WO2008040685A1

WO2008040685A1 - Electric machine

Info

Publication number: WO2008040685A1
Application number: PCT/EP2007/060317
Authority: WO
Inventors: Wilhelm Latz; Ina Constantinides; Roland Seidel; Frank Kraft
Original assignee: Robert Bosch Gmbh
Priority date: 2006-10-02
Filing date: 2007-09-28
Publication date: 2008-04-10
Also published as: DE102006047084A1

Abstract

The invention relates to an electric machine (1) having a commutator (11) with contact segments (19) and at least one brush (12) contacting the contact segments (19). According to the invention, it is provided that at least one contact segment (19) and/or the brush (12) comprises friction means (21).

Description

description

title

Electric machine

State of the art

The invention relates to an electrical machine according to the preamble of claim 1.

From DE 10 2004 051 461 Al an electric machine with a planar commutator is known, on the front side of which a plurality of contact segments are arranged, which are contacted by brushes acted upon by roller springs. In order to achieve a good efficiency of the electric machine and to improve the electromagnetic compatibility (EMC), efforts are constantly being made to optimize the contact between the brushes and the contact segments. Usually, good contact conditions occur only after a running-in phase of the electric machine, in which the contact geometries of the brushes and contact segments adapt to one another. Such a break-in phase can last up to several thousand operating hours, in which the efficiency and the EMC of the electric machine are not optimal. This in turn has a negative effect on the power consumption or output and the disturbance behavior of the electrical machine. Particularly when using electric machines in automobiles, the long break-in period can have a negative effect on a large number of other vehicle components (EMC).

From EP 0 984 546 A2 it is therefore known to shorten the break-in phase by periodic starting currents with adjustable frequency and amplitude. The streams accelerate material removal. To implement the known procedure, however, an additional control unit is needed, which is associated with high costs and an additional weight.

From US 2002 / 0130579A1 a fuel pump is known, which is driven by a DC motor, which in turn is controlled pulse width modulated. Disclosure of Invention Technical Problem

The invention is therefore based on the object, an electric machine, in particular to propose an electrically driven pump, in which the mileage, in particular the flow rate, remains as constant as possible over the life of the machine.

Technical solution

This object is achieved with the features of claim 1.

The electric machine has a commutator, in particular a planar commutator, with contact segments and at least one brush contacting the contact segments. Because at least one of the contact segments and / or the brush contains friction means, the formation of boundary layers on the carbon brushes and / or the commutator can be prevented or at least reduced.

In particular, configured as a fluid pump electric machines, such as fuel pumps for automobiles, should now run in regular production mode.

This causes an electrical voltage state of the driving electrical

Machine that is no longer constant at, for example, 12-13.7V. The voltage is rather regulated to control the flow rate of the pump, so that too

Voltages in the range of, for example, only 4V can be present. Thus, such machines are controlled in an advantageous manner pulse width modulated.

In the voltage range of 4-6 V, however, there is usually a drop in the delivery rate of the pump over its running time. This is u. a. due to the formation of boundary layers between the carbon brushes and the commutator surface which leads to a poorer electrical contacting of the friction partners of the commutation.

Due to the relative movement of the components of the electric machine equipped with friction means, the formation of boundary layers is counteracted. In particular, the addition of "mild" friction components, ie For example, small concentrations of the friction agent in the range of 0.1 to 1%, the boundary layer structure, but does not attack the actual base material.

Advantageous developments of the invention are specified in the subclaims. In addition, all combinations of at least two of the features disclosed in the description, the drawings and / or the claims fall within the scope of the invention.

Preferably, the main component of the brushes and / or the contact segments is a carbon-graphite mixture into which the friction agents are introduced as additives. The friction means can be integrated in an advantageous manner as abrasive particles in the friction partner carbon brush and commutator.

In an embodiment of the invention is advantageously provided that the abrasive particles are distributed uniformly over the contact segment or the brush. Other distributions, in particular to accelerate the running-in phase of the machine are also possible.

Such abrasive particles may for example consist of Fe ₃ O ₄ or feldspar or SiO ₂ or silicon carbide and / or a combination of these. It has proven to be advantageous if feldspar and / or silicon carbide and / or silicon oxide are used as the abrasive particles. In this case, mixtures of these particles are possible. It may be advantageous if the abrasive particles have at least one hardness which is greater than that of the main constituents of the brushes or the contact segments, in particular of the graphite-carbon mixture and / or have an electrical conductivity and / or a thermal expansion quotient, the as equal to the main component of the contact segments or the brush, in particular the graphite-carbon mixture is.

