GB2171455A - IC engine fuel injection nozzle - Google Patents

Abstract

A nozzle body (10) has a heat insulation ring (60) clamped between the front end of the nozzle body (10) and a shoulder (18) of a cap nut (12). The heat insulation ring (60) has an inner annular border (62) which sits in a distorted manner against a flat central area (16) of the body end wall and an outer annular border (66) which sits against a conical body wall section (14) to center itself relative to the nozzle body (10). The intermediate annular region (64) of the insulation ring (60) may directly engage the cap nut shoulder (70, Fig. 3) or engage a ring (50) of an electric fuel spray heater coil assembly (20). <IMAGE>

Description

SPECIFICATION Fuel injection nozzle for internal combustion engines Prior art The invention is based on a fuel injection nozzle according to the generic type of the main claim. In a known injection nozzle of this generic type (DE-A1 3,000,061, Fig. 2), the outer annular border of the heat insulation ring, in the non-deformed condition, is approximately arranged in the same axial plane as its inner annular border and, in the installed condition, sits like the latter against a flat annular area of the nozzle body end wall at the combustion chamber side. The heat insulation ring is centered by the cap nut or by a sleeve fixed to the latter, which sleeve surrounds the outer annular border of the heat insulation ring with radial clearance.The parts are assembled in such a way that first of all the nozzle body is attached onto the nozzle holder, then the heat insulation ring is placed onto the nozzle body and after that the cap nut is put over the parts. During this procedure, it may be found that the heat insulation ring drops from the nozzle body or is at least displaced relative to the nozzle body by the radial clearance.

Advantages of the invention In contrast, the arrangement according to the invention having the characterising features of the main claim has the advantage that the heat insulation ring is automatically and directly centered at the nozzle body, it can no longer fall down inadvertently from the latter during assembly and its correct installation position can be better recognised than in the known embodiment of a heat insulation ring.

Advantageous further developments of the arrangement stated in the main claim are possible by means of the measures listed in the subclaims.

It is particularly advantageous if the heat insulation ring is formed in the non-distorted condition in such a way that, when it is placed loosely onto the nozzle body, it only touches the latter at the conical wall area with its outer annular border. By this means, when the cap nut is tightened and the heat insulation ring distorted, the outer annular border of the latter also sits against the nozzle body under elastic deformation and can be used to dissipate heat to the cap nut and if necessary can perform an additional sealing function.

The elastic expansion of the outer annular border of the heat insulation ring is facilitated if the outer annular border is also conically formed.

In injection nozzles which have a heater body connected on the output side of the nozzle body, which heater body contains a passage for the spray jets and is inserted into a holder which is supported or fixed on the cap nut front end at the combustion chamber side, it is further proposed that the centre annular area of the heat insulation ring is supported on the holder for the heater body. By this means, a clearance space is formed for the current-supply element to the heater body which is sealed against the combustion chamber by the heat insulation ring and the holder.

Drawing Two illustrative embodiments of the invention are shown in the drawing and are described in greater detail, in the following description. Fig. 1 shows a section through the front end of an injection nozzle according to the first illustrative embodiment, which front end is at the combustion chamber side; Fig. 2 shows the heat insulation ring of the injection nozzle according to Fig. 1; and Fig. 3 shows the second illustrative embodiment in a representation corresponding to Fig. 1.

Description of the illustrative embodiments The injection nozzle according to Fig. 1 has a nozzle body 10, in which, as known, a valve seat is formed and a valve needle is displaceably mounted. The nozzle body 10 and a distance piece limiting the lift of the valve needle are firmly clamped by a cap nut 12 to a nozzle holder, in which is accommodated, inter alia, a locking spring which presses the valve needle against the valve seat. At the front end at the combustion chamber side, the nozzle body 10 is provided with a conical wall section 14 which merges into a flat end wall 16.

At the combustion chamber side, the cap nut 12 is lengthened beyond the nozzle holder (sic) 19 and, downstream from the end wall 16 of the latter, is provided with an inner support shoulder 18, against which sits a heater insert designated as a whole with the reference numeral 20. This has a central constructional element a heater body 22 made as a wire coil which forms a passage 24 for the spray jets 26. The heater body 22 is of such a size that the spray jets do not wet the heater body 22, but bring about an injector effect, by means of which air is drawn out of the combustion chamber into the inside of the heater body 22.

The heater body 22 is enclosed by a metallic sleeve 30 which has a cylindrical section 32 of a larger diameter and a cylindrical section 34 of smaller diameter. The transition between the sections 32 and 34 is formed by a flange section 36 which sits on the support shoulder 18 of the cap nut 12. The smaller section 34 is provided at the end with an inwardly directed annular collar 38, on which the heater body 22 is centrally supported and soldered. Downstream from the support shoulder 18, the cap nut 12 is provided with a bore section 40 which grips over the section 34 of the sleeve in matching manner. An annular collar 42 adjoins the bore section 40, which annular collar 42 protectively grips over the front end of the sleeve 30 and the heater body 22, which front end is at the combustion chamber side.

A first annular insulating body 44, a metallic contact disc 46, a second annular insulation body 48 and a metallic retaining ring 50 are inserted one after the other into the larger cylindrical section 32 of the sleeve 30. The insulating body 44 sits on the flange part 36 and the parts 44 to 50 are externally centered by the sleeve 30. The upstream-located end of the heater body 22 is soldered to the contact disc 46, which has an inner beaded edge 52 for centering the heater body 22.

