JPH1113595A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection nozzle that can effectively reduce black smoke discharged from a diesel engine. SOLUTION: Nozzle holes 9 in a hole type fuel injection nozzle 11 are offset on conical cross section with a normal 16 of a nozzle sack 8 as a reference, and a slit 9a for enlarging nozzle hole width onto the anti-offset side is provided at least at an outlet part of each nozzle hole 9. This constitution makes difference in the flow velocity of fuel in the respective cross section of the nozzle holes 9 so as to positively diffuse fuel spray. The utilization factor of air is therefore improved so as to effectively reduce discharge of black smoke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle used for a diesel engine, and more particularly to a hole type fuel injection nozzle capable of effectively reducing black smoke discharged from a diesel engine. Things.

[0002]

2. Description of the Related Art In a diesel engine which operates like a diesel engine for a vehicle and has a wide rotation / load range, a control range of a fuel injection amount is wide. Therefore, for example, when the initial injection rate is reduced in an operation region where the injection amount is small such as a light load region and the nozzle diameter is reduced to suppress generation of NOx, an injection period in a high load region where the injection amount is large is required. It becomes too long.

[0003] Further, if the injection hole diameter is increased in order to optimize the injection period in a high load range, the initial injection rate is increased even in a light load range, and NOx is easily generated. When the diameter of the nozzle hole is increased, the particle diameter of the fuel spray becomes large, so that the emission of black smoke tends to increase.

On the other hand, in order to suppress the generation of NOx,
EGR is performed to return part of the exhaust gas to the combustion chamber, or
It has been considered effective to suppress the mixing of air and fuel by performing a timing retard for delaying the fuel injection timing or reducing the swirl.

[0005] However, when EGR is performed, there is a concern that the efficiency of charging fresh air is reduced, fuel efficiency is deteriorated and black smoke is increased, and the emission of particulates is increased.
In addition, when the timing retard is performed, the engine performance is sacrificed, and when the swirl is reduced, the generation of NOx is suppressed such that the air utilization rate is reduced and the possibility of increasing the amount of black smoke is increased. Meanwhile, it was considered difficult to reduce black smoke emissions.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a fuel injection nozzle capable of effectively reducing black smoke discharged from a diesel engine. And

[0007]

In order to solve the above-mentioned problems, according to the present invention, the injection port of the hole type fuel injection nozzle is offset on a conical cross section with respect to the normal line of the nozzle sack, and the injection port width is reduced. It is characterized in that a slit that expands to the anti-offset side is provided at least at the outlet of the nozzle. In addition, while providing the deflecting means for giving a swirling flow to the fuel of the nozzle sack, the emission of black smoke can be reduced more effectively by offsetting the injection port to the upstream side of the swirling flow.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view of a nozzle tip portion showing an embodiment of a fuel injection nozzle according to the present invention.
1 is a cross-sectional view taken along line AA of FIG. 1, FIG. 3 is a front view showing a cross-sectional shape of an inlet portion of the nozzle shown in FIG. 2, FIG. 4 is a front view showing a cross-sectional shape of an outlet portion of the nozzle shown in FIG. FIG. 5 is a schematic plan view of a combustion chamber showing a state of fuel spray by the fuel injection nozzle shown in FIG.

In these figures, a pressure receiving surface 4 of a needle 3 faces a fuel reservoir 2 provided in a nozzle body 1. Then, the needle 3 is moved by a nozzle spring (not shown).
Is pressed downward in the drawing to seat the sheet portion 5 on the nozzle body 1.
In this state, the inflow passage 7 extending from the fuel reservoir 2 is normally closed to prevent fuel from flowing into the nozzle sack 8.

When the lift force acting on the needle 3 via the pressure receiving surface 4 with the increase of the fuel pressure in the fuel reservoir 2 becomes larger than the valve closing urging force of the nozzle spring, the needle 3 moves upward in the figure. Lift and seat 5
From the nozzle sheet 6. Then fuel pool 2
Fuel flows into the nozzle sack 8 through the inflow passage 7, and from the plurality of injection holes 9 provided in the nozzle sack 8, the combustion chamber 1
A Hall-type fuel injection nozzle 11 that is injected to zero is configured. In the case of a common rail type fuel injection device, when an injection signal (electric signal) is output from a control unit (not shown), the needle 3 is lifted and fuel is injected.

