GB2082399A

GB2082399A - A brush holder for electric machines

Info

Publication number: GB2082399A
Application number: GB8118129A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-06-14
Filing date: 1981-06-12
Publication date: 1982-03-03
Also published as: FR2484721B3; GB2082399B; JPS5731354A; DE3022466A1; FR2484721A1

Abstract

A brush holder for alternators has a pivotally mounted support arm 30 formed as a rigid moulding with a recess 41 receiving the brush (31) as a tight fit. The brush 31 can be secured solely by means of its fit in the recess in the support arm 30 or it can be provided with additional securing means such as is provided by connection to the leaf spring 35 which provides brush pressure and serves as an electrical contact element for the brush. <IMAGE>

Description

SPECIFICATION A brush holder for electric machines, especially alternators in motor vehicles State of the art The invention originates from a brush holder according to the preamble to the main claim.

Such a brush holder is already known (German AS 1613433) in which a moulding of elastic plastics material serves as a support arm which has a recess in which is clamped the brush together with a connecting lead.

This arrangement of a brush holder is indeed simple but can only be mechanically stressed to a limited extent and is thus only suitable for machines of low power. Under high mechanical stresses, the clamping connection for the brush in the support arm can loosen whereupon, in certain circumstances, a perfect functioning of the brush holder is no longer guaranteed.

With another known arrangement of a brush holder (German OS 25 36 018) the support arm is formed by a resilient element to which the brush is, for example soldered or sintered. That indeed produces a rigid connection between the brush and the support arm and also generally provides an economic solution easy to assemble but the sphere of application of which is likewise restricted due to the incomplete rigidity of the support arm transversely of the brush axis.

Advantages of the invention As opposed to this, the arrangement in accordance with the invention comprising the characterising features of the main claim has the advantage that an altogether rigid mounting for the brush is produced which also guarantees a reliable transmission of current between the brush and the rotating opposed contact strip even under high mechanical stresses.

Advantageous further developments of the arrangement set forth in the main claim are made possible by the measures set forth in the sub-claims.

An arrangement favourable to manufacture and furthermore especially resistant to vibration is produced when the brush is moulded in the recess in the support arm without clearance. This can take place by moulding the support arm onto the previously manufactured brush or by introducing the previously manufactured support arm and if necessary the spring engaging the support arm into the press tool and thereafter ramming the material forming the brush into the recess in the support arm and into the cavity of the pressing tool connected thereto and sintering it in a subsequent working operation.

Other advantageous possibilities of moulding the brush in the recess in the support arm without clearance consist in fixing the brush in the recess by a preferably hardened sealing compound or, after inserting the brush in the recess, to mould the material of the support arm in a depression in the periphery of the brush which can, for example, take place by means of ultrasonic caulking.

In all the above described cases, the brush may be connected to an electric terminal element directly, that is to say, without a flexible lead, which is formed automatically with advantage by the spring engaging the support arm. Thus, an economical solution is provided which is, moreover, characterised by a particularly low voltage drop.

For this purpose, the brush can be provided, in accordance with the invention, with a pin which projects from the rear of the support arm out of its recess and is connected at that location with electrical terminal elements, preferably the spring itself. The pin can be a metal part inserted in the brush or preferably be a projection formed integrally with the brush which is provided with a solderable surface layer of lead, copper, silver, tin or the like.

A special working operation for connecting the brush to the electric terminal element, preferably the spring, is superfluous if in the case of moulding the brush in the pre-manufactured support arm the electric terminal element is provided with a projection extending into the recess in the support arm and is inserted in the mould during the ramming in of the material forming the brush. In this case, with an appropriate design of the electric terminal element, the brush can in addition be rigidly held in the support arm in a positive manner.

Instead of moulding the brush into the support arm or moulding it thereon an additional fixing means abutting against the rear of the support arm can be provided for quite generally retaining the support arm in a positive manner. This additional fixing means, for example a rivet formed in the brush, can be in contact with the spring, preferably formed as a leaf spring, for pressing the brush against the rotating opposed contact strip and which in its turn can serve once again with advantage for making contact with the brush. Thus, an economical construction favourable to manufacture is provided which functions reliably due to its considerable rigidity and resistance to vibration even under high mechanical stresses.

Drawing Twelve embodiments of the invention are illustrated in the drawing and are described in detail in the following specification. Fig. 1 shows a side view of the brush holder according to the first embodiment and Figs. 2 to 1 2 show the other embodiments, each with the aid of a section through the brush and its fixing location to the support arm.

