JPS5841634B2 - Internal combustion engine spark plug - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates primarily to a spark plug for an internal combustion engine that reduces loss of ignition energy.

Generally, an ignition system for an internal combustion engine includes a distributor that distributes high-voltage ignition current generated by an ignition coil to a spark plug that generates a certain spark gap sound.

In order to supply ignition current to the spark plugs arranged in each cylinder of an internal combustion engine in a predetermined order, the distributor consists of a rotor electrode that rotates in synchronization with the engine, and a rotor electrode arranged on the circumference in correspondence with the number of spark plugs. The ignition current is distributed by discharge between the rotating rotor electrode and the surrounding electrodes that face each other with a certain gap between them.

Therefore, due to its structure, spark discharge occurs in two gaps in series, namely, the gap between the rotor electrode and the surrounding electrode, and the spark gap in the ignition plug, which causes a large loss of ignition energy and also generates radio noise. There were quite a number of shortcomings.

Therefore, in order to directly supply ignition current to the ignition plug without going through such a defective distributor, the
An ignition system like the one shown in has been proposed.

The figure is for a four-cylinder engine, and includes an ignition coil 1a that supplies ignition current to a set of ignition plugs P, , P2 connected in series, and a transistor 2a that controls the primary current of the ignition coil 1a. One ignition system with a tiger and just like this, spark plug P3? It consists of another ignition system consisting of a P4F ignition coil 1b, a transistor 2b, etc.

A set of spark plugs P0. P2 is a combination of cylinders that are 180 degrees (crankshaft) out of phase, for example, when one enters the expansion stroke, the other enters the exhaust stroke, and as shown in Fig. 1, the cylinders are not shown. When the transistor 2a interrupts the primary current of the ignition coil 1a in response to the ignition signal A (base voltage) from the control circuit, - group of ignition plugs P1. P2 is designed to generate spark discharge at the same time.

This relationship is the same for the other ignition system, only that the phase of the ignition signal B to the transistor 2b is shifted by 180 degrees with respect to A for convenience of the ignition order.

It is clear from the above explanation that the feature of this system is that it streamlines the power distribution path by supplying ignition current to another ignition plug that is not related to ignition, eliminating the need for a distributor, which has many drawbacks. Dew.

However, on the other hand, it requires one ignition coil per two cylinders, and the ignition control circuit becomes complicated, which is unfavorable in terms of cost.Furthermore, due to its configuration, spark discharge occurs between two sparks in series. This has the disadvantage of consuming extra ignition energy, making it difficult to widely adopt it as a replacement for conventional ignition systems equipped with a distributor.

The present invention was made in view of the current situation, and in order to construct an efficient ignition system that does not require a distributor, a pressure switch that opens and closes according to the internal cylinder pressure during engine operation is connected to both electrodes of the ignition plug. This provides an ignition plug that is interposed between the two and causes spark discharge to occur in the spark gap only when ignition occurs.

The present invention will be described below based on illustrated embodiments.

In FIG. 2, the spark plug (main body) 10 includes a main body 10 formed with a screw 11 for screwing into the engine cylinder head, and a substantially cylindrical insulator (electrical insulator) provided so as to penetrate through the center of the main body 10. 12, and two electrodes 13 and 14 provided in parallel through the insulator 12, respectively.

Both electrodes 13 and 14 are fixedly installed so that their respective ends protrude onto both end surfaces of the insulator 12, and the tip 15 (combustion chamber side) of one electrode 13 protrudes beyond the other tip 16. It is bent in the right angle direction to form a predetermined spark gap g.

Further, the other ends 17.18 of both electrodes 13.14 form terminals.

Furthermore, both electrodes 13 and 14 have a pressure switch section 19 located inside the insulator 12.

The pressure switch section 19 includes a cylinder section 20 formed at the center of one electrode 14 with a large diameter in the middle, a contact piece 21 made of a conductive material that is slidably housed in the cylinder section 20, and a contact piece. It consists of a coil spring 23 interposed in the cylinder portion 20 (spring chamber 22) to urge the spring 21 toward the combustion chamber.

A contact portion 24 is formed at the combustion chamber side end of the contact piece 21 so as to protrude toward the electrode 13. Correspondingly, a contact portion 24 is formed on the cylinder portion 20 so that the sliding of the contact piece 21 is controlled by a predetermined distance ( A cutout portion 25 facing the electrode 13 is formed to allow only a portion (described later).

On the other hand, the electrode 13 has a shoulder portion 26 that protrudes from the open end (combustion chamber side end) of the notch portion 25 and comes into contact with the contact portion 24 of the contact piece 21 .

A combustion chamber side passage 27 and an atmospheric pressure side passage 28 are formed through the center of the insulator 12 and reach the pressure switch section 19, respectively.

The combustion chamber side passage 27 connects the combustion chamber (not shown) and the contact piece 21.
The atmospheric pressure side passage 28 communicates with the outside (atmospheric pressure side) of the ignition plug 10 and the cylinder part 20 (spring chamber 22) behind the contact piece 21, respectively.

