JP3882611B2 - Fuel injection device and fuel injection valve for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device and a fuel injection valve for an internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art In a cylinder injection internal combustion engine mounted on a vehicle such as an automobile, fuel is directly injected from a fuel injection valve into a combustion chamber in which air is sucked from an intake passage, and a fuel spray is formed in the combustion chamber by this fuel injection. Is done. When an air-fuel mixture composed of fuel and air is ignited by a spark plug in the combustion chamber, the air-fuel mixture burns and the piston reciprocates due to the combustion energy at that time. The above-mentioned combustion mode of the air-fuel mixture includes “homogeneous combustion” in which a homogeneous air-fuel mixture in which fuel is evenly mixed with air is combusted according to engine operating conditions, etc., and stratification where a combustible air-fuel mixture exists only around the spark plug It is switched between “stratified combustion” in which the air-fuel mixture is combusted.
[0003]
When a homogeneous air-fuel mixture is formed during homogeneous combustion, fuel is injected during the intake stroke in which air is drawn from the intake passage into the combustion chamber as the piston moves. The fuel spray formed in the combustion chamber by the fuel injection during the intake stroke is entrained in the flow of air drawn into the combustion chamber from the intake passage and mixed with the air. In this way, a homogeneous mixture is formed in the combustion chamber.
[0004]
Further, when forming a stratified mixture during stratified combustion, fuel is injected during a compression stroke in which the air in the combustion chamber is compressed as the piston moves. The fuel spray formed in the combustion chamber by the fuel injection during the compression stroke is moved to the vicinity of the spark plug using the penetration force of the spray itself after hitting the top of the piston. In this way, a stratified mixture is formed in the combustion chamber.
[0005]
By the way, the fuel spray formed in the combustion chamber spreads in the width direction of the combustion chamber as shown in, for example, JP-A-2001-27170, by injecting fuel from the fuel injection valve so as to spread in the width direction of the combustion chamber. It is fan-shaped. It has been confirmed that by making the fuel spray formed in the combustion chamber into a fan shape as described above, the penetration force of the spray itself increases, and this spray shape moves the fuel spray to the vicinity of the spark plug during stratified combustion. To ensure the necessary penetrating power.
[0006]
Furthermore, by making the fuel spray formed in the combustion chamber into a fan shape as described above, the fuel spray moves near the spark plug while entraining a large amount of air during stratified combustion. Therefore, fuel vaporization can be promoted and combustion of the stratified mixture can be made better than when the fuel spray is formed in a conical shape.
[0007]
[Problems to be solved by the invention]
By injecting the fuel so that the fuel spray formed in the combustion chamber is fan-shaped as described above, the above effect can be obtained during stratified combustion. The fuel spray formed in a fan shape.
[0008]
In the homogeneous combustion, when the above-described fan-shaped fuel spray is formed in the combustion chamber by fuel injection in the intake stroke, the air sucked into the combustion chamber from the intake passage comes into contact with the fuel spray. This air is drawn to the piston side along the central axis direction of the combustion chamber (piston) as the piston moves during the intake stroke, so that the fan-shaped fuel spray is pushed in the thickness direction and the top side of the piston Or pressed against the inner wall of the combustion chamber.
[0009]
When the fuel spray in the combustion chamber is suppressed in this way, the fuel is biased to exist on the top of the piston and the inner wall of the combustion chamber in the combustion chamber. In addition, the air-fuel mixture with a high fuel concentration remains in that portion. For this reason, there has been a problem that the homogeneity of the air-fuel mixture at the time of homogeneous combustion deteriorates and it becomes difficult to obtain good combustion of the air-fuel mixture.
[0010]
The present invention has been made in view of such circumstances, and the object thereof is to form a homogeneous fuel / air mixture when a fan-shaped fuel spray is formed by fuel injection into a combustion chamber during homogeneous combustion. An object of the present invention is to provide a fuel injection device and a fuel injection valve for an internal combustion engine that can suppress the deterioration of the degree of deterioration and the failure to obtain good combustion.
[0011]
[Means for Solving the Problems]
  In the following, means for achieving the above object and its effects are described.
  In order to achieve the above object, according to the first aspect of the present invention, in the fuel injection device for an internal combustion engine that directly injects fuel into the combustion chamber in which air is sucked from the intake passage, the fan-shaped first expanding in the width direction of the combustion chamber. And a fuel injection means for forming the first fuel spray and the fan-shaped second fuel spray extending in the direction of the central axis of the combustion chamber during the same intake stroke.The fuel injection means forms the second fuel spray on the upstream side of the flow of the intake air with respect to the first fuel spray.It was.
