| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce noise with a simple constitution by providing a silencer which damps a prescribed frequency of acoustic waves generated from a motor section in a control case. SOLUTION: A control unit 8 is positioned on the right side of a motor section 1 in the axial direction. The unit 8 is constituted by providing an inverter device 10 in a control case 9. The inverter device 10 is provided with capacitors 12 and a switching element 13 mounted on a control circuit board 11 and constitutes a control circuit, etc. The space 14 in the case 9 is communicated with the inside of the motor section 1 which generates acoustic waves through a hole 15 formed through a bearing bracket 2c. The space 14 and hole 15 constitute a silencer 16. When the damping frequency of the silencer 16 is made coincident with the frequency of principal noise in the frequency band of a carrier for controlling inverter, the noise can be damped efficiently. |
