Motor

Claim 1

A motor comprising: a field magnet system comprising m-number of permanent magnetic poles arranged in a circle such that the adjacent two permanent magnetic poles have opposite polarity to each other; and an armature with p-number of poles, the outer end of each of the poles facing the magnetic poles of the field magnet system: said field magnet system having a magnetic flux generating area whose widthwise length h (θ) perpendicular to the rotational direction of the armature varies with a rotational angle θ of the armature in accordance with the following formula: ##EQU9## wherein n is an integer of (i×j)±1 where j is an even number of 2 to 20, a n is a coefficient for cosine components, b n is a coefficient for sine components and is not zero for at least one value of n, T is a period of rotation of the armature through an angle corresponding to the peripheral length of a pair of adjacent N-pole and S-pole i is an integer given by p/q where q is the greatest common measure of m/2 and p, and h o is equal to H when 0≦θ<π and equal to -H when π≦θ<2π where H is a standard widthwise length of the field magnet system.

Claim 5

A method of trimming a torque characteristic of a motor comprising a field magnet system with a constant widthwise length comprising plural permanent magnetic poles arranged in a circle such that the adjacent two permanent magnetic poles have opposite polarity to each other, and an armature with plural poles, the outer end surface of each of the poles facing the magnetic poles of the field magnet system, said method comprising the steps of: measuring the distribution of the magnetic flux generated by the field magnet system relative to the rotational angle of the armature; evaluating harmonic wave components of the magnetic flux generated by the field magnet system by expanding in a series a function expressing the distribution curve of the magnetic flux; measuring the cogging torque generated by the field magnet system relative to the rotational angle of the armature; examining the relationship between the harmonic wave components of the magnetic flux and the cogging torque; and adjusting the widthwise length of the magnetic flux generating area of the field magnet system by incorporating into the widthwise length the variation corresponding to the selected harmonic wave components which cause the cogging torque to be eliminated.

Claim 6

A method of trimming a torque characteristic of a motor comprising a field magnet system with a constant widthwise length comprising plural permanent magnetic poles arranged in a circle such that the adjacent two permanent magnetic poles have opposite polarity to each other, and an armature with plural poles, the outer end surface of each of the poles facing the magnetic poles of the field magnet system, said method comprising the steps of: measuring the distribution of the magnetic flux generated by the field magnet system relative to the rotational angle of the armature; evaluating harmonic wave components of the magnetic flux generated by the field magnet system by expanding in a series a function expressing the distribution curve of the magnetic flux; measuring the cogging torque generated by the field magnet system relative to the rotational angle of the armature; examining the relationship between the harmonic wave components of the magnetic flux and the cogging torque; and adjusting the widthwise length of the magnetic flux generating area of the field magnet system by incorporating into the widthwise length the variation corresponding to the selected harmonic wave components which cause the cogging torque to be eliminated.