Abstract: In a snap-in type spark plug voltage probe device, the insulator base has an upper half and a lower half, both ends of which are integrally connected by means of a flexible portion. The upper half and the lower half have a plurality of grooves in which spark plug cables are placed. The upper half and the lower half are joined together by the flexible portion when in a closed position. The upper half has an opening to receive a protrusion provided on the lower half of the insulator base to maintain the upper half of the insulator base along the grooves, providing static capacity between the electrode layer and the spark plug cables when voltage is applied across the spark plugs. A lead wire electrically connects the electrode layer to a microcomputer so as to analyze the burning condition based on the static capacity between the electrode layer and the spark plug cables.

Abstract: A spark plug voltage waveform detector probe for use in an internal combustion engine and which is mounted on a secondary circuit of an ignition circuit to form static capacity therebetween so as to detect a spark plug voltage waveform. The detector probe includes an insulator body and an electrode plate which is embedded in the insulator body and electrically connected to a lead wire. A pair of readily replaceable insulator plates are located under the insulator body each of the insulator plates having at least one groove, the at least one groove of each of the insulator plates opposing each other and cooperating to form an opening in which a spark plug cable is placed which is extended from the secondary circuit. Electromagnetic shield plates are provided to liquid-tightly sandwich the insulator body and the insulator plates so as to form a laminated detector probe structure. The electromagnetic shield plates are electrically connected to the internal combustion engine for grounding.

Abstract: In a spark plug voltage probe device, an electrically shield casing (301) is provided in which electrical circuit boards (302) are accommodated, the shield casing (301) having an electrically conductive wall (313) connected to the ground. An insulator base (303) is securely attached to an outer bottom of the electrical shield casing (301) and has an electrode plate (332) embedded in the insulator base to be connected to the electrical circuit boards (302). A rubber plate (342) is securely attached to a lower surface of the insulator base (303). A plurality of grooves (333, 341) are provided between the insulator base (303) and the rubber plate (342) to locate the corresponding cables (305) in the grooves (333,341) so as to form a static capacity (C1) between the electrode plate (332) and the cables (305). This makes it possible to reduce a noise level by the ratio of the static capacity (C1) to a static capacity (C2) between the electrically conductive wall (313) and the electrode plate (332).

Abstract: In a misfire detector device for internal combustion engine, an ignition coil is provided to be on-off actuated by a primary current interruptor circuit, each end of the ignition coil being connected to a spark plug installed in each cylinder of an internal combustion engine. A peak voltage detector circuit detects a peak voltage applied across the spark plug electrodes after an end of spark action of the spark plug. A peak voltage value distinction circuit recognizes a misfire when a voltage level exceeds a predetermined level which is detected by the peak voltage detector means after an end of spark action of the spark plug upon running the internal combustion engine at a high speed. A distinction circuit recognizes a variation of angles detected by the crank angle sensor so as to determine the misfire when the variation of angles exceeds a predetermined value upon running the internal combustion engine at a low speed.

Abstract: A misfire detector for use in an internal combustion engine has an ignition coil including a primary coil and a secondary coil. An interrupter circuit is provided for on-off actuation of primary current flowing through a primary circuit of the ignition coil. A distributor has a series gap provided in a secondary circuit of the ignition coil, and a spark plug is adapted to be energized from the ignition coil through the series gap of the distributor. A voltage charging circuit works to electrically charge a stray capacity inherent in the spark plug immediately after an end of a spark action of the spark plug. A spark plug voltage detector circuit distinguishes the voltage waveform of more than a predetermined reference voltage level so as to deform the voltage waveform into output signals. On the basis of the width of the output signals, a distinction circuit determines whether or not the spark action ignites an air-fuel mixture in a cylinder of the internal combustion engine.

Abstract: In a sparkplug voltage detecting probe device for use in internal combustion engine comprising, a sensor is provided to form a static capacity between the sensor and an ignition coil which is connected to a spark plug. A sparkplug voltage divider circuit has a capacitor connected between the sensor and the ground. A release circuit has a resistor connected in parallel with the capacitor so as to provide a time constant of a RC path. A short circuit is provided to instantaneously release an electrical charge from the capacitor either immediately before establishing a spark voltage for the spark plug or immediately after initiating the spark action of the spark plug. A sparkplug voltage waveform detecting circuit detects a sparkplug voltage waveform divided by the sparkplug voltage divider circuit.

