JPS61272464A - Fuel injection nozzle for internal combustion engine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a fuel injection nozzle for an internal combustion engine, which is provided with a needle valve, which is closed by a closing spring to the valve seat when viewed in the direction of fuel flow. A pressure chamber is disposed in front of the valve seat, and the surface of the pressure chamber opposite to the valve seat surrounds the needle valve and is loaded by a return spring. The needle valve is formed by a piston, through which the fuel exerts a force on the needle valve that acts against a closing spring.

BACKGROUND OF THE INVENTION In a known injection nozzle of the above-mentioned type (DE-A-2301420), the piston engages directly in the annular shoulder of the needle valve during the defined prestroke.

At the end of the piston's feed stroke, the piston rests on a shoulder fixed to the casing, after which the fuel acts on the pressure surface of the needle valve, which is directly loaded by the fuel, so that the needle valve moves to its fully open position. . A chamber located behind the piston with respect to the injection hole and receiving the return spring communicates with the pressure chamber via a flow controlled by the control edge of the piston and the control edge of the needle valve for pressure compensation purposes. Therefore, the return spring is
The piston begins to return to its starting position before the injection process has yet ended. In such known devices, a pressure stage is formed during every injection process, in which case in the first stage of the injection course the injected fuel quantity increases only slowly, and the main volume of fuel increases in the next stage. It is first injected under high pressure in two stages.

Problem to be Solved by the Invention In the known device, due to the rigid connection between the piston and the needle valve and the uniform suction amount of the piston during its feed stroke, the overall operating characteristic curve Only in a relatively narrow and limited range of these areas does the injection process take place in the desired manner. Furthermore, the injection process cannot be made dependent on the rate of pressure rise in the pressure chamber of the injection nozzle.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned problems, the piston acts on the needle valve via a liquid buffer chamber, and the liquid buffer chamber acts on the needle valve. At least part of the stroke of the valve is in communication with the chamber via the throttle passage.

Effects of the Invention The device of the invention has the advantage that the stroke of the piston is not limited to the pre-stroke and is not connected to the needle valve during the pre-stroke, so that the injection process can be shaped more advantageously. have.

Embodiment According to one advantageous embodiment of the invention, the piston controls the flow cross section leading into the pressure chamber as a function of the stroke distance. This embodiment, in combination with the subject matter of the invention, extends the injection time even during idling operation and thus reduces engine noise. On the other hand, since the injection time is not extended at full load, fuel can be saved. Furthermore, at partial load and full load, the amount of fuel injected is increased primarily at the end of injection. This also reduces engine noise and saves fuel. A liquid buffer chamber is disposed within a vertical hole of a casing that guides the piston, between a notch on the end face side of the piston and an annular 7 flange of the needle valve, and a throttle passage is arranged vertically with the outer peripheral surface of the annular flange. When formed between the hole and the inner circumferential surface of the hole, a space-saving configuration is obtained. According to this embodiment, the piston, after performing a predetermined relative movement with respect to the needle valve, i.e. after displacing a predetermined part of the liquid balance chamber, abuts the annular flange of the needle valve and closes the throttle passage. . From this point on, the piston and needle valve are rigidly connected to each other, further blocking leakage fuel between the needle valve and the piston.

The throttle passage between the annular 7-flange of the needle valve and the casing longitudinal hole may be formed by one or more grooves on the outer circumferential surface of the annular flange, or by an appropriately designed groove between the annular flange and the longitudinal hole. It may also be formed by an annular gap.

In an injection nozzle with a nozzle holder that is equipped with a leakage fuel return pipe and in which a chamber is formed for accommodating a closing spring, if the throttle valve communicates with the chamber of this nozzle holder, the liquid buffer The respective displaced fuel portion of the chamber is immediately charged, and any resulting leakage fuel is drained off without any problems. Furthermore, if the return spring for the piston is arranged in the liquid damping chamber and is supported on the annular flange of the needle valve, an arrangement that is easy to assemble is obtained.

If the return spring for the piston is adjusted to the cross-section of the throttle passage in such a way that in a certain part of the operating characteristic curve, the next injection stroke has already begun when the piston reaches its starting position. It becomes possible to adjust the injection course to predetermined operating parameters.

