Stator segment and motor

A stator segment arranged to define a portion of an annular stator includes a core segment including a core back portion arranged to extend in a circumferential direction of the stator, and a tooth portion arranged to extend from the core back portion in a radial direction of the stator; a coil wound around the tooth portion and including a pair of coil wire terminals; an insulating layer arranged between the coil and the tooth portion; and a resin layer arranged to seal the entire coil except for the pair of coil wire terminals. Circumferential end walls of the resin layer are arranged circumferentially inward of circumferential end walls of the core back portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inner-rotor motor in which a stator includes a plurality of stator segments. In particular, the present invention relates to a wiring configuration of a stator.

2. Description of the Related Art

In general, motors have a variety of potential performance levels that are varied depending on the intended purposes of the motors. The number of poles of a rotor, the number of slots of the stator, the direction of the winding of coils, the arrangement of the coils, and so on are designed in accordance with a desired performance of the motor. Thus, there are a large variety of wiring configurations available for motors.

For instance, referring toFIG. 1A, in an 8-pole 12-slot motor, a group of four coils connected in parallel may be provided for each of a U phase, a V phase, and a W phase. Moreover, the groups of coils for the respective phases may be connected in a Y configuration. A wiring configuration in which groups of coils connected in parallel are connected in the Y configuration will be referred to as “parallel connection”.

Meanwhile, a wiring configuration different from the parallel connection may be adopted for a 14-pole 12-slot motor. Specifically, referring toFIG. 1B, two coils are connected in series to define a sub-coil group. Winding directions of the two coils connected in series are opposite to each other. Two sub-coil groups are connected in parallel to define a group of coils for each of the U phase, the V phase, and the W phase, and the groups of coils for the respective phases are connected in the Y configuration. A wiring configuration in which sub-coil groups, each of which is made up of a group of coils connected in series, are used will be referred to as “series-parallel connection”.

As described above, different types of motors, even motors having the same number of slots, may have greatly different wiring configurations depending on the motor design thereof. Therefore, production equipment, such as a winding machine and so on, and a manufacturing procedure need to be suitably arranged for each type of motor. This presents an impediment to improving productivity.

Thus, a variety of configurations have been conceived to improve the productivity (see, for example, JP-A 2006-50690 and JP-A 2007-244008).

JP-A 2006-50690 discloses a stator in which a plurality of coils which are continuously wound are arranged to have the same winding direction in order to facilitate a winding operation for the coils which are continuously wound.

JP-A 2007-244008 discloses a rotary electrical machine including a power supply portion. The power supply portion includes a plurality of conductive members, each of which is arranged to connect coils to one another, and a holding member arranged to hold the plurality of conductive members. The power supply portion is configured so as to be compatible with a plurality of different wiring configurations, such as the Y configuration and a delta configuration. Specifically, the holding member includes four concentric common grooves defined therein. In addition, conductive members for the U phase, the V phase, and the W phase, a conductive member for common use, and so on are fitted in the common grooves.

JP-A 2009-017666 discloses a motor in which busbars are held in an insulator (JP-A 2009-017666).

However, in the cylindrical stator of the motor described in Japanese Patent No. 4281733, circumferential side surfaces of the resin covers of the stator segments are arranged to be in contact with one another. Therefore, it is difficult to allow the stator to have a sufficient degree of circularity for some specific purposes.

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide an improvement in an amount of circularity of a cylindrical stator defined by a plurality of stator segments that have been assembled together.

A stator according to a preferred embodiment of the present invention preferably includes stator segments which are arranged to define a portion of a substantially annular stator, and which include a core segment preferably including a core back portion arranged to extend in a circumferential direction of the stator and a tooth portion arranged to extend from the core back portion in a radial direction of the stator; a coil wound around the tooth portion and including a pair of coil wire terminals; an insulating layer arranged between the coil and the tooth portion; and a resin layer arranged to seal the entire coil except for the pair of coil wire terminals. Circumferential end walls of the resin layer are preferably arranged circumferentially inward of circumferential end walls of the core back portion.

In the above-described stator segment, the circumferential end walls of the resin layer are preferably arranged circumferentially inward of circumferential end walls of the core segment. Therefore, when stator segments according to the above-described preferred embodiment of the present invention are arranged in a substantially annular shape to thereby define the stator, the circumferential end walls of the core segments are arranged to be in contact with one another. It is therefore possible to provide a stator including accurately provided core segments. This makes it possible to achieve improved circularity of a cylindrical stator that is defined by stator segments that have been assembled together.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following description is meant to be merely illustrative, and should not be construed to restrict the scope of the present invention, applications thereof, or purposes thereof.

A stator according to a preferred embodiment of the present invention is provided with a supporting structure arranged to allow wiring members connected with coil wire terminals to be attached to and removed from the stator. Examples of such wiring members include, for example, a passage-line busbar arranged to connect a plurality of coils belonging to the same phase in series with each other, and a common busbar arranged to function as a neutral point.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to an example in which the wiring members preferably are passage-line busbars (a first preferred embodiment), and an example in which the wiring member preferably is a neutral point busbar (a second preferred embodiment).

First Preferred Embodiment

FIG. 2illustrates a motor1A according to a first preferred embodiment of the present invention. The motor1A preferably is an inner-rotor brushless motor to be installed in a vehicle, and is preferably used to drive an electric power steering, for example. In particular, the motor1A has an ability to switch between parallel connection and series-parallel connection, using the same stator. This is accomplished by attaching the passage-line busbars to the stator or removing the passage-line busbars from the stator when assembling the motor1A.

Referring toFIG. 2, the motor1A preferably includes a casing2, a busbar unit11, a stator12, a rotor13, a shaft6, and so on. A center of each of the rotor13, the stator12, and the busbar unit11coincides with a center S (i.e., a rotation axis of the motor1A) of the shaft6.

The casing2preferably includes a receptacle2awhich includes a bottom and is substantially cylindrical, and a substantially disc-shaped lid2b. The lid2bis preferably secured to a flange of the receptacle2a. The flange of the receptacle2ais arranged to project radially outward around a circumference of an opening of the receptacle2a. The stator12and so on are contained inside the receptacle2a. A through hole3is defined in a central portion of the lid2b. A bearing portion4is defined at a central portion of a bottom surface of the receptacle2a.

Bearings5are preferably arranged in the bearing portion4and inside the through hole3. The shaft6is supported through the bearings5to be rotatable with respect to the casing2. One end portion of the shaft6is arranged to project outward from the lid2bthrough the through hole3. The end portion of the shaft6is preferably connected to the electric power steering through a speed reducer (not shown), for example.

The rotor13is preferably fixed to a middle portion of the shaft6such that the rotor13and the shaft6are coaxial with each other. The rotor13preferably includes a substantially cylindrical rotor core13a, a magnet13b, and so on. The magnet13bis arranged on an outer circumferential surface of the rotor core13a. The magnet13bincludes north and south poles arranged alternately in a circumferential direction. Note that the magnet13bmay alternatively be arranged inside the rotor core13a, as long as the magnet13bis arranged near an outer circumference of the rotor core13a. The stator12of the motor1A according to the first preferred embodiment is compatible with different numbers of magnetic poles. Therefore, the number of magnetic poles of the rotor13may be set to eight, fourteen, and so on, for example.

The stator12, which is substantially cylindrical, is fixed to an inner circumferential surface of the receptacle2a, and is arranged to surround the rotor13. An inner circumferential surface of the stator12and an outer circumferential surface of the rotor13are arranged opposite each other with a slight gap therebetween. The busbar unit11is attached to an end portion of the stator12. InFIG. 2, reference numeral “7” indicates a rotation angle sensor arranged to detect a rotation angle.

The stator12preferably includes a plurality of (for example, preferably twelve in the first preferred embodiment) stator segments50joined together. Referring toFIGS. 3 and 4, each stator segment50preferably includes a core segment51, insulators52, a coil53, and a resin layer54. Specifically, the core segment51is preferably defined by, for example, laminated steel sheets each of which is substantially in the shape of the letter “T”. The core segment51preferably includes a core back portion51a, a tooth portion51b, and so on. The core back portion51aof each core segment51is joined to the core back portions51aof other core segments51. The core back portion51apreferably has across section substantially in the shape of a minor arc. The tooth portion51bis preferably arranged to extend from a substantial middle portion of the core back portion51atoward the center S. The insulators52(i.e., an insulating layer) are attached to the core segment51.

Each coil53is defined by a conductor wire, such as, for example, an enamel-coated copper wire, wound around the tooth portion51bof a separate one of the core segments51with the insulators52attached thereto. That is, the number of coils53is preferably twelve, for example, in the first preferred embodiment. Slots (i.e., gaps) are defined between adjacent ones of the tooth portions51bin the stator12, and the conductor wires of the coils53are accommodated in the slots. The coil53of each stator segment50preferably has the same winding direction.

Both end portions (hereinafter also referred to as coil wire terminals55) of the conductor wire wound around the tooth portion51bare drawn out through the same end portion (i.e., an end portion facing the opening of the receptacle2a, and hereinafter also referred to as an opening-side end portion50a) of the stator segment50. The coil wire terminals55are arranged to extend in parallel or substantially in parallel with the shaft6when arranged in the motor1A. Note that the coil wire terminals55are drawn out from each stator segment50. Therefore, a total of twenty-four coil wire terminals55are preferably drawn out from the stator12according to the first preferred embodiment.

Each coil53, except for top portions of the two coil wire terminals55, is preferably buried in the resin layer54, which is preferably defined by, for example, a molding process. A base portion of each coil wire terminal55is held by the resin layer54, so that the coil wire terminals55are positioned at predetermined positions. Moreover, the base portion of the coil wire terminal55being buried in the resin layer54makes the top portion of the coil wire terminal55, which is arranged to project out above the resin layer54, unlikely to bend. This enables the top portion of each coil wire terminal55to be stably held so as to extend substantially in a straight line.

A wiring groove segment21a(i.e., a supporting structure segment) is preferably defined in an end surface of the resin layer54which faces the opening-side end portion50a. The wiring groove segment21ais capable of accommodating a passage-line busbar24, which will be described below. In more detail, the wiring groove segment21ais arranged to extend in or substantially in a circular arc along the core back portion51a. When the stator segments50are joined together, the wiring groove segments21aof adjacent ones of the stator segments50are joined to each other to define an annular or substantially annular wiring groove21extending in a circumferential direction of the stator12. The coil wire terminals55are arranged in the circumferential direction of the stator12along the wiring groove21.

A first fixing portion22arranged to fix an adapter62, which will be described below, is preferably defined in the resin layer54. Referring toFIG. 5, the first fixing portion22according to the first preferred embodiment is preferably arranged to project radially inward from a predetermined portion of the resin layer54which faces the opening-side end portion50a. In addition, a first positioning portion23arranged to circumferentially position the adapter62is also preferably defined in the resin layer54. Referring toFIG. 6, the first positioning portion23according to the first preferred embodiment is defined by a recess defined at a predetermined portion of the end surface of the resin layer54which faces the opening-side end portion50a. Note that the first fixing portion22and a second fixing portion25are not shown inFIGS. 3,4,8, and9.

Referring toFIG. 4, a first core exposure portion51c, where a portion (specifically, a middle portion in a longitudinal direction) of the core back portion51ais exposed, is preferably arranged in the opening-side end portion50aof the stator segment50. A second core exposure portion51d, where a large portion of the core back portion51ais exposed, is preferably arranged in an end portion of the stator segment50opposite to the opening-side end portion50a. Referring toFIG. 7, when the resin layer54is molded, the second core exposure portion51dis received by a reference surface H of a mold. Then, the first core exposure portion51cis pressed toward the reference surface H as indicated by an arrow inFIG. 7. The core segment51and so on are preferably held by the mold with the first core exposure portion51cand the second core exposure portion51dsandwiched by different portions of the mold. A gate is preferably arranged on a side closer to the second core exposure portion51d. Therefore, a gate mark28is defined in the end portion of the stator segment50opposite to the opening-side end portion50a.

The busbar unit11is arranged on the end surface of the resin layer54which faces the opening-side end portion50a. Therefore, it is necessary to ensure a sufficient accuracy of a distance L between the end surface of the resin layer54which faces the opening-side end portion50aand the second core exposure portion51dof each stator segment50to allow the end surfaces of the resin layers54of all the stator segments50to be flush with one another when the stator segments50have been joined together. The sufficient accuracy of the distance L between the end surface of the resin layer54which faces the opening-side end portion50aand the second core exposure portion51dis ensured by holding the first core exposure portion51cand the second core exposure portion51din the above-described manner when molding the resin layer54, even when the stator segments50are mass-produced.

