Brush system for an electric motor

Abstract

The invention relates to a brush system (54) for an electric motor (15), comprising a brush carrier (56) with at least one brush holder (82) for the slidably movable mounting of a brush (52), which is arranged around a central shaft opening (66) for the passage of a motor shaft (28), wherein the brush carrier (56) has a one-piece molded sliding bearing (44) for the sliding mounting of the motor shaft (28) in the area of ​​the shaft opening (66).

Description

[0001] The invention relates to a brush system for an electric motor, comprising a brush holder with at least one brush holder for the displaceable mounting of a brush arranged around a central shaft opening for the passage of a motor shaft. The invention further relates to an electric motor with a brush system, an adjustment drive with such an electric motor, and a window lifter for a motor vehicle with such an adjustment drive.

[0002] Motor vehicles today typically have a number of adjustment components, such as a seat adjustment, an operable lock, window lifts, and / or an adjustable sunroof, which can be moved between different positions by means of a respective electric motor adjustment drive. The respective adjustment component is actuated by a gear driven by a DC motor or electric motor, for example in the form of a worm gear with a (drive-side) worm on the motor shaft and a (output-side) worm wheel. Conventionally, the gear is arranged in a gear housing, to which the electric motor is flanged via its motor housing.

[0003] A brushed or mechanically commutated electric motor is typically used as an electric motor. Such an electric motor, also called a commutator motor, comprises a stator and a rotor mounted on a motor shaft (rotor shaft), which is moved within the stator by an alternating magnetic field. The rotor carries a field or excitation winding, and the motor shaft has commutator segments fixed to the rotor, which are contacted by sliding contacts in the form of brushes of a brush system. The brush system and the commutator segments interact as the motor shaft rotates in such a way that an electrical reversal of polarity or current commutation of the coil windings of the rotor (rotor windings, excitation windings), and thus of the operating or motor current, is achieved.

[0004] The brushes are traditionally cuboid-shaped rods pressed from carbon powder – possibly together with metal particles. Due to the sliding contact with the commutator segments, the brushes are subject to abrasion during operation of the electric motor. To maintain contact between the brush and commutator despite this abrasion, the brushes are usually pressed against the commutator, which is concentric with the motor shaft, by means of spring elements with a spring force. During operation of the electric motor, the direct current flows via the brushes and the commutator segments into the field windings of the rotor.

[0005] The brush system is typically designed as a pre-assembled (sub-)assembly that is installed in the drive housing during assembly of the adjustment drive. The brush system typically comprises a carrier element, such as a carrier plate, serving as a so-called brush carrier, on which the components of the brush system are pre-mounted. In other words, the brushes, brush holders, springs, contacts for plugs or other interfaces, as well as interference suppression components, sensors, and thermocouples, are pre-assembled on the brush carrier, so that the brush system is subsequently assembled as a whole during assembly of the adjustment drive. This means that the brush system is typically (pre-)assembled separately from the adjustment drive and then fed into the adjustment drive production line.

[0006] For the drive-related coupling of the motor shaft to the gearbox, the brush system or brush holder has a shaft opening as a through-hole for the motor shaft. A plain bearing (sliding contact bearing) is usually provided in the area of ​​the shaft opening for the plain bearing of the motor shaft. The plain bearing is designed as a separate component, which is pressed into a bearing seat of the brush holder or the shaft opening during the pre-assembly of the brush system.

[0007] When pressing the plain bearing into the bearing seat, it may happen that the plain bearing is not pressed in completely or correctly, and / or that the plain bearing sits tilted in the bearing seat or shaft opening. Furthermore, a test measurement is required during the plain bearing assembly to determine a minimum compressive force at which the plain bearing will not detach from the brush system.

[0008] The invention is based on the object of providing a particularly suitable brush system for an electric motor. In particular, a reliable and structurally simple plain bearing for a motor shaft is to be provided, which avoids assembly errors. The invention is further based on the object of providing a particularly suitable electric motor, a particularly suitable adjustment drive, and a particularly suitable window lifter.

[0009] With regard to the brush system, the object is achieved according to the invention with the features of claim 1, with regard to the electric motor with the features of claim 6, with regard to the adjustment drive with the features of claim 8, and with regard to the window lifter with the features of claim 10. Advantageous embodiments and further developments are the subject of the dependent claims (subclaims).

[0010] The advantages and configurations mentioned with regard to the brush system can also be applied to the electric motor and / or the adjustment drive and / or the window lifter and vice versa.

