Patent Publication Number: US-2018041087-A1

Title: Rotating electric machine, coil, and coil device

Description:
TECHNICAL FIELD 
     The present invention relates to a rotating electric machine, a coil, and a coil device. 
     BACKGROUND ART 
     A rotating electric machine including a stator, which has an iron core section with cores and coils set up on the cores, and a rotor, which is rotated relative to the stator, is known as a conventional rotating electric machine (for example, Patent Literatures 1 to 4 and Non-Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         [Patent Literature 1] Japanese Unexamined Patent Publication No. 2006-101606 
         [Patent Literature 2] Japanese Unexamined Patent Publication No. 2006-254638 
         [Patent Literature 3] Japanese Unexamined Patent Publication No. 2003-116236 
         [Patent Literature 4] Japanese Unexamined Patent Publication No. 2008-172866 
       
    
     Non-Patent Literature 
     
         
         [Non-Patent Literature 1] Shinji Makita, et al., “Permanent magnet synchronous motor having new winding structure reconciling high winding factor and high space factor,” the journal D of the institute of electrical engineers (the IEEJ transactions on industry applications),  IEEJ Transactions on Industry Applications , Vol. 134, No. 12, pp 1031-1037, June 2014 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the rotating electric machine described in Patent Literature 1, coils formed by concentrically winding an enamel wire are used. In the rotating electric machine using the concentrated winding, a rotating magnetic field easily becomes a square wave, and torque ripples are generated by harmonic components. Thereby, there is a possibility of rotation becoming uneven and vibration or noise increasing. The unevenness of the rotation can be measured by checking distortion of an induced electromotive force generated by the rotation of the motor. In the rotating electric machine described in Patent Literature 1, the shape of a space defined between the neighboring cores is a specific shape, and thereby a problem with the torque ripples is solved. However, in the rotating electric machine described in Patent Literature 1, the distortion can be still generated from the waveform of the induced electromotive force. 
     As a method of removing the distortion of the waveform of the induced electromotive force, in the rotating electric machine described in Patent Literature 2, an enamel wire is subjected to distributed winding. However, in the case of the distributed winding, since ends of coils are long compared to the concentrated winding, there occurs a problem that a length of the enamel wire is increased and winding resistance is increased. To suppress a variation in torque, there is a configuration in which a flywheel is provided and weighed. However, in this configuration, there is a problem that responsiveness of a rotational frequency of the rotating electric machine is reduced. 
     In order to approximate the waveform of the induced electromotive force to a sine wave, in the rotating electric machine described in Patent Literature 3, when an axis extending in a direction of magnetic poles of the rotor is set as a d axis, and an axis extending in a direction of the centers of the magnetic poles and a direction between the magnetic poles which is shifted at an electrical angle by 90 degrees is set as a q axis, an outer circumferential surface of a rotor iron core is configured such that a radial distance from the center of the rotor iron core to an outer circumference of the rotor is shortened from the d axis to the q axis. However, a high level of technique is required to manufacture this iron core, and a manufacturing cost is increased. In addition, a dedicated special winding machine is required to wind the coil. In Patent Literature 4, a current flowing to the rotating electric machine is controlled, and thereby the torque ripples are reduced. However, a method of controlling the rotating electric machine is not a fundamental solution of the torque ripples, and performance of the rotating electric machine itself cannot be improved. 
     Further, in the motor of Non-Patent Literature 1, a manufacturing method thereof is extremely complicated, and realization of mass-production is difficult. Since the motor adopts an intermediate winding method between the distributed winding and the concentrated winding, there is a problem that ends of the coil become longer, and resistance to the winding is increased. 
     There is a possibility of an increase in the unevenness of the rotation or winding resistance caused by these torque ripples or the like being represented as a reduction in motor efficiency and causing a reduction in overall motor performance. Therefore, the overall motor performance can be evaluated by measuring the motor efficiency. 
     The present invention is directed to providing a rotating electric machine capable of improving performance, and a coil and coil device used in the rotating electric machine. 
     Solution to Problem 
     A rotating electric machine according to an aspect of the present invention includes: a stator having an iron core section with a main body part that has a circular circumferential surface and a plurality of cores that protrude from the circumferential surface of the main body part in a radial direction of the main body part and are provided at predetermined intervals in a circumferential direction of the circumferential surface, and coils arranged on the cores; and a rotor configured to rotate relative to the stator. Each of the coils includes a coil section that is formed in a spiral shape from a conductive member having conductivity, and terminal parts that are connected to opposite ends of the coil section. A width dimension of the coil section gradually increases from one side to the other side in a direction of an axis of the coil section. An insulating film having an electrical insulation property is provided on a surface of the conductive member of the coil section. 
