To provide a sufficient assisting function even after a negative pressure type assistor 3 reaches an assisting limit (full load point), and prevent a master cylinder 4 or the like from being damaged when a control valve 81 of a pressure intensifying means 12 is troubled.
When a controller 83 actuates a pump 66 of the pressure intensifying means 12 in a condition where the assistor 3 is actuated, a brake fluid is supplied to a pressure intesifying chamber 58 inside the master cylinder 4 via a conduit 65 to intensify master cylinder pressure. When the control valve 81 of the intensifying means 12 provided inside the master cylinder 4 is troubled to bring a differential pressure between fluid pressure inside the chamber 58 and delivery fluid pressure from the pump 66 into prescribed pressure or more, a differential pressure regulating valve 86 is opened to release the brake fluid delivered from the pump 66 to a conduit 73.
SAWADA MAMORU
MAKI KAZUYA
SHINNO HIROAKI
DENSO CORP
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