JP3888579B2 - Fuel injection nozzle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection nozzle that injects fuel into a combustion chamber in a direct injection internal combustion engine.
[0002]
[Prior art]
The fuel injection nozzle is for injecting fuel spray in an internal combustion engine such as an automobile engine. A nozzle body having a valve seat and a fuel passage and a nozzle front chamber as a kind of fuel injection nozzle, a needle valve having a valve portion movably disposed in the nozzle body, and a plurality of orifices attached to the nozzle body Some of them consist of orifice plates.
[0003]
In the fuel injection nozzle, atomization of the spray injected from the orifice is important from the viewpoint of reducing fuel consumption and improving exhaust emission. In particular, in an in-cylinder injection engine in which spray is directly injected into the combustion chamber and the combustion mode is switched according to the operating state, high atomization is required.
[0004]
The in-cylinder injection engine is also required to be able to change the shape of the spray (mainly determined by the length of the spray, that is, the reaching distance and the injection direction) according to the combustion mode. That is, in the homogeneous combustion mode in which the spray and air are mixed to make the same air-fuel ratio in the combustion chamber, it is necessary that the spray is largely diffused throughout the combustion chamber and the reach distance is long. Since the air-fuel mixture in which fuel and air are sufficiently mixed is ignited, combustion proceeds smoothly and high output can be obtained. On the other hand, in the stratified combustion mode in which a dense layer of spray is formed around the spark plug in the combustion chamber and a thin layer is formed in other portions, it is desirable that the spray does not diffuse so much and the reach is short.
[0005]
However, it is difficult to satisfy all the above requirements with swirl spray or slit spray. Therefore, a fuel injection nozzle including a plate having a large number of orifices has been developed. For example, a fluid ejecting nozzle disclosed in JP-A-11-70347 is known. In this fluid injection nozzle, the annular seat diameter of the contact portion seated on the valve seat is Ds, the pitch between the orifices on the opposing surface of the plate is Dh, the hole diameter of the orifice is d, and the annular seat with the contact portion of the valve seat When the vertical distance from the head to the facing surface is H and the distance from the tip surface to the facing surface when the needle valve is lifted is h, 1.5 <Ds / Dh <6, h <1.5d, H <4d Meet. Thereby, the fuel collides on each orifice while suppressing a decrease in the internal energy of the fuel flow, resulting in atomized spray.
[0006]
[Problems to be solved by the invention]
However, the fluid injection nozzle has been developed for a normal gasoline engine that is injected into the intake system, and cannot be used for a direct injection gasoline engine. The atmospheric pressure differs greatly between the intake system of a normal gasoline engine and the combustion chamber of a direct injection gasoline engine, and the conditions for atomization are different. Moreover, since spray is usually injected into the intake system in a gasoline engine, its shape and length are not a problem.
[0007]
A fuel injection nozzle for an in-cylinder injection gasoline engine including an orifice plate having a plurality of orifices is also known. However, there is no known fuel injection nozzle that is excellent in atomization of fuel and can obtain a desired spray shape.
[0008]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a fuel injection nozzle for an in-cylinder injection gasoline engine that is excellent in atomization in a homogeneous combustion mode and a stratified combustion mode and that can obtain a desired spray shape. To do.
[0009]
[Means for Solving the Problems]
The inventor of the present application describes the shape of the nozzle front chamber formed between the lower end surface of the needle valve and the bottom of the orifice plate, the diameter of the orifice, and the thickness of the orifice plate in the fuel injection nozzle used in the cylinder injection engine. And the relationship between fuel atomization and spray shape (particularly spray length). As a result, the present invention has been completed by finding that there is a certain relationship between them and that the high atomization of this relationship is a premise for obtaining a desired spray shape.
