Cooling system for an internal combustion engine

Abstract

Cooling system (4) for an internal combustion engine with at least one cylinder head (1) connected to at least one cylinder block (2) via a cylinder head sealing surface (28), with at least one first cooling jacket (5) arranged in the cylinder head (1) and flow-connected to at least one coolant inlet (27) and at least one first coolant outlet (19) of the cylinder head (1), and with at least one second cooling jacket (6) arranged in the cylinder block (2) and connected to at least one second coolant outlet (20), wherein the first and second cooling jackets (5, 6) are connected to one another via at least one connecting flow path (17) - preferably extending through an opening (17a) in the cylinder head sealing surface (28) - and through which a liquid coolant can flow one after the other, and wherein the coolant flow through the second cooling jacket (6) is controllable via at least one first valve (8), preferably a thermostatic valve,which blocks the coolant flow through the second cooling jacket (6) in a first valve position and releases it in at least one second valve position, wherein the first cooling jacket (5), preferably also the second cooling jacket (6), can be flowed through in a transverse direction of the internal combustion engine, wherein a mixing chamber (26) of the first valve (8) has a first and a second valve inlet (8a, 8b), as well as a valve outlet (8c), and the first coolant outlet (19) of the cylinder head (1) is fluidly connected to the first valve inlet (8a), the second coolant outlet (20) is fluidly connected to the second valve inlet (8b), and the valve outlet (8c) is fluidly connected to at least one return line (25) of the cooling system (4), characterized in thatthat the first coolant outlet (19) of the cylinder head (1) is constantly flow-connected to at least one return line (25) of the cooling system (4) and only the flow connection between the second valve inlet (8b) and the valve outlet (8c) can be switched by the first valve (8), and that at least one second coolant outlet (20) is arranged in the cylinder head (1).

Description

[0001] The invention relates to a cooling system for an internal combustion engine having at least one cylinder head, which is connected to at least one cylinder block via at least one cylinder head sealing surface, having at least one first cooling jacket arranged in the cylinder head, which is fluidly connected to at least one coolant inlet and at least one first coolant outlet, and having at least one second cooling jacket arranged in the cylinder block, which is connected to at least one second coolant outlet, wherein the first and the second cooling jacket are connected to one another via at least one connecting flow path - preferably running through an opening in a cylinder head sealing surface - and through which a liquid coolant can flow one after the other, and wherein the coolant flow through the second cooling jacket is controllable via at least one first valve, preferably a thermostatic valve,which, in a first valve position, blocks the coolant flow through the second cooling jacket and releases it in at least one second valve position, wherein the first cooling jacket, preferably also the second cooling jacket, can be flowed through in a transverse direction of the internal combustion engine, wherein a mixing chamber of the first valve has a first and a second valve inlet, as well as a valve outlet, and the first coolant outlet of the cylinder head is fluidly connected to the first valve inlet, the second coolant outlet is fluidly connected to the second valve inlet, and the valve outlet is fluidly connected to at least one return line of the cooling system.

[0002] GB 2 348 485 A discloses an internal combustion engine with a cylinder head and a cylinder block, each of which has a cooling jacket. The cooling jacket of the cylinder block communicates with the cooling jacket of the cylinder head, with the coolant entering the cooling jacket of the cylinder head and flowing from the cooling jacket of the cylinder head into the cooling jacket of the cylinder block.

[0003] EP 1 258 609 A2 discloses a similar water-cooled internal combustion engine with a cooling jacket in the cylinder head and a cooling jacket in the cylinder block. When cold, the coolant is directed only through the cylinder head cooling jacket, and when warm, it is also directed through the cylinder block cooling jacket and a radiator downstream of the cylinder block. The coolant from the cylinder head cooling jacket flows directly into the return line leading to the coolant pump.

[0004] In both GB 2 348 485 A and EP 1 258 609 A2, the coolant inlet and outlet of the cylinder head cooling jacket are located at different ends of the cylinder head, resulting in longitudinal flow through the cylinder head cooling jacket. This requires a relatively large cooling jacket cross-section in the cylinder head. The required relatively large coolant volume results in the disadvantage of relatively long coolant warm-up times.

