| 摘要 |
PURPOSE:To keep] air-fuel ratio in constant at all times by a method wherein an airflow speed is kept in constant by a variable venturi and the fuel is controlled by a pressure difference between before and after a fuel nozzle. CONSTITUTION:A variable venturi type piston 15 is arranged at the upstream of a throttle valve 14 and the piston moves up-and-down in accordance with the flow amount of air so as to maintain the air of a constant flow speed at the bottom surface of the piston at all times. The fuel nozzle 25 is arranged so as to oppose to the lower end of the piston 15 and is provided with a valve body 35 to change the opening area of the nozzle. The valve body 35 is operated by a diaphragm 34 and the upper chamber 42 of the diaphragm 34 is communicated with a hole 28, introducing a venturi pressure at the downstream of the nozzle 25, while the lower chamber 40 is communicated with the hole 27, introducing the venturi pressure at the downstream of the nozzle 25. When the amount of fuel injected from the nozzle 25 is increased, the speed of the jet stream of the fuel in the stream of air is increased and, therefore, the pressure is reduced and the pressure difference between the pressure of the hole 28 and the same of the hole 27 becomes lower than a given pressure difference. Accordingly, the valve body 35 moves upward due to the pressure reduction of the chamber 42 to reduce the amount of fuel and, therefore, the air-fuel ratio may be kept in constant at all times. |
