DE69032625T2 - Cooling system for an internal combustion engine - Google Patents

Description

The present invention relates to a cooling system for a multi-cylinder internal combustion engine having a cylinder head connected to a cylinder block and defining a plurality of cylinders, said cylinder head having at least one intake port extending through one side of said cylinder head and containing at least one exhaust port extending through the other side of said cylinder head, said cooling system comprising a cylinder head cooling jacket for circulating coolant between an intake and an exhaust side of said cylinder head, a cylinder block cooling jacket for circulating coolant through said cylinder block, a plurality of flow regulating elements being present in said cylinder head cooling jacket between adjacent cylinders arranged in series for regulating a cross flow of coolant through said cylinder head jacket between the intake and exhaust sides thereof, and a main coolant channel extending along one side of said cylinder head for circulating coolant through said cylinder head. the cylinder head cooling jacket is formed transversely from one side to the opposite side of the cylinder head.

As is well known, it is desirable to take care to preferably lower the temperature of the cylinder head, thereby making it possible to increase the performance of the internal combustion engine by increasing the permissible combustion temperature. Of course, such a strategy requires improved and forced cooling of the cylinder head. Therefore, it has been considered to mount the water pump directly on the cylinder head, in particular to mount it on one side of the internal combustion engine with the intention of supplying cooling water to the cylinder head before supplying cooling water to the cooling structure of the cylinder block. However, under the above-mentioned design idea, the internal combustion engine tends to become bulky because the side surface of the cylinder head in the crankshaft direction is provided with the intake and exhaust pipes and any arrangement of the water pump on the cylinder head requires avoiding interference with these pipes.

In order to provide a compact cooling structure, it has been proposed to connect the discharge port of a coolant pump to a cooling jacket for the cylinder block. The cooling jacket of the cylinder block is connected to the cooling jacket of the cylinder block via passages formed integrally in the cylinder block and the cylinder head, respectively, so that the coolant introduced into the cooling jacket of the cylinder block from the discharge side of the pump and flowing through said cooling jacket of the cylinder block flows into the cooling jacket of the cylinder head after cooling the cylinder block and then circulates through said cooling jacket of the cylinder head.

US-4 699 092 shows a cooling jacket arrangement of a cylinder head, wherein an annular coolant chamber is connected to each cylinder formed in the cylinder block and the cylinder head. The coolant is introduced into the cooling jacket of the cylinder head through inlet openings formed in the lower portion of the cylinder head and connected to the cooling jacket of the cylinder block, and flows through said coolant chamber towards the uppermost portion thereof from which a discharge channel extends.

In addition to the fact that this known cooling arrangement cannot provide forced cooling of the cylinder head since it cools the cylinder block first, it is not satisfactory with regard to the flow direction and the control of the flow rate of the coolant circulating through the cooling jacket of the cylinder head.

Furthermore, a cooling system according to the preamble of claim 1 is known from US-A-4,690,104. This document discloses that on the intake valve side, coolant passes from a coolant supply channel through supply channels and distribution channels through coolant inlet openings into a coolant circulation chamber between each pair of intake valve guide hubs and also on the outer sides of said valve guide hubs, whereas on the exhaust valve side, coolant passes from a coolant supply channel through supply channels and distribution channels through coolant inlet holes in said coolant circulation chamber near each pair of exhaust valve guide hubs. The coolant thus supplied to the coolant circulation chamber Coolant is drained from it through outlet holes in its side wall to enter a coolant outlet passage.

Since there are two separate supply channels, this system is not only quite complicated, but also has the disadvantage that due to the separate supply, the corresponding coolant flows can hinder each other, which leads to insufficient cooling.

Therefore, it is a further object of the present invention to provide an improved cooling system for an internal combustion engine, which system enables improved cooling of the cylinder head structure and compensates for the increased temperature load caused by the combustion process taking place in the combustion chamber delimited by the cylinder head structure, as is further apparent on page 2, third paragraph of the originally filed description.

According to the invention, this object is achieved in a cooling system as set out above in that the cylinder head cooling jacket is communicatively connected to the cylinder block cooling jacket for circulating the coolant therethrough after cooling the cylinder head, and in that the flow regulating elements are substantially cross-shaped and provided with guide portions for directing the coolant flowing from the inlet to the outlet side of the cylinder head towards central portions of the cylinder head which is provided with a spark plug associated with each of these cylinders.

