Abstract:
A switched reluctance motor (SRM) is disclosed which has a rotor position detecting system with magnetic switches to detect the rotor position and give signals to a logic circuit to trigger electrical phase changes among the coils of the switched reluctance motor.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a switched reluctance motor (SRM), especially related to a switched reluctance motor having a rotor position detecting system which has magnetic switches to detect the rotor position and give signals to a logic circuit to trigger electrical phase changes among the coils of the switched reluctance motor. 
         [0003]    2. Description of Related Art 
         [0004]      FIG. 1  is a prior art 
         [0005]      FIG. 1  shows a switched reluctance motor (SRM) disclosed in the WIPO Patent Application WO/2008/035876.  FIG. 1  is an exploded perspective view of partial structure of the SRM. The stator poles and rotor poles are housed in a housing P 140 . A shaft hole P 146  is configured on the front end of the housing P 140  for the accommodation of a rotary shaft. The rotor poles position detecting unit includes a sensor disk P 151  combined at a pre-set position of the rotary shaft  131  at the outer side of the housing P 140 . Two sensors P 160  are set opposite for interacting with the sensor disk P 151 . The sensor disk P 151  is fixed on the rotary shaft and rotates along with the rotation of the rotary shaft. The sensor disk P 151  includes a blocking portion P 152  and a sensing portion P 154  which have respective different lengths along a radial direction, and a shaft hole P 153  is penetratingly formed at the center thereof, through which the end portion of the rotary shaft is inserted. The opposite sensors P 160  are configured on a sensor support member. A light emitting part P 166  that emits light and a light receiving part P 167  that receives and senses light irradiated from the light emitting part P 166 . The light ray irradiated from the light emitting part P 166  shall be cut into pieces when the sensor disk P 151  rotates along with the rotation of the rotary shaft. Herein, the sensor P 160  is formed as a pair in order to detect the rotational position of the rotor poles according to each electrical phase (A and B) of the stator coil. The rotor position detecting system disclosed in the prior art is a mechanical system with a light ray detection. The deficiency is that the prior art system needs a relative expensive processor to process the signals from the paired sensors P 160  before generating any electrical phase signals for each of the coils. A simpler structure and more accurate rotor poles position detecting system is desired for cost down for a switched reluctance motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a prior art 
           [0007]      FIG. 2  shows a first embodiment according to the present invention. 
           [0008]      FIG. 3  shows an electrical system for the first embodiment. 
           [0009]      FIG. 4  shows the magnetic switch used in the first embodiment. 
           [0010]      FIG. 5  shows a relative position of the switches for the first embodiment. 
           [0011]      FIG. 6  shows a timing diagram for the motor of the first embodiment. 
           [0012]      FIG. 7  shows an exploded view for the motor of the first embodiment. 
           [0013]      FIGS. 8A-8B  shows an elevation view of the switching system for the first embodiment. 
           [0014]      FIGS. 9A-9B  shows a modified switching system for the first embodiment. 
           [0015]      FIG. 10  shows a second embodiment according to the present invention. 
           [0016]      FIG. 11  shows an electrical system for the second embodiment. 
           [0017]      FIG. 12  shows a relative position of the switches for the second embodiment. 
           [0018]      FIG. 13  shows a timing diagram for the motor of the second embodiment. 
           [0019]      FIGS. 14A-14B  shows an elevation view of the switching system for the second embodiment. 
           [0020]      FIGS. 15A-15B  shows a modified switching system for the second embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    The present invention discloses a switched reluctance motor with magnetic switches and a logic circuit to generate electrical phase signals for controlling each of the coils. The present invention uses a relatively simpler logic circuit to generate electrical phase signals for controlling each of the coils instead of using a relatively expensive processor. 
         [0022]      FIG. 2  shows a first embodiment according to the present invention. 
         [0023]      FIG. 2  shows a four-phase 8/6 SRM which has eight stator poles and six rotor poles. There are four sets of coils: coil  1 , coil  2 , coil  3  and, coil  4 . Each of the coils is electrically coupled to a logic circuit  14 . There are six magnets; each is configured in a position corresponding to one of the six rotor poles. A circuit board  16  is configured on an inner surface of a front cover  114  of the motor  1 . Two magnetic switches (or sensors) S 1 , S 2  are configured on the circuit board  16  facing the rotor poles. The switches S 1 , S 2  are electrically coupled to the logic circuit  14 . The sensors S 1 , S 2  used in the first embodiment are uni-pole Hall Effect sensors. 
         [0024]      FIG. 3  shows an electrical system for the first embodiment. 