Referring toFIGS. 8 and 9, the busbar unit11and the passage-line busbars24are preferably attached to an end portion (i.e., an end portion facing the opening of the receptacle2a, and hereinafter referred to also as an opening-side end portion12a) of the stator12through which the coil wire terminals55are drawn out.

The motor1A according to the first preferred embodiment is preferably configured such that the coils53can be connected either according to the parallel connection (i.e., a first connection state) or according to the series-parallel connection (i.e., a second connection state).FIG. 8illustrates a case where the coils53are connected according to the parallel connection, whereasFIG. 9illustrates a case where the coils53are connected according to the series-parallel connection.

A busbar unit11A (seeFIG. 8and so on) dedicated to the parallel connection or a busbar unit11B (seeFIG. 9and so on) dedicated to the series-parallel connection is preferably used as the busbar unit11of the motor1A depending on whether the parallel connection is desired or whether the series-parallel connection is desired. The busbar unit11includes a plurality of (for example, preferably four in the first preferred embodiment) busbars61and the adapter62, which has an insulating property and is arranged to support the busbars61. Details of the busbar unit11A, which is used in the case where the parallel connection is adopted, are illustrated inFIGS. 10 and 11, for example.

The busbars61according to the first preferred embodiment preferably include three phase busbars61u,61v, and61wand a common busbar61x. The phase busbars61u,61v, and61ware connected to a U phase, a V phase, and a W phase of the stator12, respectively. The common busbar61xis connected to the neutral point. That is, the coils53according to the first preferred embodiment are connected in a Y configuration.

Each of the busbars61preferably is a belt-shaped conductor having the same or substantially the same thickness in its entirety. The busbar61preferably includes a body portion65shaped like a long and narrow band plate, and a plurality of terminal portions66each shaped like a band plate. The body portion65is preferably bent in a thickness direction to assume a substantially annular shape (or alternatively the shape of the letter “C”). Each of the terminal portions66is preferably defined integrally with the body portion65as a single monolithic member, for example. In the first preferred embodiment, body portions65u,65v, and65wof the phase busbars61u,61v, and61w, respectively, are provided with four terminal portions66u,66v, and66w, respectively, while a body portion65xof the common busbar61xis provided with twelve terminal portions66x. Hereinafter, the suffixes “u”, “v”, “w”, and “x” will be omitted unless the U phase, the V phase, the W phase, and the common needs to be discriminated from one another for the sake of description. For example, each of the phase busbars61u,61v, and61w, and the common busbar61xmay be referred to simply as the busbar61.

Note that busbars61which are used in the case of the series-parallel connection are provided with different numbers of terminal portions66from those of the terminal portions66provided in the busbars61which are used in the case of the parallel connection. In the case of the series-parallel connection, each of the phase busbars61is preferably provided with two terminal portions66, while the common busbar61xis preferably provided with six terminal portions66x, for example. The shape and other characteristics of the busbars61used in the case of the series-parallel connection are otherwise similar to those of the busbars61used in the case of the parallel connection.

The phase busbars61u,61v, and61ware additionally provided with two connection end portions67u,67v, and67w, respectively, each of which is shaped like a band plate and defined integrally with the body portion65. Note that the two connection end portions67u,67v, or67wmay be joined together into one body. Each of the connection end portions67preferably has a rectangular shape or a substantially rectangular shape, for example. In addition, the connection end portions67are arranged to extend from both ends of the body portion65in the same direction perpendicular or substantially perpendicular to the body portion65. The connection end portions67are arranged on an opposite side of the body portion65with respect to the terminal portions66.

Each of the terminal portions66(66u,66v,66w, and66x) is preferably hook-shaped, and arranged at a predetermined position on a side end of the body portion65. Each terminal portion66includes a terminal overhang portion63and a terminal top portion66c. The terminal overhang portion63is arranged to project sideways from a predetermined portion of the body portion65which is longitudinally away from the connection end portions67. The terminal top portion66cis arranged to extend continuously from a top of the terminal overhang portion63. In more detail, the terminal overhang portion63preferably includes a terminal base portion66a, which has a relatively small length, and a terminal middle portion66b. The terminal base portion66ais arranged to project sideways from a predetermined portion of the side end of the body portion65to extend in a direction perpendicular or substantially perpendicular to the body portion65. The terminal middle portion66bis preferably continuous with a top of the terminal base portion66a, and is preferably arranged to bend radially outward from the top of the terminal base portion66ato extend in a direction perpendicular or substantially perpendicular to the terminal base portion66a. The terminal top portion66cis preferably continuous with the terminal middle portion66b, and is preferably arranged to bend therefrom to a side opposed to the body portion65to extend in a direction perpendicular or substantially perpendicular to the terminal middle portion66b.

The busbar61can be produced by bending an in-process material stamped out of a metal sheet (press working), for example. In the first preferred embodiment, however, the busbar61is preferably produced by processing a single bare electric wire (e.g., a bare copper wire68) without an insulating coating.

FIGS. 12A,12B,12C,12D, and12E illustrate a procedure for manufacturing the busbar61in accordance with a preferred embodiment of the present invention. First, as illustrated inFIG. 12A, the bare copper wire68(i.e., a wire) having a predetermined length is prepared. A general-purpose bare copper wire may be used as the bare copper wire68. For example, a bare copper wire having a diameter of about 2 mm, for example, may be used as the bare copper wire68.

Next, as illustrated inFIG. 12B, the bare copper wire68is bent to define body defining portions69, terminal defining portions70, and connection end defining portions71. The body defining portions69are to define the body portion65. The terminal defining portions70are to define the terminal portions66. The connection end defining portions71are to define the connection end portions67. Specifically, each terminal defining portion70is defined by bending the bare copper wire68at a predetermined middle portion thereof so that two portions of the bare copper wire68on both sides of the bend are essentially arranged to extend in parallel or substantially in parallel and at close proximity with each other, and then bending the two portions of the bare copper wire68by an angle of, for example, about 90 degrees in mutually opposite directions at positions a predetermined distance away from the aforementioned bend.

The body defining portions69and the terminal defining portions70are preferably defined one after another by bending the bare copper wire68, so that a plurality (for example, preferably four in the case of each of the phase busbars61, and preferably twelve in the case of the common busbar61x) of terminal defining portions70are defined and arranged to project sideways in a direction perpendicular or substantially perpendicular to the body defining portions69extending in a straight line or substantially in a straight line. Each of the terminal defining portions70is defined on the same side of the body defining portions69. The connection end defining portions71are defined by bending both end portions of the bare copper wire68by an angle of about 90 degrees to an opposite side of the body defining portions69with respect to the terminal defining portions70. The terminal defining portions70and the connection end defining portions71are arranged to be flush or substantially flush with one another, and extend in parallel or substantially in parallel with one another. Note that, in the case of the common busbar61x, no connection end defining portions71are defined because the common busbar61xis not provided with any connection end portion67.

Next, as illustrated inFIG. 12C, the entire bare copper wire68with the terminal defining portions70and so on defined therein is rolled, i.e., pressed from directions perpendicular to the directions in which the bare copper wire68has been bent, to define an in-process material72. The in-process material72, which is preferably shaped like a band plate and has a shape in accordance with a predetermined development, is obtained by rolling the entire bare copper wire68. If the in-process material72having the above-described shape was produced by stamping a metal sheet, a large amount of scrap metal would result after the stamping. The present method of rolling the entire bare copper wire68, however, does not produce any scrap metal, making it possible to mass-produce the in-process materials72with a yield of 100% or about 100%.

As a result of the rolling of the single bare copper wire68, each of the body defining portions69and the connection end defining portions71assumes the shape of a band plate and has the same or substantially the same width. The body portion65and the connection end portions67are thus defined. Meanwhile, as a result of the rolling of the bare copper wire68, two portions of each terminal defining portion70which are arranged to extend in parallel or substantially in parallel with each other are united into a single body, so that the terminal portion66, having a large width, is defined.

In more detail, a pair of portions (hereinafter referred to as “elongated portions61s”) each of which is shaped like a band plate and, as a result of the rolling, has the same or substantially the same width as that of the body portion65or the like are arranged to project sideways from the body portion65in abutment with each other. Each of the pair of elongated portions61sis continuous with and integrally defined with a top portion (hereinafter referred to as a “top portion61t”) which is defined by a turning portion of the bare copper wire68rolled substantially into the shape of the letter “U”. The pair of elongated portions61sand the top portion61tmay preferably be united into a single monolithic body as a result of deformation by the rolling. The pair of elongated portions61sdefines the terminal overhang portion63. The top portion61tdefines the terminal top portion66c.

Finally, as illustrated inFIG. 12D, the in-process material72is bent at predetermined portions thereof to complete the busbar. Specifically, a base portion of each terminal portion66is bent by an angle of about 90 degrees to define the terminal base portion66a. Further, a middle portion of each terminal portion66is bent by an angle of about 90 degrees to define the terminal middle portion66band the terminal top portion66c. Furthermore, the body portion65is bent in the thickness direction to bring the two connection end portions67(or, in the case of the common busbar61x, both end portions of the body portion65) into abutment with each other, so that the body portion65assumes an annular or a substantially annular shape as illustrated inFIG. 12E.

The terminal defining portions70of different ones of the phase busbars61are preferably arranged to have different lengths. The terminal base portion66ais arranged to have the same length in each of the phase busbars61. The terminal top portion66cis also arranged to have the same length in each of the phase busbars61. As a result, the terminal middle portion66bis arranged to have a predetermined length which is different in each of the phase busbars61. Moreover, the body defining portions69are arranged to have a different total length in each of the phase busbars61. The body portion65is accordingly arranged to have a different diameter in each of the phase busbars61.

According to the first preferred embodiment, each terminal defining portion70of the common busbar61xis arranged to have a smaller length than that of the terminal defining portion70of any of the phase busbars61. The terminal base portion66ais arranged to have the same length in both of the phase busbars61and the common busbar61x. The terminal top portion66cis also arranged to have the same length in both of the phase busbars61and the common busbar61x. The terminal middle portion66bof the common busbar61xis arranged to have a smaller length than that of the terminal middle portion66bof any of the phase busbars61. The number of terminal portions66provided in the common busbar61xis greater than the number of terminal portions66provided in each of the phase busbars61. Therefore, the relatively small length of each terminal portion66of the common busbar61xcontributes to a reduced quantity of the bare copper wires68used.

The adapter62is preferably an injection-molded article made of, for example, a resin material. The adapter62according to the first preferred embodiment is arranged in an annular or substantially annular shape in accordance with the shape of the stator12. The adapter62is compatible with both the parallel connection and the series-parallel connection. The adapter62preferably has a cross section in a substantially rectangular shape.

Referring toFIGS. 8,9, and11, the adapter62preferably includes an inner circumferential surface62a, an outer circumferential surface62b, and a pair of opposed surfaces defined by a front end surface62cand a rear end surface62d. The inner circumferential surface62aand the outer circumferential surface62bare arranged to be concentric or substantially concentric with and opposed to each other. The pair of the front end surface62cand the rear end surface62dare opposed to each other, and each of the front end surface62cand the rear end surface62dis arranged to be continuous with edges of both the inner circumferential surface62aand the outer circumferential surface62b. The front end surface62cof the adapter62preferably includes, for example, three terminal holes73defined therein. The connection end portions67of the respective phase busbars61are arranged to project through the terminal holes73. The rear end surface62dof the adapter62preferably includes a plurality of (for example, preferably four in the first preferred embodiment) body support grooves74and a plurality of (for example, preferably twenty-four in the first preferred embodiment) terminal support grooves75defined therein. Note that, in the case of the series-parallel connection, the number of terminal support grooves75may preferably be twelve, for example.

As also illustrated inFIGS. 13,14A,14B,14C, and14D, each of the body support grooves74is a groove preferably having an annular or substantially annular shape, and the body support grooves74are arranged one radially inside another to be substantially concentric with one another. The width of each body support groove74is preferably slightly greater than the thickness of the body portion65of the busbar. In the first preferred embodiment, first, second, and third body support grooves74u,74v, and74ware arranged on a radial inside to receive the body portions65of the three phase busbars61, while a fourth body support groove74xis arranged radially outward of the first, second, and third body support grooves74u,74v, and74wto receive the body portion65xof the common busbar61x. Each of the first to fourth body support grooves74u,74v,74w, and74xpreferably has the same or substantially the same depth.

