A brake pedal unit includes a housing defining a bore formed therein. An input piston is slidably disposed in the bore. The input piston is connected to a brake pedal such that engagement of the brake pedal causes movement of the input piston within the bore of the housing of the brake pedal unit. The brake pedal unit is defined to be in an at rest position when the brake pedal in not engaged causing movement of the input piston. A primary piston is slidably disposed in the bore for pressurizing a primary chamber. A primary passageway permits fluid communication between the primary chamber and the reservoir, wherein fluid flow through the primary passageway is blocked when the brake pedal unit is in the rest position. A secondary piston is slidably disposed in the bore for pressurizing a secondary chamber. A secondary passageway permits fluid communication between the secondary chamber and the reservoir, wherein fluid flow through the secondary passageway is blocked when the brake pedal unit is in the rest position

An electric booster including: a motor; a booster body coupled to the motor; a bolt screw rotatably installed in the booster body, connected to the motor, and rotated by the motor; a buffer mounted in the booster body and made of a material different from the booster body; and a nut screw restricted from rotating by the buffer, and screwed to the bolt screw so as to be linearly moved in the longitudinal direction of the bolt screw.

Provided is an electric booster capable of detecting a movement position of an input member in a wide range along an axial direction. The electric booster includes an input rod formed of a magnetic material, an input plunger formed of a non-magnetic material, and an input piston formed of a magnetic material. A stroke detector includes respective magnet members arranged so that magnetic poles are aligned along a movement direction of the input plunger, and a Hall sensor unit that is fixed to a housing, and detects a movement position of the input plunger in accordance with a magnetic flux density from the respective magnet members. As a result, a flat magnetic flux distribution having a wide region along the axial direction is provided, and the movement position of the input plunger can be detected relatively precisely in a wide range along the axial direction.

A method for operating a brake system for motor vehicles, comprising a master brake cylinder actuable by a brake pedal, an electrically controllable pressure provision device, a pressure medium reservoir tank, from which the master brake cylinder and the pressure provision device are supplied with pressure medium, and at least two hydraulically actuable wheel brakes and at least one electrically actuable inlet valve per wheel brake, wherein the wheel brakes are actuable either by the master brake cylinder or by the pressure provision device, the pressure medium reservoir tank is monitored by a device for determining a level of the pressure medium, wherein the wheel brakes are divided into at least one first wheel brake group and one second wheel brake group, and wherein the inlet valves of the first wheel brake group are closed when the determined level falls below a first limit value (s.sub.1).

An actuating device for a motor vehicle brake may include an actuating device/brake pedal, a pressure supply device driven by an electric motor, a (master) piston-cylinder unit that may be actuated by the actuating device, and which is connected hydraulically with a fluid reservoir, a valve assembly for wheel-specifically adjusting brake pressures and for connecting or disconnecting the wheel brakes to/from the pressure supply device and the piston-cylinder unit, an electronic control unit, and one or more sensor devices that may be used to provide sense various conditions and to provide inputs to the electronic control unit.

A hydraulic braking device comprising a master cylinder and a brake booster. The braking device comprises a control piston driven by actuating a brake pedal and mounted so as to be tightly slidable in a plunger of a piston of the brake booster. The control piston comprises a first end portion having a certain cross-sectional area and being arranged to cooperate with a gasket so as to establish, during braking, a modulated communication between the first chamber of the brake booster and a discharge chamber of the master cylinder. The braking device has an effective cross-sectional area counter-acting a pressure existing in a region comprised between a master cylinder piston and the control piston. Such area is different from the cross-sectional area of the first end portion of the control piston.

A vehicle braking system (20) has a primary braking unit (22) with a first pressure generating unit (34) and a first reservoir (26). The vehicle braking system (20) further has a secondary braking unit (24) with a second pressure generating unit (52) and second reservoir (70). A method of operating the vehicle braking system (20) includes actuating the pressure generating unit (34) of the primary braking unit (22) thereby pressurizing a fluid at a wheel cylinder (30) to slow or stop the vehicle. The wheel cylinder (30) is depressurized in response to an electrical signal provided to an electronic control unit (100,102). The fluid is transferred from the wheel cylinder (30) to the second reservoir (70). The fluid path (PI) between the wheel cylinder (30) and the second reservoir (70) is shorter and has less fluid resistance than the fluid path (P2) between the wheel cylinder (30) and the first reservoir (26). The present invention further comprises two braking systems. The present inventions are intended for fast pressure depressurization at quick start or launch control.

A safety system brake system comprises a hydraulic pressure-providing device having a pressure chamber connected to at least one brake circuit by a separating valve and into which pressure chamber a piston is moved to build up pressure. The pressure chamber is a two-stage pressure chamber having first and second sub-chambers. During pressure build-up the piston is moved into the first and then the second sub-chamber. The two sub-chamber are hydraulically closed off from each other when the piston is moved a specified distance into the second sub-chamber. A first check valve is connected to the first sub-chamber on a suction side and to a brake fluid reservoir on a blocking side. A second check valve is connected to the second sub-chamber on a suction side, and to the suction side of the first check valve on the blocking side.

An electronic brake system allows the effective braking pressure to be formed in response to occurrence of a minute leak in a hydraulic circuit, whereby the stability and reliability for braking is improved.

A brake system may include an actuation device, in particular a brake pedal; a first piston-cylinder unit with two pistons, in particular an auxiliary piston and a second piston, in order to supply brake circuits with a pressure medium via a valve device, wherein one of the pistons, in particular the auxiliary piston, can be actuated by means of the actuation device; a second piston-cylinder unit comprising an electric motor-powered drive, a transmission, and at least one piston in order to supply pressure medium to at least one of the brake circuits via a valve device; and a motor pump unit with a valve device in order to supply pressure medium to the brake circuits. The brake system may further include a hydraulic travel simulator which is connected to a pressure or working chamber of the first piston-cylinder unit.