JP3028863B2 - Fuel injection valve - 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 injection valve used for a fuel injection device for injecting fuel into an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine, it is required to control the amount of fuel injected per unit time, that is, the injection rate. In response to this request, for example, British Patent No. 22263
No. 62, the method of controlling the lift amount of the needle valve of the injection nozzle to change the injection rate, or, as shown in German Patent Publication No. There is known a method in which the control is made to be chemically variable. As a conventional fuel injection nozzle, for example, there is a standard nozzle as shown in FIG.

[0003]

However, when a conventional standard nozzle is used in the method disclosed in British Patent No. 2,226,362, the actual injection pressure as the pressure at the injection hole inlet decreases, and the spray particles become coarser. There is a problem that the penetration force is insufficient. This publication also proposes an improved shape of the suckless nozzle. However, this shape cannot effectively use the injection hole area at the maximum lift of the needle valve. There is a problem that the loss increases. Also, German Published Patent No. 39053
The injection nozzle disclosed in Japanese Patent Publication No. 91 has a problem that not only is the needle tip complicated and difficult to manufacture, but also it is difficult to control the injection hole area to be variable and the size of the entire injection valve becomes large.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a fuel in which the injection characteristics are improved without lowering the actual injection pressure even if the injection rate is controlled by needle lift control. An injection valve is provided.

[0005]

A fuel injection valve according to a first aspect of the present invention has a first conical surface formed at a predetermined angle inside a front end thereof, and a predetermined conical surface formed on the front end side of the first conical surface. angle
A second conical surface formed without a formation and a valve body having an injection hole formed in communication with the outside from the inside of the second conical surface, a columnar shaft body, a distal end of the cylindrical shaft member is, the first without the angle smaller than the conical surface, a first inclined surface forming a tangent to the lower end face is Hanaregi said first conical surface, formed at the tip of the first inclined surface, the first A second inclined surface having an angle substantially equal to the conical surface, the needle valve being movably disposed in the valve body, and having an effective flow area of the injection hole inlet in accordance with a lift amount. A needle valve which is variable, wherein the needle valve is opened when fuel is pressure-fed into the valve body, and fuel is injected from the injection hole.

In a fuel injection valve according to a second aspect of the present invention, the tip of the needle valve is located on the extension of the central axis of the injection hole, and when the needle valve is closed, the tip of the needle valve and the injection hole of the injection hole are closed. It is characterized in that a predetermined distance from the entrance is set.

In a fuel injection valve according to a third aspect of the present invention, the distance L between the needle valve and the injection hole inlet is 0.1 to 0.1.
It is characterized by being in the range of 3 mm.

In a fuel injection valve according to a fourth aspect of the present invention, a plurality of injection holes having different inclination angles are formed in the valve body, and the injection holes having a large inclination angle with respect to the central axis of the valve body are provided. 2. The fuel injection valve according to claim 1, wherein a hole is opened at a position on the tip side of the first conical surface.

[0009]

According to the fuel injection valve of the present invention, the nozzle is formed in such a manner that the nozzle injection hole area can be varied according to the needle lift based on the fluid dynamics theory, and the suck chamber volume is kept small. When the injection rate is controlled by the lift control, the spray characteristic is improved without reducing the actual injection pressure.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 show a first embodiment of a fuel injection nozzle of the present invention applied to a fuel injection device for a diesel engine.
As shown in FIG. 2, a piston 4 is slidably provided in a cylinder liner 5 fitted to the cylinder block 3 of the diesel engine 1, and the top surface of the piston 4, the inner peripheral surface of the cylinder liner 5, and the cylinder The combustion chamber 6 at the bottom with the head 2
Is defined. A fuel injection device 10 including a nozzle body 14 as a valve body and a nozzle holder 12 is attached to the cylinder head 2.
The tip of 4 is arranged in the combustion chamber 6.

