JP3040596B2 - Engine fuel supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system in which a P intake port and an S intake port are provided for each combustion chamber of an engine, and an on-off valve is provided in an intake passage on the side of the S intake port to close in a low load operation region. It concerns the device.

[0002]

2. Description of the Related Art In general, in a fuel supply system for an engine of this type, air is supplied to the combustion chamber only from a P intake port in a low load operation range, while the P / O is opened by opening the on-off valve in a high load operation range. Air is supplied from both intake ports of S. That is, in the low load operation region, the air flow from the S intake port is stopped to secure a sufficient intake flow velocity from the P intake port to generate swirl in the combustion chamber, while in the high load operation region,
A sufficient filling efficiency of the intake air from both the P and S intake ports is ensured.

[0003] In such a fuel supply apparatus, there is conventionally known a fuel supply apparatus in which a fuel injection valve is provided in an intake passage on a P intake port side and the position of the fuel injection valve is offset to an S intake port side. (For example, see Japanese Patent Publication No. 2-20828). This is because the fuel injected from the fuel injection valve collides with the wall surface of the P intake port to increase the contact area with the intake air, thereby promoting the vaporization in the low load operation range, and thus improving the combustibility. It is intended. In addition, a fuel injection valve is provided in each of the intake passages of the P and S intake ports to increase the spray angle of the P injector side fuel injection valve and to decrease the spray angle of the S intake port side fuel injector. It is also known that each one is set.
169271). This is because in the low-load operation region, the fuel from the fuel injection valve on the P intake port side is injected at a large spray angle to promote the vaporization and atomization of the fuel and air, while in the high-load operation region. ,
By injecting the fuel from the fuel injection valve on the S intake port side at a small spray angle, the intake resistance is reduced, and the charging efficiency is further improved.

That is, in the conventional fuel supply system for an engine, in a low-load operation region in which the intake from the S intake port is stopped, the more the gasification and the atomization are promoted, the more the combustion stability in the low-load operation region is improved. It is based on the idea that it can contribute to For this reason, the spray angle of the fuel injected from the fuel injection valve on the side of the P intake port is increased to increase the area in contact with the intake air, or the collision area with the wall surface of the P intake port increases the contact area with the intake air. doing.

[0005]

In recent years, in order to improve emission performance and fuel consumption performance, it has been required to achieve a so-called lean burn in which an air-fuel mixture having an air-fuel ratio leaner than the stoichiometric air-fuel ratio is burned. Have been. In this case, particularly in the low load operation region, the supplied air-fuel mixture is small and the air-fuel mixture is diluted, so that it is necessary to particularly maintain and improve the ignitability. Therefore, in an engine in which two intake ports are provided in one combustion chamber, and an ignition plug is arranged at a substantially central portion of the combustion chamber, particularly, in order to improve the ignitability in a low load operation range, the ignition plug is used. It is necessary to sufficiently stratify the surrounding air to form a relatively rich mixture layer.

However, if the fuel injection valve provided on the P intake port side is arranged offset to the S intake port side, vaporization and atomization can be promoted, but the main body of the vaporized fuel is swirled. As a result, the spark plug is flown to the circumferential side position of the combustion chamber, and it is not possible to sufficiently stratify the ignition plug disposed substantially at the center of the combustion chamber.
For this reason, the ignitability may be insufficient. Also,
If the fuel injection valve provided on the P intake port side has a large spray angle, vaporization and atomization can be promoted, but the main body of the vaporized fuel will be swirled similarly to the above. However, stratification cannot be sufficiently achieved.

On the other hand, when the air-fuel ratio is corrected to the rich side in response to a request for increasing the output in a high load operation region, it is necessary to sufficiently mix the fuel and air in the combustion chamber. In this case, if the air-fuel ratio is gradually increased from the lean burn state to the rich side in response to an output increase request, there is a disadvantage that nitrogen oxides (NOx) temporarily increase in the middle of the process.

The present invention has been made in view of such circumstances, and an object of the present invention is to improve ignitability and combustion stability by promoting stratification in a low-load operation region. It is another object of the present invention to achieve good lean burn, improve mixing in a high load operation range, and improve fuel economy as a whole. Another object is to suppress an increase in NOx generation when shifting from a low load operation range to a high load operation range.

