Patent ID: 6905321

Claim:
A rotary pump for a braking apparatus, comprising: an outer rotor having an internal tooth portion at an internal periphery thereof; an inner rotor having an external tooth portion at an external periphery thereof and for performing rotary motion with a drive shaft as an axis; a rotation portion configured by combining the outer rotor and the inner rotor such that a plurality of chambers are formed between the internal tooth portion and the external tooth portion; and a casing including a central hole into which the drive shaft is fitted, an intake port for intake of brake fluid to the rotation portion, and a discharge port for discharging brake fluid from the rotation portion, this casing housing the rotation portion, wherein brake fluid is intaken by the intake port and brake fluid is discharged by the discharge port due to rotary motion of the rotation portion, while a pressure difference between the intake port and the discharge port is maintained by a first sealed chamber having a largest volume and a second sealed chamber having a smallest volume among the plurality of chambers, the casing is configured to include a first and a second side plate that sandwich the outer rotor and the inner rotor in an axial direction of the drive shaft, at one of the drive shaft axial direction sides of the rotation portion, a gap between end surfaces of the outer rotor and the inner rotor in respective axial directions thereof and an end surface of the first side plate in an axial direction thereof is sealed by a sealing unit provided in the first side plate, at the other drive shaft axial direction side of the rotation portion, a gap between end surfaces of the outer rotor and the inner rotor in the respective axial directions thereof and an end surface of the second side plate in the axial direction thereof is sealed by a mechanical seal resulting from the outer rotor and the inner rotor being pushed against the second side plate by a discharge pressure of brake fluid that acts upon the sealing unit, a discharge trench communicating with the discharge port is formed in the axial direction end surface of the second side plate to which the mechanical seal is applied, a first extended trench extending from the discharge trench toward a first area of the axial direction end surface of the second side plate to which the mechanical seal is applied, the first area being closer to a side of the central hole than to the first sealed chamber, and a second extended trench extending from the discharge trench toward a second area of the axial direction end surface of the second side plate to which the mechanical seal is applied, the second area being closer to the side of the central hole than to the second sealed chamber.