[0012]
  Air taken into the combustion chamber from the intake passage during the intake stroke is drawn toward the piston along the central axis of the combustion chamber as the piston moves. Since the first fuel spray formed in the combustion chamber during the intake stroke has a fan-like shape extending in the width direction of the combustion chamber, it is pressed against the top of the piston and the inner wall of the combustion chamber by the air. . On the other hand, the second fuel spray formed in the combustion chamber during the same intake stroke in which the first fuel spray is formed becomes a fan-like shape extending in the direction of the central axis of the combustion chamber, and the width direction of the combustion chamber The cross-sectional area about is small. For this reason, the second fuel spray is affected by being pressed against the top of the piston and the inner wall of the combustion chamber even if the air flowing in the center axis direction hits the combustion chamber. Hateful. Therefore, by forming the second fuel spray in the combustion chamber during the intake stroke, the fuel-rich mixture remains on the top of the piston and the inner wall of the combustion chamber, and the homogeneity of the mixture deteriorates. Can be suppressed. And it can suppress that favorable combustion cannot be acquired with the homogeneity deterioration of air-fuel | gaseous mixture.
The effect of receiving the flow of air sucked into the combustion chamber from the intake passage is greater in the first fuel spray than in the second fuel spray. However, since the second fuel spray having the smaller influence is on the upstream side of the flow of the intake air than the first fuel spray, the first and second fuel sprays are caused by the flow of the intake air. When pushed to the top side and the inner wall side of the combustion chamber, the first and second fuel sprays are unlikely to overlap. Therefore, it is possible to suppress the occurrence of an excessively high fuel concentration region in the combustion chamber due to the overlapping of the fuel sprays.
[0013]
According to a second aspect of the present invention, in the first aspect of the invention, the fuel injection means forms the first fuel spray and the second fuel spray at the same time.
In an internal combustion engine in which fuel is directly injected into the combustion chamber, the heat of vaporization is taken away from the air in the combustion chamber when the fuel spray formed in the combustion chamber is vaporized. The air filling efficiency is increased and the knock resistance is improved. With respect to such an effect, the maximum effect can be obtained by performing fuel injection when the flow velocity of the air drawn into the combustion chamber from the intake passage becomes the fastest and efficiently vaporizing the fuel spray. According to the above configuration, the first fuel spray and the second fuel spray can be formed at the same time when the flow velocity of the air drawn into the combustion chamber from the intake passage becomes the fastest. Both the second fuel sprays can be efficiently vaporized and the above-described effects can be obtained at a high level.
[0014]
According to a third aspect of the present invention, in the second aspect of the present invention, when the flow rate of the air sucked into the combustion chamber from the intake passage becomes the fastest, the fuel injection means and the first fuel spray The second fuel spray was formed at the same time.
[0015]
According to the above configuration, both the first and second fuel sprays can be efficiently vaporized. Therefore, it is possible to efficiently cool the air in the combustion chamber using the heat of vaporization of the fuel, increase the efficiency of charging the air into the combustion chamber, and improve the knock resistance, at a high level. .
[0018]
  Claim4In the described invention, the claimsIn any one of 1-3In the described invention, the fuel injection means includes a single fuel injection valve that injects the fuel so as to expand in the width direction of the combustion chamber and simultaneously injects the fuel so as to extend in the direction of the central axis of the combustion chamber. It was.
[0019]
According to the above configuration, in order to form the first fuel spray and the second fuel spray, when a plurality of fuel injection valves are used, or by spraying the fuel injection nozzles (fuel injection valves) Compared with the case where a mechanism capable of changing the direction in which the fuel spreads is provided, the structure of the fuel injection device can be simplified, and an increase in cost due to the complexity of the structure can be suppressed.
[0020]
  Claim5In the described invention, the claims4In the described invention, the fuel injection valve injects fuel from the first slit extending in the width direction of the combustion chamber and the second slit extending in the central axis direction of the combustion chamber.
[0021]
According to the above configuration, the first fuel spray is formed by the fuel injection from the first slit, and the second fuel spray is formed by the fuel injection from the second slit. Thus, the first and second fuel sprays can be accurately formed.
[0022]
  Claim6In the described invention, the claims5The gist of the invention is that the second slit is formed on the upstream side of the flow of the intake air with respect to the first slit.
[0023]
According to the said structure, a 2nd fuel spray can be formed in the upstream of the flow of intake air rather than a 1st fuel spray. Therefore, when the first fuel spray that is more susceptible to the influence of the flow of the intake air than the second fuel spray is pressed against the top of the piston and the inner wall of the combustion chamber by the intake air, The first and second fuel sprays are difficult to overlap. Therefore, it is possible to suppress the occurrence of an excessively high fuel concentration region in the combustion chamber due to the overlapping of the fuel sprays.
[0024]
  Claim7In the described invention, the claims5 or 6The gist of the invention is that the first slit and the second slit are formed so as not to overlap each other.
