Prior art

The invention relates to a brushless electric motor according to the preamble of claim 1. Such an electric motor, which is known in practice, serves as part of a wiper motor and comprises a rotor mounted in several bearing devices in a rotary axis and having a magnetic element carrier. The magnetic element carrier consists of metal and is formed as a deep-drawn part. On its outer circumference there are fastened rotor magnets, which interact with a stationary positioned stator, having wire windings. Furthermore, it is known from the mentioned application to form through openings in the region of two radially encircling front faces or front faces of the magnetic element carrier, in which balancing weights can be installed. Such balancing weights can also be connected firmly to the magnetic element carrier for example by press fits, even without additional securing elements, or by glue. Since the openings each only have a depth corresponding to the material thickness of the magnetic element carrier, the balancing is limited to applications in which the imbalance does not exceed a certain measure.

Disclosure of the invention The brushless electric motor according to the invention with the features of claim 1 has the advantage that, on the one hand, it is suitable both for the arrangement of relatively large balancing masses (in regard to a particular angle position of a recess for receiving of balancing weights) and furthermore also makes possible the balancing not only in the region of two defined planes, but also in an intermediate region of the magnetic element carrier in relation to its longitudinal extension. This is accomplished, according to the invention, in that the recesses accommodating the balancing weights extend in the direction of the rotary axis of the rotor as far as the region of the rotor magnets or magnetic elements.

Advantageous modifications of the electric motor according to the invention are set forth in the dependent claims. All combinations of at least two features disclosed in the claims, the description, and/or the figures fall within the scope of the invention.

In order to maximize the possibility of accommodating balancing weights in a recess or to be able to integrate or arrange as many balancing weights as possible in such a recess, it is advantageously provided that the recesses extend continuously between the two front faces of the magnetic element carrier.

It is furthermore advantageous for the use of standardized balancing weights if the recesses have the same cross-sectional area, wherein the cross-sectional area is preferably formed in the shape of a circle. An electric motor as described by the invention or its magnetic element carrier in an especially preferred design consists of plastic material. Such a configuration has the advantage in particular that such recesses can be formed already by a corresponding design of the tool with no additional process steps such as stamping or the like, as in the prior art.

An especially simple and at the same time secure fastening of the balancing weights can be achieved if the balancing weights are received in the recesses forming a press-fit connection.

Another preferred design embodiment of the magnetic element carrier provides that the magnetic element carrier on the side facing the shaft of the rotor is connected to a sleeve-shaped spacer element consisting of metal, which is co-rotationally connected to the shaft. Such a configuration can be produced preferably, and especially in connection with the magnetic element carrier made of plastic, by injection molding the plastic of the magnetic element carrier onto the metal of the spacer element. The torque-proof fastening of the sleeve- shaped spacer element to the shaft is done preferably by a glue connection, in order to reduce a thermal stress on the material of the magnetic element carrier, such as would typically be the case if the connection between the spacer element and the shaft were made for example by a welded connection. Furthermore, in a preferred embodiment of the magnetic element carrier it is provided that this is surrounded by a magnetic sleeve on a circumferential surface, wherein the rotor magnets are connected to the magnetic sleeve on the side facing away from the magnetic carrier element. While the magnetic sleeve, by analogy with the spacer element, is preferably connected to the magnetic element carrier by injection-molding of the plastic of the magnetic element carrier onto it, the connection between the magnetic sleeve and the rotor magnets is typically done by glue connections.

In order to fix or position the magnetic elements or rotor magnets especially easily and securely on the magnetic element carrier in the longitudinal direction, it is provided that the magnetic element carrier comprises flanges extending radially around the rotary axis, between which the rotor magnets are received in the longitudinal direction.

Furthermore, one variant of the magnetic element carrier provides that a radially- extending carrier portion is moulded onto the magnetic element carrier for the fastening of further magnetic elements of a sensor device. Such further magnetic elements in combination with the mentioned sensor device, which is especially designed as a Hall sensor device, serve for detecting the rotary angle position of the rotor, so as to be able to actuate the windings of the stator in proper time and phase. In order to make possible, on the one hand, the lowest possible weight of the magnetic element carrier, and on the other hand also to save on material, it is furthermore advantageous for the magnetic element carrier to have at least one cavity for weight reduction.