[0010]
That is, the fuel injection nozzle according to the present invention includes a nozzle body in which an annular valve seat is formed on the inner peripheral wall surface, and an annular valve portion on the outer peripheral wall surface facing the inner peripheral wall surface. A needle valve that is formed and moved in the axial direction so that the valve portion is attached to and detached from the valve seat; a bottom portion that is formed with a plurality of orifices and that faces the lower end surface of the needle valve; and an attachment portion that is attached to the nozzle body And a flat nozzle front chamber is formed between the lower end surface of the needle valve and the bottom of the orifice plate. In the fuel injection nozzle used in such a direct injection internal combustion engine , each orifice has a throttle portion on the fuel inflow side and a separation promoting portion on the outflow side, and the separation promoting portion is a half circumference on the outer peripheral side of each orifice. It consists of a hollow formed only over the top.
According to this fuel injection nozzle, the throttle portion suddenly changes the flow direction of the fuel to throttle the flow rate. Further, the peeling promoting portion positively peels off the fuel flow from the orifice.
[0011]
The fuel injection nozzle according to claim 2 is the fuel injection nozzle according to claim 1, wherein the height of the nozzle front chamber when the valve portion is separated from the valve seat is h, the thickness of the orifice plate is t, and the hole diameter of the orifice is d. Then, d / 4 <h <2d and 0.5 ≦ t / d ≦ 2.0.
In this fuel injection nozzle, since the height h of the nozzle front chamber and the hole diameter d of the orifice have a relationship of d / 4 <h <2d, the entire nozzle front chamber becomes flat. In this flat nozzle front chamber, the fuel flows in the horizontal direction from the outer peripheral side toward the inner peripheral side. After that, it collides isotropically directly above the orifice, and it becomes easy to break up, and atomization is promoted.
[0012]
Further, since the thickness t of the orifice plate and the hole diameter d of the orifice are in a relationship of 0.5 ≦ t / d ≦ 2.0, the atomization of the fuel is achieved and the fuel is moved from the orifice in the axial direction thereof. It is injected and the injection direction is regulated.
[0013]
A fuel injection nozzle according to a third aspect is the fuel injection nozzle according to the first aspect, wherein the plurality of orifices are formed on a circle having a predetermined radius centered on the center of the bottom. According to this fuel injection nozzle, it is easy to form an orifice, and a spray of a hollow cone shape is formed.
[0014]
A fuel injection nozzle according to a fourth aspect is the fuel injection nozzle according to the first aspect, wherein the distance between the plurality of adjacent orifices is 1.5 d or more. According to this fuel injection nozzle, since there is an annular space around the adjacent orifice, the horizontal flows in the nozzle front chamber collide with each other, so that atomization is further promoted.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
A fuel injection nozzle according to the present invention includes a nozzle body having a fuel passage and a valve seat, a needle valve having a valve portion that is movably disposed in the axial direction in the nozzle body, and an orifice plate having a plurality of orifices. Including the first type and the second type according to the configuration of the orifice.
<First type>
In the first type, the plurality of orifices on the bottom of the orifice plate have the same hole diameter. For example, the plurality of orifices can be arranged at equal or different intervals in the circumferential direction on a circle having a center at the center of the bottom. It can also be arranged in a grid on the bottom.
[0026]
It is desirable that the axes of the plurality of orifices be inclined with respect to the bottom axis so as to be radially outward as they proceed from the upstream side to the downstream side. The inclination angle of each orifice may be the same or different. The axis of the orifice may be parallel to the axis of the bottom. For example, when it is desired to form a spray in which the axial direction of the spray is different from the axial direction of the fuel injection nozzle in the combustion chamber, the axial direction of all or some of the orifices can be directed to that direction.
<Second type>
On the other hand, in the second type fuel injection nozzle, at least two kinds of orifices having different hole diameters are formed at the bottom. When the orifices having different hole diameters are arranged at the bottom, it is desirable to arrange the first orifice having a large hole diameter on the center side of the bottom and the second orifice having a small hole diameter on the peripheral side. However, the second orifice may be arranged on the center side and the first orifice may be arranged on the peripheral side.
