JPH0222235B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a fuel injection nozzle that injects and supplies fuel to a diesel engine. This invention relates to a throttle-type fuel injection nozzle that controls the area of the nozzle hole.

(Prior Art) Conventionally, fuel injection nozzles for diesel engines have been used, for example, as disclosed in Japanese Unexamined Patent Publication No. 57-151058, by suppressing the lift of a needle valve above a predetermined lift amount. It is known in the past that fuel injection is atomized in a low load range by a pre-lift that maintains a throttle range in which the needle valve throttles the nozzle hole within the lift range of the needle valve.

However, in this conventional system, when the needle valve reaches a predetermined pre-lift amount and the valve opening pressure rises further and the needle valve lifts further, the nozzle hole area is set to increase beyond the throttle range. However, when the engine is idling or during starting supercharging, both within a certain throttle range, there may be a difference in the injection period between cylinders, resulting in a decrease in ignition performance, combustibility, etc.

That is, during idling, since the load is low, the lift amount of the needle valve is within the throttle range, and the nozzle hole is narrowed and narrowed to promote atomization and vaporization. In this state, for example,
When carbon generated in the engine's combustion chamber becomes clogged between the needle valve tip and the nozzle hole, the nozzle hole area changes and the injection period becomes longer, causing a difference in the injection period between each cylinder. This results in a decrease in ignitability and generation of idle vibration. Furthermore, manufacturing errors in the fuel injection nozzle also cause the opening area of the throttle region to change, resulting in errors in the injection period between cylinders.

On the other hand, during startup supercharging, the amount of fuel injected is greater than during idling, but because the rotational speed is low, the pressure rise is low, and fuel is injected in the throttle region, so the nozzle hole area is narrowed. Therefore, in this state, if the difference in nozzle hole area between cylinders becomes large due to nozzle clogging due to carbon or manufacturing errors as described above, the injection period ends before sufficient fuel is injected in some cylinders. However, there is a problem in that the ignitability deteriorates due to a half-misfire state.

(Object of the Invention) In view of the above circumstances, the present invention has been developed by using the lift amount in the low load range including idling as the throttle range, and adjusting the fuel injection period during idling and starting supercharging without inhibiting fuel atomization. The object of the present invention is to provide a fuel injection nozzle for a diesel engine that reduces the difference between cylinders and improves ignition performance.

(Structure of the Invention) The fuel injection nozzle of the present invention is provided with a valve-opening pressure control mechanism that gradually controls the valve-opening pressure for lifting the needle valve so that it becomes small until a predetermined pre-lift amount. The nozzle area characteristics with respect to the increase in
It has a characteristic of having a second throttle region with a larger nozzle hole area than the throttle region and a widening region, and the lift amount at the boundary between the first throttle region and the second throttle region is set to the lift amount due to the valve opening pressure at idling. Further, the prelift amount is set to a lift amount within a second throttle region.

(Effects of the Invention) According to the present invention, carbon adheres to the nozzle tip by setting the lift amount during idling in the transition area from the first throttle area to the second throttle area and increasing the nozzle hole area. Or even if there is a variation in the nozzle area due to manufacturing errors, etc.
As a result, fluctuations in the injection period are reduced, improving ignition performance and reducing the occurrence of idle vibration.

In addition, during startup supercharging when the lift amount increases to near the prelift amount, the nozzle hole area increases in the second throttle area, so even if there is a change in the nozzle hole area due to carbon adhesion or manufacturing errors, it will not be affected. It is possible to reduce fluctuations in the injection period caused by the fuel injection, ensure a predetermined injection amount, improve ignition performance, and improve startability.

On the other hand, in the low load range including the above-mentioned idling range, lift is suppressed in the first and second throttle ranges to narrow the nozzle hole area and atomize the fuel to improve combustibility, while in the high load range the lift is suppressed. By lifting the fuel injection hole beyond the expansion region to widen the nozzle hole and increase the opening area, it is possible to secure a predetermined fuel injection amount and improve output.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows a vertical cross-sectional view of a fuel injection nozzle in one embodiment, Fig. 2 is an enlarged cross-sectional view of the nozzle tip and injection hole, and Fig. 3 A and B show the lift amount of the needle valve and the injection hole area. It is an explanatory view showing the relationship with valve opening pressure.