It has proven to be advantageous if the abrasive particles have a particle size of 0.1 to 100 micrometers, particularly advantageous is a particle size of 1 to 10 micrometers.

Due to the relative movement of those equipped with higher Reibmittelkonzentrationen

Components of the electric machine to each other, also an accelerated removal of material can also be realized, whereby the contact geometries between brush and

Contact segment accelerated to be able to be aligned. Advantageous the contact area preferably increases during the break-in phase. In addition, this effect, as already described, counteracts the formation of a boundary layer of the two friction partners.

In particular, it is conceivable in order to accelerate the break-in phase and otherwise to reduce the wear of the brushes and the contact segments during operation, to provide a higher concentration of abrasive particles in the area of the contact plane, than in an area further away. For example, a linear or logarithmic particle concentration decrease in this direction is feasible.

In a development of the invention, it is advantageously provided that the abrasive particles are arranged in or concentrated in at least one limited layer. Preferably, the abrasive particles are evenly distributed within this at least one layer.

It is conceivable to arrange the abrasive layer parallel to a contact plane between the brushes and the contact segments. Preferably, a parallel layer is arranged on the end of the brush and / or contact segments in order to achieve a abrassiven effect already at the first commutator rotation.

It is within the scope of the invention to associate the abrasive particles either only at least one contact segment, or only at least one brush or both at least one contact segment and at least one brush.

As an alternative or in addition to a parallel arrangement of at least one abrasive layer, at least one abrasive layer can be arranged perpendicular to the contact plane or at an oblique angle to the latter. In this case, when providing a plurality of abrasive layers, these need not necessarily be spaced apart, but preferably equally. About the arrangement of the abrasive particles in perpendicular or at an oblique angle to the contact plane extending layers Abrasive effect can be accelerated in certain areas of the geometry and delayed in others to realize an optimal - fast - adjustment of the contact geometry. Brief description of the drawings

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawing; this shows in:

Fig. 1: a schematic representation of an electric machine in

Longitudinal section

FIGS. 2A to 2C show the brush and commutator unit during time-spaced stages during the break-in phase;

3: the unit of brushes and commutator, wherein abrasive particles are provided exclusively in the contact segments of the commutator,

Fig. 4: the unit of brushes and commutator, wherein exclusively in the

Brushing abrasive particles are provided

5 shows the unit of brushes and commutator, wherein abrasive particles are provided both in the brushes and in the contact elements,

Fig. 6: the unit of brushes and commutator, wherein the abrasive particles arranged only in a direction perpendicular to the contact plane

Layer are introduced into the brushes,

Figure 7: the unit of brushes and commutator, wherein a plurality of parallel, perpendicular to the contact plane extending Abrassive layers are provided, and

Fig. 8: the unit of brushes and commutator, wherein a plane parallel to the contact plane, frontal Abrassive layer is provided exclusively on the brush. Embodiments of the invention

In the figures, the same components and components with the same function with the same reference numerals.

In Fig. 1, a part of an electric machine 1 is shown simplified in a longitudinal section. In the present embodiment, it is a brush-type DC motor (commutator), which is for example part of a fuel pump of a motor vehicle. However, there are other applications, for example in a fan, windows, wiper drive, seat adjuster, etc. conceivable in a motor vehicle. Instead of an engine, the electric machine 1 may also be a generator.

The electric machine 1 comprises a housing, in particular a pole tube 2 and an armature 3 arranged therein. The armature 3 has an armature shaft 4 which is mounted in two end-side bearings 5, which in turn are fastened in two opposite bearing caps 6. On the inner circumference of the pole tube 12 are arranged around a fixed to the armature shaft 4 plate pack 7 around magnets 8, which cooperate with an armature winding 9 of the plate pack 7.

