JPH0138188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ignition device for an internal combustion engine.

A conventionally known ignition system for an internal combustion engine is constructed as shown in FIG.
and flows through breaker 2 to ground. The high voltage generated by the ignition coil 3 is output from one end (FIG. 1) or both ends (FIG. 2) of the secondary winding 3b and is applied to the terminal of the spark plug 4. On the other hand, the spark plug 4 is constructed as shown in FIG. It is electrically insulated from the metal fitting d. This mounting bracket d has a mounting screw for mounting to the internal combustion engine, and is tightly attached to the silling head of the internal combustion engine via a gasket k. Further, the ground electrode e is fixed to the mounting fitting d by welding or the like, and is therefore electrically connected to the cylinder head. A spark gap h for spark discharge is formed between the center electrode f and the ground electrode e.

The operation of the above conventional device is based on the ignition coil 3.
The high voltage applied from the secondary winding 3b of the spark plug 4 is applied to the center electrode f via the terminal part a of the spark plug 4. When the applied voltage exceeds the discharge voltage of the spark gap h, a discharge occurs in the spark gap h, and the air-fuel mixture It is starting to catch fire.

Incidentally, as a recent background, there has been a call for improvements in the performance of spark plugs themselves, such as improved ignition ability, anti-fouling properties, and reduced radio noise, but changes to the structure of the spark plug itself have not sufficiently addressed these points. There are limits to being satisfied.

The inventor of the present invention took a broader view of the ignition device including the spark plug, and as a result of intensive research on this ignition device, it was discovered that by improving the conventional devices shown in FIGS. I found it.

That is, the present invention electrically connects one of the two electrodes of the spark plug to the vehicle body to electrically connect a high voltage circuit having the spark plug and the secondary winding of the ignition coil to the vehicle body. This device fundamentally breaks away from the preconceived concept of conventional devices, and its feature is that it has two electrodes that are electrically insulated from the vehicle body, and a spark gap for spark discharge is formed between the two electrodes.
Each of the electrodes is electrically connected to both ends of the secondary winding of the ignition coil, and a high voltage circuit including at least the secondary winding and the two electrodes is electrically isolated from the vehicle body. It is in.

The present invention will be explained in detail below using specific examples. FIG. 4 shows an electric circuit of an ignition system applied to a vehicle having a single-cylinder two-stroke gasoline internal combustion engine, that is, a motorcycle. In the figure, the positive pole of a power supply 1 (battery) is electrically connected to the primary winding 3a of an ignition coil 3, and this primary winding 3a is electrically connected to the negative pole side of the power supply 1 via a breaker 2. connected. On the other hand, electrodes f of a spark plug 4 are electrically connected to both ends of the secondary winding 3b of the ignition coil 3, respectively. This plug 4-2
The two electrodes f are exposed in the combustion chamber 5 of the internal combustion engine, and a spark gap for spark discharge is formed between them. The two electrodes f of the plug 4 are not electrically connected to the internal combustion engine and, as a result, are not connected (grounded) to the vehicle body (motorcycle chassis). Note that the ground circuit of the internal combustion engine in FIG. 4 shows a general ground circuit, and does not indicate that the electrode f is grounded.

Next, the detailed structure of the plug 4 and the manner in which it is attached to the internal combustion engine will be explained with reference to FIGS. 5 and 6. In the figure, the structure of the plug 4 is the fifth one.
As is clear from the figure, the only difference from the conventional structure shown in FIG. 3 is that it does not have a ground electrode, and the other structure is the same as that shown in FIG. Therefore, detailed explanation will be omitted.

The plug 4 having the structure shown in FIG. 5 is installed as shown in FIG. 6, and a spark gap h is formed between the center electrodes f of the two plugs 4. In FIG. 6, 6 indicates a cylinder head, 7 indicates a cylinder, and 8 indicates a piston.

In the above configuration, the operation will be described next. When a positive voltage is applied to one terminal a of the spark plug 4 and a negative voltage of reverse polarity is applied to the other terminal a, a discharge occurs in the spark gap h and the air-fuel mixture is ignited. In the above embodiment, the plug 4 and the secondary winding 3
Since the high-voltage circuit consisting of (b) is constructed above the vehicle body, the voltage during discharge is 1/2 the voltage seen from the vehicle body compared to the conventionally known FIGS. 1 and 3. As a result, high-voltage parts such as the spark plug 4 only need to have half the withstand voltage.
Therefore, the length of the insulator b can be reduced to about 1/2 compared to the conventionally known spark plug shown in FIG. 3, making it possible to downsize the entire plug. In addition, in conventional spark plugs, when the center electrode protrudes into the combustion chamber, the ground electrode to form the gap inevitably becomes longer, resulting in overheating of the ground electrode, resulting in greater wear and tear, or inability to secure sufficient heat value. However, since the plug of the above-described embodiment does not have a ground electrode, this problem is advantageously solved.

Next, an example of the excellent effects of the present invention will be explained through experiments.