     In this rotating electric machine, the cores are provided to protrude from the circumferential surface of the main body part in the radial direction of the main body part. In this configuration, a fan-like space is defined between the neighboring the cores. In this configuration, the width dimension of the coil section gradually increases from one side to the other side in the direction of the axis of the coil section. With this configuration, since the coils are arranged on the cores, a space factor of the coil section can be enhanced in the fan-like space defined by the cores. The insulating film having an electrical insulation property is provided on the surface of the conductive member of the coil section. For this reason, the generation of creeping discharge or the like between the conductive members is suppressed. In the rotating electric machine having the coils, the distortion of a waveform of an induced electromotive force generated by rotation can be suppressed. Therefore, in the rotating electric machine, the generation of torque ripples can be suppressed, and the rotation of the rotor is made uniform. As a result, in the rotating electric machine, the performance can be improved. The improvement of this performance can be evaluated by measuring efficiency of the rotating electric machine. 
     In an embodiment, a waveform of an induced electromotive force generated by rotation may be a sine wave or a quasi-sine wave. 
     In an embodiment, the rotating electric machine may be an inner rotor type three-phase motor. 
     A coil according to an aspect of the present invention is a coil arrange on a core, and includes: a coil section formed in a spiral shape from a conductive member having conductivity; and terminal parts connected to opposite ends of the coil section. A width dimension of the coil section gradually increases from one side to the other side in a direction of an axis of the coil section, and an insulating film having an electrical insulation property is provided on a surface of the conductive member of the coil section. 
     In this coil, the width dimension of the coil section gradually increases from one side to the other side in the direction of the axis of the coil section. Thereby, for example, in a configuration in which a plurality of cores are arranged in a circumferential direction, the coils are arranged on the cores such that one side of the coil section is located at a base end side of each core with respect to each core, and thereby a space factor of the coil section can be enhanced in a fan-like space defined by the cores. In the coil, the insulating film having an electrical insulation property is provided on the surface of the conductive member of the coil section. Thereby, the electrical insulation property between the conductive members can be secured. As a result, the generation of creeping discharge or the like between the conductive members can be suppressed. In the rotating electric machine using this coil, the distortion of a waveform of the induced electromotive force generated by rotation can be suppressed. Therefore, in the rotating electric machine using this coil, the generation of torque ripples can be suppressed, and the rotation of the rotor is made uniform. As a result, in the rotating electric machine using the coil, the performance can be improved. The improvement of this performance can be evaluated by measuring efficiency of the rotating electric machine. 
     In an embodiment, the insulating film may be formed by dip coating or electrodeposition coating. Thereby, the insulating film can be well formed on the surface of the conductive member. 
     In an embodiment, the corners of the conductive member may be chamfered. When the corners of the conductive member are approximately right angles, it is difficult for the insulating film to be formed on the corners, and it is easy for the insulating film to peel off at the corners. The insulating film can be well formed even at the corners by chamfering the corners of the conductive member. Therefore, the insulation property can be even more secured in the coil section. 
     In an embodiment, the coil section may be formed by joining the plurality of conductive members. Thereby, a desired shape of the coil section can be easily formed. In this way, the coil section is formed by joining the plurality of conductive members, and thereby an inside shape of the coil section can be formed in a desired shape. For this reason, when the coil is arranged on the core, the formation of a gap between the core and the coil section can be suppressed. As a result, the space factor of the coil can be enhanced. 
     In an embodiment, a cross-sectional area of the conductive member on a plane orthogonal to an extending direction of the conductive member may be uniform throughout a circumference of the coil section. Thereby, a value of electrical resistance in the coil section becomes constant. For this reason, the performance as the coil can be improved. 
     In an embodiment, the insulating film may have a thickness of 10 μm or more. Thereby, the insulation property between the conductive members can be secured in the coil section, and the creeping discharge can be suppressed. 
