JPH07224739A - Fuel injection nozzle - Google Patents

Abstract

PURPOSE:To improve characteristic of fuel injection in the fuel injection nozzle of a direct jet type diesel engine. CONSTITUTION:A through hole 4 for introducing fuel to the top end part of a needle 5 is formed inside the needle 5, a first injection hole 3 for injecting fuel to a nozzle body 1 is formed, a first seal part 15 for shutting off communication between the through hole 4 and the first injection hole 3 so as to set the top end part 21 of the needle 5 to the needle body 1, and a cylindrical part 24 slidably fitting the outer circumferential part 22 of the needle 5 to the nozzle body 1 is formed on the side closer to the base end than the first injection hole 3. Consequently, a second injection hole 2 for injecting the fuel is opened on the way of the cylindrical part 24, and then inclination angle of the first injection hole 3 in relation to a cylinder shaft is formed smaller than that of the second injection hole 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel injection nozzle used in a direct injection diesel engine or the like.

[0002]

2. Description of the Related Art In order to reduce ignition delay of a diesel engine and realize smooth combustion, there is a fuel injection nozzle that performs fuel injection in stages.

As a fuel injection nozzle of this type, there is a conventional one shown in FIG. 11, for example (Japanese Patent Laid-Open No. 59-147862).
Gazette, reference).

Explaining this, the nozzle body 4
1, a plurality of first injection holes 43 and second injection holes 49 are respectively opened radially, and only the first injection holes 43 having a small injection hole diameter are opened when the needle 42 is initially lifted, as shown by an arrow B in FIG. In addition, a small amount of fuel is injected into the cavity 40 of the piston 45, and as the needle 42 lifts, the second injection hole 49 having a large hole is opened and a large amount of fuel is injected as indicated by arrow C. ing.

[0005]

However, in such a conventional device, the fuel injection direction of the first injection hole 43 in which the initial injection is performed is directed toward the central portion of the combustion chamber, while the second injection hole is formed. Since the fuel injection direction of 49 is directed to the lateral region of the combustion chamber, the fuel spray from the first injection hole 43 and the fuel spray from the second injection hole 49 are generated during the main injection in which a large amount of fuel is injected. There was a problem that the smoke was deteriorated by overlapping with each other and creating a region where the fuel was excessively concentrated in the combustion chamber.

In view of the above problems, the present invention aims to improve the fuel injection characteristics in a fuel injection nozzle of a direct injection type diesel engine.

[0007]

The invention according to claim 1 is
In a fuel injection nozzle in which a needle lifts and injects fuel according to the fuel pressure that is pumped in synchronism with the engine rotation from the fuel injection pump, the fuel that is pumped from the fuel injection pump into the needle is delivered to the tip of the needle. A first injection hole for injecting fuel is formed in a nozzle body accommodating the needle, and a leading end portion of the needle is seated on the nozzle body to block communication between the through hole and the first injection hole. A second seal that forms a first seal part and that slidably fits the outer peripheral part of the needle to the nozzle body is formed on the base end side of the first injection hole, and that injects fuel in the middle of the cylinder part. The hole is opened so that the inclination angle of the first injection hole with respect to the cylinder axis is smaller than that of the second injection hole.

According to a second aspect of the invention, in the invention of the first aspect, the opening area of the first injection hole is smaller than that of the second injection hole.

The invention according to claim 3 is the invention according to claim 1 or 2.
In any one of the inventions described above, the first spring and the second spring for urging the needle to close the valve are interposed in parallel, and the urging force of the second spring does not act on the needle until the needle lifts beyond the pre-lift amount. The amount of lift of the needle that opens the second injection hole is set to be larger than the amount of pre-lift.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, a means for regulating the lift amount of the needle is provided, and the timing of lifting the needle is delayed according to the operating state, and A control means is provided for restricting the lift amount of the needle within a range in which the second injection hole does not open.

[0011]

In the first aspect of the invention, when the outer periphery of the tip of the needle separates from the first seal portion during the initial injection in which the needle lifts slightly, the fuel introduced through the through hole in the needle is only the first injection hole. Is injected from the center of the combustion chamber.

When the second injection hole is opened by the outer peripheral portion of the needle during main injection in which the needle lifts above a predetermined value, the fuel introduced through the through hole in the needle causes the fuel to flow between the first injection hole and the second injection hole. Both are injected into the combustion chamber.

