Abstract:
A stator of a rotary electric machine includes a stator core, coils and magnetic bodies. The stator core includes a plurality of teeth protruding towards the rotor and being spaced apart from each other and a plurality of slots arranged between two adjacent teeth. The coils are formed out of coil bodies being stacked in radial direction, thus the direction into which the teeth are extending, and are wound inside of slots around the teeth. The magnetic bodies are arranged between adjacent coil bodies. The thickness of the magnetic bodies in radial direction increases with increasing length of the tooth or with decreasing distance towards the air gap between rotor and stator.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to stator of a rotary electric machine, that includes a stator core in which a plurality of teeth that protrude toward a rotor are arranged spaced apart from each other, and in which a slot is formed between the teeth, and a coil that passes through the slot and is wound around the teeth. 
         [0003]    2. Description of Related Art 
         [0004]    Japanese Patent Application Publication No. 2010-220387 (JP 2010-220387 A) describes a rotary electric machine in which a magnetic plate is inserted between coil wires that are stacked and wound in a concentrated winding around teeth of a stator. As a result, magnetic flux flows more easily to the magnetic plate, and is thus inhibited from flowing to the coil wires, which reduces an eddy current generated by a fluctuation in magnetic flux interlinked with the coil. 
         [0005]    When magnetic flux that flows through the teeth of the stator becomes saturated when applying magnetic flux between the stator and the rotor, the magnetic flux leaks out from the teeth and flows out through the coil positioned between adjacent teeth (i.e., in the slot). The amount of leakage flux that flows through the coil between the teeth increases toward the tip end side of the teeth that is close to the rotor where the magnetic flux acts, and decreases toward the root (i.e., the base) side of the teeth that is farther away from the rotor. Also, when leakage flux that flows through the coil between the teeth fluctuates, an eddy current is generated in the coil, and loss resulting from this eddy current occurs. In particular, an eddy current due to fluctuation in the leakage flux that flows through the coil between the teeth tends to increase, and thus loss resulting from the eddy current also tends to increase, more in the coil positioned on the tip end side of the teeth that is close to the rotor. 
         [0006]    The technology described in JP 2010-220387 A attempts to reduce an eddy current generated by a fluctuation in the magnetic flux that is interlinked with the coil, by facilitating the flow of leakage flux between the teeth to the magnetic plate inserted between the coil wires. However, the thickness of the magnetic plate inserted between the coil wires is constant from the tip end side of the teeth where the amount of leakage flux is large to the root side of the teeth where the amount of leakage flux is small. Therefore, the thickness (i.e., the width of the magnetic path) of the magnetic plate is excessive at the root side of the teeth. As a result, the conductor space factor between the teeth decreases. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention thus provides a stator of a rotary electric machine, that inhibits an eddy current from being generated in a coil due to fluctuation of leakage flux that flows between teeth, while preventing a decrease in the conductor space factor between the teeth. 
         [0008]    The stator of a rotary electric machine according to the invention employs the means described below. 
         [0009]    The invention relates to a stator of a rotary electric machine, that includes a stator core, a coil, and a magnetic body. The stator core includes a plurality of teeth and a plurality of slots. The teeth that protrude out toward a rotor are arranged spaced apart from one another, and the slot is arranged between the teeth. The coil is formed by coil bodies that are stacked, in a direction in which the teeth protrude, in the slot and wound around the teeth. The magnetic body is arranged between the coil bodies that are adjacent in the direction in which the teeth protrude, in the slot. A thickness of the magnetic body in the direction in which the teeth protrude becomes thicker as a distance to the rotor becomes shorter. 
         [0010]    In the invention described above, the coil bodies may each include a conducting portion and an insulating portion that covers an outer periphery of the conducting portion. Also, a width of the magnetic body in a direction in which the teeth are arranged may be longer than a width of the conducting portion in the direction in which the teeth are arranged. 
         [0011]    In the invention described above, the coil bodies may be arranged lined up in a row in the direction in which the teeth protrude, in the slot. 
         [0012]    According to the invention, leakage flux between the teeth is able to be inhibited from flowing through the coil bodies, by flowing through the magnetic body. As a result, an eddy current is able to be inhibited from being generated in the coil bodies. Furthermore, the thickness of the magnetic body is a thickness according to the amount of leakage flux between the teeth, so the conductor space factor between the teeth is able to be prevented from decreasing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
           [0014]      FIG. 1  is a sectional view schematically showing the structure of a stator and a rotor viewed from a rotor rotation axis direction; 
           [0015]      FIG. 2  is a sectional view schematically showing the structure of the stator and the rotor viewed from a direction orthogonal to the rotor rotation axis; 
           [0016]      FIG. 3  is a sectional view schematically showing the structure of the stator according to an example embodiment of the invention, viewed from the rotor rotation axis direction; 
           [0017]      FIG. 4  is a view showing leakage flux generated between teeth of the stator; and 
           [0018]      FIG. 5  is a view showing leakage flux generated between the teeth, in the stator according to the example embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0019]    Hereinafter, modes for carrying out the invention (hereinafter simply referred to as “example embodiments”) will be described with reference to the accompanying drawings. 
