Brush system for an electric motor with a commutator

Abstract

The invention relates to a brush system for an electric motor with a commutator. The brush system comprises a brush and a spring element with a movable spring leg, which, when in an operative connection with the brush, exerts a spring force on the brush for pressing the brush against the commutator. The brush channel has a recess as a guide contour for the spring leg on its rear side facing away from the commutator. The recess is designed such that when the spring leg is guided in the recess and the brush is inserted into the empty brush channel, the spring leg slides along the recess and moves into a locking position. In the locking position, the spring leg blocks the movement of the brush and secures the brush at a distance from the commutator in a form-fitting and / or force-fitting manner. The spring leg can be moved from the locking position (S) into a resting position in which the operative connection (W) is established, wherein the movement of the brush (8) is released.

Description

Technical Field

[0001] The present invention relates to a brush system for an electric motor having a commutator, the brush system comprising at least one brush radially guided in a brush channel and having connecting lines, and a spring element having a movable spring leg which, when operatively connected to the brush, exerts a spring force on the brush in order to hold the brush against the commutator. The invention also relates to an electric motor having such a brush system. Background Art

[0002] Motor vehicles today often have a plurality of adjustment components, such as seat adjustments, actuable locks, window regulators and / or adjustable sliding roofs, which can be moved between different adjustment positions by means of respectively assigned electric motors as adjustment drives.

[0003] In contrast to brushless electric motors, electric motors with a fixed commutator typically have two or more brushes sweeping across a number of commutator diaphragms, which transfer current to the rotor windings that rotate with the motor shaft. The diaphragms commutate the current winding by winding, generating torque on the motor shaft (rotor shaft) relative to the stator poles, which are usually stationary.

[0004] Brushes are traditionally rectangular rods pressed from carbon powder (optionally with metal particles). Due to sliding contact with the commutator diaphragm, the brushes wear during operation of the electric motor. To maintain contact between the brushes and the commutator despite wear, the brushes are usually supported displaceably in a cylindrical brush channel by a mechanical spring under its spring force. This allows the brushes to automatically realign toward the commutator over their service life. The spring force can be generated, for example, by a torsion spring, compression spring, leaf spring, or coil spring.

[0005] The respective brush channels are usually arranged on a carrier (brush carrier), for example in the form of a brush plate, which together with the brushes and springs as well as the necessary electrical contacting and any interference suppression elements (coils, chokes, capacitors) forms a brush system.

[0006] Such brush systems are usually designed as preassembled (sub)assemblies that are installed as a whole during the assembly of the actuator or electric motor. This means that the brush system is typically (pre)assembled separately, i.e., from the electric motor, and then delivered to the electric motor production line.

[0007] When assembling an electric motor, when applying a preferably annular brush system to the commutator, it is necessary to press the colliding brushes against the spring force in such a way that they are held in the brush channel, so that the commutator can be guided through the central opening of the brush system without colliding with the brushes. In the event of a collision, there is a risk of edge breakage of the brushes, which would prevent uniform wiping or contact of the commutator diaphragm during operation.

[0008] For example, retaining rings are known for retaining the brushes, which keep the guide or connection space required for the commutator free during assembly. However, such retaining rings must be used as additional components before assembling the motor and then removed again after assembly, making the assembly of the electric motor time-consuming and expensive.

[0009] Alternatively, it is also possible to install the brush, particularly in combination with a torsion spring, in the brush channel without additional components to prevent it from slipping. For this purpose, the brush typically has additional grooves and / or retaining contours that, in conjunction with mating contours on the channel side, limit the brush's insertion distance. This allows the brush to be locked in the brush channel and prevented from slipping out. However, manufacturing such brushes requires relatively complex and therefore expensive (carbon) pressing tools. Summary of the Invention

[0010] The object of the present invention is to specify a particularly suitable brush system for an electric motor. In particular, it should be possible to assemble the electric motor as simply and cost-effectively as possible. It is also an object of the present invention to specify an electric motor having such a brush system that can be manufactured as simply and cost-effectively as possible.

