JPH08247016A - Ignition device for four-cycle engine - Google Patents

Abstract

PURPOSE: To suppress an increase in cooling loss and improve fuel consumption by accelerating the combustion speed of the air-fuel mixture in a combustion chamber, and preventing the combustion temperature in the combustion chamber from becoming too high. CONSTITUTION: The air-fuel mixture 99 flowing into a combustion chamber 56 in a cylinder 25 through an intake passage 58 formed in the cylinder 25 is made tumble currents A, B in the combustion chamber 56. Discharge sections of ignition plugs are provided in the combustion chamber 56. Multiple ignition plugs are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-stroke engine ignition device.

[0002]

2. Description of the Related Art Conventionally, there is a four-cycle engine constructed as follows.

That is, the air-fuel mixture, which flows through the intake passage formed in the cylinder into the combustion chamber in the cylinder, forms a tumble flow in the combustion chamber. The tumble flow is a so-called vertical swirl that swirls around an imaginary axis extending in the left-right direction when viewed along the flow of the air-fuel mixture flowing into the combustion chamber. A spark plug is attached to the cylinder, and a discharge portion of the spark plug faces the combustion chamber.

During operation of the above engine, during the intake stroke,
The air-fuel mixture is drawn into the combustion chamber through the intake passage.
This air-fuel mixture is made into the above-mentioned tumble flow in the combustion chamber by the suction stroke and the subsequent compression stroke, and the main flow portion, which is a high-velocity air-fuel mixture layer, of this tumble flow is almost in the bore in the cylinder. It is designed to be turned to the center. Then, in the explosion stroke, the air-fuel mixture is ignited by the ignition by the discharge of the discharge part, thereby being combusted and converted into power. The gas generated by this combustion is discharged from the combustion chamber to the outside of the cylinder in the exhaust stroke.

As described above, by making the air-fuel mixture into a tumble flow, the direction of the flow is determined, so that the ignition and the combustion are performed more reliably and stably, which results in a low load. The fuel efficiency has been improved. Further, this effect is remarkable especially when the air-fuel ratio (A / F) is large.

The above combustion will be described in more detail.

In the above compression stroke, when the piston rises and approaches the top dead center, the tumble flow, which has swirled in the vertical direction, is compressed in the vertical direction and gradually collapses, causing fine turbulence. When ignition is performed in this state, the front surface area when the flame spreads due to the combustion increases, and the maximum combustion temperature is suppressed from increasing.

On the other hand, when the main flow portion of the tumble flow remaining when the above turbulence occurs, the combustion speed of this portion is high, and the combustion temperature of this portion becomes high to some extent. However, as described above, the maximum combustion temperature is suppressed, so that the overall combustion temperature can be suppressed low.

Therefore, since the temperature difference between the combustion temperature and the wall temperature of the combustion chamber is kept small, the cooling loss due to the heat radiation to the wall of the combustion chamber is suppressed to be small and the fuel consumption is improved. It will be.

[0010]

By the way, when it is desired to increase the combustion speed during high-speed operation, for example, by using an intake control valve, the tumble flow is generated more vigorously and more clearly. It is possible to do so (hereinafter, this is referred to as “strengthening” the tumble flow).

However, in this way, the tumble flow is "strengthened".
Then, in the compression stroke, the main flow portion of the "strengthened" tumble flow remains strong even at the ignition timing when the piston rises and approaches the top dead center and the subsequent combustion period.

Therefore, even if the ignition timing is disturbed and the maximum temperature in the combustion of the ignition timing is suppressed as described above, regardless of this, the combustion of the main flow portion of the tumble flow is performed. The speed may be increased and the combustion temperature may be increased overall.

In this case, the temperature difference between the combustion temperature and the wall temperature of the combustion chamber becomes large, and the cooling loss due to heat radiation to the wall of the combustion chamber increases, which hinders improvement in fuel consumption. Will be done. That is, there is a limit to increase the burning speed.

Regarding the cooling loss, there is also a problem in the following cases.

That is, in the compression stroke, the piston is ignited when it rises, and the combustion temperature is extremely high due to the rise in pressure in the combustion chamber due to the combustion after this ignition and the rise in pressure due to the rise in the piston. Become.

Therefore, if the ignition is carried out early, the combustion temperature will be already high in the initial stage of the combustion,
Therefore, after the initial stage of combustion, the period of staying in the combustion chamber becomes longer, and the amount of heat released to the wall of the combustion chamber increases accordingly. Therefore, also in this case, there is a problem that the cooling loss increases and the improvement in fuel consumption is hindered.

