Vehicle brake system with dual acting plunger assembly

A plunger assembly for use as a pressure source for a brake system, said plunger assembly comprising:

• a housing having first and second ports;
• a reversible motor mounted on said housing for driving an actuator;
• a boost conduit for supplying fluid at a boosted pressure to the brake system;
• a first outlet conduit connecting said first port to said boost conduit;
• a second outlet conduit connecting said second port to said boost conduit;
• a piston connected to said actuator, said piston slidably mounted within said housing and, in part, defining first and second chambers on opposite sides of said piston, wherein said piston pressurizes a-said first chamber when said piston is moving in a first direction to provide fluid out of said first port to said boost conduit, and wherein said piston pressurizes a-said second chamber when said piston is moving in a second direction opposite of said first direction to provide fluid out of said second port to said boost conduit;
• an electronically controlled valve located in the first outlet conduit and switchable between a first operating mode wherein said first chamber is connected to said boost conduit to (a) enable fluid flow in both directions between said first chamber and said boost conduit and (b) enable fluid flow from said first chamber into said second chamber when said piston is moved in the first direction, and a second operating mode wherein said boost conduit is disconnected from said first chamber to prevent fluid flow from said boost conduit into said first chamber when said piston is moved in the second direction.