A vehicle brake device includes a pressure adjusting device wherein as the volume of a pilot chamber is changed by the movement of a piston and the flow rate of liquid flowing in and out of the pilot chamber increases, the amount of movement of the piston increases with reference to the piston position in an equilibrium state where the force corresponding to the pilot pressure and the force corresponding to the output pressure are balanced, whereby the flow rate of the liquid flowing in and out of an output chamber increases. A control device, when judged by a limitation necessity judging portion that the gradient of output pressure should be limited, implements at least one of pressure increasing gradient limit control for opening a pressure decreasing electromagnetic valve under pressure increasing control, or pressure decreasing gradient limit control for opening a pressure increasing electromagnetic valve under pressure decreasing control.

A vehicle brake device provided with a hydraulic pressure generating portion, an actuator and a controlling portion which maintains a driving force of the driving portion when a control subject pressure in a control subject chamber is within a dead zone, wherein the control subject pressure varies in response to a variation of the master pressure and a pulsation is generated in the master pressure accompanying an operation of the actuator. The vehicle brake device further includes a rigidity information obtaining portion which obtains a rigidity information and a dead zone setting portion which sets the dead zone based on the rigidity information obtained by the rigidity information obtaining portion such that the higher the rigidity of the control subject chamber, or the higher the probability of rigidity increase of the control subject chamber, the wider the dead zone is set.

A brake control device capable of preventing a braking force from being excessive when information cannot be transmitted between a first control unit configured to control operation of a boost mechanism and a second control unit configured to control operation of a hydraulic control mechanism. When a second ECU (32) cannot transmit information to a first ECU (26) due to a disconnection of a signal line (27), the second ECU carries out backup control of detecting a braking operation amount of a driver based on signal input from hydraulic pressure sensors (29), and operating a hydraulic pressure supply device (30) based on the detected braking operation amount, to thereby pressurize insides of wheel cylinders. In this case, the second ECU decreases a pressurization amount of a pressure inside the wheel cylinders when a pressure of a master cylinder (8) exceeds a predetermined value (PM0) during the backup control.

A pressure generating device may comprise a piston-cylinder unit having a bilaterally acting piston with two effective surfaces defining two respective, separate working spaces in a sealing manner. Each working space is connected via a hydraulic line to a hydraulic circuit, wherein at least one hydraulic chamber of a consumer is connected to each hydraulic circuit, and wherein a drive drives the piston. Each working space may be in communication with a reservoir for hydraulic medium, via a respective hydraulic line having a respective switching valve. Alternatively, one or both working spaces may be in communication with a reservoir for hydraulic medium via a hydraulic line, with a switching valve in one or both hydraulic lines, and/or a respective outlet valve may be associated with one or more hydraulic chambers of the consumer, and a further connecting line having a switching valve may connect the pressure chambers and/or hydraulic lines.

A master cylinder apparatus includes: an input piston that can be moved forward by operating a brake operating member; a pressure piston that is provided in front of the input piston to be capable of moving relative to the input piston; and a stroke velocity ratio modification device that is capable of modifying a stroke velocity ratio, which is a ratio between a stroke velocity of the pressure piston and a stroke velocity of the input piston, in at least two stages while the input piston moves from a rear end portion position to a front end portion position, and that sets the stroke velocity ratio at 1 when an abnormality occursin the master cylinder apparatus.

The invention relates to an electrohydraulic motor vehicle braking system and to a method for operating an electrohydraulic motor vehicle braking system. Said electrohydraulic braking system comprises a first brake circuit with at least one wheel brake, a second brake circuit with at least one wheel brake, a first cylinder-piston assembly being designed to be fluidically coupled to at least one of the first or second brake circuits and which is used to produce hydraulic pressure in at least one of the first or second brake circuits; the first cylinder-piston assembly comprises at least one first piston, a second piston-cylinder assembly comprises at least one second piston, and a electromechanical actuator which acts on the second piston of the second cylinder-piston assembly; the second cylinder-piston assembly is designed to be fluidically coupled to the first cylinder-piston assembly in order to provide hydraulic pressure for actuating the first piston-cylinder assembly and generated in the second piston-cylinder assembly when actuating the electromechanical actuator; and the second piston-cylinder assembly is designed to be fluidically coupled to the first brake circuit and/or to the second brake circuit such that when actuating the electromechanical actuator in the second piston-cylinder assembly, the first and/or the second brake circuit can be impinged upon with hydraulic pressure generated in the second piston-cylinder assembly.

An electronically slip-controllable braking system including an actuatable master brake cylinder, to which at least one wheel brake, associated with a wheel of a front axle and at least one wheel brake, associated with a wheel of a rear axle of a vehicle, are connected. An electronically activatable first actuator system sets and regulates brake pressures different from one another in the wheel brakes as a function of the particular present slip conditions. An electronically activatable second actuator system effectuates the setting and regulating of a uniform brake pressure at the wheel brakes and a third actuator system limits the brake pressure generated by the second actuator system at the wheel brakes associated with the wheels of the rear axle. The third actuator system controls a second pressure medium connection between the associated wheel brake of the rear axle and a pressure medium storage container.

An electrohydraulic brake system includes an electromechanical actuator for actuating at least one hydraulic piston to provide a hydraulic pressure at one or more of a plurality of wheel brakes. The brake system further includes electrically activatable valve arrangements having a first valve arrangement between a cylinder accommodating the at least one hydraulic piston and each of the plurality of wheel brakes, and at least one second valve arrangement. The second valve arrangement is provided between a receptacle device for hydraulic fluid and at least one of the wheel brakes. The second valve arrangement is provided in parallel with the first valve arrangement associated with the same wheel brake as the second valve arrangement. The brake system also includes a control device or system that opens one of the first valve arrangements and the second valve arrangement connected in parallel therewith, in order to release a hydraulic pressure built up in the cylinder.

The present invention relates to an electrohydraulic braking-force generation device and to a method for operating an electrohydraulic braking-force generation device. The electrohydraulic braking-force generation device comprises: a power transmission assembly that is coupled to a brake pedal; a brake cylinder assembly that is to be actuated by the power transmission assembly, the brake cylinder assembly having a first cylinder-piston assembly and said first cylinder-piston assembly being designed to be fluidically coupled to at least one brake circuit; and a brake booster assembly comprising a second cylinder-piston assembly and at least one electromechanical actuator. The brake booster assembly is configured to apply hydraulic pressure to the brake cylinder assembly in order to boost the braking power and the power transmission assembly is configured to actuate the brake cylinder assembly, in each operating mode of the braking-force generation device, by means of a relative movement.

A method for detecting fluid leakage from a pressure-decrease valve in a hydraulic brake system having an ABS device including: a shutoff valve for shutting off supply of a working fluid from a fluid-pressure supply source to a brake device provided for a wheel; the pressure-decrease valve for discharging the working fluid from the brake device; a reservoir for storing the working fluid discharged from the pressure-decrease valve; and a return pump for returning the working fluid stored in the reservoir to a portion between the shutoff valve and the fluid-pressure supply source, the method including the steps of: activating the return pump in a state in which the hydraulic brake system is not in ABS operation, and detecting the fluid leakage from the pressure-decrease valve based on a variation in a pressure of the working fluid in the fluid-pressure supply source caused when the return pump is activated.