[0017]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to the above circumstances, and makes the combustion speed of the air-fuel mixture in the combustion chamber high and prevents the combustion temperature in the combustion chamber from becoming too high. In this way, it is intended to suppress an increase in cooling loss and improve fuel economy.

[0018]

In order to achieve the above object, the ignition system for a four-cycle engine according to the present invention flows through an intake passage 58 formed in a cylinder 25 into a combustion chamber 56 in the cylinder 25. In the four-cycle engine in which the air-fuel mixture 99 has a tumble flow (A, B) in the combustion chamber 56 and the discharge portion 93 of the ignition plug 92 faces the combustion chamber 56, a plurality of the ignition plugs 92 are provided. It is a thing.

In the above case, the ignition timings of the respective spark plugs 92 may be set substantially at the same time.

Further, a phase difference may be provided in the ignition timing of each spark plug 92.

[0021]

[Operation] The operation of the above configuration is as follows.

In FIG. 1, when the engine 23 is operating, the air-fuel mixture 99 is sucked from the intake passage 58 into the combustion chamber 56 in the cylinder 25 in the intake stroke shown by the solid line and solid line arrow in the figure. The air-fuel mixture 99 is a tumble flow (indicated by symbols A and B) in the combustion chamber 56 by the suction stroke and the compression stroke shown by the two-dot chain line and the two-dot chain arrow in the figure that follow. ) Of the tumble flow, the main flow portion 99a forming the mixture layer having a high flow velocity is directed toward the bore center of the cylinder 25.

In the above case, when the tumble flows (A, B) are "strengthened" and ignited by the ignition of the spark plug 92,
As the tumble flow (A, B) is “strengthened”, its burning speed becomes faster, which makes it possible to cope with high-speed operation and the like.

However, in this case, the combustion temperature is increased as a whole, the cooling loss is increased, and there is a possibility that the improvement of fuel consumption is hindered.

Therefore, when the ignition timing is delayed, the piston 54 comes closer to the top dead center in the compression stroke, so that the tumble flow (B) is further compressed in the vertical direction and sufficiently collapses, resulting in fine turbulence. (C) will be sufficiently generated.

When ignition is performed in this state, the front surface area when the flame spreads due to the combustion increases, and the maximum combustion temperature is prevented from increasing.

On the other hand, when the main flow portion 99a of the tumble flow (B) remaining when the turbulence (C) occurs, the combustion speed of the main flow portion 99a is high, and the combustion temperature of this portion is It will be higher to some extent. However, as described above, the maximum combustion temperature is suppressed, so that the overall combustion temperature can be suppressed low.

Therefore, since the temperature difference between the combustion temperature and the wall temperature of the combustion chamber 56 is kept small, heat radiation to the wall of the combustion chamber 56 is suppressed.

By the way, as described above, if the turbulence (C) is sufficiently generated and ignited and burned,
Although the burning rate can be surely slowed down, the burning rate may be slow, so that the burning period may be too long. In this case, in the latter stage of combustion, the exhaust stroke is entered, and the latter stage of combustion is wasted, the thermal efficiency is reduced, and the effect of improving fuel efficiency is hindered.

Therefore, in the above structure, a plurality of spark plugs 92 are provided, and these spark plugs 92, 92 are provided.
By igniting, combustion is started at a plurality of points, which suppresses the combustion period from becoming too long.

That is, according to this configuration, the mixture 99 is made into a “strengthened” tumble flow (A, B), the ignition timing by the ignition plug 92 is delayed, and a plurality of this ignition plugs 92 are provided. , Causes the following effects. First, the combustion speed of the air-fuel mixture 99 is increased,
Therefore, it is possible to handle high-speed operation and the like. Second, the combustion chamber 56
It is assumed that the combustion temperature does not become too high and the amount of heat released to the wall to the combustion chamber 56 is suppressed to a small amount.
Thirdly, the combustion period is prevented from becoming too long, and thermal efficiency is prevented from lowering.

Moreover, as described above, since the ignition timing is delayed, the combustion heat of the air-fuel mixture 99 in the combustion chamber 56 is
After this initial stage of combustion, the period of staying in the combustion chamber 56 is shortened, and the amount of heat radiation to the wall to the combustion chamber 56 is suppressed to that extent.

In the above case, the ignition timings of the respective spark plugs 92 may be set almost at the same time.