Since the first injection hole is arranged closer to the tip side of the nozzle body than the second injection hole, and the inclination angle of the first injection hole with respect to the cylinder axis is smaller than that of the second injection hole, the injection from the first injection hole is performed. The generated fuel spray and the fuel spray injected from the second injection hole can be prevented from overlapping with each other, and the fuel can be uniformly distributed in the combustion chamber to suppress the amount of smoke generated.

According to the second aspect of the invention, since the opening area of the first injection hole is smaller than that of the second injection hole, atomization of the fuel injected from the first injection hole during the initial injection with a low injection pressure is achieved. The fuel and air in the combustion chamber are sufficiently mixed, and the combustibility is improved.

Since the second injection hole opened at the time of main injection has a large opening area, a large amount of fuel injected from the second injection hole spreads to a wide range of the combustion chamber with a strong penetration force. By increasing the rate, fuel efficiency can be reduced and output can be improved. Moreover, since the fuel injection is completed within a short time, the fuel is not injected outside the combustion chamber, and the amount of unburned HC and smoke generated near the cylinder wall can be suppressed.

According to the third aspect of the present invention, when the fuel pressure supplied from the fuel injection pump is low and the load is low, the needle is suppressed to a pre-lift amount or less by the urging force of the second spring, so that the second injection hole is opened. And the entire amount of fuel is injected from the first injection hole. As a result, the fuel is atomized, the fuel and air in the combustion chamber are sufficiently mixed, and the combustibility is enhanced.

After the initial injection of a small amount of fuel from the first injection hole while the needle is kept below the pre-lift amount by the urging force of the second spring at the time of high load when the fuel pressure supplied from the fuel injection pump rises. The needle fully lifts while compressing the second spring, and a large amount of fuel is mainly injected from the first injection hole and the second injection hole. In this way, the fuel injection is performed stepwise, so that ignition delay can be reduced and smooth combustion can be performed, and vibration and noise can be reduced.

In a fourth aspect of the present invention, the piston is lifted under a predetermined operating condition by delaying the timing of lifting the needle and limiting the lift amount of the needle within a range in which the second injection hole does not open. Even if the fuel is injected in a state in which it has dropped to some extent from the top dead center, the fuel is not injected outside the combustion chamber because the injection angle of the fuel injected from the first injection hole is small, and the cylinder wall It is possible to suppress the amount of unburned HC and smoke generated near the section. Moreover, the amount of NOx generated can be suppressed by delaying the fuel injection timing.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIGS. 1 and 2, a fuel injection nozzle provided in a direct injection diesel engine has a hollow cylindrical nozzle body 1 in which a needle 5 is housed and a passage is provided from a fuel pump (not shown). The needle 5 is lifted stepwise in accordance with the fuel pressure fed via the pump so that fuel injection is performed stepwise. A combustion chamber (cavity) recessed like a dish is formed on the top surface of the piston (not shown), and the fuel injection nozzle is provided so as to face the center of the combustion chamber from the cylinder head.

In the fuel injection nozzle, a first spring 8 and a second spring 11 for urging the needle 5 to close are interposed in parallel.

The first spring 8 is the first push rod 7.
And the needle 5 is urged to close the valve via the first pressure pin 9.

The second spring 11 includes a first push rod 7, a first pressure pin 9 and a second push rod 10.
And the needle 5 is urged to close the valve via the second pressure pin 12.

As a means for restricting the urging force of the second spring 11 from being applied to the needle 5 until the needle 5 is lifted beyond the pre-lift amount, the second push rod 10 is seated and its downward displacement is restricted. A spacer 18 is provided.

When the pressure applied to the needle 5 increases beyond the initial spring force of the first spring 8 due to the fuel pressure introduced from the fuel injection pump into the fuel chamber 6, the needle 5 moves to the first position as shown in FIG. The first spring 8 is lifted while being compressed via the push rod 7 and the first pressure pin 9. Until the first pressure pin 9 contacts the second push rod 10 and the fuel pressure exceeds the biasing force of the spring force of the first spring 8 and the initial spring force of the second spring 11, the lift amount of the needle 5 is increased. Is kept below the pre-lift amount Lmin.

Next, when the pressure applied to the needle 5 exceeds the urging force of the spring force of the first spring 8 and the initial spring force of the second spring 11, the needle 5 moves to the first position as shown in FIG. While compressing the second spring 11 via the one push rod 7, the first pressure pin 9, the second push rod 10, and the second pressure pin 12, the second spring 11 is lifted beyond the pre-lift amount Lmin. When the needle 5 reaches the full lift amount Lmax, the needle 5
It abuts against the housing 19 and the lift is further restricted.