         [0025]      FIG. 3  shows that a first magnetic switch Si and a second magnetic switch S 2  are electrically coupled to a logic circuit  14  for signal processing and then output four electrical phase signals: phase A, phase B, phase C, and phase D. Each of the electrical phase signals represents the ON/OFF status of one of the coils. 
         [0026]      FIG. 4  shows the magnetic switch used in the first embodiment. 
         [0027]      FIG. 4  shows that each of the magnets  125  rotates along with the rotation of the rotor poles  125 . An ON signal shall be generated when one of the magnets  125  approaches each of the magnetic switches S 1 , S 2 . An OFF signal shall be generated when one of the magnets  125  departs each of the magnetic switches S 1 , S 2 . 
         [0028]      FIG. 5  shows a relative position of the switches for the first embodiment. 
         [0029]      FIG. 5  shows a central angle of  135  degree configured by the two switches Si and S 2  with reference to the center of the rotary shaft  121 . The switches S 1 , S 2  are configured on a surface of a circuit board  16  facing the rotor poles  122 . The circuit board  16  is configured on an inner surface of a front cover  114  of the motor  1  facing the rotor poles  122 . Each of the six magnets  125  is configured in a position corresponding to one of the rotor poles  122 . Each of the magnets  125  rotates along with the rotation of the rotor poles  122 . The magnetic field of each magnet  125  interacts with each of the switches S 1 , S 2  when passing by each of the switches S 1 , S 2 . There are four coils, coil  1 ˜ 4 , each coil winds opposite ones of the eight stator poles  112 . Four electrical phase signals, phase A˜D, are generated from the logic circuit  14  for each of the coils. Each electrical phase represents the ON/OFF status of one of the coils. 
         [0030]      FIG. 5  shows a motor which has eight stator poles  112  and four coils, coil  1 , coil  2 , coil  3 , and coil  4 . Coil  1  winds a first pair of opposite stator poles  112 . Coil  2  winds a second pair of opposite stator poles  112 . Coil  3  winds a third pair of opposite stator poles  112 . Coil  4  winds a fourth pair of opposite stator poles  112 . There are six rotor poles  122  and a rotary shaft  121  surrounded by the stator poles  112 . There are six magnets  125 ; each magnet  125  is configured in a position corresponding to one of the six rotor poles  122 . A circuit board  16  is configured on an inner surface of the front cover  114  facing the rotor poles  122 . 
         [0031]    A first magnetic switch Si is configured on the circuit board  16  at a first position for sensing a first magnetic field of a passing magnet. A second magnetic switch S 2  is configured on the circuit board  16  at a second position for sensing a second magnetic field of a passing magnet. A central angle or mechanical angle of 135 degree is exemplified, by the first magnetic switch Si and the second magnetic switch S 2  with reference to a center of the rotary shaft  121 . According to the first embodiment, the switches Si and S 2  is configured with 90 degree electrical angle difference. Because each 120 degree central angle or mechanical angle is a cycle for each 90 degree electrical angle difference, therefore the central angle or mechanical angle between the two switches S 1 , S 2  can be one selected from a group consisting of 15, 75, 135, 195, 255, and 315 degree for the first embodiment. 
         [0032]    For an ideal operation according to the first embodiment, a 7.5 degree central angle or mechanical angle prior to the sensor S 1 , S 2  is set to trigger the switch ON; and a 7.5 degree central angle or mechanical angle anterior to the switches S 1 , S 2  is set to trigger the switch OFF. A little later trigging ON or a little earlier triggering OFF can be performed but with a less efficiency for a torque output of the motor. 
         [0033]      FIG. 6  shows a timing diagram for the motor of the first embodiment. 
         [0034]      FIG. 6  shows the ON/OFF status of each of the switches S 1 , S 2 , with reference to the electrical phases for each of the coils. A first ON signal is generated when one of the magnets  125  approaches the first switch Si within a predetermined central angle, say, at 0 and 60 degree mechanical angle. A first OFF signal is generated when one of the magnets  125  departs the first switch Si beyond a predetermined central angle, say, at 30 and 9 0  degree mechanical angle. A second ON signal is generated when one of the magnets  125  approaches the second switch S 2  within a predetermined central angle, say, at 45 degree mechanical angle. A second OFF signal is generated when one of the magnets  125  departs the second switch S 2  beyond a predetermined central angle, say, at 75 degree mechanical angle. The bottom line of  FIG. 6  shows the Electrical Angle corresponding to each Mechanical Angle. 
