Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F1/00—Cylinders; Cylinder heads 
  • F02F1/24—Cylinder heads
  • F02F1/42—Shape or arrangement of intake or exhaust channels in cylinder heads
  • F02F1/4214—Shape or arrangement of intake or exhaust channels in cylinder heads specially adapted for four or more valves per cylinder
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
  • F02F1/00—Cylinders; Cylinder heads 
  • F02F1/24—Cylinder heads
  • F02F2001/244—Arrangement of valve stems in cylinder heads
  • F02F2001/245—Arrangement of valve stems in cylinder heads the valve stems being orientated at an angle with the cylinder axis

Definitions

• the present invention relates to four-valve combustion chambers for internal combustion engines, to cylinder heads and internal combustion engines incorporating the same, and to methods of forming the same.
• the invention relates to a four-valve combustion chamber for a four-stroke engine of the overhead valve type, which is a development of the combustion chamber design forming the subject of my US
• Patent No. 3,633,577 In this prior design, the combustion chamber is formed with two elongate cavities or sub-chambers disposed side-by-side, with their longer axes parallel, and with a ridge between the cavities.
• the cross section of each cavity is substantially arcuate in the direction of its shorter axis, and is arcuate at least at each end zone in the direction of its longer axis.
• An opening is provided in each end zone which constitutes, or is fitted with, a valve seat which is cooperable with the head of an associated reciprocatory poppet valve. It is beneficial to employ exhaust valves which have a smaller head diameter than that of the associated inlet valves, for reasons that are well known, as discussed, for example in my European Patent No. 0428691 .
• a four-valve combustion chamber generally of the aforementioned type, wherein the longer axes of the side-by-side cavities or sub chambers, instead of being mutually parallel, mutually converge in a direction from the inlet valve-ends of the sub chambers towards the exhaust valve - ends thereof.
• the included angle between the mutually converging longer axes and the axis of the ridge between the sub chambers is of the order of 5° to 1 2°, for example about 8° to 10° or about 6° to 9°; i.e. the included angle between the longer axes is of the order of 10° to 24°, for example about 16° to 20° or about 1 2° to 18°.
• the longer axes preferably converge symmetrically about the axis of the ridge between the sub chambers although this is not essential.
• the median planes of the sub chambers which are coincident with converging longer axes, may also be coincident with the centres of the inlet and exhaust valve heads, or their valve seats, when the combustion chamber is viewed in plan.
• this is not essential, and it may be preferable, as described later, for the spacing between the median planes/longer axes, in the region of the inlet valve heads/seats, to be greater than (or less than) the spacing between the centres of the inlet valve heads/seats, or for the median planes/longer axes to be disposed asymmetrically with respect to the centres of the inlet and/or exhaust valve heads/seats.
• the combustion chamber will still retain the two main features of the aforesaid prior type of combustion chamber, namely the ridge separating the two sub chambers, and the squish areas or lands located at opposite ends of combustion chamber between the elongate sub chambers.
• the resultant combustion chamber is much more compact than my prior design.
• the distance between the sparking plug and the farthest portions of the combustion chamber is reduced. This makes it easier to design a combustion chamber of much reduced volume, helped by the fact that the presence of the ridge reduces the volume for the same combustion chamber height.
• the effect thereof is to decrease the ignition advance necessary for efficient combustion.
• a low ignition advance requirement was observed in the engines incorporating my above-mentioned combustion chamber design, for instance in the million and a half motorcycle engines built in the last 20 years in accordance with my aforementioned US patent.
• the improvement was approximately 5° of crankshaft rotation.
• Fig. 1 is a fragmentary section of a cylinder head of an internal combustion engine according to one embodiment of the present invention, taken in a plane including the line l-l shown in Fig. 2;
• Fig. 2 is a section of the same cylinder head, taken on the line 11-11 shown in Fig. 1 , i.e. in the median plane of one of the cavities or sub chambers of one combustion chamber;
• Fig. 3 is an underneath plan view of one combustion chamber of the same cylinder head
