EP2277255A2

EP2277255A2 - Electric machine, in particular commutator machine

Info

Publication number: EP2277255A2
Application number: EP09742115A
Authority: EP
Inventors: Michael Bayer; Sven Hartmann
Original assignee: Robert Bosch GmbH
Current assignee: SEG Automotive Germany GmbH
Priority date: 2008-05-09
Filing date: 2009-05-07
Publication date: 2011-01-26
Also published as: US20110109192A1; US8917008B2; JP5669727B2; DE102008001702A1; WO2009135897A3; JP2011520415A; WO2009135897A2; KR20110021762A

Abstract

The invention relates to an electric machine, in particular a commutator machine (10), the carbon brushes (14) of which cooperate with a commutator (13) to supply the rotor with current, the carbon brushes (14) being continuously provided or provided in layer sections with different additives such as scouring material, lubricants or similar. To achieve a longer service life for the carbon brushes (14), a maximum of half, preferably less than half of all the carbon brushes (14) of the machine have a significant fraction of an additive, said fraction differing from that of the other carbon brushes (14).

Description

Electric machine, in particular commutator machine

description

The invention relates to an electrical machine, in particular a commutator machine according to the preamble of patent claim 1.

State of the art

Mechanically commutating commutator machines are often used in motor vehicles. For example, high-performance direct-current motors are used to start internal combustion engines in vehicles. The current passes through one or more pairs of brushes on a commutator and from there into the armature winding of the machine. The so-called carbon brushes usually consist of a sintered material, which mainly contains copper and graphite components. These carbon brushes and the commutator are subject to wear during operation. In this case, starters are typically for a short-term operation with 30 000 to 60 000

Designed switching cycles.

To save fuel, starters for higher loads and for longer running times, such as for a start-stop operation of the internal combustion engine, are required more recently. It is important that for a long life of Carbon brushes lubrication and cleaning on the tread of the commutator is optimally matched. Due to the long running time of the brushes, the removed brush material and also the excess lubricant on the commutator must be removed again. In order to achieve a good cleaning of the surface of the commutator, different substances are mixed into the carbon brushes, which ensure that the surface of the commutator has as constant as possible a clean and also lubricating surface.

In a known manner, the carbon brushes are mixed with a certain amount of cleaning agents as an additive. That provides for a degree of constant

Cleaning of the surfaces, but associated with a certain wear of the carbon brushes, which increases accordingly with increasing proportion of cleaning agents. Through a homogeneous distribution of the cleaning agent in all carbon brushes of the machine acts at the same coal contact pressure, the cleaning agent on all carbon brushes evenly.

In order to ensure a correspondingly longer service life of the carbon brushes at higher switching cycles, the wear behavior of the carbon brushes must be optimized by the best possible coordination of lubrication and cleaning of the commutator. It is known to provide the carbon brushes with at least two layer sections that extend beyond the height and width of the carbon brushes away to their tread. A layer section is provided to improve the Stromkommutierung with a higher graphite content and another layer section as a power layer for power management with a higher copper content. Furthermore, it has already been proposed that the carbon brushes have a cleaning agent section in at least one of the aforementioned layer section whose cleaning agent content is higher than in the other

Layer portion of carbon brushes is. Since all carbon brushes of the DC motor are also constructed the same, the effect of the various admixtures adds up accordingly. Therefore, the various parameters such as wear, lubrication, commutation and the like can only be set relatively coarse.

The present solution seeks to set one or more of the aforementioned parameters on the carbon brushes much more accurately.

Disclosure of the invention The machine according to the invention with the characterizing features of claim 1 has the advantage that the additive is no longer evenly distributed in all carbon brushes for a parameter acting on the entire commutator parameters such as lubrication or cleaning, but in only one carbon brush or only in a few carbon brushes

Machine is concentrated. In this way it is possible, for a coarse setting of the corresponding parameter, first to provide all other carbon brushes with an equal concentration of the additive and to significantly increase or reduce the concentration for fine adjustment of the parameter in a carbon brush. Since, in a corresponding manner, various additives can be finely dosed independently of each other in the carbon brushes, a further advantage results in uniform wear on all carbon brushes and a significant increase in the number of switching cycles on a starter motor.

