WO2008022631A1

WO2008022631A1 - Dc machine

Info

Publication number: WO2008022631A1
Application number: PCT/DE2007/001479
Authority: WO
Inventors: Sebastian SCHRÖDER
Original assignee: Temic Automotive Electric Motors Gmbh
Priority date: 2006-08-23
Filing date: 2007-08-22
Publication date: 2008-02-28
Also published as: DE102006039594A1; DE112007001862A5

Abstract

In a DC machine (1) with a number of carbon brushes (12), which are each arranged in a carbon guide (14) such that they can be displaced in their longitudinal direction, brush sparking should be reduced or avoided and therefore excessive noise development and radiofrequency interference largely ruled out. For this purpose, the invention provides a carbon guide (14), which is formed by a base face (20) possibly by side faces and by a number of guide faces (16) which are bevelled relative to the base face (20).

Description

description

DC machine

The invention relates to a DC machine with a number of carbon brushes, each slidably disposed in its longitudinal direction in a guide channel, the so-called coal guide.

The required for the functioning of electrical machines, such as DC machines, providing a relative to the winding rotating or traveling current on the basis of a direct current as an input current is usually on the so-called commutator, also referred to as current inverter achieved. Usually current turning means are designed as a lamella brush system, for example in DC machines. A DC machine may be implemented as a DC electric motor or as a generator that converts mechanical energy into DC power. In some applications, a DC machine can also perform both functions.

A DC machine typically includes, as essential components, a stationary outer part, the stator, and a rotatably mounted inner part, the rotor or armature. In conventional direct current machines, the immovable part comprises at least one electromagnet or, in smaller, less powerful embodiments, at least one permanent magnet.

Significant advantages of the typical DC machine, for example with respect to induction machines, is the variable operating speed, which can be controlled with the same torque over the voltage amplitude. Through this

Construction DC motors can be used in a wide speed range. In electric motors with commutators are used for tapping the electricity generated, in electric generators for feeding the current, carbon brushes. In the past, brush brushes were used as sliding contact instead of graphite, hence the term brush. Such a carbon brush is usually made of graphite and makes via slip rings or collectors a (sliding) contact to the rotating part of the machine, the rotor or anchor ago. Because of the sometimes high rotational speeds, in conventional DC machines, in the short moments when the brush is galvanically isolated from the commutator or short-circuits two differently charged fins, electrostatic discharges can occur which are visible as sparks. This is the so-called brush fire.

This so-called brush fire can be the cause of high-frequency interference, which, for example, emits the DC machine during operation and feeds it back into the line network, thus causing interference to other consumers in the line network. The rotation speed is also limited by this spark formation, since the carbon brush becomes hot at high speeds and consumes faster than in typical temperature ranges for these DC machines. Furthermore, high speeds cause a higher induction voltage, which can initialize a revolving brush fire.

Another disadvantage of the typical use of carbon brushes is the noise that occurs due to the

Shock excitations of the coal guide caused by the tangential and radial excitation of the carbon brushes by the commutator arises. Responsible for this stimulation of the carbon brushes is the play of carbon brush in the coal leadership. However, this game is necessary to allow the carbon brush, the radial contact pressure on the commutator, since in particular during heat development of this game a change due to the differential expansion of the different materials used in the carbon brush and in the carbon guide.

The invention is therefore an object of the invention to provide a DC machine of the type mentioned above, in which the brush fire is reduced or avoided and thus excessive noise and high-frequency interference are largely excluded.

This object is achieved according to the invention in that the carbon guide is formed by a base surface, optionally by side surfaces and by a number of guide surfaces bevelled relative to the base surface.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that the so-called brush fire is essentially due to the play between the carbon brush and the carbon guide. Therefore, this should be minimized. In order to maintain the free mobility of the carbon brush despite the different expansion behavior of said components of the system under the influence of temperature, suitable guidance should be provided. For this purpose, the coal guide is designed appropriately.