Another design embodiment in connection with the aforementioned spacer element provides that the rotor is rotatably supported by means of two bearing devices, and the two bearing devices are co- rotationally arranged on the shaft of the rotor, wherein the two opposite front sides of the spacer element each form an axial stop for a bearing device. Such a design makes it possible in particular that the bearing devices only need to be axially secured on the shaft in one direction, since the front sides of the spacer element provide for the axial securing in the other respective direction.

Especially preferably, an electric motor so described is formed as a part of a wiper motor.

In order to achieve the lowest possible volume of the balancing weights with the largest possible weight, they have an elongated form, preferably cylindrical.

Further advantages, features and details of the invention will emerge from the following description of preferred exemplary embodiments as well as with the aid of the drawing. In the figures:

Fig. 1 shows major components of a windscreen wiper motor with a brushless electric motor arranged therein, in an exploded view,

Fig. 2 shows the windscreen wiper motor of Fig. 1 in the installed state in a partially sectioned perspective representation,

Fig. 3 shows a rotor of the electric motor of Fig. 1 and 2 in side view,

Fig. 4 shows the components of the rotor of Fig. 3 in an exploded view,

Fig. 5 shows a perspective representation of a drum-shaped carrier element as a component of the rotor of Fig. 3 and 4 and

Fig. 6 shows a longitudinal section through the carrier element with spacer element arranged therein to illustrate different arrangements of recesses to accommodate balancing weights.

The same elements or elements with the same function are given the same reference numbers in the figures.

Fig. 1 and 2 show the major components of a wiper motor 100, such as is used for at least indirect moving or driving of a windscreen wiper in a vehicle, not shown in the figures. The wiper motor 100 comprises a brushless electric motor 10, which is arranged inside a housing 11 of the wiper motor 100. The multiple-part housing 11 in the exemplary embodiment shown comprises a transmission housing 12, made of plastic by injection molding or made of aluminium by die casting, onto which a motor housing 14 can be flanged, shown in the figures in sectional representation, and being substantially cup shaped.

A stationary positioned stator 16 with wire windings 18 is arranged at least substantially inside the motor housing 14, which windings can be electrically contacted by a projection 19 which extends into the region of the transmission housing 12. The stator 16 serves for the rotating of a rotor 20 of the electric motor 10, the rotor 20 being shown by itself in Fig. 3, and wherein the rotor 20 is rotationally mounted by means of two bearing devices 21, 22, which are arranged in the housing 11 at corresponding recesses.

The rotor 20 comprises a shaft 24, having a worm gear 26 in a partial segment arranged in the transmission housing 12. The worm gear 26 meshes with a toothing 29 fashioned as a helical gearing arranged on the outer circumference of a transmission gear 28. The transmission gear 28 is part of a single-stage transmission 30 in the exemplary embodiment. The transmission gear 28 is rotationally mounted inside the transmission housing 12 and acts on a driven shaft 32, which emerges at a bottom side 33 of the transmission housing 12 by a segment from the transmission housing 12 (not shown) in order to activate at least indirectly the mentioned windscreen wiper. Fig. 1 and 2 show the one front face 34 of the driven shaft 32 arranged inside the housing 11.

The rotor 20 furthermore comprises a magnetic element carrier 36, which is made of plastic and formed as an injection-molding. The drum- shaped magnetic element carrier 36 has a through opening 38, which runs concentrically to a longitudinal axis 40 of the magnetic element carrier 36 or to a rotary axis 41 of the rotor 20. A sleeve- shaped spacer element 44 is arranged radially inside the through opening 38, which element consists of metal and is joined by injection molding of the plastic onto the magnetic element carrier 36. The spacer element 44 has an axial length L which is larger than the axial length 1 of the magnetic element carrier 36, so that the spacer element 44 extends beyond the magnetic element carrier 36 at both ends in the direction of the longitudinal axis 40. The spacer element 44 is pushed onto the shaft 24 and preferably fastened to it in a torque-proof manner by a glue connection.

