JPH0138189B2 - - 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.
a and 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. 3, and the terminal part a and the center electrode f are fixed with a conductive glass seal g and are in an electrically conductive state, and at the same time are attached with an insulator b. It is electrically insulated from the metal fitting d. This mounting bracket d has a mounting screw for mounting on the internal combustion engine, and is tightly attached to the sill 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 above-mentioned shilling 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.

By the way, as a recent background, there has been a call for improvements in the performance of spark plugs themselves, such as improving ignition ability and reducing radio noise, while ensuring stain resistance.However, changes in the structure of the spark plug itself There is a limit to fully satisfying these points.

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, improved the various performances mentioned above by improving the conventional devices shown in FIGS. 1 and 2 and improving the spark plug itself. They found that significant improvements could be made.

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 notions of conventional devices, and its unique feature is that the spark plug mounting bracket is installed in an electrically insulated manner on the internal combustion engine, and the spark plug itself is electrically connected to the vehicle body. Insulated with an insulator, each of the spark gap forming electrodes of the spark plug is electrically connected to both ends of the secondary winding of the ignition coil,
In addition, the high voltage circuit including at least the secondary winding and the spark plug is electrically insulated from the vehicle body.

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, the secondary winding 3b of the ignition coil 3
Electrodes e and f of the spark plug 4 are electrically connected to both ends of the spark plug 4, respectively. The two electrodes e and f of this plug 4 are exposed in the combustion chamber 5 of the internal combustion engine, and a spark gap for spark discharge is formed between the two electrodes.

The two electrodes e and 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). This will be discussed later. Note that the ground circuit of the internal combustion engine in FIG. 4 shows a general ground circuit, and does not indicate that the electrodes e and f are 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 FIG. In the same figure, the basic structure of the plug 4 is the same as the conventionally known structure shown in FIG. A cylindrical insulating bushing 8, which is an insulating material made of, for example, alumina porcelain.
are screwed together. Therefore, the plug 4 is threadedly attached to the cylinder head 6 of the internal combustion engine via the mounting threaded portion 8a of the insulating bushing 8. A metal gasket q is interposed between the insulating bush 8 and the mounting bracket d, and a metal gasket k is interposed between the insulating bush 8 and the cylinder head 6.

7 is a plug cap made of heat-resistant electrically insulating resin. A ring-shaped armature 9 made of a metal with good electrical conductivity is molded into the cap 7. The end of the armature 9 is electrically connected to a connecting terminal 11 in the center of the cap 7.

When the cap 7 is inserted into the insulator b of the plug 4, the terminal portion a of the plug 4 is fitted into the metal ring 13 of the cap 7. On the other hand, the end of the armature 9 is in close contact with the outer periphery of the fitting d of the plug 4. As described above, the plug 4 has the structure shown in FIG. 3, and the side electrode e is fixed to the mounting bracket d. It is electrically connected to the high voltage cord 12a via. On the other hand, since the center electrode f is electrically connected to the terminal part a, the high voltage cord 12
electrically connected to b.

In addition, as mentioned above, the mounting bracket d of the plug 4
is electrically insulated from the cylinder head 6 by the insulating bush 8, so the side electrode e of the plug 4 is electrically connected to the cylinder head 6 and, as a result, to the vehicle body via the mounting bracket d. It will never happen.

Note that the side electrodes e of the plug 4 may face the center electrode f, instead of facing the front end face thereof.

In the above configuration, the operation will be described next. When a positive voltage is applied to the center electrode f of the spark plug 4 and a negative voltage of opposite polarity is applied to the side electrode e, a discharge occurs in the spark gap h and the air-fuel mixture is ignited.
In the above embodiment, since the high voltage circuit consisting of the plug 4 and the secondary winding 3b is constructed above the vehicle body, the voltage at the time of discharge is determined as shown in FIGS.
Compared to the figure, the voltage is 1/2 when viewed from the vehicle body.

Next, 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. The sample was assembled as shown in FIG. 6 by combining the ignition system shown in FIG. 1 with the spark plug shown in FIG. 3. The conventionally known configuration and the fourth
The ignition system shown in the figure is combined with the spark plug shown in Figure 3, and the insulating bush 8 is installed as shown in Figure 5.
The performance of both was compared.

FIG. 7 shows the results of a contamination experiment in which the internal combustion engine was operated with the check valve fully closed (rotational speed 2000 rpm) and the time (minutes) until the internal combustion engine stopped. According to FIG. 7, it can be seen that the stain resistance of this example is comparable to or slightly better than that of the conventionally known one.

