Abstract:
A DC motor includes a power source, a stator and a rotor. Permanent magnets are mounted to either the stator or the rotor. Electromagnets are mounted to the other of either the stator or the rotor. Each electromagnet includes two coils which are each branched with a capacitor. A switching means, responding to the rotor, switches between a first mode in which the power supply is connected across a branch for energizing the coil and charging the capacitor and a second mode in which the branch terminals are closed for discharging the capacitor into the coil. The switching means and branches are arranged such that the coils of a particular electromagnet maintain the same polarity while also alternating between opposite polarities.

Description:
FIELD OF THE INVENTION 
   This invention relates to a DC motor. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The present invention is a DC motor, including a power source, a stator and a rotor mounted for rotation relative to the stator about a motor axis. A set of permanent magnets is mounted to either the stator or the rotor so that the poles of the permanent magnets are equiangularly spaced about the motor axis. At least one electromagnet is mounted to the other of either the stator or the rotor such that the two poles of the electromagnet are equiangularly spaced about the motor axis. The electromagnet includes at least a first coil and a second coil which are both associated with one pole of the at least one electromagnet. The first coil is connected in series in a first branch with a first capacitor and the second coil is connected in series in a second branch with a second capacitor. A switching means responds to the rotation of the rotor and alternates between a first mode and a second mode. In the first mode, the switching means connects the first branch with the power supply causing the first coil to energize with a first polarity and the first capacitor to charge. In the first mode, the switching means also disconnects the second branch from the power supply and establishes a connection between the free terminal of the second capacitor and the second coil. This causes the second capacitor to discharge and energize the second coil with the first polarity thus reinforcing the magnetic field in the pole. In the second mode, the switching means disconnects the first branch from the power supply and establishes a connection between the free terminal of the first capacitor and the first coil causing the first coil to energize with a second, opposite polarity. Also in the second mode, the switching means connects the second branch with the power supply causing the second coil to energize with that same second, opposite polarity and the second capacitor to charge. The timing of the switching between the first mode and second mode is arranged such that the poles of the electromagnet alternately attract the approaching pole of the permanent magnet and repel the receding pole of the permanent magnet to cause powered rotation of the rotor. 
   Those skilled in the art will readily appreciate that, by way of example, the above described arrangement may be embodied in a DC motor having in a stator which includes a plurality of electromagnets wherein each pole of each electromagnet has at least two coil windings as described above which are each connected in a circuit including a capacitor, a power supply and commutator for controlling oscillations between the two modes as described above and wherein the rotor has an associated plurality of permanent magnets the poles of which alternate between being attracted to and being repulsed by the poles of the electromagnets of the stator as the rotor rotates to generate power. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a schematic showing the coil branches for the pole of an electromagnet and the commutator of a motor of the present invention where both coil branches are isolated from the power source and both coil branches are open. 
       FIG. 1B  is a schematic showing the coil branches for the pole of an electromagnet and the commutator of a motor of the present invention where the first coil branch is in communication with the power supply and the second coil branch is closed. 
       FIG. 1C  is a schematic showing the coil branches for the pole of an electromagnet and the commutator of a motor of the present invention where both coil branches are isolated from the power source and both coil branches are open. 
       FIG. 1D  is a schematic showing the coil branches for the pole of an electromagnet and the commutator of a motor of the present invention where the first coil branch is closed and the second coil branch is in communication with the power supply. 
       FIG. 1E  is a motor schematic with a multiple coil branch arranged in parallel for a motor having eight electromagnets. 
       FIG. 1F  is a schematic of a multiple coil branch arranged in series for a motor having eight electromagnets. 
       FIG. 1G  is a schematic of a multiple coil branch arranged with two sets of four coils arranged in series where the sets are arranged in parallel for a motor having eight electromagnets. 
       FIG. 2  is a side view of an embodiment of the motor of the present invention. 
       FIG. 3  is a side sectional view of an embodiment of the motor of the present invention taken from plane  3 — 3  of  FIG. 2 . 
       FIG. 4  is an end view of an embodiment of the motor of the present invention. 
       FIG. 5  is a side sectional view of an embodiment of the motor of the present invention taken from plane  5 — 5  of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings,  FIGS. 1A–1D  provide a series of schematic diagrams of a motor  10  of the present invention.  FIGS. 2–4  provide an example configuration of a motor  100  which is intended as one embodiment of motor  10 . 
