Brush system for an electric motor

Abstract

The invention relates to a brush system (1) of a commutator motor (19) comprising: - at least one carbon brush (4) having a contact surface (4a) facing a commutator (3), a bearing surface (4b) opposite this contact surface, and a connection line (7); - a brush shaft (5) receiving the carbon brush (4), which shaft has a longitudinal shaft slot (9) via which the connection line (7) is guided; and - a spring element (6) which exerts a spring force on the carbon brush (4) in its working position (PA) in the longitudinal direction (L) of the shaft, wherein the carbon brush (4) is clamped in the brush shaft (5) in a pre-assembly position (PV) by means of the spring element (6) or by means of a elastically bending spring arm (13).

Description

[0001] The invention relates to a brush system according to the preamble of claim 1. Such a brush system is known, for example, from DE 103 55 982 A1. The invention further relates to an electric motor, hereinafter referred to as a commutator motor, with such a brush system.

[0002] Motor vehicles typically have a number of adjustment components, such as seat adjustment, an operable lock, window lifts, or an adjustable sunroof, each of which can be moved between different positions by means of a respective electric motor-driven adjustment drive. Each adjustment component is actuated by a gear mechanism, such as a worm gear, driven by a DC electric motor with a rotor-side commutator, a drive-side worm on the motor shaft, and a drive-side worm gear. The gear mechanism is arranged in a gear housing, to which the electric motor (commutator motor) is flanged via its motor housing. Plug contacts are located on one end of the electric motor and are electrically connected to mating contacts arranged in the gear housing.The plug contacts are arranged in a brush system of the electric motor, typically made of plastic.

[0003] In contrast to a brushless electric motor, an electric motor with a fixed commutator (brushed) typically has two or more brushes (carbon brushes) enclosing a number of commutator segments, which transfer the electrical current to the windings of a rotor rotating with the motor shaft. The segments create a current commutation from winding to winding, which generates a torque on the motor shaft (rotor shaft) in relation to the usually fixed magnetic poles of the stator. The plug contacts are electrically connected (contacted) to the brushes (carbon brushes) by means of stranded connecting wires.

[0004] Such a brush, referred to below as a carbon brush, is typically a cuboid-like, rod-shaped carbon body pressed from carbon powder - possibly together with metal particles. The connecting lead, typically in the form of a carbon strand with several individual wires, is pressed into this. Due to the sliding contact with the commutator segments, the respective carbon brush is subject to abrasion during operation of the electric motor. To nevertheless maintain contact between the carbon brush and the commutator, the carbon brush is usually slidably mounted in a quiver-like brush shaft by means of a mechanical spring under the effect of this spring force, so that the carbon brush is automatically adjusted. The spring force can be generated, for example, by a leg spring, compression spring, leaf spring, or roller spring.

[0005] The respective brush shaft is often arranged on a carrier (brush carrier), for example designed as a brush plate, which together with the respective brush carbon and the necessary electrical contact means as well as any interference suppression elements (coils, chokes, capacitors) forms the so-called brush system.

[0006] When assembling the electric motor, when applying the preferably ring-shaped brush system to the commutator, it is necessary to press the colliding brush carbons against the spring force of the spring and to hold them back in the brush shaft in such a way that the commutator can be guided through a central opening of the brush system without colliding with the respective brush carbon.

[0007] For the detachable holding of the brush carbon in an assembly position, it is known from DE 10 2006 045 841 A1 to design the brush carbon, which is pre-tensioned by means of a retaining spring, with a notch into which a holding piece of a spring element engages.

[0008] To retain the brush carbon, it is known from DE 10 2015 220 897 A1 to provide the brush shaft (brush holder) with a longitudinal slot that has a narrow section through which the connecting cable only passes once the operative connection between the spring element and the brush carbon is established. The narrow section is arranged at a position along the longitudinal slot in the shaft such that the brush carbon does not protrude into a joining space of the brush system that accommodates the commutator, thus preventing it from colliding with the commutator during its assembly.

