Abstract:
A brushless repulsion motor which includes a stator and rotor rotatably mounted on the stator is provided. The stator and rotor are contained within a first housing, the stator having at least one pair of poles, a field winding on the stator for producing a field on the stator, and a plurality of coils on the rotor adapted to electromagnetically interact with the field of the stator winding. Switches are located on the rotor shaft outside the first housing to selectively short successive ones of the coils when the coils are in a preferred angular position relative to the stator poles. Thus, the stator field is effective to induce a current in the rotor and produce a resultant relative rotation between the rotor and the stator which can be controlled by non-contact signaling means which activate the switches.

Description:
This application is a continuation-in-part of application Ser. No. 09/248,498, filed Feb. 10, 1999, which in turn is a continuation-in-part of application Ser. No. 08/919,537, filed Aug. 28, 1997, now U.S. Pat. No. 5,936,374, which is in turn a continuation of application Ser. No. 08/535,339, filed Sep. 28, 1995, now U.S. Pat. No. 5,686,805, which is a continuation of application Ser. No. 08/305,575, filed Sep. 14, 1994, now U.S. Pat. No. 5,491,398, which is a continuation of application Ser. No. 08/037,246, filed Mar. 26, 1993, now U.S. Pat. No. 5,424,625. 
     INCORPORATION BY REFERENCE 
     U.S. Pat. No. 5,424,625 and application Ser. No. 09/248,498, filed Feb. 10, 1999, are both incorporated by reference herein, so that background information and structure of brushless as repulsion motors need not be described in detail herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to improvements in electric motors and in particular, to an improved brushless repulsion type motor. Conventional repulsion motors are typically constructed with a single phase stator and a DC rotor having an armature winding connected to a commutator. 
     Diametrically opposed carbon brushes riding on the commutator are shorted together, but are not directly connected to the AC power line. When AC power is applied to the stator winding, currents are induced in the armature to create the rotor field. Important advantages possessed by the repulsion motor are the relatively high value of the starting torque with comparatively low starting current, the ability to sustain high starting torques for long periods of time, such as may exist under conditions of high inertial load, and an adaptability to wide range speed control. 
     The speed torque curve of a repulsion motor is similar to that of universal series motors or series type DC motors. The no-load speed of the repulsion motor can be many times higher than the synchronous speed. A problem with the conventional repulsion motor is that the brushes and commutator wear out quickly due to arcing and heat generated by the brushes in contact with the commutator. As a result, basic repulsion motors are not commonly used today because of the brush wear problem. 
     Other motor types have been designed to minimize these problems. For example, a repulsion start, induction run motor is designed with a squirrel cage rotor embedded in the wound armature. Mechanical means are used to lift the brushes from the commutator when the rotor speed reaches a predetermined value, and the motor then runs as an induction motor. This is done to develop a very high starting torque for the induction motor. 
     Another motor is disclosed in U.S. Pat. No. 5,424,625, incorporated by reference herein. In accordance with that disclosure, electronic switching means is carried on the rotating armature to short individual coils at appropriate times in a cycle of rotation to eliminate the need for brush and commutator elements. Specifically, an electronic switch circuit is provided for replacing the switch and current carrying function of one pair of oppositely disposed commutator segments or bars. Electrical power needed to energize the electronic switching means and any related control circuitry on the armature is produced on the armature by induction from the stator field. The control electronics on the armature include circuitry to sense an enabling signal from stationary signaling means mounted on the stator in order to control the actuation of the electronic switches. Control circuitry is operative when a coil is at a predetermined angular position, relative to the stator. Each switch shorts the ends of an associated coil together. The result of this short is essentially the same as that achieved in the prior art by a pair of opposed shorted brushes. 
     However, the armature and induction field within such motor housing produce heat which is not easily dissipated and the temperature in the motor rises. Such elevated temperature reduces the power capability, reliability, and life of electronic switches and other components. It is also very difficult to replace or repair the electronic components within the motor housing. This involves complete disassembly of the motor, which is both time consuming and expensive. 
     SUMMARY OF THE INVENTION 
     The present invention advantageously provides an improved brushless repulsion motor which provides construction alternatives to the prior art of brushless repulsion motors. In this respect, applicant has placed the electronic switching and control circuitry outside of the motor housing, while maintaining the advantageous utilization of the electronic switches to short individual coils at appropriate times in the cycle of rotation. Therefore, the heat generated by the motor has a much reduced effect on the temperature environment of the electronic parts. In addition, with the placement of the electronic parts exterior to the motor housing, it is much easier to provide maintenance service when required. 