Since the temperature load on the cylinder head structure usually differs between its intake side and exhaust side, the coolant flows transversely through the cooling jacket between the intake and exhaust sides, and the control element is arranged in the said transverse flow so that the coolant can flow at a predetermined speed, thereby enabling very effective and highly precise cooling of the cylinder head structure.

Furthermore, the coolant flows across the cooling jacket of the cylinder head, so that an increased cooling of the cylinder head is created, and then flows into the Cooling jacket of the cylinder block and flows through it so that the cylinder block is cooled after the cylinder head has been cooled.

According to another preferred embodiment of the present invention, the cooling jacket of the cylinder head forms a first channel between adjacent cylinders on the inlet side of the cylinder head and a second channel on the outlet side of the cylinder head between these adjacent cylinders, wherein the width of said first channel is smaller than the width of said second channel.

Thus, the volume of coolant surrounding the hot outlet ports is larger than on the inlet side, and the velocity of the flowing coolant on the outlet side is reduced compared to the inlet side, so that effective cooling of the outlet side is achieved, the temperature of which is generally higher.

Further preferred embodiments of the invention are set out in the further subclaims.

In the following, the present invention is illustrated and explained in more detail by means of a preferred embodiment and the accompanying drawings, in which:

Fig. 1 is a side view showing an assembled state of a vehicular internal combustion engine according to the invention;

Fig. 2 is a plan view of Fig. 1;

Fig. 3 is a side view of the internal combustion engine shown in Fig. 1;

Fig. 4 is a front view of the internal combustion engine shown in Fig. 3;

Fig. 5 and 6 are partially cutaway side views of the internal combustion engine of Fig. 1 ;

Fig. 7 is a sectional view taken along the line VII-VII in Fig. 6;

Fig. 8 is a sectional view taken along the line VII-VII in Fig. 5; Fig. 9 is a plan view of the cylinder block of the internal combustion engine of Fig. 1 ;

Fig. 10 is a view taken along the arrow mark 1 in Fig. 9;

Fig. 11 is a sectional view taken along the line XI-XI in Fig. 10;

Fig. 12 is a vertical sectional view of the cylinder head of the internal combustion engine of Fig. 1;

Fig. 13 is a sectional view taken along the line XIII-XIII in Fig. 12;

Fig. 14 is a side view of the cylinder head of the internal combustion engine according to the invention from the side opposite to the side with a second drive chain; and

Fig. 15 is a circuit diagram of the cooling system of the internal combustion engine according to the invention.

In Fig. 1 and 2, reference number 1 designates the engine compartment of a vehicle above and between the right and left front wheels 3, which are connected to one another by means of a front drive shaft. In this engine compartment 1, an engine unit 4 with a 6-cylinder four-stroke internal combustion engine and its radiator 5 are mounted in front of the engine unit 4. The engine unit 4 has a crankshaft 6 which extends laterally to the vehicle, so that the passenger compartment is spacious.

The crankshaft 6 is rotatably supported between the cylinder block 7 and the bearing housing 8, as shown in Figs. 5 to 7, and is connected to each piston 9 in the respective cylinder by the respective connecting rod 10. As shown in Figs. 3 and 7 as double-dashed lines, a disk 90 having projections 90a on its edge is mounted at one end of the crankshaft 6, which protrude from the cylinder block 7 to to determine the rotation phase of the crankshaft by detecting the passage of the projections 90a on the disk 90 by means of a crankshaft sensor 91 mounted on the cylinder block 7. A cylinder head 11 is mounted on the cylinder block 7 and both constitute the engine E, the cylinder head 11 having a cover 12 and each cylinder having a spark plug 13.

The bearing housing 8 has an oil pan 14 which is connected to an oil tank 15 which is attached to the vehicle and extends from bottom to top over the entire height of the engine.

