DE102008044138A1 - Carbon brush for commutated electro-direct current motor, has commutator with bearing surface, where bearing surface has bearing surface radius with rib - Google Patents

Abstract

The carbon brush (1) has a commutator with a bearing surface (14). A rib (2) is arranged on the bearing surface, and is also arranged to the main axes (15,16) of the bearing surface at an angle (alpha). The bearing surface has a bearing surface radius with the rib. The bearing surface radius has a value, which is up to 0.5 millimeter larger than a commutator radius.

Description

The The invention relates to a carbon brush for commutating Electric DC motors and a corresponding commutating Electric DC motor.

such commutating electric DC motors with carbon brushes and commutator are well known and become, for example in facilities of motor vehicles, such as in adjusting drives and the like used.

• • Fertigungstoleranzen aufgrund unterschiedlicher Materialien, z. B. Grundkörper aus Kunststoff und Kohlenbürsten aus einem Verbund von Grafit, Kupfer sowie einem Bindemittel
• • Toleranzen zwischen beiden Einzelteilen aufgrund unterschiedlicher Wärmeausdehnungskoeffizienten der unterschiedlichen Materialien, sowie z. B. die Wasseraufnahme von Kunststoff
• • Prozesssteuerungen

In these DC motors, carbon brushes are kept in pots. The quivers are part of the body of the brush system, the carbon brushes are pressed by spring elements in or on the quiver on the commutator to build a physical or electrical contact. Carbon brushes and quivers are not interconnected and should be considered as individual parts between which a tolerance system exists for the following reasons.

• • Manufacturing tolerances due to different materials, eg. B. body made of plastic and carbon brushes from a composite of graphite, copper and a binder
• • Tolerances between the two parts due to different thermal expansion coefficients of the different materials, and z. B. the water absorption of plastic
• • process controls

• • Kohlenbürstenmaterial und -zusammensetzung Zeigt meist nur Erfolge bei Antrieben mit einer Vorzugsdrehrichtung, nicht jedoch bei Antrieben mit Reversierbetrieb, z. B. Fensterheber. Nachteilig sind ein höherer Preis und große fertigungstechnische Streuungen der Porösität der Bürstenkohlen durch Variation der Gefügedichte.
• • Zusätzliche Tränkung Hierbei werden so genannte Additive verwendet, die als Schmierstoff eine Gleitschicht zwischen Kohlenbürste und Kommutator aufbauen und damit einen ruhigeren Lauf (Geräuschminderung um ca. 1 dB(A)) gewährleisten sollen. Diese Additive werden mittels Tränkung oder Tamponierung in die Bürstenkohle eingebracht. Dies wird oftmals in Kombination mit so genannten PTS-(Press To Size)Kohlen eingesetzt. Nachteilig zeigt sich bei einigen Materialien eine zunehmende „Verpastung” des Kommutators über dessen Lebensdauer, was die Gefahr eines Ausfalls erhöhen kann. Ein weiterer Nachteil sind der höhere Preis und die Unsicherheit in einer Verbesserung des Geräuschverhaltens.
• • Einschleifen der Kohlenbürste Das Einschleifen der Kohlen ist eine Alternative zum Tränken. Das Einschleifen wird je nach Güte der Geräuschverbesserung bzw. Kosten eingesetzt und bringt ebenfalls einen Geräuschvorteil von ca. 1 dB(A) im Vergleich zu PTS-Standardkohlenbürsten. Es tritt keine Verpastung auf, eine bestimmte geometrische Form kann der Kohlenbürste durch Einschleifen aufgeprägt werden. Beim Einschleifen wird ein maximaler Einschleifradius verwendet, der in der Regel mindestens dem doppelten des Kommutatorradius entspricht.
• • Verringerung der Toleranzen im Köcher Ein Metallwerkstoff im Köcher anstelle eines Kunststoffes verringert die Toleranzen mit dem Nachteil eines höheren Preises. Auch eine Anpassung des Herstellungsprozesses erhöht die Kosten nachteilig.

Due to the slat jump on the commutator and shape tolerances, z. B. roundness, in the commutator / shaft, the carbon brush is excited to vibrate, which together with the spring element results in a vibratory system whose natural frequencies are determined by spring stiffness, material properties and excitation amplitude. This oscillatory system can cause disturbing noises by the tolerances present in the system quiver / carbon brush. There are various approaches to the problem of noise known:

