JP2012145048A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve having reduced penetration by atomizing fuel and diffusing fuel sprays.SOLUTION: The fuel injection valve 1 includes a nozzle body 2 for injecting fuel from a plurality of nozzles 25 provided at the front end. The nozzles 25 each have a small-diameter part 250 at the center of the nozzles 25 with its cross section having a diameter D, a first tapered part 251 continuous with the small-diameter part 250 on the upstream side of the small-diameter part 250, wherein the cross-section diameter of the nozzle 25 is gradually smaller from the upstream side toward the downstream side, and a second tapered part 252 continuous with the small-diameter part 250 on the downstream side of the small-diameter part 250, wherein the cross-section diameter of the nozzle 25 is gradually larger from the upstream side toward the downstream side. Relationships of 0<(D-D)/L<0.028 (1), 0<L/D<5.8 (2), and 0<(D-D)/L(3) are satisfied, wherein Lis the nozzle length of the first tapered part 251, Dis the diameter of the cross section at the upstream end, Lis the nozzle length of the second tapered part 252, and a Dis the diameter of the cross section at the downstream end.

Description

  The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve that injects fuel into a cylinder of an internal combustion engine.

  There is known a fuel injection device that directly injects fuel into a cylinder of an internal combustion engine. Such a fuel injection device includes a fuel injection valve provided with an injection hole, and the injection hole of the fuel injection valve is arranged in the cylinder, thereby realizing fuel injection into the cylinder. However, in a fuel injection valve that directly injects fuel into a cylinder of an internal combustion engine, when the penetration force of the fuel injected from the fuel injection valve is large, the fuel may adhere to the piston or the cylinder liner.

  The fuel adhering to the cylinder liner is dissolved in the engine oil having an oil film formed on the cylinder liner and flows out to the crankcase together with the engine oil. This dilutes the engine oil and lowers the viscosity and lubrication performance. Further, the fuel spray adhering to the cylinder liner remains in the cylinder without being vaporized, so that the air-fuel ratio in the combustion chamber changes and the amount of HC emission increases. On the other hand, Patent Documents 1 and 2 disclose configurations for suppressing fuel penetration.

  The fuel injection device of Cited Document 1 includes a tapered portion whose passage diameter increases as the injection holes arranged at a predetermined angular interval on the same circumference advance from the upstream side to the downstream side, and a downstream end of the tapered portion. A first constant-diameter portion that is continuous. According to the configuration of the fuel injection device of the cited document 1, the fuel injected from each injection hole collides with each other and mixes to form a spray that disturbs the injection direction and winds up toward the injection nozzle. Penetrating power is reduced and atomized.

  The fuel injection nozzle of the cited document 2 is characterized in that the cross section of the injection hole provided in the nozzle body first narrows toward the combustion chamber of the internal combustion engine and then expands again. According to the configuration of the fuel injection nozzle of Patent Document 2, a higher speed is generated in the throat region where the injection hole is narrowed, and a spray having small particles can be formed in the diffuser portion where the fuel injection nozzle is expanded. Thereby, the disadvantage that the maximum distribution region is shifted in the direction away from the nozzle based on the relatively high speed of the fuel jet is prevented by the diffuser portion where the fuel injection nozzle is widened. Also, the cavitation tendency is reduced by obtaining an optimal conversion of fuel jet pressure to fuel jet velocity.

JP 2010-15510 A JP 2002-527678 Gazette

  However, in the injection hole provided in the injection nozzle of Patent Document 1, the fuel peels off at the injection hole inlet portion, and the effect of providing the tapered portion is reduced. Also, the ability to atomize the spray during low pressure injection at the initial stage when the needle valve is opened is low. Furthermore, since the fuel injection nozzle of Patent Document 2 reduces the cavitation tendency, it is difficult to obtain the effect of atomizing the spray due to the collapse of the cavitation bubbles. For this reason, such a fuel injection valve still has room for improvement.

  Then, this invention makes it a subject to provide the fuel injection valve which reduced the penetration force by atomization of fuel and spreading | diffusion of spray.

A fuel injection valve of the present invention that solves such a problem includes a nozzle body that injects fuel from a plurality of injection holes provided at a tip, and the injection hole has a predetermined cross-sectional diameter at a central part of the injection hole. A small-diameter portion having a first taper portion that is continuous with the small-diameter portion upstream of the small-diameter portion and whose cross-sectional diameter decreases from the upstream side toward the downstream side, and the downstream side of the small-diameter portion A second tapered portion that is continuous with the small-diameter portion and has an enlarged cross-sectional diameter from the upstream side toward the downstream side, wherein the diameter of the cross-section of the small-diameter portion is D ₀ , When the injection hole length is L ₁ and the diameter of the cross section of the injection hole at the upstream end of the first taper portion is D ₁ ,
_{0 <(D 1 -D 0)} / L 1 <0.028 (1)
It is characterized by satisfying the relationship.

