A single cover plate structure has a cover plate at the front support point of joint, and no cover plate at the rear end. Both front and rear ends of the joint of the double cover plate are provided with a cover plate and reinforced ribs. It makes the pump carry large torque at high power and realize the stability of the size of the joint parts when delivering high-temperature media, ensuring the safe operation of the pump. The structure of this kind of pump is internationally advanced technology.