A throttle type fuel injection nozzle 1 is for a direct injection diesel engine, and a needle valve 2 is fitted and held in a front nozzle body 3 so as to be slidable in the axial direction. An intermediate nozzle main body 4 and a rear nozzle main body 5 are held in order by a nozzle holder 6 and are integrally formed. A nozzle hole 7 (see FIG. 2) is opened at the tip side (lower side in the figure) of the front nozzle body 3, and the rear nozzle body 5
A fuel inlet 8 connected to a fuel injection pump (not shown) is opened at the rear end side.

Further, from the fuel inlet 8 to the front nozzle body 3
A fuel passage 10 communicating with the nozzle hole 7 is provided, and the fuel pressure in this fuel passage 10 acts on a pressure receiving part (not shown) of the needle valve 2 to lift the needle valve 2 and inject fuel. It is injected from the hole 7. Further, the upper end of the needle valve 2 is brought into contact with a spring receiver 12 arranged in a spring chamber 11, and a nozzle spring 13 is compressed against the spring receiver 12 to bias the needle valve 2 in the closing direction. ing.

The shape of the tip of the needle valve 2 and the nozzle hole 7 is the second shape.
As shown in the figure, the nozzle hole 7 is located at the tip of the front nozzle body 3.
is opened, and the tip of the needle valve 2 moves back and forth within the nozzle hole 7 to control the nozzle hole area. At the tip of the needle valve 2, a large diameter throttle part 2b, a small diameter throttle part 2c, and a tapered part 2d are arranged so that their diameters become smaller in order from the base side, which has a sealing surface 2a for opening and closing the nozzle hole 7, toward the tip side. formed in
The gap between the outer circumferential surface of the tip end and the inner circumferential surface of the nozzle hole 7 changes according to the lift amount of the needle valve 2, so that the lift amount of the needle valve 2 and the opening area of the nozzle hole 7 change. ing.

That is, the relationship between the lift amount of the needle valve 2 and the nozzle hole area is as shown in FIG. 3B.
After the initial nozzle hole area increases as the valve opens, first, the large diameter throttle portion 2b is located within the nozzle hole 7, and the nozzle hole area is kept approximately constant by the restriction of the large diameter throttle portion 2b. Then, the large diameter throttle part 2b escapes from the nozzle hole 7, the small diameter throttle part 2c is located inside the nozzle hole 7, and the second throttle has a larger nozzle hole area than the first throttle area I. Then, as the lift amount increases, the small diameter throttle portion 2c escapes from the nozzle hole 7, and its tip taper portion 2d shifts to an expansion region where the nozzle hole area increases in proportion to the lift amount, resulting in a full lift. lifted into position.

In contrast to the above needle valve 2, this needle valve 2
A valve-opening pressure control mechanism 15 is provided to control the valve-opening pressure for lifting the valve according to the lift amount.
A plunger member 17, which is aligned with the axis of the needle valve 2, is slidably inserted into a cavity extending from the cylinder 16 on the rear side of the spring chamber 11 to the spring chamber 11. The plunger member 17 is
Rod portion 1 disposed within the spring chamber 11
7a, a plunger portion 17b fitted into the cylinder 16, and a flange portion 17c located between the rod portion 17a and the plunger portion 17b. and a stopper member 18 disposed at an intermediate portion of the spring chamber 11. Due to this contact of the flange 17c to the stopper member 18, the plunger member 1
7 is restricted from moving toward the needle valve 2, a predetermined gap d is formed between the tip of the rod portion 17a and the spring receiver 12. Note that this plunger member 17 is urged toward the needle valve 2 by a weak return spring 19.

Plunger portion 17b of the plunger member 17
The fuel inlet 8 and the cylinder 16 are provided in communication with each other so that fuel pressure from the fuel inlet 8 acts on the rear end surface. Further, a return passage 20 for discharging leaked fuel is connected to the spring chamber 11.

