WO1998001936A1

WO1998001936A1 - Brushless electromagnetic motor-generator

Info

Publication number: WO1998001936A1
Application number: PCT/CA1997/000466
Authority: WO
Inventors: Cheuk Yin Martin Lee
Original assignee: Cheuk Yin Martin Lee
Priority date: 1996-07-03
Filing date: 1997-06-30
Publication date: 1998-01-15
Also published as: AU3251097A

Abstract

A brushless electromagnetic motor-generator includes a rotor assembly; electrically conductive bearings disposed coaxially around opposite ends of the rotor assembly; mechanisms for electrically connecting the two rotating inner bearing rings to the rotor coil; and mechanisms for connecting the two stationary outer bearing rings to an external electric load.

Description

BRUSHLESS ELECTROMAGNETIC MOTOR-GENERATOR

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/021,113, filed July 3, 1996 and U.S. Provisional Patent Application Serial No. 60/034,494, filed January 13, 1997.

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

The present invention relates to alternators, generators and electric motors. More specifically, the present invention relates to a brushless electromagnetic motor-generator which transfers an electric current to or from a rotor conductor.

DESCRIPTION OF RELATED ART

In the automotive industry, DC brush-type generators were used in cars until the early 1960s. The brush- type generators suffered from a variety of commutation problems which severely restricted the reliability of the automobile's power generation system. Since that time, the automotive industry has used and continually improved a claw pole Lundell alternator. The Lundell alternator is a brush-type alternator. It includes a rotor having a single coil embedded therein which receives an electric current from a voltage regulator. The carbon brushes transfer the exciter current from the stationary regulator to the revolving coil via a pair of slip rings disposed upon the rotor. Upon rotation of the rotor, the exciter current passing through the coil establishes a multipolar bidirectional magnetic field. The rotating magnetic field, in turn, induces a current in the conductors of the stator to power the vehicle's electrical system. Brush holders and brush holder springs are employed to ensure that a continuous electrical connection exists between the brushes and slip rings. The brush holders, which are affixed to the alternator housing, hold the brushes in position over the slip rings. The brush holder springs, which are disposed within the brush holders, bias the brushes against the rotating slip rings. The pressure exerted by the brush holder springs produces friction between the brushes and the slip rings, causing various problems. Specifically, the spring pressure causes frictional energy losses, reduces the maximum rotor speed, and generates heat in the alternator wires which reduces the overall efficiency of the alternator. Also, the friction wears away the carbon brushes, thereby creating carbon dust that impairs the performance of the alternator. Over time, the brushes become worn to the point that they are too short to make reliable electrical contact with the slip rings. This necessitates periodic, costly and time-consuming maintenance of the alternator.

Thus, a need exists for a brushless electromagnetic motor-generator of the type which does not employ permanent rotor magnets. None of the known inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages inherent in the known types of motor-generators, the present invention provides an improved brushless electromagnetic motor-generator. The primary components generally include a stator; a rotor assembly including a rotor and rotor shaft which rotates in relation to the stator; a pair of electrically conductive two-part bearings disposed coaxially around the rotor assembly at opposite ends of the rotor; means for electrically connecting each rotating portion of the two bearings to the rotor coil or conductor; and means for electrically connecting each stationary portion of the two bearings to an external electric load or source. By employing electrically conductive bearings, the present invention is able to eliminate the brushes and slip rings associated with the conventional motor- generator. More specifically, the inner ring of each electrically conductive bearing is disposed coaxially around the rotor assembly for rotation therewith. The inner bearing ring's exact position upon the rotor assembly may vary. For example, the pair of inner bearing rings may be disposed upon the non-conductive shaft of the rotor assembly. In this case, electrical leads are embedded axially along the shaft, electrically connecting the two inner bearings to the opposite ends of the squirrel cage rings. Alternatively, conductive rings may be disposed around the non-conductive rotor cylinder in electrical contact with the rotor coil. The conductive rings are then sized to be received by the inner bearing rings for rotation therewith. In this fashion, a conductive path is created between the two inner bearing rings via the rotor.

