Cylinder head, cylinder head cover, cylinder head assembly and piston engine
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- WARTSILA FINLAND OY
- Filing Date
- 2023-07-04
- Publication Date
- 2026-05-13
AI Technical Summary
Conventional valve timing systems for piston engines using camshafts and hydraulic components are complex, increasing manufacturing costs and the risk of oil leakages due to intricate oil supply lines.
The cylinder head and cylinder head cover design integrates oil supply channels directly into the engine components, reducing external piping and leakages by using pressurized oil for controlling valve timing, with cooling channels connected to minimize external fluid communication.
This design simplifies the oil supply system, reduces leakage risks, and allows for efficient pressurized oil distribution to hydraulic means for variable valve timing, enhancing engine performance and reliability.
Smart Images
Figure FI2023050423_09012025_PF_FP_ABST
Abstract
Description
[0001] Cylinder head, cylinder head cover, cylinder head assembly and piston engine
[0002] Technical field of the invention
[0003] The present invention concerns a cylinder head for a piston engine, as defined in claim 1. The invention also concerns a cylinder head cover, as defined in another independent claim. The invention further concerns a cylinder head assembly and a piston engine.
[0004] Background of the invention
[0005] Each cylinder of a four-stroke piston engine is typically provided with two intake valves and two exhaust valves. A conventional way of operating the intake and exhaust valves of a piston engine is using one or more camshafts. The intake and exhaust valves are mechanically coupled to the cams of the camshafts. Mechanical, cam-operated actuating mechanisms are reliable. However, the opening and closing crank angles of the intake and exhaust valves are usually fixed. Variable valve timing has many benefits for example in terms of engine performance, emissions and fuel consumption. Therefore, valve actuating systems allowing variable valve timing are becoming more and more common. Variable valve timing can be implemented in many different ways. Typically, hydraulic and / or electrical components are utilized, but also purely mechanical systems exist.
[0006] A valve timing system utilizing both a camshaft and hydraulic components can combine the benefits of both mechanical and hydraulic systems. A drawback of such a system is that the oil supply lines needed for the operation of the valve timing system are often complex, increase the manufacturing cost of the engine and increase the number of locations where oil leakages can occur.
[0007] Summary of the invention
[0008] An object of the present invention is to provide an improved cylinder head for a piston engine. Another object of the invention is to provide an improved cylinder head cover. Further objects of the invention are to provide an improved cylinder head assembly and an improved piston engine. The cylinder head according to the invention has a bottom surface configured to delimit an upper end of a main combustion chamber of a cylinder of a piston engine, and a top surface facing an opposite direction than the bottom surface, the top surface being configured to receive a cylinder head cover that is attachable to the cylinder head. The cylinder head comprises
[0009] - an inlet port extending from a side surface of the cylinder head to the bottom surface of the cylinder head and having an inlet opening on said side surface,
[0010] - a fuel injector hole configured to receive a fuel injector,
[0011] - an oil supply channel having an inlet end and an outlet end, the outlet end opening onto the top surface of the cylinder head,
[0012] - a first injector cooling channel for supplying cooling oil to the fuel injector hole, the first injector cooling channel being arranged in fluid communication with the oil supply channel and having an outlet end opening into the fuel injector hole, and
[0013] - a second injector cooling channel for discharging cooling oil from the fuel injector hole, the second injector cooling channel having an inlet end opening into the fuel injector hole and an outlet end opening onto the top surface of the cylinder head, wherein the outlet end of the oil supply channel and the outlet end of the second cooling channel are located in an area that is configured to be covered by the cylinder head cover.
[0014] The cylinder head according to the invention allows conducting pressurized oil through the cylinder head to a cylinder head cover. The pressurized oil can be used for controlling the exhaust or intake valve timing. By connecting the injector cooling channel to the oil supply channel, the number of external oil channels can be reduced, thus reducing the risk of oil leakages.
[0015] According to an embodiment of the invention, the inlet end of the oil supply channel opens onto an outer surface of the cylinder head below the level of the inlet opening of the inlet port of the cylinder head. This allows arranging an oil supply rail below the inlet ports of the engine to supply oil to the cylinder heads.
[0016] According to an embodiment of the invention, the cylinder head comprises a lateral extension and the inlet opening of the inlet port and the inlet end of the oil supply channel are located in said extension. According to an embodiment of the invention, the inlet end of the oil supply channel opens onto a bottom surface of said extension of the cylinder head. The extension and the oil supply channel opening onto the bottom surface of the extension facilitate connection of the oil supply channel to an oil supply rail.
