IMPROVEMENTS IN STARTER MOTORS

Abstract

A framework is disclosed for holding magnets to provide a stator for an electric motor, in particular for a starter motor. The framework is adapted to removably receive, retain and space apart a plurality of magnets within the framework to form a tubular magnet array and provide said stator. The framework may provide a stator which is easier to assemble and more reliable than known stators. The framework provides a central aperture for receiving a rotor armature of said electric motor. The framework is arranged to be slidably inserted or removed from a housing of said electric motor. A frame portion, a stator, an electric motor, a vehicle drive assembly and a method of assembling an electric motor are also described. A brush housing comprising a plurality of passages for slidably retaining brushes and comprising a plurality of bias housings, and a brush assembly comprising the brush housing are also described.

Claims

1. A framework for holding magnets to provide a stator for an electric motor, wherein the framework is adapted to removably receive, retain and space apart a plurality of magnets within the framework to form a tubular magnet array adapted to accept a rotor armature arranged for rotation about a long axis of the framework, wherein the framework is arranged to slidably engage with a housing of said electric motor for insertion therein or removal therefrom.

2. (canceled)

3. The framework according to claim 2, wherein the plurality of frame portions comprises two frame portions, each of the two frame portions providing approximately half of the framework.

4. The framework according to claim 1, wherein the framework has a substantially cylindrical outer surface for sliding engagement with said housing.

5. The framework according to claim 1, wherein said magnets are curved and the framework is adapted to receive, retain and space apart said magnets to provide said tubular magnet array retained within the framework.

6. The framework according to claim 1, wherein the framework comprises a plurality of bays each adapted to receive, retain and space apart one of the said plurality of magnets.

7. The framework according to claim 6, wherein the bays are tapered to narrow from an outer surface of the assembled framework towards an inner surface of the framework.

8. (canceled)

9. The framework according to claim 1 wherein the framework is elastically deformable.

10. The framework according to claim 1, wherein the framework is shaped to accommodate elongate bolts extending substantially parallel to the long axis of the framework for assembling an electric motor incorporating the framework.

11. The framework according to claim 1, wherein the framework comprises apertures adapted to receive one or more electrical terminals for connection to one or more brushes.

12. The framework according to claim 11, wherein the framework and one of the apertures forms an electrical insulator portion for an electrical terminal in order to provide an insulated electrical terminal.

13-20. (canceled)

21. A stator comprising a framework according to claim 1 and a plurality of magnets received, retained and spaced apart within the framework to form a tubular magnet array.

22. An electric motor comprising: a stator according to claim 21; a brush housing comprising brushes, and an armature comprising an armature shaft.

23. (canceled)

24. A vehicle drive assembly comprising an engine and an electric motor according to claim 22 configured as a starter motor for the engine.

25. (canceled)

26. (canceled)

27. A brush housing for an electric motor, the brush housing comprising: a central aperture adapted to receive an armature comprising an armature shaft; a plurality of passages, each passage arranged to slidably retain a brush at least partially extending into the central aperture for contacting said armature shaft; and a plurality of bias housings, each bias housing arranged in communication with at least one of the plurality of passages through an opening and each bias housing arranged to receive and retain a bias for urging, through the opening, said brushes towards said armature shaft.

28. The brush housing according to claim 27, wherein each bias housing comprises a slot arranged on an outer surface of the brush housing through which a bias can be passed when compressed.

29. The brush housing according to claim 27, wherein the bias housings are each adapted to receive a conical or frustoconical spring as the bias.

30. The brush housing according to claim 27, wherein the passages are adapted to slidably receive brushes such that said brushes are arranged radially with respect to the central aperture.

31. The brush housing according to claim 27, wherein the bias housings are arranged outward from the passages with respect to the central aperture.

32. The brush housing according to claim 27, wherein the brush housing is formed from at least a first part and a second part and wherein the first and second parts are arranged to cooperate to retain said brushes and biases within their respective passages and bias housings.

33. A brush assembly comprising a brush housing according to claim 27; a plurality of brushes located in the passages; and a plurality of biases located in the bias housings.

34. An electric motor comprising a brush assembly according to claim 33, a stator and an armature shaft; wherein the biases bias the brushes against the armature shaft.

