The present invention refers to an automotive single-phase electrical motor of the claw pole type.

In particular, the present Invention refers to an automotive single-phase electric motor for driving secondary components or devices of the automobile. Such components or devices could be e.g. auxiliary units, actuators or pumps. Accordingly, the automotive electric motor according to the present invention is not an engine of the automobile for driving the vehicle. The automotive electrical motor comprises a motor rotor rotating around a rotation axis and a stator defined by a mating pair of annular stator bodies. Each body is provided with at least two magnetic pole claws meshing with the claws of the other body. The electrical motor further comprises a stator coil arrangement for magnetizing the stator bodies.

A claw pole type motor of this type is known from prior art US 2007/0278894 A1. The claw pole type motor comprises a motor rotor which is rotatably provided in a motor stator. The stator is defined by two stator bodies which are provided coaxially to a motor rotor axis. Each stator body provides a plurality of pole claws extending in axial direction. A stator coil is arranged axially between the stator bodies thereby surrounding the claws of the stator bodies.

The dimension of the stator coil depends on the stator dimensions, in particular on the stator diameter. Accordingly, for different types of electric motors having different stator diameters, different stator coils are required. Thus, many different stator coils have to be manufactured and stored. This fact increases the manufacturing costs of the electric motor. The object of the present invention is to provide an automotive single- phase electrical motor of the claw pole type, which can be manufactured more economically.

This object is solved by an automotive single-phase electrical motor of the daw pole type having the features of claim 1,

According to the present invention the stator coil arrangement is provided as a satellite and radial arms of the stator bodies are magnetically connected to each other at or within the stator coil arrangement. The term "satellite" according to the invention means that the stator coil arrangement is not arranged coaxially with the rotor but is arranged at an outer radial vicinity of the stator bodies. The stator bodies therefore are magnetically connected to the stator coil by radial arms. The stator coil arrangement diameter therefore is not dependent on the diameter of the stator bodies. Accordingly, the design and the dimensions of the stator coil arrangement can be provided independently of the stator bodies dimensions. For different stator bodies one or only a few types of stator coil arrangements are necessary, so that standardized stator coil arrangements can be used, so that the total manufacturing costs of the automotive electrical motor decrease. Further, as the stator coil is not arranged around the claws, the stator bodies can be provided more compact in a radial direction. The position of the coil arrangement can be variably defined. Accordingly, the electric motor can easily be adapted to an existing mounting space in the automobile. Furthermore, the inventive features have the effect that the size of the coil arrangement is independent of the stator bodies so that the coil size can be selected only in accordance with the power requirements.

Preferably, the motor rotor is permanently magnetized. An electrical motor comprising a permanently magnetized rotor has a higher efficiency. In a preferred embodiment of the present invention the stator bodies are stamped-bend-sheet-metal parts. Stator bodies manufactured by stamping and bending a metal sheet are produced cost-effectively.

In a further preferred embodiment the circumference of the stator co!l arrangement is smaller than the total circumference of the stator body claws. The outer circumference of the stator coil arrangement is defined by the length of one outer coil winding. The circumference of the stator body claws is defined as the outer circumference of a cylinder plane defined by all pole claws. The stator coil dimensions are designed as compact as eiectrically possible. As a consequence the total length of the coll wire is reduced, the electrical coil resistance is reduced and the manufacturing costs can be decreased, whereas the electric efficiency of the electric motor can be increased.

The stator coil arrangement preferably comprises several parallel coil units. A parallel coil unit according to the present invention Is an additional coii unit having the same phase but acting electrically parallel to the other coil unit. By providing several parallel coil units, the electric current per coil unit is lower. As a consequence the coil wire of the coil units can have a smaller diameter. By providing a smaller coil wire diameter the packing density of the coil unit can be increased, so that the efficiency of the coil unit is improved.

Preferably, the claws are designed rectangular-shaped. A stator body having simple rectangular-shaped claws can be easily manufactured. Accordingly, the electric motor can be manufactured more economically. Alternatively, the claws are designed trapezoidal. The smaller side of the two parallel sides of the trapezoidal is the free end of the claw. This free end is oriented to the other stator body. Trapezoidal claws reduce the magneticai interference so that the efficiency of the electric motor is improved. According to a preferred embodiment of the present invention the motor rotor is a composite part with permanent magnetic particles in a body of non-magnetic substance. The motor rotor can easily be manufactured by injection molding so that the electric motor can be manufactured more economically. Further, the motor rotor can be manufactured to have various shapes. As plastic material has a low specific weight, the total weight of the motor rotor can be reduced.