A through hole 4 is formed inside the needle 5 for guiding the fuel pumped from the fuel injection pump to the tip of the needle 5. The upper end of the through hole 4 communicates with the fuel chamber 6, and the lower end of the through hole 4 opens at the center of the needle 5. The through hole 4 is provided with the fuel inlet 14, through the fuel chamber 6, the gap between the needle 5 and the nozzle body 1 and the through hole 13 formed in the housing 15.
Communicate with. Fuel that is pumped from the fuel injection pump in synchronization with the engine rotation is introduced into the fuel inlet 14.

A conical portion 21 is formed so as to project annularly from the tip of the needle 5, and the through hole 4 is formed at the tip of the conical portion 21.
Is open.

A plurality of first injection holes 3 for injecting fuel are radially formed at the tip portion of the nozzle body 1, and the conical portion 21 of the needle 5 is seated so that the through hole 4 and the first injection hole 3 communicate with each other. The first seal portion 15 for blocking the above is formed. The first seal portion 15 is formed so as to face the conical portion 21 of the needle 5 and be concave in a conical shape.

An outer peripheral portion 22 having a right cylindrical shape is formed in the middle of the needle 5, while the outer peripheral portion 2 is formed on the nozzle body 1.
2 A cylindrical portion 24 is formed which is slidably fitted.

The cylindrical portion 24 is formed on the base end side of the first injection hole 3, and a plurality of second injection holes 2 for injecting fuel are radially opened in the middle of the cylindrical portion 24.

An annular step 25 is formed in the middle of the needle 5, while a second seal 16 for seating the step 25 is formed on the nozzle body 1.

Each of the first injection holes 3 and each of the second injection holes 2 are formed radially toward the combustion chamber of the piston. The inclination angle of each first injection hole 3 with respect to the cylinder axis is set smaller than that of the second injection hole 2. As a result, the fuel injected from each first injection hole 3 spreads to the central portion of the combustion chamber, while the fuel injected from each second injection hole 2 spreads to a wide range of the combustion chamber.

The diameter of the first injection hole 3 is smaller than that of the second injection hole 2. The injection hole diameter of the first injection hole 3 is arbitrarily set so that the injection rate required at the initial lift of the needle 5 is obtained, while the injection hole diameter of the second injection hole 2 is set to the injection rate required at the main injection. It is set arbitrarily so as to be obtained.

The fuel pressure fed from a fuel pump (not shown) through the passage changes according to the engine load and the number of revolutions,
By arbitrarily setting the biasing force of the first spring 8 and the second spring 11, etc., as shown in FIG. 5, the operating range in which the fuel is injected and supplied only from the first injection hole 3 and the fuel is first injected. An operation range in which the injection is supplied in two stages from the hole 3 and the second injection hole 2 is set.

With the above construction, the operation will be described.

As shown in FIG. 6, the internal pressure of the injection pipe introduced from the fuel injection pump introduced into the fuel chamber 6 at low speed and low load is suppressed to P ₂ or less, and the pressure applied to the needle 5 is the spring of the first spring 8. The needle 5 lifts within the range of the pre-lift amount Lmin or less without exceeding the urging force that is the sum of the force and the initial spring force of the second spring 11. When the conical portion 21 of the needle 5 is separated from the first seal portion 15 of the nozzle body 1, the first injection hole 3 is opened, but the second injection hole 2 is closed by the outer peripheral portion 22 of the needle 5.

At this time, since the entire amount of fuel is injected from the first injection hole 3 having a small injection hole diameter, atomization of the fuel proceeds even at a low injection rate, and the fuel and air in the combustion chamber are sufficiently mixed. The flammability can be improved. Further, since the entire amount of fuel is injected from the first injection hole 3 into the central portion of the combustion chamber at a small injection angle, the fuel is not injected outside the combustion chamber and is not generated near the cylinder wall portion. The amount of combustion HC and smoke can be suppressed.

When the pressure applied to the needle 5 increases beyond the initial spring force of the first spring 8 due to the fuel pressure from the fuel injection pump introduced into the fuel chamber 6 at the time of high speed and high load, the needle 5 moves to the first spring. 8 is compressed and lifted, and an initial injection for supplying a small amount of fuel from the first injection hole 3 is performed. Subsequently, when the pressure applied to the needle 5 exceeds the biasing force of the spring force of the first spring 8 and the initial spring force of the second spring 11, the needle 5 pushes the first push force as shown in FIG. The second spring 11 is lifted while being compressed via the rod 7, the first pressure pin 9, the second push rod 10 and the second pressure pin 12. At this time, the second injection hole 2 is opened by the outer peripheral portion 22 of the needle 5, and the main injection for supplying a large amount of fuel from the second injection hole 2 starts. In this way, the gradual fuel injection is performed by the initial injection and the main injection, so that stable and smooth combustibility with less ignition delay and thus less vibration and noise can be obtained.

