Brush holder and electric machine comprising such brush holder

Abstract

The invention describes a brush holder comprising at least an anti-interference element (20) and a brush (50), the anti-interference element (20) having a first connection element (21) and a second connection element (22), the second connection element (22) being electrically conductively connected to a first end (41) of an electrical line (40) and a second end (42) of the electrical line (40) being electrically conductively connected to the brush (50). The brush holder according to the invention is characterized in that the first coupling element (21) can be directly connected to the current supply in an electrically conductive manner.

Description

Technical Field

[0001] The invention relates to a brush holder for an electric machine, in particular for a DC motor, and an electric machine comprising such a brush holder according to the type of the independent claim. Background Art

[0002] Electric machines, in particular DC motors, often include interference suppression elements for reducing the propagation of high-frequency radiation generated during operation. It is essential that the interference suppression elements are directly integrated into the brush holder, thereby increasing the effectiveness of the interference suppression measures primarily due to the spatial proximity to the brushes.

[0003] DE 10 2005 060 670 A1 discloses a brush holder in which an interference-suppressing choke with a choke core is arranged on an annular plastic carrier. Here, the individual coil turns all abut against one another along the center axis of the interference-suppressing choke and therefore all have the same axial spacing relative to one another, which is approximately zero here. During operation of such a brush holder in an electric motor, despite the presence of the arranged interference-suppressing choke, interference radiation still occurs, which can negatively affect other electronic components in the motor vehicle. The object of the present invention is therefore to provide a brush holder which has an improved attenuation of electromagnetic radiation, in particular in the high-frequency range of more than 200 MHz, without the need to arrange additional interference-suppressing components. Summary of the invention

[0004] In contrast, a brush holder according to the invention and an electric machine according to the invention comprising such a brush holder have the advantage that the radiation-damping effect of the interference inductor in the brush holder is significantly improved by varying the axial spacing between the individual coil turns. By such a stretching of the individual inductor turns, the transmission characteristics of the interference-suppressing inductor in conjunction with the electrical reference mass of the entire system of the electric motor can be significantly improved.

[0005] Advantageous further developments and improvements of the design specified in the independent claim can be achieved by the measures listed in the dependent claims. It is particularly effective if the spacing between the coil windings in the middle region of the interference suppression choke is larger than in the edge region of the interference suppression choke. In this case, all axial spacings in the middle region of the interference suppression choke can be designed to be of equal size or to vary approximately continuously, for example.

[0006] In a preferred embodiment, the individual coil turns in the region approximately abut against each other in the axial direction, whereas the axial spacing in the middle region is significantly different from zero. It is particularly advantageous if the edge region is formed, for example, by two to eight coil turns, whose axial spacing is smaller than the axial spacing of the coil turns in the middle region.

[0007] The central region preferably also has two to eight coil turns, wherein their axial spacing relative to one another is, for example, 0.3 to 1.5 times the wire diameter of the coil conductor.

[0008] To produce an interference suppression choke, coil turns are wound continuously onto a choke core, which is made of plastic, for example. The length of the choke core preferably corresponds to the entire length of the interference suppression choke. However, in an alternative embodiment, the coil turns of a conventional interference suppression choke can also extend in the axial direction, so that the coil turns then extend over a larger axial area than the choke core.

[0009] The interference suppression choke can be wound particularly easily by means of a metal wire which is connected at its axial end, for example, to a supply contact or a carbon brush. Since the carbon brush is movably mounted, it can be particularly advantageously electrically connected to the interference suppression choke via a flexible current strand.

[0010] The brushes and the interference suppression choke are preferably arranged on an annular brush holder which is made of plastic, for example as an injection-molded part. In this case, the annular brush holder is arranged directly on a metal plate which serves as a reference mass for the interference arrangement. The metal plate is designed, for example, as a housing or a bearing cover of an electric motor and in particular as a component of a motor housing. The metal plate preferably also has a central aperture so that the rotor shaft of the rotor protrudes outward from the pole housing through the metal cover forming the housing cover. Since the plastic carrier is flat against the metal plate, the distance between the coil turns and the metal plate can be designed to be smaller, so that a larger capacitance is generated between the interference suppression choke and the metal plate. This can intensify the effect that not all individual coil turns have the same natural resonance, but rather the natural frequency is distributed over a larger frequency range.