As shown in FIG. 3, the fuel injection device 10 comprises:
Nozzle holder 12, nozzle body 14, and needle valve 15
The nozzle body 14 is held by the retaining nut 13 through the tip packing 16.
Is fixed to the end face 12a. A nozzle spring 19 is housed in a nozzle spring chamber 22 formed in the nozzle holder 12, and the urging force of the nozzle spring 19 pushes the pressure pin 17 downward in FIG. I'm going. The tip packing 16 regulates the maximum lift amount of the needle valve 15, and the rotation position with respect to the nozzle holder 12 is fixed by a lock pin 18. In the space around the needle valve 15 housed in the nozzle body 14, the high pressure side communicates with the high pressure fuel passage 20, and the low pressure side communicates with the fuel release passage 21 from the nozzle spring chamber 22 via the pin hole 16a. When high-pressure fuel is pumped from the high-pressure fuel passage 20, when the pressure of the fuel overcomes the spring set pressure of the nozzle spring 19, the needle valve 15 is lifted and fuel is injected from the injection holes 28 and 29 shown in FIG. . When the fuel pressure becomes equal to or lower than the set pressure of the nozzle spring 19, the needle valve 15 is seated, and the fuel around the needle valve 15 is released from the nozzle spring chamber 22 to the fuel release passage 21 through the pin hole 16a.

The tip of the nozzle body 14 is composed of a nozzle body 14 and a needle valve 15, as shown in FIG. 1. The needle valve 15 is inserted into the nozzle body 14 movably upward from a position shown in the figure. As shown in FIG. 3, the large-diameter portion 15a is held in the radial direction by the guide hole 14a. The nozzle body 14, as shown in FIG.
A cylindrical hole 24, a first conical surface 25 as a seat surface, a second conical surface 26, and injection holes 28 and 29 for communicating the inside and the outside of the spherical concave surface 27 are formed. The angle δ ₁ formed by the injection hole 28 with the central axis X is set smaller than the angle δ ₂ formed by the injection hole 29 with the central axis X. The injection holes 28 and 29 are formed on the second conical surface 26.

The needle valve 15 has a cylindrical shaft 31, a first inclined surface 32 having an angle β ₁ smaller than an angle α ₁ of the first conical surface 25 of the nozzle body 14, and an annular shape contacting the first conical surface 25. The angle α ₁ of the first conical surface 25 with respect to the tangent line 34
The second inclined surface 33 having a slightly larger angle β ₂ is formed continuously. Injection hole 28,
29 is the second inclined surface 33 of the needle valve 15 and the injection hole 28,
The nozzle body 14 is open so that the distances La and Lb from the inlet 29 are set to predetermined values. This predetermined value is to set the flow coefficient at each injection hole inlet to a predetermined value by utilizing the pressure loss due to branching and bending of the injection holes 28 and 29. When high-pressure fuel is supplied from a fuel injection pump (not shown) into the cylindrical hole 24 of the nozzle body 14, the needle valve 15 is opened (upward in FIG. 1) by the fuel pressure.
3 and is pushed in the valve closing direction (downward in FIG. 1) by the nozzle spring 22 shown in FIG.

Next, the operation of the fuel injection nozzle will be described. When the lift amount of the needle valve 15 is small, the flow coefficient is set small, and the effective injection hole area is smaller than the geometric area of the injection hole. At this time, the second inclined surface 33 and the injection hole 2
The effective injection hole area can be set from the minimum flow path area between the inlets of 8, 29, so that the actual injection pressure can be increased by recovering the pressure loss due to the seat portion, and the injection rate can be kept low without deteriorating the spray quality. Can be.

If the lift amount of the needle valve 15 is further increased, when the seat area becomes sufficiently large, the injection hole 2
The distances La and Lb between 8, 29 and the second inclined surface 33 are sufficiently large, and the flow coefficient at the injection hole inlet becomes a large value. Then, since the entire injection hole area is used effectively, there is no pressure loss and a high injection rate can be obtained. By having such a shape and positional relationship of the fuel injection nozzle, the fuel injection nozzle can be controlled by changing the lift amount of the needle valve 15.
To change the geometrical position between the nozzles and the orifices 28, 29, causing a change in the fluid properties and changing the effective orifice area. In addition, the spray form based on the difference in the opening angle between the injection holes 28 and 29 can be corrected by changing the opening position, and the difference can be provided.

Next, a comparison between the first embodiment (Example 1) and the conventional comparative examples 1 and 2 is as follows. Fuel injection nozzle 4 according to comparative example 1 shown in FIG.
Numeral 0 is a standard nozzle type having a cylindrical sack chamber 41, and there is a relatively large distance between the tip conical surface 42 formed on the needle valve 15 and the inlets of the injection holes 28 and 29. . This distance has little effect on the flow coefficient μ _H of the injection holes 28 and 29, and in this standard nozzle type fuel injection nozzle, μ _H = 1. FIG. 11 is a diagram in which the standard nozzle type fuel injection nozzle 40 is fluidly modeled.
In this case, the pressure P _S of the suck chamber 41 and the pressure P _D of the nozzle chamber 43 have a relational expression of Formula 1.