At the outer border, the contact disc 46 is provided with a connecting lug 54 which penetrates with clearance through a peripheral cutout in the sleeve 30, projects into a transverse bore 56 of the cap nut 12 and is used for fixing a connecting cable. The insulating bodies 44 and 48 preferably consist of a ceramic material and the connecting lug 54 of the contact disc 46 is preferably enclosed by an insulating sheathing. Three milled-out portions 57 distributed uniformly over the periphery are provided in the smaller section 34 of the sleeve 30, via which milled-out portions 57 the drawn-in air flows into the annular space 58 formed between the sleeve 30 and the heater body 22 and from the annular space 58 via the intermediate spaces of the coil into the inside of the heater body 22.

A metallic heat insulation ring 60 is clamped in deformed manner between the retaining ring 50 and the nozzle body 10, which heat insulation ring 60 thermally reiieves the nozzle body 10. The right-hand half of Fig. 1 shows the heat insulation ring 60 in the distorted condition, whereas the ieft-hand halves of Figs. 1 and 2 show the original shape of the heat insulation ring.

The heat insulation ring 60 has an inner annular border 62 which, in the non-distorted condition, lies in an approximately horizontal position in a plane E. A centre annular area 64 adjoins the inner annular border 62, which annular area 64 is axially offset relative to the annular border 62 by the dimension a. The outer annular border 66 of the heat insulation ring is drawn upwards beyond the plane E of the inner annular border 62 to the extent that its inner annular edge 68 lies above the plane E by the dimension b. The annular border 66 is also conically formed, and in fact at an angle which is smaller than the angle of the wall section 14 of the nozzle body 10.The dimension b and the diameter D of the annularedge 68 are adapted to the outer profile of the nozzle body 10 in such a way that the heat insulation ring (Fig. 1, left-hand hand half) held loosely on the nozzle body 10 touches the latter only with its annular edge 68.

In one embodiment, the parts 44 to 50 are soldered or cemented to one another and to the sleeve 30, so that they can be handled as an independent constructional unit before the assembly of the injection nozzle. This constructional unit is inserted from the upstreamlocated side of the cap nut 12 into the latter and displaced until seated against the support shoulder 18. The sleeve 30 can then be cemented or soldered, or welded, to the cap nut 12 at a suitable point.At the same time, the injection nozzle is expediently assembled in such a way that the nozzle holder, the distance piece and the nozzle body 10 are placed one on top of the other, the heat insulation ring 60 is placed onto the nozzle body 10 and then the cap nut 12 together with the heater insert 20 is put over the parts and screwed onto the nozzle holder, with the distorting heat insulation ring 60 being centrally held on the nozzle body 10.

In another embodiment, the parts 44 to 50, without being connected to one another, can first of all be firmly held only by friction contact in the sleeve 30. When the cap nut 12 is screwed onto the nozzle holder, the parts are then pressed by the distorting heat insulation ring 60 against the flange part 36 of the sleeve and the latter is pressed against the support shoulder 18, so that, if necessary, an additional operation for firmly connecting the sleeve 30 of the cap nut 12 can also be dispensed with.

When the heat insulation ring 60 is being distorted, its inner annular border 62 comes into firm, tight and thermally conducting contact against the flat end wall 16 of the nozzle body 10. During assembly, the heat insulation ring 60 can no longer fall down inadvertently from the nozzle body and its correct installation position can be better recognised by the raised annular border 66 than in a heat insulation ring of the known embodiment. In connection with a heater body coupled on the output side of the nozzle body, the embodiment of the heat insulation ring according to the invention has the further advantage that a clearance space (chamber 69) which can be soundly sealed towards the combustion chamber is formed for a connecting element of the heater body, so that a transverse bore, provided if necessary, in the wall of the cap nut for the connecting element to be passed through no longer needs to be sealed by a glass seal or the like.

The injection nozzle according to Fig. 3 is made without a heater body connected on the output side. In this embodiment, the heat insulation ring 60 is clamped between the nozzle body 10 and an inwardly directed annular collar 70 of a cap nut 12' which is correspondingly made in simplified manner.

Claims (5)

1. Fuel injection nozzle for internal combus tion engines, having a nozzle body which forms a valve seat, displaceably mounts a valve needle and is firmly clamped to a nozzle holder by a cap nut, and, moreover, has a heat insulation ring which, with a centre annular area which is offset axially to its inner and outer annular border, is supported on a cap nut shoulder which is arranged downstream from the nozzle body, and the inner annular border of which sits in a deformed manner against a flat central area of the nozzle body end wall at the combustion chamber side, and the outer annular border of which is centered on one of the parts, characterised in that the outer annular border (66) of the heat insulation ring (60) is drawn upwards above the plane (E) of the inner annular border (62), and that the front end of the nozzle body (10), which front end is at the combustion chamber side, is provided in a way known per se with a conical wall area (14), against which sits the outer annular border (66) of the heat insulation ring (60).

2. Injection nozzle according to Claim 1, characterised in that the heat insulation ring (60) is formed in the non-distorted condition in such a way that, when it is placed loosely onto the nozzle body (10), it only touches the latter at the conical wall area (14) with its outer annular border (66).

3. Injection nozzle according to Claim 1 or 2, characterised in that the outer annular border (66) of the heat insulation ring (60) is also conically formed.

4. Injection nozzle according to one of Claims 1 to 3, having a heater body which is connected on the output side of the nozzle body, which heater body contains a passage for the spray jets and is inserted in a holder which is supported or fixed on the cap nut front end at the combustion chamber side, characterised in that the centre annular area (64) of the heat insulation ring (60) is sup ported on the holder (30, 44, 46, 48, 50) for the heater body (22).

5. A fuel injection nozzle substantially as herein described with reference to Figs. 1 and 2, or Fig. 3, of the accompanying drawings.