The present application relates to the motorization of electric vehicles using permanent-magnet synchronous machine such as brushless DC machines, for electric vehicles such as bicycles, rolling chairs, scooters, tricycles, golf carts, trolleys and small utility vehicles, or the like.
In lightweight vehicle applications, it is often desired to produce high starting torque and to ensure variable assistance, whereby electric machines are well suited therefor as opposed to other types of motors or engines. The use of a brushless direct-current (DC) machine is particularly well adapted to these kinds of applications. Some brushless DC machines use a permanent magnet external rotor with three phases of driving coils on the stator core. According to one type of machine, the position of the rotor is sensed with sensors (e.g., Hall effect sensors) and the associated drive electronics. The coils are activated by the drive electronics, based on the detection signals from either the sensors or from the back electromotive force (EMF).
Brushless DC machines are relatively simple in construction, and cost-effective in maintenance in view of their brushless nature. However, there remains a need to produce increasingly efficient brushless DC machines, in a cost-efficient manner. For instance, the weight of the machine components must be minimized, while not affecting the structural integrity of the machine.
It is therefore an aim of the present disclosure to provide a new brushless DC machine for vehicles.
It is a further aim of the present disclosure to have a brushless DC machine that is relatively lightweight.
Therefore, in accordance with the present application, there is provided a direct-drive brushless DC motorization apparatus comprising: an outer rotor with poles constructed with segments of permanent magnet material alternatively magnetized north and south, the outer rotor adapted to be part of a wheel and rotating with the wheel about an axis thereof; a stator core of ferromagnetic material spaced inwardly of said rotor and defining a clearance gap with the rotor such that the rotor is rotatable about the stator core, said stator core having forty-two slots and defining teeth between said slots; and a three-phase winding with coils of insulated wire being wound around the teeth of the stator core, the three-phase winding being divided in two sets of consecutive teeth for each of the three phases, with each of the two sets of a same phase being diametrically opposed in the stator core.
Further in accordance with the present application, the three-phase winding are divided into two sets of seven consecutive teeth for each of the three phases.
Still further in accordance with the present application, each said phase of the three-phase winding is divided into sets of six and eight consecutive teeth.
Still further in accordance with the present application, the outer rotor comprises forty poles.
Still further in accordance with the present application, the outer rotor comprises forty-four poles.
Still further in accordance with the present application, the stator core has a hub supporting a stator yoke, wherein the hub comprises structural elements extending diametrically between centers of each said set of the same phase.
Still further in accordance with the present application, the hub has a six-pointed star shape, with an interconnection between points of the star shape and the stator yoke being in alignment with a center of each said set of teeth.
Still further in accordance with the present application, each said set comprises seven consecutive teeth.
Still further in accordance with the present application, the stator is fixed to an axle of the wheel.
Still further in accordance with the present application, the rotor is adapted to be operatively connected to a freewheel of a vehicle to rotate therewith in one rotational orientation.
Still further in accordance with the present application, the rotor is adapted to be connected to spokes of a wheel, with the spokes projecting radially from a casing of the rotor.
Still further in accordance with the present application, each said phase comprises 14 teeth.
Referring to the drawings and more particularly to
According to one embodiment, the brushless DC machine system includes a 3-phase permanent magnet brushless DC machine 10, a power supply circuit 11, a rotor position detector 12 (e.g., with Hall effect sensors), a current measurement system 13 and/or a current regulation system which is comprised of a current control circuit 14 fed by the current measuring circuit 13 and a torque reference or current reference circuit 16. The current control circuit 14 is connected to the power supply circuit 11 to control the torque of the machine 10.
It is pointed that the machine 10 is identified as being a 3-phase permanent magnet brushless DC machine. This generic identification is deemed to also include permanent magnet synchronous machines, for instance operated with sinusoidal waveform current, or the like. Moreover, reference to a brushless DC motor also covers the use of the machine or motor 10 in a motorization mode and in a generator mode.
The afore-described system is a conventional operating system for a brushless DC motor, and is one among numerous other systems that may be used to operate the brushless DC machine 10. However, the system of
Referring to
A cylindrical outer rotor 30 is mounted about the stator core 20, and is separated from the stator core 20 by a suitable clearance gap. The rotor 30 is supported for instance by the casing of the machine 10 (which itself rotates about the axle), and is rotatable with respect to the axis of the wheel. A remainder of the wheel projects radially from the rotor 30 and supports a tire. In an embodiment, spokes of the wheel project radially or peripherally from an outer surface of the rotor 30. The rotor 30 is constituted of segments of permanent magnets 31 mounted on the rotor inner surface and alternatively magnetized north and south. In
The high number of poles reduces the iron volume. By increasing the number of poles, the flux per pole during operation is reduced as compared with a machine producing a similar power output with a lesser amount of poles. Accordingly, as the sectional dimensions of teeth are proportional to the flux, the sectional dimensions for a forty-two pole machine are smaller than the sectional dimensions for the teeth of a machine with fewer poles, for a similar power output. There results a lower weight for the forty-two pole machine when compared to machines having a fewer amount of poles for a similar power output.
Referring concurrently to
Referring to
The interconnection of phases and the coil winding may be any other appropriate alternative. For instance, there may be used a single coil per slot 21. Also, as an alternative to the interconnection shown in
Still referring to
The brushless DC machine structure described in
The brushless DC motor structure described in
The present application claims priority of U.S. Provisional Patent Application No. 61/366,956, incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/CA11/50441 | 7/20/2011 | WO | 00 | 2/1/2013 |
Number | Date | Country | |
---|---|---|---|
61366956 | Jul 2010 | US |