JPH04209968A - Ignition device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce quenching action of a flame nucleus so as to improve ignitability by providing a secondary voltage control circuit, which places duration time of an induction component of a spark discharge and spark energy in a specific condition, while specifying a diameter in a point end part of a center electrode of a spark plug. CONSTITUTION:In this spark plug 1, a firing part, which is a point end of a center electrode 11, is made of platinum alloy or iridium to provide 0.3 to 0.6mm diameter. An ignition circuit 2 is constituted of an ignition coil 3, distributor 4, switching circuit 5 and a secondary voltage circuit 6. Here, the secondary voltage control circuit 6 is constituted such that duration time of an induction component of a spark discharge is 1.0msec or less and 0.2msec or more with spark energy 20millijoule or less and 5.0millijoule or more, when an engine speed is 1000rpm or less, to reduce the spark energy while shortening the duration time according to increasing the engine speed further with generated voltage by the ignition coil maintainable.

Description

[Detailed description of the invention]

['0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an internal combustion engine that improves ignitability, reduces required voltage, and improves the durability of a spark plug. [0002]

[Prior Art] Conventional ignition devices are designed for spark plugs with a large center electrode diameter (diameter 2.5 InlII to 3.01 nI).
1), and as a countermeasure to the flame-extinguishing effect in which the center electrode absorbs the thermal energy necessary for the growth of the flame nucleus, one shot was mainly made by increasing the ignition energy. [0003] It is well known that in order to reduce the required voltage of a spark plug and improve the ignition performance at the same time, it is necessary to reduce the diameter of the firing part of the center electrode. Spark plugs have been developed that have a center electrode with a diameter of 0.8 mm or more. [0004] Also, among the spark discharges of spark plugs, an inductive discharge of 500 to 600 volts (usually 2 to 3 m5ec) follows a discharge spark of 10,000 volts or more due to capacitive discharge (which is extremely short and does not contribute much to ignition). In order to level up the voltage (which contributes to ignition), for example, 2.00
An ignition device has also been proposed in which a voltage of 1,000 to 2,000 volts is applied to the secondary circuit of the ignition coil only when the engine rotates at a low speed of 0 rpm or less. [0005]

[Problems to be Solved by the Invention] However, in order to further improve ignition performance and lower the required voltage, if the center electrode is set to 0°6B or less, if the conventional power source with strong ignition energy is used as is, the internal metal Even if materials with excellent heat resistance such as
For example, it is difficult to guarantee maintenance-free operation for more than 100,000 km. [0006] It is an object of the present invention to create a thinner center electrode with a diameter of 0.8M, which was conventionally limited to a diameter of about 0.8M. To provide an ignition device for an internal combustion engine that uses a center electrode of 6 mm or less and aims to improve ignition performance while reducing required voltage, and is capable of achieving improved durability without causing a decrease in ignition performance. It is in. [0007]

[Means for Solving the Problems] In order to achieve the above object, the ignition device of the present invention has a diameter of 0.6 at the tip of the center electrode.
mm or less, 0. When using a spark plug with a diameter of 3 mm or more and an engine speed of 1,000 rpm or less, the duration of the inductive component of the spark discharge is 1. 0 msec or less, 0,
1 m5ec or more, the spark energy is 20 millijoules or less, 5.0 millijoules or more, and as the engine rotation speed increases, the duration is shortened and the spark energy is reduced, and the voltage generated by the ignition coil is operated an arrangement comprising a secondary voltage control circuit of the ignition coil to maintain it. [0008]