[0011] In a first embodiment, the individual coil turns have approximately the same distance relative to the metal plate in the direction of the rotor axis, whereby the two axial ends of the interference suppression choke can be very easily fastened to the holder on the plastic carrier of the brush holder. Preferably, the interference suppression choke is arranged in the radially outer region of the annular plastic carrier, for example with its center axis in a tangential direction relative to the plastic carrier.

[0012] In an alternative embodiment, the individual coil turns have different distances relative to the metal plate along the rotor axis, so that the interference suppression choke is mounted with its center axis inclined relative to the plane of the metal plate.

[0013] Here, the two axial ends of the interference suppression choke are also fastened to the bracket of the plastic carrier at different distances from the metal plate. Here, the center axis of the interference suppression choke forms an angle of inclination relative to the plane of the metal plate, which is, for example, between 3° and 25°. At the first axial end of the interference suppression choke, the distance between the coil winding and the metal plate along the rotor axis is, for example, less than 1.0 mm, while at the second axial end of the interference suppression choke, the distance is, for example, in the range between 1.0 mm and 5.0 mm.

[0014] In order to minimize the distance of the first axial end of the interference suppression choke relative to the metal plate, a recess is preferably formed in the annular plastic carrier, into which the interference suppression choke is at least partially embedded in the direction of the rotor axis. As a result, the distance between the coil turns and the metal plate can be configured to be smaller than the material thickness of the annular plastic carrier. Preferably, the recess extends over the entire length of the interference suppression choke, preferably in a tangential direction relative to the annular plastic carrier.

[0015] In order to keep the metal plate reliably insulated despite this small distance of the coil turns from the metal plate, an insulating layer is preferably formed on the metal plate in the region of the cutout, which insulating layer can be adhesively bonded to the metal plate, for example, as a film. The insulating layer is formed significantly thinner in the direction of the rotor axis than the material thickness of the plastic carrier.

[0016] In particular, the combination of different axial spacings of the coil turns and different distances along the rotor axis relative to the metal plate has the particular effect that, in particular in the frequency range above 200 MHz, the interference radiation of the electric motor can be significantly reduced compared to conventional brush holders, so that in particular it is also possible to dispense with the installation of interference suppression capacitors on the brush holder components, thereby saving high material costs. Furthermore, the attenuation of the interference radiation can be further optimized if necessary by positioning the interference suppression choke closer to the motor brushes or closer to the current connection.

[0017] The brush holder according to the invention can be particularly advantageously incorporated into a DC motor, such as is used, for example, in various applications in motor vehicles. Such a DC motor can be used, for example, to adjust movable parts in a motor vehicle or to drive a pump, for example, in a hydraulic unit.

[0018] The brush holder together with the motor housing made of metal forms an overall system in which the asymmetric capacity between the interference-suppressing choke and the reference mass of the housing is formed by the specific construction scheme and arrangement of the individual coil turns of the interference-suppressing choke. As a result, the interference radiation of the entire electric motor can be significantly reduced without the need for additional interference-suppressing components. Here, the rotor shaft can be led out of the motor housing through a central opening of the plastic carrier and the housing cover in order to provide an output torque for the desired application. For example, an eccentric device can be arranged on the rotor shaft, which eccentric device actuates the piston of a hydraulic pump.

[0019] At least one interference suppression choke and an electrical conductor are provided for contacting the motor brushes in the brush holder, wherein a first connection element of the interference suppression choke can be directly connected to the current supply portion in an electrically conductive manner. The first connection element can be directly connected to the current supply portion in an electrically conductive manner, preferably by means of a welded connection. A second connection element of the interference suppression choke is connected to the motor brushes in that the second connection element is electrically conductively connected to a first end of the electrical conductor, for example a carbon strand, and a second end of the electrical conductor is electrically conductively connected to the motor brushes.

[0020] Preferably, a second brush is mounted on the plastic carrier of the brush holder, and the second brush forms a brush pair with the first-mentioned brush. The second brush is arranged, for example, exactly opposite to the first-mentioned brush or at any other angle. In principle, the second brush can be contacted arbitrarily. However, the second brush is preferably directly conductively connected to the current conveying part through an interference suppression choke in the same way as the first brush. That is to say, the first coil end of the interference suppression choke is implemented so that the first coil end can be directly conductively connected to the current conveying part. Here, the second coil end is conductively connected to the second brush through a second electrical conductor, such as a carbon stranded wire. Optionally, more than one brush pair can also be arranged in the brush holder. If, for example, a second brush pair is arranged, the corresponding second ends of the first interference suppression choke and the second interference suppression choke can be directly conductively connected to the electrical conductors of the first brush and the second brush of the second brush pair, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is explained in more detail below by means of the accompanying drawings. It is shown:

[0022] Figure 1 A first embodiment of a brush holder with an interference-resistant choke is shown,

[0023] Figure 2 A second embodiment of a brush holder with an interference-resistant choke is shown,

[0024] Figure 3 A schematic diagram shows interference radiation of a conventional interference suppression inductor arrangement and an interference suppression inductor arrangement according to the invention, and

[0025] Figure 4 An electric machine comprising a brush holder according to the invention is shown. DETAILED DESCRIPTION

[0026] exist Figure 1 1 shows a brush holder 10 for an electric motor 12, such as the brush holder used, for example, for energizing a DC motor. The brush holder 10 has a plastic carrier 40, which is annularly configured and arranged on a bearing cover 15 made of metal. A brush 50 is arranged on the plastic carrier 40, which elastically abuts radially against a commutator 55 of a rotor 13 of the electric motor 12. The brush 50 is electrically connected to an interference suppression choke 20 in order to reduce the emission of interfering electromagnetic radiation. The interference suppression choke 20 consists of individual coil turns 22, which are arranged axially side by side along the axial center axis 21 of the interference suppression choke 20. The coil turns 22 are wound around the center axis 21 of the interference suppression choke 20, for example, by means of a continuous coil wire 23. Preferably, the coil turns 22 are wound onto a choke core 30, which extends along the center axis 21. In this embodiment, the coil turns 22 have a greater axial spacing 24 in the axial middle region 28 of the interference suppression choke 20 along the central axis 21 than in the edge region 26 of the interference suppression choke 20. In this embodiment, the coil turns 22 abut against each other axially in the edge region 26, for example, so that the axial spacing 24 between the coil turns 22 in the edge region 26 is almost zero. Figure 1 , for example, exactly two coil turns 22 have an axial spacing 24 in the middle region 28 on both sides relative to the axially adjacent coil turns 22, which axial spacing is between half of the coil wire 23 and the total wire diameter 25. In other embodiments not shown, more than two coil turns 22 can also have an axial spacing 24 in the middle region 28 relative to the coil turns 22 adjacent on both sides. The axial spacing 24 between the axially adjacent coil turns 22 can also vary and, in particular, continuously transform into an approximately zero axial spacing 24 in the edge region 26. The design of the axial spacing 24 between the coil turns 22 corresponds to the extension of a specific coil turn 22 in the direction of the center axis 21, which can be directly generated when winding the interference suppression choke 20. In the exemplary embodiment, the edge region 26 has, for example, four or five coil turns 22, but the number of the coil turns can also be changed accordingly depending on the application. The coil wire 23 is designed as a copper wire, for example, which has a wire diameter of 0.5 mm to 2.0 mm. The coil wire 23 of the interference suppression choke 20 is electrically connected to one of the brushes 50 at the end, for example, via a stranded wire 52. The bearing cover 15 is also designed in an annular shape, for example, so that the rotor shaft 16 of the rotor 13 protrudes from the motor housing 14 along the rotor axis 17.

[0027] In accordance with Figure 2 In another embodiment of the invention, the center axis 21 of the interference suppression choke 20 is arranged at an angle 43 to the bearing cover 15. The bearing cover 15 extends approximately transversely to the rotor axis 17 and forms an axial cover for the motor housing 14, such as Figure 4 As shown in . Due to the inclined arrangement of the interference-proof choke 20 relative to the bearing cover 15, the first axial end 31 of the interference-proof choke 20 has a smaller first distance 41 along the rotor axis 17 than the second distance 42 of the second axial end 32 of the interference-proof choke 30 in the direction of the rotor axis 17. In order to make the first distance 41 toward the bearing cover 15 as small as possible, a recess 48 is formed in the plastic carrier 40 in the circumferential region of the interference-proof choke 20, into which the interference-proof choke 20 extends along the rotor axis 17. The recess 48 is here configured as a complete through-hole along the rotor axis 17. Therefore, an insulating film 46 is fastened to the bearing cover 15 in the region of the recess 48, which prevents direct electrical contact between the coil winding 22 and the bearing cover 15. Here, the first distance 41 at the first axial end 31 of the interference-proof choke 20 relative to the bearing cover 15 has a value of 0.5 mm to 1.0 mm, for example. The second distance 42 at the second axial end 32 of the interference suppression choke 20 is, for example, in the range between 1.0 mm and 4.0 mm. The center axis 21 of the interference suppression choke 20 is oriented approximately tangentially to the annular plastic carrier 40. In order to achieve an inclined support of the center axis 21 of the interference suppression choke 20, a first retaining element 61 is formed at the plastic carrier 40 at the first axial end 31 of the interference suppression choke 20, which has a smaller distance relative to the bearing cover 15 than the distance of the second retaining element 62 at the second axial end 32 of the interference suppression choke 20 relative to the bearing cover 15. As a result, the interference suppression choke 20 is reliably held in its inclined position relative to the bearing cover 15 even in the case of external loads due to vibrations and temperature fluctuations.