Usually, the coal guide is designed as a rectangular shaft. The intended and necessary play of the carbon brush in the tangential direction in the coal guide is present over the entire height of the carbon brush and carbon guide and allows a stimulation of the carbon brush and thus the noise and the sparking, the so-called brush fire. A chamfer of the guide surfaces and the pressure of the carbon brush in the direction of the base surface and the guide surfaces beveled relative to the base achieves at least one point contact and guidance of the usual example rectangular trained carbon brush in the coal guide.

In order to form the contact between the carbon brush and the carbon guide as a surface contact, the carbon brush also has a guide surface which is adapted to the guide surface of the carbon guide.

In order to provide the formed chamfer of both the guide surfaces of the carbon brush and the guide surfaces of the carbon guide for a play-free guidance of the carbon brush in the carbon guide, advantageously a pressure force acts on the carbon brush in the direction of the base surface.

The pressure of the carbon brush in the direction of the base surface of the carbon guide is preferably carried out via the integration of an additional component such as a spiral, torsion or spiral spring in the coal guide. The spring element can also be provided in terms of production technology in the coal guide or in one of the add-on parts. In a particularly advantageous embodiment, the pressure of the carbon brush is effected by a spring bias acting in the radial direction via a lever deflection.

The advantages achieved by the invention are in particular that by the bevel of the guide surfaces of both the carbon brush and the carbon guide when pressing the carbon brush an adjustment and a lateral fixation takes place, which eliminates the sparking or the resulting by lateral Pen- your shock excitations. This minimizes the DC machine noise and improves EMC performance by reducing high-frequency noise.

Furthermore, advantages of this embodiment lie in a simpler and therefore more cost-effective production of the lamellar brush system, since the carbon brush itself and the carbon brush leführung larger manufacturing tolerances are acceptable than in the usual execution.

Furthermore, the tool life is higher than in the previous versions, since the wear of the carbon brush is reduced by minimizing the shock excitation and sparking, which also has a cost-effective effect on the operation of the DC machine.

An embodiment of the invention will be explained in more detail with reference to a drawing. Show:

FIG. 1 a DC machine in cross section,

FIG. 2 shows the DC machine according to FIG. 1 in perspective view,

FIG. 3 a coal guide the DC machine after

FIG. 1 on average, and

FIG. 4 a carbon brush of the DC machine after

FIG. 1 in three-dimensional view.

The same parts are provided with the same reference numbers in all figures.

The DC machine 1 according to FIG. 1 is basically constructed in a conventional manner, wherein a field winding 2 in a stator 4, also referred to as stator, is arranged. The excitation winding 2 generates during operation of the DC machine 1, not shown here temporally and spatially constant field. This type of execution is also referred to as Außenpolmaschine. An armature 6, also referred to as a rotor or rotor, carries a winding or armature winding 8 into which a voltage is induced when the armature 6 moves. FIG. 2 also shows a DC machine 1 and the interaction of the components. The armature winding 8 of the armature 6 is connected via a commutator 10. The contacts 12 of the commutator 10, also referred to as carbon or brush or carbon brush, are constructed such that they constantly change during the rotation of the armature 6, the polarity of the armature winding 8, not shown here. The carbon brush 12 consists of an electrically highly conductive material, such as graphite, which is also characterized by the property that during operation by the pressing of the carbon brush 12 to the commutator 10 abrasion occurs, the contact surface between carbon brush 12 and commutator 10 smears. By the concern of the carbon brush 12 on the commutator 10 and the resulting change in the Pole ment the rotary motion is ensured in a DC machine 1. If the direct current machine 1 is not designed as an electric motor but as a generator, the function of the commutator 10 produces direct current from the alternating current of the armature 6.