[0005] EP 2 562 379 A1 describes a separate coolant circuit for an internal combustion engine, wherein a cylinder head water jacket and an engine block water jacket are provided. The separate coolant circuit has a pump, a radiator, a control element, an outlet housing, and a heater, with a coolant circulating in the separate coolant. The control element is connected downstream of the cylinder head water jacket and has a thermostat and a separate proportional valve. The coolant can be supplied either to a radiator or to the engine block water jacket via the control element. The coolant flows longitudinally through both the cylinder head water jacket and the cylinder block water jacket. This longitudinal flow, as well as the relatively large number of external lines required between the cylinder head water jacket and the cylinder block water jacket, have a detrimental effect on the coolant volume.

[0006] WO 2009 / 143 866 A1 describes a cooling device for an internal combustion engine with a first cooling jacket arranged in a cylinder head and a second cooling jacket arranged in a cylinder block, wherein the coolant flow through the second cooling jacket is controlled by a valve. The first cooling jacket allows flow in a transverse direction. A similar arrangement is known from FR 2 934 319 A1 or DE 697 07 980 T2.

[0007] US 6 810 838 B1 and DE 10 2012 203 021 A1 each show cylinder head cooling systems with collecting or distribution chambers extending longitudinally between the coolant inlet and the coolant outlet.

[0008] DE 60 2005 003 433 T2 describes a cooling system for an internal combustion engine with a cylinder head and a cylinder block, through which coolant flows hydraulically in parallel and separately. The coolant outlet from the cylinder head is continuous, and the coolant outlet from the cylinder block is connected to a return line via a valve.

[0009] The object of the invention is to avoid the aforementioned disadvantages and to improve the cooling and heating behavior.

[0010] According to the invention, this is achieved in that the first coolant outlet of the cylinder head is constantly flow-connected to at least one return line of the cooling system and only the flow connection between the second valve inlet and the valve outlet can be switched by the first valve, and in that at least one second coolant outlet is arranged in the cylinder head.

[0011] The longitudinal direction of the internal combustion engine is understood here as a direction parallel to the crankshaft axis. The transverse direction of the internal combustion engine is understood as a direction oriented approximately perpendicular to the crankshaft axis and perpendicular to the cylinder axis.

[0012] Preferably, at least one collecting chamber extending substantially in the longitudinal direction of the internal combustion engine is arranged in the flow path between the first cooling jacket and the first coolant outlet and / or a distributor chamber extending substantially in the longitudinal direction of the internal combustion engine is arranged in the flow path between the coolant inlet and the first cooling jacket.

[0013] Because the flow through the first cooling jacket is transverse to the internal combustion engine, external lines between the first and second cooling jackets are eliminated, and the cross-section of the first cooling jacket—as viewed perpendicular to the crankshaft axis—can be kept small, drastically reducing the coolant volume. The second cooling jacket is activated or deactivated as needed, with the full flow of coolant always flowing through the first cooling jacket of the cylinder head. This ensures sufficient heat dissipation from the thermally highly stressed areas around the exhaust valves in the fire deck in every operating range of the internal combustion engine.

[0014] According to a first embodiment of the invention, the collection chamber for the coolant can be integrated into the cylinder block. The collection chamber is hydraulically separated from the second cooling jacket within the cylinder block. This variant has the advantage that no structural measures are required to accommodate the collection chamber in the cylinder head, which simplifies cylinder head manufacturing.

[0015] In a second embodiment of the invention, the plenum is arranged in the cylinder head, preferably between the exhaust ports and the cylinder head sealing surface. This arrangement has the advantage that the plenum integrated into the cylinder head can additionally cool the exhaust ports, and possibly also an exhaust manifold integrated into the cylinder head.

[0016] The collecting chamber can extend essentially over the entire length of the cylinder head or cylinder block

[0017] In order to enable sufficient heat transport from thermally critical areas of the cylinder head and rapid warm-up after a cold start in every operating range, it is advantageous if the second coolant outlet of the cylinder head is switchably connected to a return line of the cooling system via the first valve.

[0018] It can be provided that only the flow connection between the second valve inlet and the valve outlet can be switched by the first valve.

[0019] The return line can have a long return line with at least one radiator and a short return line bypassing the radiator, wherein the coolant flow through the short or long return line can be controlled by at least one second valve, preferably a thermostatic valve. The coolant can be returned to the coolant pump via the second valve either directly or via a radiator.