In this way, the plurality of spark plugs 92
Even if the ignition timing is sufficiently retarded, the air-fuel mixture 99 is ignited at a plurality of locations by the plurality of ignition plugs 92, 92 at substantially the same time, so that the combustion speed is increased and the air-fuel mixture 99 is burned in a short combustion period. Can be made.

Therefore, according to the present invention, it is possible to delay the ignition timing sufficiently, that is, to wait until the turbulence (C) is sufficiently generated, and then to ignite, and to perform ignition at a plurality of locations substantially at the same time. The combustion period of the air-fuel mixture 99 is reliably prevented from becoming too long.

Further, instead of making the ignition timings of the respective ignition plugs 92 substantially the same, a phase difference may be provided in the ignition timings.

By doing so, the timing of generation of the maximum temperature in each combustion of the air-fuel mixture 99 based on the ignition of each ignition plug 92 is shifted according to the provision of the phase difference,
It is reliably suppressed that the combustion temperature becomes too high.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1)

1 to 5 show the first embodiment.

2 and 3, reference numeral 1 in the drawings denotes a motorcycle which is a straddle-type vehicle, and an arrow Fr indicates the front in the traveling direction. The right and left described below means the direction toward the front. Reference numeral 2 is a road surface on which the motorcycle 1 can travel.

The vehicle body 3 of the motorcycle 1 has a vehicle body frame 4 on the stationary side of the vehicle body. This body frame 4
Has a head pipe 5 at the front end thereof, and a pair of left and right main frames 6 extends rearward and downward from the head pipe 5, and seats extend rearward and downward from respective extending ends of the main frame 6. The pillar tube 7 extends. On the other hand, a pair of left and right down tubes 8 extend rearward and downward from the head pipe 5, and the extending ends of these down tubes 8 and the extending ends of the seat pillar tubes 7 are connected to each other.

A pair of left and right seat rails 10 extend rearward and upward from the rear end of the main frame 6, and the seat rail 10 is supported by the seat pillar tube 7 by a pair of left and right back stays 11, 11. . In this case, the seat pillar tube 7 also serves as a rear arm bracket.

A front fork 14 is rotatably supported on the head pipe 5. A front wheel 15 is supported on the lower end of the front fork 14, and the front wheel 1
A front fender 16 for covering the vehicle 5 from above is provided, and the front fender 16 is fixed to a middle portion of the front fork 14 in the vertical direction. On the other hand, a handle 17 is attached to the upper end of the front fork 14 of the above.

A pivot shaft 18 is attached to the seat pillar tube 7.
Thus, the rear arm 19 is pivotally supported so as to be vertically swingable. A rear wheel 20 is supported on the swinging end of the rear arm 19. Seat pillar tube 7 of the vehicle body frame 4
A shock absorber 21 is installed between the upper end and the rear arm 19.

In the space surrounded by the main frame 6, the seat pillar tube 7, and the down tube 8, that is, in the frame of the vehicle body frame 4, the engine 2 which is an internal combustion engine.
3 is provided. This engine 23 has 4
A parallel multi-cylinder four-cycle engine including two cylinders, comprising: a crankcase 24;
Has a cylinder 25 projecting forward and upward, and is detachably supported by the body frame 4 by a fastener. A power transmission device 26 is connected to the rear surface of the crankcase 24, and the rear wheel 20 is connected to the output side of the power transmission device 26.
Are connected by a chain transmission mechanism 22.

An intake pipe 27 is provided on the rear surface of each cylinder 25.
A throttle valve 30 and a carburetor 31 are connected to each of the intake pipes 27, and an air cleaner 32 commonly used is connected to the upstream side of the carburetor 31. The throttle valve 30 is a butterfly type and is opened and closed by a manual throttle operation. Further, the carburetor 31 is of an automatic variable venturi type having a piston valve 33 which automatically opens and closes by negative pressure of intake air of the engine 23.

The same as above, an exhaust pipe 35 is provided in front of each cylinder 25.
Of the exhaust pipe 35, the other end of each exhaust pipe 35 extends rearward through the vicinity of the lower side of the down tube 8, and a silencer 36 is connected to the rear end thereof. The silencer 36 is located laterally of the rear wheel 20. It is located in the vicinity.