35. A method of assembling an electric motor, the method comprising the steps of: a) providing a stator or stator framework having a plurality of brush electrical terminals, each comprising a brush attached thereto; b) locating at least a first part of a brush housing according to claim 27 on the stator or stator framework; c) arranging each of the brushes in a passage of the brush housing; d) arranging an armature in the central aperture of the brush housing; e) arranging a bias in each of the bias housings of the brush housing such that the biases urge the brushes towards and into contact with the armature.

36. The method according to claim 35, wherein after step c) and before step d) there is a step of joining a first part of the brush housing to a second part of the brush housing to retain the brushes in the passages.

37. The method according to claim 35, wherein the biases of step d) are conical or frustoconical springs.

38. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0126] For a better understanding of the invention, and to show how example embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:

[0127] FIG. 1 is a perspective view of a framework (100) according to the first aspect.

[0128] FIG. 2 is a perspective view of two frame portions (200a and 200b) according to the second aspect which mutually interengage to form the framework (100) of FIG. 1.

[0129] FIG. 3 is a perspective view of the framework (100) shown in FIG. 1 comprising a plurality of magnets (120) to provide a stator (300) according to the third aspect.

[0130] FIG. 4 shows an exploded view of an electric motor (400) according to the fourth aspect and/or the ninth aspect, the electric motor comprising a stator (300) according to the third aspect, the stator comprising a framework (100) as shown in FIG. 1, and the electric motor comprising a brush housing (500) according to the seventh aspect.

[0131] FIG. 5 shows a perspective view of a fully assembled electric motor (400) of FIG. 4.

[0132] FIG. 6 shows a perspective view of a brush housing (500) for an electric motor according to the seventh aspect.

[0133] FIGS. 7a and 7b show perspective views of a first part (510) and second part (520) of a brush housing for an electric motor according to the seventh aspect, respectively.

[0134] FIG. 7c shows the first part of a brush housing (510) of FIG. 7a comprising brushes and biases.

[0135] FIG. 8 shows the brush housing (500) of FIG. 6 comprising a plurality of brushes and biases, according to the eighth aspect.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0136] FIG. 1 shows a framework (100) according to the first aspect of the present invention. The framework (100) comprises a body (110) formed of a polymeric material, an outer surface (111) and a central aperture (112). The framework (100) comprises elongate slots (113) for receiving elongate bolts to affix the framework into an electric motor. The framework (100) also comprises an aperture (114a) for receiving an earthed electrical terminal and an aperture (114b) for receiving an insulated electrical terminal. The insulated and earthed electrical terminals provide the positive and negative electrical connections for a brush assembly which is connected to the framework in use. The body (110) is arranged such that six bays (120) are formed in the outer surface (111) of the framework (100) to each accommodate in use one of a plurality of magnets to form a tubular magnet array. The bays (120) have a pair of longer edges (121) and a pair of shorter edges (122). The longer edges (121) are tapered such that the bays (120) are wider at the outer surface (111) of the framework (100) and narrower at an inner surface of the framework (100) which forms the central aperture (112). The shorter edges (122) are not tapered and present a straight edge perpendicular to the central axis of the framework (100) which passes through the central aperture (112). The tapering of longer edges (121) and of bays (120) ensures that a magnet with a suitably complimentary shape cannot pass through the bays (120) and into the central aperture (120). The body (110) of the framework (100) is elastically deformable and arranged to engage in a close tolerance fit with a suitably complimentary shaped magnet when said magnet is placed in a bay (120) in order to retain said magnet in place during assembly and subsequent use.

[0137] FIG. 2 shows two frame portions (200a and 200b) according to the second aspect of the invention. Each frame portion (200a and 200b) is a hollow semicylinder frame portion comprising three bays (120), two elongate slots (113) and one aperture (114a or 114b) for receiving an electrical terminal. The two frame portions (200a and 200b) shown are identical apart from the apertures (114a and 114b) which are shaped differently to accommodate either an insulated or earthed electrical terminal. The two frame portions (200a and 200b) are arranged to mutually interengage to provide a framework (100) shown in FIG. 1. The frame portions (200a and 200b) are mutually interengaged by bringing together edges (210) of one frame portion (200a) with the same edges (210) of the other frame portion (200b) in order for the male snap-fit connection parts (211) to cooperate with the female snap-fit connection parts (212) in order to hold the two frame portions (200a and 200b) together to form the framework (100). Each frame portion (200a and 200b) is made of a polymeric material by a moulding process.

