A method of conducting a diagnostic test to determine leakage within a brake system includes first providing a brake system having a plunger assembly including a housing defining a bore therein. The plunger assembly includes a piston slidably disposed therein such that movement of the piston pressurizes a pressure chamber when the piston is moved in a first direction. The pressure chamber of the plunger assembly is in fluid communication with an output, and wherein the plunger assembly further includes an electrically operated linear actuator for moving the piston within the bore. The linear actuator of the plunger assembly is actuated to provide pressure at the output of the plunger assembly at a first predetermined level. The pressure at the output of the plunger assembly is held for a predetermined length of time. The method further includes determining whether conditional criteria has been met indicating a leakage within the brake system.

To test a vehicle power braking system, a piston of a power brake pressure generator is displaced twice for a pressure build-up and in between back preferably by a longer distance. Extension of the piston travel during the second displacement is an indication of air in a cylinder of the power brake pressure generator due to an excessively low brake fluid level in a brake fluid reservoir.

An electronic brake system and a method for operating the same are disclosed. The electronic brake system includes a hydraulic-pressure supply device and a hydraulic-pressure control unit. The hydraulic-pressure supply device operates a hydraulic piston using an electric signal corresponding to a displacement of a brake pedal, and thus generates hydraulic pressure. The hydraulic-pressure control unit controls hydraulic pressure of a pressure medium supplied to individual wheel cylinders. The electronic brake system controls a plurality of valves mounted to the hydraulic-pressure control unit, and thus performs a normal operation mode, an abnormal operation mode, a regenerative braking mode, and an inspection mode using the valves.

A brake system includes a reservoir and a master cylinder operable to provide a brake signal responsive to actuation of a brake pedal connected thereto. A power transmission unit is configured for selectively providing pressurized hydraulic fluid for actuating at least one of the pair of front wheel brakes and the pair of rear wheel brakes in a normal non-failure braking mode. A plurality of iso/dump valve arrangements are each hydraulically interposed between the power transmission unit and a corresponding one of the wheel brakes. A plurality of two-position three-way valves are each hydraulically connected with the master cylinder, the power transmission unit, and at least a selected wheel brake of the pair of front wheel brakes. The three-way valves selectively control hydraulic fluid flow from a chosen one of the master cylinder and the power transmission unit to the corresponding one of the front wheel brakes.

A brake system includes a reservoir and a master cylinder operable to provide a brake signal responsive to actuation of a brake pedal connected thereto. A power transmission unit is configured for selectively providing pressurized hydraulic fluid for actuating at least one of the pair of front wheel brakes and the pair of rear wheel brakes in a normal non-failure braking mode. A plurality of iso/dump valve arrangements are each hydraulically interposed between the power transmission unit and a corresponding one of the wheel brakes. A plurality of two-position three-way valves are each hydraulically connected with the master cylinder, the power transmission unit, and at least a selected wheel brake of the pair of front wheel brakes. The three-way valves selectively control hydraulic fluid flow from a chosen one of the master cylinder and the power transmission unit to the corresponding one of the front wheel brakes.

A method for checking functionality of a motor vehicle braking system. The braking system has a main module, including: hydraulically actuatable wheel brakes, pairs being assigned to respective brake circuits; at least one electrically actuatable wheel valve per wheel brake sets wheel-specific brake pressures; a pressure provision device actively builds up pressure in the wheel brakes; a pressure-medium reservoir at atmospheric pressure, and an auxiliary module, which has for each of two wheel brakes: a pressure sensor for measuring pressure in a wheel brake line; an open when deenergized isolating valve in the wheel brake line; a pump. At least one variable is measured to assess functionality of the braking system. Using least one acceptance criterion, and checked whether the variable satisfies the acceptance criterion. Determining at least one variable representing the viscosity of the brake fluid, and the at least one acceptance criterion depends on a variable representing viscosity.

A piston-cylinder unit includes a piston delimiting at least one working chamber, in which a first seal for sealing at least one first working chamber is arranged either between the piston and cylinder or between a plunger connected to the piston and the cylinder. A second seal is arranged between the first seal and the first working chamber, and the piston-cylinder unit further includes a first channel arranged in the wall of the cylinder or in the piston, which joins the first seal and the second seal in the inner chamber of the cylinder. The first channel and/or a hydraulic line connected thereto may have a throttle device and/or a valve device. An electronic control and regulating device may have a diagnosis or monitoring function for a possible defect or failure of a seal. Multiple hydraulic devices may have such piston-cylinder units and respective control and such regulating devices.

A method of conducting a diagnostic test to determine leakage within a brake system includes first pressurizing the brake system. The pressure within the brake system is held for a predetermined length of time. The method further includes determining whether a leakage within the brake system has occurred.

