Patent Publication Number: US-2022224172-A1

Title: Redundancy resolver device and electric power steering device

Description:
TECHNICAL FIELD 
     This invention relates to a redundancy resolver device in which a stator core is provided with winding groups of a plurality of systems, and an electric power steering device including the redundancy resolver device. 
     BACKGROUND ART 
     In a related-art resolver, in order to suppress degradation in angle detection accuracy caused by magnetic interference, two sensor units are stacked in two stages in an axis line direction. Further, one sensor unit has only first output windings wound therearound, and the other sensor unit has only second output windings wound therearound (see, for example, Patent Literatures 1 and 2). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP 2009-222435 A 
     [PTL 2] JP 2009-222436 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the related-art resolver as described above, with the two sensor units being stacked in two stages in the axis line direction, a dimension in the axis line direction is increased twice that of a resolver of one system. Further, magnetic interference occurs between adjacent teeth to reduce angle detection accuracy. 
     This invention has been made to solve the above-mentioned problems, and therefore has an object to obtain a redundancy resolver device capable of suppressing an increase in dimension in an axis line direction of a resolver main body caused by redundancy, and a reduction in angle detection accuracy, and an electric power steering device including the redundancy resolver device. 
     Solution to Problem 
     According to one embodiment of this invention, there is provided a redundancy resolver device including: a resolver main body including a stator, and a rotor rotatable with respect to the stator; and a control unit including a plurality of excitation circuits, the stator including a stator core, and winding groups of a plurality of systems provided in the stator core, the stator core including a core back portion, and a plurality of teeth which protrude from the core back portion, the winding groups of different systems being arranged at different positions in a circumferential direction of the stator core, the winding groups of each of the plurality of systems including: an excitation winding group consisting of a plurality of excitation windings, and being connected to corresponding one of the plurality of excitation circuits; a first output winding group consisting of a plurality of first output windings; and a second output winding group consisting of a plurality of second output windings, each of the plurality of teeth having corresponding one of the plurality of excitation windings wound therearound, when two of the plurality of excitation windings belonging to different systems and being arranged side by side in the circumferential direction of the stator core are defined as a first end excitation winding and a second end excitation winding, respectively, the first end excitation winding and the second end excitation winding being applied with excitation signals to generate magnetic fluxes in the same direction of radial directions of the stator core. 
     Advantageous Effects of Invention 
     According to this invention, an increase in dimension in the axis line direction of the resolver main body caused by redundancy, and a reduction in angle detection accuracy can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram for illustrating a state in which a redundancy resolver device according to a first embodiment of this invention is attached to a rotating electric machine. 
         FIG. 2  is a sectional view of a resolver main body of  FIG. 1 . 
         FIG. 3  is a sectional view for illustrating a stator of  FIG. 2 . 
         FIG. 4  is a block diagram for illustrating a winding portion and a control unit of  FIG. 1 . 
         FIG. 5  is an explanatory graph for showing a number-of-turns distribution of first excitation windings and second excitation windings of  FIG. 3 . 
         FIG. 6  is an enlarged sectional view for illustrating a main part of  FIG. 3 . 
         FIG. 7  is an explanatory graph for showing a number-of-turns distribution of s excitation windings and second excitation windings of a redundancy resolver device according to a second embodiment of this invention. 
         FIG. 8  is an explanatory graph for showing a number-of-turns distribution of first excitation windings and second excitation windings of a redundancy resolver device according to a third embodiment of this invention. 
         FIG. 9  is a block diagram for illustrating a winding portion and a control unit of the redundancy resolver device according to the third embodiment. 
         FIG. 10  is an explanatory graph for showing a modification example of the number-of-turns distribution of  FIG. 8 . 
         FIG. 11  is a sectional view for illustrating a stator of a redundancy resolver device according to a fourth embodiment of this invention. 
         FIG. 12  is a block diagram for illustrating a winding portion and a control unit of the redundancy resolver device according to the fourth embodiment. 
         FIG. 13  is an explanatory graph for showing a number-of-turns distribution of first excitation windings, second excitation windings, and third excitation windings of the redundancy resolver device according to the fourth embodiment. 
         FIG. 14  is a sectional view for illustrating a stator of a redundancy resolver device according to a fifth embodiment of this invention. 