Since the second injection hole 2 opened by the main injection has a wide injection angle and a large injection hole diameter, a large amount of fuel injected from the second injection hole 2 is injected into the combustion chamber with a strong penetration force in a short time. Since it is spread over a wide range, the air utilization rate can be increased to reduce fuel consumption and output. Since the fuel injection is completed within a short time, the fuel is not injected outside the combustion chamber, and the amount of unburned HC and smoke generated near the cylinder wall can be suppressed.

Since the first injection hole 3 is arranged closer to the tip side of the nozzle body 1 than the second injection hole 2, and the inclination angle of the first injection hole 3 with respect to the cylinder axis is smaller than that of the second injection hole 2, Fuel spray injected from one injection hole 3 and second injection hole 2
Prevents the fuel spray injected from overlapping from overlapping,
It is possible to suppress the amount of smoke generated by uniformly distributing the fuel in the combustion chamber.

Next, another embodiment shown in FIG. 7 will be described. It should be noted that the same reference numerals are used for the portions corresponding to those in FIGS. 1 and 2.

A piezoelectric actuator 17 is provided above the second pressure pin 12 as a means for delaying the lift of the needle 5 and adjusting the fuel injection timing. When the piezoelectric actuator 17 is energized by the control device, its thickness increases and contacts the second pressure pin 12, thereby regulating the lift amount of the needle 5. The piezoelectric actuator 17 is formed of a magnetostrictive element or an electrostrictive element.

It should be noted that a second spring seated on the second pressure pin 12 may be provided in the same manner as in the above-described embodiment so that two-stage injection is performed at high speed and high load.

The control device inputs the detection signals of the engine speed and the load, and based on the map shown in FIG. 8, the piezoelectric actuator 1 is placed in the retard request region where the load is lower than the predetermined value.
7 is energized to delay the fuel injection timing, and the lift amount of the needle 5 is regulated to Lmin or less so that the first injection hole 3
Control is performed to inject fuel only from.

Piezoelectric actuator 1 in the retard required area
7 is energized to delay the fuel injection timing, the lift amount of the needle 5 is regulated to Lmin or less, the second injection hole 2 is closed, and the fuel is injected only from the first injection hole 3. As a result, as shown in FIG. 10, even when the piston 31 is lowered, the fuel injection angle is small, so that the fuel is not injected outside the combustion chamber 30 and is generated near the cylinder wall portion 32. The amount of unburned HC and smoke generated can be suppressed. Moreover, by delaying the fuel injection timing,
The amount of NOx generated can be suppressed.

On the other hand, when the load is high, the piezoelectric actuator 17
Energization of can be stopped. As a result, the needle 5 lifts beyond the pre-lift amount Lmin and the second injection hole 2 is opened. Since the second injection hole 2 has a large injection hole diameter, a large amount of fuel injection is completed within a short time when the piston 31 is near the top dead center. At this time, the fuel spray injected from the first injection hole 3 and the fuel spray injected from the second injection hole 2 do not overlap with each other, and the fuel is uniformly distributed in the combustion chamber 30 to reduce the amount of smoke generated. It can be suppressed.

[0048]

As described above, according to the invention of claim 1, in the fuel injection nozzle for injecting fuel, the needle is lifted according to the fuel pressure sent from the fuel injection pump in synchronization with the engine rotation, A through hole is formed inside the needle for guiding the fuel pumped from the fuel injection pump to the tip of the needle, and a first injection hole for injecting the fuel is formed in the nozzle body accommodating the needle. A first seal part is formed to seat the tip part to block the communication between the through hole and the first injection hole, and a cylindrical part for slidably fitting the outer peripheral part of the needle to the nozzle body is formed from the first injection hole. The second injection hole, which is formed on the end side and injects fuel in the middle of the cylinder, is opened, and the inclination angle of the first injection hole with respect to the cylinder axis is smaller than that of the second injection hole. Fuel injection from If prevents the suit case overlap the fuel spray injected from the second injection hole with increasing injection pressure,
Emissions of unburned HC and smoke are reduced, pollution of diesel engines is reduced, and fuel efficiency is improved.