     More particularly in this respect, a repulsion motor is provided comprising a stator and a rotor rotatably mounted on the stator for rotation about an axis. The stator and rotor are contained within a motor housing, the stator having at least one pair of poles, a field winding on the stator for producing a field in the stator, and a plurality of coils on the rotor adapted to electromagnetically interact with the field of the stator winding. In a preferred embodiment, electronic switches are located on an extension of the rotor shaft outside the motor housing and, preferably within a separate housing or enclosure, to selectively short successive ones of the rotor coils when the coils are in a desired angular position relative to the stator poles. Thus, the alternating stator field induces a current in the coils and produces a resultant relative rotation between the rotor and stator. 
     In the preferred embodiment, the signaling means and the controls for operating them are also located outside the motor housing and within the second housing. Each of the electronic switches and control circuitry is wired to a signal receiving means located on the armature outside the motor housing. The signal is then transmitted to the control circuitry, which in turn sends a signal to the electronic switches to short the ends of an associated coil together. 
     The present invention improves brushless repulsion motors significantly. Due to the location of the switches outside the motor housing, the switches are not subject to the same heat to which they are subject inside the motor housing. Placing the electronics outside the motor housing and connecting them to rotor coils inside the motor housing also adds the distinct advantage of easily allowing replacement or repair of the electronic switches and other components as necessary. There is no need to work inside confined, frequently hot spaces of the motor or the necessity to remove the bearing and end bell of the motor to obtain access to the electronic switches. In a preferred embodiment, the entire electronic switch assembly can be connected to the rotor windings by a quick connect plug or other means to allow easy separation for repair or replacement. Finally, heat sinks for the electronic switches are more effective in the cooler environment outside the motor housing. 
     It is thus an outstanding object of the present invention to provide an improved brushless repulsion motor using electronic switching to short individual coils of a repulsion motor. 
     It is yet another object of the present invention to provide an improved brushless repulsion motor in which electronic switches are easier to replace if damaged than heretofore known. 
     Still another object of the present invention is to provide an improved brushless repulsion motor in which the heat generated within the motor housing is diminished as a factor in designing the electronic switching. 
     Yet still another object of the present invention is to provide an improved brushless repulsion motor which is easy to repair and maintain. 
     Still another object of the present invention is to provide an improved brushless repulsion motor in which power transistor switches act as vanes of a fan blade for additional cooling of the motor. 
     These and other objects of the invention will become apparent to those skilled in the art upon reading and understanding the following detailed description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take physical form and certain parts and arrangement of parts, the preferred embodiment of which will be described in detail and illustrated in the accompanying drawings to form a part hereof and wherein: 
     FIG. 1 is a plan view of a brushless repulsion motor, partially in cross-section, of the present invention; 
     FIG. 2 is a schematic illustration showing the arrangement of the present invention; 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG. 1; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 1; 
     FIG. 5 is a diagram, partially in cross-section, of an embodiment of the rotor of the present invention; 
     FIG. 6 is a diagram, partially in cross-section, of another alternative embodiment of the rotor of the present invention; 
     FIG. 7 is a partial cross-sectional view of yet another alternative embodiment of the rotor of the present invention; 
     FIG. 8 is a partial cross-sectional view of a still alternative embodiment of a rotor of the present invention; 
     FIG. 9 is an end view of the rotor of the present invention; 
     FIG. 10 is a plan view of an alternative embodiment brushless repulsion motor, partially in cross-section, of the present invention; and, 
     FIG. 11 is a diagram showing alternative electronic switching for either the present invention, or the embodiment of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, wherein the purpose of illustrating the preferred embodiments of the invention only, and not for the purpose of limiting same, an electric motor  10  constructed in accordance with the invention is illustrated in FIG.  1  and diagrammatically illustrated in FIG.  2 . The motor  10  is a single-phase, two-pole brushless repulsion motor comprising a motor stator  11 , which in turn includes a pair of diametrically opposed magnetic poles  12 . Magnet poles  12  have field windings  13  that are typically connected to a 60 Hz single-phase utility power. Field windings  13  produce a magnetic field that is in a direction indicated by an imaginary line or axis  14  extending from one pole  12  to the other. Stator  11  is constructed in essentially the same manner as a conventional AC brushless repulsion motor. 