         FIG. 15  is a plan view for illustrating a divided core of  FIG. 14 . 
         FIG. 16  is a sectional view for illustrating a stator of a redundancy resolver device according to a sixth embodiment of this invention. 
         FIG. 17  is a plan view for illustrating a divided core of  FIG. 16 . 
         FIG. 18  is an explanatory view for illustrating a method of die-cutting a core piece forming a stator core in the first embodiment to the fourth embodiment from a core sheet. 
         FIG. 19  is an explanatory view for illustrating a method of die-cutting core pieces forming the divided cores in the sixth embodiment from a core sheet. 
         FIG. 20  is a sectional view for illustrating a stator core of a redundancy resolver device according to a seventh embodiment of this invention. 
         FIG. 21  is a sectional view for illustrating a state in which the stator core of  FIG. 20  is developed in straight line. 
         FIG. 22  is a side view for illustrating an example of an electric power steering device to which a redundancy resolver device of this invention is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Now, embodiments of this invention are described with reference to the drawings. 
     First Embodiment 
       FIG. 1  is a configuration diagram for illustrating a state in which a redundancy resolver device according to a first embodiment of this invention is attached to a rotating electric machine. In  FIG. 1 , a rotating electric machine  1  includes a rotating electric machine main body  2  and a rotating shaft  3 . The rotating shaft  3  is rotatable with respect to the rotating electric machine main body  2 . An end portion of the rotating shaft  3  protrudes from the rotating electric machine main body  2 . 
     A redundancy resolver device  4  includes a resolver main body  5  and a control unit  6 . The resolver main body  5  includes a rotor  7  and a stator  8 . The rotor  7  is mechanically connected to the end portion of the rotating shaft  3  to rotate integrally with the rotating shaft  3 . Further, the rotor  7  penetrates through the stator  8 , and is rotatable with respect to the stator  8 . 
     The stator  8  surrounds the rotor  7 . Further, the stator  8  includes a stator core  9  and a winding portion  10 . The winding portion  10  is provided in the stator core  9 . 
     The redundancy resolver device  4  is configured to detect a rotation angle of the rotating shaft  3  with the use of a change in permeance in a gap between the rotor  7  and the stator  8 . In other words, the redundancy resolver device  4  functions as a rotation angle detection device configured to detect the rotation angle of the rotating shaft  3 . 
       FIG. 2  is a sectional view of the resolver main body  5  of  FIG. 1 , and shows a section perpendicular to an axis line direction of the rotor  7 . The axis line direction is a direction parallel to a center of rotation of the rotor  7 . Further, radial directions are directions orthogonal to the center of rotation of the rotor  7 . Still further, a circumferential direction is a direction in which the rotor  7  rotates about the center of rotation. 
     When Nx is a natural number, the rotor  7  has Nx salient poles  7   a.  In other words, the rotor  7  has a shaft angle multiplier of Nx. The number Nx of salient poles  7   a  in the first embodiment is 5. 
     The stator core  9  includes a core back portion  9   a  having an annular shape, and a plurality of teeth  9   b  protruding inward in the radial directions from the core back portion  9   a.    
       FIG. 3  is a sectional view for illustrating the stator  8  of  FIG. 2 . The number Ns of teeth  9   b  in the first embodiment is 12. When the twelve teeth  9   b  are denoted clockwise as T 1  to T 12 , respectively, the teeth T 1  to T 6  are teeth of a first system, and the teeth T 7  to T 12  are teeth of a second system. 
     Each of the teeth T 1  to T 6  of the first system has wound therearound a corresponding first excitation winding  11   a,  a corresponding first output winding  11   b,  and a corresponding second output winding  11   c.    
     Each of the teeth T 7  to T 12  of the second system has wound therearound a corresponding second excitation winding  11   d,  a corresponding third output winding  11   e,  and a corresponding fourth output winding  11   f.  The third output winding  11   e  is a first output winding of the second system. The fourth output winding  11   f  is a second output winding of the second system. 
     As described above, each of the teeth  9   b  has wound therearound an excitation winding of one phase and output windings of two phases. Further, in the first embodiment, around each of the teeth  9   b,  the excitation winding of the one phase is wound first, and the output windings of the two phases are wound thereon. 