A fuel tank 38 is supported on the main frame 6, and fuel is supplied from the fuel tank 38 to the carburetor 31. Concave knee grips 39 are formed on both sides of the rear portion of the fuel tank 38. On the other hand, a seat 40 is supported on the seat rail 10, and a footrest 41 is provided below the seat 40 on the lower side surface of the seat pillar tube 7. Then, the rider 42 seated on the seat 40 can put his / her feet on the footrest 41, and the hand is on the handle 17
Can hold the knee and the knee has the knee grip 39 described above.
It is possible to pinch from the left and right.

A front cowling 43 is provided to cover the front portion of the vehicle body 3 and the rider 42 from the front thereof, and the front cowling 43 is supported by the head pipe 5.

When the engine 23 is driven, its power is transmitted through the power transmission device 26 and the chain transmission mechanism 22,
When transmitted to the rear wheel 20, the motorcycle 1 is allowed to travel forward on the road surface 2.

1 to 5, each of the cylinders 2
5 is a cylinder body 48 having its longitudinal axis 47.
A cylinder hole 49 formed in the cylinder body 48 on the same axis 47, a cylinder head 50 attached to a projecting end of an upper portion of the cylinder body 48, and a cylinder head cover 5 covering an upper surface side of the cylinder head 50.
1 and the cylinder head 50 includes a cylinder body 4
It is fastened detachably to bolts 8 with bolts 52.

A piston 54 is vertically slidably fitted in the cylinder hole 49 along the shaft center 47,
The piston 54 is connected to a crankshaft supported by the crankcase 24 by a connecting rod 55. A portion of the space surrounded by the cylinder body 48, the cylinder head 50, and the piston 54 on the cylinder head 50 side is a combustion chamber 56.

At the rear portion of the cylinder head 50, a single intake passage 58 extending in the front-rear direction is formed. The upstream end of the intake passage 58 is sequentially connected to the throttle valve 30, the carburetor 31, and the air cleaner 32 through the intake passage 59 in the intake pipe 27. Further, the downstream end of the intake passage 58 connects the cylinder 25 to the axial center 4 thereof.
7 (in a plan view of FIG. 4), it opens toward the inside of the rear portion of the combustion chamber 56, and this opening portion serves as an intake opening portion 60. The intake opening portion 60 is the intake opening portion 60. It is located approximately in the center of the left-right direction. Further, in the side view of FIG. 1, the portion of the intake passage 58 near the intake opening 60 is
It is bent in an arc shape from the upstream side of the intake passage 58 toward the combustion chamber 56 with a small radius.

Intake valve 62 for opening and closing the intake opening 60
Is provided. The intake valve 62 includes a valve rod 63 that is slidably supported on the cylinder head 50 in the vertical direction.
A valve body 64 integrally formed with the lower end of the valve rod 63 is provided. This valve body 64 connects the intake opening 60 to the combustion chamber 5
A spring 65 for urging the intake valve 62 so as to close from the 6 side.
Is provided.

On the other hand, a valve mechanism 67 is provided in a space surrounded by the cylinder head 50 and the cylinder head cover 51. The valve mechanism 67 has an intake cam shaft 68 that is interlocked with the crankshaft, and the intake cam shaft 68 rotates around its axis to lift the lifter 69 at the upper end of the valve rod 63.
The intake valve 62 appropriately opens and closes the intake opening 60 by means of the cam engagement and the urging force of the spring 65.

At the front portion of the cylinder head 50, a single exhaust passage 71 extending in the front-rear direction is formed. The upstream end of the exhaust passage 71 is opened toward the inside of the front portion of the combustion chamber 56 when the cylinder 25 is viewed along the axis 47 of the cylinder (in plan view in FIG. 4), and this opening is exhausted. The exhaust opening 72 is located substantially at the center of the combustion chamber 56 in the left-right direction. The downstream end of the exhaust passage 71 is connected to the exhaust pipe 35.

Exhaust valve 74 for opening and closing the exhaust opening 72
Is provided. The exhaust valve 74 includes a valve rod 75 which is slidably supported on the cylinder head 50 in the vertical direction.
A valve body 76 integrally formed with the lower end of the valve rod 75 is provided. This valve body 76 connects the exhaust opening 72 to the combustion chamber 5
A spring 77 for urging the exhaust valve 74 so as to close from the 6 side.
Is provided.

The valve operating mechanism 67 has an exhaust cam shaft 79 which interlocks with the crank shaft, and the exhaust cam shaft 79 is cam-engaged with the upper end of the valve rod 75 through a lifter 80 by the rotation around its axis. The exhaust valve 74 appropriately opens and closes the exhaust opening 72 by the cam engagement and the biasing force of the spring 77.