     FIGS. 1A–1D  show that, in its simplest form, motor  10  includes a rotor  12 , a motor shaft  12 A, a commutator  20 , a power supply branch  60 , a first coil branch  40 A and a second coil branch  40 B. Power supply branch  60  further includes a DC potential  62 , a switch  64  which remains closed for purposes of  FIG. 1A–1D . Power supply branch  60  terminates in a first power terminal  66 A and a second power terminal  66 B. First coil branch  40 A includes a first terminal  42 A, a capacitor  44 A, a coil  46 A and a second terminal  48 A. Second coil branch  40 B includes a first terminal  42 B, a capacitor  44 B, a coil  46 B and a second terminal  48 B. Commutator  20  includes a non-conductive area  22  which isolates three conductive areas on the surface of commutator  20 , namely, a central conductive area  24 , a left conductive area  26  and a right conductive area  28 . Those skilled in the art will readily appreciate that non-conductive area  22  is illustrated in  FIGS. 1A–1D  as having a substantial amount of surface area and that in actual practice, non-conductive area  22  may be arranged to have just enough surface area to prevent electrical conduction between conductive area  24 , left conductive area  26  and right conductive area  28 .  FIGS. 1A–1D  do not illustrate all the components of motor  10 . For example, the skilled reader should understand that typically, coils  46 A and  46 B are associated with the same pole of an electromagnet (not shown in  FIGS. 1A–1D ) which is preferably mounted to a stator (not shown in  FIGS. 1A–1D ). Further, at least one permanent magnet (not shown in  FIGS. 1A–1D ) is preferably mounted to rotor  12 . The electromagnet associated with coils  46 A and  46 B and the permanent magnet are preferably arranged such that their poles alternately attract and repulse each other to cause rotation of rotor  12  and motor shaft  12 A. 
     FIGS. 1A–1D  illustrate how commutator  20  controls the sequence of connections between the terminals of power supply branch  60 , first coil branch  40 A and second coil branch  40 B as commutator  20  rotates through four positions. Those skilled in the art should appreciate that commutator  20  is only one of many means for accomplishing the sequence of states described below. For example, a solid state timing device including a position sensor and solid state relays might be devised for accomplishing the sequence of operations described below. 
   In  FIG. 1A , commutator  20  may be considered as beginning a cycle of rotation in a first position. With commutator  20  in the first position, power supply branch terminals  66 A and  66 B are isolated from both coil branches and no connection is provided between the end terminals of either coil branch. 
   In  FIG. 1B , commutator  20  has rotated in the cycle of rotation to a second position. With commutator  20  in the second-position, first terminal  66 A of power supply branch  60  is connected by left conductive area  26  of commutator  20  to first terminal  42 A of first coil branch  40 A while second terminal  66 B of power supply branch  60  is connected by right conductive area  28  to second terminal  48 A of first coil branch  40 A. This connection causes capacitor  44 A to charge and coil  46 A to energize in first coil branch  40 A. At the same time, in  FIG. 1B , terminals  42 B and  48 B of second coil branch  40 B are connected by central conductive area  24 . This connection closes coil branch  40 B and causes capacitor  44 B to discharge and thus energize coil  46 B. As noted above, coils  46 A and  46 B are preferably arranged in the same electromagnet and they are also arranged such that during the configuration shown in  FIG. 1B , both coils  46 A and  46 B generate the same polarity in the magnetic field. 
   In  FIG. 1C , commutator  20  has rotated to the third position. With commutator  20  in the third position, the terminals of both coil branches  40 A and  40 B are once again isolated from each other and from power supply branch  60 . When commutator  20  is in the third position, coil branches  40 A and  40 B are not being energized and capacitors  44 A and  44 B are not discharging. 
   In  FIG. 1D , commutator  20  has rotated to the fourth position. When in the fourth position, commutator  20  connects the terminals of power supply branch  60 , first coil branch  40 A and first coil branch  40 B in a manner that is inverted from that of the second commutator position illustrated in  FIG. 1B . When in the fourth position, first power supply branch terminal  66 A is connected by left conductive area  26  to first terminal  42 B of second coil branch  40 B while second power supply branch terminal  66 B is connected by right conductive area  28  to second terminal  48 B of second coil branch  40 B. These connections cause capacitor  44 B to charge and coil  46 B to energize with a polarity which is opposite from the polarity of coil  46 B when commutator  20  was in the second position shown in  FIG. 1B . At the same time, in  FIG. 1D , terminals  42 A and  48 A of first coil branch  40 A are connected by central conductive area  24 . This connection closes first coil branch  40 A which causes capacitor  44 A to discharge and coil  46 A to energize. Again, the polarity of coil  46 A in the fourth commutator position is opposite of the polarity of coil  46 A during the second commutator position. As commutator  20  continues to rotate it returns to the first position shown in  FIG. 1A . 