• • Carbon brush material and composition Usually shows only success in drives with a preferred direction of rotation, but not in drives with reversing operation, eg. B. windows. Disadvantages are a higher price and large production-technological variations of the porosity of the brush coals by varying the structure density.
• • Additional impregnation In this case, so-called additives are used, which build up a lubricant layer between the carbon brush and commutator as a lubricant and thus ensure a smoother running (noise reduction by approx. 1 dB (A)). These additives are introduced by impregnation or tamponation in the brush coal. This is often used in combination with so-called PTS (Press To Size) coals. A disadvantage of some materials is an increasing "pasting" of the commutator over its lifetime, which can increase the risk of failure. Another disadvantage is the higher price and the uncertainty in improving the noise behavior.
• • Grinding the carbon brush Grinding the carbon is an alternative to watering. The grinding is used depending on the quality of the noise improvement or cost and also brings a noise advantage of about 1 dB (A) compared to standard PTS brushes. There is no mess on, a certain geometric shape of the carbon brush can be impressed by grinding. When grinding, a maximum grinding radius is used, which usually corresponds to at least twice the commutator radius.
• • Reduction of quiver tolerances A metal material in the quiver instead of a plastic reduces the tolerances with the disadvantage of a higher price. Also, an adjustment of the manufacturing process increases the costs adversely.

Currently become carbon brushes in commutating electric DC motors used, which has a special surface or tread, z. B. corrugated, have. This special surface has the task of mating the commutator / carbon brush as soon as possible ("einschleift"), to a good commutation or a better running noise to achieve. It is well known for a sensorless Positioning with electric DC motors with brushed Commutation to analyze the AC component of the motor current. At each commutator transition is by the Stromwend in the coils of the winding induces a current, which is a change of the current condition. This signal is called a current ripple and can be evaluated by appropriate electronics. Thus eight eight-way commutators correspond to eight full signals one revolution (calculated on four coil pairs with two carbon brushes). Thus, the position after a first referencing permanently be determined. For the evaluation, the amplitude, as well uses the energy contents of the fundamental and / or harmonics of the signal. To get an ideal signal, you need a carbon brush geometry, which ideally a long commutation period (corresponding to a large brush cover).

The patent DE 44 38 868 C2 describes a carbon brush for a DC motor, wherein the tread is designed such that two defined, as far apart, arranged substantially point or line-shaped bearing surfaces between the carbon brush and the commutator. For this purpose, the tread is provided centrally with a recess which is V-shaped or has the shape of a groove. The tread may also be arcuate. In this recess cracks may form due to the high vibration load described above.

In front It is therefore the object of the present invention to provide this background underlying, a carbon brush for a commutative Electric DC motor to improve.

According to the invention this task by a carbon brush with the features of claim 1 and a commutating electric DC motor solved with the features of claim 10.

Accordingly, becomes a carbon brush for a commutating electric DC motor provided with a commutator comprising: at least one tread; and at least one on the tread arranged rib, wherein the at least one rib at an angle is arranged to a major axis of the tread.

By the geometry of the tread of the carbon brush with the at least one rib at an angle to a major axis the tread is achieved that the carbon brush in operation in cooperation with the commutator of the commutating Electric DC motor aligns and moves in its holder, for example, a quiver, so twisted that they are in this tilted and thus the tolerance of the system quiver / brush consumes. The tilting in the quiver, however, takes place only so strong that by the spring element, a movement of the carbon brush Radial to the commutator without restrictions possible is. This is compared to the conventional solutions Achieved a significant reduction in noise performance.

Of the Angle can be an acute angle, preferably 5 °.

Under Main axes of the tread are here the two axes too one of which is parallel to the axis of rotation of the commutator and the other at right angles, d. H. tangential, to it goes.

The Use allows at least one rib on the tread a quick break in. There will be a groilling with three such Ribs preferred, which may have any cross-section. Preference is given to a triangular cross-section. Thereby becomes a point or better linear contact maintained between commutator and carbon brush. At three Ripping is also in production-related deviations in height the ribs as even as possible Edition achieved.

at According to one embodiment, the at least one rib has a Tread radius, which up to 0.5 mm larger as the commutator radius is. This can have a value which up to 0.5 mm larger than a commutator radius is. The tread radius is only slightly larger as the commutator radius, preferred are up to 0.5 mm, more preferred is that it is at least 0.15 mm larger. Thereby will be an even faster adaptation to the geometry of the commutator reached. In addition, there is a very large Brush cover, which as described above allows a required good ripple current. It will furthermore a more extensive edition of the carbon brush achieved on the commutator than in a two-point support surface. In addition, the carbon brush is on in their freedom of movement the commutator surface through this tread radius limited, as for example in a one-point edition the case is. A smaller movement on the commutator surface again, a lower noise level (typically 1 ... 2 dB (A).

at In one embodiment, the at least one tread is centrally through a substantially perpendicular to her running Recess in at least two treads, each with at least shared a single rib. Under single ribs here are themselves meant from the division of a rib devoted parts.