     One of the first output winding  11   b  and the second output winding  11   c  may be wound first. Similarly, one of the third output winding  11   e  and the fourth output winding  11   f  may be wound first. Further, teeth  9   b  around which one of the output windings of the two phases is not wound may be provided. 
     The stator core  9  is insulated from the windings  11   a  to  11   f  by an insulator (not shown). As the insulator, a holder made of a resin, insulating paper, insulation coating, or the like is used. 
       FIG. 4  is a block diagram for illustrating the winding portion  10  and the control unit  6  of  FIG. 1 . The winding portion  10  includes winding groups of a plurality of systems. The winding portion  10  in the first embodiment includes winding groups of two systems. In other words, in the first embodiment, the redundancy resolver device  4  of a dual system is illustrated. 
     The winding groups of the first system include a first excitation winding group  12   a,  a first output winding group  12   b,  and a second output winding group  12   c.  The winding groups of the second system include a second excitation winding group  12   d,  a third output winding group  12   e,  and a fourth output winding group  12   f.  The third output winding group  12   e  is a first output winding group of the second system. The fourth output winding group  12   f  is a second output winding group of the second system. 
     The first excitation winding group  12   a  consists of six first excitation windings  11   a  wound around the teeth T 1  to T 6 , respectively. The six first excitation windings  11   a  are connected in series to each other. 
     The first output winding group  12   b  consists of six first output windings  11   b  wound around the teeth T 1  to T 6 , respectively. The six first output windings  11   b  are connected in series to each other. The second output winding group  12   c  consists of six second output windings  11   c  wound around the teeth T 1  to T 6 , respectively. The six second output windings  11   c  are connected in series to each other. 
     The second excitation winding group  12   d  consists of six second excitation windings  11   d  wound around the teeth T 7  to T 12 , respectively. The six second excitation windings  11   d  are connected in series to each other. 
     The third output winding group  12   e  consists of six third output windings  11   e  wound around the teeth T 7  to T 12 , respectively. The six third output windings  11   e  are connected in series to each other. The fourth output winding group  12   f  consists of six fourth output windings  11   f  wound around the teeth T 7  to T 12 , respectively. The six fourth output windings  11   f  are connected in series to each other. 
     The winding groups of different systems are arranged different positions in the circumferential direction of the stator core  9 . Further, in each system, a tooth to start winding one of the windings therearound may be any tooth. 
     The control unit  6  includes a first excitation circuit  13 , a first angle calculation unit  14 , a second excitation circuit  15 , and a second angle calculation unit  16 . The first excitation circuit  13  and the second excitation circuit  15  are independent of each other. 
     The first excitation circuit  13  and the first angle calculation unit  14  belong to the first system. The second excitation circuit  15  and the second angle calculation unit  16  belong to the second system. 
     The first excitation winding group  12   a  is electrically connected to the first excitation circuit  13  via an excitation terminal (not shown). The first output winding group  12   b  and the second output winding group  12   c  are electrically connected to the first angle calculation unit  14  via output terminals (not shown). The excitation terminal and the output terminals are provided in an extended portion (not shown) of the resolver main body  5 . 
     The second excitation winding group  12   d  is electrically connected to the second excitation circuit  15  via an excitation terminal. The third output winding group  12   e  and the fourth output winding group  12   f  are electrically connected to the second angle calculation unit  16  via output terminals. 
     The first angle calculation unit  14  is configured to calculate a first system detection angle θ 1  of the rotor  7  based on output signals from the first output winding group  12   b  and the second output winding group  12   c,  and output the first system detection angle θ 1 . The second angle calculation unit  16  is configured to calculate a second system detection angle θ 2  of the rotor  7  based on output signals from the third output winding group  12   e  and the fourth output winding group  12   f,  and output the second system detection angle θ 2 . 
       FIG. 5  is an explanatory graph for showing a number-of-turns distribution of the first excitation windings  11   a  and the second excitation windings  11   d  of  FIG. 3 . In  FIG. 5 , the numbers of turns of the first excitation windings  11   a  and the second excitation windings  11   d  are consecutively shown. 
     Further, “+” and “−” indicate different winding polarities of the windings. In other words, when a winding direction of a wire in one winding is represented by “+”, a winding direction opposite thereto is represented by “−”. When electrical currents in the same direction flow through the winding of the winding direction “+” and the winding of the winding direction “−”, directions of generated electromagnetic fields are opposite in the radial directions of the stator core  9 . 
