Power tool
A power tool, such as a hammer driver-drill ( 1 ), includes a brushless motor ( 8 ) having a stator ( 9 ) and a rotor ( 10 ). The stator ( 9 ) has slots ( 78 ) between teeth ( 63 ) that protrude inwardly. Coils ( 64 ) are respectively wound around each tooth ( 63 ) and the coils ( 64 ) of all phases are delta-connected in series. The rotor ( 10 ) includes permanent magnets ( 68 ) and is rotatably disposed in the interior of the stator ( 9 ). A sensor circuit board ( 65 ) is fixed to the stator ( 9 ) and includes magnetic sensors ( 66 ) that detect the rotational position of the rotor ( 10 ). The magnetic sensors ( 66 ) are provided at locations that correspond at least substantially to the centers of the slots ( 78 ) in the rotational direction of the rotor ( 10 ).
1. A power tool, comprising:
a stator having a plurality of radially inwardly extending teeth separated by slots and coils respectively wound around each tooth of the plurality of teeth, wherein different sets of the coils correspond to different phases, the different sets of the coils are delta-connected in series;
a rotor having magnets and being configured to rotate in the interior of the stator; and
a sensor circuit board fixed to the stator and having magnetic sensors configured to detect rotation of the rotor;
wherein the magnetic sensors are provided at least substantially at the centers of the slots in a rotational direction of the rotor.
2. The power tool according to claim 1 , wherein the sensor circuit board is attached to an electrically insulating member on an end surface of the stator.
3. The power tool according to claim 2 , wherein:
the rotor has an outermost circumferential portion lying on a first circle and
the magnetic sensors are disposed along the first circle.
4. The power tool according to claim 1 , wherein:
the rotor has an outermost circumferential portion lying on a first circle and
the magnetic sensors are disposed along the first circle.
5. The power tool according to claim 1 , wherein the rotor has a non-circular outer shape.
6. The power tool according to claim 5 , wherein:
the rotor has a large outer circumferential portion lying on a first circle and small outer circumferential portion lying on a second circle and
the magnetic sensors are disposed on a radially outer side of the second circle.
7. The power tool according to claim 1 , wherein an axial groove is formed on an outer circumference of the stator radially outward of at least one tooth of the plurality of teeth.
8. The power tool according to claim 1 , wherein the sensor circuit board is screw fastened to the stator at a location along an extension of at least one tooth of the plurality of teeth.
9. The power tool according to claim 1 , wherein:
the sensor circuit board is attached to an electrically insulating member on an end surface of the stator,
the rotor has an outermost circumferential portion lying on a first circle,
the magnetic sensors are disposed along the first circle,
the rotor has a non-circular outer shape,
an axial groove is formed on an outer circumference of the stator radially outward of at least one tooth of the plurality of teeth, and
the sensor circuit board is screw fastened to the stator at a location along an extension of at least one tooth of the plurality of teeth.
10. The power tool according to claim 1 , further including
an electrically insulating member fixed to the stator;
wherein the coils are respectively wound around each tooth of the plurality of teeth via the electrically insulating member; and
the electrically insulating member comprises retainer walls configured to prevent the coils from collapsing inward, and reinforcing means for reinforcing the retainer walls.
11. The power tool according to claim 1 , further comprising:
an electrically insulating member that is fixed to the stator and that includes a plurality of guide ribs; and
a tool-accessory retaining part driven by the rotor,
wherein a plurality of crossover wire portions are arranged axially adjacent to one another on the plurality of guide ribs,
at least one of the plurality of crossover wire portions runs in a direction opposite the winding direction, and
the plurality of radially inwardly extending teeth are six teeth and the slots are six slots.
12. The power tool according to claim 11 , wherein two of the crossover wire portions are led out from one of the coils.
13. The power tool according to claim 11 , wherein the at least one of the plurality of crossover wire portions comprises all the plurality of crossover wire portions.
14. The power tool according to claim 11 , wherein the wire is wound around each of the six teeth starting from one side in a circumferential direction of the stator and ending on an other side in the circumferential direction of the stator.
15. The power tool according to claim 14 , wherein two of the crossover wire portions are led out from one of the coils.
16. The power tool according to claim 15 , wherein the at least one of the plurality of crossover wire portions comprises all the plurality of crossover wire portions.
17. The power tool according to claim 5 , wherein:
the rotor has a large outer circumferential portion lying on a first circle and small outer circumferential portion lying on a second circle, and
the magnetic sensors are disposed on a radially outer side of the second circle and at least partially on a radially inner side of the first circle.
18. A power tool comprising:
a stator having a plurality of radially inwardly extending teeth separated by slots and coils respectively wound around each tooth of the plurality of teeth;
a rotor having magnets and a rotor core that has a first outer circumferential width and a second outer circumferential width; and
a sensor circuit board fixed to the stator and having magnetic sensors configured to detect rotation of the rotor;
wherein the magnetic sensors are at least partially located between the first outer circumferential width and the second outer circumferential width of the rotor core.
19. The power tool according to claim 18 , wherein the rotor has four magnets and the stator has six teeth.
20. The power tool according to claim 19 , wherein six axial grooves are formed in the circumferential direction at a constant interval on an outer circumference of the stator core, the grooves being respectively disposed at locations along extensions of the respective teeth.