The measures listed in the dependent claims are advantageous

Refinements and developments of the features specified in claim 1.

Thus, an optimization of the fine tuning for setting a carbon brush parameter is achieved in that the proportion of the additive in the at least one carbon brush is relatively at least 10 percent higher than in the other carbon brushes. Expediently, furthermore, the differing proportion of the additive is introduced only in one layer section of the carbon brush, all carbon brushes of the machine having two or more layers. In this case, the layer section advantageously extends over the height and width of the carbon brush to its tread. Predominantly, the additive is a cleaning agent for cleaning the

Commutator surface.

Since with increasing abrasion of the carbon brushes of the brush springs generated contact pressure decreases on the commutator, it is advantageous in an embodiment of the invention that the proportion of the additive from the tread of the carbon brush for

Pigtail out changed, preferably increases as Putzmittel- share. In a further development of the invention, it is also expedient that at least one of the carbon brushes of the machine is provided with a portion of a further additive deviating significantly from the remaining carbon brushes. Conveniently, the further additive is a lubricant. Furthermore, it is optimized - A -

Parameter setting advantageous if one or a part of the carbon brushes a higher proportion of an additive, preferably a cleaning agent, and another or another part of the carbon brushes has a higher proportion of the second additive, preferably a lubricant. Alternatively, it is also possible, when using carbon brushes in the direction of rotation of the commutator several layer sections to introduce the one additive in one of the layer sections and the other additive in another layer section.

Brief description of the drawings

Details of the invention are explained in more detail below by way of example with reference to FIGS. Show it:

FIG. 1 shows a commutator motor in cross-section in the commutator region, FIGS. 2a and 2b show a carbon brush with and without an additive,

Figure 3 a and 3b show a carbon brush with two layer sections without and with

additives

FIG. 4 shows the four carbon brushes of an engine with an additive in one

Layer section of a carbon brush, Figure 5 shows four carbon brushes of an engine with a first additive in a first

Carbon brush and a second additive in a second carbon brush and Figure 6 shows an alternative embodiment for a motor with six carbon brushes.

Embodiments of the invention

In Figure 1, a starter motor is denoted by 10, which is shown as a commutator in its cross section at the commutator end. The starter motor 10 is used for cranking internal combustion engines in motor vehicles, which are equipped for example with a start-stop system. He has a pole housing 11 that has six unrecognizable, permanent magnetic poles on its inner circumference, which interact with a runner, not shown. At the rear end of the rotor carries on its rotor shaft 12, a commutator 13 for powering the rotor windings. For this purpose, the commutator 13 is provided at its periphery with fins 20 which cooperate with four carbon brushes 14. The carbon brushes 14 are each received with a brush spring 15 in a brush holder 16 axially displaceable and pressed with its tread 21 against the commutator. The four brush holders are accommodated on a brush plate 17, which in turn is attached to the front end of the starter motor 10 and over the pole housing 11 to ground. The carbon brushes 14 are each provided at their rear portion with a pigtail 18. The carbon brushes 14 form two plus and two minus carbon brushes. The two plus carbon brushes 14 are contacted via their pigtails 18 with a plus terminal 19 and the minus carbon brushes are welded via their connecting leads 18 to a metal strip 17 a of the brush plate 17 and are thus grounded.

In the first exemplary embodiment according to FIG. 1, three of the four carbon brushes 14 have an identical material composition throughout. They consist of a sintered material that mainly contains copper and graphite components. In this case, copper serves for better electrical conductivity and graphite serves for better commutation at the commutator lamellae 20. FIG. 2a shows one of these three brushes. The brush material also contains other additives such as cleaning agents and

Lubricants in low concentration. This material composition of the three carbon brushes 14 is denoted by A 'in FIG. 2a. The lubricants in the carbon brushes 14 form a lubricating film on the surface of the commutator 13, which reduces the mechanical abrasion of the carbon brushes 14. Nevertheless, the commutator surface is increasingly contaminated by the abraded brush material unless it is cleaned continuously or at intervals. With a higher proportion of cleaning agent in all carbon brushes 14, however, the brush abrasion would be enhanced, and thus reduces the life of the carbon brushes 14.