[0011] According to the invention, with respect to the brush system, this object is achieved by the features of claim 1, and with respect to the electric motor having this brush system, by the features of claim 10. Advantageous embodiments and developments are the subject matter of the dependent claims. The advantages and embodiments listed with respect to the brush system can also be transferred to the electric motor, and vice versa.

[0012] The brush system according to the invention is configured, suitable for and established for an electric motor with a commutator, in particular an electric motor for a motor vehicle. The brush system comprises at least one brush with a connecting line which is radially guided in a brush channel (brush barrel, brush holder, English: brush card). The brush is made in particular of an electrically conductive material, preferably of pressed carbon in powdered or granular form, wherein the connecting line and the brush are connected to one another, for example, via compacted contacts. For example, the line end of the connecting line on the brush side is placed in a conductive powder of the brush, and the powder is subsequently solidified to form a brush. Alternatively, the connecting line is introduced into the brush, for example by means of drilling and subsequent gluing. In this case, the connecting line is embodied, for example, as a braided conductive rope (braided braid) and has a litz wire end at the line end opposite the brush as a connection area for the DC power supply.

[0013] The brush system also has a spring element associated with the brush or brush channel. The spring element is particularly embodied as a torsion spring having a fixed or stationary spring leg (retaining leg) and a movable spring leg (abutment leg), wherein the movable spring leg, in its operative connection with the brush, applies a spring force to the brush in order to cause the brush to abut against the commutator. In other words, the spring element is embodied as a brush pressure spring for elastically electrically contacting the brush with the commutator. The direction of movement of the brush or the direction of brush pressure is here towards the position of the commutator when the electric motor is in the assembled state. In other words, during operation of the electric motor, the brush is pressed against the commutator by means of the spring element to form a sliding contact. The commutator is thus in electrical contact with the brush, in particular with the connecting line, and a current can flow through the rotor including the commutator to energize it.

[0014] At the rear side facing away from the commutator, the brush channel has a recess as a guide profile for the spring leg. According to the present invention, the recess or guide profile is designed so that when the spring leg is guided in the recess, that is, when the spring leg is placed or hung in the recess and the brush is pushed into the empty brush channel, the spring leg slides along the recess and moves into a locked position. In this locked position, the spring leg blocks the movement of the brush and fixes the brush to the commutator in a form-locked and / or force-locked manner. This means that in the locked position, the brush is held in a non-slip manner. The spring leg can move from the locked position to a resting position that realizes an active connection, wherein the movement of the brush in the active connection is released. This means that when the spring leg moves from the locked position to the resting position, the force-locked and / or form-locked connection for fixing the brush is released. This achieves a particularly suitable brush system.

[0015] The cutouts and spring legs thus create a retaining element that, in the locked position, retains the brush in a parked position, preventing it from colliding with the rotor or commutator during assembly of the electric motor. Thus, the spring element or spring leg prevents brush movement in the locked position and, in an operative connection, presses the brush against the commutator. This eliminates the need for additional components (retaining rings) and shaping on the brush compared to the prior art. The brush is therefore preferably designed as a cuboid, enabling its manufacture using a particularly simple pressing tool. This translates to lower production costs for the electric motor.

[0016] The conjunction “and / or” is to be understood here and below in such a way that the features linked by this conjunction can be configured not only jointly but also as alternatives to one another.

[0017] A "positive fit" or a "positive connection" between at least two parts connected to one another is understood here and hereinafter to mean that the connected parts are held together in at least one direction by direct interlocking engagement of the contours of the parts themselves or by indirect interlocking engagement via an additional connecting part. The "locking" of the mutual movement in this direction is therefore due to the shape.

[0018] A "non-positive connection" or "non-positive connection" between at least two parts connected to one another is understood here and hereinafter to mean that the connected parts are prevented from sliding apart due to friction forces acting between them. Without the "connecting force" that causes this friction force (that is, the force that presses the parts together, such as thread force or weight itself), the non-positive connection cannot be maintained and is therefore released.