         [0035]    The first ON/OFF signals and the second ON/OFF signals are sent to a logic circuit  14  for further processing. Four electrical phase signals are generated according to a predetermined logic. A first electrical phase signal, phase A, is generated for the first coil, a second electrical phase signal, phase B, is generated for the second coil, a third electrical phase signal, phase C, is generated for the third coil; and a fourth electrical phase signal, phase D, is generated for the fourth coil. 
         [0036]    Referring to  FIG. 6 , the first electrical phase, phase A, turns on for coil  1  when the first ON signal generated by switch S 1 . The second electrical phase, phase B, turns on for coil  2  when the second OFF signal generated by switch S 2 . The third electrical phase, phase C, turns on for coil  3  when the first OFF signal generated by switch S 1 . The fourth electrical phase, phase D, turns on for coil  4  when the second ON signal generated by switch S 1 . 
         [0037]    The first electrical phase, phase A, turns off for coil  1  when the first OFF signal generated by switch S 1 . The second electrical phase, phase B, turns off when the second ON signal generated by switch S 2 . The third electrical phase, phase C, turns off for coil  3  when the first ON signal generated by switch S 1 . The fourth electrical phase, phase D, turns off for coil  4  when the second OFF signal generated by switch S 2 . Each of the magnetic switches S 1 , S 2  used in the first embodiment is a unipolar hall sensors 
         [0038]      FIG. 7  shows an exploded view for the motor of the first embodiment. 
         [0039]      FIG. 7  show that a fixing plate  126  is configured on a front side of the rotor poles  122  and rotates along with the rotor poles  122 . Six magnets  125  are prepared; each of the magnets  125  is configured on a front side of the fixing plate  126  facing the circuit board  16 , and in a position corresponding to one of the rotor poles  122 . A rotary shaft  121  is configured in the center of the rotor poles  122 . A bearing  123  is configured on the end of the rotary shaft  121 . A back cover  124  is configured on a backside of the rotor poles  122 . 
         [0040]      FIGS. 8A-8B  shows an elevation view of the switching system for the first embodiment.  FIG. 8A  shows that the magnets  125  is configured on the front side of the fixing plate  126 .  FIG. 8B  shows that the switches S 1 , S 2  are configured on a surface of a circuit board  16  which is configured on an inner surface of the front cover  114 . 
         [0041]      FIGS. 9A-9B  shows a modified switching system for the first embodiment. 
         [0042]      FIG. 9A  shows that each of the six magnets  125 B is configured on the front side of one of the six rotor poles  122  facing the circuit board  16 .  FIG. 9B  shows that the switches S 1 , S 2  are mounted on a circuit board  16  which is fixed on an inner surface of the front cover  114 . Each of the switches S 1 , S 2  faces the magnets  125 B. Each of the magnets  125 B rotates along with the rotation of the rotor poles  122 . Each of the magnets  125 B interacts with the switches S 1 , S 2  through its magnetic field while passing by the switches S 1 , S 2 . 
         [0043]      FIG. 10  shows a second embodiment according to the present invention. 
         [0044]      FIG. 10  shows a three-phase 12/8 SRM which has twelve stator poles  112  and eight rotor poles  122 . There are three sets of coils: coil  1 ˜ 3 ; each of the coils is electrically coupled to a logic circuit  14 . There are eight magnets  125 C, each is configured in a position corresponding to one of the eight rotor poles facing a circuit board  16 . The circuit board  16  is configured on an inner surface of a front cover  114  of the motor  1 . Three magnetic switches (or sensors) S 1 , S 2 , S 3  are configured on the circuit board  16  facing the rotor poles  122 . The magnetic switches S 1 , S 2 , S 3  are electrically coupled to the logic circuit  14 . 
         [0045]      FIG. 11  shows an electrical system for the second embodiment. 
         [0046]      FIG. 11  shows that a first magnetic switch S 1 , a second magnetic switch S 2 , and a third magnetic switch S 3  are electrically coupled to a logic circuit  14  for signal processing. The logic circuit  14  outputs three electrical phase signals, phase A˜C, according to a predetermined logic, each of the electrical phase signals represents the ON/OFF status of one of the coils. 
         [0047]      FIG. 12  shows a relative position of the switches for the second embodiment. 
         [0048]      FIG. 12  shows that the SRM has twelve stator poles  112 . There are three coils, each coil winds opposite ones of the stator poles  112 . There are eight rotor poles  122  and a rotary shaft  121 .  FIG. 12  shows that a central angle of 30 degree is configured between switches S 1  and S 2 , and between switches S 2  and S 3 , with reference to the center of the rotary shaft  121 . Each of the switches S 1 , S 2 , S 3  is aligned with a central axis of one of the stator poles  112 . There are three coils, each coil winds opposite ones of the twelve stator poles  112 . Three electrical phase signals are generated from the logic circuit  14  according to a predetermined logic. Each electrical phase represents the ON/OFF status of one of the coils. 
