Electric work machine
An electric work machine includes: a brushless motor including: a rotor having permanent magnets fixed to a rotor core; a stator core; one or more insulators fixed to the stator core; and a stator including coils mounted on the insulator(s); magnetic sensors, which detect the position of the rotor in a rotational direction by detecting the magnetic flux of the permanent magnets; a controller, which controls energization of the coils based in part on detection signals of the magnetic sensors; and an output part driven by the rotor. The permanent magnets are each a neodymium, sintered, plate magnet. The pole count (N) is the number of permanent magnets. The stator diameter (x) is the diameter of a surface of the stator core that faces the rotor in millimeters. The following condition is satisfied: 0.16x+2.5<N<0.23x+3.6.
1 . An electric work machine comprising:
a brushless motor including: a rotor having permanent magnets fixed to a rotor core; a stator core; one or more insulators fixed to the stator core; and a stator having coils mounted on the insulator(s);
magnetic sensors configured to detect the position of the rotor in a rotational direction by detecting the magnetic flux of the permanent magnets;
a controller configured to control energization of the coils based at least in part on detection signals output by the magnetic sensors;
an output part configured to be driven by the rotor;
at least one battery-mounting part; and
at least one battery pack mounted on the at least one battery-mounting part and configured to supply electric power to generate drive currents that are supplied to the coils;
wherein:
the permanent magnets are each a neodymium, sintered, plate magnet;
a pole count (N) is defined as the number of permanent magnets;
a stator diameter (x) is defined as the diameter of a surface of the stator core that faces the rotor in millimeters;
the following condition is satisfied:
0.16 x+ 2.5< N< 0.23 x+ 3.6;
the brushless motor is a three-phase motor;
a wire-to-wire resistance of the coils is R (mΩ);
a rated voltage of the at least one battery packs is V; and
the following condition is satisfied:
R/V 2 ≤0.038.
2 . The electric work machine according to claim 1 , wherein the brushless motor is an outer rotor brushless motor in which the rotor radially surrounds an outer circumference of the stator core.
3 . The electric work machine according to claim 2 , wherein the rotor has an outer diameter in a range of 105-125 mm.
4 . The electric work machine according to claim 2 , wherein the outer diameter of the rotor is 110-120 mm.
5 . The electric work machine according to claim 2 , wherein:
the stator core comprises teeth, around which the coils are respectively wound with the insulator(s) interposed therebetween; and
each of the teeth has a width of 4-8 mm.
6 . The electric work machine according to claim 5 , wherein the permanent magnets each have a thickness of 1.5-3.5 mm and are fixed to an inner-circumferential surface of the rotor core by a bonding agent.
7 . The electric work machine according to claim 6 , further comprising:
a rotor shaft fixed to the rotor;
wherein the output part is fixed to the rotor shaft.
8 . The electric work machine according to claim 7 , wherein the output part is a lawnmower cutting blade.
9 . The electric work machine according to claim 1 , wherein:
the stator core comprises teeth, around which the coils are respectively wound with the insulator(s) interposed therebetween; and
each of the teeth has a width of 4-8 mm.
10 . The electric work machine according to claim 1 , wherein the permanent magnets each have a thickness of 1.5-3.5 mm.
11 . The electric work machine according to claim 1 , further comprising:
a rotor shaft fixed to the rotor;
wherein the output part is fixed to the rotor shaft.
12 . The electric work machine according to claim 1 , wherein:
twenty-eight permanent magnets are fixed to the rotor core; and
twenty-four coils are mounted on the insulator(s).
13 . The electric work machine according to claim 12 , wherein:
the stator core comprises teeth, around which the coils are respectively wound with the insulator(s) interposed therebetween; and
each of the teeth has a width of 4-8 mm.
14 . The electric work machine according to claim 12 , wherein the permanent magnets each have a thickness of 1.5-3.5 mm and are fixed to an inner-circumferential surface of the rotor core by a bonding agent.
15 . The electric work machine according to claim 12 , further comprising:
a rotor shaft fixed to the rotor;
wherein the output part is fixed to the rotor shaft.
16 . The electric work machine according to claim 12 , wherein:
the stator core comprises teeth, around which the coils are respectively wound with the insulator(s) interposed therebetween;
each of the teeth has a width of 4-8 mm; and
the permanent magnets each have a thickness of 1.5-3.5 mm and are fixed to an inner-circumferential surface of the rotor core by a bonding agent.
17 . The electric work machine according to claim 16 , further comprising:
a rotor shaft fixed to the rotor;
wherein the output part is a lawnmower blade that is directly fixed to the rotor shaft.
18 . The electric work machine according to claim 17 , wherein:
the rotor further includes a rotor cup that supports the rotor core; and
discharge ports penetrate through the rotor cup.
19 . The electric work machine according to claim 12 , wherein:
the brushless motor is an outer-rotor brushless motor in which the rotor is disposed around an outer circumference of the stator core; and
the rotor has an outer diameter in a range of 105-125 mm.
20 . The electric work machine according to claim 19 , wherein the outer diameter of the rotor is in a range of 110-120 mm.