WO2008000301A1

WO2008000301A1 - Direct current electrical machine

Info

Publication number: WO2008000301A1
Application number: PCT/EP2006/063738
Authority: WO
Inventors: Francesco Battistella
Original assignee: Amer S.P.A.
Priority date: 2006-06-30
Filing date: 2006-06-30
Publication date: 2008-01-03

Abstract

Direct current electrical machine (1; 100) of the type comprising: a machine body (2) consisting of a cap containing the brushes (4) and a cap for the output (4a) with a casing (3) between them defining a volume enclosing an inductor (6); an armature (7) complete with a commutator (8) associated with the shaft (9) of the machine (1; 100), at least one pair of brushes (10, 110) in contact with the commutator (8); means for the electrical connection (11) of each of the brushes (10; 110); a plurality of holders (13; 113), each of which contains one of the brushes (10; 110) with the electrical connection means (11). Each of the holders (13; 113) fits in a corresponding through hole (14; 114) in the machine body (2), the profile (14a) of which is defined by the juxtaposed perimeter edges (16, 17) of the brush cap (4) and casing (3) when they are coupled together. The through hole (14, 114) is suitable for housing a recessed portion (15) of the holder (13; 113) surrounded by surfaces (18, 19a, 19b) projecting from the bottom (20) of the recess (15) and abutting against the machine body (2) so as to engage the holder (13; 113) in a direction radial to the armature (7).

Description

"DIRECT CURRENT ELECTRICAL MACHINE".

DESCRIPTION

This invention concerns a direct current electrical machine, such as a motor or a dynamo. Known versions of direct current electrical machines, be they motors or dynamos, involve the use of a machine body containing an inductor, an armature installed coaxially inside the inductor and complete with a commutator associated with the machine's shaft, and a plurality of brushes arranged in contact with the commutator and electrically connected to the machine's power terminals.

Said brushes are in an even number, are generally two or four, depending on the number of poles required, i.e. on the power requirement.

The brushes are connected together in pairs so that one brush in each pair is connected to the positive pole and the other is connected to the negative pole of the machine's power supply.

Different embodiments of direct current electrical machines are known.

A first embodiment comprises a machine body containing a number of brass seats coinciding with the number of brushes involved and these brass seats contain the brushes. The brushes are associated with a spring, enabling them to slide elastically within the seats and the seats are associated with a load-bearing structure by welding or screwing means.

This solution has the drawback of being particularly difficult to produce, because of the plurality of separate pieces to manufacture and assemble, and complex in terms of maintenance because the association of the brass seats with the load-bearing structure is such that the failure of any of said seats makes it necessary to replace the whole load-bearing structure with the attached brass seats.

According to another embodiment, each brush is contained in a holder comprising the brass seat and a cylindrically-shaped supporting member, generally made of plastic, that is inserted by means of pressure in a through hole in the machine body.

The association between the hole and the shaped body of the holder may be achieved by mechanical interference or by means of adhesives. Though it considerably simplifies the manufacture of the machine, this type of solution still poses certain servicing problems determined by the fact that, in the event of failure of any of these holders, it takes a long time for maintenance personnel to slide out and substitute the damaged holder because they have to detach any adhesive or overcome the mechanical interference with which the holder was inserted in the hole.

According to a further, different embodiment, the association between the holder and the hole is achieved by elastic means, generally consisting of tabs, preferably but not necessarily made of the same material as the holder: once the holder has been inserted, these tabs oppose the withdrawal of the holder from the hole.

Though it overcomes the problem of how to facilitate the servicing of the electrical machine, said solution presents further drawbacks determined by the fact that the association between the holder and the machine body is achieved by means of elastic tabs: when the machine is in use, the elasticity of these tabs may decline to some degree due to the heat produced by the machine in operation, and the resulting stiffness makes them liable to failure under the stresses to which they are submitted.

Moreover, because of said loss of elasticity, the holder generates vibrations, thereby further increasing machine noise. The object of the present invention is to overcome all the aforementioned drawbacks typical of direct current electrical machines belonging to the known state of the art.

To be more precise, a first object of the present invention is to realize a direct current electrical machine wherein the means for supporting the brushes make servicing easier than for equivalent machines according to the known state of the art.