[0017]

(Equation 1)

Here, P _D : nozzle chamber pressure, P _S : suck chamber pressure, P _Z : combustion chamber pressure, μ _D : flow coefficient of seat part, μ _H :
Nozzle hole flow rate coefficient, F _D: seat passage area, F _H: a hole area. Since the injection hole area F _H is constant, the pressure ratio P _S
/ P _D is influenced by the seat passage area F _D. FIG.
The injection hole area F _H as shown in, because changes in accordance with the lift amount of the needle valve 15, the pressure ratio P _S / P _D varies with the lift of the needle valve 15.

The fuel injection nozzle 50 according to the second comparative example shown in FIG. 13 is of a VCO nozzle type. The injection holes 28 and 29 are opened in the conical surface 51 of the nozzle body 14 and when the needle valve 15 is closed. The distance between the second inclined surface 33 of the needle valve 15 and the inlets of the injection holes 28 and 29 is almost zero.

Next, FIG. 4 shows the measurement results of the relationship between the needle lift and the injection hole flow rate coefficient in Comparative Examples 1 and 2 and Example 1. As shown in FIG. 4, Comparative Example 1
Shows that the injection hole flow rate coefficient μ _H is almost constant without substantially affecting the lift amount of the needle valve 15, and the comparative example 2 and the example 1
Is the injection hole flow coefficient μ according to the lift amount of the needle valve 15.
_H changes. This amount of needle lift is
FIG. 5 shows a graph obtained by substituting the distance L between the nozzle holes 28 and 29 (the distance between the needle valve and the injection hole entrance). Needle valve and the nozzle hole inlet distance L is in relation to the nozzle hole flow rate coefficient mu _H, a relationship shown in FIG. As shown in FIG. 5, when the distance L between the needle valve and the injection hole inlet becomes a distance of about 0.3 mm or less, the injection hole flow coefficient μ _H of Comparative Example 2 and Example 1 gradually decreases. This is because various types of pressure loss, particularly branch loss and bending loss, change as a function of the distance L between the needle valve and the injection hole inlet in this case.

[0021] The results of needle lift and the relationship between the pressure ratio P _S / P _D and Comparative Example 1 and Comparative Example 2 versus Example 1 in FIG. 6. As shown in FIG. 6, when the amount of needle lift is small, Example 1 exhibits a high pressure ratio P _S / P _D than Comparative Example 1. According to this result, according to the fuel injection nozzle of the first embodiment, the injection rate can be reduced by reducing the injection hole flow coefficient μ _H at the time of the small lift of the needle valve 15, and the actual injection at the time of the small lift Since the pressure, that is, the suck chamber pressure P _S can be made higher than that in Comparative Example 1 of the standard nozzle, it is understood that the fuel spray is atomized and the penetration force can be increased.

Further, in the fuel injection nozzle according to the first embodiment of the present invention, when the nozzle is attached to the internal combustion engine at an angle, the spray is uniform between the injection holes, and the injection rate is controlled according to the needle lift amount. And high quality spray can be obtained. On the other hand, the fuel injection nozzle according to Comparative Example 2 cannot uniformly change the distance L between the injection holes, and when the nozzle is tilted and attached to a diesel engine, the inclination angle between the injection holes with respect to the center of the nozzle is small. Otherwise, the spray will be uneven between the orifices. When the needle lift is large, the flow coefficient remains small, the pressure loss is large, and the driving loss of the injection diameter becomes large.

FIG. 7 shows the relationship between the elapsed time from the start of injection and the spray particle size. The measurement results shown in FIG. 7 were obtained under the following measurement conditions. The injection pressure was 100 MPa, the injection amount was 30 mm ³ / stroke, and the atmospheric pressure was 1 MPa (in Ar gas). It can be seen that the average spray particle diameter according to Example 1 of the present invention is smaller than the average spray particle diameter according to Comparative Examples 1 and 2. That is, it can be understood that in the fuel injection nozzle according to the first embodiment, the atomized fuel is atomized to obtain an atomized spray having good atomization characteristics.

Next, FIG. 8 shows a fuel injection nozzle according to a second embodiment (Embodiment 2) of the present invention. The second embodiment is an example in which a third conical portion 61 is formed at the tip of the needle valve 15. When the lift of the needle valve 15 is zero, the distances La and Lb between the needle valve 15 and the injection holes 28 and 29 are set. In addition, the distances La and Lb are set so that the difference between the bending losses due to the inclination angles δ ₃ and δ ₄ of the individual injection holes 28 and 29 with respect to the nozzle center is corrected and the total pressure loss becomes the same. The spray between the injection holes becomes uniform, and the same effect as in the first embodiment can be obtained.