The outer bearing ring of each electrically conductive bearing is fixedly mounted by an insulated support to a stationary frame, such as the housing. The outer bearing rings are disposed coaxially around and in electrical contact with the inner bearing ring, whereby the inner bearing ring and rotor assembly may freely rotate relative to the outer bearing ring. Electrical leads are attached to the outer bearing rings to connect the electromagnetic motor-generator to a stationary source or load. The electrically conductive bearings may be constructed in a variety of designs which conducts electrical currents, while simultaneously minimizing the friction therebetween. For example, the inner and outer bearing rings may employ electrically conductive ball-bearings. Additionally, an electrically conductive lubricant may be employed. Alternatively, the inner and outer bearing rings may be in direct sliding contact, such as in a race-type bearing. Moreover, as the pair of bearings also support the weight of the rotor assembly as well as the mechanical load on the rotor shaft, the inner and outer bearing rings will necessarily remain in electrical contact, even if one of the bearing rings starts to experience wear. By employing the electrically conductive bearings in this manner, an electromagnetic motor-generator can be utilized which does not require the use of brushes and is, therefore, not prone to the problems associated with the use of brushes. Further, this design can be designed as an alternator, a direct current generator, or in a motor which runs on alternating or direct current. As such, the invention may be used in wide range of applications.

In one specific application, a squirrel cage rotor, designed according to the present invention, is supplied with an electric current for operation as a motor. Instead of providing the magnetic field via a standard stator disposed coaxially around the rotor, a solenoid is provided in axially spaced relation to the rotor to generate the magnetic field. Specifically, the electrically conductive bearings support the squirrel cage rotor assembly according to the present invention as previously disclosed. The bearings, in turn, are supported upon a base by insulated bearing supports. A solenoid is positioned in spaced axial alignment with the end of the rotor cylinder. The solenoid comprising a cylindrical ferromagnetic core and an exciter coil wrapped circumferentially around the core. When a voltage is applied across the exciter coil, the exciter current in the solenoid produces a magnetic flux which is enhanced by the ferromagnetic core. The positioning of the solenoid relative to the rotor cylinder cause the magnetic flux lines to pass radially through the rotor, normal to the plurality of squirrel cage wires. The direction of the magnetic flux lines induces a electromagnetic force upon the wires, causing the rotor to rotate. Preferably, the solenoid coil may be electrically connected in series with the squirrel cage so that the current passing through the two will alternate in unison. Accordingly, it is a principal object of the invention to provide an electromagnetic motor- generator which operates with the use of brushes .

It is another object of the invention to provide a brushless electromagnetic motor-generator which sustains a reliable electric connection with an external electric load or source.

It is a further object of the invention to provide a brushless electromagnetic motor-generator which generates one of either a direct current or an alternating current.

It is a further object of the invention to provide a brushless electromagnetic motor-generator which operates on one of either a direct current or an alternating current. Still another object of the invention is to provide a brushless electromagnetic motor-generator in which the alternator and excitor are connected in series for simultaneously changing the current direction within the stator and the rotor.

It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes. These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is perspective diagrammatic view of a brushless alternator according to the present invention depicting the bearings and the alternator rotor assembly driven by an endless belt.

Fig. 2 is an exploded perspective view, depicting an alternate embodiment of the rotor shaft assembly, the bearings and bearing supports of a brushless electromagnetic motor-generator.

Fig. 3 is a front view of the embodiment of the invention according to Fig. 2 further including a solenoid positioned in axial alignment with the rotor assembly.

Similar reference characters denote corresponding features consistently throughout the attached drawings .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig. 1 is perspective schematic view of a brushless alternator according to the present invention depicting the bearings and the alternator rotor assembly driven by an endless belt. A rotor assembly 10 comprises a non-conductive shaft 11 and rotor 11 disposed coaxially around the shaft 11. A pulley P is connected to one end of the non-conductive shaft 11. An endless belt B drives the pulley P to rotate the rotor assembly 11. A pair of electrically conductive bearings 20 are disposed coaxially around the non- conductive shaft 11 positioned at opposite ends of the rotor 12. Each electrically conductive bearing 20 comprises an outer bearing ring 22 and an inner bearing ring 25. The inner bearing ring 25 securely receives the non-conductive shaft 11 for rotation therewith. The inner bearing ring 25 is disposed in electrical contact within the outer bearing ring 22 for rotation relative thereto. Two rotor leads 30 are embedded axially along the non-conductive shaft 11. One of the rotor leads 30 is electrically connected between one of the inner bearing rings 25 and one end of the rotor conductor {not shown) of the rotor 12. The other of the rotor leads 30 is electrically connected between the other of the inner bearing rings 25 and other end of the rotor conductor (not shown) of the rotor 12. One electrically conductive outer bearing lead 40 is electrically connected to one of the outer bearing rings 22. A second electrically conductive outer bearing lead 40 is electrically connected to the other of the outer bearing rings 22. Thereby, a continuous conductive path is created between the electrically conductive outer bearing leads 40 as follows: through one of the electrically conductive outer bearing leads 40, to the outer bearing ring 22 and then inner bearing ring 25 of one of the electrically conductive bearings 20, to a first of the rotor leads 30, to the rotor conductor of the rotor 12, to the second rotor lead 30, to the second bearing 20, and to the second electrically conductive outer bearing lead 40. Fig. 2 is an exploded perspective view, depicting an alternate embodiment of the rotor shaft assembly, the bearings and bearing supports of the brushless electromagnetic motor-generator. Fig. 3 is a front view of the embodiment depicted in Fig. 2 and further includes a solenoid positioned in axial alignment with the rotor. Referring to both Fig. 2 and Fig. 3, a rotor assembly 110 comprises a non-conductive shaft 111 and a rotor 112 attached to the non-conductive shaft 111 for rotation therewith. The rotor 112 comprises a non-conductive rotor cylinder 113 disposed coaxially around the shaft a rotor conductor 114 affixed around the rotor cylinder for carrying an electric current. The rotor conductor 114 is of the squirrel cage design having a pair of spaced squirrel cage rings 115 affixed coaxially around the rotor cylinder 113 and a plurality of insulated wires 116 axially embedded within the surface of the rotor cylinder 113 and extending between the squirrel cage rings 115 in electrical contact therewith.

Fig. 2 and Fig. 3 further depict two axially aligned electrically conductive bearings 120, the bearings 120 being supported by two spaced apart non-conductive bearing supports 121. Each bearing 120 comprising an outer bearing ring 122 and an inner bearing ring 125. Each inner bearing ring 125 is disposed in electrical contact within the outer bearing ring 122 for rotation relative thereto. Two electrically conductive outer bearing leads 140 are provided: one outer bearing lead 140 electrically connected to one of the outer bearing rings 125; the other outer bearing lead 140 electrically connected to the other of the outer bearing rings 125.

The non-conductive rotor cylinder 113 passes axially through the two electrically conductive bearings 120 for axial rotation relative to the bearing supports 121. A pair of conductive rotor rings 117 is affixed coaxially around the rotor cylinder 113, attached at opposite ends and in electrical contact with the squirrel cage rings 115. The conductive rotor rings 117 are sized for secure receipt within the inner bearing rings 122 and thereby, support the rotor assembly 110 for rotation with the inner bearing rings 122 relative to the outer bearing rings 122 and bearing supports 121. The conductive rotor rings 117 also electrically connect the rotor conductor 114 between the two inner bearing rings 125.

Referring exclusively to Fig. 3, the two spaced apart non-conductive bearing supports 121 are disposed upon a base 150. The bearing supports 121 support the rotor assembly 110 for rotation as previously described. A cylindrical solenoid 200 is supported by an insulated solenoid support 205 which is attached to the base 150. The solenoid 200 comprises a cylindrical ferromagnetic core 210 and an exciter coil 220 wrapped circumferentially around the core. The exciter coil 220 has opposite ends forming solenoid leads 240. The cylindrical ferromagnetic core 210 is selectively positioned in spaced axial alignment with the rotor cylinder 113.

In operation, a voltage is applied across the solenoid leads 240 to produce an exciter current in the exciter coil 220. The exciter current causes the exciter coil 220 to produce a magnetic flux which is enhanced by the cylindrical ferromagnetic core 210. The position of the solenoid 200 relative to the rotor cylinder 113 causes the magnetic flux to pass radially through the rotor 112, normal to the rotor conductors 116. Simultaneously, a voltage is applied across the rotor leads 140 to create a current through the rotor conductors 116. The magnetic field generated by the solenoid 200 induces an electromagnetic force upon each of the rotor conductors 116. The resultant electromagnetic forces are directed tangentially to the rotor cylinder 113, thereby causing rotation of the rotor assembly 110. It is to be understood that the present invention is not limited to the sole embodiment described above, but encompasses any and all embodiments within the scope of the following claims.

Claims

1. A brushless electromagnetic motor-generator, comprising: a housing; a stator having a cylindrical passage therethrough and disposed within the housing; two no -conductive bearing supports spaced apart within the housing; two electrically conductive bearings, each bearing comprising an outer bearing ring and an inner bearing ring, the outer bearing ring fixedly mounted within one of the bearing supports in axial alignment with the cylindrical passage of the stator, the inner bearing ring disposed in electrical contact within the outer bearing ring for rotation relative thereto; a rotor assembly comprising a non-conductive shaft and a rotor, the no -conductive shaft passing axially through the cylindrical passage of the stator for axial rotation relative thereto, the rotor having a rotor cylinder disposed coaxially around the shaft between the two electrically conductive bearings within the stator passage for rotation with the shaft, and the rotor having a rotor conductor affixed around the rotor cylinder for carrying an electric current; support means for supporting the rotor assembly for rotation with the two inner bearing rings; electrical connection means for electrically connecting the rotor conductor between the two inner bearing rings; and two electrically conductive outer bearing leads, one outer bearing lead electrically connected to one of the outer bearing rings, the other outer bearing lead electrically connected to the other of the outer bearing rings .

