Fluid pressure control device for crossed piping brake system

A fluid pressure control device for a vehicle brake system having a tandem master cylinder, a first braking fluid circuit connecting a first pressure chamber of said master cylinder to the right front-wheel brake cylinder and the left rear-wheel brake cylinder, and a second braking fluid circuit connecting a second pressure chamber of said master cylinder to the left front-wheel brake cylinder and the right rear-wheel brake cylinder, comprising:

• a housing provided thereon with first inlet and outlet ports disposed within said first fluid circuit and respectively in connection with the first pressure chamber of said master cylinder and the left rear-wheel brake cylinder, second inlet and outlet ports disposed within said second fluid circuit and respectively in connection with the second pressure chamber of said master cylinder and the right rear-wheel brake cylinder, and a bypass port in connection with the first pressure chamber of said master cylinder through said first fluid circuit, said housing being provided therein with a first stepped bore in communication with said first inlet and outlet ports respectively at the small and large diameter portions thereof and a second stepped bore in communication with said second inlet and outlet ports respectively at the medium and large diameter portions thereof and in communication with said bypass port at the small diameter portion thereof;
• partition means provided between said first and second stepped bores to isolate said two stepped bores from each other;
• a first stepped piston slidably disposed within said first stepped bore to provide first and second chambers respectively in communication with said first inlet and outlet ports, wherein the smaller end of said first piston is exposed in said first chamber and the larger end in said second chamber;
• a first spring for biasing said first piston in the direction toward said first outlet port;
• a first spool slidably engaged within said first stepped piston and fixed at one end thereof with the inner wall of said housing, said first spool being provided with a first valve seat exposed in said first chamber and a passage communicating said first and second chambers to each other through said first valve seat;
• a first inertia-controlled ball housed within said first chamber to co-operate with said first valve seat to cut-off communication between said first and second chambers when said ball is subjected to a deceleration in excess of a predetermined value;
• a second stepped piston slidably disposed within the medium and large diameter portions of said second stepped bore to provide third and fourth chambers respectively in communication with said second inlet and outlet ports, wherein the smaller end of said second piston is exposed in said third chamber and the larger end in said fourth chamber;
• a second spring for biasing said second piston in the direction toward said second outlet port;
• a second stepped spool slidably engaged within said partition means and said second piston and including a larger end exposed in said first chamber and a smaller end exposed in said third chamber, said second spool being provided with a second valve seat at the smaller end thereof and a passage communicating said third and fourth chambers to each other through said second valve seat;
• a second inertia-controlled ball housed within said third chamber to co-operate with said second valve seat to cut-off communication between said third and fourth chambers when said second ball is subjected to the said predetermined deceleration;
• and
• a third stepped piston slidably disposed within the small and medium diameter portions of said second stepped bore to provide a fifth pressure chamber in communication with said bypass port, wherein the smaller end of said third piston is exposed in said fifth chamber and the larger end in said third chamber.

A fluid pressure control device for a brake system of a vehicle having two front wheels and two rear wheels, the system having a tandem master cylinder, a first braking fluid circuit connecting a first pressure chamber of said master cylinder to one front-wheel brake cylinder and the brake cylinder of one rear wheel diagonally opposite to said one front-wheel, and a second braking fluid circuit connecting a second pressure chamber of said master cylinder to the other front-wheel brake cylinder and the diagonally opposite other rear-wheel brake cylinder, comprising:

• a housing provided thereon with first inlet and outlet ports disposed within said first fluid circuit and respectively in connection with the first pressure chamber of said master cylinder and the one rear-wheel brake cylinder, second inlet and outlet ports disposed within said second fluid circuit and respectively in connection with the second pressure chamber of said master cylinder and the other rear-wheel brake cylinder, and a bypass port in connection with the first pressure chamber of said master cylinder through said first fluid circuit, said housing being provided therein with a first bore communicating said first inlet and outlet ports to each other and a second bore communicating said second inlet and outlet ports to each other and in communication with said bypass port at one end thereof;
• partition means provided between said first bore and said second bore to isolate said two bores from each other;
• a first valve seat provided within said first bore to permit fluid flow between said first inlet and outlet ports therethrough;
• a first inertia-controlled ball housed within said first bore to co-operate with said first valve seat to cut-off communication between said first inlet and outlet ports when said ball is subjected to a deceleration in excess of a predetermined value;
• a movable stepped spool slidably received by said partition means and including a larger end slidable within said first bore and a smaller end exposed within said second bore, said spool being provided with a second valve seat at the smaller end thereof and a passage communicating said second inlet and outlet ports to each other through said second valve seat;
• a second inertia-controlled ball housed within said second bore to co-operate with said second valve seat to cut-off communication between said second inlet and outlet ports when said second ball is subjected to the said deceleration;
• a piston slidably disposed within said second bore to provide a pressure chamber in communication with said bypass port, said piston being exposed at one end thereof to said pressure chamber and at the other end thereof in the portion of said second bore communicating with said second inlet port;
• and
• means for urging said piston away from said second valve seat when the pressure on the one end of the piston is the same as the pressure on the other end of the piston.