Patent ID: 8522546

Claim:
A brake booster, comprising: a housing including a cylinder bore having high-pressure and low-pressure fluid supply ports; a piston positioned within the cylinder bore, having: a piston seal that separates a first pressure chamber of the cylinder bore from a second pressure chamber of the cylinder bore, a piston bore extending axially within the piston, a first port extending between the piston bore and the first pressure chamber, a second port extending between the piston bore and the second pressure chamber, and a third port extending between the piston bore and the second pressure chamber; and a valve spool positioned within the piston bore, having: a first fluid channel extending axially within the valve spool, the first fluid channel of the valve spool being in fluid communication with the cylinder bore via the piston bore and the first port, a second fluid channel extending in the valve spool, in fluid communication with the high-pressure fluid supply port, an equalizing port extending in the valve spool and positioned such that while the valve spool is in a first position, the equalizing port places the third port in fluid communication with the first fluid channel, and a valve land positioned and configured such that, while the valve spool is in the first position, the second port is closed; while the valve spool is in a second position, the second and third ports are closed; and while the valve spool is in a third position, the third port is closed and the second port is in fluid communication with the high-pressure fluid supply port via the second fluid channel.