     A rotor or armature  17  of motor  10  is constructed in essentially the same manner as a conventional brushless repulsion motor with the inventive modifications discussed below. Rotor  17  is supported for rotation about a central shaft  16  located about a central axis A. Central shaft  16  is supported for rotation about central axis A by axially spaced bearings  15  mounted on opposite ends of rotor  17 . A plurality of axial or longitudinal slots  18  are located on the periphery of rotor  17  and into which are fitted a plurality of generally longitudinal coils  19 . Coils  19  have many turns and slots  18  may receive one or more coils  19 . The ends of coils  19  are terminated or connected to the electronic switches  21  by coil segments  20 . It will be understood that coils  19  can also be terminated in other convenient ways, since the brushless repulsion motor of the present invention eliminates the regular commutating surface of the segments  20 . Motor  10  operates generally like known brushless repulsion motors, except that it includes electronic means on shaft  16  outside a motor housing  30  to short the ends of the rotor winding coils  19 , which eliminates the need for conventional electric commutators and brushes that do the same. 
     Coils segments  20  are typically arranged in diametrically opposed pairs. By way of illustration, but not by way of limitation, there are twelve coil segments illustrated in the embodiment of FIG.  2 . Associated with each pair of coils  20  is an electronic switch circuit  21 , diagrammatically illustrated in FIGS. 1 and 2. Thus, at appropriate times in the rotation of rotor  17 , electronic switches  21  will be individually closed or rendered conductive to short and thus electrically connect their respective coils  19  together. It will be appreciated that as with conventional repulsion motors, torque and rotation are developed between rotor  17  and stator  11  with the field windings  13  energized and appropriate coil segments  20  shorted. 
     Electronic switch circuit  21  comprises a pair of power semiconductors such as MOSFET transistors  22  and a triggering device such as a phototransistor  23 . The output terminals of the power transistors  23  are connected individually to the diametrically opposed coil segments  20  numbered, clockwise  1  and  7 , while their inputs are connected in common. Phototransistor  23  and power transistors  22  are energized by related electronic circuitry comprising a pair of diodes  28 , a capacitor  29 , a resistor  31 , and a zener diode  32 . The inputs of the diodes  28  are connected to segments  20 , numbered  5  and  9 . Since voltages vary between armature windings during rotation of rotor  17 , a voltage (limited by zener diode  32 ) is developed on capacitor  29  sufficient to operate phototransistor  23  and power transistors  22 . When phototransistor  23  is illuminated by a suitable light source  24 , phototransistor  23  switches on and in turn, switches on the power transistors  22 , placing them in a conductive state. 
     Electronic switches  21 , with their associated circuitry, illustrated in FIG. 2, are replicated for each pair of coil segments  20 . For clarity, this replication is not shown. It will be understood that electronic switches  21  are suitably fixed outside motor housing  30  as described hereinafter. 
     With reference to the embodiment of FIGS. 1 and 2, it will be assumed that the angular extent and relationship with reference to the axis of rotation A of coil segments  20  to armature coils  19  is like that of conventional repulsion or universal series motors. Furthermore, phototransistors  23  each have a window or light receptor, that is centered at a bisector of the arc of an associated coil segment  20  and have a field of view, generally coextensive with the arcuate extent of a typical coil segment  20 . Thus, the angular location of each light receiving means for phototransistor  23  is at the same angular center as in associated coil segment  20 . It will be appreciated that other control signal receiving arrangements, including prisms or fiber optics for receiving a control signal from a light source  24  can be used. As shown in this embodiment, light source  24  is duplicated at diametrically opposite points transverse to the axis of rotation of rotor  17 . Also, other non-contact signaling means such as RF transmitter-receivers or electromagnets may be used instead of light. 
     Light sources  24  are arranged in an array on the end bell  90  of motor housing  30 . The position reference markers or light sources  24  are located so that the light signal or radiation emitted from them shines in a beam that radially intersects the path or orbit of the phototransistors  23 . 
     Reference markers  24  comprise known devices such as light emitting diodes (LED) or an incandescent bulb (or array of incandescent bulbs) powered by the AC line, and any necessary power supply. As shown in FIG. 2, a pair of diametrically opposed position reference markers  24  are energized at approximately the 2 o&#39;clock and 8 o&#39;clock positions. With stator windings  13  and reference marker light source  24  energized, the relevant electronic switch  21 , located outside motor housing  30 , will cause its associated coil segment  20  to be shorted. For instance, as shown at the instantaneous point of time in FIG. 2, this is segments numbered  3  and  9 . As rotor  17  rotates clockwise, segments  2  and  8 ,  1  and  7 , etc. will be shorted. This results in the light or reference marker  24  energizing phototransistor  23  to energize the associated power transistors  22 . 