As shown in Figs. 5 and 6, the cylinder bank is inclined from the vertical axis towards the rear of the vehicle. The output shaft 16 for the output of the crankshaft 6 is arranged parallel to the crankshaft 6, obliquely above it in front. The oil tank 15 for the engine oil is arranged obliquely from below the crankshaft 6 and the output shaft 16 and thus faces the front end of the vehicle, as indicated by the arrow mark FWD in Figs. 3, 4 and 6. The output shaft 16 is arranged in such a way that an acute angle can be formed between the plane of the cylinder axis L1 and the plane L2, which includes both the axis of the crankshaft 6 and the output shaft 16. The oil pan 14 has a pair of oil pipes 17 which extend vertically through both sides of the guide portion 14a, as shown in Fig. 6. The engine oil collected in the oil pan 14 is sucked through the inlet port 17a at the bottom of the oil pipe 17 and supplied to the oil tank 15 by means of discharge pumps 18 and 19 on the output shaft 16. The oil pan 14 and the oil tank 15 are separated from each other by a wall provided with oil pipes 17. The lubricating oil with which various parts of the engine have been lubricated is collected at the bottom of the crankshaft chamber A formed by the cylinder block 7, bearing housing 8 and oil pan 14, and the inlet port 17a has a filter 20 so that dust cannot be sucked in. In the oil pan 14, a plate 21 is mounted on the guide portion 14a.

The oil in the tank 15 is sucked up through a sieve 25 and a line 26 at the bottom of the tank 15 and fed to the various lubrication points in the engine by means of the oil pump 24 on the output shaft 16, passing through an oil cooler 22 and an oil filter 23, then an oil line 14b to the oil pan 14 and an oil line 8a to the bearing housing and further oil lines 7a and 11a through the cylinder block 7 and the cylinder head 11 respectively.

This oil circulation is indicated by arrow markings in Fig. 6.

The oil container 15 has an oil refill opening 15a at the top that can be closed with a refill cap 27 and also a vent area 15b that is formed by a labyrinth of partitions (not shown) in its upper area.

As can be seen in Figs. 7 and 8, the crankshaft 6 has a gear 28 formed around a crank web, and this gear 28 is in engagement with the gear 29 on the output shaft 16.

The power transmission from the crankshaft 6 to the output shaft 16 is not limited to the gears 28 and 29 as described above, but can also be via a chain, and the gears or the chain can be attached at any end or in the middle of the crankshaft.

The counter shaft 31 is rotatably supported on the cylinder head 11 on one side of the cylinder block 7, and the gear 30 on the output shaft 16 is connected to the gear 32 on the counter shaft 31 by means of a first chain 33 with a reduction ratio of, for example, 0.8. In addition, the gear 34 on the counter shaft 31 is connected to the gears 38 on the camshafts 37 for the valve actuating device 36 by means of a second chain 35 with a reduction ratio of, for example, 0.6, so that the camshafts 37 can be rotated by rotation of the crankshaft 6. The camshafts 39, which are formed as part of the camshafts 37, are rotated together with the camshafts 37 and actuate the intake and exhaust valves (not shown) to timely open/close the intake/exhaust passages 11c and 11d extending through the cylinder head 11. The camshafts 37 are rotatably supported on the cylinder head 11 via a cam cap 102. Each intake passage 11c has a fuel injection device (not shown) for timely fuel injection.

The countershaft 31 is rotatably mounted on the cylinder head above the drive shaft 16 and below the intake line 11c and an intake pipe 41 extending from the intake line 11c. The first chain 33 runs along the cylinder axes and is mounted between the cylinders X1 and X2 on one side of the cylinder X1, as shown in Figs. 8 to 10. The second chain 35 is mounted on the other side of the cylinder X1, on one side of the engine.

The cylinder head 11, which carries the counter shaft 31, has receiving openings 112 and 113 for receiving the gears 32 and 34 on the counter shaft 31, which are covered by a cap 114 and a cover 116, respectively. The receiving opening 112 on the side to which the first chain 33 is connected is opened obliquely upwards.

A drive shaft 121 for the water pump 120, mounted on the front of the engine E, is rotatably supported on the front of the cylinder block 7, parallel to the crankshaft 6 and the output shaft 16, and the gear on the drive shaft 121 is in engagement with the first chain 33 so that the drive shaft 121 is rotated by and together with the crankshaft 6. Since the drive shaft 121 is located on the same side of the cylinder axis plane L1 as the output shaft 16, which is an indispensable component for transmitting the output power of the crankshaft 6, the engine width on the side of the crankshaft is not significantly increased by the drive shaft 121.

As shown in Figs. 8 and 11, the water pump 120 is mounted transversely in the engine E, in the crankshaft direction. On the intake side of the water pump 120, a water inlet connector 123 is provided, which is connected to the outlet of the radiator 5 by a pipe 124. As can be seen from Figs. 6 and 15, the water inlet connector 123 accommodates a regulating valve 125, provided with a thermostat 126, which allows the cooling water to flow into the water pump 120 when the temperature of the cooling water in the engine exceeds a predetermined value.

