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EP-4314525-B1 - A CYLINDER HEAD FOR A LEAN-BURN GASOLINE ENGINE

EP4314525B1EP 4314525 B1EP4314525 B1EP 4314525B1EP-4314525-B1

Inventors

  • JOHNSON, JACK
  • MCWILLIAM, LYN

Dates

Publication Date
20260506
Application Date
20210326

Claims (14)

  1. A cylinder head (53) for a lean-burn gasoline engine, the cylinder head (53)) comprising: a substantially planar gasket interface surface (58); and a combustion chamber (50) extending into the cylinder head (53) away from the gasket interface surface, wherein the combustion chamber comprises: a combustion chamber roof surface (90) which intersects the gasket interface surface (58) at a combustion chamber opening; a pair of air inlet openings (91) located in the combustion chamber roof surface on an air inlet side of the combustion chamber; and a pair of exhaust outlet openings (92) located in the combustion chamber roof surface on an exhaust outlet side of the combustion chamber wherein the combustion chamber roof surface (90) comprises a plurality of machined facets, wherein: a first pair of the machined facets (188a, 188b) comprise curved surfaces located adjacent to the air inlet openings on a side of the air inlet openings closest to the exhaust outlet side of the combustion chamber, wherein a first one of the first pair of machined facets (188a) is located adjacent a first one of the air inlet openings, and a second one of the first pair of machined facets (188b) is located adjacent a second one of the air inlet openings; and a second pair of the machined facets (190a, 190b) comprise curved surfaces located adjacent the exhaust outlet openings on a side of the exhaust outlet openings closest to the air inlet side of the combustion chamber, wherein a first one of the second pair of machined facets (190a) is located adjacent a first one of the exhaust outlet openings, and a second one of the second pair of machined facets (190b) is located adjacent a second one of the exhaust outlet openings, wherein the first and second pair of machined facets are configured so that they are machinable by the same cutter; and characterized in that the combustion chamber roof surface comprises a third pair of machined facets (186a, 186b), wherein a first one of the third pair of machined facets (186a) is located between the first one of the air inlet openings and the first one of the exhaust outlet openings, and a second one of the third pair of machined facets (186b) is located between the second one of the air inlet openings and the second one of the exhaust outlet openings, wherein the third pair of machined facets comprise substantially flat surfaces.
  2. A cylinder head as claimed in claim 1, wherein the first one of the third pair of machined facets is substantially parallel to the plane of the first one of the exhaust outlet openings, and the second one of the third pair of machined facets is substantially parallel to the plane of the second one of the exhaust outlet openings.
  3. A cylinder head as claimed in claim 1 or 2, wherein the third pair of machined facets are configured so that they are machinable by the same cutter used to cut the first and second pair of machined facets.
  4. A cylinder head as claimed in any preceding claim, wherein the combustion chamber roof surface comprises: a fourth pair of machined facets comprising opposing curved surfaces located on opposite sides of the combustion chamber between the air inlet openings and the exhaust outlet openings such that the fourth pair of machined facets extend between the air inlet side of the combustion chamber and the exhaust outlet side of the combustion chamber; and a fifth pair of machined facets comprising opposing curved surfaces located on opposite sides of the combustion chamber, a first one of the fifth pair of machined facets being located on the air inlet side of the combustion chamber, and a second one of the fifth pair of machined facets being located on the exhaust outlet side of the combustion chamber, wherein the fourth pair of machined facets intersect the gasket interface surface to define a first pair of opposed curved sections of the combustion chamber opening, and the fifth pair of machined facets intersect the gasket interface surface to define a second pair of opposed curved sections of the combustion chamber opening.
  5. A cylinder head as claimed in claim 4, wherein the fourth pair of machined facets are configured so that they are machinable by the same cutter.
  6. A cylinder head as claimed in claim 5, wherein the fourth pair of machined facets are configured so that they are machinable by the same cutter used to cut the first and second pairs of machined facets, and the same cutter used to cut the third pair of machined facets where present.
  7. A cylinder head as claimed in any one of claims 4 to 6, wherein the fifth pair of machined facets are configured so that they are machinable by the same cutter.
  8. A cylinder head as claimed in any preceding claim, wherein the combustion chamber roof surface comprises a sixth pair of machined facets, wherein a first one of the sixth pair of machined facets is located between the air inlet openings, and a second one of the sixth pair of machined facets is partially located between the exhaust outlet openings, wherein the sixth pair of machined facets comprise curved surfaces.
  9. A cylinder head as claimed in claim 8, wherein the sixth pair of machined facets are configured so that they are machinable by the same cutter.
  10. A cylinder head as claimed in any one of claims 4 to 9, wherein the combustion chamber roof surface comprises a central elongate domed portion orientated across the combustion chamber in a direction substantially parallel to an intersect plane separating the air inlet side of the combustion chamber from the exhaust outlet side of the combustion chamber, wherein the central domed portion of the combustion chamber roof surface comprises the first, second and fourth pairs of machined facets, and the third pair of machined facets where present, and the sixth pair of machined facets where present.
  11. A cylinder head as claimed in any one of claims 4 to 10, wherein the combustion chamber roof surface comprises a first squish portion located on the inlet side of the combustion chamber and a second squish portion located on the exhaust outlet side of the combustion chamber, wherein the first squish portion comprises the first one of the fifth pair of machined facets and the second squish portion comprises the second one of the fifth pair of machined facets.
  12. A cylinder head as claimed in any preceding claim, wherein the cylinder head comprises a spark plug seat comprising an opening located in the combustion chamber roof surface, and a fuel injector seat comprising an opening located in the combustion chamber roof surface, wherein the spark plug seat opening and the fuel injector seat opening are positioned substantially in line with one another along a plane of symmetry of the combustion chamber perpendicular to the intersect plane separating the air inlet side of the combustion chamber from the exhaust outlet side of the combustion chamber.
  13. A lean-burn gasoline engine comprising a cylinder head as claimed in any one of claims 1 to 12.
  14. A vehicle comprising a lean-burn gasoline engine according to claim 13.