[0011] The conjunction “and / or” is to be understood here and in the following in such a way that the features linked by this conjunction can be formed both together and as alternatives to one another.

[0012] The brush system according to the invention is intended for an electric motor, in particular for a brush-commutated electric motor (commutator motor), and is suitable and configured therefor.

[0013] The brush system comprises a plate-like brush holder with a central shaft opening for the passage of a motor shaft of the electric motor. At least one brush holder for the displaceable mounting of a (carbon) brush is arranged around the shaft opening. In particular, at least two brush holders, each with a brush, are provided, which are arranged, for example, diametrically opposite one another at the shaft opening. The brushes are each electrically contacted, for example, by a spring element which, in its operative connection with the brush, exerts a spring force on the brush to engage the commutator. The brushes are resiliently contacted with a commutator located within the shaft opening when assembled.

[0014] Electrical components, in particular interference suppression elements such as chokes (interference suppression chokes), are arranged on the brush holder and are connected to the brushes. Electrical connection contacts for supplying power to the brushes or commutator are also arranged on the brush holder.

[0015] The brush holder also has a plain bearing in the area of ​​the shaft opening for supporting the motor shaft. According to the invention, the plain bearing is integrally formed, i.e., monolithically, onto the brush holder. The plain bearing is thus an integral component of the brush holder. In other words, the plain bearing is integrated into the brush holder. This creates a particularly suitable brush system.

[0016] The plain bearing is formed, for example, by additional walls that enclose or surround the motor shaft as sliding surfaces. This eliminates the need for an additional or separate plain bearing, in particular, eliminating the need for a press-in process for (pre-)assembly of the plain bearing. Consequently, the brush system according to the invention is particularly cost-effective, as an additional plain bearing, as well as the press-in process and the associated test measurements, are eliminated. Furthermore, performance problems of the electric motor due to poor alignment (parallelism) or position of the pressed-in plain bearing are essentially completely avoided.

[0017] The one-piece molding of the plain bearing also advantageously reduces the overall weight of the brush system. The one-piece plain bearing also advantageously reduces the carbon footprint (CO2 footprint) during the manufacturing of the brush system.

[0018] The (through) opening of the plain bearing for supporting the motor shaft is preferably dimensioned in terms of its clear width (opening or inner diameter) in such a way that the motor shaft sits in the plain bearing with the least possible play.

[0019] In an advantageous development, the brush holder has a tubular or hollow-cylindrical shaft guide with the shaft opening and the plain bearing. The shaft guide is, for example, a (carrier) sleeve integrally formed on the brush holder, which essentially forms a (bearing) housing of the brush holder that accommodates the plain bearing. When assembled, the shaft guide engages with the motor shaft, for example, in a corresponding receptacle in a gearbox housing. The receptacle stabilizes, in particular, the shaft guide and the plain bearing formed therein, thus ensuring reliable and operationally safe mounting of the motor shaft.

[0020] In a practical embodiment, the brush holder is designed as an injection-molded part. The plain bearing is preferably manufactured directly in the brush holder's injection mold. This advantageously makes it particularly easy to adjust the width of the molded-on plain bearing using various sliders or inserts in the injection mold. This ensures particularly simple, cost-effective, and flexible production.

[0021] In a preferred embodiment, the plain bearing has a sliding ring that supports the motor shaft. The sliding ring surrounds the motor shaft, with the inner ring wall forming the sliding bearing surfaces. The sliding ring is connected to the brush holder or the shaft guide via a number of radial struts, for example, four struts. This ensures stable and reliable mounting of the sliding ring.

[0022] An additional or further aspect of the invention provides for a pocket to be formed between each two adjacent struts. A pocket is defined as a closed (radial) wall between two webs, which has a smaller thickness or wall thickness than the struts. The pockets ensure a uniform wall thickness and quality of the struts or the plain bearing during the melt flow during an injection molding process.

[0023] The electric motor according to the invention is intended for, and is suitable and configured for, an adjustment drive of a motor vehicle, in particular for a window lift drive. The electric motor is designed as a commutator motor and has a pot-shaped motor housing or pole pot in which a stator and a rotor arranged fixedly on a motor shaft, as well as a commutator, are accommodated. The commutator is ground by a brush system described above. This results in a particularly suitable electric motor in which reliable, cost-effective, and operationally safe mounting of the motor shaft is ensured by the integrated plain bearing.