The supply port 129 on the supply side of the water pump 120 is connected to the cooling water inlet 130 on the front side (with respect to the vehicle) of the cylinder block 7, and the cooling water is supplied from the cooling water inlet 130 via a Cooling water line 131, which is formed in the cylinder block 7 around the drive shaft 121, is fed to the cooling water line 132 in the cylinder head 11. This cooling water inlet 131 only has to be mounted on the side of the vehicle facing forward and can be directed either laterally to the vehicle, as in this embodiment, or forward.

Since the water pump 120 is mounted on the cylinder block 7 so that the cooling water inlet 130 of the cylinder block 7 and the supply port 129 of the water pump 120 overlap, no piping is required for connecting the cooling water inlet 130 to the supply port 129. In addition, since the cooling water pipe 131 and the cooling water inlet 130 in the cylinder block 7 are formed on a side surface of the bearing portion 133 which is bulged forward, they do not require any special enlargement of the cylinder block 7, so that the engine E is prevented from becoming bulky.

As shown in Figs. 9 and 11, the cooling water pipe 131 formed through the cylinder block 7 is opened at the top of the cylinder block 7, and the cooling water pipe 132 of the cylinder head 11 is opened at the bottom of the cylinder head 11. The opening 131a of the cooling water pipe 131 on the cylinder block side is opposite to the opening 132a of the cooling water pipe 132 on the cylinder head side. Therefore, the cooling water pipes 131 and 132 can be easily connected to each other by mounting the cylinder head 11 on the cylinder block 7.

The cooling water line 131 is not connected to the water cooling system 134 for the cylinder block 7, but to the cooling water line 132 in the cylinder head 11, and the cooling water is supplied to the water cooling system 135 in the cylinder head 11 through the cooling water line 132. This cooling water flow is shown by arrow markings in Fig. 15.

Since the cooling water inlet 132a of the water cooling 135 for the cylinder head 11 is opened at a lower level than the intake pipe 11c and the intake tube 41, and further since the cooling water pipe 132 is formed as a part of the cylinder head 11, it will not cause mutual interference with the inlet 11c and the intake tube 41, thereby facilitating the arrangement of the cooling water pipe.

Therefore, since the water pump 120 is mounted on the cylinder block 7 as described above and the cooling water is supplied to the cylinder head water cooling means 135 through cooling water pipes 131 and 132 and independently of the cylinder block water cooling means 134, although the cylinder head 11 is cooled before the cylinder block 7, the water pump 120 can be mounted without mutual interference with the intake pipe 41, the exhaust pipe 40, etc., which enables the creation of a compact engine unit.

Furthermore, since the water pump 120 and the cooling water inlet 132a of the cylinder head water cooling 135 are mounted on the same side of the cylinder block 7 or the cylinder head 11, parallel to the crankshaft 6, there is no mutual overlap between them along the crankshaft 6, which makes it possible to shorten the engine unit along the crankshaft 6.

The fastening points 120a for the water pump 120, the cooling water inlet 132a of the cylinder head cooling 135 and the cooling water inlet 131 only have to be attached to the side surfaces of the cylinder head 11 or the cylinder block 7 parallel to the crankshaft 6 and do not necessarily have to open at right angles to the crankshaft 6. In this embodiment, however, they are open lengthways to the crankshaft 6 or to the cylinder axis.

The cooling water pipe 131 may have a hose or the like separated from the cylinder block 7. In addition, the water pump 120 and the cooling water pipe 131 may be provided on the exhaust side.

As shown in Figs. 12 and 13, the cylinder head 11 is fixed to the cylinder block 7 by bolts 137 inserted through boss portions 136 between the cylinders, and has intake passages 11c and exhaust passages 11d on both sides and above the combustion chamber, and a spark plug 13 fixed in the center of each combustion chamber.

The water cooling system 135 for the cylinder head 11 is formed around the boss portions 136, the intake pipes 11c and the exhaust pipes 11d. Between these cylinders To alleviate this problem, flow regulating members 138 having guide members 138a therein are provided for the cooling water so that the cooling water can flow at a prescribed speed to cool the cylinder head 11. The flow regulating members 138 are mounted on the exhaust side whose temperature tends to be higher than that of the intake side for effective cooling. Moreover, the guide member 138a of the flow regulating member 138 is mounted so that its tips are offset from the spark plugs 13 by a distance Z toward the exhaust side to increase the cooling performance by guiding the cooling water toward the exhaust side of the spark plugs 13. This cooling water flow in the cylinder head 11 is indicated by the arrow marks in Figs. 12 and 13.

