JPS58214674A - Ignition device for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve firing capability and stain resistance of a plug and reduce its radio noise, by mounting a metal fitting of the spark plug to be electrically insulated to a combustion chamber of an internal-combustion engine. CONSTITUTION:A heat resistant and electrically insulated cylindrical bush 8 is screwed to a mounting threaded part (p) of a mounting metal fitting (d) of a plug 4, and electrodes (e), (f) are electrically insulated from a body of a vehicle. Further a heat resistant and electrically insulated plug cap 7 is mounted to an insulator (b) of the plug. When ignition is performed, plus voltage is applied to a center electrode of the spark plug 4 while minus voltage of reverse polarity is applied to the side electrode (e), in this way, as voltage at an electric discharge is decreased to a half level, required insulation breakdown voltage of parts can be reduced, while consumption of the plug due to overheat is decreased and a sufficient thermal value is ensured, accordingly firing capability can be improved and a raido noise can be reduced.

Description

[Detailed description of the invention] The present invention relates to an ignition device for an internal combustion engine.

(1) A conventionally known ignition system for an internal combustion engine is configured as shown in Fig. M1 or Fig. 2, and current supplied from the battery 1 flows through the primary winding 3a of the ignition coil 3 and the breaker 2 to the 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.
At the same time, it is electrically insulated from the mounting bracket d by the insulator. This mounting bracket d has a mounting screw for mounting on the internal combustion engine, and is tightly attached to the shilling 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. The center electrode f
A spark gear knob h for spark discharge is connected between the ground electrode e and the ground electrode e.
It consists of

The operation of the conventional device described above is such that the high voltage applied from the secondary winding 3b of the ignition coil 3 (2) is applied to the center electrode f via the terminal 111a of the spark plug 4, and the applied voltage is the discharge voltage of the spark gap h. When this happens, electrical discharge occurs in the spark gear h and the air-fuel mixture ignites.

By the way, as a recent background, regarding the spark plug itself,
There are calls for improved performance such as improved ignition ability and reduced radio noise, but there is a limit to fully satisfying these points by changing the structure of the spark plug itself. be.

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 has been discovered that by improving the conventional devices shown in FIGS. 1 and 2 and by improving the spark plug itself, it is possible to achieve significant improvements in the various performances described above.

That is, the present invention electrically connects one of the two electrodes of the spark plug to the vehicle body, and electrically connects the high voltage circuit having the spark plug and the secondary winding of the ignition coil to the vehicle body (3). ) 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. a high voltage circuit that is insulated from the spark plug, electrically connects each of the electrodes for forming the spark gear of the spark plug to both ends of the secondary winding of the ignition coil, and that includes at least the secondary winding and the spark plug. It has a structure that is electrically isolated from the vehicle body.

The present invention will be explained in detail below using specific examples. Fourth
In the figure, FIG. 4 shows an electric circuit of an ignition device that is applicable to a vehicle having a single-cylinder two-stroke gasoline internal combustion engine, that is, an autopi. In the same figure, power supply 1
The positive pole of the battery is electrically connected to the primary winding 3a of the ignition coil 3, and the primary winding 3a is electrically connected to the negative pole of the power source 1 via the breaker 2.

On the other hand, electrodes e and f of a spark plug 4 are electrically connected to both ends of the secondary S wire 3b (4) of the ignition coil 3, respectively. The two electrodes e and f of this plug 4 are exposed in the combustion chamber 5 of the internal combustion engine, and form a spark gear for spark discharge 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 (autopi 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 figure, the basic structure of the plug 4 is the same as the conventional well-known structure shown in FIG.
A cylindrical insulating bushing 8 made of heat-resistant electrical insulating material, for example alumina porcelain, is screwed onto the mounting thread p of the mounting bracket d (5). 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 bushing 8 and the mounting fitting d, and a metal gasket k is also interposed between the insulating bushing 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 this armature 9 is electrically connected to a connection terminal 11 in the center of the camp 7.

When the cap 7 is inserted into the insulator of the plug 4, the terminal portion a of the plug 4 is fitted into the metal ring 13 of the camp 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 mentioned above, the plug 4 has the structure shown in FIG. 3, and the side electrode e is fixed to the mounting bracket d.
, are electrically connected to the high voltage cord 12a via the connection terminal 11. On the other hand, the center electrode f is electrically (6
) are connected, so this terminal part a, metal ring I3,
It is electrically connected to the high voltage cord 12b via the connection terminal 10.

As mentioned above, since the mounting bracket d of the plug 4 is electrically insulated from the cylinder head 6 by the insulating bushing 8, the side electrode e of the plug 4 is connected to the cylinder head 6, via the mounting bracket d. As a result, it is not electrically connected to the vehicle body.

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 configuration described in item 1, 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 as shown in FIG. @ Compared to Figure 3, the voltage is 1/2 when viewed from the vehicle body.

(7) Next, the excellent effects of the present invention will be explained through experiments.

The experiment was conducted using a two-cycle, 50cc 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. By using the conventionally known configuration and the configuration of this embodiment in which the spark plug shown in FIG. 3 is combined with the ignition system shown in FIG. 4 and is attached via an insulating bushing 8 as shown in FIG. Performance was compared.

