Abstract: An engine speed control unit of an internal combustion engine for controlling an engine speed so that it can reach a target value, changes the engine speed so that it can reach a target value in a period of time from the completion of the initial combustion of the engine starting to the idling steady state. The after-start engine speed peak actual value “gnepk”, which is an engine speed in the idling state in a predetermined period of time from the start of the engine, is calculated, and the after-start engine speed peak target value “tnepk” is read in from the map, and the ratio “rnepk” is found. When the ratio “rnepk” is out of the target range, it can be considered that the burning state is bad.

Abstract: A trouble-detection apparatus for an EGR system provided with an EGR control valve in an EGR passage, capable of correctly detecting a position in the EGR passage at which the clogging has occurred. The trouble-detection apparatus is applied to the system having the EGR control valve controlled by a negative pressure in the EGR passage wherein a lift amount of the EGR control valve is controlled by a lift sensor in a feedback manner in accordance with the operating state of the engine. According to the trouble-detection apparatus, the amplitude of the lift amount detected by the lift sensor is obtained and the pulses in the exhaust-gas flow are calculated from the detected amplitude. When the amplitude of the pulses in the exhaust-gas flow does not reach a threshold value preset in accordance with the operating state of the internal combustion engine, it is determined that clogging as occurred in the EGR passage.

Abstract: In the EGR system having an EGR control valve in an EGR passage, an orifice is provided on the exhaust side of the EGR control valve to define a negative pressure chamber between the EGR control valve and the orifice, and the pressure in the negative pressure chamber can be detected by a pressure-detector. When the operation state of the internal combustion engine is in a first operation zone wherein the amount of EGR is larger than a predetermined value, it is determined that clogging has occurred in the intake side EGR passage if the pressure value detected by the pressure-detector is smaller than a preset negative pressure value; while, it is determined that clogging has occurred in the exhaust side EGR passage if the pressure value detected by the pressure-detector is larger than the predetermined negative pressure value. An ON/OFF type pressure switch may be used as the pressure-detection means 17.

Abstract: A bypass control system for an internal combustion engine provided with a mechanical supercharger arranged in an intake pipe of the engine. The supercharger is connected to a crankshaft by means of a clutch operated in accordance with the engine load as well as the engine speed. A by-pass is arranged so as to by-pass the supercharger, on which by-pass a by-pass control valve is arranged. The by-pass control valve is operated in accordance with the engine speed, so that it is closed during an engine high load and high speed condition. The by-pass valve is further operated in response to the condition of the clutch so that the by-pass is closed when the clutch is under the disengaged state.

Abstract: An altitude compensation device for internal combustion engines such as automotive engines. The device has a first diaphragm device and a second diaphragm device which are provided with a first diaphragm chamber and a second diaphragm chamber defined by a first diaphragm and a second diaphragm, respectively. A choke lever connected to a choke valve is fixed to the first diaphragm while a stopper for limiting the opening of the choke valve is provided on the second diaphragm device. A first communication passage provides a communication between the first diaphragm chamber and the intake passage of the engine so as to transmit the intake vacuum to the first diaphragm chamber to drive the choke valve in such a direction as to open the choke valve. A second communication passage provides a communication between the intake passage and the second diaphragm chamber to transmit the intake vacuum thereby to move the stopper in such a direction as to afford a larger opening of the choke valve.

Abstract: An ignition timing control system for an engine using a vacuum advance unit connected to a distributor and communicated with an intake passage of the engine, which comprises: a throttle valve plate received within the intake passage; first and second ports formed in the wall of the intake passage; conduits connecting the first and second ports with the vacuum advance unit; and heat-sensitive valve means disposed in the conduit connecting the second port and the advance unit. The first port is located upstream of the valve plate and exposed to the substantially atmospheric pressure while the valve plate remains in its idle position, but exposed to the vacuum when the valve plate is opened from the idle position. The second port is kept located downstream of the valve plate and exposed to the vacuum even when the valve plate is opened to its fast-idle position. The second port is exposed to the substantially atmospheric pressure when the valve plate is further opened from the fast-idle position.

Abstract: An air-fuel ratio control device of an internal combustion engine having a carburetor. An air bleed passage is connected to a fuel outflow passage of the carburetor, and an electromagnetic control valve is arranged in the air bleed passage. The control valve is controlled by the detecting signal of an oxygen concentration detector arranged in the exhaust passage so that the air-fuel ratio of a mixture fed into the cylinder of an engine becomes equal to the stoichiometric air-fuel ratio. When the vehicle is decelerated, the mean value of the potential level, which has been applied to the electromagnetic control valve before deceleration, is stored. When the throttle valve is opened during the deceleration and, then, the oxygen concentration detector detects that a rich air-fuel mixture is fed into the cylinder of the engine, the above-mentioned mean value is instantaneously applied to the electromagnetic control valve.

Abstract: An air-fuel ratio control device of an internal combustion engine having a carburetor. An air bleed passage is connected to a fuel outflow passage of the carburetor, and an electromagnetic control valve is arranged in the air bleed passage. The control valve is controlled by the detecting signal of an oxygen concentration detector arranged in the exhaust passage so that the air-fuel ratio of a mixture fed into the cylinder of an engine becomes equal to the stoichiometric air-fuel ratio. After the completion of the warm-up of an engine, the opening area of the control valve is maintained within a fixed range. Before the completion of the warm-up of an engine, the opening degree of the control valve becomes larger than the above-mentioned fixed range.

Abstract: An exhaust gas recirculation system is disclosed, which is of the well-known type wherein an exhaust gas recirculation control valve in the exhaust gas recirculation passage controls the amount of exhaust gas recirculation. An orifice element, upstream of the exhaust gas recirculation valve in the passage, defines a pressure chamber between itself and the exhaust gas recirculation control valve. The vacuum supplied to the diaphragm chamber of the exhaust gas recirculation control valve is modified by a vacuum adjustment valve with two chambers on opposite sides of a biased diaphragm, the one chamber being supplied with the pressure in the pressure chamber, and the other chamber being supplied with atmospheric air through an air bleed means at a certain rate. The improvement of the present invention comprises varying the performance of the supply of air through the air bleed means in accordance with the load on the engine.

Abstract: A back pressure control type EGR system wherein a vacuum line for connecting an EGR port with a vacuum operated EGR valve for controlling the amount of the recirculated exhaust gas is selectively opened to an air chamber of a vacuum modulator valve responsive to the pressure of the recirculated exhaust gas. The air chamber is connected, via a vacuum line, to a second vacuum port located slightly above the EGR port. A vacuum switching valve responsive to vacuum pressure at a third port formed in an intake manifold is arranged in the vacuum line.

Abstract: A control system for use in an exhaust gas recirculation system of an internal combustion engine, in which part of exhaust gases is recirculated from an exhaust system to an intake system in an attempt to reduce the amount of harmful components contained in exhaust gases from the engine as well as to prevent lowering of the running performance of the engine, by controlling the aforesaid recirculation system. This control system includes: a recirculation control valve which controls a recirculation joint portion between the exhaust system and the intake system; a fuel control mechanism which increases the open, cross sectional area of a fuel metering member in a carburetor for compensating for the lowered running performance of the engine due to the exhaust gas recirculation; and a negative-pressure switching valve which selectively supplies an intake negative pressure to the recirculation control valve as well as to the control input end of the fuel control mechanism.