[0009] During assembly of the familiar brush system and the electric motor, the brush carbon, equipped with the connecting lead, is inserted into the brush shaft, and the spring element is mounted. The commutator is then installed as intended, with the constriction holding the connecting lead and thus the brush carbon out of the commutator's joint space. Once the commutator is in its final position, the operative connection with the spring element is established, with the spring force exerted on the brush carbon in the direction of the commutator, and the connecting lead is pushed through the constriction.

[0010] Manufacturing tolerances of the constriction and / or the connecting cable, which is designed as a carbon strand, are problematic here. If the coordinated dimensions of the constriction and the diameter of the connecting cable deviate due to process variations, there is a risk that the connecting cable will not be clamped properly in or at the constriction of the shaft's longitudinal slot. This can lead to unwanted rejects of parts of the brush system.

[0011] The invention is based on the object of providing a particularly suitable brush system for a commutator motor that is advantageously simple and, in particular, reliable to assemble. Furthermore, an electric or commutator motor with such a brush system is to be provided that is as simple and cost-effective to manufacture as possible.

[0012] With regard to the brush system, the stated object is achieved according to the invention by the features of claim 1, and with regard to an electric motor having the brush system by the features of claim 10. Advantageous embodiments and further developments are the subject of the respective subclaims.

[0013] The brush system according to the invention for a commutator motor, i.e., for an electric motor with a commutator, comprises at least one carbon brush, which is made, for example, from pressed carbon dust, and to which a flexible, stranded connecting wire is connected or preferably integrated into the carbon brush. In other words, the carbon brush comprises a carbon body and a stranded carbon wire pressed into it, in particular tangentially to the motor axis, as a connecting wire. The carbon brush has a contact surface facing a commutator and a contact surface opposite it.

[0014] The brush system further comprises a number of brush shafts corresponding to the number of brush carbons, which are also referred to below as brush or carbon quivers. Each brush shaft, in which the brush carbon is accommodated and guided, has a longitudinal shaft slot through which the connecting cable is routed. The longitudinal shaft slot is suitably provided in a lateral shaft wall of the brush shaft. The longitudinal shaft slot is expediently formed between two shaft legs of the brush shaft that are axial relative to the motor axis. The brush system also comprises a spring element that exerts a spring force on the brush carbon in the longitudinal direction of the shaft when the brush carbon is in its working position against the mounted commutator.

[0015] The brush system has a flexible spring arm that rests against the brush carbon and exerts a clamping force on it, in particular in a shaft transverse direction of the brush shaft, in order to hold the brush carbon in its pre-assembly or parking position within the brush shaft and thus to keep it out of the joining space of the commutator.

[0016] The flexible spring arm is provided at a free end of a shaft leg flanking the longitudinal slot of the brush shaft, i.e., delimiting the longitudinal slot. The flexible spring arm is designed to exert the clamping force on the brush carbon in the direction of a lateral shaft wall of the brush shaft opposite the longitudinal slot. The flexible spring arm clamps the brush carbon in the brush shaft reliably but releasably. This clamping effect is particularly effective in a pre-assembly state when the brush carbon has not yet reached or is not intended to reach its intended contact with the commutator, in order to be able to reliably assemble the commutator or brush system without the brush carbon hindering such assembly by colliding with the commutator.

[0017] According to an advantageous development, the flexible spring arm has, on the free end side of the brush, a contact edge oriented toward the brush carbon. For this purpose, the flexible spring arm suitably has a contact edge running at an acute angle to the shaft longitudinal direction. With the contact edge, the flexible spring arm undercuts (engages behind) or overlaps a brush edge formed between a side surface of the brush carbon and its contact surface, in particular a brush edge running axially relative to a motor axis (rotational axis of the commutator). This side surface is expediently the surface of the brush carbon that faces the shaft longitudinal slot.

[0018] The spring arm presses the carbon brush against the opposite side surface, thus reliably clamping the carbon brush in the desired pre-assembly position in the brush shaft. The aforementioned (acute) angle is suitably between 10° and 30°, preferably between 15° and 20°, and more preferably between 17.5° and 22.5°.

