JPH01177449A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To reduce production of HC, NOx, by a method wherein a clearance volume between a throttle shaft part at the tip of a needle valve and a slide part with which a shaft part is insertedly engaged is set in a specified range so as to lower injection rate in low revolution and raise it in high revolution. CONSTITUTION:A fuel injection nozzle is provided with a nozzle body 2 mounted to the tip of a nozzle holder, a seat part 30 of the tip part of a stem part 27 with which a needle valve contained in a nozzle holder is seated to a valve seat 36 formed to the nozzle body 2. The nozzle body 2 contains a throttle shaft part 29 at the tip of a stem part 27 in a state in which the seat part 30 is seated on the valve seat 36. A fuel injection chamber 32 has a partitioned injection part 33, and the nozzle hole part 33, and the injection hole 33 has a cylinder part 37 to surround the shaft part 29 with a given clearance therebetween. In this case, a clearance volume a(a/V) to displacement V per a cylinder is set so as to satisfy a formula of 0.017<=a/V<=0.043.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection nozzle in which a needle valve is actuated in the opening direction according to the pressure of supplied fuel to adjust the opening volume of the nozzle, and particularly relates to The present invention relates to a fuel injection nozzle that limits the amount of fuel injected by adjusting the lift amount and injection time of the needle valve according to speed and load, thereby reducing fuel noise and HClNOx.

[Prior Art] A fuel injection nozzle for supplying fuel into a fuel chamber is a "fuel injector nozzle for a diesel engine" as shown in FIG. 5 (Japanese Patent Application Laid-open No. 59-206673).
There is a proposal.

As shown in the figure, this proposal is based on the nozzle body 1
A needle valve 104 for opening and closing the nozzle 103 of the fuel chamber 102 formed at the tip of the nozzle body 101 is provided inside the nozzle body 101 so as to be movable up and down.
A fuel injector nozzle for a diesel engine is constructed by forming a throttle shaft portion 105 that maintains a constant fuel injection amount at a lift value below the maximum lift value.

[Problems to be Solved by the Invention] As shown in FIGS. 6 and 7, the above proposal provides a fuel injector nozzle with a pilot injection performance (2) in which the injection amount is constant and a main injection performance (in which the injection amount increases). ■ Also,
This is an attempt to improve combustion, improve fuel efficiency, and reduce HC and NOx.

In other words, the injection rate (injection amount per unit time) at low speed
This is because if the injection rate is increased, the fuel will not be combusted and will be emitted as HC since the combustion chamber temperature is low, and if the injection rate is lowered at high speed, the air utilization rate will decrease and NOx will be emitted. However, in this type of fuel injection nozzle, the clearance volume formed by the throttle shaft and the sliding part surrounding the throttle shaft, that is, the area of the throttle shaft relative to the sliding part, Depending on the size of the product of the fitting length A, fuel noise may increase or smoke density during idling may worsen.

In other words, if the clearance volume is too large, the needle valve will lift more than the fitting length during idling, resulting in an increase in the injection rate per unit time and a shortening of the injection period.As a result, a large amount of premixture will be created due to excess supply. On the other hand, if the clearance volume is small, the peak of the injection rate will be too low in the medium and high speed range where a high injection rate is required, resulting in an increase in the injection period. This is because fuel injection is continued until the cylinder pressure is low after the dead center, which increases the amount of smoke generated.

[Means for Solving the Problems] The present invention aims to solve the above problems. This invention provides a throttle shaft portion formed at the tip of a needle valve to inject a fixed amount of fuel from a nozzle port of a nozzle body, and a sliding portion of the body that slidably surrounds the throttle shaft portion, per cylinder. The clearance volume for the displacement is 0.017≦a/V≦0,04 where the clearance volume is a and the displacement per cylinder is V.
The fuel injection nozzle is configured within the range of 3.

[Operation] For the displacement per cylinder ■, the clearance volume a between the throttle shaft and the sliding part of the nozzle body surrounding this shaft is set within the range of 0.017≦a/■≦0.043. Because of this, the amount of fuel supplied during idling or during medium/high load is neither excessive nor insufficient, and the appropriate amount of fuel is supplied for combustion. That is, combustion noise and smoke can be suppressed to a low level.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 2, the fuel injection nozzle mainly consists of a nozzle holder 1 and a cylindrical nozzle body 2 that is integrally attached to the tip of the nozzle holder 1.