[0024] In one conceivable embodiment, the motor housing has a housing opening for the motor shaft on one side. This housing opening is closed by the brush system or brush holder. In other words, the brush holder essentially completely covers the housing opening. The brush holder thus essentially forms a housing cover or bearing plate for the motor housing. A shaft guide of the brush system extends outward.

[0025] The adjustment drive according to the invention is intended for, and is suitable and configured for, a motor vehicle. In a preferred application, the adjustment drive is designed as a window lift drive, in particular for a cable window lift. The adjustment drive comprises a gear housing with a gear part accommodated therein and an electric motor as described above. This creates a particularly suitable adjustment drive.

[0026] The electric motor or motor housing is screw-mounted to the gear housing, for example, by means of end-face flanges. The gear component is driven by the electric motor's motor shaft. For example, the adjustment drive comprises a worm gear, with the gear component being designed as a worm gear, and the motor shaft comprising a fixed worm shaft that meshes with the worm gear.

[0027] In a practical embodiment, the brush holder of the electric motor is inserted into the gear housing, at least in sections, in such a way that the plain bearing is located within the gear housing. This creates a particularly compact adjustment drive.

[0028] The window lifter according to the invention is designed, for example, as a cable window lifter for a side door of a motor vehicle. The window lifter has an adjustment drive as described above. This creates a particularly suitable window lifter.

[0029] An embodiment of the invention is explained in more detail below with reference to a drawing. In the drawings: Fig. 1 shows a schematic representation of a window lifter for a motor vehicle, Fig. 2 shows a perspective view of an electric motor adjustment drive of the window lifter in a partially disassembled state, Fig. 3 in sectional view, part of the adjustment drive, Fig. 4 in perspective view a brush system of the adjustment drive with a view to an outer side, Fig. 5 in perspective view the brush system with a view of an inner side Fig. 6 in sectional view the brush system according to the section line VI-VI in Fig. 4, and Fig. 7 in sectional view the brush system according to the section line VII-VII in Fig. 4.

[0030] Corresponding parts and sizes are always provided with the same reference symbols in all figures.

[0031] In the Fig. Figure 1 shows a simplified and schematic representation of an electric cable window lifter as a window lifter 2 for a (vehicle) window pane 4 of a motor vehicle. The (cable) window lifter 2 has an adjustment drive (cable drive) 6, which acts on the window pane 4 by means of an adjusting mechanism 8 and a driver 10. In the illustrated embodiment, the adjusting mechanism 8 has a cable pull 12 and a guide rail 14 for the driver 10.

[0032] An electric motor 15, acting as an electric actuator of the adjustment drive 6, drives a cable drum 18 of the adjustment mechanism 8 via a worm or spur gear 16. A pull cable of the cable pull 12 is arranged on the cable drum 18 in such a way that the pull cable is wound and unwound upon rotation of the cable drum 18 caused by the gear 16. The cable pull 12, designed, for example, as a Bowden cable, moves the window 4 via (cable) deflection pulleys 20 of the guide rail 14.

[0033] When the actuator 6 is actuated, the window pane 4 is moved into its (pane) position P. The window pane 4 is reversibly movable between a closed position S, which represents the highest possible position P, and an open position O, which represents the lowest possible position P. In these positions S and O, the window pane 4 is in the Fig. 1 is indicated by dashed lines. Window pane 4, on the other hand, is shown in a half-open intermediate position by solid lines.

[0034] The following information regarding the spatial directions is also provided in a vehicle coordinate system (vehicle coordinate system) for an example installation situation in a side door of a vehicle. The abscissa axis (X-axis) is oriented along the vehicle's longitudinal direction, the ordinate axis (Y-axis) along the vehicle's transverse direction, and the applicate axis (Z-axis) along the vehicle's height.

[0035] In the schematic representation of the Fig. 1, the guide rail 14 is oriented approximately parallel to the vehicle height direction Z, but the guide rail 14 is preferably oriented inclined or tilted to the Z direction.

[0036] The structure of the adjustment drive 6 is shown below using the Fig. 2 and Fig. 3. In this embodiment, the adjustment drive 6 is designed in particular as a window lifter or cable drive, by means of which the cable drum 18 is driven.

[0037] The adjustment drive 6 has a gear housing (cable drive housing) 22 in which the worm gear 24 is arranged as a gear part of the worm gear 16. Furthermore, a worm shaft 26 meshing with the worm gear 24 is accommodated in the gear housing 22 and is supported by a motor shaft 28 of the electric motor 15. Furthermore, a motor control unit 30, i.e., motor electronics and / or a controller, is accommodated in the gear housing 22, by means of which the operation of the electric motor 15—and thus of the adjustment drive 6—is controlled and / or regulated. The motor control unit 30 can be connected to a wiring harness or vehicle electrical system of the motor vehicle via a connection 32 of the gear housing 22.