     A coil device according to an aspect of the present invention includes: an iron core section having a main body part that has a circular circumferential surface and a plurality of cores that protrude from the circumferential surface of the main body part in a radial direction of the main body part and are provided at predetermined intervals in a circumferential direction of the circumferential surface; and coils arranged on the cores. Each of the coils includes a coil section that is formed in a spiral shape from a conductive member having conductivity, and terminal parts that are connected to opposite ends of the coil section. A width dimension of the coil section gradually increases from one side to the other side in a direction of an axis of the coil section, and an insulating film having an electrical insulation property is provided on a surface of the conductive member of the coil section. 
     In this coil device, the cores are provided to protrude from the circumferential surface of the main body part in the radial direction of the main body part. In this configuration, a fan-like space is defined between the neighboring the cores. In this configuration, the width dimension of the coil section gradually increases from one side to the other side in the direction of the axis of the coil section. With this configuration, since the coils are arranged on the cores, a space factor of the coil section can be enhanced in the fan-like space defined by the cores. The insulating film having an electrical insulation property is provided on the surface of the conductive member of the coil section. For this reason, the generation of creeping discharge or the like between the conductive members is suppressed. In the rotating electric machine using the coil device having the coils, the distortion of a waveform of an induced electromotive force generated by rotation can be suppressed. Therefore, in the rotating electric machine using the coil device, the generation of torque ripples can be suppressed, and the rotation of the rotor is made uniform. As a result, in the rotating electric machine using the coil device, the performance can be improved. The improvement of this performance can be evaluated by measuring efficiency of the rotating electric machine. 
     Advantageous Effects of Invention 
     According to the present invention, performance can be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a motor according to an embodiment. 
         FIG. 2  is an enlarged sectional view illustrating a part of the motor illustrated in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a coil. 
         FIG. 4  is a top view of the coil illustrated in  FIG. 3 . 
         FIG. 5  is a sectional view taken along line V-V of  FIG. 4 . 
         FIG. 6  is a diagram illustrating waveforms of an induced electromotive force of the motor according to the present embodiment. 
         FIG. 7  is a diagram illustrating waveforms of an induced electromotive force of a motor according to a comparative example. 
         FIG. 8  is a view illustrating a modification of the motor. 
         FIG. 9  is a diagram for illustrating a distortion factor. 
         FIG. 10  is a diagram illustrating a relationship of motor efficiency to rotational frequency and torque of the motor according to the present embodiment. 
         FIG. 11  is a diagram illustrating a relationship of motor efficiency to rotational frequency and torque of the motor according to the comparative example. 
         FIG. 12  is a diagram illustrating motor efficiency and rate. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings. In the description of the drawings, identical or equivalent elements are designated with the same reference signs, and duplicate description thereof will be omitted. 
       FIG. 1  is a view illustrating a motor according to an embodiment. As illustrated in  FIG. 1 , a motor (a rotating electric machine)  1  is, for example, an outer rotor type of brushless motor (three-phase motor). The motor  1  includes a stator (a coil device)  3  and a rotor  5 . 
     The stator  3  has an iron core section  7  and coils  9 . The iron core section  7  has an annular part (a main body part)  10  with an annular shape, and cores  12 . The annular part  10  and the cores  12  are, for instance, formed in one body. The annular part  10  and the cores  12  are formed, for instance, by stacking a plurality of electrical steel sheets. 
     As illustrated in  FIG. 2 , the cores  12  are provided to protrude outward from an outer circumferential surface  10   a  of the annular part  10  in a radial direction of the annular part  10 . A plurality of cores  12  are arranged at predetermined intervals in a circumferential direction of the outer circumferential surface  10   a  of the annular part  10 . The cores  12  have, for instance, a prismatic shape. A fan-like space S is defined between the two neighboring cores  12  by the two cores  12 . 
     Each of the cores  12  has a main body part  12   a  and a flange part  12   b . The main body part  12   a  extends in the radial direction of the annular part  10 , and a base end side thereof is connected to the annular part  10 . The flange part  12   b  is provided at a tip portion of the main body part  12   a  in a longitudinal direction (an extending direction) of the main body part  12   a . The flange part  12   b  is projected outward from the main body part  12   a  in a width direction. 
       FIG. 3  is a perspective view illustrating a coil.  FIG. 4  is a top view of the coil illustrated in  FIG. 3 .  FIG. 5  is a sectional view taken along line V-V of  FIG. 4 . As illustrated in  FIGS. 3 to 5 , each of the coils  9  includes a coil section  20  and terminal parts  22   a  and  22   b . The coil section  20  and the terminal parts  22   a  and  22   b  are electrically connected. The coil section  20  and the terminal parts  22   a  and  22   b  are formed of a conductive member  21  (see  FIG. 5 ) having conductivity. A material of the conductive member  21  is not particularly limited but, for instance, copper (Cu) may be used as the material. 