[0027]
For example, the first orifice is arranged on the first circle having the center at the center of the bottom at equal intervals or different intervals in the circumferential direction, and the second orifice is circled on the second circle having the center at the center of the bottom. They can be arranged at equal intervals or different intervals in the circumferential direction. Also, the first orifice and the second orifice can be arranged in a grid on the bottom. The diameter of the second circle can be about 1.2 to 2.0 times the diameter of the first circle.
[0028]
The sum of the opening areas of the plurality of first orifices may be the same as or different from the sum of the opening areas of the plurality of second orifices. It is desirable that the axes of the plurality of first orifices and the axes of the plurality of second orifices be inclined with respect to the axis of the bottom so as to be radially outward from the upstream side to the downstream side. The inclination angle of each first orifice and each second orifice may be the same or different. The first and orifice axes may be parallel to the bottom axis.
[0029]
For example, when it is desired to form a spray in which the axial direction of the spray is different from the axial direction of the fuel injection nozzle in the combustion chamber, the whole or part of the first and second orifices can be directed in that direction. Further, the inclination angle of the first orifice and the inclination angle of the second orifice may be the same or different.
<Relationship between height h of nozzle front chamber and hole diameter d of orifice>
The height h of the nozzle front chamber is larger than a quarter of the hole diameter d of the orifice and smaller than twice (d / 4 <h <2d). the relationship of h = d / 4 was determined from the πd ^2/4 = πdh. If the height h of the nozzle front chamber is smaller than a quarter of the hole diameter d, the nozzle front chamber becomes very flat, and the peripheral edge of the bottom that defines the inlet portion of the orifice acts as a throttle. On the other hand, when the height h of the nozzle front chamber is larger than twice the orifice hole diameter d, the flatness of the nozzle front chamber is reduced, and the horizontal flow of fuel is not formed, and the collision directly above each orifice is weakened. .
<Relationship between orifice diameter d and orifice plate thickness t>
The ratio of the orifice plate thickness t to the orifice diameter d is preferably greater than 0.5 and less than 2 (0.5 ≦ t / d ≦ 2.0). In other words, the thickness t is larger than half of the hole diameter d and smaller than twice (0.5d ≦ t ≦ 2.0d).
[0030]
The value of t / d increases when the thickness t is thick and when the hole diameter d is small, thereby improving atomization but reducing the spray directionality. On the other hand, the value of t / d becomes small when the thickness t is thin and when the hole diameter d is large, thereby improving the directionality of spraying but reducing atomization. If t / d is in the range of 0.5 to 2.0, both atomization and directionality are satisfied.
[0031]
【Example】
Embodiments of the present invention will be described below with reference to the accompanying drawings.
(In-cylinder injection gasoline engine)
As shown in FIG. 1, the cylinder injection gasoline engine includes a cylinder 10, a piston 20, a fuel injection valve 30, and a spark plug 25. Among these, the cylinder 10 has a cylindrical main body portion 11 and a head portion (head portion) 12 attached to the upper end opening thereof, and defines a combustion chamber 18. The suction port 13 and the exhaust port 14 formed in the head portion 12 are opened and closed by a suction valve 16 and an exhaust valve 17, respectively.
[0032]
The piston 20 has a cylindrical shape and is slidably fitted on the main body 11 of the cylinder 10. The top surface 21 of the piston 20 is not formed with a cavity as in the conventional example, but is flat. The fuel injection valve 30 is attached to the shoulder portion on the suction port 13 side at a predetermined angle with respect to the main body portion 11, and the axis thereof extends to the central portion of the top surface 21 of the piston 20. The spark plug 25 is attached to the center portion of the head portion 12.
(Fuel injection nozzle)
The fuel injection nozzle 31 whose main part is shown in FIG. 2 includes a nozzle body 32, a needle valve 38, and an orifice plate 45.