The experiment was conducted using a two-stroke, 50 c.c. gasoline internal combustion engine. Mounting the sample is shown in Figures 6 and 7.
As shown in FIG. The details of the sample shown in FIG. 6 are shown in FIG. 5, the details of the sample shown in FIG. 7 are shown in FIG. 5 with a ground electrode, and the details of FIG. 8 are shown in FIG.

The results are shown in FIG. 9, and the conditions are that the engine was operated with the engine valve fully closed (200 rpm) and the time required for the internal combustion engine to stop is shown in minutes (min). As can be seen from this result, in the conventionally known ignition system, performance is secured by using a plug with a mounting screw of 14 mm (Fig. 8), but only the plug with a mounting screw of 10 mm is used.
(Fig. 7), it becomes impossible to operate for a short period of time, and it can be seen that the performance cannot be ensured at all. on the other hand,
When using the igniter shown in FIG. 4 of the present invention, the mounting screw
Even if a 10mm small plug is used, the performance can be more than twice that of conventionally known ignition devices. This is an excellent effect that breaks the conventional wisdom that small plugs cannot be used in two-stroke engines. The reason why such a small plug can secure dirt resistance performance that is better than conventionally known plugs is that even during discharge, the vehicle body is connected to a part of the high voltage circuit of the ignition coil as in the past. This was achieved in order to configure a high-voltage circuit only with circuits that are insulated from the vehicle body.

To explain in more detail its excellent stain resistance,
In general, the fouling characteristics of an ignition device are expressed as leakage characteristics as shown in FIG. The voltage between the X terminal and the ground in the figure is as shown in A in Figure 12, whereas the voltage between M and P in Figure 11 of the present invention is due to a decrease in the insulation of only one of 6a and 6b (leakage resistance). 12th if
If the insulation of 6a and 6b similarly decreases, the result will be B in FIG. 12. In other words, assuming that the voltage at the time of discharge is 15KV, a conventionally known ignition device will misfire at 1MΩ;
It can be seen that the ignition device of the present invention does not cause misfire even at 0.5 MΩ. In other words, even with an ordinary ignition coil, characteristics close to those of a capacitive discharge ignition device (CDI) can be obtained. This means that in the conventionally known ignition system, the leakage resistor 6 forms a short circuit of the spark gap, whereas in the ignition system of the present invention, as described above, the high voltage circuit consisting of the plug and the ignition coil is connected to the vehicle body. Since the circuit is electrically insulated from the leakage resistance 6a or 6
A short circuit of the spark gap is not formed with only one of the spark gap b, but a short circuit is formed only when the leakage resistors 6a+6b are connected in series, so that such excellent effects can be obtained.

Next, FIG. 13 shows the results of measuring radio noise. Samples and their configurations are shown in FIGS. 4, 5, and 6 for the present invention, and FIGS.
This is shown in FIG. From these results, it can be seen that in the ignition device of the present invention, the radio noise radio waves become as shown in FIG. This result is due to the fact that the voltage during discharge of the spark plug can be reduced to 1/2 compared to conventional ignition systems when viewed from the vehicle body, and the fact that positive and negative voltages are applied to the spark plug. It is thought that this combined effect also resulted in the effect that the direction of the current was reversed between the two high tension cords.

Since the high-voltage circuit is electrically isolated from the vehicle body, high-frequency current in the high-voltage circuit is directly connected to the vehicle body through the capacitance (stray distributed capacitance) component formed between the high-voltage circuit and the vehicle body. As the number of radio waves flowing directly from the vehicle body decreases, the radio waves are mainly generated only from the high-frequency current in the high-voltage circuit, and the vehicle body supplements these radio waves and transmits them to various parts within the vehicle body. It can convert radio wave energy into thermal energy. In other words, the vehicle body, which is insulated from high-voltage circuits, acts as a radio wave absorber, and as a result, the radio waves reaching the outside of the vehicle become weaker, reducing the radio wave interference to TVs and radios outside the vehicle. This also reduces the possibility of causing radio wave interference to electronic devices installed in the vehicle.

FIGS. 14 to 16 show electrical wiring diagrams in other embodiments of the ignition device of the present invention. To explain each of these embodiments, FIG. 14 shows one applied to an internal combustion engine having two cylinders, which uses two ignition coils 3, 3, and connects both coils 3, 3 via a spark plug 4. Secondary winding 3
b, 3b are electrically connected, and each coil 3,
3 is configured to generate high voltage at the same time.

In FIG. 15, the plugs 4 of each cylinder are connected in series to the secondary winding 3b of one ignition coil 3.

In the embodiments shown in FIGS. 14 and 15, spark discharge is generated simultaneously by two plugs 4, 4, and one of them is used as a so-called waste fire.

FIG. 16 is a development of the embodiment of FIG. 4. In this embodiment, two electrodes n, n (electrically floating) are arranged between two electrodes f, f of the plug 4. According to this embodiment, the spark discharge at the plug 4 passes through the two electrodes n, n, thereby increasing the number of sparks and improving the ignitability.
The present invention is applied to a so-called multi-point ignition device.

FIG. 17 shows another example of the plug used in the ignition device of the present invention. According to this example, the structure is a combination of the two plugs shown in FIG. 6 above.