[0138] FIG. 3 shows the framework (100) of FIG. 1 comprising six magnets (130), each located in a bay (120) in the framework (100), which provides a stator (300) according to the third aspect. The magnets (130) are curved and so have a suitably complimentary shape to the bays (120). Magnets (130) comprise a pair of longer edges (131) and a pair of shorter edges (132). The longer edges (131) are tapered to match the tapering of longer edges (121) on bays (120) and the shorter edges (132) are not tapered and match the shape of the shorter edges (122) on bays (120). The magnets (130) are held in bays (120) by a close tolerance fit with the elastically deformable body (110) and are prevented from passing through bays (120) by the complimentary tapering of the bays (120) and the magnets (130). The framework (100) and magnets (130) form a tubular magnet array which is adapted to accept a rotor armature in an electric motor.

[0139] FIG. 4 shows an electric motor (400) according to the fourth aspect of the present invention. Electric motor (400) comprises stator (300), armature shaft (410, not shown, see FIG. 5), housing (420), front end cap (430). rear end cap (440) and brush housing (500). The armature shaft comprises armature windings (411) and commutator (412). The exploded view of

[0140] FIG. 4 shows how the electric motor (400) is assembled from these parts. Stator (300) engages with brush housing (500) and the central aperture of the stator (300) and the brush housing (500) receives armature shaft (410). Housing (420) receives the brush housing (500) and stator (300) and the electric motor is fixed together using elongate bolts (401) to affix the front end cap (430) to the rear end cap (440) with the housing (420) retained therebetween. O-rings (402), washers (403), bearings (404), seals (405) and (406) and bolts (407) are incorporated into electric motor assembly according to standard practice. Stator (300) receives electrical terminal assemblies (408a and 408b) in apertures (114a and 114b, see FIG. 1).

[0141] The assembly process of the electric motor (400) shown in FIG. 4 is greatly facilitated by the provision of framework (100) which allows magnets (130) to be simply placed in bays (120) of the framework (100) and retained and spaced apart therein to provide the tubular magnet array of stator (300). Stator (300) can then be simply slotted into housing (420) and the rest of the electric motor (400) assembled in a conventional fashion. The ease of assembly of the stator (300) of the electric motor (400) is much improved compared to known methods of assembling stators which involve either gluing magnets onto the inside of the housing (420) or involve welding spring clips onto housing (420) for use in receiving and retaining the magnets (130). The framework (100) also provides the advantage that a fracture, for example a longitudinal fracture, of any of magnets (130) in use, which is common with prolonged use of known electric motors, may not cause the magnet (130) to become dislodged from its bay (120). The tapering of the magnet (130) and bay (120) and the close tolerance fit of the magnet (130) into the bay (120) ensure that such a fractured magnet is retained in its bay (120). In known electric motors such a longitudinal fracture of any of magnets (130) may cause a magnet or part of a magnet to become displaced from its desired position in the stator/electric motor and therefore require the electric motor to be disassembled and repaired. Therefore the framework (100) and stator (300) may improve the longevity and reliability of an electric motor (400) over known stators and electric motors.

[0142] FIG. 5 shows a fully assembled electric motor (400) comprising armature shaft (410), housing (420), front end cap (430), rear end cap (440) and electrical terminal assemblies (408a and 408b).

[0143] FIG. 6 shows a brush housing (500) according to the seventh aspect of the present invention. Brush housing (500) is substantially circular and comprises central aperture (501) for receiving an armature in an electric motor assembly, and elongate slots (502) for accommodating elongate bolts used to fix together said electric motor assembly. Brush housing (500) comprises four passages (530) for receiving brushes. The passages (530) are elongate channels which are arranged radially with respect to the central aperture (501) and each passage is arranged in the same radial plane with respect to the long axis of central aperture (501). Each passage (530) is open to a bias housing (540) arranged circumferentially with respect to the central aperture (501) such that the passages (530) are between the bias housings (540) and the central aperture (501). Each of the four bias housings is arranged in the same radial plane with respect to the long axis of the central aperture (501).

[0144] Brush housing (500) is formed from first part (510) and second part (520) which are joined together by fixing bolts (not shown) arranged through fixing holes (511, not shown as underneath 521, see FIGS. 7a) and (521) in the first and second parts respectively. The first and second parts (510) and (520) are formed from a polymeric material by moulding. The first and second parts (510) and (520) have complimentary profiles which when joined together form passages (530), each for receiving a brush, and bias housings (540), each for receiving a bias to urge said brush towards the central aperture (501). The second part (520) forms slots (541) in the brush housing (500) through which can be passed a compressed bias. The slots (541) are narrower than the bias housings (540) and therefore a compressed bias passed through the slots (541) can then expand into bias housing (540) and be retained therein whilst urging said brushes towards central aperture (501).

