Patent Publication Number: US-2011057535-A1

Title: Reverse electromotive force generating motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part application of the prior application Ser. No. 12/556,129 filed Sep. 9, 2009, pending. This application claims priority of Japanese patent application No. 2009-204311, filed on Sep. 4, 2009, the entire content of which is incorporated herein by the reference. 
    
    
     BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The present invention relates to a reverse electromotive force generating motor having both a function of a power motor and a function of an electric generator. 
     When one of a three-phase alternate current changes a polarity and a voltage thereof, the voltage becomes zero at one point. A reverse electromotive force is generated when the voltage becomes zero. When the reverse electromotive force is supplied from, for example, a motor to an inverter due to a short-circuit fault of the inverter, a cable connecting the motor and the inverter may be damaged. 
     Patent Reference has disclosed a motor having a short circuit fault detecting circuit in order to prevent the problem described above. 
     Patent Reference: Japanese Patent Publication No. 2007-181345 
     In the motor disclosed in Japanese Patent Application, the short circuit fault detecting circuit has to be provided in the motor. Consequently, a more complicated process is required for manufacturing the motor, thereby increasing manufacturing cost thereof. 
     In view of the problems described above, an object of the present invention is to provide a reverse electromotive force generating motor (a motor) with a rotor functioning as both a motor and an electric generator. The motor changes a direction of a reverse electromotive force generated at a fixed coil thereof before the reverse electromotive force reaches an inverter, thereby resolving the problems described above. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to attain the objects described above, according to the present invention, a reverse electromotive force generating motor includes a stator yoke; a rotor disposed in the stator yoke; a first coil disposed in the stator yoke and connected to a first input line of a power source with a first phase; a second coil disposed in the stator yoke and connected to the first coil in series, the second coil being connected to a neutral point; a third coil disposed in the stator yoke and connected to the first input line; a fourth coil disposed in the stator yoke and connected to the third coil in series, the fourth coil being connected to a first output line for outputting power; and a rotational shaft disposed in the rotor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view showing a reverse electromotive force generating motor according to a first embodiment of the present invention; 
         FIG. 2  is a sectional view showing a stator yoke of the reverse electromotive force generating motor according to the first embodiment of the present invention; 
         FIG. 3  is a circuit diagram of the reverse electromotive force generating motor according to the first embodiment of the present invention; 
         FIG. 4  is a circuit diagram of a reverse electromotive force generating motor according to a second embodiment of the present invention. 
         FIG. 5  is a sectional view showing a stator yoke of a reverse electromotive force generating motor according to a third embodiment of the present invention; 
         FIG. 6  is a sectional view showing a reverse electromotive force generating motor according to a fourth embodiment of the present invention; 
         FIG. 7  is a sectional view showing a stator yoke of the reverse electromotive force generating motor according to the fourth embodiment of the present invention; 
         FIG. 8  is a circuit diagram of the reverse electromotive force generating motor according to the fourth embodiment of the present invention; 
         FIG. 9  is a sectional view showing a stator yoke of a reverse electromotive force generating motor according to a fifth embodiment of the present invention; and 
         FIG. 10  is a circuit diagram of the reverse electromotive force generating motor according to the fifth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereunder, embodiments of the present invention will be explained with reference to the accompanying drawing. 
     First Embodiment 
     A first embodiment of the present invention will be explained.  FIG. 1  is a sectional view showing a reverse electromotive force generating motor according to the first embodiment of the present invention. 
     As shown in  FIG. 1 , the reverse electromotive force generating motor includes a stator yoke  30 ; a rotor  40  disposed in the stator yoke  30 ; and a rotational shaft  50  disposed in the rotor  40 . 
     As shown in  FIG. 1 , the stator yoke  30  has a plurality of slots  1  to  24  (twenty four slots in the embodiment) as hollow portions. A plurality of coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  (described later) is arranged in the slots  1  to  24  for generating an electromotive force around the stator yoke  30 , so that the rotor  40  is attracted and rotates around the rotational shaft  50 . 
       FIG. 2  is a sectional view showing the stator yoke  30  of the reverse electromotive force generating motor according to the embodiment of the present invention. The stator yoke  30  is a four-pole type, and an arrangement of the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  will be explained below. 
