GB2073335A - Internal combustion engine gasket - Google Patents

Abstract

A piston internal combustion engine including an auxiliary combustion chamber (32) bounded by an inset 37 inserted from the direction of a main combustion chamber (11) into a clearance (38) in a cylinder head (12) to rest with a supporting surface which faces the main combustion chamber against a cylinder head gasket 13 made of a relatively soft material. A combustion chamber passage 23 in the cylinder head gasket is enclosed by a metallic border member 24 overlapping the soft material of the cylinder head gasket on both sides. The combustion chamber passage and the border member have a radially outwardly directed extension 40 adjacent the region of and to support the supporting surface of the auxiliary combustion chamber at an edge thereof. The extension 40 is also provided with a metallic border element, the parts 42 (43) overlying the soft material of the gasket being of greater width than the equivalent parts of the border element 24 about the combustion chamber passage 23. <IMAGE>

Description

SPECIFICATION Piston internal combustion engine This invention relates to piston internal combustion engines with auxiliary combustion chambers.

In order to obtain a more intensive mixing and hence a more intensive combustion of a fuel air mixture, it is known in piston internal combustion engines, such as diesel engines, to provide an auxiliary combustion chamber in front of the main combustion chamber, fuel being introduced by spraying into said auxiliary combustion chamber. Such auxiliary combustion chambers have become known as "turbulence chambers" or "Ricardo cham bers".

Such auxiliary combustion chambers can be integrated directly into the cylinder heads of internal combustion engines, for instance by casting. However, in many cases it has been found more advantageous from a manufacturing point of view to provide as the auxiliary combustion chamber, a turbulence chamber inset independent of the cylinder head, the inset being located in a space in the cylinder head. In such cases a distinction is made between turbulence chamber insets installed from above and turbulence chamber insets installed from below relative to the main combustion chamber, in the cylinder head.

The latter variation is often preferred for reasons of design and ease of manufacturing.

In the installed condition of the cylinder head the turbulence chamber inset has a part of its bottom wall resting on the cylinder head gasket, whereby the inset is prevented from being dislodged. The remainder of the turbulence chamber inset containing a discharge orifice for the fuel air mixture mixed in turbulent manner in the auxiliary combustion chamber then lies clear above the main combustion chamber.

As not only intensive mixing of the fuel introduced with the air on combustion takes place in the auxiliary combustion chamber, but also pre-combustion, the bottom wall of the auxiliary combustion chamber is exposed to especially high temperature stresses. Due to the heat transfer, the cylinder head gasket also is very much stressed correspondingly in that region where it touches the bottom of the auxiliary combustion chamber. When operating such an internal combustion engine in practice, there is, therefore, frequently damage and hence leakage in the cylinder head gasket at the contact with the bottom wall of the auxiliary combustion chamber. Most jeopardized by this are the arc and the directly adjoining tip of the metal combustion chamber border of the cylinder head gasket.Once the metal combustion chamber border has been damaged, both the combustion pressure and the alternating motion of the inset in the normal and transverse directions lead to a rapidly advancing destruction of the soft material of the cylinder head gasket.

It is already known to counter the above described partial destruction of the cylinder head gasket by designing the tip of the metal combustion chamber border resting against the bottom wall of the auxiliary combustion chamber in the area under discussion as a socalled "lug" i.e. enlarged. However durable success has not always been achieved thereby, so that the tip of the cylinder head gasket touching the bottom wall of the auxiliary combustion chamber must still be viewed as a pronounced weak spot.

The present invention, therefore, seeks to provide a piston internal 'combustion engines in which premature damage due to the adjoining bottom wall of the auxiliary combustion chamber no longer need be feared.

According to the present invention there is provided a piston internal combustion engine including an auxiliary combustion chamber inserted from a main combustion chamber into a clearance in a cylinder head to rest with a supporting surface which faces the main combustion chamber against a cylinder head gasket made of a relatively soft material, a combustion chamber passage in the cylinder head gasket being enclosed by a metallic border member overlapping the relatively soft material of the cylinder head gasket on both sides, the said combustion chamber passage and the border member having a radially outwardly directed projection adjacent the region of said supporting surface of the auxiliary combustion chamber.

