The impeller 22 is surrounded in an axial direction by the rotor 18 which is connected in a non rotatable manner to the impeller 22. This can be done for example by positive engagement elements.

The rotor 18 comprises a plurality of magnets at its periphery and is surrounded by the stator 20 which causes rotation of the rotor 18 about the drive axis 14.

Figure lb is a top view of the same embodiment shown in figure la, whereby figure lb shows i.a. the electrical connecting elements for the electric motor.

The embodiment shown in figure 3 is very similar to the one shown in figure 1, whereby this embodiment comprises an integrated fuel filter 38 arranged above the upper cap 32. In general it is possible to arrange an integrated fuel filter 38 inside the pump housing 12 above the pumping section in all embodiments of the present invention.

In a further preferred embodiment it is possible to use the necessary overmold of the stator as the housing of the pump module. In this embodiment it is preferred that there is at least partially an overlapping of the rotating fuel conveying element 22,24a-24c,26 with the rotor 18 in an axial direction a. However it is also possible to use the stator overmold as the pump housing in conventional pump modules which do not have any overlapping of the rotor/stator and the rotating fuel conveying element in an axial direction. Figure 4 shows the assembly of the embodiment according to figure 3. First, the stator package comprising the stator 20 and the electrical contacts 42 is assembled and is overmolded so as to form the housing element 44. This process is shown in figure 5a. Figure 5b shows the result.

The next steps are shown in figure 6a : the inlet cover which is the lower cap 34 and the impeller 22 are assembled with the rotor 18 and fixed by the upper cap 32. This assembled pump section is placed inside the stator 20. The result is shown in figure 6b.

According to figure 7a, the filter 38 is assembled on the upper cap 32. Finally, a filter cover 40 can be connected by molding or laser-welding with housing element 44, thereby forming the filter shown in figure 7b.

The assembly of the first embodiment shown in figure 1 is very similar to figure 3, whereby the filter 38 is omitted.

Figures 2a and 2b show a second embodiment which can be an independent invention . This fuel pump 10 also comprises a housing 12 which is closed at its upper end by a cover 40. The fuel pump 10 comprises an upper cap 32 and a lower cap 34, serving as a bearing for the carrying element 26. This carrying element 26 is connected in a non rotatable manner with the rotor 18 which is surrounded by the stator 20. Rotation of the carrying element 26 causes the fuel conveying screws 24a - 24c to rotate about their respective longitudinal axis, since they intermesh with the fixed screw 30. This fixed screw 30 is connected in a non rotatable manner with the upper cap 32. In this embodiment, fuel conveying takes place according to the function of a screw pump with three fuel conveying screws.