FIG. 9 shows a fuel injection nozzle according to a third embodiment of the present invention. In the fuel injection nozzle 70 according to the third embodiment, a spherical portion 71 is formed at the tip of the needle valve 15. With the formation of the spherical portion 71, the distances La and Lb between the inlets of the injection holes 28 and 29 and the tip of the needle valve 15 are selected so that predetermined spray characteristics can be obtained. As described above, according to the embodiment of the present invention, since the nozzle sack volume is reduced and the injection rate is controlled by the lift amount of the needle, it is possible to obtain high quality spray, and the variation of spray between the injection holes Can be suppressed.

[0026]

As described in detail above, according to the fuel injection valve of the present invention, the needle is set at the inlet portion of the injection hole so as to have a predetermined distance L, and the area of the injection hole inlet effective flow path is reduced. Because the shape was made fluidly variable according to the lift amount of the needle,
There is an effect that the fuel spray characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a nozzle portion of a fuel injection valve according to a first embodiment of the present invention.

FIG. 2 is a partial sectional view showing a state in which the fuel injection valve according to the first embodiment of the present invention is mounted on a diesel engine.

FIG. 3 is a sectional view showing a fuel injection valve according to a first embodiment of the present invention.

FIG. 4 is a characteristic diagram showing a relationship between a needle lift and an injection hole flow coefficient.

FIG. 5 is a characteristic diagram showing a relationship between a distance between a needle and an injection hole and an injection hole flow coefficient.

FIG. 6 is a characteristic diagram showing a relationship between a needle lift and a pressure ratio.

FIG. 7 is a characteristic diagram showing a relationship between an elapsed time from the start of injection and a spray particle size.

FIG. 8 is a sectional view showing a nozzle part of a fuel injection valve according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing a nozzle portion of a fuel injection valve according to a third embodiment of the present invention.

FIG. 10 is a sectional view showing a nozzle portion of a fuel injection valve according to a comparative example 1 of the related art.

FIG. 11 is an explanatory diagram showing a fluid model of a fuel injection valve according to Comparative Example 1 of the related art.

FIG. 12 is a characteristic diagram showing a relationship between a needle lift and a sheet passage area according to Comparative Example 1.

FIG. 13 is a cross-sectional view showing a nozzle portion of a fuel injection valve according to Comparative Example 2 of the related art.

[Explanation of symbols]

 14 Nozzle body (valve body) 15 Needle valve 25 First conical surface 26 Second conical surface 28 Injection hole 29 Injection hole 32 First inclined surface 33 Second inclined surface 34 Tangent line

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kenji Date 1-1-1 Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-53-110719 (JP, A) 128381 (JP, U) Fully open sho 61-17481 (JP, U) Fully open sho 60-143167 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02M 61/18

Claims (4)

(57) [Claims] 1. A first conical surface formed at a predetermined angle inside a distal end, and a predetermined angle at a distal end side of the first conical surface.
A second conical surface formed at an degree, a valve body having an injection hole formed in communication with the outside from the inside of the second conical surface, a columnar shaft body, a distal end of the cylindrical shaft member Formed in the first
A first inclined surface which forms an angle smaller than the conical surface and has a lower end surface tangent to the first conical surface and separates from the first conical surface, and is formed at a tip of the first inclined surface and is substantially equal to the first conical surface; A needle valve movably disposed within the valve body, the needle valve having an angled second inclined surface, the needle valve varying an effective flow area of the injection hole inlet in accordance with a lift amount. A fuel injection valve, wherein fuel is fed into the valve body to open the needle valve and fuel is injected from the injection hole. 2. A tip portion of the needle valve is located on an extension of the central axis of the injection hole. When the needle valve is closed, the tip portion of the needle valve and an inlet of the injection hole are set at a predetermined distance. The fuel injection valve according to claim 1, wherein: 3. The fuel injection valve according to claim 1, wherein a distance L between the needle valve and the injection hole inlet is in a range of 0.1 to 0.3 mm. 4. A plurality of injection holes having different inclination angles are formed in the valve body, and the injection holes forming a large inclination angle with respect to the central axis of the valve body are located at positions on the tip side of the first conical surface. 2. The fuel injection valve according to claim 1, wherein the fuel injection valve is open.