JPH0560047A - Ignition device for engine - Google Patents

Abstract

PURPOSE:To reduce an unburnt gas quantity around a combustion chamber, reduce a flame transmission distance, prevent nocking effectively, restrict an increase of an initial combustion speed, and prevent an increase of combustion noise by setting an ignition timing. CONSTITUTION:A plural first ignition gaps 12a-14a are disposed at an interval in the circumferential direction of a combustion chamber at an outer circumferential edge part of the combustion chamber 2. A second ignition gap 11a is disposed at a center of the combustion chamber 2. For igniting by all the ignition gaps 11a-14a, that is, when an engine is under a high load, for example, an ignition timing for the second ignition gap 11a is delayed to ignition timings for the first ignition gaps 12a-14a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ignition device for an engine of a multipoint ignition type.

[0002]

2. Description of the Related Art Among engine ignition systems, there is a multi-point ignition system in which a plurality of ignition gaps are provided for one combustion chamber. In Japanese Unexamined Patent Publication (Kokai) No. 57-148021, an annular holding plate is interposed between a cylinder head and a cylinder block, and a large number of spark plugs are held by the holding plate, and a cylinder is provided at an outer peripheral edge of a combustion chamber. It is disclosed that a plurality of ignition gaps are arranged at intervals in the circumferential direction. As a result, rapid combustion is performed by simultaneous ignition with a large number of ignition gaps, and an ideal equivolume combustion is obtained in the Otto-type engine.

[0003]

[Problems to be Solved by the Invention]

By the way, recently, a plurality of peripheral ignition gaps, that is, first ignition gaps are arranged at the outer peripheral edge of the combustion chamber and at intervals in the circumferential direction of the combustion chamber, and a central ignition gap, that is, a second ignition gap is provided in the center of the combustion chamber. It is considered to arrange the ignition gap. For example, switching between a first ignition mode in which ignition is performed only by the first ignition gap and a second ignition mode in which ignition is performed by both the first and second ignition gaps is performed according to the operating state of the engine. Therefore, the optimum ignition is performed according to the operating state of the engine.

More specifically, by setting the first ignition mode when the engine load is low, sufficient combustion is performed in the vicinity of the combustion chamber and the increase of HC that tends to occur in the periphery of the combustion chamber is suppressed. By colliding the flame surfaces with each other at an early stage, the spread of the flame surfaces is suppressed, the peak of combustion is suppressed, that is, the combustion ratio is made as uniform as possible, and the increase of NOx is suppressed. When the engine is under heavy load, the first
Ignition by both the second and the second ignition gap,
Prevent knocking.

As described above, in the second ignition mode in which ignition is performed by both the first and second ignition gaps,
It would be advantageous if the prevention of knocking could be further prevented. Especially when considering the second ignition mode at high load, considering that knocking is likely to occur at high load,
Such a request becomes strong.

Accordingly, an object of the present invention is to provide a first outer peripheral edge portion of a combustion chamber, which is arranged at intervals in the circumferential direction of the combustion chamber.
Provided is an engine ignition device capable of further effectively preventing knocking when ignition is performed by both the ignition gap and a second ignition gap arranged in the center of a combustion chamber. Especially.

[0008]

To achieve the above object, the present invention has the following configuration. That is, a plurality of first ignition gaps arranged at the outer peripheral edge of the combustion chamber and at intervals in the circumferential direction of the combustion chamber, and a second ignition gap located in the center of the combustion chamber are provided, and When the ignition is performed by both the first ignition gap and the second ignition gap, the ignition timing of the second ignition gap is set to be later than the ignition timing of the first ignition gap. There is.