  With such a configuration, the fuel flowing through the nozzle hole generates cavitation bubbles in the first taper portion that contracts in the fuel flow direction, and the generated cavitation bubbles collapse, thereby achieving atomization of the fuel. Disruption of the cavitation bubbles causes turbulence in the flow in the nozzle hole, so that the penetration force of the spray can be reduced. Furthermore, since the atomized fuel is diffused by the second tapered portion that expands in the flow direction, the penetration force can be reduced.

In the above fuel injection valve,
0 <L ₁ / D ₀ <5.8 (2)
It is also possible to satisfy this relationship.

  The fuel injection valve of the present invention includes a first taper portion that generates cavitation and a second taper portion that widens the spray angle, thereby achieving atomization of the fuel, diffusing the spray, and reducing the penetration force. .

It is explanatory drawing which showed the internal schematic structure by making the fuel injection valve of an Example into a cross section. It is explanatory drawing which expanded and showed the periphery of the nozzle hole of the fuel injection valve of FIG. The decrease ratio of the length of the spray is an explanatory diagram showing the effect of K ₁ factor. The decrease ratio of the length of the spray is an explanatory diagram showing the effect of K ₂ factor. The decrease ratio of the length of the spray is an explanatory diagram showing the effect of K ₃ factor.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory view showing a schematic internal structure of a cross section of the fuel injection valve 1 of this embodiment. The fuel injection valve 1 includes a nozzle body 2 and a needle 3. This fuel injection valve 1 is assembled to an internal combustion engine. In particular, the fuel injection valve 1 is assembled so as to inject fuel into a cylinder provided in the internal combustion engine. Such an internal combustion engine is used for transportation machines such as automobiles and other power engines. In the following description, the distal end side indicates the moving direction when the needle 3 is closed, that is, the lower side in the drawing, and the proximal end side is the moving direction when the needle 3 is opened, that is, the upper side in the drawing. Will be shown.

  The nozzle body 2 is a bottomed cylindrical member, and is provided with a hollow portion 21, a fuel reservoir chamber 22, a high-pressure fuel passage 23, a seat portion 24, and an injection hole 25. The needle 3 is slidably disposed in the hollow portion 21. The high-pressure fuel passage 23 connects the outside of the fuel injection valve 1 and the fuel reservoir chamber 22, and supplies high-pressure fuel from the outside of the fuel injection valve 1 to the fuel reservoir chamber 22. A plurality of nozzle holes 25 are provided in the nozzle body 2, and the plurality of nozzle holes 25 are centered on the axis of the nozzle body 2 and are provided at equal intervals on the circumference of a circle orthogonal to the axis. . The nozzle body 2 injects fuel from a plurality of injection holes 25 provided at the tip.

  The needle 3 includes a large diameter cylindrical portion 31 and a small diameter cylindrical portion 32. The small diameter cylindrical portion 32 is located on the tip side of the large diameter cylindrical portion 31. When the needle 3 is incorporated into the nozzle body 2, the joint between the large diameter cylindrical portion 31 and the small diameter cylindrical portion 32 of the needle 3 is located in the fuel reservoir chamber 22. The large-diameter cylindrical portion 31 of the needle 3 slides while being guided by the wall surface of the hollow portion 21 of the nozzle body 2. A small diameter cylindrical portion 32 of the needle 3 forms a fuel supply path 41 with the hollow portion 21 of the nozzle body 2. The fuel supply path 41 supplies fuel from the fuel reservoir chamber 22 to the tip of the nozzle body 2, that is, the nozzle hole 25.

  The distal end portion 33 of the needle 3 has a shape that tapers toward the distal end. The tip portion 33 of the needle 3 is seated on the seat portion 24 of the nozzle body 2. In a state where the needle 3 is seated, fuel injection is stopped, and in a state where the needle 3 is separated from the seat portion 24, fuel is injected from the injection hole 25.

  The fuel injection valve 1 includes a drive mechanism 5 on the base end side of the nozzle body 2. The drive mechanism 5 includes a back pressure chamber 51, an orifice 52, a valve 53, a solenoid 54, and a switch 55. The drive mechanism 5 is a mechanism that controls the sliding operation of the needle 3. The back pressure chamber 51 is located at the proximal end of the needle 3. High pressure fuel is supplied from the high pressure fuel passage 23 to the back pressure chamber 51. The back pressure chamber 51 communicates with the storage chamber 56 through the orifice 52. The valve 53 is accommodated in the storage chamber 56 so as to be movable toward the base end side. The valve 53 is urged toward the distal end side by a spring 57.

