GB2409351A

GB2409351A - Brushless commutator with an electrically conducting cog engaging with teeth on the commutator.

Info

Publication number: GB2409351A
Application number: GB0329195A
Authority: GB
Inventors: Alan Lynch
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-12-17
Filing date: 2003-12-17
Publication date: 2005-06-22
Also published as: GB0329195D0

Abstract

An electrical connection assembly for providing an electrical connection between an armature of an electric machine and electrical source or load comprises at least one commutator (102, 104) having electrically conductive teeth (122, 124) operable to mesh with a plurality of cogs (106, 108) having electrically conductive surfaces wherein the cogs act as brushes. The assembly further comprises connection parts such that the cogs engage with the stationary parts of the machine. In one embodiment teeth (110, 112) are located on the stationary device such that a connection is formed between the stationary part of the device and the commutator through the cogs. In a further embodiment the electrical machine may comprise two commutators each having their own cog assembly. The assembly may also comprise an housing for containing cog lubricating means (142). The cog lubricating means may be a reservoir of oil, preferably of an electrically insulating type through which the cogs may run.

Description

1 240935 1 An electrical connection assembly The present invention relates

to electrical connection assemblies for providing an electrical connection between a rotor and a stator and particularly, but not exclusively, electrical connection assemblies for providing an electrical connection between a rotor and a stator in an electrical machine such as an electric motor or generator.

Electric motors and generators are electrical machines used to convert electrical energy into mechanical energy, in the case of a motor, and mechanical energy into electrical energy, in the case of a generator. Electric generators also include alternators and dynamos.

Most electric machines utilise electromagnetism. However, other electromechanical phenomena may alternatively be utilised, such as, for example, the piezoelectric effect.

Also most electromagnetic machines are rotary, although linear type electromagnetic machines also exist.

Electromagnetic machines are well known and widely used in a variety of applications in which conversion between electrical energy and mechanical energy is desired. Examples of such applications include electrically powered vehicles, household appliances, such as, washing machines, and power tools, such as, electric drills.

A typical rotary electromagnetic motor generally comprises a rotating part, usually called the rotor, and a stationary part, usually called the stator. The rotor comprises an electromagnetic armature connected to an electrical source. The stator comprises opposing field magnets, which provide a permanent magnetic field in which the armature is disposed. As current is passed through the armature it interacts with the permanent magnetic field which results in exertion of a mechanical force on the armature. The repulsion and attraction of the magnetic poles of the armature and the magnetic poles of the opposing field magnets produces a torque which tends to rotate the armature. As the armature rotates its magnetic poles are alternately reversed such that the armature continues to rotate in one direction.

For an electric generator, the opposite, to that described above, occurs in that the mechanical energy is converted, through the electromagnetic armature, into electrical energy.

Electric machines are also known wherein the armature is the stator and the opposing

field magnets are the rotor.

Whichever of the above configuration of rotor and stator is used and whether it is used for a motor or generator, it is necessary to provide an electrical connection between the rotor and a stationary electrical source or load. The most common method of providing such an electrical connection is by means of a commutator, which typically comprises a split electrically conductive ring mounted on a shaft fixed to the armature. Each half of the ring is insulated from the other and provides electrical contacts for the armature.

Electrically conductive brushes, typically of metal or carbon, are positioned against the commutator as it rotates with the armature thereby electrically connecting the rotating armature to a stationary electrical source or load.

However, as the rotor rotates it continually wears the brushes down and therefore the brushes require frequent replacement. This results in inefficiency of the electric machine, as the brushes are worn down, inconvenience, in having to replace the parts and during the period when the machine is inoperable, and undesirable costs in replacing the bushes and missed working hours during the period when the machine is inoperable.

It is therefore desirable for an electric machine to comprise an electrical connection assembly, which is brushless. Furthermore, it is desirable for an electric machine to comprise an electrical connection assembly having improved resistance to wear of the connecting parts.

The present invention provides an electrical connection assembly comprising at least one commutator, having an external surface comprising a plurality of electrically conductive teeth, a plurality of stationary electrical connection parts, suitable for connection to an electrical source or load, and a plurality of cogs having electrically conductive toothed surfaces, wherein the cogs are arranged to engage with the teeth of the, or an associated, commutator and an associated stationary electrical connection part to provide an electrical connection between the rotary commutator and each stationary electrical connector part.

The plurality of stationary electrical connector parts may each have a toothed surface for engagement with at least one of the cogs. The stationary toothed surface may be spaced apart from, and arranged to face, the external surface of the commutator.