As further shown in Fig. 6, the cooling water in the cylinder head water cooling means 135 is supplied from the connecting pipes 139 passing through the lower part of the cylinder head 11 and through connecting pipes 139 passing through the cylinder block 7 to the cylinder block water cooling means 134 for cooling the cylinder block 7. Accordingly, the cooling water is first supplied to the cylinder head 11 for cooling, the temperature of which is higher due to the engine operation, and then cools the cylinder block 7, so that the engine can be effectively cooled.

The cooling water outlet 140, which is connected to the water cooling 134 of the cylinder block 7, is arranged on the front side of the cylinder block 7 near the water pump 120. An outlet fitting 127 is attached to this cooling water outlet 140, which is connected to the inlet side of the radiator 5 by a pipe 141. The radiator 5 has a fan switch 142. The radiator inlet and outlet are arranged symmetrically to each other in order to enable cooling water to flow through the radiator 5.

Accordingly, the cooling water flows as indicated by the arrow marks in Fig. 13. That is, while the engine is running and the cooling water temperature has reached a predetermined limit, the thermostat 126 in the control valve 125 closes the bypass line 128 and creates a connection between the water inlet port 123 and the water pump 120, so as to supply the cooling water from the radiator 5 with the aid of the water pump 120 through the water inlet port 123 to the cylinder head 11. and to the cylinder block 7. After cooling the cylinder block 7, the cooling water is returned to the radiator 5 through the water outlet connection 127.

As shown in Fig. 15, the water outlet port 127 has a water temperature transmitter 143 and a receiver 144. This port 127 at the water outlet 140 is connected to the water inlet connector 123 through a bypass pipe 128 on the front of the cylinder block 7, and by mounting the water outlet port 127, the water inlet connector 123 and the water pump 120 in parallel and close to each other, the bypass pipe 128 can be shortened and the piping can be facilitated while reducing the heat dissipation. In addition, the water outlet port 127 and the water pump 120 can also be mounted at the opposite positions so that the cooling water is supplied to the cylinder block in front of the cylinder head.

As shown in Fig. 15, two cooling water pipes 145 and 146 are connected to the upper portion of the cylinder head, the first 145 being connected to the water pump 120 through a heater 147 and the second 146 being connected to the pipe 145 through an oil cooler 148 which is connected to the water pump 120.

When the engine is running, the oil cooler 148 is cooled by the cooling water and the heater 147 directs warm air into the passenger compartment if necessary. Since the cooling water temperature is low shortly after the engine is started, the regulating valve 125 in the water inlet connector 123 interrupts the supply of cooling water from the radiator 5 and, through the operation of the thermostat, opens the bypass line 128 in order to circulate the cooling water from the cylinder head 11 with the aid of the water pump 120 from the water outlet connection 127, through the bypass line 128 to the cylinder head 11 and to the cylinder block 7.

After the engine has been started and the cooling water has reached a predetermined limit, the thermostat 126 of the control valve 125 connects the water inlet connector 123 to the water pump while the bypass line 128 is interrupted; and the cooling water is supplied to the radiator 5 through the water outlet connector 127 to be cooled there by heat exchange and then to cool the cylinder head 11 and the cylinder block 7 by circulation with the aid of the water pump 120.

Since the cooling water is continuously circulated from the cooling water pipe 146 through the oil cooler 148 to the cylinder head 11 when the engine is running, the accumulation of air in the cylinder head water cooling system 135 is prevented even when the cooling water is circulated from the cylinder head 11 to the cylinder block 7 for cooling.

The position of the cooling water pipe 146 is not limited to that shown in Fig. 5, but it may also be located on the front side of the cylinder head 11 opposite to the side where the second chain 35 is provided, as shown in Fig. 14. In this case, as in Fig. 14, since the cooling water pipe 146 is connected to the highest point of the water cooling 135, the water cooling 135 can be safely vented.

The cylinder head 11 has exhaust pipes 40 and intake pipes 41 connected to each cylinder. Each intake pipe 41 is connected to a feed water tank 42 which extends laterally in the vehicle and is held on the cylinder block 7 by means of supports 43. This feed water tank 42 is provided with a throttle valve 44 on the air intake side.