FIGS. 18 and 19 show a different way of forming the spark plug gap in FIG. 6. That is, according to this example, the spark gap h is formed by intersecting the center electrodes f, f of the two plugs 4, 4 at their tips. With this configuration, the gap can be formed more easily than in FIG. 6.

FIGS. 20 and 21 show a modification of FIG. 17, in which the tip of the insulator b protrudes from the end face of the mounting fitting d to improve stain resistance.

By the way, as a prior art of the present invention, Japanese Patent Application Laid-open No. 52-
156242, but the one disclosed here is the 22nd
As shown in the figure, since the high voltage circuit of the ignition coil 3 is electrically connected to the vehicle body as is well known in the art, a short circuit in the spark gap is likely to occur, and for the reason stated in Figure 10. No improvement in stain resistance can be expected.

Also, as another example of prior art,
There are 37245. As shown in FIG. 23, this is a configuration in which the middle of the secondary winding 3b of the ignition coil 3 is electrically connected to the vehicle body. In this prior example, since the electrical circuit of the secondary winding 3b of the ignition coil 3 includes the vehicle body (ground),
If one side of the spark plug becomes contaminated with carbon or the like, the output end of the secondary winding 3b of the ignition coil 3 will have leakage resistance to the ground side, similar to that shown in FIG. 10 above. Therefore, a circuit including grounding is easily formed in the secondary winding 3b of the ignition coil 3 due to contamination with carbon or the like, so that the contamination resistance of the present invention as described above cannot be expected. Further, no noise reduction effect can be expected.

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made as follows: (1) Two independent plugs are provided in one combustion chamber of an internal combustion engine. Alternatively, two gaps may be formed.

(2) Of course, the distributor may be electrically connected in the middle of the high voltage circuit consisting of the secondary winding of the ignition coil and the two electrodes of the spark plug.

(3) The plug described in JP-A-52-156242 may be used.

(4) The present invention can also be applied to a diode distribution type ignition device (for example, Japanese Patent Application Laid-open No. 43327-1983) that does not have a distributor.

(5) The present invention can also be applied to an ignition system for an internal combustion engine having four cylinders. For example, in the 4-cylinder model, the special public
The ignition device disclosed in No.-8281 may be constructed as in the present invention.

(6) It goes without saying that the present invention is applicable not only to motorcycles but also to internal combustion engines for all purposes.

(7) The present invention is applicable not only to battery ignition type ignition devices but also to magneto type ignition devices.

In summary, according to the present invention, the following effects are achieved.

(1) The discharge voltage seen from the vehicle body at the spark gap is 1/2 compared to the conventional one, and therefore,
It becomes easy to increase the gap size and improve the ignition ability.

(2) Since the discharge voltage seen from the vehicle body is lower than before, the withstand voltage design of components in the ignition system becomes easier.

(3) Since the high-voltage circuit that includes the electrodes that form the spark gap and the secondary winding of the ignition coil is electrically insulated from the vehicle body, the high-frequency current flowing through the high-voltage circuit will not reach the vehicle body. There is no flow, and therefore the effect of reducing radio wave noise is large.

(4) With the configuration described in (3) above, even if contamination occurs with conductive substances such as carbon, short circuits in the spark gap are unlikely to be formed, and therefore contamination resistance is very good.

[Brief explanation of drawings]

1 and 2 are electrical wiring diagrams showing a conventional ignition device, FIG. 3 is a sectional view showing a spark plug used in the conventional device, and FIG. 4 is an electrical diagram showing an embodiment of the ignition device of the present invention. 5 is a cross-sectional view showing the spark plug used in the device of the present invention shown in FIG. 4, FIG. 6 is a partial sectional view showing the installation mode of the plug shown in FIG. FIG. 9 is a characteristic diagram to explain the operation of the present invention, and FIG. 10 and FIG. 11 are electrical diagrams to explain the operation of the present invention. The wiring diagram, FIGS. 12 and 13 are characteristic diagrams for explaining the operation of the present invention, and FIGS. 14 to 1.
Fig. 6 is an electrical wiring diagram showing another embodiment of the device of the present invention, Fig. 17 is a sectional view showing another example of a spark plug used in the device of the present invention, and Fig. 18 is a modification of Fig. 6. 19 is a rear view of FIG. 18 seen from the inside of the cylinder head, FIG. 20 is a sectional view showing still another example of the spark plug used in the device of the present invention, and FIG. 21 is a rear view of FIG. Bottom view, 2nd
2 and 23 are electrical wiring diagrams showing conventional examples. 3...Ignition coil, 3b...Secondary winding,
4... Spark plug, 5... Combustion chamber, f... Electrode, h
...Spark gap.

Claims (1)

[Scope of Claims] 1. At least two electrodes provided in a combustion chamber of an internal combustion engine, each electrically insulated from a vehicle body, and forming a spark gap for spark discharge; a primary winding and a secondary winding; an ignition coil that applies a high voltage to these two electrodes; the at least two electrodes and the secondary winding of the ignition coil; An ignition device for an internal combustion engine, comprising a high voltage circuit formed by electrically connecting at least two electrodes, the high voltage circuit being electrically insulated from the vehicle body. .