JP2000110691A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of stably moving a needle in the inside of a nozzle main body while suppressing its injection rate at the early stage of fuel injection. SOLUTION: This fuel injection valve 10 is so constituted as to be provided with a throttling part 12 for controlling the quantity of fuel feeding to an injection port 1 at the lower part of a nozzle main body 2. The throttling part 12 is formed out of a projected part 13 formed in the inner surface of the nozzle main body 2, the outer surface of a needle 3, and of a cut-out part 14 formed in the outer surface of the needle 3. In the throttle part 12, the projected part 13 in the inner surface of the nozzle main body 2, and the outer surface of the needle 3, are kept in a state that they are faced to each other without changing respective diameters with exception of the cut-out part 14. By this constitution, the needle 3 can be moved in an exceedingly stable manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve,
In particular, the present invention relates to a fuel injection valve capable of controlling the fuel injection rate in a good manner.

[0002]

2. Description of the Related Art Generally, a fuel injection valve is provided with a needle in an axial direction in a hollow nozzle body, and by moving the needle in an axial direction, fuel is injected from an injection hole provided at a tip end of the nozzle body. Or configured to stop. In particular, in recent years, in order to reduce the NOx concentration in exhaust gas, practical use of a fuel injection valve with a suppressed initial fuel injection rate has been strongly desired.

[0003] For example, Japanese Utility Model Publication No. 6-6227 discloses a fuel injection valve configured to suppress the initial fuel injection rate. In this fuel injection valve, a small-diameter step portion is formed in the inner peripheral portion of the longitudinal middle portion of the nozzle body such that the hollow portion on the front end side is smaller in diameter than the hollow portion on the rear end side, and the longitudinal middle portion of the needle is formed. The portion is formed with a large-diameter step portion such that the rear end side of the needle has a larger diameter than the distal end side. The small-diameter step portion of the nozzle body and the large-diameter step portion of the needle are arranged at positions substantially corresponding to each other. As a result, at the beginning of fuel injection with a small lift amount of the needle, the distance between the inner surface of the nozzle body and the outer surface of the needle is kept small, and the fuel passage is narrowed. Therefore, according to such a fuel injection valve, the injection rate at the initial stage of fuel injection can be suppressed low, and the NOx concentration in exhaust gas can be reduced.

[0004]

However, if the fuel passage is throttled by using the mutual positional relationship between the small-diameter step portion of the nozzle body and the large-diameter step portion of the needle as in the prior art, the needle has a restricted range. When the large-diameter stepped portion of the needle is displaced beyond the small-diameter stepped portion of the nozzle body, the radial gap between the nozzle body and the needle becomes large, so that the needle is likely to be misaligned and the needle moves. When the shaft is displaced, excessive contact may occur between the step portion of the nozzle body and the step portion of the needle, which may lead to malfunction of the fuel injection valve.

Accordingly, it is an object of the present invention to provide a fuel injection valve capable of stably moving a needle in a nozzle body while suppressing an injection rate at an early stage of fuel injection.

[0006]

Means for Solving the Problems The present inventors diligently studied a configuration of a fuel injection valve capable of stably moving a needle in a nozzle body while suppressing an injection rate at an initial stage of fuel injection. As a result, the needle can stably move in the nozzle body by providing the throttle portion having a cutout portion formed by cutting out a part of one of the inner surface of the nozzle body and the outer surface of the needle in the circumferential direction. It has been found that this has led to the present invention. That is, the fuel injection valve according to the present invention forms a fuel supply passage between a hollow nozzle main body having an injection hole at the tip and an inner surface of the nozzle main body, and displaces the fuel by an axial displacement in the nozzle main body. A needle that opens and closes a hole, and a throttle portion that is provided in the middle of the fuel supply path and gradually increases a fuel supply amount to the injection hole with needle displacement in a direction to open the injection hole, The throttle portion is configured to have a cutout portion formed by cutting out a part of one of the inner surface of the nozzle body and the outer surface of the needle in the circumferential direction.