[0017] According to an embodiment of the invention, the outlet end of the oil supply channel is located in an area that is configured to be covered by a wall of the cylinder head cover. That allows supplying oil from the oil supply channel directly into a channel integrated into a wall of the cylinder head cover without external piping.
[0018] According to an embodiment of the invention, the outlet end of the second injector cooling channel is located in an area that is configured to open into the interior of the cylinder head cover. The oil used for cooling the fuel injector can thus be collected into a cavity of the cylinder head cover without external piping.
[0019] According to an embodiment of the invention, the cylinder head comprises a second oil supply channel having an inlet end and an outlet end, the outlet end opening onto the top surface of the cylinder head and being located in an area that is configured to be covered by the cylinder head cover. The second oil supply channel allows conducting pressurized oil via the cylinder head to the cylinder head cover for an additional use.
[0020] According to an embodiment of the invention, the inlet end of the second oil supply channel opens onto an outer surface of the cylinder head below the level of the inlet opening of the inlet port of the cylinder head. The second oil supply channel can thus be arranged in a similar way as the oil supply channel, which allows using the same oil supply rail for supplying pressurized oil to both oil supply channels.
[0021] According to an embodiment of the invention, the cylinder head comprises a lateral extension and the inlet opening of the inlet port and the inlet end of the second oil supply channel are located in said extension.
[0022] According to an embodiment of the invention, the inlet end of the second oil supply channel opens onto a bottom surface of said extension of the cylinder head. According to an embodiment of the invention, the oil supply channel and the second oil supply channel are arranged on opposite sides of the inlet port of the cylinder head.
[0023] The cylinder head cover according to the invention is configured to be attached to a cylinder head defined above and the cylinder head cover has a bottom surface that is configured to face the top surface of the cylinder head and the cylinder head cover comprises an oil supply channel having an inlet end, which is configured to be aligned with the outlet end of the oil supply channel of the cylinder head in a mounted position of the cylinder head cover. The cylinder head cover can thus receive oil directly from the oil supply channel of the cylinder head.
[0024] According to an embodiment of the invention, the oil supply channel of the cylinder head cover is configured to conduct pressurized oil to hydraulic means for variable exhaust valve timing. The cylinder head cover thus allows arranging hydraulic means for variable exhaust valve timing above the cylinder head.
[0025] According to an embodiment of the invention, the oil supply channel is integrated into a wall of the cylinder head cover. This minimizes the risk of leakages.
[0026] According to an embodiment of the invention, the cylinder head cover is configured to be attached to a cylinder head comprising a second oil supply channel and the cylinder head cover comprises a second oil supply channel having an inlet end, which is configured to be aligned with the outlet end of the second oil supply channel of the cylinder head in a mounted position of the cylinder head cover. This allows using the cylinder head cover to conduct pressurized oil for an additional use.
[0027] According to an embodiment of the invention, the second oil supply channel of the cylinder head cover is configured to conduct pressurized oil to hydraulic means for variable intake valve timing. Also means for variable intake valve timing can thus be arranged above the cylinder head.
[0028] According to an embodiment of the invention, the second oil supply channel is integrated into a wall of the cylinder head cover. This minimizes the risk of leakages. According to an embodiment of the invention, the cylinder head cover comprises a fuel injector hole configured to receive a fuel injector, and the oil supply channel and the second oil supply channel of the cylinder head cover are arranged on opposite sides of the fuel injector hole.
[0029] The cylinder head assembly according to the invention for a piston engine comprises a cylinder head defined above and a cylinder head cover defined above attached to the cylinder head.
[0030] The piston engine according to the invention comprises a cylinder head defined above.
[0031] According to an embodiment of the invention, the engine comprises hydraulic means for variable exhaust valve timing arranged in the cylinder head cover.
[0032] According to an embodiment of the invention, the engine comprises an oil supply rail extending in the longitudinal direction of the engine and arranged in fluid communication with the oil supply channel of the cylinder head for supplying pressurized oil into said oil supply channel.
[0033] Brief description of the drawings
[0034] Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which
[0035] Fig. 1 shows a cross-sectional view of parts of a piston engine,
[0036] Fig. 2 shows a cross-sectional view of a cylinder head and a cylinder head cover,
[0037] Fig. 3 shows another cross-sectional view of parts of the piston engine of figure 1 , and
[0038] Fig. 4 shows a perspective view of a cylinder head according to an embodiment of the invention.