         [0020]      FIGS. 1 to 3  are views schematically showing the structure of a rotary electric machine provided with a stator according to one example embodiment of the invention.  FIG. 1  is a schematic diagram of the structure of a stator  12  and a rotor  14  viewed from a stator axis or rotor rotation axis (hereinafter simply referred to as “rotation axis”) direction.  FIG. 2  is a schematic diagram of the stator  12  and the rotor  14  viewed from a direction orthogonal to the rotation axis.  FIG. 3  is a schematic diagram of the stator  12  viewed from the rotation axis direction. The rotary electric machine according to this example embodiment includes the stator  12  that is stationary (i.e., fixed so that it will not rotate), and the rotor  14  that is able to rotate relative to the stator  12 . In the example shown in  FIGS. 1 and 2 , the stator  12  and the rotor  14  are arranged face-to-face across a predetermined small gap, in a radial direction orthogonal to the rotation axis. The rotor  14  is arranged on an inner peripheral side of the stator  12 . 
         [0021]    The rotor  14  includes a rotor core  31  and a plurality of permanent magnets  32  that are arranged in the rotor core  31  in the circumferential direction thereof. The stator  12  includes a stator core  21 , and a coil  22  of a plurality of phases (such as three phases) arranged on the stator core  21 . A plurality of teeth  23  that protrude radially inward toward the rotor  14  are arranged on the stator core  21  at intervals (i.e., equidistant intervals) in the circumferential direction around the rotation axis. Slots  24  are formed extending in the rotation axis direction between the teeth  23  that are adjacent in the circumferential direction. A slot  24  is arranged between the teeth of each pair of adjacent teeth. In the example shown in  FIGS. 1 and 2 , the direction in which the plurality of teeth  23  are arranged matches the circumferential direction, and the direction in which the slots  24  extend matches the rotation axis direction. Magnetic poles are formed on the stator  12  by the coil  22  being wound around the teeth  23  through the slots  24  between the teeth  23 . The winding method is a distributed winding for example. 
         [0022]    As shown in  FIG. 3 , the coil  22  is formed by stacking together, in a radial direction (i.e., the direction in which the teeth protrude), a plurality of coil bodies  42  that extend in the rotation axis direction inside the slots  24 , and winding these coil bodies  42  around the teeth  23 . In  FIG. 3 , the teeth  23  and the coil  22  are only partially shown in the circumferential direction, but the structure of the portion that is not shown may be realized by the same structure as that of the portion that is shown. Each of the coil bodies  42  includes a conductor line  42   a,  and an insulator layer  42   b  that covers an outer periphery of the conductor line  42   a.  In the example shown in  FIG. 3 , the coil bodies  42  are arranged lined up in a row in the radial direction inside the slot  24 . In the example shown in  FIG. 3 , four layers of coil bodies  42  are lined up in the radial direction, but the number of coil bodies  42  that are lined up in the radial direction may be set as appropriate. 
         [0023]    In this example embodiment, magnetic layers  44  through which magnetic flux is able to easily pass are arranged sandwiched between the coil bodies  42  that are adjacent in the radial direction (i.e., in the protruding direction of the teeth protrude), as shown in  FIG. 3 . These magnetic layers  44  correspond to a magnetic body of the invention. A thickness t of the magnetic layers  44  in the radial direction becomes gradually thicker from the magnetic layer  44  arranged on the radially outer side (i.e., the root side of the teeth) toward the magnetic layer  44  arranged on the radially inner side (i.e., the tip end side of the teeth). That is, the thickness t of the magnetic layers  44  in the radial direction (i.e., the protruding direction of the teeth) becomes thicker as the distance to the rotor  14  becomes shorter. Each magnetic layer  44  extends substantially across the slot  24  (i.e., between adjacent teeth  23 ) in the circumferential direction, with a small space between the teeth  23  and both ends of the magnetic layer  44  in the circumferential direction. A width w1 of the magnetic layer  44  in the circumferential direction (i.e., the direction in which the teeth are arranged) is longer than a width w2 of the conductor line  42   a  in the circumferential direction (i.e., the direction in which the teeth are arranged). The magnetic layers  44  are thin sheets and are formed from members separate from the coil bodies  42 . However, the magnetic layers  44  may also be mounted on, or integrally formed with, a surface of the coil bodies  42  (i.e., the insulator layer  42   b ). 
         [0024]    With the rotary electric machine, each of the teeth  23  is magnetized in order, such that a rotating magnetic field that rotates in the circumferential direction is formed in the stator  12 , by flowing alternating current through the coil  22  of the plurality of phases (e.g., three phases). Also, electromagnetic interaction between the rotating magnetic field generated in the stator  12  and a field flux generated by the permanent magnets  32  of the rotor  14  applies torque (magnetic torque) to the rotor  14 , which enables the rotor  14  to be rotatably driven. This electromagnetic interaction is attraction and repulsion. In this way, the rotary electric machine is able to be made to function as an electric motor that has the rotor  14  generate power using electric power supplied to the coil  22 . On the other hand, the rotary electric machine is also able to be made to function as a generator that has the coil  22  generate electric power using the power of the rotor  14 . Also, the rotor  14  is not limited to a structure provided with the permanent magnets  32 . For example, the rotor  14  may also have a structure provided with a coil, or a structure that uses reluctance torque from a change in magnetic resistance. 
