Inner-rotor-type brushless motor having built-in bus bar

1. An inner-rotor-type brushless motor comprising a stator fixedly disposed within a motor casing; a rotor fixed to a rotation shaft; and a bus bar which connects together U-phase, V-phase, and W-phase windings wound on a stator magnetic pole core and connects them to output wires, wherein

the U-phase, V-phase, and W-phase windings are each composed of a plurality of coils which are wound around stator magnetic poles and are connected to form a Y-connection or a double Y-connection;

the bus bar, which carries a sensor board including a position detection sensor fixed thereto, includes a generally circular bus bar body formed of a resin, and bus bar legs formed integrally with the bus bar body and used for fixing the bus bar;

the bus bar includes, as conductive members for connecting the windings, only three external terminals connected to first ends of the windings and one Y-connection terminal for connecting second ends of the windings together;

the first and second ends of the windings are pulled out to positions near winding-side terminal portions of the Y-connection and external terminals to which the first and second ends are to be connected, and are connected to the corresponding Y-connection and external terminals;

the three winding-side terminal portions of the Y-connection terminal are disposed to be located adjacent to one another, the winding-side terminal portions of the three external terminals are disposed to be located adjacent to one another, and the Y-connection terminal and the external terminals are disposed to be located on one side on the circumference of the bus bar body, whereby the bus bar body has a circumferential region where the conductive members are not present; and

the sensor board is attached such that the position detection sensor is located in the circumferential region where the conductive members are not present.

2. An inner-rotor-type brushless motor according to claim 1 , wherein the stator, to which the bus bar is fixed by inserting the plurality of bus bar legs into core grooves, is fixedly disposed within the casing having a cylindrical shape.

3. An inner-rotor-type brushless motor according to claim 1 , wherein the bus bar body has a length in the radial direction determined such that the bus bar body does not block inter-coil clearances, and wherein the bus bar body is disposed at a radial position near the rotor so as to form a clearance between the bus bar body and a cylindrical portion of the core, and the first and second ends of the windings are pulled out on the radially outer side of the bus bar body for connection; or the bus bar body is disposed at a radial position corresponding to the cylindrical portion of the core, and the first and second ends of the windings are pulled out on the radially inner side of the bus bar body for connection.

4. An inner-rotor-type brushless motor according to claim 1 , wherein mutual connection between the plurality of coils which constitute each of the U-phase, V-phase, and W-phase windings is performed by means of direct serial connection such that a winding-ending-side end of a first coil and a winding-starting-side end of a second coil are serially connected, a winding-ending-side end of the second coil and a winding-starting-side end of a third coil are serially connected, and so on; and the coils of three phases are continuously wound in the order of U-phase, V-phase, and W-phase or in the order of U-phase, W-phase, and V-phase.

5. An inner-rotor-type brushless motor according to claim 4 , wherein the number of rotor magnetic poles is 2n and the number of stator magnetic poles is 3n, or the number of rotor magnetic poles is 4n and the number of stator magnetic poles is 3n, where n is an integer of 2 to 6; and winding for each phase ends at a coil adjacent to a coil from which the winding has been started.

6. An inner-rotor-type brushless motor comprising a stator fixedly disposed within a motor casing; a rotor fixed to a rotation shaft; and a bus bar which connects together U-phase, V-phase, and W-phase windings wound on a stator magnetic pole core and connects them to output wires, wherein

the U-phase, V-phase, and W-phase windings are each composed of a plurality of coils which are wound around stator magnetic poles and are connected to form a D-connection;

the bus bar, which carries a sensor board including a position detection sensor fixed thereto, includes a generally circular bus bar body formed of a resin, and bus bar legs formed integrally with the bus bar body and used for fixing the bus bar;

the bus bar includes only three external terminals as conductive members for connecting the windings;

the three external terminals include integrally-formed winding-side terminal portions, each connecting two of the first and second ends of the windings together;

the first and second ends of the U-phase, V-phase, and W-phase windings are pulled out to positions near the winding-side terminal portions to which the first and second ends are to be connected, and are connected thereto so that the U-phase, V-phase, and W-phase windings form a D-connection;

the three external terminals are disposed on the bus bar body such that the external terminals are located adjacent to one another, whereby the bus bar body has a circumferential region where the conductive members are not present; and

the sensor board is attached such that the position detection sensor is located in the circumferential region where the conductive members are not present.

7. An inner-rotor-type brushless motor according to claim 6 , wherein the stator, to which the bus bar is fixed by inserting the plurality of bus bar legs into core grooves, is fixedly disposed within the casing having a cylindrical shape.

8. An inner-rotor-type brushless motor according to claim 6 , wherein the bus bar body has a length in the radial direction determined such that the bus bar body does not block inter-coil clearances, and wherein the bus bar body is disposed at a radial position near the rotor so as to form a clearance between the bus bar body and a cylindrical portion of the core, and the first and second ends of the windings are pulled out on the radially outer side of the bus bar body for connection; or the bus bar body is disposed at a radial position corresponding to the cylindrical portion of the core, and the first and second ends of the windings are pulled out on the radially inner side of the bus bar body for connection.

9. An inner-rotor-type brushless motor according to claim 6 , wherein mutual connection between the plurality of coils which constitute each of the U-phase, V-phase, and W-phase windings is performed by means of direct serial connection such that a winding-ending-side end of a first coil and a winding-starting-side end of a second coil are serially connected, a winding-ending-side end of the second coil and a winding-starting-side end of a third coil are serially connected, and so on; and the coils of three phases are continuously wound in the order of U-phase, V-phase, and W-phase or in the order of U-phase, W-phase, and V-phase.

10. An inner-rotor-type brushless motor according to claim 9 , wherein the number of rotor magnetic poles is 2n and the number of stator magnetic poles is 3n, or the number of rotor magnetic poles is 4n and the number of stator magnetic poles is 3n, where n is an integer of 2 to 6; and winding for each phase ends at a coil adjacent to a coil from which the winding has been started.