Another object of the present invention is to realize a direct current electrical machine wherein the means for associating the brushes with the machine body ensure a lower noise level than in equivalent machines according to the known state of the art.

Said objects are achieved by a direct current electrical machine that, according to the content of the main claim, comprises:

- a machine body consisting of a cap for the brushes and an output cap, between which there is a casing defining a volume containing an inductor; - an armature complete with a commutator, installed coaxially inside said inductor and associated with the shaft of said machine;

- at least one pair of brushes in contact with said commutator;

- means for the electrical connection of each of said brushes to the contact terminals leading to an electric network separate from said machine; - a plurality of holders, each suitable for containing one of said brushes with said electrical connection means, and is characterized in that each of said holders fits into a respective through hole provided in said machine body, the profile of which is defined within the opposite perimeter edges of said brush cap and said casing, when coupled together, said hole being suitable for housing a part of said holder with a depression coming between surfaces projecting from the bottom of said depression and coming up against said machine body so as to engage said holder in a radial direction with respect to said inductor. According to the preferred embodiment, the holder comprises a core projecting in the area coming between the armature and the machine body that is contained in a corresponding seat obtained in the brush cap or casing so as to attach the holder in a direction tangential to the armature. The profile of the hole in the machine body is defined by the juxtaposition of a first profile belonging to the brush cap with a second profile belonging to the casing.

Said first and second profiles are complementary to one another and together define a closed perimeter forming a through hole in the machine body for containing the brush holder. The presence of the depression advantageously ensures the stability of the holder in the direction radial to the commutator and in the direction parallel to the machine shaft, while the presence of the core projecting from the holder and of the corresponding seat in the brush cap or casing ensures the stability of the holder in the direction tangential to the commutator. The holder is thus solidly attached to the machine body, being engaged in three directions perpendicular to one another.

Because the profile of the hole is obtained by the juxtaposition of two profiles obtained in the brush cap and casing forming the machine body, and because the association between the holder and the machine body is due exclusively to the sliding insertion of the holder in the profiles and seats provided thereby, the direct current electrical machine of the invention also advantageously allows for the replacement of any of the holders to be achieved more easily than in equivalent machines according to the known state of the art. In the light of the above considerations, the electrical machine of the invention also advantageously affords a greater simplicity of assembly than equivalent machines according to the known state of the art.

Moreover, since the association between the holder and the machine body engages the holder along three axes perpendicular to one another, the electrical machine of the invention advantageously assures a lower noise level due to vibrations of the holder and brush than in equivalent machines according to the known state of the art.

It should be noted, moreover, that the shape and size of the brush are uninfluential and the holder advantageously has the same overall dimensions whatever the brush installed. In the executive stage, it will simply be necessary to modify the part of the mold coinciding with the inside of the holder, without changing the part of the mold coinciding with the outside of the holder, to obtain electrical machines with different brushes.

As a result, the electrical machine advantageously offers a greater modularity than the electrical machines of known type, facilitating any changes in the type of brushes being used. The above-mentioned objects and advantages are further illustrated in the description of preferred embodiments of the invention provided herein as nonrestrictive examples with reference to the attached drawings, wherein: fig. 1 show an exploded view of the direct current electrical machine of the invention; - figs. 2 to 8 show certain details of the direct current electrical machine of the invention; fig. 9 shows an exploded view of an executive variant of the direct current electrical machine of the invention. The direct current electrical machine forming the object of the invention is illustrated in fig. 1 , wherein it is globally indicated by the numeral 1 and can be seen essentially to comprise a machine body 2, consisting of a brush cap 4 and an output cap 4a on either side of a casing 3, thus defining a volume containing an inductor 6, and an armature 7 complete with a commutator 8 arranged coaxially inside the inductor 6 and associated with the shaft 9 of the machine 1. Four brushes 10 are placed in contact with the commutator 8 and means for the electrical connection 11 of each of the brushes 10 to the connection terminals 12 leading to the electrical network separate from the machine 1 are inserted in four holders 13, each of which contains one of the four brushes 10 with its corresponding electrical connection means 11.