[0009]

According to the present invention having the above-described structure, basically, the flame spread distance is shortened as a whole, and knocking is prevented. Since the first ignition gap located in the periphery of the combustion chamber is ignited earlier than the second ignition gap in the center of the combustion chamber, the amount of end-burning gas, that is, the amount of end gas in the periphery of the combustion chamber is reduced, and knocking is more effective. Are prevented. Further, since the increase in the initial combustion speed is suppressed, it is preferable in preventing combustion noise. Preferred embodiments of the invention and their advantages will be apparent from the description of the examples below.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a cylinder head, 2 is a combustion chamber, and the cylinder head 1 has two intake ports 3A and 3B and two exhaust ports 4A which open into the combustion chamber 2, respectively. 4B are formed. Intake / exhaust ports 3, 3
As is known, B, 4A, and 4B are opened / closed at known timing by intake / exhaust valves (not shown) in synchronization with the rotation of the crankshaft.

The two intake ports 3A, 3B are connected to the combustion chamber 2
Are opened in the combustion chamber 2 on one side surface side of the cylinder head 1 with respect to the straight line L1 passing through the center of the cylinder and parallel to each other in the crank axis direction. Also, 2
The two exhaust ports 4A, 4B open into the combustion chamber 2 on the other side surface side of the cylinder head 1 with respect to the straight line L1,
They are formed in parallel with each other in the crankshaft direction. The intake ports 3A, 3B open on one side of the cylinder head,
The exhaust ports 4A, 4B are opened to the other side surface side of the cylinder head 1, and the cylinder head 1 is of a so-called cross flow type.

The two intake ports 3A, 3B have their downstream end portions, that is, the portions near the combustion chamber 2 as branch portions 3a, 3b defined by a partition wall 5, and their upstream portions gather together. It is a collecting unit 3c. Intake port 3A
From the upstream side to the downstream side, that is, the collecting portion 3c
From the to the branch portion 3a, it is formed in a substantially straight shape so as to be substantially orthogonal to the crankshaft.

The intake port 3B is curved from its branch portion 3b toward the collecting portion 3c. Explaining this curve, consider a straight line L2 that passes through the center of the combustion chamber 2 and is orthogonal to the crankshaft (orthogonal to the straight line L1). At this time, the upstream end of the partition wall 5 is on the straight line L2, and therefore the branch portion 3b is curved so as to be offset toward the intake port 3A side.

A swirl valve 6 is arranged in the collecting portion 3c. The swirl valve 6 is swingable around a rotary shaft 7 provided at the upstream end thereof. The state shown by the solid line in FIG. 1 is the fully closed state, and the state shown by the one-dot chain line is the fully opened state. is there. The rotating shaft 7 is located near the side wall of the collecting portion 3c on the side opposite to the intake port 3B.
The downstream end (free end) of the valve 6 is located at a small distance from the upstream end of the partition wall 5. Further, when the swirl valve 6 is fully opened, the swirl valve 6 is in a state of being substantially orthogonal to the crankshaft, that is, in a state of extending substantially parallel to the intake port 3A having a substantially straight shape. In the embodiment, the swirl valve 6 is fully closed when the load is low, the opening increases as the load increases when the load is medium, and is fully opened when the load is high.

A bulging portion 8 bulging upward is formed on the upper wall of the collecting portion 3c, and a fuel injection valve (not shown) is attached to the bulging portion 8. The downstream portion of the bulging portion 8 is branched into a branch portion 8a extending toward the intake port 3A side and a branch portion 8b extending toward the intake port 3B side. The fuel injection valve is of the two-hole type that directs the injected fuel in the two directions of the branch portions 8a and 8b, but is approximately the same as the branch spread of the branch portions 8a and 8b. It is also possible to use one injection hole type having a spray width of.

When the swirl valve 6 is fully closed, most of the intake air is supplied only from the intake port 3B, so that the intake air swirl in the clockwise direction in FIG. The swirl becomes weaker as the swirl valve 6 opens. Even when the swirl valve 6 is fully closed, a small amount of intake air flows into the intake port 3A, which prevents a large amount of fuel from adhering to the inner wall of the intake port (branch portion 3a). Even when the swirl valve 6 is fully open, the swirl is formed by the bending of the intake port 3B. At this time, the swirl valve 6
Becomes substantially parallel to the intake port 3A, which is preferable in minimizing the intake resistance of the swirl valve 6 and ensuring a fully open output.