     An absolute value of the number of turns in the winding direction “+” and an absolute value of the number of turns in the winding direction “−” are the same. In other words, when the number of turns in the winding direction “+” is +X, the number of turns in the winding direction “−” is −X. The numbers of turns of the excitation windings are standardized with amplitudes of the numbers of turns. 
     In the first excitation windings  11   a  and the second excitation windings  11   d  in the first embodiment, every two windings of the winding direction “+” and every two windings of the winding direction “−” are arranged alternately in the circumferential direction of the stator core  9 . 
     Further, a first excitation winding  11   a  and a second excitation winding  11   d  that are adjacent to each other in the circumferential direction of the stator core  9  have the same winding direction. In other words, in  FIG. 5 , a winding direction of the first excitation winding  11   a  of the tooth T 1  and a winding direction of the second excitation winding  11   d  of the tooth T 12  are the same. Similarly, a winding direction of the first excitation winding  11   a  of the tooth T 6  and a winding direction of the second excitation winding lid of the tooth T 7  are the same. 
       FIG. 6  is an enlarged sectional view for illustrating a main part of  FIG. 3 . In  FIG. 6 , magnetic fluxes generated in the tooth T 1  and the tooth T 12  and linked with the tooth T 1  and the tooth T 12  are indicated by the arrows. A direction of the magnetic flux generated in the tooth T 1  is the same as a direction of the magnetic flux generated in the tooth T 12 . Similarly, a direction of a magnetic flux generated in the tooth T 6  is the same as a direction of a magnetic flux generated in the tooth T 7 . 
     When two excitation windings  11   a  and  11   d  belonging to different systems and being arranged side by side in the circumferential direction of the stator core  9  are defined as a first end excitation winding and a second end excitation winding, respectively, the first end excitation winding and the second end excitation winding are applied with excitation signals to generate magnetic fluxes in the same direction of the radial directions of the stator core  9 . 
     Further, the first end excitation winding and the second end excitation winding are wound in the same direction. In addition, a direction in which the first end excitation winding is connected to a corresponding excitation circuit is the same as a direction in which the second end excitation winding is connected to a corresponding excitation circuit. 
     In the redundancy resolver device described above, the winding groups of different systems are arranged at different positions in the circumferential direction of the stator core  9 . Therefore, an increase in dimension in the axis line direction of the resolver main body caused by redundancy can be suppressed. 
     Further, magnetic fluxes in the same direction of the radial directions of the stator core  9  are generated in the first end excitation winding and the second end excitation winding. Therefore, the effect of magnetic interference between the adjacent teeth can be reduced, and a reduction in angle detection accuracy caused by a deviation between an excitation signal of the first system and an excitation signal of the second system can be suppressed. 
     Further, the first end excitation winding and the second end excitation winding are wound in the same direction. In addition, the direction in which the first end excitation winding is connected to a corresponding excitation circuit is the same as the direction in which the second end excitation winding is connected to a corresponding excitation circuit. Therefore, the magnetic fluxes in the same direction of the radial directions of the stator core  9  can be generated in the first end excitation winding and the second end excitation winding. 
     Second Embodiment 
     Next,  FIG. 7  is an explanatory graph for showing a number-of-turns distribution of first excitation windings  11   a  and second excitation windings  11   d  of a redundancy resolver device according to a second embodiment of this invention. In the first excitation windings  11   a  and the second excitation windings  11   d  in the second embodiment, every three windings of the winding direction “+” and every three windings of the winding direction “−” are arranged alternately in the circumferential direction of the stator core  9 . 
     A winding direction of the first excitation winding  11   a  of the tooth T 1 , a winding direction of the second excitation winding  11   d  of the tooth T 12 , a winding direction of the first excitation winding  11   a  of the tooth T 6 , and a winding direction of the second excitation winding  11   d  of the tooth T 7  are the same. All other configurations are similar or identical to those of the first embodiment. 
     Also with the above-mentioned configuration, the increase in dimension in the axis line direction of the resolver main body  5  caused by redundancy, and the reduction in angle detection accuracy can be suppressed. 