[0038] The electric motor 15 has a metallic motor housing 34. The motor housing 34 is designed as a pole pot with a circumferential pot shell 36 and a pot base 38, wherein the pot base 38 is attached to the end face of the pot shell 36 and closes it. In the illustrated embodiment, the pot base 38 is joined to the pot shell 36 in a form-fitting and / or force-fitting manner, for example by crimping. Alternatively, the motor housing 34 or the pole pot can also be designed as a single-piece, i.e., one-piece or monolithic, deep-drawn part.

[0039] The pot base 38 is designed as a bearing plate with a spherical bearing 40. A rotor or rotor 40 is arranged within the motor housing 34 and is fixedly mounted to the motor shaft 28. The motor shaft 28 is rotatably mounted in the motor housing 34 by the rotor-side spherical bearing 42 and by a gearbox-side plain bearing 44. The free end of the motor shaft 28 is mounted in the gearbox housing 22 by an additional plain bearing 46.

[0040] Permanent magnets held stationary in the motor housing 34 or on the inner wall of the pot wall 36 form the stator 48 of the electric motor 15. A commutator 50 with commutator segments (not shown in detail) is arranged fixedly on the motor shaft 28 between the rotor 40 and the plain bearing 44. The commutator 50 is provided with (carbon) brushes 52 ( Fig. 4) of a brush system 54 comprising two brushes 52 in the exemplary embodiment.

[0041] The Fig. The brush system 54 shown in more detail in Figures 4 to 7 has a brush holder 56 which, with a holder wall 58, is positively inserted into the motor housing 34 via a housing opening 60. The housing opening 60 is arranged on the end face of the pot wall 36 opposite the pot base 38. A holder base 62 of the brush holder 56 practically completely covers the housing opening 60 of the motor housing 34, thus closing the motor housing 34. For this purpose, the holder base 62 projects beyond the housing opening 60 of the motor housing 34 with a radial support collar 64, with which the brush holder 56 sits on the opening edge of the pot wall 36.

[0042] In the area of ​​a central shaft opening 66 provided in the brush holder 56, this opening is enclosed by a sleeve-like, tubular, or hollow-cylindrical shaft guide 68 that projects axially beyond the holder base 62 in the direction of the gear 16. The shaft guide 68 projects into the inside of the housing of the brush holder 56 with a corresponding sleeve section 70.

[0043] The plain bearing 44 is arranged in the shaft guide 68. The motor shaft 28, which protrudes from the shaft guide 68 through the central shaft opening 66, closes the motor housing 34 with the inserted brush holder 56 as completely as possible, forming the smallest possible annular gap.

[0044] The brush holder 56 is designed as an injection-molded part, with the shaft guide 68 being integrally formed, i.e., monolithically, onto the support base 62. Furthermore, the plain bearing 44 is integrally formed, i.e., monolithically, onto the shaft guide 68 or onto the brush holder 56.

[0045] On the end face having the brush system 54, four radially projecting retaining tabs 72 with through holes for fastening screws 74 are formed on the opening edge of the motor housing 34, which are intended for screw connection to the gear housing 22.

[0046] Two connection contacts 76 are incorporated into the brush holder 56, which protrude axially upwards on the outside of the holder base 62 in the direction of the gear housing 22. The connection contacts 76 are designed, for example, as blade contacts and are automatically contacted with the motor control unit 30 when the electric motor 15 is inserted or plugged into the gear housing 22. The connection contacts 76 are overmolded with the material of the brush holder 56 or the holder base 62.

[0047] For example, in the Fig. As can be seen in Figure 5, one end of the connection contacts 76 facing the rotor 40 is designed as an insulation displacement connection, into which electrical connecting leads 78 are pressed and contacted. These connecting leads 78 belong to or lead to interference suppression elements in the form of choke coils (interference suppression chokes) 80 and an interference suppression capacitor 81.

[0048] The brushes 52 are electrically contacted with the commutator 50 during operation. Each brush 52 is arranged in a corresponding (brush) holder (brush shaft) 82 of the support base 62, which partially surrounds the brushes along their longitudinal sides in a form-fitting manner. The positions of the brushes 52 and their respective holders 82 are offset by 180° with respect to the motor shaft 28 or the shaft guide 68, as shown in FIG. Fig. 4. In other words, the position of the brushes 52 relative to the shaft guide 68 is mirror-inverted. The brushes 52 are pressed radially against the commutator 50, for example, using a spring element (not shown in detail). For this purpose, the shaft guide 68 has corresponding openings or apertures 84 in the area of ​​the brushes 52.