     As shown in  FIG. 2 , the stator yoke  30  is a four-pole type, and has twenty four slots for winding the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403 . Alternatively, the stator yoke  30  may have forty eight slots. When a stator yoke is a six-pole type, the stator yoke may have thirty six slots or seventy two slots. 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are arranged in the slots  1  to  24  as follows. The coil  101  is disposed in the slots  1  and  6 , and is connected to an input line of a first phase. The coil  301  is disposed in the slots  13  and  18 , and is connected to the coil  101  in the input line of the first phase. The coil  201  is disposed in the slots  7  and  12 , and is connected to an output line of the first phase. The coil  401  is disposed in the slots  19  and  24 , and is connected to the coil  201  in the output line of the first phase. 
     In the embodiment, the coil  102  is disposed in the slots  5  and  10 , and is connected to an input line of a second phase. The coil  302  is disposed in the slots  17  and  22 , and is connected to the coil  102  in the input line of the second phase. The coil  202  is disposed in the slots  11  and  16 , and is connected to an output line of the second phase. The coil  402  is disposed in the slots  23  and  4 , and is connected to the coil  202  in the output line of the second phase. 
     In the embodiment, the coil  103  is disposed in the slots  9  and  14 , and is connected to an input line of a third phase. The coil  303  is disposed in the slots  21  and  2 , and is connected to the coil  103  in the input line of the third phase. The coil  203  is disposed in the slots  15  and  20 , and is connected to an output line of the third phase. The coil  403  is disposed in the slots  3  and  8 , and is connected to the coil  203  in the output line of the third phase. 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are connected as follows.  FIG. 3  is a circuit diagram of the reverse electromotive force generating motor according to the embodiment of the present invention. 
     As shown in  FIG. 3 , a power source has three input lines of three phases. The input line of the first phase is connected to the coil  101  at a connection point A, and the coil  101  is connected to the coil  301  in series. The input line of the second phase is connected to the coil  102  at a connection point B, and the coil  102  is connected to the coil  302  in series. The input line of the third phase is connected to the coil  103  at a connection point C, and the coil  103  is connected to the coil  303  in series. The coils  301 ,  302 , and  303  are connected at a neutral point D. 
     Further, in the embodiment, three output lines are connected to the connection points A to C. The output line of the first phase is connected to the coil  201  at the connection point A, and the coil  201  is connected to the coil  401  in series. The output line of the second phase is connected to the coil  202  at the connection point B, and the coil  202  is connected to the coil  402  in series. The output line of the third phase is connected to the coil  203  at the connection point C, and the coil  203  is connected to the coil  403  in series. 
     Further, in the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are wound in a specific direction. More specifically, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are wound in a same direction (e.g., a right direction) with respect to a radial line of the stator yoke  30 . 
     An operation of the reverse electromotive force generating motor will be explained. In the following description, the first phase line of the reverse electromotive force generating motor of the four-pole type will be explained as an example. The second and the third phase lines rotate and generate electric power in the same way. 
     The reverse electromotive force generating motor rotates with a three-phase alternate current of 200 V. A magnetic field is generated at the coils  101 ,  201 ,  301 , and  401  in the first phase line. When the rotor  40  includes an iron core and permanent magnets embedded in the iron core, the magnetic field thus generated attracts the permanent magnets, thereby rotating the rotor  40 . Alternatively, the rotor  40  may be formed of an electric magnet. 
     More specifically, the coil  101  and the coil  301  in the first phase line generate the magnetic field of an S pole in the stator yoke  30 , and the coil  201  and the coil  401  in the first phase line generate the magnetic field of an N pole in the stator yoke  30 . 
     When a voltage applied to the coil  101  and the coil  301  in the first phase line becomes zero, the coil  102  and the coli  302  in the second phase line generate the magnetic field of the S pole. Further, the coil  202  and the coli  402  in the second phase line generate the magnetic field of the N pole. Accordingly, the permanent magnets of the rotor  40  are attracted to the magnetic field, thereby rotating the rotor  40 . 
     When the rotor  40  rotates as described above, a magnetic flux of the N pole traverses the coil  101  and the coil  301 , thereby generating the reverse electromotive force. At the same time, a magnetic flux of the S pole traverses the coil  201  and the coil  401 , thereby generating the electromotive force. At this moment, a reverse electromotive current flows toward the input line, and an electromotive current flows toward the output line. 
     In the embodiment, the coil  101  and the coil  201  are connected to the connection point A. Accordingly, the reverse electromotive current eventually flows toward the output line as an alternate current reverse current. As a result, it is possible to generate alternate current power. 
     Second Embodiment 
     A second embodiment of the present invention will be explained next. In the second embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are arranged in the slots  1  to  24  of the stator yoke  30  in the same way as that in the first embodiment. 
