GB2158513A

GB2158513A - Glow plug

Info

Publication number: GB2158513A
Application number: GB08511715A
Authority: GB
Inventors: Leopold Muller
Original assignee: Barkas Werke VEB
Current assignee: Barkas Werke VEB
Priority date: 1984-05-11
Filing date: 1985-05-09
Publication date: 1985-11-13
Also published as: GB2158513B; GB8511715D0; DD228598A1; DE3516699C2; DE3516699A1

Abstract

The glow plug (4) has a filament (5) which extends into a swirl chamber (1) and encompasses the injected jet of fuel. To ensure good transfer of heat from the filament to a jet (6) of fuel injected into the chamber, without the filament itself being directly sprayed, the filament is constructed conically and is arranged to extend around the rim region of the jet. The filament can be mounted in the injector nozzle holder or nozzle protection plate. <IMAGE>

Description

SPECIFICATION Glow plug The present invention relates to a glow plug for an internal combustion engine with fuel injection into a combustion chamber, especially an auxiliary or swirl chamber.

Glow plugs for this purpose, particularly for Diesel engines using heavy fuels, are known. DROPS 681 735 discloses an auxiliary combustion chamber arrangement with strong throttling at the transition point to the cylinder, in which a glow coil is arranged to engage around the injected fuel jet. In that case, a special channel arrangement is provided in the transition cross-section, which, through the resulting counterflow, prevents the flow coil from being acted on by fuel. This arrangement achieves a heat exchange in the chamber for increasing the temperature and provides protection for the glow plug coil.

A similar arrangement is shown in DE-PS 834 467, wherein however a special side channel, which is acted on by hot gases from the cylinder, opens in the proximity of the lower rim of a glow plug coil encompassing an injected jet.

The afore-described arrangements are not adapted to the conditions of turbulent or swirl chamber engines. In the case of a swirl chamber, the glow plug coil usually projects into the chamber merely in the region of the chamber wall in direction of swirl in front of or behind the injection nozzle, both possibilities being represented in DR-PS 659 160 and 645 621, respectively. In such arrangements of the glow plug, only the fuel-air mixture flowing in the region of the wall is particularly influenced thermally.

It is also known to construct the injection nozzle and the glow plug as one unit. In that case, the injection nozzle sits in a nozzle holder body and the glow coil is arranged on this body in front of the nozzle opening.

The afore-described construction is shown in DR-PS 543 310, wherein, however, the glow coil is arranged in spiral shape in a plane perpendicularly to and in front of the nozzle opening in the region of the entire jet angle.

It would thus be desirable to overcome the disadvantages of the known glow plug arrangements and provide improved heat transfer to the injected fuel jet by way of the enveloping air while largely avoiding disturbance of, for example, swirl flow in a combustion chamber.

According to the present invention there is provided a glow plug for an internal combustion engine with fuel injection into a combustion chamber, the glow plug comprising an electrically heatable filament supported by support means and arranged substantially to lie on and extend around at least part of the circumference of a notional frustro-conical body, the support means being mountable in use to position the filament around a frustro-conical envelopeforfuel injected into such chamber.

Preferably, the filament comprises a coil constructed conically about corresponding to the jet angle of an injected jet and arranged to extend around the rim region of the injected jet. By this construction it is ensured that a heated air cushion formed around the filament is continuously entrained by the flow in the injected jet so as to provide improved ignitability of the fuel-air mixture.

In principle it is ensured that, rather than consumption of heat in heating a large part of the chamber volume or an external part thereof, the heat is applied only in the air region actually penetrated by the fuel jet. In that case, a local concentration of the heat is provided for the fuel to be prepared. As a result there may be an improvement in cold-start behaviour and idling at low temperatures.

Advantageously, the filament is arranged at an injector nozzle holder or nozzle protection plate.

This arrangement secures that the chamber, if a swirl chamber, has only one additional opening apart from the outflow opening to the cylinder.

The filament can be constructed with a sinuous or zig-zag shape, the longitudinal portions of which extend in an envelope plane around the jet angle. In this construction, the plug can have several current circuits, wherein the number of the surfaces in direction transverse to the course of the injected jet reduces at the same time.

Embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a sectional view of a swirl chamber of a Diesel engine with a first glow plug embodying the invention; Fig. 2 is a view of part of a second glow plug embodying the invention; and Fig. 3 is a view of a third glow plug embodying the invention.

Referring now to the drawings, there is shown in Fig. 1 a swirl chamber 1 in the cylinder head of a Diesel engine. Arranged in the upper part of the chamber is a fuel injection nozzle 2, the jet direction of which is directed transversely through the chamber 1 in a region shortly in front of a transition passage 3 to the cylinder. Arranged to project laterally into the chamber 1 is a glow plug 4, a glow coil 5 of which in the form of a conical spring encompasses the injected jet 6 with its jet angle a.

The size of the coil 5 is such that in principle it will not be sprayed with fuel. The coil 5 is disposed in the immediate proximity of the external cone of the envelope of the jet 6. Initially, the heat of the central air cushion in the interior space of the coil is drawn upon for heat exchange by way of the fuel sprayed at appreciable speed through the coil 5 and subsequently, through the injector effect of the jet 6, the warm air components between and around the coil 5 are drawn off and the heat thereof conducted to the fuel.

In the embodiment shown in Fig. 2, the glow coil 5 is arranged at an injector nozzle holder or nozzle protection plate 7 and the wall of the chamber 1 can remain largely undisturbed, so that flow in the region of the wall in usual operation can take place almost undisturbed. Only the start and end portions of the coil 5 penetrate the region near to the wall.

In Fig. 3 there is shown a glow plug with a heating filament 5 mounted in a nozzle protection plate 7, the filament having a sinuous or zig-zag shape. This construction is preferably applicable to glow plugs with two heater circuits and the filament shape also ensures only slight disturbances in the wall region of the swirl chamber. It is to be mentioned that the straight portions along the jet envelope outline 8 extend substantially parallelly to the angle a of the injected jet 6.

Claims

1. A glow plug for an internal combustion engine with fuel injection into a combustion chamber, the flow plug comprising an electrically heatable filament supported by support means and arranged substantially to lie on and extend around at least part of the circumference of a notional frustroconical body, the support means being mountable in use to position the filament around a frustro conical-envelope for fuel injected into such chamber.

2. A glow plug as claimed in claim 1, the support means comprising a protective plate for the nozzle of a fuel injector.

3. A glow plug as claimed in claim 1, the support means comprising a nozzle holder of a fuel injector.

4. A glow plug as claimed in any one of the preceding claims, wherein the filament has in part the form of a substantially helical coil.

5. A glow plug as claimed in any one of claims 1 to 3, wherein the filament is in part substantially sinusoidal or zig-zagged in shape, the portions of the filament between the turns in that shape being arranged to extend substantially in direction between the ends of said notional body.

6. A glow plug substantially as hereinbefore described with reference to Fig. 1 of the accompanying drawings.

7. A glow plug substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

8. A glow plug substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings.

9. An internal combustion engine with fuel injection into a combustion chamber, the engine being provided with a fuel injector arranged to inject fuel on a substantiallyfrustro-conical envelope into the chamber and with a glow plug as claimed in any one of the preceding claims, the filament of the plug being positioned around said path.