Abstract: Disclosed herein is an internal combustion engine provided with an exhaust gas recirculation system of so-called back pressure control type. The exhaust gas recirculation system is provided with a vacuum line connecting a so-called EGR port with a vacuum operated flow control valve, and a modulator valve having a control chamber selectively opened to the vacuum line in response to the pressure of recirculated exhaust gas for controlling vacuum signal level of the flow control valve. The control chamber of the modulator is connected to another vacuum signal port located slightly above the EGR port.

Abstract: An exhaust gas recirculation system for use in an internal combustion engine includes an intake manifold having a riser portion serving as a heating source for an intake mixture charge, an exhaust gas recirculation passage running from an exhaust manifold to an intake system for introducing part of exhaust gases from the former to the latter, and a temperature-responsive valve provided in the intake manifold in such a position as to be able to detect the temperature of the riser portion for controlling the flow rate of the recirculation exhaust gases, in accordance with the temperature of the riser position. In this exhaust gas recirculation system, the flow rate of exhaust gases to be recirculated from the exhaust manifold to the intake system may be increased by one step, or two steps, as required, in response to the temperature of the riser portion, by means of a modified temperature responsive valve attached to the intake system.

Abstract: Disclosed is a butterfly valve opening degree setting device comprising a diaphragm apparatus. The diaphragm apparatus has a diaphragm, a vacuum chamber and a control rod connected to the diaphragm. The control rod is arranged so as to be engageable with the butterfly valve disposed in the duct. The vacuum chamber of the diaphragm apparatus is connected to the vacuum port formed on the inner wall of the duct. The butterfly valve is held open at a position wherein the peripheral edge of the butterfly valve faces the vacuum port.

Abstract: Disclosed is a throttle valve opening control device for use in an internal combustion engine. When the throttle valve is rapidly closed after completion of the warm-up of the engine, the throttle valve is temporarily held at a first opening degree which is greater than an idling opening degree and, then, the throttle valve is gradually returned to its idling position. Contrary to this, when the throttle valve is rapidly closed before completion of the warm-up of the engine, the throttle valve is temporarily held at a second opening degree which is greater than said first opening degree and, then, the throttle valve is gradually returned to its idling position.

Abstract: Disclosed is a throttle valve opening control device for use in an internal combustion engine. When the throttle valve is rapidly closed after completion of the warm-up of the engine, the throttle valve is temporarily held during a first length of time at a predetermined opening degree which is greater than an idling opening degree and, then, the throttle valve is gradually returned to its idling position. Contrary to this, when the throttle valve is rapidly closed before completion of the warm-up of the engine, the throttle valve is temporarily held at the predetermined opening degree during a second length of time, which is longer than said first length of time and, then, the throttle valve is gradually returned to its idling position.