Patent Description:
In order to make a rotating electric machine compact and have technical advantages, it is necessary to wind a coil in an efficient manner and reduce loss such as copper loss or iron loss. <CIT> (<CIT>) discloses that a flat wire having a concave portion and a convex portion is used as a stator winding of a rotating electric machine and that flat-wire coils are disposed in a slot such that the convex portions and the concave portions of the adjacent flat-wire coils are fitted with each other, thereby increasing a space factor of the coils in the slot.

It is described in <CIT> (<CIT>) that a magnetic body layer that serves as a wire used for a coil of an electromagnet is provided on a surface layer of a conductor to increase an attractive force of the electromagnet. In an embodiment where this wire is used as a winding for a distributed winding coil of the stator in the rotating electric machine, the plural wires having a circular cross section are accommodated in a single slot.

It is disclosed in <CIT> (<CIT>) that thickness of an insulating layer coated on a flat coil wire or a type of an insulating material is changed between a coil end portion and a slot portion to reduce the size of the rotating electric machine. It is also described that, as a field buffer layer that reduces a steep surge voltage of an inverter, an electroconductive polymer layer or a layer of epoxy resin or the like in which a conductive filler or a semi-conductive filler is mixed is provided on a surface of a coil conductor or a surface of the insulating layer. Further prior-art is <CIT> and <CIT>.

Although the space factor can be increased with use of the flat wire that has the concave portion and the convex portion, eddy-current loss that is caused by a leakage magnetic flux may be increased due to a reduced resistance value of the conductor that consequently promotes a current flow. The eddy-current loss can be reduced by providing the magnetic body layer on the surface layer of the conductor. However, the space factor is reduced by the thickness of the magnetic body layer.

The present invention provides a stator of a rotating electric machine that can increase a space factor of a coil winding in a slot and that can reduce eddy-current loss. The invention is defined in the independent claims <NUM> and <NUM>.

Because a leakage magnetic flux in the stator of the rotating electric machine passes through the magnetic body layer provided around the flat conductor section but does not pass through the flat conductor section, it is possible to reduce the eddy-current loss in the flat conductor section. Therefore, it is possible to reduce the eddy-current loss while increasing the space factor by use of a flat wire.

In the stator of the rotating electric machine according to claim <NUM>, the coil having the magnetic body layer in the coil body is disposed one turn apart from each other in the radial direction.

In the stator of the rotating electric machine, the magnetic body layers are overlapped between the adjacent coils among the coils that are wound for plural turns in the radial direction. Accordingly, the coils having the magnetic body layer are disposed one turn apart from each other in the radial direction. Therefore, it is possible by removing the overlapped magnetic body layers to further increase the space factor of the coil body in the slot and to effectively reduce the eddy-current loss.

Furthermore, in the stator of the rotating electric machine according to claim <NUM>, the coil of one turn having the magnetic body layer in the coil body is only disposed on an innermost peripheral side of the slot.

A leakage magnetic flux from a rotor that passes through the stator of the rotating electric machine is high on the innermost peripheral side in the radial direction. The coil having the magnetic body layer is only disposed on this innermost peripheral side, and the magnetic body layer is not provided for coil of the other turns. Therefore, it is possible to effectively reduce the eddy-current loss and to further increase the space factor of the coil body in the slot.

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:.

A detailed description will hereinafter be made with reference to the drawings. In the following description, a coil body is wound according to a distributed winding method. However, the coil body may be disposed as a single conductor in a slot in a circumferential of a stator core direction and wound for plural turns in the slot in a radial direction of the stator core. For example, the coil body includes one that is wound by a wave winding method. In addition, a flat conductive wire with a rectangular cross section is used as a coil in the following description. However, a conductive wire having a substantially rectangular cross section whose corners are rounded, a conductive wire having a substantially ellipsoidal cross section, or the like may be used. The number of slots in the stator core, and the number of turns, dimension, thickness and the like of the coil, which will be described below, are for an illustrative purpose only, and thus they can appropriately be changed according to a specification of a stator in a rotating electric machine.

The same or corresponding elements are denoted with the same reference numerals below, and their description will not be repeated.

