GB2145153A

GB2145153A - Fuel injectors for i.c. engines

Info

Publication number: GB2145153A
Application number: GB08414174A
Authority: GB
Inventors: Klaus Dobler; Iwan Komaroff; Peter Egelhaaf
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1983-08-13
Filing date: 1984-06-04
Publication date: 1985-03-20
Also published as: GB2145153B; GB8414174D0; JPS6056164A

Abstract

A fuel injector for i.c. engines, particularly of the auto-ignition type, comprises an injection nozzle (10) and a surface-ignition body (30) through an opening in which fuel from the nozzle (10) passes, the body (30) being heated, for example by current flow in a heating element (44). The surface-ignition body (30) is provided with a resistive component which is pressure-sensitive and/or temperature-sensitive and may be a winding (48), or may be formed directly by the actual surface-ignition body (50) (Fig. 2). The sensitive component (48, 50) may be connected to a circuit to evaluate combustion chamber temperature and/or pressure variation which may be supplied to a display device or used to control the combustion process or the injection. <IMAGE>

Description

SPECIFICATION Device for Injecting Fuel Into the Combustion Chambers of Internal Combustion Engines, Particularly of the Auto-ignition Type The invention derives from a fuel-injection device of the generic type described in Claim 1.

These devices possess the advantage that a separate glow-plug is dispensed with, the installation of which can mean that the flow conditions within the combustion chamber must be disturbed in a manner which can lead to problems. Furthermore, the surface-ignition attachment can be provided, in an advantageous manner, with lateral ventilation openings, through which the spray jets draw in air, from the combustion chamber, as they pass through the surface-ignition attachment, as a result of an injector-like action. The air which is drawn in becomes heated, and penetrates into the edge zones of the spray jets, where it forms a fuel/air mixture which is very favourable for the ignition and combustion processes.

The arrangement according to the invention, with the characterising features specified in Claim 1, possesses the advantage that the surfaceignition attachment additionally functions as a sensor for measuring the pressure and/or the temperature in the combustion chamber of the engine, without requiring for this purpose, any additional sub-assemblies or additional installation apertures in the cylinder head of the engine. The measured values deriving from the resistive component or components affixed to the surface ignition attachment can be input to a display device, or to a unit for controlling or regulating the combustion process or, as the case may be, the injection process.

The measures cited in the sub-claims enable the arrangement according to Claim 1 to be developed into further advantageous embodiments.

All components which are suitable for converting the physical quantities, pressure and temperature, into electrical signals can be used as the resistive components. In order to acquire data describing the combustion-chamber pressure, thick-film resistors have proved particularly advantageous, these resistors being largely free of any susceptibility to breaking down, measuring without being affected by the rate at which the force is varying, being amenable to manufacture in forms suiting the production procedure, as well as being capable both of being affixed to the surface-ignition body and of receiving the appropriate connections.

When the surface-ignition body is designed in the form of an annular ceramic body, the resistive component can, in an advantageous manner, also be a conductor which varies its resistance value when subjected to the effect of pressure, this conductor being affixed, in the form of a coil, or in a meandering arrangement, or the like, to the outer surface of the surface-ignition body.

In order to eliminate, to the greatest possible extent, undesired variations in the measured values as a result of temperature-related influences, it is further proposed that a portion of the resistive component be screened from the effect of the combustion-chamber pressure, and that it should form, with each remaining portion, one arm of a bridge circuit.

It is particularly advantageous if a heating conductor belonging to the surface-ignition attachment, or, if appropriate, the actual surfaceignition body of this attachment, serves as the resistive component, so that its formation necessitates no additional part at all on the surface-ignition attachment. The heating conductor, or, as the case may be, the surfaceignition body, can be a metal helix, which may be unsupported or supported, or it can be a conducting track which has been applied to a ceramic surface-ignition body, for example by means of an infiltration-sintering process.

The decisive advantage of this solution resides in the fact that the surface-ignition and sensing functions are taken over by one and the same component, without any significant additional expenditure, thereby enabling all the cylinders of the engine to be monitored and controlled, without difficulty and at low cost.

An (sic) illustrative embodiment of the invention is represented in the drawing, and is explained in more detail in the description which follows. Figure 1 shows the first illustrative embodiment, and Figure 2 shows the second one, in each case as an enlarged partial section through that end of the injection nozzle which is located in proximity to the combustion chamber, and the surface-ignition attachment.

The device shown in Figure 1 possesses an injection nozzle 10, with a nozzle body 12, in which a valve-seat 14 is formed, and in which a valve-needle 1 6 is mounted, in a manner such that it can slide. The nozzle body 12 contains a fuel passage 18, opening into a pressure-space 22 which surrounds the valve-needle 1 6 in the region of a pressure-shoulder 20. At the beginning of the injection process, the rising fuel pressure in the pressure-space 22 lifts the valveneedle 1 6 clear of the valve-seat 14, against the force of a closing spring which is not represented in the drawing, after which the fuel enters the combustion chamber 26 in the form of a spray jet 24.

An annular body 32 and a tangential pin 34 serve to retain a ceramic surface-ignition body 30 on that end face of the nozzle body 12 which faces the combustion chamber 26. A central passage is formed in the surface-ignition body 30, in order to enable the spray jets 24 to pass through, this central passage comprising a cylindrical portion 36, a portion 38 which is narrowed in the manner of a convergent nozzle, and a portion 40 which is contiguous with the portion 38 and is widened in the manner of a diffuser. Lateral openings 42 emerge into the portion 38, through which the spray jets 24 draw in air from a region occupying part of the combustion chamber 26, which still contains a high proportion of oxygen at the moment of ignition.