   Accordingly, as commutator  20  rotates from the first position through the fourth position as described above, coils  46 A and  46 B are alternately energized or isolated and are alternately energized with polarities which alternate in polarity between the second and fourth positions described above. In the second position, coils  46 A and  46 B may be described as being energized with a first polarity for causing a first polarity in preferably the same pole of an electromagnet which is preferably associated with the stator. The difference being that, in the second position, coil  46 A of first coil branch  40 A is energized by voltage potential  62  of power supply branch  60  as capacitor  44 A is charged and coil  46 B of second coil branch  40 B is energized with the same polarity by the discharging capacitor  44 B of second coil branch  40 B. In the fourth position, coils  46 A and  46 B may be described as being energized with a second polarity for causing a second opposite polarity in preferably the same pole of the electromagnet. Here, in the fourth position, coil  46 B of second coil branch  40 B is energized by voltage potential  62  of power supply branch  60  as capacitor  44 B is charged and coil  46 A of first coil branch  40 A is energized with the same, opposite polarity by the discharging capacitor  44 A of first coil branch  40 A. Thus, for example, two coils common to one pole of an electromagnet of a stator, can be cyclically energized by drawing power from two different sources, namely the power supply or a previously charged capacitor connected in the same branch with the coil and, the two coils common to the one pole may be cyclically energized with alternating opposite polarities as each of the two coils alternate between receiving power from these two power sources. 
   The example motor of  FIGS. 1A–1D  may be configured such that each coil of the electromagnet includes, for example, approximately 1600 turns of 20 gauge copper wire. 20 gauge copper wire typically has approximately 10 ohms of resistance per 1000 feet. Accordingly, a single coil as described above may, for example, have a resistance of approximately between 25 and 30 ohms. The applicant has found, with a single pole motor of his own construction, that such a motor operating at 1000 RPM operates sufficiently well if a 1300 micro farad capacitor rated at 200 volts is used in the branches described above when the motor is supplied with current having a 118V input voltage. At 1000 RPM a single coil of a one pole motor and the branch connected with it will alternate between the above described modes approximately 500 times per minute or once every 120 milliseconds. Accordingly, with such a one pole motor, the capacitor of each branch associated with each coil would have a charge time and a discharge time of 120 milliseconds. It is important that the value of the capacitor be chosen such that the capacitor operates well within the elastic portion of the capacitor&#39;s total charge and discharge limits during normal operation. Such an arrangement as described above will result in a generally constant charge and discharge level during each portion of the above described cycles. 
     FIGS. 2–5  illustrate an example embodiment of the present motor which for clarity will be referred to as motor  100 . The skilled reader should note that the numerous repetitive structures in motor  100  are indicated with a single reference number for clarity. The skilled reader should understand that generally, only one item of a set of identical elements will be indicated and described below for motor  100 . As can be seen in  FIGS. 2–5 , motor  100  includes a stator  101  and a rotor  110 .  FIG. 2  shows that stator  101  has a casing  102  and a pattern of fasteners  102 A and that rotor  110  has a rotor shaft  112 . 
     FIGS. 3–5  show other components of stator  101  and rotor  110 .  FIG. 3  gives a cross section taken from plane  3 — 3  of  FIG. 2 .  FIG. 4  is an end view of motor  100  and  FIG. 5  is a sectional view taken from plane  5 — 5 —of  FIG. 4 . Rotor shaft  112  caries the other components of rotor  110 . Rotor  110  primarily includes a set of eight permanent magnets  160 . Permanent magnets  160  are preferably arranged so that adjacent permanent magnets  160  have alternating polarities. As can be best seen with reference to  FIGS. 3 and 5 , rotor shaft  112  is mounted to motor casing  102  by two bearings  120 A and  120 B. Shaft  112 , in turn carries a hub  172  which is preferably fashioned from aluminum. Hub  172  carries an iron ring  174  which, in turn carries permanent magnets  160 . 