With this configuration, the throttle portion gradually increases the amount of fuel supplied to the injection hole with the needle displacement in the direction of opening the injection hole, so that the fuel injection rate at the beginning of fuel injection can be suppressed. In the throttle portion of the fuel supply passage, the inner surface of the nozzle body and the outer surface of the needle are maintained in a state where they face each other without changing the diameter, except for the notch portion, so that the needle is It is possible to move extremely stably in the nozzle body.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. 1 to 3 show an embodiment in which the present invention is applied to a diesel engine equipped with a common rail fuel injection system. FIG. 1 is a diagram showing an embodiment of a fuel injection valve according to the present invention and a control system thereof. is there. The configuration of the fuel injection valve 10 will be described later, and its control system will be described first. As shown in the figure, the control system includes a pressure accumulation chamber 31 that supplies high-pressure fuel of, for example, 120 MPa to the fuel injection valve 10, a high-pressure regulator 32 that regulates fuel pressure-fed from the pressure accumulation chamber 31 to the fuel injection valve 10, A high-pressure fuel pump 33 for supplying high-pressure fuel to the chamber 31 and a low-pressure fuel pump 34 for supplying fuel from the fuel tank 40 to the high-pressure fuel pump 33
A low-pressure regulator 35 that regulates fuel pumped from the low-pressure fuel pump 34 to the high-pressure fuel pump 33; a return passage 36 that returns excess fuel in the fuel injection valve 10 to the fuel tank 40; and an electronic device that controls the fuel injection valve 10. And a control device (ECU) 20. The ECU 20 takes in various detected values such as an accelerator position 21 and an engine speed 22 from an operating state detecting means for detecting an operating state of the internal combustion engine.

The fuel injection valve 10 includes a hollow nozzle body 2 having an injection hole 1 at the tip, a needle 3 disposed axially in the hollow portion of the nozzle body 2 to open and close the injection hole 1, A fuel supply passage 4 formed between the inner surface and the outer surface of the needle 3, a fuel line 5 formed in the nozzle body 2 for introducing high-pressure fuel to the fuel supply passage 4, and an orifice for introducing high-pressure fuel to the leak chamber 6 7, a control solenoid 8 to which a control signal is applied, and an electromagnetic valve 11 for opening and closing the orifice 9 in accordance with the operation of the control solenoid 8. A throttle portion 12 is provided below the fuel injection valve 10 to control the amount of fuel supplied to the injection hole 1.

[0010] As shown in FIG.
Of the needle 3, an outer surface of the needle 3, and a notch 14 formed on the outer surface of the needle 3. The cutout portion 14 is formed of one or a plurality of slit-shaped cutouts formed by cutting out a part of the outer circumferential surface of the needle 3 in the circumferential direction over a predetermined axial length. A plurality of notches are arranged at equal intervals in the circumferential direction. The shape and number of the notches or the intervals and depths of the arrangements are appropriately determined according to the characteristics of the desired fuel injection rate. Alternatively, the notch 14 may be formed in a position opposite to that shown in the drawing, so that a notch is formed on the inner surface of the nozzle body 2 and a protrusion is formed on the outer surface of the needle 3. The lift amount of the needle 3 is, for example, 0
mm to 0.35 mm.

FIGS. 2 (a) to 2 (f) are views showing specific examples of the configuration of the aperture section 12, wherein (a), (c) and (e) are side views, respectively, (b), (d) and (d). (F) is AA ′,
It is sectional drawing of BB 'and CC'. FIG.
(B) shows a state where the needle 3 has a lift amount of 0 mm.
In this state, a narrow gap 61 is formed between the protrusion 13 on the inner surface of the nozzle body 2 and the outer surface of the needle 3,
The fuel can slightly pass through the narrow gap 61. FIGS. 3C and 3D show that the needle 3 has a lift amount of 0.
1 mm is shown. Even in this state, only a narrow gap 62 is still formed between the protrusion 13 on the inner surface of the nozzle body 2 and the outer surface of the needle 3, and the fuel can only slightly pass through the narrow gap 62. Absent. On the other hand, FIGS. 6E and 6F show a state where the lift amount of the needle 3 exceeds 0.1 mm. In this state, a wide gap 63 is formed between the protrusion 13 formed on the inner surface of the nozzle main body 2 and the cutout 14 formed on the outer surface of the needle 3, and a large amount of fuel flows through the gap 63. Can be passed. As described above, the throttle portion 12 has a characteristic that the fuel supply amount to the injection hole 1 side is gradually increased with the needle displacement in the direction in which the injection hole 1 is opened.

