JP2001082279A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lock a nozzle needle in a random position between a closed state and a fully opened state by suitably controlling a control valve. SOLUTION: This fuel injection valve is of a type having a valve element 10, a nozzle needle 12 slidably arranged inside the valve element 10, an operation part connected to the nozzle needle 12 and inserted inside a control pressure chamber 22, and control valves 38, 40, and 42 capable of controlling pressure inside the control pressure chamber 22. The operation part is provided with a holding piston 30, the holding piston 30 is slidable inside a holding chamber 32, and the control valves 38, 40, and 42 are 3/3-way directional control valves controlling an outflow part 28 of the control pressure chamber 22 and an outflow part 34 of the holding chamber 32.

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, which comprises a valve body, a nozzle needle slidably disposed in the valve body, a nozzle needle connected to the nozzle needle, and a control pressure chamber. The present invention relates to a type having an operating part to enter and a control valve capable of controlling the pressure in a control pressure chamber.

[0002]

2. Description of the Related Art A fuel injection valve of this type is known from DE 196 24 001 A1. This known fuel injection valve has an outlet, which exits the control pressure chamber and opens into the control chamber of the control valve. The control chamber is provided with two valve seats opposite each other, with which the valve needles cooperate. The outlet from the control pressure chamber is assigned to one valve seat, and the outlet from the control chamber is assigned to the other valve seat. The outlet from the control pressure chamber is thereby always closed if the valve needle is in contact with one of the valve seats. With such a configuration of the control valve, pre-injection of fuel can be obtained at relatively low cost. In the initial state, the valve needle is in contact with one of the valve seats, so that the fuel supplied to the control pressure chamber is dammed in this control pressure chamber. The closing force acting on the operating part thereby holds the nozzle needle of the fuel injection valve in the closed position. Starting from this position, the valve needle is lifted from the corresponding valve seat, moves through the valve chamber and abuts against the opposite valve seat, the fuel present in the control pressure chamber is released from the valve needle. Is 2
During this period of time when neither of the two valve seats abuts, it flows out of this control pressure chamber. During this time, the injection of fuel takes place, since the closing force acting on the operating part is reduced such that the opening force acting on the nozzle can lift the nozzle needle from the associated valve seat. The valve needle is its first
The speed of shifting from the position in contact with the valve seat to the position in contact with the second valve seat is such that a small amount of fuel corresponding to the pre-injection is injected. When the valve needle rests on the second valve seat, it remains in this position for a time corresponding to the so-called injection interruption between the pre-injection and the main injection. The valve needle is then adjusted again in the direction toward the first valve seat, whereby the valve needle, unlike the movement during the pre-injection, is again brought into contact with the first valve seat. Stays in the central position of the control room for a long time without contact. The possibility of fuel leaking from the control pressure chamber at this position allows a full opening of the nozzle needle for a long time, so that a main injection is obtained. At the end of the main injection, the valve needle returns to its initial position again.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned disadvantages of the fuel injection valve in the prior art.

[0004]

According to the present invention which solves this problem, the operating portion has a holding piston, which is slidable in the holding chamber, and the control valve is
Controls both the outlet of the control pressure chamber and the outlet of the holding chamber
It is configured as a (3-port, 3-position) directional switching valve.

[0005]

The fuel injection valve according to the present invention having the above-described configuration can be configured such that by appropriately controlling the control valve, any one of the nozzle needles can be switched between the closed state and the fully opened state. It has the advantage that it can be locked in position. The control valve completely shuts off the holding chamber with the other inlets or outlets independently of its connection to the control valve, so that the movement of the holding piston in the holding chamber and thus of the nozzle needle is prevented. . In this way, by controlling the opening stroke and the time of the opening of the nozzle needle, the injection can be coordinated with the respective driving time of the engine. Optimum combustion and emission reductions are thus obtained. In particular, the time and height of any pre-stroke used for pre-injection,
As well as a main injection with a completely open needle is obtained. In this form, the so-called “boot injection“ Boot-I
njection "" is obtained.

According to an advantageous embodiment of the invention, the control valve has a control chamber, from which the outlet branches off, on one side of the control chamber a control pressure / chamber valve seat. And a holding chamber / valve seat is formed on the other side of the control chamber,
A valve needle cooperating with a valve seat is slidably arranged in the control room. According to such a configuration, the 3/3 directional control valve can be configured to control both the pressure release of the control pressure chamber and the pressure release of the holding chamber in a mechanically simple manner.

Advantageously, a throttle is provided in the outlet of the control room. In this way, the speed of the pressure drop in the control pressure chamber can be reduced and thus the nozzle needle can be slowly opened. Furthermore, a high closing speed of the needle is obtained, since the restriction arranged in the outlet does not affect the closing speed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of a fuel injection valve, which has a valve body 10. A nozzle needle 12 is slidably disposed in the valve body 10, and is provided with a valve seat 14 for controlling injection of fuel into a cylinder of an internal combustion engine (not shown). Work together. This fuel is supplied to supply conduit 1
Prepared via 6.

An operating section 18 is connected to the nozzle needle 12, and the operating section 18 has a control pressure piston 20 at the end opposite to the nozzle needle. The control pressure piston 20 is slidably disposed in a control pressure chamber 22. The control pressure chamber 22 has an inflow portion 24 (a throttle 26 is disposed in the inflow portion 24) and an outflow portion. 28 are provided. The inflow portion 24 is connected to the fuel supply conduit 16.

The control pressure piston 20 has a holding piston 30
The holding piston 30 is slidably disposed in the holding chamber 32. Holding piston 30
Together with the control pressure piston 20 form a stepped piston.