The armature winding 9 is connected in a manner not shown with hoes 10 (see Fig. 2A) of a commutator 11. The commutator 11, which is formed in the embodiment shown as a plan commutator, is acted upon by two brushes 12 indicated by dashed lines. The brushes 12 are arranged on a brush holder 13 produced as a plastic injection molded part. The brush holder 13 has two quivers 14 for the brushes 12, wherein the two quivers 14 are arranged parallel to each other. By means of a respective roll spring 15, each brush is spring-loaded on the one hand in the direction of the end face 16 of the commutator 11 and on the other hand in the direction of a quiver wall 17. For this purpose, the roller springs 15 each engage on an inclined surface 22 and load the brush 12 in the direction of arrow with a force F. Each scroll spring 15 is fixed with a chopper 18 on a commutator 11 facing edge of each quiver 14.

It has proven to be advantageous to form the commutator as a plan commutator with frontally arranged contact elements, so that a flat

Contact surface is formed, against which the brushes. The brushes are preferred Federkraftbeaufschlagt by means of rolling springs in the direction of the contact segments. Preferably, the spring constant of the rolling springs used is close to zero, so that regardless of the residual length of the brush over the life of the brush almost the same spring force is exerted on the brush and the plan commutator and the higher damping constant of the scroll spring the vibration behavior of the at least one brush at least two contact segments of the plan commutator in always the same way over the life improved.

In order to realize the fastest possible adaptation of the contact geometries between the brush and contact segments, it is advantageously provided in an embodiment of the invention that the brushes have a curved profile on the end faces facing the contact segments or are bevelled or chamfered laterally in the circumferential direction. This ensures that the brush does not yet have the maximum contact surface in the running-in phase, as a result of which the brush can be removed faster in the running-in phase and adapted to the surface of the commutator, in particular of the planar commutator.

According to an advantageous embodiment of the invention is advantageously provided that the brushes on the contact segments facing the end face, i. Contact side, profiled, in particular serrated. As a result, a higher local contact pressure is achieved, which increases the material removal in the run-in phase.

The brushes 12 project beyond the respective quiver 15 in the axial direction and are spring-loaded on contact elements 19 on the end face 16 of the commutator 11 in an electrically conductive manner. During operation of the electric machine 1, the commutator 11 fixed on the armature shaft 14 moves with brushes 12 relative to the brush holder 13.

FIGS. 2A to 2C show different phases of the running-in phase of the electric machine 1. At the beginning of operation, ie at the beginning of the start-up phase, the

Brushes 12 a rounded, the commutator 11 facing end face 20 (see.

Fig. 2A). The brushes 12 in the embodiment of FIGS. 2A to 2C consist entirely of a graphite-carbon mixture. In contrast, in the

Contact segments, which also have a graphite-carbon mixture as the main component, introduced abrasive particles 21. The abrasive particles 21 are not only located on the surface of the contact segments 21, but enforce them Completely. The abrasive particles 21, in the present exemplary embodiment feldspar particles, are distributed homogeneously over the entire volume of the contact segments 19.

As can be seen from Fig. 2B, the end faces 20 of the brush after a relatively short time in a central portion due to the action of Abrassiven particles 21 ground evenly, whereby the contact area increases.

At the end of the break-in phase shown in FIG. 2C, the brushes 12 are ground flat over their entire cross-section, so that a maximum contact surface is realized.

In the embodiment according to FIG. 3, no abrassive particles are provided in the brushes 12, whereas the contact segments 19 of the commutator 11 are completely interspersed uniformly with abrasive particles.

In the exemplary embodiment according to FIG. 4, the contact elements 19 are designed to be abrasive-free, whereas abrasive particles 21 are distributed uniformly over the entire brushes 12.

The exemplary embodiment according to FIG. 5 unites the exemplary embodiments according to FIGS. 3 and 4, since abrasive particles 21 are distributed uniformly both in the brushes 12 and in the contact segments 19.

In the embodiment according to FIG. 6, no abrasive particles are provided in the contact segments 19. In contrast, the brushes 12 have abrasive particles. However, these are not uniformly distributed over the entire volume of the brush 12, but only in a limited layer 23 summarized with the thickness d, wherein the thickness d about one-fifth of the total thickness of the brush

12 corresponds. The layer 23 is arranged perpendicular to a plane of contact formed by the flat surface of the end face 16 and extends in the circumferential direction centrally through the respective brush 12th

In the embodiment according to FIG. 7, in addition to the vertical layer

23 of FIG. 6, two further layers 23 are provided with uniformly distributed abrasive particles, wherein all layers 23 in this embodiment, an identical

Have thickness d. The middle layer 23 with abrasive particles is spaced from surround two parallel circumferential layers 23 in the circumferential direction, which can come after some time with the end face 16 of the contact segments 19 in contact, namely, when the central region of the arcuate end face 20 of the brush 12 is removed.