[0019] The cutouts, in combination with the spring legs, are designed, in particular, as an automatic parking system for the brushes during assembly of the electric motor. This automatic parking system simplifies assembly of the brush system and the electric motor. For example, during assembly of the brush system, the spring legs are first inserted into the cutouts, and then the brushes, provided with the connecting lines, are introduced into the brush channel. During this process, the brushes are pressed against the spring legs, which prevent the brushes from being pushed in along the guide of the cutouts until the spring legs reach a locking position, thereby preventing the brushes from being pushed in and securing them in their position or location within the brush channel.

[0020] The cutouts or locking positions are designed so that the fixed or parked brushes in the locking position do not protrude from the commutator-side openings of the brush channel. Thus, in the locking position, the brushes are held or fixed in a collision-proof manner with respect to the assembly of the brush system to the rotor or commutator.

[0021] In subsequent steps, the rotor or commutator is assembled as normal, with the automatic parking system retaining the brushes outside the commutator's connection space. This connection space, in particular, is the central recess in the brush system. This prevents the brushes from negatively impacting assembly, as they do not occupy the future commutator space due to the automatic parking system. Furthermore, the risk of brush edge breakage due to collisions with the commutator is avoided in a structurally simple manner.

[0022] Only when the commutator is in its final position, i.e., after the brush system is mounted or assembled with the rotor, is the operative connection with the spring element established, so that its spring force is applied to the brushes in the direction of the commutator. Here, the spring legs are released from the locking position and moved into the pressing position or operative connection, bringing the brushes into contact with the commutator. For example, a device is provided in the production line that pre-presses the brushes against the commutator and thereby moves the spring legs into the locking position. In a subsequent workstation, another device releases the spring from the locking position in the recess in order to further press the brushes.

[0023] In the following, the descriptions of spatial directions are also described in particular in the coordinate system of the electric motor. "Axial" or "axial direction" is understood here and below in particular as a direction parallel to (coaxial with) the motor axis of the electric motor, i.e. perpendicular to the end side of the commutator or the brush system. Correspondingly, in this and below, "radial" or "radial direction" is understood to be a direction oriented perpendicularly (transversely) to the motor axis of the electric motor, in particular along the radius of the commutator or the electric motor. In this case, the radial direction is parallel to the longitudinal direction of the brush channel and parallel to the direction in which the spring element presses the brush in the active connection. "Tangential" or "tangential direction" is understood here and below in particular as a direction along the circumference of the commutator or the electric motor (circumferential direction, azimuthal direction), i.e. perpendicular to the axial direction and the radial direction.

[0024] The brush channel at least partially forms a form-fitting receptacle for the brushes, within which the brushes (relative to the motor shaft or the rotor shaft of the electric motor) can be moved radially toward the commutator. The brush channel is designed, for example, as a hollow cylinder with a substantially rectangular cross-section. A suitable clearance fit is established between the brush channel and the brushes, ensuring relatively secure guidance of the brushes and preventing wedging. This also results in relatively low friction.

[0025] The spring element (mechanical spring) is advantageously in direct mechanical contact with the brush in the operative connection and is preferably suitable and designed to compensate for operational wear of the brush, i.e., for shortening of the brush due to frictional wear. The spring element thus tracks the brush in the brush channel in the direction of contact with the brush. The rate of brush wear is relatively slow compared to the rotational speed of the commutator. To be able to track shortening of the brush over its service life, the spring element or its spring arm or spring leg interacting with the brush preferably has a spring travel corresponding to the brush length.

[0026] In an advantageous embodiment, the brush is clamped and held in the brush channel in the locked position of the spring leg. The clamping provides a non-destructive and simple fixation of the brush. In particular, the clamping can be released effortlessly, allowing the spring leg to be easily adjusted from the locked position to an operative connection.

[0027] In a preferred embodiment, in the locked position of the spring legs, the brush is clamped, in particular axially, in the brush channel by means of the spring legs. This means that the form-locking and / or force-locking connection for clamping the brush is particularly oriented axially. Preferably, in the locked position, the spring legs press against the brush from above. "From above" here means that the securing force is directed toward the channel bottom of the brush channel.