[0020] In all embodiments of the invention, the entire coolant flow flows through the first cooling jacket. The first valve is located downstream of the first cooling jacket. In a first position, this valve completely blocks the outflow of coolant from the second cooling jacket of the cylinder block. Thus, the entire coolant is fed directly into the cooling system's return line. When the first valve moves to the second position, a partial flow of coolant is directed into the second cooling jacket of the cylinder block. After flowing through the second cooling jacket, the coolant is fed back into the cylinder head via a transfer channel, where it is fed into the coolant system via the first valve.

[0021] In a further embodiment of the invention, the coolant pump can be driven by a camshaft, preferably located in the cylinder head. This measure has the advantage that the coolant volume between the coolant pump and the first cooling jacket can be reduced to a minimum, which has a beneficial effect on the coolant's heating time.

[0022] A particularly small coolant volume and thus very short heating times can be achieved if the coolant inlet, the first coolant outlet and the second coolant outlet are arranged in the cylinder head.

[0023] The invention is explained in more detail below with reference to the figures. They show: Fig. 1 the cooling jackets of a cooling system according to the invention in a first embodiment in an oblique view; Fig. 1a the second cooling jacket in a plan view of the cylinder head sealing plane; Fig. 2 the cooling jackets in another oblique view; Fig. 3 the cooling system according to the invention in a schematic representation in a first embodiment variant; Fig. 4 the cooling system Fig. 3 in a first switching position; Fig. 5 the coolant flow in the first switching position in a cross-section through the cooling jackets, Fig. 6 the cooling system Fig. 3 in a second switching position; Fig. 7 the coolant flow in the second switching position in a cross section through the cooling jackets; Fig. 8 the cooling system Fig. 3 in a third switching position; Fig. 9 the coolant flow in the third switching position in a cross section through the cooling jackets; Fig. 10 shows a cooling system according to the invention in a second embodiment in an oblique view; Fig. 10a the second cooling jacket in a plan view of the cylinder head sealing plane; Fig. 11 the cooling system according to the invention in a schematic representation in a second embodiment; Fig. 12 the cooling system Fig. 11 in a first switching position; Fig. 13 the coolant flow in the first switching position in a cross section through the cooling jackets; Fig. 14 the cooling system Fig. 11 in a second switching position; Fig. 15 the coolant flow in the second switching position in a cross section through the cooling jackets; Fig. 16 the cooling system Fig. 11 in a third switching position; Fig. 17 the coolant flow of the third switching position in a cross-section through the cooling jackets; and Fig. 18 the cooling system Fig. 11 in a side view.

[0024] Functionally identical features are provided with the same reference numerals in the embodiments.

[0025] In the Fig. 4, Fig. 6, Fig. 8 and Fig. 12, Fig. 14, Fig. 16, non-flow-through elements of the cooling system 4 are not shown for the sake of clarity.

[0026] The internal combustion engine has a cylinder head 1 and a cylinder block 2, each for several cylinders 3, as well as a cooling system 4 with a liquid coolant. A first cooling jacket 5 is arranged in the cylinder head 1 and serves to cool thermally critical areas in the cylinder head 1. The cylinder block 2 has a second cooling jacket 6, which is fluidly connected to the first cooling jacket 5. The cooling jacket 5 is fluidly connected to a coolant inlet 27 and a first coolant outlet 19 of the cylinder head 1.

[0027] In addition to the first cooling jacket 5 and the second cooling jacket 6, the cooling system 4 further comprises a coolant pump 7, a first valve 8 designed as a thermostatic valve, a second valve 9 designed as a thermostatic valve, a radiator 10, an interior heater 11, an expansion tank 12 and an oil cooler 13, as shown in the Fig. 3 and Fig. 11. Furthermore, the cooling system has a collecting chamber 14a or 14b extending in the longitudinal direction of the cylinder block 2 or the cylinder head 1, which can be arranged either in the cylinder block 2 ( Fig. 1 to 9) or in cylinder head 1 ( Fig. 10 to Fig. 17).

[0028] The components coolant pump 7, first thermostat valve 8 and second valve 9 can be combined in a pump / thermostat module. The coolant pump 7 is advantageously arranged in or on the cylinder head 1 and is driven by an overhead camshaft, which Fig. 1 is indicated by the camshaft axis 15.