As can best be seen from Fig. 3, the two bearing devices 21, 22 are also pushed onto the shaft 24, wherein the two front faces 45, 46 of the spacer element 44 each form an axial stop for the facing side of the bearing devices 21, 22. At the side facing away from the spacer element 44, the bearing device 21, 22 is secured on the shaft 24 in the axial direction by, for example, a weld connection, a caulking connection, or an additional securing element, such as one in the form of a securing ring. The magnetic element carrier 36 comprises a cylindrical segment 48, which looking in the longitudinal direction is bounded respectively by a flange 50, 51 extending radially about the longitudinal axis 40. The segment 48 is radially enclosed between the flanges 50, 51 by a sleeve- shaped magnetic sleeve 54, which is likewise preferably joined during the manufacturing process of the magnetic element carrier 36 by injection molding of the plastic of the magnetic element carrier 36 onto the magnetic sleeve 54. At the side of the magnetic sleeve 54 facing away from the magnetic element carrier 36, several first magnetic elements 55 or rotor magnets 56 are fastened in the circumferential direction between the two flanges 50, 51, preferably by glue connections. Furthermore, an annular region 58 is monolithically moulded on the magnetic element carrier 36, as is best seen from Fig. 3 and 4, at an axial spacing from the one flange 52, on the outer circumference of which are arranged second magnetic elements 60 as part of an otherwise not depicted sensor device. By means of the second magnetic elements 60 or the sensor device, the rotary angle position of the rotor 20 can be detected in a known and familiar manner.

It is furthermore evident from considering Fig. 5 and 6 together that the magnetic element carrier 36 has cavities 62 for weight savings in an intermediate radial region between the through opening 38 and the magnetic sleeve 54, running preferably at equal angular spacings about the longitudinal axis 40 in the longitudinal direction. Furthermore, a plurality of recesses 64, 66 can also be seen, arranged radially outside the cavities 62 and likewise preferably at equal angulas spacings about the longitudinal axis 40, which serve to accommodate preferably elongated or cylindrically shaped balancing weights 68.

As can best be seen from Fig. 6, the recesses 66 may be formed, for example, over the entire axial extension between the two front faces 69, 70 of the magnetic element carrier 36 bounded by the flanges 50, 51, or as recesses 64 corresponding to the upper part of Fig. 6, which reach for example from the one front side 70 to roughly the middle of the axial extension of the magnetic element carrier 36 between the flanges 50, 51. What is important, in any case, is that the recesses 64, 66 reach into the axial region of the magnetic element carrier 36 in which the first magnetic elements 55 or the rotor magnets 56 are situated. The cross section of the recesses 64, 66 is preferably in the shape of a circle each time and is somewhat smaller than the cross section of the balancing weights 68, so that the balancing weights 68 are received by press-fit connections in the recesses 64, 66, as is shown with the aid of the lower recess 66.

The electric motor 10 thus described can be altered or modified in many ways without deviating from the idea of the invention. List of reference numbers

10 Electric motor

11 Housing

12 Transmission housing

14 Motor housing

16 Stator

18 Wire winding

19 Projection

20 Rotor

21 Bearing device

22 Bearing device

24 Shaft

26 Worm gear

28 Transmission gear

29 Helical gearing

30 Transmission

32 Driven shaft

33 Bottom side

34 Front side

36 Magnetic element carrier

38 Through opening

40 Longitudinal axis

41 Rotary axis 44 Spacer element

45 Front face

46 Front face

48 Segment

50 Flange

51 Flange

54 Magnetic sleeve

55 Magnetic element

56 Rotor magnet

58 Annular region

60 Magnetic element

62 Cavity

64 Recess

66 Recess

68 Balancing weight

69 Front side

70 Front side

100 Wiper motor

L Length

1 Length