     The number of excitation windings having the same winding direction to be arranged consecutively is not limited to two or three. 
     Third Embodiment 
     Next,  FIG. 8  is an explanatory graph for showing a number-of-turns distribution of first excitation windings  11   a  and second excitation windings  11   d  of a redundancy resolver device according to a third embodiment of this invention. In the first excitation windings  11   a  and the second excitation windings  11   d  in the third embodiment, every one winding of the winding direction “+” and every one winding of the winding direction “−” are arranged alternately in the circumferential direction of the stator core  9 . 
     Therefore, a winding direction of the first excitation winding  11   a  of the tooth T 1  and a winding direction of the second excitation winding  11   d  of the tooth T 12  are opposite. Similarly, a winding direction of the first excitation winding  11   a  of the tooth T 6  and a winding direction of the second excitation winding  11   d  of the tooth T 7  are opposite. In other words, the first end excitation winding and the second end excitation winding are wound in opposite directions. 
       FIG. 9  is a block diagram for illustrating a winding portion  10  and a control unit  6  of the redundancy resolver device according to the third embodiment. A direction in which the first end excitation winding is connected to a corresponding excitation circuit is opposite to a direction in which the second end excitation winding is connected to a corresponding excitation circuit. All other configurations are similar or identical to those of the first embodiment. 
     In such a redundancy resolver device, the first end excitation winding and the second end excitation winding are wound in the opposite directions. In addition, the direction in which the first end excitation winding is connected to a corresponding excitation circuit is opposite to the direction in which the second end excitation winding is connected to a corresponding excitation circuit. 
     Therefore, magnetic fluxes in the same direction of the radial directions of the stator core  9  can be generated in the first end excitation winding and the second end excitation winding. Thus, the increase in dimension in the axis line direction of the resolver main body  5  caused by redundancy, and the reduction in angle detection accuracy can be suppressed. 
     In the third embodiment, every one excitation winding of the winding direction “+” and every one excitation winding of the winding direction “−” are arranged alternately, but two or more excitation windings of the same winding direction can be arranged consecutively. 
     For example, in  FIG. 10 , every two windings of the winding direction “+” and every two windings of the winding direction “−” are arranged alternately in the circumferential direction of the stator core  9 . Further, the first end excitation winding and the second end excitation winding are wound in opposite directions. Also in this case, when a direction in which the first end excitation winding is connected to a corresponding excitation circuit is opposite to a direction in which the second end excitation winding is connected to a corresponding excitation circuit, effects similar to those obtained in the third embodiment can be obtained. 
     Fourth Embodiment 
     Next,  FIG. 11  is a sectional view for illustrating a stator of a redundancy resolver device according to a fourth embodiment of this invention. In the fourth embodiment, teeth T 1  to T 4  are teeth of a first system, teeth T 5  to T 8  are teeth of a second system, and teeth T 9  to T 12  are teeth of a third system. 
     Each of the teeth T 1  to T 4  of the first system has wound therearound a corresponding first excitation winding  11   a,  a corresponding first output winding  11   b,  and a corresponding second output winding  11   c.    
     Each of the teeth T 5  to T 8  of the second system has wound therearound a corresponding second excitation winding  11   d,  a corresponding third output winding  11   e,  and a corresponding fourth output winding  11   f.  The third output winding  11   e  is a first output winding of the second system. The fourth output winding  11   f  is a second output winding of the second system. 
     Each of the teeth T 9  to T 12  of the third system has wound therearound a corresponding third excitation winding  11   g,  a corresponding fifth output winding  11   h,  and a corresponding sixth output winding  11   i.  The fifth output winding  11   h  is a first output winding of the third system. The sixth output winding  11   i  is a second output winding of the third system. 
       FIG. 12  is a block diagram for illustrating a winding portion  10  and a control unit  6  of the redundancy resolver device according to the fourth embodiment. The winding portion  10  in the fourth embodiment includes winding groups of three systems. In other words, in the fourth embodiment, the redundancy resolver device of a triple system is illustrated. 
     The winding groups of the third system include a third excitation winding group  12   g,  a fifth output wincing group  12   h,  and a sixth output winding group  12   i.  The fifth output winding group  12   h  is a first output winding group of the third system. The sixth output winding group  12   i  is a second output winding group of the third system. 
