STATIONARY COIL SUPPORT FOR A BRUSHLESS ALTERNATOR AND A BRUSHLESS ALTERNATOR COMPRISING THE SAME

Abstract

An alternator with a longer stationary coil support or bobbin and rotor axial and components thereof are provided.

Claims

1. A claw type, brushless alternator comprising: a drive end frame having a stationary coil assembly mounted thereto; the stationary coil assembly comprising a hollow bobbin and stationary coil wound thereon; a stator circumscribing the stationary coil assembly such that a gap is provided between the stationary coil assembly and the stator; a rotor assembly having a rotor shaft with pair of opposing claw type poles mounted thereon; wherein each claw type pole has a plurality of fingers; wherein upon installation into the alternator, the rotor shaft is mounted through the hollow bobbin and the plurality of fingers are sandwiched between the stationary coil assembly and the stator.

2. The claw type, brushless alternator of claim 1; wherein the rotor shaft is steel.

3. The claw type, brushless alternator of claim 1; wherein the stationary coil is a copper wire coil.

4. The claw type, brushless alternator of claim 1, wherein the bobbin is a steel bobbin.

5. The claw type, brushless alternator of claim 1, wherein the hollow bobbin is mounted directly to the drive end frame.

6. A bobbin assembly for use in a claw type, brushless alternator, the brushless alternator having a drive end frame and drive end bearing, the bobbin assembly comprising: a hollow bobbin with lips at each end of the hollow bobbin and defining a coil winding surface; and a stationary coil wound on the hollow bobbin; wherein one lip of the bobbin is configured for direct mounting to the drive end frame of the alternator and comprises a surface to support the drive end bearing.

7. The bobbin assembly of claim 6, wherein the drive end lip of the bobbin stepped.

8. The bobbin assembly of claim 7, wherein the step is configured engage a corresponding step of the drive end frame.

9. The bobbin assembly of claim 6, wherein each lip of the bobbin comprises an inclined surface resulting in the coil winding surface including sloped faces.

10. A claw type, brushless alternator comprising: a drive end frame having a stationary coil assembly mounted thereto; the stationary coil assembly comprising the bobbin assembly of claim 6; a stator circumscribing the stationary coil assembly such that a gap is provided between the stationary coil assembly and the stator; a rotor assembly having a rotor shaft with pair of opposing claw type poles mounted thereon; wherein each claw type pole has a plurality of fingers; wherein upon installation into the alternator, the rotor shaft is mounted through the hollow bobbin and the plurality of fingers are sandwiched between the stationary coil assembly and the stator.

11. A bobbin for use in a claw type, brushless alternator, the brushless alternator having a drive end frame and drive end bearing, the bobbin comprising: a hollow cylinder with lips at each end of the hollow cylinder and defining a coil winding surface; wherein one lip of the bobbin is configured for direct mounting to the drive end frame of the alternator and comprises a surface to support the drive end bearing.

12. The bobbin of claim 11, wherein the drive end lip of the bobbin stepped.

13. The bobbin of claim 12, wherein the step is configured engage a corresponding step of the drive end frame.

14. The bobbin of claim 11, wherein each lip of the bobbin comprises an inclined surface resulting in the coil winding surface including sloped faces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Embodiments of the invention will now be described, by way of example only, by reference to the attached Figures, wherein:

[0014] FIG. 1 illustrates a cross-sectional view of a prior art design for a typical claw type brushless alternator with all the main components properly aligned as for working condition detailing rotor shaft (1), drive end ball bearing (2), fan (3), nut (4), pulley (5), drive end frame (6), bearing cap (7), drive end screws (8), bobbin/stationary coil assembly (9), rear end screws (10), and rear end frame (11).

[0015] FIG. 2 illustrates an exploded cross-sectional view of the prior art design for a typical claw type brushless alternator shown in FIG. 1.

[0016] FIG. 3 illustrates a cross-sectional side view of one embodiment of the alternator with drive-end direct mounted stationary coil assembly detailing rotor shaft (1), drive end ball bearing (2), fan (3), nut (4), pulley (5), drive end frame (6), drive end screws (8), bobbin/stationary coil assembly (9), rear end screws (10), and rear end frame (11).

[0017] FIG. 4 illustrates an exploded cross-sectional view of the alternator shown in FIG. 3.

