JPH02230952A - Fuel injection nozzle for engine - Google Patents

Abstract

PURPOSE:To improve the cutoff of fuel by providing a reinforcing means applying an external force reinforcing the excitation force to a needle valve when the needle valve is moved in the direction to close a nozzle hole by the excitation force of a spring. CONSTITUTION:A needle valve 20 slid in the axial direction is arranged in a nozzle body 14. The needle valve 20 is invariably excited in the direction to close a nozzle hole 18 by the excitation force of the first spring 30. The second spring 35 excites the needle valve 20 in the direction to close the nozzle hole 18. A reinforcing means 50 applying an external force reinforcing the excitation force to the needle valve 20 when the needle valve 20 is moved in the direction to close the nozzle hole 18 by the excitation force of the first spring 30 is provided. The needle valve quickly closes the nozzle hole, and the cutoff of fuel can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection nozzle for an engine, and more particularly to measures to improve fuel exhaustion in a so-called two-stage spring type fuel injection nozzle.

(Prior Art) Conventionally, a so-called two-stage spring type fuel injection nozzle, as disclosed in Japanese Patent Laid-open Publication No. 63-111281, has a nozzle at its tip and pumps fuel pumped from a fuel injection pump. It has a nozzle body in which a high-pressure fuel passage leading to the nozzle is formed, and a bottle section at the tip that is inserted into the nozzle.The nozzle body is moved in the direction of opening the nozzle by the pressure of the fuel fed into the high-pressure fuel passage. ) a first spring disposed within the nozzle body to always urge the needle valve in a direction to close the nozzle; and a first spring disposed within the nozzle body so that the needle valve throttles the nozzle with a pin portion. A device is known that includes a second spring that biases the needle valve in the direction of closing the nozzle when the needle valve is further moved (lifted) in the direction of opening the nozzle. According to this two-stage spring type fuel injection nozzle, when the load is low such as when idling, the needle valve lifts against the biasing force of the first spring, but the fuel pressure delivered to the fuel injection nozzle is low. Therefore, it cannot be lifted until it resists the biasing force of the second spring.

Therefore, the amount of lift remains within the pre-lift range where only the biasing force of the first spring is applied, and the nozzle is narrowed by the pin of the needle valve, resulting in an extremely small effective nozzle area, which promotes fuel atomization and combustion. This improves combustion performance (ignitability), reduces combustion noise, and reduces the content of hydrocarbons (HC) in exhaust gas.

On the other hand, under medium and high loads, the pressure of the fuel fed to the fuel injection nozzle is high, so even after the needle valve pre-lifts, it lifts further against the biasing force of the second spring, reducing the effective nozzle area. Since the amount of fuel increases, an amount of fuel commensurate with the required output is injected. In that case, at the beginning of the travel stroke when the lift a of the needle valve is relatively small, the nozzle is throttled and the injection rate is kept low, so that the fuel is reliably ignited at the beginning of injection, and thereafter the fuel does not burn suddenly. Burns at an appropriate rate.

As a result, combustion noise is reduced and the content of hydrocarbons (HC) and nitrogen oxides (NOx) in the exhaust gas is reduced.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional device, when the needle valve moves (descends) in the nozzle closing direction in the latter half of the fuel injection period, for example, during medium load and high load, the needle valve ,
First, it is lowered by the urging force of the first spring and the second spring, and when the pre-lift state is reached, it is further lowered by the urging force of only the first spring, thereby closing the nozzle. Therefore, the biasing force of the spring becomes discontinuous and rapidly decreases in the vicinity of the pre-lift, which causes a problem in that the fuel runs out poorly due to a delay in closing the needle valve.

Moreover, when the needle valve descends and enters the throttle region where the effective nozzle area is small, the fuel pressure near the nozzle increases and prevents the needle valve from descending, which also aggravates the above-mentioned fuel shortage. .

The present invention has been made with attention to these points,
The purpose of this is to quickly close the needle valve by applying an external force other than the biasing force of the first spring when the needle valve descends from the substantially full lift state.

(Means for Solving the Problems) In order to achieve the above object, in the present invention, when the needle valve moves in the direction of closing the nozzle due to the urging force of the first spring, the reinforcing means further moves the needle valve in the direction of closing the nozzle. I'm trying to give it a boost.

