Rotary pump and brake device in which rotary pump is provided

A rotary pump, comprising:

• a rotating portion that includes an outer rotor having an internal tooth portion on its inner circumference and an inner rotor having an external tooth portion and rotates about a drive shaft as its axis, the rotating portion being assembled such that a plurality of chamber portions is formed by a meshing of the internal tooth portion and the external tooth portion;
• and
• a casing that covers the rotating portion and includes opening portions into which the drive shaft is fitted, a suction port that takes a fluid into the rotating portion, and a discharge port that discharges the fluid from the rotating portion,
• wherein the rotary pump is configured such that a pressure difference between the suction port and the discharge port is maintained by a closed portion that has the greatest volume among the plurality of chamber portions, and a rotating movement of the rotating portion causes the fluid to be sucked from the suction port and the fluid to be discharged through the discharge port,
• a seal element that is disposed within a seal groove portion that is formed in a surface of the casing that faces axial direction end faces of the inner rotor and the outer rotor, the seal element being disposed in a gap between the casing and the axial direction end faces of the inner rotor and the outer rotor, extending through a gap between the discharge port and the drive shaft, extending through the closed portion, and reaching the periphery of the outer rotor, the seal element including a sealing portion that covers the closed portion, and
• a thin-walled portion is provided in the sealing portion of the seal element, making the axial direction thicknesses of the sealing portion thinner in the area that come into contact with the axial direction end face of the outer rotor than in the area that come into contact with the axial direction end face of the inner rotor, such that the area on the outer rotor side of the sealing portion separates from the outer rotor as an internal pressure of the closed portion increases.