There are a total of four ignition gaps 1 in the combustion chamber 2.
1a, 12a, 13a, 14a are located. Of the four ignition gaps, the ignition gap 11a is located at the center of the combustion chamber 2 and has the center ignition gap, that is, the second ignition gap.
Configure the ignition gap. The other three ignition gaps 12a to 14a are arranged at the outer peripheral edge of the combustion chamber 2 and at intervals in the circumferential direction of the combustion chamber 2 to form a peripheral ignition gap, that is, a first ignition gap.

The ignition gap 12a is located between the two intake ports 3A and 3B, more specifically, below the upstream end of the partition wall 5. The ignition gap 13a is located between the intake port 3A and the exhaust port 4A.
The ignition gap 14a is formed by the intake port 3B and the exhaust port 4
It is located between B. However, the ignition gap 13
a and 14a are located closer to the exhaust ports 4A and 4B than the straight line L1 in the direction of the straight line L2. In the embodiment, the ignition gap 13a is located slightly closer to the straight line L1 than the ignition gap 14a is.

Such first ignition gaps 12a-14
The arrangement of a satisfies the condition that, when ignition is performed only by the first ignition gap, the flames generated from the ignition gaps 12a to 14a first meet at the periphery of the combustion chamber and then at the center of the combustion chamber. Or so that the condition is as close as possible to such a condition.

Spark plug 1 having a spark gap 12a
The mounting hole 22 for 2 is inclined below the intake ports 3A, 3B with respect to the straight line L2, and is formed on one side surface of the cylinder head 1 (side surface on the side where the intake ports 3A3B are open). Has been formed. More specifically, the mounting hole 22
The opening of the cylinder head 1 to the outside of the cylinder head 1 is arranged closer to the intake port 3B than the straight line L2. As a result, the ignition plug 12 is attached to the cylinder head 1 from the offset direction of the intake port 3B, and the intake port 3B is attached.
It is attached to the cylinder head 1 while avoiding interference with the inlets 3A and 3B and the intake pipes connected to the inlets 3A and 3B. By setting the mounting mode of the spark plug 12 as described above, it is not necessary to form a mounting hole for mounting the spark plug 12 in the partition wall 5, and the partition wall 5 can be thinned to reduce intake resistance. Is preferred.

Although each spark plug having the ignition gaps 11a, 13a and 14a is not shown in the drawing, its mounting hole formed in the cylinder head 1 will be described with reference to FIGS. It is attached to the cylinder head 1 by extending it in the direction in which the mounting holes extend). First, a central spark plug mounting hole 21 having an ignition gap 11a located at the center of the combustion chamber 2 extends in the cylinder axial direction and is opened above the cylinder head 1. As shown in FIG. 4, the upper portion 21a of the mounting hole 21 is formed to be elongated so as to be inclined with respect to the straight line L1, and its cross-sectional area is sufficiently larger than the maximum cross-sectional area of the spark plug (however, The opening width is slightly larger than the maximum diameter of the spark plug).

The spark plug mounting hole 23 having the ignition gap 13a also extends upward from the cylinder head 1, but is opened in the upper portion 21a at one end of the elongated upper portion 21a. There is. Similarly, the mounting hole 24 for the ignition plug having the ignition gap 14a also extends upward from the cylinder head 1.
The other end of the elongated upper portion 21a is opened in the upper portion 21a. In this way, the mounting holes 23 and 24 are formed so as to be inclined toward the mounting hole 21. Of the mounting holes 21, 23, 24, a screw portion for screwing each spark plug is formed only in a portion lower than the upper portion 21a, and no screw portion is formed in the upper portion 21a.

The attachment hole 23 for the ignition plug having the ignition gap 13a is inclined in a plane parallel to the crankshaft and extending in the cylinder axis direction. This inclination direction is shown in FIG.
It is shown by an arrow L3 in FIG. Further, the attachment hole 24 for the ignition plug having the ignition gap 14a is located in the plane inclined with respect to the straight line L1 indicating the crankshaft direction, and the intake port 3A, as it goes to the high-voltage terminal side (above the cylinder head 1). 3B, and the direction of this inclination is indicated by arrow L4 in FIGS. 1 and 2.

