Electric motor with ring rotor passing through coils

Details Electric motor with ring rotor passing through coils Electric motor with ring rotor passing through coils

1999-07-06

2001-06-26

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S083000, C310S099000, C310S267000

Reexamination Certificate

active

06252317

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to electric motors, and more specifically to a motor with a rotor assembly, having a rotor upon which permanent magnets are affixed, passing through the center of stator coils.
2. Description of Related Art
Electric motors are at the heart of many machines used in both homes and factories. Electric motors are quiet, non-polluting energy sources used in a wide variety of applications, from operating toothbrushes to golf carts, and to propelling automobiles.
Turning to FIG.
1
(
a
), a general model of an electric motor is shown, where an electric motor
10
receives an electric current
12
as an input to be applied to wound coils therein for generating a magnetic field. With the model for the electric motor of FIG.
1
(
a
), the electromagnetic fields induced in the coils are converted into output torque
14
. Although not shown, this is usually accomplished with a rotor acting on an output shaft
16
. Stated simply, FIG.
1
(
a
) shows electricity as an input and torque as an output. It would be desirable if the output torque of the motor could be increased without necessarily having to increase the input electrical energy.
Motor
10
may run in reverse as in FIG.
1
(
b
) to function as a generator. In this case, torque
18
is applied to shaft
16
and is thereby converted by the motor into output electric current
20
. Stated simply, torque is input to the motor, and electricity is output. In either case, it is desirable to convert energy as efficiently as possible.
In order to improve and to obtain high efficiency within an electric motor, the present inventors noticed a need to eliminate or overcome sources of inefficiencies.
SUMMARY OF THE INVENTION
The electric motor of the present invention includes a rotor assembly, having a rotor with associated magnets affixed thereto, passing through stator coils. In an exemplary embodiment, the electric motor comprises a structure having: a housing; the rotor assembly supported therewithin, and having a ring rotor with a plurality of magnets permanently attached thereto; and a plurality of stator coils that are supported within the housing and through which the rotor assembly completely passes when the rotor moves in a direction of rotation. The structure includes an inventive arrangement where the adjacent magnets are alternated between having respective North poles facing toward or against the direction of rotation.
According to the present invention, the stator coils are arranged in groups about the periphery of the rotor, and the application of electrical energy to each coil in a group is performed so that each coil simultaneously attracts a magnet and repels an adjacent magnet. Moreover within each group, the coils are never simultaneously energized (e.g., turned on to certain voltage level or its inverse) or de-energized (e.g., turned off to zero volts).
In an exemplary embodiment, pairs of coils are disposed about the periphery of the rotor and the electrical energy applied to one of the coils in each group is out of phase with respect to the electrical energy applied to the other coil in the group. As a first magnet passes through the center of the first coil, the first coil is de-energized. After the first magnet moves away from the first coil and when the first coil is evenly spaced between the first magnet and a second magnet of opposite polarity, the first coil is energized with a voltage level of opposite polarity so as to repel the first magnet away from the first coil and simultaneously attract the second magnet towards the first coil. This process reoccurs with the second coil, which is out of phase so as to accommodate the circumferential distance that the magnets must travel past the first coil to reach the second coil. Collectively, the energization, de-energization and energization with alternating polarity of each coil causes the rotor to continuously move in the direction of rotation with improved efficiency.
In accordance with one embodiment of the present invention, a Hall effect sensor is used to detect the position of the permanent magnets with respect to the center of the stator coils, and a motor controller is used to correspondingly control the electrical energy provided to the coils. The sensor is used to detect the position of the rotor. This information may be used by the controller to determine the angular velocity of the rotor and to control the timing of energizing the electromagnets to achieve a desired acceleration or angular velocity of the rotor.
The electric motor of the present invention may also include planetary gears meshed with a sun gear that is connected to an output shaft for providing output torque transmission. Other gears may also be coupled between the planetary gears and the sun gear for driving or powering the rotation of the output shaft. Collectively, this mechanical structure translates the rotational movement of the rotor to output motor torque.
In another aspect of the present invention, motor inefficiency found in conventional motors is improved with the use of efficient support bearings. In a preferred embodiment, the support bearings are air bearings used to reduce friction occurring around the rotor.
In yet another aspect, the present invention uses a sealed environment in which the electric motor is confined in order to avoid particulate contamination.
In one embodiment of the present invention, the air bearings may be enclosed so that air may be provided thereto and exhausted therefrom. In another embodiment, the present invention provides a “closed system”, where the interior of the motor housing is sealed from atmosphere and drawn down to near vacuum conditions. Furthermore, the same vacuum system may be used to evacuate the housing and to exhaust the air bearings. Use of a vacuum system improves motor efficiency by reducing turbulent airflow and air resistance around the rotor.
In a further aspect, the present invention includes a system for supplying air or other gas to the bearings, and for exhausting the bearings and the housing.
It is believed that motor efficiency may be improved if the stator coils of the present invention are formed from superconductive materials. It is further anticipated that if the stator coils are cooled below a critical temperature, then energy losses due to coil resistance may be reduced, and a desired degree of rotor levitation may be achieved ideally sustaining high rotational speeds with low energy dissipation. In an exemplary embodiment, the present invention includes an inventive structure for enclosing the stator coils so that a cooling agent may be used to cool the coils to operate with superconducting effects.
It is yet a further object of the present invention to provide an electric motor that is scalable and versatile so that it may be applied to a wide range of applications requiring diverse output power specifications. As already mentioned, the electric motor may increase its output torque to lend itself to applications requiring larger output torque. Additionally, a plurality of electric motors of the present invention may be coupled together (e.g., grouped together in a cell configuration, connected in series or in a chain) to operate as a system so that more power may be delivered to a final system output.
In another aspect of the present invention, conventional steel or iron cores are not used so as to reduce mutual inductance occurring within the stator windings. Instead, the present invention uses a ring rotor in an exemplary embodiment to which stator coils are disposed apart from each other so as to avoid mutual inductance from occurring therebetween. With the present invention, motor inefficiency is also improved by replacing conventional materials used for the housing, rotor, gears and supports with materials that have a minimal impact on the magnetic fields. These materials are generally non-conductive and non-magnetic in nature.
It is yet a further object of the present invention to provide an electric motor that may be operated i

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