Here, in the present embodiment, the fuel pool 2
A large-diameter portion 12 that narrows the inflow passage 7 extending from the nozzle 3 to the nozzle sack 8 is formed near the tip of the needle 3. And
The spiral guide groove 14 deflecting in the same direction as the swirl 13 induced in the combustion chamber 10 by the intake air is provided in the large-diameter portion 12. The swirl flow 15 which is directed in the same direction as the swirl 13 is generated.

In addition, the injection port 9 extending from the nozzle sack 8 to the combustion chamber 10 is offset in parallel with the normal 16 of the nozzle sack 8 and on the upstream side of the swirling flow 15 on the conical section with respect to the normal 16. Let me. The width of the orifice 9 is increased toward the downstream side of the swirl flow 15 by providing a slit 9a in the orifice 9 that gradually widens from the substantially middle portion as the starting point to the outlet.
Reference numeral 17 denotes a fuel spray, reference numeral 18 denotes a fuel passage for supplying fuel to the fuel reservoir 2, and reference numeral 19 denotes a center line of the injection port 9.

The fuel injection nozzle 1 configured as described above
In 1, the fuel discharged from a fuel injection pump or the like (not shown) is fed into the fuel reservoir 2 via a fuel passage 18 and is supplied and held in an inflow passage 7.

The pressure of the fuel in the fuel reservoir 2 acts on the needle 3 via the pressure receiving surface 4 as a lifting force. However,
Since the valve closing urging force of the needle spring (not shown) is larger than the above-mentioned lifting force at times other than the injection timing, the seat portion 5 of the needle 3 is seated and held on the nozzle seat 6 of the nozzle body 1 and Fuel inflow is blocked.

When the injection timing is reached and the pressure in the fuel reservoir 2 increases, the lift force acting on the needle 3 becomes greater than the urging force of the nozzle spring. Then, in order to lift the needle 3 upward in the drawing and lift the seat portion 5 from the nozzle sheet 6, the fuel in the fuel pool 2 is fed into the nozzle sack 8 via the inflow passage 7, and the nozzle sack 8 is discharged from the nozzle sack 8. Is injected into the combustion chamber 10 through In the case of a common rail type fuel injection device, when an injection signal (electric signal) is output from a control unit (not shown), the needle 3 is lifted and fuel is injected.

In this manner, the needle 3 is lifted, and fuel is supplied from the fuel reservoir 2 to the nozzle sack 8 through the inflow passage 7, and at the same time, fuel is supplied to the fuel reservoir 2 through the fuel passage 18. At this time, a part of the inflow passage 7 is constituted by a spiral guide groove 14 that deflects in the same direction as the swirl 13.

Therefore, the fuel which is going to flow into the nozzle sack 8 is given a deflecting force by the guide groove 14, and the flow due to this deflecting force is carried into the nozzle sack 8 as it is. Swirl flow 15 is induced in the nozzle sack 8.

The swirling flow 15 of the nozzle sack 8 induced as described above increases as the lift amount of the needle 3 increases and the amount of fuel flowing into the nozzle sack 8 increases. The nozzles 9 are each made parallel to the normal 16 of the nozzle sack 8 and then offset to the upstream side of the swirling flow 15 on the conical section with respect to the normal 16.

For this purpose, the nozzle sack 8 and the
The flow velocity of the fuel flowing into the nozzle varies depending on the cross section of the nozzle 9.
The flow velocity of the fuel at the upstream cross section of the swirl flow 15 at each injection port 9 is higher than the flow velocity of the fuel at the downstream cross section of the swirl flow 15. Accordingly, the fuel flowing through the injection port 9 is injected into the combustion chamber 10 while being deflected to the slit 9a side under the influence of the flow velocity difference. And the contact area with the contact increases.