Specifically, the solution taken by the present invention consists of a nozzle body that has a nozzle at its tip and a high-pressure fuel passage that guides fuel pumped from a fuel injection pump to the nozzle; a needle valve having a pin portion to be inserted and moved in a direction to open the nozzle by the pressure of the fuel pumped into the high-pressure fuel passage; and a needle valve disposed within the nozzle body to constantly close the nozzle. a first spring biased in the direction; and a first spring disposed within the nozzle body that urges the needle valve in the direction of closing the nozzle when the needle valve is moved from the state where the nozzle is throttled by the pin portion to the direction of opening the nozzle. and a reinforcing means for applying an external force to the needle valve to reinforce the urging force when the needle valve moves in the direction of closing the nozzle due to the urging force of the first spring. be.

(Function) With the above configuration, in the present invention, at low load,
Since the fuel pressure fed to the fuel injection nozzle is low, the needle valve cannot lift against the biasing force of the second spring and only lifts within the pre-lift range, and the nozzle is throttled by the pin of the needle valve. As a result, the effective nozzle area becomes extremely small, fuel atomization is promoted, combustibility (ignitability) is improved, combustion noise is reduced, and the content of hydrocarbons (HC) in the exhaust gas is reduced.

On the other hand, under medium and high loads, the pressure of the fuel fed to the fuel injection nozzle is high, so even after the needle valve pre-lifts, it lifts further against the biasing force of the second spring, reducing the effective nozzle area. At the same time, at the beginning of the travel stroke when the lift amount of the needle valve is relatively small, the nozzle is narrowed and the injection rate is kept low, ensuring that fuel is injected at the beginning of the injection. ignites, and then the fuel burns at an appropriate speed without combusting suddenly.

In that case, when the needle valve is lowered in the second half of the fuel injection period, the needle valve is first lowered by the biasing forces of the first spring and the second spring. Furthermore, in the pre-lift state, the needle valve attempts to further descend and close the nozzle due to the biasing force of the first spring, but the reinforcing means acts on an external force that reinforces this biasing force.
The needle valve closes the nozzle quickly and drains the fuel better.

(First example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a fuel injection nozzle according to a first embodiment of the present invention. The fuel injection nozzle is used, for example, in a direct-injection diesel engine installed in an automobile.

In the figure, 10 is a nozzle holder, 11 is a mounting nut attached to the nozzle holder 10,
A nozzle body 14 is attached to the lower end of the nozzle holder 10 via a distance piece 12 and supported by a retaining nut 16. The nozzle holder 10, the distance piece 12, and the nozzle body 14 are provided with a high-pressure fuel passage 17 for guiding the fuel, which is pressure-fed from a fuel injection pump (not shown) and introduced into the fuel introduction connector part 15, to the injection port 18. It is formed.

Further, as shown in FIG. 2, a spout 18 is formed at the tip of the nozzle body 14.

A needle valve 20 is disposed within the nozzle body 14 so as to slide in the axial direction thereof.
A pin portion 22 provided at the tip of the nozzle 0 is inserted into the nozzle 18 . Further, a first spring chamber 23 is formed within the nozzle holder 10, and the rear end portion 20a of the needle valve 20 is disposed so as to face the first spring chamber 23. Further, a spring seat 24 is disposed in the first spring chamber 23 so as to be movable in the axial direction thereof, and the spring seat 24 is fitted into the rear end portion 20H of the needle valve.

A first spring 30 is compressed between the spring seat 24 and a partition wall 28 forming the upper wall of the first spring chamber 23, and the urging force of the first spring 30 causes the needle valve 20 to The nozzle 18 is always biased in the direction of closing.

Further, a second spring chamber 32 is formed above the partition wall 28 of the nozzle holder 10. An intermediate rod 25 is disposed from the first spring chamber 23 to the second spring chamber 32 so as to be movable in the axial direction. The head 25a of the intermediate rod 25 is formed large enough to be able to come into sliding contact with the side wall of the second spring chamber 32. And this head 2
5a comes into contact with the partition wall 28 and the intermediate rod 25 assumes the lowest position (as shown in FIG. 1), a clearance hP corresponding to the prelift amount is set between the intermediate rod 25 and the spring seat 24. . Further, a spring seat 33 is formed at the upper end of the second spring chamber 32, and a second spring 35 is compressed between the spring seat 33 and the intermediate rod 25. In addition, 44 is a lid member provided on the upper part of the second spring chamber 32, and 46 is a cap provided on the upper cover of the nozzle holder 10.