[0029] From the coolant pump 7, the coolant is guided to the first cooling jacket 5 via a distribution chamber 16 extending in the longitudinal direction of the internal combustion engine within the cylinder head 1. In the exemplary embodiments, the distribution chamber 16 is arranged on the exhaust side E of the cylinder head 1. The inlet side is indicated by reference symbol I. From the distribution chamber 16, the coolant flows in the transverse direction of the cylinder head 1 through the first cooling jacket 5, cooling areas subject to high thermal stress around the exhaust valves, etc. The first cooling jacket 5 is in flow connection with the second cooling jacket 6 via openings 17a in the cylinder head sealing surface 28 or in the cylinder head gasket (not shown in detail). The first cooling jacket 5 is further connected to the collecting chamber 14a or 14b via collecting channels 18, with at least one collecting channel 18 being provided per cylinder 3.The collecting chamber 14a, 14b is connected to a first outlet 19 arranged in the cylinder head 1. Furthermore, the second cooling jacket 6 of the cylinder block 2 is fluidly connected to a second outlet 20 in the cylinder head 1 via a riser channel 21.

[0030] In the Fig. 1 to Fig. In the embodiment shown in Figure 9, the cylinder head gasket has openings 18a through which the coolant passes through the collecting channels 18 into the collecting chamber 14a. Furthermore, the cylinder head gasket has a transfer opening 18b in the area of ​​a front side of the internal combustion engine, through which the coolant passes from the collecting chamber 14a in the cylinder block 2 into an outlet channel 22 in the cylinder head 1 to the first outlet 19. The openings 17a, 18a and the transfer opening 18b are clearly the Fig. 1a.

[0031] In contrast, in the Fig. 10 to Fig. 17, the openings 18a and the transfer opening 18b in the cylinder head gasket are omitted. The collecting chamber 14b is located below, i.e. on the side facing the cylinder block 2, the exhaust ducts 29 or an exhaust manifold 30 integrated into the cylinder head 1 (see Fig. 18). The exhaust ducts are thus limited on the one hand by the distributor chamber 16 at the top and the collection chamber 14b at the bottom, which enables a particularly high heat dissipation from the area of ​​the exhaust ducts (see Fig. 10).

[0032] In both embodiments, the first coolant outlet 19 and the second coolant outlet 20 are connected to a first and second valve inlet 8a, 8b of the first valve 8, respectively, with a return line 25 leading from the valve outlet 8c of the first valve 8 back to the coolant pump 7 via a short return line 23 and a long return line 24, respectively. The radiator 10 for cooling the coolant is arranged in the long return line 24.

[0033] The path through the short return line 23 or the long return line 24 is controlled by the second valve 9. The flow direction of the coolant is indicated by arrows.

[0034] The following applies to both design variants: The entire coolant flows through the first cooling jacket 5 of the cylinder head 1. Depending on the coolant temperature, a portion of the coolant entering the first cooling jacket 5 flows through the first valve 8 of the second cooling jacket 6 in the cylinder block 2. The coolant is returned to the coolant pump 7 via the second valve 9, either via the radiator 10 or directly—bypassing the radiator 10.

[0035] The coolant flows are indicated by arrows. First design variant (Fig. 1 to Fig. 9)

[0036] In the Fig. 4, the first valve 8 and the second valve 9 are in a first valve position, wherein the first switching positions are associated with the cold state of the coolant. The coolant is pumped into the first cooling jacket 5 of the cylinder head 1 by the coolant pump 7. In the first valve position of the first valve 8, the first coolant outlet 19 is connected to the valve outlet 8c of the first thermostat valve 8, but the second coolant outlet 20 is separated from the valve outlet 8c of the first valve 8. Due to the blocked outflow from the second cooling jacket 6, the coolant cannot flow from the first cooling jacket 5 into the second cooling jacket 6, as a result of which the coolant only flows through the first cooling jacket 5 in the cylinder head 1.The entire coolant passes from the first cooling jacket 5 via the collecting channels 18 into the collecting chamber 14a arranged in the cylinder block 2 and flows from the collecting chamber 14a via the transfer opening 18b and the outlet channel 22 to the first coolant outlet 19 of the cylinder head 1 and further to the first valve inlet 8a of the first valve 8. The second valve 9 is located in the position shown in . Fig. 4, whereby the coolant drain from the radiator 10 is closed. Thus, the coolant flows directly from the first valve 8 back to the coolant pump 7. Fig. 5 shows the flow between the distribution chamber 16 and the collection chamber 14a for this first switching position of the cooling system 4.