[0039] Detailed description of embodiments of the invention
[0040] Figures 1 to 4 show different partial views of a piston engine, cylinder head 1 and cylinder head cover 4 according to embodiments of the invention. The engine 1 is a large piston engine. The expression “large piston engine” refers here to an engine having a cylinder diameter of at least 150 mm. The engine can be, for instance, an engine that is used as a main or an auxiliary engine in a ship or an engine that is used at a power plant for driving a generator for producing electricity. The engine is a multi-cylinder four-stroke engine. The engine can comprise any reasonable number of cylinders. The number of cylinders in the engine can be, for instance, 4 to 20. The cylinders can be arranged in-line or in a V-configuration.
[0041] The engine can be configured to be operable using gaseous fuel. The expression “gaseous fuel” refers here to a fuel that is gaseous in atmospheric pressure and at a temperature of 20 °C. The gaseous fuel can be, for instance, natural gas or biogas. The term “biogas” refers here to a gas that mainly consists of methane and which is obtained from renewable sources. The biogas can be produced for example from organic waste. Natural gas could be stored either as a liquefied gas (LNG) or compressed gas (CNG). Biogas could be stored in a similar manner. Instead of methane-based fuels, the gaseous fuel could be, for instance, hydrogen or ammonia or a mixture of two or more types of gaseous fuel. The gaseous fuel can be introduced into the cylinders of the engine via inlet ports. When the engine is operated using a gaseous fuel, it can utilize a liquid fuel, such as light fuel oil as a pilot fuel facilitating ignition of the gaseous fuel.
[0042] The engine can be further configured to be operable using liquid fuel, such as light fuel oil or heavy fuel oil. The liquid fuel can be injected directly into the cylinders of the engine.
[0043] The engine can be a gas engine, a dual-fuel engine or a multi-fuel engine. However, the engine could also be operable solely using one or more liquid fuels.
[0044] Each cylinder 3 of the engine is provided with an own cylinder head 1. The cylinder head 1 has a bottom surface 1 A that is configured to delimit an upper end of a main combustion chamber 2 of the cylinder 3. The cylinder head 1 has a top surface 1 B facing an opposite direction than the bottom surface 1 A. The term “bottom surface” refers to that side of the cylinder head 1 that is facing the main combustion chamber 2, but the bottom surface 1 A does not need to be a horizontal surface facing downwards. For example in a V-engine, where the axial direction of the cylinder is not vertical, the bottom and top surfaces 1 A, 1 B of the cylinder head 1 can be inclined relative to the horizontal direction.
[0045] The cylinder head 1 comprises an inlet port 9 extending from a side surface of the cylinder head 1 to the bottom surface 1A of the cylinder head 1 . The inlet port 9 has an inlet opening 9a on the side surface. Via the inlet port 9, intake air is introduced into the main combustion chamber 2 of the cylinder 3. Each cylinder 3 of the engine is provided with at least one intake valve, preferably two intake valves, for controlling the supply of intake air into the main combustion chamber 2.
[0046] The cylinder head 1 further comprises an exhaust port for discharging exhaust gas from the main combustion chamber 2. Each cylinder 3 of the engine is provided with at least one exhaust valve, preferably two exhaust valves, for controlling discharging of exhaust gas from the main combustion chamber 2.
[0047] The cylinder head 1 comprises a fuel injector hole 7. The fuel injector hole extends from the top surface 1 B of the cylinder head 1 to the bottom surface 1A of the cylinder head 1. The fuel injector hole 7 is configured to receive a fuel injector 8. The fuel injector 8 is configured to inject fuel directly into the main combustion chamber 2. The fuel injector s can be used for injecting liquid main fuel when the engine is operated in a liquid fuel mode and / or liquid pilot fuel when the engine is operated in a gas mode. The fuel injector 8 can comprise separate fuel injection nozzles and fuel injector needles for different operating modes of the engine.
[0048] The top surface 1 B of the cylinder head 1 is configured to receive a cylinder head cover 4 that is attachable to the cylinder head 1 . The cylinder head cover 4 is configured to cover at least part of the top surface 1 B of the cylinder head 1 . The cylinder head cover 4 is attached to the cylinder head 1 by means of bolts 24. The cylinder head cover 4 comprises a fuel injector hole 23 that is configured to accommodate part of the fuel injector 8. The cylinder head cover 4 is configured to accommodate further parts of the engine, such as parts of valve actuating mechanisms of the intake valves and exhaust valves.