Description of the embodiments The brush holder according to Fig. 1 has a base member 10 on which is formed a flange 11 which is provided with two bores 1 2 and 1 3 for fixing the brush holder to the housing of an alternator. A second flange, on which a voltage regulator 1 7 for the alternator is fixed by means of rivets 1 5 and 16, is formed at the top of the base member 10. The voltage regulator 1 7 has two terminal pins 1 8 and 1 9 which project into a free space 20 which is bounded at the top by the voltage regulator 17, at the sides by two perpendicular walls 21 and 22 and at the bottom by an intermediate wall 23 of the base member 10.

Beneath the intermediate wall 23 in the base member 10 a space 25 is formed which is bounded by an upright wall 26 and two side walls 27, 28 of the base member 10. A bearing pin 29 located in both side walls 27, 28 passes through the space 25, two support arms 30, each for a brush 31, lying one behind the other in the drawing and one covering the other, are pivotally mounted on the bearing pin. Each support arm 30 is formed by a rigid moulding of plastics material which has a hub section 32 including the bearing bore and an end section 33 carrying the brush 31 and arranged at an obtuse angle to the hub section. The end section 33 is provided with a longitudinal duct 34 in which is guided a leaf spring 35 which urges the brush 31 against a rotating counter contact strip 36 on the rotor of the alternator when the brush holder is installed.The central section 38 of the leaf spring 35 is in the form of an open eye bent around the hub section 32 of the support arm 30 and spaced therefrom and the end section 39 of the leaf spring 35 remote from the brush 31 is fixed to the base member 10 in a manner described in more detail in the following.

The brush 31 is moulded into a recess 41 in the support arm 30 without clearance. For this purpose, the preformed brush 31 is inserted in the press mould for the support arm 30 and the material for the support arm 30 is moulded around the inserted brush 31. The brush 31 had a flange 42 whereby the brush 31 is positively retained in the support arm 30 in both axial directions. A metal pin 41 is moulded in the brush 31 for making contact therewith and the pin projects out of the recess 41 to the rear of the support arm 30 and at that location is soldered to the end of the leaf spring 35.

In this case, the leaf spring 35 serves as an electrical contact element for the brush 31. In addition to the fixing location at the pin 43, the spring is fixed to the walls of the longitudinal duct 34 in the support arm 30 by caulking 44 and its end section 39 remote from the brush 31 is connected to a contact element fixed to the base member 10. The leaf spring 35 of the visible support arm 30 arranged at the top in the drawing, is connected to an angle contact 46 which is connected to the housing of the voltage regulator 1 7 by the metal rivet 16 and through the housing to components in the voltage regulator.The leaf spring 35 of the second support arm 30, not visible in the drawing, is connected to a contact strip 47 which forms on the one hand a soldering tag 48 for the connection of an electrical conductor and on the other hand has an extension 49 which is welded to the terminal pin 1 9 on the voltage regulator 1 7. The other terminal 1 8 of the voltage regulator 1 7 is welded to a contact strip 50 which projects through the upright wall 21 of the base member 10 and has an extension 51 engaging the flange 11 and which projects up to the region of the bore 12 and is connected to earth when the brush holder is installed.

The support arm 30 formed as a rigid moulding, in cooperation with the clearance free moulding in of the brush 31 in the recess 41 in the support arm 30, ensures that a reliable connection between the brush 31 and the rotating counter contact strip 36 takes place even under high mechanical stresses.

The soldering between the metallic pin 43 moulded in the brush 31 and the leaf spring 35 can, if necessary, be omitted if the pin 43 is formed as a rivet pin and is deformed after insertion of the spring 35. This deformation can also be provided in addition to the soldering.

Instead of the moulded-in metal pin 43, a pin of the same material as the brush itself could be integrally moulded with the brush 31 and which, for the purpose of the connection with the brush, is provided with a solderable surface layer, for example of tin or copper or another material suitable for the purpose.

In the embodiment according to Fig. 2, a brush 52 is moulded into a recess 53 in a support arm 54 without clearance in such a manner that, after inserting the brush in the recess, a section of the wall of the recess is forced by ultrasonic caulking into an annular groove 55 in the outer periphery of the brush.

However, the moulding-in could also take place due to ultrasonic welding. A pin 56 which projects out of the recess 53 and passes through a bore in the leaf spring 35, carries a solderable surface layer and is soldered to the leaf spring 35, is moulded onto the brush 52 to form the contact between the brush 52 and the leaf spring 35.