Each of the terminal support grooves75is arranged to extend in a radial direction to cross the body support groove(s)74. The terminal support grooves75are arranged in a radial configuration. The width of each terminal support groove75is slightly greater than the width of the terminal portion66of the busbar. The terminal support grooves75are preferably arranged at twenty-four positions equally or substantially equally spaced from one another in the circumferential direction, for example. The terminal support grooves75according to the first preferred embodiment preferably are made up of first, second, third, and fourth terminal support grooves75u,75v,75w, and75x, which are arranged to extend continuously from the first to fourth body support grooves74u,74v,74w, and74x, respectively.

The fourth terminal support grooves75xare preferably arranged at twelve positions equally or substantially equally spaced from one another in the circumferential direction, for example. Each of the first to third terminal support grooves75u,75v, and75wis preferably arranged between a separate pair of adjacent fourth terminal support grooves75x. The first to third terminal support grooves75u,75v, and75ware preferably arranged, for example, in this order in a counterclockwise direction: the first terminal support groove75u, the second terminal support groove75v, and the third terminal support groove75w. Each of the first to fourth terminal support grooves75u,75v,75w, and75xhas the same or substantially the same depth.

The first, second, third, and fourth terminal support grooves75u,75v,75w, and75xhave mutually different lengths. Specifically, each of the first to fourth terminal support grooves75u,75v,75w, and75xhas an end opening in the outer circumferential surface62bof the adapter62. An opposite end of each of the fourth terminal support grooves75xis arranged to open into the fourth body support groove74x, while opposite ends of the first to third terminal support grooves75u,75v, and75ware arranged to open into the first to third body support grooves74u,74v, and74w, respectively.

The body portion65and the terminal base portions66aof each busbar61are arranged in a separate one of the body support grooves74such that the body portions65of the busbars61are nested. The terminal middle portions66bof the terminal portions66are arranged individually in the terminal support grooves75. The terminal top portions66care arranged to be radially opposite the outer circumferential surface62bof the adapter62, because the terminal top portions66care arranged to be radially opposed to the body portion65.

Referring toFIG. 14A, the depth D2of each terminal support groove75is preferably greater than the thickness t of each terminal portion66. This enables the terminal portion66to be sufficiently embedded in the adapter62to prevent the busbar61from projecting above the rear end surface62dof the adapter62. A contact of the busbar61with another member is thus prevented.

The depth D1of each body support groove74is greater than the depth D2of each terminal support groove75. Moreover, a difference between the depth D1of the body support groove75and the depth D2of the terminal support groove75is greater than the width W of the body portion65. The busbar61fitted into the body support groove75is preferably prevented from moving by a mechanism, such as, for example, a snap-fit mechanism, provided in the body support groove75. Therefore, when any of the busbars61has been fitted into the adapter62, each of the terminal portions66thereof which are arranged to pass over the body portion65of any other busbar61is restrained by the corresponding terminal support groove75. A contact of the terminal portion66with the body portion65of any other busbar61is thus effectively prevented.

Each terminal top portion66cof each busbar61preferably includes a contact surface76facing radially outward. Referring toFIG. 13, when the busbars61have been fitted into the adapter62, the contact surface76of each terminal top portion66cof each busbar61is arranged to abut on a first imaginary circle77, which is centered or substantially centered on the center S of the adapter62(i.e., the busbar unit11). The coil wire terminals55are joined to the contact surfaces76when the busbar unit11is fitted to the stator12.

Referring toFIGS. 8 and 9, the busbar unit11is preferably fitted to the stator12with the rear end surface62dof the adapter62facing the opening-side end portion12aof the stator12. This arrangement contributes to preventing any busbar from coming off the adapter62, and also to preventing or substantially preventing dust or dirt from entering any body support groove74.

Referring toFIG. 5, the adapter62preferably includes the second fixing portion25, which is brought into engagement with the first fixing portion22of the stator12to fix the adapter62to the stator12. The second fixing portion25according to the first preferred embodiment is preferably hook-shaped and elastically deformable to allow the second fixing portion25to be engaged with the first fixing portion22.

Referring toFIG. 6, the adapter62preferably includes a second positioning portion26which is brought into contact with the first positioning portion23of the stator12to circumferentially position the adapter62. The second positioning portion26according to the first preferred embodiment is defined by a projection arranged to be embedded in the first positioning portion23.

Each of the passage-line busbars24(i.e., partial wiring members) according to the first preferred embodiment is preferably used in the case of the series-parallel connection to connect the coil wire terminals55from two of the coils53which are connected in series to each other. Referring toFIG. 9, each passage-line busbar24preferably includes a wire body24ashaped like a band plate, and a plurality of (for example, preferably two in the first preferred embodiment) wire terminals24beach shaped like a band plate. The wire terminals24bare arranged to extend orthogonally or substantially orthogonally from side edges of both end portions of the wire body24ain parallel or substantially in parallel with each other. Abase portion of each wire terminal24b, which is continuous with the wire body24a, includes a bend portion24carranged to extend at right angles or substantially right angles to both a remaining portion of the wire terminal24band the wire body24a. The passage-line busbar24is also preferably produced either by, for example, press working or by processing a single bare copper wire.

In the case of the series-parallel connection, coils53which have opposite winding directions may be connected in series as illustrated inFIG. 1B. It is difficult to mechanically accomplish a wiring configuration in which coils53which have opposite winding directions are connected in series, and this difficulty becomes a factor for decreased manufacturing efficiency. In the first preferred embodiment, the use of the passage-line busbars24makes it possible to accomplish the series-parallel connection using the single type of stator segments50having the same winding direction.

Specifically, each of the two wire terminals24bof each passage-line busbar24is connected to a winding-start or winding-end one of the two coil wire terminals55of a separate one of two adjacent ones of the stator segments50. While the two adjacent stator segments50are of the same type, and the coils53therein have the same winding direction, connecting the stator segments50in the above-described manner easily accomplishes an essential series connection of coils having opposite winding directions.

Referring toFIG. 9, according to the first preferred embodiment, in the case of the series-parallel connection, the wire bodies24aof six of the passage-line busbars24are fitted into predetermined portions of the wiring groove21, so that each of the two wire terminals24bof each of the six passage-line busbars24is arranged opposite to a predetermined one of the coil wire terminals55.

Referring toFIG. 15, the wiring groove21includes coming-off preventing portions27arranged to prevent the passage-line busbar24fitted to the predetermined portion of the wiring groove21from coming off the wiring groove21. In more detail, the coming-off preventing portions27include first projecting portions27aand second projecting portions27b. Each first projecting portion27ais arranged to radially project over a middle portion of the wire body24ato prevent the wire body24afrom coming off. Each second projecting portion27bis arranged to circumferentially project over the bend portion24cof the wire terminal24bto prevent the bend portion24cfrom coming off.

The passage-line busbar24is thus easily fitted to and appropriately positioned on the stator12by simply pushing the passage-line busbar24into the predetermined portion of the wiring groove21. Conversely, removal of the passage-line busbar24is easily accomplished by plucking the passage-line busbar24out from the stator12.

Referring toFIG. 16, the coil wire terminals55are arranged at substantially regular intervals in the circumferential direction of the stator12. In the first preferred embodiment, the number of coil wire terminals55is preferably twenty-four, and a central angle defined by two adjacent ones of the coil wire terminals55is therefore preferably about 15 degrees, for example. Note that the terminal portions66of the busbar unit11are arranged in accordance with the number of coil wire terminals55and the positions of the coil wire terminals55.

The coil wire terminals55are arranged radially outward of a second imaginary circle78, which is centered on the center S of the stator12, and arranged to abut on the second imaginary circle78. The second imaginary circle78preferably has the same diameter as that of the first imaginary circle77. Therefore, when the busbar unit11is attached to the stator12such that the busbar unit11and the stator12share the same center S, and the coil wire terminals55and the terminal portions66are properly positioned in the circumferential direction, each of the coil wire terminals55is arranged radially outward of the contact surface76of a separate one of the terminal portions66, and arranged to abut on the contact surface76(or, at least, arranged to be opposed to the contact surface76with a slight space therebetween), as also illustrated inFIG. 17.

Referring toFIG. 18, because the contact surface76is arranged to extend in the circumferential direction, the coil wire terminal55is arranged to be opposed to the contact surface76even if a slight displacement or flexing of the coil wire terminal55occurs. Therefore, the coil wire terminal55and the terminal portion66can preferably be securely joined to each other, and automation of the operation of joining the coil wire terminal55and the terminal portion66to each other is easy.

When the passage-line busbars24are attached to the stator12, each wire terminal24bof each of the passage-line busbars24is arranged radially outward of a separate one of the coil wire terminals55, and arranged to abut on the coil wire terminal55. Therefore, the wire terminals24band the corresponding coil wire terminals55can also be securely joined to each other, and automation of the operation of joining the wire terminals24band the corresponding coil wire terminals55to each other is also easy.

That is, it is possible to automate a series of processes for attaching the busbar unit11to the stator12when the motor1is manufactured. For example, after the busbars61are fitted onto the adapter62to complete the busbar unit11, a predetermined assembly machine (not shown) may be used to arrange the busbar unit11on the stator12such that the contact surfaces76are arranged opposite the corresponding coil wire terminals55(a positioning process). For example, the busbar unit11and the stator12are arranged to share a common central axis S, and the busbar unit11is brought closer to the opening-side end portion12aof the stator12along the central axis S up to a predetermined position. Thereafter, the busbar unit11and the stator12are turned relative to each other to properly position the coil wire terminals55and the terminal portions66in the circumferential direction. All the coil wire terminals55are thereby easily arranged to abut on the corresponding terminal portions66.

Next, referring toFIG. 19, portions of a predetermined joining machine30are arranged to have each terminal top portion66cand a corresponding one of the coil wire terminals55sandwiched therebetween from inside and outside in the radial direction, so that the coil wire terminal55is pressed against the contact surface76of the terminal top portion66c. Thereafter, the coil wire terminal55and the terminal portion66are preferably, for example, welded to each other through resistance welding, TIG welding, ultrasonic welding, or the like (a joining process).

The wire terminals24band the corresponding coil wire terminals55are also preferably welded to each other in a similar manner. All the coil wire terminals55can thus be handled collectively, leading to a reduced number of processes required and improved productivity.

For instance, in the case of an 8-pole 12-slot motor, the parallel connection as illustrated inFIG. 1Amay be adopted. Referring toFIG. 20, in the case of the parallel connection, the passage-line busbars24are removed from the stator12, and all the coil wire terminals55may be connected in a predetermined combination with the terminal portions66of the phase busbars61and the common busbar61x.

Meanwhile, in the case of a 14-pole 12-slot motor, the series-parallel connection as illustrated inFIG. 1Bmay be adopted. Referring toFIG. 21, in the case of the series-parallel connection, the passage-line busbars24are attached to predetermined portions of the stator12, and the coil wire terminals55may be connected in a predetermined combination with the terminal portions66of the phase busbars61and the common busbar61xand the wire terminals24bof the passage-line busbars24.

The first preferred embodiment enables the busbar unit to be easily attached to the stator such that the terminal portions of the busbars are connected with the coil wire terminals both in the case of the parallel connection and in the case of the series-parallel connection. In addition, the first preferred embodiment enables the required series of processes to be automated to achieve improved productivity.

Second Preferred Embodiment

FIG. 22illustrates a motor1including a rotor300according to a preferred embodiment of the present invention. The motor1preferably is an inner-rotor brushless motor to be installed in a vehicle, and is used to drive an electric power steering, for example. As illustrated inFIG. 22, the motor1preferably includes a casing2, a busbar unit100, a stator200, the rotor300, a shaft6, and so on.

The casing2preferably includes a receptacle2awhich has a bottom and is substantially cylindrical, and a substantially disc-shaped lid2b. The lid2bis preferably secured to a flange of the receptacle2a. The flange of the receptacle2ais preferably arranged to project radially outward around a circumference of an opening of the receptacle2a. The stator200and so on are contained inside the receptacle2a. A through hole3is preferably defined in a central portion of the lid2b. A bearing portion4is preferably arranged on a bottom surface of the receptacle2ato be opposed to the through hole3. Bearings5are arranged in the bearing portion4and inside the through hole3. The shaft6is supported through the bearings5to be rotatable with respect to the casing2. One end portion of the shaft6is arranged to project outward from the lid2bthrough the through hole3. The end portion of the shaft6is connected to the electric power steering through a speed reducer (not shown).