When mounting the central spark plug having the spark gap 11a, the spark plug is inserted through the mounting holes 23 and 24 in the axial direction of the cylinder. A peripheral spark plug having a spark gap 13a (second spark plug)
The spark plug) and the peripheral spark plug having the spark gap 14A are mounted through the mounting holes 21 while inserting the spark plug while being inclined with respect to the cylinder axis.

Here, the ignition gaps 12a to 14a located at the outer peripheral edge of the combustion chamber 2 are respectively substantially hemispherical plug holes 12b to 14 formed in the cylinder head 1.
located within b. When processing the plug hole, it is preferable that the processing tool is approached from the lower surface side of the cylinder head 1 and from the center of the combustion chamber, as shown by the arrow in FIG. This prevents the lower surface of the cylinder head 1 from being unnecessarily deleted by the working tool, and ensures a sufficient seal surface width S (see FIG. 2) between the cylinder head 1 and the cylinder block. It will be preferable from the above.

Further, by tilting the mounting holes 23 and 24 toward the mounting hole 21 side, the mounting holes 2 between the adjacent cylinders are
It is also preferable for increasing the interval between 3 and 24 to sufficiently secure the cross-sectional area of the cooling water passage 41 (see FIG. 3) between them.

Which of the above ignition gaps 11a to 14a is used for ignition is changed according to the operating state of the engine. FIG. 5 shows a first ignition mode in which only the surrounding first ignition gaps 12a to 14a are ignited with the engine load as a parameter, and a second ignition mode in which all the ignition gaps 11a to 14a are ignited. It is designed to switch between and.

In FIG. 5, the region where ignition is impossible is shown at the ignition timing retarded from the region shown by the chain double-dashed line. Therefore, in the example of FIG. 5, when the engine load (for example, the intake air amount) is a medium load between the predetermined values F1 and F2, the first ignition mode is performed in which only the surrounding first ignition gaps 12a to 14a are ignited. In the second ignition mode, the ignition is performed by all the ignition gaps 11a to 14a when the engine load is a low load of F1 or less and a high load of F2 or more.

In the second ignition mode, basically, the ignition timing of the second ignition gap 11a is the same as that of the first ignition gap 12
The ignition timings a to 14a are retarded. However, at the time of extremely low load, the ignition timings of all the ignition gaps are the same, but this is done especially from the viewpoint of ensuring ignitability.

Of the first ignition gaps 12a-14a,
The ignition gap 12a is excluded except under extremely low load and high load.
Ignition timing is retarded with respect to the ignition timings of the ignition gaps 13a and 14a. This is the ignition gap 1 in the embodiment.
As the air-fuel mixture near 2a becomes rich, etc., 1
It is set in consideration of the fact that the flame growth from 1a is faster than the flame growth from the ignition gaps 13a and 14a.

In the example of FIG. 5, since ignition is performed only by the surrounding ignition gaps 12a to 14a at the time of medium load, sufficient combustion is performed around the combustion chamber 2 and HC is reduced. Further, the flames generated from the ignition gaps 12a to 14a are matched with each other in the circumferential direction of the combustion chamber 2 and then with each other at the center of the combustion chamber 2. As a result, the growth rate of the flame surface is suppressed, that is, the peak value of the combustion speed is suppressed, the combustion ratio is made as uniform as possible over the entire combustion period, and NOx is reduced.

At high load, all ignition gaps 11a
Ignition by 14a is performed, the flame spread distance to each part of the combustion chamber 2 is shortened, and knocking is prevented. Since the ignition timing of the ignition gap 11a located at the center is delayed from the ignition timings of the surrounding ignition gaps 12a to 14a, the unburned gas in the peripheral portion of the combustion chamber 2 in the advanced combustion state. The amount is reduced and knocking is prevented more effectively.