[0033]
The nozzle body 32 includes an inner peripheral wall 34 that defines a fuel passage 33 and an annular valve seat 35 formed thereon. The needle valve 38 includes an outer peripheral wall 39 that faces the inner peripheral wall 34, and an annular valve portion 41 that is formed thereon and can be seated on the valve seat 35. When the needle valve 38 is moved in the axial direction in the nozzle body 32, the valve portion 41 is seated on or separated from the valve seat 35.
[0034]
As shown in FIGS. 2 and 3, the orifice plate 45 is made of a thin metal plate and includes a bottom portion 46 and a mounting portion 49 . The bottom portion 46 includes a plurality of orifices (injection holes) 47 and 48 facing the downstream side opening of the nozzle front chamber 33, and is attached to the nozzle body 32 at an attachment portion 49. A nozzle front chamber 43 is formed between the needle valve 38 and the orifice plate 45, which will be described later.
[0035]
Four orifices 47 are formed on an inner circle R ₁ of radius r ₁ having a center O at the center of the bottom 46. The inner circle R ₁ is equally divided into four in the circumferential direction, and orifices 47 are formed on a pair of orthogonal diameters (four locations), and are arranged at equal intervals in the circumferential direction. Each orifice 47 has a hole diameter d ₁ and is inclined so as to proceed outward in the radial direction as it proceeds from the upper surface 46 a of the bottom 46, that is, the upstream side, to the lower surface 46 b, that is, the downstream side. The axis l ₁ of the orifice 47 forms a predetermined angle θ ₁ with respect to the axis L of the bottom 46.
[0036]
Further, eight orifices 48 are formed on an outer circle R ₂ having a center O at the center of the bottom 46 and having a radius r ₂ larger than the radius r ₁ . On the two radii that divide the quadrant divided by the pair of orthogonal diameters into three equal parts, a total of eight orifices 48 are arranged at equal intervals in the circumferential direction. Each orifice 48 has a hole diameter d ₂ smaller than the hole diameter d ₁ , and is formed so as to proceed outward in the radial direction from the upstream side to the downstream side, and its axis l ₂ has an angle θ _{2 with} respect to the axis L. (Same as the angle θ ₁ described above).
[0037]
As a result, two orifices 47 or two orifices 48 are located on any of the six diameters. The case where the orifice 47 on the inner circle R ₁ and the outer circle orifice 48 on the R ₂ adjacent, and a case where the orifice 48 with each other on the outer circle R ₂ adjacent.
[0038]
As shown in FIG. 4, a circular and flat nozzle front chamber 43 is formed between the lower end surface 38 a of the needle valve 38 and the bottom 46 of the orifice plate 45. The height of the nozzle antechamber 43 (axial length) h equals hole diameter d ₂ of the orifice 47 (h = d _2). The thickness t of the bottom 46 of the orifice plate 45 is equal to the hole diameter d _{1 of the} orifice 47 (t = d ₁ ).
[0039]
As shown in FIGS. 5A and 5B, a throttle portion 47 a is formed on the inlet side of the orifice 47. The throttle portion 47a is defined by a portion on the upstream side of the plane p that passes through the outer edge of the orifice 47 and is orthogonal to the axis l1. Further, as shown in FIGS. 5A and 5C, a separation promoting portion 47 b is formed on the outlet side of the orifice 47. In separation promoting portion 47b downstream of the said plane p, it consists of a recess formed in substantially the same inner diameter as hole diameter d ₁ over a half of the outer peripheral side of the orifice 47.
[0040]
Although not shown, the throttle portion of the same to the orifice 48 on the outer circle R ₂ and separation promoting portion is formed.
(Function and effect)
In FIG. 1, during homogeneous combustion, gasoline is directly injected into the combustion chamber 18 from the fuel injection valve 30 during the intake process, that is, when the piston 20 is lowered. Since the atmospheric pressure is relatively low (about 0.1 MPa), the spray 19 is dispersed almost uniformly throughout the combustion chamber 18, and the air-fuel mixture is ignited by the spark plug 25.