The rotor300is fixed to a middle portion of the shaft6such that the rotor300is coaxial or substantially coaxial with the shaft6. The stator200is fixed to an inner circumferential surface of the receptacle2asuch that the stator200surrounds the rotor300. An inner circumferential surface of the stator200and an outer circumferential surface of the rotor300are arranged opposite each other with a slight gap therebetween so that the motor1can efficiently exhibit its performance. The busbar unit100is attached to an end portion of the stator200. InFIG. 22, reference numeral “7” indicates a rotation angle sensor arranged to detect a rotation angle.

The motor1is provided with a variety of configurations in order to achieve improved productivity, reduced production cost, and so on. Details thereof will now be described below.

The structure of the busbar unit100will now be described in detail below. Referring toFIGS. 23 and 24, the busbar unit100is preferably arranged on an axial end portion (i.e., an upper end portion inFIG. 23) of the stator200. The busbar unit100is electrically connected to a plurality of coil wire terminals204afrom the stator200, which will be described below. The busbar unit100is arranged to supply currents to coils204of the stator200, which will be described below.

Referring toFIGS. 25,26,27,28,29, and30, the busbar unit100preferably includes holders101u,101v, and101w, busbars120, and terminal members130. In the present preferred embodiment, the busbars120are preferably three in number, for example, and each of the busbars120is provided for a separate one of phases of the coils204of the stator200, i.e., a u phase, a v phase, and a w phase. A total of three holders are preferably provided, i.e., a u-phase holder101u, a v-phase holder101v, and a w-phase holder101w. Each holder is arranged to accommodate and hold a separate one of the busbars120independently. In addition, a plurality of terminal members130are connected to each busbar120.

Referring toFIGS. 28 and 29, each busbar120is preferably defined by an electrically conductive wire shaped in a ring. Specifically, each busbar120according to the present preferred embodiment is preferably defined by a bare electric wire (e.g., a bare copper wire) without an insulating coating. The busbar120preferably includes a plurality of terminal connection portions121arranged at predetermined positions spaced from one another in a circumferential direction. The terminal members130are connected to the terminal connection portions121. Each terminal connection portion121of the busbar120is preferably deformed to have, for example, a rectangular or substantially rectangular shape in a cross-section when the terminal connection portion121is connected to the terminal member130. The portions of the busbar120other than the terminal connection portions121are arranged to have a circular or substantially circular shape in a cross-section. In the present preferred embodiment, the area of a cross section of the busbar120is preferably greater than that of a cross section of a coil wire used for the coils204of the stator200.

Note that, in the present preferred embodiment, the busbar120may have any shape in a cross-section, as long as the busbar120is defined by an electrically conductive wire. Also note that the busbar120may not necessarily be in the shape of a ring, but may be in the shape of the letter “C”. Also note that the busbar120may be defined by an electrically conductive wire having an insulating coating arranged on an outer circumference thereof. In the case where the busbar120is defined by an electrically conductive wire having an insulating coating arranged on an outer circumference thereof, it is necessary to remove the insulating coating from the terminal connection portions121of the busbar120. The removal of the insulating coating may be accomplished either by a mechanical method or by resistance welding, as long as the terminal connection portions121are able to achieve electrical connection with the terminal members130.

Referring toFIG. 30, each terminal member130is preferably made out of a single plate material element. The terminal member130preferably includes a busbar connection portion131, which is connected with the busbar120; a coil connection portion135, which is connected with the coil wire terminal204afrom the stator200; and a joining portion134, which is arranged to extend to be continuous with the busbar connection portion131and the coil connection portion135.

The busbar connection portion131is preferably defined by two C-shaped tubular portions132and a plate portion133arranged to join end surfaces of the two C-shaped tubular portions132to each other. Each of the two C-shaped tubular portions132is a tubular portion defined by bending a plate material to assume the shape of the letter “C”. The two C-shaped tubular portions132are arranged to be coaxial with each other. The busbar120is arranged to pass through the C-shaped tubular portions132. The coil connection portion135is a tubular portion defined by bending a plate material to substantially assume the shape of the letter “C”. The coil wire terminal204ais arranged to pass through this tubular portion. The joining portion134is preferably defined by a plate material member extending from an end surface of the coil connection portion135to the plate portion133of the busbar connection portion131. The joining portion134is preferably bent midway in a plate thickness direction. Specifically, the joining portion134is arranged to extend from the end surface of the coil connection portion135in an axial direction of the coil connection portion135, and be bent in a direction perpendicular or substantially perpendicular to the axial direction of the coil connection portion135to extend up to the plate portion133. The entire terminal member130therefore substantially assumes the shape of the letter “T” in a plan view when viewed from above in the axial direction of the coil connection portion135, and substantially assumes the shape of the letter “L” in a plan view when viewed from above in the axial direction of the busbar connection portion131.

FIG. 31shows a preferred embodiment of a method for forming the terminal member130. The single plate material is preferably cut in accordance with the shape ofFIG. 31. The resulting plate material is then preferably subjected to a bending process to define the terminal member130. As is apparent fromFIG. 31, the terminal member130according to the present preferred embodiment preferably has a shape so as to achieve a high yield of the material.

Referring toFIG. 32, the busbar120is preferably inserted into the terminal members130before the busbar120is shaped into a ring. In other words, a bare electric wire shaped in a straight line is inserted into the C-shaped tubular portions132of the terminal members130. The C-shaped tubular portions132are then crimped or welded onto the corresponding terminal connection portions121of the busbar120. The busbar120(i.e., the bare electric wire) shaped in a straight line is thereafter shaped into a ring. As a result, the plurality of terminal members130are electrically connected with the busbar120(seeFIG. 28). Note that, in the present preferred embodiment, the C-shaped tubular portions132of the terminal members130may be crimped or welded onto the corresponding terminal connection portions121of the busbar120after the busbar120shaped in a straight line and having the terminal members130attached thereto is shaped into a ring.

Each of the three holders101u,101v, and101wpreferably is an annular member made of an insulating material and preferably defined in one piece, and has the same configuration. Referring toFIG. 28, each of the holders101u,101v, and101wpreferably includes a holder body105in an annular shape. An annular surface105aof the holder body105includes an annular accommodating groove106defined therein. The annular busbar120having the terminal members130connected thereto is placed and held inside the accommodating groove106. The accommodating groove106includes a plurality of (for example, preferably six in the present preferred embodiment) terminal accommodating portions107arranged at predetermined positions spaced from one another in the circumferential direction. The terminal accommodating portions107are arranged to have the terminal members130placed and held therein. Each terminal accommodating portion107of the accommodating groove106preferably includes coming-off preventing portions109arranged to prevent the terminal member130from coming off. Other portions of the accommodating groove106than the terminal accommodating portions107preferably include a plurality of coming-off preventing portions110arranged to prevent the busbar120from coming off. The coming-off preventing portions109and110of the accommodating groove106are preferably defined by claws. An outer wall of the holder body105includes cuts108arranged at the terminal accommodating portions107to allow the joining portion134of each terminal member130to pass therethrough to project radially outward from the holder body105.

An inner wall of the holder body105of each of the holders101u,101v, and101wpreferably includes a plurality of hooks111arranged at regular intervals in the circumferential direction. Specifically, each hook111is defined by a portion of the inner wall of the holder body105which is arranged to extend in an axial direction to project above the annular surface105aof the holder body105. The inner wall of the holder body105additionally preferably includes a plurality of vertical grooves112arranged at regular intervals in the circumferential direction and between the hooks111. Specifically, each of the vertical grooves112is arranged to extend in the axial direction in the inner wall of the holder body105. Each vertical groove112preferably includes a projection113arranged at a bottom thereof to project radially inward.

Referring toFIGS. 33 and 34, five of the terminal members130are connected to each of the busbars120according to the present preferred embodiment such that four of the five terminal members130are preferably arranged at regular intervals of 90 degrees, for example. The remaining terminal member130is arranged in the vicinity of one of the four terminal members130on the busbar120. In the present preferred embodiment, a manner in which the busbar120is placed inside the w-phase holder101wis slightly different from a manner in which the busbar120is placed inside each of the u-phase holder101uand the v-phase holder101v. Specifically, referring toFIG. 33, in the accommodating groove106of each of the u-phase holder101uand the v-phase holder101v, three of the terminal accommodating portions107are arranged in close vicinity to one another, and of the three terminal accommodating portions107, the terminal accommodating portion107on the far right inFIG. 33is not provided with any terminal member130. Meanwhile, referring toFIG. 34, in the accommodating groove106of the w-phase holder101w, three of the terminal accommodating portions107are arranged in close vicinity to one another, and of the three terminal accommodating portions107, the terminal accommodating portion107on the far left inFIG. 34is not provided with any terminal member130. In addition, in each of the holders101u,101v, and101whaving the busbar120placed therein, the coil connection portion135of each terminal member130is arranged to project radially outward. In addition, an axis of each coil connection portion135and an axis of each of the holders101u,101v, and101ware arranged to be parallel or substantially parallel to each other.

Referring toFIGS. 23,25,26, and27, the busbar unit100is preferably defined by the holders101u,101v, and101wplaced one upon another in an axial direction of the stator200, each of the holders101u,101v, and101whaving the corresponding busbar120installed and held therein. In the present preferred embodiment, the u-phase holder101uis placed at the top, the v-phase holder101vis placed in the middle, and the w-phase holder101wis placed at the bottom in the axial direction. Note, however, that the order in which the holders are arranged in the axial direction is not limited thereto. Referring toFIGS. 26 and 27, the annular surface105aof each of the holders101u,101v, and101wis arranged to face downward in the axial direction. That is, in the present preferred embodiment, opening surfaces of the accommodating grooves106of the holders101u,101v, and101ware arranged not to face each other.

Referring toFIGS. 25 and 26, the holders101u,101v, and101wplaced one upon another are secured to one another as a result of the hooks111and the projections113of the vertical grooves112being engaged with each other. More specifically, the hooks111of the holders101uand101vare brought into engagement with the projections113of the holders101vand101w, respectively, to secure the three holders101u,101v, and101wplaced one upon another to one another.

Referring toFIG. 35, the holders101u,101v, and101ware circumferentially displaced from one another such that no two terminal members130(130u,130v, and130w) are arranged to overlap with each other when viewed from above in the axial direction. Note that, inFIG. 35, reference symbols “130u”, “130v”, and “130w” denote the terminal members installed on the u-phase holder101u, the v-phase holder101v, and the w-phase holder101w, respectively. Also note that reference symbols within parentheses denote terminal members which are not connected with any of the coil wire terminals204afrom the stator200. Specifically, the motor1according to the present preferred embodiment preferably has a 12-slot structure, for example. Accordingly, in the present preferred embodiment, the holders101u,101v, and101ware placed one upon another such that twelve of the terminal members130(130u,130v, and130w), excluding the three terminal members130which are not connected with any of the coil wire terminals204a, are arranged at regular intervals of 30 degrees in the circumferential direction. Note that the aforementioned number of slots of the motor1is merely an example, and is not essential to the present invention.

Referring toFIGS. 27 and 36A, the annular surface105aof each of the holders101u,101v, and101wpreferably includes a plurality of raised portions114arranged at regular intervals in the circumferential direction. Referring toFIG. 36B, an annular surface of each of the holders101u,101v, and101wopposite to the annular surface105apreferably includes a plurality of recessed portions115, which correspond to the raised portions114, arranged at regular intervals in the circumferential direction. The raised portions114and the recessed portions115are used to properly position the holders101u,101v, and101wwhen the holders101u,101v, and101ware placed one upon another. That is, the raised portions114of the holders101uand101vare fitted into the recessed portions115of the holders101vand101w, respectively, to properly determine the circumferential orientation of each of the holders101u,101v, and101w. Moreover, the fitting of the raised portions114into the corresponding recessed portions115contributes to preventing a circumferential movement of each of the holders101u,101v, and101w.

Referring toFIGS. 25 and 27, the terminal members130installed on the u-phase holder101u, which is placed at the top, are arranged such that the joining portion134of each of the terminal members130is arranged to bend downward in the axial direction outside the u-phase holder101u. On the other hand, the terminal members130installed on the v-phase holder101vand the w-phase holder101w, which are placed in the middle and at the bottom, respectively, are arranged such that the joining portion134of each of the terminal members130is arranged to bend upward in the axial direction outside the v-phase holder101vand the w-phase holder101w, respectively. That is, in the busbar unit100according to the present preferred embodiment, the joining portion134of each of the terminal members130installed on the u-phase holder101u, which is placed at the top, and the joining portion134of each of the terminal members130installed on the w-phase holder101w, which is placed at the bottom, are arranged to bend so as to head for each other. Therefore, none of the terminal members130installed on the u-phase holder101u, which is placed at the top, protrudes above an upper end surface of the u-phase holder101u. Moreover, none of the terminal members130installed on the w-phase holder101w, which is placed at the bottom, protrudes below a lower end surface of the w-phase holder101w. This contributes to reducing the height of the busbar unit100.