The present invention thus may relocate the especially jeopardized arc of the border member further into the "hinderland" and thus eliminate altogether any contact between the cylinder head gasket and the especially highly thermally stressed region of the auxiiiary combustion chamber. In the invention, therefore, the arc of the border member no longer follows as previously conventional, the circular contour of the cylindrical bore of the main combustion chamber at a spacing from about 0.5 to 1 mm, rather it is locally recessed directly below the supporting surface of the auxiliary combustion chamber into a region less endangered by high temperatures.

To prevent direct contact between the soft material of the cylinder head gasket and the supporting surface of the auxiliary combustion chamber in an advantageous embodiment of the present invention the metal border member is provided in the region of the projection, at least on the side facing the auxiliary combustion chamber, with tips extending in the radial direction. The projection may be rounded and is arranged symmetrically with repect to the common central axis of the combustion chamber passage and the supporting surface of the auxiliary combustion chamber. Similarly the tips of the border member may be rounded and are arranged symmetrically with respect to the common central axis of the combustion chamber passage and the supporting surface of the auxiliary combustion chamber.

The advantages flowing from this symmetrical design and arrangement of the sealing parts touching the supporting surface of the auxiliary combustion chamber are uniform thermal stresses on the sealing region in question and hence a further lowering in the risk of premature damages. From a manufacturing point of view preferably there is a smooth transmission on both sides of the projection with a circular region of the border member.

In the preferred embodiment the projection and the radial extension of the tips of the border member are arranged symmetrically with respect to an exhaust orifice extending from the auxiliary combustion chamber to the main combustion chamber.

Preferably the radius of the projection of the border member is smaller than the radius of a lower surface of a turbulence chamber inset forming the lower closure of the auxiliary combustion chamber.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 shows the cylinder region of a single cylinder piston internal combustion engine according to the present invention in vertical section taken on the line I-I in Fig. 2; and Figure 2 is a section taken on the line ll-ll in Fig. 1 of a cylinder head gasket of the piston internal combustion engine.

In Fig. 1 , a cylinder block 10 of an internal combustion engine according to the present invention has a bore 11 within which a vertically reciprocating piston (not shown) is mounted. A cylinder head 1 2 is seated on the cylinder block 10, a cylinder head gasket 1 3 being inserted in conventional manner be- tween the cylinder block 10 and the cylinder head 1 2. The cylinder block 10 and the cylinder head 1 2 are provided with cavities or channels 14 to 1 8 through which flows cooling water.

As shown in Fig. 2, the cylinder head gasket 1 3 has apertures 19, 20, 21 allowing the passage of cooling water from the cylinder head 1 2 into the cylinder block 10 and vice versa. Five boreholes 36 of equal diameter also act as cooling water passageways through the cylinder head gasket 1 3. The cylinder head 1 2 is fastened in known manner by bolts (not shown) to the cylinder block 10 and tightened to it while compressing the cylinder head gasket 1 3. To that end the cylinder head gasket 1 3 is provided with central bores 22 for the bolts.

A large central clearance or combustion chamber passageway 23 is formed in the cylinder head gasket 13, the rim of said passage 23 being lined with a metallic border member 24. The remaining material 25 of the cylinder head gasket and indicated by crossshading in Fig. 1, is a relatively soft material possibly reinforced with metal. Faces 26, 27 of the border member 24 surround, as shown in Fig. 1, the soft material on both sides and bear against an end surface of the cylinder block 10 and the cylinder head 1 2. The rim of the passage 23, i.e. the border member 24, forms the radial boundary of a main combustion chamber 28 in the cylinder block 1 0. The border member 24 may be referred to as a "combustion chamber border".

The internal combustion engine shown in Fig. 1 is a diesel engine. A fuel injection nozzle 30 is schematically shown in a bore 29 in the cylinder head 12, a nozzle orifice 31 of the nozzle debouching into an auxiliary combustion chamber 32. A glow plug 33 is used to improve starting when the engine is cold.

Two parallel valves 34, 35 ensure alternating supply to the main combustion chamber 28 or to the bore 11.

A turbulence chamber inset 37 is mounted into an offset clearance 38 in the cylinder head 12, the inset 37 assuming an offset cylindrical shape. The inset 37 forms the lower closure of the auxiliary combustion chamber 32. A slot 39 in the inset 37 connects the auxiliary combustion chamber 32 with the main combustion chamber 28.

