Abstract: A stator, in which a rotor is rotatably accommodated, is provided with a cylindrical yoke and a magnet that is arranged so as to extend along an inner circumference of the yoke, and has a plurality of magnetic poles generating a magnetic field operable to rotate the rotor. A tip tool is coupled to the rotor and operable to perform a prescribed working in accordance with the rotation of the rotor. The yoke is includes a plurality of steel plates laminated together to form a cylindrical yoke. At least one of a groove and a rib is provided on at least one of the inner circumference of the yoke and an outer circumferential of the magnet so as to extend in an axial direction of the cylindrical yoke. The at least one of the groove and the rib is provided at a boundary between the magnetic poles.

Abstract: It is an object of the invention to provide an improved technique for controlling the output characteristic of a motor. Representative power tool includes a tool bit and a motor. The motor drives the tool bit and includes an armature, a coordinator, a plurality of segments and a plurality of armature windings. The armature has a plurality of slots. The communicator rotates together with the armature. Plurality of segments is provided on the communicator. Respective armature windings are connected at the both ends of the segments. Each of the armature windings is defined by coils that are wound between respective pairs of the slots of the armature. Each of the armature windings is formed by at least two coils connected in series. At least one of the coils defining the armature winding has a different number of turns of a wire wound between the associated slots from the other coils in the same armature winding.

Abstract: A stator, in which a rotor is rotatably accommodated, is provided with a cylindrical yoke and a magnet which is arranged so as to extend along an inner circumference of the yoke, and has a plurality of magnetic poles generating a magnetic field operable to rotate the rotor. A tip tool is coupled to the rotor and operable to perform a prescribed working in accordance with the rotation of the rotor. At least one of a groove and a rib is provided on at least one of the inner circumference of the yoke and an outer circumferential of the magnet so as to extend in an axial direction of the cylindrical yoke. The at least one of the groove and the rib is provided at a boundary between the magnetic poles.

Abstract: It is an object of the invention to provide an improved technique for controlling the output characteristic of a motor. Representative power tool includes a tool bit and a motor. The motor drives the tool bit and includes an armature, a coordinator, a plurality of segments and a plurality of armature windings. The armature has a plurality of slots. The communicator rotates together with the armature. Plurality of segments is provided on the communicator. Respective armature windings are connected at the both ends of the segments. Each of the armature windings is defined by coils that are wound between respective pairs of the slots of the armature. Each of the armature windings is formed by at least two coils connected in series. At least one of the coils defining the armature winding has a different number of turns of a wire wound between the associated slots from the other coils in the same armature winding.

Abstract: A hammer drill 1 includes a barrel 2 containing a striking mechanism. The drill further includes a motor 4 with a motor shaft 6 encased in a motor accommodating chamber 19 which has an upper opening at which a baffle plate 20 is disposed. The baffle plate 20 includes a bottom portion 21 and a partition 22. The baffle plate 20 further includes a flange 23 that extends radially around the upper edge of the partition 22 except toward the front of the partition 22 with the outer edge of the flange 23 reaching the inner surface of the motor housing 3. Additionally, a generally horizontal slot 24 is formed at the front peripheral surface of the bottom portion 21 of the baffle plate 20. Moreover, a plurality of air inlets 27 are provided at the rear end of a housing handle 5 of the drill 1, whereas a plurality of air outlets 29 are provided at the bottom of the motor housing 3.

Abstract: A battery-charging system is provided that does not require removal of batteries from an impact screwdriver (1) for recharging. The battery-charging system includes the impact screwdriver and a charger (20). The impact screwdriver (1) has a nose (3a) to which a tool bit is attached. The impact screwdriver additionally includes a grip handle (4) containing a battery unit (5) whose terminals (10) for recharging are exposed in a surface of a protrusion (7) of the grip handle. The charger (20) includes a charger circuit encased in an enclosure having a base (21) covered with a housing (22). The housing of the charger is provided with a first receiving recess (29) which can receive the nose (3a) of the screwdriver and a second receiving recess (30) which can receive the protrusion (7) of the screwdriver. The system additionally includes a pair of charge terminals of the charger circuit that resiliently projects into the second receiving recess (30).