[0049] The cylinder head 1 comprises a first oil supply channel 11 having an inlet end 11 A and an outlet end 11 B. The outlet end 11 B of the first oil supply channel 11 opens onto the top surface 1 B of the cylinder head 1 . The cylinder head 1 further comprises a first injector cooling channel 13 for supplying cooling oil to the fuel injector hole 7. The first injector cooling channel 13 is arranged in fluid communication with the first oil supply channel 11 and has an outlet end 13B opening into the fuel injector hole 7.
[0050] The cylinder head 1 further comprises a second injector cooling channel 14 for discharging cooling oil from the fuel injector hole 7. The second injector cooling channel 14 has an inlet end 15A opening into the fuel injector hole 7 and an outlet end 16B opening onto the top surface 1 B of the cylinder head 1. The outlet end 11 B of the oil supply channel 11 and the outlet end 16B of the second injector cooling channel 14 are located in an area that is covered by the cylinder head cover 4.
[0051] In the embodiment of the figures, the cylinder head 1 comprises a second oil supply channel 12. The second oil supply channel 12 has an inlet end 12A and an outlet end 12B. The outlet end 12B of the second oil supply channel 12 opens onto the top surface 1 B of the cylinder head 1 and is located in an area that is covered by the cylinder head cover 4. The first oil supply channel 11 and the second oil supply channel 12 are arranged on opposite sides of the inlet port 9 of the cylinder head 1 .
[0052] In the embodiment of the figures, the cylinder head 1 comprises a lateral extension 18. The lateral extension 18 extends radially outwards from an area covering a cylinder liner forming the cylinder 3. The lateral extensions protrudes to a direction that is perpendicular to the longitudinal direction of the engine.
[0053] The inlet opening 9A of the inlet port 9 is located in the lateral extension 18. Consequently, the inlet port 9 is partly located in the lateral extension 18. Also the inlet end 11 A of the first oil supply channel 11 and the inlet end 12A of the second oil supply channel 12 are located in the extension 18. The inlet end 11A of the first oil supply channel 11 and the inlet end 12A of the second oil supply channel 12 open onto an outer surface of the cylinder head 1 below the level of the inlet opening 9A of the inlet port 9 of the cylinder head 1 . The inlet end 11 A of the first oil supply channel 11 and the inlet end 12A of the second oil supply channel 12 open onto a bottom surface 18A of the lateral extension In the embodiment of the figures, the outlet end 11 B of the first oil supply channel 11 is located in an area that is covered by a wall of the cylinder head cover 4. Also the outlet end 12B of the second oil supply channel 12 is located in an area that is covered by a wall of the cylinder head cover 4.
[0054] In the embodiment of the figures, the outlet end 16B of the second injector cooling channel 14 is located in an area that opens into the interior of the cylinder head cover 4.
[0055] The cylinder head cover 4 has a bottom surface 4A that is configured to face the top surface 1 B of the cylinder head 1. The cylinder head cover 4 comprises a first oil supply channel 21 . The first oil supply channel 21 has an inlet end 21 A, which is configured to be aligned with the outlet end 11 B of the first oil supply channel 11 of the cylinder head 1 . The first oil supply channel 21 of the cylinder head cover 4 is integrated into a wall of the cylinder head cover 4.
[0056] The cylinder head cover 4 further comprises a second oil supply channel 22. The second oil supply channel has an inlet end 22A, which is configured to be aligned with the outlet end 12B of the second oil supply channel 12 of the cylinder head 1 . Also the second oil supply channel 22 of the cylinder head cover 4 is integrated into a wall of the cylinder head cover 4. The first oil supply channel 21 and the second oil supply channel 22 of the cylinder head cover 4 are arranged on opposite sides of the fuel injector hole 23.
[0057] In the embodiment of the figures, the engine comprises hydraulic means for variable exhaust valve timing. The engine also comprises hydraulic means for variable intake valve timing. The means for variable exhaust valve timing and intake valve timing are arranged in the cylinder head cover 4. The intake valves and exhaust valves are partly cam-controlled. The engine comprises a camshaft 27 that is configured to operate the intake and exhaust valves. The engine can comprise push rods extending from the camshaft 27 to valve actuating mechanisms arranged in the cylinder head cover 4. The means for variable exhaust valve timing and intake valve timing are configured to allow adjusting of the valve timing determined by the camshaft 27. For instance, the hydraulic means for variable exhaust and intake valve timing can allow delaying of the closing of the intake or exhaust valves. The means for variable exhaust and intake valve timing can comprise pistons on which pressurized oil can exert a force to delay the closing of the valves. The first oil supply channel 11 of the cylinder head 1 and the first oil supply channel 21 of the cylinder head cover 4 are configured to conduct pressurized oil to the means for variable exhaust valve timing. The second oil supply channel 12 of the cylinder head 1 and the second oil supply channel 22 of the cylinder head cover 4 are configured to conduct pressurized oil to the means for variable intake valve timing.
