Flywheel energy storage device

A flywheel energy storage device, comprising:

• a housing, defining an installation chamber;
• a flywheel rotor, arranged in the installation chamber and rotatable in the installation chamber, and comprising a rotor portion, a first shaft portion and a second shaft portion, wherein the first shaft portion is positioned at one side of the rotor portion, the second shaft portion is positioned at another side of the rotor portion, and the first shaft portion and the second shaft portion are arranged coaxially;
• a first bearing, arranged at the housing and to surround an outer circumference of the first shaft portion;
• a second bearing, arranged at the housing and to surround an outer circumference of the second shaft portion;
• and
• a limit assembly, arranged at an end of the first shaft portion or an end of the second shaft portion, and adapted to stop the end of the first shaft portion or the end of the second shaft portion to constrain displacement of the flywheel rotor during the flywheel rotor moving along an axial direction,
• wherein the limit assembly comprises a first bearing cover, a second bearing cover and a third bearing,
• wherein the third bearing comprises a first bearing ring and a second bearing ring, which are movable relative to each other,
• wherein one of the first bearing cover and the second bearing cover is connected to the first bearing ring, and another one of the first bearing cover and the second bearing cover is connected to the second bearing ring, and
• wherein one of the first bearing cover and the second bearing cover is adapted to stop the end of the first shaft portion or the end of the second shaft portion.