[0041]
In contrast, during stratified combustion, gasoline is injected into the combustion chamber 18 during the compression step, that is, when the piston 20 is raised. At this time, the atmospheric pressure in the combustion chamber 18 is relatively high (about 0.5 MPa). Therefore, as shown in FIG. 1, the spray 19 spreads in a conical shape, and the tip thereof reaches the vicinity between the center portion of the top surface 21 of the piston 20 and the spark plug. The spray 19 is mixed with air sucked from the intake port 13 and ignited by a spark plug 25.
[0042]
According to the present embodiment, the following effects can be obtained in the homogeneous combustion mode and the stratified combustion mode.
[0043]
First, high atomization of gasoline is achieved for three reasons.
[0044]
The first reason is due to the formation of the nozzle front chamber 43 having a predetermined shape. That is, the nozzle front chamber 43 that is circular and extends in the horizontal direction exists between the lower end surface 38 a of the needle valve 38 and the upper surface 46 a of the bottom 46 of the orifice plate 45, and the height thereof is equal to the hole diameter d _{1 of the} orifice 47. (H = d ₁ ). As a result, the gasoline becomes a horizontal flow that flows in the nozzle front chamber 43 from the outside in the radial direction toward the inside, collides with each other immediately above the orifices 47 and 48, changes the flow direction to the orifices 47 and 48, and atomizes. Promoted.
[0045]
The second reason is that an annular space is secured around the orifices 47 and 48. The orifices 47 and 48 are arranged apart from each other by a predetermined distance or more in any adjacent combination. As a result, a space in which the horizontal flows can collide with each other around the orifices 47 and 48 is secured.
[0046]
The third reason is that the orifices 47 and 48 are formed with a throttle part 47a and the like, and a separation promoting part 47b and the like. The restricting portion 47a forms an acute angle with respect to the flow direction of gasoline from the outer peripheral side toward the central portion in the nozzle front chamber 43, and the flow direction is rapidly changed to restrict the flow rate. Further, the peeling accelerating portion 47b or the like actively peels off the gasoline flow from the inner peripheral surface when the gasoline flows out from the orifices 47 and 48. As a result, a gasoline liquid film is formed and is easily atomized.
[0047]
Secondly, the spray reach distance (spray length) can be independently changed between the orifice 47 and the orifice 48, and a solid spray can be formed. The change of the reach distance is because the hole diameter of the orifice 47 on the inner circle R ₁ is increased and the hole diameter of the orifice 48 on the outer circle R ₂ is decreased.
[0048]
A relatively large amount of gasoline is injected from the orifice 47 having a large hole diameter, and the reach distance on the inner peripheral side (center side) of the spray becomes longer. On the other hand, a relatively small amount of gasoline is injected from the orifice 48 having a small hole diameter, and the reach distance on the outer peripheral side (peripheral side) is shortened. As a result, in both the homogeneous combustion mode and the stratified combustion mode, the length on the center side of the spray is long and the length on the peripheral side is short. The spray having such a shape is convenient because wet is hardly generated on the inner peripheral surface of the cylinder 10.
[0049]
In the formation of the solid-shaped spray, the opening area of each orifice 47 is made equal, the opening area of each orifice 48 is made equal, and then the total opening area of four orifices 47 and the opening area of eight orifices 48 are formed. This is because the sum of As a result, the flow rate of the spray injected from the four orifices 47 on the inner peripheral side and the flow rate of the spray injected from the eight orifices 48 on the outer peripheral side became substantially equal.
[0050]
Third, a desired injection direction of the spray can be obtained in the combustion chamber 18. This is because the thickness t of the bottom 46 and the hole diameter of the orifice 47 are made equal to d ₁ , and the inclination angle θ ₁ of the inner orifice 47 is made equal to the predetermined inclination angle θ _{2 of the} outer orifice 48. by.