         [0049]      FIG. 13  shows a timing diagram for the motor of the second embodiment. 
         [0050]      FIG. 13  shows the ON/OFF status of each of the switches S 1 , S 2 , S 3  with reference to the electrical phases for each of the coils. A first ON signal is generated when one of the magnets  125 C approaches the first switch S 1  within a predetermined central angle, say, at 15 and 60 degree mechanical angle. A second ON signal is generated when one of the magnets  125 C approaches the second switch S 2  within a predetermined central angle, say, at 0, 45, and 9 0  degree mechanical angle. A third ON signal is generated when one of the magnets  125 C approaches the third switch S 3  within a predetermined central angle, say, at 30 and 75 degree mechanical angle. The bottom line of  FIG. 13  shows the Electrical Angle corresponding to each Mechanical Angle. 
         [0051]    The first ON signals, the second ON signals, and the third ON signals are sent to a logic circuit  14  for further processing. Three electrical phase signals are generated according to a predetermined logic. A first electrical phase signal, phase A, is generated for the first coil, a second electrical phase signal, phase B, is generated for the second coil, and a third electrical phase signal, phase C, is generated for the third coil. The first electrical phase, phase A, turns on when the first ON signal is generated by the first switch S 1 . The second electrical phase, phase B, turns on when the second ON signal is generated by the second switch S 2 . The third electrical phase, phase C, turns on when the third ON signal is generated by the third switch S 3 . The first electrical phase turns off when the third ON signal is generated by the third switch S 3 . The second electrical phase turns off when the first ON signal is generated by the first switch S 1 . The third electrical phase turns off when the second ON signal is generated by the second switch S 2 . 
         [0052]      FIGS. 14A-14B  shows an elevation view of the switching system for the second embodiment. 
         [0053]      FIG. 14A  shows that there are eight magnets  125 C, each configured in a position corresponding to one of the eight rotor poles  122 .  FIG. 14A  shows that a fixing plate  126  is configured on the front side of the rotor poles  122 . Each of the magnets  125 C is configured on a front side of the fixing plate  126  facing the circuit board  16  and in a position corresponding to one of the rotor poles  122 . 
         [0054]      FIG. 14B  shows that three switches S 1 , S 2 , S 3  configured on a surface of the circuit board  16  facing the rotor poles  122 . A first magnetic switch S 1  is configured on the circuit board  16  at a first position for sensing a first magnetic field of a passing magnet  125 C. A second magnetic switch S 2  is configured on the circuit board  16  at a second position for sensing a second magnetic field of a passing magnet  125 C. A third magnetic switch S 3  is configured on the circuit board  16  at a third position for sensing a third magnetic field of a passing magnet  15 C. Each of the magnetic switches S 1 , S 2 , and S 3  used in the second embodiment is a unipolar hall sensor.  FIG. 14B  shows that a first central angle formed by the first magnetic switch Si and the second magnetic switch S 2  with reference to the center of the rotary shaft  121  is 30 degree. A second central angle formed by the second magnetic switch S 2  and the third magnetic switch S 3  with reference to the center of the rotary shaft  121  is also 30 degree. 
         [0055]      FIGS. 15A-15B  shows a modified switching system for the second embodiment. 
         [0056]      FIG. 15A  shows that each of the eight magnets  125 D is configured on the front side of one of the eight rotor poles  122  facing the circuit board  16 .  FIG. 15B  shows that the switches S 1 , S 2 , S 3  are mounted on a circuit board  16  which is fixed on an inner surface of the front cover  114 . Each of the switches S 1 , S 2 , S 3  faces the magnets  125 D. Each of the magnets  125 D rotates along with the rotation of the rotor poles  122 . Each of the magnets  125 D interacts with the switches S 1 , S 2 , S 3  through its magnetic field while passing by the switches S 1 , S 2 , S 3 . 
         [0057]    For an ideal operation according to the second embodiment is that the ON signal is triggered at a position no larger than 3.75 degree central angle or mechanical angle anterior to each of the magnetic switches S 1 , S 2 , S 3 . A little later trigging ON can also be performed but with a less efficiency for a torque output of the motor. 
         [0058]    While several embodiments have been described by way of example, it will be apparent to those skilled in the art that various modifications may be configured without departs from the spirit of the present invention. Such modifications are all within the scope of the present invention, as defined by the appended claims.