       FIG. 4  is a circuit diagram of a reverse electromotive force generating motor according to the second embodiment of the present invention. 
     As shown in  FIG. 4 , a power source has three input lines of three phases. The input line of the first phase is connected to the coil  101  at a connection point A, and the coil  101  is connected to the coil  301  in series. The input line of the second phase is connected to the coil  102  at a connection point B, and the coil  102  is connected to the coil  302  in series. The input line of the third phase is connected to the coil  103  at a connection point C, and the coil  103  is connected to the coil  303  in series. 
     In the embodiment, the coil  301  is connected to the coil  102  at a neutral point D. Similarly, the coil  302  is connected to the coil  103  at a neutral point D, and the coil  303  is connected to the coil  101  at a neutral point D. In other words, in the embodiment, there are three neutral points D. 
     Further, in the embodiment, three output lines are connected to the connection points A to C. The output line of the first phase is connected to the coil  201  at the connection point A, and the coil  201  is connected to the coil  401  in series. The output line of the second phase is connected to the coil  202  at the connection point B, and the coil  202  is connected to the coil  402  in series. The output line of the third phase is connected to the coil  203  at the connection point C, and the coil  203  is connected to the coil  403  in series. 
     Further, in the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are wound in a specific direction. More specifically, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are wound in a same direction (e.g., a right direction) with respect to a radial line of the stator yoke  30 . 
     An operation of the reverse electromotive force generating motor in the second embodiment is similar to that in the first embodiment, and a detailed explanation thereof is omitted. 
     Third Embodiment 
     A third embodiment of the present invention will be explained next. In the third embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are arranged in the slots  1  to  24  of the stator yoke  30  in a way different from that in the first embodiment. Further, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are connected in a similar way to that in the first embodiment (refer to  FIG. 3 ). 
       FIG. 5  is a sectional view showing the stator yoke  30  of the reverse electromotive force generating motor according to the third embodiment of the present invention. 
     As shown in  FIG. 5 , the coil  101  is disposed in the slots  1  and  6 , and is connected to the input line of the first phase as shown in  FIG. 3 . The coil  301  is disposed in the slots  13  and  18 , and is connected to the coil  101  in the input line of the first phase. The coil  201  is disposed in the slots  7  and  12 , and is connected to the output line of the first phase. The coil  401  is disposed in the slots  19  and  24 , and is connected to the coil  201  in the output line of the first phase. 
     In the embodiment, the coil  102  is disposed in the slots  3  and  8 , and is connected to the input line of the second phase as shown in  FIG. 3 . The coil  302  is disposed in the slots  15  and  20 , and is connected to the coil  102  in the input line of the second phase. The coil  202  is disposed in the slots  9  and  14 , and is connected to the output line of the second phase. The coil  402  is disposed in the slots  21  and  2 , and is connected to the coil  202  in the output line of the second phase. 
     In the embodiment, the coil  103  is disposed in the slots  5  and  10 , and is connected to the input line of the third phase as shown in  FIG. 3 . The coil  303  is disposed in the slots  17  and  22 , and is connected to the coil  103  in the input line of the third phase. The coil  203  is disposed in the slots  11  and  16 , and is connected to the output line of the third phase. The coil  403  is disposed in the slots  23  and  4 , and is connected to the coil  203  in the output line of the third phase. 
     Further, in the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 , and  401  to  403  are wound in a specific direction. More specifically, the coils  101 ,  201 ,  301 , and  401  are wound in a first direction with respect to a radial line of the stator yoke  30 . Further, the coils  102 ,  202 ,  302 , and  402  are wound in a second direction with respect to the radial line of the stator yoke  30 , and the second direction is opposite to the first direction. Further, the coils  103 ,  203 ,  303 , and  403  are wound in the first direction with respect to the radial line of the stator yoke  30 . 
     With the configuration described above, it is possible to obtain a strong initial torque. 
     Fourth Embodiment 
     A fourth embodiment of the present invention will be explained next.  FIG. 6  is a sectional view showing a reverse electromotive force generating motor according to the fourth embodiment of the present invention. 
     As shown in  FIG. 6 , the reverse electromotive force generating motor includes the stator yoke  30 ; the rotor  40  disposed in the stator yoke  30 ; and the rotational shaft  50  disposed in the rotor  40 . In the embodiment, the stator yoke  30  is a six-pole type. When the stator yoke  30  is the six-pole type, the stator yoke  30  may have thirty six slots or seventy two slots. 