2 (a) to 2 (f), the inner surface of the protruding portion 13 of the nozzle body 2 and the outer surface of the needle 3 except for the cutout portion 14 are different from each other.
They are kept facing each other without changing the diameter. In light of this, if the needle 3 is moved in the throttle portion, the protrusion 13
Is always φ1, and the diameter of the outer surface of the needle 3 facing it is always φ2 except for the cutout portion 14. Therefore, the needle 3 can move extremely stably in the nozzle body 2 without causing excessive contact with the step portion on the inner surface of the nozzle body at the step portion as in the related art.

The fuel injection valve 10 configured as described above operates as follows. In FIG. 1, when no valve opening signal is given from the ECU 20 to the control solenoid 8, the solenoid valve 11 is closed. At this time, since the pressure in the fuel supply passage 4 and the pressure in the leak chamber 6 are the same, the needle 3 is lifted by 0 mm.
No fuel is injected from the injection hole 1. on the other hand,
When a valve opening signal is given from the ECU 20 to the control solenoid 8, the solenoid valve 11 opens. At this time, since the pressure in the leak chamber 6 decreases, the needle 3 gradually increases the lift amount 0.3
The fuel is lifted to 5 mm, and fuel is injected from the injection hole 1 through the fuel supply path 4. When the pressure of the fuel supply passage 4 decreases and falls below the pressure of the leak chamber 6, the lift amount of the needle 3 becomes 0 m.
m, and the fuel injection from the injection hole 1 stops.

FIG. 3A is a diagram showing the relationship between the needle lift amount and time, and FIG. 3B is a diagram showing the relationship between the fuel injection rate and time. The dashed line in FIG. 3B indicates a change in the injection rate when there is no throttle in the fuel supply path, and the solid line indicates a change in the injection rate when there is the throttle. As shown by the solid line in the figure, since the initial stage of fuel injection is controlled so as to suppress the fuel injection rate, the NOx concentration in the exhaust gas can be reduced. Explaining the characteristics of the injection rate, the fuel injection valve 10 is provided with the throttle portion 12 having a notch so that the fuel pressure applied to the nozzle tip during the initial stage of the fuel injection is between 0 mm and 0.1 mm. The flow is reduced and the injection rate is suppressed. In addition, the needle lift amount is 0.1mm ~
During the period of 0.35 mm, the opening area of the throttle unit 12 rapidly increases,
The fuel pressure is sufficiently transmitted to the tip of the nozzle with almost no throttling effect, and the injection rate is increased. In this embodiment, the fuel injection rate at the initial stage of fuel injection can be suppressed in this way, and the needle can be stably moved over the entire stroke as described above.

[0015]

According to the present invention, it is possible to obtain a fuel injection valve capable of stably moving the needle in the nozzle body while suppressing the fuel injection rate at the beginning of fuel injection.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a fuel injection valve according to the present invention and a control system thereof.

FIGS. 2 (a) to 2 (f) are diagrams showing specific examples of the configuration of a throttle unit, where (a), (c) and (e) are side views, respectively.
(B), (d) and (f) are AA 'and B-
It is sectional drawing of B 'and CC'.

3A is a diagram illustrating a relationship between a needle lift amount and time, and FIG. 3B is a diagram illustrating a relationship between an injection rate and time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection hole 2 Nozzle main body 3 Needle 4 Fuel supply path 5 Fuel line 6 Leak chamber 7, 9 Orifice 8 Control solenoid 10 Fuel injection valve 11 Solenoid valve 12 Throttle section 13 Projection section 14 Notch section

Continued on front page F term (reference) 3G066 AA07 AB02 AC09 AD12 BA12 BA31 CC06T CC08T CC14 CC18 CC26 CC64T CC67 CC68U CC70 CD26 CD29 CD30 CE13 CE22 DA11 DC04 DC09

Claims (1)

[Claims] A needle for forming a fuel supply passage between a hollow nozzle body having an injection hole at an end thereof and an inner surface of the nozzle body, and opening and closing the injection hole by axial displacement in the nozzle body. A throttle provided in the middle of the fuel supply path and gradually increasing the amount of fuel supplied to the injection hole with needle displacement in a direction to open the injection hole, wherein the throttle is provided with the nozzle A fuel injection valve comprising: a notch formed by notching a part of one of an inner surface of a main body and an outer surface of the needle in a circumferential direction.