[0028] In a preferred refinement, the cutout is designed so that the spring leg deflects axially when it is guided along the cutout. In other words, the cutout is designed so that the spring leg can axially avoid the brush when it is inserted into the empty brush channel. The spring leg is particularly moved axially upward, that is, away from the bottom of the brush channel. This means that the locking position is arranged axially offset upward. This makes the spring leg easily accessible in the locked position, making it particularly simple and cost-effective to move the spring leg from the locked position to the resting position.

[0029] In one possible embodiment, the recess is oriented in at least one lateral channel wall of the brush channel. The channel wall is oriented parallel to the axial and radial planes. This makes it easy to position or arrange the spring legs in the recess.

[0030] An additional or further aspect of the present invention provides that the recess, in particular its contour, has a substantially C-shaped geometry. Preferably, the "lower C-arc" extends at an oblique angle relative to the channel bottom of the brush channel. In particular, the recess thus has essentially a half-droplet shape or a half-pear shape in the axial and radial planes. A droplet shape or a pear shape is understood here to mean, in particular, a circle that tapers on one side.

[0031] In one possible embodiment, the spring element is placed on a supporting pin arranged outside the brush channel. The spring element is in particular designed as a torsion spring or a torsion spring, which has a cylindrical middle part formed according to a helical wire. The ends of the helical wire, which preferably protrude tangentially, are each transformed into a rod-shaped spring leg. In this case, due to the middle part, the two spring legs are moved relative to each other into a preferred angular position. The spring element is preferably made in one piece from an elastic material, for example from spring steel. The swing axis, i.e. the axial axis of the middle part, is oriented in particular perpendicular to the brush. In this case, the middle part is placed on a supporting pin as a support point on the brush plate formed outside the brush channel. This enables a particularly space-saving arrangement on the brush plate of the brush system.

[0032] The brush channel, for example, has lateral guide slots for radially guiding the spring legs in the active connection. The recess is particularly arranged axially above such a guide slot. This means that the locking position and the active connection occur at two axially different heights. In a conceivable embodiment, the support pin has a mechanical stop for the spring element, wherein the spring element is arranged spaced apart from the stop in the locked position of the spring leg, and wherein the spring element is arranged on the stop in the active connection of the spring leg. During the adjustment of the spring leg from the locked position into the active connection, the spring element is thus pushed axially against the stop on the support pin. This allows for a particularly compact arrangement of the guide slots and the recess.

[0033] In one advantageous embodiment, the free ends of the spring legs are bent into a U-shape. In both the locked position and the operative connection, the spring legs rest against the brushes with the aid of the first vertical U-leg, with the second vertical U-leg being radially spaced apart from the first U-leg. The first vertical U-leg thus essentially forms the contact leg for the brushes, with the second U-leg being designed, in particular, as a gripping leg for a tool, with which the spring legs can be moved from the locked position into the operative connection. In other words, the second U-leg serves as a gripping point for moving the spring legs.

[0034] In a preferred application, the brush system is installed in an electric motor with a commutator. The use of the brush system according to the invention simplifies motor assembly and, in particular, ensures particularly simple and cost-effective production of the electric motor. The electric motor according to the invention is preferably a component of a control drive for a motor vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The embodiments of the present invention are explained in more detail below with reference to the accompanying drawings, in which:

[0036] Figure 1 A brush system with a spring element is shown in a perspective view, the spring legs of the spring element being arranged in a parked position;

[0037] Figure 2 A brush system is shown in a perspective view, wherein the spring legs are operatively connected to the brushes;

[0038] Figure 3 showing the brush channel and brushes in side view; and

[0039] Figure 4 The insertion of the brushes into the brush channels is shown schematically.

[0040] In all figures, parts and dimensions that correspond to one another are always provided with the same reference numerals. DETAILED DESCRIPTION

[0041] exist Figure 1 and 2 , a brush system 2 for an electric motor 4 having a commutator (not shown in detail) is shown. The brush system 2 comprises two brush channels 6, in each of which a brush 8 is radially guided. The brushes 8 are pressed from powdered or granular carbon, with a connecting line 10 being introduced into each brush 8. During operation of the electric motor 4, the brushes 8 are in electrically conductive contact with the commutator or the commutator diaphragm by means of sliding contact.