[0009]

In order to achieve the above object, the invention according to claim 1 promotes vaporization and atomization, particularly in order to achieve the stability of lean burn in a low load operation range. Rather, they focus on the point that it is more important to improve ignitability by promoting stratification. The swirl-generating P intake port for generating swirl in the combustion chamber and the S intake port are opened independently of each other in the combustion chamber of the engine, and the P intake passage is communicated through the P intake port. In addition, it is assumed that the S intake passage is communicated through the S intake port, and that the S intake passage is provided with an opening / closing valve that closes in a low-load operation range.
The configuration includes air-fuel ratio setting means and spray angle changing means. That is, the fuel injection valve is provided in the P intake passage of the P intake passage and the S intake passage, and its injection center axis is positioned approximately at the center of the opening of the P intake port in the combustion chamber. It is arranged so as to be directed toward the spark plug located at the center. Further, the air-fuel ratio setting means sets a lean region in which fuel is supplied at an air-fuel ratio leaner than the stoichiometric air-fuel ratio to a low-load operation region in which the on-off valve is closed, and A rich region in which fuel supply is performed at an air-fuel ratio richer than that is set to another operation region in which the on-off valve is opened. Further, the spray angle changing means sets the spray angle, which is an inner angle of a range in which fuel is diffused around the injection center axis of the fuel injection valve, in a lean area set by the air-fuel ratio setting means, to a spray area in a rich area. It is configured to be smaller than the corner.

According to a second aspect of the present invention, in the first aspect of the present invention, the air-fuel ratio setting means sets an operating state between a lean region and a rich region which is set adjacent to the lean region. It is configured to switch between them in response to each other. The spray angle changing means is configured to change the spray angle to a spray angle larger than the lean angle in synchronization with the switching from the lean region to the rich region by the air-fuel ratio setting device.

Further, the invention according to claim 3 specifies the spray angle and the direction of the injection center axis in the invention according to claim 1 more specifically. That is, the spray angle in the lean region is set to a range that does not collide with the wall surface of the P intake port, and the injection center axis is set so as to be directed to the vicinity of the ignition plug.

[0012]

According to the above-mentioned structure, according to the first aspect of the present invention,
When the engine is in the low load operation range, the on-off valve is closed, and swirl is generated in the combustion chamber by the intake air from the P intake passage.
At the same time, the lean area is set by the air-fuel ratio setting means, fuel is supplied by the air-fuel ratio on the lean side, and the spray angle of the fuel injection valve is changed to be smaller than the rich area by the spray angle changing means. As a result, the fuel is sprayed in a relatively narrow range centered on the injection center axis directed toward the spark plug from the fuel injection valve, and the main body of the sprayed fuel does not rest on the swirl, and the fuel is sprayed. It is reached near. For this reason, even if the air-fuel ratio is set in the lean region, stratification for forming a rich air-fuel mixture in the vicinity of the ignition plug is reliably achieved, and ignitability is improved. As a result, the combustion stability in the lean burn is improved, and further, the ignitability is improved, and the lean region is expanded toward the high load side.

On the other hand, when the operation state is in the high load operation region, the on-off valve is opened to take in the air from the P and S intake ports, and the spray angle of the fuel injection valve becomes larger than in the lean region. For this reason, the diffusion range of the fuel sprayed from the fuel injection valve is expanded more than the range of the lean region, and the fuel is loaded on the swirl from the P intake port. Then, the swirl on which the fuel is loaded is disturbed by the intake from the S intake port, so that the fuel and air from the P intake port are mixed. In addition, since the fuel injected from the fuel injection valve is set to the air-fuel ratio in the rich region, the output requirement in the high-load operation region is satisfied together with the promotion of the mixing.

