JPH0119048B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion chamber for an internal combustion engine such as a direct-injection diesel engine, in which the dead volume at the top dead center of a piston can be reduced to minimize incomplete combustion volume. It is something.

In conventional direct-injection diesel engines, there are variations in the thickness of the head gasket inserted between the top of the piston and the bottom of the cylinder head when tightening, and due to the dimensions of the piston, piston pin, connecting rod, crankshaft, etc. Taking into account cumulative errors such as tolerance, the piston top clearance is usually about 0.6 to 1.0 mm.

Therefore, a space is inevitably created at the top of the piston that does not directly participate in combustion. This space is called an incomplete combustion volume, ie, a dead volume, and for example, in a piston having a recess formed at the top, this space corresponds to the portion above the recess. In the case of a piston without a recess as described above, this is the space between the peripheral edge of the piston and the inner surface of the hole corresponding to the cylinder bore of the head gasket.

For the reasons mentioned above, a dead volume inevitably occurs in a normal internal combustion engine, but this dead volume lowers the compression ratio, hinders improvement in combustion efficiency, and has the disadvantage of causing incomplete combustion. .

Therefore, it is clear that it is desirable to reduce this dead volume as much as possible in order to improve the combustion efficiency of the engine. Particularly in small displacement direct injection diesel engines, the above-mentioned disadvantages are significant, causing exhaust smoke and a reduction in engine output.

Therefore, the present invention provides a combustion chamber that can reduce the dead volume between the piston and the cylinder head at the top dead center position of the piston of an internal combustion engine as much as possible, thereby reducing the exhaust smoke of the engine and improving the engine output. It is something to do.

To achieve the above object, the present invention provides a combustion chamber formed between a cylinder head and a cylinder of an internal combustion engine, in which a bottom surface of the cylinder head facing the top of a piston fitted in the cylinder is uneven. A thin plate-shaped spacer with a section facing the spacer is configured to be pressed by a piston during engine operation to reduce the gap in the combustion chamber, and a heat-resistant material is provided on at least the surface facing the piston side of the spacer. This is a combustion chamber of an internal combustion engine characterized by forming a coating layer.

The dead space is reduced by extending the head gasket interposed between the upper part of the combustion chamber, that is, the cylinder head and the cylinder body, into the combustion chamber, and pressing this extended part with the upper part when the piston operates. The present inventors are already under development. The combustion chamber having this structure is a very effective means for improving compression efficiency because the dead volume of the combustion chamber can be adjusted by actual combination.

The present invention was obtained to further improve this excellent technology, and is particularly characterized by an improved structure of a spacer that can reduce the dead volume by providing it in the upper part of the combustion chamber. be.

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are a plan view and a sectional view of a head gasket provided between a cylinder head forming a combustion chamber and an engine body, showing a first embodiment of the present invention. and a spacer 3 provided on one side of the spacer.

The gasket body 2 is a gasket that is normally inserted between the engine body and the cylinder head.
The present invention is characterized in that a flat spacer 3 is further laminated on the gasket body 2.

As shown in FIG. 2, the gasket main body 2 has the shape of a normal head gasket, but a hole 6 is cut out in a portion corresponding to the cylinder bore, and a part of the spacer 3 is formed within this hole 6 to protrude. ing. The spacer 3 is also provided with bolt holes 11, water holes 12, and oil holes 13 at predetermined locations.

As shown in the cross section of FIG. 1, the spacer 3 has a flat portion 33 with corrugated (bead-like) unevenness 32 on a flat plate 31 at a portion that protrudes into the hole 6 when viewed from the side.
This unevenness 3 is formed concentrically with the
2 and the flat portion 33 are formed over the entire surface of the portion protruding into the combustion chamber 4.

The thickness T of the gasket body 2 is usually 1.0 to 1.4 mm.
and the thickness t of the flat spacer 3
is about 0.2 to 0.3 mm, and the height H of the unevenness 32
is preferably about 1.6 to 2.0 mm.

The function of the spacer 3 is that it has a thickness (height H) that is larger than the gap formed between the top of the piston and the bottom surface of the cylinder head in the initial stage when the piston is not in operation, and when the piston is in operation. It is necessary that the spacer 3 is deformed so as to keep the dead volume in the combustion chamber 4, which is deformed by being pressed, to a minimum.

Furthermore, the material of the spacer 3 is such that it can deform when pressed between the piston, the top, and the cylinder head without damaging the piston or the cylinder head, and maintains its shape after deformation. It is necessary that the material has sufficient strength to withstand the high temperature inside the combustion chamber, and also has heat resistance and strength to withstand the high temperature inside the combustion chamber.

Specifically, heat-resistant steel plates mainly composed of stainless steel plates and nickel steel plates having a thickness of 0.2 to 0.3 mm are suitable.

Furthermore, the spacer 3 constituting the gasket provided in the upper part of the combustion chamber of the present invention is provided inside the combustion chamber to remove the dead volume generated therein, and this spacer 3 itself can remove most of this dead volume. It is difficult to do so. Therefore, in order to compensate for this point, it is preferable to configure the engine so that the dead space is minimized when the internal combustion engine is operated.

In order to satisfy this requirement, the spacer 3 according to the present invention has a wavy uneven cross section as shown in FIG. Furthermore, in the present invention, a coating layer 5 is particularly provided on at least the lower surface of the spacer 3.
The feature is that the gap between the unevenness 32 is filled by providing the above-mentioned unevenness 32.

Although the coating layer 5 needs to be provided at least on the lower surface of the spacer 3, it is clear that the coating layer 5a may also be provided on the upper surface as shown in FIG.