FIG. 6 shows the spread of the flame surface in the case of the comparative example in which the ignition timings of all the ignition gaps 11a to 14a are set to be the same under high load, and FIG. 7 shows the central ignition. The case where the ignition timing of the gap 11a is retarded relative to the ignition timing of the surrounding ignition gaps 12a to 14a is shown (setting of the ignition timing according to FIG. 5). 6 and 7, the hatched portion is the end-burning gas region, the white portion indicates the burned region, and the boundary between the hatched portion and the white portion indicates the flame surface. As is clear from comparison between FIG. 6 and FIG. 7, the amount of unburned gas in the vicinity of the combustion chamber is reduced in FIG. 7 corresponding to the present invention as compared with FIG. 6 showing a comparative example. Be understood.

Even when the engine load is low, the ignition timing of the central ignition gap 11a is delayed from the ignition timing of the peripheral ignition gaps 12a to 14a except when the engine load is extremely low. This is to balance both securement of reliable ignition and reduction of the amount of unburned fuel gas around the combustion chamber.

FIG. 4 shows each ignition gap 11a-14a.
Ignition system for is shown. In FIG. 4, U
Is a control unit constituted by using a microcomputer, 51 to 53 are igniters (only switching transistors are shown for simplification), and 54 to 56 are ignition coils. The ignition coil 54 has a central ignition gap 11a.
The ignition coil 55 is for the ignition gap 12a and the ignition coil 56 is for the two ignition gaps 13a and 14a.

Since each of the ignition coils 54 and 55 has a single ignition gap (ignition plug),
As usual, the positive side of the secondary winding is connected to the high voltage terminal of the spark plug. On the other hand, two ignition gaps 1
In the ignition coil 56 for 3a and 14a, the positive side of the secondary winding is connected to the high voltage terminal of one ignition gap 14a, and the negative side of the secondary winding is connected to the high voltage terminal of the other ignition gap 13a. To be done. By doing this,
The number of ignition coils and igniters is reduced.

The control unit U includes igniters 51-53.
On the other hand, a predetermined ignition timing signal is sent according to the operating state of the engine, etc. Therefore, the signal from the sensor group 57 is input. The sensor group 57 includes an engine speed sensor, an intake air amount sensor (engine load sensor), an engine cooling water temperature sensor, an engine intake air temperature sensor, and the like. Of course, the control unit U performs control such that the ignition timing is set as shown in FIG.

FIG. 8 shows an arrangement example of the high tension code when the present invention is applied to a 4-cylinder in-line engine. In FIG. 8, 61 and 62 are distribution views.
And 63 and 64 are ignition coils. The high tension code is 71 for the ignition gap 11a, 72 for the ignition gap 12a, and 73 for the ignition gap 13a.
The ignition gap 14a is shown at 74. The distributor 61 is for the ignition gap 12a of each cylinder. The distributor 62 is for the center ignition gap 11a of each cylinder. The ignition coil 63 is for the ignition gaps 13a and 14a in the two cylinders on the front side of the engine. The ignition coil 64 is for the ignition gaps 13a and 14a in the two cylinders on the rear side of the engine.

As described above, in the example of FIG. 8, the high tension codes having the same ignition timing are wired together, and the high tension codes having different ignition timings are wired together.
The two comrades are separated from each other (they are separated from each other in the direction perpendicular to the paper surface). The high tension codes for the ignition gaps 13a and 14a are divided into those for the front cylinder and those for the rear cylinder.

FIG. 9 shows another embodiment of the present invention.
The same components as those in the above embodiment are designated by the same reference numerals, and the description thereof will be omitted. FIG. 9 shows a case where two peripheral ignition gaps, 15a and 16a, are provided so as to be located on a straight line passing through the center of the combustion chamber. The directions in which the spark plugs of a total of three ignition gaps including the central ignition gap 11a extend are shown in simplified form by arrows in FIG. FIG. 11 shows an example of setting the ignition timing in this example. That is, with the engine load F3 as a boundary, the first ignition mode in which the ignition is performed only by the peripheral ignition gaps 15a, 16a when the load is low, and the second ignition mode that the ignition is performed by all the ignition gaps 11a, 15a, 16a in the high load is performed. It is said that.