  The ON / OFF operation of the switch 55 is performed by the control unit. The control unit includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a well-known digital computer in which input / output ports are connected by a bidirectional bus, for controlling the internal combustion engine. The internal combustion engine is controlled by exchanging signals with various sensors and actuators provided in the engine. That is, the control unit turns on the switch 55 when the fuel injection valve 1 injects fuel and energizes the solenoid 54, and interrupts the energization of the solenoid 54 that turns off the switch 55 when the fuel injection valve 1 stops fuel injection.

  When the switch 55 is turned on, the solenoid 54 is energized and the valve 53 is pulled up to the proximal end side. When the valve 53 is pulled up, the fuel in the back pressure chamber 51 escapes from the orifice 52 and the pressure in the back pressure chamber 51 decreases. Thereby, the pressure balance of the fuel concerning the needle 3 changes. That is, since the force pressing the needle 3 toward the distal end side is stronger than the force pressing the needle 3 toward the proximal end side, the needle 3 moves toward the proximal end side, and the needle 3 is separated from the seat portion 24. Thereby, fuel is supplied to the injection hole 25 and injected.

  Next, the nozzle hole 25 of the nozzle body 2 will be described in detail. FIG. 2 is an explanatory view showing the periphery of the nozzle hole 25 in FIG. 1 in an enlarged manner. The nozzle hole 25 is continuous with the small diameter part 250 on the upstream side of the small diameter part 250 at the central part of the nozzle hole 25 and the cross section of the nozzle hole 25 from the upstream side toward the downstream side. The first tapered portion 251 whose diameter is reduced and the second tapered portion 252 which is continuous with the small diameter portion 250 on the downstream side of the small diameter portion 250 and whose cross-sectional diameter of the injection hole 25 increases from the upstream side toward the downstream side. The small diameter portion 250 is a portion where the flow path is the narrowest in the nozzle hole 25. In the first taper portion 251, the cross-sectional diameter of the injection hole 25 decreases from the upstream side toward the downstream side. Further, R is formed at the upstream end of the first taper portion 251, that is, at the end portion on the inner side of the nozzle body 2. As for the 2nd taper part 252, the cross-sectional diameter of the injection hole 25 is expanded toward the downstream from the upstream.

  Next, the mode of the fuel that flows into the injection hole 25 and is injected will be described. When the needle 3 is lifted and the fuel enters from the upstream end (inlet) of the nozzle hole 25, the fuel flow is separated and cavitation bubbles cb are generated. The generated cavitation bubble cb collapses at the first taper portion 251 where the diameter of the passage is reduced. Thereby, the fuel in the nozzle hole 25 is atomized and the fuel flow is greatly disturbed. By atomizing the fuel, the sprayed fs after being injected is atomized. Further, when the fuel flow is disturbed, the speed in the fuel flowing direction is attenuated and the penetration force of the spray fs is reduced. As described above, the fuel whose flow is disturbed in the first taper portion 251 spreads in the second taper portion 252 where the diameter of the passage is enlarged, so that the spray angle is widened. Since the spray angle of the injected fuel is widened, the spray fs is diffused, and the penetration force of the spray fs is reduced. In the first taper portion 251, the collapse energy of the cavitation bubble cb is particularly large, such as tens of thousands of atmospheric pressures. Therefore, the initial splitting of the fuel is promoted, and the atomization of the spray fs is greatly affected. The atomization of the spray fs due to the collapse of the cavitation bubble cb occurs from the initial stage of the injection when the needle 3 starts to lift. For this reason, the atomization fs which is atomized from the initial stage of injection when the fuel pressure is low and the penetrating force is reduced is realized.

Furthermore, the shape of the nozzle hole 25 will be specifically described together with the relationship with the increase / decrease ratio of the spray length. The diameter of the cross section of the small diameter portion 250 is D ₀ , the length of the nozzle hole of the first taper portion 251 is L ₁ , and the diameter of the cross section of the nozzle hole 25 at the upstream end of the first taper portion 251, that is, the inner side of the nozzle body 2. When D ₁ , the nozzle hole length of the second taper part 252 is L ₂ , and the diameter of the cross section of the nozzle hole 25 on the downstream end of the second taper part 252, that is, the outside of the nozzle body 2, is D _2. 25
_{0 <(D 1 -D 0)} / L 1 <0.028 (1)
0 <L ₁ / D ₀ <5.8 (2)
_{0 <(D 2 -D 0)} / L 2 (3)
It is formed to satisfy the relationship.
here,
_{K 1 = (D 1 -D 0} ) / L 1 (4)
_{K 2 = (D 2 -D 0} ) / L 2 (5)
K ₃ = L ₁ / D ₀ (6)
And K ₁ to K ₃ are dimensionless numbers that determine the spray length. The K ₁ factor is a factor determined by the first taper portion 251. K ₂ factor is a factor determined by the shape of the second tapered portion 252. K ₃ factor is a factor determined by the size and position of the small diameter portion 250.