<FIG> is a view for showing a stator <NUM> of a rotating electric machine, in which <FIG> is a cross-sectional view of a slot and <FIG> is a cross-sectional view of the coil. The stator <NUM> of the rotating electric machine is combined with a rotor, which is not shown, to form the rotating electric machine, rotates the rotor in cooperation with the rotor by means of electromagnetic action generated by a passage of electric current to the coil, and outputs torque to a rotating shaft of the rotor.

The stator <NUM> of the rotating electric machine includes a stator core <NUM>, plural teeth <NUM>, <NUM> that are disposed in a circumferential direction of the stator core <NUM>, a slot <NUM> that is a space between the adjacent teeth <NUM>, <NUM>, and a coil body <NUM> that enters the slot <NUM> and is wound for plural turns.

The stator core <NUM> is a circular magnetic body member in which the plural teeth <NUM>, <NUM> are disposed on an inner peripheral side thereof. <FIG>, which will be described later, shows the stator core <NUM> having <NUM> of the teeth <NUM>, <NUM>. Such a stator core <NUM> is formed by stacking plural electromagnetic steel plates in a specified shape.

As shown in <FIG>, the coil body <NUM> is formed when the coils, each of which is disposed as a single conductor in the slot <NUM> in the circumferential direction, are wound for the plural turns in the slot <NUM> in the radial direction. In <FIG>, the circumferential direction is a direction θ while the radial direction is a direction R. In <FIG>, the coil body <NUM> is formed of coils <NUM>, <NUM>, <NUM>, <NUM> of four turns that are aligned in the radial direction. Each of the coils <NUM>, <NUM>, <NUM>, <NUM> is disposed between one end and another end of the slot <NUM> in the circumferential direction and is wound only for one turn. In other words, each of the coils <NUM>, <NUM>, <NUM>, <NUM> is disposed as the single conductor in the slot <NUM> in the circumferential direction.

Each of the coils <NUM>, <NUM>, <NUM>, <NUM> is inserted from one side of the stator core <NUM> in an axial direction, passes through the slot <NUM>, exits from the other end thereof, and is inserted in another slot that is six slots away from the slot along the circumferential direction of the stator core <NUM>. Accordingly, each of the coils <NUM>, <NUM>, <NUM>, <NUM> constitutes a stator winding according to the distributed winding method in which the above process is performed repeatedly.

As shown in <FIG>, the coil <NUM> includes a flat conductor section <NUM>, a magnetic body layer <NUM> that is provided around the flat conductor section <NUM>, and an insulating film <NUM> that is provided around the magnetic body layer <NUM>.

The flat conductor section <NUM> is a conductive wire having a rectangular cross section that is perpendicular to a direction in which the conductor extends. A highly conductive metal can be used as a conductor material. As the highly conductive metal, copper or the like can be used.

The magnetic body layer <NUM> is a ferromagnetic body layer having conductivity with which an entire outer periphery of the flat conductor section <NUM> is coated in a uniform and continuous manner. A material used for the magnetic body is an iron-nickel alloy, and a method of plating is used to form the magnetic body layer <NUM> on the outer periphery of the flat conductor section <NUM>. In one example, thickness of the magnetic body layer <NUM> is approximately <NUM>. A material used for the magnetic body may be a soft magnetic material, iron, or nickel.

The insulating film <NUM> is an electrically insulating resin layer with which an entire outer periphery of the magnetic body layer <NUM> is coated in the uniform and continuous manner. An enamel coating composed of polyamideimide is used for the insulating film <NUM>. Thickness of the insulating film <NUM> is determined by the insulating specification of the stator <NUM> of the rotating electric machine or the like. In one example, the thickness is approximately <NUM> to <NUM>. The enamel coating used for the insulating film <NUM> may be of polyesterimide, polyimide, polyester, formal, or the like. Alternatively, a glass fiber coating may be used in which a glass fiber is wound and impregnated with an alkyd resin or the like. In addition to the formation of a film by coating, either a film composed of polyimide, polyester, polyethylene naphthalate, or the like or a thin film sheet may be wrapped.