When the cylinder head 1 2 is in place (Fig.

1), the inset 37 is kept by the cylinder head gasket 1 3 in its installed position. Fig. 2 indicates that the passage 23 in the cylinder head gasket 1 3 comprises a radially outwardly directed protrusion or projection 40 in the region of the inset 37. The projection 40 extends symmetrically with respect to the dotdashed centre line 41 of the cylinder head gasket 13. The projection 40 causes the end faces of the inset 37 facing the main combustion chamber 38 to be located substantially clear above the main combustion chamber, that is, most of it does not touch the cylinder head gasket 1 3. Therefore the support of the turbulence chamber inset 37 by the cylinder head gasket 1 3 takes place merely at the centre point of the bore 11 in the most remote outer region. This step ensures that no overheating of and damage to the cylinder head gasket 1 3 can take place due to the inset 37 producing extremely high temperatures at its centre region. The cylinder head gasket 1 3 is further protected in the jeopardized region by the step of providing a substantial extension of tips 42, 43 of the border member 24. Fig. 2 further makes it clear that the projection 40 itself, as well as its tips 42, 43, are rounded off and that there is a smooth transition with the circular region of the border member.

In Fig. 2, the radius of the projection 40 is denoted by r1 and the radius of the supporting surface which faces the main combustion chamber 38 of the insert 37 is denoted by r2.

The radii r,, r2 must be so sized mutually that the inset 37 on the one hand is adequately supported by the cylinder head gasket 1 3 while on the other hand as much of its bottom surface as possible remains clear. It is possible to optimize empirically this requirement in that the radius r1 of the projection 40 is selected to be about 2 mm less than the radius r2 of the inset 37.

Whilst the present invention has been described in relation to a single cylinder internal combustion engine it can also be applied to piston internal combustion engines with several cylinders (for instance, 4 or 6 cylinders).

Claims (9)

1. A piston internal combustion engine including an auxiliary combustion chamber inserted from a main combustion chamber into a clearance in a cylinder head to rest with a supporting surface which faces the main combustion chamber against a cylinder head gasket made of a relatively soft material, a combustion chamber passage in the cylinder head gasket being enclosed by a metallic border member overlapping the relatively soft material of the cylinder head gasket on both sides, the said combustion chamber passage and the border member having a radially outwardly directed projection adjacent the region of said supporting surface of the auxiliary combustion chamber.

2. An internal combustion engine as claimed in claim 1 in which the border member is provided in the region of the projection, at least on the side facing the auxiliary combustion chamber, with tips extending in the radial direction.

3 --An internal combustion engine as claimed in claim 1 or 2 in which the projection is rounded and is arranged symmetrically with respect to the common central axis of the combustion chamber passage and the supporting surface of the auxiliary combustion chamber.

4. An internal combustion engine as claimed in claim 3 when dependent upon claim 2 in which the tips of the border member are rounded and are arranged symmetrically with respect to the common central axis of the combustion chamber and the supporting surface of the auxiliary combustion chamber.

5. An internal combustion engine as claimed in claim 4 in which there is a smooth transition on both sides of the projection with a circular region of the border member.

6. An internal combustion engine as claimed in claim 5 in which the projection and the radial extension of the tips of the border member are arranged symmetrically with respect to an exhaust orifice extending from the auxiliary combustion chamber to the main combustion chamber.

7. An internal combustion engine as claimed in claim 6 in which the radius of the projection of the border member is smaller than the radius of a lower surface of a turbulence chamber inset forming the lower closure of the auxiliary combustion chamber.

8. A piston internal combustion engine substantially as herein described with reference to and as shown in the accompanying drawings.

9. A cylinder head gasket for piston internal combustion engines with an auxiliary combustion chamber, in particular for diesel engines with a turbulence chamber, where a constructional component containing the auxiliary combustion chamber is inserted from the main combustion chamberinto a clearance in the cylinder head and rests by a bottom surface facing the main combustion chamber against a cylinder head gasket, consisting of a soft material possibly metallically reinforced and comprising several several passages, at least the combustion chamber passage being enclosed by a metal border overlapping the soft material on both sides, characterised in that the combustion chamber passage and the metal combustion chamber border surrounding said passage is provided with a radially outwardly pointing protrusion in the region of the bottom surface of the auxiliary combustion chamber.