     As shown in  FIG. 6 , the stator yoke  30  has a plurality of slots  1  to  36  (thirty six slots in the embodiment) as hollow portions. A plurality of coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  (described later) is arranged in the slots  1  to  36  for generating an electromotive force around the stator yoke  30 , so that the rotor  40  is attracted and rotates around the rotational shaft  50 . 
       FIG. 7  is a sectional view showing the stator yoke  30  of the reverse electromotive force generating motor according to the fourth embodiment of the present invention. The stator yoke  30  is a six-pole type, and an arrangement of the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  will be explained below. 
     As shown in  FIG. 7 , the stator yoke  30  is a six-pole type, and has thirty six slots for winding the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603 . 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are arranged in the slots  1  to  36  as follows. The coil  101  is disposed in the slots  1  and  6 , and is connected to an input line of a first phase. The coil  501  is disposed in the slots  25  and  30 , and is connected to the coil  101  in the input line of the first phase. The coil  301  is disposed in the slots  13  and  18 , and is connected to the coil  501  in the input line of the first phase. The coil  201  is disposed in the slots  7  and  12 , and is connected to an output line of the first phase. The coil  601  is disposed in the slots  31  and  36 , and is connected to the coil  201  in the output line of the first phase. The coil  401  is disposed in the slots  19  and  24 , and is connected to the coil  601  in the output line of the first phase. 
     In the embodiment, the coil  102  is disposed in the slots  3  and  8 , and is connected to an input line of a second phase. The coil  302  is disposed in the slots  15  and  20 , and is connected to the coil  102  in the input line of the second phase. The coil  502  is disposed in the slots  27  and  32 , and is connected to the coil  302  in the input line of the second phase. The coil  202  is disposed in the slots  9  and  14 , and is connected to an output line of the second phase. The coil  402  is disposed in the slots  21  and  26 , and is connected to the coil  202  in the output line of the second phase. The coil  602  is disposed in the slots  33  and  24 , and is connected to the coil  402  in the output line of the second phase. 
     In the embodiment, the coil  103  is disposed in the slots  5  and  10 , and is connected to an input line of a third phase. The coil  503  is disposed in the slots  29  and  34 , and is connected to the coil  103  in the input line of the third phase. The coil  303  is disposed in the slots  17  and  22 , and is connected to the coil  503  in the input line of the third phase. The coil  203  is disposed in the slots  11  and  16 , and is connected to an output line of the third phase. The coil  603  is disposed in the slots  35  and  4 , and is connected to the coil  203  in the output line of the third phase. The coil  403  is disposed in the slots  23  and  28 , and is connected to the coil  603  in the output line of the third phase. 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are connected as follows.  FIG. 8  is a circuit diagram of a reverse electromotive force generating motor according to the fourth embodiment of the present invention. 
     As shown in  FIG. 8 , a power source has three input lines of three phases. The input line of the first phase is connected to the coil  101  at a connection point A, and the coil  101  is connected to the coils  501  and  301  in series. The input line of the second phase is connected to the coil  102  at a connection point B, and the coil  102  is connected to the coils  302  and  502  in series. The input line of the third phase is connected to the coil  103  at a connection point C, and the coil  103  is connected to the coils  503  and  303  in series. 
     In the embodiment, the coil  301  is connected to the coil  102  at a neutral point D. Similarly, the coil  502  is connected to the coil  103  at a neutral point D, and the coil  303  is connected to the coil  101  at a neutral point D. In other words, in the embodiment, there are three neutral points D. 
     Further, in the embodiment, three output lines are connected to the connection points A to C. The output line of the first phase is connected to the coil  201  at the connection point A, and the coil  201  is connected to the coils  601  and  401  in series. The output line of the second phase is connected to the coil  202  at the connection point B, and the coil  202  is connected to the coils  402  and  602  in series. The output line of the third phase is connected to the coil  203  at the connection point C, and the coil  203  is connected to the coils  603  and  403  in series. 
     Further, in the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are wound in a specific direction. More specifically, the coils  101 ,  201 ,  301 ,  401 ,  501 , and  601  are wound in a first direction with respect to a radial line of the stator yoke  30 . Further, the coils  102 ,  202 ,  302 ,  402 ,  502 , and  602  are wound in a second direction with respect to the radial line of the stator yoke  30 , and the second direction is opposite to the first direction. Further, the coils  103 ,  203 ,  303 ,  403 ,  503 , and  603  are wound in the first direction with respect to the radial line of the stator yoke  30 . 