As shown in Fig. 1, one end of the output shaft 16 has a flywheel 45 and a clutch device (not shown) so that the power for the front wheels 3 is transmitted to the front drive shafts 2 through a gear 47. The primary side of the gear 47 is on the output shaft 16 and the secondary side on a counter shaft 48 to rotate the front drive shaft 2 through a gear 49 attached thereto.

At the other end of the output shaft 16, a power take-off pulley 50 is mounted, the outer edge of which is located in a circular cavity 51 at one end of the cylinder block 7 laterally opposite a bearing 60 for the crankshaft 6, as shown in Figure 7; and a belt 55 is placed around the power take-off pulley 50 and the auxiliary pulleys for the auxiliary devices, such as the generator 52, the servo pump 53, the air compressor, etc., so that these auxiliary devices are simultaneously driven by the output shaft 16. The tension of the belt 55 can be adjusted via a tension roller 92.

However, if a drive shaft 121, which is originally rotated to transmit the rotational movement of the output shaft 16 to the counter shaft 31 by a first chain 33, is used in this embodiment as a drive shaft to which the rotational movement of the crankshaft 6 is to be transmitted, the water pump 120 can also be provided on the output shaft 16 or on the counter shaft 31 instead.

Claims (8)

1. Cooling system for a multi-cylinder internal combustion engine with a cylinder head (11) connected to a cylinder block (7) and defining a plurality of cylinders, said cylinder head (11) having at least one inlet channel (11c) extending through one side of said cylinder head (11) and containing at least one outlet channel (11d) extending through the other side of said cylinder head (11), said cooling system comprising a cylinder head cooling jacket (135) for circulating coolant between an inlet and an outlet side of said cylinder head (11), a cylinder block cooling jacket (134) for circulating coolant through said cylinder block (7), a plurality of flow regulating elements (138) being provided in said cylinder head cooling jacket (135) between adjacent cylinders (x1, x2) arranged in series for regulating a transverse flow of coolant through the cylinder head jacket (135) between the inlet and outlet sides thereof, and a coolant main channel (135a) formed along one side of the cylinder head (11) for circulating the coolant through the cylinder head cooling jacket (135) transversely from one side to the opposite side of the cylinder head (11), characterized in that the cylinder head cooling jacket (135) is communicatively connected to the cylinder block cooling jacket (134) for circulating the coolant therethrough after cooling the cylinder head (11), and that the flow regulating elements (130) are formed substantially cross-shaped and provided with guide sections (138a) for guiding the coolant flowing from the inlet to the outlet side of the cylinder head (11) towards central sections of the cylinder head (11) which is provided with a spark plug (13) assigned to each of these cylinders (x1, x2). 2. Cooling system according to claim 1, characterized in that the flow regulating elements (138) are offset from a plane (L1) which connects the center axes of the cylinders (x1, x2) and are arranged in a line towards the outlet side of the cylinder head (11). 3. Cooling system according to claim 1 or 2, characterized in that the cylinder head cooling jacket (135) forms a first channel between adjacent cylinders (x1, x2) on the inlet side of the cylinder head (11), and a second channel on the outlet side of the cylinder head (11) between these adjacent cylinders (x1, x2), the width (A) of this first channel being smaller than the width (B) of this second channel. 4. Cooling system according to at least one of the preceding claims 1 to 3, characterized in that the guide sections (138a) are formed integrally with the regulating elements (138) on opposite sides thereof. 5. Cooling system according to at least one of the preceding claims 1 to 4, characterized in that the regulating elements (138) are formed integrally with the cylinder head (11). 6. Cooling system according to at least one of the preceding claims 1 to 5, characterized in that the cylinder head cooling jacket (135) is formed around three intake channels (11c) which are assigned to three intake valves, as well as two exhaust channels (11d) which are assigned to two exhaust valves for each cylinder (x1, x2), as well as a hub section (136) which is arranged in front of a cooling jacket channel which is fixed between two intake channels (11c) for guiding the coolant in the direction of the regulating element (138). 7. Cooling system according to claim 6, characterized in that the hub portion (136) is provided with guide tip portions for guiding the coolant flow towards the cooling jacket channel which is defined between the inlet channels (11c). 8. Cooling system according to at least one of the preceding claims 1 to 7, characterized in that the cylinder head cooling jacket (135) is connected to the cylinder block cooling jacket (134) via connecting channels (139) which are arranged on the inlet and outlet sides of the regulating element (138).