As shown in the figure, a cylindrical nozzle holder 1 is formed with a cylindrical portion 3 having an enlarged diameter on the inner circumferential surface on the rear end side, and a female thread 4 is formed on the rear end side of the cylindrical portion 3. . The sleeve 5 is fitted into the internal circumferential surface of the nozzle holder 1 on the female thread 4, and in the fitted state, the sleeve 5 on the upper end side is seated on the bottom surface of the cylindrical portion 3. A cylindrical spring housing member 6 fixed to the nozzle holder 1 is screwed together. On the other hand, a female thread 7 is also formed on the outer peripheral surface of the tip of the nozzle holder 1, and the rear end of the nozzle body 2 is airtightly seated on the tip of the nozzle holder 1 via a spacer 8. A substantially sleeve-shaped glue tening nut 9 is screwed together.

By the way, there is a first spring retainer 10 on the tip side of the nozzle boulder 1, and a spring retainer 10 between the first spring retainer 10 and the tip of the sleeve 5.
A first spring 11 that biases the valve in the valve closing direction is slidably or telescopically accommodated in the spring housing member 6.
On the rear end side, a second spring retainer 13 is formed integrally with the shaft portion 12 that is slidably fitted into the sleeve 5.
A second spring 14 that biases the second spring retainer 13 in the valve closing direction is housed in a slidable or expandable manner. In the embodiment, the set force of the second spring 14 can be adjusted by a locking plug 16 that is screwed into a female thread 15 formed on the rear end side of the spring housing member 6. The setting force can be adjusted by adjusting the axial length of the sleeper 5.

17 is a lock nut member of the plug 16, 18 is a coupling member for guiding leaked fuel from the nozzle boulder 1 to the outside, and 19, 20, 21 is a lock nut member between the first spring retainer 10 and the second spring retainer 13. This is a rod member that transmits force.

Next, the configuration of the nozzle body 2 will be explained.

The nozzle body 2 is configured to adjust the amount of fuel injected from a nozzle opening at the tip side of the nozzle body 2 in accordance with the lift amount of the needle valve.

The needle valve 25 has a first stem portion 2 on the rear end side which is thick along the axial direction.
6 and a thin second stem portion 27 on the tip side are connected by a tapered pressure receiving portion 28, and as shown in FIG. and are connected by a cone-shaped sheet portion 30.

On the other hand, the nozzle body 2 has the needle valve 25 on its axis.
It has a needle valve accommodating part 31 into which the needle valve is fitted so as to be able to rise and fall with a predetermined clearance, and a nozzle part 33 which is closed in a cap shape at the tip and defines a fuel injection chamber 32. Ru. A plurality of nozzles 35 are opened in this nozzle portion 33 at intervals in the circumferential direction, and a connecting portion between the needle valve accommodating portion 31 and the nozzle portion 33 is located on the rear end side of the nozzle nozzle 35. means the valve seat 36 on which the seat portion 30 is airtightly seated.
Connected with

By the way, as shown in FIG.
0 is seated, the throttle shaft portion 29 and the nozzle port 33 that accommodates the throttle shaft portion 29 are surrounded by a sliding surface with a predetermined clearance between the throttle shaft portion 29 and the throttle shaft portion 29 at the upper portion thereof. A cylindrical portion 37 that becomes a moving portion is formed. In the embodiment, the clearance volume a is set within the range of the following formula with respect to the displacement V per cylinder.

0.017≦a/V≦0.043 On the other hand, in the needle valve accommodating portion 31 facing the pressure receiving portion 28 when the seat portion 30 is seated, a concave fuel chamber 38 whose diameter is expanded outward in the radial direction is formed. A concave combustion chamber 38 is formed in the needle valve accommodating portion 31, which the distal end side of the second stem portion 27 faces, by expanding its diameter in the radial direction along the circumferential direction. A series of fuel passages 39 passing through the nozzle holder 1, the spacer 8, and the nozzle body 2 are connected to the fuel chamber 38, and when the pressure of the supplied fuel is applied to the pressure receiving part 29, 1. Deflect the spring 11 and open the needle valve 25.
It operates in the valve opening direction to inject fuel from the nozzle formed by opening the tip of the nozzle body 2, and then, when the amount of deflection of the first spring 11 reaches a predetermined value, it deflects the second spring 14. It is configured to increase the amount of fuel injected from the injection port 35. That is, in the embodiment, the set force of the first spring 11 with respect to the fuel oil pressure is
The set force of the spring 14 is set to be weaker than that of the spring 14. As a reference value, the amount of deflection of the first spring 11 until the second spring 14 is activated is set to approximately 0.1 degrees in the embodiment.

