Antilocking brake fluid pressure control unit for vehicle brake system

An antilocking brake fluid pressure control unit for a vehicle brake system including a main fluid passage connecting a master cylinder to a wheel cylinder of a wheel brake, said master cylinder being coupled with a brake pedal, said antilocking brake fluid pressure control unit comprising:

• fluid pressure control means for receiving an antilocking operation signal and for discharging a working fluid from said main fluid passage in response to said antilocking operation signal, thereby controlling the fluid pressure on said wheel brake;
• a working fluid return circulation passage (7, 9) having one end coupled to a feedback point (15) positioned in said main fluid passage closer to said master cylinder (2) and a second end coupled to a branching point (40) in said main fluid passage (5) near said wheel cylinder (4), said return circulation passage including a branch portion (7) connected to said branching point and a feedback portion (9) connected to said feedback point;
• a pump (12) in said feedback portion (9) for returning working fluid to said feedback point (15), a damping chamber (13) connected to said feedback portion (9) between said pump (12) and said feedback point (15) for storing a constant volume of said working fluid;
• a flow restricting orifice (14) in said feedback portion (9) between said pump (12) and said feedback point (15), and a filter (16) positioned in said feedback portion (9) between said damping chamber (13) and said feedback point (15), said filter (16) having a sufficiently small mesh size so that working fluid adheres by surface tension to said filter (16) sufficiently to stop working fluid from flowing out of said damping chamber (13) to said feedback point (15) when working fluid is bled from said main fluid passage (5).