As shown in FIG. 5, when the load is low, the needle valve 20 is moved against the biasing force of the first spring 30 via the spring seat 24 due to the fuel pressure fed to the high pressure fuel passage 17. Although the prelift is carried out within the range of the above-mentioned clearance hP, since the fuel pressure is low, the lift cannot be carried out against the biasing force of the second spring 35, and the lift does not exceed the prelift amount. Therefore, the nozzle 18 is the needle valve 2
The effective nozzle area becomes extremely small due to narrowing by the pin part 22 of 0, promoting atomization of the fuel and improving combustibility (ignitability).
combustion noise is reduced, and the content of hydrocarbons (HC) in the exhaust gas is reduced.

On the other hand, at medium load and high load, the pressure of the fuel fed to the high pressure fuel passage 17 is high, so even after the needle valve 20 prelifts, the second
The effective nozzle area increases by lifting against the urging force of the spring 35, and an amount of fuel commensurate with the required output is injected, and at the beginning of the travel stroke when the lift amount of the needle valve 20 is relatively small, the nozzle 18 is throttled to keep the injection rate low, the fuel is reliably ignited at the beginning of injection, and thereafter the fuel is combusted at an appropriate speed without combusting suddenly.

Further, the intermediate rod 25 is provided with a reinforcing means 50 for applying an external force to the needle valve 20 to reinforce the urging force when the needle valve 20 moves in the direction of closing the nozzle 18 due to the urging force of the first spring 30. It is provided.

That is, as shown in FIGS. 3 and 4, a communication passage 51 is formed in the intermediate rod 25 to communicate the first spring chamber 23 and the second spring chamber 32. As shown in FIGS. And the communication path 5
A fuel chamber 52 is provided in the middle of 1. The fuel chamber 5
2 is provided with a check valve 53 and a return spring 54 that biases the check valve 53 downward. In addition, as shown in FIG. 4, the check valve 53
Leak grooves 53a... are formed on the opening side.

When the needle valve 20 lifts in the first half of the fuel injection period, the fuel in the first spring chamber 23 leaks to the second spring chamber 32 via the communication path 51 and the leak grooves 53a. This ensures the various functions of the intermediate rod 25 and the like during the above-mentioned lift. On the other hand, when the two-dollar valve 20 descends in the latter half of the fuel injection period, the check valve 53 closes due to the increase in fuel pressure in the first spring chamber 23. That is, since the upper end 53a of the check valve 53 blocks the communication passage 51 against the biasing force of the return spring 54, the biasing force of the second spring 35 closes the first spring chamber 2.
The fuel of No. 3 is pressurized and its pressure increases, and this fuel pressure acts on the needle valve 20 and pushes the needle valve 20 down. As a result, the needle valve 20, which is further lowered from the pre-lift state, is further urged in the downward direction by the above-described downward force in addition to the urging force of the first spring 30, so that it can quickly move in the downward direction and close the nozzle. This results in better fuel consumption.

(Second Embodiment) FIG. 6 shows a fuel injection nozzle according to a second embodiment of the present invention. Since the basic configuration of the fuel injection nozzle is the same as that of the fuel injection nozzle of the first embodiment, the explanation of the members 10 to 46 will be omitted.

The fuel injection nozzle according to this embodiment is not provided with a check valve 53 or the like, but instead is provided with a solenoid 61 at the top of the nozzle holder 10. The solenoid 6
1, the magnetic force part 61a at the tip is magnetized according to the applied voltage. This solenoid 61 has a magnetic force section 61a.
is arranged in the second spring chamber 32, and its tip is provided facing the intermediate rod 25 with a predetermined clearance X therebetween. Further, the intermediate rod 25 is set so that there is no clearance between the intermediate rod 25 and the spring seat 24 when the intermediate rod 25 is at the lowest position (as shown in FIG. 1). The clearance X is set larger than the maximum lift mhN of the needle valve 20. The solenoid 61 is controlled by a control unit.

Further, a pressure sensor (not shown) for detecting fuel injection pressure is provided in a nozzle tube (not shown) connected to the connector portion 15 of the fuel injection nozzle. The output signal of the pressure sensor is input to the control unit.