Referring toFIGS. 37 and 38, the hooks111of the w-phase holder101w, which is placed at the bottom of the busbar unit100, are preferably brought into engagement with projections205gwhich are similar to the aforementioned projections113and defined in the stator200, so that the busbar unit100is secured to an axial end portion of the stator200. Moreover, the raised portions114of the w-phase holder101w, which is placed at the bottom of the busbar unit100, are preferably fitted into recessed portions205hdefined in the axial end portion of the stator200, so that the busbar unit100is properly positioned. Furthermore, the fitting of the raised portions114into the recessed portions205hcontributes to restraining a circumferential movement of the busbar unit100.

As also illustrated inFIGS. 24,26,38, and39, the busbar unit100is attached to the axial end portion of the stator200such that the busbar unit100and the stator200are coaxial or substantially coaxial with each other. With the busbar unit100and the stator200being in this situation, the busbars120are arranged above the stator200. Meanwhile, in the stator200, the coil wire terminals204a, preferably numbering twenty-four, are arranged to axially project from the axial end portion of the stator200. The coil wire terminals204aare preferably arranged at regular intervals of about 15 degrees in the circumferential direction, centering about the axis of the stator200. In other words, the coil wire terminals204aare arranged on circles having the same radius and whose center is the axis of the stator200.

The coil wire terminals204adescribed above are divided into phase terminals20a, which are provided for the respective phases and connected to the terminal members130installed in the busbar unit100, and neutral point terminals20b. The phase terminals20aand the neutral point terminals20bare preferably arranged alternately with each other. The neutral point terminals20bare connected with a neutral point busbar250through neutral point terminal members250a, which will be described below. The neutral point busbar250is preferably held by a holding portion which has been molded in the axial end portion of the stator200and which is arranged radially outward of an outer circumference of the busbar unit100. That is, the neutral point busbar250is secured to the axial end portion of the stator200. There is therefore no need to provide the busbar unit100with a holder for a neutral point, which makes it possible to reduce the height of the busbar unit100or the height of the motor1as a whole. Also, insulation between each busbar120and the neutral point busbar250is ensured more effectively.

In the present preferred embodiment, the axial direction of each coil connection portion135coincides with the axial direction of the stator200. That is, the axial direction of each coil connection portion135coincides with a direction in which each coil wire terminal204ais arranged to project. As described above, in the present preferred embodiment, each terminal member130is provided with the busbar connection portion131, which is connected with the annular busbar120extending in the circumferential direction, and the coil connection portion135, which is connected with the coil wire terminal204aextending in the axial direction of the stator200. It is therefore possible to insert the coil wire terminals204ainto the corresponding coil connection portions135by simply moving the busbar unit100in the axial direction toward the axial end portion of the stator200. Therefore, the fitting of the terminal members130of the busbar unit100and hence the fitting of the busbar unit100to the stator200can be accomplished easily without the need for an operation of adjusting the orientation of any coil wire terminal204a. This leads to shortening a procedure of fitting the busbar unit100to the stator200, leading in turn to improved productivity in manufacturing the motors1.

In the present preferred embodiment, the busbars120and the terminal members130are preferably independent of each other, and each busbar120is preferably defined by a wire. An improvement in the yield of the material is therefore achieved as compared to the case where band-shaped conductors with integral terminals are used as in related art. This leads to a reduction in the costs of the materials for the busbar unit100and the motor1, leading in turn to a reduction in the production cost.

Furthermore, in the present preferred embodiment, the terminal member130is arranged to have a shape so as to achieve a high yield of the material as described above. This contributes to further reducing the costs of the materials and the production cost.

Furthermore, the busbar120according to the present preferred embodiment is defined by a bare electric wire without an insulating coating. The lack of an insulating coating leads to an increased number of choices of how to join the terminal members130to the busbar120. For example, crimping, welding, and the like are included in the possible choices.

Furthermore, the busbar unit100according to the present preferred embodiment is provided with the plurality of holders101u,101v, and101w, each of which is arranged in an annular shape. In addition, each of the plurality of holders101u,101v, and101wincludes the annular accommodating groove106arranged to contain and hold a separate one of the busbars120individually. This leads to ensuring insulation between the busbars120.

Furthermore, in the present preferred embodiment, each of the holders101u,101v, and101wpreferably has the same configuration. This leads to an additional improvement in productivity.

Furthermore, in the present preferred embodiment, the annular surfaces105aof the holders101u,101v, and101w(hence, the opening surfaces of the accommodating grooves106of the holders101u,101v, and101w) are arranged not to face each other. This leads to further ensuring the insulation between the busbars120.

Furthermore, in the present preferred embodiment, the terminal members130installed in the busbar unit100are preferably arranged at regular intervals in the circumferential direction. This contributes to eliminating the need for the operation of adjusting the orientation of any coil wire terminal204a.

Note that the terminal member130according to the present preferred embodiment may be replaced with a terminal member140as illustrated inFIG. 40. The terminal member140is preferably made out of a single plate material element. The terminal member140preferably includes a busbar connection portion141, which is connected with the busbar120; a coil connection portion145, which is connected with the coil wire terminal204a; and a joining portion144, which is arranged to extend to be continuous with the busbar connection portion141and the coil connection portion145. The busbar connection portion141is preferably defined by one C-shaped tubular portion142and a plate portion143arranged to be continuous with an end surface of the C-shaped tubular portion142. The structure of the terminal member140is otherwise similar to that of the terminal member130illustrated inFIG. 30. The action and beneficial effects of the terminal member140are also similar to those of the terminal member130illustrated inFIG. 30. In other words, the terminal member140is preferably identical to the terminal member130illustrated inFIG. 30except that the terminal member140includes only one C-shaped tubular portion142.FIG. 41shows a preferred embodiment of a method of development of the terminal member140. The single plate material is preferably cut in accordance with this method. The resulting plate material is then preferably subjected to a bending process to thereby define the terminal member140. As is the case with the terminal member130, the terminal member140has a shape so as to achieve a high yield of the material.

In the present preferred embodiment, each of the holders101u,101v, and101wis arranged to have the same configuration. Note, however, that each of the holders101u,101v, and101wmay be arranged to have a different configuration, as long as the holders101u,101v, and101ware able to hold the corresponding busbars120while ensuring the insulation between the busbars120.

In the present preferred embodiment, the three holders101u,101v, and101ware preferably arranged to hold the busbars120individually. Note, however, that only one holder which is arranged to hold all the busbars120may be provided.

In the present preferred embodiment, each of the holders101u,101v, and101wis preferably made of an electrically insulating material. Note, however, that, in the case where each of the busbars120is defined by an electrically conductive wire having an insulating coating arranged on the outer circumference thereof, each of the holders101u,101v, and101ware not necessarily required to be made of an insulating material.

In the present preferred embodiment, each of the holders101u,101v, and101wis preferably defined by an annular member arranged to contain and hold the corresponding busbar120in its entirety. Note, however, that, in the case where each of the busbars120is defined by an electrically conductive wire having an insulating coating arranged on the outer circumference thereof, each of the holders101u,101v, and101wmay be replaced with a member or members arranged to hold the busbar120only partially in the circumferential direction.

Also note that a minimum requirement of the terminal member130is that the terminal member130is defined by a single monolithic member including the busbar connection portion131which is to be connected with the annular busbar120extending in the circumferential direction, and the coil connection portion135which is to be connected with the coil wire terminal204aextending in the axial direction of the stator200. That is, the shape of the terminal member is not limited to the shapes mentioned above.

The stator200according to the present preferred embodiment preferably includes a plurality of stator segments201. As illustrated inFIG. 23, the stator200is in the shape of a cylinder. In the present preferred embodiment, the number (hereinafter referred to as a “segment number”) of stator segments201which together define the stator200is preferably twelve, for example. A central angle of each stator segment201is therefore preferably about 30 degrees.FIG. 42is a perspective view of the stator segment201.FIG. 43is a vertical cross-sectional view of the stator segment201. As illustrated inFIG. 43, the stator segment201preferably includes a core segment202, insulators203, the coil204, and a resin layer205.

It is assumed in the following description that the axial direction or a vertical direction of the stator200or the stator segment201refers to a direction of the axis of the shaft6; that a horizontal direction refers to a direction perpendicular to the axis of the shaft6; that terms “radially inward”, “radially inner”, etc., refer to a side closer to the shaft6; and that the terms “radially outward”, “radially outer”, etc., refer to a side farther away from the shaft6.

FIG. 44is a perspective view of the core segment202. The core segment202is preferably defined by, for example, a plurality of electromagnetic steel sheets placed one upon another in the axial direction. As is apparent fromFIG. 44, a cross section of the core segment202is substantially in the shape of the letter “T”.

In more detail, the core segment202preferably includes a tooth portion202a, a core back portion202b, and an inner yoke portion202c. The core back portion202bis a portion which is arranged to extend in the circumferential direction of the stator200when the core back portion202bdefines a portion of the stator200. An angle defined between two circumferential end walls202eof the core back portion202bcorresponds to a central angle of the core segment202. In the present preferred embodiment, the central angle of the core segment202preferably is about 30 degrees, for example. The tooth portion202ais a portion which is arranged to extend from the core back portion202bin a radial direction of the stator200. The inner yoke portion202cis arranged to be continuous with a radially inner end of the tooth portion202a. The inner yoke portion202cis a portion which is arranged to extend in the circumferential direction over a distance smaller than a distance over which the core back portion202bis arranged to extend in the circumferential direction. Spaces defined between the inner yoke portion202cand the core back portion202bon both circumferential sides of the tooth portion202adefine slots202darranged to accommodate the coil204.

The insulator203is an insulating layer arranged to ensure insulation between the core segment202and the coil204. The insulator203is arranged between the coil204and the tooth portion202aas described below. That is, the insulator203is an example insulating layer according to a preferred embodiment of the present invention. The insulator203is therefore made of an electrically insulating material. A thermoplastic resin is preferably used as the insulating material in the present preferred embodiment, but any other desirable electrically insulating material could be used in its place.

FIG. 45is a perspective view of the insulator203, illustrating the structure of the insulator203. Referring toFIG. 45, the insulator203preferably includes a body portion203aand end walls203band203c. The body portion203ais preferably substantially in the shape of the letter “U”, and is fitted to the tooth portion202a.FIG. 46is a perspective view illustrating the insulators203attached to the core segment202. Two insulators203are preferably used in each stator segment201. The body portion203aof one of the two insulators203is preferably fitted to one axial end (i.e., an output-side end) of the core segment202, while the body portion203aof the other insulator203is fitted to the other axial end of the core segment202. As a result, the tooth portion202ais covered by the body portions203aof the insulators203.

When the insulator203has been fitted to the core segment202, the end walls203band203cthereof are arranged to project over an axial end wall of the core segment202. The end wall203cis arranged radially outward of an inner side surface202fof the core segment202. Referring toFIG. 45, the end wall203cpreferably includes a step portion203earranged at a position corresponding to an axial end of the core segment202.

A circumferential end wall203dof the insulator203is arranged to be slightly recessed, in the direction of the tooth portion202a(i.e., circumferentially inward), relative to the circumferential end wall202eof the core segment202. In the present preferred embodiment, there is preferably a step that measures about 0.1 mm between the circumferential end wall203dof the insulator203and the circumferential end wall202eof the core segment202.

Each coil204is preferably defined by an electric wire (i.e., a copper wire), such as an enamel-coated copper wire, wound around the core segment202in a regular winding fashion with the insulators203arranged therebetween. The winding of the wire is carried out in such a manner that the coil204preferably does not bulge over the circumferential end walls203dof the insulators203.FIG. 47is a cross-sectional view of the slot202dand its vicinity when the coil204has been wound about the core segment202. InFIG. 47, the tooth portion202ais shown at the bottom, and the copper wire is wound around the tooth portion202ain an order indicated by arrows shown inFIG. 47. InFIG. 47, numbers shown to the right of each layer of the coil204(e.g., 8·7 . . . 2·1, etc.) indicate the number of turns. For instance, a first layer of the coil204(i.e., a lowermost layer inFIG. 47) corresponds to first to eighth turns. The number of turns is determined in accordance with a rating of the motor1. The adoption of the regular winding for the coil204contributes to preventing the coil204from bulging over circumferential end surfaces of the core segment202. In the present preferred embodiment, a clearance of about 0.1 mm is preferably provided between the circumferential end surfaces of the core segment202and a line joining the circumferential end walls203dof the insulator203(i.e., a line represented by a chain double-dashed line inFIG. 47).

