JPH04148070A - Ignition plug for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the detecting capability of ion current by projecting an electrode for ion current detection up to a combustion chamber, in an ignition plug furnishing an electrode for ion current detection. CONSTITUTION:This ignition plug furnishes a central electrode 1 to generate a kindling source of combustion by discharging, an earth electrode 2 provided opposing to the central electrode 1, and an electrode 3A for ion current detection. In this case, the electrode 3A for ion current detection is provided by projecting its one end from the lower end of the inner wall of a housing 4 to reach at least the flame flow generating ions, extending a specific length lto a combustion chamber 6 side, and the detecting capacity of ion current is improved. And the ion current generated when the mixture gas is burnt by the ignition of the ignition plug is detected by the electrode 3A for ion current detection, and picked up as the detecting signal to an external ion current detecting circuit (not shown in the figure)

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark plug for an internal combustion engine, and more particularly to a spark plug for an internal combustion engine having a built-in electrode for detecting ionic current.

[Prior Art] Generally, when an air-fuel mixture in a cylinder of an internal combustion engine is combusted by ignition of a spark plug, an ion current is generated, and the combustion state of the internal combustion engine is detected by detecting this ion current. Conventionally, to detect this ion current, an ion current detection diode is used which is branched from a backflow prevention diode used in the high voltage path for ignition. However, this conventional method uses a high withstand voltage backflow prevention diode and an ion current detection diode to separate the path of the ion current detection signal and the path of the ignition high voltage, making it expensive and Since the high voltage path and the ion current detection signal path share the same cable and have a common impedance, noise at the time of ignition overlaps, making it difficult to detect the ion current signal. Therefore, in order to eliminate this drawback, it is conceivable to incorporate an ionic current detection electrode as a third electrode in the spark plug in addition to the first electrode, which is the center electrode, and the second electrode, which is the ground electrode. FIG. 2 is a configuration diagram showing an example of this. In the figure, (1) is a center electrode that generates combustion sparks by electric discharge, and (2) is a ground electrode provided opposite to this center electrode (1). , (3) is an electrode for detecting ionic current,
44) is a housing that covers a part of the insulator (not shown) through which the center electrode (1) passes;
A ground electrode (2) is attached to. (5) is an engine body to which a spark plug is attached, and (6) is a combustion chamber provided within this engine body (5). As can be seen from Fig. 2, the ion current detection electrode (3) should be placed so that its one end is at the same position as the lower end of the inner wall of the housing (4), or shorter than that, so as not to obstruct the flow of combustion gas. has been set.

Next, the operation of the conventional spark plug for an internal combustion engine shown in FIG. 2 will be explained. When a negative high voltage is generated in the ignition coil (not shown) in synchronization with the rotation of the internal combustion engine, this negative high voltage is directly supplied to the center electrode (1).
) and the ground electrode (2), which causes the spark plug to ignite. When the air-fuel mixture in the combustion chamber (6) is ignited by this ignition plug, an ionic current is generated, which is detected by the ionic current detection electrode (3), and is detected by the external ionic current detection circuit (Fig. (not shown) is extracted as a detection signal.

[Problems to be Solved by the Invention] As described above, in the conventional spark plug for an internal combustion engine, the ionic current detection electrode (3) is placed from the lower end of the inner wall of the housing (4) so as not to obstruct the flow of combustion gas. Since the electrodes were made to not protrude, the electrodes could not reach the flame stream generating ions in the combustion chamber (6), resulting in problems such as b) and t) poor detectability of the ion current. .

This invention was made to solve the above-mentioned problems, and an object thereof is to obtain a spark plug for an internal combustion engine that can improve the detectability of ion current.

[Means for Solving the Problems] A spark plug for an internal combustion engine according to the present invention is a spark plug for an internal combustion engine having an electrode for detecting ionic current, in which the electrode protrudes into the combustion chamber.

[Function] In the present invention, priority is given to improving the detectability of the ion current over the obstruction of combustion gas by the ion current detection electrode. Therefore, the ionic current detection electrode is made to protrude into the combustion chamber to improve the detectability of the ionic current.

[Example 1] An example of the present invention will be described below with reference to the drawings. 1st
The figure is a configuration diagram showing one embodiment of the present invention, (1),
(2), (4) to (6) are the same as described above. In this embodiment, the ion current detection electrode (3
A) is provided. Then, this ion electrode detection electrode (3
A) has one end protruding from the lower end of the inner wall of the housing (4), and extends over a predetermined length toward the combustion chamber (6) so as to reach at least the flame stream generating ions. In the embodiment, the reason why the ion current detection electrode (3A) is made to protrude by a predetermined length is to give priority to improving the detectability of the ion current rather than interfering with the flow of combustion gas.

Next, the operation of the embodiment of the present invention shown in FIG. 1 will be explained. When a negative high voltage is generated in the ignition coil (not shown) in synchronization with the rotation of the internal combustion engine, this negative high voltage is directly supplied to the center electrode (1), and the center electrode (1) and the ground electrode (2 ), which causes the spark plug to ignite.

When the air-fuel mixture in the combustion chamber (6) is ignited by this ignition plug, an ionic current is generated, which is detected by the ionic current detection electrode (3A) and is detected by the external ionic current detection circuit (Fig. (not shown) is extracted as a detection signal. At this time, the ion current detection electrode (3A)
Since the current reaches the flame stream that generates ions, the ion current can be easily detected.

[Effects of the Invention] As described above, according to the present invention, in a spark plug for an internal combustion engine having an electrode for detecting ionic current, the electrode is made to protrude into the combustion chamber, so that the detectability of ionic current is improved. This has the effect of providing a spark plug for use.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional spark plug for an internal combustion engine. In the figure, (3A) is an ion current detection electrode, (6)
is the combustion chamber. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A spark plug for an internal combustion engine having an electrode for detecting ionic current, characterized in that the electrode protrudes into a combustion chamber.