Further, each stator body preferably comprises three claws.

Furthermore, back iron rings magnetically connecting the claws of the respective stator bodies with each other and the claws are preferably provided at a single cylinder plane. The claws and the back iron rings lie in one cylinder plane. Thus, the stator bodies can be manufactured without bending the back Iron ring away from the claws so that the manufacturing costs can be decreased. Further, as the back iron rings are not radially bended to the outside, the stator is of smaller dimensions in radial direction.

In a further preferred embodiment the coil core is defined by an overlap of the free end portions of the radial arms. Thereby, the overlapping area is increased, whereby the magnetical connection of the stator bodies with each other is improved. Preferably, the overlapping end portions are in close contact to each other, so that the magnetical connection between the stator bodies is further improved. Thus, the overlapping end portions are arranged air-gap free to each other.

As a further preferred embodiment the motor rotor overlaps in axial direction only with the claws of the stator bodies. The axial extension of the motor rotor is defined by the back iron rings connecting the claws. The motor rotor does not overlap with the back iron rings. The efficiency of the magnetic field driving the motor rotor therefore is not significantly deteriorated by the back Iron rings. As a consequence the electric motor has a high electric efficiency.

Further advantages will become evident by the following detailed description of an embodiment of the invention in combination with the drawings, which show:

Figure 1 a perspective view of an automotive single-phase electrical motor (without motor rotor) of the claw pole type according to the present invention, and

Figure 2 side view of the electric motor shown in figure 1.

Figure 1 shows a perspective view of an automotive single-phase electrical motor 10 of the claw pole type (without motor rotor) comprising a stator 14 defined by two annular stator bodies 18, 22 made of ferromagnetic stamped-bend-sheet-metal parts. Each body 18, 22 Is provided with three magnetic rectangular-shaped claws 26 meshing with the same number of claws 26 of the other body 18, 22. The rectangular-shaped claws 26 are connected by back iron rings 30. The back iron rings 30 and the claws 26 of each stator body 18, 22 are provided at a single cylinder plane of an imaginary cylinder.

The electric motor 10 further comprises a stator coil arrangement 34 for magnetizing the stator bodies 18, 22. The stator coil arrangement 34 is provided as a satellite with respect to the stator 14 i.e. the stator coil arrangement 34 Is provided in a radial distance to the stator 14. The stator coil arrangement 34 is defined by a cuboid coil 38 comprising a plurality of windings 42 of a coil wire 46. An axial axis 50 of the windings 42 is parallel to an axial stator axis 54. The outer circumference of the stator coil arrangement 34 around the axial axis 50 of the windings 42 is smaller than a circumference of the stator body claws 26 around the axial stator axis 54. The stator coil arrangement 34 comprises a rectangular opening 58 extending along the axial axis 50 of the windings 42.

Each stator body 18, 22 comprises a radial arm 62, 66 extending laterally from the stator body 18, 22 and the arms are fixed at an axial end of the stator bodies 18, 22, respectively. Free end portions 70, 74 of the radial arms 62, 66 of both stator bodies 18, 22 are inserted from opposing sides into the rectangular opening 58 of the stator coil arrangement 34 and defining the coil core. The free end portions 70, 74 are arranged so as to overlap in the rectangular opening 58 so that the stator bodies 18, 22 are magnetically connected to each other. In the overlapping region both free end portions 70, 74 are In close contact with each other.

In Figure 2 the electric motor 10 is shown in a side view. In this figure a motor rotor 78 of the electric motor 10 is shown. The motor rotor 78 being permanently magnetized is arranged In a center of the stator bodies 18, 22 and is rotating around a rotational axis being the axial stator axis 54. A motor rotor diameter D _R is slightly smaller than an inner stator body diameter D _s . The axial length of the motor rotor 78 is defined by the back iron rings 30 of the stator bodies 18, 22, so that the motor rotor 78 does axially not overlap with the back iron rings 30 of the stator bodies 18, 22. The motor rotor 78 therefore overlaps only with the claws 26 of the stator bodies 18, 22.

Reference signs

10 electrical motor

14 stator

18 stator body

22 stator body

26 claw

30 back Iron ring

34 stator coll arrangement 38 cuboid coil

2 winding

6 coll wire

50 axial axis

54 axial stator axis/rotating axis 58 rectangular opening

2 radial arm

6 radial arm

0 free end portion

4 free end portion

8 motor rotor D _R motor rotor diameter D _S stator body diameter