[0028] like Figure 2 The embodiment with the inclined arrangement of the central axis 21 can also be combined with the embodiment according to Figure 1 The embodiment in which the axial spacing 24 between the coil turns 22 is designed differently. These two embodiments have the effect that the capacitance between each of the coil turns 22 and the bearing cover 15 is different for each turn, so that the set resonance frequency is distributed over a larger frequency range during electrical excitation. This significantly reduces electromagnetic radiation, especially in the range of more than 100 MHz, so that additional interference suppression components such as interference suppression capacitors on the brush holder 10 can be omitted if necessary.

[0029] exist Figure 3 As shown in the example Figure 3 The frequency curve of the interference radiation measured by the measuring structure of the interference suppression device. The annular plastic carrier 40 is arranged together with the interference suppression choke 20 on a metal plate, which is implemented in the motor 12, for example, by the bearing cover 15. At the two ends 31, 32 of the interference suppression choke 20, the current is divided by means of electrodes 66 and supplied to the measuring receiver. The interference suppression choke 20 is connected to the brush 50 at least at the ends 31, 32 via a stranded wire 52, which rests on the commutator 55 not shown here.

[0030] In the diagram, the frequency of the interference radiation is plotted on the x-axis 70. The amplitude of the interference radiation is shown on the y-axis 71. In the frequency response, the thin line I (upper) represents an embodiment of the interference suppression inductor 20 in which all axial distances 24 are of equal size, in particular approximately zero. The frequency response of the thick line II (lower) corresponds to the frequency response according to Figure 1 2. An embodiment of the interference suppression choke 20 according to the invention is shown, in which the axial spacing 24 in the middle region 28 is configured to be greater than the axial spacing 24 in the edge region 26. It is obvious that the interference radiation in the embodiment (II) of the interference suppression choke 20 according to the invention is significantly lower than the interference radiation in the conventional embodiment (I) of the interference suppression choke 20 in the range above 100 MHz to about 500 MHz.

[0031] Figure 4 A direct current motor is shown as the electric motor 12, wherein a stator and a rotor 13 are arranged in a pot-shaped motor housing 14. In this case, the motor housing 14 forms, for example, a magnetic circuit for the permanent magnets of the stator. The rotor has an electrical winding, which is energized via a commutator, against which the brushes rest elastically. The motor housing 14 is closed with respect to the rotor axis 17 by means of a bearing cover 15, in which a rotor bearing 18 for a rotor shaft 16 is arranged. On the lower side of the bearing cover 15, a plastic carrier 40 of the brush holder 10 is arranged, which is not visible here. The rotor shaft 15 protrudes from the motor housing 14 through the rotor bearing 18, wherein, at the free end of the rotor shaft 16, an eccentric device 80 for a drive of a hydraulic pump is arranged, for example. In addition, a current through-conductor 78 is formed in the bearing cover 15, by means of which the brushes 50 are energized. The bearing cover 15 together with the motor housing 14 has a rotation lock 76 in order to position the brushes 50 exactly relative to the stator in the circumferential direction 9. The bearing cover 15 is fastened to the motor housing 14, for example, by means of a plastic material molding 74, as can also be done, for example. Figure 2The motor housing 14 together with the bearing cover 15 and the interference suppression choke 20 form a total capacity which can be influenced by the specific design and arrangement of the coil turns 22 relative to the bearing cover 15. For example, a mounting hole 73 is formed on the motor housing 14, by means of which a flange 72 of the motor housing 14 can be fastened to the pump housing of the hydraulic unit.