FIG. 48is a perspective view of the core segment202having the insulators203fitted thereto and the coil204wound thereabout. As illustrated inFIG. 48, the coil204includes a pair of coil wire terminals204a. The coil wire terminals204aare arranged to extend in parallel or substantially in parallel with each other toward the output-side end (i.e., in the axial direction of the stator segment201). A central angle (hereinafter also referred to as a “pitch angle”) defined between the pair of coil wire terminals204ais half the central angle of the core segment202, that is, preferably about 15 degrees in the present preferred embodiment. In the present preferred embodiment, the pair of coil wire terminals204aare fixed through the resin layer205such that the central angle defined between the pair of coil wire terminals204ais half the central angle of the core segment202. When the stator segments201have been assembled together to define the stator200in the annular shape, the coil wire terminals204aare therefore preferably arranged at regular intervals of about 15 degrees. Note that the core segment202having the insulators203fitted thereto and the coil204wound thereabout will be hereinafter referred to as a subassembly206for the sake of convenience in description.

The resin layer205is preferably arranged to seal the entire coil204except for the pair of coil wire terminals204a. The coating of the entire coil204with the resin layer205contributes to preventing a short circuit (i.e., an interphase short circuit) with another stator segment201. Moreover, the resin layer205contributes to reducing an exciting vibration of the coil204.

The resin layer205is preferably molded on the subassembly206. In the present preferred embodiment, the resin layer205is preferably made of, for example, a thermoplastic resin similar to the material of the insulators203. However, the resin layer205may be made of any type of thermosetting resins that are commonly used in motors.

In the present preferred embodiment, a circumferential end wall205dof the resin layer205is preferably arranged circumferentially inward of the circumferential end wall202eof the core segment202. In addition, the resin layer205is arranged not to occupy a space over the end wall203cof the insulator203and the inner side surface202fof the core segment202.

Furthermore, an output-side end surface of the resin layer205preferably includes a groove205aarranged to accommodate the neutral point busbar250, which functions as a wiring member providing a ground (i.e., the neutral point).FIG. 49is a perspective view illustrating the groove205aarranged in the stator segment201. When the stator segments201have been assembled together to define the stator200in the annular shape, the grooves205aof the stator segments201are arranged to together define an annular groove (seeFIG. 23). A cross section of the groove205aand its vicinity is illustrated inFIG. 38.FIG. 38illustrates a situation in which the groove205ahas the neutral point busbar250arranged therein. In the present preferred embodiment, the neutral point busbar250is preferably, for example, an annular or C-shaped wiring member. Twelve neutral point terminal members250aare attached to the neutral point busbar250. Note that the number of neutral point terminal members250ais preferably equal to the segment number. Each of the neutral point terminal members250ais substantially in the shape of the letter “T”, as with the terminal members130used in the busbar unit100. Each of the neutral point terminal members250ais fixed to the neutral point busbar250preferably through, for example, swaging or the like. When the stator segments201have been assembled together to define the stator200in the annular shape, the neutral point terminal members250aare preferably arranged at regular intervals in the circumferential direction, such that every adjacent ones of the neutral point terminal members250aare circumferentially spaced from each other by an angle corresponding to a central angle of the core back portion202b.

Each of the neutral point terminal members250ais arranged in the groove205aso as to align with one of the coil wire terminals204aof a separate one of the stator segments201. The neutral point terminal member250ais then fitted to the corresponding coil wire terminal204a.FIG. 50is a diagram illustrating a situation in which the neutral point terminal member250ais fitted to the coil wire terminal204a. InFIG. 50, the neutral point busbar250is omitted for the sake of convenience in description. As illustrated inFIG. 50, one of the coil wire terminals204aof the corresponding stator segment201is inserted into each neutral point terminal member250ain the axial direction, so that the neutral point terminal member250ais electrically connected with the coil wire terminal204a.

Furthermore, referring toFIG. 49, an inside wall surface of the groove205apreferably includes a plurality of projecting portions205b. The projecting portions205bare arranged to prevent the neutral point terminal members250aand the neutral point busbar250from coming off. Referring toFIG. 38, each neutral point terminal member250ais held between the projecting portion205band a bottom portion of the groove205a. The projecting portions205bcontribute to preventing the neutral point terminal member250aand so on from coming off the groove205a. This in turn contributes to further ensuring the electrical connection between the neutral point terminal member250aand the coil wire terminal204a.

Furthermore, referring toFIG. 42, the resin layer205includes a flat portion205earranged at an output-side end thereof to have the busbar unit100mounted thereon. Furthermore, referring toFIGS. 38,42, and43, the resin layer205includes a recessed portion205fpreferably arranged at a radially inner corner of the output-side end thereof. The stator200according to the present preferred embodiment preferably includes the twelve stator segments201. Therefore, in the stator200, the recessed portions205fare preferably arranged at regular intervals of about 30 degrees. Each recessed portion205fpreferably includes the projection205garranged therein. One of the hooks111of the holder101wis mechanically engaged with the projection205g. The recessed portion205fand the projection205gtogether define an example fixing portion according to a preferred embodiment of the present invention.

FIG. 51is a perspective view illustrating a portion of a mold260used to mold the resin layer205in accordance with a preferred embodiment of the present invention.FIG. 52is a cross-sectional view of the mold260.FIG. 52illustrates a situation in which the subassembly206is set inside the mold260. The mold260preferably includes a stationary side mold portion260a, a coil wire terminal side mold portion260b, a movable side mold portion260c, and a slide portion260d.

The coil wire terminal side mold portion260bis arranged to position the pair of coil wire terminals204a. Specifically, the coil wire terminal side mold portion260bincludes two holes260earranged to have the coil wire terminals204ainserted thereinto. The holes260eare spaced from each other by a predetermined distance. This enables the coil wire terminals204aof the stator200to preferably be arranged at regular intervals of about 15 degrees (the pitch angle=15 degrees) when the stator segments201have been assembled together to define the stator200in the annular shape. The coil wire terminal side mold portion260bis provided with a predetermined seal structure to prevent an injected resin from leaking out through a gap between any coil wire terminal204aand the coil wire terminal side mold portion260b(i.e., any hole260e).

The slide portion260dis preferably slid into contact with an opposite axial end (i.e., an end opposite to the output-side end) of the core segment202before the injection of the resin.

Next, the step portion203eof the insulator203will now be described below. The stationary side mold portion260acan be assumed to have uniform dimensions because the same stationary side mold portion260ais used repeatedly. In contrast, the core segments202may have individual differences in axial dimension. In the case where the core segment202has a decreased axial dimension, an extra space is defined between the stationary side mold portion260a, the opposite axial end of the core segment202, and the end wall203cof the insulator203. The resin injected to define the resin layer205flows into the extra space. If the resin which has flowed into the extra space has a very small thickness, the resin may be removed from the inner circumferential surface of the stator200toward the rotor300. In order to prevent this from happening, the step portion203eis defined in the insulator203. The resin flows into the step portion203ewhen molding the resin layer205. As a result, the resin layer205defined has a sufficient thickness.

The stationary side mold portion260ais arranged to extend along the end wall203cof the insulator203and the inner side surface202fof the core segment202, so that the resin layer205is prevented from extending over the end wall203cand the inner side surface202fof the core segment202. Referring toFIG. 50, because of the stationary side mold portion260a, a surface205cof the resin which has flowed into the step portion203eis arranged to be flush with the inner side surface202fof the core segment202.

Furthermore, the stationary side mold portion260ais in contact with the circumferential end walls203dof the insulator203on both sides. Furthermore, the stationary side mold portion260ais also arranged in contact with the circumferential end walls202eof the core segment202on both sides. That is, the circumferential end walls203dand202eare used as references when molding the resin layer205. Because the stationary side mold portion260ais arranged in contact with the circumferential end walls202eof the core segment202on both sides, the resin layer205is prevented from extending over the circumferential end walls202eof the core segment202.

As described above, the steps are defined between the circumferential end walls202eof the core segment202and the circumferential end walls203dof the insulators203. The stationary side mold portion260aincludes steps (each preferably measuring about 0.1 mm, for example) corresponding to the steps between the circumferential end walls202eof the core segment202and the circumferential end walls203dof the insulators203. Steps of a similar size (i.e., each preferably measuring about 0.1 mm) are accordingly defined between the circumferential end walls205dof the resin layer205and the circumferential end walls202eof the core segment202. That is, the circumferential end walls205dof the resin layer205are arranged circumferentially inward of the circumferential end walls202eof the core segment202. As a result, when the stator200has been assembled, the resin layers205of adjacent ones of the stator segments201are not arranged in circumferential contact with each other, while the circumferential end walls202eof adjacent ones of the core segments202are arranged in contact with each other.

FIG. 53is an enlarged view of a cross section of the coils204of adjacent ones of the stator segments201and their vicinity. As described above, there is a step measuring about 0.1 mm, for example, between the circumferential end wall202eof the core segment202and the circumferential end wall203dof the insulator203. Therefore, as illustrated inFIG. 53, an air insulation layer (i.e., and air gap) preferably measuring more than about 0.2 mm, for example, can be secured between the adjacent stator segments201. Since each coil204and the circumferential end wall203dof the corresponding insulator203are spaced from each other by about 0.1 mm, a distance of more than about 0.4 mm is preferably secured between adjacent ones of the copper wires, for example.

As described above, in the present preferred embodiment, the circumferential end walls202eof the core segments202of the stator200are arranged in contact with one another, while the resin layers205are not arranged in circumferential contact with one another. It is therefore possible to construct the stator200with an accuracy of the core segments202according to the present preferred embodiment. Use of the stator segments201to construct the stator200therefore contributes to achieving improved circularity of an inner circumference of the stator as compared to the case where stator segments whose resin layers are arranged in circumferential contact with one another are used to construct the stator. Since the circularity of the inner circumference of the stator affects characteristics of the motor, the motor1according to the present preferred embodiment is able to achieve improved characteristics.

Furthermore, the end wall203cof the insulator203includes the step portion203e. The step portion203econtributes to absorbing a cumulative error in the axial dimension of the core segment202so as to compensate for manufacturing tolerances.

Furthermore, the resin layer205is preferably molded in a situation where the pair of coil wire terminals204aare positioned by the coil wire terminal side mold portion260b. This contributes to ensuring sufficient accuracy of the pitch angle defined between the coil wire terminals204ain each stator segment201. This in turn contributes to preventing a short circuit (i.e., a so-called intraphase short circuit) between the coil wire terminals204ain the same stator segment201. In addition, the fitting of the busbar unit100to the stator200is made easier. The increased ease of the fitting of the busbar unit100makes it possible to use an automated machine to perform the fitting of the busbar unit100. Furthermore, since the coil wire terminals204aare properly positioned, it is possible to eliminate the need for forced routing of wires. This contributes to reducing a residual stress on a joint between wires, and improving reliability of electrical connection.

Furthermore, the busbar unit100is mechanically joined to the stator segments201through the recessed portions205fthereof. This contributes to improving mechanical rigidity, vibration resistance, and impact resistance of the busbar unit100.

Furthermore, each stator segment201includes the groove205aarranged to accommodate the neutral point busbar250separately from the busbar unit100. This contributes to reducing the total length (i.e., an axial height of the motor) of the motor1as compared to the case where the wires for each phase and the wires for the ground are arranged in a single busbar unit. This in turn contributes to achieving a reduced cost.

Furthermore, the resin layer205is arranged such that the coil204is sandwiched between the insulators203and the resin layer205. This contributes to reducing the exciting vibration of the coil204.

Note that the aforementioned insulating layer may be defined by a coating (e.g., an electrodeposition coating), instead of the insulator203, in other preferred embodiments of the present invention.

Also note that the neutral point busbar250may alternatively be produced by punching out an annular or C-shaped piece from a plate material. In this case, the neutral point terminal members250amay be defined integrally with the neutral point busbar250when the neutral point busbar250is punched out from the plate material.

Also note that the aforementioned segment number of the stator200is merely a non-limiting example.

Also note that the aforementioned degree of the central angle defined between the pair of coil wire terminals204ais merely a non-limiting example. That is, the central angle defined between the pair of coil wire terminals204amay not necessarily be half the central angle of the core segment202, as in the above-described preferred embodiment.