According to the second aspect of the present invention, in addition to the operation of the first aspect of the present invention, in the air-fuel ratio setting means, the lean region and the rich region are set adjacent to each other, so that the low load operation region is set. ~ Switch between the lean region and the rich region in accordance with the operation state of the high load operation region. That is, the air-fuel ratio is not gradually increased or decreased, but is changed at once between the two air-fuel ratios on the lean side and the rich side. Therefore, the air-fuel ratio is gradually increased or decreased by setting the values of the lean-side and rich-side air-fuel ratios by selecting the lean-side and rich-side values around the value 16 where the generation of NOx is maximum. As a result, an increase in the generation of NOx is suppressed as compared with the case where the fuel is supplied at the air-fuel ratio value 16. The spray angle changing means switches the spray angle of the fuel injection valve in synchronism with the switching between the lean air-fuel ratio and the rich air-fuel ratio, so that the increase in NOx generation is more effectively suppressed. Done in

Further, according to the third aspect of the present invention, since the spray angle in the lean region is set so as not to collide with the wall surface of the P intake port, substantially all of the spray fuel is injected into the combustion chamber and the fuel injection valve is provided. The injection center axis of the fuel injector is directed to the vicinity of the spark plug, so that the spray fuel reaches the spark plug more reliably, whereby the operation according to the invention of claim 1 is more reliably achieved. .

[0016]

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

1 and 2 show an engine to which a fuel supply device according to an embodiment of the present invention is applied. Although FIG. 1 shows only one cylinder, the other cylinders have the same configuration. Therefore, hereinafter, only one cylinder will be described, and description of the other cylinders will be omitted.

In FIG. 1, reference numeral 1 denotes an engine, and the engine 1 is a cylinder block 3 forming a cylinder 2.
(Shown only in FIG. 2), a cylinder head 4 joined to the upper surface of the cylinder block 3, and a piston 5 reciprocating in the cylinder 2. In the cylinder 2, a combustion chamber 6 is defined by a lower surface of the cylinder head 4 and a top surface of the piston 5, and a spark plug 7 is provided in the combustion chamber 6 on the lower surface of the cylinder head 4. It is installed in the central position facing.

In the combustion chamber 6, two intake ports 8, 9 for P (primary) and S (secondary) and two exhaust ports 10, 11 are opened independently of each other. An intake valve 12 is provided at an opening of the combustion chamber 6 of each of the intake ports 8 and 9, and an exhaust valve 13 is provided at each of the exhaust ports 10 and 11. Each intake and exhaust valve 12,
Reference numeral 13 is opened and closed at a predetermined timing to introduce intake air into the combustion chamber 6 and extract exhaust gas.

The two intake ports 8 and 9 are located on one side of an arrangement axis L of the cylinders of the engine passing through the axis O of the cylinder 2 and the two exhaust ports 10 and 11 are located on the other side. They are arranged so that the two 8, 9, 10, 11 face each other. And the above P
The intake port 8 is opened so as to be directed in a tangential direction of the inner peripheral surface of the cylinder 2, and generates swirl, which is a vortex flowing through the cylinder 2 on the circumferential side position by the intake from the P intake port 8. It has become. Further, the S intake port 9 is opened so as to be directed downward of the cylinder 2 from the P intake port 8, and the tumble which is a vertical vortex of the cylinder 2 is generated by the intake from the S intake port 9. Is to be generated.

The P intake port 8 has a P intake passage 14
The S intake port 9 is in communication with an S intake passage 15.
Reference numerals 4 and 15 communicate with one common intake passage 16 at each upstream end position. An air cleaner, an air flow meter, a throttle valve, and the like (not shown) are provided upstream of the common intake passage 16, and outside air is introduced into the common intake passage 16 through these components. And is introduced into the two intake passages 14 and 15 of P and S.

A fuel injection valve 17 is provided at a predetermined position in the P intake passage 14. The fuel injection valve 17 is supplied by an output signal from a control unit 18 at a predetermined timing and a predetermined air-fuel ratio. The fuel is injected. An opening / closing valve 19 which is opened and closed by driving an actuator 19a is provided at a predetermined position of the S intake passage 15.
Is adapted to convert the S intake passage 15 into a fully open state, a fully closed state, or a closed state with a small opening degree at a predetermined timing based on an output signal from the control unit 18.

The injection center axis X of the fuel injection valve 17 is P
The intake port 8 is set so as to be deflected from the center of the opening to the combustion chamber 6 toward the ignition plug 7 so as to point toward the vicinity of the ignition plug 7. And, the fuel injection valve 1
7 is provided with a spray angle changing means 20 for changing the spray angle, which is the diffusion range of the fuel sprayed around the injection center axis X, into two stages, large and small. The spray angle changing means 20 includes an injection hole diameter changing member 21 for changing the injection hole diameter of the fuel injection valve 17 between large and small by position conversion by rotation.
An actuator 22 for rotating the injection hole diameter changing member 21 is provided. Then, the actuator 22 is driven by an output signal from the control unit 18 so that the spray angle of the fuel injection valve 17 is changed at a predetermined timing.