The injection nozzle of the embodiment has a nozzle body IO, and the nozzle body 1
0 is tightened and fixed to the nozzle holder I6 together with the intermediate disk 12 by a cap nut 14. The nozzle body IO has a vertical hole 18 in the center, and the vertical hole 18 has a conical valve seat 2.
0 to the nozzle hole 22. A piston 24 is mounted in the longitudinal bore 18 in a sealed manner as far as possible, yet slidable, which forms one end face of a pressure chamber between the piston itself and the valve seat surface 20. The end face of the piston 24 on the valve seat side has a conical center portion and a flat edge. The pressure chamber 26 therefore still has a certain minimum volume even in the starting position of the piston 24, in which it contacts the valve seat surface 20, as shown in the left half of the drawing.

An annular chamber 28 is formed between the nozzle body IO and the cap nut 14, and the annular chamber 28 is opened to a pressure of 0 through a plurality of narrow slits 30 evenly distributed over the circumference of the nozzle body IO. It is so close to the nozzle hole 22 when viewed in the axial direction that the end of the valve seat surface 20 is cut off. Therefore, even in the starting position of the piston 24, a small portion of the flow cross section of the slit 30 remains uncovered by the piston 24. The annular chamber 28 is connected to the intermediate disk 12 through a hole 32 formed in a span flange 34 of the nozzle body 10.
, and from which evenly distributed holes 38 lead to a second annular groove 40 . A vertical passage 42 formed in the nozzle holder 16 opens into the annular groove 40, and the vertical passage is led from a fuel connection pipe (not shown) on the upper end surface of the nozzle holder 16.

A valve needle 44 is mounted on the piston 24 in a sealing manner as far as possible and in a movable manner, which needle valve 44 is pressed by a closing spring 46 via a pressure member 48' onto the valve seat surface 20. The opening chain spring 46 controlling the injection hole 22 is arranged in a chamber 50 of the nozzle holder 16, which chamber 50 has a leakage fuel return pipe 52. The needle valve 44 has an annular flange 54 on the upper side of the piston 24, the diameter of which is only slightly smaller than the longitudinal bore 18 in which the piston 24 is slidably supported. The annular flange 54 is provided with a groove-shaped cutout at a certain position on its outer circumference, which together with a slight radial play between the annular flange 54 and the inner wall of the longitudinal bore 18 has a sign. A throttle passage indicated by 56 is formed, and the chamber formed above the annular flange 54 communicates with the chamber formed below.

The piston 24 has a cylindrical end face notch 58 at the end on the annular flange 54 side, and the notch 58 is provided with a cylindrical end surface notch 58.
It is surrounded by four axial collars 60. A return spring 62 for the piston 24 is disposed within the notch 58, and the return spring 62 is supported on the annular flange of the needle valve 44. A chamber formed between the piston 24 and the needle valve 44 is filled with fuel. A chamber 5 in the nozzle holder 16 is used as a chamber containing a spring via a throttle passage 56.
It communicates with 0.

The action of the injection nozzle of the invention is as follows: During the rest of the internal combustion engine, the piston 24 and the needle valve 44
assumes the basic position shown in the left half of the drawing, in which the volume of the pressure chamber 26 is at its minimum and the free-flow cross-section of the slit 30 is also at its minimum. In the operating state of the internal combustion engine, discharged fuel sent from the injection pump enters the pressure chamber 26 through the slit 30, pushes up the piston 24 after reaching a predetermined pressure, and passes through the liquid balancing chamber 64 to the needle valve. 44 is pushed up against the force of the closing spring 46. Therefore, fuel is injected through the open injection holes 22. During the opening stroke of the needle valve 44, and depending on the magnitude of the delivery volume, a portion of the fuel in the liquid balance chamber 64 is displaced into the chamber 50 via the throttle channel 56, in which case the piston 24 44. The piston 24 continues to control the slit 30 in the direction of increasing flow cross-section, so that the flow cross-section into the pressure chamber 26 increases until the end of injection, and the injection quantity increases accordingly. During partial load operation and full load operation,
The collar 60 of the piston 24 abuts the annular flange 54 of the needle valve 44, so that the collar 60 blocks the throttle passage 56 and the piston 24 and the needle valve 44 are rigidly connected. During the remaining opening stroke that follows, leakage of fuel between the needle valve 44 and the piston 24 is also blocked.