As will be described later, when a predetermined pressure is applied to the combustion chamber side passage 27, the contact piece 21 resists the elastic force of the coil spring 23 and descends to a position where its contact portion 24 contacts the bottom of the notch 25. However, at this time, the contact distance S between the contact part 24 and the shoulder part of the electrode 13 (see FIG. 3) is adjusted so that it is larger than the spark gap g. The dimensions and shape of the pressure switch section 19 are determined so as to form the smallest air gap at the gap g.

Next, the action of the spark plug 10 based on the above will be explained in relation to the engine operating state.

1. As the cylinder internal pressure increases during the engine compression stroke,
A force opposing the elastic force of the coil spring 23 acts on the contact piece 21 via the combustion chamber side passage 27 .

When this force exceeds the initial set load of the coil spring 23, the contact piece 21 that was in contact with the shoulder 26 of the electrode 13 is displaced and separated from the shoulder 26 while compressing the coil spring 23, and the cylinder internal pressure further increases to a predetermined level. straight (e.g. 5kg/cr
rL2), the contact piece 21 is displaced to the maximum extent and forms the already mentioned contact distance S with the shoulder 26 (see FIG. 4).

Immediately after that, ignition occurs and the fat expansion process begins, but during this time the contact distance S is maintained at 11 because the cylinder internal pressure is extremely high.

However, when the fat expansion stroke ends and the exhaust stroke begins, the cylinder internal pressure rapidly decreases, so the elastic force of the coil spring 23 overcomes the force and quickly pushes back the contact piece 21, causing the electrode 13 to rise again.
is brought into elastic contact with the shoulder portion 26 of.

After that, from the intake stroke to the early stage of the compression stroke, since the cylinder internal pressure is lower than the set position, the contact piece 21 and the shoulder 26
The pressure switch section 19 is kept in elastic contact with the pressure switch section 19, that is, the closed state of the pressure switch section 19 is maintained.

First, the ignition plug 10 is connected via the pressure switch section 19.
A short circuit occurs from the exhaust stroke to the early stage of the compression stroke, and the spark gap g is brought into a dischargeable state for the first time just before the ignition timing.

Therefore, by taking advantage of this characteristic, it is possible to construct an ignition system without a distributor, as shown in FIG. 5, for example.

FIG. 5 shows an example in which spark plugs 10 are provided in each cylinder #1 to #4 of a four-cylinder engine 30, and each of these spark plugs 10 is connected in series with an ignition coil 1 (secondary coil).

In this case, when cylinder #4 has ignited and is near the end of the compression stroke, change the ignition order to (#1-#3-#4-: #=2).
Then, the other cylinder #3. #2. Since #1 is at the end of the fat expansion stroke, intake stroke, and exhaust stroke, all the other ignition plugs 10 (pressure switch parts 19) except cylinder #4 are short-circuited as described above, and cylinder #4 spark gap g
Only the battery becomes ready for discharge.

Therefore, when the transistor 2 cuts off the primary current of the ignition coil 1 in response to the ignition signal C that is emitted in synchronization with the engine 30, only the ignition plug 10 of cylinder #4 will emit a spark into the spark gap g and ignite. , the other spark plugs 10 maintain the short-circuited state and continue to form a circuit through which current flows during this period.

The same thing is done for the other cylinders #3 to #1 according to the ignition order, and during this time the ignition plug 10 of cylinder #4 is short-circuited to form an ignition current path.

As explained above, according to the present invention, a pressure switch that opens in response to the increased cylinder internal pressure during the compression stroke is interposed between both electrodes of the ignition plug, and a state in which discharge is possible in the spark gap only near the ignition timing is achieved. Therefore, it is possible to provide a simple ignition device that does not require a distributor, which has many disadvantages, that is, an ignition device that has less energy loss and radio noise, and is inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional example of an ignition system without a distributor, and also a waveform diagram of its ignition signal. FIG. 2 is an address map showing an embodiment of the present invention, and FIG. 3 is an enlarged view of section D thereof. FIG. 4 is a characteristic diagram showing the relationship between the cylinder internal pressure and the spark gap. FIG. 5 is a schematic diagram showing an example of an ignition system obtained based on the present invention. 10... Spark plug (main body), 12... Insulator (electrical insulator), 13, 14... Electrode, 19
...Pressure switch section, 21...Contact piece, 23...Coil spring, g...Spark gap, S...Contact distance.

Claims (1)

[Claims] 1 having two electrodes arranged with a predetermined gap,
In a spark plug that induces a spark discharge when a high voltage is applied between these electrodes, a pressure switch that responds to the cylinder internal pressure and forms a contact distance larger than the spark gap when opened is housed in the spark plug body. An ignition plug for an internal combustion engine in which both electrodes are short-circuited except during the compression and expansion strokes when the internal cylinder pressure of the engine increases using a pressure switch.