[0019] The brush system further comprises a spring element that exerts a spring force on the brush carbon in the longitudinal direction of the shaft. The spring element is a leg spring mounted on a support pin located outside the brush shaft. The spring element has a spring leg, which is fixed, in particular, to the brush shaft (outside), and a movable contact leg that rests against the contact surface of the brush carbon. The spring element, which is operatively connected to the brush carbon, exerts a spring force on the brush carbon in order to move the brush carbon, which is guided in the brush shaft, toward the commutator. This direction of movement is radial, relative to the rotational axis of the commutator motor.

[0020] In a preferred application, the brush system is mounted in an electric motor, particularly a two- or four-pole one, with a commutator (commutator motor). The brush system expediently comprises at least two brush carbons, which are arranged point-symmetrically to the commutator, particularly on opposite sides of the commutator. Preferably, the brush system comprises four brush carbons, each offset by 90° from one another.

[0021] The use of a brush system according to the invention simplifies motor assembly, resulting in particularly cost-effective production of the commutator motor. The commutator motor is preferably a component of an adjustment drive of a motor vehicle. The adjustment drive, which may be a window lifter, for example, has, for example, a gear driven by the commutator motor, which is operatively connected to an adjustment part, such as a vehicle window.

[0022] An embodiment of the invention is explained in more detail below with reference to a drawing. In the drawings: Fig. 1 in a schematic plan view a representation of a brush system of an electric or commutator motor with oppositely arranged brush carbons, each of which is resiliently mounted in a brush shaft against a commutator, Fig. 2 in a perspective representation the brush carbon in the brush shaft with flexurally elastic spring arm and with a spring element with a spring leg in the park position, Fig. 3 in a sectional representation the brush carbon clamped in the brush shaft by means of the flexurally elastic spring arm in its pre-assembly or park position, Fig. 4 in a view according to Fig. 3 the brush carbon in its working position within the brush shaft, Fig. 5 in a detail view according to the Figures 3 and 4the flexible spring arm in or with a rear grip for the brush carbon rotated in the direction of an opposite shaft wall of the brush shaft, and Fig. 6 in schematic representation a window lifter as an adjustment drive of a vehicle window pane, with the electric or commutator motor and with an actuating mechanism coupled to it in terms of drive technology.

[0023] Corresponding parts and sizes are provided with the same reference numerals in all figures.

[0024] Fig. 1 shows schematically a brush system 1 of or for an electric motor, also referred to below as a commutator motor ( Fig. 6). The brush system 1 comprises an approximately circular ring-shaped brush plate 2, which is arranged concentrically around a commutator 3 of the electric motor, which is rigidly coupled to a motor shaft. The brush system 1 has two brush carbons 4, which are in electrically conductive contact with the commutator 3 during electromotive operation in the manner of sliding contacts. During operation, the motor shaft (rotor shaft) and thus the commutator 3 rotate about a common motor or rotation axis R, which is illustrated as a cross.

[0025] Furthermore, the brush system 1 comprises two brush shafts or quivers 5, which are arranged opposite one another in the exemplary embodiment and are radially offset by 180° with respect to the rotational axis R, in which the brush carbons 4 are guided in a radially displaceable manner. The brush carbons 4 and the respectively associated brush shaft 5 are arranged point-symmetrically on the brush plate 2 with respect to the rotational axis R or the commutator 3 in the exemplary embodiment. In order to generate a contact force along a radially directed brush contact direction B between the brush carbons 4 and the commutator 3, the brush system 1 has for each brush carbon 4 a Fig. 1 only schematically indicated associated spring element 6.

[0026] The brush carbons 4 are used to supply current to the commutator 3, which rotates during operation, and thus to the windings (not shown in detail) of a rotor of the electric motor. For this purpose, the brush carbons 4 each have a connecting line 7, also referred to as a carbon strand, for current transmission on an upper side facing away from the brush plate 2 or - as in the exemplary embodiment - on a brush side. The connecting line 7, which is pressed into the carbon body (not shown in detail) to form the brush carbon 4, in particular tangentially to the rotation axis R, is connected to a control unit ( Fig. 6 ) of the electric motor.

