The present invention generally relates to an electric motor incorporating permanent magnets and, in particular, to a motor having a rotor with a series of permanent magnets and a stator configured as a printed circuit board.
Electric motors of the type that include permanent magnets have become ubiquitous and part of everyday life. Such motors have many uses, including rotating small or light-weight parts of equipment in a precisely controlled manner. The basic electric design of this type of motor has not changed significantly over the years. Characteristically, current is switched to a series of conductor coils to produce a rotating field. The magnets in the motor are then acted upon by the rotating field, producing rotation of the rotor. Permanent magnet motors typically use batteries which have a limited life to produce the electric current needed to power the conductors.
It is desirable to incorporate an inexpensive electromagnetic motor in a number of applications. A significant part of the cost of such motors reside in their wire coils. It is also beneficial to have a two phase brushless system because it consumes half the energy of a typical two-phase permanent magnet motor, thereby, preserving and prolonging battery life. Finally, it is beneficial to have a permanent magnet motor which can be controlled very accurately.
Also, there is the need for a motor whose speed is independent of the level of current or voltage applied to the motor. It is also beneficial to a have a permanent magnet motor that allows variable torque and motor current so that during speed changes extra torque and current can be applied but during constant, steady rotation, the current consumption is reduced.
In accordance with one embodiment of the present invention, a printed circuit board motor is disclosed. The motor comprises a rotor that comprises a generally circular plate embedded with magnets that extend to the outer edge of the front surface of the rotor plate; an axle coupled to the back surface of the rotor plate; and a stator imprinted with a printed circuit board on its front surface that positioned adjacent and parallel to the front surface of the rotor plate. The printed circuit board comprises two conductors printed on the same surface or on opposite surfaces of the printed circuit board. The conductors are oriented 90° out of phase with each other. The two conductors produce alternating “square wave” patterns. The printed circuit board circuitry causes the direction of the current flow to reverse at prescribed intervals. The magnets embedded in the rotor plate provide a magnetic field that passes through the printed circuit board. The magnets around the edge of the rotor plate alternate north and south poles. The rotor rotates in response to the current flow in the stator. This rotation rate can be accurately controlled. The torque and average current consumption can be controlled by “chopping” the input current with relatively high frequency modulation whose duty cycle is proportional to the torque and average current consumption.
Accordingly, it is an object of the present invention to provide an inexpensive rotating electric motor that provides accurate control of rotation rate and allows for variable torque and motor current so that during speed changes extra torque and current can be applied, but during steady rotation, current consumption can be reduced, thereby, prolonging battery life.
It is also an object to increase battery life by reducing motor current to the amount needed to maintain the desired rotation rate, prolonging the battery life of the motor.
Other objects of the present invention will be apparent in light of the description of the invention embodied herein.
The following detailed description of specific embodiments of the present invention can be best understood when read in conjunction with the following drawings:
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention.
FIGS. 1A-D diagrammatically illustrate a printed circuit board motor 10 from several different viewpoints. A rotor 30 of the printed circuit board motor 10 comprises a plate 31 having a front surface 32 and a back surface 33. The rotor 30 has a plurality of magnets 40 mounted on and extended to the outer edge of the front surface 32 of the rotor plate 31 as seen in
The stator 20 comprises a printed circuit board 21 having a front surface 22 and a back surface 23. In one embodiment, the printed circuit board 21 of the stator 20 can be part of a larger printed circuit board that controls the entire product and contains all the electronics for the product. In another embodiment, the printed circuit board 21 of the stator 20 controls only the printed circuit board motor 10. The front surface of the stator 20 is positioned across from, and parallel to, the front surface of the rotor 30. The plurality of magnets 40 on the rotor 30 extend from the rotor plate 31 at a distance that allows the magnetic fields produced by the magnets 40 to pass through the printed circuit board of the stator 20 and to prevent crosstalk. The rotor 30 and stator 20 do not touch.
The front surface 22 of the printed circuit board 21 of the stator 20 is illustrated in
The printed circuit board can be made of any number of layers and made by any of the well know methods of the art. In one embodiment, a first layer of the conductor is printed on front surface 22 of the printed circuit board 21 and is illustrated in
The two conductors produce alternating “square wave” patterns that are arranged in a circle. The processor U1 causes the direction of the current flow through the conductors to reversal at intervals resulting in the rotor 30 spinning. The processor U1 controls the current flow with high frequency modulation. In addition, the torque and average current consumption of the printed circuit board motor 10 can be controlled by the processor U1. The processor U1 controls the current by “chopping” it with relatively high frequency modulation. This relatively high frequency modulation has a duty cycle that is proportional to the torque and average current consumption. The rotor 30 rotates in response to the current flow in the printed circuit board 21. This rotation rate can be accurately controlled by the processor U1. Due to the method of alternating phases of the two conductors, speed is independent of current or voltage applied to the motor. Speed, torque and power consumption are, also, independently controlled.
Because a chopped input wave is used, less electrical energy is needed to spin the rotor 30. Even though there is an increased need for current to start the printed circuit board motor 10 or to change the speed, the current consumption decreases once the rotor 30 is spinning at a constant steady speed, thereby lowering overall energy costs. Through the use of the chopped wave, half the effective electrical energy is used, thereby prolonging the battery life by twofold over the average printed circuit board motor life resulting in greater cost savings.
It is noted that terms like “preferably,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention.
Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.