Patent ID: 7719160

Claim:
A Gifford McMahon cryogenic cooler, comprising: a power unit made by a coreless and brushless direct-current motor, the 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 which 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 casing sized to receive and surround the armature coil, the outside rotor magnet, the insider rotor magnet and the sealing part with the output shaft projecting outwardly therefrom; a rotational motion-straight line motion conversion mechanism configured to convert a rotational motion of the power unit to a straight line motion, the rotational motion-straight line motion conversion mechanism including a conversion mechanism housing; a valve mechanism configured to receive a rotational output of the power unit and to switch a flow path of operation fluid sent out from a high pressure side of a compressor to a low pressure side of the compressor; a cylinder configured to take the operation fluid supplied and discharged by the valve mechanism so as to cool the operation fluid at an optional numbers of stages; and a displacer having a plurality of cold storage devices, wherein the outside casing and the conversion mechanism housing are fixedly connected to each other in a stationary manner.