         [0025]    When applying torque between the stator  12  and the rotor  14 , magnetic flux acts between the stator  12  and the rotor  14 , and this magnetic flux flows through the teeth  23  in the radial direction. However, when the magnetic flux that flows through the teeth  23  becomes saturated, magnetic flux leaks out from the teeth  23  and flows out between adjacent teeth  23  (i.e., through the slot  24 ) in the circumferential direction. In particular, when the torque of the rotor  14  is large, magnetic flux that flows through the teeth  23  tends to become saturated, so magnetic flux tends to flow between the teeth  23  in the circumferential direction. The amount of leakage flux that flows between the teeth  23  in the circumferential direction increases toward the radially inner side (i.e., the tip end side of the teeth) where the distance to the rotor  14  where the magnetic flux acts is close, and decreases toward the radially outer side (i.e., the root side of the teeth) farther away from the rotor  14 . Here, as shown in  FIG. 4 , when considering a case in which the magnetic layers  44  are not provided, leakage flux  46  between the teeth  23  will flow through the coil bodies  42  (i.e., the conductor lines  42   a ) in the circumferential direction, and the amount of leakage flux will increase in the conductor lines  42   a  that are farther toward the radially inner side where the distance to the rotor  14  is closer. Also, when the leakage flux  46  that flows through the coil bodies  42  between the teeth  23  fluctuates, an eddy current will flow through the conductor lines  42   a.  As a result, loss will occur due to this eddy current. In particular, an eddy current from a fluctuation in the leakage flux  46  between the teeth  23  tends to be larger, and thus the loss from the eddy current tends to be greater, in conductor lines  42   a  that are farther toward the radially inner side where the distance to the rotor  14  is closer. 
         [0026]    In contrast, in this example embodiment, the magnetic layers  44  are arranged between coil turns (i.e., between coil bodies  42 ) in the slots  24 , so the leakage flux  46  between the teeth  23  flows mainly through the magnetic layers  44  in the circumferential direction, as shown in  FIG. 5 . Furthermore, the thickness t of the magnetic layers  44  in the radial direction is thicker for the magnetic layers  44  that are farther toward the radially inner side where the distance to the rotor  14  is short and a large amount of leakage flux is generated. As a result, more of the leakage flux  46  flows through the magnetic layers  44  that are farther toward the radially inner side where a large amount of leakage flux is generated, and the leakage flux  46  that flows through the magnetic layers  44  becomes less farther toward the radially outer side where the leakage flux decreases. Therefore, leakage flux between the teeth  23  is able to be inhibited from flowing through the coil bodies  42  (i.e., the conductor lines  42   a ) from the tip end side of the teeth all the way to the root side of the teeth, so an eddy current can be inhibited from being generated in the conductor lines  42   a  from the tip end side of the teeth all to way to the root side of the teeth. As a result, loss due to the eddy current is able to be inhibited. Furthermore, the thickness of the magnetic layers  44  is a thickness according to the amount of leakage flux between the teeth  23 , so the conductor space factor in the slot  24  is able to be prevented from decreasing. 
         [0027]    Moreover, in this example embodiment, the width w1 of the magnetic layers  44  in the circumferential direction is longer than the width w2 of the conductor lines  42   a  in the circumferential direction, so leakage flux between the teeth  23  is able to more easily be made to flow through the magnetic layers  44 . 
         [0028]    Also, in this example embodiment, the coil bodies  42  are arranged lined up in a row in the radial direction, so the coil bodies  42  and the magnetic layers  44  are able to be arranged without gaps in between, which enables the conductor space factor in the slot  24  to be improved. 
         [0029]    In the example embodiment described above, the magnetic layer  44  does not necessarily have to be arranged between all of the coil bodies  42  that are lined up in the radial direction. For example, the magnetic layer  44  may be arranged only between the coil bodies  42  on the radially inner side (i.e., on the tip end side of the teeth) where the distance to the rotor  14  is short, and the magnetic layer  44  may be omitted between the coil bodies  42  on the radially outer side (i.e., on the root side of the teeth) farther away from the rotor  14 . 
         [0030]    In the example embodiment described above, a case in which the coil  22  is wound around the teeth  23  in a distributed winding is described, but the coil  22  may also be wound around the teeth  23  by a winding method other than a distributed winding. For example, the coil  22  may also be wound around the teeth  23  in a concentrated winding. 
         [0031]    In the example embodiment described above, a case in which the invention is applied to a radial type rotary electric machine is described, but the invention may also be applied to an axial type rotary electric machine. 
         [0032]    While the invention has been described with reference to example embodiments thereof, it should be understood that the invention is not limited in any way to these example embodiments. That is, the invention may of course be carried out in modes that have been modified in any of a variety of ways without departing from the scope thereof.