Vibration-reduced brush holder for an electric motor

Abstract

A brush holder for an electric motor includes a brush magazine forming a receiving space with a wall surface. A carbon brush having an end face and a side face is arranged in the receiving space. The brush holder also includes a spring, which is in contact with the end face and is configured to press the carbon brush in an extension direction of the receiving space. The brush holder also includes a pressing mechanism arranged on a pivot arm and configured to contact the side face and press the carbon brush by the force of the spring in a pressing direction against the wall surface. The pivot arm has a pivot shaft, to which an inner end of the spring is fastened. The pressing mechanism has a rolling surface configured to roll over the side face of the carbon brush when the carbon brush slides in the extension direction.

Claims

1. A brushholder for an electric motor comprising: a carbon cartridge forming an accommodating area with a lateral surface, wherein a carbon brush arranged in the accommodating area has an end face and a side face; a spring configured to rest on the end face and press the carbon brush in a direction of extent of the accommodating area; and a pressing mechanism arranged on a pivoting arm and configured to rest on the side face and press the carbon brush, by a force of the spring, in a pressing direction against the lateral surface, wherein the pivoting arm has a pivoting shaft on which an inner end of the spring is fixed, and wherein the pressing mechanism has a rolling surface configured to roll on the side face of the carbon brush as the carbon brush slides in the direction of extent.

2. The brushholder as claimed in claim 1, wherein the end face is transverse to the direction of extent.

3. The brushholder as claimed in claim 1, wherein the spring is a spiral spring.

4. The brushholder as claimed in claim 1, wherein the spring has an outer end configured to rest on the end face.

5. The brushholder as claimed in claim 1, wherein the pivoting shaft is configured to extend in a direction of a pivot axis about which the pivoting arm is mounted pivotably.

6. The brushholder as claimed in claim 1, wherein the pressing mechanism is arranged on an end of the carbon brush opposite the end face.

7. The brushholder as claimed in claim 1, wherein the pressing mechanism is mounted rotatably about an axis of rotation.

8. The brushholder as claimed in claim 1, wherein the pressing direction is transverse to the direction of extent.

9. The brushholder as claimed in claim 1, wherein the carbon cartridge has an opening through which the pressing mechanism engages.

10. The brushholder as claimed in claim 1, wherein the carbon cartridge and the pivoting arm are arranged on a housing component.

11. The brushholder as claimed in claim 1, wherein at least one of the carbon brush, the pressing mechanism, and the carbon cartridge has a function face configured to fix the carbon brush in the carbon cartridge both in an axial direction and in a tangential direction.

12. The brushholder as claimed in claim 11, wherein the side face and the rolling surface have function faces configured to interact with one another.

13. The brushholder as claimed in claim 12, wherein the side face and the rolling face have at least one wedge or one bevel.

14. The brushholder as claimed in claim 11, wherein the carbon cartridge and the carbon brush each have a function face in the form of a bevel, said function faces configured to correspond to one another and interact with one another.

15. The brushholder as claimed in claim 1, wherein the electric motor is a DC motor.

16. An electric motor, comprising: a brushholder, including: a carbon cartridge forming an accommodating area with a lateral surface, wherein a carbon brush arranged in the accommodating area has an end face and a side face; a spring configured to rest on the end face and press the carbon brush in a direction of extent of the accommodating area; and a pressing mechanism arranged on a pivoting arm and configured to rest on the side face and press the carbon brush, by a force of the spring, in a pressing direction against the lateral surface, wherein the pivoting arm has a pivoting shaft on which an inner end of the spring is fixed, and wherein the pressing mechanism has a rolling surface configured to roll on the side face of the carbon brush as the carbon brush slides in the direction of extent.

17. The electric motor of claim 16, wherein the electric motor is in a handheld machine tool.

18. The electric motor as claimed in claim 17, wherein the handheld machine tool is one of a drill, a hammer drill, and a jackhammer.

19. The electric motor as claimed in claim 16, wherein the electric motor is a DC motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will be described below with reference to figures. The figures are merely by way of example and do not restrict the general concept of the disclosure.

(2) FIG. 1 shows a section E-E through a commutator of a rotor of an electric motor comprising two brushholders according to the disclosure of a hammer drill as shown in FIG. 2 in a plan view,

(3) FIG. 2 shows a longitudinal section B-B through the rotor of the hammer drill shown in FIG. 1.

(4) FIG. 3 shows the brushholder according to the disclosure shown in FIG. 1, wherein FIG. 3 shows a section D-D from FIG. 4 in a plan view,

(5) FIG. 4 shows a further section C-C through the brushholder according to the disclosure from FIG. 3 in a side view, and

(6) FIG. 5 shows, schematically, a plurality of further embodiments of the brushholders according to the disclosure.

DETAILED DESCRIPTION

(7) FIG. 1 and FIG. 2 each show a section through a hammer drill 200, wherein FIG. 1 shows a section at the level of the commutator 111 in a plan view, and FIG. 2 shows a longitudinal section through the motor housing 120.

(8) The commutator 111 is arranged on a rotor shaft 112 of a rotor 110 of an electric motor 100 which drives the hammer drill 200. In order to change current branches of the rotor 110, a supply voltage is applied to the commutator 111 via two carbon brushes 2. The carbon brushes 2 are each arranged in a carbon cartridge 1 of a brushholder 10. They are held by means of a spring 3, which in this case is in the form of a spiral spring, and are pressed by means of the spring 3 in a direction of extent 81 of an accommodating area 12 formed by the carbon cartridge 1 (see FIG. 3). The spring force of the spring 3 causes the carbon brush 2 to be pressed against the commutator 111 as necessary and, in the event of wear of the carbon brush 2, additionally effects continuous tracking of the carbon brush 2 in the direction of extent 81.