     The coil section  20  is formed to be wound in a spiral shape. As illustrated in  FIGS. 2 and 3 , the coil section  20  has a width dimension continuously increased from one side to the other side in a direction of an axis L of the coil section  20  (from a downward direction to an upward direction in  FIG. 3 ). That is, when viewed in a direction along a plane orthogonal to the direction of the axis L, the coil section  20  has an approximately trapezoidal shape. In the coil section  20 , a cross-sectional area of the conductive member  21  on a plane orthogonal to an extending direction of the conductive member  21  is uniform throughout the circumference of the coil section  20 . 
     An inner side of the coil section  20  has a shape corresponding to a profile of each of the cores  12 . In the present embodiment, each of the cores  12  has a rectangular (oblong) profile, and accordingly the inner side of the coil section  20  has a rectangular (oblong) shape when viewed in the direction of the axis L of the coil section  20  as illustrated in  FIG. 4 . The shape of the inner side of the coil section  20  may be properly set according to the profile of each of the cores  12 . 
     The coil section  20  having the above configuration is formed by joining a plurality of conductive members  21 . To be specific, the coil section  20  is formed, for instance, by joining a first portion  20   a  that extends linearly in an X-axial direction in  FIGS. 3 and 4  and a second portion  20   b  that extends linearly in a Y-axial direction. For the junction between the first portion  20   a  and the second portion  20   b , a method such as cold pressure welding, electric welding, high-frequency welding, brazing, or the like may be adopted. 
     As illustrated in  FIG. 5 , an insulating film  24  is provided on an entire surface  21   a  of the conductive member  21  of the coil section  20 . The insulating film  24  is a film (a portion) having an electrical insulation property. The insulating film  24  is a synthetic resin having an electrical insulation property. The synthetic resin preferably includes a polyester resin, a polyurethane resin, an epoxy resin, a polyimide resin, a polyamide-imide resin, an esterimide resin, and so on. Particularly, from the viewpoint of heat resistance, the polyimide resin, the polyamide-imide resin, and the esterimide resin are preferred, and the polyimide resin is further preferred. To improve partial discharge resistance, it is further preferred that a filler be mixed with the insulating film  24 . The filler is not particularly limited, but an inorganic oxide such as silica, alumina, or boehmite alumina, a swellable clay such as smectite, a non-swelling clay such as talc or mica, or a layered double hydroxide such as hydrotalcite, etc. may be used. 
     For example, dip coating or electrodeposition coating may be used as a method for forming the insulating film  24 . After the coil section  20  is formed, the insulating film  24  is formed on each of the conductive members  21  of the coil section  20 . In detail, the insulating film  24  is formed after the coil section  20  is formed by joining the first portion  20   a  and the second portion  20   b.    
     A thickness dimension of the insulating film  24  is preferably greater than or equal to 10 μm, and more preferably greater than or equal to 10 μm and smaller than or equal to 50 μm. The thickness of the insulating film  24  may be adequately set according to design of the coil section  20 . The thickness of the insulating film  24  may be constant throughout the circumference of the coil section  20 , or be different in different portions of the coil section  20 . Dielectric breakdown voltage (withstand voltage) of the insulating film  24  is preferably higher than or equal to 1 kV, for instance, when the thickness dimension is 10 μm, and higher than or equal to 4 kV, for instance, when the thickness dimension is 50 μm. The insulating film  24  more preferably has heat resistance. 
     As illustrated in  FIG. 5 , in the coil section  20 , corners  21   b  of the conductive member  21  on which the insulating film  24  is formed are chamfered. In the present embodiment, the corners  21   b  are rounded. As a method of rounding the corners  21   b , a method of grinding the corners  21   b  using, for instance, a mechanical, chemical, or electrical method may be used. Each of the corners  21   b  of the conductive member  21  is not limited to a rounded shape, and may have a shape such as an angular face. It is only necessary that the corner  21   b  of the conductive member  21  not be a shape in which faces forming the corner  21   b  intersect each other approximately at right angles. 
     The terminal parts  22   a  and  22   b  are connected to respective opposite ends of the coil section  20 . The conductive members  21  of the opposite ends of the coil section  20  are lengthened, and thereby the terminal parts  22   a  and  22   b  are formed. The terminal parts  22   a  and  22   b  may be formed by connecting other members to the opposite ends of the coil section  20 . 
     As illustrated in  FIG. 2 , the coil  9  is mounted on the core  12  by a bobbin  14 . The bobbin  14  has a tubular shape. The bobbin  14  is a member that has an electrical insulation property, and is formed of, for instance, nylon, nylon containing fiberglass, a polybutylene terephthalate resin, a polyethylene terephthalate resin, an ABS resin, a polyamide resin, a polyphenylene sulfide resin, a liquid crystal polyester resin, or the like. The bobbin  14  is fitted around the core  12 , and an upper end thereof is seized by the flange part  12   b  of the core  12 . Thereby, the bobbin  14  is prevented from escaping from the core  12 . 