After the end of the discharge stroke, the closing spring 46 returns the needle valve 44 and the piston 24 to the starting position. During this return, that is to say during injection pauses of different lengths, the return spring 62 causes an additional relative movement of the piston 24 with respect to the needle valve 44, in which the fuel flows through the throttle channel 56 into the liquid buffer. It is returned to the chamber 64. The return spring 62 is
The piston 24 is adjusted to the throttle channel 56 in such a way that only during idling operation the piston 24 reaches the starting position again at the beginning of the next injection stroke. In the case of partial loads or high rotational speeds, the next injection process has already begun before the piston 24 reaches its starting position. In other words, the flow cross section of the slit 30 is already relatively wide open from the beginning of the injection process. In the case of full-load operation, the return spring 62 is no longer able to induce an effective relative movement between the piston 24 and the needle valve 44, so that the piston 24 remains against the annular flange 541. , the flow cross section of the slit 30 can be completely opened at the start of the next injection stroke. This situation is shown in the right half of the drawing.

[Brief explanation of drawings]

The drawing is a sectional view along the longitudinal axis of the fuel injection nozzle of the invention. IO... Nozzle body, 12... Intermediate disc, 14...
Cap nut, 16... nozzle holder, 18... vertical hole,
20... Valve seat surface, 22... Injection hole, 24... Piston, 26... Pressure chamber, 28... Annular chamber, 30...
- Slit, 32... hole, 34... span flange, 36... annular groove, 38... hole, 40... annular groove, 42... vertical passage, 44... needle valve, 46...
・Closing spring, 48... Annular groove, 50... Chamber, 52.
... Leak fuel return pipe, 54 ... Annular flange, 56.
...Notch, 58...Notch, 60...Color, 6
2...Return spring, 64...Liquid buffer chamber

Claims (6)

[Claims] 1. A fuel injection nozzle for an internal combustion engine, comprising a needle valve which is pressed by a closing spring towards a valve seat, viewed in the direction of fuel flow, and in which pressure is applied in front of the valve seat. a chamber is arranged, the side of the pressure chamber opposite the valve seat being formed by a piston surrounding the needle valve and loaded by a return spring;
In those types in which the fuel is adapted to exert a force on the needle valve acting against the closing spring through said piston (24), said piston (24) is connected to a liquid damping chamber (64).
through the needle valve (44), and the liquid buffer chamber (64) is connected to the throttle passage (5) over at least a portion of the stroke of the needle valve (44).
6) A fuel injection nozzle for an internal combustion engine, characterized in that it communicates with a chamber (50) via a. 2. 2. Fuel injection nozzle according to claim 1, wherein the piston (24) controls the flow cross section (30) leading into the pressure chamber (26) as a function of the stroke distance. 3. The liquid buffer chamber (64) is connected to the piston (24).
It is arranged between the notch (58) on the end face side of the piston (24) and the annular flange (54) of the needle valve (44) in the vertical hole (18) that guides the throttle passage ( 56) is the outer peripheral wall of the annular flange (54) and the vertical hole (18).
) is formed between the inner circumferential wall of claim 1.
2. The fuel injection nozzle according to any one of items 1 to 2. 4. A nozzle holder is provided with a leakage fuel return pipe and in which a chamber (50) for accommodating a closing spring is formed, and the throttle passage (56) is located in this nozzle holder (
Claim 3 communicating with the chamber (50) of 16)
Fuel injection nozzle as described in section. 5. A return spring (62) for the piston (24) is arranged in the liquid balance chamber (64) and also in the needle valve (
4. A fuel injection nozzle according to claim 3, wherein the fuel injection nozzle is supported on an annular flange (54) of the fuel injection nozzle (44). 6. In a certain part of the operating characteristic curve, the piston (24
) for the piston (24) so that the next injection stroke has already begun before the piston (24) reaches its starting position.
6. The fuel injection nozzle according to claim 1, wherein the diameter of the throttle passage (56) is adjusted to the cross section of the throttle passage (56).