Figure 7 shows the choke valve of the internal combustion engine fully closed (rotational speed 2).
000 r, p, m) and shows the time (minutes) until the internal combustion engine stops. 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 in Section 1. From this result, in this example, the radio noise intensity is as shown in Fig. 8E, whereas
The conventional well-known spark plug is shown in Figure 8F, and it can be seen that the present implementation (f) has an excellent effect of reducing radio noise (8).This effect is similar to that of the conventionally well-known spark plug. Glass seal part g (Fig. 3)
The level of the radio noise suppression effect is approximately the same as that obtained when a resistor is inserted in the circuit, and a resistor is not necessary.Additionally, if a resistor is combined with this example, an additional 10 to 20 dB of radio noise suppression effect can be achieved. It is clear that this 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, it is effective in suppressing radio noise. The amount of change in discharge pressure due to combustion fluctuations, etc. is 1
This was obtained by lowering the value to 72. Furthermore, as a result of applying a voltage of opposite polarity to the spark plug as described above, the current direction is changed to two high voltage cords 12a, 12.
It is thought that the effect of moving in the opposite direction in b was also obtained.

Since the high-voltage circuit is electrically insulated from the vehicle body, high-frequency current in the high-voltage circuit is transmitted to the vehicle body through the capacitance (stray distributed capacitance) component formed between the high-voltage circuit and the vehicle body (9). 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 the vehicle body. It is possible to convert the energy of each partial radio wave 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 TVs and radios outside the vehicle, and This also reduces the possibility of causing radio wave interference to electronic devices installed inside the room.

9 and 10 do not show electrical wiring diagrams in other embodiments of the ignition device of the present invention. To explain each of these embodiments, FIG. 9 shows one applied to an internal combustion engine having two cylinders, which has two ignition coils 3
．． 3, the secondary windings 3b, 3b of both coils 3.3 are electrically connected via two spark plugs 4, and a high voltage is generated simultaneously in each coil 3.3. be.

(10) In FIG. 10, the plugs 4 of each cylinder are connected in series to the secondary winding 3b of one ignition coil 3.

The embodiment of FIGS. 9 and 1O includes two plugs 4.
At the same time, spark discharges are generated at the four points, and one side 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. 52-156
242, but the one disclosed here is as shown in Fig. 11, and the high voltage circuit of the ignition coil 3 is electrically connected to the vehicle body as in the past, so there is no possibility of a short circuit in the spark gear. It is easy to form a circuit, 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, Japanese Patent Application Laid-Open No. 53-37245
There is. As shown in FIG. 12, this is a configuration in which the intermediate portion of the secondary winding 3b of the ignition coil 3 is electrically connected to the vehicle body. In this precedent example, ignition 3
Since the electrical circuit of the secondary winding 3b includes the vehicle body (contact), a short circuit of the spark gear is likely to occur, and stain 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 the 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 device for an internal combustion engine having four cylinders. For example, for a 4-cylinder model, the
The ignition device disclosed in the above No. 1 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 a single battery ignition type but also to a magneto type ignition device.

(7) In Fig. 5, instead of insulation pusher L8, a polyimide-based heat-resistant electrically insulating film is formed on the threaded part p of the mounting bracket d of the plug 4, and alumina is applied to the threaded part P on the side of the combustion chamber 5. It may be electrically insulated from the cylinder head 6 by forming a thermal spray coating or a heat-resistant glass coating.

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

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

(2) The discharge pressure at the spark gear as seen from the vehicle body is halved compared to the conventional one, which simplifies the voltage withstand design of the components in the ignition system, allowing the dimensions of the spark gear to be expanded. Therefore, the ignition ability can be improved.

(3) Since the high voltage circuit including the spark plug 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 (13) flows to the vehicle body. Therefore, the radio 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 wiring diagram, and FIG. 5 is a partial sectional view showing the spark plug used in the device of the present invention shown in FIG.
The figure is a partial sectional view showing how the plug is attached to explain the operation of the present invention, Figures 7 and 8 are characteristic diagrams that are used to explain the operation of the present invention, and Figures 9 and 10 are diagrams of the invention. Electrical wiring diagrams showing other embodiments of the device, FIGS. 11 and 1
FIG. 2 is an electrical wiring diagram showing a conventional example. 3...Ignition coil, 3b...2nd winding m
. 4...Spark plug, 5...Combustion chamber, 8...Insulating bushing, b...Insulator 5 d...Mounting bracket,
e... Side electrode, f... Center electrode, h... Spark gear knob. Representative patent attorney Takashi Okabe (14)

Claims (1)

[Claims] A spark gear 2-pull comprising 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 gear with the center electrode. The spark plug is electrically insulated from the vehicle body by installing the spark plug mounting bracket in the combustion chamber of the internal combustion engine in an electrically insulated manner from the internal combustion engine, and the center electrode of the spark plug is electrically insulated from the vehicle body. and a side electrode electrically connected to both ends of a secondary winding of an ignition coil, and a high voltage circuit having at least the secondary winding and the spark plug electrically insulated from the vehicle body. ignition device.