[54] METHOD OF MAKING CYLINDRICAL FERROMAGNETIC BODY AND COVER ASSEMBLY FOR ROTOR OF DC MOTOR
[75] Inventors: Toshiyuki Teshigawara, Maebashi;
Yoshikazu Kokubun, Gunma, both of
Japan
[73] Assignee: Sanden Corp., Isesaki, Japan
[21] Appl. No.: 274,636
[22] Filed: Jul. 13,1994
[30] Foreign Application Priority Data
Jul. 16, 1993 [JP] Japan 5-197710
[51] Int. CI.6 H02K 15/02
[52] U.S. CI 29/598; 29/608; 264/272.2;
310/43; 310/156
[58] Field of Search 29/598, 596, 608;
310/42, 43, 45, 156; 264/272.2, 272.19,
272.15
[56] References Cited
U.S. PATENT DOCUMENTS
4,742,259 5/1988 Schaefer et al 310/156
4,973,872 11/1990 Dohogne 310/156
5,040,286 8/1991 Stark 29/598
5,144,735 9/1992 Stark 29/732
FOREIGN PATENT DOCUMENTS
2-97244 4/1990 Japan.
A method of making a cylindrical ferromagnetic body and cover assembly for a rotor of a dc motor is provided. In a first embodiment, a blend of a powdered ferromagnetic material and a heat-curable binder is compressedly molded into a cylindrical form in a generally cylindrical non-magnetic cover material having an annular flange around the top thereof, while heat is applied to the material from a heated stationary mold through the cover material, so that the cylindrically-molded ferromagnetic body firmly adheres to the cover material in the molding process. After the ferromagnetic body is cured, an non-magnetic annular protector is placed on the top of the cylindrically-molded body and the annular flange is radially inwardly bent over onto the protector. In a second embodiment, a heated block of a powdered ferromagnetic material is deposited in a cupshaped non-magnetic cover material. The block is subsequently pressedly molded into a cup-shaped form in the cup-shaped cover material so that the molded material firmly adheres to the cover material. After the molded material is cooled, a top section and a bottom section of the cup-shaped body, together with the corresponding top section and the bottom section of the cover material, are cut off so as to obtain a cylindrical ferromagnetic body and cover assembly.