The holding chamber 32 has an outlet 34 which opens into the control chamber 36 of the control valve. In the control chamber 36, an outflow portion 28 from the control pressure chamber 22 is provided.
Is also open. The outlet portion 34 and the outlet portion 28 are open on opposite sides, with one valve seat 38 or 40 being formed in the region of the corresponding opening. An outflow portion 37 is led out of the control room 36, and this outflow portion 37
Has an aperture 39. The outlet 37 communicates with the fuel supply.

A valve needle 42 is slidably disposed inside the control chamber 36, and the valve needle 42 contacts the valve seat 38 to close the outlet 28 from the control pressure chamber 22. 1 or a second position which abuts the valve seat 40 and closes the outlet 34 of the holding chamber 32 or, as shown in FIG. Occupies a third position located approximately at the center of the two valve seats 38 and 40 are open.

The illustrated fuel injector operates as follows.

When the valve needle 42 is in its first position, the valve seat 3
8 (curve 4 for valve needle 42 in FIG. 2)
Since the outlet 28 from the control pressure chamber 22 is closed, the fuel supplied via the inlet 24 applies a high pressure to the control pressure piston 20 here. This pressure creates a closing force that is greater than the opening force applied to the nozzle needle 12 by the fuel pressure. The fuel injection valve thereby assumes a closed position in which no fuel is injected. This is the curve 12 for the nozzle needle 12 of FIG.
Indicates that the stroke is 0.

When the valve needle 42 is brought from its first position to a third position abutting the valve seat 40 (both the outlet 28 from the control pressure chamber 22 and the outlet 34 from the holding chamber 32 open). Since the pressure in the control pressure chamber 22 decreases (see section III of the curve 42 in FIG. 2), the closing force acting on the control pressure piston 20 here is smaller than the opening force acting on the nozzle needle. This allows the nozzle needle 12
Lifts from the valve seat 14. Since the pressure is reduced slowly in the control pressure chamber 22 based on the throttle 39, a relatively slow opening of the nozzle needle 12 is obtained. This is shown in FIG.

When the nozzle needle has performed the desired pre-stroke, ie, when the nozzle needle 42 is in a partially open position, the valve needle 42 is brought to its second position (section II of curve 42 in FIG. 2). reference). This second
, The valve needle 42 abuts the valve seat and the holding chamber 3
The outlet 34 from 2 is closed. The only outlet from the holding chamber 32 is thus closed, so that the holding piston 30
Further movement of the nozzle needle 12 and further opening of the nozzle needle 12 are directly blocked. This is shown in FIG. 2 as a region of constant, constant stroke of the nozzle needle 12.

Following this partially open condition, the valve needle 42 has two outlets 28, 3 if it wants to obtain a fully open position of the fuel injector for the main injection.
2 is brought back to its third position, which is opened again. The opening pressure acting on the nozzle needle 12 is moved to its fully open position where a relatively large amount of fuel is injected.

Following the fully opened state of the fuel injector, if the nozzle needle 12 is again brought to its closed position, the valve needle 42 will again be in its first position against the valve seat 38. Adjusted. As a result, the fuel prepared via the inlet 24 is again blocked in the control pressure chamber 22, so that a correspondingly high closing force acts on the operating element and thus on the nozzle needle 12. This is also Figure 2
Is shown in

FIG. 3 shows a fuel injection valve according to a second embodiment. The structure and function form correspond well to those of the first embodiment. The only difference is that the valve needle 42
Is that the arrangements of the outflow section 34 and the outflow section 28 with respect to are changed. This allows the valve needle to
When in the first position, which abuts the valve seat 38 and closes the outlet 28 of the control pressure chamber 22, there is no leakage flow through the valve needle guide.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a fuel injection valve according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a stroke of a valve needle of a control valve and a stroke of a nozzle needle obtained by the stroke.

FIG. 3 is a schematic side view of a fuel injector according to a second embodiment of the present invention;

[Explanation of symbols]

10 valve body, 12 nozzle needle, 14 valve seat,
DESCRIPTION OF SYMBOLS 16 Supply conduit, 18 operation part, 20 control pressure piston, 22 control pressure chamber, 24 inflow part, 26 throttle, 28 outflow part, 30 holding piston, 32
Holding chamber, 34 outlet, 36 control room, 38 valve seat, 39 throttle, 40 valve seat, 42 valve needle,
curve

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F02M 61/20 F02M 61/20 N

Claims (3)

[Claims] 1. A fuel injection valve, comprising: a valve element (10);
A nozzle needle (12) slidably disposed in the valve body (10), connected to the nozzle needle (12),
And an operation unit (18) which enters the control pressure chamber (22).
And a control valve (38, 40, 42) capable of controlling the pressure in the control pressure chamber (22), wherein the operation unit (18) includes a holding piston (30). And
The holding piston (30) is slidable in the holding chamber (32), and the control valve (38, 40, 42) controls the outlet (28) of the control pressure chamber (22) as well as the holding chamber (32). A fuel injection valve characterized in that it is a 3/3 directional control valve that also controls the outflow section (34) of the fuel injection valve. 2. The control valve has a control chamber (36), an outlet (37) branches off from the control chamber (36), and a control pressure chamber is provided on one side of the control chamber (36).・ Valve seat (38)
Is formed, and a holding chamber and a valve seat (4) are provided on the other side of the control chamber.
0) is formed, and a valve seat (3) is provided in the control chamber (36).
2. The fuel injection valve according to claim 1, wherein the valve needle (42) cooperating with the fuel injection valve (8, 40) is slidably arranged. 3. The fuel injection valve according to claim 2, wherein a throttle (39) is provided in the outlet (37) of the control chamber (36).