     It will be appreciated that when a pair of segments  20  in an angular position other than a line with a soft neutral axis  36  corresponding to imaginary line  14  and to the 12 o&#39;clock and 6 o&#39;clock locations or aligned with the hard neutral axis  37  corresponding to the 3 o&#39;clock and 9 o&#39;clock locations are shorted and stator windings  13  are energized with an AC voltage, rotor  17  will develop a torque and will rotate. This is illustrated in FIGS. 1 and 2, where reference marker lights  24  are disposed approximately between the 1 o&#39;clock and 5 o&#39;clock positions and 7 o&#39;clock and 11 o&#39;clock positions. At the energized position as shown by the arrows at the 2 o&#39;clock and 8 o&#39;clock positions, torque and rotation of rotor  17  will be induced in a counterclockwise direction. As the light signal associated with one of electronic circuits  21  moves away from the influence of reference marker light  24 , an adjacent electronic circuit moves into such influence and rotor rotation is thereby maintained. It will be appreciated that each separate electronic circuit  21  will be energized for shorting its respective pairs  20  twice each revolution, once at each arrival at the diametrically opposed reference marker light source  24 . From the foregoing, it will be understood that there are six electronic circuits  21  which work in combination with reference marker light sources  24  to perform the segment shorting function previously performed by electric brushes and commutator segments in conventional repulsion motors. 
     Torque and rotation can be changed on motor  10  by energizing a different set of LEDs located in light array  24 . As the angular position of the reference marker lights  24  is moved away from the 2 o&#39;clock and 8 o&#39;clock positions counterclockwise toward soft neutral axis  36 , the torque and speed developed by the motor generally decreases. With light  24  very close to soft neutral axis  36 , torque decreases and is zero when centered at this location. When lights  24  are energized and moved clockwise from the 2 o&#39;clock and 8 o&#39;clock position paths past the hard neutral axis  37  to the 4 o&#39;clock and 10 o&#39;clock positions, the rotor rotates in the opposite direction, i.e. clockwise with the torque and speed increasing with the angular displacement from neutral axis  37 . 
     Applicant has found that in order to improve the reliability and ease of replacing an electronic component, each of electronic switches  21  have been mounted on central shaft  16  outside motor housing  30  on or within control module  41 . A circuit board  42  is mounted to base plate  43  by screws  44 . It will be appreciated that circuit board  42  could be directly mounted to shaft  16 , thus eliminating base plate  43 . A cover housing  45  having a top portion  46  and depending edges  47  extending therefrom can be added, snapping onto the end bell  90  of motor housing  30 . 
     In the preferred embodiment, six separate electronic switches, S 1 -S 6 , each corresponding to electronic switch  21  are located on circuit board  42 . It will be appreciated that, as shown in FIG. 2, switch S 1  is illustrated, while switches S 1 -S 6  are diagrammatically illustrated in FIG.  11 . It will be appreciated that moving switches S 1 -S 6  and all other electronic components outside the motor housing  30  reduces their exposure to heat produced by the motor. Additionally, heat sink  51  for each of switches S 1 -S 6  on circuit board  42  further reduces heat from the switches. 
     A quick connect mechanism  52  is provided between control module  41  and specifically base plate  43 , and central shaft  16  of rotor  17  as shown in FIG.  1 . The quick connect mechanism includes male and female plug in connectors  53   a  and  53   b , respectively, which are secured by a snap ring  54 . It will be appreciated that upon removal of cover housing  45  and snap ring  54 , base plate  43  can be removed from central shaft  16  for repair or replacement of any of electronic switches  21 . 
     This significantly improves motor  10  in that it removes the difficulty of repair or replacement of switches  21  from inside the housing of the equipment. Just as important, repair and replacement are needed less frequently, since switches  21  have been removed from the source of the heat inside motor housing  30 . It will be appreciated that heat isolation of control module  41  can be augmented with insulating material  101  on the motor end plate and/or ventilation vent  102 . 
     FIGS. 5-9 show different approaches which can be used to bring the conductors, i.e. wire  61 , fiber optic  62 , or tape  63 , from inside motor housing  30  to outside bearings  15 . As seen in FIG.  1  and FIG. 5, the end of central shaft  16  is bored out and has a cylindrical conduit  64  therein, extending from an outside end  65  to an interior 90° elbow section  66 . An alternate embodiment is shown in FIG. 6 in which a keyed slot  71  is used to pass wire  61  between the interior of motor housing  30  and the exterior. As shown in FIG. 7, a hole  72  passes through bearing  15  adjacent shaft  16  allowing fiber optic  62 , or alternatively, wire  61  to pass therethrough. As shown in FIG. 8, thin strips of conductive material, commonly conductive tape  63  are placed on shaft  16  between it and bearing  15  allowing conduction between the inside and outside of motor housing  30 . Finally, as shown in FIG. 9, six grooves  71   a - 71   f  are cut within shaft  16 , similar to the single groove in FIG.  6 . In accordance with the embodiment of the present invention, two sets of wire per keyed slot  71   a - 71   f  pass from within motor housing  30  to the exterior of motor housing  30 . Since there are twelve coils, there are six slots  71   a - 71   f.    
