Patent ID: 8115163

Claim:
An encoder, having an oil mist prevention structure, including an encoding body, which includes a cylindrical base, a first sensor fixed to the cylindrical base and a secondary encoding piece corresponding to the first sensor and fixed to the cylindrical base; an oil-containing bearing, which is received and fixed in the cylindrical base; a shaft, which penetrates the oil-containing bearing to protrude beyond an end surface of the bearing; a rotary disk, which is fixed onto the shaft by being actuated to each other and covers one side of the secondary encoding piece; a second sensor, which is fixed to the cylindrical base to correspond to the first sensor and the secondary encoding piece, thereby sensing the signals emitted by the first sensor; and an oil mist prevention structure, which includes a mask integrally formed with the shaft and exposed beyond an end surface of the bearing and a ring extending from the mask for covering an outer periphery of the bearing.