As illustrated inFIGS. 54 and 55, the rotor300according to the present preferred embodiment is preferably a rotor having a two-step skew structure. The rotor300preferably includes rotor cores310, magnets320, spacers330, a rotor cover340, and so on. The rotor cores310, the magnets320, and the spacers330are securely united through the rotor cover340preferably without use of an adhesive. Note thatFIG. 55shows the rotor cover340(i.e., a base340a) before collar portions341are defined therein.

The number of rotor cores310included in the rotor300according to the present preferred embodiment is preferably two, for example. Each rotor core310preferably is a columnar member having a cross section substantially in the shape of a regular octagon. The rotor core310includes a through hole311defined at its center. The through hole311is arranged to be coaxial or substantially coaxial with a rotation axis S, and is arranged to have the shaft6secured therein. The rotor core310is preferably defined by a plurality of metal sheets placed one upon another along the rotation axis S and united in a single body, but any other desirable type of rotor core could be used.

The rotor300according to the present preferred embodiment preferably has eight poles, for example. In other words, the number of magnets320(which will be referred to collectively as a “magnet group”) attached to each rotor core310is preferably eight, for example. Each magnet320is preferably shaped like a band plate. Each magnet320includes a convex surface321arranged to project so as to assume a minor arc in a cross-section. The magnets320in each magnet group are arranged to orient the convex surfaces321thereof radially outward. Moreover, each magnet320is preferably arranged to have the convex surface321thereof extending in parallel or substantially in parallel with the through hole311. The magnets320are therefore arranged on an outer circumferential surface of the rotor core310at regular intervals in the circumferential direction with a predetermined gap defined between adjacent ones of the magnets320. The magnets320are polarized such that each of the magnets320defines a south or a north pole radially oriented. The south and north poles are arranged to alternate with each other in the circumferential direction on a radial outside.

The two rotor cores310, each with the magnet group attached thereto, are arranged one above the other along the rotation axis S. Each pair of the rotor core310and the magnet group will be referred to as a “rotor assembly301”. The two rotor assemblies301are fitted inside the rotor cover340such that the rotor assemblies301are circumferentially displaced from each other by a predetermined step angle. Each of the eight magnets320in each rotor assembly301is therefore circumferentially displaced from a corresponding one of the eight magnets320in the other rotor assembly301by the predetermined step angle. In other words, the rotor assemblies301preferably have a step skew structure.

The number of spacers330included in the rotor300according to the present preferred embodiment is preferably two. Each spacer330is preferably a member having a portion which is substantially in an annular shape and arranged to extend along an inner circumferential surface of the rotor cover340. The spacer330is arranged to have an outside diameter slightly smaller than the inside diameter of the rotor cover340. In addition, the spacer330is arranged to have an inside diameter greater than the diameter of the through hole311. The outside diameter of the spacer330is at least arranged to be smaller than the outside diameter of the rotor core310. Note that the spacer330may be made of, for example, either a metal or a resin, as long as it is made of a non-magnetic material.

Each spacer330is arranged between an end surface of a separate one of the rotor assemblies301fitted inside the rotor cover340and one of the collar portions341. Each collar portion341is preferably defined by deforming an end portion of the rotor cover340. Each spacer330is arranged to restrain an axial movement of the corresponding rotor assembly301in combination with the corresponding collar portion341. Moreover, the spacer330contributes to facilitating processing of the collar portion341, and also to preventing the magnets320and the rotor core310from being damaged during the processing. Details thereof will be described below.

The rotor cover340is a cylindrical metal article subjected to metalworking, for example. The rotor cover340includes a cylindrical circumferential wall342and openings344arranged to be open at both ends of the rotor cover340. The rotor cover340is defined by subjecting the base340a, which is substantially cylindrical and free of joints, to press working or the like. The rotor assembly301and the spacer330are placed inside the rotor cover340through each opening344and fitted to the rotor cover340. Each rotor assembly301is preferably, for example, press fitted to the rotor cover340. The rotor cover340is arranged to protect the rotor assemblies301and the spacers330, and properly position and integrally hold the rotor assemblies301and the spacers330without the use of an adhesive.

The rotor cover340preferably is essentially identical to the base340aexcept that the rotor cover340includes the collar portions341defined therein. A portion (hereinafter also referred to as a “processed edge345”) of the base340aaround each opening344is deformed radially inward to define the collar portion341projecting radially inward, so that the rotor cover340is completed. The axial dimension of the base340ais therefore designed to be greater than the total axial dimension of the rotor cores310and the magnets320.

An outer surface of the circumferential wall342of the rotor cover340includes a recessed dividing portion350depressed radially inward. The recessed dividing portion350corresponds to an intermediate space provided between the two rotor assemblies301and arranged adjacent to each other along the rotation axis S. The recessed dividing portion350according to the present preferred embodiment is defined by a straight groove arranged to extend in the circumferential direction at an axial center of the rotor cover340. The recessed dividing portion350contributes towards retaining the two rotor assemblies301such that the rotor assemblies301are not in contact with each other.

Note that the structure of the rotor cover340may be modified as long as a contact between the rotor assemblies301is avoided. That is, a gap defined between the adjacent rotor assemblies301by the recessed dividing portion350may be only slight. Note, however, that, when the rotor assemblies301are arranged in too close proximity to each other, a high-speed rotation of the rotor300may lead to occurrence of an eddy-current loss. It is therefore preferable that the recessed dividing portion350be arranged to space the two rotor assemblies301from each other preferably by about 1 mm or more, for example.

The outer surface of the circumferential wall342of the rotor cover340preferably includes a plurality of recesses346defined therein. The recesses346are arranged to extend along the rotation axis S, correspondingly to the magnets320. On both sides of the recessed dividing portion350in the rotor cover340, the recesses346are arranged not to extend over an end portion on either side.

Each recess346preferably includes a first end wall346aarranged at an end thereof closer to the opening344. The first end wall346ais arranged to extend from an outer circumferential surface of the rotor cover340radially inward in a perpendicular or substantially perpendicular manner. The first end walls346aof the recesses346are arranged substantially in a straight line in the circumferential direction. Meanwhile, an end portion of each recess346at an end closer to the recessed dividing portion350preferably has a tapered shape. The end portion of each recess346at the end closer to the recessed dividing portion350preferably includes a second end wall346barranged to extend from the outer circumferential surface of the rotor cover340radially inward in an oblique direction. Note that the shape of the second end wall346bis a result of avoiding forced removal of the base340afrom a columnar jig360when defining the recesses346.

Referring toFIG. 56, because of the recesses346, the rotor cover340includes a plurality of support regions347each preferably having a cross section in the shape of a minor arc. Each support region347is arranged to project radially outward to match the convex surface321of a separate one of the magnets320fitted inside the rotor cover340. In other words, each magnet320is arranged such that the convex surface321thereof is arranged opposite a separate one of the support regions347. In addition, each magnet320is arranged in contact with the corresponding support region347. Each magnet320is thereby prevented from moving circumferentially, and retained at a predetermined position.

Between every two support regions347adjacent to each other in the circumferential direction, a recessed portion348extending in a line along the rotation axis S and being continuous with the two support regions347is defined. In contrast to the support regions347, each recessed portion348is arranged to project radially inward to have a cross section in the shape of a minor arc. The recessed portion348is preferably a small depression which is embedded in a gap defined between every two adjacent magnets320. Each recessed portion348is arranged in a circumferential middle of a separate one of the recesses346. In addition, the recessed portion348is arranged to extend from the first end wall346ato a vicinity of the second end wall346b. The recessed portions348contribute to securely preventing a contact between any magnets320adjacent to each other in the circumferential direction.

Each support region347is preferably arranged in secure surface contact with the convex surface321of a separate one of the magnets320. This contributes to properly holding the magnets320.

Specifically, referring toFIGS. 57A and 57B, an inner surface of the support region347is arranged to have a smaller radius of curvature than that of the convex surface321. Dimensions of portions of the rotor cover340are preferably designed such that both circumferential ends of the convex surface321of each magnet320are positioned circumferentially inward of both circumferential ends of the inner surface of the corresponding support region347.

Referring toFIG. 57A, when no external force is applied to the support region347, the support region347preferably has a smaller radius of curvature than that of the convex surface321. Therefore, when the convex surface321is brought into contact with the inner surface of the support region347, two separate portions of the support region347near both circumferential ends thereof are brought into contact with the convex surface321, while a middle portion of the support region347is not in contact with the convex surface321. Referring toFIG. 57B, after the rotor core310and so on are fitted to the base340a, forces are applied to the base340aas if to increase the diameter of the base340a. As a result, both circumferential end portions of the support region347are pulled in mutually opposite directions. As a result, a force acting toward the rotation axis S is applied to the support region347to force the support region347onto the magnet320. In this manner, the inner surface of the support region347is brought into surface contact with the convex surface321in its substantial entirety.

Moreover, when the support region347has been brought into close contact with the convex surface321to have the same radius of curvature as that of the convex surface321, an arc having this radius of curvature and defined by the support region347is longer than an arc having this radius of curvature and defined by the convex surface321. This contributes to securing the surface contact between the convex surface321and the support region347. As a result, the magnet320is properly positioned circumferentially.

Referring toFIGS. 58 and 59, mathematical equations for deriving the radius of curvature of the support region347and so on will now be described below. It is assumed that Ra denotes the radius of curvature (mm) of the support region347when no external force is acting on the support region347, and that α denotes the central angle (radian) thereof. It is similarly assumed that Rb denotes the radius of curvature of the recessed portion348, and that β denotes the central angle thereof.

It is assumed that Ra′ denotes the radius of curvature of the support region347when the support region347has been deformed after the magnets320and so on are fitted to the rotor cover340, and that α′ denotes the central angle thereof. It is similarly assumed that Rb′ denotes the radius of curvature of the recessed portion348when the recessed portion348has been deformed after the magnets320and so on are fitted to the rotor cover340, and that β′ denotes the central angle thereof. Note that Ra′ is equal to the radius of curvature of the convex surface321.

It is assumed that R denotes a maximum outside diameter (mm) of the rotor cover340when the magnets320and so on have been fitted to the rotor cover340. It is also assumed that θ denotes the central angle of one pole of the rotor300, that t denotes the thickness (mm) of the rotor cover340, that L denotes the circumferential length (mm) of the rotor cover340, and that E denotes the Young's modulus of the rotor cover340.

Furthermore, when the magnets320and so on have been fitted to the rotor cover340, pulling forces F are produced at the support region347and circumferential end portions of the recessed portions348. The support region347and the recessed portions348are stretched thereby, so that the following equation holds.

The pulling forces F produced at the support region347produce a radially inward force N (i.e., a supporting force) acting on the magnet320. The supporting force N is represented by the following equation.
N=2Fsin(α′/2)  Eq. 4

Therefore, the proper holding of the magnets320is ensured by making the supporting force N calculated based on the above equations greater than a maximum centrifugal force applied to the magnets320.

Specifically, the proper holding of the magnets320is ensured when the following inequality holds:
N>Mm·Rm·S2Eq. 5
where Mm denotes the mass of each magnet320, Rm denotes the distance from the center of the through hole311to the center of gravity of the magnet320, and S denotes a maximum angular velocity of the rotor300based on a design thereof.

Next, a method of manufacturing the rotor300according to the present preferred embodiment will now be described below.

As described above, the magnets320and so on are fitted to the rotor cover340preferably without use of an adhesive to construct the rotor300in a unified manner. Specifically, the method of fitting the magnets320and so on to the rotor cover340to construct the rotor300in a unified manner preferably includes a step of defining the base340aof the rotor cover340(i.e., a base defining step); a step of defining the recessed dividing portion350in the base340a(i.e., a recessed dividing portion defining step); a step of defining the support regions347in the base340a(i.e., a support region defining step); a step of fitting the rotor cores310and the magnets320to the base340a(i.e., a fitting step); and a step of defining the collar portions341in the base340ato complete the rotor cover340(i.e., a collar portion defining step).

Referring toFIGS. 60A,60B,60C, and60D, the base340aof the rotor cover340(an initial state) is defined in the base defining step. Specifically, referring toFIG. 60A, a metal sheet is first preferably subjected to, for example, press working to define a pressed metal item which has a bottom and is substantially cylindrical and free of joints. The thickness of the metal sheet is preferably in the range of, for example, about 0.2 mm to about 0.3 mm, from the standpoint of durability and motor performance.

Next, referring toFIG. 60B, the bottom of the pressed metal item is removed therefrom to shape the pressed metal item as illustrated inFIG. 60C, and thereafter an unwanted flange portion preferably is cut off, so that a substantially cylindrical item having openings at both ends thereof and being free of joints as illustrated inFIG. 60Dis finally defined. This item is used as the base340aof the rotor cover340(the initial state).

