| 摘要 |
PURPOSE:To suppress generation of harmful substances such as NOx at the time of acceleration by diminishing the negative pressure, which is introduced into the negative pressure chamber of a servo device during transition from idling to acceleration, with the atmospheric air and thereby delaying the negative pressure spark advance temporarily. CONSTITUTION:When a suction throttle valve 11 is quickly opened to give transition from idling to acceleration, suction negative pressure at the downstream of this suction throttle valve 11 changes abruptly from high to low level. This change is introduced to the first chamber 27 of an atmosphere intake valve 21 through a signal negative pressure passage 30, and the negative pressure level in the number chamber 27 becomes lower than that in the second chamber 28. As a result, a diaphragm 25 moves toward the second chamber 28 against the action of a spring 26, so that the valve element 23 is opened through a rod 24 and the atmosphere intake conduit 22 is opened, and then the atmosphere is introduced into the compound negative pressure passage 18. Accordingly, the compound negative pressure introduced to the negative pressure chamber 17 of servo device 16 is diminished by the dilution with the atmospheric air, and the negative pressure spark advance is delayed. |