   For motor  100 , casing  102  forms part of the stator  101 —the stationary portion of the motor. Electromagnets  150  and their associated connections should be understood as separate but identical components of motor  100 . Accordingly, for clarity, features and elements associated with each of the eight electromagnets  150  will be shown and described once. The reader should understand that each of the eight electromagnets  150  have generally identical elements and connections. A pattern of eight evenly distributed electromagnets  150  are fastened by fasteners  102 A to the inside wall of casing  102 . Electromagnet  150  includes a shoe portion  150 A and a leg portion  150 B. Two coils,  146 A and  146 B are wound around the relatively narrow leg portion  150 B of electromagnet  150 . Coils  146 A and  146 B may be considered as corresponding to coils  46 A and  46 B shown in  FIGS. 1A–1D . A diagram showing the branches connected to a set of coils  146 A and  146 B associated with one of the electromagnets is given in  FIG. 3 . Branch  140 A may be considered as corresponding to branch  40 A of  FIGS. 1A–1D  and branch  140 B may be considered as corresponding to branch  40 B of  FIGS. 1A–1D . Thus capacitor  144 B corresponds to capacitor  44 B and so on. Contacts  142 A,  148 A,  142 B and  148 B are associated with a commutator or some other switching means for alternately connecting the pairs of contacts or connecting a power supply between the contacts as described above. As noted above, this arrangement is repeated eight times around the stator of motor  100  for each electromagnet  150 . 
   Although  FIGS. 3–5  illustrate a motor having eight electromagnets and eight permanent magnets, the reader should understand that a configuration may be devised having unequal numbers of electromagnets and permanent magnets. For example, a motor could be devised having eight electromagnets and six permanent magnets. A motor configuration may even have eight electromagnets or 7 or 9 permanent magnets. 
   As described above with reference to  FIGS. 1A–1D , for branches  40 A and  40 B, branches  140 A and  140 B shown in  FIG. 3  may, for example, be controlled by a commutator or some other switching device which repetitively cycles through the following steps: 1. (a) Close a connection between contacts  142 A and  148 A thus discharging capacitor  144 A to energize coil  146 A with a first polarity and at the same time—(b) Connect contacts  142 B and  148 B to the terminals of a power supply in order to charge capacitor  144 B and energize coil  146 B with the same first polarity. 2. (a) Connect contacts  142 A and  148 A to the terminals of the power supply in order to charge capacitor  144 A and energize coil  146 A with a second, opposite polarity, while, at the same time, (b) Close a connection between contacts  142 B and  148 B thus discharging capacitor  144 B to energize coil  146 B with the same second opposite polarity. If the timing of these steps is controlled for each electromagnet  150  in a way that corresponds to the angular position of rotor shaft  112  and thus the angular positions of permanent magnets  160 , then electromagnets  150  can act to alternately attract approaching poles of permanent magnets  160  and repel receding poles of permanent magnets  160  to cause powered rotation of rotor  110  relative to stator  101 . Given the internal symmetry of motor  100 , it may be possible or even preferred to connect branches  140 A and  140 B to alternating sets of coils associated with every other electromagnet shown in  FIG. 3 . And accordingly, a second pair of branches similar to branches  140 A and  140 B maybe timed 180 degrees out of phase with the first set of branches and connected to the coils of the four remaining electromagnets to energize those coils with an opposite polarity in accordance with the steps described above. 
     FIG. 1E  presents a schematic of an example arrangement with coil branches having multiple parallel coils. Multiple coil branches  140 A and  140 B, in this example, are arranged to accommodate eight coils which are wound upon eight electromagnet cores. Accordingly, branch  140 A includes coils  146 A 1 – 146 A 8  and branch  140 B includes coils  146 B 1 – 146 B 8 . Each of those coils are arranged in parallel in each of the multiple coil branches and each coil is associated with a separate electromagnet  150  shown in  FIG. 3 . As shown in  FIGS. 1F and 1G , multiple coil branches may also be arranged in series as in  FIG. 1F  or partially in series and partially in parallel as in  FIG. 1G . Pairs of coils, for example coils  146 A 1  and  146 B 1  shown in  FIG. 1E  would be wound upon the same electromagnet core such that their polarities would alternate each time the commutator turned 45 degrees. The arrangement of the commutator is not shown in  FIG. 1E  for simplicity. The commutator would need to be arranged to reverse modes every 45 degrees of rotation instead of every 180 degrees as shown in  FIGS. 1A–1D . 
   It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations are included in the following claims and allowable equivalents thereof.