As shown in detail in FIG. 3 to FIG. 5, the injection hole diameter changing member 21 has a fan-shaped main body 23 which is overlapped so as to shield the injection hole 17a at the nozzle tip of the fuel injection valve 17. And a pin 24 fixed at the base position of the main body 23. In the main body 23, a second hole 26 having a predetermined diameter larger than the first hole 25 is provided at a position on one side of a rotation trajectory where the first hole 25 having a predetermined diameter is opposed to the injection hole 17a. It is formed to penetrate the other side position. The diameter of the first hole 25 is set to a small spray angle communicating with the injection hole 17a (the state shown by the one-dot chain line in FIG. 3 and FIG. 4), and the spray angle from the fuel injection valve 17 is relatively small. It is set to be diffused in the range of θ ₁ (for example, 10 to 20 degrees). Also, the second hole 26
The pore size is the nozzle hole 17a and in communication with atmospheric spray angle setting state through (the state shown in FIG solid line of FIG. 3 and 5), the spray of the fuel injection valve 17 is relatively large spray angle theta ₂ (e.g. 30
(60 degrees). The main body 23 is supported by the pin 24 so as to be rotatable about the pin axis C between the small spray angle setting state and the large spray angle setting state. When the pin 24 is rotated forward and backward, the spray angle of the fuel injection valve 17 is mutually converted into the spray angles θ ₁ and θ ₂ .

The spray angle θ ₁ in the small spray angle setting state.
As shown by a two-dot chain line in FIGS. 1 and 2, the fuel sprayed from the fuel injection valve 17 is set particularly in a range where it does not adhere to the wall surface of the P intake port 8, and All reach the combustion chamber 6 without colliding with the P intake port 8. Further, the fuel injection center axis X is different from the flow direction of the intake air from the P intake port 8 to the combustion chamber 6 (the direction of the arrow indicated by Y in FIG. 1), and is generated by the intake air from the P intake port 8. The swirl does not carry the fuel.

Next, the control by the control unit 18 will be described with reference to FIG.

First, detected values such as an engine speed and an intake air amount are read in step S1, and an air-fuel ratio region is set in step S2 in accordance with the operating state obtained based on the detected values. The setting of the air-fuel ratio region is performed based on a map stored in advance. This map is shown in FIG.
As shown in the figure, a predetermined engine speed N ₁ (for example, 30
A low-load operation range of less than about 00 rpm) and less than a predetermined load (amount of intake air) is defined as a lean area in which fuel is supplied at a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio. ing. That is, in the low load operation region, a predetermined value of the air-fuel ratio at which the value of the ratio λ of the set air-fuel ratio to the stoichiometric air-fuel ratio is larger than 1 is set.
The area adjacent to the lean region, i.e., a load operation region and a high load operating region in greater than large and the predetermined load than the engine speed N _1,
It is determined to be a rich region in which fuel is supplied at a predetermined air-fuel ratio equal to or above the stoichiometric air-fuel ratio or on the rich side. That is, a predetermined air-fuel ratio is set such that the λ value is 1 or less in the medium / high load operation range. These steps S1
And S2 constitute an air-fuel ratio setting means 27 for setting the air-fuel ratio according to the operating state.

Next, in step S3, the determination of the air-fuel ratio region is performed. If the area is a lean area, step S
4 outputs a signal to the actuator 19a to open and close the on-off valve 19.
Is closed, a signal is output to the actuator 22 in step S5, and the injection hole diameter changing member 21 is set to the small spray angle setting state, and the process proceeds to step S8. If the result of the determination in step S3 is a rich region, a signal is output to the actuator 19a in step S6 to open the on-off valve 19, and a signal is output to the actuator 22 in step S7. The injection hole diameter changing member 21 is set to a large spray angle setting state by the above-described step S8.
Proceed to. That is, in the low-load operation region that is the lean region, the on-off valve 19 is closed and the spray angle of the fuel injection valve 17 is changed to the small spray angle θ _{1 as shown} in FIG.
Also, if such high-load operation region which is a rich region with opening the on-off valve 19, to change the spray angle to the large spray angle theta _2.