     As illustrated in  FIG. 2 , the coil section  20  of the coil  9  is mounted on the core  12  such that one side thereof having a small width dimension is located at the base end side of the core  12 . That is, the width dimension of the coil section  20  gradually increases toward a tip side of the core  12 . Thereby, in the stator  3 , a space factor of the coil section  20  in the fan-like space S formed by the core  12  can be enhanced. In the present embodiment, the space factor is, for instance, higher than or equal to 90%. 
     The rotor  5  is rotatably provided. The rotor  5  has a motor case  30  and a plurality of magnets  32 . The motor case  30  has a cylindrical shape. The magnets  32  are disposed inside the motor case  30 . To be specific, the magnets  32  are provided on an inner circumferential surface of the motor case  30  via a yoke (not shown), and are arranged in a circumferential direction of the motor case  30 . To be more specific, the magnets  32  having different polarities are alternately arranged on the inner circumferential surface of the motor case  30 . 
     In the motor  1  having the above configuration, an electric current flows to the coils  9 , and thereby the rotor  5  is rotated depending on a value of the electric current. 
     As described above, in the motor  1  according to the present embodiment, the cores  12  are provided to protrude from the outer circumferential surface  10   a  of the annular part  10  in the radial direction of the annular part  10 . In this configuration, a fan-like space S is defined between the neighboring cores  12 . In this configuration, the width dimension of the coil section  20  gradually increases from one side to the other side in the direction of the axis L of the coil section  20 . The one side of the coil section  20  is arranged on the core  12  to be located at the base end side of the core  12 . With this configuration, since the coil section  20  is arranged on the core such that the width thereof is widened toward the tip side of the core  12 , a space factor of the coil section  20  can be enhanced in the fan-like space S defined by the cores  12 . The insulating film  24  having an electrical insulation property is provided on the surface  21   a  of the conductive member  21  of the coil section  20 . For this reason, the generation of creeping discharge or the like between the conductive members  21  and  21  is suppressed. In the motor  1  having the coils  9 , the distortion of waveforms of an induced electromotive force generated by rotation can be suppressed. Therefore, in the motor  1 , the generation of torque ripples can be suppressed, and the rotation of the rotor  5  is made uniform. As a result, in the motor  1 , the performance can be improved. 
     The performance of the motor  1  will be concretely described.  FIG. 6  is a diagram illustrating waveforms of an induced electromotive force of the motor according to the present embodiment.  FIG. 7  is a diagram illustrating waveforms of an induced electromotive force of a motor according to a comparative example. The waveforms of the induced electromotive force shown in  FIG. 6  are waveforms of a motor  1 A shown in  FIG. 8 . 
     First, the motor  1 A will be described.  FIG. 8  is a view illustrating a modification of the motor. As illustrated in  FIG. 8 , the motor  1 A is an inner rotor type three-phase motor. The motor  1 A includes a stator  3 A and a rotor  5 A. The stator  3 A has an iron core section  7 A and coils  9 . The iron core section  7 A has an annular part  10 A with an annular shape, and cores  12 A. 
     The cores  12 A are provided to protrude inward from an inner circumferential surface  10 Aa of the annular part  10 A in a radial direction of the annular part  10 A. A plurality of cores  12 A are arranged at predetermined intervals in a circumferential direction of the inner circumferential surface  10 Aa of the annular part  10 A. The cores  12 A have, for instance, prismatic shapes. A fan-like space S is defined between the two neighboring cores  12 A by the two cores  12 A. The coils  9  are arranged at the cores  12 A by bobbins (not shown). Each of the coils  9  is mounted on the core  12 A such that one side thereof having a great width dimension of the coil section  20  is located at a base end side of the core  12 A. The number of turns of the coil section  20  of the coil  9  is set to “38.” 
     The rotor  5 A has a rotary body  30 A and a plurality of magnets  32 A. The rotary body  30 A has a columnar shape. The magnets  32 A are disposed outside the rotary body  30 A. To be specific, the magnets  32 A are provided on an outer circumferential surface of the rotary body  30 A via a yoke (not shown), and are arranged in a circumferential direction of the rotary body  30 A. To be more specific, the magnets  32 A having different polarities are alternately arranged on the outer circumferential surface of the rotary body  30 A. 
     The waveforms of the induced electromotive force shown in  FIG. 7  are waveforms of the motor of the comparative example which includes coils formed by concentrically winding a round enamel wire. The motor of the comparative example has a coil configuration different from that of the motor  1 A, and other configurations (cores, a rotor, etc.) identical to those of the motor  1 A. The motor of the comparative example has coils formed by winding a round enamel wire around the cores 80 times. 
     In  FIGS. 6 and 7 , (a) shows the waveforms of the induced electromotive force when a rotational frequency is 100 rpm, and (b) shows the waveforms of the induced electromotive force when a rotational frequency is 250 rpm. In the motor  1 A and the motor of the comparative example, distortion factors when the rotational frequency is changed are represented in Table 1 below. 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Rotational  
                   