A bushing rod 40 is integrally formed at the rear end of the needle valve 25 and extends rearward through the axis of the spacer 8, and the extending end 41 of the bushing rod 40 is movable up and down in the nozzle body 1. The first spring retainer 10 is provided in contact with the first spring retainer 10 that is guided by the first spring retainer 10 .

Next, the effect will be explained.

When the engine speed is low, the fuel injection pump (
(not shown) also rotates at low speed. Therefore, the interval between oil feeds of the fuel injection pump becomes longer, and the amount of oil sent to the fuel passage 38 per unit time also decreases. Therefore, the fuel pressure in the fuel chamber 38 becomes low, and the needle valve 25 is gradually lifted by this low pressure, the first spring 11 is deflected, and at the same time, fuel is injected. At this time, the throttle shaft portion 29 and the cylindrical portion 37
A certain amount of fuel flows into the nozzle 35 from the clearance formed by the
However, as mentioned above, the clearance volume a
Since V is set within an appropriate range for the displacement V per cylinder, the fuel injected from the nozzle 35 is appropriately limited. This is the pilot injection period (IV) shown in FIG. 3, in which a small amount and fixed amount of fuel is injected over a long period of time compared to the full load. Therefore, the fuel injected during the pilot injection period (IV) may be over-injected into the combustion chamber (not shown) of the internal combustion engine A, without cooling the combustion chamber. As shown in Figure 4, smoke during idling (HC
etc.) and combustion noise can be suppressed to a low level.

On the other hand, since the fuel pressure in the fuel injection chamber 32 is gradually increased by being throttled by the nozzle 35, the needle valve 32
Since the lift value of No. 5 exceeds the lift value of the pilot injection period (IV) and increases to a lift value that deflects the second spring 14, a large amount of fuel with a strong penetration force is injected from the injection port 35. Become. This becomes the main injection period (V) shown in FIG.

By the way, after the pilot injection period (IV), the fuel in the fuel chamber 38 is injected from the injection port 35.

The injection amount per unit time at this time is smaller than when the period rotational speed is high, and the injection time is also long.

This is because, as mentioned above, the amount of oil fed by the fuel injection pump is small and the intervals between oil feedings are long.

When the periodic rotational speed is low as described above, the injection rate per shift time can be lowered overall and the injection time can be lengthened, so it is possible to suppress the generation of HC in the combustion chamber. In addition, when the valve is closed, the second spring 14
, the seat portion 30 is seated on the valve seat 36 instantly by the sum of the first springs 11 (not only can excellent valve closing performance be obtained, but also the first spring 11 is Te*!I M It also functions as a town.

When the engine speed is high, the rotation speed of the fuel injection pump also increases, the amount of oil fed per unit time is large, and the oil feeding interval becomes short, so the fuel pressure in the fuel chamber 38 also increases, causing the needle valve 25 to increase. is lifted at high pressure. At this time, since the fuel pressure is high, the interval between the pilot injection periods (IV) becomes shorter and the injection rate increases. Therefore, at high speeds, the injection rate increases and the injection interval becomes shorter, which increases the air utilization rate in the fuel chamber and suppresses NOx emissions.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, when the engine rotation speed is low, the injection rate can be lowered and when the engine rotation speed is high, the injection rate can be increased. (IC), NOx can be reduced to a large IJ, and combustion noise can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged cross-sectional view of a nozzle body showing a preferred embodiment of the present invention, FIG. 2 is a cross-sectional view of a fuel injection nozzle, FIG. 3 is a performance diagram showing changes in injection rate, and FIG. A performance diagram showing smoke concentration performance and combustion noise performance of an embodiment of the present invention, FIG. 5 is a sectional view showing a throttle type injector as a conventional example, and FIGS. 6 and 7 are general diagrams of a throttle type injector. A performance diagram showing changes in injection rate. In the figure, 2 is a nozzle body, 11 is a first spring, 14
25 is a second spring, 25 is a needle valve, 2 is a throttle shaft, 35 is a nozzle, and a is a clearance volume. Patent Applicant: Isuf Jidosha Co., Ltd. Representative Patent Attorney: Nobuo Kinuya JJ Figure 1 2; / 7tki, -x 35" spout Figure 3 and Figure 4 Figure 5 Atsushi Figure 6 Figure 7 Theory

Claims (1)

[Scope of Claims] A throttle shaft portion formed at the tip of a needle valve to inject a fixed amount of fuel from a nozzle port of a nozzle body, and a sliding portion of the body that slidably surrounds the throttle shaft portion. A fuel injection nozzle characterized in that a clearance volume for a displacement per cylinder is determined based on the following formula. 0.017≦a/V≦0.043 However, a is the clearance volume V is the displacement per cylinder