When the piston 54 includes the top dead center and is located in the vicinity of the top dead center, the valve bodies 64 and 76 of the intake valve 62 and the exhaust valve 74 do not come into contact with the top surface 54a of the piston 54. A recess 81 is formed on the top surface 54a of the piston 54.

In FIGS. 1, 3 and 4, an intake control valve 82 for opening and closing the lower part of the intake passage 58 near the intake opening 60 is provided. This intake control valve 8
2 has a valve hole 83 formed in the cylinder head 50 and having a circular cross section extending in the left-right direction. An upper portion of the valve hole 83 at an intermediate portion in the axial direction is opened to the intake passage 58, and one end of the valve hole 83 is opened to an outer surface of the cylinder head 50.

The intake control valve 82 has the valve hole 83.
Has a columnar valve body 84 that is fitted in the valve body 84. The valve body 84 is rotatable in the valve hole 83 about its axis. A notch 85 is formed on the outer peripheral surface of the valve body 84 at an intermediate portion in the axial direction, and the intermediate portion is a thin portion, which serves as a valve body 86.

A pulley 88 is attached to one end of the valve element 84 protruding outward of the cylinder head 50,
An actuator 90, which is a servo motor, is connected to the pulley 88 via a wire 89. The valve body 84 is rotated by the drive of the actuator 90, whereby the valve body 86 is moved to the intake passage 5.
Open and close the upper part of 8.

When the load is low, the intake passage 58 is
By rotating the valve body 86 so as to close the valve to some extent, the cross-sectional area of the intake passage 58 is narrowed, thereby increasing the flow rate of the air-fuel mixture 99 and keeping the air-fuel mixture 99 from the ceiling of the intake passage 58. The tumble flow is “strengthened” by flowing into the combustion chamber 56 along the wall side.

A pair of left and right spark plugs 92, 92 are attached to the cylinder head 50 forming the ceiling of the combustion chamber 56. Each discharge part 93 of each spark plug 92
Faces the inside of the combustion chamber 56 near the ceiling surface of the combustion chamber 56. In addition, both of the discharge parts 93, 93 have a shaft center 47.
It is installed symmetrically to the left and right around the center.

In particular, in FIG. 4, an engine controller 95 for electronically controlling the engine 23 is provided. The engine control device 95 includes the actuator 9
0 and each spark plug 92, 92 are electrically connected. In addition, the number of revolutions of the crankshaft of the engine 23,
A sensor device 96 for detecting the throttle opening of the throttle valve 30 is provided, and this sensor device 96 is also electrically connected to the engine control device 95.

As shown by the solid line and the solid line arrow in FIG. 1, when the engine 23 is in operation, the piston 54 descends from the top dead center toward the bottom dead center during the intake stroke.
The intake opening 60 is opened by the opening operation of the intake valve 62. Then, the cylinder hole 49 and the intake passages 58, 5
Due to the negative pressure inside 9, the outside air is sucked into the carburetor 31 side through the air cleaner 32, where the fuel is mixed and the air-fuel mixture 99 is generated. This mixture 99 is the intake passage 5
The gas is sucked into the combustion chamber 56 through the gaps between the inner peripheral surface of the intake opening 60 and the valve body 64 of the intake valve 62.

As indicated by the two-dot chain line and the two-dot chain line arrow in FIG. 1, when the piston 54 rises from the bottom dead center is the compression stroke, and when the piston 54 approaches the top dead center, The air-fuel mixture 99 is sufficiently compressed in the combustion chamber 56. At this time, the air-fuel mixture 99 is ignited and burned by the ignition caused by the discharge of the discharge portion 93 under the control of the engine control device 95, and the explosion stroke occurs.
Goes down and the heat of combustion is converted into power. Further, in the subsequent exhaust stroke due to the ascent of the piston 54, the gas generated by the combustion causes the exhaust opening 72 opened by the opening operation of the exhaust valve 74, the exhaust passage 71, the exhaust pipe 35, and the silencer 36. As described above, the exhaust 100 is discharged to the outside of the cylinder 25.

Next, returning to the inhalation process,
The above-described respective steps that follow are repeated, and the engine 23 outputs power.

In the above case, due to the structure of the intake passage 58 and the intake opening 60 described above, the air-fuel mixture 99 sucked into the combustion chamber 56 in the intake stroke is burned in the intake stroke and the subsequent compression stroke. The "toughened" tumble flow is created in the chamber 56. The main flow portion 99a of the tumble flow is composed of a high-velocity and rich fuel mixture layer, and the main flow portion 99a is substantially in the bore center of the cylinder 25, that is,
It is oriented near the axis 47.