[0042] To generate a radially directed compressive force between the brushes 8 and the commutator, the brush system 2 has an associated spring element 12 for each brush 8. The spring element 12 is designed as a torsion spring having a fixed or stationary spring leg (retaining leg) 14, a movable spring leg (contact leg) 16, and a center section 18 connecting the spring legs 14, 16. The cylindrical center section 18 is formed as a helical wire and rests or plugs onto a support pin 20 arranged outside the respective brush channel 6.

[0043] The free ends of the spring legs 16 resting against the brush 8 are bent into a U-shape, wherein the vertical U-legs that transform into the middle part 18 are connected to the active connection W( Figure 2 ) is in direct mechanical contact with the brush 8.

[0044] The spring legs 14 are designed as counterholders for the spring element 12, by means of which the central part 18 is held essentially rotationally fixed, so that when the spring element 12 is stressed and the spring legs 16 are thus pivoted radially outward about the pivot axis defined by the support pin 20, a (spring) force acting radially inwards (i.e. directed towards the commutator) is applied to the brushes 8. The spring legs 14 are supported on a (support) wall of the brush system, which is not specifically designated.

[0045] The brush channel 6 is designed in the form of a hollow cylinder with a substantially rectangular cross section and thus forms a positive-locking receptacle for the brush 8. A clearance fit is preferably provided between the brush channel 6 and the brush 8. The side walls of the brush channel 6 have radially oriented longitudinal slots as guide slots 22. In the operatively connected state, the spring legs 16 are at least partially arranged inside the guide slots 22 ( Figure 2 ).

[0046] During operation of the electric motor 4, each brush 8 is worn down by sliding contact with the commutator, thereby shortening its length. As long as the brush 8 is not resting against the commutator, it offers no significant resistance to the spring legs 16 in the active connection W, causing the brush 8 to be pushed within the brush channel 6 in the direction of the brush pressure. The movement is interrupted only when the brush 8 rests with a force-locking fit against the outer circumference of the commutator. During this process, the spring element 12 at least partially relaxes.

[0047] The brush channel 6 has a substantially C-shaped recess 24 as a guide contour on the channel wall with the guide slot 22 toward the outer periphery (rear side) of the brush system 2. The recess 24 is arranged axially above the guide slot 22 open to the outer periphery. Figure 3 and Figure 4 As can be seen in FIG, the “lower C-arc segment” is oriented at an oblique angle relative to the channel bottom of the brush channel 6. In particular, the recess 24 therefore has a substantially half-drip shape or half-pear shape in the axial and radial planes.

[0048] During assembly of the electric motor 4, the brush system 2 is first equipped with the spring element 12, wherein Figure 1 As shown in FIG, the spring element 12 is first arranged at the upper end of the support pin 20 so that the spring legs 16 are arranged in the C-bend or C-arc of the recess 24. Subsequently, the brush 8 is pushed radially from the inside into the empty brush channel 6 against the subsequent brush pressing direction.

[0049] Especially from Figure 4 As can be seen in FIG, the spring legs 16 guided in the recess 24 avoid the insertion movement of the brush 8 in the radial and axial directions and are pushed axially upwards along the recess contour. Figure 4 In FIG, the brush 8 and the spring leg 16 are indicated by dashed lines at the beginning of the evacuation movement and by solid lines at the end of the evacuation movement, wherein the pushing movement and the resulting evacuation movement are indicated by arrows.

[0050] At the end of the retracting movement, the spring legs 16 are in a locking position S. In this locking position S, the brushes 8 are clamped axially from above in the brush channel 6 in a force-locked and / or form-locked manner, thereby preventing insertion and securing the brushes 8 in their position within the brush channel 6. The locking position S thus prevents the respective brushes 8 from slipping out or sliding toward the inner or outer periphery of the brush channel 6. This frees up a central recess in the brush system 2, allowing the commutator or the rotor of the electric motor 4 carrying it to be easily and collision-freely inserted and assembled. In other words, the brushes 8 do not negatively impact assembly because, due to their respective locking positions S, they do not occupy the future space of the commutator. The recess 24 and the spring legs 16 thus create a parking system for the brushes 8 during assembly of the electric motor 4.