Alternatively, referring toFIGS. 61A,61B,61C, and61D, a pressed item which has a bottom and is substantially cylindrical and free of joints and which includes a curved surface defined in a bottom portion thereof may be used to define the base340a, for example. In this case, for example, after a portion of the bottom surface is cut off, a portion of the pressed item which corresponds to the curved surface is deformed through press working to assume a cylindrical shape. An unwanted flange portion is cut off thereafter.

In the recessed dividing portion defining step, a portion of the circumferential wall342of the base340ais preferably depressed radially inward, so that an axial middle portion of the base340aincludes the recessed dividing portion350.

Referring toFIG. 62, specifically, the base340ais preferably fitted to one of a pair of predetermined half jigs380, so that the base340ais held thereby. The other of the pair of half jigs380is joined to the first half jig380, so that a recess380ais defined in an outer circumferential surface of the second half jig380. The recess380acorresponds to the recessed dividing portion350. A stamping die381including a projection defined at a top end thereof is pressed against the circumferential wall342of the base340ainto the recess380a, radially inward from outside the circumferential wall342. As a result, the recessed dividing portion350is defined at a predetermined portion of the circumferential wall342.

In the support region defining step, portions of the circumferential wall342of the base340aare depressed radially inward so that the recesses346are defined therein. As a result, the support regions347are defined therein. In the present preferred embodiment, the recessed portions348are preferably defined simultaneously with the support regions347.

The support region defining step preferably includes a first support region defining step and a second support region defining step. In the first support region defining step, the support regions347are defined in one of two axial halves of the base340adivided by the recessed dividing portion350. In the second support region defining step, the support regions347are defined in the other axial half of the base340asuch that the support regions347in the other axial half of the base340aare circumferentially displaced from the support regions347in the first axial half of the base340aby the predetermined step angle.

Referring toFIGS. 63,64,65, and66, for example, eight pressing bars361(i.e., pressing dies) and so on are preferably used in the support region defining step. The pressing bars361are arranged for the columnar jig360and the recesses346of one of the two rotor assemblies301. The axial dimension of the jig360is preferably about half the axial dimension of the base340a, and the outside diameter of the jig360is slightly smaller than the inside diameter of the base340a. An outer circumferential surface of the jig360preferably includes eight depressed portions362defined therein, for example. The depressed portions362are arranged to correspond to the recesses346in cross-section, in other words, to the support regions347and the recessed portions348in cross-section. Each of the depressed portions362is arranged to extend from an axial middle portion to an upper edge of the outer circumferential surface of the jig360. Each depressed portion362preferably includes a closed end362a, which is closed by an end surface spreading radially, and an open end362b.

Each pressing bar361includes a pressing surface361a. The pressing surface361ais arranged to project in such a manner as to correspond to the recess346in cross-section. The pressing bars361are arranged around the jig360such that the pressing surfaces361athereof are arranged to face the depressed portions362of the jig360. In addition, each pressing bar361is capable of being shifted in a radial direction. An axial end of the pressing surface361aof each pressing bar361is aligned with the closed end362aof a separate one of the depressed portions362. The other axial end of the pressing surface361aof each pressing bar361is positioned axially below an upper edge of the jig360.

Referring toFIG. 63, in the support region defining step, the base340ais preferably first fitted to the jig360in such a manner that one of the openings344of the base340ais placed over the upper edge (i.e., a fitting edge) of the jig360. Next, referring toFIG. 64, a supporting jig360ais preferably inserted into the base340athrough the opposite opening344thereof. Thereafter, the pressing bars361are pressed against the outer circumferential surface of the base340a. Predetermined portions of the circumferential wall342are thereby deformed to shape the recesses346(the first support region defining step).

Each depressed portion362includes the open end362barranged at the upper edge of the jig360. Therefore, after the pressing bars361are shifted backward, the base340acan preferably be easily removed from the jig360by simply pulling the base340aoff the jig360, without the need for a forced removal.

Next, referring toFIG. 66, the base340ais turned upside down and circumferentially displaced by the predetermined step angle. Thereafter, the base340ais again fitted to the jig360in such a manner that the opposite opening344of the base340ais placed over the upper edge of the jig360. Predetermined portions of the circumferential wall342of the base340aare then deformed to shape the recesses346in a manner similar to that described above (the second support region defining step).

The recesses346and hence the support regions347are thereby defined as illustrated inFIG. 54and other figures.

In the fitting step, which is performed after the support region defining step, the rotor cores310, the magnets320, and the spacers330are preferably fitted to the base340aso that they are temporarily assembled in a unified manner.

First, one of the rotor assemblies301is fitted to one of the axial halves of the base340a. For example, a supporting tool is used to support the rotor assembly301with the magnets320arranged at predetermined positions on the outer circumferential surface of the rotor core310. The rotor assembly301is then fitted to the base340ain such a manner that the base340ais placed over axial ends of the rotor core310and the magnets320, and is preferably, for example, press fitted to the base340aso that the magnets320are brought into contact with the recessed dividing portion350. At this time, the rotor assembly301is circumferentially aligned with the base340asuch that both circumferential ends of the convex surface321of each magnet320are positioned circumferentially inward of both circumferential ends of the inner surface of the corresponding support region347.

When the rotor assembly301is circumferentially aligned with the base340asuch that both circumferential ends of the convex surface321of each magnet320are positioned circumferentially inward of both circumferential ends of the inner surface of the corresponding support region347, the convex surfaces321are arranged in surface contact with the corresponding support regions347. The magnets320are thereby held securely in the circumferential direction. Moreover, the recessed portions348are embedded between every pair of adjacent magnets320. This contributes to preventing a contact between the magnets320.

Next, the other rotor assembly301is fitted to the other axial half of the base340asuch that the other rotor assembly301is preferably circumferentially displaced from the first rotor assembly301by the predetermined step angle. For example, the supporting tool is used to support the second rotor assembly301with the magnets320arranged at predetermined positions on the outer circumferential surface of the rotor core310thereof. The second rotor assembly301is then fitted to the base340ain such a manner that the base340ais placed over axial ends of the rotor core310and the magnets320thereof, and is preferably press fitted to the base340aso that the rotor core310thereof is brought into contact with the rotor core310of the first rotor assembly301, and that the magnets320thereof are brought into contact with the recessed dividing portion350. At this time, the second rotor assembly301is circumferentially aligned with the base340asuch that both circumferential ends of the convex surface321of each magnet320are positioned circumferentially inward of both circumferential ends of the inner surface of the corresponding support region347.

Finally, the spacer330is arranged on an end surface, facing the opening344, of each of the rotor assemblies301fitted to the base340a. When the rotor cores310, the magnets320, and the spacers330have been properly fitted to the base340a, each end portion (i.e., the processed edge345) of the base340aaround the opening344is arranged to protrude over an end surface of the corresponding spacer330.

In the collar portion defining step, which is performed after the fitting step, the processed edges345of the base340aare deformed to define the collar portions341. The collar portions341are arranged to seal the magnets320and so on inside the rotor cover340.

The collar portion defining step will now be described below with reference toFIGS. 67,68, and69. In the collar portion defining step, a dedicated lathe apparatus370is preferably used to define the collar portions341as illustrated inFIGS. 67 to 69. The lathe apparatus370preferably includes a chuck371which is capable of being rotated about the rotation axis S, a tail stock372, and so on. The tail stock372is arranged to be opposed to the chuck371along the rotation axis S, and is arranged to rotate in synchronism with the chuck371while supporting one of the spacers330.

The lathe apparatus370further includes a small-diameter roller (i.e., a cam follower373) arranged on a top thereof and being freely rotatable. The lathe apparatus370further includes a crimping tool374. The crimping tool374is capable of being shifted in a radial direction with respect to the rotation axis S of the chuck371and so on. In addition, the crimping tool374is capable of being tilted at least within a range between the rotation axis S and an axis perpendicular to the rotation axis S. Furthermore, the lathe apparatus370preferably further includes a touch probe375used to determine a reference position during processing. The lathe apparatus370further includes a control apparatus and so on (not shown) which are used to perform centralized control of the chuck371, the tail stock372, the cam follower373, the crimping tool374, and the touch probe375. The lathe apparatus370is arranged to automatically perform a series of processes which define the collar portions341.

In the collar portion defining step, first, the base340ahaving the rotor cores310and so on fitted thereto is preferably held by the chuck371such that one of the openings344of the base340ais arranged to face outward. At this time, the chuck371and the base340aare arranged to be coaxial or substantially coaxial with each other to share the same rotation axis S. Referring toFIG. 67, once the lathe apparatus370is activated, the touch probe375is driven. The touch probe375is then brought preferably into contact with the end surface of the spacer330. A reference surface to be used as a reference during the processing is set thereby. Note that performing the processing based on the reference surface contributes to coping with variations in the dimensions of different parts.

Referring toFIG. 68, the tail stock372starts operating based on the set reference surface. The tail stock372is then properly pressed against the spacer330toward the chuck371. The base340ais thereby held by the lathe apparatus370. In addition, the base340ais caused to rotate about the rotation axis S at a predetermined rotation rate, together with the chuck371and the tail stock372.

Referring toFIG. 69, while the base340ais rotating, the cam follower373is pressed against the processed edge345of the base340a. Referring toFIG. 68, the cam follower373is then preferably tilted in a stepwise manner, so that the processed edge345is deformed radially inward to define the collar portion341. When the collar portion341has been defined, the spacer330is held between the collar portion341and an end portion of the rotor core310.

The cam follower373is arranged to rotate as needed at this time. The rotation of the cam follower373contributes to preventing occurrence of an excessive frictional force (i.e., frictional force resulting in an aggressive wear) and an unwanted force between the processed edge345and the cam follower373. Furthermore, the spacer330contributes to preventing or substantially preventing damage of any magnet320and the end portion of the rotor core310. Furthermore, the spacer330also contributes to retaining the circular shape of the processed edge345against influence of the recesses346. The spacer330thus facilitates the shaping of the collar portion341.

The collar portion341is thereby shaped so as to extend evenly in the radial direction to have a fine finish. The collar portion341is preferably arranged in close contact with the spacer330to restrain the movement of the spacer330.

The collar portion341is preferably arranged to project radially inward from the circumferential wall342by more than about 1 mm, for example. The projection of more than about 1 mm ensures that the collar portion341is reliably shaped to be flat without being corrugated, and also ensures secure retention of the spacer330. Note that the collar portion341may not necessarily be arranged to extend uniformly along the entire circumference thereof. That is, a cut or cuts may be defined in a portion or portions of the collar portion341.

Thereafter, the base340ais preferably placed in the lathe apparatus370in reverse orientation, and the above-described series of processes is performed in a similar manner to deform the other processed edge345to define the other collar portion341.

The rotor cover340is completed when the other collar portion341has been defined. The collar portions341, the spacers330, and the recessed dividing portion350combine to prevent the axial movement of the rotor cores310and the magnets320fitted inside the rotor cover340. The rotor cores310and the magnets320are thereby retained at predetermined positions. As described above, the rotor300can be constructed without use of an adhesive, according to the present preferred embodiment. This leads to improved productivity and reduced production cost. Furthermore, it is possible to arrange the magnets at substantially regular intervals in the circumferential direction without use of an intervening adhesive. This leads to an improvement in the degree of imbalance of the rotor.

Note that the present invention is not limited to the rotor300and so on according to the above-described preferred embodiments. It is to be understood by those skilled in the art that variations and modifications can be made without departing from the scope and spirit of the present invention.

For example, the shape of the cross section of the rotor core310is not limited to an octagon. The shape of the cross section of the rotor core310may be changed to a circle, any of a variety of other polygons, or the like suitably in accordance with the number of magnets320arranged on the rotor core310and the shape of each magnet320.

Also note that it may be so arranged that the number of rotor cores310is one while a plurality of groups of magnets are arranged one above the other along a rotation axis of the rotor core310.

Also note that the recessed dividing portion defining step may be performed after the support region defining step. Also note that the recessed dividing portion may not necessarily be arranged to extend continuously along the entire circumference thereof, but may be defined by a portion or portions arranged discontinuously in the circumferential direction, as long as the magnets are axially held thereby.

Other Preferred Embodiments

The stator12and so on of the motor1A according to the first preferred embodiment and the stator200and so on of the motor1according to the second preferred embodiment preferably share basic structures. Therefore, the above descriptions of the second preferred embodiment may include a description of a feature of the motor1A. Conversely, the above descriptions of the first preferred embodiment may include a description of a feature of the motor1. Further, one or more features of the motor1A and one or more features of the motor1may be combined as appropriate.