                 Motor of comparative 
               
               
                 frequency 
                 Motor 1A 
                 example 
               
            
           
           
               
               
            
               
                 [rpm] 
                 Distortion factor [%] 
               
               
                   
               
            
           
           
               
               
               
            
               
                 100 
                 4.6 
                 14.8 
               
               
                 150 
                 4.7 
                 10.9 
               
               
                 250 
                 3.0 
                 5.2 
               
               
                   
               
            
           
         
       
     
     As illustrated in  FIGS. 6 and 7 , the waveforms of the induced electromotive forces of the motor  1 A and the motor of the comparative example, that is the waveforms of the induced electromotive forces generated when the motors are rotated, are approximate sine waves. Here, the sine wave is a waveform (a waveform indicated in  FIG. 9  by a solid line) in which the distortion factor to be described below is 0%, and an approximate sine wave is a waveform that is extremely close to the sine wave or a waveform that is regarded as the sine wave. As shown in Table 1, in comparison with the waveforms of the induced electromotive force of the motor of the comparative example, the waveforms of the induced electromotive force of the motor  1 A are small in the distortion factor from the sine wave even at any of 100 rpm, 150 rpm, and 250 rpm despite the fact that the number of turns in the coil is less than or equal to ½. Here, the distortion factor from the sine wave will be described with reference to  FIG. 9 . 
     In the present embodiment, the distortion factor indicates a ratio of a harmonic component amplitude to a fundamental component amplitude at a peak point of the waveform of the induced electromotive force. As illustrated in  FIG. 9 , the fundamental component amplitude is an amplitude of a fundamental wave (a distortion-free sine wave). The harmonic component amplitude is an amplitude of a higher frequency component of the integral multiple of the fundamental wave. The distortion factor is obtained from the following expression. In Table 1, the distortion factors of all three of the phases are calculated on the basis of the following expression, and are averaged to calculate the distortion factor. 
       Distortion factor=((Harmonic component amplitude)/(Fundamental component amplitude))×100[%]
 