When changing the spray angle, if the fuel injection valve 17 performs timed injection in which injection is performed for each cylinder in accordance with the intake stroke, the change in the spray angle is adjusted to the end timing of the injection. Do it.

Then, fuel is injected from the fuel injection valve 17 at a predetermined spray angle based on the air-fuel ratio set in step S8, and the routine returns.

In the fuel supply device having the above-described structure, when the operating state is in the low-load operation range, the on-off valve 19 is closed, the air is taken only from the P intake passage 14, and the S intake passage 15 is shut off. As the minute intake flow rate increases,
Since the P intake port 8 is directed in the tangential direction of the combustion chamber 6, a swirl in the circumferential direction of the combustion chamber 6 is generated. At the same time, the spray angle of the fuel injection valve 17 is changed to the small spray angle θ1, so that the sprayed fuel does not collide with the wall surface of the P intake port 8 and the injection center axis X is directed to the vicinity of the ignition plug 7.
Is sprayed in a relatively narrow range centered at the center, and therefore, the main body portion of the sprayed fuel can reach the vicinity of the ignition plug 7 without mounting on the swirl. Thereby, a layer of rich air-fuel mixture can be formed in the vicinity of the ignition plug 7, and stratification of the ignition plug 7 can be reliably achieved. Therefore, even if the setting of the air-fuel ratio is in the lean region, the ignitability can be improved, whereby the combustion stability in lean burn can be improved.

Further, since the ignitability can be improved as described above, the operating region for setting the lean region can be expanded to the higher load side than the low load operating region, or the lean region can be improved. The limit (lean limit) in the lean setting of the air-fuel ratio can be expanded. In this regard, in FIG. 9 showing the result of examining the change characteristics of the lean limit of the air-fuel ratio that can ensure the ignitability with respect to the spray angle, when the spray angle is gradually reduced from the maximum value, the lean The limit shifts from the rich side to the lean side, that is, expands. This is because initially the spray angle is large, so that the spray fuel adhered to the wall surface of the P intake port 8 gradually decreases, and the fuel directly reaching the spark plug 7 increases by that much, and the ignitability increases. It is thought to improve. The lean limit is substantially constant in a range from a spray angle θ ₀ (approximately 20 degrees) at which fuel does not adhere to the wall surface to a small spray angle. Therefore, the fuel injection valve 17 in the lean region is based on the spray angle θ _{0 at} which the spray fuel can be blown into the combustion chamber 6 without colliding with the wall surface of the P intake port 8.
By setting the spray angle to a value smaller than the above θ ₀ , the lean limit can be expanded.

On the other hand, when the operation state is in the high load operation region, the on-off valve 19 is opened to open the P and S intake passages 14,
With the air intake from 15, the spray angle of the fuel injection valve 17 is changed to a large spray angle theta _2. For this reason, the diffusion range of the spray fuel from the fuel injection valve 17 is limited to the large spray angle θ _2.
And a part of the fuel can be collided with the wall surface of the P intake port 8 to promote vaporization and atomization, and the fuel can be placed on the swirl from the P intake port 8. And the swirl with this fuel is S
Since the tumble generated by the intake from the intake port 9 collides with and is disturbed, the fuel and air from the P intake port 8 can be sufficiently mixed. In addition, since the fuel injected from the fuel injection valve 17 has the air-fuel ratio set in the rich region, the output requirement in the high-load operation region can be sufficiently satisfied together with the promotion of the mixing. be able to.

FIG. 10 shows a change characteristic of the torque with respect to the spray angle of the fuel injection valve 17, and the output torque increases as the spray angle increases. This is presumably because the larger the spray angle, the more the fuel vaporization, atomization and mixing with air can be promoted as described above.

That is, in the low load operation region, the stratification is promoted with emphasis on the ignitability, so that the combustion stability of the lean burn and the lean region can be expanded. The required output can be reliably exhibited by promoting the vaporization, atomization and mixing with the air, and the fuel efficiency can be improved as a whole.

