Braking device

A braking system comprising:

• a brake operating member operated by an operator of a motor vehicle;
• a master cylinder for generating a fluid pressure based on an operation of said brake operating member;
• a brake including a brake cylinder which is connected through a primary passage to said master cylinder and which is activated by the fluid pressure supplied through said primary passage, to restrain rotation of a wheel of the motor vehicle;
• and
• a pressure increasing device for increasing the fluid pressure in said brake cylinder, so as to be higher than the fluid pressure in said master cylinder, said pressure increasing device including:
• (a) a fluid flow control device which is disposed in said primary passage and which has a plurality of selectively established states including a first state for permitting flows of a working fluid in opposite directions between said master cylinder and said brake cylinder, and a second state for inhibiting at least the flow of the fluid from said brake cylinder toward said master cylinder,
• (b) a hydraulic pressure source which is connected through an auxiliary passage to a portion of said primary passage between said fluid flow control device and said brake cylinder and which is operated to pressurize the working fluid to deliver the pressurized working fluid,
• (c) a hydraulic pressure source control device for commanding said hydraulic pressure source to deliver the pressurized working fluid when the fluid pressure in said brake cylinder is required to be higher than the fluid pressure in said master cylinder during operation of said brake operating member, and
• (d) a pressure changing device for changing the fluid pressure in said brake cylinder to a level higher than that in said master cylinder, such that said level changes with a change of an operating force acting on said brake operating member.