GB2113762A

GB2113762A - I.C. engine combustion chamber

Info

Publication number: GB2113762A
Application number: GB08301658A
Authority: GB
Inventors: Isao Matsuno
Original assignee: Fuji Jukogyo KK; Fuji Heavy Industries Ltd
Current assignee: Subaru Corp
Priority date: 1982-01-25
Filing date: 1983-01-21
Publication date: 1983-08-10
Also published as: GB8301658D0; JPS58128417A; FR2520442B1; GB2113762B; DE3302232A1; JPH0519008B2; FR2520442A1

Abstract

The cylinder head combustion chamber 5 is defined by an upper horizontal wall 5a extending in the direction of the crankshaft axis, a vertical wall 5b at one side of the upper horizontal wall, a peripheral lower horizontal wall 5c at a lower side of the vertical wall 5b and an inclined wall 5d at the other side of the upper horizontal wall 5a. A projection 4b is formed on the top of a piston 4; the projection 4b has an inclined wall 4c which is closely adjacent to the inclined wall 5d of the recess 5 when the piston 4 is at top dead centre, to form a first squish zone 7. The lower horizontal wall 5c and the top of the piston 4b are so disposed as to form a second squish zone 6 when the piston is at top dead centre. The inlet valve 8 of the engine is positioned towards an end of the upper horizontal wall 5a so that a valve disk 8a of the inlet valve 8 is orientated in parallel with the upper horizontal wall 5a. The inlet passage 10 is substantially tangentially orientated at with respect to the cylinder 1 and extends above the vertical wall 5b to cause charge swirl about the cylinder axis. <IMAGE>

Description

SPECIFICATION An internal combustion engine The present invention relates to an internal combustion engine, and more particularly, though not exclusively, to a combustion chamber suitable for an oversquare engine having a recess in a cylinder head.

A combustion chamber having a recess in a cylinder head is disclosed, for example, in Japanese Utility Model specification No.

54-101205. In this prior art, on the top of the piston is a projection which enters into the recess in the cylinder head at the end of the compression stroke to form a 'squish' zone for upwardly ejecting unburned mixture at an oblique angle, so that a vertical swirl is created in the combustion chamber. Such a vertical swirl serves to mix the remainder of gases in a central portion of the combustion chamber with air and to scavenge gases around a spark plug. However, scavenging of a peripheral portion of the combustion chamber and cooling of hot spots which often generate in peripheral portions of the chamber cannot be performed by such a vertical swirl.

The present invention seeks to provide a combustion chamber shape which imparts a horizontal swirl during the suction stroke in addition to a vertical swirl during the compression stroke, whereby scavenging of remainder gases in peripheral portions and cooling of hot spots in the inner wall of the chamber may be accomplished, thereby improving combustion efficiency.

According to the present invention, there is provided an internal combustion engine, having a cylinder, a cylinder head, a piston, an inlet valve assembly, and an exhaust valve assembly, wherein the cylinder head has an elongate recess which extends in the direction of the length of the crankshaft of the engine, said recess being defined by an upper horizontal wall, a vertical wall at one side of the upper horizontal wall and offset inwardly along part of its length from the cylinder wall by a lower horizontal wall, and an inclined wall at the opposite side of the upper horizontal wall; a projection formed on the top of the piston; the projection having an inclined wall which is closely adjacent to the inclined wall of the recess when the piston is at top dead centre, to form a squish zone; the lower horizontal wall and the top of the piston being so disposed as to form another squish zone when the piston is at top dead centre; the inlet valve assembly being positioned towards one end of the upper horizontal wall, with a valve disk of the inlet valve oriented in parallel with the upper horizontal wall; and an inlet duct communicates tangentially with the valve port and is positioned above the vertical wall.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a sectional view of a combustion chamber of an internal combustion engine; Figure 2 is a bottom view of a cylinder head as viewed from line Il-Il of Figure 1; Figures 3a and 3b are sectional views of the combustion chamber showing conditions at the suction stroke and compression stroke; and Figure 4 is a view similar to Figure 2 showing a horizontal swirl.

Referring to Figures 1 and 2, a cylinder block 1 has a cylinder 3 in which a piston 4 is slidably engaged, and a cylinder head 2 has a recess 5.

The longitudinal axis of the recess 5 is parallel to the axial line Z-Z of the crankshaft of the engine and is defined by a central upper lateral (horizontal) plane or wall 5a perpendicular to the axial line of the cylinder 3, a longitudinal (vertical) wall 5b perpendicular to the lateral plane and at one side thereof, a peripheral lower lateral (horizontal) wall Sc at the lower side of the vertical wall 5b, and an inclined wall 5d extending from the other side of the upper horizontal wall 5a to the periphery of the recess 5. The peripheral horizontal wall Sc is closely adjacent to a top 4a of the piston 4 at top dead centre to form a first squish zone 6.A projection 4b is formed on the top 4a to closely approach the inclined wall 5d when the piston is at top dead centre. The projection 4b has a triangular cross section and extends along the inclined wall 5d. The projection 4b has an inclined wall 4c corresponding to the inclined plane 5d to form a second squish zone 7.