An electropneumatic brake system (EBS) of a vehicle, which electronically controls a brake-pressure, including: a) a service-brake actuating-element, which is actuatable by a driver, of a service-brake-actuating-device, which has an electrical-channel and at least one pneumatic-channel, wherein, depending on the actuation of the service-brake-actuating-element, an electrical-brake-request-signal, representing a setpoint-brake-pressure, is generated in the electrical-channel and a pneumatic-backup-pressure is generated in the pneumatic-channel; b) a first electronic-control-system, which, depending on a brake-request-signal output by the electrical-channel, outputs an electrical-brake-control-signal; c) at least one electropneumatic-pressure-control-module, which, depending on the electrical-brake-control-signal, outputs an actual-brake-pressure, in the course of a brake-pressure-control adjusts the actual-brake-pressure to the setpoint-brake-pressure and inputs this into at least one pneumatic-brake-actuator; d) wherein the pressure-control-module includes at least one electromagnetic-control-valve-device (EV, AV), at least one relay-valve (RLV), at least one electromagnetic-backup-solenoid-valve (BV), a second electronic-control-system and at least one pressure-sensor (DS), wherein, depending on the electrical-brake-control-signal, the electromagnetic-control-valve-device (EV, AV) generates a control-pressure for a control-input of the relay-valve (RLV), which, depending on the control-pressure, generates an actual-brake-pressure for the at least one pneumatic-brake-actuator, which the pressure-sensor (DS) measures/reports to the second electronic-control-system of the pressure-control-module, e) wherein the electromagnetic-control-valve-device (EV, AV) and the at least one electromagnetic-backup-solenoid-valve (BV) are electrically-controlled by the second electronic-control system, f) wherein the electromagnetic-backup-solenoid-valve (BV) is connected by an input to the pneumatic-channel and by an output to the control-input of the relay-valve (RLV) and can be switched between a pass-through-position, in which the input is connected to the output, and a shut-off position, in which the input is shut-off with respect to the output, g) wherein the electromagnetic-control-valve-device (EV, AV) connects the control-input of the relay-valve (RLV) to a pressure-sink or to a compressed-air-supply or shuts it off from the pressure-sink and from the compressed-air-supply, h) wherein a pneumatic-backup-brake-circuit of the electropneumatic-brake-system includes at least the pneumatic-channel of the service-brake-actuating-device, the relay-valve (RLV), the at leas

An electropneumatic brake system (EBS) of a vehicle, which electronically controls a brake-pressure, including: a) a service-brake actuating-element, which is actuatable by a driver, of a service-brake-actuating-device, which has an electrical-channel and at least one pneumatic-channel, wherein, depending on the actuation of the service-brake-actuating-element, an electrical-brake-request-signal, representing a setpoint-brake-pressure, is generated in the electrical-channel and a pneumatic-backup-pressure is generated in the pneumatic-channel; b) a first electronic-control-system, which, depending on a brake-request-signal output by the electrical-channel, outputs an electrical-brake-control-signal; c) at least one electropneumatic-pressure-control-module, which, depending on the electrical-brake-control-signal, outputs an actual-brake-pressure, in the course of a brake-pressure-control adjusts the actual-brake-pressure to the setpoint-brake-pressure and inputs this into at least one pneumatic-brake-actuator; d) wherein the pressure-control-module includes at least one electromagnetic-control-valve-device (EV, AV), at least one relay-valve (RLV), at least one electromagnetic-backup-solenoid-valve (BV), a second electronic-control-system and at least one pressure-sensor (DS), wherein, depending on the electrical-brake-control-signal, the electromagnetic-control-valve-device (EV, AV) generates a control-pressure for a control-input of the relay-valve (RLV), which, depending on the control-pressure, generates an actual-brake-pressure for the at least one pneumatic-brake-actuator, which the pressure-sensor (DS) measures/reports to the second electronic-control-system of the pressure-control-module, e) wherein the electromagnetic-control-valve-device (EV, AV) and the at least one electromagnetic-backup-solenoid-valve (BV) are electrically-controlled by the second electronic-control system, f) wherein the electromagnetic-backup-solenoid-valve (BV) is connected by an input to the pneumatic-channel and by an output to the control-input of the relay-valve (RLV) and can be switched between a pass-through-position, in which the input is connected to the output, and a shut-off position, in which the input is shut-off with respect to the output, g) wherein the electromagnetic-control-valve-device (EV, AV) connects the control-input of the relay-valve (RLV) to a pressure-sink or to a compressed-air-supply or shuts it off from the pressure-sink and from the compressed-air-supply, h) wherein a pneumatic-backup-brake-circuit of the electropneumatic-brake-system includes at least the pneumatic-channel of the service-brake-actuating-device, the relay-valve (RLV), the at leas