     As shown in Table 1, in the waveforms of the induced electromotive force of the motor of the comparative example, the distortion factor from the sine wave is 14.8% at 100 rpm, whereas in the waveforms of the induced electromotive force of the motor  1 A, the distortion factor from the sine wave is 4.6%. That is, the distortion factor from the sine wave at 100 rpm in the waveforms of the induced electromotive force of the motor  1 A is about ⅓ of the distortion factor from the sine wave in the waveforms of the induced electromotive force of the motor of the comparative example. The distortion factor (3.0%) from the sine wave even at 250 rpm in the waveforms of the induced electromotive force of the motor  1 A is smaller than the distortion factor (5.2%) from the sine wave in the waveforms of the induced electromotive force of the motor of the comparative example. That is, in comparison with the motor of the comparative example, the motor  1 A according to the present embodiment is small in the distortion factor over a wide range from a case in which the rotational frequency is low to a case in which the rotational frequency is high. 
     In the motor  1 A according to the present embodiment, the distortion factor at a rotational frequency of 100 rpm is preferably less than or equal to 10%, and more preferably less than or equal to 5%. In the motor  1 A, the distortion factor at a rotational frequency of 150 rpm is preferably less than or equal to 10%, and more preferably less than or equal to 5%. In addition, in the motor  1 A, the distortion factor at a rotational frequency of 250 rpm is preferably less than or equal to 5%, and more preferably less than or equal to 3%. 
     In general, the motor has a smaller torque ripple in the case in which the distortion factor is small (the ratio of the harmonic component is small, and the distortion of the sine wave is small) than in the case in which the distortion factor is great (the ratio of the harmonic component is great, and the sine wave is distorted). For this reason, in the motor  1 A, it is confirmed that, in comparison with the coil configured by the concentrical winding of the enamel wire, a variation in torque caused by the torque ripple is small, and the rotation is smooth. Thereby, even in a low rotation region, the rotor  5 A is smoothly rotated. This result is similarly obtained in the motor  1  (the outer rotor type). 
       FIG. 10  is a diagram illustrating a relationship (hereinafter referred to as “efficiency map”) of motor efficiency to rotational frequency and torque of the motor  1 A according to the present embodiment.  FIG. 11  is a diagram illustrating an efficiency map of the motor according to the comparative example. The efficiency maps shown in  FIGS. 10 and 11  are measured with a reducer connected to the motor. For this reason, in the efficiency maps shown in  FIGS. 10 and 11 , the rotational frequency of the motor is ¼ times, and the torque is four times.  FIGS. 10( a ) and 11( a )  illustrate the efficiency map of a case measured at room temperature, and  FIGS. 10( b ) and 11( b )  illustrate the efficiency map of a case measured at a high temperature (60° C.). 
       FIG. 12  is a diagram illustrating motor efficiency and rate. In  FIG. 12 , to quantitatively evaluate the efficiency maps of  FIGS. 10 and 11 , a value of the motor efficiency is shown in units of 2% and as a rate with respect to an entire measurement range.  FIG. 12( a )  shows results of the motor  1 A, and  FIG. 12( b )  shows results of the motor of the comparative example. In Table 2, rates with respect to an entire driving range in which the motor efficiency is greater than or equal to 90% and a maximum efficiency are shown. 
     
       
         
           
               
               
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                   
                 Rate [%] with respect to  
                   
               
               
                   
                 entire driving range in which  
                   
               
               
                   
                 motor efficiency is greater  
                 Maximum  
               
               
                   
                 than or equal to 90% 
                 efficiency [%] 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Room 
                 High 
                 Room 
                 High 
               
               
                   
                 temperature 
                 temperature 
                 temperature 
                 temperature 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Motor 1A 
                 13.6 
                 7.6 
                 92.0 
                 91.6 
               
               
                 Motor of 
                 0.1 
                 0 
                 90.6 
                 85.6 
               
               
                 comparative 
                   
                   
                   
                   
               
               
                 example 
               
               
                   
               
            
           
         
       
     