[0025]
If the first slit and the second slit overlap, the resistance at the time of fuel injection is reduced in the overlapping portion, so the fuel injection amount per unit area is larger than in other portions. Become. As a result, in the combustion chamber, the fuel concentration in the region corresponding to the overlapping portion of the first and second slits is higher than the others, which is disadvantageous in obtaining good combustion. However, according to the above configuration, since the first slit and the second slit are separated from each other and do not overlap with each other, it is possible to suppress the occurrence of the above problem.
[0026]
  Claim8In the described invention, claims 1 to7In the invention according to any one of the above, the intake passage is connected to the combustion chamber in a state of being divided into a plurality of branches, and communicates and blocks between the plurality of intake passages and the combustion chamber. A plurality of intake valves that open and close as much as possible are provided, and the fuel injection means forms the second fuel spray between two adjacent intake valves of the plurality of intake valves.
[0027]
According to the above configuration, when the plurality of intake valves open and protrude into the combustion chamber during the intake stroke, the second fuel spray in the combustion chamber hits at least one of the intake valves, and accordingly the fuel is injected into the combustion chamber. This makes it possible to suppress the deterioration of the homogeneity of the air-fuel mixture due to the uneven distribution of the air-fuel ratio and the decrease in the charge for improving the charging efficiency using the heat of vaporization.
[0028]
  Claim9In the described invention, the fuel injection valve injects fuel into the combustion chamber of the internal combustion engine, and the first and second slits for injecting the fuel extend in directions orthogonal to each other.And the second slit is positioned on the upstream side of the flow of intake air of the internal combustion engine with respect to the first slit.Formed.
[0029]
  According to the above configuration, the first fuel spray spreading in a fan shape is formed by fuel injection from the first slit, and the second fuel spray is formed so as to spread in a fan shape by fuel injection from the second slit. Thus, the first and second fuel sprays spread in directions orthogonal to each other. Therefore, for example, by providing a fuel injection valve in the internal combustion engine so that the first fuel spray spreads in the width direction of the combustion chamber, the second fuel spray spreads in the direction of the central axis of the combustion chamber. When the first and second fuel sprays are formed in the combustion chamber by injecting fuel from the fuel injection valve during the intake stroke of the internal combustion engine, the first fuel spray is applied to the central axis of the combustion chamber as the piston moves. Along with the air from the intake passage drawn along the piston side, it is pressed against the top of the piston and the inner wall of the combustion chamber. On the other hand, since the second fuel spray has a small cross-sectional area in the width direction of the combustion chamber, when the intake air flowing along the central axis direction of the combustion chamber hits the piston, Less susceptible to being pressed against the top of the head and the inner wall of the combustion chamber. Therefore, by forming the second fuel spray in the combustion chamber, it is possible to prevent the air-fuel mixture having a high fuel concentration from remaining on the top of the piston and the inner wall of the combustion chamber and deteriorating the homogeneity of the air-fuel mixture. be able to. And it can suppress that favorable combustion cannot be acquired with the homogeneity deterioration of air-fuel | gaseous mixture.
Further, according to the above configuration in which the second slit is positioned upstream of the flow of the intake air of the internal combustion engine relative to the first slit, the second fuel spray is more flowed of the intake air than the first fuel spray. It can be formed upstream. Therefore, when the first fuel spray that is more susceptible to the influence of the flow of the intake air than the second fuel spray is pressed against the top of the piston and the inner wall of the combustion chamber by the intake air, The first and second fuel sprays are difficult to overlap. Therefore, it is possible to suppress the occurrence of an excessively high fuel concentration region in the combustion chamber due to the overlapping of the fuel sprays.
[0030]
  Claim10In the described invention, the claims9The gist of the invention is that the first slit and the second slit are formed so as not to overlap each other.
[0031]
If the first slit and the second slit overlap, the resistance at the time of fuel injection is reduced in the overlapping portion, so the fuel injection amount per unit area is larger than in other portions. Become. As a result, in the combustion chamber, the fuel concentration in the region corresponding to the overlapping portion of the first and second slits is higher than the others, which is disadvantageous in obtaining good combustion. However, according to the above configuration, since the first slit and the second slit are separated from each other and do not overlap with each other, it is possible to suppress the occurrence of the above problem.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to an in-cylinder injection spark ignition engine mounted on an automobile will be described with reference to FIGS.
[0033]
FIG. 1 is an enlarged cross-sectional view showing the periphery of the combustion chamber 2 in the engine 1.
The engine 1 is provided with a cylinder block 4 having a plurality of cylinders 3 (only one is shown in FIG. 1), a cylinder head 5 attached to the cylinder block 4, and a reciprocating movement in the cylinder 3. And a piston 6. The cylinder block 4, the cylinder head 5, and the piston 6 define the combustion chamber 2.
