GB2200949A

GB2200949A - I.C. engine pre-combustion chamber cup

Info

Publication number: GB2200949A
Application number: GB08801570A
Authority: GB
Inventors: David John Gaskell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-02-05
Filing date: 1988-01-25
Publication date: 1988-08-17
Also published as: GB8801570D0

Abstract

The main body of the cup 16, is formed from non-electrical conductive silicon aluminium oxynitride but it is provided with an electrically conductive lining 22 or layer below the surface of the same material which is connected to terminals connected in use to an electric supply. Current flowing through the lining or layer causes heating thereof to facilitate the ignition of fuel sprayed into the combustion chamber 11. The cup may be produced by sintering a preform of the two forms of ceramic material or the surface layer deposited by plasma spraying. <IMAGE>

Description

"ENGINE COMPONENT" This invention relates to a cylinder head insert for a so-called indirect injection compression ignition engine.

In such an engine fuel is injected into a pre-combustion chamber which communicates with the associated cylinder of the engine by way of a passage.

The pre-combustion chamber is formed in the cylinder head of the engine part of the chamber being defined by the cylinder head and the remaining part of the chamber together with the passage, being defined by an insert which is fitted into the cylinder head.

In order to start such an engine some form of starting aid is required to provide a heated zone within the combustion chamber and the usual practice is to provide an electrically powered starting aid which is accommodated within a bore formed in the cylinder head and extending to the wall of the combustion chamber. In addition, it is necessary to provide a further bore for the injection nozzle.

The object of the present invention is to provide a cylinder head insert for a so-called indirect injection compression ignition engine which besides its usual duty of defining part of a combustion chamber of the engine, is also able to supply heat to the combustion chamber for engine starting purposes.

According to the invention a cylinder head insert comprises a body formed from an electrically insulating material, the body being shaped to define a recess which in use forms part of the wall of a combustion chamber of the engine, the body also defining a passage extending from said recess, at least part of the wall of said recess having an electrically conductive lining and terminal pieces connected to said lining whereby in use, when said terminal pieces are connected to a source of electric supply the lining will become heated to facilitate starting of the engine.

An example of an insert in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a portion of a cylinder head of a compression ignition engine showing the usual form of starting aid but also showing an insert in accordance with the invention, and Figure 2 is a perspective view of the insert shown in Figure 1.

Referring to the drawings there is indicated at 10 part of the cylinder head of a compression ignition engine. Indicated at 11 is a pre-combustion chamber into which fuel can be sprayed by means of an injection nozzle generally indicated at 12, the nozzle having a fuel inlet 13 and being located in a bore 14 formed in the cylinder head.

The combustion chamber is of generally spherical form with the inner part of the combustion chamber, that is to say the part of the combustion chamber remote from the f-ace 15 of the cylinder which abuts the cylinder block, formed directly in the cylinder head.

The remaining portion of the combustion- chamber is defined by a recess which is formed in a flanged insert 16 which is located within a- suitably shaped recess 17 formed in the cylinder head. The insert 16 defines a passage 18 which communicates with the associated engine cylinder. The passage 18 in the particul-ar example, is tangentially disposed.

Figure 1 also illustrates the provision of a starting aid which is generally indicated at 19, the starting aid being located in a bore 20 which extends into the combustion chamber and the starting aid is electrically powered and has a projecting portion 21 which in use forms a heated surface within the combustion chamber to facilitate starting of the engine.

The provision of the starting aid 19 does require the machining of the bore 20 apart from the provision of the starting aid itself. Moreover, the fact that the projecting portion 21 extends into the combustion chamber does cause some disturbance of the gas flow within the combustion chamber.

In accordance with the invention it is proposed to provide a lining 22 on the wall of the recess in the insert. The lining is formed from electrically conductive material and terminal means is provided whereby the lining can be connected to a source of electric supply which when connected results in the lining becoming heated to form a heated zone within the combustion chamber to facilitate starting of the engine. With this arrangement therefore there is no longer any need to provide the bore 20 or the starting aid 19 and as a result the flow of gases within the combustion chamber is not disturbed.

Figure 2 shows a perspective view of the insert.

It is proposed to form the main body of the insert together with the flange, from an electrically non-conducting ceramic material such as a sialon, an example of such a material being Syalon 101 produced by Lucas-Cookson Syalon Limited. The lining can be formed from an electrically conducting sialon such as Syalon 501 also produced by Lucas-Cookson Syalon Limited. As shown in Figure 2, the terminal pieces are formed from the conducting sialon but are of increased thickness and also extend to the periphery of the insert. One of the terminal pieces can be connected to the body of the cylinder head and the other terminal piece to an electrically insulated connector piece mounted in the cylinder head.

Conveniently the conducting sialon is formed as a band about the recess with the thickness of the material being chosen to obtain substantially equal heating throughout the layer. Alternatively instead of a single band, a plurality of bands could be provided again connected to the terminal pieces 23.

The two types of sialon are preformed together and are then sintered to produce a monolithic block.

An alternative arrangement is to provide a more localized zone of conducting material again connected to terminal pieces so that more localized heating will be obtained.

A further alternative is to locate the conductive material below the general surface of the recess.

The lining may be formed from material which is applied to the surface of the insert by a plasma spraying operation.

Claims

1. A cylinder- head insert for an indirect injection compression ignition engine comprises a body formed from an electrically insulating material, the body being shaped to define a recess which in use forms part of the wall of a combustion chamber of the engine, the body also defining a passage extending from said recess, at least part of the wall of said recess having an electrically conductive lining and terminal pieces connected to said lining whereby in use, when said terminal pieces are connected to a source of electric supply the lining will become heated to facilitate starting of the engine.

2. A cylinder head insert according to Claim 1 in which the main portion of the insert and also the lining are formed from non-electrically conductive and electrically conductive sialons respectively.

3. A cylinder head insert for an indirect injection compression ignition engine substantially as hereinbefore described.