Abstract: In a misfire detector device for use in internal combustion engine, an electrical interrupter circuit on-off actuates a primary current flowing through a primary circuit of an ignition coil to induce a spark plug voltage. A check diode is provided in a secondary circuit of the ignition coil to prevent a current flowing back to the ignition coil. The spark plug has a center electrode, a front end of which is projected from an insulator, and an outer surface area of the projected front end being 25 mm.sup.2 or more. A spark plug voltage detector circuit detects an attenuation time length of a spark plug voltage waveform presented subsequent to a predetermined time period occurring after an end of a spark action of the spark plug. On the basis of the attenuation time length, a distinction circuit determines whether a misfire occurs in a cylinder of an internal combustion engine.

Abstract: In a misfire detector device for use in internal combustion engine, an electrical interrupter circuit on-off actuates a primary current flowing through a primary circuit of an ignition coil to induce a sparkplug voltage which is applied to a multi-electrode type spark plug. A check diode or a series gap is provided in a secondary circuit of the ignition coil so as to prevent a current flowing back to the ignition coil. A sparkplug voltage detector circuit detects an attenuation time length of a sparkplug voltage waveform presented subsequent to a predetermined time period after an end of a spark action of the spark plug. On the basis of the attenuation time length, a distinction circuit determines whether a misfire occurs in a cylinder of an internal combustion engine.

Abstract: A spark plug voltage probe detects a voltage applied to a spark plug installed in an internal combustion engine so as to analyze a burning condition in the internal combustion engine on the basis of the voltage applied to the spark plug. A rubber collar (74) is provided to surround a rubber cap (7) which is secured to a high tension terminal (71a) of the spark plug (71) so as form a static capacity between the high tension terminal (71a) and the rubber collar (74). An electrical conductor (73) is provided between the rubber cap (7) and the rubber collar (74) and is electrically connected to a microcomputer by way of an output cable (64).

Abstract: A retaining ring is provided for temporarily holding a pressure sensor in place within a spark plug attaching hole prior to installation of a spark plug. The retaining ring is resiliently deformed into a stressed positioned to attach itself to a circumferential wall of the spark plug attaching hole. In one embodiment, a gasket is adapted to serve also as such a retaining ring.

Abstract: In equipment for recognizing misfire in an internal combustion engine, a first voltage waveform is obtained at an intermediate point (A) between a high impedance element (41) and a low impedance element (42). The first voltage waveform has a capacitive discharge component and an inductive discharge component during the spark and a voltage component after completion of the spark. The first voltage waveform is inversely amplified by a comparator (51) and divided by a shunt circuit (52) to obtain a second voltage waveform. In an integration circuit (53), a condenser (C1) is electrically charged by an output voltage from the comparator (51) to obtain a third voltage waveform. The second voltage waveform and the third voltage are compared by a comparator (54) to generate an output pulse.

Abstract: In a misfire detector for use in an internal combustion engine having an ignition coil, an electrical interrupter circuit interrupts a primary current flowing through a primary circuit of the ignition coil by which a spark plug is energized. A voltage divider circuit detects a divided voltage of a spark plug voltage applied across the spark plug. A spark plug voltage detector circuit is provided to detect an attenuation characteristic of a spark plug voltage waveform presented subsequent to a time period predetermined either during a spark action of the spark plug or after an end of the spark action of the spark plug. A peak hold circuit is provided to hold a peak voltage of the spark plug voltage waveform presented after the end of the spark action of the spark plug, so that a distinction circuit determines a misfire on the basis of a peak voltage level or the attenuation characteristics of the spark plug voltage waveform.

Abstract: In a burning condition detecting device in an internal combustion engine in which a high voltage is applied to a spark plug by way of a diode and a series gap of a distributor. A voltage charger circuit is provided to on-off actuates the primary coil to induce a charging voltage in the secondary circuit either during establishing the spark discharge or during a predetermined period of time immediately after an end of the spark discharge. The charging voltage is applied to the spark plug to electrically charge a stray capacity inherent in the spark plug so as to form a sparkplug voltage. A voltage divider circuit is provided to divide the sparkplug voltage in accordance with a high impedance element and a low impedance element. A voltage level detecting circuit is provided to detect a sparkplug voltage waveform divided by the voltage divider circuit.