[0034]
An intake passage 7 and an exhaust passage 8 are connected to the combustion chamber 2. The combustion chamber 2 and the intake passage 7 are connected and cut off by the opening / closing operation of the intake valve 9, and the combustion chamber 2 and the exhaust passage 8 are connected and cut off by the opening / closing operation of the exhaust valve 10. The intake valve 9 is opened during the intake stroke of the engine 1, and the exhaust valve 10 is opened during the exhaust stroke of the engine 1.
[0035]
The intake passage 7 is connected to the combustion chamber 2 in a state of being branched into two as shown in FIG. Two intake valves 9 described above are provided for each combustion chamber 2 so that the intake passages 7 branched into two and the combustion chambers 2 can be communicated with each other.
[0036]
When the intake valve 9 is opened during the intake stroke of the engine 1, air is sucked into the combustion chamber 2 from the intake passage 7 branched into two. This air is drawn toward the piston 6 in the combustion chamber 2 as the piston 6 moves downward in FIG. 1, and flows along the central axis L1 of the combustion chamber 2 (the central axis of the cylinder 3 and the piston 6). It becomes like this.
[0037]
The engine 1 is provided with a fuel injection valve 11 that directly injects fuel into the combustion chamber 2 and a spark plug 12 that ignites an air-fuel mixture composed of fuel and air existing in the combustion chamber 2. . When the air-fuel mixture burns based on ignition by the spark plug 12, the piston 6 reciprocates due to the combustion energy at that time, and the engine 1 is driven. The fuel injection of the fuel injection valve 11 is controlled through an electronic control device 13 mounted on the automobile so as to control the operation of the engine 1.
[0038]
The combustion mode of the air-fuel mixture is “homogeneous combustion” in which a homogeneous air-fuel mixture in which fuel is evenly mixed with air is combusted according to the engine operating condition and the like, and there is a combustible air-fuel mixture only around the spark plug 12. It is switched between “stratified combustion” in which the stratified mixture is burned.
[0039]
When a homogeneous mixture is formed during homogeneous combustion, fuel is injected into the combustion chamber 2 from the fuel injection valve 11 during the intake stroke. The fuel spray formed in the combustion chamber 2 by this fuel injection is entrained in the flow of air drawn into the combustion chamber 2 from the intake passage 7 and mixed with the air. In this way, a homogeneous mixture is formed in the combustion chamber 2, and homogeneous combustion is realized by burning the mixture.
[0040]
Further, when forming a stratified mixture during stratified combustion, fuel is injected from the fuel injection valve 11 into the combustion chamber 2 during the compression stroke. The fuel spray formed in the combustion chamber 2 by this fuel injection hits the inner wall of the concave cavity 6a formed at the top of the piston 6, and uses the penetration force of the spray itself and the cavity 6a to make the spark plug 12 Moved closer. Thus, a stratified mixture is formed in the combustion chamber, and stratified combustion is realized by burning the mixture.
[0041]
Next, the fuel injection valve 11 will be described in detail with reference to FIGS.
FIG. 3 is a front view showing the injection hole shape of the fuel injection valve 11. The fuel injection valve 11 is formed with first and second slits 14 and 15 extending in directions orthogonal to each other as injection holes for injecting fuel. The first slit 14 extends in the radial direction of the fuel injection valve 11. On the other hand, the second slit 15 is in the radial direction of the fuel injection valve 11 and at the position corresponding to the center in the longitudinal direction of the first slit 14 and is spaced apart from the slit 14 by a predetermined distance. 14 extends in a direction orthogonal to 14.
[0042]
When fuel injection from the fuel injection valve 11 is executed, fuel is injected through the first and second slits 14 and 15 as shown in FIGS. 5 shows the first fuel spray 16 formed by the fuel injected through the first slit 14 and the second fuel spray 17 formed by the fuel injected through the second slit 15. The spray shape when viewed from the side is shown. FIG. 6 shows the spray shape when the first and second fuel sprays 16 and 17 are viewed from above.
[0043]
As can be seen from these drawings, the first fuel spray 16 has a fan shape extending in the radial direction of the fuel injection valve 11, and the second fuel spray 17 has a fan shape extending in a direction orthogonal to the first fuel spray 16. ing. Further, the first fuel spray 16 and the second fuel spray 17 are formed so as not to overlap each other. This is because the first slit 14 for forming the first fuel spray 16 and the second slit 15 for forming the second fuel spray 17 are formed so as not to overlap each other. It is.
[0044]
If the first and second slits 14 and 15 are overlapped, the resistance at the time of fuel injection is reduced in the overlapped portion, so that the overlapped portion is compared with other portions. The amount of fuel injection per unit area becomes large. As a result, in the fuel spray formed when fuel injection is performed, the fuel concentration in the portion corresponding to the portion where the first and second slits 14 and 15 overlap is higher than the others, and good combustion is obtained. It will be disadvantageous. However, by forming the first slit 14 and the second slit 15 so as to be separated from each other as described above, the first fuel spray 16 and the second fuel spray 17 are separated from each other. It is possible to suppress the occurrence of such a problem.