In the embodiment according to Fig. 3, a brush 58 is moulded without clearance in a support arm 59 in such a manner that the preformed support arm 59 is inserted in a press tool for the brush 58 and thereafter the material for the brush 58 is rammed into a recess 60 in the support arm 59 and into a cavity in the press tool connected thereto whereafter the parts are subjected to a heat treatment for sintering the material of the brush. The brush 58 has a flange 61 which positively supports the brush against the contact pressure on the support arm 59. The bent-over end 62 of a leaf spring 63 serves for the positive retention of the brush 58 in the other axial direction and the bent end 62 has been so inserted in the press tool together with the support arm 59 during the manufacture of the brush 58 that the bent section 62 projects into the recess 60.The section 62 has a bore 64 through which the material of the brush 58 passes and forms the positive connection between the parts. Also, with this arrangement, the leaf spring 63 serves as an electrical terminal element for the brush 58 wherein this arrangement has the advantage that an additional working operation for electrically connecting the leaf spring 63 to the brush 58 by means of a conductor is not required.

A solution is illustrated in Fig. 4 in which a brush 67 provided with a flange 66 is fixed or moulded without clearance in a support arm 69 by means of a thermosetting sealing mass 68. Also with this arrangement, the support arm 69 has a recess 70 in which are provided a shoulder for engagement with a flange 66 and a groove 71 for the positive anchoring of the sealing compound 68. A pin 72 on the brush 67 is soldered to the leaf spring 35 which covers the recess 70 at the rear of the support arm 69. A metallic pin could also be moulded in the brush 67, as illustrated in Fig.

1, instead of the moulded-on pin 72.

In the embodiment according to Fig. 5, an additional fixing means in the form of a threaded nut 77 are provided supported against the rear of the support arm 76 for positively fixing a brush 74 in a recess 75 in the support arm 76, the nut being screwed onto a threaded pin 78 moulded in the brush 74. The nut 77 pulls the brush 74 hard against a shoulder 79 in the recess 75 whereby the brush 74 is rigidly held in the support arm 76 positively in both axial directions. The clearance-free fitting of the brush 74 in the recess 75 makes sure that the brush 74 is rigidly connected to support arm 76 also in a radial direction. With this arrangement, the leaf spring 35 also acts as a contact element which for this purpose extends beneath the nut 77 and is clamped by the latter against the rear of the support arm 76.For especially high mechanical stresses, the brush 74 can be secured in addition in the recess 75 by an adhesive.

The embodiment according to Fig. 6 differs from that according to Fig. 5 simply by the fact that, instead of a threaded pin 78, a rivet pin 80 is moulded in a brush 81 and serves to positively retain the brush in the support arm 76.

In the arrangement according to Fig. 7, a pin-like plug element 83 is moulded in a brush 82 and engages in a resiliently widenable collar aperture 84 in a leaf spring 86 engaging the rear of support arm 85. Furthermore, the brush 82 is fixed in the support arm 85 as with the brush holders according to Figs. 5 and 6. To assist the retaining force in the collar aperture 85, the brush 82 can, in this case, be additionally secured to the support arm by an adhesive.

In the embodiment according to Fig. 8, a brush 87 is provided with a conical section 88 and a cylindrical pin 89 connected thereto which carries a solderable surface layer. The brush 87 is pushed into a recess in a support arm 90 which is fitted to the conical section 88 and to the pin 89 of the brush and supports the brush against the contact pressure. The pin 89 is connected by a soldered location 91 to the leaf spring 35 supported by the rear of the support arm 90, the leaf spring 35, in association with the soldered location 91, forming the additional fixing element for positively retaining the brush 87 in the support arm 90.

The brush holder according to Fig. 9 differs from that according to Fig. 8 simply by the fact that instead of a conical transition from a pin 92 to the remaining portion of a brush 93, a level transition shoulder 94 is formed against which the brush is supported in a support arm 95 against the contact pressure.

In the embodiment according to Fig. 10, the leaf spring 35 in association with a soldered location 96 is once again provided as an additional fixing element for a brush 97 in a support arm 98. With this arrangement, the brush 97 is clamped in the support arm 98 which, for this purpose, is provided with a resiliently widenable receiving opening 99.

For improving the resilient properties, slots 100 are provided in the support arm 98 and which subdivide the wall section surrounding its receiving opening 99. In the receiving opening 99, an annular rib 101 is provided which engages in an annular groove in the brush 97. The brush 97 can be additionally retained in the support arm 98 by an adhesive.

In the embodiment according to Fig. 11, a brush 102 is forced into a receiving opening 103 in the form of a blind bore in a support arm 104 and is rigidly held in the support arm by a shrunk-on tube 105.