[0027] In electromotive operation, the brush carbon 4 rests with its contact surface 4a on the commutator 3 (working position), while the spring element 6 rests on a Fig. 1 unspecified contact surface radially opposite the contact surface 4a ( Fig. 2 ) of the brush carbon 4 in order to press the brush carbon 4 within the associated brush shaft 5 in the brush pressure direction B.

[0028] In the Figures 2 to 4 1 shows a section of the brush system 1 with the brush plate 2 and with a brush shaft 5 with the brush carbon 4 arranged therein. The respective brush shaft 5 is formed onto the brush plate 2 and designed in the manner of a radially extending hollow cylinder with a rectangular cross-section for the essentially form-fitting reception of the brush carbon 4, which is guided in the brush shaft 5. The approximately cuboid-shaped brush carbon 4 is arranged within the brush shaft 5. The radially inner contact surface 4a of the brush carbon 4 is rounded to complement the outer contour of the commutator 3.

[0029] In the working position ( Fig. 4) a spring or contact leg 6a of the spring element 6 rests against the contact surface 4b of the brush carbon 4 opposite the contact surface 4a. The spring element 6 is a leg spring which sits on an axial support pin 8 arranged outside the brush shaft 5 and which is integrally formed on the brush plate 2. A spring leg 6b ( Fig. 3 and 4 ) of the spring element 6 rests on the outside of the brush shaft 5 and is fixed there. The spring element 6 causes the brush carbon 4, which is subject to wear during operation, to be guided radially against the commutator 3 in the brush pressure direction B.

[0030] The brush shaft 5, in which the respective brush carbon 4 is accommodated and guided, has a shaft longitudinal slot 9, which is oriented in the brush pressure direction B and, in the exemplary embodiment, runs radially with respect to the rotation axis R. The connecting cable 7 is routed via the shaft longitudinal slot 9. The shaft longitudinal slot 9 is provided in one of the lateral shaft walls 10, 11 of the brush shaft 5. The shaft walls 10, 11 run in the brush pressure direction B, i.e., radially with respect to the rotation axis R in the exemplary embodiment. The shaft wall having the shaft longitudinal slot 9, here the shaft wall 10, is located on the side opposite the spring element 6 and its support pin 8, on which the other shaft wall 11 runs. The shaft longitudinal slot 9 is formed between two shaft legs 10a, 10b of the lateral shaft walls 10 of the brush shaft 5.

[0031] As in the Figures 2 and 3As illustrated, the spring or contact leg 6a of the spring element 6 is located in a pre-assembly or parking position Pv in a notch or groove 12 of a wall 11a, which is arranged, for example, in the axial extension of the shaft wall 11 facing the support pin 8 on the brush plate 2 and is in turn suitably formed onto the latter.

[0032] A flexible spring arm (finger, mandrel) 13 is provided on the brush shaft 5, which exerts a force on the brush carbon 4 in a shaft transverse direction of the brush shaft 5. This clamps the brush carbon 4 in the brush shaft 5. The flexible spring arm 13 is provided at a free end of the first shaft leg 10a of the shaft wall 10, which delimits the shaft longitudinal slot 9 of the brush shaft 5 and faces away from the brush plate 2 of the brush system 1. In other words, the flexible spring arm 13 is located on the (upper) shaft leg 10a whose axial distance from the brush plate 2 is greater than the distance of the other (lower) shaft leg 10b. The spring arm 13 is a component of the brush shaft 5, which preferably together with the brush plate 2 is a plastic injection-molded part, i.e. a molded part made of a plastic.