[0018] FIG. 5 illustrates cross-sectional and side views of a prior art design for a stationary coil assembly.

[0019] FIG. 6 illustrates cross-sectional and side views of a stationary coil assembly according to one embodiment of the invention.

[0020] FIG. 7 illustrates cross-sectional and side views of a stationary coil assembly according to one embodiment of the invention.

[0021] FIG. 8 illustrates an alternative design wherein the front bearing in this case is wider. The front bearing is longitudinally clamped between the drive end housing and bobbin. In this embodiment, the bobbin is axially located by the outer race of the bearing.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to FIGS. 1, 2, and 5, in an alternator with a conventional stationary coil the drive end ball bearing (2) is radially located into the drive end frame (6). Axially, the drive end bearing (2) is supported to the left by the drive end frame (6) and to the right by the bearing cap (7) through the drive end screws (8). The drive end screws (8) clamp the outer race of drive end bearing (2) between the drive end frame (6) and the bearing cap (7). In this traditional design the bobbin of the stationary coil (9) does not rest against bearing (2). The stationary coil assembly (9) is mounted to the rear end frame (11) using screws (10). The bobbin of the stationary coil (9) rests against rear frame (11) interfacing with the rear frame (11) at mounting face “A0” and locating surface “D0” as shown on FIG. 5.

[0023] Referring to FIGS. 3, 4 and 6, this invention provides an alternator with a longer stationary coil support (bobbin) and rotor axial thereby increasing the output or efficiency of the alternator. The invention further provides a simplified design and more robust design. In particular, the drive end ball bearing (2) is radially located into the drive end frame (6) and is supported by the drive end frame (6) and the stationary bobbin (9). The drive end screws (8) clamp the drive end bearing (2) between the drive end frame (6) and the stationary bobbin (9). The bearing cap/retainer (7) found in conventional designs is therefore eliminated together with screws (10). As shown in FIGS. 3, 4 and 6 the bobbin (9) rests against the outer race of the bearing (2) through mounting surface “A1” and locating surface “D1”. The new design is simpler as screws (8) and bearing cap/retainer (7) are eliminated). The space created by deleting the cap (7) is now allocated to the bobbin and rotor axial length increasing the output or efficiency of the alternator.

[0024] By removing the bearing retainer and using a bobbin of the invention there is more room available to increase the rotor and bobbin assembly length. In some embodiments, the increase in length is approximately 6 mm.

[0025] With reference to FIGS. 6 and 7, in operation, the new bobbin effectively charges the stator stack with increased levels of magnetism. The magnetic flux received by the bobbin from the rotor through surface Ta/Ta1 is transferred to inner surface Tb1/Tb and from here to radial surface C1/C. Second magnetic path appears when magnetic flux flows also sideways through bobbin bottom material Td1 and finally reaching axial gap surface B1 or B.

[0026] Without being limited by theory, it is believed that the magnetic flux carried by the new bobbin design as described in FIGS. 6 and 7 is superior to the traditional one as shown in FIG. 5 because of the increased thickness Tb1 or (Tb) and Td1 (Td), also increased magnetic flux going through surfaces B1 or B and surfaces C1 or C as opposed to reduced surface Tb0 and limited thickness Td0 and respectively reduced flux through surfaces C0 and B0.

[0027] To gain a better understanding of the invention described herein, the following examples are set forth. It will be understood that these examples are intended to describe illustrative embodiments of the invention and are not intended to limit the scope of the invention in any way.

EXAMPLE

[0028] By using the design described herein, a 75 mm long rotor and bobbin assembly can be increased to 81 mm without physically increasing the size of the alternator. This represents by volume (rotor diameter stays the same) an 8% increase in the rotor & bobbin volume. The new rotor and bobbin assembly can be properly redesigned (“stretched”) to take advantage of the additional 6 mm. This will result in approximately 8% more power output delivered by the new alternator (all in the same package requirement.

[0029] Experimental Data: [0030] 28V test alternator output tests:

TABLE-US-00001 shorter rotor 6 mm longer rotor rotor speed output output (rpm) (Amps) (Amps) 1800 45 48 2000 54 59 3000 77 83 4000 88 94 5000 98 104 6000 105 110 6500 107 112

[0031] Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention.

[0032] The invention includes all such variations and modifications as fall within the scope of the appended claims.