On-demand power brake system and method

A hydraulic booster, comprising:

• a housing configured to be coupled to a master cylinder, and having a cylinder bore and first and second fluid supply ports;
• a piston, having first and second sides, positioned within the cylinder bore with the first fluid supply port opening into the cylinder bore on the first side of the piston and in fluid communication therewith, the piston configured to move within the cylinder bore in response to a difference in fluid pressures between the first and second sides of the piston, the piston further having:
• a piston bore extending axially therein,
• a first fluid port extending between piston bore and the second side of the piston, and
• a second fluid port extending between the piston bore and the second side of the piston;
• and
• a valve spool positioned within the piston bore and movable to any of three valve positions, including:
• a first valve position, in which a land of the valve spool closes the first fluid port and the first and second sides of the piston are placed in fluid communication with each other via the second fluid port,
• a second valve position, in which the land closes the first and second fluid ports, and
• a third position in which the land closes the second fluid port and the first fluid port is placed in fluid communication with the second fluid supply port.

A hydraulic booster, comprising:

• a housing configured to be coupled to a master cylinder, and having a cylinder bore and first and second fluid supply ports;
• a piston, having first and second sides, positioned within the cylinder bore with the first fluid supply port opening into the cylinder bore on the first side of the piston and in fluid communication therewith, the piston configured to move within the cylinder bore in response to a difference in fluid pressures between the first and second sides, the piston further having a valve assembly movable to any of three valve positions, including:
• a first valve position, in which the first and second sides of the piston are placed in fluid communication with each other,
• a second valve position, in which the first side of the piston is isolated from the second side of the piston, and
• a third valve position, in which the first side of the piston is isolated from the second side of the piston and the second side of the piston is placed in fluid communication with the second fluid supply port,
• the valve assembly including first and second poppet-type valves, the first valve configured to regulate fluid communication between the first and second sides of the piston, and the second valve configured to regulate fluid communication between the second side of the piston and the second fluid supply port and wherein movement of a poppet of the first valve a first distance in a first direction moves a sealing surface of the poppet of the first valve against a valve seat of the first valve and movement of the poppet of the first valve a second distance in the first direction moves an element comprising the valve seat of the first valve against a poppet of the second valve and moves the poppet of the second valve away from a valve seat of the second valve.

A brake boosting system of a vehicle, comprising:

• a high-pressure fluid accumulator configured to supply fluid pressure for motive power for propelling the vehicle via a rotary hydraulic motor;
• a low-pressure fluid accumulator;
• a master brake cylinder;
• and
• a brake booster having a high-pressure fluid supply port coupled to the high-pressure fluid accumulator, a low-pressure fluid supply port coupled to the low-pressure fluid accumulator, and a boost piston positioned within a cylinder bore and coupled to the master brake cylinder, the brake booster configured to place first and second sides of the boost piston in fluid communication with each other and with the low-pressure fluid accumulator while a brake pedal of the vehicle is in a default position, to place the first side of the boost piston in fluid communication with the low-pressure fluid accumulator and isolate the second side of the boost piston from the first side and from the high- and low-pressure fluid accumulators while the brake pedal is not at the default position and is depressed less than a threshold, and to place the second side of the piston in fluid communication with the high-pressure accumulator and the first side of the piston in fluid communication with the low-pressure accumulator while the brake pedal is depressed farther than the threshold.