US 6,199,265 B1Granted

Method of securing magnets of revolving electric machine

AssigneeMitsuba Corporation

InventorsKatsutoshi Itou, Shuji Uehara, Hiroshi Hiruma

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Abstract

When a magnet cover 21 is press-fitted into the inner peripheral surfaces of magnets 18 annularly arranged on the inner peripheral surface of a hollow cylindrical yoke 11 having at an end thereof a closure wall 12, the magnets 18 are arranged peripherally at regular intervals on the outer peripheral surface of the magnet cover 21 that is supported by the lower die 34. The yoke 11 is held by the upper die 31 and arranged coaxially relative to the magnet cover 21 with open end 14 directed to the magnet cover 21. As the upper die 31 and the lower die 34 are closed relative to each other, the magnets 18 and the magnet cover 21 are press-fitted into the yoke 11 as the outer peripheral surfaces 19 of the magnets 18 are pressed by the inner peripheral surface of the yoke 11. Thus, the magnets 18 are rigidly secured to the yoke 11 without arranging a through hole in the closure wall 12 of the yoke. Since magnets 18 and the magnet cover 21 can be press-fitted into the yoke 11 without boring a through hole in the closure wall 12 of the yoke 11, the process of filling the through hole after assembling the motor can be omitted to reduce the cost of manufacturing the motor.

A method of securing magnets of a revolving electric machine such that a plurality of magnets are annularly and peripherally arranged at regular intervals on an inner peripheral surface of a hollow cylindrical yoke, having a closed upper end and an open lower end, and rigidly secured to the yoke by a thin-walled hollow cylindrical magnet cover press-fitted to inner peripheral surfaces of the magnets, comprising the steps of:

providing a press frame having upper and lower dies to be closed relative to each other,
providing said lower die with an upwardly extending cylindrical column having an upper smaller diameter section and a lower larger diameter section separated from one another by an annular horizontal step,
providing a hollow thin walled cylindrical magnet cover having a main body and a horizontal outwardly extending collar at the lower end of the main body,
placing the magnet cover over the upper section of the column with the collar resting on the column step,
providing an annular holding member surrounding and vertically movable relative to the column,
biasing the holding member upwardly to an upper limit position at which at least a part of the holding member extends upwardly beyond the collar resting on the column step to form an upwardly open annular groove between the holding member and a bottom part of the magnet cover main body,
arranging a plurality of magnets such as aforesaid in annularly spaced condition about an outer periphery of the magnet cover body with lower ends of said magnets being received in said groove,
providing a yoke such as aforesaid,
securing said yoke to the upper die of said press frame with said yoke positioned coaxially relative to said magnet cover with the open end of said yoke directed to said magnet cover, and
then closing said upper die and said lower die relative to each other to push the yoke over the magnets and to thereby press-fit said magnets and said magnet cover into said yoke,
said yoke having a vertical length greater than that of said upper column section so that as the yoke is pushed over the magnets a lower end of the yoke engages the holding member and displaces the holding member downwardly to a position at which the holding member is located below the magnet cover.

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Abstract

Claims9