[0045]
The fuel injection valve 11 is preferably attached to the engine 1 so as to satisfy the following conditions [1] to [4].
[1] The first fuel spray 16 spreads in the width direction of the combustion chamber 2 (the width direction of the cylinder 3 and the piston 6), and the second fuel spray 17 spreads in the central axis direction of the combustion chamber 2 (the cylinder 3 and the piston 6). It spreads in the central axis direction).
[0046]
[2] When fuel is injected during the intake stroke to perform homogeneous combustion, the first fuel spray 16 is formed at a position closer to the piston 6 than the position when the intake valve 9 is opened.
[3] The second fuel spray 17 is formed on the upstream side of the flow of intake air in the intake stroke with respect to the first fuel spray 16 so as not to hit the spark plug 12.
[0047]
[4] The second fuel spray 17 is formed between the two intake valves 9 indicated by a two-dot chain line in FIG. 6 so that the distances X from both the valves 9 are equal to each other.
Here, regarding the advantage of forming the fuel spray by the fuel injection from the fuel injection valve 11 as shown in the above [1] to [4], only the fan-shaped fuel spray spreading in the width direction of the combustion chamber 2 is formed. This will be described based on a comparison with the prior art.
[0048]
During the intake stroke of the engine 1, as described above, the air drawn into the combustion chamber 2 from the intake passage 7 is drawn toward the piston 6 and flows along the central axis direction of the combustion chamber 2. Therefore, conventionally, when fuel injection is performed in the intake stroke in order to perform homogeneous combustion, the air flowing as described above hits the fuel spray that spreads in a fan shape in the combustion chamber 2, and this spray is the top side of the piston 6 or combustion It is pressed against the inner wall side of the chamber 2. In this case, it becomes difficult for the fuel spray and the air to be mixed, and even after the transition from the intake stroke to the compression stroke, as shown by the two-dot chain line in FIG. It comes to exist.
[0049]
Accordingly, even when ignition is performed by the spark plug 12, the fuel-rich mixture in the combustion chamber 2 remains with the fuel-rich portion and the thin portion, and the homogeneity of the mixture during homogeneous combustion deteriorates. It becomes difficult to obtain good combustion of the air-fuel mixture. Further, if the heat in the fuel spray 2 is used to efficiently cool the air in the combustion chamber 2 to increase the charging efficiency of the air into the combustion chamber 2 and to improve the knock resistance, the combustion from the intake passage 7 occurs. When the flow rate of the air sucked into the chamber 2 is increased and the fuel is easily vaporized, the fuel spray must be formed. In this case, the fuel spray in the combustion chamber 2 is more easily pressed against the top of the piston 6 or the inner wall of the combustion chamber 2 due to the flow of air having a high flow velocity, and the above-described problem becomes significant.
[0050]
On the other hand, in this embodiment, when fuel injection is performed in the intake stroke to perform homogeneous combustion, the first and second fuel sprays 16 and 17 are in the combustion chamber during the same intake stroke as described above. 2 is formed. The formation of the first and second fuel sprays 16 and 17 is achieved by, for example, the flow rate of the air sucked into the combustion chamber 2 from the intake passage 7 in the intake stroke by the drive control of the fuel injection valve 11 by the electronic control unit 13. Done during the period of speed.
[0051]
Since the first fuel spray 16 has a fan shape that extends in the width direction of the combustion chamber 2, the air flowing along the central axis direction of the combustion chamber 2 causes the top of the piston 6 and the inner wall side of the combustion chamber 2 to move toward the top. Pressed down. However, since the second fuel spray 17 has a fan-like shape extending in the direction of the central axis of the combustion chamber 2 and the cross-sectional area in the width direction of the combustion chamber 2 is small, the head of the piston 6 when the air hits it. It is less susceptible to being pressed against the top side and the inner wall side of the combustion chamber 2.
[0052]
Therefore, by forming the second fuel spray 17 in the combustion chamber 2 during the intake stroke, the air-fuel mixture having a high fuel concentration remains on the top of the piston 6 and the inner wall side of the combustion chamber 2 so that the air-fuel mixture is homogeneous. The degree of deterioration can be suppressed. And it can suppress that favorable combustion is no longer obtained with the deterioration of the homogeneity of the air-fuel mixture at the time of homogeneous combustion.
[0053]
During the same intake stroke that the second fuel spray 17 is formed, a fan-shaped first fuel spray 16 that extends in the width direction of the combustion chamber 2 is also formed. Therefore, although the first fuel spray 16 is pressed against the top of the piston 6 and the inner wall of the combustion chamber 2 by the intake air during the intake stroke, the first fuel spray 16 causes the combustion chamber 2 to It becomes possible to promote the diffusion of fuel in the width direction.