The characteristic of the valve opening pressure with respect to the lift amount of the needle valve 2 to which the valve opening pressure control mechanism 15 is attached is as shown in FIG. 3A. That is, as the fuel pressure increases, the needle valve 2 lifts against the nozzle spring 13, and the spring receiver 12 at the upper end of the needle valve 2 lifts against the nozzle spring 13.
The needle valve 2 and the plunger member 17 are pre-lifted until they come into contact with the plunger member 17, and the valve opening pressure is increased stepwise by this pre-lift amount _H2 , and when this is exceeded, the needle valve 2 and the plunger member 17 begin to lift as one.

In the lift amount up to the pre-lift amount _H2 , the valve opening pressure increases in response to the urging force of the nozzle spring 13. At prelift amount H ₂ ,
Lift suppression is increased by the fuel pressure acting on the end face of the plunger portion 17b of the plunger member 17, and the valve opening pressure corresponding to the area difference between the plunger portion 17b and the pressure receiving portion of the needle valve 2 is greater than or equal to the urging force of the nozzle spring 13. When the pre-lift amount H2 increases, the lift amount of the needle valve ₂ increases beyond the pre-lift amount H2. In this way, the valve opening pressure for lifting the needle valve 2 by the valve opening pressure control mechanism 15 is small until the predetermined prelift amount H _{2 .}
In the above, control is performed to increase the size in stages.

In the characteristics of the nozzle hole area and valve opening pressure with respect to the lift amount as shown in Fig. 3A and B,
The lift amount of the nozzle hole area at the boundary between the first throttle region I and the second throttle region is set to the lift amount H ₁ due to the valve opening pressure during idling, and the prelift amount in which the valve opening pressure increases stepwise. H ₂ is set to the lift amount corresponding to the nozzle hole area in the second throttle area.

With the above settings, in a low load range where the fuel pressure from the fuel injection pump is low, the lift amount is regulated to the first or second throttle region I, and the nozzle hole area is narrowed. 7, the fuel is injected at high speed to promote atomization of the fuel and improve ignitability and combustibility. In addition, in a high load range, the fuel pressure rises and the valve opening pressure exceeds the prelift amount _H2 , and the needle valve 2 lifts beyond the throttle range to the widening range, increasing the nozzle hole area and increasing the required Increasing amounts of fuel are injected within a predetermined injection period to ensure fuel supply and improve engine output.

On the other hand, during idling, the lift amount H ₁ due to the valve opening pressure at the maximum fuel pressure is set in the enlarged area of the nozzle hole area at the boundary between the first throttle area I and the second throttle area.
Injection in the first throttle region I atomizes the fuel, and even if the nozzle hole area becomes narrow due to carbon adhesion to the nozzle or manufacturing errors, the nozzle hole area at the above lift amount H ₁ increases, and the injection rate increases in this part, so the difference in injection period becomes smaller compared to injecting with the nozzle hole area of the first throttle area I, and by securing a predetermined injection amount, ignition performance is improved and idle vibration is reduced.

Furthermore, during starting supercharging, the amount of fuel delivered from the fuel injection pump increases compared to the above-mentioned idling time, and the valve opening pressure increases accordingly, so the lift amount at this time is equal to the above-mentioned lift amount during idling.
The prelift amount increases from H ₁ to near the prelift amount H ₂ , and the nozzle hole area becomes the second throttle region, and the nozzle hole area increases from the first throttle region I, and the
Fuel is atomized by injection in throttle region I, and even if the nozzle hole area becomes narrow due to carbon adhesion to the nozzle or manufacturing errors, the nozzle hole area becomes larger and the injection rate increases. Therefore, the difference in injection period is similarly reduced, and by ensuring a predetermined injection amount, ignition performance is improved and startability is improved.

Next, FIG. 4 shows a modification of the fuel injection nozzle 1', and the one in FIG. 1 shows a valve opening pressure control mechanism 15 that applies fuel pressure to the upper end of the plunger member 17. In this example, two nozzle springs are used to obtain similar valve opening pressure characteristics.