To achieve the highest possible and equally long service life of all carbon brushes

Now, the cleaning performance is optimized by the fact that at the fourth carbon brush 14a a targeted fine adjustment of the cleaning effect takes place by the detergent portion is increased by at least 10 percent relative to the other carbon brushes 14 here. FIG. 2b shows the carbon brush 14a with the other material composition A'a. While the proportion of cleaning agent in the material A 'of the three carbon brushes according to FIG. 2a is about 0.5%, it is significantly increased in the material A'a of the fourth carbon brush 14a according to FIG. 2b at 0.7%.

In a second exemplary embodiment according to FIGS. 3 a and 3 b, the carbon brushes 14 are in a known manner in the direction of rotation of the commutator 13 in two layer sections A. and B divided. The accumulating first layer section A is here provided with an increased copper content for better current conduction and the second, running layer section B contains a higher graphite content for optimal commutation. The material in the layer section A is also with a small proportion of a cleaning agent and the material of the layer section B is with a small proportion of a

Lubricant provided.

In order to optimally adjust the wear behavior on the one hand and the cleaning behavior on the other hand on the carbon brushes 14 independently of one another, the fourth carbon brush 14a is changed in such a way that in its first layer section Aa of FIG

Cleaning agent content compared to the other carbon brushes 14 is significantly increased and that in the second layer section Bb, the lubricant content compared to the other carbon brushes 14 is significantly increased. In this solution, therefore, a first additive is contained in the first layer section and a second additive in a significantly higher concentration in the second layer section than in the remaining carbon brushes 14.

FIG. 4 likewise shows four carbon brushes 14, each having two layer sections A and B for a starter motor according to FIG. 1, in a third exemplary embodiment. While the material composition in the layer sections B of all brushes is the same, only in the layer section Aa of the fourth carbon brush 14a is the proportion of cleaning agent significantly higher than that of the layer sections A of the remaining carbon brushes 14.

In the exemplary embodiment according to FIG. 5, all carbon brushes are likewise provided with two layer sections A and B. There, however, only the first two have

Carbon brushes 14 a same material composition. In this case, the carbon brush 14a has an increased proportion of cleaning agent in its layer section Aa, and the carbon brush 14b has an increased lubricant proportion only in the layer section Bb. As the carbon brushes 14 become shorter and shorter with increasing service life due to wear, their contact pressure on the commutator 13 steadily decreases due to the longer spring travel of the brush springs 15. In order to ensure a sufficient cleaning of the commutator even then, takes on the carbon brush 14a of the cleaning agent content in the layer section Aa of the tread 21 of the carbon brush to the pigtail out. Alternatively or at the same time, it would also be possible, due to the decreasing pressure force on the carbon brushes, to remove the lubricant in the layer section Bb of the carbon brush 14b decrease from the tread to the pigtail out.

In the six-pole starter motor 10 according to Figure 1, the plus and minus carbon brushes 14 are each offset by 60 ° to each other. This leaves an angle of 120 ° between the two plus brushes and the two minus brushes. In powerful six-pole machines, however, six carbon brushes 14 are used, which are offset by 60 ° to each other. Again, the solution according to the invention can be used advantageously. FIG. 6 shows, as a further exemplary embodiment, the six carbon brushes of such a machine with two each

Layer sections A and B. While four of these six carbon brushes 14 are the same in their composition of matter, the two remaining carbon brushes 14a have a different composition of matter. Thus, in the layer section Aa of the two carbon brushes 14a an increased proportion of cleaning agent and in the layer section Bb each introduced an increased proportion of lubricant. The fine adjustment of the parameters cleaning and sliding takes place here via two carbon brushes 14a.