More specifically, in the inhalation stroke, as shown in FIGS.
A large tumble flow (A), which swirls greatly in the vertical direction, is shown by the solid line, and in the compression stroke, the large tumble flow (A) is from the vertical direction as shown by the chain double-dashed line in FIG. It is compressed into a small tumble flow (B). When this small tumble stream (B) is further compressed,
As shown by the alternate long and short dash line in FIG. 1, turbulence (C) begins to occur by colliding with the ceiling surface of the combustion chamber 56 and the valve bodies 64 and 76 from the leading end side thereof. Then, the air-fuel mixture 9 in this state
9 is ignited and burned as described later.

The engine controller 95, which receives the detection signal from the sensor device 96, detects the operating state of the engine 23. If it is determined by this detection that the engine 23 is in a low-medium speed, low-load state,
It is judged that the air-fuel mixture 99 passing through the intake passage 58 is small,
As shown in FIGS. 1 and 3, the lower portion of the intake passage 58 is closed by the operation of the actuator 90, and
The tumble flow due to a is generated faster and more clearly.

On the other hand, by the engine control device 95,
If it is determined that the engine 23 is in the high speed and high load state, it is determined that the air-fuel mixture 99 passing through the intake passage 58 is large, and the lower portion of the intake passage 58 is opened by the operation of the actuator 90, so that the speed of the tumble flow is increased. Is weakened to some extent, and a smooth flow of the air-fuel mixture 99 in the intake passage 58 is secured.

In the above case, when the tumble flow (A, B) is "strengthened" and ignited by the ignition of the spark plug 92 under the control of the engine controller 95, the tumble flow is "strengthened". , Its combustion speed becomes faster, which makes it possible to cope with high-speed operation and the like.

However, in this case, the combustion temperature is increased as a whole, the cooling loss is increased, and there is a possibility that the improvement in fuel consumption is hindered.

Therefore, when the ignition timing is delayed, the piston 54 comes closer to the top dead center in the compression stroke, and the tumble flow (B) is further compressed in the vertical direction and sufficiently collapses, resulting in fine turbulence. (C) will be sufficiently generated.

When the ignition is performed in this state, the front surface area when the flame spreads due to the combustion increases, and the maximum combustion temperature is prevented from increasing.

On the other hand, when the main flow portion 99a of the tumble flow (B) remaining when the turbulence (C) occurs, the combustion speed of the main flow portion 99a is high, and the combustion temperature of this portion is It will be higher to some extent. However, as described above, the maximum combustion temperature is suppressed, so that the overall combustion temperature can be suppressed low.

Therefore, since the temperature difference between the combustion temperature and the wall temperature of the combustion chamber 56 is kept small, the cooling loss due to the heat radiation to the wall of the combustion chamber 56 is suppressed to be small and the fuel consumption is improved. Will be done.

By the way, as described above, when the turbulence (C) is sufficiently generated and ignited and burned,
The combustion speed can be surely slowed down, but the combustion speed is slow, so that the combustion period may be too long. And in this case, in the latter stage of combustion,
After the transition to the exhaust stroke, the latter stage of this combustion is wasted, the thermal efficiency is reduced, and the effect of improving fuel efficiency is hindered.

Therefore, as described above, the spark plug 92
A plurality of spark plugs 92, 9 are provided.
When the ignition is performed by 2, the combustion is started at a plurality of places, and thus, the combustion period is prevented from being too long.

Moreover, the tumble flow (B) is seen in a plan view.
While the main flow portion 99a of the spark plug 92 flows substantially through the axial center 47 which is substantially the center of the bore in the cylinder 25, the discharge portions 93 of the respective spark plugs 92 are arranged on the left and right sides of the axial center 47, respectively. Since it is deviated from the main flow portion 99a, it is prevented that it takes too long for the flame to propagate from the discharge portion 93 side through the shaft center 47 to the other side.

That is, although combustion tends to be delayed at a location away from the mainstream portion 99a, a plurality of spark plugs 92 are provided and arranged as described above, whereby the flame propagation distance is shortened, and thus, the flame propagation distance is shortened. , The propagation time is shortened.