The leadership of the carbon brush 12 of a commutator 10 is carried out in a so-called coal shaft 14, also referred to as a carbon guide, according to FIG. 3. During operation of the DC machine 1 and by the concern of the carbon brush 12 on the commutator 10 heat is generated, which increases with increasing speed. Since the carbon guide 14 and the carbon brush 12 are made of different materials, these expand when heated in the operation of the DC machine 1 differently. For this purpose, a clearance is provided between the inner wall of the carbon guide 14 and the carbon brush 12, which catches the different expansions. Through an air gap created by the game, the carbon brush 12 in the carbon guide 14 is tangential and radially movable and generated by the inevitable tangential and radial movement and the impact of the carbon brush 12 on the inner wall of the carbon guide 14 a noise. This noise increases with increasing speed of the DC machine. 1

In order to avoid the air gap between the carbon brush 12 and the inner wall of the carbon guide 14 and thus the movement of the carbon brush 12 in the tangential direction at the commutator 10 side, but still to ensure sufficient clearance for the different expansion behavior of the components are the Guide surfaces 16 of the coal 14, as shown in FIG. 3, bevelled.

In order to achieve a substantial reinforcement of the guiding effect of the carbon brush 12 in the carbon guide 14 provided with a chamfer to the base surface, the guide surface 18 of the carbon brush 12 is designed with a chamfer adapted to the guide surface 16 of the carbon guide 14.

Due to the chamfering of the guide surface 16 in the carbon guide 14 relative to the base surface 20, the guidance of the carbon brush 12 is ensured at least in the contact region. For this purpose, advantageously, a pressing of the carbon brush 12 in the direction of the base surface 20 to the commutator 10 so that the carbon brush 12 remains in the chamfered portion of the guide surface 16 of the carbon guide 14. The contact pressure acts axially on the carbon brush 12, to which end a device for generating the contact pressure is integrated into the carbon guide 14, which is usually designed as a spiral, torsion or bending spring, not shown here.

A particularly advantageous design of the device for generating the contact pressure is shown in FIG. 4. A spring 22 generates by its bias a pressure on a lever 24 which is integrated laterally to the carbon brush 12 in the coal guide 14. By a lever deflection via a lever 24, the axis 26 extends in the tangential direction, creates an axial contact pressure on the carbon brush 12 in the direction of the base surface 20 of the carbon guide 14th Due to the bevel of the guide surface 18 of the carbon brush 12 and the bevel of the guide surface 16 of the carbon guide 14 in conjunction with the axial contact pressure exerted on the carbon brush 12 in the direction of the base surface 20 of the carbon guide 14 is formed between the guide surface 16 of the coal guide 14 and the guide surface 18 of the carbon brush 12 line contact or surface contact.

The design of the contact between the carbon guide 14 and the carbon brush 12 as surface contact largely reduces the noise, such as by shock excitation between the carbon guide 14 and the carbon brush 12, and the so-called brush fire, at the contact surface between coal guide 14 and the carbon brush 12 can arise.

By generating the contact pressure of the carbon brush 12 to the commutator 10 in the direction of the base surface 20 of the carbon guide 14 via a deflection system according to FIG. 4 and a suitable design of the spring 22 can be largely ensured that the contact pressure in each state region of the carbon brush 12, which is dependent on temperature and degree of wear is the same. For a uniform running behavior of the DC machine 1 is achieved. A damping of the movement of the carbon brush 12 in the carbon guide 14 by the contact pressure generated via the lever 24 and the spring 22 can be achieved.

LIST OF REFERENCE NUMBERS

1 DC machine

2 exciter winding 4 stands

6 anchors

8 armature winding

10 commutator

12 carbon brush 14 carbon guide

16 guide surface of the coal guide

18 guide surface of the carbon brush

20 base area

22 spring 24 lever

26 axis of the lever

Claims

claims

A direct current machine (1) having a number of carbon brushes (12) each slidably disposed in its longitudinal direction in a guide channel (14) which is defined by a base surface (20), optionally by side surfaces and a number relative to Base surface (20) beveled guide surfaces (16) is formed.

2. DC machine (1) according to claim 1, whose carbon brushes (12) in their contouring on the guide surfaces (16) adapted bevelled contact surfaces (18).

3. DC machine (1) according to claim 1 or 2, the carbon guide (14) has a to the base surface (20) directed on the carbon brush (12) acting pressure device.