Abstract: A liquid mixing ratio detecting sensor has cylindrical holder which is immersed in sulfuric acid solution. The holder is filled with silicone oil. A glass plate is placed within the holder. A light emitting diode emits light beams which enter the glass plate through its vertical side, and totally reflect from a boundary between the glass plate and the sulfuric acid solution. The light beams coming out from the glass plate is reflected by a reflection plate to enter into the glass plate through its vertical side, and totally reflected from a reference boundary between the glass plate and the silicone oil when a refractive index of the sulfuric acid solution is greater than that of silicone oil. On the other hand, the light beams entered into the glass plate refracts at the reference boundary to fall on a photo diode when the refractive index of the sulfuric acid solution decreases to be smaller than that of silicone oil.

Abstract: A mixing ratio detecting device for composite liquid has a transparent column placed so that a bottom of the column is in contact with a mixing liquid, and a light emitting diode disposed so that light beams therefrom are incident on one side of the column to pass therethrough so as to impinge on an interface between the bottom of the column and the mixing liquid. The light beams impinged on the interface less than a critical angle are refracted, while the light beams impinged on the interface more than the critical angle totally reflected to escape from other side of the column. A photo diode is provided to receive the light beams escaped from the other side of the column so as to generate an output. An effective photo-receiving area of the photo diode is in the form of an inversed trapezoid to compensate for characteristics of the output from the photo diode.

Abstract: In a mixing liquid ratio detector device, a LED and a photo diode are provided in a manner to sandwich an optically permeable column. The light emitting area of the LED and the light receiving area of the photo diode are each arranged in the neighborhood of the column in generally perpendicular relationship with a boundary between a mixing liquid and the column, such that light beams from the LED enter the boundary through one side of the column, the light beams incident on the boundary at an angle more than a critical angle being totally reflected from the boundary, and advancing through an inner portion of the column to come out from the other side of the column, and impinging on the photo diode.

Abstract: A detector device for mixing ratio for gasoline and alcohol include an optically permeable column, one end of which is coated with a light-reflective layer. The circumferential surface of the column is at least partly immersed in mixing liquid of gasoline and alcohol.The light beams enter the column to be incident on said circumferential surface of the column and reflect from the circumferential surface to be incident on said light reflective-layer to reflect therefrom. The reflected light beams impinge on a photo diode which outputs in accordance with the intensity of the light beams impinged.The diametrical and lengthwise dimension of the column being determined such as to provide incidence angles of the reflected light beams changing from a minimum angle corresponding to the critical angle when the mixing liquid ratio is at the lower limit of the predetermined range to a maximum angle corresponding to the critical angle when the mixing liquid ratio is at the upper limit of the predetermined range.

Abstract: A detector device for determining the mixing ratio of gasoline and alcohol includes a flint glass plate, one side of which is placed to be in direct contact with a mixing liquid of gasoline and alcohol, a light emitting diode is located at the other side of the flint glass plate to be opposite to the mixing liquid so that light beams emitted from the diode enter the flint glass plate to be incident on a boundary between the plate and the mixing liquid and a photo diode having a rectangular shape and located in coplanar relationship with the light emitting diode to receive the light beams totally reflected from the boundary.

Abstract: Deterioration detector system for catalyst in use for emission gas purifier, comprising; an emission passageway through which exhaust gas from internal combustion engine, passes by way of catalyst to facilitate the reducing and oxidizing reaction among the toxicant component of hydrocarbon, carbon monoxide and nitrogen oxide; a sensor placed at the emission passageway to position downstream of the catalyst against the exhaust gas flow so as to generate an output in direct proportion to air-fuel ratio in the exhaust gas; an annunciator arranged to activate in response to the output of more than the predetermined level generated from the air- fuel ratio sensor.

Abstract: A sensor for mixing ratio of liquid fuel comprising, a cylindrical enclosure having both inlet and outlet openings to act as a passage through which a mixing liquid fuel flows. A transparent column concentrically disposed in the enclosure to make the outer surface thereof contact with the liquid fuel, each end of the column is inserted into a ring-shaped wall provided with the inner side of the open end portion of the enclosure. A light emitting diode and a photo diode are provided so as to sandwich the column in the lengthwise direction, so that the light emitted from the former enters the column through its one end and reflects at the boundary of the column and the liquid fuel, and go onto the other end thereof to fall on the latter. A metallic sleeve sealant is provided, one side of which is liquid tightly telescoped into each end of the column, the other side of which is liquid tightly secured to the outer side of the wall to hermetically seal between the liquid fuel and the column.