In principle, this solution can also be transferred to an electric machine with four carbon brushes, which is particularly advantageous when the two plus carbon brushes have different direction of rotation-dependent commutation behavior compared to the minus carbon brushes. In addition to a fine adjustment can thus be compensated in this way even commutation differences. In such a solution, a first portion 14a of the carbon brushes 14 is expediently provided with a higher proportion of one additive and a further portion 14b of the carbon brushes 14 with a higher proportion of another additive.

Alternatively, the carbon brushes 14 may also be provided with a third layer section C, as shown by dashed lines on the left carbon brush 14 in FIG. This layer C may contain other additives or no additives.

The invention is not limited to the illustrated embodiments. Thus, it is possible to concentrate the respective additive only in the selected carbon brushes 14a, 14b or in one of their layer sections Aa, Bb and to omit the additive in the other carbon brushes 14. It is also possible for brushes with several layer sections in the selected carbon brushes 14a, 14b to introduce an additive in both layer sections Aa and Bb of the carbon brush 14a with an increased proportion. Furthermore, it is possible to dose the selected carbon brushes with three different additives in carbon brushes with three layer sections higher. In principle, instead of a higher dosage, the proportion of an additive in the selected carbon brushes can also be significantly smaller than in the other carbon brushes. Due to the decreasing over the lifetime pressure force of the carbon brushes on the commutator, it is also possible within the scope of the invention not to introduce the respective additive over the entire height of the carbon brush but only over a lower part of the height.

As a cleaning agent usually natural ash or alumina are used. As a lubricant, e.g. Molypdehyde sulfide used. The invention is also applicable not only to starter motors for motor vehicles to achieve a longer life, but also good at commutator for other applications.

Claims

claims

Electric machine, in particular commutator machine (10), which is provided with carbon brushes (14) for powering a rotor, which cooperate with the slats (20) of a commutator (13), wherein the carbon brushes continuously or in layer sections (A, B ) with various additives (Aa, Bb) such as cleaning agents,

Lubricant, means for increasing the ohmic resistance or for increasing the electrical conductivity and the like is provided, characterized in that at most half, preferably less than half of all carbon brushes (14) of the machine (10) is significantly different from the remaining carbon brushes (14 ) has a different proportion of an additive (Aa, Bb).

2. Electrical machine according to claim 1, characterized in that only one carbon brush (14a) of the machine (10) of the other carbon brushes (14) deviating proportion of the additive (Aa).

3. Electrical machine according to claim 1 or 2, characterized in that the proportion of the additive (Aa) in the at least one carbon brush (14a) is relatively at least 10 percent higher than in the other carbon brushes (14).

4. Electrical machine according to one of the preceding claims, characterized in that the differing proportion of the additive is introduced only in one layer section (Aa; Bb) of the carbon brush (14a).

5. Electrical machine according to claim 4, characterized in that the layer section (Aa) over the height and width of the carbon brush (14a) away up to their

Tread (21) is enough.

6. Electrical machine according to one of the preceding claims, characterized in that the additive is a cleaning agent for cleaning the commutator surface.

7. Electrical machine according to one of the preceding claims, characterized in that the proportion of the additive from the running surface (21) of the carbon brush (14a) for pigtail (18) out, preferably as a proportion of cleaning agent increases or as a lubricant proportion decreases.

8. Electrical machine according to one of the preceding claims, characterized in that at least one of the carbon brushes (14b) of the machine (10) with a significantly different from the other carbon brushes (14) portion of another additive (Bb) is provided.

9. Electrical machine according to claim 8, characterized in that the further additive is a lubricant.

10. Electrical machine according to one of the preceding claims, characterized in that a first part (14a) of the carbon brushes (14) has a higher proportion of one additive, preferably a cleaning agent, and another part (14b) of the carbon brushes (14) a higher Proportion of another additive, preferably a lubricant has.

11. Electrical machine according to claims 1 to 9, characterized in that at

Carbon brushes (14a, 14b) in the direction of the commutator several layer sections (A, B) of an additive in one of the layer sections (Aa) and the other additive in another layer section (Bb) is included.