Manually/electrically operated brake system

A manually/electrically operated brake system for applying a brake to a wheel of a vehicle, comprising:

• a brake operating member;
• a master cylinder operated by said brake operating member, to generate a manually controlled fluid braking pressure according to an operation of said brake operating member;
• a wheel brake cylinder for applying a brake to said wheel;
• a primary fluid passage for connecting said master cylinder to said wheel brake cylinder;
• electrically controlled pressure generating means for generating an electrically controlled fluid braking pressure to produce a required braking effect which is determined based on at least one of an operating force and an operating stroke of said brake operating member;
• and
• switching valve means provided in said primary fluid passage, for applying said electrically controlled braking pressure to said wheel brake cylinder while disconnecting said master cylinder from said wheel brake cylinder when said electrically controlled pressure generating means is operative, and for applying said manually controlled braking pressure to said wheel brake cylinder while disconnecting said electrically controlled pressure generating means from said wheel brake cylinder in the event of a failure of said electrically controlled pressure generating means;
• said electrically controlled pressure generating means comprising:
• a reservoir for storing a brake fluid;
• a pump for pumping the brake fluid from said reservoir;
• an accumulator for storing the brake fluid pumped by said pump, at a pressure within a predetermined range;
• an operating-force sensor for sensing the operating force applied to said brake operating member;
• a braking-effect sensor for sensing an actual braking effect provided by said wheel brake cylinder;
• a solenoid-operated pressure regulating valve disposed in a fluid passage between said accumulator and said switching means, for supplying said electrically controlled braking pressure to said switching means, by reducing the pressure of the brake fluid supplied from said accumulator;
• and
• main control means for controlling said solenoid-operated pressure regulating valve such that said electrically controlled braking pressure is determined so that said actual braking effect sensed by said braking-effect sensor coincides with said required braking effect determined based on said operating force sensed by said operating-force sensor.