[0051] Immediately after the rotor or commutator is assembled, the spring legs 16 are released from the locking position S and the central part 18 of the spring element 12 is axially pushed onto the support pin 20 as far as the stop 26. In this position, the spring legs 16 are arranged at the level of the guide slots 22, wherein the spring legs 16 are finally moved into the active connection W, i.e., into mechanical contact with the brush 8. As a result, a spring force is exerted on the brush 8 in the brush-pressing direction, so that the brush 8 and its associated contact surface are pressed against the commutator in accordance with the function.

[0052] The present invention is not limited to the above-described embodiments. On the contrary, those skilled in the art may derive other variations of the present invention therefrom without departing from the subject matter of the present invention. In particular, all individual features described in conjunction with the embodiments may also be combined with one another in other ways without departing from the subject matter of the present invention.

[0053] Reference Signs List

[0054] 2 Brush system

[0055] 4 electric motors

[0056] 6 brush channels

[0057] 8 brushes

[0058] 10 Connection lines

[0059] 12 Spring elements

[0060] 14 Spring Legs

[0061] 16 Spring Legs

[0062] 18 middle part

[0063] 20 Load pin

[0064] 22 Guide Gap

[0065] 24 blank space

[0066] 26 Stop

[0067] S locked position

[0068] W action connection

Claims

1. A brush system (2) for an electric motor (4) having a commutator, the brush system comprising: At least one brush (8) with a connecting line (10) guided radially in a brush channel (6), and a spring element (12) with a movable spring leg (16) which, in its operative connection (W) with the brush (8), exerts a spring force on the brush in order to hold the brush against the commutator. wherein the brush channel (6) has a recess (24) as a guide contour for the spring leg (16) on the rear side facing away from the commutator, - wherein the recess (24) is designed such that when the spring leg (16) is guided in the recess (24) and the brush (8) is pushed into the empty brush channel (6), the spring leg (16) slides along the recess (24) and moves into a locking position (S) in which the spring leg (16) blocks the movement of the brush (8) and secures the brush (8) at a distance from the commutator in a form-fitting and / or force-fitting manner, and - wherein the spring leg (16) is movable from the locking position (S) into a rest position in which the operative connection (W) is established, wherein the movement of the brush (8) is released.

2. The brush system (2) according to claim 1, It is characterized by: In the locking position (S) of the spring leg (16), the brush (8) is clamped and held in the brush channel (6).

3. The brush system (2) according to claim 1 or 2, It is characterized by: In the locking position (S) of the spring leg (16), the brush (8) is axially clamped and held in the brush channel (6) by means of the spring leg (16).

4. The brush system (2) according to any one of claims 1 to 3, It is characterized by: The cutout (24) is designed such that the spring leg (16) is axially deflected when the spring leg (16) is guided along the cutout (24).

5. The brush system (2) according to any one of claims 1 to 4, It is characterized by: The recess (24) is provided in at least one lateral channel wall of the brush channel (6).

6. The brush system (2) according to any one of claims 1 to 5, It is characterized by: The recess (24) has a substantially C-shaped geometry.

7. The brush system (2) according to any one of claims 1 to 6, It is characterized by: The spring element (12) rests on a bearing pin (20) arranged outside the brush channel (6).

8. The brush system (2) according to claim 7, It is characterized by: The supporting pin (20) has a mechanical stop (26) for the spring element (12), wherein in the locking position (S) of the spring leg (16), the spring element (12) is arranged spaced apart from the stop (26), and wherein in the operative connection (W) of the spring leg (16), the spring element (12) is arranged on the stop (26).

9. The brush system (2) according to any one of claims 1 to 8, It is characterized by: The free end of the spring leg (16) is bent into a U shape.

10. An electric motor (4) comprising a commutator and a brush system (2) according to claim 1.

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