     The first excitation winding group  12   a  consists of four first excitation windings  11   a  wound around the teeth T 1  to T 4 , respectively. The four first excitation windings  11   a  are connected in series to each other. 
     The first output winding group  12   b  consists of four first output windings  11   b  wound around the teeth T 1  to T 4 , respectively. The four first output windings  11   b  are connected in series to each other. The second output winding group  12   c  consists of four second output windings  11   c  wound around the teeth T 1  to T 4 , respectively. The four second output windings  11   c  are connected in series to each other. 
     The second excitation winding group  12   d  consists of four second excitation windings  11   d  wound around the teeth T 5  to T 8 , respectively. The four second excitation windings  11   d  are connected in series to each other. 
     The third output winding group  12   e  consists of four third output windings  11   e  wound around the teeth T 5  to T 8 , respectively. The four third output windings  11   e  are connected in series to each other. The fourth output winding group  12   f  consists of four fourth out windings  11   f  wound around the teeth T 5  to T 8 , respectively. The four fourth output windings  11   f  are connected in series to each other. 
     The third excitation winding group  12   g  consists of four third excitation windings  11   g  wound around the teeth T 9  to T 12 , respectively. The four third excitation windings  11   g  are connected in series to each other. 
     The fifth output winding group  12   h  consists of four fifth output windings  11   h  wound around the teeth T 9  to T 12 , respectively. The four fifth output windings  11   h  are connected in series to each other. The sixth output winding group  12   i  consists of four sixth output windings  11   i  wound around the teeth T 9  to T 12 , respectively. The four sixth output windings  11   i  are connected in series to each other. 
     The control unit  6  in the fourth embodiment includes a first excitation circuit  13 , a first angle calculation unit  14 , a second excitation circuit  15 , a second angle calculation unit  16 , a third excitation circuit  17 , and a third angle calculation unit  18 . The first excitation circuit  13 , the second excitation circuit  15 , and the third excitation circuit  17  are independent of each other. 
     The third excitation circuit  17  and the third angle calculation unit  18  belong to the third system. 
     The third excitation winding group  12   g  is electrically connected to the third excitation circuit  17  via an excitation terminal. The fifth output winding group  12   h  and the sixth output winding group  12   i  are electrically connected to the third angle calculation unit  18  via output terminals. 
     The third angle calculation unit  18  is configured to calculate a third system detection angle θ 3  of the rotor  7  based on output signals from the fifth output winding group  12   h  and the sixth output winding group  12   i,  and output the third system detection angle θ 3 . 
       FIG. 13  is an explanatory graph for showing a number-of-turns distribution of the first excitation windings  11   a,  the second excitation windings  11   d,  and the third excitation windings  11   g  in the fourth embodiment. In  FIG. 13 , the numbers of turns of the first excitation windings  11   a,  the second excitation windings  11   d,  and the third excitation windings  11   g  are consecutively shown. 
     In the first excitation windings  11   a,  the second excitation windings  11   d,  and the third excitation windings  11   g  in the fourth embodiment, every two windings of the winding direction “+” and every two windings of the winding direction “−” are arranged alternately in the circumferential direction of the stator core  9 . 
     Further, a first excitation winding  11   a  and a second excitation winding  11   d  that are adjacent to each other in the circumferential direction of the stator core  9  have the same winding direction. Still further, a second excitation winding  11   d  and a third excitation winding  11   g  that are adjacent to each other in the circumferential direction of the stator core  9  have the same winding direction. Yet further, a third excitation winding  11   g  and a first excitation winding that are adjacent to each other in the circumferential direction of the stator core  9  have the same winding direction. 
     In other words, in  FIG. 13 , a winding direction of the first excitation winding  11   a  of the tooth T 1  and a winding direction of the third excitation winding  11   g  of the tooth T 12  are the same. Similarly, a winding direction of the first excitation winding  11   a  of the tooth T 4  and a winding direction of the second excitation winding  11   d  of the tooth T 5  are the same. Similarly, a winding direction of the second excitation winding  11   d  of the tooth T 8  and a winding direction of the third excitation winding  11   g  of the tooth T 9  are the same. 