According to the invention, each of the holders 13 is housed in a corresponding through hole 14 in the machine body 2 having a profile 14a defined by the juxtaposed perimeter edges 16, 17 of the casing 3 and brush cap 4 when coupled together. The hole 14 houses a recessed part 15 of the holder 13 which, as shown in figs. 2 and 3, is surrounded by surfaces 18, 19a, 19b that project from the bottom 20 of said recess 15 and come up against the machine body 2, thereby engaging the holder 13 in a direction radial to the armature 7. According to the preferred embodiment described and illustrated particularly in fig. 3, the holder 13 comprises a first projecting core 21 in the area between the armature 7 and the machine body 2, that fits into a corresponding seat 22, illustrated in fig. 1 , in the brush cap 4, thereby engaging the holder 13 in a direction tangential to the armature 7. The profile 14a of the hole 14 in the machine body 2 consists of a first profile 14b belonging to the casing 3 and a corresponding second profile 14c belonging to the brush cap 4, which together define a closed perimeter. To be more precise, the first profile 14b is flat, while the second profile 14c is concave. This solution is not intended to be restrictive, however, since different executive embodiments, wherein both profiles are concave, or the first profile is concave and the second is flat, are equally feasible; or the casing and output cap may be made in a single piece.

As illustrated in fig. 4, the holder 13 comprises a main body 25, developing mainly in the longitudinal direction along an axis Z, wherein the first projecting core 21 and the recess 15 surrounded by the projecting surfaces 18, 19a and 19b are defined.

At one end 26, the holder 13 is complete with a shaped plate 27. Said plate and the main body 25 of the holder include cavities 28 for containing means for the electrical connection 11 of the brush 10 to the connection terminals 12 leading to the electrical network outside the machine 1. The projecting surfaces 18, 19a and 19b surrounding the recess 15 are defined, as shown in figs. 3 and 4, by the wall 18 of the plate 27 facing towards the main body 25, by a first in lateral abutment surface 19a belonging to the first projecting core 21 and facing towards the plate 27, and by a second lateral abutment surface 19b belonging to a second projecting core 30 and facing towards the plate 27.

The holder 13 also has a through hole 31 , developing longitudinally along the axis Z of the main body 25, for the insertion and stable engagement of a tubular conductor element 32, which slidingly contains the brush 10. According to the preferred embodiment described herein, the brush is parallelepiped in shape, with a rectangular cross-section. Said solution shall not be intended as restrictive of other embodiments wherein, for instance, the brushes may be parallelepiped in shape but with a trapeze-shaped cross-section, or they may be cylindrical or in any other shape. As mentioned previously, therefore, it should be noted that the shape and size of the brushes are of no consequence, so brushes of different shape and size can be used at any time simply by using a holder with the same overall dimensions but a different tubular cross-section. This considerably increases the modularity and flexibility in use of the electrical machine of the invention.

The cavities 28 for the electrical connection means 11 comprise a recess 28a, shown in detail in fig. 5, made in the shaped plate 27, on the side opposite the surface 18 in contact with the main body 25, that communicates with two side channels 28b, 28c in the main body 25 running parallel to the longitudinal axis Z.

As shown in figs. 4 and 6, for each holder 13, the electrical connection means 11 comprise a bracket 35 associated with the corresponding brush 10 and consisting of:

- a central body 36, complete at one extremity with a lug 37 for anchoring the connection terminals 12 leading to the electrical network, which fits into the recess 28a of the shaped plate 27;

- three bent fins 38, projecting from the central body 36, two of which 38b, 38c are for holding Faston connectors attached to electrical connection wires and fit into a corresponding side channels 28b, 28c, while the third 38a provides an electrical contact with the tubular conductor element 32 of the holder 13.

According to a further embodiment of the bracket, illustrated in fig. 7 and identified by the numeral 135, the lug is replaced by a fourth bent fin 137 for providing a further electrical contact with the tubular conductor element of the holder.

Each bracket 35, 135 is associated with the corresponding brush 10 electrically by means of a conductor and elastically by means of a spring 40. The holders 13 also comprise an insulating element 41 inserted in the recess 28a of the shaped plate 27 and in contact with the central body 36 of the bracket 35.

The outer perimeter 42 of said insulating element and the inner perimeter of the recess 28a of the shaped plate 27 are coupled by mechanical interference. According to different embodiments, not illustrated or described herein, the insulating element and plate are held together by means of adhesive substances applied between the outer perimeter of the insulating element and the inner perimeter of the recess in the plate, or by screwing means. In practice, the assembly stage involves fitting each holder 13 in the machine body 2 and then inserting first the tubular conductor element 32, then the brush 10 associated with the spring 40 and with the electrical conductor for connection to the bracket 35.

