Patent ID: 8053946

Claim:
A pulse tube cryogenic cooler, comprising: a cold head including a cool storage device and a pulse tube; a compressor configured to supply operation gas with a high pressure to the cold head and receive the operation gas from the cold head as low pressure gas; a valve unit connected between the cold head and the compressor and mutually connecting a high pressure side and a low pressure side of the compressor to the cold head; a buffer tank configured to control phase difference between pressure change and a flow rate change of the operation gas; and a coreless and brushless direct-current motor, including: an armature coil wound without core and formed in the shape of a saddle, the armature coil including a plurality of coils separately provided on an external surface with a cylindrical circumference, the armature coil generating a magnetic field in a case where a direct current is applied; an outside rotor magnet formed by a permanent magnet, the outside rotor magnet being provided at an outside of the armature coil in the shape of a cylinder so as to face the armature coil, the outside rotor magnet being rotated by the magnetic field; an inside rotor magnet formed by a permanent magnet, the inside rotor magnet being provided in the shape of a cylinder at an inside of the armature coil so that the inside rotor magnet has a pole opposite to the outside rotor magnet and a rotational shaft is independently provided, the inside rotor magnet rotated synchronously with the outside rotor magnet by the magnetic field; an output shaft connected to the inside rotor magnet, the output shaft being rotated following rotation of the inside rotor magnet and making a connected driven device rotate; a sealing part of a barrier structure in which the sealing part partitions the armature coil and the outside rotor magnet to an outside of the inside rotor magnet and seals the armature coil and the outside rotor magnet; and an outside case surrounding the armature coil and the outside rotor magnet and sized for rotational movement of the outside rotor therein, the outside case connected to and supported by the sealing part of the barrier structure, the coreless and brushless direct-current motor being configured to rotate the valve unit.