     Therefore, a direction of a magnetic flux generated in the tooth T 1  is the same as a direction of a magnetic flux generated in the tooth T 12 . Similarly, a direction of a magnetic flux generated in the tooth T 4  is the same as a direction of a magnetic flux generated in the tooth T 5 . Similarly, a direction of a magnetic flux generated in the tooth T 8  is the same as a direction of a magnetic flux generated in the tooth T 9 . All other configurations are similar or identical to those of the first embodiment. 
     As described above, also with the redundancy resolver device of the triple system, the increase in dimension in the axis line direction of the resolver main body caused by redundancy, and the reduction in angle detection accuracy can be suppressed. 
     In the fourth embodiment, a first end excitation winding and a second end excitation winding may be wound in opposite directions. Also in this case, similarly to the third embodiment, it is only required that a direction in which the first end excitation winding is connected to a corresponding excitation circuit be opposite to a direction in which the second end excitation winding is connected to a corresponding excitation circuit. 
     Fifth Embodiment 
     Next,  FIG. 14  is a sectional view for illustrating a stator of a redundancy resolver device according to a fifth embodiment of this invention. In the fifth embodiment, a stator core  9  is divided into two in the circumferential direction. In other words, the stator core  9  is formed by combining two arc-shaped divided cores  9 A.  FIG. 15  is a plan view for illustrating a divided core  9 A of  FIG. 14 . All other configurations are similar or identical to those in one of the first to fourth embodiments. 
     With the above-mentioned configuration, by winding windings around teeth  9   b  before combining the two divided cores  9 A, winding operation becomes easier, and manufacturability can be increased. 
     Sixth Embodiment 
     Next,  FIG. 16  is a sectional view for illustrating a stator of a redundancy resolver device according to a sixth embodiment of this invention. In the sixth embodiment, a stator core  9  is divided into four in the circumferential direction. In other words, the stator core  9  is formed by combining four arc-shaped divided cores  9 B.  FIG. 17  is a plan view for illustrating a divided core  9 B of  FIG. 16 . All other configurations are similar or identical to those in one of the first to fourth embodiments. 
     With the above-mentioned configuration, by winding windings around teeth  9   b  before combining the four divided cores  9 B, winding operation becomes easier, and manufacturability can be increased. 
     Here, the stator core  9  as described in the first to sixth embodiments is formed by laminating a plurality of core pieces made of an electromagnetic steel sheet in an axial direction. Therefore, in the stator core  9  in the first to fourth embodiments, as illustrated in  FIG. 18 , a core piece  22  having an annular shape, which is die-cut from a core sheet  21 , is used. 
     Meanwhile, in the stator core  9  in the sixth embodiment, as illustrated in  FIG. 19 , a core piece  23  having an arc shape, which is die-cut from the core sheet  21 , is used. 
     The size of each of the core pieces  23  in the sixth embodiment is smaller than the size of the core piece  22  in the first to fourth embodiments. Therefore, in the sixth embodiment, as compared to the first to fourth embodiments, a narrower roll material can be used as the core sheet  21 , and yields can be increased. 
     Further, in the sixth embodiment, the effect of magnetic anisotropy of the electromagnetic steel sheet forming the stator core  9  can be reduced, and angle detection accuracy can be increased. 
     The division number in the circumferential direction of the stator core  9  is not limited to two or four, and may be three, or equal to or more than five, for example. 
     Seventh Embodiment 
     Next,  FIG. 20  is a sectional view for illustrating a stator core  9  of a redundancy resolver device according to a seventh embodiment of this invention. The stator core  9  in the seventh embodiment consists of the same number of core blocks  24  as the number of teeth  9   b.    
     Each pair of adjacent core blocks  24  are rotatably connected at a connecting portion  25 . As a result, the stator core  9  is transformable between a state in which the core blocks  24  are arrayed in an annular shape as illustrated in  FIG. 20 , and a state in which the core blocks  24  are developed in straight line as illustrated in  FIG. 21 . All other configurations are similar or identical to those in one of the first to fourth embodiments. 
     In this configuration, when the stator core  9  is developed in straight line, a gap between each pair of adjacent teeth  9   b  is increased. When winding operation of the windings is performed under this state, the winding operation becomes easier, and manufacturability can be increased. 
     A core piece forming a rotor core may be die-cut from the same electromagnetic steel sheet as that of the core pieces forming the stator core. 