     It will be appreciated that the embodiment of FIGS. 1 and 2 may be significantly modified with other control circuitry. For instance, a control system can be utilized whereby the brushless repulsion motor can be directly connected to an AC power source and operated at over a controlled speed range of 0-15,000 rpm. Such a control system  80  is illustrated in FIG.  11 . 
     Therein, it is shown that control system  80  comprises a counter  81  driven by an oscillator  82  having an adjustable output frequency controlled by a rheostat  83 . The output of counter  81  is a succession of switch activating signals T 1 -T 6 , which are provided in sequence by counter  81  at the rate determined by the frequency of oscillator  82 . Thus, the rate of cycling through switch closing signals T 1 -T 6  is a fixed rate determined by the frequency from oscillator  82  as adjusted by rheostat  83 . Switch triggering signals in lines T 1 -T 6  close successive switches that short, sequentially, the circumferentially spaced coils C 1 -C 6 , as shown in FIG.  11 . Previously, such control system  80  was mounted on rotor  17  within housing  30 . The present invention allows that the entire control system  80  can be mounted on or within control module  41 . 
     As disclosed in FIGS. 1 and 2, it will be appreciated that an opening  91  is cut within base plate  43  of control module  41  at a radial point from axis A below the location of each phototransistor  23 . Alternatively, the plate  43  could be made smaller in diameter to permit light transmission. As discussed above, light source  24  is preferably an LED array arranged at a radial distance from axis A equidistant to that radial distance on which opening  91  lies. Indeed, array  24  lies on a concentric circle from axis A at the equidistant radial distance. As control module  41  rotates with rotor  17  on central shaft  16 , light source array  24  actuates each of electronic switches S 1 -S 6 . A controller  103  is wired to each of light sources  24  in order that the actual location of light source  24  can be changed from the shown 2 o&#39;clock and 8 o&#39;clock positions to anywhere between 1 o&#39;clock and 5 o&#39;clock locations and 7 o′ clock to 11 o′ clock locations. The signal is changed simply by deactivating one light on the array  24  and activating a different light on the array in a conventional manner. Light diodes  24  are mounted on end bell  90  by screws  93 . 
     In an alternative embodiment shown in FIGS. 3 and 4, light diode  24 ′ is mounted as a single light diode mounted on an arcuate slide  92  attached to end bell  90 ′ by screws  93 ′ . Within arcuate slide  92  are slots  94  and  95 . In this manner, the location of light diodes  24 ′ can be changed from, as shown, the 2 o&#39;clock and 8 o&#39;clock positions to anywhere along the circumference of the end bell. As described above with respect to FIGS. 1 and 2, the location of light diodes  24 ′ affects the torque and rotation of rotor  17  by energizing each circuit  21  for shorting its respective segment pairs  20 . Thus, the torque, rotation and direction of the motor can be changed by manually moving light diodes  24  on the end bell  90 , by the LED array disclosed in FIGS. 1 and 2, or by some remotely controlled mechanism. In addition to light, other contactless means may be employed to transmit command signals and feedback information to and from the control module. This includes electromagnets and RF transmitter-receivers. 
     Referring now to FIG. 10, the electronic circuitry of FIGS. 1 and 2 is shown therein. 
     However, as shown, coils  19 ′, coil segment  20 ′, and phototransistor  23 ′ remain on rotor  17 . Electronic switches  21 ′ are located within control module  41 ′. It will be appreciated that control module  41 ′ can be smaller than the control module disclosed in FIGS. 1 and 2, since phototransistors  23 ′ remain within motor housing  30 ′. As shown in FIG. 10, light source  24 ′ is a single light-emitting diode (LED). It will be appreciated that an LED array such as disclosed in FIGS. 1 and 2 may also be substituted. The purpose of FIG. 10 is to illustrate an alternative embodiment of the invention only, and not for the purpose of limiting same. 
     The invention has been described with specific reference to the preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they have come within the scope of the invention. 
     The power switching transistors can be mounted on the circuit board  42  (which can be shaped as a control disc), such that they are upright. In this position, the body of each power transistor switch acts as a vane or fin of a fan blade. The power transistors are equally spaced around the control disc, and when the armature rotates, the transistors will, by fan action, remove heat from the power switches, and also blow air out of control module  41  over the motor for cooling purposes. Normally, a totally enclosed motor has an external fan mounted on the rear shaft. The invention allows that the power transistors can provide this function.