At the same time as the ignition is turned on, the solenoid 61 is energized to magnetize the magnetic part 61a, and the intermediate rod 25
is raised by the clearance hp corresponding to the prelift amount. As a result, as in the case of the first embodiment, when the load is low, the needle valve 20 resists the urging force of the first spring 30 via the spring seat 24 due to the fuel pressure fed to the high pressure fuel passage 17. However, since the fuel pressure is low, it cannot be lifted against the biasing force of the second spring 35, and it does not lift beyond the prelift amount. Therefore, the nozzle 18 is constricted by the bottle part 22 of the needle valve 20, and the effective nozzle area becomes extremely small, promoting atomization of the fuel, improving combustibility (ignitability), reducing combustion noise, and reducing exhaust gas. The content of hydrocarbons (HC) in the fuel is reduced.

On the other hand, at medium load and high load, the pressure of the fuel fed to the high pressure fuel passage 17 is high, so even after the needle valve 20 prelifts, the second
The valve lifts against the biasing force of the spring 35, increasing the effective nozzle surface, injecting an amount of fuel commensurate with the required output, and at the beginning of the travel stroke when the lift amount of the needle valve 20 is relatively small. The nozzle 18 is narrowed to suppress the injection rate to a low level, and the fuel is reliably ignited at the initial stage of injection, and then the fuel is combusted at an appropriate speed without being suddenly combusted.

In that case, in each injection period, when the fuel injection pressure exceeds the peak value based on the fuel injection pressure detected by the pressure sensor, the energization to the solenoid 61 is stopped and the intermediate rod 25 is returned to the lowest position. let As a result, when the needle valve 20 descends in the latter half of the fuel injection period, the biasing force of the second spring 35 acts on the needle valve 20 via the intermediate rod 25 and the spring seat 24 to push down the needle valve 20. The needle valve 20, which is further lowered from the pre-lift state, is further urged in the downward direction by the pressing force in addition to the urging force of the first spring 30, so it quickly moves in the downward direction and closes the nozzle, and the fuel Cuts better.

Therefore, the control unit or the like causes the needle valve 20 to close to the nozzle 1 due to the biasing force of the first spring 30.
A reinforcing means 50' is provided for applying an external force to the needle valve 20 to reinforce the biasing force when the needle valve 8 is moved in the closing direction.

(Third Embodiment) FIG. 7 shows a fuel injection nozzle according to a third embodiment of the present invention. Since the basic configuration of the fuel injection nozzle is the same as that of the fuel injection nozzle of the first embodiment, the explanation of the members 10 to 46 will be omitted.

The fuel injection nozzle according to this embodiment is not provided with a check valve 53, a solenoid 61, etc., and instead, a rod holder 71 is provided in the second spring chamber 32 so as to be slidable in the axial direction thereof. As shown in FIG. 8, the rod holder 71 includes a bottomed cylindrical cylindrical member 71a having a through hole 71c formed at the lower end into which the intermediate rod 25 can be loosely fitted, and a cylindrical member 71a attached to the upper end of the cylindrical member 71a. It consists of a lid member 7lb. On the other hand, the upper end of the intermediate rod 25 has the through hole 7
A flange portion 25b having a larger diameter than 1c is formed.

The intermediate rod 25 and the rod holder 71 are assembled so that the flange portion 25b is located inside the cylindrical member 71a, and the intermediate rod 25 is in a fixed position (the position shown in FIG. 7) inside the rod holder. It is possible to descend a predetermined amount from A set spring 72 is compressed between the flange portion 25b of the intermediate mouth 25 and the bottom wall of the cylindrical portion (r471a).

The set spring 72 exerts the minimum biasing force necessary to hold the intermediate rod 25 in a fixed position.

This rod holder 71 is at the lowest position (as shown in Fig. 7)
A clearance hP corresponding to the prelift amount is set between the rod holder 71 and the spring seat 24 when the intermediate rod 25 is in the normal position. Therefore, when the load is low, the needle valve 20 resists the biasing force of the first spring 30 via the spring seat 24 due to the fuel pressure fed to the high-pressure fuel passage 17 within the range of the above-mentioned clearance hp. However, since the fuel pressure is low, it cannot be lifted against the biasing force of the second spring 35, and does not lift beyond the prelift amount.

Therefore, the nozzle 18 is narrowed by the pin portion 22 of the needle valve 20, and the effective nozzle area becomes extremely small, promoting atomization of the fuel, improving combustibility (ignitability), reducing combustion noise, and reducing exhaust gas. The content of hydrocarbons (HC) in the fuel is reduced.

