1. Field of the Invention
The present invention relates to a vehicle brake system for controlling the braking force of a vehicle.
2. Background Art
A brake system for a vehicle generally called an automobile uses a booster which uses negative pressure of an engine in order to assist a driver in the brake operation force. A brake system has been proposed recently, which performs a boosting operation by using an electric motor instead of negative pressure. This art is disclosed in, for example, JP Patent Publication (Kokai) No. 2008-162482. In JP Patent Publication (Kokai) No. 2008-162482, the brake system controls an electric motor 40 by detecting the state of an input piston 32 operated by a driver, and can assist the driver in the brake force by driving a boost piston 31. By including the aforementioned configuration, which is one example of the booster, a boosting operation of generating a large braking force with a small operation force is enabled.
The aforementioned vehicle brake system is demanded to have the characteristic of stopping the vehicle in a short distance in an emergency while the operation thereof is requested to be stable or quiet, and adaptation to the different requests for responsiveness and quietness of brake control is required.