[0037] Fig. 6 shows the cooling system 4 when the internal combustion engine is warm, with the first valve 8 in the second valve position and the second valve 9 still in the first valve position. The second valve position of the first valve 8 is associated with warm or hot coolant temperatures. In the second valve position of the first valve 8, both the first valve inlet 8a and the second valve inlet 8b of the first valve 8 are fluidly connected to the valve outlet 8c. This allows outflow from the second valve outlet 20 and thus from the second cooling jacket 6 of the cylinder block 2. The coolant now flows both via the collecting channels 18 into the collecting chamber 14a and via the connecting flow paths 17 and the openings 17a of the cylinder head sealing surface 28 or the cylinder head gasket into the second cooling jacket 6 arranged in the second cylinder block 2.From the second cooling jacket 6, the coolant flows via the riser duct 21 to the second outlet 20 of the cylinder head 1. Within the first valve 8, the partial flow flowing through the first cooling jacket 5 and the second cooling jacket 6 is combined in a mixing chamber 26 of the first valve 8. The coolant is returned directly to the coolant pump 7 via the second valve 9, which is in the first valve position. Fig. 7 shows the flow between the distribution chamber 16 and the second cooling jacket 6 or the collecting chamber 14a for this second switching position of the cooling system 4.

[0038] If the temperature of the internal combustion engine and thus the temperature of the coolant continues to rise, the second valve 9 switches to the second valve position, as shown in Fig. 8. In this second valve position, the outflow from the radiator 10 to the coolant pump 7 is released, whereby the coolant flows through the long return line 24 and the radiator 10. The flow through the first and second cooling jackets 5, 6 is analogous to the Fig. 6 and Fig. 7, as in Fig. 9 is shown. Second design variant (Fig. 10 to Fig. 17)

[0039] This embodiment differs from the one in the Fig. 1 to Fig. 9 in that the collecting chamber 14b is now not located in the cylinder block 2, but in the cylinder head 1. This has the advantage that the coolant volume can be further reduced and the cylinder block 2 can be designed more simply. As shown in Fig. 10a, significantly fewer openings 17a are required in the cylinder head sealing surface 28.

[0040] The Fig. 12 and Fig. 13 show a first switching position of the cooling system 4 for the second embodiment variant, wherein the first valve 8 and the second valve 9 are each in the first valve position, wherein the first valve positions are assigned to the cold internal combustion engine and the cold coolant, respectively. The coolant flows from the coolant pump 7 into the distributor chamber 16 and further into the first cooling jacket 5 of the cylinder head 1, through which it flows in the transverse direction. The coolant then passes through collecting channels 18 into the collecting chamber 14b, which is also arranged in the cylinder head 1. Since the flow connection between the second valve inlet 8b and the valve outlet 8c is blocked by the first valve 8, the outflow from the second cooling jacket 6 of the cylinder block 2 is prevented, thus preventing the coolant from overflowing from the first cooling jacket 5 into the second cooling jacket 6.All of the coolant from the first cooling jacket 5 flows from the collecting chamber 14b to the first coolant outlet 19 of the cylinder head 1, which is connected to the first valve inlet 8a of the first valve 8. Since the flow connection between the first valve inlet 8a and the valve outlet 8c is opened within the first valve 8 and the outflow from the radiator 10 is blocked by the first valve position of the second valve 9, the coolant flowing out of the first cooling jacket 5 flows back to the coolant pump 7 through the short return line 23.

[0041] As soon as the coolant has exceeded a first switching temperature for the first thermostat valve 8, the first valve 8 is switched to the second valve position, as shown in Fig. 14. In this position, both the flow connection between the first valve inlet 8a and the valve outlet 8c of the first valve 8 and the flow connection between the second valve inlet 8b and the valve outlet 8c are released. As a result, a portion of the coolant flows from the first cooling jacket 5 of the cylinder head 1 via the connecting flow paths 17 into the second cooling jacket 6 and from there via the riser channel 21 to the second coolant outlet 20 of the cylinder head 1. After the partial coolant flows originating from the first cooling jacket 5 and the second cooling jacket 6 have been brought together in the mixing chamber 26 of the first valve 8, the coolant is returned to the coolant pump 7 via the short return line 23. Fig. 15 shows the flow between the distribution chamber 16 and the second cooling jacket 6 or the collecting chamber 14b for this second switching position of the cooling system 4.