The Recess may be V-shaped.

at In one embodiment, one of each is at least two Single ribs in the transition into the recess with an outer radius Mistake. This makes the carbon brush especially light slide between two successive lamellae of the commutator and thus contribute to reducing the noise level.

Farther it is preferred that in each case at a transition of a Bottom of the recess to a respective one of the at least two single ribs an inner radius is arranged, which for stability of the carbon material in the recess serves and cracking prevented. By a combination with the above Tread radius can reduce the depth of the recess which also gives greater stability results.

One inventive commutating electric DC motor with a commutator exhibits at least two of the ones described above Carbon brushes on.

The Carbon brushes are especially for commuting Electric DC motors suitable for reversing Operation are provided.

The Invention will be described below with reference to an embodiment with reference to the accompanying figures of the drawing closer explained. Hereby shows:

1 a plan view of a tread of a first embodiment of the carbon brush according to the invention;

1a a schematic, perspective and enlarged view of the carbon brush after 1 ;

2 a plan view of a tread of a second embodiment of the carbon brush according to the invention;

2a a side view of the second embodiment according to 2 ;

2 B a schematic perspective view of the second tread after 2 ;

3 a schematic perspective view of the carbon brush 2 with a commutator;

4 a side view too 3 ;

5 a side view of a first embodiment of a carbon brush according to the invention;

6 a plan view of a tread of the first embodiment according to 5 ;

7 a side view of a second embodiment of the carbon brush according to the invention;

8th a perspective view of the first and second embodiments according to 1 and 2 together with a commutator; and

9 a plan view of the arrangement according to 8th ,

In the figures, the same or functionally identical components are provided with the same reference numerals, unless stated otherwise. For orientation, a coordinate system with x, y and z axis is inserted in each figure. The x-axis runs parallel to a motor / commutator axis 6 (please refer 3 ). The y-axis extends in a longitudinal direction of the carbon brush 1 radial to the motor / commutator axis 6 (please refer 4 ), wherein the z-axis is tangent to the direction of rotation of a commutator 7 (please refer 4 ).

In 1 is a first embodiment of a carbon brush according to the invention 1 illustrated. A first major axis 15 a tread 14 runs in the direction of the z-axis and thus in the direction of rotation of a commutator 7 ( 4 ). A second major axis 16 the tread 14 runs in the direction of the x-axis and the motor / commutator axis 6 ( 3 and 4 ). The tread 14 is with ribs 2 and spaces 3 (please refer 1a ) Mistake. The ribs run to the main axes 15 respectively. 16 the tread 14 at an angle α which is acute and preferably 5 °.

1a shows an example of the carbon brush 1 with the tread 14 that a grooving with three ribs 2 and two spaces 3 having. Due to the special shape touches the carbon brush 1 the in 3 . 4 illustrated commutator 7 in a point of contact 4 ,

To create two touch points 4 ' is the tread 14 through a central recess 5 in 2 divided, resulting in this division single ribs 2 ' from the ribs 2 result. This two-point support by means of two points of contact 4 ' , which can also be lines of contact, ensures a constant contact between carbon brush 1 and commutator 7 ,

2a illustrates a side view of the second embodiment according to 2 , The carbon brush 1 is shown in its longitudinal direction along the y-axis. The tread 14 or the single ribs 2 ' are circular arc provided with a tread radius R3, the center here at the intersection of y-axis and motor / Kommutatorachse 6 lies. The tread radius R3 is below with 7 explained in more detail.

2 B shows an enlarged view of 2 ,

3 shows the commutator 7 , the motor / commutator axis 6 and the carbon brush 1 pulled apart, taking 4 a side view of 3 represents. The commutator 7 has a commutator radius R4.

The recess 5 may be a groove, for example a V-shaped one. The recess is formed such that the commutator 7 is touched only at the outermost points, but not too deep, after a short break-in period, a flat contact with the commutator 7 to reach.

5 shows a side view of a first embodiment of an inventive carbon brush 1 , The recess 5 has at its edges in the transition from heads of single ribs 2 ' each a radius R1 and at its bottom side in transition to the feet of the individual ribs 2 ' each have a radius R2. The radii R1 allow a particularly easy sliding of the carbon brush 1 on the commutator 7 between its slats 8th (please refer 10 and 11 ). This dampens and reduces a noise level. The inner radii R2 serve the stability of the carbon material in the recess 5 and prevent cracking at these sites. A depth D of the recess 5 depends on the commutator diameter R4 (see 4 , A ratio of a carbon brush length H1 to a recess length H2 is given by the respective nature (parameters here: of the overall commutation system).

