GB2302999A

GB2302999A - Mechanical commutated electric motor

Info

Publication number: GB2302999A
Application number: GB9611409A
Authority: GB
Inventors: Guillermo Havenstein
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1995-06-30
Filing date: 1996-05-31
Publication date: 1997-02-05
Anticipated expiration: 2016-05-31
Also published as: ITMI961269A0; GB9611409D0; GB2302999B; IT1284056B1; DE19523896B4; CH690391A5; CN1068714C; CN1139829A; FR2738087A1; ITMI961269A1; DE19523896A1; FR2738087B1

Description

1 Mechanically commutated electric motor

Background art

2302999 The invention proceeds from a mechanically commutated electric motor according to the preamble of claim 1 and from a brush holder according to the preamble of claim 10. It is already known in a mechanically commutated electric motor to provide a brush holder with guide rails, which are disposed spaced-apart and parallel to one another and between each pair of which a location opening for brushes is formed. The guide rails engage into corresponding guide slots in the brushes and are so disposed that the brushes lie substantially radially relative to an axis of rotation of the electric motor. Such brush holders are disclosed, for example, in EP 24 121 Bl, WO 84/000645 and EP 482 235 Al.

What all of said brush holders have in common is that the location opening formed between the guide rails lies in a plane extending substantially at right angles to the motor axis. As a result of said arrangement, the guide slots of the brushes are disposed in each case in a - viewed in the direction of motion of the commutator - front and rear end face of the respective brush, i.e. the interfaces of the guide slots with the collector-side underside of the brush are offset relative to one another viewed in the direction of motion. Experience has shown that, compared to conventional brushes guided in cartridges, such brush arrangements with guide rails lead to higher brush abrasion and to sparking. For said reason, brush holders with guide rails have hitherto been usable only with relatively low-power electric motors.

2 Advantages of the invention In contrast, the electric motor according to the invention having the characterizing features of claim 1 has the advantage of decreasing brush abrasion and reducing sparking. It is therefore possible to broaden the range of application of brush holders with guide rails, which are inexpensive to manufacture. A brush holder which is particularly easy to manufacture is indicated in claim 10.

By virtue of the measures indicated in the sub-claims, advantageous developments and improvements of the electric motor described in claim 1 are possible.

Drawings An embodiment of.the invention is illustrated in a simplified manner in the drawings and explained in detail in the following description. Figure 1 shows a perspective view of a brush holder of an electric motor, Figure 2 a side view of the brush holder, Figure 3 a front view of the brush holder and Figure 4 a section along line IV-IV in Figure 3.

Description of the embodiment

In Figure 1, 10 denotes a brush holder which is used to hold a brush 11. The brush holder 10 comprises two strip-like limbs 12, 13, which extend at a distance from and parallel to one another and form between them a location opening 14 for the brush 11. The limbs 12, 13 are connected to one another at the ends by yokes 15, 16. The brush holder 10 as a whole is made of plate-like material, the basic shape being acquired, for example, by blanking from the starting material and the yokes 15, 16 subsequently being bent at an angle. The brush holder 10 is preferably made of sheet metal. It may however alternatively be made of plastic material. The regions of the limbs 12, 13 facing the location opening 14 serve as guide 3 rails 17, 18 (see Figure 4), which are designed for engagement into corresponding guide grooves 19, 20 in the brush 11. The guide rails 17, 18 and the guide grooves 19, 20 together form a longitudinal guide for the brush 11, which permits an axial displacement of the brush 11 inside the location opening 14. To guarantee the axial displacement of the brush 11, at least the collector-side yoke 15 extends in a substantially U- shaped manner around the location opening 14.

The brush holder 10 is so disposed relative to a collector 21 of the electric motor that the location opening 14 for the brush 11 lies substantially in a plane formed by a motor axis 22, which corresponds to the axis of rotation of the collector 21, and by a perpendicular 37 to the motor axis 22. A spring 23 is inserted into the location opening 14 between the brush 11 and the yoke 16 remote from the collector 21 and holds the brush 11 applied against an outer periphery of the collector 21. The yoke 16, like the yoke 15, is bent substantially at right angles to the limbs 12, 13. Lugs 26, 27 are formed on connecting webs 24, 25 of the yokes 15, 16 respectively, the lug 26 being bent substantially into a Vshape and being movable so that the bottom edge of the V is applied against an end face 11a of the brush 11. The lug 26 therefore takes the form of a brush brake for facilitating assembly when the brush 11 is inserted. The lug 27 disposed at the other end of the brush holder 10 extends substantially at right angles to the location opening 14 away from the connecting web 25 and serves as a support for the spring 23. A tab connector 28 used to contact a receptacle 29 is additionally provided on the limb 12 on a lug which is likewise bent at right angles to the location opening 14. The receptacle 29 is used for the electrical contacting of a shunt 30, which in turn electrically contacts the brush 11.

