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.

A vehicle brake system, including: a first-braking-force control mechanism configured to control a first braking force, a second-braking-force control mechanism configured to control a second braking force, an abnormal-state detecting device configured to detect whether the first-braking-force control mechanism is in an abnormal state, a pseudo-abnormal-state detecting device configured to detect whether the first-braking-force control mechanism is in a pseudo abnormal state in which the first-braking-force control mechanism is suspected to be in the abnormal state, and a controller including a pseudo abnormal state controller configured to control the second-braking-force control mechanism in an operating state of the first-braking-force control mechanism so as to control the second braking force when the pseudo-abnormal-state detecting device detects that the first-braking-force control mechanism is in the pseudo abnormal state.

An actuating device for a vehicle brake system may include a first piston-cylinder unit, the at least one working space of which is to be connected to at least one wheel brake of the vehicle via at least one hydraulic line, an electromechanical drive device and an actuating device, in particular a brake pedal. Methods for operating a vehicle brake system including such an actuating device and for diagnosing various portions of a vehicle brake system (e.g., but not limited to, a feed valve or a travel simulator) are also presented.

A brake control apparatus includes: a master cylinder that outputs a brake fluid at a master pressure; a master pressure changing device that is configured to change the master pressure irrespective of an operation of a brake pedal; a brake actuator; and a control unit that executes vehicle stability control by changing a brake pressure of a target wheel. Modes of the vehicle stability control include a normal mode and a pseudo mode. In the pseudo mode, the control unit operates the master pressure changing device such that the master pressure obtains a target value of the brake pressure of the target wheel, and changes the brake pressure of the target wheel in an interlocking manner with the master pressure. When the normal mode is unavailable, the control unit executes the vehicle stability control in the pseudo mode.

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 diagnostic method to identify a leak in simulator valve in a vehicle brake system includes the steps of: (1) providing a simulator partially filled with a pressure medium and a de-energized simulator valve; (2) energizing a pumping valve, a secondary three-way valve, and a plurality of apply valves; (3) applying and retracting a plunger in a plunger assembly at least two cycles so that a predetermined pressure is achieved; (3) holding a plunger in position within the plunger assembly while maintaining a replenishing check valve in a closed/de-energized position and energizing the simulator valve; (4) obtaining a measured master cylinder secondary pressure decay; (5) comparing the measured master cylinder secondary pressure decay to a predetermined pressure decay value; and (7) identifying a leak in the simulator valve if the measured master cylinder secondary pressure decay does not match the predetermined master cylinder secondary pressure decay.

A brake control apparatus includes: a master cylinder that outputs a brake fluid at a master pressure; a master pressure changing device that can change the master pressure irrespective of an operation of a brake pedal; a brake actuator; and a control unit that executes antilock control by reducing a brake pressure of a target wheel. Modes of the antilock control include a normal mode and a pseudo mode. In the pseudo mode, the control unit operates the master pressure changing device such that the master pressure obtains a target value of the brake pressure of the target wheel, and changes the brake pressure of the target wheel in an interlocking manner with the master pressure. When the normal mode is unavailable, the control unit executes the antilock control in the pseudo mode.

An abnormality detection device includes a control target hydraulic pressure calculating portion that calculates a control target hydraulic pressure according to an operation state of a brake pedal, the hydraulic pressure obtaining portion that obtains the hydraulic pressure of the operating fluid controlled to become the control target hydraulic pressure calculated by the control target hydraulic pressure calculating portion from the pressure sensor; a second determination threshold value changing portion that changes a threshold value to be closer to the control target hydraulic pressure calculated by the control target hydraulic pressure calculating portion in a stepwise manner when a state determining portion determines that the control target hydraulic pressure is in a maintaining state, and the abnormality determining portion that determines the hydraulic pressure braking force generating device is abnormal when the hydraulic pressure obtained by the hydraulic pressure obtaining portion deviates from the permissible divergence range.

An electrohydraulic vehicle brake system includes an electromechanical actuator for actuating at least one hydraulic piston to build hydraulic pressure at wheel brakes. The brake system provides a set of electrically activatable valve arrangements having a first valve arrangement between a cylinder accommodating the at least one hydraulic piston and each of the wheel brakes, and at least one second valve arrangement 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 which is associated with the same wheel brake as the second valve arrangement. A control device or system activates the first valve arrangements and the electromechanical actuator, in order to build up a hydraulic pressure at at least one of the wheel brakes and via the opened first valve arrangement associated with that wheel brake and to reduce a built-up hydraulic pressure via the opened first valve arrangement. The activation of the first valve arrangements can take place in a time multiplex operation.

A brake ECU (abnormality detection device) includes: an operating amount obtaining portion configured to obtain a measurement value of a stroke; a hydraulic pressure obtaining portion configured to obtain a measurement value of a reaction force hydraulic pressure having a mutual relationship with respect to the stroke; an operation direction determining portion configured to determine directions of operation of outputs from a stroke sensor and a pressure sensor; a failure detection range switching portion configured to switch the failure detection range for detecting failures of a hydraulic pressure braking force generating device in accordance with the direction of operation; and a failure determining portion configured to determine the failure of the hydraulic pressure braking force generating device from the failure detection range switched by the failure detection range switching portion, the measurement value of the stroke, and the measurement value of the reaction force hydraulic pressure.