Abstract: A discharge tube of the present invention is disclosed comprising an electrically insulated container which is further provided with a pair of electrodes at opposite sides thereof and with inert gas and mercury enclosed therein, wherein the enclosed quantity of the mercury is 0.01 to 1 mg per one cubic centimeter of the capacity of the container and the enclosing pressure of the inert gas is 8 to 15 kgf/cm.sup.2.

Abstract: An ignition plug cap having at least a plug cap terminal and a discharge tube as a series gap at one end of a high-tension cord for providing electric high-voltage pulses to an ignition plug in a vehicle, wherein the ignition plug cap further comprises an electrically insulating casing for accommodating the plug cap terminal and the discharge tube, which is formed with heat dissipating means such as a plurality of fins formed on the external surface thereof either in parallel or at right angles with vertical axis of the electrically insulating casing, or they can be simultaneously formed otherwise, apart from a spiral fin and so on. With this construction, heat generated therein is effectively dissipated for controlling a rise of temperature, whereby the components of the ignition plug cap in general will not be readily deteriorated even in long-term severe driving conditions.

Abstract: A gas-filled discharge tube includes a cylindrical casing (11, 31), a terminal member (12, 13; 32, 33) for closing an open end of the casing, an inert gas sealed within the casing, a gas sealing tube (16, 38) connected to an outside of the terminal member, and gas introduction paths (17, 40) formed in the terminal member so as to communicate between an inner space of the gas sealing tube and an inner space of the casing.

Abstract: A discharge tube according to the present invention is constructed such that it comprises a cylindrical container made of an insulation tube, a pair of discharge electrodes provided at opposite ends of the cylindrical container, a plurality of insulation coated lines containing a gas-ionization accelerator therein, which insulation coated lines being provided on the inner surface of the cylindrical container covering the regions surrounding a cathode and a discharge space therein in a substantially parallel relation with a center axis of the cylindrical container, wherein the gas-ionization accelerator is made of a silicate powder selected from the group of alkaline metal, alkaline earth metal and so on, or of electrically conductive finely divided particles selected from the group of carbon, metal, metal oxide and so on.

Abstract: A discharge tube according to the present invention is constructed such that it includes a cylindrical container made of an insulation tube, a pair of discharge electrodes provided at opposite ends of the container, a plurality of insulation coated lines containing a gas-ionization accelerator therein, which insulation coated lines being provided in the grooves formed on the inner surface of the container covering the regions surrounding a cathode and a discharge space therein in a substantially same distance from a center axis of the container, wherein the container further comprises a flange portion formed at the cathode-side thereof in such a way that it protrudes inwardly, and the insulation coated lines are provided on the inner surface of the container except the inner side of the flange portion.

Abstract: Only one pre-gap is arranged between the ignition coil and the distributor so that it is connected in series with each of the ignition plugs in the engine. A relay device is connected in parallel with the pre-gap. The relay device is normally closed to supply a high voltage from the ignition coil to the distributor, bypassing the pre-gap. Only when sensor signals indicate that the air-fuel combustion state is bad, the relay device is opened to cause the high voltage from the ignition coil to be applied to the pre-gap before being supplied to the distributor. This construction permits the single pre-gap to serve all the cylinders in the engine and prolongs the working life of the pre-gap.

Abstract: A flange, which is integrally formed with the inner surface of the cylindrical member, is located at an intermediate point between the end surface position of the cylindrical member to which the electrode plate of one of the discharge electrodes is sealed and the tip position of the discharge electrode portion of that electrode. Both end surfaces of the cylindrical member are hermetically attached with the discharge electrodes. This arrangement prevents inner flashovers without affecting the discharge characteristics of the discharge tube and also ensures manufacture of discharge tubes with no possibility of gas leakage with very high yields even if the machining precision is not so high.

Abstract: The discharge tube consists of an electrically insulating cylindrical body and a pair of electrodes disposed facing each other in the cylindrical body, and is sealed with an inert gas. An activation layer of a silicate compound of alkaline metal is formed over at least a part of the inner wall surface and the electrode surface, other than the discharge surface, that are exposed to the sealed gas. This activation layer helps keep the discharge inception voltage stable even when the discharge frequency changes greatly, which in turn extends the longevity of the discharge tube.

Abstract: An ignition system has a series-gap discharge-bulb through which a high voltage is supplied to a center electrode of an ignition plug. A short-circuit element is made of a material that reversibly deforms when it is heated to a predetermined temperature when an engine is operated in a steady state. The short-circuit element is electrically connected to the plug such that two discharging electrodes are short-circuited by the short-circuit element when the short-circuit element is heated to thermally deform. The discharging electrodes may be made of a reversibly deformable material so that the electrodes deform into contact with each other when they are heated to a predetermined temperature.