The electrical connection assembly may comprise first and second commutators, first and second cogs and first and second stationary electrical connection parts wherein the first cog engages the first commutator and the first stationary electrical connector part to provide an electrical connection therebetween and wherein the second cog engages the second commutator and the second stationary electrical connector part to provide an electrical connection therebetween.

Alternatively, each stationary electrical connection part comprises a slip ring assembly having a slip ring and a spindle.

The commutator teeth may extend at an angle relative to the direction of the longitudinal axis of the commutator. Additionally, or alternatively, the teeth of each cog may extend at an angle relative to the direction of the longitudinal axis of the respective cog.

The electrical connection assembly may further comprise a housing having cog lubricating means. The cog lubricating means may comprise a reservoir of oil disposed s such that, in use, at least part of at least one cog passes through the reservoir. The oil may also act as an electrical insulator.

The present invention also provides an electric machine comprising an electrical connection assembly as described above. The electric machine may be an electric motor or generator, alternator or dynamo, or the like.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure I is a schematic drawing of a first embodiment of an electrical connection assembly according to the present invention; Figure 2 is an enlarged schematic representation of two teeth disposed on the commutator as shown in Figure 1; Figure 3 is a schematic drawing of a commutator, cog and internal toothed surface of the electrical connection assembly of Figure 1; Figure 4 is a schematic diagram of an electric machine comprising the electrical connection assembly of Figure 1; Figure 5 is a schematic drawing of a second embodiment of an electrical assembly according to the present invention; Figure 6 is a schematic drawing of a commutator and plurality of cogs according to the electrical connection assembly of Figure S; and, Figure 7 is a schematic drawing of an electrical machine comprising the electrical connection assembly of Figure S. Referring to Figure 1, a first embodiment of an electrical connection assembly l DO comprises first and second commutators, 102 and 104, first and second cogs, 106 and 108, first and second stationary electrical connection parts having toothed surfaces, 110 and 112, and a housing 114.

The first and second commutators, 102 and 104, have a shared longitudinal axis 116.

Each of the first and second commutators comprises an external surface, 118 and 120, respectively, having a plurality of parallel discrete electrically conductive teeth, 122 and 124, respectively, disposed thereon, as shown in Figures 2 and 3. The commutator teeth, 122 and l 24, extend along the respective external surface in the direction of the longitudinal axis 116, of the respective commutator, but are formed at an acute angle thereto. Each commutator tooth is connected to one, or a set, of windings l 26 of an armature 128. Each tooth is separated from an adjacent tooth by an electrically insulated region 130 therebctwocn, as shown in Figure 2.

The first and second cogs, 106 and 108, each comprise an external surface having a plurality of parallel teeth, 132 and 134, respectively, disposed thereon. The cogs are electrical conductive, at least around the circumference of their external surface. The teeth of the first and second cogs extend along the respective external surfaces in the direction of the longitudinal axis, but are formed at an acute angle thereto, such that the teeth of the first cog 106 are engageable with the teeth of the first commutator 102 and the teeth of the second cog 108 are engageable with the teeth of the second commutator 104.

The first and second stationary toothed surfaces, I 10 and 1 12, are circular and formed from part of the internal surface of the housing 114. Alternatively, the stationary toothed surfaces may be formed from internal surfaces of separate elements, such as, for example, first and second annul), which are fixed to the housing. Alternatively, the stationary toothed surfaces may be linear. However, the first and second stationary surfaces must be electrically insulated from each other.

The housing 114 comprises first and second shaft plates, 136 and 138, through which a shaft 140 enters and exits the housing 114. The housing further comprises a reservoir 142 for holding an electrically insulating lubricant, such as arc-quenching oil. First and second seals, 144 and 145, are provided between the first and second shaft plates, 136 and 138, respectively, and the walls of the housing 1 14.

The first and second commutators, 102 and 104, are spaced apart, along the longitudinal axis 116, and fixed to the shaft 140, extending from an armature 128 of an electric machine, to rotate therewith. The first and second stationary toothed surfaces, 110 and 112, are disposed to face and surround the respective external surfaces of the first and second commutators, 102 and 104, and are spaced apart therefrom. The first and second cogs, 106 and 108, are disposed in the space between the respective first and second stationary toothed surfaces, 110 and 112, and the respective external surface of the first and second commutators, 102 and 104, such that the teeth of the first and second cogs engage with the teeth of the respective first and second commutators and the stationary toothed surface, as shown in Figure 3. Upon rotation of the shaft 140 the first and second commutators, 102 and 104, rotate, causing the respective first and second cogs, 106 and 108, to rotate and travel along the respective stationary toothed surface, 110 and 112, that is, around the circumference thereof.