[0049] Each of the brushes 20 is electrically connected to a choke 80 via a connecting wire 86. The chokes 80 themselves are connected to the connecting contacts 76 via any additional electronic components, such as capacitors or resistors.

[0050] The plain bearing 44 is formed by additional radial walls of the shaft guide 68, which enclose or surround the motor shaft 28 as sliding surfaces. The plain bearing 44 has a sliding ring 88 supporting the motor shaft 28, which is held centrally in the shaft guide 68 by means of four radial struts 90. A pocket 92 is formed between each two adjacent struts 90. A pocket 92 is understood to be a closed (radial) wall between two webs 90, which has a smaller thickness or wall thickness than the struts 90. The pockets 92 are provided with reference numerals in the figures merely as examples.

[0051] The claimed invention is not limited to the exemplary embodiments described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art within the scope of the disclosed claims without departing from the subject matter of the claimed invention. In particular, all individual features described in connection with the various exemplary embodiments can also be combined in other ways within the scope of the disclosed claims without departing from the subject matter of the claimed invention. List of reference symbols 2 window regulators 4 window pane 6 Adjustment drive 8 Adjusting mechanism 10 carriers 12 cable pull 14 Guide rail 15 Electric motor 16 worm / spur gears 18 rope drum 20 pulleys 22 Gearbox housing 24 Worm gear / gear part 26 Worm shaft 28 Motor shaft 30 Engine control 32 connection 34 Engine housing 36 Pot wall 38 Pot bottom 40 rotor 42 spherical bearings 44 plain bearings 46 plain bearings 48 Stator 50 Commutator 52 brush 54 brush system 56 brush holders 58 support wall 60 housing opening 62 support floor 64 support collars 66 shaft opening 68 Shaft guide 70 cuff section 72 retaining tab 74 Fixing screw 76 connection contact 78 connecting cable 80 interference suppression choke 81 Suppression capacitor 82 brush holders 84 Breakthrough 86 connecting wire 88 sliding ring 90 strut 92 bag X Vehicle longitudinal direction Y vehicle transverse direction Z Vehicle height direction P Disc position O Disclosure S Closed position

Claims

[1] Brush system (54) for an electric motor (15), comprising a brush holder (56) with at least one brush holder (82) for the displaceable mounting of a brush (52), which is arranged around a central shaft opening (66) for the passage of a motor shaft (28), wherein the brush holder (56) has an integrally formed sliding bearing (44) for the sliding mounting of the motor shaft (28) in the region of the shaft opening (66). [2] Brush system (54) according to claim 1, characterized by that the brush holder (56) has a tubular shaft guide (68) with the shaft opening (66) and with the sliding bearing (44). [3] Brush system (54) according to claim 1 or 2, characterized by that the brush holder (56) is designed as an injection-molded part. [4] Brush system (54) according to one of claims 1 to 3, characterized bythat the sliding bearing (44) has a sliding ring (88) which supports the motor shaft (28) and is connected to the brush holder (56) via a number of radial struts (90). [5] Brush system (54) according to claim 4, characterized by that a pocket (92) is formed between each two adjacent struts (90). [6] Electric motor (15) for an adjustment drive (6) of a motor vehicle, comprising a pot-shaped motor housing (34) in which a stator (48) and a rotor (40) arranged on a motor shaft (28) in a shaft-fixed manner and a commutator (50) ground by a brush system (54) according to one of claims 1 to 5 are accommodated. [7] Electric motor (15) according to claim 6, characterized by that the motor housing (34) has a housing opening (60) for the motor shaft (28) on one side, and that the brush holder (56) closes the motor housing (34). [8] Adjustment drive (6) for a motor vehicle, comprising a transmission housing (22) with a transmission part (24) accommodated therein, and an electric motor (15) according to claim 6 or 7, wherein the transmission part (24) is driven by the electric motor (15) via the motor shaft (28). [9] Adjustment drive (6) according to claim 8, characterized by that the brush holder (56) is at least partially inserted into the gear housing (22) in such a way that the sliding bearing (44) is arranged within the gear housing (22). [10] Window lifter (2) for a motor vehicle, comprising an adjusting drive (6) according to claim 8 or 9 as window lifter drive.

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