[0145] FIGS. 7a and 7b show the first part (510) and the second part (520) of the brush housing (500) respectively whereby the upper profile of first part (510) and the lower profile of second part (520) can be seen in more detail. First part (510) comprises open channels (512) and second part (520) comprises complimentary open channels (522). When the first (510) and second (520) parts are brought together to assemble the brush housing (500) the open channels (512) and (522) are brought into contact to form passages (530). First part (510) comprises abutments (513) and second part (520) comprises protruding square edge portions (523). When the first and second parts are brought together to form brush housing (500) the abutments (513) and the protruding square edge portions (523) are interengaged to form bias housings (540) with slots (541) for receiving compressed biases.

[0146] FIG. 7c shows the first part (510) comprising brushes (550) located in open channels (512) and biases (560) located in open channels (522) to illustrate the intended arrangement of brushes and biases in the assembled brush housing (500). The brushes (550) each comprise a lip (551) on the face of the brush arranged to contact the bias (560) at an upper end of said face, the lip being arranged to prevent lateral movement of the biases (560) in the bias housings (540) along the axis of the central aperture (501) and therefore prevent the biases (560) moving out of the bias housings (540) and/or out of contact with the brushes (550).

[0147] FIG. 8 shows brush housing (500) comprising four brushes (550) each located in a passage (530) and four biases (560) in the form of frustoconical springs each located in a bias housing (540). The biases (560) act to urge the brushes (550) towards the central aperture (501) of the brush housing (500).

[0148] The arrangement of the brush housing (500) greatly facilitates assembly of an electric motor incorporating the brush housing, specifically in the construction of a brush gear assembly comprising a brush housing, brushes and related biases. Such a brush gear assembly is assembled by fixing together the first part (510) and second part (520) by passing bolts through fixing holes (511) and (521) to provide a brush housing (500) with four passages (530) and four bias housings (540). Electrical cabling connecting the brushes to a brush electrical terminal may have already been arranged in the first part (510), for example through an aperture. A brush (550) is then placed in each of the passages (530) and pushed inwards towards bias housing (540). Alternatively, the brushes may be placed in the open channels (512) of the first part (510) before the first and second parts of the brush housing are fixed together. The brush housing comprising the brushes is then placed onto an armature which is received through central aperture (501). In order to urge the brushes into contact with the armature shaft (not shown) frustoconical springs (560) are compressed and passed through slots (541) into bias housings (540). Once in bias housing (540), the frustoconical springs (560) expand to urge the brushes into contact with the armature shaft, through a commutator, to complete the necessary electrical circuit in order for the brush gear to function in said electric motor. This arrangement of brush housing (500) allows a more straightforward and reliable assembly process than is possible with known brush housings.

[0149] Each of the framework (100) and the brush housing (500) allow a more straightforward assembly process which may result in significant cost savings in the manufacture of electric motors incorporating the framework (100) and the brush housing (500). The framework (100) and brush housing (500) also allow these parts to be manufactured from polymeric materials by moulding and therefore provide a significant cost saving in the material and manufacture cost of these parts and also provide a reduction in weight of an electric motor incorporating these parts. Both framework (100) and the brush housing (500) therefore provide significant improvements in relation to the manufacture and performance of electric motors, in particular starter motors.

[0150] Although a few preferred embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

[0151] In summary, a framework is disclosed for holding magnets to provide a stator for an electric motor, in particular for a starter motor. The framework is adapted to removably receive, retain and space apart a plurality of magnets within the framework to form a tubular magnet array and provide said stator. The framework may provide a stator which is easier to assemble and more reliable than known stators. The framework provides a central aperture for receiving a rotor armature of said electric motor. The framework is arranged to be slidably inserted or removed from a housing of said electric motor. A frame portion, a stator, an electric motor, a vehicle drive assembly and a method of assembling an electric motor are also described. A brush housing comprising a plurality of passages for slidably retaining brushes and comprising a plurality of bias housings, and a brush assembly comprising the brush housing are also described.

[0152] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0153] All of the features disclosed in this specification (including any accompanying claims, and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0154] Each feature disclosed in this specification (including any accompanying claims, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0155] The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.