According to the above construction, in short, by making the air-fuel mixture 99 into a tumble flow (A, B), delaying the ignition timing by the ignition plug 92, and providing a plurality of this ignition plugs 92. First, the combustion speed of the air-fuel mixture 99 is increased, and thus it is possible to cope with high-speed operation and the like. Second, this combustion chamber 56
It is assumed that the combustion temperature in the above does not become too high, and the amount of heat radiation to the wall to the combustion chamber 56 is suppressed to a small amount. Thirdly, the combustion period is prevented from becoming too long, and thermal efficiency is prevented from decreasing.

Moreover, as described above, since the ignition timing is delayed, the combustion heat of the air-fuel mixture 99 in the combustion chamber 56 is
After this initial stage of combustion, the period of staying in the combustion chamber 56 is shortened, and the amount of heat radiation to the wall to the combustion chamber 56 is suppressed to that extent.

In the above case, the ignition timings of the respective spark plugs 92 are set to be substantially the same under the control of the engine control unit 95.

Then, the ignition timing by the ignition plug 92 is sufficiently delayed so that the air-fuel mixture 99 is ignited at a plurality of locations by the plurality of ignition plugs 92, 92 at substantially the same time, so that the air-fuel mixture 99 is discharged in a short combustion period. It is designed to burn.

In other words, the ignition is performed after waiting until the turbulence (C) is sufficiently generated, and the combustion period of the air-fuel mixture 99 is surely prevented from becoming too long by igniting at a plurality of locations substantially at the same time. .

Instead of setting the ignition timings of the respective spark plugs 92 to be substantially the same, a phase difference may be provided in the ignition timings under the control of the engine control unit 95.

In this way, the generation timing of the maximum temperature in each combustion of the air-fuel mixture 99 based on the ignition of each spark plug 92 is shifted according to the provision of the above phase difference.
It is reliably suppressed that the combustion temperature becomes too high.

Although the above is based on the illustrated example, the intake passage 58 is branched into a plurality (for example, three) as it goes from the upstream end side toward the downstream end side, and each of these branched ends is taken into the intake opening 60. As an alternative, the intake valve 62 may be provided in each of the intake openings 60 so as to communicate with the combustion chamber 56. In this case, the intake opening 60 at the center in the left-right direction, through which the air-fuel mixture 99 is most (50% or more), is positioned substantially at the center in the left-right direction of the combustion chamber 56, and the air-fuel mixture 99 passing through this is located.
Is preferably a tumble flow.

Further, the exhaust passage 71 is branched into a plurality from the downstream end side toward the upstream end side, and the respective branched ends are made to communicate with the combustion chamber 56 as the exhaust opening portions 72, respectively, and An exhaust valve 74 may be provided in each 72.

(Example 2)

6 and 7 show the second embodiment.

According to this, the intake passage 58 is branched into a plurality (two) as it goes from the upstream end side to the downstream end side, and these branched intake passages 111, 111 burn through the intake opening portions 60. It is opened into the chamber 56.

On the other hand, the exhaust passage 71 is branched into a plurality (two) as it goes from the downstream end side to the upstream end side, and these branched exhaust passages 112, 112 pass through each exhaust opening 72 and inside the combustion chamber 56. It is opened to.

A pair of left and right spark plugs 92, 92 are attached to the cylinder head 50.
The second discharge part 93 faces both left and right ends in the combustion chamber 56.

Since other configurations and operations are the same as those of the first embodiment, common reference numerals are given to the drawings and the description thereof will be omitted.

[0099]

According to the present invention, the air-fuel mixture flowing into the combustion chamber in the cylinder through the intake passage formed in the cylinder is made to be a tumble flow in the combustion chamber, and the ignition plug is inserted in the combustion chamber. In the four-cycle engine facing the discharge part, a plurality of spark plugs are provided. Therefore, the following effects are produced.

That is, when the tumble flow of the air-fuel mixture flowing through the intake passage formed in the cylinder is “strengthened” and ignited by ignition of the spark plug, the tumble flow is “strengthened”, The combustion speed becomes faster, which makes it possible to cope with high-speed operation and the like.

However, in this case, the combustion temperature is raised as a whole, the cooling loss increases, and there is a risk that the improvement in fuel consumption is impeded.

Therefore, when the ignition timing is delayed, the piston comes closer to the top dead center in the compression stroke.
The tumble flow is more compressed in the vertical direction and fully collapses,
Slight disturbances will occur.

When ignition is performed in this state, the front surface area when the flame spreads due to the combustion increases, and the maximum combustion temperature is suppressed from increasing.