Further, the air-fuel ratio setting means 27 sets the lean region and the rich region adjacent to each other in the low-load operation region to the high-load operation region, and sets a predetermined value of the lean-side air-fuel ratio in accordance with the operation state. And the predetermined value of the rich air-fuel ratio. In other words, since the air-fuel ratio is not gradually increased or decreased but is changed at a stroke between the lean-side and rich-side air-fuel ratios, the setting of each value of the lean-side and rich-side air-fuel ratios is performed, for example, by the air-fuel ratio. By selecting the values on the lean side and the rich side with the fuel ratio around 16, the generation of NOx can be effectively suppressed. That is, NOx generally has a maximum generation amount near the air-fuel ratio 16, and tends to rapidly decrease at a leaner or richer air-fuel ratio. Therefore, the air-fuel ratio 16 is the maximum generation stage of NOx. By performing the conversion of the air-fuel ratio while jumping over the vicinity, the amount of generated NOx can be reduced as compared with the case where the air-fuel ratio is gradually increased or decreased. Moreover, the spray angle changing means 20
Since the magnitude of the spray angle of the fuel injection valve 17 is switched in synchronization with the switching between the lean air-fuel ratio and the rich air-fuel ratio, the generation of the NOx can be more effectively suppressed. .

It should be noted that the present invention is not limited to the above-described embodiment, but includes various other modifications. That is, in the above embodiment, the fuel injection valve 17 is fixedly provided at a predetermined position, but is not limited thereto.
The fuel injection valve may be slightly advanced toward the combustion chamber 6 on the injection center axis X in addition to the change of the spray angle from large to small with the switching to the lean region. In this case, the same small spray angle θ ₁
However, the projected area of the sprayed fuel at the opening from the P intake port 8 to the combustion chamber 6 can be reduced by the amount of advance, so that the sprayed fuel is not placed on the swirl from the P intake port 8 and the spark plug 7 can be more reliably reached. As a result, the ignitability can be further improved, and as a result, the lean limit can be further increased as shown by the one-dot chain line in FIG.

In the above embodiment, the air-fuel ratio setting means 27 sets a lean region or a rich region and sets one air-fuel ratio value in each region. However, the present invention is not limited to this. Alternatively, two or more values may be set stepwise according to the operating state.

In the above embodiment, the spray angle changing means 2
Nozzle hole diameter changing member 2 having two large and small holes 25, 26
1 is used to change the spray angle between the lean region and the rich region into two large and small spray angles θ ₁ and θ _2. However, the present invention is not limited to this, and for example, three or more with different diameters May be sequentially formed, and the spray angle may be changed stepwise in the lean region or the rich region according to the operation state.

Further, in the above embodiment, the common intake passage 16
Although a detailed description of the upstream side of the fuel injection valve is omitted, another fuel injection valve is provided at an upstream position of the common intake passage 16, and fuel injection is performed from this fuel injection valve according to the operation state. Is also good.

[0041]

As described above, according to the fuel supply system for an engine according to the first aspect of the present invention, when the engine is in the low load operation range, the air-fuel ratio setting means sets the engine to the lean region so as to be lower than the stoichiometric air-fuel ratio. Since the fuel is supplied at the air-fuel ratio on the lean side and the spray angle of the fuel injection valve is changed to a smaller spray angle than the rich region by the spray angle changing means, the spray center is directed toward the spark plug. The fuel is injected in a relatively narrow range around the axis, and the main body of the spray fuel can reach the vicinity of the spark plug without being mounted on the swirl from the P intake port. For this reason, even if the air-fuel ratio is set in the lean region, stratification with respect to the ignition plug can be reliably achieved, and ignitability can be improved, thereby improving combustion stability in lean burn. Can be planned. Further, since the ignitability can be improved as described above, the lean region can be further expanded to a higher load side.

On the other hand, in the high load operation region, the spray angle of the spray fuel is larger than in the lean region and the contact range with the intake air through the P intake port is large, so that vaporization and atomization can be promoted. It can be placed on the swirl from the P intake port. Since the swirl on which the fuel is loaded is disturbed by the intake air from the S intake port, the mixing between the spray fuel and the air can be sufficiently performed.