     With the configuration described above, it is possible to obtain a strong initial torque. 
     Fifth Embodiment 
     A fifth embodiment of the present invention will be explained next. In the fifth embodiment, the reverse electromotive force generating motor includes the stator yoke  30 ; the rotor  40  disposed in the stator yoke  30 ; and the rotational shaft  50  disposed in the rotor  40  as shown in  FIG. 6 . 
       FIG. 9  is a sectional view showing the stator yoke  30  of the reverse electromotive force generating motor according to the fifth embodiment of the present invention. The stator yoke  30  is a six-pole type, and an arrangement of the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  will be explained below. 
     As shown in  FIG. 9 , the stator yoke  30  is a six-pole type, and has thirty six slots for winding the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603 . 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are arranged in the slots  1  to  36  as follows. The coil  101  is disposed in the slots  1  and  6 , and is connected to an input line of a first phase. The coil  501  is disposed in the slots  25  and  30 , and is connected to the coil  101  in the input line of the first phase. The coil  301  is disposed in the slots  13  and  18 , and is connected to the coil  501  in the input line of the first phase. The coil  201  is disposed in the slots  7  and  12 , and is connected to an output line of the first phase. The coil  601  is disposed in the slots  31  and  36 , and is connected to the coil  201  in the output line of the first phase. The coil  401  is disposed in the slots  19  and  24 , and is connected to the coil  601  in the output line of the first phase. 
     In the embodiment, the coil  102  is disposed in the slots  5  and  10 , and is connected to an input line of a second phase. The coil  502  is disposed in the slots  29  and  34 , and is connected to the coil  102  in the input line of the second phase. The coil  302  is disposed in the slots  17  and  22 , and is connected to the coil  502  in the input line of the second phase. The coil  202  is disposed in the slots  11  and  16 , and is connected to an output line of the second phase. The coil  602  is disposed in the slots  4  and  35 , and is connected to the coil  202  in the output line of the second phase. The coil  402  is disposed in the slots  23  and  28 , and is connected to the coil  602  in the output line of the second phase. 
     In the embodiment, the coil  103  is disposed in the slots  9  and  14 , and is connected to an input line of a third phase. The coil  503  is disposed in the slots  2  and  33 , and is connected to the coil  103  in the input line of the third phase. The coil  303  is disposed in the slots  21  and  26 , and is connected to the coil  503  in the input line of the third phase. The coil  203  is disposed in the slots  15  and  20 , and is connected to an output line of the third phase. The coil  603  is disposed in the slots  3  and  8 , and is connected to the coil  203  in the output line of the third phase. The coil  403  is disposed in the slots  32  and  27 , and is connected to the coil  603  in the output line of the third phase. 
     In the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are connected as follows.  FIG. 10  is a circuit diagram of a reverse electromotive force generating motor according to the fifth embodiment of the present invention. 
     As shown in  FIG. 8 , a power source has three input lines of three phases. The input line of the first phase is connected to the coil  101  at a connection point A, and the coil  101  is connected to the coils  501  and  301  in series. The input line of the second phase is connected to the coil  102  at a connection point B, and the coil  102  is connected to the coils  502  and  302  in series. The input line of the third phase is connected to the coil  103  at a connection point C, and the coil  103  is connected to the coils  503  and  303  in series. 
     In the embodiment, the coil  301  is connected to the coil  102  at a neutral point D. Similarly, the coil  302  is connected to the coil  103  at a neutral point D, and the coil  303  is connected to the coil  101  at a neutral point D. In other words, in the embodiment, there are three neutral points D. 
     Further, in the embodiment, three output lines are connected to the connection points A to C. The output line of the first phase is connected to the coil  201  at the connection point A, and the coil  201  is connected to the coils  601  and  401  in series. The output line of the second phase is connected to the coil  202  at the connection point B, and the coil  202  is connected to the coils  602  and  402  in series. The output line of the third phase is connected to the coil  203  at the connection point C, and the coil  203  is connected to the coils  603  and  403  in series. 
     Further, in the embodiment, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are wound in a specific direction. More specifically, the coils  101  to  103 ,  201  to  203 ,  301  to  303 ,  401  to  403 ,  501  to  503 , and  601  to  603  are wound in a same direction (e.g., a right direction) with respect to a radial line of the stator yoke  30 . 
     With the configuration described above, it is possible to obtain a strong initial torque. 
     The disclosure of Japanese Patent Application No. 2009-204311, filed on Sep. 4, 2009 is incorporated in the application by reference. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.