That portion 40 of the surface-ignition body 30 which is widened in the manner of a diffuser is provided, on the inner surface, with a heating helix 44 in the form of a shallow conducting track, running in a meandering arrangement. One of the ends of the heating helix 44 is connected to a connecting cable 46 which is led through the nozzle body 12, in a manner whereby it is insulated, and is connected to a switching device for the purpose of preheating the injection nozzle.

The other end of the heating helix 44 is earthed, via the nozzle body 12.

On its outer wall surface, the surface-ignition body 30 carries an electrical component, 48, of a resistive nature, this component 48 expediently being configured as a conducting track, running in a meandering arrangement and implemented in thin-film or thick-film technology. The combustion-chamber pressure acts directly on the resistive component 48, which is composed of a material exhibiting resistance values which can be caused to vary as a result of being subjected to external pressure. In order to embody temperature compensation, a portion of the resistive component 48 is screened from the combustion-chamber pressure and is connected to form, with each remaining portion, one arm of a bridge circuit.This bridge circuit is part of a circuit for evaluating the manner in which the combustion process proceeds, and/or the course of the injection process, this evaluating circuit being connected to the two arms of the resistive component 48, and to its mid-point via lines which are contained within the connecting cable 46, or which, separate from this cable, are led through the nozzle body 12.

When the internal combustion engine is operating, the spray jets 24, in passing through the surface-ignition body 30, draw in air from the combustion chamber 26, through the lateral openings 42. The air which is drawn in becomes heated to a temperature level which is higher than in the remainder of the combustion chamber 26, and penetrates into the edge zones of the spray jets, where the resulting fuel/air mixture is very favourable for the ignition and combustion processes, this mixture igniting, in a reliable manner, once it has entered the combustion chamber 26. The resistive component 48 acquires data describing the pressure variations in the combustion chamber 26, and outputs these data, as signals, to the evaluating circuit, which subjects them to further processing in the desired manner.

In the csae of the device shown in Figure 2, an inherently stable glow-coil 50 is provided, as the surface-ignition body, this coil 50 being capable of surviving without a ceramic support. One connection end 51 of the glow-coil 50 is connected directly to a connecting conductor 52 which ieads elsewhere, while its other connection end, 53, is fastened to a metal flange ring 54, via which it is earthed. The flange ring 54 is inserted, centrally, into a clamping nut 56, and is provided with a plurality of through-holes, 58 and 60, through which air from the combustion chamber 26 enters annular spaces 62 and 64, whence it then reaches the spray jets 24.

In the case of this embodiment, the glow-coil 50 forms, at the same time, an electrical component of a resistive nature, this component being part of an evaluating circuit which generates data describing the manner in which the combustionchamber pressure varies, and/or data describing the manner in which the combustion-chamber temperature varies. The glow-coil 50 is led, via the line 52, and via earth, to terminals 66 and 68, via which, on the one hand, it is supplied with the necessary heating current, from a source of electrical power which is not shown, and via which, on the other hand however, data describing the value of the resistance of the flowcoil 50, at any given instant, are acquired.

According to the illustrative embodiment, this is effected with the aid of a bridge circuit which is provided with resistors 70 and 72. These resistors are connected in series, both one end-point of the series-connected arrangement and its mid-point being led to circuitry means 74, and the other point being connected to the terminal 66. The terminal 68 is likewise connected to the circuitry means 74.

The circuitry means 74 include an amplifier for small electrical signals, this amplifier being of a type known per se, preferably of the type used for evaluating strain-gauge signals. in addition, the circuitry means 74 can contain, for example, a circuit for evaluating knock signals. Because the glow-coil 50 varies its electrical properties under the influence both of the combustion-chamber pressure and of the combustion-chamber temperature, it is possible, by selecting a suitable material, for the glow-coil, to use this coil both for measuring the combustion-chamber pressure and for analysing the temperature variation with a view to subjecting the combustion process to measurement.

Claims

1. Device for injecting fuel into the combustion chambers of internal combustion engines, particularly of the auto-ignition type, this device possessing an injection nozzle and a surfaceignition attachment which is assigned to the spray opening of the injection nozzle, this surfaceignition attachment possessing a surface-ignition body containing a passage which is surrounded by structures capable of being heated, and through which passage the fuel spray jets pass, at least without any significant hindrance, according to Patent (Patent Application P 33 07 109.8), characterised in that the surfaceignition attachment (30, 50) carries at least one electrical component (48, 50) of a resistive nature, this component (48, 50) having a resistance value which is pressure-dependent and/or temperature-dependent and being provided with connections for an electrical evaluating circuit (74).

2. Device according to Claim 1, characterised in that the resistive component (48) is a thick-film resistor.

3. Device according to Claim 1, characterised in that the resistive component is a conductor which varies its resiswance value when subjected to the effect of pressure, this conductor being affixed, in the form of a coil, or in a meandering arrangement, or the like, to the outer surface of a ceramic surface-ignition body (30).

4. Device according to Claim 2 or 3, characterised in that a portion of the resistive component is screened from the effect of the combustion-chamber pressure, and forms, with each remaining portion, one arm of a bridge circuit.

5. Device according to Claim 1, characterised in that a heating conductor belonging to the surface-ignition attachment, or, if appropriate, the actual surface-ignition body (50) of this attachment, serves as the resistive component.

6. A fuel injection device substantially as herein described with reference to Figure 1 or Figure 2 of the accompanying drawing.