Next, with reference to FIGS. 3-5, illustrating the relationship between the increase and decrease ratio of the length of K ₃ and the spray from K _1. Figure 3 is an explanatory diagram showing the effect of K ₁ factor for increasing or decreasing the ratio of the length of the spray. Figure 4 is an explanatory diagram showing the effect of K ₂ factor for increasing or decreasing the ratio of the length of the spray. Figure 5 is an explanatory diagram showing the effect of K ₃ factor for increasing or decreasing the ratio of the length of the spray. The relationship between FIGS. 3 to 5 is obtained by measuring the spray length at the timing when the needle is fully lifted (fully opened). Specifically, a value measured at a timing of 1.2 ms after the start of injection is used. Moreover, the increase / decrease ratio of the spray length was measured when the number of nozzle holes was 3 and when the number of nozzle holes was 10, and it was confirmed by continuously measuring up to an injection pressure of 120 MPa. In addition, from the measurement results up to 120 MPa, it is estimated that the effects are still universally effective when the pressure is 120 MPa or more.

According to FIG. 3, it is shown that the spray length decreases when the value of K ₁ factor is between 0 and 0.028. That is, (when the equation (1) is satisfied) when the value of K ₁ factor is a value from 0 to 0.028, the length of the spray is reduced. Therefore, the penetration force of spraying falls by satisfy | filling Formula (1).

According to FIG. 4, if the value of K ₂ factor of 0 or more, the length of the spray has been shown to decrease. That is, (when the (3) is satisfied) when the value of K ₂ factor is greater than zero, the length of the spray is reduced. Therefore, the penetration force of spraying falls by satisfy | filling Formula (3). Further, as shown in FIG. 4, the larger the K _2-factor, the length of the spray is reduced. The K ₂ factor increases as the diameter D ₂ of the cross section of the nozzle hole 25 at the downstream end of the second tapered portion 252 increases. Therefore, to reduce the length of the spray, it is desirable to increase the diameter D ₂ of the cross section of the injection hole 25 at the downstream end of the second tapered portion 252. However, if too large a diameter D _2, it will interfere with the adjacent injection holes. Therefore, the diameter D ₂ can take the maximum value to the extent that interference does not occur between the adjacent injection holes.

According to FIG. 5, the length of the spray value of K ₃ factor between 0 and 5.8 it is shown to reduce. That is, (when the (2) is satisfied) when the value of K ₃ factor is a value from 0 to 5.8, the length of the spray is reduced. Therefore, by satisfying the formula (2), the penetration force of the spray is reduced.

  As described above, the fuel spray injected from the nozzle hole 25 formed so as to satisfy the expressions (1) to (3) is atomized by the collapse of the cavitation bubbles generated in the fuel flow, and the spray is further diffused. As a result, the penetrating power decreases. By reducing the spray penetration force, it is possible to suppress the fuel from adhering to the piston and cylinder liner of the internal combustion engine. Thereby, the increase in HC caused by performance deterioration due to oil dilution and wall surface adhesion can be suppressed.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Nozzle body 25 Injection hole 250 Small diameter part 251 1st taper part 252 2nd taper part 3 Needle cb Cavitation bubble fs Spray

Claims (2)

A nozzle body for injecting fuel from a plurality of nozzle holes provided at the tip;
The nozzle hole is
A small-diameter portion having a predetermined cross-sectional diameter at the center of the nozzle hole;
A first taper portion that is continuous with the small diameter portion on the upstream side of the small diameter portion, and whose cross-sectional diameter decreases from the upstream side toward the downstream side;
A second taper portion that is continuous with the small diameter portion on the downstream side of the small diameter portion, and whose cross-sectional diameter increases from the upstream side toward the downstream side;
Have
When the diameter of the cross section of the small diameter portion is D ₀ , the nozzle hole length of the first taper portion is L ₁ , and the diameter of the cross section of the nozzle hole at the upstream end of the first taper portion is D ₁ ,
_{0 <(D 1 -D 0)} / L 1 <0.028 (1)
A fuel injection valve characterized by satisfying the relationship 0 <L ₁ / D ₀ <5.8 (2)
The fuel injection valve according to claim 1, wherein the relationship is satisfied.

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