Abstract: A secondary air supply system for an internal combustion engine includes a first hydraulic passage including a first hydraulic motor for an engine cooling fan. The system further includes a second hydraulic passage including a second hydraulic motor for a secondary air supply pump. At a connecting point of the first hydraulic passage and the second hydraulic passage, a hydraulic passage switching valve is installed. The hydraulic passage switching valve causes oil to flow through the second hydraulic passage to drive the air pump for a few minutes after engine start and then switches to cause the oil to flow through the first hydraulic passage to drive the engine cooling fan. In this way, the secondary air supply pump is driven not by a pulley-belt assembly but by a hydraulic system, and a single hydraulic pump can be used for driving both the engine cooling fan and the secondary air supply pump.

Abstract: A small-sized spark plug for internal combustion engines is disclosed which is composed of a center electrode having a shaft portion surrounded by an insulator layer and a terminal end portion adapted to act as a spark generation portion; and an earthed electrode having a terminal end portion which is spaced apart from and is opposite to the terminal end portion of the center electrode so that a spark gap is defined along a surface of the insulator layer. The shortest distance .delta. (mm) between each end portion of the two electrodes and the surface of the insulation layer and the distance l between the forward end portions of the two electrodes have the following relationship:.delta..gtoreq.0.25 l, and 0.8 mm.ltoreq.l.ltoreq.2.0 mm.A recessed portion may be provided on the surface of the insulation layer.

Abstract: A position detector for detecting the piston TDC position in a piston engine has a cylindrical casing penetrating the top wall defining a combustion chamber of the engine and fixed thereto, a light emission element, a light reception element each being accommodated within the upper half of the casing, an inlet optical fiber connected to the light emission element and an outlet optical fiber connected to the light reception element. These optical fibers are inserted into the lower half of the casing. The lower end of each optical fiber is opposed to the upper surface of the piston at a predetermined distance therefrom when the piston is located in the vicinity of the TDC position. The light emitted by the light emission element is applied to the upper surface of the piston, after passing the inlet optical fiber. The reflected light from the upper surface of the piston is received and sent to the light reception element by the outlet optical fiber.

Abstract: An engine has cylinder head and cylinder block cooling jackets. A control system controls a valve system to circulate fluid through a conduit system, the jackets and a radiator in various flow patterns. If the block jacket cooling fluid temperature is less than a warmup completion temperature, the control system establishes a combined conduit circuit including both the head and the block cooling jacket but not including the radiator, and makes a cooling fan system for the radiator blow relatively weakly.

Abstract: A vane-type rotary pump and a vane-type rotary compressor are integrated into a single unit and are driven by a common shaft. The compressor assembly is positioned at the rear of the pump assembly to minimize the number of mechanical seals required to seal the pump assembly along the shaft. The combined pump and compressor unit is provided with a regulating mechanism for reducing the compressor output during moderate or off modes of the refrigerant circuit.

Abstract: In response to the occurrence of knocking in an internal combustion engine, the basic ignition timing is corrected in a direction to retard it through the charging and discharging of an integrator circuit. The integrated current output of the integrator circuit is varied in accordance with a voltage corresponding to the speed of the engine so as to limit the maximum amount of ignition timing retard at low speeds or high speeds of the engine.

Abstract: The temperature and air-fuel ratio of the exhaust gases of an internal combustion engine are sensed to generate signals indicative thereof and the amount of fuel to be injected into the engine is determined in accordance with the signals, thus controlling the air-fuel ratio at a predetermined value and thereby decreasing the abnormal temperature rise in the exhaust system.

Abstract: A method for detecting knock for an internal combustion engine having a plurality of cylinders in which a vibration sensor is attached to each cylinder and a peak value of vibration detected by the sensor is sampled over a predetermined interval near the top dead center. The sampled value is converted from analog to digital and stored for a predetermined number of sampling times to obtain the average value for each cylinder. Then the frequency of occurrences in which the ratio between the sampled peak value and the average value exceeds a reference value is obtained, and the knock is determined when the frequency of occurrences in any one cylinder exceeds a predetermined value or when the average frequency of occurrences of the all cylinders exceed another predetermined value.

Abstract: An apparatus for detecting knock for an internal combustion engine having a plurality of cylinders in which a vibration sensor is attached to each cylinder and a peak value of vibration detected by the sensor is sampled over a predetermined range near the top dead center. The sampled value is converted from analog to digital and stored for a predetermined number of sampling times to obtain the average value for each cylinder. Then the frequency of occurrences in which the ratio between the sampled peak value and the average value exceeds a reference value is obtained, and the knock is determined when the frequency of occurrences in any one cylinder exceeds a predetermined value or when the average frequency of occurrences of the all cylinders exceeds another predetermined value.

Abstract: An internal combustion engine comprising an intake duct and a turbocharger arranged in the intake duct. A primary throttle valve connected to the accelerator pedal is arranged in the intake duct located downstream of the turbocharger. A secondary throttle valve is arranged in the intake duct located downstream of the primary throttle valve. An auxiliary intake passage is branched off from the intake duct located between the primary and the secondary throttle valves and is connected to the intake passage located downstream of the secondary throttle valve. The secondary throttle valve is gradually closed from the full open position as the level of the vacuum or the positive pressure, which are produced in the intake duct located between the primary and the secondary throttle valves, is increased.