Description

TECHNICAL FIELD The present disclosure relates to a cylinder head for a lean-burn gasoline engine, to a lean-burn gasoline engine and to a vehicle with such an engine. BACKGROUND In classic internal combustion engines, gasoline burns best when it is mixed with air in proportions of around 14.7:1 (lambda = 1) depending on the particular type of fuel. Most modern gasoline engines used in vehicles tend to operate at or near this so-called stoichiometric point for most of the time. Ideally, when burning fuel in an engine, only carbon dioxide (CO2) and water (H2O) are produced. In practice, the exhaust gas of an internal combustion engine also comprises significant amounts of carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons. It is desirable to increase fuel efficiency and reduce unwanted emissions. One possible route for increasing fuel efficiency is to burn the fuel with an excess of air. Burning fuel in such an oxygen-rich environment is usually called lean-burning. Typical lean-burn engines may mix air and fuel in proportions of, for example, 20:1 (lambda > 1.3) or even 30:1 (lambda > 2). Advantages of lean-burn engines include, for example, that they produce lower levels of CO2 and hydrocarbon emissions by better combustion control and more complete fuel burning inside the engine cylinders. The engines designed for lean burning can employ higher compression ratios and thus provide better performance, more efficient fuel use and lower exhaust hydrocarbon emissions than conventional gasoline engines. Additionally, lean-burn modes help to reduce throttling losses, which originate from the extra work that is required for pumping air through a partially closed throttle. When using more air to burn the fuel, the throttle can be kept more open when the demand for engine power is reduced. Lean burning of fuel does, however, also come with some technical challenges that have to be overcome for providing an engine that is suitable and optimised for efficiently burning hydrocarbons in an oxygen-rich environment. For example, if the mixture is too lean, the engine may fail to combust. Especially at low loads and engine speeds, reduced flammability may affect the stability of the combustion process and introduce problems with engine knock. Further, a lower fuel concentration leads to less output. Because of such disadvantages, lean burn is currently only used for part of the engine map and most lean-burning modern engines, for example, tend to cruise and coast at or near the stoichiometric point. In order to enable the lean burning of fuel over a larger portion of the engine map, the engine needs to be designed in such a way to enable a large airflow into the combustion chamber and to ensure a reliable combustion process that will effectively burn all fuel, despite the oxygen rich conditions. US 3 633 577 A discloses a cylinder head with two pairs of machined facets comprising curved surfaces and configured so that they are machinable by the same cutter. It is an aim of the present invention to provide an improved lean-burn gasoline engine. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a cylinder head for an engine, an engine, and a vehicle with such an engine. The engine may be suitable for use with fuels including gasoline, diesel, hydrogen, LPG or any other suitable combustible fuel. The engine may be a lean-burn engine. According to the present invention there is provided a cylinder head for an engine, the cylinder head comprising: a substantially planar gasket interface surface; anda combustion chamber extending into the cylinder head away from the gasket interface surface, wherein the combustion chamber comprises: a combustion chamber roof surface which intersects the gasket interface surface at a combustion chamber opening;a pair of air inlet openings located in the combustion chamber roof surface on an air inlet side of the combustion chamber; anda pair of exhaust outlet openings located in the combustion chamber roof surface on an exhaust outlet side of the combustion chamberwherein the combustion chamber roof surface comprises a plurality of machined facets, wherein: a first pair of the machined facets comprise curved surfaces located adjacent to the air inlet openings on a side of the air inlet openings closest to the exhaust outlet side of the combustion chamber, wherein a first one of the first pair of machined facets is located adjacent a first one of the air inlet openings, and a second one of the first pair of machined facets is located adjacent a second one of the air inlet openings; anda second pair of the machined facets comprise curved surfaces located adjacent the exhaust outlet openings on a side of the exhaust outlet openings closest to the air inlet side of the combustion chamber, wherein a first one of the second pair of machined facets is located adjacent a first one of the exhaust outlet openings, and a second one of the second pair of machined f