Power transmission device

A power transmission device comprising:

• a drive-side magnet that includes a plurality of poles and rotates;
• a housing that houses the drive-side magnet;
• a stationary magnet that has a number of poles larger than a number of poles of the drive-side magnet and is fixed to the housing;
• a pole piece that includes a plurality of magnetic body portions and rotates by modulating a magnetic flux between the drive-side magnet and the stationary magnet;
• and
• a sealing member that partitions an inside of the housing into a driving side space where the drive-side magnet is disposed and a driven side space where the stationary magnet and the pole piece are disposed, the sealing member sealing fluid between the driving side space and the driven side space, wherein
• the pole piece and the stationary magnet have a cylindrical shape and are disposed coaxially with and radially outer side of the drive-side magnet, and
• the sealing member includes a sealing cylinder portion positioned radially outer side of the drive-side magnet, and a sealing bottom surface portion covering the sealing cylinder portion from the driving side space.