| 摘要 |
PURPOSE:To constantly accumulate sufficient negative pressure by changing over an electromagnetic change-over valve according to vehicle speed to selectively accumulate the negative pressure in the intake pipe of an engine or the negative pressure generated by a negative pressure generation pump driven by the output shaft of a transmission, in a negative pressure reserve tank placed in a negative pressure passage. CONSTITUTION:An electromagnetic change-over valve 21 is placed in a line of negative pressure passages 20 and 25, which opens to the intake pipe 19 of an engine 1 at the position lower than a throttle valve 19a and is communicated with various negative pressure actuators via a negative pressure reserve tank 22, between the opening of said line and the tank 22. And a negative pressure generation pump 24 which is driven by the output shaft 7 of a transmission 3 is mounted in communication with the change-over valve 21 to have the valve 21 changed over according to the output of a vehicle speed decision means. When the vehicle speed is lower than the preset value, the intake pipe 19 is communicated with the tank 22 and when the vehicle speed is over the preset value, the pump 24 is communicated with the tank 22. The sufficient negative pressure is constantly accumulated inside the tank 22 so that a negative pressure actuator such as a brake duplicating device 27 or the like using the negative pressure may be operated reliably. |