According to a second aspect of the present invention, in the first aspect of the invention, the opening area of the first injection hole is smaller than that of the second injection hole, so that the injection pressure is low and the injection is performed from the first injection hole. The fuel is atomized, the fuel and air in the combustion chamber are sufficiently mixed, and the combustibility is improved. Since the second injection hole that opens as the injection pressure rises has a large opening area, a large amount of fuel injected from the second injection hole spreads to a wide range of the combustion chamber with a strong penetration force, and the air in the combustion chamber is used. By increasing the rate, the amount of unburned HC and smoke generated can be suppressed, and the fuel consumption can be reduced and the output can be improved.

The invention according to claim 3 is the same as claim 1 or 2.
In any one of the inventions described above, the first spring and the second spring for urging the needle to close the valve are interposed in parallel, and the urging force of the second spring does not act on the needle until the needle lifts beyond the pre-lift amount. Since the lift amount of the needle that opens the second injection hole is set larger than the pre-lift amount, the fuel is atomized because the entire amount of fuel is injected from the first injection hole when the load is low. It comes off and the flammability can be improved. On the other hand, when the load is high, the fuel injection is performed step by step from the first injection hole and the second injection hole, so that the ignition delay is reduced and smooth combustion is performed, and vibration and noise can be reduced.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, a means for restricting the lift amount of the needle is provided to delay the timing of lifting the needle according to the operating state, and Since the control means for restricting the lift amount of the needle within the range in which the second injection hole does not open is provided, NOx is delayed by delaying the fuel injection timing.
Is suppressed, and even if the fuel is injected with the piston lowered to some extent from the top dead center, the injection angle of the fuel injected from the first injection hole is small, so that the fuel is discharged outside the combustion chamber. The amount of unburned HC and smoke generated near the cylinder wall is suppressed without being injected.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a fuel injection nozzle showing an embodiment of the present invention.

FIG. 2 is an overall sectional view of the fuel injection nozzle.

FIG. 3 is a partial cross-sectional view of the fuel injection nozzle similarly showing an operating state at the time of low load and the like.

FIG. 4 is a partial cross-sectional view of the fuel injection nozzle similarly showing an operating state at the time of high load.

FIG. 5 is a control characteristic diagram of the same.

FIG. 6 is an explanatory view of fuel injection characteristics.

FIG. 7 is an overall sectional view of a fuel injection nozzle showing another embodiment.

FIG. 8 is a control characteristic diagram of the same.

FIG. 9 is a sectional view of the engine similarly showing an operating state at the standard injection timing.

FIG. 10 is a sectional view of the engine similarly showing an operating state when the injection timing is delayed.

FIG. 11 is a partial cross-sectional view of a fuel injection nozzle showing a conventional example.

FIG. 12 is a sectional view of a combustion chamber and the like showing an operating state of the same.

[Explanation of symbols]

 1 Nozzle body 2 Second injection hole 3 First injection hole 4 Through hole 5 Needle 8 First spring 11 Second spring 15 First seal part 17 Piezoelectric actuator 18 Spacer 21 Conical part 22 Outer peripheral part 24 Cylindrical part

Claims (4)

[Claims] 1. In a fuel injection nozzle in which a needle lifts and injects fuel in response to fuel pressure that is pumped from a fuel injection pump in synchronization with engine rotation, the fuel that is pumped from the fuel injection pump is injected into the needle. A through hole that leads to the tip of the needle is formed, a first injection hole for injecting fuel is formed in the nozzle body that houses the needle, and the tip of the needle is seated in the nozzle body to form the through hole and the first injection hole. A first seal part is formed to block the communication between the nozzle body and a cylindrical part that slidably fits the outer peripheral part of the needle to the nozzle body is formed on the base end side from the first injection hole. A fuel injection nozzle characterized in that a second injection hole for injection is opened, and an inclination angle of the first injection hole with respect to the cylinder axis is formed smaller than that of the second injection hole. 2. The fuel injection nozzle according to claim 1, wherein the opening area of the first injection hole is smaller than that of the second injection hole. 3. A first spring and a second spring for urging the needle to close the valve are provided in parallel, and the urging force of the second spring is restricted so as not to act on the needle until the needle is lifted beyond a pre-lift amount. Means are provided, and the lift amount of the needle for opening the second injection hole is set to be larger than the pre-lift amount.
5. The fuel injection nozzle according to any one of 1. 4. A control means comprising means for regulating the lift amount of the needle, delaying the timing of lifting the needle according to operating conditions, and regulating the lift amount of the needle within a range in which the second injection hole is not opened. The fuel injection nozzle according to any one of claims 1 to 3, further comprising: