Operation of an internal combustion engine

Abstract

A four-stroke internal combustion engine (1) operating on fuel (21) supplied directly only to the pre-chamber (14) comprises a vortex tube (23) which, by means of compressed air (101) from a compressor (25), provides a cold air stream (102) which is directed to the pre-chamber wall (31) to provide a cooling of said pre-chamber (14) during the operation of said internal combustion engine (1).

Description

[0001] OPERATION OF AN INTERNAL COMBUSTION ENGINE

[0002] FIELD OF THE INVENTION

[0003] The invention relates to the cooling of a pre-chamber in a four-stroke internal combustion engine operating on a fuel supplied directly into the pre-chamber.

[0004] DESCRIPTION OF THE PRIOR ART

[0005] A pre-combustion chamber (a pre-chamber) is a spherical cavity separated from the engine cylinder and usually incorporated into the cylinder head of an internal combustion engine, whereby is associated with a corresponding cylinder via a combustion duct. Said pre-chamber is usually cooled by water. In the state of the art, the internal combustion engine is known, document No. US202201 12834 Al, which operates with the pre-chamber whose volume is less than 18% of the combined volume of the pre-chamber and the main combustion chamber when the corresponding piston is in the top dead position, whereby all the fuel for engine operation is supplied directly to the said prechamber only, and said combustion engine operates with a subcooling of the charge air in the inlet channel of the cylinder by means of the venturi effect to a temperature less than -5°C (23°F) at full load. This subcooled charge air, when mixed with gasoline, reduces a temperature of the gasoline-air mixture, and in this way prevents unwanted spontaneous ignition of said gasoline-air mixture during compression of the piston. The engine pistons, cylinders, cylinder head and intake valves are cooled by the subcooled charge air. An internal combustion engine of this type does not need a water cooling. But the problem of the internal combustion engine that works with a subcooling of the charge air in the cylinder inlet channel and with the fuel-air mixture formation only in a pre-chamber is that the subcooled charge air during the first stroke of the piston only cools the piston and cylinder itself, partially is cooled the cylinder head. The pre-chamber is cooled with the subcooled charge air only during the compression of the piston, when said piston pushes said subcooled charge air into the pre-chamber as well. From this reason, the prechamber is cooled by the subcooled charge air for a 50 % shorter time as the cylinder or as the piston. Therefore, cooling of the pre-chamber in which the entire formation of a fuel-air mixture takes place is less efficient as the cooling of the piston or the cylinder. Insufficient pre-chamber cooling in an internal combustion engine which operates with the fuel - air mixture formation only in said pre-chamber, reduces the efficiency of such internal combustion engine.

[0006] OBJECT OF THE INVENTION

[0007] The object of the invention is to provide an extra cooling of the pre-chamber in a four-stroke internal combustion engine which operates with the fuelair mixture formation only in the pre-chamber, in order to reduce a temperature of said pre-chamber during operation of said internal combustion engine.

[0008] DISCLOSURE OF THE INVENTION

[0009] In order to reach the object of the invention, a four-stroke internal combustion engine comprising at least one cylinder and one piston, a cylinder head defining with the piston a main combustion chamber in the at least one cylinder, an inlet channel and an outlet channel associated with the cylinder, a prechamber having a wall, an engine control unit, a cooling air discharge pipe, a cooling channel surrounding the pre-chamber wall associated with the cooling air discharge pipe, a compressor and a vortex tube for cooling of the prechamber, which comprises an air inlet, a cold air outlet, and a hot air outlet, the air inlet of the vortex tube is supplied with a compressed air from the compressor with a pressure up to 7 Bar, and the vortex tube is designed to separate the compressed air into a hot air stream flowing from the hot air outlet and a cold air stream flowing from the cold air outlet, whereby the cold air stream flowing from the cold air outlet of the vortex tube is directed at least on a portion of the pre-chamber wall, further flows through the cooling chan- nel surrounding the pre-chamber wall, and consequently after cooling of the pre-chamber flows from the cooling channel as a used cooling air into the cooling air discharge pipe. The internal combustion engine further includes a fuel injector having a nozzle located in the pre-chamber wall for supplying a fuel directly into the pre-chamber, whereby the cold air stream flowing from the cold outlet of the vortex tube is directly directed on a portion of the prechamber wall where the nozzle of the fuel injector is located. The internal combustion engine operates with a subcooled charge air in the inlet channel of the cylinder by means of a venturi effect to a temperature less than -5°C (23 °F) at full load, and a volume of the pre-chamber is less than 17 % of a combined volume of the pre-chamber and the main combustion chamber when the piston is in a top dead position. The cooling air discharge pipe includes an air temperature sensor which controls an exceedance of a predetermined maximum temperature of the used cooling air flowing via this discharge pipe after cooling of the pre-chamber, and the engine control unit, by controlling an operation of the compressor, causes a temperature of the cold air stream flowing from the cold air outlet of the vortex tube to cool the prechamber is decreasing by increasing the pressure of the compressed air supplied into the inlet of the vortex tube, when is exceeded the predetermined maximum temperature of the used cooling air flowing via the cooling air discharge pipe after cooling of the pre-chamber measured by the air temperature sensor located in the cooling air discharge pipe. All the fuel for operation of the internal combustion engine is injected into the pre-chamber through the fuel injector the nozzle of which is cooled by the cold air stream flowing from the cold air outlet of the vortex tube. A four-stroke internal combustion engine operating on fuel supplied directly only into the pre-chamber of the cylinder comprises a vortex tube which, by means of a compressed air from a compressor, provides a cold air stream which is directed to the pre-chamber wall to provide a cooling of said pre-chamber during the operation of said internal combustion engine. This cooling of the pre-chamber using the cooling air flowing from the vortex tube lowers the temperature of the pre-chamber during combustion engine operation, and in this way increases an efficiency of an internal combustion engine operating only on the fuel supplied directly to the pre-chamber.

[0010] BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 shows from the top view, a partial cross-section of the additional cooling of a pre-chamber in an internal combustion engine according to the invention.

[0012] Fig. 2 in more detail shows in a cross-section the additional cooling of a prechamber, according to the invention.

[0013] Fig. 3 shows in a partial cross-section a four-stroke internal combustion engine operating with the additional cooling of a pre-chamber according to the invention.

[0014] Fig. 4 shows a four-stroke internal combustion engine in a cross-sectional view comprising at least two cylinders and two pre-chambers, whereby said pre-chambers are cooled according to the invention.

[0015] DETAILED DESCRIPTION OF THE INVENTION

[0016] Fig.l shows from the top view, a partial cross-section of the additional cooling of a pre-chamber 14 in an internal combustion engine 1, specifically in more detail is shown a pre-chamber 14 having a wall 31 built in the cylinder head 4, a compressor 25, an electric motor 40 for driving the compressor 25, a vortex tube 23 for cooling of the pre-chamber 14, a compressed air supply pipe 38 for the vortex tube 23, an engine control unit 12, a compressed air water separator 24, and a cooling air discharge pipe 34, which is designed to divert a used cooling air 103 away from said cylinder head 4 after cooling of the pre-chamber 14. The cylinder head 4 is designed such that at least a part of the pre-chamber wall 31 is accessible for a direct contact with the cold air stream 102 flowing from the cold outlet 35 of the vortex tube 23, and a cooling channel 42 is designed between the pre-chamber wall 31 and the wall 41 of the cylinder head 4. The cooling channel 42 surrounding (at least partially) the pre-chamber wall 31 is associated with the cooling air discharge pipe 34. In operation, the internal combustion engine 1 using a vortex tube 23 for a cooling of the pre-chamber 14, which comprises an air inlet 26, a cold air outlet 35, and a hot air outlet 28, the air inlet 26 of the vortex tube 23 is supplied with a compressed air 101 from the compressor 25 with a pressure up to 7 Bar, and the vortex tube 23 is designed to separate the compressed air

[0017] 101 into a hot air stream 29 flowing from the hot air outlet 28 and a cold air stream 102 flowing from the cold air outlet 35, whereby the cold air stream

[0018] 102 flowing from the cold air outlet 35 of the vortex tube 23 is directed at least on a portion of the pre-chamber wall 31 (from an outside of the prechamber wall 31), further flows via the cooling channel 42 surrounding the pre-chamber wall 31, and consequently after cooling of the pre-chamber 14 flows from the cooling channel 42 as a used cooling air 103 into the cooling air discharge pipe 34. The cold outlet 35 of the vortex tube 23 is optimally located within 5 centimetres (within 2 inches) from the wall 31 of the prechamber 14. The cooling air discharge pipe 34 includes an air temperature sensor 10 which controls an exceeding of a predetermined maximum temperature of the used cooling air 103 flowing via this discharge pipe 34 after cooling of the pre-chamber 14, and the engine control unit 12, by controlling an operation of the compressor 25, causes a temperature of the cold air stream 102 flowing from the cold air outlet 35 of the vortex tube 23 to cool the prechamber 14 is decreasing by increasing the pressure of the compressed air 101 supplied to the inlet 26 of the vortex tube 23 when is exceeded the predetermined maximum temperature of the used cooling air 103 flowing via the cooling air discharge pipe 34 after cooling of the pre-chamber 14 measured by the air temperature sensor 10 located in the cooling air discharge pipe 34. The air temperature sensor 10 for a measuring the temperature of the used cooling air 103 after cooling of the pre-chamber 14, which is disposed in the cooling air discharge pipe 34, is configured by means of the engine control unit 12 to regulate the operation of the compressor 25, in order to maintain a predetermined temperature of the used cooling air 103 which flows via the cooling air discharge pipe 34, after cooling the pre-chamber 14, for example 28°C (82°F), over the entire load range of the engine 1. If the temperature of the used cooling air 103 which flows via the cooling air discharge pipe 34 after cooling of the pre-chamber 14 rises above the desired temperature (28 °C) due to increased load of the combustion engine 1, for example from 30 % to 60 % in which more fuel is burned in the pre-chamber 14, the operation of the compressor 25 is increased by the engine control unit 12 based on a temperature measurement of the used cooling air 103 by the air sensor 10, to achieve higher pressure of the compressed air 101 to the vortex tube 23, resulting in a lower temperature of the cooling air 102 flowing from the vortex tube outlet 35. This reduced temperature of the cooling air 102 flowing from the vortex tube outlet 35 results in more efficient cooling of the prechamber 14 and a consequent reduction in the temperature of the used cooling air 103 flowing via the cooling air discharge pipe 34 after cooling of the pre-chamber 14 to the desired temperature (28°C), which is monitored by the air temperature sensor 10. In contrast, if the temperature of the used cooling air 103 flowing after cooling of the pre-chamber 14 through the cooling air discharge pipe 34 starts to fall below the desired value (28°C) (82°F) due to decreased load of the internal combustion engine 1, the engine control unit 12 on the instruction from the cooling air temperature sensor 10 will reduce the operation of the compressor 25 and thus also the temperature of the cold air stream 102 flowing from the cold outlet 35 of the venturi tube 23 is reduced, which will keep the temperature of the used cooling air 103 after cooling of the pre-chamber 14 closer to the desired level (28°C). The change in temperature of the used cooling air 103 which flows after cooling of the pre-chamber 14 through the cooling air discharge pipe 34 occurs especially due to an increase or decrease in the load of the combustion engine 1 when different amounts of a fuel are burned in the pre-chamber 14 and thus the heat load on the pre-chamber 14 changes. Another factor that affects the cooling of the pre-chamber 14 using the vortex tube 23 is the temperature of the air 100 entering the compressor 25. The air 100 for cooling of the pre-chamber 14 is sucked by the compressor 25, further is supplied to the vortex tube 23 as a compressed air 101, further flows from the cold outlet 35 of the vortex tube 23 as a cold air stream 102 on the pre-chamber wall 31, and continues as the used cooling air 103 after cooling of the pre-chamber 14 into the cooling air discharge pipe 34. The temperature of the air 100 entering the compressor 25 affects the temperature of the compressed air 101 supplied to the vortex tube 23, resulting temperature of the cold air stream 102 exiting the from the cold outlet 35 of the vortex tube 23 for a cooling of the pre-chamber 14 and, consequently, the temperature of the used cooling air 103 after cooling of the pre-chamber 14. Therefore, when the temperature of the air 100 sucked by the compressor 25 at the inlet 39 rises, the temperature of the used cooling air 103 in the discharge pipe 34 also rises and the air temperature sensor 10 in this discharge pipe 34 issues an instruction to the compressor 25 to increase a pressure of the air 101 to the vortex tube 23 in order to reduce the temperature of the cold air stream 102 flowing from the vortex tube outlet 35, what resulting to a reduction the temperature of the used cooling air 103 flowing in the cooling air discharge pipe 34 after cooling of the pre-chamber 14. Temperature control of the cold air stream 102 which flows from the vortex tube outlet 35, based on the temperature measuring of the used cooling air 103 flowing via the discharge pipe 34 after cooling the pre-chamber 14 by the air temperature sensor 10, ensures optimum cooling of the pre-chamber 14 also when the temperature of the intake air 100 to the compressor 25 varies. Due to the fact that for a cooling of the pre-chamber 14 by means of the vortex tube 23, it is needed to take into account the temperature of the air 100 sucked by the compressor 25 and, in addition, the changing thermal load of the pre-chamber 14 according to the load of the combustion engine 1 in order to reach efficient cooling of the pre-chamber 14 under all conditions, the tem- perature of the used cooling air 103 that flows via the discharge pipe 34 after cooling of the pre-chamber 14 measured by the air temperature sensor 10, is a decisive factor for controlling the operation of the compressor 25. The compressed air supply pipe 38 for the vortex tube 23 also contains a compressed air water separator 24. The separator 24 removes the water content from the compressed air 101 to prevent the vortex tube 23 from freezing during prolonged operation at low temperatures -10°C (14°F) or lower of the cold air stream 102. The additional cooling of the pre-chamber 14 can also operate without the use of a water separator 24 of the compressed air 101, but in this case, it is necessary to use a higher temperature of the cold air stream 102 flowing from the cold outlet 35 of the vortex tube 23 than -1°C (30°F), in order to avoid freezing of the vortex tube 23 during cooling of the pre-cham- ber 14. Optimally for cooling of the pre-chamber 14, a compressed air 101 generated from the compressor 25 into the vortex tube 23 is used which is filtered. Further the compressed air 101 can be cooled between the compres- sor 25 and the vortex tube 23.

[0019] Fig.2 in more detail shows a cross-section of the additional cooling of the pre-chamber 14 used in the internal combustion engine 1, whereby is shown the pre-chamber 14 having a wall 31, a spark plug 18 and air injector 20 fac- ing into the pre-chamber 14, a vortex tube 23 for cooling of the pre-chamber 14, a discharge pipe 34 to divert a used cooling air 103 after cooling of the pre-chamber 14, which includes the air temperature sensor 10, a replaceable pre-combustion device 22 fixed in the cylinder head 4. In operation, the inlet 26 of the vortex tube 23 is supplied with a compressed air 101 from the compressor (said compressor is not shown), subsequently from the hot air outlet 28 flows the hot air stream 29, and from the cold air outlet 35 of the vortex tube 23 flows a cold air stream 102, whereby said cold air stream 102 is directed on the pre-chamber wall 31, and after cooling of the pre-chamber 14 continues further to the cooling air discharge pipe 34 as the used cooling air 103. The internal combustion engine 1 further includes a fuel injector 19 having a nozzle 33 (or outlet) located in the pre-chamber wall 31 for supplying a fuel 21 directly into the pre-chamber 14, whereby the cold air stream 102 flowing from the cold outlet 35 of the vortex tube 23 is directly directed on a portion 30 of the pre-chamber wall 31 where the nozzle 33 (outlet) of the fuel injector 19 is located. By directing of the cold outlet 35 of the vortex tube 23 to that portion 30 of the pre-chamber wall 31 where the fuel injector nozzle 33 is located, allows by the cold air stream 102 flowing from the vortex tube outlet 35 at the same time when is cooled pre-chamber 14, also is cooled too the nozzle 33 of the fuel injector 19. The additional cooling of the fuel injector nozzle 33 which is thermally loaded during combustion of the fuel - air mixture in the pre-chamber 14, reduces a temperature of the fuel injector 19 and also a temperature of the fuel 21 directly before injection into the prechamber 14. Thus if an internal combustion engine 1 operates with fuel injection into the pre-chamber 14 and simultaneously into the main combustion chamber 5 (fuel injection to the main combustion chamber 5 is not shown), then only a part of the fuel 21 for operation of the internal combustion engine 1 which passes through the fuel injector 19 into the pre-chamber 14, is addi- tionally cooled by the vortex tube 23. But preferentially, the internal com- bustion engine 1 operates with the fuel 21 supplied into the pre-chamber 14, whereby all the fuel 21 for operation of the internal combustion engine 1 is injected into the pre-chamber 14 through the fuel injector 19 the nozzle 33 (outlet) of which is cooled by the cold air stream 102 flowing from the cold air outlet 35 of the vortex tube 23. Injection of all fuel 21 for the operation of the internal combustion engine 1 into the pre-chamber 14 via the fuel injector 19 the nozzle 33 of which is cooled, reduces the temperature of the pre-chamber 14 during the formation of the fuel-air mixture.

[0020] Fig. 3 shows a four-stroke internal combustion engine 1 in a cross-sectional view comprising at least one cylinder 2 with a piston 3, a cylinder head 4 defining with the piston 3 a main combustion chamber 5 in the at least one cylinder 2, an inlet channel 7 and an outlet channel 8 associated with the cylinder 2, a pre-chamber 14 having a wall 31, a combustion duct 15 connecting the pre-chamber 14 with the cylinder 2, a cooling air discharge pipe 34, an engine control unit 12, a compressor 25, a charge air pipe 6, a throttle valve 9 of a charge air 11, and an engine charge air compressor 13. The engine charge air compressor 13 is designed as a part of an exhaust driven turbocharger or an engine driven supercharger. The engine charge air compressor 13 is designed to generate into the charge air pipe 6 the pressure of the charge air 11 up to 4 BAR at full load of said engine 1. The combustion engine 1 is designed to operate with a lower pressure of the charge air 111 in the inlet channel 7 of the cylinder 2, than generates the engine charge air compressor 13, optimally 1,2 Bar at full load, further with an effective compression ratio higher than 13:1, and without a water cooling. The internal combustion engine 1 further comprising said pre-chamber 14 having a wall 31 (or a swirl chamber) which is associated with the cylinder 2 through a combustion duct 15, whereby a volume of the pre-chamber 14 is less than 41%, preferably less 17% of the combined volume of said pre-chamber 14 and its associated main combustion chamber 5 when the piston 3 is at top dead position 16. The combustion duct 15 includes a number of orifices 17 providing fluent communication between the pre-chamber 14 and the corresponding cylinder 2. If the internal combustion engine 1 includes multiple cylinders, so each cylinder 2 is provided with at least one pre-chamber 14. The engine 1 further comprising a spark plug 18, or a glow plug for diesel combustion (said glow plug is not shown), further a fuel injector 19 and an air injector 20. The spark plug 18, fuel injector 19 and air injector 20 facing into the pre-chamber 14. The internal combustion engine 1 is designed to operate on the fuel 21 supplied directly only into the pre-chamber 14. The internal combustion engine 1 further comprising a replaceable pre-combustion device 22 (replaceable housing), which is screwed in the thread 32 in the cylinder head 4 and said pre-chamber 14, fuel injector 19, air injector 20, spark plug 18 and said combustion duct 15 are located in this replaceable pre-combustion device 22. This device 22 facilitates changing the size of the pre-chamber 14 or the type of fuel to be used in the combustion engine 1. The internal combustion engine 1 further includes a compressed air water separator 43, which is disposed in the charge air pipe 6. In operation of the combustion engine 1, the compressor 13 supplies a charge air 11 into the pipe 6 before the throttle valve 9 with a pressure up to 4 Bar at full load of the combustion engine 1, even though only 1.2 Bar pressure of the charge air 111 in the inlet channel 7 of the cylinder 2 is required for optimum operation of said engine 1 at full load. The compressor 13 thus generates in the charge air pipe 6 at full load of the engine 1 an excess pressure of the charge air 11 up to 2,8 Bar higher that is required in the inlet channel 7 of the cylinder 2 for operation of said engine 1. Therefore, the compressed engine charge air 11 is throttled by the throttle valve 9 and is converted by the Venturi effect into subcooled engine charge air 111 having a temperature of -5°C (23°F) or less, and a pressure 1,2 Bar. More precisely, the engine control unit 12 monitors the pressure of the charge air 11 which generates the compressor 13 in the charge air pipe 6 before the throttle valve 9 and adjusts the opening 36 of the throttle valve 9 to this pressure in order the greater the pressure of the charge air 11 in the charge air pipe 6 the smaller the range of the throttle valve opening 36, resulting in the throttle valve 9 is opened only up to 30 % in full load of the engine 1 in order to reduce the pressure of the charge air 11 between the charge air pipe 6 and the inlet channel 7 of the cylinder 2 from 4 to 1.2 Bar in order to achieve the adiabatic expansion of said charge air 111 in the inlet channel 7 of the cylinder 2 resulting in a subcooling of the charge air 111 in said inlet channel 7 by the Venturi effect to a lower temperature than -5°C (23°F), at full load of the combustion engine 1. The compressed air water separator 43 removes a water content from the compressed engine charge air 11 to prevent freezing of the throttle valve 9 when, during operation of the engine 1, the compressed engine charge air 11 is throttled with the throttle valve 9 and is converted by the Venturi effect into subcooled engine charge air 111 having a temperature of -5°C (23°F) or less. The subcooled charge air 111 without a fuel enters during the intake stroke of the piston 3 from the inlet channel 7 to the cylinder 2. During compression stroke of the piston 3 the subcooled charge air 111 is pushed by said piston 3 into the pre-chamber 14, whereby a partial cooling of the pre-chamber 14 by the said subcooled charge air 111 occurs and at the same time a predetermined amount of a fuel 21 is injected by the fuel injector 19 into the pre-chamber 14, to provide a fuel-air mixture formation in said pre-chamber 14, combustion of which provides all the power necessary for operation of the combustion engine 1. The fuel-air mixture in the pre-cham- ber 14 is in the entire load range of the said combustion engine 1 rich, and only the charge air 111 (without fuel) is present in the cylinder 2 during com- pression of the piston 3, whereby at higher load of the engine 1, the fuel-air mixture in the pre-chamber 14 is richer than at lower load of the combustion engine 1. The proportion of fuel 21 in the fuel-air mixture in the pre-chamber 14 increases or decreases with increasing or decreasing load of the engine 1, whereby said fuel-air mixture in the pre-chamber 14 is ignitable and bums out completely in the entire load range of the internal combustion engine 1. During the exhaust phase and / or the intake phase of the piston 3 the air injector 20 supplies a compressed air 37 into the pre-chamber 14, in order to displace from the pre-chamber 14 a residual gases of a previous combustion event.

[0021] In order to provide, according to the invention, the additional cooling of the pre-chamber 14 during operation of the internal combustion engine 1 which operates with a subcooled charge air 111 in the inlet channel 7 of the cylinder 2 by means of a venturi effect to a temperature less than -5°C (23 °F) at full load, whereby a volume of the pre-chamber 14 is less than 17 % of a combined volume of the pre-chamber 14 and the main combustion chamber 5 when the piston 3 is in a top dead position 16 as described above, the internal combustion engine 1 further includes a vortex tube 23 to provide a cooling of the pre-chamber 14, an electric motor (not shown) for driving the compressor 25, a cooling air discharge pipe 34, and a compressed air water separator 24 located in the compressed air supply pipe 38 for the vortex tube 23. The vortex tube 23 is located in the replaceable pre-combustion device 22. This replaceable pre-combustion device 22 is designed such that at least a portion of the pre-chamber wall 31 is accessible for a direct contact with the cold air stream 102 flowing from the cold outlet 35 of the vortex tube 23. The compressor 25 is driven by the internal combustion engine 1, but preferably by the electric motor (not shown). The vortex tube 23 for cooling of the pre-chamber 14, which comprises an air inlet 26, a cold air outlet 35, and a hot air outlet 28, the air inlet 26 of the vortex tube 23 is supplied with a compressed air 101 from the compressor 25 with a pressure up to 7 Bar, the vortex tube 23 is designed to separate the compressed air 101 into a hot air stream 29 flowing from the hot air outlet 28 and a cold air stream 102 flowing from the cold air outlet 35, whereby the cold air stream 102 flowing from the cold air outlet 35 of the vortex tube 23 is (directly) directed at least on a portion of the prechamber wall 31 from an outside of the pre-chamber wall 31, and after cooling of the pre-chamber 14 flows as a used cooling air 103 into the cooling air discharge pipe 34. The cooling air discharge pipe 34 includes an air temperature sensor 10, which is designed to control a reaching a predetermined uniform temperature of the used cooling air 103 flowing via this discharge pipe 34 after cooling of the pre-chamber 14 over the entire load range of the internal combustion engine 1, whereby based on instructions from said air temperature sensor 10 the engine control unit 12, by controlling an operation of the compressor 25, adjusts a temperature of the cold air stream 102 flowing from the cold air outlet 35 of the vortex tube 23 to cool the pre-chamber 14 by increasing or decreasing the pressure of the compressed air 101 supplied into the inlet 26 of the vortex tube 23, for the reaching of the predetermined uniform temperature of the used cooling air 103 flowing via the cooling air discharge pipe 34 after cooling of the pre-chamber 14, over the entire load range of the internal combustion engine 1. Monitoring the temperature of the used cooling air 103 by the air temperature sensor 10 in the cooling air discharge pipe 34 at the end of the entire cooling process of the pre-chamber 14, provides a sufficient cooling of the pre-chamber 14 if a load of the combustion engine 1 changes, when the temperature of the intake air 100 into the compressor 25 changes, or when changes the altitude during driving of a car in which the internal combustion engine 1 is used. A vehicle (not shown), in which the internal combustion engine 1 is mounted, includes an ambient air temperature sensor 44, whereby the compressor 25 for a cooling of the prechamber 14 is in operation when the ambient air temperature sensor 44 measures an air temperature higher than -1°C (30°F). Thus, if the temperature of the ambient air of a vehicle (not shown) measured by the ambient air temperature sensor 44 is -1°C (30°F) or lower, then the subcooling of the charge air 111 in the cylinder inlet channel 7 is sufficient to cool the pre-chamber 14 as well, and there is no need for the additional cooling of the pre-chamber 14 to be in operation. However, if a combustion engine 1 operates without subcooling of the charge air 111 in the inlet channel 7 of the cylinder 2, for example at low load up to 30 %, or when idling of the internal combustion engine 1, when a pressure of the charge air 11 in the pipe 6 is not sufficient to achieve a subcooling of charge air 111 in the cylinder inlet channel 7, the additional cooling of the pre-chamber 14 with the vortex tube 23 is in operation, even if the ambient air temperature sensor 44 measures a temperature -1°C (30°F) or lower. If the internal combustion engine 1 comprises more than one cylinder 2, and each cylinder is associated with at least one pre-chamber 14, so each pre-chamber in said internal combustion engine 1 is cooled at least by one vortex tube 23, or for a cooling of a pre-chamber 14 of each cylinder 2 in the engine 1 may be used two or more than two vortex tubes (not shown).

[0022] Fig. 4 shows a four-stroke internal combustion engine 1 in a cross-sectional view comprising at least two cylinders 2, 2', two pistons 3, 3', compressor 25. Further is shown a cylinder head 4 which includes two pre-chambers 14, 14', whereby one vortex tube 23 provides a cooling of two pre-chambers 14, 14', in one internal combustion engine 1 by means of an additional pipe 27 for guiding of the cold air stream 102 flowing from vortex tube 23, whereby the vortex tube 23 may be located outside the structure of the internal combustion engine 1. A single vortex tube 23 can to provide a cooling of more than two pre-chambers (not shown), in one internal combustion engine 1 by means of an additional pipe 27.

[0023] INDUSTRIAL APPLICABILITY

[0024] The additional cooling of the pre-chamber 14 (or swirl chamber) with the use of the vortex tube 23 is designed for all types of internal combustion engines operating on a fuel 21 supplied directly into the pre-chamber 14, but preferably for a specific type of the internal combustion engine 1 (described in Fig. 3) operating with the subcooled engine charge air 111 by the venturi effect in the inlet channel 7 of the cylinder 2 to a temperature less than -5°C (23°F) in full load and with a pre-chamber 14 whose volume is less than 17 % of a combined volume of the pre-chamber 14 and the main combustion chamber 5, when the piston 3 is in the top dead position 16, whereby the entire formation of the fuel-air mixture takes place only in the pre-chamber 14. The additional cooling of the pre-chamber 14 by means of the vortex tube 23 allows to reduce the temperature of said pre-chamber 14 over the entire load range of the combustion engine 1 and allows to avoid unwanted spontaneous combustion of the gasoline-air mixture during compression of the piston 3, even when a high compression ratio up to 16:1 is used in the internal combustion engine 1. A fuel-air mixture formation only in the small pre-chamber 14 whose volume is less than 17 % of a combined volume of the pre-chamber 14 and the main combustion chamber 5, when the piston 3 is in the top dead position 16 allows to reliably ignite and bum even a small amount of fuel 21 (gasoline) for one working cycle of the piston 3 resulting in significant fuel savings (up to 70 %), whereby the high compression ratio up to 16:1 allows the combustion engine 1 to operate with low fuel 21 consumption without a decrease in power, compared to conventional engines known of the prior art. Further, said spark-ignition internal combustion engine 1 operates with a full volume of the charge air 111 in the cylinder 2 and in the pre-chamber 14 at part load as well as at full load, thus with maximum compression pressure at part load as well as at full load, whereby the effective compression ratio in medium load is higher than in a spark-ignition engines with direct injection of fuel into the cylinders at full load, which are known from the actual state of the art. This advantage significantly increases engine efficiency at medium load. A spark-ignition engine 1 or diesel engine (diesel engine is not shown) using the additional cooling of the pre-chamber 14 can to operate with flame temperatures during combustion less than 1500°C (2732 °F), which allows to prevent the formation of unwanted nitrogen oxide (NOx), whereby said internal combustion engine 1 does not operate with direct fuel injection into the cylinder 2 and therefore no particulate matter is formed during combustion. Said engine 1 therefore does not need a particulate filter in the exhaust pipe. The combustion engine 1 according to the invention does not need to operate with exhaust gas catalyst and, in addition, there is no need for the recirculation of the exhaust gases into the cylinder intake channel 7, what prevents to the unwanted carbonisation of the intake channel 7 of the cylinder 2 in the engine 1. The high compression ratio up to 16:1 is suitable for diesel combustion, but with additional cooling of the pre-chamber 14 is also applicable for gasoline combustion. This advantage allows simpler modify the engine type in manufacturing in the factory from spark ignition engine to a diesel engine, because the replaceable pre-combustion device 22 which is screwed in the thread 32 in the cylinder head 4, is possible simply to replace by other replaceable pre-combustion device which includes instead of a spark plug 18, a glow plug (not shown), and a larger or a smaller pre-chamber 14 as required. This advantage allows to use the same engine parts such as, pistons, connecting rods, crankshaft, engine block, cylinder head, in the manufacture of a gasoline and diesel engines which reduces their manufacturing cost. LIST OF REFERENCES

[0025] 1 Internal combustion engine

[0026] 2 Cylinder

[0027] 2' Cylinder

[0028] 3 Piston

[0029] 3' Piston

[0030] 4 Cylinder head

[0031] 5 Main combustion chamber

[0032] 6 Charge air pipe

[0033] 7 Inlet channel of the cylinder

[0034] 8 Outlet channel of the cylinder

[0035] 9 Throttle valve

[0036] 10 Air Temperature sensor

[0037] 11 Engine charge air

[0038] 12 Engine control unit

[0039] 13 Engine charge air compressor

[0040] 14 Pre-chamber

[0041] 14' Pre-chamber

[0042] 15 Combustion duct

[0043] 16 Top dead position of the piston

[0044] 17 Number of orifices

[0045] 18 Spark plug

[0046] 19 Fuel injector

[0047] 20 Air injector

[0048] 21 Fuel

[0049] 22 Replaceable pre-combustion device

[0050] 23 Vortex tube

[0051] 24 Compressed air water separator for the vortex tube 25 Compressor (for the vortex tube)

[0052] 26 Air inlet of the vortex tube

[0053] 27 Additional pipe for guiding cooling air from the vortex tube

[0054] 28 Hot air outlet of the vortex tube

[0055] 29 Hot air stream

[0056] 30 Portion of the pre-chamber wall where a fuel injector nozzle is located.

[0057] 31 Pre-chamber wall

[0058] 32 Thread (for attachment of a replaceable pre-combustion device 22)

[0059] 33 Nozzle of the fuel injector

[0060] 34 Cooling air discharge pipe

[0061] 35 Cold air outlet of the vortex tube

[0062] 36 Throttle opening range

[0063] 37 Compressed air (for the air injector 20)

[0064] 38 Compressed air supply pipe (for the vortex tube)

[0065] 39 Inlet pipe (of the compressor for the vortex tube)

[0066] 40 Electric motor

[0067] 41 Wall of the cylinder head

[0068] 42 Cooling channel surrounding the pre-chamber wall

[0069] 43 Compressed air water separator of the engine charge air

[0070] 44 Ambient air temperature sensor

[0071] 100 Intake air (into the compressor for the vortex tube)

[0072] 101 Compressed air (into the vortex tube)

[0073] 102 Cold air stream flowing from the vortex tube

[0074] 103 Used cooling air after cooling of the pre-chamber

[0075] 111 Subcooled engine charge air

Claims

AMENDED CLAIMS received by the International Bureau on 12 November 2025 (12.11.2025)1. A four-stroke internal combustion engine (1) comprising: at least one cylinder (2) and one piston (3); a cylinder head (4) defining with the piston (3) a main combustion chamber (5) in the at least one cylinder (2); an inlet channel (7) and an outlet channel (8) associated with the cylinder (2); a prechamber (14) having a wall (31); an engine control unit (12); a cooling air discharge pipe (34); a cooling channel (42) surrounding the pre-chamber wall (31) associated with the cooling air discharge pipe (34); a compressor (25); whereby the four-stroke internal combustion engine (1) comprising a vortex tube (23) for cooling of the pre-chamber (14), which comprises an air inlet (26), a cold air outlet (35), and a hot air outlet (28), the air inlet (26) of the vortex tube (23) is supplied with a compressed air (101) from the compressor (25) with a pressure up to 7 Bar, and the vortex tube (23) is designed to separate the compressed air (101) into a hot air stream (29) flowing from the hot air out let (28) and a cold air stream (102) flowing from the cold air outlet (35), and the cold air stream (102) flowing from the cold air outlet (35) of the vortex tube (23) is directed at least on a portion of the pre-chamber wall (31) further flows via the cooling channel (42) surrounding the pre-chamber wall (31), and consequently after cooling of the pre-chamber (14) flows from the cooling channel (42) as a used cooling air (103) to the cooling air discharge pipe (34).

2. The internal combustion engine according to claim 1, further includes a fuel injector (19) having a nozzle (33) located in the pre-chamber wall (31) for supplying a fuel (21) directly into the pre-chamber (14), whereby the cold air stream (102) flowing from the cold outlet (35) of the vortex tube (23) is directly directed on a portion (30) of the pre-chamber wall (31) where the nozzle (33) of the fuel injector (19) is located.

3. The internal combustion engine according to claim 1, whereby the internal combustion engine (1) operates with a subcooled charge air (111) in the inlet channel (7) of the cylinder (2) by means of a venturi effect to a temperature less than -5°C (23°F) at full load.

4. The internal combustion engine according to claim 1, whereby a volume of the pre-chamber (14) is less than 17 % of a combined volume of the prechamber (14) and the main combustion chamber (5) when the piston (3) is in a top dead position (16).

5. The internal combustion engine according to claim 1, whereby the cooling air discharge pipe (34) includes an air temperature sensor (10) which controls an exceeding of a predetermined maximum temperature of the used cooling air (103) flowing via the discharge pipe (34) after cooling of the prechamber (14) , and the engine control unit (12), by controlling an operation of the compressor (25), causes a temperature of the cold air stream (102) flowing from the cold air outlet (35) of the vortex tube (23) to cool the prechamber (14) is decreasing by increasing the pressure of the compressed air (101) supplied into the inlet (26) of the vortex tube (23) when is exceeded the predetermined maximum temperature of the used cooling air (103) flowing via the cooling air discharge pipe (34) after cooling of the pre-chamber (14) measured by the air temperature sensor (10) located in the cooling air discharge pipe (34).

6. The internal combustion engine according to claims 1 and 2, whereby all the fuel (21) for operation of the internal combustion engine (1) is injected into the pre-chamber (14) through the fuel injector (19) the nozzle (33) of which is cooled by the cold air stream (102) flowing from the cold air outlet (35) of the vortex tube (23).

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