That is, the tip of the needle valve 2 inserted into the front nozzle body 3 is formed in the same manner as shown in FIG. 2, and has nozzle hole area characteristics with respect to lift amount as shown in FIG. 3B. , the needle valve 2 is activated by the fuel pressure in the fuel passage 30 communicating with the fuel inlet 28.
is lifted, and fuel is injected from the nozzle hole 7. In contrast to the front nozzle body 3, the intermediate nozzle body 2
A valve-opening pressure control mechanism 35 for controlling the valve-opening pressure is disposed on the rear nozzle main body 25 connected to the nozzle holder 26 via the nozzle holder 26 .

At the upper end of the needle valve 2 is a first spring receiver 3 that supports the lower end of the first nozzle spring 33.
The upper end of the first nozzle spring 33 is in contact with the stopper part 3 in the middle part of the spring chamber 31.
8 is engaged. This first spring receiver 3
The upper end of the plunger member 37 connected to the
It is positioned with a predetermined gap with respect to the second spring receiver 34, and this second spring receiver 34
A second nozzle spring 36 is disposed above the nozzle. The second nozzle spring 36 is provided so as to be adjustable by an adjusting bolt 39 at the other end.

According to the above structure, the plunger member 37 is the first
Up to the pre-lift amount H ₂ when it lifts against the nozzle spring 33 and comes into contact with the second spring receiver 34 , the needle valve 2 lifts with a small valve opening pressure against the first nozzle spring 33 , while the pre-lift amount H ₂ or more Since the needle valve 2 is lifted against the first and second nozzle springs 33 and 36, the valve opening pressure increases stepwise, and the valve opening is substantially the same as that shown in FIG. 3A above. This provides pressure characteristics.

For the above characteristics, the lift amount H ₁ due to the valve opening pressure during idling is set at the boundary between the first throttle region I and the second throttle region, and the prelift amount H ₂ is further set within the second throttle region. Therefore, the same action and effect as the previous example can be obtained.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a fuel injection nozzle in an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the tip of the fuel injection nozzle in FIG. 1, and FIG. 3 is a needle in the fuel injection nozzle in FIG. 1. A characteristic diagram showing the relationship between the lift amount of the valve, the injection hole area, and the valve opening pressure, and FIG. 4 is a longitudinal sectional view of a fuel injection nozzle in another embodiment. 1, 1'...Fuel injection nozzle, 2...Needle valve, 2a...Sealing surface, 2b...Large diameter throttle part, 2c...Small diameter throttle part, 2d...Tapered part, 3...Front nozzle body , 5, 25... Rear nozzle body, 7... Nozzle hole, 8, 28... Fuel inlet, 10... Fuel passage, 11, 31... Spring chamber, 12, 32, 34... Spring receiver, 1
3, 33, 36... Nozzle spring, 15, 3
5... Valve opening pressure control mechanism, 17, 37... Plunger member, I... First throttle area,... Second throttle area,... Expansion area.

Claims (1)

[Claims] 1. In a throttle type fuel injection nozzle in which the needle valve tip moves back and forth within the nozzle nozzle hole and the nozzle hole area is controlled by the outer circumferential surface of the needle valve tip and the inner circumferential surface of the nozzle hole,
A valve opening pressure control mechanism is provided to control the opening pressure for lifting the needle valve stepwise so that it is small up to a predetermined pre-lift amount and becomes large above this pre-lift amount. , a large-diameter throttle part, a small-diameter throttle part, and a tapered part are formed, and the nozzle hole area characteristics with respect to the increase in the lift amount of the needle valve are determined by forming a first throttle area by the large-diameter throttle part and an injection hole from the first throttle area. The throttle has a characteristic of having a second throttle area formed by the small diameter throttle part with a large hole area and a widening area formed by the tapered part, and the lift amount at the boundary between the first throttle area and the second throttle area is determined by the valve opening during idling. A fuel injection nozzle for a diesel engine, characterized in that the lift amount is set to a lift amount based on pressure, and a predetermined prelift amount in the valve opening pressure control mechanism is set to a lift amount within the second throttle region.