As for the coil <NUM>, only the single conductor is disposed in the circumferential direction of the slot <NUM>. In other words, the coil <NUM> of only one turn is disposed in the circumferential direction in the slot <NUM>. The flat conductor section <NUM> of the coil <NUM> has the rectangular cross section, and each side of the rectangular shape is parallel with or perpendicular to an inner wall surface of the slot <NUM>. Accordingly, the magnetic body layer <NUM> has a rectangular frame shape, and each side of the rectangular frame shape is also parallel with or perpendicular to the inner wall surface of the slot <NUM>.

A detailed description will be made on advantages of the above configuration with reference to <FIG> and <FIG>. These drawings correspond to <FIG>, and the coils of four turns are disposed in the radial direction of the slot <NUM>. Of the coils of four turns, only one of them is denoted with a reference numeral. <FIG> shows an example using a coil <NUM> of related art that is not provided with the magnetic body layer and only has the flat conductor section <NUM> and the insulating film <NUM>. <FIG> is a view that corresponds to <FIG>, and a coil <NUM> that is provided with the magnetic body layer <NUM> is used.

<FIG> shows directions of leakage magnetic fluxes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> that are leaked from a rotor side of the rotating electric machine to the stator core <NUM> side. The leakage magnetic flux passes through the coil <NUM> in the slot <NUM> when it enters the tooth <NUM> from the rotor side and then to the tooth <NUM>. The coil <NUM> is formed of the flat conductor section <NUM> made of copper and the insulating film <NUM> of an insulating body, and has lower magnetic permeability than the teeth <NUM>, <NUM>. Accordingly, the directions of the leakage magnetic fluxes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are not influenced by the presence or absence of the coil <NUM>. In consideration of above, it can be understood that the leakage magnetic fluxes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> pass through a copper portion of the flat conductor section <NUM> in the coil <NUM>, and this is where the eddy-current loss occurs.

In <FIG>, the coil <NUM> has the magnetic body layer <NUM> with which the periphery of the flat conductor section <NUM> is coated. Because the magnetic body layer <NUM> is a ferromagnetic body, the magnetic permeability thereof is hundreds of times higher than the magnetic permeability of the flat conductor section <NUM> that is made of copper. Accordingly, the magnetic fluxes tend to pass through the magnetic body layer <NUM> instead of the flat conductor section <NUM> made of copper. As shown in <FIG>, leakage magnetic fluxes <NUM>, <NUM>, <NUM>, <NUM>, <NUM> from the rotor side pass through the magnetic body layer <NUM> but does not pass through the flat conductor section <NUM> made of copper. Therefore, compared to a case in <FIG>, the eddy-current loss that occurs in the flat conductor section <NUM> is significantly reduced.

In addition, the magnetic body layer <NUM> is not a separate component that is combined with the flat conductor section <NUM>, but is integrally formed with the magnetic body layer <NUM> by plating such that the periphery of the flat conductor section <NUM> is coated therewith. Accordingly, a special assembling process is not necessary to dispose the magnetic body layer <NUM>, and thus the flat conductor section <NUM> and the magnetic body layer <NUM> are not displaced with respect to each other when the coils <NUM>, <NUM>, <NUM>, <NUM> are inserted and wound in the slot <NUM>.

<FIG> is a view for showing a configuration according to an embodiment of the claimed invention in which, among the coils <NUM>, <NUM>, <NUM>, <NUM> of four turns that are disposed in the radial direction of the coil body <NUM>, only the coils <NUM>, <NUM> that are disposed one turn apart from each other in the radial direction are provided with the magnetic body layer <NUM> while the coils <NUM>, <NUM> are not provided with the magnetic body layer <NUM>. If the magnetic body layer <NUM> is provided for all of the coils <NUM>, <NUM>, <NUM>, <NUM> as shown in <FIG>, the magnetic body layers <NUM> are circumferentially overlapped between the adjacent coils due to the rectangular cross sections of the coils <NUM>, <NUM>, <NUM>, <NUM>. In <FIG>, the coils <NUM>, <NUM> that have the magnetic body layer <NUM> are disposed one turn apart from each other, and thus two of the overlapped magnetic body layers <NUM> are removed.

<FIG> shows directions of leakage magnetic fluxes <NUM>, <NUM>, <NUM> in the configuration shown in <FIG>. The magnetic body layer <NUM> has the magnetic permeability that is hundreds of times higher than copper. Accordingly, even when one of the circumferentially overlapped magnetic body layers <NUM> between the adjacent coils is removed, the directions of the leakage magnetic fluxes <NUM>, <NUM>, <NUM> are hardly changed from those shown in <FIG>. In addition, among the coils <NUM>, <NUM>, <NUM>, <NUM> of four turns that are accommodated in the single slot <NUM>, the coils <NUM>, <NUM> of two turns are not provided with the magnetic body layer <NUM>. Accordingly, it is possible to increase a sectional area of the flat conductor section <NUM> of each of the coils <NUM>, <NUM>, <NUM>, <NUM> by thickness of the magnetic body layers <NUM> that are not provided in the coils <NUM>, <NUM>. Therefore, compared to the configuration in <FIG>, it is possible to minimize a reduction in a space factor that is caused by providing the magnetic body layer <NUM> while equally reducing the eddy-current loss, and thus it is possible to restrict a reduction in copper loss that is caused by providing the magnetic body layer <NUM>.

<FIG> is a view for showing a configuration of an embodiment according to the claimed invention in which, among the coils <NUM>, <NUM>, <NUM>, <NUM> of four turns in the radial direction of the coil body <NUM>, only the coil <NUM> of one turn that is disposed on an innermost peripheral side of the slot <NUM> has the magnetic body layer <NUM>. The leakage of magnetic flux from the rotor side is higher in a position near the rotor and is lower in a position away from the rotor. Accordingly, the eddy-current loss that is caused by the leakage magnetic flux is the highest in the coil <NUM> on the innermost peripheral side of the slot <NUM>, while the eddy-current loss is gradually reduced in the order of the coils <NUM>, <NUM>, <NUM> that are disposed on the outer peripheral side in the slot <NUM>.

<FIG> shows directions of leakage magnetic fluxes <NUM>, <NUM> in the configuration shown in <FIG>. Because the coil <NUM> on the innermost peripheral side in the slot <NUM> has the magnetic body layer <NUM>, the leakage magnetic flux <NUM> having the highest amount of magnetic flux can pass through this magnetic body layer <NUM>. This prevents the leakage magnetic flux <NUM> from passing through the flat conductor section <NUM> in the coil <NUM> on the innermost peripheral side. Meanwhile, the coil <NUM> that is adjacent to the coil <NUM> on the outer peripheral side is not provided with the magnetic body layer <NUM>. Because the leakage magnetic flux <NUM> is introduced to and passes through the magnetic body layer <NUM> of the coil <NUM>, the leakage magnetic flux <NUM> hardly passes through the flat conductor section <NUM> of the coil <NUM>. Furthermore, although the coils <NUM>, <NUM> provided on the further outer peripheral side are not provided with the magnetic body layer <NUM>, the leakage magnetic flux that passes through the flat conductor sections <NUM> thereof is extremely low.

Claim 1:
A stator of a rotating electric machine, the stator comprising
a stator core having plural slots (<NUM>) disposed in a circumferential direction of the stator core (<NUM>); and
a coil body (<NUM>) comprising a plurality of coils, each coil of the plurality of coils being disposed as a single conductor in a slot of the plural slots in the circumferential direction of the stator core, and each of the plurality of coils being wound for a single turn in the slot of the plurality of slots in a radial direction of the stator core, characterized in that
the coil body includes a plurality of first coils (<NUM>, <NUM>) and one or more second coils (<NUM>, <NUM>), wherein the plurality of first coils are disposed one turn apart from each other in a radial direction of the stator core,
the plurality of first coils are each configured with a flat conductor section (<NUM>), a magnetic body layer (<NUM>) provided around the flat conductor section and an insulating film (<NUM>) provided around the magnetic body layer, wherein only the plurality of first coils are provided with the magnetic body layer, and
the one or more second coils are each configured with a flat conductor section, and an insulating film.