Motor with brush

Abstract

A brushed motor includes a rotation shaft, a commutator including a plurality of segments separated by a plurality of undercuts arranged at unequal intervals, an armature, a plurality of permanent magnets, a voltage equalizing line, a positive electrode brush, and a negative electrode brush. When Pz is the number of the permanent magnets and N is the number of the segments, a relationship of N=Pz(K−0.5) is satisfied. Pz is an even number that is greater than or equal to four. K is a constant and is a natural number that is greater than or equal to two. The plurality of undercuts includes at least one set of undercuts arranged at an undercut interval that differs from a reference angle θz. The reference angle θz is specified by a relational expression of θz=(360 degrees/Pz)±(360 degrees/2N).

1 . A brushed motor comprising:
 a rotation shaft;   a commutator fixed to the rotation shaft, wherein the commutator includes a plurality of segments insulated and separated by a plurality of undercuts, and the plurality of undercuts are arranged at unequal angular intervals about a center axis of the rotation shaft;   an armature fixed to the rotation shaft;   a plurality of permanent magnets located at an outer side of the armature, wherein the plurality of permanent magnets are arranged at equal intervals so that directions of magnetic poles differ in adjacent ones of the permanent magnets;   a voltage equalizing line that connects different ones of the segments; and   a positive electrode brush and a negative electrode brush arranged on an outer circumference of the commutator at positions that are not facing each other;   wherein when Pz is the number of the permanent magnets and N is the number of the segments, a relationship of N=Pz(K−0.5) is satisfied,   where Pz is an even number that is greater than or equal to four,   K is a constant and is a natural number that is greater than or equal to two, and   the plurality of undercuts includes at least one set of undercuts arranged at an undercut interval that differs from a reference angle θz, and   the reference angle θz is specified by a relational expression of θz=(360 degrees/Pz) (360 degrees/2N).   
     
     
         2 . The brushed motor according to  claim 1 , wherein
 when θb is a brush arrangement angle and θy is a deviation angle, the positive electrode brush and the negative electrode brush are arranged at positions specified by θb+θy,   θb=360 degrees/(Pz×K) is satisfied, wherein K is a constant and a natural number,   θy<360 degrees/2Pz is satisfied, and   the reference angle θz is specified by a relational expression of θz=(360 degrees/Pz)±(360/2N)±θy.   
     
     
         3 . A brushed motor comprising:
 a rotation shaft;   a commutator fixed to the rotation shaft, wherein the commutator includes a plurality of segments insulated and separated by a plurality of undercuts, wherein the plurality of undercuts are arranged at unequal angular intervals about a center axis of the rotation shaft;   an armature fixed to the rotation shaft;   a plurality of permanent magnets located at an outer side of the armature, wherein the plurality of permanent magnets are arranged at equal intervals so that directions of magnetic poles differ in adjacent ones of the permanent magnets;   a voltage equalizing line that connects different ones of the segments; and   a positive electrode brush and a negative electrode brush arranged on an outer circumference of the commutator at positions that are not facing each other;   wherein when Pz is the number of permanent magnets and N is the number of segments, a relationship of N=Pz×K is satisfied,   where Pz is an even number that is greater than or equal to four, and   K is a constant and is a natural number that is greater than or equal to two,   the plurality of undercuts includes at least one set of undercuts arranged at an undercut interval that differs from a reference angle θz, and   the reference angle θz is specified by a relational expression of θz=360 degrees/Pz.   
     
     
         4 . The brushed motor according to  claim 3 , wherein
 when θb is a brush arrangement angle and θy is a deviation angle, the positive electrode brush and the negative electrode brush are arranged at positions specified by θb+θy,   θb=360 degrees/(Pz×K) is satisfied, where K is a constant and a natural number,   θy<360 degrees/2Pz is satisfied; and   the reference angle θz is specified by a relational expression of θz=(360 degrees/Pz)±θy.   
     
     
         5 . A brushed motor comprising:
 a rotation shaft;   a commutator fixed to the rotation shaft, wherein the commutator includes a plurality of segments insulated and separated by a plurality of undercuts, the plurality of undercuts are arranged at unequal angular intervals about a center axis of the rotation shaft;   an armature fixed to the rotation shaft;   a plurality of permanent magnets arranged at a radially outer side of the armature; and   a brush arranged on an outer circumference of the commutator,   wherein the rotation shaft, the commutator, and the armature are integrally rotatable in forward and reverse directions;   N is the number of the segments and the number of the plurality of undercuts,   circumferential center positions of the plurality of undercuts are shifted in a forward rotation direction and a reverse rotation direction from a corresponding circumferential center position when the plurality of undercuts are formed at an equal angle,   Z 1  is the total of the deviation angle of each of the undercuts shifted in the forward rotation direction,   Z 2  is the total of the deviation angle of each of the undercuts shifted in the reverse rotation direction,   Z is the sum of the deviation angles,   Z=Z 1 +Z 2  is satisfied,   when P is the number of pole pairs of the magnetic poles of the permanent magnets, Q=(Z/N)/P represents an index value Q, and   the index value Q is −0.5 degrees<Q<+0.5 degrees.   
     
     
         6 . The brushed motor according to  claim 5 , wherein
 the plurality of undercuts is divided by the number of pole pairs, and a sum of the deviation angles of the undercuts belonging to each of the divided group is obtained for each divided group, and   the index value Q is −0.5 degrees<Q<+0.5 degrees for each group.   
     
     
         7 . The brushed motor according to  claim 5 , wherein
 the armature includes a plurality of slots,   the number of slots is a number not dividable by the number of plurality of magnetic poles, and   (Wmin+2×G)/2>0.8×F is satisfied when F is a circumferential width of the brush, the plurality of segments each having a segment width that is a circumferential width, Wmin is a minimum segment width in the plurality of segments, and G is a circumferential width of each of the undercuts.   
     
     
         8 . The brushed motor according to  claim 7 , wherein the number of pole pairs is two, and the number of the segments and the number of the slots are each ten. 
     
     
         9 . The brushed motor according to  claim 5 , wherein
 the armature includes a plurality of slots,   the number of slots is a number dividable by the number of plurality of magnetic poles, and   (Wmin+2×G)>0.8×F is satisfied when F is a circumferential width of the brush, the plurality of segments each having a segment width that is a circumferential width, Wmin is a minimum segment width in the plurality of segments, and G is a circumferential width of each of the undercuts.   
     
     
         10 . The brushed motor according to  claim 9 , wherein the number of pole pairs is two, and the number of the segments and the number of the slots are twelve.