The reservoir 142 is disposed in the housing 114 such that the path of the first and second cogs, 106 and 108, extends through the lubricating oil disposed in the reservoir. The oil lubricates and electrically insulates the cogs.

The first and second stationary toothed surfaces, 110 and 112, arc each electrically connected to either an external electrical source 148, where the electric machine is an electric motor, or an external electrical load 148, where the electric machine is a generator, alternator or dynamo.

In use, whether acting as an electric motor or generator, alternator or dynamo, an electrical connection exists between one set, or more, of windings 126 of the armature 128 and the electrical source or load 148, via an electrically conductive path passing through the first and second commutators, 102 and 104, cogs, 106 and 108, and stationary toothed surfaces, 110 and 112. As the shaft 140 rotates, the first and second commutators, 102 and 104, rotate, causing the first and second cogs, 106 and 108, to travel along the respective stationary toothed surfaces, 110 and 112, thereby addressing each set of windings 126 in turn as the cogs engage with each, or each set, of the commutator teeth, 122 and 124, in turn. The meshing of the teeth of the respective cogs and commutators break the layer of electrically insulating lubricating oil to provide a connection therebetween. The electrical connection assembly 100 thereby provides an electrical connection between the rotating armature 128 and the stationary toothed surfaces, 110 and 112, which are connected to the electrical source or load 148.

Referring to Figure 4, an electric machine 200 comprises the electrical connection assembly 100 as described above. The electric machine may be an electric motor or an electric generator, alternator or dynamo, or the like. The electric machine 200 further comprises standard known components including a pair of opposing field magnets 201 providing a permanent magnetic field in which the armature 128 is disposed. The electric machine operates as an electric motor or generator, alternator or dynamo, or the like, in a conventional manner, which rotates the shaft. The electrical connection between the rotating armature 128 and the stationary electrical source or load 148 is formed through the electrical connection assembly 100, as described above.

Referring to Figure 5, a second embodiment of an electrical connection assembly 300 comprises a commutator 302, first and second cogs, 306 and 308, first and second stationary electrical connection parts comprising electrical slip ring assemblies, 310 and 312, and a housing 314. The commutator 303 has a longitudinal axis 316.

The commutator 302 comprises an external surface having a plurality of discrete electrically conductive teeth 322 disposed thereon. The commutator teeth 322 extend along the external surface thereof in the direction of the longitudinal axis 316, but are formed at an acute angle thereto. Each commutator tooth is connected to one, or a set, of windings 326 of an armarturc 328. Each electrically conductive tooth 322 is spaced apart from an adjacent tooth by an electrically insulated region 330, disposed therebetween, as shown in Figure 2 The first and second cogs, 306 and 308, each comprise an external surface having a plurality of teeth, 332 and 334, respectively, disposed thereon. The cogs are electrically conductive. The teeth of the first and second cogs, 306 and 308, extend along the respective external surfaces in the direction of the longitudinal axis 316, but are formed at an acute angle thereto, such that the teeth of the first and second cogs, 306 and 308, are engageable with the teeth of the commutator 302.

The commutator teeth and the cog teeth are formed at an acute angle to enable a plurality of electrical connections to be formed simultaneously as the commutator teeth mesh with the cog teeth.

Each ofthe first and second slip ring assemblies, 310 and 312, comprise a slip ring, 350 and 352, and a spindle, 354 and 356, respectively. The first slip ring assembly 310 is associated with the first cog 306 and the second slip ring assembly is associated with the second cog 308.

The commutator 302 is fixed to a shaft 340 to rotate therewith. The shaft 340 extends from the armature 328 of an electric machine such as an electric motor or generator, alternator or dynamo, or the like.

The first and second cogs, 306 and 308, are arranged such that the respective teeth, 332 and 334, engage with the teeth 322 of the commutator 302, as shown in Figure 6.

The first slip ring 350 is disposed in the first cog, 304, along the longitudinal axis thereof.

Similarly, the second slip ring 352 is disposed in the second cog, 306, along the longitudinal axis thereof. The first and second spindles, 354 and 356, are disposed within the respective first and second slip rings, 350 and 352, along the longitudinal axis thereof.

The first and second spindles arc electrically connected to an electrical source or load 348.

The housing 314 comprises first and second shaft plates, 336 and 338, through which the shaft 340 enters and exits the housing 314. The housing further comprises a reservoir 342 for holding an electrically insulating lubricant, such as are-quenching oil. The reservoir is disposed in the housing such that the teeth of the second cog 308 pass through it.

