WO2009095119A2

WO2009095119A2 - Electric machine, in particular a three-phase machine with a slip ring rotor

Info

Publication number: WO2009095119A2
Application number: PCT/EP2008/065901
Authority: WO
Inventors: Uwe Wieselow; Martin Paetzold
Original assignee: Robert Bosch Gmbh
Priority date: 2008-01-31
Filing date: 2008-11-20
Publication date: 2009-08-06
Also published as: DE102008007076A1; DE102008007076B4; WO2009095119A3

Abstract

The invention relates to an electric machine (10) with a slip ring rotor (15), the slip rings (20) of which cooperate with the carbon brushes of a brush holder (21) that is fixed to the exterior of a rear end shield (11) and is covered by a protective cap (31), said slip rings (20) being enclosed by a ventilated slip ring capsule (40) that is placed on the brush holder. To ventilate and humidify the slip rings (20) in measured doses, the slip ring capsule (40) should be fixed to the electric machine (10) in such a way that the front capsule opening (41) lies behind the protective cap (31) at a short distance (50) from the latter to allow air to enter and the outer wall (43) should be smooth, thus permitting the incoming cooling air to flow without turbulence along the outer wall (43) to the air inlet windows (11c) of the end shield (11) to create an air pressure drop in the slip ring capsule (40).

Description

Electric machine, in particular three-phase machine with slip ring rotor

description

The invention relates to an electrical machine, in particular a three-phase machine with a slip ring rotor whose slip rings are arranged at the rear end of the rotor shaft, according to the preamble of claim 1.

State of the art

Such an electric machine is already known from the publication DE 199 50 126 Al. There, the slip rings are surrounded at the rear rotor shaft end of a retrofittable slip ring capsule, which is clipped in its mounting on the brush holder of the machine and is closed at the front. To eliminate the

Brush abrasion and the resulting heat during operation of the machine is passed there through a labyrinth between brush holder and cap a metered air flow from the end of the rotor shaft ago axially through the slip ring capsule, which air then exits in the region of the rear engine bearing from the cap to them together with the sucked by a fan cooling air to the stator winding of

To transport the machine. However, this solution has the disadvantage that the very small flow of cooling air in the slip ring capsule of the slip ring system is already heated in the labyrinth system by the temperature of the brush holder and is therefore relatively dry. This results in high loads on the machine, as they often occur as three-phase alternator in motor vehicles, to reduce the Lubricating film between the slip rings and their carbon brushes (Rothmann skin). As a result, brush wear increases with increasing temperatures. A further disadvantage is that in the area of the brush holder and the slip ring capsule, the cooling air flowing in is swirled before it reaches the fan through the air inlet window of the rear bearing plate, whereby the cooling air flow rate of the machine is impaired.

These disadvantages are more or less apparent in a further embodiment of a slip ring encapsulation known from the publication US Pat. No. 6,664,699 B2, in which the center of a protective cap together with the brush holder forms a labyrinth for supplying a very small air flow to the slip ring space.

The slip ring capsule for the slip rings, which has to be clipped onto the brush holder, is thereby made simpler, but the air flowing through it is first heated up disadvantageously in the labyrinth.

Since it may be possible to dispense with an encapsulation of the slip rings depending on the application and the installation location of the electrical machine, it makes sense for reasons of cost if the rear position range of the machine with the brush holder, the slip rings and the protective cap for a rectifier unit configured in such a way is that, if necessary, a slip ring capsule for the slip rings can be retrofitted.

The aim of the present solution is to make the retrofittable encapsulation of the slip rings so that it does not hinder the main cooling air flow and that the very small cooling air flow can reach the slip ring capsule of the slip rings directly and without preheating.