According to the embodiment described herein, there are four brushes 10 with their respective holders 13 and the electrical connection is as follows: - the positive and negative electrical connection wires are connected to the lugs 37 of two adjacent holders 13; - the electrical connection for the other two brushes 10 is obtained by means of electric wires 45, 46 fitted with Faston connectors that, inside the machine body 2, connect the brackets 35, 135 of each of the holders 13 for said brushes 10 to a respective holder 13 among those connected to the power supply wires. In this case, the two holders 13 that are not connected directly to the machine's electric connection wires use the executive variant of the brackets 135 without any cable lugs.

The user consequently takes action to connect the brushes 10 in pairs, as illustrated in fig. 8, by means of the electric wires 45, 46 fitted with Faston connectors, which are hooked onto the bent fins 38b, 38c, 138b, 138c of the brackets 35, 135.

Then the user inserts the insulating element 41 in the recess 28a in the plate

27 and inserts the holder 13 in the second profile 14c belonging to the brush cap 4. After inserting the other component parts of the machine 1 , the user couples the brush cap 4 with the casing 3 and the output cap 4a, and connects the lugs

37 of the holders 13 to the electric connection terminals 12 of the machine 1.

According to an executive variant shown in fig. 9, the machine 100 of the invention has only two brushes 110. As shown in the figure, these brushes are arranged one opposite the other and the other two holes 114 are closed with the aid of two plugs 150.

No internal electric connections are needed and, since each holder 113 is connected to a respective electric power wire, only the executive form of the bracket 35 complete with the lug 37 is used. It should be noted that switching from a four-brush machine to a two-brush machine can advantageously be achieved simply by removing two brushes and closing the corresponding holes in the machine body with two plugs.

In the light of the above, the direct current electrical machine of the invention fulfills all the previously stated objects. To be more specific, the direct current electrical machine of the invention achieves the object of facilitating its maintenance by comparison with equivalent machines according to the known state of the art.

Moreover, it achieves the object of providing a direct current electrical machine in which the means for associating the brushes with the machine body ensure a lower noise level for the machine of the invention than in equivalent machines according to the known state of the art.

In the executive stages, the direct current electrical machine forming the object of the invention may undergo further variants.

Even if such variants are not illustrated in the drawings or described herein, they shall nonetheless come within the context of the following claims and be protected by the present patent.

Where technical features mentioned in any claim are followed by reference signs, those reference sings have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

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Claims

1 ) Direct current electrical machine (1 ; 100) of the type comprising:

- a machine body (2) consisting of a brush cap (4) and an output cap (4a), with a casing (3) between the two for defining a volume enclosing an inductor (6);

- an armature (7) complete with a commutator (8), arranged coaxially inside said inductor (6) and associated with the shaft (9) of said machine (1 ; 100);

- at least one pair of brushes (10; 110) in contact with said commutator (8);

- means for the electrical connection (11) of each of said brushes (10; 110) to the terminals for electric connection (12) to the network outside said machine (1 ; 100);

- a plurality of holders (13; 113) each suitable for containing one of said brushes (10; 110) with said electrical connection means (11 ), characterized in that each of said holders (13; 113) fits into a corresponding through hole (14; 114) in said machine body (2) the profile (14a) of which is defined by the juxtaposed perimeter edges (16, 17) of said brush cap (4) and said casing (3), when coupled together, said through hole (14; 114) being suitable for containing a recessed portion (15) of said holder (13; 113) surrounded by surfaces (18, 19a, 19b) projecting from the bottom (20) of said recess (15) and abutting against said machine body (2) so as to engage said holder (13; 113) in a radial direction with respect to said armature (7).

2) Machine (1 ; 100) according to claim 1) characterized in that said holder (13; 113) comprises at least a first projecting core (21 ) in the area coming between said armature (7) and said machine body (2), that fits into a corresponding seat (22) in at least one of said brush cap (4) and said casing (3) so as to engage said holder (13; 113) in a direction tangential to said armature (7).

3) Machine (1 ; 100) according to claim 1) characterized in that said profile (14a) of said through hole (14) in said machine body (2) comprises a first profile (14b) belonging to said casing (3) and a second profile (14c) belonging to said brush cap (4), said first (14b) and second profiles (14c) being juxtaposed with one another to define a closed perimeter.

4) Machine according to claim 3) characterized in that said first and second profiles are concave. 5) Machine according to claim 3) characterized in that said first profile is concave and said second profile is flat.

6) Machine (1 ; 100) according to claim 3) characterized in that said first profile (14b) is flat and said second profile (14c) is concave.

7) Machine (1 ; 100) according to claim 1) characterized in that said holder (13; 113) comprises a main body (25) developing mainly in the longitudinal direction of the axis (Z), consisting of said first projecting core (21 ) and said recessed portion (15) surrounded by said projecting surfaces (18, 19a, 19b), complete at one end (26) with a shaped plate (27), said shaped plate (27) and said main body (25) containing one or more cavities (28) for said means (11 ) for the electrical connection of said brush (10; 110) to said electrical connection terminals (12) of said machine (1 ; 100).

8) Machine (1 ; 100) according to claim 7) characterized in that said projecting surfaces (18, 19a, 19b) surrounding said recess (15) are defined by the wall (18) of said plate (27), by a first lateral abutment surface (19a) belonging to said first projecting core (21 ) and by a second lateral abutment surface (19b) belonging to a second projecting core (30).

9) Machine (1 ; 100) according to claim 7) characterized in that said holder (13; 113) has a through hole (31 ), developing mainly longitudinally along said axis (Z) of said main body (25), wherein there is a tubular conductor element (32) for slidingly holding said brush (10; 110).

10) Machine (1 ; 100) according to claim 7) characterized in that said cavities (28) for said electrical connection means (11 ) comprise a recess (28a) created in said shaped plate (27) on the side opposite the surface (18) of contact with said main body (25), that is in communication with one or more side channels (28b, 28c) created in said main body (25) and running parallel to said longitudinal axis (Z).

11 ) Machine (1 ; 100) according to claim 10) characterized in that said electrical connection means (11 ) consist of a bracket (35) associated with said brush (10; 110) and comprising: - a central body (36), complete at one end with a cable lug (37) for anchoring said connection terminals (12), fitting into said recess (28a) of said shaped plate (27);

- at least one bent fin (38b, 38c), for holding a Faston connector attached to an electric connection wire, projecting from said central body (36) and located inside a corresponding side channel (28b, 28c). 12) Machine (1 ; 100) according to claim 10) characterized in that said electrical connection means (11) comprise a bracket (135) associated with said brush (10; 110) and having:

- a central body (136) inserted in said recess (28a) of said shaped plate (27); - at least one bent fin (138b, 138c) for holding a Faston connector attached to an electric connection wire, projecting from said central body (136) and located in a corresponding side channel (28b, 28c).

13) Machine (1 ; 100) according to claim 11) or 12) characterized in that it comprises an insulating element (41) inserted in said recess (28a) of said shaped plate (27) and in contact with said central body (36) of said bracket (35).

14) Machine (1 ; 100) according to claim 13) characterized in that the outer perimeter (42) of said insulating element (41) is fitted by mechanical interference inside the inner perimeter of said recess (28a) of said shaped plate (27).

15) Machine according to claim 13) characterized in that said insulating element and said plate are attached together by means of adhesive substances applied between the outer perimeter of said insulating element and the inner perimeter of said recess of said plate. 16) Machine according to claim 13) characterized in that said insulating element and said plate are held together by means of screws.

17) Machine (1 ; 100) according to claim 1) characterized in that said bracket (35; 135) is electrically associated with said brush (10; 110) by means of an electrical conductor and elastically associated with said brush (10; 110) by means of a spring (40).

18) Machine (1 ; 100) according to claim 1) characterized in that said brush (10; 110) is parallelepiped in shape with a rectangular cross-section.

19) Machine according to claim 1) characterized in that said brush is parallelepiped in shape with a trapeze-shaped cross-section. 20) Machine according to claim 1) characterized in that said brush is cylindrical in shape.

21 ) Machine according to claim 1) characterized in that it is a direct current motor.

22) Machine according to claim 1) characterized in that it is a dynamo. 23) Machine according to claim 1) characterized in that said casing and said output cap are made in one piece.