In the embodiment according to FIG. 8, only a single layer 24 with abrasive particles with a thickness d is provided. The layer 24 is not perpendicular, but parallel to the end face 16 of the commutator 11. Stated another way, the entire arcuate, frontal region of the brush 12 is provided with abrasive particles 21, whereas in a remote from the contact plane area no abrasive particles 21 are provided ,

In addition to the described advantages of an accelerated running-in phase of the electric machine can be achieved by the friction means according to the invention also an improved capacity of the pump over its life characterized in that at least one of the contact segments and / or the brush contains friction, the formation of boundary layers on the carbon brushes and / or prevents the commutator, or at least reduced.

In particular, configured as a fluid pump electric machines, such as fuel pumps for automobiles, should now run in regular production mode. This causes an electrical voltage state of the driving electric machine, which is no longer constant at, for example, 12 - 13.7 V. The voltage is rather regulated to control the flow rate of the pump, so that voltages in the range of, for example, only 4 V can be present. Thus, such machines are controlled in an advantageous manner pulse width modulated. In the voltage range of 4-6 V, however, there is usually a drop in the delivery rate of the pump over its running time. In particular, in a sudden high regulation on the nominal voltage state of, for example, 12-13 V no longer reaches the original capacity. For this purpose, the concept of a "tired pump" has become established, which is due in part to the formation of boundary layers between the carbon brushes and the commutator surface.

In particular, by the nature and concentration of the friction means both an improvement, ie, for example, achieve a shortening of the running-in phase, as opposed to the formation of boundary layers between the friction partners become. For this purpose, different friction means or different Reibmittel- concentrations can be introduced staggered in the friction partners.

The addition according to the invention of friction agent to the material of the brushes or of the commutator of a pulse-width-modulated controlled electric machine and in particular of such a fuel pump can therefore advantageously keep the delivery rate of the pump virtually constant over its service life, so that the effect of the "tired pump" not completely avoided, but can be significantly reduced

Claims

claims

1. Electrical machine with a commutator, in particular a plan commutator (11), with contact segments (19) and with at least one contact segments (19) contacting brush (12), characterized in that at least one of the contact segments (19) and / or the brush (12) contains friction means (21).

2. Electrical machine according to claim 1, characterized in that the

Friction means are formed as abrasive particles (21).

3. Electrical machine according to claim 1 or 2, characterized in that the friction means (21) Fe ₃ O ₄ or feldspar or SiO ₂ or silicon carbide and / or a combination of these.

4. Electrical machine according to one of the preceding claims, characterized in that the abrasive particles have a particle size of 0.1 to 100

Micrometer, in particular have a particle size of 1 to 10 microns.

5. Electrical machine according to one of the preceding claims, characterized in that the friction means (21) homogeneously over the entire

Contact segment (19) and / or the entire brush (12) are arranged distributed.

6. Electrical machine according to one of claims 1 to 4, characterized in that the friction means (21) in at least one limited layer (21, 23, 24) are arranged.

7. Electrical machine according to one of claims 1 to 4, characterized in that the Reibmittelkonzentration in the contact segment (19) and / or the contacting brush (12) (21) changes.

8. Electrical machine according to one of claims 1 to 4, 6, characterized in that the abrassive layer (21, 23, 24) is arranged parallel to a contact plane between the brush (12) and the Konatktsegmenten (19).

9. Electrical machine according to one of claims 1 to 4, 6, characterized in that the abrassive layer (21, 23, 24) is arranged perpendicular or obliquely to a contact plane between the brush (12) and the contact segments (19).

10. Electrical machine according to one of claims 6 to 9, characterized in that a plurality of parallel Abrassive layers (21, 23, 24) are provided.

11. Electrical machine according to one of the preceding claims, characterized in that the machine is controlled pulse width modulated.

12. Electrical machine according to one of the preceding claims, characterized in that the machine is a fluid pump.

13. Electrical machine according to one of the preceding claims, characterized in that the machine is a fuel pump.