2. The brushless electromagnetic motor-generator according to claim 1, wherein the support means and the electrical connection means comprise a pair of conductive rotor rings coaxially attached to the rotor cylinder at opposite ends of the rotor conductor, the conductive rotor rings sized for secure receipt within the inner bearing rings for supporting the rotor assembly for rotation therewith and for electrically connecting the rotor conductor between the two inner bearing rings .

3. The brushless electromagnetic motor-generator according to claim 1, wherein: the support means comprises the non-conductive shaft being sized for secure receipt within the inner bearing rings for rotation therewith; and the electrical connection means comprises two rotor leads embedded axially along the non-conductive shaft, the first rotor lead electrically connected between one of the inner bearing rings and one end of the rotor conductor, and the second rotor lead electrically connected between the other of the inner bearing rings and the other end of the rotor conductor.

4. The brushless electromagnetic motor-generator according to claim 1, wherein the rotor conductor comprises a squirrel cage having a pair of spaced squirrel cage rings affixed coaxially around the rotor cylinder and a plurality of insulated wires axially embedded within the surface of the rotor cylinder and extending between the squirrel cage rings in electrical contact therewith.

5. The brushless electromagnetic motor-generator according to claim 1, wherein:. the stator carries an exciter current; and the rotor conductor carries an induced current for rotating the rotor shaft assembly in response to receipt of a magnetic flux produced by the exciter current.

6. The brushless electromagnetic motor-generator according to claim 1, wherein: the stator carries an exciter current; and rotation of the rotor shaft assembly induces a current in the rotor conductor in response to a magnetic flux produced by the exciter current.

7. The brushless electromagnetic motor-generator according to claim 1, wherein: the rotor conductor carries an exciter current; and rotation of the rotor shaft assembly induces a current in the stator in response to a magnetic flux produced by the exciter current .

8. The brushless electromagnetic motor-generator according to claim 1, wherein: the rotor conductor carries an exciter current; and the stator carries an induced current for rotating the rotor shaft assembly in response to receipt of a magnetic flux produced by the exciter current.

9. The brushless electromagnetic motor-generator according to claim 1, wherein the motor-generator generates an alternating current.

10. The brushless electromagnetic motor-generator according to claim 1, wherein the motor-generator generates a direct current .

11. A brushless electromagnetic motor-generator, comprising: a base ; two non-conductive bearing supports spaced apart on the base; two electrically conductive bearings, each bearing comprising an outer bearing ring and an inner bearing ring, the two outer bearing rings fixed in axial alignment within the two bearing supports, the inner bearing rings disposed in electrical contact within the outer bearing rings for rotation relative thereto; a rotor assembly, further comprising: a non-conductive shaft passing axially through the two electrically conductive bearings for axial rotation relative to the bearing supports; a rotor having a non-conductive rotor cylinder disposed coaxially around the shaft between the two electrically conductive bearings for rotation with the shaft, the rotor having a rotor conductor affixed around the rotor cylinder for carrying an electric current ; and a pair of conductive rotor rings affixed coaxially around the rotor cylinder at opposite ends of the rotor conductor for rotation therewith and in electric connection with the opposite ends of the rotor conductor, the conductive rotor rings sized for secure receipt within the inner bearing rings for supporting the rotor assembly for rotation therewith and for electrically connecting the rotor conductor between the two inner bearing rings; two electrically conductive outer bearing leads for producing a current across the rotor conductor, one outer bearing lead electrically connected to one of the outer bearing rings, the other outer bearing lead electrically connected to the other of the outer bearing rings; and a solenoid, comprising a cylindrical ferromagnetic core and an exciter coil wrapped circumferentially around the core, the cylindrical ferromagnetic core positioned in spaced axial alignment with the rotor cylinder for generating a magnetic flux passing radially through the rotor normal to the rotor conductors, and the exciter coil having opposite ends forming solenoid leads.

12. The brushless electromagnetic motor-generator according to claim 11, wherein the rotor conductor comprises a squirrel cage having a pair of spaced squirrel cage rings affixed coaxially around the rotor cylinder and a plurality of insulated wires axially embedded within the surface of the rotor cylinder and extending between the squirrel cage rings in electrical contact therewith.

13. The brushless electromagnetic motor-generator according to claim 11, wherein the rotor leads and the solenoid leads are connected to the same circuit in series for simultaneously changing the current direction within the solenoid and the rotor.