The flow rate of each fuel spray 17 is equal to the swirl 1
3 is different between the upstream side and the downstream side, and the influence of the flow velocity difference improves the air intake and improves the mixing with the air, so that the emission of black smoke is reduced. Therefore, even if the EGR is performed to suppress the generation of NOx or the swirl is reduced, the emission amount of the black smoke does not increase.

In a state where the fuel spray 17 is not affected by the swirl 13, the fuel spray 17 is distributed as shown by a solid line in FIG. However, in fact, since the swirl 13 is subjected to the swirling action, the swirl 13 diffuses toward the downstream side of the swirl 13 and is mixed with air as shown by a two-dot chain line in FIG. Therefore, by inducing the swirl 13 of moderate strength in the combustion chamber 10, the contact area between the fuel spray 17 and the air can be further increased, and the mixing is further promoted to more accurately discharge the black smoke. Can be reduced to

By the way, the diffusion speed of the fuel spray 17 changes in response to the difference between the flow velocity of the fuel at each cross section of the injection port 9 and the strength of the swirl 13. Is strong, there is a possibility that the fuel spray injected from the passage located on the upstream side of the swirl 13 catches and overlaps the fuel spray injected from the adjacent downstream nozzle. Therefore, when there is a possibility that the fuel sprays overlap each other, as shown by a two-dot chain line or a broken line in FIG. , The distribution of the fuel spray 17 in the depth direction of the combustion chamber 10 can be improved to further increase the air utilization rate.

In the above embodiment, the slit 9 has a constant thickness.
a is continuously provided on the downstream side of the swirl flow 15 in the nozzle 9, but as shown in FIG. 6, a slit 9 a having a gradually decreasing thickness is continuously provided on the downstream side of the swirl flow 15 in the nozzle 9. The distribution state of the fuel spray 17 can also be changed.

Further, as shown in FIG. 7, a slit 9a having a gradually increasing width is formed over the entire area from the inlet end to the outlet end of the injection port 9 to further enhance the spreading performance of the fuel spray 17, or FIG. As shown, while keeping the width of the slit 9a constant near the entrance end, the width of the slit 9a is gradually widened toward the exit end, so that the nozzle sack 8 and the slit 9a do not obliquely intersect. As a result, it is possible to reduce the variation in the cross-sectional area of the inlet end of the nozzle 9 due to a processing error.

When the slit 9a is provided over the entire area of the injection port 9 as in the embodiment shown in FIGS. 7 and 8, the slit 9a at the entrance end is provided as shown in FIG.
And the width of the slit 9a can be gradually increased toward the outlet end as shown in FIG. Note that the thickness of the slit 9a does not need to be the same as shown in FIGS.
As shown in FIG. 2, the thickness of the slit 9a can be gradually reduced as the distance from the injection port 9 increases.

In each of the above embodiments, a case is described in which the slits 9a whose width gradually increases toward the outlet end are provided. However, as shown in FIG. Is advantageous in that the workability of the slit 9a is improved. 14 is a sectional view of the nozzle 9 shown in FIG. 13, and FIG. 15 is a sectional view of the nozzle 9 showing a modification of the slit 9a.

In the above embodiment, the combustion chamber 10
Swirl flow 1 in the same direction as swirl 13 induced by wind
5 is generated in the nozzle sack 8, and the nozzles 9 are offset to the upstream side of the swirling flow 15 while keeping the nozzles 9 in parallel with the normal 16 of the nozzle sack 8, respectively.
The fuel flow velocity difference in each cross section of the injection port 9 is positively secured to ensure the spread of the fuel spray. However, the swirl flow 15 in the direction opposite to the swirl 13 is generated in the nozzle sack 8. You may.

