The invention discloses a low-speed high-torque and permanent-
magnet synchronous high-speed automatic tool-changing electric spindle. The electric spindle comprises a motor body, and a
stator, a rotor, a rotor shaft, a spring pre-tightening mechanism, a front bearing and a rear bearing are arranged inside the motor body. The electric spindle further comprises a connection base fixed to the rear end of the motor body, a connector fixedly connected to the connection base, a steam cylinder
assembly fixedly connected to the connector, a rear cover arranged at the end of the steam cylinder
assembly and a front end cover connected to the front end of the motor body. A tool loosening and pulling mechanism is arranged in the center of the rotor shaft, a pulling claw is arranged at the front end of the tool loosening and pulling mechanism, a disc spring
assembly is installed in the middle of the tool loosening and pulling mechanism, a high-performance sensor is adopted together, and therefore automatic tool changing is more convenient and accurate and rapider. A
magneto-electric coder is adopted at the rear end, so that low-speed torque output is more balanced.
Compressed air is adopted for non-contact air sealing so that higher rotation speed can be obtained. The electric spindle is simple and compact in structure and powerful in function, is smaller than common electric spindles with the same power in size, has the advantages that the speed is low and the torque is high and can be widely applied to high-speed and low-speed precision
machining of various materials.