Disclosure of the invention

The electric machine with the characterizing features of claim 1 has the advantage that the design and installation of the slip ring capsule at the rear

Bearing shield of the machine, a turbulence of the cooling air is avoided at the air inlet windows of the bearing plate, so that there forms a negative pressure area through which without intervention in the existing configuration of the rear bearing plate by a suction effect in front of the bearing the slip ring system is sufficiently ventilated and moistened. Through the front capsule opening, the cooling air can now without Preheat reach directly to the slip rings and ensure adequate humidification of the brush surface. Another advantage is that the slip ring capsule is inexpensive to manufacture and assemble due to their simple design. Since the electric machine without the retrofittable slip ring capsule swirls the sucked in cooling air in the area of the air inlet window of the bearing plate more or less strongly, with the help of the slip ring capsule can also improve the cooling air flow and thus increase the amount of cooling air.

The measures listed in the dependent claims, advantageous refinements and developments of the features specified in claim 1.

Thus, the cooling air flow on the outer wall of the slip ring capsule can be optimized in that the outer wall of the slip ring capsule is axially cylindrical in the region of the outer protective cap and widens concavely conically in its region facing the end plate. To form a streamlined

Air duct at the air outlet of the slip ring capsule is proposed that the bearing plate on the outside of its bearing bore has an annular shoulder on which the slip ring capsule bears frontally and which is provided with a plurality of circumferentially distributed, associated with the interior of the slip ring caps breakthroughs. It is particularly favorable for the air duct when the openings of the shoulder are connected via an axial air gap to the rear bearing of the rotor shaft with the interior of the slip ring capsule. Furthermore, it is advantageous if the openings on the outer side of the shoulder extend at least partially radially outwards beyond the edge of the slip ring capsule. To improve the air outlet in the storage area, it is also advantageous if the conically enlarged end of the

Slip ring capsule to the shoulder of the bearing plate has an axial distance. To achieve such a sufficiently large axial distance, it is provided that the slip ring capsule is centered and mounted on its bearing plate end with a collar projecting axially on the inner circumference on the outside of the annular shoulder of the bearing plate.

For a good cooling air flow, it is also expedient if the slip ring capsule reaches with the rear edge of its outer wall to just below the inlet window of the bearing plate. For a simple and reliable assembly, the slip ring capsule has a front open axial recess for receiving the brush holder, - A -

wherein the recess is provided at its rear end with a stop for the brush holder which is integrally formed on the circumference of the rear end of the slip ring capsule projecting collar.

Brief description of the drawings

The invention will be explained in more detail below by way of example with reference to FIGS. Show it:

1 shows the rear part of the electric machine according to the invention to the central axis in longitudinal section without slip ring encapsulation,

2 shows a retrofittable slip ring capsule for the machine of Figure 1 in a three-dimensional view,

FIG. 3 shows the preassembled unit of brush holder and slip ring capsule from FIG. 2 in FIG

Outbreak and spatial representation; FIG. 4 shows the electrical machine according to FIG. 1 with a retrofitted slip ring capsule in longitudinal section,

Figure 5 shows an outbreak of the bearing plate in the storage area in raumbildlicher

Presentation and

Figure 6 shows an enlarged view of the storage area of the machine in longitudinal section with the course of the air flow on the outside and inside of the slip ring capsule.

Embodiment of the invention

FIG. 1 shows in simplified form the rear part of an electric machine 10 in longitudinal section up to the central axis. The machine 10 is designed as an AC

Synchronous generator formed with a claw-pole rotor and controlled electrical excitation of the rotor for use in motor vehicles. It has a multi-part metal housing, consisting of a respective end shield on both end faces, of which only the rear end plate 11 is shown. The end shields are cup-shaped with frontal and Umfangsseitgen air inlet and outlet windows l lc and 1 Id.

Between the two end shields 11, a stand is attached, which consists of a Bleckpaket 13, which is made in a known manner from a plurality of laminations 12. In the Bleckpaket 13, a three-phase stator winding 14 is used, which is housed in axially parallel to each other, radially inwardly open grooves of the Bleckpaketes 13. Within the cylindrical Bleckpaketes 13 is a Claw-pole rotor 15 is arranged and rotatably mounted with its rotor shaft 16 in the bearing plates 11. The claw-pole rotor 15 consists of two claw-pole halves 15a and 15b fastened on the rotor shaft 16, between which a pole core 17 is clamped, which carries an annular excitation winding 18. Each of the two pot-shaped claw pole halves 15a and 15b is made of solid iron and has along the

Circumference to a plurality of axially extending claws 15 c, which engage in the circumferential direction with a uniform angular pitch spaced from each other. The claws 15c overlap mutually the excitation winding 18 and form the rotor circumference alternating south and north poles. On the outer end faces of the two claw pole halves 15 a and 15 b, a fan 19 is attached in each case, which sucks the required cooling air through the inlet window 11 c of the bearing plate 11 during operation of the machine. The sucked cooling air flow is thereby transported by the fan 19 radially outward to the stator winding 14, the front side of the Bleckpaket 13 formed annular winding heads are located directly in the radial flow of cooling air. The heated cooling air then exits through the outlet window 1 Id of the bearing plate 11 again. At the rear free shaft end 16a, a slip ring pair 20 is arranged to supply power to the field winding 18 that cooperates with two guided in a brush holder 21 carbon brushes. The slip rings 20 are partially embedded in a cylindrical insulating body 22 which is placed on the shaft end 16 a of the machine 10, wherein the connecting conductors of the slip rings 20 are felt in an undetectable manner in the insulating body 22 under the rear ball bearing 23 of the machine, where they with the ends of the exciter winding 18 are contacted. The ball bearing 23 is fixed via a bush 24 made of insulating material in a bearing bore 25 of the bearing plate 11. The bearing plate 11 has on the outside of its bearing bore 25 has an annular shoulder 26 which, with several, on the

Circumferentially distributed openings 27 is provided. The output from the stator winding 14 three-phase current is supplied via a rectifier unit 28 to the electrical system of the motor vehicle, the rectifier unit is arranged outside the rear end plate 11. Furthermore, there is a controller which influences the power supply of the field winding 18 such that the rectifier unit 28 of the

Vehicle electrical system supplied voltage is kept constant regardless of the speed and load of the machine. In this case, the controller 29 is summarized in accordance with Figure 3 with the brush holder 21 to form a unit 30 which is bolted to the back of the rear end plate 11. Rectifier unit 28 and brush holder 21 and controller 29 are covered by a protective cap 31 made of insulating material, in turn is attached to the back of the rear end plate 11. The protective cap 31 has distributed over its circumference a plurality of air inlet openings 32, by the fan 19 sucked cooling air for cooling the rectifier unit 28 and the brush holder 21 enters before it reaches the inlet windows l lc of the bearing plate 11.

In normal use of the electric machine 10, this is arranged as an alternator in the engine compartment of motor vehicles so that it is operated without special protection of the slip rings 20 and the co-operating carbon brushes. Such open systems therefore require no special ventilation or

Humidification of carbon brushes. However, for installation sites subject to heavy contamination by dirt, water and oil, open slip ring systems are subject to the risk of severe abrasion and the risk of jamming brushes. Since a complete encapsulation of the slip rings 20 due to excessive heating and thus insufficient humidity with the result of insufficient lubrication of the

Carbon brushes is not eligible for such uses of the machine 10 is a retrofittable, ventilated encapsulation of the slip rings 20 is required. The encapsulation is designed so that it can be retrofitted without interference with the existing configuration of the rear end plate 11 and the brush holder 21 and the outer cap 31 in case of need on the machine in the simplest possible way. Furthermore, it must be ensured by a sufficient ventilation of the slip ring space that the brush abrasion is removed and the humidity forms a Rothmann skin called lubricating film on the tread of carbon brushes.

Figures 2 to 6 show such a retrofittable encapsulation of the slip rings and the

Function of their metered ventilation. FIG. 2 shows a slip ring capsule 40, which is required for this purpose and made of plastic, in a three-dimensional representation. It has a front capsule opening 41 and an axial recess 42 for receiving the brush holder 21. It also has a smooth outer wall 43 which is axially cylindrical at its front, the protective cap 31 of the machine 10 facing region 43 a and in their the End shield 11 facing rear portion 43b concave conically expanded. The slip ring capsule 40 also has at its bearing-side end an axially projecting collar 44, which is located in the region of the inner wall 45 of the slip ring cap 40. At the collar 44, an axial stop 46 is further formed for the brush holder 21. To retrofit the electric machine 10 from FIG. 1 with an encapsulation of the slip rings 20, the slip ring capsule 40 from FIG. 2 is first preassembled on the brush holder 21. Figure 3 shows the assembly 30 of the brush holder 21 and the controller 29 with the slip ring capsule shown in longitudinal section 40. The brush holder 21 is provided at its lower end on both sides with one shoulder 21a, so that the slip ring capsule 40 with its axial recess 42 of is pushed back to its stop 46 on the brush holder 21. The shoulders 21a of the brush holder 21 bear on the inner wall 45 of the slip ring capsule 40. The assembly 30 with the slip ring capsule 40 can now be mounted on the electric machine 10 of Figure 1 by the brush holder 21 is screwed together with the controller 29 on the back of the rear end plate 11.

FIG. 4 shows the electric machine 10 from FIG. 1 with the now retrofitted ventilated slip ring encapsulation. The slip ring capsule 40 is in the field of

Fixed bearing bore 25 of the rear end plate 11 and there now surrounds the slip rings 20. Her front, located at the end of the rotor shaft 16a capsule opening 41 is there at a small distance 50 of, for example, 2 mm behind the protective cap 31 of the machine.

FIG. 5 shows, in a three-dimensional representation, an outbreak of the bearing plate 11 in the region of its bearing point. There, one recognizes the inlet window 1 Ic for the cooling air and the annular shoulder 26 on the outside of the bearing bore 25 with the circumferentially distributed apertures 27. According to Figure 4, the slip ring cap 40 is at its rear, end plate side with its axially projecting collar 44 on the Outside of the

Ring shoulder 26 of the bearing plate 11 centered placed. The openings 27 are connected via the bearing bore 25 with the interior of the slip ring cap 40 by the annular shoulder 26 on the outside of the bearing bore 25 to the rear ball bearing 23 of the rotor shaft 16 16 leaves an axial air gap. To achieve a metered ventilation of the slip ring space is further provided that the flared

End portion 43 b of the slip ring cap 40 to the shoulder 26 of the bearing bore 25 on the bearing plate 11 has an axial distance which forms an annular gap 47.

FIG. 6 shows a detail from FIG. 4 with the encapsulation of the slip rings 20 on an enlarged scale. There is the occurring while the machine is running Cooling air flow in the slip ring capsule 40 shown by arrows. The broad arrows 48 form the main cooling air flow, which enters via the radially inner air inlet openings 32 of the cap 31 at the rear of the machine and flows without turbulence along the smooth outer wall 43 of the slip ring cap 40 to the inlet windows l lc of the bearing plate 11, where the cooling air then from the fan

19 is detected and pressed radially outward. In this case, outside of the slip ring capsule 40 in the region of the annular gap 47 to the bearing plate 11 an air pressure gradient in the interior of the slip ring cap 40 is generated by a small metered air flow branches off immediately behind the cap 31 from the main air stream 48. This characterized by narrow arrows 49 aeration flow passes through the small distance 50 of the slip ring cap 40 to the cap 31 in the front capsule opening 41. About the slip rings 20 away this ventilation stream 49 reaches the rear end of the slip ring cap 40 to the ball bearing 23. He passes from there the air gap 47 of the ball bearing 23 to the annular shoulder 26 of the bearing bore 25 and through the openings 27 in the annular gap 47 between the

Ring shoulder 26 and the slip ring capsule 40. Since the slip ring capsule 40 with the rear edge 43c of its outer wall 43 extends to just below the inlet window l lc of the bearing plate 11, where the ventilation flow 49 of the slip ring cap 40 is entrained by the main air stream 48 without turbulence.

The invention is not limited to the illustrated embodiment, since the dimensioning of the slip ring capsule 40 depends both on the size of the machine as well as their operating conditions. A dosage of the aeration flow 49 in the interior of the slip ring capsule 40 can optionally be changed by changing the distance 50 of the slip ring capsule 40 to the protective cap 31 of the machine or the axial distance 47 of the rear edge 43c of the slip ring capsule 40 to the bearing plate 11. Furthermore, for metering the aeration flow 49 in the slip ring capsule 40, the air pressure gradient along the outer wall 43 of the slip ring capsule 40 can also be influenced, for example by flattening the rear conical region 43b of the outer wall 43 of the slip ring capsule 40. Should leakage currents occur due to manufacturing tolerances on the slip ring capsule, which could impair the ventilation and humidification of the slip rings and carbon brushes, these can be provided by a seal between the brush holder 21 and the slip ring capsule 40 or between the axial collar 44 of the slip ring capsule 40 and the annular shoulder 26 on the bearing bore 25 of the end shield 11 reliably be prevented. The slip ring encapsulation according to the invention is generally applicable to electric machines with a slip ring rotor and thus not limited to machines with claw snubber.

Claims

claims

1. Electrical machine, in particular three-phase machine (10), with slip ring rotor (15) whose slip rings (20) at the rear end of the rotor shaft (16) are arranged and cooperate with in a brush holder (21) guided carbon brushes, wherein the brush holder preferably with a Regulator (29) and a rectifier unit (28) on the outside of a rear end shield (11) is fixed, and by a protective cap (31) is distributed over its circumference distributed a plurality of Lufteintrittsöffhungen (32), by the cooling air from a fan (19) mounted behind the bearing plate provided with inlet windows (Hc) on the rotor shaft is sucked in and wherein the slip rings (20) are seated on a brush holder

Slip ring capsule (40) are enclosed and are ventilated by a portion of the sucked cooling air, characterized in that the slip ring capsule (40) on the electric machine (10) is fixed so that a front, located at the end of the rotor shaft (16) capsule opening ( 41) to the air inlet at a small distance (50) behind the protective cap (31) and that its outer wall (43) is smooth, so that for generating an air pressure gradient in the slip ring capsule (40) the inflowing cooling air without turbulence along the outer wall (43 ) to the inlet windows (1 Ic) of the bearing plate (11) is able to flow.

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

Outer wall (43) of the slip ring capsule (40) in its protective cap (31) facing region (43 a) is formed axially cylindrical, in its the bearing plate (11) facing region (43 b) conically, preferably concave conically.

3. Electrical machine according to claim 1 or 2, characterized in that the bearing plate (11) on the outside of its bearing bore (25) has an annular shoulder (26) on which the slip ring capsule (40) abuts the front side and with several, on the Circumference distributed, with the interior of the slip ring cap (40) connected openings (27) is provided.

4. Electrical machine according to spoke 3, characterized in that the openings (27) of the annular shoulder (26) via an axial air gap (46) to the rear bearing (23) of the rotor shaft (16) with the interior of the slip ring capsule (40) are connected ,

5. Electrical machine according to spoke 3 or 4, characterized in that the flared end portion (43b) of the slip ring capsule (40) to the annular shoulder (26) of the bearing plate (11) has an axial distance which forms an annular gap (47).

6. Electrical machine according to one of the claims 3 to 5, characterized in that the slip ring capsule (40) at its bearing-side end with a, on the inner circumference axially projecting collar (44) on the annular shoulder (26) of the bearing plate (11) is placed centered ,

7. Electrical machine according to one of the preceding claims, characterized in that the slip ring capsule (40) with the rear edge (43c) of its outer wall (43) to just below the inlet window (1 Ic) of the bearing plate (11) extends.

8. Electrical machine according to one of the preceding claims, characterized in that the slip ring capsule (40) has a front open axial recess (42) for receiving the brush holder (21), wherein the recess (42) at its rear end with a stop ( 44a) is provided for the brush holder (21).

9. Electrical machine according to spoke 6 and 8, characterized in that the stop (44 a) on the circumference of the rear end of the slip ring capsule (40) axially projecting collar (44) is formed.

10. Electrical machine according to one of the claims 3 to 9, characterized in that the openings (27) on the outside of the annular shoulder (26) extend at least partially radially outwardly beyond the edge (43c) of the slip ring capsule (40) addition.