Further, in each of the above-described embodiments, the case where four nozzles 9 are provided is described. However, the number of nozzles 9 is not limited to that of the embodiment, and five or more nozzles 9 are provided. The present invention can also be applied to an apparatus provided with an injection port or three or less injection ports. Depending on the characteristics of the engine, the turning means such as the guide groove 14 may be omitted, or the swirl 13 of the combustion chamber 10 may be omitted. Even in the case of an engine in which the generation of NOx is suppressed by weakening or eliminating the swirl 13, the difference in the flow velocity of the fuel in each cross section of the injection port 9 obtained by offsetting the injection port 9 makes the fuel spray 17 Spreading and air entrapment can be made sufficiently high to improve mixing with air, so that the emission of black smoke does not increase.

[0029]

As is apparent from the above description, according to the present invention, the injection port of the Hall type fuel injection nozzle is offset on the conical cross section with respect to the normal of the nozzle sack, and the injection port width is increased to the anti-offset side. By providing a slit at least at the outlet of the nozzle, the difference in the flow velocity of the fuel at each cross section of the nozzle is provided to actively diffuse the fuel spray, thereby improving the air utilization rate and discharging black smoke. Is effectively reduced, so that NO
Even if EGR is performed to suppress the generation of x or the swirl is reduced, the amount of black smoke emitted does not increase.

In the case where the deflecting means for imparting a swirling flow to the fuel of the slack is provided as in the second aspect of the present invention, and the nozzle is offset to the upstream side of the swirling flow, the flow velocity of the fuel at each cross section of the nozzle is provided. Because the difference can be increased, black smoke emissions can be more effectively reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a nozzle tip showing one embodiment of a fuel injection nozzle according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a front view showing a cross-sectional shape of an inlet of the nozzle shown in FIG. 2;

FIG. 4 is a front view showing a cross-sectional shape of an outlet of the nozzle shown in FIG. 2;

FIG. 5 is a schematic plan view of a combustion chamber showing a state of fuel spray by a fuel injection nozzle shown in FIG. 1;

FIG. 6 is a front view showing a cross-sectional shape of an outlet portion according to a modified example of the slit of the nozzle shown in FIG. 2;

FIG. 7 is a cross-sectional view of a modified example of a slit corresponding to the AA cross section in FIG. 1;

FIG. 8 is a sectional view of another modification of the slit corresponding to the AA section in FIG. 1;

FIG. 9 is a front view showing a cross-sectional shape of an inlet portion of the nozzle shown in FIGS. 7 and 8;

FIG. 10 is a front view showing a cross-sectional shape of an outlet portion of the nozzle shown in FIGS. 7 and 8;

FIG. 11 is a front view showing a cross-sectional shape of an inlet portion according to a modification of the slit of the nozzle shown in FIGS. 7 and 8;

FIG. 12 is a front view showing a cross-sectional shape of an outlet portion according to a modified example of the slit of the nozzle shown in FIGS. 7 and 8.

FIG. 13 is a cross-sectional view corresponding to an AA cross section in FIG. 1 according to another modification of the slit.

FIG. 14 is a front view showing a cross-sectional shape of the nozzle shown in FIG.

FIG. 15 is a front view showing a cross-sectional shape according to a modified example of the slit of the nozzle shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle body 2 Fuel reservoir 3 Needle 4 Pressure receiving surface 5 Seat part 6 Nozzle sheet 7 Inflow passage 8 Nozzle sack 9 Injection port 9a Slit 10 Combustion chamber 11 Fuel injection nozzle 12 Large diameter part 13 Swirl 14 Guide groove 15 Swirling flow 16 Nozzle sack 8 Normal line 17 Fuel spray 18 Fuel passage 19 Center line of nozzle

Claims (2)

[Claims] 1. A hall-type fuel injection nozzle having a plurality of nozzles along a normal line of a nozzle sack, wherein the nozzle holes are offset on a conical cross section with respect to the normal line of the nozzle sack, and the width of the nozzle hole is anti-offset. A hole-type fuel injection nozzle characterized in that a slit extending to the side is provided at least at an outlet of the injection port. 2. The fuel injection nozzle according to claim 1, further comprising a deflecting means for imparting a swirling flow to the fuel of the nozzle sack, and wherein an injection port is offset upstream of the swirling flow.