     As shown in  FIGS. 10, 11 and 12  and Table 2, the motor  1 A has higher efficiency than the motor of the comparative example in a wide driving range. Further, even with regard to the rates and the maximum efficiency with respect to the entire driving range in which the motor efficiency is greater than or equal to 90% at a high temperature, the motor  1 A is higher than the motor of the comparative example. 
     In general, the motor having high maximum efficiency as well as high efficiency in the wide driving range is obtained. It is found from the results shown in  FIGS. 10, 11 and 12  and Table 2 that the motor  1 A is high in performance compared to the motor of the comparative example. 
     In the present embodiment, the insulating film  24  is formed by dip coating or electrodeposition coating. Thereby, the insulating film  24  can be formed well on the surface  21   a  of the conductive member  21 . 
     In the present embodiment, the corners  21   b  of the conductive member  21  are chamfered. When the corners  21   b  of the conductive member  21  are approximately right angles, it is difficult for the insulating film  24  to be formed on the corners  21   b , and it is easy for the insulating film  24  to peel off at the corners  21   b . The insulating film  24  can be formed well even at the corners  21   b  by chamfering the corners  21   b  of the conductive member  21 . Therefore, the insulation property can be even more secured in the coil section  20 . 
     In the present embodiment, the coil section  20  is formed by joining the plurality of conductive members  21 . Thereby, a desired shape of the coil section  20  can be easily formed. For this reason, the formation of a gap between the core  12  and the coil section  20  can be suppressed. As a result, the space factor of the coil  9  can be enhanced. 
     In the present embodiment, the cross-sectional area of the conductive member  21  on the plane orthogonal to the extending direction of the conductive member  21  is uniform throughout the circumference of the coil section  20 . Thereby, a value of electrical resistance becomes constant in the coil section  20 . For this reason, the performance of the coil  9  can be improved. 
     In the present embodiment, the insulating film  24  has a thickness of 10 μm or more. Thereby, the insulation property between the conductive members  21  in the coil section  20  can be secured, and the creeping discharge can be suppressed. 
     The present invention is not limited to the above embodiments. For example, in the above embodiments, the motor  1  (the motor  1 A) acting as the rotating electric machine has been described by way of example. However, the rotating electric machine may be, for instance, an electric generator or the like. 
     In the above embodiments, the configuration in which the cross-sectional area of the conductive member  21  is uniform over the entirety of the coil section  20  has been described by way of example. However, the cross-sectional area of the conductive member  21  is not necessarily uniform over the entirety. 
     In the above embodiments, the configuration in which the motor  1  or  1 A is illustrated in  FIG. 1 or 8  has been described by way of example. However, the number of cores  12  or  12 A (the number of coils  9 ) and the number of magnets  32  or  32 A may be adequately set depending on design. 
     In the above embodiments, the configuration in which the plurality of conductive members  21  are joined to form the coil  9  has been described by way of example. However, the method of forming the coil  9  is not limited thereto. 
     In the above embodiments, the configuration in which the coil section  20  is formed by joining the first portion  20   a  of a linear shape and the second portion  20   b  of a linear shape has been described by way of example. However, the formation of the coil section  20  is not limited to the junction between the first and second portions  20   a  and  20   b  of the linear shapes. The coil section  20  may be formed by joining first and second portions having other shapes. 
     In the above embodiments, the configuration in which the iron core section  7  has the annular part  10  of an annular shape has been described by way of example. However, the profile of the main body part may have a circular shape and, for instance, a disc shape. 
     In the above embodiments, the configuration in which the insulating film  24  is formed by dip coating or electrodeposition coating has been described by way of example. However, the method of forming the insulating film  24  is not limited thereto. 
     In the above embodiments, the configuration in which the coil  9  is mounted on the bobbin  14  has been described by way of example. However, the bobbin  14  may not be provided. In this case, the coil  9  is integrally molded by covering an outside of the insulating film  24  with a resin. Thereby, the bobbin  14  can be omitted, and the coil device can be simplified. The resin used to mold the coil  9  can be the same resin as the bobbin  14 . Aside from the material of the aforementioned bobbin  14 , thermosetting resins such as an epoxy resin or thermoplastic resins may be used. As the method of molding the coil  9 , an injection molding method or a powder fluidized bed dipping method may be used. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 ,  1 A Motor (rotating electric machine, coil device) 
               7 ,  7 A Iron core section 
               9  Coil 
               10 ,  10 A Annular part (main body part) 
               10   a  Outer circumferential surface (circumferential surface) 
               10 Aa Inner circumferential surface (circumferential surface) 
               12 ,  12 A Core 
               20  Coil section 
               21  Conductive member 
               21   a  Surface 
               21   b  Corner 
               22   a ,  22   b  Terminal part 
               24  Insulating film 
             L Axis