First and second seals, 344 and 345, are provided between the first and second shaft plates and the walls of the housing 314 and the shaft 340, respectively.

In use, whether acting as an electric motor or generator, alternator or dynamo, or the like, an electrical connection exists between one, or more, sets of windings 326 of the armature 328 and the electrical source or load 348, via an electrically conductive path through the commutator 302, the first and second cogs, 306 and 308, and the first and second slip ring assemblies, 310 and 312. As the shaft 340 rotates, the commutator 302 rotates, causing the first and second cogs, 306 and 308, to rotate. As the first and second cogs rotate each address a set of windings in turn as the teeth of each cog engage each, or each set of, commutator teeth 322 in turn, thereby providing an electrical connection between the cogs and each of the sets of windings, in turn. The meshing of the commutator teeth and the teeth of the first and second cog breaking the layer of oil to form the electrical connection therebetween.

An electrical connection is also provided between the first and second cogs, 306 and 308, and the electrical source or load 348 via the associated slip ring assemblies, 310 and 312, wherein the spindles, 354 and 356, are stationary and the slip rings, 350 and 352, rotate with the associated cogs. The spindles are electrically connected to the electrical source or load. Alternatively, the spindles may rotate and the slip rings may be stationary, in which case the slip rings would be electrically connected to the electrical source or load.

The electrical assembly connection 300 thereby provides an electrical connection between each, or each set, of windings of the rotating armature 328 and the stationary electrical source or load 348, in tune.

Referring to Figure 7, an electric machine 400 comprises the electrical connection assembly 300 as described above. The electric machine may be an electric motor or an electric generator, alternator or dynamo, or the like. The electric machine further comprises standard known components including a pair of opposing field magnets 401 providing a pcomanent magnetic field in which the armature 328 is disposed. The electric machine operates as an electric motor or electric generator, alternator or dynamo, in a conventional manner, which rotates the shaft 340. The electrical connection between the rotating armature 328 and the stationary electrical source or load 348 is formed though the electrical connection assembly 300.

Claims

CLAIMS: I. An electrical connection assembly comprising at least one

commutator, having an external surface comprising a plurality of electrically conductive teeth, a plurality of stationary electrical connection parts, suitable for connection to an electrical source or load, and a plurality of cogs having electrically conductive toothed surfaces, wherein the cogs are arranged to engage with the teeth of the, or an associated, commutator and an associated stationary electrical connection part to provide an electrical connection between the rotary commutator and each stationary electrical connector part.
2 An electrical comlection assembly as claimed in Claim 1, wherein the plurality of stationary electrical connector parts each have a toothed surface for engagement with at least one cog.
3. An electrical connection assembly as claimed in Claim 2, wherein the stationary toothed surface is spaced apart from, and arranged to face, the external surface of the commutator.
4 An electrical connection assembly as claimed in any of the preceding claims comprising first and second commutators, first and second cogs and first and second stationary electrical connection parts wherein the first cog engages the first commutator and the first stationary electrical connector part to provide an electrical connection therebetween and wherein the second cog engages the second commutator and the second electrical connection part to provide an electrical connection therebetween.
5. An electric generator as herein described with reference to, as shown in, the accompanying drawings.

5. An electrical connection assembly as claimed in Claim 1, wherein each stationary electrical connection part comprises a slip ring assembly having a slip ring and a spindle.

6. An electrical connection assembly as claimed in any of the preceding claims, wherein each of the commutator teeth extend at an acute angle relative to the direction of the longitudinal axis of the commutator 7. An electrical connection assembly as claimed in any of the preceding claims, wherein the cog teeth extend at an acute angle relative to the direction of the longitudinal axis of the cog on which they are disposed.

8. An electrical connection assembly as claimed in any of the preceding claims, comprising a housing having cog lubricating means.

9. An electrical connection assembly as claimed in Claim 8, wherein the cog lubricating means comprises a reservoir of lubricating oil disposed such that, in use, at least part of at least one cog passes through the reservoir.

10. An electrical connection assembly as claimed in Claim 9, wherein the lubricating oil is an electrical insulant.

i. An electrical motor comprising an electrical connection assembly as claimed in any of the preceding claims.

At. An electrical generator comprising an electrical connection assembly as claimed in any of the preceding claims.

3. An electrical connection assembly as herein described with reference to, as shown in, the accompanying drawings.

4. An electric motor as herein described with reference to, as shown in, the accompanying drawings.