Hydraulic circuit having a rotary type pump and brake apparatus for a vehicle provided with the same

A brake apparatus having a master cylinder, wheel cylinder and a rotary pump for supplying brake fluid to the wheel cylinder so as to more increase brake fluid pressure in the wheel cylinder than that in the master cylinder, rotary pump comprising:

• a casing having intake and discharge ports;
• an outer rotor having inner teeth portions at inner periphery thereof;
• an inner rotor having outer teeth portions at outer periphery thereof, the inner and outer rotors being housed in the casing so as to constitute a plurality of gaps formed between the inner and outer teeth portions which are in mesh with each other and the gaps being communicated with the intake and discharge ports;
• and
• a drive shaft for driving the inner rotor in the casing, brake fluid being sucked from the intake port and, via the gaps, discharged from the discharge port according to a rotation of the drive shaft,
• wherein the outer and inner rotors are made of bearing steel and have circumferential surfaces of the inner and outer teeth portions which are respectively processed by at least one of nitriding hardening and carbo-nitriding hardening so that nitrogen is diffused into the first and second rotors to form a layer including CrN.