On the other hand, under medium load and high load, the pressure of the fuel fed to the high pressure fuel passage 17 is high, so even after the needle valve 20 has pre-lifted, the biasing force of the second spring 35 is applied via the intermediate rod 25 and the rod holder 71. The nozzle 18 is throttled at the beginning of the travel stroke when the amount of lift of the needle valve 20 is relatively small. The injection rate is kept low, the fuel is reliably ignited at the beginning of injection, and then the fuel burns at an appropriate speed without combusting suddenly.

In that case, when the needle valve 20 lifts in the first half of the fuel injection period, the set spring 72 causes the intermediate rod to
Since the intermediate rod 25 and the rod holder 71 are held in place, the intermediate rod 25 and the rod holder 71 are lifted together. on the other hand,
When the needle valve 20 descends in the latter half of the fuel injection period,
Even if the rod holder 71 stops at the lowest position, the intermediate rod 25 continues to descend against the biasing force of the set spring 72 due to its inertial force in the descending direction. The needle valve 20 is moved through the spring seat 24 by lowering the intermediate rod 25.
act to push down the needle valve 20. This causes the needle valve 20 to further descend from the pre-lift state.
In addition to the biasing force of the first spring 30, the fuel injection valve is further biased in the downward direction by the above-mentioned pushing down force, so that it quickly moves in the downward direction and closes the nozzle, which improves the exhaustion of fuel.

Therefore, the needle valve 20 is moved to the nozzle 18 by the biasing force of the first spring 30 due to the nozzle holder 71 and the like.
A reinforcing means 50'' is configured to apply an external force to the needle valve 20 to reinforce the biasing force when the needle valve 20 moves in the closing direction.

(Effects of the Invention) As explained above, according to the fuel injection nozzle for an engine of the present invention, a high-pressure fuel passage is formed that has a nozzle at the tip and guides the fuel pumped from the fuel injection pump to the nozzle. a nozzle body; a needle valve having a pin portion at its tip portion to be inserted into the nozzle nozzle; and a needle valve that is moved in a direction to open the nozzle nozzle by the pressure of fuel pumped into the high-pressure fuel passage; and a needle valve disposed within the nozzle body. a first spring that always biases the needle valve in a direction to close the nozzle; a second spring that biases the needle valve in the direction of closing the nozzle; and reinforcement that applies an external force to the needle valve to reinforce the biasing force when the needle valve moves in the direction of closing the nozzle due to the biasing force of the first spring. This means that the needle valve quickly closes the nozzle while achieving the basic function of extremely small effective nozzle area at low loads and increasing the effective nozzle area at medium and high loads. It can help you run out of fuel better.

[Brief explanation of the drawing]

1 to 5 illustrate a first embodiment of the present invention, FIG. 1 is a vertical side view of a fuel injection nozzle, FIG. 2 is an enlarged vertical side view of the vicinity of the needle valve, and FIG. 3 is a main part. Enlarged longitudinal side view of
FIG. 4 is a bottom view of the check valve, and FIG. 5 is an explanatory diagram showing the spring load and nozzle area for lift. 6 is a view corresponding to FIG. 1 showing the second embodiment, FIG. 7 is a view corresponding to FIG. 1 showing the third embodiment, and FIG. 8 is an enlarged longitudinal sectional side view of the main part of the third embodiment. 50''...Nozzle holder...High pressure fuel passage...Nozzle port...Needle valve...Pin section...First spring...Second spring...Reinforcement means...Reinforcement means' ... Reinforcement means ... Nozzle holder ... High pressure fuel passage ... Nozzle needle valve ... Bottle section ... First spring ... Second spring ... Reinforcement means ... Reinforcement means ... Reinforcement means 2 Fig. Needle valve rift 4 Fig. 5 gJ1 4 25b Fig. 8 -426-1

Claims (1)

[Claims] (1) The nozzle body has a nozzle at its tip and is formed with a high-pressure fuel passage that guides the fuel pumped from the fuel injection pump to the nozzle, and has a pin at its tip to be inserted into the nozzle, a needle valve that is moved in the direction of opening the nozzle by the pressure of the fuel pumped into the high-pressure fuel passage; a first spring disposed within the nozzle body that always biases the needle valve in the direction of closing the nozzle; A second spring is disposed in the nozzle body and biases the needle valve in the direction of closing the nozzle when the needle valve is moved from the state where the nozzle is constricted by the pin portion to the direction of opening the nozzle; A fuel injection nozzle for an engine, comprising a reinforcing means for applying an external force to the needle valve to reinforce the urging force of the needle valve when the needle valve moves in the direction of closing the injection port due to the urging force of the first spring.