(9) In this case, the direction of extent 81 is the radial direction of the electric motor 100. In this direction 81, the carbon brush 2 has its greatest degree of freedom of movement. However, conventionally, vibrations of the carbon brush 2 in the accommodating area 12 can arise during operation of an electric motor 100, inter alia owing to a required play S (see FIG. 4) between the carbon cartridge 1 and the carbon brush 2. Owing to this play S, the carbon brush 2 also has degrees of freedom of movement in the tangential direction 82 and the axial direction 83 of the electric motor 100 in the carbon cartridge 1. Conventionally, therefore, different vibration excitations can effect vibratory movements of the carbon brush 2 in all three spatial directions.

(10) In order to reduce these vibratory movements or even to prevent them and, as a result, to improve the quality of the commutation, the brushholder 10 according to the disclosure comprises a pressing means 4, which presses the carbon brush 2 against a lateral surface 13 (see FIG. 3) of the accommodating area 12. The pressing means 4 is arranged on a pivoting arm 5.

(11) FIG. 3 and FIG. 4 show the brushholder 10 according to the disclosure, in each case in a sectional illustration.

(12) The brushholder 10 according to the disclosure comprises a carbon cartridge 1, which forms an accommodating area 12. The accommodating area 12 extends in a direction of extent 81 and is delimited by a lateral surface 13. A carbon brush 2 is arranged in the accommodating area 12. In the present exemplary embodiment, the carbon brush 2 and the carbon cartridge 1 are approximately rectangular in cross section.

(13) Furthermore, the brushholder 10 comprises a pivoting arm 5, which has a pivoting shaft 51. The pivoting shaft 51 extends along a pivot axis 52 in the axial direction 83 and is mounted on a housing component 101 rotatably about the pivot axis 52, with the carbon cartridge 1 also being fixed on said housing component.

(14) Furthermore, the brushholder 10 comprises a contact plug 9 for connection of an electrical conductor (not shown), which can be electrically connected to the carbon brush 2.

(15) The pivoting arm 5 has a lever arm 53, at whose end a pressing means 4 is mounted rotatably about an axis of rotation 42. In the present exemplary embodiment, the axis of rotation 42 also extends in the axial direction 83. The pressing means 4 is in the form of a roller and has a rolling face 41.

(16) An opening 6, which in this case is in the form of a groove, is provided in the carbon cartridge 1. The opening 6 extends virtually over the entire longitudinal extent of the carbon cartridge 1. The pressing means 4 can be caused to rest with its rolling face 41 on the carbon brush 2 through the opening 6.

(17) In order to press the carbon brush 2 in the direction of extent 81 against the commutator 111 (see FIGS. 1 and 2) of the electric motor 100, a spring 3 is provided which in this case is in the form of a spiral spring. The terms spring 3 and spiral spring will be used synonymously in the text which follows. The spiral spring has an outer end 32, with which it rests on an end face 22 of the carbon brush 2. The end face 22 of the carbon brush 2 is provided at that end of the carbon brush 2 which is remote from the commutator 111. Therefore, the carbon brush 2 is pressed by means of the spring 3 in the direction of extent 81, which is the radial direction 81 of the electric motor 100.

(18) Furthermore, the spiral spring 3 has an inner end 31, which is fixed in rotationally fixed fashion on the pivoting shaft 51. In this case, for this purpose it is inserted into a groove 54 which is provided in the pivoting shaft 51.

(19) By rotation of the spring 3, therefore, pretensioning can be produced which presses the pressing means 4 in a pressing direction 82 with its rolling face 41 against a side face 21 of the carbon brush 2, with the result that said carbon brush is caused to rest on the lateral surface 13 of the accommodating area 12 without play. In this case, the pressing means 4 is provided at an end of the carbon brush 2 which is opposite the end face 22. As a result, it is provided very close to a contact area 23 of the carbon brush 2 with respect to the commutator 111, with the result that it very effectively prevents a vibrating movement of the carbon brush 2 in the accommodating area 12 close to the contact area 23.

(20) The pressing direction 82 is in this case provided transversely to the direction of extent 81 and corresponds to the tangential direction 82 of the electric motor 100 (see FIGS. 1 and 2). In principle, however, embodiments are also conceivable in which the pressing direction also has a directional component in the axial direction 83 of the electric motor 100.

(21) In the case of tracking of the carbon brush 2, the pressing means 4 does not impede the carbon brush 2 since the rolling face 41 rolls on the side face 21.

(22) FIG. 5 shows, schematically, a plurality of further embodiments of brushholders 10 according to the disclosure.

(23) The brushholders shown in FIGS. 5(a)-(c) differ from one another and from the embodiment shown in FIGS. 3 and 4 primarily owing to the differently configured function faces 7 on the carbon brush 2, the pressing means 4 and/or the carbon cartridge 1. The function faces 7 have the effect that the carbon brush 2 is fixed in the carbon cartridge 1 both in the axial direction 83 and in the tangential direction 82.

(24) In the exemplary embodiments shown in FIGS. 5(a) and (b), the carbon brush 2 and the pressing means 4 each have a function face 7 for this purpose, which function faces interact with one another. To be precise, the side face 21 and the rolling face 41 have, in FIG. 5(a), a bevel and, in FIG. 5(b), a wedge, which bevel and wedge form the function faces 7. In the exemplary embodiment shown in FIG. 5(c), on the other hand, the carbon cartridge 1 and the carbon brush 2 each have a function face 7 in the form of a bevel, which function faces correspond to one another and interact with one another.