[0042] If the internal combustion engine and thus the coolant are further heated, the second valve 9 also switches from a second switching temperature into the second valve position, which is Fig. 16. This blocks the short return line 23 and releases the flow from the radiator 10 to the coolant pump 7. The coolant leaving the first valve 8 now flows through the radiator 10 via the long return line 24 and, after passing the second valve 9, reaches the coolant pump 7. Fig. The flow through the first cooling jacket 5 and the second cooling jacket 6 shown in Figure 17 is analogous to Fig. 14 and Fig. 15.

[0043] The second embodiment variant with the collecting chamber 14b arranged in the cylinder head 1 between at least one exhaust port 29 and the cylinder head sealing surface 28 of the cylinder head 1 has the advantage that the coolant volume of the cooling system 4 can be designed to be very small and that, on the other hand, a particularly high heat dissipation from the area of ​​the exhaust ports 29 is possible, in particular if the exhaust manifold 30 is also integrated into the cylinder head 1, as can be seen from Fig. 18. This, in turn, has a particularly beneficial effect on the heating time of the coolant during a cold start of the internal combustion engine.

Claims

Cooling system (4) for an internal combustion engine with at least one cylinder head (1) connected to at least one cylinder block (2) via a cylinder head sealing surface (28), with at least one first cooling jacket (5) arranged in the cylinder head (1) and flow-connected to at least one coolant inlet (27) and at least one first coolant outlet (19) of the cylinder head (1), and with at least one second cooling jacket (6) arranged in the cylinder block (2) and connected to at least one second coolant outlet (20), wherein the first and second cooling jackets (5, 6) are connected to one another via at least one connecting flow path (17) - preferably extending through an opening (17a) in the cylinder head sealing surface (28) - and through which a liquid coolant can flow one after the other, and wherein the coolant flow through the second cooling jacket (6) is controllable via at least one first valve (8), preferably a thermostatic valve,which blocks the coolant flow through the second cooling jacket (6) in a first valve position and releases it in at least one second valve position, wherein the first cooling jacket (5), preferably also the second cooling jacket (6), can be flowed through in a transverse direction of the internal combustion engine, wherein a mixing chamber (26) of the first valve (8) has a first and a second valve inlet (8a, 8b), as well as a valve outlet (8c), and the first coolant outlet (19) of the cylinder head (1) is fluidly connected to the first valve inlet (8a), the second coolant outlet (20) is fluidly connected to the second valve inlet (8b), and the valve outlet (8c) is fluidly connected to at least one return line (25) of the cooling system (4), characterized in thatthat the first coolant outlet (19) of the cylinder head (1) is constantly flow-connected to at least one return line (25) of the cooling system (4) and only the flow connection between the second valve inlet (8b) and the valve outlet (8c) can be switched by the first valve (8), and that at least one second coolant outlet (20) is arranged in the cylinder head (1). Cooling system (4) according to claim 1, characterized in that a collecting chamber (14a) is arranged in the cylinder block (2). Cooling system (4) according to claim 1, characterized in that a collecting chamber (14b) is arranged in the cylinder head (1). Cooling system (4) according to claim 3, characterized in that the collecting space (14b) is arranged between at least one outlet channel (29) and / or an exhaust manifold (30) integrated into the cylinder head (1), and the cylinder head sealing surface (28) of the cylinder head (1). Cooling system (4) according to one of claims 2 to 4, characterized in that in the flow path between the first cooling jacket (5) and the first coolant outlet (19) at least one collecting chamber (14a, 14b) extending substantially in the longitudinal direction of the internal combustion engine and / or in the flow path between the coolant inlet (27) and the first cooling jacket (5) a distributor chamber (16) extending substantially in the longitudinal direction of the internal combustion engine is arranged. Cooling system (4) according to one of claims 1 to 5, characterized in that the second coolant outlet (20) of the cylinder head (1) is switchably connected to a return line (25) of the cooling system (4) via the first valve (8). Cooling system (4) according to claim 5 or 6, characterized in that the return line (25) has a long return line (24) with at least one radiator (10) and a short return line (23) bypassing the radiator (10), wherein the coolant flow through the short or long return line (23, 24) is controllable by at least one second valve (9), preferably a thermostatic valve. Cooling system (4) according to one of claims 1 to 7, characterized in that the coolant pump (7) is driven by a camshaft preferably arranged in the cylinder head (1). Cooling system (4) according to one of claims 1 to 8, characterized in that at least one coolant inlet (27) and / or at least one first coolant outlet (19) are arranged in the cylinder head (1).

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