[0054]
Further, the second fuel spray 17 that is less affected by the intake air flow is located at the position on the intake passage 7 side in the combustion chamber 2 than the first fuel spray 16 having the greater influence, that is, the intake stroke. It is formed upstream of the first fuel spray 16 in the flow of intake air. For this reason, when the first and second fuel sprays 16 and 17 are pushed to the top of the piston 6 and the inner wall of the combustion chamber 2 by the flow of the intake air, the first and second fuel sprays 16 and 16 17 is difficult to overlap. And it can suppress that the area | region where the fuel density | concentration is excessively deep in the combustion chamber 2 arises in connection with the 1st and 2nd fuel sprays 16 and 17 overlapping.
[0055]
Further, the second fuel spray 17 is formed between the two intake valves 9. Therefore, when the intake valve 9 opens during the intake stroke and protrudes into the combustion chamber 2, the second fuel spray 17 hits the intake valve 9, thereby causing uneven distribution of fuel in the combustion chamber 2 and mixing. It becomes possible to suppress the deterioration of the homogeneity of qi.
[0056]
Next, the difference in the combustion fluctuation rate of the air-fuel mixture between when the fuel spray is formed as in the prior art and when the fuel spray is formed as in the present embodiment will be described with reference to FIG.
[0057]
FIG. 8 is a graph showing how the combustion fluctuation rate of the air-fuel mixture changes with respect to changes in the fuel injection timing when fuel is injected during the intake stroke to perform homogeneous combustion. In the figure, the broken line indicates the transition of the combustion fluctuation rate with respect to the change in the fuel injection timing when the fuel spray is formed as in the conventional case, and the solid line indicates the fuel injection when the fuel spray is formed as in the present embodiment. It shows the change of the combustion fluctuation rate with respect to the change of time.
[0058]
As can be seen from this figure, in the period A in which the flow velocity of the air sucked into the combustion chamber 2 from the intake passage 7 becomes faster, the combustion fluctuation rate has deteriorated in the prior art (broken line), whereas in the present embodiment (solid line) ) Suppresses the deterioration of the combustion fluctuation rate. This is because, in the present embodiment, good combustion cannot be obtained due to the deterioration of the homogeneity of the air-fuel mixture described above in the period A, whereas in the present embodiment, the first and second fuel sprays 16 and 17 in the combustion chamber 2 are not possible. This is because the homogeneity of the air-fuel mixture in the period A is improved and good combustion is obtained. Therefore, in the period A, the fuel consumption rate is also deteriorated as the combustion fluctuation rate is deteriorated. In the present embodiment, the deterioration of the combustion fluctuation rate is suppressed, so that the fuel consumption rate is favorably maintained. Become.
[0059]
In FIG. 8, the two-dot chain line forms the second fuel spray 17 closer to the piston 6 than the first fuel spray 16, that is, closer to the first fuel spray 16 in the intake air flow. It shows the transition of the combustion fluctuation rate when As the injection hole shape of the fuel injection valve 11 in this case, for example, it can be considered as shown in FIG. The nozzle hole shape and the nozzle hole shape shown in FIG. 3 indicate whether the position of the second slit 15 is on one side of the widthwise sides of the first slit 14 or on the other side. The only difference is that.
[0060]
Even when the injection hole shape of the fuel injection valve 11 is as shown in FIG. 4, the combustion fluctuation of the air-fuel mixture is better in the period A than in the conventional case (broken line) as shown by the two-dot chain line in FIG. Thus, the fuel consumption rate is also improved compared to the conventional case, so that it is possible to adopt such a nozzle hole shape.
[0061]
According to the embodiment described in detail above, the following effects can be obtained.
(1) During the intake stroke during homogeneous combustion, not only the fan-shaped first fuel spray 16 spreading in the width direction of the combustion chamber 2 but also the fan-shaped second spreading in the direction of the central axis of the combustion chamber 2 is formed. The fuel spray 17 is also formed. With respect to the second fuel spray 17, the cross-sectional area in the width direction of the combustion chamber 2 is smaller than that of the first fuel spray 16. Therefore, when the air sucked into the combustion chamber 2 from the intake passage 7 during the intake stroke flows along the central axis direction of the combustion chamber 2 as the piston 6 moves and hits the second fuel spray 17, the fuel The influence that the spray 17 is pushed to the top of the piston 6 and the inner wall of the combustion chamber 2 is small. By forming the second fuel spray 17 in the combustion chamber 2 during the intake stroke in this way, a large amount of air-fuel mixture with a high fuel concentration remains on the top of the piston 6 and the inner wall of the combustion chamber 2 during homogeneous combustion. Thus, deterioration of the homogeneity of the air-fuel mixture can be suppressed. And it can suppress that favorable combustion cannot be acquired with the homogeneity deterioration of air-fuel | gaseous mixture.
