| 摘要 |
PROBLEM TO BE SOLVED: To eliminate the necessity of providing an exclusive atmospheric pressure sensor and reduce cost by measuring differential pressure of pressure within a negative pressure chamber and atmospheric pressure by a signal from a pressure sensor for booster and a signal from a pedal sensor. SOLUTION: Because a negative pressure chamber 32a and an atmospheric pressure chamber 32b of a brake booster main body 32 are interrupted from atmosphere by being communicated when a brake pedal 12 is not stepped, a pressure sensor 33 for booster which is communicated with the atmospheric pressure chamber 32b detects pressure within the negative pressure chamber 32a. Because the atmospheric pressure chamber 32b is communicated with atmosphere when the brake pedal 12 is stepped, the pressure sensor 33 detects atmospheric pressure. A pedal sensor 34 detects the stepping state of the brake pedal 12. A control part 31 stores a signal from the pressure sensor 33 when the brake pedal 12 is stepped by prescribed quantity or more as atmospheric pressure. Thus, the signal from the pressure sensor 33 when the brake pedal 12 is not stepped is defined as pressure within the negative pressure chamber 32a, the pressure is compared with latest atmospheric pressure and differential pressure can be determined. |