• Fig. 4 is a fragmentary perspective view of the same cylinder head, in an inverted position, showing the combustion chamber embodying the invention
• Fig. 5 is a fragmentary side elevation of a cutting tool for machining one of the cavities or sub chambers of the combustion chamber embodying the invention.
• Fig. 6 is a view, similar to Fig. 3, of a prior combustion chamber design of the type disclosed in my US Patent No. 3,633,577.
• the cylinder 1 of an internal combustion engine is surmounted by a cylinder head 2 into which are fitted valves 3', 3" and 4', 4" respectively, controlling the induction ports 5' , 5" and exhaust ports
• each combustion chamber 8 is formed by two side-by-side, elongated, part-spherical cavities or sub-chambers 8', 8" of radius R.
• the cavities are divided by a ridge 1 1 .
• the present invention takes advantage of the fact that the exhaust valve heads, and therefore the exhaust valve seats, are of smaller diameter than the inlet valve heads and their associated seats, enabling the locations of the exhaust valves and their seats to be moved closer together whilst still maintaining an adequate gap therebetween.
• the longer axes X-X', X-X" of the side-by-side sub chambers 8', 8" may be arranged to correspondingly mutually converge in a direction from the inlet valve seat-ends of the sub chambers towards the exhaust valve seat-ends thereof, as clearly shown in Fig. 3.
• the longer axes X-X', X'-X" may coincide, or approximately coincide, with the centres of the inlet and exhaust valve seats.
• These axes are symmetrical about the median plane of the combustion chamber, i.e. about the central longer axis X-X coincident with the ridge 1 1 , each making an included angle ⁇ with the central axis X-X (shown as approximately 8° in Fig. 3 as one specific but non-limiting example).
• the shape of the combustion chamber may be obtained directly during the cylinder head casting operation. It could alternatively be entirely obtained, or the cast combustion chamber could be finished, by milling or otherwise machining when accuracy is needed, more simply than for a classical pent-roof four-valve combustion chamber. In one embodiment, in which milling is involved, the finishing of each sub chamber may be carried out separately by means of left and right-handed rotary cutting tools 9 of the type shown in
• the cutter 9 is located with its rotational axis at right angles to the longer axis of one of the sub chambers (e.g. 8') as viewed in Fig. 3, centrally of the longitudinal extremities of that sub chamber, with the lateral zone 9' remote from the ridge 1 1 .
• the cutter is simply traversed towards and away from the face of the cylinder head to mill the sub chamber to the required depth in a single operation.
• a similar procedure is carried out on the other sub chamber (e.g. 8") with an opposite-handed cutter, or with the illustrated cutter reversed, i.e. with the zone 9' of the cutter on the other side, located with its rotational axis at right angles to the longer axis of that sub chamber.
• each sub chamber includes a part-spherical side surface 12 which blends the part-spherical region of the sub chamber with the face of the cylinder head, so that the edge 13 of the side surface approximately coincides with the upper end of the cylinder bore 1 .
• These side surfaces are formed by the lateral zone 9' of the cutter. These side surfaces 12 appear as curved zones or segments when the cylinder head is viewed in plan, as shown in Fig. 3.
• 2 ⁇ the included angle between the median planes common to the centres or axes of the pairs of inlet and exhaust valve heads/seats.
• the volume of the combustion chamber i.e. the combined volume of the sub chambers 8', 8"
• the volume of the combustion chamber will be significantly less than that of the combustion chamber disclosed in US Patent No. 3,633,577, thus giving rise to a higher compression ratio, and a more compact combustion chamber in which the distance between the sparking plug and the farthest extremities of the combustion chamber is reduced.
• combustion chamber shape may be incorporated in single or multi-cylinder spark ignition internal combustion engines.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Combustion Methods Of Internal-Combustion Engines (AREA)
• Cylinder Crankcases Of Internal Combustion Engines (AREA)

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• 1997
  • 1997-06-03 GB GBGB9711445.8A patent/GB9711445D0/en active Pending
• 1998
  • 1998-06-03 EP EP98925817A patent/EP0986705A1/de not_active Ceased
  • 1998-06-03 WO PCT/GB1998/001615 patent/WO1998055753A1/en not_active Application Discontinuation
  • 1998-06-03 JP JP50184899A patent/JP2002502476A/ja active Pending

Non-Patent Citations (1)

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