On the other hand, when the main flow portion of the tumble flow remaining when the above turbulence occurs, the combustion speed of this portion is high, and the combustion temperature of this portion becomes high to some extent. However, as described above, the maximum combustion temperature is suppressed, so that the overall combustion temperature can be suppressed low.

Therefore, since the temperature difference between the combustion temperature and the wall temperature of the combustion chamber is kept small, the cooling loss due to the heat radiation to the wall of the combustion chamber is suppressed to be small and the fuel consumption is improved. It will be.

By the way, as described above, when the turbulence is sufficiently generated and ignited and burned, the combustion speed can be surely slowed down, but since the combustion speed is slow, this combustion period May become too long. In this case, in the latter stage of combustion, the exhaust stroke is entered, the latter stage of combustion is wasted, the thermal efficiency is lowered, and the effect of improving fuel efficiency is hindered.

Therefore, in the present invention, a plurality of spark plugs are provided, and if ignition is performed by these spark plugs, combustion will start at a plurality of locations, which may result in an excessively long combustion period. Suppressed.

That is, according to the present invention, the following effects are brought about by making the air-fuel mixture a "tightened" tumble flow, delaying the ignition timing by the spark plugs, and providing a plurality of these spark plugs. . First, the combustion speed of the air-fuel mixture is increased, so that high speed operation or the like can be supported. Secondly, it is assumed that the combustion temperature in this combustion chamber does not become too high, so that the amount of heat radiation to the wall to the combustion chamber is suppressed to a low level, thus suppressing an increase in cooling loss, that is, improving fuel efficiency. To be done. Thirdly, it is possible to prevent the combustion period from becoming too long and prevent the thermal efficiency from decreasing, thus achieving the improvement in fuel consumption.

Moreover, as described above, since the ignition timing is delayed, the period during which the combustion heat of the air-fuel mixture in the combustion chamber remains in the combustion chamber after the initial stage of this combustion is shortened, and the combustion amount is increased accordingly. The amount of heat radiated to the wall to the room can be suppressed to a low level.

Therefore, also in this respect, the cooling loss is suppressed to a small level, and the fuel economy is improved.

In the above case, the ignition timings of the respective spark plugs may be set substantially at the same time.

In this way, even if the ignition timing by the plurality of ignition plugs is sufficiently delayed, the mixture is ignited at a plurality of locations by the plurality of ignition plugs substantially at the same time, so that the mixture is produced in a short combustion period. Can be burned.

Therefore, according to the present invention, the ignition timing can be delayed sufficiently, that is, the ignition can be performed after waiting until the turbulence is sufficiently generated, and the mixture can be ignited at substantially the same time. It is surely prevented that the combustion period of is too long.

Further, as described above, instead of making the ignition timings of the respective ignition plugs substantially the same, a phase difference may be provided in the ignition timings.

In this way, the generation timing of the maximum temperature in each combustion of the air-fuel mixture based on the ignition of each spark plug is
Since the phase difference causes the deviation, the combustion temperature is surely prevented from becoming too high.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a partially enlarged operation of FIG. 3 in the first embodiment.

FIG. 2 is an overall side view of the motorcycle according to the first embodiment.

3 is a partially enlarged cross-sectional view of FIG. 2 in Embodiment 1. FIG.

4 is a sectional view taken along line 4-4 of FIG. 3 in Embodiment 1. FIG.

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 1 in the first embodiment.

FIG. 6 is a diagram corresponding to FIG. 1 in the second embodiment.

7 is a sectional view taken along line 7-7 of FIG. 6 in Example 2. FIG.

[Explanation of symbols]

 23 Engine 25 Cylinder 54 Piston 56 Combustion Chamber 58 Intake Passage 92 Spark Plug 93 Discharge Section 99 Mixture 99a Main Flow Section A, B Tumble Flow C Turbulence

Claims (3)

[Claims] 1. An air-fuel mixture that flows into a combustion chamber in the cylinder through an intake passage formed in the cylinder so as to form a tumble flow in the combustion chamber, and the discharge portion of the ignition plug faces the combustion chamber. A four-cycle engine ignition device for a four-cycle engine, comprising a plurality of the above-mentioned spark plugs. 2. The ignition device for a four-cycle engine according to claim 1, wherein the ignition timings of the respective spark plugs are substantially the same. 3. The ignition system for a four-cycle engine according to claim 1, wherein a phase difference is provided between the ignition timings of the respective spark plugs.