In the region of the starting point of the yoke 15 on the limbs 12, 13, the limbs 12, 13 are slotted substantially centrally (see Figure 3), the outer cross section being bent 4 to form the U-shaped yoke 24 and the inner cross section forming the guide rails 17, 18. Corresponding slots 35, 36 between the inner guide regions and the outer bent-round regions are clearly visible in Figure 3.

An important feature is the arrangement of the guide rails 17, 18 substantially in a plane formed by the motor axis 22 and its perpendicular 37. As a result, the edges 31, 32 between the end faces lia and a collector-side underside of the brush 11, which lie substantially parallel to the motor axis 22 and are offset in the direction of rotation of the collector 21, are uninterrupted. Only edges 33, 34 at side faces lib and at the underside of the brush 11 are interrupted by the ends of the guide grooves 19, 20.

Two brush holders 10 are preferably disposed diametrically offset relative to the collector 21. The brush holders 10 may be connected to one another by a carrier part (not shown), e.g. an end shield or a housing part. Under certain circumstances it may be advantageous to tilt the brush holder 10 slightly relative to the plane formed by the motor axis 22 and its perpendicular 37.

R Z --- 2 RO 6-7 28--;-0,6-.9-5- Md/Pi ROBERT BOSCH GMBH, 70442 Stuttgart

Claims

Claims

2.

Mechanically commutated electric motor havinga brush holder (10), which comprises guide rails (17, 18) extending in each case in pairs parallel to one another and aligned substantially radially relative to a motor axis (22), each two guide rails (17, 18) forming between them a location opening (14) for a brush (11) and being designed for longitudinally guiding engagement into corresponding guide grooves (19, 20) of the brush (11), characterized in that the location opening (14) formed between the guide rails (17, 18) lies substantially in a plane formed by the motor axis (22) and a perpendicular (37) to the motor axis (22).

Electric motor according to claim 1, characterized in that the guide rails (17, 18) are formed on limbs (12, 13) of the brush holder (10), the limbs (12, 13) being connected to one another by yokes (15, 16).

3. Electric motor according to claim 2, characterized in that the yokes (15, 16) at the ends of the limbs (12, 13) are bent substantially at right angles to said limbs.

4. Electric motor according to claim 3, characterized in that at least the one collector-side yoke (15) is disposed in a substantially U-shaped manner around the location opening (14) with the carbon brush (11).

5.

Electric motor according to claim 2 or 4, characterized in that provided in the region of the starting points of the yoke (15) on the limbs (12, 13) are open-edged slots 6 (35, 36) which enable the outer regions of the limbs (12, 13) to be bent at an angle relative to the inner regions serving as guide rails (17, 18).

6.

7.

8.

Electric motor according to claim 5, characterized in that provided on the yoke (15) at a side facing the location opening (14) is a lug (26), which is bent substantially into a V shape and serves as a brush brake.

Electric motor according to one of claims 2 to 5, characterized in that formed on the other yoke (16) disposed above the brush (11) is a lug (27), which is used to support the spring (23).

Electric motor according to one of claims 2 to 5, characterized in that formed on one of the limbs (12, 13) is a tab connector (28), which is used to contact a receptacle (29) for the electrical contacting of a shunt (30).

Electric motor according to one of the preceding claims, characterized in that the brush holder (10) is manufactured as a bent blank from sheet metal.

10. Brush holder for a mechanically commutated electric motor, comprising guide rails (17, 18) extending at a distance from and parallel to one another, the guide rails (17, 18) between them forming a location opening (14), characterized in that the brush holder (10) comprises two platelike limbs (12, 13) on which the guide rails (17, 18) are formed, the limbs (12, 13) being connected to one another at the ends by yokes (15, 16) bent substantially at right angles.

7 A mechanically commutated electric motor substantially as herein described with reference to the accompanying drawing.

12. A brush holder substantially as herein described with reference to the accompanying drawing.