Therefore, the fuel economy can be improved as a whole.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, the air-fuel ratio setting means sets the air-fuel ratio in the lean region according to the operating state of the low load operation region to the high load operation region. And the rich region, the values of the air-fuel ratio in the lean region and the rich region are set to values on the lean side and the rich side with respect to the vicinity of the value 16 at which the generation of NOx becomes maximum. Thus, it is possible to suppress an increase in the generation of NOx as compared with the case where the air-fuel ratio is gradually increased or decreased to supply the fuel at the air-fuel ratio value 16. In addition, the spray angle changing means switches the size of the spray angle of the fuel injection valve in synchronization with the switching between the lean region and the rich region.
It is possible to more effectively suppress the occurrence of x.

Further, according to the third aspect of the present invention, the spray angle of the fuel injection valve in the lean region is set within a range that does not collide with the wall surface of the P intake port, so that substantially all of the spray fuel is injected into the combustion chamber. Since the injection center axis of the fuel injection valve is directed to the vicinity of the spark plug, the spray fuel can more reliably reach the spark plug. Thereby, the effect of the invention described in claim 1 can be more reliably achieved.

[Brief description of the drawings]

FIG. 1 is a simplified plan view showing an embodiment of the present invention.

FIG. 2 is a simplified front sectional view of the embodiment of FIG. 1;

FIG. 3 is an arrow view of the nozzle hole diameter changing member viewed from line AA in FIG. 5;

FIG. 4 is a sectional view of a fuel injection valve and an injection hole diameter changing member in a small spray angle setting state.

FIG. 5 is a sectional view of a fuel injection valve and an injection hole diameter changing member in a large spray angle setting state.

FIG. 6 is a flowchart showing control by a control unit.

FIG. 7 is a map of an air-fuel ratio region in a relationship between an engine speed and a load.

FIG. 8 is a map of a spray angle in a relationship between an engine speed and a load.

FIG. 9 is a relationship diagram between a spray angle and a lean limit.

FIG. 10 is a relationship diagram between a spray angle and a torque.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Cylinder 6 Combustion chamber 7 Spark plug 8 P intake port 9 S intake port 14 P intake passage 15 S intake passage 17 Fuel injection valve 19 On-off valve 20 Spray angle changing means 27 Air-fuel ratio setting means X Injection center axis

Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 305 F02D 41/04 305C 45/00 301 45/00 301G F02M 69/00 360 F02M 69/00 360C No.3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-62-255529 (JP, A) JP-A-61-255262 (JP, A) JP-A-63-61774 ( JP, A) Shokai 62-61993 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 69/04 F02M 69/00 360 F02M 61/04 F02M 61/18 360 F02D 41/00-45/00 395

Claims (3)

(57) [Claims] 1. A swirl generating P intake port for generating a swirl in the combustion chamber of an engine,
The intake port is opened independently of each other, the P intake passage is communicated through the P intake port, and the S intake passage is
In the fuel supply device for an engine, which is communicated via an intake port and has an on-off valve that closes in the low-load operation region in the S intake passage, the fuel supply device is provided in a P intake passage of the P intake passage and the S intake passage. A fuel injection valve arranged such that the injection center axis is directed from the center position of the opening of the P intake port in the combustion chamber toward a spark plug disposed substantially at the center of the combustion chamber; A lean region in which fuel is supplied at an air-fuel ratio leaner than the air-fuel ratio is set as a low-load operation region in which the on-off valve is closed, and fuel is supplied at an air-fuel ratio richer than the stoichiometric air-fuel ratio. And an air-fuel ratio setting unit that sets a rich region in which the opening and closing valve is opened to another operation region in which the on-off valve is opened; and a lean region that is set by the air-fuel ratio setting unit. The fuel supply apparatus for an engine fuel characterized in that it comprises a spray angle changing means to be smaller than the spray angle in the rich region the spray angle is interior angle range to be spread as. 2. The air-fuel ratio setting means is configured to switch between a lean region and a rich region which is set adjacent to the lean region in accordance with an operation state. 2. The engine fuel supply device according to claim 1, wherein the spray angle is changed to a spray angle larger than a spray angle in the lean region in synchronization with the switching from the lean region to the rich region by the air-fuel ratio setting means. 3. The fuel for an engine according to claim 1, wherein the spray angle in the lean region is set within a range that does not collide with the wall surface of the P intake port, and the injection center axis is set to point in the vicinity of the spark plug. Feeding device.