JP2768522B2 - Fuel injection nozzle for internal combustion engines - Google Patents

Description

Description: TECHNICAL FIELD The invention relates to a fuel injection nozzle of the type described in the preamble of claim 1.

BACKGROUND ART Known fuel injection nozzles of the type described above (DE-OS 300006)
In the specification of Japanese Patent Application Laid-Open No. H11-260, the inner support portion of the heat shield plate that comes into contact with the bottom of the nozzle body is formed by an inner edge directly connected to the annular pleated portion. Are open without covering a relatively large central area of the nozzle bottom. This configuration is inadequate for many applications to cool the nozzle bottom to keep carbon deposition on the nozzle opening within a desired time. In the case of the injection nozzles of the type mentioned at the beginning, the so-called throttle pin nozzles, the temperature at the bottom of the nozzle must not exceed 200 ° C. Thin-walled heat shields of known construction types burn or generally burn when subjected to extremely high thermal loads due to the relatively small contact surface with the annular flange on the additional part of the clamping nut. There is danger.

DISCLOSURE OF THE INVENTION The feature of the present invention is as described in claim 1.

The configuration of the present invention having the features described in claim 1 has the following advantages over the prior art. That is, the larger surface of the nozzle bottom is covered by the heat shield, so that the nozzle body is perfectly protected from heat radiation. At the same time, the contact surface between the annular flange at the additional portion of the tightening nut and the heat shield plate is large, so that good heat transfer to the cylinder head of the internal combustion engine can be obtained.

According to the features described in claim 2 and the following, the present invention can be advantageously further developed.

The heat shield plate includes a boss portion forming a collar having a greater wall thickness than the other heat shield plate portions, and the boss portion forms, on one end surface side, an inner support portion abutting on the nozzle bottom. In addition, a configuration having a central through hole extending in the fuel flow direction is particularly advantageous. The large wall thickness of the boss reduces the risk of damage to the heat shield when extremely high thermal loads are applied. The good shielding effect is achieved by the heat shield being fitted in the area of the central through-hole to the clamping nut, whereby a heat shield for the interior of the heat shield is obtained. The through-hole tapering towards the bottom of the nozzle faces the combustion gas flowing towards the bottom of the nozzle, along with which the dust particles adhered adhere to the walls of the through-hole, whereby the nozzle It has the further advantage of reducing carbon deposition on the pores.

BRIEF DESCRIPTION OF THE DRAWINGS Drawings Three embodiments of the invention are shown in the drawings and are explained in detail in the following description. 1, 2 and 3 are partially enlarged longitudinal sectional views of the injection nozzle according to the first, second and third embodiments, respectively.

BEST MODE FOR CARRYING OUT THE INVENTION The injection nozzle of FIG. 1 has a nozzle body 10 which is fixed together with an intermediate plate 12 to a nozzle holder (not shown) by a tightening nut 14. . For this purpose, the clamping nut 14 has an inwardly directed annular shoulder 16, which rests on an outwardly directed annular shoulder 18 of the nozzle body 10. The locking nut 14 further has an external thread radially outside the area of the annular shoulder 16, which is screwed into an internal thread in a mounting hole 22 in the cylinder head 24 of the internal combustion engine. The cylindrical additional portion 26 of the tightening nut 14, which surrounds the outer periphery of the nozzle body 10 below the annular shoulder 18, is provided with an outwardly facing support shoulder 28, which is
When the injection nozzle is mounted, it is pressed via a ring packing 30 against an inwardly facing support shoulder 32 in the mounting hole 22.

The injection nozzle shown is a so-called throttle pin-nozzle (Dr
osselzapfendse), the inwardly opening valve needle being provided with a throttle pin 34,
Penetrates into the nozzle opening that opens to the combustion chamber side during the valve needle feed stroke, narrows the nozzle opening, and forms a narrow throttle gap. In such an injection valve, the nozzle bottom 36 of the nozzle body 10 must be cooled particularly well in order to keep the carbon deposition on the throttle gap within limits. For this purpose, the heat shielding plate 40 is axially tightened between the nozzle bottom portion 36 and the annular flange 38 facing the inside of the additional portion 26 of the tightening nut 14 while being elastically deformed. The heat shield plate 40 shields a part of the nozzle bottom 36 from heat radiation and allows heat to escape to the tightening nut 14. Heat travels from here to the cylinder head 24 via a short path.

The heat shield plate 40 has a flat, thin-walled outer edge 42 that abuts the nozzle bottom 36. An outer edge 42 is also followed by a thin-walled annular fold 44, the top 46 of which is a clamping nut.
It is in contact with 14 annular flanges 38. Annular pleats 44
Has moved to the boss portion 50 via the thin-walled intermediate portion 48,
The wall thickness of the boss portion 50 is significantly larger than the wall thickness of other portions of the heat shield plate. The boss portion 50 fits into a central through hole 52 of the clamping nut 14 which is surrounded by the annular flange 38, and tapers conically in the clamping nut 14 itself toward the nozzle body 10. Has a through hole 54.