[0062]
(2) During the same intake stroke that the second fuel spray 17 is formed, a fan-shaped first fuel spray 16 extending in the width direction of the combustion chamber 2 is also formed. Therefore, although the first fuel spray 16 is pressed against the top of the piston 6 and the inner wall of the combustion chamber 2 by the intake air during the intake stroke, the first fuel spray 16 causes the combustion chamber 2 to Fuel diffusion in the width direction can be promoted.
[0063]
(3) In the engine 1 in which fuel is directly injected into the combustion chamber 2, the heat of vaporization is deprived from the air in the combustion chamber 2 when the fuel spray formed in the combustion chamber 2 is vaporized. The air is cooled, so that there is an effect that the efficiency of filling the combustion chamber 2 with air is increased. With regard to such an effect, the maximum effect can be obtained by performing fuel injection when the flow velocity of the air sucked into the combustion chamber 2 from the intake passage 7 becomes the fastest and efficiently vaporizing the fuel spray. Therefore, by forming the first and second fuel sprays 16 and 17 in the period A in which the flow velocity of the intake air becomes the fastest during the intake stroke during homogeneous combustion, the fuel sprays 16 and 17 are efficiently vaporized. The above-described effects can be obtained at a high level.
[0064]
(4) The effect of receiving the flow of air sucked into the combustion chamber 2 from the intake passage 7 is greater in the first fuel spray 16 than in the second fuel spray 17. However, the second fuel spray 17 having a smaller influence is formed on the upstream side of the flow of the intake air than the first fuel spray 16. Therefore, when the first and second fuel sprays 16 and 17 are pushed to the top of the piston 6 and the inner wall of the combustion chamber 2 by the intake air flow, the first and second fuel sprays 16 and 17 are pressed. Are difficult to overlap. Accordingly, it is possible to suppress the occurrence of a region where the fuel concentration is excessively high in the combustion chamber 2 due to the overlapping of the fuel sprays.
[0065]
(5) Since the first and second slits 14 and 15 are formed as injection holes for injecting fuel into the fuel injection valve 11, the first and second fuel sprays 16 and 17 are made to be a single fuel injection valve 11. Can be formed accurately. Therefore, for example, the structure of the fuel injection device of the engine 1 can be simplified as compared with the case where a plurality of fuel injection valves are used to form the first fuel spray 16 and the second fuel spray 17, for example. An increase in cost due to the complexity of the structure can be suppressed.
[0066]
(6) Since the second slit 15 is formed on the upstream side of the flow of the intake air with respect to the first slit 14, the second fuel spray 17 is made to flow with the intake air more than the first fuel spray 16. Can be accurately formed on the upstream side.
[0067]
(7) The first slit 14 and the second slit 15 are formed so as to be separated from each other. Therefore, as in the case where the first and second slits 14 and 15 overlap each other, the fuel concentration of the portion corresponding to the overlapping portion in the fuel spray formed when fuel injection is performed is higher than the others. It is possible to suppress disadvantages in obtaining good combustion.
[0068]
(8) The second fuel spray 17 is formed between the two intake valves 9. Therefore, when the intake valve 9 opens during the intake stroke at the time of homogeneous combustion and protrudes into the combustion chamber 2, the second fuel spray 17 hits the intake valve 9, whereby the fuel is unevenly distributed in the combustion chamber 2. This can suppress the deterioration of the homogeneity of the air-fuel mixture.
[0069]
(9) Since the second fuel spray 17 is formed so as to have an equal distance X between the two intake valves 9, the second fuel spray 17 is placed on one of the two intake valves 9 for some reason. It is possible to avoid the second fuel spray 17 from hitting the intake valve 9 as much as possible when it is biased.
[0070]
In addition, the said embodiment can also be changed as follows, for example.
When the second fuel spray 17 is formed between the two intake valves 9, the distance between the second fuel spray 17 and the two intake valves 9 is not necessarily equal to each other.
[0071]
The present invention may be applied to an engine connected to the combustion chamber 2 with the intake passage 7 branched into three or more. In this case, the number of intake valves 9 corresponding to the number of branches of the intake passage 7 is provided for each combustion chamber 2, and the intake passages 7 and the combustion chambers 2 are communicated and blocked by opening and closing the intake valves 9. The The fuel injection valve 11 is attached to the engine 1 so that a second fuel spray 17 is formed between two adjacent intake valves 9 among the plurality of intake valves 9.
[0072]
-As FIG. 9 shows, the 1st slit 14 and the 2nd slit 15 in the fuel injection valve 11 may overlap.