Fig. 1 2 shows an arrangement in which a brush 108 is forced without clearance into or moulded-in a recess 109 formed as a blind bore in a support arm 11 0. The additional means for positively retaining the brush 108 in-the support arm 110 consist in this instance of a flexible copper conductor 111 which is rigidly connected to the brush 108, passes fittingly through a bore 11 2 in the support arm 110 and is sharpely bent twice at its rear. The central section of the flexible copper conductor 111 extending from the first bend engages the rear of the support arm 110. The end section 11 3 of the flexible copper conductor 111 behind the second bend is raised and is welded to the raised end of a leaf spring 114. In this case, the leaf spring 114 also serves as a contact element for the brush 108 and in the vicinity thereof is fixed in a suitable manner (not shown) to the support arm 110.

Claims

1. A brush holder for electric machines, especially for alternators in motor vehicles, comprising at least one pivotally mounted support arm to which is fixed a brush, also comprising means for electrically connecting the brush to a contact fixed to the frame and comprising a spring engaging the support arm for pressing the brush against a rotating counter contact strip, characterised in that, the support arm in the form of a rigid moulding is provided with a recess for receiving the brush and the brush is secured positively and clearance-free in the recess in the support arm.

2. A brush holder according to claim 1, characterised in that, the brush is moulded in the recess in the support arm without clearance.

3. A brush holder according to claim 2, characterised in that, the section of the brush pushed into the support arm is provided with projections and/or depressions.

4. A brush holder according to claim 2 or 3, characterised in that, the support arm is moulded onto the preformed brush.

5. A brush holder according to claim 4, characterised in that, the brush has a depression in which engages a projection on the wall of the recess in the support arm formed by caulking.

6. A brush holder according to claim 2 or 3, characterised in that, the brush is moulded in the recess in the preformed support arm.

7. A brush holder according to claim 2 or 3, characterised in that, the brush is secured in the recess in the support arm by a sealing compound.

8. A brush holder according to claim 1, characterised in that, an additional fixing element supported at the rear of the support arm is provided for positively securing the brush in the support arm.

9. A brush holder according to claim 8, characterised in that, an end section of a leaf spring engaging the rear of the support arm and bent into the recess in the support arm serves as an additional fixing element.

10. A brush holder according to claim 9, characterised in that, the bent end section of the leaf spring is provided with a bore through which passes the material of the brush moulded in the recess in the support arm.

11. A brush holder according to claim 8, characterised in that, the additional fixing means is a threaded nut which is screwed onto a threaded pin moulded into the brush.

1 2. A brush holder according to claim 8, characterised in that, the additional fixing means is a rivet pin moulded in the brush.

1 3. A brush holder according to claim 8, characterised in that, a plug-like latching element is moulded in the brush and engages in a resiliently widenable collar aperture in a leaf spring engaging the rear of the support arm.

14. A brush holder according to claim 8, characterised in that, the brush is provided with a pin of solderable material or having a solderable outer layer, which is soldered to a leaf spring engaging the rear of the support arm.

1 5. A brush holder according to claim 8, characterised in that, the additional means for positively securing the brush in the support arm is a shrunk on tube drawn over the facing ends of the said two parts.

16. A brush holder according to claim 8, characterised in that, the additional means for positively securing the brush in the support arm is a flexible connector for the brush, which passes through a bore in the support arm and is anchored against longitudinal displacement to the spring engaging the support arm.

1 7. A brush holder according to one of claims 8 to 16, characterised in that, the brush is positively supported against the contact pressure by a shoulder in the recess in the support arm.

1 8. A brush holder according to claim 17, characterised in that, the shoulder is formed by a conical section in the recess in the support arm.

1 9. A brush holder according to claim 18, characterised in that, the shoulder is formed by a projection on the wall of the recess of the support arm and resiliently engaging in an annular groove in the brush.

20. A brush holder according to one of claims 8 to 19, characterised in that, the brush is secured in the recess in the support arm by an adhesive.

21. A brush holder according to one of the preceding claims, characterised in that, the spring engaging the support arm for pressing the brush against the rotating counter contact strip serves simultaneously as an electrical connecting element for the brush.

22. A brush holder according to claim 21, characterised in that, the brush moulded into the support arm has a pin with an electrically conducting surface which is in electrically conducting contact with a leaf spring engaging the support arm.

23. A brush holder according to claim 22, characterised in that, the pin is a metal member moulded into the brush.

24. A brush holder according to claims 23 and 11 or 23 and 12, characterised in that, the leaf spring projects beneath the threaded nut or the head of the rivet pin.

25. A brush holder according to claim 22, characterised in that, the pin is integrally moulded to the brush.

26. A brush holder according to claim 25, characterised in that the pin is provided with a solderable surface layer and is soldered to the leaf spring.

27. A brush holder substantially as herein described with reference to any one of Figs. 1 to 1 2 of the accompanying drawings.