[Operation and Effects of the Invention] By adopting a thin electrode with a diameter of 0.6 cm or less, the required voltage necessary for reliable ignition is reduced, and the area of the center electrode is reduced.
The quenching effect of the flame kernel is reduced and the ignitability is improved. [0009] This makes it possible to reduce the required voltage of the spark plug and the energy required for ignition over the entire rotation range of the engine. At the same time, a high voltage is applied to the secondary circuit of the ignition coil that mainly increases the level of the induced component of spark discharge, increasing the ignition performance at low engine speeds of 1,000 rpm or less, and As a measure to prevent wear and tear on the center electrode, the excess energy (excessive continuation of inductive discharge) that is excessive for reliable ignition and only contributes to wear due to electrode sparks is mainly removed from the engine at speeds above 1,000 rpm. control in the high-speed rotation range. [00101 i.e. 0. A spark plug equipped with a center electrode made of a precious metal having a narrow diameter of 6 mm or less is used to supply the minimum necessary ignition energy to the spark plug commensurate with the narrow diameter. At the same time, the secondary voltage is increased by up to 1,000 volts in the secondary circuit of the ignition coil to increase the spark energy of the induced discharge component, and the voltage level of the secondary circuit is adjusted according to the engine speed. A circuit is incorporated to reduce the increase in the spark energy and reduce the increase in the spark energy. This not only increases ignition performance but also reduces wear on the center electrode, significantly extending the life of the spark plug. [00111] [Example] This invention will be explained with reference to the embodiment shown in the drawings. [00121 FIG. 1 shows an ignition system for an internal combustion engine, where 1 is a spark plug and 2 is an ignition circuit that supplies high voltage to the spark plug. [0013] The spark plug 1, as shown in FIG.
The firing part at the tip of the center electrode 11 is made of platinum alloy, iridium, or iridium alloy, and has a diameter of 0.3 to 0. It is 6mm. Reference numeral 12 denotes a ground electrode made of a nickel alloy whose tip 13 is about 1. 0m
It is formed into a tapered shape of m. Reference numeral 14 is an insulator on which the center electrode is disposed, and 15 is an annular end face 16 that holds the insulator and has the ground electrode joined to it. [00141 The ignition circuit 2 includes an ignition coil 3, a distributor 4 interposed between the secondary coil 31 of the ignition coil and the spark plug 1, a switching circuit (igniter) 5 for the secondary coil 32, and an ignition coil. It consists of a secondary voltage control circuit 6. [0015] The igniter 5 includes a drive circuit 51 that inputs the output of the engine crank angle sensor 21, and a power switching element 52 that is inserted into the primary circuit of the ignition coil and uses the output of the drive circuit as an input signal. so that the ignition advance angle corresponds to the engine rotation speed.
- intermittent current; [0016] The secondary voltage control circuit 6 includes a capacitor C inserted in the secondary circuit of the ignition coil, a resistor R inserted in parallel with the capacitor, and a charging voltage to the capacitor C (voltage at point A). It consists of a frequency control circuit 61 and a DC-DC converter 62, and lowers the voltage at point A as the engine rotational speed increases, as shown by a straight or stepped polygonal line N shown in FIG. [0017] Thereby, the secondary voltage applied to the spark plug 1 and the charge charged in the capacitor C are reduced without reducing the voltage generated by the ignition coil 3 (secondary voltage). Therefore, the spark energy generated by the spark plug also decreases as the engine speed increases. [0018] In the above, the center electrode of the spark plug is set to 0. 6mm or less, 0. 3 mm or more and the engine speed is 1,000 rpm or less, the duration of the induced component of the spark discharge is 1°0 msec or more, and the spark energy is 20 millijoules or less and 5.0 millijoules or more for the following reasons. [00191 The graph in FIG. 4 shows the center electrode diameter, spark discharge gap size, and minimum spark energy required for ignition at an air-fuel ratio of 16.0. Further, the graph of FIG. 5 shows the relationship between spark energy and wearability of the center electrode due to sparks. Furthermore, FIG. 6 shows the relationship between the engine speed and the minimum duration of spark caused by induced discharge required for reliable ignition. [00201 From these characteristic graphs, the following is clear. [00211a) When the spark discharge gap is set to a practical value of 1.0M or more, the diameter of the center electrode is 0.0M or more. When the diameter is 6 mm or less, reliable ignition is possible even if the spark energy due to induced discharge is 20 millijoules or less. Also, the diameter is 0.3m
m may be 10 millijoules or less, but 5 millijoules or more is required. (0022) A) When operating with spark energy of 20 millijoules or less, the electrode will be 0. By the time 1mm is consumed,
The center electrode has a diameter of 0. With a diameter of 6 mm, approximately 9 billion sparks can be generated, and with a diameter of 0.3 mm, approximately 1 billion sparks can be generated. Even a normal spark plug requires 1 billion sparks, so the lower limit of the center electrode diameter is set at 0. 3m
It was set as m. Furthermore, if 9 billion sparks can be generated, it will be possible for a car to travel 100,000 km without maintenance. [0023] T) The spark duration due to induced discharge necessary for reliable ignition is 1.
It is 0 msec, and gradually shortens as the rotation speed increases. However, even at 5,000 rpm or more, 0. 2ms
EC level is necessary. Therefore, from the viewpoint of the durability of the spark plug, it is desirable to control the spark duration due to the induced discharge so that it approaches the characteristic curve shown in FIG. 6 as much as possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram of an internal combustion engine ignition system according to the present invention.

FIG. 2 is a side view of the spark plug.

FIG. 3 is a graph showing the characteristics of the voltage applied to the secondary circuit of the ignition coil.

FIG. 4 is a graph showing characteristic curves of center electrode diameter, spark discharge gap size, and minimum spark energy required for ignition.

FIG. 5 is a graph showing the relationship between spark energy and the wearability of the center electrode due to sparks.

FIG. 6 is a graph illustrating the relationship between engine speed and minimum induced discharge spark duration.

[Explanation of symbols]

1 Spark plug 2 Ignition circuit 3 Ignition coil 4 Distributor 5 Igniter 6 Secondary voltage control circuit

[Figure 1]

Claims (1)

[Claims] Claim 1: A spark plug in which the diameter of the tip of the center electrode is 0.6 mm or less and 0.3 mm or more, and the duration of the induced component of spark discharge is 1.0 msec or less when the engine rotation speed is 1,000 rpm or less. , 0.2 msec or more,
The spark energy is 20 millijoules or less and 5.0 millijoules or more, and as the engine rotation speed increases,
An ignition device for an internal combustion engine, comprising an ignition coil secondary voltage control circuit that shortens the duration and reduces the spark energy while maintaining the voltage generated by the ignition coil.