These coating layers 5 and 5a have a function of deforming to fit the gap formed between the upper surface and the lower surface of the cylinder head when the piston rises to the top dead center (deforming according to the actual condition). It is necessary to have the ability to

Therefore, this coating layer needs to be heat resistant, easily deformed by the pressing force of the piston, and have adhesive strength between it and the spacer 3.

Specifically, the materials constituting the coating layer include heat-resistant resins such as polyimide, silicone, and fluorine-based resins, resins having properties such as self-extinguishing properties,
In some cases, zirconia-based ceramics or the like may be used.

Further, the material constituting the coating layer may be thermosetting. This characteristic allows for easy deformation when the internal combustion engine is assembled, making it possible to prevent large forces from being applied to the piston or cylinder head, but once the internal combustion engine is in operation, its combustion A material is selected in which the coating layer is hardened by the generated heat and becomes part of the material constituting the upper structure of the combustion chamber. In this way, the coating layer is soft in the initial stage, but when the internal combustion engine is started, the property of gradually hardening is important in the sense that unnecessary stress is not applied to the internal combustion engine.

This coating layer has the function of reducing the dead volume by crushing the irregularities formed on the surface of the spacer, and a material having a certain degree of elasticity and adhesion to the spacer is selected.

FIG. 3 shows a second embodiment, and in the case of the spacer 3 shown in FIG.
3, but in this embodiment, a continuous wave-shaped unevenness 32 is formed, and furthermore, this unevenness 3
2 are filled with coating layers 5, 5a.

Note that both the embodiment shown in FIG. 1 and the embodiment shown in FIG. The stacking position is not particularly limited.

FIG. 4 shows a third embodiment, in which a spacer 3 having coating layers 5, 5a shown in FIG. 1 on both sides is laminated on the underside of a gasket body 2.

FIG. 5 shows a fourth embodiment. In the embodiments shown in FIGS. 1 and 4, the unevenness 32 was projected on the combustion chamber side, but in this embodiment, the combustion chamber A recess 32a is formed upwardly.

FIG. 6 shows the general shape of a combustion chamber according to the present invention. A cylinder head 21 is stacked on top of a cylinder 20 via a head gasket 1 and fixed with bolts or the like.

As shown in FIG. 1, this gasket 1 has a spacer 3 laminated on the upper surface of a gasket main body 2, with coating layers 5, 5a provided on both sides. Further, a piston 22 is housed inside the cylinder 20 so as to be reciprocatable.

The combustion chamber according to the present invention is constructed as shown in FIG. 6, in which a spacer 3 protruding from the upper part of the combustion chamber 23 is formed with unevenness, and a coating layer 5 is provided so as to fill at least the side of the combustion chamber 23 of the unevenness. Therefore, it is possible to achieve the following effects.

In the internal combustion engine having a combustion chamber according to the present invention, a spacer 3 having the coating layers 5, 5a is provided between the upper surface of the piston 22 and the lower surface of the cylinder head 21 constituting the combustion chamber 23 when the piston 22 operates. Since the combustion chamber 2 is deformed by pressing
The dead volume within 3 can be kept to a minimum.

The spacer, which is an important component of the present invention, is a metal plate processed into an uneven shape, and a heat-resistant coating layer is provided on at least the lower surface of the spacer, so the surface of the spacer is flattened.
Furthermore, since the piston is pressed by the upper part of the piston and its shape is traced (matched to the actual item), the dead volume at the upper part of the piston can be considerably reduced.

Although not shown in the examples, some pistons have a depression or the like formed in the center of their upper surface in order to improve combustion efficiency. It is necessary to design a spacer with a structure that takes this into account.

In the present invention, as in the above embodiment, the head gasket interposed between the cylinder head and the cylinder body is constituted by a laminate of a normal gasket body and a spacer, and the spacer is formed with unevenness so that it can be easily deformed. Furthermore, a heat-resistant coating layer is provided to fill in the unevenness on the surface of this spacer, and when the piston is operated, the spacer is placed between the top surface of the piston and the bottom surface of the cylinder head at the top dead center of the piston. It is characterized by being configured so that it can be deformed by being pressed.

By configuring the present invention as described above, when the piston rises to the top dead center, it is possible to reduce as much as possible the gap formed between the upper surface of the piston and the lower surface of the cylinder head. Since it is possible to prevent the formation of dead volume within the combustion chamber, the compression ratio is significantly improved compared to conventional internal combustion engines.

Therefore, an internal combustion engine having a combustion chamber according to the present invention can improve combustion efficiency and reduce harmful components in exhaust gas.

Furthermore, when carrying out the present invention, the head gasket may be formed into a composite structure as described above;
This can be implemented without changing the structure of a conventional internal combustion engine.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a part of a gasket having a composite structure for carrying out the present invention, and FIG. 2 is a plan view of the head gasket. 3, 4, and 5 are cross-sectional views showing a part of the head gasket showing the second, third, and fourth embodiments.
The figure is a sectional view showing an example of a main part of a combustion chamber of an internal combustion engine according to the present invention. 1... Head gasket, 2... Gasket body, 3... Spacer, 20... Cylinder, 21
...Cylinder head, 22...Piston, 23...
...Combustion chamber, 31...Flat plate, 32...Irregularities, 33...
...flat area.

Claims (1)

[Claims] 1. In a combustion chamber formed between a cylinder head and a cylinder of an internal combustion engine, a thin plate-shaped spacer with an uneven portion is provided on the lower surface of the cylinder head facing the top of the piston fitted in the cylinder. The spacer is configured to be pressed by a piston during engine operation to reduce waste volume in the combustion chamber, and a heat-resistant coating layer is formed on at least the surface of the spacer facing the piston side. combustion chamber of an internal combustion engine.