[0051]
The bottom 46 having a thickness t equal to the hole diameter d _{1 of the} orifice 47 can satisfy both atomization of the spray and injection directionality of the spray. By making the inclination angles equal between the orifices 47 and 48, it is difficult to form a gap between the annular spray formed by the orifice 47 and the annular spray formed by the orifice 48.
[0052]
Fourth, the strength of the bottom 46 can be ensured despite the formation of a large number of orifices 47 and 48. The orifices 47 and 48 are arranged so that there are only two orifices on any diameter passing through the center O of the bottom 46. Therefore, even if a large number of orifices 47 and 48 are formed, the strength of the bottom 46 does not become insufficient (if three or more orifices 47 and 48 are arranged on the same diameter, these orifices are perforated). And the bottom 46 is likely to break along the diameter).
[0053]
【The invention's effect】
Described so as have, according to the present invention, there is a relationship between the pore diameter d of the height h and the orifice of the nozzle front chamber d / 4 <h <2d, also the pore size of the thickness t and the orifice of the orifice plate d has a relationship of 0.5 ≦ t / d ≦ 2.0. As a result, the fuel collides in the centripetal direction directly above the orifice in the nozzle front chamber, and then the flow direction is suddenly changed toward the orifice to promote atomization. Further, the fuel is injected from the orifice in the axial direction, and the injection direction is regulated.
[0054]
In addition to the above advantages, spray injected from the large diameter of the orifice by attaching a difference in pore size of the plurality of orifices is long, the length of the spray injected from the small orifice can Shorten. As a result, a desired spray shape can be realized by combining the size of the orifice diameter and the axial direction of the orifice.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a direct injection gasoline engine in which a fuel injection nozzle is used.
FIG. 2 is a longitudinal sectional view of an essential part showing an embodiment of a fuel injection nozzle of the present invention.
FIG. 3 is a bottom view of FIG. 2, showing the bottom of the orifice plate.
4 is an enlarged view of a main part of FIG.
5A is an enlarged view of a main part of FIG. 4, FIG. 5B is an XX sectional view in FIG. 4A, and FIG. 5C is a YY sectional view in FIG.
[Explanation of symbols]
31: Fuel injection nozzle 32: Nozzle body 35: Valve seat 38: Needle valve 41: Valve part 45: Orifice plate 46: Bottom part 47, 48: Orifice 47a: Restriction part 47b: Separation promoting part (recess)
49: Mounting part

Claims (4)

A nozzle body in which an annular valve seat is formed on the inner peripheral wall surface;
An annular valve portion is formed on the outer peripheral wall surface facing the inner peripheral wall surface, and the valve portion is separated from and seated on the valve seat by being moved in the axial direction;
An orifice plate including a bottom portion formed with a plurality of orifices and facing a lower end surface of the needle valve; and an attachment portion attached to the nozzle body;
A fuel injection nozzle used in a cylinder injection internal combustion engine, wherein a flat nozzle front chamber is formed between a lower end surface of the needle valve and a bottom portion of the orifice plate,
Each of the orifices is provided with a throttle portion on the fuel inflow side and a separation promoting portion on the outflow side, and the separation promoting portion is formed by a depression formed only on the outer circumference side of each orifice. Fuel injection nozzle. H the height of the nozzle antechamber in unseated when from the valve seat before Kiben portion, when the thickness of the bottom t, the diameter of the orifice was d, d / 4 <h < 2d, and a fuel injection nozzle according to 0.5 ≦ t / d ≦ 2.0 der Ru claim 1. The fuel injection nozzle according to claim 1, wherein the plurality of orifices are arranged on a circle centering on a center of the bottom portion.  The fuel injection nozzle according to claim 1, wherein a distance between the plurality of adjacent orifices is 1.5 d or more.

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