     Further, in the above-mentioned examples, the redundancy resolver devices of the dual system and the triple system have been described, but a quadruple or more system may be adopted. 
     Still further, the above-mentioned examples, the number of slots is 12, and the shaft angle multiplier is 5. However, this invention is not limited thereto, and similar effects can be obtained even with other configurations. 
     Yet further, in the above-mentioned examples, the excitation winding of the one phase and the output windings of the two phases are arrayed and wound in the circumferential direction, but this invention is not thereto. Similar effects may be obtained even when the excitation winding of the one phase and the output windings of the two phases are arrayed in the radial directions, or when the order in which the excitation winding of the one phase and the output windings of the two phases are wound around each tooth is changed, for example. 
     Yet further, the redundancy resolver device in each of the first to seventh embodiments may be applied to an electric power steering device. 
       FIG. 22  is a side view for illustrating an example of an electric power steering device to which the redundancy resolver device of this invention is applied. An electric power steering device  100  includes an electric drive device  101  and a gearbox portion  102 . 
     The electric drive device  101  includes the rotating electric machine  1 , an electronic control unit (ECU)  103 , and the redundancy resolver device  4  described in one of the first to seventh embodiments. The rotating electric machine  1  in the electric power steering device  100  is an electric motor. Though not shown in  FIG. 22 , the redundancy resolver device  4  is attached to the rotating shaft  3  of the rotating electric machine  1 . 
     The ECU  103  includes a first connector  103   a,  a second connector  103   b,  and a power supply connector  103   c.  Power is supplied from a battery or an alternator to the ECU  103  via the power supply connector  103   c.    
     The gearbox portion  102  is attached to a housing  104 . The gearbox portion  102  includes a belt (not shown) and a ball screw (not shown). The housing  104  includes a rack shaft (not shown). 
     The gearbox portion  102  is configured to decelerate rotation of the rotating electric machine  1 , and transmit the decelerated rotation to the rack shaft. The rotating electric machine  1  is arranged parallel to the rack shaft. 
     When a driver steers a steering wheel (not shown), torque is transmitted to an input shaft  105  through a steering shaft (not shown). The torque transmitted to the input shaft  105  is detected by a torque sensor  106 . 
     The torque detected by the torque sensor  106  is converted to an electric signal to be input to the first connector  103   a  through a cable (not shown). Meanwhile, vehicle information including vehicle speed information is converted to an electric signal to be input to the second connector  103   b.    
     The ECU  103  is configured to calculate required assist torque based on the signal from the torque sensor  106  and the vehicle information, and supply an electric current corresponding to the assist torque to the rotating electric machine  1  via an inverter. 
     Torque generated in the rotating electric machine  1  is input, as thrust for moving the rack shaft in a direction of an arrow d of  FIG. 22 , to the rack shaft via the gearbox portion  102 . As a result, a pair of tie rods  107  are moved to steer a pair of tires (not shown) so that the vehicle can be turned. 
     As a result, the driver is assisted by the torque or the rotating electric machine  1 , and can turn the vehicle with a small steering effort. At both ends of the housing  104 , a pair of rack boots  108  are provided. The pair of rack boots  108  prevent foreign matters from entering the housing  104 . 
     REFERENCE SIGNS LIST 
       4  redundancy resolver device,  5  resolver main body,  6  control unit,  7  rotor,  8  stator,  9  stator core,  9   a  core back portion,  9   b  tooth,  9 A,  9 B divided core,  11   a  first excitation winding,  11   b  first output winding,  11   c  second output winding,  11   d  second excitation winding,  11   e  third output winding (first output winding of second system),  11   f  fourth output winding (second output winding of second system),  11   g  third excitation winding,  11   h  fifth output winding (first output winding of third system),  11   i  sixth output winding (second output winding of third system),  12   a  first excitation winding group,  12   b  first output winding group,  12   c  second output winding group,  12   d  second excitation winding group,  12   e  third output winding group (first output winding group of second system),  12   f  fourth output winding group (second output winding group of second system),  12   g  third excitation winding group,  12   h  fifth output winding group (first output winding group of third system),  12   i  sixth output winding group (second output winding group of third system),  13  first excitation circuit,  15  second excitation circuit,  17  third excitation circuit,  24  core block,  100  electric power steering device