[0058] The engine comprises an oil supply rail 17 extending in the longitudinal direction of the engine and arranged in fluid communication with the first oil supply channel 11 and the second oil supply channel 12 of the cylinder head 1 for supplying pressurized oil into the first oil supply channel 11 and the second oil supply channel 12.
[0059] A first connecting pipe 25 connects the oil supply rail 17 to the first oil supply channel 11 of the cylinder head 1 . A second connecting pipe 26 connects the oil supply rail 17 to the second oil supply channel 12 of the cylinder head 1.
[0060] The pressurized oil supplied into the first oil supply channel 11 of the cylinder head 1 flows to the first oil supply channel 21 of the cylinder head cover 4. Part of the oil flows into the first injector cooling channel 13, which is branched from the first oil supply channel 11 of the cylinder head 1 . Via the first injector cooling channel 13, the oil can flow into the fuel injector hole 7, where it cools down the fuel injector 8. From the fuel injector hole 7, the oil flows via the second injector cooling channel 14 to the cylinder head cover 4. In the embodiment of the figures, the second injector cooling channel 14 comprises a first portion 15 and a second portion 16. The second portion 16 is branched from the first portion 15.
[0061] The pressurized oil supplied into the second oil supply channel 12 of the cylinder head 1 flows to the second oil supply channel 22 of the cylinder head cover 4.
[0062] Via the first oil supply channel 21 of the cylinder head cover 4, the pressurized oil flows to the means for variable exhaust valve timing. Via the second oil supply channel 22 of the cylinder head cover 4, the pressurized oil flows to the means for variable intake valve timing. The oil is returned from the cylinder head cover 4 to the camshaft 27 and further into an oil sump. Also the oil used for cooling the fuel injector 8 returns via the camshaft 27 into the oil sump.
Claims
Claims:
1. A cylinder head (1 ) for a piston engine, the cylinder head (1 ) having a bottom surface (1 A) configured to delimit an upper end of a main combustion chamber (2) of a cylinder (3) of a piston engine, and a top surface (1 B) facing an opposite direction than the bottom surface (1 A), the top surface (1 B) being configured to receive a cylinder head cover (4) that is attachable to the cylinder head (1 ), the cylinder head (1 ) comprising- an inlet port (9) extending from a side surface of the cylinder head (1 ) to the bottom surface (1A) of the cylinder head (1 ) and having an inlet opening (9a) on said side surface,- a fuel injector hole (7) configured to receive a fuel injector (8),- an oil supply channel (11 ) having an inlet end (11 A) and an outlet end (11 B), the outlet end (11 B) opening onto the top surface (1 B) of the cylinder head (1 ),- a first injector cooling channel (13) for supplying cooling oil to the fuel injector hole (7), the first injector cooling channel (13) being arranged in fluid communication with the oil supply channel (11 ) and having an outlet end (13B) opening into the fuel injector hole (7), and- a second injector cooling channel (14) for discharging cooling oil from the fuel injector hole (7), the second injector cooling channel (14) having an inlet end (15A) opening into the fuel injector hole (7) and an outlet end (16B) opening onto the top surface (1 B) of the cylinder head (1 ), wherein the outlet end (11 B) of the oil supply channel (11 ) and the outlet end (16B) of the second injector cooling channel (14) are located in an area that is configured to be covered by the cylinder head cover (4).
2. A cylinder head (1 ) according to claim 1 , wherein the inlet end (11 A) of the oil supply channel (11 ) opens onto an outer surface of the cylinder head (1 ) below the level of the inlet opening (9A) of the inlet port (9) of the cylinder head (1 ).
3. A cylinder head (1 ) according to claim 2, wherein the cylinder head (1 ) comprises a lateral extension (18) and the inlet opening (9a) of the inlet port (9) and the inlet end (11 A) of the oil supply channel (11 ) are located in said extension (18).