FIG. 12 shows an arrangement example of the high tension code in the case shown in FIG. 9, and corresponds to FIG.
In FIG. 12, 66 is a distributor, 67,
68 is an ignition coil. Further, the high tension code for the ignition gap 11a is indicated by 71, and the ignition gap 1
The high tension code for 5a is shown at 75 and the high tension code for the ignition gap 16a is shown at 76. In FIG. 12, the high tension code is arranged from the same viewpoint as in FIG.

FIG. 13 shows an example of connection of the ignition coil 67 (same for 68) to the ignition gaps 15a and 16a. That is, the ignition coil 67 has two ignition coils 67a and 67b, and one ignition coil 67a is, for example, the ignition gaps 15a and 16a of the third cylinder.
And the other ignition coil 67b is used, for example, for the ignition gaps 15a and 16a of the fourth cylinder (the same connection method as the ignition coil 56 of FIG. 4).

FIG. 14 shows a modification of the structure shown in FIG. 12, in which wiring is performed using the distributors 66, 69 or 70 for all ignition gaps. Each ignition gap 11a, 15a, 16a
The same code as in the case shown in FIG. 12 is attached to the high tension code for, and the duplicated description is omitted.

15 and 16 show an example of the distributor 69 (70) shown in FIG. In FIGS. 15 and 16, an insulating plate 82 is integrated with a shaft 81 that is rotated in synchronization with the crankshaft, and the insulating plate 82 is
Two sets of power supply terminals 8 at 180-degree target positions around the shaft 81
3, 84 are configured. One of the power supply terminals 83 and 84 is always conducted to the positive side of the secondary winding of the ignition coil 85,
The other of the power supply terminals is always connected to the negative side of the secondary winding.

A total of four power receiving terminals 86 to 89 are arranged around the insulating plate 82. Power is supplied to the power receiving terminals 86 to 89 aligned with the power feeding terminal 83 or 84, and the ignition gap corresponding to the power receiving terminal thus fed is ignited. Depending on the setting of the positions of the power receiving terminals 86 to 89, ignition is performed simultaneously in the peripheral ignition gaps 15a and 16a of one cylinder, more specifically, the second cylinder in FIG. The two peripheral ignition gaps 15a, 16a are also ignited at the same time.

17 and 18 show a seal with the outside of the spark plug (for the ignition gaps 11a, 13a and 14a in the case of FIG. 1, and for the ignition gaps 11a, 15a and 16a in the case of FIG. 9). It shows a structure. In FIG. 17, reference numerals 91 to 93 are connection caps detachably connected to the high-voltage terminal of the ignition plug, and 94 is a head cover.
It is a lid member (sealing member) that closes the upper opening 95a of 95. The main bodies of the connection caps 91 to 93 are made of synthetic resin, and the lid member 94 is made of an elastic body such as rubber.

On the lower surface of the lid member 94, there are three protrusions 94.
a to 94c are formed to project, and the projections 94a to 94c are formed.
Connection caps 91 to 93 are formed integrally with the portions. By utilizing the elastic deformation of the protrusions 94a to 94c, the connection caps 91 to 93 can be inclined in different directions according to the inclination direction of the corresponding spark plug. Of course, the high tension cords 91a to 93a extending from the connection caps 91 to 93 are the lid members 9
18 and extends to the outside as shown in FIG.

FIGS. 19 and 20 show a modification of the portion corresponding to FIGS. 17 and 18. In this embodiment, the connection caps 91 to 93 and the lid member 96 are formed separately from each other, a slit 96a is formed in the center of the lid member 96 made of an elastic material such as rubber, and each slit 96a is passed through the slit 96a. High tension codes 91a to 93a extending from the connection caps 91 to 93 are extended to the outside of the lid member 96.

FIG. 21 shows a seal for the spark plug,
Spark plug mounting holes 101 to 103 of the cylinder head 1
This is done on the upper surface (corresponding to 21, 23, and 24 in FIG. 3). That is, the cylinder head 1 is provided with a locking surface 1b on which the large diameter portion of the spark plug is seated at a position higher than the middle deck surface 1a, and the locking surface 1b portion is used for mounting the spark plug. It is designed to be sealed by a washer. As a result, the locking surface 1
Water adhering to b is the middle deck surface 1a in the low position.
The water on the middle deck surface 1a flows down to the drain hole 1
It is discharged from c to the outside.