As shown in FIG. 10, second slits 15 a and 15 b may be formed on both sides in the width direction of the first slit 14 in the fuel injection valve 11.
[0073]
The first fuel spray 16 and the second fuel spray 17 may be formed by separate fuel injection valves instead of the single fuel injection valve 11. Further, only one slit as a fuel injection nozzle hole may be provided in the fuel injection valve, and a mechanism capable of controlling the direction in which the fuel spray spreads by rotating the nozzle hole (fuel injection valve) may be provided. In this case, by rotating the fuel injection valve by 90 ° during the same intake stroke and performing fuel injection before and after the rotation, two types of fuel sprays with different directions of 90 ° are formed in the combustion chamber 2. Become so. In any of the above-described modifications, the timing for forming the first fuel spray 16 and the timing for forming the second fuel spray 17 can be appropriately shifted.
[Brief description of the drawings]
FIG. 1 is an enlarged sectional view showing the vicinity of a combustion chamber of an engine to which a fuel injection device and a fuel injection valve of an embodiment are applied.
FIG. 2 is a schematic diagram showing the shape of an intake passage of the engine.
FIG. 3 is a front view showing an injection hole shape of the fuel injection valve.
FIG. 4 is a front view showing another example of the injection hole shape of the fuel injection valve.
FIG. 5 is a side view showing the shape of fuel spray formed by fuel injection from a fuel injection valve.
FIG. 6 is a plan view showing the shape of fuel spray formed by fuel injection from a fuel injection valve.
FIG. 7 is an enlarged cross-sectional view showing fuel distribution in a combustion chamber when conventional fuel injection is performed.
FIG. 8 is a graph showing how the combustion fluctuation rate of the air-fuel mixture changes when the fuel injection timing is changed during fuel injection in the intake stroke.
FIG. 9 is a front view showing another example of the injection hole shape of the fuel injection valve.
FIG. 10 is a front view showing another example of the injection hole shape of the fuel injection valve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Combustion chamber, 3 ... Cylinder, 4 ... Cylinder block, 5 ... Cylinder head, 6 ... Piston, 6a ... Cavity, 7 ... Intake passage, 8 ... Exhaust passage, 9 ... Intake valve, 10 ... Exhaust valve DESCRIPTION OF SYMBOLS 11 ... Fuel injection valve, 12 ... Spark plug, 13 ... Electronic control unit, 14 ... 1st slit, 15 ... 2nd slit, 16 ... 1st fuel spray, 17 ... 2nd fuel spray.

Claims (10)

In a fuel injection device for an internal combustion engine that directly injects fuel into a combustion chamber in which air is sucked from an intake passage,
Fuel injection means for forming a fan-shaped first fuel spray spreading in the width direction of the combustion chamber and a fan-shaped second fuel spray spreading in the central axis direction of the combustion chamber in the same intake stroke ;
The fuel injection device for an internal combustion engine, wherein the fuel injection means forms the second fuel spray on an upstream side of the flow of the intake air with respect to the first fuel spray . The fuel injection device for an internal combustion engine according to claim 1, wherein the fuel injection means forms the first fuel spray and the second fuel spray simultaneously. The fuel injection means forms the first fuel spray and the second fuel spray at the same time when the flow velocity of the air sucked into the combustion chamber from the intake passage becomes the fastest. A fuel injection device for an internal combustion engine as described. The fuel injection means may be injection to spread the fuel in the width direction of the combustion chamber, therewith claims 1 to 3 comprising a single fuel injection valve for simultaneously injecting to spread the fuel in the central axis direction of the combustion chamber The fuel injection device for an internal combustion engine according to any one of the above. The internal combustion engine according to claim 4 , wherein the fuel injection valve injects fuel from a first slit extending in a width direction of the combustion chamber and a second slit extending in a central axis direction of the combustion chamber . Fuel injection device. The fuel injection device for an internal combustion engine according to claim 5, wherein the second slit is formed on the upstream side of the flow of the intake air with respect to the first slit . The fuel injection device for an internal combustion engine according to claim 5 or 6, wherein the first slit and the second slit are formed so as not to overlap each other . The intake passage is connected to the combustion chamber in a state of being branched into a plurality of, and a plurality of intake valves that open and close to communicate and block between the intake passage branched into the plurality of combustion passages and the combustion chamber. wherein said fuel injection means is a fuel injection system for an internal combustion engine according to any one of claims 1 to 7, the second fuel spray formed between the two intake valves adjacent of the plurality of intake valves . A fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine,
  The first and second slits for injecting the fuel extend in directions orthogonal to each other, and the second slit is located upstream of the flow of intake air of the internal combustion engine from the first slit. Formed to be located
  The fuel injection valve characterized by the above-mentioned. The fuel injection valve according to claim 8, wherein the first slit and the second slit are formed so as not to overlap each other .

Images