6 illustrates a plan view of the tread 14 of the first embodiment according to 5 , The single ribs 2 ' are on both sides of the recess 5 with gaps 3 arranged and are centered on the carbon brush bottom. The grooving can assume any geometry, preferably a triangular, but always in such a way that a point or better linear contact between the commutator 7 and carbon brush 1 is complied with. The number of grooves, ie ribs 2 . 2 ' and spaces 3 is arbitrary, preferably three, so that by production-related deviations in the height of the ribs 2 . 2 ' as even as possible an edition by at least two points on the commutator 7 he follows.

7 is a side view of a second embodiment of the carbon brush according to the invention 1 , Here is the tread 14 with the single ribs 2 ' provided with a tread radius R3, which is only slightly larger than the commutator radius R4. The tread radius R3 is preferably up to 0.5 mm larger than the commutator radius R4. It is particularly preferred that the tread radius R3 is not smaller than the commutator radius R4 + 0.15 mm. It is off 7 can be seen that the recess by the tread radius R3 fails in depth, whereby the recess 5 continues to gain stability.

8th is a perspective view of the first and second embodiments according to 1 and 2 together with the commutator and 9 shows a plan view of the arrangement according to 8th , The commutator 7 is shown in more detail here. On an insulator body 9 are slats 8th with intermediate commutator grooves 13 arranged. The slats 8th are with winding hooks 12 connected. It is a carbon brush 1 represented, which (see 9 ) by the rotational movement of the commutator 7 around the motor / commutator axis 6 and the interaction of ribs 2 with the slats 8th is twisted by an angle. This angle is here the angle α, around which the ribs 2 . 2 ' to the main axis 15 respectively. 16 are arranged. By the rotary movement of the commutator 7 become the initially slanted ribs 2 . 2 ' aligned and thus the carbon brush 1 twisted about its longitudinal axis in y-direction. The carbon brush 1 is in a quiver 10 that is only schematic and not completely in 9 shown is held. By twisting, she tilts in the quiver 10 , However, this canting is only so strong that by a spring element (not shown), a movement of the carbon brush 1 radially in y-direction to the commutator 7 without restrictions is possible. The tilting dampens a vibration of the system carbon brush 1 - quiver 10 - Spring element and thus reduces the noise level.

The Invention is not limited to the specified embodiment limited, but modifiable in many ways.

So it is conceivable, for example, that the quiver 10 rotated by an angle on the commutator 7 is arranged, the ribs 2 . 2 ' on the carbon brush 1 in the direction of the first main axis 15 can be arranged.

1

carbon brush

2

rib

2 '

single rib

3

gap

4, 4 '

point of contact

5

recess

6

Motor / commutator

7

commutator

8th

lamella

9

insulator body

10

quiver

11

connecting cable

12

winding hooks

13

Kommutatornut

14

tread

15

First main axis

16

Second main axis

D

recess depth

H1

carbon length

H2

recess length

R1

outer radius

R2

inner radius

R3

Tread radius

R4

Kommutatorradius

x, Y Z

coordinates angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4438868 C2 [0006]

Claims (10)

Carbon brush ( 1 ) for a commutating electric DC motor with a commutator ( 7 ), comprising: at least one tread ( 14 ); and at least one on the tread ( 14 ) arranged rib ( 2 ), wherein the at least one rib ( 2 ) at an angle (α) to a major axis ( 15 . 16 ) of the tread ( 14 ) is arranged. Carbon brush ( 1 ) according to claim 1, characterized in that the at least one tread ( 14 ) with the at least one rib ( 2 ) has a tread radius (R3). Carbon brush ( 1 ) according to claim 2, characterized in that the tread radius (R3) has a value which is up to 0.5 mm larger than a Kommutatorradius (R4). Carbon brush ( 1 ) according to claim 2 or 3, characterized in that the tread radius (R3) has a value which is up to 0.5 mm, but at least 0.15 mm, greater than a Kommutatorradius (R4). Carbon brush ( 1 ) according to at least one of the preceding claims, characterized in that the at least one tread ( 14 ) centrally through a substantially perpendicular to its recess ( 5 ) in at least two treads ( 14 ) each with at least one single rib ( 2 ' ) is shared. Carbon brush ( 1 ) according to claim 5, characterized in that the recess ( 5 ) Is V-shaped. Carbon brush ( 1 ) according to claim 5 or 6, characterized in that in each case one of the at least two single ribs ( 2 ' ) in the transition into the recess ( 5 ) is provided with an outer radius (R1). Carbon brush ( 1 ) according to at least one of claims 5 to 7, characterized in that in each case at a transition of a bottom of the recess ( 5 ) to a respective one of the at least two single ribs ( 2 ' ) An inner radius (R2) is arranged. Carbon brush ( 1 ) according to at least one of the preceding claims, characterized in that the angle (α) is an acute angle, which is preferably 5 °. Commutating electric DC motor with a commutator ( 7 ) with at least two carbon brushes ( 1 ) according to at least one of the preceding claims.