An inlet valve assembly 8 and an exhaust valve assembly 9 are provided in the horizontal wall 5a in alignment with the crankshaft axis Z-Z. The inlet valve assembly 8 is arranged vertically so that a valve disk 8a at the valve port has a horizontal upper surface parallel to the top 4a of the piston. The lift of the inlet valve 8 is selected to a value slightly smaller than the height of the vertical plane 5b.

As shown in Figure 2, an inlet duct 10 communicates tangentially with the valve port and is positioned above the vertical wall 5b.

A pair of spark plugs 11 and 1 2 are provided along a line Y-Y perpendicular to the crankshaft line Z-Z at positions in the upper parts of the vertical wall 5b and inclined wall 5d, respectively.

The spark plugs are spaced apart at a distance of 0.3-0.7 times the bore of the cylinder.

During the suction stroke, the inlet valve disk 8a lifts to a position adjacent to the lower end of the vertical wall 5b, Figure 3a, so that air-fuel mixture inducted into the combustion chamber through the inlet duct 10 and valve port, is deflected in the horizontal direction by the horizontal valve disk 8a and a horizontal swirl of the mixture is created by the tangential arrangement of the inlet duct 10 as shown in Figure 4. The horizontal swirl of the mixture scavenges the internal periphery of the combustion chamber and areas around the spark plugs where burned gases are liable to remain, and further cools hot spots in the periphery.

During the compression stroke, inlet and exhaust valves 8 and 9 close flush with the upper horizontal wall 5a as shown in Figure 3b. As the piston 4 rises the mixture is compressed by the inclined wall 5d, so that the mixture in the squish zone 7 is ejected upwardly along the inclined walls 4c and 5d. The mixture flow is deflected in the horizontal direction by the upper flat wall and then deflected to the vertical by the vertical wall 5b.

Thus, vertical swirl is created in the mixture to urge the mixing of the mixture with the remainder.

The end of the compression stroke, the vertical is promoted by the squish effect from the squish zone 6 thereby increasing the velocity of the vertical swirl and enhancing the mixing effect.

Thus, conditions for complete combustion of the mixture is established.

Ignition of the mixture is rapidly made by a pair of spark plugs. Flame generated by the spark plug 11 is propagated downwards by the high speed vertical swirl and the flame by the spark plug 12 is propagated upwards. Thus, flame propagation is performed effectively, so that high speed flame propagation and uniform combustion can be achieved.

The described embodiment of the present invention produces horizontal swirl of the mixture during the suction stroke as well as vertical swirl which effects scavenging of the periphery of the combustion chamber and cooling of hot spots in the peripheral portion. Thus, high compression ratios and a large amount of EGR (exhaust gas recirculation) can be permitted in order to accomplish improvement of fuel consumption and reduction of NOx. Further, high speed flame propagation by violet swirl of the mixture enables the use of lean air-fuel mixtures, and thus the improvement of fuel consumption and emission control.

Claims

1. An internal combustion engine, having a cylinder, a cylinder head, a piston, an inlet valve assembly, and an exhaust valve assembly, wherein the cylinder head has an elongate recess which extends in the direction of the length of the crankshaft of the engine, said recess being defined by an upper horizontal wall, a vertical wall at one side of the upper horizontal wall and offset inwardly along part of its length from the cylinder wall by a lower horizontal wall, and an inclined wall at the opposite side of the upper horizontal wall; a projection formed on the top of the piston; the projection having an inclined wall which is closely adjacent to the inclined wall of the recess when the piston is at top dead centre, to form a squish zone; the lower horizontal wall and the top of the piston being so disposed as to form another squish zone when the piston is at top dead centre; the inlet valve assembly being positioned towards one end of the upper horizontal wall, with a valve disk of the inlet valve oriented in parallel with the upper horizontal wall; and an inlet duct communicates tangentially with the valve port and is positioned above the vertical wall.

2. An internal combustion engine as claimed in claim 1 wherein a pair of spark plugs are disposed in upper parts of vertical wall and inclined wall, respectively.

3. An internal combustion engine as claimed in claim 1 or 2 wherein the projection has a triangular cross-section.

4. An internal combustion engine as claimed in claim 1, 2 or 3 wherein said inlet valve has a lift substantially equal to the height of said vertical plane.

5. An internal combustion engine as herein described, with reference to the accompanying drawings.