Although the embodiment has been described above, the number of peripheral ignition gaps may be four or more. Also, always
Ignition may be performed by the peripheral first ignition gap and the central second ignition gap.

[Brief description of drawings]

FIG. 1 is a plan view showing an arrangement relationship of an ignition gap with respect to a combustion chamber.

FIG. 2 is a view of the cylinder head as seen from its lower surface.

FIG. 3 is a cross-sectional view of FIG. 2 showing a positional relationship of mounting holes for a spark plug.

FIG. 4 is a diagram showing an example of an ignition system.

FIG. 5 is a diagram showing an example of setting ignition timing.

FIG. 6 is a diagram showing a state of combustion when the ignition timings of all the ignition gaps are the same.

FIG. 7 is a diagram showing a state of combustion when the ignition timing of the central second ignition gap is retarded from the ignition timing of the peripheral first ignition gap.

FIG. 8 is a view showing an arrangement example of a high tension code when the ignition gap is arranged as shown in FIG.

FIG. 9 is a diagram showing another arrangement example of the peripheral ignition gap.

10 is a view showing the mounting direction of the spark plug when the ignition gap is arranged as shown in FIG.
Sectional drawing corresponding to 10-X10 line.

11 is a diagram showing an example of setting an ignition timing when the ignition gap is arranged as in FIG.

FIG. 12 is a view showing an arrangement example of a high tension code when the ignition gap is arranged as shown in FIG.

FIG. 13 is a diagram showing details of an ignition coil portion in the case shown in FIG. 12;

FIG. 14 is a view showing another arrangement example of the high tension code when the ignition gap is arranged as shown in FIG.

FIG. 15 is a plan view showing details of the distributor shown in FIG.

16 is a sectional view corresponding to line X16-X16 of FIG.

FIG. 17 is a view showing an example of a seal portion for a spark plug.

18 is a top view of FIG.

FIG. 19 is a view showing another example of the seal portion for the spark plug.

FIG. 20 is a top view of FIG. 19.

FIG. 21 is a diagram showing a preferred example of a structure for discharging water from the vicinity of a spark plug mounting hole.

[Explanation of symbols]

 1 Cylinder Head 2 Combustion Chamber 3A Intake Port 3B Intake Port 4A Exhaust Port 4B Exhaust Port 11a Ignition Gap (Second Ignition Gap) 12a Ignition Gap (First Ignition Gap) 13a Ignition Gap (First) Ignition gap) 14a Ignition gap (first ignition gap) 15a Ignition gap (first ignition gap) 16a Ignition gap (first ignition gap)

Claims (5)

[Claims] 1. A plurality of first ignition gaps, each of which is arranged at an outer peripheral edge portion of the combustion chamber and spaced apart in the circumferential direction of the combustion chamber, and a second ignition gap located at a central portion of the combustion chamber. The ignition timing of the second ignition gap is set to be later than the ignition timing of the first ignition gap when ignition is performed by both the first ignition gap and the second ignition gap. An engine ignition device characterized by the above. 2. The first ignition mode according to claim 1, wherein ignition is performed only by the first ignition gap, and ignition by both the first ignition gap and the second ignition gap, according to an operating state of an engine. It is set so that switching to the second ignition mode in which ignition is performed by the gap is performed, and the ignition timing of the second ignition gap is delayed in the second ignition mode. 3. The engine according to claim 2, wherein the first ignition mode is set when the engine load is low, and the second ignition mode is set when the engine load is high. 4. The engine according to claim 2, wherein the first ignition mode is performed when the engine has a medium load, and the second ignition mode is used when the engine has a low load and a high load. 5. The ignition timing retardation of the second ignition gap by the retardation means is prohibited when the engine has an extremely low load, and the ignition timing of the first ignition gap and the ignition of the second ignition gap are controlled. Those set at the same time as the time.