FIG. 8 shows the results of measuring radio noise using the same ignition device as in the anti-fouling experiment described above. From this result, in this example, the radio noise intensity is as shown in Figure 8E, whereas in the conventionally known one, it is as shown in Figure 8F, and this example has an excellent effect of reducing radio noise. It turns out that it has. This effect is approximately the same level as the radio noise suppression effect when a resistor is inserted into the glass seal part g (Fig. 3) of a conventional well-known spark plug, and a resistor is not necessary, and this implementation It is clear that if a resistor is combined with the example, a further 10 to 20 dB of radio noise suppression effect can be achieved. The reason why the device of the present invention is effective in suppressing radio noise is that the voltage during discharge of the spark plug can be reduced to 1/2 compared to the conventionally known device as mentioned above, and at the same time This is achieved by reducing the amount of change in discharge voltage due to fluctuations, etc. to 1/2 compared to the conventional method. Furthermore, as a result of applying a voltage of opposite polarity to the spark plug as described above, the effect that the direction of current is reversed between the two high voltage cords 12a and 12b is also obtained.

Since the high voltage circuit is electrically isolated from the vehicle body, the high frequency current in the high voltage circuit is directly connected to the vehicle body via the capacitance (stray distributed capacitance) component formed between the high voltage circuit and the vehicle body. As a result, there are no radio waves directly generated from the vehicle body, and radio waves are mainly generated only from the high frequency current in the high voltage circuit, and the vehicle body captures 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 radio wave interference to televisions and radios outside the vehicle, and This also reduces the possibility of causing radio wave interference to electronic devices installed inside the room.

FIGS. 9 and 10 show electrical wiring diagrams in other embodiments of the ignition device of the present invention. To explain each of these embodiments, Fig. 9 is applied to an internal combustion engine having two cylinders;
Two ignition coils 3, 3 are used, and the secondary windings 3b, 3b of both coils 3, 3 are electrically connected via two spark plugs 4, and a high voltage is applied simultaneously to each coil 3, 3. It is configured to generate.

In FIG. 10, 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. 9 and 10, two plugs 4, 4 simultaneously generate spark discharge, and one of them is used as a so-called waste fire.

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 11th
As shown in the figure, since the high voltage circuit of the ignition coil 3 is electrically connected to the vehicle body as in the past, a short circuit in the spark gap is likely to occur, and no improvement in stain resistance can be expected. Further, the noise reduction effect cannot be expected much.

Also, as another example of prior art,
There are 37245. As shown in FIG. 12, 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 3 includes the vehicle body (ground), a short circuit in the spark gap is likely to occur, and the contamination resistance is poor. Further, the noise reduction effect cannot be expected much.

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 of the aforementioned plugs may be installed in one combustion chamber of an internal combustion engine.

(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 spark plug.

(3) The present invention can also be applied to a diode distribution type ignition device (for example, Japanese Patent Laid-Open No. 50-43327) that does not have a distributor.

(4) 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.

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

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

(7) In Fig. 5, the threaded part p of the mounting bracket d of the plug 4 is replaced with the insulating bush 8, which is an insulator.
It may be electrically insulated from the cylinder head 6 by forming a polyimide-based heat-resistant electrically insulating coating on the threaded portion P and forming an alumina spray coating or a heat-resistant glass coating on the combustion chamber 5 side of the threaded portion P. .

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

(1) Existing spark plugs can be used, and therefore reliability is high and the structure is simple.

(2) The discharge pressure seen from the vehicle body at the spark gap is halved compared to the conventional one, which simplifies the withstand voltage design of components in the ignition system, making it possible to expand the dimensions of the spark gap and As a result, the ignition ability can be improved.

(3) Spark plug and ignition coil 2
Since the high voltage circuit including the secondary winding is electrically insulated from the vehicle body, the high frequency current flowing through the high voltage circuit does not flow to the vehicle body, and therefore the electrical noise reduction effect is large.

[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 partial cross-sectional view showing the spark plug used in the apparatus of the present invention shown in FIG. 4 and its installation mode; FIG. 6 is a partial sectional view showing the installation mode of the plug for explaining the operation of the present invention. A sectional view, FIGS. 7 and 8 are characteristic diagrams for explaining the operation of the present invention, FIGS. 9 and 10 are electrical wiring diagrams showing other embodiments of the device of the present invention, and FIG.
1 and 12 are electrical wiring diagrams showing a conventional example. 3...Ignition coil, 3b...Secondary winding,
4... Spark plug, 5... Combustion chamber, 8... Insulating bush, b... Insulator, d... Mounting bracket, e... Side electrode, f... Center electrode, h... Spark gap.

Claims (1)

[Scope of Claims] 1. Consisting of an insulator holding a center electrode, a mounting bracket fixed to the outer periphery of the insulator, and side electrodes provided on the bracket and forming a spark gap with the center electrode, The mounting bracket is provided between a spark plug attached to a combustion chamber of an internal combustion engine, and the mounting bracket of the spark plug and the internal combustion engine, and electrically insulates the mounting bracket and the internal combustion engine. and an insulating member that electrically insulates the spark plug from a vehicle body, the center electrode and the side electrodes of the spark plug being electrically connected to both ends of a secondary winding of an ignition coil, respectively. An ignition device for an internal combustion engine, comprising: a high voltage circuit connected to the secondary winding and having at least the secondary winding and the spark plug, the high voltage circuit being electrically insulated from the vehicle body.