[0033] As from Fig. 3, which represents the parking position Pv of the brush carbon 4 within the brush shaft, and Fig. 4 , which represents the working position PA of the brush carbon 4, the flexurally elastic spring arm 13 is oriented or deflected in the direction of the lateral shaft wall 11 of the brush shaft 5 opposite the shaft longitudinal slot 9 in order to exert the clamping force. In other words, the clamping force exerted by the flexurally elastic spring arm (finger, mandrel) 13 acts in such a way that the brush carbon 4 is pressed (pressed) within the brush shaft 5, at least in the west, against the shaft wall 11 opposite the shaft longitudinal slot 9. This clamping force acts in the pre-assembled state in which the brush carbon 4, in its parked position Pv within the brush shaft 5, does not rest against the commutator 3, so that the commutator can be guided unhindered into or through the central recess of the brush plate 2 or the brush plate can be guided over the commutator 3.

[0034] As from Fig. 5 As can be seen comparatively clearly, the flexible spring arm 13 has a contact edge or surface 14 on its free end oriented in the direction of the brush carbon 4. Relative to the brush pressure direction B, which here corresponds to the radially extending shaft longitudinal direction L, the contact edge 14 of the flexible spring arm 13 extends at an acute angle α. The angle is suitably between 15° and 25°, preferably between 17.5° and 22.5°.

[0035] With the contact edge 14, the flexible spring arm 13 undercuts or engages behind the brush carbon 4. The undercut (engagement) takes place on a brush edge 15 formed between a side surface 4c of the brush carbon 4 and its contact surface 4b ( Fig. 4). Relative to the rotational axis R, which corresponds to the motor axis or the rotational axis of the commutator 3, this brush edge 15 runs axially. The corresponding side surface 4c is the surface of the brush carbon 4 facing the shaft longitudinal slot 9. By means of the spring arm 13, the brush carbon 4 is reliably clamped in the desired pre-assembly position in the brush shaft 5.

[0036] In one of the Fig. 6The adjustment drive 16 shown is an electric window lifter for a window pane 17 of a motor vehicle. The adjustment drive 16 is expediently integrated into a vehicle door (not shown in detail) of the motor vehicle. The adjustment drive 16 comprises a control unit 18, which is suitably formed by a microcontroller with implemented control and evaluation software. The control unit 18 is provided and configured for the signal-based control of the commutator motor (electric motor) 20 with an integrated brush system 1, which has a motor shaft 19. The commutator motor 20, in which the brush system 1 is arranged in a manner not shown in detail, acts on the window pane 17 via an adjustment mechanism 21, in particular in the form of a single- or double-strand cable window lifter.

[0037] When the electric or commutator motor 20 is actuated, the window pane 17 is moved. The window pane 17 can be reversibly moved between a closed position S, which corresponds to the highest possible position x, and an open position O, which represents the lowest possible position x. In these positions S and O, the window pane 17 is indicated by dashed lines. In contrast, the window pane 17 is shown in a half-open intermediate position with solid lines.

[0038] To determine the current position x of the window pane 17, a ring magnet 22 is arranged on the motor shaft 19, which ring magnet has an even number of magnetic poles distributed around the circumference. A Hall sensor 23, which serves as a position transmitter, interacts with the ring magnet 22. When the motor shaft 19 rotates, this sensor detects a fluctuating magnetic field of the ring magnet 22 and generates a correspondingly pulsating Hall signal H, which is output to the control unit 18. By counting and summing the pulses of the Hall signal H, the control unit 18 determines a position measurement that is proportional to the position x of the window pane 17. An actuating process, in which the window pane 17 is to be moved from its closed position S towards the open position O, is triggered by a vehicle user pressing a button 24.

[0039] In summary, the invention relates to a brush system 1 with at least one brush carbon 4 having a connecting cable 7 and a brush shaft 5 having a longitudinal slot 9 for passing the connecting cable 7, as well as a spring element 6 and a flexurally elastic spring arm 13 that rests against the brush carbon 4 in its pre-assembly or parking position Pv and exerts a clamping force thereon. It further relates to a commutator motor 20 having such a brush system 1 as a (DC) electric motor.

[0040] The invention is not limited to the exemplary embodiment described above. Rather, other variants of the invention can also be derived therefrom by those skilled in the art without departing from the subject matter of the 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.