The tapered through hole 54 in the boss 50 has an annular edge
The annular edge 56 abuts the nozzle bottom 36 and forms a support inside the heat shield 40. Such a configuration of the heat shield plate 40 covers a larger area of the nozzle bottom 36 than a heat shield plate of known configuration without a boss portion. In addition, heat shield plate 40
Due to the large area of the contact surface between the heat shield plate and the annular flange 38, good heat radiation can be obtained, and as a result, damage to the radially outer portion of the thin wall of the heat shield plate 40 due to excessive heating can be avoided. Soot or dust adheres to the conical tapered wall surface of the through-hole 54 in the boss portion 50 from the combustion gas flowing toward the nozzle bottom 36 during the injection, thereby causing the nozzle opening (illustrated portion) Carbon deposition in the middle throttle gap is reduced.

The injection nozzle of FIG. 2 is provided with a heat shield plate 40a, which is basically identical to the heat shield plate 40 of FIG. 1, and is different in that it is manufactured by another manufacturing method. It's just The heat shield plate 40a is pressed with the material in a fluid state and therefore has a markedly rounded edge, resulting in a diffuser-shaped section on the nozzle side.
A through hole 54 having 54a is formed. Other structural parts of the injection nozzle are the same as those in FIG.

The spray nozzle of FIG. 3 is provided with a heat shield plate 60, which is made from a completely thin-walled sheet. This heat shield
The outer edge of 60 and the basic structure of the injection nozzle are identical to those of the previously described embodiment, and therefore the same parts are assigned the same reference numerals. The inner (nozzle body side) support portion 42 of the heat shield plate 60 abutting on the nozzle bottom portion 36 directly follows the annular fold portion 44 and fits into the central through hole 52 of the tightening nut 14. Moving to the matching color section 64.

This collar section 64 is followed by a wall section 66 bent towards the nozzle body 10, which surrounds a through-hole 68 which tapers towards the nozzle bottom 36. This wall section 66 does not extend all the way to the nozzle bottom 36, and thus forms a free edge 70, on which free dust and soot particles in the combustion gas are entrained. Adhere to. Due to the wall section 66 being bent towards the nozzle body 10, the nozzle bottom 36 differs from the embodiment of FIGS. 1 and 2 in that the support 62 is located further radially outward. Covered over the same size range.

Claims (4)

(57) [Claims] 1. A fuel injection nozzle for an internal combustion engine, comprising a nozzle body, wherein a valve seat is formed in a nozzle opening, and a valve needle is movably supported on the nozzle body. The needle has at least one throttle pin which penetrates into the nozzle opening during the feed stroke of the valve needle, and comprises a clamping nut for clamping the nozzle body to the nozzle holder, the clamping nut clamping the nozzle body. A sleeve-shaped additional part which surrounds on the downstream side in the direction of fuel flow of the shoulder, the additional part having an inwardly directed annular flange at the end facing the combustion chamber; Is
Around the center through hole for the jet flow, the annular heat shield is elastically deformed and fastened to the bottom of the nozzle body,
The heat shield plate is in contact with the bottom of the nozzle body at an inner support portion surrounding the center through hole and an outer annular edge portion, and the heat shield plate is connected to the inner support portion and the outer annular edge portion. And a heat shield plate (40, 60) having a ring-shaped ridge between the ring and the top of the ridge that abuts against an annular flange of an additional portion of the tightening nut. A collar (50, 64) projecting from the plane of the heat shield outer edge (42) to the same side as the pleats (44), surrounded by the pleats (44). , The color (50,6
A fuel injection nozzle for an internal combustion engine, characterized in that 4) fits into a central through hole (52) surrounded by an annular flange (38) of a tightening nut (14). 2. The boss portion (5), wherein the heat shield plate (40) forms a collar and has a greater wall thickness than the other heat shield plate portions.
0), and the boss portion (50) has, on one end surface thereof, an inner support portion (56) contacting the bottom portion (36) of the nozzle body (10), and the boss portion (50) 2. The fuel injection nozzle according to claim 1, wherein the part has a central through-hole extending in the fuel flow direction. 3. A heat shield plate (60) made of a thin metal plate has a collar section (64) provided on an inner supporting portion (62) of the heat shield plate (60) which abuts against a bottom portion (36) of a nozzle body (10). 2. The fuel injection according to claim 1, wherein the wall section (66) directly following the collar section (64) is bent obliquely toward the nozzle body (10). nozzle. 4. A sleeve-shaped additional portion (26) of the clamping nut (14) surrounding the nozzle body (10) has an annular shoulder (28) on the outer periphery, the annular shoulder (28). Are fastened to an annular shoulder (32) in a mounting hole (22) of the fuel injection nozzle by a tightening nut (14) for fixing the fuel injection nozzle in a mounting position. Item 4. The fuel injection nozzle according to any one of Items 1 to 3.