[0032] It should be noted that various possible combinations of the individual features are possible with respect to the embodiments shown in the drawings and the description. Thus, the specific construction, arrangement and number of the coil turns 22 and their axial spacing 24 from one another and their distances 41 , 42 relative to the bearing cap 15 can be varied accordingly, for example. Likewise, the precise position and construction of the plastic ring 40 , the recess 48 and the retaining elements 61 , 62 can be adapted to the requirements of electromagnetic compatibility requirements. The invention is particularly suitable for electric direct current motors, such as those used, for example, to drive assemblies and to adjust movable parts in motor vehicles, such as electric seat adjusters, window lifts and sliding roof drives. However, the application should not be limited to this application.

Claims

1. A brush holder (10) for a DC motor, the brush holder comprising at least one brush (50) which is electrically connected to at least one interference-suppression choke (20), wherein: The interference suppression choke (20) has a plurality of coil turns (22) which are arranged axially adjacent to one another with respect to a center axis (21) of the interference suppression choke (20), wherein the axial spacings (24) between the individual coil turns (22) are configured to be of different sizes over an axial length (34) of the interference suppression choke (50).

2. The brush holder (10) according to claim 1, characterized in that: The axial spacing (24) between the individual coil windings (22) is smaller in an axial edge region (26) of the interference suppression choke (20) than in an axial center region (28) of the interference suppression choke (20).

3. The brush holder (10) according to claim 1 or 2, characterized in that: The coil turns (22), in particular two to six coil turns, respectively, approximately abut one another in the axial direction in two edge regions (26).

4. A brush holder (10) according to any one of the preceding claims, characterized in that The axial spacing (24) between the coil turns (22), in particular between two to six coil turns, lies in the middle region (28) between half the wire diameter (25) of the coil turns (22) and the total wire diameter.

5. The brush holder (10) according to any one of the preceding claims, characterized in that The coil turns (22) are wound onto a cylindrical choke core (30), which extends in particular over the entire axial length (34) of the interference suppression choke (20).

6. A brush holder (10) according to any one of the preceding claims, characterized in that The coil turns (22) are wound from a copper conductor (23) which is electrically connected to one of the brushes (50) at least at the axial ends (31, 32) of the interference suppression choke (30), preferably via a flexible stranded wire (52).

7. A brush holder (10) according to any one of the preceding claims, characterized in that The interference suppression choke (30) is arranged on an annular plastic carrier (40) which is arranged directly along a bearing cover (15) made of metal and which closes a motor housing (14), wherein in particular the rotor shaft (16) along the rotor axis (17) penetrates both the plastic carrier (40) and the bearing cover (15).

8. A brush holder (10) according to any one of the preceding claims, characterized in that The center axis (21) of the interference suppression choke (20) extends parallel to the plane of the bearing cover (15) and in particular tangentially to the annular plastic carrier (40).

9. A brush holder (10) according to any one of the preceding claims, characterized in that The center axis (21) of the interference suppression choke (20) is arranged at an inclination angle (43), preferably an inclination angle of 5° to 20°, relative to the plane of the bearing cover (15).

10. The brush holder (10) according to any one of the preceding claims, characterized in that Compared to the second axial end (32) of the interference-resistant choke (30), the first axial end (31) of the interference-resistant choke (30) has a smaller first distance (41) relative to the bearing cover (15), in particular a first distance less than 1.0 mm, and the second axial end has a larger second distance (42) relative to the bearing cover (15), in particular a second distance of 1.0 mm to 4.0 mm.

11. A brush holder (10) according to any one of the preceding claims, characterized in that In the region of the interference suppression choke (20), a recess (48) is formed in the annular plastic carrier (40) along the rotor axis (17), into which recess the interference suppression choke (20) is embedded in the direction of the rotor axis (17), so that at least one axial end (31) of the interference suppression choke (20) has a distance (41) from the bearing cover (15) that is smaller than a thickness (44) of the annular plastic carrier (40) in the direction of the rotor axis (17).

12. The brush holder (10) according to any one of the preceding claims, characterized in that An insulating film (46) is mounted on the bearing cover (15) in the region of the recess (48) opposite the interference suppression inductor (20).

13. An electric machine (12), in particular for a hydraulic unit in a motor vehicle, having a brush holder (10) according to any one of the preceding claims.

14. The electric machine (12) according to claim 13, characterized in that The brush holder (10) together with the interference suppression choke (20) is completely surrounded by the metallic motor housing (14) and the bearing cover (15) made of metal, and a rotor bearing (18) for the rotor shaft (16) is inserted into a central aperture (19) of the bearing cover (15), and in particular no interference suppression capacitors for the brushes (50) are arranged on the brush holder (10).

Images