[0041] Thus, the brush carbon 4 can also be clamped in the pre-assembly or parking position Pv within the brush shaft 5 by means of the spring or contact leg 6a, for example, by guiding it between the upper shaft wall and the brush carbon 4. For the working position PA, the spring or contact leg 6a is inserted into the Fig. 3 or 4 shown position.

[0042] In addition, the solution described can be used not only in the specific application case described, but also in a similar design in other automotive applications, such as door and tailgate systems, vehicle locks, adjustable seat and interior systems, and other electrical drives in the vehicle. List of reference symbols

[0043] 1Brush system 2Brush plate 3Commutator 4Brush / brush carbon 4aContact surface 4bContact surface 4cSide surface 5Brush shaft / quiver 6Spring element / leg spring 6aSpring / contact leg 6bSpring leg 7Connecting cable 8Support pin 9Longitudinal shaft slot 10Shaft wall 10a(upper) shaft leg 10b(lower) shaft leg 11Shaft wall 11aWall 12Notch / groove 13Spring arm 14Contact edge / surface 15Brush edge 16Adjustment drive 17Window pane 18Control unit 19Motor shaft 20Commutator / electric motor 21Adjusting mechanism 22Ring magnet 23Hall sensor 24Button BBrush pressure direction HHall signal LLongitudinal shaft direction OOpening position PA Working position PvPre-assembly / parking position RMotor / rotation axis SClosing position UMotor voltage xDisc position

Claims

1. Brush system (1) of a commutator motor (19), having - at least one carbon brush (4) having a contact surface (4a) facing a commutator (3), and having a bearing surface (4b) lying opposite the said contact surface, and having a connection line (7), - a brush shaft (5) which receives the carbon brush (4) and has a shaft longitudinal slot (9), via which the connection line (7) is guided - a spring element (6) which exerts a spring force in the shaft longitudinal direction (L) on the carbon brush (4) in the working position (PA) thereof, - wherein the spring element (6) is a leg spring which is placed on a support pin (8) arranged outside the brush shaft (5), wherein the spring element (6) has a fixed spring leg (6b) and a movable bearing leg (6a) which bears against the bearing surface (4b) of the carbon brush (4), - wherein, in a preassembly position (PV), the carbon brush (4) is clamped in the brush shaft (5) by means of a flexurally elastic spring arm (13) which bears against the carbon brush (4) and exerts a clamping force thereon, - wherein the shaft longitudinal slot (9) is formed between two shaft limbs (10a, 10b) of the brush shaft (5), characterized in that the flexurally elastic spring arm (13) is provided at a free end of a shaft limb (10a) flanking the shaft longitudinal slot (9) of the brush shaft (5), and - in that the flexurally elastic spring arm (13) is designed to exert the clamping force on the carbon brush (4) in the direction of a shaft wall (11) of the brush shaft (5) lying opposite the shaft longitudinal slot (9).

2. Brush system (1) according to Claim 1, characterized in that the shaft longitudinal slot (9) is formed in a lateral shaft wall (10) of the brush shaft (5).

3. Brush system (1) according to Claim 1 or 2, characterized in that the flexurally elastic spring arm (13) is designed to exert the clamping force on the carbon brush (4) in a shaft transverse direction of the brush shaft (5).

4. Brush system (1) according to one of Claims 1 to 3, characterized in that the flexurally elastic spring arm (13) has, on the free end side, a bearing edge (14) oriented in the direction of the carbon brush (5).

5. Brush system (1) according to one of Claims 1 to 4, characterized in that the flexurally elastic spring arm (13) has a bearing edge (14) which runs at an acute angle (α) with respect to the shaft longitudinal direction (L) and by way of which the flexurally elastic spring arm (13) undercuts a brush edge (15) formed between a side face (4c) of the carbon brush (4) and the bearing surface (4b) thereof.

6. Brush system (1) according to Claim 5, characterized in that the bearing edge (14) of the flexurally elastic spring arm (13) runs at an acute angle (α), in particular at an angle α = (20 ± 2.5)°, with respect to the shaft longitudinal direction (L).

7. Electric motor (20), in particular of a window lifter of a motor vehicle, having a brush system (1) according to one of Claims 1 to 6.

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