Patent ID: 8042886

Claim:
A vehicle brake system comprising: a hydraulic brake device for generating by a master cylinder a base hydraulic pressure corresponding to a braking operation and for applying the generated base hydraulic pressure to wheel cylinders of wheels which are connected to the master cylinder through fluid passages having a hydraulic control valve to generate a base hydraulic brake force on the wheels, the hydraulic brake device being provided also for driving a pump by driving an electric motor in dependence on a controlled hydraulic pressure command value to generate and apply a controlled hydraulic pressure to the wheel cylinders and to generate a controlled hydraulic brake force on the wheels; the hydraulic control valve being an electromagnetic valve which is switchable between a pressure difference state in which a controlled pressure difference is generated between the master cylinder side and the wheel cylinder side and a direct communication state in which the controlled pressure difference is not generated between the master cylinder side and the wheel cylinder side; a regenerative brake device for generating a regenerative brake force corresponding to the state of the braking operation, on any of the wheels; gradient calculation means for calculating a gradient as a time-dependent fluctuation of the controlled hydraulic pressure command value: a map representing a relation between a rotational speed of the electric motor and a drive pressure difference which the hydraulic pressure, generated by driving of the pump, causes to be generated between a master cylinder side of the hydraulic control valve and a wheel cylinder side of the hydraulic control valve; and controlled hydraulic brake force control means for decreasing the rotational speed of the electric motor as specified by the map when at least both of the regenerative brake force and the controlled hydraulic brake force are applied, when the gradient of the controlled hydraulic pressure command value given to the hydraulic bake device is downhill or is not present, and when a command is issued to the hydraulic control valve to make the controlled pressure difference across the hydraulic control valve zero.