4. A cylinder head (1 ) according to claim 3, wherein the inlet end (11 A) of the oil supply channel (11 ) opens onto a bottom surface (18A) of said extension (18) of the cylinder head (1 ).
5. A cylinder head (1 ) according to any of the preceding claims, wherein the outlet end (11 B) of the oil supply channel (11 ) is located in an area that is configured to be covered by a wall of the cylinder head cover (4).
6. A cylinder head (1 ) according to any of the preceding claims, wherein the outlet end (16B) of the second injector cooling channel (14) is located in an area that is configured to open into the interior of the cylinder head cover (4).
7. A cylinder head (1 ) according to any of the preceding claims, wherein the cylinder head (1 ) comprises a second oil supply channel (12) having an inlet end (12A) and an outlet end (12B), the outlet end (12B) opening onto the top surface (1 B) of the cylinder head (1 ) and being located in an area that is configured to be covered by the cylinder head cover (4).
8. A cylinder head (1 ) according to claim 7, wherein the inlet end (12A) of the second oil supply channel (12) opens onto an outer surface of the cylinder head (1 ) below the level of the inlet opening (9A) of the inlet port (9) of the cylinder head (1 ).
9. A cylinder head (1 ) according to claim 8, wherein the cylinder head (1 ) comprises a lateral extension (18) and the inlet opening (9a) of the inlet port (9) and the inlet end (12A) of the second oil supply channel (12) are located in said extension (18).
10. A cylinder head (1 ) according to claim 9, wherein the inlet end (12A) of the second oil supply channel (12) opens onto a bottom surface (18A) of said extension (18) of the cylinder head (1 ).
11. A cylinder head (1 ) according to any of claims 7-10, wherein the oil supply channel (11 ) and the second oil supply channel (12) are arranged on opposite sides of the inlet port (9) of the cylinder head (1 ).
12. A cylinder head cover (4) that is configured to be attached to a cylinder head (1 ) according to any of the preceding claims, wherein the cylinder headcover (4) has a bottom surface (4A) that is configured to face the top surface (1 B) of the cylinder head (1 ) and the cylinder head cover (4) comprises an oil supply channel (21 ) having an inlet end (21 A), which is configured to be aligned with the outlet end (11 B) of the oil supply channel (11 ) of the cylinder head (1 ) in a mounted position of the cylinder head cover (4).
13. A cylinder head cover (4) according to claim 12, wherein the oil supply channel (21 ) of the cylinder head cover (4) is configured to conduct pressurized oil to hydraulic means for variable exhaust valve timing.
14. A cylinder head cover (4) according to claim 12 or 13, wherein the oil supply channel (21 ) is integrated into a wall of the cylinder head cover (4).
15. A cylinder head cover (4) according to any of claims 12-14, wherein the cylinder head cover (4) is configured to be attached to a cylinder head (1 ) according to any of claims 7-11 and the cylinder head cover (4) comprises a second oil supply channel (22) having an inlet end (22A), which is configured to be aligned with the outlet end (12B) of the second oil supply channel (12) of the cylinder head (1 ) in a mounted position of the cylinder head cover (4).
16. A cylinder head cover (4) according to claim 15, wherein the second oil supply channel (22) of the cylinder head cover (4) is configured to conduct pressurized oil to hydraulic means for variable intake valve timing.
17. A cylinder head cover (4) according to claim 15 or 16, wherein the second oil supply channel (22) is integrated into a wall of the cylinder head cover (4).
18. A cylinder head cover (4) according to claim any of claims 15-17, wherein the cylinder head cover (4) comprises a fuel injector hole (23) configured to receive a fuel injector (8), and the oil supply channel (21 ) and the second oil supply channel (22) of the cylinder head cover (4) are arranged on opposite sides of the fuel injector hole (23).
19. A cylinder head assembly for a piston engine, the cylinder head assembly comprising a cylinder head (1 ) according to any of claims 1-11 and a cylinder head cover (4) according to any of claims 12-18 attached to the cylinder head (1 ).
20. A piston engine comprising a cylinder head assembly according to claim 19.
21. A piston engine according to claim 20, wherein the engine comprises hydraulic means for variable exhaust valve timing arranged in the cylinder head cover (4).
22. A piston engine according to claim 20 or 21 , wherein the engine comprises an oil supply rail (17) extending in the longitudinal direction of the engine and arranged in fluid communication with the oil supply channel (11 ) of the cylinder head (1 ) for supplying pressurized oil into said oil supply channel (11 ).