	US 7,497,523 B2
	Pressure locking master cylinder
Gary C. Fulks, Dayton, Ohio (US); Douglas E. Poole, Dayton, Ohio (US); and Timothy A. Haerr, Enon, Ohio (US)
Assigned to Delphi Technologies, Inc., Troy, Mich. (US)
Filed on Mar. 08, 2005, as Appl. No. 11/74,460.
Claims priority of provisional application 60/552874, filed on Mar. 12, 2004.
Prior Publication US 2005/0200196 A1, Sep. 15, 2005
Int. Cl. B60T 13/74 (2006.01); B60T 11/00 (2006.01)

U.S. Cl. 303—3 [303/15; 303/89; 91/43; 60/589]

4 Claims

1. A pressure locking master cylinder comprising:

a fluid reservoir for storing a hydraulic fluid;

a housing;

a first piston slidably received within said housing, said first piston defining a first working chamber and a blocking chamber, wherein said blocking chamber is in fluid communication with said reservoir by way of a bidirectional fluid path;

a first return spring positioned within said first working chamber;

a second piston slidably received within said housing, said second piston defining said first working chamber and a second working chamber;

a second return spring positioned within said second working chamber;

a check valve connected to said first piston, wherein said check valve allows said hydraulic fluid to flow from said reservoir, through said first piston, and into said blocking chamber and prevents said hydraulic fluid from flowing from said blocking chamber back through said first piston; and

a normally open solenoid valve positioned between said blocking chamber and said reservoir in said bidirectional fluid path,

wherein said normally open solenoid valve is adapted to selectively prevent a flow of said hydraulic fluid from said blocking chamber to said reservoir by way of said bidirectional fluid path.