Patent ID: 7861524

Claim:
A master cylinder of a brake comprising: a cylinder body connected with an oil tank and defining therein a first pressure chamber and a second pressure chamber, which are separated from each other by a partition; a first piston to perform reciprocating movements in the first pressure chamber; a second piston to perform reciprocating movements in the second pressure chamber; a first return spring to elastically support the first piston in the first pressure chamber; and a second return spring to elastically support the second piston in the second pressure chamber, wherein the first piston has a plurality of recesses formed at one end thereof to assure smooth supply of oil during braking, the first piston has a plurality of protrusions arranged along a circumference of the end thereof to prevent fluctuation of the first piston during reciprocating movements thereof, the second piston has a plurality of recesses formed at one end thereof to assure smooth supply of oil during braking, the second piston has a plurality of protrusions arranged along a circumference of the end thereof to prevent fluctuation of the second piston during reciprocating movements thereof, the recesses extend through the inner and outer peripheries of corresponding first and second pistons, and the protrusions protrude radially outward from a distal end of fingers defined by the recesses.